Time domain analog circuit simulation
Fijnvandraat, J.G.; Houben, S.H.M.J.; Maten, ter E.J.W.; Peters, J.M.F.
2006-01-01
Recent developments of new methods for simulating electric circuits are described. Emphasis is put on methods that fit existing datastructures for backward differentiation formulae methods. These methods can be modified to apply to hierarchically organized datastructures, which allows for efficient
Time-Domain Simulation of RF Couplers
International Nuclear Information System (INIS)
Smithe, David; Carlsson, Johan; Austin, Travis
2009-01-01
We have developed a finite-difference time-domain (FDTD) fluid-like approach to integrated plasma-and-coupler simulation [1], and show how it can be used to model LH and ICRF couplers in the MST and larger tokamaks.[2] This approach permits very accurate 3-D representation of coupler geometry, and easily includes non-axi-symmetry in vessel wall, magnetic equilibrium, and plasma density. The plasma is integrated with the FDTD Maxwell solver in an implicit solve that steps over electron time-scales, and permits tenuous plasma in the coupler itself, without any need to distinguish or interface between different regions of vacuum and/or plasma. The FDTD algorithm is also generalized to incorporate a time-domain sheath potential [3] on metal structures within the simulation, to look for situations where the sheath potential might generate local sputtering opportunities. Benchmarking of the time-domain sheath algorithm has been reported in the references. Finally, the time-domain software [4] permits the use of particles, either as field diagnostic (test particles) or to self-consistently compute plasma current from the applied RF power.
Time domain simulations of beam-loading
International Nuclear Information System (INIS)
Koscielniak, S.
1989-09-01
We present the results of computer simulations of high current beam loading in a proton storage ring. The model integrates the differential equation for gap voltage, and iterates the difference equations for particle longitudinal motion. The effects of cavity fields on the bunch shape and of the fundamental component of the beam on the cavity are treated in a self-consistent manner. The simulation model is applied to verify the dipole-quadrupole hybrid Robinson instability criterion, which differs from the dipole-mode criterion
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.
The Simulation Realization of Pavement Roughness in the Time Domain
XU, H. L.; He, L.; An, D.
2017-10-01
As the needs for the dynamic study on the vehicle-pavement system and the simulated vibration table test, how to simulate the pavement roughness actually is important guarantee for whether calculation and test can reflect the actual situation or not. Using the power spectral density function, the simulation of pavement roughness can be realized by Fourier inverse transform. The main idea of this method was that the spectrum amplitude and random phase were obtained separately according to the power spectrum, and then the simulation of pavement roughness was obtained in the time domain through the Fourier inverse transform (IFFT). In the process, the sampling interval (Δl) was 0.1m, and the sampling points(N) was 4096, which satisfied the accuracy requirements. Using this method, the simulate results of pavement roughness (A~H grades) were obtain in the time domain.
DRK methods for time-domain oscillator simulation
Sevat, M.F.; Houben, S.H.M.J.; Maten, ter E.J.W.; Di Bucchianico, A.; Mattheij, R.M.M.; Peletier, M.A.
2006-01-01
This paper presents a new Runge-Kutta type integration method that is well-suited for time-domain simulation of oscillators. A unique property of the new method is that its damping characteristics can be controlled by a continuous parameter.
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.
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...
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
Numerical simulation of electromagnetic wave propagation using time domain meshless method
International Nuclear Information System (INIS)
Ikuno, Soichiro; Fujita, Yoshihisa; Itoh, Taku; Nakata, Susumu; Nakamura, Hiroaki; Kamitani, Atsushi
2012-01-01
The electromagnetic wave propagation in various shaped wave guide is simulated by using meshless time domain method (MTDM). Generally, Finite Differential Time Domain (FDTD) method is applied for electromagnetic wave propagation simulation. However, the numerical domain should be divided into rectangle meshes if FDTD method is applied for the simulation. On the other hand, the node disposition of MTDM can easily describe the structure of arbitrary shaped wave guide. This is the large advantage of the meshless time domain method. The results of computations show that the damping rate is stably calculated in case with R < 0.03, where R denotes a support radius of the weight function for the shape function. And the results indicate that the support radius R of the weight functions should be selected small, and monomials must be used for calculating the shape functions. (author)
International Nuclear Information System (INIS)
Jamali, J.; Aghajafari, R.; Moini, R.; Sadeghi, H.
2002-01-01
A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper
International Nuclear Information System (INIS)
Hu, Xiao-feng; Chen, Xiang; Wei, Ming
2013-01-01
Shielding effectiveness (SE) of materials of current testing standards is often carried out by using continuous-wave measurement and amplitude-frequency characteristics curve is used to characterize the results. However, with in-depth study of high-power electromagnetic pulse (EMP) interference, it was discovered that only by frequency-domain SE of materials cannot be completely characterized by shielding performance of time-domain pulsed-field. And there is no uniform testing methods and standards of SE of materials against EMP. In this paper, the method of minimum phase transfer function is used to reconstruct shielded time-domain waveform based on the analysis of the waveform reconstruction method. Pulse of plane waves through an infinite planar material is simulated by using CST simulation software. The reconstructed waveform and simulation waveform is compared. The results show that the waveform reconstruction method based on the minimum phase can be well estimated EMP waveform through the infinite planar materials.
Jia, Shouqing; La, Dongsheng; Ma, Xuelian
2018-04-01
The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.
CSIR Research Space (South Africa)
Loveday, PW
2007-03-01
Full Text Available Piezoelectric transducers are commonly used to excite waves in elastic waveguides such as pipes, rock bolts and rails. While it is possible to simulate the operation of these transducers attached to the waveguide, in the time domain, using...
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
Finite-difference time-domain simulation of thermal noise in open cavities
International Nuclear Information System (INIS)
Andreasen, Jonathan; Cao Hui; Taflove, Allen; Kumar, Prem; Cao Changqi
2008-01-01
A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal radiation penetrates the cavity in the grid. The calculated amount of thermal noise in a one-dimensional dielectric cavity recovers the standard result of the quantum Langevin equation in the Markovian regime. Our FDTD simulation also demonstrates that in the non-Markovian regime the buildup of the intracavity noise field depends on the ratio of the cavity photon lifetime to the coherence time of thermal radiation. The advantage of our numerical method is that the thermal noise is introduced in the time domain without prior knowledge of cavity modes
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.
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.
Merrikh-Bayat, Farshad
2011-04-01
One main approach for time-domain simulation of the linear output-feedback systems containing fractional-order controllers is to approximate the transfer function of the controller with an integer-order transfer function and then perform the simulation. In general, this approach suffers from two main disadvantages: first, the internal stability of the resulting feedback system is not guaranteed, and second, the amount of error caused by this approximation is not exactly known. The aim of this paper is to propose an efficient method for time-domain simulation of such systems without facing the above mentioned drawbacks. For this purpose, the fractional-order controller is approximated with an integer-order transfer function (possibly in combination with the delay term) such that the internal stability of the closed-loop system is guaranteed, and then the simulation is performed. It is also shown that the resulting approximate controller can effectively be realized by using the proposed method. Some formulas for estimating and correcting the simulation error, when the feedback system under consideration is subjected to the unit step command or the unit step disturbance, are also presented. Finally, three numerical examples are studied and the results are compared with the Oustaloup continuous approximation method. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.
Helicopter time-domain electromagnetic numerical simulation based on Leapfrog ADI-FDTD
Guan, S.; Ji, Y.; Li, D.; Wu, Y.; Wang, A.
2017-12-01
We present a three-dimension (3D) Alternative Direction Implicit Finite-Difference Time-Domain (Leapfrog ADI-FDTD) method for the simulation of helicopter time-domain electromagnetic (HTEM) detection. This method is different from the traditional explicit FDTD, or ADI-FDTD. Comparing with the explicit FDTD, leapfrog ADI-FDTD algorithm is no longer limited by Courant-Friedrichs-Lewy(CFL) condition. Thus, the time step is longer. Comparing with the ADI-FDTD, we reduce the equations from 12 to 6 and .the Leapfrog ADI-FDTD method will be easier for the general simulation. First, we determine initial conditions which are adopted from the existing method presented by Wang and Tripp(1993). Second, we derive Maxwell equation using a new finite difference equation by Leapfrog ADI-FDTD method. The purpose is to eliminate sub-time step and retain unconditional stability characteristics. Third, we add the convolution perfectly matched layer (CPML) absorbing boundary condition into the leapfrog ADI-FDTD simulation and study the absorbing effect of different parameters. Different absorbing parameters will affect the absorbing ability. We find the suitable parameters after many numerical experiments. Fourth, We compare the response with the 1-Dnumerical result method for a homogeneous half-space to verify the correctness of our algorithm.When the model contains 107*107*53 grid points, the conductivity is 0.05S/m. The results show that Leapfrog ADI-FDTD need less simulation time and computer storage space, compared with ADI-FDTD. The calculation speed decreases nearly four times, memory occupation decreases about 32.53%. Thus, this algorithm is more efficient than the conventional ADI-FDTD method for HTEM detection, and is more precise than that of explicit FDTD in the late time.
Time domain SAR raw data simulation using CST and image focusing of 3D objects
Saeed, Adnan; Hellwich, Olaf
2017-10-01
This paper presents the use of a general purpose electromagnetic simulator, CST, to simulate realistic synthetic aperture radar (SAR) raw data of three-dimensional objects. Raw data is later focused in MATLAB using range-doppler algorithm. Within CST Microwave Studio a replica of TerraSAR-X chirp signal is incident upon a modeled Corner Reflector (CR) whose design and material properties are identical to that of the real one. Defining mesh and other appropriate settings reflected wave is measured at several distant points within a line parallel to the viewing direction. This is analogous to an array antenna and is synthesized to create a long aperture for SAR processing. The time domain solver in CST is based on the solution of differential form of Maxwells equations. Exported data from CST is arranged into a 2-d matrix of axis range and azimuth. Hilbert transform is applied to convert the real signal to complex data with phase information. Range compression, range cell migration correction (RCMC), and azimuth compression are applied in time domain to obtain the final SAR image. This simulation can provide valuable information to clarify which real world objects cause images suitable for high accuracy identification in the SAR images.
On using moving windows in finite element time domain simulation for long accelerator structures
International Nuclear Information System (INIS)
Lee, L.-Q.; Candel, Arno; Ng, Cho; Ko, Kwok
2010-01-01
A finite element moving window technique is developed to simulate the propagation of electromagnetic waves induced by the transit of a charged particle beam inside large and long structures. The window moving along with the beam in the computational domain adopts high-order finite element basis functions through p refinement and/or a high-resolution mesh through h refinement so that a sufficient accuracy is attained with substantially reduced computational costs. Algorithms to transfer discretized fields from one mesh to another, which are the keys to implementing a moving window in a finite element unstructured mesh, are presented. Numerical experiments are carried out using the moving window technique to compute short-range wakefields in long accelerator structures. The results are compared with those obtained from the normal finite element time domain (FETD) method and the advantages of using the moving window technique are discussed.
Time-domain simulation and nonlinear analysis on ride performance of four-wheel vehicles
Energy Technology Data Exchange (ETDEWEB)
Wang, Y S; He, H; Geng, A L [School of Automobile and Traffic Engineering, Liaoning University of Technology, Jinzhou 121001 (China)], E-mail: jzwbt@163.com
2008-02-15
A nonlinear dynamic model with eight DOFs of a four-wheel vehicle is established in this paper. After detaching the nonlinear characteristics of the leaf springs and shock absorbers, the multi-step linearizing method is used to simulate the vehicle vibration in time domain, under a correlated four-wheel road roughness model. Experimental verifications suggest that the newly built vehicle model and simulation procedure are reasonable and feasible to be used in vehicle vibration analysis. Furthermore, some nonlinear factors of the leaf springs and shock absorbers, which affect the vehicle ride performance (or comfort), are investigated under different vehicle running speeds. Some substaintial rules of the nonlinear vehicle vibrations are revealed in this paper.
Cvetkovic, V.; Molin, S.
2012-02-01
We present a methodology that combines numerical simulations of groundwater flow and advective transport in heterogeneous porous media with analytical retention models for computing the infection risk probability from pathogens in aquifers. The methodology is based on the analytical results presented in [1,2] for utilising the colloid filtration theory in a time-domain random walk framework. It is shown that in uniform flow, the results from the numerical simulations of advection yield comparable results as the analytical TDRW model for generating advection segments. It is shown that spatial variability of the attachment rate may be significant, however, it appears to affect risk in a different manner depending on if the flow is uniform or radially converging. In spite of the fact that numerous issues remain open regarding pathogen transport in aquifers on the field scale, the methodology presented here may be useful for screening purposes, and may also serve as a basis for future studies that would include greater complexity.
Time-domain simulation and nonlinear analysis on ride performance of four-wheel vehicles
International Nuclear Information System (INIS)
Wang, Y S; He, H; Geng, A L
2008-01-01
A nonlinear dynamic model with eight DOFs of a four-wheel vehicle is established in this paper. After detaching the nonlinear characteristics of the leaf springs and shock absorbers, the multi-step linearizing method is used to simulate the vehicle vibration in time domain, under a correlated four-wheel road roughness model. Experimental verifications suggest that the newly built vehicle model and simulation procedure are reasonable and feasible to be used in vehicle vibration analysis. Furthermore, some nonlinear factors of the leaf springs and shock absorbers, which affect the vehicle ride performance (or comfort), are investigated under different vehicle running speeds. Some substaintial rules of the nonlinear vehicle vibrations are revealed in this paper
Application of the symplectic finite-difference time-domain scheme to electromagnetic simulation
International Nuclear Information System (INIS)
Sha, Wei; Huang, Zhixiang; Wu, Xianliang; Chen, Mingsheng
2007-01-01
An explicit fourth-order finite-difference time-domain (FDTD) scheme using the symplectic integrator is applied to electromagnetic simulation. A feasible numerical implementation of the symplectic FDTD (SFDTD) scheme is specified. In particular, new strategies for the air-dielectric interface treatment and the near-to-far-field (NFF) transformation are presented. By using the SFDTD scheme, both the radiation and the scattering of three-dimensional objects are computed. Furthermore, the energy-conserving characteristic hold for the SFDTD scheme is verified under long-term simulation. Numerical results suggest that the SFDTD scheme is more efficient than the traditional FDTD method and other high-order methods, and can save computational resources
Towards dual recycling with the aid of time and frequency domain simulations
International Nuclear Information System (INIS)
Malec, M; Grote, H; Freise, A; Heinzel, G; Strain, K A; Hough, J; Danzmann, K
2004-01-01
Dual recycling, the combination of the interferometric techniques of power and signal recycling, allows the improvement of the shot noise limited sensitivity of interferometric gravitational wave detectors. GEO 600 is the first km-scale gravitational wave detector using dual recycling. The hardware installation is completed and dual recycling has become a great challenge in terms of commissioning of GEO 600. Simulations show that lock acquisition of the optical system can only be achieved in certain detector states. Thus as we need to start with a locked detector in such a specific state, an appropriate strategy is needed to change the state of detector operation without losing lock. The basic concepts and first results based on time and frequency domain simulations will be presented in this paper
Simulation of acoustic streaming by means of the finite-difference time-domain method
DEFF Research Database (Denmark)
Santillan, Arturo Orozco
2012-01-01
Numerical simulations of acoustic streaming generated by a standing wave in a narrow twodimensional cavity are presented. In this case, acoustic streaming arises from the viscous boundary layers set up at the surfaces of the walls. It is known that streaming vortices inside the boundary layer have...... directions of rotation that are opposite to those of the outer streaming vortices (Rayleigh streaming). The general objective of the work described in this paper has been to study the extent to which it is possible to simulate both the outer streaming vortices and the inner boundary layer vortices using...... the finite-difference time-domain method. To simplify the problem, thermal effects are not considered. The motivation of the described investigation has been the possibility of using the numerical method to study acoustic streaming, particularly under non-steady conditions. Results are discussed for channels...
Time domain simulation of the response of geometrically nonlinear panels subjected to random loading
Moyer, E. Thomas, Jr.
1988-01-01
The response of composite panels subjected to random pressure loads large enough to cause geometrically nonlinear responses is studied. A time domain simulation is employed to solve the equations of motion. An adaptive time stepping algorithm is employed to minimize intermittent transients. A modified algorithm for the prediction of response spectral density is presented which predicts smooth spectral peaks for discrete time histories. Results are presented for a number of input pressure levels and damping coefficients. Response distributions are calculated and compared with the analytical solution of the Fokker-Planck equations. RMS response is reported as a function of input pressure level and damping coefficient. Spectral densities are calculated for a number of examples.
Directory of Open Access Journals (Sweden)
Benjamin M. Cowan
2013-04-01
Full Text Available We describe a modification to the finite-difference time-domain algorithm for electromagnetics on a Cartesian grid which eliminates numerical dispersion error in vacuum for waves propagating along a grid axis. We provide details of the algorithm, which generalizes previous work by allowing 3D operation with a wide choice of aspect ratio, and give conditions to eliminate dispersive errors along one or more of the coordinate axes. We discuss the algorithm in the context of laser-plasma acceleration simulation, showing significant reduction—up to a factor of 280, at a plasma density of 10^{23} m^{-3}—of the dispersion error of a linear laser pulse in a plasma channel. We then compare the new algorithm with the standard electromagnetic update for laser-plasma accelerator stage simulations, demonstrating that by controlling numerical dispersion, the new algorithm allows more accurate simulation than is otherwise obtained. We also show that the algorithm can be used to overcome the critical but difficult challenge of consistent initialization of a relativistic particle beam and its fields in an accelerator simulation.
Time domain simulation of Gd3+-Gd3+ distance measurements by EPR
Manukovsky, Nurit; Feintuch, Akiva; Kuprov, Ilya; Goldfarb, Daniella
2017-07-01
Gd3+-based spin labels are useful as an alternative to nitroxides for intramolecular distance measurements at high fields in biological systems. However, double electron-electron resonance (DEER) measurements using model Gd3+ complexes featured a low modulation depth and an unexpected broadening of the distance distribution for short Gd3+-Gd3+ distances, when analysed using the software designed for S = 1/2 pairs. It appears that these effects result from the different spectroscopic characteristics of Gd3+—the high spin, the zero field splitting (ZFS), and the flip-flop terms in the dipolar Hamiltonian that are often ignored for spin-1/2 systems. An understanding of the factors affecting the modulation frequency and amplitude is essential for the correct analysis of Gd3+-Gd3+ DEER data and for the educated choice of experimental settings, such as Gd3+ spin label type and the pulse parameters. This work uses time-domain simulations of Gd3+-Gd3+ DEER by explicit density matrix propagation to elucidate the factors shaping Gd3+ DEER traces. The simulations show that mixing between the |+½, -½> and |-½, +½> states of the two spins, caused by the flip-flop term in the dipolar Hamiltonian, leads to dampening of the dipolar modulation. This effect may be mitigated by a large ZFS or by pulse frequency settings allowing for a decreased contribution of the central transition and the one adjacent to it. The simulations reproduce both the experimental line shapes of the Fourier-transforms of the DEER time domain traces and the trends in the behaviour of the modulation depth, thus enabling a more systematic design and analysis of Gd3+ DEER experiments.
Liang, Fayun; Chen, Haibing; Huang, Maosong
2017-07-01
To provide appropriate uses of nonlinear ground response analysis for engineering practice, a three-dimensional soil column with a distributed mass system and a time domain numerical analysis were implemented on the OpenSees simulation platform. The standard mesh of a three-dimensional soil column was suggested to be satisfied with the specified maximum frequency. The layered soil column was divided into multiple sub-soils with a different viscous damping matrix according to the shear velocities as the soil properties were significantly different. It was necessary to use a combination of other one-dimensional or three-dimensional nonlinear seismic ground analysis programs to confirm the applicability of nonlinear seismic ground motion response analysis procedures in soft soil or for strong earthquakes. The accuracy of the three-dimensional soil column finite element method was verified by dynamic centrifuge model testing under different peak accelerations of the earthquake. As a result, nonlinear seismic ground motion response analysis procedures were improved in this study. The accuracy and efficiency of the three-dimensional seismic ground response analysis can be adapted to the requirements of engineering practice.
Features of a time domain simulation tool for rigid riser design
Energy Technology Data Exchange (ETDEWEB)
Morooka, Celso K.; Brandt, Dustin M. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia de Petroleo; Matt, Cyntia G.C.; Franciss, Ricardo [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas
2008-07-01
This paper present a number of numerical implementations designed for the analysis of rigid riser's static and dynamic behavior that includes the effects of vortex induced vibrations (VIV) and marine hydrodynamic loads in time domain. Features include the ability to consider pipe with a free-span utilizing a soil/riser interaction model. An implementation of a numerical coupling scheme to couple the vertical riser and platform dynamics was developed to allow prediction of the sub sea Blow-Out Preventer (BOP) re-entry into a sub sea petroleum well when drilling different phases of deep and ultra-deep wells. The developments contains support for the consideration of the Self Standing Hybrid Riser (SSHR) configuration which has been shown to be a promising riser configuration in deep and ultra-deep waters. A graphical interface was also created to better grasp the results and aid in the modeling, processing and to help analyze the numerical simulations, contributing to enhance agility and quality of the riser design and analysis processes. (author)
Ruggiero, Michael T; Zeitler, J Axel
2016-11-17
Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is the driving force of vibrational relaxation processes, mechanisms that are integral to the proper function of numerous chemical processes. However, elucidating its origins has proven difficult due to experimental and theoretical challenges, specifically related to separating the anharmonic contributions from other unrelated effects. While no one technique is particularly suited for providing a complete picture of anharmonicity, by combining multiple complementary methods such a characterization can be made. In this study the role of individual atomic interactions on the anharmonic properties of crystalline purine, the building block of many DNA and RNA nucleobases, is studied by experimental terahertz time-domain spectroscopy and first-principles density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD). In particular, the detailed vibrational information provided by the DFT calculations is used to interpret the atomic origins of anharmonic-related effects as determined by the AIMD calculations, which are in good agreement with the experimental data. The results highlight that anharmonicity is especially pronounced in the intermolecular interactions, particularly along the amine hydrogen bond coordinate, and yields valuable insight into what is similarly observed complex biosystems and crystalline solids.
Finite-difference time-domain simulation of electromagnetic bandgap and bi-anisotropic metamaterials
Bray, Matthew G.
The term "Metamaterial" has been introduced into the electromagnetic lexicon in recent years to describe new artificial materials with electromagnetic properties that are not found in naturally occurring materials. Metamaterials exhibit electromagnetic properties that are not observed in its constituent materials, and/or not observed in nature. This thesis will analyze two different classes of metamaterials through the use of the finite-difference time-domain (FDTD) technique. The first class of metamaterials are artificial magnetic conductors (AMC) which approximate the behavior of a perfect magnetic conductor (PMC) over a finite frequency range. The AMC metamaterials are created through the use of an electromagnetic bandgap (EBG) structure. A periodic FDTD code is used to simulate a full-wave model of the metallodielectric EBG structures. The AMCs developed with the aid of the FDTD tool are then used to create low-profile antenna systems consisting of a dipole antenna in close proximity to an AMC surface. Through the use of this FDTD tool, several original contributions were made to the electromagnetic community. These include the first dual-band independently tunable EBG AMC ground plane and the first linearly polarized single-band and dual-band tunable antenna/EBG systems. The second class of materials analyzed are bi-anisotropic metamaterials. Bi-anisotropic media are the largest class of linear media which is able to describe the macroscopic material properties of artificial dielectrics, artificial magnetics, artificial chiral materials, left-handed materials, and other composite materials. The dispersive properties of these materials can be approximated by the oscillator model. This model assumes a Lorentzian frequency profile for the permittivity and permeability and a Condon model for chirality. A new FDTD formulation is introduced which can simulate this type of bi-anisotropic media. This FDTD method incorporates the dispersive material properties through
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.
Wind Energy System Time-domain (WEST) analyzers using hybrid simulation techniques
Hoffman, J. A.
1979-01-01
Two stand-alone analyzers constructed for real time simulation of the complex dynamic characteristics of horizontal-axis wind energy systems are described. Mathematical models for an aeroelastic rotor, including nonlinear aerodynamic and elastic loads, are implemented with high speed digital and analog circuitry. Models for elastic supports, a power train, a control system, and a rotor gimbal system are also included. Limited correlation efforts show good comparisons between results produced by the analyzers and results produced by a large digital simulation. The digital simulation results correlate well with test data.
Simulation for light extraction in light emitting diode using finite domain time difference method
International Nuclear Information System (INIS)
Hong, Jun Hee; Park, Si Hyun
2008-01-01
InGaN based LEDs are indispensable to traffic light, full color displays, back lights in liquid crystals, and general lighting. The demand for high efficiency LEDs is on the increase. Recently we have reported the improvement of the light extraction efficiency of InGaN based LED. In this paper we show suitable a three dimensional (3 D)FDTD simulation method for LED simulation and we apply our FDTD simulation to our PNS LED structures, comparing the simulation results with the experimental results. For real FDTD simulation, we first must consider the spatial and temporal grid size. In order to obtain an accurate result, the spatial grid size must be so small that the feature of the field can be resolved. We computed the field power at each time at the surface 0.3mm away from the surface between GaN and air and integrate over surface. The calculations were conducted for the PNS LEDs employing the different height of SiO_2 columns, that is, h=160nm, h=350nm, h=550nm, h=750nm, and h=950nm. Simulation results according to different height is shown in Fig. 1(a,b). All simulation curves follow rough trend that it increases with column height and reaches the maximum at about 600nm height and then decreases with height. And this is a consistent with the trend from our experiments. Our FDTD simulation gives a possibility for design of LED structures of high extraction efficiency
International Nuclear Information System (INIS)
Wang Shumin; Duyn, Jeff H
2008-01-01
A hybrid method that combines the finite-difference time-domain (FDTD) method and the finite-element time-domain (FETD) method is presented for simulating radio-frequency (RF) coils in magnetic resonance imaging. This method applies a high-fidelity FETD method to RF coils, while the human body is modeled with a low-cost FDTD method. Since the FDTD and the FETD methods are applied simultaneously, the dynamic interaction between RF coils and the human body is fully accounted for. In order to simplify the treatment of the highly irregular FDTD/FETD interface, composite elements are proposed. Two examples are provided to demonstrate the validity and effectiveness of the hybrid method in high-field receive-and-transmit coil design. This approach is also applicable to general bio-electromagnetic simulations
High-speed extended-term time-domain simulation for online cascading analysis of power system
Fu, Chuan
A high-speed extended-term (HSET) time domain simulator (TDS), intended to become a part of an energy management system (EMS), has been newly developed for use in online extended-term dynamic cascading analysis of power systems. HSET-TDS includes the following attributes for providing situational awareness of high-consequence events: (i) online analysis, including n-1 and n-k events, (ii) ability to simulate both fast and slow dynamics for 1-3 hours in advance, (iii) inclusion of rigorous protection-system modeling, (iv) intelligence for corrective action ID, storage, and fast retrieval, and (v) high-speed execution. Very fast on-line computational capability is the most desired attribute of this simulator. Based on the process of solving algebraic differential equations describing the dynamics of power system, HSET-TDS seeks to develop computational efficiency at each of the following hierarchical levels, (i) hardware, (ii) strategies, (iii) integration methods, (iv) nonlinear solvers, and (v) linear solver libraries. This thesis first describes the Hammer-Hollingsworth 4 (HH4) implicit integration method. Like the trapezoidal rule, HH4 is symmetrically A-Stable but it possesses greater high-order precision (h4 ) than the trapezoidal rule. Such precision enables larger integration steps and therefore improves simulation efficiency for variable step size implementations. This thesis provides the underlying theory on which we advocate use of HH4 over other numerical integration methods for power system time-domain simulation. Second, motivated by the need to perform high speed extended-term time domain simulation (HSET-TDS) for on-line purposes, this thesis presents principles for designing numerical solvers of differential algebraic systems associated with power system time-domain simulation, including DAE construction strategies (Direct Solution Method), integration methods(HH4), nonlinear solvers(Very Dishonest Newton), and linear solvers(SuperLU). We have
Energy Technology Data Exchange (ETDEWEB)
Koenig, Michael [Institut fuer Theoretische Festkoerperphysik, Universitaet Karlsruhe (Germany); Karlsruhe School of Optics and Photonics (KSOP), Universitaet Karlsruhe (Germany); Niegemann, Jens; Tkeshelashvili, Lasha; Busch, Kurt [Institut fuer Theoretische Festkoerperphysik, Universitaet Karlsruhe (Germany); DFG Forschungszentrum Center for Functional Nanostructures (CFN), Universitaet Karlsruhe (Germany); Karlsruhe School of Optics and Photonics (KSOP), Universitaet Karlsruhe (Germany)
2008-07-01
Numerical simulations of metallic nano-structures are crucial for the efficient design of plasmonic devices. Conventional time-domain solvers such as FDTD introduce large numerical errors especially at metallic surfaces. Our approach combines a discontinuous Galerkin method on an adaptive mesh for the spatial discretisation with a Krylov-subspace technique for the time-stepping procedure. Thus, the higher-order accuracy in both time and space is supported by unconditional stability. As illustrative examples, we compare numerical results obtained with our method against analytical reference solutions and results from FDTD calculations.
International Nuclear Information System (INIS)
Ford, Patrick J.; Beeson, Sterling R.; Krompholz, Hermann G.; Neuber, Andreas A.
2012-01-01
A finite-difference algorithm was developed to calculate several RF breakdown parameters, for example, the formative delay time that is observed between the initial application of a RF field to a dielectric surface and the formation of field-induced plasma interrupting the RF power flow. The analysis is focused on the surface being exposed to a background gas pressure above 50 Torr. The finite-difference algorithm provides numerical solutions to partial differential equations with high resolution in the time domain, making it suitable for simulating the time evolving interaction of microwaves with plasma; in lieu of direct particle tracking, a macroscopic electron density is used to model growth and transport. This approach is presented as an alternative to particle-in-cell methods due to its low complexity and runtime leading to more efficient analysis for a simulation of a microsecond scale pulse. The effect and development of the plasma is modeled in the simulation using scaling laws for ionization rates, momentum transfer collision rates, and diffusion coefficients, as a function of electric field, gas type and pressure. The incorporation of plasma material into the simulation involves using the Z-transform to derive a time-domain algorithm from the complex frequency-dependent permittivity of plasma. Therefore, the effect of the developing plasma on the instantaneous microwave field is calculated. Simulation results are compared with power measurements using an apparatus designed to facilitate surface flashover across a polycarbonate boundary in a controlled N 2 , air, or argon environment at pressures exceeding 50 Torr.
Huang, Shi-Hao; Wang, Shiang-Jiu; Tseng, Snow H.
2015-03-01
Optical coherence tomography (OCT) provides high resolution, cross-sectional image of internal microstructure of biological tissue. We use the Finite-Difference Time-Domain method (FDTD) to analyze the data acquired by OCT, which can help us reconstruct the refractive index of the biological tissue. We calculate the refractive index tomography and try to match the simulation with the data acquired by OCT. Specifically, we try to reconstruct the structure of melanin, which has complex refractive indices and is the key component of human pigment system. The results indicate that better reconstruction can be achieved for homogenous sample, whereas the reconstruction is degraded for samples with fine structure or with complex interface. Simulation reconstruction shows structures of the Melanin that may be useful for biomedical optics applications.
Voutilainen, M.; Sardini, P.; Togneri, L.; Siitari-Kauppi, M.; Timonen, J.
2010-12-01
In this work an effect of rock heterogeneity on diffusion was investigated. Time domain diffusion simulations were used to compare behavior of diffusion in homogeneous and heterogeneous 3D media. Tomographic images were used as heterogeneous rock media. One altered tonalite sample from Sievi, Finland, was chosen as test case for introduced analysis procedure. Effective diffusion coefficient of tonalite sample was determined with lab-scale experiments and the same coefficient was used also for homogeneous media. Somewhat technically complicated mathematical solution for analysis of through diffusion experiment is shortly described. Computed tomography (CT) is already quite widely used in many geological, petrological, and paleontological applications when the three-dimensional (3D) structure of the material is of interest, and is an excellent method for gaining information especially about its heterogeneity, grain size, or porosity. In addition to offering means for quantitative characterization, CT provides a lot of qualitative information [1]. A through -diffusion laboratory experiment using radioactive tracer was fitted using the Time Domain Diffusion (TDD) method. This rapid particle tracking method allows simulation of the heterogeneous diffusion based on pore-scale images and local values of diffusivities [2]. As a result we found out that heterogeneity has only a small effect to diffusion coefficient and in-diffusion profile for used geometry. Also direction dependency was tested and was found to be negligible. Whereas significant difference between generally accepted value and value obtained from simulations for constant m in Archie’s law was found. [1] Voutilainen, M., Siitari-Kauppi, M., Sardini, P., and Timonen, J., (2010). On pore-space characterization of an altered tonalite by X-ray µCT and the 14C-PMMA method (in progress). [2] Sardini, P., Robinet, J., Siitari-Kauppi, M., Delay, F., and Hellmuth, K-H, (2007). On direct simulation of heterogeneous
An FFT-accelerated time-domain multiconductor transmission line simulator
Bagci, Hakan; Yilmaz, Ali E.; Michielssen, Eric
2010-01-01
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
Time-Domain Simulations of Transient Species in Experimentally Relevant Environments
Energy Technology Data Exchange (ETDEWEB)
Ueltschi, Tyler W.; Fischer, Sean A.; Apra, Edoardo; Tarnovsky, Alexander N.; Govind, Niranjan; El-Khoury, Patrick Z.; Hess, Wayne P.
2016-02-04
Simulating the spectroscopic properties of short-lived thermal and photochemical reaction intermediates and products is a challenging task, as these species often feature atypical molecular and electronic structures. The complex environments in which such species typically reside in practice add further complexity to the problem. Herein, we tackle this problem in silico using ab initio molecular dynamics (AIMD) simulations, employing iso-CHBr3, namely H(Br)C-Br-Br, as a prototypical system. This species was chosen because it features both a non-conventional C-Br-Br bonding pattern, as well as a strong dependence of its spectral features on the local environment in which it resides, as illustrated in recent experimental reports. The spectroscopic properties of iso-CHBr3 were measured by several groups that captured this transient intermediate in the photochemistry of CHBr3 in the gas phase, in rare gas matrices at 5K, and in solution under ambient laboratory conditions. We simulate the UV-Vis and IR spectra of iso-CHBr3 in all three media, including a Ne cluster (64 atoms) and a methylcyclohexane cage (14 solvent molecules) representative of the matrix isolated and solvated species. We exclusively perform fully quantum mechanical static and dynamic simulations. By comparing our condensed phase simulations to their experimental analogues, we stress the importance of (i) conformational sampling, even at cryogenic temperatures, and (ii) using a fully quantum mechanical description of both solute and bath to properly account for the experimental observables.
Jiménez, Noé; Camarena, Francisco; Redondo, Javier; Sánchez-Morcillo, Víctor; Konofagou, Elisa E.
2015-10-01
We report a numerical method for solving the constitutive relations of nonlinear acoustics, where multiple relaxation processes are included in a generalized formulation that allows the time-domain numerical solution by an explicit finite differences scheme. Thus, the proposed physical model overcomes the limitations of the one-way Khokhlov-Zabolotskaya-Kuznetsov (KZK) type models and, due to the Lagrangian density is implicitly included in the calculation, the proposed method also overcomes the limitations of Westervelt equation in complex configurations for medical ultrasound. In order to model frequency power law attenuation and dispersion, such as observed in biological media, the relaxation parameters are fitted to both exact frequency power law attenuation/dispersion media and also empirically measured attenuation of a variety of tissues that does not fit an exact power law. Finally, a computational technique based on artificial relaxation is included to correct the non-negligible numerical dispersion of the finite difference scheme, and, on the other hand, improve stability trough artificial attenuation when shock waves are present. This technique avoids the use of high-order finite-differences schemes leading to fast calculations. The present algorithm is especially suited for practical configuration where spatial discontinuities are present in the domain (e.g. axisymmetric domains or zero normal velocity boundary conditions in general). The accuracy of the method is discussed by comparing the proposed simulation solutions to one dimensional analytical and k-space numerical solutions.
Time Domain Induced Polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
2012-01-01
Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use...... of time-domaininduced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function......, to reconstruct the distribution of the Cole-Cole parameters of the earth. The accurate modeling of the transmitter waveform had a strong influence on the forward response, and we showed that the difference between a solution using a step response and a solution using the accurate modeling often is above 100...
International Nuclear Information System (INIS)
Lee, Jungpyo; Cappelli, Mark A
2008-01-01
In this paper, we present finite difference time domain (FDTD) simulations of millimetre-wave propagation through the near-field plasma plume of low power Hall thrusters. The simulations are intended to address potential issues (collisions, magnetic fields) that may affect the validity of simple theory used for phase shift determination in the recent measurements of plasma density using microwave interferometry (Cappelli et al 2006 J. Phys. D: Appl. Phys. 39 4582). One-dimensional plane wave FDTD simulations indicate that plasma non-uniformities along the direction of wave propagation have only a minor effect on the phase shifts estimated from collisionless, non-magnetized wave propagation through a path-length averaged plasma slab. Three-dimensional FDTD simulations that also account for electron collisions and magnetic fields indicate that the departure from the use of usual simple models is no more than about 15%, well within the limits of uncertainty in the experimental measurements taken within the near field of these plasma sources
Directory of Open Access Journals (Sweden)
N. Dadashzadeh
2013-09-01
Full Text Available Ultra-short pulse is a promising technology for achieving ultra-high data rate transmission which is required to follow the increased demand of data transport over an optical communication system. Therefore, the propagation of such type of pulses and the effects that it may suffer during its transmission through an optical waveguide has received a great deal of attention in the recent years. We provide an overview of recent theoretical developments in a numerical modeling of Maxwell's equations to analyze the propagation of short laser pulses in photonic structures. The process of short light pulse propagation through 2D periodic and quasi-periodic photonic structures is simulated based on Finite-Difference Time-Domain calculations of Maxwell’s equations.
iTesla Power Systems Library (iPSL): A Modelica library for phasor time-domain simulations
Vanfretti, L.; Rabuzin, T.; Baudette, M.; Murad, M.
The iTesla Power Systems Library (iPSL) is a Modelica package providing a set of power system components for phasor time-domain modeling and simulation. The Modelica language provides a systematic approach to develop models using a formal mathematical description, that uniquely specifies the physical behavior of a component or the entire system. Furthermore, the standardized specification of the Modelica language (Modelica Association [1]) enables unambiguous model exchange by allowing any Modelica-compliant tool to utilize the models for simulation and their analyses without the need of a specific model transformation tool. As the Modelica language is being developed with open specifications, any tool that implements these requirements can be utilized. This gives users the freedom of choosing an Integrated Development Environment (IDE) of their choice. Furthermore, any integration solver can be implemented within a Modelica tool to simulate Modelica models. Additionally, Modelica is an object-oriented language, enabling code factorization and model re-use to improve the readability of a library by structuring it with object-oriented hierarchy. The developed library is released under an open source license to enable a wider distribution and let the user customize it to their specific needs. This paper describes the iPSL and provides illustrative application examples.
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.
Chao, Guo-Shan; Sung, Kung-Bin
2010-02-01
Backscattered light spectra have been used to extract size distribution of cell nuclei in epithelial tissues for noninvasive detection of precancerous lesions. In existing experimental studies, size estimation is achieved by assuming nuclei as homogeneous spheres or spheroids and fitting the measured data with models based on Mie theory. However, the validity of simplifying nuclei as homogeneous spheres has not been thoroughly examined. In this study, we investigate the spectral characteristics of backscattering from models of spheroidal nuclei under plane wave illumination using three-dimensional finite-difference time-domain (FDTD) simulation. A modulated Gaussian pulse is used to obtain wavelength dependent scattering intensity with a single FDTD run. The simulated model of nuclei consists of a nucleolus and randomly distributed chromatin condensation in homogeneous cytoplasm and nucleoplasm. The results show that backscattering spectra from spheroidal nuclei have similar oscillating patterns to those from homogeneous spheres with the diameter equal to the projective length of the spheroidal nucleus along the propagation direction. The strength of backscattering is enhanced in heterogeneous spheroids as compared to homogeneous spheroids. The degree of which backscattering spectra of heterogeneous nuclei deviate from Mie theory is highly dependent on the distribution of chromatin/nucleolus but not sensitive to nucleolar size, refractive index fluctuation or chromatin density.
Directory of Open Access Journals (Sweden)
Adailton S. Borges
Full Text Available Abstract A broad class of engineering systems can be satisfactory modeled under the assumptions of small deformations and linear material properties. However, many mechanical systems used in modern applications, like structural elements typical of aerospace and petroleum industries, have been characterized by increased slenderness and high static and dynamic loads. In such situations, it becomes indispensable to consider the nonlinear geometric effects and/or material nonlinear behavior. At the same time, in many cases involving dynamic loads, there comes the need for attenuation of vibration levels. In this context, this paper describes the development and validation of numerical models of viscoelastic slender beam-like structures undergoing large displacements. The numerical approach is based on the combination of the nonlinear Cosserat beam theory and a viscoelastic model based on Fractional Derivatives. Such combination enables to derive nonlinear equations of motion that, upon finite element discretization, can be used for predicting the dynamic behavior of the structure in the time domain, accounting for geometric nonlinearity and viscoelastic damping. The modeling methodology is illustrated and validated by numerical simulations, the results of which are compared to others available in the literature.
Energy Technology Data Exchange (ETDEWEB)
Rees, M [Aerodyn Energiesysteme gmbH, Rendsburg (Germany)
1996-09-01
The Germanische Lloyd guideline allows calculations of load spectra in two fundamentally different ways. In the case of the so-called `simplified load spectra` the maximum amplitude of fluctuation of a load component is formed as {+-}75% of the average value of the purely aerodynamic loads of this component at rated wind conditions, together with an overlay of mass-related loads. The second method allowed in the GL guideline is the calculation of load spectra from simulation results in the time domain. For a number of average wind speeds the time-dependent characteristics of the load components are calculated taking account of the natural spatial turbulence of the wind. These are converted into load spectra using the rainflow method. In a parametric study the load spectra are calculated according to both methods and compared. The calculations are performed for turbines with rated powers of 100 kW to 2000 kW, with two and three blades, and also for stall-controlled and pitch-controlled turbines. The calculated load spectra are compared with each by means of 1 P fatigue equivalent load spectra. The influence of individual parameters is presented, as is the validity of the simplified load spectra. (au)
DEFF Research Database (Denmark)
Celestinos, Adrian; Nielsen, Sofus Birkedal
2008-01-01
Small- and medium-size rectangular rooms have a strong influence on the low-frequency performance of loudspeakers. A simulation program based on the finite-difference time-domain (FDTD) method is introduced to analyze the sound field produced by loudspeakers in rectangular rooms at low frequencies...
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
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)
Banerjee, Saswatee; Hoshino, Tetsuya; Cole, James B
2008-08-01
We introduce a new implementation of the finite-difference time-domain (FDTD) algorithm with recursive convolution (RC) for first-order Drude metals. We implemented RC for both Maxwell's equations for light polarized in the plane of incidence (TM mode) and the wave equation for light polarized normal to the plane of incidence (TE mode). We computed the Drude parameters at each wavelength using the measured value of the dielectric constant as a function of the spatial and temporal discretization to ensure both the accuracy of the material model and algorithm stability. For the TE mode, where Maxwell's equations reduce to the wave equation (even in a region of nonuniform permittivity) we introduced a wave equation formulation of RC-FDTD. This greatly reduces the computational cost. We used our methods to compute the diffraction characteristics of metallic gratings in the visible wavelength band and compared our results with frequency-domain calculations.
2017-10-17
SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6...0704-0188 3. DATES COVERED (From - To) - Approved for public release; distribution is unlimited. UU UU UU UU 17-10-2017 25-Jul-2016 24-Jul-2017 Final...Report: Acquisition of a Multi-Domain Advanced Real- Time Simulator to Support DoD-focused Interdisciplinary Research at CSUB The views, opinions and
Impedance models in time domain
Rienstra, S.W.
2005-01-01
Necessary conditions for an impedance function are derived. Methods available in the literature are discussed. A format with recipe is proposed for an exact impedance condition in time domain on a time grid, based on the Helmholtz resonator model. An explicit solution is given of a pulse reflecting
DEFF Research Database (Denmark)
Santillan, Arturo Orozco
2013-01-01
, and the complete equations of conservation of mass and conservation of momentum were used together with the state equation for and adiabatic process in and ideal gas. Thermal effects were neglected to simplify the problem. The obtained numerical results illustrate the applicability of the method. The simulations...
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...
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
Directory of Open Access Journals (Sweden)
Kyoung-Rok Lee
2013-12-01
Full Text Available A floating Oscillating Water Column (OWC wave energy converter, a Backward Bent Duct Buoy (BBDB, was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.
Time versus frequency domain measurements: layered model ...
African Journals Online (AJOL)
... their high frequency content while among TEM data sets with low frequency content, the averaging times for the FEM ellipticity were shorter than the TEM quality. Keywords: ellipticity, frequency domain, frequency electromagnetic method, model parameter, orientation error, time domain, transient electromagnetic method
Lattice gas simulations of replicating domains
International Nuclear Information System (INIS)
Dawson, S.P.; Hasslacher, B.; Pearson, J.E.
1993-01-01
We use the lattice gas cellular automation (LGCA) developed to simulate a process of pattern-formation recently observed in reaction-diffusion systems. We study the reaction mechanism, which is an extension of the Selkov model for glycolytic oscillations. We are able to reproduce the self-replicating domains observed in this work. We use the LGCA simulation to estimate the smallest length-scale on which this process can occur under conditions encountered in the cell. These estimates are similar to those obtained for Turing patterns in the same setting
Lattice gas simulations of replicating domains
Energy Technology Data Exchange (ETDEWEB)
Dawson, S.P.; Hasslacher, B.; Pearson, J.E.
1993-12-31
We use the lattice gas cellular automation (LGCA) developed to simulate a process of pattern-formation recently observed in reaction-diffusion systems. We study the reaction mechanism, which is an extension of the Selkov model for glycolytic oscillations. We are able to reproduce the self-replicating domains observed in this work. We use the LGCA simulation to estimate the smallest length-scale on which this process can occur under conditions encountered in the cell. These estimates are similar to those obtained for Turing patterns in the same setting.
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....
Simulating detectors dead time
International Nuclear Information System (INIS)
Rustom, Ibrahim Farog Ibrahim
2015-06-01
Nuclear detectors are used in all aspects of nuclear measurements. All nuclear detectors are characterized by their dead time i.e. the time needed by a detector to recover from a previous incident. A detector dead time influences measurements taken by a detector and specially when measuring high decay rate (>) where is the detector dead time. Two models are usually used to correct for the dead time effect: the paralayzable and the non-paralayzable models. In the current work we use Monte Carlo simulation techniques to simulate radioactivity and the effect of dead time and the count rate of a detector with a dead time =5x10 - 5s assuming the non-paralayzable model. The simulation indicates that assuming a non -paralayzable model could be used to correct for decay rate measured by a detector. The reliability of the non-paralayzable model to correct the measured decay rate could be gauged using the Monte Carlo simulation. (Author)
Eulerian Time-Domain Filtering for Spatial LES
Pruett, C. David
1997-01-01
Eulerian time-domain filtering seems to be appropriate for LES (large eddy simulation) of flows whose large coherent structures convect approximately at a common characteristic velocity; e.g., mixing layers, jets, and wakes. For these flows, we develop an approach to LES based on an explicit second-order digital Butterworth filter, which is applied in,the time domain in an Eulerian context. The approach is validated through a priori and a posteriori analyses of the simulated flow of a heated, subsonic, axisymmetric jet.
Casimir forces in the time domain: Theory
International Nuclear Information System (INIS)
Rodriguez, Alejandro W.; McCauley, Alexander P.; Joannopoulos, John D.; Johnson, Steven G.
2009-01-01
We present a method to compute Casimir forces in arbitrary geometries and for arbitrary materials based on the finite-difference time-domain (FDTD) scheme. The method involves the time evolution of electric and magnetic fields in response to a set of current sources, in a modified medium with frequency-independent conductivity. The advantage of this approach is that it allows one to exploit existing FDTD software, without modification, to compute Casimir forces. In this paper, we focus on the derivation, implementation choices, and essential properties of the time-domain algorithm, both considered analytically and illustrated in the simplest parallel-plate geometry.
Generating Dynamic Persistence in the Time Domain
Guerrero, A.; Smith, L. A.; Smith, L. A.; Kaplan, D. T.
2001-12-01
Many dynamical systems present long-range correlations. Physically, these systems vary from biological to economical, including geological or urban systems. Important geophysical candidates for this type of behaviour include weather (or climate) and earthquake sequences. Persistence is characterised by slowly decaying correlation function; that, in theory, never dies out. The Persistence exponent reflects the degree of memory in the system and much effort has been expended creating and analysing methods that successfully estimate this parameter and model data that exhibits persistence. The most widely used methods for generating long correlated time series are not dynamical systems in the time domain, but instead are derived from a given spectral density. Little attention has been drawn to modelling persistence in the time domain. The time domain approach has the advantage that an observation at certain time can be calculated using previous observations which is particularly suitable when investigating the predictability of a long memory process. We will describe two of these methods in the time domain. One is a traditional approach using fractional ARIMA (autoregressive and moving average) models; the second uses a novel approach to extending a given series using random Fourier basis functions. The statistical quality of the two methods is compared, and they are contrasted with weather data which shows, reportedly, persistence. The suitability of this approach both for estimating predictability and for making predictions is discussed.
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...
Structural Time Domain Identification Toolbox User's Guide
DEFF Research Database (Denmark)
Andersen, P.; Kirkegaard, Poul Henning; Brincker, Rune
This manual describes the Structural Time Domain Identification toolbox for use with MA TLAB. This version of the tool box has been developed using the PC-based MA TLAB version 4.2c, but is compatible with prior versions of MATLAB and UNIX-based versions. The routines of the toolbox are the so...
Böckmann, Marcus; Doltsinis, Nikos L; Marx, Dominik
2015-06-09
An extended Lagrangian formalism that allows for a smooth transition between two different descriptions of interactions during a molecular dynamics simulation is presented. This time-adaptive method is particularly useful in the context of multiscale simulation as it provides a sound recipe to switch on demand between different hierarchical levels of theory, for instance between ab initio ("QM") and force field ("MM") descriptions of a given (sub)system in the course of a molecular dynamics simulation. The equations of motion can be integrated straightforwardly using the usual propagators, such as the Verlet algorithm. First test cases include a bath of harmonic oscillators, of which a subset is switched to a different force constant and/or equilibrium position, as well as an all-MM to QM/MM transition in a hydrogen-bonded water dimer. The method is then applied to a smectic 8AB8 liquid crystal and is shown to be able to switch dynamically a preselected 8AB8 molecule from an all-MM to a QM/MM description which involves partition boundaries through covalent bonds. These examples show that the extended Lagrangian approach is not only easy to implement into existing code but that it is also efficient and robust. The technique moreover provides easy access to a conserved energy quantity, also in cases when Nosé-Hoover chain thermostatting is used throughout dynamical switching. A simple quadratic driving potential proves to be sufficient to guarantee a smooth transition whose time scale can be easily tuned by varying the fictitious mass parameter associated with the auxiliary variable used to extend the Lagrangian. The method is general and can be applied to time-adaptive switching on demand between two different levels of theory within the framework of hybrid scale-bridging simulations.
Nikolskiy, V. P.; Stegailov, V. V.
2018-01-01
Metal nanoparticles (NPs) serve as important tools for many modern technologies. However, the proper microscopic models of the interaction between ultrashort laser pulses and metal NPs are currently not very well developed in many cases. One part of the problem is the description of the warm dense matter that is formed in NPs after intense irradiation. Another part of the problem is the description of the electromagnetic waves around NPs. Description of wave propagation requires the solution of Maxwell’s equations and the finite-difference time-domain (FDTD) method is the classic approach for solving them. There are many commercial and free implementations of FDTD, including the open source software that supports graphics processing unit (GPU) acceleration. In this report we present the results on the FDTD calculations for different cases of the interaction between ultrashort laser pulses and metal nanoparticles. Following our previous results, we analyze the efficiency of the GPU acceleration of the FDTD algorithm.
Parametric time-frequency domain spatial audio
Delikaris-Manias, Symeon; Politis, Archontis
2018-01-01
This book provides readers with the principles and best practices in spatial audio signal processing. It describes how sound fields and their perceptual attributes are captured and analyzed within the time-frequency domain, how essential representation parameters are coded, and how such signals are efficiently reproduced for practical applications. The book is split into four parts starting with an overview of the fundamentals. It then goes on to explain the reproduction of spatial sound before offering an examination of signal-dependent spatial filtering. The book finishes with coverage of both current and future applications and the direction that spatial audio research is heading in. Parametric Time-frequency Domain Spatial Audio focuses on applications in entertainment audio, including music, home cinema, and gaming--covering the capturing and reproduction of spatial sound as well as its generation, transduction, representation, transmission, and perception. This book will teach readers the tools needed...
Subjective time pressure: general or domain specific?
Kleiner, Sibyl
2014-09-01
Chronic time pressure has been identified as a pervasive societal problem, exacerbated by high demands of the labor market and the home. Yet time pressure has not been disaggregated and examined separately across home and work contexts, leaving many unanswered questions regarding the sources and potentially stressful consequences of time pressure. Using data collected in the United States General Social Survey waves 2002 and 2004, this study disaggregates time pressure into the domains of home and work, and asks whether considering time pressures within distinct work and home contexts reveals distinct predictors or associations with stress. Findings show that both predictors and stress associations differ across work and home pressures, revealing both methodological and theoretical implications for the study of time pressure and work and family life more generally. Copyright © 2014 Elsevier Inc. All rights reserved.
Metrology for terahertz time-domain spectrometers
Molloy, John F.; Naftaly, Mira
2015-12-01
In recent years the terahertz time-domain spectrometer (THz TDS) [1] has emerged as a key measurement device for spectroscopic investigations in the frequency range of 0.1-5 THz. To date, almost every type of material has been studied using THz TDS, including semiconductors, ceramics, polymers, metal films, liquid crystals, glasses, pharmaceuticals, DNA molecules, proteins, gases, composites, foams, oils, and many others. Measurements with a TDS are made in the time domain; conversion from the time domain data to a frequency spectrum is achieved by applying the Fourier Transform, calculated numerically using the Fast Fourier Transform (FFT) algorithm. As in many other types of spectrometer, THz TDS requires that the sample data be referenced to similarly acquired data with no sample present. Unlike frequency-domain spectrometers which detect light intensity and measure absorption spectra, a TDS records both amplitude and phase information, and therefore yields both the absorption coefficient and the refractive index of the sample material. The analysis of the data from THz TDS relies on the assumptions that: a) the frequency scale is accurate; b) the measurement of THz field amplitude is linear; and c) that the presence of the sample does not affect the performance characteristics of the instrument. The frequency scale of a THz TDS is derived from the displacement of the delay line; via FFT, positioning errors may give rise to frequency errors that are difficult to quantify. The measurement of the field amplitude in a THz TDS is required to be linear with a dynamic range of the order of 10 000. And attention must be given to the sample positioning and handling in order to avoid sample-related errors.
Using random response input in Ibrahim Time Domain
DEFF Research Database (Denmark)
Olsen, Peter; Brincker, R.
2013-01-01
In this paper the time domain technique Ibrahim Time Domain (ITD) is used to analyze random time data. ITD is known to be a technique for identification of output only systems. The traditional formulation of ITD is claimed to be limited, when identifying closely spaced modes, because....... In this article it is showed that when using the modified ITD random time data can be analyzed. The application of the technique is displayed by a case study, with simulations and experimental data....... of the technique being Single Input Multiple Output (SIMO). It has earlier been showed that when modifying ITD with Toeplitz matrix averaging. Identification of time data with closely spaced modes is improved. In the traditional formulation of ITD the time data has to be free decays or impulse response functions...
New Flutter Analysis Technique for Time-Domain Computational Aeroelasticity
Pak, Chan-Gi; Lung, Shun-Fat
2017-01-01
A new time-domain approach for computing flutter speed is presented. Based on the time-history result of aeroelastic simulation, the unknown unsteady aerodynamics model is estimated using a system identification technique. The full aeroelastic model is generated via coupling the estimated unsteady aerodynamic model with the known linear structure model. The critical dynamic pressure is computed and used in the subsequent simulation until the convergence of the critical dynamic pressure is achieved. The proposed method is applied to a benchmark cantilevered rectangular wing.
Ultrabroadband THz time-domain spectroscopy of biomolecular crystals
DEFF Research Database (Denmark)
Kaltenecker, Korbinian J.; Engelbrecht, Sebastian; Iwaszczuk, Krzysztof
2016-01-01
Ultrabroadband THz time-domain spectroscopy based on two-color plasma generation and air biased coherent detection is used for the investigation of molecular dynamics of crystalline materials in the frequency range from 0.3 THz to 20 THz. We show that the spectral features in this extended...... frequency range are a result of inter- and intramolecular vibrations which are identified by means of simulations of the crystalline materials....
Time-domain multiple-quantum NMR
International Nuclear Information System (INIS)
Weitekamp, D.P.
1982-11-01
The development of time-domain multiple-quantum nuclear magnetic resonance is reviewed through mid 1982 and some prospects for future development are indicated. Particular attention is given to the problem of obtaining resolved, interpretable, many-quantum spectra for anisotropic magnetically isolated systems of coupled spins. New results are presented on a number of topics including the optimization of multiple-quantum-line intensities, analysis of noise in two-dimensional spectroscopy, and the use of order-selective excitation for cross polarization between nuclear-spin species
The time domain triple probe method
International Nuclear Information System (INIS)
Meier, M.A.; Hallock, G.A.; Tsui, H.Y.W.; Bengtson, R.D.
1994-01-01
A new Langmuir probe technique based on the triple probe method is being developed to provide simultaneous measurement of plasma temperature, potential, and density with the temporal and spatial resolution required to accurately characterize plasma turbulence. When the conventional triple probe method is used in an inhomogeneous plasma, local differences in the plasma measured at each probe introduce significant error in the estimation of turbulence parameters. The Time Domain Triple Probe method (TDTP) uses high speed switching of Langmuir probe potential, rather than spatially separated probes, to gather the triple probe information thus avoiding these errors. Analysis indicates that plasma response times and recent electronics technology meet the requirements to implement the TDTP method. Data reduction techniques of TDTP data are to include linear and higher order correlation analysis to estimate fluctuation induced particle and thermal transport, as well as energy relationships between temperature, density, and potential fluctuations
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
Coherent combining pulse bursts in time domain
Galvanauskas, Almantas
2018-01-09
A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.
Simulation and Domain Identification of Sea Ice Thermodynamic System
Directory of Open Access Journals (Sweden)
Bing Tan
2012-01-01
Full Text Available Based on the measured data and characteristics of sea ice temperature distribution in space and time, this study is intended to consider a parabolic partial differential equation of the thermodynamic field of sea ice (coupled by snow, ice, and sea water layers with a time-dependent domain and its parameter identification problem. An optimal model with state constraints is presented with the thicknesses of snow and sea ice as parametric variables and the deviation between the calculated and measured sea ice temperatures as the performance criterion. The unique existence of the weak solution of the thermodynamic system is proved. The properties of the identification problem and the existence of the optimal parameter are discussed, and the one-order necessary condition is derived. Finally, based on the nonoverlapping domain decomposition method and semi-implicit difference scheme, an optimization algorithm is proposed for the numerical simulation. Results show that the simulated temperature of sea ice fit well with the measured data, and the better fit is corresponding to the deeper sea ice.
Combinatorial geometry domain decomposition strategies for Monte Carlo simulations
Energy Technology Data Exchange (ETDEWEB)
Li, G.; Zhang, B.; Deng, L.; Mo, Z.; Liu, Z.; Shangguan, D.; Ma, Y.; Li, S.; Hu, Z. [Institute of Applied Physics and Computational Mathematics, Beijing, 100094 (China)
2013-07-01
Analysis and modeling of nuclear reactors can lead to memory overload for a single core processor when it comes to refined modeling. A method to solve this problem is called 'domain decomposition'. In the current work, domain decomposition algorithms for a combinatorial geometry Monte Carlo transport code are developed on the JCOGIN (J Combinatorial Geometry Monte Carlo transport INfrastructure). Tree-based decomposition and asynchronous communication of particle information between domains are described in the paper. Combination of domain decomposition and domain replication (particle parallelism) is demonstrated and compared with that of MERCURY code. A full-core reactor model is simulated to verify the domain decomposition algorithms using the Monte Carlo particle transport code JMCT (J Monte Carlo Transport Code), which has being developed on the JCOGIN infrastructure. Besides, influences of the domain decomposition algorithms to tally variances are discussed. (authors)
Combinatorial geometry domain decomposition strategies for Monte Carlo simulations
International Nuclear Information System (INIS)
Li, G.; Zhang, B.; Deng, L.; Mo, Z.; Liu, Z.; Shangguan, D.; Ma, Y.; Li, S.; Hu, Z.
2013-01-01
Analysis and modeling of nuclear reactors can lead to memory overload for a single core processor when it comes to refined modeling. A method to solve this problem is called 'domain decomposition'. In the current work, domain decomposition algorithms for a combinatorial geometry Monte Carlo transport code are developed on the JCOGIN (J Combinatorial Geometry Monte Carlo transport INfrastructure). Tree-based decomposition and asynchronous communication of particle information between domains are described in the paper. Combination of domain decomposition and domain replication (particle parallelism) is demonstrated and compared with that of MERCURY code. A full-core reactor model is simulated to verify the domain decomposition algorithms using the Monte Carlo particle transport code JMCT (J Monte Carlo Transport Code), which has being developed on the JCOGIN infrastructure. Besides, influences of the domain decomposition algorithms to tally variances are discussed. (authors)
Finite difference time domain analysis of a chiro plasma
International Nuclear Information System (INIS)
Torres-Silva, H.; Obligado, A.; Reggiani, N.; Sakanaka, P.H.
1995-01-01
The finite difference time-domain (FDTD) method is one of the most widely used computational methods in electromagnetics. Using FDTD, Maxwell's equations are solved directly in the time domain via finite differences and time stepping. The basic approach is relatively easy to understand and is an alternative to the more usual frequency-domain approaches. (author). 5 refs
Reengineering observatory operations for the time domain
Seaman, Robert L.; Vestrand, W. T.; Hessman, Frederic V.
2014-07-01
Observatories are complex scientific and technical institutions serving diverse users and purposes. Their telescopes, instruments, software, and human resources engage in interwoven workflows over a broad range of timescales. These workflows have been tuned to be responsive to concepts of observatory operations that were applicable when various assets were commissioned, years or decades in the past. The astronomical community is entering an era of rapid change increasingly characterized by large time domain surveys, robotic telescopes and automated infrastructures, and - most significantly - of operating modes and scientific consortia that span our individual facilities, joining them into complex network entities. Observatories must adapt and numerous initiatives are in progress that focus on redesigning individual components out of the astronomical toolkit. New instrumentation is both more capable and more complex than ever, and even simple instruments may have powerful observation scripting capabilities. Remote and queue observing modes are now widespread. Data archives are becoming ubiquitous. Virtual observatory standards and protocols and astroinformatics data-mining techniques layered on these are areas of active development. Indeed, new large-aperture ground-based telescopes may be as expensive as space missions and have similarly formal project management processes and large data management requirements. This piecewise approach is not enough. Whatever challenges of funding or politics facing the national and international astronomical communities it will be more efficient - scientifically as well as in the usual figures of merit of cost, schedule, performance, and risks - to explicitly address the systems engineering of the astronomical community as a whole.
Toward practical terahertz time-domain spectroscopy
Brigada, David J.
Terahertz time-domain spectroscopy is a promising technology for the identification of explosive and pharmaceutical substances in adverse conditions. It interacts strongly with intermolecular vibrational and rotational modes. Terahertz also passes through many common dielectric covering materials, allowing for the identification of substances in envelopes, wrapped in opaque plastic, or otherwise hidden. However, there are several challenges preventing the adoption of terahertz spectroscopy outside the laboratory. This dissertation examines the problems preventing widespread adoption of terahertz technology and attempts to resolve them. In order to use terahertz spectroscopy to identify substances, a spectrum measured of the target sample must be compared to the spectra of various known standard samples. This dissertation examines various methods that can be employed throughout the entire process of acquiring and transforming terahertz waveforms to improve the accuracy of these comparisons. The concepts developed in this dissertation directly apply to terahertz spectroscopy, but also carry implications for other spectroscopy methods, from Raman to mass spectrometry. For example, these techniques could help to lower the rate of false positives at airport security checkpoints. This dissertation also examines the implementation of several of these methods as a way to realize a fully self-contained, handheld, battery-operated terahertz spectrometer. This device also employs techniques to allow minimally-trained operators use terahertz to detect different substances of interest. It functions as a proof-of-concept of the true benefits of the improvements that have been developed in this dissertation.
Agent-based Simulation of the Maritime Domain
Directory of Open Access Journals (Sweden)
O. Vaněk
2010-01-01
Full Text Available In this paper, a multi-agent based simulation platform is introduced that focuses on legitimate and illegitimate aspects of maritime traffic, mainly on intercontinental transport through piracy afflicted areas. The extensible architecture presented here comprises several modules controlling the simulation and the life-cycle of the agents, analyzing the simulation output and visualizing the entire simulated domain. The simulation control module is initialized by various configuration scenarios to simulate various real-world situations, such as a pirate ambush, coordinated transit through a transport corridor, or coastal fishing and local traffic. The environmental model provides a rich set of inputs for agents that use the geo-spatial data and the vessel operational characteristics for their reasoning. The agent behavior model based on finite state machines together with planning algorithms allows complex expression of agent behavior, so the resulting simulation output can serve as a substitution for real world data from the maritime domain.
Time-domain modeling of electromagnetic diffusion with a frequency-domain code
Mulder, W.A.; Wirianto, M.; Slob, E.C.
2007-01-01
We modeled time-domain EM measurements of induction currents for marine and land applications with a frequency-domain code. An analysis of the computational complexity of a number of numerical methods shows that frequency-domain modeling followed by a Fourier transform is an attractive choice if a
Ulku, Huseyin Arda; Sayed, Sadeed Bin; Bagci, Hakan
2014-01-01
solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation
A time domain phase-gradient based ISAR autofocus algorithm
CSIR Research Space (South Africa)
Nel, W
2011-10-01
Full Text Available . Results on simulated and measured data show that the algorithm performs well. Unlike many other ISAR autofocus techniques, the algorithm does not make use of several computationally intensive iterations between the data and image domains as part...
Simulation of two-phase flows by domain decomposition
International Nuclear Information System (INIS)
Dao, T.H.
2013-01-01
This thesis deals with numerical simulations of compressible fluid flows by implicit finite volume methods. Firstly, we studied and implemented an implicit version of the Roe scheme for compressible single-phase and two-phase flows. Thanks to Newton method for solving nonlinear systems, our schemes are conservative. Unfortunately, the resolution of nonlinear systems is very expensive. It is therefore essential to use an efficient algorithm to solve these systems. For large size matrices, we often use iterative methods whose convergence depends on the spectrum. We have studied the spectrum of the linear system and proposed a strategy, called Scaling, to improve the condition number of the matrix. Combined with the classical ILU pre-conditioner, our strategy has reduced significantly the GMRES iterations for local systems and the computation time. We also show some satisfactory results for low Mach-number flows using the implicit centered scheme. We then studied and implemented a domain decomposition method for compressible fluid flows. We have proposed a new interface variable which makes the Schur complement method easy to build and allows us to treat diffusion terms. Using GMRES iterative solver rather than Richardson for the interface system also provides a better performance compared to other methods. We can also decompose the computational domain into any number of sub-domains. Moreover, the Scaling strategy for the interface system has improved the condition number of the matrix and reduced the number of GMRES iterations. In comparison with the classical distributed computing, we have shown that our method is more robust and efficient. (author) [fr
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.
Direct time-domain techniques for transient radiation and scattering
International Nuclear Information System (INIS)
Miller, E.K.; Landt, J.A.
1976-01-01
A tutorial introduction to transient electromagnetics, focusing on direct time-domain techniques, is presented. Physical, mathematical, numerical, and experimental aspects of time-domain methods, with emphasis on wire objects excited as antennas or scatters are examined. Numerous computed examples illustrate the characteristics of direct time-domain procedures, especially where they may offer advantages over procedures in the more familiar frequency domain. These advantages include greater solution efficiency for many types of problems, the ability to handle nonlinearities, improved physical insight and interpretability, availability of wide-band information from a single calculation, and the possibility of isolating interactions among various parts of an object using time-range gating
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...
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 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.
SVD compression for magnetic resonance fingerprinting in the time domain.
McGivney, Debra F; Pierre, Eric; Ma, Dan; Jiang, Yun; Saybasili, Haris; Gulani, Vikas; Griswold, Mark A
2014-12-01
Magnetic resonance (MR) fingerprinting is a technique for acquiring and processing MR data that simultaneously provides quantitative maps of different tissue parameters through a pattern recognition algorithm. A predefined dictionary models the possible signal evolutions simulated using the Bloch equations with different combinations of various MR parameters and pattern recognition is completed by computing the inner product between the observed signal and each of the predicted signals within the dictionary. Though this matching algorithm has been shown to accurately predict the MR parameters of interest, one desires a more efficient method to obtain the quantitative images. We propose to compress the dictionary using the singular value decomposition, which will provide a low-rank approximation. By compressing the size of the dictionary in the time domain, we are able to speed up the pattern recognition algorithm, by a factor of between 3.4-4.8, without sacrificing the high signal-to-noise ratio of the original scheme presented previously.
Transformation Algorithm of Dielectric Response in Time-Frequency Domain
Directory of Open Access Journals (Sweden)
Ji Liu
2014-01-01
Full Text Available A transformation algorithm of dielectric response from time domain to frequency domain is presented. In order to shorten measuring time of low or ultralow frequency dielectric response characteristics, the transformation algorithm is used in this paper to transform the time domain relaxation current to frequency domain current for calculating the low frequency dielectric dissipation factor. In addition, it is shown from comparing the calculation results with actual test data that there is a coincidence for both results over a wide range of low frequencies. Meanwhile, the time domain test data of depolarization currents in dry and moist pressboards are converted into frequency domain results on the basis of the transformation. The frequency domain curves of complex capacitance and dielectric dissipation factor at the low frequency range are obtained. Test results of polarization and depolarization current (PDC in pressboards are also given at the different voltage and polarization time. It is demonstrated from the experimental results that polarization and depolarization current are affected significantly by moisture contents of the test pressboards, and the transformation algorithm is effective in ultralow frequency of 10−3 Hz. Data analysis and interpretation of the test results conclude that analysis of time-frequency domain dielectric response can be used for assessing insulation system in power transformer.
Full waveform inversion in the frequency domain using classified time-domain residual wavefields
Son, Woohyun; Koo, Nam-Hyung; Kim, Byoung-Yeop; Lee, Ho-Young; Joo, Yonghwan
2017-04-01
We perform the acoustic full waveform inversion in the frequency domain using residual wavefields that have been separated in the time domain. We sort the residual wavefields in the time domain according to the order of absolute amplitudes. Then, the residual wavefields are separated into several groups in the time domain. To analyze the characteristics of the residual wavefields, we compare the residual wavefields of conventional method with those of our residual separation method. From the residual analysis, the amplitude spectrum obtained from the trace before separation appears to have little energy at the lower frequency bands. However, the amplitude spectrum obtained from our strategy is regularized by the separation process, which means that the low-frequency components are emphasized. Therefore, our method helps to emphasize low-frequency components of residual wavefields. Then, we generate the frequency-domain residual wavefields by taking the Fourier transform of the separated time-domain residual wavefields. With these wavefields, we perform the gradient-based full waveform inversion in the frequency domain using back-propagation technique. Through a comparison of gradient directions, we confirm that our separation method can better describe the sub-salt image than the conventional approach. The proposed method is tested on the SEG/EAGE salt-dome model. The inversion results show that our algorithm is better than the conventional gradient based waveform inversion in the frequency domain, especially for deeper parts of the velocity model.
Parameter Estimation in Continuous Time Domain
Directory of Open Access Journals (Sweden)
Gabriela M. ATANASIU
2016-12-01
Full Text Available This paper will aim to presents the applications of a continuous-time parameter estimation method for estimating structural parameters of a real bridge structure. For the purpose of illustrating this method two case studies of a bridge pile located in a highly seismic risk area are considered, for which the structural parameters for the mass, damping and stiffness are estimated. The estimation process is followed by the validation of the analytical results and comparison with them to the measurement data. Further benefits and applications for the continuous-time parameter estimation method in civil engineering are presented in the final part of this paper.
Time Domain Astronomy with Swift and Fermi
African Journals Online (AJOL)
J.D. Myers
sources not usually associated with high-energy emission − e.g., novae and flare ... spectacular transient emission from tidal disruption events and supernova shock ... 3×10−4 for a white dwarf (WD) and ∼2×10. −6 for a 1M⊙ main sequence star. .... outbursts; the strongest was ∼104 times more energetic than the largest.
Underwater Advanced Time-Domain Electromagnetic System
2017-03-03
was determined that the signal was being read in, but was extremely low and was not being recognized by the acquisition software. Further testing...timing window by transmitting some FMC delays during startup and these delay values are determined empirically, during testing. Geometrics is in
Cost efficient CFD simulations: Proper selection of domain partitioning strategies
Haddadi, Bahram; Jordan, Christian; Harasek, Michael
2017-10-01
Computational Fluid Dynamics (CFD) is one of the most powerful simulation methods, which is used for temporally and spatially resolved solutions of fluid flow, heat transfer, mass transfer, etc. One of the challenges of Computational Fluid Dynamics is the extreme hardware demand. Nowadays super-computers (e.g. High Performance Computing, HPC) featuring multiple CPU cores are applied for solving-the simulation domain is split into partitions for each core. Some of the different methods for partitioning are investigated in this paper. As a practical example, a new open source based solver was utilized for simulating packed bed adsorption, a common separation method within the field of thermal process engineering. Adsorption can for example be applied for removal of trace gases from a gas stream or pure gases production like Hydrogen. For comparing the performance of the partitioning methods, a 60 million cell mesh for a packed bed of spherical adsorbents was created; one second of the adsorption process was simulated. Different partitioning methods available in OpenFOAM® (Scotch, Simple, and Hierarchical) have been used with different numbers of sub-domains. The effect of the different methods and number of processor cores on the simulation speedup and also energy consumption were investigated for two different hardware infrastructures (Vienna Scientific Clusters VSC 2 and VSC 3). As a general recommendation an optimum number of cells per processor core was calculated. Optimized simulation speed, lower energy consumption and consequently the cost effects are reported here.
Time step MOTA thermostat simulation
International Nuclear Information System (INIS)
Guthrie, G.L.
1978-09-01
The report details the logic, program layout, and operating procedures for the time-step MOTA (Materials Open Test Assembly) thermostat simulation program known as GYRD. It will enable prospective users to understand the operation of the program, run it, and interpret the results. The time-step simulation analysis was the approach chosen to determine the maximum value gain that could be used to minimize steady temperature offset without risking undamped thermal oscillations. The advantage of the GYRD program is that it directly shows hunting, ringing phenomenon, and similar events. Programs BITT and CYLB are faster, but do not directly show ringing time
Microresonator-Based Optical Frequency Combs: A Time Domain Perspective
2016-04-19
AFRL-AFOSR-VA-TR-2016-0165 (BRI) Microresonator-Based Optical Frequency Combs: A Time Domain Perspective Andrew Weiner PURDUE UNIVERSITY 401 SOUTH...Optical Frequency Combs: A Time Domain Perspective 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0236 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data
Atom optics in the time domain
Arndt, M.; Szriftgiser, P.; Dalibard, J.; Steane, A. M.
1996-05-01
Atom-optics experiments are presented using a time-modulated evanescent light wave as an atomic mirror in the trampoline configuration, i.e., perpendicular to the direction of the atomic free fall. This modulated mirror is used to accelerate cesium atoms, to focus their trajectories, and to apply a ``multiple lens'' to separately focus different velocity classes of atoms originating from a point source. We form images of a simple two-slit object to show the resolution of the device. The experiments are modelled by a general treatment analogous to classical ray optics.
Evaluation of Damping Using Time Domain OMA Techniques
DEFF Research Database (Denmark)
Bajric, Anela; Brincker, Rune; Georgakis, Christos T.
2014-01-01
. In this paper a comparison is made of the effectiveness of three existing OMA techniques in providing accurate damping estimates for varying loadings, levels of noise, number of added measurement channels and structural damping. The evaluated techniques are derived in the time domain and are namely the Ibrahim...... Time Domain (ITD), Eigenvalue Realization Algorithm (ERA) and the Polyreference Time Domain (PTD). The response of a two degree-of-freedom (2DOF) system is numerically established from specified modal parameters with well separated and closely spaced modes. Two types of response are considered, free...
Space moving target detection using time domain feature
Wang, Min; Chen, Jin-yong; Gao, Feng; Zhao, Jin-yu
2018-01-01
The traditional space target detection methods mainly use the spatial characteristics of the star map to detect the targets, which can not make full use of the time domain information. This paper presents a new space moving target detection method based on time domain features. We firstly construct the time spectral data of star map, then analyze the time domain features of the main objects (target, stars and the background) in star maps, finally detect the moving targets using single pulse feature of the time domain signal. The real star map target detection experimental results show that the proposed method can effectively detect the trajectory of moving targets in the star map sequence, and the detection probability achieves 99% when the false alarm rate is about 8×10-5, which outperforms those of compared algorithms.
Molecular dynamics simulations of ferroelectric domain formation by oxygen vacancy
Zhu, Lin; You, Jeong Ho; Chen, Jinghong; Yeo, Changdong
2018-05-01
An oxygen vacancy, known to be detrimental to ferroelectric properties, has been investigated numerically for the potential uses to control ferroelectric domains in films using molecular dynamics simulations based on the first-principles effective Hamiltonian. As an electron donor, an oxygen vacancy generates inhomogeneous electrostatic and displacement fields which impose preferred polarization directions near the oxygen vacancy. When the oxygen vacancies are placed at the top and bottom interfaces, the out-of-plane polarizations are locally developed near the interfaces in the directions away from the interfaces. These polarizations from the interfaces are in opposite directions so that the overall out-of-plane polarization becomes significantly reduced. In the middle of the films, the in-plane domains are formed with containing 90° a 1/a 2 domain walls and the films are polarized along the [1 1 0] direction even when no electric field is applied. With oxygen vacancies placed at the top interface only, the films exhibit asymmetric hysteresis loops, confirming that the oxygen vacancies are one of the possible sources of ferroelectric imprint. It has been qualitatively demonstrated that the domain structures in the imprint films can be turned on and off by controlling an external field along the thickness direction. This study shows qualitatively that the oxygen vacancies can be utilized for tuning ferroelectric domain structures in films.
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.
Ultrasound breast imaging using frequency domain reverse time migration
Roy, O.; Zuberi, M. A. H.; Pratt, R. G.; Duric, N.
2016-04-01
Conventional ultrasonography reconstruction techniques, such as B-mode, are based on a simple wave propagation model derived from a high frequency approximation. Therefore, to minimize model mismatch, the central frequency of the input pulse is typically chosen between 3 and 15 megahertz. Despite the increase in theoretical resolution, operating at higher frequencies comes at the cost of lower signal-to-noise ratio. This ultimately degrades the image contrast and overall quality at higher imaging depths. To address this issue, we investigate a reflection imaging technique, known as reverse time migration, which uses a more accurate propagation model for reconstruction. We present preliminary simulation results as well as physical phantom image reconstructions obtained using data acquired with a breast imaging ultrasound tomography prototype. The original reconstructions are filtered to remove low-wavenumber artifacts that arise due to the inclusion of the direct arrivals. We demonstrate the advantage of using an accurate sound speed model in the reverse time migration process. We also explain how the increase in computational complexity can be mitigated using a frequency domain approach and a parallel computing platform.
Self-consistent field theory simulations of polymers on arbitrary domains
Energy Technology Data Exchange (ETDEWEB)
Ouaknin, Gaddiel, E-mail: gaddielouaknin@umail.ucsb.edu [Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106-5070 (United States); Laachi, Nabil; Delaney, Kris [Materials Research Laboratory, University of California, Santa Barbara, CA 93106-5080 (United States); Fredrickson, Glenn H. [Materials Research Laboratory, University of California, Santa Barbara, CA 93106-5080 (United States); Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080 (United States); Department of Materials, University of California, Santa Barbara, CA 93106-5050 (United States); Gibou, Frederic [Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106-5070 (United States); Department of Computer Science, University of California, Santa Barbara, CA 93106-5110 (United States)
2016-12-15
We introduce a framework for simulating the mesoscale self-assembly of block copolymers in arbitrary confined geometries subject to Neumann boundary conditions. We employ a hybrid finite difference/volume approach to discretize the mean-field equations on an irregular domain represented implicitly by a level-set function. The numerical treatment of the Neumann boundary conditions is sharp, i.e. it avoids an artificial smearing in the irregular domain boundary. This strategy enables the study of self-assembly in confined domains and enables the computation of physically meaningful quantities at the domain interface. In addition, we employ adaptive grids encoded with Quad-/Oc-trees in parallel to automatically refine the grid where the statistical fields vary rapidly as well as at the boundary of the confined domain. This approach results in a significant reduction in the number of degrees of freedom and makes the simulations in arbitrary domains using effective boundary conditions computationally efficient in terms of both speed and memory requirement. Finally, in the case of regular periodic domains, where pseudo-spectral approaches are superior to finite differences in terms of CPU time and accuracy, we use the adaptive strategy to store chain propagators, reducing the memory footprint without loss of accuracy in computed physical observables.
Directory of Open Access Journals (Sweden)
A. Becker
2007-06-01
Full Text Available In this paper a hybrid method combining the Time-Domain Method of Moments (TD-MoM, the Time-Domain Uniform Theory of Diffraction (TD-UTD and the Finite-Difference Time-Domain Method (FDTD is presented. When applying this new hybrid method, thin-wire antennas are modeled with the TD-MoM, inhomogeneous bodies are modelled with the FDTD and large perfectly conducting plates are modelled with the TD-UTD. All inhomogeneous bodies are enclosed in a so-called FDTD-volume and the thin-wire antennas can be embedded into this volume or can lie outside. The latter avoids the simulation of white space between antennas and inhomogeneous bodies. If the antennas are positioned into the FDTD-volume, their discretization does not need to agree with the grid of the FDTD. By using the TD-UTD large perfectly conducting plates can be considered efficiently in the solution-procedure. Thus this hybrid method allows time-domain simulations of problems including very different classes of objects, applying the respective most appropriate numerical techniques to every object.
Time-domain analysis of frequency dependent inertial wave forces on cylinders
DEFF Research Database (Denmark)
Krenk, Steen
2013-01-01
a simple time-domain procedure for the inertial force, in which the frequency dependence is represented via a simple explicit time filter on the wave particle acceleration or velocity. The frequency dependence of the inertia coefficient is known analytically as a function of the wave......-number, and the relevant range of waves shorter than about six times the diameter typically corresponds to deep water waves. This permits a universal non-dimensional frequency representation, that is converted to rational form to provide the relevant filter equation. Simple time-domain simulations demonstrate...... the reduction of the resonant part of the response for natural structural frequencies above the dominating wave frequency....
Time domain optical spectrometry with fiber optic waveguides
International Nuclear Information System (INIS)
Whitten, W.B.
1983-01-01
Spectrometers which use optical fibers to obtain time domain spectral dispersion are reviewed. Pulse transmission through fiber optic waveguides is discussed and the basic requirements for sources and detectors are given. Multiplex spectrometry and time-of-flight spectrometry are then discussed. Resolution, fiber requirements, instrumentation and specific spectrometers are presented
Measuring time and risk preferences: Reliability, stability, domain specificity
Wölbert, E.M.; Riedl, A.M.
2013-01-01
To accurately predict behavior economists need reliable measures of individual time preferences and attitudes toward risk and typically need to assume stability of these characteristics over time and across decision domains. We test the reliability of two choice tasks for eliciting discount rates,
Energy Technology Data Exchange (ETDEWEB)
Radhakrishnan, B., E-mail: radhakrishnb@ornl.gov; Eisenbach, M.; Burress, T.A.
2017-06-15
Highlights: • Developed new scaling technique for dipole–dipole interaction energy. • Developed new scaling technique for exchange interaction energy. • Used scaling laws to extend atomistic simulations to micrometer length scale. • Demonstrated transition from mono-domain to vortex magnetic structure. • Simulated domain wall width and transition length scale agree with experiments. - Abstract: A new scaling approach has been proposed for the spin exchange and the dipole–dipole interaction energy as a function of the system size. The computed scaling laws are used in atomistic Monte Carlo simulations of magnetic moment evolution to predict the transition from single domain to a vortex structure as the system size increases. The width of a 180° – domain wall extracted from the simulated structures is in close agreement with experimentally values for an F–Si alloy. The transition size from a single domain to a vortex structure is also in close agreement with theoretically predicted and experimentally measured values for Fe.
MULTILOOP PI CONTROLLER FOR ACHIEVING SIMULTANEOUS TIME AND FREQUENCY DOMAIN SPECIFICATIONS
Directory of Open Access Journals (Sweden)
M. SENTHILKUMAR
2015-08-01
Full Text Available Most of the controllers in control system are designed to satisfy either time domain or frequency domain specifications. This work presents the computation of a multiloop PI controller for achieving time and frequency domain specifications simultaneously. The desired time and frequency domain measures are to be specified initially to the design. To obtain the desired value of the performance measures the graphical relationship between the PI controller and the performance criteria is given. Thus by using graphical method a set of PI controller parameters to meet the desired performance measures are obtained in an effective and simpler way. The coupled tank has become a classic design of control engineering for multivariable process. The proposed control strategy has been implemented in the same coupled tank process and validated through simulation studies.
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
Molenaar, P.C.M.
1987-01-01
Outlines a frequency domain analysis of the dynamic factor model and proposes a solution to the problem of constructing a causal filter of lagged factor loadings. The method is illustrated with applications to simulated and real multivariate time series. The latter applications involve topographic
Fast damage imaging using the time-reversal technique in the frequency–wavenumber domain
International Nuclear Information System (INIS)
Zhu, R; Huang, G L; Yuan, F G
2013-01-01
The time-reversal technique has been successfully used in structural health monitoring (SHM) for quantitative imaging of damage. However, the technique is very time-consuming when it is implemented in the time domain. In this paper, we study the technique in the frequency–wavenumber (f–k) domain for fast real-time imaging of multiple damage sites in plates using scattered flexural plate waves. Based on Mindlin plate theory, the time reversibility of dispersive flexural waves in an isotropic plate is theoretically investigated in the f–k domain. A fast damage imaging technique is developed by using the cross-correlation between the back-propagated scattered wavefield and the incident wavefield in the frequency domain. Numerical simulations demonstrate that the proposed technique cannot only localize multiple damage sites but also potentially identify their sizes. Moreover, the time-reversal technique in the f–k domain is about two orders of magnitude faster than the method in the time domain. Finally, experimental testing of an on-line SHM system with a sparse piezoelectric sensor array is conducted for fast multiple damage identification using the proposed technique. (paper)
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.
A pseudospectral collocation time-domain method for diffractive optics
DEFF Research Database (Denmark)
Dinesen, P.G.; Hesthaven, J.S.; Lynov, Jens-Peter
2000-01-01
We present a pseudospectral method for the analysis of diffractive optical elements. The method computes a direct time-domain solution of Maxwell's equations and is applied to solving wave propagation in 2D diffractive optical elements. (C) 2000 IMACS. Published by Elsevier Science B.V. All rights...
Finite difference time domain modelling of particle accelerators
International Nuclear Information System (INIS)
Jurgens, T.G.; Harfoush, F.A.
1989-03-01
Finite Difference Time Domain (FDTD) modelling has been successfully applied to a wide variety of electromagnetic scattering and interaction problems for many years. Here the method is extended to incorporate the modelling of wake fields in particle accelerators. Algorithmic comparisons are made to existing wake field codes, such as MAFIA T3. 9 refs., 7 figs
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...
Al-Jabr, Ahmad; Alsunaidi, Mohammad A.
2010-01-01
A time-domain analysis of the propagation properties of surface-plasmon-polaritons (SPP) in Silver nanostructures is presented. The analysis is based on a simulation algorithm that unifies the formulation of different dispersion models and multi
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.
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.
Nucleation of holin domains and holes optimizes lysis timing of E. coli by phage λ
Ryan, Gillian; Rutenberg, Andrew
2007-03-01
Holin proteins regulate the precise scheduling of Escherichia coli lysis during infection by bacteriophage λ. Inserted into the host bacterium's inner membrane during infection, holins aggregate to form rafts and then holes within those rafts. We present a two-stage nucleation model of holin action, with the nucleation of condensed holin domains followed by the nucleation of holes within these domains. Late nucleation of holin rafts leads to a weak dependence of lysis timing on host cell size, though both nucleation events contribute equally to timing errors. Our simulations recover the accurate scheduling observed experimentally, and also suggest that phage-λ lysis of E.coli is optimized.
THz time domain spectroscopy of biomolecular conformational modes
International Nuclear Information System (INIS)
Markelz, Andrea; Whitmire, Scott; Hillebrecht, Jay; Birge, Robert
2002-01-01
We discuss the use of terahertz time domain spectroscopy for studies of conformational flexibility and conformational change in biomolecules. Protein structural dynamics are vital to biological function with protein flexibility affecting enzymatic reaction rates and sensory transduction cycling times. Conformational mode dynamics occur on the picosecond timescale and with the collective vibrational modes associated with these large scale structural motions in the 1-100 cm -1 range. We have performed THz time domain spectroscopy (TTDS) of several biomolecular systems to explore the sensitivity of TTDS to distinguish different molecular species, different mutations within a single species and different conformations of a given biomolecule. We compare the measured absorbances to normal mode calculations and find that the TTDS absorbance reflects the density of normal modes determined by molecular mechanics calculations, and is sensitive to both conformation and mutation. These early studies demonstrate some of the advantages and limitations of using TTDS for the study of biomolecules
Time domain spectroscopy to monitor the condition of cable insulation
International Nuclear Information System (INIS)
Mopsik, F.I.; Martzloff, F.D.
1989-01-01
The use of Time Domain Spectroscopy, the measurement of dielectric constant and loss using time-domain response, the monitoring the aging of reactor cable insulation is examined. The method is presented, showing its sensitivity, accuracy and wide frequency range. The method's ability to acquire a great deal of information in a short time and its superiority to conventional single frequency data is shown. Different cable samples are examined before and after exposure to radiation and changes with exposure are clearly seen to occur. Also it is shown that a wide range of behavior can be found in different insulation systems. The requirements for performing valid measurements is presented. The need for controlled samples and correlation with other criteria for aging is discussed. 14 refs., 9 figs
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
Evaluation of skin moisturizer effects using terahertz time domain imaging
Martinez-Meza, L. H.; Rojas-Landeros, S. C.; Castro-Camus, E.; Alfaro-Gomez, M.
2018-02-01
We use terahertz time domain imaging for the evaluation of the effects of skin-moisturizers in vivo. We evaluate three principal substances used in commercial moisturizers: glycerin, hyaluronic acid and lanolin. We image the interaction of the forearm with each of the substances taking terahertz spectra at sequential times. With this, we are able to measure the effect of the substances on the hydration level of the skin in time, determining the feasibility of using THz imaging for the evaluation of the products and their effects on the hydration levels of the skin.
Molecular Frame Reconstruction Using Time-Domain Photoionization Interferometry.
Marceau, Claude; Makhija, Varun; Platzer, Dominique; Naumov, A Yu; Corkum, P B; Stolow, Albert; Villeneuve, D M; Hockett, Paul
2017-08-25
Photoionization of molecular species is, essentially, a multipath interferometer with both experimentally controllable and intrinsic molecular characteristics. In this work, XUV photoionization of impulsively aligned molecular targets (N_{2}) is used to provide a time-domain route to "complete" photoionization experiments, in which the rotational wave packet controls the geometric part of the photoionization interferometer. The data obtained is sufficient to determine the magnitudes and phases of the ionization matrix elements for all observed channels, and to reconstruct molecular frame interferograms from lab frame measurements. In principle, this methodology provides a time-domain route to complete photoionization experiments and the molecular frame, which is generally applicable to any molecule (no prerequisites), for all energies and ionization channels.
Drug detection by terahertz time-domain spectroscopy
International Nuclear Information System (INIS)
Duan Ruixin; Zhu Yiming; Zhao Hongwei
2013-01-01
Due to unique spectral region, functional imaging ability, excellent penetration and safety characteristics of terahertz radiation, the terahertz technology rapidly becomes a vital method to detect and analyze drugs. In this paper, firstly, we identify the functional groups of anti-diabetic drugs by density functional theory (DFT), HIPHOP models and experimental results from terahertz time-domain spectroscopy measurements. Secondly, we identify four kinds of herbs of radix curcumae by using the support vector machine (SVM) analysis. Besides, we analyze the absorption of anhydrous and hydrous glucose, and determine the state of water in the crystalized D-glucose·H 2 O through the results of differential scanning calorimetry measurement. Finally, we summarize the advantages and disadvantages of terahertz time-domain spectroscopy method in drug detection and analyzing. (authors)
Advances in spectral inversion of time-domain induced polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts in charg......The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts...... in chargeability parameters, towards a quantitative analysis of the investigated media, which allows for detailed soil- and rock-type characterization. In this work a review of the recent advances in spectral inversion of TDIP data is presented, in terms of: supported IP parameterizations; modelling of transmitter...
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
A convenient accuracy criterion for time domain FE-calculations
DEFF Research Database (Denmark)
Jensen, Morten Skaarup
1997-01-01
An accuracy criterion that is well suited to tome domain finite element (FE) calculations is presented. It is then used to develop a method for selecting time steps and element meshes that produce accurate results without significantly overburderning the computer. Use of this method is illustrated...... with a simple example, where comparison with an analytical solution shows that results are sufficiently accurate, which is not always the case with more primitive mthods for determining the discretisation....
International Nuclear Information System (INIS)
Bernado, Pau; Fernandes, Miguel X.; Jacobs, Doris M.; Fiebig, Klaus; Garcia de la Torre, Jose; Pons, Miquel
2004-01-01
Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1
Energy Technology Data Exchange (ETDEWEB)
Bernado, Pau [Institut de Biologie Structurale, Jean Pierre Ebel (France); Fernandes, Miguel X. [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Jacobs, Doris M. [Johann Wolfgang Goethe-Universitaet Frankfurt, Institut fuer Organische Chemie und Chemische Biologie (Germany); Fiebig, Klaus [Affinium Pharmaceuticals (Canada); Garcia de la Torre, Jose [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Pons, Miquel [Laboratori de RMN de Biomolecules, Parc Cientific de Barcelona (Spain)], E-mail: mpons@ub.edu
2004-05-15
Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1.
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.
CORRTEX: a compact and versatile system for time domain reflectometry
International Nuclear Information System (INIS)
Deupree, R.G.; Eilers, D.D.; McKown, T.O.; Storey, W.H.
1981-01-01
The CORRTEX (COntinuous Reflectometry for Radius versus Time EXperiments) system was designed to be an adaptable and versatile unit for performing time domain reflectometry (TDR). The system consists of a coaxial cable, a digital TDR, which uses a Motorola 6800 microprocessor, a power source or battery pack, and an output terminal or recording driver. Desirable criteria for the system are discussed as well as the operation of the CORRTEX system. The types of present applications of the CORRTEX system are summarized and data presented
Physical optics far field inverse scattering in the time domain
International Nuclear Information System (INIS)
Bleistein, N.
1976-01-01
The physical optics far field inverse scattering (POFFIS) identity relates the phase and range normalized far field back scattering amplitude to the spatial Fourier transform of the characteristic function of the scattering obstacle. The characteristic function is equal to unity in the region occupied by the obstacle and zero elsewhere. The original identity was derived by Bojarski for impulsive point sources. The result is extended to sources of arbitrary time dependence. One obtains an alternative form of Bojarski's POFFIS identity. One also derives a POFFIS identity in the time domain. Numerically synthesized checks on the method are provided
A Time Domain Waveform for Testing General Relativity
International Nuclear Information System (INIS)
Huwyler, Cédric; Jetzer, Philippe; Porter, Edward K
2015-01-01
Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signals coming from supermassive black hole inspirals using these corrected waveforms. (paper)
DEFF Research Database (Denmark)
Santillan, Arturo Orozco
2011-01-01
The aim of the work described in this paper has been to investigate the use of the finite-difference time-domain method to describe the interactions between a moving object and a sound field. The main objective was to simulate oscillational instabilities that appear in single-axis acoustic...... levitation devices and to describe their evolution in time to further understand the physical mechanism involved. The study shows that the method gives accurate results for steady state conditions, and that it is a promising tool for simulations with a moving object....
Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission
DEFF Research Database (Denmark)
Verhulst, Sarah; Dau, Torsten; Shera, Christopher A.
2012-01-01
This paper describes the implementation and performance of a nonlinear time-domain model of the cochlea for transient stimulation and human otoacoustic emission generation. The nonlinearity simulates compressive growth of measured basilar-membrane impulse responses. The model accounts...... for reflection and distortion-source otoacoustic emissions (OAEs) and simulates spontaneous OAEs through manipulation of the middle-ear reflectance. The model was calibrated using human psychoacoustical and otoacoustic tuning parameters. It can be used to investigate time-dependent properties of cochlear...
A time domain inverse dynamic method for the end point tracking control of a flexible manipulator
Kwon, Dong-Soo; Book, Wayne J.
1991-01-01
The inverse dynamic equation of a flexible manipulator was solved in the time domain. By dividing the inverse system equation into the causal part and the anticausal part, we calculated the torque and the trajectories of all state variables for a given end point trajectory. The interpretation of this method in the frequency domain was explained in detail using the two-sided Laplace transform and the convolution integral. The open loop control of the inverse dynamic method shows an excellent result in simulation. For real applications, a practical control strategy is proposed by adding a feedback tracking control loop to the inverse dynamic feedforward control, and its good experimental performance is presented.
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
Simulation of power fluctuation of wind farms based on frequency domain
DEFF Research Database (Denmark)
Lin, Jin; Sun, Yuanzhang; Li, Guojie
2011-01-01
The wind power fluctuation model built up in the frequency domain is mathematically equivalent with that in the time domain, and has a clearer physical meaning therefore describes the fluctuation more accurately. However, the simulation of this model is required to deal with the time......-frequency transformation related to the power spectrum density (PSD), which is more special and complicated than normal transformations. Meanwhile, the computational complexity also increases significantly, more computation resources are needed. These problems negatively affect the engineering application of the model....... To overcome these disadvantages, the physical meaning of PSD based on fundamental concepts is presented, so that the specialties of this model compared with conventional ones can be understood. Then the time-frequency transformation algorithm is derived, which is fast to be implemented in digital computers...
Tanaka, T.; Tachikawa, Y.; Ichikawa, Y.; Yorozu, K.
2017-12-01
Flood is one of the most hazardous disasters and causes serious damage to people and property around the world. To prevent/mitigate flood damage through early warning system and/or river management planning, numerical modelling of flood-inundation processes is essential. In a literature, flood-inundation models have been extensively developed and improved to achieve flood flow simulation with complex topography at high resolution. With increasing demands on flood-inundation modelling, its computational burden is now one of the key issues. Improvements of computational efficiency of full shallow water equations are made from various perspectives such as approximations of the momentum equations, parallelization technique, and coarsening approaches. To support these techniques and more improve the computational efficiency of flood-inundation simulations, this study proposes an Automatic Domain Updating (ADU) method of 2-D flood-inundation simulation. The ADU method traces the wet and dry interface and automatically updates the simulation domain in response to the progress and recession of flood propagation. The updating algorithm is as follow: first, to register the simulation cells potentially flooded at initial stage (such as floodplains nearby river channels), and then if a registered cell is flooded, to register its surrounding cells. The time for this additional process is saved by checking only cells at wet and dry interface. The computation time is reduced by skipping the processing time of non-flooded area. This algorithm is easily applied to any types of 2-D flood inundation models. The proposed ADU method is implemented to 2-D local inertial equations for the Yodo River basin, Japan. Case studies for two flood events show that the simulation is finished within two to 10 times smaller time showing the same result as that without the ADU method.
Sharma, Monika; Anirudh, C R
2017-10-03
STAR proteins are evolutionary conserved mRNA-binding proteins that post-transcriptionally regulate gene expression at all stages of RNA metabolism. These proteins possess conserved STAR domain that recognizes identical RNA regulatory elements as YUAAY. Recently reported crystal structures show that STAR domain is composed of N-terminal QUA1, K-homology domain (KH) and C-terminal QUA2, and mRNA binding is mediated by KH-QUA2 domain. Here, we present simulation studies done to investigate binding of mRNA to STAR protein, mammalian Quaking protein (QKI). We carried out conventional MD simulations of STAR domain in presence and absence of mRNA, and studied the impact of mRNA on the stability, dynamics and underlying allosteric mechanism of STAR domain. Our unbiased simulations results show that presence of mRNA stabilizes the overall STAR domain by reducing the structural deviations, correlating the 'within-domain' motions, and maintaining the native contacts information. Absence of mRNA not only influenced the essential modes of motion of STAR domain, but also affected the connectivity of networks within STAR domain. We further explored the dissociation of mRNA from STAR domain using umbrella sampling simulations, and the results suggest that mRNA binding to STAR domain occurs in multi-step: first conformational selection of mRNA backbone conformations, followed by induced fit mechanism as nucleobases interact with STAR domain.
Two-phase flow steam generator simulations on parallel computers using domain decomposition method
International Nuclear Information System (INIS)
Belliard, M.
2003-01-01
Within the framework of the Domain Decomposition Method (DDM), we present industrial steady state two-phase flow simulations of PWR Steam Generators (SG) using iteration-by-sub-domain methods: standard and Adaptive Dirichlet/Neumann methods (ADN). The averaged mixture balance equations are solved by a Fractional-Step algorithm, jointly with the Crank-Nicholson scheme and the Finite Element Method. The algorithm works with overlapping or non-overlapping sub-domains and with conforming or nonconforming meshing. Computations are run on PC networks or on massively parallel mainframe computers. A CEA code-linker and the PVM package are used (master-slave context). SG mock-up simulations, involving up to 32 sub-domains, highlight the efficiency (speed-up, scalability) and the robustness of the chosen approach. With the DDM, the computational problem size is easily increased to about 1,000,000 cells and the CPU time is significantly reduced. The difficulties related to industrial use are also discussed. (author)
Gabran, S R I; Saad, J H; Salama, M M A; Mansour, R R
2009-01-01
This paper demonstrates the electromagnetic modeling and simulation of an implanted Medtronic deep brain stimulation (DBS) electrode using finite difference time domain (FDTD). The model is developed using Empire XCcel and represents the electrode surrounded with brain tissue assuming homogenous and isotropic medium. The model is created to study the parameters influencing the electric field distribution within the tissue in order to provide reference and benchmarking data for DBS and intra-cortical electrode development.
Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope
2016-10-19
angular random walk (ARW), bias instability, and scale factor instability. While there are methods to address issues with bias and scale factor...effects. Thus, it is expected that it will have low bias and scale factor instabilities. Simulated ARW performance of a particular incarnation of the...1 2. PARAMETRIC SYSTEM IDENTIFICATION BASED ON TIME-DOMAIN SWITCHING ........ 2 3. FINITE ELEMENT MODELING OF RESONATOR
Time domain passivity controller for 4-channel time-delay bilateral teleoperation.
Rebelo, Joao; Schiele, Andre
2015-01-01
This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.
Terahertz time-domain spectroscopy and imaging of artificial RNA
DEFF Research Database (Denmark)
Fischer, Bernd M.; Hoffmann, Matthias; Helm, Hanspeter
2005-01-01
We use terahertz time-domain spectroscopy (THz-TDS) to measure the far-infrared dielectric function of two artificial RNA single strands, composed of polyadenylic acid (poly-A) and polycytidylic acid (poly-C). We find a significant difference in the absorption between the two types of RNA strands......, and we show that we can use this difference to record images of spot arrays of the RNA strands. Under controlled conditions it is possible to use the THz image to distinguish between the two RNA strands. We discuss the requirements to sample preparation imposed by the lack of sharp spectral features...
Terahertz time-domain transmission and reflection spectroscopy of niobium
International Nuclear Information System (INIS)
Hong, Tae Yoon; Choi, Kyu Jin; Park, Byoung Cheol; Ha, Tae Woo; Sim, Kyung Ik; Kim, Jea Hoon; Ha, Dong Gwang; Chang, Yonuk
2013-01-01
We have developed a terahertz time-domain spectroscopy (THz-TDS) system for transmission and reflection measurements of metallic thin films. Using our THz-TDS system, we studied the conventional superconductor niobium (Nb) in the normal state in the spectral range from 5 to 50 cm -1 . Both the real and imaginary parts of the conductivity are acquired without Kramers-Kronig analysis. Nb exhibits a nearly frequency independent real conductivity spectrum in the terahertz range, with a very small imaginary part.
Solution of the Burgers Equation in the Time Domain
Directory of Open Access Journals (Sweden)
M. Bednařík
2002-01-01
Full Text Available This paper deals with a theoretical description of the propagation of a finite amplitude acoustic waves. The theory based on the homogeneous Burgers equation of the second order of accuracy is presented here. This equation takes into account both nonlinear effects and dissipation. The method for solving this equation, using the well-known Cole-Hopf transformation, is presented. Two methods for numerical solution of these equations in the time domain are presented. The first is based on the simple Simpson method, which is suitable for smaller Goldberg numbers. The second uses the more advanced saddle point method, and is appropriate for large Goldberg numbers.
Finite difference time domain modeling of spiral antennas
Penney, Christopher W.; Beggs, John H.; Luebbers, Raymond J.
1992-01-01
The objectives outlined in the original proposal for this project were to create a well-documented computer analysis model based on the finite-difference, time-domain (FDTD) method that would be capable of computing antenna impedance, far-zone radiation patterns, and radar cross-section (RCS). The ability to model a variety of penetrable materials in addition to conductors is also desired. The spiral antennas under study by this project meet these requirements since they are constructed of slots cut into conducting surfaces which are backed by dielectric materials.
Perfectly matched layer for the time domain finite element method
International Nuclear Information System (INIS)
Rylander, Thomas; Jin Jianming
2004-01-01
A new perfectly matched layer (PML) formulation for the time domain finite element method is described and tested for Maxwell's equations. In particular, we focus on the time integration scheme which is based on Galerkin's method with a temporally piecewise linear expansion of the electric field. The time stepping scheme is constructed by forming a linear combination of exact and trapezoidal integration applied to the temporal weak form, which reduces to the well-known Newmark scheme in the case without PML. Extensive numerical tests on scattering from infinitely long metal cylinders in two dimensions show good accuracy and no signs of instabilities. For a circular cylinder, the proposed scheme indicates the expected second order convergence toward the analytic solution and gives less than 2% root-mean-square error in the bistatic radar cross section (RCS) for resolutions with more than 10 points per wavelength. An ogival cylinder, which has sharp corners supporting field singularities, shows similar accuracy in the monostatic RCS
Time domain optical memories using rare earth ions
International Nuclear Information System (INIS)
Sellars, M.J.; Dyke, T.; Pryde, G.J.; Manson, N.B.
1998-01-01
Full text: Rare earth doped crystals are the chosen materials for the next generation of optical memories where the process of spectral holeburning can be employed to provide an extra dimension of frequency or time to spatial dimensions and with certain rare earth ions increases of the order of 10 7 in storage capacity can be achieved over conventional optical memories. Time domain techniques are preferred over frequency domain techniques and are now well developed. In these techniques arbitrary pulse sequences are stored in the material and read out at some later time with a single read pulse using a stimulated photon echo process. Long pulse sequences will enable more data to be stored but necessitates the use of materials with long dephasing times (corresponding to narrow spectral lines) and it is this characteristic of rare earth systems that makes them the preferred material for the new time domain optical memories. The storage time can range from hours to days but in a practical device will require refreshing or re-enforcing and this puts special requirements on the stability of the laser used for storing the information. The storage process itself can also be weak and more reliable storage can be achieved by recording the data several times with the same pulse sequence. For this to be successful the laser must be at held at a constant frequency and be stable in phase over the entire duration of the pulse sequence. The procedure of reinforcing the data sequence has been proposed before and attempted without attention to the laser frequency stability. However, if the laser is not stable although some data bits will be reinforced or increased in size others will be decreased or even erased. Indeed the reliability of the memory is degraded by the introducing the rewrite process. For our work we have developed a laser with the excellent stability and able to demonstrate reproducible reinforcement of the data sequence. Thus with the rewrite sequence we are able to
Finite-difference time-domain analysis of time-resolved terahertz spectroscopy experiments
DEFF Research Database (Denmark)
Larsen, Casper; Cooke, David G.; Jepsen, Peter Uhd
2011-01-01
In this paper we report on the numerical analysis of a time-resolved terahertz (THz) spectroscopy experiment using a modified finite-difference time-domain method. Using this method, we show that ultrafast carrier dynamics can be extracted with a time resolution smaller than the duration of the T...
Near-infrared laser, time domain, breast tumour detection system
International Nuclear Information System (INIS)
Joblin, A.J.
1996-01-01
Full text: The use of near-infrared laser, time domain techniques have been proposed for some time now as an alternative to X-ray mammography, as a means of mass screening for breast disease. The great driving force behind this research has been that near-infrared photons are a non-ionising radiation, which affords a greater degree of patient safety than when using X-rays. This would mean that women at risk of breast disease could be screened with a near-infrared laser imaging system, much more regularly than with an X-ray mammography system, which should allow for the earlier detection and treatment of breast disease. This paper presents a theoretical investigation of the performance of a near-infrared, time domain breast imaging system. The performance of the imaging system is characterised by the resolution and contrast parameters, which were studied using a numerical finite difference calculation method. The finite difference method is used to solve the diffusion equation for the photon transport through the inhomogeneous breast tissue medium. Optimal performance was found to be obtained with short photon times of flight. However the signal to noise ratio decreases rapidly as the photon time of flight is decreased. The system performance will therefore be limited by the noise equivalent power of the time resolved detection system, which is the signal incident on the time resolved detection system which gives a signal to noise ratio of 1:1. Photon times of flight shorter than 500 ps are not practical with current technology, which places limits on the resolution and contrast. The photon signal throughput can be increased by increasing the size of the laser beam width, by increasing the size of the aperture stop of the detector, by increasing the laser pulse duration or decreasing the detector time resolution. Best system performance is found by optimising these parameters for a given time gating and detector system characteristic (NEP). It was found that the
Time domain series system definition and gear set reliability modeling
International Nuclear Information System (INIS)
Xie, Liyang; Wu, Ningxiang; Qian, Wenxue
2016-01-01
Time-dependent multi-configuration is a typical feature for mechanical systems such as gear trains and chain drives. As a series system, a gear train is distinct from a traditional series system, such as a chain, in load transmission path, system-component relationship, system functioning manner, as well as time-dependent system configuration. Firstly, the present paper defines time-domain series system to which the traditional series system reliability model is not adequate. Then, system specific reliability modeling technique is proposed for gear sets, including component (tooth) and subsystem (tooth-pair) load history description, material priori/posterior strength expression, time-dependent and system specific load-strength interference analysis, as well as statistically dependent failure events treatment. Consequently, several system reliability models are developed for gear sets with different tooth numbers in the scenario of tooth root material ultimate tensile strength failure. The application of the models is discussed in the last part, and the differences between the system specific reliability model and the traditional series system reliability model are illustrated by virtue of several numerical examples. - Highlights: • A new type of series system, i.e. time-domain multi-configuration series system is defined, that is of great significance to reliability modeling. • Multi-level statistical analysis based reliability modeling method is presented for gear transmission system. • Several system specific reliability models are established for gear set reliability estimation. • The differences between the traditional series system reliability model and the new model are illustrated.
Time domain NMR evaluation of poly(vinyl alcohol) xerogels
Energy Technology Data Exchange (ETDEWEB)
Rodrigues, Elton Jorge da Rocha; Cavalcante, Maxwell de Paula; Tavares, Maria Ines Bruno, E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia. Instituto de Macromoleculas Professora Eloisa Mano
2016-05-15
Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO{sub 2}), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO{sub 2} does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO{sub 2}. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials. (author)
Synchronous machine parameter identification in frequency and time domain
Directory of Open Access Journals (Sweden)
Hasni M.
2007-01-01
Full Text Available This paper presents the results of a frequency and time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. The objective of this study is to use several input signals to identify the model structure and parameters of a salient-pole synchronous machine from standstill test data. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We estimate the parameters of operational impedances, or in other words the reactance and the time constants. The tests were carried out on synchronous machine of 1.5 kVA 380V 1500 rpm.
Böddeker, B.; Teichler, H.
The MD simulation program TABB is motivated by the need of long time simulations for the investigation of slow processes near the glass transition of glass forming alloys. TABB is written in C++ with a high degree of flexibility: TABB allows the use of any short ranged pair potentials or EAM potentials, by generating and using a spline representation of all functions and their derivatives. TABB supports several numerical integration algorithms like the Runge-Kotta or the modified Gear-predictor-corrector algorithm of order five. The boundary conditions can be chosen to resemble the geometry of bulk materials or films. The simulation box length or the pressure can be fixed for each dimension separately. TABB may be used in isokinetic, isoenergeric or canonic (with random forces) mode. TABB contains a simple instruction interpreter to easily control the parameters and options during the simulation. The same source code can be compiled either for workstations or for parallel computers. The main optimization goal of TABB is to allow long time simulations of medium or small sized systems. To make this possible, much attention is spent on the optimized communication between the nodes. TABB uses a domain decomposition procedure. To use many nodes with a small system, the domain size has to be small compared to the range of particle interactions. In the limit of many nodes for only few atoms, the bottle neck of communication is the latency time. TABB minimizes the number of pairs of domains containing atoms that interact between these domains. This procedure minimizes the need of communication calls between pairs of nodes. TABB decides automatically, to how many, and to which directions the decomposition shall be applied. E.g., in the case of one dimensional domain decomposition, the simulation box is only split into "slabs" along a selected direction. The three dimensional domain decomposition is best with respect to the number of interacting domains only for simulations
A hybrid method of estimating pulsating flow parameters in the space-time domain
Pałczyński, Tomasz
2017-05-01
This paper presents a method for estimating pulsating flow parameters in partially open pipes, such as pipelines, internal combustion engine inlets, exhaust pipes and piston compressors. The procedure is based on the method of characteristics, and employs a combination of measurements and simulations. An experimental test rig is described, which enables pressure, temperature and mass flow rate to be measured within a defined cross section. The second part of the paper discusses the main assumptions of a simulation algorithm elaborated in the Matlab/Simulink environment. The simulation results are shown as 3D plots in the space-time domain, and compared with proposed models of phenomena relating to wave propagation, boundary conditions, acoustics and fluid mechanics. The simulation results are finally compared with acoustic phenomena, with an emphasis on the identification of resonant frequencies.
Numerical integration of the Teukolsky equation in the time domain
International Nuclear Information System (INIS)
Pazos-Avalos, Enrique; Lousto, Carlos O.
2005-01-01
We present a fourth-order convergent (2+1)-dimensional, numerical formalism to solve the Teukolsky equation in the time domain. Our approach is first to rewrite the Teukolsky equation as a system of first-order differential equations. In this way we get a system that has the form of an advection equation. This is then used in combination with a series expansion of the solution in powers of time. To obtain a fourth-order scheme we kept terms up to fourth derivative in time and use the advectionlike system of differential equations to substitute the temporal derivatives by spatial derivatives. This scheme is applied to evolve gravitational perturbations in the Schwarzschild and Kerr backgrounds. Our numerical method proved to be stable and fourth-order convergent in r* and θ directions. The correct power-law tail, ∼1/t 2l+3 , for general initial data, and ∼1/t 2l+4 , for time-symmetric data, was found in our runs. We noted that it is crucial to resolve accurately the angular dependence of the mode at late times in order to obtain these values of the exponents in the power-law decay. In other cases, when the decay was too fast and round-off error was reached before a tail was developed, then the quasinormal modes frequencies provided a test to determine the validity of our code
Heliborne time-domain electromagnetic (TEM) surveys for uranium exploration
International Nuclear Information System (INIS)
Chaturvedi, A.K.
2015-01-01
Airborne geophysical surveys have been used extensively in petroleum, mineral exploration, and environmental mapping. Of all the geophysical methods, Electromagnetic (EM) methods, both ground and airborne are used to map the conductive ore bodies buried in the resistive bed rock. Mapping resistivity variations can help unravel complex geological problems and identify areas of hidden potential. Besides the traditional applications to ground water investigations and other natural resource exploration and geological mapping, a number of new applications have been reported. These include hazardous-waste characterization studies, precision agriculture applications, archaeological surveys etc. Airborne Electromagnetic (AEM) methods have undergone rapid improvements over the past few decades. Several new airborne Time Do-main EM (TDEM) systems appeared; existing systems were updated and/or enhanced. The use of natural field (passive) EM surveys continued to increase, with new or improved systems becoming available for both airborne and ground surveys. The number of large airborne survey systems with combined EM, magnetic, gravimetric and gamma-ray spectrometric capabilities also increased. Exploration of a mineral deposit is a multi-stage and multi-disciplinary approach that commences from regional investigations and concludes with establishing of a deposit. As economics play a major role in exploration, a proper integrated study is always beneficial in narrowing down the potential mineral target zones. Heliborne geophysical surveys are being conducted world-wide for exploration of base metals, gold, phosphorite, oil, uranium etc. that are very effective tool in identifying zones of interest accurately, economically and with less span of time. These surveys give a very good insight of surface and sub-surface geophysical signatures that can be attributed to geology with proper modeling. Heliborne Time - domain Electromagnetic (TEM) methods are well known for search of
Directory of Open Access Journals (Sweden)
Alok K. Sharma
2014-02-01
Full Text Available Background: Molecular dynamics (MD simulations provide valuable information on the conformational changes that accompany time-dependent motions in proteins. The reported crystal structure of rat prestin (PDB 3LLO is remarkable for an α1-α2 inter-helical angle that differs substantially from those observed in bacterial STAS domains of SulP anion transporters and anti-sigma factor antagonists. However, NMR data on the rat prestin STAS domain in solution suggests dynamic features at or near the α1-α2 helical region (Pasqualetto et al JMB, 2010. We therefore performed a 100 ns 300K MD simulation study comparing the STAS domains of rat prestin and (modeled human pendrin, to explore possible conformational flexibility in the region of the α1 and α2 helices. Methods: The conformation of the loop missing in the crystal structure of rat prestin STAS (11 amino acids between helix α1 and strand β3 was built using Modeller. MD simulations were performed with GROMACSv4.6 using GROMOS96 53a6 all-atom force field. Results: A subset of secondary structured elements of the STAS domains exhibits significant conformational changes during the simulation time course. The conformationally perturbed segments include the majority of loop regions, as well as the α1 and α2 helices. A significant decrease in the α1-α2 inter-helical angle observed across the simulation trajectory leads to closer helical packing at their C-termini. The end-simulation conformations of the prestin and pendrin STAS domains, including their decreased α1-α2 inter-helical angles, resemble more closely the packing of corresponding helices in the STAS structures of bacterial SulP transporters Rv1739c and ychM, as well as those of the anti-sigma factor antagonists. Several structural segments of the modeled human pendrin STAS domain exhibit larger atomic motions and greater conformational deviations than the corresponding regions of rat prestin, predicting that the human pendrin STAS
Fast simulation approaches for power fluctuation model of wind farm based on frequency domain
DEFF Research Database (Denmark)
Lin, Jin; Gao, Wen-zhong; Sun, Yuan-zhang
2012-01-01
This paper discusses one model developed by Riso, DTU, which is capable of simulating the power fluctuation of large wind farms in frequency domain. In the original design, the “frequency-time” transformations are time-consuming and might limit the computation speed for a wind farm of large size....... Under this background, this paper proposes four efficient approaches to accelerate the simulation speed. Two of them are based on physical model simplifications, and the other two improve the numerical computation. The case study demonstrates the efficiency of these approaches. The acceleration ratio...... is more than 300 times if all these approaches are adopted, in any low, medium and high wind speed test scenarios....
Computational electrodynamics the finite-difference time-domain method
Taflove, Allen
2005-01-01
This extensively revised and expanded third edition of the Artech House bestseller, Computational Electrodynamics: The Finite-Difference Time-Domain Method, offers engineers the most up-to-date and definitive resource on this critical method for solving Maxwell's equations. The method helps practitioners design antennas, wireless communications devices, high-speed digital and microwave circuits, and integrated optical devices with unsurpassed efficiency. There has been considerable advancement in FDTD computational technology over the past few years, and the third edition brings professionals the very latest details with entirely new chapters on important techniques, major updates on key topics, and new discussions on emerging areas such as nanophotonics. What's more, to supplement the third edition, the authors have created a Web site with solutions to problems, downloadable graphics and videos, and updates, making this new edition the ideal textbook on the subject as well.
Iterative Refinement Methods for Time-Domain Equalizer Design
Directory of Open Access Journals (Sweden)
Evans Brian L
2006-01-01
Full Text Available Commonly used time domain equalizer (TEQ design methods have been recently unified as an optimization problem involving an objective function in the form of a Rayleigh quotient. The direct generalized eigenvalue solution relies on matrix decompositions. To reduce implementation complexity, we propose an iterative refinement approach in which the TEQ length starts at two taps and increases by one tap at each iteration. Each iteration involves matrix-vector multiplications and vector additions with matrices and two-element vectors. At each iteration, the optimization of the objective function either improves or the approach terminates. The iterative refinement approach provides a range of communication performance versus implementation complexity tradeoffs for any TEQ method that fits the Rayleigh quotient framework. We apply the proposed approach to three such TEQ design methods: maximum shortening signal-to-noise ratio, minimum intersymbol interference, and minimum delay spread.
In vitro osteosarcoma biosensing using THz time domain spectroscopy
Ferguson, Bradley S.; Liu, Haibo; Hay, Shelley; Findlay, David; Zhang, Xi-Cheng; Abbott, Derek
2004-03-01
Terahertz time domain spectroscopy (THz-TDS) has a wide range of applications from semiconductor diagnostics to biosensing. Recent attention has focused on bio-applications and several groups have noted the ability of THz-TDS to differentiate basal cell carcinoma tissue from healthy dermal tissue ex vivo. The contrast mechanism is unclear but has been attributed to increased interstitial water in cancerous tissue. In this work we investigate the THz response of human osteosarcoma cells and normal human bone cells grown in culture to isolate the cells' responses from other effects. A classification algorithms based on a frequency selection by genetic algorithm is used to attempt to differentiate between the cell types based on the THz spectra. Encouraging preliminary results have been obtained.
Modern linear control design a time-domain approach
Caravani, Paolo
2013-01-01
This book offers a compact introduction to modern linear control design. The simplified overview presented of linear time-domain methodology paves the road for the study of more advanced non-linear techniques. Only rudimentary knowledge of linear systems theory is assumed - no use of Laplace transforms or frequency design tools is required. Emphasis is placed on assumptions and logical implications, rather than abstract completeness; on interpretation and physical meaning, rather than theoretical formalism; on results and solutions, rather than derivation or solvability. The topics covered include transient performance and stabilization via state or output feedback; disturbance attenuation and robust control; regional eigenvalue assignment and constraints on input or output variables; asymptotic regulation and disturbance rejection. Lyapunov theory and Linear Matrix Inequalities (LMI) are discussed as key design methods. All methods are demonstrated with MATLAB to promote practical use and comprehension. ...
Differentiation of illicit drugs with THz time-domain spectroscopy
International Nuclear Information System (INIS)
Liu Guifeng; Ma Shihua; Ji Te; Zhao Hongwei; Wang Wenfeng
2010-01-01
The tera hertz time-domain spectroscopy (THz-TDS) was used for sensing and identifying illicit drugs. The absorption spectra of seven illicit drug samples(morphine and its hydrochloride, cocaine hydrochloride, codeine phosphate, papaverine hydrochloride, pethidine hydrochloride, and thebaine) were studied by THz-TDS at 0.3-2.0 THz at room temperature. The geometric structure and vibration frequencies of morphine were calculated by density functional theory. The four absorption features were dominated by intra-/inter-molecular collective or lattice vibration modes. Each illicit drug has a distinct signature in its THz spectra. The results indicate that the THz-TDS can be used to identify and discriminate illicit drugs by their characteristic fingerprints. (authors)
Terahertz time-domain spectroscopy of edible oils
Dinovitser, Alex; Valchev, Dimitar G.; Abbott, Derek
2017-06-01
Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05-2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.
Time-domain Hydroelasticity Theory of Ships Responding to Waves
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui
1997-01-01
free surface flow. The general interface boundary condition is used in the mathematical formulation of the fluid motion around the flexible structure. The general time-domain theory is simplified to a slender-body theory for the analysis of wave-induced global responses of monohull ships. The structure...... is represented by a non-uniform beam, while the generalized hydrodynamic coefficients can be obtained from two-dimensional potential flow theory. The linear slender body theory is generalized to treat the non-linear loading effects of rigid motion and structural response of ships travelling in rough seas....... The non-linear hydrostatic restoring force and hydrodynamic momentum action are considered. A numerical solution is presented for the slender body theory. Numerical examples are given for two ship cases with different geometry features, a warship hull and the S175 containership with two different bow...
Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates
DEFF Research Database (Denmark)
Takeya, Kei; Zhang, Caihong; Kawayama, Iwao
2009-01-01
For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has...... a characteristic broad absorption peak at 0.5 THz corresponding to the dipole moment of THF molecules. The refractive indices of THF and propane hydrates are 1.725 and 1.775 at 1 THz, respectively, and show a slight but clear difference from the refractive index of ice (1.79). THz-TDS is a potentially useful...... technique for the ondestructive inspection of gas hydrates. # 2009 The Japan Society of Applied Physics...
Detection of Poisonous Herbs by Terahertz Time-Domain Spectroscopy
Zhang, H.; Li, Z.; Chen, T.; Liu, J.-J.
2018-03-01
The aim of this paper is the application of terahertz (THz) spectroscopy combined with chemometrics techniques to distinguish poisonous and non-poisonous herbs which both have a similar appearance. Spectra of one poisonous and two non-poisonous herbs (Gelsemium elegans, Lonicera japonica Thunb, and Ficus Hirta Vahl) were obtained in the range 0.2-1.4 THz by using a THz time-domain spectroscopy system. Principal component analysis (PCA) was used for feature extraction. The prediction accuracy of classification is between 97.78 to 100%. The results demonstrate an efficient and applicative method to distinguish poisonous herbs, and it may be implemented by using THz spectroscopy combined with chemometric algorithms.
Real time simulator for material testing reactor
Energy Technology Data Exchange (ETDEWEB)
Takemoto, Noriyuki; Imaizumi, Tomomi; Izumo, Hironobu; Hori, Naohiko; Suzuki, Masahide [Japan Atomic Energy Agency, Oarai Research and Development Center, Oarai, Ibaraki (Japan); Ishitsuka, Tatsuo; Tamura, Kazuo [ITOCHU Techno-Solutions Corp., Tokyo (Japan)
2012-03-15
Japan Atomic Energy Agency (JAEA) is now developing a real time simulator for a material testing reactor based on Japan Materials Testing Reactor (JMTR). The simulator treats reactor core system, primary and secondary cooling system, electricity system and irradiation facility systems. Possible simulations are normal reactor operation, unusual transient operation and accidental operation. The developed simulator also contains tool to revise/add facility in it for the future development. (author)
Real time simulator for material testing reactor
International Nuclear Information System (INIS)
Takemoto, Noriyuki; Imaizumi, Tomomi; Izumo, Hironobu; Hori, Naohiko; Suzuki, Masahide; Ishitsuka, Tatsuo; Tamura, Kazuo
2012-01-01
Japan Atomic Energy Agency (JAEA) is now developing a real time simulator for a material testing reactor based on Japan Materials Testing Reactor (JMTR). The simulator treats reactor core system, primary and secondary cooling system, electricity system and irradiation facility systems. Possible simulations are normal reactor operation, unusual transient operation and accidental operation. The developed simulator also contains tool to revise/add facility in it for the future development. (author)
Acoustic, finite-difference, time-domain technique development
International Nuclear Information System (INIS)
Kunz, K.
1994-01-01
A close analog exists between the behavior of sound waves in an ideal gas and the radiated waves of electromagnetics. This analog has been exploited to obtain an acoustic, finite-difference, time-domain (AFDTD) technique capable of treating small signal vibrations in elastic media, such as air, water, and metal, with the important feature of bending motion included in the behavior of the metal. This bending motion is particularly important when the metal is formed into sheets or plates. Bending motion does not have an analog in electromagnetics, but can be readily appended to the acoustic treatment since it appears as a single additional term in the force equation for plate motion, which is otherwise analogous to the electromagnetic wave equation. The AFDTD technique has been implemented in a code architecture that duplicates the electromagnetic, finite-difference, time-domain technique code. The main difference in the implementation is the form of the first-order coupled differential equations obtained from the wave equation. The gradient of pressure and divergence of velocity appear in these equations in the place of curls of the electric and magnetic fields. Other small changes exist as well, but the codes are essentially interchangeable. The pre- and post-processing for model construction and response-data evaluation of the electromagnetic code, in the form of the TSAR code at Lawrence Livermore National Laboratory, can be used for the acoustic version. A variety of applications is possible, pending validation of the bending phenomenon. The applications include acoustic-radiation-pattern predictions for a submerged object; mine detection analysis; structural noise analysis for cars; acoustic barrier analysis; and symphonic hall/auditorium predictions and speaker enclosure modeling
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.; Beghein, Yves; Nair, Naveen V.; Cools, Kristof; Bagci, Hakan; Shanker, Balasubramaniam
2014-01-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method's efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
VERSE - Virtual Equivalent Real-time Simulation
Zheng, Yang; Martin, Bryan J.; Villaume, Nathaniel
2005-01-01
Distributed real-time simulations provide important timing validation and hardware in the- loop results for the spacecraft flight software development cycle. Occasionally, the need for higher fidelity modeling and more comprehensive debugging capabilities - combined with a limited amount of computational resources - calls for a non real-time simulation environment that mimics the real-time environment. By creating a non real-time environment that accommodates simulations and flight software designed for a multi-CPU real-time system, we can save development time, cut mission costs, and reduce the likelihood of errors. This paper presents such a solution: Virtual Equivalent Real-time Simulation Environment (VERSE). VERSE turns the real-time operating system RTAI (Real-time Application Interface) into an event driven simulator that runs in virtual real time. Designed to keep the original RTAI architecture as intact as possible, and therefore inheriting RTAI's many capabilities, VERSE was implemented with remarkably little change to the RTAI source code. This small footprint together with use of the same API allows users to easily run the same application in both real-time and virtual time environments. VERSE has been used to build a workstation testbed for NASA's Space Interferometry Mission (SIM PlanetQuest) instrument flight software. With its flexible simulation controls and inexpensive setup and replication costs, VERSE will become an invaluable tool in future mission development.
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.
Inversion of time-domain induced polarization data based on time-lapse concept
Kim, Bitnarae; Nam, Myung Jin; Kim, Hee Joon
2018-05-01
Induced polarization (IP) surveys, measuring overvoltage phenomena of the medium, are widely and increasingly performed not only for exploration of mineral resources but also for engineering applications. Among several IP survey methods such as time-domain, frequency-domain and spectral IP surveys, this study introduces a noble inversion method for time-domain IP data to recover the chargeability structure of target medium. The inversion method employs the concept of 4D inversion of time-lapse resistivity data sets, considering the fact that measured voltage in time-domain IP survey is distorted by IP effects to increase from the instantaneous voltage measured at the moment the source current injection starts. Even though the increase is saturated very fast, we can consider the saturated and instantaneous voltages as a time-lapse data set. The 4D inversion method is one of the most powerful method for inverting time-lapse resistivity data sets. Using the developed IP inversion algorithm, we invert not only synthetic but also field IP data to show the effectiveness of the proposed method by comparing the recovered chargeability models with those from linear inversion that was used for the inversion of the field data in a previous study. Numerical results confirm that the proposed inversion method generates reliable chargeability models even though the anomalous bodies have large IP effects.
International Nuclear Information System (INIS)
Chen, Xiang; Chen, Yong Guang; Wei, Ming; Hu, Xiao Feng
2013-01-01
Shielding effectiveness (SE) of materials against electromagnetic pulse (EMP) cannot be well estimated by traditional test method of SE of materials which only consider the amplitude-frequency characteristic of materials, but ignore the phase-frequency ones. In order to solve this problem, the model of SE of materials against EMP was established based on system identification (SI) method with time-domain linear cosine frequency sweep signal. The feasibility of the method in this paper was examined depending on infinite planar material and the simulation research of coaxial test method and windowed semi-anechoic box of materials. The results show that the amplitude-frequency and phase-frequency information of each frequency can be fully extracted with this method. SE of materials against strong EMP can be evaluated with time-domain low field strength (voltage) of cosine frequency sweep signal. And SE of materials against a variety EMP will be predicted by the model.
Wang, Xu; Gao, Zhensen; Kataoka, Nobuyuki; Wada, Naoya
2010-05-10
A novel scheme using single phase modulator for simultaneous time domain spectral phase encoding (SPE) signal generation and DPSK data modulation is proposed and experimentally demonstrated. Array- Waveguide-Grating and Variable-Bandwidth-Spectrum-Shaper based devices can be used for decoding the signal directly in spectral domain. The effects of fiber dispersion, light pulse width and timing error on the coding performance have been investigated by simulation and verified in experiment. In the experiment, SPE signal with 8-chip, 20GHz/chip optical code patterns has been generated and modulated with 2.5 Gbps DPSK data using single modulator. Transmission of the 2.5 Gbps data over 34km fiber with BEROCDMA) and secure optical communication applications. (c) 2010 Optical Society of America.
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.
Wideband Radar Echo Frequency-domain Simulation and Analysis for High Speed Moving Targets
Directory of Open Access Journals (Sweden)
Ning Chao
2014-04-01
Full Text Available A frequency-domain method is proposed for wideband radar echo simulation of high-speed moving targets. Based on the physical process of electromagnetic waves observing a moving target, a frequency-domain echo model of wideband radar is constructed, and the block diagram of the radar echo simulation in frequency-domain is presented. Then, the impacts of radial velocity and slant range on the matching filtering of LFM radar are analyzed, and some quantitative conclusions on the shift and expansion of the radar profiles are obtained. Simulation results illustrate the correctness and efficiency of the proposed method.
Time Simulation of Bone Adaptation
DEFF Research Database (Denmark)
Bagge, Mette
1998-01-01
The structural adaptation of a three-dimensional finite element model ofthe proximal femur is considered. Presuming the bone possesses the optimalstructure under the given loads, the bone material distribution is foundby minimizing the strain energy averaged over ten load cases with avolume....... The remodeling algorithm is derived directly from theoptimization recurrence formula, and in a time increment the materialdistribution changes towards the optimal structure for the present load case.The speed of remodeling is taken from clinical data.Numerical examples of respectively increasing and reducing...
Application of Time Domain Reflectometers in Urban Settings ...
Time domain reflectometers (TDRs) are sensors that measure the volumetric water content of soils and porous media. The sensors consist of stainless steel rods connected to a circuit board in an epoxy housing. An electromagnetic pulse is propagated along the rods. The time, or period, required for the signal to travel down the rods and back varies with the volumetric water content of the surrounding media and temperature. A calibration curve is needed for the specific media. TDRs were developed mostly for agricultural applications; however, the technology has also been applied to forestry and ecological research. This study demonstrates the use of TDRs for quantifying drainage properties in low impact development (LID) stormwater controls, specifically permeable pavement and rain garden systems. TDRs were successfully used to monitor the responses of urban fill, engineered bioretention media, and the aggregate storage layer under permeable pavement to multiple rain events of varying depth, intensity, and duration. The hydrologic performance of permeable pavement and rain garden systems has previously been quantified for underdrain systems, but there have been few studies of systems that drain to the underlying soils. We know of no published studies outlining the use of TDR technology to document drainage properties in media other than soil. In this study TDRs were installed at multiple locations and depths in underlying urban fill soils, engineered bior
The Future of the Time Domain with LSST
Walkowicz, Lucianne M.
2012-04-01
abstract-type="normal">SummaryIn the coming decade LSST's combination of all-sky coverage, consistent long-term monitoring and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. Time-domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theories. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space. LSST will generate `alerts' within 60 seconds of detecting a new transient, permitting the community to follow up unusual events in greater detail. However, follow-up will remain a challenge as the volume of transients will easily saturate available spectroscopic resources. Characterization of events and access to appropriate ancillary data (e.g. from prior observations, either in the optical or in other passbands) will be of the utmost importance in prioritizing follow-up observations. The incredible scientific opportunities and unique challenges afforded by LSST demand organization, forethought and creativity from the astronomical community. To learn more about the telescope specifics and survey design, as well as obtaining a overview of the variety of the scientific investigations that LSST will enable, readers are encouraged to look at the LSST Science Book: http://www.lsst.org/lsst/scibook. Organizational details of the LSST science collaborations and management may be found at http://www.lsstcorp.org.
Image simulation for HardWare In the Loop simulation in EO domain
Cathala, Thierry; Latger, Jean
2015-10-01
Infrared camera as a weapon sub system for automatic guidance is a key component for military carrier such as missile for example. The associated Image Processing, that controls the navigation, needs to be intensively assessed. Experimentation in the real world is very expensive. This is the main reason why hybrid simulation also called HardWare In the Loop (HWIL) is more and more required nowadays. In that field, IR projectors are able to cast IR fluxes of photons directly onto the IR camera of a given weapon system, typically a missile seeker head. Though in laboratory, the missile is so stimulated exactly like in the real world, provided a realistic simulation tool enables to perform synthetic images to be displayed by the IR projectors. The key technical challenge is to render the synthetic images at the required frequency. This paper focuses on OKTAL-SE experience in this domain through its product SE-FAST-HWIL. It shows the methodology and Return of Experience from OKTAL-SE. Examples are given, in the frame of the SE-Workbench. The presentation focuses on trials on real operational complex 3D cases. In particular, three important topics, that are very sensitive with regards to IG performance, are detailed: first the 3D sea surface representation, then particle systems rendering especially to simulate flares and at last sensor effects modelling. Beyond "projection mode", some information will be given on the SE-FAST-HWIL new capabilities dedicated to "injection mode".
Time-Domain Finite Elements for Virtual Testing of Electromagnetic Compatibility
Directory of Open Access Journals (Sweden)
V. Sedenka
2013-04-01
Full Text Available The paper presents a time-domain finite-element solver developed for simulations related to solving electromagnetic compatibility issues. The software is applied as a module integrated into a computational framework developed within a FP7 European project High Intensity Radiated Field – Synthetic Environment (HIRF SE able to simulate a large class of problems. In the paper, the mathematical formulation is briefly presented, and special emphasis is put on the user point of view on the simulation tool-chain. The functionality is demonstrated on the computation of shielding effectiveness of two composite materials. Results are validated through experimental measurements and agreement is confirmed by automatic feature selective algorithms.
A comparison of three time-domain anomaly detection methods
Energy Technology Data Exchange (ETDEWEB)
Schoonewelle, H.; Hagen, T.H.J.J. van der; Hoogenboom, J.E. [Delft University of Technology (Netherlands). Interfaculty Reactor Institute
1996-01-01
Three anomaly detection methods based on a comparison of signal values with predictions from an autoregressive model are presented. These methods are: the extremes method, the {chi}{sup 2} method and the sequential probability ratio test. The methods are used to detect a change of the standard deviation of the residual noise obtained from applying an autoregressive model. They are fast and can be used in on-line applications. For each method some important anomaly detection parameters are determined by calculation or simulation. These parameters are: the false alarm rate, the average time to alarm and - being of minor importance -the alarm failure rate. Each method is optimized with respect to the average time to alarm for a given value of the false alarm rate. The methods are compared with each other, resulting in the sequential probability ratio test being clearly superior. (author).
A comparison of three time-domain anomaly detection methods
International Nuclear Information System (INIS)
Schoonewelle, H.; Hagen, T.H.J.J. van der; Hoogenboom, J.E.
1996-01-01
Three anomaly detection methods based on a comparison of signal values with predictions from an autoregressive model are presented. These methods are: the extremes method, the χ 2 method and the sequential probability ratio test. The methods are used to detect a change of the standard deviation of the residual noise obtained from applying an autoregressive model. They are fast and can be used in on-line applications. For each method some important anomaly detection parameters are determined by calculation or simulation. These parameters are: the false alarm rate, the average time to alarm and - being of minor importance -the alarm failure rate. Each method is optimized with respect to the average time to alarm for a given value of the false alarm rate. The methods are compared with each other, resulting in the sequential probability ratio test being clearly superior. (author)
A combined ADER-DG and PML approach for simulating wave propagation in unbounded domains
Amler, Thomas
2012-09-19
In this work, we present a numerical approach for simulating wave propagation in unbounded domains which combines discontinuous Galerkin methods with arbitrary high order time integration (ADER-DG) and a stabilized modification of perfectly matched layers (PML). Here, the ADER-DG method is applied to Bérenger’s formulation of PML. The instabilities caused by the original PML formulation are treated by a fractional step method that allows to monitor whether waves are damped in PML region. In grid cells where waves are amplified by the PML, the contribution of damping terms is neglected and auxiliary variables are reset. Results of 2D simulations in acoustic media with constant and discontinuous material parameters are presented to illustrate the performance of the method.
PSpice modeling of broadband RF cavities for transient and frequency domain simulations
Energy Technology Data Exchange (ETDEWEB)
Harzheim, Jens [Institut fuer Theorie Elektromagnetischer Felder, Fachgebiet Beschleunigertechnik, TU Darmstadt (Germany)
2016-07-01
In the future accelerator facility FAIR, Barrier-Bucket Systems will play an important role for different longitudinal beam manipulations. As the function of this type of system is to provide single sine gap voltages, the components of the system have to operate in a broad frequency range. To investigate the different effects and to design the different system components, the whole Barrier-Bucket System is to be modeled in PSpice. While for low power signals, the system shows linear behavior, nonlinear effects arise at higher amplitudes. Therefore, simulations in both, frequency and time domain are needed. The highly frequency dependent magnetic alloy ring cores of the future Barrier-Bucket cavity have been mod eled in a first step and based on these models, the whole cavity was analyzed in PSpice. The simulation results show good agreement with former measurements.
Real time simulation techniques in Taiwan - Maanshan compact simulator
International Nuclear Information System (INIS)
Liang, K.-S.; Chuang, Y.-M.; Ko, H.-T.
2004-01-01
Recognizing the demand and potential market of simulators in various industries, a special project for real time simulation technology transfer was initiated in Taiwan in 1991. In this technology transfer program, the most advanced real-time dynamic modules for nuclear power simulation were introduced. Those modules can be divided into two categories; one is modeling related to catch dynamic response of each system, and the other is computer related to provide special real time computing environment and man-machine interface. The modeling related modules consist of the thermodynamic module, the three-dimensional core neutronics module and the advanced balance of plant module. As planned in the project, the technology transfer team should build a compact simulator for the Maanshan power plant before the end of the project to demonstrate the success of the technology transfer program. The compact simulator was designed to support the training from the regular full scope simulator which was already equipped in the Maanshan plant. The feature of this compact simulator focused on providing know-why training by the enhanced graphic display. The potential users were identified as senior operators, instructors and nuclear engineers. Total about 13 important systems were covered in the scope of the compact simulator, and multi-graphic displays from three color monitors mounted on the 10 feet compact panel were facilitated to help the user visualize detailed phenomena under scenarios of interest. (author)
Nonlinear time-dependent simulation of helix traveling wave tubes
International Nuclear Information System (INIS)
Peng Wei-Feng; Yang Zhong-Hai; Hu Yu-Lu; Li Jian-Qing; Lu Qi-Ru; Li Bin
2011-01-01
A one-dimensional nonlinear time-dependent theory for helix traveling wave tubes is studied. A generalized electromagnetic field is applied to the expression of the radio frequency field. To simulate the variations of the high frequency structure, such as the pitch taper and the effect of harmonics, the spatial average over a wavelength is substituted by a time average over a wave period in the equation of the radio frequency field. Under this assumption, the space charge field of the electron beam can be treated by a space charge wave model along with the space charge coefficient. The effects of the radio frequency and the space charge fields on the electrons are presented by the equations of the electron energy and the electron phase. The time-dependent simulation is compared with the frequency-domain simulation for a helix TWT, which validates the availability of this theory. (interdisciplinary physics and related areas of science and technology)
Energy Technology Data Exchange (ETDEWEB)
Potter, Jr., B.G.; Tikare, V.; Tuttle, B.A.
1999-06-30
A 2-D, lattice-Monte Carlo approach was developed to simulate ferroelectric domain structure. The model currently utilizes a Hamiltonian for the total energy based only upon electrostatic terms involving dipole-dipole interactions, local polarization gradients and the influence of applied electric fields. The impact of boundary conditions on the domain configurations obtained was also examined. In general, the model exhibits domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. The model was also extended to enable the simulation of ferroelectric hysteresis behavior. Simulated hysteresis loops were found to be very similar in appearance to those observed experimentally in actual materials. This qualitative agreement between the simulated hysteresis loop characteristics and real ferroelectric behavior was also confirmed in simulations run over a range of simulation temperatures and applied field frequencies.
Pandey, Bharati; Grover, Abhinav; Sharma, Pradeep
2018-02-12
The WRKY transcription factors are a class of DNA-binding proteins involved in diverse plant processes play critical roles in response to abiotic and biotic stresses. Genome-wide divergence analysis of WRKY gene family in Hordeum vulgare provided a framework for molecular evolution and functional roles. So far, the crystal structure of WRKY from barley has not been resolved; moreover, knowledge of the three-dimensional structure of WRKY domain is pre-requisites for exploring the protein-DNA recognition mechanisms. Homology modelling based approach was used to generate structures for WRKY DNA binding domain (DBD) and its variants using AtWRKY1 as a template. Finally, the stability and conformational changes of the generated model in unbound and bound form was examined through atomistic molecular dynamics (MD) simulations for 100 ns time period. In this study, we investigated the comparative binding pattern of WRKY domain and its variants with W-box cis-regulatory element using molecular docking and dynamics (MD) simulations assays. The atomic insight into WRKY domain exhibited significant variation in the intermolecular hydrogen bonding pattern, leading to the structural anomalies in the variant type and differences in the DNA-binding specificities. Based on the MD analysis, residual contribution and interaction contour, wild-type WRKY (HvWRKY46) were found to interact with DNA through highly conserved heptapeptide in the pre- and post-MD simulated complexes, whereas heptapeptide interaction with DNA was missing in variants (I and II) in post-MD complexes. Consequently, through principal component analysis, wild-type WRKY was also found to be more stable by obscuring a reduced conformational space than the variant I (HvWRKY34). Lastly, high binding free energy for wild-type and variant II allowed us to conclude that wild-type WRKY-DNA complex was more stable relative to variants I. The results of our study revealed complete dynamic and structural information
Numerical simulations of time-resolved quantum electronics
International Nuclear Information System (INIS)
Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier
2014-01-01
Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects–mathematical and numerical–associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation
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
Time domain functional NIRS imaging for human brain mapping.
Torricelli, Alessandro; Contini, Davide; Pifferi, Antonio; Caffini, Matteo; Re, Rebecca; Zucchelli, Lucia; Spinelli, Lorenzo
2014-01-15
This review is aimed at presenting the state-of-the-art of time domain (TD) functional near-infrared spectroscopy (fNIRS). We first introduce the physical principles, the basics of modeling and data analysis. Basic instrumentation components (light sources, detection techniques, and delivery and collection systems) of a TD fNIRS system are described. A survey of past, existing and next generation TD fNIRS systems used for research and clinical studies is presented. Performance assessment of TD fNIRS systems and standardization issues are also discussed. Main strengths and weakness of TD fNIRS are highlighted, also in comparison with continuous wave (CW) fNIRS. Issues like quantification of the hemodynamic response, penetration depth, depth selectivity, spatial resolution and contrast-to-noise ratio are critically examined, with the help of experimental results performed on phantoms or in vivo. Finally we give an account on the technological developments that would pave the way for a broader use of TD fNIRS in the neuroimaging community. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
Time-domain Brillouin scattering assisted by diffraction gratings
Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi
2018-02-01
Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.
Landfill cover performance monitoring using time domain reflectometry
International Nuclear Information System (INIS)
Neher, E.R.; Cotten, G.B.; McElroy, D.
1998-01-01
Time domain reflectometry (TDR) systems were installed to monitor soil moisture in two newly constructed landfill covers at the Idaho National Engineering and Environmental Laboratory. Each TDR system includes four vertical arrays with each array consisting of four TDR probes located at depths of 15, 30, 45, and 60 cm. The deepest probes at 60 cm were installed beneath a compacted soil layer to analyze infiltration through the compacted layer. Based on the TDR data, infiltration through the two covers between March and October, 1997 ranged from less than measurable to 1.5 cm. However, due to a prohibition on penetrating the buried waste and resulting limits on probe placement depths, deeper percolation was not evaluated. Some of the advantages found in the application of TDR for infiltration monitoring at this site are the relative low cost and rugged nature of the equipment. Also, of particular importance, the ability to collect frequent moisture measurements allows the capture and evaluation of soil moisture changes resulting from episodic precipitation events. Disadvantages include the inability to install the probes into the waste, difficulties in interpretation of infiltration during freeze/thaw periods, and some excessive noise in the data
Time domain structures in a colliding magnetic flux rope experiment
Tang, Shawn Wenjie; Gekelman, Walter; Dehaas, Timothy; Vincena, Steve; Pribyl, Patrick
2017-10-01
Electron phase-space holes, regions of positive potential on the scale of the Debye length, have been observed in auroras as well as in laboratory experiments. These potential structures, also known as Time Domain Structures (TDS), are packets of intense electric field spikes that have significant components parallel to the local magnetic field. In an ongoing investigation at UCLA, TDS were observed on the surface of two magnetized flux ropes produced within the Large Plasma Device (LAPD). A barium oxide (BaO) cathode was used to produce an 18 m long magnetized plasma column and a lanthanum hexaboride (LaB6) source was used to create 11 m long kink unstable flux ropes. Using two probes capable of measuring the local electric and magnetic fields, correlation analysis was performed on tens of thousands of these structures and their propagation velocities, probability distribution function and spatial distribution were determined. The TDS became abundant as the flux ropes collided and appear to emanate from the reconnection region in between them. In addition, a preliminary analysis of the permutation entropy and statistical complexity of the data suggests that the TDS signals may be chaotic in nature. Work done at the Basic Plasma Science Facility (BaPSF) at UCLA which is supported by DOE and NSF.
Demonstration of Time Domain Multiplexed Readout for Magnetically Coupled Calorimeters
Porst, J.-P.; Adams, J. S.; Balvin, M.; Bandler, S.; Beyer, J.; Busch, S. E.; Drung, D.; Seidel, G. M.; Smith, S. J.; Stevenson, T. R.
2012-01-01
Magnetically coupled calorimeters (MCC) have extremely high potential for x-ray applications due to the inherent high energy resolution capability and being non-dissipative. Although very high energy-resolution has been demonstrated, until now there has been no demonstration of multiplexed read-out. We report on the first realization of a time domain multiplexed (TDM) read-out. While this has many similarities with TDM of transition-edge-sensors (TES), for MGGs the energy resolution is limited by the SQUID read-out noise and requires the well established scheme to be altered in order to minimize degradation due to noise aliasing effects. In cur approach, each pixel is read out by a single first stage SQUID (SQ1) that is operated in open loop. The outputs of the SQ1 s are low-pass filtered with an array of low cross-talk inductors, then fed into a single-stage SQUID TD multiplexer. The multiplexer is addressed from room temperature and read out through a single amplifier channel. We present results achieved with a new detector platform. Noise performance is presented and compared to expectations. We have demonstrated multiplexed X-ray spectroscopy at 5.9keV with delta_FWHM=10eV. In an optimized setup, we show it is possible to multiplex 32 detectors without significantly degrading the Intrinsic detector resolution.
A time-domain finite element boundary integral approach for elastic wave scattering
Shi, F.; Lowe, M. J. S.; Skelton, E. A.; Craster, R. V.
2018-04-01
The response of complex scatterers, such as rough or branched cracks, to incident elastic waves is required in many areas of industrial importance such as those in non-destructive evaluation and related fields; we develop an approach to generate accurate and rapid simulations. To achieve this we develop, in the time domain, an implementation to efficiently couple the finite element (FE) method within a small local region, and the boundary integral (BI) globally. The FE explicit scheme is run in a local box to compute the surface displacement of the scatterer, by giving forcing signals to excitation nodes, which can lie on the scatterer itself. The required input forces on the excitation nodes are obtained with a reformulated FE equation, according to the incident displacement field. The surface displacements computed by the local FE are then projected, through time-domain BI formulae, to calculate the scattering signals with different modes. This new method yields huge improvements in the efficiency of FE simulations for scattering from complex scatterers. We present results using different shapes and boundary conditions, all simulated using this approach in both 2D and 3D, and then compare with full FE models and theoretical solutions to demonstrate the efficiency and accuracy of this numerical approach.
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.
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.
International Nuclear Information System (INIS)
Li Wenjun; China Academy of Engineering Physics, Mianyang; Xu Zhou; Li Ming; Yang Xingfan; Chen Yanan; Liu Jie; Jin Xiao; Lin Yuzheng
2008-01-01
In this paper, a time-domain equivalent circuit method is applied to solve dispersion of coupled-cavity travelling-wave tube (CCTWT). First, the time-domain circuit equations of CCTWT coupled-cavity chain are deduced from the equivalent circuit model. Then, the equations are solved numerically by fourth-order Runge-Kutta method and a program CTTDCP is developed using MATLAB. Last, a L-band CCTWT is calculated using CTTDCP and the cavity pass-band of this tube is computed to be 1.08-1.48 GHz, which is consistent with the experimental results and the simulation results of electromagnetic code and demonstrates the validity of the time-domain equivalent circuit method. In addition, a new design method which uses the equivalent circuit method and electromagnetic simulation together to optimize the cold cavity characteristics of CCTWT is proposed. (authors)
Regional climate simulations with COSMO-CLM over MENA-CORDEX domain
Galluccio, Salvatore; Bucchignani, Edoardo; Mercogliano, Paola; Montesarchio, Myriam
2014-05-01
as the scaling factor for the thickness of the laminar boundary layer for heat, which defines the layer with non-turbulent characteristics, mean entrainment rate for shallow convection, cloud ice threshold for autoconversion, radiation and clouds. We choose such parameters following several literature works, which showed that these parameters mostly affect the fields simulated by the model. However, it is known that the sensitivity of a RCM with respect to parameter variations depends, in general, on the model domain, the temporal and spatial scales and the model variables considered. We made a first set of simulations varying one parameter at a time, using Taylor's diagrams, as well as seasonal cycles and bias maps to take tracking changes in the model performance. Successively, we run a second set of simulations in which we varied two or three parameters at a time to get an optimal configuration. The selected configuration is being used to carry out simulations on a 30-years past period, starting from 1979, for three horizontal resolutions, namely 0.44°, 0.22° and 0.11°.
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.
Electroporation-Induced Cell Modifications Detected with THz Time-Domain Spectroscopy
Romeo, Stefania; Vernier, P. Thomas; Zeni, Olga
2018-04-01
Electroporation (electropermeabilization) increases the electrical conductivity of biological cell membranes and lowers transport barriers for normally impermeant materials. Molecular simulations suggest that electroporation begins with the reorganization of water and lipid head group dipoles in the phospholipid bilayer interface, driven by an externally applied electric field, and the evolution of the resulting defects into water-filled, lipid pores. The interior of the electroporated membrane thus contains water, which should provide a signature for detection of the electropermeabilized state. In this feasibility study, we use THz time-domain spectroscopy, a powerful tool for investigating biomolecular systems and their interactions with water, to detect electroporation in human cells subjected to permeabilizing pulsed electric fields (PEFs). The time-domain response of electroporated human monocytes was acquired with a commercial THz, time-domain spectrometer. For each sample, frequency spectra were calculated, and the absorption coefficient and refractive index were extracted in the frequency range between 0.2 and 1.5 THz. This analysis reveals a higher absorption of THz radiation by PEF-exposed cells, with respect to sham-exposed ones, consistent with the intrusion of water into the cell through the permeabilized membrane that is presumed to be associated with electroporation.
Time-Domain Studies as a Probe of Stellar Evolution
Miller, Adam Andrew
This dissertation focuses on the use of time-domain techniques to discover and characterize these rare astrophysical gems, while also addressing some gaps in our understanding of the earliest and latest stages of stellar evolution. The observational studies presented herein can be grouped into three parts: (i) the study of stellar death (supernovae); (ii) the study of stellar birth; and (iii) the use of modern machine-learning algorithms to discover and classify variable sources. I present observations of supernova (SN) 2006gy, the most luminous SN ever at the time of discovery, and the even-more luminous SN 2008es. Together, these two supernovae (SNe) demonstrate that core-collapse SNe can be significantly more luminous than thermonuclear type Ia SNe, and that there are multiple channels for producing these brilliant core-collapse explosions. For SN 2006gy I show that the progenitor star experienced violent, eruptive mass loss on multiple occasions during the centuries prior to explosion, a scenario that was completely unexpected within the cannon of massive-star evolution theory. I also present observations of SN 2008iy, one of the most unusual SNe ever discovered. Typical SNe take ≲3 weeks to reach peak luminosity; SN 2008iy exhibited a slow and steady rise for ˜400 days before reaching maximum brightness. The best explanation for such behavior is that the progenitor of SN 2008iy experienced an episodic phase of mass loss ˜100 yr prior to explosion. The three SNe detailed in this dissertation have altered our understanding of massive-star mass loss, namely, these SNe provide distinct evidence that post-main sequence mass loss, for at least some massive stars, occurs in sporatic fits, rather than being steady. They also demonstrate that core collapse is not restricted to the red supergiant and Wolf-Rayet stages of stellar evolution as theory predicted. Instead, some massive stars explode while in a luminous blue variable-like state. I also present
International Nuclear Information System (INIS)
Duan Zhisheng; Wang Jinzhi; Yang Ying; Huang Lin
2009-01-01
This paper surveys frequency-domain and time-domain methods for feedback nonlinear systems and their possible applications to chaos control, coupled systems and complex dynamical networks. The absolute stability of Lur'e systems with single equilibrium and global properties of a class of pendulum-like systems with multi-equilibria are discussed. Time-domain and frequency-domain criteria for the convergence of solutions are presented. Some latest results on analysis and control of nonlinear systems with multiple equilibria and applications to chaos control are reviewed. Finally, new chaotic oscillating phenomena are shown in a pendulum-like system and a new nonlinear system with an attraction/repulsion function.
Speeding Up Network Simulations Using Discrete Time
Lucas, Aaron; Armbruster, Benjamin
2013-01-01
We develop a way of simulating disease spread in networks faster at the cost of some accuracy. Instead of a discrete event simulation (DES) we use a discrete time simulation. This aggregates events into time periods. We prove a bound on the accuracy attained. We also discuss the choice of step size and do an analytical comparison of the computational costs. Our error bound concept comes from the theory of numerical methods for SDEs and the basic proof structure comes from the theory of numeri...
Time-Domain Modeling of RF Antennas and Plasma-Surface Interactions
Directory of Open Access Journals (Sweden)
Jenkins Thomas G.
2017-01-01
Full Text Available Recent advances in finite-difference time-domain (FDTD modeling techniques allow plasma-surface interactions such as sheath formation and sputtering to be modeled concurrently with the physics of antenna near- and far-field behavior and ICRF power flow. Although typical sheath length scales (micrometers are much smaller than the wavelengths of fast (tens of cm and slow (millimeter waves excited by the antenna, sheath behavior near plasma-facing antenna components can be represented by a sub-grid kinetic sheath boundary condition, from which RF-rectified sheath potential variation over the surface is computed as a function of current flow and local plasma parameters near the wall. These local time-varying sheath potentials can then be used, in tandem with particle-in-cell (PIC models of the edge plasma, to study sputtering effects. Particle strike energies at the wall can be computed more accurately, consistent with their passage through the known potential of the sheath, such that correspondingly increased accuracy of sputtering yields and heat/particle fluxes to antenna surfaces is obtained. The new simulation capabilities enable time-domain modeling of plasma-surface interactions and ICRF physics in realistic experimental configurations at unprecedented spatial resolution. We will present results/animations from high-performance (10k-100k core FDTD/PIC simulations of Alcator C-Mod antenna operation.
Integral ceramic superstructure evaluation using time domain optical coherence tomography
Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.
2014-02-01
Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.
Boiling water reactor stability analysis in the time domain
International Nuclear Information System (INIS)
Borkowski, J.A.
1991-01-01
Boiling water nuclear reactors may experience density wave instabilities. These instabilities cause the density, and consequently the mass flow rate, to oscillate in the shrouded fuel bundles. This effect causes the nuclear power generation to oscillate due to the tight coupling of flow to power, especially under gravity-driven circulation. In order to predict the amplitude of the power oscillation, a time domain transient analysis tool may be employed. The modeling tool must have sufficient hydrodynamic detail to model natural circulation in two-phase flow as well as the coupled nuclear feedback. TRAC/BF1 is a modeling code with such capabilities. A dynamic system model has been developed for a typical boiling water reactor. Using this tool it has been demonstrated that density waxes may be modeled in this fashion and that their resultant hydrodynamic and nuclear behavior correspond well to simple theory. Several cases have been analyzed using this model, the goal being to determine the coupling between the channel hydrodynamics and the nuclear power. From that study it has been concluded that two-phase friction controls the extent of the oscillation and that the existing conventional methodologies of implementing two-phase friction into analysis codes of this type can lead to significant deviation in results from case to case. It has also been determined that higher dimensional nuclear feedback models reduce the extent of the oscillation. It has also been confirmed from a nonlinear dynamic standpoint that the birth of this oscillation may be described as a Hopf Bifurcation
THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS
Energy Technology Data Exchange (ETDEWEB)
Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others
2015-06-20
We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.
Opportunities and challenges for time domain astronomy with LSST
Ivezic, Zeljko
2014-01-01
The Large Synoptic Survey Telescope (LSST) will enable faint optical time-domain astronomy by carrying out an imaging survey covering the sky that is visible from Cerro Pachon in Northern Chile. Of the order thousand 9.6 sq. deg. images (3.2 Gigapix) will be obtained per night using pairs of 15-second back-to-back exposures, with typical 5-sigma depth for point sources of 24.5 (AB). With close to 1000 observations of a 18,000 sq. deg. region in ugrizy bands over a 10-year period, these data will enable a deep stack across half the sky reaching five magnitudes deeper than the SDSS survey ( 27.5, 5 sigma, point source), and with twice as good seeing (0.7 arcsec median seeing in the r band). The measured and archived properties of newly discovered and known astrometric and photometric transients will be publicly reported within 60 sec after closing the shutter. Automated classification of the expected several million alerts per night, and selection of transient events requiring immediate follow-up, is an outstanding problem for the community. These data will represent a treasure trove for follow-up programs using other ground and space-based telescopes, such as fast-response fast-cadence photometric observations and spectroscopy, as well as for facilities operating at non-optical wavelengths and for gravitational wave programs. I will describe the relevant data products to be delivered by LSST and will summarize challenges that will need to be addressed by the community at large.
THz Time-Domain Spectroscopy of Interstellar Ice Analogs
Ioppolo, Sergio; McGuire, Brett A.; de Vries, Xander; Carroll, Brandon; Allodi, Marco; Blake, Geoffrey
2015-08-01
The unambiguous identification of nearly 200 molecular species in different astronomical environments proves that our cosmos is a ‘Molecular Universe’. The cumulative outcome of recent observations, laboratory studies, and astrochemical models indicates that there is a strong interplay between the gas and the solid phase throughout the process of forming molecules in space. Observations of interstellar ices are generally limited to lines-of-sight along which infrared absorption spectroscopy is possible. Therefore, the identification of more complex prebiotic molecules in the mid-IR is difficult because of their low expected interstellar abundances and the overlap of their absorption features with those from the more abundant species. In the THz region, telescopes can detect Interstellar ices in emission or absorption against dust continuum. Thus, THz searches do not require a background point source. Moreover, since THz spectra are the fingerprint of inter- and intramolecular forces, complex species can present unique modes that do not overlap with those from simpler, more abundant molecules. THz modes are also sensitive to temperature and phase changes in the ice. Therefore, spectroscopy at THz frequencies has the potential to better characterize the physics and chemistry of the ISM. Currently, the Herschel Space Telescope, SOFIA, and ALMA databases contain a vast amount of new THz spectral data that require THz laboratory spectra for interpretation. The latter, however, are largely lacking. We have recently constructed a new THz time-domain spectroscopy system operating in the range between 0.3 - 7.5 THz. This work focuses on the laboratory investigation of the composition and structure of the most abundant interstellar ice analogs compared to some more complex species. Different temperatures, mixing ratios, and matrix isolation experiments will be shown. The ultimate goal of this research is to provide the scientific community with an extensive THz ice
Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes
Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng
2016-09-01
Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.
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
Energy Technology Data Exchange (ETDEWEB)
Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburg, PA (United States); Dickey, Elizabeth C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States)
2017-02-15
A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO{sub 3} single crystals. Further, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system. - Highlights: • A novel technique to directly polar domains utilizing EBSD is demonstrated. • The technique relies on dynamical diffraction simulations of EBSD patterns. • The technique is demonstrated by mapping 180° domains in LiNbO{sub 3} single crystals. • Further application of this technique to other materials classes is discussed.
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
A time-domain method to generate artificial time history from a given reference response spectrum
Energy Technology Data Exchange (ETDEWEB)
Shin, Gang Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Song, Oh Seop [Dept. of Mechanical Engineering, Chungnam National University, Daejeon (Korea, Republic of)
2016-06-15
Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance.
A time-domain method to generate artificial time history from a given reference response spectrum
International Nuclear Information System (INIS)
Shin, Gang Sik; Song, Oh Seop
2016-01-01
Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance
Action simulation: time course and representational mechanisms
Springer, Anne; Parkinson, Jim; Prinz, Wolfgang
2013-01-01
The notion of action simulation refers to the ability to re-enact foreign actions (i.e., actions observed in other individuals). Simulating others' actions implies a mirroring of their activities, based on one's own sensorimotor competencies. Here, we discuss theoretical and experimental approaches to action simulation and the study of its representational underpinnings. One focus of our discussion is on the timing of internal simulation and its relation to the timing of external action, and a paradigm that requires participants to predict the future course of actions that are temporarily occluded from view. We address transitions between perceptual mechanisms (referring to action representation before and after occlusion) and simulation mechanisms (referring to action representation during occlusion). Findings suggest that action simulation runs in real-time; acting on newly created action representations rather than relying on continuous visual extrapolations. A further focus of our discussion pertains to the functional characteristics of the mechanisms involved in predicting other people's actions. We propose that two processes are engaged, dynamic updating and static matching, which may draw on both semantic and motor information. In a concluding section, we discuss these findings in the context of broader theoretical issues related to action and event representation, arguing that a detailed functional analysis of action simulation in cognitive, neural, and computational terms may help to further advance our understanding of action cognition and motor control. PMID:23847563
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.
Molecular dynamics simulations from putative transition states of alpha-spectrin SH3 domain
Periole, Xavier; Vendruscolo, Michele; Mark, Alan E.
2007-01-01
A series of molecular dynamics simulations in explicit solvent were started from nine structural models of the transition state of the SH3 domain of alpha-spectrin, which were generated by Lindorff Larsen et al. (Nat Struct Mol Biol 2004;11:443-449) using molecular dynamics simulations in which
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.
Time and frequency domain analyses of the Hualien Large-Scale Seismic Test
International Nuclear Information System (INIS)
Kabanda, John; Kwon, Oh-Sung; Kwon, Gunup
2015-01-01
Highlights: • Time- and frequency-domain analysis methods are verified against each other. • The two analysis methods are validated against Hualien LSST. • The nonlinear time domain (NLTD) analysis resulted in more realistic response. • The frequency domain (FD) analysis shows amplification at resonant frequencies. • The NLTD analysis requires significant modeling and computing time. - Abstract: In the nuclear industry, the equivalent-linear frequency domain analysis method has been the de facto standard procedure primarily due to the method's computational efficiency. This study explores the feasibility of applying the nonlinear time domain analysis method for the soil–structure-interaction analysis of nuclear power facilities. As a first step, the equivalency of the time and frequency domain analysis methods is verified through a site response analysis of one-dimensional soil, a dynamic impedance analysis of soil–foundation system, and a seismic response analysis of the entire soil–structure system. For the verifications, an idealized elastic soil–structure system is used to minimize variables in the comparison of the two methods. Then, the verified analysis methods are used to develop time and frequency domain models of Hualien Large-Scale Seismic Test. The predicted structural responses are compared against field measurements. The models are also analyzed with an amplified ground motion to evaluate discrepancies of the time and frequency domain analysis methods when the soil–structure system behaves beyond the elastic range. The analysis results show that the equivalent-linear frequency domain analysis method amplifies certain frequency bands and tends to result in higher structural acceleration than the nonlinear time domain analysis method. A comparison with field measurements shows that the nonlinear time domain analysis method better captures the frequency distribution of recorded structural responses than the frequency domain
A two-dimensional time domain near zone to far zone transformation
Luebbers, Raymond J.; Ryan, Deirdre; Beggs, John H.; Kunz, Karl S.
1991-01-01
In a previous paper, a time domain transformation useful for extrapolating 3-D near zone finite difference time domain (FDTD) results to the far zone was presented. In this paper, the corresponding 2-D transform is outlined. While the 3-D transformation produced a physically observable far zone time domain field, this is not convenient to do directly in 2-D, since a convolution would be required. However, a representative 2-D far zone time domain result can be obtained directly. This result can then be transformed to the frequency domain using a Fast Fourier Transform, corrected with a simple multiplicative factor, and used, for example, to calculate the complex wideband scattering width of a target. If an actual time domain far zone result is required it can be obtained by inverse Fourier transform of the final frequency domain result.
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.
TeraHertz Time Domain Spectroscopy of Astrophysical Analog Materials
Blake, Geoffrey
The section of the electromagnetic spectrum extending roughly from wavelengths of 3 millimeters to 30 microns is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the successful deployments of the Herschel and SOFIA observatories, and the emerging capabilities of ALMA, are both revolutionizing our understanding of THz astrophysics and placing stringent demands on the generation of accurate laboratory data on the relevant gas phase and solid state materials detected. With APRA support, we have constructed a combined high bandwidth and high spectral resolution femtosecond THz Time Domain Spectroscopy (THz TDS) system and an FT-IR spectrometer, and coupled these instruments to a high vacuum chamber and cryostat and to gas phase cells including a molecular beam system. We have investigated solid materials from room temperature to 10 K, and can examine both refractory matter such as silicates and molecular ices. For the latter, we have demonstrated that the THz bands observed are uniquely sensitive to both the molecular structure of the ice and its thermal history, and thus that THz observations can provide novel insight into the dominant condensable materials in dense, cold regions. In the gas phase we can record doppler-limited data over at least a decade in bandwidth. While quite capable, the high vacuum cryostat can only study thick samples, especially ices, due to the fairly rapid adsorption of gases onto surfaces at low temperature under such conditions. It is therefore not possible to examine highly layered/structured samples or reactive species. We therefore propose here to upgrade the chamber/cryostat to ultrahigh vacuum, and implement additional sample preparation and characterization tools. With such modifications
Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements
Dragonetti, Giovanna; Comegna, Alessandro; Ajeel, Ali; Piero Deidda, Gian; Lamaddalena, Nicola; Rodriguez, Giuseppe; Vignoli, Giulio; Coppola, Antonio
2018-02-01
This paper deals with the issue of monitoring the spatial distribution of bulk electrical conductivity, σb, in the soil root zone by using electromagnetic induction (EMI) sensors under different water and salinity conditions. To deduce the actual distribution of depth-specific σb from EMI apparent electrical conductivity (ECa) measurements, we inverted the data by using a regularized 1-D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss-Newton method with truncated generalized singular value decomposition (TGSVD). The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI results in the presence of sharp boundaries (otherwise smeared out after the application of more standard Occam-like regularization strategies searching for smooth solutions). Time-domain reflectometry (TDR) data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean, and irrigated with water at two different salinity levels and using two different irrigation volumes. Clearly, this induces different salinity and water contents within the soil profiles. For each transect, 26 regularly spaced monitoring soundings (1 m apart) were selected for the collection of (i) Geonics EM-38 and (ii) Tektronix reflectometer data. Despite the original discrepancies in the EMI and TDR data, we found a significant correlation of the means and standard deviations of the two data series; in particular, after a low-pass spatial filtering of the TDR data. Based on these findings, this paper introduces a novel methodology to calibrate EMI-based electrical conductivities via TDR direct measurements. This
Time simulation of flutter with large stiffness changes
Karpel, Mordechay; Wieseman, Carol D.
1992-01-01
Time simulation of flutter, involving large local structural changes, is formulated with a state-space model that is based on a relatively small number of generalized coordinates. Free-free vibration modes are first calculated for a nominal finite-element model with relatively large fictitious masses located at the area of structural changes. A low-frequency subset of these modes is then transformed into a set of structural modal coordinates with which the entire simulation is performed. These generalized coordinates and the associated oscillatory aerodynamic force coefficient matrices are used to construct an efficient time-domain, state-space model for a basic aeroelastic case. The time simulation can then be performed by simply changing the mass, stiffness, and damping coupling terms when structural changes occur. It is shown that the size of the aeroelastic model required for time simulation with large structural changes at a few apriori known locations is similar to that required for direct analysis of a single structural case. The method is applied to the simulation of an aeroelastic wind-tunnel model. The diverging oscillations are followed by the activation of a tip-ballast decoupling mechanism that stabilizes the system but may cause significant transient overshoots.
A domain decomposition method for pseudo-spectral electromagnetic simulations of plasmas
International Nuclear Information System (INIS)
Vay, Jean-Luc; Haber, Irving; Godfrey, Brendan B.
2013-01-01
Pseudo-spectral electromagnetic solvers (i.e. representing the fields in Fourier space) have extraordinary precision. In particular, Haber et al. presented in 1973 a pseudo-spectral solver that integrates analytically the solution over a finite time step, under the usual assumption that the source is constant over that time step. Yet, pseudo-spectral solvers have not been widely used, due in part to the difficulty for efficient parallelization owing to global communications associated with global FFTs on the entire computational domains. A method for the parallelization of electromagnetic pseudo-spectral solvers is proposed and tested on single electromagnetic pulses, and on Particle-In-Cell simulations of the wakefield formation in a laser plasma accelerator. The method takes advantage of the properties of the Discrete Fourier Transform, the linearity of Maxwell’s equations and the finite speed of light for limiting the communications of data within guard regions between neighboring computational domains. Although this requires a small approximation, test results show that no significant error is made on the test cases that have been presented. The proposed method opens the way to solvers combining the favorable parallel scaling of standard finite-difference methods with the accuracy advantages of pseudo-spectral methods
International Nuclear Information System (INIS)
Wei Biao; Feng Peng; Yang Fan; Ren Yong
2014-01-01
To deal with the disadvantages of the homogeneous signature of the nuclear material identification system (NMIS) and limited methods to extract the characteristic parameters of the nuclear materials, an enhanced method using the combination of the Time-of-Flight (TOF) and the Pulse Shape Discrimination (PSD) was introduced into the traditional characteristic parameters extraction and recognition system of the NMIS. With the help of the PSD, the γ signal and the neutron signal can be discriminated. Further based on the differences of the neutron-γ flight time of the detectors in various positions, a new time-domain signature reflecting the position information of unknown nuclear material was investigated. The simulation result showed that the algorithm is feasible and helpful to identify the relative position of unknown nuclear material. (authors)
Studies in astronomical time series analysis. I - Modeling random processes in the time domain
Scargle, J. D.
1981-01-01
Several random process models in the time domain are defined and discussed. Attention is given to the moving average model, the autoregressive model, and relationships between and combinations of these models. Consideration is then given to methods for investigating pulse structure, procedures of model construction, computational methods, and numerical experiments. A FORTRAN algorithm of time series analysis has been developed which is relatively stable numerically. Results of test cases are given to study the effect of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the light curve of the quasar 3C 272 is considered as an example.
Cable Damage Detection System and Algorithms Using Time Domain Reflectometry
Energy Technology Data Exchange (ETDEWEB)
Clark, G A; Robbins, C L; Wade, K A; Souza, P R
2009-03-24
This report describes the hardware system and the set of algorithms we have developed for detecting damage in cables for the Advanced Development and Process Technologies (ADAPT) Program. This program is part of the W80 Life Extension Program (LEP). The system could be generalized for application to other systems in the future. Critical cables can undergo various types of damage (e.g. short circuits, open circuits, punctures, compression) that manifest as changes in the dielectric/impedance properties of the cables. For our specific problem, only one end of the cable is accessible, and no exemplars of actual damage are available. This work addresses the detection of dielectric/impedance anomalies in transient time domain reflectometry (TDR) measurements on the cables. The approach is to interrogate the cable using time domain reflectometry (TDR) techniques, in which a known pulse is inserted into the cable, and reflections from the cable are measured. The key operating principle is that any important cable damage will manifest itself as an electrical impedance discontinuity that can be measured in the TDR response signal. Machine learning classification algorithms are effectively eliminated from consideration, because only a small number of cables is available for testing; so a sufficient sample size is not attainable. Nonetheless, a key requirement is to achieve very high probability of detection and very low probability of false alarm. The approach is to compare TDR signals from possibly damaged cables to signals or an empirical model derived from reference cables that are known to be undamaged. This requires that the TDR signals are reasonably repeatable from test to test on the same cable, and from cable to cable. Empirical studies show that the repeatability issue is the 'long pole in the tent' for damage detection, because it is has been difficult to achieve reasonable repeatability. This one factor dominated the project. The two-step model
Membrane Sculpting by F-BAR Domains Studied by Molecular Dynamics Simulations
Yu, Hang; Schulten, Klaus
2013-01-01
Interplay between cellular membranes and their peripheral proteins drives many processes in eukaryotic cells. Proteins of the Bin/Amphiphysin/Rvs (BAR) domain family, in particular, play a role in cellular morphogenesis, for example curving planar membranes into tubular membranes. However, it is still unclear how F-BAR domain proteins act on membranes. Electron microscopy revealed that, in vitro, F-BAR proteins form regular lattices on cylindrically deformed membrane surfaces. Using all-atom and coarse-grained (CG) molecular dynamics simulations, we show that such lattices, indeed, induce tubes of observed radii. A 250 ns all-atom simulation reveals that F-BAR domain curves membranes via the so-called scaffolding mechanism. Plasticity of the F-BAR domain permits conformational change in response to membrane interaction, via partial unwinding of the domains 3-helix bundle structure. A CG simulation covering more than 350 µs provides a dynamic picture of membrane tubulation by lattices of F-BAR domains. A series of CG simulations identified the optimal lattice type for membrane sculpting, which matches closely the lattices seen through cryo-electron microscopy. PMID:23382665
Simulations of Chemotaxis and Random Motility in Finite Domains
National Research Council Canada - National Science Library
Jabbarzadeh, Ehsan; Abrams, Cameron F
2005-01-01
.... The model couples fully time-dependent finite-difference solution of a reaction-diffusion equation for the concentration field of a generic chemoattractant to biased random walks representing individual moving cells...
Energy Technology Data Exchange (ETDEWEB)
Campione, Salvatore [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Warne, Larry K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schiek, Richard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Basilio, Lorena I. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-09-01
This report details the modeling results for the response of a finite-length dissipative conductor interacting with a conducting ground to a hypothetical nuclear device with the same output energy spectrum as the Fat Man device. We use a time-domain method based on transmission line theory that allows accounting for time-varying air conductivities. We implemented such method in a code we call ATLOG - Analytic Transmission Line Over Ground. Results are compared the frequency-domain version of ATLOG previously developed and to the circuit simulator Xyce in some instances. Intentionally Left Blank
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.
Time domain reshuffling for OFDM based indoor visible light communication systems.
You, Xiaodi; Chen, Jian; Yu, Changyuan; Zheng, Huanhuan
2017-05-15
For orthogonal frequency division multiplexing (OFDM) based indoor visible light communication (VLC) systems, partial non-ideal transmission conditions such as insufficient guard intervals and a dispersive channel can result in severe inter-symbol crosstalk (ISC). By deriving from the inverse Fourier transform, we present a novel time domain reshuffling (TDR) concept for both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM VLC systems. By using only simple operations in the frequency domain, potential high peaks can be relocated within each OFDM symbol to alleviate ISC. To simplify the system, we also propose an effective unified design of the TDR schemes for both DCO- and ACO-OFDM. Based on Monte-Carlo simulations, we demonstrate the statistical distribution of the signal high peak values and the complementary cumulative distribution function of the peak-to-average power ratio under different cases for comparison. Simulation results indicate improved bit error rate (BER) performance by adopting TDR to counteract ISC deterioration. For example, for binary phase shift keying at a BER of 10 -3 , the signal to noise ratio gains are ~1.6 dB and ~6.6 dB for DCO- and ACO-OFDM, respectively, with ISC of 1/64. We also show a reliable transmission by adopting TDR for rectangle 8-quadrature amplitude modulation with ISC of < 1/64.
A frequency-domain method for solving linear time delay systems with constant coefficients
Jin, Mengshi; Chen, Wei; Song, Hanwen; Xu, Jian
2018-03-01
In an active control system, time delay will occur due to processes such as signal acquisition and transmission, calculation, and actuation. Time delay systems are usually described by delay differential equations (DDEs). Since it is hard to obtain an analytical solution to a DDE, numerical solution is of necessity. This paper presents a frequency-domain method that uses a truncated transfer function to solve a class of DDEs. The theoretical transfer function is the sum of infinite items expressed in terms of poles and residues. The basic idea is to select the dominant poles and residues to truncate the transfer function, thus ensuring the validity of the solution while improving the efficiency of calculation. Meanwhile, the guideline of selecting these poles and residues is provided. Numerical simulations of both stable and unstable delayed systems are given to verify the proposed method, and the results are presented and analysed in detail.
A Compact Unconditionally Stable Method for Time-Domain Maxwell's Equations
Directory of Open Access Journals (Sweden)
Zhuo Su
2013-01-01
Full Text Available Higher order unconditionally stable methods are effective ways for simulating field behaviors of electromagnetic problems since they are free of Courant-Friedrich-Levy conditions. The development of accurate schemes with less computational expenditure is desirable. A compact fourth-order split-step unconditionally-stable finite-difference time-domain method (C4OSS-FDTD is proposed in this paper. This method is based on a four-step splitting form in time which is constructed by symmetric operator and uniform splitting. The introduction of spatial compact operator can further improve its performance. Analyses of stability and numerical dispersion are carried out. Compared with noncompact counterpart, the proposed method has reduced computational expenditure while keeping the same level of accuracy. Comparisons with other compact unconditionally-stable methods are provided. Numerical dispersion and anisotropy errors are shown to be lower than those of previous compact unconditionally-stable methods.
Transient analysis of printed lines using finite-difference time-domain method
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Shahid [Thomas Jefferson National Accelerator Facility, 12050 Jefferson Avenue, Suite 704, Newport News, VA, 23606, USA
2012-03-29
Comprehensive studies of ultra-wideband pulses and electromagnetic coupling on printed coupled lines have been performed using full-wave 3D finite-difference time-domain analysis. Effects of unequal phase velocities of coupled modes, coupling between line traces, and the frequency dispersion on the waveform fidelity and crosstalk have been investigated in detail. To discriminate the contributions of different mechanisms into pulse evolution, single and coupled microstrip lines without (ϵ_{r} = 1) and with (ϵ_{r} > 1) dielectric substrates have been examined. To consistently compare the performance of the coupled lines with substrates of different permittivities and transients of different characteristic times, a generic metric similar to the electrical wavelength has been introduced. The features of pulse propagation on coupled lines with layered and pedestal substrates and on the irregular traces have been explored. Finally, physical interpretations of the simulation results are discussed in the paper.
A model of the formation of illusory conjunctions in the time domain.
Botella, J; Suero, M; Barriopedro, M I
2001-12-01
The authors present a model to account for the miscombination of features when stimuli are presented using the rapid serial visual presentation (RSVP) technique (illusory conjunctions in the time domain). It explains the distributions of responses through a mixture of trial outcomes. In some trials, attention is successfully focused on the target, whereas in others, the responses are based on partial information. Two experiments are presented that manipulated the mean processing time of the target-defining dimension and of the to-be-reported dimension, respectively. As predicted, the average origin of the responses is delayed when lengthening the target-defining dimension, whereas it is earlier when lengthening the to-be-reported dimension; in the first case the number of correct responses is dramatically reduced, whereas in the second it does not change. The results, a review of other research, and simulations carried out with a formal version of the model are all in close accordance with the predictions.
Spencer, E. A.; Clark, D. C.; Vadepu, S. K.; Patra, S.
2017-12-01
A Time Domain Impedance Probe (TDIP) measures electron density and electron neutral collision frequencies in the ionosphere. This instrument has been tested on a sounding rocket flight and is now being further developed to fly on a NASA Undergraduate Student Instrument Program (USIP) cubesat to be launched out of the ISS in 2019. Here we report on the development of a new combined TDIP and plasma wave instrument that can be used on cubesat platforms to measure local electron parameters, and also to receive or transmit electron scale waves. This combined instrument can be used to study short time and space scale phenomena in the upper ionosphere using only RF signals. The front end analog circuitry is dual-purposed to perform active or passive probing of the ambient plasma. Two dipole antennas are used, one is optimzed for impedance measurements, while the other is optimized for transmitter-receiver performance. We show our circuit realization, and initial results from laboratory measurements using the TDIP prototype modified for receiver function. We also show Finite Difference Time Domain (FDTD) simulations of an electrically long antenna immersed in a magnetized plasma used to optimize the transmitter receiver performance.
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.
Simulation of power fluctuation of wind farms based on frequency domain
DEFF Research Database (Denmark)
Lin, Jin; Sun, Yuanzhang; Li, Guojie
2011-01-01
, however, is incapable of completely explaining the physical mechanism of randomness of power fluctuation. To remedy such a situation, fluctuation modeling based on the frequency domain is proposed. The frequency domain characteristics of stochastic fluctuation on large wind farms are studied using...... the power spectral density of wind speed, the frequency domain model of a wind power generator and the information on weather and geography of the wind farms. The correctness and effectiveness of the model are verified by comparing the measurement data with simulation results of a certain wind farm. © 2011...
Frequency-domain criterion for the chaos synchronization of time ...
Indian Academy of Sciences (India)
of time-delay power systems under linear feedback control ... arbitrary dimension of the time-delay systems can keep their chaotic characteristic as long as ... As a basic theory on chaotic secure communication, synchronization of time-delay.
Studies in astronomical time series analysis: Modeling random processes in the time domain
Scargle, J. D.
1979-01-01
Random process models phased in the time domain are used to analyze astrophysical time series data produced by random processes. A moving average (MA) model represents the data as a sequence of pulses occurring randomly in time, with random amplitudes. An autoregressive (AR) model represents the correlations in the process in terms of a linear function of past values. The best AR model is determined from sampled data and transformed to an MA for interpretation. The randomness of the pulse amplitudes is maximized by a FORTRAN algorithm which is relatively stable numerically. Results of test cases are given to study the effects of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the optical light curve of the quasar 3C 273 is given.
On spurious resonant modes in the MOT solution of time domain EFIE
Shi, Yifei; Bagci, Hakan; Lu, Mingyu
2013-01-01
Theoretically, internal resonant modes should not be induced in the marching-on-in-time (MOT) solution of the time domain electric field integral equation since zero initial conditions are enforced at the beginning of time marching and the internal
On the initial condition problem of the time domain PMCHWT surface integral equation
Uysal, Ismail Enes; Bagci, Hakan; Ergin, A. Arif; Ulku, H. Arda
2017-01-01
Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced
Study of time-domain digital pulse shaping algorithms for nuclear signals
International Nuclear Information System (INIS)
Zhou Jianbin; Tuo Xianguo; Zhu Xing; Liu Yi; Zhou Wei; Lei Jiarong
2012-01-01
With the development on high-speed integrated circuit, fast high resolution sampling ADC and digital signal processors are replacing analog shaping amplifier circuit. This paper firstly presents the numerical analysis and simulation on R-C shaping circuit model and C-R shaping circuit model. Mathematic models are established based on 1 st order digital differential method and Kirchhoff Current Law in time domain, and a simulation and error evaluation experiment on an ideal digital signal are carried out with Excel VBA. A digital shaping test for a semiconductor X-ray detector in real time is also presented. Then a numerical analysis for Sallen-Key(S-K) low-pass filter circuit model is implemented based on the analysis of digital R-C and digital C-R shaping methods. By applying the 2 nd order non-homogeneous differential equation,the authors implement a digital Gaussian filter model for a standard exponential-decaying signal and a nuclear pulse signal. Finally, computer simulations and experimental tests are carried out and the results show the possibility of the digital pulse processing algorithms. (authors)
A new image cipher in time and frequency domains
Abd El-Latif, Ahmed A.; Niu, Xiamu; Amin, Mohamed
2012-10-01
Recently, various encryption techniques based on chaos have been proposed. However, most existing chaotic encryption schemes still suffer from fundamental problems such as small key space, weak security function and slow performance speed. This paper introduces an efficient encryption scheme for still visual data that overcome these disadvantages. The proposed scheme is based on hybrid Linear Feedback Shift Register (LFSR) and chaotic systems in hybrid domains. The core idea is to scramble the pixel positions based on 2D chaotic systems in frequency domain. Then, the diffusion is done on the scrambled image based on cryptographic primitive operations and the incorporation of LFSR and chaotic systems as round keys. The hybrid compound of LFSR, chaotic system and cryptographic primitive operations strengthen the encryption performance and enlarge the key space required to resist the brute force attacks. Results of statistical and differential analysis show that the proposed algorithm has high security for secure digital images. Furthermore, it has key sensitivity together with a large key space and is very fast compared to other competitive algorithms.
A symmetrical image encryption scheme in wavelet and time domain
Luo, Yuling; Du, Minghui; Liu, Junxiu
2015-02-01
There has been an increasing concern for effective storages and secure transactions of multimedia information over the Internet. Then a great variety of encryption schemes have been proposed to ensure the information security while transmitting, but most of current approaches are designed to diffuse the data only in spatial domain which result in reducing storage efficiency. A lightweight image encryption strategy based on chaos is proposed in this paper. The encryption process is designed in transform domain. The original image is decomposed into approximation and detail components using integer wavelet transform (IWT); then as the more important component of the image, the approximation coefficients are diffused by secret keys generated from a spatiotemporal chaotic system followed by inverse IWT to construct the diffused image; finally a plain permutation is performed for diffusion image by the Logistic mapping in order to reduce the correlation between adjacent pixels further. Experimental results and performance analysis demonstrate the proposed scheme is an efficient, secure and robust encryption mechanism and it realizes effective coding compression to satisfy desirable storage.
Real-time inextensible surgical thread simulation.
Xu, Lang; Liu, Qian
2018-03-27
This paper discusses a real-time simulation method of inextensible surgical thread based on the Cosserat rod theory using position-based dynamics (PBD). The method realizes stable twining and knotting of surgical thread while including inextensibility, bending, twisting and coupling effects. The Cosserat rod theory is used to model the nonlinear elastic behavior of surgical thread. The surgical thread model is solved with PBD to achieve a real-time, extremely stable simulation. Due to the one-dimensional linear structure of surgical thread, the direct solution of the distance constraint based on tridiagonal matrix algorithm is used to enhance stretching resistance in every constraint projection iteration. In addition, continuous collision detection and collision response guarantee a large time step and high performance. Furthermore, friction is integrated into the constraint projection process to stabilize the twining of multiple threads and complex contact situations. Through comparisons with existing methods, the surgical thread maintains constant length under large deformation after applying the direct distance constraint in our method. The twining and knotting of multiple threads correspond to stable solutions to contact and friction forces. A surgical suture scene is also modeled to demonstrate the practicality and simplicity of our method. Our method achieves stable and fast simulation of inextensible surgical thread. Benefiting from the unified particle framework, the rigid body, elastic rod, and soft body can be simultaneously simulated. The method is appropriate for applications in virtual surgery that require multiple dynamic bodies.
CUDA-based real time surgery simulation.
Liu, Youquan; De, Suvranu
2008-01-01
In this paper we present a general software platform that enables real time surgery simulation on the newly available compute unified device architecture (CUDA)from NVIDIA. CUDA-enabled GPUs harness the power of 128 processors which allow data parallel computations. Compared to the previous GPGPU, it is significantly more flexible with a C language interface. We report implementation of both collision detection and consequent deformation computation algorithms. Our test results indicate that the CUDA enables a twenty times speedup for collision detection and about fifteen times speedup for deformation computation on an Intel Core 2 Quad 2.66 GHz machine with GeForce 8800 GTX.
Directory of Open Access Journals (Sweden)
Reza Ahmadi
2014-12-01
Full Text Available To date, a number of numerical methods, including the popular Finite-Difference Time Domain (FDTD technique, have been proposed to simulate Ground-Penetrating Radar (GPR responses. Despite having a number of advantages, the finite-difference method also has pitfalls such as being very time consuming in simulating the most common case of media with high dielectric permittivity, causing the forward modelling process to be very long lasting, even with modern high-speed computers. In the present study the well-known hyperbolic pattern response of horizontal cylinders, usually found in GPR B-Scan images, is used as a basic model to examine the possibility of reducing the forward modelling execution time. In general, the simulated GPR traces of common reflected objects are time shifted, as with the Normal Moveout (NMO traces encountered in seismic reflection responses. This suggests the application of Fourier transform to the GPR traces, employing the time-shifting property of the transformation to interpolate the traces between the adjusted traces in the frequency domain (FD. Therefore, in the present study two post-processing algorithms have been adopted to increase the speed of forward modelling while maintaining the required precision. The first approach is based on linear interpolation in the Fourier domain, resulting in increasing lateral trace-to-trace interval of appropriate sampling frequency of the signal, preventing any aliasing. In the second approach, a super-resolution algorithm based on 2D-wavelet transform is developed to increase both vertical and horizontal resolution of the GPR B-Scan images through preserving scale and shape of hidden hyperbola features. Through comparing outputs from both methods with the corresponding actual high-resolution forward response, it is shown that both approaches can perform satisfactorily, although the wavelet-based approach outperforms the frequency-domain approach noticeably, both in amplitude and
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...
Zhang, Xiao-bo
2017-06-01
The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge storage consumption in the gradient preconditioning algorithms based on Hessian matrices in time-domain full waveform inversion (FWI), but the accuracy is affected by the energy of reflected waves when strong reflectors are present in velocity model. To address this problem, we propose a gradient preconditioning method, which scales the gradient based on the energy of the “approximated transmitted wavefield” simulated by the nonreflecting acoustic wave equation. The method does not require computing or storing the Hessian matrix or its inverse. Furthermore, it can effectively eliminate the effects caused by geometric diffusion and non-uniformity illumination on gradient. The results of model experiments confirm that the time-domain FWI using the gradient preconditioning based on transmitted waves energy can achieve higher inversion precision for high-velocity body and the deep strata below when compared with using the gradient preconditioning based on seismic waves energy.
Parallel time domain solvers for electrically large transient scattering problems
Liu, Yang; Yucel, Abdulkadir; Bagcý , Hakan; Michielssen, Eric
2014-01-01
scattering from perfect electrically conducting objects are obtained by enforcing electric field boundary conditions and implicitly time advance electric surface current densities by iteratively solving sparse systems of equations at all time steps. Contrary
Energy Technology Data Exchange (ETDEWEB)
Salque, B
1998-07-01
This work deals with the equation of radiosity, this equation describes the transport of light energy through a diffuse medium, its resolution enables us to simulate the presence of light sources. The equation of radiosity is an integral equation who admits a unique solution in realistic cases. The different methods of solving are reviewed. The equation of radiosity can not be formulated as the integral form of a classical partial differential equation, but this work shows that the technique of domain decomposition can be successfully applied to the equation of radiosity if this approach is framed by considerations of physics. This method provides a system of independent equations valid for each sub-domain and whose main parameter is luminance. Some numerical examples give an idea of the convergence of the algorithm. This method is applied to the optimization of the shape of a light reflector.
Pucher, PH; Tamblyn, R; Boorman, D; Dixon-Woods, Mary Margaret; Donaldson, L; Draycott, T; Forster, A; Nadkarni, V; Power, C; Sevdalis, N; Aggarwal, R
2017-01-01
The use of simulation-based training has established itself in healthcare but its implementation has been varied and mostly limited to technical and non-technical skills training. This article discusses the possibilities of the use of simulation as part of an overarching approach to improving patient safety, and represents the views of the Simnovate Patient Safety Domain Group, an international multidisciplinary expert group dedicated to the improvement of patient safety. The application and ...
Architecture for time or transform domain decoding of reed-solomon codes
Shao, Howard M. (Inventor); Truong, Trieu-Kie (Inventor); Hsu, In-Shek (Inventor); Deutsch, Leslie J. (Inventor)
1989-01-01
Two pipeline (255,233) RS decoders, one a time domain decoder and the other a transform domain decoder, use the same first part to develop an errata locator polynomial .tau.(x), and an errata evaluator polynominal A(x). Both the time domain decoder and transform domain decoder have a modified GCD that uses an input multiplexer and an output demultiplexer to reduce the number of GCD cells required. The time domain decoder uses a Chien search and polynomial evaluator on the GCD outputs .tau.(x) and A(x), for the final decoding steps, while the transform domain decoder uses a transform error pattern algorithm operating on .tau.(x) and the initial syndrome computation S(x), followed by an inverse transform algorithm in sequence for the final decoding steps prior to adding the received RS coded message to produce a decoded output message.
THE PSTD ALGORITHM: A TIME-DOMAIN METHOD REQUIRING ONLY TWO CELLS PER WAVELENGTH. (R825225)
A pseudospectral time-domain (PSTD) method is developed for solutions of Maxwell's equations. It uses the fast Fourier transform (FFT), instead of finite differences on conventional finite-difference-time-domain (FDTD) methods, to represent spatial derivatives. Because the Fourie...
On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain
DEFF Research Database (Denmark)
Østerberg, Frederik Westergaard; Rizzi, Giovanni; Hansen, Mikkel Fougt
2013-01-01
the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s...
Implicit time accurate simulation of unsteady flow
van Buuren, René; Kuerten, Hans; Geurts, Bernard J.
2001-03-01
Implicit time integration was studied in the context of unsteady shock-boundary layer interaction flow. With an explicit second-order Runge-Kutta scheme, a reference solution to compare with the implicit second-order Crank-Nicolson scheme was determined. The time step in the explicit scheme is restricted by both temporal accuracy as well as stability requirements, whereas in the A-stable implicit scheme, the time step has to obey temporal resolution requirements and numerical convergence conditions. The non-linear discrete equations for each time step are solved iteratively by adding a pseudo-time derivative. The quasi-Newton approach is adopted and the linear systems that arise are approximately solved with a symmetric block Gauss-Seidel solver. As a guiding principle for properly setting numerical time integration parameters that yield an efficient time accurate capturing of the solution, the global error caused by the temporal integration is compared with the error resulting from the spatial discretization. Focus is on the sensitivity of properties of the solution in relation to the time step. Numerical simulations show that the time step needed for acceptable accuracy can be considerably larger than the explicit stability time step; typical ratios range from 20 to 80. At large time steps, convergence problems that are closely related to a highly complex structure of the basins of attraction of the iterative method may occur. Copyright
Analytical approximate solutions of the time-domain diffusion equation in layered slabs.
Martelli, Fabrizio; Sassaroli, Angelo; Yamada, Yukio; Zaccanti, Giovanni
2002-01-01
Time-domain analytical solutions of the diffusion equation for photon migration through highly scattering two- and three-layered slabs have been obtained. The effect of the refractive-index mismatch with the external medium is taken into account, and approximate boundary conditions at the interface between the diffusive layers have been considered. A Monte Carlo code for photon migration through a layered slab has also been developed. Comparisons with the results of Monte Carlo simulations showed that the analytical solutions correctly describe the mean path length followed by photons inside each diffusive layer and the shape of the temporal profile of received photons, while discrepancies are observed for the continuous-wave reflectance or transmittance.
Calibrating a Salt Water Intrusion Model with Time-Domain Electromagnetic Data
DEFF Research Database (Denmark)
Herckenrath, Daan; Odlum, Nick; Nenna, Vanessa
2013-01-01
Salt water intrusion models are commonly used to support groundwater resource management in coastal aquifers. Concentration data used for model calibration are often sparse and limited in spatial extent. With airborne and ground-based electromagnetic surveys, electrical resistivity models can......, we perform a coupled hydrogeophysical inversion (CHI) in which we use a salt water intrusion model to interpret the geophysical data and guide the geophysical inversion. We refer to this methodology as a Coupled Hydrogeophysical Inversion-State (CHI-S), in which simulated salt concentrations...... are transformed to an electrical resistivity model, after which a geophysical forward response is calculated and compared with the measured geophysical data. This approach was applied for a field site in Santa Cruz County, California, where a time-domain electromagnetic (TDEM) dataset was collected...
International Nuclear Information System (INIS)
Khaizer, A.N.; Hussain, I.
2015-01-01
This paper presents a time-domain approach for identification of longitudinal dynamics of single rotor model helicopter. A frequency sweep excitation input signal is applied for hover flying mode widely used for space state linearized model. A fully automated programmed flight test method provides high quality flight data for system identification using the computer controlled flight simulator X-plane. The flight test data were recorded, analyzed and reduced using the SIDPAC (System Identification Programs for Air Craft) toolbox for MATLAB, resulting in an aerodynamic model of single rotor helicopter. Finally, the identified model of single rotor helicopter is validated on Raptor 30-class model helicopter at hover showing the reliability of proposed approach. (author)
Li, Xuebao; Li, Dayong; Chen, Bo; Cui, Xiang; Lu, Tiebing; Li, Yinfei
2018-04-01
The corona-generated electromagnetic interference commonly known as radio interference (RI) has become a limiting factor for the design of high voltage direct current transmission lines. In this paper, a time-domain measurement system is developed to measure the time-domain characteristics of corona-generated RI from a single corona source under a positive corona source. In the experiments, the corona current pulses are synchronously measured through coupling capacitors. The one-to-one relationship between the corona current pulse and measured RI voltage pulse is observed. The statistical characteristics of pulse parameters are analyzed, and the correlations between the corona current pulse and RI voltage pulse in the time-domain and frequency-domain are analyzed. Depending on the measured corona current pulses, the time-domain waveform of corona-generated RI is calculated on the basis of the propagation model of corona current on the conductor, the dipolar model for electric field calculation, and the antenna model for inducing voltage calculation. The well matched results between measured and simulated waveforms of RI voltage can show the validity of the measurement and calculation method presented in this paper, which also further show the close correlation between corona current and corona-generated RI.
Modeling ferrite electromagnetic response in the time domain
International Nuclear Information System (INIS)
Johnson, J.; DeFord, J.F.; Craig, G.D.
1989-01-01
The behavior of ferrite loads commonly found in induction accelertors has important consequences for the performance of these accelerators. Previous work by the authors on modeling the electromagnetic fields in induction cavities has focussed upon use of a simple, phenomenological model for the process of magnetization reversal in these ferrite loads. In this paper we consider a model for magnetization reversal which is more deeply rooted in theory, and present a simulation of the reversal process based upon this model for an idealized set of boundary conditions. 7 refs., 3 figs
Noise Reduction in the Time Domain using Joint Diagonalization
DEFF Research Database (Denmark)
Nørholm, Sidsel Marie; Benesty, Jacob; Jensen, Jesper Rindom
2014-01-01
, an estimate of the desired signal is found by subtraction of the noise estimate from the observed signal. The filter can be designed to obtain a desired trade-off between noise reduction and signal distortion, depending on the number of eigenvectors included in the filter design. This is explored through...... simulations using a speech signal corrupted by car noise, and the results confirm that the output signal-to-noise ratio and speech distortion index both increase when more eigenvectors are included in the filter design....
Domain-growth kinetics and aspects of pinning: A Monte Carlo simulation study
DEFF Research Database (Denmark)
Castán, T.; Lindgård, Per-Anker
1991-01-01
By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic transformati......By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic...... to cross over from n = 1/4 at T approximately 0 to n = 1/2 with temperature for models with pinnings of types (a) and (b). For topological pinnings at T approximately 0, n is consistent with n = 1/8, a value conceivable for several levels of hierarchically interrelated domain-wall movement. When...
Talebi, Hassan; Asghari, Omid; Emery, Xavier
2013-12-01
An accurate estimation of mineral grades in ore deposits with heterogeneous spatial variations requires defining geological domains that differentiate the types of mineralogy, alteration and lithology. Deterministic models define the layout of the domains based on the interpretation of the drill holes and do not take into account the uncertainty in areas with fewer data. Plurigaussian simulation (PGS) can be an alternative to generate multiple numerical models of the ore body, with the aim of assessing the uncertainty in the domain boundaries and improving the geological controls in the characterization of quantitative attributes. This study addresses the application of PGS to Sungun porphyry copper deposit (Iran), in order to simulate the layout of four hypogene alteration zones: potassic, phyllic, propylitic and argillic. The aim of this study is to construct numerical models in which the alteration structures reflect the evolution observed in the geology.
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin; Ulku, Huseyin Arda; Bagci, Hakan
2015-01-01
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin
2015-05-16
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Gu, X.; Blackmore, K. L.
2015-01-01
This paper presents the results of a systematic review of agent-based modelling and simulation (ABMS) applications in the higher education (HE) domain. Agent-based modelling is a "bottom-up" modelling paradigm in which system-level behaviour (macro) is modelled through the behaviour of individual local-level agent interactions (micro).…
Explicit solution of Calderon preconditioned time domain integral equations
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2013-01-01
operators and a PE(CE)m type linear multistep to march on in time. Unlike its implicit counterpart, the proposed explicit solver requires the solution of an MOT system with a Gram matrix that is sparse and well-conditioned independent of the time step size
Directory of Open Access Journals (Sweden)
B. U. Musa
2017-04-01
Full Text Available The C++ programming language was used to implement three-dimensional (3-D finite-difference time-domain (FDTD technique to simulate radiation of high frequency electromagnetic waves in free space. To achieve any meaningful results the computational domain of interest should have to be truncated in some way and this is achieved by applying absorbing boundary conditions. A uniaxial perfectly matched layer (UPML absorbing boundary condition is used in this work. The discretised equations of the UPML in FDTD time stepping scheme were derived and has been successfully implemented using the computer program. Simulation results showed that the UPML behaves as an absorber. This was confirmed by comparing the results with another boundary condition, the Mur ABC.
Managing Time-Based Conflict Across Life Domains In Nigeria: A ...
African Journals Online (AJOL)
Managing Time-Based Conflict Across Life Domains In Nigeria: A Decision Making Perspective. ... which employees in a developing country attempt to resolve time-based conflict between work, family and other activities. A decision making ...
Mixed Discretization of the Time Domain MFIE at Low Frequencies
Ulku, Huseyin Arda
2017-01-10
Solution of the magnetic field integral equation (MFIE), which is obtained by the classical marching on-in-time (MOT) scheme, becomes inaccurate when the time step is large, i.e., under low-frequency excitation. It is shown here that the inaccuracy stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring the correct scaling of the current’s Helmholtz components under low-frequency excitation.
Uysal, Ismail Enes
2016-10-01
Plasmonic structures are utilized in many applications ranging from bio-medicine to solar energy generation and transfer. Numerical schemes capable of solving equations of classical electrodynamics have been the method of choice for characterizing scattering properties of such structures. However, as dimensions of these plasmonic structures reduce to nanometer scale, quantum mechanical effects start to appear. These effects cannot be accurately modeled by available classical numerical methods. One of these quantum effects is the tunneling, which is observed when two structures are located within a sub-nanometer distance of each other. At these small distances electrons “jump" from one structure to another and introduce a path for electric current to flow. Classical equations of electrodynamics and the schemes used for solving them do not account for this additional current path. This limitation can be lifted by introducing an auxiliary tunnel with material properties obtained using quantum models and applying a classical solver to the structures connected by this auxiliary tunnel. Early work on this topic focused on quantum models that are generated using a simple one-dimensional wave function to find the tunneling probability and assume a simple Drude model for the permittivity of the tunnel. These tunnel models are then used together with a classical frequency domain solver. In this thesis, a time domain surface integral equation solver for quantum corrected analysis of transient plasmonic interactions is proposed. This solver has several advantages: (i) As opposed to frequency domain solvers, it provides results at a broad band of frequencies with a single simulation. (ii) As opposed to differential equation solvers, it only discretizes surfaces (reducing number of unknowns), enforces the radiation condition implicitly (increasing the accuracy), and allows for time step selection independent of spatial discretization (increasing efficiency). The quantum model
Mixed Discretization of the Time Domain MFIE at Low Frequencies
Ulku, Huseyin Arda; Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco Paolo; Bagci, Hakan
2017-01-01
stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring
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....
From medium heterogeneity to flow and transport: A time-domain random walk approach
Hakoun, V.; Comolli, A.; Dentz, M.
2017-12-01
The prediction of flow and transport processes in heterogeneous porous media is based on the qualitative and quantitative understanding of the interplay between 1) spatial variability of hydraulic conductivity, 2) groundwater flow and 3) solute transport. Using a stochastic modeling approach, we study this interplay through direct numerical simulations of Darcy flow and advective transport in heterogeneous media. First, we study flow in correlated hydraulic permeability fields and shed light on the relationship between the statistics of log-hydraulic conductivity, a medium attribute, and the flow statistics. Second, we determine relationships between Eulerian and Lagrangian velocity statistics, this means, between flow and transport attributes. We show how Lagrangian statistics and thus transport behaviors such as late particle arrival times are influenced by the medium heterogeneity on one hand and the initial particle velocities on the other. We find that equidistantly sampled Lagrangian velocities can be described by a Markov process that evolves on the characteristic heterogeneity length scale. We employ a stochastic relaxation model for the equidistantly sampled particle velocities, which is parametrized by the velocity correlation length. This description results in a time-domain random walk model for the particle motion, whose spatial transitions are characterized by the velocity correlation length and temporal transitions by the particle velocities. This approach relates the statistical medium and flow properties to large scale transport, and allows for conditioning on the initial particle velocities and thus to the medium properties in the injection region. The approach is tested against direct numerical simulations.
Wessels, Philipp; Ewald, Johannes; Wieland, Marek; Nisius, Thomas; Vogel, Andreas; Viefhaus, Jens; Meier, Guido; Wilhein, Thomas; Drescher, Markus
2014-11-01
The destruction and formation of equilibrium multidomain patterns in permalloy (Ni80Fe20 ) microsquares has been captured using pump-probe x-ray magnetic circular dichroism (XMCD) spectromicroscopy at a new full-field magnetic transmission soft x-ray microscopy endstation with subnanosecond time resolution. The movie sequences show the dynamic magnetization response to intense Oersted field pulses of approximately 200-ps root mean square (rms) duration and the magnetization reorganization to the ground-state domain configuration. The measurements display how a vortex flux-closure magnetization distribution emerges out of a nonequilibrium uniform single-domain state. During the destruction of the initial vortex pattern, we have traced the motion of the central vortex core that is ejected out of the microsquare at high velocities exceeding 1 km/s. A reproducible recovery into a defined final vortex state with stable chirality and polarity could be achieved. Using an additional external bias field, the transient reversal of the square magnetization direction could be monitored and consistently reproduced by micromagnetic simulations.
Finite-time thermodynamics and simulated annealing
International Nuclear Information System (INIS)
Andresen, B.
1989-01-01
When the general, global optimization technique simulated annealing was introduced by Kirkpatrick et al. (1983), this mathematical algorithm was based on an analogy to the statistical mechanical behavior of real physical systems like spin glasses, hence the name. In the intervening span of years the method has proven exceptionally useful for a great variety of extremely complicated problems, notably NP-problems like the travelling salesman, DNA sequencing, and graph partitioning. Only a few highly optimized heuristic algorithms (e.g. Lin, Kernighan 1973) have outperformed simulated annealing on their respective problems (Johnson et al. 1989). Simulated annealing in its current form relies only on the static quantity 'energy' to describe the system, whereas questions of rate, as in the temperature path (annealing schedule, see below), are left to intuition. We extent the connection to physical systems and take over further components from thermodynamics like ensemble, heat capacity, and relaxation time. Finally we refer to finite-time thermodynamics (Andresen, Salomon, Berry 1984) for a dynamical estimate of the optimal temperature path. (orig.)
Time reversibility, computer simulation, algorithms, chaos
Hoover, William Graham
2012-01-01
A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful vocabulary and a set of concepts, which allow a fuller explanation of irreversibility than that available to Boltzmann or to Green, Kubo and Onsager. Clear illustration of concepts is emphasized throughout, and reinforced with a glossary of technical terms from the specialized fields which have been combined here to focus on a common theme. The book begins with a discussion, contrasting the idealized reversibility of ba...
Multi-time-step domain coupling method with energy control
DEFF Research Database (Denmark)
Mahjoubi, N.; Krenk, Steen
2010-01-01
the individual time step. It is demonstrated that displacement continuity between the subdomains leads to cancelation of the interface contributions to the energy balance equation, and thus stability and algorithmic damping properties of the original algorithms are retained. The various subdomains can...... by a numerical example using a refined mesh around concentrated forces. Copyright © 2010 John Wiley & Sons, Ltd....
Hybrid time/frequency domain modeling of nonlinear components
DEFF Research Database (Denmark)
Wiechowski, Wojciech Tomasz; Lykkegaard, Jan; Bak, Claus Leth
2007-01-01
This paper presents a novel, three-phase hybrid time/frequency methodology for modelling of nonlinear components. The algorithm has been implemented in the DIgSILENT PowerFactory software using the DIgSILENT Programming Language (DPL), as a part of the work described in [1]. Modified HVDC benchmark...
Finite Difference Time Domain Modeling at USA Instruments, Inc.
Curtis, Richard
2003-10-01
Due to the competitive nature of the commercial MRI industry, it is essential for the financial health of a participating company to innovate new coil designs and bring product to market rapidly in response to ever-changing market conditions. However, the technology of MRI coil design is still early in its stage of development and its principles are yet evolving. As a result, it is not always possible to know the relevant electromagnetic effects of a given design since the interaction of coil elements is complex and often counter-intuitive. Even if the effects are known qualitatively, the quantitative results are difficult to obtain. At USA Instruments, Inc., the acquisition of the XFDTDâ electromagnetic simulation tool from REMCOM, Inc., has been helpful in determining the electromagnetic performance characteristics of existing coil designs in the prototype stage before the coils are released for production. In the ideal case, a coil design would be modeled earlier at the conceptual stage, so that only good designs will make it to the prototyping stage and the electromagnetic characteristics better understood very early in the design process and before the testing stage has begun. This paper is a brief overview of using FDTD modeling for MRI coil design at USA Instruments, Inc., and shows some of the highlights of recent FDTD modeling efforts on Birdcage coils, a staple of the MRI coil design portfolio.
Illusory conjunctions in the time domain and the resulting time-course of the attentional blink.
Botella, Juan; Arend, Isabel; Suero, Manuel
2004-05-01
Illusory conjunctions in the time domain are errors made in binding stimulus features presented In the same spatial position in Rapid Serial Visual Presentation (RSVP) conditions. Botella, Barriopedro, and Suero (2001) devised a model to explain how the distribution of responses originating from stimuli around the target in the series is generated. They proposed two routes consisting of two sequential attempts to make a response. The second attempt (sophisticated guessing) is only employed if the first one (focal attention) fails in producing an integrated perception. This general outline enables specific predictions to be made and tested related to the efficiency of focal attention in generating responses in the first attempt. Participants had to report the single letter in an RSVP stream of letters that was presented in a previously specified color (first target, T1) and then report whether an X (second target, T2) was or was not presented. Performance on T2 showed the typical U-shaped function across the T1-T2 lag that reflects the attentional blink phenomenon. However, as was predicted by Botella, Barriopedro, and Suero's model, the time-course of the interference was shorter for trials with a correct response to T1 than for trials with a T1 error. Furthermore, longer time-courses of interference associated with pre-target and post-target errors to the first target were indistinguishable.
Miguez-Macho, Gonzalo; Stenchikov, Georgiy L.; Robock, Alan
2004-07-01
It is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations. Here we study the physical mechanisms of this sensitivity. We conducted simulations with the Regional Atmospheric Modeling System (RAMS) for June 2000 over North America at 50 km horizontal resolution using a 7500 km × 5400 km grid and NCEP/NCAR reanalysis as boundary conditions. The position of the domain was displaced in several directions, always maintaining the U.S. in the interior, out of the buffer zone along the lateral boundaries. Circulation biases developed a large scale structure, organized by the Rocky Mountains, resulting from a systematic shifting of the synoptic wave trains that crossed the domain. The distortion of the large-scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered. This changed the large-scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the Great Plains in the summer season. As a consequence, precipitation results varied, sometimes greatly, among the experiments with the different grid positions. To eliminate the dependence of results on the position of the domain, we used spectral nudging of waves longer than 2500 km above the boundary layer. Moisture was not nudged at any level. This constrained the synoptic scales to follow reanalysis while allowing the model to develop the small-scale dynamics responsible for the rainfall. Nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved. We suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models.
Mössbauer forward scattering: time-domain spectra
Energy Technology Data Exchange (ETDEWEB)
Sadykov, E. K., E-mail: esadykov@kpfu.ru; Yurichuk, A. A.; Gainov, R. R.; Vagizov, F. G. [Kazan (Volga Region) Federal University (Russian Federation)
2016-12-15
The transmission of the Mössbauer radiation through an absorber being in the acoustic oscillation mode under forward scattering (FS) conditions has been analyzed. The modification of the existing models of the FS spectra (frequency and time) formation to the case of the arbitrary phase correlation of nuclear oscillations in the sample has been proposed. An adequate description of the time delayed experiments with the {sup 57}Fe Mössbauer resonance using the modulation of the single-photon wave packet by acoustic field has been obtained. One has been done in the frame of the Raman scattering of Mössbauer photons. The models extended this way can be used to control the degree of phase correlation of nuclear oscillations (or other processes) induced in the sample by external fields.
Time domain NMR and conductivity study of apple pectin biopolymers
International Nuclear Information System (INIS)
Mattos, Ritamara I.; Souto, Sergio; Tambelli, Caio E.
2015-01-01
This communication presents results of "1H nuclear magnetic resonance of continuous distributions of spin-spin relaxation time (T_2) and A.C. conductivity of apple pectin biopolymers plasticized with glycerol and containing acetic acid. The continuous distributions reveals up to three components of spin-spin relaxation times (T_2). The two short T_2 components were associated with protons of pectin polymer chain and the longer T_2 can be attributed with the protons of the glycerol. The conductivity values increase with glycerol concentration with maximum at 7.9 x 10"-"4 S cm"-"1 for sample with 3.0 g of glycerol at 83 deg C. The behavior of activation energy and T_2 continuous distribution indicate an increase of proton mobility due the structural changes caused by glycerol addition. (author)
Wake force computation in the time domain for long structures
International Nuclear Information System (INIS)
Bane, K.; Weiland, T.
1983-07-01
One is often interested in calculating the wake potentials for short bunches in long structures using TBCI. For ultra-relativistic particles it is sufficient to solve for the fields only over a window containing the bunch and moving along with it. This technique reduces both the memory and the running time required by a factor that equals the ratio of the structure length to the window length. For example, for a bunch with sigma/sub z/ of one picosecond traversing a single SLAC cell this improvement factor is 15. It is thus possible to solve for the wakefields in very long structures: for a given problem, increasing the structure length will not change the memory required while only adding linearly to the CPU time needed
Interferometry in the era of time-domain astronomy
Schaefer, Gail H.; Cassan, Arnaud; Gallenne, Alexandre; Roettenbacher, Rachael M.; Schneider, Jean
2018-04-01
The physical nature of time variable objects is often inferred from photometric light-curves and spectroscopic variations. Long-baseline optical interferometry has the power to resolve the spatial structure of time variable sources directly in order to measure their physical properties and test the physics of the underlying models. Recent interferometric studies of variable objects include measuring the angular expansion and spatial structure during the early stages of novae outbursts, studying the transits and tidal distortions of the components in eclipsing and interacting binaries, measuring the radial pulsations in Cepheid variables, monitoring changes in the circumstellar discs around rapidly rotating massive stars, and imaging starspots. Future applications include measuring the image size and centroid displacements in gravitational microlensing events, and imaging the transits of exoplanets. Ongoing and upcoming photometric surveys will dramatically increase the number of time-variable objects detected each year, providing many potential targets to observe interferometrically. For short-lived transient events, it is critical for interferometric arrays to have the flexibility to respond rapidly to targets of opportunity and optimize the selection of baselines and beam combiners to provide the necessary resolution and sensitivity to resolve the source as its brightness and size change. We discuss the science opportunities made possible by resolving variable sources using long baseline optical interferometry.
Directory of Open Access Journals (Sweden)
Min-Jhong Gu
2014-08-01
Full Text Available This article describes the development of a suite of programs that is capable of simulating the radiation properties of a random rough surface (RRS. The fundamental approach involves the generation, by fast Fourier transform (FFT built with rigorous finite difference time domain (FDTD, as the theoretical basis for the simulation of a bidirectional reflectance distribution function (BRDF of the RRS. The results are compared with the measurements and modeling of existing work to verify the feasibility of customized programming. It was found that the results of this study were a better match to the measurement data than those achieved in other modeling work.
Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles
International Nuclear Information System (INIS)
Jordanovic, J.; Frandsen, C.; Beleggia, M.; Schiøtz, J.
2015-01-01
We simulate the formation of domain walls in two-dimensional assemblies of magnetic nanoparticles. Particle parameters are chosen to match recent electron holography and Lorentz microscopy studies of almost monodisperse cobalt nanoparticles assembled into regular, elongated lattices. As the particles are small enough to consist of a single magnetic domain each, their magnetic interactions can be described by a spin model in which each particle is assigned a macroscopic “superspin.” Thus, the magnetic behaviour of these lattices may be compared to magnetic crystals with nanoparticle superspins taking the role of the atomic spins. The coupling is, however, different. The superspins interact only by dipolar interactions as exchange coupling between individual nanoparticles may be neglected due to interparticle spacing. We observe that it is energetically favorable to introduce domain walls oriented along the long dimension of nanoparticle assemblies rather than along the short dimension. This is unlike what is typically observed in continuous magnetic materials, where the exchange interaction introduces an energetic cost proportional to the area of the domain walls. Structural disorder, which will always be present in realistic assemblies, pins longitudinal domain walls when the external field is reversed, and makes a gradual reversal of the magnetization by migration of longitudinal domain walls possible, in agreement with previous experimental results
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)
Bodin, Jacques
2015-03-01
In this study, new multi-dimensional time-domain random walk (TDRW) algorithms are derived from approximate one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) analytical solutions of the advection-dispersion equation and from exact 1-D, 2-D, and 3-D analytical solutions of the pure-diffusion equation. These algorithms enable the calculation of both the time required for a particle to travel a specified distance in a homogeneous medium and the mass recovery at the observation point, which may be incomplete due to 2-D or 3-D transverse dispersion or diffusion. The method is extended to heterogeneous media, represented as a piecewise collection of homogeneous media. The particle motion is then decomposed along a series of intermediate checkpoints located on the medium interface boundaries. The accuracy of the multi-dimensional TDRW method is verified against (i) exact analytical solutions of solute transport in homogeneous media and (ii) finite-difference simulations in a synthetic 2-D heterogeneous medium of simple geometry. The results demonstrate that the method is ideally suited to purely diffusive transport and to advection-dispersion transport problems dominated by advection. Conversely, the method is not recommended for highly dispersive transport problems because the accuracy of the advection-dispersion TDRW algorithms degrades rapidly for a low Péclet number, consistent with the accuracy limit of the approximate analytical solutions. The proposed approach provides a unified methodology for deriving multi-dimensional time-domain particle equations and may be applicable to other mathematical transport models, provided that appropriate analytical solutions are available.
Manual Choice Reaction Times in the Rate-Domain
Directory of Open Access Journals (Sweden)
Chris eHarris
2014-06-01
Full Text Available Over the last 150 years, human manual reaction times (RTs have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modelled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process. However, latency distribution of saccades are very close to the reciprocal Normal, suggesting that ‘rate’ (reciprocal RT may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination and two instruction sets (urgent vs. accurate. We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks subjects they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be
Time-domain fiber loop ringdown sensor and sensor network
Kaya, Malik
parallel by using a 2x1 micro-electromechanical system optical switch to control sensors individually. For both configurations, contributions of each sensor to two or three coupled signals were simulated theoretically. Results show that numerous FLRD sensors can be connected in different configurations, and a sensor network can be built up for multi-function sensing applications.
Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows
Tseng, K.; Morino, L.
1978-01-01
The Green's Function Method for linearized 3D unsteady potential flow (embedded in the computer code SOUSSA P) is extended to include the time-domain analysis as well as the nonlinear term retained in the transonic small disturbance equation. The differential-delay equations in time, as obtained by applying the Green's Function Method (in a generalized sense) and the finite-element technique to the transonic equation, are solved directly in the time domain. Comparisons are made with both linearized frequency-domain calculations and existing nonlinear results.
Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.
Wang, Xu; Wada, Naoya
2007-06-11
We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.
Time- and Frequency-domain Comparisons of the Wavepiston Wave Energy Converter
DEFF Research Database (Denmark)
Read, Robert; Bingham, Harry
Analysis of wave-energy converters is most frequently undertaken in the time-domain. This formulation allows the direct inclusion of nonlinear time-varying loads such as power take-off (PTO) reactions, mooring forces, and viscous drag. However, integrating the governing equations of motion...... forces arising from both the PTO reactions and the non-negligible viscous drag acting on the plate. Equivalent linear damping coeffcients are used to model these forces in the frequency domain, while they are included explicitly in the time domain. The main idea of this paper is to quantify...
Directory of Open Access Journals (Sweden)
Qian Yang
2017-01-01
Full Text Available The near fields of electric dipole are commonly used in wide-band analysis of complex electromagnetic problems. In this paper, we propose new near field time-domain expressions for electric dipole. The analytical expressions for the frequency-domain of arbitrarily oriented electric dipole are given at first; next we give the time-domain expressions by time-frequency transformation. The proposed expressions are used in hybrid TDIE/DGTD method for analysis of circular antenna with radome. The accuracy of the proposed algorithm is verified by numerical examples.
Time-Domain Astronomy with the Fermi GBM
Hui, C. M.
2017-01-01
The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument sensitive to energies from 8 keV to 40 MeV. Over the past 8 years of operation, the GBM has detected over 240 gamma-ray bursts per year and provided timely GCN notices with localization to few-degree accuracy for follow-up observations. In addition to GRBs, Galactic transients, solar flares, and terrestrial gamma-ray flashes have also been observed. In recent years we have also been searching the continuous GBM data for electromagnetic counterpart to astrophysical neutrinos and gravitational wave events, as these are believed to be associated with gamma-ray bursts. With continuous data downlink every few hours and a temporal resolution of 2 microseconds, GBM is well suited for observing transients and supporting EM follow-up in the era of multi-messenger astronomy.
Time-Domain Analysis of Coupled Carbon Nano tube Interconnects
International Nuclear Information System (INIS)
Fathi, D.
2014-01-01
This paper describes a new method for the analysis of coupling effects including the crosstalk effects between two driven coupled single-walled carbon nano tubes (SWCNTs) and the intertalk effects between two neighboring shells in a multi walled carbon nano tube (MWCNT), based on transmission line circuit modeling. Using rigorous calculations, a new parametric transfer function has been obtained for the analysis of the impact of aggressor line on the victim line, which depends on the various coupling parameters such as the mutual inductance, the coupling capacitance, and the tunneling resistance. The influences of various parameters such as the contact resistance and the switching factor on the time behavior of coupling effects between the two coupled CNTs and an important effect named “crosstalk-induced delay” are studied and analyzed
International Nuclear Information System (INIS)
Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M.; Kirsten, Lars; Cimalla, Peter; Koch, Edmund
2017-01-01
We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Energy Technology Data Exchange (ETDEWEB)
Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M. [Technische Universitaet Dresden, Institute of Applied Physics and Center for Advancing Electronics Dresden (cfaed), Dresden (Germany); Kirsten, Lars; Cimalla, Peter; Koch, Edmund [Technische Universitaet Dresden, Faculty of Medicine Carl Gustav Carus, Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden (Germany)
2017-08-15
We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
Yesylevskyy S. O.
2010-04-01
Full Text Available Aim. Despite a large number of existing domain identification techniques there is no universally accepted method, which identifies the hierarchy of dynamic domains using the data of molecular dynamics (MD simulations. The goal of this work is to develop such technique. Methods. The dynamic domains are identified by eliminating systematic motions from MD trajectories recursively in a model-free manner. Results. The technique called the Hierarchical Domain-Wise Alignment (HDWA to identify hierarchically organized dynamic domains in proteins using the MD trajectories has been developed. Conclusion. A new method of domain identification in proteins is proposed
Using travel times to simulate multi-dimensional bioreactive transport in time-periodic flows.
Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A
2016-04-01
In travel-time models, the spatially explicit description of reactive transport is replaced by associating reactive-species concentrations with the travel time or groundwater age at all locations. These models have been shown adequate for reactive transport in river-bank filtration under steady-state flow conditions. Dynamic hydrological conditions, however, can lead to fluctuations of infiltration velocities, putting the validity of travel-time models into question. In transient flow, the local travel-time distributions change with time. We show that a modified version of travel-time based reactive transport models is valid if only the magnitude of the velocity fluctuates, whereas its spatial orientation remains constant. We simulate nonlinear, one-dimensional, bioreactive transport involving oxygen, nitrate, dissolved organic carbon, aerobic and denitrifying bacteria, considering periodic fluctuations of velocity. These fluctuations make the bioreactive system pulsate: The aerobic zone decreases at times of low velocity and increases at those of high velocity. For the case of diurnal fluctuations, the biomass concentrations cannot follow the hydrological fluctuations and a transition zone containing both aerobic and obligatory denitrifying bacteria is established, whereas a clear separation of the two types of bacteria prevails in the case of seasonal velocity fluctuations. We map the 1-D results to a heterogeneous, two-dimensional domain by means of the mean groundwater age for steady-state flow in both domains. The mapped results are compared to simulation results of spatially explicit, two-dimensional, advective-dispersive-bioreactive transport subject to the same relative fluctuations of velocity as in the one-dimensional model. The agreement between the mapped 1-D and the explicit 2-D results is excellent. We conclude that travel-time models of nonlinear bioreactive transport are adequate in systems of time-periodic flow if the flow direction does not change
Li, Ping; Shi, Yifei; Jiang, Lijun; Bagci, Hakan
2014-01-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer's shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Large Scale Simulation of Hydrogen Dispersion by a Stabilized Balancing Domain Decomposition Method
Directory of Open Access Journals (Sweden)
Qing-He Yao
2014-01-01
Full Text Available The dispersion behaviour of leaking hydrogen in a partially open space is simulated by a balancing domain decomposition method in this work. An analogy of the Boussinesq approximation is employed to describe the connection between the flow field and the concentration field. The linear systems of Navier-Stokes equations and the convection diffusion equation are symmetrized by a pressure stabilized Lagrange-Galerkin method, and thus a balancing domain decomposition method is enabled to solve the interface problem of the domain decomposition system. Numerical results are validated by comparing with the experimental data and available numerical results. The dilution effect of ventilation is investigated, especially at the doors, where flow pattern is complicated and oscillations appear in the past research reported by other researchers. The transient behaviour of hydrogen and the process of accumulation in the partially open space are discussed, and more details are revealed by large scale computation.
Directory of Open Access Journals (Sweden)
Rafael Cisneros-Magaña
2018-06-01
Full Text Available This paper proposes a time-domain methodology based on the unscented Kalman filter to estimate voltage sags and their characteristics, such as magnitude and duration in power systems represented by nonlinear models. Partial and noisy measurements from the electrical network with nonlinear loads, used as data, are assumed. The characteristics of voltage sags can be calculated in a discrete form with the unscented Kalman filter to estimate all the busbar voltages; being possible to determine the rms voltage magnitude and the voltage sag starting and ending time, respectively. Voltage sag state estimation results can be used to obtain the power quality indices for monitored and unmonitored busbars in the power grid and to design adequate mitigating techniques. The proposed methodology is successfully validated against the results obtained with the time-domain system simulation for the power system with nonlinear components, being the normalized root mean square error less than 3%.
Minimum Time Search in Uncertain Dynamic Domains with Complex Sensorial Platforms
Lanillos, Pablo; Besada-Portas, Eva; Lopez-Orozco, Jose Antonio; de la Cruz, Jesus Manuel
2014-01-01
The minimum time search in uncertain domains is a searching task, which appears in real world problems such as natural disasters and sea rescue operations, where a target has to be found, as soon as possible, by a set of sensor-equipped searchers. The automation of this task, where the time to detect the target is critical, can be achieved by new probabilistic techniques that directly minimize the Expected Time (ET) to detect a dynamic target using the observation probability models and actual observations collected by the sensors on board the searchers. The selected technique, described in algorithmic form in this paper for completeness, has only been previously partially tested with an ideal binary detection model, in spite of being designed to deal with complex non-linear/non-differential sensorial models. This paper covers the gap, testing its performance and applicability over different searching tasks with searchers equipped with different complex sensors. The sensorial models under test vary from stepped detection probabilities to continuous/discontinuous differentiable/non-differentiable detection probabilities dependent on distance, orientation, and structured maps. The analysis of the simulated results of several static and dynamic scenarios performed in this paper validates the applicability of the technique with different types of sensor models. PMID:25093345
Numerical study of time domain analogy applied to noise prediction from rotating blades
Fedala, D.; Kouidri, S.; Rey, R.
2009-04-01
Aeroacoustic formulations in time domain are frequently used to model the aerodynamic sound of airfoils, the time data being more accessible. The formulation 1A developed by Farassat, an integral solution of the Ffowcs Williams and Hawkings equation, holds great interest because of its ability to handle surfaces in arbitrary motion. The aim of this work is to study the numerical sensitivity of this model to specified parameters used in the calculation. The numerical algorithms, spatial and time discretizations, and approximations used for far-field acoustic simulation are presented. An approach of quantifying of the numerical errors resulting from implementation of formulation 1A is carried out based on Isom's and Tam's test cases. A helicopter blade airfoil, as defined by Farassat to investigate Isom's case, is used in this work. According to Isom, the acoustic response of a dipole source with a constant aerodynamic load, ρ0c02, is equal to the thickness noise contribution. Discrepancies are observed when the two contributions are computed numerically. In this work, variations of these errors, which depend on the temporal resolution, Mach number, source-observer distance, and interpolation algorithm type, are investigated. The results show that the spline interpolating algorithm gives the minimum error. The analysis is then extended to Tam's test case. Tam's test case has the advantage of providing an analytical solution for the first harmonic of the noise produced by a specific force distribution.
Application of spatial time domain reflectometry measurements in heterogeneous, rocky substrates
Gonzales, C.; Scheuermann, A.; Arnold, S.; Baumgartl, T.
2016-10-01
Measurement of soil moisture across depths using sensors is currently limited to point measurements or remote sensing technologies. Point measurements have limitations on spatial resolution, while the latter, although covering large areas may not represent real-time hydrologic processes, especially near the surface. The objective of the study was to determine the efficacy of elongated soil moisture probes—spatial time domain reflectometry (STDR)—and to describe transient soil moisture dynamics of unconsolidated mine waste rock materials. The probes were calibrated under controlled conditions in the glasshouse. Transient soil moisture content was measured using the gravimetric method and STDR. Volumetric soil moisture content derived from weighing was compared with values generated from a numerical model simulating the drying process. A calibration function was generated and applied to STDR field data sets. The use of elongated probes effectively assists in the real-time determination of the spatial distribution of soil moisture. It also allows hydrologic processes to be uncovered in the unsaturated zone, especially for water balance calculations that are commonly based on point measurements. The elongated soil moisture probes can potentially describe transient substrate processes and delineate heterogeneity in terms of the pore size distribution in a seasonally wet but otherwise arid environment.
Time-domain soil-structure interaction analysis of nuclear facilities
International Nuclear Information System (INIS)
Coleman, Justin L.; Bolisetti, Chandrakanth; Whittaker, Andrew S.
2016-01-01
The Nuclear Regulatory Commission (NRC) regulation 10 CFR Part 50 Appendix S requires consideration of soil-structure interaction (SSI) in nuclear power plant (NPP) analysis and design. Soil-structure interaction analysis for NPPs is routinely carried out using guidance provided in the ASCE Standard 4-98 titled “Seismic Analysis of Safety-Related Nuclear Structures and Commentary”. This Standard, which is currently under revision, provides guidance on linear seismic soil-structure-interaction (SSI) analysis of nuclear facilities using deterministic and probabilistic methods. A new appendix has been added to the forthcoming edition of ASCE Standard 4 to provide guidance for time-domain, nonlinear SSI (NLSSI) analysis. Nonlinear SSI analysis will be needed to simulate material nonlinearity in soil and/or structure, static and dynamic soil pressure effects on deeply embedded structures, local soil failure at the foundation-soil interface, nonlinear coupling of soil and pore fluid, uplift or sliding of the foundation, nonlinear effects of gaps between the surrounding soil and the embedded structure and seismic isolation systems, none of which can be addressed explicitly at present. Appendix B of ASCE Standard 4 provides general guidance for NLSSI analysis but will not provide a methodology for performing the analysis. This paper provides a description of an NLSSI methodology developed for application to nuclear facilities, including NPPs. This methodology is described as series of sequential steps to produce reasonable results using any time-domain numerical code. These steps require some numerical capabilities, such as nonlinear soil constitutive models, which are also described in the paper.
Analytical Time-Domain Solution of Plane Wave Propagation Across a Viscoelastic Rock Joint
Zou, Yang; Li, Jianchun; Laloui, Lyesse; Zhao, Jian
2017-10-01
The effects of viscoelastic filled rock joints on wave propagation are of great significance in rock engineering. The solutions in time domain for plane longitudinal ( P-) and transverse ( S-) waves propagation across a viscoelastic rock joint are derived based on Maxwell and Kelvin models which are, respectively, applied to describe the viscoelastic deformational behaviour of the rock joint and incorporated into the displacement discontinuity model (DDM). The proposed solutions are verified by comparing with the previous studies on harmonic waves, which are simulated by sinusoidal incident P- and S-waves. Comparison between the predicted transmitted waves and the experimental data for P-wave propagation across a joint filled with clay is conducted. The Maxwell is found to be more appropriate to describe the filled joint. The parametric studies show that wave propagation is affected by many factors, such as the stiffness and the viscosity of joints, the incident angle and the duration of incident waves. Furthermore, the dependences of the transmission and reflection coefficients on the specific joint stiffness and viscosity are different for the joints with Maxwell and Kelvin behaviours. The alternation of the reflected and transmitted waveforms is discussed, and the application scope of this study is demonstrated by an illustration of the effects of the joint thickness. The solutions are also extended for multiple parallel joints with the virtual wave source method and the time-domain recursive method. For an incident wave with arbitrary waveform, it is convenient to adopt the present approach to directly calculate wave propagation across a viscoelastic rock joint without additional mathematical methods such as the Fourier and inverse Fourier transforms.
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2017-01-01
In this paper, a discontinuous Galerkin time-domain (DGTD) method is developed to analyze the power-ground planes taking into account the decoupling capacitors. In the presence of decoupling capacitors, the whole physical system can be split
On the mixed discretization of the time domain magnetic field integral equation
Ulku, Huseyin Arda; Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco P.; Bagci, Hakan
2012-01-01
Time domain magnetic field integral equation (MFIE) is discretized using divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming Buffa-Christiansen (BC) functions as spatial basis and testing functions, respectively. The resulting mixed
Valdé s, Felipe; Andriulli, Francesco P.; Bagci, Hakan; Michielssen, Eric
2013-01-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase I
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a high speed automated time domain terahertz computed axial tomography (TD-THz CT) non destructive...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase II
National Aeronautics and Space Administration — In this Phase 2 project, we propose to develop, construct, and deliver to NASA a computed axial tomography time-domain terahertz (CT TD-THz) non destructive...
Zhang, Xiao-bo; Tan, Jun; Song, Peng; Li, Jin-shan; Xia, Dong-ming; Liu, Zhao-lun
2017-01-01
The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge storage consumption in the gradient preconditioning algorithms based on Hessian matrices in time-domain full waveform inversion (FWI), but the accuracy
Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles
DEFF Research Database (Denmark)
Jordanovic, Jelena; Beleggia, Marco; Schiøtz, Jakob
2015-01-01
We simulate the formation of domain walls in two-dimensional assemblies of magnetic nanoparticles. Particle parameters are chosen to match recent electron holography and Lorentz microscopy studies of almost monodisperse cobalt nanoparticles assembled into regular, elongated lattices. As the parti......We simulate the formation of domain walls in two-dimensional assemblies of magnetic nanoparticles. Particle parameters are chosen to match recent electron holography and Lorentz microscopy studies of almost monodisperse cobalt nanoparticles assembled into regular, elongated lattices...... taking the role of the atomic spins. The coupling is, however, different. The superspins interact only by dipolar interactions as exchange coupling between individual nanoparticles may be neglected due to interparticle spacing. We observe that it is energetically favorable to introduce domain walls...... oriented along the long dimension of nanoparticle assemblies rather than along the short dimension. This is unlike what is typically observed in continuous magnetic materials, where the exchange interaction introduces an energetic cost proportional to the area of the domain walls. Structural disorder...
Perturbative evolution of particle orbits around Kerr black holes: time-domain calculation
Energy Technology Data Exchange (ETDEWEB)
Lopez-Aleman, Ramon [Physical Sciences Department, University of Puerto Rico-Rio Piedras, San Juan, PR 00931 (Puerto Rico); Khanna, Gaurav [Natural Science Division, Long Island University, Southampton, NY 11968 (United States); Pullin, Jorge [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States)
2003-07-21
We consider the problem of the gravitational waves produced by a particle of negligible mass orbiting a Kerr black hole. We treat the Teukolsky perturbation equation in the time domain numerically as a 2 + 1 partial differential equation. We model the particle by smearing the singularities in the source term by the use of narrow Gaussian distributions. We have been able to reproduce earlier results for equatorial circular orbits that were computed using the frequency-domain formalism. The time-domain approach is however geared for a more general evolution, for instance of nearly geodesic orbits under the effects of radiation reaction.
Perturbative evolution of particle orbits around Kerr black holes: time-domain calculation
International Nuclear Information System (INIS)
Lopez-Aleman, Ramon; Khanna, Gaurav; Pullin, Jorge
2003-01-01
We consider the problem of the gravitational waves produced by a particle of negligible mass orbiting a Kerr black hole. We treat the Teukolsky perturbation equation in the time domain numerically as a 2 + 1 partial differential equation. We model the particle by smearing the singularities in the source term by the use of narrow Gaussian distributions. We have been able to reproduce earlier results for equatorial circular orbits that were computed using the frequency-domain formalism. The time-domain approach is however geared for a more general evolution, for instance of nearly geodesic orbits under the effects of radiation reaction
Kelbert, Anna; Balch, Christopher C.; Pulkkinen, Antti; Egbert, Gary D.; Love, Jeffrey J.; Rigler, E. Joshua; Fujii, Ikuko
2017-07-01
Geoelectric fields at the Earth's surface caused by magnetic storms constitute a hazard to the operation of electric power grids and related infrastructure. The ability to estimate these geoelectric fields in close to real time and provide local predictions would better equip the industry to mitigate negative impacts on their operations. Here we report progress toward this goal: development of robust algorithms that convolve a magnetic storm time series with a frequency domain impedance for a realistic three-dimensional (3-D) Earth, to estimate the local, storm time geoelectric field. Both frequency domain and time domain approaches are presented and validated against storm time geoelectric field data measured in Japan. The methods are then compared in the context of a real-time application.
Free-Space Squeezing Assists Perfectly Matched Layers in Simulations on a Tight Domain
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Ivinskaya, Aliaksandra; Lavrinenko, Andrei
2010-01-01
outside the object, as in simulations of eigenmodes or scattering at a wavelength comparable to or larger than the object itself. Here, we show how, in addition to applying the perfectly matched layers (PMLs), outer free space can be squeezed to avoid cutting the evanescent field tails by the PMLs...... or computational domain borders. Adding the squeeze-transform layers to the standard PMLs requires no changes to the finite-difference algorithms....
Microprocessor-controlled time domain reflectometer for dynamic shock position measurements
International Nuclear Information System (INIS)
Virchow, C.F.; Conrad, G.E.; Holt, D.M.; Hodson, E.K.
1980-01-01
Time-domain reflectometry is used in a novel way to measure dynamically shock propagation in various media. The primary component in this measurement system is a digital time domain reflectometer, which uses local intelligence, a Motorola 6800 microprocessor, to make the unit adaptable and versatile. The recorder, its operating theory and its method of implementation are described and typical data are reviewed. Applications include nuclear explosion yield estimates and explosive energy flow measurements
Windowing of THz time-domain spectroscopy signals: A study based on lactose
Vázquez-Cabo, José; Chamorro-Posada, Pedro; Fraile-Peláez, Francisco Javier; Rubiños-López, Óscar; López-Santos, José María; Martín-Ramos, Pablo
2016-05-01
Time-domain spectroscopy has established itself as a reference method for determining material parameters in the terahertz spectral range. This procedure requires the processing of the measured time-domain signals in order to estimate the spectral data. In this work, we present a thorough study of the properties of the signal windowing, a step previous to the parameter extraction algorithm, that permits to improve the accuracy of the results. Lactose has been used as sample material in the study.
A New Multiscale Technique for Time-Accurate Geophysics Simulations
Omelchenko, Y. A.; Karimabadi, H.
2006-12-01
Large-scale geophysics systems are frequently described by multiscale reactive flow models (e.g., wildfire and climate models, multiphase flows in porous rocks, etc.). Accurate and robust simulations of such systems by traditional time-stepping techniques face a formidable computational challenge. Explicit time integration suffers from global (CFL and accuracy) timestep restrictions due to inhomogeneous convective and diffusion processes, as well as closely coupled physical and chemical reactions. Application of adaptive mesh refinement (AMR) to such systems may not be always sufficient since its success critically depends on a careful choice of domain refinement strategy. On the other hand, implicit and timestep-splitting integrations may result in a considerable loss of accuracy when fast transients in the solution become important. To address this issue, we developed an alternative explicit approach to time-accurate integration of such systems: Discrete-Event Simulation (DES). DES enables asynchronous computation by automatically adjusting the CPU resources in accordance with local timescales. This is done by encapsulating flux- conservative updates of numerical variables in the form of events, whose execution and synchronization is explicitly controlled by imposing accuracy and causality constraints. As a result, at each time step DES self- adaptively updates only a fraction of the global system state, which eliminates unnecessary computation of inactive elements. DES can be naturally combined with various mesh generation techniques. The event-driven paradigm results in robust and fast simulation codes, which can be efficiently parallelized via a new preemptive event processing (PEP) technique. We discuss applications of this novel technology to time-dependent diffusion-advection-reaction and CFD models representative of various geophysics applications.
Improved real-time dynamics from imaginary frequency lattice simulations
Directory of Open Access Journals (Sweden)
Pawlowski Jan M.
2018-01-01
Full Text Available The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between ω0 and ω1 = 2πT, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.
Improved real-time dynamics from imaginary frequency lattice simulations
Pawlowski, Jan M.; Rothkopf, Alexander
2018-03-01
The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between ω0 and ω1 = 2πT, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.
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....
The development of efficient numerical time-domain modeling methods for geophysical wave propagation
Zhu, Lieyuan
This Ph.D. dissertation focuses on the numerical simulation of geophysical wave propagation in the time domain including elastic waves in solid media, the acoustic waves in fluid media, and the electromagnetic waves in dielectric media. This thesis shows that a linear system model can describe accurately the physical processes of those geophysical waves' propagation and can be used as a sound basis for modeling geophysical wave propagation phenomena. The generalized stability condition for numerical modeling of wave propagation is therefore discussed in the context of linear system theory. The efficiency of a series of different numerical algorithms in the time-domain for modeling geophysical wave propagation are discussed and compared. These algorithms include the finite-difference time-domain method, pseudospectral time domain method, alternating directional implicit (ADI) finite-difference time domain method. The advantages and disadvantages of these numerical methods are discussed and the specific stability condition for each modeling scheme is carefully derived in the context of the linear system theory. Based on the review and discussion of these existing approaches, the split step, ADI pseudospectral time domain (SS-ADI-PSTD) method is developed and tested for several cases. Moreover, the state-of-the-art stretched-coordinate perfect matched layer (SCPML) has also been implemented in SS-ADI-PSTD algorithm as the absorbing boundary condition for truncating the computational domain and absorbing the artificial reflection from the domain boundaries. After algorithmic development, a few case studies serve as the real-world examples to verify the capacities of the numerical algorithms and understand the capabilities and limitations of geophysical methods for detection of subsurface contamination. The first case is a study using ground penetrating radar (GPR) amplitude variation with offset (AVO) for subsurface non-aqueous-liquid (NAPL) contamination. The
Comparison of Cole-Cole and Constant Phase Angle modeling in time-domain induced polarization
DEFF Research Database (Denmark)
Lajaunie, Myriam; Maurya, Pradip Kumar; Fiandaca, Gianluca
The Cole-Cole model and the constant phase angle (CPA) model are two prevailing phenomenological descriptions of the induced polarization (IP), used for both frequency domain (FD) and time domain (TD) modeling. The former one is a 4-parameter description, while the latest one involves only two......, forward modeling of quadrupolar sequences on 1D and 2D heterogeneous CPA models shows that the CPA decays differ among each other only by a multiplication factor. Consequently, the inspection of field data in log-log plots gives insight on the modeling needed for fitting them: the CPA inversion cannot...... is reflected in TDIP data, and therefore, at identifying (1) if and when it is possible to distinguish, in time domain, between a Cole-Cole description and a CPA one, and (2) if features of time domain data exist in order to know, from a simple data inspection, which model will be the most adapted to the data...
Mixed time slicing in path integral simulations
International Nuclear Information System (INIS)
Steele, Ryan P.; Zwickl, Jill; Shushkov, Philip; Tully, John C.
2011-01-01
A simple and efficient scheme is presented for using different time slices for different degrees of freedom in path integral calculations. This method bridges the gap between full quantization and the standard mixed quantum-classical (MQC) scheme and, therefore, still provides quantum mechanical effects in the less-quantized variables. Underlying the algorithm is the notion that time slices (beads) may be 'collapsed' in a manner that preserves quantization in the less quantum mechanical degrees of freedom. The method is shown to be analogous to multiple-time step integration techniques in classical molecular dynamics. The algorithm and its associated error are demonstrated on model systems containing coupled high- and low-frequency modes; results indicate that convergence of quantum mechanical observables can be achieved with disparate bead numbers in the different modes. Cost estimates indicate that this procedure, much like the MQC method, is most efficient for only a relatively few quantum mechanical degrees of freedom, such as proton transfer. In this regime, however, the cost of a fully quantum mechanical simulation is determined by the quantization of the least quantum mechanical degrees of freedom.
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.
Ultrasound-based measurement of liquid-layer thickness: A novel time-domain approach
Praher, Bernhard; Steinbichler, Georg
2017-01-01
Measuring the thickness of a thin liquid layer between two solid materials is important when the adequate separation of metallic parts by a lubricant film (e.g., in bearings or mechanical seals) is to be assessed. The challenge in using ultrasound-based systems for such measurements is that the signal from the liquid layer is a superposition of multiple reflections. We have developed an algorithm for reconstructing this superimposed signal in the time domain. By comparing simulated and measured signals, the time-of-flight of the ultrasonic pulse in a layer can be estimated. With the longitudinal sound velocity known, the layer thickness can then be calculated. In laboratory measurements, we validate successfully (maximum relative error 4.9%) our algorithm for layer thicknesses ranging from 30 μm to 200 μm. Furthermore, we tested our method in the high-temperature environment of polymer processing by measuring the clearance between screw and barrel in the plasticisation unit of an injection moulding machine. The results of such measurements can indicate (i) the wear status of the tribo-mechanical screw-barrel system and (ii) unsuitable process conditions.
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.
Innovation of floating time domain electromagnetic method in the case of environmental geophysics
Nurjanah, Siti; Widodo
2017-07-01
Geophysics has some methods that can be used to reveal the subsurface structure of the earth. The physical features obtained from the acquisition then analyzed and interpreted, so that it can be a great lead to interpret the physical contents, determine its position and its distribution. Geophysical methods also can be used to help the environment contamination survey which is referred to environmental geophysics. There are many sources of pollution that can harm the nature, for example, the source in the form of solid waste, liquid waste containing heavy metals, or radioactive, and etc. As time passes, these sources might settle in any sedimentary area and become sediments. Time Domain Electromagnetic (TDEM) is a trustworthy method to detect the presence of conductive anomaly due to sediment accumulation. Innovation of floating TDEM created to maximize the potential of the method, so that it can be used in aquatic environments. The configuration of TDEM modified using pipes and tires during the process of measurements. We conducted numerical simulation using Marquardt and Occam Algorithms towards synthetic model to ensure the capability of the proposed design. The development of this innovation is expected to be very useful to repair the natural conditions, especially in the water.
Lagrangian Particle Tracking Simulation for Warm-Rain Processes in Quasi-One-Dimensional Domain
Kunishima, Y.; Onishi, R.
2017-12-01
Conventional cloud simulations are based on the Euler method and compute each microphysics process in a stochastic way assuming infinite numbers of particles within each numerical grid. They therefore cannot provide the Lagrangian statistics of individual particles in cloud microphysics (i.e., aerosol particles, cloud particles, and rain drops) nor discuss the statistical fluctuations due to finite number of particles. We here simulate the entire precipitation process of warm-rain, with tracking individual particles. We use the Lagrangian Cloud Simulator (LCS), which is based on the Euler-Lagrangian framework. In that framework, flow motion and scalar transportation are computed with the Euler method, and particle motion with the Lagrangian one. The LCS tracks particle motions and collision events individually with considering the hydrodynamic interaction between approaching particles with a superposition method, that is, it can directly represent the collisional growth of cloud particles. It is essential for trustworthy collision detection to take account of the hydrodynamic interaction. In this study, we newly developed a stochastic model based on the Twomey cloud condensation nuclei (CCN) activation for the Lagrangian tracking simulation and integrated it into the LCS. Coupling with the Euler computation for water vapour and temperature fields, the initiation and condensational growth of water droplets were computed in the Lagrangian way. We applied the integrated LCS for a kinematic simulation of warm-rain processes in a vertically-elongated domain of, at largest, 0.03×0.03×3000 (m3) with horizontal periodicity. Aerosol particles with a realistic number density, 5×107 (m3), were evenly distributed over the domain at the initial state. Prescribed updraft at the early stage initiated development of a precipitating cloud. We have confirmed that the obtained bulk statistics fairly agree with those from a conventional spectral-bin scheme for a vertical column
International Nuclear Information System (INIS)
Zhang Jian-Zhong; Cui Bao-Tong; Zhuang Bo
2017-01-01
A guidance policy for controller performance enhancement utilizing mobile sensor–actuator networks (MSANs) is proposed for a class of distributed parameter systems (DPSs), which are governed by diffusion partial differential equations (PDEs) with time-dependent spatial domains. Several sufficient conditions for controller performance enhancement are presented. First, the infinite dimensional operator theory is used to derive an abstract evolution equation of the systems under some rational assumptions on the operators, and a static output feedback controller is designed to control the spatial process. Then, based on Lyapunov stability arguments, guidance policies for collocated and non-collocated MSANs are provided to enhance the performance of the proposed controller, which show that the time-dependent characteristic of the spatial domains can significantly affect the design of the mobile scheme. Finally, a simulation example illustrates the effectiveness of the proposed policy. (paper)
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.
Airoldi, Edoardo M.; Bai, Xue; Malin, Bradley A.
2011-01-01
We live in an increasingly mobile world, which leads to the duplication of information across domains. Though organizations attempt to obscure the identities of their constituents when sharing information for worthwhile purposes, such as basic research, the uncoordinated nature of such environment can lead to privacy vulnerabilities. For instance, disparate healthcare providers can collect information on the same patient. Federal policy requires that such providers share “de-identified” sensitive data, such as biomedical (e.g., clinical and genomic) records. But at the same time, such providers can share identified information, devoid of sensitive biomedical data, for administrative functions. On a provider-by-provider basis, the biomedical and identified records appear unrelated, however, links can be established when multiple providers’ databases are studied jointly. The problem, known as trail disclosure, is a generalized phenomenon and occurs because an individual’s location access pattern can be matched across the shared databases. Due to technical and legal constraints, it is often difficult to coordinate between providers and thus it is critical to assess the disclosure risk in distributed environments, so that we can develop techniques to mitigate such risks. Research on privacy protection has so far focused on developing technologies to suppress or encrypt identifiers associated with sensitive information. There is growing body of work on the formal assessment of the disclosure risk of database entries in publicly shared databases, but a less attention has been paid to the distributed setting. In this research, we review the trail disclosure problem in several domains with known vulnerabilities and show that disclosure risk is influenced by the distribution of how people visit service providers. Based on empirical evidence, we propose an entropy metric for assessing such risk in shared databases prior to their release. This metric assesses risk by
A multi-domain spectral method for time-fractional differential equations
Chen, Feng; Xu, Qinwu; Hesthaven, Jan S.
2015-07-01
This paper proposes an approach for high-order time integration within a multi-domain setting for time-fractional differential equations. Since the kernel is singular or nearly singular, two main difficulties arise after the domain decomposition: how to properly account for the history/memory part and how to perform the integration accurately. To address these issues, we propose a novel hybrid approach for the numerical integration based on the combination of three-term-recurrence relations of Jacobi polynomials and high-order Gauss quadrature. The different approximations used in the hybrid approach are justified theoretically and through numerical examples. Based on this, we propose a new multi-domain spectral method for high-order accurate time integrations and study its stability properties by identifying the method as a generalized linear method. Numerical experiments confirm hp-convergence for both time-fractional differential equations and time-fractional partial differential equations.
Analysis of noise in energy-dispersive spectrometers using time-domain methods
Goulding, F S
2002-01-01
This paper presents an integrated time domain approach to the optimization of the signal-to-noise ratio in all spectrometer systems that contain a detector that converts incoming quanta of radiation into electrical pulse signals that are amplified and shaped by an electronic pulse shaper. It allows analysis of normal passive pulse shapers as well as time-variant systems where switching of shaping elements occurs in synchronism with the signal. It also deals comfortably with microcalorimeters (sometimes referred to as bolometers), where noise-determining elements, such as the temperature-sensing element's resistance and temperature, change with time in the presence of a signal. As part of the purely time-domain approach, a new method of calculating the Johnson noise in resistors using only the statistics of electron motion is presented. The result is a time-domain analog of the Nyquist formula.
Impact of non-white noises in pulse amplitude measurements: a time-domain approach
International Nuclear Information System (INIS)
Pullia, A.
1998-01-01
The contribution of the 1/f-noise to the spectral line broadening in pulse amplitude measurements is derived with a time-domain analysis. The known time-domain relationships which provide the contributions of the series and parallel white noises are generalised for the case of 1/f and other typical non-white noises, by using the fractional derivative of either the system impulse response (time-invariant linear filters) or its weight function folded (time-variant linear filters). It is shown that a time-domain approach is also effective to determine the contribution of Lorentzian noises. A simple rule suitable to derive numerically the fractional derivative is given, which permits to calculate the effect of non-white noises even when the filter impulse response is not known analytically but only in sampled form. (orig.)
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
Frequency-domain interferometer simulation with higher-order spatial modes
International Nuclear Information System (INIS)
Freise, A; Heinzel, G; Lueck, H; Schilling, R; Willke, B; Danzmann, K
2004-01-01
FINESSE is a software simulation allowing one to compute the optical properties of laser interferometers used by interferometric gravitational-wave detectors today. This fast and versatile tool has already proven to be useful in the design and commissioning of gravitational-wave detectors. The basic algorithm of FINESSE numerically computes the light amplitudes inside an interferometer using Hermite-Gauss modes in the frequency domain. In addition, FINESSE provides a number of commands for easily generating and plotting the most common signals including power enhancement, error and control signals, transfer functions and shot-noise-limited sensitivities. Among the various simulation tools available to the gravitational wave community today, FINESSE provides an advanced and versatile optical simulation based on a general analysis of user-defined optical setups and is quick to install and easy to use
International Nuclear Information System (INIS)
Schleier, W.; Besold, G.; Heinz, K.
1992-01-01
The authors study the applicability of parallelized/vectorized Monte Carlo (MC) algorithms to the simulation of domain growth in two-dimensional lattice gas models undergoing an ordering process after a rapid quench below an order-disorder transition temperature. As examples they consider models with 2 x 1 and c(2 x 2) equilibrium superstructures on the square and rectangular lattices, respectively. They also study the case of phase separation ('1 x 1' islands) on the square lattice. A generalized parallel checkerboard algorithm for Kawasaki dynamics is shown to give rise to artificial spatial correlations in all three models. However, only if superstructure domains evolve do these correlations modify the kinetics by influencing the nucleation process and result in a reduced growth exponent compared to the value from the conventional heat bath algorithm with random single-site updates. In order to overcome these artificial modifications, two MC algorithms with a reduced degree of parallelism ('hybrid' and 'mask' algorithms, respectively) are presented and applied. As the results indicate, these algorithms are suitable for the simulation of superstructure domain growth on parallel/vector computers. 60 refs., 10 figs., 1 tab
A domain-decomposed multi-model plasma simulation of collisionless magnetic reconnection
Datta, I. A. M.; Shumlak, U.; Ho, A.; Miller, S. T.
2017-10-01
Collisionless magnetic reconnection is a process relevant to many areas of plasma physics in which energy stored in magnetic fields within highly conductive plasmas is rapidly converted into kinetic and thermal energy. Both in natural phenomena such as solar flares and terrestrial aurora as well as in magnetic confinement fusion experiments, the reconnection process is observed on timescales much shorter than those predicted by a resistive MHD model. As a result, this topic is an active area of research in which plasma models with varying fidelity have been tested in order to understand the proper physics explaining the reconnection process. In this research, a hybrid multi-model simulation employing the Hall-MHD and two-fluid plasma models on a decomposed domain is used to study this problem. The simulation is set up using the WARPXM code developed at the University of Washington, which uses a discontinuous Galerkin Runge-Kutta finite element algorithm and implements boundary conditions between models in the domain to couple their variable sets. The goal of the current work is to determine the parameter regimes most appropriate for each model to maintain sufficient physical fidelity over the whole domain while minimizing computational expense. This work is supported by a Grant from US AFOSR.
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
Jang, Hae-Won; Ih, Jeong-Guon
2012-04-01
The time domain boundary element method (BEM) is associated with numerical instability that typically stems from the time marching scheme. In this work, a formulation of time domain BEM is derived to deal with all types of boundary conditions adopting a multi-input, multi-output, infinite impulse response structure. The fitted frequency domain impedance data are converted into a time domain expression as a form of an infinite impulse response filter, which can also invoke a modeling error. In the calculation, the response at each time step is projected onto the wave vector space of natural radiation modes, which can be obtained from the eigensolutions of the single iterative matrix. To stabilize the computation, unstable oscillatory modes are nullified, and the same decay rate is used for two nonoscillatory modes. As a test example, a transient sound field within a partially lined, parallelepiped box is used, within which a point source is excited by an octave band impulse. In comparison with the results of the inverse Fourier transform of a frequency domain BEM, the average of relative difference norm in the stabilized time response is found to be 4.4%.
Optimal identification of semi-rigid domains in macromolecules from molecular dynamics simulation.
Directory of Open Access Journals (Sweden)
Stefan Bernhard
Full Text Available Biological function relies on the fact that biomolecules can switch between different conformations and aggregation states. Such transitions involve a rearrangement of parts of the biomolecules involved that act as dynamic domains. The reliable identification of such domains is thus a key problem in biophysics. In this work we present a method to identify semi-rigid domains based on dynamical data that can be obtained from molecular dynamics simulations or experiments. To this end the average inter-atomic distance-deviations are computed. The resulting matrix is then clustered by a constrained quadratic optimization problem. The reliability and performance of the method are demonstrated for two artificial peptides. Furthermore we correlate the mechanical properties with biological malfunction in three variants of amyloidogenic transthyretin protein, where the method reveals that a pathological mutation destabilizes the natural dimer structure of the protein. Finally the method is used to identify functional domains of the GroEL-GroES chaperone, thus illustrating the efficiency of the method for large biomolecular machines.
Marks, Gary N.
2016-01-01
Multi-domain and longitudinal studies of student achievement routinely find moderate to strong correlations across achievement domains and even stronger within-domain correlations over time. The purpose of this study is to examine the sources of these patterns analysing student achievement in 5 domains across Years 3, 5 and 7. The analysis is of…
Thermal denaturation of protein studied by terahertz time-domain spectroscopy
Fu, Xiuhua; Li, Xiangjun; Liu, Jianjun; Du, Yong; Hong, Zhi
2012-12-01
In this study, the absorption spectra of native or thermal protein were measured in 0.2-1.4THz using terahertz time-domain spectroscopy (THz-TDS) system at room temperature, their absorption spectra and the refractive spectra were obtained. Experimental results indicate that protein both has strong absorption but their characteristics were not distinct in the THz region, and the absorption decreased during thermal denatured state. In order to prove protein had been denatured, we used Differential scanning calorimeter (DSC) measured their denatured temperature, from their DSC heating traces, collagen Td=101℃, Bovine serum albumin Td=97℃. While we also combined the Fourier transform infrared spectrometer (FTIR) to investigate their secondary and tertiary structure before and after denatuation, but the results did not have the distinct changes. We turned the absorption spectra and the refractive spectra to the dielectric spectra, and used the one-stage Debye model simulated the terahertz dielectric spectra of protein before and after denaturation. This research proved that the terahertz spectrum technology is feasible in testing protein that were affected by temperature or other factors which can provide theoretical foundation in the further study about the THz spectrum of protein and peptide temperature stability.
Directory of Open Access Journals (Sweden)
Rasha Al-Hujazy
2018-03-01
Full Text Available Microfluidic platforms have received much attention in recent years. In particular, there is interest in combining spectroscopy with microfluidic platforms. This work investigates the integration of microfluidic platforms and terahertz time-domain spectroscopy (THz-TDS systems. A semiclassical computational model is used to simulate the emission of THz radiation from a GaAs photoconductive THz emitter. This model incorporates white noise with increasing noise amplitude (corresponding to decreasing dynamic range values. White noise is selected over other noise due to its contributions in THz-TDS systems. The results from this semiclassical computational model, in combination with defined sample thicknesses, can provide the maximum measurable absorption coefficient for a microfluidic-based THz-TDS system. The maximum measurable frequencies for such systems can be extracted through the relationship between the maximum measurable absorption coefficient and the absorption coefficient for representative biofluids. The sample thickness of the microfluidic platform and the dynamic range of the THz-TDS system play a role in defining the maximum measurable frequency for microfluidic-based THz-TDS systems. The results of this work serve as a design tool for the development of such systems.
A Proposal for the Time Domain Modeling of Split Air Conditioners for Consumer Reimbursement Studies
Rezende, Paulo Henrique Oliveira; Almeida Junior, Afonso Bernardino; Gondim, Isaque Nogueira; Oliveira, José Carlos
2015-04-01
This paper deals with computer application procedures for the evaluation of the causal consistency between anomalous phenomena manifested in electrical networks, along with the physical damage associated with electrical equipment and possible reimbursement requests. The focus is on the development of an air conditioner appliance model of the type known as split founded upon a representation, in the time domain, in accordance with the Alternative Transients Program (ATP) simulator requirements. This approach permits investigations concerning the performance of the product when submitted to ideal and non-ideal supply conditions. Once the equipment model is implemented in the program, a set of investigative studies are carried out to show the device performance under specific energy quality disturbance conditions. In addition, there are still the results for the validation of the process established through the correlation between computational performance of the air conditioner with corresponding studies carried out experimentally, which are presented herein. Moreover, once the effectiveness of the developed model is verified, it is implemented into the Requests for Reimbursement Software. Investigations related to the correlation between disturbances and the levels of thermal and dielectric tolerance are then performed aiming at illustrating the use of the research results for the reimbursement analyzes purposes.
Solving the Schroedinger equation using the finite difference time domain method
International Nuclear Information System (INIS)
Sudiarta, I Wayan; Geldart, D J Wallace
2007-01-01
In this paper, we solve the Schroedinger equation using the finite difference time domain (FDTD) method to determine energies and eigenfunctions. In order to apply the FDTD method, the Schroedinger equation is first transformed into a diffusion equation by the imaginary time transformation. The resulting time-domain diffusion equation is then solved numerically by the FDTD method. The theory and an algorithm are provided for the procedure. Numerical results are given for illustrative examples in one, two and three dimensions. It is shown that the FDTD method accurately determines eigenfunctions and energies of these systems
A Time Domain Update Method for Reservoir History Matching of Electromagnetic Data
Katterbauer, Klemens
2014-03-25
The oil & gas industry has been the backbone of the world\\'s economy in the last century and will continue to be in the decades to come. With increasing demand and conventional reservoirs depleting, new oil industry projects have become more complex and expensive, operating in areas that were previously considered impossible and uneconomical. Therefore, good reservoir management is key for the economical success of complex projects requiring the incorporation of reliable uncertainty estimates for reliable production forecasts and optimizing reservoir exploitation. Reservoir history matching has played here a key role incorporating production, seismic, electromagnetic and logging data for forecasting the development of reservoirs and its depletion. With the advances in the last decade, electromagnetic techniques, such as crosswell electromagnetic tomography, have enabled engineers to more precisely map the reservoirs and understand their evolution. Incorporating the large amount of data efficiently and reducing uncertainty in the forecasts has been one of the key challenges for reservoir management. Computing the conductivity distribution for the field for adjusting parameters in the forecasting process via solving the inverse problem has been a challenge, due to the strong ill-posedness of the inversion problem and the extensive manual calibration required, making it impossible to be included into an efficient reservoir history matching forecasting algorithm. In the presented research, we have developed a novel Finite Difference Time Domain (FDTD) based method for incorporating electromagnetic data directly into the reservoir simulator. Based on an extended Archie relationship, EM simulations are performed for both forecasted and Porosity-Saturation retrieved conductivity parameters being incorporated directly into an update step for the reservoir parameters. This novel direct update method has significant advantages such as that it overcomes the expensive and ill
Comparison of SAR calculation algorithms for the finite-difference time-domain method
International Nuclear Information System (INIS)
Laakso, Ilkka; Uusitupa, Tero; Ilvonen, Sami
2010-01-01
Finite-difference time-domain (FDTD) simulations of specific-absorption rate (SAR) have several uncertainty factors. For example, significantly varying SAR values may result from the use of different algorithms for determining the SAR from the FDTD electric field. The objective of this paper is to rigorously study the divergence of SAR values due to different SAR calculation algorithms and to examine if some SAR calculation algorithm should be preferred over others. For this purpose, numerical FDTD results are compared to analytical solutions in a one-dimensional layered model and a three-dimensional spherical object. Additionally, the implications of SAR calculation algorithms for dosimetry of anatomically realistic whole-body models are studied. The results show that the trapezium algorithm-based on the trapezium integration rule-is always conservative compared to the analytic solution, making it a good choice for worst-case exposure assessment. In contrast, the mid-ordinate algorithm-named after the mid-ordinate integration rule-usually underestimates the analytic SAR. The linear algorithm-which is approximately a weighted average of the two-seems to be the most accurate choice overall, typically giving the best fit with the shape of the analytic SAR distribution. For anatomically realistic models, the whole-body SAR difference between different algorithms is relatively independent of the used body model, incident direction and polarization of the plane wave. The main factors affecting the difference are cell size and frequency. The choice of the SAR calculation algorithm is an important simulation parameter in high-frequency FDTD SAR calculations, and it should be explained to allow intercomparison of the results between different studies. (note)
Hird, Megan A; Vesely, Kristin A; Fischer, Corinne E; Graham, Simon J; Naglie, Gary; Schweizer, Tom A
2017-01-01
The areas of driving impairment characteristic of mild cognitive impairment (MCI) remain unclear. This study compared the simulated driving performance of 24 individuals with MCI, including amnestic single-domain (sd-MCI, n = 11) and amnestic multiple-domain MCI (md-MCI, n = 13), and 20 age-matched controls. Individuals with MCI committed over twice as many driving errors (20.0 versus 9.9), demonstrated difficulty with lane maintenance, and committed more errors during left turns with traffic compared to healthy controls. Specifically, individuals with md-MCI demonstrated greater driving difficulty compared to healthy controls, relative to those with sd-MCI. Differentiating between different subtypes of MCI may be important when evaluating driving safety.
Cai, Hongzhu; Hu, Xiangyun; Xiong, Bin; Zhdanov, Michael S.
2017-12-01
The induced polarization (IP) method has been widely used in geophysical exploration to identify the chargeable targets such as mineral deposits. The inversion of the IP data requires modeling the IP response of 3D dispersive conductive structures. We have developed an edge-based finite-element time-domain (FETD) modeling method to simulate the electromagnetic (EM) fields in 3D dispersive medium. We solve the vector Helmholtz equation for total electric field using the edge-based finite-element method with an unstructured tetrahedral mesh. We adopt the backward propagation Euler method, which is unconditionally stable, with semi-adaptive time stepping for the time domain discretization. We use the direct solver based on a sparse LU decomposition to solve the system of equations. We consider the Cole-Cole model in order to take into account the frequency-dependent conductivity dispersion. The Cole-Cole conductivity model in frequency domain is expanded using a truncated Padé series with adaptive selection of the center frequency of the series for early and late time. This approach can significantly increase the accuracy of FETD modeling.
Bécares, Laia; Zhang, Nan
2018-01-01
Abstract Experiencing discrimination is associated with poor mental health, but how cumulative experiences of perceived interpersonal discrimination across attributes, domains, and time are associated with mental disorders is still unknown. Using data from the Study of Women’s Health Across the Nation (1996–2008), we applied latent class analysis and generalized linear models to estimate the association between cumulative exposure to perceived interpersonal discrimination and older women’s mental health. We found 4 classes of perceived interpersonal discrimination, ranging from cumulative exposure to discrimination over attributes, domains, and time to none or minimal reports of discrimination. Women who experienced cumulative perceived interpersonal discrimination over time and across attributes and domains had the highest risk of depression (Center for Epidemiologic Studies Depression Scale score ≥16) compared with women in all other classes. This was true for all women regardless of race/ethnicity, although the type and severity of perceived discrimination differed across racial/ethnic groups. Cumulative exposure to perceived interpersonal discrimination across attributes, domains, and time has an incremental negative long-term association with mental health. Studies that examine exposure to perceived discrimination due to a single attribute in 1 domain or at 1 point in time underestimate the magnitude and complexity of discrimination and its association with health. PMID:29036550
An investigation into multi-domain simulation for a pantographcatenary system
Directory of Open Access Journals (Sweden)
Zdziebko Paweł
2017-01-01
Full Text Available There is a need for modelling various phenomena present in a pantograph-catenary structure, (e.g. wave propagation and its reflections, friction, aerodynamic and electromagnetic forces, which allows for a more reliable study on the dynamic behaviours of a railway pantograph, particularly in the case of high-speed trains. Hence, the creation a complex pantograph-catenary multi-domain model should help to effectively meet the above-mentioned requirements. The work presents a co-simulation approach to investigate the pantograph-catenary dynamic interaction. The elaborated co-simulation algorithm assumes data exchange between multibody models of a pantograph and finite element model of a catenary. The presented approach explores multi-domain phenomena that have an influence on the pantograph-catenary interaction. The nonlinear finite element catenary model takes into account the slackening of droppers, relatively large displacements and contact with the pantograph’s slider, while the multibody model of the pantograph considers friction forces and suspension springs. Additionally, aerodynamic forces caused by wind acting on the pantograph were computed using the fluid structure interaction method and implemented in the dynamic simulation. The influence on the pantograph-catenary interaction caused by electromagnetic force acting on the pantograph was investigated, along with the influence of the locomotive’s vertical vibrations and tilt.
Böhringer, Klaus; Hess, Ortwin
The spatio-temporal dynamics of novel semiconductor lasers is discussed on the basis of a space- and momentum-dependent full time-domain approach. To this means the space-, time-, and momentum-dependent Full-Time Domain Maxwell Semiconductor Bloch equations, derived and discussed in our preceding paper I [K. Böhringer, O. Hess, A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. I. Theoretical formulation], are solved by direct numerical integration. Focussing on the device physics of novel semiconductor lasers that profit, in particular, from recent advances in nanoscience and nanotechnology, we discuss the examples of photonic band edge surface emitting lasers (PBE-SEL) and semiconductor disc lasers (SDLs). It is demonstrated that photonic crystal effects can be obtained for finite crystal structures, and leading to a significant improvement in laser performance such as reduced lasing thresholds. In SDLs, a modern device concept designed to increase the power output of surface-emitters in combination with near-diffraction-limited beam quality, we explore the complex interplay between the intracavity optical fields and the quantum well gain material in SDL structures. Our simulations reveal the dynamical balance between carrier generation due to pumping into high energy states, momentum relaxation of carriers, and stimulated recombination from states near the band edge. Our full time-domain approach is shown to also be an excellent framework for the modelling of the interaction of high-intensity femtosecond and picosecond pulses with semiconductor nanostructures. It is demonstrated that group velocity dispersion, dynamical gain saturation and fast self-phase modulation (SPM) are the main causes for the induced changes and asymmetries in the amplified pulse shape and spectrum of an ultrashort high-intensity pulse. We attest that the time constants of the intraband scattering processes are critical to gain recovery. Moreover, we present
Efficient scattering of electrons below few keV by Time Domain Structures around injection fronts
Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.
2016-12-01
Van Allen Probes observations show an abundance of non-linear large-amplitude electrostatic spikes around injection fronts in the outer radiation belt. These spikes referred to as Time Domain Structures (TDS) include electron holes, double layers and more complicated solitary waves. The electron scattering driven by TDS may not be evaluated via the standard quasi-linear theory, since TDS are in principle non-linear plasma modes. In this paper we analyze the scattering of electrons by three-dimensional TDS (with non-negligible perpendicular electric field) around injection fronts. We derive the analytical formulas describing the local scattering by single TDS and show that the most efficiently scattered electrons are those in the first cyclotron resonance (electrons crossing TDS on a time scale comparable with their gyroperiod). The analytical formulas are verified via the test-particle simulation. We compute the bounce-averaged diffusion coefficients and demonstrate their dependence on the TDS spatial distribution, individual TDS parameters and L shell. We show that TDS are able to provide the pitch-angle scattering of <5 keV electrons at rate 10-2-10-4 s-1 and, thus, can be responsible for driving loss of electrons out of injections fronts on a time scale from few minutes to few hours. TDS can be, thus, responsible for driving diffuse aurora precipitations conjugated to injection fronts. We show that the pitch-angle scattering rates driven by TDS are comparable with those due to chorus waves and exceed those due to electron cyclotron harmonics. For injections fronts with no significant wave activity in the frequency range corresponding to chorus waves, TDS can be even dominant mechanism for losses of below few keV electrons.
OpenPSTD : The open source implementation of the pseudospectral time-domain method
Krijnen, T.; Hornikx, M.C.J.; Borkowski, B.
2014-01-01
An open source implementation of the pseudospectral time-domain method for the propagation of sound is presented, which is geared towards applications in the built environment. Being a wavebased method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory
Reflection terahertz time-domain imaging for analysis of an 18th century neoclassical easel painting
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Filtenborg, Troels; Fukunaga, Kaori
2015-01-01
Terahertz time-domain imaging (THz-TDI) has been applied for imaging a hidden portrait and other subsurfacecomposition layers of an 18th century (18C) easel painting by Nicolai Abildgaard, the most important 18CDanish neoclassical painter of historical and mythological subjects. For the first time...
Time-domain incomplete Gauss-Newton full-waveform inversion of Gulf of Mexico data
AlTheyab, Abdullah; Wang, Xin; Schuster, Gerard T.
2013-01-01
We apply the incomplete Gauss-Newton full-waveform inversion (TDIGN-FWI) to Gulf of Mexico (GOM) data in the space-time domain. In our application, iterative least-squares reverse-time migration (LSRTM) is used to estimate the model update at each
Measuring the Moisture Content of Green Wood Using Time Domain Reflectometry
Laurence Schimleck; Kim Love-Myers; Joe Sanders; Heath Raybon; Richard Daniels; Jerry Mahon; Edward Andrews; Erik Schilling
2011-01-01
The responsible usage of water by facilities that rely on wet log storage in the southern United States has become an issue of great importance as restrictions on water usage have grown in recent years. In order to learn about the dynamics of moisture content in wet-stored logs over time, it is necessary to conduct continuous monitoring of log piles. Time domain...
Estimating primary production from oxygen time series: A novel approach in the frequency domain
Cox, T.J.S.; Maris, T.; Soetaert, K.; Kromkamp, J.C.; Meire, P.; Meysman, F.J.R.
2015-01-01
Based on an analysis in the frequency domain of the governing equation of oxygen dynamics in aquatic systems, we derive a new method for estimating gross primary production (GPP) from oxygen time series. The central result of this article is a relation between time averaged GPP and the amplitude of
A wavelet-based PWTD algorithm-accelerated time domain surface integral equation solver
Liu, Yang; Yucel, Abdulkadir C.; Gilbert, Anna C.; Bagci, Hakan; Michielssen, Eric
2015-01-01
© 2015 IEEE. The multilevel plane-wave time-domain (PWTD) algorithm allows for fast and accurate analysis of transient scattering from, and radiation by, electrically large and complex structures. When used in tandem with marching-on-in-time (MOT
International Nuclear Information System (INIS)
Wang Yue; Wang Jian-Guo; Chen Zai-Gao
2015-01-01
Based on conformal construction of physical model in a three-dimensional Cartesian grid, an integral-based conformal convolutional perfectly matched layer (CPML) is given for solving the truncation problem of the open port when the enlarged cell technique conformal finite-difference time-domain (ECT-CFDTD) method is used to simulate the wave propagation inside a perfect electric conductor (PEC) waveguide. The algorithm has the same numerical stability as the ECT-CFDTD method. For the long-time propagation problems of an evanescent wave in a waveguide, several numerical simulations are performed to analyze the reflection error by sweeping the constitutive parameters of the integral-based conformal CPML. Our numerical results show that the integral-based conformal CPML can be used to efficiently truncate the open port of the waveguide. (paper)
Nonlinear behavior in the time domain in argon atmospheric dielectric-barrier discharges
International Nuclear Information System (INIS)
Shi Hong; Wang Yanhui; Wang Dezhen
2008-01-01
A vast majority of nonlinear behavior in atmospheric pressure discharges has so far been studied in the space domain, and their time-domain characters are often believed to exact the periodicity of the externally applied voltage. In this paper, based on one-dimensional fluid mode, we study complex nonlinear behavior in the time domain in argon atmospheric dielectric-barrier discharges at very broad frequency range from kilohertz to megahertz. Under certain conditions, the discharge not only can be driven to chaos from time-periodic state through period-doubling bifurcation, but also can return stable periodic motion from chaotic state through an inverse period-doubling bifurcation sequence. Upon changing the parameter the discharge undergoes alternatively chaotic and periodic behavior. Some periodic windows embedded in chaos, as well as the secondary bifurcation occurring in the periodic windows can also be observed. The corresponding discharge characteristics are investigated.
Optimal time-domain combination of the two calibrated output quadratures of GEO 600
International Nuclear Information System (INIS)
Hewitson, M; Grote, H; Hild, S; Lueck, H; Ajith, P; Smith, J R; Strain, K A; Willke, B; Woan, G
2005-01-01
GEO 600 is an interferometric gravitational wave detector with a 600 m arm-length and which uses a dual-recycled optical configuration to give enhanced sensitivity over certain frequencies in the detection band. Due to the dual-recycling, GEO 600 has two main output signals, both of which potentially contain gravitational wave signals. These two outputs are calibrated to strain using a time-domain method. In order to simplify the analysis of the GEO 600 data set, it is desirable to combine these two calibrated outputs to form a single strain signal that has optimal signal-to-noise ratio across the detection band. This paper describes a time-domain method for doing this combination. The method presented is similar to one developed for optimally combining the outputs of two colocated gravitational wave detectors. In the scheme presented in this paper, some simplifications are made to allow its implementation using time-domain methods
Progress in parallel implementation of the multilevel plane wave time domain algorithm
Liu, Yang
2013-07-01
The computational complexity and memory requirements of classical schemes for evaluating transient electromagnetic fields produced by Ns dipoles active for Nt time steps scale as O(NtN s 2) and O(Ns 2), respectively. The multilevel plane wave time domain (PWTD) algorithm [A.A. Ergin et al., Antennas and Propagation Magazine, IEEE, vol. 41, pp. 39-52, 1999], viz. the extension of the frequency domain fast multipole method (FMM) to the time domain, reduces the above costs to O(NtNslog2Ns) and O(Ns α) with α = 1.5 for surface current distributions and α = 4/3 for volumetric ones. Its favorable computational and memory costs notwithstanding, serial implementations of the PWTD scheme unfortunately remain somewhat limited in scope and ill-suited to tackle complex real-world scattering problems, and parallel implementations are called for. © 2013 IEEE.
Power-feedwater enthalpy operating domain for SBWR applying Monte Carlo simulation
International Nuclear Information System (INIS)
Quezada-Garcia, S.; Espinosa-Martinez, E.-G.; Vazquez-Rodriguez, A.; Varela-Ham, J.R.; Espinosa-Paredes, G.
2014-01-01
In this work the analyses of the feedwater enthalpy effects on reactor power in a simplified boiling water reactor (SBWR) applying a methodology based on Monte Carlo's simulation (MCS), is presented. The MCS methodology was applied systematically to establish operating domain, due that the SBWR are not yet in operation, the analysis of the nuclear and thermalhydraulic processes must rely on numerical modeling, with the purpose of developing or confirming the design basis and qualifying the existing or new computer codes to enable reliable analyses. (author)
Al-Jabr, Ahmad
2010-01-01
A time-domain analysis of the propagation properties of surface-plasmon-polaritons (SPP) in Silver nanostructures is presented. The analysis is based on a simulation algorithm that unifies the formulation of different dispersion models and multi-pole relations into one form. The main objective of this work is to perform a comparative analysis between different dispersion models used for Silver, including Debye, Drude and multi-pole Lorentz-Drude models. The quantities that are used in the comparison are the SPP propagation length and propagation speed. Experimental results reported in literature are used to support the conclusions.
On the initial condition problem of the time domain PMCHWT surface integral equation
Uysal, Ismail Enes
2017-05-13
Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced properly. This problem can be remedied by solving the time integral of the surface integral for auxiliary currents that are defined to be the time derivatives of the equivalent currents. Then the equivalent currents are obtained by numerically differentiating the auxiliary ones. In this work, this approach is applied to the marching on-in-time solution of the time domain Poggio-Miller-Chan-Harrington-Wu-Tsai surface integral equation enforced on dispersive/plasmonic scatterers. Accuracy of the proposed method is demonstrated by a numerical example.
Forooghian, Farzin; Cukras, Catherine; Meyerle, Catherine B; Chew, Emily Y; Wong, Wai T
2008-10-01
To evaluate macular thickness and volume measurements and their intrasession repeatability in two optical coherence tomography (OCT) systems: the Stratus OCT, a time domain system, and the Cirrus HD-OCT, a spectral domain system (both by Carl Zeiss Meditec, Inc., Dublin, CA), in the context of diabetic macular edema (DME). Thirty-three eyes of 33 diabetic patients with clinically significant macular edema (CSME) were scanned in a single session by a single operator on both OCT systems. Macular thickness measurements of nine standard macular subfields and total macular volume were obtained and analyzed. Bland-Altman plots were constructed to assess agreement in macular measurements. Intraclass correlation coefficients (ICCs), coefficients of repeatability (CR(W)), and coefficients of variation (CV(W)) were used to assess intrasession repeatability. Macular thickness in nine retinal subfields and macular volume were significantly higher in the Cirrus HD-OCT system compared with the Stratus OCT system. Subfield thickness and total volume measurements, respectively, were 30 to 55 microm and 3.2 mm(3) greater for the Cirrus HD-OCT system compared with the Stratus OCT system. Both Stratus OCT and Cirrus HD-OCT systems demonstrated high intrasession repeatability, with overlapping ranges for CR(W), CV(W), and ICC. Repeatability measures (CR(W) and CV(W)) differed significantly between systems in only one of nine subfields (outer temporal subfield). Absolute measures of macular thickness and volume in patients with DME differed significantly in magnitude between the Stratus OCT and Cirrus HD-OCT systems. However, both OCT systems demonstrated high intrasessional repeatability. Although the two systems may not be used interchangeably, they appear equally reliable in generating macular measurements for clinical practice and research.
Time-resolved magnetization dynamics of cross-tie domain walls in permalloy microstructures
International Nuclear Information System (INIS)
Miguel, J; Kurde, J; Piantek, M; Kuch, W; Sanchez-Barriga, J; Heitkamp, B; Kronast, F; Duerr, H A; Bayer, D; Aeschlimann, M
2009-01-01
We report on a picosecond time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of the evolution of the magnetization components of a microstructured permalloy platelet comprising three cross-tie domain walls. A laser-excited photoswitch has been used to apply a triangular 80 Oe, 160 ps magnetic pulse. Micromagnetic calculations agree well with the experimental results, both in time and frequency, illustrating the large angle precession in the magnetic domains with magnetization perpendicular to the applied pulse, and showing how the magnetic vortices revert their core magnetization while the antivortices remain unaffected.
DEFF Research Database (Denmark)
Mackenzie, David; Buron, Jonas Christian Due; Bøggild, Peter
2016-01-01
We perform contactless full-wafer maps of the electrical conductance of a 4-inch wafer of single-layer CVD graphene using terahertz time-domain spectroscopy both before and after deposition of metal contacts and fabrication of devices via laser ablation. We find that there is no significant change...... in the measured conductance of graphene before and after device fabrication. We also show that precise terahertz time-domain spectroscopy can be performed when the beam spot is at sufficient distance (>1.2 mm) from metal contacts....
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe
2013-05-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
Nonlinear System Identification via Basis Functions Based Time Domain Volterra Model
Directory of Open Access Journals (Sweden)
Yazid Edwar
2014-07-01
Full Text Available This paper proposes basis functions based time domain Volterra model for nonlinear system identification. The Volterra kernels are expanded by using complex exponential basis functions and estimated via genetic algorithm (GA. The accuracy and practicability of the proposed method are then assessed experimentally from a scaled 1:100 model of a prototype truss spar platform. Identification results in time and frequency domain are presented and coherent functions are performed to check the quality of the identification results. It is shown that results between experimental data and proposed method are in good agreement.
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe; Ghaffari-Miab, Mohsen; Andriulli, Francesco P.; Cools, Kristof; Michielssen,
2013-01-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
Nonlinear system identification NARMAX methods in the time, frequency, and spatio-temporal domains
Billings, Stephen A
2013-01-01
Nonlinear System Identification: NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains describes a comprehensive framework for the identification and analysis of nonlinear dynamic systems in the time, frequency, and spatio-temporal domains. This book is written with an emphasis on making the algorithms accessible so that they can be applied and used in practice. Includes coverage of: The NARMAX (nonlinear autoregressive moving average with exogenous inputs) modelThe orthogonal least squares algorithm that allows models to be built term by
Time-resolved magnetization dynamics of cross-tie domain walls in permalloy microstructures
Energy Technology Data Exchange (ETDEWEB)
Miguel, J; Kurde, J; Piantek, M; Kuch, W [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany); Sanchez-Barriga, J; Heitkamp, B; Kronast, F; Duerr, H A [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany); Bayer, D; Aeschlimann, M, E-mail: jorge.miguel@fu-berlin.d [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger Strasse 46, D-67663 Kaiserslautern (Germany)
2009-12-02
We report on a picosecond time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of the evolution of the magnetization components of a microstructured permalloy platelet comprising three cross-tie domain walls. A laser-excited photoswitch has been used to apply a triangular 80 Oe, 160 ps magnetic pulse. Micromagnetic calculations agree well with the experimental results, both in time and frequency, illustrating the large angle precession in the magnetic domains with magnetization perpendicular to the applied pulse, and showing how the magnetic vortices revert their core magnetization while the antivortices remain unaffected.
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics
Gedney, Stephen
2011-01-01
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics provides a comprehensive tutorial of the most widely used method for solving Maxwell's equations -- the Finite Difference Time-Domain Method. This book is an essential guide for students, researchers, and professional engineers who want to gain a fundamental knowledge of the FDTD method. It can accompany an undergraduate or entry-level graduate course or be used for self-study. The book provides all the background required to either research or apply the FDTD method for the solution of Maxwell's equations to p
DWDM-TO-OTDM Conversion by Time-Domain Optical Fourier Transformation
DEFF Research Database (Denmark)
Mulvad, Hans Christian Hansen; Hu, Hao; Galili, Michael
2011-01-01
We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated.......We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated....
Hayward, S.; Kitao, A.; Berendsen, H.J.C.
Model-free methods are introduced to determine quantities pertaining to protein domain motions from normal mode analyses and molecular dynamics simulations, For the normal mode analysis, the methods are based on the assumption that in low frequency modes, domain motions can be well approximated by
Shi, Yifei
2013-08-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although \\'relaxed initial conditions,\\' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made \\'invisible\\' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
Shi, Yifei; Bagci, Hakan; Lu, Mingyu
2013-01-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although 'relaxed initial conditions,' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made 'invisible' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
International Nuclear Information System (INIS)
Hassan, M.A.; Rogers, R.J.; Gerber, A.G.
2009-01-01
This paper presents simulations of a loosely supported multi-span tube subjected to turbulence and fluidelastic instability forces. Several time-domain fluid force models simulating the damping controlled fluidelastic instability mechanism in tube arrays have been presented. These models include the negative damping model based on the Connors equation, fluid force coefficient-based models (Chen and Tanaka and Takahara), and two semi-analytical models (Price and Paidoussis; and Lever and Weaver) were implemented in an in-house finite code. Time domain modeling challenges for each of these theories were discussed. The implemented models were validated against available experimental data. The linear simulations showed that the Connors-equation based model exhibits the most conservative prediction of the critical flow velocity when the recommended design values for the Connors equation were used. The models were then utilized to simulate the nonlinear response of a three-span cantilever tube in a square lattice bar support subjected to air crossflow. The tube was subjected to a single-phase flow passing over one of the tube's spans. For each of these models the flow velocity and the support clearance were varied. Special attention was paid to the tube/support interaction parameters that affect wear, such as impact forces, contact ratio, and normal work rate. As the prediction of the linear threshold varies depending on the utilized model, the nonlinear response also differs. The investigated models exhibit similar response characteristics for the impact force, tip lift response, and work rate. Simulation results show that the Connors-based model underestimates the response and the tube/support interaction parameters for the loose support case. (author)
Reduced order for nuclear reactor model in frequency and time domain
International Nuclear Information System (INIS)
Nugroho, D.H.
1997-01-01
In control system theory, a model can be represented by frequency or time domain. In frequency domain, the model was represented by transfer function. in time domain, the model was represented by state space. for the sake of simplification in computation, it is necessary to reduce the model order. the main aim of this research is to find the best in nuclear reactor model. Model order reduction in frequency domain can be done utilizing pole-zero cancellation method; while in time domain utilizing balanced aggregation method the balanced aggregation method was developed by moore (1981). In this paper, the two kinds of method were applied to reduce a nuclear reactor model which was constructed by neutron dynamics and heat transfer equations. to validate that the model characteristics were not change when model order reduction applied, the response was utilized for full and reduced order. it was shown that the nuclear reactor order model can be reduced from order 8 to 2 order 2 is the best order for nuclear reactor model
The Trick Simulation Toolkit: A NASA/Opensource Framework for Running Time Based Physics Models
Penn, John M.
2016-01-01
The Trick Simulation Toolkit is a simulation development environment used to create high fidelity training and engineering simulations at the NASA Johnson Space Center and many other NASA facilities. Its purpose is to generate a simulation executable from a collection of user-supplied models and a simulation definition file. For each Trick-based simulation, Trick automatically provides job scheduling, numerical integration, the ability to write and restore human readable checkpoints, data recording, interactive variable manipulation, a run-time interpreter, and many other commonly needed capabilities. This allows simulation developers to concentrate on their domain expertise and the algorithms and equations of their models. Also included in Trick are tools for plotting recorded data and various other supporting utilities and libraries. Trick is written in C/C++ and Java and supports both Linux and MacOSX computer operating systems. This paper describes Trick's design and use at NASA Johnson Space Center.
Real-time GPS Signal Simulator
National Aeronautics and Space Administration — With a minimal FTE investment and no additional procurement funds, the development of a low fidelity orbital GPS Signal simulator would is possible. This IRAD...
An investigation of time-dependent domain wall pinning effects in Tb/Fe multilayer thin flms
Phillips, G.N.; O'grady, K.; El-Hilo, M.
2002-01-01
Reverse domain nucleation time measurements have been performed on two Tb/Fe multilayer magneto-optic films exhibiting different degrees of domain wall pinning.A linear relationship between ln (reverse domain nucleation time) and the applied field has been predicted and observed for a sample
Quasi-exact evaluation of time domain MFIE MOT matrix elements
Shi, Yifei
2013-07-01
A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2012-01-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
Quasi-exact evaluation of time domain MFIE MOT matrix elements
Shi, Yifei; Bagci, Hakan; Shanker, Balasubramaniam; Lu, Mingyu; Michielssen, Eric
2013-01-01
A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.
Ulku, Huseyin Arda
2012-09-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
Pettermann, Heinz E.; DeSimone, Antonio
2017-09-01
A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.
International Nuclear Information System (INIS)
Hao Yun-Qi; Ye Qing; Pan Zheng-Qing; Cai Hai-Wen; Qu Rong-Hui
2014-01-01
The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card (DAQ). A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator (LO) in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio (SNR) has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement. (general)
Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics
DEFF Research Database (Denmark)
D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa
2014-01-01
-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...... index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....
THEORETICAL RESEARCH ON HYDRODYNAMICS OF A GEOMETRIC SPAR IN FREQUENCY- AND TIME-DOMAINS
Institute of Scientific and Technical Information of China (English)
WANG Ying; YANG Jian-min; HU Zhi-qiang; XIAO Long-fei
2008-01-01
Considering the coupling effects of the vessel and its riser and mooring system, hydrodynamic analyses of a geometric spar were performed both in frequency- and time-domains. Based on the boundary element method, the 3-D panel model of the geometric spar and the related free water surface model were established, and the first-order and second-order difference-frequency wave loads and other hydrodynamic coefficients were calculated. Frequency domain analysis of the motion Response Amplitude Operators (RAO) and Quadratic Transfer Functions (QTF) and time domain analysis of the response series and spectra in an extreme wave condition were conducted for the coupled system with the mooring lines and risers involved. These analyses were further validated by the physical model test results.
Quantum-corrected plasmonic field analysis using a time domain PMCHWT integral equation
Uysal, Ismail E.
2016-03-13
When two structures are within sub-nanometer distance of each other, quantum tunneling, i.e., electrons "jumping" from one structure to another, becomes relevant. Classical electromagnetic solvers do not directly account for this additional path of current. In this work, an auxiliary tunnel made of Drude material is used to "connect" the structures as a support for this current path (R. Esteban et al., Nat. Commun., 2012). The plasmonic fields on the resulting connected structure are analyzed using a time domain surface integral equation solver. Time domain samples of the dispersive medium Green function and the dielectric permittivities are computed from the analytical inverse Fourier transform applied to the rational function representation of their frequency domain samples.
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...
Sensitivity of simulated regional Arctic climate to the choice of coupled model domain
Directory of Open Access Journals (Sweden)
Dmitry V. Sein
2014-07-01
Full Text Available The climate over the Arctic has undergone changes in recent decades. In order to evaluate the coupled response of the Arctic system to external and internal forcing, our study focuses on the estimation of regional climate variability and its dependence on large-scale atmospheric and regional ocean circulations. A global ocean–sea ice model with regionally high horizontal resolution is coupled to an atmospheric regional model and global terrestrial hydrology model. This way of coupling divides the global ocean model setup into two different domains: one coupled, where the ocean and the atmosphere are interacting, and one uncoupled, where the ocean model is driven by prescribed atmospheric forcing and runs in a so-called stand-alone mode. Therefore, selecting a specific area for the regional atmosphere implies that the ocean–atmosphere system can develop ‘freely’ in that area, whereas for the rest of the global ocean, the circulation is driven by prescribed atmospheric forcing without any feedbacks. Five different coupled setups are chosen for ensemble simulations. The choice of the coupled domains was done to estimate the influences of the Subtropical Atlantic, Eurasian and North Pacific regions on northern North Atlantic and Arctic climate. Our simulations show that the regional coupled ocean–atmosphere model is sensitive to the choice of the modelled area. The different model configurations reproduce differently both the mean climate and its variability. Only two out of five model setups were able to reproduce the Arctic climate as observed under recent climate conditions (ERA-40 Reanalysis. Evidence is found that the main source of uncertainty for Arctic climate variability and its predictability is the North Pacific. The prescription of North Pacific conditions in the regional model leads to significant correlation with observations, even if the whole North Atlantic is within the coupled model domain. However, the inclusion of the
Molecular dynamics simulations and in silico peptide ligand screening of the Elk-1 ETS domain
Directory of Open Access Journals (Sweden)
Hussain Abrar
2011-11-01
Full Text Available Abstract Background The Elk-1 transcription factor is a member of a group of proteins called ternary complex factors, which serve as a paradigm for gene regulation in response to extracellular signals. Its deregulation has been linked to multiple human diseases including the development of tumours. The work herein aims to inform the design of potential peptidomimetic compounds that can inhibit the formation of the Elk-1 dimer, which is key to Elk-1 stability. We have conducted molecular dynamics simulations of the Elk-1 ETS domain followed by virtual screening. Results We show the ETS dimerisation site undergoes conformational reorganisation at the α1β1 loop. Through exhaustive screening of di- and tri-peptide libraries against a collection of ETS domain conformations representing the dynamics of the loop, we identified a series of potential binders for the Elk-1 dimer interface. The di-peptides showed no particular preference toward the binding site; however, the tri-peptides made specific interactions with residues: Glu17, Gln18 and Arg49 that are pivotal to the dimer interface. Conclusions We have shown molecular dynamics simulations can be combined with virtual peptide screening to obtain an exhaustive docking protocol that incorporates dynamic fluctuations in a receptor. Based on our findings, we suggest experimental binding studies to be performed on the 12 SILE ranked tri-peptides as possible compounds for the design of inhibitors of Elk-1 dimerisation. It would also be reasonable to consider the score-ranked tri-peptides as a comparative test to establish whether peptide size is a determinant factor of binding to the ETS domain.
Time-domain representation of frequency-dependent foundation impedance functions
Safak, E.
2006-01-01
Foundation impedance functions provide a simple means to account for soil-structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.
Layered and Laterally Constrained 2D Inversion of Time Domain Induced Polarization Data
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Auken, Esben
description of the transmitter waveform and of the receiver transfer function allowing for a quantitative interpretation of the parameters. The code has been optimized for parallel computation and the inversion time is comparable to codes inverting just for direct current resistivity. The new inversion......In a sedimentary environment, quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. We have developed a new layered and laterally constrained inversion algorithm for time domain induced polarization data. The algorithm is based on the time...... transform of a complex resistivity forward response and the inversion extracts the spectral information of the time domain measures in terms of the Cole-Cole parameters. The developed forward code and inversion algorithm use the full time decay of the induced polarization response, together with an accurate...
Comparison between time-and frequency-domain induced polarisation parameters
CSIR Research Space (South Africa)
Van Schoor, Abraham M
2009-09-01
Full Text Available of mineralised rocks and of the contrast between different rock types. It is further shown that a multi-frequency (spectral) approach can be used to avoid this pitfall; similarly, the calculation of different time-domain induced polarisation (IP) parameters...
Pagan Munoz, R.; Hornikx, M.C.J.
The wave-based Fourier Pseudospectral time-domain (Fourier-PSTD) method was shown to be an effective way of modeling outdoor acoustic propagation problems as described by the linearized Euler equations (LEE), but is limited to real-valued frequency independent boundary conditions and predominantly
Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy
DEFF Research Database (Denmark)
Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup
2016-01-01
The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR), and lin...
Stationary echo canceling in velocity estimation by time-domain cross-correlation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated...
Postural Analysis in Time and Frequency Domains in Patients with Ehlers-Danlos Syndrome
Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo
2011-01-01
The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30 s in two conditions: open eyes (OE) and closed…
Shape optimization for non-Newtonian fluids in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Sokolowski, J.; Stebel, Jan
2014-01-01
Roč. 3, č. 2 (2014), s. 331-348 ISSN 2163-2480 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : shape optimization * time - dependent domain * incompressible viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.373, year: 2014 http://www.aimsciences.org/journals/home.jsp?journalID=25
Non-Causal Time-Domain Filters for Single-Channel Noise Reduction
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Benesty, Jacob; Christensen, Mads Græsbøll
2012-01-01
suppression and signal distortion by allowing the filters to be non-causal. Non-causal time-domain filters require knowledge of the future, and are therefore not directly implementable. If the observed signal is processed in blocks, however, the non-causal filters are implementable. In this paper, we propose...
Dekkers, Birgit L.; Kort, de Daan W.; Grabowska, Katarzyna J.; Tian, Bei; As, Van Henk; Goot, van der Atze Jan
2016-01-01
We present a combined time domain NMR and rheology approach to quantify the water distribution in a phase separated protein blend. The approach forms the basis for a new tool to assess the microstructural properties of phase separated biopolymer blends, making it highly relevant for many food and
Effects of the airwave in time-domain marine controlled-source electromagnetics
Hunziker, J.W.; Slob, E.C.; Mulder, W.
2011-01-01
In marine time-domain controlled-source electromagnetics (CSEM), there are two different acquisition methods: with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave. Illustrations of the electric field as a function of space
Gisolf, J.; Immink, R. V.; van Lieshout, J. J.; Stok, W. J.; Karemaker, J. M.
2005-01-01
Reduction in plasma volume is a major contributor to orthostatic tachycardia and hypotension after spaceflight. We set out to determine time- and frequency-domain baroreflex (BRS) function during preflight baseline and venous occlusion and postflight orthostatic stress, testing the hypothesis that a
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
-layer structures are analyzed. Results show that this method matches satisfactorily the Nyquist sampling theorem in terms of spatial discretization. By comparing the given results, it is found that the PSTD method outperforms the finite-difference time-domain (FDTD) method in general, especially in terms...
Optimal time-domain technique for pulse width modulation in power electronics
Directory of Open Access Journals (Sweden)
I. Mayergoyz
2018-05-01
Full Text Available Optimal time-domain technique for pulse width modulation is presented. It is based on exact and explicit analytical solutions for inverter circuits, obtained for any sequence of input voltage rectangular pulses. Two optimal criteria are discussed and illustrated by numerical examples.
A time-domain binaural detection model and its predictions temporal-resolution data
Breebaart, D.J.; Par, van de S.L.J.D.E.; Kohlrausch, A.G.
2002-01-01
This paper discusses the application of a time-domain binaural signal-detection model in the context of estimates of the temporal resolution of the binaural auditory system. It is demonstrated that the optimal detector which is present in the model is crucial to account for specific temporal
Non-linear wave loads and ship responses by a time-domain strip theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hydroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented as a Timoshenko beam. Numerical calculations are presented for the S175 Containership...
Non-Linear Wave Loads and Ship responses by a time-domain Strip Theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hyroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented by the Timoshenko beam theory. Numerical calculations are presented for the S175...
Driven by the future : Future time perspective across life domains and cultures
Andre, L.
2018-01-01
Contemplating about the future is inevitable for our life and goal strivings. Consequently, Future Time Perspective (FTP) – individuals’ attitudes towards the future as a motivator for attitudes and behaviors – has been researched across disciplines and life domains. However, little is known about
Continuous performance test assessed with time-domain functional near infrared spectroscopy
Torricelli, Alessandro; Contini, Davide; Spinelli, Lorenzo; Caffini, Matteo; Butti, Michele; Baselli, Giuseppe; Bianchi, Anna M.; Bardoni, Alessandra; Cerutti, Sergio; Cubeddu, Rinaldo
2007-07-01
A time-domain fNIRS multichannel system was used in a sustained attention protocol (continuous performance test) to study activation of the prefrontal cortex. Preliminary results on volounteers show significant activation (decrease in deoxy-hemoglobin and increase in oxy-hemoglobin) in both left and right prefrontal cortex.
Broadband time domain acoustic holography based on the discrete orthonormal S-transform
Zhou, H.; Lopez Arteaga, I.; Nijmeijer, H.; Lim, Kian Meng
2015-01-01
The purpose of this paper is to deal with the problem of nonstationary broadband sound fields more efficiently. A basis function of the discrete orthonormal S-transform (DOST) is used to analyze the measured signal. With respect to the time domain signal in a certain band, DOST leads to a
Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...
Quantitative terahertz time-domain spectroscopy and analysis in chemistry and biology
DEFF Research Database (Denmark)
Jepsen, Peter Uhd
2005-01-01
I will describe how Terahertz Time-Domain Spectroscopy (THz-TDS) can be used for quantitative, broadband spectroscopy in the far-infrared spectral region. Thz-TDS is sensitive to long-range, non-covalent interactions in the condensed phase, for instance intermolecular hydrogen bonding in molecula...
PLASTIQUE: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain
International Nuclear Information System (INIS)
De Stasio, G.; Zema, N.; Antonangeli, F.; Parasassi, T.; Rosato, N.
1991-01-01
PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in the frequency domain. These experiments are extremely valuable sources of informations on the structure and dynamics of molecules. The beamline and some examples of initial data are described
Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain
De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.
1991-06-01
PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.
DEFF Research Database (Denmark)
Hu, Hao; Kong, Deming; Palushani, Evarist
2013-01-01
We demonstrate transmission of a 1.28-Tbaud Nyquist-OTDM signal over a record distance of 100 km with detection by time-domain optical Fourier transformation followed by FEC decoding, resulting in error-free performance for all tributaries....
320 Gb/s Nyquist OTDM received by polarization-insensitive time-domain OFT
DEFF Research Database (Denmark)
Hu, Hao; Kong, Deming; Palushani, Evarist
2014-01-01
We have demonstrated the generation of a 320 Gb/s Nyquist-OTDM signal by rectangular filtering on an RZ-OTDM signal with the filter bandwidth (320 GHz) equal to the baud rate (320 Gbaud) and the reception of such a Nyquist-OTDM signal using polarization-insensitive time-domain optical Fourier tra...
Fra Angelico’s painting technique revealed by terahertz time-domain imaging (THz-TDI)
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Picollo, Marcello; Cucci, Costanza
2016-01-01
We have investigated with terahertz time-domain imaging (THz-TDI) the well-known Lamentation over the dead Christ panel painting (San Marco Museum, Florence) painted by Fra Giovanni Angelico within 1436 and 1441. The investigation provided a better understanding of the construction and gilding te...
OpenPSTD : The open source pseudospectral time-domain method for acoustic propagation
Hornikx, M.C.J.; Krijnen, T.F.; van Harten, L.
2016-01-01
An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in
Energy Technology Data Exchange (ETDEWEB)
Terashima, Kenichi; Suzuki, Kenji; Yamaguchi, Katsuhiko, E-mail: yama@sss.fukushima-u.ac.jp
2016-04-01
Monte Carlo simulations were performed for temperature dependences of closure domain parameter for a magnetic micro-torus ring cluster under magnetic field on limited temperature regions. Simulation results show that magnetic field on tiny limited temperature region can reverse magnetic closure domain structures when the magnetic field is applied at a threshold temperature corresponding to intensity of applied magnetic field. This is one of thermally assisted switching phenomena through a self-organization process. The results show the way to find non-wasteful pairs between intensity of magnetic field and temperature region for reversing closure domain structure by temperature dependence of the fluctuation of closure domain parameter. Monte Carlo method for this simulation is very valuable to optimize the design of thermally assisted switching devices.
Turbine modelling for real time simulators
International Nuclear Information System (INIS)
Oliveira Barroso, A.C. de; Araujo Filho, F. de
1992-01-01
A model for vapor turbines and its peripherals has been developed. All the important variables have been included and emphasis has been given for the computational efficiency to obtain a model able to simulate all the modeled equipment. (A.C.A.S.)
Methodology for Time-Domain Estimation of Storm-Time Electric Fields Using the 3D Earth Impedance
Kelbert, A.; Balch, C. C.; Pulkkinen, A. A.; Egbert, G. D.; Love, J. J.; Rigler, E. J.; Fujii, I.
2016-12-01
Magnetic storms can induce geoelectric fields in the Earth's electrically conducting interior, interfering with the operations of electric-power grid industry. The ability to estimate these electric fields at Earth's surface in close to real-time and to provide local short-term predictions would improve the ability of the industry to protect their operations. At any given time, the electric field at the Earth's surface is a function of the time-variant magnetic activity (driven by the solar wind), and the local electrical conductivity structure of the Earth's crust and mantle. For this reason, implementation of an operational electric field estimation service requires an interdisciplinary, collaborative effort between space science, real-time space weather operations, and solid Earth geophysics. We highlight in this talk an ongoing collaboration between USGS, NOAA, NASA, Oregon State University, and the Japan Meteorological Agency, to develop algorithms that can be used for scenario analyses and which might be implemented in a real-time, operational setting. We discuss the development of a time domain algorithm that employs discrete time domain representation of the impedance tensor for a realistic 3D Earth, known as the discrete time impulse response (DTIR), convolved with the local magnetic field time series, to estimate the local electric field disturbances. The algorithm is validated against measured storm-time electric field data collected in the United States and Japan. We also discuss our plans for operational real-time electric field estimation using 3D Earth impedances.
Pan, Yudi; Gao, Lingli; Bohlen, Thomas
2018-05-01
Correct estimation of near-surface seismic-wave velocity when encountering lateral heterogeneity and free surface topography is one of the challenges to current shallow seismic. We propose to use time-domain full-waveform inversion (FWI) of surface waves, including both Rayleigh and Love waves, to solve this problem. We adopt a 2D time-domain finite-difference method with an improved vacuum formulation (IVF) to simulate shallow-seismic Rayleigh wave in presence of free-surface topography. We modify the IVF for SH-wave equation for the simulation of Love wave in presence of topographic free surface and prove its accuracy by benchmark tests. Checkboard model tests are performed in both cases when free-surface topography is included or neglected in FWI. Synthetic model containing a dipping planar free surface and lateral heterogeneity was then tested, in both cases of considering and neglecting free-surface topography. Both checkerboard and synthetic models show that Rayleigh- and Love-wave FWI have similar ability of reconstructing near-surface structures when free-surface topography is considered, while Love-wave FWI could reconstruct near-surface structures better than Rayleigh-wave when free-surface topography is neglected.
Gastric Emptying Assessment in Frequency and Time Domain Using Bio-impedance: Preliminary Results
Huerta-Franco, R.; Vargas-Luna, M.; Hernández, E.; Córdova, T.; Sosa, M.; Gutiérrez, G.; Reyes, P.; Mendiola, C.
2006-09-01
The impedance assessment to measure gastric emptying and in general gastric activity has been reported since 1985. The physiological interpretation of these measurements, is still under research. This technique usually uses a single frequency, and the conductivity parameter. The frequency domain and the Fourier analysis of the time domain behavior of the gastric impedance in different gastric conditions (fasting state, and after food administration) has not been explored in detail. This work presents some insights of the potentiality of these alternative methodologies to measure gastric activity.
Measurement of electron paramagnetic resonance using terahertz time-domain spectroscopy.
Kozuki, Kohei; Nagashima, Takeshi; Hangyo, Masanori
2011-12-05
We present a frequency-domain electron spin resonance (ESR) measurement system using terahertz time-domain spectroscopy. A crossed polarizer technique is utilized to increase the sensitivity in detecting weak ESR signals of paramagnets caused by magnetic dipole transitions between magnetic sublevels. We demonstrate the measurements of ESR signal of paramagnetic copper(II) sulfate pentahydrate with uniaxial anisotropy of the g-factor under magnetic fields up to 10 T. The lineshape of the obtained ESR signals agrees well with the theoretical predictions for a powder sample with the uniaxial anisotropy.
Simulation of time-dependent free-surface Navier-Stokes flows
International Nuclear Information System (INIS)
Muldowney, G.P.
1989-01-01
Two numerical methods for simulation of time-dependent free-surface Navier-Stokes flows are developed. Both techniques are based on semi-implicit time advancement of the momentum equations, integral formulation of the spatial problem at each timestep, and spectral-element discretization to solve the resulting integral equation. Central to each algorithm is a boundary-specific solution step which permits the spatial treatment in two dimensions to be performed in O(N 3 ) operations per timestep despite the presence of deforming geometry. The first approach is a domain-integral formulation involving integrals over the entire flow domain of kernel functions which arise in time-differencing the Navier-Stokes equations. The second is a particular-solution formulation which replaces domain integration with an iterative scheme to generate particular velocity and pressure fields on individual elements, followed by a patching step to produce a particular solution continuous over the full domain. Two of the most difficult aspects of viscous free-surface flow simulations, namely time-dependent geometry and nontrivial boundary conditions, are well accommodated by these integral equation techniques. In addition the methods offer spectral accuracy in space and admit arbitrarily high-order discretization in time. For large-scale computations and/or long-term time advancement the domain-integral algorithm must be executed on a supercomputer to deliver results in reasonable processing time. A detailed simulation of gas liquid flow with full resolution of the free phase boundary requires approximately five CPU hours at 80 megaflops
Ulku, Huseyin Arda; Bagci, Hakan; Michielssen, Eric
2013-01-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
Ulku, Huseyin Arda
2013-08-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
International Nuclear Information System (INIS)
Khorasani, A.; Mousavi Shalmani, M. A.; Piervali Bieranvand, N.
2011-01-01
An accurate, precise, fast and ease as well as the ability for measurements in depth are the characteristics that are desirable in measuring soil moisture methods. To compare methods (time domain reflectometry and capacitance) with neutron scattering for soil water monitoring, an experiment was carried out in a randomized complete block design (Split Split plot) on tomato with three replications on the experimental field of International Atomic Energy Agency (Seibersdorf-Austria). The treatment instruments for the soil moisture monitoring (main factor) consist of neutron gauge, Diviner 2000, time domain reflectometer and an EnviroScan and different irrigation systems (first sub factor) consist of trickle and furrow irrigations and different depths of soil (second sub factor) consist of 0-20, 20-40 and 40-60 cm. The results showed that for the neutron gauge and time domain reflectometer the amount of soil moisture in both of trickle and furrow irrigations were the same, but the significant differences were recorded in Diviner 2000 and EnviroScan measurements. The results of this study showed that the neutron gauge is an acceptable and reliable means with the modern technology, with a precision of ±2 mm in 450 mm soil water to a depth of 1.5 meter and can be considered as the most practical method for measuring soil moisture profiles and irrigation planning program. The time domain reflectometer method in most mineral soils, without the need for calibration, with an accuracy ±0.01m 3 m -3 has a good performance in soil moisture and electrical conductivity measurements. The Diviner 2000 and EnviroScan are not well suitable for the above conditions for several reasons such as much higher soil moisture and a large error measurement and also its sensitivity to the soil gap and to the small change in the soil moisture in comparison with the neutron gauge and the time domain reflectometer methods.
Zhang, Zhendong
2017-07-11
Full waveform inversion for reection events is limited by its linearized update re-quirements given by a process equivalent to migration. Unless the background velocity model is reasonably accurate, the resulting gradient can have an inaccurate update direction leading the inversion to converge what we refer to as local minima of the objective function. In our approach, we consider mild lateral variation in the model, and thus, use a gradient given by the oriented time-domain imaging method. Specifically, we apply the oriented time-domain imaging on the data residual to obtain the geometrical features of the velocity perturbation. After updating the model in the time domain, we convert the perturbation from the time domain to depth using the average velocity. Considering density is constant, we can expand the conventional 1D impedance inversion method to 2D or 3D velocity inversion within the process of full waveform inversion. This method is not only capable of inverting for velocity, but it is also capable of retrieving anisotropic parameters relying on linearized representations of the reection response. To eliminate the cross-talk artifacts between different parameters, we utilize what we consider being an optimal parametrization for this step. To do so, we extend the prestack time-domain migration image in incident angle dimension to incorporate angular dependence needed by the multiparameter inversion. For simple models, this approach provides an efficient and stable way to do full waveform inversion or modified seismic inversion and makes the anisotropic inversion more practicable. The proposed method still needs kinematically accurate initial models since it only recovers the high-wavenumber part as conventional full waveform inversion method does. Results on synthetic data of isotropic and anisotropic cases illustrate the benefits and limitations of this method.
Wang, P.; Becker, A. A.; Jones, I. A.; Glover, A. T.; Benford, S. D.; Vloeberghs, M.
2009-08-01
A virtual-reality real-time simulation of surgical operations that incorporates the inclusion of a hard tumour is presented. The software is based on Boundary Element (BE) technique. A review of the BE formulation for real-time analysis of two-domain deformable objects, using the pre-solution technique, is presented. The two-domain BE software is incorporated into a surgical simulation system called VIRS to simulate the initiation of a cut on the surface of the soft tissue and extending the cut deeper until the tumour is reached.
International Nuclear Information System (INIS)
Wang, P; Becker, A A; Jones, I A; Glover, A T; Benford, S D; Vloeberghs, M
2009-01-01
A virtual-reality real-time simulation of surgical operations that incorporates the inclusion of a hard tumour is presented. The software is based on Boundary Element (BE) technique. A review of the BE formulation for real-time analysis of two-domain deformable objects, using the pre-solution technique, is presented. The two-domain BE software is incorporated into a surgical simulation system called VIRS to simulate the initiation of a cut on the surface of the soft tissue and extending the cut deeper until the tumour is reached.
Domain-Specific and Unspecific Reaction Times in Experienced Team Handball Goalkeepers and Novices.
Helm, Fabian; Reiser, Mathias; Munzert, Jörn
2016-01-01
In our everyday environments, we are constantly having to adapt our behavior to changing conditions. Hence, processing information is a fundamental cognitive activity, especially the linking together of perceptual and action processes. In this context, expertise research in the sport domain has concentrated on arguing that superior processing performance is driven by an advantage to be found in anticipatory processes (see Williams et al., 2011, for a review). This has resulted in less attention being paid to the benefits coming from basic internal perceptual-motor processing. In general, research on reaction time (RT) indicates that practicing a RT task leads to an increase in processing speed (Mowbray and Rhoades, 1959; Rabbitt and Banerji, 1989). Against this background, the present study examined whether the speed of internal processing is dependent on or independent from domain-specific motor expertise in unpredictable stimulus-response tasks and in a double stimulus-response paradigm. Thirty male participants (15 team handball goalkeepers and 15 novices) performed domain-unspecific simple or choice stimulus-response (CSR) tasks as well as CSR tasks that were domain-specific only for goalkeepers. As expected, results showed significantly faster RTs for goalkeepers on domain-specific tasks, whereas novices' RTs were more frequently excessively long. However, differences between groups in the double stimulus-response paradigm were not significant. It is concluded that the reported expertise advantage might be due to recalling stored perceptual-motor representations for the domain-specific tasks, implying that experience with (practice of) a motor task explicitly enhances the internal processing of other related domain-specific tasks.
Online Identification of a Mechanical System in the Frequency Domain with Short-Time DFT
Directory of Open Access Journals (Sweden)
Niko Nevaranta
2015-07-01
Full Text Available A proper system identification method is of great importance in the process of acquiring an analytical model that adequately represents the characteristics of the monitored system. While the use of different time-domain online identification techniques has been widely recognized as a powerful approach for system diagnostics, the frequency domain identification techniques have primarily been considered for offline commissioning purposes. This paper addresses issues in the online frequency domain identification of a flexible two-mass mechanical system with varying dynamics, and a particular attention is paid to detect the changes in the system dynamics. An online identification method is presented that is based on a recursive Kalman filter configured to perform like a discrete Fourier transform (DFT at a selected set of frequencies. The experimental online identification results are compared with the corresponding values obtained from the offline-identified frequency responses. The results show an acceptable agreement and demonstrate the feasibility of the proposed identification method.
Uschold, Michael
1992-01-01
We are concerned with two important issues in simulation modelling: model comprehension and model construction. Model comprehension is limited because many important choices taken during the modelling process are not documented. This makes it difficult for models to be modified or used by others. A key factor hindering model construction is the vast modelling search space which must be navigated. This is exacerbated by the fact that many modellers are unfamiliar with the terms and concepts catered to by current tools. The root of both problems is the lack of facilities for representing or reasoning about domain concepts in current simulation technology. The basis for our achievements in both of these areas is the development of a language with two distinct levels; one for representing domain information, and the other for representing the simulation model. Of equal importance, is the fact that we make formal connections between these two levels. The domain we are concerned with is ecological modelling. This language, called Elklogic, is based on the typed lambda calculus. Important features include a rich type structure, the use of various higher order functions, and semantics. This enables complex expressions to be constructed from relatively few primitives. The meaning of each expression can be determined in terms of the domain, the simulation model, or the relationship between the two. We describe a novel representation for sets and substructure, and a variety of other general concepts that are especially useful in the ecological domain. We use the type structure in a novel way: for controlling the modelling search space, rather than a proof search space. We facilitate model comprehension by representing modelling decisions that are embodied in the simulation model. We represent the simulation model separately from, but in terms of a domain mode. The explicit links between the two models constitute the modelling decisions. The semantics of Elklogic enables
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2018-01-01
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
Li, Ping
2018-04-13
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
Postural analysis in time and frequency domains in patients with Ehlers-Danlos syndrome.
Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo
2011-01-01
The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30s in two conditions: open eyes (OE) and closed eyes (CE). In order to compare pathological group we acquired in the same conditions a control group composed by 20 healthy participants. The obtained center of pressure (COP) signal was analyzed in time and frequency domain using an AR model. Results revealed differences between pathological and control group: EDS participants pointed out difficulties in controlling COP displacements trying to keep it inside the BOS in AP direction and for this reason increased the use of ML mechanism in order to avoid the risk of fall. Also in CE conditions they demonstrated more difficulties in maintaining posture revealing the proprioceptive system is impaired, due to ligament laxity that characterized EDS participants. Frequency domain analysis showed no differences between the two groups, affirming that the changes in time domain reflected really the impairment to the postural control mechanism and not a different strategy assumed by EDS participants. These data could help in decision-making process to establish a correct rehabilitation approach, based on the reinforcing of muscle tone to supply the ligament laxity in order to prevent risks of falls and its consequences. Copyright © 2010 Elsevier Ltd. All rights reserved.
Plasmonic Resonances for Spectroscopy Applications using 3D Finite-Difference Time-Domain Models
Ravi, Aruna
Tuning plasmonic extinction resonances of sub-wavelength scale structures is essential to achieve maximum sensitivity and accuracy. These resonances can be controlled with careful design of nanoparticle geometries and incident wave attributes. In the first part of this dissertation, plasmonically enhanced effects on hexagonal-arrays of metal nanoparticles, metal-hole arrays (micro-mesh), and linear-arrays of metal nanorings are analyzed using three-dimensional Finite-Difference Time-Domain (3D-FDTD) simulations. The effect of particle size, lattice spacing, and lack of monodispersity of a self-assembled, hexagonal array layer of silver (Ag) nanoparticles on the extinction resonance is investigated to help determine optimal design specifications for efficient organic solar power harvesting. The enhancement of transmission resonances using plasmonic thin metal films with arrays of holes which enable recording of scatter-free infrared (IR) transmission spectra of individual particles is also explored. This method is quantitative, non-destructive and helps in better understanding the interaction of light with sub-wavelength particles. Next, plasmonically enhanced effects on linear arrays of gold (Au) rings are studied. Simulations employing 3D-FDTD can be used to determine the set of geometrical parameters to attain localized surface plasmon resonance (LSPR). The shifts in resonances due to changes in the effective dielectric of the structure are investigated, which is useful in sensing applications. Computational models enrich experimental studies. In the second part of this dissertation, the effect of particle size, shape and orientation on the IR spectra is investigated using 3D-FDTD and Mie-Bruggeman models. This computational analysis is extended to include clusters of particles of mixed composition. The prediction of extinction and absorption spectra of single particles of mixed composition helps in interpreting their physical properties and predict chemical
Bi, Chuan-Xing; Geng, Lin; Zhang, Xiao-Zheng
2016-05-01
In the sound field with multiple non-stationary sources, the measured pressure is the sum of the pressures generated by all sources, and thus cannot be used directly for studying the vibration and sound radiation characteristics of every source alone. This paper proposes a separation model based on the interpolated time-domain equivalent source method (ITDESM) to separate the pressure field belonging to every source from the non-stationary multi-source sound field. In the proposed method, ITDESM is first extended to establish the relationship between the mixed time-dependent pressure and all the equivalent sources distributed on every source with known location and geometry information, and all the equivalent source strengths at each time step are solved by an iterative solving process; then, the corresponding equivalent source strengths of one interested source are used to calculate the pressure field generated by that source alone. Numerical simulation of two baffled circular pistons demonstrates that the proposed method can be effective in separating the non-stationary pressure generated by every source alone in both time and space domains. An experiment with two speakers in a semi-anechoic chamber further evidences the effectiveness of the proposed method.
Causality and associative holography of time-and-space domain events
International Nuclear Information System (INIS)
Rebane, Aleksander
2014-01-01
We consider reference-free associative recall of time-and-space domain holograms of arbitrary non-stationary optical object amplitudes or events. We show that if the probe fragment correlates with the recorded event either in space or in time coordinates or in both, then the hologram faithfully reproduces those missing parts (sub-events) that occur simultaneously or later in time with respect to the probe fragment. However, if a missing sub-event occurred before the fragment used as associative probe, then the hologram will not play this information back due to the time arrow imposed by causality. (paper)
Zaghloul, Mohamed A S; Wang, Mohan; Milione, Giovanni; Li, Ming-Jun; Li, Shenping; Huang, Yue-Kai; Wang, Ting; Chen, Kevin P
2018-04-12
Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores' temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%).
Directory of Open Access Journals (Sweden)
Mohamed A. S. Zaghloul
2018-04-01
Full Text Available Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz, which is 2.63 (3.67 times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%.
Efficient reconstruction of dispersive dielectric profiles using time domain reflectometry (TDR
Directory of Open Access Journals (Sweden)
P. Leidenberger
2006-01-01
Full Text Available We present a numerical model for time domain reflectometry (TDR signal propagation in dispersive dielectric materials. The numerical probe model is terminated with a parallel circuit, consisting of an ohmic resistor and an ideal capacitance. We derive analytical approximations for the capacitance, the inductance and the conductance of three-wire probes. We couple the time domain model with global optimization in order to reconstruct water content profiles from TDR traces. For efficiently solving the inverse problem we use genetic algorithms combined with a hierarchical parameterization. We investigate the performance of the method by reconstructing synthetically generated profiles. The algorithm is then applied to retrieve dielectric profiles from TDR traces measured in the field. We succeed in reconstructing dielectric and ohmic profiles where conventional methods, based on travel time extraction, fail.
Directory of Open Access Journals (Sweden)
Haibo Yu
2007-02-01
Full Text Available Although the major structural transitions in molecular motors are often argued to couple to the binding of Adenosine triphosphate (ATP, the recovery stroke in the conventional myosin has been shown to be dependent on the hydrolysis of ATP. To obtain a clearer mechanistic picture for such "mechanochemical coupling" in myosin, equilibrium active-site simulations with explicit solvent have been carried out to probe the behavior of the motor domain as functions of the nucleotide chemical state and conformation of the converter/relay helix. In conjunction with previous studies of ATP hydrolysis with different active-site conformations and normal mode analysis of structural flexibility, the results help establish an energetics-based framework for understanding the mechanochemical coupling. It is proposed that the activation of hydrolysis does not require the rotation of the lever arm per se, but the two processes are tightly coordinated because both strongly couple to the open/close transition of the active site. The underlying picture involves shifts in the dominant population of different structural motifs as a consequence of changes elsewhere in the motor domain. The contribution of this work and the accompanying paper [] is to propose the actual mechanism behind these "population shifts" and residues that play important roles in the process. It is suggested that structural flexibilities at both the small and large scales inherent to the motor domain make it possible to implement tight couplings between different structural motifs while maintaining small free-energy drops for processes that occur in the detached states, which is likely a feature shared among many molecular motors. The significantly different flexibility of the active site in different X-ray structures with variable level arm orientations supports the notation that external force sensed by the lever arm may transmit into the active site and influence the chemical steps (nucleotide
Measuring Time in Sporting Competitions with the Domain-Specific Language EasyTime
Fister Jr., Iztok; Fister, Iztok
2012-01-01
Measuring time in mass sporting competitions is unthinkable manually today because of their long duration and unreliability. Besides, automatic timing devices based on the RFID technology have become cheaper. However, these devices cannot operate stand-alone. To work efficiently, they need a computer timing system for monitoring results. Such system should be capable of processing the incoming events, encoding and assigning results to a individual competitor, sorting results according to the ...
Valdés, Felipe
2013-03-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis functions and a collocation testing procedure, thus allowing for a marching-on-in-time (MOT) solution scheme. Unlike dual-source formulations, single-source equations involve space-time domain operator products, for which spatial discretization techniques developed for standalone operators do not apply. Here, the spatial discretization of the single-source time-domain integral equations is achieved by using the high-order divergence-conforming basis functions developed by Graglia alongside the high-order divergence-and quasi curl-conforming (DQCC) basis functions of Valdés The combination of these two sets allows for a well-conditioned mapping from div-to curl-conforming function spaces that fully respects the space-mapping properties of the space-time operators involved. Numerical results corroborate the fact that the proposed procedure guarantees accuracy and stability of the MOT scheme. © 2012 IEEE.
Cheng, Jiubing; Alkhalifah, Tariq Ali; Wu, Zedong; Zou, Peng; Wang, Chenlong
2016-01-01
In elastic imaging, the extrapolated vector fields are decoupled into pure wave modes, such that the imaging condition produces interpretable images. Conventionally, mode decoupling in anisotropic media is costly because the operators involved are dependent on the velocity, and thus they are not stationary. We have developed an efficient pseudospectral approach to directly extrapolate the decoupled elastic waves using low-rank approximate mixed-domain integral operators on the basis of the elastic displacement wave equation. We have applied k-space adjustment to the pseudospectral solution to allow for a relatively large extrapolation time step. The low-rank approximation was, thus, applied to the spectral operators that simultaneously extrapolate and decompose the elastic wavefields. Synthetic examples on transversely isotropic and orthorhombic models showed that our approach has the potential to efficiently and accurately simulate the propagations of the decoupled quasi-P and quasi-S modes as well as the total wavefields for elastic wave modeling, imaging, and inversion.
Cheng, Jiubing
2016-03-15
In elastic imaging, the extrapolated vector fields are decoupled into pure wave modes, such that the imaging condition produces interpretable images. Conventionally, mode decoupling in anisotropic media is costly because the operators involved are dependent on the velocity, and thus they are not stationary. We have developed an efficient pseudospectral approach to directly extrapolate the decoupled elastic waves using low-rank approximate mixed-domain integral operators on the basis of the elastic displacement wave equation. We have applied k-space adjustment to the pseudospectral solution to allow for a relatively large extrapolation time step. The low-rank approximation was, thus, applied to the spectral operators that simultaneously extrapolate and decompose the elastic wavefields. Synthetic examples on transversely isotropic and orthorhombic models showed that our approach has the potential to efficiently and accurately simulate the propagations of the decoupled quasi-P and quasi-S modes as well as the total wavefields for elastic wave modeling, imaging, and inversion.
Time-domain SFG spectroscopy using mid-IR pulse shaping: practical and intrinsic advantages.
Laaser, Jennifer E; Xiong, Wei; Zanni, Martin T
2011-03-24
Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra. © 2011 American Chemical Society
Power-feedwater temperature operating domain for Sbwr applying Monte Carlo simulation
Energy Technology Data Exchange (ETDEWEB)
Aguilar M, L. A.; Quezada G, S.; Espinosa M, E. G.; Vazquez R, A.; Varela H, J. R.; Cazares R, R. I.; Espinosa P, G., E-mail: sequega@gmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico)
2014-10-15
In this work the analyses of the feedwater temperature effects on reactor power in a simplified boiling water reactor (Sbwr) applying a methodology based on Monte Carlo simulation is presented. The Monte Carlo methodology was applied systematically to establish operating domain, due that the Sbwr are not yet in operation, the analysis of the nuclear and thermal-hydraulic processes must rely on numerical modeling, with the purpose of developing or confirming the design basis and qualifying the existing or new computer codes to enable reliable analyses. The results show that the reactor power is inversely proportional to the temperature of the feedwater, reactor power changes at 8% when the feed water temperature changes in 8%. (Author)
Power-feedwater temperature operating domain for Sbwr applying Monte Carlo simulation
International Nuclear Information System (INIS)
Aguilar M, L. A.; Quezada G, S.; Espinosa M, E. G.; Vazquez R, A.; Varela H, J. R.; Cazares R, R. I.; Espinosa P, G.
2014-10-01
In this work the analyses of the feedwater temperature effects on reactor power in a simplified boiling water reactor (Sbwr) applying a methodology based on Monte Carlo simulation is presented. The Monte Carlo methodology was applied systematically to establish operating domain, due that the Sbwr are not yet in operation, the analysis of the nuclear and thermal-hydraulic processes must rely on numerical modeling, with the purpose of developing or confirming the design basis and qualifying the existing or new computer codes to enable reliable analyses. The results show that the reactor power is inversely proportional to the temperature of the feedwater, reactor power changes at 8% when the feed water temperature changes in 8%. (Author)
A Model-free Approach to Fault Detection of Continuous-time Systems Based on Time Domain Data
Institute of Scientific and Technical Information of China (English)
Ping Zhang; Steven X. Ding
2007-01-01
In this paper, a model-free approach is presented to design an observer-based fault detection system of linear continuoustime systems based on input and output data in the time domain. The core of the approach is to directly identify parameters of the observer-based residual generator based on a numerically reliable data equation obtained by filtering and sampling the input and output signals.