Signal-to-noise characterization of time-gated intensifiers used for wide-field time-domain FLIM
Energy Technology Data Exchange (ETDEWEB)
McGinty, J; Requejo-Isidro, J; Munro, I; Talbot, C B; Dunsby, C; Neil, M A A; French, P M W [Photonics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2BW (United Kingdom); Kellett, P A; Hares, J D, E-mail: james.mcginty@imperial.ac.u [Kentech Instruments Ltd, Isis Building, Howbery Park, Wallingford, OX10 8BA (United Kingdom)
2009-07-07
Time-gated imaging using gated optical intensifiers provides a means to realize high speed fluorescence lifetime imaging (FLIM) for the study of fast events and for high throughput imaging. We present a signal-to-noise characterization of CCD-coupled micro-channel plate gated intensifiers used with this technique and determine the optimal acquisition parameters (intensifier gain voltage, CCD integration time and frame averaging) for measuring mono-exponential fluorescence lifetimes in the shortest image acquisition time for a given signal flux. We explore the use of unequal CCD integration times for different gate delays and show that this can improve the lifetime accuracy for a given total acquisition time.
Funane, Tsukasa; Hou, Steven S.; Zoltowska, Katarzyna Marta; van Veluw, Susanne J.; Berezovska, Oksana; Kumar, Anand T. N.; Bacskai, Brian J.
2018-05-01
We have developed an imaging technique which combines selective plane illumination microscopy with time-domain fluorescence lifetime imaging microscopy (SPIM-FLIM) for three-dimensional volumetric imaging of cleared mouse brains with micro- to mesoscopic resolution. The main features of the microscope include a wavelength-adjustable pulsed laser source (Ti:sapphire) (near-infrared) laser, a BiBO frequency-doubling photonic crystal, a liquid chamber, an electrically focus-tunable lens, a cuvette based sample holder, and an air (dry) objective lens. The performance of the system was evaluated with a lifetime reference dye and micro-bead phantom measurements. Intensity and lifetime maps of three-dimensional human embryonic kidney (HEK) cell culture samples and cleared mouse brain samples expressing green fluorescent protein (GFP) (donor only) and green and red fluorescent protein [positive Förster (fluorescence) resonance energy transfer] were acquired. The results show that the SPIM-FLIM system can be used for sample sizes ranging from single cells to whole mouse organs and can serve as a powerful tool for medical and biological research.
Clinical multiphoton FLIM tomography
König, Karsten
2012-03-01
This paper gives an overview on current clinical high resolution multiphoton fluorescence lifetime imaging in volunteers and patients. Fluorescence lifetime imaging (FLIM) in Life Sciences was introduced in Jena/Germany in 1988/89 based on a ZEISS confocal picosecond dye laser scanning microscope equipped with a single photon counting unit. The porphyrin distribution in living cells and living tumor-bearing mice was studied with high spatial, temporal, and spectral resolution. Ten years later, time-gated cameras were employed to detect dental caries in volunteers based on one-photon excitation of autofluorescent bacteria with long fluorescence lifetimes. Nowadays, one-photon FLIM based on picosecond VIS laser diodes are used to study ocular diseases in humans. Already one decade ago, first clinical twophoton FLIM images in humans were taken with the certified clinical multiphoton femtosecond laser tomograph DermaInspectTM. Multiphoton tomographs with FLIM modules are now operating in hospitals at Brisbane, Tokyo, Berlin, Paris, London, Modena and other European cities. Multiple FLIM detectors allow spectral FLIM with a temporal resolution down to 20 ps (MCP) / 250 ps (PMT) and a spectral resolution of 10 nm. Major FLIM applications include the detection of intradermal sunscreen and tattoo nanoparticles, the detection of different melanin types, the early diagnosis of dermatitis and malignant melanoma, as well as the measurement of therapeutic effects in pateints suffering from dermatitis. So far, more than 1,000 patients and volunteers have been investigated with the clinical multiphoton FLIM tomographs DermaInspectTM and MPTflexTM.
Accurate Rapid Lifetime Determination on Time-Gated FLIM Microscopy with Optical Sectioning.
Silva, Susana F; Domingues, José Paulo; Morgado, António Miguel
2018-01-01
Time-gated fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to assess the biochemistry of cells and tissues. When applied to living thick samples, it is hampered by the lack of optical sectioning and the need of acquiring many images for an accurate measurement of fluorescence lifetimes. Here, we report on the use of processing techniques to overcome these limitations, minimizing the acquisition time, while providing optical sectioning. We evaluated the application of the HiLo and the rapid lifetime determination (RLD) techniques for accurate measurement of fluorescence lifetimes with optical sectioning. HiLo provides optical sectioning by combining the high-frequency content from a standard image, obtained with uniform illumination, with the low-frequency content of a second image, acquired using structured illumination. Our results show that HiLo produces optical sectioning on thick samples without degrading the accuracy of the measured lifetimes. We also show that instrument response function (IRF) deconvolution can be applied with the RLD technique on HiLo images, improving greatly the accuracy of the measured lifetimes. These results open the possibility of using the RLD technique with pulsed diode laser sources to determine accurately fluorescence lifetimes in the subnanosecond range on thick multilayer samples, providing that offline processing is allowed.
Kim, Byungyeon; Park, Byungjun; Lee, Seungrag; Won, Youngjae
2016-01-01
We demonstrated GPU accelerated real-time confocal fluorescence lifetime imaging microscopy (FLIM) based on the analog mean-delay (AMD) method. Our algorithm was verified for various fluorescence lifetimes and photon numbers. The GPU processing time was faster than the physical scanning time for images up to 800 × 800, and more than 149 times faster than a single core CPU. The frame rate of our system was demonstrated to be 13 fps for a 200 × 200 pixel image when observing maize vascular tissue. This system can be utilized for observing dynamic biological reactions, medical diagnosis, and real-time industrial inspection. PMID:28018724
Time-resolved fluorescence microscopy (FLIM) as an analytical tool in skin nanomedicine.
Alexiev, Ulrike; Volz, Pierre; Boreham, Alexander; Brodwolf, Robert
2017-07-01
The emerging field of nanomedicine provides new approaches for the diagnosis and treatment of diseases, for symptom relief, and for monitoring of disease progression. Topical application of drug-loaded nanoparticles for the treatment of skin disorders is a promising strategy to overcome the stratum corneum, the upper layer of the skin, which represents an effective physical and biochemical barrier. The understanding of drug penetration into skin and enhanced penetration into skin facilitated by nanocarriers requires analytical tools that ideally allow to visualize the skin, its morphology, the drug carriers, drugs, their transport across the skin and possible interactions, as well as effects of the nanocarriers within the different skin layers. Here, we review some recent developments in the field of fluorescence microscopy, namely Fluorescence Lifetime Imaging Microscopy (FLIM)), for improved characterization of nanocarriers, their interactions and penetration into skin. In particular, FLIM allows for the discrimination of target molecules, e.g. fluorescently tagged nanocarriers, against the autofluorescent tissue background and, due to the environmental sensitivity of the fluorescence lifetime, also offers insights into the local environment of the nanoparticle and its interactions with other biomolecules. Thus, FLIM shows the potential to overcome several limits of intensity based microscopy. Copyright © 2017 Elsevier B.V. All rights reserved.
Time-Domain Fluorescence Lifetime Imaging Techniques Suitable for Solid-State Imaging Sensor Arrays
Directory of Open Access Journals (Sweden)
Robert K. Henderson
2012-05-01
Full Text Available We have successfully demonstrated video-rate CMOS single-photon avalanche diode (SPAD-based cameras for fluorescence lifetime imaging microscopy (FLIM by applying innovative FLIM algorithms. We also review and compare several time-domain techniques and solid-state FLIM systems, and adapt the proposed algorithms for massive CMOS SPAD-based arrays and hardware implementations. The theoretical error equations are derived and their performances are demonstrated on the data obtained from 0.13 μm CMOS SPAD arrays and the multiple-decay data obtained from scanning PMT systems. In vivo two photon fluorescence lifetime imaging data of FITC-albumin labeled vasculature of a P22 rat carcinosarcoma (BD9 rat window chamber are used to test how different algorithms perform on bi-decay data. The proposed techniques are capable of producing lifetime images with enough contrast.
Gutierrez-Navarro, Omar; Campos-Delgado, Daniel U; Arce-Santana, Edgar R; Maitland, Kristen C; Cheng, Shuna; Jabbour, Joey; Malik, Bilal; Cuenca, Rodrigo; Jo, Javier A
2014-05-19
Multispectral fluorescence lifetime imaging (m-FLIM) can potentially allow identifying the endogenous fluorophores present in biological tissue. Quantitative description of such data requires estimating the number of components in the sample, their characteristic fluorescent decays, and their relative contributions or abundances. Unfortunately, this inverse problem usually requires prior knowledge about the data, which is seldom available in biomedical applications. This work presents a new methodology to estimate the number of potential endogenous fluorophores present in biological tissue samples from time-domain m-FLIM data. Furthermore, a completely blind linear unmixing algorithm is proposed. The method was validated using both synthetic and experimental m-FLIM data. The experimental m-FLIM data include in-vivo measurements from healthy and cancerous hamster cheek-pouch epithelial tissue, and ex-vivo measurements from human coronary atherosclerotic plaques. The analysis of m-FLIM data from in-vivo hamster oral mucosa identified healthy from precancerous lesions, based on the relative concentration of their characteristic fluorophores. The algorithm also provided a better description of atherosclerotic plaques in term of their endogenous fluorophores. These results demonstrate the potential of this methodology to provide quantitative description of tissue biochemical composition.
Yahav, Gilad; Fixler, Dror; Gershanov, Sivan; Goldenberg-Cohen, Nitza
2016-03-01
Brain tumors are the second leading cause of cancer-related deaths in children, after leukemia. Patients with cancer in the central nervous system have a very low recovery rate. Today known imaging and cytology techniques are not always sensitive enough for an early detection of both tumor and its metastatic spread, moreover the detection is generally limited, reviewer dependent and takes a relatively long time. Medulloblastoma (MB) is the most common malignant brain tumor in children. The aim of our talk is to present the frequency domain fluorescence lifetime imaging microscopy system as a possible method for an early detection of MB and its metastatic spread in the cerebrospinal fluids within the pediatric population.
Energy Technology Data Exchange (ETDEWEB)
Lee, Seok-Yong [Univ. of California, Berkeley, CA (United States)
2003-04-10
Protein phosphorylation is a general mechanism for signal transduction as well as regulation of cellular function. Unlike phosphorylation in eukaryotic systems that uses Ser/Thr for the sites of modification, two-component signal transduction systems, which are prevalent in bacteria, archea, and lower eukaryotes, use an aspartate as the site of phosphorylation. Two-component systems comprise a histidine kinase and a receiver domain. The conformational change of the receiver domain upon phosphorylation leads to signal transfer to the downstream target, a process that had not been understood well at the molecular level. The transient nature of the phospho-Asp bond had made structural studies difficult. The discovery of an excellent analogue for acylphosphate, BeF_{3}^{-}, enabled structural study of activated receiver domains. The structure of activated Chemotaxis protein Y (CheY) was determined both by NMR spectroscopy and X-ray crystallography. These structures revealed the molecular basis of the conformational change that is coupled to phosphorylation. Phosphorylation of the conserved Asp residue in the active site allows hydrogen bonding of the T87 Oγ to phospho-aspartate, which in turn leads to the rotation of Y106 into the ''in'' position (termed Y-T coupling). The structure of activated CheY complexed with the 16 N-terminal residues of FliM (N16-FliM), its target, was also determined by X-ray crystallography and confirmed the proposed mechanism of activation (Y-T coupling). First, N16-FliM binds to the region on CheY that undergoes a significant conformational change. Second, the ''in'' position of Y106 presents a better binding surface for FliM because the sidechain of Y106 in the inactive form of CheY (''out'' position) sterically interferes with binding of N16-FliM. In addition to confirmation of Y-T coupling, the structure of the activated CheY-N16-FliM complex suggested that the
Time Domain Induced Polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
2012-01-01
Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use...... of time-domaininduced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function......, to reconstruct the distribution of the Cole-Cole parameters of the earth. The accurate modeling of the transmitter waveform had a strong influence on the forward response, and we showed that the difference between a solution using a step response and a solution using the accurate modeling often is above 100...
Multiwavelength FLIM: new concept for fluorescence diagnosis
Rück, Angelika; Lorenz, S.; Hauser, Carmen; Mosch, S.; Kalinina, S.
2012-03-01
Fluorescence guided tumor resection is very well accepted in the case of bladder cancer and brain tumor, respectively. However, false positive results are one of the major problems, which will make the discrimination between tumor tissue and inflammation difficult. In contrast fluorescence lifetime imaging (FLIM) and especially spectral resolved FLIM (SLIM) can significantly improve the analysis. The fluorescence decay of a fluorophore in many cases does not show a simple monoexponential profile. A very complex situation arises, when more than one compound has to be analyzed. This could be the case when endogenous fluorophores of living cells and tissues have to be discriminated to identify oxidative metabolic changes. Other examples are PDT, when different photosensitizer metabolites are observed simultaneously. In those cases a considerable improvement could be achieved when time-resolved and spectral-resolved techniques are simultaneously incorporated. Within this presentation the principles of spectral and time-resolved fluorescence imaging will be discussed. Successful applications as autofluorescence and 5-ALA induced porphyrin fluorescence will be described in more detail.
Directory of Open Access Journals (Sweden)
Ruud G J Detert Oude Weme
Full Text Available Protein-protein interactions can be studied in vitro, e.g. with bacterial or yeast two-hybrid systems or surface plasmon resonance. In contrast to in vitro techniques, in vivo studies of protein-protein interactions allow examination of spatial and temporal behavior of such interactions in their native environment. One approach to study protein-protein interactions in vivo is via Förster Resonance Energy Transfer (FRET. Here, FRET efficiency of selected FRET-pairs was studied at the single cell level using sensitized emission and Frequency Domain-Fluorescence Lifetime Imaging Microscopy (FD-FLIM. For FRET-FLIM, a prototype Modulated Electron-Multiplied FLIM system was used, which is, to the best of our knowledge, the first account of Frequency Domain FLIM to analyze FRET in single bacterial cells. To perform FRET-FLIM, we first determined and benchmarked the best fluorescent protein-pair for FRET in Bacillus subtilis using a novel BglBrick-compatible integration vector. We show that GFP-tagRFP is an excellent donor-acceptor pair for B. subtilis in vivo FRET studies. As a proof of concept, selected donor and acceptor fluorescent proteins were fused using a linker that contained a tobacco etch virus (TEV-protease recognition sequence. Induction of TEV-protease results in loss of FRET efficiency and increase in fluorescence lifetime. The loss of FRET efficiency after TEV induction can be followed in time in single cells via time-lapse microscopy. This work will facilitate future studies of in vivo dynamics of protein complexes in single B. subtilis cells.
Heliborne time domain electromagnetic system
International Nuclear Information System (INIS)
Bhattacharya, S.
2009-01-01
Atomic Minerals Directorate (AMD), are using heliborne and ground time domain electromagnetic (TDEM) system for the exploration of deep seated unconformity type uranium deposits. Uranium has been explored in various parts of the world like Athabasca basin using time domain electromagnetic system. AMD has identified some areas in India where such deposits are available. Apart from uranium exploration, the TDEM systems are used for the exploration of deep seated minerals like diamonds. Bhabha Atomic Research Centre (BARC) is involved in the indigenous design of the heliborne time domain system since this system is useful for DAE and also it has a scope of wide application. In this paper we discuss about the principle of time domain electromagnetic systems, their capabilities and the development and problems of such system for various other mineral exploration. (author)
Impedance models in time domain
Rienstra, S.W.
2005-01-01
Necessary conditions for an impedance function are derived. Methods available in the literature are discussed. A format with recipe is proposed for an exact impedance condition in time domain on a time grid, based on the Helmholtz resonator model. An explicit solution is given of a pulse reflecting
Flexible time domain averaging technique
Zhao, Ming; Lin, Jing; Lei, Yaguo; Wang, Xiufeng
2013-09-01
Time domain averaging(TDA) is essentially a comb filter, it cannot extract the specified harmonics which may be caused by some faults, such as gear eccentric. Meanwhile, TDA always suffers from period cutting error(PCE) to different extent. Several improved TDA methods have been proposed, however they cannot completely eliminate the waveform reconstruction error caused by PCE. In order to overcome the shortcomings of conventional methods, a flexible time domain averaging(FTDA) technique is established, which adapts to the analyzed signal through adjusting each harmonic of the comb filter. In this technique, the explicit form of FTDA is first constructed by frequency domain sampling. Subsequently, chirp Z-transform(CZT) is employed in the algorithm of FTDA, which can improve the calculating efficiency significantly. Since the signal is reconstructed in the continuous time domain, there is no PCE in the FTDA. To validate the effectiveness of FTDA in the signal de-noising, interpolation and harmonic reconstruction, a simulated multi-components periodic signal that corrupted by noise is processed by FTDA. The simulation results show that the FTDA is capable of recovering the periodic components from the background noise effectively. Moreover, it can improve the signal-to-noise ratio by 7.9 dB compared with conventional ones. Experiments are also carried out on gearbox test rigs with chipped tooth and eccentricity gear, respectively. It is shown that the FTDA can identify the direction and severity of the eccentricity gear, and further enhances the amplitudes of impulses by 35%. The proposed technique not only solves the problem of PCE, but also provides a useful tool for the fault symptom extraction of rotating machinery.
Time domain electromagnetic metal detectors
International Nuclear Information System (INIS)
Hoekstra, P.
1996-01-01
This presentation focuses on illustrating by case histories the range of applications and limitations of time domain electromagnetic (TDEM) systems for buried metal detection. Advantages claimed for TDEM metal detectors are: independent of instrument response (Geonics EM61) to surrounding soil and rock type; simple anomaly shape; mitigation of interference by ambient electromagnetic noise; and responsive to both ferrous and non-ferrous metallic targets. The data in all case histories to be presented were acquired with the Geonics EM61 TDEM system. Case histories are a test bed site on Molokai, Hawaii; Fort Monroe, Virginia; and USDOE, Rocky Flats Plant. The present limitations of this technology are: discrimination capabilities in terms of type of ordnance, and depth of burial is limited, and ability of resolving targets with small metallic ambient needs to be improved
Oxygen sensing PLIM together with FLIM of intrinsic cellular fluorophores for metabolic mapping
Kalinina, Sviatlana; Schaefer, Patrick; Breymayer, Jasmin; Bisinger, Dominik; Chakrabortty, Sabyasachi; Rueck, Angelika
2018-02-01
Otical imaging techniques based on time correlated single photon counting (TCSPC) has found wide applications in medicine and biology. Non-invasive and information-rich fluorescence lifetime imaging microscopy (FLIM) is successfully used for monitoring fluorescent intrinsic metabolic coenzymes as NAD(P)H (nicotinamide adenine dinucleotide (phosphate)) and FAD+ (flavin adenine dinucleotide) in living cells and tissues. The ratio between proteinbound and free coenzymes gives an information about the balance between oxidative phosphorylation and glycolysis in the cells. The changes of the ratio reflects major cellular disorders. A correlation exists between metabolic activity, redox ratio and fluorescence lifetime during stem cell differentiation, neurodegenerative diseases, and carcinogenesis. A multichannel FLIM detection system was designed for monitoring the redox state of NAD(P)H and FAD+ and other intrinsic fluorophores as protoporphyrin IX. In addition, the unique upgrade is useful to perform FLIM and PLIM (phosphorescence lifetime imaging microscopy) simultaneously. PLIM is a promising method to investigate oxygen sensing in biomedical samples. In detail, the oxygen-dependent quenching of phosphorescence of some compounds as transition metal complexes enables measuring of oxygen partial pressure (pO2). Using a two-channel FLIM/PLIM system we monitored intrinsic pO2 by PLIM simultaneously with NAD(P)H by FLIM providing complex metabolic and redox imaging of living cells. Physico-chemical properties of oxygen sensitive probes define certain parameters including their localisation. We present results of some ruthenium based complexes including those specifically bound to mitochondria.
High frame-rate TCSPC-FLIM using a novel SPAD-based image sensor
Gersbach, M.; Trimananda, R.; Maruyama, Y.; Fishburn, M.; Cahrbon, E. et al
2010-01-01
Imaging techniques based on time-correlated single photon counting (TCSPC), such as fluorescence lifetime imaging microscopy (FLIM), rely on fast single-photon detectors as well as timing electronics in the form of time-to-digital or time-to-analog converters. Conventional systems rely on
QUANTIFYING THE SHORT LIFETIME WITH TCSPC-FLIM: FIRST MOMENT VERSUS FITTING METHODS
Directory of Open Access Journals (Sweden)
LINGLING XU
2013-10-01
Full Text Available Combing the time-correlated single photon counting (TCSPC with fluorescence lifetime imaging microscopy (FLIM provides promising opportunities in revealing important information on the microenvironment of cells and tissues, but the applications are thus far mainly limited by the accuracy and precision of the TCSPC-FLIM technique. Here we present a comprehensive investigation on the performance of two data analysis methods, the first moment (M1 method and the conventional least squares (Fitting method, in quantifying fluorescence lifetime. We found that the M1 method is more superior than the Fitting method when the lifetime is short (70 ~ 400 ps or the signal intensity is weak (<103 photons.
Time versus frequency domain measurements: layered model ...
African Journals Online (AJOL)
... their high frequency content while among TEM data sets with low frequency content, the averaging times for the FEM ellipticity were shorter than the TEM quality. Keywords: ellipticity, frequency domain, frequency electromagnetic method, model parameter, orientation error, time domain, transient electromagnetic method
Calibration of TAMA300 in time domain
International Nuclear Information System (INIS)
Telada, Souichi; Tatsumi, Daisuke; Akutsu, Tomomi; Ando, Masaki; Kanda, Nobuyuki
2005-01-01
We could reconstruct the strain of gravitational wave signals from acquired data in the time domain by using the infinite impulse response filter technique in TAMA300. We would like to analyse the waveform in the time domain for burst-like signal, merger phase waveform of binary neutron stars, and so on. We established the way to make a continuous time-series gravitational wave strain signal. We compared the time-domain reconstruction with the Fourier-space reconstruction. Both coincided within 3% in the observation range. We could also produce the voltage signal which would be recorded by the data-acquisition system from a simulated gravitational wave. This is useful for some analyses of simulations and signal injections. We could extract the waveform of the hardware injection signal in an observational run in the time domain. The extracted waveform was similar to the injection signal
Casimir forces in the time domain: Theory
International Nuclear Information System (INIS)
Rodriguez, Alejandro W.; McCauley, Alexander P.; Joannopoulos, John D.; Johnson, Steven G.
2009-01-01
We present a method to compute Casimir forces in arbitrary geometries and for arbitrary materials based on the finite-difference time-domain (FDTD) scheme. The method involves the time evolution of electric and magnetic fields in response to a set of current sources, in a modified medium with frequency-independent conductivity. The advantage of this approach is that it allows one to exploit existing FDTD software, without modification, to compute Casimir forces. In this paper, we focus on the derivation, implementation choices, and essential properties of the time-domain algorithm, both considered analytically and illustrated in the simplest parallel-plate geometry.
Generating Dynamic Persistence in the Time Domain
Guerrero, A.; Smith, L. A.; Smith, L. A.; Kaplan, D. T.
2001-12-01
Many dynamical systems present long-range correlations. Physically, these systems vary from biological to economical, including geological or urban systems. Important geophysical candidates for this type of behaviour include weather (or climate) and earthquake sequences. Persistence is characterised by slowly decaying correlation function; that, in theory, never dies out. The Persistence exponent reflects the degree of memory in the system and much effort has been expended creating and analysing methods that successfully estimate this parameter and model data that exhibits persistence. The most widely used methods for generating long correlated time series are not dynamical systems in the time domain, but instead are derived from a given spectral density. Little attention has been drawn to modelling persistence in the time domain. The time domain approach has the advantage that an observation at certain time can be calculated using previous observations which is particularly suitable when investigating the predictability of a long memory process. We will describe two of these methods in the time domain. One is a traditional approach using fractional ARIMA (autoregressive and moving average) models; the second uses a novel approach to extending a given series using random Fourier basis functions. The statistical quality of the two methods is compared, and they are contrasted with weather data which shows, reportedly, persistence. The suitability of this approach both for estimating predictability and for making predictions is discussed.
Time-Domain Simulation of RF Couplers
International Nuclear Information System (INIS)
Smithe, David; Carlsson, Johan; Austin, Travis
2009-01-01
We have developed a finite-difference time-domain (FDTD) fluid-like approach to integrated plasma-and-coupler simulation [1], and show how it can be used to model LH and ICRF couplers in the MST and larger tokamaks.[2] This approach permits very accurate 3-D representation of coupler geometry, and easily includes non-axi-symmetry in vessel wall, magnetic equilibrium, and plasma density. The plasma is integrated with the FDTD Maxwell solver in an implicit solve that steps over electron time-scales, and permits tenuous plasma in the coupler itself, without any need to distinguish or interface between different regions of vacuum and/or plasma. The FDTD algorithm is also generalized to incorporate a time-domain sheath potential [3] on metal structures within the simulation, to look for situations where the sheath potential might generate local sputtering opportunities. Benchmarking of the time-domain sheath algorithm has been reported in the references. Finally, the time-domain software [4] permits the use of particles, either as field diagnostic (test particles) or to self-consistently compute plasma current from the applied RF power.
Structural Time Domain Identification Toolbox User's Guide
DEFF Research Database (Denmark)
Andersen, P.; Kirkegaard, Poul Henning; Brincker, Rune
This manual describes the Structural Time Domain Identification toolbox for use with MA TLAB. This version of the tool box has been developed using the PC-based MA TLAB version 4.2c, but is compatible with prior versions of MATLAB and UNIX-based versions. The routines of the toolbox are the so...
Multiple Shooting and Time Domain Decomposition Methods
Geiger, Michael; Körkel, Stefan; Rannacher, Rolf
2015-01-01
This book offers a comprehensive collection of the most advanced numerical techniques for the efficient and effective solution of simulation and optimization problems governed by systems of time-dependent differential equations. The contributions present various approaches to time domain decomposition, focusing on multiple shooting and parareal algorithms. The range of topics covers theoretical analysis of the methods, as well as their algorithmic formulation and guidelines for practical implementation. Selected examples show that the discussed approaches are mandatory for the solution of challenging practical problems. The practicability and efficiency of the presented methods is illustrated by several case studies from fluid dynamics, data compression, image processing and computational biology, giving rise to possible new research topics. This volume, resulting from the workshop Multiple Shooting and Time Domain Decomposition Methods, held in Heidelberg in May 2013, will be of great interest to applied...
Parametric time-frequency domain spatial audio
Delikaris-Manias, Symeon; Politis, Archontis
2018-01-01
This book provides readers with the principles and best practices in spatial audio signal processing. It describes how sound fields and their perceptual attributes are captured and analyzed within the time-frequency domain, how essential representation parameters are coded, and how such signals are efficiently reproduced for practical applications. The book is split into four parts starting with an overview of the fundamentals. It then goes on to explain the reproduction of spatial sound before offering an examination of signal-dependent spatial filtering. The book finishes with coverage of both current and future applications and the direction that spatial audio research is heading in. Parametric Time-frequency Domain Spatial Audio focuses on applications in entertainment audio, including music, home cinema, and gaming--covering the capturing and reproduction of spatial sound as well as its generation, transduction, representation, transmission, and perception. This book will teach readers the tools needed...
Subjective time pressure: general or domain specific?
Kleiner, Sibyl
2014-09-01
Chronic time pressure has been identified as a pervasive societal problem, exacerbated by high demands of the labor market and the home. Yet time pressure has not been disaggregated and examined separately across home and work contexts, leaving many unanswered questions regarding the sources and potentially stressful consequences of time pressure. Using data collected in the United States General Social Survey waves 2002 and 2004, this study disaggregates time pressure into the domains of home and work, and asks whether considering time pressures within distinct work and home contexts reveals distinct predictors or associations with stress. Findings show that both predictors and stress associations differ across work and home pressures, revealing both methodological and theoretical implications for the study of time pressure and work and family life more generally. Copyright © 2014 Elsevier Inc. All rights reserved.
Metrology for terahertz time-domain spectrometers
Molloy, John F.; Naftaly, Mira
2015-12-01
In recent years the terahertz time-domain spectrometer (THz TDS) [1] has emerged as a key measurement device for spectroscopic investigations in the frequency range of 0.1-5 THz. To date, almost every type of material has been studied using THz TDS, including semiconductors, ceramics, polymers, metal films, liquid crystals, glasses, pharmaceuticals, DNA molecules, proteins, gases, composites, foams, oils, and many others. Measurements with a TDS are made in the time domain; conversion from the time domain data to a frequency spectrum is achieved by applying the Fourier Transform, calculated numerically using the Fast Fourier Transform (FFT) algorithm. As in many other types of spectrometer, THz TDS requires that the sample data be referenced to similarly acquired data with no sample present. Unlike frequency-domain spectrometers which detect light intensity and measure absorption spectra, a TDS records both amplitude and phase information, and therefore yields both the absorption coefficient and the refractive index of the sample material. The analysis of the data from THz TDS relies on the assumptions that: a) the frequency scale is accurate; b) the measurement of THz field amplitude is linear; and c) that the presence of the sample does not affect the performance characteristics of the instrument. The frequency scale of a THz TDS is derived from the displacement of the delay line; via FFT, positioning errors may give rise to frequency errors that are difficult to quantify. The measurement of the field amplitude in a THz TDS is required to be linear with a dynamic range of the order of 10 000. And attention must be given to the sample positioning and handling in order to avoid sample-related errors.
Time-domain multiple-quantum NMR
International Nuclear Information System (INIS)
Weitekamp, D.P.
1982-11-01
The development of time-domain multiple-quantum nuclear magnetic resonance is reviewed through mid 1982 and some prospects for future development are indicated. Particular attention is given to the problem of obtaining resolved, interpretable, many-quantum spectra for anisotropic magnetically isolated systems of coupled spins. New results are presented on a number of topics including the optimization of multiple-quantum-line intensities, analysis of noise in two-dimensional spectroscopy, and the use of order-selective excitation for cross polarization between nuclear-spin species
The time domain triple probe method
International Nuclear Information System (INIS)
Meier, M.A.; Hallock, G.A.; Tsui, H.Y.W.; Bengtson, R.D.
1994-01-01
A new Langmuir probe technique based on the triple probe method is being developed to provide simultaneous measurement of plasma temperature, potential, and density with the temporal and spatial resolution required to accurately characterize plasma turbulence. When the conventional triple probe method is used in an inhomogeneous plasma, local differences in the plasma measured at each probe introduce significant error in the estimation of turbulence parameters. The Time Domain Triple Probe method (TDTP) uses high speed switching of Langmuir probe potential, rather than spatially separated probes, to gather the triple probe information thus avoiding these errors. Analysis indicates that plasma response times and recent electronics technology meet the requirements to implement the TDTP method. Data reduction techniques of TDTP data are to include linear and higher order correlation analysis to estimate fluctuation induced particle and thermal transport, as well as energy relationships between temperature, density, and potential fluctuations
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
Coherent combining pulse bursts in time domain
Galvanauskas, Almantas
2018-01-09
A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.
Finite difference time domain analysis of a chiro plasma
International Nuclear Information System (INIS)
Torres-Silva, H.; Obligado, A.; Reggiani, N.; Sakanaka, P.H.
1995-01-01
The finite difference time-domain (FDTD) method is one of the most widely used computational methods in electromagnetics. Using FDTD, Maxwell's equations are solved directly in the time domain via finite differences and time stepping. The basic approach is relatively easy to understand and is an alternative to the more usual frequency-domain approaches. (author). 5 refs
Reengineering observatory operations for the time domain
Seaman, Robert L.; Vestrand, W. T.; Hessman, Frederic V.
2014-07-01
Observatories are complex scientific and technical institutions serving diverse users and purposes. Their telescopes, instruments, software, and human resources engage in interwoven workflows over a broad range of timescales. These workflows have been tuned to be responsive to concepts of observatory operations that were applicable when various assets were commissioned, years or decades in the past. The astronomical community is entering an era of rapid change increasingly characterized by large time domain surveys, robotic telescopes and automated infrastructures, and - most significantly - of operating modes and scientific consortia that span our individual facilities, joining them into complex network entities. Observatories must adapt and numerous initiatives are in progress that focus on redesigning individual components out of the astronomical toolkit. New instrumentation is both more capable and more complex than ever, and even simple instruments may have powerful observation scripting capabilities. Remote and queue observing modes are now widespread. Data archives are becoming ubiquitous. Virtual observatory standards and protocols and astroinformatics data-mining techniques layered on these are areas of active development. Indeed, new large-aperture ground-based telescopes may be as expensive as space missions and have similarly formal project management processes and large data management requirements. This piecewise approach is not enough. Whatever challenges of funding or politics facing the national and international astronomical communities it will be more efficient - scientifically as well as in the usual figures of merit of cost, schedule, performance, and risks - to explicitly address the systems engineering of the astronomical community as a whole.
Toward practical terahertz time-domain spectroscopy
Brigada, David J.
Terahertz time-domain spectroscopy is a promising technology for the identification of explosive and pharmaceutical substances in adverse conditions. It interacts strongly with intermolecular vibrational and rotational modes. Terahertz also passes through many common dielectric covering materials, allowing for the identification of substances in envelopes, wrapped in opaque plastic, or otherwise hidden. However, there are several challenges preventing the adoption of terahertz spectroscopy outside the laboratory. This dissertation examines the problems preventing widespread adoption of terahertz technology and attempts to resolve them. In order to use terahertz spectroscopy to identify substances, a spectrum measured of the target sample must be compared to the spectra of various known standard samples. This dissertation examines various methods that can be employed throughout the entire process of acquiring and transforming terahertz waveforms to improve the accuracy of these comparisons. The concepts developed in this dissertation directly apply to terahertz spectroscopy, but also carry implications for other spectroscopy methods, from Raman to mass spectrometry. For example, these techniques could help to lower the rate of false positives at airport security checkpoints. This dissertation also examines the implementation of several of these methods as a way to realize a fully self-contained, handheld, battery-operated terahertz spectrometer. This device also employs techniques to allow minimally-trained operators use terahertz to detect different substances of interest. It functions as a proof-of-concept of the true benefits of the improvements that have been developed in this dissertation.
A novel clinical multimodal multiphoton tomograph for AF, SHG, CARS imaging, and FLIM
Weinigel, Martin; Breunig, Hans Georg; König, Karsten
2014-02-01
We report on a flexible nonlinear medical tomograph with multiple miniaturized detectors for simultaneous acquisition of two-photon autofluorescence (AF), second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) images. The simultaneous visualization of the distribution of endogenous fluorophores NAD(P)H, melanin and elastin, SHG-active collagen and as well as non-fluorescent lipids within human skin in vivo is possible. Furthermore, fluorescence lifetime images (FLIM) can be generated using time-correlated single photon counting.
Byrne, Richard D; Larijani, Banafshé; Poccia, Dominic L
2016-01-01
FRET-FLIM techniques have wide application in the study of protein and protein-lipid interactions in cells. We have pioneered an imaging platform for accurate detection of functional states of proteins and their interactions in fixed cells. This platform, two-site-amplified Förster resonance energy transfer (a-FRET), allows greater signal generation while retaining minimal noise thus enabling application of fluorescence lifetime imaging microscopy (FLIM) to be routinely deployed in different types of cells and tissue. We have used the method described here, time-resolved FRET monitored by two-photon FLIM, to demonstrate the direct interaction of Phospholipase Cγ (PLCγ) by Src Family Kinase 1 (SFK1) during nuclear envelope formation and during male and female pronuclear membrane fusion in fertilized sea urchin eggs. We describe here a generic method that can be applied to monitor any proteins of interest.
Time-domain modeling of electromagnetic diffusion with a frequency-domain code
Mulder, W.A.; Wirianto, M.; Slob, E.C.
2007-01-01
We modeled time-domain EM measurements of induction currents for marine and land applications with a frequency-domain code. An analysis of the computational complexity of a number of numerical methods shows that frequency-domain modeling followed by a Fourier transform is an attractive choice if a
Direct time-domain techniques for transient radiation and scattering
International Nuclear Information System (INIS)
Miller, E.K.; Landt, J.A.
1976-01-01
A tutorial introduction to transient electromagnetics, focusing on direct time-domain techniques, is presented. Physical, mathematical, numerical, and experimental aspects of time-domain methods, with emphasis on wire objects excited as antennas or scatters are examined. Numerous computed examples illustrate the characteristics of direct time-domain procedures, especially where they may offer advantages over procedures in the more familiar frequency domain. These advantages include greater solution efficiency for many types of problems, the ability to handle nonlinearities, improved physical insight and interpretability, availability of wide-band information from a single calculation, and the possibility of isolating interactions among various parts of an object using time-range gating
Multiparametric analysis of cisplatin-induced changes in cancer cells using FLIM
Shirmanova, Marina V.; Sergeeva, Tatiana F.; Gavrina, Alena I.; Dudenkova, Varvara V.; Lukyanov, Konstantin A.; Zagaynova, Elena V.
2018-02-01
Cisplatin is an effective anticancer drug commonly used in the treatment of solid tumors. Although DNA is considered as the primary target, the cisplatin action at the cellular level remains unknown. Advanced fluorescence microscopy techniques allow probing various physiological and physicochemical parameters in living cells and tissues with unsurpassed sensitivity in real time. This study was focused on the investigation of cellular bioenergetics and cytosolic pH in colorectal cancer cells during chemotherapy with cisplatin. Special attention was given to the changes in cisplatininduced apoptosis that was identified using genetically encoded FLIM/FRET sensor of caspase-3 activity. Metabolic measurements using FLIM of the metabolic cofactor NAD(P)H showed decreased contribution from free NAD(P)H (a1, %) in all treated cells with more pronounced alterations in the cells undergoing apoptosis. Analysis of cytosolic pH using genetically encoded fluorescent sensor SypHer1 revealed a rapid increase of the pH value upon cisplatin exposure irrespective of the induction of apoptosis. To the best of our knowledge, a simultaneous assessment of metabolic state, cytosolic pH and caspase-3 activity after treatment with cisplatin was performed for the first time. These findings improve our understanding of the cell response to chemotherapy and mechanisms of cisplatin action.
Conversion of Dielectric Data from the Time Domain to the Frequency Domain
Directory of Open Access Journals (Sweden)
Vladimir Durman
2005-01-01
Full Text Available Polarisation and conduction processes in dielectric systems can be identified by the time domain or the frequency domain measurements. If the systems is a linear one, the results of the time domain measurements can be transformed into the frequency domain, and vice versa. Commonly, the time domain data of the absorption conductivity are transformed into the frequency domain data of the dielectric susceptibility. In practice, the relaxation are mainly evaluated by the frequency domain data. In the time domain, the absorption current measurement were prefered up to now. Recent methods are based on the recovery voltage measurements. In this paper a new method of the recovery data conversion from the time the frequency domain is proposed. The method is based on the analysis of the recovery voltage transient based on the Maxwell equation for the current density in a dielectric. Unlike the previous published solutions, the Laplace fransform was used to derive a formula suitable for practical purposes. the proposed procedure allows also calculating of the insulation resistance and separating the polarisation and conduction losses.
Transformation Algorithm of Dielectric Response in Time-Frequency Domain
Directory of Open Access Journals (Sweden)
Ji Liu
2014-01-01
Full Text Available A transformation algorithm of dielectric response from time domain to frequency domain is presented. In order to shorten measuring time of low or ultralow frequency dielectric response characteristics, the transformation algorithm is used in this paper to transform the time domain relaxation current to frequency domain current for calculating the low frequency dielectric dissipation factor. In addition, it is shown from comparing the calculation results with actual test data that there is a coincidence for both results over a wide range of low frequencies. Meanwhile, the time domain test data of depolarization currents in dry and moist pressboards are converted into frequency domain results on the basis of the transformation. The frequency domain curves of complex capacitance and dielectric dissipation factor at the low frequency range are obtained. Test results of polarization and depolarization current (PDC in pressboards are also given at the different voltage and polarization time. It is demonstrated from the experimental results that polarization and depolarization current are affected significantly by moisture contents of the test pressboards, and the transformation algorithm is effective in ultralow frequency of 10−3 Hz. Data analysis and interpretation of the test results conclude that analysis of time-frequency domain dielectric response can be used for assessing insulation system in power transformer.
Full waveform inversion in the frequency domain using classified time-domain residual wavefields
Son, Woohyun; Koo, Nam-Hyung; Kim, Byoung-Yeop; Lee, Ho-Young; Joo, Yonghwan
2017-04-01
We perform the acoustic full waveform inversion in the frequency domain using residual wavefields that have been separated in the time domain. We sort the residual wavefields in the time domain according to the order of absolute amplitudes. Then, the residual wavefields are separated into several groups in the time domain. To analyze the characteristics of the residual wavefields, we compare the residual wavefields of conventional method with those of our residual separation method. From the residual analysis, the amplitude spectrum obtained from the trace before separation appears to have little energy at the lower frequency bands. However, the amplitude spectrum obtained from our strategy is regularized by the separation process, which means that the low-frequency components are emphasized. Therefore, our method helps to emphasize low-frequency components of residual wavefields. Then, we generate the frequency-domain residual wavefields by taking the Fourier transform of the separated time-domain residual wavefields. With these wavefields, we perform the gradient-based full waveform inversion in the frequency domain using back-propagation technique. Through a comparison of gradient directions, we confirm that our separation method can better describe the sub-salt image than the conventional approach. The proposed method is tested on the SEG/EAGE salt-dome model. The inversion results show that our algorithm is better than the conventional gradient based waveform inversion in the frequency domain, especially for deeper parts of the velocity model.
Parameter Estimation in Continuous Time Domain
Directory of Open Access Journals (Sweden)
Gabriela M. ATANASIU
2016-12-01
Full Text Available This paper will aim to presents the applications of a continuous-time parameter estimation method for estimating structural parameters of a real bridge structure. For the purpose of illustrating this method two case studies of a bridge pile located in a highly seismic risk area are considered, for which the structural parameters for the mass, damping and stiffness are estimated. The estimation process is followed by the validation of the analytical results and comparison with them to the measurement data. Further benefits and applications for the continuous-time parameter estimation method in civil engineering are presented in the final part of this paper.
Time Domain Astronomy with Swift and Fermi
African Journals Online (AJOL)
J.D. Myers
sources not usually associated with high-energy emission − e.g., novae and flare ... spectacular transient emission from tidal disruption events and supernova shock ... 3×10−4 for a white dwarf (WD) and ∼2×10. −6 for a 1M⊙ main sequence star. .... outbursts; the strongest was ∼104 times more energetic than the largest.
Underwater Advanced Time-Domain Electromagnetic System
2017-03-03
was determined that the signal was being read in, but was extremely low and was not being recognized by the acquisition software. Further testing...timing window by transmitting some FMC delays during startup and these delay values are determined empirically, during testing. Geometrics is in
Microresonator-Based Optical Frequency Combs: A Time Domain Perspective
2016-04-19
AFRL-AFOSR-VA-TR-2016-0165 (BRI) Microresonator-Based Optical Frequency Combs: A Time Domain Perspective Andrew Weiner PURDUE UNIVERSITY 401 SOUTH...Optical Frequency Combs: A Time Domain Perspective 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0236 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data
Atom optics in the time domain
Arndt, M.; Szriftgiser, P.; Dalibard, J.; Steane, A. M.
1996-05-01
Atom-optics experiments are presented using a time-modulated evanescent light wave as an atomic mirror in the trampoline configuration, i.e., perpendicular to the direction of the atomic free fall. This modulated mirror is used to accelerate cesium atoms, to focus their trajectories, and to apply a ``multiple lens'' to separately focus different velocity classes of atoms originating from a point source. We form images of a simple two-slit object to show the resolution of the device. The experiments are modelled by a general treatment analogous to classical ray optics.
Evaluation of Damping Using Time Domain OMA Techniques
DEFF Research Database (Denmark)
Bajric, Anela; Brincker, Rune; Georgakis, Christos T.
2014-01-01
. In this paper a comparison is made of the effectiveness of three existing OMA techniques in providing accurate damping estimates for varying loadings, levels of noise, number of added measurement channels and structural damping. The evaluated techniques are derived in the time domain and are namely the Ibrahim...... Time Domain (ITD), Eigenvalue Realization Algorithm (ERA) and the Polyreference Time Domain (PTD). The response of a two degree-of-freedom (2DOF) system is numerically established from specified modal parameters with well separated and closely spaced modes. Two types of response are considered, free...
Space moving target detection using time domain feature
Wang, Min; Chen, Jin-yong; Gao, Feng; Zhao, Jin-yu
2018-01-01
The traditional space target detection methods mainly use the spatial characteristics of the star map to detect the targets, which can not make full use of the time domain information. This paper presents a new space moving target detection method based on time domain features. We firstly construct the time spectral data of star map, then analyze the time domain features of the main objects (target, stars and the background) in star maps, finally detect the moving targets using single pulse feature of the time domain signal. The real star map target detection experimental results show that the proposed method can effectively detect the trajectory of moving targets in the star map sequence, and the detection probability achieves 99% when the false alarm rate is about 8×10-5, which outperforms those of compared algorithms.
Three Dimensional Energy Transmitting Boundary in the Time Domain
Directory of Open Access Journals (Sweden)
Naohiro eNakamura
2015-11-01
Full Text Available Although the energy transmitting boundary is accurate and efficient for the FEM earthquake response analysis, it could be applied in the frequency domain only. In the previous papers, the author proposed an earthquake response analysis method using the time domain energy transmitting boundary for two dimensional problems. In this paper, this technique is expanded for three dimensional problems. The inner field is supposed to be a hexahedron shape and the approximate time domain boundary is explained, first. Next, two dimensional anti-plane time domain boundary is studied for a part of the approximate three dimensional boundary method. Then, accuracy and efficiency of the proposed method are confirmed by example problems.
Probing energy metabolism and microviscosity in cancer using FLIM
Shirmanova, Marina V.; Lukina, Maria M.; Shimolina, Lyubov'E.; Kuimova, Marina K.; Dudenkova, Varvara V.; Shcheslavskiy, Vladislav I.; Zagaynova, Elena V.
2017-07-01
Fluorescence lifetime imaging microscopy (FLIM) is a promising non-invasive highly sensitive technique for probing multiple physiological and physicochemical parameters in living cells and tissues. The present study is focused on the investigation of bioenergetics and microscopic viscosity of cultured cancer cells and animal tumors using FLIM during natural growth and chemotherapy. Fluorescence lifetime measurements of the metabolic cofactor NAD(P)H revealed a decrease of the relative amplitude of free NAD(P)H after cisplatin treatment, indicating a change towards a more oxidative metabolic state. Microviscosity mapping performed with the use of fluorescent molecular rotor BODIPY-2 showed a pronounced increase in the plasma membrane viscosity in cancer cells exposed to cisplatin. Although biochemical mechanisms underlying the metabolic and viscosity alterations during chemotherapy have yet to be clarified, our data suggest that the cisplatin-induced changes in cellular metabolism and membrane viscosity play a role in the cytotoxicity of the drug. The results of the study contribute to an understanding of mechanisms of cisplatin action and will be useful for development new approach for assessing response to a therapy.
Thermal Loss of High-Q Antennas in Time Domain vs. Frequency Domain Solver
DEFF Research Database (Denmark)
Bahramzy, Pevand; Pedersen, Gert Frølund
2014-01-01
High-Q structures pose great challenges to their loss simulations in Time Domain Solvers (TDS). Therefore, in this work the thermal loss of high-Q antennas is calculated both in TDS and Frequency Domain Solver (FDS), which are then compared with each other and with the actual measurements....... The thermal loss calculation in FDS is shown to be more accurate for high-Q antennas....
Time domain optical spectrometry with fiber optic waveguides
International Nuclear Information System (INIS)
Whitten, W.B.
1983-01-01
Spectrometers which use optical fibers to obtain time domain spectral dispersion are reviewed. Pulse transmission through fiber optic waveguides is discussed and the basic requirements for sources and detectors are given. Multiplex spectrometry and time-of-flight spectrometry are then discussed. Resolution, fiber requirements, instrumentation and specific spectrometers are presented
Simulation of compressible viscous flow in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Česenek, J.; Feistauer, M.; Horáček, Jaromír; Kučera, V.; Prokopova, J.
2013-01-01
Roč. 219, č. 13 (2013), s. 7139-7150 ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : time dependent domain * ALE method * semi-implicit time discretization * shock indicator Subject RIV: BI - Acoustics Impact factor: 1.600, year: 2013
Measuring time and risk preferences: Reliability, stability, domain specificity
Wölbert, E.M.; Riedl, A.M.
2013-01-01
To accurately predict behavior economists need reliable measures of individual time preferences and attitudes toward risk and typically need to assume stability of these characteristics over time and across decision domains. We test the reliability of two choice tasks for eliciting discount rates,
Sun, Yuansheng; Coskun, Ulas; Liao, Shih-Chu Jeff; Barbieri, Beniamino
2018-02-01
Photoluminescence (PL) refers to light emission initiated by any form of photon excitation. PL spectroscopy and microscopy imaging has been widely applied in material, chemical and life sciences. Measuring its lifetime yields a new dimension of the PL imaging and opens new opportunities for many PL applications. In solar cell research, quantification of the PL lifetime has become an important evaluation for the characteristics of the Perovskite thin film. Depending upon the PL process (fluorescence, phosphorescence, photon upconversion, etc.), the PL lifetimes to be measured can vary in a wide timescale range (e.g. from sub-nanoseconds to microseconds or even milliseconds) - it is challenging to cover this wide range of lifetime measurements by a single technique efficiently. Here, we present a novel digital frequency domain (DFD) technique named FastFLIM, capable of measuring the PL lifetime from 100 ps to 100 ms at the high data collection efficiency (up to 140-million counts per second). Other than the traditional nonlinear leastsquare fitting analysis, the raw data acquired by FastFLIM can be directly processed by the model-free phasor plots approach for instant and unbiased lifetime results, providing the ideal routine for the PL lifetime microscopy imaging.
Eulerian Time-Domain Filtering for Spatial LES
Pruett, C. David
1997-01-01
Eulerian time-domain filtering seems to be appropriate for LES (large eddy simulation) of flows whose large coherent structures convect approximately at a common characteristic velocity; e.g., mixing layers, jets, and wakes. For these flows, we develop an approach to LES based on an explicit second-order digital Butterworth filter, which is applied in,the time domain in an Eulerian context. The approach is validated through a priori and a posteriori analyses of the simulated flow of a heated, subsonic, axisymmetric jet.
Modern EMC analysis I time-domain computational schemes
Kantartzis, Nikolaos V
2008-01-01
The objective of this two-volume book is the systematic and comprehensive description of the most competitive time-domain computational methods for the efficient modeling and accurate solution of contemporary real-world EMC problems. Intended to be self-contained, it performs a detailed presentation of all well-known algorithms, elucidating on their merits or weaknesses, and accompanies the theoretical content with a variety of applications. Outlining the present volume, the analysis covers the theory of the finite-difference time-domain, the transmission-line matrix/modeling, and the finite i
Using random response input in Ibrahim Time Domain
DEFF Research Database (Denmark)
Olsen, Peter; Brincker, R.
2013-01-01
In this paper the time domain technique Ibrahim Time Domain (ITD) is used to analyze random time data. ITD is known to be a technique for identification of output only systems. The traditional formulation of ITD is claimed to be limited, when identifying closely spaced modes, because....... In this article it is showed that when using the modified ITD random time data can be analyzed. The application of the technique is displayed by a case study, with simulations and experimental data....... of the technique being Single Input Multiple Output (SIMO). It has earlier been showed that when modifying ITD with Toeplitz matrix averaging. Identification of time data with closely spaced modes is improved. In the traditional formulation of ITD the time data has to be free decays or impulse response functions...
Explicit solution of Calderon preconditioned time domain integral equations
Ulku, Huseyin Arda
2013-07-01
An explicit marching on-in-time (MOT) scheme for solving Calderon-preconditioned time domain integral equations is proposed. The scheme uses Rao-Wilton-Glisson and Buffa-Christiansen functions to discretize the domain and range of the integral operators and a PE(CE)m type linear multistep to march on in time. Unlike its implicit counterpart, the proposed explicit solver requires the solution of an MOT system with a Gram matrix that is sparse and well-conditioned independent of the time step size. Numerical results demonstrate that the explicit solver maintains its accuracy and stability even when the time step size is chosen as large as that typically used by an implicit solver. © 2013 IEEE.
FLIM-FRET image analysis of tryptophan in prostate cancer cells
Periasamy, Ammasi; Alam, Shagufta R.; Svindrych, Zdenek; Wallrabe, Horst
2017-07-01
A region of interest (ROI) based quantitative FLIM-FRET image analysis is developed to quantitate the autofluorescence signals of the essential amino acid tryptophan as a biomarker to investigate the metabolism in prostate cancer cells.
Single pulse two photon fluorescence lifetime imaging (SP-FLIM) with MHz pixel rate.
Eibl, Matthias; Karpf, Sebastian; Weng, Daniel; Hakert, Hubertus; Pfeiffer, Tom; Kolb, Jan Philip; Huber, Robert
2017-07-01
Two-photon-excited fluorescence lifetime imaging microscopy (FLIM) is a chemically specific 3-D sensing modality providing valuable information about the microstructure, composition and function of a sample. However, a more widespread application of this technique is hindered by the need for a sophisticated ultra-short pulse laser source and by speed limitations of current FLIM detection systems. To overcome these limitations, we combined a robust sub-nanosecond fiber laser as the excitation source with high analog bandwidth detection. Due to the long pulse length in our configuration, more fluorescence photons are generated per pulse, which allows us to derive the lifetime with a single excitation pulse only. In this paper, we show high quality FLIM images acquired at a pixel rate of 1 MHz. This approach is a promising candidate for an easy-to-use and benchtop FLIM system to make this technique available to a wider research community.
A pseudospectral collocation time-domain method for diffractive optics
DEFF Research Database (Denmark)
Dinesen, P.G.; Hesthaven, J.S.; Lynov, Jens-Peter
2000-01-01
We present a pseudospectral method for the analysis of diffractive optical elements. The method computes a direct time-domain solution of Maxwell's equations and is applied to solving wave propagation in 2D diffractive optical elements. (C) 2000 IMACS. Published by Elsevier Science B.V. All rights...
Finite difference time domain modelling of particle accelerators
International Nuclear Information System (INIS)
Jurgens, T.G.; Harfoush, F.A.
1989-03-01
Finite Difference Time Domain (FDTD) modelling has been successfully applied to a wide variety of electromagnetic scattering and interaction problems for many years. Here the method is extended to incorporate the modelling of wake fields in particle accelerators. Algorithmic comparisons are made to existing wake field codes, such as MAFIA T3. 9 refs., 7 figs
DRK methods for time-domain oscillator simulation
Sevat, M.F.; Houben, S.H.M.J.; Maten, ter E.J.W.; Di Bucchianico, A.; Mattheij, R.M.M.; Peletier, M.A.
2006-01-01
This paper presents a new Runge-Kutta type integration method that is well-suited for time-domain simulation of oscillators. A unique property of the new method is that its damping characteristics can be controlled by a continuous parameter.
Structural Time Domain Identification (STDI) Toolbox for Use with MATLAB
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
1997-01-01
The Structural Time Domain Identification (STDI) toolbox for use with MATLABTM is developed at Aalborg University, Denmark, based on the system identification research performed during recent years. By now, a reliable set of functions offers a wide spectrum of services for all the important steps...
Structural Time Domain Identification (STDI) Toolbox for Use with MATLAB
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
The Structural Time Domain Identification (STDI) toolbox for use with MATLABTM is developed at Aalborg University, Denmark, based on the system identification research performed during recent years. By now, a reliable set of functions offers a wide spectrum of services for all the important steps...
Assessment of perceptual diffuseness in the time domain
DEFF Research Database (Denmark)
Garcia, Julian Martinez-Villalba; Jeong, Cheol-Ho; Brunskog, Jonas
2017-01-01
This study proposes a numerical and experimental framework for evaluating the perceptual aspect of the diffuse field condition with intended final use in music auditoria. Multiple Impulse Responses are simulated based on the time domain Poisson process with increasing reflection density. Different...
Differences between time domain and Fourier domain optical coherence tomography in imaging tissues.
Gao, W; Wu, X
2017-11-01
It has been numerously demonstrated that both time domain and Fourier domain optical coherence tomography (OCT) can generate high-resolution depth-resolved images of living tissues and cells. In this work, we compare the common points and differences between two methods when the continuous and random properties of live tissue are taken into account. It is found that when relationships that exist between the scattered light and tissue structures are taken into account, spectral interference measurements in Fourier domain OCT (FDOCT) is more advantageous than interference fringe envelope measurements in time domain OCT (TDOCT) in the cases where continuous property of tissue is taken into account. It is also demonstrated that when random property of tissue is taken into account FDOCT measures the Fourier transform of the spatial correlation function of the refractive index and speckle phenomena will limit the effective limiting imaging resolution in both TDOCT and FDOCT. Finally, the effective limiting resolution of both TDOCT and FDOCT are given which can be used to estimate the effective limiting resolution in various practical applications. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.
Time Domain Partitioning of Electricity Production Cost Simulations
Energy Technology Data Exchange (ETDEWEB)
Barrows, C. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hummon, M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Jones, W. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hale, E. [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2014-01-01
Production cost models are often used for planning by simulating power system operations over long time horizons. The simulation of a day-ahead energy market can take several weeks to compute. Tractability improvements are often made through model simplifications, such as: reductions in transmission modeling detail, relaxation of commitment variable integrality, reductions in cost modeling detail, etc. One common simplification is to partition the simulation horizon so that weekly or monthly horizons can be simulated in parallel. However, horizon partitions are often executed with overlap periods of arbitrary and sometimes zero length. We calculate the time domain persistence of historical unit commitment decisions to inform time domain partitioning of production cost models. The results are implemented using PLEXOS production cost modeling software in an HPC environment to improve the computation time of simulations while maintaining solution integrity.
Alibhai, Dominic; Kumar, Sunil; Kelly, Douglas; Warren, Sean; Alexandrov, Yuriy; Munro, Ian; McGinty, James; Talbot, Clifford; Murray, Edward J.; Stuhmeier, Frank; Neil, Mark A. A.; Dunsby, Chris; French, Paul M. W.
2011-03-01
We describe an optically-sectioned FLIM multiwell plate reader that combines Nipkow microscopy with wide-field time-gated FLIM, and its application to high content analysis of FRET. The system acquires sectioned FLIM images in fluorescent protein. It has been applied to study the formation of immature HIV virus like particles (VLPs) in live cells by monitoring Gag-Gag protein interactions using FLIM FRET of HIV-1 Gag transfected with CFP or YFP. VLP formation results in FRET between closely packed Gag proteins, as confirmed by our FLIM analysis that includes automatic image segmentation.
A phasor approach analysis of multiphoton FLIM measurements of three-dimensional cell culture models
Lakner, P. H.; Möller, Y.; Olayioye, M. A.; Brucker, S. Y.; Schenke-Layland, K.; Monaghan, M. G.
2016-03-01
Fluorescence lifetime imaging microscopy (FLIM) is a useful approach to obtain information regarding the endogenous fluorophores present in biological samples. The concise evaluation of FLIM data requires the use of robust mathematical algorithms. In this study, we developed a user-friendly phasor approach for analyzing FLIM data and applied this method on three-dimensional (3D) Caco-2 models of polarized epithelial luminal cysts in a supporting extracellular matrix environment. These Caco-2 based models were treated with epidermal growth factor (EGF), to stimulate proliferation in order to determine if FLIM could detect such a change in cell behavior. Autofluorescence from nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) in luminal Caco-2 cysts was stimulated by 2-photon laser excitation. Using a phasor approach, the lifetimes of involved fluorophores and their contribution were calculated with fewer initial assumptions when compared to multiexponential decay fitting. The phasor approach simplified FLIM data analysis, making it an interesting tool for non-experts in numerical data analysis. We observed that an increased proliferation stimulated by EGF led to a significant shift in fluorescence lifetime and a significant alteration of the phasor data shape. Our data demonstrates that multiphoton FLIM analysis with the phasor approach is a suitable method for the non-invasive analysis of 3D in vitro cell culture models qualifying this method for monitoring basic cellular features and the effect of external factors.
Parallel time domain solvers for electrically large transient scattering problems
Liu, Yang
2014-09-26
Marching on in time (MOT)-based integral equation solvers represent an increasingly appealing avenue for analyzing transient electromagnetic interactions with large and complex structures. MOT integral equation solvers for analyzing electromagnetic scattering from perfect electrically conducting objects are obtained by enforcing electric field boundary conditions and implicitly time advance electric surface current densities by iteratively solving sparse systems of equations at all time steps. Contrary to finite difference and element competitors, these solvers apply to nonlinear and multi-scale structures comprising geometrically intricate and deep sub-wavelength features residing atop electrically large platforms. Moreover, they are high-order accurate, stable in the low- and high-frequency limits, and applicable to conducting and penetrable structures represented by highly irregular meshes. This presentation reviews some recent advances in the parallel implementations of time domain integral equation solvers, specifically those that leverage multilevel plane-wave time-domain algorithm (PWTD) on modern manycore computer architectures including graphics processing units (GPUs) and distributed memory supercomputers. The GPU-based implementation achieves at least one order of magnitude speedups compared to serial implementations while the distributed parallel implementation are highly scalable to thousands of compute-nodes. A distributed parallel PWTD kernel has been adopted to solve time domain surface/volume integral equations (TDSIE/TDVIE) for analyzing transient scattering from large and complex-shaped perfectly electrically conducting (PEC)/dielectric objects involving ten million/tens of millions of spatial unknowns.
THz time domain spectroscopy of biomolecular conformational modes
International Nuclear Information System (INIS)
Markelz, Andrea; Whitmire, Scott; Hillebrecht, Jay; Birge, Robert
2002-01-01
We discuss the use of terahertz time domain spectroscopy for studies of conformational flexibility and conformational change in biomolecules. Protein structural dynamics are vital to biological function with protein flexibility affecting enzymatic reaction rates and sensory transduction cycling times. Conformational mode dynamics occur on the picosecond timescale and with the collective vibrational modes associated with these large scale structural motions in the 1-100 cm -1 range. We have performed THz time domain spectroscopy (TTDS) of several biomolecular systems to explore the sensitivity of TTDS to distinguish different molecular species, different mutations within a single species and different conformations of a given biomolecule. We compare the measured absorbances to normal mode calculations and find that the TTDS absorbance reflects the density of normal modes determined by molecular mechanics calculations, and is sensitive to both conformation and mutation. These early studies demonstrate some of the advantages and limitations of using TTDS for the study of biomolecules
Time domain spectroscopy to monitor the condition of cable insulation
International Nuclear Information System (INIS)
Mopsik, F.I.; Martzloff, F.D.
1989-01-01
The use of Time Domain Spectroscopy, the measurement of dielectric constant and loss using time-domain response, the monitoring the aging of reactor cable insulation is examined. The method is presented, showing its sensitivity, accuracy and wide frequency range. The method's ability to acquire a great deal of information in a short time and its superiority to conventional single frequency data is shown. Different cable samples are examined before and after exposure to radiation and changes with exposure are clearly seen to occur. Also it is shown that a wide range of behavior can be found in different insulation systems. The requirements for performing valid measurements is presented. The need for controlled samples and correlation with other criteria for aging is discussed. 14 refs., 9 figs
Evaluation of skin moisturizer effects using terahertz time domain imaging
Martinez-Meza, L. H.; Rojas-Landeros, S. C.; Castro-Camus, E.; Alfaro-Gomez, M.
2018-02-01
We use terahertz time domain imaging for the evaluation of the effects of skin-moisturizers in vivo. We evaluate three principal substances used in commercial moisturizers: glycerin, hyaluronic acid and lanolin. We image the interaction of the forearm with each of the substances taking terahertz spectra at sequential times. With this, we are able to measure the effect of the substances on the hydration level of the skin in time, determining the feasibility of using THz imaging for the evaluation of the products and their effects on the hydration levels of the skin.
Molecular Frame Reconstruction Using Time-Domain Photoionization Interferometry.
Marceau, Claude; Makhija, Varun; Platzer, Dominique; Naumov, A Yu; Corkum, P B; Stolow, Albert; Villeneuve, D M; Hockett, Paul
2017-08-25
Photoionization of molecular species is, essentially, a multipath interferometer with both experimentally controllable and intrinsic molecular characteristics. In this work, XUV photoionization of impulsively aligned molecular targets (N_{2}) is used to provide a time-domain route to "complete" photoionization experiments, in which the rotational wave packet controls the geometric part of the photoionization interferometer. The data obtained is sufficient to determine the magnitudes and phases of the ionization matrix elements for all observed channels, and to reconstruct molecular frame interferograms from lab frame measurements. In principle, this methodology provides a time-domain route to complete photoionization experiments and the molecular frame, which is generally applicable to any molecule (no prerequisites), for all energies and ionization channels.
Drug detection by terahertz time-domain spectroscopy
International Nuclear Information System (INIS)
Duan Ruixin; Zhu Yiming; Zhao Hongwei
2013-01-01
Due to unique spectral region, functional imaging ability, excellent penetration and safety characteristics of terahertz radiation, the terahertz technology rapidly becomes a vital method to detect and analyze drugs. In this paper, firstly, we identify the functional groups of anti-diabetic drugs by density functional theory (DFT), HIPHOP models and experimental results from terahertz time-domain spectroscopy measurements. Secondly, we identify four kinds of herbs of radix curcumae by using the support vector machine (SVM) analysis. Besides, we analyze the absorption of anhydrous and hydrous glucose, and determine the state of water in the crystalized D-glucose·H 2 O through the results of differential scanning calorimetry measurement. Finally, we summarize the advantages and disadvantages of terahertz time-domain spectroscopy method in drug detection and analyzing. (authors)
Advances in spectral inversion of time-domain induced polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts in charg......The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts...... in chargeability parameters, towards a quantitative analysis of the investigated media, which allows for detailed soil- and rock-type characterization. In this work a review of the recent advances in spectral inversion of TDIP data is presented, in terms of: supported IP parameterizations; modelling of transmitter...
The Simulation Realization of Pavement Roughness in the Time Domain
XU, H. L.; He, L.; An, D.
2017-10-01
As the needs for the dynamic study on the vehicle-pavement system and the simulated vibration table test, how to simulate the pavement roughness actually is important guarantee for whether calculation and test can reflect the actual situation or not. Using the power spectral density function, the simulation of pavement roughness can be realized by Fourier inverse transform. The main idea of this method was that the spectrum amplitude and random phase were obtained separately according to the power spectrum, and then the simulation of pavement roughness was obtained in the time domain through the Fourier inverse transform (IFFT). In the process, the sampling interval (Δl) was 0.1m, and the sampling points(N) was 4096, which satisfied the accuracy requirements. Using this method, the simulate results of pavement roughness (A~H grades) were obtain in the time domain.
A convenient accuracy criterion for time domain FE-calculations
DEFF Research Database (Denmark)
Jensen, Morten Skaarup
1997-01-01
An accuracy criterion that is well suited to tome domain finite element (FE) calculations is presented. It is then used to develop a method for selecting time steps and element meshes that produce accurate results without significantly overburderning the computer. Use of this method is illustrated...... with a simple example, where comparison with an analytical solution shows that results are sufficiently accurate, which is not always the case with more primitive mthods for determining the discretisation....
Ultrabroadband THz time-domain spectroscopy of biomolecular crystals
DEFF Research Database (Denmark)
Kaltenecker, Korbinian J.; Engelbrecht, Sebastian; Iwaszczuk, Krzysztof
2016-01-01
Ultrabroadband THz time-domain spectroscopy based on two-color plasma generation and air biased coherent detection is used for the investigation of molecular dynamics of crystalline materials in the frequency range from 0.3 THz to 20 THz. We show that the spectral features in this extended...... frequency range are a result of inter- and intramolecular vibrations which are identified by means of simulations of the crystalline materials....
New Flutter Analysis Technique for Time-Domain Computational Aeroelasticity
Pak, Chan-Gi; Lung, Shun-Fat
2017-01-01
A new time-domain approach for computing flutter speed is presented. Based on the time-history result of aeroelastic simulation, the unknown unsteady aerodynamics model is estimated using a system identification technique. The full aeroelastic model is generated via coupling the estimated unsteady aerodynamic model with the known linear structure model. The critical dynamic pressure is computed and used in the subsequent simulation until the convergence of the critical dynamic pressure is achieved. The proposed method is applied to a benchmark cantilevered rectangular wing.
CORRTEX: a compact and versatile system for time domain reflectometry
International Nuclear Information System (INIS)
Deupree, R.G.; Eilers, D.D.; McKown, T.O.; Storey, W.H.
1981-01-01
The CORRTEX (COntinuous Reflectometry for Radius versus Time EXperiments) system was designed to be an adaptable and versatile unit for performing time domain reflectometry (TDR). The system consists of a coaxial cable, a digital TDR, which uses a Motorola 6800 microprocessor, a power source or battery pack, and an output terminal or recording driver. Desirable criteria for the system are discussed as well as the operation of the CORRTEX system. The types of present applications of the CORRTEX system are summarized and data presented
Physical optics far field inverse scattering in the time domain
International Nuclear Information System (INIS)
Bleistein, N.
1976-01-01
The physical optics far field inverse scattering (POFFIS) identity relates the phase and range normalized far field back scattering amplitude to the spatial Fourier transform of the characteristic function of the scattering obstacle. The characteristic function is equal to unity in the region occupied by the obstacle and zero elsewhere. The original identity was derived by Bojarski for impulsive point sources. The result is extended to sources of arbitrary time dependence. One obtains an alternative form of Bojarski's POFFIS identity. One also derives a POFFIS identity in the time domain. Numerically synthesized checks on the method are provided
A Time Domain Waveform for Testing General Relativity
International Nuclear Information System (INIS)
Huwyler, Cédric; Jetzer, Philippe; Porter, Edward K
2015-01-01
Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signals coming from supermassive black hole inspirals using these corrected waveforms. (paper)
Refractive index sensing using Fluorescence Lifetime Imaging (FLIM)
International Nuclear Information System (INIS)
Jones, Carolyn; Suhling, Klaus
2006-01-01
The fluorescence lifetime is a function of the refractive index of the fluorophore's environment, for example in the case of the biologically important green fluorescent protein (GFP). In order to address the question whether this effect can be exploited to image the local environment of specific proteins in cell biology, we need to determine the distance over which the fluorophore's lifetime is sensitive to the refractive index. To this end, we employ Fluorescence Lifetime Imaging (FLIM) of fluorescein in NaOH buffer at an interface. This approach allows us to map the fluorescence lifetime as a function of distance from a buffer/air and buffer/oil interface. Preliminary data show that the fluorescence lifetime of fluorescein increases near a buffer/air interface and decreases near a buffer/oil interface. The range over which this fluorescence lifetime change occurs is found to be of the order several μm which is consistent with a theoretical model based on the full width at half maximum of the emission spectrum proposed by Toptygin
A Full Parallel Event Driven Readout Technique for Area Array SPAD FLIM Image Sensors
Directory of Open Access Journals (Sweden)
Kaiming Nie
2016-01-01
Full Text Available This paper presents a full parallel event driven readout method which is implemented in an area array single-photon avalanche diode (SPAD image sensor for high-speed fluorescence lifetime imaging microscopy (FLIM. The sensor only records and reads out effective time and position information by adopting full parallel event driven readout method, aiming at reducing the amount of data. The image sensor includes four 8 × 8 pixel arrays. In each array, four time-to-digital converters (TDCs are used to quantize the time of photons’ arrival, and two address record modules are used to record the column and row information. In this work, Monte Carlo simulations were performed in Matlab in terms of the pile-up effect induced by the readout method. The sensor’s resolution is 16 × 16. The time resolution of TDCs is 97.6 ps and the quantization range is 100 ns. The readout frame rate is 10 Mfps, and the maximum imaging frame rate is 100 fps. The chip’s output bandwidth is 720 MHz with an average power of 15 mW. The lifetime resolvability range is 5–20 ns, and the average error of estimated fluorescence lifetimes is below 1% by employing CMM to estimate lifetimes.
Time domain passivity controller for 4-channel time-delay bilateral teleoperation.
Rebelo, Joao; Schiele, Andre
2015-01-01
This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.
Terahertz time-domain spectroscopy and imaging of artificial RNA
DEFF Research Database (Denmark)
Fischer, Bernd M.; Hoffmann, Matthias; Helm, Hanspeter
2005-01-01
We use terahertz time-domain spectroscopy (THz-TDS) to measure the far-infrared dielectric function of two artificial RNA single strands, composed of polyadenylic acid (poly-A) and polycytidylic acid (poly-C). We find a significant difference in the absorption between the two types of RNA strands......, and we show that we can use this difference to record images of spot arrays of the RNA strands. Under controlled conditions it is possible to use the THz image to distinguish between the two RNA strands. We discuss the requirements to sample preparation imposed by the lack of sharp spectral features...
Terahertz time-domain transmission and reflection spectroscopy of niobium
International Nuclear Information System (INIS)
Hong, Tae Yoon; Choi, Kyu Jin; Park, Byoung Cheol; Ha, Tae Woo; Sim, Kyung Ik; Kim, Jea Hoon; Ha, Dong Gwang; Chang, Yonuk
2013-01-01
We have developed a terahertz time-domain spectroscopy (THz-TDS) system for transmission and reflection measurements of metallic thin films. Using our THz-TDS system, we studied the conventional superconductor niobium (Nb) in the normal state in the spectral range from 5 to 50 cm -1 . Both the real and imaginary parts of the conductivity are acquired without Kramers-Kronig analysis. Nb exhibits a nearly frequency independent real conductivity spectrum in the terahertz range, with a very small imaginary part.
Solution of the Burgers Equation in the Time Domain
Directory of Open Access Journals (Sweden)
M. Bednařík
2002-01-01
Full Text Available This paper deals with a theoretical description of the propagation of a finite amplitude acoustic waves. The theory based on the homogeneous Burgers equation of the second order of accuracy is presented here. This equation takes into account both nonlinear effects and dissipation. The method for solving this equation, using the well-known Cole-Hopf transformation, is presented. Two methods for numerical solution of these equations in the time domain are presented. The first is based on the simple Simpson method, which is suitable for smaller Goldberg numbers. The second uses the more advanced saddle point method, and is appropriate for large Goldberg numbers.
Finite difference time domain modeling of spiral antennas
Penney, Christopher W.; Beggs, John H.; Luebbers, Raymond J.
1992-01-01
The objectives outlined in the original proposal for this project were to create a well-documented computer analysis model based on the finite-difference, time-domain (FDTD) method that would be capable of computing antenna impedance, far-zone radiation patterns, and radar cross-section (RCS). The ability to model a variety of penetrable materials in addition to conductors is also desired. The spiral antennas under study by this project meet these requirements since they are constructed of slots cut into conducting surfaces which are backed by dielectric materials.
Perfectly matched layer for the time domain finite element method
International Nuclear Information System (INIS)
Rylander, Thomas; Jin Jianming
2004-01-01
A new perfectly matched layer (PML) formulation for the time domain finite element method is described and tested for Maxwell's equations. In particular, we focus on the time integration scheme which is based on Galerkin's method with a temporally piecewise linear expansion of the electric field. The time stepping scheme is constructed by forming a linear combination of exact and trapezoidal integration applied to the temporal weak form, which reduces to the well-known Newmark scheme in the case without PML. Extensive numerical tests on scattering from infinitely long metal cylinders in two dimensions show good accuracy and no signs of instabilities. For a circular cylinder, the proposed scheme indicates the expected second order convergence toward the analytic solution and gives less than 2% root-mean-square error in the bistatic radar cross section (RCS) for resolutions with more than 10 points per wavelength. An ogival cylinder, which has sharp corners supporting field singularities, shows similar accuracy in the monostatic RCS
Time domain optical memories using rare earth ions
International Nuclear Information System (INIS)
Sellars, M.J.; Dyke, T.; Pryde, G.J.; Manson, N.B.
1998-01-01
Full text: Rare earth doped crystals are the chosen materials for the next generation of optical memories where the process of spectral holeburning can be employed to provide an extra dimension of frequency or time to spatial dimensions and with certain rare earth ions increases of the order of 10 7 in storage capacity can be achieved over conventional optical memories. Time domain techniques are preferred over frequency domain techniques and are now well developed. In these techniques arbitrary pulse sequences are stored in the material and read out at some later time with a single read pulse using a stimulated photon echo process. Long pulse sequences will enable more data to be stored but necessitates the use of materials with long dephasing times (corresponding to narrow spectral lines) and it is this characteristic of rare earth systems that makes them the preferred material for the new time domain optical memories. The storage time can range from hours to days but in a practical device will require refreshing or re-enforcing and this puts special requirements on the stability of the laser used for storing the information. The storage process itself can also be weak and more reliable storage can be achieved by recording the data several times with the same pulse sequence. For this to be successful the laser must be at held at a constant frequency and be stable in phase over the entire duration of the pulse sequence. The procedure of reinforcing the data sequence has been proposed before and attempted without attention to the laser frequency stability. However, if the laser is not stable although some data bits will be reinforced or increased in size others will be decreased or even erased. Indeed the reliability of the memory is degraded by the introducing the rewrite process. For our work we have developed a laser with the excellent stability and able to demonstrate reproducible reinforcement of the data sequence. Thus with the rewrite sequence we are able to
Real-time histology in liver disease using multiphoton microscopy with fluorescence lifetime imaging
Wang, Haolu; Liang, Xiaowen; Mohammed, Yousuf H.; Thomas, James A.; Bridle, Kim R.; Thorling, Camilla A.; Grice, Jeffrey E.; Xu, Zhi Ping; Liu, Xin; Crawford, Darrell H. G.; Roberts, Michael S.
2015-01-01
Conventional histology with light microscopy is essential in the diagnosis of most liver diseases. Recently, a concept of real-time histology with optical biopsy has been advocated. In this study, live mice livers (normal, with fibrosis, steatosis, hepatocellular carcinoma and ischemia-reperfusion injury) were imaged by MPM-FLIM for stain-free real-time histology. The acquired MPM-FLIM images were compared with conventional histological images. MPM-FLIM imaged subsurface cellular and subcellu...
Finite-difference time-domain analysis of time-resolved terahertz spectroscopy experiments
DEFF Research Database (Denmark)
Larsen, Casper; Cooke, David G.; Jepsen, Peter Uhd
2011-01-01
In this paper we report on the numerical analysis of a time-resolved terahertz (THz) spectroscopy experiment using a modified finite-difference time-domain method. Using this method, we show that ultrafast carrier dynamics can be extracted with a time resolution smaller than the duration of the T...
Near-infrared laser, time domain, breast tumour detection system
International Nuclear Information System (INIS)
Joblin, A.J.
1996-01-01
Full text: The use of near-infrared laser, time domain techniques have been proposed for some time now as an alternative to X-ray mammography, as a means of mass screening for breast disease. The great driving force behind this research has been that near-infrared photons are a non-ionising radiation, which affords a greater degree of patient safety than when using X-rays. This would mean that women at risk of breast disease could be screened with a near-infrared laser imaging system, much more regularly than with an X-ray mammography system, which should allow for the earlier detection and treatment of breast disease. This paper presents a theoretical investigation of the performance of a near-infrared, time domain breast imaging system. The performance of the imaging system is characterised by the resolution and contrast parameters, which were studied using a numerical finite difference calculation method. The finite difference method is used to solve the diffusion equation for the photon transport through the inhomogeneous breast tissue medium. Optimal performance was found to be obtained with short photon times of flight. However the signal to noise ratio decreases rapidly as the photon time of flight is decreased. The system performance will therefore be limited by the noise equivalent power of the time resolved detection system, which is the signal incident on the time resolved detection system which gives a signal to noise ratio of 1:1. Photon times of flight shorter than 500 ps are not practical with current technology, which places limits on the resolution and contrast. The photon signal throughput can be increased by increasing the size of the laser beam width, by increasing the size of the aperture stop of the detector, by increasing the laser pulse duration or decreasing the detector time resolution. Best system performance is found by optimising these parameters for a given time gating and detector system characteristic (NEP). It was found that the
Time domain series system definition and gear set reliability modeling
International Nuclear Information System (INIS)
Xie, Liyang; Wu, Ningxiang; Qian, Wenxue
2016-01-01
Time-dependent multi-configuration is a typical feature for mechanical systems such as gear trains and chain drives. As a series system, a gear train is distinct from a traditional series system, such as a chain, in load transmission path, system-component relationship, system functioning manner, as well as time-dependent system configuration. Firstly, the present paper defines time-domain series system to which the traditional series system reliability model is not adequate. Then, system specific reliability modeling technique is proposed for gear sets, including component (tooth) and subsystem (tooth-pair) load history description, material priori/posterior strength expression, time-dependent and system specific load-strength interference analysis, as well as statistically dependent failure events treatment. Consequently, several system reliability models are developed for gear sets with different tooth numbers in the scenario of tooth root material ultimate tensile strength failure. The application of the models is discussed in the last part, and the differences between the system specific reliability model and the traditional series system reliability model are illustrated by virtue of several numerical examples. - Highlights: • A new type of series system, i.e. time-domain multi-configuration series system is defined, that is of great significance to reliability modeling. • Multi-level statistical analysis based reliability modeling method is presented for gear transmission system. • Several system specific reliability models are established for gear set reliability estimation. • The differences between the traditional series system reliability model and the new model are illustrated.
Time-Domain Diversity in Ultra-Wideband MIMO Communications
Directory of Open Access Journals (Sweden)
Alain Sibille
2005-03-01
Full Text Available The development of ultra-wideband (UWB communications is impeded by the drastic transmitted power limitations imposed by regulation authorities due to the Ã¢Â€ÂœpollutingÃ¢Â€Â character of these radio emissions with respect to existing services. Technical solutions must be researched in order either to limit the level of spectral pollution by UWB devices or to increase their reception sensitivity. In the present work, we consider pulse-based modulations and investigate time-domain multiple-input multiple-output (MIMO diversity as one such possible solution. The basic principles of time-domain diversity in the extreme (low multipath density or intermediate (dense multipath UWB regimes are addressed, which predict the possibility of a MIMO gain equal to the product NtÃƒÂ—Nr of the numbers of transmit/receive antenna elements when the channel is not too severe. This analysis is confirmed by simulations using a parametric empirical stochastic double-directional channel model. They confirm the potential interest of MIMO approaches solutions in order to bring a valuable performance gain in UWB communications.
Time domain NMR evaluation of poly(vinyl alcohol) xerogels
Energy Technology Data Exchange (ETDEWEB)
Rodrigues, Elton Jorge da Rocha; Cavalcante, Maxwell de Paula; Tavares, Maria Ines Bruno, E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia. Instituto de Macromoleculas Professora Eloisa Mano
2016-05-15
Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO{sub 2}), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO{sub 2} does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO{sub 2}. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials. (author)
Synchronous machine parameter identification in frequency and time domain
Directory of Open Access Journals (Sweden)
Hasni M.
2007-01-01
Full Text Available This paper presents the results of a frequency and time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. The objective of this study is to use several input signals to identify the model structure and parameters of a salient-pole synchronous machine from standstill test data. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We estimate the parameters of operational impedances, or in other words the reactance and the time constants. The tests were carried out on synchronous machine of 1.5 kVA 380V 1500 rpm.
Numerical integration of the Teukolsky equation in the time domain
International Nuclear Information System (INIS)
Pazos-Avalos, Enrique; Lousto, Carlos O.
2005-01-01
We present a fourth-order convergent (2+1)-dimensional, numerical formalism to solve the Teukolsky equation in the time domain. Our approach is first to rewrite the Teukolsky equation as a system of first-order differential equations. In this way we get a system that has the form of an advection equation. This is then used in combination with a series expansion of the solution in powers of time. To obtain a fourth-order scheme we kept terms up to fourth derivative in time and use the advectionlike system of differential equations to substitute the temporal derivatives by spatial derivatives. This scheme is applied to evolve gravitational perturbations in the Schwarzschild and Kerr backgrounds. Our numerical method proved to be stable and fourth-order convergent in r* and θ directions. The correct power-law tail, ∼1/t 2l+3 , for general initial data, and ∼1/t 2l+4 , for time-symmetric data, was found in our runs. We noted that it is crucial to resolve accurately the angular dependence of the mode at late times in order to obtain these values of the exponents in the power-law decay. In other cases, when the decay was too fast and round-off error was reached before a tail was developed, then the quasinormal modes frequencies provided a test to determine the validity of our code
Heliborne time-domain electromagnetic (TEM) surveys for uranium exploration
International Nuclear Information System (INIS)
Chaturvedi, A.K.
2015-01-01
Airborne geophysical surveys have been used extensively in petroleum, mineral exploration, and environmental mapping. Of all the geophysical methods, Electromagnetic (EM) methods, both ground and airborne are used to map the conductive ore bodies buried in the resistive bed rock. Mapping resistivity variations can help unravel complex geological problems and identify areas of hidden potential. Besides the traditional applications to ground water investigations and other natural resource exploration and geological mapping, a number of new applications have been reported. These include hazardous-waste characterization studies, precision agriculture applications, archaeological surveys etc. Airborne Electromagnetic (AEM) methods have undergone rapid improvements over the past few decades. Several new airborne Time Do-main EM (TDEM) systems appeared; existing systems were updated and/or enhanced. The use of natural field (passive) EM surveys continued to increase, with new or improved systems becoming available for both airborne and ground surveys. The number of large airborne survey systems with combined EM, magnetic, gravimetric and gamma-ray spectrometric capabilities also increased. Exploration of a mineral deposit is a multi-stage and multi-disciplinary approach that commences from regional investigations and concludes with establishing of a deposit. As economics play a major role in exploration, a proper integrated study is always beneficial in narrowing down the potential mineral target zones. Heliborne geophysical surveys are being conducted world-wide for exploration of base metals, gold, phosphorite, oil, uranium etc. that are very effective tool in identifying zones of interest accurately, economically and with less span of time. These surveys give a very good insight of surface and sub-surface geophysical signatures that can be attributed to geology with proper modeling. Heliborne Time - domain Electromagnetic (TEM) methods are well known for search of
Regulatory assembly of the vacuolar proton pump VoV1-ATPase in yeast cells by FLIM-FRET
Ernst, Stefan; Batisse, Claire; Zarrabi, Nawid; Böttcher, Bettina; Börsch, Michael
2010-02-01
We investigate the reversible disassembly of VOV1-ATPase in life yeast cells by time resolved confocal FRET imaging. VOV1-ATPase in the vacuolar membrane pumps protons from the cytosol into the vacuole. VOV1-ATPase is a rotary biological nanomotor driven by ATP hydrolysis. The emerging proton gradient is used for secondary transport processes as well as for pH and Ca2+ homoeostasis in the cell. The activity of the VOV1-ATPase is regulated through assembly / disassembly processes. During starvation the two parts of VOV1-ATPase start to disassemble. This process is reversed after addition of glucose. The exact mechanisms are unknown. To follow the disassembly / reassembly in vivo we tagged two subunits C and E with different fluorescent proteins. Cellular distributions of C and E were monitored using a duty cycle-optimized alternating laser excitation scheme (DCO-ALEX) for time resolved confocal FRET-FLIM measurements.
Computational electrodynamics the finite-difference time-domain method
Taflove, Allen
2005-01-01
This extensively revised and expanded third edition of the Artech House bestseller, Computational Electrodynamics: The Finite-Difference Time-Domain Method, offers engineers the most up-to-date and definitive resource on this critical method for solving Maxwell's equations. The method helps practitioners design antennas, wireless communications devices, high-speed digital and microwave circuits, and integrated optical devices with unsurpassed efficiency. There has been considerable advancement in FDTD computational technology over the past few years, and the third edition brings professionals the very latest details with entirely new chapters on important techniques, major updates on key topics, and new discussions on emerging areas such as nanophotonics. What's more, to supplement the third edition, the authors have created a Web site with solutions to problems, downloadable graphics and videos, and updates, making this new edition the ideal textbook on the subject as well.
Iterative Refinement Methods for Time-Domain Equalizer Design
Directory of Open Access Journals (Sweden)
Evans Brian L
2006-01-01
Full Text Available Commonly used time domain equalizer (TEQ design methods have been recently unified as an optimization problem involving an objective function in the form of a Rayleigh quotient. The direct generalized eigenvalue solution relies on matrix decompositions. To reduce implementation complexity, we propose an iterative refinement approach in which the TEQ length starts at two taps and increases by one tap at each iteration. Each iteration involves matrix-vector multiplications and vector additions with matrices and two-element vectors. At each iteration, the optimization of the objective function either improves or the approach terminates. The iterative refinement approach provides a range of communication performance versus implementation complexity tradeoffs for any TEQ method that fits the Rayleigh quotient framework. We apply the proposed approach to three such TEQ design methods: maximum shortening signal-to-noise ratio, minimum intersymbol interference, and minimum delay spread.
In vitro osteosarcoma biosensing using THz time domain spectroscopy
Ferguson, Bradley S.; Liu, Haibo; Hay, Shelley; Findlay, David; Zhang, Xi-Cheng; Abbott, Derek
2004-03-01
Terahertz time domain spectroscopy (THz-TDS) has a wide range of applications from semiconductor diagnostics to biosensing. Recent attention has focused on bio-applications and several groups have noted the ability of THz-TDS to differentiate basal cell carcinoma tissue from healthy dermal tissue ex vivo. The contrast mechanism is unclear but has been attributed to increased interstitial water in cancerous tissue. In this work we investigate the THz response of human osteosarcoma cells and normal human bone cells grown in culture to isolate the cells' responses from other effects. A classification algorithms based on a frequency selection by genetic algorithm is used to attempt to differentiate between the cell types based on the THz spectra. Encouraging preliminary results have been obtained.
Modern linear control design a time-domain approach
Caravani, Paolo
2013-01-01
This book offers a compact introduction to modern linear control design. The simplified overview presented of linear time-domain methodology paves the road for the study of more advanced non-linear techniques. Only rudimentary knowledge of linear systems theory is assumed - no use of Laplace transforms or frequency design tools is required. Emphasis is placed on assumptions and logical implications, rather than abstract completeness; on interpretation and physical meaning, rather than theoretical formalism; on results and solutions, rather than derivation or solvability. The topics covered include transient performance and stabilization via state or output feedback; disturbance attenuation and robust control; regional eigenvalue assignment and constraints on input or output variables; asymptotic regulation and disturbance rejection. Lyapunov theory and Linear Matrix Inequalities (LMI) are discussed as key design methods. All methods are demonstrated with MATLAB to promote practical use and comprehension. ...
Differentiation of illicit drugs with THz time-domain spectroscopy
International Nuclear Information System (INIS)
Liu Guifeng; Ma Shihua; Ji Te; Zhao Hongwei; Wang Wenfeng
2010-01-01
The tera hertz time-domain spectroscopy (THz-TDS) was used for sensing and identifying illicit drugs. The absorption spectra of seven illicit drug samples(morphine and its hydrochloride, cocaine hydrochloride, codeine phosphate, papaverine hydrochloride, pethidine hydrochloride, and thebaine) were studied by THz-TDS at 0.3-2.0 THz at room temperature. The geometric structure and vibration frequencies of morphine were calculated by density functional theory. The four absorption features were dominated by intra-/inter-molecular collective or lattice vibration modes. Each illicit drug has a distinct signature in its THz spectra. The results indicate that the THz-TDS can be used to identify and discriminate illicit drugs by their characteristic fingerprints. (authors)
Terahertz time-domain spectroscopy of edible oils
Dinovitser, Alex; Valchev, Dimitar G.; Abbott, Derek
2017-06-01
Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05-2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.
SVD compression for magnetic resonance fingerprinting in the time domain.
McGivney, Debra F; Pierre, Eric; Ma, Dan; Jiang, Yun; Saybasili, Haris; Gulani, Vikas; Griswold, Mark A
2014-12-01
Magnetic resonance (MR) fingerprinting is a technique for acquiring and processing MR data that simultaneously provides quantitative maps of different tissue parameters through a pattern recognition algorithm. A predefined dictionary models the possible signal evolutions simulated using the Bloch equations with different combinations of various MR parameters and pattern recognition is completed by computing the inner product between the observed signal and each of the predicted signals within the dictionary. Though this matching algorithm has been shown to accurately predict the MR parameters of interest, one desires a more efficient method to obtain the quantitative images. We propose to compress the dictionary using the singular value decomposition, which will provide a low-rank approximation. By compressing the size of the dictionary in the time domain, we are able to speed up the pattern recognition algorithm, by a factor of between 3.4-4.8, without sacrificing the high signal-to-noise ratio of the original scheme presented previously.
Time-domain Hydroelasticity Theory of Ships Responding to Waves
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui
1997-01-01
free surface flow. The general interface boundary condition is used in the mathematical formulation of the fluid motion around the flexible structure. The general time-domain theory is simplified to a slender-body theory for the analysis of wave-induced global responses of monohull ships. The structure...... is represented by a non-uniform beam, while the generalized hydrodynamic coefficients can be obtained from two-dimensional potential flow theory. The linear slender body theory is generalized to treat the non-linear loading effects of rigid motion and structural response of ships travelling in rough seas....... The non-linear hydrostatic restoring force and hydrodynamic momentum action are considered. A numerical solution is presented for the slender body theory. Numerical examples are given for two ship cases with different geometry features, a warship hull and the S175 containership with two different bow...
Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates
DEFF Research Database (Denmark)
Takeya, Kei; Zhang, Caihong; Kawayama, Iwao
2009-01-01
For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has...... a characteristic broad absorption peak at 0.5 THz corresponding to the dipole moment of THF molecules. The refractive indices of THF and propane hydrates are 1.725 and 1.775 at 1 THz, respectively, and show a slight but clear difference from the refractive index of ice (1.79). THz-TDS is a potentially useful...... technique for the ondestructive inspection of gas hydrates. # 2009 The Japan Society of Applied Physics...
Detection of Poisonous Herbs by Terahertz Time-Domain Spectroscopy
Zhang, H.; Li, Z.; Chen, T.; Liu, J.-J.
2018-03-01
The aim of this paper is the application of terahertz (THz) spectroscopy combined with chemometrics techniques to distinguish poisonous and non-poisonous herbs which both have a similar appearance. Spectra of one poisonous and two non-poisonous herbs (Gelsemium elegans, Lonicera japonica Thunb, and Ficus Hirta Vahl) were obtained in the range 0.2-1.4 THz by using a THz time-domain spectroscopy system. Principal component analysis (PCA) was used for feature extraction. The prediction accuracy of classification is between 97.78 to 100%. The results demonstrate an efficient and applicative method to distinguish poisonous herbs, and it may be implemented by using THz spectroscopy combined with chemometric algorithms.
Acoustic, finite-difference, time-domain technique development
International Nuclear Information System (INIS)
Kunz, K.
1994-01-01
A close analog exists between the behavior of sound waves in an ideal gas and the radiated waves of electromagnetics. This analog has been exploited to obtain an acoustic, finite-difference, time-domain (AFDTD) technique capable of treating small signal vibrations in elastic media, such as air, water, and metal, with the important feature of bending motion included in the behavior of the metal. This bending motion is particularly important when the metal is formed into sheets or plates. Bending motion does not have an analog in electromagnetics, but can be readily appended to the acoustic treatment since it appears as a single additional term in the force equation for plate motion, which is otherwise analogous to the electromagnetic wave equation. The AFDTD technique has been implemented in a code architecture that duplicates the electromagnetic, finite-difference, time-domain technique code. The main difference in the implementation is the form of the first-order coupled differential equations obtained from the wave equation. The gradient of pressure and divergence of velocity appear in these equations in the place of curls of the electric and magnetic fields. Other small changes exist as well, but the codes are essentially interchangeable. The pre- and post-processing for model construction and response-data evaluation of the electromagnetic code, in the form of the TSAR code at Lawrence Livermore National Laboratory, can be used for the acoustic version. A variety of applications is possible, pending validation of the bending phenomenon. The applications include acoustic-radiation-pattern predictions for a submerged object; mine detection analysis; structural noise analysis for cars; acoustic barrier analysis; and symphonic hall/auditorium predictions and speaker enclosure modeling
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.; Beghein, Yves; Nair, Naveen V.; Cools, Kristof; Bagci, Hakan; Shanker, Balasubramaniam
2014-01-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method's efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
Inversion of time-domain induced polarization data based on time-lapse concept
Kim, Bitnarae; Nam, Myung Jin; Kim, Hee Joon
2018-05-01
Induced polarization (IP) surveys, measuring overvoltage phenomena of the medium, are widely and increasingly performed not only for exploration of mineral resources but also for engineering applications. Among several IP survey methods such as time-domain, frequency-domain and spectral IP surveys, this study introduces a noble inversion method for time-domain IP data to recover the chargeability structure of target medium. The inversion method employs the concept of 4D inversion of time-lapse resistivity data sets, considering the fact that measured voltage in time-domain IP survey is distorted by IP effects to increase from the instantaneous voltage measured at the moment the source current injection starts. Even though the increase is saturated very fast, we can consider the saturated and instantaneous voltages as a time-lapse data set. The 4D inversion method is one of the most powerful method for inverting time-lapse resistivity data sets. Using the developed IP inversion algorithm, we invert not only synthetic but also field IP data to show the effectiveness of the proposed method by comparing the recovered chargeability models with those from linear inversion that was used for the inversion of the field data in a previous study. Numerical results confirm that the proposed inversion method generates reliable chargeability models even though the anomalous bodies have large IP effects.
König, Karsten
2016-03-01
Monitoring the oral cavity noninvasively with superior 3D resolution is realized by clinical multiphoton tomography and high NA two-photon endoscopy without the need of additional contrast agents. The technology behind this investigation is based on nonlinear optical contrast of the multiphoton tomograph MPTflex®. Furthermore, the miniaturized GRIN endoscope was used to realize more accessibility for more demanding wound conditions in skin. The MPTflex® distinguishes autofluorescence (AF) signals from second harmonic generation (SHG) signals simultaneously. Fluorescence lifetime imaging (FLIM) based on time correlated single photon counting (TCSPC) technology offers additional information on the functional level of the intratissue fluorophores, their binding status, and the contribution of SHG signals in chronic wounds.
Ultrasound breast imaging using frequency domain reverse time migration
Roy, O.; Zuberi, M. A. H.; Pratt, R. G.; Duric, N.
2016-04-01
Conventional ultrasonography reconstruction techniques, such as B-mode, are based on a simple wave propagation model derived from a high frequency approximation. Therefore, to minimize model mismatch, the central frequency of the input pulse is typically chosen between 3 and 15 megahertz. Despite the increase in theoretical resolution, operating at higher frequencies comes at the cost of lower signal-to-noise ratio. This ultimately degrades the image contrast and overall quality at higher imaging depths. To address this issue, we investigate a reflection imaging technique, known as reverse time migration, which uses a more accurate propagation model for reconstruction. We present preliminary simulation results as well as physical phantom image reconstructions obtained using data acquired with a breast imaging ultrasound tomography prototype. The original reconstructions are filtered to remove low-wavenumber artifacts that arise due to the inclusion of the direct arrivals. We demonstrate the advantage of using an accurate sound speed model in the reverse time migration process. We also explain how the increase in computational complexity can be mitigated using a frequency domain approach and a parallel computing platform.
Application of Time Domain Reflectometers in Urban Settings ...
Time domain reflectometers (TDRs) are sensors that measure the volumetric water content of soils and porous media. The sensors consist of stainless steel rods connected to a circuit board in an epoxy housing. An electromagnetic pulse is propagated along the rods. The time, or period, required for the signal to travel down the rods and back varies with the volumetric water content of the surrounding media and temperature. A calibration curve is needed for the specific media. TDRs were developed mostly for agricultural applications; however, the technology has also been applied to forestry and ecological research. This study demonstrates the use of TDRs for quantifying drainage properties in low impact development (LID) stormwater controls, specifically permeable pavement and rain garden systems. TDRs were successfully used to monitor the responses of urban fill, engineered bioretention media, and the aggregate storage layer under permeable pavement to multiple rain events of varying depth, intensity, and duration. The hydrologic performance of permeable pavement and rain garden systems has previously been quantified for underdrain systems, but there have been few studies of systems that drain to the underlying soils. We know of no published studies outlining the use of TDR technology to document drainage properties in media other than soil. In this study TDRs were installed at multiple locations and depths in underlying urban fill soils, engineered bior
The Future of the Time Domain with LSST
Walkowicz, Lucianne M.
2012-04-01
abstract-type="normal">SummaryIn the coming decade LSST's combination of all-sky coverage, consistent long-term monitoring and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. Time-domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theories. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space. LSST will generate `alerts' within 60 seconds of detecting a new transient, permitting the community to follow up unusual events in greater detail. However, follow-up will remain a challenge as the volume of transients will easily saturate available spectroscopic resources. Characterization of events and access to appropriate ancillary data (e.g. from prior observations, either in the optical or in other passbands) will be of the utmost importance in prioritizing follow-up observations. The incredible scientific opportunities and unique challenges afforded by LSST demand organization, forethought and creativity from the astronomical community. To learn more about the telescope specifics and survey design, as well as obtaining a overview of the variety of the scientific investigations that LSST will enable, readers are encouraged to look at the LSST Science Book: http://www.lsst.org/lsst/scibook. Organizational details of the LSST science collaborations and management may be found at http://www.lsstcorp.org.
Time domain functional NIRS imaging for human brain mapping.
Torricelli, Alessandro; Contini, Davide; Pifferi, Antonio; Caffini, Matteo; Re, Rebecca; Zucchelli, Lucia; Spinelli, Lorenzo
2014-01-15
This review is aimed at presenting the state-of-the-art of time domain (TD) functional near-infrared spectroscopy (fNIRS). We first introduce the physical principles, the basics of modeling and data analysis. Basic instrumentation components (light sources, detection techniques, and delivery and collection systems) of a TD fNIRS system are described. A survey of past, existing and next generation TD fNIRS systems used for research and clinical studies is presented. Performance assessment of TD fNIRS systems and standardization issues are also discussed. Main strengths and weakness of TD fNIRS are highlighted, also in comparison with continuous wave (CW) fNIRS. Issues like quantification of the hemodynamic response, penetration depth, depth selectivity, spatial resolution and contrast-to-noise ratio are critically examined, with the help of experimental results performed on phantoms or in vivo. Finally we give an account on the technological developments that would pave the way for a broader use of TD fNIRS in the neuroimaging community. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
Time-domain Brillouin scattering assisted by diffraction gratings
Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi
2018-02-01
Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.
Time domain simulations of preliminary breakdown pulses in natural lightning.
Carlson, B E; Liang, C; Bitzer, P; Christian, H
2015-06-16
Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mechanism. Preliminary breakdown pulses can be reproduced by simulated channel extension Channel heating and corona sheath formation are crucial to proper pulse shape Extension processes and channel orientation significantly affect observations.
Landfill cover performance monitoring using time domain reflectometry
International Nuclear Information System (INIS)
Neher, E.R.; Cotten, G.B.; McElroy, D.
1998-01-01
Time domain reflectometry (TDR) systems were installed to monitor soil moisture in two newly constructed landfill covers at the Idaho National Engineering and Environmental Laboratory. Each TDR system includes four vertical arrays with each array consisting of four TDR probes located at depths of 15, 30, 45, and 60 cm. The deepest probes at 60 cm were installed beneath a compacted soil layer to analyze infiltration through the compacted layer. Based on the TDR data, infiltration through the two covers between March and October, 1997 ranged from less than measurable to 1.5 cm. However, due to a prohibition on penetrating the buried waste and resulting limits on probe placement depths, deeper percolation was not evaluated. Some of the advantages found in the application of TDR for infiltration monitoring at this site are the relative low cost and rugged nature of the equipment. Also, of particular importance, the ability to collect frequent moisture measurements allows the capture and evaluation of soil moisture changes resulting from episodic precipitation events. Disadvantages include the inability to install the probes into the waste, difficulties in interpretation of infiltration during freeze/thaw periods, and some excessive noise in the data
Time domain structures in a colliding magnetic flux rope experiment
Tang, Shawn Wenjie; Gekelman, Walter; Dehaas, Timothy; Vincena, Steve; Pribyl, Patrick
2017-10-01
Electron phase-space holes, regions of positive potential on the scale of the Debye length, have been observed in auroras as well as in laboratory experiments. These potential structures, also known as Time Domain Structures (TDS), are packets of intense electric field spikes that have significant components parallel to the local magnetic field. In an ongoing investigation at UCLA, TDS were observed on the surface of two magnetized flux ropes produced within the Large Plasma Device (LAPD). A barium oxide (BaO) cathode was used to produce an 18 m long magnetized plasma column and a lanthanum hexaboride (LaB6) source was used to create 11 m long kink unstable flux ropes. Using two probes capable of measuring the local electric and magnetic fields, correlation analysis was performed on tens of thousands of these structures and their propagation velocities, probability distribution function and spatial distribution were determined. The TDS became abundant as the flux ropes collided and appear to emanate from the reconnection region in between them. In addition, a preliminary analysis of the permutation entropy and statistical complexity of the data suggests that the TDS signals may be chaotic in nature. Work done at the Basic Plasma Science Facility (BaPSF) at UCLA which is supported by DOE and NSF.
Demonstration of Time Domain Multiplexed Readout for Magnetically Coupled Calorimeters
Porst, J.-P.; Adams, J. S.; Balvin, M.; Bandler, S.; Beyer, J.; Busch, S. E.; Drung, D.; Seidel, G. M.; Smith, S. J.; Stevenson, T. R.
2012-01-01
Magnetically coupled calorimeters (MCC) have extremely high potential for x-ray applications due to the inherent high energy resolution capability and being non-dissipative. Although very high energy-resolution has been demonstrated, until now there has been no demonstration of multiplexed read-out. We report on the first realization of a time domain multiplexed (TDM) read-out. While this has many similarities with TDM of transition-edge-sensors (TES), for MGGs the energy resolution is limited by the SQUID read-out noise and requires the well established scheme to be altered in order to minimize degradation due to noise aliasing effects. In cur approach, each pixel is read out by a single first stage SQUID (SQ1) that is operated in open loop. The outputs of the SQ1 s are low-pass filtered with an array of low cross-talk inductors, then fed into a single-stage SQUID TD multiplexer. The multiplexer is addressed from room temperature and read out through a single amplifier channel. We present results achieved with a new detector platform. Noise performance is presented and compared to expectations. We have demonstrated multiplexed X-ray spectroscopy at 5.9keV with delta_FWHM=10eV. In an optimized setup, we show it is possible to multiplex 32 detectors without significantly degrading the Intrinsic detector resolution.
Detection of Ionic liquid using terahertz time-domain spectroscopy
Wang, Cuicui; Zhao, Xiaojing; Liu, Shangjian; Zuo, Jian; Zhang, Cunlin
2018-01-01
Terahertz (THz, THz+1012Hz) spectroscopy is a far-infrared analytical technology with spectral bands locating between microware and infrared ranges. Being of excellent transmission, non-destruction and high discrimination, this technology has been applied in various fields such as physics, chemistry, nondestructive detection, communication, biomedicine public security. Terahertz spectrum is corresponding with vibration and rotation of liquid molecules, which is suitable to identify and study the liquid molecular dynamics. It is as a powerful spectral detection technology, terahertz time-domain spectroscopy is widely used in solution detection. can enable us to extract the material parameters or dielectric spectrum that show material micro-structure and dynamics by measuring amplitude and phase from coherent terahertz pulses. Ionic liquid exists in most biological tissues, and it is very important for life. It has recently been suggested that near-fired terahertz ionic contrast microscopy can be employed to image subtle changes in ionic concentrations arising from neuronal activity. In this paper, we detected Ionic liquid with different concentrations at room temperature by THz-TDS technique in the range of 0.2-1.5 THz. The liquid cell with a thickness of 0.2mm is made of quartz. The absorption coefficient, refractive index and dielectric function of solutions can be extracted based on THz-TDS. We use an expanded model for fitting the dielectric function based on a combination of a Debye relation for the anions and cations. We find A linear increase of the real and imaginary part of the dielectric function compared with pure water with increasing ion concentrations. A good agreement between the model and the experimental results is obtained. By means of dielectric relaxation process, it was found that the characteristic time of molecular movement and the information related to the liquid molecular structure and movement was obtained.
A time domain phase-gradient based ISAR autofocus algorithm
CSIR Research Space (South Africa)
Nel, W
2011-10-01
Full Text Available . Results on simulated and measured data show that the algorithm performs well. Unlike many other ISAR autofocus techniques, the algorithm does not make use of several computationally intensive iterations between the data and image domains as part...
Time-Reversal MUSIC Imaging with Time-Domain Gating Technique
Choi, Heedong; Ogawa, Yasutaka; Nishimura, Toshihiko; Ohgane, Takeo
A time-reversal (TR) approach with multiple signal classification (MUSIC) provides super-resolution for detection and localization using multistatic data collected from an array antenna system. The theory of TR-MUSIC assumes that the number of antenna elements is greater than that of scatterers (targets). Furthermore, it requires many sets of frequency-domain data (snapshots) in seriously noisy environments. Unfortunately, these conditions are not practical for real environments due to the restriction of a reasonable antenna structure as well as limited measurement time. We propose an approach that treats both noise reduction and relaxation of the transceiver restriction by using a time-domain gating technique accompanied with the Fourier transform before applying the TR-MUSIC imaging algorithm. Instead of utilizing the conventional multistatic data matrix (MDM), we employ a modified MDM obtained from the gating technique. The resulting imaging functions yield more reliable images with only a few snapshots regardless of the limitation of the antenna arrays.
Time-Domain Studies as a Probe of Stellar Evolution
Miller, Adam Andrew
This dissertation focuses on the use of time-domain techniques to discover and characterize these rare astrophysical gems, while also addressing some gaps in our understanding of the earliest and latest stages of stellar evolution. The observational studies presented herein can be grouped into three parts: (i) the study of stellar death (supernovae); (ii) the study of stellar birth; and (iii) the use of modern machine-learning algorithms to discover and classify variable sources. I present observations of supernova (SN) 2006gy, the most luminous SN ever at the time of discovery, and the even-more luminous SN 2008es. Together, these two supernovae (SNe) demonstrate that core-collapse SNe can be significantly more luminous than thermonuclear type Ia SNe, and that there are multiple channels for producing these brilliant core-collapse explosions. For SN 2006gy I show that the progenitor star experienced violent, eruptive mass loss on multiple occasions during the centuries prior to explosion, a scenario that was completely unexpected within the cannon of massive-star evolution theory. I also present observations of SN 2008iy, one of the most unusual SNe ever discovered. Typical SNe take ≲3 weeks to reach peak luminosity; SN 2008iy exhibited a slow and steady rise for ˜400 days before reaching maximum brightness. The best explanation for such behavior is that the progenitor of SN 2008iy experienced an episodic phase of mass loss ˜100 yr prior to explosion. The three SNe detailed in this dissertation have altered our understanding of massive-star mass loss, namely, these SNe provide distinct evidence that post-main sequence mass loss, for at least some massive stars, occurs in sporatic fits, rather than being steady. They also demonstrate that core collapse is not restricted to the red supergiant and Wolf-Rayet stages of stellar evolution as theory predicted. Instead, some massive stars explode while in a luminous blue variable-like state. I also present
International Nuclear Information System (INIS)
Duan Zhisheng; Wang Jinzhi; Yang Ying; Huang Lin
2009-01-01
This paper surveys frequency-domain and time-domain methods for feedback nonlinear systems and their possible applications to chaos control, coupled systems and complex dynamical networks. The absolute stability of Lur'e systems with single equilibrium and global properties of a class of pendulum-like systems with multi-equilibria are discussed. Time-domain and frequency-domain criteria for the convergence of solutions are presented. Some latest results on analysis and control of nonlinear systems with multiple equilibria and applications to chaos control are reviewed. Finally, new chaotic oscillating phenomena are shown in a pendulum-like system and a new nonlinear system with an attraction/repulsion function.
Integral ceramic superstructure evaluation using time domain optical coherence tomography
Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.
2014-02-01
Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.
Boiling water reactor stability analysis in the time domain
International Nuclear Information System (INIS)
Borkowski, J.A.
1991-01-01
Boiling water nuclear reactors may experience density wave instabilities. These instabilities cause the density, and consequently the mass flow rate, to oscillate in the shrouded fuel bundles. This effect causes the nuclear power generation to oscillate due to the tight coupling of flow to power, especially under gravity-driven circulation. In order to predict the amplitude of the power oscillation, a time domain transient analysis tool may be employed. The modeling tool must have sufficient hydrodynamic detail to model natural circulation in two-phase flow as well as the coupled nuclear feedback. TRAC/BF1 is a modeling code with such capabilities. A dynamic system model has been developed for a typical boiling water reactor. Using this tool it has been demonstrated that density waxes may be modeled in this fashion and that their resultant hydrodynamic and nuclear behavior correspond well to simple theory. Several cases have been analyzed using this model, the goal being to determine the coupling between the channel hydrodynamics and the nuclear power. From that study it has been concluded that two-phase friction controls the extent of the oscillation and that the existing conventional methodologies of implementing two-phase friction into analysis codes of this type can lead to significant deviation in results from case to case. It has also been determined that higher dimensional nuclear feedback models reduce the extent of the oscillation. It has also been confirmed from a nonlinear dynamic standpoint that the birth of this oscillation may be described as a Hopf Bifurcation
THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS
Energy Technology Data Exchange (ETDEWEB)
Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others
2015-06-20
We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.
Opportunities and challenges for time domain astronomy with LSST
Ivezic, Zeljko
2014-01-01
The Large Synoptic Survey Telescope (LSST) will enable faint optical time-domain astronomy by carrying out an imaging survey covering the sky that is visible from Cerro Pachon in Northern Chile. Of the order thousand 9.6 sq. deg. images (3.2 Gigapix) will be obtained per night using pairs of 15-second back-to-back exposures, with typical 5-sigma depth for point sources of 24.5 (AB). With close to 1000 observations of a 18,000 sq. deg. region in ugrizy bands over a 10-year period, these data will enable a deep stack across half the sky reaching five magnitudes deeper than the SDSS survey ( 27.5, 5 sigma, point source), and with twice as good seeing (0.7 arcsec median seeing in the r band). The measured and archived properties of newly discovered and known astrometric and photometric transients will be publicly reported within 60 sec after closing the shutter. Automated classification of the expected several million alerts per night, and selection of transient events requiring immediate follow-up, is an outstanding problem for the community. These data will represent a treasure trove for follow-up programs using other ground and space-based telescopes, such as fast-response fast-cadence photometric observations and spectroscopy, as well as for facilities operating at non-optical wavelengths and for gravitational wave programs. I will describe the relevant data products to be delivered by LSST and will summarize challenges that will need to be addressed by the community at large.
THz Time-Domain Spectroscopy of Interstellar Ice Analogs
Ioppolo, Sergio; McGuire, Brett A.; de Vries, Xander; Carroll, Brandon; Allodi, Marco; Blake, Geoffrey
2015-08-01
The unambiguous identification of nearly 200 molecular species in different astronomical environments proves that our cosmos is a ‘Molecular Universe’. The cumulative outcome of recent observations, laboratory studies, and astrochemical models indicates that there is a strong interplay between the gas and the solid phase throughout the process of forming molecules in space. Observations of interstellar ices are generally limited to lines-of-sight along which infrared absorption spectroscopy is possible. Therefore, the identification of more complex prebiotic molecules in the mid-IR is difficult because of their low expected interstellar abundances and the overlap of their absorption features with those from the more abundant species. In the THz region, telescopes can detect Interstellar ices in emission or absorption against dust continuum. Thus, THz searches do not require a background point source. Moreover, since THz spectra are the fingerprint of inter- and intramolecular forces, complex species can present unique modes that do not overlap with those from simpler, more abundant molecules. THz modes are also sensitive to temperature and phase changes in the ice. Therefore, spectroscopy at THz frequencies has the potential to better characterize the physics and chemistry of the ISM. Currently, the Herschel Space Telescope, SOFIA, and ALMA databases contain a vast amount of new THz spectral data that require THz laboratory spectra for interpretation. The latter, however, are largely lacking. We have recently constructed a new THz time-domain spectroscopy system operating in the range between 0.3 - 7.5 THz. This work focuses on the laboratory investigation of the composition and structure of the most abundant interstellar ice analogs compared to some more complex species. Different temperatures, mixing ratios, and matrix isolation experiments will be shown. The ultimate goal of this research is to provide the scientific community with an extensive THz ice
Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes
Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng
2016-09-01
Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.
Long, Yuchen; Stahl, Yvonne; Weidtkamp-Peters, Stefanie; Smet, Wouter; Du, Yujuan; Gadella, Theodorus W. J.; Goedhart, Joachim; Scheres, Ben; Blilou, Ikram
2018-01-01
Protein complex formation has been extensively studied using Förster resonance energy transfer (FRET) measured by Fluorescence Lifetime Imaging Microscopy (FLIM). However, implementing this technology to detect protein interactions in living
Improved methods for nightside time domain Lunar Electromagnetic Sounding
Fuqua-Haviland, H.; Poppe, A. R.; Fatemi, S.; Delory, G. T.; De Pater, I.
2017-12-01
Time Domain Electromagnetic (TDEM) Sounding isolates induced magnetic fields to remotely deduce material properties at depth. The first step of performing TDEM Sounding at the Moon is to fully characterize the dynamic plasma environment, and isolate geophysically induced currents from concurrently present plasma currents. The transfer function method requires a two-point measurement: an upstream reference measuring the pristine solar wind, and one downstream near the Moon. This method was last performed during Apollo assuming the induced fields on the nightside of the Moon expand as in an undisturbed vacuum within the wake cavity [1]. Here we present an approach to isolating induction and performing TDEM with any two point magnetometer measurement at or near the surface of the Moon. Our models include a plasma induction model capturing the kinetic plasma environment within the wake cavity around a conducting Moon, and a geophysical forward model capturing induction in a vacuum. The combination of these two models enable the analysis of magnetometer data within the wake cavity. Plasma hybrid models use the upstream plasma conditions and interplanetary magnetic field (IMF) to capture the wake current systems formed around the Moon. The plasma kinetic equations are solved for ion particles with electrons as a charge-neutralizing fluid. These models accurately capture the large scale lunar wake dynamics for a variety of solar wind conditions: ion density, temperature, solar wind velocity, and IMF orientation [2]. Given the 3D orientation variability coupled with the large range of conditions seen within the lunar plasma environment, we characterize the environment one case at a time. The global electromagnetic induction response of the Moon in a vacuum has been solved numerically for a variety of electrical conductivity models using the finite-element method implemented within the COMSOL software. This model solves for the geophysically induced response in vacuum to
ASIC-enabled High Resolution Optical Time Domain Reflectometer
Skendzic, Sandra
Fiber optics has become the preferred technology in communication systems because of what it has to offer: high data transmission rates, immunity to electromagnetic interference, and lightweight, flexible cables. An optical time domain reflectometer (OTDR) provides a convenient method of locating and diagnosing faults (e.g. break in a fiber) along a fiber that can obstruct crucial optical pathways. Both the ability to resolve the precise location of the fault and distinguish between two discrete, closely spaced faults are figures of merit. This thesis presents an implementation of a high resolution OTDR through the use of a compact and programmable ASIC (application specific integrated circuit). The integration of many essential OTDR functions on a single chip is advantageous over existing commercial instruments because it enables small, lightweight packaging, and offers low power and cost efficiency. Furthermore, its compactness presents the option of placing multiple ASICs in parallel, which can conceivably ease the characterization of densely populated fiber optic networks. The OTDR ASIC consists of a tunable clock, pattern generator, precise timer, electrical receiver, and signal sampling circuit. During OTDR operation, the chip generates narrow electrical pulse, which can then be converted to optical format when coupled with an external laser diode driver. The ASIC also works with an external photodetector to measure the timing and amplitude of optical reflections in a fiber. It has a 1 cm sampling resolution, which allows for a 2 cm spatial resolution. While this OTDR ASIC has been previously demonstrated for multimode fiber fault diagnostics, this thesis focuses on extending its functionality to single mode fiber. To validate this novel approach to OTDR, this thesis is divided into five chapters: (1) introduction, (2) implementation, (3), performance of ASIC-based OTDR, (4) exploration in optical pre-amplification with a semiconductor optical amplifier, and
Time-Domain Terahertz Computed Axial Tomography NDE System
Zimdars, David
2012-01-01
NASA has identified the need for advanced non-destructive evaluation (NDE) methods to characterize aging and durability in aircraft materials to improve the safety of the nation's airline fleet. 3D THz tomography can play a major role in detection and characterization of flaws and degradation in aircraft materials, including Kevlar-based composites and Kevlar and Zylon fabric covers for soft-shell fan containment where aging and durability issues are critical. A prototype computed tomography (CT) time-domain (TD) THz imaging system has been used to generate 3D images of several test objects including a TUFI tile (a thermal protection system tile used on the Space Shuttle and possibly the Orion or similar capsules). This TUFI tile had simulated impact damage that was located and the depth of damage determined. The CT motion control gan try was designed and constructed, and then integrated with a T-Ray 4000 control unit and motion controller to create a complete CT TD-THz imaging system prototype. A data collection software script was developed that takes multiple z-axis slices in sequence and saves the data for batch processing. The data collection software was integrated with the ability to batch process the slice data with the CT TD-THz image reconstruction software. The time required to take a single CT slice was decreased from six minutes to approximately one minute by replacing the 320 ps, 100-Hz waveform acquisition system with an 80 ps, 1,000-Hz waveform acquisition system. The TD-THZ computed tomography system was built from pre-existing commercial off-the-shelf subsystems. A CT motion control gantry was constructed from COTS components that can handle larger samples. The motion control gantry allows inspection of sample sizes of up to approximately one cubic foot (.0.03 cubic meters). The system reduced to practice a CT-TDTHz system incorporating a COTS 80- ps/l-kHz waveform scanner. The incorporation of this scanner in the system allows acquisition of 3D
A time-domain method to generate artificial time history from a given reference response spectrum
Energy Technology Data Exchange (ETDEWEB)
Shin, Gang Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Song, Oh Seop [Dept. of Mechanical Engineering, Chungnam National University, Daejeon (Korea, Republic of)
2016-06-15
Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance.
A time-domain method to generate artificial time history from a given reference response spectrum
International Nuclear Information System (INIS)
Shin, Gang Sik; Song, Oh Seop
2016-01-01
Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.
2014-12-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method\\'s efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
Time and frequency domain analyses of the Hualien Large-Scale Seismic Test
International Nuclear Information System (INIS)
Kabanda, John; Kwon, Oh-Sung; Kwon, Gunup
2015-01-01
Highlights: • Time- and frequency-domain analysis methods are verified against each other. • The two analysis methods are validated against Hualien LSST. • The nonlinear time domain (NLTD) analysis resulted in more realistic response. • The frequency domain (FD) analysis shows amplification at resonant frequencies. • The NLTD analysis requires significant modeling and computing time. - Abstract: In the nuclear industry, the equivalent-linear frequency domain analysis method has been the de facto standard procedure primarily due to the method's computational efficiency. This study explores the feasibility of applying the nonlinear time domain analysis method for the soil–structure-interaction analysis of nuclear power facilities. As a first step, the equivalency of the time and frequency domain analysis methods is verified through a site response analysis of one-dimensional soil, a dynamic impedance analysis of soil–foundation system, and a seismic response analysis of the entire soil–structure system. For the verifications, an idealized elastic soil–structure system is used to minimize variables in the comparison of the two methods. Then, the verified analysis methods are used to develop time and frequency domain models of Hualien Large-Scale Seismic Test. The predicted structural responses are compared against field measurements. The models are also analyzed with an amplified ground motion to evaluate discrepancies of the time and frequency domain analysis methods when the soil–structure system behaves beyond the elastic range. The analysis results show that the equivalent-linear frequency domain analysis method amplifies certain frequency bands and tends to result in higher structural acceleration than the nonlinear time domain analysis method. A comparison with field measurements shows that the nonlinear time domain analysis method better captures the frequency distribution of recorded structural responses than the frequency domain
A two-dimensional time domain near zone to far zone transformation
Luebbers, Raymond J.; Ryan, Deirdre; Beggs, John H.; Kunz, Karl S.
1991-01-01
In a previous paper, a time domain transformation useful for extrapolating 3-D near zone finite difference time domain (FDTD) results to the far zone was presented. In this paper, the corresponding 2-D transform is outlined. While the 3-D transformation produced a physically observable far zone time domain field, this is not convenient to do directly in 2-D, since a convolution would be required. However, a representative 2-D far zone time domain result can be obtained directly. This result can then be transformed to the frequency domain using a Fast Fourier Transform, corrected with a simple multiplicative factor, and used, for example, to calculate the complex wideband scattering width of a target. If an actual time domain far zone result is required it can be obtained by inverse Fourier transform of the final frequency domain result.
TeraHertz Time Domain Spectroscopy of Astrophysical Analog Materials
Blake, Geoffrey
The section of the electromagnetic spectrum extending roughly from wavelengths of 3 millimeters to 30 microns is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the successful deployments of the Herschel and SOFIA observatories, and the emerging capabilities of ALMA, are both revolutionizing our understanding of THz astrophysics and placing stringent demands on the generation of accurate laboratory data on the relevant gas phase and solid state materials detected. With APRA support, we have constructed a combined high bandwidth and high spectral resolution femtosecond THz Time Domain Spectroscopy (THz TDS) system and an FT-IR spectrometer, and coupled these instruments to a high vacuum chamber and cryostat and to gas phase cells including a molecular beam system. We have investigated solid materials from room temperature to 10 K, and can examine both refractory matter such as silicates and molecular ices. For the latter, we have demonstrated that the THz bands observed are uniquely sensitive to both the molecular structure of the ice and its thermal history, and thus that THz observations can provide novel insight into the dominant condensable materials in dense, cold regions. In the gas phase we can record doppler-limited data over at least a decade in bandwidth. While quite capable, the high vacuum cryostat can only study thick samples, especially ices, due to the fairly rapid adsorption of gases onto surfaces at low temperature under such conditions. It is therefore not possible to examine highly layered/structured samples or reactive species. We therefore propose here to upgrade the chamber/cryostat to ultrahigh vacuum, and implement additional sample preparation and characterization tools. With such modifications
Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements
Dragonetti, Giovanna; Comegna, Alessandro; Ajeel, Ali; Piero Deidda, Gian; Lamaddalena, Nicola; Rodriguez, Giuseppe; Vignoli, Giulio; Coppola, Antonio
2018-02-01
This paper deals with the issue of monitoring the spatial distribution of bulk electrical conductivity, σb, in the soil root zone by using electromagnetic induction (EMI) sensors under different water and salinity conditions. To deduce the actual distribution of depth-specific σb from EMI apparent electrical conductivity (ECa) measurements, we inverted the data by using a regularized 1-D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss-Newton method with truncated generalized singular value decomposition (TGSVD). The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI results in the presence of sharp boundaries (otherwise smeared out after the application of more standard Occam-like regularization strategies searching for smooth solutions). Time-domain reflectometry (TDR) data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean, and irrigated with water at two different salinity levels and using two different irrigation volumes. Clearly, this induces different salinity and water contents within the soil profiles. For each transect, 26 regularly spaced monitoring soundings (1 m apart) were selected for the collection of (i) Geonics EM-38 and (ii) Tektronix reflectometer data. Despite the original discrepancies in the EMI and TDR data, we found a significant correlation of the means and standard deviations of the two data series; in particular, after a low-pass spatial filtering of the TDR data. Based on these findings, this paper introduces a novel methodology to calibrate EMI-based electrical conductivities via TDR direct measurements. This
Studies in astronomical time series analysis. I - Modeling random processes in the time domain
Scargle, J. D.
1981-01-01
Several random process models in the time domain are defined and discussed. Attention is given to the moving average model, the autoregressive model, and relationships between and combinations of these models. Consideration is then given to methods for investigating pulse structure, procedures of model construction, computational methods, and numerical experiments. A FORTRAN algorithm of time series analysis has been developed which is relatively stable numerically. Results of test cases are given to study the effect of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the light curve of the quasar 3C 272 is considered as an example.
Cable Damage Detection System and Algorithms Using Time Domain Reflectometry
Energy Technology Data Exchange (ETDEWEB)
Clark, G A; Robbins, C L; Wade, K A; Souza, P R
2009-03-24
This report describes the hardware system and the set of algorithms we have developed for detecting damage in cables for the Advanced Development and Process Technologies (ADAPT) Program. This program is part of the W80 Life Extension Program (LEP). The system could be generalized for application to other systems in the future. Critical cables can undergo various types of damage (e.g. short circuits, open circuits, punctures, compression) that manifest as changes in the dielectric/impedance properties of the cables. For our specific problem, only one end of the cable is accessible, and no exemplars of actual damage are available. This work addresses the detection of dielectric/impedance anomalies in transient time domain reflectometry (TDR) measurements on the cables. The approach is to interrogate the cable using time domain reflectometry (TDR) techniques, in which a known pulse is inserted into the cable, and reflections from the cable are measured. The key operating principle is that any important cable damage will manifest itself as an electrical impedance discontinuity that can be measured in the TDR response signal. Machine learning classification algorithms are effectively eliminated from consideration, because only a small number of cables is available for testing; so a sufficient sample size is not attainable. Nonetheless, a key requirement is to achieve very high probability of detection and very low probability of false alarm. The approach is to compare TDR signals from possibly damaged cables to signals or an empirical model derived from reference cables that are known to be undamaged. This requires that the TDR signals are reasonably repeatable from test to test on the same cable, and from cable to cable. Empirical studies show that the repeatability issue is the 'long pole in the tent' for damage detection, because it is has been difficult to achieve reasonable repeatability. This one factor dominated the project. The two-step model
Ato protein interactions in yeast plasma membrane revealed by fluorescence lifetime imaging (FLIM)
Czech Academy of Sciences Publication Activity Database
Strachotová, Dita; Holoubek, A.; Kučerová, Helena; Benda, Aleš; Humpolíčková, Jana; Váchová, Libuše; Palková, Z.
2012-01-01
Roč. 1818, č. 9 (2012), s. 2126-2134 ISSN 0005-2736 R&D Projects: GA ČR GA204/08/0718; GA MŠk(CZ) LC06063; GA MŠk(CZ) LC531 Institutional research plan: CEZ:AV0Z40400503 Institutional support: RVO:61388971 Keywords : Ammonium exporters Ato1p * Ato2p and Ato3p * FLIM-photobleaching technique Subject RIV: CE - Biochemistry Impact factor: 3.389, year: 2012
Measuring upconversion nanoparticles photoluminescence lifetime with FastFLIM and phasor plots
Sun, Yuansheng; Lee, Hsien-Ming; Qiu, Hailin; Liao, Shih-Chu Jeff; Coskun, Ulas; Barbieri, Beniamino
2018-02-01
Photon upconversion is a nonlinear process in which the sequential of absorption of two or more photons leads to the anti-stoke emission. Different than the conventional multiphoton excitation process, upconversion can be efficiently performed at low excitation densities. Recent developments in lanthanide-doped upconversion nanoparticles (UCNPs) have led to a diversity of applications, including detecting and sensing of biomolecules, imaging of live cells, tissues and animals, cancer diagnostic and therapy, etc. Measuring the upconversion lifetime provides a new dimension of its imaging and opens a new window for its applications. Due to the long metastable intermediate excited state, UCNP typically has a long excited state lifetime ranging from sub-microseconds to milliseconds. Here, we present a novel development using the FastFLIM technique to measure UCNP lifetime by laser scanning confocal microscopy. FastFLIM is capable of measuring lifetime from 100 ps to 100 ms and features the high data collection efficiency (up to 140-million counts per second). Other than the traditional nonlinear least-square fitting analysis, the raw data acquired by FastFLIM can be directly processed by the model-free phasor plots approach for instant and unbiased lifetime results, providing the ideal routine for the UCNP photoluminescence lifetime microscopy imaging.
Frequency-domain criterion for the chaos synchronization of time ...
Indian Academy of Sciences (India)
of time-delay power systems under linear feedback control ... arbitrary dimension of the time-delay systems can keep their chaotic characteristic as long as ... As a basic theory on chaotic secure communication, synchronization of time-delay.
Studies in astronomical time series analysis: Modeling random processes in the time domain
Scargle, J. D.
1979-01-01
Random process models phased in the time domain are used to analyze astrophysical time series data produced by random processes. A moving average (MA) model represents the data as a sequence of pulses occurring randomly in time, with random amplitudes. An autoregressive (AR) model represents the correlations in the process in terms of a linear function of past values. The best AR model is determined from sampled data and transformed to an MA for interpretation. The randomness of the pulse amplitudes is maximized by a FORTRAN algorithm which is relatively stable numerically. Results of test cases are given to study the effects of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the optical light curve of the quasar 3C 273 is given.
On spurious resonant modes in the MOT solution of time domain EFIE
Shi, Yifei; Bagci, Hakan; Lu, Mingyu
2013-01-01
Theoretically, internal resonant modes should not be induced in the marching-on-in-time (MOT) solution of the time domain electric field integral equation since zero initial conditions are enforced at the beginning of time marching and the internal
On the initial condition problem of the time domain PMCHWT surface integral equation
Uysal, Ismail Enes; Bagci, Hakan; Ergin, A. Arif; Ulku, H. Arda
2017-01-01
Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced
A new image cipher in time and frequency domains
Abd El-Latif, Ahmed A.; Niu, Xiamu; Amin, Mohamed
2012-10-01
Recently, various encryption techniques based on chaos have been proposed. However, most existing chaotic encryption schemes still suffer from fundamental problems such as small key space, weak security function and slow performance speed. This paper introduces an efficient encryption scheme for still visual data that overcome these disadvantages. The proposed scheme is based on hybrid Linear Feedback Shift Register (LFSR) and chaotic systems in hybrid domains. The core idea is to scramble the pixel positions based on 2D chaotic systems in frequency domain. Then, the diffusion is done on the scrambled image based on cryptographic primitive operations and the incorporation of LFSR and chaotic systems as round keys. The hybrid compound of LFSR, chaotic system and cryptographic primitive operations strengthen the encryption performance and enlarge the key space required to resist the brute force attacks. Results of statistical and differential analysis show that the proposed algorithm has high security for secure digital images. Furthermore, it has key sensitivity together with a large key space and is very fast compared to other competitive algorithms.
A symmetrical image encryption scheme in wavelet and time domain
Luo, Yuling; Du, Minghui; Liu, Junxiu
2015-02-01
There has been an increasing concern for effective storages and secure transactions of multimedia information over the Internet. Then a great variety of encryption schemes have been proposed to ensure the information security while transmitting, but most of current approaches are designed to diffuse the data only in spatial domain which result in reducing storage efficiency. A lightweight image encryption strategy based on chaos is proposed in this paper. The encryption process is designed in transform domain. The original image is decomposed into approximation and detail components using integer wavelet transform (IWT); then as the more important component of the image, the approximation coefficients are diffused by secret keys generated from a spatiotemporal chaotic system followed by inverse IWT to construct the diffused image; finally a plain permutation is performed for diffusion image by the Logistic mapping in order to reduce the correlation between adjacent pixels further. Experimental results and performance analysis demonstrate the proposed scheme is an efficient, secure and robust encryption mechanism and it realizes effective coding compression to satisfy desirable storage.
Calculation of nonzero-temperature Casimir forces in the time domain
International Nuclear Information System (INIS)
Pan, Kai; Reid, M. T. Homer; McCauley, Alexander P.; Rodriguez, Alejandro W.; White, Jacob K.; Johnson, Steven G.
2011-01-01
We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example, using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a nonmonotonic behavior previously demonstrated in a pistonlike geometry.
Parallel time domain solvers for electrically large transient scattering problems
Liu, Yang; Yucel, Abdulkadir; Bagcý , Hakan; Michielssen, Eric
2014-01-01
scattering from perfect electrically conducting objects are obtained by enforcing electric field boundary conditions and implicitly time advance electric surface current densities by iteratively solving sparse systems of equations at all time steps. Contrary
Architecture for time or transform domain decoding of reed-solomon codes
Shao, Howard M. (Inventor); Truong, Trieu-Kie (Inventor); Hsu, In-Shek (Inventor); Deutsch, Leslie J. (Inventor)
1989-01-01
Two pipeline (255,233) RS decoders, one a time domain decoder and the other a transform domain decoder, use the same first part to develop an errata locator polynomial .tau.(x), and an errata evaluator polynominal A(x). Both the time domain decoder and transform domain decoder have a modified GCD that uses an input multiplexer and an output demultiplexer to reduce the number of GCD cells required. The time domain decoder uses a Chien search and polynomial evaluator on the GCD outputs .tau.(x) and A(x), for the final decoding steps, while the transform domain decoder uses a transform error pattern algorithm operating on .tau.(x) and the initial syndrome computation S(x), followed by an inverse transform algorithm in sequence for the final decoding steps prior to adding the received RS coded message to produce a decoded output message.
THE PSTD ALGORITHM: A TIME-DOMAIN METHOD REQUIRING ONLY TWO CELLS PER WAVELENGTH. (R825225)
A pseudospectral time-domain (PSTD) method is developed for solutions of Maxwell's equations. It uses the fast Fourier transform (FFT), instead of finite differences on conventional finite-difference-time-domain (FDTD) methods, to represent spatial derivatives. Because the Fourie...
On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain
DEFF Research Database (Denmark)
Østerberg, Frederik Westergaard; Rizzi, Giovanni; Hansen, Mikkel Fougt
2013-01-01
the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s...
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin; Ulku, Huseyin Arda; Bagci, Hakan
2015-01-01
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin
2015-05-16
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Explicit solution of Calderon preconditioned time domain integral equations
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2013-01-01
operators and a PE(CE)m type linear multistep to march on in time. Unlike its implicit counterpart, the proposed explicit solver requires the solution of an MOT system with a Gram matrix that is sparse and well-conditioned independent of the time step size
Managing Time-Based Conflict Across Life Domains In Nigeria: A ...
African Journals Online (AJOL)
Managing Time-Based Conflict Across Life Domains In Nigeria: A Decision Making Perspective. ... which employees in a developing country attempt to resolve time-based conflict between work, family and other activities. A decision making ...
Mixed Discretization of the Time Domain MFIE at Low Frequencies
Ulku, Huseyin Arda
2017-01-10
Solution of the magnetic field integral equation (MFIE), which is obtained by the classical marching on-in-time (MOT) scheme, becomes inaccurate when the time step is large, i.e., under low-frequency excitation. It is shown here that the inaccuracy stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring the correct scaling of the current’s Helmholtz components under low-frequency excitation.
Mixed Discretization of the Time Domain MFIE at Low Frequencies
Ulku, Huseyin Arda; Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco Paolo; Bagci, Hakan
2017-01-01
stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring
Finite Difference Time Domain (FDTD) Simulations Using Graphics Processors
National Research Council Canada - National Science Library
Adams, Samuel; Payne, Jason; Boppana, Rajendra
2007-01-01
.... This paper shows how GPUs can be used to greatly speedup FDTD simulations. The main objective is to leverage GPU processing power for FDTD update calculations and complete computationally expensive simulations in reasonable time...
Joint time-frequency domain proportional fair scheduler with HARQ for 3GPP LTE systems
Beh, KC; Doufexi, A; Armour, SMD
2008-01-01
This paper explores the potential gain of joint diversity in both frequency domain and time domain which can be exploited to achieve spectral efficiency gains whilst simultaneously facilitating QoS/ fairness in an OFDMA system particularly in 3GPP Long Term Evolution (LTE)). The performance of several joint time-frequency schedulers is investigated. Simulation results show that joint time frequency schedulers achieve significantly superior performance compared to a more conventional time doma...
Time-Domain Optical Fourier Transformation for OTDM-DWDM and DWDM-OTDM Conversion
DEFF Research Database (Denmark)
Mulvad, Hans Christian Hansen; Palushani, Evarist; Galili, Michael
2011-01-01
Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats.......Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats....
Multi-time-step domain coupling method with energy control
DEFF Research Database (Denmark)
Mahjoubi, N.; Krenk, Steen
2010-01-01
the individual time step. It is demonstrated that displacement continuity between the subdomains leads to cancelation of the interface contributions to the energy balance equation, and thus stability and algorithmic damping properties of the original algorithms are retained. The various subdomains can...... by a numerical example using a refined mesh around concentrated forces. Copyright © 2010 John Wiley & Sons, Ltd....
Hybrid time/frequency domain modeling of nonlinear components
DEFF Research Database (Denmark)
Wiechowski, Wojciech Tomasz; Lykkegaard, Jan; Bak, Claus Leth
2007-01-01
This paper presents a novel, three-phase hybrid time/frequency methodology for modelling of nonlinear components. The algorithm has been implemented in the DIgSILENT PowerFactory software using the DIgSILENT Programming Language (DPL), as a part of the work described in [1]. Modified HVDC benchmark...
Illusory conjunctions in the time domain and the resulting time-course of the attentional blink.
Botella, Juan; Arend, Isabel; Suero, Manuel
2004-05-01
Illusory conjunctions in the time domain are errors made in binding stimulus features presented In the same spatial position in Rapid Serial Visual Presentation (RSVP) conditions. Botella, Barriopedro, and Suero (2001) devised a model to explain how the distribution of responses originating from stimuli around the target in the series is generated. They proposed two routes consisting of two sequential attempts to make a response. The second attempt (sophisticated guessing) is only employed if the first one (focal attention) fails in producing an integrated perception. This general outline enables specific predictions to be made and tested related to the efficiency of focal attention in generating responses in the first attempt. Participants had to report the single letter in an RSVP stream of letters that was presented in a previously specified color (first target, T1) and then report whether an X (second target, T2) was or was not presented. Performance on T2 showed the typical U-shaped function across the T1-T2 lag that reflects the attentional blink phenomenon. However, as was predicted by Botella, Barriopedro, and Suero's model, the time-course of the interference was shorter for trials with a correct response to T1 than for trials with a T1 error. Furthermore, longer time-courses of interference associated with pre-target and post-target errors to the first target were indistinguishable.
A comparison of three time-domain anomaly detection methods
Energy Technology Data Exchange (ETDEWEB)
Schoonewelle, H.; Hagen, T.H.J.J. van der; Hoogenboom, J.E. [Delft University of Technology (Netherlands). Interfaculty Reactor Institute
1996-01-01
Three anomaly detection methods based on a comparison of signal values with predictions from an autoregressive model are presented. These methods are: the extremes method, the {chi}{sup 2} method and the sequential probability ratio test. The methods are used to detect a change of the standard deviation of the residual noise obtained from applying an autoregressive model. They are fast and can be used in on-line applications. For each method some important anomaly detection parameters are determined by calculation or simulation. These parameters are: the false alarm rate, the average time to alarm and - being of minor importance -the alarm failure rate. Each method is optimized with respect to the average time to alarm for a given value of the false alarm rate. The methods are compared with each other, resulting in the sequential probability ratio test being clearly superior. (author).
A comparison of three time-domain anomaly detection methods
International Nuclear Information System (INIS)
Schoonewelle, H.; Hagen, T.H.J.J. van der; Hoogenboom, J.E.
1996-01-01
Three anomaly detection methods based on a comparison of signal values with predictions from an autoregressive model are presented. These methods are: the extremes method, the χ 2 method and the sequential probability ratio test. The methods are used to detect a change of the standard deviation of the residual noise obtained from applying an autoregressive model. They are fast and can be used in on-line applications. For each method some important anomaly detection parameters are determined by calculation or simulation. These parameters are: the false alarm rate, the average time to alarm and - being of minor importance -the alarm failure rate. Each method is optimized with respect to the average time to alarm for a given value of the false alarm rate. The methods are compared with each other, resulting in the sequential probability ratio test being clearly superior. (author)
Mössbauer forward scattering: time-domain spectra
Energy Technology Data Exchange (ETDEWEB)
Sadykov, E. K., E-mail: esadykov@kpfu.ru; Yurichuk, A. A.; Gainov, R. R.; Vagizov, F. G. [Kazan (Volga Region) Federal University (Russian Federation)
2016-12-15
The transmission of the Mössbauer radiation through an absorber being in the acoustic oscillation mode under forward scattering (FS) conditions has been analyzed. The modification of the existing models of the FS spectra (frequency and time) formation to the case of the arbitrary phase correlation of nuclear oscillations in the sample has been proposed. An adequate description of the time delayed experiments with the {sup 57}Fe Mössbauer resonance using the modulation of the single-photon wave packet by acoustic field has been obtained. One has been done in the frame of the Raman scattering of Mössbauer photons. The models extended this way can be used to control the degree of phase correlation of nuclear oscillations (or other processes) induced in the sample by external fields.
Time domain NMR and conductivity study of apple pectin biopolymers
International Nuclear Information System (INIS)
Mattos, Ritamara I.; Souto, Sergio; Tambelli, Caio E.
2015-01-01
This communication presents results of "1H nuclear magnetic resonance of continuous distributions of spin-spin relaxation time (T_2) and A.C. conductivity of apple pectin biopolymers plasticized with glycerol and containing acetic acid. The continuous distributions reveals up to three components of spin-spin relaxation times (T_2). The two short T_2 components were associated with protons of pectin polymer chain and the longer T_2 can be attributed with the protons of the glycerol. The conductivity values increase with glycerol concentration with maximum at 7.9 x 10"-"4 S cm"-"1 for sample with 3.0 g of glycerol at 83 deg C. The behavior of activation energy and T_2 continuous distribution indicate an increase of proton mobility due the structural changes caused by glycerol addition. (author)
Wake force computation in the time domain for long structures
International Nuclear Information System (INIS)
Bane, K.; Weiland, T.
1983-07-01
One is often interested in calculating the wake potentials for short bunches in long structures using TBCI. For ultra-relativistic particles it is sufficient to solve for the fields only over a window containing the bunch and moving along with it. This technique reduces both the memory and the running time required by a factor that equals the ratio of the structure length to the window length. For example, for a bunch with sigma/sub z/ of one picosecond traversing a single SLAC cell this improvement factor is 15. It is thus possible to solve for the wakefields in very long structures: for a given problem, increasing the structure length will not change the memory required while only adding linearly to the CPU time needed
Interferometry in the era of time-domain astronomy
Schaefer, Gail H.; Cassan, Arnaud; Gallenne, Alexandre; Roettenbacher, Rachael M.; Schneider, Jean
2018-04-01
The physical nature of time variable objects is often inferred from photometric light-curves and spectroscopic variations. Long-baseline optical interferometry has the power to resolve the spatial structure of time variable sources directly in order to measure their physical properties and test the physics of the underlying models. Recent interferometric studies of variable objects include measuring the angular expansion and spatial structure during the early stages of novae outbursts, studying the transits and tidal distortions of the components in eclipsing and interacting binaries, measuring the radial pulsations in Cepheid variables, monitoring changes in the circumstellar discs around rapidly rotating massive stars, and imaging starspots. Future applications include measuring the image size and centroid displacements in gravitational microlensing events, and imaging the transits of exoplanets. Ongoing and upcoming photometric surveys will dramatically increase the number of time-variable objects detected each year, providing many potential targets to observe interferometrically. For short-lived transient events, it is critical for interferometric arrays to have the flexibility to respond rapidly to targets of opportunity and optimize the selection of baselines and beam combiners to provide the necessary resolution and sensitivity to resolve the source as its brightness and size change. We discuss the science opportunities made possible by resolving variable sources using long baseline optical interferometry.
Partial Fourier analysis of time-harmonic Maxwell's equations in axisymmetric domains
International Nuclear Information System (INIS)
Nkemzi, Boniface
2003-01-01
We analyze the Fourier method for treating time-harmonic Maxwell's equations in three-dimensional axisymmetric domains with non-axisymmetric data. The Fourier method reduces the three-dimensional boundary value problem to a system of decoupled two-dimensional boundary value problems on the plane meridian domain of the axisymmetric domain. The reduction process is fully described and suitable weighted spaces are introduced on the meridian domain to characterize the two-dimensional solutions. In particular, existence and uniqueness of solutions of the two-dimensional problems is proved and a priori estimates for the solutions are given. (author)
Manual Choice Reaction Times in the Rate-Domain
Directory of Open Access Journals (Sweden)
Chris eHarris
2014-06-01
Full Text Available Over the last 150 years, human manual reaction times (RTs have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modelled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process. However, latency distribution of saccades are very close to the reciprocal Normal, suggesting that ‘rate’ (reciprocal RT may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination and two instruction sets (urgent vs. accurate. We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks subjects they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be
Wind energy system time-domain (WEST) analyzers
Dreier, M. E.; Hoffman, J. A.
1981-01-01
A portable analyzer which simulates in real time the complex nonlinear dynamics of horizontal axis wind energy systems was constructed. Math models for an aeroelastic rotor featuring nonlinear aerodynamic and inertial terms were implemented with high speed digital controllers and analog calculation. This model was combined with other math models of elastic supports, control systems, a power train and gimballed rotor kinematics. A stroboscopic display system graphically depicting distributed blade loads, motion, and other aerodynamic functions on a cathode ray tube is included. Limited correlation efforts showed good comparison between the results of this analyzer and other sophisticated digital simulations. The digital simulation results were successfully correlated with test data.
Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows
Tseng, K.; Morino, L.
1978-01-01
The Green's Function Method for linearized 3D unsteady potential flow (embedded in the computer code SOUSSA P) is extended to include the time-domain analysis as well as the nonlinear term retained in the transonic small disturbance equation. The differential-delay equations in time, as obtained by applying the Green's Function Method (in a generalized sense) and the finite-element technique to the transonic equation, are solved directly in the time domain. Comparisons are made with both linearized frequency-domain calculations and existing nonlinear results.
Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.
Wang, Xu; Wada, Naoya
2007-06-11
We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.
Time- and Frequency-domain Comparisons of the Wavepiston Wave Energy Converter
DEFF Research Database (Denmark)
Read, Robert; Bingham, Harry
Analysis of wave-energy converters is most frequently undertaken in the time-domain. This formulation allows the direct inclusion of nonlinear time-varying loads such as power take-off (PTO) reactions, mooring forces, and viscous drag. However, integrating the governing equations of motion...... forces arising from both the PTO reactions and the non-negligible viscous drag acting on the plate. Equivalent linear damping coeffcients are used to model these forces in the frequency domain, while they are included explicitly in the time domain. The main idea of this paper is to quantify...
Directory of Open Access Journals (Sweden)
Qian Yang
2017-01-01
Full Text Available The near fields of electric dipole are commonly used in wide-band analysis of complex electromagnetic problems. In this paper, we propose new near field time-domain expressions for electric dipole. The analytical expressions for the frequency-domain of arbitrarily oriented electric dipole are given at first; next we give the time-domain expressions by time-frequency transformation. The proposed expressions are used in hybrid TDIE/DGTD method for analysis of circular antenna with radome. The accuracy of the proposed algorithm is verified by numerical examples.
Directory of Open Access Journals (Sweden)
A. Becker
2007-06-01
Full Text Available In this paper a hybrid method combining the Time-Domain Method of Moments (TD-MoM, the Time-Domain Uniform Theory of Diffraction (TD-UTD and the Finite-Difference Time-Domain Method (FDTD is presented. When applying this new hybrid method, thin-wire antennas are modeled with the TD-MoM, inhomogeneous bodies are modelled with the FDTD and large perfectly conducting plates are modelled with the TD-UTD. All inhomogeneous bodies are enclosed in a so-called FDTD-volume and the thin-wire antennas can be embedded into this volume or can lie outside. The latter avoids the simulation of white space between antennas and inhomogeneous bodies. If the antennas are positioned into the FDTD-volume, their discretization does not need to agree with the grid of the FDTD. By using the TD-UTD large perfectly conducting plates can be considered efficiently in the solution-procedure. Thus this hybrid method allows time-domain simulations of problems including very different classes of objects, applying the respective most appropriate numerical techniques to every object.
Time-Domain Astronomy with the Fermi GBM
Hui, C. M.
2017-01-01
The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument sensitive to energies from 8 keV to 40 MeV. Over the past 8 years of operation, the GBM has detected over 240 gamma-ray bursts per year and provided timely GCN notices with localization to few-degree accuracy for follow-up observations. In addition to GRBs, Galactic transients, solar flares, and terrestrial gamma-ray flashes have also been observed. In recent years we have also been searching the continuous GBM data for electromagnetic counterpart to astrophysical neutrinos and gravitational wave events, as these are believed to be associated with gamma-ray bursts. With continuous data downlink every few hours and a temporal resolution of 2 microseconds, GBM is well suited for observing transients and supporting EM follow-up in the era of multi-messenger astronomy.
Time-Domain Analysis of Coupled Carbon Nano tube Interconnects
International Nuclear Information System (INIS)
Fathi, D.
2014-01-01
This paper describes a new method for the analysis of coupling effects including the crosstalk effects between two driven coupled single-walled carbon nano tubes (SWCNTs) and the intertalk effects between two neighboring shells in a multi walled carbon nano tube (MWCNT), based on transmission line circuit modeling. Using rigorous calculations, a new parametric transfer function has been obtained for the analysis of the impact of aggressor line on the victim line, which depends on the various coupling parameters such as the mutual inductance, the coupling capacitance, and the tunneling resistance. The influences of various parameters such as the contact resistance and the switching factor on the time behavior of coupling effects between the two coupled CNTs and an important effect named “crosstalk-induced delay” are studied and analyzed
International Nuclear Information System (INIS)
Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M.; Kirsten, Lars; Cimalla, Peter; Koch, Edmund
2017-01-01
We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Energy Technology Data Exchange (ETDEWEB)
Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M. [Technische Universitaet Dresden, Institute of Applied Physics and Center for Advancing Electronics Dresden (cfaed), Dresden (Germany); Kirsten, Lars; Cimalla, Peter; Koch, Edmund [Technische Universitaet Dresden, Faculty of Medicine Carl Gustav Carus, Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden (Germany)
2017-08-15
We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Li, Ping; Shi, Yifei; Jiang, Lijun; Bagci, Hakan
2014-01-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer's shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2017-01-01
In this paper, a discontinuous Galerkin time-domain (DGTD) method is developed to analyze the power-ground planes taking into account the decoupling capacitors. In the presence of decoupling capacitors, the whole physical system can be split
On the mixed discretization of the time domain magnetic field integral equation
Ulku, Huseyin Arda; Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco P.; Bagci, Hakan
2012-01-01
Time domain magnetic field integral equation (MFIE) is discretized using divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming Buffa-Christiansen (BC) functions as spatial basis and testing functions, respectively. The resulting mixed
Valdé s, Felipe; Andriulli, Francesco P.; Bagci, Hakan; Michielssen, Eric
2013-01-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase I
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a high speed automated time domain terahertz computed axial tomography (TD-THz CT) non destructive...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase II
National Aeronautics and Space Administration — In this Phase 2 project, we propose to develop, construct, and deliver to NASA a computed axial tomography time-domain terahertz (CT TD-THz) non destructive...
Zhang, Xiao-bo; Tan, Jun; Song, Peng; Li, Jin-shan; Xia, Dong-ming; Liu, Zhao-lun
2017-01-01
The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge storage consumption in the gradient preconditioning algorithms based on Hessian matrices in time-domain full waveform inversion (FWI), but the accuracy
Ulku, Huseyin Arda; Sayed, Sadeed Bin; Bagci, Hakan
2014-01-01
solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation
Fast damage imaging using the time-reversal technique in the frequency–wavenumber domain
International Nuclear Information System (INIS)
Zhu, R; Huang, G L; Yuan, F G
2013-01-01
The time-reversal technique has been successfully used in structural health monitoring (SHM) for quantitative imaging of damage. However, the technique is very time-consuming when it is implemented in the time domain. In this paper, we study the technique in the frequency–wavenumber (f–k) domain for fast real-time imaging of multiple damage sites in plates using scattered flexural plate waves. Based on Mindlin plate theory, the time reversibility of dispersive flexural waves in an isotropic plate is theoretically investigated in the f–k domain. A fast damage imaging technique is developed by using the cross-correlation between the back-propagated scattered wavefield and the incident wavefield in the frequency domain. Numerical simulations demonstrate that the proposed technique cannot only localize multiple damage sites but also potentially identify their sizes. Moreover, the time-reversal technique in the f–k domain is about two orders of magnitude faster than the method in the time domain. Finally, experimental testing of an on-line SHM system with a sparse piezoelectric sensor array is conducted for fast multiple damage identification using the proposed technique. (paper)
Perturbative evolution of particle orbits around Kerr black holes: time-domain calculation
Energy Technology Data Exchange (ETDEWEB)
Lopez-Aleman, Ramon [Physical Sciences Department, University of Puerto Rico-Rio Piedras, San Juan, PR 00931 (Puerto Rico); Khanna, Gaurav [Natural Science Division, Long Island University, Southampton, NY 11968 (United States); Pullin, Jorge [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States)
2003-07-21
We consider the problem of the gravitational waves produced by a particle of negligible mass orbiting a Kerr black hole. We treat the Teukolsky perturbation equation in the time domain numerically as a 2 + 1 partial differential equation. We model the particle by smearing the singularities in the source term by the use of narrow Gaussian distributions. We have been able to reproduce earlier results for equatorial circular orbits that were computed using the frequency-domain formalism. The time-domain approach is however geared for a more general evolution, for instance of nearly geodesic orbits under the effects of radiation reaction.
Perturbative evolution of particle orbits around Kerr black holes: time-domain calculation
International Nuclear Information System (INIS)
Lopez-Aleman, Ramon; Khanna, Gaurav; Pullin, Jorge
2003-01-01
We consider the problem of the gravitational waves produced by a particle of negligible mass orbiting a Kerr black hole. We treat the Teukolsky perturbation equation in the time domain numerically as a 2 + 1 partial differential equation. We model the particle by smearing the singularities in the source term by the use of narrow Gaussian distributions. We have been able to reproduce earlier results for equatorial circular orbits that were computed using the frequency-domain formalism. The time-domain approach is however geared for a more general evolution, for instance of nearly geodesic orbits under the effects of radiation reaction
Kelbert, Anna; Balch, Christopher C.; Pulkkinen, Antti; Egbert, Gary D.; Love, Jeffrey J.; Rigler, E. Joshua; Fujii, Ikuko
2017-07-01
Geoelectric fields at the Earth's surface caused by magnetic storms constitute a hazard to the operation of electric power grids and related infrastructure. The ability to estimate these geoelectric fields in close to real time and provide local predictions would better equip the industry to mitigate negative impacts on their operations. Here we report progress toward this goal: development of robust algorithms that convolve a magnetic storm time series with a frequency domain impedance for a realistic three-dimensional (3-D) Earth, to estimate the local, storm time geoelectric field. Both frequency domain and time domain approaches are presented and validated against storm time geoelectric field data measured in Japan. The methods are then compared in the context of a real-time application.
Microprocessor-controlled time domain reflectometer for dynamic shock position measurements
International Nuclear Information System (INIS)
Virchow, C.F.; Conrad, G.E.; Holt, D.M.; Hodson, E.K.
1980-01-01
Time-domain reflectometry is used in a novel way to measure dynamically shock propagation in various media. The primary component in this measurement system is a digital time domain reflectometer, which uses local intelligence, a Motorola 6800 microprocessor, to make the unit adaptable and versatile. The recorder, its operating theory and its method of implementation are described and typical data are reviewed. Applications include nuclear explosion yield estimates and explosive energy flow measurements
Windowing of THz time-domain spectroscopy signals: A study based on lactose
Vázquez-Cabo, José; Chamorro-Posada, Pedro; Fraile-Peláez, Francisco Javier; Rubiños-López, Óscar; López-Santos, José María; Martín-Ramos, Pablo
2016-05-01
Time-domain spectroscopy has established itself as a reference method for determining material parameters in the terahertz spectral range. This procedure requires the processing of the measured time-domain signals in order to estimate the spectral data. In this work, we present a thorough study of the properties of the signal windowing, a step previous to the parameter extraction algorithm, that permits to improve the accuracy of the results. Lactose has been used as sample material in the study.
Real-time all-optical OFDM transmission system based on time-domain optical fourier transformation
DEFF Research Database (Denmark)
Guan, Pengyu; Kong, Deming; Røge, Kasper Meldgaard
2014-01-01
We propose a novel simple all-optical OFDM transmission system based on time-domain OFT using time-lenses. A real-time 160 Gbit/s DPSK OFDM transmission with 16 decorrelated data subcarriers is successfully demonstrated over 100 km....
Towards early detection of age-related macular degeneration with tetracyclines and FLIM
Szmacinski, Henryk; Hegde, Kavita; Zeng, Hui-Hui; Eslami, Katayoun; Puche, Adam; Lakowicz, Joseph R.; Lengyel, Imre; Thompson, Richard B.
2018-02-01
Recently, we discovered microscopic spherules of hydroxyapatite (HAP) in aged human sub-retinal pigment epithelial (sub-RPE) deposits in the retinas of aged humans (PMID: 25605911), and developed evidence that the spherules may act to nucleate the growth of sub-RPE deposits such as drusen. Drusen are clinical hallmarks of age-related macular degeneration (AMD). We found that tetracycline-family antibiotics, long known to stain HAP in teeth and bones, also stained the HAP spherules, but in general the HAP-bound fluorescence excitation and emission spectra overlapped with the well-known autofluorescence of the RPE overlying drusen, making them difficult to resolve. However, we also found that certain tetracyclines exhibited substantial increases in fluorescence lifetime upon binding to HAP, and moreover these lifetimes were substantially greater than those previously observed (Dysli, et al., 2014) for autofluorescence in the human retina in vivo. Thus we were able to image the HAP spherules by fluorescence lifetime imaging microscopy (FLIM) in cadaveric retinas of aged humans. These findings suggest that FLIM imaging of tetracycline binding to HAP could become a diagnostic tool for the development and progression of AMD.
MULTILOOP PI CONTROLLER FOR ACHIEVING SIMULTANEOUS TIME AND FREQUENCY DOMAIN SPECIFICATIONS
Directory of Open Access Journals (Sweden)
M. SENTHILKUMAR
2015-08-01
Full Text Available Most of the controllers in control system are designed to satisfy either time domain or frequency domain specifications. This work presents the computation of a multiloop PI controller for achieving time and frequency domain specifications simultaneously. The desired time and frequency domain measures are to be specified initially to the design. To obtain the desired value of the performance measures the graphical relationship between the PI controller and the performance criteria is given. Thus by using graphical method a set of PI controller parameters to meet the desired performance measures are obtained in an effective and simpler way. The coupled tank has become a classic design of control engineering for multivariable process. The proposed control strategy has been implemented in the same coupled tank process and validated through simulation studies.
Comparison of Cole-Cole and Constant Phase Angle modeling in time-domain induced polarization
DEFF Research Database (Denmark)
Lajaunie, Myriam; Maurya, Pradip Kumar; Fiandaca, Gianluca
The Cole-Cole model and the constant phase angle (CPA) model are two prevailing phenomenological descriptions of the induced polarization (IP), used for both frequency domain (FD) and time domain (TD) modeling. The former one is a 4-parameter description, while the latest one involves only two......, forward modeling of quadrupolar sequences on 1D and 2D heterogeneous CPA models shows that the CPA decays differ among each other only by a multiplication factor. Consequently, the inspection of field data in log-log plots gives insight on the modeling needed for fitting them: the CPA inversion cannot...... is reflected in TDIP data, and therefore, at identifying (1) if and when it is possible to distinguish, in time domain, between a Cole-Cole description and a CPA one, and (2) if features of time domain data exist in order to know, from a simple data inspection, which model will be the most adapted to the data...
Numerical simulation of electromagnetic wave propagation using time domain meshless method
International Nuclear Information System (INIS)
Ikuno, Soichiro; Fujita, Yoshihisa; Itoh, Taku; Nakata, Susumu; Nakamura, Hiroaki; Kamitani, Atsushi
2012-01-01
The electromagnetic wave propagation in various shaped wave guide is simulated by using meshless time domain method (MTDM). Generally, Finite Differential Time Domain (FDTD) method is applied for electromagnetic wave propagation simulation. However, the numerical domain should be divided into rectangle meshes if FDTD method is applied for the simulation. On the other hand, the node disposition of MTDM can easily describe the structure of arbitrary shaped wave guide. This is the large advantage of the meshless time domain method. The results of computations show that the damping rate is stably calculated in case with R < 0.03, where R denotes a support radius of the weight function for the shape function. And the results indicate that the support radius R of the weight functions should be selected small, and monomials must be used for calculating the shape functions. (author)
Common-image gathers in the offset domain from reverse-time migration
Zhan, Ge
2014-04-01
Kirchhoff migration is flexible to output common-image gathers (CIGs) in the offset domain by imaging data with different offsets separately. These CIGs supply important information for velocity model updates and amplitude-variation-with-offset (AVO) analysis. Reverse-time migration (RTM) offers more insights into complex geology than Kirchhoff migration by accurately describing wave propagation using the two-way wave equation. But, it has difficulty to produce offset domain CIGs like Kirchhoff migration. In this paper, we develop a method for obtaining offset domain CIGs from RTM. The method first computes the RTM operator of an offset gather, followed by a dot product of the operator and the offset data to form a common-offset RTM image. The offset domain CIGs are then achieved after separately migrating data with different offsets. We generate offset domain CIGs on both the Marmousi synthetic data and 2D Gulf of Mexico real data using this approach. © 2014.
Jia, Shouqing; La, Dongsheng; Ma, Xuelian
2018-04-01
The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.
Time-domain analysis of frequency dependent inertial wave forces on cylinders
DEFF Research Database (Denmark)
Krenk, Steen
2013-01-01
a simple time-domain procedure for the inertial force, in which the frequency dependence is represented via a simple explicit time filter on the wave particle acceleration or velocity. The frequency dependence of the inertia coefficient is known analytically as a function of the wave......-number, and the relevant range of waves shorter than about six times the diameter typically corresponds to deep water waves. This permits a universal non-dimensional frequency representation, that is converted to rational form to provide the relevant filter equation. Simple time-domain simulations demonstrate...... the reduction of the resonant part of the response for natural structural frequencies above the dominating wave frequency....
Lidke, D.S.; Nagy, P.; Barisas, B.G.; Heintzmann, R.; Post, Janine Nicole; Lidke, K.A.; Clayton, A.H.A.; Arndt-jovin, D.J.; Jovin, T.M.
2003-01-01
We report the implementation and exploitation of fluorescence polarization measurements, in the form of anisotropy fluorescence lifetime imaging microscopy (rFLIM) and energy migration Förster resonance energy transfer (emFRET) modalities, for wide-field, confocal laser-scanning microscopy and flow
A multi-domain spectral method for time-fractional differential equations
Chen, Feng; Xu, Qinwu; Hesthaven, Jan S.
2015-07-01
This paper proposes an approach for high-order time integration within a multi-domain setting for time-fractional differential equations. Since the kernel is singular or nearly singular, two main difficulties arise after the domain decomposition: how to properly account for the history/memory part and how to perform the integration accurately. To address these issues, we propose a novel hybrid approach for the numerical integration based on the combination of three-term-recurrence relations of Jacobi polynomials and high-order Gauss quadrature. The different approximations used in the hybrid approach are justified theoretically and through numerical examples. Based on this, we propose a new multi-domain spectral method for high-order accurate time integrations and study its stability properties by identifying the method as a generalized linear method. Numerical experiments confirm hp-convergence for both time-fractional differential equations and time-fractional partial differential equations.
Analysis of noise in energy-dispersive spectrometers using time-domain methods
Goulding, F S
2002-01-01
This paper presents an integrated time domain approach to the optimization of the signal-to-noise ratio in all spectrometer systems that contain a detector that converts incoming quanta of radiation into electrical pulse signals that are amplified and shaped by an electronic pulse shaper. It allows analysis of normal passive pulse shapers as well as time-variant systems where switching of shaping elements occurs in synchronism with the signal. It also deals comfortably with microcalorimeters (sometimes referred to as bolometers), where noise-determining elements, such as the temperature-sensing element's resistance and temperature, change with time in the presence of a signal. As part of the purely time-domain approach, a new method of calculating the Johnson noise in resistors using only the statistics of electron motion is presented. The result is a time-domain analog of the Nyquist formula.
Impact of non-white noises in pulse amplitude measurements: a time-domain approach
International Nuclear Information System (INIS)
Pullia, A.
1998-01-01
The contribution of the 1/f-noise to the spectral line broadening in pulse amplitude measurements is derived with a time-domain analysis. The known time-domain relationships which provide the contributions of the series and parallel white noises are generalised for the case of 1/f and other typical non-white noises, by using the fractional derivative of either the system impulse response (time-invariant linear filters) or its weight function folded (time-variant linear filters). It is shown that a time-domain approach is also effective to determine the contribution of Lorentzian noises. A simple rule suitable to derive numerically the fractional derivative is given, which permits to calculate the effect of non-white noises even when the filter impulse response is not known analytically but only in sampled form. (orig.)
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
Electromagnetic Field Theory in (N+1)-Space-Time : AModern Time-Domain Tensor/Array Introduction
De Hoop, A.T.
2012-01-01
In this paper, a modern time-domain introduction is presented for electromagnetic field theory in (N+1)-spacetime. It uses a consistent tensor/array notation that accommodates the description of electromagnetic phenomena in N-dimensional space (plus time), a requirement that turns up in present-day
Time domain calculation of connector loads of a very large floating structure
Gu, Jiayang; Wu, Jie; Qi, Enrong; Guan, Yifeng; Yuan, Yubo
2015-06-01
Loads generated after an air crash, ship collision, and other accidents may destroy very large floating structures (VLFSs) and create additional connector loads. In this study, the combined effects of ship collision and wave loads are considered to establish motion differential equations for a multi-body VLFS. A time domain calculation method is proposed to calculate the connector load of the VLFS in waves. The Longuet-Higgins model is employed to simulate the stochastic wave load. Fluid force and hydrodynamic coefficient are obtained with DNV Sesam software. The motion differential equation is calculated by applying the time domain method when the frequency domain hydrodynamic coefficient is converted into the memory function of the motion differential equation of the time domain. As a result of the combined action of wave and impact loads, high-frequency oscillation is observed in the time history curve of the connector load. At wave directions of 0° and 75°, the regularities of the time history curves of the connector loads in different directions are similar and the connector loads of C1 and C2 in the X direction are the largest. The oscillation load is observed in the connector in the Y direction at a wave direction of 75° and not at 0°. This paper presents a time domain calculation method of connector load to provide a certain reference function for the future development of Chinese VLFS
Jang, Hae-Won; Ih, Jeong-Guon
2012-04-01
The time domain boundary element method (BEM) is associated with numerical instability that typically stems from the time marching scheme. In this work, a formulation of time domain BEM is derived to deal with all types of boundary conditions adopting a multi-input, multi-output, infinite impulse response structure. The fitted frequency domain impedance data are converted into a time domain expression as a form of an infinite impulse response filter, which can also invoke a modeling error. In the calculation, the response at each time step is projected onto the wave vector space of natural radiation modes, which can be obtained from the eigensolutions of the single iterative matrix. To stabilize the computation, unstable oscillatory modes are nullified, and the same decay rate is used for two nonoscillatory modes. As a test example, a transient sound field within a partially lined, parallelepiped box is used, within which a point source is excited by an octave band impulse. In comparison with the results of the inverse Fourier transform of a frequency domain BEM, the average of relative difference norm in the stabilized time response is found to be 4.4%.
Marks, Gary N.
2016-01-01
Multi-domain and longitudinal studies of student achievement routinely find moderate to strong correlations across achievement domains and even stronger within-domain correlations over time. The purpose of this study is to examine the sources of these patterns analysing student achievement in 5 domains across Years 3, 5 and 7. The analysis is of…
Solving the Schroedinger equation using the finite difference time domain method
International Nuclear Information System (INIS)
Sudiarta, I Wayan; Geldart, D J Wallace
2007-01-01
In this paper, we solve the Schroedinger equation using the finite difference time domain (FDTD) method to determine energies and eigenfunctions. In order to apply the FDTD method, the Schroedinger equation is first transformed into a diffusion equation by the imaginary time transformation. The resulting time-domain diffusion equation is then solved numerically by the FDTD method. The theory and an algorithm are provided for the procedure. Numerical results are given for illustrative examples in one, two and three dimensions. It is shown that the FDTD method accurately determines eigenfunctions and energies of these systems
Bécares, Laia; Zhang, Nan
2018-01-01
Abstract Experiencing discrimination is associated with poor mental health, but how cumulative experiences of perceived interpersonal discrimination across attributes, domains, and time are associated with mental disorders is still unknown. Using data from the Study of Women’s Health Across the Nation (1996–2008), we applied latent class analysis and generalized linear models to estimate the association between cumulative exposure to perceived interpersonal discrimination and older women’s mental health. We found 4 classes of perceived interpersonal discrimination, ranging from cumulative exposure to discrimination over attributes, domains, and time to none or minimal reports of discrimination. Women who experienced cumulative perceived interpersonal discrimination over time and across attributes and domains had the highest risk of depression (Center for Epidemiologic Studies Depression Scale score ≥16) compared with women in all other classes. This was true for all women regardless of race/ethnicity, although the type and severity of perceived discrimination differed across racial/ethnic groups. Cumulative exposure to perceived interpersonal discrimination across attributes, domains, and time has an incremental negative long-term association with mental health. Studies that examine exposure to perceived discrimination due to a single attribute in 1 domain or at 1 point in time underestimate the magnitude and complexity of discrimination and its association with health. PMID:29036550
OpenPSTD : The open source implementation of the pseudospectral time-domain method
Krijnen, T.; Hornikx, M.C.J.; Borkowski, B.
2014-01-01
An open source implementation of the pseudospectral time-domain method for the propagation of sound is presented, which is geared towards applications in the built environment. Being a wavebased method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory
Reflection terahertz time-domain imaging for analysis of an 18th century neoclassical easel painting
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Filtenborg, Troels; Fukunaga, Kaori
2015-01-01
Terahertz time-domain imaging (THz-TDI) has been applied for imaging a hidden portrait and other subsurfacecomposition layers of an 18th century (18C) easel painting by Nicolai Abildgaard, the most important 18CDanish neoclassical painter of historical and mythological subjects. For the first time...
Time-domain incomplete Gauss-Newton full-waveform inversion of Gulf of Mexico data
AlTheyab, Abdullah; Wang, Xin; Schuster, Gerard T.
2013-01-01
We apply the incomplete Gauss-Newton full-waveform inversion (TDIGN-FWI) to Gulf of Mexico (GOM) data in the space-time domain. In our application, iterative least-squares reverse-time migration (LSRTM) is used to estimate the model update at each
Measuring the Moisture Content of Green Wood Using Time Domain Reflectometry
Laurence Schimleck; Kim Love-Myers; Joe Sanders; Heath Raybon; Richard Daniels; Jerry Mahon; Edward Andrews; Erik Schilling
2011-01-01
The responsible usage of water by facilities that rely on wet log storage in the southern United States has become an issue of great importance as restrictions on water usage have grown in recent years. In order to learn about the dynamics of moisture content in wet-stored logs over time, it is necessary to conduct continuous monitoring of log piles. Time domain...
Estimating primary production from oxygen time series: A novel approach in the frequency domain
Cox, T.J.S.; Maris, T.; Soetaert, K.; Kromkamp, J.C.; Meire, P.; Meysman, F.J.R.
2015-01-01
Based on an analysis in the frequency domain of the governing equation of oxygen dynamics in aquatic systems, we derive a new method for estimating gross primary production (GPP) from oxygen time series. The central result of this article is a relation between time averaged GPP and the amplitude of
A wavelet-based PWTD algorithm-accelerated time domain surface integral equation solver
Liu, Yang; Yucel, Abdulkadir C.; Gilbert, Anna C.; Bagci, Hakan; Michielssen, Eric
2015-01-01
© 2015 IEEE. The multilevel plane-wave time-domain (PWTD) algorithm allows for fast and accurate analysis of transient scattering from, and radiation by, electrically large and complex structures. When used in tandem with marching-on-in-time (MOT
Nonlinear behavior in the time domain in argon atmospheric dielectric-barrier discharges
International Nuclear Information System (INIS)
Shi Hong; Wang Yanhui; Wang Dezhen
2008-01-01
A vast majority of nonlinear behavior in atmospheric pressure discharges has so far been studied in the space domain, and their time-domain characters are often believed to exact the periodicity of the externally applied voltage. In this paper, based on one-dimensional fluid mode, we study complex nonlinear behavior in the time domain in argon atmospheric dielectric-barrier discharges at very broad frequency range from kilohertz to megahertz. Under certain conditions, the discharge not only can be driven to chaos from time-periodic state through period-doubling bifurcation, but also can return stable periodic motion from chaotic state through an inverse period-doubling bifurcation sequence. Upon changing the parameter the discharge undergoes alternatively chaotic and periodic behavior. Some periodic windows embedded in chaos, as well as the secondary bifurcation occurring in the periodic windows can also be observed. The corresponding discharge characteristics are investigated.
Optimal time-domain combination of the two calibrated output quadratures of GEO 600
International Nuclear Information System (INIS)
Hewitson, M; Grote, H; Hild, S; Lueck, H; Ajith, P; Smith, J R; Strain, K A; Willke, B; Woan, G
2005-01-01
GEO 600 is an interferometric gravitational wave detector with a 600 m arm-length and which uses a dual-recycled optical configuration to give enhanced sensitivity over certain frequencies in the detection band. Due to the dual-recycling, GEO 600 has two main output signals, both of which potentially contain gravitational wave signals. These two outputs are calibrated to strain using a time-domain method. In order to simplify the analysis of the GEO 600 data set, it is desirable to combine these two calibrated outputs to form a single strain signal that has optimal signal-to-noise ratio across the detection band. This paper describes a time-domain method for doing this combination. The method presented is similar to one developed for optimally combining the outputs of two colocated gravitational wave detectors. In the scheme presented in this paper, some simplifications are made to allow its implementation using time-domain methods
Progress in parallel implementation of the multilevel plane wave time domain algorithm
Liu, Yang
2013-07-01
The computational complexity and memory requirements of classical schemes for evaluating transient electromagnetic fields produced by Ns dipoles active for Nt time steps scale as O(NtN s 2) and O(Ns 2), respectively. The multilevel plane wave time domain (PWTD) algorithm [A.A. Ergin et al., Antennas and Propagation Magazine, IEEE, vol. 41, pp. 39-52, 1999], viz. the extension of the frequency domain fast multipole method (FMM) to the time domain, reduces the above costs to O(NtNslog2Ns) and O(Ns α) with α = 1.5 for surface current distributions and α = 4/3 for volumetric ones. Its favorable computational and memory costs notwithstanding, serial implementations of the PWTD scheme unfortunately remain somewhat limited in scope and ill-suited to tackle complex real-world scattering problems, and parallel implementations are called for. © 2013 IEEE.
On the initial condition problem of the time domain PMCHWT surface integral equation
Uysal, Ismail Enes
2017-05-13
Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced properly. This problem can be remedied by solving the time integral of the surface integral for auxiliary currents that are defined to be the time derivatives of the equivalent currents. Then the equivalent currents are obtained by numerically differentiating the auxiliary ones. In this work, this approach is applied to the marching on-in-time solution of the time domain Poggio-Miller-Chan-Harrington-Wu-Tsai surface integral equation enforced on dispersive/plasmonic scatterers. Accuracy of the proposed method is demonstrated by a numerical example.
Forooghian, Farzin; Cukras, Catherine; Meyerle, Catherine B; Chew, Emily Y; Wong, Wai T
2008-10-01
To evaluate macular thickness and volume measurements and their intrasession repeatability in two optical coherence tomography (OCT) systems: the Stratus OCT, a time domain system, and the Cirrus HD-OCT, a spectral domain system (both by Carl Zeiss Meditec, Inc., Dublin, CA), in the context of diabetic macular edema (DME). Thirty-three eyes of 33 diabetic patients with clinically significant macular edema (CSME) were scanned in a single session by a single operator on both OCT systems. Macular thickness measurements of nine standard macular subfields and total macular volume were obtained and analyzed. Bland-Altman plots were constructed to assess agreement in macular measurements. Intraclass correlation coefficients (ICCs), coefficients of repeatability (CR(W)), and coefficients of variation (CV(W)) were used to assess intrasession repeatability. Macular thickness in nine retinal subfields and macular volume were significantly higher in the Cirrus HD-OCT system compared with the Stratus OCT system. Subfield thickness and total volume measurements, respectively, were 30 to 55 microm and 3.2 mm(3) greater for the Cirrus HD-OCT system compared with the Stratus OCT system. Both Stratus OCT and Cirrus HD-OCT systems demonstrated high intrasession repeatability, with overlapping ranges for CR(W), CV(W), and ICC. Repeatability measures (CR(W) and CV(W)) differed significantly between systems in only one of nine subfields (outer temporal subfield). Absolute measures of macular thickness and volume in patients with DME differed significantly in magnitude between the Stratus OCT and Cirrus HD-OCT systems. However, both OCT systems demonstrated high intrasessional repeatability. Although the two systems may not be used interchangeably, they appear equally reliable in generating macular measurements for clinical practice and research.
Ultra-fast HPM detectors improve NAD(P)H FLIM
Becker, Wolfgang; Wetzker, Cornelia; Benda, Aleš
2018-02-01
Metabolic imaging by NAD(P)H FLIM requires the decay functions in the individual pixels to be resolved into the decay components of bound and unbound NAD(P)H. Metabolic information is contained in the lifetime and relative amplitudes of the components. The separation of the decay components and the accuracy of the amplitudes and lifetimes improves substantially by using ultra-fast HPM-100-06 and HPM-100-07 hybrid detectors. The IRF width in combination with the Becker & Hickl SPC-150N and SPC-150NX TCSPC modules is less than 20 ps. An IRF this fast does not interfere with the fluorescence decay. The usual deconvolution process in the data analysis then virtually becomes a simple curve fitting, and the parameters of the NAD(P)H decay components are obtained at unprecedented accuracy.
Energy Technology Data Exchange (ETDEWEB)
Santner, G.
2006-07-01
This short article discusses the experience gained by the local electricity utility in Flims, Switzerland, on reading out its customers' electricity meters via the Internet. The utility uses the cable-TV network - which it also operates - to automatically transmit counter values to the utility's central server. Remote locations send data via the GPRS mobile network. The system provides consumers with monthly bills and allows the utility to plan mains-loading in a better way. The advantages of the system are discussed, in particular with respect to the liberalisation of the electricity market. The extension of the system to provide remote metering of gas and water is also discussed.
Time-resolved magnetization dynamics of cross-tie domain walls in permalloy microstructures
International Nuclear Information System (INIS)
Miguel, J; Kurde, J; Piantek, M; Kuch, W; Sanchez-Barriga, J; Heitkamp, B; Kronast, F; Duerr, H A; Bayer, D; Aeschlimann, M
2009-01-01
We report on a picosecond time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of the evolution of the magnetization components of a microstructured permalloy platelet comprising three cross-tie domain walls. A laser-excited photoswitch has been used to apply a triangular 80 Oe, 160 ps magnetic pulse. Micromagnetic calculations agree well with the experimental results, both in time and frequency, illustrating the large angle precession in the magnetic domains with magnetization perpendicular to the applied pulse, and showing how the magnetic vortices revert their core magnetization while the antivortices remain unaffected.
DEFF Research Database (Denmark)
Mackenzie, David; Buron, Jonas Christian Due; Bøggild, Peter
2016-01-01
We perform contactless full-wafer maps of the electrical conductance of a 4-inch wafer of single-layer CVD graphene using terahertz time-domain spectroscopy both before and after deposition of metal contacts and fabrication of devices via laser ablation. We find that there is no significant change...... in the measured conductance of graphene before and after device fabrication. We also show that precise terahertz time-domain spectroscopy can be performed when the beam spot is at sufficient distance (>1.2 mm) from metal contacts....
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe
2013-05-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
Nonlinear System Identification via Basis Functions Based Time Domain Volterra Model
Directory of Open Access Journals (Sweden)
Yazid Edwar
2014-07-01
Full Text Available This paper proposes basis functions based time domain Volterra model for nonlinear system identification. The Volterra kernels are expanded by using complex exponential basis functions and estimated via genetic algorithm (GA. The accuracy and practicability of the proposed method are then assessed experimentally from a scaled 1:100 model of a prototype truss spar platform. Identification results in time and frequency domain are presented and coherent functions are performed to check the quality of the identification results. It is shown that results between experimental data and proposed method are in good agreement.
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe; Ghaffari-Miab, Mohsen; Andriulli, Francesco P.; Cools, Kristof; Michielssen,
2013-01-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
Nonlinear system identification NARMAX methods in the time, frequency, and spatio-temporal domains
Billings, Stephen A
2013-01-01
Nonlinear System Identification: NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains describes a comprehensive framework for the identification and analysis of nonlinear dynamic systems in the time, frequency, and spatio-temporal domains. This book is written with an emphasis on making the algorithms accessible so that they can be applied and used in practice. Includes coverage of: The NARMAX (nonlinear autoregressive moving average with exogenous inputs) modelThe orthogonal least squares algorithm that allows models to be built term by
Time-resolved magnetization dynamics of cross-tie domain walls in permalloy microstructures
Energy Technology Data Exchange (ETDEWEB)
Miguel, J; Kurde, J; Piantek, M; Kuch, W [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany); Sanchez-Barriga, J; Heitkamp, B; Kronast, F; Duerr, H A [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany); Bayer, D; Aeschlimann, M, E-mail: jorge.miguel@fu-berlin.d [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger Strasse 46, D-67663 Kaiserslautern (Germany)
2009-12-02
We report on a picosecond time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of the evolution of the magnetization components of a microstructured permalloy platelet comprising three cross-tie domain walls. A laser-excited photoswitch has been used to apply a triangular 80 Oe, 160 ps magnetic pulse. Micromagnetic calculations agree well with the experimental results, both in time and frequency, illustrating the large angle precession in the magnetic domains with magnetization perpendicular to the applied pulse, and showing how the magnetic vortices revert their core magnetization while the antivortices remain unaffected.
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics
Gedney, Stephen
2011-01-01
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics provides a comprehensive tutorial of the most widely used method for solving Maxwell's equations -- the Finite Difference Time-Domain Method. This book is an essential guide for students, researchers, and professional engineers who want to gain a fundamental knowledge of the FDTD method. It can accompany an undergraduate or entry-level graduate course or be used for self-study. The book provides all the background required to either research or apply the FDTD method for the solution of Maxwell's equations to p
DWDM-TO-OTDM Conversion by Time-Domain Optical Fourier Transformation
DEFF Research Database (Denmark)
Mulvad, Hans Christian Hansen; Hu, Hao; Galili, Michael
2011-01-01
We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated.......We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated....
Development and application of dispersive soft ferrite models for time-domain simulation
International Nuclear Information System (INIS)
DeFord, J.F.; Kamin, G.; Craig, G.D.; Walling, L.
1992-01-01
Ferrite has a variety of applications in accelerator components, and the capability to model this magnetic material in the time domain is an important adjunct to currently available accelerator modeling tool. We describe in this report a material model we have developed for the magnetic characteristics of PE11BL, the ferrite found in the ETA-II (Experimental Test Accelerator-II) induction module. This model, which includes the important magnetic dispersion effects found in most soft ferrites, has been implemented in 1-D and 2-D finite-difference time-domain (FDTD) electromagnetic simulators, and comparisons with analytic and experimental results are presented
Nucleation of holin domains and holes optimizes lysis timing of E. coli by phage λ
Ryan, Gillian; Rutenberg, Andrew
2007-03-01
Holin proteins regulate the precise scheduling of Escherichia coli lysis during infection by bacteriophage λ. Inserted into the host bacterium's inner membrane during infection, holins aggregate to form rafts and then holes within those rafts. We present a two-stage nucleation model of holin action, with the nucleation of condensed holin domains followed by the nucleation of holes within these domains. Late nucleation of holin rafts leads to a weak dependence of lysis timing on host cell size, though both nucleation events contribute equally to timing errors. Our simulations recover the accurate scheduling observed experimentally, and also suggest that phage-λ lysis of E.coli is optimized.
Shi, Yifei
2013-08-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although \\'relaxed initial conditions,\\' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made \\'invisible\\' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
Shi, Yifei; Bagci, Hakan; Lu, Mingyu
2013-01-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although 'relaxed initial conditions,' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made 'invisible' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
Reduced order for nuclear reactor model in frequency and time domain
International Nuclear Information System (INIS)
Nugroho, D.H.
1997-01-01
In control system theory, a model can be represented by frequency or time domain. In frequency domain, the model was represented by transfer function. in time domain, the model was represented by state space. for the sake of simplification in computation, it is necessary to reduce the model order. the main aim of this research is to find the best in nuclear reactor model. Model order reduction in frequency domain can be done utilizing pole-zero cancellation method; while in time domain utilizing balanced aggregation method the balanced aggregation method was developed by moore (1981). In this paper, the two kinds of method were applied to reduce a nuclear reactor model which was constructed by neutron dynamics and heat transfer equations. to validate that the model characteristics were not change when model order reduction applied, the response was utilized for full and reduced order. it was shown that the nuclear reactor order model can be reduced from order 8 to 2 order 2 is the best order for nuclear reactor model
An investigation of time-dependent domain wall pinning effects in Tb/Fe multilayer thin flms
Phillips, G.N.; O'grady, K.; El-Hilo, M.
2002-01-01
Reverse domain nucleation time measurements have been performed on two Tb/Fe multilayer magneto-optic films exhibiting different degrees of domain wall pinning.A linear relationship between ln (reverse domain nucleation time) and the applied field has been predicted and observed for a sample
Quasi-exact evaluation of time domain MFIE MOT matrix elements
Shi, Yifei
2013-07-01
A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2012-01-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
Quasi-exact evaluation of time domain MFIE MOT matrix elements
Shi, Yifei; Bagci, Hakan; Shanker, Balasubramaniam; Lu, Mingyu; Michielssen, Eric
2013-01-01
A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.
Ulku, Huseyin Arda
2012-09-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
Fast time- and frequency-domain finite-element methods for electromagnetic analysis
Lee, Woochan
Fast electromagnetic analysis in time and frequency domain is of critical importance to the design of integrated circuits (IC) and other advanced engineering products and systems. Many IC structures constitute a very large scale problem in modeling and simulation, the size of which also continuously grows with the advancement of the processing technology. This results in numerical problems beyond the reach of existing most powerful computational resources. Different from many other engineering problems, the structure of most ICs is special in the sense that its geometry is of Manhattan type and its dielectrics are layered. Hence, it is important to develop structure-aware algorithms that take advantage of the structure specialties to speed up the computation. In addition, among existing time-domain methods, explicit methods can avoid solving a matrix equation. However, their time step is traditionally restricted by the space step for ensuring the stability of a time-domain simulation. Therefore, making explicit time-domain methods unconditionally stable is important to accelerate the computation. In addition to time-domain methods, frequency-domain methods have suffered from an indefinite system that makes an iterative solution difficult to converge fast. The first contribution of this work is a fast time-domain finite-element algorithm for the analysis and design of very large-scale on-chip circuits. The structure specialty of on-chip circuits such as Manhattan geometry and layered permittivity is preserved in the proposed algorithm. As a result, the large-scale matrix solution encountered in the 3-D circuit analysis is turned into a simple scaling of the solution of a small 1-D matrix, which can be obtained in linear (optimal) complexity with negligible cost. Furthermore, the time step size is not sacrificed, and the total number of time steps to be simulated is also significantly reduced, thus achieving a total cost reduction in CPU time. The second contribution
International Nuclear Information System (INIS)
Hao Yun-Qi; Ye Qing; Pan Zheng-Qing; Cai Hai-Wen; Qu Rong-Hui
2014-01-01
The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card (DAQ). A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator (LO) in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio (SNR) has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement. (general)
Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics
DEFF Research Database (Denmark)
D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa
2014-01-01
-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...... index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....
THEORETICAL RESEARCH ON HYDRODYNAMICS OF A GEOMETRIC SPAR IN FREQUENCY- AND TIME-DOMAINS
Institute of Scientific and Technical Information of China (English)
WANG Ying; YANG Jian-min; HU Zhi-qiang; XIAO Long-fei
2008-01-01
Considering the coupling effects of the vessel and its riser and mooring system, hydrodynamic analyses of a geometric spar were performed both in frequency- and time-domains. Based on the boundary element method, the 3-D panel model of the geometric spar and the related free water surface model were established, and the first-order and second-order difference-frequency wave loads and other hydrodynamic coefficients were calculated. Frequency domain analysis of the motion Response Amplitude Operators (RAO) and Quadratic Transfer Functions (QTF) and time domain analysis of the response series and spectra in an extreme wave condition were conducted for the coupled system with the mooring lines and risers involved. These analyses were further validated by the physical model test results.
Quantum-corrected plasmonic field analysis using a time domain PMCHWT integral equation
Uysal, Ismail E.
2016-03-13
When two structures are within sub-nanometer distance of each other, quantum tunneling, i.e., electrons "jumping" from one structure to another, becomes relevant. Classical electromagnetic solvers do not directly account for this additional path of current. In this work, an auxiliary tunnel made of Drude material is used to "connect" the structures as a support for this current path (R. Esteban et al., Nat. Commun., 2012). The plasmonic fields on the resulting connected structure are analyzed using a time domain surface integral equation solver. Time domain samples of the dispersive medium Green function and the dielectric permittivities are computed from the analytical inverse Fourier transform applied to the rational function representation of their frequency domain samples.
International Nuclear Information System (INIS)
Hu, Xiao-feng; Chen, Xiang; Wei, Ming
2013-01-01
Shielding effectiveness (SE) of materials of current testing standards is often carried out by using continuous-wave measurement and amplitude-frequency characteristics curve is used to characterize the results. However, with in-depth study of high-power electromagnetic pulse (EMP) interference, it was discovered that only by frequency-domain SE of materials cannot be completely characterized by shielding performance of time-domain pulsed-field. And there is no uniform testing methods and standards of SE of materials against EMP. In this paper, the method of minimum phase transfer function is used to reconstruct shielded time-domain waveform based on the analysis of the waveform reconstruction method. Pulse of plane waves through an infinite planar material is simulated by using CST simulation software. The reconstructed waveform and simulation waveform is compared. The results show that the waveform reconstruction method based on the minimum phase can be well estimated EMP waveform through the infinite planar materials.
CSIR Research Space (South Africa)
Vogt, D
2008-06-01
Full Text Available published borehole radar antennas have achieved directivity by post processing data received in the frequency domain, or by constructing an aperture antenna, where borehole dimensions allowed this. In this paper, a time-domain technique is investigated...
Time-domain representation of frequency-dependent foundation impedance functions
Safak, E.
2006-01-01
Foundation impedance functions provide a simple means to account for soil-structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.
Layered and Laterally Constrained 2D Inversion of Time Domain Induced Polarization Data
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Auken, Esben
description of the transmitter waveform and of the receiver transfer function allowing for a quantitative interpretation of the parameters. The code has been optimized for parallel computation and the inversion time is comparable to codes inverting just for direct current resistivity. The new inversion......In a sedimentary environment, quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. We have developed a new layered and laterally constrained inversion algorithm for time domain induced polarization data. The algorithm is based on the time...... transform of a complex resistivity forward response and the inversion extracts the spectral information of the time domain measures in terms of the Cole-Cole parameters. The developed forward code and inversion algorithm use the full time decay of the induced polarization response, together with an accurate...
Comparison between time-and frequency-domain induced polarisation parameters
CSIR Research Space (South Africa)
Van Schoor, Abraham M
2009-09-01
Full Text Available of mineralised rocks and of the contrast between different rock types. It is further shown that a multi-frequency (spectral) approach can be used to avoid this pitfall; similarly, the calculation of different time-domain induced polarisation (IP) parameters...
Pagan Munoz, R.; Hornikx, M.C.J.
The wave-based Fourier Pseudospectral time-domain (Fourier-PSTD) method was shown to be an effective way of modeling outdoor acoustic propagation problems as described by the linearized Euler equations (LEE), but is limited to real-valued frequency independent boundary conditions and predominantly
The finite-difference time-domain method for electromagnetics with Matlab simulations
Elsherbeni, Atef Z
2016-01-01
This book introduces the powerful Finite-Difference Time-Domain method to students and interested researchers and readers. An effective introduction is accomplished using a step-by-step process that builds competence and confidence in developing complete working codes for the design and analysis of various antennas and microwave devices.
Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy
DEFF Research Database (Denmark)
Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup
2016-01-01
The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR), and lin...
CSIR Research Space (South Africa)
Loveday, PW
2007-03-01
Full Text Available Piezoelectric transducers are commonly used to excite waves in elastic waveguides such as pipes, rock bolts and rails. While it is possible to simulate the operation of these transducers attached to the waveguide, in the time domain, using...
Stationary echo canceling in velocity estimation by time-domain cross-correlation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated...
Postural Analysis in Time and Frequency Domains in Patients with Ehlers-Danlos Syndrome
Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo
2011-01-01
The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30 s in two conditions: open eyes (OE) and closed…
Shape optimization for non-Newtonian fluids in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Sokolowski, J.; Stebel, Jan
2014-01-01
Roč. 3, č. 2 (2014), s. 331-348 ISSN 2163-2480 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : shape optimization * time - dependent domain * incompressible viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.373, year: 2014 http://www.aimsciences.org/journals/home.jsp?journalID=25
Non-Causal Time-Domain Filters for Single-Channel Noise Reduction
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Benesty, Jacob; Christensen, Mads Græsbøll
2012-01-01
suppression and signal distortion by allowing the filters to be non-causal. Non-causal time-domain filters require knowledge of the future, and are therefore not directly implementable. If the observed signal is processed in blocks, however, the non-causal filters are implementable. In this paper, we propose...
Dekkers, Birgit L.; Kort, de Daan W.; Grabowska, Katarzyna J.; Tian, Bei; As, Van Henk; Goot, van der Atze Jan
2016-01-01
We present a combined time domain NMR and rheology approach to quantify the water distribution in a phase separated protein blend. The approach forms the basis for a new tool to assess the microstructural properties of phase separated biopolymer blends, making it highly relevant for many food and
Effects of the airwave in time-domain marine controlled-source electromagnetics
Hunziker, J.W.; Slob, E.C.; Mulder, W.
2011-01-01
In marine time-domain controlled-source electromagnetics (CSEM), there are two different acquisition methods: with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave. Illustrations of the electric field as a function of space
Gisolf, J.; Immink, R. V.; van Lieshout, J. J.; Stok, W. J.; Karemaker, J. M.
2005-01-01
Reduction in plasma volume is a major contributor to orthostatic tachycardia and hypotension after spaceflight. We set out to determine time- and frequency-domain baroreflex (BRS) function during preflight baseline and venous occlusion and postflight orthostatic stress, testing the hypothesis that a
Molenaar, P.C.M.
1987-01-01
Outlines a frequency domain analysis of the dynamic factor model and proposes a solution to the problem of constructing a causal filter of lagged factor loadings. The method is illustrated with applications to simulated and real multivariate time series. The latter applications involve topographic
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
-layer structures are analyzed. Results show that this method matches satisfactorily the Nyquist sampling theorem in terms of spatial discretization. By comparing the given results, it is found that the PSTD method outperforms the finite-difference time-domain (FDTD) method in general, especially in terms...
Optimal time-domain technique for pulse width modulation in power electronics
Directory of Open Access Journals (Sweden)
I. Mayergoyz
2018-05-01
Full Text Available Optimal time-domain technique for pulse width modulation is presented. It is based on exact and explicit analytical solutions for inverter circuits, obtained for any sequence of input voltage rectangular pulses. Two optimal criteria are discussed and illustrated by numerical examples.
A time-domain binaural detection model and its predictions temporal-resolution data
Breebaart, D.J.; Par, van de S.L.J.D.E.; Kohlrausch, A.G.
2002-01-01
This paper discusses the application of a time-domain binaural signal-detection model in the context of estimates of the temporal resolution of the binaural auditory system. It is demonstrated that the optimal detector which is present in the model is crucial to account for specific temporal
Non-linear wave loads and ship responses by a time-domain strip theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hydroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented as a Timoshenko beam. Numerical calculations are presented for the S175 Containership...
Non-Linear Wave Loads and Ship responses by a time-domain Strip Theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hyroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented by the Timoshenko beam theory. Numerical calculations are presented for the S175...
Driven by the future : Future time perspective across life domains and cultures
Andre, L.
2018-01-01
Contemplating about the future is inevitable for our life and goal strivings. Consequently, Future Time Perspective (FTP) – individuals’ attitudes towards the future as a motivator for attitudes and behaviors – has been researched across disciplines and life domains. However, little is known about
Continuous performance test assessed with time-domain functional near infrared spectroscopy
Torricelli, Alessandro; Contini, Davide; Spinelli, Lorenzo; Caffini, Matteo; Butti, Michele; Baselli, Giuseppe; Bianchi, Anna M.; Bardoni, Alessandra; Cerutti, Sergio; Cubeddu, Rinaldo
2007-07-01
A time-domain fNIRS multichannel system was used in a sustained attention protocol (continuous performance test) to study activation of the prefrontal cortex. Preliminary results on volounteers show significant activation (decrease in deoxy-hemoglobin and increase in oxy-hemoglobin) in both left and right prefrontal cortex.
Broadband time domain acoustic holography based on the discrete orthonormal S-transform
Zhou, H.; Lopez Arteaga, I.; Nijmeijer, H.; Lim, Kian Meng
2015-01-01
The purpose of this paper is to deal with the problem of nonstationary broadband sound fields more efficiently. A basis function of the discrete orthonormal S-transform (DOST) is used to analyze the measured signal. With respect to the time domain signal in a certain band, DOST leads to a
Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...
Quantitative terahertz time-domain spectroscopy and analysis in chemistry and biology
DEFF Research Database (Denmark)
Jepsen, Peter Uhd
2005-01-01
I will describe how Terahertz Time-Domain Spectroscopy (THz-TDS) can be used for quantitative, broadband spectroscopy in the far-infrared spectral region. Thz-TDS is sensitive to long-range, non-covalent interactions in the condensed phase, for instance intermolecular hydrogen bonding in molecula...
PLASTIQUE: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain
International Nuclear Information System (INIS)
De Stasio, G.; Zema, N.; Antonangeli, F.; Parasassi, T.; Rosato, N.
1991-01-01
PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in the frequency domain. These experiments are extremely valuable sources of informations on the structure and dynamics of molecules. The beamline and some examples of initial data are described
Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain
De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.
1991-06-01
PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.
DEFF Research Database (Denmark)
Hu, Hao; Kong, Deming; Palushani, Evarist
2013-01-01
We demonstrate transmission of a 1.28-Tbaud Nyquist-OTDM signal over a record distance of 100 km with detection by time-domain optical Fourier transformation followed by FEC decoding, resulting in error-free performance for all tributaries....
320 Gb/s Nyquist OTDM received by polarization-insensitive time-domain OFT
DEFF Research Database (Denmark)
Hu, Hao; Kong, Deming; Palushani, Evarist
2014-01-01
We have demonstrated the generation of a 320 Gb/s Nyquist-OTDM signal by rectangular filtering on an RZ-OTDM signal with the filter bandwidth (320 GHz) equal to the baud rate (320 Gbaud) and the reception of such a Nyquist-OTDM signal using polarization-insensitive time-domain optical Fourier tra...
Fra Angelico’s painting technique revealed by terahertz time-domain imaging (THz-TDI)
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Picollo, Marcello; Cucci, Costanza
2016-01-01
We have investigated with terahertz time-domain imaging (THz-TDI) the well-known Lamentation over the dead Christ panel painting (San Marco Museum, Florence) painted by Fra Giovanni Angelico within 1436 and 1441. The investigation provided a better understanding of the construction and gilding te...
OpenPSTD : The open source pseudospectral time-domain method for acoustic propagation
Hornikx, M.C.J.; Krijnen, T.F.; van Harten, L.
2016-01-01
An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in
Energy Technology Data Exchange (ETDEWEB)
Jeannin, P.-Y.; Haeuselmann, P. [Schweizerisches Institut fuer Spelaeologie und Karstkunde SISKA, La Chaux-de-Fonds (Switzerland); Wildberger, A. [Dr. von Moos AG, Geotechnisches Buero, Zuerich (Switzerland)
2007-12-15
This report describes the modelling of the influence of the 'Flimserstein' tunnel on the Lag Tiert karstic spring in Flims, Switzerland. When the tunnel, that provides a by-pass for the mountain village of Flims, was built, a karstic system was broached. As a result, several springs dried up and others had their capacity reduced. Also, the quantity of water available for a local hydropower station was reduced. The report describes how the situation as far as the underground watercourses are concerned was modelled and how exactly the tunnel construction changed the water-quantities at the various springs. The results of the study are presented and discussed and recommendations are made concerning the modelling of such karstic systems.
Methodology for Time-Domain Estimation of Storm-Time Electric Fields Using the 3D Earth Impedance
Kelbert, A.; Balch, C. C.; Pulkkinen, A. A.; Egbert, G. D.; Love, J. J.; Rigler, E. J.; Fujii, I.
2016-12-01
Magnetic storms can induce geoelectric fields in the Earth's electrically conducting interior, interfering with the operations of electric-power grid industry. The ability to estimate these electric fields at Earth's surface in close to real-time and to provide local short-term predictions would improve the ability of the industry to protect their operations. At any given time, the electric field at the Earth's surface is a function of the time-variant magnetic activity (driven by the solar wind), and the local electrical conductivity structure of the Earth's crust and mantle. For this reason, implementation of an operational electric field estimation service requires an interdisciplinary, collaborative effort between space science, real-time space weather operations, and solid Earth geophysics. We highlight in this talk an ongoing collaboration between USGS, NOAA, NASA, Oregon State University, and the Japan Meteorological Agency, to develop algorithms that can be used for scenario analyses and which might be implemented in a real-time, operational setting. We discuss the development of a time domain algorithm that employs discrete time domain representation of the impedance tensor for a realistic 3D Earth, known as the discrete time impulse response (DTIR), convolved with the local magnetic field time series, to estimate the local electric field disturbances. The algorithm is validated against measured storm-time electric field data collected in the United States and Japan. We also discuss our plans for operational real-time electric field estimation using 3D Earth impedances.
A time domain inverse dynamic method for the end point tracking control of a flexible manipulator
Kwon, Dong-Soo; Book, Wayne J.
1991-01-01
The inverse dynamic equation of a flexible manipulator was solved in the time domain. By dividing the inverse system equation into the causal part and the anticausal part, we calculated the torque and the trajectories of all state variables for a given end point trajectory. The interpretation of this method in the frequency domain was explained in detail using the two-sided Laplace transform and the convolution integral. The open loop control of the inverse dynamic method shows an excellent result in simulation. For real applications, a practical control strategy is proposed by adding a feedback tracking control loop to the inverse dynamic feedforward control, and its good experimental performance is presented.
Gastric Emptying Assessment in Frequency and Time Domain Using Bio-impedance: Preliminary Results
Huerta-Franco, R.; Vargas-Luna, M.; Hernández, E.; Córdova, T.; Sosa, M.; Gutiérrez, G.; Reyes, P.; Mendiola, C.
2006-09-01
The impedance assessment to measure gastric emptying and in general gastric activity has been reported since 1985. The physiological interpretation of these measurements, is still under research. This technique usually uses a single frequency, and the conductivity parameter. The frequency domain and the Fourier analysis of the time domain behavior of the gastric impedance in different gastric conditions (fasting state, and after food administration) has not been explored in detail. This work presents some insights of the potentiality of these alternative methodologies to measure gastric activity.
Measurement of electron paramagnetic resonance using terahertz time-domain spectroscopy.
Kozuki, Kohei; Nagashima, Takeshi; Hangyo, Masanori
2011-12-05
We present a frequency-domain electron spin resonance (ESR) measurement system using terahertz time-domain spectroscopy. A crossed polarizer technique is utilized to increase the sensitivity in detecting weak ESR signals of paramagnets caused by magnetic dipole transitions between magnetic sublevels. We demonstrate the measurements of ESR signal of paramagnetic copper(II) sulfate pentahydrate with uniaxial anisotropy of the g-factor under magnetic fields up to 10 T. The lineshape of the obtained ESR signals agrees well with the theoretical predictions for a powder sample with the uniaxial anisotropy.
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2013-01-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
Ulku, Huseyin Arda
2013-08-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
International Nuclear Information System (INIS)
Khorasani, A.; Mousavi Shalmani, M. A.; Piervali Bieranvand, N.
2011-01-01
An accurate, precise, fast and ease as well as the ability for measurements in depth are the characteristics that are desirable in measuring soil moisture methods. To compare methods (time domain reflectometry and capacitance) with neutron scattering for soil water monitoring, an experiment was carried out in a randomized complete block design (Split Split plot) on tomato with three replications on the experimental field of International Atomic Energy Agency (Seibersdorf-Austria). The treatment instruments for the soil moisture monitoring (main factor) consist of neutron gauge, Diviner 2000, time domain reflectometer and an EnviroScan and different irrigation systems (first sub factor) consist of trickle and furrow irrigations and different depths of soil (second sub factor) consist of 0-20, 20-40 and 40-60 cm. The results showed that for the neutron gauge and time domain reflectometer the amount of soil moisture in both of trickle and furrow irrigations were the same, but the significant differences were recorded in Diviner 2000 and EnviroScan measurements. The results of this study showed that the neutron gauge is an acceptable and reliable means with the modern technology, with a precision of ±2 mm in 450 mm soil water to a depth of 1.5 meter and can be considered as the most practical method for measuring soil moisture profiles and irrigation planning program. The time domain reflectometer method in most mineral soils, without the need for calibration, with an accuracy ±0.01m 3 m -3 has a good performance in soil moisture and electrical conductivity measurements. The Diviner 2000 and EnviroScan are not well suitable for the above conditions for several reasons such as much higher soil moisture and a large error measurement and also its sensitivity to the soil gap and to the small change in the soil moisture in comparison with the neutron gauge and the time domain reflectometer methods.
Zhang, Zhendong
2017-07-11
Full waveform inversion for reection events is limited by its linearized update re-quirements given by a process equivalent to migration. Unless the background velocity model is reasonably accurate, the resulting gradient can have an inaccurate update direction leading the inversion to converge what we refer to as local minima of the objective function. In our approach, we consider mild lateral variation in the model, and thus, use a gradient given by the oriented time-domain imaging method. Specifically, we apply the oriented time-domain imaging on the data residual to obtain the geometrical features of the velocity perturbation. After updating the model in the time domain, we convert the perturbation from the time domain to depth using the average velocity. Considering density is constant, we can expand the conventional 1D impedance inversion method to 2D or 3D velocity inversion within the process of full waveform inversion. This method is not only capable of inverting for velocity, but it is also capable of retrieving anisotropic parameters relying on linearized representations of the reection response. To eliminate the cross-talk artifacts between different parameters, we utilize what we consider being an optimal parametrization for this step. To do so, we extend the prestack time-domain migration image in incident angle dimension to incorporate angular dependence needed by the multiparameter inversion. For simple models, this approach provides an efficient and stable way to do full waveform inversion or modified seismic inversion and makes the anisotropic inversion more practicable. The proposed method still needs kinematically accurate initial models since it only recovers the high-wavenumber part as conventional full waveform inversion method does. Results on synthetic data of isotropic and anisotropic cases illustrate the benefits and limitations of this method.
Domain-Specific and Unspecific Reaction Times in Experienced Team Handball Goalkeepers and Novices.
Helm, Fabian; Reiser, Mathias; Munzert, Jörn
2016-01-01
In our everyday environments, we are constantly having to adapt our behavior to changing conditions. Hence, processing information is a fundamental cognitive activity, especially the linking together of perceptual and action processes. In this context, expertise research in the sport domain has concentrated on arguing that superior processing performance is driven by an advantage to be found in anticipatory processes (see Williams et al., 2011, for a review). This has resulted in less attention being paid to the benefits coming from basic internal perceptual-motor processing. In general, research on reaction time (RT) indicates that practicing a RT task leads to an increase in processing speed (Mowbray and Rhoades, 1959; Rabbitt and Banerji, 1989). Against this background, the present study examined whether the speed of internal processing is dependent on or independent from domain-specific motor expertise in unpredictable stimulus-response tasks and in a double stimulus-response paradigm. Thirty male participants (15 team handball goalkeepers and 15 novices) performed domain-unspecific simple or choice stimulus-response (CSR) tasks as well as CSR tasks that were domain-specific only for goalkeepers. As expected, results showed significantly faster RTs for goalkeepers on domain-specific tasks, whereas novices' RTs were more frequently excessively long. However, differences between groups in the double stimulus-response paradigm were not significant. It is concluded that the reported expertise advantage might be due to recalling stored perceptual-motor representations for the domain-specific tasks, implying that experience with (practice of) a motor task explicitly enhances the internal processing of other related domain-specific tasks.
Online Identification of a Mechanical System in the Frequency Domain with Short-Time DFT
Directory of Open Access Journals (Sweden)
Niko Nevaranta
2015-07-01
Full Text Available A proper system identification method is of great importance in the process of acquiring an analytical model that adequately represents the characteristics of the monitored system. While the use of different time-domain online identification techniques has been widely recognized as a powerful approach for system diagnostics, the frequency domain identification techniques have primarily been considered for offline commissioning purposes. This paper addresses issues in the online frequency domain identification of a flexible two-mass mechanical system with varying dynamics, and a particular attention is paid to detect the changes in the system dynamics. An online identification method is presented that is based on a recursive Kalman filter configured to perform like a discrete Fourier transform (DFT at a selected set of frequencies. The experimental online identification results are compared with the corresponding values obtained from the offline-identified frequency responses. The results show an acceptable agreement and demonstrate the feasibility of the proposed identification method.
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2018-01-01
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
Li, Ping
2018-04-13
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
Postural analysis in time and frequency domains in patients with Ehlers-Danlos syndrome.
Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo
2011-01-01
The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30s in two conditions: open eyes (OE) and closed eyes (CE). In order to compare pathological group we acquired in the same conditions a control group composed by 20 healthy participants. The obtained center of pressure (COP) signal was analyzed in time and frequency domain using an AR model. Results revealed differences between pathological and control group: EDS participants pointed out difficulties in controlling COP displacements trying to keep it inside the BOS in AP direction and for this reason increased the use of ML mechanism in order to avoid the risk of fall. Also in CE conditions they demonstrated more difficulties in maintaining posture revealing the proprioceptive system is impaired, due to ligament laxity that characterized EDS participants. Frequency domain analysis showed no differences between the two groups, affirming that the changes in time domain reflected really the impairment to the postural control mechanism and not a different strategy assumed by EDS participants. These data could help in decision-making process to establish a correct rehabilitation approach, based on the reinforcing of muscle tone to supply the ligament laxity in order to prevent risks of falls and its consequences. Copyright © 2010 Elsevier Ltd. All rights reserved.
Numerical results for near surface time domain electromagnetic exploration: a full waveform approach
Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.
2015-12-01
Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two
Causality and associative holography of time-and-space domain events
International Nuclear Information System (INIS)
Rebane, Aleksander
2014-01-01
We consider reference-free associative recall of time-and-space domain holograms of arbitrary non-stationary optical object amplitudes or events. We show that if the probe fragment correlates with the recorded event either in space or in time coordinates or in both, then the hologram faithfully reproduces those missing parts (sub-events) that occur simultaneously or later in time with respect to the probe fragment. However, if a missing sub-event occurred before the fragment used as associative probe, then the hologram will not play this information back due to the time arrow imposed by causality. (paper)
Zaghloul, Mohamed A S; Wang, Mohan; Milione, Giovanni; Li, Ming-Jun; Li, Shenping; Huang, Yue-Kai; Wang, Ting; Chen, Kevin P
2018-04-12
Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores' temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%).
Directory of Open Access Journals (Sweden)
Mohamed A. S. Zaghloul
2018-04-01
Full Text Available Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz, which is 2.63 (3.67 times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%.
Efficient reconstruction of dispersive dielectric profiles using time domain reflectometry (TDR
Directory of Open Access Journals (Sweden)
P. Leidenberger
2006-01-01
Full Text Available We present a numerical model for time domain reflectometry (TDR signal propagation in dispersive dielectric materials. The numerical probe model is terminated with a parallel circuit, consisting of an ohmic resistor and an ideal capacitance. We derive analytical approximations for the capacitance, the inductance and the conductance of three-wire probes. We couple the time domain model with global optimization in order to reconstruct water content profiles from TDR traces. For efficiently solving the inverse problem we use genetic algorithms combined with a hierarchical parameterization. We investigate the performance of the method by reconstructing synthetically generated profiles. The algorithm is then applied to retrieve dielectric profiles from TDR traces measured in the field. We succeed in reconstructing dielectric and ohmic profiles where conventional methods, based on travel time extraction, fail.
Finite-difference time-domain simulation of thermal noise in open cavities
International Nuclear Information System (INIS)
Andreasen, Jonathan; Cao Hui; Taflove, Allen; Kumar, Prem; Cao Changqi
2008-01-01
A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal radiation penetrates the cavity in the grid. The calculated amount of thermal noise in a one-dimensional dielectric cavity recovers the standard result of the quantum Langevin equation in the Markovian regime. Our FDTD simulation also demonstrates that in the non-Markovian regime the buildup of the intracavity noise field depends on the ratio of the cavity photon lifetime to the coherence time of thermal radiation. The advantage of our numerical method is that the thermal noise is introduced in the time domain without prior knowledge of cavity modes
Measuring Time in Sporting Competitions with the Domain-Specific Language EasyTime
Fister Jr., Iztok; Fister, Iztok
2012-01-01
Measuring time in mass sporting competitions is unthinkable manually today because of their long duration and unreliability. Besides, automatic timing devices based on the RFID technology have become cheaper. However, these devices cannot operate stand-alone. To work efficiently, they need a computer timing system for monitoring results. Such system should be capable of processing the incoming events, encoding and assigning results to a individual competitor, sorting results according to the ...
Valdés, Felipe
2013-03-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis functions and a collocation testing procedure, thus allowing for a marching-on-in-time (MOT) solution scheme. Unlike dual-source formulations, single-source equations involve space-time domain operator products, for which spatial discretization techniques developed for standalone operators do not apply. Here, the spatial discretization of the single-source time-domain integral equations is achieved by using the high-order divergence-conforming basis functions developed by Graglia alongside the high-order divergence-and quasi curl-conforming (DQCC) basis functions of Valdés The combination of these two sets allows for a well-conditioned mapping from div-to curl-conforming function spaces that fully respects the space-mapping properties of the space-time operators involved. Numerical results corroborate the fact that the proposed procedure guarantees accuracy and stability of the MOT scheme. © 2012 IEEE.
Time-domain SFG spectroscopy using mid-IR pulse shaping: practical and intrinsic advantages.
Laaser, Jennifer E; Xiong, Wei; Zanni, Martin T
2011-03-24
Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra. © 2011 American Chemical Society
Long, Yuchen
2018-05-15
Protein complex formation has been extensively studied using Förster resonance energy transfer (FRET) measured by Fluorescence Lifetime Imaging Microscopy (FLIM). However, implementing this technology to detect protein interactions in living multicellular organism at single-cell resolution and under native condition is still difficult to achieve. Here we describe the optimization of the labeling conditions to detect FRET-FLIM in living plants. This study exemplifies optimization procedure involving the identification of the optimal position for the labels either at the N or C terminal region and the selection of the bright and suitable, fluorescent proteins as donor and acceptor labels for the FRET study. With an effective optimization strategy, we were able to detect the interaction between the stem cell regulators SHORT-ROOT and SCARECROW at endogenous expression levels in the root pole of living Arabidopsis embryos and developing lateral roots by FRET-FLIM. Using this approach we show that the spatial profile of interaction between two transcription factors can be highly modulated in reoccurring and structurally resembling organs, thus providing new information on the dynamic redistribution of nuclear protein complex configurations in different developmental stages. In principle, our optimization procedure for transcription factor complexes is applicable to any biological system.
A Model-free Approach to Fault Detection of Continuous-time Systems Based on Time Domain Data
Institute of Scientific and Technical Information of China (English)
Ping Zhang; Steven X. Ding
2007-01-01
In this paper, a model-free approach is presented to design an observer-based fault detection system of linear continuoustime systems based on input and output data in the time domain. The core of the approach is to directly identify parameters of the observer-based residual generator based on a numerically reliable data equation obtained by filtering and sampling the input and output signals.
Ulku, Huseyin Arda
2014-07-06
Effects of material nonlinearities on electromagnetic field interactions become dominant as field amplitudes increase. A typical example is observed in plasmonics, where highly localized fields “activate” Kerr nonlinearities. Naturally, time domain solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation easier and the material nonlinearity can be easily accounted for using an auxiliary differential equation (J.H. Green and A. Taflove, Opt. Express, 14(18), 8305-8310, 2006). On the other hand, explicit marching on-in-time (MOT)-based time domain integral equation (TDIE) solvers have never been used for the same purpose even though they offer several advantages over FDTD (E. Michielssen, et al., ECCOMAS CFD, The Netherlands, Sep. 5-8, 2006). This is because explicit MOT solvers have never been stabilized until not so long ago. Recently an explicit but stable MOT scheme has been proposed for solving the time domain surface magnetic field integral equation (H.A. Ulku, et al., IEEE Trans. Antennas Propag., 61(8), 4120-4131, 2013) and later it has been extended for the time domain volume electric field integral equation (TDVEFIE) (S. B. Sayed, et al., Pr. Electromagn. Res. S., 378, Stockholm, 2013). This explicit MOT scheme uses predictor-corrector updates together with successive over relaxation during time marching to stabilize the solution even when time step is as large as in the implicit counterpart. In this work, an explicit MOT-TDVEFIE solver is proposed for analyzing electromagnetic wave interactions on scatterers exhibiting Kerr nonlinearity. Nonlinearity is accounted for using the constitutive relation between the electric field intensity and flux density. Then, this relation and the TDVEFIE are discretized together by expanding the intensity and flux - sing half
Dancing with the Electrons: Time-Domain and CW In Vivo EPR Imaging
Directory of Open Access Journals (Sweden)
Murali C. Krishna
2008-01-01
Full Text Available The progress in the development of imaging the distribution of unpaired electrons in living systems and the functional and the potential diagnostic dimensions of such an imaging process, using Electron Paramagnetic Resonance Imaging (EPRI, is traced from its origins with emphasis on our own work. The importance of EPR imaging stems from the fact that many paramagnetic probes show oxygen dependent spectral broadening. Assessment of in vivo oxygen concentration is an important factor in radiation oncology in treatment-planning and monitoring treatment-outcome. The emergence of narrow-line trairylmethyl based, bio-compatible spin probes has enabled the development of radiofrequency time-domain EPRI. Spectral information in time-domain EPRI can be achieved by generating a time sequence of T2* or T2 weighted images. Progress in CW imaging has led to the use of rotating gradients, more recently rapid scan with direct detection, and a combination of all the three. Very low field MRI employing Dynamic Nuclear polarization (Overhauser effect is also employed for monitoring tumor hypoxia, and re-oxygenation in vivo. We have also been working on the co-registration of MRI and time domain EPRI on mouse tumor models at 300 MHz using a specially designed resonator assembly. The mapping of the unpaired electron distribution and unraveling the spectral characteristics by using magnetic resonance in presence of stationary and rotating gradients in indeed ‘dancing with the (unpaired electrons’, metaphorically speaking.
Dancing with the Electrons: Time-Domain and CW EPR Imaging
Directory of Open Access Journals (Sweden)
Sankaran Subramanian
2008-01-01
Full Text Available The progress in the development of imaging the distribution of unpaired electrons in living systems and the functional and the potential diagnostic dimensions of such an imaging process, using Electron Paramagnetic Resonance Imaging (EPRI, is traced from its origins with emphasis on our own work. The importance of EPR imaging stems from the fact that many paramagnetic probes show oxygen dependent spectral broadening. Assessment of in vivo oxygen concentration is an important factor in radiation oncology in treatment-planning and monitoring treatment-outcome. The emergence of narrow-line trairylmethyl based, bio-compatible spin probes has enabled the development of radiofrequency time-domain EPRI. Spectral information in time-domain EPRI can be achieved by generating a time sequence of T 2 * or T 2 weighted images. Progress in CW imaging has led to the use of rotating gradients, more recently rapid scan with direct detection, and a combination of all the three. Very low field MRI employing Dynamic Nuclear polarization (Overhauser effect is also employed for monitoring tumor hypoxia, and re-oxygenation in vivo . We have also been working on the co-registration of MRI and time domain EPRI on mouse tumor models at 300 MHz using a specially designed resonator assembly. The mapping of the unpaired electron distribution and unraveling the spectral characteristics by using magnetic resonance in presence of stationary and rotating gradients in indeed ‘dancing with the ( unpaired electrons’, metaphorically speaking.
Seismic response of three-dimensional topographies using a time-domain boundary element method
Janod, François; Coutant, Olivier
2000-08-01
We present a time-domain implementation for a boundary element method (BEM) to compute the diffraction of seismic waves by 3-D topographies overlying a homogeneous half-space. This implementation is chosen to overcome the memory limitations arising when solving the boundary conditions with a frequency-domain approach. This formulation is flexible because it allows one to make an adaptive use of the Green's function time translation properties: the boundary conditions solving scheme can be chosen as a trade-off between memory and cpu requirements. We explore here an explicit method of solution that requires little memory but a high cpu cost in order to run on a workstation computer. We obtain good results with four points per minimum wavelength discretization for various topographies and plane wave excitations. This implementation can be used for two different aims: the time-domain approach allows an easier implementation of the BEM in hybrid methods (e.g. coupling with finite differences), and it also allows one to run simple BEM models with reasonable computer requirements. In order to keep reasonable computation times, we do not introduce any interface and we only consider homogeneous models. Results are shown for different configurations: an explosion near a flat free surface, a plane wave vertically incident on a Gaussian hill and on a hemispherical cavity, and an explosion point below the surface of a Gaussian hill. Comparison is made with other numerical methods, such as finite difference methods (FDMs) and spectral elements.
Impact of time-domain IP pulse length on measured data and inverted models
DEFF Research Database (Denmark)
Olsson, P. I.; Fiandaca, G.; Dahlin, T.
2015-01-01
The duration of time domain (TD) induced polarization (IP) current injections has significant impact on the acquired IP data as well as on the inversion models, if the standard evaluation procedure is followed. However, it is still possible to retrieve similar inversion models if the waveform...... of the injected current and the IP response waveform are included in the inversion. The on-time also generally affects the signal-tonoise ratio (SNR) where an increased on-time gives higher SNR for the IP data....
Al Jarro, Ahmed; Salem, Mohamed; Bagci, Hakan; Benson, Trevor; Sewell, Phillip D.; Vuković, Ana
2012-01-01
An explicit marching-on-in-time (MOT) scheme for solving the time domain volume integral equation is presented. The proposed method achieves its stability by employing, at each time step, a corrector scheme, which updates/corrects fields computed by the explicit predictor scheme. The proposedmethod is computationally more efficient when compared to the existing filtering techniques used for the stabilization of explicit MOT schemes. Numerical results presented in this paper demonstrate that the proposed method maintains its stability even when applied to the analysis of electromagnetic wave interactions with electrically large structures meshed using approximately half a million discretization elements.
Al Jarro, Ahmed
2012-11-01
An explicit marching-on-in-time (MOT) scheme for solving the time domain volume integral equation is presented. The proposed method achieves its stability by employing, at each time step, a corrector scheme, which updates/corrects fields computed by the explicit predictor scheme. The proposedmethod is computationally more efficient when compared to the existing filtering techniques used for the stabilization of explicit MOT schemes. Numerical results presented in this paper demonstrate that the proposed method maintains its stability even when applied to the analysis of electromagnetic wave interactions with electrically large structures meshed using approximately half a million discretization elements.
Rander, D. N.; Joshi, Y. S.; Kanse, K. S.; Kumbharkhane, A. C.
2016-01-01
The measurements of complex dielectric permittivity of xylitol-water mixtures have been carried out in the frequency range of 10 MHz-30 GHz using a time domain reflectometry technique. Measurements have been done at six temperatures from 0 to 25 °C and at different weight fractions of xylitol (0 xylitol-water can be well described by Cole-Davidson model having an asymmetric distribution of relaxation times. The dielectric parameters such as static dielectric constant and relaxation time for the mixtures have been evaluated. The molecular interaction between xylitol and water molecules is discussed using the Kirkwood correlation factor ( g eff ) and thermodynamic parameter.
Multichannel Signal Enhancement using Non-Causal, Time-Domain Filters
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Christensen, Mads Græsbøll; Benesty, Jacob
2013-01-01
In the vast amount of time-domain filtering methods for speech enhancement, the filters are designed to be causal. Recently, however, it was shown that the noise reduction and signal distortion capabilities of such single-channel filters can be improved by allowing the filters to be non-causal. W......In the vast amount of time-domain filtering methods for speech enhancement, the filters are designed to be causal. Recently, however, it was shown that the noise reduction and signal distortion capabilities of such single-channel filters can be improved by allowing the filters to be non......-causal, multichannel filters for enhancement based on an orthogonal decomposition is proposed. The evaluation shows that there is a potential gain in noise reduction and signal distortion by introducing non-causality. Moreover, experiments on real-life speech show that we can improve the perceptual quality....
International Nuclear Information System (INIS)
Jamali, J.; Aghajafari, R.; Moini, R.; Sadeghi, H.
2002-01-01
A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper
International Nuclear Information System (INIS)
Chen, Xiang; Chen, Yong Guang; Wei, Ming; Hu, Xiao Feng
2013-01-01
Shielding effectiveness (SE) of materials against electromagnetic pulse (EMP) cannot be well estimated by traditional test method of SE of materials which only consider the amplitude-frequency characteristic of materials, but ignore the phase-frequency ones. In order to solve this problem, the model of SE of materials against EMP was established based on system identification (SI) method with time-domain linear cosine frequency sweep signal. The feasibility of the method in this paper was examined depending on infinite planar material and the simulation research of coaxial test method and windowed semi-anechoic box of materials. The results show that the amplitude-frequency and phase-frequency information of each frequency can be fully extracted with this method. SE of materials against strong EMP can be evaluated with time-domain low field strength (voltage) of cosine frequency sweep signal. And SE of materials against a variety EMP will be predicted by the model.
Wang, Xu; Gao, Zhensen; Kataoka, Nobuyuki; Wada, Naoya
2010-05-10
A novel scheme using single phase modulator for simultaneous time domain spectral phase encoding (SPE) signal generation and DPSK data modulation is proposed and experimentally demonstrated. Array- Waveguide-Grating and Variable-Bandwidth-Spectrum-Shaper based devices can be used for decoding the signal directly in spectral domain. The effects of fiber dispersion, light pulse width and timing error on the coding performance have been investigated by simulation and verified in experiment. In the experiment, SPE signal with 8-chip, 20GHz/chip optical code patterns has been generated and modulated with 2.5 Gbps DPSK data using single modulator. Transmission of the 2.5 Gbps data over 34km fiber with BEROCDMA) and secure optical communication applications. (c) 2010 Optical Society of America.
Numerical modeling of time domain 3-D problems in accelerator physics
International Nuclear Information System (INIS)
Harfoush, F.A.; Jurgens, T.G.
1990-06-01
Time domain analysis is relevant in particle accelerators to study the electromagnetic field interaction of a moving source particle on a lagging test particle as the particles pass an accelerating cavity or some other structure. These fields are called wake fields. The travelling beam inside a beam pipe may undergo more complicated interactions with its environment due to the presence of other irregularities like wires, thin slots, joints and other types of obstacles. Analytical solutions of such problems is impossible and one has to resort to a numerical method. In this paper we present results of our first attempt to model these problems in 3-D using our finite difference time domain (FDTD) code. 10 refs., 9 figs
Two dimensional microcirculation mapping with real time spatial frequency domain imaging
Zheng, Yang; Chen, Xinlin; Lin, Weihao; Cao, Zili; Zhu, Xiuwei; Zeng, Bixin; Xu, M.
2018-02-01
We present a spatial frequency domain imaging (SFDI) study of local hemodynamics in the human finger cuticle of healthy volunteers performing paced breathing and the forearm of healthy young adults performing normal breathing with our recently developed Real Time Single Snapshot Multiple Frequency Demodulation - Spatial Frequency Domain Imaging (SSMD-SFDI) system. A two-layer model was used to map the concentrations of deoxy-, oxy-hemoglobin, melanin, epidermal thickness and scattering properties at the subsurface of the forearm and the finger cuticle. The oscillations of the concentrations of deoxy- and oxy-hemoglobin at the subsurface of the finger cuticle and forearm induced by paced breathing and normal breathing, respectively, were found to be close to out-of-phase, attributed to the dominance of the blood flow modulation by paced breathing or heartbeat. Our results suggest that the real time SFDI platform may serve as one effective imaging modality for microcirculation monitoring.
Fault Detection of Aircraft Cable via Spread Spectrum Time Domain Reflectometry
Directory of Open Access Journals (Sweden)
Xudong SHI
2014-03-01
Full Text Available As the airplane cable fault detection based on TDR (time domain reflectometry is affected easily by various noise signals, which makes the reflected signal attenuate and distort heavily, failing to locate the fault. In order to solve these problems, a method of spread spectrum time domain reflectometry (SSTDR is introduced in this paper, taking the advantage of the sharp peak of correlation function. The test signal is generated from ML sequence (MLS modulated by sine wave in the same frequency. Theoretically, the test signal has the very high immunity of noise, which can be applied with excellent precision to fault location on the aircraft cable. In this paper, the method of SSTDR was normally simulated in MATLAB. Then, an experimental setup, based on LabVIEW, was organized to detect and locate the fault on the aircraft cable. It has been demonstrated that SSTDR has the high immunity of noise, reducing some detection errors effectively.
A wearable microwave antenna array for time-domain breast tumor screening
Porter, Emily; Bahrami, Hadi; Santorelli, Adam; Gosselin, Benoit; Rusch, Leslie; Popovic, Milica
2016-01-01
In this work, we present a clinical prototype with a wearable patient interface for microwave breast cancer detection. The long-term aim of the prototype is a breast health monitoring application. The system operates using multistatic time-domain pulsed radar, with 16 flexible antennas embedded into a bra. Unlike the previously reported, table-based prototype with a rigid cup-like holder, the wearable one requires no immersion medium and enables simple localization of breast surface. In compa...
Mini Tensiometer-Time Domain Reflectometry Coil Probe for Measuring Soil Water Retention Properties
DEFF Research Database (Denmark)
Subedi, Shaphal; Kawamoto, Ken; Karunarathna, Anurudda Kumara
2013-01-01
Time domain reflectometry (TDR) is used widely for measuring soil-water content. New TDR coil probe technology facilitates the development of small, nondestructive probes for simultaneous measurement of soil-water content (θ) and soil-water potential (ψ). In this study we developed mini tensiomet...... between measured soil-water retention curves (ψ > –100 cm H2O) by the new T-TDR coil probes and independent measurements by the hanging water column method....
DEFF Research Database (Denmark)
Mackenzie, David M.A.; Whelan, Patrick Rebsdorf; Bøggild, Peter
2018-01-01
We present a comparative study of electrical measurements of graphene using terahertz time-domain spectroscopy in transmission and reflection mode, and compare the measured sheet conductivity values to electrical van der Pauw measurements made independently in three different laboratories. Overall......, while offering the additional advantages associated with contactless mapping, such as high throughput, no lithography requirement, and with the spatial mapping directly revealing the presence of any inhomogeneities or isolating defects. The confirmation of the accuracy of reflection-mode removes...
Results of time-domain electromagnetic soundings in Everglades National Park, Florida
Fitterman, D.V.; Deszcz-Pan, Maria; Stoddard, C.E.
1999-01-01
This report describes the collection, processing, and interpretation of time-domain electromagnetic soundings from Everglades National Park. The results are used to locate the extent of seawater intrusion in the Biscayne aquifer and to map the base of the Biscayne aquifer in regions where well coverage is sparse. The data show no evidence of fresh, ground-water flows at depth into Florida Bay.
Fast and non-destructive pore structure analysis using terahertz time-domain spectroscopy.
Markl, Daniel; Bawuah, Prince; Ridgway, Cathy; van den Ban, Sander; Goodwin, Daniel J; Ketolainen, Jarkko; Gane, Patrick; Peiponen, Kai-Erik; Zeitler, Jochen Axel
2018-01-01
Pharmaceutical tablets are typically manufactured by the uni-axial compaction of powder that is confined radially by a rigid die. The directional nature of the compaction process yields not only anisotropic mechanical properties (e.g. tensile strength) but also directional properties of the pore structure in the porous compact. This study derives a new quantitative parameter, $S_a$, to describe the anisotropy in pore structure of pharmaceutical tablets based on terahertz time-domain spectrosc...
Gabran, S R I; Saad, J H; Salama, M M A; Mansour, R R
2009-01-01
This paper demonstrates the electromagnetic modeling and simulation of an implanted Medtronic deep brain stimulation (DBS) electrode using finite difference time domain (FDTD). The model is developed using Empire XCcel and represents the electrode surrounded with brain tissue assuming homogenous and isotropic medium. The model is created to study the parameters influencing the electric field distribution within the tissue in order to provide reference and benchmarking data for DBS and intra-cortical electrode development.
Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope
2016-10-19
angular random walk (ARW), bias instability, and scale factor instability. While there are methods to address issues with bias and scale factor...effects. Thus, it is expected that it will have low bias and scale factor instabilities. Simulated ARW performance of a particular incarnation of the...1 2. PARAMETRIC SYSTEM IDENTIFICATION BASED ON TIME-DOMAIN SWITCHING ........ 2 3. FINITE ELEMENT MODELING OF RESONATOR
Shape optimization for non-Newtonian fluids in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Sokolowski, J.; Stebel, Jan
2014-01-01
Roč. 3, č. 2 (2014), s. 331-348 ISSN 2163-2480 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : shape optimization * time-dependent domain * incompressible viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.373, year: 2014 http://www.aimsciences.org/journals/home.jsp?journalID=25
Concept of an ionizing time-domain matter-wave interferometer
Nimmrichter, Stefan; Haslinger, Philipp; Hornberger, Klaus; Arndt, Markus
2011-01-01
We discuss the concept of an all-optical and ionizing matter-wave interferometer in the time domain. The proposed setup aims at testing the wave nature of highly massive clusters and molecules, and it will enable new precision experiments with a broad class of atoms, using the same laser system. The propagating particles are illuminated by three pulses of a standing ultraviolet laser beam, which detaches an electron via efficient single photon-absorption. Optical gratings may have periods as ...
Time coordination of heterogeneous distance protections using a domain specific language
Marcin Kowalski; Jan Magott
2012-01-01
BACKGROUND: Distance protections are widely used in protection of energy transmission lines, but their time coordination is still an important and difficult problem. Inappropriate configuration leads to a hazard event: remote circuit breaker tripping provided the local circuit breaker can be opened, which severely impairs power system operation.OBJECTIVE: To describe a method and provide software tools to alleviate the hazard in power systems.METHODS: A domain specific language (DSL) for repr...
DEFF Research Database (Denmark)
Andersen, P.; Skjærbæk, P. S.; Kirkegaard, Poul Henning
with the smoothed quanties which have been obtained from SARCOF. The results show the usefulness of the technique for identification of a time varying civil engineering structure. It is found that all the techniques give reliable estiates of the frequencies of the two lowest modes and the first mode shape. Only...
A new non-parametric stationarity test of time series in the time domain
Jin, Lei; Wang, Suojin; Wang, Haiyan
2014-01-01
© 2015 The Royal Statistical Society and Blackwell Publishing Ltd. We propose a new double-order selection test for checking second-order stationarity of a time series. To develop the test, a sequence of systematic samples is defined via Walsh
Electroporation-Induced Cell Modifications Detected with THz Time-Domain Spectroscopy
Romeo, Stefania; Vernier, P. Thomas; Zeni, Olga
2018-04-01
Electroporation (electropermeabilization) increases the electrical conductivity of biological cell membranes and lowers transport barriers for normally impermeant materials. Molecular simulations suggest that electroporation begins with the reorganization of water and lipid head group dipoles in the phospholipid bilayer interface, driven by an externally applied electric field, and the evolution of the resulting defects into water-filled, lipid pores. The interior of the electroporated membrane thus contains water, which should provide a signature for detection of the electropermeabilized state. In this feasibility study, we use THz time-domain spectroscopy, a powerful tool for investigating biomolecular systems and their interactions with water, to detect electroporation in human cells subjected to permeabilizing pulsed electric fields (PEFs). The time-domain response of electroporated human monocytes was acquired with a commercial THz, time-domain spectrometer. For each sample, frequency spectra were calculated, and the absorption coefficient and refractive index were extracted in the frequency range between 0.2 and 1.5 THz. This analysis reveals a higher absorption of THz radiation by PEF-exposed cells, with respect to sham-exposed ones, consistent with the intrusion of water into the cell through the permeabilized membrane that is presumed to be associated with electroporation.
Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves
Directory of Open Access Journals (Sweden)
Shukui Liu
2011-03-01
Full Text Available Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.
Time Domains of the Hypoxic Ventilatory Response and Their Molecular Basis
Pamenter, Matthew E.; Powell, Frank L.
2016-01-01
Ventilatory responses to hypoxia vary widely depending on the pattern and length of hypoxic exposure. Acute, prolonged, or intermittent hypoxic episodes can increase or decrease breathing for seconds to years, both during the hypoxic stimulus, and also after its removal. These myriad effects are the result of a complicated web of molecular interactions that underlie plasticity in the respiratory control reflex circuits and ultimately control the physiology of breathing in hypoxia. Since the time domains of the physiological hypoxic ventilatory response (HVR) were identified, considerable research effort has gone toward elucidating the underlying molecular mechanisms that mediate these varied responses. This research has begun to describe complicated and plastic interactions in the relay circuits between the peripheral chemoreceptors and the ventilatory control circuits within the central nervous system. Intriguingly, many of these molecular pathways seem to share key components between the different time domains, suggesting that varied physiological HVRs are the result of specific modifications to overlapping pathways. This review highlights what has been discovered regarding the cell and molecular level control of the time domains of the HVR, and highlights key areas where further research is required. Understanding the molecular control of ventilation in hypoxia has important implications for basic physiology and is emerging as an important component of several clinical fields. PMID:27347896
Mapping of landfills using time-domain spectral induced polarization data
DEFF Research Database (Denmark)
Gazoty, Aurélie; Fiandaca, Gianluca; Pedersen, Jesper Bjergsted
2012-01-01
This study uses time-domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral informat......This study uses time-domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral...... information from time-domain IP data. Thirteen IP/DC profiles were collected in the area, supplemented by el-log drilling for accurate correlation between the geophysics and the lithology. The data were inverted using a laterally constrained 1D inversion considering the full decay curves to retrieve the four......-log measurements giving in situ values, for which the Cole-Cole parameters were computed. The 3D shape of the waste body was pinpointed and well-defined. The inversion of the IP data also shows a strong correlation with the initial stage of the waste dump and its composition combining an aerial map with acquired...
Real-time decision support and information gathering system for financial domain
Tseng, Chiu-Che; Gmytrasiewicz, Piotr J.
2006-05-01
The challenge of the investment domain is that a large amount of diverse information can be potentially relevant to an investment decision, and that, frequently, the decisions have to be made in a timely manner. This presents the potential for better decision support, but poses the challenge of building a decision support agent that gathers information from different sources and incorporates it for timely decision support. These problems motivate us to investigate ways in which the investors can be equipped with a flexible real-time decision support system to be practical in time-critical situations. The flexible real-time decision support system considers a tradeoff between decision quality and computation cost. For this purpose, we propose a system that uses the object oriented Bayesian knowledge base (OOBKB) design to create a decision model at the most suitable level of detail to guide the information gathering activities, and to produce an investment recommendation within a reasonable length of time. The decision models our system uses are implemented as influence diagrams. We validate our system with experiments in a simplified investment domain. The experiments show that our system produces a quality recommendation under different urgency situations. The contribution of our system is that it provides the flexible decision recommendation for an investor under time constraints in a complex environment.
Multiobjective Optimization for Electronic Circuit Design in Time and Frequency Domains
Directory of Open Access Journals (Sweden)
J. Dobes
2013-04-01
Full Text Available The multiobjective optimization provides an extraordinary opportunity for the finest design of electronic circuits because it allows to mathematically balance contradictory requirements together with possible constraints. In this paper, an original and substantial improvement of an existing method for the multiobjective optimization known as GAM (Goal Attainment Method is suggested. In our proposal, the GAM algorithm itself is combined with a procedure that automatically provides a set of parameters -- weights, coordinates of the reference point -- for which the method generates noninferior solutions uniformly spread over an appropriately selected part of the Pareto front. Moreover, the resulting set of obtained solutions is then presented in a suitable graphic form so that the solution representing the most satisfactory tradeoff can be easily chosen by the designer. Our system generates various types of plots that conveniently characterize results of up to four-dimensional problems. Technically, the procedures of the multiobjective optimization were created as a software add-on to the CIA (Circuit Interactive Analyzer program. This way enabled us to utilize many powerful features of this program, including the sensitivity analyses in time and frequency domains. As a result, the system is also able to perform the multiobjective optimization in the time domain and even highly nonlinear circuits can be significantly improved by our program. As a demonstration of this feature, a multiobjective optimization of a C-class power amplifier in the time domain is thoroughly described in the paper. Further, a four-dimensional optimization of a video amplifier is demonstrated with an original graphic representation of the Pareto front, and also some comparison with the weighting method is done. As an example of improving noise properties, a multiobjective optimization of a low-noise amplifier is performed, and the results in the frequency domain are shown
A new non-parametric stationarity test of time series in the time domain
Jin, Lei
2014-11-07
© 2015 The Royal Statistical Society and Blackwell Publishing Ltd. We propose a new double-order selection test for checking second-order stationarity of a time series. To develop the test, a sequence of systematic samples is defined via Walsh functions. Then the deviations of the autocovariances based on these systematic samples from the corresponding autocovariances of the whole time series are calculated and the uniform asymptotic joint normality of these deviations over different systematic samples is obtained. With a double-order selection scheme, our test statistic is constructed by combining the deviations at different lags in the systematic samples. The null asymptotic distribution of the statistic proposed is derived and the consistency of the test is shown under fixed and local alternatives. Simulation studies demonstrate well-behaved finite sample properties of the method proposed. Comparisons with some existing tests in terms of power are given both analytically and empirically. In addition, the method proposed is applied to check the stationarity assumption of a chemical process viscosity readings data set.
DEFF Research Database (Denmark)
Santillan, Arturo Orozco
2011-01-01
The aim of the work described in this paper has been to investigate the use of the finite-difference time-domain method to describe the interactions between a moving object and a sound field. The main objective was to simulate oscillational instabilities that appear in single-axis acoustic...... levitation devices and to describe their evolution in time to further understand the physical mechanism involved. The study shows that the method gives accurate results for steady state conditions, and that it is a promising tool for simulations with a moving object....
Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission
DEFF Research Database (Denmark)
Verhulst, Sarah; Dau, Torsten; Shera, Christopher A.
2012-01-01
This paper describes the implementation and performance of a nonlinear time-domain model of the cochlea for transient stimulation and human otoacoustic emission generation. The nonlinearity simulates compressive growth of measured basilar-membrane impulse responses. The model accounts...... for reflection and distortion-source otoacoustic emissions (OAEs) and simulates spontaneous OAEs through manipulation of the middle-ear reflectance. The model was calibrated using human psychoacoustical and otoacoustic tuning parameters. It can be used to investigate time-dependent properties of cochlear...
On the mixed discretization of the time domain magnetic field integral equation
Ulku, Huseyin Arda
2012-09-01
Time domain magnetic field integral equation (MFIE) is discretized using divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming Buffa-Christiansen (BC) functions as spatial basis and testing functions, respectively. The resulting mixed discretization scheme, unlike the classical scheme which uses RWG functions as both basis and testing functions, is proper: Testing functions belong to dual space of the basis functions. Numerical results demonstrate that the marching on-in-time (MOT) solution of the mixed discretized MFIE yields more accurate results than that of classically discretized MFIE. © 2012 IEEE.
Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators
Talukdar, Abdul Hafiz Ibne
2012-07-28
Traditionally, the necessary and sufficient condition for any system to be oscillating is that its poles are located on the imaginary (jω) axis. In this paper, for the first time, we have shown that systems can oscillate with time-domain oscillating poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating resistance and triangular shape of FFT are also demonstrated with mathematical reasoning and simulation results to support the unusual and surprising characteristics. © 2009 IEEE.
Nonextreme and ultraextreme domain walls and their global space-times
International Nuclear Information System (INIS)
Cvetic, M.; Griffies, S.; Soleng, H.H.
1993-01-01
Nonextreme walls (bubbles with two insides) and ultraextreme walls (bubbles of false vacuum decay) are discussed. Their respective energy densities are higher and lower than that of the corresponding extreme (supersymmetric), planar domain wall. These singularity free space-times exhibit nontrivial causal structure analogous to certain nonextreme black holes. We focus on anti--de Sitter--Minkowski walls and comment on Minkowski-Minkowski walls with trivial extreme limit, as well as walls adjacent to de Sitter space-times with no extreme limit
Time domain-nuclear magnetic resonance study of chars from southern hardwoods
International Nuclear Information System (INIS)
Elder, Thomas; Labbe, Nicole; Harper, David; Rials, Timothy
2006-01-01
Chars from the thermal degradation of silver maple (Acer saccharinum), red maple (Acer rubrum), sugar maple (Acer saccharum), and white oak (Quercus spp.), performed at temperatures from 250 to 350 o C, were examined using time domain-nuclear magnetic resonance spectroscopy. Prior to analysis, the chars were equilibrated under conditions insuring the presence of bound water only and both bound water and free water. Transverse relaxation times were found to be related to the moisture content of the chars, which varied with temperature. At elevated temperatures the number of signals assigned to free water decreased, indicative of an increase in pore size within the chars
Time-domain calculation of sub-nanosecond pulse launched by a proton beam
International Nuclear Information System (INIS)
Chan, Kwok-Chi Dominic; Cooper, R.K.
1990-01-01
Using the finite-difference time-domain code TBCI, we have numerically calculated the radiation from a sub-nanosecond 800-MeV proton bunch as it is launched into space. The calculation is compared to measurements of the time history of the radiated fields and good agreement is found. A movie showing the development of the radiation pattern will be shown during the presentation at this conference, namely, the First Los Alamos Symposium on Ultra-Wideband Radar. 6 refs., 7 figs
Thermal diffusivity of a metallic thin layer using the time-domain thermo reflectance technique
International Nuclear Information System (INIS)
Battaglia, J-L; Kusiak, A; Rossignol, C; Chigarev, N
2007-01-01
The time domain thermo reflectance (TDTR) is widely used in the field of acoustic and thermal characterization of thin layers at the nano and micro scale. In this paper, we propose to derive a simple analytical expression of the thermal diffusivity of the layer. This relation is based on the analytical solution of one-dimensional heat transfer in the medium using integral transforms. For metals, the two-temperature model shows that the capacitance effect at the short times is essentially governed by the electronic contribution
Durations and domains of daily aerobic activity: evidence from the 2010 Canadian time-use survey.
Millward, Hugh; Spinney J, E L; Scott, Darren
2014-07-01
This study employs national time-diary data to evaluate how much aerobic activity Canadians engage in on a daily basis, how that activity is apportioned by activity domain, and how subgroups within the population vary in their aerobic attainment. The study employs time-use data from the 2010 General Social Survey of Canada, for 15,390 respondents aged 15 and older. To estimate effort levels, the authors harmonized survey codes with those in the Compendium of Physical Activities. Aerobic activity was defined as moderate or vigorous effort at 3.5 Metabolic Equivalent of Task (MET) or higher. Among the 4 activity domains, aerobic participation is highest in leisure activities, followed by chores, paid work, and active transportation (AT). Only a minority (42%) of respondents recorded at least 20 mins/day of aerobic activity. Aerobic totals were particularly low for women and those in poor or fair health, and low for students, 15- to 24-year-olds, and those residing in Quebec, Ontario, and larger cities. The majority of Canadian adults are failing to meet recommended aerobic activity levels. However, there is considerable opportunity to increase aerobic participation for some groups, particularly women and young adults, especially in the leisure and AT domains.
Okawa, S; Endo, Y; Hoshi, Y; Yamada, Y
2012-01-01
A method to reduce noise for time-domain diffuse optical tomography (DOT) is proposed. Poisson noise which contaminates time-resolved photon counting data is reduced by use of maximum a posteriori estimation. The noise-free data are modeled as a Markov random process, and the measured time-resolved data are assumed as Poisson distributed random variables. The posterior probability of the occurrence of the noise-free data is formulated. By maximizing the probability, the noise-free data are estimated, and the Poisson noise is reduced as a result. The performances of the Poisson noise reduction are demonstrated in some experiments of the image reconstruction of time-domain DOT. In simulations, the proposed method reduces the relative error between the noise-free and noisy data to about one thirtieth, and the reconstructed DOT image was smoothed by the proposed noise reduction. The variance of the reconstructed absorption coefficients decreased by 22% in a phantom experiment. The quality of DOT, which can be applied to breast cancer screening etc., is improved by the proposed noise reduction.
A novel time-domain signal processing algorithm for real time ventricular fibrillation detection
International Nuclear Information System (INIS)
Monte, G E; Scarone, N C; Liscovsky, P O; Rotter, P
2011-01-01
This paper presents an application of a novel algorithm for real time detection of ECG pathologies, especially ventricular fibrillation. It is based on segmentation and labeling process of an oversampled signal. After this treatment, analyzing sequence of segments, global signal behaviours are obtained in the same way like a human being does. The entire process can be seen as a morphological filtering after a smart data sampling. The algorithm does not require any ECG digital signal pre-processing, and the computational cost is low, so it can be embedded into the sensors for wearable and permanent applications. The proposed algorithms could be the input signal description to expert systems or to artificial intelligence software in order to detect other pathologies.
A novel time-domain signal processing algorithm for real time ventricular fibrillation detection
Monte, G. E.; Scarone, N. C.; Liscovsky, P. O.; Rotter S/N, P.
2011-12-01
This paper presents an application of a novel algorithm for real time detection of ECG pathologies, especially ventricular fibrillation. It is based on segmentation and labeling process of an oversampled signal. After this treatment, analyzing sequence of segments, global signal behaviours are obtained in the same way like a human being does. The entire process can be seen as a morphological filtering after a smart data sampling. The algorithm does not require any ECG digital signal pre-processing, and the computational cost is low, so it can be embedded into the sensors for wearable and permanent applications. The proposed algorithms could be the input signal description to expert systems or to artificial intelligence software in order to detect other pathologies.
On using moving windows in finite element time domain simulation for long accelerator structures
International Nuclear Information System (INIS)
Lee, L.-Q.; Candel, Arno; Ng, Cho; Ko, Kwok
2010-01-01
A finite element moving window technique is developed to simulate the propagation of electromagnetic waves induced by the transit of a charged particle beam inside large and long structures. The window moving along with the beam in the computational domain adopts high-order finite element basis functions through p refinement and/or a high-resolution mesh through h refinement so that a sufficient accuracy is attained with substantially reduced computational costs. Algorithms to transfer discretized fields from one mesh to another, which are the keys to implementing a moving window in a finite element unstructured mesh, are presented. Numerical experiments are carried out using the moving window technique to compute short-range wakefields in long accelerator structures. The results are compared with those obtained from the normal finite element time domain (FETD) method and the advantages of using the moving window technique are discussed.
Time-domain representation of frequency dependent inertial forces on offshore structures
DEFF Research Database (Denmark)
Krenk, Steen
2013-01-01
dependence is then approximated by a rational function, corresponding to a set of ordinary differential equations in the time domain. The MacCamy-Fuchs solution leads to a representation of the inertial force coefficient as a complex function with argument mainly corresponding to a 'phase lead', in contrast...... history of the inertial force is determined by processing the stable part of the transformation by a forward time integration, followed by an integration in the negative time-direction to obtain the final inertial force time history. The differential equations of the local inertial force at a cross......The inertial wave force on a vertical cylinder decreases with decreasing wave length, when the wave length is less than about six times the diameter of the diameter of the cylinder. In structures with a largediameter component like mono-towers the resonance frequency of the structure is typically...
An FFT-accelerated time-domain multiconductor transmission line simulator
Bagci, Hakan
2010-02-01
A fast time-domain multiconductor transmission line (MTL) simulator for analyzing general MTL networks is presented. The simulator models the networks as homogeneous MTLs that are excited by external fields and driven/terminated/ connected by potentially nonlinear lumped circuitry. It hybridizes an MTL solver derived from time-domain integral equations (TDIEs) in unknown wave coefficients for each MTL with a circuit solver rooted in modified nodal analysis equations in unknown node voltages and voltage-source currents for each circuit. These two solvers are rigorously interfaced at MTL and circuit terminals, and the resulting coupled system of equations is solved simultaneously for all MTL and circuit unknowns at each time step. The proposed simulator is amenable to hybridization, is fast Fourier transform (FFT)-accelerated, and is highly accurate: 1) It can easily be hybridized with TDIE-based field solvers (in a fully rigorous mathematical framework) for performing electromagnetic interference and compatibility analysis on electrically large and complex structures loaded with MTL networks. 2) It is accelerated by an FFT algorithm that calculates temporal convolutions of time-domain MTL Green functions in only O(Ntlog2 N t) rather than O(Ntt2) operations, where N t is the number of time steps of simulation. Moreover, the algorithm, which operates on temporal samples of MTL Green functions, is indifferent to the method used to obtain them. 3) It approximates MTL voltages, currents, and wave coefficients, using high-order temporal basis functions. Various numerical examples, including the crosstalk analysis of a (twisted) unshielded twisted-pair (UTP)-CAT5 cable and the analysis of field coupling into UTP-CAT5 and RG-58 cables located on an airplane, are presented to demonstrate the accuracy, efficiency, and versatility of the proposed simulator. © 2010 IEEE.
Liu, Yang
2016-03-25
A parallel plane-wave time-domain (PWTD)-accelerated explicit marching-on-in-time (MOT) scheme for solving the time domain electric field volume integral equation (TD-EFVIE) is presented. The proposed scheme leverages pulse functions and Lagrange polynomials to spatially and temporally discretize the electric flux density induced throughout the scatterers, and a finite difference scheme to compute the electric fields from the Hertz electric vector potentials radiated by the flux density. The flux density is explicitly updated during time marching by a predictor-corrector (PC) scheme and the vector potentials are efficiently computed by a scalar PWTD scheme. The memory requirement and computational complexity of the resulting explicit PWTD-PC-EFVIE solver scale as ( log ) s s O N N and ( ) s t O N N , respectively. Here, s N is the number of spatial basis functions and t N is the number of time steps. A scalable parallelization of the proposed MOT scheme on distributed- memory CPU clusters is described. The efficiency, accuracy, and applicability of the resulting (parallelized) PWTD-PC-EFVIE solver are demonstrated via its application to the analysis of transient electromagnetic wave interactions on canonical and real-life scatterers represented with up to 25 million spatial discretization elements.
Liu, Yang; Al-Jarro, Ahmed; Bagci, Hakan; Michielssen, Eric
2016-01-01
A parallel plane-wave time-domain (PWTD)-accelerated explicit marching-on-in-time (MOT) scheme for solving the time domain electric field volume integral equation (TD-EFVIE) is presented. The proposed scheme leverages pulse functions and Lagrange polynomials to spatially and temporally discretize the electric flux density induced throughout the scatterers, and a finite difference scheme to compute the electric fields from the Hertz electric vector potentials radiated by the flux density. The flux density is explicitly updated during time marching by a predictor-corrector (PC) scheme and the vector potentials are efficiently computed by a scalar PWTD scheme. The memory requirement and computational complexity of the resulting explicit PWTD-PC-EFVIE solver scale as ( log ) s s O N N and ( ) s t O N N , respectively. Here, s N is the number of spatial basis functions and t N is the number of time steps. A scalable parallelization of the proposed MOT scheme on distributed- memory CPU clusters is described. The efficiency, accuracy, and applicability of the resulting (parallelized) PWTD-PC-EFVIE solver are demonstrated via its application to the analysis of transient electromagnetic wave interactions on canonical and real-life scatterers represented with up to 25 million spatial discretization elements.
DEFF Research Database (Denmark)
Clausen, Anders; Guan, Pengyu; Mulvad, Hans Christian Hansen
2014-01-01
All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented.......All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented....
Lansing, Faiza S.; Rascoe, Daniel L.
1993-01-01
This paper presents a modified Finite-Difference Time-Domain (FDTD) technique using a generalized conformed orthogonal grid. The use of the Conformed Orthogonal Grid, Finite Difference Time Domain (GFDTD) enables the designer to match all the circuit dimensions, hence eliminating a major source o error in the analysis.
Time-domain analytic solutions of two-wire transmission line excited by a plane-wave field
International Nuclear Information System (INIS)
Ni Guyan; Yan Li; Yuan Naichang
2008-01-01
This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain. By the frequency-domain Baum–Liu–Tesche (BLT) equation, the time-domain analytic solutions are obtained and expressed in an infinite geometric series. Moreover, it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval. In other word, the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval. The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform, and the agreement is excellent. (the physics of elementary particles and fields)
Time-domain analytic Solutions of two-wire transmission line excited by a plane-wave field
Institute of Scientific and Technical Information of China (English)
Ni Gu-Yan; Yan Li; Yuan Nai-Chang
2008-01-01
This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain.By the frequency-domain Baum-Liu-Tesche(BLT)equation,the time-domain analytic solutions are obtained and expressed in an infinite geometric series.Moreover,it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval.In other word.the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval.The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform,and the agreement is excellent.
3D airborne EM modeling based on the spectral-element time-domain (SETD) method
Cao, X.; Yin, C.; Huang, X.; Liu, Y.; Zhang, B., Sr.; Cai, J.; Liu, L.
2017-12-01
In the field of 3D airborne electromagnetic (AEM) modeling, both finite-difference time-domain (FDTD) method and finite-element time-domain (FETD) method have limitations that FDTD method depends too much on the grids and time steps, while FETD requires large number of grids for complex structures. We propose a time-domain spectral-element (SETD) method based on GLL interpolation basis functions for spatial discretization and Backward Euler (BE) technique for time discretization. The spectral-element method is based on a weighted residual technique with polynomials as vector basis functions. It can contribute to an accurate result by increasing the order of polynomials and suppressing spurious solution. BE method is a stable tine discretization technique that has no limitation on time steps and can guarantee a higher accuracy during the iteration process. To minimize the non-zero number of sparse matrix and obtain a diagonal mass matrix, we apply the reduced order integral technique. A direct solver with its speed independent of the condition number is adopted for quickly solving the large-scale sparse linear equations system. To check the accuracy of our SETD algorithm, we compare our results with semi-analytical solutions for a three-layered earth model within the time lapse 10-6-10-2s for different physical meshes and SE orders. The results show that the relative errors for magnetic field B and magnetic induction are both around 3-5%. Further we calculate AEM responses for an AEM system over a 3D earth model in Figure 1. From numerical experiments for both 1D and 3D model, we draw the conclusions that: 1) SETD can deliver an accurate results for both dB/dt and B; 2) increasing SE order improves the modeling accuracy for early to middle time channels when the EM field diffuses fast so the high-order SE can model the detailed variation; 3) at very late time channels, increasing SE order has little improvement on modeling accuracy, but the time interval plays
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Lavrinenko, Andrei
2007-01-01
A complex-coordinate method known under the guise of the perfectly matched layer (PML) method for treating unbounded domains in computational electrodynamics is related to similar techniques in fluid dynamics and classical quantum theory. It may also find use in electronic-structure finite......-difference simulations. Straightforward transfer of the PML formulation to other fields does not seem feasible, however, since it is a unique feature of electrodynamics - the natural invariance - that allows analytic trick of complex coordinate scaling to be represented as pure modification of local material parameters...
Design of a coil sensor for time domain electromagnetic system for uranium exploration
International Nuclear Information System (INIS)
Keshwani, R.T.; Bhattacharya, S.
2011-01-01
Time domain electromagnetic system is used for exploration of deep seated deposits under the Earth surface. The basic principle is to set up eddy currents in conductors using pulsed excited transmitter coil during on time of a pulse. The decay time of eddy currents during off time of a pulse is a function conductivity, permeability and depth of conductor located under the Earth surface. The technology is being developed to carry out exploration of mineral deposits (basically uranium) under the Earth surface. The decay of eddy currents is eddy using J coil sensor located coplanar with the transmitter coil. The depth upto which successful exploration can be carried is strong function of design of receiver coil. The design parameters include number of turns, bandwidth, stray capacitance and resistance of a coil. This paper describes various designs tried out and their characterization results. Field results for a ground based system developed are also described. (author)
Integration of domain and resource-based reasoning for real-time control in dynamic environments
Morgan, Keith; Whitebread, Kenneth R.; Kendus, Michael; Cromarty, Andrew S.
1993-01-01
A real-time software controller that successfully integrates domain-based and resource-based control reasoning to perform task execution in a dynamically changing environment is described. The design of the controller is based on the concept of partitioning the process to be controlled into a set of tasks, each of which achieves some process goal. It is assumed that, in general, there are multiple ways (tasks) to achieve a goal. The controller dynamically determines current goals and their current criticality, choosing and scheduling tasks to achieve those goals in the time available. It incorporates rule-based goal reasoning, a TMS-based criticality propagation mechanism, and a real-time scheduler. The controller has been used to build a knowledge-based situation assessment system that formed a major component of a real-time, distributed, cooperative problem solving system built under DARPA contract. It is also being employed in other applications now in progress.
Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis
Mailhiot, Sarah E.; Zong, Fangrong; Maneval, James E.; June, Ronald K.; Galvosas, Petrik; Seymour, Joseph D.
2018-02-01
Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T1-T2 correlation experiments. By using time domain analysis of T2-T2 exchange spectroscopy, the diffusive exchange time can be quantified by measurements that use a single mixing time. Measured characteristic times for exchange are commensurate with T1 in this material and so impacts the observed T1 behavior. The approach used here allows for reliable quantification of NMR relaxation behavior in cartilage in the presence of diffusive fluid exchange between two environments.
Finite difference time domain solution of electromagnetic scattering on the hypercube
International Nuclear Information System (INIS)
Calalo, R.H.; Lyons, J.R.; Imbriale, W.A.
1988-01-01
Electromagnetic fields interacting with a dielectric or conducting structure produce scattered electromagnetic fields. To model the fields produced by complicated, volumetric structures, the finite difference time domain (FDTD) method employs an iterative solution to Maxwell's time dependent curl equations. Implementations of the FDTD method intensively use memory and perform numerous calculations per time step iteration. The authors have implemented an FDTD code on the California Institute of Technology/Jet Propulsion Laboratory Mark III Hypercube. This code allows to solve problems requiring as many as 2,048,000 unit cells on a 32 node Hypercube. For smaller problems, the code produces solutions in a fraction of the time to solve the same problems on sequential computers
DEFF Research Database (Denmark)
Cai, Hongzhu; Hu, Xiangyun; Xiong, Bin
2017-01-01
method which is unconditionally stable. We solve the diffusion equation for the electric field with a total field formulation. The finite element system of equation is solved using the direct method. The solutions of electric field, at different time, can be obtained using the effective time stepping...... method with trivial computation cost once the matrix is factorized. We try to keep the same time step size for a fixed number of steps using an adaptive time step doubling (ATSD) method. The finite element modeling domain is also truncated using a semi-adaptive method. We proposed a new boundary...... condition based on approximating the total field on the modeling boundary using the primary field corresponding to a layered background model. We validate our algorithm using several synthetic model studies....
Time Domain Filtering of Resolved Images of Sgr A{sup ∗}
Energy Technology Data Exchange (ETDEWEB)
Shiokawa, Hotaka; Doeleman, Sheperd S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gammie, Charles F. [Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801 (United States)
2017-09-01
The goal of the Event Horizon Telescope (EHT) is to provide spatially resolved images of Sgr A*, the source associated with the Galactic Center black hole. Because Sgr A* varies on timescales that are short compared to an EHT observing campaign, it is interesting to ask whether variability contains information about the structure and dynamics of the accretion flow. In this paper, we introduce “time-domain filtering,” a technique to filter time fluctuating images with specific temporal frequency ranges and to demonstrate the power and usage of the technique by applying it to mock millimeter wavelength images of Sgr A*. The mock image data is generated from the General Relativistic Magnetohydrodynamic (GRMHD) simulation and the general relativistic ray-tracing method. We show that the variability on each line of sight is tightly correlated with a typical radius of emission. This is because disk emissivity fluctuates on a timescale of the order of the local orbital period. Time-domain filtered images therefore reflect the model dependent emission radius distribution, which is not accessible in time-averaged images. We show that, in principle, filtered data have the power to distinguish between models with different black-hole spins, different disk viewing angles, and different disk orientations in the sky.
An explicit marching on-in-time solver for the time domain volume magnetic field integral equation
Sayed, Sadeed Bin
2014-07-01
Transient scattering from inhomogeneous dielectric objects can be modeled using time domain volume integral equations (TDVIEs). TDVIEs are oftentimes solved using marching on-in-time (MOT) techniques. Classical MOT-TDVIE solvers expand the field induced on the scatterer using local spatio-temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation in space and time yields a system of equations that is solved by time marching. Depending on the type of the basis and testing functions and the time step, the time marching scheme can be implicit (N. T. Gres, et al., Radio Sci., 36(3), 379-386, 2001) or explicit (A. Al-Jarro, et al., IEEE Trans. Antennas Propag., 60(11), 5203-5214, 2012). Implicit MOT schemes are known to be more stable and accurate. However, under low-frequency excitation, i.e., when the time step size is large, they call for inversion of a full matrix system at very time step.
An explicit marching on-in-time solver for the time domain volume magnetic field integral equation
Sayed, Sadeed Bin; Ulku, Huseyin Arda; Bagci, Hakan
2014-01-01
Transient scattering from inhomogeneous dielectric objects can be modeled using time domain volume integral equations (TDVIEs). TDVIEs are oftentimes solved using marching on-in-time (MOT) techniques. Classical MOT-TDVIE solvers expand the field induced on the scatterer using local spatio-temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation in space and time yields a system of equations that is solved by time marching. Depending on the type of the basis and testing functions and the time step, the time marching scheme can be implicit (N. T. Gres, et al., Radio Sci., 36(3), 379-386, 2001) or explicit (A. Al-Jarro, et al., IEEE Trans. Antennas Propag., 60(11), 5203-5214, 2012). Implicit MOT schemes are known to be more stable and accurate. However, under low-frequency excitation, i.e., when the time step size is large, they call for inversion of a full matrix system at very time step.
Helicopter time-domain electromagnetic numerical simulation based on Leapfrog ADI-FDTD
Guan, S.; Ji, Y.; Li, D.; Wu, Y.; Wang, A.
2017-12-01
We present a three-dimension (3D) Alternative Direction Implicit Finite-Difference Time-Domain (Leapfrog ADI-FDTD) method for the simulation of helicopter time-domain electromagnetic (HTEM) detection. This method is different from the traditional explicit FDTD, or ADI-FDTD. Comparing with the explicit FDTD, leapfrog ADI-FDTD algorithm is no longer limited by Courant-Friedrichs-Lewy(CFL) condition. Thus, the time step is longer. Comparing with the ADI-FDTD, we reduce the equations from 12 to 6 and .the Leapfrog ADI-FDTD method will be easier for the general simulation. First, we determine initial conditions which are adopted from the existing method presented by Wang and Tripp(1993). Second, we derive Maxwell equation using a new finite difference equation by Leapfrog ADI-FDTD method. The purpose is to eliminate sub-time step and retain unconditional stability characteristics. Third, we add the convolution perfectly matched layer (CPML) absorbing boundary condition into the leapfrog ADI-FDTD simulation and study the absorbing effect of different parameters. Different absorbing parameters will affect the absorbing ability. We find the suitable parameters after many numerical experiments. Fourth, We compare the response with the 1-Dnumerical result method for a homogeneous half-space to verify the correctness of our algorithm.When the model contains 107*107*53 grid points, the conductivity is 0.05S/m. The results show that Leapfrog ADI-FDTD need less simulation time and computer storage space, compared with ADI-FDTD. The calculation speed decreases nearly four times, memory occupation decreases about 32.53%. Thus, this algorithm is more efficient than the conventional ADI-FDTD method for HTEM detection, and is more precise than that of explicit FDTD in the late time.
Discontinuous Galerkin time-domain analysis of power/ground plate pairs with wave port excitation
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2018-01-01
In this work, a discontinuous Galerkin time-domain method is developed to analyze the power/ground plate pairs taking into account arbitrarily shaped antipads. To implement proper source excitations over the antipads, the magnetic surface current expanded by the electric eigen-modes supported by the corresponding antipad is employed as the excitation. For irregularly shaped antipads, the eigen-modes are obtained by numerical approach. Accordingly, the methodology for the S-parameter extraction is derived based on the orthogonal properties of the different modes. Based on the approach, the transformation between different modes can be readily evaluated.
Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons
Hussain, A.
2010-06-17
There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states although there is no theoretical model that directly supports such a proposal. We have experimentally re-examined the studies of phonons in bismuth and gallium arsenide, and find no evidence of any phase-dependent noise signature associated with the phonons. We place an upper limit on any such noise at least 40–50 dB lower than previously reported.
Directory of Open Access Journals (Sweden)
Jakub Bernat
2017-06-01
Full Text Available This paper addresses the issue of estimating current waveforms in a switched reluctance motor required to achieve a desired electromagnetic torque. The methodology employed exploits the recently-developed method based on the transformation from the time to the position domain. This transformation takes account of nonlinearities caused by a doubly-salient structure. Owing to this new modelling technique it is possible to solve optimization problems with reference torque, constrained voltage, and parameter sensitivity accounted for. The proposed methodology is verified against published solutions and illustrated through simulations and experiments.
Perfectly Matched Layer for the Wave Equation Finite Difference Time Domain Method
Miyazaki, Yutaka; Tsuchiya, Takao
2012-07-01
The perfectly matched layer (PML) is introduced into the wave equation finite difference time domain (WE-FDTD) method. The WE-FDTD method is a finite difference method in which the wave equation is directly discretized on the basis of the central differences. The required memory of the WE-FDTD method is less than that of the standard FDTD method because no particle velocity is stored in the memory. In this study, the WE-FDTD method is first combined with the standard FDTD method. Then, Berenger's PML is combined with the WE-FDTD method. Some numerical demonstrations are given for the two- and three-dimensional sound fields.
Scattering analysis of periodic structures using finite-difference time-domain
ElMahgoub, Khaled; Elsherbeni, Atef Z
2012-01-01
Periodic structures are of great importance in electromagnetics due to their wide range of applications such as frequency selective surfaces (FSS), electromagnetic band gap (EBG) structures, periodic absorbers, meta-materials, and many others. The aim of this book is to develop efficient computational algorithms to analyze the scattering properties of various electromagnetic periodic structures using the finite-difference time-domain periodic boundary condition (FDTD/PBC) method. A new FDTD/PBC-based algorithm is introduced to analyze general skewed grid periodic structures while another algor
Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei
2017-01-01
Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly...... by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares...
Detection and characterization of corrosion of bridge cables by time domain reflectometry
Liu, Wei; Hunsperger, Robert G.; Folliard, Kevin; Chajes, Michael J.; Barot, Jignesh; Jhaveri, Darshan; Kunz, Eric
1999-02-01
In this paper, we develop and demonstrate a nondestructive evaluation technique for corrosion detection of embedded or encased steel cables. This technique utilizes time domain reflectometry (TDR), which has been traditionally used to detect electrical discontinuities in transmission lines. By applying a sensor wire along with the bridge cable, we can model the cable as an asymmetric, twin-conductor transmission line. Physical defects of the bridge cable will change the electromagnetic properties of the line and can be detected by TDR. Furthermore, different types of defects can be modeled analytically, and identified using TDR. TDR measurement results from several fabricated bridge cable sections with built-in defects are reported.
Discontinuous Galerkin time-domain analysis of power/ground plate pairs with wave port excitation
Li, Ping
2018-04-06
In this work, a discontinuous Galerkin time-domain method is developed to analyze the power/ground plate pairs taking into account arbitrarily shaped antipads. To implement proper source excitations over the antipads, the magnetic surface current expanded by the electric eigen-modes supported by the corresponding antipad is employed as the excitation. For irregularly shaped antipads, the eigen-modes are obtained by numerical approach. Accordingly, the methodology for the S-parameter extraction is derived based on the orthogonal properties of the different modes. Based on the approach, the transformation between different modes can be readily evaluated.
Numerical modeling of wind turbine aerodynamic noise in the time domain.
Lee, Seunghoon; Lee, Seungmin; Lee, Soogab
2013-02-01
Aerodynamic noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge noise model is used to determine the unsteady pressure on the blade surface. The far-field noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine noise can be quite different with respect to the distance and direction from the wind turbine.
Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons
Hussain, A.; Andrews, S. R.
2010-01-01
There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states although there is no theoretical model that directly supports such a proposal. We have experimentally re-examined the studies of phonons in bismuth and gallium arsenide, and find no evidence of any phase-dependent noise signature associated with the phonons. We place an upper limit on any such noise at least 40–50 dB lower than previously reported.
Discrete-Time Domain Modelling of Voltage Source Inverters in Standalone Applications
DEFF Research Database (Denmark)
Federico, de Bosio; de Sousa Ribeiro, Luiz Antonio; Freijedo Fernandez, Francisco Daniel
2017-01-01
modelling of the LC plant with consideration of delay and sample-and-hold effects on the state feedback cross-coupling decoupling is derived. From this plant formulation, current controllers with wide bandwidth and good relative stability properties are developed. Two controllers based on lead compensation......The decoupling of the capacitor voltage and inductor current has been shown to improve significantly the dynamic performance of voltage source inverters in standalone applications. However, the computation and PWM delays still limit the achievable bandwidth. In this paper a discrete-time domain...
Time-resolved experiments in the frequency domain using synchrotron radiation (invited)
De Stasio, Gelsomina; Giusti, A. M.; Parasassi, T.; Ravagnan, G.; Sapora, O.
1992-01-01
PLASTIQUE is the only synchrotron radiation beam line in the world that performs time-resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and the dynamics of molecules. This technique measures fluorescence lifetimes with picosecond resolution in the near UV spectral range. Such accurate measurements are rendered possible by taking phase and modulation data, and by the advantages of the cross-correlation technique. A successful experiment demonstrated the radiation damage induced by low doses of radiation on rabbit blood cell membranes.
Spencer, E. A.; Clark, D. C.; Vadepu, S. K.; Patra, S.
2017-12-01
A Time Domain Impedance Probe (TDIP) measures electron density and electron neutral collision frequencies in the ionosphere. This instrument has been tested on a sounding rocket flight and is now being further developed to fly on a NASA Undergraduate Student Instrument Program (USIP) cubesat to be launched out of the ISS in 2019. Here we report on the development of a new combined TDIP and plasma wave instrument that can be used on cubesat platforms to measure local electron parameters, and also to receive or transmit electron scale waves. This combined instrument can be used to study short time and space scale phenomena in the upper ionosphere using only RF signals. The front end analog circuitry is dual-purposed to perform active or passive probing of the ambient plasma. Two dipole antennas are used, one is optimzed for impedance measurements, while the other is optimized for transmitter-receiver performance. We show our circuit realization, and initial results from laboratory measurements using the TDIP prototype modified for receiver function. We also show Finite Difference Time Domain (FDTD) simulations of an electrically long antenna immersed in a magnetized plasma used to optimize the transmitter receiver performance.
Algorithm for determining two-periodic steady-states in AC machines directly in time domain
Directory of Open Access Journals (Sweden)
Sobczyk Tadeusz J.
2016-09-01
Full Text Available This paper describes an algorithm for finding steady states in AC machines for the cases of their two-periodic nature. The algorithm enables to specify the steady-state solution identified directly in time domain despite of the fact that two-periodic waveforms are not repeated in any finite time interval. The basis for such an algorithm is a discrete differential operator that specifies the temporary values of the derivative of the two-periodic function in the selected set of points on the basis of the values of that function in the same set of points. It allows to develop algebraic equations defining the steady state solution reached in a chosen point set for the nonlinear differential equations describing the AC machines when electrical and mechanical equations should be solved together. That set of those values allows determining the steady state solution at any time instant up to infinity. The algorithm described in this paper is competitive with respect to the one known in literature an approach based on the harmonic balance method operated in frequency domain.
Time-domain incomplete Gauss-Newton full-waveform inversion of Gulf of Mexico data
AlTheyab, Abdullah
2013-09-22
We apply the incomplete Gauss-Newton full-waveform inversion (TDIGN-FWI) to Gulf of Mexico (GOM) data in the space-time domain. In our application, iterative least-squares reverse-time migration (LSRTM) is used to estimate the model update at each non-linear iteration, and the number of LSRTM iterations is progressively increased after each non-linear iteration. With this method, model updating along deep reflection wavepaths are automatically enhanced, which in turn improves imaging below the reach of diving-waves. The forward and adjoint operators are implemented in the space-time domain to simultaneously invert the data over a range of frequencies. A multiscale approach is used where higher frequencies are down-weighted significantly at early iterations, and gradually included in the inversion. Synthetic data results demonstrate the effectiveness of reconstructing both the high- and low-wavenumber features in the model without relying on diving waves in the inversion. Results with Gulf of Mexico field data show a significantly improved migration image in both the shallow and deep sections.
Faes, Luca; Erla, Silvia; Porta, Alberto; Nollo, Giandomenico
2013-08-28
We present an approach for the quantification of directional relations in multiple time series exhibiting significant zero-lag interactions. To overcome the limitations of the traditional multivariate autoregressive (MVAR) modelling of multiple series, we introduce an extended MVAR (eMVAR) framework allowing either exclusive consideration of time-lagged effects according to the classic notion of Granger causality, or consideration of combined instantaneous and lagged effects according to an extended causality definition. The spectral representation of the eMVAR model is exploited to derive novel frequency domain causality measures that generalize to the case of instantaneous effects the known directed coherence (DC) and partial DC measures. The new measures are illustrated in theoretical examples showing that they reduce to the known measures in the absence of instantaneous causality, and describe peculiar aspects of directional interaction among multiple series when instantaneous causality is non-negligible. Then, the issue of estimating eMVAR models from time-series data is faced, proposing two approaches for model identification and discussing problems related to the underlying model assumptions. Finally, applications of the framework on cardiovascular variability series and multichannel EEG recordings are presented, showing how it allows one to highlight patterns of frequency domain causality consistent with well-interpretable physiological interaction mechanisms.
Time-Domain Modeling of RF Antennas and Plasma-Surface Interactions
Directory of Open Access Journals (Sweden)
Jenkins Thomas G.
2017-01-01
Full Text Available Recent advances in finite-difference time-domain (FDTD modeling techniques allow plasma-surface interactions such as sheath formation and sputtering to be modeled concurrently with the physics of antenna near- and far-field behavior and ICRF power flow. Although typical sheath length scales (micrometers are much smaller than the wavelengths of fast (tens of cm and slow (millimeter waves excited by the antenna, sheath behavior near plasma-facing antenna components can be represented by a sub-grid kinetic sheath boundary condition, from which RF-rectified sheath potential variation over the surface is computed as a function of current flow and local plasma parameters near the wall. These local time-varying sheath potentials can then be used, in tandem with particle-in-cell (PIC models of the edge plasma, to study sputtering effects. Particle strike energies at the wall can be computed more accurately, consistent with their passage through the known potential of the sheath, such that correspondingly increased accuracy of sputtering yields and heat/particle fluxes to antenna surfaces is obtained. The new simulation capabilities enable time-domain modeling of plasma-surface interactions and ICRF physics in realistic experimental configurations at unprecedented spatial resolution. We will present results/animations from high-performance (10k-100k core FDTD/PIC simulations of Alcator C-Mod antenna operation.
openPSTD: The open source pseudospectral time-domain method for acoustic propagation
Hornikx, Maarten; Krijnen, Thomas; van Harten, Louis
2016-06-01
An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. In the implementation it has been opted to model the physical geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. For accelerating the software, an option has been included to accelerate the calculations by a partial implementation of the code on the Graphical Processing Unit (GPU), which increases the throughput by up to fifteen times. The details of the implementation are reported, as well as the accuracy of the code.
On the DC loop modes in the MOT solution of the time domain EFIE
Shi, Yifei
2014-07-01
When marching-on-in-time (MOT) method is applied to solve the time domain electric field integral equation (TD-EFIE), DC loop modes are always observed in the solution. In theory these modes should not be observed since they do not satisfy the relaxed initial conditions. Their appearance is attributed to numerical errors. It is shown here that when Rao-Wilton-Glisson basis and Lagrange interpolation functions are used to discretize the TD-EFIE, errors due to this space-time discretization have zero impact on the DC loop modes. Numerical experiments demonstrate that the numerical errors due to approximate solution of the MOT matrix system have more dominant impact on DC loop modes in the MOT solution.
Parallel, explicit, and PWTD-enhanced time domain volume integral equation solver
Liu, Yang
2013-07-01
Time domain volume integral equations (TDVIEs) are useful for analyzing transient scattering from inhomogeneous dielectric objects in applications as varied as photonics, optoelectronics, and bioelectromagnetics. TDVIEs typically are solved by implicit marching-on-in-time (MOT) schemes [N. T. Gres et al., Radio Sci., 36, 379-386, 2001], requiring the solution of a system of equations at each and every time step. To reduce the computational cost associated with such schemes, [A. Al-Jarro et al., IEEE Trans. Antennas Propagat., 60, 5203-5215, 2012] introduced an explicit MOT-TDVIE method that uses a predictor-corrector technique to stably update field values throughout the scatterer. By leveraging memory-efficient nodal spatial discretization and scalable parallelization schemes [A. Al-Jarro et al., in 28th Int. Rev. Progress Appl. Computat. Electromagn., 2012], this solver has been successfully applied to the analysis of scattering phenomena involving 0.5 million spatial unknowns. © 2013 IEEE.
On spurious resonant modes in the MOT solution of time domain EFIE
Shi, Yifei
2013-07-01
Theoretically, internal resonant modes should not be induced in the marching-on-in-time (MOT) solution of the time domain electric field integral equation since zero initial conditions are enforced at the beginning of time marching and the internal resonant modes do not satisfy these initial conditions. However, these spurious modes are always observed in the MOT solution. It has been conjectured in the past that numerical errors might establish the necessary initial conditions and allow the incident field to induce the internal resonant modes. Systematic numerical experiments carried out in this work prove this conjecture by demonstrating that the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors and the spectrum of the incident field. © 2013 IEEE.
Hardware architecture design of image restoration based on time-frequency domain computation
Wen, Bo; Zhang, Jing; Jiao, Zipeng
2013-10-01
The image restoration algorithms based on time-frequency domain computation is high maturity and applied widely in engineering. To solve the high-speed implementation of these algorithms, the TFDC hardware architecture is proposed. Firstly, the main module is designed, by analyzing the common processing and numerical calculation. Then, to improve the commonality, the iteration control module is planed for iterative algorithms. In addition, to reduce the computational cost and memory requirements, the necessary optimizations are suggested for the time-consuming module, which include two-dimensional FFT/IFFT and the plural calculation. Eventually, the TFDC hardware architecture is adopted for hardware design of real-time image restoration system. The result proves that, the TFDC hardware architecture and its optimizations can be applied to image restoration algorithms based on TFDC, with good algorithm commonality, hardware realizability and high efficiency.
Time Domain Analysis of Graphene Nanoribbon Interconnects Based on Transmission Line Model
Directory of Open Access Journals (Sweden)
S. Haji Nasiri
2012-03-01
Full Text Available Time domain analysis of multilayer graphene nanoribbon (MLGNR interconnects, based on transmission line modeling (TLM using a six-order linear parametric expression, has been presented for the first time. We have studied the effects of interconnect geometry along with its contact resistance on its step response and Nyquist stability. It is shown that by increasing interconnects dimensions their propagation delays are increased and accordingly the system becomes relatively more stable. In addition, we have compared time responses and Nyquist stabilities of MLGNR and SWCNT bundle interconnects, with the same external dimensions. The results show that under the same conditions, the propagation delays for MLGNR interconnects are smaller than those of SWCNT bundle interconnects are. Hence, SWCNT bundle interconnects are relatively more stable than their MLGNR rivals.
International Nuclear Information System (INIS)
Wei Biao; Feng Peng; Yang Fan; Ren Yong
2014-01-01
To deal with the disadvantages of the homogeneous signature of the nuclear material identification system (NMIS) and limited methods to extract the characteristic parameters of the nuclear materials, an enhanced method using the combination of the Time-of-Flight (TOF) and the Pulse Shape Discrimination (PSD) was introduced into the traditional characteristic parameters extraction and recognition system of the NMIS. With the help of the PSD, the γ signal and the neutron signal can be discriminated. Further based on the differences of the neutron-γ flight time of the detectors in various positions, a new time-domain signature reflecting the position information of unknown nuclear material was investigated. The simulation result showed that the algorithm is feasible and helpful to identify the relative position of unknown nuclear material. (authors)
On the DC loop modes in the MOT solution of the time domain EFIE
Shi, Yifei; Bagci, Hakan; Lu, Mingyu
2014-01-01
When marching-on-in-time (MOT) method is applied to solve the time domain electric field integral equation (TD-EFIE), DC loop modes are always observed in the solution. In theory these modes should not be observed since they do not satisfy the relaxed initial conditions. Their appearance is attributed to numerical errors. It is shown here that when Rao-Wilton-Glisson basis and Lagrange interpolation functions are used to discretize the TD-EFIE, errors due to this space-time discretization have zero impact on the DC loop modes. Numerical experiments demonstrate that the numerical errors due to approximate solution of the MOT matrix system have more dominant impact on DC loop modes in the MOT solution.
Zhang, Shengli; Tang, Jiong
2016-04-01
Gearbox is one of the most vulnerable subsystems in wind turbines. Its healthy status significantly affects the efficiency and function of the entire system. Vibration based fault diagnosis methods are prevalently applied nowadays. However, vibration signals are always contaminated by noise that comes from data acquisition errors, structure geometric errors, operation errors, etc. As a result, it is difficult to identify potential gear failures directly from vibration signals, especially for the early stage faults. This paper utilizes synchronous averaging technique in time-frequency domain to remove the non-synchronous noise and enhance the fault related time-frequency features. The enhanced time-frequency information is further employed in gear fault classification and identification through feature extraction algorithms including Kernel Principal Component Analysis (KPCA), Multilinear Principal Component Analysis (MPCA), and Locally Linear Embedding (LLE). Results show that the LLE approach is the most effective to classify and identify different gear faults.
Time domain simulation of the response of geometrically nonlinear panels subjected to random loading
Moyer, E. Thomas, Jr.
1988-01-01
The response of composite panels subjected to random pressure loads large enough to cause geometrically nonlinear responses is studied. A time domain simulation is employed to solve the equations of motion. An adaptive time stepping algorithm is employed to minimize intermittent transients. A modified algorithm for the prediction of response spectral density is presented which predicts smooth spectral peaks for discrete time histories. Results are presented for a number of input pressure levels and damping coefficients. Response distributions are calculated and compared with the analytical solution of the Fokker-Planck equations. RMS response is reported as a function of input pressure level and damping coefficient. Spectral densities are calculated for a number of examples.
Uysal, Ismail Enes
2016-10-01
Plasmonic structures are utilized in many applications ranging from bio-medicine to solar energy generation and transfer. Numerical schemes capable of solving equations of classical electrodynamics have been the method of choice for characterizing scattering properties of such structures. However, as dimensions of these plasmonic structures reduce to nanometer scale, quantum mechanical effects start to appear. These effects cannot be accurately modeled by available classical numerical methods. One of these quantum effects is the tunneling, which is observed when two structures are located within a sub-nanometer distance of each other. At these small distances electrons “jump" from one structure to another and introduce a path for electric current to flow. Classical equations of electrodynamics and the schemes used for solving them do not account for this additional current path. This limitation can be lifted by introducing an auxiliary tunnel with material properties obtained using quantum models and applying a classical solver to the structures connected by this auxiliary tunnel. Early work on this topic focused on quantum models that are generated using a simple one-dimensional wave function to find the tunneling probability and assume a simple Drude model for the permittivity of the tunnel. These tunnel models are then used together with a classical frequency domain solver. In this thesis, a time domain surface integral equation solver for quantum corrected analysis of transient plasmonic interactions is proposed. This solver has several advantages: (i) As opposed to frequency domain solvers, it provides results at a broad band of frequencies with a single simulation. (ii) As opposed to differential equation solvers, it only discretizes surfaces (reducing number of unknowns), enforces the radiation condition implicitly (increasing the accuracy), and allows for time step selection independent of spatial discretization (increasing efficiency). The quantum model
Hybrid Fourier pseudospectral/discontinuous Galerkin time-domain method for wave propagation
Pagán Muñoz, Raúl; Hornikx, Maarten
2017-11-01
The Fourier Pseudospectral time-domain (Fourier PSTD) method was shown to be an efficient way of modelling acoustic propagation problems as described by the linearized Euler equations (LEE), but is limited to real-valued frequency independent boundary conditions and predominantly staircase-like boundary shapes. This paper presents a hybrid approach to solve the LEE, coupling Fourier PSTD with a nodal Discontinuous Galerkin (DG) method. DG exhibits almost no restrictions with respect to geometrical complexity or boundary conditions. The aim of this novel method is to allow the computation of complex geometries and to be a step towards the implementation of frequency dependent boundary conditions by using the benefits of DG at the boundaries, while keeping the efficient Fourier PSTD in the bulk of the domain. The hybridization approach is based on conformal meshes to avoid spatial interpolation of the DG solutions when transferring values from DG to Fourier PSTD, while the data transfer from Fourier PSTD to DG is done utilizing spectral interpolation of the Fourier PSTD solutions. The accuracy of the hybrid approach is presented for one- and two-dimensional acoustic problems and the main sources of error are investigated. It is concluded that the hybrid methodology does not introduce significant errors compared to the Fourier PSTD stand-alone solver. An example of a cylinder scattering problem is presented and accurate results have been obtained when using the proposed approach. Finally, no instabilities were found during long-time calculation using the current hybrid methodology on a two-dimensional domain.
Time-domain least-squares migration using the Gaussian beam summation method
Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo
2018-04-01
With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modeling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modeling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a preconditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.
Rapid screening of fatty acid alkyl esters in olive oils by time domain reflectometry.
Berardinelli, Annachiara; Ragni, Luigi; Bendini, Alessandra; Valli, Enrico; Conte, Lanfranco; Guarnieri, Adriano; Toschi, Tullia Gallina
2013-11-20
The main aim of the present research is to assess the possibility of quickly screening fatty acid alkyl esters (FAAE) in olive oils using time domain reflectometry (TDR) and partial least-squares (PLS) multivariate statistical analysis. Eighteen virgin olive oil samples with fatty acid alkyl ester contents and fatty acid ethyl ester/methyl ester ratios (FAEE/FAME) ranging from 3 to 100 mg kg(-1) and from 0.3 to 2.6, respectively, were submitted to tests with time domain resolution of 1 ps. The results obtained in test set validation demonstrated that this new and fast analytical approach is able to predict FAME, FAEE, and FAME + FAEE contents with R(2) values of 0.905, 0.923, and 0.927, respectively. Further measurements on mixtures between olive oil and FAAE standards confirmed that the prediction is based on a direct influence of fatty acid alkyl esters on the TDR signal. The suggested technique appeared potentially suitable for monitoring one of the most important quality attribute of the olive oil in the extraction process.
Zhang, Xiao-bo
2017-06-01
The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge storage consumption in the gradient preconditioning algorithms based on Hessian matrices in time-domain full waveform inversion (FWI), but the accuracy is affected by the energy of reflected waves when strong reflectors are present in velocity model. To address this problem, we propose a gradient preconditioning method, which scales the gradient based on the energy of the “approximated transmitted wavefield” simulated by the nonreflecting acoustic wave equation. The method does not require computing or storing the Hessian matrix or its inverse. Furthermore, it can effectively eliminate the effects caused by geometric diffusion and non-uniformity illumination on gradient. The results of model experiments confirm that the time-domain FWI using the gradient preconditioning based on transmitted waves energy can achieve higher inversion precision for high-velocity body and the deep strata below when compared with using the gradient preconditioning based on seismic waves energy.
An innovative application of time-domain spectroscopy on localized surface plasmon resonance sensing
Li, Meng-Chi; Chang, Ying-Feng; Wang, Huai-Yi; Lin, Yu-Xen; Kuo, Chien-Cheng; Annie Ho, Ja-An; Lee, Cheng-Chung; Su, Li-Chen
2017-03-01
White-light scanning interferometry (WLSI) is often used to study the surface profiles and properties of thin films because the strength of the technique lies in its ability to provide fast and high resolution measurements. An innovative attempt is made in this paper to apply WLSI as a time-domain spectroscopic system for localized surface plasmon resonance (LSPR) sensing. A WLSI-based spectrometer is constructed with a breadboard of WLSI in combination with a spectral centroid algorithm for noise reduction and performance improvement. Experimentally, the WLSI-based spectrometer exhibits a limit of detection (LOD) of 1.2 × 10-3 refractive index units (RIU), which is better than that obtained with a conventional UV-Vis spectrometer, by resolving the LSPR peak shift. Finally, the bio-applicability of the proposed spectrometer was investigated using the rs242557 tau gene, an Alzheimer’s and Parkinson’s disease biomarker. The LOD was calculated as 15 pM. These results demonstrate that the proposed WLSI-based spectrometer could become a sensitive time-domain spectroscopic biosensing platform.
Application of Time-Frequency Domain Transform to Three-Dimensional Interpolation of Medical Images.
Lv, Shengqing; Chen, Yimin; Li, Zeyu; Lu, Jiahui; Gao, Mingke; Lu, Rongrong
2017-11-01
Medical image three-dimensional (3D) interpolation is an important means to improve the image effect in 3D reconstruction. In image processing, the time-frequency domain transform is an efficient method. In this article, several time-frequency domain transform methods are applied and compared in 3D interpolation. And a Sobel edge detection and 3D matching interpolation method based on wavelet transform is proposed. We combine wavelet transform, traditional matching interpolation methods, and Sobel edge detection together in our algorithm. What is more, the characteristics of wavelet transform and Sobel operator are used. They deal with the sub-images of wavelet decomposition separately. Sobel edge detection 3D matching interpolation method is used in low-frequency sub-images under the circumstances of ensuring high frequency undistorted. Through wavelet reconstruction, it can get the target interpolation image. In this article, we make 3D interpolation of the real computed tomography (CT) images. Compared with other interpolation methods, our proposed method is verified to be effective and superior.
Time domain SAR raw data simulation using CST and image focusing of 3D objects
Saeed, Adnan; Hellwich, Olaf
2017-10-01
This paper presents the use of a general purpose electromagnetic simulator, CST, to simulate realistic synthetic aperture radar (SAR) raw data of three-dimensional objects. Raw data is later focused in MATLAB using range-doppler algorithm. Within CST Microwave Studio a replica of TerraSAR-X chirp signal is incident upon a modeled Corner Reflector (CR) whose design and material properties are identical to that of the real one. Defining mesh and other appropriate settings reflected wave is measured at several distant points within a line parallel to the viewing direction. This is analogous to an array antenna and is synthesized to create a long aperture for SAR processing. The time domain solver in CST is based on the solution of differential form of Maxwells equations. Exported data from CST is arranged into a 2-d matrix of axis range and azimuth. Hilbert transform is applied to convert the real signal to complex data with phase information. Range compression, range cell migration correction (RCMC), and azimuth compression are applied in time domain to obtain the final SAR image. This simulation can provide valuable information to clarify which real world objects cause images suitable for high accuracy identification in the SAR images.
A time-domain finite element boundary integral approach for elastic wave scattering
Shi, F.; Lowe, M. J. S.; Skelton, E. A.; Craster, R. V.
2018-04-01
The response of complex scatterers, such as rough or branched cracks, to incident elastic waves is required in many areas of industrial importance such as those in non-destructive evaluation and related fields; we develop an approach to generate accurate and rapid simulations. To achieve this we develop, in the time domain, an implementation to efficiently couple the finite element (FE) method within a small local region, and the boundary integral (BI) globally. The FE explicit scheme is run in a local box to compute the surface displacement of the scatterer, by giving forcing signals to excitation nodes, which can lie on the scatterer itself. The required input forces on the excitation nodes are obtained with a reformulated FE equation, according to the incident displacement field. The surface displacements computed by the local FE are then projected, through time-domain BI formulae, to calculate the scattering signals with different modes. This new method yields huge improvements in the efficiency of FE simulations for scattering from complex scatterers. We present results using different shapes and boundary conditions, all simulated using this approach in both 2D and 3D, and then compare with full FE models and theoretical solutions to demonstrate the efficiency and accuracy of this numerical approach.
Time-domain electromagnetic energy in a frequency-dispersive left-handed medium
International Nuclear Information System (INIS)
Cui Tiejun; Kong Jinau
2004-01-01
From Maxwell's equations and the Poynting theorem, the time-domain electric and magnetic energy densities are generally defined in the frequency-dispersive media based on the conservation of energy. As a consequence, a general definition of electric and magnetic energy is proposed. Comparing with existing formulations of electric and magnetic energy in frequency-dispersive media, the new definition is more reasonable and is valid in any case. Using the new definition and staring from the equation of motion, we have shown rigorously that the total energy density and the individual electric and magnetic energy densities are always positive in a realistic artificial left-handed medium (LHM) [R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001)], which obeys actually the Lorentz medium model, although such a LHM has negative permittivity and negative permeability simultaneously in a certain frequency range. We have also shown that the conservation of energy is not violated in LHM. The earlier conclusions can be easily extended to the Drude medium model and the cold plasma medium model. Through an exact analysis of a one-dimensional transient current source radiating in LHM, numerical results are given to demonstrate that the work done by source, the power flowing outwards a surface, and the electric and magnetic energy stored in a volume are all positive in the time domain
Merrikh-Bayat, Farshad
2011-04-01
One main approach for time-domain simulation of the linear output-feedback systems containing fractional-order controllers is to approximate the transfer function of the controller with an integer-order transfer function and then perform the simulation. In general, this approach suffers from two main disadvantages: first, the internal stability of the resulting feedback system is not guaranteed, and second, the amount of error caused by this approximation is not exactly known. The aim of this paper is to propose an efficient method for time-domain simulation of such systems without facing the above mentioned drawbacks. For this purpose, the fractional-order controller is approximated with an integer-order transfer function (possibly in combination with the delay term) such that the internal stability of the closed-loop system is guaranteed, and then the simulation is performed. It is also shown that the resulting approximate controller can effectively be realized by using the proposed method. Some formulas for estimating and correcting the simulation error, when the feedback system under consideration is subjected to the unit step command or the unit step disturbance, are also presented. Finally, three numerical examples are studied and the results are compared with the Oustaloup continuous approximation method. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.
Pichette, Charles; Giudice, Andrea; Thibault, Simon; Bérubé-Lauzière, Yves
2016-11-20
Single-photon avalanche diodes (SPADs) achieving high timing resolution (≈20-50 ps) developed for time-correlated single-photon counting (TCSPC) generally have very small photosensitive areas (25-100 μm in diameter). This limits the achievable photon counting rate and signal-to-noise ratio and may lead to long counting times. This is detrimental in applications requiring several measurements, such as fluorescence lifetime imaging (FLIM) microscopy, which requires scanning, and time-domain diffuse optical tomography (TD-DOT). We show in this work that the use of an immersion lens directly affixed onto the photosensitive area of the SPAD helps alleviate this problem by allowing more light to be concentrated onto the detector. Following careful optical design and simulations, our experimental results show that it is actually possible to achieve the predicted theoretical increase in the photon counting rate (we achieve a factor of ≈4 here). This work is of high relevance in high timing resolution TCSPC with small photosensitive area detectors and should find widespread interest in FLIM and TD-DOT with SPADs.
A frequency-domain method for solving linear time delay systems with constant coefficients
Jin, Mengshi; Chen, Wei; Song, Hanwen; Xu, Jian
2018-03-01
In an active control system, time delay will occur due to processes such as signal acquisition and transmission, calculation, and actuation. Time delay systems are usually described by delay differential equations (DDEs). Since it is hard to obtain an analytical solution to a DDE, numerical solution is of necessity. This paper presents a frequency-domain method that uses a truncated transfer function to solve a class of DDEs. The theoretical transfer function is the sum of infinite items expressed in terms of poles and residues. The basic idea is to select the dominant poles and residues to truncate the transfer function, thus ensuring the validity of the solution while improving the efficiency of calculation. Meanwhile, the guideline of selecting these poles and residues is provided. Numerical simulations of both stable and unstable delayed systems are given to verify the proposed method, and the results are presented and analysed in detail.
A Compact Unconditionally Stable Method for Time-Domain Maxwell's Equations
Directory of Open Access Journals (Sweden)
Zhuo Su
2013-01-01
Full Text Available Higher order unconditionally stable methods are effective ways for simulating field behaviors of electromagnetic problems since they are free of Courant-Friedrich-Levy conditions. The development of accurate schemes with less computational expenditure is desirable. A compact fourth-order split-step unconditionally-stable finite-difference time-domain method (C4OSS-FDTD is proposed in this paper. This method is based on a four-step splitting form in time which is constructed by symmetric operator and uniform splitting. The introduction of spatial compact operator can further improve its performance. Analyses of stability and numerical dispersion are carried out. Compared with noncompact counterpart, the proposed method has reduced computational expenditure while keeping the same level of accuracy. Comparisons with other compact unconditionally-stable methods are provided. Numerical dispersion and anisotropy errors are shown to be lower than those of previous compact unconditionally-stable methods.
Transient analysis of printed lines using finite-difference time-domain method
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Shahid [Thomas Jefferson National Accelerator Facility, 12050 Jefferson Avenue, Suite 704, Newport News, VA, 23606, USA
2012-03-29
Comprehensive studies of ultra-wideband pulses and electromagnetic coupling on printed coupled lines have been performed using full-wave 3D finite-difference time-domain analysis. Effects of unequal phase velocities of coupled modes, coupling between line traces, and the frequency dispersion on the waveform fidelity and crosstalk have been investigated in detail. To discriminate the contributions of different mechanisms into pulse evolution, single and coupled microstrip lines without (ϵ_{r} = 1) and with (ϵ_{r} > 1) dielectric substrates have been examined. To consistently compare the performance of the coupled lines with substrates of different permittivities and transients of different characteristic times, a generic metric similar to the electrical wavelength has been introduced. The features of pulse propagation on coupled lines with layered and pedestal substrates and on the irregular traces have been explored. Finally, physical interpretations of the simulation results are discussed in the paper.
Using the time domain reflectometer to check for a locate a fault
International Nuclear Information System (INIS)
Ramphal, M.; Sadok, E.
1995-01-01
The Time Domain Reflectometer (TDR) is one of the most useful tools for finding cable faults (opens, shorts, bad cable splices). The TDR is connected to the end of the line and shows the distance to the fault. It uses a low voltage signal that will not damage the line or interfere with nearby lines. The TDR sends a pulse or energy down the cable under test; when the pulse encounters the end of the cable or any cable fault, a portion of the pulse energy is reflected. The elapsed time of the reflected pulse is and indication of the distance to the fault. The shape of the reflected pulse uniquely identifies the type of cable fault. (author)
Application of Time Domain PARET to the measured responses of a building
International Nuclear Information System (INIS)
Lager, D.L.
1979-01-01
The application of the Time Domain PARET (TDP) algorithm to data obtained from the measured responses of a three story reinforced concrete building approximately 465 feet long by 220 feet wide by 40 feet high, with 12 to 18 inch thick walls, is described. The measurements were taken by Agbabian Associates, El Segundo, California. The structure was excited by a device developed at Agbabian that uses a mass sliding down a rod to cut metal disks attached to the rod. The result is a series of impulse forces driving the building at the attachment point of the rod. The responses measured were the accelerations at two locations on the structure. A constraint imposed was that the equipment in the building must remain operating during the time the measurements were made
Huang, Chongyang; Zhou, Qi; Gao, Shan; Bao, Qingjia; Chen, Fang; Liu, Chaoyang
2016-01-20
Different ginger cultivars may contain different nutritional and medicinal values. In this study, a time-domain nuclear magnetic resonance method was employed to study water dynamics in different ginger cultivars. Significant differences in transverse relaxation time T2 values assigned to the distribution of water in different parts of the plant were observed between Henan ginger and four other ginger cultivars. Ion concentration and metabolic analysis showed similar differences in Mn ion concentrations and organic solutes among the different ginger cultivars, respectively. On the basis of Pearson's correlation analysis, many organic solutes and 6-gingerol, the main active substance of ginger, exhibited significant correlations with water distribution as determined by NMR T2 relaxation, suggesting that the organic solute differences may impact water distribution. Our work demonstrates that low-field NMR relaxometry provides useful information about water dynamics in different ginger cultivars as affected by the presence of different organic solutes.
Retarded potentials and time domain boundary integral equations a road map
Sayas, Francisco-Javier
2016-01-01
This book offers a thorough and self-contained exposition of the mathematics of time-domain boundary integral equations associated to the wave equation, including applications to scattering of acoustic and elastic waves. The book offers two different approaches for the analysis of these integral equations, including a systematic treatment of their numerical discretization using Galerkin (Boundary Element) methods in the space variables and Convolution Quadrature in the time variable. The first approach follows classical work started in the late eighties, based on Laplace transforms estimates. This approach has been refined and made more accessible by tailoring the necessary mathematical tools, avoiding an excess of generality. A second approach contains a novel point of view that the author and some of his collaborators have been developing in recent years, using the semigroup theory of evolution equations to obtain improved results. The extension to electromagnetic waves is explained in one of the appendices...
A model of the formation of illusory conjunctions in the time domain.
Botella, J; Suero, M; Barriopedro, M I
2001-12-01
The authors present a model to account for the miscombination of features when stimuli are presented using the rapid serial visual presentation (RSVP) technique (illusory conjunctions in the time domain). It explains the distributions of responses through a mixture of trial outcomes. In some trials, attention is successfully focused on the target, whereas in others, the responses are based on partial information. Two experiments are presented that manipulated the mean processing time of the target-defining dimension and of the to-be-reported dimension, respectively. As predicted, the average origin of the responses is delayed when lengthening the target-defining dimension, whereas it is earlier when lengthening the to-be-reported dimension; in the first case the number of correct responses is dramatically reduced, whereas in the second it does not change. The results, a review of other research, and simulations carried out with a formal version of the model are all in close accordance with the predictions.
The development of efficient numerical time-domain modeling methods for geophysical wave propagation
Zhu, Lieyuan
This Ph.D. dissertation focuses on the numerical simulation of geophysical wave propagation in the time domain including elastic waves in solid media, the acoustic waves in fluid media, and the electromagnetic waves in dielectric media. This thesis shows that a linear system model can describe accurately the physical processes of those geophysical waves' propagation and can be used as a sound basis for modeling geophysical wave propagation phenomena. The generalized stability condition for numerical modeling of wave propagation is therefore discussed in the context of linear system theory. The efficiency of a series of different numerical algorithms in the time-domain for modeling geophysical wave propagation are discussed and compared. These algorithms include the finite-difference time-domain method, pseudospectral time domain method, alternating directional implicit (ADI) finite-difference time domain method. The advantages and disadvantages of these numerical methods are discussed and the specific stability condition for each modeling scheme is carefully derived in the context of the linear system theory. Based on the review and discussion of these existing approaches, the split step, ADI pseudospectral time domain (SS-ADI-PSTD) method is developed and tested for several cases. Moreover, the state-of-the-art stretched-coordinate perfect matched layer (SCPML) has also been implemented in SS-ADI-PSTD algorithm as the absorbing boundary condition for truncating the computational domain and absorbing the artificial reflection from the domain boundaries. After algorithmic development, a few case studies serve as the real-world examples to verify the capacities of the numerical algorithms and understand the capabilities and limitations of geophysical methods for detection of subsurface contamination. The first case is a study using ground penetrating radar (GPR) amplitude variation with offset (AVO) for subsurface non-aqueous-liquid (NAPL) contamination. The
From blackbirds to black holes: Investigating capture-recapture methods for time domain astronomy
Laycock, Silas G. T.
2017-07-01
In time domain astronomy, recurrent transients present a special problem: how to infer total populations from limited observations. Monitoring observations may give a biassed view of the underlying population due to limitations on observing time, visibility and instrumental sensitivity. A similar problem exists in the life sciences, where animal populations (such as migratory birds) or disease prevalence, must be estimated from sparse and incomplete data. The class of methods termed Capture-Recapture is used to reconstruct population estimates from time-series records of encounters with the study population. This paper investigates the performance of Capture-Recapture methods in astronomy via a series of numerical simulations. The Blackbirds code simulates monitoring of populations of transients, in this case accreting binary stars (neutron star or black hole accreting from a stellar companion) under a range of observing strategies. We first generate realistic light-curves for populations of binaries with contrasting orbital period distributions. These models are then randomly sampled at observing cadences typical of existing and planned monitoring surveys. The classical capture-recapture methods, Lincoln-Peterson, Schnabel estimators, related techniques, and newer methods implemented in the Rcapture package are compared. A general exponential model based on the radioactive decay law is introduced which is demonstrated to recover (at 95% confidence) the underlying population abundance and duty cycle, in a fraction of the observing visits (10-50%) required to discover all the sources in the simulation. Capture-Recapture is a promising addition to the toolbox of time domain astronomy, and methods implemented in R by the biostats community can be readily called from within python.
Two-Dimensional Time-Domain Antenna Arrays for Optimum Steerable Energy Pattern with Low Side Lobes
Directory of Open Access Journals (Sweden)
Alberto Reyna
2014-01-01
Full Text Available This document presents the synthesis of different two-dimensional time-domain antenna arrays for steerable energy patterns with side lobe levels. The research is focused on the uniform and nonuniform distributions of true-time exciting delays and positions of antenna elements. The uniform square array, random array, uniform concentric ring array, and rotated nonuniform concentric ring array geometries are particularly studied. These geometries are synthesized by using the well-known sequential quadratic programming. The synthesis regards the optimal true-time exciting delays and optimal positions of pulsed antenna elements. The results show the capabilities of the different antenna arrays to steer the beam in their energy pattern in time domain and how their performance is in frequency domain after the synthesis in time domain.
Directory of Open Access Journals (Sweden)
Simon Gorin
Full Text Available Several models in the verbal domain of short-term memory (STM consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression. They were required to decide whether all items of the probe list matched those of the memory list (item condition or whether the order of the items in the probe sequence matched the order in the memory list (order condition. In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.
Gorin, Simon; Kowialiewski, Benjamin; Majerus, Steve
2016-01-01
Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.
Time domain reshuffling for OFDM based indoor visible light communication systems.
You, Xiaodi; Chen, Jian; Yu, Changyuan; Zheng, Huanhuan
2017-05-15
For orthogonal frequency division multiplexing (OFDM) based indoor visible light communication (VLC) systems, partial non-ideal transmission conditions such as insufficient guard intervals and a dispersive channel can result in severe inter-symbol crosstalk (ISC). By deriving from the inverse Fourier transform, we present a novel time domain reshuffling (TDR) concept for both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM VLC systems. By using only simple operations in the frequency domain, potential high peaks can be relocated within each OFDM symbol to alleviate ISC. To simplify the system, we also propose an effective unified design of the TDR schemes for both DCO- and ACO-OFDM. Based on Monte-Carlo simulations, we demonstrate the statistical distribution of the signal high peak values and the complementary cumulative distribution function of the peak-to-average power ratio under different cases for comparison. Simulation results indicate improved bit error rate (BER) performance by adopting TDR to counteract ISC deterioration. For example, for binary phase shift keying at a BER of 10 -3 , the signal to noise ratio gains are ~1.6 dB and ~6.6 dB for DCO- and ACO-OFDM, respectively, with ISC of 1/64. We also show a reliable transmission by adopting TDR for rectangle 8-quadrature amplitude modulation with ISC of < 1/64.
Wessels, Philipp; Ewald, Johannes; Wieland, Marek; Nisius, Thomas; Vogel, Andreas; Viefhaus, Jens; Meier, Guido; Wilhein, Thomas; Drescher, Markus
2014-11-01
The destruction and formation of equilibrium multidomain patterns in permalloy (Ni80Fe20 ) microsquares has been captured using pump-probe x-ray magnetic circular dichroism (XMCD) spectromicroscopy at a new full-field magnetic transmission soft x-ray microscopy endstation with subnanosecond time resolution. The movie sequences show the dynamic magnetization response to intense Oersted field pulses of approximately 200-ps root mean square (rms) duration and the magnetization reorganization to the ground-state domain configuration. The measurements display how a vortex flux-closure magnetization distribution emerges out of a nonequilibrium uniform single-domain state. During the destruction of the initial vortex pattern, we have traced the motion of the central vortex core that is ejected out of the microsquare at high velocities exceeding 1 km/s. A reproducible recovery into a defined final vortex state with stable chirality and polarity could be achieved. Using an additional external bias field, the transient reversal of the square magnetization direction could be monitored and consistently reproduced by micromagnetic simulations.
Baawain, Mahad S.; Al-Futaisi, Ahmed M.; Ebrahimi, A.; Omidvarborna, Hamid
2018-04-01
Time Domain Electromagnetic (TDEM) survey as well as drilling investigations were conducted to identify possible contamination of a dumping site in an unsaturated zone located in Barka, Oman. The method was applied to evaluate conductivity of the contaminated plumes in hot and arid/semiarid region, where high temperatures commonly ranged between 35 and 50 °C. The drilling investigation was carried out over the survey area to verify the geophysical results. The low-resistivity zone (90 Ωm) was correlated with compacted or cemented gravels and cobbles, particularly that of medium dense to very dense gravels and cobbles. Additionally, the TDEM profiles suggested that the plume migration followed a preferential flow path. The resistivity range 40-80 Ωm considered as contaminated areas; however, the drilling results showed the close resistivity domain in the depth >70 m below water table for some profiles (BL1, BL2, BL3, BL4 and BL5). The combined results of drilling wells, piezometers, and TDEM apparent resistivity maps showed a coincidence of the migrated leachate plume and water table. Predicted zone of the probable contamination was located at the depth of around 65 m and horizontal offset ranges 0-280 m, 80-240 m, and 40-85 m in the sounding traverses of BL4, BL6 and BL7, respectively.
Singular trajectories: space-time domain topology of developing speckle fields
Vasil'ev, Vasiliy; Soskin, Marat S.
2010-02-01
It is shown the space-time dynamics of optical singularities is fully described by singularities trajectories in space-time domain, or evolution of transverse coordinates(x, y) in some fixed plane z0. The dynamics of generic developing speckle fields was realized experimentally by laser induced scattering in LiNbO3:Fe photorefractive crystal. The space-time trajectories of singularities can be divided topologically on two classes with essentially different scenario and duration. Some of them (direct topological reactions) consist from nucleation of singularities pair at some (x, y, z0, t) point, their movement and annihilation. They possess form of closed loops with relatively short time of existence. Another much more probable class of trajectories are chain topological reactions. Each of them consists from sequence of links, i.e. of singularities nucleation in various points (xi yi, ti) and following annihilation of both singularities in other space-time points with alien singularities of opposite topological indices. Their topology and properties are established. Chain topological reactions can stop on the borders of a developing speckle field or go to infinity. Examples of measured both types of topological reactions for optical vortices (polarization C points) in scalar (elliptically polarized) natural developing speckle fields are presented.
Bodin, Jacques
2015-03-01
In this study, new multi-dimensional time-domain random walk (TDRW) algorithms are derived from approximate one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) analytical solutions of the advection-dispersion equation and from exact 1-D, 2-D, and 3-D analytical solutions of the pure-diffusion equation. These algorithms enable the calculation of both the time required for a particle to travel a specified distance in a homogeneous medium and the mass recovery at the observation point, which may be incomplete due to 2-D or 3-D transverse dispersion or diffusion. The method is extended to heterogeneous media, represented as a piecewise collection of homogeneous media. The particle motion is then decomposed along a series of intermediate checkpoints located on the medium interface boundaries. The accuracy of the multi-dimensional TDRW method is verified against (i) exact analytical solutions of solute transport in homogeneous media and (ii) finite-difference simulations in a synthetic 2-D heterogeneous medium of simple geometry. The results demonstrate that the method is ideally suited to purely diffusive transport and to advection-dispersion transport problems dominated by advection. Conversely, the method is not recommended for highly dispersive transport problems because the accuracy of the advection-dispersion TDRW algorithms degrades rapidly for a low Péclet number, consistent with the accuracy limit of the approximate analytical solutions. The proposed approach provides a unified methodology for deriving multi-dimensional time-domain particle equations and may be applicable to other mathematical transport models, provided that appropriate analytical solutions are available.
Use of the finite-difference time-domain method in electromagnetic dosimetry
International Nuclear Information System (INIS)
Sullivan, D.M.
1987-01-01
Although there are acceptable methods for calculating whole body electromagnetic absorption, no completely acceptable method for calculating the local specific absorption rate (SAR) at points within the body has been developed. Frequency domain methods, such as the method of moments (MoM) have achieved some success; however, the MoM requires computer storage on the order of (3N) 2 , and computation time on the order of (3N) 3 where N is the number of cells. The finite-difference time-domain (FDTD) method has been employed extensively in calculating the scattering from metallic objects, and recently is seeing some use in calculating the interaction of EM fields with complex, lossy dielectric bodies. Since the FDTD method has storage and time requirements proportional to N, it presents an attractive alternative to calculating SAR distribution in large bodies. This dissertation describes the FDTD method and evaluates it by comparing its results with analytic solutions in 2 and 3 dimensions. The results obtained demonstrate that the FDTD method is capable of calculating internal SAR distribution with acceptable accuracy. The construction of a data base to provide detailed, inhomogeneous man models for use with the FDTD method is described. Using this construction method, a model of 40,000 1.31 cm. cells is developed for use at 350 MHz, and another model consisting of 5000 2.62 cm. cells is developed for use at 100 MHz. To add more realism to the problem, a ground plane is added to the FDTD software. The needed changes to the software are described, along with a test which confirms its accuracy. Using the CRAY II supercomputer, SAR distributions in human models are calculated using incident frequencies of 100 MHz and 350 MHz for three different cases: (1) A homogeneous man model in free space, (2) an inhomogeneous man model in free space, and (3) an inhomogeneous man model standing on a ground plane
All-Digital Time-Domain CMOS Smart Temperature Sensor with On-Chip Linearity Enhancement.
Chen, Chun-Chi; Chen, Chao-Lieh; Lin, Yi
2016-01-30
This paper proposes the first all-digital on-chip linearity enhancement technique for improving the accuracy of the time-domain complementary metal-oxide semiconductor (CMOS) smart temperature sensor. To facilitate on-chip application and intellectual property reuse, an all-digital time-domain smart temperature sensor was implemented using 90 nm Field Programmable Gate Arrays (FPGAs). Although the inverter-based temperature sensor has a smaller circuit area and lower complexity, two-point calibration must be used to achieve an acceptable inaccuracy. With the help of a calibration circuit, the influence of process variations was reduced greatly for one-point calibration support, reducing the test costs and time. However, the sensor response still exhibited a large curvature, which substantially affected the accuracy of the sensor. Thus, an on-chip linearity-enhanced circuit is proposed to linearize the curve and achieve a new linearity-enhanced output. The sensor was implemented on eight different Xilinx FPGA using 118 slices per sensor in each FPGA to demonstrate the benefits of the linearization. Compared with the unlinearized version, the maximal inaccuracy of the linearized version decreased from 5 °C to 2.5 °C after one-point calibration in a range of -20 °C to 100 °C. The sensor consumed 95 μW using 1 kSa/s. The proposed linearity enhancement technique significantly improves temperature sensing accuracy, avoiding costly curvature compensation while it is fully synthesizable for future Very Large Scale Integration (VLSI) system.
UV--Visible observations with HST in the JWST North Ecliptic Pole Time-Domain Field
Jansen, Rolf A.; Windhorst, Rogier; Grogin, Norman; Koekemoer, Anton; Royle, Patricia; Hathi, Nimish; Jones, Victoria; Cohen, Seth; Ashcraft, Teresa; Willmer, Christopher; Conselice, Christopher; White, Cameron; Frye, Brenda; HST-GO-15278 team; and the Webb Medium Deep Fields IDS GTO team.
2018-01-01
We report the first results from a UV–Visible HST imaging survey of the JWST North Ecliptic Pole (NEP) Time-Domain Field (TDF). Using CVZ and near-CVZ opportunities we observed the first two out of nine tiles with WFC3/UVIS in F275W and with ACS/WFC in F435W and F606W. Over the course of the next 13 months, this survey is designed to provide near-contiguous 3-filter coverage of the central r ≤ 5‧ of this new community field for time-domain science with JWST. The JWST NEP TDF is located within JWST's northern Continuous Viewing Zone, will span ~14‧ in diameter (~10‧ with NIRISS coverage), is devoid of sources bright enough to saturate the NIRCam detectors, has low Galactic foreground extinction, and will be roughly circular in shape (initially sampled during Cycle 1 at 4 distinct orientations with JWST/NIRCam — the JWST “windmill”). NIRISS slitless grism spectroscopy will be taken in parallel, overlapping an alternate NIRCam orientation. This is the only region in the sky where JWST can observe a clean extragalactic deep survey field of this size at arbitrary cadence or at arbitrary orientation. This will crucially enable a wide range of new and exciting time-domain science, including high redshift transient searches and monitoring (e.g., SNe), variability studies from Active Galactic Nuclei to brown dwarf atmospheres, as well as proper motions of extreme scattered Kuiper Belt and Oort Cloud Objects, and of nearby Galactic brown dwarfs, low-mass stars, and ultracool white dwarfs. Ancillary data across the electromagnetic spectrum will exist for this field when JWST science operations commence in the second half of 2019. This includes deep (mAB ~ 26 mag) wide-field (~23‧×25‧) Ugriz photometry of this field and its surroundings from LBT/LBC and Subaru/HSC, JHK from MMT/MMIRS, VLA 3 GHz and VLBA 4.5 GHz radio observations, and Chandra/ACIS X-ray images. Proposals for (sub)mm observations and spectroscopy to mAB ~ 24 mag are pending.
Time domain numerical calculations of the short electron bunch wakefields in resistive structures
Energy Technology Data Exchange (ETDEWEB)
Tsakanian, Andranik
2010-10-15
The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of
Choi, Yun Seok; Alkhalifah, Tariq Ali
2011-01-01
Full waveform inversion requires a good estimation of the source wavelet to improve our chances of a successful inversion. This is especially true for an encoded multisource time-domain implementation, which, conventionally, requires separate
Al-Jabr, Ahmad; Alsunaidi, Mohammad A.
2010-01-01
A time-domain analysis of the propagation properties of surface-plasmon-polaritons (SPP) in Silver nanostructures is presented. The analysis is based on a simulation algorithm that unifies the formulation of different dispersion models and multi
Directory of Open Access Journals (Sweden)
Jaeyun Lee
2016-01-01
Full Text Available We developed a method to distinguish bursts and suppressions for EEG burst suppression from the treatments of status epilepticus, employing the joint time-frequency domain. We obtained the feature used in the proposed method from the joint use of the time and frequency domains, and we estimated the decision as to whether the measured EEG was a burst segment or suppression segment by the maximum likelihood estimation. We evaluated the performance of the proposed method in terms of its accordance with the visual scores and estimation of the burst suppression ratio. The accuracy was higher than the sole use of the time or frequency domains, as well as conventional methods conducted in the time domain. In addition, probabilistic modeling provided a more simplified optimization than conventional methods. Burst suppression quantification necessitated precise burst suppression segmentation with an easy optimization; therefore, the excellent discrimination and the easy optimization of burst suppression by the proposed method appear to be beneficial.
Sirenko, Kostyantyn
2013-07-01
Exact absorbing and periodic boundary conditions allow to truncate grating problems\\' infinite physical domains without introducing any errors. This work presents exact absorbing boundary conditions for 3D diffraction gratings and describes their discretization within a high-order time-domain discontinuous Galerkin finite element method (TD-DG-FEM). The error introduced by the boundary condition discretization matches that of the TD-DG-FEM; this results in an optimal solver in terms of accuracy and computation time. Numerical results demonstrate the superiority of this solver over TD-DG-FEM with perfectly matched layers (PML)-based domain truncation. © 2013 IEEE.
Beghein, Yves
2013-03-01
The time domain combined field integral equation (TD-CFIE), which is constructed from a weighted sum of the time domain electric and magnetic field integral equations (TD-EFIE and TD-MFIE) for analyzing transient scattering from closed perfect electrically conducting bodies, is free from spurious resonances. The standard marching-on-in-time technique for discretizing the TD-CFIE uses Galerkin and collocation schemes in space and time, respectively. Unfortunately, the standard scheme is theoretically not well understood: stability and convergence have been proven for only one class of space-time Galerkin discretizations. Moreover, existing discretization schemes are nonconforming, i.e., the TD-MFIE contribution is tested with divergence conforming functions instead of curl conforming functions. We therefore introduce a novel space-time mixed Galerkin discretization for the TD-CFIE. A family of temporal basis and testing functions with arbitrary order is introduced. It is explained how the corresponding interactions can be computed efficiently by existing collocation-in-time codes. The spatial mixed discretization is made fully conforming and consistent by leveraging both Rao-Wilton-Glisson and Buffa-Christiansen basis functions and by applying the appropriate bi-orthogonalization procedures. The combination of both techniques is essential when high accuracy over a broad frequency band is required. © 2012 IEEE.
Acceleration for 2D time-domain elastic full waveform inversion using a single GPU card
Jiang, Jinpeng; Zhu, Peimin
2018-05-01
Full waveform inversion (FWI) is a challenging procedure due to the high computational cost related to the modeling, especially for the elastic case. The graphics processing unit (GPU) has become a popular device for the high-performance computing (HPC). To reduce the long computation time, we design and implement the GPU-based 2D elastic FWI (EFWI) in time domain using a single GPU card. We parallelize the forward modeling and gradient calculations using the CUDA programming language. To overcome the limitation of relatively small global memory on GPU, the boundary saving strategy is exploited to reconstruct the forward wavefield. Moreover, the L-BFGS optimization method used in the inversion increases the convergence of the misfit function. A multiscale inversion strategy is performed in the workflow to obtain the accurate inversion results. In our tests, the GPU-based implementations using a single GPU device achieve >15 times speedup in forward modeling, and about 12 times speedup in gradient calculation, compared with the eight-core CPU implementations optimized by OpenMP. The test results from the GPU implementations are verified to have enough accuracy by comparing the results obtained from the CPU implementations.
Granet, Gérard
2013-01-01
This paper focuses on scatterometry problems arising in lithography production of periodic gratings. Namely, the paper introduces a theoretical and numerical-modeling-oriented approach to scatterometry problems and discusses its capabilities. The approach allows for reliable detection of deviations in gratings\\' critical dimensions (CDs) during the manufacturing process. The core of the approach is the one-to-one correspondence between the electromagnetic (EM) characteristics and the geometric/material properties of gratings. The approach is based on highly accurate solutions of initial boundary-value problems describing EM waves\\' interaction on periodic gratings. The advantage of the approach is the ability to perform simultaneously and interactively both in frequency and time domains under conditions of possible resonant scattering of EM waves by infinite or finite gratings. This allows a detection of CDs for a wide range of gratings, and, thus is beneficial for the applied scatterometry. (C) 2013 Optical Society of America
Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy
International Nuclear Information System (INIS)
Fischer, B M; Walther, M; Jepsen, P Uhd
2002-01-01
The far-infrared dielectric function of a wide range of organic molecules is dominated by vibrations involving a substantial fraction of the atoms forming the molecule and motion associated with intermolecular hydrogen bond vibrations. Due to their collective nature such modes are highly sensitive to the intra- and intermolecular structure and thus provide a unique fingerprint of the conformational state of the molecule and effects of its environment. We demonstrate the use of terahertz time-domain spectroscopy (THz-TDS) for recording the far-infrared (0.5-4.0 THz) dielectric function of the four nucleobases and corresponding nucleosides forming the building blocks of deoxyribose nucleic acid (DNA). We observe numerous distinct spectral features with large differences between the molecules in both frequency-dependent absorption coefficient and index of refraction. Assisted by results from density-functional calculations we interpret the origin of the observed resonances as vibrations of hydrogen bonds between the molecules
Directory of Open Access Journals (Sweden)
Ana Paula Delowski Ciniello
Full Text Available Abstract The present paper aims at presenting a methodology for characterizing viscoelastic materials in time domain, taking into account the fractional Zener constitutive model and the influence of temperature through Williams, Landel, and Ferry’s model. To that effect, a set of points obtained experimentally through uniaxial tensile tests with different constant strain rates is considered. The approach is based on the minimization of the quadratic relative distance between the experimental stress-strain curves and the corresponding ones given by the theoretical model. In order to avoid the local minima in the process of optimization, a hybrid technique based on genetic algorithms and non-linear programming techniques is used. The methodology is applied in the characterization of two different commercial viscoelastic materials. The results indicate that the proposed methodology is effective in identifying thermorheologically simple viscoelastic materials.
Quantify Glucose Level in Freshly Diabetic's Blood by Terahertz Time-Domain Spectroscopy
Chen, Hua; Chen, Xiaofeng; Ma, Shihua; Wu, Xiumei; Yang, Wenxing; Zhang, Weifeng; Li, Xiao
2018-04-01
We demonstrate the capability of terahertz (THz) time-domain spectroscopy (TDS) to quantify glucose level in ex vivo freshly diabetic's blood. By investigating the THz spectra of different human blood, we find out THz absorption coefficients reflect a high sensitivity to the glucose level in blood. With a quantitative analysis of 70 patients, we demonstrate that the THz absorption coefficients and the blood glucose levels perform a linear relationship. A comparative experiment between THz measurement and glucometers is also conducted with another 20 blood samples, and the results confirm that the relative error is as less as 15%. Our ex vivo human blood study indicates that THz technique has great potential application to diagnose blood glucose level in clinical practice.
Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)
Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei; Kiriyama, Kyoko; Matsuda, Kazutaka; Jepsen, Peter Uhd
2017-04-01
Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly composed of organic materials, such as urushi, wood, carbon black, and fabrics which are very X-ray transparent, standard X-ray radiography has some problems in achieving clear X-ray radiographic images. Therefore, we wanted to contribute to the understanding of the lacquer manufacturing technique by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares substructures, aiding in the comprehension of the manufacturing technology yielding to these precious artefacts.
Analytical approximate solutions of the time-domain diffusion equation in layered slabs.
Martelli, Fabrizio; Sassaroli, Angelo; Yamada, Yukio; Zaccanti, Giovanni
2002-01-01
Time-domain analytical solutions of the diffusion equation for photon migration through highly scattering two- and three-layered slabs have been obtained. The effect of the refractive-index mismatch with the external medium is taken into account, and approximate boundary conditions at the interface between the diffusive layers have been considered. A Monte Carlo code for photon migration through a layered slab has also been developed. Comparisons with the results of Monte Carlo simulations showed that the analytical solutions correctly describe the mean path length followed by photons inside each diffusive layer and the shape of the temporal profile of received photons, while discrepancies are observed for the continuous-wave reflectance or transmittance.
Time-domain vibrational study on defects in ion-irradiated crystal
International Nuclear Information System (INIS)
Kitajima, M.
2003-01-01
We have studied the effects of point defects on coherent phonons in ion-implanted bismuth and graphite. Ultrafast dynamics of coherent phonons and photo-generated carriers in the femtosecond time-domain have been investigated by means of pump-probe reflectivity measurements. Point defects are introduced by irradiating graphite with 5 keV He + ions. For Bi the dephasing rate of the A 1g phonon increases linearly with increasing ion dose, which is explained by the additional dephasing process of the coherent phonon originated from scattering of phonons by the defects. For graphite, introduction of the defects enhances the carrier relaxation by opening a decay channel via vacancy-states, which competes efficiently with carrier-phonon scattering. The coherent acoustic phonon relaxation is also accelerated due to an additional scattering by defects. The linear fluence-dependence of the decay rate is understood as scattering of propagating acoustic phonon by single vacancies. (author)
Use of Time- and Frequency-Domain Approaches for Damage Detection in Civil Engineering Structures
Directory of Open Access Journals (Sweden)
V. H. Nguyen
2014-01-01
Full Text Available The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life civil engineering structures and to assess their capability for damage detection. The methodology is based on Principal Component Analysis of the Hankel matrix built from output-only measurements and of Frequency Response Functions. Damage detection is performed using the concept of subspace angles between a current (possibly damaged state and a reference (undamaged state. The first structure is the Champangshiehl Bridge located in Luxembourg. Several damage levels were intentionally created by cutting a growing number of prestressed tendons and vibration data were acquired by the University of Luxembourg for each damaged state. The second example consists in reinforced and prestressed concrete panels. Successive damages were introduced in the panels by loading heavy weights and by cutting steel wires. The illustrations show different consequences in damage identification by the considered techniques.
Time-domain simulation and nonlinear analysis on ride performance of four-wheel vehicles
Energy Technology Data Exchange (ETDEWEB)
Wang, Y S; He, H; Geng, A L [School of Automobile and Traffic Engineering, Liaoning University of Technology, Jinzhou 121001 (China)], E-mail: jzwbt@163.com
2008-02-15
A nonlinear dynamic model with eight DOFs of a four-wheel vehicle is established in this paper. After detaching the nonlinear characteristics of the leaf springs and shock absorbers, the multi-step linearizing method is used to simulate the vehicle vibration in time domain, under a correlated four-wheel road roughness model. Experimental verifications suggest that the newly built vehicle model and simulation procedure are reasonable and feasible to be used in vehicle vibration analysis. Furthermore, some nonlinear factors of the leaf springs and shock absorbers, which affect the vehicle ride performance (or comfort), are investigated under different vehicle running speeds. Some substaintial rules of the nonlinear vehicle vibrations are revealed in this paper.
Cvetkovic, V.; Molin, S.
2012-02-01
We present a methodology that combines numerical simulations of groundwater flow and advective transport in heterogeneous porous media with analytical retention models for computing the infection risk probability from pathogens in aquifers. The methodology is based on the analytical results presented in [1,2] for utilising the colloid filtration theory in a time-domain random walk framework. It is shown that in uniform flow, the results from the numerical simulations of advection yield comparable results as the analytical TDRW model for generating advection segments. It is shown that spatial variability of the attachment rate may be significant, however, it appears to affect risk in a different manner depending on if the flow is uniform or radially converging. In spite of the fact that numerous issues remain open regarding pathogen transport in aquifers on the field scale, the methodology presented here may be useful for screening purposes, and may also serve as a basis for future studies that would include greater complexity.
Time-domain simulation and nonlinear analysis on ride performance of four-wheel vehicles
International Nuclear Information System (INIS)
Wang, Y S; He, H; Geng, A L
2008-01-01
A nonlinear dynamic model with eight DOFs of a four-wheel vehicle is established in this paper. After detaching the nonlinear characteristics of the leaf springs and shock absorbers, the multi-step linearizing method is used to simulate the vehicle vibration in time domain, under a correlated four-wheel road roughness model. Experimental verifications suggest that the newly built vehicle model and simulation procedure are reasonable and feasible to be used in vehicle vibration analysis. Furthermore, some nonlinear factors of the leaf springs and shock absorbers, which affect the vehicle ride performance (or comfort), are investigated under different vehicle running speeds. Some substaintial rules of the nonlinear vehicle vibrations are revealed in this paper
Calibrating a Salt Water Intrusion Model with Time-Domain Electromagnetic Data
DEFF Research Database (Denmark)
Herckenrath, Daan; Odlum, Nick; Nenna, Vanessa
2013-01-01
Salt water intrusion models are commonly used to support groundwater resource management in coastal aquifers. Concentration data used for model calibration are often sparse and limited in spatial extent. With airborne and ground-based electromagnetic surveys, electrical resistivity models can......, we perform a coupled hydrogeophysical inversion (CHI) in which we use a salt water intrusion model to interpret the geophysical data and guide the geophysical inversion. We refer to this methodology as a Coupled Hydrogeophysical Inversion-State (CHI-S), in which simulated salt concentrations...... are transformed to an electrical resistivity model, after which a geophysical forward response is calculated and compared with the measured geophysical data. This approach was applied for a field site in Santa Cruz County, California, where a time-domain electromagnetic (TDEM) dataset was collected...
CALCULATION OF CONTROL CIRCUITS IN TIME DOMAIN USING SCILAB / XCOS ENVIRONMENT
Directory of Open Access Journals (Sweden)
Chioncel Petru
2014-10-01
Full Text Available The paper presents the computing of control circuits in time domain, starting from the mathematical model of the control path described by differential equation’s with constant coefficients, whose solution can be obtained through Laplace transform and transfer functions. In the field of electric drives, the control circuits can be reduced to elements of PT1 and PT2 type, for which, the responses obtained from step and impulse function in the test process, are analyzed. The presented calculation, done in Scilab, highlights the test responses of the process and, the speed control circuit implemented as block diagrams in Xcos, reveals the improve of the process parameter through the control loop.
Granet, Gé rard; Melezhik, Petr N.; Sirenko, Kostyantyn; Yashina, Nataliya P.
2013-01-01
This paper focuses on scatterometry problems arising in lithography production of periodic gratings. Namely, the paper introduces a theoretical and numerical-modeling-oriented approach to scatterometry problems and discusses its capabilities. The approach allows for reliable detection of deviations in gratings' critical dimensions (CDs) during the manufacturing process. The core of the approach is the one-to-one correspondence between the electromagnetic (EM) characteristics and the geometric/material properties of gratings. The approach is based on highly accurate solutions of initial boundary-value problems describing EM waves' interaction on periodic gratings. The advantage of the approach is the ability to perform simultaneously and interactively both in frequency and time domains under conditions of possible resonant scattering of EM waves by infinite or finite gratings. This allows a detection of CDs for a wide range of gratings, and, thus is beneficial for the applied scatterometry. (C) 2013 Optical Society of America
Time-Domain Finite Elements for Virtual Testing of Electromagnetic Compatibility
Directory of Open Access Journals (Sweden)
V. Sedenka
2013-04-01
Full Text Available The paper presents a time-domain finite-element solver developed for simulations related to solving electromagnetic compatibility issues. The software is applied as a module integrated into a computational framework developed within a FP7 European project High Intensity Radiated Field – Synthetic Environment (HIRF SE able to simulate a large class of problems. In the paper, the mathematical formulation is briefly presented, and special emphasis is put on the user point of view on the simulation tool-chain. The functionality is demonstrated on the computation of shielding effectiveness of two composite materials. Results are validated through experimental measurements and agreement is confirmed by automatic feature selective algorithms.
Time domain acoustic contrast control implementation of sound zones for low-frequency input signals
DEFF Research Database (Denmark)
Schellekens, Daan H. M.; Møller, Martin Bo; Olsen, Martin
2016-01-01
Sound zones are two or more regions within a listening space where listeners are provided with personal audio. Acoustic contrast control (ACC) is a sound zoning method that maximizes the average squared sound pressure in one zone constrained to constant pressure in other zones. State......-of-the-art time domain broadband acoustic contrast control (BACC) methods are designed for anechoic environments. These methods are not able to realize a flat frequency response in a limited frequency range within a reverberant environment. Sound field control in a limited frequency range is a requirement...... to accommodate the effective working range of the loudspeakers. In this paper, a new BACC method is proposed which results in an implementation realizing a flat frequency response in the target zone. This method is applied in a bandlimited low-frequency scenario where the loudspeaker layout surrounds two...
Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing.
Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A Ping; Lu, Chao
2016-12-16
We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes.
Gonçalves, Rui; Farzamian, Mohammad; Monteiro Santos, Fernando A.; Represas, Patrícia; Mota Gomes, A.; Lobo de Pina, A. F.; Almeida, Eugénio P.
2017-11-01
Santiago Island, the biggest and most populated island of the Cape Verde Republic, is characterised by limited surface waters and strong dependence on groundwater sources as the primary source of natural water supply for extensive agricultural activity and human use. However, as a consequence of the scarce precipitation and high evaporation as well as the intense overexploitation of the groundwater resources, the freshwater management is also in a delicate balance with saltwater at coastal areas. The time-domain electromagnetic (TDEM) method is used to locate the extent of saltwater intrusion in four important agricultural regions in Santiago Island; São Domingos, Santa Cruz, São Miguel, and Tarrafal. The application of this method in Santiago Island proves it to be a successful tool in imaging the fresh/saltwater interface location. Depths to the saline zones and extensions of saline water are mapped along eight TDEM profiles.
Time-Domain Reflectometry for Tamper Indication in Unattended Monitoring Systems for Safeguards
Energy Technology Data Exchange (ETDEWEB)
Tedeschi, Jonathan R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Leon E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Moore, David E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sheen, David M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Conrad, Ryan C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2014-12-01
The International Atomic Energy Agency (IAEA) continues to expand its use of unattended, remotely monitored measurement systems. An increasing number of systems and an expanding family of instruments create challenges in terms of deployment efficiency and the implementation of data authentication measures. Pacific Northwest National Laboratory (PNNL) leads a collaboration that is exploring various tamper-indicating (TI) measures that could help to address some of the long-standing detector and data-transmission authentication challenges with IAEA’s unattended systems. PNNL is investigating the viability of active time-domain reflectometry (TDR) along two parallel but interconnected paths: (1) swept-frequency TDR as the highly flexible, laboratory gold standard to which field-deployable options can be compared, and (2) a low-cost commercially available spread-spectrum TDR technology as one option for field implementation. This report describes PNNL’s progress and preliminary findings from the first year of the study, and describes the path forward.
Ultrabroadband THz Time-Domain Spectroscopy of a Free-Flowing Water Film
DEFF Research Database (Denmark)
Wang, Tianwu; Pedersen, Pernille Klarskov; Jepsen, Peter Uhd
2014-01-01
of liquid water using two different THz-TDS setups. The extracted absorption coefficient and refractive index of water are in agreement with previous results reported in the literature. With this we show that the thin free-flowing liquid film is a versatile tool for windowless, ultrabroadband THz......We demonstrate quantitative ultrabroadband THz time-domain spectroscopy (THz-TDS) of water by application of a 17-$\\mu$m thick gravity-driven wire-guided flow jet of water. The thickness and stability of the water film is accurately measured by an optical intensity crosscorrelator, and the standard...... deviation of the film thickness is less than 500 nm. The cross section of the water film is found to have a biconcave cylindrical lens shape. By transmitting through such a thin film, we perform the first ultrabroadband (0.2–30 THz) THz-TDS across the strongest absorbing part of the infrared spectrum...
Application of the symplectic finite-difference time-domain scheme to electromagnetic simulation
International Nuclear Information System (INIS)
Sha, Wei; Huang, Zhixiang; Wu, Xianliang; Chen, Mingsheng
2007-01-01
An explicit fourth-order finite-difference time-domain (FDTD) scheme using the symplectic integrator is applied to electromagnetic simulation. A feasible numerical implementation of the symplectic FDTD (SFDTD) scheme is specified. In particular, new strategies for the air-dielectric interface treatment and the near-to-far-field (NFF) transformation are presented. By using the SFDTD scheme, both the radiation and the scattering of three-dimensional objects are computed. Furthermore, the energy-conserving characteristic hold for the SFDTD scheme is verified under long-term simulation. Numerical results suggest that the SFDTD scheme is more efficient than the traditional FDTD method and other high-order methods, and can save computational resources
Towards dual recycling with the aid of time and frequency domain simulations
International Nuclear Information System (INIS)
Malec, M; Grote, H; Freise, A; Heinzel, G; Strain, K A; Hough, J; Danzmann, K
2004-01-01
Dual recycling, the combination of the interferometric techniques of power and signal recycling, allows the improvement of the shot noise limited sensitivity of interferometric gravitational wave detectors. GEO 600 is the first km-scale gravitational wave detector using dual recycling. The hardware installation is completed and dual recycling has become a great challenge in terms of commissioning of GEO 600. Simulations show that lock acquisition of the optical system can only be achieved in certain detector states. Thus as we need to start with a locked detector in such a specific state, an appropriate strategy is needed to change the state of detector operation without losing lock. The basic concepts and first results based on time and frequency domain simulations will be presented in this paper
Beam diagnostics based on time-domain bunch-by-bunch data
International Nuclear Information System (INIS)
Teytelman, D.; Fox, J.; Hindi, H.; Limborg, C.; Linscott, I.; Prabhakar, S.; Sebek, J.; Young, A.; Drago, A.; Serio, M.; Barry, W.; Stover, G.
1998-01-01
A bunch-by-bunch longitudinal feedback system has been used to control coupled-bunch longitudinal motion and study the behavior of the beam at ALS, SPEAR, PEP-II, and DAΦNE. Each of these machines presents unique challenges to feedback control of unstable motion and data analysis. Here we present techniques developed to adapt this feedback system to operating conditions at these accelerators. A diverse array of techniques has been developed to extract information on different aspects of beam behavior from the time-domain data captured by the feedback system. These include measurements of growth and damping rates of coupled-bunch modes, bunch-by-bunch current monitoring, measurements of bunch-by-bunch synchronous phases and longitudinal tunes, and beam noise spectra. A technique is presented which uses the longitudinal feedback system to measure transverse growth and damping rates. Techniques are illustrated with data acquired at all of the four above-mentioned machines
Implementation of a custom time-domain firmware trigger for RADAR-based cosmic ray detection
Prohira, S.; Besson, D.; Kunwar, S.; Ratzlaff, K.; Young, R.
2018-05-01
Interest in Radio-based detection schemes for ultra-high energy cosmic rays (UHECR) has surged in recent years, owing to the potentially very low cost/detection ratio. The method of radio-frequency (RF) scatter has been proposed as potentially the most economical detection technology. Though the first dedicated experiment to employ this method, the Telescope Array RADAR experiment (TARA) reported no signal, efforts to develop more robust and sensitive trigger techniques continue. This paper details the development of a time-domain firmware trigger that exploits characteristics of the expected scattered signal from an UHECR extensive-air shower (EAS). The improved sensitivity of this trigger is discussed, as well as implementation in two separate field deployments from 2016 to 2017.
Dispersive finite-difference time-domain (FDTD) analysis of the elliptic cylindrical cloak
Energy Technology Data Exchange (ETDEWEB)
Lee, Y. Y.; Ahn, D. [University of Seoul, Seoul (Korea, Republic of)
2012-05-15
A dispersive full-wave finite-difference time-domain (FDTD) model is used to calculate the performance of elliptic cylindrical cloaking devices. The permittivity and the permeability tensors for the cloaking structure are derived by using an effective medium approach in general relativity. The elliptic cylindrical invisibility devices are found to show imperfect cloaking, and the cloaking performance is found to depend on the polarization of the incident waves, the direction of the propagation of those waves, the semi-focal distances and the loss tangents of the meta-material. When the semifocal distance of the elliptic cylinder decreases, the performance of the cloaking becomes very good, with neither noticeable scatterings nor field penetrations. For a larger semi-focal distance, only the TM wave with a specific propagation direction shows good cloaking performance. Realistic cloaking materials with loss still show a cloak that is working, but attenuated back-scattering waves exist.
Simulation of acoustic streaming by means of the finite-difference time-domain method
DEFF Research Database (Denmark)
Santillan, Arturo Orozco
2012-01-01
Numerical simulations of acoustic streaming generated by a standing wave in a narrow twodimensional cavity are presented. In this case, acoustic streaming arises from the viscous boundary layers set up at the surfaces of the walls. It is known that streaming vortices inside the boundary layer have...... directions of rotation that are opposite to those of the outer streaming vortices (Rayleigh streaming). The general objective of the work described in this paper has been to study the extent to which it is possible to simulate both the outer streaming vortices and the inner boundary layer vortices using...... the finite-difference time-domain method. To simplify the problem, thermal effects are not considered. The motivation of the described investigation has been the possibility of using the numerical method to study acoustic streaming, particularly under non-steady conditions. Results are discussed for channels...
Bao, Rima; Wu, Zhikui; Li, Hao; Wang, Fang; Miao, Xinyang; Feng, Chengjing
2017-01-01
The study of fluid inclusion is one of the important means to understanding the evolution of mineral crystals, and can therefore provide original information of mineral evolution. In the process of evolution, outside factors such as temperature and pressure, directly affect the number and size of inclusions, and thus are related to the properties of crystals. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to detect sodium sulfate crystals with different growth temperatures, and absorption coefficient spectra of the samples were obtained. It is suggested that the evolution of sodium sulfate could be divided into two stages, and 80°C was the turning point. X-ray diffraction (XRD) and polarizing microscopy were used to support this conclusion. The research showed that THz-TDS could characterize the evolution of mineral crystals, and it had a unique advantage in terms of crystal evolution.
Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing
Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A. Ping; Lu, Chao
2016-01-01
We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes. PMID:27999250
Degradation diagnosis of transformer insulating oils with terahertz time-domain spectroscopy
Kang, Seung Beom; Kim, Won-Seok; Chung, Dong Chul; Joung, Jong Man; Kwak, Min Hwan
2017-12-01
We report the frequency-dependent complex optical constants, refractive index and absorption, and complex dielectric properties over the frequency range from 0.2 to 3.0 THz for aged power transformer mineral insulating oils. These results have been obtained using terahertz time-domain spectroscopy (THz-TDS) and demonstrate the double-Debye relaxation behavior of the mineral insulating oil. The measured complex optical and dielectric characteristics can be important benchmarks for liquid molecular dynamics and theoretical studies of insulating oils. Due to clear differences in THz responses of aged mineral insulating oils, THz-TDS can be used as a novel on-site diagnostic technique to monitor the insulation condition in aged power transformers and may be valuable alternative to characterize other developing eco-friendly insulating oils and industrial liquids.
International Nuclear Information System (INIS)
Liu, J.; Lan, T.; Qin, H.
2017-01-01
Traditional data cleaning identifies dirty data by classifying original data sequences, which is a class-imbalanced problem since the proportion of incorrect data is much less than the proportion of correct ones for most diagnostic systems in Magnetic Confinement Fusion (MCF) devices. When using machine learning algorithms to classify diagnostic data based on class-imbalanced training set, most classifiers are biased towards the major class and show very poor classification rates on the minor class. By transforming the direct classification problem about original data sequences into a classification problem about the physical similarity between data sequences, the class-balanced effect of Time-Domain Global Similarity (TDGS) method on training set structure is investigated in this paper. Meanwhile, the impact of improved training set structure on data cleaning performance of TDGS method is demonstrated with an application example in EAST POlarimetry-INTerferometry (POINT) system.
International Nuclear Information System (INIS)
Evett, S.R.
2000-01-01
Soil-water measurements encounter particular problems related to the physics of the method used. For time domain reflectometry (TDR), these relate to wave form shape changes caused by soil, soil water, and TDR probe properties. Methods of wave form interpretation that overcome these problems are discussed and specific computer algorithms are presented. Neutron scattering is well understood, but calibration methods remain critical to accuracy and precision, and are discussed with recommendations for field calibration and use. Capacitance probes tend to exhibit very small radii of influence, thus are sensitive to small-scale changes in soil properties, and are difficult or impossible to field calibrate. Field comparisons of neutron and capacitance probes are presented. (author)
Pressure-dependent refractive indices of gases by THz time-domain spectroscopy.
Sang, Bark Hyeon; Jeon, Tea-In
2016-12-12
Noncontact terahertz time-domain spectroscopy was employed to measure pressure-dependent refractive indices of gases such as helium (He), argon (Ar), krypton (Kr), oxygen (O2), nitrogen (N2), methane (CH4), and carbon dioxide (CO2). The refractive indices of these gases scaled linearly with pressure, for pressures in the 55-3,750 torr range. At the highest pressure, the refractive indices ((n-1) x 106) of He and CO2 were 170 and 2,390, respectively. The refractive index of CO2 was 14.1-fold higher than that of He, owing to the stronger polarizability of CO2. Although the studied gases differed in terms of their molecular structure, their refractive indices were strongly determined by polarizability. The measured refractive indices agreed well with the theoretical calculations.
International Nuclear Information System (INIS)
Khaizer, A.N.; Hussain, I.
2015-01-01
This paper presents a time-domain approach for identification of longitudinal dynamics of single rotor model helicopter. A frequency sweep excitation input signal is applied for hover flying mode widely used for space state linearized model. A fully automated programmed flight test method provides high quality flight data for system identification using the computer controlled flight simulator X-plane. The flight test data were recorded, analyzed and reduced using the SIDPAC (System Identification Programs for Air Craft) toolbox for MATLAB, resulting in an aerodynamic model of single rotor helicopter. Finally, the identified model of single rotor helicopter is validated on Raptor 30-class model helicopter at hover showing the reliability of proposed approach. (author)
A VLSI Implementation of Rank-Order Searching Circuit Employing a Time-Domain Technique
Directory of Open Access Journals (Sweden)
Trong-Tu Bui
2013-01-01
Full Text Available We present a compact and low-power rank-order searching (ROS circuit that can be used for building associative memories and rank-order filters (ROFs by employing time-domain computation and floating-gate MOS techniques. The architecture inherits the accuracy and programmability of digital implementations as well as the compactness and low-power consumption of analog ones. We aim to implement identification function as the first priority objective. Filtering function would be implemented once the location identification function has been carried out. The prototype circuit was designed and fabricated in a 0.18 μm CMOS technology. It consumes only 132.3 μW for an eight-input demonstration case.
New developments in THz-time domain spectroscopy involving ML-VECSELs
Apostolopoulos, Vasilis; Tropper, Anne C.; Keenlyside, Benjamin; Chen-Sverre, Theo; Woods, Jonathan R. C.
2018-02-01
The THz time domain spectrometer (THz-TDS) has revolutionized the adoption of THz science in fields such as medicine, material characterization, pharmaceutical research and biology among others. Traditionally a THz-TDS was based on a titanium sapphire laser, while most of the commercially sold spectrometers today adopt fiber lasers. Vertical External Cavity Surface emitting lasers or VECSELs have potential to be the future laser of choice for the implementation of THz spectrometers, as they are small, low-cost, low noise and high repetition rate. Here I will outline the progress in our laboratory and the general community concerning VECSEL-THz technology and I will account the problems that have to be solved for the VECSEL-THz technology to succeed.
Rotation commensurate echo of asymmetric molecules—Molecular fingerprints in the time domain
Energy Technology Data Exchange (ETDEWEB)
Chesnokov, E. N., E-mail: chesnok@kinetics.nsc.ru [Institute of Chemical Kinetics and Combustion, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Kubarev, V. V. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Koshlyakov, P. V. [Institute of Chemical Kinetics and Combustion, Novosibirsk 630090 (Russian Federation)
2014-12-29
Using the pulses of terahertz free electron laser and ultra-fast Schottky diode detectors, we observed the coherent transients within a free induction decay of gaseous nitrogen dioxide NO{sub 2}. The laser excited different sub-bands of rotation spectra of NO{sub 2} containing about 50–70 lines. The free induction signal continued more than 30 ns and consisted of many echo-like bursts duration about 0.2 ns. Unlike the similar effect observed previously for linear and symmetric top molecules, the sequence of echo bursts is not periodic. The values for delay of individual echo are stable, and the set of these delays can be considered as a “molecular fingerprint” in the time domain.
A hybrid method of estimating pulsating flow parameters in the space-time domain
Pałczyński, Tomasz
2017-05-01
This paper presents a method for estimating pulsating flow parameters in partially open pipes, such as pipelines, internal combustion engine inlets, exhaust pipes and piston compressors. The procedure is based on the method of characteristics, and employs a combination of measurements and simulations. An experimental test rig is described, which enables pressure, temperature and mass flow rate to be measured within a defined cross section. The second part of the paper discusses the main assumptions of a simulation algorithm elaborated in the Matlab/Simulink environment. The simulation results are shown as 3D plots in the space-time domain, and compared with proposed models of phenomena relating to wave propagation, boundary conditions, acoustics and fluid mechanics. The simulation results are finally compared with acoustic phenomena, with an emphasis on the identification of resonant frequencies.
International Nuclear Information System (INIS)
Hasegawa, M.; Nakai, S.; Watanabe, T.
1985-01-01
A practical method for elasto-plastic seismic response analysis is described under considerations of nonlinear material law of a structure and dynamic soil-structure interaction. The method is essentially based on the substructure approach of time domain analysis. Verification of the present method is carried out for typical BWR-MARK II type reactor building which is embedded in a soil, and the results are compared with those of the frequency response analysis which gives good accuracy for linear system. As a result, the present method exhibits sufficient accuracy. Furthermore, elasto-plastic analyses considering the soil-structure interaction are made as an application of the present method, and nonlinear behaviors of the structure and embedment effects are discussed. (orig.)
Time-domain soil-structure interaction analysis of nuclear facilities
International Nuclear Information System (INIS)
Coleman, Justin L.; Bolisetti, Chandrakanth; Whittaker, Andrew S.
2016-01-01
The Nuclear Regulatory Commission (NRC) regulation 10 CFR Part 50 Appendix S requires consideration of soil-structure interaction (SSI) in nuclear power plant (NPP) analysis and design. Soil-structure interaction analysis for NPPs is routinely carried out using guidance provided in the ASCE Standard 4-98 titled “Seismic Analysis of Safety-Related Nuclear Structures and Commentary”. This Standard, which is currently under revision, provides guidance on linear seismic soil-structure-interaction (SSI) analysis of nuclear facilities using deterministic and probabilistic methods. A new appendix has been added to the forthcoming edition of ASCE Standard 4 to provide guidance for time-domain, nonlinear SSI (NLSSI) analysis. Nonlinear SSI analysis will be needed to simulate material nonlinearity in soil and/or structure, static and dynamic soil pressure effects on deeply embedded structures, local soil failure at the foundation-soil interface, nonlinear coupling of soil and pore fluid, uplift or sliding of the foundation, nonlinear effects of gaps between the surrounding soil and the embedded structure and seismic isolation systems, none of which can be addressed explicitly at present. Appendix B of ASCE Standard 4 provides general guidance for NLSSI analysis but will not provide a methodology for performing the analysis. This paper provides a description of an NLSSI methodology developed for application to nuclear facilities, including NPPs. This methodology is described as series of sequential steps to produce reasonable results using any time-domain numerical code. These steps require some numerical capabilities, such as nonlinear soil constitutive models, which are also described in the paper.
Integral equation approach to time-dependent kinematic dynamos in finite domains
International Nuclear Information System (INIS)
Xu Mingtian; Stefani, Frank; Gerbeth, Gunter
2004-01-01
The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of the Biot-Savart law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos, with stationary dynamo sources, in finite domains. The time dependence is restricted to the magnetic field, whereas the velocity or corresponding mean-field sources of dynamo action are supposed to be stationary. For the spherically symmetric α 2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and toroidal field components. The integral equation formulation for spherical dynamos with general stationary velocity fields is also derived. Two numerical examples - the α 2 dynamo model with radially varying α and the Bullard-Gellman model - illustrate the equivalence of the approach with the usual differential equation method. The main advantage of the method is exemplified by the treatment of an α 2 dynamo in rectangular domains