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......%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D...
Convergence of Wachspress coordinates: from polygons to curved domains
Kosinka, Jiří
2014-08-08
Given a smooth, strictly convex planar domain, we investigate point-wise convergence of the sequence of Wachspress coordinates defined over finer and finer inscribed polygonal approximations of the domain. Based on a relation between the discrete Wachspress case and the limit smooth case given by the Wachspress kernel defined by Warren et al., we show that the corresponding sequences of Wachspress interpolants and mappings converge as 𝓞(h2) for a sampling step size h of the boundary curve of the domain as h → 0. Several examples are shown to numerically validate the results and to visualise the behaviour of discrete interpolants and mappings as they converge to their smooth counterparts. Empirically, the same convergence order is observed also for mean value coordinates. Moreover, our numerical tests suggest that the convergence of interpolants and mappings is uniform both in the Wachspress and mean value cases. © 2014 Springer Science+Business Media New York.
Higher dimensional curved domain walls on Kähler surfaces
International Nuclear Information System (INIS)
Akbar, Fiki T.; Gunara, Bobby E.; Radjabaycolle, Flinn C.; Wijaya, Rio N.
2017-01-01
In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.
Higher dimensional curved domain walls on Kähler surfaces
Energy Technology Data Exchange (ETDEWEB)
Akbar, Fiki T., E-mail: ftakbar@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Gunara, Bobby E., E-mail: bobby@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Radjabaycolle, Flinn C. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Departement of Physics, Faculty of Mathematics and Natural Sciences, Cendrawasih University, Jl. Kampwolker Kampus Uncen Baru Waena-Jayapura 99351 (Indonesia); Wijaya, Rio N. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia)
2017-03-15
In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.
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)
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.
Energy Technology Data Exchange (ETDEWEB)
Sato, S., E-mail: 231504@gmail.com; Kumagai, S.; Sugita, R.
2015-03-01
In this paper, in order to confirm the sub-domain structure in stacked media demagnetized with in-plane field, initial magnetization curves and magnetic domain size distribution were investigated. Both experimental and simulation results showed that an initial magnetization curve for the medium demagnetized with in-plane field (MDI) initially rose faster than that for the medium demagnetized with perpendicular field (MDP). It is inferred that this is because the MDI has a larger number of domain walls than the MDP due to the existence of the sub-domains, resulting in an increase in the probability of domain wall motion. Dispersion of domain size for the MDI was larger than that for the MDP. This is because sub-domains are formed not only inside the domain but also at the domain boundary region, and they change the position of the domain boundary to affect the domain size. - Highlights: • An initial magnetization curve for MDI initially rose faster than that for MDP. • Dispersion of domain size for the MDI was larger than that for the MDP. • Experimental and simulation results can be explained by existence of sub-domains.
Quantum fields in curved space-times
International Nuclear Information System (INIS)
Ashtekar, A.; Magnon, A.
1975-01-01
The problem of obtaining a quantum description of the (real) Klein-Gordon system in a given curved space-time is discussed. An algebraic approach is used. The *-algebra of quantum operators is constructed explicitly and the problem of finding its *-representation is reduced to that of selecting a suitable complex structure on the real vector space of the solutions of the (classical) Klein-Gordon equation. Since, in a static space-time, there already exists, a satisfactory quantum field theory, in this case one already knows what the 'correct' complex structure is. A physical characterization of this 'correct' complex structure is obtained. This characterization is used to extend quantum field theory to non-static space-times. Stationary space-times are considered first. In this case, the issue of extension is completely straightforward and the resulting theory is the natural generalization of the one in static space-times. General, non-stationary space-times are then considered. In this case the issue of extension is quite complicated and only a plausible extension is presented. Although the resulting framework is well-defined mathematically, the physical interpretation associated with it is rather unconventional. Merits and weaknesses of this framework are discussed. (author)
Supertube domain walls and elimination of closed timelike curves in string theory
International Nuclear Information System (INIS)
Drukker, Nadav
2004-01-01
We show that some novel physics of supertubes removes closed timelike curves from many supersymmetric spaces which naively suffer from this problem. The main claim is that supertubes naturally form domain walls, so while analytical continuation of the metric would lead to closed timelike curves, across the domain wall the metric is nondifferentiable, and the closed timelike curves are eliminated. In the examples we study, the metric inside the domain wall is always of the Goedel type, while outside the shell it looks like a localized rotating object, often a rotating black hole. Thus this mechanism prevents the appearance of closed timelike curves behind the horizons of certain rotating black holes
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
Exploration of the Time Domain (Abstract)
Djorgovski, G.
2017-06-01
(Abstract only) Time-domain astronomy is one of the most active and growing areas of astronomical research today, thanks to the new generation of synoptic sky surveys, and leading to LSST. Catalina Real-Time Transient Survey (CRTS; http://crts.caltech.edu) is systematically exploring and characterizing the variable sky since 2008, with the archival data going back to 2005. The survey covers the total area of 33,000 deg2, down to 19±21 mag per exposure, with time baselines from 10 min to 10 years, and growing; there are now typically 200±400 exposures per pointing, and coadded images reach deeper than 23 magnitude. The survey has so far detected over 13,000 unique, high-amplitude transients, including 4,000 confirmed or likely supernovae, nearly 2,000 CVs (the great majority of them previously uncatalogued), about 4,000 blazars and other flaring AGN, and a broad variety of other types of objects. Many of these objects can benefit from a follow-up by the amateur community. CRTS is intended to be a data resource for the entire astronomical community. We have a completely open data policy: all discovered transient events are published in real time with no proprietary delay period, and all data are made public, in order to better serve the entire community, and maximize the scientific returns. This includes an archive of 500 million light curves, which are being updated continuously. This is an unprecedented data set for the exploration of the time domain, in terms of the area, depth, and temporal coverage. Numerous scientific projects have been enabled by this data stream, including: discoveries of ultraluminous and otherwise peculiar SNe; unusual CVs and dwarf novae; mapping of the structure in the Galactic halo using RR Lyrae; variability-based discovery of AGN and probes of their physics; and so on.
Feynman propagator in curved space-time
International Nuclear Information System (INIS)
Candelas, P.; Raine, D.J.
1977-01-01
The Wick rotation is generalized in a covariant manner so as to apply to curved manifolds in a way that is independent of the analytic properties of the manifold. This enables us to show that various methods for defining a Feynman propagator to be found in the literature are equivalent where they are applicable. We are also able to discuss the relation between certain regularization methods that have been employed
High-order wide-band frequency domain identification using composite curve fitting
Bayard, D. S.
1992-01-01
A method is presented for curve fitting nonparametric frequency domain data so as to identify a parametric model composed of two models in parallel, where each model has dynamics in a specified portion of the frequency band. This decomposition overcomes the problem of numerical sensitivity since lower order polynomials can be used compared to existing methods which estimate the model as a single entity. Consequently, composite curve fitting is useful for frequency domain identification of high-order systems and/or systems whose dynamics are spread over a large bandwidth. The approach can be extended to identify an arbitrary number of parallel subsystems in specified frequency regimes.
Essential Boundary Conditions with Straight C1 Finite Elements in Curved Domains
International Nuclear Information System (INIS)
Ferraro, N.M.; Jardin, S.C.; Luo, X.
2010-01-01
The implementation of essential boundary conditions in C1 finite element analysis requires proper treatment of both the boundary conditions on second-order differentials of the solution and the curvature of the domain boundary. A method for the imposition of essential boundary conditions using straight elements (where the elements are not deformed to approximate a curved domain) is described. It is shown that pre-multiplication of the matrix equation by the local rotation matrix at each boundary node is not the optimal transformation. The uniquely optimal transformation is found, which does not take the form of a similarity transformation due to the non-orthogonality of the transformation to curved coordinates.
An Interoperability Consideration in Selecting Domain Parameters for Elliptic Curve Cryptography
Ivancic, Will (Technical Monitor); Eddy, Wesley M.
2005-01-01
Elliptic curve cryptography (ECC) will be an important technology for electronic privacy and authentication in the near future. There are many published specifications for elliptic curve cryptosystems, most of which contain detailed descriptions of the process for the selection of domain parameters. Selecting strong domain parameters ensures that the cryptosystem is robust to attacks. Due to a limitation in several published algorithms for doubling points on elliptic curves, some ECC implementations may produce incorrect, inconsistent, and incompatible results if domain parameters are not carefully chosen under a criterion that we describe. Few documents specify the addition or doubling of points in such a manner as to avoid this problematic situation. The safety criterion we present is not listed in any ECC specification we are aware of, although several other guidelines for domain selection are discussed in the literature. We provide a simple example of how a set of domain parameters not meeting this criterion can produce catastrophic results, and outline a simple means of testing curve parameters for interoperable safety over doubling.
Axial model in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J.; Farina, C.; Vaidya, A.N.
1986-12-11
We study the axial model in a background gravitational field. Using the zeta-function regularization, we obtain explicitly the anomalous divergence of the axial-vector current and the exact generating functional of the theory. We show that, as a consequence of a space-time-dependent metric, all differential equations involved in the theory generalize to their covariantized forms. We also comment on the finite-mass renormalization exhibited by the pseudoscalar field and the form of the fermion propagator.
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
A time domain technique for mechanism extraction
Dominek, Allen K.; Peters, Leon, Jr.; Burnside, Walter D.
1987-01-01
The properties of scattered fields from a structure can be better evaluated from the characteristics of the individual scatterers. Decomposition techniques can be classified either as a matrix or an integral formulation. With either formulation, aspect pattern of frequency information of a scattering center can be obtained. Emphasis is placed on an integral (time domain) isolation extraction technique to obtain the frequency characteristics of scattering mechanisms. This technique has its origins in the time domain interpretation of scattered fields.
Quaternion wave equations in curved space-time
Edmonds, J. D., Jr.
1974-01-01
The quaternion formulation of relativistic quantum theory is extended to include curvilinear coordinates and curved space-time in order to provide a framework for a unified quantum/gravity theory. Six basic quaternion fields are identified in curved space-time, the four-vector basis quaternions are identified, and the necessary covariant derivatives are obtained. Invariant field equations are derived, and a general invertable coordinate transformation is developed. The results yield a way of writing quaternion wave equations in curvilinear coordinates and curved space-time as well as a natural framework for solving the problem of second quantization for gravity.
Applications of Frequency Domain Curve-fitting in the EFDD Technique
DEFF Research Database (Denmark)
Jacobsen, Niels-Jørgen; Andersen, Palle; Brincker, Rune
2008-01-01
Over the years different methods have been proposed for how to deal with the presence of harmonic components in operational modal analysis. In this paper a method for detection of harmonic components using Fast Kurtosis Checking will be introduced along with a new frequency domain curve-fitting v......Over the years different methods have been proposed for how to deal with the presence of harmonic components in operational modal analysis. In this paper a method for detection of harmonic components using Fast Kurtosis Checking will be introduced along with a new frequency domain curve......-fitting version of the Enhanced Frequency Domain Decomposition (EFDD) technique. This combined approach makes it possible to extract structural modes fast even when several harmonic components are present and even when the harmonic components are located exactly at the natural frequencies of the structural modes...
Real-Time Exponential Curve Fits Using Discrete Calculus
Rowe, Geoffrey
2010-01-01
An improved solution for curve fitting data to an exponential equation (y = Ae(exp Bt) + C) has been developed. This improvement is in four areas -- speed, stability, determinant processing time, and the removal of limits. The solution presented avoids iterative techniques and their stability errors by using three mathematical ideas: discrete calculus, a special relationship (be tween exponential curves and the Mean Value Theorem for Derivatives), and a simple linear curve fit algorithm. This method can also be applied to fitting data to the general power law equation y = Ax(exp B) + C and the general geometric growth equation y = Ak(exp Bt) + C.
On the study of the magnetic domain pattern via the initial magnetization curve
International Nuclear Information System (INIS)
Wu, T.
1997-01-01
This study inquires into the relationships between the initial magnetization curve and the magnetic domain pattern in the demagnetized states for amorphous TbFeCo as well as multilayered Co/Pd thin film samples. This was done specifically through an investigation of different demagnetized states of samples demagnetized by a variety of methods. The magnetic domain pattern for the sample demagnetized by an in-plane magnetic field and for the sample demagnetized by a perpendicular magnetic field was found to be quite different even though both states have zero magnetization. The former state has denser and finer domains than the latter. In addition, both states were studied in light of the initial magnetization curves obtained by measurements of the magneto-optic Kerr effect and the extraordinary Hall effect. Moreover, the initial magnetization for the fine domains increases with an increase in magnetic field, while for the coarse domains, the initial magnetization remains at zero for magnetic field below coercivity H c , then rises sharply to saturated magnetization when magnetic field is nearly equal to H c . copyright 1997 American Institute of Physics
Time Domain Astronomy with Swift and Fermi
African Journals Online (AJOL)
J.D. Myers
Time Domain Astronomy with Swift and Fermi. N. Gehrels1, J. K. Cannizzo23. 1NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771, USA. 2CRESST and Astroparticle Physics Laboratory, NASA/GSFC, Greenbelt, MD 20771, USA. 3Department of Physics, University of Maryland, Baltimore County, ...
Time-domain analysis of EPR measurements of polyacetylene and soliton diffusion
International Nuclear Information System (INIS)
Tang, J.; Lin, C.P.; Bowman, M.K.; Norris, J.R.; Isoya, J.; Shirakawa, H.
1983-01-01
A novel analysis of EPR measurements on polyacetylene is demonstrated by the analysis of the conventional line shape in time domain. Quantitative results of the hyperfine-coupling constant, the on-chain diffusion rate, and the off-chain hopping rate were extracted by nonlinear curve fitting to the time-domain signals, and they are consistent with the soliton model of polyacetylene
Wimmers, Paul F; Lee, Ming
2015-05-01
To determine the direction and extent to which medical student scores (as observed by small-group tutors) on four problem-based-learning-related domains change over nine consecutive blocks during a two-year period (Domains: Problem Solving/Use of Information/Group Process/Professionalism). Latent growth curve modeling is used to analyze performance trajectories in each domain of two cohorts of 1st and 2nd year students (n = 296). Slopes of the growth trajectories show similar linear increments in the first three domains. Further analysis revealed relative strong individual variability in initial scores but not in their later increments. Professionalism, on the other hand, shows low variability and has very small, insignificant slope increments. In this study, we showed that the learning domains (Problem Solving, Use of Information, and Group Process) observed during PBL tutorials are not only related to each other but also develop cumulatively over time. Professionalism, in contrast to the other domains studied, is less affected by the curriculum suggesting that this represents a stable characteristic. The observation that the PBL tutorial has an equal benefit to all students is noteworthy and needs further investigation.
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...
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 Diffraction by Composite Structures
Riccio, Giovanni; Frongillo, Marcello
2017-04-01
Time domain (TD) diffraction problems are receiving great attention because of the widespread use of ultra wide band (UWB) communication and radar systems. It is commonly accepted that, due to the large bandwidth of the UWB signals, the analysis of the wave propagation mechanisms in the TD framework is preferable to the frequency domain (FD) data processing. Furthermore, the analysis of transient scattering phenomena is also of importance for predicting the effects of electromagnetic pulses on civil structures. Diffraction in the TD framework represents a challenging problem and numerical discretization techniques can be used to support research and industry activities. Unfortunately, these methods become rapidly intractable when considering excitation pulses with high frequency content. This contribution deals with the TD diffraction phenomenon related to composite structures containing a dielectric wedge with arbitrary apex angle when illuminated by a plane wave. The approach is the same used in [1]-[3]. The transient diffracted field originated by an arbitrary function plane wave is evaluated via a convolution integral involving the TD diffraction coefficients, which are determined in closed form starting from the knowledge of the corresponding FD counterparts. In particular, the inverse Laplace transform is applied to the FD Uniform Asymptotic Physical Optics (FD-UAPO) diffraction coefficients available for the internal region of the structure and the surrounding space. For each observation domain, the FD-UAPO expressions are obtained by considering electric and magnetic equivalent PO surface currents located on the interfaces. The surface radiation integrals using these sources is assumed as starting point and manipulated for obtaining integrals able to be solved by means of the Steepest Descent Method and the Multiplicative Method. [1] G. Gennarelli and G. Riccio, "Time domain diffraction by a right-angled penetrable wedge," IEEE Trans. Antennas Propag., Vol
Radiation reaction in curved space-time:. local method
Gal'Tsov, Dmitri; Spirin, Pavel; Staub, Simona
Although consensus seems to exist about the validity of equations accounting for radiation reaction in curved space-time, their previous derivations were criticized recently as not fully satisfactory: some ambiguities were noticed in the procedure of integration of the field momentum over the tube surrounding the world-line. To avoid these problems we suggest a purely local derivation dealing with the field quantities defined only on the world-line. We consider point particle interacting with scalar, vector (electromagnetic) and linearized gravitational fields in the (generally non-vacuum) curved space-time. To properly renormalize the self-action in the gravitational case, we use a manifestly reparameterization-invariant formulation of the theory. Scalar and vector divergences are shown to cancel for a certain ratio of the corresponding charges. We also report on a modest progress in extending the results for the gravitational radiation reaction to the case of non-vacuum background.
Domain walls of gauged supergravity, M-branes and algebraic curves
Bakas, I.; Sfetsos, K.
1999-01-01
We provide an algebraic classification of all supersymmetric domain wall solutions of maximal gauged supergravity in four and seven dimensions, in the presence of non-trivial scalar fields in the coset SL(8,R)/SO(8) and SL(5,R)/SO(5) respectively. These solutions satisfy first-order equations, which can be obtained using the method of Bogomol'nyi. From an eleven-dimensional point of view they correspond to various continuous distributions of M2- and M5-branes. The Christoffel-Schwarz transformation and the uniformization of the associated algebraic curves are used in order to determine the Schrodinger potential for the scalar and graviton fluctuations on the corresponding backgrounds. In many cases we explicitly solve the Schrodinger problem by employing techniques of supersymmetric quantum mechanics. The analysis is parallel to the construction of domain walls of five-dimensional gauged supergravity, with scalar fields in the coset SL(6,R)/SO(6), using algebraic curves or continuous distributions of D3-brane...
Mass Formulae for Broken Supersymmetry in Curved Space-Time
Ferrara, Sergio
2016-01-01
We derive the mass formulae for ${\\cal N}=1$, $D=4$ matter-coupled Supergravity for broken (and unbroken) Supersymmetry in curved space-time. These formulae are applicable to de Sitter configurations as is the case for inflation. For unbroken Supersymmetry in anti-de Sitter (AdS) one gets the mass relations modified by the AdS curvature. We compute the mass relations both for the potential and its derivative non-vanishing.
String dynamics in curved space-time revisited
International Nuclear Information System (INIS)
Marrakchi, A.L.; Singh, L.P.
1989-09-01
The equations of motion of the general background of curved space-time, Einstein's equations, are derived simply by demanding the renormalized energy-momentum tensor of a bosonic string propagating in this background to be traceless. The energy-momentum tensor of such a string is then separable into a holomorphic and an antiholomorphic parts as a consequence of the conformal invariance of the theory regained at the quantum level. (author). 8 refs
Architectures for Time-domain Astronomy
Seaman, R.; Allan, A.; Pierfederici, F.; Williams, R.
2009-09-01
Wonder at the changing sky predates recorded history. Empirical studies of time-varying celestial phenomena date back to Galileo and Tycho. Telegrams conveying news of transient and recurrent events have been key astronomical infrastructure since the nineteenth century. Recent micro-lensing, supernova and gamma-ray burst studies have lead to a succession of exciting discoveries, but massive new time-domain surveys will soon overwhelm our nineteenth century transient response technologies. Meeting this challenge demands new autonomous architectures for astronomy. These Architectures should reach from proposing new research, through experimental design and the scheduling of telescope operations, to the archiving and pipeline-processing of data to discover new transients, to the publishing of these events, through automated follow-up via robotic and ToO assets, and to the display and analysis of observational results. All will lead to adaptive adjustment of time-domain investigations. The IVOA VOEvent protocol provides an engine for purpose-built astronomical architectures.
Analytic comparison of time- and frequency-domain electromagnetic methods
Energy Technology Data Exchange (ETDEWEB)
Stoyer, C.H.
1980-01-01
The time- and frequency-domain methods of electromagnetic geophysical prospecting are compared to determine the similarities and differences and to recommend system choices for particular field situations. Only the wire-loop configuration is considered, as this array is quite standard in geothermal prospecting. Comparisons are carried out using hardware and physical considerations, a large catalog of 3-layer model curves, 2D-3D model calculations, and by comparing Fourier transforms and layered inversions of field data from the Randsburg KGRA in California. The results generally indicate that frequency-domain methods offer better resolution and more practical hardware design for long-offset shallow applications. They also have a much better backup in terms of modelling tools for interpretation and history of experience. Transient methods are better suited for deeper probing, for both long- and short-offset applications. Frequency-domain methods are limited by the primary field, which is subject to distortion from near-surface inhomogeneites; this is also the case for early-time transients. Transient measurements in late time are limited by ambient electromagnetic noise and dynamic range of receiving equipment.
Simulation of time curves in small animal PET using GATE
International Nuclear Information System (INIS)
Simon, Luc; Strul, Daniel; Santin, Giovanni; Krieguer, Magalie; Morel, Christian
2004-01-01
The ClearPET project of the Crystal Clear Collaboration (CCC) is building spin-off technology for high resolution small animal Positron Emission Tomography (PET). Monte Carlo simulation is essential for optimizing the specifications of these systems with regards to their most important characteristics, such as spatial resolution, sensitivity, or count rate performance. GATE, the Geant4 Application for Tomographic Emission simulates the passing of time during real acquisitions, allowing to handle dynamic systems such as decaying source distributions or moving detectors. GATE output is analyzed on an event-by-event basis. The time associated with each single event allows to sort coincidences and to model dead-time. This leads to the study of time curves for a prospective small animal PET scanner design. The count rates of true, and random coincidences are discussed together with the corresponding Noise Equivalent Count (NEC) rates as a function of some PET scanner specifications such as detector dead time, or coincidence time window
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.
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.
Time-Domain Analysis of Scrotal Thermoregulatory Impairment in Varicocele
Directory of Open Access Journals (Sweden)
Enas eIsmail
2014-09-01
Full Text Available Varicocele is a common male disease defined as the pathological dilatation of the pampiniform plexus and scrotal veins with venous blood reflux. Varicocele usually impairs the scrotal thermoregulation via a hemodynamic alteration, thus inducing an increase in cutaneous temperature. The investigation of altered scrotal thermoregulation by means of thermal infrared imaging has been proved to be useful in the study of the functional thermal impairment. In this study, we use the Control System Theory to analyze the time-domain dynamics of the scrotal thermoregulation in response to a mild cold challenge. Four standard time-domain dynamic parameters of a prototype second order control system (Delay Time, Rise Time, closed poles locations, steady state error and the static basal temperatures were directly estimated from thermal recovery curves. Thermal infrared imaging data from 31 healthy controls (HCS and 95 varicocele patients were processed. True-positive predictions, by comparison with standard echo color Doppler findings, higher than 87 % were achieved into the proper classification of the disease stage. The proposed approach could help to understand at which specific level the presence of the disease impacts the scrotal thermoregulation, which is also involved into normal spermatogenesis process.
Transmission assets investment timing using net present value curves
International Nuclear Information System (INIS)
Garcia, Reinaldo C.; Contreras, Javier; Munoz, Jose I.; Correia, Pedro F.
2010-01-01
Improvement and expansion of the transmission grid is still an unresolved issue in the new competitive environment. In current electricity markets, transmission lines have become assets that need financial instruments for investors who wish to ensure steady long-term returns and to withstand short-term market volatility. The timing and the combination of new transmission investments is key to analyze their long-term effects. This paper presents the concept of net present value (NPV) curve to estimate the best investment time for the investor, where the curve is constructed by calculating the NPVs resulting from the investment in successive years. A specific contract model based on financial transmission rights (FTR) is used for the NPV evaluation of transmission assets, and the stochastic properties of all variables related to the investment market structure are considered. The model is applied to the IEEE 24-bus Reliability Test System (RTS) showing the approach capabilities as a decision-aid tool for transmission investors. (author)
Domain enhanced lookup time accelerated BLAST
Directory of Open Access Journals (Sweden)
Boratyn Grzegorz M
2012-04-01
Full Text Available Abstract Background BLAST is a commonly-used software package for comparing a query sequence to a database of known sequences; in this study, we focus on protein sequences. Position-specific-iterated BLAST (PSI-BLAST iteratively searches a protein sequence database, using the matches in round i to construct a position-specific score matrix (PSSM for searching the database in round i + 1. Biegert and Söding developed Context-sensitive BLAST (CS-BLAST, which combines information from searching the sequence database with information derived from a library of short protein profiles to achieve better homology detection than PSI-BLAST, which builds its PSSMs from scratch. Results We describe a new method, called domain enhanced lookup time accelerated BLAST (DELTA-BLAST, which searches a database of pre-constructed PSSMs before searching a protein-sequence database, to yield better homology detection. For its PSSMs, DELTA-BLAST employs a subset of NCBI’s Conserved Domain Database (CDD. On a test set derived from ASTRAL, with one round of searching, DELTA-BLAST achieves a ROC5000 of 0.270 vs. 0.116 for CS-BLAST. The performance advantage diminishes in iterated searches, but DELTA-BLAST continues to achieve better ROC scores than CS-BLAST. Conclusions DELTA-BLAST is a useful program for the detection of remote protein homologs. It is available under the “Protein BLAST” link at http://blast.ncbi.nlm.nih.gov. Reviewers This article was reviewed by Arcady Mushegian, Nick V. Grishin, and Frank Eisenhaber.
Directory of Open Access Journals (Sweden)
Le Botlan D.
2006-12-01
Full Text Available Dans un champ magnétique hétérogène, le signal RMN de précession libre (FID suit une évolution gaussienne. Le traitement du signal par une méthode discrète peut donner des composantes qui ne correspondent pas à un état physique réel. Par contre l'utilisation d'une méthode de déconvolution continue nous a donné des résultats quantitatifs tout à fait satisfaisants permettant de déterminer les distributions de temps de relaxation correspondant à des états intermédiaires entre les phases solides et liquides. La RMN du domaine du temps peut ainsi être considérée comme une méthode analytique complémentaire des techniques habituellement utilisées pour l'étude de composés complexes hétérogènes ATD, ACD, isothermes de sorption, etc. In a heterogeneous magnetic field, the freely precessing NMR signal (FID describes a Gaussian curve. Processing the signal using a discrete method can give rise to components that do not correspond to a real physical state. However, with a continuous deconvolution method, which gives quite satisfactory quantitative results, it is possible to determine the distributions of relaxation times that correspond to intermediate states between solid and liquid phases. Time-dependent NMR can thus be used to supplement the usual analytical methods, such as DTA, DCA and sorption isotherms, for studying complex heterogeneous compounds.
Huang, Huan; Baddour, Natalie; Liang, Ming
2018-02-01
Under normal operating conditions, bearings often run under time-varying rotational speed conditions. Under such circumstances, the bearing vibrational signal is non-stationary, which renders ineffective the techniques used for bearing fault diagnosis under constant running conditions. One of the conventional methods of bearing fault diagnosis under time-varying speed conditions is resampling the non-stationary signal to a stationary signal via order tracking with the measured variable speed. With the resampled signal, the methods available for constant condition cases are thus applicable. However, the accuracy of the order tracking is often inadequate and the time-varying speed is sometimes not measurable. Thus, resampling-free methods are of interest for bearing fault diagnosis under time-varying rotational speed for use without tachometers. With the development of time-frequency analysis, the time-varying fault character manifests as curves in the time-frequency domain. By extracting the Instantaneous Fault Characteristic Frequency (IFCF) from the Time-Frequency Representation (TFR) and converting the IFCF, its harmonics, and the Instantaneous Shaft Rotational Frequency (ISRF) into straight lines, the bearing fault can be detected and diagnosed without resampling. However, so far, the extraction of the IFCF for bearing fault diagnosis is mostly based on the assumption that at each moment the IFCF has the highest amplitude in the TFR, which is not always true. Hence, a more reliable T-F curve extraction approach should be investigated. Moreover, if the T-F curves including the IFCF, its harmonic, and the ISRF can be all extracted from the TFR directly, no extra processing is needed for fault diagnosis. Therefore, this paper proposes an algorithm for multiple T-F curve extraction from the TFR based on a fast path optimization which is more reliable for T-F curve extraction. Then, a new procedure for bearing fault diagnosis under unknown time-varying speed
Point splitting in a curved space-time background
International Nuclear Information System (INIS)
Liggatt, P.A.J.; Macfarlane, A.J.
1979-01-01
A prescription is given for point splitting in a curved space-time background which is a natural generalization of that familiar in quantum electrodynamics and Yang-Mills theory. It is applied (to establish its validity) to the verification of the gravitational anomaly in the divergence of a fermion axial current. Notable features of the prescription are that it defines a point-split current that can be differentiated straightforwardly, and that it involves a natural way of averaging (four-dimensionally) over the directions of point splitting. The method can extend directly from the spin-1/2 fermion case treated to other cases, e.g., to spin-3/2 Rarita-Schwinger fermions. (author)
Momentum-subtraction renormalization techniques in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Foda, O.
1987-10-01
Momentum-subtraction techniques, specifically BPHZ and Zimmermann's Normal Product algorithm, are introduced as useful tools in the study of quantum field theories in the presence of background fields. In a model of a self-interacting massive scalar field, conformally coupled to a general asymptotically-flat curved space-time with a trivial topology, momentum-subtractions are shown to respect invariance under general coordinate transformations. As an illustration, general expressions for the trace anomalies are derived, and checked by explicit evaluation of the purely gravitational contributions in the free field theory limit. Furthermore, the trace of the renormalized energy-momentum tensor is shown to vanish at the Gell-Mann Low eigenvalue as it should.
Momentum-subtraction renormalization techniques in curved space-time
International Nuclear Information System (INIS)
Foda, O.
1987-01-01
Momentum-subtraction techniques, specifically BPHZ and Zimmermann's Normal Product algorithm, are introduced as useful tools in the study of quantum field theories in the presence of background fields. In a model of a self-interacting massive scalar field, conformally coupled to a general asymptotically-flat curved space-time with a trivial topology, momentum-subtractions are shown to respect invariance under general coordinate transformations. As an illustration, general expressions for the trace anomalies are derived, and checked by explicit evaluation of the purely gravitational contributions in the free field theory limit. Furthermore, the trace of the renormalized energy-momentum tensor is shown to vanish at the Gell-Mann Low eigenvalue as it should
Labruyère, Rob; van Hedel, Hubertus J
2012-05-01
To investigate whether a figure-of-8-shaped walking test can estimate various domains of walking in subjects with incomplete spinal cord injury (iSCI) better than the 10-meter walk test (10MWT), and to explore similarities and differences between the 2 tests and between subjects with iSCI and age-matched, healthy controls. Case-control study. Spinal cord injury center of a university hospital. A convenience sample of subjects with iSCI (n=15; mean age, 50y; 40% women; neurologic level from C3 to L5; median time since injury, 5mo) was compared with an age-matched control group (47% women). Not applicable. The figure-of-8 test (FET) included 6 conditions to test the subjects' ability to adapt their gait to several circumstances. These conditions covered normal and maximal walking speed, constrained vision, obstacles, foamed soles, and a dual task. Additionally, subjects were tested for lower extremity muscle strength, gait capacity (10MWT) and balance, independence, and fear of falling. (1) Preferred straight-walking speed correlated with the different FET conditions in both groups; (2) if normalized to preferred straight-walking speed, FET conditions showed significant differences between both groups; (3) if normalized to preferred curve-walking speed, these differences seemed to disappear; and (4) the 10MWT appeared superior to the different conditions of the FET in estimating various walking-related functions. Subjects with iSCI seem to have difficulties with curve walking compared with straight walking. We therefore recommend the implementation of curve walking into rehabilitation training programs. However, the FET did not provide a better estimate of functional ambulation performance after an iSCI compared with the 10MWT. Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Exactly solvable string models of curved space-time backgrounds
International Nuclear Information System (INIS)
Russo, J.G.
1995-01-01
We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the ''dilatonic'' (a=1) and ''Kaluza-Klein'' (a=√(3)) Melvin solutions and the uniform magnetic field solution, as well as some singular space-times. Solvability of the string σ-model is related to its connection via duality to a simpler model which is a ''twisted'' product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model (tachyonic instabilities in the spectrum, gyromagnetic ratio, issue of singularities, etc.). It provides one of the first examples of a consistent solvable conformal string model with explicit D=4 curved space-time interpretation. (orig.)
On the late-time behavior of tracer test breakthrough curves
Energy Technology Data Exchange (ETDEWEB)
HAGGERTY, ROY; MCKENNA, SEAN A; MEIGS, LUCY C
2000-06-12
The authors investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual or multi-porosity systems) and found that the late-time concentration, c, is given by the simple expression: c = t{sub ad} (c{sub 0}g {minus} m{sub 0}{partial_derivative}g/{partial_derivative}t), for t >> t{sub ad} and t{sub a} >> t{sub ad} where t{sub ad} is the advection time, c{sub 0} is the initial concentration in the medium, m{sub 0} is the 0th moment of the injection pulse; and t{sub a} is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain, the authors tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression they examine the behavior of late-time concentration for a number of mass transfer models. One key results is that if rate-limited mass transfer causes the BTC to behave as a power-law at late-time (i.e., c {approximately} t{sup {minus}k}), then the underlying density function of rate coefficients must also be a power-law with the form a{sup k{minus}}, as a {r_arrow}0. This is true for both density functions of first-order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment and possibly infinite, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. They apply their analysis to breakthrough curves from Single-Well Injection-Withdrawal tests at the Waste Isolation Pilot Plant, New Mexico.
Utility of time activity curve of scrotal scintigraphy in varicoceles
Energy Technology Data Exchange (ETDEWEB)
Mukaijo, Toshifumi; Harada, Masafumi; Tanouchi, Miki; Kitsukawa, Kaoru; Tokuyama, Noritami; Sui, Osamu; Nishitani, Hiromu (Tokushima Univ. (Japan). School of Medicine)
1991-03-01
Scrotal scintigraphy was performed in 37 patients with suspected varicocele. Time activity curves (TAC) were prepared and were divided into three types: Type I in which radioactivity was increased in the left testis rapidly after iv injection (n=7), Type II in which a significantly increased RI pooling was seen in the left testis after gradual RI increase (n=20), and Type III in which there was no bilateral difference in RI pooling (n=10). Because ten patients in the group of Type II showed bilateral difference in RI pooling during the static phase (after the first 120 seconds), collecting data for at least 3 to 4 minutes was considered necessary for the detection of abnormality. Among 30 patients with clinical varicocele, 25 patients (83%) had bilateral difference on TAC, as compared with 67% (20/30) for visual method on scintigrams. In addition, 2 other subclinical patients had it on TAC, although visual method failed to detect it in any of the subclinical patients. An average number of spermatozoa was larger for Type I than Type II, suggesting that factors other than reflux from the renal vein might be involved in spermatogenic function. Since scrotal scintigraphy reflects physical blood circulation, it seems to be useful in searching for the relationship between varicocele and male infertility. (N.K.).
Power-Time Curve Comparison between Weightlifting Derivatives.
Suchomel, Timothy J; Sole, Christopher J
2017-09-01
This study examined the power production differences between weightlifting derivatives through a comparison of power-time (P-t) curves. Thirteen resistance-trained males performed hang power clean (HPC), jump shrug (JS), and hang high pull (HHP) repetitions at relative loads of 30%, 45%, 65%, and 80% of their one repetition maximum (1RM) HPC. Relative peak power (PP Rel ), work (W Rel ), and P-t curves were compared. The JS produced greater PP Rel than the HPC (p < 0.001, d = 2.53) and the HHP (p < 0.001, d = 2.14). In addition, the HHP PP Rel was statistically greater than the HPC (p = 0.008, d = 0.80). Similarly, the JS produced greater W Rel compared to the HPC (p < 0.001, d = 1.89) and HHP (p < 0.001, d = 1.42). Furthermore, HHP W Rel was statistically greater than the HPC (p = 0.003, d = 0.73). The P-t profiles of each exercise were similar during the first 80-85% of the movement; however, during the final 15-20% of the movement the P-t profile of the JS was found to be greater than the HPC and HHP. The JS produced greater PP Rel and W Rel compared to the HPC and HHP with large effect size differences. The HHP produced greater PP Rel and W Rel than the HPC with moderate effect size differences. The JS and HHP produced markedly different P-t profiles in the final 15-20% of the movement compared to the HPC. Thus, these exercises may be superior methods of training to enhance PP Rel . The greatest differences in PP Rel between the JS and HHP and the HPC occurred at lighter loads, suggesting that loads of 30-45% 1RM HPC may provide the best training stimulus when using the JS and HHP. In contrast, loads ranging 65-80% 1RM HPC may provide an optimal stimulus for power production during the HPC.
Power-Time Curve Comparison between Weightlifting Derivatives
Directory of Open Access Journals (Sweden)
Timothy J. Suchomel, Christopher J. Sole
2017-09-01
Full Text Available This study examined the power production differences between weightlifting derivatives through a comparison of power-time (P-t curves. Thirteen resistance-trained males performed hang power clean (HPC, jump shrug (JS, and hang high pull (HHP repetitions at relative loads of 30%, 45%, 65%, and 80% of their one repetition maximum (1RM HPC. Relative peak power (PPRel, work (WRel, and P-t curves were compared. The JS produced greater PPRel than the HPC (p < 0.001, d = 2.53 and the HHP (p < 0.001, d = 2.14. In addition, the HHP PPRel was statistically greater than the HPC (p = 0.008, d = 0.80. Similarly, the JS produced greater WRel compared to the HPC (p < 0.001, d = 1.89 and HHP (p < 0.001, d = 1.42. Furthermore, HHP WRel was statistically greater than the HPC (p = 0.003, d = 0.73. The P-t profiles of each exercise were similar during the first 80-85% of the movement; however, during the final 15-20% of the movement the P-t profile of the JS was found to be greater than the HPC and HHP. The JS produced greater PPRel and WRel compared to the HPC and HHP with large effect size differences. The HHP produced greater PPRel and WRel than the HPC with moderate effect size differences. The JS and HHP produced markedly different P-t profiles in the final 15-20% of the movement compared to the HPC. Thus, these exercises may be superior methods of training to enhance PPRel. The greatest differences in PPRel between the JS and HHP and the HPC occurred at lighter loads, suggesting that loads of 30-45% 1RM HPC may provide the best training stimulus when using the JS and HHP. In contrast, loads ranging 65-80% 1RM HPC may provide an optimal stimulus for power production during the HPC.
Brailean, A; Aartsen, M J; Muniz-Terrera, G; Prince, M; Prina, A M; Comijs, H C; Huisman, M; Beekman, A
2017-03-01
Cognitive impairment and depression often co-occur in older adults, but it is not clear whether depression is a risk factor for cognitive decline, a psychological reaction to cognitive decline, or whether changes in depressive symptoms correlate with changes in cognitive performance over time. The co-morbid manifestation of depression and cognitive impairment may reflect either a causal effect or a common cause, depending on the specific symptoms experienced and the cognitive functions affected. The study sample comprised 1506 community-dwelling older adults aged ⩾65 years from the Longitudinal Aging Study Amsterdam (LASA). We conducted cross-domain latent growth curve analyses to examine longitudinal associations between late-life depression dimensions (i.e. depressed affect, positive affect, and somatic symptoms) and specific domains of cognitive functioning (i.e. processing speed, inductive reasoning, immediate recall, and delayed recall). Poorer delayed recall performance at baseline predicted a steeper increase in depressed affect over time. Steeper decline in processing speed correlated with a steeper increase in somatic symptoms of depression over time. Our findings suggest a prospective association between memory function and depressed affect, whereby older adults may experience an increase in depressed affect in reaction to poor memory function. Somatic symptoms of depression increased concurrently with declining processing speed, which may reflect common neurodegenerative processes. Our findings do not support the hypothesis that depression symptoms may be a risk factor for cognitive decline in the general population. These findings have potential implications for the treatment of late-life depression and for the prognosis of cognitive outcomes.
Using learning curves and confidence intervals in a time study for the calculation of standard times
Directory of Open Access Journals (Sweden)
Mitzy Natalia Roncancio Avila
2017-10-01
Full Text Available Introduction: This article explores the use of learning curves and confidence intervals in a time study carry out in a scale assembly line during a laboratory practice at the University of La Salle. Objective: The objective of this research is to show the use of confidence intervals and learning curves for the identification of stable processes and subsequent standardization of timing Methodology: The methodology used consists in two phases: Analysis for the study of times and establishment of standard times; the first consist in the calculation of the number of cycles, depuration of atypical data and the use of the curves to determine the processes suitable for the standardization, and the second phase is the calculation of the standard times. Results: The analysis allowed to determine that is only possible to standardize two of the five processes of the system under study because of the variability of them. Conclusions: Given the research, is possible to conclude that a process should be standardized only if it presents a stable behavior respect to the normal rhythm of work, which is showed in the learning curve; otherwise, the process will obtain partial standard times.
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
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.
Time-domain radio pulses from particle showers
International Nuclear Information System (INIS)
Alvarez-Muñiz, Jaime; Romero-Wolf, Andrés; Zas, Enrique
2012-01-01
The time-domain properties of the far-field coherent radio emission from electromagnetic showers are studied in depth. A purely time-domain technique for mapping the electromagnetic fields of charged tracks is developed. The method is applied to the ZHS shower code to produce electric fields. It is demonstrated that the technique is equivalent to the frequency domain methods used in the ZHS code and produces consistent results. In addition, a model for mapping the longitudinal charge profile of a shower to a time-domain electromagnetic field is developed. It is shown that the model is in good agreement to the results of shower simulation.
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
Alternating Direction Implicit Finite Difference Time Domain Acoustic ...
African Journals Online (AJOL)
A time domain numerical technique is presented for the modelling of acoustic wave phenomena. The technique is an adaptation of the alternating direction implicit finite difference time domain method. The stability condition for the algorithm is given. Simple illustrations of propagation in an infinite homogeneous medium are ...
Forgetting Curve: Experiments on Intervals and Total Time in Recall
Ping Zhan; Jeffrey Hanks
2015-01-01
This manuscript is a continuation of our previous work ([1], [2]). In [1], we mainly tested the spacing effect and whether intervals affect the recall ratio in recalling English words. From the forgetting curve, learning data like English words and their definitions, it has been assumed that initial intervals should be shorter than later ones. But our experiments showed that the ratio of remembered words is not related to the patterns of intervals, (1) initial intervals shorter than later one...
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...... of multivariate time domain system identification of time-variant as well as time-invariant civil engineering structures from ambient testing data. A graphical user interface (GUI) is also developed to make the toolbox more user friendly....
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.
Underwater Advanced Time-Domain Electromagnetic System
2017-03-03
sufficiently waterproofed ...................................................................... 20 Objective: Calibration method can be used both topside... additional background variability is observed at early times, as illustrated in Figure 15. The layout of this figure is the same as Figure 14. Now the...are discussed in the following sections and summarized in Table 5. Objective: System is sufficiently waterproofed The array remained underwater up to
Aspects of quantum field theory in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Fulling, S.A. (Texas A and M Univ., College Station, TX (USA). Dept. of Mathematics)
1989-01-01
The theory of quantum fields on curved spacetimes has attracted great attention since the discovery, by Stephen Hawking, of black-hole evaporation. It remains an important subject for the understanding of such contemporary topics as inflationary cosmology, quantum gravity and superstring theory. The topics covered include normal-mode expansions for a general elliptic operator, Fock space, the Casimir effect, the Klein 'paradox', particle definition and particle creation in expanding universes, asymptotic expansion of Green's functions and heat kernels, and renormalization of the stress tensor. (author).
Aspects of quantum field theory in curved space-time
International Nuclear Information System (INIS)
Fulling, S.A.
1989-01-01
The theory of quantum fields on curved spacetimes has attracted great attention since the discovery, by Stephen Hawking, of black-hole evaporation. It remains an important subject for the understanding of such contemporary topics as inflationary cosmology, quantum gravity and superstring theory. The topics covered include normal-mode expansions for a general elliptic operator, Fock space, the Casimir effect, the Klein 'paradox', particle definition and particle creation in expanding universes, asymptotic expansion of Green's functions and heat kernels, and renormalization of the stress tensor. (author)
The association between BMI and different frailty domains : A U-shaped curve?
Rietman, M. Liset; van der A, D. L.; van Oostrom, S. H.; Picavet, H. S J; Dollé, M. E T; van Steeg, H.; Verschuren, W. M M; Spijkerman, A. M W
2018-01-01
Objectives: Previous studies showed a U-shaped association between BMI and (physical) frailty. We studied the association between BMI and physical, cognitive, psychological, and social frailty. Furthermore, the overlap between and prevalence of these frailty domains was examined. Design:
International Nuclear Information System (INIS)
Géré, Antoine; Hack, Thomas-Paul; Pinamonti, Nicola
2016-01-01
We develop a renormalisation scheme for time-ordered products in interacting field theories on curved space–times that consists of an analytic regularisation of Feynman amplitudes and a minimal subtraction of the resulting pole parts. This scheme is directly applicable to space–times with Lorentzian signature, manifestly generally covariant, invariant under any space–time isometries present, and constructed to all orders in perturbation theory. Moreover, the scheme correctly captures the nongeometric state-dependent contribution of Feynman amplitudes, and it is well suited for practical computations. To illustrate this last point, we compute explicit examples on a generic curved space–time and demonstrate how momentum space computations in cosmological space–times can be performed in our scheme. In this work, we discuss only scalar fields in four space–time dimensions, but we argue that the renormalisation scheme can be directly generalised to other space–time dimensions and field theories with higher spin as well as to theories with local gauge invariance. (paper)
Time Domain Astrochemistry in Protoplanetary Disks
Cleeves, Lauren Ilsedore
2018-01-01
The chemistry of protoplanetary disks sets the initial composition of newly formed planets and may regulate the efficiency by which planets form. Disk chemical abundances typically evolve over timescales spanning thousands if not millions of years. Consequently, it was a surprise when ALMA observations taken over the course of a single year showed significantly variable emission in H13CO+ relative to the otherwise constant thermal dust emission in the IM Lup protoplanetary disk. HCO+ is a known X-ray sensitive molecule, and by using simple time-evolving chemical models including stellar activity, we demonstrate that stellar X-ray flares are a viable explanation for the observed H13CO+ variability. If this link between chemistry and stellar activity is confirmed, simultaneous observations can provide a new tool to measure (and potentially map) fundamental disk parameters, such as electron density, as the light from X-ray flares propagates across the disk.
Mapping of landfills using time-domain spectral induced polarization data
DEFF Research Database (Denmark)
Gazoty, Aurélie; Fiandaca, Gianluca; Pedersen, Jesper Bjergsted
2012-01-01
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......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...... Cole-Cole parameters. For all profiles, the results reveal a highly chargeable unit that shows a very good agreement to the findings from 15 boreholes covering the area, where the extent of the waste deposits was measured. The thickness and depth of surface measurements were furthermore validated by el-log...
A time domain phase-gradient based ISAR autofocus algorithm
CSIR Research Space (South Africa)
Nel, W
2011-10-01
Full Text Available Autofocus is a well known required step in ISAR (and SAR) processing to compensate translational motion. This research proposes a time domain autofocus algorithm and discusses its relation to the well known phase gradient autofocus (PGA) technique...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation Project
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 referencing in intensity modulation fiber optic sensing systems
Adamovsky, G.
1986-01-01
Intensity modulation sensors are classified depending on the way in which the reference and signal channels are separated: in space, wavelength (frequency), or time domains. To implement the time domain referencing different types of fiber optic (FO) loops have been used. A pulse of short duration sent into the loop results in a series of pulses of different amplitudes. The information about the measured parameter is retrieved from the relative amplitudes of pulses in the same train.
Time domain modeling of tunable response of graphene
DEFF Research Database (Denmark)
Prokopeva, Ludmila; Emani, Naresh K.; Boltasseva, Alexandra
2013-01-01
We present a causal numerical model for time domain simulations of the optical response of graphene. The dielectric function is approximated with a conductivity term, a Drude term and a number of the critical points terms.......We present a causal numerical model for time domain simulations of the optical response of graphene. The dielectric function is approximated with a conductivity term, a Drude term and a number of the critical points terms....
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....
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.
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....
Broadband Beamspace DOA Estimation: Frequency-Domain and Time-Domain Processing Approaches
Directory of Open Access Journals (Sweden)
Yan Shefeng
2007-01-01
Full Text Available Frequency-domain and time-domain processing approaches to direction-of-arrival (DOA estimation for multiple broadband far field signals using beamspace preprocessing structures are proposed. The technique is based on constant mainlobe response beamforming. A set of frequency-domain and time-domain beamformers with constant (frequency independent mainlobe response and controlled sidelobes is designed to cover the spatial sector of interest using optimal array pattern synthesis technique and optimal FIR filters design technique. These techniques lead the resulting beampatterns higher mainlobe approximation accuracy and yet lower sidelobes. For the scenario of strong out-of-sector interfering sources, our approaches can form nulls or notches in the direction of them and yet guarantee that the mainlobe response of the beamformers is constant over the design band. Numerical results show that the proposed time-domain processing DOA estimator has comparable performance with the proposed frequency-domain processing method, and that both of them are able to resolve correlated source signals and provide better resolution at lower signal-to-noise ratio (SNR and lower root-mean-square error (RMSE of the DOA estimate compared with the existing method. Our beamspace DOA estimators maintain good DOA estimation and spatial resolution capability in the scenario of strong out-of-sector interfering sources.
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 of the techn....... 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....
Monitoring moisture storage in trees using time domain reflectometry
Constantz, J.; Murphy, F.
1990-01-01
Laboratory and field tests were performed to examine the feasibility of using time domain reflectometry (TDR) to monitor changes in the moisture storage of the woody parts of trees. To serve as wave guides for the TDR signal, pairs of stainless steel rods (13 cm long, 0.32 cm in diameter, and 2.5 cm separation) were driven into parallel pilot holes drilled into the woody parts of trees, and a cable testing oscilloscope was used to determine the apparent dielectric constant. A laboratory calibration test was performed on two sapwood samples, so that the relation between the volumetric water content and the apparent dielectric constant of the sapwood could be determined over a range of water contents. The resulting calibration curve for these sapwood samples was significantly different than the general calibration curve used for soils, showing a smaller change in the apparent dielectric constant for a given change in the volumetric water content than is typical for soils. The calibration curve was used to estimate the average volumetric water content to a depth of 13 cm in living trees. One field experiment was conducted on an English walnut tree (Juglans regia) with a diameter of 40 cm, growing in a flood-irrigated orchard on a Hanford sandy loam near Modesto, California (U.S.A.). Rods were driven into the tree at about 50 cm above the soil surface and monitored hourly for the month of August, 1988. The moisture content determined by TDR showed a gradual decrease from 0.44 to 0.42 cm3 cm-3 over a two week period prior to flood irrigation, followed by a rapid rise to 0.47 cm3 cm-3 over a four day period after irrigation, then again a gradual decline approaching the next irrigation. A second field experiment was made on ten evergreen and deciduous trees with diameters ranging from 30 to 120 cm, growing in the foothills of the Coast Range of central California. Rods were driven into each tree at 50 to 100 cm above the soil surface and monitored on a biweekly to monthly
Frequency and voice: perspectives in the time domain.
Roark, Rick M
2006-09-01
Frequency variation is one of the most primitive features of voice production, endowing language and communication with richness and efficiency and enhancing enjoyment of the voice arts. In the first of two tutorial articles, the subject of frequency is examined formally, beginning in the time domain. A companion article explores the topic of frequency and voice from the frequency domain perspective. Frequency is a well-defined quantity of the sinusoidal function and of periodic functions of time. However, voice is inherently nonstationary, even over short time segments, to degrees that range from minor (stable vowels of a healthy voice) to major (singing voice and voiced consonants). For signals that are not periodic, the notion of frequency is ambiguous and often altogether unclear, which has led to a multitude of frequency-measurement techniques and discrepancy of measures. This article identifies the source of these discrepancies for a variety of time-domain techniques that are examined in the absence of noise. In the time domain, the subject of frequency is inherently coupled to the topic of signal modeling, which is explored in some detail. Sinusoidal models having time-varying phase are examined with the objective of achieving a frequency description of voice that is both continuous and instantaneous. The analytic signal method of mathematical physics is discussed and applied to the technology of empirical mode decomposition to demonstrate that the frequencies of voice may be comprehensively examined from the time domain point of view.
What have we learned from quantum field theory in curved space-time
International Nuclear Information System (INIS)
Fulling, S.A.
1984-01-01
The paper reviews the quantum field theory in curved space-time. Field quantization in gravitational backgrounds; particle creation by black holes; Hawking radiation; quantum field theory in curved space-time; covariant renormalization of the stress-energy-momentum tensor; quantum field theory and quantum gravity; are all discussed. (U.K.)
The Association between BMI and Different Frailty Domains: A U-Shaped Curve?
Rietman, M L; van der A, D L; van Oostrom, S H; Picavet, H S J; Dollé, M E T; van Steeg, H; Verschuren, W M M; Spijkerman, A M W
2018-01-01
Previous studies showed a U-shaped association between BMI and (physical) frailty. We studied the association between BMI and physical, cognitive, psychological, and social frailty. Furthermore, the overlap between and prevalence of these frailty domains was examined. Cross-sectional study. The Doetinchem Cohort Study is a longitudinal population-based study starting in 1987-1991 examining men and women aged 20-59 with follow-up examinations every 5 yrs. For the current analyses, we used data from round 5 (2008-2012) with 4019 participants aged 41-81 yrs. Physical frailty was defined as having ≥ 2 of 4 frailty criteria from the Frailty Phenotype (unintentional weight loss, exhaustion, physical activity, handgrip strength). Cognitive frailty was defined as the BMI was divided into four classes. Analyses were adjusted for sex, age, level of education, and smoking. A U-shaped association was observed between BMI and physical frailty, a small linear association for BMI and cognitive frailty and no association between BMI and psychological and social frailty. The four frailty domains showed only a small proportion of overlap. The prevalence of physical, cognitive and social frailty increased with age, whereas psychological frailty did not. We confirm that not only underweight but also obesity is associated with physical frailty. Obesity also seems to be associated with cognitive frailty. Further, frailty prevention should focus on multiple domains and target individuals at a younger age (<65yrs).
Quantum Dynamics of Test Particle in Curved Space-Time
International Nuclear Information System (INIS)
Piechocki, W.
2002-01-01
To reveal the nature of space-time singularities of removable type we examine classical and quantum dynamics of a free particle in the Sitter type spacetimes. Consider space-times have different topologies otherwise are isometric. Our systems are integrable and we present analytic solutions of the classical dynamics. We quantize the systems by making use of the group theoretical method: we find an essentially self-adjoint representation of the algebra of observables integrable to the irreducible unitarity representation of the symmetry group of each consider gravitational system. The massless particle dynamics is obtained in the zero-mass limit of the massive case. Global properties of considered gravitational systems are of primary importance for the quantization procedure. Systems of a particle in space-times with removable singularities appear to be quantizable. We give specific proposal for extension of our analysis to space-times with essential type singularities. (author)
Runaway domain wall and space-time varying α
International Nuclear Information System (INIS)
Chiba, Takeshi; Yamaguchi, Masahide
2011-01-01
Recently spatial as well as temporal variations of the fine structure constant α have been reported. We show that a ''runaway domain wall , which arises for the scalar field potential without minima, can account for such variations simultaneously. The time variation is induced by a runaway potential and the spatial variation is induced by the formation of a domain wall. The model is consistent with the current cosmological data and can be tested by the future experiments to test the equivalence principle
Cerenkov radio pulses from electromagnetic showers in the time domain
International Nuclear Information System (INIS)
Alvarez-Muniz, Jaime; Romero-Wolf, Andres; Zas, Enrique
2010-01-01
The electric field of the Cerenkov radio pulse produced by a single charged particle track in a dielectric medium is derived from first principles. An algorithm is developed to obtain the pulse in the time domain for numerical calculations. The algorithm is implemented in a Monte Carlo simulation of electromagnetic showers in dense media (specifically designed for coherent radio emission applications) as might be induced by interactions of ultrahigh energy neutrinos. The coherent Cerenkov radio emission produced by such showers is obtained simultaneously both in the time and frequency domains. A consistency check performed by Fourier transforming the pulse in time and comparing it to the frequency spectrum obtained directly in the simulations yields, as expected, fully consistent results. The reversal of the time structure inside the Cerenkov cone and the signs of the corresponding pulses are addressed in detail. The results, besides testing algorithms used for reference calculations in the frequency domain, shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cerenkov direction. This information can be of great practical importance for interpreting actual data.
Characterization of time series via Rényi complexity-entropy curves
Jauregui, M.; Zunino, L.; Lenzi, E. K.; Mendes, R. S.; Ribeiro, H. V.
2018-05-01
One of the most useful tools for distinguishing between chaotic and stochastic time series is the so-called complexity-entropy causality plane. This diagram involves two complexity measures: the Shannon entropy and the statistical complexity. Recently, this idea has been generalized by considering the Tsallis monoparametric generalization of the Shannon entropy, yielding complexity-entropy curves. These curves have proven to enhance the discrimination among different time series related to stochastic and chaotic processes of numerical and experimental nature. Here we further explore these complexity-entropy curves in the context of the Rényi entropy, which is another monoparametric generalization of the Shannon entropy. By combining the Rényi entropy with the proper generalization of the statistical complexity, we associate a parametric curve (the Rényi complexity-entropy curve) with a given time series. We explore this approach in a series of numerical and experimental applications, demonstrating the usefulness of this new technique for time series analysis. We show that the Rényi complexity-entropy curves enable the differentiation among time series of chaotic, stochastic, and periodic nature. In particular, time series of stochastic nature are associated with curves displaying positive curvature in a neighborhood of their initial points, whereas curves related to chaotic phenomena have a negative curvature; finally, periodic time series are represented by vertical straight lines.
Power-time, force-time, and velocity-time curve analysis during the jump squat: impact of load.
Cormie, Prue; McBride, Jeffrey M; McCaulley, Grant O
2008-05-01
The purpose of this investigation was to examine the impact of load on the power-, force- and velocity-time curves during the jump squat. The analysis of these curves for the entire movement at a sampling frequency of 200-500 Hz averaged across 18 untrained male subjects is the most novel aspect of this study. Jump squat performance was assessed in a randomized fashion across five different external loads: 0, 20, 40, 60, and 80 kg (equivalent to 0 +/- 0, 18 +/- 4, 37 +/- 8, 55 +/- 12, 74 +/- 15% of 1RM, respectively). The 0-kg loading condition (i.e., body mass only) was the load that maximized peak power output, displaying a significantly (p time curves changed significantly as the load applied to the jump squat increased. There was a significantly greater rate of power development in the 0 kg load in comparison with all other loads examined. As the first comprehensive illustration of how the entire power-, force-, and velocity-time curves change across various loading conditions, this study provides extensive evidence that a load equaling an individuals body mass (i.e., external load = 0 kg) maximizes power output in untrained individuals during the jump squat.
Quantum field theory in curved space-time
International Nuclear Information System (INIS)
Najmi, A.-H.
1982-09-01
The problem of constructing states for quantum field theories in nonstationary background space-times is set out. A formalism in which the problem of constructing states can be attacked more easily than at present is presented. The ansatz of energy-minimization as a means of constructing states is formulated in this formalism and its general solution for the free scalar field is found. It has been known, in specific cases, that such states suffer from the problem of unitary inequivalence (the pathology). An example in Minowski space-time is presented in which global operators, such as the particle-number operator, do not exist but all physical observables, such as the renormalized energy density are finite. This model has two Fock-sectors as its space of physical states. A simple extension of this model, i.e. enlarging the Fock-space of states is found not to remedy the pathology: in a Robertson-Walker space-time the quantum field acquires an infinite amount of renormalized energy density to the future of the hypersurface on which the energy density is minimized. Finally, the solution of the ansatz of energy minimization for the free, massive Hermitian fermion field is presented. (author)
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
Multi-time-step domain coupling method with energy control
DEFF Research Database (Denmark)
Mahjoubi, N.; Krenk, Steen
2010-01-01
A multi-time-step integration method is proposed for solving structural dynamics problems on multiple domains. The method generalizes earlier state-space integration algorithms by introducing displacement constraints via Lagrange multipliers, representing the time-integrated constraint forces over...
On quantum field theory in curved space-time
International Nuclear Information System (INIS)
Hajicek, P.
1976-01-01
It is well known that the existence of quanta or particles of a given field is directly revealed by only a subset of all possible experiments with the field. It is considered a class of such experiments performable at any regular point of any space-time, which includes all terrestrial particle experiments as well as asymptotic observations of an evaporating black hole. A definition based on this class keeps the quanta observable and renders the notion of particle relative and local. Any complicated mathematics is avoided with the intention to emphasize the physical ideas
Li, Yi; Chen, Yuren
2016-12-30
To make driving assistance system more humanized, this study focused on the prediction and assistance of drivers' perception-response time on mountain highway curves. Field tests were conducted to collect real-time driving data and driver vision information. A driver-vision lane model quantified curve elements in drivers' vision. A multinomial log-linear model was established to predict perception-response time with traffic/road environment information, driver-vision lane model, and mechanical status (last second). A corresponding assistance model showed a positive impact on drivers' perception-response times on mountain highway curves. Model results revealed that the driver-vision lane model and visual elements did have important influence on drivers' perception-response time. Compared with roadside passive road safety infrastructure, proper visual geometry design, timely visual guidance, and visual information integrality of a curve are significant factors for drivers' perception-response time.
Exactly solvable string models of curved space-time backgrounds
Russo, J.G.; Russo, J G; Tseytlin, A A
1995-01-01
We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the dilatonic Melvin solution and the uniform magnetic field solution discussed earlier as well as some singular space-times. Solvability of the string sigma model is related to its connection via duality to a much simpler looking model which is a "twisted" product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model as well as a number of generalizations leading to larger classes of exact 4-dimensional string solutions.
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 charact......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...
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
[Terahertz time-domain spectroscopy of Clenbuterol hydrochloride].
Chen, Xi-ai; Hou, Di-bo; Huang, Ping-jie; Kang, Xu-sheng; Zhang, Guang-xin; Zhou, Ze-kui
2011-12-01
The terahertz spectra of Clenbuterol hydrochloride in the range of 0.2 to 2.6 THz were obtained by THz time-domain spectroscopy, the absorption and refraction spectra of Clenbuterol hydrochloride was got meanwhile. The structure and vibrational frequencies of Clenbuterol molecule, Clenbuterol hydrochloride molecule and Clenbuterol hydrochloride crystal in the THz range were simulated. Based on the difference between experimental and theoretical results, the origin of the vibrational frequencies was analyzed. This study demonstrated the feasibility of time-domain terahertz spectroscopy for the identification of Clenbuterol hydrochloride and provides a new way for the detection of Clenbuterol hydrochloride.
Amino Terminal Region of Dengue Virus NS4A Cytosolic Domain Binds to Highly Curved Liposomes
Directory of Open Access Journals (Sweden)
Yu-Fu Hung
2015-07-01
Full Text Available Dengue virus (DENV is an important human pathogen causing millions of disease cases and thousands of deaths worldwide. Non-structural protein 4A (NS4A is a vital component of the viral replication complex (RC and plays a major role in the formation of host cell membrane-derived structures that provide a scaffold for replication. The N-terminal cytoplasmic region of NS4A(1–48 is known to preferentially interact with highly curved membranes. Here, we provide experimental evidence for the stable binding of NS4A(1–48 to small liposomes using a liposome floatation assay and identify the lipid binding sequence by NMR spectroscopy. Mutations L6E;M10E were previously shown to inhibit DENV replication and to interfere with the binding of NS4A(1–48 to small liposomes. Our results provide new details on the interaction of the N-terminal region of NS4A with membranes and will prompt studies of the functional relevance of the curvature sensitive membrane anchor at the N-terminus of NS4A.
Amino Terminal Region of Dengue Virus NS4A Cytosolic Domain Binds to Highly Curved Liposomes.
Hung, Yu-Fu; Schwarten, Melanie; Hoffmann, Silke; Willbold, Dieter; Sklan, Ella H; Koenig, BerndW
2015-07-21
Dengue virus (DENV) is an important human pathogen causing millions of disease cases and thousands of deaths worldwide. Non-structural protein 4A (NS4A) is a vital component of the viral replication complex (RC) and plays a major role in the formation of host cell membrane-derived structures that provide a scaffold for replication. The N-terminal cytoplasmic region of NS4A(1-48) is known to preferentially interact with highly curved membranes. Here, we provide experimental evidence for the stable binding of NS4A(1-48) to small liposomes using a liposome floatation assay and identify the lipid binding sequence by NMR spectroscopy. Mutations L6E;M10E were previously shown to inhibit DENV replication and to interfere with the binding of NS4A(1-48) to small liposomes. Our results provide new details on the interaction of the N-terminal region of NS4A with membranes and will prompt studies of the functional relevance of the curvature sensitive membrane anchor at the N-terminus of NS4A.
Li, Yi; Chen, Yuren
2016-01-01
To make driving assistance system more humanized, this study focused on the prediction and assistance of drivers’ perception-response time on mountain highway curves. Field tests were conducted to collect real-time driving data and driver vision information. A driver-vision lane model quantified curve elements in drivers’ vision. A multinomial log-linear model was established to predict perception-response time with traffic/road environment information, driver-vision lane model, and mechanica...
Real-time background suppression during frequency domain lifetime measurements.
Herman, Petr; Maliwal, Badri P; Lakowicz, Joseph R; Maliwal, Baldri P
2002-10-01
We describe real time background suppression of autofluorescence from biological samples during frequency domain or phase modulation measurements of intensity decays. For these measurements the samples were excited with a train of light pulses with widths below 1 ps. The detector was gated off for a short time period of 10 to 40 ns during and shortly after the excitation pulse. The reference signal needed for the frequency domain measurement was provided by a long-lifetime reference fluorophore which continues to emit following the off-gating pulse. Both the sample and the reference were measured under identical optical and electronic conditions avoiding the need for correction of the photomultiplier tube signal for the gating sequence. We demonstrate frequency domain background suppression using a mixture of short- and long-lifetime probes and for a long-lifetime probe in human plasma with significant autofluorescence.
Bezier-curve Navigation Guidance for Impact Time and Angle Control
Directory of Open Access Journals (Sweden)
Gun-Hee MOON
2018-03-01
Full Text Available This paper addresses a novel impact time and angle control guidance law using a Bézier curve. The 2nd order Bézier curve consists of one control point and two boundary points; initial point P0, middle point P1 and end point P2. The curve is tangent to the line P0-P1 and the line P1-P2, respectively, and always exists in the convex hull of the control points. Proposed Bézier curve navigation guidance, makes the missile follow the Bézier curve with the feedback form of guidance command so that the missile hits the target on the desired time in the desired direction. We conducted numerical simulations on several terminal conditions to demonstrate the performance of proposed method.
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.
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...
Nonlinear time-domain modeling of balanced-armature receivers
DEFF Research Database (Denmark)
Jensen, Joe; Agerkvist, Finn T.; Harte, James
2011-01-01
of the loudspeaker diaphragm inevitably changes the magnetic and electrical characteristics of the loudspeaker. A numerical time-domain model capable of describing these nonlinearities is presented. By simulation it is demonstrated how the output distortion could potentially be reduced significantly through careful...
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...
Frequency-domain criterion for the chaos synchronization of time ...
Indian Academy of Sciences (India)
This paper studies the global synchronization of non-autonomous, time-delay, chaotic power systems via linear state-error feedback control. The frequency domain criterion and the LMI criterion are proposed and applied to design the coupling matrix. Some algebraic criteria via a single-variable linear coupling are derived ...
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...
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 freque...
Time-domain seismic reliability of nonlinear structures
Indian Academy of Sciences (India)
Abstract. A novel reliability analysis technique is presented to estimate the reli- ability of real structural systems. Its unique feature is that the dynamic loadings can be applied in time domain. It is a nonlinear stochastic finite element logarithm combined with the response surface method (RSM). It generates the response sur-.
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...
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.
EBADA, Khaled
2014-01-01
This study aims to identify Growth rates, Relative strength, and performance time for female lifters and defining Curved characteristics best suited for growth rates, relative strength, and performance Time of female Olympic weightlifters and evaluate the performance of snatch and Clean & Jerk for female lifters, coaches use the curved characteristics as standard guide them through planning and preparing training programs. The study Applied on a sample of 88 female lifter participants...
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.
Anderson localization and Mott insulator phase in the time domain
Sacha, Krzysztof
2015-01-01
Particles in space periodic potentials constitute standard models for investigation of crystalline phenomena in solid state physics. Time periodicity of periodically driven systems is a close analogue of space periodicity of solid state crystals. There is an intriguing question if solid state phenomena can be observed in the time domain. Here we show that wave-packets localized on resonant classical trajectories of periodically driven systems are ideal elements to realize Anderson localization or Mott insulator phase in the time domain. Uniform superpositions of the wave-packets form stationary states of a periodically driven particle. However, an additional perturbation that fluctuates in time results in disorder in time and Anderson localization effects emerge. Switching to many-particle systems we observe that depending on how strong particle interactions are, stationary states can be Bose-Einstein condensates or single Fock states where definite numbers of particles occupy the periodically evolving wave-packets. Our study shows that non-trivial crystal-like phenomena can be observed in the time domain. PMID:26074169
Evaluation of left ventricular diastolic function by appreciating the shape of time activity curve
International Nuclear Information System (INIS)
Nishimura, Tohru; Taya, Makoto; Shimoyama, Katsuya; Sasaki, Akira; Mizuno, Haruyoshi; Tahara, Yorio; Ono, Akifumi; Ishikawa, Kyozo
1993-01-01
To determine left ventricular diastolic function (LVDF), the shape of time activity curve and primary differential curve, as acquired by Tc-99m radionuclide angiography, were visually assessed. The study popoulation consisted of 1647 patients with heart disease, such as hypertension, ischemic heart disease, cardiomyopathy and valvular disease. Fifty-six other patients were served as controls. The LVDF was divided into 4 degrees: 0=normal, I=slight disturbance, II=moderate disturbance, and III=severe disturbance. LVDF variables, including time to peak filling (TPF), TPF/time to end-systole, peak filling rate (PFR), PFR/t, 1/3 filling fraction (1/3 FR), and 1/3 FR/t, were calculated from time activity curve. There was no definitive correlation between each variable and age or heart rate. Regarding these LVDF variables, except for 1/3 FR, there was no significant difference between the group 0 of heart disease patients and the control group. Among the groups 0-III of heart disease patients, there were significant difference in LVDF variables. Visual assessement concurred with left ventricular ejection fraction, PFR/end-diastolic curve, and filling rate/end-diastolic curve. Visual assessment using time activity curve was considered useful in the semiquantitative determination of early diastolic function. (N.K.)
Efficient smoothed finite element time domain analysis for photonic devices.
Atia, Khaled S R; Heikal, A M; Obayya, S S A
2015-08-24
In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagation in photonic devices. Dissimilar to conventional FEM, efficient "inter-element" matrices are accurately formed through smoothing the field derivatives across element boundaries. In this sense, the new approach is termed "smoothed FEM" (SFETD). For time domain analysis, the propagation is made via the time domain beam propagation method (TD-BPM). Relying on first order elements, our suggested SFETD-BPM enjoys accuracy levels comparable to second-order conventional FEM; thanks to the element smoothing. The proposed method numerical performance is tested through applicating on analysis of a single mode slab waveguide, optical grating structure, and photonic crystal cavity. It is clearly demonstrated that our method is not only accurate but also more computationally efficient (far few run time, and memory requirements) than the conventional FEM approach. The SFETD-BPM is also extended to deal with the very challenging problem of dispersive materials. The material dispersion is smartly utilized to enhance the quality factor of photonic crystal cavity.
Time Alignment as a Necessary Step in the Analysis of Sleep Probabilistic Curves
Rošt'áková, Zuzana; Rosipal, Roman
2018-02-01
Sleep can be characterised as a dynamic process that has a finite set of sleep stages during the night. The standard Rechtschaffen and Kales sleep model produces discrete representation of sleep and does not take into account its dynamic structure. In contrast, the continuous sleep representation provided by the probabilistic sleep model accounts for the dynamics of the sleep process. However, analysis of the sleep probabilistic curves is problematic when time misalignment is present. In this study, we highlight the necessity of curve synchronisation before further analysis. Original and in time aligned sleep probabilistic curves were transformed into a finite dimensional vector space, and their ability to predict subjects' age or daily measures is evaluated. We conclude that curve alignment significantly improves the prediction of the daily measures, especially in the case of the S2-related sleep states or slow wave sleep.
[Terahertz time-domain spectroscopy of ractopamine hydrochloride].
Chen, Xi-ai; Huang, Ping-jie; Hou, Di-bo; Kang, Xu-sheng; Zhang, Guang-xin; Zhou, Ze-kui
2011-03-01
The terahertz spectra of Ractopamine hydrochloride in the range of 0.2 to 2.2 THz was obtained by THz time-domain spectroscopy, and the absorption and refraction spectra of Ractopamine hydrochloride was got meanwhile. The structure and vibrational frequencies of Ractopamine molecule in the THz range were simulated by density functional theory. The difference between experimental and theoretical results was analyzed. And assisted by Gaussian View 3.09, the origin of the vibrational frequencies was recognized. The results show that besides the intramolecular vibrations, THz absorption of Ractopamine hydrochloride originated from the intermolecular hydrogen bond network and Van der Waals force between molecules. This study demonstrated the feasibility of time-domain terahertz spectroscopy for the identification of Ractopamine hydrochloride and provided a new way for the detection of Ractopamine hydrochloride.
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...
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)
Time-domain Hydroelasticity Theory of Ships Responding to Waves
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui
1997-01-01
flare forms. The predicted results include linear and non-linear rigid motions and structural responses of ships advancing in regular and irregular waves. The results clearly demonstrate the importance and the magnitude of non-linear effects in ship motions and internal forces. Numerical calculations......A time-domain linear theory of fluid-structure interaction between floating structures and the incident waves is presented. The structure is assumed to be elastic and represented by general separation of variables, whereas the fluid is described as an initial boundary value problem of potential...... 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...
Evaluation of Damping Using Time Domain OMA Techniques
DEFF Research Database (Denmark)
Bajric, Anela; Brincker, Rune; Georgakis, Christos T.
2014-01-01
The prevailing Operational Modal Analysis (OMA) techniques provide in most cases reasonably accurate estimates of structural frequencies and mode shapes. In contrast though, they are known to often produce poor structural damping estimates, which is mainly due to inherent random and/or bias errors...... 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...... response and random response from white noise loading. Finally, the results of the numerical study are presented, in which the error of the structural damping estimates obtained by each OMA technique is shown for a range of damping levels. From this, it is clear that there are notable differences...
DEFF Research Database (Denmark)
Vaz, C.M.P.; Hopmans, J.W.; Macedo, A.
2002-01-01
in situ soil water retention data from simultaneous soil water matric potential and water content measurements within approximately the same small soil volume around the combined probe, but requires soil specific calibration because of slight desaturation of the porous cup of the tensiometer.......The objective of the presented study was to develop a single probe that can be used to determine soil water retention curves in both laboratory and field conditions, by including a coiled time domain reflectometry (TDR) probe around the porous cup of a standard tensiometer. The combined tensiometer...
On time-domain and frequency-domain MMSE-based TEQ design for DMT transmission
Vanbleu, K; Moonen, M; Ysebaert, G; 10.1109/TSP.2005.851161
2005-01-01
We reconsider the minimum mean square error (MMSE) time-domain equalizer (TEQ), bitrate maximizing TEQ (BM-TEQ), and per-tone equalizer design (PTEQ) for discrete multitone (DMT) transmission and cast them in a common least-squares (LS) based framework. The MMSE- TEQ design criterion can be formulated as a constrained linear least-squares (CLLS) criterion that minimizes a time-domain (TD) error energy. From this CLLS-based TD-MMSE-TEQ criterion, we derive two new least-squares (LS) based frequency-domain (FD) MMSE-TEQ design criteria: a CLLS-based FD-MMSE-TEQ criterion and a so-called separable nonlinear LS (SNLLS) based FD-MMSE-TEQ design. Finally, the original BM-TEQ design is shown to be equivalent to a so-called iteratively-reweighted (IR) version of the SNLLS-based FD-MMSE-TEQ design. This LS-based framework then results in the following contributions. The new, IR-SNLLS-based BM-TEQ design criterion gives rise to an elegant, iterative, fast converging, Gauss-Newton-based design algorithm that exploits th...
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
Efficient time-domain model of the graphene dielectric function
Prokopeva, Ludmila J.; Kildishev, Alexander V.
2013-09-01
A honey-comb monolayer lattice of carbon atoms, graphene, is not only ultra-thin, ultra-light, flexible and strong, but also highly conductive when doped and exhibits strong interaction with electromagnetic radiation in the spectral range from microwaves to the ultraviolet. Moreover, this interaction can be effectively controlled electrically. High flexibility and conductivity makes graphene an attractive material for numerous photonic applications requiring transparent conducting electrodes: touchscreens, liquid crystal displays, organic photovoltaic cells, and organic light-emitting diodes. Meanwhile, its tunability makes it desirable for optical modulators, tunable filters and polarizers. This paper deals with the basics of the time-domain modeling of the graphene dielectric function under a random-phase approximation. We focus at applicability of Padé approximants to the interband dielectric function (IDF) of single layer graphene. Our study is centered on the development of a two-critical points approximation (2CPA) of the IDF within a single-electron framework with negligible carrier scattering and a realistic range of chemical potential at room temperature. This development is successfully validated by comparing reflection and transmission spectra computed by a numerical method in time-domain versus semi-analytical calculations in frequency domain. Finally, we sum up our results - (1) high-quality approximation, (2) tunability, and (3) second-order accurate numerical FDTD implementation of the 2CPA of IDF demonstrated across the desired range of the chemical potential to temperature ratios (4 - 23). Finally, we put forward future directions for time-domain modeling of optical response of graphene with wide range of tunable and fabrication-dependent parameters, including other broadening factors and variations of temperature and chemical potentials.
Thermodynamics in Curved Space-Time and Its Application to Holography
Directory of Open Access Journals (Sweden)
Yong Xiao
2015-03-01
Full Text Available The thermodynamic behaviors of a system living in a curved space-time are different from those of a system in a flat space-time. We have investigated the thermodynamics for a system consisting of relativistic massless bosons. We show that a strongly curved metric will produce a large enhancement of the degrees of freedom in the formulae of energy and entropy of the system, as a comparison to the case in a flat space-time. We are mainly concerned with its implications to holography, including the derivations of holographic entropy and holographic screen.
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)
Zheng, WeiJia; Luo, Ying; Wang, XiaoHong; Pi, YouGuo; Chen, YangQuan
2017-05-01
In order to achieve a desired control performance characterized by satisfying specifications in both frequency-domain and time-domain simultaneously, an optimal fractional order proportional integral derivative (PI λ D μ ) controller design strategy is proposed based on analytical calculation and Differential Evolution algorithm for a permanent magnet synchronous motor (PMSM) servo system in this paper. In this controller design, the frequency-domain specifications can guarantee the system stability with both gain margin and phase margin, and also the system robustness to loop gain variations. The time-domain specifications can ensure the desired step response performance with rapid rising curve, constrained overshoot, and proper power consuming. Compared with the PI λ controller and the traditional PID controller, PI λ D μ controller can get obvious benefits from two more degrees of freedom of the fractional orders λ and μ on satisfying multiple constraints simultaneously and achieving better servo tracking performance for the PMSM servo system. PMSM speed tracking simulations and experiments are demonstrated to show the significant advantages of using the proposed optimal PI λ D μ controller over the optimal fractional order PI λ controller and traditional integer order PID controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Frequency and Time Domain Modeling of Acoustic Liner Boundary Conditions
Bliss, Donald B.
1982-01-01
As part of a research program directed at the acoustics of advanced subsonic propulsion systems undertaken at NASA Langley, Duke University was funded to develop a boundary condition model for bulk-reacting nacelle liners. The overall objective of the Langley program was to understand and predict noise from advanced subsonic transport engines and to develop related noise control technology. The overall technical areas included: fan and propeller source noise, acoustics of ducts and duct liners, interior noise, subjective acoustics, and systems noise prediction. The Duke effort was directed toward duct liner acoustics for the development of analytical methods to characterize liner behavior in both frequency domain and time domain. A review of duct acoustics and liner technology can be found in Reference [1]. At that time, NASA Langley was investigating the propulsion concept of an advanced ducted fan, with a large diameter housed inside a relatively short duct. Fan diameters in excess of ten feet were proposed. The lengths of both the inlet and exhaust portions of the duct were to be short, probably less than half the fan diameter. The nacelle itself would be relatively thin-walled for reasons of aerodynamic efficiency. The blade-passage frequency was expected to be less than I kHz, and very likely in the 200 to 300 Hz range. Because of the design constraints of a short duct, a thin nacelle, and long acoustic wavelengths, the application of effective liner technology would be especially challenging. One of the needs of the NASA Langley program was the capability to accurately and efficiently predict the behavior of the acoustic liner. The traditional point impedance method was not an adequate model for proposed liner designs. The method was too restrictive to represent bulk reacting liners and to allow for the characterization of many possible innovative liner concepts. In the research effort at Duke, an alternative method, initially developed to handle bulk
Path integrals and the solution of the Schwinger model in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J.; Das, A.
1986-04-15
We use the path-integral formalism to derive the solution of the Schwinger model in curved space-time. We show that the nature of flat--space-time solutions persists even in the presence of a background gravitational field.
Time course of attentional modulation in the frontal eye field during curve tracing
Khayat, P. S.; Pooresmaeili, A.; Roelfsema, P. R.
2009-01-01
Neurons in the frontal eye fields (FEFs) register incoming visual information and select visual stimuli that are relevant for behavior. Here we investigated the timing of the visual response and the timing of selection by recording from single FEF neurons in a curve-tracing task that requires shifts
Time Course of Attentional Modulation in the Frontal Eye Field During Curve Tracing
Khayat, P.S.; Pooresmaeili, A.; Roelfsema, P.R.
2009-01-01
Neurons in the frontal eye fields (FEFs) register incoming visual information and select visual stimuli that are relevant for behavior. Here we investigated the timing of the visual response and the timing of selection by recording from single FEF neurons in a curve-tracing task that requires shifts
A standard curve based method for relative real time PCR data processing
Directory of Open Access Journals (Sweden)
Krause Andreas
2005-03-01
Full Text Available Abstract Background Currently real time PCR is the most precise method by which to measure gene expression. The method generates a large amount of raw numerical data and processing may notably influence final results. The data processing is based either on standard curves or on PCR efficiency assessment. At the moment, the PCR efficiency approach is preferred in relative PCR whilst the standard curve is often used for absolute PCR. However, there are no barriers to employ standard curves for relative PCR. This article provides an implementation of the standard curve method and discusses its advantages and limitations in relative real time PCR. Results We designed a procedure for data processing in relative real time PCR. The procedure completely avoids PCR efficiency assessment, minimizes operator involvement and provides a statistical assessment of intra-assay variation. The procedure includes the following steps. (I Noise is filtered from raw fluorescence readings by smoothing, baseline subtraction and amplitude normalization. (II The optimal threshold is selected automatically from regression parameters of the standard curve. (III Crossing points (CPs are derived directly from coordinates of points where the threshold line crosses fluorescence plots obtained after the noise filtering. (IV The means and their variances are calculated for CPs in PCR replicas. (V The final results are derived from the CPs' means. The CPs' variances are traced to results by the law of error propagation. A detailed description and analysis of this data processing is provided. The limitations associated with the use of parametric statistical methods and amplitude normalization are specifically analyzed and found fit to the routine laboratory practice. Different options are discussed for aggregation of data obtained from multiple reference genes. Conclusion A standard curve based procedure for PCR data processing has been compiled and validated. It illustrates that
On the Analysis Methods for the Time Domain and Frequency Domain Response of a Buried Objects*
Poljak, Dragan; Šesnić, Silvestar; Cvetković, Mario
2014-05-01
There has been a continuous interest in the analysis of ground-penetrating radar systems and related applications in civil engineering [1]. Consequently, a deeper insight of scattering phenomena occurring in a lossy half-space, as well as the development of sophisticated numerical methods based on Finite Difference Time Domain (FDTD) method, Finite Element Method (FEM), Boundary Element Method (BEM), Method of Moments (MoM) and various hybrid methods, is required, e.g. [2], [3]. The present paper deals with certain techniques for time and frequency domain analysis, respectively, of buried conducting and dielectric objects. Time domain analysis is related to the assessment of a transient response of a horizontal straight thin wire buried in a lossy half-space using a rigorous antenna theory (AT) approach. The AT approach is based on the space-time integral equation of the Pocklington type (time domain electric field integral equation for thin wires). The influence of the earth-air interface is taken into account via the simplified reflection coefficient arising from the Modified Image Theory (MIT). The obtained results for the transient current induced along the electrode due to the transmitted plane wave excitation are compared to the numerical results calculated via an approximate transmission line (TL) approach and the AT approach based on the space-frequency variant of the Pocklington integro-differential approach, respectively. It is worth noting that the space-frequency Pocklington equation is numerically solved via the Galerkin-Bubnov variant of the Indirect Boundary Element Method (GB-IBEM) and the corresponding transient response is obtained by the aid of inverse fast Fourier transform (IFFT). The results calculated by means of different approaches agree satisfactorily. Frequency domain analysis is related to the assessment of frequency domain response of dielectric sphere using the full wave model based on the set of coupled electric field integral
Time domain random walks for hydrodynamic transport in heterogeneous media
Russian, Anna; Dentz, Marco; Gouze, Philippe
2016-05-01
We derive a general formulation of the time domain random walk (TDRW) approach to model the hydrodynamic transport of inert solutes in complex geometries and heterogeneous media. We demonstrate its formal equivalence with the discretized advection-dispersion equation and show that the TDRW is equivalent to a continuous time random walk (CTRW) characterized by space-dependent transition times and transition probabilities. The transition times are exponentially distributed. We discuss the implementation of different concentration boundary conditions and initial conditions as well as the occurrence of numerical dispersion. Furthermore, we propose an extension of the TDRW scheme to account for mobile-immobile multirate mass transfer. Finally, the proposed TDRW scheme is validated by comparison to analytical solutions for spatially homogeneous and heterogeneous transport scenarios.
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 transmission and reflection spectroscopy of niobium
Energy Technology Data Exchange (ETDEWEB)
Hong, Tae Yoon; Choi, Kyu Jin; Park, Byoung Cheol; Ha, Tae Woo; Sim, Kyung Ik; Kim, Jea Hoon [Dept. of Physics, Yonsei University, Seoul (Korea, Republic of); Ha, Dong Gwang; Chang, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)
2013-03-15
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{sup -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.
A wavefront analyzer for terahertz time-domain spectrometers
DEFF Research Database (Denmark)
Abraham, E.; Brossard, M.; Fauche, P.
2017-01-01
We report on the development of a terahertz wavefront sensor able to determine the optical aberrations of a terahertz time-domain spectrometer. The system measures point-by-point the amplitude and phase of the terahertz electric field in a given plane. From this measurement, we reconstruct...... the terahertz wavefront and calculate its Zernike coefficients. In particular, we especially show that the focus spot of the spectrometer suffers from optical aberrations such as remaining defocus, first and second order astigmatisms, as well as spherical aberration. This opens a route to wavefront correction...... for improved terahertz imaging and spectroscopy....
Detection probabilities for time-domain velocity estimation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1991-01-01
Estimation of blood velocities by time-domain cross-correlation of successive high frequency sampled ultrasound signals is investigated. It is shown that any velocity can result from the estimator regardless of the true velocity due to the nonlinear technique employed. Using a simple simulation...... as a filter with a transfer function depending on the actual velocity. This influences the detection probability, which gets lower at certain velocities. An index directly reflecting the probability of detection can easily be calculated from the cross-correlation estimated. This makes it possible to assess...
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.
Time domain terahertz electro- and magneto-optic spectroscopy
Moore, G P
2001-01-01
sub i sub c sub u sub l sub a sub r = 0 centre dot 19m sub e and m sub p sub a sub r sub a sub l sub l sub e sub l = 0 centre dot 90m sub e. The temperature dependence of the cyclotron resonance was measured over the range 5K to 80 K, and a peak is found at approx 30 K which can be explained in terms of ionised and neutral impurity scattering at temperatures below 30 K and by phonon scattering above 30 K. The measurement of small amplitude ferromagnetic resonance oscillations in the time domain in thin films of permalloy (78), iron and cobalt has been achieved by using the time resolved magneto-optic Kerr effect. A stripline device was fabricated to provide an out of plane broadband magnetic pulse with a peak strength of approx 5 Oe. The observed frequencies are shown to agree well with the established theory. A time domain terahertz spectrometer and a bolometer have been used to study the coherent THz radiation emitted from n- and p-type InAs surfaces illuminated by femtosecond near infrared pulses. The magn...
Processing grounded-wire TEM signal in time-frequency-pseudo-seismic domain: A new paradigm
Khan, M. Y.; Xue, G. Q.; Chen, W.; Huasen, Z.
2017-12-01
Grounded-wire TEM has received great attention in mineral, hydrocarbon and hydrogeological investigations for the last several years. Conventionally, TEM soundings have been presented as apparent resistivity curves as function of time. With development of sophisticated computational algorithms, it became possible to extract more realistic geoelectric information by applying inversion programs to 1-D & 3-D problems. Here, we analyze grounded-wire TEM data by carrying out analysis in time, frequency and pseudo-seismic domain supported by borehole information. At first, H, K, A & Q type geoelectric models are processed using a proven inversion program (1-D Occam inversion). Second, time-to-frequency transformation is conducted from TEM ρa(t) curves to magneto telluric MT ρa(f) curves for the same models based on all-time apparent resistivity curves. Third, 1-D Bostick's algorithm was applied to the transformed resistivity. Finally, EM diffusion field is transformed into propagating wave field obeying the standard wave equation using wavelet transformation technique and constructed pseudo-seismic section. The transformed seismic-like wave indicates that some reflection and refraction phenomena appear when the EM wave field interacts with geoelectric interface at different depth intervals due to contrast in resistivity. The resolution of the transformed TEM data is significantly improved in comparison to apparent resistivity plots. A case study illustrates the successful hydrogeophysical application of proposed approach in recovering water-filled mined-out area in a coal field located in Ye county, Henan province, China. The results support the introduction of pseudo-seismic imaging technology in short-offset version of TEM which can also be an useful aid if integrated with seismic reflection technique to explore possibilities for high resolution EM imaging in future.
A time domain frequency-selective multivariate Granger causality approach.
Leistritz, Lutz; Witte, Herbert
2016-08-01
The investigation of effective connectivity is one of the major topics in computational neuroscience to understand the interaction between spatially distributed neuronal units of the brain. Thus, a wide variety of methods has been developed during the last decades to investigate functional and effective connectivity in multivariate systems. Their spectrum ranges from model-based to model-free approaches with a clear separation into time and frequency range methods. We present in this simulation study a novel time domain approach based on Granger's principle of predictability, which allows frequency-selective considerations of directed interactions. It is based on a comparison of prediction errors of multivariate autoregressive models fitted to systematically modified time series. These modifications are based on signal decompositions, which enable a targeted cancellation of specific signal components with specific spectral properties. Depending on the embedded signal decomposition method, a frequency-selective or data-driven signal-adaptive Granger Causality Index may be derived.
Acoustic Finite Element Calculations in the Time Domain
DEFF Research Database (Denmark)
Jensen, Morten Skaarup
The use of the finite element method (FEM) for making predictions for acoustic fields in the time domain is investigated. First, an introduction to FEM for acoustics is given. This includes a description of important present day algorithms and a derivation of FEM. The overall performance...... of these algorithms is then examined with particular emphasis on accuracy and computational costs. It is shown that the most important error is one that takes the form of a falsely predicted dispersion. The dispersion error can be reduced by using smaller elements and time steps, but this is very costly. Attempts...... and consequences of the dispersion error has been obtained. This led to a new method for determining the optimum element and time step size. The method is valuable because the present way of doing this is not theoretically well-founded....
Body waves separation in the time-frequency domain
Herrera, R. H.; Tary, J.; Van der Baan, M.
2013-12-01
Arrival times of body waves generated by small magnitude microseismic events are usually very close and their limited bandwidth can cause even partial overlap in the time and frequency domains. The separation of P and S waves is then a challenging task that if solved could bring more insights about nature and location of the generating source. Differences in arrival times and frequency content of P and S waves can be seen by using time-frequency decomposition. The traditional time-frequency representation based on the Fourier Transform is limited by its trade-off between time and frequency resolutions, while other alternatives like the Wavelet Transform are still limited by the Heisenberg box. A new derivation of the Continuous Wavelet Transform, called Synchrosqueezing, stretches these boundaries using a mixture of the reassignment method with instantaneous frequency, giving a better frequency representation with improved time localization. Furthermore, all the individual components of the signal are separated in the time domain. This means that we are able to isolate the waveforms of a complex microseismic trace. Each spectral component can then be matched with a body wave plus its associated coda. Proper parameters have to be selected prior to the computation, such as the central frequency and bandwidth of the mother wavelet. We thus include a signal characterization first to find the best matching mother wavelet. In this paper we use the Synchrosqueezing transform to perform the time frequency representation of short brittle events recorded during microseismic experiments. Decomposition results for these examples show that the Synchrosqueezing transform outperforms the Short-Time Fourier Transform. The different components of each body waves (first arrival, coda, frequency components) can then be identified in the time-frequency plane. For some microseismic events, a first P-wave arrival is followed by another arrival at lower frequency that could be a P
Czech Academy of Sciences Publication Activity Database
Perevertov, Oleksiy; Schäfer, R.
2012-01-01
Roč. 45, č. 13 (2012), "135001-1"-"135001-11" ISSN 0022-3727 Grant - others:GA AV ČR(CZ) M100100906 Institutional research plan: CEZ:AV0Z10100520 Keywords : hysteresis curve * magnetic domains * compressive stress * goss steel * effective field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.528, year: 2012
Space-time discontinuous Galerkin method for parabolic problems in time-dependent domains
Janivita Joto Sudirham, J.J.S.; Sudirham, J.J.; van der Vegt, Jacobus J.W.; van Damme, Rudolf M.J.
2004-01-01
In this report a space-time discontinuous Galerkin (DG) finite element method for the solution of the advection-diffusion-reaction equation in time-dependent domains is presented and analyzed. The variational formulation is based on a combination of the space-time DG method developed by van der Vegt
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 THz...
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)
Divergence identities in curved space-time. A resolution of the stress-energy problem
International Nuclear Information System (INIS)
Yilmaz, H.; Tufts Univ., Medford, MA
1989-01-01
It is noted that the joint use of two basic differential identities in curved space-time, namely. 1) the Einstein-Hilbert identity (1915), and 2) the identity of P. Freud (1939), permits a viable alternative to general relativity and a resolution of the field stress-energy' problem of the gravitational theory. (orig.)
Using Growth Curves To Determine the Timing of the Booster Sessions.
Hennessy, Michael; Bolan, Gail A.; Hoxworth, Tamara; Iatesta, Michael; Rhodes, Fen; Zenilman, Jonathan M.
1999-01-01
Demonstrates an application of a method for using growth curves to determine the timing of booster sessions to reinforce the cognitive messages or behavior changes of interventions. Uses data from a multisite randomized experiment that compared three counseling and testing methods for preventing sexual disease transmission. Presents…
SUPERLUMINOUS SUPERNOVAE POWERED BY MAGNETARS: LATE-TIME LIGHT CURVES AND HARD EMISSION LEAKAGE
International Nuclear Information System (INIS)
Wang, S. Q.; Wang, L. J.; Dai, Z. G.; Wu, X. F.
2015-01-01
Recently, research performed by two groups has revealed that the magnetar spin-down energy injection model with full energy trapping can explain the early-time light curves of SN 2010gx, SN 2013dg, LSQ12dlf, SSS120810, and CSS121015 but fails to fit the late-time light curves of these superluminous supernovae (SLSNe). These results imply that the original magnetar-powered model is challenged in explaining these SLSNe. Our paper aims to simultaneously explain both the early- and late-time data/upper limits by considering the leakage of hard emissions. We incorporate quantitatively the leakage effect into the original magnetar-powered model and derive a new semianalytical equation. Comparing the light curves reproduced by our revised magnetar-powered model with the observed data and/or upper limits of these five SLSNe, we found that the late-time light curves reproduced by our semianalytical equation are in good agreement with the late-time observed data and/or upper limits of SN 2010gx, CSS121015, SN 2013dg, and LSQ12dlf and the late-time excess of SSS120810, indicating that the magnetar-powered model might be responsible for these SLSNe and that the gamma-ray and X-ray leakages are unavoidable when the hard photons were down-Comptonized to softer photons. To determine the details of the leakage effect and unveil the nature of SLSNe, more high-quality bolometric light curves and spectra of SLSNe are required
Phillips Curve In A Small Open Economy: A Time Series Exploration Of North Cyprus
Directory of Open Access Journals (Sweden)
Muhammad Shahbaz
2011-12-01
Full Text Available he paper explores the existence and the stability of Phillips curve for North Cyprus, a small developing economy, using time series data. ADF unit root test is employed to check for stationarity. ARDL and DOLS approaches to cointegration have been used to explore the long run relation and ECM to understand short run dynamics. The predictive properties DOLS are better than those of the conventional methods. The estimates point to the existence of Phillips curve both in the long and the short run. CUSUM and CUSUMsq tests confirm a stable relation.
Historical Cost Curves for Hydrogen Masers and Cesium Beam Frequency and Timing Standards
Remer, D. S.; Moore, R. C.
1985-01-01
Historical cost curves were developed for hydrogen masers and cesium beam standards used for frequency and timing calibration in the Deep Space Network. These curves may be used to calculate the cost of future hydrogen masers or cesium beam standards in either future or current dollars. The cesium beam standards are decreasing in cost by about 2.3% per year since 1966, and hydrogen masers are decreasing by about 0.8% per year since 1978 relative to the National Aeronautics and Space Administration inflation index.
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.
Local differential geometry of null curves in conformally flat space-time
International Nuclear Information System (INIS)
Urbantke, H.
1989-01-01
The conformally invariant differential geometry of null curves in conformally flat space-times is given, using the six-vector formalism which has generalizations to higher dimensions. This is then paralleled by a twistor description, with a twofold merit: firstly, sometimes the description is easier in twistor terms, sometimes in six-vector terms, which leads to a mutual enlightenment of both; and secondly, the case of null curves in timelike pseudospheres or 2+1 Minkowski space we were only able to treat twistorially, making use of an invariant differential found by Fubini and Cech. The result is the expected one: apart from stated exceptional cases there is a conformally invariant parameter and two conformally invariant curvatures which, when specified in terms of this parameter, serve to characterize the curve up to conformal transformations. 12 refs. (Author)
Path Integral Quantum Mechanics in Curved Space-Time a New Perspective
Singh, Dinesh; Mobed, Nader
2012-07-01
A new approach to path integral quantum mechanics in curved space-time for a scalar particle is presented in terms of local curvature involving Fermi or Riemann normal co-ordinates. This approach involves use of a local time translation operator with Lie transport that, while strictly non-unitary in form, nonetheless yields the correct expression for the curved space-time free-particle Lagrangian in the sum-over-histories, with additional terms corresponding to a curvature-dependent violation of probability. These terms simultaneously induce a breakdown of time-reversal symmetry at the quantum mechanical level, and also a violation of the weak equivalence principle at the particle's Compton wavelength scale. Furthermore, the scalar propagator generates a gravitational analogue of the Aharonov-Bohm effect and Berry's phase through the appearance of an overall gauge-invariant phase factor. Future directions to follow from this initial research are presented.
Terahertz time-domain reflectometry of multilayered systems
Jackson, J. Bianca
Presented in this work are applications of terahertz pulse ranging, spectroscopy and imaging to the nondestructive evaluation of three disparate multilayer systems for the detection and measurement of hidden layers, as well as the extraction of system information that will aid in its maintenance, repair or replacement. Thermal protection systems for turbine engine components were investigated. Thermal barrier coatings (TBC) and thermally-grown oxide (TGO) thicknesses were determined with 10 micron resolution using time-of-flight and refractive index calculations. Two alternative methods of monitoring TGO growth using reflection amplitudes and spectral shifts were proposed for the prediction of TBC failure. Laser-machined defects as narrow as 50 microns were resolved in one- and two-dimensional images. The light and dark rings of trees, which reflect the changes in tree growth density over the course of a year, are measurable using pulsed terahertz beams. Tree-rings of bare and painted wood specimen were laterally and axially tomographically imaged in order to facilitate the dendrochronological cross-dating of artifacts. Comparisons were made between photographs and terahertz images to demonstrate the reliability of the technique. Historically, numerous unique artworks have been lost through the act of being covered over time. Samples of paintings, drawings and mosaics were imaged beneath layers of paint and plaster using pulsed-terahertz techniques to demonstrate the efficacy of the technique for art history and restoration. Sketch materials and pigments were measured, between 0.05 and 1.0 THz, to help identify colors in spectroscopic images. Other computational and processing methods were used to optimize the distinction between color domains. Additional time-domain terahertz applications for the examination of artwork and other artifacts were proposed.
Study on the Algorithm for Real-time Interpolation of NURBS Curve and Simulation
Hui Jizhuang; Wei Fangsheng; Gao Kai
2013-01-01
In the paper, In order to meet the needs of high-speed and high- accuracy computerized numerical control machining and guarantee the smooth running in the interpolation processing, A NURBS curve calculation based on adaptive acceleration and deceleration control of look-ahead s-shaped for the real-time interpolation is presented in this paper. The algorithm has merits such as higher position accuracy, short processing time, no variation and so on. Through dynamic path simulation and interpol...
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.
Dynamic linear models to explore time-varying suspended sediment-discharge rating curves
Ahn, Kuk-Hyun; Yellen, Brian; Steinschneider, Scott
2017-06-01
This study presents a new method to examine long-term dynamics in sediment yield using time-varying sediment-discharge rating curves. Dynamic linear models (DLMs) are introduced as a time series filter that can assess how the relationship between streamflow and sediment concentration or load changes over time in response to a wide variety of natural and anthropogenic watershed disturbances or long-term changes. The filter operates by updating parameter values using a recursive Bayesian design that responds to 1 day-ahead forecast errors while also accounting for observational noise. The estimated time series of rating curve parameters can then be used to diagnose multiscale (daily-decadal) variability in sediment yield after accounting for fluctuations in streamflow. The technique is applied in a case study examining changes in turbidity load, a proxy for sediment load, in the Esopus Creek watershed, part of the New York City drinking water supply system. The results show that turbidity load exhibits a complex array of variability across time scales. The DLM highlights flood event-driven positive hysteresis, where turbidity load remained elevated for months after large flood events, as a major component of dynamic behavior in the rating curve relationship. The DLM also produces more accurate 1 day-ahead loading forecasts compared to other static and time-varying rating curve methods. The results suggest that DLMs provide a useful tool for diagnosing changes in sediment-discharge relationships over time and may help identify variability in sediment concentrations and loads that can be used to inform dynamic water quality management.
Assessment of perceptual diffuseness in the time domain
DEFF Research Database (Denmark)
Garcia, Julian Martinez-Villalba; Jeong, Cheol-Ho; Brunskog, Jonas
2017-01-01
acoustic environment to examine how sensitive the human auditory system is to changes in the diffuseness condition, which factors are most crucial and which conditions are most favourable in music halls. Two types of stimuli, a music signal and an impulse response, are tested under the same diffuseness......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...... conditions. The study shows that subjective diffuseness is highly correlated to the parameters of Surround, Source Width, and Timbre, and is modelled with relevant acoustic parameters such as LG, LF and uniformity of the incident sound....
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...
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. ...
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.
DBS artifact suppression using a time-frequency domain filter.
Santillán-Guzmán, Alina; Heute, Ulrich; Muthuraman, Muthuraman; Stephani, Ulrich; Galka, Andreas
2013-01-01
Electroencephalogram (EEG) is a useful tool for brain research. However, during Deep-Brain Stimulation (DBS), there are large artifacts that obscure the physiological EEG signals. In this paper, we aim at suppressing the DBS artifacts by means of a time-frequency-domain filter. As a pre-processing step, Empirical-Mode Decomposition (EMD) is applied to detrend the raw data. The detrended signals are then filtered iteratively until, by visual inspection, the quality is good enough for interpretation. The proposed algorithm is demonstrated by an application to a clinical DBS-EEG data set in resting state and in finger-tapping condition. Moreover, a comparison with a Low-Pass filter (LPF) is provided, by visual inspection and by a quantitative measure.
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.
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.
Parallel finite-difference time-domain method
Yu, Wenhua
2006-01-01
The finite-difference time-domain (FTDT) method has revolutionized antenna design and electromagnetics engineering. This book raises the FDTD method to the next level by empowering it with the vast capabilities of parallel computing. It shows engineers how to exploit the natural parallel properties of FDTD to improve the existing FDTD method and to efficiently solve more complex and large problem sets. Professionals learn how to apply open source software to develop parallel software and hardware to run FDTD in parallel for their projects. The book features hands-on examples that illustrate the power of parallel FDTD and presents practical strategies for carrying out parallel FDTD. This detailed resource provides instructions on downloading, installing, and setting up the required open source software on either Windows or Linux systems, and includes a handy tutorial on parallel programming.
International Nuclear Information System (INIS)
Grohs, B.
1983-01-01
The ALOK-technique allows the simultaneous detection of flaws and their evaluation with respect to type, location and dimension by interpretation of the transit time behaviour during scanning of the reflector. The accuracy of information obtained by means of this technique can be further improved both during interference elimination and reconstruction owing to the ability of exact calculation of possible transit time locus curves of given reflectors. The mathematical solution of transit time locus curve calculations refers here to pulse echo testing in consideration of the refraction of sound on the forward wedge/test object - interface. The method of solving the problem is equivalent to the Fermat's principle in optics. (orig.) [de
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 low-power time-domain VCO-based ADC in 65 nm CMOS
Chenluan, Wang; Shengxi, Diao; Fujiang, Lin
2014-10-01
A low-power, high-FoM (figure of merit), time-domain VCO (voltage controlled oscillator)-based ADC (analog-to-digital converter) in 65 nm CMOS technology is proposed. An asynchronous sigma—delta modulator (ASDM) is used to convert the voltage input signal to a square wave time signal, where the information is contained in its pulse-width. A time-domain quantizer, which uses VCO to convert voltage to frequency, is adopted, while the XOR (exclusive-OR) gate circuits convert the frequency information to digital representatives. The ASDM does not need an external clock, so there is no quantization noise. At the same time, the ASDM applies a harmonic-distortion-cancellation technique to its transconductance stage, which increases the SNDR (signal to noise and distortion ratio) performance of the ASDM. Since the output of the ASDM is a two-level voltage signal, the VCO's V—F (voltage to frequency) conversion curve is always linear. The XOR phase quantizer has an inherent feature of first-order noise-shaping. It puts the ADC's low-frequency output noise to high-frequency which is further filtered out by a low-pass filter. The proposed ADC achieves an SNR/SNDR of 54. dB/54.3 dB in the 8 MHz bandwidth, while consuming 2.8 mW. The FoM of the proposed ADC is a 334 fJ/conv-step.
Linear time domain model of the acoustic potential field.
Lesniewski, Peter J
2002-08-01
A new time domain formulation of the acoustic wave is developed to avoid approximating assumptions of the linearized scalar wave equation that limit its validity to low Mach particle velocity modeling or to a smooth potential field in a stationary medium. The proposed model offers precision of the moving frame while retaining the form of the widely used linearized scalar wave equation although with respect to modified coordinates. It is applicable to field calculations involving transient waves with unlimited particle velocity, propagating in inhomogenous fluids or in those with time varying density. The model is based on the exact flux continuity equation and the equation of motion, both using the moving reference frame. The resulting closed-form free space scalar wave equation employing total derivatives is converted back to the partial differential form by using modified independent variables. The modified variables are related to the common coordinates of space and time following integral expressions involving transient particle velocity representing wave radiated by each point of a stationary source. Consequently, transient field produced by complex surface velocity sources can be calculated following existing surface integrals of the radiation theory although using modified coordinates. The use of the proposed model is presented in a numerical simulation of a transient velocity source vibrating at selected magnitudes, leading to the determination of the propagating pressure and velocity wave at any point.
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.
Hilbert Spectrum for Time-Domain Measurement Data and Its Application
National Research Council Canada - National Science Library
Peng, H. M; Chang, P. C; Chang, F. R
2003-01-01
In this paper, a new method for analyzing the time domain data is introduced. As one knows, the time domain phase measurements are nonstationary and the differencing technique is usually adopted for generating stationary data...
Non-deteriorating time domain numerical algorithms for Maxwell's electrodynamics
Petropavlovsky, S.; Tsynkov, S.
2017-05-01
The Huygens' principle and lacunae can help construct efficient far-field closures for the numerical simulation of unsteady waves propagating over unbounded regions. Those closures can be either standalone or combined with other techniques for the treatment of artificial outer boundaries. A standalone lacunae-based closure can be thought of as a special artificial boundary condition (ABC) that is provably free from any error associated with the domain truncation. If combined with a different type of ABC or a perfectly matched layer (PML), a lacunae-based approach can help remove any long-time deterioration (e.g., instability) that arises at the outer boundary regardless of why it occurs in the first place. A specific difficulty associated with Maxwell's equations of electromagnetism is that in general their solutions do not have classical lacunae and rather have quasi-lacunae. Unlike in the classical case, the field inside the quasi-lacunae is not zero; instead, there is an electrostatic solution driven by the electric charges that accumulate over time. In our previous work [23], we have shown that quasi-lacunae can also be used for building the far-field closures. However, for achieving a provably non-deteriorating performance over arbitrarily long time intervals, the accumulated charges need to be known ahead of time. The main contribution of the current paper is that we remove this limitation and modify the algorithm in such a way that one can rather avoid the accumulation of charge all together. Accordingly, the field inside the quasi-lacunae becomes equal to zero, which facilitates obtaining the temporally uniform error estimates as in the case of classical lacunae. The performance of the modified algorithm is corroborated by a series of numerical simulations. The range of problems that the new method can address includes important combined formulations, for which the interior subproblem may be non-Huygens', and only the exterior subproblem, i.e., the far
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.
Beyond Rating Curves: Time Series Models for in-Stream Turbidity Prediction
Wang, L.; Mukundan, R.; Zion, M.; Pierson, D. C.
2012-12-01
The New York City Department of Environmental Protection (DEP) manages New York City's water supply, which is comprised of over 20 reservoirs and supplies over 1 billion gallons of water per day to more than 9 million customers. DEP's "West of Hudson" reservoirs located in the Catskill Mountains are unfiltered per a renewable filtration avoidance determination granted by the EPA. While water quality is usually pristine, high volume storm events occasionally cause the reservoirs to become highly turbid. A logical strategy for turbidity control is to temporarily remove the turbid reservoirs from service. While effective in limiting delivery of turbid water and reducing the need for in-reservoir alum flocculation, this strategy runs the risk of negatively impacting water supply reliability. Thus, it is advantageous for DEP to understand how long a particular turbidity event will affect their system. In order to understand the duration, intensity and total load of a turbidity event, predictions of future in-stream turbidity values are important. Traditionally, turbidity predictions have been carried out by applying streamflow observations/forecasts to a flow-turbidity rating curve. However, predictions from rating curves are often inaccurate due to inter- and intra-event variability in flow-turbidity relationships. Predictions can be improved by applying an autoregressive moving average (ARMA) time series model in combination with a traditional rating curve. Since 2003, DEP and the Upstate Freshwater Institute have compiled a relatively consistent set of 15-minute turbidity observations at various locations on Esopus Creek above Ashokan Reservoir. Using daily averages of this data and streamflow observations at nearby USGS gauges, flow-turbidity rating curves were developed via linear regression. Time series analysis revealed that the linear regression residuals may be represented using an ARMA(1,2) process. Based on this information, flow-turbidity regressions with
Zhengang, Lu; Hongyang, Yu; Xi, Yang
2017-05-01
The Modular Multilevel Converter (MMC) is one of the most attractive topologies in recent years for medium or high voltage industrial applications, such as high voltage dc transmission (HVDC) and medium voltage varying speed motor drive. The wide adoption of MMCs in industry is mainly due to its flexible expandability, transformer-less configuration, common dc bus, high reliability from redundancy, and so on. But, when the sub module number of MMC is more, the test of MMC controller will cost more time and effort. Hardware in the loop test based on real time simulator will save a lot of time and money caused by the MMC test. And due to the flexible of HIL, it becomes more and more popular in the industry area. The MMC modelling method remains an important issue for the MMC HIL test. Specifically, the VSC model should realistically reflect the nonlinear device switching characteristics, switching and conduction losses, tailing current, and diode reverse recovery behaviour of a realistic converter. In this paper, an IGBT switching characteristic curve embedded half-bridge MMC modelling method is proposed. This method is based on the switching curve referring and sample circuit calculation, and it is sample for implementation. Based on the proposed method, a FPGA real time simulation is carried out with 200ns sample time. The real time simulation results show the proposed method is correct.
Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines
International Nuclear Information System (INIS)
Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen; Jacobsen, Christina; Lynnerup, Niels
2010-01-01
Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy of a few years by radiocarbon dating.
Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines
DEFF Research Database (Denmark)
Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen
2010-01-01
, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy......Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth...
Refined algebraic quantization and quantum field theory in a curved space-time
International Nuclear Information System (INIS)
Rumpf, H.
1998-01-01
Application of the so-called refined algebraic quantization scheme for constrained systems to relativistic particles provides an inner product that defines a unique Fock representation for a scalar field in a curved space-time. The construction can be made rigorous for a general globally hyperbolic space-time, but the quasifree state so obtained turns out to be unphysical in general. We exhibit a closely related pair of Fock representations that is also defined generically and conforms to the notion of in- and outgoing states in those situations where particle creation by an external field is expected
Time domain attenuation estimation method from ultrasonic backscattered signals.
Ghoshal, Goutam; Oelze, Michael L
2012-07-01
Ultrasonic attenuation is important not only as a parameter for characterizing tissue but also for compensating other parameters that are used to classify tissues. Several techniques have been explored for estimating ultrasonic attenuation from backscattered signals. In the present study, a technique is developed to estimate the local ultrasonic attenuation coefficient by analyzing the time domain backscattered signal. The proposed method incorporates an objective function that combines the diffraction pattern of the source/receiver with the attenuation slope in an integral equation. The technique was assessed through simulations and validated through experiments with a tissue mimicking phantom and fresh rabbit liver samples. The attenuation values estimated using the proposed technique were compared with the attenuation estimated using insertion loss measurements. For a data block size of 15 pulse lengths axially and 15 beamwidths laterally, the mean attenuation estimates from the tissue mimicking phantoms were within 10% of the estimates using insertion loss measurements. With a data block size of 20 pulse lengths axially and 20 beamwidths laterally, the error in the attenuation values estimated from the liver samples were within 10% of the attenuation values estimated from the insertion loss measurements.
Seismic analysis of wind turbines in the time domain
Energy Technology Data Exchange (ETDEWEB)
Witcher, D. [Garrad Hassan and Partners Ltd., Bristol (United Kingdom)
2004-07-01
The analysis of wind turbine loading associated with earthquakes is clearly important when designing for and assessing the feasibility of wind farms in seismically active regions. The approach taken for such analysis is generally based on codified methods which have been developed for the assessment of seismic loads acting on buildings. These methods are not able to deal properly with the aeroelastic interaction of the dynamic motion of the wind turbine structure with either the wind loading acting on the rotor blades or the response of the turbine controller. This article presents an alternative approach, which is to undertake the calculation in the time domain. In this case a full aeroelastic model of the wind turbine subject to turbulent wind loading is further excited by ground motion corresponding to the earthquake. This capability has been introduced to the GH Bladed wind turbine simulation package. The software can be used to compute the combined wind and earthquake loading of a wind turbine given a definition of the external conditions for an appropriate series of load cases. This article discusses the method and presents example results. (Author)
Seismic analysis of wind turbines in the time domain
Energy Technology Data Exchange (ETDEWEB)
Witcher, D. [Garrad Hassan and Partners, Bristol (United Kingdom)
2005-07-01
The analysis of wind turbine loading associated with earthquakes is clearly important when designing for and assessing the feasibility of wind farms in seismically active regions. The approach taken for such analysis is generally based on codified methods which have been developed for the assessment of seismic loads acting on buildings. These methods are not able to deal properly with the aeroelastic interaction of the dynamic motion of the wind turbine structure with either the wind loading acting on the rotor blades or the response of the turbine controller. This article presents an alternative approach, which is to undertake the calculation in the time domain. In this case a full aeroelastic model of the wind turbine subject to turbulent wind loading is further excited by ground motion corresponding to the earthquake. This capability has been introduced to the GH Bladed wind turbine simulation package. The software can be used to compute the combined wind and earthquake loading of a wind turbine given a definition of the external conditions for an appropriate series of load cases. This article discusses the method and presents example results. (author)
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.
A 128 Multiplexing Factor Time-Domain SQUID Multiplexer
Prêle, D.; Voisin, F.; Piat, M.; Decourcelle, T.; Perbost, C.; Chapron, C.; Rambaud, D.; Maestre, S.; Marty, W.; Montier, L.
2016-07-01
A cryogenic 128:1 Time-Domain Multiplexer (TDM) has been developed for the readout of kilo-pixel Transition Edge Sensor (TES) arrays dedicated to the Q&U Bolometric Interferometer for Cosmology (QUBIC) instrument which aims to measure the B-mode polarization of the Cosmic Microwave Background. Superconducting QUantum Interference Devices (SQUIDs) are usually used to read out TESs. Moreover, SQUIDs are used to build TDM by biasing sequentially the SQUIDs connected together—one for each TES. In addition to this common technique which allows a typical 32 multiplexing factor, a cryogenic integrated circuit provides a 4:1 second multiplexing stage. This cryogenic integrated circuit is one of the original part of our TDM achieving an unprecedented 128 multiplexing factor. We present these two dimension TDM stages: topology of the SQUID multiplexer, operation of the cryogenic integrated circuit, and integration of the full system to read out a TES array dedicated to the QUBIC instrument. Flux-locked loop operation in multiplexed mode is also discussed.
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.
Modal participation in multiple input Ibrahim time domain identification
DEFF Research Database (Denmark)
Brincker, Rune; Olsen, Peter; Amador, Sandro
2017-01-01
The Ibrahim time domain (ITD) identification technique was one of the first techniques formulated for multiple output modal analysis based on impulse response functions or general free decays. However, the technique has not been used much in recent decades due to the fact that the technique was o...... of the identification technique are investigated in a simulation study with closely spaced modes. The simulation study shows that the multiple-input formulation provides estimates with significantly smaller errors on both mode shape and natural frequency estimates....... was originally formulated for single input systems that suffer from well-known problems in case of closely spaced modes. In this paper, a known, but more modern formulation of the ITD technique is discussed. In this formulation the technique becomes multiple input by adding some Toeplitz matrices over a set...... matrix has full rank. This secures that all modes will be contained in the estimated system matrix. Finally, it is discussed how correlation functions estimated from the operational responses of structures can be used as free decays for the multiple-input ITD formulation, and the estimation errors...
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
Landfill cover performance monitoring using time domain reflectometry
Energy Technology Data Exchange (ETDEWEB)
Neher, E.R.; Cotten, G.B. [Parsons Infrastructure & Technology Group, Inc., Idaho Falls, ID (United States); McElroy, D. [Lockheed-Martin Idaho Technologies Company, Idaho Falls, ID (United States)
1998-03-01
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.
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.
Estimation of Bid Curves in Power Exchanges using Time-varying Simultaneous-Equations Models
Ofuji, Kenta; Yamaguchi, Nobuyuki
Simultaneous-equations model (SEM) is generally used in economics to estimate interdependent endogenous variables such as price and quantity in a competitive, equilibrium market. In this paper, we have attempted to apply SEM to JEPX (Japan Electric Power eXchange) spot market, a single-price auction market, using the publicly available data of selling and buying bid volumes, system price and traded quantity. The aim of this analysis is to understand the magnitude of influences to the auctioned prices and quantity from the selling and buying bids, than to forecast prices and quantity for risk management purposes. In comparison with the Ordinary Least Squares (OLS) estimation where the estimation results represent average values that are independent of time, we employ a time-varying simultaneous-equations model (TV-SEM) to capture structural changes inherent in those influences, using State Space models with Kalman filter stepwise estimation. The results showed that the buying bid volumes has that highest magnitude of influences among the factors considered, exhibiting time-dependent changes, ranging as broad as about 240% of its average. The slope of the supply curve also varies across time, implying the elastic property of the supply commodity, while the demand curve remains comparatively inelastic and stable over time.
Optical time-domain analog pattern correlator for high-speed real-time image recognition.
Kim, Sang Hyup; Goda, Keisuke; Fard, Ali; Jalali, Bahram
2011-01-15
The speed of image processing is limited by image acquisition circuitry. While optical pattern recognition techniques can reduce the computational burden on digital image processing, their image correlation rates are typically low due to the use of spatial optical elements. Here we report a method that overcomes this limitation and enables fast real-time analog image recognition at a record correlation rate of 36.7 MHz--1000 times higher rates than conventional methods. This technique seamlessly performs image acquisition, correlation, and signal integration all optically in the time domain before analog-to-digital conversion by virtue of optical space-to-time mapping.
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.
Energy Technology Data Exchange (ETDEWEB)
Kelly, Brandon C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Becker, Andrew C. [Department of Astronomy, University of Washington, P.O. Box 351580, Seattle, WA 98195-1580 (United States); Sobolewska, Malgosia [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716, Warsaw (Poland); Siemiginowska, Aneta [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Uttley, Phil [Astronomical Institute Anton Pannekoek, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands)
2014-06-10
We present the use of continuous-time autoregressive moving average (CARMA) models as a method for estimating the variability features of a light curve, and in particular its power spectral density (PSD). CARMA models fully account for irregular sampling and measurement errors, making them valuable for quantifying variability, forecasting and interpolating light curves, and variability-based classification. We show that the PSD of a CARMA model can be expressed as a sum of Lorentzian functions, which makes them extremely flexible and able to model a broad range of PSDs. We present the likelihood function for light curves sampled from CARMA processes, placing them on a statistically rigorous foundation, and we present a Bayesian method to infer the probability distribution of the PSD given the measured light curve. Because calculation of the likelihood function scales linearly with the number of data points, CARMA modeling scales to current and future massive time-domain data sets. We conclude by applying our CARMA modeling approach to light curves for an X-ray binary, two active galactic nuclei, a long-period variable star, and an RR Lyrae star in order to illustrate their use, applicability, and interpretation.
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.
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.
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.
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab...
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab-layer str...
Numerical analysis of the photo-injection time-of-flight curves in molecularly doped polymers
Tyutnev, A. P.; Ikhsanov, R. Sh.; Saenko, V. S.; Nikerov, D. V.
2018-03-01
We have performed numerical analysis of the charge carrier transport in a specific molecularly doped polymer using the multiple trapping model. The computations covered a wide range of applied electric fields, temperatures and most importantly, of the initial energies of photo injected one-sign carriers (in our case, holes). Special attention has been given to comparison of time of flight curves measured by the photo-injection and radiation-induced techniques which has led to a problematic situation concerning an interpretation of the experimental data. Computational results have been compared with both analytical and experimental results available in literature.
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
Energy Technology Data Exchange (ETDEWEB)
Soriguera Marti, F.; Martinez-Diaz, M.; Perez Perez, I.
2016-07-01
Travel time is probably the most important indicator of the level of service of a highway, and it is also the most appreciated information for its users. Administrations and private companies make increasing efforts to improve its real time estimation. The appearance of new technologies makes the precise measurement of travel times easier than never before. However, direct measurements of travel time are, by nature, outdated in real time, and lack of the desired forecasting capabilities. This paper introduces a new methodology to improve the real time estimation of travel times by using the equipment usually present in most highways, i.e., loop detectors, in combination with Automatic Vehicle Identification or Tracking Technologies. One of the most important features of the method is the usage of cumulative counts at detectors as an input, avoiding the drawbacks of common spot-speed methodologies. Cumulative count curves have great potential for freeway travel time information systems, as they provide spatial measurements and thus allow the calculation of instantaneous travel times. In addition, they exhibit predictive capabilities. Nevertheless, they have not been used extensively mainly because of the error introduced by the accumulation of the detector drift. The proposed methodology solves this problem by correcting the deviations using direct travel time measurements. The method results highly beneficial for its accuracy as well as for its low implementation cost. (Author)
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
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
Directory of Open Access Journals (Sweden)
Lázcoz Paula
2008-02-01
Full Text Available Abstract Background We present two melting curve analysis (MCA-based semiquantitative real time PCR techniques to detect the promoter methylation status of genes. The first, MCA-MSP, follows the same principle as standard MSP but it is performed in a real time thermalcycler with results being visualized in a melting curve. The second, MCA-Meth, uses a single pair of primers designed with no CpGs in its sequence. These primers amplify both unmethylated and methylated sequences. In clinical applications the MSP technique has revolutionized methylation detection by simplifying the analysis to a PCR-based protocol. MCA-analysis based techniques may be able to further improve and simplify methylation analyses by reducing starting DNA amounts, by introducing an all-in-one tube reaction and by eliminating a final gel stage for visualization of the result. The current study aimed at investigating the feasibility of both MCA-MSP and MCA-Meth in the analysis of promoter methylation, and at defining potential advantages and shortcomings in comparison to currently implemented techniques, i.e. bisulfite sequencing and standard MSP. Methods The promoters of the RASSF1A (3p21.3, BLU (3p21.3 and MGMT (10q26 genes were analyzed by MCA-MSP and MCA-Meth in 13 astrocytoma samples, 6 high grade glioma cell lines and 4 neuroblastoma cell lines. The data were compared with standard MSP and validated by bisulfite sequencing. Results Both, MCA-MSP and MCA-Meth, successfully determined promoter methylation. MCA-MSP provided information similar to standard MSP analyses. However the analysis was possible in a single tube and avoided the gel stage. MCA-Meth proved to be useful in samples with intermediate methylation status, reflected by a melting curve position shift in dependence on methylation extent. Conclusion We propose MCA-MSP and MCA-Meth as alternative or supplementary techniques to MSP or bisulfite sequencing.
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.
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.
Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements
Directory of Open Access Journals (Sweden)
G. Dragonetti
2018-02-01
Full Text Available 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
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
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
DEFF Research Database (Denmark)
Andersen, Fredrik; Østerås, Olav; Reksen, Olav
2011-01-01
This study was carried out to determine if an association exists between the shape of the lactation curve before it is influenced by the event of conception and the time from calving to conception in Norwegian dairy cattle. Lactation curves of Norwegian Red cows during 5 to 42 days in milk (DIM...
On renormalisation of lambda phi4 field theory in curved space-time
International Nuclear Information System (INIS)
Bunch, T.S.; Panangaden, P.
1980-01-01
An explicit renormalisation of all second-order physical processes occurring in lambdaphi 4 field theory in conformally flat space-time, including vacuum-to-vacuum processes, is performed. Although divergences dependent on the definition of the vacuum state appear in some Feynman diagrams, physical amplitudes obtained by summing all diagrams which contribute to a single physical process are independent of these divergences. Consequently, the theory remains renormalisable in curved space-time, at least to second order in lambda. Renormalisations of the mass m, the coupling constant lambda and the constant xi which couples the field to the Ricci scalar are required to make two- and four-particle creation amplitudes finite. (author)
The time ending the shallow decay of the X-ray light curves of long GRBs
Dado, S; De Rújula, Alvaro; Dado, Shlomo; Dar, Arnon
2007-01-01
We show that the mean values and distributions of the time ending the shallow decay of the light curve of the X-ray afterglow of long gamma ray bursts (GRBs), the equivalent isotropic energy in the X-ray afterglow up to that time and the equivalent isotropic GRB energy, as well as the correlations between them, are precisely those predicted by the cannonball (CB) model of GRBs. Correlations between prompt and afterglow observables are important in that they test the overall consistency of a GRB model. In the CB model, the prompt and afterglow spectra, the endtime, the complex canonical shape of the X-ray afterglows and the correlations between GRB observables are not surprises, but predictions.
Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves
Energy Technology Data Exchange (ETDEWEB)
Jiang, Yan-Fei [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Green, Paul J.; Pancoast, Anna; MacLeod, Chelsea L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Morganson, Eric; Shen, Yue [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Grier, C. J. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Rix, H.-W. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Protopapas, Pavlos [Institute for Applied Computational Science, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Scott, Caroline [Astrophysics, Imperial College London, Blackett Laboratory, London SW7 2AZ (United Kingdom); Burgett, W. S.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States); and others
2017-02-20
We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band ( g , r , i , z ) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN , we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g − r to g − i and then to g − z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.
International Nuclear Information System (INIS)
Spears, Robert Edward; Coleman, Justin Leigh
2015-01-01
Currently the Department of Energy (DOE) and the nuclear industry perform seismic soil-structure interaction (SSI) analysis using equivalent linear numerical analysis tools. For lower levels of ground motion, these tools should produce reasonable in-structure response values for evaluation of existing and new facilities. For larger levels of ground motion these tools likely overestimate the in-structure response (and therefore structural demand) since they do not consider geometric nonlinearities (such as gaping and sliding between the soil and structure) and are limited in the ability to model nonlinear soil behavior. The current equivalent linear SSI (SASSI) analysis approach either joins the soil and structure together in both tension and compression or releases the soil from the structure for both tension and compression. It also makes linear approximations for material nonlinearities and generalizes energy absorption with viscous damping. This produces the potential for inaccurately establishing where the structural concerns exist and/or inaccurately establishing the amplitude of the in-structure responses. Seismic hazard curves at nuclear facilities have continued to increase over the years as more information has been developed on seismic sources (i.e. faults), additional information gathered on seismic events, and additional research performed to determine local site effects. Seismic hazard curves are used to develop design basis earthquakes (DBE) that are used to evaluate nuclear facility response. As the seismic hazard curves increase, the input ground motions (DBE's) used to numerically evaluation nuclear facility response increase causing larger in-structure response. As ground motions increase so does the importance of including nonlinear effects in numerical SSI models. To include material nonlinearity in the soil and geometric nonlinearity using contact (gaping and sliding) it is necessary to develop a nonlinear time domain methodology. This
Temchin, Andrei N.; Recio-Spinoso, Alberto; Ruggero, Mario A.
2010-01-01
Links between frequency tuning and timing were explored in the responses to sound of auditory-nerve fibers. Synthetic transfer functions were constructed by combining filter functions, derived via minimum-phase computations from average frequency-threshold tuning curves of chinchilla auditory-nerve fibers with high spontaneous activity (A. N. Temchin et al., J. Neurophysiol. 100: 2889–2898, 2008), and signal-front delays specified by the latencies of basilar-membrane and auditory-nerve fiber responses to intense clicks (A. N. Temchin et al., J. Neurophysiol. 93: 3635–3648, 2005). The transfer functions predict several features of the phase-frequency curves of cochlear responses to tones, including their shape transitions in the regions with characteristic frequencies of 1 kHz and 3–4 kHz (A. N. Temchin and M. A. Ruggero, JARO 11: 297–318, 2010). The transfer functions also predict the shapes of cochlear impulse responses, including the polarities of their frequency sweeps and their transition at characteristic frequencies around 1 kHz. Predictions are especially accurate for characteristic frequencies < 1 kHz. PMID:20951191
The role of rating curve uncertainty in real-time flood forecasting
Ocio, David; Le Vine, Nataliya; Westerberg, Ida; Pappenberger, Florian; Buytaert, Wouter
2017-05-01
Data assimilation has been widely tested for flood forecasting, although its use in operational systems is mainly limited to a simple statistical error correction. This can be due to the complexity involved in making more advanced formal assumptions about the nature of the model and measurement errors. Recent advances in the definition of rating curve uncertainty allow estimating a flow measurement error that includes both aleatory and epistemic uncertainties more explicitly and rigorously than in the current practice. The aim of this study is to understand the effect such a more rigorous definition of the flow measurement error has on real-time data assimilation and forecasting. This study, therefore, develops a comprehensive probabilistic framework that considers the uncertainty in model forcing data, model structure, and flow observations. Three common data assimilation techniques are evaluated: (1) Autoregressive error correction, (2) Ensemble Kalman Filter, and (3) Regularized Particle Filter, and applied to two locations in the flood-prone Oria catchment in the Basque Country, northern Spain. The results show that, although there is a better match between the uncertain forecasted and uncertain true flows, there is a low sensitivity for the threshold exceedances used to issue flood warnings. This suggests that a standard flow measurement error model, with a spread set to a fixed flow fraction, represents a reasonable trade-off between complexity and realism. Standard models are therefore recommended for operational flood forecasting for sites with well-defined stage-discharge curves that are based on a large range of flow observations.
Quantum field theory in spaces with closed time-like curves
Energy Technology Data Exchange (ETDEWEB)
Boulware, D.G.
1992-12-31
Gott spacetime has closed timelike curves, but no locally anomalous stress-energy. A complete orthonormal set of eigenfunctions of the wave operator is found in the special case of a spacetime in which the total deficit angle is 27{pi}. A scalar quantum field theory is constructed using these eigenfunctions. The resultant interacting quantum field theory is not unitary because the field operators can create real, on-shell, particles in the acausal region. These particles propagate for finite proper time accumulating an arbitrary phase before being annihilated at the same spacetime point as that at which they were created. As a result, the effective potential within the acausal region is complex, and probability is not conserved. The stress tensor of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in the case of a sufficiently small Compton wavelength of the field, the stress tensor is regular and cannot prevent the formation of the Cauchy horizon.
Quantum field theory in spaces with closed time-like curves
International Nuclear Information System (INIS)
Boulware, D.G.
1992-01-01
Gott spacetime has closed timelike curves, but no locally anomalous stress-energy. A complete orthonormal set of eigenfunctions of the wave operator is found in the special case of a spacetime in which the total deficit angle is 27π. A scalar quantum field theory is constructed using these eigenfunctions. The resultant interacting quantum field theory is not unitary because the field operators can create real, on-shell, particles in the acausal region. These particles propagate for finite proper time accumulating an arbitrary phase before being annihilated at the same spacetime point as that at which they were created. As a result, the effective potential within the acausal region is complex, and probability is not conserved. The stress tensor of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in the case of a sufficiently small Compton wavelength of the field, the stress tensor is regular and cannot prevent the formation of the Cauchy horizon
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.
Impedance based time-domain modeling of lithium-ion batteries: Part I
Gantenbein, Sophia; Weiss, Michael; Ivers-Tiffée, Ellen
2018-03-01
This paper presents a novel lithium-ion cell model, which simulates the current voltage characteristic as a function of state of charge (0%-100%) and temperature (0-30 °C). It predicts the cell voltage at each operating point by calculating the total overvoltage from the individual contributions of (i) the ohmic loss η0, (ii) the charge transfer loss of the cathode ηCT,C, (iii) the charge transfer loss and the solid electrolyte interface loss of the anode ηSEI/CT,A, and (iv) the solid state and electrolyte diffusion loss ηDiff,A/C/E. This approach is based on a physically meaningful equivalent circuit model, which is parametrized by electrochemical impedance spectroscopy and time domain measurements, covering a wide frequency range from MHz to μHz. The model is exemplarily parametrized to a commercial, high-power 350 mAh graphite/LiNiCoAlO2-LiCoO2 pouch cell and validated by continuous discharge and charge curves at varying temperature. For the first time, the physical background of the model allows the operator to draw conclusions about the performance-limiting factor at various operating conditions. Not only can the model help to choose application-optimized cell characteristics, but it can also support the battery management system when taking corrective actions during operation.
Pulkkinen, Aki; Tarvainen, Tanja
2013-03-01
The radiative transfer equation (RTE) is widely accepted to accurately describe light transport in a medium with scattering particles, and it has been successfully applied as a light-transport model, for example, in diffuse optical tomography. Due to the computationally expensive nature of the RTE, most of these applications have been in the frequency domain. In this paper, an efficient solution method for the time-domain RTE is proposed. The method is based on solving the frequency-domain RTE at multiple modulation frequencies and using the Fourier-series representation of the radiance to obtain approximation of the time-domain solution. The approach is tested with simulations. The results show that the method can be used to obtain the solution of the time-domain RTE with good accuracy and with significantly fewer computational resources than are needed in the direct time-domain solution.
Estimation of error on the cross-correlation, phase and time lag between evenly sampled light curves
Misra, R.; Bora, A.; Dewangan, G.
2018-04-01
Temporal analysis of radiation from Astrophysical sources like Active Galactic Nuclei, X-ray Binaries and Gamma-ray bursts provides information on the geometry and sizes of the emitting regions. Establishing that two light-curves in different energy bands are correlated, and measuring the phase and time-lag between them is an important and frequently used temporal diagnostic. Generally the estimates are done by dividing the light-curves into large number of adjacent intervals to find the variance or by using numerically expensive simulations. In this work we have presented alternative expressions for estimate of the errors on the cross-correlation, phase and time-lag between two shorter light-curves when they cannot be divided into segments. Thus the estimates presented here allow for analysis of light-curves with relatively small number of points, as well as to obtain information on the longest time-scales available. The expressions have been tested using 200 light curves simulated from both white and 1 / f stochastic processes with measurement errors. We also present an application to the XMM-Newton light-curves of the Active Galactic Nucleus, Akn 564. The example shows that the estimates presented here allow for analysis of light-curves with relatively small (∼ 1000) number of points.
Isiordia, Marilu; Conger, Rand; Robins, Richard W; Ferrer, Emilio
2017-12-01
Research in family psychology often focuses on understanding how multiple familial constructs develop over time. To examine these developmental processes, researchers frequently use a multivariate latent growth model (LGM) in which univariate LGMs are specified for each individual construct and then correlations are examined between the slopes and intercepts of different pairs of constructs. However, if the developmental associations among the constructs are hypothesized to derive from a higher-order common "cause" or factor, then a more appropriate model is the factor of curves (FOCUS) model. In this paper, we describe the FOCUS model for assessing the covariation among multiple developmental measures over time. We use empirical data to illustrate the benefits of the FOCUS model for testing whether a common factor, family academic orientation, is responsible for the interrelations among parental school perception, parental educational involvement, and children's academic competence from elementary school to high school. Results support that a higher-order family academic orientation construct can be used to characterize the developmental associations among parental school perception, parental educational involvement, and children's academic competence over time. We emphasize the importance of selecting a statistical model that matches one's theory of developmental change. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
Time dependent ROC curves for the estimation of true prognostic capacity of microarray data.
Foucher, Yohann; Danger, Richard
2012-11-22
Microarray data can be used to identify prognostic signatures based on time-to-event data. The analysis of microarrays is often associated with overfitting and many papers have dealt with this issue. However, little attention has been paid to incomplete time-to-event data (truncated and censored follow-up). We have adapted the 0.632+ bootstrap estimator for the evaluation of time-dependent ROC curves. The interpretation of ROC-based results is well-established among the scientific and medical community. Moreover, the results do not depend on the incidence of the event, as opposed to many other prognostic statistics. Here, we have tested this methodology by simulations. We have illustrated its utility by analyzing a data set of diffuse large-B-cell lymphoma patients. Our results demonstrate the well-adapted properties of the 0.632+ ROC-based approach to evaluate the true prognostic capacity of a microarray-based signature. This method has been implemented in an R package ROCt632.
Time-dependent Reliability Analysis of Flood Defence Assets Using Generic Fragility Curve
Directory of Open Access Journals (Sweden)
Nepal Jaya
2016-01-01
Full Text Available Flood defence assets such as earth embankments comprise the vital part of linear flood defences in many countries including the UK and protect inland from flooding. The risks of flooding are likely to increase in the future due to increasing pressure on land use, increasing rainfall events and rising sea level caused by climate change also affect aging flood defence assets. Therefore, it is important that the flood defence assets are maintained at a high level of safety and serviceability. The high costs associated with preserving these deteriorating flood defence assets and the limited funds available for their maintenance require the development of systematic approaches to ensure the sustainable flood-risk management system. The integration of realistic deterioration measurement and reliabilitybased performance assessment techniques has tremendous potential for structural safety and economic feasibility of flood defence assets. Therefore, the need for reliability-based performance assessment is evident. However, investigations on time-dependent reliability analysis of flood defence assets are limited. This paper presents a novel approach for time-dependent reliability analysis of flood defence assets. In the analysis, time-dependent fragility curve is developed by using the state-based stochastic deterioration model. The applicability of the proposed approach is then demonstrated with a case study.
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.
Attractive new technologies for 7-wavelength time domain optical mammography
Ferocino, Edoardo; Martinenghi, Edoardo; Dalla Mora, Alberto; Pifferi, Antonio; Cubeddu, Rinaldo; Taroni, Paola
2017-07-01
An 8-channel Silicon PhotoMultiplier (SiPM) probe and Time-to-Digital-Converter (TDC) realize a higher-throughput, cheaper and compact detection chain for time-resolved optical mammography than photomultiplier tubes (PMTs) and Time Correlated Single Photon Counting (TCSPC) boards, providing comparable estimate of optical properties with increased optical responsivity.
A general structure for a time-domain model of the cochlea
Duifhuis, H; Wada, H; Takasaka, T; Ikeda, K; Koike, T
2000-01-01
This study presents an implementation of our basic ideas about a time-domain nonlinear model of the cochlea. The time-domain approach is considered necessary because it allows implementation of nonlinearity in general and of a proper temporal analysis of natural transient responses in particular. It
The detection of amoxicillin medicines by terahertz time-domain spectroscopy
Meng, Kun; Li, Zeren; Liu, Qiao
2012-03-01
Terahertz time-domain spectroscopy (THz-TDS) is a new spectroscopic technique, which improve a good complement for other spectroscopic techniques and has broad application prospects in the biomedical field. In this paper, a terahertz time-domain spectroscopy system is set up. Using this system, the amoxicillin drugs are detected, and the spectrum are analyzed.
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...
Conceptualizing and Re-Evaluating Resilience across Levels of Risk, Time, and Domains of Competence
Vanderbilt-Adriance, Ella; Shaw, Daniel S.
2008-01-01
This article examines potential theoretical constraints on resilience across levels of risk, time, and domain of outcome. Studies of resilience are reviewed as they relate to the prevalence of resilience across levels of risk (e.g., single life events vs. cumulative risk), time, and domains of adjustment. Based on a thorough review of pertinent…
Sun, Haoyu; Ge, Hongming; Zheng, Min; Lin, Zhifen; Liu, Ying
2016-09-01
Previous studies have identified a phenomenon in which the concentration-response curves (CRCs) for mixtures cross the curves for concentration addition model when predicting or judging joint toxic actions. However, mechanistic investigations of this phenomenon are extremely limited. In this study, a similar phenomenon was observed when we determined the joint toxic actions of sulfonamides (SAs) and erythromycin (ERY) on Escherichia coli (E. coli), which we named the “cross-phenomenon”, and it was characterized by antagonism in the low-concentration range, addition in the medium-concentration range, and synergism in the high-concentration range. The mechanistic investigation of the cross-phenomenon was as follows: SAs and ERY could form a double block to inhibit the bacterial growth by exhibiting a synergistic effect; however, the hormetic effect of SAs on E. coli led to antagonism in the low-concentration range, resulting from the stimulation of sdiA mRNA expression by SAs, which increased the expression of the efflux pump (AcrAB-TolC) to discharge ERY. Furthermore, this cross-phenomenon was observed to be a time-dependent process induced by the increase of both the concentration and extent of stimulation of sdiA mRNA with exposure time. This work explains the dose-dependent and time-dependent cross-phenomenon and provides evidence regarding the interaction between hormesis and cross-phenomenon.
The Biasing Effects of Unmodeled ARMA Time Series Processes on Latent Growth Curve Model Estimates
Sivo, Stephen; Fan, Xitao; Witta, Lea
2005-01-01
The purpose of this study was to evaluate the robustness of estimated growth curve models when there is stationary autocorrelation among manifest variable errors. The results suggest that when, in practice, growth curve models are fitted to longitudinal data, alternative rival hypotheses to consider would include growth models that also specify…
Optimal I-V Curve Scan Time of Solar Cells and Modules in Light of Irradiance Level
Directory of Open Access Journals (Sweden)
Matic Herman
2012-01-01
Full Text Available High-efficiency solar cells and modules exhibit strong capacitive character resulting in limited speed of transient responses. A too fast I-V curve measurement can thus introduce a significant error due to its internal capacitances. This paper analyses the I-V curve error of a measured solar cell or module in light of scan time and irradiance level. It rests on a two-diode solar cell model extended by two bias-dependent capacitances, modelling the junction, and the diffusion capacitance. A method for determination of all extended model parameters from a quasistatic I-V curve and open-circuit voltage decay measurement is presented and validated. Applicability of the extended model and the developed parameter extraction method to PV modules is demonstrated and confirmed. SPICE simulations of the extended model are used to obtain the I-V curve error versus scan time dependence and the I-V curve hysteresis. Determination of the optimal scan time is addressed, and finally the influence of the irradiance level on the I-V curve scan time and error is revealed. The method is applied but is not limited to three different wafer-based silicon solar cell types.
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.
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.
International Nuclear Information System (INIS)
Wu Chunxue; Wang Xiaoying; Qin Naishan; Jiang Xuexiang
2010-01-01
Objective: To investigate the clinical value of the type and the steepest slope of tumor's time-intensity curve (TIC) in assessing the pathologic response of locally advanced breast cancer treated with neoadjuvant chemotherapy (NAC). Methods: Thirty-six patients with pathologically confirmed locally advanced breast cancer who finished four courses of neoadjuvant chemotherapy underwent preoperative breast MRI three times during the NAC. Pathologic response was assessed according Miller-Payne grading system, grade 4 and 5 were defined as major histological response (MHR, n=16) group, and grade 1 to 3 as non- major histological response(NMHR, n=20)group. The type and the steepest slope of tumor's TIC were compared between two groups before NAC, after the second cycle and after the fourth cycle of NAC. ROC analysis was carded out to assess the clinical value of the TIC parameters. Results: After the second cycle of NAC, the steepest slope of TIC and its first change rate were different between the MHR group [(1.93± 0.88)%/s, median 35.6%] and NMHR group [(2.73±1.22)%/s, median -11.4%] (P= 0.045 and 0.01, t=1.09, Z=-3.64). After the fourth cycle, the proportion of type I in MHR group (62.5%, 10/16) was significantly higher than that in NMHR group (10.0%, 2/20, P=0.01, Z=-2.02), and the proportion of type III in MHR group (6.2%, 1/16) was significantly lower than that in NMH1R group (60.0%, 12/20, P=0.01, Z=-1.48). The steepest slope and its second change rate were different between the MHR group [(1.33±0.52)%/s, median 56.8%] and NMHR group [(2.33± 0.94)%/s, median 15.8%] (P<0.01, t=1.82, Z=-3.58). After the second cycle, the area under curve of the steepest slope of TIC and its first change rate were 0.70 (P=0.04), 0.80 (P=0.01), respectively. After the fourth cycle, the area under curve of the type I , the type I + II, the steepest slope and its second change were 0.78 (P=0.03), 0.69 (P=0.06), 0.82 (P=0.01), 0.92 (P=0.01), respectively. Conclusion: The steepest
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...
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....
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 and frequency domain models for multiaxial fatigue life estimation under random loading
Directory of Open Access Journals (Sweden)
Andrea Carpinteri
2015-07-01
Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.
Limited sampling strategy for determining metformin area under the plasma concentration-time curve
DEFF Research Database (Denmark)
Santoro, Ana Beatriz; Stage, Tore Bjerregaard; Struchiner, Claudio José
2016-01-01
AIM: The aim was to develop and validate limited sampling strategy (LSS) models to predict the area under the plasma concentration-time curve (AUC) for metformin. METHODS: Metformin plasma concentrations (n = 627) at 0-24 h after a single 500 mg dose were used for LSS development, based on all...... subsets linear regression analysis. The LSS-derived AUC(0,24 h) was compared with the parameter 'best estimate' obtained by non-compartmental analysis using all plasma concentration data points. Correlation between the LSS-derived and the best estimated AUC(0,24 h) (r(2) ), bias and precision of the LSS.......9-7.7%. The accuracy of the two point LSS model was verified in study cohorts of individuals receiving single 500 or 1000 mg (r(2) = -0.933-0.934) or seven 1000 mg daily doses (r(2) = 0.918), as well as using data from 16 published studies covering a wide range of metformin doses, demographics, clinical...
The real-time fitting of radioactive decay curves. Pt. 2
International Nuclear Information System (INIS)
Hartley, B.M.
1994-01-01
The method of time evolved least squares (TELS) fitting of radioactive decay curves has been developed in a previous paper. That paper contained the general method for determining the activities of a number of different isotopes present in a sample when counted by different counting systems. The method allows for the determination of the numbers of atoms of isotopes present in a sample when they form part of a decay chain, as well as in a mixture of isotopes. The theory given allows for different efficiencies of detection of radiation in different counting systems to be used and for the detection of radiation from one type of decay in different detectors. This paper shows the potential application of the method to the counting of radiation from the descendants of radon and the determination of the numbers of atoms of each isotope in the decay chain. Two examples illustrate the use of the methodology in the determination of the numbers of atoms of the descendants of radon in a sample. The statistical uncertainty in the results of the determination have been found by Monte Carlo simulations of the decay and the counting. (orig.)
Left ventricular time volume curve analysis in the detection of limited ischaemic heart disease
International Nuclear Information System (INIS)
Liechtenstein, M.; Blanchett, W.; Andrews, J.; Hunt, D.
1982-01-01
The aim of the study was to determine whether limited coronary artery disease (CAD) could be accurately detected using the Cardiac Gated Blood Pool (CGBP) scan with exercise. Regional left ventricular time volume curves (RLTVD) were generated from 52 studies (46 patients: 22 normals, 24 abnormals). The parameters assessed both globally and regionally and at rest (R) and exercise (Ex) were: (1) the ejection fraction (EF) (2) the change in ejection fraction from R to Ex (δEF) (3) an early contraction index (ECI) (4) a maximal emptying index (DR) and (5) a maximal refilling index (AR). After careful analysis of these parameters it was decided that our diagnostic criteria would rely on the following: (1) the EF at R and Ex (2) the δ EF (3) the ECI at Ex (4) the AR at Ex This study showed that both the sensitivity and the specificity of the CGBP scan can be improved considerably with the inclusion of RLTVC from the levels obtained when the EF parameters alone are considered. It is possible with this technique to accurately diagnose limited CAD. (Author)
Ikemoto, Yukio; Demura, Shinichi; Yamaji, Shunsuke
2004-04-01
Individual differences in muscle contractile speed during static explosive muscle contraction are reflected in the developmental phase of the force-time curve. The purposes of this study were to clarify the properties and reliability of the inflection point of force-time, statistically dividing speed during static explosive grip into two phases and to assess the relations between that inflection point and others. Static explosive grip data were measured two times with a 5-min. rest (sampling frequency; 100 Hz). 32 healthy, young men (age: 15.5 +/- 0.8 yr., height: 173.9 +/- 7.3 cm, body mass: 71.5 +/- 11.2 kg) participated. 8 static explosive grip parameters were selected: time of reaching, integrated area, and quotient values of the integrated areas up to 0.25, 0.5, and 1.0 sec. divided by maximal grip force. The inflection point was calculated statistically from two regression lines fitted to a developmental phase and the almost steady-state phase of reaching maximal grip force by applying a two-phase regression model. The reliabilities of maximal grip force, time of reaching 90% of maximal grip force, and the integrated area until 0.5 sec. and 1.0 sec. after the onset of grip were good (ICC=.77 to .93). The time of reaching an inflection force value appeared at 0.3 sec. after the onset of grip, corresponding to 80% of maximal grip force, and the reliabilities of the parameters regarding inflection point were good (ICC=.77 to .95). The time determined by boundary data between the former and the latter regression data set and the regression coefficient during the developmental phase correlated significantly with the time of reaching 90% of maximal grip force, the integrated area, and the quotient values of the integrated areas up to 0.25, 0.5, and 1.0 sec. divided by maximal grip force (rs=-.78 to -.96 and -.75 to 0.88, respectively, pforce. A force during the developmental phase and maximal grip force can depend on different physiological factors. The time
Ignee, Andre; Jedrejczyk, Maciej; Schuessler, Gudrun; Jakubowski, Wieslaw; Dietrich, Christoph F
2010-01-01
Time intensity curves for real-time contrast enhanced low MI ultrasound is a promising technique since it adds objective data to the more subjective conventional contrast enhanced technique. Current developments showed that the amount of uptake in modern targeted therapy strategies correlates with therapy response. Nevertheless no basic research has been done concerning the reliability and validity of the method. Videos sequences of 31 consecutive patients for at least 60s were recorded. Parameters analysed: area under the curve, maximum intensity, mean transit time, perfusion index, time to peak, rise time. The influence of depth, lateral shift as well as size and shape of the region of interest was analysed. The parameters time to peak and rise time showed a good stability in different depths. Overall there was a variation >50% for all other parameters. Mean transit time, time to peak and rise time were stable from 3 to 10cm depths, whereas all other parameters showed only satisfying results at 4-6cm. Time to peak and rise time were stable as well against lateral shifting whereas all other parameters had again variations over 50%. Size and shape of the region of interest did not influence the results. (1) It is important to compare regions of interest, e.g. in a tumour vs. representative parenchyma in the same depths. (2) Time intensity curves should not be analysed in a depth of less than 4cm. (3) The parameters area under the curve, perfusion index and maximum intensity should not be analysed in a depth more than 6cm. (4) Size and shape of a region of interest in liver parenchyma do not affect time intensity curves. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.
International Nuclear Information System (INIS)
Ignee, Andre; Jedrejczyk, Maciej; Schuessler, Gudrun; Jakubowski, Wieslaw; Dietrich, Christoph F.
2010-01-01
Introduction: Time intensity curves for real-time contrast enhanced low MI ultrasound is a promising technique since it adds objective data to the more subjective conventional contrast enhanced technique. Current developments showed that the amount of uptake in modern targeted therapy strategies correlates with therapy response. Nevertheless no basic research has been done concerning the reliability and validity of the method. Patients and methods: Videos sequences of 31 consecutive patients for at least 60 s were recorded. Parameters analysed: area under the curve, maximum intensity, mean transit time, perfusion index, time to peak, rise time. The influence of depth, lateral shift as well as size and shape of the region of interest was analysed. Results: The parameters time to peak and rise time showed a good stability in different depths. Overall there was a variation >50% for all other parameters. Mean transit time, time to peak and rise time were stable from 3 to 10 cm depths, whereas all other parameters showed only satisfying results at 4-6 cm. Time to peak and rise time were stable as well against lateral shifting whereas all other parameters had again variations over 50%. Size and shape of the region of interest did not influence the results. Discussion: (1) It is important to compare regions of interest, e.g. in a tumour vs. representative parenchyma in the same depths. (2) Time intensity curves should not be analysed in a depth of less than 4 cm. (3) The parameters area under the curve, perfusion index and maximum intensity should not be analysed in a depth more than 6 cm. (4) Size and shape of a region of interest in liver parenchyma do not affect time intensity curves.
A linearization time-domain CMOS smart temperature sensor using a curvature compensation oscillator.
Chen, Chun-Chi; Chen, Hao-Wen
2013-08-28
This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a -40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of -1.2 to 0.2 °C is achieved in an operation range of -40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s.
A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator
Directory of Open Access Journals (Sweden)
Hao-Wen Chen
2013-08-01
Full Text Available This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a −40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT. Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of −1.2 to 0.2 °C is achieved in an operation range of −40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s.
DEFF Research Database (Denmark)
Tan, Qihua; Thomassen, Mads; Hjelmborg, Jacob V B
2011-01-01
-course pattern in a gene by gene manner. We introduce a growth curve model with fractional polynomials to automatically capture the various time-dependent expression patterns and meanwhile efficiently handle missing values due to incomplete observations. For each gene, our procedure compares the performances...... among fractional polynomial models with power terms from a set of fixed values that offer a wide range of curve shapes and suggests a best fitting model. After a limited simulation study, the model has been applied to our human in vivo irritated epidermis data with missing observations to investigate...... time-dependent transcriptional responses to a chemical irritant. Our method was able to identify the various nonlinear time-course expression trajectories. The integration of growth curves with fractional polynomials provides a flexible way to model different time-course patterns together with model...
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...
International Nuclear Information System (INIS)
Liu Wei; Zhang Shengdong; Wang Yangyuan; Li Wei; Ren Peng; Lin Qinglong
2009-01-01
A time-domain digitally controlled oscillator (DCO) is proposed. The DCO is composed of a free-running ring oscillator (FRO) and a two lap-selectors integrated flying-adder (FA). With a coiled cell array which allows uniform loading capacitances of the delay cells, the FRO produces 32 outputs with consistent tap spacing for the FA as reference clocks. The FA uses the outputs from the FRO to generate the output of the DCO according to the control number, resulting in a linear dependence of the output period, instead of the frequency on the digital controlling word input. Thus the proposed DCO ensures a good conversion linearity in a time-domain, and is suitable for time-domain all-digital phase locked loop applications. The DCO was implemented in a standard 0.13 μm digital logic CMOS process. The measurement results show that the DCO has a linear and monotonic tuning curve with gain variation of less than 10%, and a very low root mean square period jitter of 9.3 ps in the output clocks. The DCO works well at supply voltages ranging from 0.6 to 1.2 V, and consumes 4 mW of power with 500 MHz frequency output at 1.2 V supply voltage.
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
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 1 H 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)
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.
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)
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.......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....
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-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.
Crystallization of amorphous lactose at high humidity studied by terahertz time domain spectroscopy
McIntosh, Alexander I.; Yang, Bin; Goldup, Stephen M.; Watkinson, Michael; Donnan, Robert S.
2013-02-01
We report the first use of terahertz time-domain spectroscopy (THz-TDS) to study the hydration and crystallization of an amorphous molecular solid at high humidity. Lactose in its amorphous and monohydrate forms exhibits different terahertz spectra due to the lack of long range order in the amorphous material. This difference allowed the transformation of amorphous lactose to its monohydrate form at high humidity to be studied in real time. Spectral fitting of frequency-domain data allowed kinetic data to be obtained and the crystallization was found to obey Avrami kinetics. Bulk changes during the crystallization could also be observed in the time-domain.
Guo, Yongmei; Jiang, Xinqing; Liu, Guoshun; Huang, Yunhai; Xu, Xiangdong
2015-12-01
To evaluate signal intensity-time (SI-Time) curve and quantitative dynamic contrast-enhanced 3.0T magnetic resonance imaging in diagnosis and differentiating neoplasm of uterus. A total of 42 cases of uterine neoplasm (20 were malignant and 22 were benign) were evaluated in our study. All cases received dynamic contrast-enhanced scanning on 3.0T MRI. The raw data was processed by Siemens Tissue 4D software and the SI-Time curve was obtained and analyzed. Pharmacokinetic modeling of Tofts with a modeled vascular input function was used for calculating volume parameters: volume transfer constant (Ktrans), reverse volume transfer constant (Kep), the extravascular extracellular space volume per unit volume of tissue (Ve). The correlation of these parameters at each groups were investigated. The SI-Time curve and the data of perfusion parameters between the 2 groups were compared by T test. Among 20 malignant tumors, 12 were cervical carcinoma and 8 were endometrial cancer. Among the benign tumors, 13 were leiomyomas, 3 were endometrial polyp, 3 were endometrial hyperplasia, and 3 were adenomyosis. 59.1% cases of benign tumors belong to Type I curve and 65% cases of malignant tumors belong to Type II curve. There was significant difference in SI-Time curve between benign and malignant tumors (P=0.011). If Type I curve was used as diagnostic criteria for benign tumors, and Type II and III curve were for malignant tumors, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value were 90.0%, 59.1%, 66.7%, and 86.7%, respectively. Ve was 0.477 ± 0.143 in malignant and 0.614 ± 0.146 in control group with significant difference (P=0.004). Ve was 0.477 ± 0.143 in malignant and 0.589 0.176 in benign group with significant difference (P=0.004). Ktrans was (0.178 ± 0.067) min⁻¹ in malignant and (0.263 ± 0.111) min⁻¹ in control group with significant difference (P=0.003). Ktrans was (0.182 ± 0.096) min⁻¹ in benign and (0
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.
Becker, A.; Hansen, V.
2007-06-01
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 Exploration with the Palomar-QUEST Sky Survey
Mahabal, Ashish A.; Drake, A. J.; Djorgovski, S. G.; Donalek, C.; Glikman, E.; Graham, M. J.; Williams, R.; Baltay, C.; Rabinowitz, D.; PQ Team Caltech; Yale; NCSA; Indiana; , ...
2007-05-01
Palomar-QUEST (PQ) synoptic sky survey has now been routinely processing data from driftscans in real-time. As four photometric bandpasses are utilized in nearly simultaneously, PQ is well suited to search for transient and highly variable objects. Using a series of software filters i.e. programs to select/deselect objects based on certain criteria we shorten the list of candidates from the initially flagged candidate transients. Such filters include looking for known asteroids, known variables, as well as moving, but previously uncatalogued objects based on their motion within a scan as well as between successive scans. Some software filters also deal with instrumental artifacts, edge effects, and use clustering of spurious detections around bright stars. During a typical night when we cover about 500 sq. degrees, we detect hundreds of asteroids, the primary contaminants in the search for astrophysical transients beyond our solar system. Here we describe some statistics based on the software filters we employ and the nature of the objects that seem to survive the process. We also discuss the usefulness of this to amateur astronomers, projects like VOEventNet, and other synoptic sky surveys. We also present an outline of the work we have started on quantifying the variability of quasars, blazars, as well as various classes of Galactic sources, by combining the large number of PQ scans with other existing data sources federated in the Virtual Observatory environment. The PQ survey is partially supported by the U.S. National Science Foundation (NSF).
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
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.
Brenier, Yann; Duan, Xianglong
2018-02-01
We provide several examples of dissipative systems that can be obtained from conservative ones through a simple, quadratic, change of time. A typical example is the curve-shortening flow in {R^d}, which is a particular case of mean-curvature flow with a co-dimension higher than one (except in the case d = 2). Through such a change of time, this flow can be formally derived from the conservative model of vibrating strings obtained from the Nambu-Goto action. Using the concept of "relative entropy" (or "modulated energy"), borrowed from the theory of hyperbolic systems of conservation laws, we introduce a notion of generalized solutions, that we call dissipative solutions, for the curve-shortening flow. For given initial conditions, the set of generalized solutions is convex and compact, if not empty. Smooth solutions to the curve-shortening flow are always unique in this setting.
Time-domain reflectometry of water content in portland cement concrete
1997-11-01
Time-domain reflectometry is useful for measuring the moisture content of solids. However, little information exists on its use with portland cement concrete. By monitoring the response from TDR sensors embedded in concrete as the concrete dried, the...
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...
3D parallel inversion of time-domain airborne EM data
Liu, Yun-He; Yin, Chang-Chun; Ren, Xiu-Yan; Qiu, Chang-Kai
2016-12-01
To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM "footprint" concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.
Time-Domain Terahertz Reflection Holograhic Tomography Nondestructive Evaluation System Project
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a single-sided time-domain terahertz reflection holographic tomographic imaging (TD-THz RHT) nondestructive...
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...
Time-Domain Convolutive Blind Source Separation Employing Selective-Tap Adaptive Algorithms
Directory of Open Access Journals (Sweden)
Pan Qiongfeng
2007-01-01
Full Text Available We investigate novel algorithms to improve the convergence and reduce the complexity of time-domain convolutive blind source separation (BSS algorithms. First, we propose MMax partial update time-domain convolutive BSS (MMax BSS algorithm. We demonstrate that the partial update scheme applied in the MMax LMS algorithm for single channel can be extended to multichannel time-domain convolutive BSS with little deterioration in performance and possible computational complexity saving. Next, we propose an exclusive maximum selective-tap time-domain convolutive BSS algorithm (XM BSS that reduces the interchannel coherence of the tap-input vectors and improves the conditioning of the autocorrelation matrix resulting in improved convergence rate and reduced misalignment. Moreover, the computational complexity is reduced since only half of the tap inputs are selected for updating. Simulation results have shown a significant improvement in convergence rate compared to existing techniques.
Time-Domain Convolutive Blind Source Separation Employing Selective-Tap Adaptive Algorithms
Directory of Open Access Journals (Sweden)
Qiongfeng Pan
2007-04-01
Full Text Available We investigate novel algorithms to improve the convergence and reduce the complexity of time-domain convolutive blind source separation (BSS algorithms. First, we propose MMax partial update time-domain convolutive BSS (MMax BSS algorithm. We demonstrate that the partial update scheme applied in the MMax LMS algorithm for single channel can be extended to multichannel time-domain convolutive BSS with little deterioration in performance and possible computational complexity saving. Next, we propose an exclusive maximum selective-tap time-domain convolutive BSS algorithm (XM BSS that reduces the interchannel coherence of the tap-input vectors and improves the conditioning of the autocorrelation matrix resulting in improved convergence rate and reduced misalignment. Moreover, the computational complexity is reduced since only half of the tap inputs are selected for updating. Simulation results have shown a significant improvement in convergence rate compared to existing techniques.
Directory of Open Access Journals (Sweden)
Tariq Jamil Saifullah Khanzada
2012-01-01
Full Text Available The OFDM (Orthogonal Frequency Division Multiplexing is well-known, most utilized wideband communication technique of the current era. SCT (Single Carrier Transmission provides equivalent performance in time domain while decision equalizer is implemented in frequency domain. SCT annihilates the ICT (Inter Carrier Interference and the PAPR (Peak to Average Power Ratio which is inherent to OFDM and degrades its performance in time varying channels. An efficient channel model is presented in this contribution, to implement OFDM and SCT in time domain using impulse responses. Both OFDM and SCT models are derived dialectically to model the channel impulse responses. Our model enhances the performance of time domain SCT compared with OFDM and subsides the PAPR and ICI problems of OFDM. SCT is implemented at symbol level contained in blocks. Simulation results implementing Digital Radio Monadiale (DRM assert the performance gain of SCT over OFDM.
Botts, Jonathan; Savioja, Lauri
2015-04-01
For time-domain modeling based on the acoustic wave equation, spectral methods have recently demonstrated promise. This letter presents an extension of a spectral domain decomposition approach, previously used to solve the lossless linear wave equation, which accommodates frequency-dependent atmospheric attenuation and assignment of arbitrary dispersion relations. Frequency-dependence is straightforward to assign when time-stepping is done in the spectral domain, so combined losses from molecular relaxation, thermal conductivity, and viscosity can be approximated with little extra computation or storage. A mode update free from numerical dispersion is derived, and the model is confirmed with a numerical experiment.
DEFF Research Database (Denmark)
Madsen, Kristoffer Hougaard; Hansen, Lars Kai; Mørup, Morten
2009-01-01
representation we demonstrate how the class of objective functions that are separable in either time or frequency instances allow the gradient in the time or frequency domain to be converted to the opposing domain. We further demonstrate the usefulness of this framework for three different models; Shifted Non-negative...... Matrix Factorization, Convolutive Sparse Coding as well as Smooth and Sparse Matrix Factorization. Matlab implementation of the proposed algorithms are available for download at www.erpwavelab.org....
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.
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 reflect......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...
Time-domain effects on error rates of multilevel digital pulse interval modulation systems
Wei, Wei; Zhang, Xiaohui; Rao, Jionghui; Pan, Chen
2011-10-01
A channel discretization was applied to investigate time-domain effects on error rates of Multilevel Digital Pulse Interval Modulation (MDPIM) underwater optical wireless communication systems imposed by water scattering. Taking time domain dispersion into account, package error rates of MDPIM were analyzed. The deterioration of package error rates were computed at various link ranges and transmitted rates. Theory model is an agreement with Monte Carlo simulation.
On the Schwinger-De Witt expansion for the Feynman propagator in a curved space-time
International Nuclear Information System (INIS)
John, R.W.
1986-01-01
The Feynman propagator in curved space-time is defined in a manifestly covariant way by the help of the Schwinger-De Witt representation. Building elements of the Schwinger-De Witt expansion are obtained on a model space-time being of non-constant curvature and yielding not identically vanishing Hadamard coefficients. The world function can be calculated exactly and in closed form for special representatives of highly symmetric space-time only
Application of time domain induced polarization to the mapping of lithotypes in a landfill site
Directory of Open Access Journals (Sweden)
A. Gazoty
2012-06-01
Full Text Available A direct current (DC resistivity and time domain induced polarization (TDIP survey was undertaken at a decommissioned landfill site situated in Hørløkke, Denmark, for the purpose of mapping the waste deposits and to discriminate important geological units that control the hydrology of the surrounding area. It is known that both waste deposits and clay have clear signatures in TDIP data, making it possible to enhance the resolution of geological structures compared to DC surveys alone.
Four DC/TDIP profiles were carried out crossing the landfill, and another seven profiles in the surroundings provide a sufficiently dense coverage of the entire area. The whole dataset was inverted using a 1-D laterally constrained inversion scheme, recently implemented for TDIP data, in order to use the entire decay curves for reconstructing the electrical parameters of the soil in terms of the Cole-Cole polarization model.
Results show that it is possible to resolve both the geometry of the buried waste body and key geological structures. In particular, it was possible to find a silt/clay lens at depth that correlates with the flow direction of the pollution plume spreading out from the landfill and to map a shallow sandy layer rich in clay that likely has a strong influence on the hydrology of the site. This interpretation of the geophysical findings was constrained by borehole data, in terms of geology and gamma ray logging. The results of this study are important for the impact of the resolved geological units on the hydrology of the area, making it possible to construct more realistic scenarios of the variation of the pollution plume as a function of the climate change.
Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro
2013-01-01
We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599
Zhao, Xiaofeng; McGough, Robert J.
2016-01-01
The attenuation of ultrasound propagating in human tissue follows a power law with respect to frequency that is modeled by several different causal and noncausal fractional partial differential equations. To demonstrate some of the similarities and differences that are observed in three related time-fractional partial differential equations, time-domain Green's functions are calculated numerically for the power law wave equation, the Szabo wave equation, and for the Caputo wave equation. These Green's functions are evaluated for water with a power law exponent of y = 2, breast with a power law exponent of y = 1.5, and liver with a power law exponent of y = 1.139. Simulation results show that the noncausal features of the numerically calculated time-domain response are only evident very close to the source and that these causal and noncausal time-domain Green's functions converge to the same result away from the source. When noncausal time-domain Green's functions are convolved with a short pulse, no evidence of noncausal behavior remains in the time-domain, which suggests that these causal and noncausal time-fractional models are equally effective for these numerical calculations. PMID:27250193
N. Basturk (Nalan); C. Cakmakli (Cem); S.P. Ceyhan (Pinar); H.K. van Dijk (Herman)
2012-01-01
textabstractChanging time series properties of US inflation and economic activity are analyzed within a class of extended Phillips Curve (PC) models. First, the misspecification effects of mechanical removal of low frequency movements of these series on posterior inference of a basic PC model are
Basturk, N.; Cakmakli, C.; Ceyhan, P.; van Dijk, H.K.
2013-01-01
Changing time series properties of US inflation and economic activity are analyzed within a class of extended Phillips Curve (PC) models. First, the misspecification effects of mechanical removal of low frequency movements of these series on posterior inference of a basic PC model are analyzed using
DEFF Research Database (Denmark)
Srinivas, Nuggehally R; Syed, Muzeeb
2016-01-01
concentration–time curve (AUC) and minimum plasma drug concentration (Cmin) versus AUC relationship was established by linear regression models. The predictions of the AUC values were performed using published mean/median Cmax or Cmin data and appropriate regression lines. The quotient of observed and predicted...
Frequency- and Time-Domain Methods in Soil-Structure Interaction Analysis
Energy Technology Data Exchange (ETDEWEB)
Bolisetti, Chandrakanth; Whittaker, Andrew S.; Coleman, Justin L.
2015-06-01
Soil-structure interaction (SSI) analysis in the nuclear industry is currently performed using linear codes that function in the frequency domain. There is a consensus that these frequency-domain codes give reasonably accurate results for low-intensity ground motions that result in almost linear response. For higher intensity ground motions, which may result in nonlinear response in the soil, structure or at the vicinity of the foundation, the adequacy of frequency-domain codes is unproven. Nonlinear analysis, which is only possible in the time domain, is theoretically more appropriate in such cases. These methods are available but are rarely used due to the large computational requirements and a lack of experience with analysts and regulators. This paper presents an assessment of the linear frequency-domain code, SASSI, which is widely used in the nuclear industry, and the time-domain commercial finite-element code, LS-DYNA, for SSI analysis. The assessment involves benchmarking the SSI analysis procedure in LS-DYNA against SASSI for linearly elastic models. After affirming that SASSI and LS-DYNA result in almost identical responses for these models, they are used to perform nonlinear SSI analyses of two structures founded on soft soil. An examination of the results shows that, in spite of using identical material properties, the predictions of frequency- and time-domain codes are significantly different in the presence of nonlinear behavior such as gapping and sliding of the foundation.
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.
Time and frequency domain methods for quantifying common modulation of motor unit firing patterns
Directory of Open Access Journals (Sweden)
Myers Lance J
2004-10-01
Full Text Available Abstract Background In investigations of the human motor system, two approaches are generally employed toward the identification of common modulating drives from motor unit recordings. One is a frequency domain method and uses the coherence function to determine the degree of linear correlation between each frequency component of the signals. The other is a time domain method that has been developed to determine the strength of low frequency common modulations between motor unit spike trains, often referred to in the literature as 'common drive'. Methods The relationships between these methods are systematically explored using both mathematical and experimental procedures. A mathematical derivation is presented that shows the theoretical relationship between both time and frequency domain techniques. Multiple recordings from concurrent activities of pairs of motor units are studied and linear regressions are performed between time and frequency domain estimates (for different time domain window sizes to assess their equivalence. Results Analytically, it may be demonstrated that under the theoretical condition of a narrowband point frequency, the two relations are equivalent. However practical situations deviate from this ideal condition. The correlation between the two techniques varies with time domain moving average window length and for window lengths of 200 ms, 400 ms and 800 ms, the r2 regression statistics (p Conclusions Although theoretically equivalent and experimentally well correlated there are a number of minor discrepancies between the two techniques that are explored. The time domain technique is preferred for short data segments and is better able to quantify the strength of a broad band drive into a single index. The frequency domain measures are more encompassing, providing a complete description of all oscillatory inputs and are better suited to quantifying narrow ranges of descending input into a single index. In general the
Regional wage adjustments and unemployment: estimating the time-varying wage curve
Czech Academy of Sciences Publication Activity Database
Galuščák, K.; Münich, Daniel
2005-01-01
Roč. 55, 1-2 (2005), s. 68-82 ISSN 0015-1920 R&D Projects: GA ČR GA403/03/0340 Institutional research plan: CEZ:AV0Z70850503 Keywords : wage curve * wage flexibility * unemployment Subject RIV: AH - Economics Impact factor: 0.173, year: 2005 http://journal.fsv.cuni.cz/storage/1007_s_068_082.pdf
Tan, Qihua; Thomassen, Mads; Hjelmborg, Jacob v. B.; Clemmensen, Anders; Andersen, Klaus Ejner; Petersen, Thomas K.; McGue, Matthew; Christensen, Kaare; Kruse, Torben A.
2011-01-01
Identifying the various gene expression response patterns is a challenging issue in expression microarray time-course experiments. Due to heterogeneity in the regulatory reaction among thousands of genes tested, it is impossible to manually characterize a parametric form for each of the time-course pattern in a gene by gene manner. We introduce a growth curve model with fractional polynomials to automatically capture the various time-dependent expression patterns and meanwhile efficiently handle missing values due to incomplete observations. For each gene, our procedure compares the performances among fractional polynomial models with power terms from a set of fixed values that offer a wide range of curve shapes and suggests a best fitting model. After a limited simulation study, the model has been applied to our human in vivo irritated epidermis data with missing observations to investigate time-dependent transcriptional responses to a chemical irritant. Our method was able to identify the various nonlinear time-course expression trajectories. The integration of growth curves with fractional polynomials provides a flexible way to model different time-course patterns together with model selection and significant gene identification strategies that can be applied in microarray-based time-course gene expression experiments with missing observations. PMID:21966290
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.
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.
Siebelmann, Sebastian; Gehlsen, Uta; Le Blanc, Carolin; Stanzel, Tisha Prabriputaloong; Cursiefen, Claus; Steven, Philipp
2016-12-01
Correct early graft attachment is believed to be crucial for final visual outcome after Descemet membrane endothelial keratoplasty (DMEK). Nonetheless, it is not yet known which imaging technique gives superior results for examining early postoperative graft adherence status. We compared imaging data taken with two different OCT devices to examine the development of graft adherence immediately after DMEK and to determine the superior device in terms of visualization of graft adherence. Ten consecutive patients (1 man/9 women) were examined three times postoperatively within the first 7 h after DMEK surgery using spectral domain OCT (SD-OCT) and time domain OCT (TD-OCT), as prospective case series and retrospective image data analyses. The parameters analyzed were localization and number, visibility and size of graft detachments. TD-OCT was able to detect a greater number of graft detachments after DMEK; however, SD-OCT provided better resolution of minor detachments. Graft detachments varied in position and degree at different time points immediately after surgery. All patients had some graft detachment within the first 7 h after DMEK surgery. TD-OCT enabled better overall analysis of graft detachments, even in the periphery, whereas SD-OCT allowed for the detection of even minor detachments, which suggests that a combination of the two techniques is optimal. Our results indicate that dynamic processes affecting the DMEK graft immediately after transplantation are responsible for changes in the attachment of donor tissue at an early postoperative stage. Modulation of early graft attachment may improve the final graft attachment.
Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.;
2013-01-01
We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in approximately 40 deg(exp 2) of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of approximately 3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5 sigma level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to absolute value(?m) = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV less than 23 mag and absolute value(?m) greater than 0.2 mag of approximately 8.0, 7.7, and 1.8 deg(exp -2) for quasars, active galactic nuclei, and RR Lyrae stars
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-Frequency Signal Representations Using Interpolations in Joint-Variable Domains
2016-06-14
frequently encountered in various radar applications. Data interpolators play a unique role in TF signal representations under missing samples. When...applied in the instantaneous autocorrelation domain over the time variable, the low-pass filter characteristic underlying linear interpolators lends...itself to cross-terms reduction in the ambiguity domain. This is in contrast to interpolation performed over the lag variable or a direct interpolation
Are Total and Domain-Specific Sedentary Time Associated with Overweight in Older Taiwanese Adults?
Directory of Open Access Journals (Sweden)
Ming-Chun Hsueh
2015-10-01
Full Text Available This study investigated the associations between total and domain-specific sedentary time with the risk of overweight in older adults. A cross-sectional study was conducted by administering computer-assisted telephone interviews to 1046 Taiwanese older adults (aged ≥65 years residing in two regions in Taiwan in 2015. Odds ratios (ORs and 95% confidence intervals (CIs were calculated to examine the associations between self-reported total and six domain-specific sedentary times and body mass index status (calculating by self-reported height and weight by using logistic regression analyses. The results showed that compared with older women in the lowest quartile of the total sedentary time, those in the highest quartile were 1.87 (95% CI: 1.10–3.21 times more likely to be overweight, after adjustment for potential confounders. The total sedentary time was stratified into six specific domains, and only watching television more than 2 h per day was positively associated with overweight (OR, 1.55; 95% CI: 1.08–2.25 in older women, whereas no other sedentary time domains were associated with the risk of overweight. No significant associations were observed in older men. Further studies using prospective designs are required to confirm the presently observed effects of total and domain-specific sedentary behavior on the health of older adults.
Are Total and Domain-Specific Sedentary Time Associated with Overweight in Older Taiwanese Adults?
Hsueh, Ming-Chun; Liao, Yung; Chang, Shao-Hsi
2015-10-12
This study investigated the associations between total and domain-specific sedentary time with the risk of overweight in older adults. A cross-sectional study was conducted by administering computer-assisted telephone interviews to 1046 Taiwanese older adults (aged ≥65 years) residing in two regions in Taiwan in 2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to examine the associations between self-reported total and six domain-specific sedentary times and body mass index status (calculating by self-reported height and weight) by using logistic regression analyses. The results showed that compared with older women in the lowest quartile of the total sedentary time, those in the highest quartile were 1.87 (95% CI: 1.10-3.21) times more likely to be overweight, after adjustment for potential confounders. The total sedentary time was stratified into six specific domains, and only watching television more than 2 h per day was positively associated with overweight (OR, 1.55; 95% CI: 1.08-2.25) in older women, whereas no other sedentary time domains were associated with the risk of overweight. No significant associations were observed in older men. Further studies using prospective designs are required to confirm the presently observed effects of total and domain-specific sedentary behavior on the health of older adults.
Tian, Lu; Xu, Xinlong
2018-03-01
The thermal analysis and optical properties of paraffin wax, beeswax, and liquid paraffin annealed at variable temperatures have been conducted using terahertz time-domain spectroscopy (THz-TDS) coupled with SEM methods. The characteristic optical properties of natural waxes can be used to analyze natural wax adulteration. The lamellar structure of paraffin wax and beeswax grew by a sheet of chain expansion. Furthermore, the crystallization process of paraffin wax can be assigned: rotator-solid transition and liquid-solid ones. According to the temperature-dependent refractive index curves, the refractive index of paraffin wax varies from large to small followed by rotator-liquid transition, untreated one, and liquid-solid one, respectively. The results indicated that THz-TDS has been proved to be of great potential in identification the crystallization of waxes.
Directory of Open Access Journals (Sweden)
Suyan Tian
2016-01-01
Full Text Available In order to test if two chemically or pharmaceutically equivalent products have the same efficacy and/or toxicity, a bioequivalence (BE study is conducted. The 80%/125% rule is the most commonly used criteria for BE and states that BE cannot be claimed unless the 90% CIs for the ratio of selected pharmacokinetics (PK parameters of the tested to the reference drug are within 0.8 to 1.25. Considering that estimates of these PK parameters are derived from the concentration-versus-time curves, a direct comparison between these curves motivates an alternative and more flexible approach to test BE. Here, we propose to frame the BE test in terms of an equivalence of concentration-versus-time curves which are constructed using local polynomial smoother (LPS. A metric is presented to quantify the distance between the curves and its 90% CIs are calculated via bootstrapping. Then, we applied the proposed procedures to data from an animal study and found that BE between a generic drug and its brand name cannot be concluded, which was consistent with the results by applying the 80%/125% rule. However, the proposed procedure has the advantage of testing only on a single metric, instead of all PK parameters.
Directory of Open Access Journals (Sweden)
Xavier João B
2011-06-01
Full Text Available Abstract Background Online spectrophotometric measurements allow monitoring dynamic biological processes with high-time resolution. Contrastingly, numerous other methods require laborious treatment of samples and can only be carried out offline. Integrating both types of measurement would allow analyzing biological processes more comprehensively. A typical example of this problem is acquiring quantitative data on rhamnolipid secretion by the opportunistic pathogen Pseudomonas aeruginosa. P. aeruginosa cell growth can be measured by optical density (OD600 and gene expression can be measured using reporter fusions with a fluorescent protein, allowing high time resolution monitoring. However, measuring the secreted rhamnolipid biosurfactants requires laborious sample processing, which makes this an offline measurement. Results Here, we propose a method to integrate growth curve data with endpoint measurements of secreted metabolites that is inspired by a model of exponential cell growth. If serial diluting an inoculum gives reproducible time series shifted in time, then time series of endpoint measurements can be reconstructed using calculated time shifts between dilutions. We illustrate the method using measured rhamnolipid secretion by P. aeruginosa as endpoint measurements and we integrate these measurements with high-resolution growth curves measured by OD600 and expression of rhamnolipid synthesis genes monitored using a reporter fusion. Two-fold serial dilution allowed integrating rhamnolipid measurements at a ~0.4 h-1 frequency with high-time resolved data measured at a 6 h-1 frequency. We show how this simple method can be used in combination with mutants lacking specific genes in the rhamnolipid synthesis or quorum sensing regulation to acquire rich dynamic data on P. aeruginosa virulence regulation. Additionally, the linear relation between the ratio of inocula and the time-shift between curves produces high-precision measurements of
International Nuclear Information System (INIS)
John, R.W.
1987-01-01
First, in connection with their construction due to Hadamard, the mathematical and physical meaning of covariant Green's functions in relativistic gravitational fields - according to Einstein: on curved space-time - is discussed. Then, in the case of a general static spherically symmetric space-time the construction equations for a scalar Green's function are cast into symmetry-adapted form providing a convenient starting point for an explicit calculation of the Hadamard building elements. In applying the obtained basic scheme to a special one-parameter family of model metrics one succeeds in advancing to the explicit exact calculation of tail-term coefficients of a massless Green's function which are simultaneously coefficients in the Schwinger-De Witt expansion of the Feynman propagator for the corresponding massive Klein-Gordon equation on curved space-time. (author)
Mie scattering in the time domain. Part II. The role of diffraction.
Lock, James A; Laven, Philip
2011-06-01
The p=0 term of the Mie-Debye scattering amplitude contains the effects of external reflection and diffraction. We computed the reflected intensity in the time domain as a function of the scattering angle and delay time for a short electromagnetic pulse incident on a spherical particle and compared it to the predicted behavior in the forward-focusing region, the specular reflection region, and the glory region. We examined the physical consequences of three different approaches to the exact diffraction amplitude, and determined the signature of diffraction in the time domain. The external reflection surface wave amplitude gradually replaces the diffraction amplitude in the angular transition region between forward-focusing and the region of specular reflection. The details of this replacement were studied in the time domain.
Implementation of ultrasound time-domain cross-correlation blood velocity estimators
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The implementation of real-time blood velocity estimators using time-domain cross-correlation is investigated. The basic algorithm for stationary echo canceling, cross-correlation estimation and subsequent velocity estimation is presented. Sampled data acquired at rates of approximately 20 MHz...
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...
ANALYSIS AND DESIGN OF CONTROL SYSTEMS BY MEANS OF TIME DOMAIN MATRICES
The time domain matrix method is presented and illustrated as a method of analysis and design of linear, nonlinear, and time varying systems of the...intermediate points throughout the loops are readily available. Also, systems with multiple nonlinearities may be investigated, for which there is not a presently available method of analysis and design.
Wang, Rui; Hu, Zhiping; Zhang, Dan; Wang, Qiyao
2017-12-01
The dynamic behavior of filled joints is mostly controlled by the filled medium. In addition to nonlinear elastic behavior, viscoelastic behavior of filled joints is also of great significance. Here, a theoretical study of stress wave propagation through a filled rock joint with linear viscoelastic deformation behavior has been carried out using a modified time-domain recursive method (TDRM). A displacement discontinuity model was extended to form a displacement and stress discontinuity model, and the differential constitutive relationship of viscoelastic model was adopted to introduce the mass and viscoelastic behavior of filled medium. A standard linear solid model, which can be degenerated into the Kelvin and Maxwell models, was adopted in deriving this method. Transmission and reflection coefficients were adopted to verify this method. Besides, the effects of some parameters on wave propagation across a filled rock joint with linear viscoelastic deformation behavior were discussed. Then, a comparison of the time-history curves calculated by the present method with those by frequency-domain method (FDM) was performed. The results indicated that change tendencies of the transmission and reflection coefficients for these viscoelastic models versus incident angle were the same as each other but not frequency. The mass and viscosity coupling of filled medium did not fundamentally change wave propagation. The modified TDRM was found to be more efficient than the FDM.
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
Scatterer size estimation using the center frequency assessed from ultrasound time domain data.
Erlöv, Tobias; Jansson, Tomas; Persson, Hans W; Cinthio, Magnus
2016-10-01
Scatterer size estimation is useful when characterizing tissue using ultrasound. In all previous studies on scatterer size, the estimations are performed in the frequency domain and are thus subjected to a trade off in time-frequency resolution. This study focused on the feasibility of estimating scatterer size in the time domain using only the ultrasound center frequency, assuming a Gaussian-shaped pulse. A model for frequency normalization was derived and the frequency-dependent attenuation was compensated. Five phantoms with well-defined sizes of spherical glass beads were made and scanned with two different linear array transducers with variable center frequencies. A strong correlation (r = 0.99, p estimation of scatterer size is possible using only the center frequency assessed in the time domain.
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.
International Nuclear Information System (INIS)
Grohs, B.; Barbian, O.A.; Kappes, W.; Paul, H.
1981-01-01
With automatic ultrasonic testing, flaws can be detected and described and thus characterized according to their type, position and dimensions. During scanning of a test object, the flaws are registered by many different pathways and many different acoustic irradiation directions. The transit time locus curve represents the distance between the relfecting points of a flaw and the source in dependence of the probe position; hence, information on flaw position and dimensions can be derived from this curve. If the sound velocity is known, the transit path can then be calculated from the transit time. This requires, above all, a constant sound velocity along the whole transit path. Various methods are presented for reconstructing the flaw border in the plane of incidence. (orig./RW) [de
Local momentum space and two-loop renormalizability of λφ 4 field theory in curved space-time
Bunch, T. S.
1981-07-01
A generalization is given of some previous work in which a momentum space representation for the Feynman propagator,G(x, y), of a scalar field in an arbitrary curved space-time was obtained. The pointsx andy are allowed to vary in a normal neighborhood of an arbitrary fixed pointz which is taken as an origin of normal coordinates and the representation is obtained by Fourier transformation in the coordinate differencex α-y α. The generality of this representation enables it to be applied to the evaluation of the divergences in any Feynman graph. As an example, the third-order (two-loop) corrections to the four-point function of λø4 field theory are shown to be renormalizable in curved space-time.
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.
Naohito, NAKAZAWA; Research Institute for Theoretical Physics Hiroshima University
1985-01-01
We formulate a field-theoretical method at finite temperature to calculate a thermal energy-momentum tensor in arbitrary curved space-times using a momentum-space representation of the thermal Green's function in terms of Riemann normal coordinates. In particular, the thermal energy-momentum tensor for a massive scalar field is calculated by the high-temperature expansion. A locally observed temperature is obtained by requiring the conservation law of the thermal energy-momentum tensor.
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
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....
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.
Design of one-dimensional optical pulse-shaping filters by time-domain topology optimization
DEFF Research Database (Denmark)
Yang, Lirong; Lavrinenko, Andrei; Hvam, Jørn Märcher
2009-01-01
Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems.......Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems....
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.
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
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
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.
International Nuclear Information System (INIS)
Zhang Jing; Liang Wei; Li Xiaosong; Zhang Wei; Liu Wei; Zhang Jingxiu; Feng Suchen; Cheng Xiaoguang
2009-01-01
Objective: To investigate the value of time-intensity curve of dynamic contrast enhancement MR imaging in the discrimination of benign and malignancy in musculoskeletal tumors. Methods: Ninety patients were examined with fast acquisition with multiphase enhanced fast GRE series. The TIC of lesions were obtained using slope images in which pixel intensity reflected the slope value. The curves were classified according to their shapes as type I, washout enhancement; type II, plateau enhancement; type III, gradual enhancement. Taking pathological diagnosis as gold standard, the power of the maximal enhancement slope and curve types in discriminating benign and malignant lesions was evaluated by appropriate statistic analysis. Results: There were 49 malignant and 44 benign lesions. The distribution of curve types for malignant tumors was type I 75.5% (37/49), type II 24.5% (12/49). While the numbers for benign tumors was type I 59.1% (26/44), type II 15.9% (7/44) and type III 25.0% (11/44), respectively. The patterns of curve types in malignant lesions were different from benign lesions significantly (X 2 = 14.008, P 0.05). Thye I and type II ( excluding lesions with typical benign morphology) were suggestive of malignant tumors. Type III was indicator of a benign lesion. The diagnostic indices for the shape of TIC criterion were: sensitivity 100%, specificity 50%, positive predictive value 78%, negative predictive value 100% and accuracy 82%, respectively. Conclusion: Combined with the characteristic of morphology, the TIC improves the power of MR imaging in discriminating benign from malignant musculoskeletal tumors. (authors)
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
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
Time-domain Helmholtz-Kirchhoff integral for surface scattering in a refractive medium.
Choo, Youngmin; Song, H C; Seong, Woojae
2017-03-01
The time-domain Helmholtz-Kirchhoff (H-K) integral for surface scattering is derived for a refractive medium, which can handle shadowing effects. The starting point is the H-K integral in the frequency domain. In the high-frequency limit, the Green's function can be calculated by ray theory, while the normal derivative of the incident pressure from a point source is formulated using the ray geometry and ray-based Green's function. For a corrugated pressure-release surface, a stationary phase approximation can be applied to the H-K integral, reducing the surface integral to a line integral. Finally, a computationally-efficient, time-domain H-K integral is derived using an inverse Fourier transform. A broadband signal scattered from a sinusoidal surface in an upwardly refracting medium is evaluated with and without geometric shadow corrections, and compared to the result from a conventional ray model.
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.
Energy Technology Data Exchange (ETDEWEB)
van Milligen, B. Ph. [Asociacion EURATOM-CIEMAT; Calvo, Ivan [CIEMAT, Madrid; Sanchez, Raul [ORNL
2008-01-01
The present work studies continuous time random walks (CTRWs) in a finite domain. A broad class of boundary conditions, of which absorbing and reflecting boundaries are particular cases, is considered. It is shown how any CTRW in this class can be mapped to a CTRW in an infinite domain. This may allow applying well-known techniques for infinite CTRWs to the problem of obtaining the fluid limit for finite domain CTRWs, where the fluid limit (or hydrodynamic limit) refers to the partial differential equation describing the long time and large distance behavior of the system. As an illustration, the fluid limit equation and its propagator are obtained explicitly in the case of purely reflecting boundaries. We also derive the modification of the Riemann-Liouville fractional differential operators implementing the reflecting boundary conditions.
Energy Technology Data Exchange (ETDEWEB)
Milligen, B Ph van; Calvo, I [Asociacion EURATOM-CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain); Sanchez, R [Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)], E-mail: boudewijn.vanmilligen@ciemat.es
2008-05-30
The present work studies continuous time random walks (CTRWs) in a finite domain. A broad class of boundary conditions, of which absorbing and reflecting boundaries are particular cases, is considered. It is shown how any CTRW in this class can be mapped to a CTRW in an infinite domain. This may allow applying well-known techniques for infinite CTRWs to the problem of obtaining the fluid limit for finite domain CTRWs, where the fluid limit (or hydrodynamic limit) refers to the partial differential equation describing the long time and large distance behaviour of the system. As an illustration, the fluid limit equation and its propagator are obtained explicitly in the case of purely reflecting boundaries. We also derive the modification of the Riemann-Liouville fractional differential operators implementing the reflecting boundary conditions.
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 approach for multi-exciter random environment test
Cui, Song; Chen, Huai-hai; He, Xu-dong
2017-06-01
This paper presents a time-domain method for multi-exciter random environment tests. Traditional random environment test theory has been formulated in the frequency domain, where an important step is taking the inverse of the frequency response function matrices (FRFMs). The accuracy of this inversion tends to be poor, particularly at frequencies near lightly damped resonances. The currently used control algorithms face difficulties in suppressing abnormal spectral lines caused by this inverse problem. In this paper, traditional formulations of the environment test are reformed, and the time-domain method is adopted; this results in a more precise inverse operation in environment tests. To achieve this, reference spectra are converted into time-domain response signals. The finite long driving signals are derived by the state-space method with estimated state vectors. During the process, the inverse of rank-deficient Toeplitz matrices are stabilized with truncated singular value decomposition (TSVD) to suppress all abnormally high-level components in the driving forces; thus, overall, the spectra lines produced by noise within the frequency band are filtered out. A numerical simulation of a single-axis random vibration test of a cantilever beam is conducted using the traditional frequency-domain procedure (FDP) and the proposed time-domain procedure (TDP). The response spectra generated by both procedures are tested by control algorithms, and the result shows that responses generated by the proposed TDP are more easily controlled. The conditions of stability for both the FDP and the TDP are also determined and introduced in the simulation. Moreover, a multi-axis vibration experiment further validates the effectiveness of the TDP.
Sabino, C. P.; Garcez, A. S.; Núñez, S. C.; Ribeiro, M. S.; Hamblin, M. R.
2014-01-01
Antimicrobial photodynamic therapy (APDT) combined with endodontic treatment has been recognized as an alternative approach to complement conventional root canal disinfection methods on bacterial biofilms. We developed an in vitro model of bioluminescent Candida albicans biofilm inside curved dental root canals and investigated the microbial reduction produced when different light delivery methods are employed. Each light delivery method was evaluated in respect to the light distribution provided inside curved root canals. After conventional endodontic preparation, teeth were sterilized before canals were contaminated by a bioluminescent strain of C. albicans (CEC789). Methylene blue (90 µM) was introduced into the canals and then irradiated (λ=660 nm, P=100 mW, beam diameter=2 mm) with laser tip either in contact with pulp chamber or within the canal using an optical diffuser fiber. Light distribution was evaluated by CCD camera, and microbial reduction was monitored through bioluminescence imaging. Our findings demonstrated that the bioluminescent C. albicans biofilm model had good reproducibility and uniformity. Light distribution in dental tissue was markedly dependent on the light delivery system, and this strategy was directly related to microbial destruction. Both light delivery systems performed significant fungal inactivation. However, when irradiation was performed with optical diffuser fiber, microbial burden reduction was nearly 100 times more effective. Bioluminescence is an interesting real-time analysis to endodontic C. albicans biofilm inactivation. APDT showed to be an effective way to inactivate C. albicans biofilms. Diffuser fibers provided optimized light distribution inside curved root canals and significantly increased APDT efficiency. PMID:25060900
International Nuclear Information System (INIS)
Saito, Ryo; Naruko, Atsushi; Hiramatsu, Takashi; Sasaki, Misao
2014-01-01
In this paper, we introduce a new approach to a treatment of the gravitational effects (redshift, time delay and lensing) on the observed cosmic microwave background (CMB) anisotropies based on the Boltzmann equation. From the Liouville's theorem in curved spacetime, the intensity of photons is conserved along a photon geodesic when non-gravitational scatterings are absent. Motivated by this fact, we derive a second-order line-of-sight formula by integrating the Boltzmann equation along a perturbed geodesic (curve) instead of a background geodesic (line). In this approach, the separation of the gravitational and intrinsic effects are manifest. This approach can be considered as a generalization of the remapping approach of CMB lensing, where all the gravitational effects can be treated on the same footing
DEFF Research Database (Denmark)
Tanev, Stoyan; Sun, Wenbo
2012-01-01
This chapter reviews the fundamental methods and some of the applications of the three-dimensional (3D) finite-difference time-domain (FDTD) technique for the modeling of light scattering by arbitrarily shaped dielectric particles and surfaces. The emphasis is on the details of the FDTD algorithm...
Managing Time-Based Conflict Across Life Domains In Nigeria: A ...
African Journals Online (AJOL)
which employees in a developing country attempt to resolve time-based conflict between work, family and other activities. A decision making framework is used to study the way Nigerian managers handled conflicting pressures from their various life domains. Participants were asked to write a diary, in a free-response format ...
Range/velocity limitations for time-domain blood velocity estimation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The traditional range/velocity limitation for blood velocity estimation systems using ultrasound is elucidated. It is stated that the equation is a property of the estimator used, not the actual physical measurement situation, as higher velocities can be estimated by the time domain cross...
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.
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...
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
A Time-Domain Method for Separating Incident and Reflected Irregular Waves
DEFF Research Database (Denmark)
Frigaard, Peter; Brorsen, Michael
of the model test. Goda and Suzuki (1976) presented a frequency method for estimation of irregular incident and reflected waves in random waves. Mansard and Funke (1980) improved this method uaing a least squares technique. In the following, a time-domain method for seperating the incident waves...
Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope
2016-10-19
TECHNICAL DOCUMENT 3308 September 2016 Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope Andrew B. Sabater Paul...angular random walk (ARW), bias instability, and scale factor instability. While there are methods to address issues with bias and scale factor...8 4. ANGULAR RANDOM WALK CHARACTERIZATION
Wang, Zhaojun; Zhou, Xiaoming
2016-12-01
The authors study the wave propagation in continuum acoustic metamaterials whose all or not all of the principal elements of the mass tensor or the scalar compressibility can be negative due to wave dispersion. Their time-domain wave characteristics are particularly investigated by the finite-difference time-domain (FDTD) method, in which algorithms for the Drude and Lorentz dispersion pertinent to acoustic metamaterials are provided necessarily. Wave propagation nature of anisotropic acoustic metamaterials with all admissible material parameters are analyzed in a general manner. It is found that anomalous negative refraction phenomena can appear in several dispersion regimes, and their unique time-domain signatures have been discovered by the FDTD modeling. It is further proposed that two different metamaterial layers with specially assigned dispersions could comprise a conjugate pair that permits wave propagation only at specific points in the wave vector space. The time-domain pulse simulation verifies that acoustic directive radiation capable of modulating radiation angle with the wave frequency can be realized with this conjugate pair. The study provides the detailed analysis of wave propagation in anisotropic and dispersive acoustic mediums, which makes a further step toward dispersion engineering and transient wave control through acoustic metamaterials.
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...
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…
Time domain-nuclear magnetic resonance study of chars from southern hardwoods
Thomas Elder; Nicole Labbe; David Harper; Timothy Rials
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 oC, were examined using time domain-nuclear magnetic resonance...
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.
Development of a method for reconstruction of crowded NMR spectra from undersampled time-domain data
Energy Technology Data Exchange (ETDEWEB)
Ueda, Takumi; Yoshiura, Chie; Matsumoto, Masahiko; Kofuku, Yutaka; Okude, Junya; Kondo, Keita; Shiraishi, Yutaro [The University of Tokyo, Graduate School of Pharmaceutical Sciences (Japan); Takeuchi, Koh [Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology (Japan); Shimada, Ichio, E-mail: shimada@iw-nmr.f.u-tokyo.ac.jp [The University of Tokyo, Graduate School of Pharmaceutical Sciences (Japan)
2015-05-15
NMR is a unique methodology for obtaining information about the conformational dynamics of proteins in heterogeneous biomolecular systems. In various NMR methods, such as transferred cross-saturation, relaxation dispersion, and paramagnetic relaxation enhancement experiments, fast determination of the signal intensity ratios in the NMR spectra with high accuracy is required for analyses of targets with low yields and stabilities. However, conventional methods for the reconstruction of spectra from undersampled time-domain data, such as linear prediction, spectroscopy with integration of frequency and time domain, and analysis of Fourier, and compressed sensing were not effective for the accurate determination of the signal intensity ratios of the crowded two-dimensional spectra of proteins. Here, we developed an NMR spectra reconstruction method, “conservation of experimental data in analysis of Fourier” (Co-ANAFOR), to reconstruct the crowded spectra from the undersampled time-domain data. The number of sampling points required for the transferred cross-saturation experiments between membrane proteins, photosystem I and cytochrome b{sub 6}f, and their ligand, plastocyanin, with Co-ANAFOR was half of that needed for linear prediction, and the peak height reduction ratios of the spectra reconstructed from truncated time-domain data by Co-ANAFOR were more accurate than those reconstructed from non-uniformly sampled data by compressed sensing.
DEFF Research Database (Denmark)
Maurya, Pradip Kumar; Fiandaca, Gianluca; Auken, Esben
study a large contaminated site in Denmark was investigated using direct current resistivity and time domain induced polarization (DCIP). For this purpose 14 profiles were collected alongside a stream in order to investigate the contamination and delineate the lithological units. 2D inversion using...
Insensitivity of single particle time domain measurements to laser velocimeter 'Doppler ambiguity.'
Johnson, D. A.
1973-01-01
It is shown that single particle time domain measurements in high speed gas flows obtained by a laser velocimeter technique developed for use in wind tunnels are not affected by the so-called 'Doppler ambiguity.' A comparison of hot-wire anemometer and laser velocimeter measurements taken under similar flow conditions is used for the demonstration.
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...
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...
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
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...
Temperature effects in soil water content determined with time domain reflectometry
Halbertsma, J.; Elsen, van den E.; Bohl, H.; Skierucha, W.
1996-01-01
The relative permittivity of water decreases with increasing temperature. Therefore, it is likely that the soil water content determined with time domain reflectometry is influenced by temperature. This study showed that significant temperature effects may occur. The magnitude of these effects is a
Characterization of Flaws in the Elastic Medium by Time Domain Born Approximation
International Nuclear Information System (INIS)
Yi, J. Y.; Lee, S. K.; Lee, J. O.; Kim, Y. H.
1983-01-01
The impulse response function are studied using time domain Born approximation in two cases; firstly when the material parameters of a flaw are constant, secondly when the parameters are varying with positions. From the impulse response functions, characteristics can be learned about a flaw with high symmetry
Engelen, Carolin; Moritz, Andreas; Barthel, Franziska; Bauer, Natali
2017-11-29
Thrombelastography is a useful tool in assessment of hemostasis. Beside the traditional variables, the velocity curve and the variable delta have lately earned attention. The velocity curve provides knowledge about the speed of clot formation including information about thrombin generation. Delta, which only reflects enzymatic coagulation, allows the determination of the origin of hypercoagulability when compared to clot rigidity, a variable that reflects both platelet and enzymatic activity. The aim was to establish preliminary reference intervals for feline thrombelastography including the velocity curve variables and delta obtained after 60 min of storage including the assessment of coefficients of variation. Furthermore, the effect of citrate storage time (30 versus 60 min) on feline thrombelastography will be determined. Prolonged storage times significantly reduced reaction (R) (P = 0.019) and clotting (K) (P = 0.008) times, split point (SP) (P = 0.019) and time to maximum rate of thrombus generation (TMRTG) (P = 0.023) values whereas maximum rate of thrombus generation (MRTG) significantly increased (P = 0.040). Preliminary reference intervals: R (min): 2.7-18.1; K (min): 0.8-3.9; alpha (°): 27.6-75.2; maximum amplitude (mm): 18.5-62.5; clot rigidity (dyn/cm 2 ): 1.2-8.2; coagulation index: -4.6 - 2.6; SP (min): 2.4-15.4; delta (min): 0.3-3.1; thrombus generation (mm/min): 255.3-751.2; MRTG (mm/min): 4.0-19.3; TMRTG (min): 3.5-22.0; maximum rate of lysis (mm/min): 0.0-4.7 and time to maximum rate of lysis (min): 0.4-55.8. Storage for 60 versus 30 min induces hypercoagulable tracings including the velocity curve, some of which variables (MRTG, TMRTG) might function as sensitive markers for changes in the coagulation activity. Because of the impact of citrate storage time on thrombelastography, reference intervals have to be established using a specific and constant storage time in each laboratory.
Directory of Open Access Journals (Sweden)
Konishi Tsuyoshi
2010-01-01
Full Text Available We propose and demonstrate a wavelength- and time-selective reconfigurable optical add/drop multiplexer (ROADM using time-frequency domain processing. The proposed ROADM is realized by allocating wavelength channels and time slots to corresponding 2D spatial channels on a MEMS optical switch. Experimental results show the wavelength- and time-selective drop operation for a signal with equivalent 3.2 Tb/s (0.64 channels, and the reconfigurability by the switching operation of the MEMS optical switch.
Directory of Open Access Journals (Sweden)
Tsuyoshi Konishi
2010-01-01
Full Text Available We propose and demonstrate a wavelength- and time-selective reconfigurable optical add/drop multiplexer (ROADM using time-frequency domain processing. The proposed ROADM is realized by allocating wavelength channels and time slots to corresponding 2D spatial channels on a MEMS optical switch. Experimental results show the wavelength- and time-selective drop operation for a signal with equivalent 3.2 Tb/s (0.64 Tb/s×5 channels, and the reconfigurability by the switching operation of the MEMS optical switch.
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.
Suppression of Time-domain Jitter of Impulse Radio Ultra-wide Band Radar
Directory of Open Access Journals (Sweden)
Liang Fu-lai
2015-08-01
Full Text Available For Impulse Radio Ultra-Wide Band (IR-UWB radar, the time jitter transforms the static clutters to dynamic clutters. Thus, strong residue exists and false alarms form after traditional direct current suppression. The effect of the time-domain jitter on the life detection capacity is analyzed, and then the phenomenon that the relative time delays between the coupling echoes can reflect the time jitter is pointed out. Based on the coupling echo, a method of time jitter suppression is proposed. Experimental data demonstrate that the proposed method can effectively suppress the residue of strong static clutter, and further improve the life-detection capacity.
Bacillus spores and their relevant chemicals studied by terahertz time domain spectroscopy
Tang, Jianhua; Yang, Bin; Llewellyn, Ian; Cutler, Ronald R.; Donnan, Robert S.
2014-01-01
Terahertz time domain spectroscopy has been used to investigate 0.2-2.2 THz transmission responses of Bacillus spores and their related chemical components. Whilst no THz signatures could be clearly associated with either sporulated cells or their chief chemical components, differing degrees of signal attenuation and frequency-dependent light scattering were observed depending on spore composition and culture media. The observed monotonic increase in absorption by spores over this THz spectral domain is mainly from Mie scattering and also from remnant water bound to the spores.
Time and space domain separation of pulsed X-ray beams diffracted from vibrating crystals
Energy Technology Data Exchange (ETDEWEB)
Nosik, V. L., E-mail: v-nosik@yandex.ru, E-mail: nosik@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation)
2016-11-15
It is known that a set of additional reflections (satellites) may arise on rocking curves in the case of X-ray diffraction in the Bragg geometry from crystals where high-frequency ultrasonic vibrations are excited. It is shown that, under certain conditions, the pulse wave fields of the satellites and main reflection may be intersected in space (playing the role of pump and probe beams) and in time (forming interference superlattices).
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.
[Identification of Official Rhubarb Samples by Using PLS and Terahertz Time-Domain Spectroscopy].
Wang, Jing-rong; Zhang, Zhuo-yong; Zhang, Zhen-wei; Xiang, Yu-hong
2016-02-01
The development of terahertz technology is attracting broad intention in recent years. The quality identification is important for the quality control of Chinese medicine production. In the present work, terahertz time-domain spectroscopy (THz-TDS) combined with partial least squares (PLS) were used for the identification model building and studied based on 41 official and unofficial rhubarb samples. First, the THz-TDS spectra of rhubarb samples were collected and were preprocessed by using chemometrics methods rather than transformed to absorption spectra. The identification models were then established based on the processed terahertz time domain spectra. The spectral preprocessing methods include Savitzky-Golay (S-G) first derivative, detrending, standard normal transformation (SNV), autoscaling, and mean centering. The identification accuracy of 90% was accomplished by using proper pretreatment methods, which was higher than the classified accuracy of 80% without any preprocessing for the time domain spectra. The component number of the PLS model was evaluated by leave-one-out cross-validation (LOOCV). The minimum values of the root-mean squared error of cross-validation (RMSECV) and root-mean squared error of prediction (RMSEP) were 0.076 6 and 0.169 0 by using mean centering method, respectively. The results of this work showed that the combination of terahertz time domain spectroscopy technology with chemometrics methods, as well as PLS can be applied for the recognition of genuine and counterfeit Chinese herbal medicines, as well as official and unofficial rhubarbs. The advantage of using terahertz time domain spectra directly with no transformation into absorption spectra is: (1) the thickness of samples could not be considered in the model establishment, and (2) the spectral processing was simplified. The proposed method based on the combination of THz-TDS and chemometrics proved to be rapid, simple, non-pollution and solvent free, suitable to be
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.
On the determination of the post-irradiation time from the glow curve of TLD-100
International Nuclear Information System (INIS)
Weinstein, M.; German, U.; Dubinsky, S.; Alfassi, Z.B.
2003-01-01
The ratio of peak 3 to the sum of peaks 4 + 5 in TLD-100 was measured for various pre-irradiation and post-irradiation time periods, under conditions characteristic of routine personal dosimetry. It was confirmed that the value of this ratio depends only on the elapsed time between the prior readout and the present one, independent of the moment when the irradiation took place during the total time interval (storage time). This effect indicates that fading of peak 3 seems to be due mainly to changes in the unoccupied traps, and not to decay of trapped charges, being almost independent of the presence of electrons or holes in the traps. This observation leads to the conclusion that the suggestions in the past to use the decay of peak 3 in TLD-100 for the measurement of the elapsed time between irradiation and readout may have been wrong. On the other hand, the decay of peak 2 can be used to measure the elapsed time from irradiation, since the rate of decay is different when related to pre-irradiation and post-irradiation times, indicating a much higher decay rate of the trapped charges (Randall-Wilkins decay). However, because of the fast decay rate of peak 2, its use for determination of the elapsed time since irradiation is of little practical significance. (author)
Directory of Open Access Journals (Sweden)
Dovrat Kohen
2017-06-01
Full Text Available When subjects are intentionally preparing a curved trajectory, they are engaged in a time-consuming trajectory planning process that is separate from target selection. To investigate the construction of such a plan, we examined the effect of artificially shortening preparation time on the performance of intentionally curved trajectories using the Timed Response task that enforces initiation of movements prematurely. Fifteen subjects performed obstacle avoidance movements toward one of four targets that were presented 25 or 350 ms before the “go” signal, imposing short and long preparation time conditions with mean values of 170 ms and 493 ms, respectively. While trajectories with short preparation times showed target specificity at their onset, they were significantly more variable and showed larger angular deviations from the lines connecting their initial position and the target, compared to the trajectories with long preparation times. Importantly, the trajectories of the short preparation time movements still reached their end-point targets accurately, with comparable movement durations. We hypothesize that success in the short preparation time condition is a result of an online control mechanism that allows further refinement of the plan during its execution and study this control mechanism with a novel trajectory analysis approach using minimum jerk optimization and geometrical modeling approaches. Results show a later agreement of the short preparation time trajectories with the optimal minimum jerk trajectory, accompanied by a later initiation of a parabolic segment. Both observations are consistent with the existence of an online trajectory planning process.Our results suggest that when preparation time is not sufficiently long, subjects execute a more variable and less optimally prepared initial trajectory and exploit online control mechanisms to refine their actions on the fly.
Kohen, Dovrat; Karklinsky, Matan; Meirovitch, Yaron; Flash, Tamar; Shmuelof, Lior
2017-01-01
When subjects are intentionally preparing a curved trajectory, they are engaged in a time-consuming trajectory planning process that is separate from target selection. To investigate the construction of such a plan, we examined the effect of artificially shortening preparation time on the performance of intentionally curved trajectories using the Timed Response task that enforces initiation of movements prematurely. Fifteen subjects performed obstacle avoidance movements toward one of four targets that were presented 25 or 350 ms before the “go” signal, imposing short and long preparation time conditions with mean values of 170 ms and 493 ms, respectively. While trajectories with short preparation times showed target specificity at their onset, they were significantly more variable and showed larger angular deviations from the lines connecting their initial position and the target, compared to the trajectories with long preparation times. Importantly, the trajectories of the short preparation time movements still reached their end-point targets accurately, with comparable movement durations. We hypothesize that success in the short preparation time condition is a result of an online control mechanism that allows further refinement of the plan during its execution and study this control mechanism with a novel trajectory analysis approach using minimum jerk optimization and geometrical modeling approaches. Results show a later agreement of the short preparation time trajectories with the optimal minimum jerk trajectory, accompanied by a later initiation of a parabolic segment. Both observations are consistent with the existence of an online trajectory planning process.Our results suggest that when preparation time is not sufficiently long, subjects execute a more variable and less optimally prepared initial trajectory and exploit online control mechanisms to refine their actions on the fly. PMID:28706478
Layered and Laterally Constrained 2D Inversion of Time Domain Induced Polarization Data
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Auken, Esben
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...... algorithm retrieves consistent values for both the Cole-Cole parameters and the layer thicknesses and is a promising tool for identifying formation boundaries, e.g. in for discriminating sand and clay layers or pollution fans, due to the chargeability of these layers.......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...
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.
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.
Razanskaite-Virbickiene, Dovile; Danyte, Evalda; Mockeviciene, Giedre; Dobrovolskiene, Rimante; Verkauskiene, Rasa; Zalinkevicius, Rimantas
2017-01-19
Cardiovascular autonomic neuropathy (CAN) increases morbidity and mortality in diabetes through association with a high risk of cardiac arrhythmias and sudden death, possibly related to silent myocardial ischemia. During the sub-clinical stage, CAN can be detected through reduction in heart rate variability (HRV). The aim of our study was to estimate if the time and frequency-domain analysis can be valuable for detecting CAN in young patients with type 1 diabetes mellitus (T1DM). For this case control study of evaluation of cardiovascular autonomic function the 15-25 years age group of patients with duration of T1DM more than 9 years (n = 208, 89 males and 119 females) were selected. 67 patients with confirmed CAN were assigned to the "case group" and 141 patients without CAN served as a control group, the duration of T1DM was similar (15.07 ± 4.89 years vs.13.66 ± 4.02 years; p = 0.06) in both groups. Cardiovascular autonomic reflex tests and time and frequency domains analysis of HRV were performed for all subjects. Time domain measures were significantly lower in CAN group compared with control (p patients with CAN. Receivers operating characteristic (ROC) curves were constructed to compare the accuracies of the parameters of time-domain analysis for diagnosing CAN. We estimated a more reliable cut-off value of parameters of time-domain. The CV values in supine position cardiovascular autonomic function, providing more information about sympathetic and parasympathetic activity. The coefficient of variation (time-domain analysis) especially during deep breathing could be valuable for detecting CAN.
International Nuclear Information System (INIS)
Hwang, Young Tae; Jo, Seong Seock; Choi, Jong Won; Ko, Nak Youl
2012-01-01
Based on the data observed and analyzed on a groundwater flow system in the KURT (KAERI Underground Research Tunnel) site, the transport of radionuclides, which were assumed to be released at the supposed position, was calculated on the time-domain. A groundwater pathway from the release position to the surface was identified by simulating the groundwater flow model with the hydrogeological characteristics measured from the field tests in the KURT site. The elapsed time when the radionuclides moved through the pathway is evaluated using TDRW (Time Domain Random Walk) method for simulating the transport on the time-domain. Some retention mechanisms, such as radioactive decay, equilibrium sorption, and matrix diffusion, as well as the advection dispersion were selected as the factors to influence on the elapsed time. From the simulation results, the effects of the sorption and matrix diffusion, determined by the properties of the radionuclides and underground media, on the transport of the radionuclides were analyzed and a decay chain of the radionuclides was also examined. The radionuclide ratio of the mass discharge into the surface environment to the mass released from the supposed repository did not exceed 10 -3 , and it decreased when the matrix diffusion were considered. The method used in this study could be used in preparing the data on radionuclide transport for a safety assessment of a geological disposal facility because the method could evaluate the travel time of the radionuclides considering the transport retention mechanism.
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
International Nuclear Information System (INIS)
Hawking, S.W.; King, A.R.; McCarthy, P.J.
1976-01-01
A new topology is proposed for strongly causal space--times. Unlike the standard manifold topology (which merely characterizes continuity properties), the new topology determines the causal, differential, and conformal structures of space--time. The topology is more appealing, physical, and manageable than the topology previously proposed by Zeeman for Minkowski space. It thus seems that many calculations involving the above structures may be made purely topological
Axes of Discovery: The Time Domain and the Radio Synoptic Survey Telescope
Cordes, J. M.
2008-08-01
As Heraclitus might have said, ``You don't observe the same universe twice,'' and in modern times we recognize the time domain as an important dimension in the overall phase space of variables that characterizes the observable universe. Examples abound across the electromagnetic spectrum and in non-photonic regimes (neutrinos, gravitational waves, cosmic rays). However, while we can glimpse the richness of time-domain phenomena at radio wavelengths, the radio sky is largely unexplored in any comprehensive sense, especially when compared to the successes of wide-field surveys at high energies. Known radio transients are as short as 0.4 ns with an equivalent brightness temperature of 1042 K tep{jmc:he07} related to the coherent nature of pulsar radiation; others with incoherent emission extend to hour and longer time scales with thermal brightness temperatures. Some time-domain properties are intrinsic to sources while others are imposed by multi-path propagation through intervening plasma. This paper discusses both known and speculative aspects of the radio transient sky, with an emphasis on discoveries that can be made with new, appropriately designed instrumentation and telescopes. A generalized survey figure of merit is presented that takes into account the rate and duration of transient celestial events. The key for expanding discovery space is a wide field of view (FoV) combined with adequate sensitivity and high-resolution sampling in time and frequency. I discuss implementation of time-domain studies as an integral part of synoptic survey modes and the potential for cross-wavelength and joint photonic/non-photonic studies. In particular, I make the case for designing and operating the mid-frequency-range Square Kilometer Array as a Radio Synoptic Survey Telescope.
Formation and life-time of memory domains in the dissipative quantum model of brain
Alfinito, E.; Vitiello, G.
2000-01-01
We show that in the dissipative quantum model of brain the time-dependence of the frequencies of the electrical dipole wave quanta leads to the dynamical organization of the memories in space (i.e. to their localization in more or less diffused regions of the brain) and in time (i.e. to their longer or shorter life-time). The life-time and the localization in domains of the memory states also depend on internal parameters and on the number of links that the brain establishes with the external...
Real time control of curved laser welding processes by cellular neural networks (CNN): first results
Nicolosi, L.; Tetzlaff, R.
2010-10-01
In the last decades the laser beam welding (LBW) has outclassed older welding techniques in the industrial scenario. Despite the improvement in welding technology, sophisticated methods of fault detection are not commonly used in commercially available equipments yet. A recent analysis of process images have revealed the possibility to build up a real time closed loop control system. By the use of image based quality features, a feedback signal can be provided to maintain the process in the desired state. The development of the presented visual control system has been focused on the adjustment of the laser power according to the detection of the so called full penetration hole. Due to the high dynamics of the laser welding, a fast real time image processing with controlling rates in the multi kilo Hertz range is necessary to have a robust feedback control. In this paper an algorithm for the real time control of welding processes is described. It has been implemented on the Eye-RIS v1.2, a visual system which mounts a cellular structure. By applying this algorithm in real time applications, controlling rates of about 7 kHz can be reached. In the following some real time control results are also described.
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.
Fictitious Domain Technique for the Calculation of Time-Periodic Solutions of Scattering Problem
Directory of Open Access Journals (Sweden)
Ling Rao
2011-01-01
Full Text Available The fictitious domain technique is coupled to the improved time-explicit asymptotic method for calculating time-periodic solution of wave equation. Conventionally, the practical implementation of fictitious domain method relies on finite difference time discretizations schemes and finite element approximation. Our new method applies finite difference approximations in space instead of conventional finite element approximation. We use the Dirac delta function to transport the variational forms of the wave equations to the differential form and then solve it by finite difference schemes. Our method is relatively easier to code and requires fewer computational operations than conventional finite element method. The numerical experiments show that the new method performs as well as the method using conventional finite element approximation.
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
Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time-domain spe......Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time...... 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....
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-Varying Degree of Wage Indexation and the New Keynesian Wage Phillips Curve
J.A. Attey (Jonathan)
2016-01-01
textabstractCost-of-Living-Adjustment (COLA) coverage figures suggest a time variation in the degree of wage indexation. In spite of this observation, most current literature conveniently assume a constant degree of indexation as this variable is not directly observable. This study intends to
Analysis of subnanosecond fluorescence decay curves with a 5GHz real time detection system
International Nuclear Information System (INIS)
Cunin, B.; Heisel, F.; Knispel, G.; Miehe, J.A.; Sipp, B.
1975-01-01
This paper presents a detailed description and a review on the characteristics of a fast vacuum photoelectric cell associated with a high speed cathode ray tube. In addition, this system is used to measure short-lived fluorescence decay times [fr
An application of modular inclusion to quantum field theory in curved space-time
International Nuclear Information System (INIS)
Summers, S.J.; Verch, R.
1993-09-01
Applying recent results by Borchers connecting geometric modular action, modular inclusion and the spectrum condition, earlier results by Kay and Wald concerning the temperature of physically significant states of the linear Hermitean scalar field propagating in the background of a space-time with a bifurcate Killing horizon are generalized. (orig.)
Temporal Dominance of Sensations: Construction of the TDS curves and comparison with time-intensity
Pineau, N.; Schlich, P.; Cordelle, S.; Mathonniére, C.; Issanchou, S.; Imbert, A.; Rogeaux, M.; Etiévant, P.; Köster, E.P.
2009-01-01
The evaluation of the temporality of the sensory perception in food products is mainly assessed using the time¿intensity (TI) methodology. This approach is useful for studying the temporal aspects of the perception of a given sensory attribute in a product. When TI is used for several attributes, it
International Nuclear Information System (INIS)
Wollenweber, S.D.; Hichwa, R.D.; Ponto, L.L.B.
1996-01-01
A simple, automated on-line detector system has been fabricated and implemented to detect the arterial time-activity curve (TAC) for water PET studies. This system offers two significant improvements over existing systems: a pump mechanism is not required to control arterial blood flow through the detector and dispersion correction of the time-activity curve is unnecessary. The positrons emanating from a thin-walled, 0.134 cm inner-diameter plastic tube are detected by a 0.5 cm wide by 1.0 cm long by 0.1 cm thick plastic scintillator mounted to a miniature PMT. Photon background is shielded by a 2.0 cm thick cylindrical lead shield. Mean cerebral blood flow (mCBF) calculated from the TAC determined by 1-second automated sampling was compared to that calculated from every 5-second integrated manual samples. Improvements in timing resolution (1-sec vs. 5-sec) cause small but significant differences between the two sampling methods. Dispersion is minimized due to small tubing diameters, short lengths of tubing between the radial arterial sampling site and the detector and the presence of a 3-way valve 10 cm proximal to the detector
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
Real time control of curved laser welding processes by cellular neural networks (CNN): first results
Nicolosi, L.; Tetzlaff, R.
2010-01-01
In the last decades the laser beam welding (LBW) has outclassed older welding techniques in the industrial scenario. Despite the improvement in welding technology, sophisticated methods of fault detection are not commonly used in commercially available equipments yet. A recent analysis of process images have revealed the possibility to build up a real time closed loop control system. By the use of image based quality features, a feedback signal can be provided to maintain th...
Fadel, Maya Abou; de Juan, Anna; Vezin, Hervé; Duponchel, Ludovic
2016-12-01
Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that is able to characterize radicals formed in kinetic reactions. However, spectral characterization of individual chemical species is often limited or even unmanageable due to the severe kinetic and spectral overlap among species in kinetic processes. Therefore, we applied, for the first time, multivariate curve resolution-alternating least squares (MCR-ALS) method to EPR time evolving data sets to model and characterize the different constituents in a kinetic reaction. Here we demonstrate the advantage of multivariate analysis in the investigation of radicals formed along the kinetic process of hydroxycoumarin in alkaline medium. Multiset analysis of several EPR-monitored kinetic experiments performed in different conditions revealed the individual paramagnetic centres as well as their kinetic profiles. The results obtained by MCR-ALS method demonstrate its prominent potential in analysis of EPR time evolved spectra. Copyright © 2016 Elsevier B.V. All rights reserved.
Logan, G D
1992-09-01
The instance theory assumes that automatic performance is based on single-step direct-access retrieval from memory of prior solutions to present problems. The theory predicts that the shape of the learning curve depends on the shape of the distribution of retrieval times. One can deduce from the fundamental assumptions of the theory that (1) the entire distribution of reaction times, not just the mean, will decrease as a power function of practice; (2) asymptotically, the retrieval-time distribution must be a Weibull distribution; and (3) the exponent of the Weibull, which is the parameter that determines its shape, must be the reciprocal of the exponent of the power function. These predictions were tested and mostly confirmed in 12 data sets from 2 experiments. The ability of the instance theory to predict the power law is contrasted with the ability of other theories to account for it.
Mathematical Framework for Hydromechanical Time-Domain Simulation of Wave Energy Converters
Directory of Open Access Journals (Sweden)
J. Seixas de Medeiros
2018-01-01
Full Text Available Efficient design of wave energy converters based on floating body motion heavily depends on the capacity of the designer to accurately predict the device’s dynamics, which ultimately leads to the power extraction. We present a (quasi-nonlinear time-domain hydromechanical dynamic model to simulate a particular type of pitch-resonant WEC which uses gyroscopes for power extraction. The dynamic model consists of a time-domain three-dimensional Rankine panel method coupled, during time integration, with a MATLAB algorithm that solves for the equations of the gyroscope and Power Take-Off (PTO. The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time integration using a 4th-order Runge-Kutta method. The panel method, accounting for the gyroscope and PTO dynamics, is then used for the calculation of the optimal flywheel spin, PTO damping, and average power extracted, completing the basic design cycle of the WEC. The proposed numerical method framework is capable of considering virtually any type of nonlinear force (e.g., nonlinear wave loads and it is applied and verified in the paper against the traditional frequency domain linear model. It proved to be a versatile tool to verify performance in resonant conditions.
Petrov, Oleg V.; Stapf, Siegfried
2017-06-01
This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials. On the other hand, the calculation of LMs does not require knowing the actual distribution function and is reduced to a numerical integration of original data. The performance of this method has been tested on both synthetic and experimental NMR relaxation data which differ in a signal-to-noise ratio, the sampling range and the sampling rate. The calculation of two lower-order LMs, the log-mean time and the log-variance, has proved robust against deficiencies of the experiment such as scattered data point and incomplete sampling. One may consider using them as such to monitor formation of a heterogeneous structure, e.g., in phase separation, vitrification, polymerization, hydration, aging, contrast agent propagation processes. It may also assist in interpreting frequency and temperature dependences of relaxation, revealing a crossover from slow to fast exchange between populations. The third LM was found to be a less reliable quantity due to its susceptibility to the noise and must be used with caution.
Time domain characterization for the electric field considering a Chinese female physical phantom
Yang, Xiaodong; Zhang, Qing
2015-02-01
Recently, wireless communications around the human body, which are essential for wireless vital data monitoring, have been widely studied. Besides statistical channel modeling, characterization of time-varying electric field is also highly necessary to understand the communication mechanism in this area; however, few studies have been conducted. In this paper, time-varying electric fields, both on the digital human body and in the two-dimensional space around the human body, were studied through the finite-difference time-domain (FDTD) numerical analysis.
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.
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....
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.
THE SOLUTION OF THE CABLE EQUATIONS BY MEANS OF FINITE DIFFERENCE TIME DOMAIN METHOD
Directory of Open Access Journals (Sweden)
Patsiuk V.I.
2010-04-01
Full Text Available The analysis and comparison of accuracy of numerical solutions received by Finite Difference Time Domain (FDTD method and Godunov's method at the solution of the cable equations is carried out. It is demonstrated, that at sudden short circuits and at transition to idling mode in numerical solutions received by means of FDTD method for long lines with the distributed parameters appear strong nonphysical oscillations. It is shown, that the settlement scheme offered by authors on the basis of Godunov's method is deprived these lacks and provides high accuracy for the numerical solutions received at the analysis of dynamic modes in long lines, caused by sudden short circuits and line transitions in an idling mode. Key words: cable equations, finite difference time domain method, Godunov’s scheme.
Abedi, Reza; Mudaliar, Saba
2017-12-01
We present an asynchronous spacetime discontinuous Galerkin (aSDG) method for time domain electromagnetics in which space and time are directly discretized. By using differential forms we express Maxwell's equations and consequently their discontinuous Galerkin discretization for arbitrary domains in spacetime. The elements are discretized with electric and magnetic basis functions that are discontinuous across all inter-element boundaries and can have arbitrary high and per element spacetime orders. When restricted to unstructured grids that satisfy a specific causality constraint, the method has a local and asynchronous solution procedure with linear solution complexity in terms of the number of elements. We numerically investigate the convergence properties of the method for 1D to 3D uniform grids for energy dissipation, an error relative to the exact solution, and von Neumann dissipation and dispersion errors. Two dimensional simulations demonstrate the effectiveness of the method in resolving sharp wave fronts.
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
Terahertz quasi time-domain spectroscopy based on telecom technology for 1550 nm.
Kohlhaas, Robert B; Rehn, Arno; Nellen, Simon; Koch, Martin; Schell, Martin; Dietz, Roman J B; Balzer, Jan C
2017-05-29
We present a fiber-coupled terahertz quasi time-domain spectroscopy system driven by a laser with a central wavelength of 1550 nm. By using a commercially available multimode laser diode in combination with state-of-the-art continuous wave antennas, a bandwidth of more than 1.8 THz is achieved. The peak signal-to-noise ratio is around 60 dB. A simulation based on the optical spectrum of the laser diode and the transfer function of the THz path is in agreement with the experimental results. The system is used to extract the refractive index from two different samples and the results indicate that the performance is up to 1.8 THz comparable to a terahertz time-domain spectroscopy system.
Chen, Chien-Hung; Chiu, Chien-Ching; Sun, Chi-Hsien; Chang, Wan-Ling
2011-01-01
This paper reports a two-dimensional time-domain inverse scattering algorithm based upon the finite-difference time domain method (FDTD) for determining the shape of a perfectly conducting cylinder. FDTD is used to solve the scattering electromagnetic wave of a perfectly conducting cylinder. The inverse problem is resolved by an optimization approach and the global searching scheme asynchronous particle swarm optimization is then employed to search the parameter space. By properly processing the scattered field, some electromagnetic properties can be reconstructed. A set of representative numerical results is presented to demonstrate that the proposed approach is able to efficiently reconstruct the electromagnetic properties of metallic scatterer even when the initial guess is far away from the exact one. In addition, the effects of Gaussian noises on imaging reconstruction are also investigated.
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.
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.
General-Covariant Quantum Mechanics of Dirac Particle in Curved Space-Times
International Nuclear Information System (INIS)
Tagirov, Eh.A.
1994-01-01
A general covariant analog of the standard non-relativistic Quantum Mechanics with relativistic corrections in normal geodesic frames in the general Riemannian space-time is constructed for the Dirac particle. Not only the Pauli equation with hermitian Hamiltonian and the pre-Hilbert structure of space of its solutions but also the matrix elements of hermitian operators of momentum, (curvilinear) spatial coordinates and spin of the particle are deduced as general-covariant asymptotic approximation in c -2 , c being the velocity of light, to their naturally determined general-relativistic pre images. It is shown that the Hamiltonian in the Pauli equation originated by the Dirac equation is unitary equivalent to the operator of energy, originated by the metric energy-momentum tensor of the spinor field. Commutation and other properties of the observables connected with the considered change of geometrical background of Quantum Mechanics are briefly discussed. 7 refs
Water percolation estimated with time domain reflectometry (TDR) in drainage lysimeters
Alisson Jadavi Pereira da Silva; Eugênio Ferreira Coelho
2013-01-01
Due to the difficulty of estimating water percolation in unsaturated soils, the purpose of this study was to estimate water percolation based on time-domain reflectometry (TDR). In two drainage lysimeters with different soil textures TDR probes were installed, forming a water monitoring system consisting of different numbers of probes. The soils were saturated and covered with plastic to prevent evaporation. Tests of internal drainage were carried out using a TDR 100 unit with constant dielec...
Control of linear systems subject to time-domain constraints with polynomial pole placement and LMIs
Czech Academy of Sciences Publication Activity Database
Henrion, D.; Tarbouriech, S.; Kučera, Vladimír
2005-01-01
Roč. 50, č. 9 (2005), s. 1360-1364 ISSN 0018-9286 R&D Projects: GA MŠk 1M0567; GA ČR GA102/05/0011 Institutional research plan: CEZ:AV0Z10750506 Keywords : linear matrix inequality (LMI) * linear systems * pole placement * polynomials * time-domain constraints Subject RIV: BC - Control Systems Theory Impact factor: 2.159, year: 2005
Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study
Di Sieno, Laura; Zouaoui, Judy; Hervé, Lionel; Pifferi, Antonio; Farina, Andrea; Martinenghi, Edoardo; Derouard, Jacques; Dinten, Jean-Marc; Dalla Mora, Alberto
2016-01-01
International audience; Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thu...
Modelling and analysis of nonlinear thermoacoustic systems using frequency and time domain methods
Orchini, Alessandro
2017-01-01
In this thesis, low-order nonlinear models for the prediction of the nonlinear behaviour of thermoacoustic systems are developed. These models are based on thermoacoustic networks, in which linear acoustics is combined with a nonlinear heat release model. The acoustic networks considered in this thesis can take into account mean flow and non-trivial acoustic reflection coefficients, and are cast in state-space form to enable analysis both in the frequency and time domains. Starting from l...
1972-01-01
The theoretical basis for the ASYSTD program is discussed in detail. In addition, the extensive bibliography given in this document illustrates some of the extensive work accomplished in the area of time domain simulation. Additions have been in the areas of modeling and language program enhancements, orthogonal transform modeling, error analysis, general filter models, BER measurements, etc. Several models have been developed which utilize the COMSAT generated orthogonal transform algorithms.
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...
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
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...
Factor models in high-dimensional time series : A time-domain approach
Hallin, M.; Lippi, M.
2013-01-01
High-dimensional time series may well be the most common type of dataset in the so-called “big data” revolution, and have entered current practice in many areas, including meteorology, genomics, chemometrics, connectomics, complex physics simulations, biological and environmental research, finance
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...
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
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.
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.
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.
Do "Consumer-Directed" health plans bend the cost curve over time?
Haviland, Amelia M; Eisenberg, Matthew D; Mehrotra, Ateev; Huckfeldt, Peter J; Sood, Neeraj
2016-03-01
"Consumer-Directed" Health Plans (CDHPs), those with high deductibles and personal medical accounts, are intended to reduce health care spending through greater patient cost exposure. Prior research agrees that in the first year, CDHPs reduce spending. There is little research and in it results are mixed regarding the impact of CDHPs over the longer term. We add to this literature with an intent-to-treat, difference-in-differences analysis of health care spending over up to three years post CDHP offer among 13 million person-years of data from 54 large US firms, half of which offered CDHPs. To strengthen the identification, we balance observables over time within firm, by developing weights through a machine learning algorithm, generalized boosted regression. We find that spending is reduced for those in firms offering CDHPs in all three years post offer relative to firms continuing to offer lower-deductible plans. The reductions are driven by spending decreases in outpatient care and pharmaceuticals, with no evidence of increases in emergency department or inpatient care over the three-year window. Copyright © 2016 Elsevier B.V. All rights reserved.
DEFF Research Database (Denmark)
Sichani, Mahdi Teimouri; Brincker, Rune
2008-01-01
Computing displacements of a structure from its measured accelerations has been major concern of some fields of engineering such as earthquake engineering. In vibration engineering also displacements are preferred to acceleration histories occasionally i.e. in the determination of forces applied...... on a structure. In brief the major problem that accompanies reconstruction of true displacement from acceleration record is the unreal drift observed in the double integrated acceleration. Purpose of the present work is to address source of the problem, introduce its treatments, show how they work and compare...
Formenti, P; Umbrello, M; Graf, J; Adams, A B; Dries, D J; Marini, J J
2017-08-01
The stress index (SI) is a parameter that characterizes the shape of the airway pressure-time profile (P/t). It indicates the slope progression of the curve, reflecting both lung and chest wall properties. The presence of pleural effusion alters the mechanical properties of the respiratory system decreasing transpulmonary pressure (Ptp). We investigated whether the SI computed using Ptp tracing would provide reliable insight into tidal recruitment/overdistention during the tidal cycle in the presence of unilateral effusion. Unilateral pleural effusion was simulated in anesthetized, mechanically ventilated pigs. Respiratory system mechanics and thoracic computed tomography (CT) were studied to assess P/t curve shape and changes in global lung aeration. SI derived from airway pressure (Paw) was compared with that calculated by Ptp under the same conditions. These results were themselves compared with quantitative CT analysis as a gold standard for tidal recruitment/hyperinflation. Despite marked changes in tidal recruitment, mean values of SI computed either from Paw or Ptp were remarkably insensitive to variations of PEEP or condition. After the instillation of effusion, SI indicates a preponderant over-distension effect, not detected by CT. After the increment in PEEP level, the extent of CT-determined tidal recruitment suggest a huge recruitment effect of PEEP as reflected by lung compliance. Both SI in this case were unaffected. We showed that the ability of SI to predict tidal recruitment and overdistension was significantly reduced in a model of altered chest wall-lung relationship, even if the parameter was computed from the Ptp curve profile.
International Nuclear Information System (INIS)
Kim, Ok-Hwa
1986-01-01
The noninvasive nature of the radionuclide angiocardiography provided a useful approach for the evaluation of left-to-right cardiac shunts (LRCS). While the qualitative information can be obtained by inspection of serial radionuclide angiocardiograms, the quantitative information of radionuclide angiocardiography can be obtained by the analysis of time-activity curves using advanced computer system. The count ratios method and pulmonary-to-systemic flow ratio (QP/QS) by gamma variate fit method were used to evaluate the accuracy of detection and localization of LRCS. One hundred and ten time-activity curves were analyzed. There were 46 LRCS (atrial septal defects 11, ventricular septal defects 22, patent ductus arteriosus 13) and 64 normal subjects. By computer analysis of time-activity histograms of the right atrium, ventricle and the lungs separately, the count ratios modified by adding the mean cardiac transit time were calculated in each anatomic site. In normal subjects the mean count ratios in the right atrium, ventricle and lungs were 0.24 on average. In atrial septal defects, the count ratios were high in the right atrium, ventricle and lungs, whereas in ventricular septal defects the count ratios were higher only in the right ventricle and lungs. Patent ductus arteriosus showed normal count ratios in the heart but high count ratios were obtained in the lungs. Thus, this count ratios method could be separated normal from those with intracardiac or extracardiac shunts, and moreover, with this method the localization of the shunts level was possible in LRCS. Another method that could differentiate the intracardiac shunts from extracardiac shunts was measuring QP/QS in the left and right lungs. In patent ductus arteriosus, the left lung QP/QS was hight than those of the right lung, whereas in atrial septal defects and ventricular septal defects QP/QS ratios were equal in both lungs. (J.P.N.)
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.
International Nuclear Information System (INIS)
Kim, Byung Ki; Lee, Hui Joong; Lee, Jong Min; Kim, Yong Joo; Kang, Duck Sik
1999-01-01
To determine the usefulness of MgSO 4 for measuring the systemic circulation time. Systemic circulation time, defined as elapsed time from the injection of MgSO 4 solution to the point of pharyngeal burning sensation, was measured in 63 volunteers. MgSO 4 was injected into a superficial vein of an upper extremity. Using dynamic electron beam computed tomography at the level of the abdominal aorta and celiac axis, a time-intensity curve was plotted, and for these two locations, maximal enhancement time was compared. For 60 of the 63 subjects, both systemic circulation time and maximal enhancement time were determined. Average systemic circulation time was 17.4 (SD:3.6) secs. and average maximal enhancement times at the level of the abdominal aorta and celiac axis were 17.5 (SD:3.0) secs. and 18.5 (SD:3.2) secs., respectively. Correlation coefficients between systemic circulation time and maximal enhancement time for the abdominal aorta and celiac axis were 0.73 (p 4 injection and maximal enhancement time for the abdominal aorta showed significant correlation. Thus, to determine the appropriate scanning time in contrast-enhanced radiological studies, MgSO 4 can be used instead of a test bolus study
Singh, Prashant; Mustapha, Azlin
2014-12-01
Multiple drug resistance in Salmonella is an emerging problem in the area of food safety. Depending on the virulence and antibiotic resistance characteristics of the Salmonella strain, infections of varying severity could result. In this study, a multiplex melt curve real-time PCR assay for the detection of virulent and antibiotic resistance strains of Salmonella was developed with two primer sets. The first set targets the virulence gene, invasin (invA), and tetracycline (tetG), streptomycin (aadA2) and sulphonamide (sulI) antibiotic resistance genes, and the second set amplifies ampicillin (blaPSE,blaTEM) and chloramphenicol (floR) resistance genes. The multiplex assay was evaluated using 41 Salmonella strains and was further tested on eight different artificially inoculated food samples. The fluorescent DNA intercalating dye, SYTO9, generated high resolution melt curve peaks and, hence, was used for the development of the assay. This multiplex assay worked efficiently over a DNA concentration range of 20 ng-200 fg and showed a sensitivity of 290 CFU/mL with serially diluted broth cultures. The detection limit for un-enriched artificially inoculated food samples was 10(4) CFU/g, but an enrichment period of 6 h allowed for detection of 10 CFU/g of cells in the samples. Copyright © 2014 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
María Ballester
Full Text Available BACKGROUND: Real-time quantitative PCR (qPCR is still the gold-standard technique for gene-expression quantification. Recent technological advances of this method allow for the high-throughput gene-expression analysis, without the limitations of sample space and reagent used. However, non-commercial and user-friendly software for the management and analysis of these data is not available. RESULTS: The recently developed commercial microarrays allow for the drawing of standard curves of multiple assays using the same n-fold diluted samples. Data Analysis Gene (DAG Expression software has been developed to perform high-throughput gene-expression data analysis using standard curves for relative quantification and one or multiple reference genes for sample normalization. We discuss the application of DAG Expression in the analysis of data from an experiment performed with Fluidigm technology, in which 48 genes and 115 samples were measured. Furthermore, the quality of our analysis was tested and compared with other available methods. CONCLUSIONS: DAG Expression is a freely available software that permits the automated analysis and visualization of high-throughput qPCR. A detailed manual and a demo-experiment are provided within the DAG Expression software at http://www.dagexpression.com/dage.zip.
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
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.
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
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.
Mie scattering in the time domain. Part 1. The role of surface waves.
Lock, James A; Laven, Philip
2011-06-01
We computed the Debye series p=1 and p=2 terms of the Mie scattered intensity as a function of scattering angle and delay time for a linearly polarized plane wave pulse incident on a spherical dielectric particle and physically interpreted the resulting numerical data. Radiation shed by electromagnetic surface waves plays a prominent role in the scattered intensity. We determined the surface wave phase and damping rate and studied the structure of the p=1,2 surface wave glory in the time domain.
Giuggioli, Luca; Pérez-Becker, Sebastian; Sanders, David P.
2013-02-01
We develop an analytical method to calculate encounter times of two random walkers in one dimension when each individual is segregated in its own spatial domain and shares with its neighbor only a fraction of the available space, finding very good agreement with numerically exact calculations. We model a population of susceptible and infected territorial individuals with this spatial arrangement, and which may transmit an epidemic when they meet. We apply the results on encounter times to determine analytically the macroscopic propagation speed of the epidemic as a function of the microscopic characteristics: the confining geometry, the animal diffusion constant, and the infection transmission probability.
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.
Pliquett, Uwe; Schönfeldt, Markus; Barthel, Andreas; Frense, Dieter; Nacke, Thomas; Beckmann, Dieter
2011-07-01
Fast impedance measurements are often performed in time domain utilizing broad bandwidth excitation signals. Other than in frequency domain measurements harmonic distortion cannot be compensated which requires careful design of the analog front end. In order to minimize the influence of electrode polarization and noise, especially in low-frequency measurements, current injection shows several advantages compared to voltage application. Here, we show an active front end based on a voltage-controlled current source for a wide range of impedances. Using proper feedback, the majority of the parasitic capacitances are compensated. The bandwidth ranges from dc to 20 MHz for impedance magnitude below 5 kΩ. The output is a symmetric signal without dc-offset which is accomplished by combination of a current conveyor and a voltage inverter. An independent feedback loop compensates the offset arising from asymmetries within the circuitry. We focused especially on the stability of the current source for usage with small metal electrodes in aqueous solutions. At the monitor side two identical, high input impedance difference amplifiers convert the net current through the object and the voltage dropping across into a 50 Ω symmetric output. The entire circuitry is optimized for step response making it suitable for fast time domain measurements.
Quantum mechanics in curved space-time and its consequences for the theory on the flat space-time
International Nuclear Information System (INIS)
Tagirov, E.A.
1997-01-01
Thus, the structure is extracted from the initial general-relativistic setting of the quantum theory of the scalar field φ that can be considered as quantum mechanics in V 1,3 in the Schroedinger picture, which includes relativistic corrections not only in the Hamiltonian of the Schroedinger equation but also in the operators of primary observables. In the terms pertaining to these corrections the operators differ from their counterparts resulting from quantization of a classical spinless particle. In general, they do not commute at all and thus the quantum phase space loses the feature that half its coordinates retain a manifold structure, which Biedenharn called 'a miracle of quantization'. This non-commutativity expands up to the exact (in the sense 'non-asymptotic in c -2 ') quantum mechanics of a free motion in the Minkowski space-time if curvilinear coordinates are taken as observables, which are necessary if non-inertial frames of references are considered
Soueid Ahmed, A.; Revil, A.
2018-04-01
Induced polarization (IP) of porous rocks can be associated with a secondary source current density, which is proportional to both the intrinsic chargeability and the primary (applied) current density. This gives the possibility of reformulating the time domain induced polarization (TDIP) problem as a time-dependent self-potential-type problem. This new approach implies a change of strategy regarding data acquisition and inversion, allowing major time savings for both. For inverting TDIP data, we first retrieve the electrical resistivity distribution. Then, we use this electrical resistivity distribution to reconstruct the primary current density during the injection/retrieval of the (primary) current between the current electrodes A and B. The time-lapse secondary source current density distribution is determined given the primary source current density and a distribution of chargeability (forward modelling step). The inverse problem is linear between the secondary voltages (measured at all the electrodes) and the computed secondary source current density. A kernel matrix relating the secondary observed voltages data to the source current density model is computed once (using the electrical conductivity distribution), and then used throughout the inversion process. This recovered source current density model is in turn used to estimate the time-dependent chargeability (normalized voltages) in each cell of the domain of interest. Assuming a Cole-Cole model for simplicity, we can reconstruct the 3-D distributions of the relaxation time τ and the Cole-Cole exponent c by fitting the intrinsic chargeability decay curve to a Cole-Cole relaxation model for each cell. Two simple cases are studied in details to explain this new approach. In the first case, we estimate the Cole-Cole parameters as well as the source current density field from a synthetic TDIP data set. Our approach is successfully able to reveal the presence of the anomaly and to invert its Cole
A Moving Window Technique in Parallel Finite Element Time Domain Electromagnetic Simulation
Energy Technology Data Exchange (ETDEWEB)
Lee, Lie-Quan; Candel, Arno; Ng, Cho; Ko, Kwok; /SLAC
2010-06-07
A moving window technique for the finite element time domain (FETD) method 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 key 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 FETD method and the advantages of using the moving window technique are discussed.
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.
Enhanced Measurement of Paper Basis Weight Using Phase Shift in Terahertz Time-Domain Spectroscopy
Directory of Open Access Journals (Sweden)
Mengbao Fan
2017-01-01
Full Text Available THz time-domain spectroscopy has evolved as a noncontact, safe, and efficient technique for paper characterization. Our previous work adopted peak amplitude and delay time as features to determine paper basis weight using terahertz time-domain spectroscopy. However, peak amplitude and delay time tend to suffer from noises, resulting in degradation of accuracy and robustness. This paper proposes a noise-robust phase-shift based method to enhance measurements of paper basis weight. Based on Fresnel Formulae, the physical relationship between phase shift and paper basis weight is formulated theoretically neglecting multiple reflections in the case of normal incidence. The established formulation indicates that phase shift correlates linearly with paper basis weight intrinsically. Subsequently, paper sheets were stacked to fabricate the samples with different basis weights, and experimental results verified the developed mathematical formulation. Moreover, a comparison was made between phase shift, peak amplitude, and delay time with respect to linearity, accuracy, and noise robustness. The results show that phase shift is superior to the others.
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.
David-Neto, Elias; Araujo, Lilian Pereira; Feres Alves, Cristiane; Sumita, Nairo; Romano, Pascoalina; Yagyu, Elisa Midori; Nahas, William Carlos; Ianhez, Luiz Estevam
2002-08-01
The complete area under the time-concentration curve (AUC) is considered the gold standard for cyclosporin A (CsA) monitoring, particularly in pediatric kidney graft recipients who have great absorption and drug clearance variability. However, complete AUC is time-consuming and expensive. For this reason, we retrospectively reviewed 131 complete 4-h AUC (AUC0-4) performed in 34 children (mean age 10.6 +/- 2 yr) in order to construct an equation to calculate AUC0-4. The median time after transplantation was 540 (range: 247-1,358) days. Multiple regression analysis was performed either with a single variable or with a combination of two variables. CsA blood concentration at the second hour after the oral morning dose (C2) was the best predictor of AUC0-4, where AUC0-4 = 424 + (2.65 x C2), R2 = 0.81, p time-periods, C2 was the best parameter to use to calculate AUC0-4. The equations obtained during these two time-periods were very close to the one for the whole population. Our data shows that C2 can be safely used to estimate AUC0-4. However, for values above 4,000 ng/h/mL, the formula overestimates the trapezoidal AUC0-4. The C2 equation simplifies the CsA monitoring as a result of its high predictive value and clinical feasibility.
Fukunaga, Kaori; Ikari, Tomofumi; Iwai, Kikuko
2016-02-01
The terahertz pulsed time-domain imaging technique and near-infrared observation were applied to investigate an oil painting on canvas by Pablo Picasso. The multilayer structure is clearly observed in cross-sectional image by terahertz pulsed time-domain imaging, and particular Cubism style lines were revealed under newly painted area by near-infrared image.
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....
Gao, Xueping; Zhao, Guixia; Zhang, Chen; Wang, Yan
2018-02-07
Exposure time is an important characteristic for hydrodynamics that has simultaneous impacts on the biochemical processes in tidal systems. To eliminate man-made errors, decrease computational effort, and increase simulation efficiency, exposure time was evaluated under different hydrodynamic conditions for a bay to investigate the impact of the external domain on the accuracy of the computational results for exposure time. The exposure time was explicitly defined and computed using a hydrodynamic model and tracer experiments for a set of ten external domain sizes (EDS), five external domain lengths (EDL), and three special hydrodynamic conditions. The results indicated that the external domain had a significant influence on the exposure time, and the intensity of this influence was related to hydrodynamic conditions. The sensitivity of the exposure time to the external domain increased with increasing tidal range, while freshwater inflows decreased this sensitivity. However, the variation trends for exposure time with different EDS and EDL were independent of the hydrodynamic conditions. Considering the computational efficiency (maximum), the calculated error (minimum) of the exposure time, and the impact of the boundary conditions (minimum), the recommended EDS and EDL range from 9 to 13 times the initial domain size and 1.30 to 1.45 times the length in the bay, respectively. The research regarding exposure time and external domains not only helps to eliminate the errors caused by man-made factors and reduce the computational effort but also provides a reference for understanding the interrelationship between coastal waters, reciprocating flow, and the water environment.
In-Situ Measurement of Vitamin C Content in Commercial Tablet Products by Terahertz Time-Domain
Kang, JuHee; Song, Jeonghun; Jung, Tae Sub; Kwak, Kyungwon; Chun, Hyang Sook
2018-01-01
Terahertz time-domain spectroscopy (THz-TDS) was applied to investigate the feasibility of in-situ measuring vitamin C content in commercial tablet products without any pretreatments. Characteristic absorption peaks of vitamin C were analyzed with quantum mechanical calculation to reveal the molecular origin of them. The peak appearing at 1.08 THz was then selected and tested for its suitability as a fingerprint signal for analyzing the vitamin C content in dietary supplement tablets. There are a couple of factors influencing THz absorbance other than concentration. Among those, the effects of tablet thickness and types of excipients in the tablet products were found to be significant, and were corrected with the calibration curve to determine vitamin C concentration in tablet forms. Furthermore, commercial tablet products in the market were analyzed using THz-TDS and the measured vitamin C contents were in good agreement with those determined using a reference method (high-performance liquid chromatography). Thus, our results suggest that THz-TDS can be used for the in-situ analysis of vitamin C in commercial tablet products.
Azad, Abul Kalam; Khan, Faisal Nadeem; Alarashi, Waled Hussein; Guo, Nan; Lau, Alan Pak Tao; Lu, Chao
2017-07-10
We propose and experimentally demonstrate the use of principal component analysis (PCA) based pattern recognition to extract temperature distribution from the measured Brillouin gain spectra (BGSs) along the fiber under test (FUT) obtained by Brillouin optical time domain analysis (BOTDA) system. The proposed scheme employs a reference database consisting of relevant ideal BGSs with known temperature attributes. PCA is then applied to the BGSs in the reference database as well as to the measured BGSs so as to reduce their size by extracting their most significant features. Now, for each feature vector of the measured BGS, we determine its best match in the reference database comprised of numerous reduced-size feature vectors of the ideal BGSs. The known temperature attribute corresponding to the best-matched BGS in the reference database is then taken as the extracted temperature of the measured BGS. We analyzed the performance of PCA-based pattern recognition algorithm in detail and compared it with that of curve fitting method. The experimental results validate that the proposed technique can provide better accuracy, faster processing speed and larger noise tolerance for the measured BGSs. Therefore, the proposed PCA-based pattern recognition algorithm can be considered as an attractive method for extracting temperature distributions along the fiber in BOTDA sensors.
In-Situ Measurement of Vitamin C Content in Commercial Tablet Products by Terahertz Time-Domain
Kang, JuHee; Song, Jeonghun; Jung, Tae Sub; Kwak, Kyungwon; Chun, Hyang Sook
2018-04-01
Terahertz time-domain spectroscopy (THz-TDS) was applied to investigate the feasibility of in-situ measuring vitamin C content in commercial tablet products without any pretreatments. Characteristic absorption peaks of vitamin C were analyzed with quantum mechanical calculation to reveal the molecular origin of them. The peak appearing at 1.08 THz was then selected and tested for its suitability as a fingerprint signal for analyzing the vitamin C content in dietary supplement tablets. There are a couple of factors influencing THz absorbance other than concentration. Among those, the effects of tablet thickness and types of excipients in the tablet products were found to be significant, and were corrected with the calibration curve to determine vitamin C concentration in tablet forms. Furthermore, commercial tablet products in the market were analyzed using THz-TDS and the measured vitamin C contents were in good agreement with those determined using a reference method (high-performance liquid chromatography). Thus, our results suggest that THz-TDS can be used for the in-situ analysis of vitamin C in commercial tablet products.
Duncan, Eilidh M; Francis, Jill J; Johnston, Marie; Davey, Peter; Maxwell, Simon; McKay, Gerard A; McLay, James; Ross, Sarah; Ryan, Cristín; Webb, David J; Bond, Christine
2012-09-11
Prescribing errors are a major source of morbidity and mortality and represent a significant patient safety concern. Evidence suggests that trainee doctors are responsible for most prescribing errors. Understanding the factors that influence prescribing behavior may lead to effective interventions to reduce errors. Existing investigations of prescribing errors have been based on Human Error Theory but not on other relevant behavioral theories. The aim of this study was to apply a broad theory-based approach using the Theoretical Domains Framework (TDF) to investigate prescribing in the hospital context among a sample of trainee doctors. Semistructured interviews, based on 12 theoretical domains, were conducted with 22 trainee doctors to explore views, opinions, and experiences of prescribing and prescribing errors. Content analysis was conducted, followed by applying relevance criteria and a novel stage of critical appraisal, to identify which theoretical domains could be targeted in interventions to improve prescribing. Seven theoretical domains met the criteria of relevance: "social professional role and identity," "environmental context and resources," "social influences," "knowledge," "skills," "memory, attention, and decision making," and "behavioral regulation." From critical appraisal of the interview data, "beliefs about consequences" and "beliefs about capabilities" were also identified as potentially important domains. Interrelationships between domains were evident. Additionally, the data supported theoretical elaboration of the domain behavioral regulation. In this investigation of hospital-based prescribing, participants' attributions about causes of errors were used to identify domains that could be targeted in interventions to improve prescribing. In a departure from previous TDF practice, critical appraisal was used to identify additional domains that should also be targeted, despite participants' perceptions that they were not relevant to
International Nuclear Information System (INIS)
Liggatt, P.A.J.; Macfarlane, A.J.
1978-01-01
A prescription is given for point-splitting in a curved space-time background which is a natural generalization of that familiar in quantum electrodynamics and Yang-Mills theory. It is applied (to establish its validity) to the verification of the gravitational anomaly in the divergence of a fermion axial current. Notable features of the prescription are that it defines a point-split current which can be differentiated straightforwardly, and that it involves a natural way of averaging (four dimensionally) over the directions of point splitting. The method can extend directly from the spin-1/2 fermion case treated to other cases, e.g. to spin -3/2 Rarita-Schwinger fermions. (author)
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)
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
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.
Directory of Open Access Journals (Sweden)
Andrea Farina
2017-11-01
Full Text Available Based on recent developments in both single-photon detectors and timing electronic circuits, we designed a compact and cost effective time-domain diffuse optical tomography system operated at 1 Hz acquisition rate, based on eight silicon photomultipliers and an 8-channel time-to-digital converter. The compact detectors are directly hosted on the probe in a circular arrangement around a single light injection fiber, so to maximize light harvesting. Tomography is achieved exploiting the depth sensitivity that is encoded in the arrival time of detected photons. The system performances were evaluated on simulations to assess possible the limitations arising from the use of a single injection point, and then on phantoms and in vivo to prove the eligibility of these technologies for diffuse optical tomography.
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....
Directory of Open Access Journals (Sweden)
Burns Malcolm J
2005-12-01
Full Text Available Abstract Background As real-time quantitative PCR (RT-QPCR is increasingly being relied upon for the enforcement of legislation and regulations dependent upon the trace detection of DNA, focus has increased on the quality issues related to the technique. Recent work has focused on the identification of factors that contribute towards significant measurement uncertainty in the real-time quantitative PCR technique, through investigation of the experimental design and operating procedure. However, measurement uncertainty contributions made during the data analysis procedure have not been studied in detail. This paper presents two additional approaches for standardising data analysis through the novel application of statistical methods to RT-QPCR, in order to minimise potential uncertainty in results. Results Experimental data was generated in order to develop the two aspects of data handling and analysis that can contribute towards measurement uncertainty in results. This paper describes preliminary aspects in standardising data through the application of statistical techniques to the area of RT-QPCR. The first aspect concerns the statistical identification and subsequent handling of outlying values arising from RT-QPCR, and discusses the implementation of ISO guidelines in relation to acceptance or rejection of outlying values. The second aspect relates to the development of an objective statistical test for the comparison of calibration curves. Conclusion The preliminary statistical tests for outlying values and comparisons between calibration curves can be applied using basic functions found in standard spreadsheet software. These two aspects emphasise that the comparability of results arising from RT-QPCR needs further refinement and development at the data-handling phase. The implementation of standardised approaches to data analysis should further help minimise variation due to subjective judgements. The aspects described in this paper will
Tao, Laifa; Lu, Chen; Noktehdan, Azadeh
2015-10-01
Battery capacity estimation is a significant recent challenge given the complex physical and chemical processes that occur within batteries and the restrictions on the accessibility of capacity degradation data. In this study, we describe an approach called dynamic spatial time warping, which is used to determine the similarities of two arbitrary curves. Unlike classical dynamic time warping methods, this approach can maintain the invariance of curve similarity to the rotations and translations of curves, which is vital in curve similarity search. Moreover, it utilizes the online charging or discharging data that are easily collected and do not require special assumptions. The accuracy of this approach is verified using NASA battery datasets. Results suggest that the proposed approach provides a highly accurate means of estimating battery capacity at less time cost than traditional dynamic time warping methods do for different individuals and under various operating conditions.
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...
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.
3D time-domain airborne EM forward modeling with topography
Yin, Changchun; Qi, Yanfu; Liu, Yunhe; Cai, Jing
2016-11-01
The time-domain finite-difference method has been widely used in simulation of the electromagnetic field diffusion. However, this method is severely restricted by the mesh size and time step. To overcome the defect, we adopted edge finite-element method for unstructured grid with Backward Euler method to conduct 3D airborne electromagnetic forward modeling directly in time-domain. The tetrahedral meshes provide the flexibility required for representing the rugged topography and complex-shape anomalous bodies. We simulated the practical shape, size and attitude of transmitting source by directly setting the loop into the well-generated grids. The characteristic properties of vector basic functions guarantee automatic satisfaction of divergence-free property of electric fields. The Galerkin's method is used to discretize the governing equations and a direct solver is adopted to solve the large sparse linear system. We adopted an algorithm with constant step in each time segment to speed up the forward modeling. Further we introduced the local mesh strategy to reduce the calculations, in which an optimized grid is designed for each sounding station. We check the accuracy of our 3D modeling results against the solution for a homogenous half-space and those for a buried vertical plate model using integral equation. The numerical experiments for a hill, a valley or undulating topography model with buried anomalous bodies were further studied that show that the topography has a serious effect on airborne EM data.
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.
Energy Technology Data Exchange (ETDEWEB)
Fadel, Maya Abou [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France); Juan, Anna de [Chemometrics Group, Section of Analytical Chemistry, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Vezin, Hervé [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France); Duponchel, Ludovic, E-mail: ludovic.duponchel@univ-lille1.fr [LASIR CNRS UMR 8516, Université Lille 1, Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France)
2016-12-01
Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that is able to characterize radicals formed in kinetic reactions. However, spectral characterization of individual chemical species is often limited or even unmanageable due to the severe kinetic and spectral overlap among species in kinetic processes. Therefore, we applied, for the first time, multivariate curve resolution-alternating least squares (MCR-ALS) method to EPR time evolving data sets to model and characterize the different constituents in a kinetic reaction. Here we demonstrate the advantage of multivariate analysis in the investigation of radicals formed along the kinetic process of hydroxycoumarin in alkaline medium. Multiset analysis of several EPR-monitored kinetic experiments performed in different conditions revealed the individual paramagnetic centres as well as their kinetic profiles. The results obtained by MCR-ALS method demonstrate its prominent potential in analysis of EPR time evolved spectra. - Highlights: • A new strategy to identify radicals in a time evolving EPR data set. • Extraction of pure EPR spectral signatures and corresponding kinetic profiles. • The proposed method does not require any prior knowledge of the chemical system. • A multiset analysis in order to decrease rotational ambiguity.
Time domain parameters of heart rate variability in children born as small-for-gestational age.
Zamecznik, Agata; Stańczyk, Jerzy; Wosiak, Agnieszka; Niewiadomska-Jarosik, Katarzyna
2017-05-01
According to metabolic programming theory, small-for-gestational age patients are at high risk of cardiovascular diseases also because of the possible malfunction of the autonomic nervous system. Autonomic disorders can be assessed by heart rate variability. The aims of this study were to compare time domain parameters of heart rate variability in children born as small-for-gestational age and appropriate-for-gestational age and to assess the correlation of the postnatal and current somatic parameters with the time domain parameters. The small-for-gestational age group consisted of 68 children aged 5-10 years who were born with birth weight below the 10th percentile. The appropriate-for-gestational age group consisted of 30 healthy peers, matched in terms of gender and age. On the basis of Holter monitoring, slightly higher average heart rate was observed in the small-for-gestational age group than in the appropriate-for-gestational age group. It was found that all the time domain parameters (SDNN, SDNNi, SDANNi, rMSSD, pNN50) were lower in the small-for-gestational age group than in the appropriate-for-gestational age group. In the small-for-gestational age group, girls had lower heart rate and some of the heart rate variability parameters (SDNN, SDNNi, SDANNi) in comparison with boys. Children born as small-for-gestational age have impaired function of the autonomic nervous system. Moreover, in the small-for-gestational age group, autonomic balance moved towards the sympathetic component, which was evidenced by higher heart rate. Children with faster heart rate and lower heart rate variability parameters may be at risk of cardiovascular disease.
Clements, Keith; Wall, John
2017-01-01
The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.
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.
Gutierrez, Juan B; Lai, Ming-Jun; Slavov, George
2015-12-01
We study a time dependent partial differential equation (PDE) which arises from classic models in ecology involving logistic growth with Allee effect by introducing a discrete weak solution. Existence, uniqueness and stability of the discrete weak solutions are discussed. We use bivariate splines to approximate the discrete weak solution of the nonlinear PDE. A computational algorithm is designed to solve this PDE. A convergence analysis of the algorithm is presented. We present some simulations of population development over some irregular domains. Finally, we discuss applications in epidemiology and other ecological problems. Copyright © 2015 Elsevier Inc. All rights reserved.
Plasmonic enhanced terahertz time-domain spectroscopy system for identification of common explosives
Demiraǧ, Yiǧit; Bütün, Bayram; Özbay, Ekmel
2017-05-01
In this study, we present a classification algorithm for terahertz time-domain spectroscopy systems (THz-TDS) that can be trained to identify most commonly used explosives (C4, HMX, RDX, PETN, TNT, composition-B and blackpowder) and some non-explosive samples (lactose, sucrose, PABA). Our procedure can be used in any THz-TDS system that detects either transmission or reflection spectra at room conditions. After preprocessing the signal in low THz regime (0.1 - 3 THz), our algorithm takes advantages of a latent space transformation based on principle component analysis in order to classify explosives with low false alarm rate.
Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study.
Di Sieno, Laura; Zouaoui, Judy; Hervé, Lionel; Pifferi, Antonio; Farina, Andrea; Martinenghi, Edoardo; Derouard, Jacques; Dinten, Jean-Marc; Mora, Alberto Dalla
2016-11-01
Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thus opening the way to the use of SiPMs for DOT, with the possibility to conceive a new generation of low-cost and reliable multichannel tomographic systems.
A RF time domain approach for electric arcs detection and localization systems
Deacu, Daniela; Tamas, Razvan; Petrescu, Teodor; Paun, Mirel; Anchidin, Liliana; Algiu, Madalina
2016-12-01
In this paper we propose a new method for detection and localization of electric arcs by using two ultra-wide band (UWB) antennas together with data processing in the time-domain. The source of electric arcs is localized by computing an average on the inter-correlation functions of the signals received on two channels. By calculating the path length difference to the antennas, the direction of the electric arcs is then found. The novelty of the method consists in the spatial averaging in order to reduce the incertitude caused by the finite sampling rate.
Fedorov, A K; Anufriev, M N; Zhirnov, A A; Stepanov, K V; Nesterov, E T; Namiot, D E; Karasik, V E; Pnev, A B
2016-03-01
We propose a novel approach to the recognition of particular classes of non-conventional events in signals from phase-sensitive optical time-domain-reflectometry-based sensors. Our algorithmic solution has two main features: filtering aimed at the de-nosing of signals and a Gaussian mixture model to cluster them. We test the proposed algorithm using experimentally measured signals. The results show that two classes of events can be distinguished with the best-case recognition probability close to 0.9 at sufficient numbers of training samples.
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...
Pappas, C. G.; Beall, J.; Brevick, J.; Cho, H. M.; Devlin, M. J.; Fox, A.; Grace, E. A.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; Klein, J.; Li, D.; Lungu, M.; Newburgh, L. B.; Nibarger, J. P.; Niemack, M. D.; McMahon, J. J.; Page, L. A.; Schmitt, B. L.; Staggs, S. T.; Van Lanen, J.; Wollack, E. J.
2014-09-01
We present new data on feedhorn-coupled transition-edge sensor devices fabricated for the second-generation receiver (ACTPol) for the Atacama cosmology telescope (ACT). First, we describe optical efficiency measurements of the latest ACTPol detector wafer, which has a average optical efficiency. Next, we discuss measurements of the TES resistance as a function of temperature and bias current () using the ACTPol time-domain multiplexing electronics. Qualitative agreement between data at low bias current and the two-fluid model prediction is shown. Using the two-fluid model and low bias current data, and at our operating bias current are calculated.
3D time-domain spectral elements for stress waves modelling
International Nuclear Information System (INIS)
Kudela, P; Ostachowicz, W
2009-01-01
Elastic stress waves induced by piezoelectric transducers are extensively used for damage detection purposes. Induced high frequency impulse signals cause that stress wave modelling by the finite element method is inefficient. Instead, numerical model based on the time-domain spectral element method has been developed to simulate stress wave propagation in metallic structures induced by the piezoelectric transducers. The model solves the coupled electromechanical field equations simultaneously in three-dimensional case. Visualisation of the propagating elastic waves generated by the actuator of different shapes and properties has been performed.
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
Calibrating a Salt Water Intrusion Model with Time-Domain Electromagnetic Data
DEFF Research Database (Denmark)
Herckenrath, Daan; Odlum, Nick; Nenna, Vanessa
2013-01-01
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......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...
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.
Resolving spectral information from time domain induced polarization data through 2-D inversion
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Binley, A.
2013-01-01
SUMMARY Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given...... these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD...
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.
Finite Difference Time-Domain Modelling of Metamaterials: GPU Implementation of Cylindrical Cloak
Directory of Open Access Journals (Sweden)
A. Dawood
2013-08-01
Full Text Available Finite difference time-domain (FDTD technique can be used to model metamaterials by treating them as dispersive material. Drude or Lorentz model can be incorporated into the standard FDTD algorithm for modelling negative permittivity and permeability. FDTD algorithm is readily parallelisable and can take advantage of GPU acceleration to achieve speed-ups of 5x-50x depending on hardware setup. Metamaterial scattering problems are implemented using dispersive FDTD technique on GPU resulting in performance gain of 10x-15x compared to conventional CPU implementation.
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.
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 linearity of detection have been characterized. Moreover, the performance of a photomultiplier tube (PMT) and an avalanche photodiode (APD) as photodetector in the ABCD have been compared. We have observed nonlinear behavior of PMT detector, which leads to artificial gain factor in TDS spectroscopy. The APD...
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.
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.
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.