WorldWideScience

Sample records for low-noise dynamic reconstruction

  1. High dynamic range low-noise focal plane readout for VLWIR applications implemented with current mode background subtraction

    Science.gov (United States)

    Yang, Guang; Sun, Chao; Shaw, Timothy; Wrigley, Chris; Peddada, Pavani; Blazejewski, Edward R.; Pain, Bedabrata

    1998-09-01

    Design and operation of a low noise CMOS focal pa;ne readout circuit with ultra-high charge handling capacity is presented. Designed for high-background, VLWIR detector readout, each readout unit cell use an accurate dynamic current memory for automatic subtraction of the dark pedestal in current domain enabling measurement of small signals 85 dB below the dark level. The redout circuit operates with low-power dissipation, high linearity, and is capable of handling pedestal currents up to 300 nA. Measurements indicate an effective charge handling capacity of over 5 X 10(superscript 9) charges/pixel with less than 10(superscript 5) electrons of input referred noise.

  2. Configurable Electronics with Low Noise and 14-bit Dynamic Range for Photodiode-based Photon Detectors

    CERN Document Server

    Müller, H; Yin, Z; Zhou, D; Cao, X; Li, Q; Liu, Y; Zou, F; Skaali, B; Awes, T C

    2006-01-01

    We describe the principles and measured performance characteristics of custom configurable 32-channel shaper/digitizer Front End Electronics (FEE) cards with 14-bit dynamic range for use with gain-adjustable photon detectors. The electronics has been designed for the PHOS calorimeter of ALICE with avalanche photodiode (APD) readout operated at -25 C ambient temperature and a signal shaping time of $1 {\\mu}s$. The electronics has also been adopted by the EMCal detector of ALICE with the same APD readout, but operated at an ambient temperature of +20 C and with a shaping time of 100ns. The CR-RC2 signal shapers on the FEE cards are implemented in discrete logic on a 10-layer board with two shaper sections for each input channel. The two shaper sections with gain ratio of 16:1 are digitized by 10-bit ADCs and provide an effective dynamic range of 14 bits. Gain adjustment for each individual APD is available through 32 bias voltage control registers of 10-bit range. The fixed gains and shaping times of the pole-z...

  3. Low-power low-noise mixed-mode VLSI ASIC for infinite dynamic range imaging applications

    Science.gov (United States)

    Turchetta, Renato; Hu, Y.; Zinzius, Y.; Colledani, C.; Loge, A.

    1998-11-01

    Solid state solutions for imaging are mainly represented by CCDs and, more recently, by CMOS imagers. Both devices are based on the integration of the total charge generated by the impinging radiation, with no processing of the single photon information. The dynamic range of these devices is intrinsically limited by the finite value of noise. Here we present the design of an architecture which allows efficient, in-pixel, noise reduction to a practically zero level, thus allowing infinite dynamic range imaging. A detailed calculation of the dynamic range is worked out, showing that noise is efficiently suppressed. This architecture is based on the concept of single-photon counting. In each pixel, we integrate both the front-end, low-noise, low-power analog part and the digital part. The former consists of a charge preamplifier, an active filter for optimal noise bandwidth reduction, a buffer and a threshold comparator, and the latter is simply a counter, which can be programmed to act as a normal shift register for the readout of the counters' contents. Two different ASIC's based on this concept have been designed for different applications. The first one has been optimized for silicon edge-on microstrips detectors, used in a digital mammography R and D project. It is a 32-channel circuit, with a 16-bit binary static counter.It has been optimized for a relatively large detector capacitance of 5 pF. Noise has been measured to be equal to 100 + 7*Cd (pF) electron rms with the digital part, showing no degradation of the noise performances with respect to the design values. The power consumption is 3.8mW/channel for a peaking time of about 1 microsecond(s) . The second circuit is a prototype for pixel imaging. The total active area is about (250 micrometers )**2. The main differences of the electronic architecture with respect to the first prototype are: i) different optimization of the analog front-end part for low-capacitance detectors, ii) in- pixel 4-bit comparator

  4. Industrial dynamic tomographic reconstruction

    International Nuclear Information System (INIS)

    Oliveira, Eric Ferreira de

    2016-01-01

    The state of the art methods applied to industrial processes is currently based on the principles of classical tomographic reconstructions developed for tomographic patterns of static distributions, or is limited to cases of low variability of the density distribution function of the tomographed object. Noise and motion artifacts are the main problems caused by a mismatch in the data from views acquired in different instants. All of these add to the known fact that using a limited amount of data can result in the presence of noise, artifacts and some inconsistencies with the distribution under study. One of the objectives of the present work is to discuss the difficulties that arise from implementing reconstruction algorithms in dynamic tomography that were originally developed for static distributions. Another objective is to propose solutions that aim at reducing a temporal type of information loss caused by employing regular acquisition systems to dynamic processes. With respect to dynamic image reconstruction it was conducted a comparison between different static reconstruction methods, like MART and FBP, when used for dynamic scenarios. This comparison was based on a MCNPx simulation as well as an analytical setup of an aluminum cylinder that moves along the section of a riser during the process of acquisition, and also based on cross section images from CFD techniques. As for the adaptation of current tomographic acquisition systems for dynamic processes, this work established a sequence of tomographic views in a just-in-time fashion for visualization purposes, a form of visually disposing density information as soon as it becomes amenable to image reconstruction. A third contribution was to take advantage of the triple color channel necessary to display colored images in most displays, so that, by appropriately scaling the acquired values of each view in the linear system of the reconstruction, it was possible to imprint a temporal trace into the regularly

  5. Synchronized dynamic dose reconstruction

    International Nuclear Information System (INIS)

    Litzenberg, Dale W.; Hadley, Scott W.; Tyagi, Neelam; Balter, James M.; Ten Haken, Randall K.; Chetty, Indrin J.

    2007-01-01

    Variations in target volume position between and during treatment fractions can lead to measurable differences in the dose distribution delivered to each patient. Current methods to estimate the ongoing cumulative delivered dose distribution make idealized assumptions about individual patient motion based on average motions observed in a population of patients. In the delivery of intensity modulated radiation therapy (IMRT) with a multi-leaf collimator (MLC), errors are introduced in both the implementation and delivery processes. In addition, target motion and MLC motion can lead to dosimetric errors from interplay effects. All of these effects may be of clinical importance. Here we present a method to compute delivered dose distributions for each treatment beam and fraction, which explicitly incorporates synchronized real-time patient motion data and real-time fluence and machine configuration data. This synchronized dynamic dose reconstruction method properly accounts for the two primary classes of errors that arise from delivering IMRT with an MLC: (a) Interplay errors between target volume motion and MLC motion, and (b) Implementation errors, such as dropped segments, dose over/under shoot, faulty leaf motors, tongue-and-groove effect, rounded leaf ends, and communications delays. These reconstructed dose fractions can then be combined to produce high-quality determinations of the dose distribution actually received to date, from which individualized adaptive treatment strategies can be determined

  6. Low noise SQUIDS

    International Nuclear Information System (INIS)

    Waal, V.J. de.

    1983-01-01

    The design, fabrication and limitations of very sensitive SQUID magnetometers are described. The SQUID magnetometer is based on the Josephson effect. A very low-noise niobium SQUID is described. It is fabricated with ultra-small niobium junctions with an overlapping area smaller than 1 μm 2 . The photolithographic technique developed for its fabrication, is described. Also an integrated system with a SQUID and a first-order gradiometer on a single substrate is presented. Calculations of the resolution of a dc SQUID containing ideal Josephson junctions according to the RSJ model are presented including a parasitic capacitance. The usefulness of the fabricated SQUIDS as well as some remarks on their performance is considered. (Auth.)

  7. A Low Noise Electronic Circuit

    NARCIS (Netherlands)

    Annema, Anne J.; Leenaerts, Dominicus M.W.; de Vreede, Petrus W.H.

    2002-01-01

    An electronic circuit, which can be used as a Low Noise Amplifier (LNA), comprises two complementary Field Effect Transistors (M1, M2; M5, M6), each having a gate, a source and a drain. The gates are connected together as a common input terminal, and the drains are connected together as a

  8. Invited article: The fast readout low noise camera as a versatile x-ray detector for time resolved dispersive extended x-ray absorption fine structure and diffraction studies of dynamic problems in materials science, chemistry, and catalysis

    International Nuclear Information System (INIS)

    Labiche, Jean-Claude; Mathon, Olivier; Pascarelli, Sakura; Newton, Mark A.; Ferre, Gemma Guilera; Curfs, Caroline; Vaughan, Gavin; Homs, Alejandro; Carreiras, David Fernandez

    2007-01-01

    Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an 'area' detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [J.-C. Labiche, ESRF Newsletter 25, 41 (1996)] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors

  9. Superconducting low-noise oscillator

    International Nuclear Information System (INIS)

    Riebman, L.

    1992-01-01

    This patent describes a cryogenic oscillator having low phase noise and low noise. It comprises resonant circuit means formed of superconducting material for generating a signal at a desired frequency; linear amplifier means electrically connected to the resonant circuit means at first and second locations thereon; limiter means electrically connected to the resonant circuit means at a third location thereon; and buffer amplifier means for applying the signal generated by the resonant circuit means to a load and electrically connected to the resonant circuit means at a fourth location thereon. This patent also describes a method of minimizing phase noise and 1/f noise in an oscillator circuit of the type having a resonant circuit driving a load and at least a linear amplifier connected to the resonant circuit defining a closed loop having a loop gain greater than unity, and having a limiter for stabilizing the oscillator. It comprises connecting between the resonant circuit and the load a buffer amplifier and connecting the linear amplifier and the buffer amplifier to the resonant circuit

  10. Reconstructing time-dependent dynamics

    OpenAIRE

    Clemson, Philip; Lancaster, Gemma; Stefanovska, Aneta

    2016-01-01

    The usefulness of the information extracted from biomedical data relies heavily on the underlying theory of the methods used in its extraction. The assumptions of stationarity and autonomicity traditionally applied to dynamical systems break down when considering living systems, due to their inherent time-variability. Living systems are thermodynamically open, and thus constantly interacting with their environment. This results in highly nonlinear, time-dependent dynamics. The aim of signal a...

  11. Application of iterative reconstruction in dynamic studies

    International Nuclear Information System (INIS)

    Meikle, S.R.

    1998-01-01

    Full text: The conventional approach to analysing dynamic tomographic data (SPECT or PET) is to reconstruct projections corresponding to each time interval separately and then fit a suitable tracer kinetic model to the dynamic sequence (method 1 ) . This approach assumes that the tracer distribution remains static during any given time interval and, for practical reasons, filtered back-projection (FBP) is the preferred reconstruction algorithm. However, alternative approaches exist which lend themselves to iterative algorithms, such as EM. One approach is to fit the model directly to the projection data, followed by EM reconstruction of the parameter estimates (method 2). This requires that the tracer model can be expressed as a linear function of the unknown model parameters. A third alternative is to incorporate the tracer model into the reconstruction algorithm (method 3). Such an extension was described during the early development of the EM algorithm, referred to as the EM parametric image reconstruction algorithm (EM-PIRA). We have investigated these various strategies for analysing dynamic data and their relative pros and cons. Tracer modelling was performed using a general model, referred to as spectral analysis, which makes no restriction on the number of physiological compartments and satisfies the linearity requirement of method 2. A kinetic software phantom was created and used to test the convergence and noise properties of the different approaches. In summary, method 2 is the most practical as it reduces the number of reconstructions by at least an order of magnitude and provides improved signal-to-noise ratios compared with method 1. EM-PIRA allows greater flexibility in the choice of parametric images and appears to have a regularising effect on convergence. Methods 2 and 3 are also better suited to dynamic scanning with a rotating camera, as they can potentially account for changes in tracer distribution between projections

  12. Nonlinearly stacked low noise turbofan stator

    Science.gov (United States)

    Schuster, William B. (Inventor); Nolcheff, Nick A. (Inventor); Gunaraj, John A. (Inventor); Kontos, Karen B. (Inventor); Weir, Donald S. (Inventor)

    2009-01-01

    A nonlinearly stacked low noise turbofan stator vane having a characteristic curve that is characterized by a nonlinear sweep and a nonlinear lean is provided. The stator is in an axial fan or compressor turbomachinery stage that is comprised of a collection of vanes whose highly three-dimensional shape is selected to reduce rotor-stator and rotor-strut interaction noise while maintaining the aerodynamic and mechanical performance of the vane. The nonlinearly stacked low noise turbofan stator vane reduces noise associated with the fan stage of turbomachinery to improve environmental compatibility.

  13. Reconstruction of dynamical systems from interspike intervals

    International Nuclear Information System (INIS)

    Sauer, T.

    1994-01-01

    Attractor reconstruction from interspike interval (ISI) data is described, in rough analogy with Taken's theorem for attractor reconstruction from time series. Assuming a generic integrate-and-fire model coupling the dynamical system to the spike train, there is a one-to-one correspondence between the system states and interspike interval vectors of sufficiently large dimension. The correspondence has an important implication: interspike intervals can be forecast from past history. We show that deterministically driven ISI series can be distinguished from stochastically driven ISI series on the basis of prediction error

  14. Low noise monolithic CMOS front end electronics

    International Nuclear Information System (INIS)

    Lutz, G.; Bergmann, H.; Holl, P.; Manfredi, P.F.

    1987-01-01

    Design considerations for low noise charge measurement and their application in CMOS electronics are described. The amplifier driver combination whose noise performance has been measured in detail as well as the analog multiplexing silicon strip detector readout electronics are designed with low power consumption and can be operated in pulsed mode so as to reduce heat dissipation even further in many applications. (orig.)

  15. Programmable, very low noise current source

    Science.gov (United States)

    Scandurra, G.; Cannatà, G.; Giusi, G.; Ciofi, C.

    2014-12-01

    We propose a new approach for the realization of very low noise programmable current sources mainly intended for application in the field of low frequency noise measurements. The design is based on a low noise Junction Field Effect Transistor (JFET) acting as a high impedance current source and programmability is obtained by resorting to a low noise, programmable floating voltage source that allows to set the sourced current at the desired value. The floating voltage source is obtained by exploiting the properties of a standard photovoltaic MOSFET driver. Proper filtering and a control network employing super-capacitors allow to reduce the low frequency output noise to that due to the low noise JFET down to frequencies as low as 100 mHz while allowing, at the same time, to set the desired current by means of a standard DA converter with an accuracy better than 1%. A prototype of the system capable of supplying currents from a few hundreds of μA up to a few mA demonstrates the effectiveness of the approach we propose. When delivering a DC current of about 2 mA, the power spectral density of the current fluctuations at the output is found to be less than 25 pA/√Hz at 100 mHz and less than 6 pA/√Hz for f > 1 Hz, resulting in an RMS noise in the bandwidth from 0.1 to 10 Hz of less than 14 pA.

  16. Dynamic dual-tracer PET reconstruction.

    Science.gov (United States)

    Gao, Fei; Liu, Huafeng; Jian, Yiqiang; Shi, Pengcheng

    2009-01-01

    Although of important medical implications, simultaneous dual-tracer positron emission tomography reconstruction remains a challenging problem, primarily because the photon measurements from dual tracers are overlapped. In this paper, we propose a simultaneous dynamic dual-tracer reconstruction of tissue activity maps based on guidance from tracer kinetics. The dual-tracer reconstruction problem is formulated in a state-space representation, where parallel compartment models serve as continuous-time system equation describing the tracer kinetic processes of dual tracers, and the imaging data is expressed as discrete sampling of the system states in measurement equation. The image reconstruction problem has therefore become a state estimation problem in a continuous-discrete hybrid paradigm, and H infinity filtering is adopted as the estimation strategy. As H infinity filtering makes no assumptions on the system and measurement statistics, robust reconstruction results can be obtained for the dual-tracer PET imaging system where the statistical properties of measurement data and system uncertainty are not available a priori, even when there are disturbances in the kinetic parameters. Experimental results on digital phantoms, Monte Carlo simulations and physical phantoms have demonstrated the superior performance.

  17. EUDP Project: Low Noise Airfoil - Final Report

    DEFF Research Database (Denmark)

    This document summarizes the scientific results achieved during the EUDP-funded project `Low-Noise Airfoil'. The goals of this project are, on one side to develop a measurement technique that permits the evaluation of trailing edge noise in a classical aerodynamic wind tunnel, and on the other side...... to develop and implement a design procedure to manufacture airfoil profiles with low noise emission. The project involved two experimental campaigns: one in the LM Wind Power wind tunnel, a classical aerodynamic wind tunnel, in Lunderskov (DK), the second one in the Virginia Tech Stability Wind Tunnel....... In particular, the so-called TNO trailing edge noise model could be significantly improved by introducing turbulence anisotropy in its formulation, as well as the influence of the boundary layer mean pressure gradient. This two characteristics are inherent to airfoil flows but were neglected in the original...

  18. Low noise electronics for experiments at LHC

    International Nuclear Information System (INIS)

    Manfredi, P.F.

    1984-01-01

    The need of reducing the collection times of solid state detectors will lead to thin layers, 150 to 200 μm thickness. Consequently, the charge made available by minimum ionizing particles will be rather small, between 1.2 x 10 4 and 1.6 x 10 4 electrons for unity muliplicity. Front-end electronics with adequately low noise must be designed to detect such small amounts of charge and the problem looks to be harder if the short times available to process the signals are accounted for. (orig.)

  19. Well coupled, low noise, dc SQUIDS

    International Nuclear Information System (INIS)

    Muhlfelder, B.; Beall, J.A.; Cromar, M.W.; Johnson, W.W.; Ono, R.H.

    1985-01-01

    The authors have designed, fabricated, and tested a Double Transformer (DT) coupled dc SQUID (Superconducting Quantum Interference Device) with low noise, an input inductance of 1μH and a smooth input-output characteristic. A transmission line model is presented to explain a resonance in the input-output characteristic of early versions of this device. Guided by the results of numerical simulations a new version of this device has been built and tested. Experimental results are presented that show that the resonance can be moved to a higher voltage by reducing the area of the SQUID loop. The voltage-external flux characteristic of some of these new devices agrees to within 10% with computer simulations. The minimum detectable energy per unit bandwidth (MDE) referred to the SQUID loop, is 10h, where h is Planck's constant. Computer simulations indicate an MDE of 6h

  20. Design of low noise imaging system

    Science.gov (United States)

    Hu, Bo; Chen, Xiaolai

    2017-10-01

    In order to meet the needs of engineering applications for low noise imaging system under the mode of global shutter, a complete imaging system is designed based on the SCMOS (Scientific CMOS) image sensor CIS2521F. The paper introduces hardware circuit and software system design. Based on the analysis of key indexes and technologies about the imaging system, the paper makes chips selection and decides SCMOS + FPGA+ DDRII+ Camera Link as processing architecture. Then it introduces the entire system workflow and power supply and distribution unit design. As for the software system, which consists of the SCMOS control module, image acquisition module, data cache control module and transmission control module, the paper designs in Verilog language and drives it to work properly based on Xilinx FPGA. The imaging experimental results show that the imaging system exhibits a 2560*2160 pixel resolution, has a maximum frame frequency of 50 fps. The imaging quality of the system satisfies the requirement of the index.

  1. Low noise amplifier for ZnS(Ag) scintillation chamber

    International Nuclear Information System (INIS)

    Do Hoang Cuong

    1998-01-01

    A new pulse amplifier that can be used with standard photomultiplier tubes coupled with Zn(Ag) scintillation chamber is presented. The amplifier based on an IC operational amplifier LF 356N consists of a low-noise charge sensitive preamplifier and pulse shaping circuits for optimization of signal to noise ratio. Temperature instability is ≤ 0.05%/ o C. Dynamic range for linear output signals is equal +7 V. The presented amplifier is used in a measuring head for 0.17 L Lucas chambers developed in Department of Nuclear Instruments and Methods of the INCT in laboratory investigations aimed to develop methods and instruments for measurement of radon concentration in the air. The amplifier can also be employed for measurement of ionizing radiation by means of other scintillators coupled to PM tube. The amplifier is followed by a pulse discriminator with adjustable discrimination level. The amplifier output signal and discriminator output pulses are fed to external devices. (author)

  2. Ultra Low Noise Poroelastic Road Surfaces

    Directory of Open Access Journals (Sweden)

    Jerzy A. Ejsmont

    2016-04-01

    Full Text Available Noise is one of the most important environmental problems related to road traffic. During the last decades, the noise emitted by the engines and powertrains of vehicles was greatly reduced and tires became a clearly dominant noise source. The article describes the concept of low noise poroelastic road surfaces that are composed of mineral and rubber aggregate bound by polyurethane resin. Those surfaces have a porous structure and are much more flexible than standard asphalt or cement concrete pavements due to high content of rubber aggregate and elastic binder. Measurements performed in several European countries indicate that such surfaces decrease tire/road noise between 7 dB and 12 dB with respect to reference surfaces such as dense asphalt concrete or stone matrix asphalt. Furthermore, poroelastic road surfaces ascertain the rolling resistance of car tires, which is comparable to classic pavements. One of the unforeseen properties of the poroelastic road surfaces is their ability to decrease the risks related to car fires with fuel spills. The article presents the road and laboratory results of noise, rolling resistance, and fire tests performed on a few types of poroelastic road surfaces.

  3. Tensor-based Dictionary Learning for Dynamic Tomographic Reconstruction

    Science.gov (United States)

    Tan, Shengqi; Zhang, Yanbo; Wang, Ge; Mou, Xuanqin; Cao, Guohua; Wu, Zhifang; Yu, Hengyong

    2015-01-01

    In dynamic computed tomography (CT) reconstruction, the data acquisition speed limits the spatio-temporal resolution. Recently, compressed sensing theory has been instrumental in improving CT reconstruction from far few-view projections. In this paper, we present an adaptive method to train a tensor-based spatio-temporal dictionary for sparse representation of an image sequence during the reconstruction process. The correlations among atoms and across phases are considered to capture the characteristics of an object. The reconstruction problem is solved by the alternating direction method of multipliers. To recover fine or sharp structures such as edges, the nonlocal total variation is incorporated into the algorithmic framework. Preclinical examples including a sheep lung perfusion study and a dynamic mouse cardiac imaging demonstrate that the proposed approach outperforms the vectorized dictionary-based CT reconstruction in the case of few-view reconstruction. PMID:25779991

  4. Tensor-based dictionary learning for dynamic tomographic reconstruction

    International Nuclear Information System (INIS)

    Tan, Shengqi; Wu, Zhifang; Zhang, Yanbo; Mou, Xuanqin; Wang, Ge; Cao, Guohua; Yu, Hengyong

    2015-01-01

    In dynamic computed tomography (CT) reconstruction, the data acquisition speed limits the spatio-temporal resolution. Recently, compressed sensing theory has been instrumental in improving CT reconstruction from far few-view projections. In this paper, we present an adaptive method to train a tensor-based spatio-temporal dictionary for sparse representation of an image sequence during the reconstruction process. The correlations among atoms and across phases are considered to capture the characteristics of an object. The reconstruction problem is solved by the alternating direction method of multipliers. To recover fine or sharp structures such as edges, the nonlocal total variation is incorporated into the algorithmic framework. Preclinical examples including a sheep lung perfusion study and a dynamic mouse cardiac imaging demonstrate that the proposed approach outperforms the vectorized dictionary-based CT reconstruction in the case of few-view reconstruction. (paper)

  5. Low Noise Research Fan Stage Design

    Science.gov (United States)

    Hobbs, David E.; Neubert, Robert J.; Malmborg, Eric W.; Philbrick, Daniel H.; Spear, David A.

    1995-01-01

    This report describes the design of a Low Noise ADP Research Fan stage. The fan is a variable pitch design which is designed at the cruise pitch condition. Relative to the cruise setting, the blade is closed at takeoff and opened for reverse thrust operation. The fan stage is a split flow design with fan exit guide vanes and core stators. This fan stage design was combined with a nacelle and engine core duct to form a powered fan/nacelle, subscale model. This model is intended for use in aerodynamic performance, acoustic and structural testing in a wind tunnel. The model has a 22-inch outer fan diameter and a hub-to-top ratio of 0.426 which permits the use of existing NASA fan and cowl force balance designs and rig drive system. The design parameters were selected to permit valid acoustic and aerodynamic comparisons with the PW 17-inch rig previously tested under NASA contract. The fan stage design is described in detail. The results of the design axisymmetric analysis at aerodynamic design condition are included. The structural analysis of the fan rotor and attachment is described including the material selections and stress analysis. The blade and attachment are predicted to have adequate low cycle fatigue life, and an acceptable operating range without resonant stress or flutter. The stage was acoustically designed with airfoil counts in the fan exit guide vane and core stator to minimize noise. A fan-FEGV tone analysis developed separately under NASA contract was used to determine these airfoil counts. The fan stage design was matched to a nacelle design to form a fan/nacelle model for wind tunnel testing. The nacelle design was developed under a separate NASA contract. The nacelle was designed with an axisymmetric inlet, cowl and nozzle for convenience in testing and fabrication. Aerodynamic analysis of the nacelle confirmed the required performance at various aircraft operating conditions.

  6. Wideband Low Noise Amplifiers Exploiting Thermal Noise Cancellation

    NARCIS (Netherlands)

    Bruccoleri, F.; Klumperink, Eric A.M.; Nauta, Bram

    2005-01-01

    Low Noise Amplifiers (LNAs) are commonly used to amplify signals that are too weak for direct processing for example in radio or cable receivers. Traditionally, low noise amplifiers are implemented via tuned amplifiers, exploiting inductors and capacitors in resonating LC-circuits. This can render

  7. Dynamic scintigraphic studies after oesophageal reconstruction

    International Nuclear Information System (INIS)

    Maliska, C.M.; Maliska, C.; Pinto, E.; Castro, L.; Fonseca, L.B.E; Miranda, M.

    1997-01-01

    Full text: We have studied the oesophageal transit and gastric emptying in the monitoring of the effect of oesophageal reconstruction surgery. Oncologic patients were evaluated after oesophageal reconstruction surgery with gastric (14 patients) or colonic (5 patients) tube and they were compared with 15 healthy volunteers, using scintigraphic method with liquid food (S-colloid-Tc99m). In the oesophageal transit studies there were no significant statistical differences among the three groups, when we have just considered to two superior (of the three) segments, as oesophagus, showing that the distal neo-tube works just like the stomach of normal volunteers

  8. Reconstructing the competitive dynamics of mixed-oak neighborhoods

    Science.gov (United States)

    Eric K. Zenner; Daniel J. Heggenstaller; Patrick H. Brose; JeriLynn E. Peck; Kim C. Steiner

    2012-01-01

    The disparity between the potential for latent oak dominance within a stand and their region-wide decline in importance value raises questions about the competitiveness of oaks in early stand dynamics. We reconstructed tree height growth dynamics in mixed-species neighborhoods to determine if currently dominant oaks were ever shorter than their competitors and at what...

  9. Class of reconstructed discontinuous Galerkin methods in computational fluid dynamics

    International Nuclear Information System (INIS)

    Luo, Hong; Xia, Yidong; Nourgaliev, Robert

    2011-01-01

    A class of reconstructed discontinuous Galerkin (DG) methods is presented to solve compressible flow problems on arbitrary grids. The idea is to combine the efficiency of the reconstruction methods in finite volume methods and the accuracy of the DG methods to obtain a better numerical algorithm in computational fluid dynamics. The beauty of the resulting reconstructed discontinuous Galerkin (RDG) methods is that they provide a unified formulation for both finite volume and DG methods, and contain both classical finite volume and standard DG methods as two special cases of the RDG methods, and thus allow for a direct efficiency comparison. Both Green-Gauss and least-squares reconstruction methods and a least-squares recovery method are presented to obtain a quadratic polynomial representation of the underlying linear discontinuous Galerkin solution on each cell via a so-called in-cell reconstruction process. The devised in-cell reconstruction is aimed to augment the accuracy of the discontinuous Galerkin method by increasing the order of the underlying polynomial solution. These three reconstructed discontinuous Galerkin methods are used to compute a variety of compressible flow problems on arbitrary meshes to assess their accuracy. The numerical experiments demonstrate that all three reconstructed discontinuous Galerkin methods can significantly improve the accuracy of the underlying second-order DG method, although the least-squares reconstructed DG method provides the best performance in terms of both accuracy, efficiency, and robustness. (author)

  10. Network Reconstruction of Dynamic Biological Systems

    OpenAIRE

    Asadi, Behrang

    2013-01-01

    Inference of network topology from experimental data is a central endeavor in biology, since knowledge of the underlying signaling mechanisms a requirement for understanding biological phenomena. As one of the most important tools in bioinformatics area, development of methods to reconstruct biological networks has attracted remarkable attention in the current decade. Integration of different data types can lead to remarkable improvements in our ability to identify the connectivity of differe...

  11. Reconstruction of dynamical equations for traffic flow

    OpenAIRE

    Kriso, S.; Friedrich, R.; Peinke, J.; Wagner, P.

    2001-01-01

    Traffic flow data collected by an induction loop detector on the highway close to Koeln-Nord are investigated with respect to their dynamics including the stochastic content. In particular we present a new method, with which the flow dynamics can be extracted directly from the measured data. As a result a Langevin equation for the traffic flow is obtained. From the deterministic part of the flow dynamics, stable fixed points are extracted and set into relation with common features of the fund...

  12. Cross Linked Metal Particles for Low Noise Bolometer Materials

    Science.gov (United States)

    2016-12-12

    Our results indicate that the CLMPs can simultaneously have a high temperature coefficient of resistivity and a low noise, and therefore have a...indicate that the CLMPs can simultaneously have a high temperature co- efficient of resistivity and a low noise, and therefore have a great potential...current as a function of the inverse of applied bias for CLMP films at different temperatures. It is seen that the I-V curves are highly nonlinear as 7 0

  13. Qualitative criteria and thresholds for low noise asphalt mixture design

    Science.gov (United States)

    Vaitkus, A.; Andriejauskas, T.; Gražulytė, J.; Šernas, O.; Vorobjovas, V.; Kleizienė, R.

    2018-05-01

    Low noise asphalt pavements are cost efficient and cost effective alternative for road traffic noise mitigation comparing with noise barriers, façade insulation and other known noise mitigation measures. However, design of low noise asphalt mixtures strongly depends on climate and traffic peculiarities of different regions. Severe climate regions face problems related with short durability of low noise asphalt mixtures in terms of considerable negative impact of harsh climate conditions (frost-thaw, large temperature fluctuations, hydrological behaviour, etc.) and traffic (traffic loads, traffic volumes, studded tyres, etc.). Thus there is a need to find balance between mechanical and acoustical durability as well as to ensure adequate pavement skid resistance for road safety purposes. Paper presents analysis of the qualitative criteria and design parameters thresholds of low noise asphalt mixtures. Different asphalt mixture composition materials (grading, aggregate, binder, additives, etc.) and relevant asphalt layer properties (air void content, texture, evenness, degree of compaction, etc.) were investigated and assessed according their suitability for durable and effective low noise pavements. Paper concluded with the overview of requirements, qualitative criteria and thresholds for low noise asphalt mixture design for severe climate regions.

  14. A Total Variation-Based Reconstruction Method for Dynamic MRI

    Directory of Open Access Journals (Sweden)

    Germana Landi

    2008-01-01

    Full Text Available In recent years, total variation (TV regularization has become a popular and powerful tool for image restoration and enhancement. In this work, we apply TV minimization to improve the quality of dynamic magnetic resonance images. Dynamic magnetic resonance imaging is an increasingly popular clinical technique used to monitor spatio-temporal changes in tissue structure. Fast data acquisition is necessary in order to capture the dynamic process. Most commonly, the requirement of high temporal resolution is fulfilled by sacrificing spatial resolution. Therefore, the numerical methods have to address the issue of images reconstruction from limited Fourier data. One of the most successful techniques for dynamic imaging applications is the reduced-encoded imaging by generalized-series reconstruction method of Liang and Lauterbur. However, even if this method utilizes a priori data for optimal image reconstruction, the produced dynamic images are degraded by truncation artifacts, most notably Gibbs ringing, due to the spatial low resolution of the data. We use a TV regularization strategy in order to reduce these truncation artifacts in the dynamic images. The resulting TV minimization problem is solved by the fixed point iteration method of Vogel and Oman. The results of test problems with simulated and real data are presented to illustrate the effectiveness of the proposed approach in reducing the truncation artifacts of the reconstructed images.

  15. Wide Band Low Noise Love Wave Magnetic Field Sensor System.

    Science.gov (United States)

    Kittmann, Anne; Durdaut, Phillip; Zabel, Sebastian; Reermann, Jens; Schmalz, Julius; Spetzler, Benjamin; Meyners, Dirk; Sun, Nian X; McCord, Jeffrey; Gerken, Martina; Schmidt, Gerhard; Höft, Michael; Knöchel, Reinhard; Faupel, Franz; Quandt, Eckhard

    2018-01-10

    We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/[Formula: see text], a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. A range of additional measures to further increase the sensitivity are investigated with simulations.

  16. Reconstructing latent dynamical noise for better forecasting observables

    Science.gov (United States)

    Hirata, Yoshito

    2018-03-01

    I propose a method for reconstructing multi-dimensional dynamical noise inspired by the embedding theorem of Muldoon et al. [Dyn. Stab. Syst. 13, 175 (1998)] by regarding multiple predictions as different observables. Then, applying the embedding theorem by Stark et al. [J. Nonlinear Sci. 13, 519 (2003)] for a forced system, I produce time series forecast by supplying the reconstructed past dynamical noise as auxiliary information. I demonstrate the proposed method on toy models driven by auto-regressive models or independent Gaussian noise.

  17. Dynamic Ising model: reconstruction of evolutionary trees

    International Nuclear Information System (INIS)

    De Oliveira, P M C

    2013-01-01

    An evolutionary tree is a cascade of bifurcations starting from a single common root, generating a growing set of daughter species as time goes by. ‘Species’ here is a general denomination for biological species, spoken languages or any other entity which evolves through heredity. From the N currently alive species within a clade, distances are measured through pairwise comparisons made by geneticists, linguists, etc. The larger is such a distance that, for a pair of species, the older is their last common ancestor. The aim is to reconstruct the previously unknown bifurcations, i.e. the whole clade, from knowledge of the N(N − 1)/2 quoted distances, which are taken for granted. A mechanical method is presented and its applicability is discussed. (paper)

  18. Reconstruction dynamics of recorded holograms in photochromic glass

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, Mona; Pavel, Eugen; Nicolae, Vasile B.

    2011-06-20

    We have investigated the dynamics of the record-erase process of holograms in photochromic glass using continuum Nd:YVO{sub 4} laser radiation ({lambda}=532 nm). A bidimensional microgrid pattern was formed and visualized in photochromic glass, and its diffraction efficiency decay versus time (during reconstruction step) gave us information (D, {Delta}n) about the diffusion process inside the material. The recording and reconstruction processes were carried out in an off-axis setup, and the images of the reconstructed object were recorded by a CCD camera. Measurements realized on reconstructed object images using holograms recorded at a different incident power laser have shown a two-stage process involved in silver atom kinetics.

  19. Industrial dynamic tomographic reconstruction; Reconstrucao tomografica dinamica industrial

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Eric Ferreira de

    2016-07-01

    The state of the art methods applied to industrial processes is currently based on the principles of classical tomographic reconstructions developed for tomographic patterns of static distributions, or is limited to cases of low variability of the density distribution function of the tomographed object. Noise and motion artifacts are the main problems caused by a mismatch in the data from views acquired in different instants. All of these add to the known fact that using a limited amount of data can result in the presence of noise, artifacts and some inconsistencies with the distribution under study. One of the objectives of the present work is to discuss the difficulties that arise from implementing reconstruction algorithms in dynamic tomography that were originally developed for static distributions. Another objective is to propose solutions that aim at reducing a temporal type of information loss caused by employing regular acquisition systems to dynamic processes. With respect to dynamic image reconstruction it was conducted a comparison between different static reconstruction methods, like MART and FBP, when used for dynamic scenarios. This comparison was based on a MCNPx simulation as well as an analytical setup of an aluminum cylinder that moves along the section of a riser during the process of acquisition, and also based on cross section images from CFD techniques. As for the adaptation of current tomographic acquisition systems for dynamic processes, this work established a sequence of tomographic views in a just-in-time fashion for visualization purposes, a form of visually disposing density information as soon as it becomes amenable to image reconstruction. A third contribution was to take advantage of the triple color channel necessary to display colored images in most displays, so that, by appropriately scaling the acquired values of each view in the linear system of the reconstruction, it was possible to imprint a temporal trace into the regularly

  20. Quantum and Private Capacities of Low-Noise Channels

    Science.gov (United States)

    Leditzky, Felix; Leung, Debbie; Smith, Graeme

    2018-04-01

    We determine both the quantum and the private capacities of low-noise quantum channels to leading orders in the channel's distance to the perfect channel. It has been an open problem for more than 20 yr to determine the capacities of some of these low-noise channels such as the depolarizing channel. We also show that both capacities are equal to the single-letter coherent information of the channel, again to leading orders. We thus find that, in the low-noise regime, superadditivity and degenerate codes have a negligible benefit for the quantum capacity, and shielding does not improve the private capacity beyond the quantum capacity, in stark contrast to the situation when noisier channels are considered.

  1. Low noise constant current source for bias dependent noise measurements

    International Nuclear Information System (INIS)

    Talukdar, D.; Bose, Suvendu; Bardhan, K. K.; Chakraborty, R. K.

    2011-01-01

    A low noise constant current source used for measuring the 1/f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 μA to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noise voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described.

  2. A programmable ultra-low noise X-band exciter.

    Science.gov (United States)

    MacMullen, A; Hoover, L R; Justice, R D; Callahan, B S

    2001-07-01

    A programmable ultra-low noise X-band exciter has been developed using commercial off-the-shelf components. Its phase noise is more than 10 dB below the best available microwave synthesizers. It covers a 7% frequency band with 0.1-Hz resolution. The X-band output at +23 dBm is a combination of signals from an X-band sapphire-loaded cavity oscillator (SLCO), a low noise UHF frequency synthesizer, and special-purpose frequency translation and up-conversion circuitry.

  3. Transistor design considerations for low-noise preamplifiers

    International Nuclear Information System (INIS)

    Fair, R.B.

    1976-01-01

    A review is presented of design considerations for GaAs Schottky-barrier FETs and other types of transistors in low-noise amplifiers for capacitive sources which are used in nuclear radiation detectors and high speed fiber-optic communication systems. Ultimate limits on performance are evaluated in terms of the g/sub m//C/sub i/ ratio and the gate leakage current to minimize the noise sources. Si bipolar transistors and the future prospects of GaAs, Si and InAs MISFETs are discussed, and performance is compared to FETs currently being used in low-noise preamplifiers

  4. A low noise ASIC for two dimensional neutron gas detector with performance of high spatial resolution (Contract research)

    International Nuclear Information System (INIS)

    Yamagishi, Hideshi; Toh, Kentaro; Nakamura, Tatsuya; Sakasai, Kaoru; Soyama, Kazuhiko

    2012-02-01

    An ASD-ASIC (Amplifier-Shaper-Discriminator ASIC) with fast response and low noise performances has been designed for two-dimensional position sensitive neutron gas detectors (InSPaD). The InSPaD is a 2D neutron detector system with 3 He gas and provides a high spatial resolution by making distinction between proton and triton particles generated in the gas chamber. The new ASD-ASIC is required to have very low noise, a wide dynamic range, good output linearity and high counting rate. The new ASD-ASIC has been designed by using CMOS and consisted of 64-channel ASDs, a 16-channel multiplexer with LVTTL drivers and sum amplifier system for summing all analog signals. The performances were evaluated by the Spice simulation. It was confirmed that the new ASD-ASIC had very low noise performance, wide dynamic range and fast signal processing functions. (author)

  5. Muscular activity during dynamic squats in patients with ACL reconstruction.

    Science.gov (United States)

    Ceaglio, Sebastian; Alberto, Federico; Catalfamo, Paola Andrea; Braidot, Ariel Andres

    2010-01-01

    One of the most frequent injuries in subjects who practice sport is the rupture of the anterior cruciate ligament (ACL). Appropriate reconstruction and rehabilitation are key issues in full recovery of patients and their return to previous activities. This paper presents a new method to estimate muscle strength during a dynamic exercise from kinematic and electromyographic (EMG) data. Recovery of patients with ACL rupture and reconstruction was evaluated 4 and 6 months after surgery by assessing the differences in knee extensor and flexor muscle activity between the unimpaired and injured limbs. The results show that squat EMGs from the extensor muscles of the knee from the injured and unimpaired limb could help assess rehabilitation outputs in patients who had undergone an ACL reconstructive surgery.

  6. External Peltier Cooler For Low-Noise Amplifier

    Science.gov (United States)

    Soper, Terry A.

    1990-01-01

    Inexpensive Peltier-effect cooling module made of few commercially available parts used to reduce thermal noise in microwave amplifier. Retrofitted to almost any microwave low-noise amplifier or receiver preamplifier used in communication, telemetry, or radar. Includes copper or aluminum cold plate held tightly against unit to be cooled by strap-type worm-gear clamps.

  7. Sparse/Low Rank Constrained Reconstruction for Dynamic PET Imaging.

    Directory of Open Access Journals (Sweden)

    Xingjian Yu

    Full Text Available In dynamic Positron Emission Tomography (PET, an estimate of the radio activity concentration is obtained from a series of frames of sinogram data taken at ranging in duration from 10 seconds to minutes under some criteria. So far, all the well-known reconstruction algorithms require known data statistical properties. It limits the speed of data acquisition, besides, it is unable to afford the separated information about the structure and the variation of shape and rate of metabolism which play a major role in improving the visualization of contrast for some requirement of the diagnosing in application. This paper presents a novel low rank-based activity map reconstruction scheme from emission sinograms of dynamic PET, termed as SLCR representing Sparse/Low Rank Constrained Reconstruction for Dynamic PET Imaging. In this method, the stationary background is formulated as a low rank component while variations between successive frames are abstracted to the sparse. The resulting nuclear norm and l1 norm related minimization problem can also be efficiently solved by many recently developed numerical methods. In this paper, the linearized alternating direction method is applied. The effectiveness of the proposed scheme is illustrated on three data sets.

  8. Simultaneous reconstruction and segmentation for dynamic SPECT imaging

    International Nuclear Information System (INIS)

    Burger, Martin; Rossmanith, Carolin; Zhang, Xiaoqun

    2016-01-01

    This work deals with the reconstruction of dynamic images that incorporate characteristic dynamics in certain subregions, as arising for the kinetics of many tracers in emission tomography (SPECT, PET). We make use of a basis function approach for the unknown tracer concentration by assuming that the region of interest can be divided into subregions with spatially constant concentration curves. Applying a regularised variational framework reminiscent of the Chan-Vese model for image segmentation we simultaneously reconstruct both the labelling functions of the subregions as well as the subconcentrations within each region. Our particular focus is on applications in SPECT with the Poisson noise model, resulting in a Kullback–Leibler data fidelity in the variational approach. We present a detailed analysis of the proposed variational model and prove existence of minimisers as well as error estimates. The latter apply to a more general class of problems and generalise existing results in literature since we deal with a nonlinear forward operator and a nonquadratic data fidelity. A computational algorithm based on alternating minimisation and splitting techniques is developed for the solution of the problem and tested on appropriately designed synthetic data sets. For those we compare the results to those of standard EM reconstructions and investigate the effects of Poisson noise in the data. (paper)

  9. A temporal interpolation approach for dynamic reconstruction in perfusion CT

    International Nuclear Information System (INIS)

    Montes, Pau; Lauritsch, Guenter

    2007-01-01

    This article presents a dynamic CT reconstruction algorithm for objects with time dependent attenuation coefficient. Projection data acquired over several rotations are interpreted as samples of a continuous signal. Based on this idea, a temporal interpolation approach is proposed which provides the maximum temporal resolution for a given rotational speed of the CT scanner. Interpolation is performed using polynomial splines. The algorithm can be adapted to slow signals, reducing the amount of data acquired and the computational cost. A theoretical analysis of the approximations made by the algorithm is provided. In simulation studies, the temporal interpolation approach is compared with three other dynamic reconstruction algorithms based on linear regression, linear interpolation, and generalized Parker weighting. The presented algorithm exhibits the highest temporal resolution for a given sampling interval. Hence, our approach needs less input data to achieve a certain quality in the reconstruction than the other algorithms discussed or, equivalently, less x-ray exposure and computational complexity. The proposed algorithm additionally allows the possibility of using slow rotating scanners for perfusion imaging purposes

  10. LNA A 1.9 GHZ low noise amplifier

    Directory of Open Access Journals (Sweden)

    Jorge Julián Moreno-Rubio

    2006-12-01

    Full Text Available This paper shows the design, the simulation, and the layout from a low noise amplifier (LNA, designed with and approximate band from 25 to 80 MHz. The design results of the matching neworks are shown, its noise figure, its available and transduced gain according to its non lineal model (TOM, the DC network, crash inductors and matching capacitors with the large impedance transmission lines.

  11. Reconstructing Interlaced High-Dynamic-Range Video Using Joint Learning.

    Science.gov (United States)

    Inchang Choi; Seung-Hwan Baek; Kim, Min H

    2017-11-01

    For extending the dynamic range of video, it is a common practice to capture multiple frames sequentially with different exposures and combine them to extend the dynamic range of each video frame. However, this approach results in typical ghosting artifacts due to fast and complex motion in nature. As an alternative, video imaging with interlaced exposures has been introduced to extend the dynamic range. However, the interlaced approach has been hindered by jaggy artifacts and sensor noise, leading to concerns over image quality. In this paper, we propose a data-driven approach for jointly solving two specific problems of deinterlacing and denoising that arise in interlaced video imaging with different exposures. First, we solve the deinterlacing problem using joint dictionary learning via sparse coding. Since partial information of detail in differently exposed rows is often available via interlacing, we make use of the information to reconstruct details of the extended dynamic range from the interlaced video input. Second, we jointly solve the denoising problem by tailoring sparse coding to better handle additive noise in low-/high-exposure rows, and also adopt multiscale homography flow to temporal sequences for denoising. We anticipate that the proposed method will allow for concurrent capture of higher dynamic range video frames without suffering from ghosting artifacts. We demonstrate the advantages of our interlaced video imaging compared with the state-of-the-art high-dynamic-range video methods.

  12. Experiments of reconstructing discrete atmospheric dynamic models from data (I)

    Science.gov (United States)

    Lin, Zhenshan; Zhu, Yanyu; Deng, Ziwang

    1995-03-01

    In this paper, we give some experimental results of our study in reconstructing discrete atmospheric dynamic models from data. After a great deal of numerical experiments, we found that the logistic map, x n + 1 = 1- μx {2/n}, could be used in monthly mean temperature prediction when it was approaching the chaotic region, and its predictive results were in reverse states to the practical data. This means that the nonlinear developing behavior of the monthly mean temperature system is bifurcating back into the critical chaotic states from the chaotic ones.

  13. Nonlinear rotor dynamics of 2D molecular array: topology reconstruction

    International Nuclear Information System (INIS)

    Lykah, V.A.; Syrkin, E.S.

    2011-01-01

    Molecular layers with rotational degrees of freedom and quadrupolar interaction between linear molecules are investigated theoretically. We found earlier that alternative orientation of the molecules along and perpendicular to an axis of the rectangular lattice is preferable. Here we find the integral of motion and give the topology analysis of the possible dynamical phases and special points in the long-wave limit. We find the strong anisotropy in the angle space: directions of easy excitation ('valleys') exist. We show the potential relief reconstruction in dependence on the adsorbed lattice anisotropy.

  14. Image reconstruction of dynamic infrared single-pixel imaging system

    Science.gov (United States)

    Tong, Qi; Jiang, Yilin; Wang, Haiyan; Guo, Limin

    2018-03-01

    Single-pixel imaging technique has recently received much attention. Most of the current single-pixel imaging is aimed at relatively static targets or the imaging system is fixed, which is limited by the number of measurements received through the single detector. In this paper, we proposed a novel dynamic compressive imaging method to solve the imaging problem, where exists imaging system motion behavior, for the infrared (IR) rosette scanning system. The relationship between adjacent target images and scene is analyzed under different system movement scenarios. These relationships are used to build dynamic compressive imaging models. Simulation results demonstrate that the proposed method can improve the reconstruction quality of IR image and enhance the contrast between the target and the background in the presence of system movement.

  15. Motion estimation and compensation in dynamic spiral CT reconstruction

    International Nuclear Information System (INIS)

    Kimdon, J.; Grangeat, P.; Koenig, A.; Bonnet, St.

    2004-01-01

    Respiratory and cardiac motion causes blurring in dynamic X-ray Computed Tomography (CT). Fast scans reduce this problem, but they require a higher radiation dose per time period to maintain the signal to noise ratio of the resulting images, thereby magnifying the health risk to the patient. As an alternative to increased radiation, our team has already developed a cone-beam reconstruction algorithm based on a dynamic particle model that estimates, predicts, and compensates for respiratory motion in circular X-ray CT. The current paper presents an extension of this method to spiral CT, applicable to modern multi-slice scanners that take advantage of the speed and dose benefits of helical trajectories. We adapted all three main areas of the algorithm: backprojection, prediction, and compensation/accumulation. In backprojection, we changed the longitudinal re-binning technique, filter direction, and the method of enforcing the data sufficiency requirements. For prediction, we had to be careful of objects appearing and disappearing as the scanner bed advanced. For compensation/accumulation, we controlled the reconstruction time and combined images to cover a greater longitudinal extent for each phase in the respiratory or cardiac cycle. Tests with moving numerical phantoms demonstrate that the algorithm successfully improves the temporal resolution of the images without increasing the dose or reducing the signal-to-noise ratio. (authors)

  16. Self-expressive Dictionary Learning for Dynamic 3D Reconstruction.

    Science.gov (United States)

    Zheng, Enliang; Ji, Dinghuang; Dunn, Enrique; Frahm, Jan-Michael

    2017-08-22

    We target the problem of sparse 3D reconstruction of dynamic objects observed by multiple unsynchronized video cameras with unknown temporal overlap. To this end, we develop a framework to recover the unknown structure without sequencing information across video sequences. Our proposed compressed sensing framework poses the estimation of 3D structure as the problem of dictionary learning, where the dictionary is defined as an aggregation of the temporally varying 3D structures. Given the smooth motion of dynamic objects, we observe any element in the dictionary can be well approximated by a sparse linear combination of other elements in the same dictionary (i.e. self-expression). Our formulation optimizes a biconvex cost function that leverages a compressed sensing formulation and enforces both structural dependency coherence across video streams, as well as motion smoothness across estimates from common video sources. We further analyze the reconstructability of our approach under different capture scenarios, and its comparison and relation to existing methods. Experimental results on large amounts of synthetic data as well as real imagery demonstrate the effectiveness of our approach.

  17. Precise Characterization and Multiobjective Optimization of Low Noise Amplifiers

    Directory of Open Access Journals (Sweden)

    J. Dobes

    2015-09-01

    Full Text Available Although practically all function blocks of the satellite navigation receivers are realized using the CMOS digital integrated circuits, it is appropriate to create a separate low noise antenna preamplifier based on a low noise pHEMT. Such an RF front end can be strongly optimized to attain a suitable tradeoff between the noise figure and transducer power gain. Further, as all the four principal navigation systems (GPS, GLONASS, Galileo, and COMPASS work in similar frequency bands (roughly from 1.1 to 1.7 GHz, it is reasonable to create the low noise preamplifier for all of them. In the paper, a sophisticated method of the amplifier design is suggested based on multiobjective optimization. A substantial improvement of a standard optimization method is also outlined to satisfy a uniform coverage of Pareto front. Moreover, for enhancing efficiency of many times repeated solutions of large linear systems during the optimization, a new modification of the Markowitz criterion is suggested compatible with fast modes of the LU factorization. Extraordinary attention was also given to the accuracy of modeling. First, an extraction of pHEMT model parameters was performed including its noise part, and several models were compared. The extraction was carried out by an original identification procedure based on a combination of metaheuristic and direct methods. Second, the equations of the passive elements (including transmission lines and T-splitters were carefully defined using frequency dispersion of their parameters as Q, ESR, etc. Third, an optimal selection of the operating point and essential passive elements was performed using the improved optimization method. Finally, the s-parameters and noise figure of the amplifier were measured, and stability and third-order intermodulation products were also checked.

  18. Obtaining and Estimating Low Noise Floors in Vibration Sensors

    DEFF Research Database (Denmark)

    Brincker, Rune; Larsen, Jesper Abildgaard

    2007-01-01

    For some applications like seismic applications and measuring ambient vibrations in structures, it is essential that the noise floors of the sensors and other system components are low and known to the user. Some of the most important noise sources are reviewed and it is discussed how the sensor...... can be designed in order to obtain a low noise floor. Techniques to estimate the noise floors for sensors are reviewed and are demonstrated on a commercial commonly used sensor for vibration testing. It is illustrated how the noise floor can be calculated using the coherence between simultaneous...

  19. Reconstruction of missing daily streamflow data using dynamic regression models

    Science.gov (United States)

    Tencaliec, Patricia; Favre, Anne-Catherine; Prieur, Clémentine; Mathevet, Thibault

    2015-12-01

    River discharge is one of the most important quantities in hydrology. It provides fundamental records for water resources management and climate change monitoring. Even very short data-gaps in this information can cause extremely different analysis outputs. Therefore, reconstructing missing data of incomplete data sets is an important step regarding the performance of the environmental models, engineering, and research applications, thus it presents a great challenge. The objective of this paper is to introduce an effective technique for reconstructing missing daily discharge data when one has access to only daily streamflow data. The proposed procedure uses a combination of regression and autoregressive integrated moving average models (ARIMA) called dynamic regression model. This model uses the linear relationship between neighbor and correlated stations and then adjusts the residual term by fitting an ARIMA structure. Application of the model to eight daily streamflow data for the Durance river watershed showed that the model yields reliable estimates for the missing data in the time series. Simulation studies were also conducted to evaluate the performance of the procedure.

  20. Application of DIRI dynamic infrared imaging in reconstructive surgery

    Science.gov (United States)

    Pawlowski, Marek; Wang, Chengpu; Jin, Feng; Salvitti, Matthew; Tenorio, Xavier

    2006-04-01

    We have developed the BioScanIR System based on QWIP (Quantum Well Infrared Photodetector). Data collected by this sensor are processed using the DIRI (Dynamic Infrared Imaging) algorithms. The combination of DIRI data processing methods with the unique characteristics of the QWIP sensor permit the creation of a new imaging modality capable of detecting minute changes in temperature at the surface of the tissue and organs associated with blood perfusion due to certain diseases such as cancer, vascular disease and diabetes. The BioScanIR System has been successfully applied in reconstructive surgery to localize donor flap feeding vessels (perforators) during the pre-surgical planning stage. The device is also used in post-surgical monitoring of skin flap perfusion. Since the BioScanIR is mobile; it can be moved to the bedside for such monitoring. In comparison to other modalities, the BioScanIR can localize perforators in a single, 20 seconds scan with definitive results available in minutes. The algorithms used include (FFT) Fast Fourier Transformation, motion artifact correction, spectral analysis and thermal image scaling. The BioScanIR is completely non-invasive and non-toxic, requires no exogenous contrast agents and is free of ionizing radiation. In addition to reconstructive surgery applications, the BioScanIR has shown promise as a useful functional imaging modality in neurosurgery, drug discovery in pre-clinical animal models, wound healing and peripheral vascular disease management.

  1. Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

    International Nuclear Information System (INIS)

    Kiran, P. Prem; Bagchi, Suman; Kumar, G. Ravindra; Krishnan, Siva Rama; Arnold, C. L.; Couairon, A.

    2010-01-01

    We observe the complete dynamics of the propagation of very intense, femtosecond laser pulses in air under tight focusing conditions via direct imaging of the entire interaction zone. The whole life history of the focused pulses is then reconstructed by means of numerical simulations. We show that beam breakup leads to a dual-rate increase in filament numbers with laser power. Linearly and circularly polarized pulses give rise to beam breakup and fusion governed by external focusing conditions. For tight focusing conditions, intensity saturation due to plasma generation and nonlinear losses does not limit the intensity growth, thereby giving access to a new propagation regime featured by an efficient laser energy deposition in fully ionized air and intense 10 15 W/cm 2 pulses at the focus.

  2. Dynamic Error Analysis Method for Vibration Shape Reconstruction of Smart FBG Plate Structure

    Directory of Open Access Journals (Sweden)

    Hesheng Zhang

    2016-01-01

    Full Text Available Shape reconstruction of aerospace plate structure is an important issue for safe operation of aerospace vehicles. One way to achieve such reconstruction is by constructing smart fiber Bragg grating (FBG plate structure with discrete distributed FBG sensor arrays using reconstruction algorithms in which error analysis of reconstruction algorithm is a key link. Considering that traditional error analysis methods can only deal with static data, a new dynamic data error analysis method are proposed based on LMS algorithm for shape reconstruction of smart FBG plate structure. Firstly, smart FBG structure and orthogonal curved network based reconstruction method is introduced. Then, a dynamic error analysis model is proposed for dynamic reconstruction error analysis. Thirdly, the parameter identification is done for the proposed dynamic error analysis model based on least mean square (LMS algorithm. Finally, an experimental verification platform is constructed and experimental dynamic reconstruction analysis is done. Experimental results show that the dynamic characteristics of the reconstruction performance for plate structure can be obtained accurately based on the proposed dynamic error analysis method. The proposed method can also be used for other data acquisition systems and data processing systems as a general error analysis method.

  3. Advanced Low-Noise Research Fan Stage Design

    Science.gov (United States)

    Neubert, Robert; Bock, Larry; Malmborg, Eric; Owen-Peer, William

    1997-01-01

    This report describes the design of the Advanced Low-Noise Research Fan stage. The fan is a variable pitch design, which is designed at the cruise pitch condition. Relative to the cruise setting, the blade is closed at takeoff and opened for reverse thrust operation. The fan stage is a split flow design with fan exit guide vanes (FEGVs) and core stators. The fan stage design is combined with a nacelle and engine core duct to form a powered fan/nacelle subscale model. This model is intended for use in combined aerodynamic, acoustic, and structural testing in a wind tunnel. The fan has an outer diameter of 22 in. and a hub-to-tip of 0.426 in., which allows the use of existing NASA fan and cowl force balance and rig drive systems. The design parameters were selected to permit valid acoustic and aerodynamic comparisons with the Pratt & Whitney (P&W) 17- and 22-in. rigs previously tested under NASA contract. The fan stage design is described in detail. The results of the design axisymmetric and Navier-Stokes aerodynamic analysis are presented at the critical design conditions. The structural analysis of the fan rotor and attachment is included. The blade and attachment are predicted to have adequate low-cycle fatigue life and an acceptable operating range without resonant stress or flutter. The stage was acoustically designed with airfoil counts in the FEGV and core stator to minimize noise. A fan/FEGV tone analysis developed separately under NASA contract was used to determine the optimum airfoil counts. The fan stage was matched to the existing nacelle, designed under the previous P&W low-noise contract, to form a fan/nacelle model for wind tunnel testing. It is an axisymmetric nacelle for convenience in testing and analysis. Previous testing confirmed that the nacelle performed as required at various aircraft operating conditions.

  4. Reconstructing a nonlinear dynamical framework for testing quantum mechanics

    International Nuclear Information System (INIS)

    Jordan, T.F.

    1993-01-01

    The nonlinear generalization of quantum dynamics constructed by Weinberg as a basis for experimental tests is reconstructed in terms of density-matrix elements to allow independent dynamics for subsystems. Dynamics is generated with a Lie bracket and a nonlinear Hamiltonian function. It takes density matrices to density matrices and pure states to pure states. Each density matrix has a Hamiltonian operator that makes its evolution for an infinitesimal time, but the Hamiltonian operator may be different for different density matrices and may change in time as the density matrix changes. A Hamiltonian function for a subsystem serves also for the entire system. Independence of separate subsystems is confirmed by seeing that brackets are zero for functions from different subsystems and by looking at the Hamiltonian operator for each density matrix. Scaling properties of Hamiltonian functions are found to be important in connection with locality. An example of all this is obtained from every one of the local nonlinear Schroedinger equations described by Bialynicki-Birula and Mycielski. Examples are worked out for spins coupled together or to fields, demonstrating Hamiltonian functions and equations of motion written directly in terms of physical mean values. Observables and states are taken to be the same as in ordinary quantum mechanics. An attempt to find nonlinear representations of observables by characterizing propositions as functions equal to their squares yields a negative result. Sharper interpretation of mixed states is proposed. In a mixture of parts that are prepared separately, time dependence must be calculated separately for each part so different mixtures that yield the same density matrix can be distinguished. No criticism has shown that a consistent interpretation cannot be made this way. Thus, nonlinearity remains a viable hypothesis for experimental tests. 16 refs

  5. A computationally efficient OMP-based compressed sensing reconstruction for dynamic MRI

    International Nuclear Information System (INIS)

    Usman, M; Prieto, C; Schaeffter, T; Batchelor, P G; Odille, F; Atkinson, D

    2011-01-01

    Compressed sensing (CS) methods in MRI are computationally intensive. Thus, designing novel CS algorithms that can perform faster reconstructions is crucial for everyday applications. We propose a computationally efficient orthogonal matching pursuit (OMP)-based reconstruction, specifically suited to cardiac MR data. According to the energy distribution of a y-f space obtained from a sliding window reconstruction, we label the y-f space as static or dynamic. For static y-f space images, a computationally efficient masked OMP reconstruction is performed, whereas for dynamic y-f space images, standard OMP reconstruction is used. The proposed method was tested on a dynamic numerical phantom and two cardiac MR datasets. Depending on the field of view composition of the imaging data, compared to the standard OMP method, reconstruction speedup factors ranging from 1.5 to 2.5 are achieved. (note)

  6. A pseudoproxy assessment of data assimilation for reconstructing the atmosphere-ocean dynamics of hydroclimate extremes

    Science.gov (United States)

    Steiger, Nathan J.; Smerdon, Jason E.

    2017-10-01

    Because of the relatively brief observational record, the climate dynamics that drive multiyear to centennial hydroclimate variability are not adequately characterized and understood. Paleoclimate reconstructions based on data assimilation (DA) optimally fuse paleoclimate proxies with the dynamical constraints of climate models, thus providing a coherent dynamical picture of the past. DA is therefore an important new tool for elucidating the mechanisms of hydroclimate variability over the last several millennia. But DA has so far remained untested for global hydroclimate reconstructions. Here we explore whether or not DA can be used to skillfully reconstruct global hydroclimate variability along with the driving climate dynamics. Through a set of idealized pseudoproxy experiments, we find that an established DA reconstruction approach can in principle be used to reconstruct hydroclimate at both annual and seasonal timescales. We find that the skill of such reconstructions is generally highest near the proxy sites. This set of reconstruction experiments is specifically designed to estimate a realistic upper bound for the skill of this DA approach. Importantly, this experimental framework allows us to see where and for what variables the reconstruction approach may never achieve high skill. In particular for tree rings, we find that hydroclimate reconstructions depend critically on moisture-sensitive trees, while temperature reconstructions depend critically on temperature-sensitive trees. Real-world DA-based reconstructions will therefore likely require a spatial mixture of temperature- and moisture-sensitive trees to reconstruct both temperature and hydroclimate variables. Additionally, we illustrate how DA can be used to elucidate the dynamical mechanisms of drought with two examples: tropical drivers of multiyear droughts in the North American Southwest and in equatorial East Africa. This work thus provides a foundation for future DA-based hydroclimate

  7. Benchmarking burnup reconstruction methods for dynamically operated research reactors

    Energy Technology Data Exchange (ETDEWEB)

    Sternat, Matthew R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Charlton, William S. [Univ. of Nebraska, Lincoln, NE (United States). National Strategic Research Institute; Nichols, Theodore F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-03-01

    The burnup of an HEU fueled dynamically operated research reactor, the Oak Ridge Research Reactor, was experimentally reconstructed using two different analytic methodologies and a suite of signature isotopes to evaluate techniques for estimating burnup for research reactor fuel. The methods studied include using individual signature isotopes and the complete mass spectrometry spectrum to recover the sample’s burnup. The individual, or sets of, isotopes include 148Nd, 137Cs+137Ba, 139La, and 145Nd+146Nd. The storage documentation from the analyzed fuel material provided two different measures of burnup: burnup percentage and the total power generated from the assembly in MWd. When normalized to conventional units, these two references differed by 7.8% (395.42GWd/MTHM and 426.27GWd/MTHM) in the resulting burnup for the spent fuel element used in the benchmark. Among all methods being evaluated, the results were within 11.3% of either reference burnup. The results were mixed in closeness to both reference burnups; however, consistent results were achieved from all three experimental samples.

  8. Dynamic MRI reconstruction as a moment problem. Pt. 1

    International Nuclear Information System (INIS)

    Zwaan, M.

    1989-03-01

    This paper deals with some mathematical aspects of magnetic resonance imaging (MRI) concerning the beating heart. Some of the basic theory behind magnetic resonance is given. Of special interest is the mathematical theory concerning MRI and the ideas and problems in mathematical terms will be formulated. If one uses MRI to measure and display a so colled 'dynamic' organ, like the beating heart, the situation is more complex than the case of a static organ. Strategy is described how a cross section of a beating human heart is measured in practice and how the measurements are arranged before an image can be made. This technique is called retrospective synchronization. If the beating heart is measured and displayed with help of this method, artefacts often deteriorate the image quality. Some of these artefacts have a physical cause, while others are caused by the reconstruction algorithm. Perhaps mathematical techniques may be used to improve these algorithms hich are currently used in practice. The aim of this paper is not to solve problems, but to give an adequate mathematical formulation of the inversion problem concerning retrospective synchronization. (author). 3 refs.; 4 figs

  9. Low-noise analog readout channel for SDD in X-ray spectrometry

    Science.gov (United States)

    Atkin, E.; Gusev, A.; Krivchenko, A.; Levin, V.; Malankin, E.; Normanov, D.; Rotin, A.; Sagdiev, I.; Samsonov, V.

    2016-01-01

    A low-noise analog readout channel optimized for operation with the Silicon Drift Detectors (SDDs) with built-in JFET is presented. The Charge Sensitive Amplifier (CSA) operates in a pulse reset mode using the reset diode built-in the SDD detector. The shaper is a 6th order semi-Gaussian filter with switchable discrete shaping times. The readout channel provides the Equivalent Noise Charge (ENC) of 12e- (simulation) and input dynamic range of 30 keV . The measured energy resolution at the 5,89 keV line of a 55Fe X-ray source is 336 eV (FWHM). The channel was prototyped via Europractice in the AMS 350 nm process as miniASIC. The simulation and first measurement results are presented in the paper.

  10. An investigation of temporal regularization techniques for dynamic PET reconstructions using temporal splines

    International Nuclear Information System (INIS)

    Verhaeghe, Jeroen; D'Asseler, Yves; Vandenberghe, Stefaan; Staelens, Steven; Lemahieu, Ignace

    2007-01-01

    The use of a temporal B-spline basis for the reconstruction of dynamic positron emission tomography data was investigated. Maximum likelihood (ML) reconstructions using an expectation maximization framework and maximum A-posteriori (MAP) reconstructions using the generalized expectation maximization framework were evaluated. Different parameters of the B-spline basis of such as order, number of basis functions and knot placing were investigated in a reconstruction task using simulated dynamic list-mode data. We found that a higher order basis reduced both the bias and variance. Using a higher number of basis functions in the modeling of the time activity curves (TACs) allowed the algorithm to model faster changes of the TACs, however, the TACs became noisier. We have compared ML, Gaussian postsmoothed ML and MAP reconstructions. The noise level in the ML reconstructions was controlled by varying the number of basis functions. The MAP algorithm penalized the integrated squared curvature of the reconstructed TAC. The postsmoothed ML was always outperformed in terms of bias and variance properties by the MAP and ML reconstructions. A simple adaptive knot placing strategy was also developed and evaluated. It is based on an arc length redistribution scheme during the reconstruction. The free knot reconstruction allowed a more accurate reconstruction while reducing the noise level especially for fast changing TACs such as blood input functions. Limiting the number of temporal basis functions combined with the adaptive knot placing strategy is in this case advantageous for regularization purposes when compared to the other regularization techniques

  11. Ultra-low noise miniaturized neural amplifier with hardware averaging.

    Science.gov (United States)

    Dweiri, Yazan M; Eggers, Thomas; McCallum, Grant; Durand, Dominique M

    2015-08-01

    Peripheral nerves carry neural signals that could be used to control hybrid bionic systems. Cuff electrodes provide a robust and stable interface but the recorded signal amplitude is small (concept of hardware averaging to nerve recordings obtained with cuff electrodes. An optimization procedure is developed to minimize noise and power simultaneously. The novel design was based on existing neural amplifiers (Intan Technologies, LLC) and is validated with signals obtained from the FINE in chronic dog experiments. We showed that hardware averaging leads to a reduction in the total recording noise by a factor of 1/√N or less depending on the source resistance. Chronic recording of physiological activity with FINE using the presented design showed significant improvement on the recorded baseline noise with at least two parallel operation transconductance amplifiers leading to a 46.1% reduction at N = 8. The functionality of these recordings was quantified by the SNR improvement and shown to be significant for N = 3 or more. The present design was shown to be capable of generating hardware averaging on noise improvement for neural recording with cuff electrodes, and can accommodate the presence of high source impedances that are associated with the miniaturized contacts and the high channel count in electrode arrays. This technique can be adopted for other applications where miniaturized and implantable multichannel acquisition systems with ultra-low noise and low power are required.

  12. A Low Noise Amplifier for Neural Spike Recording Interfaces

    Directory of Open Access Journals (Sweden)

    Jesus Ruiz-Amaya

    2015-09-01

    Full Text Available This paper presents a Low Noise Amplifier (LNA for neural spike recording applications. The proposed topology, based on a capacitive feedback network using a two-stage OTA, efficiently solves the triple trade-off between power, area and noise. Additionally, this work introduces a novel transistor-level synthesis methodology for LNAs tailored for the minimization of their noise efficiency factor under area and noise constraints. The proposed LNA has been implemented in a 130 nm CMOS technology and occupies 0.053 mm-sq. Experimental results show that the LNA offers a noise efficiency factor of 2.16 and an input referred noise of 3.8 μVrms for 1.2 V power supply. It provides a gain of 46 dB over a nominal bandwidth of 192 Hz–7.4 kHz and consumes 1.92 μW. The performance of the proposed LNA has been validated through in vivo experiments with animal models.

  13. A compact, multichannel, and low noise arbitrary waveform generator.

    Science.gov (United States)

    Govorkov, S; Ivanov, B I; Il'ichev, E; Meyer, H-G

    2014-05-01

    A new type of high functionality, fast, compact, and easy programmable arbitrary waveform generator for low noise physical measurements is presented. The generator provides 7 fast differential waveform channels with a maximum bandwidth up to 200 MHz frequency. There are 6 fast pulse generators on the generator board with 78 ps time resolution in both duration and delay, 3 of them with amplitude control. The arbitrary waveform generator is additionally equipped with two auxiliary slow 16 bit analog-to-digital converters and four 16 bit digital-to-analog converters for low frequency applications. Electromagnetic shields are introduced to the power supply, digital, and analog compartments and with a proper filter design perform more than 110 dB digital noise isolation to the output signals. All the output channels of the board have 50 Ω SubMiniature version A termination. The generator board is suitable for use as a part of a high sensitive physical equipment, e.g., fast read out and manipulation of nuclear magnetic resonance or superconducting quantum systems and any other application, which requires electromagnetic interference free fast pulse and arbitrary waveform generation.

  14. A high and low noise model for strong motion accelerometers

    Science.gov (United States)

    Clinton, J. F.; Cauzzi, C.; Olivieri, M.

    2010-12-01

    We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular interest for the SED, this study provides acceptable noise limits for candidate sites for the on-going Strong Motion Network modernisation.

  15. A compact, multichannel, and low noise arbitrary waveform generator

    International Nuclear Information System (INIS)

    Govorkov, S.; Ivanov, B. I.; Il'ichev, E.; Meyer, H.-G.

    2014-01-01

    A new type of high functionality, fast, compact, and easy programmable arbitrary waveform generator for low noise physical measurements is presented. The generator provides 7 fast differential waveform channels with a maximum bandwidth up to 200 MHz frequency. There are 6 fast pulse generators on the generator board with 78 ps time resolution in both duration and delay, 3 of them with amplitude control. The arbitrary waveform generator is additionally equipped with two auxiliary slow 16 bit analog-to-digital converters and four 16 bit digital-to-analog converters for low frequency applications. Electromagnetic shields are introduced to the power supply, digital, and analog compartments and with a proper filter design perform more than 110 dB digital noise isolation to the output signals. All the output channels of the board have 50 Ω SubMiniature version A termination. The generator board is suitable for use as a part of a high sensitive physical equipment, e.g., fast read out and manipulation of nuclear magnetic resonance or superconducting quantum systems and any other application, which requires electromagnetic interference free fast pulse and arbitrary waveform generation

  16. Integrating deep Earth dynamics in paleogeographic reconstructions of Australia

    Science.gov (United States)

    Heine, Christian; Müller, R. Dietmar; Steinberger, Bernhard; DiCaprio, Lydia

    2010-03-01

    It is well documented that the Cenozoic progressive flooding of Australia, contemporaneous with a eustatic sea level fall, requires a downward tilting of the Australian Plate towards the SE Asian subduction system. Previously, this large-scale, mantle-convection driven dynamic topography effect has been approximated by computing the time-dependent vertical shifts and tilts of a plane, but the observed subsidence and uplift anomalies indicate a more complex interplay between time-dependent mantle convection and plate motion. We combine plate kinematics with a global mantle backward-advection model based on shear-wave mantle tomography, paleogeographic data, eustatic sea level estimates and basin stratigraphy to reconstruct the Australian flooding history for the last 70 Myrs on a continental scale. We compute time-dependent dynamic surface topography and continental inundation of a digital elevation model adjusted for sediment accumulation. Our model reveals two evolving dynamic topography lows, over which the Australian plate has progressively moved. We interpret the southern low to be caused by sinking slab material with an origin along the eastern Gondwana subduction zone in the Cretaceous, whereas the northern low, which first straddles northern Australia in the Oligocene, is mainly attributable to material subducted north and northeast of Australia. Our model accounts for the Paleogene exposure of the Gulf of Carpentaria region at a time when sea level was much higher than today, and explains anomalous Late Tertiary subsidence on Australia's northern, western and southern margins. The resolution of our model, which excludes short-wavelength mantle density anomalies and is restricted to depths larger than 220 km, is not sufficient to model the two well recorded episodes of major transgressions in South Australia in the Eocene and Miocene. However, the overall, long-wavelength spatio-temporal pattern of Australia's inundation record is well captured by combining

  17. A robust state-space kinetics-guided framework for dynamic PET image reconstruction

    International Nuclear Information System (INIS)

    Tong, S; Alessio, A M; Kinahan, P E; Liu, H; Shi, P

    2011-01-01

    Dynamic PET image reconstruction is a challenging issue due to the low SNR and the large quantity of spatio-temporal data. We propose a robust state-space image reconstruction (SSIR) framework for activity reconstruction in dynamic PET. Unlike statistically-based frame-by-frame methods, tracer kinetic modeling is incorporated to provide physiological guidance for the reconstruction, harnessing the temporal information of the dynamic data. Dynamic reconstruction is formulated in a state-space representation, where a compartmental model describes the kinetic processes in a continuous-time system equation, and the imaging data are expressed in a discrete measurement equation. Tracer activity concentrations are treated as the state variables, and are estimated from the dynamic data. Sampled-data H ∞ filtering is adopted for robust estimation. H ∞ filtering makes no assumptions on the system and measurement statistics, and guarantees bounded estimation error for finite-energy disturbances, leading to robust performance for dynamic data with low SNR and/or errors. This alternative reconstruction approach could help us to deal with unpredictable situations in imaging (e.g. data corruption from failed detector blocks) or inaccurate noise models. Experiments on synthetic phantom and patient PET data are performed to demonstrate feasibility of the SSIR framework, and to explore its potential advantages over frame-by-frame statistical reconstruction approaches.

  18. Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions.

    Science.gov (United States)

    Rood, Akkie; Hannink, Gerjon; Lenting, Anke; Groenen, Karlijn; Koëter, Sander; Verdonschot, Nico; van Kampen, Albert

    2015-10-01

    Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixation. Static MPFL reconstruction is most commonly used. However, dynamic reconstruction deforms more easily and presumably functions more like the native MPFL. The aim of the study was to evaluate the effect of the different MPFL fixation techniques on patellofemoral pressures compared with the native situation. The hypothesis was that dynamic reconstruction would result in patellofemoral pressures closer to those generated in an intact knee. Controlled laboratory study. Seven fresh-frozen knee specimens were tested in an in vitro knee joint loading apparatus. Tekscan pressure-sensitive films fixed to the retropatellar cartilage measured mean patellofemoral and peak pressures, contact area, and location of the center of force (COF) at fixed flexion angles from 0° to 110°. Four different conditions were tested: intact, dynamic, partial dynamic, and static MPFL reconstruction. Data were analyzed using linear mixed models. Static MPFL reconstruction resulted in higher peak and mean pressures from 60° to 110° of flexion (P .05). The COF in the static reconstruction group moved more medially on the patella from 50° to 110° of flexion compared with the other conditions. The contact area showed no significant differences between the test conditions. After static MPFL reconstruction, the patellofemoral pressures in flexion angles from 60° to 110° were 3 to 5 times higher than those in the intact situation. The pressures after dynamic MPFL reconstruction were similar as compared with those in the intact situation, and therefore, dynamic MPFL reconstruction could be a safer option than static reconstruction for stabilizing the patella. This study showed that static MPFL reconstruction

  19. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, A B [Centre for Marine and Environmental Research (CIMA), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)], E-mail: abarbosa@ualg.pt

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N{sub 2} uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO{sub 2} and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  20. Dynamics of living phytoplankton: Implications for paleoenvironmental reconstructions

    International Nuclear Information System (INIS)

    Barbosa, A B

    2009-01-01

    Phytoplankton is the dominant primary producer in aquatic ecosystems and is considered a gauge of ecological condition and change. Some phytoplankton groups, namely diatoms, dinoflagellates, and coccolithophores, produce morphological or chemical fossils that can be used for paleoenvironmental reconstruction. This study aims to review the processes that regulate dynamics in living phytoplankton and to highlight how this knowledge is used in paleoecological studies. The distribution patterns of phytoplankton in present-day aquatic ecosystems are shaped by the interplay between processes that regulate cell growth and cell death. Cell growth and cell death are regulated by the internal environment of phytoplankton (e.g., specific environmental tolerances, resource uptake properties, cell size, density and morphology, alternative nutritional strategies such as mixotrophy or N 2 uptake, motility, intracellular storage capacities, grazing resistance properties), and by its external environment. The external environment includes variables dependent on the availability of resources (e.g., light intensity, concentration of CO 2 and dissolved inorganic macronutrients and micronutrients, availability of living prey in case of mixotrophs) and variables independent of resources (e.g., temperature, salinity, turbulence, ultraviolet radiation, bioactive compounds, activity of grazers, viruses, and eukaryotic parasites). The importance of recently described loss processes, such as grazing by phagotrophic protists, viral lyses, and programmed cell death, is discussed in the context of its potential impact upon phytoplankton vertical fluxes. Examples of the use of different phytoplankton metrics (e.g. abundance, species composition, species morphology, and elemental composition) to infer contemporaneous as well as past environmental and ecological conditions are critically evaluated.

  1. Patellofemoral pressure changes after static and dynamic medial patellofemoral ligament reconstructions

    NARCIS (Netherlands)

    Rood, A.; Hannink, G.; Lenting, A.; Groenen, K.; Koëter, S.; Verdonschot, Nicolaas Jacobus Joseph; van Kampen, A.

    2015-01-01

    Background: Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue

  2. Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions

    NARCIS (Netherlands)

    Rood, A.; Hannink, G.; Lenting, A.; Groenen, K.; Koeter, S.; Verdonschot, N.J.; Kampen, A. van

    2015-01-01

    BACKGROUND: Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue

  3. Dynamic PET Image reconstruction for parametric imaging using the HYPR kernel method

    Science.gov (United States)

    Spencer, Benjamin; Qi, Jinyi; Badawi, Ramsey D.; Wang, Guobao

    2017-03-01

    Dynamic PET image reconstruction is a challenging problem because of the ill-conditioned nature of PET and the lowcounting statistics resulted from short time-frames in dynamic imaging. The kernel method for image reconstruction has been developed to improve image reconstruction of low-count PET data by incorporating prior information derived from high-count composite data. In contrast to most of the existing regularization-based methods, the kernel method embeds image prior information in the forward projection model and does not require an explicit regularization term in the reconstruction formula. Inspired by the existing highly constrained back-projection (HYPR) algorithm for dynamic PET image denoising, we propose in this work a new type of kernel that is simpler to implement and further improves the kernel-based dynamic PET image reconstruction. Our evaluation study using a physical phantom scan with synthetic FDG tracer kinetics has demonstrated that the new HYPR kernel-based reconstruction can achieve a better region-of-interest (ROI) bias versus standard deviation trade-off for dynamic PET parametric imaging than the post-reconstruction HYPR denoising method and the previously used nonlocal-means kernel.

  4. Low noise InP-based MMIC receivers for W-band

    Science.gov (United States)

    Leonard, Regis F.

    1991-01-01

    A program to develop a monolithic W-band low noise amplifier (a critical element in any W-band communications, sensors, or radar application) is described. Goals of the program include a completely monolithic low noise amplifier, less than a 3.5 dB noise figure, and a monolithic mixer suitable for integration with the LNA.

  5. GaAs Wideband Low Noise Amplifier Design for Breast Cancer Detection System

    DEFF Research Database (Denmark)

    Yan, Lei; Krozer, Viktor; Delcourt, Sebastien

    2009-01-01

    Modern wideband systems require low-noise receivers with bandwidth approaching 10 GHz. This paper presents ultra-wideband stable low-noise amplifier MMIC with cascode and source follower buffer configuration using GaAs technology. Source degeneration, gate and shunt peaking inductors are used...

  6. MR-guided dynamic PET reconstruction with the kernel method and spectral temporal basis functions

    Science.gov (United States)

    Novosad, Philip; Reader, Andrew J.

    2016-06-01

    Recent advances in dynamic positron emission tomography (PET) reconstruction have demonstrated that it is possible to achieve markedly improved end-point kinetic parameter maps by incorporating a temporal model of the radiotracer directly into the reconstruction algorithm. In this work we have developed a highly constrained, fully dynamic PET reconstruction algorithm incorporating both spectral analysis temporal basis functions and spatial basis functions derived from the kernel method applied to a co-registered T1-weighted magnetic resonance (MR) image. The dynamic PET image is modelled as a linear combination of spatial and temporal basis functions, and a maximum likelihood estimate for the coefficients can be found using the expectation-maximization (EM) algorithm. Following reconstruction, kinetic fitting using any temporal model of interest can be applied. Based on a BrainWeb T1-weighted MR phantom, we performed a realistic dynamic [18F]FDG simulation study with two noise levels, and investigated the quantitative performance of the proposed reconstruction algorithm, comparing it with reconstructions incorporating either spectral analysis temporal basis functions alone or kernel spatial basis functions alone, as well as with conventional frame-independent reconstruction. Compared to the other reconstruction algorithms, the proposed algorithm achieved superior performance, offering a decrease in spatially averaged pixel-level root-mean-square-error on post-reconstruction kinetic parametric maps in the grey/white matter, as well as in the tumours when they were present on the co-registered MR image. When the tumours were not visible in the MR image, reconstruction with the proposed algorithm performed similarly to reconstruction with spectral temporal basis functions and was superior to both conventional frame-independent reconstruction and frame-independent reconstruction with kernel spatial basis functions. Furthermore, we demonstrate that a joint spectral

  7. Direct reconstruction of pharmacokinetic parameters in dynamic fluorescence molecular tomography by the augmented Lagrangian method

    Science.gov (United States)

    Zhu, Dianwen; Zhang, Wei; Zhao, Yue; Li, Changqing

    2016-03-01

    Dynamic fluorescence molecular tomography (FMT) has the potential to quantify physiological or biochemical information, known as pharmacokinetic parameters, which are important for cancer detection, drug development and delivery etc. To image those parameters, there are indirect methods, which are easier to implement but tend to provide images with low signal-to-noise ratio, and direct methods, which model all the measurement noises together and are statistically more efficient. The direct reconstruction methods in dynamic FMT have attracted a lot of attention recently. However, the coupling of tomographic image reconstruction and nonlinearity of kinetic parameter estimation due to the compartment modeling has imposed a huge computational burden to the direct reconstruction of the kinetic parameters. In this paper, we propose to take advantage of both the direct and indirect reconstruction ideas through a variable splitting strategy under the augmented Lagrangian framework. Each iteration of the direct reconstruction is split into two steps: the dynamic FMT image reconstruction and the node-wise nonlinear least squares fitting of the pharmacokinetic parameter images. Through numerical simulation studies, we have found that the proposed algorithm can achieve good reconstruction results within a small amount of time. This will be the first step for a combined dynamic PET and FMT imaging in the future.

  8. Maximum a posteriori reconstruction of the Patlak parametric image from sinograms in dynamic PET

    International Nuclear Information System (INIS)

    Wang Guobao; Fu Lin; Qi Jinyi

    2008-01-01

    Parametric imaging using the Patlak graphical method has been widely used to analyze dynamic PET data. Conventionally a Patlak parametric image is generated by reconstructing a sequence of dynamic images first and then performing Patlak graphical analysis on the time-activity curves pixel-by-pixel. However, because it is rather difficult to model the noise distribution in reconstructed images, the spatially variant noise correlation is simply ignored in the Patlak analysis, which leads to sub-optimal results. In this paper we present a Bayesian method for reconstructing Patlak parametric images directly from raw sinogram data by incorporating the Patlak plot model into the image reconstruction procedure. A preconditioned conjugate gradient algorithm is used to find the maximum a posteriori solution. The proposed direct method is statistically more efficient than the conventional indirect approach because the Poisson noise distribution in PET data can be accurately modeled in the direct reconstruction. The computation cost of the direct method is similar to reconstruction time of two dynamic frames. Therefore, when more than two dynamic frames are used in the Patlak analysis, the direct method is faster than the conventional indirect approach. We conduct computer simulations to validate the proposed direct method. Comparisons with the conventional indirect approach show that the proposed method results in a more accurate estimate of the parametric image. The proposed method has been applied to dynamic fully 3D PET data from a microPET scanner

  9. Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

    Science.gov (United States)

    Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

    2017-11-01

    Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

  10. Pathgroups, a dynamic data structure for genome reconstruction problems.

    Science.gov (United States)

    Zheng, Chunfang

    2010-07-01

    Ancestral gene order reconstruction problems, including the median problem, quartet construction, small phylogeny, guided genome halving and genome aliquoting, are NP hard. Available heuristics dedicated to each of these problems are computationally costly for even small instances. We present a data structure enabling rapid heuristic solution to all these ancestral genome reconstruction problems. A generic greedy algorithm with look-ahead based on an automatically generated priority system suffices for all the problems using this data structure. The efficiency of the algorithm is due to fast updating of the structure during run time and to the simplicity of the priority scheme. We illustrate with the first rapid algorithm for quartet construction and apply this to a set of yeast genomes to corroborate a recent gene sequence-based phylogeny. http://albuquerque.bioinformatics.uottawa.ca/pathgroup/Quartet.html chunfang313@gmail.com Supplementary data are available at Bioinformatics online.

  11. Evaluation of Low-Noise, Improved-Bearing-Contact Spiral Bevel Gears

    National Research Council Canada - National Science Library

    Lewicki, Davide

    2003-01-01

    .... Experimental tests were performed on the OH-58D helicopter main-rotor transmission in the NASA Glenn 500-hp Helicopter Transmission Test Stand Low-noise, improved-bearing- contact spiral-bevel gears...

  12. Low Cost/Low Noise Variable Pitch Ducted Fan, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — ACI proposes a design for a Propulsor (Low Cost/Low Noise Variable Pitch Ducted Fan) that has wide application in all sectors of Aviation. Propulsor hardware of this...

  13. W-band InP based HEMT MMIC low noise amplifiers

    Science.gov (United States)

    Lin, K. Y.; Tang, Y. L.; Wang, H.; Gaier, T.; Gough, R. G.; Sinclair, M.

    2002-01-01

    This paper presents the designs and measurement results of a three-stage and a four-stage W-band monolithic microwave integrated circuits (MMIC) including a three-stage and a four-stage low noise amplifiers.

  14. 3.5D dynamic PET image reconstruction incorporating kinetics-based clusters

    International Nuclear Information System (INIS)

    Lu Lijun; Chen Wufan; Karakatsanis, Nicolas A; Rahmim, Arman; Tang Jing

    2012-01-01

    Standard 3D dynamic positron emission tomographic (PET) imaging consists of independent image reconstructions of individual frames followed by application of appropriate kinetic model to the time activity curves at the voxel or region-of-interest (ROI). The emerging field of 4D PET reconstruction, by contrast, seeks to move beyond this scheme and incorporate information from multiple frames within the image reconstruction task. Here we propose a novel reconstruction framework aiming to enhance quantitative accuracy of parametric images via introduction of priors based on voxel kinetics, as generated via clustering of preliminary reconstructed dynamic images to define clustered neighborhoods of voxels with similar kinetics. This is then followed by straightforward maximum a posteriori (MAP) 3D PET reconstruction as applied to individual frames; and as such the method is labeled ‘3.5D’ image reconstruction. The use of cluster-based priors has the advantage of further enhancing quantitative performance in dynamic PET imaging, because: (a) there are typically more voxels in clusters than in conventional local neighborhoods, and (b) neighboring voxels with distinct kinetics are less likely to be clustered together. Using realistic simulated 11 C-raclopride dynamic PET data, the quantitative performance of the proposed method was investigated. Parametric distribution-volume (DV) and DV ratio (DVR) images were estimated from dynamic image reconstructions using (a) maximum-likelihood expectation maximization (MLEM), and MAP reconstructions using (b) the quadratic prior (QP-MAP), (c) the Green prior (GP-MAP) and (d, e) two proposed cluster-based priors (CP-U-MAP and CP-W-MAP), followed by graphical modeling, and were qualitatively and quantitatively compared for 11 ROIs. Overall, the proposed dynamic PET reconstruction methodology resulted in substantial visual as well as quantitative accuracy improvements (in terms of noise versus bias performance) for parametric DV

  15. Low-noise Collision Operators for Particle-in-cell Simulations

    International Nuclear Information System (INIS)

    Lewandowski, J.L.V.

    2005-01-01

    A new method to implement low-noise collision operators in particle-in-cell simulations is presented. The method is based on the fact that relevant collision operators can be included naturally in the Lagrangian formulation that exemplifies the particle-in-cell simulation method. Numerical simulations show that the momentum and energy conservation properties of the simulated plasma associated with the low-noise collision operator are improved as compared with standard collision algorithms based on random numbers

  16. Theoretical analysis of quantum dot amplifiers with high saturation power and low noise figure

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    Semiconductor quantum dot amplifiers are predicted to exhibit superior characteristics such as high gain, and output power and low noise. The analysis provides criteria and design guidelines for the realization of high quality amplifiers.......Semiconductor quantum dot amplifiers are predicted to exhibit superior characteristics such as high gain, and output power and low noise. The analysis provides criteria and design guidelines for the realization of high quality amplifiers....

  17. A Linear Dynamical Systems Approach to Streamflow Reconstruction Reveals History of Regime Shifts in Northern Thailand

    Science.gov (United States)

    Nguyen, Hung T. T.; Galelli, Stefano

    2018-03-01

    Catchment dynamics is not often modeled in streamflow reconstruction studies; yet, the streamflow generation process depends on both catchment state and climatic inputs. To explicitly account for this interaction, we contribute a linear dynamic model, in which streamflow is a function of both catchment state (i.e., wet/dry) and paleoclimatic proxies. The model is learned using a novel variant of the Expectation-Maximization algorithm, and it is used with a paleo drought record—the Monsoon Asia Drought Atlas—to reconstruct 406 years of streamflow for the Ping River (northern Thailand). Results for the instrumental period show that the dynamic model has higher accuracy than conventional linear regression; all performance scores improve by 45-497%. Furthermore, the reconstructed trajectory of the state variable provides valuable insights about the catchment history—e.g., regime-like behavior—thereby complementing the information contained in the reconstructed streamflow time series. The proposed technique can replace linear regression, since it only requires information on streamflow and climatic proxies (e.g., tree-rings, drought indices); furthermore, it is capable of readily generating stochastic streamflow replicates. With a marginal increase in computational requirements, the dynamic model brings more desirable features and value to streamflow reconstructions.

  18. Low-Noise CMOS Circuits for On-Chip Signal Processing in Focal-Plane Arrays

    Science.gov (United States)

    Pain, Bedabrata

    The performance of focal-plane arrays can be significantly enhanced through the use of on-chip signal processing. Novel, in-pixel, on-focal-plane, analog signal-processing circuits for high-performance imaging are presented in this thesis. The presence of a high background-radiation is a major impediment for infrared focal-plane array design. An in-pixel, background-suppression scheme, using dynamic analog current memory circuit, is described. The scheme also suppresses spatial noise that results from response non-uniformities of photo-detectors, leading to background limited infrared detector readout performance. Two new, low-power, compact, current memory circuits, optimized for operation at ultra-low current levels required in infrared-detection, are presented. The first one is a self-cascading current memory that increases the output impedance, and the second one is a novel, switch feed-through reducing current memory, implemented using error-current feedback. This circuit can operate with a residual absolute -error of less than 0.1%. The storage-time of the memory is long enough to also find applications in neural network circuits. In addition, a voltage-mode, accurate, low-offset, low-power, high-uniformity, random-access sample-and-hold cell, implemented using a CCD with feedback, is also presented for use in background-suppression and neural network applications. A new, low noise, ultra-low level signal readout technique, implemented by individually counting photo-electrons within the detection pixel, is presented. The output of each unit-cell is a digital word corresponding to the intensity of the photon flux, and the readout is noise free. This technique requires the use of unit-cell amplifiers that feature ultra-high-gain, low-power, self-biasing capability and noise in sub-electron levels. Both single-input and differential-input implementations of such amplifiers are investigated. A noise analysis technique is presented for analyzing sampled

  19. Temperature characterization of deep and shallow defect centers of low noise silicon JFETs

    International Nuclear Information System (INIS)

    Arnaboldi, Claudio; Fascilla, Andrea; Lund, M.W.; Pessina, Gianluigi

    2004-01-01

    We have selected different low noise JFET processes that have shown outstanding dynamic and noise performance at both room temperature and low temperatures. We have studied JFETs made with a process optimized for cryogenic operation, testing several devices of varying capacitance. For most of them, we have been able to detect the presence of shallow individual traps at low temperature which create low frequency (LF) Generation-Recombination (G-R) noise. For one device type no evidence of traps has been observed at the optimum temperature of operation (around 100 K). It had a very small residual LF noise. This device has been cooled down to 14 K. From below 100 K down to 14 K the noise was observed to increase due to G-R noise originating from donor atoms (dopants) inside the channel. A very simple theoretical interpretation confirms the nature of G-R noise from these very shallow trapping centers. We also studied devices from a process optimized for room temperature operation and found noise corresponding to the presence of a single deep level trap. Even for this circumstance the theory was experimentally confirmed. The measurement approach we used allowed us to achieve a very high accuracy in the modeling of the measured G-R noise. The ratio of the density of the atoms responsible for G-R noise above the doping concentration, N T /N d , has been verified with a sensitivity around 10 -7

  20. Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing

    Energy Technology Data Exchange (ETDEWEB)

    Vissers, M. R.; Erickson, R. P.; Ku, H.-S.; Vale, Leila; Wu, Xian; Hilton, G. C.; Pappas, D. P., E-mail: David.Pappas@NIST.gov [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    2016-01-04

    We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone, we are able to generate parametric amplification using three-wave mixing (3WM). The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. We compare these results directly to the four-wave mixing amplification mode, i.e., without DC-biasing. We find that the 3WM mode allows operation with the pump at lower RF power and at frequencies far from the signal. We have used this knowledge to redesign the amplifiers to utilize primarily 3WM amplification, thereby allowing for direct integration into large scale qubit and detector applications.

  1. Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing

    Science.gov (United States)

    Vissers, M. R.; Erickson, R. P.; Ku, H.-S.; Vale, Leila; Wu, Xian; Hilton, G. C.; Pappas, D. P.

    2016-01-01

    We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone, we are able to generate parametric amplification using three-wave mixing (3WM). The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. We compare these results directly to the four-wave mixing amplification mode, i.e., without DC-biasing. We find that the 3WM mode allows operation with the pump at lower RF power and at frequencies far from the signal. We have used this knowledge to redesign the amplifiers to utilize primarily 3WM amplification, thereby allowing for direct integration into large scale qubit and detector applications.

  2. Observation of Synchrotron Radiation Using Low Noise Block (LNB) at ANKA

    CERN Document Server

    Judin, V; Hofmann, A; Huttel, E; Kehrer, B; Klein, M; Marsching, S; Muller, A-S; Smale, N; Caspers, F

    2011-01-01

    Generally Coherent Synchrotron Radiation (CSR) is emitted for wavelengths longer than or equal the bunch length, so for CSR in the THz-range short bunches are required. There are two types of detectors in this range of the spectrum: slow detectors like a golay cell or pyrometric detectors (used for e.g. imaging, spectroscopy) and fast detectors like superconducting bolometer detector systems and Schottky Barrier diodes (used for e.g. the investigation of dynamic processes in accelerator physics). The hot electron bolometer (HEB) detector system is a member of second group. It is very fast and has broad spectral characteristics, but unfortunately very expensive and have to be cooled using liquid helium. If the broad spectral response is not important, it will be suitably to use a Schottky Barrier diode instead. These detectors are massively cheaper but also slower. As an alternative to a Schottky diode a LNB (Low Noise Block) can be also used. It is usually used in standard TV-SAT-receivers. Due to mass produc...

  3. Design of low noise transimpedance amplifier for intravascular ultrasound

    KAUST Repository

    Reda, Dina

    2009-11-01

    In this paper, we study transimpedance amplifiers for capacitive sensing applications with a focus on Intravascular Ultra Sound (IVUS). We employ RF noise cancellation technique on capacitive feedback based transimpedance amplifiers. This technique eliminates the input-referred noise of TIAs completely and enhances the dynamic range of front-end electronics. Simulation results verify the proposed technique used in two different TIA topologies employing shunt-shunt feedback. ©2009 IEEE.

  4. Low Noise Frequency Comb Sources Based on Synchronously Pumped Doubly Resonant Optical Parametric Oscillators

    Science.gov (United States)

    Wan, Chenchen

    Optical frequency combs are coherent light sources consist of thousands of equally spaced frequency lines. Frequency combs have achieved success in applications of metrology, spectroscopy and precise pulse manipulation and control. The most common way to generate frequency combs is based on mode-locked lasers which has the output spectrum of comb structures. To generate stable frequency combs, the output from mode-locked lasers need to be phase stabilized. The whole comb lines will be stabilized if the pulse train repetition rate corresponding to comb spacing and the pulse carrier envelope offset (CEO) frequency are both stabilized. The output from a laser always has fluctuations in parameters known as noise. In laser applications, noise is an important factor to limit the performance and often need to be well controlled. For example in precision measurement such as frequency metrology and precise spectroscopy, low laser intensity and phase noise is required. In mode-locked lasers there are different types of noise like intensity noise, pulse temporal position noise also known as timing jitter, optical phase noise. In term for frequency combs, these noise dynamics is more complex and often related. Understanding the noise behavior is not only of great interest in practical applications but also help understand fundamental laser physics. In this dissertation, the noise of frequency combs and mode-locked lasers will be studied in two projects. First, the CEO frequency phase noise of a synchronously pumped doubly resonant optical parametric oscillators (OPO) will be explored. This is very important for applications of the OPO as a coherent frequency comb source. Another project will focus on the intensity noise coupling in a soliton fiber oscillator, the finding of different noise coupling in soliton pulses and the dispersive waves generated from soliton perturbation can provide very practical guidance for low noise soliton laser design. OPOs are used to generate

  5. Motion estimation and compensation in dynamic spiral CT reconstruction; Estimation et compensation de mouvement en reconstruction dynamique de tomodensitometrie helicoidale

    Energy Technology Data Exchange (ETDEWEB)

    Kimdon, J.; Grangeat, P.; Koenig, A.; Bonnet, St

    2004-07-01

    Respiratory and cardiac motion causes blurring in dynamic X-ray Computed Tomography (CT). Fast scans reduce this problem, but they require a higher radiation dose per time period to maintain the signal to noise ratio of the resulting images, thereby magnifying the health risk to the patient. As an alternative to increased radiation, our team has already developed a cone-beam reconstruction algorithm based on a dynamic particle model that estimates, predicts, and compensates for respiratory motion in circular X-ray CT. The current paper presents an extension of this method to spiral CT, applicable to modern multi-slice scanners that take advantage of the speed and dose benefits of helical trajectories. We adapted all three main areas of the algorithm: backprojection, prediction, and compensation/accumulation. In backprojection, we changed the longitudinal re-binning technique, filter direction, and the method of enforcing the data sufficiency requirements. For prediction, we had to be careful of objects appearing and disappearing as the scanner bed advanced. For compensation/accumulation, we controlled the reconstruction time and combined images to cover a greater longitudinal extent for each phase in the respiratory or cardiac cycle. Tests with moving numerical phantoms demonstrate that the algorithm successfully improves the temporal resolution of the images without increasing the dose or reducing the signal-to-noise ratio. (authors)

  6. Reconstructing Dynamic Promoter Activity Profiles from Reporter Gene Data.

    Science.gov (United States)

    Kannan, Soumya; Sams, Thomas; Maury, Jérôme; Workman, Christopher T

    2018-03-16

    Accurate characterization of promoter activity is important when designing expression systems for systems biology and metabolic engineering applications. Promoters that respond to changes in the environment enable the dynamic control of gene expression without the necessity of inducer compounds, for example. However, the dynamic nature of these processes poses challenges for estimating promoter activity. Most experimental approaches utilize reporter gene expression to estimate promoter activity. Typically the reporter gene encodes a fluorescent protein that is used to infer a constant promoter activity despite the fact that the observed output may be dynamic and is a number of steps away from the transcription process. In fact, some promoters that are often thought of as constitutive can show changes in activity when growth conditions change. For these reasons, we have developed a system of ordinary differential equations for estimating dynamic promoter activity for promoters that change their activity in response to the environment that is robust to noise and changes in growth rate. Our approach, inference of dynamic promoter activity (PromAct), improves on existing methods by more accurately inferring known promoter activity profiles. This method is also capable of estimating the correct scale of promoter activity and can be applied to quantitative data sets to estimate quantitative rates.

  7. Reconstructing Dynamic Promoter Activity Profiles from Reporter Gene Data

    DEFF Research Database (Denmark)

    Kannan, Soumya; Sams, Thomas; Maury, Jérôme

    2018-01-01

    activity despite the fact that the observed output may be dynamic and is a number of steps away from the transcription process. In fact, some promoters that are often thought of as constitutive can show changes in activity when growth conditions change. For these reasons, we have developed a system......Accurate characterization of promoter activity is important when designing expression systems for systems biology and metabolic engineering applications. Promoters that respond to changes in the environment enable the dynamic control of gene expression without the necessity of inducer compounds......, for example. However, the dynamic nature of these processes poses challenges for estimating promoter activity. Most experimental approaches utilize reporter gene expression to estimate promoter activity. Typically the reporter gene encodes a fluorescent protein that is used to infer a constant promoter...

  8. Statistical dynamic image reconstruction in state-of-the-art high-resolution PET

    International Nuclear Information System (INIS)

    Rahmim, Arman; Cheng, J-C; Blinder, Stephan; Camborde, Maurie-Laure; Sossi, Vesna

    2005-01-01

    Modern high-resolution PET is now more than ever in need of scrutiny into the nature and limitations of the imaging modality itself as well as image reconstruction techniques. In this work, we have reviewed, analysed and addressed the following three considerations within the particular context of state-of-the-art dynamic PET imaging: (i) the typical average numbers of events per line-of-response (LOR) are now (much) less than unity (ii) due to the physical and biological decay of the activity distribution, one requires robust and efficient reconstruction algorithms applicable to a wide range of statistics and (iii) the computational considerations in dynamic imaging are much enhanced (i.e., more frames to be stored and reconstructed). Within the framework of statistical image reconstruction, we have argued theoretically and shown experimentally that the sinogram non-negativity constraint (when using the delayed-coincidence and/or scatter-subtraction techniques) is especially expected to result in an overestimation bias. Subsequently, two schemes are considered: (a) subtraction techniques in which an image non-negativity constraint has been imposed and (b) implementation of random and scatter estimates inside the reconstruction algorithms, thus enabling direct processing of Poisson-distributed prompts. Both techniques are able to remove the aforementioned bias, while the latter, being better conditioned theoretically, is able to exhibit superior noise characteristics. We have also elaborated upon and verified the applicability of the accelerated list-mode image reconstruction method as a powerful solution for accurate, robust and efficient dynamic reconstructions of high-resolution data (as well as a number of additional benefits in the context of state-of-the-art PET)

  9. Adaptive Pulsed Laser Line Extraction for Terrain Reconstruction using a Dynamic Vision Sensor

    Directory of Open Access Journals (Sweden)

    Christian eBrandli

    2014-01-01

    Full Text Available Mobile robots need to know the terrain in which they are moving for path planning and obstacle avoidance. This paper proposes the combination of a bio-inspired, redundancy-suppressing dynamic vision sensor with a pulsed line laser to allow fast terrain reconstruction. A stable laser stripe extraction is achieved by exploiting the sensor’s ability to capture the temporal dynamics in a scene. An adaptive temporal filter for the sensor output allows a reliable reconstruction of 3D terrain surfaces. Laser stripe extractions up to pulsing frequencies of 500Hz were achieved using a line laser of 3mW at a distance of 45cm using an event-based algorithm that exploits the sparseness of the sensor output. As a proof of concept, unstructured rapid prototype terrain samples have been successfully reconstructed with an accuracy of 2mm.

  10. Direct parametric reconstruction in dynamic PET myocardial perfusion imaging: in vivo studies

    Science.gov (United States)

    Petibon, Yoann; Rakvongthai, Yothin; El Fakhri, Georges; Ouyang, Jinsong

    2017-05-01

    Dynamic PET myocardial perfusion imaging (MPI) used in conjunction with tracer kinetic modeling enables the quantification of absolute myocardial blood flow (MBF). However, MBF maps computed using the traditional indirect method (i.e. post-reconstruction voxel-wise fitting of kinetic model to PET time-activity-curves-TACs) suffer from poor signal-to-noise ratio (SNR). Direct reconstruction of kinetic parameters from raw PET projection data has been shown to offer parametric images with higher SNR compared to the indirect method. The aim of this study was to extend and evaluate the performance of a direct parametric reconstruction method using in vivo dynamic PET MPI data for the purpose of quantifying MBF. Dynamic PET MPI studies were performed on two healthy pigs using a Siemens Biograph mMR scanner. List-mode PET data for each animal were acquired following a bolus injection of ~7-8 mCi of 18F-flurpiridaz, a myocardial perfusion agent. Fully-3D dynamic PET sinograms were obtained by sorting the coincidence events into 16 temporal frames covering ~5 min after radiotracer administration. Additionally, eight independent noise realizations of both scans—each containing 1/8th of the total number of events—were generated from the original list-mode data. Dynamic sinograms were then used to compute parametric maps using the conventional indirect method and the proposed direct method. For both methods, a one-tissue compartment model accounting for spillover from the left and right ventricle blood-pools was used to describe the kinetics of 18F-flurpiridaz. An image-derived arterial input function obtained from a TAC taken in the left ventricle cavity was used for tracer kinetic analysis. For the indirect method, frame-by-frame images were estimated using two fully-3D reconstruction techniques: the standard ordered subset expectation maximization (OSEM) reconstruction algorithm on one side, and the one-step late maximum a posteriori (OSL-MAP) algorithm on the other

  11. Direct parametric reconstruction in dynamic PET myocardial perfusion imaging: in-vivo studies

    Science.gov (United States)

    Petibon, Yoann; Rakvongthai, Yothin; Fakhri, Georges El; Ouyang, Jinsong

    2017-01-01

    Dynamic PET myocardial perfusion imaging (MPI) used in conjunction with tracer kinetic modeling enables the quantification of absolute myocardial blood flow (MBF). However, MBF maps computed using the traditional indirect method (i.e. post-reconstruction voxel-wise fitting of kinetic model to PET time-activity-curves -TACs) suffer from poor signal-to-noise ratio (SNR). Direct reconstruction of kinetic parameters from raw PET projection data has been shown to offer parametric images with higher SNR compared to the indirect method. The aim of this study was to extend and evaluate the performance of a direct parametric reconstruction method using in-vivo dynamic PET MPI data for the purpose of quantifying MBF. Dynamic PET MPI studies were performed on two healthy pigs using a Siemens Biograph mMR scanner. List-mode PET data for each animal were acquired following a bolus injection of ~7-8 mCi of 18F-flurpiridaz, a myocardial perfusion agent. Fully-3D dynamic PET sinograms were obtained by sorting the coincidence events into 16 temporal frames covering ~5 min after radiotracer administration. Additionally, eight independent noise realizations of both scans - each containing 1/8th of the total number of events - were generated from the original list-mode data. Dynamic sinograms were then used to compute parametric maps using the conventional indirect method and the proposed direct method. For both methods, a one-tissue compartment model accounting for spillover from the left and right ventricle blood-pools was used to describe the kinetics of 18F-flurpiridaz. An image-derived arterial input function obtained from a TAC taken in the left ventricle cavity was used for tracer kinetic analysis. For the indirect method, frame-by-frame images were estimated using two fully-3D reconstruction techniques: the standard Ordered Subset Expectation Maximization (OSEM) reconstruction algorithm on one side, and the One-Step Late Maximum a Posteriori (OSL-MAP) algorithm on the other

  12. Theoretical Analysis of Penalized Maximum-Likelihood Patlak Parametric Image Reconstruction in Dynamic PET for Lesion Detection.

    Science.gov (United States)

    Yang, Li; Wang, Guobao; Qi, Jinyi

    2016-04-01

    Detecting cancerous lesions is a major clinical application of emission tomography. In a previous work, we studied penalized maximum-likelihood (PML) image reconstruction for lesion detection in static PET. Here we extend our theoretical analysis of static PET reconstruction to dynamic PET. We study both the conventional indirect reconstruction and direct reconstruction for Patlak parametric image estimation. In indirect reconstruction, Patlak parametric images are generated by first reconstructing a sequence of dynamic PET images, and then performing Patlak analysis on the time activity curves (TACs) pixel-by-pixel. In direct reconstruction, Patlak parametric images are estimated directly from raw sinogram data by incorporating the Patlak model into the image reconstruction procedure. PML reconstruction is used in both the indirect and direct reconstruction methods. We use a channelized Hotelling observer (CHO) to assess lesion detectability in Patlak parametric images. Simplified expressions for evaluating the lesion detectability have been derived and applied to the selection of the regularization parameter value to maximize detection performance. The proposed method is validated using computer-based Monte Carlo simulations. Good agreements between the theoretical predictions and the Monte Carlo results are observed. Both theoretical predictions and Monte Carlo simulation results show the benefit of the indirect and direct methods under optimized regularization parameters in dynamic PET reconstruction for lesion detection, when compared with the conventional static PET reconstruction.

  13. Novel active signal compression in low-noise analog readout at future X-ray FEL facilities

    Science.gov (United States)

    Manghisoni, M.; Comotti, D.; Gaioni, L.; Lodola, L.; Ratti, L.; Re, V.; Traversi, G.; Vacchi, C.

    2015-04-01

    This work presents the design of a low-noise front-end implementing a novel active signal compression technique. This feature can be exploited in the design of analog readout channels for application to the next generation free electron laser (FEL) experiments. The readout architecture includes the low-noise charge sensitive amplifier (CSA) with dynamic signal compression, a time variant shaper used to process the signal at the preamplifier output and a 10-bit successive approximation register (SAR) analog-to-digital converter (ADC). The channel will be operated in such a way to cope with the high frame rate (exceeding 1 MHz) foreseen for future XFEL machines. The choice of a 65 nm CMOS technology has been made in order to include all the building blocks in the target pixel pitch of 100 μm. This work has been carried out in the frame of the PixFEL Project funded by the Istituto Nazionale di Fisica Nucleare (INFN), Italy.

  14. Dynamic PET image reconstruction integrating temporal regularization associated with respiratory motion correction for applications in oncology

    Science.gov (United States)

    Merlin, Thibaut; Visvikis, Dimitris; Fernandez, Philippe; Lamare, Frédéric

    2018-02-01

    Respiratory motion reduces both the qualitative and quantitative accuracy of PET images in oncology. This impact is more significant for quantitative applications based on kinetic modeling, where dynamic acquisitions are associated with limited statistics due to the necessity of enhanced temporal resolution. The aim of this study is to address these drawbacks, by combining a respiratory motion correction approach with temporal regularization in a unique reconstruction algorithm for dynamic PET imaging. Elastic transformation parameters for the motion correction are estimated from the non-attenuation-corrected PET images. The derived displacement matrices are subsequently used in a list-mode based OSEM reconstruction algorithm integrating a temporal regularization between the 3D dynamic PET frames, based on temporal basis functions. These functions are simultaneously estimated at each iteration, along with their relative coefficients for each image voxel. Quantitative evaluation has been performed using dynamic FDG PET/CT acquisitions of lung cancer patients acquired on a GE DRX system. The performance of the proposed method is compared with that of a standard multi-frame OSEM reconstruction algorithm. The proposed method achieved substantial improvements in terms of noise reduction while accounting for loss of contrast due to respiratory motion. Results on simulated data showed that the proposed 4D algorithms led to bias reduction values up to 40% in both tumor and blood regions for similar standard deviation levels, in comparison with a standard 3D reconstruction. Patlak parameter estimations on reconstructed images with the proposed reconstruction methods resulted in 30% and 40% bias reduction in the tumor and lung region respectively for the Patlak slope, and a 30% bias reduction for the intercept in the tumor region (a similar Patlak intercept was achieved in the lung area). Incorporation of the respiratory motion correction using an elastic model along with a

  15. Sequential reconstruction of driving-forces from nonlinear nonstationary dynamics

    Science.gov (United States)

    Güntürkün, Ulaş

    2010-07-01

    This paper describes a functional analysis-based method for the estimation of driving-forces from nonlinear dynamic systems. The driving-forces account for the perturbation inputs induced by the external environment or the secular variations in the internal variables of the system. The proposed algorithm is applicable to the problems for which there is too little or no prior knowledge to build a rigorous mathematical model of the unknown dynamics. We derive the estimator conditioned on the differentiability of the unknown system’s mapping, and smoothness of the driving-force. The proposed algorithm is an adaptive sequential realization of the blind prediction error method, where the basic idea is to predict the observables, and retrieve the driving-force from the prediction error. Our realization of this idea is embodied by predicting the observables one-step into the future using a bank of echo state networks (ESN) in an online fashion, and then extracting the raw estimates from the prediction error and smoothing these estimates in two adaptive filtering stages. The adaptive nature of the algorithm enables to retrieve both slowly and rapidly varying driving-forces accurately, which are illustrated by simulations. Logistic and Moran-Ricker maps are studied in controlled experiments, exemplifying chaotic state and stochastic measurement models. The algorithm is also applied to the estimation of a driving-force from another nonlinear dynamic system that is stochastic in both state and measurement equations. The results are judged by the posterior Cramer-Rao lower bounds. The method is finally put into test on a real-world application; extracting sun’s magnetic flux from the sunspot time series.

  16. Reconstructing ancient river dynamics from the stratigraphic record: can lessons from the past inform our future?

    Science.gov (United States)

    Hajek, E. A.; Chamberlin, E.; Baisden, T.

    2014-12-01

    The richness of the deep-time record and its potential for revealing important characteristics of ancient fluvial landscapes has been demonstrated time and again, including compelling examples of rivers altering their behavior in response to changes in vegetation patterns or abrupt shifts in water and sediment discharge. At present, reconstructions of ancient river and floodplain dynamics are commonly qualitative, and when quantitative metrics are used, it is often for comparison among ancient deposits. Without being able to reconstruct, more comprehensively, important aspects of ancient river and floodplains dynamics, this information has only anecdotal relevance for evaluating and managing present-day landscapes. While methods for reconstructing hydrodynamic and morphodynamic aspects of ancient rivers and floodplains are useful, uncertainties associated with these snapshots complicate the ability to translate observations from geologic to engineering scales, thereby limiting the utility of insight from Earth's past in decision-making and development of sustainable landscape-management practices for modern fluvial landscapes. Here, we explore the degree to which paleomorphodynamic reconstructions from ancient channel and floodplain deposits can be used to make specific, quantitative inferences about ancient river dynamics. We compare a suite of paleoenvironmental measurements from a variety of ancient fluvial deposits (including reconstructions of paleoflow depth, paleoslope, paleo-channel mobility, the caliber of paleo-sediment load, and paleo-floodplain heterogeneity) in an effort to evaluate sampling and empirical uncertainties associated with these methods and identify promising avenues for developing more detailed landscape reconstructions. This work is aimed at helping to develop strategies for extracting practicable information from the stratigraphic record that is relevant for sustainably managing and predicting changes in today's environments.

  17. Validation of a laboratory method for evaluating dynamic properties of reconstructed equine racetrack surfaces.

    Directory of Open Access Journals (Sweden)

    Jacob J Setterbo

    Full Text Available Racetrack surface is a risk factor for racehorse injuries and fatalities. Current research indicates that race surface mechanical properties may be influenced by material composition, moisture content, temperature, and maintenance. Race surface mechanical testing in a controlled laboratory setting would allow for objective evaluation of dynamic properties of surface and factors that affect surface behavior.To develop a method for reconstruction of race surfaces in the laboratory and validate the method by comparison with racetrack measurements of dynamic surface properties.Track-testing device (TTD impact tests were conducted to simulate equine hoof impact on dirt and synthetic race surfaces; tests were performed both in situ (racetrack and using laboratory reconstructions of harvested surface materials. Clegg Hammer in situ measurements were used to guide surface reconstruction in the laboratory. Dynamic surface properties were compared between in situ and laboratory settings. Relationships between racetrack TTD and Clegg Hammer measurements were analyzed using stepwise multiple linear regression.Most dynamic surface property setting differences (racetrack-laboratory were small relative to surface material type differences (dirt-synthetic. Clegg Hammer measurements were more strongly correlated with TTD measurements on the synthetic surface than the dirt surface. On the dirt surface, Clegg Hammer decelerations were negatively correlated with TTD forces.Laboratory reconstruction of racetrack surfaces guided by Clegg Hammer measurements yielded TTD impact measurements similar to in situ values. The negative correlation between TTD and Clegg Hammer measurements confirms the importance of instrument mass when drawing conclusions from testing results. Lighter impact devices may be less appropriate for assessing dynamic surface properties compared to testing equipment designed to simulate hoof impact (TTD.Dynamic impact properties of race surfaces

  18. Reconstructing source-sink dynamics in a population with a pelagic dispersal phase.

    Directory of Open Access Journals (Sweden)

    Kun Chen

    Full Text Available For many organisms, the reconstruction of source-sink dynamics is hampered by limited knowledge of the spatial assemblage of either the source or sink components or lack of information on the strength of the linkage for any source-sink pair. In the case of marine species with a pelagic dispersal phase, these problems may be mitigated through the use of particle drift simulations based on an ocean circulation model. However, when simulated particle trajectories do not intersect sampling sites, the corroboration of model drift simulations with field data is hampered. Here, we apply a new statistical approach for reconstructing source-sink dynamics that overcomes the aforementioned problems. Our research is motivated by the need for understanding observed changes in jellyfish distributions in the eastern Bering Sea since 1990. By contrasting the source-sink dynamics reconstructed with data from the pre-1990 period with that from the post-1990 period, it appears that changes in jellyfish distribution resulted from the combined effects of higher jellyfish productivity and longer dispersal of jellyfish resulting from a shift in the ocean circulation starting in 1991. A sensitivity analysis suggests that the source-sink reconstruction is robust to typical systematic and random errors in the ocean circulation model driving the particle drift simulations. The jellyfish analysis illustrates that new insights can be gained by studying structural changes in source-sink dynamics. The proposed approach is applicable for the spatial source-sink reconstruction of other species and even abiotic processes, such as sediment transport.

  19. Design and validation of the high performance and low noise CQU-DTU-LN1 airfoils

    DEFF Research Database (Denmark)

    Cheng, Jiangtao; Zhu, Wei Jun; Fischer, Andreas

    2014-01-01

    with the blade element momentum theory, the viscous-inviscid XFOIL code and an airfoil self-noise prediction model, an optimization algorithm has been developed for designing the high performance and low noise CQU-DTU-LN1 series of airfoils with targets of maximum power coefficient and low noise emission...... emission between the CQU-DTU-LN118 airfoil and the National Advisory Committee for Aeronautics (NACA) 64618 airfoil, which is used in modern wind turbine blades, are carried out. Copyright © 2013 John Wiley & Sons, Ltd....

  20. Performance of a fast low noise front-end preamplifier for the MAGIC imaging Cherenkov telescope

    International Nuclear Information System (INIS)

    Blanch, O.; Blanchot, G.; Bosman, M.

    1999-01-01

    The observation of high energy cosmic gamma rays with an energy threshold of 15 GeV using the proposed MAGIC ground based air imaging Cherenkov telescope requires the development of new low noise fast preamplifiers for the camera photosensors. The speed and noise performance of a transimpedance preamplifier that resolves the multi photoelectron peaks from a hybrid photomultiplier with a peaking time below 7 ns is presented. The new front-end circuit is designed with RF low noise bipolar transistors and provides fast output pulses that allow for fast trigger settings

  1. Designing charge-sensitive preamplifiers based on low-noise analog integrated circuits

    International Nuclear Information System (INIS)

    Agakhanyan, T.M.

    1998-01-01

    The methodology for designing charge-sensitive preamplifiers on the low-noise analog integral circuits, including all the stages: the mathematical synthesis with optimization of the intermediate function; the scheme-technical synthesis with parametric optimization of the scheme and analysis of draft projects with the parameter verification is presented. The designing is conducted on the basis of requirements for signal parameters and noise indices of the preamplifier. The system of automated designing of the charge-sensitive preamplifiers on the low-noise analog integral circuits is developed [ru

  2. Patient-adapted reconstruction and acquisition dynamic imaging method (PARADIGM) for MRI

    International Nuclear Information System (INIS)

    Aggarwal, Nitin; Bresler, Yoram

    2008-01-01

    Dynamic magnetic resonance imaging (MRI) is a challenging problem because the MR data acquisition is often not fast enough to meet the combined spatial and temporal Nyquist sampling rate requirements. Current approaches to this problem include hardware-based acceleration of the acquisition, and model-based image reconstruction techniques. In this paper we propose an alternative approach, called PARADIGM, which adapts both the acquisition and reconstruction to the spatio-temporal characteristics of the imaged object. The approach is based on time-sequential sampling theory, addressing the problem of acquiring a spatio-temporal signal under the constraint that only a limited amount of data can be acquired at a time instant. PARADIGM identifies a model class for the particular imaged object using a scout MR scan or auxiliary data. This object-adapted model is then used to optimize MR data acquisition, such that the imaging constraints are met, acquisition speed requirements are minimized, essentially perfect reconstruction of any object in the model class is guaranteed, and the inverse problem of reconstructing the dynamic object has a condition number of one. We describe spatio-temporal object models for various dynamic imaging applications including cardiac imaging. We present the theory underlying PARADIGM and analyze its performance theoretically and numerically. We also propose a practical MR imaging scheme for 2D dynamic cardiac imaging based on the theory. For this application, PARADIGM is predicted to provide a 10–25 × acceleration compared to the optimal non-adaptive scheme. Finally we present generalized optimality criteria and extend the scheme to dynamic imaging with three spatial dimensions

  3. Non-stationary reconstruction for dynamic fluorescence molecular tomography with extended kalman filter.

    Science.gov (United States)

    Liu, Xin; Wang, Hongkai; Yan, Zhuangzhi

    2016-11-01

    Dynamic fluorescence molecular tomography (FMT) plays an important role in drug delivery research. However, the majority of current reconstruction methods focus on solving the stationary FMT problems. If the stationary reconstruction methods are applied to the time-varying fluorescence measurements, the reconstructed results may suffer from a high level of artifacts. In addition, based on the stationary methods, only one tomographic image can be obtained after scanning one circle projection data. As a result, the movement of fluorophore in imaged object may not be detected due to the relative long data acquisition time (typically >1 min). In this paper, we apply extended kalman filter (EKF) technique to solve the non-stationary fluorescence tomography problem. Especially, to improve the EKF reconstruction performance, the generalized inverse of kalman gain is calculated by a second-order iterative method. The numerical simulation, phantom, and in vivo experiments are performed to evaluate the performance of the method. The experimental results indicate that by using the proposed EKF-based second-order iterative (EKF-SOI) method, we cannot only clearly resolve the time-varying distributions of fluorophore within imaged object, but also greatly improve the reconstruction time resolution (~2.5 sec/frame) which makes it possible to detect the movement of fluorophore during the imaging processes.

  4. A method for climate and vegetation reconstruction through the inversion of a dynamic vegetation model

    Energy Technology Data Exchange (ETDEWEB)

    Garreta, Vincent; Guiot, Joel; Hely, Christelle [CEREGE, UMR 6635, CNRS, Universite Aix-Marseille, Europole de l' Arbois, Aix-en-Provence (France); Miller, Paul A.; Sykes, Martin T. [Lund University, Department of Physical Geography and Ecosystems Analysis, Geobiosphere Science Centre, Lund (Sweden); Brewer, Simon [Universite de Liege, Institut d' Astrophysique et de Geophysique, Liege (Belgium); Litt, Thomas [University of Bonn, Paleontological Institute, Bonn (Germany)

    2010-08-15

    Climate reconstructions from data sensitive to past climates provide estimates of what these climates were like. Comparing these reconstructions with simulations from climate models allows to validate the models used for future climate prediction. It has been shown that for fossil pollen data, gaining estimates by inverting a vegetation model allows inclusion of past changes in carbon dioxide values. As a new generation of dynamic vegetation model is available we have developed an inversion method for one model, LPJ-GUESS. When this novel method is used with high-resolution sediment it allows us to bypass the classic assumptions of (1) climate and pollen independence between samples and (2) equilibrium between the vegetation, represented as pollen, and climate. Our dynamic inversion method is based on a statistical model to describe the links among climate, simulated vegetation and pollen samples. The inversion is realised thanks to a particle filter algorithm. We perform a validation on 30 modern European sites and then apply the method to the sediment core of Meerfelder Maar (Germany), which covers the Holocene at a temporal resolution of approximately one sample per 30 years. We demonstrate that reconstructed temperatures are constrained. The reconstructed precipitation is less well constrained, due to the dimension considered (one precipitation by season), and the low sensitivity of LPJ-GUESS to precipitation changes. (orig.)

  5. Direct Parametric Reconstruction With Joint Motion Estimation/Correction for Dynamic Brain PET Data.

    Science.gov (United States)

    Jiao, Jieqing; Bousse, Alexandre; Thielemans, Kris; Burgos, Ninon; Weston, Philip S J; Schott, Jonathan M; Atkinson, David; Arridge, Simon R; Hutton, Brian F; Markiewicz, Pawel; Ourselin, Sebastien

    2017-01-01

    Direct reconstruction of parametric images from raw photon counts has been shown to improve the quantitative analysis of dynamic positron emission tomography (PET) data. However it suffers from subject motion which is inevitable during the typical acquisition time of 1-2 hours. In this work we propose a framework to jointly estimate subject head motion and reconstruct the motion-corrected parametric images directly from raw PET data, so that the effects of distorted tissue-to-voxel mapping due to subject motion can be reduced in reconstructing the parametric images with motion-compensated attenuation correction and spatially aligned temporal PET data. The proposed approach is formulated within the maximum likelihood framework, and efficient solutions are derived for estimating subject motion and kinetic parameters from raw PET photon count data. Results from evaluations on simulated [ 11 C]raclopride data using the Zubal brain phantom and real clinical [ 18 F]florbetapir data of a patient with Alzheimer's disease show that the proposed joint direct parametric reconstruction motion correction approach can improve the accuracy of quantifying dynamic PET data with large subject motion.

  6. A capacitor cross-coupled common-gate low-noise amplifier

    NARCIS (Netherlands)

    Zhuo, W.; Li, X.; Shekhar, S.; Embabi, S.H.K.; Pineda de Gyvez, J.; Allstot, D.J.; Sanchez-Sinencio, E.

    2005-01-01

    The conventional common-gate low-noise amplifier (CGLNA) exhibits a relatively high noise figure (NF) at low operating frequencies relative to the MOSFET fT, which has limited its adoption notwithstanding its superior linearity, input matching, and stability compared to the inductively degenerated

  7. Design of low noise wind turbine blades using Betz and Joukowski concepts

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Hrgovan, Iva; Okulov, Valery

    2014-01-01

    This paper presents the aerodynamic design of low noise wind turbine blades using Betz and Joukowski concepts. The aerodynamic model is based on Blade Element Momentum theory whereas the aeroacoustic prediction model is based on the BPM model. The investigation is started with a 3MW baseline...

  8. Low noise Nb-SIS mixers at far above the gap frequency

    NARCIS (Netherlands)

    Gao, [No Value; vandeStadt, H; Jegers, JBM; Kovtonyuk, S; Hulshoff, W; Whyborn, ND; Klapwijk, TM; deGraauw, T; Liao, FJ; Liu, JY

    1996-01-01

    There are great interests in developing Nb SIS mixers because of the extremely low noise temperatures and because of the need of low local oscillator (LO) power. Several groups have demonstrated experimentally that Nb SIS mixers with integrated tuning elements can perform near the quantum noise

  9. Efficient network reconstruction from dynamical cascades identifies small-world topology of neuronal avalanches.

    Directory of Open Access Journals (Sweden)

    Sinisa Pajevic

    2009-01-01

    Full Text Available Cascading activity is commonly found in complex systems with directed interactions such as metabolic networks, neuronal networks, or disease spreading in social networks. Substantial insight into a system's organization can be obtained by reconstructing the underlying functional network architecture from the observed activity cascades. Here we focus on Bayesian approaches and reduce their computational demands by introducing the Iterative Bayesian (IB and Posterior Weighted Averaging (PWA methods. We introduce a special case of PWA, cast in nonparametric form, which we call the normalized count (NC algorithm. NC efficiently reconstructs random and small-world functional network topologies and architectures from subcritical, critical, and supercritical cascading dynamics and yields significant improvements over commonly used correlation methods. With experimental data, NC identified a functional and structural small-world topology and its corresponding traffic in cortical networks with neuronal avalanche dynamics.

  10. Cryotherapy with dynamic intermittent compression for analgesia after anterior cruciate ligament reconstruction. Preliminary study.

    Science.gov (United States)

    Murgier, J; Cassard, X

    2014-05-01

    Cryotherapy is a useful adjunctive analgesic measure in patients with postoperative pain following anterior cruciate ligament (ACL) surgery. Either static permanent compression or dynamic intermittent compression can be added to increase the analgesic effect of cryotherapy. Our objective was to compare the efficacy of these two compression modalities combined with cryotherapy in relieving postoperative pain and restoring range of knee motion after ligament reconstruction surgery. When combined with cryotherapy, a dynamic and intermittent compression is associated with decreased analgesic drug requirements, less postoperative pain, and better range of knee motion compared to static compression. We conducted a case-control study of consecutive patients who underwent anterior cruciate ligament reconstruction at a single institution over a 3-month period. Both groups received the same analgesic drug protocol. One group was managed with cryotherapy and dynamic intermittent compression (Game Ready(®)) and the other with cryotherapy and static compression (IceBand(®)). Of 39 patients, 20 received dynamic and 19 static compression. In the post-anaesthesia recovery unit, the mean visual analogue scale (VAS) pain score was 2.4 (range, 0-6) with dynamic compression and 2.7 (0-7) with static compression (P=0.3); corresponding values were 1.85 (0-9) vs. 3 (0-8) (P=0.16) after 6 hours and 0.6 (0-3) vs. 1.14 (0-3) (P=0.12) at discharge. The cumulative mean tramadol dose per patient was 57.5mg (0-200mg) with dynamic compression and 128.6 mg (0-250 mg) with static compression (P=0.023); corresponding values for morphine were 0mg vs. 1.14 mg (0-8 mg) (Pcryotherapy decreases analgesic drug requirements after ACL reconstruction and improves the postoperative recovery of range of knee motion. Level III, case-control study. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  11. Image-Based Reconstruction and Analysis of Dynamic Scenes in a Landslide Simulation Facility

    Science.gov (United States)

    Scaioni, M.; Crippa, J.; Longoni, L.; Papini, M.; Zanzi, L.

    2017-12-01

    The application of image processing and photogrammetric techniques to dynamic reconstruction of landslide simulations in a scaled-down facility is described. Simulations are also used here for active-learning purpose: students are helped understand how physical processes happen and which kinds of observations may be obtained from a sensor network. In particular, the use of digital images to obtain multi-temporal information is presented. On one side, using a multi-view sensor set up based on four synchronized GoPro 4 Black® cameras, a 4D (3D spatial position and time) reconstruction of the dynamic scene is obtained through the composition of several 3D models obtained from dense image matching. The final textured 4D model allows one to revisit in dynamic and interactive mode a completed experiment at any time. On the other side, a digital image correlation (DIC) technique has been used to track surface point displacements from the image sequence obtained from the camera in front of the simulation facility. While the 4D model may provide a qualitative description and documentation of the experiment running, DIC analysis output quantitative information such as local point displacements and velocities, to be related to physical processes and to other observations. All the hardware and software equipment adopted for the photogrammetric reconstruction has been based on low-cost and open-source solutions.

  12. IMAGE-BASED RECONSTRUCTION AND ANALYSIS OF DYNAMIC SCENES IN A LANDSLIDE SIMULATION FACILITY

    Directory of Open Access Journals (Sweden)

    M. Scaioni

    2017-12-01

    Full Text Available The application of image processing and photogrammetric techniques to dynamic reconstruction of landslide simulations in a scaled-down facility is described. Simulations are also used here for active-learning purpose: students are helped understand how physical processes happen and which kinds of observations may be obtained from a sensor network. In particular, the use of digital images to obtain multi-temporal information is presented. On one side, using a multi-view sensor set up based on four synchronized GoPro 4 Black® cameras, a 4D (3D spatial position and time reconstruction of the dynamic scene is obtained through the composition of several 3D models obtained from dense image matching. The final textured 4D model allows one to revisit in dynamic and interactive mode a completed experiment at any time. On the other side, a digital image correlation (DIC technique has been used to track surface point displacements from the image sequence obtained from the camera in front of the simulation facility. While the 4D model may provide a qualitative description and documentation of the experiment running, DIC analysis output quantitative information such as local point displacements and velocities, to be related to physical processes and to other observations. All the hardware and software equipment adopted for the photogrammetric reconstruction has been based on low-cost and open-source solutions.

  13. A STUDY ON DYNAMIC LOAD HISTORY RECONSTRUCTION USING PSEUDO-INVERSE METHODS

    OpenAIRE

    Santos, Ariane Rebelato Silva dos; Marczak, Rogério José

    2017-01-01

    Considering that the vibratory forces generally cannot be measured directly at the interface of two bodies, an inverse method is studied in the present work to recover the load history in such cases. The proposed technique attempts to reconstruct the dynamic loads history by using a frequency domain analysis and Moore-Penrose pseudo-inverses of the frequency response function (FRF) of the system. The methodology consists in applying discrete dynamic loads on a finite element model in the time...

  14. Power Holders and Social Dynamics of Participatory Development and Reconstruction: Cases from the Democratic Republic of Congo

    NARCIS (Netherlands)

    Kyamusugulwa, P.M.; Hilhorst, D.

    2015-01-01

    One of the challenges of participatory development and reconstruction programs is how and where to engage with power holders. This paper analyses the dynamics of power relations within a community-driven reconstruction program in the Democratic Republic of Congo. It shows that, in some

  15. A dynamic state observer for real-time reconstruction of the tokamak plasma profile state and disturbances

    NARCIS (Netherlands)

    Felici, F.; De Baar, M.; Steinbuch, M.

    2014-01-01

    A dynamic observer is presented which can reconstruct the internal state of a tokamak fusion plasma, consisting of the spatial distribution of current and temperature, from measurements. Today, the internal plasma state is usually reconstructed by solving an ill-conditioned inversion problem using a

  16. Three Dimensional Dynamic Model Based Wind Field Reconstruction from Lidar Data

    International Nuclear Information System (INIS)

    Raach, Steffen; Schlipf, David; Haizmann, Florian; Cheng, Po Wen

    2014-01-01

    Using the inflowing horizontal and vertical wind shears for individual pitch controller is a promising method if blade bending measurements are not available. Due to the limited information provided by a lidar system the reconstruction of shears in real-time is a challenging task especially for the horizontal shear in the presence of changing wind direction. The internal model principle has shown to be a promising approach to estimate the shears and directions in 10 minutes averages with real measurement data. The static model based wind vector field reconstruction is extended in this work taking into account a dynamic reconstruction model based on Taylor's Frozen Turbulence Hypothesis. The presented method provides time series over several seconds of the wind speed, shears and direction, which can be directly used in advanced optimal preview control. Therefore, this work is an important step towards the application of preview individual blade pitch control under realistic wind conditions. The method is tested using a turbulent wind field and a detailed lidar simulator. For the simulation, the turbulent wind field structure is flowing towards the lidar system and is continuously misaligned with respect to the horizontal axis of the wind turbine. Taylor's Frozen Turbulence Hypothesis is taken into account to model the wind evolution. For the reconstruction, the structure is discretized into several stages where each stage is reduced to an effective wind speed, superposed with a linear horizontal and vertical wind shear. Previous lidar measurements are shifted using again Taylor's Hypothesis. The wind field reconstruction problem is then formulated as a nonlinear optimization problem, which minimizes the residual between the assumed wind model and the lidar measurements to obtain the misalignment angle and the effective wind speed and the wind shears for each stage. This method shows good results in reconstructing the wind characteristics of a three

  17. Reconstruction of dynamic structures of experimental setups based on measurable experimental data only

    Science.gov (United States)

    Chen, Tian-Yu; Chen, Yang; Yang, Hu-Jiang; Xiao, Jing-Hua; Hu, Gang

    2018-03-01

    Nowadays, massive amounts of data have been accumulated in various and wide fields, it has become today one of the central issues in interdisciplinary fields to analyze existing data and extract as much useful information as possible from data. It is often that the output data of systems are measurable while dynamic structures producing these data are hidden, and thus studies to reveal system structures by analyzing available data, i.e., reconstructions of systems become one of the most important tasks of information extractions. In the past, most of the works in this respect were based on theoretical analyses and numerical verifications. Direct analyses of experimental data are very rare. In physical science, most of the analyses of experimental setups were based on the first principles of physics laws, i.e., so-called top-down analyses. In this paper, we conducted an experiment of “Boer resonant instrument for forced vibration” (BRIFV) and inferred the dynamic structure of the experimental set purely from the analysis of the measurable experimental data, i.e., by applying the bottom-up strategy. Dynamics of the experimental set is strongly nonlinear and chaotic, and itʼs subjects to inevitable noises. We proposed to use high-order correlation computations to treat nonlinear dynamics; use two-time correlations to treat noise effects. By applying these approaches, we have successfully reconstructed the structure of the experimental setup, and the dynamic system reconstructed with the measured data reproduces good experimental results in a wide range of parameters.

  18. Dynamic concision for three-dimensional reconstruction of human organ built with virtual reality modelling language (VRML)*

    Science.gov (United States)

    Yu, Zheng-yang; Zheng, Shu-sen; Chen, Lei-ting; He, Xiao-qian; Wang, Jian-jun

    2005-01-01

    This research studies the process of 3D reconstruction and dynamic concision based on 2D medical digital images using virtual reality modelling language (VRML) and JavaScript language, with a focus on how to realize the dynamic concision of 3D medical model with script node and sensor node in VRML. The 3D reconstruction and concision of body internal organs can be built with such high quality that they are better than those obtained from the traditional methods. With the function of dynamic concision, the VRML browser can offer better windows for man-computer interaction in real-time environment than ever before. 3D reconstruction and dynamic concision with VRML can be used to meet the requirement for the medical observation of 3D reconstruction and have a promising prospect in the fields of medical imaging. PMID:15973760

  19. Dynamical reconstruction of the global ocean state during the Last Glacial Maximum

    Science.gov (United States)

    Kurahashi-Nakamura, Takasumi; Paul, André; Losch, Martin

    2017-04-01

    The global ocean state for the modern age and for the Last Glacial Maximum (LGM) was dynamically reconstructed with a sophisticated data assimilation technique. A substantial amount of data including global seawater temperature, salinity (only for the modern estimate), and the isotopic composition of oxygen and carbon (only in the Atlantic for the LGM) were integrated into an ocean general circulation model with the help of the adjoint method, thereby the model was optimized to reconstruct plausible continuous fields of tracers, overturning circulation and water mass distribution. The adjoint-based LGM state estimation of this study represents the state of the art in terms of the length of forward model runs, the number of observations assimilated, and the model domain. Compared to the modern state, the reconstructed continuous sea-surface temperature field for the LGM shows a global-mean cooling of 2.2 K, and the reconstructed LGM ocean has a more vigorous Atlantic meridional overturning circulation, shallower North Atlantic Deep Water (NADW) equivalent, stronger stratification, and more saline deep water.

  20. A rapid and low noise switch from RANS to WMLES on curvilinear grids with compressible flow solvers

    Science.gov (United States)

    Deck, Sébastien; Weiss, Pierre-Elie; Renard, Nicolas

    2018-06-01

    A turbulent inflow for a rapid and low noise switch from RANS to Wall-Modelled LES on curvilinear grids with compressible flow solvers is presented. It can be embedded within the computational domain in practical applications with WMLES grids around three-dimensional geometries in a flexible zonal hybrid RANS/LES modelling context. It relies on a physics-motivated combination of Zonal Detached Eddy Simulation (ZDES) as the WMLES technique together with a Dynamic Forcing method processing the fluctuations caused by a Zonal Immersed Boundary Condition describing roughness elements. The performance in generating a physically-sound turbulent flow field with the proper mean skin friction and turbulent profiles after a short relaxation length is equivalent to more common inflow methods thanks to the generation of large-scale streamwise vorticity by the roughness elements. Comparisons in a low Mach-number zero-pressure-gradient flat-plate turbulent boundary layer up to Reθ = 6 100 reveal that the pressure field is dominated by the spurious noise caused by the synthetic turbulence methods (Synthetic Eddy Method and White Noise injection), contrary to the new low-noise approach which may be used to obtain the low-frequency component of wall pressure and reproduce its intermittent nature. The robustness of the method is tested in the flow around a three-element airfoil with WMLES in the upper boundary layer near the trailing edge of the main element. In spite of the very short relaxation distance allowed, self-sustainable resolved turbulence is generated in the outer layer with significantly less spurious noise than with the approach involving White Noise. The ZDES grid count for this latter test case is more than two orders of magnitude lower than the Wall-Resolved LES requirement and a unique mesh is involved, which is much simpler than some multiple-mesh strategies devised for WMLES or turbulent inflow.

  1. Sparse dynamical Boltzmann machine for reconstructing complex networks with binary dynamics

    Science.gov (United States)

    Chen, Yu-Zhong; Lai, Ying-Cheng

    2018-03-01

    Revealing the structure and dynamics of complex networked systems from observed data is a problem of current interest. Is it possible to develop a completely data-driven framework to decipher the network structure and different types of dynamical processes on complex networks? We develop a model named sparse dynamical Boltzmann machine (SDBM) as a structural estimator for complex networks that host binary dynamical processes. The SDBM attains its topology according to that of the original system and is capable of simulating the original binary dynamical process. We develop a fully automated method based on compressive sensing and a clustering algorithm to construct the SDBM. We demonstrate, for a variety of representative dynamical processes on model and real world complex networks, that the equivalent SDBM can recover the network structure of the original system and simulates its dynamical behavior with high precision.

  2. Colon stem cell and crypt dynamics exposed by cell lineage reconstruction.

    Directory of Open Access Journals (Sweden)

    Yitzhak Reizel

    2011-07-01

    Full Text Available Stem cell dynamics in vivo are often being studied by lineage tracing methods. Our laboratory has previously developed a retrospective method for reconstructing cell lineage trees from somatic mutations accumulated in microsatellites. This method was applied here to explore different aspects of stem cell dynamics in the mouse colon without the use of stem cell markers. We first demonstrated the reliability of our method for the study of stem cells by confirming previously established facts, and then we addressed open questions. Our findings confirmed that colon crypts are monoclonal and that, throughout adulthood, the process of monoclonal conversion plays a major role in the maintenance of crypts. The absence of immortal strand mechanism in crypts stem cells was validated by the age-dependent accumulation of microsatellite mutations. In addition, we confirmed the positive correlation between physical and lineage proximity of crypts, by showing that the colon is separated into small domains that share a common ancestor. We gained new data demonstrating that colon epithelium is clustered separately from hematopoietic and other cell types, indicating that the colon is constituted of few progenitors and ruling out significant renewal of colonic epithelium from hematopoietic cells during adulthood. Overall, our study demonstrates the reliability of cell lineage reconstruction for the study of stem cell dynamics, and it further addresses open questions in colon stem cells. In addition, this method can be applied to study stem cell dynamics in other systems.

  3. A 7-13 GHz low-noise tuned optical front-end amplifier for heterodyne transmission system application

    DEFF Research Database (Denmark)

    Ebskamp, Frank; Schiellerup, Gert; Høgdal, Morten

    1991-01-01

    The authors present a 7-13 GHz low-noise bandpass tuned optical front-end amplifier, showing 46±1 dBΩ transimpedance, and a noise spectral density of about 12 pA/√Hz. This is the first time such a flat response and such low noise were obtained simultaneously at these frequencies, without any...

  4. Reconstruction of tissue dynamics in the compressed breast using multiplexed measurements and temporal basis functions

    Science.gov (United States)

    Boverman, Gregory; Miller, Eric L.; Brooks, Dana H.; Fang, Qianqian; Carp, S. A.; Selb, J. J.; Boas, David A.

    2007-02-01

    In the course of our experiments imaging the compressed breast in conjunction with digital tomosynthesis, we have noted that significant changes in tissue optical properties, on the order of 5%, occur during our imaging protocol. These changes seem to consistent with changes both in total Hemoglobin concentration as well as in oxygen saturation, as was the case for our standalone breast compression study, which made use of reflectance measurements. Simulation experiments show the importance of taking into account the temporal dynamics in the image reconstruction, and demonstrate the possibility of imaging the spatio-temporal dynamics of oxygen saturation and total Hemoglobin in the breast. In the image reconstruction, we make use of spatio-temporal basis functions, specifically a voxel basis for spatial imaging, and a cubic spline basis in time, and we reconstruct the spatio-temporal images using the entire data set simultaneously, making use of both absolute and relative measurements in the cost function. We have modified the sequence of sources used in our imaging acquisition protocol to improve our temporal resolution, and preliminary results are shown for normal subjects.

  5. Design and analysis of high gain and low noise figure CMOS low noise amplifier for Q-band nano-sensor application

    Science.gov (United States)

    Suganthi, K.; Malarvizhi, S.

    2018-03-01

    A high gain, low power, low Noise figure (NF) and wide band of milli-meter Wave (mmW) circuits design at 50 GHz are used for Radio Frequency (RF) front end. The fundamental necessity of a receiver front-end includes perfect output and input impedance matching and port-to-port isolation with high gain and low noise over the entire band of interest. In this paper, a design of Cascade-Cascode CMOS LNA circuit at 50 GHz for Q-band application is proposed. The design of Low noise amplifier at 50 GHz using Agilent ADS tool with microstrip lines which provides simplicity in fabrication and less chip area. The low off-leakage current Ioff can be maintained with high K-dielectrics CMOS structure. Nano-scale electronics can be achieved with increased robustness. The design has overall gain of 11.091 dB and noise figure of 2.673 dB for the Q-band of 48.3 GHz to 51.3 GHz. Impedance matching is done by T matching network and the obtained input and output reflection coefficients are S11 = <-10 dB and S22 = <-10 dB. Compared to Silicon (Si) material, Wide Band Gap semiconductor materials used attains higher junction temperatures which is well matched to ceramics used in packaging technology, the protection and reliability also can be achieved with the electronic packaging. The reverse transmission coefficient S21 is less than -21 dB has shown that LNA has better isolation between input and output, Stability factor greater than 1 and Power is also optimized in this design. Layout is designed, power gain of 4.6 dB is achieved and area is optimized which is nearly equal to 502 740 μm2. The observed results show that the proposed Cascade-Cascode LNA design can find its suitability in future milli-meter Wave Radar application.

  6. Electron and photon reconstruction and performance in ATLAS using a dynamical, topological cell clustering-based approach

    CERN Document Server

    The ATLAS collaboration

    2017-01-01

    The electron and photon reconstruction in ATLAS has moved towards the use of a dynamical, topo- logical cell-based approach for cluster building, owing to advancements in the calibration procedure which allow for such a method to be applied. The move to this new technique allows for improved measurements of electron and photon energies, particularly in situations where an electron radiates a bremsstrahlung photon, or a photon converts to an electron-poistron pair. This note details the changes to the ATLAS electron and photon reconstruction software, and assesses its performance under current LHC luminosity conditions using simulated data. Changes to the converted photon reconstruction are also detailed, which improve the reconstruction efficiency of double-track converted photons, as well as reducing the reconstruction of spurious one-track converted photons. The performance of the new reconstruction algorithm is also presented in a number of important topologies relevant to precision Standard Model physics,...

  7. Fabrication and Characterisation of Low-noise Monolithic Mode-locked Lasers

    DEFF Research Database (Denmark)

    Larsson, David

    2007-01-01

    This thesis deals with the fabrication and characterisation of monolithic semiconductor mode-locked lasers for use in optical communication systems. Other foreseeable applications may be as sources in microwave photonics and optical sampling. The thesis also deals with the design and fabrication...... of intracavity monolithically integrated filters. The common dnominator among the diffrent parts of the thesis is how to achieve and measure the lowest possible noise. Achieving low noise has been pinpointed as one of the most important and difficult challenges for semiconductor mode-locked lasers. The main...... result of this thesis are a fabrication process of a monolithic and deeply etched distributed Bragg reflector and a characterisation system for measurement of quantum limitid timing noise at high repetition rates. The Bragg reflector is a key component in achieving transform limited pulses with low noise...

  8. Low-noise audio amplifiers and preamplifier for use with intrinsic thermocouples

    International Nuclear Information System (INIS)

    Langner, G.C.; Sachs, R.D.; Stewart, F.L.

    1979-03-01

    Two simple, low-noise audio amplifiers and one low-noise preamplifier for use with intrinsic thermocouples were designed, built, and tested. The amplifiers and the preamplifier have different front end designs. One amplifier uses ultralow-noise operational amplifiers; the other amplifier uses a hybrid component. The preamplifier uses ultralow-noise discrete components. The amplifiers' equivalent noise inputs, at maximum gain, are 4.09 nV and 50 nV; the preamplifier's input is 4.05 μV. Their bandwidths are 15 600 Hz, 550 Hz, and 174 kHz, respectively. the amplifiers' equivalent noise inputs were measured from approx. 0 to 100 Hz, whereas the preamplifier's equivalent noise input was measured from approx. 0 to 174 kHz

  9. Dynamic SPECT reconstruction from few projections: a sparsity enforced matrix factorization approach

    Science.gov (United States)

    Ding, Qiaoqiao; Zan, Yunlong; Huang, Qiu; Zhang, Xiaoqun

    2015-02-01

    The reconstruction of dynamic images from few projection data is a challenging problem, especially when noise is present and when the dynamic images are vary fast. In this paper, we propose a variational model, sparsity enforced matrix factorization (SEMF), based on low rank matrix factorization of unknown images and enforced sparsity constraints for representing both coefficients and bases. The proposed model is solved via an alternating iterative scheme for which each subproblem is convex and involves the efficient alternating direction method of multipliers (ADMM). The convergence of the overall alternating scheme for the nonconvex problem relies upon the Kurdyka-Łojasiewicz property, recently studied by Attouch et al (2010 Math. Oper. Res. 35 438) and Attouch et al (2013 Math. Program. 137 91). Finally our proof-of-concept simulation on 2D dynamic images shows the advantage of the proposed method compared to conventional methods.

  10. Magnonic Crystal as a Delay Line for Low-Noise Auto-Oscillator

    Science.gov (United States)

    2015-05-12

    Magnonic crystal as a delay line for low-noise auto-oscillator Elena Bankowski and Thomas Meitzler U.S. Army TARDEC, Warren, Michigan 48397, USA...authors propose to use the magnonic crystal patterned on the YIG magnetic film as an efficient delay line in the feedback loop of tunable auto-oscillator...increasing the thickness of such delay line as compare to the YIG film with no pattern. In turn, use of this magnonic crystal opens a way to improve

  11. A low noise charge sensitive amplifier for use in vacuum photo diode readout

    International Nuclear Information System (INIS)

    Stephenson, R.

    1982-08-01

    The amplifier described consists of a charge sensitive pre-amplifier optimised for low noise with low values of input shunt capacitance, and a shaping amplifier providing both differentiation and integration. Amplifier gain is adjustable up to a maximum of approximately 100 μV/electron with a rise time of 2 μS to the peak of the output voltage, and with an open circuit input noise level of 150 electrons RMS. (author)

  12. Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Yinghua [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Chen, Guang-Hong [Department of Medical Physics and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Hacker, Timothy A.; Raval, Amish N. [Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53792 (United States); Van Lysel, Michael S.; Speidel, Michael A., E-mail: speidel@wisc.edu [Department of Medical Physics and Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

    2014-07-15

    Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

  13. Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

    International Nuclear Information System (INIS)

    Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.

    2014-01-01

    Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

  14. An ultra low noise AC beam transformer for deceleration and diagnostics of low intensity beams

    CERN Document Server

    González, C

    1999-01-01

    The design of a broad band ultra-low noise ferrite loaded AC beam transformer is presented. It is designed for use in the CERN Antiproton Decelerator (AD), where beams of a few 107 charges must be decelerated from 3.5 GeV/c to 100 MeV/c. It is used in the RF beam-phase loop, and for intensity and bunch shape measurements during deceleration. When the beam is debunched for cooling on magnetic flat tops, the pick-up is used for measurements of intensity and momentum distribution by means of longitudinal Schottky scans. When used as Schottky pick-up, the signal to noise ratio should be better by about 40 dB than the existing stripline based longitudinal Schottky pick-up. The integrated design of pick-up and associated low-noise amplifier is presented. The achieved noise performance of a few from 1 to 3 MHz is obtained by attaching a low-noise, high-impedance silicon JFET (junction field effect transistor) amplifier to a high-Q resonant ferrite loaded cavity, and then eliminating the resonant response by low-nois...

  15. Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement

    Science.gov (United States)

    Xie, Kai; Shi, Xueyou; Zhao, Kai; Guo, Lixin; Zhang, Hanlu

    2017-02-01

    Temperature stability and noise characteristics often run contradictory in microcurrent (e.g., pA-scale) measurement instruments because low-noise performance requires high-value resistors with relatively poor temperature coefficients. A low-noise transimpedance amplifier with high-temperature stability, which involves an active compensation mechanism to overcome the temperature drift mainly caused by high-value resistors, is presented. The implementation uses a specially designed R-2R compensating network to provide programmable current gain with extra-fine trimming resolution. The temperature drifts of all components (e.g., feedback resistors, operational amplifiers, and the R-2R network itself) are compensated simultaneously. Therefore, both low-temperature drift and ultra-low-noise performance can be achieved. With a current gain of 1011 V/A, the internal current noise density was about 0.4 fA/√Hz, and the average temperature coefficient was 4.3 ppm/K at 0-50 °C. The amplifier module maintains accuracy across a wide temperature range without additional thermal stabilization, and its compact size makes it especially suitable for high-precision, low-current measurement in outdoor environments for applications such as electrochemical emission supervision, air pollution particles analysis, radiation monitoring, and bioelectricity.

  16. Optimized molecular reconstruction procedure combining hybrid reverse Monte Carlo and molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bousige, Colin; Boţan, Alexandru; Coasne, Benoît, E-mail: coasne@mit.edu [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); UMI 3466 CNRS-MIT, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Ulm, Franz-Josef [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Pellenq, Roland J.-M. [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); UMI 3466 CNRS-MIT, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); CINaM, CNRS/Aix Marseille Université, Campus de Luminy, 13288 Marseille Cedex 09 (France)

    2015-03-21

    We report an efficient atom-scale reconstruction method that consists of combining the Hybrid Reverse Monte Carlo algorithm (HRMC) with Molecular Dynamics (MD) in the framework of a simulated annealing technique. In the spirit of the experimentally constrained molecular relaxation technique [Biswas et al., Phys. Rev. B 69, 195207 (2004)], this modified procedure offers a refined strategy in the field of reconstruction techniques, with special interest for heterogeneous and disordered solids such as amorphous porous materials. While the HRMC method generates physical structures, thanks to the use of energy penalties, the combination with MD makes the method at least one order of magnitude faster than HRMC simulations to obtain structures of similar quality. Furthermore, in order to ensure the transferability of this technique, we provide rational arguments to select the various input parameters such as the relative weight ω of the energy penalty with respect to the structure optimization. By applying the method to disordered porous carbons, we show that adsorption properties provide data to test the global texture of the reconstructed sample but are only weakly sensitive to the presence of defects. In contrast, the vibrational properties such as the phonon density of states are found to be very sensitive to the local structure of the sample.

  17. Dynamic concision for three-dimensional reconstruction of human organ built with virtual reality modelling language (VRML)*

    OpenAIRE

    Yu, Zheng-yang; Zheng, Shu-sen; Chen, Lei-ting; He, Xiao-qian; Wang, Jian-jun

    2005-01-01

    This research studies the process of 3D reconstruction and dynamic concision based on 2D medical digital images using virtual reality modelling language (VRML) and JavaScript language, with a focus on how to realize the dynamic concision of 3D medical model with script node and sensor node in VRML. The 3D reconstruction and concision of body internal organs can be built with such high quality that they are better than those obtained from the traditional methods. With the function of dynamic c...

  18. Dynamic Penile Corpora Cavernosa Reconstruction Using Bilateral Innervated Gracilis Muscles: A Preclinical Investigation.

    Science.gov (United States)

    Yin, Zhuming; Liu, Liqiang; Xue, Bingjian; Fan, Jincai; Chen, Wenlin; Liu, Zheng

    2018-03-07

    Prosthesis-assisted penile reconstruction has been performed extensively to restore a cosmetically acceptable phallus. However, a large number of patients will undergo revision surgery for various prosthesis-related complications. To develop a 1-stage prosthesis-free dynamic cavernosa reconstruction method using bilateral innervated gracilis muscles and to investigate the feasibility and reliability of the surgical design. 10 fresh cadavers were dissected to assess the availability of bilateral gracilis muscles for functional cavernosa rebuilding. 11 mongrel female dogs were involved in the penile reconstruction surgery. The neophallus consisted of bilateral gracilis muscles as the neo-cavernosa, a right gracilis skin flap as the neourethra, and a lower abdominal flap with an anterior rectus sheath as the skin envelope and neo-tunica albuginea. The function and structure of the neo-phalli were assessed 7 months postoperatively. The neurovascular pedicle length of the gracilis muscles and the volume of the gracilis venter musculi were measured in the cadaveric investigation. The average dimensions of the canine neo-phalli at rest and during electrostimulated erection were obtained and the muscular fatigue-resistant curve was drawn. Histologic evaluations also were performed. The neurovascular pedicle length and volume of the gracilis muscles were sufficient to yield a nearly normal appearance of the neo-cavernosa in the cadaveric and animal studies. The muscular fatigue-resistant curve demonstrated adequate length, stiffness, and duration of erection of the neo-phalli to accomplish normal coitus. Histologic evaluations showed an intact neourethra and nearly normal muscle structure in the inner layer of the canine neo-cavernosa, except for significantly increased amount of collagen fibers and type I/III collagen ratio in the outer layer of the neo-cavernosa. The percentage of type II (fatigue-prone) muscle fibers did not change significantly. Our preclinical

  19. An ab initio approach to free-energy reconstruction using logarithmic mean force dynamics

    International Nuclear Information System (INIS)

    Nakamura, Makoto; Obata, Masao; Morishita, Tetsuya; Oda, Tatsuki

    2014-01-01

    We present an ab initio approach for evaluating a free energy profile along a reaction coordinate by combining logarithmic mean force dynamics (LogMFD) and first-principles molecular dynamics. The mean force, which is the derivative of the free energy with respect to the reaction coordinate, is estimated using density functional theory (DFT) in the present approach, which is expected to provide an accurate free energy profile along the reaction coordinate. We apply this new method, first-principles LogMFD (FP-LogMFD), to a glycine dipeptide molecule and reconstruct one- and two-dimensional free energy profiles in the framework of DFT. The resultant free energy profile is compared with that obtained by the thermodynamic integration method and by the previous LogMFD calculation using an empirical force-field, showing that FP-LogMFD is a promising method to calculate free energy without empirical force-fields

  20. Characterization of the disruption of neural control strategies for dynamic fingertip forces from attractor reconstruction.

    Directory of Open Access Journals (Sweden)

    Lorenzo Peppoloni

    Full Text Available The Strength-Dexterity (SD test measures the ability of the pulps of the thumb and index finger to compress a compliant and slender spring prone to buckling at low forces (<3N. We know that factors such as aging and neurodegenerative conditions bring deteriorating physiological changes (e.g., at the level of motor cortex, cerebellum, and basal ganglia, which lead to an overall loss of dexterous ability. However, little is known about how these changes reflect upon the dynamics of the underlying biological system. The spring-hand system exhibits nonlinear dynamical behavior and here we characterize the dynamical behavior of the phase portraits using attractor reconstruction. Thirty participants performed the SD test: 10 young adults, 10 older adults, and 10 older adults with Parkinson's disease (PD. We used delayed embedding of the applied force to reconstruct its attractor. We characterized the distribution of points of the phase portraits by their density (number of distant points and interquartile range and geometric features (trajectory length and size. We find phase portraits from older adults exhibit more distant points (p = 0.028 than young adults and participants with PD have larger interquartile ranges (p = 0.001, trajectory lengths (p = 0.005, and size (p = 0.003 than their healthy counterparts. The increased size of the phase portraits with healthy aging suggests a change in the dynamical properties of the system, which may represent a weakening of the neural control strategy. In contrast, the distortion of the attractor in PD suggests a fundamental change in the underlying biological system, and disruption of the neural control strategy. This ability to detect differences in the biological mechanisms of dexterity in healthy and pathological aging provides a simple means to assess their disruption in neurodegenerative conditions and justifies further studies to understand the link with the physiological changes.

  1. Assessing the viability of successful reconstruction of the dynamics of dark energy using varying fundamental couplings

    Energy Technology Data Exchange (ETDEWEB)

    Avelino, P.P., E-mail: ppavelin@fc.up.pt [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Losano, L., E-mail: losano@fisica.ufpb.br [Departamento de Fisica, Universidade Federal da Paraiba, 58051-970 Joao Pessoa, Paraiba (Brazil); Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Menezes, R., E-mail: rmenezes@dce.ufpb.br [Departamento de Ciencias Exatas, Universidade Federal da Paraiba, 58297-000 Rio Tinto, PB (Brazil); Departamento de Fisica, Universidade Federal de Campina Grande, 58109-970 Campina Grande, Paraiba (Brazil); Oliveira, J.C.R.E., E-mail: jespain@fe.up.pt [Centro de Fisica do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Departamento de Engenharia Fisica da Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto (Portugal)

    2012-10-31

    We assess the viability of successful reconstruction of the evolution of the dark energy equation of state using varying fundamental couplings, such as the fine structure constant or the proton-to-electron mass ratio. We show that the same evolution of the dark energy equation of state parameter with cosmic time may be associated with arbitrary variations of the fundamental couplings. Various examples of models with the same (different) background evolution and different (the same) time variation of fundamental couplings are studied in the Letter. Although we demonstrate that, for a broad family of models, it is possible to redefine the scalar field in such a way that its dynamics is that of a standard quintessence scalar field, in general such redefinition leads to the breakdown of the linear relation between the scalar field and the variation of fundamental couplings. This implies that the assumption of a linear coupling is not sufficient to guarantee a successful reconstruction of the dark energy dynamics and consequently additional model dependent assumptions about the scalar field responsible for the dark energy need to be made.

  2. Unveiling the development of intracranial injury using dynamic brain EIT: an evaluation of current reconstruction algorithms.

    Science.gov (United States)

    Li, Haoting; Chen, Rongqing; Xu, Canhua; Liu, Benyuan; Tang, Mengxing; Yang, Lin; Dong, Xiuzhen; Fu, Feng

    2017-08-21

    Dynamic brain electrical impedance tomography (EIT) is a promising technique for continuously monitoring the development of cerebral injury. While there are many reconstruction algorithms available for brain EIT, there is still a lack of study to compare their performance in the context of dynamic brain monitoring. To address this problem, we develop a framework for evaluating different current algorithms with their ability to correctly identify small intracranial conductivity changes. Firstly, a simulation 3D head phantom with realistic layered structure and impedance distribution is developed. Next several reconstructing algorithms, such as back projection (BP), damped least-square (DLS), Bayesian, split Bregman (SB) and GREIT are introduced. We investigate their temporal response, noise performance, location and shape error with respect to different noise levels on the simulation phantom. The results show that the SB algorithm demonstrates superior performance in reducing image error. To further improve the location accuracy, we optimize SB by incorporating the brain structure-based conductivity distribution priors, in which differences of the conductivities between different brain tissues and the inhomogeneous conductivity distribution of the skull are considered. We compare this novel algorithm (called SB-IBCD) with SB and DLS using anatomically correct head shaped phantoms with spatial varying skull conductivity. Main results and Significance: The results showed that SB-IBCD is the most effective in unveiling small intracranial conductivity changes, where it can reduce the image error by an average of 30.0% compared to DLS.

  3. Low noise wing slat system with rigid cove-filled slat

    Science.gov (United States)

    Shmilovich, Arvin (Inventor); Yadlin, Yoram (Inventor)

    2013-01-01

    Concepts and technologies described herein provide for a low noise aircraft wing slat system. According to one aspect of the disclosure provided herein, a cove-filled wing slat is used in conjunction with a moveable panel rotatably attached to the wing slat to provide a high lift system. The moveable panel rotates upward against the rear surface of the slat during deployment of the slat, and rotates downward to bridge a gap width between the stowed slat and the lower wing surface, completing the continuous outer mold line shape of the wing, when the cove-filled slat is retracted to the stowed position.

  4. LOW-NOISE PAVEMENT AS A WAY OF LIMITATION OF TRAFFIC NOISE LEVEL

    Directory of Open Access Journals (Sweden)

    Władysław Gardziejczyk

    2014-11-01

    Full Text Available Road surface can significantlyreduce the trafficnoise level. Depending on the characteristic of the upper surface layers the differences between the maximum rolling noise levels from passing vehicles to reach values about 10 dB (A. A special group is low-noise pavements characterized by the presence of voids above 15%. Application the porous asphalt layers or asphalt mixture type BBTM affects a significantreduction the width of land surrounded the roads where permissible equivalent sound level is exceeded. Such solutions in some cases can replace acoustic barriers. Road pavements with a higher content of voids require proper maintenance because their acoustic performances are reduced during operation.

  5. A Tunable Low Noise Active Bandpass Filter Using a Noise Canceling Technique

    OpenAIRE

    Soltani, N.

    2016-01-01

    A monolithic tunable low noise active bandpass filter is presented in this study. Biasing voltages can control the center frequency and quality factor. By keeping the gain constant, the center frequency shift is 300 MHz. The quality factor can range from 90 to 290 at the center frequency. By using a noise cancelling circuit, noise is kept lower than 2.8 dB. The proposed filter is designed using MMIC technology with a center frequency of 2.4 GHz and a power consumption of 180 mW. ED02AH techno...

  6. A Tunable Low Noise Active Bandpass Filter Using a Noise Canceling Technique

    Directory of Open Access Journals (Sweden)

    N. Soltani

    2016-12-01

    Full Text Available A monolithic tunable low noise active bandpass filter is presented in this study. Biasing voltages can control the center frequency and quality factor. By keeping the gain constant, the center frequency shift is 300 MHz. The quality factor can range from 90 to 290 at the center frequency. By using a noise cancelling circuit, noise is kept lower than 2.8 dB. The proposed filter is designed using MMIC technology with a center frequency of 2.4 GHz and a power consumption of 180 mW. ED02AH technology is used to simulate the circuit elements.

  7. Low noise buffer amplifiers and buffered phase comparators for precise time and frequency measurement and distribution

    Science.gov (United States)

    Eichinger, R. A.; Dachel, P.; Miller, W. H.; Ingold, J. S.

    1982-01-01

    Extremely low noise, high performance, wideband buffer amplifiers and buffered phase comparators were developed. These buffer amplifiers are designed to distribute reference frequencies from 30 KHz to 45 MHz from a hydrogen maser without degrading the hydrogen maser's performance. The buffered phase comparators are designed to intercompare the phase of state of the art hydrogen masers without adding any significant measurement system noise. These devices have a 27 femtosecond phase stability floor and are stable to better than one picosecond for long periods of time. Their temperature coefficient is less than one picosecond per degree C, and they have shown virtually no voltage coefficients.

  8. A Two-Step A/D Conversion and Column Self-Calibration Technique for Low Noise CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Jaeyoung Bae

    2014-07-01

    Full Text Available In this paper, a 120 frames per second (fps low noise CMOS Image Sensor (CIS based on a Two-Step Single Slope ADC (TS SS ADC and column self-calibration technique is proposed. The TS SS ADC is suitable for high speed video systems because its conversion speed is much faster (by more than 10 times than that of the Single Slope ADC (SS ADC. However, there exist some mismatching errors between the coarse block and the fine block due to the 2-step operation of the TS SS ADC. In general, this makes it difficult to implement the TS SS ADC beyond a 10-bit resolution. In order to improve such errors, a new 4-input comparator is discussed and a high resolution TS SS ADC is proposed. Further, a feedback circuit that enables column self-calibration to reduce the Fixed Pattern Noise (FPN is also described. The proposed chip has been fabricated with 0.13 μm Samsung CIS technology and the chip satisfies the VGA resolution. The pixel is based on the 4-TR Active Pixel Sensor (APS. The high frame rate of 120 fps is achieved at the VGA resolution. The measured FPN is 0.38 LSB, and measured dynamic range is about 64.6 dB.

  9. A Fast Multiple Sampling Method for Low-Noise CMOS Image Sensors With Column-Parallel 12-bit SAR ADCs

    Directory of Open Access Journals (Sweden)

    Min-Kyu Kim

    2015-12-01

    Full Text Available This paper presents a fast multiple sampling method for low-noise CMOS image sensor (CIS applications with column-parallel successive approximation register analog-to-digital converters (SAR ADCs. The 12-bit SAR ADC using the proposed multiple sampling method decreases the A/D conversion time by repeatedly converting a pixel output to 4-bit after the first 12-bit A/D conversion, reducing noise of the CIS by one over the square root of the number of samplings. The area of the 12-bit SAR ADC is reduced by using a 10-bit capacitor digital-to-analog converter (DAC with four scaled reference voltages. In addition, a simple up/down counter-based digital processing logic is proposed to perform complex calculations for multiple sampling and digital correlated double sampling. To verify the proposed multiple sampling method, a 256 × 128 pixel array CIS with 12-bit SAR ADCs was fabricated using 0.18 μm CMOS process. The measurement results shows that the proposed multiple sampling method reduces each A/D conversion time from 1.2 μs to 0.45 μs and random noise from 848.3 μV to 270.4 μV, achieving a dynamic range of 68.1 dB and an SNR of 39.2 dB.

  10. Development of a low-noise, two-dimensional amplifier array

    International Nuclear Information System (INIS)

    Kishishita, Tetsuichi; Ikeda, Hirokazu; Sakumura, Takuto; Tamura, Ken-ichi; Takahashi, Tadayuki

    2009-01-01

    This paper describes the recent development of a low-noise, two-dimensional analog front-end ASIC for hybrid pixel imaging detectors. Based on the Open-IP LSI project, the ASIC is designed to meet a low-noise requirement of better than 100e - (rms) with self-triggering capability. The ASIC is intended for the readout of pixel sensors utilizing silicon (Si) and cadmium telluride (CdTe) as detector materials for spectroscopic imaging observations in the X-ray and gamma-ray regions. The readout chip consists of a 4x4 matrix of identical 270μmx270μm pixel cells and was implemented with TSMC 0.35-μm CMOS technology. Each pixel cell contains a charge-sensitive amplifier, pole-zero cancellation circuit, shaper, comparator, and peak hold circuit. Preliminary testing of the ASIC achieved an 88e - (rms) equivalent noise charge and a 25e - /pF noise slope with power consumption of 150μW per pixel.

  11. A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording

    Directory of Open Access Journals (Sweden)

    Marco Crescentini

    2016-05-01

    Full Text Available High-throughput screening (HTS using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i design of scalable microfluidic devices; (ii design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter.

  12. A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording.

    Science.gov (United States)

    Crescentini, Marco; Bennati, Marco; Saha, Shimul Chandra; Ivica, Josip; de Planque, Maurits; Morgan, Hywel; Tartagni, Marco

    2016-05-19

    High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter.

  13. Design of CMOS Tunable Image-Rejection Low-Noise Amplifier with Active Inductor

    Directory of Open Access Journals (Sweden)

    Ler Chun Lee

    2008-01-01

    Full Text Available A fully integrated CMOS tunable image-rejection low-noise amplifier (IRLNA has been designed using Silterra's industry standard 0.18 μm RF CMOS process. The notch filter is designed using an active inductor. Measurement results show that the notch filter designed using active inductor contributes additional 1.19 dB to the noise figure of the low-noise amplifier (LNA. A better result is possible if the active inductor is optimized. Since active inductors require less die area, the die area occupied by the IRLNA is not significantly different from a conventional LNA, which was designed for comparison. The proposed IRLNA exhibits S21 of 11.8 dB, S11 of −17.8 dB, S22 of −10.7 dB, and input 1 dB compression point of −12 dBm at 3 GHz

  14. Molecular dynamics simulation of boron implanted into diamond (0 0 1) 2 x 1 reconstruction surface

    International Nuclear Information System (INIS)

    Li Rongbin; Dai Yongbin; Hu Xiaojun; Sheng Heshen; He Xianchang

    2003-01-01

    Molecular dynamic simulations, utilizing the Tersoff many-body potential, are used to investigate the microscopic processes of a single boron atom with energy of 500 eV implanted into the diamond (0 0 1) 2 x 1 reconstruction surface. The lifetime of thermal spike created by B bombardment is about 0.18 ps by calculating the variation of the mean coordination numbers with time. The formation of the split-interstitial composed of projectile and lattice atom (B-C) is observed. The total potential energy of the system decreases about 0.56 eV with a stable B split-interstitial in diamond. The lattice relaxations in the diamond (0 0 1) 2 x 1 reconstruction surface or near surface of simulated have been discussed. The outermost layer atoms tend to move inward, and the other atoms move outward. The interplanar distance between the outermost layer and the second layer has been shortened by 15% compared with its starting interplanar distance. Stress distribution in the calculated diamond configuration is inhomogeneous. After boron implanted into diamond with the energy of 500 eV, there is an excess of compressively stressed atoms in the lattice, which induces the total stress being compressive

  15. Dynamic Non-Rigid Objects Reconstruction with a Single RGB-D Sensor

    Directory of Open Access Journals (Sweden)

    Sen Wang

    2018-03-01

    Full Text Available This paper deals with the 3D reconstruction problem for dynamic non-rigid objects with a single RGB-D sensor. It is a challenging task as we consider the almost inevitable accumulation error issue in some previous sequential fusion methods and also the possible failure of surface tracking in a long sequence. Therefore, we propose a global non-rigid registration framework and tackle the drifting problem via an explicit loop closure. Our novel scheme starts with a fusion step to get multiple partial scans from the input sequence, followed by a pairwise non-rigid registration and loop detection step to obtain correspondences between neighboring partial pieces and those pieces that form a loop. Then, we perform a global registration procedure to align all those pieces together into a consistent canonical space as guided by those matches that we have established. Finally, our proposed model-update step helps fixing potential misalignments that still exist after the global registration. Both geometric and appearance constraints are enforced during our alignment; therefore, we are able to get the recovered model with accurate geometry as well as high fidelity color maps for the mesh. Experiments on both synthetic and various real datasets have demonstrated the capability of our approach to reconstruct complete and watertight deformable objects.

  16. A Bayesian nonparametric approach to reconstruction and prediction of random dynamical systems

    Science.gov (United States)

    Merkatas, Christos; Kaloudis, Konstantinos; Hatjispyros, Spyridon J.

    2017-06-01

    We propose a Bayesian nonparametric mixture model for the reconstruction and prediction from observed time series data, of discretized stochastic dynamical systems, based on Markov Chain Monte Carlo methods. Our results can be used by researchers in physical modeling interested in a fast and accurate estimation of low dimensional stochastic models when the size of the observed time series is small and the noise process (perhaps) is non-Gaussian. The inference procedure is demonstrated specifically in the case of polynomial maps of an arbitrary degree and when a Geometric Stick Breaking mixture process prior over the space of densities, is applied to the additive errors. Our method is parsimonious compared to Bayesian nonparametric techniques based on Dirichlet process mixtures, flexible and general. Simulations based on synthetic time series are presented.

  17. A Bayesian nonparametric approach to reconstruction and prediction of random dynamical systems.

    Science.gov (United States)

    Merkatas, Christos; Kaloudis, Konstantinos; Hatjispyros, Spyridon J

    2017-06-01

    We propose a Bayesian nonparametric mixture model for the reconstruction and prediction from observed time series data, of discretized stochastic dynamical systems, based on Markov Chain Monte Carlo methods. Our results can be used by researchers in physical modeling interested in a fast and accurate estimation of low dimensional stochastic models when the size of the observed time series is small and the noise process (perhaps) is non-Gaussian. The inference procedure is demonstrated specifically in the case of polynomial maps of an arbitrary degree and when a Geometric Stick Breaking mixture process prior over the space of densities, is applied to the additive errors. Our method is parsimonious compared to Bayesian nonparametric techniques based on Dirichlet process mixtures, flexible and general. Simulations based on synthetic time series are presented.

  18. Reconstruction of an input function from a dynamic PET water image using multiple tissue curves

    Science.gov (United States)

    Kudomi, Nobuyuki; Maeda, Yukito; Yamamoto, Yuka; Nishiyama, Yoshihiro

    2016-08-01

    Quantification of cerebral blood flow (CBF) is important for the understanding of normal and pathologic brain physiology. When CBF is assessed using PET with {{\\text{H}}2} 15O or C15O2, its calculation requires an arterial input function, which generally requires invasive arterial blood sampling. The aim of the present study was to develop a new technique to reconstruct an image derived input function (IDIF) from a dynamic {{\\text{H}}2} 15O PET image as a completely non-invasive approach. Our technique consisted of using a formula to express the input using tissue curve with rate constant parameter. For multiple tissue curves extracted from the dynamic image, the rate constants were estimated so as to minimize the sum of the differences of the reproduced inputs expressed by the extracted tissue curves. The estimated rates were used to express the inputs and the mean of the estimated inputs was used as an IDIF. The method was tested in human subjects (n  =  29) and was compared to the blood sampling method. Simulation studies were performed to examine the magnitude of potential biases in CBF and to optimize the number of multiple tissue curves used for the input reconstruction. In the PET study, the estimated IDIFs were well reproduced against the measured ones. The difference between the calculated CBF values obtained using the two methods was small as around  PET imaging. This suggests the possibility of using a completely non-invasive technique to assess CBF in patho-physiological studies.

  19. DYNAMICS OF COGNITIVE FUNCTION OF PATIENTS WITH DEFECTS OF THE SKULL AFTER RECONSTRUCTIVE SURGERY

    Directory of Open Access Journals (Sweden)

    E. V. Sinbukhova

    2017-01-01

    Full Text Available Due to  the  high social significance of traumatic  brain injury and its consequences,  dynamics of cognitive functions  at  the  background  of the reduction of reconstructive and plastic surgery is of interest to researchers in the world, but this topic is not sufficiently studied. A large number of patients with bone defects of the skull due to a traumatic  brain injury and skull defects after surgery for tumors, and as a consequence of possible cognitive deficits of these patients  makes it necessary to study and assess the possibility of its compensation  as a result of reconstructive  plastic surgery of the skull. Material and methods. In our study, we examined 54 patients  (12 women and 42 men in surgical treatment neurotrauma department (reconstructive  surgery after traumatic  brain injury or skull defect after surgical removal of tumors. The average age of patients  is33,09 years. All patients  were examined by a psychologist before surgery, and on the first, third, and seventh-eighth day after the surgery. MoCA, FAB, Schulte tables, HADS, Spielberger-Hanin anxiety test, a set of stimulus materials for neuropsychological diagnosis, all patients were asked to subjectively evaluate their appearance:  until defect acquisition prior to surgery after treatment (see questionnaire  by Sinbukhova E.[8], also was used projective drawing method, where patients were asked to perform a series of drawings on the given topics. In our study to reduce the high level of situational and personal anxiety of the patients they had Art-therapy sessions with a psychologist before surgery and from the second day after it. The purpose of research is to study the changes in cognitive function, level of depression, anxiety of patients  with postoperative bone defects of the skull after a reconstructive-plastic surgery. Keywords cognitive function, depression, anxiety, reconstructive  surgery. Results On the 3 days after surgery, a

  20. Impact of time-of-flight on indirect 3D and direct 4D parametric image reconstruction in the presence of inconsistent dynamic PET data

    NARCIS (Netherlands)

    Kotasidis, F. A.; Mehranian, A.; Zaidi, H.

    2016-01-01

    Kinetic parameter estimation in dynamic PET suffers from reduced accuracy and precision when parametric maps are estimated using kinetic modelling following image reconstruction of the dynamic data. Direct approaches to parameter estimation attempt to directly estimate the kinetic parameters from

  1. Ultra-Low-Noise Sub-mm/Far-IR Detectors for Space-Based Telescopes

    Science.gov (United States)

    Rostem, Karwan

    The sub-mm and Far-IR spectrum is rich with information from a wide range of astrophysical sources, including exoplanet atmospheres and galaxies at the peak star formation. In the 10-400 μm range, the spectral lines of important chemical species such H2O, HD, and [OI] can be used to map the formation and evolution of planetary systems. Dust emission in this spectral range is also an important tool for characterizing the morphology of debris disks and interstellar magnetic fields. At larger scales, accessing the formation and distribution of luminous Far-IR and sub-mm galaxies is essential to understanding star formation triggers, as well as the last stages of reionization at z 6. Detector technology is essential to realizing the full science potential of a next-generation Far-IR space telescope (Far-IR Surveyor). The technology gap in large-format, low-noise and ultra-low-noise Far-IR direct detectors is specifically highlighted by NASA's Cosmic Origins Program, and prioritized for development now to enable a flagship mission such as the Far-IR Surveyor that will address the key Cosmic Origins science questions of the next two decades. The detector requirements for a mid-resolution spectrometer are as follows: (1) Highly sensitive detectors with performance approaching 10^-19 - 10^-20 WHz 1/2 for background- limited operation in telescopes with cold optics. (2) Detector time constant in the sub- millisecond range. (3) Scalable architecture to a kilo pixel array with uniform detector characteristics. (4) Compatibility with space operation in the presence of particle radiation. We propose phononic crystals to meet the requirements of ultra-low-noise thermal detectors. By design, a phononic crystal exhibits phonon bandgaps where heat transport is forbidden. The size and location of the bandgaps depend on the elastic properties of the dielectric and the geometry of the phononic unit cell. A wide-bandwidth low-pass thermal filter with a cut-off frequency of 1.5 GHz and

  2. WE-G-18C-08: Real Time Tumor Imaging Using a Novel Dynamic Keyhole MRI Reconstruction Technique

    International Nuclear Information System (INIS)

    Lee, D; Pollock, S; Whelan, B; Keall, P; Greer, P; Kim, T

    2014-01-01

    Purpose: To test the hypothesis that the novel Dynamic Keyhole MRI reconstruction technique can accelerate image acquisition whilst maintaining high image quality for lung cancer patients. Methods: 18 MRI datasets from 5 lung cancer patients were acquired using a 3T MRI scanner. These datasets were retrospectively reconstructed using (A) The novel Dynamic Keyhole technique, (B) The conventional keyhole technique and (C) the conventional zero filling technique. The dynamic keyhole technique in MRI refers to techniques in which previously acquired k-space data is used to supplement under sampled data obtained in real time. The novel Dynamic Keyhole technique utilizes a previously acquired a library of kspace datasets in conjunction with central k-space datasets acquired in realtime. A simultaneously acquired respiratory signal is utilized to sort, match and combine the two k-space streams with respect to respiratory displacement. Reconstruction performance was quantified by (1) comparing the keyhole size (which corresponds to imaging speed) required to achieve the same image quality, and (2) maintaining a constant keyhole size across the three reconstruction methods to compare the resulting image quality to the ground truth image. Results: (1) The dynamic keyhole method required a mean keyhole size which was 48% smaller than the conventional keyhole technique and 60% smaller than the zero filling technique to achieve the same image quality. This directly corresponds to faster imaging. (2) When a constant keyhole size was utilized, the Dynamic Keyhole technique resulted in the smallest difference of the tumor region compared to the ground truth. Conclusion: The dynamic keyhole is a simple and adaptable technique for clinical applications requiring real-time imaging and tumor monitoring such as MRI guided radiotherapy. Based on the results from this study, the dynamic keyhole method could increase the imaging frequency by a factor of five compared with full k

  3. Influence of dose reduction and iterative reconstruction on CT calcium scores : a multi-manufacturer dynamic phantom study

    NARCIS (Netherlands)

    van der Werf, N R; Willemink, M J; Willems, T P; Greuter, M J W; Leiner, T

    To evaluate the influence of dose reduction in combination with iterative reconstruction (IR) on coronary calcium scores (CCS) in a dynamic phantom on state-of-the-art CT systems from different manufacturers. Calcified inserts in an anthropomorphic chest phantom were translated at 20 mm/s

  4. A Minimum Fuel Based Estimator for Maneuver and Natrual Dynamics Reconstruction

    Science.gov (United States)

    Lubey, D.; Scheeres, D.

    2013-09-01

    The vast and growing population of objects in Earth orbit (active and defunct spacecraft, orbital debris, etc.) offers many unique challenges when it comes to tracking these objects and associating the resulting observations. Complicating these challenges are the inaccurate natural dynamical models of these objects, the active maneuvers of spacecraft that deviate them from their ballistic trajectories, and the fact that spacecraft are tracked and operated by separate agencies. Maneuver detection and reconstruction algorithms can help with each of these issues by estimating mismodeled and unmodeled dynamics through indirect observation of spacecraft. It also helps to verify the associations made by an object correlation algorithm or aid in making those associations, which is essential when tracking objects in orbit. The algorithm developed in this study applies an Optimal Control Problem (OCP) Distance Metric approach to the problems of Maneuver Reconstruction and Dynamics Estimation. This was first developed by Holzinger, Scheeres, and Alfriend (2011), with a subsequent study by Singh, Horwood, and Poore (2012). This method estimates the minimum fuel control policy rather than the state as a typical Kalman Filter would. This difference ensures that the states are connected through a given dynamical model and allows for automatic covariance manipulation, which can help to prevent filter saturation. Using a string of measurements (either verified or hypothesized to correlate with one another), the algorithm outputs a corresponding string of adjoint and state estimates with associated noise. Post-processing techniques are implemented, which when applied to the adjoint estimates can remove noise and expose unmodeled maneuvers and mismodeled natural dynamics. Specifically, the estimated controls are used to determine spacecraft dependent accelerations (atmospheric drag and solar radiation pressure) using an adapted form of the Optimal Control based natural dynamics

  5. A high rate, low noise, x-ray silicon strip detector system

    International Nuclear Information System (INIS)

    Ludewigt, B.; Jaklevic, J.; Kipnis, I.; Rossington, C.; Spieler, H.

    1993-11-01

    An x-ray detector system, based on a silicon strip detector wire-bonded to a low noise charge-senstive amplifier integrated circuit, has been developed for synchrotron radiation experiments which require very high count rates and good energy resolution. Noise measurements and x-ray spectra were taken using a 6 mm long, 55 μm pitch strip detector in conjunction with a prototype 16-channel charge-sensitive preamplifier, both fabricated using standard 1.2 μm CMOS technology. The detector system currently achieves an energy resolution of 350 eV FWHM at 5.9 key, 2 μs peaking time, when cooled to -5 degree C

  6. Design of low noise class D amplifiers using an integrated filter

    International Nuclear Information System (INIS)

    Wang Haishi; Zhang Bo

    2012-01-01

    This paper investigates the noise sources in a single-ended class D amplifier (SECDA) and suggests corresponding ways to lower the noise. The total output noise could be expressed as a function of the gain and noises from different sources. According to the function, the bias voltage (V B ) is a primary noise source, especially for a SECDA with a large gain. A low noise SECDA is obtained by integrating a filter into the SECDA to lower the noise of the V B . The filter utilizes an active resister and an 80 pF capacitance to get a 3 Hz pole. A noise test and fast Fourier transform analysis show that the noise performance of this SECDA is the same as that of a SECDA with an external filter. (semiconductor integrated circuits)

  7. Ultra low-noise differential ac-coupled photodetector for sensitive pulse detection applications

    International Nuclear Information System (INIS)

    Windpassinger, Patrick J; Boisen, Axel; Kjærgaard, Niels; Polzik, Eugene S; Müller, Jörg Helge; Kubasik, Marcin; Koschorreck, Marco

    2009-01-01

    We report on the performance of ultra low-noise differential photodetectors especially designed for probing of atomic ensembles with weak light pulses. The working principle of the detectors is described together with the analysis procedures employed to extract the photon shot noise of light pulses with ∼1 μs duration. As opposed to frequency response peaked detectors, our approach allows for broadband quantum noise measurements. The equivalent noise charge (ENC) for two different hardware approaches is evaluated to 280 and 340 electrons per pulse, respectively, which corresponds to a dark noise equivalent photon number of n 3dB = 0.8 × 10 5 and n 3dB = 1.2 × 10 5 in the two approaches. Finally, we discuss the possibility of removing classical correlations in the output signal caused by detector imperfection by using double-correlated sampling methods

  8. Low-noise humidity controller for imaging water mediated processes in atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gaponenko, I., E-mail: iaroslav.gaponenko@unige.ch; Gamperle, L.; Herberg, K.; Muller, S. C.; Paruch, P. [DQMP, University of Geneva, 24 Quai E. Ansermet, 1211 Geneva 4 (Switzerland)

    2016-06-15

    We demonstrate the construction of a novel low-noise continuous flow humidity controller and its integration with a commercial variable-temperature atomic force microscope fluid cell, allowing precise control of humidity and temperature at the sample during nanoscale measurements. Based on wet and dry gas mixing, the design allows a high mechanical stability to be achieved by means of an ultrasonic atomiser for the generation of water-saturated gas, improving upon previous bubbler-based architectures. Water content in the flow is measured both at the inflow and outflow of the fluid cell, enabling the monitoring of water condensation and icing, and allowing controlled variation of the sample temperature independently of the humidity. To benchmark the performance of the controller, the results of detailed noise studies and time-based imaging of the formation of ice layers on highly oriented pyrolytic graphite are shown.

  9. High-Tc Superconducting Bolometer Noise Measurement Using Low Noise Transformers - Theory and Optimization

    Science.gov (United States)

    Aslam, Shahid; Jones, Hollis H.

    2011-01-01

    Care must always be taken when performing noise measurements on high-Tc superconducting materials to ensure that the results are not from the measurement system itself. One situation likely to occur is with low noise transformers. One of the least understood devices, it provides voltage gain for low impedance inputs (< 100 ), e.g., YBaCuO and GdBaCuO thin films, with comparatively lower noise levels than other devices for instance field effect and bipolar junction transistors. An essential point made in this paper is that because of the complex relationships between the transformer ports, input impedance variance alters the transformer s transfer function in particular, the low frequency cutoff shift. The transfer of external and intrinsic transformer noise to the output along with optimization and precautions are treated; all the while, we will cohesively connect the transfer function shift, the load impedance, and the actual noise at the transformer output.

  10. Low-noise magnetic observatory variometer with race-track sensors

    International Nuclear Information System (INIS)

    Janošek, M; Petrucha, V; Vlk, M

    2016-01-01

    We present a low-noise, high-stability observatory magnetometer with race-track sensors, as developed by the Czech Technical University in Prague for National Observatory of Athens. As opposed to the standard instruments, we used our novel race-track fluxgate sensors with planar oval core which were cut by state-of-the art pico-second UV-laser. The noise performance of the complete electronics and sensor chain is below 6 pT/√Hz @ 1 Hz. The electronics uses 24-bit 200-Hz A/D converter with simultaneous sampling and all digital processing is done in FPGA. The variometer with the sensors mounted on a MACOR cube has been successfully calibrated by scalar method. (paper)

  11. Nb{sub 3}Al thin film deposition for low-noise terahertz electronics

    Energy Technology Data Exchange (ETDEWEB)

    Dochev, D; Pavolotsky, A B; Belitsky, V; Olofsson, H [Group for Advanced Receiver Development and Onsala Space Observatory, Department of Radio- and Space Science, Chalmers University of Technology, SE 412 96 Gothenburg (Sweden)], E-mail: dimitar.dochev@chalmers.se

    2008-02-01

    Higher energy gap superconducting materials were always interesting for low-noise mixer applications such as superconductor-insulator-superconductor tunnel junctions (SIS) and hot-electron bolometer (HEB) used in sub-millimeter and terahertz parts of electro-magnetic spectrum. Here, we report a novel approach for producing Nb{sub 3}Al thin film by co-sputtering from two confocally arranged Nb and Al dc-magnetrons onto substrate heated up to 830 deg. C. Characterization of the deposited films revealed presence of the A15 phase and measured critical temperature was up to 15.7 K with the transition width 0.2-0.3 K for a 300 nm thick film. We measured the film critical magnetic field and studied influence of annealing on the film properties. We have investigated compositional depth profile of the deposited films by spectroscopy of reflected electrons.

  12. Nb3Al thin film deposition for low-noise terahertz electronics

    International Nuclear Information System (INIS)

    Dochev, D; Pavolotsky, A B; Belitsky, V; Olofsson, H

    2008-01-01

    Higher energy gap superconducting materials were always interesting for low-noise mixer applications such as superconductor-insulator-superconductor tunnel junctions (SIS) and hot-electron bolometer (HEB) used in sub-millimeter and terahertz parts of electro-magnetic spectrum. Here, we report a novel approach for producing Nb 3 Al thin film by co-sputtering from two confocally arranged Nb and Al dc-magnetrons onto substrate heated up to 830 deg. C. Characterization of the deposited films revealed presence of the A15 phase and measured critical temperature was up to 15.7 K with the transition width 0.2-0.3 K for a 300 nm thick film. We measured the film critical magnetic field and studied influence of annealing on the film properties. We have investigated compositional depth profile of the deposited films by spectroscopy of reflected electrons

  13. Low-Noise Operation of All-Fiber Femtosecond Cherenkov Laser

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Villanueva Ibáñez, Guillermo Eduardo; Lægsgaard, Jesper

    2013-01-01

    We investigate the noise properties of a femtosecond all-fiber Cherenkov radiation source with emission wavelength around 600 nm, based on an Yb-fiber laser and a highly-nonlinear photonic crystal fiber. A relative intensity noise as low as - 103 dBc/Hz, corresponding to 2.48 % pulse-to-pulse...... fluctuation in energy, was observed at the Cherenkov radiation output power of 4.3 mW, or 150 pJ pulse energy. This pulse-to-pulse fluctuation is at least 10.6 dB lower compared to spectrally-sliced supercontinuum sources traditionally used for ultrafast fiberbased generation at visible wavelengths. Low noise...... makes allfiber Cherenkov sources promising for biophotonics applications such as multi-photon microscopy, where minimum pulse-to-pulse energy fluctuation is required. We present the dependency of the noise figure on both the Cherenkov radiation output power and its spectrum....

  14. Ultra-low noise TES bolometer arrays for SAFARI instrument on SPICA

    Science.gov (United States)

    Khosropanah, P.; Suzuki, T.; Ridder, M. L.; Hijmering, R. A.; Akamatsu, H.; Gottardi, L.; van der Kuur, J.; Gao, J. R.; Jackson, B. D.

    2016-07-01

    SRON is developing ultra-low noise Transition Edge Sensors (TESs) based on a superconducting Ti/Au bilayer on a suspended SiN island with SiN legs for the SAFARI instrument aboard the SPICA mission. We successfully fabricated TESs with very narrow (0.5-0.7 μm) and thin (0.25 μm) SiN legs on different sizes of SiN islands using deep reactiveion etching process. The pixel size is 840x840 μm2 and there are variety of designs with and without optical absorbers. For TESs without absorbers, we measured electrical NEPs as low as <1x10-19 W/√Hz with response time of 0.3 ms and reached the phonon noise limit. Using TESs with absorbers, we quantified the darkness of our setup and confirmed a photon noise level of 2x10-19 W/√Hz.

  15. Fabrication of Low-Noise TES Arrays for the SAFARI Instrument on SPICA

    Science.gov (United States)

    Ridder, M. L.; Khosropanah, P.; Hijmering, R. A.; Suzuki, T.; Bruijn, M. P.; Hoevers, H. F. C.; Gao, J. R.; Zuiddam, M. R.

    2016-07-01

    Ultra-low-noise transition edge sensors (TES) with noise equivalent power lower than 2 × 10^{-19} W/Hz^{1/2 } have been fabricated by SRON, which meet the sensitivity requirements for the far-infrared SAFARI instrument on space infrared telescope for cosmology and astrophysics. Our TES detector is based on a titanium/gold (Ti/Au) thermistor on a silicon nitride (SiN) island. The island is thermally linked with SiN legs to a silicon support structure at the bath temperature. The SiN legs are very thin (250 nm), narrow (500 nm), and long (above 300 {\\upmu } m); these dimensions are needed in leg-isolated bolometers to achieve the required level of sensitivity. In this paper, we describe the latest fabrication process for our TES bolometers with improved sensitivity.

  16. Low-noise, transformer-coupled resonant photodetector for squeezed state generation.

    Science.gov (United States)

    Chen, Chaoyong; Shi, Shaoping; Zheng, Yaohui

    2017-10-01

    In an actual setup of squeezed state generation, the stability of a squeezing factor is mainly limited by the performance of the servo-control system, which is mainly influenced by the shot noise and gain of a photodetector. We present a unique transformer-coupled LC resonant amplifier as a photodetector circuit to reduce the electronic noise and increase the gain of the photodetector. As a result, we obtain a low-noise, high gain photodetector with the gain of more than 1.8×10 5 V/A, and the input current noise of less than 4.7 pA/Hz. By adjusting the parameters of the transformer, the quality factor Q of the resonant circuit is close to 100 in the frequency range of more than 100 MHz, which meets the requirement for weak power detection in the application of squeezed state generation.

  17. A single-to-differential low-noise amplifier with low differential output imbalance

    International Nuclear Information System (INIS)

    Duan Lian; Ma Chengyan; He Xiaofeng; Ye Tianchun; Huang Wei; Jin Yuhua

    2012-01-01

    This paper presents a single-ended input differential output low-noise amplifier intended for GPS applications. We propose a method to reduce the gain/amplitude and phase imbalance of a differential output exploiting the inductive coupling of a transformer or center-tapped differential inductor. A detailed analysis of the theory of imbalance reduction, as well as a discussion on the principle of choosing the dimensions of a transformer, are given. An LNA has been implemented using TSMC 0.18 μm technology with ESD-protected. Measurement on board shows a voltage gain of 24.6 dB at 1.575 GHz and a noise figure of 3.2 dB. The gain imbalance is below 0.2 dB and phase imbalance is less than 2 degrees. The LNA consumes 5.2 mA from a 1.8 V supply. (semiconductor integrated circuits)

  18. A wideband CMOS inductorless low noise amplifier employing noise cancellation for digital TV tuner applications

    International Nuclear Information System (INIS)

    Zhang Jihong; Bai Xuefei; Huang Lu

    2013-01-01

    A wideband inductorless low noise amplifier for digital TV tuner applications is presented. The proposed LNA scheme uses a composite NMOS/PMOS cross-coupled transistor pair to provide partial cancellation of noise generated by the input transistors. The chip is implemented in SMIC 0.18 μm CMOS technology. Measurement shows that the proposed LNA achieves 12.2–15.2 dB voltage gain from 300 to 900 MHz, the noise figure is below 3.1 dB and has a minimum value of 2.3 dB, and the best input-referred 1-dB compression point (IP1dB) is − 17 dBm at 900 MHz. The core consumes 7 mA current with a supply voltage of 1.8 V and occupies an area of 0.5 × 0.35 mm 2 . (semiconductor integrated circuits)

  19. A High-Linearity Low-Noise Amplifier with Variable Bandwidth for Neural Recoding Systems

    Science.gov (United States)

    Yoshida, Takeshi; Sueishi, Katsuya; Iwata, Atsushi; Matsushita, Kojiro; Hirata, Masayuki; Suzuki, Takafumi

    2011-04-01

    This paper describes a low-noise amplifier with multiple adjustable parameters for neural recording applications. An adjustable pseudo-resistor implemented by cascade metal-oxide-silicon field-effect transistors (MOSFETs) is proposed to achieve low-signal distortion and wide variable bandwidth range. The amplifier has been implemented in 0.18 µm standard complementary metal-oxide-semiconductor (CMOS) process and occupies 0.09 mm2 on chip. The amplifier achieved a selectable voltage gain of 28 and 40 dB, variable bandwidth from 0.04 to 2.6 Hz, total harmonic distortion (THD) of 0.2% with 200 mV output swing, input referred noise of 2.5 µVrms over 0.1-100 Hz and 18.7 µW power consumption at a supply voltage of 1.8 V.

  20. A low-noise, wideband, integrated CMOS transimpedance preamplifier for photodiode applications

    International Nuclear Information System (INIS)

    Binkley, D.M.; Paulus, M.J.; Casey, M.E.; Rochelle, J.M.

    1992-01-01

    In this paper, a low-noise, wideband, integrated CMOS transimpedance preamplifier is presented for silicon avalanche photodiode (APD) applications. The preamplifier, fabricated in a standard 2μ CMOS technology, features a transimpedance gain of 45 kΩ, a risetime of 22 ns, a series noise of 1.6nV/Hz 1/2 , and a wideband equivalent input-noise current of 12 nA for a source capacitance of 12 pF. The measured 22 Na timing resolution of 9.2-ns FWHM and energy resolution of 22.4% FWHM for the RCA C30994 BGO/APD detector module coupled to the preamplifier is comparable to the performance reported using charge-sensitive preamplifiers. This illustrates that transimpedance preamplifiers should be considered for APD applications, especially where APD noise current dominates noise from feedback resistors in the 1--kΩ to 50-kΩ range

  1. Using the Moon As A Low-Noise Seismic Detector For Strange Quark Nuggets

    Science.gov (United States)

    Banerdt, W. Bruce; Chui, Talso; Griggs, Cornelius E.; Herrin, Eugene T.; Nakamura, Yosio; Paik, Ho Jung; Penanen, Konstantin; Rosenbaum, Doris; Teplitz, Vigdor L.; Young, Joseph

    2006-01-01

    Strange quark matter made of up, down and strange quarks has been postulated by Witten [1]. Strange quark matter would be nearly charge neutral and would have density of nuclear matter (10(exp 14) gm/cu cm). Witten also suggested that nuggets of strange quark matter, or strange quark nuggets (SQNs), could have formed shortly after the Big Bang, and that they would be viable candidates for cold dark matter. As suggested by de Rujula and Glashow [2], an SQN may pass through a celestial body releasing detectable seismic energy along a straight line. The Moon, being much quieter seismically than the Earth, would be a favorable place to search for such events. We review previous searches for SQNs to illustrate the parameter space explored by using the Moon as a low-noise detector of SQNs. We also discuss possible detection schemes using a single seismometer, and using an International Lunar Seismic Network.

  2. Low-noise humidity controller for imaging water mediated processes in atomic force microscopy

    Science.gov (United States)

    Gaponenko, I.; Gamperle, L.; Herberg, K.; Muller, S. C.; Paruch, P.

    2016-06-01

    We demonstrate the construction of a novel low-noise continuous flow humidity controller and its integration with a commercial variable-temperature atomic force microscope fluid cell, allowing precise control of humidity and temperature at the sample during nanoscale measurements. Based on wet and dry gas mixing, the design allows a high mechanical stability to be achieved by means of an ultrasonic atomiser for the generation of water-saturated gas, improving upon previous bubbler-based architectures. Water content in the flow is measured both at the inflow and outflow of the fluid cell, enabling the monitoring of water condensation and icing, and allowing controlled variation of the sample temperature independently of the humidity. To benchmark the performance of the controller, the results of detailed noise studies and time-based imaging of the formation of ice layers on highly oriented pyrolytic graphite are shown.

  3. Low-noise humidity controller for imaging water mediated processes in atomic force microscopy

    International Nuclear Information System (INIS)

    Gaponenko, I.; Gamperle, L.; Herberg, K.; Muller, S. C.; Paruch, P.

    2016-01-01

    We demonstrate the construction of a novel low-noise continuous flow humidity controller and its integration with a commercial variable-temperature atomic force microscope fluid cell, allowing precise control of humidity and temperature at the sample during nanoscale measurements. Based on wet and dry gas mixing, the design allows a high mechanical stability to be achieved by means of an ultrasonic atomiser for the generation of water-saturated gas, improving upon previous bubbler-based architectures. Water content in the flow is measured both at the inflow and outflow of the fluid cell, enabling the monitoring of water condensation and icing, and allowing controlled variation of the sample temperature independently of the humidity. To benchmark the performance of the controller, the results of detailed noise studies and time-based imaging of the formation of ice layers on highly oriented pyrolytic graphite are shown.

  4. Linearizing of Low Noise Power Amplifier Using 5.8GHz Double Loop Feedforward Linearization Technique

    Directory of Open Access Journals (Sweden)

    Abdulkareem Mokif Obais

    2017-05-01

    Full Text Available In this paper, a double loop feedforward linearization technique is analyzed and built with a MMIC low noise amplifier “HMC753” as main amplifier and a two-stage class-A power amplifier as error amplifier. The system is operated with 5V DC supply at a center frequency of 5.8GHz and a bandwidth of 500MHz. The proposed technique, increases the linearity of the MMIC amplifier from 18dBm at 1dB compression point to more than 26dBm. In addition, the proposed system is tested with OFDM signal and it reveals good response in maximizing the linearity region and eliminating distortions. The proposed system is designed and simulated onAdvanced Wave Research-Microwave Office (AWR-MWO.

  5. Dynamic Regulatory Network Reconstruction for Alzheimer’s Disease Based on Matrix Decomposition Techniques

    Directory of Open Access Journals (Sweden)

    Wei Kong

    2014-01-01

    Full Text Available Alzheimer’s disease (AD is the most common form of dementia and leads to irreversible neurodegenerative damage of the brain. Finding the dynamic responses of genes, signaling proteins, transcription factor (TF activities, and regulatory networks of the progressively deteriorative progress of AD would represent a significant advance in discovering the pathogenesis of AD. However, the high throughput technologies of measuring TF activities are not yet available on a genome-wide scale. In this study, based on DNA microarray gene expression data and a priori information of TFs, network component analysis (NCA algorithm is applied to determining the TF activities and regulatory influences on TGs of incipient, moderate, and severe AD. Based on that, the dynamical gene regulatory networks of the deteriorative courses of AD were reconstructed. To select significant genes which are differentially expressed in different courses of AD, independent component analysis (ICA, which is better than the traditional clustering methods and can successfully group one gene in different meaningful biological processes, was used. The molecular biological analysis showed that the changes of TF activities and interactions of signaling proteins in mitosis, cell cycle, immune response, and inflammation play an important role in the deterioration of AD.

  6. Reconstruction of Grønfjordbreen dynamics (West Spitsbergen in the Holocene

    Directory of Open Access Journals (Sweden)

    O. V. Kokin

    2017-01-01

    Full Text Available In the past 80 years, the Grønfjord Glacier front retreated for a distance longer than 2.5 km, and thus, a big part of the proglacial zone became free of ice. The detailed geomorphological survey of this zone made pos‑ sible to identify the following landforms: exaration-glacial, glacial-accumulative, exaration-extrusive, pushmoraine (thrusting, fluvioglacial and limnoglacial ones. Geomorphological analysis of the forms indicat‑ ing the Grønfjord Glacier movement and degradation allowed establishing its dynamics over the last glacial cycle. The river running from the moraine-dammed lake erodes a great thickness of a push-moraine (up to 20‑25  m which is composed by marine sediments, accumulated on the site of the present-day proglacial zone under a relatively higher sea level than now. Careful investigation of lithology and stratigraphy of the push-moraine together with radiocarbon dating of marine shells resulted in determination of chronology of the main sedimentation stages during the Holocene within area of the present-day proglacial zone. During the reconstruction evidences of only two stages of the significant Grønfjord Glacier advance were revealed: in the early Holocene (9.5‑10 thousand years ago and in the little ice age (before beginning of XX century, with the maximum advance at the last stage. Basing on the results of the reconstruction the suggestion had been made that during the little ice age the Grønfjord Glacier was a surging one.

  7. Reconstructing dynamic mental models of facial expressions in prosopagnosia reveals distinct representations for identity and expression.

    Science.gov (United States)

    Richoz, Anne-Raphaëlle; Jack, Rachael E; Garrod, Oliver G B; Schyns, Philippe G; Caldara, Roberto

    2015-04-01

    The human face transmits a wealth of signals that readily provide crucial information for social interactions, such as facial identity and emotional expression. Yet, a fundamental question remains unresolved: does the face information for identity and emotional expression categorization tap into common or distinct representational systems? To address this question we tested PS, a pure case of acquired prosopagnosia with bilateral occipitotemporal lesions anatomically sparing the regions that are assumed to contribute to facial expression (de)coding (i.e., the amygdala, the insula and the posterior superior temporal sulcus--pSTS). We previously demonstrated that PS does not use information from the eye region to identify faces, but relies on the suboptimal mouth region. PS's abnormal information use for identity, coupled with her neural dissociation, provides a unique opportunity to probe the existence of a dichotomy in the face representational system. To reconstruct the mental models of the six basic facial expressions of emotion in PS and age-matched healthy observers, we used a novel reverse correlation technique tracking information use on dynamic faces. PS was comparable to controls, using all facial features to (de)code facial expressions with the exception of fear. PS's normal (de)coding of dynamic facial expressions suggests that the face system relies either on distinct representational systems for identity and expression, or dissociable cortical pathways to access them. Interestingly, PS showed a selective impairment for categorizing many static facial expressions, which could be accounted for by her lesion in the right inferior occipital gyrus. PS's advantage for dynamic facial expressions might instead relate to a functionally distinct and sufficient cortical pathway directly connecting the early visual cortex to the spared pSTS. Altogether, our data provide critical insights on the healthy and impaired face systems, question evidence of deficits

  8. Complementary frame reconstruction: a low-biased dynamic PET technique for low count density data in projection space

    International Nuclear Information System (INIS)

    Hong, Inki; Cho, Sanghee; Michel, Christian J; Casey, Michael E; Schaefferkoetter, Joshua D

    2014-01-01

    A new data handling method is presented for improving the image noise distribution and reducing bias when reconstructing very short frames from low count dynamic PET acquisition. The new method termed ‘Complementary Frame Reconstruction’ (CFR) involves the indirect formation of a count-limited emission image in a short frame through subtraction of two frames with longer acquisition time, where the short time frame data is excluded from the second long frame data before the reconstruction. This approach can be regarded as an alternative to the AML algorithm recently proposed by Nuyts et al, as a method to reduce the bias for the maximum likelihood expectation maximization (MLEM) reconstruction of count limited data. CFR uses long scan emission data to stabilize the reconstruction and avoids modification of algorithms such as MLEM. The subtraction between two long frame images, naturally allows negative voxel values and significantly reduces bias introduced in the final image. Simulations based on phantom and clinical data were used to evaluate the accuracy of the reconstructed images to represent the true activity distribution. Applicability to determine the arterial input function in human and small animal studies is also explored. In situations with limited count rate, e.g. pediatric applications, gated abdominal, cardiac studies, etc., or when using limited doses of short-lived isotopes such as 15 O-water, the proposed method will likely be preferred over independent frame reconstruction to address bias and noise issues. (paper)

  9. Improving Filtered Backprojection Reconstruction by Data-Dependent Filtering

    NARCIS (Netherlands)

    D.M. Pelt (Daniël); K.J. Batenburg (Joost)

    2014-01-01

    htmlabstractFiltered backprojection, one of the most widely used reconstruction methods in tomography, requires a large number of low-noise projections to yield accurate reconstructions. In many applications of tomography, complete projection data of high quality cannot be obtained, because of

  10. Reconstruction of Undersampled Big Dynamic MRI Data Using Non-Convex Low-Rank and Sparsity Constraints

    Directory of Open Access Journals (Sweden)

    Ryan Wen Liu

    2017-03-01

    Full Text Available Dynamic magnetic resonance imaging (MRI has been extensively utilized for enhancing medical living environment visualization, however, in clinical practice it often suffers from long data acquisition times. Dynamic imaging essentially reconstructs the visual image from raw (k,t-space measurements, commonly referred to as big data. The purpose of this work is to accelerate big medical data acquisition in dynamic MRI by developing a non-convex minimization framework. In particular, to overcome the inherent speed limitation, both non-convex low-rank and sparsity constraints were combined to accelerate the dynamic imaging. However, the non-convex constraints make the dynamic reconstruction problem difficult to directly solve through the commonly-used numerical methods. To guarantee solution efficiency and stability, a numerical algorithm based on Alternating Direction Method of Multipliers (ADMM is proposed to solve the resulting non-convex optimization problem. ADMM decomposes the original complex optimization problem into several simple sub-problems. Each sub-problem has a closed-form solution or could be efficiently solved using existing numerical methods. It has been proven that the quality of images reconstructed from fewer measurements can be significantly improved using non-convex minimization. Numerous experiments have been conducted on two in vivo cardiac datasets to compare the proposed method with several state-of-the-art imaging methods. Experimental results illustrated that the proposed method could guarantee the superior imaging performance in terms of quantitative and visual image quality assessments.

  11. Large-area, low-noise, high-speed, photodiode-based fluorescence detectors with fast overdrive recovery

    International Nuclear Information System (INIS)

    Bickman, S.; DeMille, D.

    2005-01-01

    Two large-area, low-noise, high-speed fluorescence detectors have been built. One detector consists of a photodiode with an area of 28 mmx28 mm and a low-noise transimpedance amplifier. This detector has a input light-equivalent spectral noise density of less than 3 pW/√(Hz), can recover from a large scattered light pulse within 10 μs, and has a bandwidth of at least 900 kHz. The second detector consists of a 16-mm-diam avalanche photodiode and a low-noise transimpedance amplifier. This detector has an input light-equivalent spectral noise density of 0.08 pW/√(Hz), also can recover from a large scattered light pulse within 10 μs, and has a bandwidth of 1 MHz

  12. Hydrographical and dynamical reconstruction of the Warm Core Cyprus Eddy from gliders data

    Science.gov (United States)

    Bosse, Anthony; Testor, Pierre; Hayes, Dan; Ruiz, Simon; Mauri, Elena; Charantonis, Anastase; d'Ortenzio, Fabrizio; Mortier, Laurent

    2016-04-01

    In the 80s, the POEM (Physical Oceanography of the Eastern Mediterranean) cruises in the Levantine Basin first revealed the presence of a very pronounced dynamical structure off Cyprus: The Cyprus Warm Core Eddy. Since then, a large amount of data have been collected thanks to the use of autonomous oceanic gliders (+8000 profiles since 2009). Part of those profiles were carried out in the upper layers down to 200 m, and we take benefit of a novel approach named ITCOMP SOM that uses a statistical approach to extend them down to 1000 m (see [1] for more details). This dataset have a particularly good spatio-temporal coverage in 2009 for about a month, thanks to simultaneous deployments of several gliders (up to 6). In this study, we present a set of 3D reconstruction of the dynamical and hydrographical characteristics of the Warm Core Cyprus Eddy between 2009 and 2015. Moreover, chlorophyll-a fluorescence data measured by the gliders give evidence to strong vertical velocities at the edge of the eddy. We discuss possible mechanisms (frontogenesis, symmetric instability) that could generate such signals and provide an assessment of the role of this peculiar circulation feature on the circulation and biogeochemistry of the Levantine basin. Reference: [1] Charantonis, A., P. Testor, L. Mortier, F. D'Ortenzio, S. Thiria (2015): Completion of a sparse GLIDER database using multi-iterative Self-Organizing Maps (ITCOMP SOM), Procedia Computer Science, 51(1):2198-2206. DOI: 10.1016/j.procs.2015.05.496

  13. EEG source reconstruction reveals frontal-parietal dynamics of spatial conflict processing.

    Directory of Open Access Journals (Sweden)

    Michael X Cohen

    Full Text Available Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict processing. Human subjects performed a Simon task, in which conflict was induced by incongruence between spatial location and response hand. We found an early (∼200 ms post-stimulus conflict modulation in stimulus-contralateral parietal gamma (30-50 Hz, followed by a later alpha-band (8-12 Hz conflict modulation, suggesting an early detection of spatial conflict and inhibition of spatial location processing. Inter-regional connectivity analyses assessed via cross-frequency coupling of theta (4-8 Hz, alpha, and gamma power revealed conflict-induced shifts in cortical network interactions: Congruent trials (relative to incongruent trials had stronger coupling between frontal theta and stimulus-contrahemifield parietal alpha/gamma power, whereas incongruent trials had increased theta coupling between medial frontal and lateral frontal regions. These findings shed new light into the large-scale network dynamics of spatial conflict processing, and how those networks are shaped by oscillatory interactions.

  14. EEG source reconstruction reveals frontal-parietal dynamics of spatial conflict processing.

    Science.gov (United States)

    Cohen, Michael X; Ridderinkhof, K Richard

    2013-01-01

    Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict processing. Human subjects performed a Simon task, in which conflict was induced by incongruence between spatial location and response hand. We found an early (∼200 ms post-stimulus) conflict modulation in stimulus-contralateral parietal gamma (30-50 Hz), followed by a later alpha-band (8-12 Hz) conflict modulation, suggesting an early detection of spatial conflict and inhibition of spatial location processing. Inter-regional connectivity analyses assessed via cross-frequency coupling of theta (4-8 Hz), alpha, and gamma power revealed conflict-induced shifts in cortical network interactions: Congruent trials (relative to incongruent trials) had stronger coupling between frontal theta and stimulus-contrahemifield parietal alpha/gamma power, whereas incongruent trials had increased theta coupling between medial frontal and lateral frontal regions. These findings shed new light into the large-scale network dynamics of spatial conflict processing, and how those networks are shaped by oscillatory interactions.

  15. EEG Source Reconstruction Reveals Frontal-Parietal Dynamics of Spatial Conflict Processing

    Science.gov (United States)

    Cohen, Michael X; Ridderinkhof, K. Richard

    2013-01-01

    Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict processing. Human subjects performed a Simon task, in which conflict was induced by incongruence between spatial location and response hand. We found an early (∼200 ms post-stimulus) conflict modulation in stimulus-contralateral parietal gamma (30–50 Hz), followed by a later alpha-band (8–12 Hz) conflict modulation, suggesting an early detection of spatial conflict and inhibition of spatial location processing. Inter-regional connectivity analyses assessed via cross-frequency coupling of theta (4–8 Hz), alpha, and gamma power revealed conflict-induced shifts in cortical network interactions: Congruent trials (relative to incongruent trials) had stronger coupling between frontal theta and stimulus-contrahemifield parietal alpha/gamma power, whereas incongruent trials had increased theta coupling between medial frontal and lateral frontal regions. These findings shed new light into the large-scale network dynamics of spatial conflict processing, and how those networks are shaped by oscillatory interactions. PMID:23451201

  16. Reconstruction of the dynamics of the 1800-1801 Hualalai eruption: Implications for planetary lava flows

    Science.gov (United States)

    Baloga, Stephen; Spudis, Paul

    1993-01-01

    The 1800-1801 eruption of alkalic basalt from the Hualalai volcano, Hawaii provides a unique opportunity for investigating the dynamics of lava flow emplacement with eruption rates and compositions comparable to those that have been suggested for planetary eruptions. Field observations suggest new considerations must be used to reconstruct the emplacement of these lava flows. These observations are: (1) the flow traversed the 15 km from the vent to the sea so rapidly that no significant crust formed and an observation of the eruption reported that the flow reach the sea from the vent in approximately 1 hour; (2) the drainage of beds of xenolith nodules indicates a highly fluid, low viscosity lava; (3) overspills and other morphologic evidence for a very low viscosity host fluid; (4) no significant longitudinal increase in flow thickness that might be associated with an increase in the rheological properties of the lava; and (5) the relatively large size of channels associated with the flow, up to 80 meters across and several km long. Models for many geologic mass movements and fast moving fluids with various loadings and suspensions are discussed.

  17. Using fire dynamics simulator to reconstruct a hydroelectric power plant fire accident.

    Science.gov (United States)

    Chi, Jen-Hao; Wu, Sheng-Hung; Shu, Chi-Min

    2011-11-01

    The location of the hydroelectric power plant poses a high risk to occupants seeking to escape in a fire accident. Calculating the heat release rate of transformer oil as 11.5 MW/m(2), the fire at the Taiwan Dajia-River hydroelectric power plant was reconstructed using the fire dynamics simulator (FDS). The variations at the escape route of the fire hazard factors temperature, radiant heat, carbon monoxide, and oxygen were collected during the simulation to verify the causes of the serious casualties resulting from the fire. The simulated safe escape time when taking temperature changes into account is about 236 sec, 155 sec for radiant heat changes, 260 sec for carbon monoxide changes, and 235-248 sec for oxygen changes. These escape times are far less than the actual escape time of 302 sec. The simulation thus demonstrated the urgent need to improve escape options for people escaping a hydroelectric power plant fire. © 2011 American Academy of Forensic Sciences.

  18. Dynamic network reconstruction from gene expression data applied to immune response during bacterial infection.

    Science.gov (United States)

    Guthke, Reinhard; Möller, Ulrich; Hoffmann, Martin; Thies, Frank; Töpfer, Susanne

    2005-04-15

    The immune response to bacterial infection represents a complex network of dynamic gene and protein interactions. We present an optimized reverse engineering strategy aimed at a reconstruction of this kind of interaction networks. The proposed approach is based on both microarray data and available biological knowledge. The main kinetics of the immune response were identified by fuzzy clustering of gene expression profiles (time series). The number of clusters was optimized using various evaluation criteria. For each cluster a representative gene with a high fuzzy-membership was chosen in accordance with available physiological knowledge. Then hypothetical network structures were identified by seeking systems of ordinary differential equations, whose simulated kinetics could fit the gene expression profiles of the cluster-representative genes. For the construction of hypothetical network structures singular value decomposition (SVD) based methods and a newly introduced heuristic Network Generation Method here were compared. It turned out that the proposed novel method could find sparser networks and gave better fits to the experimental data. Reinhard.Guthke@hki-jena.de.

  19. Bracing of the Reconstructed and Osteoarthritic Knee during High Dynamic Load Tasks.

    Science.gov (United States)

    Hart, Harvi F; Crossley, Kay M; Collins, Natalie J; Ackland, David C

    2017-06-01

    Lateral compartment osteoarthritis accompanied by abnormal knee biomechanics is frequently reported in individuals with knee osteoarthritis after anterior cruciate ligament reconstruction (ACLR). The aim of this study was to evaluate changes in knee biomechanics produced by an adjusted and unadjusted varus knee brace during high dynamic loading activities in individuals with lateral knee osteoarthritis after ACLR and valgus malalignment. Nineteen participants who had undergone ACLR 5 to 20 yr previously and had symptomatic and radiographic lateral knee osteoarthritis with valgus malalignment were assessed. Quantitative motion analysis experiments were conducted during hopping, stair ascent, and descent under three test conditions: (i) no brace, (ii) unadjusted brace with sagittal plane support and neutral frontal plane alignment, and (iii) adjusted brace with sagittal plane support and varus realignment (valgus to neutral). Sagittal, frontal, and transverse plane knee kinematics, external joint moment, and angular impulse data were calculated. Relative to an unbraced knee, braced conditions significantly increased knee flexion and adduction angles during hopping (P = 0.003 and P = 0.005; respectively), stair ascent (P = 0.003 and P stair ascent (P = 0.008) and flexion moments during stair descent (P = 0.006). There were no significant differences between the adjusted and the unadjusted brace conditions (P > 0.05). A knee brace, with or without varus alignment, can modulate knee kinematics and external joint moments during hopping, stairs ascent, and descent in individuals with predominant lateral knee osteoarthritis after ACLR. Longer-term use of a brace may have implications in slowing osteoarthritis progression.

  20. EUDP project 'Low noise airfoil' - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bertagnolio, F. (ed.)

    2012-06-15

    This document summarizes the scientific results achieved during the EUDP-funded project 'Low-Noise Airfoil'. The goals of this project are, on one side to develop a measurement technique that permits the evaluation of trailing edge noise in a classical aerodynamic wind tunnel, and on the other side to develop and implement a design procedure to manufacture airfoil profiles with low noise emission. The project involved two experimental campaigns: one in the LM Wind Power wind tunnel, a classical aerodynamic wind tunnel, in Lunderskov (Denmark), the second one in the Virginia Tech Stability Wind Tunnel at the Aerospace and Ocean Engineering Department of Virginia Tech (Blacksburg, VA, USA), also a classical aerodynamic wind tunnel but equipped with an anechoic chamber that allow to perform acoustic measurements. On the theoretical side, the above experiments yield a series of model validations and improvements. In particular, the so-called TNO trailing edge noise model could be significantly improved by introducing turbulence anisotropy in its formulation, as well as the influence of the boundary layer mean pressure gradient. This two characteristics are inherent to airfoil flows but were neglected in the original approach. In addition, the experimental results are confronted to detailed Large Eddy Simulations of the airfoil flow giving more insight into the flow turbulence characteristics. The methodology which consists in measuring surface pressure spectra directly on the airfoil surface using flush-mounted microphones in order to evaluate far-field noise emission using additional theoretical results has been validated. This technique presents the advantage that it can easily be used in a classical aerodynamic wind tunnel and does not require the use of an anechoic facility. It was developed as a substitute to the original plan that consisted in measuring acoustic waves using hot-wire velocimetry. This last technique proved ineffective in the LM Wind

  1. Modeling economic costs of disasters and recovery involving positive effects of reconstruction: analysis using a dynamic CGE model

    Science.gov (United States)

    Xie, W.; Li, N.; Wu, J.-D.; Hao, X.-L.

    2013-11-01

    Disaster damages have negative effects on economy, whereas reconstruction investments have positive effects. The aim of this study is to model economic causes of disasters and recovery involving positive effects of reconstruction activities. Computable general equilibrium (CGE) model is a promising approach because it can incorporate these two kinds of shocks into a unified framework and further avoid double-counting problem. In order to factor both shocks in CGE model, direct loss is set as the amount of capital stock reduced on supply side of economy; A portion of investments restore the capital stock in existing period; An investment-driven dynamic model is formulated due to available reconstruction data, and the rest of a given country's saving is set as an endogenous variable. The 2008 Wenchuan Earthquake is selected as a case study to illustrate the model, and three scenarios are constructed: S0 (no disaster occurs), S1 (disaster occurs with reconstruction investment) and S2 (disaster occurs without reconstruction investment). S0 is taken as business as usual, and the differences between S1 and S0 and that between S2 and S0 can be interpreted as economic losses including reconstruction and excluding reconstruction respectively. The study showed that output from S1 is found to be closer to real data than that from S2. S2 overestimates economic loss by roughly two times that under S1. The gap in economic aggregate between S1 and S0 is reduced to 3% in 2011, a level that should take another four years to achieve under S2.

  2. Development of Low-Noise Small-Area 24 GHz CMOS Radar Sensor

    Directory of Open Access Journals (Sweden)

    Min Yoon

    2016-01-01

    Full Text Available We present a low-noise small-area 24 GHz CMOS radar sensor for automotive collision avoidance. This sensor is based on direct-conversion pulsed-radar architecture. The proposed circuit is implemented using TSMC 0.13 μm RF (radio frequency CMOS (fT/fmax=120/140 GHz technology, and it is powered by a 1.5 V supply. This circuit uses transmission lines to reduce total chip size instead of real bulky inductors for input and output impedance matching. The layout techniques for RF are used to reduce parasitic capacitance at the band of 24 GHz. The proposed sensor has low cost and low power dissipation since it is realized using CMOS process. The proposed sensor showed the lowest noise figure of 2.9 dB and the highest conversion gain of 40.2 dB as compared to recently reported research results. It also showed small chip size of 0.56 mm2, low power dissipation of 39.5 mW, and wide operating temperature range of −40 to +125°C.

  3. NASA's Pursuit of Low-Noise Propulsion for Low-Boom Commercial Supersonic Vehicles

    Science.gov (United States)

    Bridges, James; Brown, Clifford A.; Seidel, Jonathan A.

    2018-01-01

    Since 2006, when the Fundamental Aeronautics Program was instituted within NASA's Aeronautics Mission Directorate, there has been a Project looking at the technical barriers to commercial supersonic flight. Among the barriers is the noise produced by aircraft during landing and takeoff. Over the years that followed, research was carried out at NASA aeronautics research centers, often in collaboration with academia and industry, addressing the problem. In 2013, a high-level milestone was established, described as a Technical Challenge, with the objective of demonstrating the feasibility of a low-boom supersonic airliner that could meet current airport noise regulations. The Technical Challenge was formally called "Low Noise Propulsion for Low Boom Aircraft", and was completed in late 2016. This paper reports the technical findings from this Technical Challenge, reaching back almost 10 years to review the technologies and tools that were developed along the way. It also discusses the final aircraft configuration and propulsion systems required for a supersonic civilian aircraft to meet noise regulations using the technologies available today. Finally, the paper documents the model-scale tests that validated the acoustic performance of the study aircraft.

  4. A low-noise MEMS accelerometer for unattended ground sensor applications

    Science.gov (United States)

    Speller, Kevin E.; Yu, Duli

    2004-09-01

    A low-noise micro-machined servo accelerometer has been developed for use in Unattended Ground Sensors (UGS). Compared to conventional coil-and-magnet based velocity transducers, this Micro-Electro-Mechanical System (MEMS) accelerometer offers several key benefits for battlefield monitoring. Many UGS require a compass to determine deployment orientation with respect to magnetic North. This orientation information is critical for determining the bearing of incoming signals. Conventional sensors with sensing technology based on a permanent magnet can cause interference with a compass when used in close proximity. This problem is solved with a MEMS accelerometer which does not require any magnetic materials. Frequency information below 10 Hz is valuable for identification of signal sources. Conventional seismometers used in UGS are typically limited in frequency response from 20 to 200 Hz. The MEMS accelerometer has a flat frequency response from DC to 5 kHz. The wider spectrum of signals received improves detection, classification and monitoring on the battlefield. The DC-coupled output of the MEMS accelerometer also has the added benefit of providing tilt orientation data for the deployed UGS. Other performance parameters of the MEMS accelerometer that are important to UGS such as size, weight, shock survivability, phase response, distortion, and cross-axis rejection will be discussed. Additionally, field test data from human footsteps recorded with the MEMS accelerometer will be presented.

  5. The Majorana Low-noise Low-background Front-end Electronics

    Science.gov (United States)

    Abgrall, N.; Aguayo, E.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, D. G.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C.-H.; Yumatov, V.

    The MAJORANA DEMONSTRATOR will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope 76Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the 76Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolution performances. We present here the low-noise low- background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the MAJORANA DEMONSTRATOR. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.

  6. Novel matched amplifiers with low noise positive feedback. Part II: Resistive-capacitive feedback

    Science.gov (United States)

    Bruck, Y.; Zakharenko, V.

    2010-02-01

    This article is a continuation of consideration for an amplifier with resistive positive feedback (RPF) (Bruck (2008), 'Novel Matched LNA with Low Noise Positive Feedback. Part 1: General Features and Resistive Feedback', International Journal of Electronics, 95, 441-456). We propose here new configuration schematics of a transformer-less selective LNA with resistive-capacitive positive feedback (RCPF). A circuit of an amplifier with a transistor connected into a circuit with a common base (CB) configuration is analysed in detail. RCPF and RPF circuits are compared. It is shown that the LNA RCPF provides any pass-band, a good level of input and output matching, a minimum noise temperature which is significantly lower than that of the LNA RPF, a rather high linearity, and stability of amplification. The simulation results and some experimental data for the amplifiers intended for use in the LOFAR radiotelescope (Konovalenko et al. (2003), 'Thirty Element Array Antenna as a Prototype of a Huge Low-Frequency Radio Telescope,' Experimental Astronomy, 16, 149-164; Konovalenko (2007), 'Ukrainian Contribution to LOFAR', A scientific workshop, organised by LOFAR/ASTRON' Emmen, Netherlands, 23-27. http://www.lofar.org/workshop) are given. It is assumed that such devices are of a special interest for high-frequency integral circuits (IC).

  7. Perancangan Low Noise Amplifier dengan Teknik Non Simultaneous Conjugate Match untuk Aplikasi Radar S-Band

    Directory of Open Access Journals (Sweden)

    Yana Taryana

    2016-06-01

    Full Text Available Radar merupakan sistem pemancar dan penerima gelombang elektromagnetik untuk mendeteksi, mengukur jarak dan membuat peta benda benda seperti pesawat terbang, kapal laut, kendaran bermotor dan informasi cuaca. Salah satu kendala yang dihadapi pada sistem radar adalah sinyal pantulan yang memiliki daya yang rendah sehingga kualitas penerimaan menjadi kurang baik. Untuk mengatasi kendala tersebut dibutuhkan penguat daya pada sistem penerima yaitu Low Noise Amplifier (LNA. Oleh karena itu, tulisan ini memaparkan perancangan LNA dengan menggunakan teknik Non Simultaneous Conjugate Match (NSCM untuk aplikasi radar S-Band. Teknik ini memberikan kemudahan dalam menentukan nilai trade off (TO untuk nilai gain, noise figure (NF dan Voltage Standing Wave Ratio (VSWR yang diinginkan. Dalam proses perancangannya, perangkat lunak Agilent Design System (ADS 2011 digunakan untuk mendapatkan hubungan antara lingkaran gain, lingkaran NF, lingkaran VSWR, dan lingkaran mismatch factor (M. Dari hubungan tersebut diperoleh nilai impedansi masukan dan keluaran dari komponen aktif. Dalam tulisan ini, LNA dirancang dua tingkat untuk mendapatkan penguatan yang tinggi. Masing-masing tingkat menggunakan komponen aktif BJT BFP420 dengan penguatan dirancang sebesar 13,50 dB untuk tingkat pertama dan kedua, dan M sebesar 0,98. Sedangkan untuk saluran penyesuai impedansinya menggunakan substrat teflon fiberglass DiClad527. Hasil simulasi menunjukkan karakteristik LNA pada frekuensi 3 GHz yaitu gain sebesar 28,80 dB, NF sebesar 2,80 dB, VSWRin sebesar 1,05 dan VSWRout sebesar 1,1.

  8. Fabrication of Low Noise Borosilicate Glass Nanopores for Single Molecule Sensing.

    Directory of Open Access Journals (Sweden)

    Jayesh A Bafna

    Full Text Available We show low-cost fabrication and characterization of borosilicate glass nanopores for single molecule sensing. Nanopores with diameters of ~100 nm were fabricated in borosilicate glass capillaries using laser assisted glass puller. We further achieve controlled reduction and nanometer-size control in pore diameter by sculpting them under constant electron beam exposure. We successfully fabricate pore diameters down to 6 nm. We next show electrical characterization and low-noise behavior of these borosilicate nanopores and compare their taper geometries. We show, for the first time, a comprehensive characterization of glass nanopore conductance across six-orders of magnitude (1M-1μM of salt conditions, highlighting the role of buffer conditions. Finally, we demonstrate single molecule sensing capabilities of these devices with real-time translocation experiments of individual λ-DNA molecules. We observe distinct current blockage signatures of linear as well as folded DNA molecules as they undergo voltage-driven translocation through the glass nanopores. We find increased signal to noise for single molecule detection for higher trans-nanopore driving voltages. We propose these nanopores will expand the realm of applications for nanopore platform.

  9. Updated design for a low-noise, wideband transimpedance photodiode amplifier

    International Nuclear Information System (INIS)

    Paul, S. F.; Marsala, R.

    2006-01-01

    The high-speed rotation diagnostic developed for Columbia's HBT-EP tokamak requires a high quantum efficiency, very low drift detector/amplifier combination. An updated version of the circuit developed originally for the beam emission spectroscopy experiment on TFTR is being used. A low dark current (2 nA at 15 V bias), low input source capacitance (2 pF) FFD-040 N-type Si photodiode is operated in photoconductive mode. It has a quantum efficiency of 40% at the 468.6 nm (He II line that is being observed). A low-noise field-effect transistor (InterFET IFN152 with e Na =1.2 nV/√Hz) is used to reduce the noise in the transimpedance preamplifier (A250 AMPTEK op-amp) and a very high speed (unity-gain bandwidth=200 MHz) voltage feedback amplifier (LM7171) is used to restore the frequency response up to 100 kHz. This type of detector/amplifier is photon-noise limited at this bandwidth for incident light with a power of >∼2 nW. The circuit has been optimized using SIMETRIX 4.0 SPICE software and a prototype circuit has been tested successfully. Though photomultipliers and avalanche photodiodes can detect much lower light levels, for light levels >2 nW and a 10 kHz bandwidth, this detector/amplifier combination is more sensitive because of the absence of excess (internally generated) noise

  10. Self Oscillating Mixer with Dielectric Resonator for Low Noise Block Application

    Directory of Open Access Journals (Sweden)

    Endon Bharata

    2011-08-01

    Full Text Available In this paper, the development of a self oscillating mixer (SOM as part of a low noise block (LNB for a satellite television receiver is investigated numerically and experimentally. In contrast to other mixers, the developed SOM requires no separate local oscillator as it generates own local oscillator signal. The SOM is developed using a monolithic microwave integrated circuit (MMIC comprised of two bipolar transistors coupled as a Darlington pair and a dielectric resonator to establish a local oscillator signal. The SOM is designed to oscillate at 3.62GHz driven from 50W signal generator. The prototype of SOM is fabricated on a dielectric substrate of glass-reinforced hydrocarbon/ceramic lamination (RO4350B board which has a thickness of 0.762mm and relative permittivity of 3.66. The prototype is then characterized experimentally and exhibits a conversion gain of 8dB with the input and output voltage standing wave ratio (VSWR less than 2 across the 2520MHz to 2670MHz operating frequency band.

  11. A low-noise ac-bridge amplifier for ballistocardiogram measurement on an electronic weighing scale

    International Nuclear Information System (INIS)

    Inan, O T; Kovacs, G T A

    2010-01-01

    Ballistocardiography is a non-invasive technique for evaluating cardiovascular health. This note presents an ac-bridge amplifier for low-noise ballistocardiogram (BCG) recording from a modified weighing scale. The strain gauges in a commercial scale were excited by an ac source—square or sine wave—and the differential output voltage resulting from the BCG was amplified and demodulated synchronously with the excitation waveform. A standard BCG amplifier, with a simple dc-bridge excitation, was also built and the performance was compared to both the square- and sine-wave excited ac-bridge amplifiers. The total input-referred voltage noise (rms) integrated over the relevant BCG bandwidth of 0.3–10 Hz was found to be 30 nV (square wave source) or 25 nV (sine-wave source) for the ac-bridge amplifier and 52 nV for the standard amplifier: an improvement of 4.8 dB or 6 dB, respectively. These correspond to input-referred force noise (rms) values of 5 mN, 4 mN and 8.3 mN. The improvement in SNR was also observed in recorded waveforms from a seated subject whose BCG signal was measured with both dc- and ac-bridge circuits. (note)

  12. Instrumentation for low noise nanopore-based ionic current recording under laser illumination

    Science.gov (United States)

    Roelen, Zachary; Bustamante, José A.; Carlsen, Autumn; Baker-Murray, Aidan; Tabard-Cossa, Vincent

    2018-01-01

    We describe a nanopore-based optofluidic instrument capable of performing low-noise ionic current recordings of individual biomolecules under laser illumination. In such systems, simultaneous optical measurements generally introduce significant parasitic noise in the electrical signal, which can severely reduce the instrument sensitivity, critically hindering the monitoring of single-molecule events in the ionic current traces. Here, we present design rules and describe simple adjustments to the experimental setup to mitigate the different noise sources encountered when integrating optical components to an electrical nanopore system. In particular, we address the contributions to the electrical noise spectra from illuminating the nanopore during ionic current recording and mitigate those effects through control of the illumination source and the use of a PDMS layer on the SiNx membrane. We demonstrate the effectiveness of our noise minimization strategies by showing the detection of DNA translocation events during membrane illumination with a signal-to-noise ratio of ˜10 at 10 kHz bandwidth. The instrumental guidelines for noise minimization that we report are applicable to a wide range of nanopore-based optofluidic systems and offer the possibility of enhancing the quality of synchronous optical and electrical signals obtained during single-molecule nanopore-based analysis.

  13. Fully integrated low-noise readout circuit with automatic offset cancellation loop for capacitive microsensors.

    Science.gov (United States)

    Song, Haryong; Park, Yunjong; Kim, Hyungseup; Cho, Dong-Il Dan; Ko, Hyoungho

    2015-10-14

    Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL) for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR) logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with an active area of 1.76 mm². The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of -250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms.

  14. Fully Integrated Low-Noise Readout Circuit with Automatic Offset Cancellation Loop for Capacitive Microsensors

    Directory of Open Access Journals (Sweden)

    Haryong Song

    2015-10-01

    Full Text Available Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS process with an active area of 1.76 mm2. The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of −250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms.

  15. CASTOR a VLSI CMOS mixed analog-digital circuit for low noise multichannel counting applications

    International Nuclear Information System (INIS)

    Comes, G.; Loddo, F.; Hu, Y.; Kaplon, J.; Ly, F.; Turchetta, R.; Bonvicini, V.; Vacchi, A.

    1996-01-01

    In this paper we present the design and first experimental results of a VLSI mixed analog-digital 1.2 microns CMOS circuit (CASTOR) for multichannel radiation detectors applications demanding low noise amplification and counting of radiation pulses. This circuit is meant to be connected to pixel-like detectors. Imaging can be obtained by counting the number of hits in each pixel during a user-controlled exposure time. Each channel of the circuit features an analog and a digital part. In the former one, a charge preamplifier is followed by a CR-RC shaper with an output buffer and a threshold discriminator. In the digital part, a 16-bit counter is present together with some control logic. The readout of the counters is done serially on a common tri-state output. Daisy-chaining is possible. A 4-channel prototype has been built. This prototype has been optimised for use in the digital radiography Syrmep experiment at the Elettra synchrotron machine in Trieste (Italy): its main design parameters are: shaping time of about 850 ns, gain of 190 mV/fC and ENC (e - rms)=60+17 C (pF). The counting rate per channel, limited by the analog part, can be as high as about 200 kHz. Characterisation of the circuit and first tests with silicon microstrip detectors are presented. They show the circuit works according to design specification and can be used for imaging applications. (orig.)

  16. A low noise preamplifier with optoelectronic overload protection for radioactivity measurement

    International Nuclear Information System (INIS)

    Sephton, J.P.; Williams, J.M.; Johansson, L.C.; Philips, H.C.

    2012-01-01

    Pulses from detectors used for radioactivity measurement can vary in size by several orders of magnitude. Large pulses will lead to saturation at the preamplifier output and extension of the pulse length. As a consequence, the dead time of the system increases and pulses may be lost. Electronic design techniques employed to protect against overloading tend to increase the amplifier noise level. However, an optoelectronic method of overload protection has been devised which has only a negligible effect on noise. An infrared light emitting diode interfaced to the output of the preamplifier is linked by fibre optic cable to an ultra-low leakage photodiode at the input. The conduction of the photodiode increases with the amplitude of the preamplifier output signal. Excess current is thereby prevented from entering the preamplifier and causing saturation. The preamplifier has been tested on 4π beta–gamma and gas counting systems and found to give good protection against overloading. - Highlights: ► A preamplifier for radioactivity measurements has been developed. ► Low noise. ► Current sensitive. ► Optoelectronic overload protection.

  17. Flexible CMOS low-noise amplifiers for beyond-3G wireless hand-held devices

    Science.gov (United States)

    Becerra-Alvarez, Edwin C.; Sandoval-Ibarra, Federico; de la Rosa, José M.

    2009-05-01

    This paper explores the use of reconfigurable Low-Noise Amplifiers (LNAs) for the implementation of CMOS Radio Frequency (RF) front-ends in the next generation of multi-standard wireless transceivers. Main circuit strategies reported so far for multi-standard LNAs are reviewed and a novel flexible LNA intended for Beyond-3G RF hand-held terminals is presented. The proposed LNA circuit consists of a two-stage topology that combines inductive-source degeneration with PMOS-varactor based tuning network and a programmable load to adapt its performance to different standard specifications without penalizing the circuit noise and with a reduced number of inductors as compared to previous reported reconfigurable LNAs. The circuit has been designed in a 90-nm CMOS technology to cope with the requirements of the GSM, WCDMA, Bluetooth and WLAN (IEEE 802.11b-g) standards. Simulation results, including technology and packaging parasitics, demonstrate correct operation of the circuit for all the standards under study, featuring NF13.3dB and IIP3>10.9dBm, over a 1.85GHz-2.4GHz band, with an adaptive power consumption between 17mW and 22mW from a 1-V supply voltage. Preliminary experimental measurements are included, showing a correct reconfiguration operation within the operation band.

  18. Op-amp based low noise amplifier for magnetic particle spectroscopy

    Directory of Open Access Journals (Sweden)

    Malhotra Ankit

    2017-09-01

    Full Text Available Magnetic particle spectrometry (MPS is a novel technique used to measure the magnetization response of superparamagnetic iron oxide nanoparticles (SPIONs. Therefore, it is one of the most important tools for the characterization of the SPIONs for imaging modalities such as magnetic particle imaging (MPI and Magnetic Resonance Imaging (MRI. In MPS, change in the particle magnetization induces a voltage in a dedicated receive coil. The amplitude of the signal can be very low (ranging from a few nV to 100 μV depending upon the concentration of the nanoparticles. Hence, the received signal needs to be amplified with a low noise amplifier (LNA. LNA’s paramount task is to amplify the received signal while keeping the noise induced by its own circuitry minimum. In the current research, we purpose modeling, design, and development of a prototyped LNA for MPS. The designed prototype LNA is based on the parallelization technique of Op-amps. The prototyped LNA consists of 16 Op-amps in parallel and is manufactured on a printed circuit board (PCB, with a size of 110.38 mm × 59.46 mm and 234 components. The input noise of the amplifier is approx. 546 pV/√Hz with a noise figure (NF of approx. 1.4 dB with a receive coil termination. Furthermore, a comparison between the prototyped LNA and a commercially available amplifier is shown.

  19. Low-Gain, Low-Noise Integrated Neuronal Amplifier for Implantable Artifact-Reduction Recording System

    Directory of Open Access Journals (Sweden)

    Abdelhamid Benazzouz

    2013-09-01

    Full Text Available Brain neuroprostheses for neuromodulation are being designed to monitor the neural activity of the brain in the vicinity of the region being stimulated using a single macro-electrode. Using a single macro-electrode, recent neuromodulation studies show that recording systems with a low gain neuronal amplifier and successive amplifier stages can reduce or reject stimulation artifacts. These systems were made with off-the-shelf components that are not amendable for future implant design. A low-gain, low-noise integrated neuronal amplifier (NA with the capability of recording local field potentials (LFP and spike activity is presented. In vitro and in vivo characterizations of the tissue/electrode interface, with equivalent impedance as an electrical model for recording in the LFP band using macro-electrodes for rodents, contribute to the NA design constraints. The NA occupies 0.15 mm2 and dissipates 6.73 µW, and was fabricated using a 0.35 µm CMOS process. Test-bench validation indicates that the NA provides a mid-band gain of 20 dB and achieves a low input-referred noise of 4 µVRMS. Ability of the NA to perform spike recording in test-bench experiments is presented. Additionally, an awake and freely moving rodent setup was used to illustrate the integrated NA ability to record LFPs, paving the pathway for future implantable systems for neuromodulation.

  20. Tunable Balun Low-Noise Amplifier in 65nm CMOS Technology

    Directory of Open Access Journals (Sweden)

    J. Sturm

    2014-04-01

    Full Text Available The presented paper includes the design and implementation of a 65 nm CMOS low-noise amplifier (LNA based on inductive source degeneration. The amplifier is realized with an active balun enabling a single-ended input which is an important requirement for low-cost system on chip implementations. The LNA has a tunable bandpass characteristics from 4.7 GHz up to 5.6 GHz and a continuously tunable gain from 22 dB down to 0 dB, which enables the required flexibility for multi-standard, multi-band receiver architectures. The gain and band tuning is realized with an optimized tunable active resistor in parallel to a tunable L-C tank amplifier load. The amplifier achieves an IIP3 linearity of -8dBm and a noise figure of 2.7 dB at the highest gain and frequency setting with a low power consumption of 10 mW. The high flexibility of the proposed LNA structure together with the overall good performance makes it well suited for future multi-standard low-cost receiver front-ends.

  1. Design and Characterization of Low-noise Dewar for High-sensitivity SQUID Operation

    International Nuclear Information System (INIS)

    Yu, K. K.; Lee, Y. H.; Kim, K.; Kwon, H.; Kim, J. M.

    2010-01-01

    We have fabricated the low noise liquid helium(LHe) dewar with a different shape of thermal shield to apply the 64-channel SQUID(Superconducting Quantum Interference Device) gradiometer. The first shape of thermal shield was made of an aluminum plate with a wide width of 100 mm slit and the other shape was modified with a narrow width of 20 mm slit. The two types of dewars were estimated by comparing the thermal noise and the signal-to-noise ratio(SNR) of magnetocardiography(MCG) using the 1st order SQUID gradiometer system cooled each dewar. The white noise was different as a point of the dewar. The noise was increased as close as the edge of dewar, and also increased at the thermal shield with the more wide width slit. The white noise of the dewar with thermal shield of 100 mm slit was 6.5 fT/Hz 1/2 at the center of dewar and 25 fT/Hz 1/2 at the edge, and the white noise of the other one was 3.5 - 7 fT/Hz 1/2 . We measured the MCG using 64-channel SQUID gradiometer cooled at each LHe dewar and compared the SNR of MCG signal. The SNR was improved of 10 times at the LHe dewar with a modified thermal shield.

  2. The normalized interaural correlation : accounting for NoSp thresholds obtained with Gaussian and 'low-noise' masking noise

    NARCIS (Netherlands)

    Bernstein, L.R.; Par, van de S.L.J.D.E.; Trahiotis, C.T.

    1999-01-01

    Recently, [J. Acoust. Soc. Am. 103, 2578–2589 (1998)] and [J. Acoust. Soc. Am. 103, 2573–2577 (1998)] independently reported that greater masking of interaurally phase-reversed (Sp) tones was produced by diotic low-noise noise than by diotic Gaussian noise. Based on quantitative analyses, Eddins and

  3. Column-Parallel Single Slope ADC with Digital Correlated Multiple Sampling for Low Noise CMOS Image Sensors

    NARCIS (Netherlands)

    Chen, Y.; Theuwissen, A.J.P.; Chae, Y.

    2011-01-01

    This paper presents a low noise CMOS image sensor (CIS) using 10/12 bit configurable column-parallel single slope ADCs (SS-ADCs) and digital correlated multiple sampling (CMS). The sensor used is a conventional 4T active pixel with a pinned-photodiode as photon detector. The test sensor was

  4. Mutual information as a measure of reconstruction quality in 3D dynamic lung EIT

    International Nuclear Information System (INIS)

    Crabb, M G; Lionheart, W R B; Davidson, J L; Wright, P; McCann, H; Little, R; Naish, J H; Parker, G J M; Kikinis, R

    2013-01-01

    We report on a pilot study with healthy subjects who had an MR scan in addition to EIT data acquired with the Manchester fEITER system. The MR images are used to inform the external shape of a 3D EIT reconstruction model of the thorax, and small changes in the boundary that occur during respiration are addressed by incorporating the sensitivity with respect to boundary shape into a robust reconstruction algorithm. A quantitative comparison of the image quality for different EIT reconstructions is achieved through calculation of their mutual information with a segmented MR image. A shape corrected reconstruction algorithm reduces boundary artefacts relative to a standard reconstruction, and has a greater mutual information of approximately 4% with the segmented MR image.

  5. Drivers of drift sand dynamics; a reconstruction for the Wekeromse Zand, the Netherlands

    Science.gov (United States)

    Hendriks, Chantal; Sonneveld, Marthijn; Wallinga, Jakob

    2013-04-01

    Inland active drift sand landscapes are regarded as unique ecosystems of great historical and geomorphological value. Recent studies have highlighted the role of multiple factors in the initiation and stabilization of drift sand landscapes. To unravel the importance of different forcings (e.g. agricultural practices, climate) and their interplay, insight in the chronology of drift sand dynamics is essential. In this study, we aimed to reconstruct the dynamics of the drift sand landscape of the Wekeromse Zand (central Netherlands) and to develop a conceptual model to understand the processes involved. The Wekeromse Zand study area (370 ha) is located on the border of a central push moraine and is characterised by open active drift sands (14 ha) and vegetated hills and valleys. The surroundings are dominated by modern agricultural practices, and remnants from ancient iron age Celtic Field systems showing that the area has been in agricultural use since at least the Iron Age. For the study area we: i) analysed historical maps going back to the early 19th century, ii) performed a field survey to map the palaeolandscape (before drift sand activation) and iii) employed optically stimulated luminescence (OSL) dating of drift sand deposits on 11 samples from two locations to determine the timing of drift sand deposition. Analysis of the available topographic maps showed no substantial aeolean activity of the area outside its morphological boundaries. OSL dating revealed that two drift sand layers were deposited between 1373 and 1462 AD and between 1680 and 1780 AD. A layer with a higher organic matter content was found at one of the sites. This suggests that the Wekeromse Zand has known three relatively stable periods: i) a period between the start of the Holocene to the Late Medieval Period, ii) in between the Medieval climatic optimum and the climatic Maunder minimum, and iii) current situation. Despite the fact that agricultural activities occurred in this area from the

  6. Rapid manufacturing of low-noise membranes for nanopore sensors by trans-chip illumination lithography

    International Nuclear Information System (INIS)

    Janssen, Xander J A; Jonsson, Magnus P; Plesa, Calin; Soni, Gautam V; Dekker, Cees; Dekker, Nynke H

    2012-01-01

    In recent years, the concept of nanopore sensing has matured from a proof-of-principle method to a widespread, versatile technique for the study of biomolecular properties and interactions. While traditional nanopore devices based on a nanopore in a single layer membrane supported on a silicon chip can be rapidly fabricated using standard microfabrication methods, chips with additional insulating layers beyond the membrane region can provide significantly lower noise levels, but at the expense of requiring more costly and time-consuming fabrication steps. Here we present a novel fabrication protocol that overcomes this issue by enabling rapid and reproducible manufacturing of low-noise membranes for nanopore experiments. The fabrication protocol, termed trans-chip illumination lithography, is based on illuminating a membrane-containing wafer from its backside such that a photoresist (applied on the wafer’s top side) is exposed exclusively in the membrane regions. Trans-chip illumination lithography permits the local modification of membrane regions and hence the fabrication of nanopore chips containing locally patterned insulating layers. This is achieved while maintaining a well-defined area containing a single thin membrane for nanopore drilling. The trans-chip illumination lithography method achieves this without relying on separate masks, thereby eliminating time-consuming alignment steps as well as the need for a mask aligner. Using the presented approach, we demonstrate rapid and reproducible fabrication of nanopore chips that contain small (12 μm × 12 μm) free-standing silicon nitride membranes surrounded by insulating layers. The electrical noise characteristics of these nanopore chips are shown to be superior to those of simpler designs without insulating layers and comparable in quality to more complex designs that are more challenging to fabricate. (paper)

  7. Ultra-low-noise transition edge sensors for the SAFARI L-band on SPICA

    Science.gov (United States)

    Goldie, D. J.; Gao, J. R.; Glowacka, D. M.; Griffin, D. K.; Hijmering, R.; Khosropanah, P.; Jackson, B. D.; Mauskopf, P. D.; Morozov, D.; Murphy, J. A.; Ridder, M.; Trappe, N.; O'Sullivan, C.; Withington, S.

    2012-09-01

    The Far-Infrared Fourier transform spectrometer instrument SAFARI-SPICA which will operate with cooled optics in a low-background space environment requires ultra-sensitive detector arrays with high optical coupling efficiencies over extremely wide bandwidths. In earlier papers we described the design, fabrication and performance of ultra-low-noise Transition Edge Sensors (TESs) operated close to 100mk having dark Noise Equivalent Powers (NEPs) of order 4 × 10-19W/√Hz close to the phonon noise limit and an improvement of two orders of magnitude over TESs for ground-based applications. Here we describe the design, fabrication and testing of 388-element arrays of MoAu TESs integrated with far-infrared absorbers and optical coupling structures in a geometry appropriate for the SAFARI L-band (110 - 210 μm). The measured performance shows intrinsic response time τ ~ 11ms and saturation powers of order 10 fW, and a dark noise equivalent powers of order 7 × 10-19W/√Hz. The 100 × 100μm2 MoAu TESs have transition temperatures of order 110mK and are coupled to 320×320μm2 thin-film β-phase Ta absorbers to provide impedance matching to the incoming fields. We describe results of dark tests (i.e without optical power) to determine intrinsic pixel characteristics and their uniformity, and measurements of the optical performance of representative pixels operated with flat back-shorts coupled to pyramidal horn arrays. The measured and modeled optical efficiency is dominated by the 95Ω sheet resistance of the Ta absorbers, indicating a clear route to achieve the required performance in these ultra-sensitive detectors.

  8. Design of low noise airfoil with high aerodynamic performance for use on small wind turbines

    Institute of Scientific and Technical Information of China (English)

    Taehyung; KIM; Seungmin; LEE; Hogeon; KIM; Soogab; LEE

    2010-01-01

    Wind power is one of the most reliable renewable energy sources and internationally installed capacity is increasing radically every year.Although wind power has been favored by the public in general,the problem with the impact of wind turbine noise on people living in the vicinity of the turbines has been increased.Low noise wind turbine design is becoming more and more important as noise is spreading more adverse effect of wind turbine to public.This paper demonstrates the design of 10 kW class wind turbines,each of three blades,a rotor diameter 6.4 m,a rated rotating speed 200 r/min and a rated wind speed 10 m/s.The optimized airfoil is dedicated for the 75% spanwise position because the dominant source of a wind turbine blade is trailing edge noise from the outer 25% of the blade.Numerical computations are performed for incompressible flow and for Mach number at 0.145 and for Reynolds numbers at 1.02×106 with a lift performance,which is resistant to surface contamination and turbulence intensity.The objectives in the design process are to reduce noise emission,while sustaining high aerodynamic efficiency.Dominant broadband noise sources are predicted by semi-empirical formulas composed of the groundwork by Brooks et al.and Lowson associated with typical wind turbine operation conditions.During the airfoil redesign process,the aerodynamic performance is analyzed to reduce the wind turbine power loss.The results obtained from the design process show that the design method is capable of designing airfoils with reduced noise using a commercial 10 kW class wind turbine blade airfoil as a basis.Therefore,the new optimized airfoil showing 2.9 dB reductions of total sound pressure level(SPL) and higher aerodynamic performance are achieved.

  9. Seismic and resistivity anisotropy analysis at the Low-Noise Underground Laboratory (LSBB) of Rustrel (France)

    Science.gov (United States)

    Zeyen, H. J.; Bereš, J.; Gaffet, S.; Sénéchal, G.; Rousset, D.; Pessel, M.

    2011-12-01

    Many geological materials exhibit anisotropic behaviour. A limestone massif, especially if cracked with fractures and faults in a predominant orientation is expected to manifest seismic and electric resistivity anisotropy. Seismic velocity within air- or water-filled cracks is smaller than in the rock matrix. Therefore, the velocity parallel to fractures, controlled mainly by the rock matrix, is expected to be faster than perpendicular to the fractures, where waves have to cross fractures and rock matrix. Seismic and resistivity measurements were conducted in three underground galleries of the Low-Noise Underground Gallery (LSBB) in southern France forming a horse-shoe setting. The galleries are located inside a karstic limestone massif. Around 22500 first arrival travel-times were picked and different types of pole-pole and dipole-dipole resistivity measurement were carried out in parallel. Resistivities and velocities vary strongly with direction of observation. The direction of fast velocities is at right angle with the one of slow velocities, a typical sign for anisotropy. Observation of a system of subparallel fractures allows to approximate the actual rock anisotropy by a horizontal transverse isotropy model. The dataset was treated by different approaches, including simple cosine fit, inversion of average anisotropy parameters using a Monte-Carlo approach, isotropic and anisotropic tomography inversion. All of the above confirm the directions of fast and slow velocities (30°N and 120°N respectively) and an anisotropy of about 10%. Common measurements of seismic and resistivity data at different periods of the year will have the potential to determine quantitatively the fracture density and the free water content in this karst massif.

  10. Low noise 874 GHz receivers for the International Submillimetre Airborne Radiometer (ISMAR)

    Science.gov (United States)

    Hammar, A.; Sobis, P.; Drakinskiy, V.; Emrich, A.; Wadefalk, N.; Schleeh, J.; Stake, J.

    2018-05-01

    We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the International Submillimetre Airborne Radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 °C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 °C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials led to a reduction in noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24 W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%-9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5° and side lobe levels below -20 dB. Return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to 750-1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below -25 dB and are dominated by the external waveguide interface.

  11. Reconstruction of neuronal input through modeling single-neuron dynamics and computations

    International Nuclear Information System (INIS)

    Qin, Qing; Wang, Jiang; Yu, Haitao; Deng, Bin; Chan, Wai-lok

    2016-01-01

    Mathematical models provide a mathematical description of neuron activity, which can better understand and quantify neural computations and corresponding biophysical mechanisms evoked by stimulus. In this paper, based on the output spike train evoked by the acupuncture mechanical stimulus, we present two different levels of models to describe the input-output system to achieve the reconstruction of neuronal input. The reconstruction process is divided into two steps: First, considering the neuronal spiking event as a Gamma stochastic process. The scale parameter and the shape parameter of Gamma process are, respectively, defined as two spiking characteristics, which are estimated by a state-space method. Then, leaky integrate-and-fire (LIF) model is used to mimic the response system and the estimated spiking characteristics are transformed into two temporal input parameters of LIF model, through two conversion formulas. We test this reconstruction method by three different groups of simulation data. All three groups of estimates reconstruct input parameters with fairly high accuracy. We then use this reconstruction method to estimate the non-measurable acupuncture input parameters. Results show that under three different frequencies of acupuncture stimulus conditions, estimated input parameters have an obvious difference. The higher the frequency of the acupuncture stimulus is, the higher the accuracy of reconstruction is.

  12. Reconstruction of neuronal input through modeling single-neuron dynamics and computations

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Qing; Wang, Jiang; Yu, Haitao; Deng, Bin, E-mail: dengbin@tju.edu.cn; Chan, Wai-lok [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China)

    2016-06-15

    Mathematical models provide a mathematical description of neuron activity, which can better understand and quantify neural computations and corresponding biophysical mechanisms evoked by stimulus. In this paper, based on the output spike train evoked by the acupuncture mechanical stimulus, we present two different levels of models to describe the input-output system to achieve the reconstruction of neuronal input. The reconstruction process is divided into two steps: First, considering the neuronal spiking event as a Gamma stochastic process. The scale parameter and the shape parameter of Gamma process are, respectively, defined as two spiking characteristics, which are estimated by a state-space method. Then, leaky integrate-and-fire (LIF) model is used to mimic the response system and the estimated spiking characteristics are transformed into two temporal input parameters of LIF model, through two conversion formulas. We test this reconstruction method by three different groups of simulation data. All three groups of estimates reconstruct input parameters with fairly high accuracy. We then use this reconstruction method to estimate the non-measurable acupuncture input parameters. Results show that under three different frequencies of acupuncture stimulus conditions, estimated input parameters have an obvious difference. The higher the frequency of the acupuncture stimulus is, the higher the accuracy of reconstruction is.

  13. Dynamic knee stability and ballistic knee movement after ACL reconstruction: an application on instep soccer kick.

    Science.gov (United States)

    Cordeiro, Nuno; Cortes, Nelson; Fernandes, Orlando; Diniz, Ana; Pezarat-Correia, Pedro

    2015-04-01

    The instep soccer kick is a pre-programmed ballistic movement with a typical agonist-antagonist coordination pattern. The coordination pattern of the kick can provide insight into deficient neuromuscular control. The purpose of this study was to investigate knee kinematics and hamstrings/quadriceps coordination pattern during the knee ballistic extension phase of the instep kick in soccer players after anterior cruciate ligament reconstruction (ACL reconstruction). Seventeen players from the Portuguese Soccer League participated in this study. Eight ACL-reconstructed athletes (experimental group) and 9 healthy individuals (control group) performed three instep kicks. Knee kinematics (flexion and extension angles at football contact and maximum velocity instants) were calculated during the kicks. Rectus femoris (RF), vastus lateralis, vastus medialis, biceps femoralis, and semitendinosus muscle activations were quantified during the knee extension phase. The ACL-reconstructed group had significantly lower knee extension angle (-1.2 ± 1.6, p ballistic control movement pattern between normal and ACL-reconstructed subjects. Performing open kinetic chain exercises using ballistic movements can be beneficial when recovering from ACL reconstruction. The exercises should focus on achieving multi-joint coordination and full knee extension (range of motion). III.

  14. Exact reconstruction in 2D dynamic CT: compensation of time-dependent affine deformations

    International Nuclear Information System (INIS)

    Roux, Sebastien; Desbat, Laurent; Koenig, Anne; Grangeat, Pierre

    2004-01-01

    This work is dedicated to the reduction of reconstruction artefacts due to motion occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensation algorithms, where the model of motion is included in the reconstruction formula. We address two fundamental questions. First what conditions on the deformation are required for the reconstruction of the object from projections acquired sequentially during the deformation, and second how do we reconstruct the object from those projections. Here we answer these questions in the particular case of 2D general time-dependent affine deformations, assuming the motion parameters are known. We treat the problem of admissibility conditions on the deformation in the parallel-beam and fan-beam cases. Then we propose exact reconstruction methods based on rebinning or sequential FBP formulae for each of these geometries and present reconstructed images obtained with the fan-beam algorithm on simulated data

  15. Cardiac-gated parametric images from 82 Rb PET from dynamic frames and direct 4D reconstruction.

    Science.gov (United States)

    Germino, Mary; Carson, Richard E

    2018-02-01

    Cardiac perfusion PET data can be reconstructed as a dynamic sequence and kinetic modeling performed to quantify myocardial blood flow, or reconstructed as static gated images to quantify function. Parametric images from dynamic PET are conventionally not gated, to allow use of all events with lower noise. An alternative method for dynamic PET is to incorporate the kinetic model into the reconstruction algorithm itself, bypassing the generation of a time series of emission images and directly producing parametric images. So-called "direct reconstruction" can produce parametric images with lower noise than the conventional method because the noise distribution is more easily modeled in projection space than in image space. In this work, we develop direct reconstruction of cardiac-gated parametric images for 82 Rb PET with an extension of the Parametric Motion compensation OSEM List mode Algorithm for Resolution-recovery reconstruction for the one tissue model (PMOLAR-1T). PMOLAR-1T was extended to accommodate model terms to account for spillover from the left and right ventricles into the myocardium. The algorithm was evaluated on a 4D simulated 82 Rb dataset, including a perfusion defect, as well as a human 82 Rb list mode acquisition. The simulated list mode was subsampled into replicates, each with counts comparable to one gate of a gated acquisition. Parametric images were produced by the indirect (separate reconstructions and modeling) and direct methods for each of eight low-count and eight normal-count replicates of the simulated data, and each of eight cardiac gates for the human data. For the direct method, two initialization schemes were tested: uniform initialization, and initialization with the filtered iteration 1 result of the indirect method. For the human dataset, event-by-event respiratory motion compensation was included. The indirect and direct methods were compared for the simulated dataset in terms of bias and coefficient of variation as a

  16. Reconstructing populations dynamics: Mortality and recruitment of the southern geoduck Panopea abbreviata

    Science.gov (United States)

    Zaidman, Paula C.; Morsan, Enrique

    2018-05-01

    In the development of management measures for sustainable fisheries, estimating the natural mortality rate and recruitment are fundamental. In northern Patagonia, Argentina, the southern geoduck, Panopea abbreviata, a long-lived clam that forms spatially disjunct subpopulations, supports an unregulated fishery. In this study, we estimate natural mortality. We studied the age structure of beds within the northern Patagonia gulfs, San Matías Gulf (SMG) and San Jose Gulf (SJG), and we estimated a time series for back-reconstructed recruitment to explore spatial coherence in relation to local oceanographic conditions and to elucidate its population dynamics. We constructed a cumulative frequency distribution of the age of dead shells collected and used the exponential and Weibull models to model mortality. Live geoducks were sampled from six populations between 2000 and 2006. Age-frequency distributions and mortality models were used to back-calculate the time series of recruitment for each population. The recruitment time series was analysed using continuous wavelet transform. The value of natural mortality estimated by the exponential model was 0.054 years-1, whereas those estimated by the Weibull model were α = 0.00085 years-1 and β = 2.1. For the latter, M values for cohorts were 0.01 for 10 years, 0.02 for 20 years, 0.04 for 30 years and 0.05 for 40 years. The Weibull model was observed to be the best fit to the data. The natural mortality rate of P. abbreviata estimated in this study was lower than that estimated in a previous work for populations from SMG. The back-calculated time series for recruitment demonstrated considerable yearly variation, suggesting that local conditions have an important role in recruitment regulation. At a decadal temporal scale, a clear increasing recruitment trend was evident over the last 20 years in all populations. Populations in SMG were settled >60 years ago. In contrast, no individuals older than 30 years were observed in

  17. Input Stage for Low-Voltage, Low-Noise Preamplifiers Based on a Floating-Gate MOS Transistor

    DEFF Research Database (Denmark)

    Igor, Mucha

    1997-01-01

    A novel input stage for low-voltage, low-noise preamplifiers for integrated capacitive sensors is presented. The input stage of the preamplifier employs floating-gate MOS transistors which are capable of storing the operation point of the input stage over several years without any severe degradat......A novel input stage for low-voltage, low-noise preamplifiers for integrated capacitive sensors is presented. The input stage of the preamplifier employs floating-gate MOS transistors which are capable of storing the operation point of the input stage over several years without any severe...... degradation of the performance of the circuit and without the need for a repeating programming. In this way the noise originating from any resistance previously used for the definition of the operating point is avoided completely and, moreover, by avoiding the input high-pass filter both the saturation...

  18. Dynamic PET reconstruction using temporal patch-based low rank penalty for ROI-based brain kinetic analysis

    International Nuclear Information System (INIS)

    Kim, Kyungsang; Ye, Jong Chul; Son, Young Don; Cho, Zang Hee; Bresler, Yoram; Ra, Jong Beom

    2015-01-01

    Dynamic positron emission tomography (PET) is widely used to measure changes in the bio-distribution of radiopharmaceuticals within particular organs of interest over time. However, to retain sufficient temporal resolution, the number of photon counts in each time frame must be limited. Therefore, conventional reconstruction algorithms such as the ordered subset expectation maximization (OSEM) produce noisy reconstruction images, thus degrading the quality of the extracted time activity curves (TACs). To address this issue, many advanced reconstruction algorithms have been developed using various spatio-temporal regularizations. In this paper, we extend earlier results and develop a novel temporal regularization, which exploits the self-similarity of patches that are collected in dynamic images. The main contribution of this paper is to demonstrate that the correlation of patches can be exploited using a low-rank constraint that is insensitive to global intensity variations. The resulting optimization framework is, however, non-Lipschitz and non-convex due to the Poisson log-likelihood and low-rank penalty terms. Direct application of the conventional Poisson image deconvolution by an augmented Lagrangian (PIDAL) algorithm is, however, problematic due to its large memory requirements, which prevents its parallelization. Thus, we propose a novel optimization framework using the concave-convex procedure (CCCP) by exploiting the Legendre–Fenchel transform, which is computationally efficient and parallelizable. In computer simulation and a real in vivo experiment using a high-resolution research tomograph (HRRT) scanner, we confirm that the proposed algorithm can improve image quality while also extracting more accurate region of interests (ROI) based kinetic parameters. Furthermore, we show that the total reconstruction time for HRRT PET is significantly accelerated using our GPU implementation, which makes the algorithm very practical in clinical environments

  19. High reliability - low noise radionuclide signature identification algorithms for border security applications

    Science.gov (United States)

    Lee, Sangkyu

    Illicit trafficking and smuggling of radioactive materials and special nuclear materials (SNM) are considered as one of the most important recent global nuclear threats. Monitoring the transport and safety of radioisotopes and SNM are challenging due to their weak signals and easy shielding. Great efforts worldwide are focused at developing and improving the detection technologies and algorithms, for accurate and reliable detection of radioisotopes of interest in thus better securing the borders against nuclear threats. In general, radiation portal monitors enable detection of gamma and neutron emitting radioisotopes. Passive or active interrogation techniques, present and/or under the development, are all aimed at increasing accuracy, reliability, and in shortening the time of interrogation as well as the cost of the equipment. Equally important efforts are aimed at advancing algorithms to process the imaging data in an efficient manner providing reliable "readings" of the interiors of the examined volumes of various sizes, ranging from cargos to suitcases. The main objective of this thesis is to develop two synergistic algorithms with the goal to provide highly reliable - low noise identification of radioisotope signatures. These algorithms combine analysis of passive radioactive detection technique with active interrogation imaging techniques such as gamma radiography or muon tomography. One algorithm consists of gamma spectroscopy and cosmic muon tomography, and the other algorithm is based on gamma spectroscopy and gamma radiography. The purpose of fusing two detection methodologies per algorithm is to find both heavy-Z radioisotopes and shielding materials, since radionuclides can be identified with gamma spectroscopy, and shielding materials can be detected using muon tomography or gamma radiography. These combined algorithms are created and analyzed based on numerically generated images of various cargo sizes and materials. In summary, the three detection

  20. Integrated low noise low power interface for neural bio-potentials recording and conditioning

    Science.gov (United States)

    Bottino, Emanuele; Martinoia, Sergio; Valle, Maurizio

    2005-06-01

    The recent progress in both neurobiology and microelectronics suggests the creation of new, powerful tools to investigate the basic mechanisms of brain functionality. In particular, a lot of efforts are spent by scientific community to define new frameworks devoted to the analysis of in-vitro cultured neurons. One possible approach is recording their spiking activity to monitor the coordinated cellular behaviour and get insights about neural plasticity. Due to the nature of neurons action-potentials, when considering the design of an integrated microelectronic-based recording system, a number of problems arise. First, one would desire to have a high number of recording sites (i.e. several hundreds): this poses constraints on silicon area and power consumption. In this regard, our aim is to integrate-through on-chip post-processing techniques-hundreds of bio-compatible microsensors together with CMOS standard-process low-power (i.e. some tenths of uW per channel) conditioning electronics. Each recording channel is provided with sampling electronics to insure synchronous recording so that, for example, cross-correlation between signals coming from different sites can be performed. Extra-cellular potentials are in the range of [50-150] uV, so a comparison in terms of noise-efficiency was carried out among different architectures and very low-noise pre-amplification electronics (i.e. less than 5 uVrms) was designed. As spikes measurements are made with respect to the voltage of a reference electrode, we opted for an AC-coupled differential-input preamplifier provided with band-pass filtering capability. To achieve this, we implemented large time-constant (up to seconds) integrated components in the preamp feedback path. Thus, we got rid also of random slow-drifting DC-offsets and common mode signals. The paper will present our achievements in the design and implementation of a fully integrated bio-abio interface to record neural spiking activity. In particular

  1. A low-cost, ultra-fast and ultra-low noise preamplifier for silicon avalanche photodiodes

    Science.gov (United States)

    Gasmi, Khaled

    2018-02-01

    An ultra-fast and ultra-low noise preamplifier for amplifying the fast and weak electrical signals generated by silicon avalanche photodiodes has been designed and developed. It is characterized by its simplicity, compactness, reliability and low cost of construction. A very wide bandwidth of 300 MHz, a very good linearity from 1 kHz to 280 MHz, an ultra-low noise level at the input of only 1.7 nV Hz-1/2 and a very good stability are its key features. The compact size (70 mm  ×  90 mm) and light weight (45 g), as well as its excellent characteristics, make this preamplifier very competitive compared to any commercial preamplifier. The preamplifier, which is a main part of the detection system of a homemade laser remote sensing system, has been successfully tested. In addition, it is versatile and can be used in any optical detection system requiring high speed and very low noise electronics.

  2. Performance Assessment of Low-Noise Road Surfaces in the Leopoldo Project: Comparison and Validation of Different Measurement Methods

    Directory of Open Access Journals (Sweden)

    Gaetano Licitra

    2015-01-01

    Full Text Available In almost all urban contexts and in many extra-urban conurbations, where road traffic is the main noise pollution source, the use of barriers is not allowed. In these cases, low-noise road surfaces are the most used mitigation action together with traffic flow reduction. Selecting the optimal surface is only the first problem that the public administration has to face. In the second place, it has to consider the issue of assessing the efficacy of the mitigation action. The purpose of the LEOPOLDO project was to improve the knowledge in the design and the characterization of low-noise road surfaces, producing guidelines helpful to the public administrations. Several experimental road surfaces were tested. Moreover, several measurement methods were implemented aiming to select those that are suitable for a correct assessment of the pavement performances laid as mitigation planning. In this paper, the experience gained in the LEOPOLDO project will be described, focusing on both the measurement methods adopted to assess the performance of a low-noise road surface and the criteria by which the experimental results have to be evaluated, presenting a comparison of the obtained results and their monitoring along time.

  3. Noise Reduction Effect of Multiple-Sampling-Based Signal-Readout Circuits for Ultra-Low Noise CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Shoji Kawahito

    2016-11-01

    Full Text Available This paper discusses the noise reduction effect of multiple-sampling-based signal readout circuits for implementing ultra-low-noise image sensors. The correlated multiple sampling (CMS technique has recently become an important technology for high-gain column readout circuits in low-noise CMOS image sensors (CISs. This paper reveals how the column CMS circuits, together with a pixel having a high-conversion-gain charge detector and low-noise transistor, realizes deep sub-electron read noise levels based on the analysis of noise components in the signal readout chain from a pixel to the column analog-to-digital converter (ADC. The noise measurement results of experimental CISs are compared with the noise analysis and the effect of noise reduction to the sampling number is discussed at the deep sub-electron level. Images taken with three CMS gains of two, 16, and 128 show distinct advantage of image contrast for the gain of 128 (noise(median: 0.29 e−rms when compared with the CMS gain of two (2.4 e−rms, or 16 (1.1 e−rms.

  4. Hybrid spectral CT reconstruction.

    Directory of Open Access Journals (Sweden)

    Darin P Clark

    Full Text Available Current photon counting x-ray detector (PCD technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID. In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM. Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with

  5. Hybrid spectral CT reconstruction

    Science.gov (United States)

    Clark, Darin P.

    2017-01-01

    Current photon counting x-ray detector (PCD) technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID). In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM). Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with a spectral

  6. EEG source reconstruction reveals frontal-parietal dynamics of spatial conflict processing

    NARCIS (Netherlands)

    Cohen, M.X.; Ridderinkhof, K.R.

    2013-01-01

    Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict

  7. Managing the Dynamics of the Bologna Reforms: How Institutional Actors Re-Construct the Policy Framework

    Science.gov (United States)

    Veiga, Amélia; Neave, Guy

    2015-01-01

    How do the constituencies in higher education re-interpret Bologna's function with regard to the European Higher Education Area? This research examines how institutional actors re-construct the policy framework in the light of their own institutional agendas. Drawing on empirical data from a survey of academics, students and administrative and…

  8. Direct Patlak Reconstruction From Dynamic PET Data Using the Kernel Method With MRI Information Based on Structural Similarity.

    Science.gov (United States)

    Gong, Kuang; Cheng-Liao, Jinxiu; Wang, Guobao; Chen, Kevin T; Catana, Ciprian; Qi, Jinyi

    2018-04-01

    Positron emission tomography (PET) is a functional imaging modality widely used in oncology, cardiology, and neuroscience. It is highly sensitive, but suffers from relatively poor spatial resolution, as compared with anatomical imaging modalities, such as magnetic resonance imaging (MRI). With the recent development of combined PET/MR systems, we can improve the PET image quality by incorporating MR information into image reconstruction. Previously, kernel learning has been successfully embedded into static and dynamic PET image reconstruction using either PET temporal or MRI information. Here, we combine both PET temporal and MRI information adaptively to improve the quality of direct Patlak reconstruction. We examined different approaches to combine the PET and MRI information in kernel learning to address the issue of potential mismatches between MRI and PET signals. Computer simulations and hybrid real-patient data acquired on a simultaneous PET/MR scanner were used to evaluate the proposed methods. Results show that the method that combines PET temporal information and MRI spatial information adaptively based on the structure similarity index has the best performance in terms of noise reduction and resolution improvement.

  9. Evaluation of dynamic infrared thermography as an alternative to CT angiography for perforator mapping in breast reconstruction: a clinical study

    International Nuclear Information System (INIS)

    Weum, Sven; Mercer, James B.; Weerd, Louis de

    2016-01-01

    The current gold standard for preoperative perforator mapping in breast reconstruction with a DIEP flap is CT angiography (CTA). Dynamic infrared thermography (DIRT) is an imaging method that does not require ionizing radiation or contrast injection. We evaluated if DIRT could be an alternative to CTA in perforator mapping. Twenty-five patients scheduled for secondary breast reconstruction with a DIEP flap were included. Preoperatively, the lower abdomen was examined with hand-held Doppler, DIRT and CTA. Arterial Doppler sound locations were marked on the skin. DIRT examination involved rewarming of the abdominal skin after a mild cold challenge. The locations of hot spots on DIRT were compared with the arterial Doppler sound locations. The rate and pattern of rewarming of the hot spots were analyzed. Multiplanar CT reconstructions were used to see if hot spots were related to perforators on CTA. All flaps were based on the perforator selected with DIRT and the surgical outcome was analyzed. First appearing hot spots were always associated with arterial Doppler sounds and clearly visible perforators on CTA. The hot spots on DIRT images were always slightly laterally located in relation to the exit points of the associated perforators through the rectus abdominis fascia on CTA. Some periumbilical perforators were not associated with hot spots and showed communication with the superficial inferior epigastric vein on CTA. The selected perforators adequately perfused all flaps. This study confirms that perforators selected with DIRT have arterial Doppler sound, are clearly visible on CTA and provide adequate perfusion for DIEP breast reconstruction. Retrospectively registered at ClinicalTrials.gov with identifier NCT02806518

  10. Dynamic three-dimensional display of common congenital cardiac defects from reconstruction of two-dimensional echocardiographic images.

    Science.gov (United States)

    Hsieh, K S; Lin, C C; Liu, W S; Chen, F L

    1996-01-01

    Two-dimensional echocardiography had long been a standard diagnostic modality for congenital heart disease. Further attempts of three-dimensional reconstruction using two-dimensional echocardiographic images to visualize stereotypic structure of cardiac lesions have been successful only recently. So far only very few studies have been done to display three-dimensional anatomy of the heart through two-dimensional image acquisition because such complex procedures were involved. This study introduced a recently developed image acquisition and processing system for dynamic three-dimensional visualization of various congenital cardiac lesions. From December 1994 to April 1995, 35 cases were selected in the Echo Laboratory here from about 3000 Echo examinations completed. Each image was acquired on-line with specially designed high resolution image grazmber with EKG and respiratory gating technique. Off-line image processing using a window-architectured interactive software package includes construction of 2-D ehcocardiographic pixel to 3-D "voxel" with conversion of orthogonal to rotatory axial system, interpolation, extraction of region of interest, segmentation, shading and, finally, 3D rendering. Three-dimensional anatomy of various congenital cardiac defects was shown, including four cases with ventricular septal defects, two cases with atrial septal defects, and two cases with aortic stenosis. Dynamic reconstruction of a "beating heart" is recorded as vedio tape with video interface. The potential application of 3D display of the reconstruction from 2D echocardiographic images for the diagnosis of various congenital heart defects has been shown. The 3D display was able to improve the diagnostic ability of echocardiography, and clear-cut display of the various congenital cardiac defects and vavular stenosis could be demonstrated. Reinforcement of current techniques will expand future application of 3D display of conventional 2D images.

  11. Alluvial plain dynamics and human occupation in SW Amazonia during the Holocene: A paleosol-based reconstruction

    Science.gov (United States)

    Lombardo, Umberto; Rodrigues, Leonor; Veit, Heinz

    2018-01-01

    The present study reconstructs Holocene fluvial dynamics in the southern Amazonian foreland basin through the analysis of 36 stratigraphic profiles taken along a 300 km long transect across the Llanos de Moxos (LM), in the Bolivian Amazon. Based on 50 radiocarbon ages from paleosols intercalated with fluvial sediments, the most important changes in floodplain dynamics on a millennial scale are reconstructed and the links between pre-Columbian cultural processes and environmental change in the region explored. Results show that the frequency of river avulsions and crevasses, as inferred from the number and age of the cored paleosols, is stable from 8k cal. yrs BP to 4k cal. yrs BP and increases significantly from 4k to 2k cal. yrs BP, following the strengthening of el Niño/la Niña cycle and an increase in average precipitation. Fluvial activity then decreases and reaches its minimum after 2k cal BP. A comparison between the stratigraphic record and the archaeological record shows a match between periods of landscape stability in SW Amazonia (low river activity) and periods of pre-Columbian human occupation. The first Amazonians lived in the LM until 4k yrs. BP, when an abrupt increase in the frequency of river avulsions and crevasses forced the abandonment of the region. After two thousand years of archaeological hiatus, which matches the period of highest river activity in the region, agriculturists reoccupied the Bolivian Amazon.

  12. Joint reconstruction of dynamic PET activity and kinetic parametric images using total variation constrained dictionary sparse coding

    Science.gov (United States)

    Yu, Haiqing; Chen, Shuhang; Chen, Yunmei; Liu, Huafeng

    2017-05-01

    Dynamic positron emission tomography (PET) is capable of providing both spatial and temporal information of radio tracers in vivo. In this paper, we present a novel joint estimation framework to reconstruct temporal sequences of dynamic PET images and the coefficients characterizing the system impulse response function, from which the associated parametric images of the system macro parameters for tracer kinetics can be estimated. The proposed algorithm, which combines statistical data measurement and tracer kinetic models, integrates a dictionary sparse coding (DSC) into a total variational minimization based algorithm for simultaneous reconstruction of the activity distribution and parametric map from measured emission sinograms. DSC, based on the compartmental theory, provides biologically meaningful regularization, and total variation regularization is incorporated to provide edge-preserving guidance. We rely on techniques from minimization algorithms (the alternating direction method of multipliers) to first generate the estimated activity distributions with sub-optimal kinetic parameter estimates, and then recover the parametric maps given these activity estimates. These coupled iterative steps are repeated as necessary until convergence. Experiments with synthetic, Monte Carlo generated data, and real patient data have been conducted, and the results are very promising.

  13. EEG source reconstruction reveals frontal-parietal dynamics of spatial conflict processing

    OpenAIRE

    Cohen, M.X.; Ridderinkhof, K.R.

    2013-01-01

    Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict processing. Human subjects performed a Simon task, in which conflict was induced by incongruence between spatial location and response hand. We found an early (?200 ms post-stimulus) conflict modulation in ...

  14. Reconstructed streamflow for Citarum River, Java, Indonesia: linkages to tropical climate dynamics

    Energy Technology Data Exchange (ETDEWEB)

    D' Arrigo, Rosanne [Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Palisades, NY (United States); Abram, Nerilie [The Australian National University, Research School of Earth Sciences, Canberra (Australia); Natural Environment Research Council, British Antarctic Survey, Cambridge (United Kingdom); Ummenhofer, Caroline [University of New South Wales, Sydney, NSW (Australia); Palmer, Jonathan [Gondwana Tree-Ring Laboratory, Canterbury (New Zealand); Mudelsee, Manfred [Climate Risk Analysis, Hannover (Germany)

    2011-02-15

    The Citarum river basin of western Java, Indonesia, which supplies water to 10 million residents in Jakarta, has become increasingly vulnerable to anthropogenic change. Citarum's streamflow record, only {proportional_to}45 years in length (1963-present), is too short for understanding the full range of hydrometeorological variability in this important region. Here we present a tree-ring based reconstruction of September-November Citarum streamflow (AD 1759-2006), one of the first such records available for monsoon Asia. Close coupling is observed between decreased tree growth and low streamflow levels, which in turn are associated with drought caused by ENSO warm events in the tropical Pacific and Indian Ocean positive dipole-type variability. Over the full length of record, reconstructed variance was at its weakest during the interval from {proportional_to}1905-1960, overlapping with a period of unusually-low variability (1920-1960) in the ENSO-Indian Ocean dipole systems. In subsequent decades, increased variance in both the streamflow anomalies and a coral-based SST reconstruction of the Indian Ocean Dipole Mode signal the potential for intensified drought activity and related consequences for water supply and crop productivity in western Java, where much of the country's rice is grown. (orig.)

  15. Reconstructed streamflow for Citarum River, Java, Indonesia: linkages to tropical climate dynamics

    Science.gov (United States)

    D'Arrigo, Rosanne; Abram, Nerilie; Ummenhofer, Caroline; Palmer, Jonathan; Mudelsee, Manfred

    2011-02-01

    The Citarum river basin of western Java, Indonesia, which supplies water to 10 million residents in Jakarta, has become increasingly vulnerable to anthropogenic change. Citarum's streamflow record, only ~45 years in length (1963-present), is too short for understanding the full range of hydrometeorological variability in this important region. Here we present a tree-ring based reconstruction of September-November Citarum streamflow (AD 1759-2006), one of the first such records available for monsoon Asia. Close coupling is observed between decreased tree growth and low streamflow levels, which in turn are associated with drought caused by ENSO warm events in the tropical Pacific and Indian Ocean positive dipole-type variability. Over the full length of record, reconstructed variance was at its weakest during the interval from ~1905-1960, overlapping with a period of unusually-low variability (1920-1960) in the ENSO-Indian Ocean dipole systems. In subsequent decades, increased variance in both the streamflow anomalies and a coral-based SST reconstruction of the Indian Ocean Dipole Mode signal the potential for intensified drought activity and related consequences for water supply and crop productivity in western Java, where much of the country's rice is grown.

  16. A hybrid, broadband, low noise charge preamplifier for simultaneous high resolution energy and time information with large capacitance semiconductor detector

    International Nuclear Information System (INIS)

    Goyot, M.

    1975-05-01

    A broadband and low noise charge preamplifier was developed in hybrid form, for a recoil spectrometer requiring large capacitance semiconductor detectors. This new hybrid and low cost preamplifier permits good timing information without compromising energy resolution. With a 500 pF external input capacity, it provides two simultaneous outputs: (i) the faster, current sensitive, with a rise time of 9 nsec and 2 mV/MeV on 50 ohms load, (ii) the lower, charge sensitive, with an energy resolution of 14 keV (FWHM Si) using a RC-CR ungated filter of 2 μsec and a FET input protection [fr

  17. Simple, low-noise piezo driver with feed-forward for broad tuning of external cavity diode lasers.

    Science.gov (United States)

    Doret, S Charles

    2018-02-01

    We present an inexpensive, low-noise (piezo driver suitable for frequency tuning of external-cavity diode lasers. This simple driver improves upon many commercially available drivers by incorporating circuitry to produce a "feed-forward" signal appropriate for making simultaneous adjustments to the piezo voltage and laser current, enabling dramatic improvements in a mode-hop-free laser frequency tuning range. We present the theory behind our driver's operation, characterize its output noise, and demonstrate its use in absorption spectroscopy on the rubidium D 1 line.

  18. Ultra-Low Noise Vertical Takeoff and Landing, or Development of an Uber Self-Flying, Helipad-Capable, Quiet V-ESTOL Personal Transporter Integrated Flight Demonstrator

    Data.gov (United States)

    National Aeronautics and Space Administration — Several aspects of this research are completely unique compared to prior attempts to achieve low noise vertical lift solutions, and are an artifact of the incredible...

  19. Dynamic evaluation of pelvic floor reconstructive surgery using radiopaque meshes and three-dimensional helical CT

    Directory of Open Access Journals (Sweden)

    Paulo Palma

    2010-04-01

    Full Text Available PURPOSE: This prospective study was performed to achieve visualization of the reestablishment of anatomy after reconstructive surgery in the different pelvic compartments with non-absorbable radiopaque meshes, providing valuable anatomic information for surgeons implanting meshes. MATERIALS AND METHODS: A total of 30 female patients with stress urinary incontinence (SUI, anterior and posterior vaginal wall prolapse, or both underwent surgical repair using radiopaque meshes after written informed consent. Patients with SUI underwent five different surgeries. Patients with anterior vaginal prolapse underwent a procedure using a combined pre-pubic and transobturator mesh, and those with posterior vaginal prolapse underwent posterior slingplasty. Three-dimensional reconstruction using helical CT was performed four weeks postoperatively. RESULTS: In all cases, the mesh was clearly visualized. Transobturator slings were shown at the midurethra, and the anchoring tails perforated the obturator foramen at the safety region. Mini-slings were in the proper place, and computed angiography revealed that the anchoring system was away from the obturator vessels. In patients undergoing procedure for anterior vaginal prolapse, both pre-pubic armpit and obturator slings were clearly seen and the mesh was in the proper position, supporting the bladder base and occluding the distal part of the urogenital hiatus. Transcoccygeal sacropexy revealed indirectly a well-supported "neo rectovaginal fascia" and the anchoring tails at the level of ischial spines. CONCLUSION: Three-dimensional helical tomography images of the female pelvis using radiopaque meshes have a potential role in improving our understanding of pelvic floor reconstructive surgeries. These radiopaque meshes might be the basis of a new investigative methodology.

  20. A Prospective Analysis of Dynamic Loss of Breast Projection in Tissue Expander-Implant Reconstruction

    Directory of Open Access Journals (Sweden)

    Lauren M Mioton

    2015-05-01

    Full Text Available BackgroundBreast projection is a critical element of breast reconstruction aesthetics, but little has been published regarding breast projection as the firm expander is changed to a softer implant. Quantitative data representing this loss in projection may enhance patient education and improve our management of patient expectations.MethodsFemale patients who were undergoing immediate tissue-expander breast reconstruction with the senior author were enrolled in this prospective study. Three-dimensional camera software was used for all patient photographs and data analysis. Projection was calculated as the distance between the chest wall and the point of maximal projection of the breast form. Values were calculated for final tissue expander expansion and at varying intervals 3, 6, and 12 months after implant placement.ResultsFourteen breasts from 12 patients were included in the final analysis. Twelve of the 14 breasts had a loss of projection at three months following the implant placement or beyond. The percentage of projection lost in these 12 breasts ranged from 6.30% to 43.4%, with an average loss of projection of 21.05%.ConclusionsThis study is the first prospective quantitative analysis of temporal changes in breast projection after expander-implant reconstruction. By prospectively capturing projection data with three-dimensional photographic software, we reveal a loss of projection in this population by three months post-implant exchange. These findings will not only aid in managing patient expectations, but our methodology provides a foundation for future objective studies of the breast form.

  1. Progress towards the use of publicly available data networks to conduct cross-scale historical reconstructions of carbon dynamics in US Drylands

    Science.gov (United States)

    Washington-Allen, R. A.; Landolt, K.; Emanuel, R. E.; Therrell, M. D.; Nagle, N.; Grissino-Mayer, H. D.; Poulter, B.

    2016-12-01

    Emergent scale properties of water-limited or Dryland ecosystem's carbon flux are unknown at spatial scales from local to global and time scales of 10 - 1000 years or greater. The width of a tree ring is a metric of production that has been correlated with the amount of precipitation. This relationship has been used to reconstruct rainfall and fire histories in the Drylands of the southwestern US. The normalized difference vegetation index (NDVI) is globally measured by selected satellite sensors and is highly correlated with the fraction of solar radiation which is absorbed for photosynthesis by plants (FPAR), as well as with vegetation biomass, net primary productivity (NPP), and tree ring width. Publicly available web-based archives of free NDVI and tree ring data exist and have allowed historical temporal reconstructions of carbon dynamics for the past 300 to 500 years. Climate and tree ring databases have been used to spatially reconstruct drought dynamics for the last 500 years in the western US. In 2007, we hypothesized that NDVI and tree ring width could be used to spatially reconstruct carbon dynamics in US Drylands. In 2015, we succeeded with a 300-year historical spatial reconstruction of NPP in California using a Blue Oak tree ring chronology. Online eddy covariance flux tower measures of NPP are well correlated with satellite measures of NPP. This suggests that net ecosystem exchange (NEE = NPP - soil Respiration) could be historically reconstructed across Drylands. Ongoing research includes 1) scaling historical spatial reconstruction to US Drylands, 2) comparing the use of single versus multiple tree ring species (r2 = 68) and 3) use of the eddy flux tower network, remote sensing, and tree ring data to historically spatially reconstruct Dryland NEE.

  2. Spatio-temporal reconstruction of brain dynamics from EEG with a Markov prior

    DEFF Research Database (Denmark)

    Hansen, Sofie Therese; Hansen, Lars Kai

    2016-01-01

    the functional dynamics of the brain. Solving the inverse problem of EEG is however highly ill-posed as there are many more potential locations of the EEG generators than EEG measurement points. Several well-known properties of brain dynamics can be exploited to alleviate this problem. More short ranging......Electroencephalography (EEG) can capture brain dynamics in high temporal resolution. By projecting the scalp EEG signal back to its origin in the brain also high spatial resolution can be achieved. Source localized EEG therefore has potential to be a very powerful tool for understanding...

  3. Eulerian velocity reconstruction in ideal atmospheric dynamics using potential vorticity and potential temperature

    Science.gov (United States)

    Blender, R.

    2009-04-01

    An approach for the reconstruction of atmospheric flow is presented which uses space- and time-dependent fields of density ?, potential vorticity Q and potential temperature Î& cedil;[J. Phys. A, 38, 6419 (2005)]. The method is based on the fundamental equations without approximation. The basic idea is to consider the time-dependent continuity equation as a condition for zero divergence of momentum in four dimensions (time and space, with unit velocity in time). This continuity equation is solved by an ansatz for the four-dimensional momentum using three conserved stream functions, the potential vorticity, potential temperature and a third field, denoted as ?-potential. In zonal flows, the ?-potential identifies the initial longitude of particles, whereas potential vorticity and potential temperature identify mainly meridional and vertical positions. Since the Lagrangian tracers Q, Î&,cedil; and ? determine the Eulerian velocity field, the reconstruction combines the Eulerian and the Lagrangian view of hydrodynamics. In stationary flows, the ?-potential is related to the Bernoulli function. The approach requires that the gradients of the potential vorticity and potential temperature do not vanish when the velocity remains finite. This behavior indicates a possible interrelation with stability conditions. Examples with analytical solutions are presented for a Rossby wave and zonal and rotational shear flows.

  4. Design and Measurement of a Low-Noise 64-Channels Front-End Readout ASIC for CdZnTe Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Bo; Wei, Tingcun; Gao, Wu; Liu, Hui; Hu, Yann [School of Computer Science and Technology, Northwestern Polytechnical University, Xi' an (China)

    2015-07-01

    Cadmium zinc telluride (CdZnTe) detectors, as one of the principal detectors for the next-generation X-ray and γ-ray imagers, have high energy resolution and supporting electrode patterning in the radiation environment at room-temperature. In the present, a number of internationally renowned research institutions and universities are actively using these detector systems to carry out researches of energy spectrum analysis, medical imaging, materials characterization, high-energy physics, nuclear plant monitoring, and astrophysics. As the most important part of the readout system for the CdZnTe detector, the front-end readout application specific integrated circuit (ASIC) would have an important impact on the performances of the whole detector system. In order to ensure the small signal to noise ratio (SNR) and sufficient range of the output signal, it is necessary to design a front-end readout ASIC with very low noise and very high dynamic range. In addition, radiation hardness should be considered when the detectors are utilized in the space applications and high energy physics experiments. In this paper, we present measurements and performances of a novel multi-channel radiation-hardness low-noise front-end readout ASIC for CdZnTe detectors. The readout circuits in each channel consist of charge sensitive amplifier, leakage current compensation circuit (LCC), CR-RC shaper, S-K filter, inverse proportional amplifier, peak detect and hold circuit (PDH), discriminator and trigger logic, time sequence control circuit and driving buffer. All of 64 readout channels' outputs enter corresponding inputs of a 64 channel multiplexer. The output of the mux goes directly out of the chip via the output buffer. The 64-channel readout ASIC is implemented using the TSMC 0.35 μm mixed-signal CMOS technology. The die size of the prototype chip is 2.7 mm x 8 mm. At room temperature, the equivalent noise level of a typical channel reaches 66 e{sup -} (rms) at zero farad for a

  5. Toward VIP-PIX: A Low Noise Readout ASIC for Pixelated CdTe Gamma-Ray Detectors for Use in the Next Generation of PET Scanners.

    Science.gov (United States)

    Macias-Montero, Jose-Gabriel; Sarraj, Maher; Chmeissani, Mokhtar; Puigdengoles, Carles; Lorenzo, Gianluca De; Martínez, Ricardo

    2013-08-01

    VIP-PIX will be a low noise and low power pixel readout electronics with digital output for pixelated Cadmium Telluride (CdTe) detectors. The proposed pixel will be part of a 2D pixel-array detector for various types of nuclear medicine imaging devices such as positron-emission tomography (PET) scanners, Compton gamma cameras, and positron-emission mammography (PEM) scanners. Each pixel will include a SAR ADC that provides the energy deposited with 10-bit resolution. Simultaneously, the self-triggered pixel which will be connected to a global time-to-digital converter (TDC) with 1 ns resolution will provide the event's time stamp. The analog part of the readout chain and the ADC have been fabricated with TSMC 0.25 μ m mixed-signal CMOS technology and characterized with an external test pulse. The power consumption of these parts is 200 μ W from a 2.5 V supply. It offers 4 switchable gains from ±10 mV/fC to ±40 mV/fC and an input charge dynamic range of up to ±70 fC for the minimum gain for both polarities. Based on noise measurements, the expected equivalent noise charge (ENC) is 65 e - RMS at room temperature.

  6. A Low-Noise, Modular, and Versatile Analog Front-End Intended for Processing In Vitro Neuronal Signals Detected by Microelectrode Arrays

    Directory of Open Access Journals (Sweden)

    Giulia Regalia

    2015-01-01

    Full Text Available The collection of good quality extracellular neuronal spikes from neuronal cultures coupled to Microelectrode Arrays (MEAs is a binding requirement to gather reliable data. Due to physical constraints, low power requirement, or the need of customizability, commercial recording platforms are not fully adequate for the development of experimental setups integrating MEA technology with other equipment needed to perform experiments under climate controlled conditions, like environmental chambers or cell culture incubators. To address this issue, we developed a custom MEA interfacing system featuring low noise, low power, and the capability to be readily integrated inside an incubator-like environment. Two stages, a preamplifier and a filter amplifier, were designed, implemented on printed circuit boards, and tested. The system is characterized by a low input-referred noise (70 dB, and signal-to-noise ratio values of neuronal recordings comparable to those obtained with the benchmark commercial MEA system. In addition, the system was successfully integrated with an environmental MEA chamber, without harming cell cultures during experiments and without being damaged by the high humidity level. The devised system is of practical value in the development of in vitro platforms to study temporally extended neuronal network dynamics by means of MEAs.

  7. A Low Noise CMOS Readout Based on a Polymer-Coated SAW Array for Miniature Electronic Nose

    Directory of Open Access Journals (Sweden)

    Cheng-Chun Wu

    2016-10-01

    Full Text Available An electronic nose (E-Nose is one of the applications for surface acoustic wave (SAW sensors. In this paper, we present a low-noise complementary metal–oxide–semiconductor (CMOS readout application-specific integrated circuit (ASIC based on an SAW sensor array for achieving a miniature E-Nose. The center frequency of the SAW sensors was measured to be approximately 114 MHz. Because of interference between the sensors, we designed a low-noise CMOS frequency readout circuit to enable the SAW sensor to obtain frequency variation. The proposed circuit was fabricated in Taiwan Semiconductor Manufacturing Company (TSMC 0.18 μm 1P6M CMOS process technology. The total chip size was nearly 1203 × 1203 μm2. The chip was operated at a supply voltage of 1 V for a digital circuit and 1.8 V for an analog circuit. The least measurable difference between frequencies was 4 Hz. The detection limit of the system, when estimated using methanol and ethanol, was 0.1 ppm. Their linearity was in the range of 0.1 to 26,000 ppm. The power consumption levels of the analog and digital circuits were 1.742 mW and 761 μW, respectively.

  8. A 55 nm CMOS ΔΣ fractional-N frequency synthesizer for WLAN transceivers with low noise filters

    International Nuclear Information System (INIS)

    Chen Mingyi; Chu Xiaojie; Yu Peng; Yan Jun; Shi Yin

    2013-01-01

    A fully integrated ΔΣ fractional-N frequency synthesizer fabricated in a 55 nm CMOS technology is presented for the application of IEEE 802.11b/g wireless local area network (WLAN) transceivers. A low noise filter, occupying a small die area, whose power supply is given by a high PSRR and low noise LDO regulator, is integrated on chip. The proposed synthesizer needs no off-chip components and occupies an area of 0.72 mm 2 excluding PAD. Measurement results show that in all channels, the phase noise of the synthesizer achieves −99 dBc/Hz and −119 dBc/Hz in band and out of band respectively with a reference frequency of 40 MHz and a loop bandwidth of 200 kHz. The integrated RMS phase error is no more than 0.6°. The proposed synthesizer consumes a total power of 15.6 mW. (semiconductor integrated circuits)

  9. Dynamic re-weighted total variation technique and statistic Iterative reconstruction method for x-ray CT metal artifact reduction

    Science.gov (United States)

    Peng, Chengtao; Qiu, Bensheng; Zhang, Cheng; Ma, Changyu; Yuan, Gang; Li, Ming

    2017-07-01

    Over the years, the X-ray computed tomography (CT) has been successfully used in clinical diagnosis. However, when the body of the patient to be examined contains metal objects, the image reconstructed would be polluted by severe metal artifacts, which affect the doctor's diagnosis of disease. In this work, we proposed a dynamic re-weighted total variation (DRWTV) technique combined with the statistic iterative reconstruction (SIR) method to reduce the artifacts. The DRWTV method is based on the total variation (TV) and re-weighted total variation (RWTV) techniques, but it provides a sparser representation than TV and protects the tissue details better than RWTV. Besides, the DRWTV can suppress the artifacts and noise, and the SIR convergence speed is also accelerated. The performance of the algorithm is tested on both simulated phantom dataset and clinical dataset, which are the teeth phantom with two metal implants and the skull with three metal implants, respectively. The proposed algorithm (SIR-DRWTV) is compared with two traditional iterative algorithms, which are SIR and SIR constrained by RWTV regulation (SIR-RWTV). The results show that the proposed algorithm has the best performance in reducing metal artifacts and protecting tissue details.

  10. An improved wavelet-Galerkin method for dynamic response reconstruction and parameter identification of shear-type frames

    Science.gov (United States)

    Bu, Haifeng; Wang, Dansheng; Zhou, Pin; Zhu, Hongping

    2018-04-01

    An improved wavelet-Galerkin (IWG) method based on the Daubechies wavelet is proposed for reconstructing the dynamic responses of shear structures. The proposed method flexibly manages wavelet resolution level according to excitation, thereby avoiding the weakness of the wavelet-Galerkin multiresolution analysis (WGMA) method in terms of resolution and the requirement of external excitation. IWG is implemented by this work in certain case studies, involving single- and n-degree-of-freedom frame structures subjected to a determined discrete excitation. Results demonstrate that IWG performs better than WGMA in terms of accuracy and computation efficiency. Furthermore, a new method for parameter identification based on IWG and an optimization algorithm are also developed for shear frame structures, and a simultaneous identification of structural parameters and excitation is implemented. Numerical results demonstrate that the proposed identification method is effective for shear frame structures.

  11. Impact of time-of-flight on indirect 3D and direct 4D parametric image reconstruction in the presence of inconsistent dynamic PET data

    Science.gov (United States)

    Kotasidis, F. A.; Mehranian, A.; Zaidi, H.

    2016-05-01

    Kinetic parameter estimation in dynamic PET suffers from reduced accuracy and precision when parametric maps are estimated using kinetic modelling following image reconstruction of the dynamic data. Direct approaches to parameter estimation attempt to directly estimate the kinetic parameters from the measured dynamic data within a unified framework. Such image reconstruction methods have been shown to generate parametric maps of improved precision and accuracy in dynamic PET. However, due to the interleaving between the tomographic and kinetic modelling steps, any tomographic or kinetic modelling errors in certain regions or frames, tend to spatially or temporally propagate. This results in biased kinetic parameters and thus limits the benefits of such direct methods. Kinetic modelling errors originate from the inability to construct a common single kinetic model for the entire field-of-view, and such errors in erroneously modelled regions could spatially propagate. Adaptive models have been used within 4D image reconstruction to mitigate the problem, though they are complex and difficult to optimize. Tomographic errors in dynamic imaging on the other hand, can originate from involuntary patient motion between dynamic frames, as well as from emission/transmission mismatch. Motion correction schemes can be used, however, if residual errors exist or motion correction is not included in the study protocol, errors in the affected dynamic frames could potentially propagate either temporally, to other frames during the kinetic modelling step or spatially, during the tomographic step. In this work, we demonstrate a new strategy to minimize such error propagation in direct 4D image reconstruction, focusing on the tomographic step rather than the kinetic modelling step, by incorporating time-of-flight (TOF) within a direct 4D reconstruction framework. Using ever improving TOF resolutions (580 ps, 440 ps, 300 ps and 160 ps), we demonstrate that direct 4D TOF image

  12. A dynamic evolutionary clustering perspective: Community detection in signed networks by reconstructing neighbor sets

    Science.gov (United States)

    Chen, Jianrui; Wang, Hua; Wang, Lina; Liu, Weiwei

    2016-04-01

    Community detection in social networks has been intensively studied in recent years. In this paper, a novel similarity measurement is defined according to social balance theory for signed networks. Inter-community positive links are found and deleted due to their low similarity. The positive neighbor sets are reconstructed by this method. Then, differential equations are proposed to imitate the constantly changing states of nodes. Each node will update its state based on the difference between its state and average state of its positive neighbors. Nodes in the same community will evolve together with time and nodes in the different communities will evolve far away. Communities are detected ultimately when states of nodes are stable. Experiments on real world and synthetic networks are implemented to verify detection performance. The thorough comparisons demonstrate the presented method is more efficient than two acknowledged better algorithms.

  13. Improving High-Throughput Sequencing Approaches for Reconstructing the Evolutionary Dynamics of Upper Paleolithic Human Groups

    DEFF Research Database (Denmark)

    Seguin-Orlando, Andaine

    the development and testing of innovative molecular approaches aiming at improving the amount of informative HTS data one can recover from ancient DNA extracts. We have characterized important ligation and amplification biases in the sequencing library building and enrichment steps, which can impede further...... been mainly driven by the development of High-Throughput DNA Sequencing (HTS) technologies but also by the implementation of novel molecular tools tailored to the manipulation of ultra short and damaged DNA molecules. Our ability to retrieve traces of genetic material has tremendously improved, pushing......, that impact on the overall efficacy of the method. In a second part, we implemented some of these molecular tools to the processing of five Upper Paleolithic human samples from the Kostenki and Sunghir sites in Western Eurasia, in order to reconstruct the deep genomic history of European populations...

  14. Order reconstruction phenomena and temperature-driven dynamics in a 3D zenithally bistable device

    KAUST Repository

    Raisch, A.

    2014-07-01

    We model the zenithally bistable device (ZBD) in three dimensions (3D), within the Landau-de Gennes theory, and find three stable static states in 3D without an applied field: the vertically aligned nematic (VAN) state, the hybrid aligned nematic (HAN) state and a third, high-tilt state, which we call the THAN state, with an interior and a surface defect. We recover the order reconstruction (OR) phenomenon around the defects in the HAN and THAN states and the 3D THAN and HAN solutions exhibit stable biaxial cylinders connecting defects on opposite faces of the ZBD device. We demonstrate a two-way temperature-driven switching between high-tilt and low-tilt states through controlled heating and cooling procedures in two dimensions (2D), with no applied fields. © CopyrightEPLA, 2014.

  15. Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

    Science.gov (United States)

    Greenwood, Sarah L.; Clark, Chris D.

    2009-12-01

    The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid

  16. Free Energy Reconstruction from Logarithmic Mean-Force Dynamics Using Multiple Nonequilibrium Trajectories.

    Science.gov (United States)

    Morishita, Tetsuya; Yonezawa, Yasushige; Ito, Atsushi M

    2017-07-11

    Efficient and reliable estimation of the mean force (MF), the derivatives of the free energy with respect to a set of collective variables (CVs), has been a challenging problem because free energy differences are often computed by integrating the MF. Among various methods for computing free energy differences, logarithmic mean-force dynamics (LogMFD) [ Morishita et al., Phys. Rev. E 2012 , 85 , 066702 ] invokes the conservation law in classical mechanics to integrate the MF, which allows us to estimate the free energy profile along the CVs on-the-fly. Here, we present a method called parallel dynamics, which improves the estimation of the MF by employing multiple replicas of the system and is straightforwardly incorporated in LogMFD or a related method. In the parallel dynamics, the MF is evaluated by a nonequilibrium path-ensemble using the multiple replicas based on the Crooks-Jarzynski nonequilibrium work relation. Thanks to the Crooks relation, realizing full-equilibrium states is no longer mandatory for estimating the MF. Additionally, sampling in the hidden subspace orthogonal to the CV space is highly improved with appropriate weights for each metastable state (if any), which is hardly achievable by typical free energy computational methods. We illustrate how to implement parallel dynamics by combining it with LogMFD, which we call logarithmic parallel dynamics (LogPD). Biosystems of alanine dipeptide and adenylate kinase in explicit water are employed as benchmark systems to which LogPD is applied to demonstrate the effect of multiple replicas on the accuracy and efficiency in estimating the free energy profiles using parallel dynamics.

  17. Dynamic magnetic resonance imaging for assessment of minimally invasive pelvic floor reconstruction with polypropylene implant

    International Nuclear Information System (INIS)

    Siegmann, Katja C.; Reisenauer, Christl; Speck, Sina; Barth, Sonja; Kraemer, Bernhard; Claussen, Claus D.

    2011-01-01

    Introduction: The purpose of the study was to assess the usefulness of dynamic MRI in patients with pelvic organ prolapse after pelvic floor repair with polypropylene mesh. Materials and methods: Fifteen consecutive patients (mean age 66.5 years) who were scheduled for either anterior (n = 9) or posterior (n = 6) pelvic floor repair were prospectively evaluated by clinical assessment and dynamic MRI 1 day before and 3 months after surgery. MRI diagnoses and MRI measurements of relevant anatomical points at rest and on straining were analysed before and after surgery. Results: At follow-up assessment 93.3% of all patients were clinically cured. Dynamic MRI showed newly developed (n = 6) or increased (n = 6) pelvic organ prolapse in 80% (n = 12) of all patients 3 months after pelvic floor repair. Most of them (n = 11; 91.7%) affected the untreated pelvic floor compartment. On straining anatomical points of reference in the anterior pelvic floor compartment were significantly (p < 0.05) elevated after anterior repair and rectal bulging was significantly (p = 0.036) reduced after posterior pelvic floor repair. Conclusions: In this study dynamic MRI could verify the effective support of anterior and posterior pelvic floor structures by anterior and posterior polypropylene implant respectively. But dynamic MRI demonstrates if one compartment of the pelvic floor is repaired another compartment frequently (73.3%) develops dysfunction. These results did not correspond to clinical symptoms on short-term follow-up (3 months). Studies with long-term follow-up are necessary to prove if dynamic MRI can reliably identify clinically significant pelvic organ prolapse after pelvic floor repair before the onset of symptoms.

  18. An inverse dynamics model for the analysis, reconstruction and prediction of bipedal walking

    NARCIS (Netherlands)

    Koopman, Hubertus F.J.M.; Grootenboer, H.J.; de Jongh, Henk J.; Huijing, P.A.J.B.M.; de Vries, J.

    1995-01-01

    Walking is a constrained movement which may best be observed during the double stance phase when both feet contact the floor. When analyzing a measured movement with an inverse dynamics model, a violation of these constrains will always occur due to measuring errors and deviations of the segments

  19. Towards reconstructing herbaceous biome dynamics and associated precipitation in Africa: insights from the classification of grass morphological traits

    Science.gov (United States)

    Pasturel, Marine; Alexandre, Anne; Novello, Alice; Moctar Dieye, Amadou; Wele, Abdoulaye; Paradis, Laure; Hely, Christelle

    2014-05-01

    proxies will be quantified in order to reconstruct the past dynamics of herbaceous ecosystems and associated mean annual precipitation domains.

  20. Pain following double-bundle anterior cruciate ligament reconstruction: Correlation with morphological graft findings and dynamic contrast-enhanced MRI

    International Nuclear Information System (INIS)

    Lin, Y.-C.; Mhuircheartaigh, J.N.; Cheung, Y.-C.; Juan, Y.-H.; Chiu, C.-H.; Yeh, W.-L.; Wu, J.S.

    2014-01-01

    Aim: To determine the relationship between knee pain following anterior cruciate ligament (ACL) graft placement with morphological graft findings and dynamic contrast enhancement as assessed at MRI. Material and methods: Following institutional review board approval, 37 consecutive patients with double-bundle ACL reconstruction were enrolled. Thirteen patients had pain and 24 were asymptomatic. Imaging was performed using a 1.5 T MRI machine an average of 7.6 months after surgery. Graft-related (increase signal intensity, abnormal orientation, discontinuity, cystic degeneration, anterior translation of lateral tibia, arthrofibrosis), and non-graft related causes of knee pain (meniscal tear, cartilage injury, loose bodies, and synovitis) were evaluated. During dynamic contrast enhancement analysis, peak enhancement (ePeak) was calculated by placing a region of interest at the osteoligamentous interface of each bundle. Student's t-test was used for continuous variables analysis and chi-square or Fisher's exact test was used for categorical variables analysis. Results: There was no difference between symptomatic and asymptomatic patients regarding morphological graft-related or non-graft-related causes of knee pain. For dynamic contrast enhancement analysis, symptomatic patients had significantly lower ePeak values than asymptomatic patients in the anteromedial (p = 0.008) and posterolateral (p = 0.001) bundles or when using the higher ePeak value in either bundle (p = 0.003). Conclusion: Morphological ACL graft findings as assessed at MRI could not be used to distinguish between symptomatic and asymptomatic patients. However, lower ePeak values had a significant association with knee pain. This may indicate poor neovascularization of the graft, potentially leading to graft failure. - Highlights: • Morphologic graft findings of MRI are poorly associated with knee pain. • Lower contrast enhancement values are significantly associated with knee pain

  1. Low-noise encoding of active touch by layer 4 in the somatosensory cortex.

    Science.gov (United States)

    Hires, Samuel Andrew; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-08-06

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.

  2. Dynamic surface self-reconstruction is the key of highly active perovskite nano-electrocatalysts for water splitting

    Science.gov (United States)

    Fabbri, Emiliana; Nachtegaal, Maarten; Binninger, Tobias; Cheng, Xi; Kim, Bae-Jung; Durst, Julien; Bozza, Francesco; Graule, Thomas; Schäublin, Robin; Wiles, Luke; Pertoso, Morgan; Danilovic, Nemanja; Ayers, Katherine E.; Schmidt, Thomas J.

    2017-09-01

    The growing need to store increasing amounts of renewable energy has recently triggered substantial R&D efforts towards efficient and stable water electrolysis technologies. The oxygen evolution reaction (OER) occurring at the electrolyser anode is central to the development of a clean, reliable and emission-free hydrogen economy. The development of robust and highly active anode materials for OER is therefore a great challenge and has been the main focus of research. Among potential candidates, perovskites have emerged as promising OER electrocatalysts. In this study, by combining a scalable cutting-edge synthesis method with time-resolved X-ray absorption spectroscopy measurements, we were able to capture the dynamic local electronic and geometric structure during realistic operando conditions for highly active OER perovskite nanocatalysts. Ba0.5Sr0.5Co0.8Fe0.2O3-δ as nano-powder displays unique features that allow a dynamic self-reconstruction of the material’s surface during OER, that is, the growth of a self-assembled metal oxy(hydroxide) active layer. Therefore, besides showing outstanding performance at both the laboratory and industrial scale, we provide a fundamental understanding of the operando OER mechanism for highly active perovskite catalysts. This understanding significantly differs from design principles based on ex situ characterization techniques.

  3. Demography of the Early Neolithic Population in Central Balkans: Population Dynamics Reconstruction Using Summed Radiocarbon Probability Distributions.

    Directory of Open Access Journals (Sweden)

    Marko Porčić

    Full Text Available The Central Balkans region is of great importance for understanding the spread of the Neolithic in Europe but the Early Neolithic population dynamics of the region is unknown. In this study we apply the method of summed calibrated probability distributions to a set of published radiocarbon dates from the Republic of Serbia in order to reconstruct population dynamics in the Early Neolithic in this part of the Central Balkans. The results indicate that there was a significant population growth after ~6200 calBC, when the Neolithic was introduced into the region, followed by a bust at the end of the Early Neolithic phase (~5400 calBC. These results are broadly consistent with the predictions of the Neolithic Demographic Transition theory and the patterns of population booms and busts detected in other regions of Europe. These results suggest that the cultural process that underlies the patterns observed in Central and Western Europe was also in operation in the Central Balkan Neolithic and that the population increase component of this process can be considered as an important factor for the spread of the Neolithic as envisioned in the demic diffusion hypothesis.

  4. Trend extraction of rail corrugation measured dynamically based on the relevant low-frequency principal components reconstruction

    International Nuclear Information System (INIS)

    Li, Yanfu; Liu, Hongli; Ma, Ziji

    2016-01-01

    Rail corrugation dynamic measurement techniques are critical to guarantee transport security and guide rail maintenance. During the inspection process, low-frequency trends caused by rail fluctuation are usually superimposed on rail corrugation and seriously affect the assessment of rail maintenance quality. In order to extract and remove the nonlinear and non-stationary trends from original mixed signals, a hybrid model based ensemble empirical mode decomposition (EEMD) and modified principal component analysis (MPCA) is proposed in this paper. Compared with the existing de-trending methods based on EMD, this method first considers low-frequency intrinsic mode functions (IMFs) thought to be underlying trend components that maybe contain some unrelated components, such as white noise and low-frequency signal itself, and proposes to use PCA to accurately extract the pure trends from the IMFs containing multiple components. On the other hand, due to the energy contribution ratio between trends and mixed signals is prior unknown, and the principal components (PCs) decomposed by PCA are arranged in order of energy reduction without considering frequency distribution, the proposed method modifies traditional PCA and just selects relevant low-frequency PCs to reconstruct the trends based on the zero-crossing numbers (ZCN) of each PC. Extensive tests are presented to illustrate the effectiveness of the proposed method. The results show the proposed EEMD-PCA-ZCN is an effective tool for trend extraction of rail corrugation measured dynamically. (paper)

  5. Low noise monolithic Si JFETs for operation in the 90-300K Range and in high radiation environments

    International Nuclear Information System (INIS)

    Radeka, V.; Citterio, M.; Rescia, S.; Manfredi, P.F.; Speziali, V.

    1994-12-01

    Development of low noise preamplifters for large ionization chambers with liquid argon (LAr) and liquid krypton (LKr) used in high energy physics experiments for measurement of energy of charged particles and photons requires die choice of a technology able to withstand the environment: a temperature of 90 K -120 K; an ionizing radiation dose of 1-2 Mrad; a neutron fluence of 0.5 -1.10 14 n/cm 2 . Silicon JFETs by virtue of their reliable noise behavior and their intrinsic radiation hardness appear to be very suitable devices for applications both at room and cryogenic temperatures. We describe the noise properties of JFET devices and a monolithic preamplifier suitable for amplification of charge and current signals

  6. A Discrete Component Low-Noise Preamplifier Readout for a Linear (1x16) SiC Photodiode Array

    Science.gov (United States)

    Kahle, Duncan; Aslam, Shahid; Herrero, Frederico A.; Waczynski, Augustyn

    2016-01-01

    A compact, low-noise and inexpensive preamplifier circuit has been designed and fabricated to optimally readout a common cathode (1x16) channel 4H-SiC Schottky photodiode array for use in ultraviolet experiments. The readout uses an operational amplifier with 10 pF capacitor in the feedback loop in parallel with a low leakage switch for each of the channels. This circuit configuration allows for reiterative sample, integrate and reset. A sampling technique is given to remove Johnson noise, enabling a femtoampere level readout noise performance. Commercial-off-the-shelf acquisition electronics are used to digitize the preamplifier analogue signals. The data logging acquisition electronics has a different integration circuit, which allows the bandwidth and gain to be independently adjusted. Using this readout, photoresponse measurements across the array between spectral wavelengths 200 nm and 370 nm are made to establish the array pixels external quantum efficiency, current responsivity and noise equivalent power.

  7. Hybrid and electric low-noise cars cause an increase in traffic accidents involving vulnerable road users in urban areas.

    Science.gov (United States)

    Brand, Stephan; Petri, Maximilian; Haas, Philipp; Krettek, Christian; Haasper, Carl

    2013-01-01

    Due to resource scarcity, the number of low-noise and electric cars is expected to increase rapidly. The frequent use of these cars will lead to a significant reduction of traffic related noise and pollution. On the other hand, due to the adaption and conditioning of vulnerable road users the number of traffic accidents involving pedestrians and bicyclists is postulated to increase as well. Children, older people with reduced eyesight and the blind are especially reliant on a combination of acoustic and visual warning signals with approaching or accelerating vehicles. This is even more evident in urban areas where the engine sound is the dominating sound up to 30 kph (kilometres per hour). Above this, tyre-road interaction is the main cause of traffic noise. With the missing typical engine sound a new sound design is necessary to prevent traffic accidents in urban areas. Drivers should not be able to switch the sound generator off.

  8. Design of a 1 _s real-time low-noise data acquisition for power converters control loop

    CERN Document Server

    AUTHOR|(SzGeCERN)712364; Arpaia, Pasquale; Cerqueira Bastos, Miguel; Martino, Michele

    2015-01-01

    The proof of principle of a real-time data acquisition system to be integrated into a digital control loop for controlling the power converters of the Compact LInear Collider is presented. The system is based on an ultra low noise analogue front-end with 1:1 ppm RMS noise (referred to input), and about 1 _s of real-time delay. After the analogue conditioning, a fully-differential analogue-todigital converter is foreseen. The requirements of this system, directly derived from the accelerator performance, are discussed and translated into design specification. The results obtained by means of Pspice simulations are reported in order to prove that the design is feasible with the proposed architecture. Finally, the results of the experimental validation of the prototype, currently under design, will be included in the final paper.

  9. Effect of drain current on appearance probability and amplitude of random telegraph noise in low-noise CMOS image sensors

    Science.gov (United States)

    Ichino, Shinya; Mawaki, Takezo; Teramoto, Akinobu; Kuroda, Rihito; Park, Hyeonwoo; Wakashima, Shunichi; Goto, Tetsuya; Suwa, Tomoyuki; Sugawa, Shigetoshi

    2018-04-01

    Random telegraph noise (RTN), which occurs in in-pixel source follower (SF) transistors, has become one of the most critical problems in high-sensitivity CMOS image sensors (CIS) because it is a limiting factor of dark random noise. In this paper, the behaviors of RTN toward changes in SF drain current conditions were analyzed using a low-noise array test circuit measurement system with a floor noise of 35 µV rms. In addition to statistical analysis by measuring a large number of transistors (18048 transistors), we also analyzed the behaviors of RTN parameters such as amplitude and time constants in the individual transistors. It is demonstrated that the appearance probability of RTN becomes small under a small drain current condition, although large-amplitude RTN tends to appear in a very small number of cells.

  10. A discrete component low-noise preamplifier readout for a linear (1×16) SiC photodiode array

    Energy Technology Data Exchange (ETDEWEB)

    Kahle, Duncan [NASA, Goddard Space Flight Center, Detector Systems Branch, Greenbelt, MD 20771 (United States); Aslam, Shahid, E-mail: shahid.aslam-1@nasa.gov [NASA, Goddard Space Flight Center, Planetary Systems Laboratory, Greenbelt, MD 20771 (United States); Herrero, Federico A.; Waczynski, Augustyn [NASA, Goddard Space Flight Center, Detector Systems Branch, Greenbelt, MD 20771 (United States)

    2016-09-11

    A compact, low-noise and inexpensive preamplifier circuit has been designed and fabricated to optimally readout a common cathode (1×16) channel 4H-SiC Schottky photodiode array for use in ultraviolet experiments. The readout uses an operational amplifier with 10 pF capacitor in the feedback loop in parallel with a low leakage switch for each of the channels. This circuit configuration allows for reiterative sample, integrate and reset. A sampling technique is given to remove Johnson noise, enabling a femtoampere level readout noise performance. Commercial-off-the-shelf acquisition electronics are used to digitize the preamplifier analog signals. The data logging acquisition electronics has a different integration circuit, which allows the bandwidth and gain to be independently adjusted. Using this readout, photoresponse measurements across the array between spectral wavelengths 200 nm and 370 nm are made to establish the array pixels external quantum efficiency, current responsivity and noise equivalent power.

  11. Regime Behavior in Paleo-Reconstructed Streamflow: Attributions to Atmospheric Dynamics, Synoptic Circulation and Large-Scale Climate Teleconnection Patterns

    Science.gov (United States)

    Ravindranath, A.; Devineni, N.

    2017-12-01

    Studies have shown that streamflow behavior and dynamics have a significant link with climate and climate variability. Patterns of persistent regime behavior from extended streamflow records in many watersheds justify investigating large-scale climate mechanisms as potential drivers of hydrologic regime behavior and streamflow variability. Understanding such streamflow-climate relationships is crucial to forecasting/simulation systems and the planning and management of water resources. In this study, hidden Markov models are used with reconstructed streamflow to detect regime-like behaviors - the hidden states - and state transition phenomena. Individual extreme events and their spatial variability across the basin are then verified with the identified states. Wavelet analysis is performed to examine the signals over time in the streamflow records. Joint analyses of the climatic data in the 20th century and the identified states are undertaken to better understand the hydroclimatic connections within the basin as well as important teleconnections that influence water supply. Compositing techniques are used to identify atmospheric circulation patterns associated with identified states of streamflow. The grouping of such synoptic patterns and their frequency are then examined. Sliding time-window correlation analysis and cross-wavelet spectral analysis are performed to establish the synchronicity of basin flows to the identified synoptic and teleconnection patterns. The Missouri River Basin (MRB) is examined in this study, both as a means of better understanding the synoptic climate controls in this important watershed and as a case study for the techniques developed here. Initial wavelet analyses of reconstructed streamflow at major gauges in the MRB show multidecadal cycles in regime behavior.

  12. The smartag framework for the dynamic reconstruction of adaptive web content

    OpenAIRE

    Belk, Mario

    2009-01-01

    Mass customization should be more than just configuring a specific component (hardware or software), but should be seen as the co-design of an entire system, including services, experiences and human satisfaction at the individual as well as at the community level. The main objective of this thesis is to implement and evaluate a dynamic Web-based framework, called smarTag, for achieving mass customization on the Web based on human factors. SmarTag is an easy to use framework that enables any ...

  13. A Fully Reconfigurable Low-Noise Biopotential Sensing Amplifier With 1.96 Noise Efficiency Factor.

    Science.gov (United States)

    Tzu-Yun Wang; Min-Rui Lai; Twigg, Christopher M; Sheng-Yu Peng

    2014-06-01

    A fully reconfigurable biopotential sensing amplifier utilizing floating-gate transistors is presented in this paper. By using the complementary differential pairs along with the current reuse technique, the theoretical limit for the noise efficiency factor of the proposed amplifier is below 1.5. Without consuming any extra power, floating-gate transistors are employed to program the low-frequency cutoff corner of the amplifier and to implement the common-mode feedback. A concept proving prototype chip was designed and fabricated in a 0.35 μm CMOS process occupying 0.17 mm (2) silicon area. With a supply voltage of 2.5 V, the measured midband gain is 40.7 dB and the measured input-referred noise is 2.8 μVrms. The chip was tested under several configurations with the amplifier bandwidth being programmed to 100 Hz, 1 kHz , and 10 kHz. The measured noise efficiency factors in these bandwidth settings are 1.96, 2.01, and 2.25, respectively, which are among the best numbers reported to date. The measured common-mode rejection and the supply rejection are above 70 dB . When the bandwidth is configured to be 10 kHz, the dynamic range measured at 1 kHz is 60 dB with total harmonic distortion less than 0.1%. The proposed amplifier is also demonstrated by recording electromyography (EMG), electrocardiography (ECG), electrooculography (EOG), and electroencephalography (EEG) signals from human bodies.

  14. Reconstructing a Network of Stress-Response Regulators via Dynamic System Modeling of Gene Regulation

    Directory of Open Access Journals (Sweden)

    Wei-Sheng Wu

    2008-01-01

    Full Text Available Unicellular organisms such as yeasts have evolved mechanisms to respond to environmental stresses by rapidly reorganizing the gene expression program. Although many stress-response genes in yeast have been discovered by DNA microarrays, the stress-response transcription factors (TFs that regulate these stress-response genes remain to be investigated. In this study, we use a dynamic system model of gene regulation to describe the mechanism of how TFs may control a gene’s expression. Then, based on the dynamic system model, we develop the Stress Regulator Identification Algorithm (SRIA to identify stress-response TFs for six kinds of stresses. We identified some general stress-response TFs that respond to various stresses and some specific stress-response TFs that respond to one specifi c stress. The biological significance of our findings is validated by the literature. We found that a small number of TFs is probably suffi cient to control a wide variety of expression patterns in yeast under different stresses. Two implications can be inferred from this observation. First, the response mechanisms to different stresses may have a bow-tie structure. Second, there may be regulatory cross-talks among different stress responses. In conclusion, this study proposes a network of stress-response regulators and the details of their actions.

  15. Responsiveness of Static and Dynamic Postural Balance Measures in Patients with Anterior Cruciate Ligament Reconstruction Following Physiotherapy Intervention

    Directory of Open Access Journals (Sweden)

    Neda Mostafaee

    2017-05-01

    Full Text Available Background:The main goal of physiotherapy for patients with anterior cruciate ligament reconstruction (ACL-R is to improve postural control and retain knee function. Therefore, clinicians need to use evaluative tools that assess postural changes during physiotherapy. To maximize the clinical utility of the results of these tools, the extracted measures should have appropriate psychometric properties of reliability, validity and responsiveness. No study has yet addressed responsiveness of postural measures in these patients. This study was designed to investigate the responsiveness and determine the minimal clinically important changes (MCIC of static and dynamic postural measures in patients with (ACL-R following physiotherapy. Methods: Static and dynamic postural measures were evaluated at first occasion and again after four weeks physiotherapy. The static measures consisted of center of pressure (COP parameters while dynamic measures included the stability indices. Correlation analysis and ROC curve were applied for assessing the responsiveness. Results:The meanand SD velocity of COP had acceptable responsiveness in both conditions of standing on injured leg with open-eyes and on uninjured leg with closed-eyes, both with nocognitive task. For dynamic measures, stability indices in double-leg standing with closed-eyes with cognitive task condition attained acceptable responsiveness. MCICs for mean and SD velocity in anteroposterior and mediolateral directions were 0.28cm/s, 0.008cm/s, 0.02cm/s, respectively in standing on injured leg with open-eyes; and 0.14cm/s, 0.07cm/s, 0.06cm/s, respectively in uninjured leg with closed-eyes condition. Also, MCICs for anteroposterior, mediolateral and total stability indices were 0.51◦, 0.37◦, 0.34◦, respectively in DCT condition. Conclusion:Our findings provide evidence for selection of appropriate static and dynamic postural measures for assessment of changes in these patients. MCICs for these

  16. Reconstruction of glacier variability from lake sediments reveals dynamic Holocene climate in Svalbard

    Science.gov (United States)

    van der Bilt, Willem G. M.; Bakke, Jostein; Vasskog, Kristian; D'Andrea, William J.; Bradley, Raymond S.; Ólafsdóttir, Sædis

    2015-10-01

    The Arctic is warming faster than anywhere else on Earth. Holocene proxy time-series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. However, available datasets are scarce, unevenly distributed and often of coarse resolution. Glaciers are sensitive recorders of climate shifts and variations in rock-flour production transfer this signal to the lacustrine sediment archives of downstream lakes. Here, we present the first full Holocene record of continuous glacier variability on Svalbard from glacier-fed Lake Hajeren. This reconstruction is based on an undisturbed lake sediment core that covers the entire Holocene and resolves variability on centennial scales owing to 26 dating points. A toolbox of physical, geochemical (XRF) and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record. Evidence from variations in sediment density, validated by changes in Ti concentrations, reveal glaciers remained present in the catchment following deglaciation prior to 11,300 cal BP, culminating in a Holocene maximum between 9.6 and 9.5 ka cal BP. Correspondence with freshwater pulses from Hudson Strait suggests that Early Holocene glacier advances were driven by the melting Laurentide Ice Sheet (LIS). We find that glaciers disappeared from the catchment between 7.4 and 6.7 ka cal BP, following a late Hypsithermal. Glacier reformation around 4250 cal BP marks the onset of the Neoglacial, supporting previous findings. Between 3380 and 3230 cal BP, we find evidence for a previously unreported centennial-scale glacier advance. Both events are concurrent with well-documented episodes of North Atlantic cooling. We argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling. These findings highlight the

  17. Reconstruction of annual carbon dynamics and balance for an oligotrophic pine fen

    Energy Technology Data Exchange (ETDEWEB)

    Alm, J; Silvola, J; Aaltonen, H [Joensuu Univ. (Finland). Dept. of Biology; Talanov, A; Ikkonen, E [Karelian Research Centre of Russian Academy of Sciences (Russian Federation). Inst. of Biology; Nykaenen, H; Martikainen, P J [National Public Health Inst. Kuopio (Finland). Dept. of Environmental Microbiology

    1997-12-31

    Atmospheric carbon dioxide (CO{sub 2}) is bound by mire vegetation in photosynthesis during the growing season, and is re-released by respiration of plants, soil animals and microorganisms consuming dead organic matter. A small proportion of annual primary production may fall below the water table to anoxic conditions and thus escapes the oxidative decomposition. Also from anoxic peat, carbon is released with clear seasonal and spatial variation as methane (CH{sub 4}.). The rate of carbon accumulation in peat depends on the annual inbalance of plant production and litter decomposition. Exchange of CO{sub 2} and CH{sub 4} between peat, vegetation and the atmosphere thus reflects the dynamics of carbon flows in the ecosystem. Net ecosystem CO{sub 2} exchange (PN), total CO{sub 2} release (RTOT) and CH{sub 4} release (D) from different treeless surfaces of low-sedge Sphagnum papillosum pine fen was studied in eastern Finland. (8 refs.)

  18. Reconstruction of annual carbon dynamics and balance for an oligotrophic pine fen

    Energy Technology Data Exchange (ETDEWEB)

    Alm, J.; Silvola, J.; Aaltonen, H. [Joensuu Univ. (Finland). Dept. of Biology; Talanov, A.; Ikkonen, E. [Karelian Research Centre of Russian Academy of Sciences (Russian Federation). Inst. of Biology; Nykaenen, H.; Martikainen, P.J. [National Public Health Inst. Kuopio (Finland). Dept. of Environmental Microbiology

    1996-12-31

    Atmospheric carbon dioxide (CO{sub 2}) is bound by mire vegetation in photosynthesis during the growing season, and is re-released by respiration of plants, soil animals and microorganisms consuming dead organic matter. A small proportion of annual primary production may fall below the water table to anoxic conditions and thus escapes the oxidative decomposition. Also from anoxic peat, carbon is released with clear seasonal and spatial variation as methane (CH{sub 4}.). The rate of carbon accumulation in peat depends on the annual inbalance of plant production and litter decomposition. Exchange of CO{sub 2} and CH{sub 4} between peat, vegetation and the atmosphere thus reflects the dynamics of carbon flows in the ecosystem. Net ecosystem CO{sub 2} exchange (PN), total CO{sub 2} release (RTOT) and CH{sub 4} release (D) from different treeless surfaces of low-sedge Sphagnum papillosum pine fen was studied in eastern Finland. (8 refs.)

  19. Multichannel monolithic front-end system design. Part II. Microwave bipolar-JFET process for low-noise charge-sensitive preamplifiers

    International Nuclear Information System (INIS)

    Baturitsky, M.A.; Reutovich, S.I.; Solomashenko, N.F.

    1996-01-01

    For pt. I see ibid., vol.378, p.564-569, 1996. New monolithic low-noise process has been developed for simultaneous fabrication of high-speed low-noise 4-terminal and 3-terminal pJFETs and microwave low-noise npn BJTs. A new ion-implanted 4-terminal structure of JFET having 300 MHz cut-off frequency is designed. The process provides direct contact to a top gate and independent access to the top and bottom gates. Application of p-channel implant makes it possible to optimize the JFET pinch-off voltage without deterioration of bipolar transistor characteristics: f T ≥3 GHz, current gain β≥150, R bb' ≤15-40 Ω. (orig.)

  20. Image-based reconstruction of the Newtonian dynamics of solar coronal ejecta

    Science.gov (United States)

    Uritsky, Vadim M.; Thompson, Barbara J.

    2016-10-01

    We present a new methodology for analyzing rising and falling dynamics of unstable coronal material as represented by high-cadence SDO AIA images. The technique involves an adaptive spatiotemporal tracking of propagating intensity gradients and their characterization in terms of time-evolving areas swept out by the position vector originated from the Sun disk center. The measured values of the areal velocity and acceleration are used to obtain quantitative information on the angular momentum and acceleration along the paths of the rising and falling coronal plasma. In the absence of other forces, solar gravitation results in purely ballistic motions consistent with the Kepler's second law; non-central forces such as the Lorentz force introduce non-zero torques resulting in more complex motions. The developed algorithms enable direct evaluation of the line-of-sight component of the net torque applied to a unit mass of the ejected coronal material which is proportional to the image-plane projection of the observed areal acceleration. The current implementation of the method cannot reliably distinguish torque modulations caused by the coronal force field from those imposed by abrupt changes of plasma mass density and nontrivial projection effects. However, it can provide valid observational constraints on the evolution of large-scale unstable magnetic topologies driving major solar-coronal eruptions as demonstrated in the related talk by B. Thompson et al.

  1. Variable disparity estimation based intermediate view reconstruction in dynamic flow allocation over EPON-based access networks

    Science.gov (United States)

    Bae, Kyung-Hoon; Lee, Jungjoon; Kim, Eun-Soo

    2008-06-01

    In this paper, a variable disparity estimation (VDE)-based intermediate view reconstruction (IVR) in dynamic flow allocation (DFA) over an Ethernet passive optical network (EPON)-based access network is proposed. In the proposed system, the stereoscopic images are estimated by a variable block-matching algorithm (VBMA), and they are transmitted to the receiver through DFA over EPON. This scheme improves a priority-based access network by converting it to a flow-based access network with a new access mechanism and scheduling algorithm, and then 16-view images are synthesized by the IVR using VDE. Some experimental results indicate that the proposed system improves the peak-signal-to-noise ratio (PSNR) to as high as 4.86 dB and reduces the processing time to 3.52 s. Additionally, the network service provider can provide upper limits of transmission delays by the flow. The modeling and simulation results, including mathematical analyses, from this scheme are also provided.

  2. CT urography in the urinary bladder: To compare excretory phase images using a low noise index and a high noise index with adaptive noise reduction filter

    International Nuclear Information System (INIS)

    Takeyama, Nobuyuki; Hayashi, Takaki; Ohgiya, Yoshimitsu

    2011-01-01

    Background: Although CT urography (CTU) is widely used for the evaluation of the entire urinary tract, the most important drawback is the radiation exposure. Purpose: To evaluate the effect of a noise reduction filter (NRF) using a phantom and to quantitatively and qualitatively compare excretory phase (EP) images using a low noise index (NI) with those using a high NI and postprocessing NRF (pNRF). Material and Methods: Each NI value was defined for a slice thickness of 5 mm, and reconstructed images with a slice thickness of 1.25 mm were assessed. Sixty patients who were at high risk of developing bladder tumors (BT) were divided into two groups according to whether their EP images were obtained using an NI of 9.88 (29 patients; group A) or an NI of 20 and pNRF (31 patients; group B). The CT dose index volume (CTDI vol ) and the contrast-to-noise ratio (CNR) of the bladder with respect to the anterior pelvic fat were compared in both groups. Qualitative assessment of the urinary bladder for image noise, sharpness, streak artifacts, homogeneity, and the conspicuity of polypoid or sessile-shaped BTs with a short-axis diameter greater than 10 mm was performed using a 3-point scale. Results: The phantom study showed noise reduction of approximately 40% and 76% dose reduction between group A and group B. CTDI vol demonstrated a 73% reduction in group B (4.6 ± 1.1 mGy) compared with group A (16.9 ± 3.4 mGy). The CNR value was not significantly different (P = 0.60) between group A (16.1 ± 5.1) and group B (16.6 ± 7.6). Although group A was superior (P < 0.01) to group B with regard to image noise, other qualitative analyses did not show significant differences. Conclusion: EP images using a high NI and pNRF were quantitatively and qualitatively comparable to those using a low NI, except with regard to image noise

  3. Reconstruction of the Greenland ice sheet dynamics in a fully coupled Earth System Model

    Science.gov (United States)

    Rybak, Oleg; Volodin, Evgeny; Huybrechts, Philippe

    2016-04-01

    Earth system models (ESMs) are undoubtedly effective tools for studying climate dynamics. Incorporation of evolving ice sheets to ESMs is a challenging task because response times of the climate system and of ice sheets differ by several orders of magnitude. Besides, AO GCMs operate on spatial and temporal resolutions substantially differing from those of ice sheet models (ICMs). Therefore elaboration of an effective coupling methodology of an AO GCM and an ICM is the key problem of an ESM construction and utilization. Several downscaling strategies of varying complexity exist now of data exchange between modeled climate system and ice sheets. Application of a particular strategy depends on the research objectives. In our view, the optimum approach for model studying of significant environmental changes (e.g. glacial/interglacial transitions) when ice sheets undergo substantial evolution of geometry and volume would be an asynchronous coupling. The latter allows simulation in the interactive way of growth and decay of ice sheets in the changing climatic conditions. In the focus of the presentation, is the overview of coupling aspects of an AO GCM INMCM32 elaborated in the Institute of Numerical Mathematics (Moscow, Russia) to the Greenland ice sheet model (GrISM, Vrije Uninersiteit Brussel, Belgium). To provide interactive coupling of INMCM32 (spatial resolution 5°×4°, 21 vertical layers and temporal resolution 6 min. in the atmospheric block) and GrISM (spatial resolution 20×20 km, 51 vertical layers and 1 yr temporal resolution), we employ a special energy- and water balance model (EWBM-G), which serves as a buffer providing effective data exchange between INMCM32 and GrISM. EWBM-G operates in a rectangle domain including Greenland. Transfer of daily meanings of simulated climatic variables (air surface temperature and specific humidity) is provided on the lateral boundarias of the domain and inside the domain (sea level air pressure, wind speed and total

  4. Reconstructing the Nd oceanic cycle using a coupled dynamical – biogeochemical model

    Directory of Open Access Journals (Sweden)

    T. Arsouze

    2009-12-01

    Full Text Available The decoupled behaviour observed between Nd isotopic composition (Nd IC, also referred as εNd and Nd concentration cycles has led to the notion of a "Nd paradox". While εNd behaves in a quasi-conservative way in the open ocean, leading to its broad use as a water-mass tracer, Nd concentration displays vertical profiles that increase with depth, together with a deep-water enrichment along the global thermohaline circulation. This non-conservative behaviour is typical of nutrients affected by scavenging in surface waters and remineralisation at depth. In addition, recent studies suggest the only way to reconcile both concentration and Nd IC oceanic budgets, is to invoke a "Boundary Exchange" process (BE, defined as the co-occurrence of transfer of elements from the margin to the sea with removal of elements from the sea by Boundary Scavenging as a source-sink term. However, these studies do not simulate the input/output fluxes of Nd to the ocean, and therefore prevents from crucial information that limits our understanding of Nd decoupling. To investigate this paradox on a global scale, this study uses for the first time a fully prognostic coupled dynamical/biogeochemical model with an explicit representation of Nd sources and sinks to simulate the Nd oceanic cycle. Sources considered include dissolved river fluxes, atmospheric dusts and margin sediment re-dissolution. Sinks are scavenging by settling particles. This model simulates the global features of the Nd oceanic cycle well, and produces a realistic distribution of Nd concentration (correct order of magnitude, increase with depth and along the conveyor belt, 65% of the simulated values fit in the ±10 pmol/kg envelop when compared to the data and isotopic composition (inter-basin gradient, characterization of the main water-masses, more than 70% of the simulated values fit in the ±3 εNd envelop when compared to the data, though a slight overestimation of

  5. Low noise SQUIDs

    Science.gov (United States)

    de Waal, V. J.

    1983-02-01

    The present investigation deals with the design, fabrication, and limitations of very sensitive SQUID (Superconducting Quantum Interference Device) magnetometers. The SQUID magnetometer is based on a utilization of the Josephson effect. A description of the theoretical background is provided, and high performance DC SQUIDs with submicron niobium Josephson junctions are discussed, taking into account design considerations, fabrication, junction characterization, the performance of the SQUID and input coil, and the gradiometer performance. The simulation and optimization of a DC SQUID with finite capacitance is considered, giving attention to the implementation of a simulation procedure on a hybrid computer.

  6. Low noise SQUIDs

    Energy Technology Data Exchange (ETDEWEB)

    De Waal, V.J.

    1983-01-01

    The present investigation deals with the design, fabrication, and limitations of very sensitive SQUID (Superconducting Quantum Interference Device) magnetometers. The SQUID magnetometer is based on a utilization of the Josephson effect. A description of the theoretical background is provided, and high performance DC SQUIDs with submicron niobium Josephson junctions are discussed, taking into account design considerations, fabrication, junction characterization, the performance of the SQUID and input coil, and the gradiometer performance. The simulation and optimization of a DC SQUID with finite capacitance is considered, giving attention to the implementation of a simulation procedure on a hybrid computer. 129 references.

  7. Low noise control valve

    International Nuclear Information System (INIS)

    Christie, R.S.

    1975-01-01

    Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included

  8. A Baseband Ultra-Low Noise SiGe:C BiCMOS 0.25 µm Amplifier And Its Application For An On-Chip Phase-Noise Measurement Circuit

    OpenAIRE

    Godet , Sylvain; Tournier , Éric; Llopis , Olivier; Cathelin , Andreia; Juyon , Julien

    2009-01-01

    4 pages; International audience; The design and realization of an ultra-low noise operational amplifier is presented. Its applications are integrated low-frequency noise measurements in electronic devices and on-chip phase-noise measurement circuit. This paper discusses the SiGe:C BiCMOS 0.25 µm design improvements used for low noise applications. The proposed three-stage operational amplifier uses parallel bipolar transistor connection as input differential pair for low noise behavior. This ...

  9. Design of low noise front-end ASIC and DAQ system for CdZnTe detector

    International Nuclear Information System (INIS)

    Luo Jie; Deng Zhi; Liu Yinong

    2012-01-01

    A low noise front-end ASIC has been designed for CdZnTe detector. This chip contains 16 channels and each channel consists of a dual-stage charge sensitive preamplifier, 4th order semi-Gaussian shaper, leakage current compensation (LCC) circuit, discriminator and output buffer. This chip has been fabricated in Chartered 0.35 μm CMOS process, the preliminary results show that it works well. The total channel charge gain can be adjusted from 100 mV/fC to 400 mV/fC and the peaking time can be adjusted from 1 μs to 4 μs. The minimum measured ENC at zero input capacitance is 70 e and minimum noise slope is 20 e/pF. The peak detector and derandomizer (PDD) ASIC developed by BNL and an associated USB DAQ board are also introduced in this paper. Two front-end ASICs can be connected to the PDD ASIC on the USB DAQ board and compose a 32 channels DAQ system for CdZnTe detector. (authors)

  10. Low-Noise Free-Running High-Rate Photon-Counting for Space Communication and Ranging

    Science.gov (United States)

    Lu, Wei; Krainak, Michael A.; Yang, Guan; Sun, Xiaoli; Merritt, Scott

    2016-01-01

    We present performance data for low-noise free-running high-rate photon counting method for space optical communication and ranging. NASA GSFC is testing the performance of two types of novel photon-counting detectors 1) a 2x8 mercury cadmium telluride (HgCdTe) avalanche array made by DRS Inc., and a 2) a commercial 2880-element silicon avalanche photodiode (APD) array. We successfully measured real-time communication performance using both the 2 detected-photon threshold and logic AND-gate coincidence methods. Use of these methods allows mitigation of dark count, after-pulsing and background noise effects without using other method of Time Gating The HgCdTe APD array routinely demonstrated very high photon detection efficiencies (50) at near infrared wavelength. The commercial silicon APD array exhibited a fast output with rise times of 300 ps and pulse widths of 600 ps. On-chip individually filtered signals from the entire array were multiplexed onto a single fast output. NASA GSFC has tested both detectors for their potential application for space communications and ranging. We developed and compare their performances using both the 2 detected photon threshold and coincidence methods.

  11. A GEM-TPC prototype with low-Noise highly integrated front-end electronics for linear collider studies

    CERN Document Server

    Kappler, Steffen; Kaminski, Jochen; Ledermann, Bernhard; Müller, Thomas; Ronan, Michael T; Ropelewski, Leszek; Sauli, Fabio; Settles, Ronald

    2004-01-01

    Connected to the linear collider project, studies on the readout of time projection chambers (TPCs) based on the gas electron multiplier (GEM) are ongoing. Higher granularity and intrinsically suppressed ion feedback are the major advantages of this technology. After a short discussion of these issues, we present the design of a small and very flexible TPC prototype, whose cylindrical drift volume can be equipped with endcaps of different gas detector types. An endcap with multi-GEM readout is currently set up and successfully operated with a low-noise highly integrated front-end electronics. We discuss results of measurements with this system in high intensity particle beams at CERN, where 99.3 plus or minus 0.2% single-pad-row efficiency could be achieved at an effective gain of 2.5 multiplied by 10**3 only, and spatial resolutions down to 63 plus or minus 3 mum could be demonstrated. Finally, these results are extrapolated to the high magnetic field in a linear collider TPC. 5 Refs.

  12. A high-efficiency, low-noise power solution for a dual-channel GNSS RF receiver

    International Nuclear Information System (INIS)

    Shi Jian; Mo Taishan; Gan Yebing; Ma Chengyan; Ye Tianchun; Le Jianlian

    2012-01-01

    A high-efficiency low-noise power solution for a dual-channel GNSS RF receiver is presented. The power solution involves a DC—DC buck converter and a followed low-dropout regulator (LDO). The pulse-width-modulation (PWM) control method is adopted for better noise performance. An improved low-power high-frequency PWM control circuit is proposed, which halves the average quiescent current of the buck converter to 80 μA by periodically shutting down the OTA. The size of the output stage has also been optimized to achieve high efficiency under a light load condition. In addition, a novel soft-start circuit based on a current limiter has been implemented to avoid inrush current. Fabricated with commercial 180-nm CMOS technology, the DC—DC converter achieves a peak efficiency of 93.1% under a 2 MHz working frequency. The whole receiver consumes only 20.2 mA from a 3.3 V power supply and has a noise figure of 2.5 dB. (semiconductor integrated circuits)

  13. An eight channel low-noise CMOS readout circuit for silicon detectors with on-chip front-end FET

    International Nuclear Information System (INIS)

    Fiorini, C.; Porro, M.

    2006-01-01

    We propose a CMOS readout circuit for the processing of signals from multi-channel silicon detectors to be used in X-ray spectroscopy and γ-ray imaging applications. The circuit is composed by eight channels, each one featuring a low-noise preamplifier, a 6th-order semigaussian shaping amplifier with four selectable peaking times, from 1.8 up to 6 μs, a peak stretcher and a discriminator. The circuit is conceived to be used with silicon detectors with a front-end FET integrated on the detector chips itself, like silicon drift detectors with JFET and pixel detectors with DEPMOS. The integrated time constants used for the shaping are implemented by means of an RC-cell, based on the technique of demagnification of the current flowing in a resistor R by means of the use of current mirrors. The eight analog channels of the chip are multiplexed to a single analog output. A suitable digital section provides self-resetting of each channel and trigger output and is able to set independent thresholds on the analog channels by means of a programmable serial register and 3-bit DACs. The circuit has been realized in the 0.35 μm CMOS AMS technology. In this work, the main features of the circuit are presented along with the experimental results of its characterization

  14. Wide-bandwidth electron bolometric mixers - A 2DEG prototype and potential for low-noise THz receivers

    Science.gov (United States)

    Yang, Jian-Xun; Agahi, Farid; Dai, Dong; Musante, Charles F.; Grammer, Wes; Lau, Kei M.; Yngvesson, K. S.

    1993-01-01

    This paper presents a new type of electron bolometric ('hot electron') mixer. We have demonstrated a 3 order-of-magnitude improvement in the bandwidth compared with previously known types of electron bolometric mixers, by using the two-dimensional electron gas (2DEG) medium at the heterointerface between AlGaAs and GaAs. We have tested both in-house MOCVD-grown material and MBE material, with similar results. The conversion loss (Lc) at 94 GHz is presently 18 dB for a mixer operating at 20 K, and calculations indicate that Lc can be decreased to about 10 dB in future devices. Calculated and measured curves of Lc versus P(LO), and I(DC), respectively, agree well. We argue that there are several different configurations of electron bolometric mixers, which will all show wide bandwidth, and that these devices are likely to become important as low-noise THz receivers in the future.

  15. Design and test results of a low-noise readout integrated circuit for high-energy particle detectors

    International Nuclear Information System (INIS)

    Zhang Mingming; Chen Zhongjian; Zhang Yacong; Lu Wengao; Ji Lijiu

    2010-01-01

    A low-noise readout integrated circuit for high-energy particle detector is presented. The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration. Continuous-time semi-Gaussian filter is chosen to avoid switch noise. The peaking time of pulse shaper and the gain can be programmed to satisfy multi-application. The readout integrated circuit has been designed and fabricated using a 0.35 μm double-poly triple-metal CMOS technology. Test results show the functions of the readout integrated circuit are correct. The equivalent noise charge with no detector connected is 500-700 e in the typical mode, the gain is tunable within 13-130 mV/fC and the peaking time varies from 0.7 to 1.6 μs, in which the average gain is about 20.5 mV/fC, and the linearity reaches 99.2%. (authors)

  16. Low noise signal-to-noise ratio enhancing readout circuit for current-mediated active pixel sensors

    International Nuclear Information System (INIS)

    Ottaviani, Tony; Karim, Karim S.; Nathan, Arokia; Rowlands, John A.

    2006-01-01

    Diagnostic digital fluoroscopic applications continuously expose patients to low doses of x-ray radiation, posing a challenge to both the digital imaging pixel and readout electronics when amplifying small signal x-ray inputs. Traditional switch-based amorphous silicon imaging solutions, for instance, have produced poor signal-to-noise ratios (SNRs) at low exposure levels owing to noise sources from the pixel readout circuitry. Current-mediated amorphous silicon pixels are an improvement over conventional pixel amplifiers with an enhanced SNR across the same low-exposure range, but whose output also becomes nonlinear with increasing dosage. A low-noise SNR enhancing readout circuit has been developed that enhances the charge gain of the current-mediated active pixel sensor (C-APS). The solution takes advantage of the current-mediated approach, primarily integrating the signal input at the desired frequency necessary for large-area imaging, while adding minimal noise to the signal readout. Experimental data indicates that the readout circuit can detect pixel outputs over a large bandwidth suitable for real-time digital diagnostic x-ray fluoroscopy. Results from hardware testing indicate that the minimum achievable C-APS output current that can be discerned at the digital fluoroscopic output from the enhanced SNR readout circuit is 0.341 nA. The results serve to highlight the applicability of amorphous silicon current-mediated pixel amplifiers for large-area flat panel x-ray imagers

  17. Ge/graded-SiGe multiplication layers for low-voltage and low-noise Ge avalanche photodiodes on Si

    Science.gov (United States)

    Miyasaka, Yuji; Hiraki, Tatsurou; Okazaki, Kota; Takeda, Kotaro; Tsuchizawa, Tai; Yamada, Koji; Wada, Kazumi; Ishikawa, Yasuhiko

    2016-04-01

    A new structure is examined for low-voltage and low-noise Ge-based avalanche photodiodes (APDs) on Si, where a Ge/graded-SiGe heterostructure is used as the multiplication layer of a separate-absorption-carrier-multiplication structure. The Ge/SiGe heterojunction multiplication layer is theoretically shown to be useful for preferentially enhancing impact ionization for photogenerated holes injected from the Ge optical-absorption layer via the graded SiGe, reflecting the valence band discontinuity at the Ge/SiGe interface. This property is effective not only for the reduction of operation voltage/electric field strength in Ge-based APDs but also for the reduction of excess noise resulting from the ratio of the ionization coefficients between electrons and holes being far from unity. Such Ge/graded-SiGe heterostructures are successfully fabricated by ultrahigh-vacuum chemical vapor deposition. Preliminary pin diodes having a Ge/graded-SiGe multiplication layer act reasonably as photodetectors, showing a multiplication gain larger than those for diodes without the Ge/SiGe heterojunction.

  18. Real-time dynamic MR image reconstruction using compressed sensing and principal component analysis (CS-PCA): Demonstration in lung tumor tracking.

    Science.gov (United States)

    Dietz, Bryson; Yip, Eugene; Yun, Jihyun; Fallone, B Gino; Wachowicz, Keith

    2017-08-01

    This work presents a real-time dynamic image reconstruction technique, which combines compressed sensing and principal component analysis (CS-PCA), to achieve real-time adaptive radiotherapy with the use of a linac-magnetic resonance imaging system. Six retrospective fully sampled dynamic data sets of patients diagnosed with non-small-cell lung cancer were used to investigate the CS-PCA algorithm. Using a database of fully sampled k-space, principal components (PC's) were calculated to aid in the reconstruction of undersampled images. Missing k-space data were calculated by projecting the current undersampled k-space data onto the PC's to generate the corresponding PC weights. The weighted PC's were summed together, and the missing k-space was iteratively updated. To gain insight into how the reconstruction might proceed at lower fields, 6× noise was added to the 3T data to investigate how the algorithm handles noisy data. Acceleration factors ranging from 2 to 10× were investigated using CS-PCA and Split Bregman CS for comparison. Metrics to determine the reconstruction quality included the normalized mean square error (NMSE), as well as the dice coefficients (DC) and centroid displacement of the tumor segmentations. Our results demonstrate that CS-PCA performed superior than CS alone. The CS-PCA patient averaged DC for 3T and 6× noise added data remained above 0.9 for acceleration factors up to 10×. The patient averaged NMSE gradually increased with increasing acceleration; however, it remained below 0.06 up to an acceleration factor of 10× for both 3T and 6× noise added data. The CS-PCA reconstruction speed ranged from 5 to 20 ms (Intel i7-4710HQ CPU @ 2.5 GHz), depending on the chosen parameters. A real-time reconstruction technique was developed for adaptive radiotherapy using a Linac-MRI system. Our CS-PCA algorithm can achieve tumor contours with DC greater than 0.9 and NMSE less than 0.06 at acceleration factors of up to, and including, 10×. The

  19. The silicon tracking system of the CBM experiment at FAIR. Development of microstrip sensors and signal transmission lines for a low-mass, low-noise system

    International Nuclear Information System (INIS)

    Singla, Minni

    2014-01-01

    In this thesis, different physical and electrical aspects of silicon microstrip sensors and low-mass multi-line readout cables have been investigated. These silicon microstrip sensors and readout cables will be used in the Silicon Tracking System (STS) of the fixed-target heavy-ion Compressed Baryonic Matter (CBM) experiment which is under development at the upcoming Facility for Antiproton and ion Research (FAIR) in Darmstadt, Germany. The highly segmented low-mass tracking system is a central CBM detector system to resolve the high tracking densities of charged particles originating from beam-target interactions. Considering the low material budget requirement the double-sided silicon microstrip detectors have been used in several planar tracking stations. The readout electronics is planned to be installed at the periphery of the tracking stations along with the cooling system. Low-mass multi-line readout cables shall bridge the distance between the microstrip sensors and the readout electronics. The CBM running operational scenario suggests that some parts of the tracking stations are expected to be exposed to a total integrated particle fluence of the order of 1 x 10 14 n eq /cm 2 . After 1 x 10 14 n eq /cm 2 the damaged modules in the tracking stations will be replaced. Thus radiation hard sensor is an important requirement for the sensors. Moreover, to cope with the high reaction rates, free-streaming (triggerless) readout electronics with online event reconstruction must be used which require high signal-to-noise (SNR) ratio (i.e., high signal efficiency, low noise contributions). Therefore, reduction in noise is a major goal of the sensor and cable development. For better insight into the different aspects of the silicon microstrip sensors and multi-line readout cables, the simulation study has been performed using SYNOPSYS TCAD tools. 3D models of the silicon microstrip sensors and the readout cables were implemented which is motivated by the stereoscopic

  20. Quantitative evaluation of the tibial tunnel after anterior cruciate ligament reconstruction using diffusion weighted and dynamic contrast enhanced MRI: a follow-up feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Rupreht, Mitja; Seruga, Tomaz; Jevsek, Marko [University Medical Centre Maribor, Radiology Department, Maribor (Slovenia); Jevtic, Vladimir [University of Ljubljana, Medical Faculty, Ljubljana (Slovenia); Sersa, Igor [Jozef Stefan Institute, MRI Laboratory, Ljubljana (Slovenia); Vogrin, Matjaz [University of Medical Centre of Maribor, Department of Orthopaedics, Maribor (Slovenia)

    2012-05-15

    The aim of the study was to evaluate the feasibility of two quantitative MRI methods: diffusion weighted imaging (DWI) and dynamic contrast enhanced imaging (DCEI), for follow-up assessment of the tibial tunnel after reconstruction of the anterior cruciate ligament (ACL). Twenty-three patients were examined by MRI at 1 and 6 months following ACL reconstruction. DWI and DCEI were utilized for evaluating the region of interest (ROI) within the proximal part of the tibial tunnel. From the resulting apparent diffusion coefficient (ADC) maps, ADC values were calculated. DCEI data were used to extract the enhancement factor (f{sub enh}) and the enhancement gradient (g{sub enh}) for the same ROI. Calculated ADC as well as the f{sub enh} and g{sub enh} had diminished to a statistically significant extent by 6 months after ACL reconstruction. The average ADC value diminished from 1.48 (10{sup -3} mm{sup 2}/s) at 1 month to 1.30 (10{sup -3} mm{sup 2}/s) at 6 months after reconstruction. The average f{sub enh} value decreased from 1.21 at 1 month to 0.50 at 6 months and the average g{sub enh} value decreased from 2.01%/s to 1.15%/s at 6 months, respectively. The study proved feasibility of DWI and DCEI for quantitative assessment of the tibial tunnel at 1 and 6 months after ACL reconstruction. Both methods have the potential for use as an additional tool in the evaluation of new methods of ACL reconstruction. To our knowledge, this is the first time quantitative MRI has been used in the follow-up to the ACL graft healing process. (orig.)

  1. Using a dynamical advection to reconstruct a part of the SSH evolution in the context of SWOT, application to the Mediterranean Sea

    Science.gov (United States)

    Rogé, Marine; Morrow, Rosemary; Ubelmann, Clément; Dibarboure, Gérald

    2017-08-01

    The main oceanographic objective of the future SWOT mission is to better characterize the ocean mesoscale and sub-mesoscale circulation, by observing a finer range of ocean topography dynamics down to 20 km wavelength. Despite the very high spatial resolution of the future satellite, it will not capture the time evolution of the shorter mesoscale signals, such as the formation and evolution of small eddies. SWOT will have an exact repeat cycle of 21 days, with near repeats around 5-10 days, depending on the latitude. Here, we investigate a technique to reconstruct the missing 2D SSH signal in the time between two satellite revisits. We use the dynamical interpolation (DI) technique developed by Ubelmann et al. (2015). Based on potential vorticity (hereafter PV) conservation using a one and a half layer quasi-geostrophic model, it features an active advection of the SSH field. This model has been tested in energetic open ocean regions such as the Gulf Stream and the Californian Current, and has given promising results. Here, we test this model in the Western Mediterranean Sea, a lower energy region with complex small scale physics, and compare the SSH reconstruction with the high-resolution Symphonie model. We investigate an extension of the simple dynamical model including a separated mean circulation. We find that the DI gives a 16-18% improvement in the reconstruction of the surface height and eddy kinetic energy fields, compared with a simple linear interpolation, and a 37% improvement in the Northern Current subregion. Reconstruction errors are higher during winter and autumn but statistically, the improvement from the DI is also better for these seasons.

  2. Design of low power common-gate low noise amplifier for 2.4 GHz wireless sensor network applications

    International Nuclear Information System (INIS)

    Zhang Meng; Li Zhiqun

    2012-01-01

    This paper presents a differential low power low noise amplifier designed for the wireless sensor network (WSN) in a TSMC 0.18 μm RF CMOS process. A two-stage cross-coupling cascaded common-gate (CG) topology has been designed as the amplifier. The first stage is a capacitive cross-coupling topology. It can reduce the power and noise simultaneously. The second stage is a positive feedback cross-coupling topology, used to set up a negative resistance to enhance the equivalent Q factor of the inductor at the load to improve the gain of the LNA. A differential inductor has been designed as the load to achieve reasonable gain. This inductor has been simulated by the means of momentum electromagnetic simulation in ADS. A 'π' circuit model has been built as the inductor model by iteration in ADS. The inductor has been fabricated separately to verify the model. The LNA has been fabricated and measured. The LNA works well centered at 2.44 GHz. The measured gain S 21 is variable with high gain at 16.8 dB and low gain at 1 dB. The NF (noise figure) at high gain mode is 3.6 dB, the input referenced 1 dB compression point (IP1dB) is about −8 dBm and the IIP3 is 2 dBm at low gain mode. The LNA consumes about 1.2 mA current from 1.8 V power supply.

  3. Ultra-low noise supercontinuum source for ultra-high resolution optical coherence tomography at 1300 nm

    Science.gov (United States)

    Gonzalo, I. B.; Maria, M.; Engelsholm, R. D.; Feuchter, T.; Leick, L.; Moselund, P. M.; Podoleanu, A.; Bang, O.

    2018-02-01

    Supercontinuum (SC) sources are of great interest for many applications due to their ultra-broad optical bandwidth, good beam quality and high power spectral density [1]. In particular, the high average power over large bandwidths makes SC light sources excellent candidates for ultra-high resolution optical coherence tomography (UHR-OCT) [2-5]. However, conventional SC sources suffer from high pulse-to-pulse intensity fluctuations as a result of the noise-sensitive nonlinear effects involved in the SC generation process [6-9]. This intensity noise from the SC source can limit the performance of OCT, resulting in a reduced signal-to-noise ratio (SNR) [10-12]. Much work has been done to reduce the noise of the SC sources for instance with fiber tapers [7,8] or increasing the repetition rate of the pump laser for averaging in the spectrometer [10,12]. An alternative approach is to use all-normal dispersion (ANDi) fibers [13,14] to generate SC light from well-known coherent nonlinear processes [15-17]. In fact, reduction of SC noise using ANDi fibers compared to anomalous dispersion SC pumped by sub-picosecond pulses has been recently demonstrated [18], but a cladding mode was used to stabilize the ANDi SC. In this work, we characterize the noise performance of a femtosecond pumped ANDi based SC and a commercial SC source in an UHR-OCT system at 1300 nm. We show that the ANDi based SC presents exceptional noise properties compared to a commercial source. An improvement of 5 dB in SNR is measured in the UHR-OCT system, and the noise behavior resembles that of a superluminiscent diode. This preliminary study is a step forward towards development of an ultra-low noise SC source at 1300 nm for ultra-high resolution OCT.

  4. SENSROC4: An Multichannel Low-Noise Front-End Readout ASIC Dedicated to CZT Detectors for PET Imaging

    International Nuclear Information System (INIS)

    Gao, W.; Liu, H.; Gao, D.; Gan, B.; Wei, T.; Hu, Y.

    2013-06-01

    In this paper, we present the design of a novel low-noise front-end readout application-specific integrated circuit (ASIC) for our small animal PET systems which objective is to achieve the following performances, the spatial resolution of 1 mm 3 , the detection efficiency of 15 % and the time resolution of 1 ns. A cascade amplifier based on the PMOS input transistor is selected to realize the charge-sensitive amplifier (CSA) for the sake of good noise performances. The output of the CSA is split into two branches. One is connected to a slow shaper for energy measurements. The other is connected to a fast shaper for time acquisition. A novel monostable circuit is designed to adjust the time delay of the trigger signals so that the peak value of the shaped voltages can be sampled and stored. Based on the above techniques, an eight-channel front-end readout prototype chip is designed and implemented in 0.35 μm CMOS process. The die size is 2.286 mm x 2.282 mm. The input range of the ASIC is from 2000 e- to 180000 e-, reflecting to the energy of the gamma ray from 11.2 keV to 1 MeV. The gain of the readout channel is 65 V/pC. The best test result of ENC is 86.5 e- at zero farad plus 9.3 e- per pico-farad. The nonlinearity is less than 3 %. The crosstalk is less than 2 %. The power dissipation is about 9 mW/channel (authors)

  5. A CMOS power-efficient low-noise current-mode front-end amplifier for neural signal recording.

    Science.gov (United States)

    Wu, Chung-Yu; Chen, Wei-Ming; Kuo, Liang-Ting

    2013-04-01

    In this paper, a new current-mode front-end amplifier (CMFEA) for neural signal recording systems is proposed. In the proposed CMFEA, a current-mode preamplifier with an active feedback loop operated at very low frequency is designed as the first gain stage to bypass any dc offset current generated by the electrode-tissue interface and to achieve a low high-pass cutoff frequency below 0.5 Hz. No reset signal or ultra-large pseudo resistor is required. The current-mode preamplifier has low dc operation current to enhance low-noise performance and decrease power consumption. A programmable current gain stage is adopted to provide adjustable gain for adaptive signal scaling. A following current-mode filter is designed to adjust the low-pass cutoff frequency for different neural signals. The proposed CMFEA is designed and fabricated in 0.18-μm CMOS technology and the area of the core circuit is 0.076 mm(2). The measured high-pass cutoff frequency is as low as 0.3 Hz and the low-pass cutoff frequency is adjustable from 1 kHz to 10 kHz. The measured maximum current gain is 55.9 dB. The measured input-referred current noise density is 153 fA /√Hz , and the power consumption is 13 μW at 1-V power supply. The fabricated CMFEA has been successfully applied to the animal test for recording the seizure ECoG of Long-Evan rats.

  6. A low noise single-transistor transimpedance preamplifier for Fourier-transform mass spectrometry using a T feedback network.

    Science.gov (United States)

    Lin, Tzu-Yung; Green, Roger J; O'Connor, Peter B

    2012-09-01

    A novel single-transistor transimpedance preamplifier has been introduced for improving performance in Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. A low noise junction field-effect transistor (JFET), BF862, is used as the main amplification stage of this trans-impedance preamplifier, and a T-shaped feedback network is introduced as both the feedback and the gate biasing solutions. The T feedback network has been studied using an operational amplifier (Op Amp), AD8099. Such a feedback system allows ~100-fold less feedback resistance at a given transimpedance, hence preserving bandwidth, which is beneficial to applications demanding high gain. The single-transistor preamplifier yields a tested transimpedance of ~10(4) Ω (80 dBΩ) in the frequency range between 1 kHz and 1 MHz (mass-to-charge ratio, m/z, of around 180-180k for a 12-T FT-ICR system), with a low power consumption of ~6 mW, which implies that this preamplifier is well suited to a 12-T FT-ICR mass spectrometer. In trading noise performance for higher trans-impedance, an alternative preamplifier design, an AD8099 preamplifier with the T feedback network, has also been studied with a capability of ~10(6) Ω (120 dBΩ) transimpedance in the same frequency range. The resistive components in the T feedback network reported here can be replaced by complex impedances, which allows adaptation of this feedback system to other frequency, transimpedance, and noise characteristics for applications not only in other mass spectrometers, such as Orbitrap, time-of-flight (TOF), and ion trap systems, but also in other charge/current detecting systems such as spectroscopy systems, microscopy systems, optical communication systems, or charge-coupled devices (CCDs).

  7. Medial Patellofemoral Ligament Reconstruction: Impact of Knee Flexion Angle During Graft Fixation on Dynamic Patellofemoral Contact Pressure-A Biomechanical Study.

    Science.gov (United States)

    Lorbach, Olaf; Zumbansen, Nikolaus; Kieb, Matthias; Efe, Turgay; Pizanis, Antonius; Kohn, Dieter; Haupert, Alexander

    2018-04-01

    Objective evaluation of the optimal graft tension angle to fully restore patellofemoral contact pressure in reconstruction of the medial patellofemoral ligament (MPFL) in comparison to the native knee. Twelve cadaveric knee specimens were fixed in a custom-made fixation device. A sensitive pressure film (Tekscan) was fixed in the patellofemoral joint, and patellofemoral contact pressure was assessed during a dynamic flexion movement from 0° to 90°. The MPFL was cut and measurements were repeated. Reconstruction of the MPFL was performed with the gracilis tendon subsequently fixed in the femur at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion under controlled tension (2 N). The sequence of the flexion angles was alternated. Pressure measurements were repeated after every fixation of the graft. No significant differences were seen in the overall patellofemoral contact pressure compared to the native knee (P > .05). However, medial patellofemoral pressure showed a significant increased patellofemoral contact pressure after MPFL reconstruction at a knee flexion angle during graft fixation of 15° (P = .027), 45° (P = .050, P = .044), and 75° (P = .039). Moreover, proximal/distal patellofemoral contact pressure revealed a significantly reduced contact pressure at 15° (P = .003), 30° (P = .009), 45° (P = .025), 75° (P = .021), and 90° (P = .022) of flexion distal after MPFL reconstruction compared with the intact knee. Lateral patellofemoral contact pressure was significantly reduced in all performed reconstructions (P angle during graft fixation for MPFL reconstruction did not have a significant impact on the overall patellofemoral contact pressure. However, selective medial, proximal, distal, and lateral patellofemoral contact pressure was significantly altered for all reconstructions. Fixation of the MPFL graft at 60° of flexion was able to most closely restore patellofemoral contact pressure compared with the intact knee. Based on the

  8. Influence of the partial volume correction method on (18)F-fluorodeoxyglucose brain kinetic modelling from dynamic PET images reconstructed with resolution model based OSEM.

    Science.gov (United States)

    Bowen, Spencer L; Byars, Larry G; Michel, Christian J; Chonde, Daniel B; Catana, Ciprian

    2013-10-21

    Kinetic parameters estimated from dynamic (18)F-fluorodeoxyglucose ((18)F-FDG) PET acquisitions have been used frequently to assess brain function in humans. Neglecting partial volume correction (PVC) for a dynamic series has been shown to produce significant bias in model estimates. Accurate PVC requires a space-variant model describing the reconstructed image spatial point spread function (PSF) that accounts for resolution limitations, including non-uniformities across the field of view due to the parallax effect. For ordered subsets expectation maximization (OSEM), image resolution convergence is local and influenced significantly by the number of iterations, the count density, and background-to-target ratio. As both count density and background-to-target values for a brain structure can change during a dynamic scan, the local image resolution may also concurrently vary. When PVC is applied post-reconstruction the kinetic parameter estimates may be biased when neglecting the frame-dependent resolution. We explored the influence of the PVC method and implementation on kinetic parameters estimated by fitting (18)F-FDG dynamic data acquired on a dedicated brain PET scanner and reconstructed with and without PSF modelling in the OSEM algorithm. The performance of several PVC algorithms was quantified with a phantom experiment, an anthropomorphic Monte Carlo simulation, and a patient scan. Using the last frame reconstructed image only for regional spread function (RSF) generation, as opposed to computing RSFs for each frame independently, and applying perturbation geometric transfer matrix PVC with PSF based OSEM produced the lowest magnitude bias kinetic parameter estimates in most instances, although at the cost of increased noise compared to the PVC methods utilizing conventional OSEM. Use of the last frame RSFs for PVC with no PSF modelling in the OSEM algorithm produced the lowest bias in cerebral metabolic rate of glucose estimates, although by less than 5% in

  9. A Dynamic Multi-Projection-Contour Approximating Framework for the 3D Reconstruction of Buildings by Super-Generalized Optical Stereo-Pairs.

    Science.gov (United States)

    Yan, Yiming; Su, Nan; Zhao, Chunhui; Wang, Liguo

    2017-09-19

    In this paper, a novel framework of the 3D reconstruction of buildings is proposed, focusing on remote sensing super-generalized stereo-pairs (SGSPs). As we all know, 3D reconstruction cannot be well performed using nonstandard stereo pairs, since reliable stereo matching could not be achieved when the image-pairs are collected at a great difference of views, and we always failed to obtain dense 3D points for regions of buildings, and cannot do further 3D shape reconstruction. We defined SGSPs as two or more optical images collected in less constrained views but covering the same buildings. It is even more difficult to reconstruct the 3D shape of a building by SGSPs using traditional frameworks. As a result, a dynamic multi-projection-contour approximating (DMPCA) framework was introduced for SGSP-based 3D reconstruction. The key idea is that we do an optimization to find a group of parameters of a simulated 3D model and use a binary feature-image that minimizes the total differences between projection-contours of the building in the SGSPs and that in the simulated 3D model. Then, the simulated 3D model, defined by the group of parameters, could approximate the actual 3D shape of the building. Certain parameterized 3D basic-unit-models of typical buildings were designed, and a simulated projection system was established to obtain a simulated projection-contour in different views. Moreover, the artificial bee colony algorithm was employed to solve the optimization. With SGSPs collected by the satellite and our unmanned aerial vehicle, the DMPCA framework was verified by a group of experiments, which demonstrated the reliability and advantages of this work.

  10. The robustness of two tomography reconstructing techniques with heavily noisy dynamical experimental data from a high speed gamma-ray tomograph

    International Nuclear Information System (INIS)

    Vasconcelos, Geovane Vitor; Melo, Silvio de Barros; Dantas, Carlos Costa; Moreira, Icaro Malta; Johansen, Geira; Maad, Rachid

    2013-01-01

    The PSIRT (Particle Systems Iterative Reconstructive Technique) is, just like the ART method, an iterative tomographic reconstruction technique with the recommended use in the reconstruction of catalytic density distribution in the refining process of oil in the FCC-type riser. The PSIRT is based upon computer graphics' particle systems, where the reconstructing material is initially represented as composed of particles subject to a force field emanating from the beams, whose intensities are parameterized by the differences between the experimental readings of a given beam trajectory, and the values corresponding to the current amount of particles landed in this trajectory. A dynamical process is set as the beams fields of attracting forces dispute the particles. At the end, with the equilibrium established, the particles are replaced by the corresponding regions of pixels. The High Speed Gamma-ray Tomograph is a 5-source-fan-beam device with a 17-detector deck per source, capable of producing up to a thousand complete sinograms per second. Around 70.000 experimental sinograms from this tomograph were produced simulating the move of gas bubbles in different angular speeds immersed in oil within the vessel, through the use of a two-hole-polypropylene phantom. The sinogram frames were set with several different detector integration times. This article studies and compares the robustness of both ART and PSIRT methods in this heavily noisy scenario, where this noise comes not only from limitations in the dynamical sampling, but also from to the underlying apparatus that produces the counting in the tomograph. These experiments suggest that PSIRT is a more robust method than ART for noisy data. Visual inspection on the resulting images suggests that PSIRT is a more robust method than ART for noisy data, since it almost never presents globally scattered noise. (author)

  11. S-band low noise amplifier and 40 kW high power amplifier subsystems of Japanese Deep Space Earth Station

    Science.gov (United States)

    Honma, K.; Handa, K.; Akinaga, W.; Doi, M.; Matsuzaki, O.

    This paper describes the design and the performance of the S-band low noise amplifier and the S-band high power amplifier that have been developed for the Usuda Deep Space Station of the Institute of Space and Astronautical Science (ISAS), Japan. The S-band low noise amplifier consists of a helium gas-cooled parametric amplifier followed by three-stage FET amplifiers and has a noise temperature of 8 K. The high power amplifier is composed of two 28 kW klystrons, capable of transmitting 40 kW continuously when two klystrons are combined. Both subsystems are operating quite satisfactorily in the tracking of Sakigake and Suisei, the Japanese interplanetary probes for Halley's comet exploration, launched by ISAS in 1985.

  12. Versatile quantitative phase imaging system applied to high-speed, low noise and multimodal imaging (Conference Presentation)

    Science.gov (United States)

    Federici, Antoine; Aknoun, Sherazade; Savatier, Julien; Wattellier, Benoit F.

    2017-02-01

    Quadriwave lateral shearing interferometry (QWLSI) is a well-established quantitative phase imaging (QPI) technique based on the analysis of interference patterns of four diffraction orders by an optical grating set in front of an array detector [1]. As a QPI modality, this is a non-invasive imaging technique which allow to measure the optical path difference (OPD) of semi-transparent samples. We present a system enabling QWLSI with high-performance sCMOS cameras [2] and apply it to perform high-speed imaging, low noise as well as multimodal imaging. This modified QWLSI system contains a versatile optomechanical device which images the optical grating near the detector plane. Such a device is coupled with any kind of camera by varying its magnification. In this paper, we study the use of a sCMOS Zyla5.5 camera from Andor along with our modified QWLSI system. We will present high-speed live cell imaging, up to 200Hz frame rate, in order to follow intracellular fast motions while measuring the quantitative phase information. The structural and density information extracted from the OPD signal is complementary to the specific and localized fluorescence signal [2]. In addition, QPI detects cells even when the fluorophore is not expressed. This is very useful to follow a protein expression with time. The 10 µm spatial pixel resolution of our modified QWLSI associated to the high sensitivity of the Zyla5.5 enabling to perform high quality fluorescence imaging, we have carried out multimodal imaging revealing fine structures cells, like actin filaments, merged with the morphological information of the phase. References [1]. P. Bon, G. Maucort, B. Wattellier, and S. Monneret, "Quadriwave lateral shearing interferometry for quantitative phase microscopy of living cells," Opt. Express, vol. 17, pp. 13080-13094, 2009. [2] P. Bon, S. Lécart, E. Fort and S. Lévêque-Fort, "Fast label-free cytoskeletal network imaging in living mammalian cells," Biophysical journal, 106

  13. Advanced Subsonic Technology (AST) 22-Inch Low Noise Research Fan Rig Preliminary Design of ADP-Type Fan 3

    Science.gov (United States)

    Jeracki, Robert J. (Technical Monitor); Topol, David A.; Ingram, Clint L.; Larkin, Michael J.; Roche, Charles H.; Thulin, Robert D.

    2004-01-01

    This report presents results of the work completed on the preliminary design of Fan 3 of NASA s 22-inch Fan Low Noise Research project. Fan 3 was intended to build on the experience gained from Fans 1 and 2 by demonstrating noise reduction technology that surpasses 1992 levels by 6 dB. The work was performed as part of NASA s Advanced Subsonic Technology (AST) program. Work on this task was conducted in the areas of CFD code validation, acoustic prediction and validation, rotor parametric studies, and fan exit guide vane (FEGV) studies up to the time when a NASA decision was made to cancel the design, fabrication and testing phases of the work. The scope of the program changed accordingly to concentrate on two subtasks: (1) Rig data analysis and CFD code validation and (2) Fan and FEGV optimization studies. The results of the CFD code validation work showed that this tool predicts 3D flowfield features well from the blade trailing edge to about a chord downstream. The CFD tool loses accuracy as the distance from the trailing edge increases beyond a blade chord. The comparisons of noise predictions to rig test data showed that both the tone noise tool and the broadband noise tool demonstrated reasonable agreement with the data to the degree that these tools can reliably be used for design work. The section on rig airflow and inlet separation analysis describes the method used to determine total fan airflow, shows the good agreement of predicted boundary layer profiles to measured profiles, and shows separation angles of attack ranging from 29.5 to 27deg for the range of airflows tested. The results of the rotor parametric studies were significant in leading to the decision not to pursue a new rotor design for Fan 3 and resulted in recommendations to concentrate efforts on FEGV stator designs. The ensuing parametric study on FEGV designs showed the potential for 8 to 10 EPNdB noise reduction relative to the baseline.

  14. A low-noise X-band microstrip VCO with 2.5 GHz tuning range using a GaN-on-SiC p-HEMT

    NARCIS (Netherlands)

    Maas, A.M.P.; Vliet, F.E. van

    2005-01-01

    A low-noise X-band microstrip hybrid VCO has been designed and realised using a 2 × 50 μm GaN-on-SiC pseudo-morphic HEMT as the active device. The transistor has been manufactured by TIGER and features a gate-length of 0.15 μm, an fT of 22 GHz, a break-down voltage of 42 Volts and an Idss, close to

  15. 100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun [Department of Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul 151-742 (Korea, Republic of); Park, June; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Heukseok-Dong, Dongjak-Gu, Seoul 156-756 (Korea, Republic of); Jhon, Young Min, E-mail: mseong@cau.ac.kr, E-mail: shong@phya.snu.ac.kr [Korea Institute of Science and Technology, Hawolgok-Dong, Seongbuk-Gu, Seoul 136-791 (Korea, Republic of)

    2010-02-05

    Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of {approx}1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

  16. 100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

    International Nuclear Information System (INIS)

    Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun; Park, June; Seong, Maeng-Je; Jhon, Young Min

    2010-01-01

    Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ∼1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

  17. 100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

    Science.gov (United States)

    Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Park, June; Jhon, Young Min; Seong, Maeng-Je; Hong, Seunghun

    2010-02-01

    Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ~1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

  18. RADIANCE DOMAIN COMPOSITING FOR HIGH DYNAMIC RANGE IMAGING

    Directory of Open Access Journals (Sweden)

    M.R. Renu

    2013-02-01

    Full Text Available High dynamic range imaging aims at creating an image with a range of intensity variations larger than the range supported by a camera sensor. Most commonly used methods combine multiple exposure low dynamic range (LDR images, to obtain the high dynamic range (HDR image. Available methods typically neglect the noise term while finding appropriate weighting functions to estimate the camera response function as well as the radiance map. We look at the HDR imaging problem in a denoising frame work and aim at reconstructing a low noise radiance map from noisy low dynamic range images, which is tone mapped to get the LDR equivalent of the HDR image. We propose a maximum aposteriori probability (MAP based reconstruction of the HDR image using Gibb’s prior to model the radiance map, with total variation (TV as the prior to avoid unnecessary smoothing of the radiance field. To make the computation with TV prior efficient, we extend the majorize-minimize method of upper bounding the total variation by a quadratic function to our case which has a nonlinear term arising from the camera response function. A theoretical justification for doing radiance domain denoising as opposed to image domain denoising is also provided.

  19. Source coding for transmission of reconstructed dynamic geometry: a rate-distortion-complexity analysis of different approaches

    NARCIS (Netherlands)

    R.N. Mekuria (Rufael); P.S. Cesar Garcia (Pablo Santiago); D.C.A. Bulterman (Dick)

    2014-01-01

    htmlabstractLive 3D reconstruction of a human as a 3D mesh with commodity electronics is becoming a reality. Immersive applications (i.e. cloud gaming, tele-presence) benefit from effective transmission of such content over a bandwidth limited link. In this paper we outline different approaches for

  20. Comparison of Absorbable Mesh Plate versus Titanium-Dynamic Mesh Plate in Reconstruction of Blow-Out Fracture: An Analysis of Long-Term Outcomes

    Directory of Open Access Journals (Sweden)

    Woon Il Baek

    2014-07-01

    Full Text Available Background A blow-out fracture is one of the most common facial injuries in midface trauma. Orbital wall reconstruction is extremely important because it can cause various functional and aesthetic sequelae. Although many materials are available, there are no uniformly accepted guidelines regarding material selection for orbital wall reconstruction. Methods From January 2007 to August 2012, a total of 78 patients with blow-out fractures were analyzed. 36 patients received absorbable mesh plates, and 42 patients received titanium-dynamic mesh plates. Both groups were retrospectively evaluated for therapeutic efficacy and safety according to the incidence of three different complications: enophthalmos, extraocular movement impairment, and diplopia. Results For all groups (inferior wall fracture group, medial wall fractrue group, and combined inferomedial wall fracture group, there were improvements in the incidence of each complication regardless of implant types. Moreover, a significant improvement of enophthalmos occurred for both types of implants in group 1 (inferior wall fracture group. However, we found no statistically significant differences of efficacy or complication rate in every groups between both implant types. Conclusions Both types of implants showed good results without significant differences in long-term follow up, even though we expected the higher recurrent enophthalmos rate in patients with absorbable plate. In conclusion, both types seem to be equally effective and safe for orbital wall reconstruction. In particular, both implant types significantly improve the incidence of enophthalmos in cases of inferior orbital wall fractures.

  1. Mutual information as a measure of image quality for 3D dynamic lung imaging with EIT.

    Science.gov (United States)

    Crabb, M G; Davidson, J L; Little, R; Wright, P; Morgan, A R; Miller, C A; Naish, J H; Parker, G J M; Kikinis, R; McCann, H; Lionheart, W R B

    2014-05-01

    We report on a pilot study of dynamic lung electrical impedance tomography (EIT) at the University of Manchester. Low-noise EIT data at 100 frames per second were obtained from healthy male subjects during controlled breathing, followed by magnetic resonance imaging (MRI) subsequently used for spatial validation of the EIT reconstruction. The torso surface in the MR image and electrode positions obtained using MRI fiducial markers informed the construction of a 3D finite element model extruded along the caudal-distal axis of the subject. Small changes in the boundary that occur during respiration were accounted for by incorporating the sensitivity with respect to boundary shape into a robust temporal difference reconstruction algorithm. EIT and MRI images were co-registered using the open source medical imaging software, 3D Slicer. A quantitative comparison of quality of different EIT reconstructions was achieved through calculation of the mutual information with a lung-segmented MR image. EIT reconstructions using a linear shape correction algorithm reduced boundary image artefacts, yielding better contrast of the lungs, and had 10% greater mutual information compared with a standard linear EIT reconstruction.

  2. Can low-dose CT with iterative reconstruction reduce both the radiation dose and the amount of iodine contrast medium in a dynamic CT study of the liver?

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Hiroto; Okada, Masahiro; Hyodo, Tomoko; Hidaka, Syojiro; Kagawa, Yuki; Matsuki, Mitsuru; Tsurusaki, Masakatsu; Murakami, Takamichi, E-mail: murakami@med.kindai.ac.jp

    2014-04-15

    Purpose: To investigate whether low-dose dynamic CT of the liver with iterative reconstruction can reduce both the radiation dose and the amount of contrast medium. Materials and methods: This study was approved by our institutional review board. 113 patients were randomly assigned to one of two groups. Group A/group B (fifty-eight/fifty-five patients) underwent liver dynamic CT at 120/100 kV, with 0/40% adaptive statistical iterative reconstruction (ASIR), with a contrast dose of 600/480 mg I/kg, respectively. Radiation exposure was estimated based on the manufacturer's phantom data. The enhancement value of the hepatic parenchyma, vessels and the tumor-to-liver contrast of hepatocellular carcinomas (HCCs) were compared between two groups. Two readers independently assessed the CT images of the hepatic parenchyma and HCCs. Results: The mean CT dose indices: 6.38/4.04 mGy, the dose-length products: 194.54/124.57 mGy cm, for group A/group B. The mean enhancement value of the hepatic parenchyma and the tumor-to-liver contrast of HCCs with diameters greater than 1 cm in the post-contrast all phases did not differ significantly between two groups (P > 0.05). The enhancement values of vessels in group B were significantly higher than that in group A in the delayed phases (P < 0.05). Two reader's confidence levels for the hepatic parenchyma in the delayed phases and HCCs did not differ significantly between the groups (P > 0.05). Conclusions: Low-dose dynamic CT with ASIR can reduce both the radiation dose and the amount of contrast medium without image quality degradation, compared to conventional dynamic CT without ASIR.

  3. Estimating liver perfusion from free-breathing continuously acquired dynamic gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced acquisition with compressed sensing reconstruction.

    Science.gov (United States)

    Chandarana, Hersh; Block, Tobias Kai; Ream, Justin; Mikheev, Artem; Sigal, Samuel H; Otazo, Ricardo; Rusinek, Henry

    2015-02-01

    The purpose of this study was to estimate perfusion metrics in healthy and cirrhotic liver with pharmacokinetic modeling of high-temporal resolution reconstruction of continuously acquired free-breathing gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced acquisition in patients undergoing clinically indicated liver magnetic resonance imaging. In this Health Insurance Portability and Accountability Act-compliant prospective study, 9 cirrhotic and 10 noncirrhotic patients underwent clinical magnetic resonance imaging, which included continuously acquired radial stack-of-stars 3-dimensional gradient recalled echo sequence with golden-angle ordering scheme in free breathing during contrast injection. A total of 1904 radial spokes were acquired continuously in 318 to 340 seconds. High-temporal resolution data sets were formed by grouping 13 spokes per frame for temporal resolution of 2.2 to 2.4 seconds, which were reconstructed using the golden-angle radial sparse parallel technique that combines compressed sensing and parallel imaging. High-temporal resolution reconstructions were evaluated by a board-certified radiologist to generate gadolinium concentration-time curves in the aorta (arterial input function), portal vein (venous input function), and liver, which were fitted to dual-input dual-compartment model to estimate liver perfusion metrics that were compared between cirrhotic and noncirrhotic livers. The cirrhotic livers had significantly lower total plasma flow (70.1 ± 10.1 versus 103.1 ± 24.3 mL/min per 100 mL; P The mean transit time was higher in the cirrhotic livers (24.4 ± 4.7 versus 15.7 ± 3.4 seconds; P the hepatocellular uptake rate was lower (3.03 ± 2.1 versus 6.53 ± 2.4 100/min; P < 0.05). Liver perfusion metrics can be estimated from free-breathing dynamic acquisition performed for every clinical examination without additional contrast injection or time. This is a novel paradigm for dynamic liver imaging.

  4. Design and construction of a high-stability, low-noise power supply for use with high-resolution electron energy loss spectrometers

    International Nuclear Information System (INIS)

    Katz, J.E.; Davies, P.W.; Crowell, J.E.; Somorjai, G.A.

    1982-01-01

    The design and construction of a high-stability, low-noise power supply which provides potentials for the lens and analyzer elements of a 127 0 Ehrhardt-type high-resolution electron energy loss spectrometer (HREELS) is described. The supply incorporates a filament emission-control circuit and facilities for measuring electron beam current at each spectrometer element, thus facilitating optimal tuning of the spectrometer. Spectra obtained using this supply are shown to have a four-fold improvement in signal-to-noise ratio and a higher resolution of the vibrational loss features when compared with spectra taken using a previously existing supply based on passive potential divider networks

  5. Microfocal X-ray computed tomography post-processing operations for optimizing reconstruction volumes of stented arteries during 3D computational fluid dynamics modeling.

    Science.gov (United States)

    Ladisa, John F; Olson, Lars E; Ropella, Kristina M; Molthen, Robert C; Haworth, Steven T; Kersten, Judy R; Warltier, David C; Pagel, Paul S

    2005-08-01

    Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to generate geometrically accurate flow domains within the localized region of a stent several weeks after implantation. Microfocal X-ray CT reconstruction volumes were subjected to an automated program to perform arterial thresholding, spatial orientation, and surface smoothing of stented and unstented rabbit iliac arteries several weeks after antegrade implantation. A transfer function was obtained for the current post-processing methodology containing reconstructed 16 mm stents implanted into rabbit iliac arteries for up to 21 days after implantation and resolved at circumferential and axial resolutions of 32 and 50 microm, respectively. The results indicate that the techniques presented are sufficient to resolve distributions of WSS with 80% accuracy in segments containing 16 surface perturbations over a 16 mm stented region. These methods will be used to test the hypothesis that reductions in normalized wall shear stress (WSS) and increases in the spatial disparity of WSS immediately after stent implantation may spatially correlate with the temporal development of NH within the stented region.

  6. The use of compressive sensing and peak detection in the reconstruction of microtubules length time series in the process of dynamic instability.

    Science.gov (United States)

    Mahrooghy, Majid; Yarahmadian, Shantia; Menon, Vineetha; Rezania, Vahid; Tuszynski, Jack A

    2015-10-01

    Microtubules (MTs) are intra-cellular cylindrical protein filaments. They exhibit a unique phenomenon of stochastic growth and shrinkage, called dynamic instability. In this paper, we introduce a theoretical framework for applying Compressive Sensing (CS) to the sampled data of the microtubule length in the process of dynamic instability. To reduce data density and reconstruct the original signal with relatively low sampling rates, we have applied CS to experimental MT lament length time series modeled as a Dichotomous Markov Noise (DMN). The results show that using CS along with the wavelet transform significantly reduces the recovery errors comparing in the absence of wavelet transform, especially in the low and the medium sampling rates. In a sampling rate ranging from 0.2 to 0.5, the Root-Mean-Squared Error (RMSE) decreases by approximately 3 times and between 0.5 and 1, RMSE is small. We also apply a peak detection technique to the wavelet coefficients to detect and closely approximate the growth and shrinkage of MTs for computing the essential dynamic instability parameters, i.e., transition frequencies and specially growth and shrinkage rates. The results show that using compressed sensing along with the peak detection technique and wavelet transform in sampling rates reduces the recovery errors for the parameters. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. A Low-Noise CMOS THz Imager Based on Source Modulation and an In-Pixel High-Q Passive Switched-Capacitor N-Path Filter.

    Science.gov (United States)

    Boukhayma, Assim; Dupret, Antoine; Rostaing, Jean-Pierre; Enz, Christian

    2016-03-03

    This paper presents the first low noise complementary metal oxide semiconductor (CMOS) deletedCMOS terahertz (THz) imager based on source modulation and in-pixel high-Q filtering. The 31 × 31 focal plane array has been fully integrated in a 0 . 13 μ m standard CMOS process. The sensitivity has been improved significantly by modulating the active THz source that lights the scene and performing on-chip high-Q filtering. Each pixel encompass a broadband bow tie antenna coupled to an N-type metal-oxide-semiconductor (NMOS) detector that shifts the THz radiation, a low noise adjustable gain amplifier and a high-Q filter centered at the modulation frequency. The filter is based on a passive switched-capacitor (SC) N-path filter combined with a continuous-time broad-band Gm-C filter. A simplified analysis that helps in designing and tuning the passive SC N-path filter is provided. The characterization of the readout chain shows that a Q factor of 100 has been achieved for the filter with a good matching between the analytical calculation and the measurement results. An input-referred noise of 0 . 2 μ V RMS has been measured. Characterization of the chip with different THz wavelengths confirms the broadband feature of the antenna and shows that this THz imager reaches a total noise equivalent power of 0 . 6 nW at 270 GHz and 0 . 8 nW at 600 GHz.

  8. A Ka-band low-noise amplifier with a coplanar waveguide (CPW) structure with 0.15-μm GaAs pHEMT technology

    International Nuclear Information System (INIS)

    Wu Chia-Song; Chang Chien-Huang; Liu Hsing-Chung; Lin Tah-Yeong; Wu Hsien-Ming

    2010-01-01

    This investigation explores a low-noise amplifier (LNA) with a coplanar waveguide (CPW) structure, in which a two-stage amplifier is associated with a cascade schematic circuit, implemented in 0.15-μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology in a Ka-band (26.5-40.0 GHz) microwave monolithic integrated circuit (MMIC). The experimental results demonstrate that the proposed LNA has a peak gain of 12.53 dB at 30 GHz and a minimum noise figure of 3.3 dB at 29.5 GHz, when biased at a V ds of 2 V and a V gs of -0.6 V with a drain current of 16 mA in the circuit. The results show that the millimeter-wave LNA with coplanar waveguide structure has a higher gain and wider bandwidth than a conventional circuit. Finally, the overall LNA characterization exhibits high gain and low noise, indicating that the LNA has a compact circuit and favorable RF characteristics. The strong RF character exhibited by the LNA circuit can be used in millimeter-wave circuit applications. (semiconductor integrated circuits)

  9. Reconstruction of the relative dynamics of 90Sr intake for the residents of the Techa river settlements

    International Nuclear Information System (INIS)

    Krivoschapov, Victor A.; Zalyapin, Vladimir I.

    2002-01-01

    Radioactive releases from the Mayak plutonium production complex (Souther Urals, Russia) during 1949-1956 into the Techa river resulted in chronic external and internal exposure of about 30,000 residents of riverside communities. Strontium-90 made a significant contribution in doses of internal exposure. The calculation of the internal exposure dose and the dynamics of 90 Sr intake is an important problem. The obtained solution qualitatively correctly reflects the dynamics of 90 Sr intake and is in agreement with available experimental data - substitution of the solution into initial integral relation showed the consistency between calculated and observed values

  10. A statistical-dynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables

    Energy Technology Data Exchange (ETDEWEB)

    Cassou, Christophe; Minvielle, Marie; Terray, Laurent [CERFACS/CNRS, Climate Modelling and Global Change Team, Toulouse (France); Perigaud, Claire [JPL-NASA, Ocean Science Element, Pasadena, CA (United States)

    2011-01-15

    The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500 hPa geopotential height and 1,000 hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50 years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our

  11. A scatter-corrected list-mode reconstruction and a practical scatter/random approximation technique for dynamic PET imaging

    International Nuclear Information System (INIS)

    Cheng, J-C; Rahmim, Arman; Blinder, Stephan; Camborde, Marie-Laure; Raywood, Kelvin; Sossi, Vesna

    2007-01-01

    We describe an ordinary Poisson list-mode expectation maximization (OP-LMEM) algorithm with a sinogram-based scatter correction method based on the single scatter simulation (SSS) technique and a random correction method based on the variance-reduced delayed-coincidence technique. We also describe a practical approximate scatter and random-estimation approach for dynamic PET studies based on a time-averaged scatter and random estimate followed by scaling according to the global numbers of true coincidences and randoms for each temporal frame. The quantitative accuracy achieved using OP-LMEM was compared to that obtained using the histogram-mode 3D ordinary Poisson ordered subset expectation maximization (3D-OP) algorithm with similar scatter and random correction methods, and they showed excellent agreement. The accuracy of the approximated scatter and random estimates was tested by comparing time activity curves (TACs) as well as the spatial scatter distribution from dynamic non-human primate studies obtained from the conventional (frame-based) approach and those obtained from the approximate approach. An excellent agreement was found, and the time required for the calculation of scatter and random estimates in the dynamic studies became much less dependent on the number of frames (we achieved a nearly four times faster performance on the scatter and random estimates by applying the proposed method). The precision of the scatter fraction was also demonstrated for the conventional and the approximate approach using phantom studies

  12. New Very Low Noise Multilayer And Graded-Gap Avalanche Photodiodes For The 0.8 To 1 .8 μm Wavelength Region

    Science.gov (United States)

    Capasso, F.; Tsang, W. T.; Williams, G. F.

    1982-12-01

    Recent experimental and theoretical results on a new class of low noise avalanche photo-diodes are reviewed. A large enhancement of the impact ionization rates ratio (a/(3=10) has been demonstrated in AlGaAs/GaAs superlattices and graded band gap detector structures. In addition two novel photodiodes ("staircase" and "channeling" APDs) where only electrons multiply, have been proposed. The staircase APD is the solid state analog of the photo-multiplier with discrete dynodes. It has a low operating voltage (5-20 volts) and a lower excess noise factor, in the ideal case, than that of an ideal conventional APD The channeling APD is instead the solid state analog of a channeltron photomultiplier and has the unique feature of an ultrahigh a/β, ratio (≍∞) compatible with high gain (>100).

  13. Development of a low-noise, 4th-order readout ASIC for CdZnTe detectors in gamma spectrometer applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jia, E-mail: jwang@nwpu.edu.cn [School of Computer Science and Engineering, Northwestern Polytechnical University, 127 West Youyixi Road, 710072 Xi' an (China); Su, Lin; Wei, Xiaomin; Zheng, Ran [School of Computer Science and Engineering, Northwestern Polytechnical University, 127 West Youyixi Road, 710072 Xi' an (China); Hu, Yann [IPHC, University of Strasbourg, 23 rue du loess, 67037 Strasbourg Cedex 02 (France)

    2016-09-21

    This paper presents an ASIC readout circuit development, which aims to achieve low noise. In order to compensate the leakage current and improve gain, a dual-stage CSA has been utilized. A 4th-order high-linearity shaper is proposed to obtain a Semi-Gaussian wave and further decrease the noise induced by the leakage current. The ASIC has been designed and fabricated in a standard commercial 2P4M 0.35 μm CMOS process. Die area of one channel is about 1190 μm×147 μm. The input charge range is 1.8 fC. The peaking time can be adjusted from 1 μs to 3 μs. Measured ENC is about 55e{sup −} (rms) at input capacitor of 0 F. The gain is 271 mV/fC at the peaking time of 1 μs.

  14. Developing novel peat isotope proxies from vascular plant-dominated peatlands of New Zealand to reconstruct Southern Hemisphere climate dynamics

    Science.gov (United States)

    Roland, T.; Amesbury, M. J.; Charman, D.; Newnham, R.; Royles, J.; Griffiths, H.; Ratcliffe, J.; Rees, A.; Campbell, D.; Baisden, T.; Keller, E. D.

    2017-12-01

    The Southern Annular Mode (SAM) is a key control on the strength and position of the southern westerly winds (SWW), which are a major influence on Southern Hemisphere (SH) mid- to high-latitude climate. A shift towards a more positive SAM has occurred since the 1950s, driven by ozone layer thinning and enhanced by greenhouse gas driven warming. Although these recent changes are thought to be unprecedented over the last 1000 years, the longer-term behaviour of the SAM is poorly understood. We are developing stable isotope proxies from plant cellulose in vascular plant-dominated (Empodisma spp.) peatlands in New Zealand that we hypothesise are related to changes in past temperature (δ13C) and precipitation moisture source (δ18O). The moisture source signal is driven by the balance between Southern Ocean sources (depleted δ18O) and sub-tropical sources (enriched δ18O), reflecting the relative states of SAM and the El Niño-Southern Oscillation. We aim to provide palaeoclimatic context for the recent positive trend in the SAM, and explore the long-term relationship between the SAM and ENSO, testing the contention that tropical Pacific variability is a key influence on past and future SAM variability. Terrestrial palaeoclimate records in the Southern Hemisphere are often spatially isolated and temporally fragmented. However, New Zealand is ideally placed to test such hypotheses as it registers strong correlations between SAM, temperature and precipitation, and it straddles the zone of interaction between the SWW and sub-tropical moisture sources, reflected in a strong precipitation δ18O gradient. We report data from surface samples across New Zealand and explore the spatial and temporal patterns in stable isotopes in cellulose and water that we will use to interpret the palaeoenvironmental data. Preliminary downcore data will be used to demonstrate the efficacy of this approach to reconstructing moisture sources and temperature linked to moisture source variability.

  15. Pollen-based biome reconstructions for Colombia at 3000, 6000, 15 000 and 18 000 14C yr ago : Late Quaternary tropical vegetation dynamics

    NARCIS (Netherlands)

    Marchant, R.; Behling, H.; Berrío, J.C.; Cleef, A.M.; Duivenvoorden, J.; Hooghiemstra, H.; Kuhry, P.; Melief, B.; Schreve-Brinkman, E.; Geel, van B.; Hammen, van der T.; Reenen, van G.

    2002-01-01

    Colombian biomes are reconstructed at 45 sites from the modern period extending to the Last Glacial Maximum (LGM). The basis for our reconstruction is pollen data assigned to plant functional types and biomes at six 3000-yr intervals. A reconstruction of modern biomes is used to check the treatment

  16. A Low-Noise CMOS THz Imager Based on Source Modulation and an In-Pixel High-Q Passive Switched-Capacitor N-Path Filter

    Science.gov (United States)

    Boukhayma, Assim; Dupret, Antoine; Rostaing, Jean-Pierre; Enz, Christian

    2016-01-01

    This paper presents the first low noise complementary metal oxide semiconductor (CMOS) terahertz (THz) imager based on source modulation and in-pixel high-Q filtering. The 31×31 focal plane array has been fully integrated in a 0.13μm standard CMOS process. The sensitivity has been improved significantly by modulating the active THz source that lights the scene and performing on-chip high-Q filtering. Each pixel encompass a broadband bow tie antenna coupled to an N-type metal-oxide-semiconductor (NMOS) detector that shifts the THz radiation, a low noise adjustable gain amplifier and a high-Q filter centered at the modulation frequency. The filter is based on a passive switched-capacitor (SC) N-path filter combined with a continuous-time broad-band Gm-C filter. A simplified analysis that helps in designing and tuning the passive SC N-path filter is provided. The characterization of the readout chain shows that a Q factor of 100 has been achieved for the filter with a good matching between the analytical calculation and the measurement results. An input-referred noise of 0.2μV RMS has been measured. Characterization of the chip with different THz wavelengths confirms the broadband feature of the antenna and shows that this THz imager reaches a total noise equivalent power of 0.6 nW at 270 GHz and 0.8 nW at 600 GHz. PMID:26950131

  17. Novel WSi/Au T-shaped gate GaAs metal-semiconductor field-effect-transistor fabrication process for super low-noise microwave monolithic integrated circuit amplifiers

    International Nuclear Information System (INIS)

    Takano, H.; Hosogi, K.; Kato, T.

    1995-01-01

    A fully ion-implanted self-aligned T-shaped gate Ga As metal-semiconductor field-effect transistor (MESFET) with high frequency and extremely low-noise performance has been successfully fabricated for super low-noise microwave monolithic integrated circuit (MMIC) amplifiers. A subhalf-micrometer gate structure composed of WSi/Ti/Mo/Au is employed to reduce gate resistance effectively. This multilayer gate structure is formed by newly developed dummy SiON self-alignment technology and a photoresist planarization process. At an operating frequency of 12 GHz, a minimum noise figure of 0.87 dB with an associated gain of 10.62 dB has been obtained. Based on the novel FET process, a low-noise single-stage MMIC amplifier with an excellent low-noise figure of 1.2 dB with an associated gain of 8 dB in the 14 GHz band has been realized. This is the lowest noise figure ever reported at this frequency for low-noise MMICs based on ion-implanted self-aligned gate MESFET technology. 14 refs., 9 figs

  18. Development of high-performance and low-noise axial-flow fan units in their local operating region

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Seung; Ha, Min Ho; Cheong, Cheol Ung [Pusan National University, Busan (Korea, Republic of); Kim, Tae Hoon [LG Electronics Inc., Changwon (Korea, Republic of)

    2015-09-15

    Aerodynamic and aeroacoustic performances of an axial-flow fan unit are improved by modifying its housing structure without changing the fan blade. The target axial-flow fan system is used to lower temperature of a compressor and a condenser in the machine room of a household refrigerator which has relatively high system resistance due to complex layout of structures inside it. First, the performance of the fan system is experimentally characterized by measuring its volume flow rate versus static pressure using a fan performance tester satisfying the AMCA (Air Movement and Control Association) regulation, AMCA 210-07. The detailed structure of flow driven by the fan is numerically investigated using a virtual fan performance tester based on computational fluid dynamics techniques. The prediction result reveals possible loss due to radial and tangential velocity components in the wake flow downstream of the fan. The length of the fan housing is chosen as a design parameter for improving the aerodynamic and aeroacoustic performances of the fan unit by reducing the identified radial and tangential velocity components. Three fan units with different housing lengths longer than the original are analyzed using the virtual fan performance tester. The results confirm the improved aerodynamic performance of the proposed three designs. The flow field driven by the proposed fan unit is closely examined to find the causes for the observed performance improvements, which ensures that the radial and tangential velocity components in the wake flow are reduced. Finally, the improved performance of the proposed fan systems is validated by comparing the P-Q and efficiency curves measured using the fan performance tester. The noise emission from the household refrigerator is also found to be lessened when the new fan units are installed.

  19. Applying 3D Dynamic Visualisation to (Palaeo) Geomorphic Reconstruction: Modelling a Tenth Century Jökulhlaup at Sólheimajökull Glacier, South Iceland.

    Science.gov (United States)

    Booth, Laura; Isaacs, John

    2014-05-01

    Models of the area with aerial photography to create a 3D virtual environment, which provides the basis for entering field data to the geomorphic reconstruction. The result is a visual simulation of Sólheimajökull's Tenth Century physical environment which places the flood into geomorphic and topographic context. The wider implications of developing this tool are many when considering its ease of use and first-person navigational controls. The animations allow immediate exposure to environments that are otherwise lost in reality. VolcVis is a powerful tool in bringing reconstructed palaeo-environments back to life, albeit in the virtual sphere. It allows a uniquely contemporary appreciation of an elapsed event; yet which was a critical episode in the geomorphic evolution of this dynamic region. When field data are pieced together into a simulation, they hold a greater cohesive strength, giving the results wider applicability and relevance to a range of users and decision-makers, serving both technical and nontechnical perspectives. VolcVis' ability to dynamically display field data presents new possibilities for generating hypotheses, and for data sharing with Icelandic hazard mitigation authorities and the general public.

  20. Ruminant Metabolic Systems Biology: Reconstruction and Integration of Transcriptome Dynamics Underlying Functional Responses of Tissues to Nutrition and Physiological Statea

    Science.gov (United States)

    Bionaz, Massimo; Loor, Juan J.

    2012-01-01

    High-throughput ‘omics’ data analysis via bioinformatics is one key component of the systems biology approach. The systems approach is particularly well-suited for the study of the interactions between nutrition and physiological state with tissue metabolism and functions during key life stages of organisms such as the transition from pregnancy to lactation in mammals, ie, the peripartal period. In modern dairy cows with an unprecedented genetic potential for milk synthesis, the nature of the physiologic and metabolic adaptations during the peripartal period is multifaceted and involves key tissues such as liver, adipose, and mammary. In order to understand such adaptation, we have reviewed several works performed in our and other labs. In addition, we have used a novel bioinformatics approach, Dynamic Impact Approach (DIA), in combination with partly previously published data to help interpret longitudinal biological adaptations of bovine liver, adipose, and mammary tissue to lactation using transcriptomics datasets. Use of DIA with transcriptomic data from those tissues during normal physiological adaptations and in animals fed different levels of energy prepartum allowed visualization and integration of most-impacted metabolic pathways around the time of parturition. The DIA is a suitable tool for applying the integrative systems biology approach. The ultimate goal is to visualize the complexity of the systems at study and uncover key molecular players involved in the tissue’s adaptations to physiological state or nutrition. PMID:22807626

  1. Microcirculation in the murine liver: a computational fluid dynamic model based on 3D reconstruction from in vivo microscopy.

    Science.gov (United States)

    Piergiovanni, Monica; Bianchi, Elena; Capitani, Giada; Li Piani, Irene; Ganzer, Lucia; Guidotti, Luca G; Iannacone, Matteo; Dubini, Gabriele

    2017-10-03

    The liver is organized in hexagonal functional units - termed lobules - characterized by a rather peculiar blood microcirculation, due to the presence of a tangled network of capillaries - termed sinusoids. A better understanding of the hemodynamics that governs liver microcirculation is relevant to clinical and biological studies aimed at improving our management of liver diseases and transplantation. Herein, we built a CFD model of a 3D sinusoidal network, based on in vivo images of a physiological mouse liver obtained with a 2-photon microscope. The CFD model was developed with Fluent 16.0 (ANSYS Inc., Canonsburg, PA), particular care was taken in imposing the correct boundary conditions representing a physiological state. To account for the remaining branches of the sinusoids, a lumped parameter model was used to prescribe the correct pressure at each outlet. The effect of an adhered cell on local hemodynamics is also investigated for different occlusion degrees. The model here proposed accurately reproduces the fluid dynamics in a portion of the sinusoidal network in mouse liver. Mean velocities and mass flow rates are in agreement with literature values from in vivo measurements. Our approach provides details on local phenomena, hardly described by other computational studies, either focused on the macroscopic hepatic vasculature or based on homogeneous porous medium model. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Climate Reconstructions

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Paleoclimatology Program archives reconstructions of past climatic conditions derived from paleoclimate proxies, in addition to the Program's large holdings...

  3. Accelerated dynamic cardiac MRI exploiting sparse-Kalman-smoother self-calibration and reconstruction (k  −  t SPARKS)

    International Nuclear Information System (INIS)

    Park, Suhyung; Park, Jaeseok

    2015-01-01

    Accelerated dynamic MRI, which exploits spatiotemporal redundancies in k  −  t space and coil dimension, has been widely used to reduce the number of signal encoding and thus increase imaging efficiency with minimal loss of image quality. Nonetheless, particularly in cardiac MRI it still suffers from artifacts and amplified noise in the presence of time-drifting coil sensitivity due to relative motion between coil and subject (e.g. free breathing). Furthermore, a substantial number of additional calibrating signals is to be acquired to warrant accurate calibration of coil sensitivity. In this work, we propose a novel, accelerated dynamic cardiac MRI with sparse-Kalman-smoother self-calibration and reconstruction (k  −  t SPARKS), which is robust to time-varying coil sensitivity even with a small number of calibrating signals. The proposed k  −  t SPARKS incorporates Kalman-smoother self-calibration in k  −  t space and sparse signal recovery in x  −   f space into a single optimization problem, leading to iterative, joint estimation of time-varying convolution kernels and missing signals in k  −  t space. In the Kalman-smoother calibration, motion-induced uncertainties over the entire time frames were included in modeling state transition while a coil-dependent noise statistic in describing measurement process. The sparse signal recovery iteratively alternates with the self-calibration to tackle the ill-conditioning problem potentially resulting from insufficient calibrating signals. Simulations and experiments were performed using both the proposed and conventional methods for comparison, revealing that the proposed k  −  t SPARKS yields higher signal-to-error ratio and superior temporal fidelity in both breath-hold and free-breathing cardiac applications over all reduction factors. (paper)

  4. Urban Youth in the Reconstruction of Social Order in Ouagadougou: Generational mobility as an indicator of social dynamics

    Directory of Open Access Journals (Sweden)

    Jean-Bernard Ouédraogo

    2011-10-01

    Full Text Available The aim of this paper is to analyze information based on a survey of young urban people in the city of Ouagadougou, Burkina Faso, looking at the way in which their position is clearly articulated in urban social dynamics. The hypothesis defended is that the emergence and evolution of the youth group stresses a movement which is at the heart of the reproduction and transformation of the entire society. To better understand the historical function of youths, the sketch of this sociology of generations will revisit the theoretical notions and make a critical comparison of this polysemic conceptualisation of a practical process in the roots of evolution. This dynamics is only visible in the observation of individual and collective strategies, but simultaneously represents the ratio of youths in the ancient order of things. It is the collective social position, the youthful social ideal and the forms of generational stabilization in the general course of history. The paper ends with a presentation of a theoretical attempt to formulate a strictly sociological design of the concept of “youths”, which will enable practical usage of a category hitherto marked a priori by common sense.O objectivo deste trabalho é analisar, a partir de um inquérito junto de jovens urbanos da cidade de Ouagadougou, Burkina Faso, a maneira pela qual a sua posição se articula na dinâmica social urbana. A hipótese que aqui se defende é a do surgimento e evolução do grupo jovens acentuar um movimento que está no cerne da reprodução e transformação de toda a sociedade. Para entender melhor a função histórica da juventude, o esboço desta sociologia de gerações revisita as principais teorias sobre este conceito e confronta, de forma crítica, a conceptualização polissémica de um processo concreto de evolução de itinerários. Uma dinâmica que só será visível através da observação de estratégias individuais e colectivas que descrevem

  5. Low-noise Magnetic Sensors

    KAUST Repository

    Kosel, Jü rgen; Sun, Jian

    2014-01-01

    Magnetic sensors are disclosed, as well as methods for fabricating and using the same. In some embodiments, an EMR effect sensor includes a semiconductor layer. In some embodiments, the EMR effect sensor may include a conductive layer substantially coupled to the semiconductor layer. In some embodiments, the EMR effect sensor may include a voltage lead coupled to the conductive layer. In some embodiments, the voltage lead may be configured to provide a voltage for measurement by a voltage measurement circuit. In some embodiments, the EMR effect sensor may include a second voltage lead coupled to the semiconductor layer. In some embodiments, the second voltage lead may be configured to provide a voltage for measurement by a voltage measurement circuit. Embodiments of a Hall effect sensor having the same or similar structure are also disclosed.

  6. Low-noise Magnetic Sensors

    KAUST Repository

    Kosel, Jurgen

    2014-03-27

    Magnetic sensors are disclosed, as well as methods for fabricating and using the same. In some embodiments, an EMR effect sensor includes a semiconductor layer. In some embodiments, the EMR effect sensor may include a conductive layer substantially coupled to the semiconductor layer. In some embodiments, the EMR effect sensor may include a voltage lead coupled to the conductive layer. In some embodiments, the voltage lead may be configured to provide a voltage for measurement by a voltage measurement circuit. In some embodiments, the EMR effect sensor may include a second voltage lead coupled to the semiconductor layer. In some embodiments, the second voltage lead may be configured to provide a voltage for measurement by a voltage measurement circuit. Embodiments of a Hall effect sensor having the same or similar structure are also disclosed.

  7. Fast, low noise transimpedance preamplifier

    International Nuclear Information System (INIS)

    Parlakyan, L.K.

    1995-01-01

    A single-channel transimpedance preamplifier for fast dielectric detectors is described. The main specifications of the preamplifier are: rise time is 1,5 ns; gain is 3,5 mV/μ A (with two section- 210 mV/μ A); r.m.s input noise is 30 n A; power consumption is 22 m W. Depending on supply voltage, the parameters may vary in a wide range. 5 refs

  8. Design of a low noise distributed amplifier with adjustable gain control in 0.15 μm GaAs PHEMT

    International Nuclear Information System (INIS)

    Zhang Ying; Wang Zhigong; Xu Jian; Luo Yin

    2012-01-01

    A low noise distributed amplifier consisting of 9 gain cells is presented. The chip is fabricated with 0.15-μm GaAs pseudomorphic high electron mobility transistor (PHEMT) technology from Win Semiconductor of Taiwan. A special optional gate bias technique is introduced to allow an adjustable gain control range of 10 dB. A novel cascode structure is adopted to extend the output voltage and bandwidth. The measurement results show that the amplifier gives an average gain of 15 dB with a gain flatness of ±1 dB in the 2–20 GHz band. The noise figure is between 2 and 4.1 dB during the band from 2 to 20 GHz. The amplifier also provides 13.8 dBm of output power at a 1 dB gain compression point and 10.5 dBm of input third order intercept point (IIP3), which demonstrates the excellent performance of linearity. The power consumption is 300 mW with a supply of 5 V, and the chip area is 2.36 × 1.01 mm 2 . (semiconductor integrated circuits)

  9. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m-1(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  10. A source of illumination for low-noise ‘Violin-Mode’ shadow sensors, intended for use in interferometric gravitational wave detectors

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.; Strain, K. A.

    2014-12-01

    A low-noise source of illumination is described for shadow sensors having a displacement sensitivity of (69  ±  13) picometres (rms)/√Hz, at 500 Hz, over a measuring span of ±0.1 mm. These sensors were designed to detect ‘Violin-Mode’ resonances in the suspension fibres of the test-masses/mirrors for the Advanced LIGO (Laser Interferometer Gravitational wave Observatory) gravitational wave detectors. The source of illumination (emitter) described here used a single column of 8 × miniature near infrared LEDs (λ = 890 nm). These emitters cast the shadows of 400 μm diameter fused silica suspension fibres onto their complementary shadow-displacement detectors, located at a distance of 74 fibre diameters (29.6 mm) behind the axes of the fibres themselves. Violin-Mode vibrations of each fibre were sensed as differential ac photocurrents in the corresponding ‘split-photodiode’ detector. This paper describes the design, construction, noise analysis, and measures that were taken in the conception of the emitters, in order to produce high-contrast shadows at such distant detectors. In this way it proved possible to obtain, simultaneously, a very high transfer sensitivity to Violin-Mode vibration of the fibres, and a very low level of detection noise—close to the fundamental shot noise limit—whilst remaining within the constraints of this simple design of emitter. The shadow detector is described in an accompanying paper.

  11. A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    International Nuclear Information System (INIS)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-01-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m −1 (rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm

  12. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

    Science.gov (United States)

    Lockerbie, N A; Tokmakov, K V

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  13. The ALICE experiment: $\\rm D^{+}$-meson production in heavy-ion collisions and silicon low noise sensors characterization for the ITS Upgrade.

    CERN Document Server

    AUTHOR|(CDS)2084697; Bruna, Elena

    This thesis collects my work on two aspects of the ALICE experiment at the Large Hadron Collider: the measurement of $\\rm D^{+}$-meson production in Pb-Pb collisions at $\\sqrt{s_{\\rm {NN}}}= 2.76$ TeV and the characterization of silicon low noise sensors for the Inner Tracking System Upgrade. I worked within the INFN group of Torino that it is involved in the ALICE experiment both in the physics program related to the study of heavy-flavour production and in the project of the ITS Upgrade. ALICE is one of the main experiment of the LHC and it is the only one optimized to study ultra-relativistic heavy-ion collisions. The main goal is to study the properties of the Quark Gluon Plasma (QGP), a phase of matter where quarks and gluons are deconned. Heavy quarks are a powerful tool to study such properties because they can be created only in hard scattering processes at the initial stage of the collision and, subsequently, they interact with the QGP. The measurement of charmed meson production in Pb-P...

  14. ALDO: A radiation-tolerant, low-noise, adjustable low drop-out linear regulator in 0.35 μm CMOS technology

    International Nuclear Information System (INIS)

    Carniti, P.; Cassina, L.; Gotti, C.; Maino, M.; Pessina, G.

    2016-01-01

    In this work we present ALDO, an adjustable low drop-out linear regulator designed in AMS 0.35 μm CMOS technology. It is specifically tailored for use in the upgraded LHCb RICH detector in order to improve the power supply noise for the front end readout chip (CLARO). ALDO is designed with radiation-tolerant solutions such as an all-MOS band-gap voltage reference and layout techniques aiming to make it able to operate in harsh environments like High Energy Physics accelerators. It is capable of driving up to 200 mA while keeping an adequate power supply filtering capability in a very wide frequency range from 10 Hz up to 100 MHz. This property allows us to suppress the noise and high frequency spikes that could be generated by a DC/DC regulator, for example. ALDO also shows a very low noise of 11.6 μV RMS in the same frequency range. Its output is protected with over-current and short detection circuits for a safe integration in tightly packed environments. Design solutions and measurements of the first prototype are presented.

  15. ALDO: A radiation-tolerant, low-noise, adjustable low drop-out linear regulator in 0.35 μm CMOS technology

    Energy Technology Data Exchange (ETDEWEB)

    Carniti, P., E-mail: paolo.carniti@mib.infn.it [INFN, Sezione di Milano Bicocca, I-20126 Milano (Italy); Dipartimento di Fisica, Università di Milano Bicocca, I-20126 Milano (Italy); Cassina, L.; Gotti, C.; Maino, M.; Pessina, G. [INFN, Sezione di Milano Bicocca, I-20126 Milano (Italy); Dipartimento di Fisica, Università di Milano Bicocca, I-20126 Milano (Italy)

    2016-07-11

    In this work we present ALDO, an adjustable low drop-out linear regulator designed in AMS 0.35 μm CMOS technology. It is specifically tailored for use in the upgraded LHCb RICH detector in order to improve the power supply noise for the front end readout chip (CLARO). ALDO is designed with radiation-tolerant solutions such as an all-MOS band-gap voltage reference and layout techniques aiming to make it able to operate in harsh environments like High Energy Physics accelerators. It is capable of driving up to 200 mA while keeping an adequate power supply filtering capability in a very wide frequency range from 10 Hz up to 100 MHz. This property allows us to suppress the noise and high frequency spikes that could be generated by a DC/DC regulator, for example. ALDO also shows a very low noise of 11.6 μV RMS in the same frequency range. Its output is protected with over-current and short detection circuits for a safe integration in tightly packed environments. Design solutions and measurements of the first prototype are presented.

  16. ALDO: A radiation-tolerant, low-noise, adjustable low drop-out linear regulator in 0.35 μm CMOS technology

    Science.gov (United States)

    Carniti, P.; Cassina, L.; Gotti, C.; Maino, M.; Pessina, G.

    2016-07-01

    In this work we present ALDO, an adjustable low drop-out linear regulator designed in AMS 0.35 μm CMOS technology. It is specifically tailored for use in the upgraded LHCb RICH detector in order to improve the power supply noise for the front end readout chip (CLARO). ALDO is designed with radiation-tolerant solutions such as an all-MOS band-gap voltage reference and layout techniques aiming to make it able to operate in harsh environments like High Energy Physics accelerators. It is capable of driving up to 200 mA while keeping an adequate power supply filtering capability in a very wide frequency range from 10 Hz up to 100 MHz. This property allows us to suppress the noise and high frequency spikes that could be generated by a DC/DC regulator, for example. ALDO also shows a very low noise of 11.6 μV RMS in the same frequency range. Its output is protected with over-current and short detection circuits for a safe integration in tightly packed environments. Design solutions and measurements of the first prototype are presented.

  17. Metal artifact reduction using a patch-based reconstruction for digital breast tomosynthesis

    Science.gov (United States)

    Borges, Lucas R.; Bakic, Predrag R.; Maidment, Andrew D. A.; Vieira, Marcelo A. C.

    2017-03-01

    Digital breast tomosynthesis (DBT) is rapidly emerging as the main clinical tool for breast cancer screening. Although several reconstruction methods for DBT are described by the literature, one common issue is the interplane artifacts caused by out-of-focus features. For breasts containing highly attenuating features, such as surgical clips and large calcifications, the artifacts are even more apparent and can limit the detection and characterization of lesions by the radiologist. In this work, we propose a novel method of combining backprojected data into tomographic slices using a patch-based approach, commonly used in denoising. Preliminary tests were performed on a geometry phantom and on an anthropomorphic phantom containing metal inserts. The reconstructed images were compared to a commercial reconstruction solution. Qualitative assessment of the reconstructed images provides evidence that the proposed method reduces artifacts while maintaining low noise levels. Objective assessment supports the visual findings. The artifact spread function shows that the proposed method is capable of suppressing artifacts generated by highly attenuating features. The signal difference to noise ratio shows that the noise levels of the proposed and commercial methods are comparable, even though the commercial method applies post-processing filtering steps, which were not implemented on the proposed method. Thus, the proposed method can produce tomosynthesis reconstructions with reduced artifacts and low noise levels.

  18. FRED (a Framework for Reconstructing Epidemic Dynamics): an open-source software system for modeling infectious diseases and control strategies using census-based populations.

    Science.gov (United States)

    Grefenstette, John J; Brown, Shawn T; Rosenfeld, Roni; DePasse, Jay; Stone, Nathan T B; Cooley, Phillip C; Wheaton, William D; Fyshe, Alona; Galloway, David D; Sriram, Anuroop; Guclu, Hasan; Abraham, Thomas; Burke, Donald S

    2013-10-08

    Mathematical and computational models provide valuable tools that help public health planners to evaluate competing health interventions, especially for novel circumstances that cannot be examined through observational or controlled studies, such as pandemic influenza. The spread of diseases like influenza depends on the mixing patterns within the population, and these mixing patterns depend in part on local factors including the spatial distribution and age structure of the population, the distribution of size and composition of households, employment status and commuting patterns of adults, and the size and age structure of schools. Finally, public health planners must take into account the health behavior patterns of the population, patterns that often vary according to socioeconomic factors such as race, household income, and education levels. FRED (a Framework for Reconstructing Epidemic Dynamics) is a freely available open-source agent-based modeling system based closely on models used in previously published studies of pandemic influenza. This version of FRED uses open-access census-based synthetic populations that capture the demographic and geographic heterogeneities of the population, including realistic household, school, and workplace social networks. FRED epidemic models are currently available for every state and county in the United States, and for selected international locations. State and county public health planners can use FRED to explore the effects of possible influenza epidemics in specific geographic regions of interest and to help evaluate the effect of interventions such as vaccination programs and school closure policies. FRED is available under a free open source license in order to contribute to the development of better modeling tools and to encourage open discussion of modeling tools being used to evaluate public health policies. We also welcome participation by other researchers in the further development of FRED.

  19. Vaginal reconstruction

    International Nuclear Information System (INIS)

    Lesavoy, M.A.

    1985-01-01

    Vaginal reconstruction can be an uncomplicated and straightforward procedure when attention to detail is maintained. The Abbe-McIndoe procedure of lining the neovaginal canal with split-thickness skin grafts has become standard. The use of the inflatable Heyer-Schulte vaginal stent provides comfort to the patient and ease to the surgeon in maintaining approximation of the skin graft. For large vaginal and perineal defects, myocutaneous flaps such as the gracilis island have been extremely useful for correction of radiation-damaged tissue of the perineum or for the reconstruction of large ablative defects. Minimal morbidity and scarring ensue because the donor site can be closed primarily. With all vaginal reconstruction, a compliant patient is a necessity. The patient must wear a vaginal obturator for a minimum of 3 to 6 months postoperatively and is encouraged to use intercourse as an excellent obturator. In general, vaginal reconstruction can be an extremely gratifying procedure for both the functional and emotional well-being of patients

  20. ACL Reconstruction

    Science.gov (United States)

    ... in moderate exercise and recreational activities, or play sports that put less stress on the knees. ACL reconstruction is generally recommended if: You're an athlete and want to continue in your sport, especially if the sport involves jumping, cutting or ...

  1. Merging fluxgate and induction coil data to produce low-noise geomagnetic observatory data meeting the INTERMAGNET definitive 1 s data standard

    Science.gov (United States)

    Brunke, Heinz-Peter; Widmer-Schnidrig, Rudolf; Korte, Monika

    2017-11-01

    For frequencies above 30 mHz the instrument intrinsic noise level of typical fluxgate magnetometers used at geomagnetic observatories usually masks ambient magnetic field variations on magnetically quiet days. This is especially true for stations located at middle and low latitudes, where variations are generally smaller than at high latitudes. INTERMAGNET has set a minimum quality standard for definitive 1 s data. Natural field variations referred to as pulsations (Pc-1, Pc-2, Pi-1) fall in this band. Usually their intensity is so small that they rarely surpass the instrumental noise of fluxgate magnetometers. Moreover, high-quality magnetic field observations in the band 30 mHz-0.5 Hz contain interesting information, e.g., for the study of ionospheric electron interactions with electromagnetic ion cyclotron plasma waves. We propose a method to improve 1 Hz observatory data by merging data from the proven and tested fluxgate magnetometers currently in use with induction coil magnetometers into a single data stream. We show how measurements of both instruments can be combined without information loss or phase distortion. The result is a time series of the magnetic field vector components, combining the benefits of both instruments: long-term stability (fluxgate) and low noise at high frequencies (induction coil). This new data stream fits perfectly into the data management procedures of INTERMAGNET and meets the requirements defined in the definitive 1 s data standard. We describe the applied algorithm and validate the result by comparing power spectra of the fluxgate magnetometer output with the merged signal. Daily spectrograms from the Niemegk observatory show that the resulting data series reveal information at frequencies above 30 mHz that cannot be seen in raw fluxgate data.

  2. A source of illumination for low-noise ‘Violin-Mode’ shadow sensors, intended for use in interferometric gravitational wave detectors

    International Nuclear Information System (INIS)

    Lockerbie, N A; Tokmakov, K V; Strain, K A

    2014-01-01

    A low-noise source of illumination is described for shadow sensors having a displacement sensitivity of (69  ±  13) picometres (rms)/√Hz, at 500 Hz, over a measuring span of ±0.1 mm. These sensors were designed to detect ‘Violin-Mode’ resonances in the suspension fibres of the test-masses/mirrors for the Advanced LIGO (Laser Interferometer Gravitational wave Observatory) gravitational wave detectors. The source of illumination (emitter) described here used a single column of 8 × miniature near infrared LEDs (λ = 890 nm). These emitters cast the shadows of 400 μm diameter fused silica suspension fibres onto their complementary shadow-displacement detectors, located at a distance of 74 fibre diameters (29.6 mm) behind the axes of the fibres themselves. Violin-Mode vibrations of each fibre were sensed as differential ac photocurrents in the corresponding ‘split-photodiode’ detector. This paper describes the design, construction, noise analysis, and measures that were taken in the conception of the emitters, in order to produce high-contrast shadows at such distant detectors. In this way it proved possible to obtain, simultaneously, a very high transfer sensitivity to Violin-Mode vibration of the fibres, and a very low level of detection noise—close to the fundamental shot noise limit—whilst remaining within the constraints of this simple design of emitter. The shadow detector is described in an accompanying paper. (paper)

  3. A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Lockerbie, N. A.; Tokmakov, K. V. [SUPA (Scottish Universities Physics Alliance) Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG (United Kingdom)

    2014-11-15

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m{sup −1}(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  4. Merging fluxgate and induction coil data to produce low-noise geomagnetic observatory data meeting the INTERMAGNET definitive 1 s data standard

    Directory of Open Access Journals (Sweden)

    H.-P. Brunke

    2017-11-01

    Full Text Available For frequencies above 30 mHz the instrument intrinsic noise level of typical fluxgate magnetometers used at geomagnetic observatories usually masks ambient magnetic field variations on magnetically quiet days. This is especially true for stations located at middle and low latitudes, where variations are generally smaller than at high latitudes. INTERMAGNET has set a minimum quality standard for definitive 1 s data. Natural field variations referred to as pulsations (Pc-1, Pc-2, Pi-1 fall in this band. Usually their intensity is so small that they rarely surpass the instrumental noise of fluxgate magnetometers. Moreover, high-quality magnetic field observations in the band 30 mHz–0.5 Hz contain interesting information, e.g., for the study of ionospheric electron interactions with electromagnetic ion cyclotron plasma waves. We propose a method to improve 1 Hz observatory data by merging data from the proven and tested fluxgate magnetometers currently in use with induction coil magnetometers into a single data stream. We show how measurements of both instruments can be combined without information loss or phase distortion. The result is a time series of the magnetic field vector components, combining the benefits of both instruments: long-term stability (fluxgate and low noise at high frequencies (induction coil. This new data stream fits perfectly into the data management procedures of INTERMAGNET and meets the requirements defined in the definitive 1 s data standard. We describe the applied algorithm and validate the result by comparing power spectra of the fluxgate magnetometer output with the merged signal. Daily spectrograms from the Niemegk observatory show that the resulting data series reveal information at frequencies above 30 mHz that cannot be seen in raw fluxgate data.

  5. Maxillary reconstruction

    Directory of Open Access Journals (Sweden)

    Brown James

    2007-12-01

    Full Text Available This article aims to discuss the various defects that occur with maxillectomy with a full review of the literature and discussion of the advantages and disadvantages of the various techniques described. Reconstruction of the maxilla can be relatively simple for the standard low maxillectomy that does not involve the orbital floor (Class 2. In this situation the structure of the face is less damaged and the there are multiple reconstructive options for the restoration of the maxilla and dental alveolus. If the maxillectomy includes the orbit (Class 4 then problems involving the eye (enopthalmos, orbital dystopia, ectropion and diplopia are avoided which simplifies the reconstruction. Most controversy is associated with the maxillectomy that involves the orbital floor and dental alveolus (Class 3. A case is made for the use of the iliac crest with internal oblique as an ideal option but there are other methods, which may provide a similar result. A multidisciplinary approach to these patients is emphasised which should include a prosthodontist with a special expertise for these defects.

  6. Development and validation of a numerical method for computing two-phase flows without interface reconstruction. Application to Taylor bubbles dynamics

    International Nuclear Information System (INIS)

    Benkenida, Adlene

    1999-01-01

    This work is devoted to the development and the use of a numerical code aimed to compute complex two-phase flows in which the topology of the interfaces evolves in time. The solution strategy makes use of a fixed grid on which interfaces evolve freely. The governing equations of the model (one-fluid model) are obtained by adding the local, instantaneous Navier-Stokes equations of each phase after a spatial filtering. The use of an Eulerian approach yields difficulties in estimating several of the two-phase quantities, especially the viscous stress tensor. This problem is overcome by deriving and validating an expression of the stress tensor valid for any Eulerian treatment and whatever the orientation of the interfaces with respect to the grid. To simplify the governing equations of the model, it is assumed that no phase change occurs, that no local slip exists between both phases, and that no small-scale turbulence is present. The possibility to remove some of these hypotheses is discussed, especially with the future aim of developing a large-eddy simulation approach of two-phase flows in which the motion and the effects of small-scale two-phase structures could be taken into account. Interface transport is performed by using a FCT front capturing method without any interface reconstruction procedure. It is shown through several tests that the version of Zalesak's (1979) algorithm in which each direction is treated independently yields the best results, even though a tendency for interfacial regions to thicken artificially is observed in regions with high stretching rates.The code is validated by performing simulations on some simple two-phase flows and by comparing numerical results with available analytical solutions, experiments, or previous computations. Among the results of these tests, those concerning the bouncing of a bubble on a rigid wall are the most original and shed new light on this phenomenon, especially by revealing the time evolution of the

  7. Computer Based Road Accident Reconstruction Experiences

    Directory of Open Access Journals (Sweden)

    Milan Batista

    2005-03-01

    Full Text Available Since road accident analyses and reconstructions are increasinglybased on specific computer software for simulationof vehicle d1iving dynamics and collision dynamics, and forsimulation of a set of trial runs from which the model that bestdescribes a real event can be selected, the paper presents anoverview of some computer software and methods available toaccident reconstruction experts. Besides being time-saving,when properly used such computer software can provide moreauthentic and more trustworthy accident reconstruction, thereforepractical experiences while using computer software toolsfor road accident reconstruction obtained in the TransportSafety Laboratory at the Faculty for Maritime Studies andTransport of the University of Ljubljana are presented and discussed.This paper addresses also software technology for extractingmaximum information from the accident photo-documentationto support accident reconstruction based on the simulationsoftware, as well as the field work of reconstruction expertsor police on the road accident scene defined by this technology.

  8. A step-wise steerable source of illumination for low-noise "Violin-Mode" shadow sensors, intended for use in interferometric gravitational wave detectors

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.

    2016-01-01

    A steerable low-noise source of illumination is described for shadow-sensors having a displacement sensitivity of ˜100 pm (rms)/√Hz, at 500 Hz, over a measuring span of at least ±0.5 mm. These sensors were designed to detect lateral "Violin-Mode" resonances in the highly tensioned fused-silica suspension fibres of the test-masses/mirrors for the Advanced Laser Interferometer Gravitational Wave Observatory gravitational wave detectors. The shadow sensors—one intended for each of the four fibres in a suspension—comprised a source of Near InfraRed (NIR) radiation (emitter) and a differential shadow-displacement sensor (detector), these bracketing the fibre under test. The suspension fibres themselves were approximately 600 mm long by 0.4 mm in diameter, and when illuminated from the side, they cast narrow, vertical, shadows onto their respective detectors—these being located at an effective distance of 50 fibre diameters behind the axes of the fibres themselves. The emitter described here was designed to compensate for a significant degree of mechanical drift or creep over time in the mean position of its suspension fibre. This was achieved by employing five adjacent columns of 8 × miniature NIR LEDs (Light Emitting Diodes, λ = 890 nm), with one column being activated at a time. When used in conjunction with a "reverse Galilean" telescope, the LED sources allowed the collimated beam from the emitter to be steered azimuthally in fine angular increments (0.65°), causing the fibre's shadow to move laterally, in a step-wise manner, across the plane of its facing detector. Each step in shadow position was approximately 0.23 mm in size, and this allowed the fibre's shadow to be re-centred, so as to bridge once again both elements of its photodiode detector—even if the fibre was off-centred by as much as ±0.5 mm. Re-centring allowed Violin-Mode vibrations of the fibre to be sensed once again as differential AC photocurrents, these flowing in anti-phase in the

  9. A step-wise steerable source of illumination for low-noise “Violin-Mode” shadow sensors, intended for use in interferometric gravitational wave detectors

    International Nuclear Information System (INIS)

    Lockerbie, N. A.; Tokmakov, K. V.

    2016-01-01

    A steerable low-noise source of illumination is described for shadow-sensors having a displacement sensitivity of ∼100 pm (rms)/√Hz, at 500 Hz, over a measuring span of at least ±0.5 mm. These sensors were designed to detect lateral “Violin-Mode” resonances in the highly tensioned fused-silica suspension fibres of the test-masses/mirrors for the Advanced Laser Interferometer Gravitational Wave Observatory gravitational wave detectors. The shadow sensors—one intended for each of the four fibres in a suspension—comprised a source of Near InfraRed (NIR) radiation (emitter) and a differential shadow-displacement sensor (detector), these bracketing the fibre under test. The suspension fibres themselves were approximately 600 mm long by 0.4 mm in diameter, and when illuminated from the side, they cast narrow, vertical, shadows onto their respective detectors—these being located at an effective distance of 50 fibre diameters behind the axes of the fibres themselves. The emitter described here was designed to compensate for a significant degree of mechanical drift or creep over time in the mean position of its suspension fibre. This was achieved by employing five adjacent columns of 8  × miniature NIR LEDs (Light Emitting Diodes, λ = 890 nm), with one column being activated at a time. When used in conjunction with a “reverse Galilean” telescope, the LED sources allowed the collimated beam from the emitter to be steered azimuthally in fine angular increments (0.65°), causing the fibre’s shadow to move laterally, in a step-wise manner, across the plane of its facing detector. Each step in shadow position was approximately 0.23 mm in size, and this allowed the fibre’s shadow to be re-centred, so as to bridge once again both elements of its photodiode detector—even if the fibre was off-centred by as much as ±0.5 mm. Re-centring allowed Violin-Mode vibrations of the fibre to be sensed once again as differential AC photocurrents, these flowing in

  10. A step-wise steerable source of illumination for low-noise “Violin-Mode” shadow sensors, intended for use in interferometric gravitational wave detectors

    Energy Technology Data Exchange (ETDEWEB)

    Lockerbie, N. A.; Tokmakov, K. V. [SUPA (Scottish Universities Physics Alliance), Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG (United Kingdom)

    2016-01-15

    A steerable low-noise source of illumination is described for shadow-sensors having a displacement sensitivity of ∼100 pm (rms)/√Hz, at 500 Hz, over a measuring span of at least ±0.5 mm. These sensors were designed to detect lateral “Violin-Mode” resonances in the highly tensioned fused-silica suspension fibres of the test-masses/mirrors for the Advanced Laser Interferometer Gravitational Wave Observatory gravitational wave detectors. The shadow sensors—one intended for each of the four fibres in a suspension—comprised a source of Near InfraRed (NIR) radiation (emitter) and a differential shadow-displacement sensor (detector), these bracketing the fibre under test. The suspension fibres themselves were approximately 600 mm long by 0.4 mm in diameter, and when illuminated from the side, they cast narrow, vertical, shadows onto their respective detectors—these being located at an effective distance of 50 fibre diameters behind the axes of the fibres themselves. The emitter described here was designed to compensate for a significant degree of mechanical drift or creep over time in the mean position of its suspension fibre. This was achieved by employing five adjacent columns of 8  × miniature NIR LEDs (Light Emitting Diodes, λ = 890 nm), with one column being activated at a time. When used in conjunction with a “reverse Galilean” telescope, the LED sources allowed the collimated beam from the emitter to be steered azimuthally in fine angular increments (0.65°), causing the fibre’s shadow to move laterally, in a step-wise manner, across the plane of its facing detector. Each step in shadow position was approximately 0.23 mm in size, and this allowed the fibre’s shadow to be re-centred, so as to bridge once again both elements of its photodiode detector—even if the fibre was off-centred by as much as ±0.5 mm. Re-centring allowed Violin-Mode vibrations of the fibre to be sensed once again as differential AC photocurrents, these flowing in

  11. Jet Propulsion Laboratory/NASA Lewis Research Center space qualified hybrid high temperature superconducting/semiconducting 7.4 GHz low-noise downconverter for NRL HTSSE-II program

    International Nuclear Information System (INIS)

    Javadi, H.H.S.; Bowen, J.G.; Rascoe, D.L.; Chorey, C.M.

    1996-01-01

    A deep space satellite downconverter receiver was proposed by Jet Propulsion Laboratory (JPL) and NASA Lewis Research Center (LeRC) for the Naval Research Laboratory's (NRL) high temperature superconductivity space experiment, phase-II (HTSSE-II) program. Space qualified low-noise cryogenic downconverter receivers utilizing thin-film high temperature superconducting (HTS) passive circuitry and semiconductor active devices were developed and delivered to NRL. The downconverter consists of an HTS preselect filter, a cryogenic low-noise amplifier, a cryogenic mixer, and a cryogenic oscillator with an HTS resonator. HTS components were inserted as the front-end filter and the local oscillator resonator for their superior 77 K performance over the conventional components. The semiconducting low noise amplifier also benefited from cooling to 77 K. The mixer was designed specifically for cryogenic applications and provided low conversion loss and low power consumption. In addition to an engineering model, two space qualified units (qualification, flight) were built and delivered to NRL. Manufacturing, integration and test of the space qualified downconverters adhered to the requirements of JPL class-D space instruments and partially to MIL-STD-883D specifications. The qualification unit has ∼50 K system noise temperature which is a factor of three better than a conventional downconverter at room temperature

  12. Ulysses S. Grant and Reconstruction.

    Science.gov (United States)

    Wilson, David L.

    1989-01-01

    Discusses the role played by Ulysses S. Grant during the four years of Reconstruction before he became President of the United States. Describes the dynamics of the relationship between Grant and Andrew Johnson. Points out that Grant's attitude of service to the laws created by Congress submerged his desire to create a new South. (KO)

  13. PET reconstruction

    International Nuclear Information System (INIS)

    O'Sullivan, F.; Pawitan, Y.; Harrison, R.L.; Lewellen, T.K.

    1990-01-01

    In statistical terms, filtered backprojection can be viewed as smoothed Least Squares (LS). In this paper, the authors report on improvement in LS resolution by: incorporating locally adaptive smoothers, imposing positivity and using statistical methods for optimal selection of the resolution parameter. The resulting algorithm has high computational efficiency relative to more elaborate Maximum Likelihood (ML) type techniques (i.e. EM with sieves). Practical aspects of the procedure are discussed in the context of PET and illustrations with computer simulated and real tomograph data are presented. The relative recovery coefficients for a 9mm sphere in a computer simulated hot-spot phantom range from .3 to .6 when the number of counts ranges from 10,000 to 640,000 respectively. The authors will also present results illustrating the relative efficacy of ML and LS reconstruction techniques

  14. Clinical evaluation of iterative reconstruction (ordered-subset expectation maximization) in dynamic positron emission tomography: quantitative effects on kinetic modeling with N-13 ammonia in healthy subjects

    DEFF Research Database (Denmark)

    Hove, Jens D; Rasmussen, Rune; Freiberg, Jacob

    2008-01-01

    BACKGROUND: The purpose of this study was to investigate the quantitative properties of ordered-subset expectation maximization (OSEM) on kinetic modeling with nitrogen 13 ammonia compared with filtered backprojection (FBP) in healthy subjects. METHODS AND RESULTS: Cardiac N-13 ammonia positron...... emission tomography (PET) studies from 20 normal volunteers at rest and during dipyridamole stimulation were analyzed. Image data were reconstructed with either FBP or OSEM. FBP- and OSEM-derived input functions and tissue curves were compared together with the myocardial blood flow and spillover values...... and OSEM flow values were observed with a flow underestimation of 45% (rest/dipyridamole) in the septum and of 5% (rest) and 15% (dipyridamole) in the lateral myocardial wall. CONCLUSIONS: OSEM reconstruction of myocardial perfusion images with N-13 ammonia and PET produces high-quality images for visual...

  15. Clinical evaluation of iterative reconstruction (ordered-subset expectation maximization) in dynamic positron emission tomography: quantitative effects on kinetic modeling with N-13 ammonia in healthy subjects

    DEFF Research Database (Denmark)

    Hove, Jens Dahlgaard; Rasmussen, R.; Freiberg, J.

    2008-01-01

    emission tomography (PET) studies from 20 normal volunteers at rest and during dipyridamole stimulation were analyzed. Image data were reconstructed with either FBP or OSEM. FBP- and OSEM-derived input functions and tissue curves were compared together with the myocardial blood flow and spillover values...... and OSEM flow values were observed with a flow underestimation of 45% (rest/dipyridamole) in the septum and of 5% (rest) and 15% (dipyridamole) in the lateral myocardial wall. CONCLUSIONS: OSEM reconstruction of myocardial perfusion images with N-13 ammonia and PET produces high-quality images for visual...... interpretation. However, compared with FBP, OSEM is associated with substantial underestimation of perfusion on quantitative imaging. Our findings indicate that OSEM should be used with precaution in clinical PET studies Udgivelsesdato: 2008/7...

  16. Reconstructing mantle heterogeneity with data assimilation based on the back-and-forth nudging method: Implications for mantle-dynamic fitting of past plate motions

    Science.gov (United States)

    Glišović, Petar; Forte, Alessandro

    2016-04-01

    The paleo-distribution of density variations throughout the mantle is unknown. To address this question, we reconstruct 3-D mantle structure over the Cenozoic era using a data assimilation method that implements a new back-and-forth nudging algorithm. For this purpose, we employ convection models for a compressible and self-gravitating mantle that employ 3-D mantle structure derived from joint seismic-geodynamic tomography as a starting condition. These convection models are then integrated backwards in time and are required to match geologic estimates of past plate motions derived from marine magnetic data. Our implementation of the nudging algorithm limits the difference between a reconstruction (backward-in-time solution) and a prediction (forward-in-time solution) on over a sequence of 5-million-year time windows that span the Cenozoic. We find that forward integration of reconstructed mantle heterogeneity that is constrained to match past plate motions delivers relatively poor fits to the seismic-tomographic inference of present-day mantle heterogeneity in the upper mantle. We suggest that uncertainties in the past plate motions, related for example to plate reorganization episodes, could partly contribute to the poor match between predicted and observed present-day heterogeneity. We propose that convection models that allow tectonic plates to evolve freely in accord with the buoyancy forces and rheological structure in the mantle could provide additional constraints on geologic estimates of paleo-configurations of the major tectonic plates.

  17. Breast Reconstruction After Mastectomy

    Science.gov (United States)

    ... Cancer Prevention Genetics of Breast & Gynecologic Cancers Breast Cancer Screening Research Breast Reconstruction After Mastectomy On This Page What is breast reconstruction? How do surgeons use implants to reconstruct a woman’s breast? How do surgeons ...

  18. Breast reconstruction - implants

    Science.gov (United States)

    Breast implants surgery; Mastectomy - breast reconstruction with implants; Breast cancer - breast reconstruction with implants ... harder to find a tumor if your breast cancer comes back. Getting breast implants does not take as long as breast reconstruction ...

  19. Dynamic Liver Magnetic Resonance Imaging in Free-Breathing: Feasibility of a Cartesian T1-Weighted Acquisition Technique With Compressed Sensing and Additional Self-Navigation Signal for Hard-Gated and Motion-Resolved Reconstruction.

    Science.gov (United States)

    Kaltenbach, Benjamin; Bucher, Andreas M; Wichmann, Julian L; Nickel, Dominik; Polkowski, Christoph; Hammerstingl, Renate; Vogl, Thomas J; Bodelle, Boris

    2017-11-01

    The aim of this study was to assess the feasibility of a free-breathing dynamic liver imaging technique using a prototype Cartesian T1-weighted volumetric interpolated breathhold examination (VIBE) sequence with compressed sensing and simultaneous acquisition of a navigation signal for hard-gated and motion state-resolved reconstruction. A total of 43 consecutive oncologic patients (mean age, 66 ± 11 years; 44% female) underwent free-breathing dynamic liver imaging for the evaluation of liver metastases from colorectal cancer using a prototype Cartesian VIBE sequence (field of view, 380 × 345 mm; image matrix, 320 × 218; echo time/repetition time, 1.8/3.76 milliseconds; flip angle, 10 degrees; slice thickness, 3.0 mm; acquisition time, 188 seconds) with continuous data sampling and additionally acquired self-navigation signal. Data were iteratively reconstructed using 2 different approaches: first, a hard-gated reconstruction only using data associated to the dominating motion state (CS VIBE, Compressed Sensing VIBE), and second, a motion-resolved reconstruction with 6 different motion states as additional image dimension (XD VIBE, eXtended dimension VIBE). Continuous acquired data were grouped in 16 subsequent time increments with 11.57 seconds each to resolve arterial and venous contrast phases. For image quality assessment, both CS VIBE and XD VIBE were compared with the patient's last staging dynamic liver magnetic resonance imaging including a breathhold (BH) VIBE as reference standard 4.5 ± 1.2 months before. Representative quality parameters including respiratory artifacts were evaluated for arterial and venous phase images independently, retrospectively and blindly by 3 experienced radiologists, with higher scores indicating better examination quality. To assess diagnostic accuracy, same readers evaluated the presence of metastatic lesions for XD VIBE and CS VIBE compared with reference BH examination in a second session. Compared with CS VIBE, XD VIBE

  20. Maps From Mud—Using the Multiple Scenario Approach to Reconstruct Land Cover Dynamics From Pollen Records: A Case Study of Two Neolithic Landscapes

    Directory of Open Access Journals (Sweden)

    M. Jane Bunting

    2018-04-01

    Full Text Available Pollen records contain a wide range of information about past land cover, but translation from the pollen diagram to other formats remains a challenge. In this paper, we present LandPolFlow, a software package enabling Multiple Scenario Approach (MSA based land cover reconstruction from pollen records for specific landscapes. It has two components: a basic Geographic Information System which takes grids of landscape constraints (e.g., topography, geology and generates possible “scenarios” of past land cover using a combination of probabilistic and deterministic placement rules to distribute defined plant communities within the landscape, and a pollen dispersal and deposition model which simulates pollen loading at specified points within each scenario and compares that statistically with actual pollen assemblages from the same location. Goodness of fit statistics from multiple pollen site locations are used to identify which scenarios are likely reconstructions of past land cover. We apply this approach to two case studies of Neolithisation in Britain, the first from the Somerset Levels and Moors and the second from Mainland, Orkney. Both landscapes contain significant evidence of Neolithic activity, but present contrasting contexts. In Somerset, wet-preserved Neolithic remains such as trackways are abundant, but little dry land settlement archaeology is known, and the pre-Neolithic landscape was extensively wooded. In Orkney, the Neolithic archaeology includes domestic and monumental stone-built structures forming a UNESCO World Heritage Site, and the pre-Neolithic landscape was largely treeless. Existing pollen records were collated from both landscapes and correlated within new chronological frameworks (presented elsewhere. This allowed pollen data to be grouped into 200 year periods, or “timeslices,” for reconstruction of land cover through time using the MSA. Reconstruction suggests that subtle but clear and persistent impacts of

  1. Adaptive algebraic reconstruction technique

    International Nuclear Information System (INIS)

    Lu Wenkai; Yin Fangfang

    2004-01-01

    Algebraic reconstruction techniques (ART) are iterative procedures for reconstructing objects from their projections. It is proven that ART can be computationally efficient by carefully arranging the order in which the collected data are accessed during the reconstruction procedure and adaptively adjusting the relaxation parameters. In this paper, an adaptive algebraic reconstruction technique (AART), which adopts the same projection access scheme in multilevel scheme algebraic reconstruction technique (MLS-ART), is proposed. By introducing adaptive adjustment of the relaxation parameters during the reconstruction procedure, one-iteration AART can produce reconstructions with better quality, in comparison with one-iteration MLS-ART. Furthermore, AART outperforms MLS-ART with improved computational efficiency

  2. The Development of the Silurian Trilobite Aulacopleura koninckii Reconstructed by Applying Inferred Growth and Segmentation Dynamics: A Case Study in Paleo-Evo-Devo

    Directory of Open Access Journals (Sweden)

    Nigel C. Hughes

    2017-05-01

    Full Text Available Fossilized growth series provide rare glimpses into the development of ancient organisms, illustrating descriptively how size and shape changed through ontogeny. Occasionally fossil preservation is such that it is feasible to test alternative possibilities about how ancient development was regulated. Here we apply inferred developmental parameters pertaining to size, shape, and segmentation in the abundant and well-preserved 429 Myr old trilobite Aulacopleura koninckii that we have investigated previously to reconstruct the post-embryonic ontogeny of this ancient arthropod. Our published morphometric analyses associated with model testing have shown that: specification of the adult number of trunk segments (polymorphic in this species was determined precociously in ontogeny; that growth regulation was targeted (i.e., compensatory, such that each developmental stage exhibited comparable variance in size and shape; and that growth gradients operating along the main body axis, both during juvenile and adult ontogeny, resulted from a form of growth control based on positional specification. While such developmental features are common among extant organisms, our results represent the oldest evidence for them within Metazoa. Herein, the novel reconstruction of the development of Aulacopleura koninckii permits visualization of patterns of relative and absolute growth and segmentation as never before possible for a fossilized arthropod ontogeny. By conducting morphometric analysis of appropriate data sets it is thus possible to move beyond descriptive ontogenetic studies and to address questions of high interest for evolutionary developmental biology using data from fossils, which can help elucidate both how developmental processes themselves evolve and how they affect the evolution of organismal body patterning. By extending similar analyses to other cases of exceptional preservation of fossilized ontogeny, we can anticipate beginning to realize the

  3. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  4. Dynamic restraint capacity of the hamstring muscles has important functional implications after anterior cruciate ligament injury and anterior cruciate ligament reconstruction.

    Science.gov (United States)

    Bryant, Adam L; Creaby, Mark W; Newton, Robert U; Steele, Julie R

    2008-12-01

    The purpose of this study was to investigate the relation between knee functionality of anterior cruciate ligament deficient (ACLD) and anterior cruciate ligament reconstruction (ACLR) patients and hamstring antagonist torque generated during resisted knee extension. Cross-sectional. Laboratory based. Male ACLD subjects (n=10) (18-35 y) and 27 matched males who had undergone ACLR (14 patella tendon [PT] grafts and 13 combined semitendinosus/gracilis tendon grafts). Not applicable. Knee functionality was rated (0- to 100-point scale) by using the Cincinnati Knee Rating System. Using electromyography data from the semitendinosus (ST) and biceps femoris muscles, we created a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10 degrees intervals from 80 degrees to 10 degrees knee flexion. Pearson product-moment correlations revealed that more functional ACLD subjects generated significantly (Phamstring antagonist torque throughout knee extension. In contrast, more functional PT subjects produced significantly lower hamstring antagonist torque at 80 degrees to 70 degrees knee flexion, whereas no significant associations were found between hamstring antagonist torque and knee functionality for the ST/gracilis tendon subjects. An increased hamstring antagonist torque generated by the more functional ACLD subjects, reflective of increased hamstring contractile force, is thought to represent a protective mechanism to compensate for mechanical instability. The restoration of anterior knee stability through ACLR negates the need for augmented hamstring antagonist torque.

  5. Fire activity and hydrological dynamics in the past 5700 years reconstructed from Sphagnum peatlands along the oceanic-continental climatic gradient in northern Poland

    Science.gov (United States)

    Marcisz, Katarzyna; Gałka, Mariusz; Pietrala, Patryk; Miotk-Szpiganowicz, Grażyna; Obremska, Milena; Tobolski, Kazimierz; Lamentowicz, Mariusz

    2017-12-01

    Fire is a critical component of many ecosystems and, as predicted by various climate models, fire activity may increase significantly in the following years due to climate change. Therefore, knowledge about the past fire activity of various ecosystems is highly important for future nature conservation purposes. We present results of high-resolution investigation of fire activity and hydrological changes in northern Poland. We analyzed microscopic charcoal from three Sphagnum-dominated peatlands located on the south of Baltic, on the oceanic-continental (west-east) climatic gradient, and reconstructed the history of fire in the last 5700 years. We hypothesize that air circulation patterns are highly important for local fire activity, and that fire activity is more intensive in peatlands influenced by continental air masses. We have found out that forest fires have been occurring regularly since the past millennia and were linked to climatic conditions. We show that fire activity (related to climate and fuel availability) was significantly higher in sites dominated by continental climate (northeastern Poland) than in the site located under oceanic conditions (northwestern Poland)-microscopic charcoal influx was 13.3 times higher in the eastern study site of the gradient, compared to the western study site. Recorded fire activity patterns were different between the sites in a long timescale. Moreover, most of the recorded charcoal peaks occurred during high water tables. Rising human pressure has caused droughts and water table instability, and substantial increase in fire activity in the last 400 years.

  6. Breast reconstruction - natural tissue

    Science.gov (United States)

    ... flap; TRAM; Latissimus muscle flap with a breast implant; DIEP flap; DIEAP flap; Gluteal free flap; Transverse upper gracilis flap; TUG; Mastectomy - breast reconstruction with natural tissue; Breast cancer - breast reconstruction with natural tissue

  7. Breast reconstruction after mastectomy

    Directory of Open Access Journals (Sweden)

    Daniel eSchmauss

    2016-01-01

    Full Text Available Breast cancer is the leading cause of cancer death in women worldwide. Its surgical approach has become less and less mutilating in the last decades. However, the overall number of breast reconstructions has significantly increased lately. Nowadays breast reconstruction should be individualized at its best, first of all taking into consideration oncological aspects of the tumor, neo-/adjuvant treatment and genetic predisposition, but also its timing (immediate versus delayed breast reconstruction, as well as the patient’s condition and wish. This article gives an overview over the various possibilities of breast reconstruction, including implant- and expander-based reconstruction, flap-based reconstruction (vascularized autologous tissue, the combination of implant and flap, reconstruction using non-vascularized autologous fat, as well as refinement surgery after breast reconstruction.

  8. Noninvasive, low-noise, fast imaging of blood volume and deoxygenation changes in muscles using light-emitting diode continuous-wave imager

    Science.gov (United States)

    Lin, Yuanqing; Lech, Gwen; Nioka, Shoko; Intes, Xavier; Chance, Britton

    2002-08-01

    This article focuses on optimizing the signal to noise ratio (SNR) of a three-wavelength light-emitting diode (LED) near-infrared continuous-wave (cw) imager and its application to in vivo muscle metabolism measurement. The shot-noise limited SNR is derived and calculated to be 2 x104 for the physiological blood concentrations of muscle. Aiming at shot-noise limited SNR performance and fast imaging, we utilize sample and hold circuits to reduce high-frequency noise. These circuits have also been designed to be parallel integrating, through which SNR of 2 x103 and 2 Hz imaging acquisition rate have been achieved when the probe is placed on a muscle model. The noise corresponds to 2 x10-4 optical density error, which suggests an in vitro resolution of 15. 4 nM blood volume and 46.8 nM deoxygenation changes. A 48 dB digital gain control circuit with 256 steps is employed to enlarge the dynamic range of the imager. We utilize cuff ischemia as a living model demonstration and its results are reported. The instrument is applied during exercise to measure the changes of blood volume and deoxygenation, which provides important information about muscle metabolism. We find that the primary source of noise encountered during exercise experiment is from the random motion of muscle. The results demonstrate that the LED cw imager is ideal for the noninvasive study of muscle metabolism.

  9. Dynamics of metallic contaminants at a basin scale--Spatial and temporal reconstruction from four sediment cores (Loire fluvial system, France).

    Science.gov (United States)

    Dhivert, E; Grosbois, C; Courtin-Nomade, A; Bourrain, X; Desmet, M

    2016-01-15

    From the 19th century, the Loire basin (France) presents potentially pollutant activities such as mining and heavy industries. This paper shows spatio-temporal distribution of trace elements in sediments at a basin-scale, based on a comparison of archived temporal signals recorded in four sedimentary cores. Anthropogenic sources contributing to sediment contamination are also characterized, using geochemical signatures recorded in river bank sediments of the most industrialized tributaries. This study highlights upstream-downstream differences concerning recorded contamination phases in terms of spatial influence and temporality of archiving processes. Such differences were related to (i) various spatial influences of contamination sources and (ii) polluted sediments dispersion controlled by transport capacity of metal-carrier phases and hydrosedimentary dynamics. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Reconstructing a lost Eocene Paradise, Part II: On the utility of dynamic global vegetation models in pre-Quaternary climate studies

    Science.gov (United States)

    Shellito, Cindy J.; Sloan, Lisa C.

    2006-02-01

    Models that allow vegetation to respond to and interact with climate provide a unique method for addressing questions regarding feedbacks between the ecosystem and climate in pre-Quaternary time periods. In this paper, we consider how Dynamic Global Vegetation Models (DGVMs), which have been developed for simulations with present day climate, can be used for paleoclimate studies. We begin with a series of tests in the NCAR Land Surface Model (LSM)-DGVM with Eocene geography to examine (1) the effect of removing C 4 grasses from the available plant functional types in the model; (2) model sensitivity to a change in soil texture; and (3), model sensitivity to a change in the value of pCO 2 used in the photosynthetic rate equations. The tests were designed to highlight some of the challenges of using these models and prompt discussion of possible improvements. We discuss how lack of detail in model boundary conditions, uncertainties in the application of modern plant functional types to paleo-flora simulations, and inaccuracies in the model climatology used to drive the DGVM can affect interpretation of model results. However, we also review a number of DGVM features that can facilitate understanding of past climates and offer suggestions for improving paleo-DGVM studies.

  11. The Uluzzian technology of Grotta di Fumane and its implication for reconstructing cultural dynamics in the Middle-Upper Palaeolithic transition of Western Eurasia.

    Science.gov (United States)

    Peresani, Marco; Cristiani, Emanuela; Romandini, Matteo

    2016-02-01

    From the intricate ensemble of evidence related to the Middle-Upper Palaeolithic transition and the presumed first spread of anatomically modern humans in Europe, the Uluzzian has attracted major attention in the past few years. Although the Uluzzian has been viewed as a supposed product of modern humans settling in Mediterranean Europe, the techno-cultural complex has been the subject of few investigations aiming to clarify its chronology, bone industry, and settlement dynamics. Further, little is known of its technological structure. This article presents the results of an extensive study of the lithic and bone technologies from assemblages recovered at Fumane Cave in the north of Italy. Results confirm that the Uluzzian is a flake-dominated industry that brings together a set of technological innovations. The Levallois is the most used method in the initial phase, which is replaced by more varied flaking procedures and an increase in bladelets and flake-blades. Sidescrapers and points also represent a Mousterian feature in the initial phase, while splintered pieces, backed knives and other Upper Palaeolithic tools increase in the later phase. Our results suggest that the Uluzzian is rooted in the Mousterian lithic technological context and cannot be viewed as a proxy for anatomically modern humans, the carriers of the abrupt cultural changes related to the Aurignacian. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Isokinetic Testing in Evaluation Rehabilitation Outcome After ACL Reconstruction

    OpenAIRE

    Cvjetkovic, Dragana Dragicevic; Bijeljac, Sinisa; Palija, Stanislav; Talic, Goran; Radulovic, Tatjana Nozica; Kosanovic, Milkica Glogovac; Manojlovic, Slavko

    2015-01-01

    Introduction: Numerous rehab protocols have been used in rehabilitation after ACL reconstruction. Isokinetic testing is an objective way to evaluate dynamic stability of the knee joint that estimates the quality of rehabilitation outcome after ACL reconstruction. Our investigation goal was to show importance of isokinetic testing in evaluation thigh muscle strength in patients which underwent ACL reconstruction and rehabilitation protocol. Subjects and methods: In prospective study, we evalua...

  13. An approach to reconstruction of a natural crack using signals of eddy current testing. 1. Reconstruction of an idealized natural crack

    International Nuclear Information System (INIS)

    Chen, Zhenmao

    1998-12-01

    In this paper, an approach to the reconstruction of an idealized natural crack of non-vanishing conductivity is proposed with use of signals of eddy current testing. Two numerical models are introduced at first for modeling a Stress Corrosion Crack (SCC) in order it possibly to be represented by a set of crack parameters. A method for rapid prediction of the eddy current testing signals arisen from these idealized cracks is given then by extending a knowledge based fast forward solver developed by authors to the case of a non-vanishing conductivity. On the other hand, the inverse algorithm of conjugate gradient method is improved to reconstruct the crack parameters and is implemented with the pick-up signals and gradients calculated by using the rapid forward solver. Several examples are presented finally for validating the proposed strategy. The results verified that both of the models can give reasonable reconstruction results in case of a low noise level. The model concerning the touch of crack surfaces with a conducting band region surrounded by the crack edge, however, is proved more efficient that the model using a conductivity distribution from the point of view of both reconstruction speed and accuracy. (author)

  14. Reconstruction of paleo-inlet dynamics using sedimentologic analyses, geomorphic features, and benthic foraminiferal assemblages: former ephemeral inlets of Cedar Island, Virginia, USA

    Science.gov (United States)

    McBride, R.; Wood, E. T.

    2017-12-01

    Cedar Island, VA is a low-profile, washover-dominated barrier island that has breached at least three times in the past sixty years. Cedar Island Inlet, a former wave-dominated tidal inlet, was open for the following time periods: 1) 1956-1962, 2) 1992-1997, and 3) 1998-2007. Air photos, satellite imagery, and geomorphic features (i.e., relict flood tidal deltas, recurved-spit ridges) record the spatial and temporal extent of the three ephemeral inlets. Based on three sediment vibracores, benthic foraminiferal and sedimentologic analyses offer high resolution insights of inlet dynamics and lifecycle evolution. Four foraminiferal biofacies are completely dominated by Elphidium excavatum (54-100%) and contain unique assemblages of accessory species based on cluster analyses: tidal inlet floor (low abundance estuarine and shelf species; 23% Haynesina germanica); flood tidal delta/inlet fill (high abundance estuarine and shelf species; 2% Buccella frigida, 2% Ammonia parkinsoniana, and 2% Haynesina germanica); high-energy inlet fill (low abundance, low diversity shelf species; 9% Elphidium gunteri); and washover/beach/aeolian (low abundance, predominantly shelf species; 3% Buccella frigida and 3% Ammonia parkinsoniana). The estuarine biofacies is barren of all foraminifera. Grain size trends indicate a first order coarsening-upward succession with second order coarsening- and fining-upwards packages in inlet throat deposits, while a first order fining-upward succession is observed in flood tidal delta deposits with two second order coarsening-upward packages in the proximal flood tidal delta. Contrary to typical wave-dominated tidal inlets that open, migrate laterally in the direction of net longshore transport, and close, the 1998-2007 tidal inlet, and possibly the 1956-1962 inlet, migrated laterally and rotated, whereas the 1992-1997 inlet remained stationary and did not rotate. In the vicinity of the vibracores, preserved deposits are attributed to the 1956-1962 and

  15. Reconstructing Fire History: An Exercise in Dendrochronology

    Science.gov (United States)

    Lafon, Charles W.

    2005-01-01

    Dendrochronology is used widely to reconstruct the history of forest disturbances. I created an exercise that introduces the use of dendrochronology to investigate fire history and forest dynamics. The exercise also demonstrates how the dendrochronological technique of crossdating is employed to age dead trees and identify missing rings. I…

  16. Improved reconstruction for IDEAL spiral CSI

    DEFF Research Database (Denmark)

    Hansen, Rie Beck; Mariager, Christian; Laustsen, Christoffer

    2017-01-01

    In this study we demonstrate how reconstruction for IDEAL spiral CSI (spectroscopic imaging scheme developed for hyperpolarized dynamic metabolic MR imaging) can be improved by using regularization with a sparsity constraint. By exploiting sparsity of the spectral domain, IDEAL spiral CSI can...

  17. Psychosocial reconstruction inventory : a postdictal instrument in aircraft accident investigation.

    Science.gov (United States)

    1972-01-01

    A new approach to the investigation of aviation accidents has recently been initiated, utilizing a follow-on to the psychological autopsy. This approach, the psychosocial reconstruction inventory, enables the development of a dynamic, retrospective p...

  18. Effects on the pouch of different digestive tract reconstruction modes assessed by radionuclide scintigraphy

    OpenAIRE

    Li, Dong-Sheng; Xu, Hui-Mian; Han, Chun-Qi; Li, Ya-Ming

    2010-01-01

    AIM: To determine the effect of three digestive tract reconstruction procedures on pouch function, after radical surgery undertaken because of gastric cancer, as assessed by radionuclide dynamic imaging.

  19. Low-noise polymeric nanomechanical biosensors

    DEFF Research Database (Denmark)

    Calleja, M.; Tamayo, J.; Nordström, Maria

    2006-01-01

    A sensor device based on a single polymer cantilever and optical readout has been developed for detection of molecular recognition reactions without the need of a reference cantilever for subtraction of unspecific signals. Microcantilevers have been fabricated in the photoresist SU-8 with one sur...

  20. Low noise PWC cathode readout system

    International Nuclear Information System (INIS)

    Cisneros, E.; Hutchinson, D.; McShurley, D.; Richter, R.; Shapiro, S.

    1980-10-01

    A system has been developed, primarily to detect the induced charge deposited on PWC cathodes, which is versatile, fast and has a good signal to noise ratio for signals of greater than or equal to 10 -14 Coulomb input. The amplifier system, which is completely separated from the detector by 95 Ω coaxial cables, is followed by a new charge integrating, version of the SHAM/BADC system developed at SLAC. This SHAM IV system is CAMAC based, allowing for computer calibration of the entire system from amplifier through ADC

  1. Image Reconstruction. Chapter 13

    Energy Technology Data Exchange (ETDEWEB)

    Nuyts, J. [Department of Nuclear Medicine and Medical Imaging Research Center, Katholieke Universiteit Leuven, Leuven (Belgium); Matej, S. [Medical Image Processing Group, Department of Radiology, University of Pennsylvania, Philadelphia, PA (United States)

    2014-12-15

    This chapter discusses how 2‑D or 3‑D images of tracer distribution can be reconstructed from a series of so-called projection images acquired with a gamma camera or a positron emission tomography (PET) system [13.1]. This is often called an ‘inverse problem’. The reconstruction is the inverse of the acquisition. The reconstruction is called an inverse problem because making software to compute the true tracer distribution from the acquired data turns out to be more difficult than the ‘forward’ direction, i.e. making software to simulate the acquisition. There are basically two approaches to image reconstruction: analytical reconstruction and iterative reconstruction. The analytical approach is based on mathematical inversion, yielding efficient, non-iterative reconstruction algorithms. In the iterative approach, the reconstruction problem is reduced to computing a finite number of image values from a finite number of measurements. That simplification enables the use of iterative instead of mathematical inversion. Iterative inversion tends to require more computer power, but it can cope with more complex (and hopefully more accurate) models of the acquisition process.

  2. Update on orbital reconstruction.

    Science.gov (United States)

    Chen, Chien-Tzung; Chen, Yu-Ray

    2010-08-01

    Orbital trauma is common and frequently complicated by ocular injuries. The recent literature on orbital fracture is analyzed with emphasis on epidemiological data assessment, surgical timing, method of approach and reconstruction materials. Computed tomographic (CT) scan has become a routine evaluation tool for orbital trauma, and mobile CT can be applied intraoperatively if necessary. Concomitant serious ocular injury should be carefully evaluated preoperatively. Patients presenting with nonresolving oculocardiac reflex, 'white-eyed' blowout fracture, or diplopia with a positive forced duction test and CT evidence of orbital tissue entrapment require early surgical repair. Otherwise, enophthalmos can be corrected by late surgery with a similar outcome to early surgery. The use of an endoscope-assisted approach for orbital reconstruction continues to grow, offering an alternative method. Advances in alloplastic materials have improved surgical outcome and shortened operating time. In this review of modern orbital reconstruction, several controversial issues such as surgical indication, surgical timing, method of approach and choice of reconstruction material are discussed. Preoperative fine-cut CT image and thorough ophthalmologic examination are key elements to determine surgical indications. The choice of surgical approach and reconstruction materials much depends on the surgeon's experience and the reconstruction area. Prefabricated alloplastic implants together with image software and stereolithographic models are significant advances that help to more accurately reconstruct the traumatized orbit. The recent evolution of orbit reconstruction improves functional and aesthetic results and minimizes surgical complications.

  3. Alpha image reconstruction (AIR): A new iterative CT image reconstruction approach using voxel-wise alpha blending

    International Nuclear Information System (INIS)

    Hofmann, Christian; Sawall, Stefan; Knaup, Michael; Kachelrieß, Marc

    2014-01-01

    Purpose: Iterative image reconstruction gains more and more interest in clinical routine, as it promises to reduce image noise (and thereby patient dose), to reduce artifacts, or to improve spatial resolution. Among vendors and researchers, however, there is no consensus of how to best achieve these aims. The general approach is to incorporatea priori knowledge into iterative image reconstruction, for example, by adding additional constraints to the cost function, which penalize variations between neighboring voxels. However, this approach to regularization in general poses a resolution noise trade-off because the stronger the regularization, and thus the noise reduction, the stronger the loss of spatial resolution and thus loss of anatomical detail. The authors propose a method which tries to improve this trade-off. The proposed reconstruction algorithm is called alpha image reconstruction (AIR). One starts with generating basis images, which emphasize certain desired image properties, like high resolution or low noise. The AIR algorithm reconstructs voxel-specific weighting coefficients that are applied to combine the basis images. By combining the desired properties of each basis image, one can generate an image with lower noise and maintained high contrast resolution thus improving the resolution noise trade-off. Methods: All simulations and reconstructions are performed in native fan-beam geometry. A water phantom with resolution bar patterns and low contrast disks is simulated. A filtered backprojection (FBP) reconstruction with a Ram-Lak kernel is used as a reference reconstruction. The results of AIR are compared against the FBP results and against a penalized weighted least squares reconstruction which uses total variation as regularization. The simulations are based on the geometry of the Siemens Somatom Definition Flash scanner. To quantitatively assess image quality, the authors analyze line profiles through resolution patterns to define a contrast

  4. Low-noise behavior of InGaAs quantum-well-structured modulation-doped FET's from 10 to the -2nd to 10 to the 8 Hz

    Science.gov (United States)

    Liu, Shih-Ming J.; Das, Mukunda B.; Peng, Chin-Kun; Klem, John; Henderson, Timothy S.

    1986-01-01

    Equivalent gate noise voltage spectra of 1-micron gate-length modulation-doped FET's with pseudomorphic InGaAs quantum-well structure have been measured for the frequency range of 0.01 Hz to 100 MHz and commpared with the noise spectra of conventional AlGaAs/GaAs MODFET's and GaAs MESFET's. The prominent generation-recombination (g-r) noise bulge commonly observed in the vicinity of 10 kHz in conventional MODFET's at 300 K does not appear in the case of the new InGaAs quantum-well MODFET. Instead, its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced 1/f noise. The LF noise intensity in the new device appears to be the lowest among those observed in any MODFET or MESFET. The noise spectra at 82 K in the new device represent nearly true 1/f noise. This unusual low-noise behavior of the new structure suggests the effectiveness of electron confinement in the quantum well that significantaly reduces electron trapping in the n-AlGaAs, and thus eliminates the g-r noise bulge observed in conventional MODFET's.

  5. A 0.1-1.4 GHz inductorless low-noise amplifier with 13 dBm IIP3 and 24 dBm IIP2 in 180 nm CMOS

    Science.gov (United States)

    Guo, Benqing; Chen, Jun; Chen, Hongpeng; Wang, Xuebing

    2018-01-01

    An inductorless noise-canceling CMOS low-noise amplifier (LNA) with wideband linearization technique is proposed. The complementary configuration by stacked NMOS/PMOS is employed to compensate second-order nonlinearity of the circuit. The third-order distortion of the auxiliary stage is also mitigated by that of the weak inversion transistors in the main path. The bias and scaling size combined by digital control words are further tuned to obtain enhanced linearity over the desired band. Implemented in a 0.18 μm CMOS process, simulated results show that the proposed LNA provides a voltage gain of 16.1 dB and a NF of 2.8-3.4 dB from 0.1 GHz to 1.4 GHz. The IIP3 and IIP2 of 13-18.9 and 24-40 dBm are obtained, respectively. The circuit core consumes 19 mW from a 1.8 V supply.

  6. Permutationally invariant state reconstruction

    DEFF Research Database (Denmark)

    Moroder, Tobias; Hyllus, Philipp; Tóth, Géza

    2012-01-01

    Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a nonlinear large-scale opti...... optimization, which has clear advantages regarding speed, control and accuracy in comparison to commonly employed numerical routines. First prototype implementations easily allow reconstruction of a state of 20 qubits in a few minutes on a standard computer.......-scale optimization problem, this is a major challenge in the design of scalable tomography schemes. Here we present an efficient state reconstruction scheme for permutationally invariant quantum state tomography. It works for all common state-of-the-art reconstruction principles, including, in particular, maximum...

  7. Proposal to negotiate an amendment to an existing contract for the supply of four additional low-noise Thyristor-Controlled Reactor coils for a new Static VAR Compensator on the 18 kV electrical network on the Meyrin site

    CERN Document Server

    2017-01-01

    Proposal to negotiate an amendment to an existing contract for the supply of four additional low-noise Thyristor-Controlled Reactor coils for a new Static VAR Compensator on the 18 kV electrical network on the Meyrin site

  8. Reconstructing the post-LGM decay of the Eurasian Ice Sheets with Ice Sheet Models; data-model comparison and focus on the Storfjorden (Svalbard) ice stream dynamics history

    Science.gov (United States)

    Petrini, Michele; Kirchner, Nina; Colleoni, Florence; Camerlenghi, Angelo; Rebesco, Michele; Lucchi, Renata G.; Forte, Emanuele; Colucci, Renato R.

    2017-04-01

    The challenge of reconstructing palaeo-ice sheets past growth and decay represent a critical task to better understand mechanisms of present and future global climate change. Last Glacial Maximum (LGM), and the subsequent deglaciation until Pre-Industrial time (PI) represent an excellent testing ground for numerical Ice Sheet Models (ISMs), due to the abundant data available that can be used in an ISM as boundary conditions, forcings or constraints to test the ISMs results. In our study, we simulate with ISMs the post-LGM decay of the Eurasian Ice Sheets, with a focus on the marine-based Svalbard-Barents Sea-Kara Sea Ice Sheet. In particular, we aim to reconstruct the Storfjorden ice stream dynamics history by comparing the model results with the marine geological data (MSGLs, GZWs, sediment cores analysis) available from the area, e.g., Pedrosa et al. 2011, Rebesco et al. 2011, 2013, Lucchi et al. 2013. Two hybrid SIA/SSA ISMs are employed, GRISLI, Ritz et al. 2001, and PSU, Pollard&DeConto 2012. These models differ mainly in the complexity with which grounding line migration is treated. Climate forcing is interpolated by means of climate indexes between LGM and PI climate. Regional climate indexes are constructed based on the non-accelerated deglaciation transient experiment carried out with CCSM3, Liu et al. 2009. Indexes representative of the climate evolution over Siberia, Svalbard and Scandinavia are employed. The impact of such refined representation as opposed to the common use of the NGRIP δ18O index for transient experiments is analysed. In this study, the ice-ocean interaction is crucial to reconstruct the Storfjorden ice stream dynamics history. To investigate the sensitivity of the ice shelf/stream retreat to ocean temperature, we allow for a space-time variation of basal melting under the ice shelves by testing two-equations implementations based on Martin et al. 2011 forced with simulated ocean temperature and salinity from the TraCE-21ka coupled

  9. Simbol-X Formation Flight and Image Reconstruction

    Science.gov (United States)

    Civitani, M.; Djalal, S.; Le Duigou, J. M.; La Marle, O.; Chipaux, R.

    2009-05-01

    Simbol-X is the first operational mission relying on two satellites flying in formation. The dynamics of the telescope, due to the formation flight concept, raises a variety of problematic, like image reconstruction, that can be better evaluated via a simulation tools. We present here the first results obtained with Simulos, simulation tool aimed to study the relative spacecrafts navigation and the weight of the different parameters in image reconstruction and telescope performance evaluation. The simulation relies on attitude and formation flight sensors models, formation flight dynamics and control, mirror model and focal plane model, while the image reconstruction is based on the Line of Sight (LOS) concept.

  10. Reconstruction of Undersampled Atomic Force Microscopy Images

    DEFF Research Database (Denmark)

    Jensen, Tobias Lindstrøm; Arildsen, Thomas; Østergaard, Jan

    2013-01-01

    Atomic force microscopy (AFM) is one of the most advanced tools for high-resolution imaging and manipulation of nanoscale matter. Unfortunately, standard AFM imaging requires a timescale on the order of seconds to minutes to acquire an image which makes it complicated to observe dynamic processes....... Moreover, it is often required to take several images before a relevant observation region is identified. In this paper we show how to significantly reduce the image acquisition time by undersampling. The reconstruction of an undersampled AFM image can be viewed as an inpainting, interpolating problem...... should be reconstructed using interpolation....

  11. An Intelligent Actuator Fault Reconstruction Scheme for Robotic Manipulators.

    Science.gov (United States)

    Xiao, Bing; Yin, Shen

    2018-02-01

    This paper investigates a difficult problem of reconstructing actuator faults for robotic manipulators. An intelligent approach with fast reconstruction property is developed. This is achieved by using observer technique. This scheme is capable of precisely reconstructing the actual actuator fault. It is shown by Lyapunov stability analysis that the reconstruction error can converge to zero after finite time. A perfect reconstruction performance including precise and fast properties can be provided for actuator fault. The most important feature of the scheme is that, it does not depend on control law, dynamic model of actuator, faults' type, and also their time-profile. This super reconstruction performance and capability of the proposed approach are further validated by simulation and experimental results.

  12. Optimization of the alpha image reconstruction. An iterative CT-image reconstruction with well-defined image quality metrics

    International Nuclear Information System (INIS)

    Lebedev, Sergej; Sawall, Stefan; Knaup, Michael; Kachelriess, Marc

    2017-01-01

    Optimization of the AIR-algorithm for improved convergence and performance. TThe AIR method is an iterative algorithm for CT image reconstruction. As a result of its linearity with respect to the basis images, the AIR algorithm possesses well defined, regular image quality metrics, e.g. point spread function (PSF) or modulation transfer function (MTF), unlike other iterative reconstruction algorithms. The AIR algorithm computes weighting images α to blend between a set of basis images that preferably have mutually exclusive properties, e.g. high spatial resolution or low noise. The optimized algorithm uses an approach that alternates between the optimization of rawdata fidelity using an OSSART like update and regularization using gradient descent, as opposed to the initially proposed AIR using a straightforward gradient descent implementation. A regularization strength for a given task is chosen by formulating a requirement for the noise reduction and checking whether it is fulfilled for different regularization strengths, while monitoring the spatial resolution using the voxel-wise defined modulation transfer function for the AIR image. The optimized algorithm computes similar images in a shorter time compared to the initial gradient descent implementation of AIR. The result can be influenced by multiple parameters that can be narrowed down to a relatively simple framework to compute high quality images. The AIR images, for instance, can have at least a 50% lower noise level compared to the sharpest basis image, while the spatial resolution is mostly maintained. The optimization improves performance by a factor of 6, while maintaining image quality. Furthermore, it was demonstrated that the spatial resolution for AIR can be determined using regular image quality metrics, given smooth weighting images. This is not possible for other iterative reconstructions as a result of their non linearity. A simple set of parameters for the algorithm is discussed that provides

  13. Optimization of the alpha image reconstruction. An iterative CT-image reconstruction with well-defined image quality metrics

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, Sergej; Sawall, Stefan; Knaup, Michael; Kachelriess, Marc [German Cancer Research Center, Heidelberg (Germany).

    2017-10-01

    Optimization of the AIR-algorithm for improved convergence and performance. TThe AIR method is an iterative algorithm for CT image reconstruction. As a result of its linearity with respect to the basis images, the AIR algorithm possesses well defined, regular image quality metrics, e.g. point spread function (PSF) or modulation transfer function (MTF), unlike other iterative reconstruction algorithms. The AIR algorithm computes weighting images α to blend between a set of basis images that preferably have mutually exclusive properties, e.g. high spatial resolution or low noise. The optimized algorithm uses an approach that alternates between the optimization of rawdata fidelity using an OSSART like update and regularization using gradient descent, as opposed to the initially proposed AIR using a straightforward gradient descent implementation. A regularization strength for a given task is chosen by formulating a requirement for the noise reduction and checking whether it is fulfilled for different regularization strengths, while monitoring the spatial resolution using the voxel-wise defined modulation transfer function for the AIR image. The optimized algorithm computes similar images in a shorter time compared to the initial gradient descent implementation of AIR. The result can be influenced by multiple parameters that can be narrowed down to a relatively simple framework to compute high quality images. The AIR images, for instance, can have at least a 50% lower noise level compared to the sharpest basis image, while the spatial resolution is mostly maintained. The optimization improves performance by a factor of 6, while maintaining image quality. Furthermore, it was demonstrated that the spatial resolution for AIR can be determined using regular image quality metrics, given smooth weighting images. This is not possible for other iterative reconstructions as a result of their non linearity. A simple set of parameters for the algorithm is discussed that provides

  14. Overview of image reconstruction

    International Nuclear Information System (INIS)

    Marr, R.B.

    1980-04-01

    Image reconstruction (or computerized tomography, etc.) is any process whereby a function, f, on R/sup n/ is estimated from empirical data pertaining to its integrals, ∫f(x) dx, for some collection of hyperplanes of dimension k < n. The paper begins with background information on how image reconstruction problems have arisen in practice, and describes some of the application areas of past or current interest; these include radioastronomy, optics, radiology and nuclear medicine, electron microscopy, acoustical imaging, geophysical tomography, nondestructive testing, and NMR zeugmatography. Then the various reconstruction algorithms are discussed in five classes: summation, or simple back-projection; convolution, or filtered back-projection; Fourier and other functional transforms; orthogonal function series expansion; and iterative methods. Certain more technical mathematical aspects of image reconstruction are considered from the standpoint of uniqueness, consistency, and stability of solution. The paper concludes by presenting certain open problems. 73 references

  15. The evolving breast reconstruction

    DEFF Research Database (Denmark)

    Thomsen, Jørn Bo; Gunnarsson, Gudjon Leifur

    2014-01-01

    The aim of this editorial is to give an update on the use of the propeller thoracodorsal artery perforator flap (TAP/TDAP-flap) within the field of breast reconstruction. The TAP-flap can be dissected by a combined use of a monopolar cautery and a scalpel. Microsurgical instruments are generally...... not needed. The propeller TAP-flap can be designed in different ways, three of these have been published: (I) an oblique upwards design; (II) a horizontal design; (III) an oblique downward design. The latissimus dorsi-flap is a good and reliable option for breast reconstruction, but has been criticized...... for oncoplastic and reconstructive breast surgery and will certainly become an invaluable addition to breast reconstructive methods....

  16. Forging Provincial Reconstruction Teams

    National Research Council Canada - National Science Library

    Honore, Russel L; Boslego, David V

    2007-01-01

    The Provincial Reconstruction Team (PRT) training mission completed by First U.S. Army in April 2006 was a joint Service effort to meet a requirement from the combatant commander to support goals in Afghanistan...

  17. Breast Reconstruction with Implants

    Science.gov (United States)

    ... your surgical options and discuss the advantages and disadvantages of implant-based reconstruction, and may show you ... Policy Notice of Privacy Practices Notice of Nondiscrimination Advertising Mayo Clinic is a not-for-profit organization ...

  18. Reconstruction of abstract quantum theory

    International Nuclear Information System (INIS)

    Drieschner, M.; Goernitz, T.; von Weizsaecker, C.F.

    1988-01-01

    Understanding quantum theory as a general theory of prediction, we reconstruct abstract quantum theory. Abstract means the general frame of quantum theory, without reference to a three-dimensional position space, to concepts like particle or field, or to special laws of dynamics. Reconstruction is the attempt to do this by formulating simple and plausible postulates on prediction in order to derive the basic concepts of quantum theory from them. Thereby no law of classical physics is presupposed which would then have to be quantized. We briefly discuss the relationship of theory and interpretation in physics and the fundamental role of time as a basic concept for physics. Then a number of assertions are given, formulated as succinctly as possible in order to make them easily quotable and comparable. The assertations are arranged in four groups: heuristic principles, verbal definitions of some terms, three basic postulates, and consequences. The three postulates of separable alternatives, indeterminism, and kinematics are the central points of this work. These brief assertions are commented upon, and their relationship with the interpretation of quantum theory is discussed. Also given are an outlook on the further development into concrete quantum theory and some philosophical reflections

  19. Alternative reconstruction after pancreaticoduodenectomy

    Directory of Open Access Journals (Sweden)

    Cooperman Avram M

    2008-01-01

    Full Text Available Abstract Background Pancreaticoduodenectomy is the procedure of choice for tumors of the head of the pancreas and periampulla. Despite advances in surgical technique and postoperative care, the procedure continues to carry a high morbidity rate. One of the most common morbidities is delayed gastric emptying with rates of 15%–40%. Following two prolonged cases of delayed gastric emptying, we altered our reconstruction to avoid this complication altogether. Subsequently, our patients underwent a classic pancreaticoduodenectomy with an undivided Roux-en-Y technique for reconstruction. Methods We reviewed the charts of our last 13 Whipple procedures evaluating them for complications, specifically delayed gastric emptying. We compared the outcomes of those patients to a control group of 15 patients who underwent the Whipple procedure with standard reconstruction. Results No instances of delayed gastric emptying occurred in patients who underwent an undivided Roux-en-Y technique for reconstruction. There was 1 wound infection (8%, 1 instance of pneumonia (8%, and 1 instance of bleeding from the gastrojejunal staple line (8%. There was no operative mortality. Conclusion Use of the undivided Roux-en-Y technique for reconstruction following the Whipple procedure may decrease the incidence of delayed gastric emptying. In addition, it has the added benefit of eliminating bile reflux gastritis. Future randomized control trials are recommended to further evaluate the efficacy of the procedure.

  20. Three-dimensional breast image reconstruction from a limited number of views

    Science.gov (United States)

    McCauley, Thomas G.; Stewart, Alexander X.; Stanton, Martin J.; Wu, Tao; Phillips, Walter C.

    2000-04-01

    Typically in three-dimensional (3D) computed tomography (CT) imaging, hundreds or thousands of x-ray projection images are recorded. The image-collection time and patient dose required rule out conventional CT as a tool for screening mammography. We have developed a CT method that overcomes these limitations by using (1) a novel image collection geometry, (2) new digital electronic x-ray detector technology, and (3) modern image reconstruction procedures. The method, which we call Computed Planar Mammography (CPM), is made possible by the full-field, low-noise, high-resolution CCD-based detector design that we have previously developed. With this method, we need to record only a limited number (10 - 50) of low-dose x- ray images of the breast. The resulting 3D full breast image has a resolution in two orientations equal to the full detector resolution (47 microns), and a lower, variable resolution (0.5 - 10 mm) in the third orientation. This 3D reconstructed image can then be viewed as a series of cross- sectional layers, or planes, each at the full detector resolution. Features due to overlapping tissue, which could not be differentiated in a conventional mammogram, are separated into layers at different depths. We demonstrate the features and capabilities of this method by presenting reconstructed images of phantoms and mastectomy specimens. Finally, we discuss outstanding issues related to the further development of this procedure, as well as considerations for its clinical implementation.

  1. Reconstructing random media

    International Nuclear Information System (INIS)

    Yeong, C.L.; Torquato, S.

    1998-01-01

    We formulate a procedure to reconstruct the structure of general random heterogeneous media from limited morphological information by extending the methodology of Rintoul and Torquato [J. Colloid Interface Sci. 186, 467 (1997)] developed for dispersions. The procedure has the advantages that it is simple to implement and generally applicable to multidimensional, multiphase, and anisotropic structures. Furthermore, an extremely useful feature is that it can incorporate any type and number of correlation functions in order to provide as much morphological information as is necessary for accurate reconstruction. We consider a variety of one- and two-dimensional reconstructions, including periodic and random arrays of rods, various distribution of disks, Debye random media, and a Fontainebleau sandstone sample. We also use our algorithm to construct heterogeneous media from specified hypothetical correlation functions, including an exponentially damped, oscillating function as well as physically unrealizable ones. copyright 1998 The American Physical Society

  2. Delayed breast implant reconstruction

    DEFF Research Database (Denmark)

    Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne

    2012-01-01

    We evaluated the association between radiation therapy and severe capsular contracture or reoperation after 717 delayed breast implant reconstruction procedures (288 1- and 429 2-stage procedures) identified in the prospective database of the Danish Registry for Plastic Surgery of the Breast during...... of radiation therapy was associated with a non-significantly increased risk of reoperation after both 1-stage (HR = 1.4; 95% CI: 0.7-2.5) and 2-stage (HR = 1.6; 95% CI: 0.9-3.1) procedures. Reconstruction failure was highest (13.2%) in the 2-stage procedures with a history of radiation therapy. Breast...... reconstruction approaches other than implants should be seriously considered among women who have received radiation therapy....

  3. Attractor reconstruction for non-linear systems: a methodological note

    Science.gov (United States)

    Nichols, J.M.; Nichols, J.D.

    2001-01-01

    Attractor reconstruction is an important step in the process of making predictions for non-linear time-series and in the computation of certain invariant quantities used to characterize the dynamics of such series. The utility of computed predictions and invariant quantities is dependent on the accuracy of attractor reconstruction, which in turn is determined by the methods used in the reconstruction process. This paper suggests methods by which the delay and embedding dimension may be selected for a typical delay coordinate reconstruction. A comparison is drawn between the use of the autocorrelation function and mutual information in quantifying the delay. In addition, a false nearest neighbor (FNN) approach is used in minimizing the number of delay vectors needed. Results highlight the need for an accurate reconstruction in the computation of the Lyapunov spectrum and in prediction algorithms.

  4. HEEL BONE RECONSTRUCTIVE OSTEOSYNTHESIS

    Directory of Open Access Journals (Sweden)

    A. N. Svetashov

    2010-01-01

    Full Text Available To detect the most appropriate to heel bone injury severity variants of reconstructive osteosynthesis it was analyzed treatment results of 56 patients. In 15 (26.8% patients classic methods of surgical service were applied, in 41 (73.2% cases to restore the defect porous implants were used. Osteosynthesis without heel bone plastic restoration accomplishment was ineffective in 60% patients from control group. Reconstructive osteosynthesis method ensures long-term good functional effect of rehabilitation in 96.4% patients from the basic group.

  5. Vertex reconstruction in CMS

    International Nuclear Information System (INIS)

    Chabanat, E.; D'Hondt, J.; Estre, N.; Fruehwirth, R.; Prokofiev, K.; Speer, T.; Vanlaer, P.; Waltenberger, W.

    2005-01-01

    Due to the high track multiplicity in the final states expected in proton collisions at the LHC experiments, novel vertex reconstruction algorithms are required. The vertex reconstruction problem can be decomposed into a pattern recognition problem ('vertex finding') and an estimation problem ('vertex fitting'). Starting from least-squares methods, robustifications of the classical algorithms are discussed and the statistical properties of the novel methods are shown. A whole set of different approaches for the vertex finding problem is presented and compared in relevant physics channels

  6. Vertex Reconstruction in CMS

    CERN Document Server

    Chabanat, E; D'Hondt, J; Vanlaer, P; Prokofiev, K; Speer, T; Frühwirth, R; Waltenberger, W

    2005-01-01

    Because of the high track multiplicity in the final states expected in proton collisions at the LHC experiments, novel vertex reconstruction algorithms are required. The vertex reconstruction problem can be decomposed into a pattern recognition problem ("vertex finding") and an estimation problem ("vertex fitting"). Starting from least-square methods, ways to render the classical algorithms more robust are discussed and the statistical properties of the novel methods are shown. A whole set of different approaches for the vertex finding problem is presented and compared in relevant physics channels.

  7. IRVE-II Post-Flight Trajectory Reconstruction

    Science.gov (United States)

    O'Keefe, Stephen A.; Bose, David M.

    2010-01-01

    NASA s Inflatable Re-entry Vehicle Experiment (IRVE) II successfully demonstrated an inflatable aerodynamic decelerator after being launched aboard a sounding rocket from Wallops Flight Facility (WFF). Preliminary day of flight data compared well with pre-flight Monte Carlo analysis, and a more complete trajectory reconstruction performed with an Extended Kalman Filter (EKF) approach followed. The reconstructed trajectory and comparisons to an attitude solution provided by NASA Sounding Rocket Operations Contract (NSROC) personnel at WFF are presented. Additional comparisons are made between the reconstructed trajectory and pre and post-flight Monte Carlo trajectory predictions. Alternative observations of the trajectory are summarized which leverage flight accelerometer measurements, the pre-flight aerodynamic database, and on-board flight video. Finally, analysis of the payload separation and aeroshell deployment events are presented. The flight trajectory is reconstructed to fidelity sufficient to assess overall project objectives related to flight dynamics and overall, IRVE-II flight dynamics are in line with expectations

  8. Reconstruction of network topology using status-time-series data

    Science.gov (United States)

    Pandey, Pradumn Kumar; Badarla, Venkataramana

    2018-01-01

    Uncovering the heterogeneous connection pattern of a networked system from the available status-time-series (STS) data of a dynamical process on the network is of great interest in network science and known as a reverse engineering problem. Dynamical processes on a network are affected by the structure of the network. The dependency between the diffusion dynamics and structure of the network can be utilized to retrieve the connection pattern from the diffusion data. Information of the network structure can help to devise the control of dynamics on the network. In this paper, we consider the problem of network reconstruction from the available status-time-series (STS) data using matrix analysis. The proposed method of network reconstruction from the STS data is tested successfully under susceptible-infected-susceptible (SIS) diffusion dynamics on real-world and computer-generated benchmark networks. High accuracy and efficiency of the proposed reconstruction procedure from the status-time-series data define the novelty of the method. Our proposed method outperforms compressed sensing theory (CST) based method of network reconstruction using STS data. Further, the same procedure of network reconstruction is applied to the weighted networks. The ordering of the edges in the weighted networks is identified with high accuracy.

  9. Reconstructing the dark sector interaction with LISA

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Rong-Gen; Yang, Tao [CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Tamanini, Nicola, E-mail: cairg@itp.ac.cn, E-mail: nicola.tamanini@cea.fr, E-mail: yangtao@itp.ac.cn [Institut de Physique Théorique, CEA-Saclay, CNRS UMR 3681, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

    2017-05-01

    We perform a forecast analysis of the ability of the LISA space-based interferometer to reconstruct the dark sector interaction using gravitational wave standard sirens at high redshift. We employ Gaussian process methods to reconstruct the distance-redshift relation in a model independent way. We adopt simulated catalogues of standard sirens given by merging massive black hole binaries visible by LISA, with an electromagnetic counterpart detectable by future telescopes. The catalogues are based on three different astrophysical scenarios for the evolution of massive black hole mergers based on the semi-analytic model of E. Barausse, Mon. Not. Roy. Astron. Soc. 423 (2012) 2533. We first use these standard siren datasets to assess the potential of LISA in reconstructing a possible interaction between vacuum dark energy and dark matter. Then we combine the LISA cosmological data with supernovae data simulated for the Dark Energy Survey. We consider two scenarios distinguished by the time duration of the LISA mission: 5 and 10 years. Using only LISA standard siren data, the dark sector interaction can be well reconstructed from redshift z ∼1 to z ∼3 (for a 5 years mission) and z ∼1 up to z ∼5 (for a 10 years mission), though the reconstruction is inefficient at lower redshift. When combined with the DES datasets, the interaction is well reconstructed in the whole redshift region from 0 z ∼ to z ∼3 (5 yr) and z ∼0 to z ∼5 (10 yr), respectively. Massive black hole binary standard sirens can thus be used to constrain the dark sector interaction at redshift ranges not reachable by usual supernovae datasets which probe only the z ∼< 1.5 range. Gravitational wave standard sirens will not only constitute a complementary and alternative way, with respect to familiar electromagnetic observations, to probe the cosmic expansion, but will also provide new tests to constrain possible deviations from the standard ΛCDM dynamics, especially at high redshift.

  10. Reconstructing Neutrino Mass Spectrum

    OpenAIRE

    Smirnov, A. Yu.

    1999-01-01

    Reconstruction of the neutrino mass spectrum and lepton mixing is one of the fundamental problems of particle physics. In this connection we consider two central topics: (i) the origin of large lepton mixing, (ii) possible existence of new (sterile) neutrino states. We discuss also possible relation between large mixing and existence of sterile neutrinos.

  11. Position reconstruction in LUX

    Science.gov (United States)

    Akerib, D. S.; Alsum, S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Brás, P.; Byram, D.; Cahn, S. B.; Carmona-Benitez, M. C.; Chan, C.; Currie, A.; Cutter, J. E.; Davison, T. J. R.; Dobi, A.; Druszkiewicz, E.; Edwards, B. N.; Fallon, S. R.; Fan, A.; Fiorucci, S.; Gaitskell, R. J.; Genovesi, J.; Ghag, C.; Gilchriese, M. G. D.; Hall, C. R.; Hanhardt, M.; Haselschwardt, S. J.; Hertel, S. A.; Hogan, D. P.; Horn, M.; Huang, D. Q.; Ignarra, C. M.; Jacobsen, R. G.; Ji, W.; Kamdin, K.; Kazkaz, K.; Khaitan, D.; Knoche, R.; Larsen, N. A.; Lenardo, B. G.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Manalaysay, A.; Mannino, R. L.; Marzioni, M. F.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morad, J. A.; Murphy, A. St. J.; Nehrkorn, C.; Nelson, H. N.; Neves, F.; O'Sullivan, K.; Oliver-Mallory, K. C.; Palladino, K. J.; Pease, E. K.; Rhyne, C.; Shaw, S.; Shutt, T. A.; Silva, C.; Solmaz, M.; Solovov, V. N.; Sorensen, P.; Sumner, T. J.; Szydagis, M.; Taylor, D. J.; Taylor, W. C.; Tennyson, B. P.; Terman, P. A.; Tiedt, D. R.; To, W. H.; Tripathi, M.; Tvrznikova, L.; Uvarov, S.; Velan, V.; Verbus, J. R.; Webb, R. C.; White, J. T.; Whitis, T. J.; Witherell, M. S.; Wolfs, F. L. H.; Xu, J.; Yazdani, K.; Young, S. K.; Zhang, C.

    2018-02-01

    The (x, y) position reconstruction method used in the analysis of the complete exposure of the Large Underground Xenon (LUX) experiment is presented. The algorithm is based on a statistical test that makes use of an iterative method to recover the photomultiplier tube (PMT) light response directly from the calibration data. The light response functions make use of a two dimensional functional form to account for the photons reflected on the inner walls of the detector. To increase the resolution for small pulses, a photon counting technique was employed to describe the response of the PMTs. The reconstruction was assessed with calibration data including 83mKr (releasing a total energy of 41.5 keV) and 3H (β- with Q = 18.6 keV) decays, and a deuterium-deuterium (D-D) neutron beam (2.45 MeV) . Within the detector's fiducial volume, the reconstruction has achieved an (x, y) position uncertainty of σ = 0.82 cm and σ = 0.17 cm for events of only 200 and 4,000 detected electroluminescence photons respectively. Such signals are associated with electron recoils of energies ~0.25 keV and ~10 keV, respectively. The reconstructed position of the smallest events with a single electron emitted from the liquid surface (22 detected photons) has a horizontal (x, y) uncertainty of 2.13 cm.

  12. A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction

    International Nuclear Information System (INIS)

    Lougovski, A; Hofheinz, F; Maus, J; Schramm, G; Will, E; Hoff, J van den

    2014-01-01

    The aim of this study is the evaluation of on-the-fly volume of intersection computation for system’s geometry modelling in 3D PET image reconstruction. For this purpose we propose a simple geometrical model in which the cubic image voxels on the given Cartesian grid are approximated with spheres and the rectangular tubes of response (ToRs) are approximated with cylinders. The model was integrated into a fully 3D list-mode PET reconstruction for performance evaluation. In our model the volume of intersection between a voxel and the ToR is only a function of the impact parameter (the distance between voxel centre to ToR axis) but is independent of the relative orientation of voxel and ToR. This substantially reduces the computational complexity of the system matrix calculation. Based on phantom measurements it was determined that adjusting the diameters of the spherical voxel size and the ToR in such a way that the actual voxel and ToR volumes are conserved leads to the best compromise between high spatial resolution, low noise, and suppression of Gibbs artefacts in the reconstructed images. Phantom as well as clinical datasets from two different PET systems (Siemens ECAT HR + and Philips Ingenuity-TF PET/MR) were processed using the developed and the respective vendor-provided (line of intersection related) reconstruction algorithms. A comparison of the reconstructed images demonstrated very good performance of the new approach. The evaluation showed the respective vendor-provided reconstruction algorithms to possess 34–41% lower resolution compared to the developed one while exhibiting comparable noise levels. Contrary to explicit point spread function modelling our model has a simple straight-forward implementation and it should be easy to integrate into existing reconstruction software, making it competitive to other existing resolution recovery techniques. (paper)

  13. The structure of reconstructed chalcopyrite surfaces

    Science.gov (United States)

    Thinius, Sascha; Islam, Mazharul M.; Bredow, Thomas

    2018-03-01

    Chalcopyrite (CuFeS2) surfaces are of major interest for copper exploitation in aqueous solution, called leaching. Since leaching is a surface process knowledge of the surface structure, bonding pattern and oxidation states is important for improving the efficiency. At present such information is not available from experimental studies. Therefore a detailed computational study of chalcopyrite surfaces is performed. The structures of low-index stoichiometric chalcopyrite surfaces {hkl} h, k, l ∈ {0, 1, 2} have been studied with density functional theory (DFT) and global optimization strategies. We have applied ab initio molecular dynamics (MD) in combination with simulated annealing (SA) in order to explore possible reconstructions via a minima hopping (MH) algorithm. In almost all cases reconstruction involving substantial rearrangement has occurred accompanied by reduction of the surface energy. The analysis of the change in the coordination sphere and migration during reconstruction reveals that S-S dimers are formed on the surface. Further it was observed that metal atoms near the surface move toward the bulk forming metal alloys passivated by sulfur. The obtained surface energies of reconstructed surfaces are in the range of 0.53-0.95 J/m2.

  14. Fast GPU-based Monte Carlo code for SPECT/CT reconstructions generates improved 177Lu images.

    Science.gov (United States)

    Rydén, T; Heydorn Lagerlöf, J; Hemmingsson, J; Marin, I; Svensson, J; Båth, M; Gjertsson, P; Bernhardt, P

    2018-01-04

    Full Monte Carlo (MC)-based SPECT reconstructions have a strong potential for correcting for image degrading factors, but the reconstruction times are long. The objective of this study was to develop a highly parallel Monte Carlo code for fast, ordered subset expectation maximum (OSEM) reconstructions of SPECT/CT images. The MC code was written in the Compute Unified Device Architecture language for a computer with four graphics processing units (GPUs) (GeForce GTX Titan X, Nvidia, USA). This enabled simulations of parallel photon emissions from the voxels matrix (128 3 or 256 3 ). Each computed tomography (CT) number was converted to attenuation coefficients for photo absorption, coherent scattering, and incoherent scattering. For photon scattering, the deflection angle was determined by the differential scattering cross sections. An angular response function was developed and used to model the accepted angles for photon interaction with the crystal, and a detector scattering kernel was used for modeling the photon scattering in the detector. Predefined energy and spatial resolution kernels for the crystal were used. The MC code was implemented in the OSEM reconstruction of clinical and phantom 177 Lu SPECT/CT images. The Jaszczak image quality phantom was used to evaluate the performance of the MC reconstruction in comparison with attenuated corrected (AC) OSEM reconstructions and attenuated corrected OSEM reconstructions with resolution recovery corrections (RRC). The performance of the MC code was 3200 million photons/s. The required number of photons emitted per voxel to obtain a sufficiently low noise level in the simulated image was 200 for a 128 3 voxel matrix. With this number of emitted photons/voxel, the MC-based OSEM reconstruction with ten subsets was performed within 20 s/iteration. The images converged after around six iterations. Therefore, the reconstruction time was around 3 min. The activity recovery for the spheres in the Jaszczak phantom was

  15. Algebraic reconstruction techniques for spectral reconstruction in diffuse optical tomography

    International Nuclear Information System (INIS)

    Brendel, Bernhard; Ziegler, Ronny; Nielsen, Tim

    2008-01-01

    Reconstruction in diffuse optical tomography (DOT) necessitates solving the diffusion equation, which is nonlinear with respect to the parameters that have to be reconstructed. Currently applied solving methods are based on the linearization of the equation. For spectral three-dimensional reconstruction, the emerging equation system is too large for direct inversion, but the application of iterative methods is feasible. Computational effort and speed of convergence of these iterative methods are crucial since they determine the computation time of the reconstruction. In this paper, the iterative methods algebraic reconstruction technique (ART) and conjugated gradients (CGs) as well as a new modified ART method are investigated for spectral DOT reconstruction. The aim of the modified ART scheme is to speed up the convergence by considering the specific conditions of spectral reconstruction. As a result, it converges much faster to favorable results than conventional ART and CG methods

  16. Arctic Sea Level Reconstruction

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde

    Reconstruction of historical Arctic sea level is very difficult due to the limited coverage and quality of tide gauge and altimetry data in the area. This thesis addresses many of these issues, and discusses strategies to help achieve a stable and plausible reconstruction of Arctic sea level from...... 1950 to today.The primary record of historical sea level, on the order of several decades to a few centuries, is tide gauges. Tide gauge records from around the world are collected in the Permanent Service for Mean Sea Level (PSMSL) database, and includes data along the Arctic coasts. A reasonable...... amount of data is available along the Norwegian and Russian coasts since 1950, and most published research on Arctic sea level extends cautiously from these areas. Very little tide gauge data is available elsewhere in the Arctic, and records of a length of several decades,as generally recommended for sea...

  17. Reconstructing warm inflation

    Science.gov (United States)

    Herrera, Ramón

    2018-03-01

    The reconstruction of a warm inflationary universe model from the scalar spectral index n_S(N) and the tensor to scalar ratio r( N) as a function of the number of e-folds N is studied. Under a general formalism we find the effective potential and the dissipative coefficient in terms of the cosmological parameters n_S and r considering the weak and strong dissipative stages under the slow roll approximation. As a specific example, we study the attractors for the index n_S given by nS-1∝ N^{-1} and for the ratio r∝ N^{-2}, in order to reconstruct the model of warm inflation. Here, expressions for the effective potential V(φ ) and the dissipation coefficient Γ (φ ) are obtained.

  18. Jet Vertex Charge Reconstruction

    CERN Document Server

    Nektarijevic, Snezana; The ATLAS collaboration

    2015-01-01

    A newly developed algorithm called the jet vertex charge tagger, aimed at identifying the sign of the charge of jets containing $b$-hadrons, referred to as $b$-jets, is presented. In addition to the well established track-based jet charge determination, this algorithm introduces the so-called \\emph{jet vertex charge} reconstruction, which exploits the charge information associated to the displaced vertices within the jet. Furthermore, the charge of a soft muon contained in the jet is taken into account when available. All available information is combined into a multivariate discriminator. The algorithm has been developed on jets matched to generator level $b$-hadrons provided by $t\\bar{t}$ events simulated at $\\sqrt{s}$=13~TeV using the full ATLAS detector simulation and reconstruction.

  19. Segmentation-DrivenTomographic Reconstruction

    DEFF Research Database (Denmark)

    Kongskov, Rasmus Dalgas

    such that the segmentation subsequently can be carried out by use of a simple segmentation method, for instance just a thresholding method. We tested the advantages of going from a two-stage reconstruction method to a one stage segmentation-driven reconstruction method for the phase contrast tomography reconstruction......The tomographic reconstruction problem is concerned with creating a model of the interior of an object from some measured data, typically projections of the object. After reconstructing an object it is often desired to segment it, either automatically or manually. For computed tomography (CT...

  20. LHCb jet reconstruction

    International Nuclear Information System (INIS)

    Francisco, Oscar; Rangel, Murilo; Barter, William; Bursche, Albert; Potterat, Cedric; Coco, Victor

    2012-01-01

    Full text: The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than 4 X 10 32 cm -2 s -1 and the integrated luminosity reached the value of 1,02fb -1 on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test perturbative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space ηX φ and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the colorimeters are used on the LHCb experiment to create objects called particle flow objects that are used as input to anti-kt algorithm. The LHCb is specially interesting for jets studies because its η region is complementary to the others main experiments on LHC. We will present the first results of jet reconstruction using 2011 LHCb data. (author)

  1. LHCb jet reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Francisco, Oscar; Rangel, Murilo [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Barter, William [University of Cambridge, Cambridge (United Kingdom); Bursche, Albert [Universitat Zurich, Zurich (Switzerland); Potterat, Cedric [Universitat de Barcelona, Barcelona (Spain); Coco, Victor [Nikhef National Institute for Subatomic Physics, Amsterdam (Netherlands)

    2012-07-01

    Full text: The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than 4 X 10{sup 32} cm{sup -2}s{sup -1} and the integrated luminosity reached the value of 1,02fb{sup -1} on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test perturbative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space {eta}X {phi} and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the colorimeters are used on the LHCb experiment to create objects called particle flow objects that are used as input to anti-kt algorithm. The LHCb is specially interesting for jets studies because its {eta} region is complementary to the others main experiments on LHC. We will present the first results of jet reconstruction using 2011 LHCb data. (author)

  2. [Reconstructive methods after Fournier gangrene].

    Science.gov (United States)

    Wallner, C; Behr, B; Ring, A; Mikhail, B D; Lehnhardt, M; Daigeler, A

    2016-04-01

    Fournier's gangrene is a variant of the necrotizing fasciitis restricted to the perineal and genital region. It presents as an acute life-threatening disease and demands rapid surgical debridement, resulting in large soft tissue defects. Various reconstructive methods have to be applied to reconstitute functionality and aesthetics. The objective of this work is to identify different reconstructive methods in the literature and compare them to our current concepts for reconstructing defects caused by Fournier gangrene. Analysis of the current literature and our reconstructive methods on Fournier gangrene. The Fournier gangrene is an emergency requiring rapid, calculated antibiotic treatment and radical surgical debridement. After the acute phase of the disease, appropriate reconstructive methods are indicated. The planning of the reconstruction of the defect depends on many factors, especially functional and aesthetic demands. Scrotal reconstruction requires a higher aesthetic and functional reconstructive degree than perineal cutaneous wounds. In general, thorough wound hygiene, proper pre-operative planning, and careful consideration of the patient's demands are essential for successful reconstruction. In the literature, various methods for reconstruction after Fournier gangrene are described. Reconstruction with a flap is required for a good functional result in complex regions as the scrotum and penis, while cutaneous wounds can be managed through skin grafting. Patient compliance and tissue demand are crucial factors in the decision-making process.

  3. Hopfield neural network in HEP track reconstruction

    International Nuclear Information System (INIS)

    Muresan, R.; Pentia, M.

    1997-01-01

    In experimental particle physics, pattern recognition problems, specifically for neural network methods, occur frequently in track finding or feature extraction. Track finding is a combinatorial optimization problem. Given a set of points in Euclidean space, one tries the reconstruction of particle trajectories, subject to smoothness constraints.The basic ingredients in a neural network are the N binary neurons and the synaptic strengths connecting them. In our case the neurons are the segments connecting all possible point pairs.The dynamics of the neural network is given by a local updating rule wich evaluates for each neuron the sign of the 'upstream activity'. An updating rule in the form of sigmoid function is given. The synaptic strengths are defined in terms of angle between the segments and the lengths of the segments implied in the track reconstruction. An algorithm based on Hopfield neural network has been developed and tested on the track coordinates measured by silicon microstrip tracking system

  4. Pseudoproxy Experiments Using the BARCAST Reconstruction Technique: Effects on Spatiotemporal Persistence Properties

    Science.gov (United States)

    Nilsen, T.; Divine, D.; Rypdal, M.; Werner, J.; Rypdal, K.

    2016-12-01

    A modified two-dimensional stochastic-diffusive energy balance model (EBM) defined on a sphere was used for generating pseudoproxy/instrumental data and target data for surface temperature. The EBM is described in Rypdal et al. (2015). The target field has prescribed long-range memory (LRM) properties in time, and a frequency-dependent autocorrelation function in space. The Bayesian hierarchical model BARCAST, was used to generate surface temperature field reconstructions of an area corresponding to the European landmass for the past millennium. BARCAST has a built-in multivariate AR(1) model for the evolution of the temperature field, with an exponential, spatial covariance function, (Tingley & Huybers, 2010). The AR(1) process has a short-range memory, and we seek to find out how the competing spatiotemporal models influence the persistence of the reconstruction. A number of pseudoproxy experiments were performed with a fixed proxy network, using different signal-to-noise ratios (SNR) and colors of noise, (white/red). To study the persistence properties, the power-law relation of the power spectral density for LRM processes was used: S(f) f-β. The spectral exponent β was estimated both for local data and the spatial mean of the full region. The local β for the target varies between (0.1, 0.4), and for the spatial mean β 0.6. Results for the reconstructions show that the local and global memory is influenced by the noise color and level. Low noise levels or absence of noise results in reconstructions that exhibit similar properties as the target, while for higher noise levels the reconstructions have memory properties of a white/red character, (SNR=0.3 by standard deviation). Since an SNR of 0.5-0.25 is considered realistic for real proxy records, this implies that estimates of temporal persistence from proxy-based reconstructions reflect the proxy noise to a high degree, and not the signal as desired. Rypdal et al., 2015: Spatiotemporal Long-Range Persistence

  5. Distributed 3-D iterative reconstruction for quantitative SPECT

    International Nuclear Information System (INIS)

    Ju, Z.W.; Frey, E.C.; Tsui, B.M.W.

    1995-01-01

    The authors describe a distributed three dimensional (3-D) iterative reconstruction library for quantitative single-photon emission computed tomography (SPECT). This library includes 3-D projector-backprojector pairs (PBPs) and distributed 3-D iterative reconstruction algorithms. The 3-D PBPs accurately and efficiently model various combinations of the image degrading factors including attenuation, detector response and scatter response. These PBPs were validated by comparing projection data computed using the projectors with that from direct Monte Carlo (MC) simulations. The distributed 3-D iterative algorithms spread the projection-backprojection operations for all the projection angles over a heterogeneous network of single or multi-processor computers to reduce the reconstruction time. Based on a master/slave paradigm, these distributed algorithms provide dynamic load balancing and fault tolerance. The distributed algorithms were verified by comparing images reconstructed using both the distributed and non-distributed algorithms. Computation times for distributed 3-D reconstructions running on up to 4 identical processors were reduced by a factor approximately 80--90% times the number of the processors participating, compared to those for non-distributed 3-D reconstructions running on a single processor. When combined with faster affordable computers, this library provides an efficient means for implementing accurate reconstruction and compensation methods to improve quality and quantitative accuracy in SPECT images

  6. Reconstruction of coupling architecture of neural field networks from vector time series

    Science.gov (United States)

    Sysoev, Ilya V.; Ponomarenko, Vladimir I.; Pikovsky, Arkady

    2018-04-01

    We propose a method of reconstruction of the network coupling matrix for a basic voltage-model of the neural field dynamics. Assuming that the multivariate time series of observations from all nodes are available, we describe a technique to find coupling constants which is unbiased in the limit of long observations. Furthermore, the method is generalized for reconstruction of networks with time-delayed coupling, including the reconstruction of unknown time delays. The approach is compared with other recently proposed techniques.

  7. Photometric Lunar Surface Reconstruction

    Science.gov (United States)

    Nefian, Ara V.; Alexandrov, Oleg; Morattlo, Zachary; Kim, Taemin; Beyer, Ross A.

    2013-01-01

    Accurate photometric reconstruction of the Lunar surface is important in the context of upcoming NASA robotic missions to the Moon and in giving a more accurate understanding of the Lunar soil composition. This paper describes a novel approach for joint estimation of Lunar albedo, camera exposure time, and photometric parameters that utilizes an accurate Lunar-Lambertian reflectance model and previously derived Lunar topography of the area visualized during the Apollo missions. The method introduced here is used in creating the largest Lunar albedo map (16% of the Lunar surface) at the resolution of 10 meters/pixel.

  8. Penile surgery and reconstruction.

    Science.gov (United States)

    Perovic, Sava V; Djordjevic, Miroslav L J; Kekic, Zoran K; Djakovic, Nenad G

    2002-05-01

    This review will highlight recent advances in the field of penile reconstructive surgery in the paediatric and adult population. It is based on the work published during the year 2001. Besides the anatomical and histological studies of the penis, major contributions have been described in congenital and acquired penile anomalies. Also, a few new techniques and modifications of old procedures are described in order to improve the final functional and aesthetic outcome. The techniques for penile enlargement present a trend in the new millennium, but are still at the stage of investigation.

  9. Progressive Reconstruction: A Methodology for Stabilization and Reconstruction Operations

    National Research Council Canada - National Science Library

    Rohr, Karl C

    2006-01-01

    ... these nations in accordance with stated United States' goals. The argument follows closely current and developing United States military doctrine on stabilization, reconstruction, and counterinsurgency operations...

  10. Bartlett's concept of schema in reconstruction

    DEFF Research Database (Denmark)

    Wagoner, Brady

    2013-01-01

    dimensions in relation to embodied action and memory “reconstruction,” shows how these temporal dynamics are later abandoned by early cognitive “schema” theories which revert to the metaphor of storage, and explores strategies by which we might fruitfully bring schema back into psychology as an embodied...... an activity of “turning around upon schemata,” humans can create ruptures in their seamless flow of activity in an environment and take active control over mind and behavior. This paper contextualizes Bartlett’s concept of schema within broader theoretical developments of his time, examines its temporal...

  11. LHCb; LHCb Jet Reconstruction

    CERN Multimedia

    Augusto, O

    2012-01-01

    The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than $4 \\times 10^{32} cm^{-2} s^{-1}$ and the integrated luminosity reached the value of 1.02 $fb^{-1}$ on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test pertubative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space $\\eta \\times \\phi$ and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the calo...

  12. Three-dimensional ICT reconstruction

    International Nuclear Information System (INIS)

    Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia

    2005-01-01

    The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context, qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)

  13. Three-dimensional ICT reconstruction

    International Nuclear Information System (INIS)

    Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia

    2004-01-01

    The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by order, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)

  14. Kinematic analysis of anterior cruciate ligament reconstruction in total knee arthroplasty

    OpenAIRE

    Liu, Hua-Wei; Ni, Ming; Zhang, Guo-Qiang; Li, Xiang; Chen, Hui; Zhang, Qiang; Chai, Wei; Zhou, Yong-Gang; Chen, Ji-Ying; Liu, Yu-Liang; Cheng, Cheng-Kung; Wang, Yan

    2016-01-01

    Background: This study aims to retain normal knee kinematics after knee replacement surgeries by reconstructing anterior cruciate ligament during total knee arthroplasty. Method: We use computational simulation tools to establish four dynamic knee models, including normal knee model, posterior cruciate ligament retaining knee model, posterior cruciate ligament substituting knee model, and anterior cruciate ligament reconstructing knee model. Our proposed method utilizes magnetic resonance ima...

  15. Virtual 3-D Facial Reconstruction

    Directory of Open Access Journals (Sweden)

    Martin Paul Evison

    2000-06-01

    Full Text Available Facial reconstructions in archaeology allow empathy with people who lived in the past and enjoy considerable popularity with the public. It is a common misconception that facial reconstruction will produce an exact likeness; a resemblance is the best that can be hoped for. Research at Sheffield University is aimed at the development of a computer system for facial reconstruction that will be accurate, rapid, repeatable, accessible and flexible. This research is described and prototypical 3-D facial reconstructions are presented. Interpolation models simulating obesity, ageing and ethnic affiliation are also described. Some strengths and weaknesses in the models, and their potential for application in archaeology are discussed.

  16. Entropy and transverse section reconstruction

    International Nuclear Information System (INIS)

    Gullberg, G.T.

    1976-01-01

    A new approach to the reconstruction of a transverse section using projection data from multiple views incorporates the concept of maximum entropy. The principle of maximizing information entropy embodies the assurance of minimizing bias or prejudice in the reconstruction. Using maximum entropy is a necessary condition for the reconstructed image. This entropy criterion is most appropriate for 3-D reconstruction of objects from projections where the system is underdetermined or the data are limited statistically. This is the case in nuclear medicine time limitations in patient studies do not yield sufficient projections

  17. 3D reconstructions of a controlled bus bombing

    DEFF Research Database (Denmark)

    Villa, Chiara; Hansen, Nikolaj Friis; Hansen, Kamilla Maria

    2018-01-01

    Objectives: to demonstrate the usefulness of 3D reconstructions to better understand the dynamic of a controlled bus bombing. Materials and methods: 3D models of the victims (pigs) were created from post-mortem CT scanning using Mimic software; 3D models of the crime scene (bus) were generated by...

  18. Practical implementation of tetrahedral mesh reconstruction in emission tomography

    Science.gov (United States)

    Boutchko, R.; Sitek, A.; Gullberg, G. T.

    2013-05-01

    This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

  19. Practical implementation of tetrahedral mesh reconstruction in emission tomography

    International Nuclear Information System (INIS)

    Boutchko, R; Gullberg, G T; Sitek, A

    2013-01-01

    This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

  20. Optimal reconstruction angles

    International Nuclear Information System (INIS)

    Cook, G.O. Jr.; Knight, L.

    1979-07-01

    The question of optimal projection angles has recently become of interest in the field of reconstruction from projections. Here, studies are concentrated on the n x n pixel space, where literative algorithms such as ART and direct matrix techniques due to Katz are considered. The best angles are determined in a Gauss--Markov statistical sense as well as with respect to a function-theoretical error bound. The possibility of making photon intensity a function of angle is also examined. Finally, the best angles to use in an ART-like algorithm are studied. A certain set of unequally spaced angles was found to be preferred in several contexts. 15 figures, 6 tables