Sud, Dhruv
2008-12-01
Steady-state fluorescence imaging is routinely employed to obtain physiological information but is susceptible to artifacts such as absorption and photobleaching. FLIM provides an additional source of contrast oblivious to these but is affected by factors such as pH, gases, and temperature. Here we focused on developing a resolution-enhanced FLIM system for quantitative oxygen sensing. Oxygen is one of the most critical components of metabolic machinery and affects growth, differentiation, and death. FLIM-based oxygen sensing provides a valuable tool for biologists without the need of alternate technologies. We also developed novel computational approaches to improve spatial resolution of FLIM images, extending its potential for thick tissue studies. We designed a wide-field time-domain UV-vis-NIR FLIM system with high temporal resolution (50 ps), large temporal dynamic range (750 ps -- 1 mus), short data acquisition/processing times (15 s) and noise-removal capability. Lifetime calibration of an oxygen-sensitive, ruthenium dye (RTDP) enabled in vivo oxygen level measurements (resolution = 8 muM, range = 1 -- 300 muM). Combining oxygen sensing with endogenous imaging allowed for the study of two key molecules (NADH and oxygen) consumed at the termini of the oxidative phosphorylation pathway in Barrett's adenocarcinoma columnar (SEG-1) cells and Esophageal normal squamous cells (HET-1). Starkly higher intracellular oxygen and NADH levels in living SEG-1 vs. HET-1 cells were detected by FLIM and attributed to altered metabolic pathways in malignant cells. We performed FLIM studies in microfluidic bioreactors seeded with mouse myoblasts. For these systems, oxygen concentrations play an important role in cell behavior and gene expression. Oxygen levels decreased with increasing cell densities and were consistent with simulated model outcomes. In single bioreactor loops, FLIM detected spatial heterogeneity in oxygen levels as high as 20%. We validated our calibration
van Munster, E.B.; Gadella, Th.W.J.
2004-01-01
In conventional wide-field frequency-domain fluorescence lifetime imaging microscopy (FLIM), excitation light is intensity-modulated at megahertz frequencies. Emitted fluorescence is recorded by a CCD camera through an image intensifier, which is modulated at the same frequency. From images recorded
Clinical multiphoton FLIM tomography
König, Karsten
2012-03-01
This paper gives an overview on current clinical high resolution multiphoton fluorescence lifetime imaging in volunteers and patients. Fluorescence lifetime imaging (FLIM) in Life Sciences was introduced in Jena/Germany in 1988/89 based on a ZEISS confocal picosecond dye laser scanning microscope equipped with a single photon counting unit. The porphyrin distribution in living cells and living tumor-bearing mice was studied with high spatial, temporal, and spectral resolution. Ten years later, time-gated cameras were employed to detect dental caries in volunteers based on one-photon excitation of autofluorescent bacteria with long fluorescence lifetimes. Nowadays, one-photon FLIM based on picosecond VIS laser diodes are used to study ocular diseases in humans. Already one decade ago, first clinical twophoton FLIM images in humans were taken with the certified clinical multiphoton femtosecond laser tomograph DermaInspectTM. Multiphoton tomographs with FLIM modules are now operating in hospitals at Brisbane, Tokyo, Berlin, Paris, London, Modena and other European cities. Multiple FLIM detectors allow spectral FLIM with a temporal resolution down to 20 ps (MCP) / 250 ps (PMT) and a spectral resolution of 10 nm. Major FLIM applications include the detection of intradermal sunscreen and tattoo nanoparticles, the detection of different melanin types, the early diagnosis of dermatitis and malignant melanoma, as well as the measurement of therapeutic effects in pateints suffering from dermatitis. So far, more than 1,000 patients and volunteers have been investigated with the clinical multiphoton FLIM tomographs DermaInspectTM and MPTflexTM.
pawFLIM: reducing bias and uncertainty to enable lower photon count in FLIM experiments
Silberberg, Mauro; Grecco, Hernán E.
2017-06-01
Förster resonant energy transfer measured by fluorescence lifetime imaging microscopy (FRET-FLIM) is the method of choice for monitoring the spatio-temporal dynamics of protein interactions in living cells. To obtain an accurate estimate of the molecular fraction of interacting proteins requires a large number of photons, which usually precludes the observation of a fast process, particularly with time correlated single photon counting (TCSPC) based FLIM. In this work, we propose a novel method named pawFLIM (phasor analysis via wavelets) that allows the denoising of FLIM datasets by adaptively and selectively adjusting the desired compromise between spatial and molecular resolution. The method operates by applying a weighted translational-invariant Haar-wavelet transform denoising algorithm to phasor images. This results in significantly less bias and mean square error than other existing methods. We also present a new lifetime estimator (named normal lifetime) with a smaller mean squared error and overall bias as compared to frequency domain phase and modulation lifetimes. Overall, we present an approach that will enable the observation of the dynamics of biological processes at the molecular level with better temporal and spatial resolution.
Time-Domain Fluorescence Lifetime Imaging Techniques Suitable for Solid-State Imaging Sensor Arrays
Directory of Open Access Journals (Sweden)
Robert K. Henderson
2012-05-01
Full Text Available We have successfully demonstrated video-rate CMOS single-photon avalanche diode (SPAD-based cameras for fluorescence lifetime imaging microscopy (FLIM by applying innovative FLIM algorithms. We also review and compare several time-domain techniques and solid-state FLIM systems, and adapt the proposed algorithms for massive CMOS SPAD-based arrays and hardware implementations. The theoretical error equations are derived and their performances are demonstrated on the data obtained from 0.13 μm CMOS SPAD arrays and the multiple-decay data obtained from scanning PMT systems. In vivo two photon fluorescence lifetime imaging data of FITC-albumin labeled vasculature of a P22 rat carcinosarcoma (BD9 rat window chamber are used to test how different algorithms perform on bi-decay data. The proposed techniques are capable of producing lifetime images with enough contrast.
Time Domain Induced Polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
2012-01-01
Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use...... of time-domaininduced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function......%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D...
Yahav, Gilad; Fixler, Dror; Gershanov, Sivan; Goldenberg-Cohen, Nitza
2016-03-01
Brain tumors are the second leading cause of cancer-related deaths in children, after leukemia. Patients with cancer in the central nervous system have a very low recovery rate. Today known imaging and cytology techniques are not always sensitive enough for an early detection of both tumor and its metastatic spread, moreover the detection is generally limited, reviewer dependent and takes a relatively long time. Medulloblastoma (MB) is the most common malignant brain tumor in children. The aim of our talk is to present the frequency domain fluorescence lifetime imaging microscopy system as a possible method for an early detection of MB and its metastatic spread in the cerebrospinal fluids within the pediatric population.
Energy Technology Data Exchange (ETDEWEB)
Lee, Seok-Yong [Univ. of California, Berkeley, CA (United States)
2003-04-10
Protein phosphorylation is a general mechanism for signal transduction as well as regulation of cellular function. Unlike phosphorylation in eukaryotic systems that uses Ser/Thr for the sites of modification, two-component signal transduction systems, which are prevalent in bacteria, archea, and lower eukaryotes, use an aspartate as the site of phosphorylation. Two-component systems comprise a histidine kinase and a receiver domain. The conformational change of the receiver domain upon phosphorylation leads to signal transfer to the downstream target, a process that had not been understood well at the molecular level. The transient nature of the phospho-Asp bond had made structural studies difficult. The discovery of an excellent analogue for acylphosphate, BeF_{3}^{-}, enabled structural study of activated receiver domains. The structure of activated Chemotaxis protein Y (CheY) was determined both by NMR spectroscopy and X-ray crystallography. These structures revealed the molecular basis of the conformational change that is coupled to phosphorylation. Phosphorylation of the conserved Asp residue in the active site allows hydrogen bonding of the T87 Oγ to phospho-aspartate, which in turn leads to the rotation of Y106 into the ''in'' position (termed Y-T coupling). The structure of activated CheY complexed with the 16 N-terminal residues of FliM (N16-FliM), its target, was also determined by X-ray crystallography and confirmed the proposed mechanism of activation (Y-T coupling). First, N16-FliM binds to the region on CheY that undergoes a significant conformational change. Second, the ''in'' position of Y106 presents a better binding surface for FliM because the sidechain of Y106 in the inactive form of CheY (''out'' position) sterically interferes with binding of N16-FliM. In addition to confirmation of Y-T coupling, the structure of the activated CheY-N16-FliM complex suggested that the
Heliborne time domain electromagnetic system
International Nuclear Information System (INIS)
Bhattacharya, S.
2009-01-01
Atomic Minerals Directorate (AMD), are using heliborne and ground time domain electromagnetic (TDEM) system for the exploration of deep seated unconformity type uranium deposits. Uranium has been explored in various parts of the world like Athabasca basin using time domain electromagnetic system. AMD has identified some areas in India where such deposits are available. Apart from uranium exploration, the TDEM systems are used for the exploration of deep seated minerals like diamonds. Bhabha Atomic Research Centre (BARC) is involved in the indigenous design of the heliborne time domain system since this system is useful for DAE and also it has a scope of wide application. In this paper we discuss about the principle of time domain electromagnetic systems, their capabilities and the development and problems of such system for various other mineral exploration. (author)
Flexible time domain averaging technique
Zhao, Ming; Lin, Jing; Lei, Yaguo; Wang, Xiufeng
2013-09-01
Time domain averaging(TDA) is essentially a comb filter, it cannot extract the specified harmonics which may be caused by some faults, such as gear eccentric. Meanwhile, TDA always suffers from period cutting error(PCE) to different extent. Several improved TDA methods have been proposed, however they cannot completely eliminate the waveform reconstruction error caused by PCE. In order to overcome the shortcomings of conventional methods, a flexible time domain averaging(FTDA) technique is established, which adapts to the analyzed signal through adjusting each harmonic of the comb filter. In this technique, the explicit form of FTDA is first constructed by frequency domain sampling. Subsequently, chirp Z-transform(CZT) is employed in the algorithm of FTDA, which can improve the calculating efficiency significantly. Since the signal is reconstructed in the continuous time domain, there is no PCE in the FTDA. To validate the effectiveness of FTDA in the signal de-noising, interpolation and harmonic reconstruction, a simulated multi-components periodic signal that corrupted by noise is processed by FTDA. The simulation results show that the FTDA is capable of recovering the periodic components from the background noise effectively. Moreover, it can improve the signal-to-noise ratio by 7.9 dB compared with conventional ones. Experiments are also carried out on gearbox test rigs with chipped tooth and eccentricity gear, respectively. It is shown that the FTDA can identify the direction and severity of the eccentricity gear, and further enhances the amplitudes of impulses by 35%. The proposed technique not only solves the problem of PCE, but also provides a useful tool for the fault symptom extraction of rotating machinery.
Schützhold, Vera; Fandrey, Joachim; Prost-Fingerle, Katrin
2018-01-01
Fluorescence resonance energy transfer (FRET) is widely used as a method to investigate protein-protein interactions in living cells. A FRET pair donor fluorophore in close proximity to an appropriate acceptor fluorophore transfers emission energy to the acceptor, resulting in a shorter lifetime of the donor fluorescence. When the respective FRET donor and acceptor are fused with two proteins of interest, a reduction in donor lifetime, as detected by fluorescence lifetime imaging microscopy (FLIM), can be taken as proof of close proximity between the fluorophores and therefore interaction between the proteins of interest. Here, we describe the usage of time-domain FLIM-FRET in hypoxia-related research when we record the interaction of the hypoxia-inducible factor-1 (HIF-1) subunits HIF-1α and HIF-1β in living cells in a temperature- and CO 2 -controlled environment under the microscope.
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)
Ruud G J Detert Oude Weme
Full Text Available Protein-protein interactions can be studied in vitro, e.g. with bacterial or yeast two-hybrid systems or surface plasmon resonance. In contrast to in vitro techniques, in vivo studies of protein-protein interactions allow examination of spatial and temporal behavior of such interactions in their native environment. One approach to study protein-protein interactions in vivo is via Förster Resonance Energy Transfer (FRET. Here, FRET efficiency of selected FRET-pairs was studied at the single cell level using sensitized emission and Frequency Domain-Fluorescence Lifetime Imaging Microscopy (FD-FLIM. For FRET-FLIM, a prototype Modulated Electron-Multiplied FLIM system was used, which is, to the best of our knowledge, the first account of Frequency Domain FLIM to analyze FRET in single bacterial cells. To perform FRET-FLIM, we first determined and benchmarked the best fluorescent protein-pair for FRET in Bacillus subtilis using a novel BglBrick-compatible integration vector. We show that GFP-tagRFP is an excellent donor-acceptor pair for B. subtilis in vivo FRET studies. As a proof of concept, selected donor and acceptor fluorescent proteins were fused using a linker that contained a tobacco etch virus (TEV-protease recognition sequence. Induction of TEV-protease results in loss of FRET efficiency and increase in fluorescence lifetime. The loss of FRET efficiency after TEV induction can be followed in time in single cells via time-lapse microscopy. This work will facilitate future studies of in vivo dynamics of protein complexes in single B. subtilis cells.
Multiwavelength FLIM: new concept for fluorescence diagnosis
Rück, Angelika; Lorenz, S.; Hauser, Carmen; Mosch, S.; Kalinina, S.
2012-03-01
Fluorescence guided tumor resection is very well accepted in the case of bladder cancer and brain tumor, respectively. However, false positive results are one of the major problems, which will make the discrimination between tumor tissue and inflammation difficult. In contrast fluorescence lifetime imaging (FLIM) and especially spectral resolved FLIM (SLIM) can significantly improve the analysis. The fluorescence decay of a fluorophore in many cases does not show a simple monoexponential profile. A very complex situation arises, when more than one compound has to be analyzed. This could be the case when endogenous fluorophores of living cells and tissues have to be discriminated to identify oxidative metabolic changes. Other examples are PDT, when different photosensitizer metabolites are observed simultaneously. In those cases a considerable improvement could be achieved when time-resolved and spectral-resolved techniques are simultaneously incorporated. Within this presentation the principles of spectral and time-resolved fluorescence imaging will be discussed. Successful applications as autofluorescence and 5-ALA induced porphyrin fluorescence will be described in more detail.
Calibration of TAMA300 in time domain
International Nuclear Information System (INIS)
Telada, Souichi; Tatsumi, Daisuke; Akutsu, Tomomi; Ando, Masaki; Kanda, Nobuyuki
2005-01-01
We could reconstruct the strain of gravitational wave signals from acquired data in the time domain by using the infinite impulse response filter technique in TAMA300. We would like to analyse the waveform in the time domain for burst-like signal, merger phase waveform of binary neutron stars, and so on. We established the way to make a continuous time-series gravitational wave strain signal. We compared the time-domain reconstruction with the Fourier-space reconstruction. Both coincided within 3% in the observation range. We could also produce the voltage signal which would be recorded by the data-acquisition system from a simulated gravitational wave. This is useful for some analyses of simulations and signal injections. We could extract the waveform of the hardware injection signal in an observational run in the time domain. The extracted waveform was similar to the injection signal
A time domain technique for mechanism extraction
Dominek, Allen K.; Peters, Leon, Jr.; Burnside, Walter D.
1987-01-01
The properties of scattered fields from a structure can be better evaluated from the characteristics of the individual scatterers. Decomposition techniques can be classified either as a matrix or an integral formulation. With either formulation, aspect pattern of frequency information of a scattering center can be obtained. Emphasis is placed on an integral (time domain) isolation extraction technique to obtain the frequency characteristics of scattering mechanisms. This technique has its origins in the time domain interpretation of scattered fields.
Time Domain Astronomy with Swift and Fermi
African Journals Online (AJOL)
J.D. Myers
Time Domain Astronomy with Swift and Fermi. N. Gehrels1, J. K. Cannizzo23. 1NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771, USA. 2CRESST and Astroparticle Physics Laboratory, NASA/GSFC, Greenbelt, MD 20771, USA. 3Department of Physics, University of Maryland, Baltimore County, ...
Multiple Shooting and Time Domain Decomposition Methods
Geiger, Michael; Körkel, Stefan; Rannacher, Rolf
2015-01-01
This book offers a comprehensive collection of the most advanced numerical techniques for the efficient and effective solution of simulation and optimization problems governed by systems of time-dependent differential equations. The contributions present various approaches to time domain decomposition, focusing on multiple shooting and parareal algorithms. The range of topics covers theoretical analysis of the methods, as well as their algorithmic formulation and guidelines for practical implementation. Selected examples show that the discussed approaches are mandatory for the solution of challenging practical problems. The practicability and efficiency of the presented methods is illustrated by several case studies from fluid dynamics, data compression, image processing and computational biology, giving rise to possible new research topics. This volume, resulting from the workshop Multiple Shooting and Time Domain Decomposition Methods, held in Heidelberg in May 2013, will be of great interest to applied...
Parametric time-frequency domain spatial audio
Delikaris-Manias, Symeon; Politis, Archontis
2018-01-01
This book provides readers with the principles and best practices in spatial audio signal processing. It describes how sound fields and their perceptual attributes are captured and analyzed within the time-frequency domain, how essential representation parameters are coded, and how such signals are efficiently reproduced for practical applications. The book is split into four parts starting with an overview of the fundamentals. It then goes on to explain the reproduction of spatial sound before offering an examination of signal-dependent spatial filtering. The book finishes with coverage of both current and future applications and the direction that spatial audio research is heading in. Parametric Time-frequency Domain Spatial Audio focuses on applications in entertainment audio, including music, home cinema, and gaming--covering the capturing and reproduction of spatial sound as well as its generation, transduction, representation, transmission, and perception. This book will teach readers the tools needed...
Sun, Yuansheng; Coskun, Ulas; Ferreon, Allan Chris; Barbieri, Beniamino; Liao, Shih-Chu Jeff
2016-03-01
The crosstalk between two fluorescent species causes problems in fluorescence microscopy imaging, especially for quantitative measurements such as co-localization, Förster resonance energy transfer (FRET), fluorescence cross correlation spectroscopy (FCCS). In laser scanning confocal microscopy, the lasers can be switched on and off by acousto-optic tunable filters (AOTF) in the microsecond scale for alternative line scanning in order to avoid the crosstalk while minimizing the time delay between two lasers on the same pixel location. In contrast, the pulsed interleaved excitation (PIE) technique synchronizes two pulsed lasers of different wavelengths in the nanosecond scale to enable measuring superfast dynamics of two fluorescent species simultaneously and yet quantitatively without the crosstalk contamination. This feature is critical for many cell biology applications, e.g. accurate determination of stoichiometry in FRET measurements for studying protein-protein interactions or cell signal events, detection of weaker bindings in FCCS by eliminating the false cross correlation due to the crosstalk. The PIE has been used with the time correlated single photon counting (TCSPC) electronics. Here, we describe a novel PIE development using the digital frequency domain (DFD) technique -- FastFLIM, which provides tunable PIE setups and synchronized gating detections, tailored and optimized to specific applications. A few PIE setups by FastFLIM and measurement examples are described. Combined with the sensitivity of Alba and Q2 systems, the PIE allowed us to quantitatively measure the fast dynamics of single molecules.
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.
Atherosclerosis staging: imaging using FLIM technique
Sicchieri, Leticia B.; Barioni, Marina Berardi; Silva, Mônica Nascimento; Monteiro, Andrea Moreira; Figueiredo Neto, Antonio Martins; Ito, Amando S.; Courrol, Lilia C.
2014-03-01
In this work it was used fluorescence lifetime imaging (FLIM) to analyze biochemical composition of atherosclerotic plaque. For this purpose an animal experimentation was done with New Zealand rabbits divided into two groups: a control group of 4 rabbits that received a regular diet for 0, 20, 40 and 60 days; and an experimental group of 9 rabbits, divided in 3 subgroups, that were fed with 1% cholesterol diet for 20, 40 and 60 days respectively. The aortas slices stained with europium chlortetracycline were analyzed by FLIM exciting samples at 440 nm. The results shown an increase in the lifetime imaging of rabbits fed with cholesterol. It was observed that is possible to detect the metabolic changes associated with atherosclerosis at an early stage using FLIM technique exciting the tissue around 440 nm and observing autofluorescence lifetime. Lifetimes longer than 1.75 ns suggest the presence of porphyrins in the tissue and consequently, inflammation and the presence of macrophages.
High frame-rate TCSPC-FLIM using a novel SPAD-based image sensor
Gersbach, M.; Trimananda, R.; Maruyama, Y.; Fishburn, M.; Cahrbon, E. et al
2010-01-01
Imaging techniques based on time-correlated single photon counting (TCSPC), such as fluorescence lifetime imaging microscopy (FLIM), rely on fast single-photon detectors as well as timing electronics in the form of time-to-digital or time-to-analog converters. Conventional systems rely on
Time Domain Diffraction by Composite Structures
Riccio, Giovanni; Frongillo, Marcello
2017-04-01
Time domain (TD) diffraction problems are receiving great attention because of the widespread use of ultra wide band (UWB) communication and radar systems. It is commonly accepted that, due to the large bandwidth of the UWB signals, the analysis of the wave propagation mechanisms in the TD framework is preferable to the frequency domain (FD) data processing. Furthermore, the analysis of transient scattering phenomena is also of importance for predicting the effects of electromagnetic pulses on civil structures. Diffraction in the TD framework represents a challenging problem and numerical discretization techniques can be used to support research and industry activities. Unfortunately, these methods become rapidly intractable when considering excitation pulses with high frequency content. This contribution deals with the TD diffraction phenomenon related to composite structures containing a dielectric wedge with arbitrary apex angle when illuminated by a plane wave. The approach is the same used in [1]-[3]. The transient diffracted field originated by an arbitrary function plane wave is evaluated via a convolution integral involving the TD diffraction coefficients, which are determined in closed form starting from the knowledge of the corresponding FD counterparts. In particular, the inverse Laplace transform is applied to the FD Uniform Asymptotic Physical Optics (FD-UAPO) diffraction coefficients available for the internal region of the structure and the surrounding space. For each observation domain, the FD-UAPO expressions are obtained by considering electric and magnetic equivalent PO surface currents located on the interfaces. The surface radiation integrals using these sources is assumed as starting point and manipulated for obtaining integrals able to be solved by means of the Steepest Descent Method and the Multiplicative Method. [1] G. Gennarelli and G. Riccio, "Time domain diffraction by a right-angled penetrable wedge," IEEE Trans. Antennas Propag., Vol
Architectures for Time-domain Astronomy
Seaman, R.; Allan, A.; Pierfederici, F.; Williams, R.
2009-09-01
Wonder at the changing sky predates recorded history. Empirical studies of time-varying celestial phenomena date back to Galileo and Tycho. Telegrams conveying news of transient and recurrent events have been key astronomical infrastructure since the nineteenth century. Recent micro-lensing, supernova and gamma-ray burst studies have lead to a succession of exciting discoveries, but massive new time-domain surveys will soon overwhelm our nineteenth century transient response technologies. Meeting this challenge demands new autonomous architectures for astronomy. These Architectures should reach from proposing new research, through experimental design and the scheduling of telescope operations, to the archiving and pipeline-processing of data to discover new transients, to the publishing of these events, through automated follow-up via robotic and ToO assets, and to the display and analysis of observational results. All will lead to adaptive adjustment of time-domain investigations. The IVOA VOEvent protocol provides an engine for purpose-built astronomical architectures.
Exploration of the Time Domain (Abstract)
Djorgovski, G.
2017-06-01
(Abstract only) Time-domain astronomy is one of the most active and growing areas of astronomical research today, thanks to the new generation of synoptic sky surveys, and leading to LSST. Catalina Real-Time Transient Survey (CRTS; http://crts.caltech.edu) is systematically exploring and characterizing the variable sky since 2008, with the archival data going back to 2005. The survey covers the total area of 33,000 deg2, down to 19±21 mag per exposure, with time baselines from 10 min to 10 years, and growing; there are now typically 200±400 exposures per pointing, and coadded images reach deeper than 23 magnitude. The survey has so far detected over 13,000 unique, high-amplitude transients, including 4,000 confirmed or likely supernovae, nearly 2,000 CVs (the great majority of them previously uncatalogued), about 4,000 blazars and other flaring AGN, and a broad variety of other types of objects. Many of these objects can benefit from a follow-up by the amateur community. CRTS is intended to be a data resource for the entire astronomical community. We have a completely open data policy: all discovered transient events are published in real time with no proprietary delay period, and all data are made public, in order to better serve the entire community, and maximize the scientific returns. This includes an archive of 500 million light curves, which are being updated continuously. This is an unprecedented data set for the exploration of the time domain, in terms of the area, depth, and temporal coverage. Numerous scientific projects have been enabled by this data stream, including: discoveries of ultraluminous and otherwise peculiar SNe; unusual CVs and dwarf novae; mapping of the structure in the Galactic halo using RR Lyrae; variability-based discovery of AGN and probes of their physics; and so on.
Coherent combining pulse bursts in time domain
Galvanauskas, Almantas
2018-01-09
A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
Domain enhanced lookup time accelerated BLAST
Directory of Open Access Journals (Sweden)
Boratyn Grzegorz M
2012-04-01
Full Text Available Abstract Background BLAST is a commonly-used software package for comparing a query sequence to a database of known sequences; in this study, we focus on protein sequences. Position-specific-iterated BLAST (PSI-BLAST iteratively searches a protein sequence database, using the matches in round i to construct a position-specific score matrix (PSSM for searching the database in round i + 1. Biegert and Söding developed Context-sensitive BLAST (CS-BLAST, which combines information from searching the sequence database with information derived from a library of short protein profiles to achieve better homology detection than PSI-BLAST, which builds its PSSMs from scratch. Results We describe a new method, called domain enhanced lookup time accelerated BLAST (DELTA-BLAST, which searches a database of pre-constructed PSSMs before searching a protein-sequence database, to yield better homology detection. For its PSSMs, DELTA-BLAST employs a subset of NCBI’s Conserved Domain Database (CDD. On a test set derived from ASTRAL, with one round of searching, DELTA-BLAST achieves a ROC5000 of 0.270 vs. 0.116 for CS-BLAST. The performance advantage diminishes in iterated searches, but DELTA-BLAST continues to achieve better ROC scores than CS-BLAST. Conclusions DELTA-BLAST is a useful program for the detection of remote protein homologs. It is available under the “Protein BLAST” link at http://blast.ncbi.nlm.nih.gov. Reviewers This article was reviewed by Arcady Mushegian, Nick V. Grishin, and Frank Eisenhaber.
Studying membrane properties using Fluorescence Lifetime Imaging Microscopy (FLIM)
Stöckl, M.T.; Bizzarri, R.; Subramaniam, Vinod; Mely, Y.; Duportail, G.
2012-01-01
Fluorescence lifetime imaging microscopy (FLIM) is a powerful tool to investigate the structure and composition of biological membranes. A wide variety of fluorescent probes suitable for FLIM experiments have been described. These compounds differ strongly in the details of their incorporation into
de Almeida, Rodrigo F M; Loura, Luís M S; Prieto, Manuel
2009-02-01
Membrane microdomains and their involvement in cellular processes are part of the current paradigm of biomembranes. However, a better characterization of domains, namely lipid rafts, is needed. In this review, it is shown how the use of time-resolved fluorescence, with the adequate parameters and probes, helps elucidating the type, number, fraction, composition and size of lipid phases and domains in multicomponent model systems. The determination of phase diagrams for lipid mixtures containing sphingolipids and/or cholesterol is exemplified. The use of fluorescence quenching and Förster resonance energy transfer (FRET) are also illustrated. Strategies for studying protein-induced domains are presented. The advantages of using single point microscopic decays and fluorescence lifetime imaging microscopy (FLIM) in systems with three-phase coexistence are explained. Finally, the introduction of FLIM allows studies in live cell membranes, and the nature of the microdomains observed is readily elucidated due to the information retrieved from fluorescence lifetimes.
Conversion of Dielectric Data from the Time Domain to the Frequency Domain
Directory of Open Access Journals (Sweden)
Vladimir Durman
2005-01-01
Full Text Available Polarisation and conduction processes in dielectric systems can be identified by the time domain or the frequency domain measurements. If the systems is a linear one, the results of the time domain measurements can be transformed into the frequency domain, and vice versa. Commonly, the time domain data of the absorption conductivity are transformed into the frequency domain data of the dielectric susceptibility. In practice, the relaxation are mainly evaluated by the frequency domain data. In the time domain, the absorption current measurement were prefered up to now. Recent methods are based on the recovery voltage measurements. In this paper a new method of the recovery data conversion from the time the frequency domain is proposed. The method is based on the analysis of the recovery voltage transient based on the Maxwell equation for the current density in a dielectric. Unlike the previous published solutions, the Laplace fransform was used to derive a formula suitable for practical purposes. the proposed procedure allows also calculating of the insulation resistance and separating the polarisation and conduction losses.
Time-domain radio pulses from particle showers
International Nuclear Information System (INIS)
Alvarez-Muñiz, Jaime; Romero-Wolf, Andrés; Zas, Enrique
2012-01-01
The time-domain properties of the far-field coherent radio emission from electromagnetic showers are studied in depth. A purely time-domain technique for mapping the electromagnetic fields of charged tracks is developed. The method is applied to the ZHS shower code to produce electric fields. It is demonstrated that the technique is equivalent to the frequency domain methods used in the ZHS code and produces consistent results. In addition, a model for mapping the longitudinal charge profile of a shower to a time-domain electromagnetic field is developed. It is shown that the model is in good agreement to the results of shower simulation.
Eibl, Matthias; Karpf, Sebastian; Hakert, Hubertus; Weng, Daniel; Pfeiffer, Tom; Kolb, Jan Philip; Huber, Robert
2017-07-01
Newly developed microscopy methods have the goal to give researches in bio-molecular science a better understanding of processes ongoing on a cellular level. Especially two-photon excited fluorescence (TPEF) microscopy is a readily applied and widespread modality. Compared to one photon fluorescence imaging, it is possible to image not only the surface but also deeper lying structures. Together with fluorescence lifetime imaging (FLIM), which provides information on the chemical composition of a specimen, deeper insights on a molecular level can be gained. However, the need for elaborate light sources for TPEF and speed limitations for FLIM hinder an even wider application. In this contribution, we present a way to overcome this limitations by combining a robust and inexpensive fiber laser for nonlinear excitation with a fast analog digitization method for rapid FLIM imaging. The applied sub nanosecond pulsed laser source is perfectly suited for fiber delivery as typically limiting non-linear effects like self-phase or cross-phase modulation (SPM, XPM) are negligible. Furthermore, compared to the typically applied femtosecond pulses, our longer pulses produce much more fluorescence photons per single shot. In this paper, we show that this higher number of fluorescence photons per pulse combined with a high analog bandwidth detection makes it possible to not only use a single pulse per pixel for TPEF imaging but also to resolve the exponential time decay for FLIM. To evaluate our system, we acquired FLIM images of a dye solution with single exponential behavior to assess the accuracy of our lifetime determination and also FLIM images of a plant stem at a pixel rate of 1 MHz to show the speed performance of our single pulse two-photon FLIM (SP-FLIM) system.
Alternating Direction Implicit Finite Difference Time Domain Acoustic ...
African Journals Online (AJOL)
A time domain numerical technique is presented for the modelling of acoustic wave phenomena. The technique is an adaptation of the alternating direction implicit finite difference time domain method. The stability condition for the algorithm is given. Simple illustrations of propagation in an infinite homogeneous medium are ...
Structural Time Domain Identification (STDI) Toolbox for Use with MATLAB
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
1997-01-01
The Structural Time Domain Identification (STDI) toolbox for use with MATLABTM is developed at Aalborg University, Denmark, based on the system identification research performed during recent years. By now, a reliable set of functions offers a wide spectrum of services for all the important steps...... of multivariate time domain system identification of time-variant as well as time-invariant civil engineering structures from ambient testing data. A graphical user interface (GUI) is also developed to make the toolbox more user friendly....
Parameter Estimation in Continuous Time Domain
Directory of Open Access Journals (Sweden)
Gabriela M. ATANASIU
2016-12-01
Full Text Available This paper will aim to presents the applications of a continuous-time parameter estimation method for estimating structural parameters of a real bridge structure. For the purpose of illustrating this method two case studies of a bridge pile located in a highly seismic risk area are considered, for which the structural parameters for the mass, damping and stiffness are estimated. The estimation process is followed by the validation of the analytical results and comparison with them to the measurement data. Further benefits and applications for the continuous-time parameter estimation method in civil engineering are presented in the final part of this paper.
Underwater Advanced Time-Domain Electromagnetic System
2017-03-03
sufficiently waterproofed ...................................................................... 20 Objective: Calibration method can be used both topside... additional background variability is observed at early times, as illustrated in Figure 15. The layout of this figure is the same as Figure 14. Now the...are discussed in the following sections and summarized in Table 5. Objective: System is sufficiently waterproofed The array remained underwater up to
Time Domain Astrochemistry in Protoplanetary Disks
Cleeves, Lauren Ilsedore
2018-01-01
The chemistry of protoplanetary disks sets the initial composition of newly formed planets and may regulate the efficiency by which planets form. Disk chemical abundances typically evolve over timescales spanning thousands if not millions of years. Consequently, it was a surprise when ALMA observations taken over the course of a single year showed significantly variable emission in H13CO+ relative to the otherwise constant thermal dust emission in the IM Lup protoplanetary disk. HCO+ is a known X-ray sensitive molecule, and by using simple time-evolving chemical models including stellar activity, we demonstrate that stellar X-ray flares are a viable explanation for the observed H13CO+ variability. If this link between chemistry and stellar activity is confirmed, simultaneous observations can provide a new tool to measure (and potentially map) fundamental disk parameters, such as electron density, as the light from X-ray flares propagates across the disk.
A time domain phase-gradient based ISAR autofocus algorithm
CSIR Research Space (South Africa)
Nel, W
2011-10-01
Full Text Available Autofocus is a well known required step in ISAR (and SAR) processing to compensate translational motion. This research proposes a time domain autofocus algorithm and discusses its relation to the well known phase gradient autofocus (PGA) technique...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation Project
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a high speed automated time domain terahertz computed axial tomography (TD-THz CT) non destructive...
Directory of Open Access Journals (Sweden)
Changyong Cheng
2018-02-01
Full Text Available Listeria monocytogenes is a food-associated bacterium that is responsible for food-related illnesses worldwide. In the L. monocytogenes EGD-e genome, FlhB, FliM, and FliY (encoded by lmo0679, lmo0699, and lmo0700, respectively are annotated as putative flagella biosynthesis factors, but their functions remain unknown. To explore whether FlhB, FliM, and FliY are involved in Listeria flagella synthesis, we constructed flhB, fliM, fliY, and other flagellar-related gene deletion mutants using a homologous recombination strategy. Then, we analyzed the motility, flagella synthesis, and protein expression of these mutant strains. Motility and flagella synthesis were completely abolished in the absence of flhB, fliM, or fliY. These impaired phenotypes were fully restored in the complemented strains CΔflhB, CΔfliM, and CΔfliY. The transcriptional levels of flagellar-related genes, including flaA, fliM, fliY, lmo0695, lmo0698, fliI, and fliS, were downregulated markedly in the absence of flhB, fliM, or fliY. Deletion of flhB resulted in the complete abolishment of FlaA expression, while it decreased FliM and FliY expression. The expression of FlaA was abolished completely in the absence of fliM or fliY. No significant changes were found in the expression of FlhF and two flagella synthesis regulatory factors, MogR and GmaR. We demonstrate for the first time that FlhB, FliM, and FliY not only mediate Listeria motility, but also are involved in regulating flagella synthesis. This study provides novel insights that increase our understanding of the roles played by FlhB, FliM, and FliY in the flagellar type III secretion system in L. monocytogenes.
Time domain referencing in intensity modulation fiber optic sensing systems
Adamovsky, G.
1986-01-01
Intensity modulation sensors are classified depending on the way in which the reference and signal channels are separated: in space, wavelength (frequency), or time domains. To implement the time domain referencing different types of fiber optic (FO) loops have been used. A pulse of short duration sent into the loop results in a series of pulses of different amplitudes. The information about the measured parameter is retrieved from the relative amplitudes of pulses in the same train.
Time domain modeling of tunable response of graphene
DEFF Research Database (Denmark)
Prokopeva, Ludmila; Emani, Naresh K.; Boltasseva, Alexandra
2013-01-01
We present a causal numerical model for time domain simulations of the optical response of graphene. The dielectric function is approximated with a conductivity term, a Drude term and a number of the critical points terms.......We present a causal numerical model for time domain simulations of the optical response of graphene. The dielectric function is approximated with a conductivity term, a Drude term and a number of the critical points terms....
Three Dimensional Energy Transmitting Boundary in the Time Domain
Directory of Open Access Journals (Sweden)
Naohiro eNakamura
2015-11-01
Full Text Available Although the energy transmitting boundary is accurate and efficient for the FEM earthquake response analysis, it could be applied in the frequency domain only. In the previous papers, the author proposed an earthquake response analysis method using the time domain energy transmitting boundary for two dimensional problems. In this paper, this technique is expanded for three dimensional problems. The inner field is supposed to be a hexahedron shape and the approximate time domain boundary is explained, first. Next, two dimensional anti-plane time domain boundary is studied for a part of the approximate three dimensional boundary method. Then, accuracy and efficiency of the proposed method are confirmed by example problems.
Thermal Loss of High-Q Antennas in Time Domain vs. Frequency Domain Solver
DEFF Research Database (Denmark)
Bahramzy, Pevand; Pedersen, Gert Frølund
2014-01-01
High-Q structures pose great challenges to their loss simulations in Time Domain Solvers (TDS). Therefore, in this work the thermal loss of high-Q antennas is calculated both in TDS and Frequency Domain Solver (FDS), which are then compared with each other and with the actual measurements....... The thermal loss calculation in FDS is shown to be more accurate for high-Q antennas....
Broadband Beamspace DOA Estimation: Frequency-Domain and Time-Domain Processing Approaches
Directory of Open Access Journals (Sweden)
Yan Shefeng
2007-01-01
Full Text Available Frequency-domain and time-domain processing approaches to direction-of-arrival (DOA estimation for multiple broadband far field signals using beamspace preprocessing structures are proposed. The technique is based on constant mainlobe response beamforming. A set of frequency-domain and time-domain beamformers with constant (frequency independent mainlobe response and controlled sidelobes is designed to cover the spatial sector of interest using optimal array pattern synthesis technique and optimal FIR filters design technique. These techniques lead the resulting beampatterns higher mainlobe approximation accuracy and yet lower sidelobes. For the scenario of strong out-of-sector interfering sources, our approaches can form nulls or notches in the direction of them and yet guarantee that the mainlobe response of the beamformers is constant over the design band. Numerical results show that the proposed time-domain processing DOA estimator has comparable performance with the proposed frequency-domain processing method, and that both of them are able to resolve correlated source signals and provide better resolution at lower signal-to-noise ratio (SNR and lower root-mean-square error (RMSE of the DOA estimate compared with the existing method. Our beamspace DOA estimators maintain good DOA estimation and spatial resolution capability in the scenario of strong out-of-sector interfering sources.
Using random response input in Ibrahim Time Domain
DEFF Research Database (Denmark)
Olsen, Peter; Brincker, R.
2013-01-01
In this paper the time domain technique Ibrahim Time Domain (ITD) is used to analyze random time data. ITD is known to be a technique for identification of output only systems. The traditional formulation of ITD is claimed to be limited, when identifying closely spaced modes, because of the techn....... In this article it is showed that when using the modified ITD random time data can be analyzed. The application of the technique is displayed by a case study, with simulations and experimental data....
Frequency and voice: perspectives in the time domain.
Roark, Rick M
2006-09-01
Frequency variation is one of the most primitive features of voice production, endowing language and communication with richness and efficiency and enhancing enjoyment of the voice arts. In the first of two tutorial articles, the subject of frequency is examined formally, beginning in the time domain. A companion article explores the topic of frequency and voice from the frequency domain perspective. Frequency is a well-defined quantity of the sinusoidal function and of periodic functions of time. However, voice is inherently nonstationary, even over short time segments, to degrees that range from minor (stable vowels of a healthy voice) to major (singing voice and voiced consonants). For signals that are not periodic, the notion of frequency is ambiguous and often altogether unclear, which has led to a multitude of frequency-measurement techniques and discrepancy of measures. This article identifies the source of these discrepancies for a variety of time-domain techniques that are examined in the absence of noise. In the time domain, the subject of frequency is inherently coupled to the topic of signal modeling, which is explored in some detail. Sinusoidal models having time-varying phase are examined with the objective of achieving a frequency description of voice that is both continuous and instantaneous. The analytic signal method of mathematical physics is discussed and applied to the technology of empirical mode decomposition to demonstrate that the frequencies of voice may be comprehensively examined from the time domain point of view.
Runaway domain wall and space-time varying α
International Nuclear Information System (INIS)
Chiba, Takeshi; Yamaguchi, Masahide
2011-01-01
Recently spatial as well as temporal variations of the fine structure constant α have been reported. We show that a ''runaway domain wall , which arises for the scalar field potential without minima, can account for such variations simultaneously. The time variation is induced by a runaway potential and the spatial variation is induced by the formation of a domain wall. The model is consistent with the current cosmological data and can be tested by the future experiments to test the equivalence principle
Cerenkov radio pulses from electromagnetic showers in the time domain
International Nuclear Information System (INIS)
Alvarez-Muniz, Jaime; Romero-Wolf, Andres; Zas, Enrique
2010-01-01
The electric field of the Cerenkov radio pulse produced by a single charged particle track in a dielectric medium is derived from first principles. An algorithm is developed to obtain the pulse in the time domain for numerical calculations. The algorithm is implemented in a Monte Carlo simulation of electromagnetic showers in dense media (specifically designed for coherent radio emission applications) as might be induced by interactions of ultrahigh energy neutrinos. The coherent Cerenkov radio emission produced by such showers is obtained simultaneously both in the time and frequency domains. A consistency check performed by Fourier transforming the pulse in time and comparing it to the frequency spectrum obtained directly in the simulations yields, as expected, fully consistent results. The reversal of the time structure inside the Cerenkov cone and the signs of the corresponding pulses are addressed in detail. The results, besides testing algorithms used for reference calculations in the frequency domain, shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cerenkov direction. This information can be of great practical importance for interpreting actual data.
Simulation of compressible viscous flow in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Česenek, J.; Feistauer, M.; Horáček, Jaromír; Kučera, V.; Prokopova, J.
2013-01-01
Roč. 219, č. 13 (2013), s. 7139-7150 ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : time dependent domain * ALE method * semi-implicit time discretization * shock indicator Subject RIV: BI - Acoustics Impact factor: 1.600, year: 2013
Multi-time-step domain coupling method with energy control
DEFF Research Database (Denmark)
Mahjoubi, N.; Krenk, Steen
2010-01-01
A multi-time-step integration method is proposed for solving structural dynamics problems on multiple domains. The method generalizes earlier state-space integration algorithms by introducing displacement constraints via Lagrange multipliers, representing the time-integrated constraint forces over...
Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates
DEFF Research Database (Denmark)
Takeya, Kei; Zhang, Caihong; Kawayama, Iwao
2009-01-01
For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has a charact......For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has...
Modern EMC analysis I time-domain computational schemes
Kantartzis, Nikolaos V
2008-01-01
The objective of this two-volume book is the systematic and comprehensive description of the most competitive time-domain computational methods for the efficient modeling and accurate solution of contemporary real-world EMC problems. Intended to be self-contained, it performs a detailed presentation of all well-known algorithms, elucidating on their merits or weaknesses, and accompanies the theoretical content with a variety of applications. Outlining the present volume, the analysis covers the theory of the finite-difference time-domain, the transmission-line matrix/modeling, and the finite i
[Terahertz time-domain spectroscopy of Clenbuterol hydrochloride].
Chen, Xi-ai; Hou, Di-bo; Huang, Ping-jie; Kang, Xu-sheng; Zhang, Guang-xin; Zhou, Ze-kui
2011-12-01
The terahertz spectra of Clenbuterol hydrochloride in the range of 0.2 to 2.6 THz were obtained by THz time-domain spectroscopy, the absorption and refraction spectra of Clenbuterol hydrochloride was got meanwhile. The structure and vibrational frequencies of Clenbuterol molecule, Clenbuterol hydrochloride molecule and Clenbuterol hydrochloride crystal in the THz range were simulated. Based on the difference between experimental and theoretical results, the origin of the vibrational frequencies was analyzed. This study demonstrated the feasibility of time-domain terahertz spectroscopy for the identification of Clenbuterol hydrochloride and provides a new way for the detection of Clenbuterol hydrochloride.
Real-time background suppression during frequency domain lifetime measurements.
Herman, Petr; Maliwal, Badri P; Lakowicz, Joseph R; Maliwal, Baldri P
2002-10-01
We describe real time background suppression of autofluorescence from biological samples during frequency domain or phase modulation measurements of intensity decays. For these measurements the samples were excited with a train of light pulses with widths below 1 ps. The detector was gated off for a short time period of 10 to 40 ns during and shortly after the excitation pulse. The reference signal needed for the frequency domain measurement was provided by a long-lifetime reference fluorophore which continues to emit following the off-gating pulse. Both the sample and the reference were measured under identical optical and electronic conditions avoiding the need for correction of the photomultiplier tube signal for the gating sequence. We demonstrate frequency domain background suppression using a mixture of short- and long-lifetime probes and for a long-lifetime probe in human plasma with significant autofluorescence.
Explicit solution of Calderon preconditioned time domain integral equations
Ulku, Huseyin Arda
2013-07-01
An explicit marching on-in-time (MOT) scheme for solving Calderon-preconditioned time domain integral equations is proposed. The scheme uses Rao-Wilton-Glisson and Buffa-Christiansen functions to discretize the domain and range of the integral operators and a PE(CE)m type linear multistep to march on in time. Unlike its implicit counterpart, the proposed explicit solver requires the solution of an MOT system with a Gram matrix that is sparse and well-conditioned independent of the time step size. Numerical results demonstrate that the explicit solver maintains its accuracy and stability even when the time step size is chosen as large as that typically used by an implicit solver. © 2013 IEEE.
Structural Time Domain Identification (STDI) Toolbox for Use with MATLAB
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
1997-01-01
The Structural Time Domain Identification (STDI) toolbox for use with MATLABTM is developed at Aalborg University, Denmark, based on the system identification research performed during recent years. By now, a reliable set of functions offers a wide spectrum of services for all the important steps...
Structural Time Domain Identification (STDI) Toolbox for Use with MATLAB
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Andersen, P.; Brincker, Rune
The Structural Time Domain Identification (STDI) toolbox for use with MATLABTM is developed at Aalborg University, Denmark, based on the system identification research performed during recent years. By now, a reliable set of functions offers a wide spectrum of services for all the important steps...
Nonlinear time-domain modeling of balanced-armature receivers
DEFF Research Database (Denmark)
Jensen, Joe; Agerkvist, Finn T.; Harte, James
2011-01-01
of the loudspeaker diaphragm inevitably changes the magnetic and electrical characteristics of the loudspeaker. A numerical time-domain model capable of describing these nonlinearities is presented. By simulation it is demonstrated how the output distortion could potentially be reduced significantly through careful...
A pseudospectral collocation time-domain method for diffractive optics
DEFF Research Database (Denmark)
Dinesen, P.G.; Hesthaven, J.S.; Lynov, Jens-Peter
2000-01-01
We present a pseudospectral method for the analysis of diffractive optical elements. The method computes a direct time-domain solution of Maxwell's equations and is applied to solving wave propagation in 2D diffractive optical elements. (C) 2000 IMACS. Published by Elsevier Science B.V. All rights...
Frequency-domain criterion for the chaos synchronization of time ...
Indian Academy of Sciences (India)
This paper studies the global synchronization of non-autonomous, time-delay, chaotic power systems via linear state-error feedback control. The frequency domain criterion and the LMI criterion are proposed and applied to design the coupling matrix. Some algebraic criteria via a single-variable linear coupling are derived ...
Assessment of perceptual diffuseness in the time domain
DEFF Research Database (Denmark)
Garcia, Julian Martinez-Villalba; Jeong, Cheol-Ho; Brunskog, Jonas
2017-01-01
This study proposes a numerical and experimental framework for evaluating the perceptual aspect of the diffuse field condition with intended final use in music auditoria. Multiple Impulse Responses are simulated based on the time domain Poisson process with increasing reflection density. Different...
Ultrabroadband THz time-domain spectroscopy of biomolecular crystals
DEFF Research Database (Denmark)
Kaltenecker, Korbinian J.; Engelbrecht, Sebastian; Iwaszczuk, Krzysztof
2016-01-01
Ultrabroadband THz time-domain spectroscopy based on two-color plasma generation and air biased coherent detection is used for the investigation of molecular dynamics of crystalline materials in the frequency range from 0.3 THz to 20 THz. We show that the spectral features in this extended freque...
Time-domain seismic reliability of nonlinear structures
Indian Academy of Sciences (India)
Abstract. A novel reliability analysis technique is presented to estimate the reli- ability of real structural systems. Its unique feature is that the dynamic loadings can be applied in time domain. It is a nonlinear stochastic finite element logarithm combined with the response surface method (RSM). It generates the response sur-.
Terahertz time-domain spectroscopy and imaging of artificial RNA
DEFF Research Database (Denmark)
Fischer, Bernd M.; Hoffmann, Matthias; Helm, Hanspeter
2005-01-01
We use terahertz time-domain spectroscopy (THz-TDS) to measure the far-infrared dielectric function of two artificial RNA single strands, composed of polyadenylic acid (poly-A) and polycytidylic acid (poly-C). We find a significant difference in the absorption between the two types of RNA strands...
Differences between time domain and Fourier domain optical coherence tomography in imaging tissues.
Gao, W; Wu, X
2017-11-01
It has been numerously demonstrated that both time domain and Fourier domain optical coherence tomography (OCT) can generate high-resolution depth-resolved images of living tissues and cells. In this work, we compare the common points and differences between two methods when the continuous and random properties of live tissue are taken into account. It is found that when relationships that exist between the scattered light and tissue structures are taken into account, spectral interference measurements in Fourier domain OCT (FDOCT) is more advantageous than interference fringe envelope measurements in time domain OCT (TDOCT) in the cases where continuous property of tissue is taken into account. It is also demonstrated that when random property of tissue is taken into account FDOCT measures the Fourier transform of the spatial correlation function of the refractive index and speckle phenomena will limit the effective limiting imaging resolution in both TDOCT and FDOCT. Finally, the effective limiting resolution of both TDOCT and FDOCT are given which can be used to estimate the effective limiting resolution in various practical applications. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.
Time Domain Partitioning of Electricity Production Cost Simulations
Energy Technology Data Exchange (ETDEWEB)
Barrows, C. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hummon, M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Jones, W. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hale, E. [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2014-01-01
Production cost models are often used for planning by simulating power system operations over long time horizons. The simulation of a day-ahead energy market can take several weeks to compute. Tractability improvements are often made through model simplifications, such as: reductions in transmission modeling detail, relaxation of commitment variable integrality, reductions in cost modeling detail, etc. One common simplification is to partition the simulation horizon so that weekly or monthly horizons can be simulated in parallel. However, horizon partitions are often executed with overlap periods of arbitrary and sometimes zero length. We calculate the time domain persistence of historical unit commitment decisions to inform time domain partitioning of production cost models. The results are implemented using PLEXOS production cost modeling software in an HPC environment to improve the computation time of simulations while maintaining solution integrity.
Parallel time domain solvers for electrically large transient scattering problems
Liu, Yang
2014-09-26
Marching on in time (MOT)-based integral equation solvers represent an increasingly appealing avenue for analyzing transient electromagnetic interactions with large and complex structures. MOT integral equation solvers for analyzing electromagnetic scattering from perfect electrically conducting objects are obtained by enforcing electric field boundary conditions and implicitly time advance electric surface current densities by iteratively solving sparse systems of equations at all time steps. Contrary to finite difference and element competitors, these solvers apply to nonlinear and multi-scale structures comprising geometrically intricate and deep sub-wavelength features residing atop electrically large platforms. Moreover, they are high-order accurate, stable in the low- and high-frequency limits, and applicable to conducting and penetrable structures represented by highly irregular meshes. This presentation reviews some recent advances in the parallel implementations of time domain integral equation solvers, specifically those that leverage multilevel plane-wave time-domain algorithm (PWTD) on modern manycore computer architectures including graphics processing units (GPUs) and distributed memory supercomputers. The GPU-based implementation achieves at least one order of magnitude speedups compared to serial implementations while the distributed parallel implementation are highly scalable to thousands of compute-nodes. A distributed parallel PWTD kernel has been adopted to solve time domain surface/volume integral equations (TDSIE/TDVIE) for analyzing transient scattering from large and complex-shaped perfectly electrically conducting (PEC)/dielectric objects involving ten million/tens of millions of spatial unknowns.
Anderson localization and Mott insulator phase in the time domain
Sacha, Krzysztof
2015-01-01
Particles in space periodic potentials constitute standard models for investigation of crystalline phenomena in solid state physics. Time periodicity of periodically driven systems is a close analogue of space periodicity of solid state crystals. There is an intriguing question if solid state phenomena can be observed in the time domain. Here we show that wave-packets localized on resonant classical trajectories of periodically driven systems are ideal elements to realize Anderson localization or Mott insulator phase in the time domain. Uniform superpositions of the wave-packets form stationary states of a periodically driven particle. However, an additional perturbation that fluctuates in time results in disorder in time and Anderson localization effects emerge. Switching to many-particle systems we observe that depending on how strong particle interactions are, stationary states can be Bose-Einstein condensates or single Fock states where definite numbers of particles occupy the periodically evolving wave-packets. Our study shows that non-trivial crystal-like phenomena can be observed in the time domain. PMID:26074169
Byrne, Richard D; Larijani, Banafshé; Poccia, Dominic L
2016-01-01
FRET-FLIM techniques have wide application in the study of protein and protein-lipid interactions in cells. We have pioneered an imaging platform for accurate detection of functional states of proteins and their interactions in fixed cells. This platform, two-site-amplified Förster resonance energy transfer (a-FRET), allows greater signal generation while retaining minimal noise thus enabling application of fluorescence lifetime imaging microscopy (FLIM) to be routinely deployed in different types of cells and tissue. We have used the method described here, time-resolved FRET monitored by two-photon FLIM, to demonstrate the direct interaction of Phospholipase Cγ (PLCγ) by Src Family Kinase 1 (SFK1) during nuclear envelope formation and during male and female pronuclear membrane fusion in fertilized sea urchin eggs. We describe here a generic method that can be applied to monitor any proteins of interest.
Efficient smoothed finite element time domain analysis for photonic devices.
Atia, Khaled S R; Heikal, A M; Obayya, S S A
2015-08-24
In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagation in photonic devices. Dissimilar to conventional FEM, efficient "inter-element" matrices are accurately formed through smoothing the field derivatives across element boundaries. In this sense, the new approach is termed "smoothed FEM" (SFETD). For time domain analysis, the propagation is made via the time domain beam propagation method (TD-BPM). Relying on first order elements, our suggested SFETD-BPM enjoys accuracy levels comparable to second-order conventional FEM; thanks to the element smoothing. The proposed method numerical performance is tested through applicating on analysis of a single mode slab waveguide, optical grating structure, and photonic crystal cavity. It is clearly demonstrated that our method is not only accurate but also more computationally efficient (far few run time, and memory requirements) than the conventional FEM approach. The SFETD-BPM is also extended to deal with the very challenging problem of dispersive materials. The material dispersion is smartly utilized to enhance the quality factor of photonic crystal cavity.
[Terahertz time-domain spectroscopy of ractopamine hydrochloride].
Chen, Xi-ai; Huang, Ping-jie; Hou, Di-bo; Kang, Xu-sheng; Zhang, Guang-xin; Zhou, Ze-kui
2011-03-01
The terahertz spectra of Ractopamine hydrochloride in the range of 0.2 to 2.2 THz was obtained by THz time-domain spectroscopy, and the absorption and refraction spectra of Ractopamine hydrochloride was got meanwhile. The structure and vibrational frequencies of Ractopamine molecule in the THz range were simulated by density functional theory. The difference between experimental and theoretical results was analyzed. And assisted by Gaussian View 3.09, the origin of the vibrational frequencies was recognized. The results show that besides the intramolecular vibrations, THz absorption of Ractopamine hydrochloride originated from the intermolecular hydrogen bond network and Van der Waals force between molecules. This study demonstrated the feasibility of time-domain terahertz spectroscopy for the identification of Ractopamine hydrochloride and provided a new way for the detection of Ractopamine hydrochloride.
Advances in spectral inversion of time-domain induced polarization
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest
The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts in charg......The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts...... in chargeability parameters, towards a quantitative analysis of the investigated media, which allows for detailed soil- and rock-type characterization. In this work a review of the recent advances in spectral inversion of TDIP data is presented, in terms of: supported IP parameterizations; modelling of transmitter...
Drug detection by terahertz time-domain spectroscopy
International Nuclear Information System (INIS)
Duan Ruixin; Zhu Yiming; Zhao Hongwei
2013-01-01
Due to unique spectral region, functional imaging ability, excellent penetration and safety characteristics of terahertz radiation, the terahertz technology rapidly becomes a vital method to detect and analyze drugs. In this paper, firstly, we identify the functional groups of anti-diabetic drugs by density functional theory (DFT), HIPHOP models and experimental results from terahertz time-domain spectroscopy measurements. Secondly, we identify four kinds of herbs of radix curcumae by using the support vector machine (SVM) analysis. Besides, we analyze the absorption of anhydrous and hydrous glucose, and determine the state of water in the crystalized D-glucose·H 2 O through the results of differential scanning calorimetry measurement. Finally, we summarize the advantages and disadvantages of terahertz time-domain spectroscopy method in drug detection and analyzing. (authors)
Time-domain Hydroelasticity Theory of Ships Responding to Waves
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui
1997-01-01
flare forms. The predicted results include linear and non-linear rigid motions and structural responses of ships advancing in regular and irregular waves. The results clearly demonstrate the importance and the magnitude of non-linear effects in ship motions and internal forces. Numerical calculations......A time-domain linear theory of fluid-structure interaction between floating structures and the incident waves is presented. The structure is assumed to be elastic and represented by general separation of variables, whereas the fluid is described as an initial boundary value problem of potential...... free surface flow. The general interface boundary condition is used in the mathematical formulation of the fluid motion around the flexible structure. The general time-domain theory is simplified to a slender-body theory for the analysis of wave-induced global responses of monohull ships. The structure...
Evaluation of Damping Using Time Domain OMA Techniques
DEFF Research Database (Denmark)
Bajric, Anela; Brincker, Rune; Georgakis, Christos T.
2014-01-01
The prevailing Operational Modal Analysis (OMA) techniques provide in most cases reasonably accurate estimates of structural frequencies and mode shapes. In contrast though, they are known to often produce poor structural damping estimates, which is mainly due to inherent random and/or bias errors...... Time Domain (ITD), Eigenvalue Realization Algorithm (ERA) and the Polyreference Time Domain (PTD). The response of a two degree-of-freedom (2DOF) system is numerically established from specified modal parameters with well separated and closely spaced modes. Two types of response are considered, free...... response and random response from white noise loading. Finally, the results of the numerical study are presented, in which the error of the structural damping estimates obtained by each OMA technique is shown for a range of damping levels. From this, it is clear that there are notable differences...
On time-domain and frequency-domain MMSE-based TEQ design for DMT transmission
Vanbleu, K; Moonen, M; Ysebaert, G; 10.1109/TSP.2005.851161
2005-01-01
We reconsider the minimum mean square error (MMSE) time-domain equalizer (TEQ), bitrate maximizing TEQ (BM-TEQ), and per-tone equalizer design (PTEQ) for discrete multitone (DMT) transmission and cast them in a common least-squares (LS) based framework. The MMSE- TEQ design criterion can be formulated as a constrained linear least-squares (CLLS) criterion that minimizes a time-domain (TD) error energy. From this CLLS-based TD-MMSE-TEQ criterion, we derive two new least-squares (LS) based frequency-domain (FD) MMSE-TEQ design criteria: a CLLS-based FD-MMSE-TEQ criterion and a so-called separable nonlinear LS (SNLLS) based FD-MMSE-TEQ design. Finally, the original BM-TEQ design is shown to be equivalent to a so-called iteratively-reweighted (IR) version of the SNLLS-based FD-MMSE-TEQ design. This LS-based framework then results in the following contributions. The new, IR-SNLLS-based BM-TEQ design criterion gives rise to an elegant, iterative, fast converging, Gauss-Newton-based design algorithm that exploits th...
Fast algorithms for the analysis of spectral FLIM data
Gregor, I.; Krämer, B.; Koberling, F.; Erdmann, R.; Enderlein, J.; Wahl, M.; Fore, S.
2011-03-01
The combination of simultaneous spectral detection together with Fluorescence Lifetime Imaging (sFLIM) allows collecting the complete information inherent to the fluorescence signal. Their fingerprint of lifetime and spectral properties identify the fluorescent labels unambiguously. Multiple labels can be investigated in parallel and separated from inherent auto-fluorescence of the sample. In addition, spectral FLIM FRET has the prospect to allow simultaneous detection of multiple FRET signals with quantitative analysis of FRET-efficiency and degree of binding. Spectral FLIM measurements generate huge amount of data. Suitable analysis procedures must be found to condense the inherent information to answer the scientific questions in a straightforward way. Different analysis techniques have been evaluated for a diversity of applications as multiplex labeling, quantitative determination of environmental parameters and distance measurements via FLIM FRET. In order to reach highest sensitivity in single photon detection, different detector types are investigated and developed. SPAD arrays equipped with micro-lenses promise superior detection efficiency while the integration of a spectrograph with a PMT array is easier to realize and allows for a higher number of detection channels. High detection speed can be realized through parallel TCSPC channels. In order to overcome the limits of the USB 2.0 interface, new interface solutions have been realized for the multichannel TCSPC unit HydraHarp 400.
Analytic comparison of time- and frequency-domain electromagnetic methods
Energy Technology Data Exchange (ETDEWEB)
Stoyer, C.H.
1980-01-01
The time- and frequency-domain methods of electromagnetic geophysical prospecting are compared to determine the similarities and differences and to recommend system choices for particular field situations. Only the wire-loop configuration is considered, as this array is quite standard in geothermal prospecting. Comparisons are carried out using hardware and physical considerations, a large catalog of 3-layer model curves, 2D-3D model calculations, and by comparing Fourier transforms and layered inversions of field data from the Randsburg KGRA in California. The results generally indicate that frequency-domain methods offer better resolution and more practical hardware design for long-offset shallow applications. They also have a much better backup in terms of modelling tools for interpretation and history of experience. Transient methods are better suited for deeper probing, for both long- and short-offset applications. Frequency-domain methods are limited by the primary field, which is subject to distortion from near-surface inhomogeneites; this is also the case for early-time transients. Transient measurements in late time are limited by ambient electromagnetic noise and dynamic range of receiving equipment.
Efficient time-domain model of the graphene dielectric function
Prokopeva, Ludmila J.; Kildishev, Alexander V.
2013-09-01
A honey-comb monolayer lattice of carbon atoms, graphene, is not only ultra-thin, ultra-light, flexible and strong, but also highly conductive when doped and exhibits strong interaction with electromagnetic radiation in the spectral range from microwaves to the ultraviolet. Moreover, this interaction can be effectively controlled electrically. High flexibility and conductivity makes graphene an attractive material for numerous photonic applications requiring transparent conducting electrodes: touchscreens, liquid crystal displays, organic photovoltaic cells, and organic light-emitting diodes. Meanwhile, its tunability makes it desirable for optical modulators, tunable filters and polarizers. This paper deals with the basics of the time-domain modeling of the graphene dielectric function under a random-phase approximation. We focus at applicability of Padé approximants to the interband dielectric function (IDF) of single layer graphene. Our study is centered on the development of a two-critical points approximation (2CPA) of the IDF within a single-electron framework with negligible carrier scattering and a realistic range of chemical potential at room temperature. This development is successfully validated by comparing reflection and transmission spectra computed by a numerical method in time-domain versus semi-analytical calculations in frequency domain. Finally, we sum up our results - (1) high-quality approximation, (2) tunability, and (3) second-order accurate numerical FDTD implementation of the 2CPA of IDF demonstrated across the desired range of the chemical potential to temperature ratios (4 - 23). Finally, we put forward future directions for time-domain modeling of optical response of graphene with wide range of tunable and fabrication-dependent parameters, including other broadening factors and variations of temperature and chemical potentials.
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)
FLIM data analysis of NADH and Tryptophan autofluorescence in prostate cancer cells
O'Melia, Meghan J.; Wallrabe, Horst; Svindrych, Zdenek; Rehman, Shagufta; Periasamy, Ammasi
2016-03-01
Fluorescence lifetime imaging microscopy (FLIM) is one of the most sensitive techniques to measure metabolic activity in living cells, tissues and whole animals. We used two- and three-photon fluorescence excitation together with time-correlated single photon counting (TCSPC) to acquire FLIM signals from normal and prostate cancer cell lines. FLIM requires complex data fitting and analysis; we explored different ways to analyze the data to match diverse cellular morphologies. After non-linear least square fitting of the multi-photon TCSPC images by the SPCImage software (Becker & Hickl), all image data are exported and further processed in ImageJ. Photon images provide morphological, NAD(P)H signal-based autofluorescent features, for which regions of interest (ROIs) are created. Applying these ROIs to all image data parameters with a custom ImageJ macro, generates a discrete, ROI specific database. A custom Excel (Microsoft) macro further analyzes the data with charts and statistics. Applying this highly automated assay we compared normal and cancer prostate cell lines with respect to their glycolytic activity by analyzing the NAD(P)H-bound fraction (a2%), NADPH/NADH ratio and efficiency of energy transfer (E%) for Tryptophan (Trp). Our results show that this assay is able to differentiate the effects of glucose stimulation and Doxorubicin in these prostate cell lines by tracking the changes in a2% of NAD(P)H, NADPH/NADH ratio and the changes in Trp E%. The ability to isolate a large, ROI-based data set, reflecting the heterogeneous cellular environment and highlighting even subtle changes -- rather than whole cell averages - makes this assay particularly valuable.
Frequency and Time Domain Modeling of Acoustic Liner Boundary Conditions
Bliss, Donald B.
1982-01-01
As part of a research program directed at the acoustics of advanced subsonic propulsion systems undertaken at NASA Langley, Duke University was funded to develop a boundary condition model for bulk-reacting nacelle liners. The overall objective of the Langley program was to understand and predict noise from advanced subsonic transport engines and to develop related noise control technology. The overall technical areas included: fan and propeller source noise, acoustics of ducts and duct liners, interior noise, subjective acoustics, and systems noise prediction. The Duke effort was directed toward duct liner acoustics for the development of analytical methods to characterize liner behavior in both frequency domain and time domain. A review of duct acoustics and liner technology can be found in Reference [1]. At that time, NASA Langley was investigating the propulsion concept of an advanced ducted fan, with a large diameter housed inside a relatively short duct. Fan diameters in excess of ten feet were proposed. The lengths of both the inlet and exhaust portions of the duct were to be short, probably less than half the fan diameter. The nacelle itself would be relatively thin-walled for reasons of aerodynamic efficiency. The blade-passage frequency was expected to be less than I kHz, and very likely in the 200 to 300 Hz range. Because of the design constraints of a short duct, a thin nacelle, and long acoustic wavelengths, the application of effective liner technology would be especially challenging. One of the needs of the NASA Langley program was the capability to accurately and efficiently predict the behavior of the acoustic liner. The traditional point impedance method was not an adequate model for proposed liner designs. The method was too restrictive to represent bulk reacting liners and to allow for the characterization of many possible innovative liner concepts. In the research effort at Duke, an alternative method, initially developed to handle bulk
On the Analysis Methods for the Time Domain and Frequency Domain Response of a Buried Objects*
Poljak, Dragan; Šesnić, Silvestar; Cvetković, Mario
2014-05-01
There has been a continuous interest in the analysis of ground-penetrating radar systems and related applications in civil engineering [1]. Consequently, a deeper insight of scattering phenomena occurring in a lossy half-space, as well as the development of sophisticated numerical methods based on Finite Difference Time Domain (FDTD) method, Finite Element Method (FEM), Boundary Element Method (BEM), Method of Moments (MoM) and various hybrid methods, is required, e.g. [2], [3]. The present paper deals with certain techniques for time and frequency domain analysis, respectively, of buried conducting and dielectric objects. Time domain analysis is related to the assessment of a transient response of a horizontal straight thin wire buried in a lossy half-space using a rigorous antenna theory (AT) approach. The AT approach is based on the space-time integral equation of the Pocklington type (time domain electric field integral equation for thin wires). The influence of the earth-air interface is taken into account via the simplified reflection coefficient arising from the Modified Image Theory (MIT). The obtained results for the transient current induced along the electrode due to the transmitted plane wave excitation are compared to the numerical results calculated via an approximate transmission line (TL) approach and the AT approach based on the space-frequency variant of the Pocklington integro-differential approach, respectively. It is worth noting that the space-frequency Pocklington equation is numerically solved via the Galerkin-Bubnov variant of the Indirect Boundary Element Method (GB-IBEM) and the corresponding transient response is obtained by the aid of inverse fast Fourier transform (IFFT). The results calculated by means of different approaches agree satisfactorily. Frequency domain analysis is related to the assessment of frequency domain response of dielectric sphere using the full wave model based on the set of coupled electric field integral
Time domain random walks for hydrodynamic transport in heterogeneous media
Russian, Anna; Dentz, Marco; Gouze, Philippe
2016-05-01
We derive a general formulation of the time domain random walk (TDRW) approach to model the hydrodynamic transport of inert solutes in complex geometries and heterogeneous media. We demonstrate its formal equivalence with the discretized advection-dispersion equation and show that the TDRW is equivalent to a continuous time random walk (CTRW) characterized by space-dependent transition times and transition probabilities. The transition times are exponentially distributed. We discuss the implementation of different concentration boundary conditions and initial conditions as well as the occurrence of numerical dispersion. Furthermore, we propose an extension of the TDRW scheme to account for mobile-immobile multirate mass transfer. Finally, the proposed TDRW scheme is validated by comparison to analytical solutions for spatially homogeneous and heterogeneous transport scenarios.
Time-Domain Analysis of Scrotal Thermoregulatory Impairment in Varicocele
Directory of Open Access Journals (Sweden)
Enas eIsmail
2014-09-01
Full Text Available Varicocele is a common male disease defined as the pathological dilatation of the pampiniform plexus and scrotal veins with venous blood reflux. Varicocele usually impairs the scrotal thermoregulation via a hemodynamic alteration, thus inducing an increase in cutaneous temperature. The investigation of altered scrotal thermoregulation by means of thermal infrared imaging has been proved to be useful in the study of the functional thermal impairment. In this study, we use the Control System Theory to analyze the time-domain dynamics of the scrotal thermoregulation in response to a mild cold challenge. Four standard time-domain dynamic parameters of a prototype second order control system (Delay Time, Rise Time, closed poles locations, steady state error and the static basal temperatures were directly estimated from thermal recovery curves. Thermal infrared imaging data from 31 healthy controls (HCS and 95 varicocele patients were processed. True-positive predictions, by comparison with standard echo color Doppler findings, higher than 87 % were achieved into the proper classification of the disease stage. The proposed approach could help to understand at which specific level the presence of the disease impacts the scrotal thermoregulation, which is also involved into normal spermatogenesis process.
Time domain passivity controller for 4-channel time-delay bilateral teleoperation.
Rebelo, Joao; Schiele, Andre
2015-01-01
This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.
Terahertz time-domain transmission and reflection spectroscopy of niobium
Energy Technology Data Exchange (ETDEWEB)
Hong, Tae Yoon; Choi, Kyu Jin; Park, Byoung Cheol; Ha, Tae Woo; Sim, Kyung Ik; Kim, Jea Hoon [Dept. of Physics, Yonsei University, Seoul (Korea, Republic of); Ha, Dong Gwang; Chang, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)
2013-03-15
We have developed a terahertz time-domain spectroscopy (THz-TDS) system for transmission and reflection measurements of metallic thin films. Using our THz-TDS system, we studied the conventional superconductor niobium (Nb) in the normal state in the spectral range from 5 to 50 cm{sup -1}. Both the real and imaginary parts of the conductivity are acquired without Kramers-Kronig analysis. Nb exhibits a nearly frequency independent real conductivity spectrum in the terahertz range, with a very small imaginary part.
A wavefront analyzer for terahertz time-domain spectrometers
DEFF Research Database (Denmark)
Abraham, E.; Brossard, M.; Fauche, P.
2017-01-01
We report on the development of a terahertz wavefront sensor able to determine the optical aberrations of a terahertz time-domain spectrometer. The system measures point-by-point the amplitude and phase of the terahertz electric field in a given plane. From this measurement, we reconstruct...... the terahertz wavefront and calculate its Zernike coefficients. In particular, we especially show that the focus spot of the spectrometer suffers from optical aberrations such as remaining defocus, first and second order astigmatisms, as well as spherical aberration. This opens a route to wavefront correction...... for improved terahertz imaging and spectroscopy....
Detection probabilities for time-domain velocity estimation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1991-01-01
Estimation of blood velocities by time-domain cross-correlation of successive high frequency sampled ultrasound signals is investigated. It is shown that any velocity can result from the estimator regardless of the true velocity due to the nonlinear technique employed. Using a simple simulation...... as a filter with a transfer function depending on the actual velocity. This influences the detection probability, which gets lower at certain velocities. An index directly reflecting the probability of detection can easily be calculated from the cross-correlation estimated. This makes it possible to assess...
Solution of the Burgers Equation in the Time Domain
Directory of Open Access Journals (Sweden)
M. Bednařík
2002-01-01
Full Text Available This paper deals with a theoretical description of the propagation of a finite amplitude acoustic waves. The theory based on the homogeneous Burgers equation of the second order of accuracy is presented here. This equation takes into account both nonlinear effects and dissipation. The method for solving this equation, using the well-known Cole-Hopf transformation, is presented. Two methods for numerical solution of these equations in the time domain are presented. The first is based on the simple Simpson method, which is suitable for smaller Goldberg numbers. The second uses the more advanced saddle point method, and is appropriate for large Goldberg numbers.
Time domain terahertz electro- and magneto-optic spectroscopy
Moore, G P
2001-01-01
sub i sub c sub u sub l sub a sub r = 0 centre dot 19m sub e and m sub p sub a sub r sub a sub l sub l sub e sub l = 0 centre dot 90m sub e. The temperature dependence of the cyclotron resonance was measured over the range 5K to 80 K, and a peak is found at approx 30 K which can be explained in terms of ionised and neutral impurity scattering at temperatures below 30 K and by phonon scattering above 30 K. The measurement of small amplitude ferromagnetic resonance oscillations in the time domain in thin films of permalloy (78), iron and cobalt has been achieved by using the time resolved magneto-optic Kerr effect. A stripline device was fabricated to provide an out of plane broadband magnetic pulse with a peak strength of approx 5 Oe. The observed frequencies are shown to agree well with the established theory. A time domain terahertz spectrometer and a bolometer have been used to study the coherent THz radiation emitted from n- and p-type InAs surfaces illuminated by femtosecond near infrared pulses. The magn...
A time domain frequency-selective multivariate Granger causality approach.
Leistritz, Lutz; Witte, Herbert
2016-08-01
The investigation of effective connectivity is one of the major topics in computational neuroscience to understand the interaction between spatially distributed neuronal units of the brain. Thus, a wide variety of methods has been developed during the last decades to investigate functional and effective connectivity in multivariate systems. Their spectrum ranges from model-based to model-free approaches with a clear separation into time and frequency range methods. We present in this simulation study a novel time domain approach based on Granger's principle of predictability, which allows frequency-selective considerations of directed interactions. It is based on a comparison of prediction errors of multivariate autoregressive models fitted to systematically modified time series. These modifications are based on signal decompositions, which enable a targeted cancellation of specific signal components with specific spectral properties. Depending on the embedded signal decomposition method, a frequency-selective or data-driven signal-adaptive Granger Causality Index may be derived.
Acoustic Finite Element Calculations in the Time Domain
DEFF Research Database (Denmark)
Jensen, Morten Skaarup
The use of the finite element method (FEM) for making predictions for acoustic fields in the time domain is investigated. First, an introduction to FEM for acoustics is given. This includes a description of important present day algorithms and a derivation of FEM. The overall performance...... of these algorithms is then examined with particular emphasis on accuracy and computational costs. It is shown that the most important error is one that takes the form of a falsely predicted dispersion. The dispersion error can be reduced by using smaller elements and time steps, but this is very costly. Attempts...... and consequences of the dispersion error has been obtained. This led to a new method for determining the optimum element and time step size. The method is valuable because the present way of doing this is not theoretically well-founded....
Body waves separation in the time-frequency domain
Herrera, R. H.; Tary, J.; Van der Baan, M.
2013-12-01
Arrival times of body waves generated by small magnitude microseismic events are usually very close and their limited bandwidth can cause even partial overlap in the time and frequency domains. The separation of P and S waves is then a challenging task that if solved could bring more insights about nature and location of the generating source. Differences in arrival times and frequency content of P and S waves can be seen by using time-frequency decomposition. The traditional time-frequency representation based on the Fourier Transform is limited by its trade-off between time and frequency resolutions, while other alternatives like the Wavelet Transform are still limited by the Heisenberg box. A new derivation of the Continuous Wavelet Transform, called Synchrosqueezing, stretches these boundaries using a mixture of the reassignment method with instantaneous frequency, giving a better frequency representation with improved time localization. Furthermore, all the individual components of the signal are separated in the time domain. This means that we are able to isolate the waveforms of a complex microseismic trace. Each spectral component can then be matched with a body wave plus its associated coda. Proper parameters have to be selected prior to the computation, such as the central frequency and bandwidth of the mother wavelet. We thus include a signal characterization first to find the best matching mother wavelet. In this paper we use the Synchrosqueezing transform to perform the time frequency representation of short brittle events recorded during microseismic experiments. Decomposition results for these examples show that the Synchrosqueezing transform outperforms the Short-Time Fourier Transform. The different components of each body waves (first arrival, coda, frequency components) can then be identified in the time-frequency plane. For some microseismic events, a first P-wave arrival is followed by another arrival at lower frequency that could be a P
Space-time discontinuous Galerkin method for parabolic problems in time-dependent domains
Janivita Joto Sudirham, J.J.S.; Sudirham, J.J.; van der Vegt, Jacobus J.W.; van Damme, Rudolf M.J.
2004-01-01
In this report a space-time discontinuous Galerkin (DG) finite element method for the solution of the advection-diffusion-reaction equation in time-dependent domains is presented and analyzed. The variational formulation is based on a combination of the space-time DG method developed by van der Vegt
Finite-difference time-domain analysis of time-resolved terahertz spectroscopy experiments
DEFF Research Database (Denmark)
Larsen, Casper; Cooke, David G.; Jepsen, Peter Uhd
2011-01-01
In this paper we report on the numerical analysis of a time-resolved terahertz (THz) spectroscopy experiment using a modified finite-difference time-domain method. Using this method, we show that ultrafast carrier dynamics can be extracted with a time resolution smaller than the duration of the THz...
Time domain series system definition and gear set reliability modeling
International Nuclear Information System (INIS)
Xie, Liyang; Wu, Ningxiang; Qian, Wenxue
2016-01-01
Time-dependent multi-configuration is a typical feature for mechanical systems such as gear trains and chain drives. As a series system, a gear train is distinct from a traditional series system, such as a chain, in load transmission path, system-component relationship, system functioning manner, as well as time-dependent system configuration. Firstly, the present paper defines time-domain series system to which the traditional series system reliability model is not adequate. Then, system specific reliability modeling technique is proposed for gear sets, including component (tooth) and subsystem (tooth-pair) load history description, material priori/posterior strength expression, time-dependent and system specific load-strength interference analysis, as well as statistically dependent failure events treatment. Consequently, several system reliability models are developed for gear sets with different tooth numbers in the scenario of tooth root material ultimate tensile strength failure. The application of the models is discussed in the last part, and the differences between the system specific reliability model and the traditional series system reliability model are illustrated by virtue of several numerical examples. - Highlights: • A new type of series system, i.e. time-domain multi-configuration series system is defined, that is of great significance to reliability modeling. • Multi-level statistical analysis based reliability modeling method is presented for gear transmission system. • Several system specific reliability models are established for gear set reliability estimation. • The differences between the traditional series system reliability model and the new model are illustrated.
Time-Domain Diversity in Ultra-Wideband MIMO Communications
Directory of Open Access Journals (Sweden)
Alain Sibille
2005-03-01
Full Text Available The development of ultra-wideband (UWB communications is impeded by the drastic transmitted power limitations imposed by regulation authorities due to the Ã¢Â€ÂœpollutingÃ¢Â€Â character of these radio emissions with respect to existing services. Technical solutions must be researched in order either to limit the level of spectral pollution by UWB devices or to increase their reception sensitivity. In the present work, we consider pulse-based modulations and investigate time-domain multiple-input multiple-output (MIMO diversity as one such possible solution. The basic principles of time-domain diversity in the extreme (low multipath density or intermediate (dense multipath UWB regimes are addressed, which predict the possibility of a MIMO gain equal to the product NtÃƒÂ—Nr of the numbers of transmit/receive antenna elements when the channel is not too severe. This analysis is confirmed by simulations using a parametric empirical stochastic double-directional channel model. They confirm the potential interest of MIMO approaches solutions in order to bring a valuable performance gain in UWB communications.
Time domain NMR evaluation of poly(vinyl alcohol) xerogels
Energy Technology Data Exchange (ETDEWEB)
Rodrigues, Elton Jorge da Rocha; Cavalcante, Maxwell de Paula; Tavares, Maria Ines Bruno, E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia. Instituto de Macromoleculas Professora Eloisa Mano
2016-05-15
Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO{sub 2}), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO{sub 2} does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO{sub 2}. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials. (author)
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.
Terahertz time-domain reflectometry of multilayered systems
Jackson, J. Bianca
Presented in this work are applications of terahertz pulse ranging, spectroscopy and imaging to the nondestructive evaluation of three disparate multilayer systems for the detection and measurement of hidden layers, as well as the extraction of system information that will aid in its maintenance, repair or replacement. Thermal protection systems for turbine engine components were investigated. Thermal barrier coatings (TBC) and thermally-grown oxide (TGO) thicknesses were determined with 10 micron resolution using time-of-flight and refractive index calculations. Two alternative methods of monitoring TGO growth using reflection amplitudes and spectral shifts were proposed for the prediction of TBC failure. Laser-machined defects as narrow as 50 microns were resolved in one- and two-dimensional images. The light and dark rings of trees, which reflect the changes in tree growth density over the course of a year, are measurable using pulsed terahertz beams. Tree-rings of bare and painted wood specimen were laterally and axially tomographically imaged in order to facilitate the dendrochronological cross-dating of artifacts. Comparisons were made between photographs and terahertz images to demonstrate the reliability of the technique. Historically, numerous unique artworks have been lost through the act of being covered over time. Samples of paintings, drawings and mosaics were imaged beneath layers of paint and plaster using pulsed-terahertz techniques to demonstrate the efficacy of the technique for art history and restoration. Sketch materials and pigments were measured, between 0.05 and 1.0 THz, to help identify colors in spectroscopic images. Other computational and processing methods were used to optimize the distinction between color domains. Additional time-domain terahertz applications for the examination of artwork and other artifacts were proposed.
Assessment of perceptual diffuseness in the time domain
DEFF Research Database (Denmark)
Garcia, Julian Martinez-Villalba; Jeong, Cheol-Ho; Brunskog, Jonas
2017-01-01
acoustic environment to examine how sensitive the human auditory system is to changes in the diffuseness condition, which factors are most crucial and which conditions are most favourable in music halls. Two types of stimuli, a music signal and an impulse response, are tested under the same diffuseness......This study proposes a numerical and experimental framework for evaluating the perceptual aspect of the diffuse field condition with intended final use in music auditoria. Multiple Impulse Responses are simulated based on the time domain Poisson process with increasing reflection density. Different...... conditions. The study shows that subjective diffuseness is highly correlated to the parameters of Surround, Source Width, and Timbre, and is modelled with relevant acoustic parameters such as LG, LF and uniformity of the incident sound....
Time-domain Hydroelasticity Theory of Ships Responding to Waves
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui
1997-01-01
free surface flow. The general interface boundary condition is used in the mathematical formulation of the fluid motion around the flexible structure. The general time-domain theory is simplified to a slender-body theory for the analysis of wave-induced global responses of monohull ships. The structure...... is represented by a non-uniform beam, while the generalized hydrodynamic coefficients can be obtained from two-dimensional potential flow theory. The linear slender body theory is generalized to treat the non-linear loading effects of rigid motion and structural response of ships travelling in rough seas....... The non-linear hydrostatic restoring force and hydrodynamic momentum action are considered. A numerical solution is presented for the slender body theory. Numerical examples are given for two ship cases with different geometry features, a warship hull and the S175 containership with two different bow...
Modern linear control design a time-domain approach
Caravani, Paolo
2013-01-01
This book offers a compact introduction to modern linear control design. The simplified overview presented of linear time-domain methodology paves the road for the study of more advanced non-linear techniques. Only rudimentary knowledge of linear systems theory is assumed - no use of Laplace transforms or frequency design tools is required. Emphasis is placed on assumptions and logical implications, rather than abstract completeness; on interpretation and physical meaning, rather than theoretical formalism; on results and solutions, rather than derivation or solvability. The topics covered include transient performance and stabilization via state or output feedback; disturbance attenuation and robust control; regional eigenvalue assignment and constraints on input or output variables; asymptotic regulation and disturbance rejection. Lyapunov theory and Linear Matrix Inequalities (LMI) are discussed as key design methods. All methods are demonstrated with MATLAB to promote practical use and comprehension. ...
Computational electrodynamics the finite-difference time-domain method
Taflove, Allen
2005-01-01
This extensively revised and expanded third edition of the Artech House bestseller, Computational Electrodynamics: The Finite-Difference Time-Domain Method, offers engineers the most up-to-date and definitive resource on this critical method for solving Maxwell's equations. The method helps practitioners design antennas, wireless communications devices, high-speed digital and microwave circuits, and integrated optical devices with unsurpassed efficiency. There has been considerable advancement in FDTD computational technology over the past few years, and the third edition brings professionals the very latest details with entirely new chapters on important techniques, major updates on key topics, and new discussions on emerging areas such as nanophotonics. What's more, to supplement the third edition, the authors have created a Web site with solutions to problems, downloadable graphics and videos, and updates, making this new edition the ideal textbook on the subject as well.
DBS artifact suppression using a time-frequency domain filter.
Santillán-Guzmán, Alina; Heute, Ulrich; Muthuraman, Muthuraman; Stephani, Ulrich; Galka, Andreas
2013-01-01
Electroencephalogram (EEG) is a useful tool for brain research. However, during Deep-Brain Stimulation (DBS), there are large artifacts that obscure the physiological EEG signals. In this paper, we aim at suppressing the DBS artifacts by means of a time-frequency-domain filter. As a pre-processing step, Empirical-Mode Decomposition (EMD) is applied to detrend the raw data. The detrended signals are then filtered iteratively until, by visual inspection, the quality is good enough for interpretation. The proposed algorithm is demonstrated by an application to a clinical DBS-EEG data set in resting state and in finger-tapping condition. Moreover, a comparison with a Low-Pass filter (LPF) is provided, by visual inspection and by a quantitative measure.
Terahertz time-domain spectroscopy of edible oils.
Dinovitser, Alex; Valchev, Dimitar G; Abbott, Derek
2017-06-01
Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05-2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.
Terahertz time-domain spectroscopy of edible oils
Dinovitser, Alex; Valchev, Dimitar G.; Abbott, Derek
2017-06-01
Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05-2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.
Parallel finite-difference time-domain method
Yu, Wenhua
2006-01-01
The finite-difference time-domain (FTDT) method has revolutionized antenna design and electromagnetics engineering. This book raises the FDTD method to the next level by empowering it with the vast capabilities of parallel computing. It shows engineers how to exploit the natural parallel properties of FDTD to improve the existing FDTD method and to efficiently solve more complex and large problem sets. Professionals learn how to apply open source software to develop parallel software and hardware to run FDTD in parallel for their projects. The book features hands-on examples that illustrate the power of parallel FDTD and presents practical strategies for carrying out parallel FDTD. This detailed resource provides instructions on downloading, installing, and setting up the required open source software on either Windows or Linux systems, and includes a handy tutorial on parallel programming.
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
Zhang, Xuan; Shastry, Sathvik; Bradforth, Stephen E.; Nadeau, Jay L.
2014-11-01
Fluorescence lifetime imaging microscopy (FLIM) has been used to image free and encapsulated doxorubicin (Dox) uptake into cells, since interaction of Dox with DNA leads to a characteristic lifetime change. However, none of the reported Dox conjugates were able to enter cell nuclei. In this work, we use FLIM to show nuclear uptake of 2.7 nm mean diameter Au nanoparticles conjugated to Dox. The pattern of labelling differed substantially from what was seen with free Dox, with slower nuclear entry and stronger cytoplasmic labelling at all time points. As the cells died, the pattern of labelling changed further as intracellular structures disintegrated, consistent with association of Au-Dox to membranes. The patterns of Au distribution and intracellular structure changes were confirmed using electron microscopy, and indicate different mechanisms of cytotoxicity with stable Au-Dox conjugates compared to Dox alone. Such conjugates are promising tools for overcoming resistance in Dox-resistant cancers.Fluorescence lifetime imaging microscopy (FLIM) has been used to image free and encapsulated doxorubicin (Dox) uptake into cells, since interaction of Dox with DNA leads to a characteristic lifetime change. However, none of the reported Dox conjugates were able to enter cell nuclei. In this work, we use FLIM to show nuclear uptake of 2.7 nm mean diameter Au nanoparticles conjugated to Dox. The pattern of labelling differed substantially from what was seen with free Dox, with slower nuclear entry and stronger cytoplasmic labelling at all time points. As the cells died, the pattern of labelling changed further as intracellular structures disintegrated, consistent with association of Au-Dox to membranes. The patterns of Au distribution and intracellular structure changes were confirmed using electron microscopy, and indicate different mechanisms of cytotoxicity with stable Au-Dox conjugates compared to Dox alone. Such conjugates are promising tools for overcoming resistance in
Linear time domain model of the acoustic potential field.
Lesniewski, Peter J
2002-08-01
A new time domain formulation of the acoustic wave is developed to avoid approximating assumptions of the linearized scalar wave equation that limit its validity to low Mach particle velocity modeling or to a smooth potential field in a stationary medium. The proposed model offers precision of the moving frame while retaining the form of the widely used linearized scalar wave equation although with respect to modified coordinates. It is applicable to field calculations involving transient waves with unlimited particle velocity, propagating in inhomogenous fluids or in those with time varying density. The model is based on the exact flux continuity equation and the equation of motion, both using the moving reference frame. The resulting closed-form free space scalar wave equation employing total derivatives is converted back to the partial differential form by using modified independent variables. The modified variables are related to the common coordinates of space and time following integral expressions involving transient particle velocity representing wave radiated by each point of a stationary source. Consequently, transient field produced by complex surface velocity sources can be calculated following existing surface integrals of the radiation theory although using modified coordinates. The use of the proposed model is presented in a numerical simulation of a transient velocity source vibrating at selected magnitudes, leading to the determination of the propagating pressure and velocity wave at any point.
The Future of the Time Domain with LSST
Walkowicz, Lucianne M.
2012-04-01
abstract-type="normal">SummaryIn the coming decade LSST's combination of all-sky coverage, consistent long-term monitoring and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. Time-domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theories. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space. LSST will generate `alerts' within 60 seconds of detecting a new transient, permitting the community to follow up unusual events in greater detail. However, follow-up will remain a challenge as the volume of transients will easily saturate available spectroscopic resources. Characterization of events and access to appropriate ancillary data (e.g. from prior observations, either in the optical or in other passbands) will be of the utmost importance in prioritizing follow-up observations. The incredible scientific opportunities and unique challenges afforded by LSST demand organization, forethought and creativity from the astronomical community. To learn more about the telescope specifics and survey design, as well as obtaining a overview of the variety of the scientific investigations that LSST will enable, readers are encouraged to look at the LSST Science Book: http://www.lsst.org/lsst/scibook. Organizational details of the LSST science collaborations and management may be found at http://www.lsstcorp.org.
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
Hilbert Spectrum for Time-Domain Measurement Data and Its Application
National Research Council Canada - National Science Library
Peng, H. M; Chang, P. C; Chang, F. R
2003-01-01
In this paper, a new method for analyzing the time domain data is introduced. As one knows, the time domain phase measurements are nonstationary and the differencing technique is usually adopted for generating stationary data...
Non-deteriorating time domain numerical algorithms for Maxwell's electrodynamics
Petropavlovsky, S.; Tsynkov, S.
2017-05-01
The Huygens' principle and lacunae can help construct efficient far-field closures for the numerical simulation of unsteady waves propagating over unbounded regions. Those closures can be either standalone or combined with other techniques for the treatment of artificial outer boundaries. A standalone lacunae-based closure can be thought of as a special artificial boundary condition (ABC) that is provably free from any error associated with the domain truncation. If combined with a different type of ABC or a perfectly matched layer (PML), a lacunae-based approach can help remove any long-time deterioration (e.g., instability) that arises at the outer boundary regardless of why it occurs in the first place. A specific difficulty associated with Maxwell's equations of electromagnetism is that in general their solutions do not have classical lacunae and rather have quasi-lacunae. Unlike in the classical case, the field inside the quasi-lacunae is not zero; instead, there is an electrostatic solution driven by the electric charges that accumulate over time. In our previous work [23], we have shown that quasi-lacunae can also be used for building the far-field closures. However, for achieving a provably non-deteriorating performance over arbitrarily long time intervals, the accumulated charges need to be known ahead of time. The main contribution of the current paper is that we remove this limitation and modify the algorithm in such a way that one can rather avoid the accumulation of charge all together. Accordingly, the field inside the quasi-lacunae becomes equal to zero, which facilitates obtaining the temporally uniform error estimates as in the case of classical lacunae. The performance of the modified algorithm is corroborated by a series of numerical simulations. The range of problems that the new method can address includes important combined formulations, for which the interior subproblem may be non-Huygens', and only the exterior subproblem, i.e., the far
Time domain attenuation estimation method from ultrasonic backscattered signals.
Ghoshal, Goutam; Oelze, Michael L
2012-07-01
Ultrasonic attenuation is important not only as a parameter for characterizing tissue but also for compensating other parameters that are used to classify tissues. Several techniques have been explored for estimating ultrasonic attenuation from backscattered signals. In the present study, a technique is developed to estimate the local ultrasonic attenuation coefficient by analyzing the time domain backscattered signal. The proposed method incorporates an objective function that combines the diffraction pattern of the source/receiver with the attenuation slope in an integral equation. The technique was assessed through simulations and validated through experiments with a tissue mimicking phantom and fresh rabbit liver samples. The attenuation values estimated using the proposed technique were compared with the attenuation estimated using insertion loss measurements. For a data block size of 15 pulse lengths axially and 15 beamwidths laterally, the mean attenuation estimates from the tissue mimicking phantoms were within 10% of the estimates using insertion loss measurements. With a data block size of 20 pulse lengths axially and 20 beamwidths laterally, the error in the attenuation values estimated from the liver samples were within 10% of the attenuation values estimated from the insertion loss measurements.
Seismic analysis of wind turbines in the time domain
Energy Technology Data Exchange (ETDEWEB)
Witcher, D. [Garrad Hassan and Partners Ltd., Bristol (United Kingdom)
2004-07-01
The analysis of wind turbine loading associated with earthquakes is clearly important when designing for and assessing the feasibility of wind farms in seismically active regions. The approach taken for such analysis is generally based on codified methods which have been developed for the assessment of seismic loads acting on buildings. These methods are not able to deal properly with the aeroelastic interaction of the dynamic motion of the wind turbine structure with either the wind loading acting on the rotor blades or the response of the turbine controller. This article presents an alternative approach, which is to undertake the calculation in the time domain. In this case a full aeroelastic model of the wind turbine subject to turbulent wind loading is further excited by ground motion corresponding to the earthquake. This capability has been introduced to the GH Bladed wind turbine simulation package. The software can be used to compute the combined wind and earthquake loading of a wind turbine given a definition of the external conditions for an appropriate series of load cases. This article discusses the method and presents example results. (Author)
Seismic analysis of wind turbines in the time domain
Energy Technology Data Exchange (ETDEWEB)
Witcher, D. [Garrad Hassan and Partners, Bristol (United Kingdom)
2005-07-01
The analysis of wind turbine loading associated with earthquakes is clearly important when designing for and assessing the feasibility of wind farms in seismically active regions. The approach taken for such analysis is generally based on codified methods which have been developed for the assessment of seismic loads acting on buildings. These methods are not able to deal properly with the aeroelastic interaction of the dynamic motion of the wind turbine structure with either the wind loading acting on the rotor blades or the response of the turbine controller. This article presents an alternative approach, which is to undertake the calculation in the time domain. In this case a full aeroelastic model of the wind turbine subject to turbulent wind loading is further excited by ground motion corresponding to the earthquake. This capability has been introduced to the GH Bladed wind turbine simulation package. The software can be used to compute the combined wind and earthquake loading of a wind turbine given a definition of the external conditions for an appropriate series of load cases. This article discusses the method and presents example results. (author)
Time domain functional NIRS imaging for human brain mapping.
Torricelli, Alessandro; Contini, Davide; Pifferi, Antonio; Caffini, Matteo; Re, Rebecca; Zucchelli, Lucia; Spinelli, Lorenzo
2014-01-15
This review is aimed at presenting the state-of-the-art of time domain (TD) functional near-infrared spectroscopy (fNIRS). We first introduce the physical principles, the basics of modeling and data analysis. Basic instrumentation components (light sources, detection techniques, and delivery and collection systems) of a TD fNIRS system are described. A survey of past, existing and next generation TD fNIRS systems used for research and clinical studies is presented. Performance assessment of TD fNIRS systems and standardization issues are also discussed. Main strengths and weakness of TD fNIRS are highlighted, also in comparison with continuous wave (CW) fNIRS. Issues like quantification of the hemodynamic response, penetration depth, depth selectivity, spatial resolution and contrast-to-noise ratio are critically examined, with the help of experimental results performed on phantoms or in vivo. Finally we give an account on the technological developments that would pave the way for a broader use of TD fNIRS in the neuroimaging community. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
A 128 Multiplexing Factor Time-Domain SQUID Multiplexer
Prêle, D.; Voisin, F.; Piat, M.; Decourcelle, T.; Perbost, C.; Chapron, C.; Rambaud, D.; Maestre, S.; Marty, W.; Montier, L.
2016-07-01
A cryogenic 128:1 Time-Domain Multiplexer (TDM) has been developed for the readout of kilo-pixel Transition Edge Sensor (TES) arrays dedicated to the Q&U Bolometric Interferometer for Cosmology (QUBIC) instrument which aims to measure the B-mode polarization of the Cosmic Microwave Background. Superconducting QUantum Interference Devices (SQUIDs) are usually used to read out TESs. Moreover, SQUIDs are used to build TDM by biasing sequentially the SQUIDs connected together—one for each TES. In addition to this common technique which allows a typical 32 multiplexing factor, a cryogenic integrated circuit provides a 4:1 second multiplexing stage. This cryogenic integrated circuit is one of the original part of our TDM achieving an unprecedented 128 multiplexing factor. We present these two dimension TDM stages: topology of the SQUID multiplexer, operation of the cryogenic integrated circuit, and integration of the full system to read out a TES array dedicated to the QUBIC instrument. Flux-locked loop operation in multiplexed mode is also discussed.
Time domain simulations of preliminary breakdown pulses in natural lightning.
Carlson, B E; Liang, C; Bitzer, P; Christian, H
2015-06-16
Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mechanism. Preliminary breakdown pulses can be reproduced by simulated channel extension Channel heating and corona sheath formation are crucial to proper pulse shape Extension processes and channel orientation significantly affect observations.
Modal participation in multiple input Ibrahim time domain identification
DEFF Research Database (Denmark)
Brincker, Rune; Olsen, Peter; Amador, Sandro
2017-01-01
The Ibrahim time domain (ITD) identification technique was one of the first techniques formulated for multiple output modal analysis based on impulse response functions or general free decays. However, the technique has not been used much in recent decades due to the fact that the technique was o...... of the identification technique are investigated in a simulation study with closely spaced modes. The simulation study shows that the multiple-input formulation provides estimates with significantly smaller errors on both mode shape and natural frequency estimates....... was originally formulated for single input systems that suffer from well-known problems in case of closely spaced modes. In this paper, a known, but more modern formulation of the ITD technique is discussed. In this formulation the technique becomes multiple input by adding some Toeplitz matrices over a set...... matrix has full rank. This secures that all modes will be contained in the estimated system matrix. Finally, it is discussed how correlation functions estimated from the operational responses of structures can be used as free decays for the multiple-input ITD formulation, and the estimation errors...
Landfill cover performance monitoring using time domain reflectometry
International Nuclear Information System (INIS)
Neher, E.R.; Cotten, G.B.; McElroy, D.
1998-01-01
Time domain reflectometry (TDR) systems were installed to monitor soil moisture in two newly constructed landfill covers at the Idaho National Engineering and Environmental Laboratory. Each TDR system includes four vertical arrays with each array consisting of four TDR probes located at depths of 15, 30, 45, and 60 cm. The deepest probes at 60 cm were installed beneath a compacted soil layer to analyze infiltration through the compacted layer. Based on the TDR data, infiltration through the two covers between March and October, 1997 ranged from less than measurable to 1.5 cm. However, due to a prohibition on penetrating the buried waste and resulting limits on probe placement depths, deeper percolation was not evaluated. Some of the advantages found in the application of TDR for infiltration monitoring at this site are the relative low cost and rugged nature of the equipment. Also, of particular importance, the ability to collect frequent moisture measurements allows the capture and evaluation of soil moisture changes resulting from episodic precipitation events. Disadvantages include the inability to install the probes into the waste, difficulties in interpretation of infiltration during freeze/thaw periods, and some excessive noise in the data
Landfill cover performance monitoring using time domain reflectometry
Energy Technology Data Exchange (ETDEWEB)
Neher, E.R.; Cotten, G.B. [Parsons Infrastructure & Technology Group, Inc., Idaho Falls, ID (United States); McElroy, D. [Lockheed-Martin Idaho Technologies Company, Idaho Falls, ID (United States)
1998-03-01
Time domain reflectometry (TDR) systems were installed to monitor soil moisture in two newly constructed landfill covers at the Idaho National Engineering and Environmental Laboratory. Each TDR system includes four vertical arrays with each array consisting of four TDR probes located at depths of 15, 30, 45, and 60 cm. The deepest probes at 60 cm were installed beneath a compacted soil layer to analyze infiltration through the compacted layer. Based on the TDR data, infiltration through the two covers between March and October, 1997 ranged from less than measurable to 1.5 cm. However, due to a prohibition on penetrating the buried waste and resulting limits on probe placement depths, deeper percolation was not evaluated. Some of the advantages found in the application of TDR for infiltration monitoring at this site are the relative low cost and rugged nature of the equipment. Also, of particular importance, the ability to collect frequent moisture measurements allows the capture and evaluation of soil moisture changes resulting from episodic precipitation events. Disadvantages include the inability to install the probes into the waste, difficulties in interpretation of infiltration during freeze/thaw periods, and some excessive noise in the data.
Detection of Ionic liquid using terahertz time-domain spectroscopy
Wang, Cuicui; Zhao, Xiaojing; Liu, Shangjian; Zuo, Jian; Zhang, Cunlin
2018-01-01
Terahertz (THz, THz+1012Hz) spectroscopy is a far-infrared analytical technology with spectral bands locating between microware and infrared ranges. Being of excellent transmission, non-destruction and high discrimination, this technology has been applied in various fields such as physics, chemistry, nondestructive detection, communication, biomedicine public security. Terahertz spectrum is corresponding with vibration and rotation of liquid molecules, which is suitable to identify and study the liquid molecular dynamics. It is as a powerful spectral detection technology, terahertz time-domain spectroscopy is widely used in solution detection. can enable us to extract the material parameters or dielectric spectrum that show material micro-structure and dynamics by measuring amplitude and phase from coherent terahertz pulses. Ionic liquid exists in most biological tissues, and it is very important for life. It has recently been suggested that near-fired terahertz ionic contrast microscopy can be employed to image subtle changes in ionic concentrations arising from neuronal activity. In this paper, we detected Ionic liquid with different concentrations at room temperature by THz-TDS technique in the range of 0.2-1.5 THz. The liquid cell with a thickness of 0.2mm is made of quartz. The absorption coefficient, refractive index and dielectric function of solutions can be extracted based on THz-TDS. We use an expanded model for fitting the dielectric function based on a combination of a Debye relation for the anions and cations. We find A linear increase of the real and imaginary part of the dielectric function compared with pure water with increasing ion concentrations. A good agreement between the model and the experimental results is obtained. By means of dielectric relaxation process, it was found that the characteristic time of molecular movement and the information related to the liquid molecular structure and movement was obtained.
Optical time-domain analog pattern correlator for high-speed real-time image recognition.
Kim, Sang Hyup; Goda, Keisuke; Fard, Ali; Jalali, Bahram
2011-01-15
The speed of image processing is limited by image acquisition circuitry. While optical pattern recognition techniques can reduce the computational burden on digital image processing, their image correlation rates are typically low due to the use of spatial optical elements. Here we report a method that overcomes this limitation and enables fast real-time analog image recognition at a record correlation rate of 36.7 MHz--1000 times higher rates than conventional methods. This technique seamlessly performs image acquisition, correlation, and signal integration all optically in the time domain before analog-to-digital conversion by virtue of optical space-to-time mapping.
Time-Reversal MUSIC Imaging with Time-Domain Gating Technique
Choi, Heedong; Ogawa, Yasutaka; Nishimura, Toshihiko; Ohgane, Takeo
A time-reversal (TR) approach with multiple signal classification (MUSIC) provides super-resolution for detection and localization using multistatic data collected from an array antenna system. The theory of TR-MUSIC assumes that the number of antenna elements is greater than that of scatterers (targets). Furthermore, it requires many sets of frequency-domain data (snapshots) in seriously noisy environments. Unfortunately, these conditions are not practical for real environments due to the restriction of a reasonable antenna structure as well as limited measurement time. We propose an approach that treats both noise reduction and relaxation of the transceiver restriction by using a time-domain gating technique accompanied with the Fourier transform before applying the TR-MUSIC imaging algorithm. Instead of utilizing the conventional multistatic data matrix (MDM), we employ a modified MDM obtained from the gating technique. The resulting imaging functions yield more reliable images with only a few snapshots regardless of the limitation of the antenna arrays.
Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes
Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng
2016-09-01
Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.
Integral ceramic superstructure evaluation using time domain optical coherence tomography
Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.
2014-02-01
Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.
THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS
Energy Technology Data Exchange (ETDEWEB)
Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others
2015-06-20
We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.
Opportunities and challenges for time domain astronomy with LSST
Ivezic, Zeljko
2014-01-01
The Large Synoptic Survey Telescope (LSST) will enable faint optical time-domain astronomy by carrying out an imaging survey covering the sky that is visible from Cerro Pachon in Northern Chile. Of the order thousand 9.6 sq. deg. images (3.2 Gigapix) will be obtained per night using pairs of 15-second back-to-back exposures, with typical 5-sigma depth for point sources of 24.5 (AB). With close to 1000 observations of a 18,000 sq. deg. region in ugrizy bands over a 10-year period, these data will enable a deep stack across half the sky reaching five magnitudes deeper than the SDSS survey ( 27.5, 5 sigma, point source), and with twice as good seeing (0.7 arcsec median seeing in the r band). The measured and archived properties of newly discovered and known astrometric and photometric transients will be publicly reported within 60 sec after closing the shutter. Automated classification of the expected several million alerts per night, and selection of transient events requiring immediate follow-up, is an outstanding problem for the community. These data will represent a treasure trove for follow-up programs using other ground and space-based telescopes, such as fast-response fast-cadence photometric observations and spectroscopy, as well as for facilities operating at non-optical wavelengths and for gravitational wave programs. I will describe the relevant data products to be delivered by LSST and will summarize challenges that will need to be addressed by the community at large.
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab...
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab-layer str...
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
Time-Domain Terahertz Computed Axial Tomography NDE System
Zimdars, David
2012-01-01
NASA has identified the need for advanced non-destructive evaluation (NDE) methods to characterize aging and durability in aircraft materials to improve the safety of the nation's airline fleet. 3D THz tomography can play a major role in detection and characterization of flaws and degradation in aircraft materials, including Kevlar-based composites and Kevlar and Zylon fabric covers for soft-shell fan containment where aging and durability issues are critical. A prototype computed tomography (CT) time-domain (TD) THz imaging system has been used to generate 3D images of several test objects including a TUFI tile (a thermal protection system tile used on the Space Shuttle and possibly the Orion or similar capsules). This TUFI tile had simulated impact damage that was located and the depth of damage determined. The CT motion control gan try was designed and constructed, and then integrated with a T-Ray 4000 control unit and motion controller to create a complete CT TD-THz imaging system prototype. A data collection software script was developed that takes multiple z-axis slices in sequence and saves the data for batch processing. The data collection software was integrated with the ability to batch process the slice data with the CT TD-THz image reconstruction software. The time required to take a single CT slice was decreased from six minutes to approximately one minute by replacing the 320 ps, 100-Hz waveform acquisition system with an 80 ps, 1,000-Hz waveform acquisition system. The TD-THZ computed tomography system was built from pre-existing commercial off-the-shelf subsystems. A CT motion control gantry was constructed from COTS components that can handle larger samples. The motion control gantry allows inspection of sample sizes of up to approximately one cubic foot (.0.03 cubic meters). The system reduced to practice a CT-TDTHz system incorporating a COTS 80- ps/l-kHz waveform scanner. The incorporation of this scanner in the system allows acquisition of 3D
Improved methods for nightside time domain Lunar Electromagnetic Sounding
Fuqua-Haviland, H.; Poppe, A. R.; Fatemi, S.; Delory, G. T.; De Pater, I.
2017-12-01
Time Domain Electromagnetic (TDEM) Sounding isolates induced magnetic fields to remotely deduce material properties at depth. The first step of performing TDEM Sounding at the Moon is to fully characterize the dynamic plasma environment, and isolate geophysically induced currents from concurrently present plasma currents. The transfer function method requires a two-point measurement: an upstream reference measuring the pristine solar wind, and one downstream near the Moon. This method was last performed during Apollo assuming the induced fields on the nightside of the Moon expand as in an undisturbed vacuum within the wake cavity [1]. Here we present an approach to isolating induction and performing TDEM with any two point magnetometer measurement at or near the surface of the Moon. Our models include a plasma induction model capturing the kinetic plasma environment within the wake cavity around a conducting Moon, and a geophysical forward model capturing induction in a vacuum. The combination of these two models enable the analysis of magnetometer data within the wake cavity. Plasma hybrid models use the upstream plasma conditions and interplanetary magnetic field (IMF) to capture the wake current systems formed around the Moon. The plasma kinetic equations are solved for ion particles with electrons as a charge-neutralizing fluid. These models accurately capture the large scale lunar wake dynamics for a variety of solar wind conditions: ion density, temperature, solar wind velocity, and IMF orientation [2]. Given the 3D orientation variability coupled with the large range of conditions seen within the lunar plasma environment, we characterize the environment one case at a time. The global electromagnetic induction response of the Moon in a vacuum has been solved numerically for a variety of electrical conductivity models using the finite-element method implemented within the COMSOL software. This model solves for the geophysically induced response in vacuum to
ASIC-enabled High Resolution Optical Time Domain Reflectometer
Skendzic, Sandra
Fiber optics has become the preferred technology in communication systems because of what it has to offer: high data transmission rates, immunity to electromagnetic interference, and lightweight, flexible cables. An optical time domain reflectometer (OTDR) provides a convenient method of locating and diagnosing faults (e.g. break in a fiber) along a fiber that can obstruct crucial optical pathways. Both the ability to resolve the precise location of the fault and distinguish between two discrete, closely spaced faults are figures of merit. This thesis presents an implementation of a high resolution OTDR through the use of a compact and programmable ASIC (application specific integrated circuit). The integration of many essential OTDR functions on a single chip is advantageous over existing commercial instruments because it enables small, lightweight packaging, and offers low power and cost efficiency. Furthermore, its compactness presents the option of placing multiple ASICs in parallel, which can conceivably ease the characterization of densely populated fiber optic networks. The OTDR ASIC consists of a tunable clock, pattern generator, precise timer, electrical receiver, and signal sampling circuit. During OTDR operation, the chip generates narrow electrical pulse, which can then be converted to optical format when coupled with an external laser diode driver. The ASIC also works with an external photodetector to measure the timing and amplitude of optical reflections in a fiber. It has a 1 cm sampling resolution, which allows for a 2 cm spatial resolution. While this OTDR ASIC has been previously demonstrated for multimode fiber fault diagnostics, this thesis focuses on extending its functionality to single mode fiber. To validate this novel approach to OTDR, this thesis is divided into five chapters: (1) introduction, (2) implementation, (3), performance of ASIC-based OTDR, (4) exploration in optical pre-amplification with a semiconductor optical amplifier, and
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.
Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements
Directory of Open Access Journals (Sweden)
G. Dragonetti
2018-02-01
Full Text Available This paper deals with the issue of monitoring the spatial distribution of bulk electrical conductivity, σb, in the soil root zone by using electromagnetic induction (EMI sensors under different water and salinity conditions. To deduce the actual distribution of depth-specific σb from EMI apparent electrical conductivity (ECa measurements, we inverted the data by using a regularized 1-D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss–Newton method with truncated generalized singular value decomposition (TGSVD. The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI results in the presence of sharp boundaries (otherwise smeared out after the application of more standard Occam-like regularization strategies searching for smooth solutions. Time-domain reflectometry (TDR data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean, and irrigated with water at two different salinity levels and using two different irrigation volumes. Clearly, this induces different salinity and water contents within the soil profiles. For each transect, 26 regularly spaced monitoring soundings (1 m apart were selected for the collection of (i Geonics EM-38 and (ii Tektronix reflectometer data. Despite the original discrepancies in the EMI and TDR data, we found a significant correlation of the means and standard deviations of the two data series; in particular, after a low-pass spatial filtering of the TDR data. Based on these findings, this paper introduces a novel methodology to calibrate EMI-based electrical conductivities via TDR
Calibrating electromagnetic induction conductivities with time-domain reflectometry measurements
Dragonetti, Giovanna; Comegna, Alessandro; Ajeel, Ali; Piero Deidda, Gian; Lamaddalena, Nicola; Rodriguez, Giuseppe; Vignoli, Giulio; Coppola, Antonio
2018-02-01
This paper deals with the issue of monitoring the spatial distribution of bulk electrical conductivity, σb, in the soil root zone by using electromagnetic induction (EMI) sensors under different water and salinity conditions. To deduce the actual distribution of depth-specific σb from EMI apparent electrical conductivity (ECa) measurements, we inverted the data by using a regularized 1-D inversion procedure designed to manage nonlinear multiple EMI-depth responses. The inversion technique is based on the coupling of the damped Gauss-Newton method with truncated generalized singular value decomposition (TGSVD). The ill-posedness of the EMI data inversion is addressed by using a sharp stabilizer term in the objective function. This specific stabilizer promotes the reconstruction of blocky targets, thereby contributing to enhance the spatial resolution of the EMI results in the presence of sharp boundaries (otherwise smeared out after the application of more standard Occam-like regularization strategies searching for smooth solutions). Time-domain reflectometry (TDR) data are used as ground-truth data for calibration of the inversion results. An experimental field was divided into four transects 30 m long and 2.8 m wide, cultivated with green bean, and irrigated with water at two different salinity levels and using two different irrigation volumes. Clearly, this induces different salinity and water contents within the soil profiles. For each transect, 26 regularly spaced monitoring soundings (1 m apart) were selected for the collection of (i) Geonics EM-38 and (ii) Tektronix reflectometer data. Despite the original discrepancies in the EMI and TDR data, we found a significant correlation of the means and standard deviations of the two data series; in particular, after a low-pass spatial filtering of the TDR data. Based on these findings, this paper introduces a novel methodology to calibrate EMI-based electrical conductivities via TDR direct measurements. This
TeraHertz Time Domain Spectroscopy of Astrophysical Analog Materials
Blake, Geoffrey
The section of the electromagnetic spectrum extending roughly from wavelengths of 3 millimeters to 30 microns is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the successful deployments of the Herschel and SOFIA observatories, and the emerging capabilities of ALMA, are both revolutionizing our understanding of THz astrophysics and placing stringent demands on the generation of accurate laboratory data on the relevant gas phase and solid state materials detected. With APRA support, we have constructed a combined high bandwidth and high spectral resolution femtosecond THz Time Domain Spectroscopy (THz TDS) system and an FT-IR spectrometer, and coupled these instruments to a high vacuum chamber and cryostat and to gas phase cells including a molecular beam system. We have investigated solid materials from room temperature to 10 K, and can examine both refractory matter such as silicates and molecular ices. For the latter, we have demonstrated that the THz bands observed are uniquely sensitive to both the molecular structure of the ice and its thermal history, and thus that THz observations can provide novel insight into the dominant condensable materials in dense, cold regions. In the gas phase we can record doppler-limited data over at least a decade in bandwidth. While quite capable, the high vacuum cryostat can only study thick samples, especially ices, due to the fairly rapid adsorption of gases onto surfaces at low temperature under such conditions. It is therefore not possible to examine highly layered/structured samples or reactive species. We therefore propose here to upgrade the chamber/cryostat to ultrahigh vacuum, and implement additional sample preparation and characterization tools. With such modifications
Probing energy metabolism and microviscosity in cancer using FLIM
Shirmanova, Marina V.; Lukina, Maria M.; Shimolina, Lyubov'E.; Kuimova, Marina K.; Dudenkova, Varvara V.; Shcheslavskiy, Vladislav I.; Zagaynova, Elena V.
2017-07-01
Fluorescence lifetime imaging microscopy (FLIM) is a promising non-invasive highly sensitive technique for probing multiple physiological and physicochemical parameters in living cells and tissues. The present study is focused on the investigation of bioenergetics and microscopic viscosity of cultured cancer cells and animal tumors using FLIM during natural growth and chemotherapy. Fluorescence lifetime measurements of the metabolic cofactor NAD(P)H revealed a decrease of the relative amplitude of free NAD(P)H after cisplatin treatment, indicating a change towards a more oxidative metabolic state. Microviscosity mapping performed with the use of fluorescent molecular rotor BODIPY-2 showed a pronounced increase in the plasma membrane viscosity in cancer cells exposed to cisplatin. Although biochemical mechanisms underlying the metabolic and viscosity alterations during chemotherapy have yet to be clarified, our data suggest that the cisplatin-induced changes in cellular metabolism and membrane viscosity play a role in the cytotoxicity of the drug. The results of the study contribute to an understanding of mechanisms of cisplatin action and will be useful for development new approach for assessing response to a therapy.
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
Monitoring moisture storage in trees using time domain reflectometry
Constantz, J.; Murphy, F.
1990-01-01
Laboratory and field tests were performed to examine the feasibility of using time domain reflectometry (TDR) to monitor changes in the moisture storage of the woody parts of trees. To serve as wave guides for the TDR signal, pairs of stainless steel rods (13 cm long, 0.32 cm in diameter, and 2.5 cm separation) were driven into parallel pilot holes drilled into the woody parts of trees, and a cable testing oscilloscope was used to determine the apparent dielectric constant. A laboratory calibration test was performed on two sapwood samples, so that the relation between the volumetric water content and the apparent dielectric constant of the sapwood could be determined over a range of water contents. The resulting calibration curve for these sapwood samples was significantly different than the general calibration curve used for soils, showing a smaller change in the apparent dielectric constant for a given change in the volumetric water content than is typical for soils. The calibration curve was used to estimate the average volumetric water content to a depth of 13 cm in living trees. One field experiment was conducted on an English walnut tree (Juglans regia) with a diameter of 40 cm, growing in a flood-irrigated orchard on a Hanford sandy loam near Modesto, California (U.S.A.). Rods were driven into the tree at about 50 cm above the soil surface and monitored hourly for the month of August, 1988. The moisture content determined by TDR showed a gradual decrease from 0.44 to 0.42 cm3 cm-3 over a two week period prior to flood irrigation, followed by a rapid rise to 0.47 cm3 cm-3 over a four day period after irrigation, then again a gradual decline approaching the next irrigation. A second field experiment was made on ten evergreen and deciduous trees with diameters ranging from 30 to 120 cm, growing in the foothills of the Coast Range of central California. Rods were driven into each tree at 50 to 100 cm above the soil surface and monitored on a biweekly to monthly
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.
FLIM-FRET image analysis of tryptophan in prostate cancer cells
Periasamy, Ammasi; Alam, Shagufta R.; Svindrych, Zdenek; Wallrabe, Horst
2017-07-01
A region of interest (ROI) based quantitative FLIM-FRET image analysis is developed to quantitate the autofluorescence signals of the essential amino acid tryptophan as a biomarker to investigate the metabolism in prostate cancer cells.
Pulkkinen, Aki; Tarvainen, Tanja
2013-03-01
The radiative transfer equation (RTE) is widely accepted to accurately describe light transport in a medium with scattering particles, and it has been successfully applied as a light-transport model, for example, in diffuse optical tomography. Due to the computationally expensive nature of the RTE, most of these applications have been in the frequency domain. In this paper, an efficient solution method for the time-domain RTE is proposed. The method is based on solving the frequency-domain RTE at multiple modulation frequencies and using the Fourier-series representation of the radiance to obtain approximation of the time-domain solution. The approach is tested with simulations. The results show that the method can be used to obtain the solution of the time-domain RTE with good accuracy and with significantly fewer computational resources than are needed in the direct time-domain solution.
Studying inner ear protein–protein interactions using FRET and FLIM
Hallworth, Richard; Currall, Benjamin; Nichols, Michael G.; Wu, Xudong; Zuo, Jian
2006-01-01
Molecular genetic studies of the inner ear have recently revealed a large number of previously undescribed proteins, but their functions remain unclear. Optical methods such as FRET and FLIM are just beginning to be applied to the study of functional interactions between novel inner ear proteins. This review discusses the various methods for employing FRET and FLIM in protein–protein interaction studies, their advantages and pitfalls, with examples drawn from inner ear studies.
Calculation of nonzero-temperature Casimir forces in the time domain
International Nuclear Information System (INIS)
Pan, Kai; Reid, M. T. Homer; McCauley, Alexander P.; Rodriguez, Alejandro W.; White, Jacob K.; Johnson, Steven G.
2011-01-01
We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example, using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a nonmonotonic behavior previously demonstrated in a pistonlike geometry.
Attractive new technologies for 7-wavelength time domain optical mammography
Ferocino, Edoardo; Martinenghi, Edoardo; Dalla Mora, Alberto; Pifferi, Antonio; Cubeddu, Rinaldo; Taroni, Paola
2017-07-01
An 8-channel Silicon PhotoMultiplier (SiPM) probe and Time-to-Digital-Converter (TDC) realize a higher-throughput, cheaper and compact detection chain for time-resolved optical mammography than photomultiplier tubes (PMTs) and Time Correlated Single Photon Counting (TCSPC) boards, providing comparable estimate of optical properties with increased optical responsivity.
Time-domain analysis of EPR measurements of polyacetylene and soliton diffusion
International Nuclear Information System (INIS)
Tang, J.; Lin, C.P.; Bowman, M.K.; Norris, J.R.; Isoya, J.; Shirakawa, H.
1983-01-01
A novel analysis of EPR measurements on polyacetylene is demonstrated by the analysis of the conventional line shape in time domain. Quantitative results of the hyperfine-coupling constant, the on-chain diffusion rate, and the off-chain hopping rate were extracted by nonlinear curve fitting to the time-domain signals, and they are consistent with the soliton model of polyacetylene
A general structure for a time-domain model of the cochlea
Duifhuis, H; Wada, H; Takasaka, T; Ikeda, K; Koike, T
2000-01-01
This study presents an implementation of our basic ideas about a time-domain nonlinear model of the cochlea. The time-domain approach is considered necessary because it allows implementation of nonlinearity in general and of a proper temporal analysis of natural transient responses in particular. It
The detection of amoxicillin medicines by terahertz time-domain spectroscopy
Meng, Kun; Li, Zeren; Liu, Qiao
2012-03-01
Terahertz time-domain spectroscopy (THz-TDS) is a new spectroscopic technique, which improve a good complement for other spectroscopic techniques and has broad application prospects in the biomedical field. In this paper, a terahertz time-domain spectroscopy system is set up. Using this system, the amoxicillin drugs are detected, and the spectrum are analyzed.
On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain
DEFF Research Database (Denmark)
Østerberg, Frederik Westergaard; Rizzi, Giovanni; Hansen, Mikkel Fougt
2013-01-01
the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s...
Conceptualizing and Re-Evaluating Resilience across Levels of Risk, Time, and Domains of Competence
Vanderbilt-Adriance, Ella; Shaw, Daniel S.
2008-01-01
This article examines potential theoretical constraints on resilience across levels of risk, time, and domain of outcome. Studies of resilience are reviewed as they relate to the prevalence of resilience across levels of risk (e.g., single life events vs. cumulative risk), time, and domains of adjustment. Based on a thorough review of pertinent…
Kim, Byungyeon; Lee, Minsuk; Park, Byungjun; Lee, Seungrag; Won, Youngjae
2017-02-01
Analog mean-delay (AMD) method is a new powerful alternative method in determining the lifetime of a fluorescence molecule for high-speed confocal fluorescence lifetime imaging microscopy (FLIM). Even though the photon economy and the lifetime precision of the AMD method are proven to be as good as the state-of-the-art time-correlated single photon counting (TC-SPC) method, there have been some speculations and concerns about the accuracy of this method. In the AMD method, the temporal waveform of an emitted fluorescence signal is directly recorded with a slow digitizer whose bandwidth is much lower than the temporal resolution of lifetime to be measured. We found that the drifts and the fluctuations of the absolute zero position in a measured temporal waveform are the major problems in the AMD method. As a referencing technique, we already proposed dual-channel waveform measurement scheme that may suppress these errors. In this study, we have demonstrated real-time confocal AMD-FLIM system with dual-channel waveform measurement technique.
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin
2015-05-16
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Mixed Discretization of the Time Domain MFIE at Low Frequencies
Ulku, Huseyin Arda
2017-01-10
Solution of the magnetic field integral equation (MFIE), which is obtained by the classical marching on-in-time (MOT) scheme, becomes inaccurate when the time step is large, i.e., under low-frequency excitation. It is shown here that the inaccuracy stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring the correct scaling of the current’s Helmholtz components under low-frequency excitation.
Finite Difference Time Domain (FDTD) Simulations Using Graphics Processors
National Research Council Canada - National Science Library
Adams, Samuel; Payne, Jason; Boppana, Rajendra
2007-01-01
.... This paper shows how GPUs can be used to greatly speedup FDTD simulations. The main objective is to leverage GPU processing power for FDTD update calculations and complete computationally expensive simulations in reasonable time...
Time-Domain Optical Fourier Transformation for OTDM-DWDM and DWDM-OTDM Conversion
DEFF Research Database (Denmark)
Mulvad, Hans Christian Hansen; Palushani, Evarist; Galili, Michael
2011-01-01
Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats.......Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats....
Joint time-frequency domain proportional fair scheduler with HARQ for 3GPP LTE systems
Beh, KC; Doufexi, A; Armour, SMD
2008-01-01
This paper explores the potential gain of joint diversity in both frequency domain and time domain which can be exploited to achieve spectral efficiency gains whilst simultaneously facilitating QoS/ fairness in an OFDMA system particularly in 3GPP Long Term Evolution (LTE)). The performance of several joint time-frequency schedulers is investigated. Simulation results show that joint time frequency schedulers achieve significantly superior performance compared to a more conventional time doma...
Time and frequency domain models for multiaxial fatigue life estimation under random loading
Directory of Open Access Journals (Sweden)
Andrea Carpinteri
2015-07-01
Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.
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...
Wake force computation in the time domain for long structures
International Nuclear Information System (INIS)
Bane, K.; Weiland, T.
1983-07-01
One is often interested in calculating the wake potentials for short bunches in long structures using TBCI. For ultra-relativistic particles it is sufficient to solve for the fields only over a window containing the bunch and moving along with it. This technique reduces both the memory and the running time required by a factor that equals the ratio of the structure length to the window length. For example, for a bunch with sigma/sub z/ of one picosecond traversing a single SLAC cell this improvement factor is 15. It is thus possible to solve for the wakefields in very long structures: for a given problem, increasing the structure length will not change the memory required while only adding linearly to the CPU time needed
Time domain NMR and conductivity study of apple pectin biopolymers
International Nuclear Information System (INIS)
Mattos, Ritamara I.; Souto, Sergio; Tambelli, Caio E.
2015-01-01
This communication presents results of 1 H nuclear magnetic resonance of continuous distributions of spin-spin relaxation time (T 2 ) and A.C. conductivity of apple pectin biopolymers plasticized with glycerol and containing acetic acid. The continuous distributions reveals up to three components of spin-spin relaxation times (T 2 ). The two short T 2 components were associated with protons of pectin polymer chain and the longer T 2 can be attributed with the protons of the glycerol. The conductivity values increase with glycerol concentration with maximum at 7.9 x 10 -4 S cm -1 for sample with 3.0 g of glycerol at 83 deg C. The behavior of activation energy and T 2 continuous distribution indicate an increase of proton mobility due the structural changes caused by glycerol addition. (author)
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.
Wind energy system time-domain (WEST) analyzers
Dreier, M. E.; Hoffman, J. A.
1981-01-01
A portable analyzer which simulates in real time the complex nonlinear dynamics of horizontal axis wind energy systems was constructed. Math models for an aeroelastic rotor featuring nonlinear aerodynamic and inertial terms were implemented with high speed digital controllers and analog calculation. This model was combined with other math models of elastic supports, control systems, a power train and gimballed rotor kinematics. A stroboscopic display system graphically depicting distributed blade loads, motion, and other aerodynamic functions on a cathode ray tube is included. Limited correlation efforts showed good comparison between the results of this analyzer and other sophisticated digital simulations. The digital simulation results were successfully correlated with test data.
Partial Fourier analysis of time-harmonic Maxwell's equations in axisymmetric domains
International Nuclear Information System (INIS)
Nkemzi, Boniface
2003-01-01
We analyze the Fourier method for treating time-harmonic Maxwell's equations in three-dimensional axisymmetric domains with non-axisymmetric data. The Fourier method reduces the three-dimensional boundary value problem to a system of decoupled two-dimensional boundary value problems on the plane meridian domain of the axisymmetric domain. The reduction process is fully described and suitable weighted spaces are introduced on the meridian domain to characterize the two-dimensional solutions. In particular, existence and uniqueness of solutions of the two-dimensional problems is proved and a priori estimates for the solutions are given. (author)
Real-time all-optical OFDM transmission system based on time-domain optical fourier transformation
DEFF Research Database (Denmark)
Guan, Pengyu; Kong, Deming; Røge, Kasper Meldgaard
2014-01-01
We propose a novel simple all-optical OFDM transmission system based on time-domain OFT using time-lenses. A real-time 160 Gbit/s DPSK OFDM transmission with 16 decorrelated data subcarriers is successfully demonstrated over 100 km.......We propose a novel simple all-optical OFDM transmission system based on time-domain OFT using time-lenses. A real-time 160 Gbit/s DPSK OFDM transmission with 16 decorrelated data subcarriers is successfully demonstrated over 100 km....
Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.
Wang, Xu; Wada, Naoya
2007-06-11
We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.
Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows
Tseng, K.; Morino, L.
1978-01-01
The Green's Function Method for linearized 3D unsteady potential flow (embedded in the computer code SOUSSA P) is extended to include the time-domain analysis as well as the nonlinear term retained in the transonic small disturbance equation. The differential-delay equations in time, as obtained by applying the Green's Function Method (in a generalized sense) and the finite-element technique to the transonic equation, are solved directly in the time domain. Comparisons are made with both linearized frequency-domain calculations and existing nonlinear results.
Crystallization of amorphous lactose at high humidity studied by terahertz time domain spectroscopy
McIntosh, Alexander I.; Yang, Bin; Goldup, Stephen M.; Watkinson, Michael; Donnan, Robert S.
2013-02-01
We report the first use of terahertz time-domain spectroscopy (THz-TDS) to study the hydration and crystallization of an amorphous molecular solid at high humidity. Lactose in its amorphous and monohydrate forms exhibits different terahertz spectra due to the lack of long range order in the amorphous material. This difference allowed the transformation of amorphous lactose to its monohydrate form at high humidity to be studied in real time. Spectral fitting of frequency-domain data allowed kinetic data to be obtained and the crystallization was found to obey Avrami kinetics. Bulk changes during the crystallization could also be observed in the time-domain.
Time-Domain Astronomy with the Fermi GBM
Hui, C. M.
2017-01-01
The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument sensitive to energies from 8 keV to 40 MeV. Over the past 8 years of operation, the GBM has detected over 240 gamma-ray bursts per year and provided timely GCN notices with localization to few-degree accuracy for follow-up observations. In addition to GRBs, Galactic transients, solar flares, and terrestrial gamma-ray flashes have also been observed. In recent years we have also been searching the continuous GBM data for electromagnetic counterpart to astrophysical neutrinos and gravitational wave events, as these are believed to be associated with gamma-ray bursts. With continuous data downlink every few hours and a temporal resolution of 2 microseconds, GBM is well suited for observing transients and supporting EM follow-up in the era of multi-messenger astronomy.
Becker, A.; Hansen, V.
2007-06-01
In this paper a hybrid method combining the Time-Domain Method of Moments (TD-MoM), the Time-Domain Uniform Theory of Diffraction (TD-UTD) and the Finite-Difference Time-Domain Method (FDTD) is presented. When applying this new hybrid method, thin-wire antennas are modeled with the TD-MoM, inhomogeneous bodies are modelled with the FDTD and large perfectly conducting plates are modelled with the TD-UTD. All inhomogeneous bodies are enclosed in a so-called FDTD-volume and the thin-wire antennas can be embedded into this volume or can lie outside. The latter avoids the simulation of white space between antennas and inhomogeneous bodies. If the antennas are positioned into the FDTD-volume, their discretization does not need to agree with the grid of the FDTD. By using the TD-UTD large perfectly conducting plates can be considered efficiently in the solution-procedure. Thus this hybrid method allows time-domain simulations of problems including very different classes of objects, applying the respective most appropriate numerical techniques to every object.
A Full Parallel Event Driven Readout Technique for Area Array SPAD FLIM Image Sensors
Directory of Open Access Journals (Sweden)
Kaiming Nie
2016-01-01
Full Text Available This paper presents a full parallel event driven readout method which is implemented in an area array single-photon avalanche diode (SPAD image sensor for high-speed fluorescence lifetime imaging microscopy (FLIM. The sensor only records and reads out effective time and position information by adopting full parallel event driven readout method, aiming at reducing the amount of data. The image sensor includes four 8 × 8 pixel arrays. In each array, four time-to-digital converters (TDCs are used to quantize the time of photons’ arrival, and two address record modules are used to record the column and row information. In this work, Monte Carlo simulations were performed in Matlab in terms of the pile-up effect induced by the readout method. The sensor’s resolution is 16 × 16. The time resolution of TDCs is 97.6 ps and the quantization range is 100 ns. The readout frame rate is 10 Mfps, and the maximum imaging frame rate is 100 fps. The chip’s output bandwidth is 720 MHz with an average power of 15 mW. The lifetime resolvability range is 5–20 ns, and the average error of estimated fluorescence lifetimes is below 1% by employing CMM to estimate lifetimes.
A Full Parallel Event Driven Readout Technique for Area Array SPAD FLIM Image Sensors.
Nie, Kaiming; Wang, Xinlei; Qiao, Jun; Xu, Jiangtao
2016-01-27
This paper presents a full parallel event driven readout method which is implemented in an area array single-photon avalanche diode (SPAD) image sensor for high-speed fluorescence lifetime imaging microscopy (FLIM). The sensor only records and reads out effective time and position information by adopting full parallel event driven readout method, aiming at reducing the amount of data. The image sensor includes four 8 × 8 pixel arrays. In each array, four time-to-digital converters (TDCs) are used to quantize the time of photons' arrival, and two address record modules are used to record the column and row information. In this work, Monte Carlo simulations were performed in Matlab in terms of the pile-up effect induced by the readout method. The sensor's resolution is 16 × 16. The time resolution of TDCs is 97.6 ps and the quantization range is 100 ns. The readout frame rate is 10 Mfps, and the maximum imaging frame rate is 100 fps. The chip's output bandwidth is 720 MHz with an average power of 15 mW. The lifetime resolvability range is 5-20 ns, and the average error of estimated fluorescence lifetimes is below 1% by employing CMM to estimate lifetimes.
Time Domain Exploration with the Palomar-QUEST Sky Survey
Mahabal, Ashish A.; Drake, A. J.; Djorgovski, S. G.; Donalek, C.; Glikman, E.; Graham, M. J.; Williams, R.; Baltay, C.; Rabinowitz, D.; PQ Team Caltech; Yale; NCSA; Indiana; , ...
2007-05-01
Palomar-QUEST (PQ) synoptic sky survey has now been routinely processing data from driftscans in real-time. As four photometric bandpasses are utilized in nearly simultaneously, PQ is well suited to search for transient and highly variable objects. Using a series of software filters i.e. programs to select/deselect objects based on certain criteria we shorten the list of candidates from the initially flagged candidate transients. Such filters include looking for known asteroids, known variables, as well as moving, but previously uncatalogued objects based on their motion within a scan as well as between successive scans. Some software filters also deal with instrumental artifacts, edge effects, and use clustering of spurious detections around bright stars. During a typical night when we cover about 500 sq. degrees, we detect hundreds of asteroids, the primary contaminants in the search for astrophysical transients beyond our solar system. Here we describe some statistics based on the software filters we employ and the nature of the objects that seem to survive the process. We also discuss the usefulness of this to amateur astronomers, projects like VOEventNet, and other synoptic sky surveys. We also present an outline of the work we have started on quantifying the variability of quasars, blazars, as well as various classes of Galactic sources, by combining the large number of PQ scans with other existing data sources federated in the Virtual Observatory environment. The PQ survey is partially supported by the U.S. National Science Foundation (NSF).
Energy Technology Data Exchange (ETDEWEB)
Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M. [Technische Universitaet Dresden, Institute of Applied Physics and Center for Advancing Electronics Dresden (cfaed), Dresden (Germany); Kirsten, Lars; Cimalla, Peter; Koch, Edmund [Technische Universitaet Dresden, Faculty of Medicine Carl Gustav Carus, Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden (Germany)
2017-08-15
We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Time-domain reflectometry of water content in portland cement concrete
1997-11-01
Time-domain reflectometry is useful for measuring the moisture content of solids. However, little information exists on its use with portland cement concrete. By monitoring the response from TDR sensors embedded in concrete as the concrete dried, the...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase I
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a high speed automated time domain terahertz computed axial tomography (TD-THz CT) non destructive...
3D parallel inversion of time-domain airborne EM data
Liu, Yun-He; Yin, Chang-Chun; Ren, Xiu-Yan; Qiu, Chang-Kai
2016-12-01
To improve the inversion accuracy of time-domain airborne electromagnetic data, we propose a parallel 3D inversion algorithm for airborne EM data based on the direct Gauss-Newton optimization. Forward modeling is performed in the frequency domain based on the scattered secondary electrical field. Then, the inverse Fourier transform and convolution of the transmitting waveform are used to calculate the EM responses and the sensitivity matrix in the time domain for arbitrary transmitting waves. To optimize the computational time and memory requirements, we use the EM "footprint" concept to reduce the model size and obtain the sparse sensitivity matrix. To improve the 3D inversion, we use the OpenMP library and parallel computing. We test the proposed 3D parallel inversion code using two synthetic datasets and a field dataset. The time-domain airborne EM inversion results suggest that the proposed algorithm is effective, efficient, and practical.
Time-Domain Terahertz Reflection Holograhic Tomography Nondestructive Evaluation System Project
National Aeronautics and Space Administration — We propose to demonstrate key elements of feasibility for a single-sided time-domain terahertz reflection holographic tomographic imaging (TD-THz RHT) nondestructive...
Time Domain Terahertz Axial Computed Tomography Non Destructive Evaluation, Phase II
National Aeronautics and Space Administration — In this Phase 2 project, we propose to develop, construct, and deliver to NASA a computed axial tomography time-domain terahertz (CT TD-THz) non destructive...
Time-Domain Convolutive Blind Source Separation Employing Selective-Tap Adaptive Algorithms
Directory of Open Access Journals (Sweden)
Pan Qiongfeng
2007-01-01
Full Text Available We investigate novel algorithms to improve the convergence and reduce the complexity of time-domain convolutive blind source separation (BSS algorithms. First, we propose MMax partial update time-domain convolutive BSS (MMax BSS algorithm. We demonstrate that the partial update scheme applied in the MMax LMS algorithm for single channel can be extended to multichannel time-domain convolutive BSS with little deterioration in performance and possible computational complexity saving. Next, we propose an exclusive maximum selective-tap time-domain convolutive BSS algorithm (XM BSS that reduces the interchannel coherence of the tap-input vectors and improves the conditioning of the autocorrelation matrix resulting in improved convergence rate and reduced misalignment. Moreover, the computational complexity is reduced since only half of the tap inputs are selected for updating. Simulation results have shown a significant improvement in convergence rate compared to existing techniques.
Time-Domain Convolutive Blind Source Separation Employing Selective-Tap Adaptive Algorithms
Directory of Open Access Journals (Sweden)
Qiongfeng Pan
2007-04-01
Full Text Available We investigate novel algorithms to improve the convergence and reduce the complexity of time-domain convolutive blind source separation (BSS algorithms. First, we propose MMax partial update time-domain convolutive BSS (MMax BSS algorithm. We demonstrate that the partial update scheme applied in the MMax LMS algorithm for single channel can be extended to multichannel time-domain convolutive BSS with little deterioration in performance and possible computational complexity saving. Next, we propose an exclusive maximum selective-tap time-domain convolutive BSS algorithm (XM BSS that reduces the interchannel coherence of the tap-input vectors and improves the conditioning of the autocorrelation matrix resulting in improved convergence rate and reduced misalignment. Moreover, the computational complexity is reduced since only half of the tap inputs are selected for updating. Simulation results have shown a significant improvement in convergence rate compared to existing techniques.
Directory of Open Access Journals (Sweden)
Tariq Jamil Saifullah Khanzada
2012-01-01
Full Text Available The OFDM (Orthogonal Frequency Division Multiplexing is well-known, most utilized wideband communication technique of the current era. SCT (Single Carrier Transmission provides equivalent performance in time domain while decision equalizer is implemented in frequency domain. SCT annihilates the ICT (Inter Carrier Interference and the PAPR (Peak to Average Power Ratio which is inherent to OFDM and degrades its performance in time varying channels. An efficient channel model is presented in this contribution, to implement OFDM and SCT in time domain using impulse responses. Both OFDM and SCT models are derived dialectically to model the channel impulse responses. Our model enhances the performance of time domain SCT compared with OFDM and subsides the PAPR and ICI problems of OFDM. SCT is implemented at symbol level contained in blocks. Simulation results implementing Digital Radio Monadiale (DRM assert the performance gain of SCT over OFDM.
Signal-dependent turnover of the bacterial flagellar switch protein FliM
Delalez, Nicolas J.; Wadhams, George H.; Rosser, Gabriel; Xue, Quan; Brown, Mostyn T.; Dobbie, Ian M.; Berry, Richard M.; Leake, Mark C.; Armitage, Judith P.
2010-01-01
Most biological processes are performed by multiprotein complexes. Traditionally described as static entities, evidence is now emerging that their components can be highly dynamic, exchanging constantly with cellular pools. The bacterial flagellar motor contains ∼13 different proteins and provides an ideal system to study functional molecular complexes. It is powered by transmembrane ion flux through a ring of stator complexes that push on a central rotor. The Escherichia coli motor switches direction stochastically in response to binding of the response regulator CheY to the rotor switch component FliM. Much is known of the static motor structure, but we are just beginning to understand the dynamics of its individual components. Here we measure the stoichiometry and turnover of FliM in functioning flagellar motors, by using high-resolution fluorescence microscopy of E. coli expressing genomically encoded YPet derivatives of FliM at physiological levels. We show that the ∼30 FliM molecules per motor exist in two discrete populations, one tightly associated with the motor and the other undergoing stochastic turnover. This turnover of FliM molecules depends on the presence of active CheY, suggesting a potential role in the process of motor switching. In many ways the bacterial flagellar motor is as an archetype macromolecular assembly, and our results may have further implications for the functional relevance of protein turnover in other large molecular complexes. PMID:20498085
Botts, Jonathan; Savioja, Lauri
2015-04-01
For time-domain modeling based on the acoustic wave equation, spectral methods have recently demonstrated promise. This letter presents an extension of a spectral domain decomposition approach, previously used to solve the lossless linear wave equation, which accommodates frequency-dependent atmospheric attenuation and assignment of arbitrary dispersion relations. Frequency-dependence is straightforward to assign when time-stepping is done in the spectral domain, so combined losses from molecular relaxation, thermal conductivity, and viscosity can be approximated with little extra computation or storage. A mode update free from numerical dispersion is derived, and the model is confirmed with a numerical experiment.
DEFF Research Database (Denmark)
Madsen, Kristoffer Hougaard; Hansen, Lars Kai; Mørup, Morten
2009-01-01
representation we demonstrate how the class of objective functions that are separable in either time or frequency instances allow the gradient in the time or frequency domain to be converted to the opposing domain. We further demonstrate the usefulness of this framework for three different models; Shifted Non-negative...... Matrix Factorization, Convolutive Sparse Coding as well as Smooth and Sparse Matrix Factorization. Matlab implementation of the proposed algorithms are available for download at www.erpwavelab.org....
Windowing of THz time-domain spectroscopy signals: A study based on lactose
Vázquez-Cabo, José; Chamorro-Posada, Pedro; Fraile-Peláez, Francisco Javier; Rubiños-López, Óscar; López-Santos, José María; Martín-Ramos, Pablo
2016-05-01
Time-domain spectroscopy has established itself as a reference method for determining material parameters in the terahertz spectral range. This procedure requires the processing of the measured time-domain signals in order to estimate the spectral data. In this work, we present a thorough study of the properties of the signal windowing, a step previous to the parameter extraction algorithm, that permits to improve the accuracy of the results. Lactose has been used as sample material in the study.
Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission
DEFF Research Database (Denmark)
Verhulst, Sarah; Dau, Torsten; Shera, Christopher A.
2012-01-01
This paper describes the implementation and performance of a nonlinear time-domain model of the cochlea for transient stimulation and human otoacoustic emission generation. The nonlinearity simulates compressive growth of measured basilar-membrane impulse responses. The model accounts for reflect......This paper describes the implementation and performance of a nonlinear time-domain model of the cochlea for transient stimulation and human otoacoustic emission generation. The nonlinearity simulates compressive growth of measured basilar-membrane impulse responses. The model accounts...
Time-domain effects on error rates of multilevel digital pulse interval modulation systems
Wei, Wei; Zhang, Xiaohui; Rao, Jionghui; Pan, Chen
2011-10-01
A channel discretization was applied to investigate time-domain effects on error rates of Multilevel Digital Pulse Interval Modulation (MDPIM) underwater optical wireless communication systems imposed by water scattering. Taking time domain dispersion into account, package error rates of MDPIM were analyzed. The deterioration of package error rates were computed at various link ranges and transmitted rates. Theory model is an agreement with Monte Carlo simulation.
Refractive index sensing using Fluorescence Lifetime Imaging (FLIM)
International Nuclear Information System (INIS)
Jones, Carolyn; Suhling, Klaus
2006-01-01
The fluorescence lifetime is a function of the refractive index of the fluorophore's environment, for example in the case of the biologically important green fluorescent protein (GFP). In order to address the question whether this effect can be exploited to image the local environment of specific proteins in cell biology, we need to determine the distance over which the fluorophore's lifetime is sensitive to the refractive index. To this end, we employ Fluorescence Lifetime Imaging (FLIM) of fluorescein in NaOH buffer at an interface. This approach allows us to map the fluorescence lifetime as a function of distance from a buffer/air and buffer/oil interface. Preliminary data show that the fluorescence lifetime of fluorescein increases near a buffer/air interface and decreases near a buffer/oil interface. The range over which this fluorescence lifetime change occurs is found to be of the order several μm which is consistent with a theoretical model based on the full width at half maximum of the emission spectrum proposed by Toptygin
Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro
2013-01-01
We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599
Zhao, Xiaofeng; McGough, Robert J.
2016-01-01
The attenuation of ultrasound propagating in human tissue follows a power law with respect to frequency that is modeled by several different causal and noncausal fractional partial differential equations. To demonstrate some of the similarities and differences that are observed in three related time-fractional partial differential equations, time-domain Green's functions are calculated numerically for the power law wave equation, the Szabo wave equation, and for the Caputo wave equation. These Green's functions are evaluated for water with a power law exponent of y = 2, breast with a power law exponent of y = 1.5, and liver with a power law exponent of y = 1.139. Simulation results show that the noncausal features of the numerically calculated time-domain response are only evident very close to the source and that these causal and noncausal time-domain Green's functions converge to the same result away from the source. When noncausal time-domain Green's functions are convolved with a short pulse, no evidence of noncausal behavior remains in the time-domain, which suggests that these causal and noncausal time-fractional models are equally effective for these numerical calculations. PMID:27250193
Frequency- and Time-Domain Methods in Soil-Structure Interaction Analysis
Energy Technology Data Exchange (ETDEWEB)
Bolisetti, Chandrakanth; Whittaker, Andrew S.; Coleman, Justin L.
2015-06-01
Soil-structure interaction (SSI) analysis in the nuclear industry is currently performed using linear codes that function in the frequency domain. There is a consensus that these frequency-domain codes give reasonably accurate results for low-intensity ground motions that result in almost linear response. For higher intensity ground motions, which may result in nonlinear response in the soil, structure or at the vicinity of the foundation, the adequacy of frequency-domain codes is unproven. Nonlinear analysis, which is only possible in the time domain, is theoretically more appropriate in such cases. These methods are available but are rarely used due to the large computational requirements and a lack of experience with analysts and regulators. This paper presents an assessment of the linear frequency-domain code, SASSI, which is widely used in the nuclear industry, and the time-domain commercial finite-element code, LS-DYNA, for SSI analysis. The assessment involves benchmarking the SSI analysis procedure in LS-DYNA against SASSI for linearly elastic models. After affirming that SASSI and LS-DYNA result in almost identical responses for these models, they are used to perform nonlinear SSI analyses of two structures founded on soft soil. An examination of the results shows that, in spite of using identical material properties, the predictions of frequency- and time-domain codes are significantly different in the presence of nonlinear behavior such as gapping and sliding of the foundation.
Common-image gathers in the offset domain from reverse-time migration
Zhan, Ge
2014-04-01
Kirchhoff migration is flexible to output common-image gathers (CIGs) in the offset domain by imaging data with different offsets separately. These CIGs supply important information for velocity model updates and amplitude-variation-with-offset (AVO) analysis. Reverse-time migration (RTM) offers more insights into complex geology than Kirchhoff migration by accurately describing wave propagation using the two-way wave equation. But, it has difficulty to produce offset domain CIGs like Kirchhoff migration. In this paper, we develop a method for obtaining offset domain CIGs from RTM. The method first computes the RTM operator of an offset gather, followed by a dot product of the operator and the offset data to form a common-offset RTM image. The offset domain CIGs are then achieved after separately migrating data with different offsets. We generate offset domain CIGs on both the Marmousi synthetic data and 2D Gulf of Mexico real data using this approach. © 2014.
Time and frequency domain methods for quantifying common modulation of motor unit firing patterns
Directory of Open Access Journals (Sweden)
Myers Lance J
2004-10-01
Full Text Available Abstract Background In investigations of the human motor system, two approaches are generally employed toward the identification of common modulating drives from motor unit recordings. One is a frequency domain method and uses the coherence function to determine the degree of linear correlation between each frequency component of the signals. The other is a time domain method that has been developed to determine the strength of low frequency common modulations between motor unit spike trains, often referred to in the literature as 'common drive'. Methods The relationships between these methods are systematically explored using both mathematical and experimental procedures. A mathematical derivation is presented that shows the theoretical relationship between both time and frequency domain techniques. Multiple recordings from concurrent activities of pairs of motor units are studied and linear regressions are performed between time and frequency domain estimates (for different time domain window sizes to assess their equivalence. Results Analytically, it may be demonstrated that under the theoretical condition of a narrowband point frequency, the two relations are equivalent. However practical situations deviate from this ideal condition. The correlation between the two techniques varies with time domain moving average window length and for window lengths of 200 ms, 400 ms and 800 ms, the r2 regression statistics (p Conclusions Although theoretically equivalent and experimentally well correlated there are a number of minor discrepancies between the two techniques that are explored. The time domain technique is preferred for short data segments and is better able to quantify the strength of a broad band drive into a single index. The frequency domain measures are more encompassing, providing a complete description of all oscillatory inputs and are better suited to quantifying narrow ranges of descending input into a single index. In general the
Analysis of noise in energy-dispersive spectrometers using time-domain methods
Goulding, F S
2002-01-01
This paper presents an integrated time domain approach to the optimization of the signal-to-noise ratio in all spectrometer systems that contain a detector that converts incoming quanta of radiation into electrical pulse signals that are amplified and shaped by an electronic pulse shaper. It allows analysis of normal passive pulse shapers as well as time-variant systems where switching of shaping elements occurs in synchronism with the signal. It also deals comfortably with microcalorimeters (sometimes referred to as bolometers), where noise-determining elements, such as the temperature-sensing element's resistance and temperature, change with time in the presence of a signal. As part of the purely time-domain approach, a new method of calculating the Johnson noise in resistors using only the statistics of electron motion is presented. The result is a time-domain analog of the Nyquist formula.
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
Siebelmann, Sebastian; Gehlsen, Uta; Le Blanc, Carolin; Stanzel, Tisha Prabriputaloong; Cursiefen, Claus; Steven, Philipp
2016-12-01
Correct early graft attachment is believed to be crucial for final visual outcome after Descemet membrane endothelial keratoplasty (DMEK). Nonetheless, it is not yet known which imaging technique gives superior results for examining early postoperative graft adherence status. We compared imaging data taken with two different OCT devices to examine the development of graft adherence immediately after DMEK and to determine the superior device in terms of visualization of graft adherence. Ten consecutive patients (1 man/9 women) were examined three times postoperatively within the first 7 h after DMEK surgery using spectral domain OCT (SD-OCT) and time domain OCT (TD-OCT), as prospective case series and retrospective image data analyses. The parameters analyzed were localization and number, visibility and size of graft detachments. TD-OCT was able to detect a greater number of graft detachments after DMEK; however, SD-OCT provided better resolution of minor detachments. Graft detachments varied in position and degree at different time points immediately after surgery. All patients had some graft detachment within the first 7 h after DMEK surgery. TD-OCT enabled better overall analysis of graft detachments, even in the periphery, whereas SD-OCT allowed for the detection of even minor detachments, which suggests that a combination of the two techniques is optimal. Our results indicate that dynamic processes affecting the DMEK graft immediately after transplantation are responsible for changes in the attachment of donor tissue at an early postoperative stage. Modulation of early graft attachment may improve the final graft attachment.
Electromagnetic Field Theory in (N+1)-Space-Time : AModern Time-Domain Tensor/Array Introduction
De Hoop, A.T.
2012-01-01
In this paper, a modern time-domain introduction is presented for electromagnetic field theory in (N+1)-spacetime. It uses a consistent tensor/array notation that accommodates the description of electromagnetic phenomena in N-dimensional space (plus time), a requirement that turns up in present-day
Time-Frequency Signal Representations Using Interpolations in Joint-Variable Domains
2016-06-14
frequently encountered in various radar applications. Data interpolators play a unique role in TF signal representations under missing samples. When...applied in the instantaneous autocorrelation domain over the time variable, the low-pass filter characteristic underlying linear interpolators lends...itself to cross-terms reduction in the ambiguity domain. This is in contrast to interpolation performed over the lag variable or a direct interpolation
Are Total and Domain-Specific Sedentary Time Associated with Overweight in Older Taiwanese Adults?
Directory of Open Access Journals (Sweden)
Ming-Chun Hsueh
2015-10-01
Full Text Available This study investigated the associations between total and domain-specific sedentary time with the risk of overweight in older adults. A cross-sectional study was conducted by administering computer-assisted telephone interviews to 1046 Taiwanese older adults (aged ≥65 years residing in two regions in Taiwan in 2015. Odds ratios (ORs and 95% confidence intervals (CIs were calculated to examine the associations between self-reported total and six domain-specific sedentary times and body mass index status (calculating by self-reported height and weight by using logistic regression analyses. The results showed that compared with older women in the lowest quartile of the total sedentary time, those in the highest quartile were 1.87 (95% CI: 1.10–3.21 times more likely to be overweight, after adjustment for potential confounders. The total sedentary time was stratified into six specific domains, and only watching television more than 2 h per day was positively associated with overweight (OR, 1.55; 95% CI: 1.08–2.25 in older women, whereas no other sedentary time domains were associated with the risk of overweight. No significant associations were observed in older men. Further studies using prospective designs are required to confirm the presently observed effects of total and domain-specific sedentary behavior on the health of older adults.
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
Are Total and Domain-Specific Sedentary Time Associated with Overweight in Older Taiwanese Adults?
Hsueh, Ming-Chun; Liao, Yung; Chang, Shao-Hsi
2015-10-12
This study investigated the associations between total and domain-specific sedentary time with the risk of overweight in older adults. A cross-sectional study was conducted by administering computer-assisted telephone interviews to 1046 Taiwanese older adults (aged ≥65 years) residing in two regions in Taiwan in 2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to examine the associations between self-reported total and six domain-specific sedentary times and body mass index status (calculating by self-reported height and weight) by using logistic regression analyses. The results showed that compared with older women in the lowest quartile of the total sedentary time, those in the highest quartile were 1.87 (95% CI: 1.10-3.21) times more likely to be overweight, after adjustment for potential confounders. The total sedentary time was stratified into six specific domains, and only watching television more than 2 h per day was positively associated with overweight (OR, 1.55; 95% CI: 1.08-2.25) in older women, whereas no other sedentary time domains were associated with the risk of overweight. No significant associations were observed in older men. Further studies using prospective designs are required to confirm the presently observed effects of total and domain-specific sedentary behavior on the health of older adults.
Mie scattering in the time domain. Part II. The role of diffraction.
Lock, James A; Laven, Philip
2011-06-01
The p=0 term of the Mie-Debye scattering amplitude contains the effects of external reflection and diffraction. We computed the reflected intensity in the time domain as a function of the scattering angle and delay time for a short electromagnetic pulse incident on a spherical particle and compared it to the predicted behavior in the forward-focusing region, the specular reflection region, and the glory region. We examined the physical consequences of three different approaches to the exact diffraction amplitude, and determined the signature of diffraction in the time domain. The external reflection surface wave amplitude gradually replaces the diffraction amplitude in the angular transition region between forward-focusing and the region of specular reflection. The details of this replacement were studied in the time domain.
Implementation of ultrasound time-domain cross-correlation blood velocity estimators
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The implementation of real-time blood velocity estimators using time-domain cross-correlation is investigated. The basic algorithm for stationary echo canceling, cross-correlation estimation and subsequent velocity estimation is presented. Sampled data acquired at rates of approximately 20 MHz...
Measuring the Moisture Content of Green Wood Using Time Domain Reflectometry
Laurence Schimleck; Kim Love-Myers; Joe Sanders; Heath Raybon; Richard Daniels; Jerry Mahon; Edward Andrews; Erik Schilling
2011-01-01
The responsible usage of water by facilities that rely on wet log storage in the southern United States has become an issue of great importance as restrictions on water usage have grown in recent years. In order to learn about the dynamics of moisture content in wet-stored logs over time, it is necessary to conduct continuous monitoring of log piles. Time domain...
ANALYSIS AND DESIGN OF CONTROL SYSTEMS BY MEANS OF TIME DOMAIN MATRICES
The time domain matrix method is presented and illustrated as a method of analysis and design of linear, nonlinear, and time varying systems of the...intermediate points throughout the loops are readily available. Also, systems with multiple nonlinearities may be investigated, for which there is not a presently available method of analysis and design.
Optimal time-domain combination of the two calibrated output quadratures of GEO 600
International Nuclear Information System (INIS)
Hewitson, M; Grote, H; Hild, S; Lueck, H; Ajith, P; Smith, J R; Strain, K A; Willke, B; Woan, G
2005-01-01
GEO 600 is an interferometric gravitational wave detector with a 600 m arm-length and which uses a dual-recycled optical configuration to give enhanced sensitivity over certain frequencies in the detection band. Due to the dual-recycling, GEO 600 has two main output signals, both of which potentially contain gravitational wave signals. These two outputs are calibrated to strain using a time-domain method. In order to simplify the analysis of the GEO 600 data set, it is desirable to combine these two calibrated outputs to form a single strain signal that has optimal signal-to-noise ratio across the detection band. This paper describes a time-domain method for doing this combination. The method presented is similar to one developed for optimally combining the outputs of two colocated gravitational wave detectors. In the scheme presented in this paper, some simplifications are made to allow its implementation using time-domain methods
Scatterer size estimation using the center frequency assessed from ultrasound time domain data.
Erlöv, Tobias; Jansson, Tomas; Persson, Hans W; Cinthio, Magnus
2016-10-01
Scatterer size estimation is useful when characterizing tissue using ultrasound. In all previous studies on scatterer size, the estimations are performed in the frequency domain and are thus subjected to a trade off in time-frequency resolution. This study focused on the feasibility of estimating scatterer size in the time domain using only the ultrasound center frequency, assuming a Gaussian-shaped pulse. A model for frequency normalization was derived and the frequency-dependent attenuation was compensated. Five phantoms with well-defined sizes of spherical glass beads were made and scanned with two different linear array transducers with variable center frequencies. A strong correlation (r = 0.99, p estimation of scatterer size is possible using only the center frequency assessed in the time domain.
Progress in parallel implementation of the multilevel plane wave time domain algorithm
Liu, Yang
2013-07-01
The computational complexity and memory requirements of classical schemes for evaluating transient electromagnetic fields produced by Ns dipoles active for Nt time steps scale as O(NtN s 2) and O(Ns 2), respectively. The multilevel plane wave time domain (PWTD) algorithm [A.A. Ergin et al., Antennas and Propagation Magazine, IEEE, vol. 41, pp. 39-52, 1999], viz. the extension of the frequency domain fast multipole method (FMM) to the time domain, reduces the above costs to O(NtNslog2Ns) and O(Ns α) with α = 1.5 for surface current distributions and α = 4/3 for volumetric ones. Its favorable computational and memory costs notwithstanding, serial implementations of the PWTD scheme unfortunately remain somewhat limited in scope and ill-suited to tackle complex real-world scattering problems, and parallel implementations are called for. © 2013 IEEE.
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.
Nonlinear system identification NARMAX methods in the time, frequency, and spatio-temporal domains
Billings, Stephen A
2013-01-01
Nonlinear System Identification: NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains describes a comprehensive framework for the identification and analysis of nonlinear dynamic systems in the time, frequency, and spatio-temporal domains. This book is written with an emphasis on making the algorithms accessible so that they can be applied and used in practice. Includes coverage of: The NARMAX (nonlinear autoregressive moving average with exogenous inputs) modelThe orthogonal least squares algorithm that allows models to be built term by
DWDM-TO-OTDM Conversion by Time-Domain Optical Fourier Transformation
DEFF Research Database (Denmark)
Mulvad, Hans Christian Hansen; Hu, Hao; Galili, Michael
2011-01-01
We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated.......We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated....
Nonlinear System Identification via Basis Functions Based Time Domain Volterra Model
Directory of Open Access Journals (Sweden)
Yazid Edwar
2014-07-01
Full Text Available This paper proposes basis functions based time domain Volterra model for nonlinear system identification. The Volterra kernels are expanded by using complex exponential basis functions and estimated via genetic algorithm (GA. The accuracy and practicability of the proposed method are then assessed experimentally from a scaled 1:100 model of a prototype truss spar platform. Identification results in time and frequency domain are presented and coherent functions are performed to check the quality of the identification results. It is shown that results between experimental data and proposed method are in good agreement.
Design of one-dimensional optical pulse-shaping filters by time-domain topology optimization
DEFF Research Database (Denmark)
Yang, Lirong; Lavrinenko, Andrei; Hvam, Jørn Märcher
2009-01-01
Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems.......Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems....
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe
2013-05-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics
Gedney, Stephen
2011-01-01
Introduction to the Finite-Difference Time-Domain (FDTD) Method for Electromagnetics provides a comprehensive tutorial of the most widely used method for solving Maxwell's equations -- the Finite Difference Time-Domain Method. This book is an essential guide for students, researchers, and professional engineers who want to gain a fundamental knowledge of the FDTD method. It can accompany an undergraduate or entry-level graduate course or be used for self-study. The book provides all the background required to either research or apply the FDTD method for the solution of Maxwell's equations to p
Development and application of dispersive soft ferrite models for time-domain simulation
International Nuclear Information System (INIS)
DeFord, J.F.; Kamin, G.; Craig, G.D.; Walling, L.
1992-01-01
Ferrite has a variety of applications in accelerator components, and the capability to model this magnetic material in the time domain is an important adjunct to currently available accelerator modeling tool. We describe in this report a material model we have developed for the magnetic characteristics of PE11BL, the ferrite found in the ETA-II (Experimental Test Accelerator-II) induction module. This model, which includes the important magnetic dispersion effects found in most soft ferrites, has been implemented in 1-D and 2-D finite-difference time-domain (FDTD) electromagnetic simulators, and comparisons with analytic and experimental results are presented
Shi, Yifei
2013-08-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although \\'relaxed initial conditions,\\' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made \\'invisible\\' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
Quasi-exact evaluation of time domain MFIE MOT matrix elements
Shi, Yifei
2013-07-01
A previously proposed quasi-exact scheme for evaluating matrix elements resulting from the marching-on-in-time (MOT) discretization of the time domain electric field integral equation (EFIE) is extended to matrix entries resulting from the discretization of its magnetic field integral equation (MFIE) counterpart. Numerical results demonstrate the accuracy of the scheme as well as the late-time stability of the resulting MOT-MFIE solver. © 2013 IEEE.
Ulku, Huseyin Arda
2012-09-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
Fast time- and frequency-domain finite-element methods for electromagnetic analysis
Lee, Woochan
Fast electromagnetic analysis in time and frequency domain is of critical importance to the design of integrated circuits (IC) and other advanced engineering products and systems. Many IC structures constitute a very large scale problem in modeling and simulation, the size of which also continuously grows with the advancement of the processing technology. This results in numerical problems beyond the reach of existing most powerful computational resources. Different from many other engineering problems, the structure of most ICs is special in the sense that its geometry is of Manhattan type and its dielectrics are layered. Hence, it is important to develop structure-aware algorithms that take advantage of the structure specialties to speed up the computation. In addition, among existing time-domain methods, explicit methods can avoid solving a matrix equation. However, their time step is traditionally restricted by the space step for ensuring the stability of a time-domain simulation. Therefore, making explicit time-domain methods unconditionally stable is important to accelerate the computation. In addition to time-domain methods, frequency-domain methods have suffered from an indefinite system that makes an iterative solution difficult to converge fast. The first contribution of this work is a fast time-domain finite-element algorithm for the analysis and design of very large-scale on-chip circuits. The structure specialty of on-chip circuits such as Manhattan geometry and layered permittivity is preserved in the proposed algorithm. As a result, the large-scale matrix solution encountered in the 3-D circuit analysis is turned into a simple scaling of the solution of a small 1-D matrix, which can be obtained in linear (optimal) complexity with negligible cost. Furthermore, the time step size is not sacrificed, and the total number of time steps to be simulated is also significantly reduced, thus achieving a total cost reduction in CPU time. The second contribution
Time-domain Helmholtz-Kirchhoff integral for surface scattering in a refractive medium.
Choo, Youngmin; Song, H C; Seong, Woojae
2017-03-01
The time-domain Helmholtz-Kirchhoff (H-K) integral for surface scattering is derived for a refractive medium, which can handle shadowing effects. The starting point is the H-K integral in the frequency domain. In the high-frequency limit, the Green's function can be calculated by ray theory, while the normal derivative of the incident pressure from a point source is formulated using the ray geometry and ray-based Green's function. For a corrugated pressure-release surface, a stationary phase approximation can be applied to the H-K integral, reducing the surface integral to a line integral. Finally, a computationally-efficient, time-domain H-K integral is derived using an inverse Fourier transform. A broadband signal scattered from a sinusoidal surface in an upwardly refracting medium is evaluated with and without geometric shadow corrections, and compared to the result from a conventional ray model.
Quantum-corrected plasmonic field analysis using a time domain PMCHWT integral equation
Uysal, Ismail E.
2016-03-13
When two structures are within sub-nanometer distance of each other, quantum tunneling, i.e., electrons "jumping" from one structure to another, becomes relevant. Classical electromagnetic solvers do not directly account for this additional path of current. In this work, an auxiliary tunnel made of Drude material is used to "connect" the structures as a support for this current path (R. Esteban et al., Nat. Commun., 2012). The plasmonic fields on the resulting connected structure are analyzed using a time domain surface integral equation solver. Time domain samples of the dispersive medium Green function and the dielectric permittivities are computed from the analytical inverse Fourier transform applied to the rational function representation of their frequency domain samples.
Energy Technology Data Exchange (ETDEWEB)
van Milligen, B. Ph. [Asociacion EURATOM-CIEMAT; Calvo, Ivan [CIEMAT, Madrid; Sanchez, Raul [ORNL
2008-01-01
The present work studies continuous time random walks (CTRWs) in a finite domain. A broad class of boundary conditions, of which absorbing and reflecting boundaries are particular cases, is considered. It is shown how any CTRW in this class can be mapped to a CTRW in an infinite domain. This may allow applying well-known techniques for infinite CTRWs to the problem of obtaining the fluid limit for finite domain CTRWs, where the fluid limit (or hydrodynamic limit) refers to the partial differential equation describing the long time and large distance behavior of the system. As an illustration, the fluid limit equation and its propagator are obtained explicitly in the case of purely reflecting boundaries. We also derive the modification of the Riemann-Liouville fractional differential operators implementing the reflecting boundary conditions.
Energy Technology Data Exchange (ETDEWEB)
Milligen, B Ph van; Calvo, I [Asociacion EURATOM-CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain); Sanchez, R [Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)], E-mail: boudewijn.vanmilligen@ciemat.es
2008-05-30
The present work studies continuous time random walks (CTRWs) in a finite domain. A broad class of boundary conditions, of which absorbing and reflecting boundaries are particular cases, is considered. It is shown how any CTRW in this class can be mapped to a CTRW in an infinite domain. This may allow applying well-known techniques for infinite CTRWs to the problem of obtaining the fluid limit for finite domain CTRWs, where the fluid limit (or hydrodynamic limit) refers to the partial differential equation describing the long time and large distance behaviour of the system. As an illustration, the fluid limit equation and its propagator are obtained explicitly in the case of purely reflecting boundaries. We also derive the modification of the Riemann-Liouville fractional differential operators implementing the reflecting boundary conditions.
CSIR Research Space (South Africa)
Vogt, D
2008-06-01
Full Text Available published borehole radar antennas have achieved directivity by post processing data received in the frequency domain, or by constructing an aperture antenna, where borehole dimensions allowed this. In this paper, a time-domain technique is investigated...
Time-domain approach for multi-exciter random environment test
Cui, Song; Chen, Huai-hai; He, Xu-dong
2017-06-01
This paper presents a time-domain method for multi-exciter random environment tests. Traditional random environment test theory has been formulated in the frequency domain, where an important step is taking the inverse of the frequency response function matrices (FRFMs). The accuracy of this inversion tends to be poor, particularly at frequencies near lightly damped resonances. The currently used control algorithms face difficulties in suppressing abnormal spectral lines caused by this inverse problem. In this paper, traditional formulations of the environment test are reformed, and the time-domain method is adopted; this results in a more precise inverse operation in environment tests. To achieve this, reference spectra are converted into time-domain response signals. The finite long driving signals are derived by the state-space method with estimated state vectors. During the process, the inverse of rank-deficient Toeplitz matrices are stabilized with truncated singular value decomposition (TSVD) to suppress all abnormally high-level components in the driving forces; thus, overall, the spectra lines produced by noise within the frequency band are filtered out. A numerical simulation of a single-axis random vibration test of a cantilever beam is conducted using the traditional frequency-domain procedure (FDP) and the proposed time-domain procedure (TDP). The response spectra generated by both procedures are tested by control algorithms, and the result shows that responses generated by the proposed TDP are more easily controlled. The conditions of stability for both the FDP and the TDP are also determined and introduced in the simulation. Moreover, a multi-axis vibration experiment further validates the effectiveness of the TDP.
DEFF Research Database (Denmark)
Tanev, Stoyan; Sun, Wenbo
2012-01-01
This chapter reviews the fundamental methods and some of the applications of the three-dimensional (3D) finite-difference time-domain (FDTD) technique for the modeling of light scattering by arbitrarily shaped dielectric particles and surfaces. The emphasis is on the details of the FDTD algorithm...
Managing Time-Based Conflict Across Life Domains In Nigeria: A ...
African Journals Online (AJOL)
which employees in a developing country attempt to resolve time-based conflict between work, family and other activities. A decision making framework is used to study the way Nigerian managers handled conflicting pressures from their various life domains. Participants were asked to write a diary, in a free-response format ...
Range/velocity limitations for time-domain blood velocity estimation
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt
1993-01-01
The traditional range/velocity limitation for blood velocity estimation systems using ultrasound is elucidated. It is stated that the equation is a property of the estimator used, not the actual physical measurement situation, as higher velocities can be estimated by the time domain cross...
The finite-difference time-domain method for electromagnetics with Matlab simulations
Elsherbeni, Atef Z
2016-01-01
This book introduces the powerful Finite-Difference Time-Domain method to students and interested researchers and readers. An effective introduction is accomplished using a step-by-step process that builds competence and confidence in developing complete working codes for the design and analysis of various antennas and microwave devices.
Non-Causal Time-Domain Filters for Single-Channel Noise Reduction
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Benesty, Jacob; Christensen, Mads Græsbøll
2012-01-01
suppression and signal distortion by allowing the filters to be non-causal. Non-causal time-domain filters require knowledge of the future, and are therefore not directly implementable. If the observed signal is processed in blocks, however, the non-causal filters are implementable. In this paper, we propose...
Effects of the airwave in time-domain marine controlled-source electromagnetics
Hunziker, J.W.; Slob, E.C.; Mulder, W.
2011-01-01
In marine time-domain controlled-source electromagnetics (CSEM), there are two different acquisition methods: with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave. Illustrations of the electric field as a function of space
A Time-Domain Method for Separating Incident and Reflected Irregular Waves
DEFF Research Database (Denmark)
Frigaard, Peter; Brorsen, Michael
of the model test. Goda and Suzuki (1976) presented a frequency method for estimation of irregular incident and reflected waves in random waves. Mansard and Funke (1980) improved this method uaing a least squares technique. In the following, a time-domain method for seperating the incident waves...
Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope
2016-10-19
TECHNICAL DOCUMENT 3308 September 2016 Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope Andrew B. Sabater Paul...angular random walk (ARW), bias instability, and scale factor instability. While there are methods to address issues with bias and scale factor...8 4. ANGULAR RANDOM WALK CHARACTERIZATION
Wang, Zhaojun; Zhou, Xiaoming
2016-12-01
The authors study the wave propagation in continuum acoustic metamaterials whose all or not all of the principal elements of the mass tensor or the scalar compressibility can be negative due to wave dispersion. Their time-domain wave characteristics are particularly investigated by the finite-difference time-domain (FDTD) method, in which algorithms for the Drude and Lorentz dispersion pertinent to acoustic metamaterials are provided necessarily. Wave propagation nature of anisotropic acoustic metamaterials with all admissible material parameters are analyzed in a general manner. It is found that anomalous negative refraction phenomena can appear in several dispersion regimes, and their unique time-domain signatures have been discovered by the FDTD modeling. It is further proposed that two different metamaterial layers with specially assigned dispersions could comprise a conjugate pair that permits wave propagation only at specific points in the wave vector space. The time-domain pulse simulation verifies that acoustic directive radiation capable of modulating radiation angle with the wave frequency can be realized with this conjugate pair. The study provides the detailed analysis of wave propagation in anisotropic and dispersive acoustic mediums, which makes a further step toward dispersion engineering and transient wave control through acoustic metamaterials.
Fra Angelico’s painting technique revealed by terahertz time-domain imaging (THz-TDI)
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Picollo, Marcello; Cucci, Costanza
2016-01-01
We have investigated with terahertz time-domain imaging (THz-TDI) the well-known Lamentation over the dead Christ panel painting (San Marco Museum, Florence) painted by Fra Giovanni Angelico within 1436 and 1441. The investigation provided a better understanding of the construction and gilding...
Postural Analysis in Time and Frequency Domains in Patients with Ehlers-Danlos Syndrome
Galli, Manuela; Rigoldi, Chiara; Celletti, Claudia; Mainardi, Luca; Tenore, Nunzio; Albertini, Giorgio; Camerota, Filippo
2011-01-01
The goal of this work is to analyze postural control in Ehlers-Danlos syndrome (EDS) participants in time and frequency domain. This study considered a pathological group composed by 22 EDS participants performing a postural test consisting in maintaining standing position over a force platform for 30 s in two conditions: open eyes (OE) and closed…
Time domain-nuclear magnetic resonance study of chars from southern hardwoods
Thomas Elder; Nicole Labbe; David Harper; Timothy Rials
2006-01-01
Chars from the thermal degradation of silver maple (Acer saccharinum), red maple (Acer rubrum), sugar maple (Acer saccharum), and white oak (Quercus spp.), performed at temperatures from 250 to 350 oC, were examined using time domain-nuclear magnetic resonance...
Continuous performance test assessed with time-domain functional near infrared spectroscopy
Torricelli, Alessandro; Contini, Davide; Spinelli, Lorenzo; Caffini, Matteo; Butti, Michele; Baselli, Giuseppe; Bianchi, Anna M.; Bardoni, Alessandra; Cerutti, Sergio; Cubeddu, Rinaldo
2007-07-01
A time-domain fNIRS multichannel system was used in a sustained attention protocol (continuous performance test) to study activation of the prefrontal cortex. Preliminary results on volounteers show significant activation (decrease in deoxy-hemoglobin and increase in oxy-hemoglobin) in both left and right prefrontal cortex.
Development of a method for reconstruction of crowded NMR spectra from undersampled time-domain data
Energy Technology Data Exchange (ETDEWEB)
Ueda, Takumi; Yoshiura, Chie; Matsumoto, Masahiko; Kofuku, Yutaka; Okude, Junya; Kondo, Keita; Shiraishi, Yutaro [The University of Tokyo, Graduate School of Pharmaceutical Sciences (Japan); Takeuchi, Koh [Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology (Japan); Shimada, Ichio, E-mail: shimada@iw-nmr.f.u-tokyo.ac.jp [The University of Tokyo, Graduate School of Pharmaceutical Sciences (Japan)
2015-05-15
NMR is a unique methodology for obtaining information about the conformational dynamics of proteins in heterogeneous biomolecular systems. In various NMR methods, such as transferred cross-saturation, relaxation dispersion, and paramagnetic relaxation enhancement experiments, fast determination of the signal intensity ratios in the NMR spectra with high accuracy is required for analyses of targets with low yields and stabilities. However, conventional methods for the reconstruction of spectra from undersampled time-domain data, such as linear prediction, spectroscopy with integration of frequency and time domain, and analysis of Fourier, and compressed sensing were not effective for the accurate determination of the signal intensity ratios of the crowded two-dimensional spectra of proteins. Here, we developed an NMR spectra reconstruction method, “conservation of experimental data in analysis of Fourier” (Co-ANAFOR), to reconstruct the crowded spectra from the undersampled time-domain data. The number of sampling points required for the transferred cross-saturation experiments between membrane proteins, photosystem I and cytochrome b{sub 6}f, and their ligand, plastocyanin, with Co-ANAFOR was half of that needed for linear prediction, and the peak height reduction ratios of the spectra reconstructed from truncated time-domain data by Co-ANAFOR were more accurate than those reconstructed from non-uniformly sampled data by compressed sensing.
DEFF Research Database (Denmark)
Maurya, Pradip Kumar; Fiandaca, Gianluca; Auken, Esben
study a large contaminated site in Denmark was investigated using direct current resistivity and time domain induced polarization (DCIP). For this purpose 14 profiles were collected alongside a stream in order to investigate the contamination and delineate the lithological units. 2D inversion using...
Insensitivity of single particle time domain measurements to laser velocimeter 'Doppler ambiguity.'
Johnson, D. A.
1973-01-01
It is shown that single particle time domain measurements in high speed gas flows obtained by a laser velocimeter technique developed for use in wind tunnels are not affected by the so-called 'Doppler ambiguity.' A comparison of hot-wire anemometer and laser velocimeter measurements taken under similar flow conditions is used for the demonstration.
Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...
Non-linear wave loads and ship responses by a time-domain strip theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hydroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented as a Timoshenko beam. Numerical calculations are presented for the S175 Containership...
Non-Linear Wave Loads and Ship responses by a time-domain Strip Theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
. Based on this time-domain strip theory, an efficient non-linear hyroelastic method of wave- and slamming-induced vertical motions and structural responses of ships is developed, where the structure is represented by the Timoshenko beam theory. Numerical calculations are presented for the S175...
Discrete-Time Domain Modelling of Voltage Source Inverters in Standalone Applications
DEFF Research Database (Denmark)
Federico, de Bosio; de Sousa Ribeiro, Luiz Antonio; Freijedo Fernandez, Francisco Daniel
2017-01-01
The decoupling of the capacitor voltage and inductor current has been shown to improve significantly the dynamic performance of voltage source inverters in standalone applications. However, the computation and PWM delays still limit the achievable bandwidth. In this paper a discrete-time domain...
Temperature effects in soil water content determined with time domain reflectometry
Halbertsma, J.; Elsen, van den E.; Bohl, H.; Skierucha, W.
1996-01-01
The relative permittivity of water decreases with increasing temperature. Therefore, it is likely that the soil water content determined with time domain reflectometry is influenced by temperature. This study showed that significant temperature effects may occur. The magnitude of these effects is a
Characterization of Flaws in the Elastic Medium by Time Domain Born Approximation
International Nuclear Information System (INIS)
Yi, J. Y.; Lee, S. K.; Lee, J. O.; Kim, Y. H.
1983-01-01
The impulse response function are studied using time domain Born approximation in two cases; firstly when the material parameters of a flaw are constant, secondly when the parameters are varying with positions. From the impulse response functions, characteristics can be learned about a flaw with high symmetry
Directory of Open Access Journals (Sweden)
Konishi Tsuyoshi
2010-01-01
Full Text Available We propose and demonstrate a wavelength- and time-selective reconfigurable optical add/drop multiplexer (ROADM using time-frequency domain processing. The proposed ROADM is realized by allocating wavelength channels and time slots to corresponding 2D spatial channels on a MEMS optical switch. Experimental results show the wavelength- and time-selective drop operation for a signal with equivalent 3.2 Tb/s (0.64 channels, and the reconfigurability by the switching operation of the MEMS optical switch.
Directory of Open Access Journals (Sweden)
Tsuyoshi Konishi
2010-01-01
Full Text Available We propose and demonstrate a wavelength- and time-selective reconfigurable optical add/drop multiplexer (ROADM using time-frequency domain processing. The proposed ROADM is realized by allocating wavelength channels and time slots to corresponding 2D spatial channels on a MEMS optical switch. Experimental results show the wavelength- and time-selective drop operation for a signal with equivalent 3.2 Tb/s (0.64 Tb/s×5 channels, and the reconfigurability by the switching operation of the MEMS optical switch.
Ulku, Huseyin Arda
2013-08-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
Suppression of Time-domain Jitter of Impulse Radio Ultra-wide Band Radar
Directory of Open Access Journals (Sweden)
Liang Fu-lai
2015-08-01
Full Text Available For Impulse Radio Ultra-Wide Band (IR-UWB radar, the time jitter transforms the static clutters to dynamic clutters. Thus, strong residue exists and false alarms form after traditional direct current suppression. The effect of the time-domain jitter on the life detection capacity is analyzed, and then the phenomenon that the relative time delays between the coupling echoes can reflect the time jitter is pointed out. Based on the coupling echo, a method of time jitter suppression is proposed. Experimental data demonstrate that the proposed method can effectively suppress the residue of strong static clutter, and further improve the life-detection capacity.
Bacillus spores and their relevant chemicals studied by terahertz time domain spectroscopy
Tang, Jianhua; Yang, Bin; Llewellyn, Ian; Cutler, Ronald R.; Donnan, Robert S.
2014-01-01
Terahertz time domain spectroscopy has been used to investigate 0.2-2.2 THz transmission responses of Bacillus spores and their related chemical components. Whilst no THz signatures could be clearly associated with either sporulated cells or their chief chemical components, differing degrees of signal attenuation and frequency-dependent light scattering were observed depending on spore composition and culture media. The observed monotonic increase in absorption by spores over this THz spectral domain is mainly from Mie scattering and also from remnant water bound to the spores.
International Nuclear Information System (INIS)
Khorasani, A.; Mousavi Shalmani, M. A.; Piervali Bieranvand, N.
2011-01-01
An accurate, precise, fast and ease as well as the ability for measurements in depth are the characteristics that are desirable in measuring soil moisture methods. To compare methods (time domain reflectometry and capacitance) with neutron scattering for soil water monitoring, an experiment was carried out in a randomized complete block design (Split Split plot) on tomato with three replications on the experimental field of International Atomic Energy Agency (Seibersdorf-Austria). The treatment instruments for the soil moisture monitoring (main factor) consist of neutron gauge, Diviner 2000, time domain reflectometer and an EnviroScan and different irrigation systems (first sub factor) consist of trickle and furrow irrigations and different depths of soil (second sub factor) consist of 0-20, 20-40 and 40-60 cm. The results showed that for the neutron gauge and time domain reflectometer the amount of soil moisture in both of trickle and furrow irrigations were the same, but the significant differences were recorded in Diviner 2000 and EnviroScan measurements. The results of this study showed that the neutron gauge is an acceptable and reliable means with the modern technology, with a precision of ±2 mm in 450 mm soil water to a depth of 1.5 meter and can be considered as the most practical method for measuring soil moisture profiles and irrigation planning program. The time domain reflectometer method in most mineral soils, without the need for calibration, with an accuracy ±0.01m 3 m -3 has a good performance in soil moisture and electrical conductivity measurements. The Diviner 2000 and EnviroScan are not well suitable for the above conditions for several reasons such as much higher soil moisture and a large error measurement and also its sensitivity to the soil gap and to the small change in the soil moisture in comparison with the neutron gauge and the time domain reflectometer methods.
[Identification of Official Rhubarb Samples by Using PLS and Terahertz Time-Domain Spectroscopy].
Wang, Jing-rong; Zhang, Zhuo-yong; Zhang, Zhen-wei; Xiang, Yu-hong
2016-02-01
The development of terahertz technology is attracting broad intention in recent years. The quality identification is important for the quality control of Chinese medicine production. In the present work, terahertz time-domain spectroscopy (THz-TDS) combined with partial least squares (PLS) were used for the identification model building and studied based on 41 official and unofficial rhubarb samples. First, the THz-TDS spectra of rhubarb samples were collected and were preprocessed by using chemometrics methods rather than transformed to absorption spectra. The identification models were then established based on the processed terahertz time domain spectra. The spectral preprocessing methods include Savitzky-Golay (S-G) first derivative, detrending, standard normal transformation (SNV), autoscaling, and mean centering. The identification accuracy of 90% was accomplished by using proper pretreatment methods, which was higher than the classified accuracy of 80% without any preprocessing for the time domain spectra. The component number of the PLS model was evaluated by leave-one-out cross-validation (LOOCV). The minimum values of the root-mean squared error of cross-validation (RMSECV) and root-mean squared error of prediction (RMSEP) were 0.076 6 and 0.169 0 by using mean centering method, respectively. The results of this work showed that the combination of terahertz time domain spectroscopy technology with chemometrics methods, as well as PLS can be applied for the recognition of genuine and counterfeit Chinese herbal medicines, as well as official and unofficial rhubarbs. The advantage of using terahertz time domain spectra directly with no transformation into absorption spectra is: (1) the thickness of samples could not be considered in the model establishment, and (2) the spectral processing was simplified. The proposed method based on the combination of THz-TDS and chemometrics proved to be rapid, simple, non-pollution and solvent free, suitable to be
Zhang, Zhendong
2017-07-11
Full waveform inversion for reection events is limited by its linearized update re-quirements given by a process equivalent to migration. Unless the background velocity model is reasonably accurate, the resulting gradient can have an inaccurate update direction leading the inversion to converge what we refer to as local minima of the objective function. In our approach, we consider mild lateral variation in the model, and thus, use a gradient given by the oriented time-domain imaging method. Specifically, we apply the oriented time-domain imaging on the data residual to obtain the geometrical features of the velocity perturbation. After updating the model in the time domain, we convert the perturbation from the time domain to depth using the average velocity. Considering density is constant, we can expand the conventional 1D impedance inversion method to 2D or 3D velocity inversion within the process of full waveform inversion. This method is not only capable of inverting for velocity, but it is also capable of retrieving anisotropic parameters relying on linearized representations of the reection response. To eliminate the cross-talk artifacts between different parameters, we utilize what we consider being an optimal parametrization for this step. To do so, we extend the prestack time-domain migration image in incident angle dimension to incorporate angular dependence needed by the multiparameter inversion. For simple models, this approach provides an efficient and stable way to do full waveform inversion or modified seismic inversion and makes the anisotropic inversion more practicable. The proposed method still needs kinematically accurate initial models since it only recovers the high-wavenumber part as conventional full waveform inversion method does. Results on synthetic data of isotropic and anisotropic cases illustrate the benefits and limitations of this method.
Layered and Laterally Constrained 2D Inversion of Time Domain Induced Polarization Data
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Auken, Esben
transform of a complex resistivity forward response and the inversion extracts the spectral information of the time domain measures in terms of the Cole-Cole parameters. The developed forward code and inversion algorithm use the full time decay of the induced polarization response, together with an accurate...... algorithm retrieves consistent values for both the Cole-Cole parameters and the layer thicknesses and is a promising tool for identifying formation boundaries, e.g. in for discriminating sand and clay layers or pollution fans, due to the chargeability of these layers.......In a sedimentary environment, quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. We have developed a new layered and laterally constrained inversion algorithm for time domain induced polarization data. The algorithm is based on the time...
Domain-Specific and Unspecific Reaction Times in Experienced Team Handball Goalkeepers and Novices.
Helm, Fabian; Reiser, Mathias; Munzert, Jörn
2016-01-01
In our everyday environments, we are constantly having to adapt our behavior to changing conditions. Hence, processing information is a fundamental cognitive activity, especially the linking together of perceptual and action processes. In this context, expertise research in the sport domain has concentrated on arguing that superior processing performance is driven by an advantage to be found in anticipatory processes (see Williams et al., 2011, for a review). This has resulted in less attention being paid to the benefits coming from basic internal perceptual-motor processing. In general, research on reaction time (RT) indicates that practicing a RT task leads to an increase in processing speed (Mowbray and Rhoades, 1959; Rabbitt and Banerji, 1989). Against this background, the present study examined whether the speed of internal processing is dependent on or independent from domain-specific motor expertise in unpredictable stimulus-response tasks and in a double stimulus-response paradigm. Thirty male participants (15 team handball goalkeepers and 15 novices) performed domain-unspecific simple or choice stimulus-response (CSR) tasks as well as CSR tasks that were domain-specific only for goalkeepers. As expected, results showed significantly faster RTs for goalkeepers on domain-specific tasks, whereas novices' RTs were more frequently excessively long. However, differences between groups in the double stimulus-response paradigm were not significant. It is concluded that the reported expertise advantage might be due to recalling stored perceptual-motor representations for the domain-specific tasks, implying that experience with (practice of) a motor task explicitly enhances the internal processing of other related domain-specific tasks.
Li, Ping
2018-04-13
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
International Nuclear Information System (INIS)
Hwang, Young Tae; Jo, Seong Seock; Choi, Jong Won; Ko, Nak Youl
2012-01-01
Based on the data observed and analyzed on a groundwater flow system in the KURT (KAERI Underground Research Tunnel) site, the transport of radionuclides, which were assumed to be released at the supposed position, was calculated on the time-domain. A groundwater pathway from the release position to the surface was identified by simulating the groundwater flow model with the hydrogeological characteristics measured from the field tests in the KURT site. The elapsed time when the radionuclides moved through the pathway is evaluated using TDRW (Time Domain Random Walk) method for simulating the transport on the time-domain. Some retention mechanisms, such as radioactive decay, equilibrium sorption, and matrix diffusion, as well as the advection dispersion were selected as the factors to influence on the elapsed time. From the simulation results, the effects of the sorption and matrix diffusion, determined by the properties of the radionuclides and underground media, on the transport of the radionuclides were analyzed and a decay chain of the radionuclides was also examined. The radionuclide ratio of the mass discharge into the surface environment to the mass released from the supposed repository did not exceed 10 -3 , and it decreased when the matrix diffusion were considered. The method used in this study could be used in preparing the data on radionuclide transport for a safety assessment of a geological disposal facility because the method could evaluate the travel time of the radionuclides considering the transport retention mechanism.
Numerical results for near surface time domain electromagnetic exploration: a full waveform approach
Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.
2015-12-01
Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two
Axes of Discovery: The Time Domain and the Radio Synoptic Survey Telescope
Cordes, J. M.
2008-08-01
As Heraclitus might have said, ``You don't observe the same universe twice,'' and in modern times we recognize the time domain as an important dimension in the overall phase space of variables that characterizes the observable universe. Examples abound across the electromagnetic spectrum and in non-photonic regimes (neutrinos, gravitational waves, cosmic rays). However, while we can glimpse the richness of time-domain phenomena at radio wavelengths, the radio sky is largely unexplored in any comprehensive sense, especially when compared to the successes of wide-field surveys at high energies. Known radio transients are as short as 0.4 ns with an equivalent brightness temperature of 1042 K tep{jmc:he07} related to the coherent nature of pulsar radiation; others with incoherent emission extend to hour and longer time scales with thermal brightness temperatures. Some time-domain properties are intrinsic to sources while others are imposed by multi-path propagation through intervening plasma. This paper discusses both known and speculative aspects of the radio transient sky, with an emphasis on discoveries that can be made with new, appropriately designed instrumentation and telescopes. A generalized survey figure of merit is presented that takes into account the rate and duration of transient celestial events. The key for expanding discovery space is a wide field of view (FoV) combined with adequate sensitivity and high-resolution sampling in time and frequency. I discuss implementation of time-domain studies as an integral part of synoptic survey modes and the potential for cross-wavelength and joint photonic/non-photonic studies. In particular, I make the case for designing and operating the mid-frequency-range Square Kilometer Array as a Radio Synoptic Survey Telescope.
Formation and life-time of memory domains in the dissipative quantum model of brain
Alfinito, E.; Vitiello, G.
2000-01-01
We show that in the dissipative quantum model of brain the time-dependence of the frequencies of the electrical dipole wave quanta leads to the dynamical organization of the memories in space (i.e. to their localization in more or less diffused regions of the brain) and in time (i.e. to their longer or shorter life-time). The life-time and the localization in domains of the memory states also depend on internal parameters and on the number of links that the brain establishes with the external...
Efficient reconstruction of dispersive dielectric profiles using time domain reflectometry (TDR
Directory of Open Access Journals (Sweden)
P. Leidenberger
2006-01-01
Full Text Available We present a numerical model for time domain reflectometry (TDR signal propagation in dispersive dielectric materials. The numerical probe model is terminated with a parallel circuit, consisting of an ohmic resistor and an ideal capacitance. We derive analytical approximations for the capacitance, the inductance and the conductance of three-wire probes. We couple the time domain model with global optimization in order to reconstruct water content profiles from TDR traces. For efficiently solving the inverse problem we use genetic algorithms combined with a hierarchical parameterization. We investigate the performance of the method by reconstructing synthetically generated profiles. The algorithm is then applied to retrieve dielectric profiles from TDR traces measured in the field. We succeed in reconstructing dielectric and ohmic profiles where conventional methods, based on travel time extraction, fail.
Fictitious Domain Technique for the Calculation of Time-Periodic Solutions of Scattering Problem
Directory of Open Access Journals (Sweden)
Ling Rao
2011-01-01
Full Text Available The fictitious domain technique is coupled to the improved time-explicit asymptotic method for calculating time-periodic solution of wave equation. Conventionally, the practical implementation of fictitious domain method relies on finite difference time discretizations schemes and finite element approximation. Our new method applies finite difference approximations in space instead of conventional finite element approximation. We use the Dirac delta function to transport the variational forms of the wave equations to the differential form and then solve it by finite difference schemes. Our method is relatively easier to code and requires fewer computational operations than conventional finite element method. The numerical experiments show that the new method performs as well as the method using conventional finite element approximation.
Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics
DEFF Research Database (Denmark)
D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa
2014-01-01
Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time-domain spe......Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....
Valdés, Felipe
2013-03-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis functions and a collocation testing procedure, thus allowing for a marching-on-in-time (MOT) solution scheme. Unlike dual-source formulations, single-source equations involve space-time domain operator products, for which spatial discretization techniques developed for standalone operators do not apply. Here, the spatial discretization of the single-source time-domain integral equations is achieved by using the high-order divergence-conforming basis functions developed by Graglia alongside the high-order divergence-and quasi curl-conforming (DQCC) basis functions of Valdés The combination of these two sets allows for a well-conditioned mapping from div-to curl-conforming function spaces that fully respects the space-mapping properties of the space-time operators involved. Numerical results corroborate the fact that the proposed procedure guarantees accuracy and stability of the MOT scheme. © 2012 IEEE.
Zheng, WeiJia; Luo, Ying; Wang, XiaoHong; Pi, YouGuo; Chen, YangQuan
2017-05-01
In order to achieve a desired control performance characterized by satisfying specifications in both frequency-domain and time-domain simultaneously, an optimal fractional order proportional integral derivative (PI λ D μ ) controller design strategy is proposed based on analytical calculation and Differential Evolution algorithm for a permanent magnet synchronous motor (PMSM) servo system in this paper. In this controller design, the frequency-domain specifications can guarantee the system stability with both gain margin and phase margin, and also the system robustness to loop gain variations. The time-domain specifications can ensure the desired step response performance with rapid rising curve, constrained overshoot, and proper power consuming. Compared with the PI λ controller and the traditional PID controller, PI λ D μ controller can get obvious benefits from two more degrees of freedom of the fractional orders λ and μ on satisfying multiple constraints simultaneously and achieving better servo tracking performance for the PMSM servo system. PMSM speed tracking simulations and experiments are demonstrated to show the significant advantages of using the proposed optimal PI λ D μ controller over the optimal fractional order PI λ controller and traditional integer order PID controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
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
Mathematical Framework for Hydromechanical Time-Domain Simulation of Wave Energy Converters
Directory of Open Access Journals (Sweden)
J. Seixas de Medeiros
2018-01-01
Full Text Available Efficient design of wave energy converters based on floating body motion heavily depends on the capacity of the designer to accurately predict the device’s dynamics, which ultimately leads to the power extraction. We present a (quasi-nonlinear time-domain hydromechanical dynamic model to simulate a particular type of pitch-resonant WEC which uses gyroscopes for power extraction. The dynamic model consists of a time-domain three-dimensional Rankine panel method coupled, during time integration, with a MATLAB algorithm that solves for the equations of the gyroscope and Power Take-Off (PTO. The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time integration using a 4th-order Runge-Kutta method. The panel method, accounting for the gyroscope and PTO dynamics, is then used for the calculation of the optimal flywheel spin, PTO damping, and average power extracted, completing the basic design cycle of the WEC. The proposed numerical method framework is capable of considering virtually any type of nonlinear force (e.g., nonlinear wave loads and it is applied and verified in the paper against the traditional frequency domain linear model. It proved to be a versatile tool to verify performance in resonant conditions.
Time domain characterization for the electric field considering a Chinese female physical phantom
Yang, Xiaodong; Zhang, Qing
2015-02-01
Recently, wireless communications around the human body, which are essential for wireless vital data monitoring, have been widely studied. Besides statistical channel modeling, characterization of time-varying electric field is also highly necessary to understand the communication mechanism in this area; however, few studies have been conducted. In this paper, time-varying electric fields, both on the digital human body and in the two-dimensional space around the human body, were studied through the finite-difference time-domain (FDTD) numerical analysis.
Al Jarro, Ahmed
2012-11-01
An explicit marching-on-in-time (MOT) scheme for solving the time domain volume integral equation is presented. The proposed method achieves its stability by employing, at each time step, a corrector scheme, which updates/corrects fields computed by the explicit predictor scheme. The proposedmethod is computationally more efficient when compared to the existing filtering techniques used for the stabilization of explicit MOT schemes. Numerical results presented in this paper demonstrate that the proposed method maintains its stability even when applied to the analysis of electromagnetic wave interactions with electrically large structures meshed using approximately half a million discretization elements.
Impact of time-domain IP pulse length on measured data and inverted models
DEFF Research Database (Denmark)
Olsson, P. I.; Fiandaca, G.; Dahlin, T.
2015-01-01
The duration of time domain (TD) induced polarization (IP) current injections has significant impact on the acquired IP data as well as on the inversion models, if the standard evaluation procedure is followed. However, it is still possible to retrieve similar inversion models if the waveform...... of the injected current and the IP response waveform are included in the inversion. The on-time also generally affects the signal-tonoise ratio (SNR) where an increased on-time gives higher SNR for the IP data....
Rander, D. N.; Joshi, Y. S.; Kanse, K. S.; Kumbharkhane, A. C.
2016-01-01
The measurements of complex dielectric permittivity of xylitol-water mixtures have been carried out in the frequency range of 10 MHz-30 GHz using a time domain reflectometry technique. Measurements have been done at six temperatures from 0 to 25 °C and at different weight fractions of xylitol (0 xylitol-water can be well described by Cole-Davidson model having an asymmetric distribution of relaxation times. The dielectric parameters such as static dielectric constant and relaxation time for the mixtures have been evaluated. The molecular interaction between xylitol and water molecules is discussed using the Kirkwood correlation factor ( g eff ) and thermodynamic parameter.
THE SOLUTION OF THE CABLE EQUATIONS BY MEANS OF FINITE DIFFERENCE TIME DOMAIN METHOD
Directory of Open Access Journals (Sweden)
Patsiuk V.I.
2010-04-01
Full Text Available The analysis and comparison of accuracy of numerical solutions received by Finite Difference Time Domain (FDTD method and Godunov's method at the solution of the cable equations is carried out. It is demonstrated, that at sudden short circuits and at transition to idling mode in numerical solutions received by means of FDTD method for long lines with the distributed parameters appear strong nonphysical oscillations. It is shown, that the settlement scheme offered by authors on the basis of Godunov's method is deprived these lacks and provides high accuracy for the numerical solutions received at the analysis of dynamic modes in long lines, caused by sudden short circuits and line transitions in an idling mode. Key words: cable equations, finite difference time domain method, Godunov’s scheme.
Abedi, Reza; Mudaliar, Saba
2017-12-01
We present an asynchronous spacetime discontinuous Galerkin (aSDG) method for time domain electromagnetics in which space and time are directly discretized. By using differential forms we express Maxwell's equations and consequently their discontinuous Galerkin discretization for arbitrary domains in spacetime. The elements are discretized with electric and magnetic basis functions that are discontinuous across all inter-element boundaries and can have arbitrary high and per element spacetime orders. When restricted to unstructured grids that satisfy a specific causality constraint, the method has a local and asynchronous solution procedure with linear solution complexity in terms of the number of elements. We numerically investigate the convergence properties of the method for 1D to 3D uniform grids for energy dissipation, an error relative to the exact solution, and von Neumann dissipation and dispersion errors. Two dimensional simulations demonstrate the effectiveness of the method in resolving sharp wave fronts.
Multichannel Signal Enhancement using Non-Causal, Time-Domain Filters
DEFF Research Database (Denmark)
Jensen, Jesper Rindom; Christensen, Mads Græsbøll; Benesty, Jacob
2013-01-01
In the vast amount of time-domain filtering methods for speech enhancement, the filters are designed to be causal. Recently, however, it was shown that the noise reduction and signal distortion capabilities of such single-channel filters can be improved by allowing the filters to be non-causal. W......In the vast amount of time-domain filtering methods for speech enhancement, the filters are designed to be causal. Recently, however, it was shown that the noise reduction and signal distortion capabilities of such single-channel filters can be improved by allowing the filters to be non......-causal, multichannel filters for enhancement based on an orthogonal decomposition is proposed. The evaluation shows that there is a potential gain in noise reduction and signal distortion by introducing non-causality. Moreover, experiments on real-life speech show that we can improve the perceptual quality....
International Nuclear Information System (INIS)
Jamali, J.; Aghajafari, R.; Moini, R.; Sadeghi, H.
2002-01-01
A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper
Mapping of landfills using time-domain spectral induced polarization data
DEFF Research Database (Denmark)
Gazoty, Aurélie; Fiandaca, Gianluca; Pedersen, Jesper Bjergsted
2012-01-01
information from time-domain IP data. Thirteen IP/DC profiles were collected in the area, supplemented by el-log drilling for accurate correlation between the geophysics and the lithology. The data were inverted using a laterally constrained 1D inversion considering the full decay curves to retrieve the four......This study uses time-domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral...... Cole-Cole parameters. For all profiles, the results reveal a highly chargeable unit that shows a very good agreement to the findings from 15 boreholes covering the area, where the extent of the waste deposits was measured. The thickness and depth of surface measurements were furthermore validated by el-log...
Terahertz quasi time-domain spectroscopy based on telecom technology for 1550 nm.
Kohlhaas, Robert B; Rehn, Arno; Nellen, Simon; Koch, Martin; Schell, Martin; Dietz, Roman J B; Balzer, Jan C
2017-05-29
We present a fiber-coupled terahertz quasi time-domain spectroscopy system driven by a laser with a central wavelength of 1550 nm. By using a commercially available multimode laser diode in combination with state-of-the-art continuous wave antennas, a bandwidth of more than 1.8 THz is achieved. The peak signal-to-noise ratio is around 60 dB. A simulation based on the optical spectrum of the laser diode and the transfer function of the THz path is in agreement with the experimental results. The system is used to extract the refractive index from two different samples and the results indicate that the performance is up to 1.8 THz comparable to a terahertz time-domain spectroscopy system.
Chen, Chien-Hung; Chiu, Chien-Ching; Sun, Chi-Hsien; Chang, Wan-Ling
2011-01-01
This paper reports a two-dimensional time-domain inverse scattering algorithm based upon the finite-difference time domain method (FDTD) for determining the shape of a perfectly conducting cylinder. FDTD is used to solve the scattering electromagnetic wave of a perfectly conducting cylinder. The inverse problem is resolved by an optimization approach and the global searching scheme asynchronous particle swarm optimization is then employed to search the parameter space. By properly processing the scattered field, some electromagnetic properties can be reconstructed. A set of representative numerical results is presented to demonstrate that the proposed approach is able to efficiently reconstruct the electromagnetic properties of metallic scatterer even when the initial guess is far away from the exact one. In addition, the effects of Gaussian noises on imaging reconstruction are also investigated.
Wang, Xu; Gao, Zhensen; Kataoka, Nobuyuki; Wada, Naoya
2010-05-10
A novel scheme using single phase modulator for simultaneous time domain spectral phase encoding (SPE) signal generation and DPSK data modulation is proposed and experimentally demonstrated. Array- Waveguide-Grating and Variable-Bandwidth-Spectrum-Shaper based devices can be used for decoding the signal directly in spectral domain. The effects of fiber dispersion, light pulse width and timing error on the coding performance have been investigated by simulation and verified in experiment. In the experiment, SPE signal with 8-chip, 20GHz/chip optical code patterns has been generated and modulated with 2.5 Gbps DPSK data using single modulator. Transmission of the 2.5 Gbps data over 34km fiber with BEROCDMA) and secure optical communication applications. (c) 2010 Optical Society of America.
Fault Detection of Aircraft Cable via Spread Spectrum Time Domain Reflectometry
Directory of Open Access Journals (Sweden)
Xudong SHI
2014-03-01
Full Text Available As the airplane cable fault detection based on TDR (time domain reflectometry is affected easily by various noise signals, which makes the reflected signal attenuate and distort heavily, failing to locate the fault. In order to solve these problems, a method of spread spectrum time domain reflectometry (SSTDR is introduced in this paper, taking the advantage of the sharp peak of correlation function. The test signal is generated from ML sequence (MLS modulated by sine wave in the same frequency. Theoretically, the test signal has the very high immunity of noise, which can be applied with excellent precision to fault location on the aircraft cable. In this paper, the method of SSTDR was normally simulated in MATLAB. Then, an experimental setup, based on LabVIEW, was organized to detect and locate the fault on the aircraft cable. It has been demonstrated that SSTDR has the high immunity of noise, reducing some detection errors effectively.
Water percolation estimated with time domain reflectometry (TDR) in drainage lysimeters
Alisson Jadavi Pereira da Silva; Eugênio Ferreira Coelho
2013-01-01
Due to the difficulty of estimating water percolation in unsaturated soils, the purpose of this study was to estimate water percolation based on time-domain reflectometry (TDR). In two drainage lysimeters with different soil textures TDR probes were installed, forming a water monitoring system consisting of different numbers of probes. The soils were saturated and covered with plastic to prevent evaporation. Tests of internal drainage were carried out using a TDR 100 unit with constant dielec...
Mini Tensiometer-Time Domain Reflectometry Coil Probe for Measuring Soil Water Retention Properties
DEFF Research Database (Denmark)
Subedi, Shaphal; Kawamoto, Ken; Karunarathna, Anurudda Kumara
2013-01-01
Time domain reflectometry (TDR) is used widely for measuring soil-water content. New TDR coil probe technology facilitates the development of small, nondestructive probes for simultaneous measurement of soil-water content (θ) and soil-water potential (ψ). In this study we developed mini tensiomet...... between measured soil-water retention curves (ψ > –100 cm H2O) by the new T-TDR coil probes and independent measurements by the hanging water column method....
Control of linear systems subject to time-domain constraints with polynomial pole placement and LMIs
Czech Academy of Sciences Publication Activity Database
Henrion, D.; Tarbouriech, S.; Kučera, Vladimír
2005-01-01
Roč. 50, č. 9 (2005), s. 1360-1364 ISSN 0018-9286 R&D Projects: GA MŠk 1M0567; GA ČR GA102/05/0011 Institutional research plan: CEZ:AV0Z10750506 Keywords : linear matrix inequality (LMI) * linear systems * pole placement * polynomials * time-domain constraints Subject RIV: BC - Control Systems Theory Impact factor: 2.159, year: 2005
Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study
Di Sieno, Laura; Zouaoui, Judy; Hervé, Lionel; Pifferi, Antonio; Farina, Andrea; Martinenghi, Edoardo; Derouard, Jacques; Dinten, Jean-Marc; Dalla Mora, Alberto
2016-01-01
International audience; Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thu...
Modelling and analysis of nonlinear thermoacoustic systems using frequency and time domain methods
Orchini, Alessandro
2017-01-01
In this thesis, low-order nonlinear models for the prediction of the nonlinear behaviour of thermoacoustic systems are developed. These models are based on thermoacoustic networks, in which linear acoustics is combined with a nonlinear heat release model. The acoustic networks considered in this thesis can take into account mean flow and non-trivial acoustic reflection coefficients, and are cast in state-space form to enable analysis both in the frequency and time domains. Starting from l...
1972-01-01
The theoretical basis for the ASYSTD program is discussed in detail. In addition, the extensive bibliography given in this document illustrates some of the extensive work accomplished in the area of time domain simulation. Additions have been in the areas of modeling and language program enhancements, orthogonal transform modeling, error analysis, general filter models, BER measurements, etc. Several models have been developed which utilize the COMSAT generated orthogonal transform algorithms.
DEFF Research Database (Denmark)
Mackenzie, David M.A.; Whelan, Patrick Rebsdorf; Bøggild, Peter
2018-01-01
We present a comparative study of electrical measurements of graphene using terahertz time-domain spectroscopy in transmission and reflection mode, and compare the measured sheet conductivity values to electrical van der Pauw measurements made independently in three different laboratories. Overall......, while offering the additional advantages associated with contactless mapping, such as high throughput, no lithography requirement, and with the spatial mapping directly revealing the presence of any inhomogeneities or isolating defects. The confirmation of the accuracy of reflection-mode removes...
Shape optimization for non-Newtonian fluids in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Sokolowski, J.; Stebel, Jan
2014-01-01
Roč. 3, č. 2 (2014), s. 331-348 ISSN 2163-2480 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : shape optimization * time-dependent domain * incompressible viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.373, year: 2014 http://www.aimsciences.org/journals/home.jsp?journalID=25
Time coordination of heterogeneous distance protections using a domain specific language
Marcin Kowalski; Jan Magott
2012-01-01
BACKGROUND: Distance protections are widely used in protection of energy transmission lines, but their time coordination is still an important and difficult problem. Inappropriate configuration leads to a hazard event: remote circuit breaker tripping provided the local circuit breaker can be opened, which severely impairs power system operation.OBJECTIVE: To describe a method and provide software tools to alleviate the hazard in power systems.METHODS: A domain specific language (DSL) for repr...
Factor models in high-dimensional time series : A time-domain approach
Hallin, M.; Lippi, M.
2013-01-01
High-dimensional time series may well be the most common type of dataset in the so-called “big data” revolution, and have entered current practice in many areas, including meteorology, genomics, chemometrics, connectomics, complex physics simulations, biological and environmental research, finance
DEFF Research Database (Denmark)
Andersen, P.; Skjærbæk, P. S.; Kirkegaard, Poul Henning
with the smoothed quanties which have been obtained from SARCOF. The results show the usefulness of the technique for identification of a time varying civil engineering structure. It is found that all the techniques give reliable estiates of the frequencies of the two lowest modes and the first mode shape. Only...
Time Domains of the Hypoxic Ventilatory Response and Their Molecular Basis
Pamenter, Matthew E.; Powell, Frank L.
2016-01-01
Ventilatory responses to hypoxia vary widely depending on the pattern and length of hypoxic exposure. Acute, prolonged, or intermittent hypoxic episodes can increase or decrease breathing for seconds to years, both during the hypoxic stimulus, and also after its removal. These myriad effects are the result of a complicated web of molecular interactions that underlie plasticity in the respiratory control reflex circuits and ultimately control the physiology of breathing in hypoxia. Since the time domains of the physiological hypoxic ventilatory response (HVR) were identified, considerable research effort has gone toward elucidating the underlying molecular mechanisms that mediate these varied responses. This research has begun to describe complicated and plastic interactions in the relay circuits between the peripheral chemoreceptors and the ventilatory control circuits within the central nervous system. Intriguingly, many of these molecular pathways seem to share key components between the different time domains, suggesting that varied physiological HVRs are the result of specific modifications to overlapping pathways. This review highlights what has been discovered regarding the cell and molecular level control of the time domains of the HVR, and highlights key areas where further research is required. Understanding the molecular control of ventilation in hypoxia has important implications for basic physiology and is emerging as an important component of several clinical fields. PMID:27347896
Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves
Directory of Open Access Journals (Sweden)
Shukui Liu
2011-03-01
Full Text Available Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.
Electroporation-Induced Cell Modifications Detected with THz Time-Domain Spectroscopy
Romeo, Stefania; Vernier, P. Thomas; Zeni, Olga
2018-04-01
Electroporation (electropermeabilization) increases the electrical conductivity of biological cell membranes and lowers transport barriers for normally impermeant materials. Molecular simulations suggest that electroporation begins with the reorganization of water and lipid head group dipoles in the phospholipid bilayer interface, driven by an externally applied electric field, and the evolution of the resulting defects into water-filled, lipid pores. The interior of the electroporated membrane thus contains water, which should provide a signature for detection of the electropermeabilized state. In this feasibility study, we use THz time-domain spectroscopy, a powerful tool for investigating biomolecular systems and their interactions with water, to detect electroporation in human cells subjected to permeabilizing pulsed electric fields (PEFs). The time-domain response of electroporated human monocytes was acquired with a commercial THz, time-domain spectrometer. For each sample, frequency spectra were calculated, and the absorption coefficient and refractive index were extracted in the frequency range between 0.2 and 1.5 THz. This analysis reveals a higher absorption of THz radiation by PEF-exposed cells, with respect to sham-exposed ones, consistent with the intrusion of water into the cell through the permeabilized membrane that is presumed to be associated with electroporation.
Real-time decision support and information gathering system for financial domain
Tseng, Chiu-Che; Gmytrasiewicz, Piotr J.
2006-05-01
The challenge of the investment domain is that a large amount of diverse information can be potentially relevant to an investment decision, and that, frequently, the decisions have to be made in a timely manner. This presents the potential for better decision support, but poses the challenge of building a decision support agent that gathers information from different sources and incorporates it for timely decision support. These problems motivate us to investigate ways in which the investors can be equipped with a flexible real-time decision support system to be practical in time-critical situations. The flexible real-time decision support system considers a tradeoff between decision quality and computation cost. For this purpose, we propose a system that uses the object oriented Bayesian knowledge base (OOBKB) design to create a decision model at the most suitable level of detail to guide the information gathering activities, and to produce an investment recommendation within a reasonable length of time. The decision models our system uses are implemented as influence diagrams. We validate our system with experiments in a simplified investment domain. The experiments show that our system produces a quality recommendation under different urgency situations. The contribution of our system is that it provides the flexible decision recommendation for an investor under time constraints in a complex environment.
Multiobjective Optimization for Electronic Circuit Design in Time and Frequency Domains
Directory of Open Access Journals (Sweden)
J. Dobes
2013-04-01
Full Text Available The multiobjective optimization provides an extraordinary opportunity for the finest design of electronic circuits because it allows to mathematically balance contradictory requirements together with possible constraints. In this paper, an original and substantial improvement of an existing method for the multiobjective optimization known as GAM (Goal Attainment Method is suggested. In our proposal, the GAM algorithm itself is combined with a procedure that automatically provides a set of parameters -- weights, coordinates of the reference point -- for which the method generates noninferior solutions uniformly spread over an appropriately selected part of the Pareto front. Moreover, the resulting set of obtained solutions is then presented in a suitable graphic form so that the solution representing the most satisfactory tradeoff can be easily chosen by the designer. Our system generates various types of plots that conveniently characterize results of up to four-dimensional problems. Technically, the procedures of the multiobjective optimization were created as a software add-on to the CIA (Circuit Interactive Analyzer program. This way enabled us to utilize many powerful features of this program, including the sensitivity analyses in time and frequency domains. As a result, the system is also able to perform the multiobjective optimization in the time domain and even highly nonlinear circuits can be significantly improved by our program. As a demonstration of this feature, a multiobjective optimization of a C-class power amplifier in the time domain is thoroughly described in the paper. Further, a four-dimensional optimization of a video amplifier is demonstrated with an original graphic representation of the Pareto front, and also some comparison with the weighting method is done. As an example of improving noise properties, a multiobjective optimization of a low-noise amplifier is performed, and the results in the frequency domain are shown
A new non-parametric stationarity test of time series in the time domain
Jin, Lei
2014-11-07
© 2015 The Royal Statistical Society and Blackwell Publishing Ltd. We propose a new double-order selection test for checking second-order stationarity of a time series. To develop the test, a sequence of systematic samples is defined via Walsh functions. Then the deviations of the autocovariances based on these systematic samples from the corresponding autocovariances of the whole time series are calculated and the uniform asymptotic joint normality of these deviations over different systematic samples is obtained. With a double-order selection scheme, our test statistic is constructed by combining the deviations at different lags in the systematic samples. The null asymptotic distribution of the statistic proposed is derived and the consistency of the test is shown under fixed and local alternatives. Simulation studies demonstrate well-behaved finite sample properties of the method proposed. Comparisons with some existing tests in terms of power are given both analytically and empirically. In addition, the method proposed is applied to check the stationarity assumption of a chemical process viscosity readings data set.
Thermal diffusivity of a metallic thin layer using the time-domain thermo reflectance technique
International Nuclear Information System (INIS)
Battaglia, J-L; Kusiak, A; Rossignol, C; Chigarev, N
2007-01-01
The time domain thermo reflectance (TDTR) is widely used in the field of acoustic and thermal characterization of thin layers at the nano and micro scale. In this paper, we propose to derive a simple analytical expression of the thermal diffusivity of the layer. This relation is based on the analytical solution of one-dimensional heat transfer in the medium using integral transforms. For metals, the two-temperature model shows that the capacitance effect at the short times is essentially governed by the electronic contribution
Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators
Talukdar, Abdul Hafiz Ibne
2012-07-28
Traditionally, the necessary and sufficient condition for any system to be oscillating is that its poles are located on the imaginary (jω) axis. In this paper, for the first time, we have shown that systems can oscillate with time-domain oscillating poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating resistance and triangular shape of FFT are also demonstrated with mathematical reasoning and simulation results to support the unusual and surprising characteristics. © 2009 IEEE.
Time domain-nuclear magnetic resonance study of chars from southern hardwoods
International Nuclear Information System (INIS)
Elder, Thomas; Labbe, Nicole; Harper, David; Rials, Timothy
2006-01-01
Chars from the thermal degradation of silver maple (Acer saccharinum), red maple (Acer rubrum), sugar maple (Acer saccharum), and white oak (Quercus spp.), performed at temperatures from 250 to 350 o C, were examined using time domain-nuclear magnetic resonance spectroscopy. Prior to analysis, the chars were equilibrated under conditions insuring the presence of bound water only and both bound water and free water. Transverse relaxation times were found to be related to the moisture content of the chars, which varied with temperature. At elevated temperatures the number of signals assigned to free water decreased, indicative of an increase in pore size within the chars
On the mixed discretization of the time domain magnetic field integral equation
Ulku, Huseyin Arda
2012-09-01
Time domain magnetic field integral equation (MFIE) is discretized using divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming Buffa-Christiansen (BC) functions as spatial basis and testing functions, respectively. The resulting mixed discretization scheme, unlike the classical scheme which uses RWG functions as both basis and testing functions, is proper: Testing functions belong to dual space of the basis functions. Numerical results demonstrate that the marching on-in-time (MOT) solution of the mixed discretized MFIE yields more accurate results than that of classically discretized MFIE. © 2012 IEEE.
Mie scattering in the time domain. Part 1. The role of surface waves.
Lock, James A; Laven, Philip
2011-06-01
We computed the Debye series p=1 and p=2 terms of the Mie scattered intensity as a function of scattering angle and delay time for a linearly polarized plane wave pulse incident on a spherical dielectric particle and physically interpreted the resulting numerical data. Radiation shed by electromagnetic surface waves plays a prominent role in the scattered intensity. We determined the surface wave phase and damping rate and studied the structure of the p=1,2 surface wave glory in the time domain.
Giuggioli, Luca; Pérez-Becker, Sebastian; Sanders, David P.
2013-02-01
We develop an analytical method to calculate encounter times of two random walkers in one dimension when each individual is segregated in its own spatial domain and shares with its neighbor only a fraction of the available space, finding very good agreement with numerically exact calculations. We model a population of susceptible and infected territorial individuals with this spatial arrangement, and which may transmit an epidemic when they meet. We apply the results on encounter times to determine analytically the macroscopic propagation speed of the epidemic as a function of the microscopic characteristics: the confining geometry, the animal diffusion constant, and the infection transmission probability.
Okawa, S; Endo, Y; Hoshi, Y; Yamada, Y
2012-01-01
A method to reduce noise for time-domain diffuse optical tomography (DOT) is proposed. Poisson noise which contaminates time-resolved photon counting data is reduced by use of maximum a posteriori estimation. The noise-free data are modeled as a Markov random process, and the measured time-resolved data are assumed as Poisson distributed random variables. The posterior probability of the occurrence of the noise-free data is formulated. By maximizing the probability, the noise-free data are estimated, and the Poisson noise is reduced as a result. The performances of the Poisson noise reduction are demonstrated in some experiments of the image reconstruction of time-domain DOT. In simulations, the proposed method reduces the relative error between the noise-free and noisy data to about one thirtieth, and the reconstructed DOT image was smoothed by the proposed noise reduction. The variance of the reconstructed absorption coefficients decreased by 22% in a phantom experiment. The quality of DOT, which can be applied to breast cancer screening etc., is improved by the proposed noise reduction.
Pliquett, Uwe; Schönfeldt, Markus; Barthel, Andreas; Frense, Dieter; Nacke, Thomas; Beckmann, Dieter
2011-07-01
Fast impedance measurements are often performed in time domain utilizing broad bandwidth excitation signals. Other than in frequency domain measurements harmonic distortion cannot be compensated which requires careful design of the analog front end. In order to minimize the influence of electrode polarization and noise, especially in low-frequency measurements, current injection shows several advantages compared to voltage application. Here, we show an active front end based on a voltage-controlled current source for a wide range of impedances. Using proper feedback, the majority of the parasitic capacitances are compensated. The bandwidth ranges from dc to 20 MHz for impedance magnitude below 5 kΩ. The output is a symmetric signal without dc-offset which is accomplished by combination of a current conveyor and a voltage inverter. An independent feedback loop compensates the offset arising from asymmetries within the circuitry. We focused especially on the stability of the current source for usage with small metal electrodes in aqueous solutions. At the monitor side two identical, high input impedance difference amplifiers convert the net current through the object and the voltage dropping across into a 50 Ω symmetric output. The entire circuitry is optimized for step response making it suitable for fast time domain measurements.
A Moving Window Technique in Parallel Finite Element Time Domain Electromagnetic Simulation
Energy Technology Data Exchange (ETDEWEB)
Lee, Lie-Quan; Candel, Arno; Ng, Cho; Ko, Kwok; /SLAC
2010-06-07
A moving window technique for the finite element time domain (FETD) method is developed to simulate the propagation of electromagnetic waves induced by the transit of a charged particle beam inside large and long structures. The window moving along with the beam in the computational domain adopts high-order finite-element basis functions through p refinement and/or a high-resolution mesh through h refinement so that a sufficient accuracy is attained with substantially reduced computational costs. Algorithms to transfer discretized fields from one mesh to another, which are the key to implementing a moving window in a finite-element unstructured mesh, are presented. Numerical experiments are carried out using the moving window technique to compute short-range wakefields in long accelerator structures. The results are compared with those obtained from the normal FETD method and the advantages of using the moving window technique are discussed.
An FFT-accelerated time-domain multiconductor transmission line simulator
Bagci, Hakan
2010-02-01
A fast time-domain multiconductor transmission line (MTL) simulator for analyzing general MTL networks is presented. The simulator models the networks as homogeneous MTLs that are excited by external fields and driven/terminated/ connected by potentially nonlinear lumped circuitry. It hybridizes an MTL solver derived from time-domain integral equations (TDIEs) in unknown wave coefficients for each MTL with a circuit solver rooted in modified nodal analysis equations in unknown node voltages and voltage-source currents for each circuit. These two solvers are rigorously interfaced at MTL and circuit terminals, and the resulting coupled system of equations is solved simultaneously for all MTL and circuit unknowns at each time step. The proposed simulator is amenable to hybridization, is fast Fourier transform (FFT)-accelerated, and is highly accurate: 1) It can easily be hybridized with TDIE-based field solvers (in a fully rigorous mathematical framework) for performing electromagnetic interference and compatibility analysis on electrically large and complex structures loaded with MTL networks. 2) It is accelerated by an FFT algorithm that calculates temporal convolutions of time-domain MTL Green functions in only O(Ntlog2 N t) rather than O(Ntt2) operations, where N t is the number of time steps of simulation. Moreover, the algorithm, which operates on temporal samples of MTL Green functions, is indifferent to the method used to obtain them. 3) It approximates MTL voltages, currents, and wave coefficients, using high-order temporal basis functions. Various numerical examples, including the crosstalk analysis of a (twisted) unshielded twisted-pair (UTP)-CAT5 cable and the analysis of field coupling into UTP-CAT5 and RG-58 cables located on an airplane, are presented to demonstrate the accuracy, efficiency, and versatility of the proposed simulator. © 2010 IEEE.
Enhanced Measurement of Paper Basis Weight Using Phase Shift in Terahertz Time-Domain Spectroscopy
Directory of Open Access Journals (Sweden)
Mengbao Fan
2017-01-01
Full Text Available THz time-domain spectroscopy has evolved as a noncontact, safe, and efficient technique for paper characterization. Our previous work adopted peak amplitude and delay time as features to determine paper basis weight using terahertz time-domain spectroscopy. However, peak amplitude and delay time tend to suffer from noises, resulting in degradation of accuracy and robustness. This paper proposes a noise-robust phase-shift based method to enhance measurements of paper basis weight. Based on Fresnel Formulae, the physical relationship between phase shift and paper basis weight is formulated theoretically neglecting multiple reflections in the case of normal incidence. The established formulation indicates that phase shift correlates linearly with paper basis weight intrinsically. Subsequently, paper sheets were stacked to fabricate the samples with different basis weights, and experimental results verified the developed mathematical formulation. Moreover, a comparison was made between phase shift, peak amplitude, and delay time with respect to linearity, accuracy, and noise robustness. The results show that phase shift is superior to the others.
Liu, Yang
2016-03-25
A parallel plane-wave time-domain (PWTD)-accelerated explicit marching-on-in-time (MOT) scheme for solving the time domain electric field volume integral equation (TD-EFVIE) is presented. The proposed scheme leverages pulse functions and Lagrange polynomials to spatially and temporally discretize the electric flux density induced throughout the scatterers, and a finite difference scheme to compute the electric fields from the Hertz electric vector potentials radiated by the flux density. The flux density is explicitly updated during time marching by a predictor-corrector (PC) scheme and the vector potentials are efficiently computed by a scalar PWTD scheme. The memory requirement and computational complexity of the resulting explicit PWTD-PC-EFVIE solver scale as ( log ) s s O N N and ( ) s t O N N , respectively. Here, s N is the number of spatial basis functions and t N is the number of time steps. A scalable parallelization of the proposed MOT scheme on distributed- memory CPU clusters is described. The efficiency, accuracy, and applicability of the resulting (parallelized) PWTD-PC-EFVIE solver are demonstrated via its application to the analysis of transient electromagnetic wave interactions on canonical and real-life scatterers represented with up to 25 million spatial discretization elements.
Fukunaga, Kaori; Ikari, Tomofumi; Iwai, Kikuko
2016-02-01
The terahertz pulsed time-domain imaging technique and near-infrared observation were applied to investigate an oil painting on canvas by Pablo Picasso. The multilayer structure is clearly observed in cross-sectional image by terahertz pulsed time-domain imaging, and particular Cubism style lines were revealed under newly painted area by near-infrared image.
DEFF Research Database (Denmark)
Clausen, Anders; Guan, Pengyu; Mulvad, Hans Christian Hansen
2014-01-01
All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented.......All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented....
Gao, Xueping; Zhao, Guixia; Zhang, Chen; Wang, Yan
2018-02-07
Exposure time is an important characteristic for hydrodynamics that has simultaneous impacts on the biochemical processes in tidal systems. To eliminate man-made errors, decrease computational effort, and increase simulation efficiency, exposure time was evaluated under different hydrodynamic conditions for a bay to investigate the impact of the external domain on the accuracy of the computational results for exposure time. The exposure time was explicitly defined and computed using a hydrodynamic model and tracer experiments for a set of ten external domain sizes (EDS), five external domain lengths (EDL), and three special hydrodynamic conditions. The results indicated that the external domain had a significant influence on the exposure time, and the intensity of this influence was related to hydrodynamic conditions. The sensitivity of the exposure time to the external domain increased with increasing tidal range, while freshwater inflows decreased this sensitivity. However, the variation trends for exposure time with different EDS and EDL were independent of the hydrodynamic conditions. Considering the computational efficiency (maximum), the calculated error (minimum) of the exposure time, and the impact of the boundary conditions (minimum), the recommended EDS and EDL range from 9 to 13 times the initial domain size and 1.30 to 1.45 times the length in the bay, respectively. The research regarding exposure time and external domains not only helps to eliminate the errors caused by man-made factors and reduce the computational effort but also provides a reference for understanding the interrelationship between coastal waters, reciprocating flow, and the water environment.
Time-domain analytic solutions of two-wire transmission line excited by a plane-wave field
International Nuclear Information System (INIS)
Ni Guyan; Yan Li; Yuan Naichang
2008-01-01
This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain. By the frequency-domain Baum–Liu–Tesche (BLT) equation, the time-domain analytic solutions are obtained and expressed in an infinite geometric series. Moreover, it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval. In other word, the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval. The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform, and the agreement is excellent. (the physics of elementary particles and fields)
3D airborne EM modeling based on the spectral-element time-domain (SETD) method
Cao, X.; Yin, C.; Huang, X.; Liu, Y.; Zhang, B., Sr.; Cai, J.; Liu, L.
2017-12-01
In the field of 3D airborne electromagnetic (AEM) modeling, both finite-difference time-domain (FDTD) method and finite-element time-domain (FETD) method have limitations that FDTD method depends too much on the grids and time steps, while FETD requires large number of grids for complex structures. We propose a time-domain spectral-element (SETD) method based on GLL interpolation basis functions for spatial discretization and Backward Euler (BE) technique for time discretization. The spectral-element method is based on a weighted residual technique with polynomials as vector basis functions. It can contribute to an accurate result by increasing the order of polynomials and suppressing spurious solution. BE method is a stable tine discretization technique that has no limitation on time steps and can guarantee a higher accuracy during the iteration process. To minimize the non-zero number of sparse matrix and obtain a diagonal mass matrix, we apply the reduced order integral technique. A direct solver with its speed independent of the condition number is adopted for quickly solving the large-scale sparse linear equations system. To check the accuracy of our SETD algorithm, we compare our results with semi-analytical solutions for a three-layered earth model within the time lapse 10-6-10-2s for different physical meshes and SE orders. The results show that the relative errors for magnetic field B and magnetic induction are both around 3-5%. Further we calculate AEM responses for an AEM system over a 3D earth model in Figure 1. From numerical experiments for both 1D and 3D model, we draw the conclusions that: 1) SETD can deliver an accurate results for both dB/dt and B; 2) increasing SE order improves the modeling accuracy for early to middle time channels when the EM field diffuses fast so the high-order SE can model the detailed variation; 3) at very late time channels, increasing SE order has little improvement on modeling accuracy, but the time interval plays
Design of a coil sensor for time domain electromagnetic system for uranium exploration
International Nuclear Information System (INIS)
Keshwani, R.T.; Bhattacharya, S.
2011-01-01
Time domain electromagnetic system is used for exploration of deep seated deposits under the Earth surface. The basic principle is to set up eddy currents in conductors using pulsed excited transmitter coil during on time of a pulse. The decay time of eddy currents during off time of a pulse is a function conductivity, permeability and depth of conductor located under the Earth surface. The technology is being developed to carry out exploration of mineral deposits (basically uranium) under the Earth surface. The decay of eddy currents is eddy using J coil sensor located coplanar with the transmitter coil. The depth upto which successful exploration can be carried is strong function of design of receiver coil. The design parameters include number of turns, bandwidth, stray capacitance and resistance of a coil. This paper describes various designs tried out and their characterization results. Field results for a ground based system developed are also described. (author)
Integration of domain and resource-based reasoning for real-time control in dynamic environments
Morgan, Keith; Whitebread, Kenneth R.; Kendus, Michael; Cromarty, Andrew S.
1993-01-01
A real-time software controller that successfully integrates domain-based and resource-based control reasoning to perform task execution in a dynamically changing environment is described. The design of the controller is based on the concept of partitioning the process to be controlled into a set of tasks, each of which achieves some process goal. It is assumed that, in general, there are multiple ways (tasks) to achieve a goal. The controller dynamically determines current goals and their current criticality, choosing and scheduling tasks to achieve those goals in the time available. It incorporates rule-based goal reasoning, a TMS-based criticality propagation mechanism, and a real-time scheduler. The controller has been used to build a knowledge-based situation assessment system that formed a major component of a real-time, distributed, cooperative problem solving system built under DARPA contract. It is also being employed in other applications now in progress.
Directory of Open Access Journals (Sweden)
Andrea Farina
2017-11-01
Full Text Available Based on recent developments in both single-photon detectors and timing electronic circuits, we designed a compact and cost effective time-domain diffuse optical tomography system operated at 1 Hz acquisition rate, based on eight silicon photomultipliers and an 8-channel time-to-digital converter. The compact detectors are directly hosted on the probe in a circular arrangement around a single light injection fiber, so to maximize light harvesting. Tomography is achieved exploiting the depth sensitivity that is encoded in the arrival time of detected photons. The system performances were evaluated on simulations to assess possible the limitations arising from the use of a single injection point, and then on phantoms and in vivo to prove the eligibility of these technologies for diffuse optical tomography.
DEFF Research Database (Denmark)
Cai, Hongzhu; Hu, Xiangyun; Xiong, Bin
2017-01-01
method which is unconditionally stable. We solve the diffusion equation for the electric field with a total field formulation. The finite element system of equation is solved using the direct method. The solutions of electric field, at different time, can be obtained using the effective time stepping...... method with trivial computation cost once the matrix is factorized. We try to keep the same time step size for a fixed number of steps using an adaptive time step doubling (ATSD) method. The finite element modeling domain is also truncated using a semi-adaptive method. We proposed a new boundary...... condition based on approximating the total field on the modeling boundary using the primary field corresponding to a layered background model. We validate our algorithm using several synthetic model studies....
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Lavrinenko, Andrei
2007-01-01
A complex-coordinate method known under the guise of the perfectly matched layer (PML) method for treating unbounded domains in computational electrodynamics is related to similar techniques in fluid dynamics and classical quantum theory. It may also find use in electronic-structure finite......-difference simulations. Straightforward transfer of the PML formulation to other fields does not seem feasible, however, since it is a unique feature of electrodynamics - the natural invariance - that allows analytic trick of complex coordinate scaling to be represented as pure modification of local material parameters...
Time Domain Filtering of Resolved Images of Sgr A{sup ∗}
Energy Technology Data Exchange (ETDEWEB)
Shiokawa, Hotaka; Doeleman, Sheperd S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gammie, Charles F. [Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801 (United States)
2017-09-01
The goal of the Event Horizon Telescope (EHT) is to provide spatially resolved images of Sgr A*, the source associated with the Galactic Center black hole. Because Sgr A* varies on timescales that are short compared to an EHT observing campaign, it is interesting to ask whether variability contains information about the structure and dynamics of the accretion flow. In this paper, we introduce “time-domain filtering,” a technique to filter time fluctuating images with specific temporal frequency ranges and to demonstrate the power and usage of the technique by applying it to mock millimeter wavelength images of Sgr A*. The mock image data is generated from the General Relativistic Magnetohydrodynamic (GRMHD) simulation and the general relativistic ray-tracing method. We show that the variability on each line of sight is tightly correlated with a typical radius of emission. This is because disk emissivity fluctuates on a timescale of the order of the local orbital period. Time-domain filtered images therefore reflect the model dependent emission radius distribution, which is not accessible in time-averaged images. We show that, in principle, filtered data have the power to distinguish between models with different black-hole spins, different disk viewing angles, and different disk orientations in the sky.
3D time-domain airborne EM forward modeling with topography
Yin, Changchun; Qi, Yanfu; Liu, Yunhe; Cai, Jing
2016-11-01
The time-domain finite-difference method has been widely used in simulation of the electromagnetic field diffusion. However, this method is severely restricted by the mesh size and time step. To overcome the defect, we adopted edge finite-element method for unstructured grid with Backward Euler method to conduct 3D airborne electromagnetic forward modeling directly in time-domain. The tetrahedral meshes provide the flexibility required for representing the rugged topography and complex-shape anomalous bodies. We simulated the practical shape, size and attitude of transmitting source by directly setting the loop into the well-generated grids. The characteristic properties of vector basic functions guarantee automatic satisfaction of divergence-free property of electric fields. The Galerkin's method is used to discretize the governing equations and a direct solver is adopted to solve the large sparse linear system. We adopted an algorithm with constant step in each time segment to speed up the forward modeling. Further we introduced the local mesh strategy to reduce the calculations, in which an optimized grid is designed for each sounding station. We check the accuracy of our 3D modeling results against the solution for a homogenous half-space and those for a buried vertical plate model using integral equation. The numerical experiments for a hill, a valley or undulating topography model with buried anomalous bodies were further studied that show that the topography has a serious effect on airborne EM data.
A low-power time-domain VCO-based ADC in 65 nm CMOS
Chenluan, Wang; Shengxi, Diao; Fujiang, Lin
2014-10-01
A low-power, high-FoM (figure of merit), time-domain VCO (voltage controlled oscillator)-based ADC (analog-to-digital converter) in 65 nm CMOS technology is proposed. An asynchronous sigma—delta modulator (ASDM) is used to convert the voltage input signal to a square wave time signal, where the information is contained in its pulse-width. A time-domain quantizer, which uses VCO to convert voltage to frequency, is adopted, while the XOR (exclusive-OR) gate circuits convert the frequency information to digital representatives. The ASDM does not need an external clock, so there is no quantization noise. At the same time, the ASDM applies a harmonic-distortion-cancellation technique to its transconductance stage, which increases the SNDR (signal to noise and distortion ratio) performance of the ASDM. Since the output of the ASDM is a two-level voltage signal, the VCO's V—F (voltage to frequency) conversion curve is always linear. The XOR phase quantizer has an inherent feature of first-order noise-shaping. It puts the ADC's low-frequency output noise to high-frequency which is further filtered out by a low-pass filter. The proposed ADC achieves an SNR/SNDR of 54. dB/54.3 dB in the 8 MHz bandwidth, while consuming 2.8 mW. The FoM of the proposed ADC is a 334 fJ/conv-step.
An explicit marching on-in-time solver for the time domain volume magnetic field integral equation
Sayed, Sadeed Bin
2014-07-01
Transient scattering from inhomogeneous dielectric objects can be modeled using time domain volume integral equations (TDVIEs). TDVIEs are oftentimes solved using marching on-in-time (MOT) techniques. Classical MOT-TDVIE solvers expand the field induced on the scatterer using local spatio-temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation in space and time yields a system of equations that is solved by time marching. Depending on the type of the basis and testing functions and the time step, the time marching scheme can be implicit (N. T. Gres, et al., Radio Sci., 36(3), 379-386, 2001) or explicit (A. Al-Jarro, et al., IEEE Trans. Antennas Propag., 60(11), 5203-5214, 2012). Implicit MOT schemes are known to be more stable and accurate. However, under low-frequency excitation, i.e., when the time step size is large, they call for inversion of a full matrix system at very time step.
Time domain parameters of heart rate variability in children born as small-for-gestational age.
Zamecznik, Agata; Stańczyk, Jerzy; Wosiak, Agnieszka; Niewiadomska-Jarosik, Katarzyna
2017-05-01
According to metabolic programming theory, small-for-gestational age patients are at high risk of cardiovascular diseases also because of the possible malfunction of the autonomic nervous system. Autonomic disorders can be assessed by heart rate variability. The aims of this study were to compare time domain parameters of heart rate variability in children born as small-for-gestational age and appropriate-for-gestational age and to assess the correlation of the postnatal and current somatic parameters with the time domain parameters. The small-for-gestational age group consisted of 68 children aged 5-10 years who were born with birth weight below the 10th percentile. The appropriate-for-gestational age group consisted of 30 healthy peers, matched in terms of gender and age. On the basis of Holter monitoring, slightly higher average heart rate was observed in the small-for-gestational age group than in the appropriate-for-gestational age group. It was found that all the time domain parameters (SDNN, SDNNi, SDANNi, rMSSD, pNN50) were lower in the small-for-gestational age group than in the appropriate-for-gestational age group. In the small-for-gestational age group, girls had lower heart rate and some of the heart rate variability parameters (SDNN, SDNNi, SDANNi) in comparison with boys. Children born as small-for-gestational age have impaired function of the autonomic nervous system. Moreover, in the small-for-gestational age group, autonomic balance moved towards the sympathetic component, which was evidenced by higher heart rate. Children with faster heart rate and lower heart rate variability parameters may be at risk of cardiovascular disease.
Clements, Keith; Wall, John
2017-01-01
The baseline stability margins for NASA's Space Launch System (SLS) launch vehicle were generated via the classical approach of linearizing the system equations of motion and determining the gain and phase margins from the resulting frequency domain model. To improve the fidelity of the classical methods, the linear frequency domain approach can be extended by replacing static, memoryless nonlinearities with describing functions. This technique, however, does not address the time varying nature of the dynamics of a launch vehicle in flight. An alternative technique for the evaluation of the stability of the nonlinear launch vehicle dynamics along its trajectory is to incrementally adjust the gain and/or time delay in the time domain simulation until the system exhibits unstable behavior. This technique has the added benefit of providing a direct comparison between the time domain and frequency domain tools in support of simulation validation.
DEFF Research Database (Denmark)
Vaz, C.M.P.; Hopmans, J.W.; Macedo, A.
2002-01-01
in situ soil water retention data from simultaneous soil water matric potential and water content measurements within approximately the same small soil volume around the combined probe, but requires soil specific calibration because of slight desaturation of the porous cup of the tensiometer.......The objective of the presented study was to develop a single probe that can be used to determine soil water retention curves in both laboratory and field conditions, by including a coiled time domain reflectometry (TDR) probe around the porous cup of a standard tensiometer. The combined tensiometer...
Numerical modeling of wind turbine aerodynamic noise in the time domain.
Lee, Seunghoon; Lee, Seungmin; Lee, Soogab
2013-02-01
Aerodynamic noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge noise model is used to determine the unsteady pressure on the blade surface. The far-field noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine noise can be quite different with respect to the distance and direction from the wind turbine.
Gutierrez, Juan B; Lai, Ming-Jun; Slavov, George
2015-12-01
We study a time dependent partial differential equation (PDE) which arises from classic models in ecology involving logistic growth with Allee effect by introducing a discrete weak solution. Existence, uniqueness and stability of the discrete weak solutions are discussed. We use bivariate splines to approximate the discrete weak solution of the nonlinear PDE. A computational algorithm is designed to solve this PDE. A convergence analysis of the algorithm is presented. We present some simulations of population development over some irregular domains. Finally, we discuss applications in epidemiology and other ecological problems. Copyright © 2015 Elsevier Inc. All rights reserved.
Plasmonic enhanced terahertz time-domain spectroscopy system for identification of common explosives
Demiraǧ, Yiǧit; Bütün, Bayram; Özbay, Ekmel
2017-05-01
In this study, we present a classification algorithm for terahertz time-domain spectroscopy systems (THz-TDS) that can be trained to identify most commonly used explosives (C4, HMX, RDX, PETN, TNT, composition-B and blackpowder) and some non-explosive samples (lactose, sucrose, PABA). Our procedure can be used in any THz-TDS system that detects either transmission or reflection spectra at room conditions. After preprocessing the signal in low THz regime (0.1 - 3 THz), our algorithm takes advantages of a latent space transformation based on principle component analysis in order to classify explosives with low false alarm rate.
Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study.
Di Sieno, Laura; Zouaoui, Judy; Hervé, Lionel; Pifferi, Antonio; Farina, Andrea; Martinenghi, Edoardo; Derouard, Jacques; Dinten, Jean-Marc; Mora, Alberto Dalla
2016-11-01
Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thus opening the way to the use of SiPMs for DOT, with the possibility to conceive a new generation of low-cost and reliable multichannel tomographic systems.
A RF time domain approach for electric arcs detection and localization systems
Deacu, Daniela; Tamas, Razvan; Petrescu, Teodor; Paun, Mirel; Anchidin, Liliana; Algiu, Madalina
2016-12-01
In this paper we propose a new method for detection and localization of electric arcs by using two ultra-wide band (UWB) antennas together with data processing in the time-domain. The source of electric arcs is localized by computing an average on the inter-correlation functions of the signals received on two channels. By calculating the path length difference to the antennas, the direction of the electric arcs is then found. The novelty of the method consists in the spatial averaging in order to reduce the incertitude caused by the finite sampling rate.
Fedorov, A K; Anufriev, M N; Zhirnov, A A; Stepanov, K V; Nesterov, E T; Namiot, D E; Karasik, V E; Pnev, A B
2016-03-01
We propose a novel approach to the recognition of particular classes of non-conventional events in signals from phase-sensitive optical time-domain-reflectometry-based sensors. Our algorithmic solution has two main features: filtering aimed at the de-nosing of signals and a Gaussian mixture model to cluster them. We test the proposed algorithm using experimentally measured signals. The results show that two classes of events can be distinguished with the best-case recognition probability close to 0.9 at sufficient numbers of training samples.
Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)
DEFF Research Database (Denmark)
Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei
2017-01-01
Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly...... by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares...
Pappas, C. G.; Beall, J.; Brevick, J.; Cho, H. M.; Devlin, M. J.; Fox, A.; Grace, E. A.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; Klein, J.; Li, D.; Lungu, M.; Newburgh, L. B.; Nibarger, J. P.; Niemack, M. D.; McMahon, J. J.; Page, L. A.; Schmitt, B. L.; Staggs, S. T.; Van Lanen, J.; Wollack, E. J.
2014-09-01
We present new data on feedhorn-coupled transition-edge sensor devices fabricated for the second-generation receiver (ACTPol) for the Atacama cosmology telescope (ACT). First, we describe optical efficiency measurements of the latest ACTPol detector wafer, which has a average optical efficiency. Next, we discuss measurements of the TES resistance as a function of temperature and bias current () using the ACTPol time-domain multiplexing electronics. Qualitative agreement between data at low bias current and the two-fluid model prediction is shown. Using the two-fluid model and low bias current data, and at our operating bias current are calculated.
3D time-domain spectral elements for stress waves modelling
International Nuclear Information System (INIS)
Kudela, P; Ostachowicz, W
2009-01-01
Elastic stress waves induced by piezoelectric transducers are extensively used for damage detection purposes. Induced high frequency impulse signals cause that stress wave modelling by the finite element method is inefficient. Instead, numerical model based on the time-domain spectral element method has been developed to simulate stress wave propagation in metallic structures induced by the piezoelectric transducers. The model solves the coupled electromechanical field equations simultaneously in three-dimensional case. Visualisation of the propagating elastic waves generated by the actuator of different shapes and properties has been performed.
Scattering analysis of periodic structures using finite-difference time-domain
ElMahgoub, Khaled; Elsherbeni, Atef Z
2012-01-01
Periodic structures are of great importance in electromagnetics due to their wide range of applications such as frequency selective surfaces (FSS), electromagnetic band gap (EBG) structures, periodic absorbers, meta-materials, and many others. The aim of this book is to develop efficient computational algorithms to analyze the scattering properties of various electromagnetic periodic structures using the finite-difference time-domain periodic boundary condition (FDTD/PBC) method. A new FDTD/PBC-based algorithm is introduced to analyze general skewed grid periodic structures while another algor
Calibrating a Salt Water Intrusion Model with Time-Domain Electromagnetic Data
DEFF Research Database (Denmark)
Herckenrath, Daan; Odlum, Nick; Nenna, Vanessa
2013-01-01
are transformed to an electrical resistivity model, after which a geophysical forward response is calculated and compared with the measured geophysical data. This approach was applied for a field site in Santa Cruz County, California, where a time-domain electromagnetic (TDEM) dataset was collected......Salt water intrusion models are commonly used to support groundwater resource management in coastal aquifers. Concentration data used for model calibration are often sparse and limited in spatial extent. With airborne and ground-based electromagnetic surveys, electrical resistivity models can...
Discontinuous Galerkin time-domain analysis of power/ground plate pairs with wave port excitation
Li, Ping
2018-04-06
In this work, a discontinuous Galerkin time-domain method is developed to analyze the power/ground plate pairs taking into account arbitrarily shaped antipads. To implement proper source excitations over the antipads, the magnetic surface current expanded by the electric eigen-modes supported by the corresponding antipad is employed as the excitation. For irregularly shaped antipads, the eigen-modes are obtained by numerical approach. Accordingly, the methodology for the S-parameter extraction is derived based on the orthogonal properties of the different modes. Based on the approach, the transformation between different modes can be readily evaluated.
Resolving spectral information from time domain induced polarization data through 2-D inversion
DEFF Research Database (Denmark)
Fiandaca, Gianluca; Ramm, James; Binley, A.
2013-01-01
SUMMARY Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given...... these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD...
Perfectly Matched Layer for the Wave Equation Finite Difference Time Domain Method
Miyazaki, Yutaka; Tsuchiya, Takao
2012-07-01
The perfectly matched layer (PML) is introduced into the wave equation finite difference time domain (WE-FDTD) method. The WE-FDTD method is a finite difference method in which the wave equation is directly discretized on the basis of the central differences. The required memory of the WE-FDTD method is less than that of the standard FDTD method because no particle velocity is stored in the memory. In this study, the WE-FDTD method is first combined with the standard FDTD method. Then, Berenger's PML is combined with the WE-FDTD method. Some numerical demonstrations are given for the two- and three-dimensional sound fields.
Finite Difference Time-Domain Modelling of Metamaterials: GPU Implementation of Cylindrical Cloak
Directory of Open Access Journals (Sweden)
A. Dawood
2013-08-01
Full Text Available Finite difference time-domain (FDTD technique can be used to model metamaterials by treating them as dispersive material. Drude or Lorentz model can be incorporated into the standard FDTD algorithm for modelling negative permittivity and permeability. FDTD algorithm is readily parallelisable and can take advantage of GPU acceleration to achieve speed-ups of 5x-50x depending on hardware setup. Metamaterial scattering problems are implemented using dispersive FDTD technique on GPU resulting in performance gain of 10x-15x compared to conventional CPU implementation.
Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons
Hussain, A.
2010-06-17
There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states although there is no theoretical model that directly supports such a proposal. We have experimentally re-examined the studies of phonons in bismuth and gallium arsenide, and find no evidence of any phase-dependent noise signature associated with the phonons. We place an upper limit on any such noise at least 40–50 dB lower than previously reported.
Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy
DEFF Research Database (Denmark)
Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup
2016-01-01
The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR......), and linearity of detection have been characterized. Moreover, the performance of a photomultiplier tube (PMT) and an avalanche photodiode (APD) as photodetector in the ABCD have been compared. We have observed nonlinear behavior of PMT detector, which leads to artificial gain factor in TDS spectroscopy. The APD...
Directory of Open Access Journals (Sweden)
Jakub Bernat
2017-06-01
Full Text Available This paper addresses the issue of estimating current waveforms in a switched reluctance motor required to achieve a desired electromagnetic torque. The methodology employed exploits the recently-developed method based on the transformation from the time to the position domain. This transformation takes account of nonlinearities caused by a doubly-salient structure. Owing to this new modelling technique it is possible to solve optimization problems with reference torque, constrained voltage, and parameter sensitivity accounted for. The proposed methodology is verified against published solutions and illustrated through simulations and experiments.
openPSTD: The open source pseudospectral time-domain method for acoustic propagation
Hornikx, Maarten; Krijnen, Thomas; van Harten, Louis
2016-06-01
An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. In the implementation it has been opted to model the physical geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. For accelerating the software, an option has been included to accelerate the calculations by a partial implementation of the code on the Graphical Processing Unit (GPU), which increases the throughput by up to fifteen times. The details of the implementation are reported, as well as the accuracy of the code.
Time-domain incomplete Gauss-Newton full-waveform inversion of Gulf of Mexico data
AlTheyab, Abdullah
2013-09-22
We apply the incomplete Gauss-Newton full-waveform inversion (TDIGN-FWI) to Gulf of Mexico (GOM) data in the space-time domain. In our application, iterative least-squares reverse-time migration (LSRTM) is used to estimate the model update at each non-linear iteration, and the number of LSRTM iterations is progressively increased after each non-linear iteration. With this method, model updating along deep reflection wavepaths are automatically enhanced, which in turn improves imaging below the reach of diving-waves. The forward and adjoint operators are implemented in the space-time domain to simultaneously invert the data over a range of frequencies. A multiscale approach is used where higher frequencies are down-weighted significantly at early iterations, and gradually included in the inversion. Synthetic data results demonstrate the effectiveness of reconstructing both the high- and low-wavenumber features in the model without relying on diving waves in the inversion. Results with Gulf of Mexico field data show a significantly improved migration image in both the shallow and deep sections.
SPATIOTEMPORAL DOMAIN DECOMPOSITION FOR MASSIVE PARALLEL COMPUTATION OF SPACE-TIME KERNEL DENSITY
Directory of Open Access Journals (Sweden)
A. Hohl
2015-07-01
Full Text Available Accelerated processing capabilities are deemed critical when conducting analysis on spatiotemporal datasets of increasing size, diversity and availability. High-performance parallel computing offers the capacity to solve computationally demanding problems in a limited timeframe, but likewise poses the challenge of preventing processing inefficiency due to workload imbalance between computing resources. Therefore, when designing new algorithms capable of implementing parallel strategies, careful spatiotemporal domain decomposition is necessary to account for heterogeneity in the data. In this study, we perform octtree-based adaptive decomposition of the spatiotemporal domain for parallel computation of space-time kernel density. In order to avoid edge effects near subdomain boundaries, we establish spatiotemporal buffers to include adjacent data-points that are within the spatial and temporal kernel bandwidths. Then, we quantify computational intensity of each subdomain to balance workloads among processors. We illustrate the benefits of our methodology using a space-time epidemiological dataset of Dengue fever, an infectious vector-borne disease that poses a severe threat to communities in tropical climates. Our parallel implementation of kernel density reaches substantial speedup compared to sequential processing, and achieves high levels of workload balance among processors due to great accuracy in quantifying computational intensity. Our approach is portable of other space-time analytical tests.
Spatiotemporal Domain Decomposition for Massive Parallel Computation of Space-Time Kernel Density
Hohl, A.; Delmelle, E. M.; Tang, W.
2015-07-01
Accelerated processing capabilities are deemed critical when conducting analysis on spatiotemporal datasets of increasing size, diversity and availability. High-performance parallel computing offers the capacity to solve computationally demanding problems in a limited timeframe, but likewise poses the challenge of preventing processing inefficiency due to workload imbalance between computing resources. Therefore, when designing new algorithms capable of implementing parallel strategies, careful spatiotemporal domain decomposition is necessary to account for heterogeneity in the data. In this study, we perform octtree-based adaptive decomposition of the spatiotemporal domain for parallel computation of space-time kernel density. In order to avoid edge effects near subdomain boundaries, we establish spatiotemporal buffers to include adjacent data-points that are within the spatial and temporal kernel bandwidths. Then, we quantify computational intensity of each subdomain to balance workloads among processors. We illustrate the benefits of our methodology using a space-time epidemiological dataset of Dengue fever, an infectious vector-borne disease that poses a severe threat to communities in tropical climates. Our parallel implementation of kernel density reaches substantial speedup compared to sequential processing, and achieves high levels of workload balance among processors due to great accuracy in quantifying computational intensity. Our approach is portable of other space-time analytical tests.
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.
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.
A Real-Time Wavelet-Domain Video Denoising Implementation in FPGA
Directory of Open Access Journals (Sweden)
Wilfried Philips
2006-07-01
Full Text Available The use of field-programmable gate arrays (FPGAs for digital signal processing (DSP has increased with the introduction of dedicated multipliers, which allow the implementation of complex algorithms. This architecture is especially effective for data-intensive applications with extremes in data throughput. Recent studies prove that the FPGAs offer better solutions for real-time multiresolution video processing than any available processor, DSP or general-purpose. FPGA design of critically sampled discrete wavelet transforms has been thoroughly studied in literature over recent years. Much less research was done towards FPGA design of overcomplete wavelet transforms and advanced wavelet-domain video processing algorithms. This paper describes the parallel implementation of an advanced wavelet-domain noise filtering algorithm, which uses a nondecimated wavelet transform and spatially adaptive Bayesian wavelet shrinkage. The implemented arithmetic is decentralized and distributed over two FPGAs. The standard composite television video stream is digitalized and used as a source for real-time video sequences. The results demonstrate the effectiveness of the developed scheme for real-time video processing.
A Real-Time Wavelet-Domain Video Denoising Implementation in FPGA
Directory of Open Access Journals (Sweden)
Pižurica Aleksandra
2006-01-01
Full Text Available The use of field-programmable gate arrays (FPGAs for digital signal processing (DSP has increased with the introduction of dedicated multipliers, which allow the implementation of complex algorithms. This architecture is especially effective for data-intensive applications with extremes in data throughput. Recent studies prove that the FPGAs offer better solutions for real-time multiresolution video processing than any available processor, DSP or general-purpose. FPGA design of critically sampled discrete wavelet transforms has been thoroughly studied in literature over recent years. Much less research was done towards FPGA design of overcomplete wavelet transforms and advanced wavelet-domain video processing algorithms. This paper describes the parallel implementation of an advanced wavelet-domain noise filtering algorithm, which uses a nondecimated wavelet transform and spatially adaptive Bayesian wavelet shrinkage. The implemented arithmetic is decentralized and distributed over two FPGAs. The standard composite television video stream is digitalized and used as a source for real-time video sequences. The results demonstrate the effectiveness of the developed scheme for real-time video processing.
Faes, Luca; Erla, Silvia; Porta, Alberto; Nollo, Giandomenico
2013-08-28
We present an approach for the quantification of directional relations in multiple time series exhibiting significant zero-lag interactions. To overcome the limitations of the traditional multivariate autoregressive (MVAR) modelling of multiple series, we introduce an extended MVAR (eMVAR) framework allowing either exclusive consideration of time-lagged effects according to the classic notion of Granger causality, or consideration of combined instantaneous and lagged effects according to an extended causality definition. The spectral representation of the eMVAR model is exploited to derive novel frequency domain causality measures that generalize to the case of instantaneous effects the known directed coherence (DC) and partial DC measures. The new measures are illustrated in theoretical examples showing that they reduce to the known measures in the absence of instantaneous causality, and describe peculiar aspects of directional interaction among multiple series when instantaneous causality is non-negligible. Then, the issue of estimating eMVAR models from time-series data is faced, proposing two approaches for model identification and discussing problems related to the underlying model assumptions. Finally, applications of the framework on cardiovascular variability series and multichannel EEG recordings are presented, showing how it allows one to highlight patterns of frequency domain causality consistent with well-interpretable physiological interaction mechanisms.
Terahertz time domain spectroscopy of epoxy resin composite with various carbon inclusions
International Nuclear Information System (INIS)
Macutkevic, J.; Seliuta, D.; Valusis, G.; Adomavicius, R.; Kuzhir, P.; Paddubskaya, A.; Shuba, M.; Maksimenko, S.; Coderoni, L.; Micciulla, F.; Sacco, I.; Bellucci, S.
2012-01-01
Highlights: ► Epoxy resin with carbon inclusions is studied by terahertz time domain spectroscopy. ► The resonance dielectric dispersion is observed for all investigated samples. ► Dielectric properties are modeled by Maxwell–Garnett and nanoelectromagnetic formalism. -- Abstract: The propagation properties of terahertz waves through epoxy resin filled with small amounts (0.25–1.5 wt.%) of commercially available carbon black (CB) and CVD made single-walled and multi-walled carbon nanotubes (CNT) have been investigated by terahertz time domain spectroscopy. High electromagnetic attenuation specified substantially with absorption of THz radiation and strongly decreasing with the decrease of frequency from 0.2 to 1.5 THz has been found for both types of CNT fillers starting from 1 wt.% of nanocarbon concentration. At the same time CB in the same concentration does not make any impact to THz transmission spectrum. The resonance dielectric dispersion has been observed for all investigated samples, which can be attributed to phonon resonance in epoxy resin matrix. The availability of Maxwell–Garnett model for epoxy resin filled with 0.25–1.5 wt.% of CNT was also addressed in the paper.
Zhang, Shengli; Tang, Jiong
2016-04-01
Gearbox is one of the most vulnerable subsystems in wind turbines. Its healthy status significantly affects the efficiency and function of the entire system. Vibration based fault diagnosis methods are prevalently applied nowadays. However, vibration signals are always contaminated by noise that comes from data acquisition errors, structure geometric errors, operation errors, etc. As a result, it is difficult to identify potential gear failures directly from vibration signals, especially for the early stage faults. This paper utilizes synchronous averaging technique in time-frequency domain to remove the non-synchronous noise and enhance the fault related time-frequency features. The enhanced time-frequency information is further employed in gear fault classification and identification through feature extraction algorithms including Kernel Principal Component Analysis (KPCA), Multilinear Principal Component Analysis (MPCA), and Locally Linear Embedding (LLE). Results show that the LLE approach is the most effective to classify and identify different gear faults.
International Nuclear Information System (INIS)
Wei Biao; Feng Peng; Yang Fan; Ren Yong
2014-01-01
To deal with the disadvantages of the homogeneous signature of the nuclear material identification system (NMIS) and limited methods to extract the characteristic parameters of the nuclear materials, an enhanced method using the combination of the Time-of-Flight (TOF) and the Pulse Shape Discrimination (PSD) was introduced into the traditional characteristic parameters extraction and recognition system of the NMIS. With the help of the PSD, the γ signal and the neutron signal can be discriminated. Further based on the differences of the neutron-γ flight time of the detectors in various positions, a new time-domain signature reflecting the position information of unknown nuclear material was investigated. The simulation result showed that the algorithm is feasible and helpful to identify the relative position of unknown nuclear material. (authors)
On spurious resonant modes in the MOT solution of time domain EFIE
Shi, Yifei
2013-07-01
Theoretically, internal resonant modes should not be induced in the marching-on-in-time (MOT) solution of the time domain electric field integral equation since zero initial conditions are enforced at the beginning of time marching and the internal resonant modes do not satisfy these initial conditions. However, these spurious modes are always observed in the MOT solution. It has been conjectured in the past that numerical errors might establish the necessary initial conditions and allow the incident field to induce the internal resonant modes. Systematic numerical experiments carried out in this work prove this conjecture by demonstrating that the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors and the spectrum of the incident field. © 2013 IEEE.
On the DC loop modes in the MOT solution of the time domain EFIE
Shi, Yifei
2014-07-01
When marching-on-in-time (MOT) method is applied to solve the time domain electric field integral equation (TD-EFIE), DC loop modes are always observed in the solution. In theory these modes should not be observed since they do not satisfy the relaxed initial conditions. Their appearance is attributed to numerical errors. It is shown here that when Rao-Wilton-Glisson basis and Lagrange interpolation functions are used to discretize the TD-EFIE, errors due to this space-time discretization have zero impact on the DC loop modes. Numerical experiments demonstrate that the numerical errors due to approximate solution of the MOT matrix system have more dominant impact on DC loop modes in the MOT solution.
Parallel, explicit, and PWTD-enhanced time domain volume integral equation solver
Liu, Yang
2013-07-01
Time domain volume integral equations (TDVIEs) are useful for analyzing transient scattering from inhomogeneous dielectric objects in applications as varied as photonics, optoelectronics, and bioelectromagnetics. TDVIEs typically are solved by implicit marching-on-in-time (MOT) schemes [N. T. Gres et al., Radio Sci., 36, 379-386, 2001], requiring the solution of a system of equations at each and every time step. To reduce the computational cost associated with such schemes, [A. Al-Jarro et al., IEEE Trans. Antennas Propagat., 60, 5203-5215, 2012] introduced an explicit MOT-TDVIE method that uses a predictor-corrector technique to stably update field values throughout the scatterer. By leveraging memory-efficient nodal spatial discretization and scalable parallelization schemes [A. Al-Jarro et al., in 28th Int. Rev. Progress Appl. Computat. Electromagn., 2012], this solver has been successfully applied to the analysis of scattering phenomena involving 0.5 million spatial unknowns. © 2013 IEEE.
Ground penetrating radar data analyzed in frequency and time domain for engineering issues
Capozzoli, Luigi; Giampaolo, Valeria; Votta, Mario; Rizzo, Enzo
2014-05-01
Non-destructive testing (NDT) allows to analyze reinforced concrete and masonry structures, in order to identify gaps, defects, delaminations, and fracture. In the field of engineering, non-invasive diagnostic is used to test the processes of construction and maintenance of buildings and artifacts of the individual components, to reduce analysis time and costs of intervention (Proto et al., 2010). Ground penetrating radar (GPR) allows to evaluate with a good effectiveness the state of conservation of engineering construction (Mellet 1995)). But there are some uncertainties in GPR data due to the complexity of artificial objects. In this work we try to evaluate the capability of GPR for the characterization of building structures in the laboratory and in-situ. In particular the focus of this research consists in integrate spectral analysis to time domain data to enhance information obtained in a classical GPR processing approach. For this reason we have applied spectral analysis to localize and characterize the presence of extraneous bodies located in a test site rebuilt in laboratory to simulate a part of a typical concrete road. The test site is a segment of a road superimposed on two different layers of sand and gravel of varying thickness inside which were introduced steel rebar, PVC and aluminium pipes. This structure has also been cracked in a predetermined area and hidden internal fractures were investigated. The GPR has allowed to characterize the panel in a non-invasive mode and radargrams were acquired using two-dimensional and three-dimensional models from data obtained with the use of 400, 900, 1500 and 2000 Mhz antennas. We have also studied with 2 GHz antenna a beam of 'to years precast bridge characterized by a high state of decay. The last case study consisted in the characterization of a radiant floor analyzed with an integrated use of GPR and infrared thermography. In the frequency domain analysis has been possible to determine variations in the
Bohlen, Thomas; Wittkamp, Florian
2016-03-01
We analyse the performance of a higher order accurate staggered viscoelastic time-domain finite-difference method, in which the staggered Adams-Bashforth (ABS) third-order and fourth-order accurate time integrators are used for temporal discretization. ABS is a multistep method that uses previously calculated wavefields to increase the order of accuracy in time. The analysis shows that the numerical dispersion is much lower than that of the widely used second-order leapfrog method. Numerical dissipation is introduced by the ABS method which is significantly smaller for fourth-order than third-order accuracy. In 1-D and 3-D simulation experiments, we verify the convincing improvements of simulation accuracy of the fourth-order ABS method. In a realistic elastic 3-D scenario, the computing time reduces by a factor of approximately 2.4, whereas the memory requirements increase by approximately a factor of 2.2. The ABS method thus provides an alternative strategy to increase the simulation accuracy in time by investing computer memory instead of computing time.
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
Time domain analysis of superradiant instability for the charged stringy black hole–mirror system
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Ran Li
2015-11-01
Full Text Available It has been proved that the charged stringy black holes are stable under the perturbations of massive charged scalar fields. However, superradiant instability can be generated by adding the mirror-like boundary condition to the composed system of charged stringy black hole and scalar field. The unstable boxed quasinormal modes have been calculated by using both analytical and numerical methods. In this paper, we further provide a time domain analysis by performing a long time evolution of charged scalar field configuration in the background of the charged stringy black hole with the mirror-like boundary condition imposed. We have used the ingoing Eddington–Finkelstein coordinates to derive the evolution equation, and adopted Pseudo-spectral method and the forth-order Runge–Kutta method to evolve the scalar field with the initial Gaussian wave packet. It is shown by our numerical scheme that Fourier transforming the evolution data coincides well with the unstable modes computed from frequency domain analysis. The existence of the rapid growth mode makes the charged stringy black hole a good test ground to study the nonlinear development of superradiant instability.
Application of Time-Frequency Domain Transform to Three-Dimensional Interpolation of Medical Images.
Lv, Shengqing; Chen, Yimin; Li, Zeyu; Lu, Jiahui; Gao, Mingke; Lu, Rongrong
2017-11-01
Medical image three-dimensional (3D) interpolation is an important means to improve the image effect in 3D reconstruction. In image processing, the time-frequency domain transform is an efficient method. In this article, several time-frequency domain transform methods are applied and compared in 3D interpolation. And a Sobel edge detection and 3D matching interpolation method based on wavelet transform is proposed. We combine wavelet transform, traditional matching interpolation methods, and Sobel edge detection together in our algorithm. What is more, the characteristics of wavelet transform and Sobel operator are used. They deal with the sub-images of wavelet decomposition separately. Sobel edge detection 3D matching interpolation method is used in low-frequency sub-images under the circumstances of ensuring high frequency undistorted. Through wavelet reconstruction, it can get the target interpolation image. In this article, we make 3D interpolation of the real computed tomography (CT) images. Compared with other interpolation methods, our proposed method is verified to be effective and superior.
A time-domain finite element boundary integration method for ultrasonic nondestructive evaluation.
Shi, Fan; Choi, Wonjae; Skelton, Elizabeth A; Lowe, Michael J S; Craster, Richard V
2014-12-01
A 2-D and 3-D numerical modeling approach for calculating the elastic wave scattering signals from complex stress-free defects is evaluated. In this method, efficient boundary integration across the complex boundary of the defect is coupled with a time-domain finite element (FE) solver. The model is designed to simulate time-domain ultrasonic nondestructive evaluation in bulk media. This approach makes use of the hybrid concept of linking a local numerical model to compute the near-field scattering behavior and theoretical mathematical formulas for postprocessing to calculate the received signals. It minimizes the number of monitoring signals from the FE calculation so that the computation effort in postprocessing decreases significantly. In addition, by neglecting the conventional regular monitoring box, the region for FE calculation can be made smaller. In this paper, the boundary integral method is implemented in a commercial FE code, and it is validated by comparing the scattering signals with results from corresponding full FE models. The coupled method is then implemented in real inspection scenarios in both 2-D and 3-D, and the accuracy and the efficiency are demonstrated. The limitations of the proposed model and future works are also discussed.
Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status
Directory of Open Access Journals (Sweden)
Luis Gonzaga Santesteban
2015-06-01
Full Text Available Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if THz time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years old plant, using a general purpose THz emitter receiver head.Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity.
Application of modified integration rule to time-domain finite-element acoustic simulation of rooms.
Okuzono, Takeshi; Otsuru, Toru; Tomiku, Reiji; Okamoto, Noriko
2012-08-01
The applicability of the modified integration rule for time-domain finite-element analysis is tested in sound field analysis of rooms involving rectangular elements, distorted elements, and finite impedance boundary conditions. Dispersion error analysis in three dimensions is conducted to evaluate the dispersion error in time-domain finite-element analysis using eight-node hexahedral elements. The results of analysis confirmed that fourth-order accuracy with respect to dispersion error is obtainable using the Fox-Goodwin method (FG) with a modified integration rule, even for rectangular elements. The stability condition in three-dimensional analysis using the modified integration rule is also presented. Numerical experiments demonstrate that FG with a modified integration rule performs much better than FG with the conventional integration rule for problems with rectangular elements, distorted elements, and with finite impedance boundary conditions. Further, as another advantage, numerical results revealed that the use of modified integration rule engenders faster convergence of the iterative solver than a conventional rule for problems with the same degrees of freedom.
A Time-Domain Analog Spatial Compressed Sensing Encoder for Multi-Channel Neural Recording.
Okazawa, Takayuki; Akita, Ippei
2018-01-11
A time-domain analog spatial compressed sensing encoder for neural recording applications is proposed. Owing to the advantage of MEMS technologies, the number of channels on a silicon neural probe array has doubled in 7.4 years, and therefore, a greater number of recording channels and higher density of front-end circuitry is required. Since neural signals such as action potential (AP) have wider signal bandwidth than that of an image sensor, a data compression technique is essentially required for arrayed neural recording systems. In this paper, compressed sensing (CS) is employed for data reduction, and a novel time-domain analog CS encoder is proposed. A simpler and lower power circuit than conventional analog or digital CS encoders can be realized by using the proposed CS encoder. A prototype of the proposed encoder was fabricated in a 180 nm 1P6M CMOS process, and it achieved an active area of 0.0342 mm 2 / ch . and an energy efficiency of 25.0 pJ / ch . · conv .
High-speed camera with real time processing for frequency domain imaging.
Shia, Victor; Watt, David; Faris, Gregory W
2011-07-01
We describe a high-speed camera system for frequency domain imaging suitable for applications such as in vivo diffuse optical imaging and fluorescence lifetime imaging. 14-bit images are acquired at 2 gigapixels per second and analyzed with real-time pipeline processing using field programmable gate arrays (FPGAs). Performance of the camera system has been tested both for RF-modulated laser imaging in combination with a gain-modulated image intensifier and a simpler system based upon an LED light source. System amplitude and phase noise are measured and compared against theoretical expressions in the shot noise limit presented for different frequency domain configurations. We show the camera itself is capable of shot noise limited performance for amplitude and phase in as little as 3 ms, and when used in combination with the intensifier the noise levels are nearly shot noise limited. The best phase noise in a single pixel is 0.04 degrees for a 1 s integration 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.
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.
Time-domain electromagnetic energy in a frequency-dispersive left-handed medium
International Nuclear Information System (INIS)
Cui Tiejun; Kong Jinau
2004-01-01
From Maxwell's equations and the Poynting theorem, the time-domain electric and magnetic energy densities are generally defined in the frequency-dispersive media based on the conservation of energy. As a consequence, a general definition of electric and magnetic energy is proposed. Comparing with existing formulations of electric and magnetic energy in frequency-dispersive media, the new definition is more reasonable and is valid in any case. Using the new definition and staring from the equation of motion, we have shown rigorously that the total energy density and the individual electric and magnetic energy densities are always positive in a realistic artificial left-handed medium (LHM) [R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001)], which obeys actually the Lorentz medium model, although such a LHM has negative permittivity and negative permeability simultaneously in a certain frequency range. We have also shown that the conservation of energy is not violated in LHM. The earlier conclusions can be easily extended to the Drude medium model and the cold plasma medium model. Through an exact analysis of a one-dimensional transient current source radiating in LHM, numerical results are given to demonstrate that the work done by source, the power flowing outwards a surface, and the electric and magnetic energy stored in a volume are all positive in the time domain
Kiyan, Duygu; Rath, Volker; Delhaye, Robert
2017-04-01
The frequency- and time-domain airborne electromagnetic (AEM) data collected under the Tellus projects of the Geological Survey of Ireland (GSI) which represent a wealth of information on the multi-dimensional electrical structure of Ireland's near-surface. Our project, which was funded by GSI under the framework of their Short Call Research Programme, aims to develop and implement inverse techniques based on various Bayesian methods for these densely sampled data. We have developed a highly flexible toolbox using Python language for the one-dimensional inversion of AEM data along the flight lines. The computational core is based on an adapted frequency- and time-domain forward modelling core derived from the well-tested open-source code AirBeo, which was developed by the CSIRO (Australia) and the AMIRA consortium. Three different inversion methods have been implemented: (i) Tikhonov-type inversion including optimal regularisation methods (Aster el al., 2012; Zhdanov, 2015), (ii) Bayesian MAP inversion in parameter and data space (e.g. Tarantola, 2005), and (iii) Full Bayesian inversion with Markov Chain Monte Carlo (Sambridge and Mosegaard, 2002; Mosegaard and Sambridge, 2002), all including different forms of spatial constraints. The methods have been tested on synthetic and field data. This contribution will introduce the toolbox and present case studies on the AEM data from the Tellus projects.
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.
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......, a real hidden portraiton an easel painting has been imaged by THz-TDI, with an unexpected richness of detail. THz C- andB-scans have been compared with images obtained by x-ray radiography and invasive cross-sectional imaging,leading to a deeper understanding of the strengths and limitations...... in practical applications of the technique. Interfaces between layers ofthe painting have been successfully imaged, contributing substantially to the understanding of the structure of the painting....
Time domain analysis method for aerodynamic noises from wind turbine blades
Directory of Open Access Journals (Sweden)
Hua ZHAO
2015-04-01
Full Text Available The issue of the aerodynamic noises from wind turbine blades affecting the surrounding residents life begins to attract researcher's attention. Most of the existing researches are based on CFD software or experimental data fitting method to analyze the aerodynamic noises, so it is difficult to adapt the demand to dynamic analysis of the aerodynamic noises from wind speed variation. In this paper, the operation parameters, the inflow wind speed and the receiver location are considered, and a modified model to calculate aerodynamic noises from wind turbine blades which is based on traditional acoustic formulas is established. The program to calculate the aerodynamic noises from the 2 MW wind turbine blades is compiled using a time-domain analysis method based on the Simulink modular in Matlab software. And the pressure time sequence diagrams of the aerodynamic noises from wind turbine blades are drawn. It has provided a theoretical foundation to develop low noise wind turbine blades.
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 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.
Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry.
Jiang, Shoulin; Ma, Lin; Fan, Xinyu; Wang, Bin; He, Zuyuan
2016-05-05
We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability. The resolution achieved for speed measurement in our demonstration is 1 × 10(-3) m/s. We studied the fibre fuse propagation speed dependence on the launched power in different fibres. Our method is promising for both real time fibre fuse monitoring and future studies on its propagation and termination.
Retarded potentials and time domain boundary integral equations a road map
Sayas, Francisco-Javier
2016-01-01
This book offers a thorough and self-contained exposition of the mathematics of time-domain boundary integral equations associated to the wave equation, including applications to scattering of acoustic and elastic waves. The book offers two different approaches for the analysis of these integral equations, including a systematic treatment of their numerical discretization using Galerkin (Boundary Element) methods in the space variables and Convolution Quadrature in the time variable. The first approach follows classical work started in the late eighties, based on Laplace transforms estimates. This approach has been refined and made more accessible by tailoring the necessary mathematical tools, avoiding an excess of generality. A second approach contains a novel point of view that the author and some of his collaborators have been developing in recent years, using the semigroup theory of evolution equations to obtain improved results. The extension to electromagnetic waves is explained in one of the appendices...
Investigation of Ag2O Thermal Decomposition by Terahertz Time-Domain Spectroscopy
International Nuclear Information System (INIS)
Hua, Chen; Li, Wang
2009-01-01
Application of terahertz time-domain spectroscopy is demonstrated to study the process of Ag 2 O thermal decomposition. In the process of decomposition, the time-resolved signals are characterized by broad oscillations and decreased intensity, and THz pulse essentially contains two broad spectral components: one centered at around 0.35 THz and a band with a maximum at around 0.81 THz shift to 0.71 THz. Optical absorption spectra of different specimens are studied in the frequency range 0.3–1.4 THz and the data are analyzed by the relevant theory of the effective medium approach combined with the Drude–Lorentz model. The analysis suggests that optical properties stem from the Drude term for the metallic phase and the Lorentz term for the insulator phase in the complex system. (fundamental areas of phenomenology(including applications))
A 2D Time Domain DRBEM Computer Model for MagnetoThermoelastic Coupled Wave Propagation Problems
Directory of Open Access Journals (Sweden)
Mohamed Abdelsabour Fahmy
2014-07-01
Full Text Available A numerical computer model based on the dual reciprocity boundary element method (DRBEM is extended to study magneto-thermoelastic coupled wave propagation problems with relaxation times involving anisotropic functionally graded solids. The model formulation is tested through its application to the problem of a solid placed in a constant primary magnetic field acting in the direction of the z-axis and rotating about this axis with a constant angular velocity. In the case of two-dimensional deformation, an implicit-explicit time domain DRBEM was presented and implemented to obtain the solution for the displacement and temperature fields. A comparison of the results is presented graphically in the context of Lord and Shulman (LS and Green and Lindsay (GL theories. Numerical results that demonstrate the validity of the proposed method are also presented graphically.
Using the time domain reflectometer to check for a locate a fault
International Nuclear Information System (INIS)
Ramphal, M.; Sadok, E.
1995-01-01
The Time Domain Reflectometer (TDR) is one of the most useful tools for finding cable faults (opens, shorts, bad cable splices). The TDR is connected to the end of the line and shows the distance to the fault. It uses a low voltage signal that will not damage the line or interfere with nearby lines. The TDR sends a pulse or energy down the cable under test; when the pulse encounters the end of the cable or any cable fault, a portion of the pulse energy is reflected. The elapsed time of the reflected pulse is and indication of the distance to the fault. The shape of the reflected pulse uniquely identifies the type of cable fault. (author)
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 Is Not Space: Core Computations and Domain-Specific Networks for Mental Travels.
Gauthier, Baptiste; van Wassenhove, Virginie
2016-11-23
Humans can consciously project themselves in the future and imagine themselves at different places. Do mental time travel and mental space navigation abilities share common cognitive and neural mechanisms? To test this, we recorded fMRI while participants mentally projected themselves in time or in space (e.g., 9 years ago, in Paris) and ordered historical events from their mental perspective. Behavioral patterns were comparable for mental time and space and shaped by self-projection and by the distance of historical events to the mental position of the self, suggesting the existence of egocentric mapping in both dimensions. Nonetheless, self-projection in space engaged the medial and lateral parietal cortices, whereas self-projection in time engaged a widespread parietofrontal network. Moreover, while a large distributed network was found for spatial distances, temporal distances specifically engaged the right inferior parietal cortex and the anterior insula. Across these networks, a robust overlap was only found in a small region of the inferior parietal lobe, adding evidence for its role in domain-general egocentric mapping. Our findings suggest that mental travel in time or space capitalizes on egocentric remapping and on distance computation, which are implemented in distinct dimension-specific cortical networks converging in inferior parietal lobe. As humans, we can consciously imagine ourselves at a different time (mental time travel) or at a different place (mental space navigation). Are such abilities domain-general, or are the temporal and spatial dimensions of our conscious experience separable? Here, we tested the hypothesis that mental time travel and mental space navigation required the egocentric remapping of events, including the estimation of their distances to the self. We report that, although both remapping and distance computation are foundational for the processing of the temporal and spatial dimensions of our conscious experience, their
EthniCity of Leisure : A Domains Approach to Ethnic Integration During Free Time Activities
Kamenik, K.; Tammaru, T.; van Ham, M.
This paper takes a domains approach to understanding ethnic segregation; ethnic segregation occurs in different ways in different domains (such as the residential neighbourhood, workplaces, leisure, etc.). Where most studies focus on residential segregation, this study focusses on ethnic segregation
Gorin, Simon; Kowialiewski, Benjamin; Majerus, Steve
2016-01-01
Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.
Time domain reshuffling for OFDM based indoor visible light communication systems.
You, Xiaodi; Chen, Jian; Yu, Changyuan; Zheng, Huanhuan
2017-05-15
For orthogonal frequency division multiplexing (OFDM) based indoor visible light communication (VLC) systems, partial non-ideal transmission conditions such as insufficient guard intervals and a dispersive channel can result in severe inter-symbol crosstalk (ISC). By deriving from the inverse Fourier transform, we present a novel time domain reshuffling (TDR) concept for both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM VLC systems. By using only simple operations in the frequency domain, potential high peaks can be relocated within each OFDM symbol to alleviate ISC. To simplify the system, we also propose an effective unified design of the TDR schemes for both DCO- and ACO-OFDM. Based on Monte-Carlo simulations, we demonstrate the statistical distribution of the signal high peak values and the complementary cumulative distribution function of the peak-to-average power ratio under different cases for comparison. Simulation results indicate improved bit error rate (BER) performance by adopting TDR to counteract ISC deterioration. For example, for binary phase shift keying at a BER of 10 -3 , the signal to noise ratio gains are ~1.6 dB and ~6.6 dB for DCO- and ACO-OFDM, respectively, with ISC of 1/64. We also show a reliable transmission by adopting TDR for rectangle 8-quadrature amplitude modulation with ISC of < 1/64.
Least-squares reverse time migration in frequency domain using the adjoint-state method
International Nuclear Information System (INIS)
Ren, Haoran; Chen, Shengchang; Wang, Huazhong
2013-01-01
A new scheme is presented to implement a least-squares frequency domain reverse time migration (LS-FRTM). This scheme expresses the gradient of the misfit function with respect to the model as the product of the conjugated Green's functions and the data residuals in the frequency domain based on the adjoint state method. In the 2D case, for each frequency all the Green's functions from the shots to the reflectors and from the reflectors to the receivers which depend on the background velocity can be calculated once using the lower/upper decomposition. The pseudo-Hessian matrix which is also expressed as a function of the Green's function is used as a substitute for the approximate Hessian to amplitude compensation for the gradient. Since the linearized inversion does not update the background velocity, the Green's function needs to be calculated only once. An iteration based LS-FRTM can be implemented with high efficiency. As examples supporting our assertion, we present the results obtained by applying our method to the 2D Marmousi model. (paper)
Baawain, Mahad S.; Al-Futaisi, Ahmed M.; Ebrahimi, A.; Omidvarborna, Hamid
2018-04-01
Time Domain Electromagnetic (TDEM) survey as well as drilling investigations were conducted to identify possible contamination of a dumping site in an unsaturated zone located in Barka, Oman. The method was applied to evaluate conductivity of the contaminated plumes in hot and arid/semiarid region, where high temperatures commonly ranged between 35 and 50 °C. The drilling investigation was carried out over the survey area to verify the geophysical results. The low-resistivity zone (waste disposal activities. The combination of TDEM survey results with the lithology of piezometers showed that higher resistivity (>90 Ωm) was correlated with compacted or cemented gravels and cobbles, particularly that of medium dense to very dense gravels and cobbles. Additionally, the TDEM profiles suggested that the plume migration followed a preferential flow path. The resistivity range 40-80 Ωm considered as contaminated areas; however, the drilling results showed the close resistivity domain in the depth >70 m below water table for some profiles (BL1, BL2, BL3, BL4 and BL5). The combined results of drilling wells, piezometers, and TDEM apparent resistivity maps showed a coincidence of the migrated leachate plume and water table. Predicted zone of the probable contamination was located at the depth of around 65 m and horizontal offset ranges 0-280 m, 80-240 m, and 40-85 m in the sounding traverses of BL4, BL6 and BL7, respectively.
Electromagnetic Characterization of a Composite (RE-CB-MT by Time Domain Spectroscopy
Directory of Open Access Journals (Sweden)
Amina Bounar
2017-01-01
Full Text Available The aim of this article is to study the dielectric behavior (ε, σ in microwaves domain of composites made with Epoxy Resin (RE, Carbon Black (CB, and Magnesium Titanate (MT on a large band of frequency. This kind of composites is very solicited for applications and miniaturization of the components circuits (cavities, antennas, substrates, etc. in hyperfrequency electronics. In this study we have also highlighted the effect of the fillers nature and their concentrations on the behavior of these composites. The results obtained by time domain spectroscopy (TDS have revealed the strong dependence of complex permittivity of the composite materials on both the nature and the concentration of conductive environment. Low frequency analysis (500 MHz has been investigated to determine the conductivity of composites which is related to the percolation phenomenon. Moreover, the comparison between experimental results and theoretical models shows that the modeling Lichtenecker law is applicable to the ternary mixture in this frequency range and is in accordance with the approach postulated by Bottreau.
Time-domain Astronomy with the Advanced X-ray Imaging Satellite
Winter, Lisa M.; Vestrand, Tom; Smith, Karl; Kippen, Marc; Schirato, Richard
2018-01-01
The Advanced X-ray Imaging Satellite (AXIS) is a concept NASA Probe class mission that will enable time-domain X-ray observations after the conclusion of the successful Swift Gamma-ray burst mission. AXIS will achieve rapid response, like Swift, with an improved X-ray monitoring capability through high angular resolution (similar to the 0.5 arc sec resolution of the Chandra X-ray Observatory) and high sensitivity (ten times the Chandra count rate) observations in the 0.3-10 keV band. In the up-coming decades, AXIS’s fast slew rate will provide the only rapid X-ray capability to study explosive transient events. Increased ground-based monitoring with next-generation survey telescopes like the Large Synoptic Survey Telescope will provide a revolution in transient science through the discovery of many new known and unknown phenomena – requiring AXIS follow-ups to establish the highest energy emission from these events. This synergy between AXIS and ground-based detections will constrain the rapid rise through decline in energetic emission from numerous transients including: supernova shock breakout winds, gamma-ray burst X-ray afterglows, ionized gas resulting from the activation of a hidden massive black hole in tidal disruption events, and intense flares from magnetic reconnection processes in stellar coronae. Additionally, the combination of high sensitivity and angular resolution will allow deeper and more precise monitoring for prompt X-ray signatures associated with gravitational wave detections. We present a summary of time-domain science with AXIS, highlighting its capabilities and expected scientific gains from rapid high quality X-ray imaging of transient phenomena.
Use of the finite-difference time-domain method in electromagnetic dosimetry
International Nuclear Information System (INIS)
Sullivan, D.M.
1987-01-01
Although there are acceptable methods for calculating whole body electromagnetic absorption, no completely acceptable method for calculating the local specific absorption rate (SAR) at points within the body has been developed. Frequency domain methods, such as the method of moments (MoM) have achieved some success; however, the MoM requires computer storage on the order of (3N) 2 , and computation time on the order of (3N) 3 where N is the number of cells. The finite-difference time-domain (FDTD) method has been employed extensively in calculating the scattering from metallic objects, and recently is seeing some use in calculating the interaction of EM fields with complex, lossy dielectric bodies. Since the FDTD method has storage and time requirements proportional to N, it presents an attractive alternative to calculating SAR distribution in large bodies. This dissertation describes the FDTD method and evaluates it by comparing its results with analytic solutions in 2 and 3 dimensions. The results obtained demonstrate that the FDTD method is capable of calculating internal SAR distribution with acceptable accuracy. The construction of a data base to provide detailed, inhomogeneous man models for use with the FDTD method is described. Using this construction method, a model of 40,000 1.31 cm. cells is developed for use at 350 MHz, and another model consisting of 5000 2.62 cm. cells is developed for use at 100 MHz. To add more realism to the problem, a ground plane is added to the FDTD software. The needed changes to the software are described, along with a test which confirms its accuracy. Using the CRAY II supercomputer, SAR distributions in human models are calculated using incident frequencies of 100 MHz and 350 MHz for three different cases: (1) A homogeneous man model in free space, (2) an inhomogeneous man model in free space, and (3) an inhomogeneous man model standing on a ground plane
Time domain numerical calculations of the short electron bunch wakefields in resistive structures
International Nuclear Information System (INIS)
Tsakanian, Andranik
2010-10-01
The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of structures are performed
Time domain numerical calculations of the short electron bunch wakefields in resistive structures
Energy Technology Data Exchange (ETDEWEB)
Tsakanian, Andranik
2010-10-15
The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of
Beghein, Yves
2013-03-01
The time domain combined field integral equation (TD-CFIE), which is constructed from a weighted sum of the time domain electric and magnetic field integral equations (TD-EFIE and TD-MFIE) for analyzing transient scattering from closed perfect electrically conducting bodies, is free from spurious resonances. The standard marching-on-in-time technique for discretizing the TD-CFIE uses Galerkin and collocation schemes in space and time, respectively. Unfortunately, the standard scheme is theoretically not well understood: stability and convergence have been proven for only one class of space-time Galerkin discretizations. Moreover, existing discretization schemes are nonconforming, i.e., the TD-MFIE contribution is tested with divergence conforming functions instead of curl conforming functions. We therefore introduce a novel space-time mixed Galerkin discretization for the TD-CFIE. A family of temporal basis and testing functions with arbitrary order is introduced. It is explained how the corresponding interactions can be computed efficiently by existing collocation-in-time codes. The spatial mixed discretization is made fully conforming and consistent by leveraging both Rao-Wilton-Glisson and Buffa-Christiansen basis functions and by applying the appropriate bi-orthogonalization procedures. The combination of both techniques is essential when high accuracy over a broad frequency band is required. © 2012 IEEE.
Sirenko, Kostyantyn
2013-07-01
Exact absorbing and periodic boundary conditions allow to truncate grating problems\\' infinite physical domains without introducing any errors. This work presents exact absorbing boundary conditions for 3D diffraction gratings and describes their discretization within a high-order time-domain discontinuous Galerkin finite element method (TD-DG-FEM). The error introduced by the boundary condition discretization matches that of the TD-DG-FEM; this results in an optimal solver in terms of accuracy and computation time. Numerical results demonstrate the superiority of this solver over TD-DG-FEM with perfectly matched layers (PML)-based domain truncation. © 2013 IEEE.
Le, Thien-Phu; ARGOUL, Pierre
2015-01-01
The time-frequency domain decomposition technique has been proposed for modal identification in ambient vibration testing. In the presence of harmonic excitations, the modal identification process can provide not only structural modes but also non-structural ones relative to harmonic components. It is thus important to distinguish between them. In this study, by using the time-frequency domain decomposition technique, it is demonstrated that the distinction between non-structural harmonic com...
Wozniak, P.; Borozdin, K.; Galassi, M.; Priedhorsky, W.; Starr, D.; Vestrand, W. T.; White, R.; Wren, J.
2002-01-01
The mining of Virtual Observatories (VOs) is becoming a powerful new method for discovery in astronomy. Here we report on the development of SkyDOT (Sky Database for Objects in the Time domain), a new Virtual Observatory, which is dedicated to the study of sky variability. The site will confederate a number of massive variability surveys and enable exploration of the time domain in astronomy. We discuss the architecture of the database and the functionality of the user interface. An important...
Acceleration for 2D time-domain elastic full waveform inversion using a single GPU card
Jiang, Jinpeng; Zhu, Peimin
2018-05-01
Full waveform inversion (FWI) is a challenging procedure due to the high computational cost related to the modeling, especially for the elastic case. The graphics processing unit (GPU) has become a popular device for the high-performance computing (HPC). To reduce the long computation time, we design and implement the GPU-based 2D elastic FWI (EFWI) in time domain using a single GPU card. We parallelize the forward modeling and gradient calculations using the CUDA programming language. To overcome the limitation of relatively small global memory on GPU, the boundary saving strategy is exploited to reconstruct the forward wavefield. Moreover, the L-BFGS optimization method used in the inversion increases the convergence of the misfit function. A multiscale inversion strategy is performed in the workflow to obtain the accurate inversion results. In our tests, the GPU-based implementations using a single GPU device achieve >15 times speedup in forward modeling, and about 12 times speedup in gradient calculation, compared with the eight-core CPU implementations optimized by OpenMP. The test results from the GPU implementations are verified to have enough accuracy by comparing the results obtained from the CPU implementations.
The Stranglehold on Time-Domain Astronomy: Preserve the Plates or Lose the Science
Griffin, Elizabeth
2012-09-01
Many celestial objects of all types exhibit changes within the time-frame of humanity's collective memory. Investigating, analysing and understanding those changes---be they periodic, irregular, slow, recurring or explosive---is at the very heart of most astrophysics. But essential progress in our science is limited to the time-span of the observational data which can be readily accessed and incorporated into modern analyses, and that time-span is currently no longer than that of our all-digital data archives---a mere 15 years at most. A great many important changes are longer than that, but we have no way of learning about them even though almost all the observations ever recorded by most observatories still exist. Those inherited data may be absolutely critical to solving a problem, and many enable science that cannot otherwise be even attempted, but they are not in electronic format so today's astronomers cannot get access to the information which they need. Our wealth of inherited observations, mostly in observatory plate stores, are in increasing danger of loss from a multitude of causes, and moves are afoot to digitize them appropriately in order to provide that much-needed broadening of astrophysical understanding. The scientific case is irrefutable, the technology is understood, and expertise is still available; it is only money that is in short supply. Once the preservation and correct digitization of those older data can be funded, astronomy will quickly be benefiting from a greatly extended baseline for time-domain studies.
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......, number of samples in the range gate, and number of A-lines employed in the estimation. Quantitative results calculated by a simple simulation program are given for the variation in probability from these parameters. An index reflecting the reliability of the estimate at hand can be calculated from...... the actual cross-correlation estimate by a simple formula and used in rejecting poor estimates or in displaying the reliability of the velocity estimated...
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.
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
DEFF Research Database (Denmark)
Viezzoli, Andrea; Kaminskiy, Vladislav; Fiandaca, Gianluca
2017-01-01
We have developed a synthetic multiparametric modeling and inversion exercise undertaken to study the robustness of inverting airborne time-domain electromagnetic (TDEM) data to extract Cole-Cole parameters. The following issues were addressed: nonuniqueness, ill posedness, dependency on manual...... constrained multiparametric inversion was evaluated, including recovery of chargeability distributions from shallow and deep targets based on analysis of induced polarization (IP) effects, simulated in airborne TDEM data. Different scenarios were studied, including chargeable targets associated...... by a shallower chargeable target, became possible only when full Cole-Cole modeling was used in the inversion. Lateral constraints improved the recoverability of model parameters. Finally, modeling IP effects increased the accuracy of recovered electrical resistivity models....
Optimization of neural networks for time-domain simulation of mooring lines
DEFF Research Database (Denmark)
Christiansen, Niels Hørbye; Voie, Per Erlend Torbergsen; Winther, Ole
2016-01-01
When using artificial neural networks in methods for dynamic analysis of slender structures, the computational effort associated with time-domain response simulation may be reduced drastically compared to classic solution strategies. This article demonstrates that the network structure...... of an artificial neural network, which has been trained to simulate forces in a mooring line of a floating offshore platform, can be optimized and reduced by different optimization procedures. The procedures both detect and prune the least salient network weights successively, and besides trimming the network......, they also can be used to rank the importance of the various network inputs. The dynamic response of slender marine structures often depends on several external load components, and by applying the optimization procedures to a trained artificial neural network, it is possible to classify the external force...
Mahendraprabu, A.; Kumbharkhane, A. C.; Joshi, Y. S.; Shaikh, S. S.; Kannan, P. P.; Karthick, N. K.; Arivazhagan, G.
2017-05-01
Spectroscopic (FTIR and 13C NMR) and time domain reflectometry (in the frequency range from 10 MHz to 25 GHz) studies have been carried out on the binary solutions of acetonitrile (AN) with ethylene glycol (EG). The presence of EG-EG multimers of various orders in neat EG has been confirmed by spectroscopic studies. AN-EG association through the formation of ∁ ≡ N ⋯ H - O , ∁ ≡ N ⋯ H - C(EG) and (EG) C - O ⋯ H - C(AN) hydrogen bonds have been identified using spectral studies. The principal relaxation process of the heteromolecular entities that involve higher order alcohol association in ethylene glycol rich solutions is found to be relatively slower than that in acetonitrile rich solutions in which lower order alcohol association involves in heterointeraction. The angular correlation among the dipoles appears to be described more precisely when the experimental ε∞ values rather than ε∞ =n2 are used for the calculation of geff .
Slater, Gregory L.; Schiff, David; De Pontieu, Bart; Tarbell, Theodore D.; Freeland, Samuel L.
2017-08-01
We present Cruiser, a new web tool for the precision interactive blending of image series across time and wavelength domains. Scrolling in two dimensions enables discovery and investigation of similarities and differences in structure and evolution across multiple wavelengths. Cruiser works in the latest versions of standards compliant browsers on both desktop and IOS platforms. Co-aligned data cubes have been generated for AIA, IRIS, and Hinode SOT FG, and image data from additional instruments, both space-based and ground-based, can be data sources. The tool has several movie playing and image adjustment controls which will be described in the poster and demonstrated on a MacOS notebook and iPad.
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...
Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing.
Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A Ping; Lu, Chao
2016-12-16
We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes.
International Nuclear Information System (INIS)
Liu, J.; Lan, T.; Qin, H.
2017-01-01
Traditional data cleaning identifies dirty data by classifying original data sequences, which is a class-imbalanced problem since the proportion of incorrect data is much less than the proportion of correct ones for most diagnostic systems in Magnetic Confinement Fusion (MCF) devices. When using machine learning algorithms to classify diagnostic data based on class-imbalanced training set, most classifiers are biased towards the major class and show very poor classification rates on the minor class. By transforming the direct classification problem about original data sequences into a classification problem about the physical similarity between data sequences, the class-balanced effect of Time-Domain Global Similarity (TDGS) method on training set structure is investigated in this paper. Meanwhile, the impact of improved training set structure on data cleaning performance of TDGS method is demonstrated with an application example in EAST POlarimetry-INTerferometry (POINT) system.
DEFF Research Database (Denmark)
Bauer-Gottwein, Peter; Gondwe, Bibi Ruth Neuman; Christiansen, Lars
2010-01-01
Delta is presented. Evaporative salt enrichment causes a strong salinity anomaly under the island. We show that the TDEM field data cannot be interpreted in terms of standard one-dimensional layered-earth TDEM models, because of the strongly three-dimensional nature of the salinity anomaly. Three......The time-domain electromagnetic method (TDEM) is widely used in groundwater exploration and geological mapping applications. TDEM measures subsurface electrical conductivity, which is strongly correlated with groundwater salinity. TDEM offers a cheap and non-invasive option for mapping saltwater...... intrusion and groundwater salinization. Traditionally, TDEM data is interpreted using one-dimensional layered-earth models of the subsurface. However, most saltwater intrusion and groundwater salinization phenomena are characterized by three-dimensional anomalies. To fully exploit the information content...
International Nuclear Information System (INIS)
Hasegawa, M.; Nakai, S.; Watanabe, T.
1985-01-01
A practical method for elasto-plastic seismic response analysis is described under considerations of nonlinear material law of a structure and dynamic soil-structure interaction. The method is essentially based on the substructure approach of time domain analysis. Verification of the present method is carried out for typical BWR-MARK II type reactor building which is embedded in a soil, and the results are compared with those of the frequency response analysis which gives good accuracy for linear system. As a result, the present method exhibits sufficient accuracy. Furthermore, elasto-plastic analyses considering the soil-structure interaction are made as an application of the present method, and nonlinear behaviors of the structure and embedment effects are discussed. (orig.)
Time-domain vibrational study on defects in ion-irradiated crystal
International Nuclear Information System (INIS)
Kitajima, M.
2003-01-01
We have studied the effects of point defects on coherent phonons in ion-implanted bismuth and graphite. Ultrafast dynamics of coherent phonons and photo-generated carriers in the femtosecond time-domain have been investigated by means of pump-probe reflectivity measurements. Point defects are introduced by irradiating graphite with 5 keV He + ions. For Bi the dephasing rate of the A 1g phonon increases linearly with increasing ion dose, which is explained by the additional dephasing process of the coherent phonon originated from scattering of phonons by the defects. For graphite, introduction of the defects enhances the carrier relaxation by opening a decay channel via vacancy-states, which competes efficiently with carrier-phonon scattering. The coherent acoustic phonon relaxation is also accelerated due to an additional scattering by defects. The linear fluence-dependence of the decay rate is understood as scattering of propagating acoustic phonon by single vacancies. (author)
Time-Domain Reflectometry for Tamper Indication in Unattended Monitoring Systems for Safeguards
Energy Technology Data Exchange (ETDEWEB)
Tedeschi, Jonathan R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Leon E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Moore, David E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sheen, David M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Conrad, Ryan C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2014-12-01
The International Atomic Energy Agency (IAEA) continues to expand its use of unattended, remotely monitored measurement systems. An increasing number of systems and an expanding family of instruments create challenges in terms of deployment efficiency and the implementation of data authentication measures. Pacific Northwest National Laboratory (PNNL) leads a collaboration that is exploring various tamper-indicating (TI) measures that could help to address some of the long-standing detector and data-transmission authentication challenges with IAEA’s unattended systems. PNNL is investigating the viability of active time-domain reflectometry (TDR) along two parallel but interconnected paths: (1) swept-frequency TDR as the highly flexible, laboratory gold standard to which field-deployable options can be compared, and (2) a low-cost commercially available spread-spectrum TDR technology as one option for field implementation. This report describes PNNL’s progress and preliminary findings from the first year of the study, and describes the path forward.
Directory of Open Access Journals (Sweden)
Ana Paula Delowski Ciniello
Full Text Available Abstract The present paper aims at presenting a methodology for characterizing viscoelastic materials in time domain, taking into account the fractional Zener constitutive model and the influence of temperature through Williams, Landel, and Ferry’s model. To that effect, a set of points obtained experimentally through uniaxial tensile tests with different constant strain rates is considered. The approach is based on the minimization of the quadratic relative distance between the experimental stress-strain curves and the corresponding ones given by the theoretical model. In order to avoid the local minima in the process of optimization, a hybrid technique based on genetic algorithms and non-linear programming techniques is used. The methodology is applied in the characterization of two different commercial viscoelastic materials. The results indicate that the proposed methodology is effective in identifying thermorheologically simple viscoelastic materials.
Study of a Miniaturized Quasi-Self-Complementary UWB Antenna in Frequency and Time Domain
Directory of Open Access Journals (Sweden)
L. Guo
2009-12-01
Full Text Available A compact antenna for UWB communication systems has been realized by employing a quasi-selfcomplementary structure together with a triangular notch on microstrip feed line in this paper. The optimal design of this type of antenna can offer an ultra wide return loss bandwidth with reasonable radiation properties. It features a quite small physical dimension of 16 mm x 25 mm, corresponding to an electrically size of 0.24 λ. A good agreement is achieved between the simulated and the measured antenna characteristics. The major parameters that influence the performance of the antenna are investigated numerically to gain an insight into the antenna operation. Time domain performance of the antenna is also examined in order to assess its suitability for impulse radio applications.
Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)
Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei; Kiriyama, Kyoko; Matsuda, Kazutaka; Jepsen, Peter Uhd
2017-04-01
Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly composed of organic materials, such as urushi, wood, carbon black, and fabrics which are very X-ray transparent, standard X-ray radiography has some problems in achieving clear X-ray radiographic images. Therefore, we wanted to contribute to the understanding of the lacquer manufacturing technique by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares substructures, aiding in the comprehension of the manufacturing technology yielding to these precious artefacts.
An Analytical Time Domain Solution for the Forced Vibration Analysis of Thick-Walled Cylinders
Directory of Open Access Journals (Sweden)
Bashir Movahedian
Full Text Available Abstract In this paper, we propose a time domain analytical solution for the forced vibration analysis of thick-walled hollow cylinders in presence of polar orthotropy. In this regard, solution of the governing equation is decomposed into two parts. The role of the first one is to satisfy boundary conditions utilizing the method of separation of variables besides of Fourier series expansion of the non-homogenous boundary conditions. The second part has been also expressed as the series of orthogonal characteristic functions with the aim of satisfaction of initial conditions. The proposed analytical solution has been implemented to evaluate the dynamic response of the cylinder in solution of some sample problems which are chosen from previous studies.
[Application of terahertz time domain spectroscopy to explosive and illegal drug].
Liu, Gui-Feng; Zhao, Hong-Wei; Ge, Min; Wang, Wen-Feng
2008-05-01
Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many explosives and illicit drugs show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons, explosives and illegal drugs, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. Moreover, THz can penetrate many barrier materials, such as clothing and common packaging materials. THz technique has a great potential and advantage in antiterrorism and security inspection of explosives and illegal drugs due to the ability of high-sensitivity, nondestructive and stand-off inspection of many substances. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to explosives and illegal drugs. Studies on RDX are discussed in details and many factors affecting experiments are also introduced.
Er, Li; Xiangying, Zeng
2014-01-01
To simulate the variation of biochemical oxygen demand (BOD) in the tidal Foshan River, inverse calculations based on time domain are applied to the longitudinal dispersion coefficient (E(x)) and BOD decay rate (K(x)) in the BOD model for the tidal Foshan River. The derivatives of the inverse calculation have been respectively established on the basis of different flow directions in the tidal river. The results of this paper indicate that the calculated values of BOD based on the inverse calculation developed for the tidal Foshan River match the measured ones well. According to the calibration and verification of the inversely calculated BOD models, K(x) is more sensitive to the models than E(x) and different data sets of E(x) and K(x) hardly affect the precision of the models.
Application of time domain electromagnetic method to study Lembang fault, West Java
Widodo, Rasyid, Faeruz Maulana
2017-07-01
Lembang Fault is an active fault structure lied beneath a populous area of West Java. It is located at about 9 km from the city centre of Bandung. We have conducted an electromagnetic survey in the area suggested as the zone of Lembang Fault, the Karyawangi Village, West Bandung. Time domain electromagnetic (TDEM) measurements were carried out using two profiles, with a total number of 34 soundings. The TDEM data gives detail information of the shallow conductivity structure down to a depth of 100 m. The 1-D models consist of three layers in the research area. The first layer at the depth between 0 to 3 meters is dominated by low resistivity (resistivity (> 100 Ωm). The third layer with a resistivity of 10 - 100 Ωm corresponds to sandstone. The model indicates a local fault structure in the study area.
Ultrabroadband THz Time-Domain Spectroscopy of a Free-Flowing Water Film
DEFF Research Database (Denmark)
Wang, Tianwu; Pedersen, Pernille Klarskov; Jepsen, Peter Uhd
2014-01-01
of liquid water using two different THz-TDS setups. The extracted absorption coefficient and refractive index of water are in agreement with previous results reported in the literature. With this we show that the thin free-flowing liquid film is a versatile tool for windowless, ultrabroadband THz......We demonstrate quantitative ultrabroadband THz time-domain spectroscopy (THz-TDS) of water by application of a 17-$\\mu$m thick gravity-driven wire-guided flow jet of water. The thickness and stability of the water film is accurately measured by an optical intensity crosscorrelator, and the standard...... deviation of the film thickness is less than 500 nm. The cross section of the water film is found to have a biconcave cylindrical lens shape. By transmitting through such a thin film, we perform the first ultrabroadband (0.2–30 THz) THz-TDS across the strongest absorbing part of the infrared spectrum...
Far-infrared characteristics of ZnS nanoparticles measured by terahertz time-domain spectroscopy.
Han, Jiaguang; Zhang, Weili; Chen, Wei; Thamizhmani, L; Azad, Abul K; Zhu, Zhiyuan
2006-02-09
The optical and dielectric properties of ZnS nanoparticles are studied by use of terahertz time-domain spectroscopy (THz-TDS) over the frequency range from 0.3 to 3.0 THz. The effective medium approach combined with the pseudo-harmonic model of the dielectric response, where nanoparticles are embedded in the host medium, provides a good fit on the experimental results. The extrapolation of the measured data indicates that the absorption is dominated by the transverse optical mode localized at 11.6+/-0.2 THz. Meanwhile, the low-frequency phonon resonance of ZnS nanoparticles is compared with the single-crystal ZnS. The THz-TDS clearly reveals the remarkable distinction in the low-frequency phonon resonances between ZnS nanoparticles and single-crystal ZnS. The results demonstrate that the acoustic phonons become confined in small-size nanoparticles.
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.
Gonçalves, Rui; Farzamian, Mohammad; Monteiro Santos, Fernando A.; Represas, Patrícia; Mota Gomes, A.; Lobo de Pina, A. F.; Almeida, Eugénio P.
2017-11-01
Santiago Island, the biggest and most populated island of the Cape Verde Republic, is characterised by limited surface waters and strong dependence on groundwater sources as the primary source of natural water supply for extensive agricultural activity and human use. However, as a consequence of the scarce precipitation and high evaporation as well as the intense overexploitation of the groundwater resources, the freshwater management is also in a delicate balance with saltwater at coastal areas. The time-domain electromagnetic (TDEM) method is used to locate the extent of saltwater intrusion in four important agricultural regions in Santiago Island; São Domingos, Santa Cruz, São Miguel, and Tarrafal. The application of this method in Santiago Island proves it to be a successful tool in imaging the fresh/saltwater interface location. Depths to the saline zones and extensions of saline water are mapped along eight TDEM profiles.
Rotation commensurate echo of asymmetric molecules—Molecular fingerprints in the time domain
Energy Technology Data Exchange (ETDEWEB)
Chesnokov, E. N., E-mail: chesnok@kinetics.nsc.ru [Institute of Chemical Kinetics and Combustion, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Kubarev, V. V. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Koshlyakov, P. V. [Institute of Chemical Kinetics and Combustion, Novosibirsk 630090 (Russian Federation)
2014-12-29
Using the pulses of terahertz free electron laser and ultra-fast Schottky diode detectors, we observed the coherent transients within a free induction decay of gaseous nitrogen dioxide NO{sub 2}. The laser excited different sub-bands of rotation spectra of NO{sub 2} containing about 50–70 lines. The free induction signal continued more than 30 ns and consisted of many echo-like bursts duration about 0.2 ns. Unlike the similar effect observed previously for linear and symmetric top molecules, the sequence of echo bursts is not periodic. The values for delay of individual echo are stable, and the set of these delays can be considered as a “molecular fingerprint” in the time domain.
Evaluation of Waveform Structure Features on Time Domain Target Recognition under Cross Polarization
Selver, M. A.; Seçmen, M.; Zoral, E. Y.
2016-08-01
Classification of aircraft targets from scattered electromagnetic waves is a challenging application, which suffers from aspect angle dependency. In order to eliminate the adverse effects of aspect angle, various strategies were developed including the techniques that rely on extraction of several features and design of suitable classification systems to process them. Recently, a hierarchical method, which uses features that take advantage of waveform structure of the scattered signals, is introduced and shown to have effective results. However, this approach has been applied to the special cases that consider only a single planar component of electric field that cause no-cross polarization at the observation point. In this study, two small scale aircraft models, Boeing-747 and DC-10, are selected as the targets and various polarizations are used to analyse the cross-polarization effects on system performance of the aforementioned method. The results reveal the advantages and the shortcomings of using waveform structures in time-domain target identification.
Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy
International Nuclear Information System (INIS)
Fischer, B M; Walther, M; Jepsen, P Uhd
2002-01-01
The far-infrared dielectric function of a wide range of organic molecules is dominated by vibrations involving a substantial fraction of the atoms forming the molecule and motion associated with intermolecular hydrogen bond vibrations. Due to their collective nature such modes are highly sensitive to the intra- and intermolecular structure and thus provide a unique fingerprint of the conformational state of the molecule and effects of its environment. We demonstrate the use of terahertz time-domain spectroscopy (THz-TDS) for recording the far-infrared (0.5-4.0 THz) dielectric function of the four nucleobases and corresponding nucleosides forming the building blocks of deoxyribose nucleic acid (DNA). We observe numerous distinct spectral features with large differences between the molecules in both frequency-dependent absorption coefficient and index of refraction. Assisted by results from density-functional calculations we interpret the origin of the observed resonances as vibrations of hydrogen bonds between the molecules
Granet, Gérard
2013-01-01
This paper focuses on scatterometry problems arising in lithography production of periodic gratings. Namely, the paper introduces a theoretical and numerical-modeling-oriented approach to scatterometry problems and discusses its capabilities. The approach allows for reliable detection of deviations in gratings\\' critical dimensions (CDs) during the manufacturing process. The core of the approach is the one-to-one correspondence between the electromagnetic (EM) characteristics and the geometric/material properties of gratings. The approach is based on highly accurate solutions of initial boundary-value problems describing EM waves\\' interaction on periodic gratings. The advantage of the approach is the ability to perform simultaneously and interactively both in frequency and time domains under conditions of possible resonant scattering of EM waves by infinite or finite gratings. This allows a detection of CDs for a wide range of gratings, and, thus is beneficial for the applied scatterometry. (C) 2013 Optical Society of America
A new IEEE Std 1459-2000 - Compatible time-domain formulation for apparent power
Energy Technology Data Exchange (ETDEWEB)
de Almeida, Jose Eugenio Lopes; da Silveira, Paulo Marcio; de Abreu, Jose Policarpo Goncalves; Arango, Hector [Institute of Electrical Systems and Energy, Itajuba Federal University, Av. BPS, 1303, CEP 37 500-903 Itajuba, M.G. (Brazil)
2009-04-15
This paper presents the development of new time-domain equations related to the definition of apparent power. These equations are compatible with the IEEE Std 1459-2000 Standard. When the application of these formulations involves an adequate quantity of samples, thus obeying the Nyquist Criterion, they can be utilized without restrictions regarding distortion, imbalance and asymmetry. Thus, they may be used in numeric meters for power measurements. In addition, unlike the above-mentioned standard, they do not oversimplify with respect to the phase and neutral resistance ratio or the percentage of delta-connected and wye-connected loads. This paper uses these formulations to present several illustrative examples regarding the apparent power definition. Simulated cases have confirmed that both approaches, American and European, lead to similar results, which differ only if the voltage homopolar component is present. (author)
Dispersive finite-difference time-domain (FDTD) analysis of the elliptic cylindrical cloak
Energy Technology Data Exchange (ETDEWEB)
Lee, Y. Y.; Ahn, D. [University of Seoul, Seoul (Korea, Republic of)
2012-05-15
A dispersive full-wave finite-difference time-domain (FDTD) model is used to calculate the performance of elliptic cylindrical cloaking devices. The permittivity and the permeability tensors for the cloaking structure are derived by using an effective medium approach in general relativity. The elliptic cylindrical invisibility devices are found to show imperfect cloaking, and the cloaking performance is found to depend on the polarization of the incident waves, the direction of the propagation of those waves, the semi-focal distances and the loss tangents of the meta-material. When the semifocal distance of the elliptic cylinder decreases, the performance of the cloaking becomes very good, with neither noticeable scatterings nor field penetrations. For a larger semi-focal distance, only the TM wave with a specific propagation direction shows good cloaking performance. Realistic cloaking materials with loss still show a cloak that is working, but attenuated back-scattering waves exist.
International Nuclear Information System (INIS)
Evett, S.R.
2000-01-01
Soil-water measurements encounter particular problems related to the physics of the method used. For time domain reflectometry (TDR), these relate to wave form shape changes caused by soil, soil water, and TDR probe properties. Methods of wave form interpretation that overcome these problems are discussed and specific computer algorithms are presented. Neutron scattering is well understood, but calibration methods remain critical to accuracy and precision, and are discussed with recommendations for field calibration and use. Capacitance probes tend to exhibit very small radii of influence, thus are sensitive to small-scale changes in soil properties, and are difficult or impossible to field calibrate. Field comparisons of neutron and capacitance probes are presented. (author)
The analysis of reactively loaded microstrip antennas by finite difference time domain modelling
Hilton, G. S.; Beach, M. A.; Railton, C. J.
1990-01-01
In recent years, much interest has been shown in the use of printed circuit antennas in mobile satellite and communications terminals at microwave frequencies. Although such antennas have many advantages in weight and profile size over more conventional reflector/horn configurations, they do, however, suffer from an inherently narrow bandwidth. A way of optimizing the bandwidth of such antennas by an electronic tuning technique using a loaded probe mounted within the antenna structure is examined, and the resulting far-field radiation patterns are shown. Simulation results from a 2D finite difference time domain (FDTD) model for a rectangular microstrip antenna loaded with shorting pins are given and compared to results obtained with an actual antenna. It is hoped that this work will result in a design package for the analysis of microstrip patch antenna elements.
Quantify Glucose Level in Freshly Diabetic's Blood by Terahertz Time-Domain Spectroscopy
Chen, Hua; Chen, Xiaofeng; Ma, Shihua; Wu, Xiumei; Yang, Wenxing; Zhang, Weifeng; Li, Xiao
2018-04-01
We demonstrate the capability of terahertz (THz) time-domain spectroscopy (TDS) to quantify glucose level in ex vivo freshly diabetic's blood. By investigating the THz spectra of different human blood, we find out THz absorption coefficients reflect a high sensitivity to the glucose level in blood. With a quantitative analysis of 70 patients, we demonstrate that the THz absorption coefficients and the blood glucose levels perform a linear relationship. A comparative experiment between THz measurement and glucometers is also conducted with another 20 blood samples, and the results confirm that the relative error is as less as 15%. Our ex vivo human blood study indicates that THz technique has great potential application to diagnose blood glucose level in clinical practice.
Use of Time- and Frequency-Domain Approaches for Damage Detection in Civil Engineering Structures
Directory of Open Access Journals (Sweden)
V. H. Nguyen
2014-01-01
Full Text Available The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life civil engineering structures and to assess their capability for damage detection. The methodology is based on Principal Component Analysis of the Hankel matrix built from output-only measurements and of Frequency Response Functions. Damage detection is performed using the concept of subspace angles between a current (possibly damaged state and a reference (undamaged state. The first structure is the Champangshiehl Bridge located in Luxembourg. Several damage levels were intentionally created by cutting a growing number of prestressed tendons and vibration data were acquired by the University of Luxembourg for each damaged state. The second example consists in reinforced and prestressed concrete panels. Successive damages were introduced in the panels by loading heavy weights and by cutting steel wires. The illustrations show different consequences in damage identification by the considered techniques.
A VLSI Implementation of Rank-Order Searching Circuit Employing a Time-Domain Technique
Directory of Open Access Journals (Sweden)
Trong-Tu Bui
2013-01-01
Full Text Available We present a compact and low-power rank-order searching (ROS circuit that can be used for building associative memories and rank-order filters (ROFs by employing time-domain computation and floating-gate MOS techniques. The architecture inherits the accuracy and programmability of digital implementations as well as the compactness and low-power consumption of analog ones. We aim to implement identification function as the first priority objective. Filtering function would be implemented once the location identification function has been carried out. The prototype circuit was designed and fabricated in a 0.18 μm CMOS technology. It consumes only 132.3 μW for an eight-input demonstration case.
Research of biological liquid albumin based on terahertz time domain spectroscopy
Yang, Shuai; Liu, Shang-jian; Zuo, Jian; Zhang, Cun-lin
2016-11-01
There is no corresponding fingerprint characteristic spectrum detecting complex ensemble biological samples in liquid, in the paper, such urine of kidney disease patients as samples of the research, using terahertz time-domain spectroscopy emphatically explores response characteristics of the urine albumin in the terahertz spectrum characteristics, and combined with stoichiometric method, we find a certain kind of relationship between terahertz spectrum data and the content of urine albumin, which offsets the defects of other spectroscopy in measuring liquid protein, and in accordance with hospital clinical data. This study established a semi-qualitative method of using terahertz spectroscopy in detecting non-purification of biological liquid sample, which provides a simple, nondestructive, cheap and fast reference method in identifying the early nephropathy for medical test.
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.
Single trial time-frequency domain analysis of error processing in post-traumatic stress disorder.
Clemans, Zachary A; El-Baz, Ayman S; Hollifield, Michael; Sokhadze, Estate M
2012-09-13
Error processing studies in psychology and psychiatry are relatively common. Event-related potentials (ERPs) are often used as measures of error processing, two such response-locked ERPs being the error-related negativity (ERN) and the error-related positivity (Pe). The ERN and Pe occur following committed error in reaction time tasks as low frequency (4-8 Hz) electroencephalographic (EEG) oscillations registered at the midline fronto-central sites. We created an alternative method for analyzing error processing using time-frequency analysis in the form of a wavelet transform. A study was conducted in which subjects with PTSD and healthy control completed a forced-choice task. Single trial EEG data from errors in the task were processed using a continuous wavelet transform. Coefficients from the transform that corresponded to the theta range were averaged to isolate a theta waveform in the time-frequency domain. Measures called the time-frequency ERN and Pe were obtained from these waveforms for five different channels and then averaged to obtain a single time-frequency ERN and Pe for each error trial. A comparison of the amplitude and latency for the time-frequency ERN and Pe between the PTSD and control group was performed. A significant group effect was found on the amplitude of both measures. These results indicate that the developed single trial time-frequency error analysis method is suitable for examining error processing in PTSD and possibly other psychiatric disorders. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
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.
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.
Improving time-frequency domain sleep EEG classification via singular spectrum analysis.
Mahvash Mohammadi, Sara; Kouchaki, Samaneh; Ghavami, Mohammad; Sanei, Saeid
2016-11-01
Manual sleep scoring is deemed to be tedious and time consuming. Even among automatic methods such as time-frequency (T-F) representations, there is still room for more improvement. To optimise the efficiency of T-F domain analysis of sleep electroencephalography (EEG) a novel approach for automatically identifying the brain waves, sleep spindles, and K-complexes from the sleep EEG signals is proposed. The proposed method is based on singular spectrum analysis (SSA). The single-channel EEG signal (C3-A2) is initially decomposed and then the desired components are automatically separated. In addition, the noise is removed to enhance the discrimination ability of features. The obtained T-F features after preprocessing stage are classified using a multi-class support vector machines (SVMs) and used for the identification of four sleep stages over three sleep types. Furthermore, to emphasise on the usefulness of the proposed method the automatically-determined spindles are parameterised to discriminate three sleep types. The four sleep stages are classified through SVM twice: with and without preprocessing stage. The mean accuracy, sensitivity, and specificity for before the preprocessing stage are: 71.5±0.11%, 56.1±0.09% and 86.8±0.04% respectively. However, these values increase significantly to 83.6±0.07%, 70.6±0.14% and 90.8±0.03% after applying SSA. The new T-F representation has been compared with the existing benchmarks. Our results prove that, the proposed method well outperforms the previous methods in terms of identification and representation of sleep stages. Experimental results confirm the performance improvement in terms of classification rate and also representative T-F domain. Copyright © 2016 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Pettersen, Bjoernar Hauknes
1997-12-31
Many problems in offshore oil production and multiphase transport are related to surface and colloid chemistry. This thesis applies dielectric spectroscopy as an experimental technique to study the behaviour of particle suspensions in polar media. The thesis opens with an introduction to suspensions and time domain dielectric spectroscopy. It then investigates the dielectric properties of silica and alumina dispersed in polar solvents. It is found that theoretical models can be used to calculate the volume fraction disperse phase in the suspension and that the particle sedimentation depends on the wetting of the particles, charge on the particle surface and viscosity of the solvent, and that this dependency can be measured by time domain dielectric spectroscopy. When the surface properties of silica and alumina particles were modified by coating them with a non-ionic polymer and a non-ionic surfactant, then different degrees of packing in the sedimented phase at the bottom of the sedimentation vessel occurred. Chemometrical methods on the synthesis of monodisperse silica particles were used to investigate what factors influence the particle size. It turned out that it is insufficient to consider only main variables when discussing the results of the synthesis. By introducing interaction terms, the author could explain the variation in the size of particles synthesized. The difference in the sedimentation rate of monodisperse silica particles upon variation of volume fraction particles, pH, salinity, amount of silanol groups at the particle surface and temperature was studied. The cross interactions play an important role and a model explaining the variation in sedimentation is introduced. Finally, magnetic particles dispersed in water and in an external magnetic field were used to study the impact on the sedimentation due to the induced flocculation. 209 refs., 90 figs., 9 tabs.
Integral equation approach to time-dependent kinematic dynamos in finite domains
International Nuclear Information System (INIS)
Xu Mingtian; Stefani, Frank; Gerbeth, Gunter
2004-01-01
The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of the Biot-Savart law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos, with stationary dynamo sources, in finite domains. The time dependence is restricted to the magnetic field, whereas the velocity or corresponding mean-field sources of dynamo action are supposed to be stationary. For the spherically symmetric α 2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and toroidal field components. The integral equation formulation for spherical dynamos with general stationary velocity fields is also derived. Two numerical examples - the α 2 dynamo model with radially varying α and the Bullard-Gellman model - illustrate the equivalence of the approach with the usual differential equation method. The main advantage of the method is exemplified by the treatment of an α 2 dynamo in rectangular domains
The Time-domain Spectroscopic Survey: Target Selection for Repeat Spectroscopy
MacLeod, Chelsea L.; Green, Paul J.; Anderson, Scott F.; Eracleous, Michael; Ruan, John J.; Runnoe, Jessie; Nielsen Brandt, William; Badenes, Carles; Greene, Jenny; Morganson, Eric; Schmidt, Sarah J.; Schwope, Axel; Shen, Yue; Amaro, Rachael; Lebleu, Amy; Filiz Ak, Nurten; Grier, Catherine J.; Hoover, Daniel; McGraw, Sean M.; Dawson, Kyle; Hall, Patrick B.; Hawley, Suzanne L.; Mariappan, Vivek; Myers, Adam D.; Pâris, Isabelle; Schneider, Donald P.; Stassun, Keivan G.; Bershady, Matthew A.; Blanton, Michael R.; Seo, Hee-Jong; Tinker, Jeremy; Fernández-Trincado, J. G.; Chambers, Kenneth; Kaiser, Nick; Kudritzki, R.-P.; Magnier, Eugene; Metcalfe, Nigel; Waters, Chris Z.
2018-01-01
As astronomers increasingly exploit the information available in the time domain, spectroscopic variability in particular opens broad new channels of investigation. Here we describe the selection algorithms for all targets intended for repeat spectroscopy in the Time Domain Spectroscopic Survey (TDSS), part of the extended Baryon Oscillation Spectroscopic Survey within the Sloan Digital Sky Survey (SDSS)-IV. Also discussed are the scientific rationale and technical constraints leading to these target selections. The TDSS includes a large “repeat quasar spectroscopy” (RQS) program delivering ∼13,000 repeat spectra of confirmed SDSS quasars, and several smaller “few-epoch spectroscopy” (FES) programs targeting specific classes of quasars as well as stars. The RQS program aims to provide a large and diverse quasar data set for studying variations in quasar spectra on timescales of years, a comparison sample for the FES quasar programs, and an opportunity for discovering rare, serendipitous events. The FES programs cover a wide variety of phenomena in both quasars and stars. Quasar FES programs target broad absorption line quasars, high signal-to-noise ratio normal broad line quasars, quasars with double-peaked or very asymmetric broad emission line profiles, binary supermassive black hole candidates, and the most photometrically variable quasars. Strongly variable stars are also targeted for repeat spectroscopy, encompassing many types of eclipsing binary systems, and classical pulsators like RR Lyrae. Other stellar FES programs allow spectroscopic variability studies of active ultracool dwarf stars, dwarf carbon stars, and white dwarf/M dwarf spectroscopic binaries. We present example TDSS spectra and describe anticipated sample sizes and results.
Study of stability of time-domain features for electromyographic pattern recognition
Directory of Open Access Journals (Sweden)
Huang He
2010-05-01
Full Text Available Abstract Background Significant progress has been made towards the clinical application of human-machine interfaces (HMIs based on electromyographic (EMG pattern recognition for various rehabilitation purposes. Making this technology practical and available to patients with motor deficits requires overcoming real-world challenges, such as physical and physiological changes, that result in variations in EMG signals and systems that are unreliable for long-term use. In this study, we aimed to address these challenges by (1 investigating the stability of time-domain EMG features during changes in the EMG signals and (2 identifying the feature sets that would provide the most robust EMG pattern recognition. Methods Variations in EMG signals were introduced during physical experiments. We identified three disturbances that commonly affect EMG signals: EMG electrode location shift, variation in muscle contraction effort, and muscle fatigue. The impact of these disturbances on individual features and combined feature sets was quantified by changes in classification performance. The robustness of feature sets was evaluated by a stability index developed in this study. Results Muscle fatigue had the smallest effect on the studied EMG features, while electrode location shift and varying effort level significantly reduced the classification accuracy for most of the features. Under these disturbances, the most stable EMG feature set with combination of four features produced at least 16.0% higher classification accuracy than the least stable set. EMG autoregression coefficients and cepstrum coefficients showed the most robust classification performance of all studied time-domain features. Conclusions Selecting appropriate EMG feature combinations can overcome the impact of the studied disturbances on EMG pattern classification to a certain extent; however, this simple solution is still inadequate. Stabilizing electrode contact locations and developing
Becker, A.; Hansen, V.
2003-05-01
In this paper a hybrid method combining the FDTD/FIT with a Time Domain Boundary-Integral Marching-on-in-Time Algorithm (TD-BIM) is presented. Inhomogeneous regions are modelled with the FIT-method, an alternative formulation of the FDTD. Homogeneous regions (which is in the presented numerical example the open space) are modelled using a TD-BIM with equivalent electric and magnetic currents flowing on the boundary between the inhomogeneous and the homogeneous regions. The regions are coupled by the tangential magnetic fields just outside the inhomogeneous regions. These fields are calculated by making use of a Mixed Potential Integral Formulation for the magnetic field. The latter consists of equivalent electric and magnetic currents on the boundary plane between the homogeneous and the inhomogeneous region. The magnetic currents result directly from the electric fields of the Yee lattice. Electric currents in the same plane are calculated by making use of the TD-BIM and using the electric field of the Yee lattice as boundary condition. The presented hybrid method only needs the interpolations inherent in FIT and no additional interpolation. A numerical result is compared to a calculation that models both regions with FDTD.
Directory of Open Access Journals (Sweden)
A. Becker
2003-01-01
Full Text Available In this paper a hybrid method combining the FDTD/FIT with a Time Domain Boundary-Integral Marching-on-in-Time Algorithm (TD-BIM is presented. Inhomogeneous regions are modelled with the FIT-method, an alternative formulation of the FDTD. Homogeneous regions (which is in the presented numerical example the open space are modelled using a TD-BIM with equivalent electric and magnetic currents flowing on the boundary between the inhomogeneous and the homogeneous regions. The regions are coupled by the tangential magnetic fields just outside the inhomogeneous regions. These fields are calculated by making use of a Mixed Potential Integral Formulation for the magnetic field. The latter consists of equivalent electric and magnetic currents on the boundary plane between the homogeneous and the inhomogeneous region. The magnetic currents result directly from the electric fields of the Yee lattice. Electric currents in the same plane are calculated by making use of the TD-BIM and using the electric field of the Yee lattice as boundary condition. The presented hybrid method only needs the interpolations inherent in FIT and no additional interpolation. A numerical result is compared to a calculation that models both regions with FDTD.
Linear and nonlinear frequency- and time-domain spectroscopy with multiple frequency combs
Bennett, Kochise; Rouxel, Jeremy R.; Mukamel, Shaul
2017-09-01
Two techniques that employ equally spaced trains of optical pulses to map an optical high frequency into a low frequency modulation of the signal that can be detected in real time are compared. The development of phase-stable optical frequency combs has opened up new avenues to metrology and spectroscopy. The ability to generate a series of frequency spikes with precisely controlled separation permits a fast, highly accurate sampling of the material response. Recently, pairs of frequency combs with slightly different repetition rates have been utilized to down-convert material susceptibilities from the optical to microwave regime where they can be recorded in real time. We show how this one-dimensional dual comb technique can be extended to multiple dimensions by using several combs. We demonstrate how nonlinear susceptibilities can be quickly acquired using this technique. In a second class of techniques, sequences of ultrafast mode locked laser pulses are used to recover pathways of interactions contributing to nonlinear susceptibilities by using a photo-acoustic modulation varying along the sequences. We show that these techniques can be viewed as a time-domain analog of the multiple frequency comb scheme.
Directory of Open Access Journals (Sweden)
You Zhai
2018-02-01
Full Text Available This paper uses a newly defined functional connectome and connectome values calculated in time domain of simulated neurotransmitter release (NTR from an electrocorticogram (ECoG to distinguish between conditioned and unconditioned stimuli. The NTR derived from multiple channels releasing one quantum at the same time suggests that one functional connectome occurs across those channels at that time. During the first 600 ms after conditional stimulation, the connectome indexes of the 64-channel NTR trains were sorted from the 8 to 20 Hz band obtained from filtered rabbit ECoGs recorded from the visual cortices. In the small scale visual cortex area, this association was significantly larger than the habituation, even though the trial-to-trail variability of large scale synchrony after conditional stimulation is increased, which is also consistent with the hypothesis that attention decreases coherence of lower frequency within each cortical area. The increased conectome index suggests that the stimuli related to association are able to generate stronger substantial responses in the small scale visual cortex than habituation. That is, besides of the background cortical states as well as attention-related decreases in synchrony of lower frequency, the increased part of neurotransmitters released simultaneously from the pre-synaptic terminals of small scale visual cortex for association is larger than habituation.
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.
Numerical dispersion and stability characteristics of time-domain methods on nonorthogonal meshes
International Nuclear Information System (INIS)
Ray, S.L.
1993-01-01
The familiar finite-difference, time-domain method for discretizing Maxwell's curl equations on orthogonal grids has been extended to nonorthogonal grids by a number of researchers. While it is difficult to determine the dispersion and stability characteristics of these methods when applied on arbitrary grids, analysis of the idealized but representative case of a uniform skewed mesh proves to be quite tractable in 2-D. This analysis demonstrates that numerical dispersion errors are small for well-resolved spatial wavelengths and that these methods converge to the continuous-space solution in the limit as the cell and time step sizes vanish. Grid anisotropy (variations in wave propagation speed as a function of the propagation angle relative to the mesh coordinates) increases as the mesh is skewed. In spite of this, there exist some angles where waves propagate through the skewed mesh with virtually no dispersion. This analysis also provides a stability limit for the time step size in terms of geometrical mesh quantities
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
Time domain localization technique with sparsity constraint for imaging acoustic sources
Padois, Thomas; Doutres, Olivier; Sgard, Franck; Berry, Alain
2017-09-01
This paper addresses source localization technique in time domain for broadband acoustic sources. The objective is to accurately and quickly detect the position and amplitude of noise sources in workplaces in order to propose adequate noise control options and prevent workers hearing loss or safety risk. First, the generalized cross correlation associated with a spherical microphone array is used to generate an initial noise source map. Then a linear inverse problem is defined to improve this initial map. Commonly, the linear inverse problem is solved with an l2 -regularization. In this study, two sparsity constraints are used to solve the inverse problem, the orthogonal matching pursuit and the truncated Newton interior-point method. Synthetic data are used to highlight the performances of the technique. High resolution imaging is achieved for various acoustic sources configurations. Moreover, the amplitudes of the acoustic sources are correctly estimated. A comparison of computation times shows that the technique is compatible with quasi real-time generation of noise source maps. Finally, the technique is tested with real data.
Cole, Matthew O. T.; Shinonawanik, Praween; Wongratanaphisan, Theeraphong
2018-05-01
Structural flexibility can impact negatively on machine motion control systems by causing unmeasured positioning errors and vibration at locations where accurate motion is important for task execution. To compensate for these effects, command signal prefiltering may be applied. In this paper, a new FIR prefilter design method is described that combines finite-time vibration cancellation with dynamic compensation properties. The time-domain formulation exploits the relation between tracking error and the moment values of the prefilter impulse response function. Optimal design solutions for filters having minimum H2 norm are derived and evaluated. The control approach does not require additional actuation or sensing and can be effective even without complete and accurate models of the machine dynamics. Results from implementation and testing on an experimental high-speed manipulator having a Delta robot architecture with directionally compliant end-effector are presented. The results show the importance of prefilter moment values for tracking performance and confirm that the proposed method can achieve significant reductions in both peak and RMS tracking error, as well as settling time, for complex motion patterns.
A method for intermediate flooding and sinking simulation of a damaged floater in time domain
Directory of Open Access Journals (Sweden)
Ju-Sung Kim
2017-01-01
Full Text Available When a floater such as a ship or an offshore structure is damaged in the sea, it is necessary to determine whether the floater will sink in water or not. If the floater will sink, the time to sink should be estimated to make an emergency plan. In addition, causes of the flooding should be investigated carefully. For this purpose, a method for performing intermediate flooding and sinking simulation of the damaged floater in time domain is proposed in this study. Overall process of the proposed method consists of several steps. In the first step, data of the damaged floater such as hull form and compartments are prepared. In the second step, physical characteristics of the floater such as the increased weight considering incoming water, the center of gravity, the changed buoyancy, and the center of buoyancy are calculated at every time step. In the third step, the quasi-static equilibrium position of the floater is calculated. The second and third steps are repeated until the floater reaches to sink or to be in equilibrium. As a result, the final condition of the floater can be determined. To check the feasibility of the proposed method, it is applied to a simple box problem. Finally, it is applied to intermediate flooding simulation of a barge-type damaged floater. Two cases having damaged holes of different locations are selected. As a result, it was confirmed that the floater can be in equilibrium or sink according to the damaged position. The time to be in equilibrium or the time to sink was estimated.
Delfino, Leandro D; Dos Santos Silva, Diego A; Tebar, William R; Zanuto, Edner F; Codogno, Jamile S; Fernandes, Rômulo A; Christofaro, Diego G
2018-03-01
Sedentary behaviors in adolescents are associated with using screen devices, analyzed as the total daily time in television viewing, using the computer and video game. However, an independent and clustered analysis of devices allows greater understanding of associations with physical inactivity domains and eating habits in adolescents. Sample of adolescents aged 10-17 years (N.=1011) from public and private schools, randomly selected. The use of screen devices was measured by hours per week spent in each device: TV, computer, videogames and mobile phone/tablet. Physical inactivity domains (school, leisure and sports), eating habits (weekly food consumption frequency) and socioeconomic status were assessed by questionnaire. The prevalence of high use of mobile phone/tablet was 70% among adolescents, 63% showed high use of TV or computer and 24% reported high use of videogames. High use of videogames was greater among boys and high use of mobile phone/tablet was higher among girls. Significant associations of high use of TV (OR=1.43, 95% CI: 1.04-1.99), computer (OR=1.44, 95% CI: 1.03-2.02), videogames (OR=1.65, 95% CI: 1.13-2.69) and consumption of snacks were observed. High use of computer was associated with fried foods consumption (OR=1.32, 95% CI: 1.01-1.75) and physical inactivity (OR=1.41, 95% CI: 1.03-1.95). Mobile phone was associated with consumption of sweets (OR=1.33, 95% CI: 1.00-1.80). Cluster using screen devices showed associations with high consumption of snacks, fried foods and sweets, even after controlling for confounding variables. The high use of screen devices was associated with high consumption of snacks, fried foods, sweets and physical inactivity in adolescents.
Rao, Prethy; Yonekawa, Yoshihiro; Thomas, Benjamin J; Drenser, Kimberly A
2017-03-10
To compare the sensitivities of spectral-domain optical coherence tomography (SD-OCT) versus time-domain OCT (TD-OCT) in identifying epiretinal membranes (ERM) preoperatively in patients who underwent surgery for full-thickness macular holes (FTMH). This is an interventional retrospective case series of 59 eyes diagnosed with FTMHs who underwent 25-G pars plana vitrectomy with internal limiting membrane peeling between 2009 and 2015. Preoperative OCTs were obtained by SD-OCT (Spectralis, Heidelberg, Germany) or TD-OCT (Stratus, Carl Zeiss Meditec, Dublin, CA, USA). Volume scans were reviewed for ERM accompanying the FTMH. This was compared to indocyanine green-negative staining and intraoperative findings of ERM as the gold standard. Baseline characteristics between the SD-OCT and TD-OCT groups were comparable. Mean duration of postoperative follow-up was 41.4 weeks (±49.0). Of 59 eyes, 33 (55.9%) exhibited an ERM intraoperatively. Four ERMs (SD-OCT group) compared to 12 (TD-OCT group) were not visualized on preoperative OCT (p = 0.003). Sensitivity and specificity of SD-OCT in ERM detection was 79% and 100% compared to 14% and 91% for TD-OCT. Visual acuity improved in both arms (0.5 and 0.3 logMAR units in SD-OCT and TD-OCT, respectively (p = 0.002, 0.0002). We found that SD-OCT was superior to TD-OCT in identifying the presence of ERM preoperatively in patients who underwent macular hole surgery. Since ERMs may decrease the chance of successful pharmacologic vitreolysis, we recommend using SD-OCT over TD-OCT in the evaluation of patients with FTMH to more accurately identify ERMs and allow more comprehensive treatment decisions (pharmacologic versus surgical).
Combining sparse coding and time-domain features for heart sound classification.
Whitaker, Bradley M; Suresha, Pradyumna B; Liu, Chengyu; Clifford, Gari D; Anderson, David V
2017-07-31
This paper builds upon work submitted as part of the 2016 PhysioNet/CinC Challenge, which used sparse coding as a feature extraction tool on audio PCG data for heart sound classification. In sparse coding, preprocessed data is decomposed into a dictionary matrix and a sparse coefficient matrix. The dictionary matrix represents statistically important features of the audio segments. The sparse coefficient matrix is a mapping that represents which features are used by each segment. Working in the sparse domain, we train support vector machines (SVMs) for each audio segment (S1, systole, S2, diastole) and the full cardiac cycle. We train a sixth SVM to combine the results from the preliminary SVMs into a single binary label for the entire PCG recording. In addition to classifying heart sounds using sparse coding, this paper presents two novel modifications. The first uses a matrix norm in the dictionary update step of sparse coding to encourage the dictionary to learn discriminating features from the abnormal heart recordings. The second combines the sparse coding features with time-domain features in the final SVM stage. The original algorithm submitted to the challenge achieved a cross-validated mean accuracy (MAcc) score of 0.8652 (Se = 0.8669 and Sp = 0.8634). After incorporating the modifications new to this paper, we report an improved cross-validated MAcc of 0.8926 (Se = 0.9007 and Sp = 0.8845). Our results show that sparse coding is an effective way to define spectral features of the cardiac cycle and its sub-cycles for the purpose of classification. In addition, we demonstrate that sparse coding can be combined with additional feature extraction methods to improve classification accuracy.
Revisiting the time domain induced polarization technique, from linearization to inversion
Kang, S.; Oldenburg, D.
2015-12-01
The induced polarization (IP) technique has been successful in mineral exploration, particularly for finding disseminated sulphide or porphyry deposits, but also in helping solve geotechnical and environmental problems. Electrical induced polarization (EIP) surveys use grounded electrodes and take measurements of the electric field while the current is both "on" and "off". Currently, 2D and 3D inversions of EIP data are generally carried out by first finding a background conductivity from the asymptotic "on-time" measurements. The DC resistivity problem is then linearized about that conductivity to obtain a linear relationship between the off-time data and the "pseudo-chargeability". The distribution of pseudo-chargeability in the earth is then interpreted within the context of the initial geoscience problem pursued. Despite its success, the current EIP implementation does have challenges. A fundamental assumption, that there is no electromagnetic induction (EM) effect, breaks down when the background is conductive. This is especially problematic in regions having conductive overburden. EM induction complicates, and sometimes overwhelms, the IP signal. To ameliorate this effect, we estimate the inductive signal, subtract it from the "off-time" data and invert the resultant IP data using the linearized formulation. We carefully examine the conditions under which this works. We also investigate the potential alterations to the linearized sensitivity function that are needed to allow a linearized inversion to be carried out. Inversions of EIP data recover a "chargeability" but this is not a uniquely defined quantity. There are multiple definitions of this property because there are a diverse number of ways in which an IP datum is defined. In time domain IP surveys, the data might be mV/V or a time-integrated voltage with units of ms. In reality however, data from an EIP survey have many time channels and each one can be inverted separately to produce a chargeability
International Nuclear Information System (INIS)
Spears, Robert Edward; Coleman, Justin Leigh
2015-01-01
Currently the Department of Energy (DOE) and the nuclear industry perform seismic soil-structure interaction (SSI) analysis using equivalent linear numerical analysis tools. For lower levels of ground motion, these tools should produce reasonable in-structure response values for evaluation of existing and new facilities. For larger levels of ground motion these tools likely overestimate the in-structure response (and therefore structural demand) since they do not consider geometric nonlinearities (such as gaping and sliding between the soil and structure) and are limited in the ability to model nonlinear soil behavior. The current equivalent linear SSI (SASSI) analysis approach either joins the soil and structure together in both tension and compression or releases the soil from the structure for both tension and compression. It also makes linear approximations for material nonlinearities and generalizes energy absorption with viscous damping. This produces the potential for inaccurately establishing where the structural concerns exist and/or inaccurately establishing the amplitude of the in-structure responses. Seismic hazard curves at nuclear facilities have continued to increase over the years as more information has been developed on seismic sources (i.e. faults), additional information gathered on seismic events, and additional research performed to determine local site effects. Seismic hazard curves are used to develop design basis earthquakes (DBE) that are used to evaluate nuclear facility response. As the seismic hazard curves increase, the input ground motions (DBE's) used to numerically evaluation nuclear facility response increase causing larger in-structure response. As ground motions increase so does the importance of including nonlinear effects in numerical SSI models. To include material nonlinearity in the soil and geometric nonlinearity using contact (gaping and sliding) it is necessary to develop a nonlinear time domain methodology. This
Calleja, Véronique; Leboucher, Pierre; Larijani, Banafshé
2012-01-01
Analytical time resolved Förster resonance energy transfer (FRET) can be exploited for assessing, in cells and tumor micro arrays, the activation status and dynamics of oncoproteins such as epidermal growth factor receptor (EGFR1) and their downstream effectors such as protein kinase B (PKB) and 3-phosphoinositide-dependent protein kinase 1 (PDK1). The outcome of our research involving the application of quantitative imaging for investigating molecular mechanisms of phosphoinositide-dependant enzymes, such as PKB and PDK1, has resulted in a refined model describing the dynamics and regulation of these two oncoproteins in live cells. Our translational research exploits a quantitative FRET method for establishing the activation status of predictive biomarkers in tumor micro arrays. We developed a two-site FRET assay monitored by automated frequency domain Fluorescence lifetime imaging microscopy (FLIM). As a proof of principle, we tested our methodology by assessing EGFR1 activation status in tumor micro arrays from head and neck patients. Our two-site FRET assay, by high-throughput frequency domain FLIM, has great potential to provide prognostic and perhaps predictive biomarkers. Copyright Â© 2012 Elsevier Inc. All rights reserved.
Non-destructive evaluation of specialty coating degradation using terahertz time-domain spectroscopy
Nicoletti, Carley R.; Cramer, Laura; Fletcher, Alan; Zimdars, David; Iqbal, Zafar; Federici, John F.
2017-05-01
The Terahertz Time Domain Reflection Spectroscopy (THz-TDS) method of paint layer diagnostics is a non-contact electromagnetic technique analogous to pulsed-ultrasound with the added capability of spectroscopic characterization. The THz-TDS sensor emits a near-single cycle electromagnetic pulse with a bandwidth from 0.1 to 3 THz. This wide bandwidth pulse is focused on the coating, and echo pulses are generated from each interface (air-coating, layer-layer, coating-substrate). In this paper, the THz-TDS method is applied to specialty aircraft coatings. The THz-TDS method is able to penetrate the whole coating stack and sample the properties of each layer. Because the reflected pulses from individual layers typically overlap in time, the complex permittivity function and thickness of each layer is determined by a best fit of the measured reflection (either in time or frequency domain) to a layered model of the paint. The THz- TDS method is applied to specialty coatings prior to and during accelerated aging on a series of test coupons. The coupons are also examined during aging using ATR (attenuated total reflectance)-FTIR spectroscopy, Raman scattering spectroscopy, and Scanning Electron Microscopy (SEM) to ascertain, quantify, and understand the breakdown mechanisms of the coatings. In addition, the same samples are characterized using THz-TDS techniques to determine if the THz-TDS method can be utilized as a non-destructive evaluation technique to sense degradation of the coatings. Our results suggest that the degradation mechanism begins in the top coat layer. In this layer, 254 nm UV illumination in combination with the presence of moisture works partially with oxides as catalysts to decompose the polymer matrix thereby creating porosity in the top coat layer. Since the catalytic effect is partial, loss of the oxides by chemical reaction can also occur. As the topcoat layer becomes more porous, it allows water vapor to permeate the topcoat layer and interact
Satriani, A.; Loperte, A.; Catalano, M.
2012-04-01
This abstract deals with the joint use of the Time Domain Reflectometry (TDR) and Electrical Resistivity Tomography (ERT) for soil moisture monitoring and spatial distribution estimation in agriculture. In fact, an effective use of irrigation water for a sustainable agriculture helps to cut irrigation cost and the exploitation of technologies for water resource monitoring and management can help to achieve this objective. The work has regarded a flat experimental vegetable area of about 1000 m2 with the bean crop (Phaseolus vulgaris L), which was an subdivided in two adjacent plots of land five meters distant each from other. From sowing and for the whole cultural cycle, irrigation monitoring was performed by using non-invasive surveys, based on measurements of physical properties of the soil, as the dielectric constant and the electrical resistivity. A drip irrigation system was used with the water pumped by a nearby water reserve, represented by a small artificial lake, but a different irrigation treatment was performed for each plot. In the plot A, the irrigation water supply was managed by the farmer, with an intensive irrigation treatment. Differently, in the plot B, the irrigation water supply was decided on the basis of the results of the TDR and ERT surveys. In particular, the amount and the time of irrigation were determined on the basis of the measurements of physical properties of the soil using TDR and ERT, with a specific focus to the soil moisture content estimation and spatial distribution . In fact, during the crop cycle, the soil moisture was measured weekly before and after irrigation, by a 20 cm vertical time domain reflectometry probe located at the center and at the ends of the bean rows. Moreover, the soil water distribution was determined by an electrical resistivity tomography using a multielectrode method. On the basis of the TDR and ERT results, a reduced water supply was performed, which did not affect the bean yield, and moreover
Stevens, G.
1983-01-01
A technological and economic assessment is made of providing low data rate service to small earth stations by satellite at Ka-band. Various Frequency Domain Multiple Access (FDMA) and Time Domain Multiple Access (TDMA) scenarios are examined and compared on the basis of cost to the end user. Very small stations (1 to 2 meters in diameter) are found not to be viable alternatives to available terrestrial services. However, medium size (3 to 5 meters) earth stations appear to be very competitive if a minimum throughput of about 1.5 Mbs is maintained. This constrains the use of such terminals to large users and shared use by smaller users. No advantage was found to the use of FDMA. TDMA had a slight advantage from a total system viewpoint and a very significant advantage in the space segment (about 1/3 the required payload weight for an equivalent capacity).
Terahertz time domain interferometry of a SIS tunnel junction and a quantum point contact
International Nuclear Information System (INIS)
Karadi, C.; Lawrence Berkeley Lab., CA
1995-09-01
The author has applied the Terahertz Time Domain Interferometric (THz-TDI) technique to probe the ultrafast dynamic response of a Superconducting-Insulating-Superconducting (SIS) tunnel junction and a Quantum Point Contact (QPC). The THz-TDI technique involves monitoring changes in the dc current induced by interfering two picosecond electrical pulses on the junction as a function of time delay between them. Measurements of the response of the Nb/AlO x /Nb SIS tunnel junction from 75--200 GHz are in full agreement with the linear theory for photon-assisted tunneling. Likewise, measurements of the induced current in a QPC as a function of source-drain voltage, gate voltage, frequency, and magnetic field also show strong evidence for photon-assisted transport. These experiments together demonstrate the general applicability of the THz-TDI technique to the characterization of the dynamic response of any micron or nanometer scale device that exhibits a non-linear I-V characteristic. 133 refs., 49 figs
Accurate Behavioral Simulator of All-Digital Time-Domain Smart Temperature Sensors by Using SIMULINK
Directory of Open Access Journals (Sweden)
Chun-Chi Chen
2016-08-01
Full Text Available This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs.
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.
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.
Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui
2010-03-01
Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives.
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.
Biedermann, Benjamin R; Wieser, Wolfgang; Eigenwillig, Christoph M; Palte, Gesa; Adler, Desmond C; Srinivasan, Vivek J; Fujimoto, James G; Huber, Robert
2008-11-01
We demonstrate en face swept source optical coherence tomography (ss-OCT) without requiring a Fourier transformation step. The electronic optical coherence tomography (OCT) interference signal from a k-space linear Fourier domain mode-locked laser is mixed with an adjustable local oscillator, yielding the analytic reflectance signal from one image depth for each frequency sweep of the laser. Furthermore, a method for arbitrarily shaping the spectral intensity profile of the laser is presented, without requiring the step of numerical apodization. In combination, these two techniques enable sampling of the in-phase and quadrature signal with a slow analog-to-digital converter and allow for real-time display of en face projections even for highest axial scan rates. Image data generated with this technique is compared to en face images extracted from a three-dimensional OCT data set. This technique can allow for real-time visualization of arbitrarily oriented en face planes for the purpose of alignment, registration, or operator-guided survey scans while simultaneously maintaining the full capability of high-speed volumetric ss-OCT functionality.
Biedermann, Benjamin R.; Wieser, Wolfgang; Eigenwillig, Christoph M.; Palte, Gesa; Adler, Desmond C.; Srinivasan, Vivek J.; Fujimoto, James G.; Huber, Robert
2009-01-01
We demonstrate en face swept source optical coherence tomography (ss-OCT) without requiring a Fourier transformation step. The electronic optical coherence tomography (OCT) interference signal from a k-space linear Fourier domain mode-locked laser is mixed with an adjustable local oscillator, yielding the analytic reflectance signal from one image depth for each frequency sweep of the laser. Furthermore, a method for arbitrarily shaping the spectral intensity profile of the laser is presented, without requiring the step of numerical apodization. In combination, these two techniques enable sampling of the in-phase and quadrature signal with a slow analog-to-digital converter and allow for real-time display of en face projections even for highest axial scan rates. Image data generated with this technique is compared to en face images extracted from a three-dimensional OCT data set. This technique can allow for real-time visualization of arbitrarily oriented en face planes for the purpose of alignment, registration, or operator-guided survey scans while simultaneously maintaining the full capability of high-speed volumetric ss-OCT functionality. PMID:18978919
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)
Chen, Chun-Chi; Chen, Chao-Lieh; Lin, You-Ting
2016-08-08
This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM) by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs.
A wavelet-based PWTD algorithm-accelerated time domain surface integral equation solver
Liu, Yang
2015-10-26
© 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)-based surface integral equation (SIE) solvers, it reduces the computational and memory costs of transient analysis from equation and equation to equation and equation, respectively, where Nt and Ns denote the number of temporal and spatial unknowns (Ergin et al., IEEE Trans. Antennas Mag., 41, 39-52, 1999). In the past, PWTD-accelerated MOT-SIE solvers have been applied to transient problems involving half million spatial unknowns (Shanker et al., IEEE Trans. Antennas Propag., 51, 628-641, 2003). Recently, a scalable parallel PWTD-accelerated MOT-SIE solver that leverages a hiearchical parallelization strategy has been developed and successfully applied to the transient problems involving ten million spatial unknowns (Liu et. al., in URSI Digest, 2013). We further enhanced the capabilities of this solver by implementing a compression scheme based on local cosine wavelet bases (LCBs) that exploits the sparsity in the temporal dimension (Liu et. al., in URSI Digest, 2014). Specifically, the LCB compression scheme was used to reduce the memory requirement of the PWTD ray data and computational cost of operations in the PWTD translation stage.
Non-local effect in Brillouin optical time-domain analyzer based on Raman amplification
International Nuclear Information System (INIS)
Jia Xinhong; Rao Yunjiang; Wang Zinan; Zhang Weili; Ran Zengling; Deng Kun; Yang Zixin
2012-01-01
Compared with conventional Brillouin optical time-domain analyzer (BOTDA), the BOTDA based on Raman amplification allows longer sensing range, higher signal-to-noise ratio and higher measurement accuracy. However, the non-local effect induced by pump depletion significantly restricts the probe optical power injected to sensing fiber, thereby limiting the further extension for sensing distance. In this paper, the coupled equations including the interaction of probe light, Brillouin and Raman pumps are applied to the study on the non-local characteristics of BOTDA based on Raman amplification. The results show that, the system error induced by non-local effect worsens with increased powers of probe wave and Raman pump. The frequency-division-multiplexing (cascading the fibers with various Brillouin frequency shifts) and time-division-multiplexing (modulating both of the Brillouin pump and probe lights) technologies are efficient approaches to suppress the non-local effect, through shortening the effective interaction range between Brillouin pump and probe lights. (authors)
Terahertz time domain interferometry of a SIS tunnel junction and a quantum point contact
Energy Technology Data Exchange (ETDEWEB)
Karadi, Chandu [Univ. of California, Berkeley, CA (United States). Dept. of Physics
1995-09-01
The author has applied the Terahertz Time Domain Interferometric (THz-TDI) technique to probe the ultrafast dynamic response of a Superconducting-Insulating-Superconducting (SIS) tunnel junction and a Quantum Point Contact (QPC). The THz-TDI technique involves monitoring changes in the dc current induced by interfering two picosecond electrical pulses on the junction as a function of time delay between them. Measurements of the response of the Nb/AlO_{x}Nb SIS tunnel junction from 75--200 GHz are in full agreement with the linear theory for photon-assisted tunneling. Likewise, measurements of the induced current in a QPC as a function of source-drain voltage, gate voltage, frequency, and magnetic field also show strong evidence for photon-assisted transport. These experiments together demonstrate the general applicability of the THz-TDI technique to the characterization of the dynamic response of any micron or nanometer scale device that exhibits a non-linear I-V characteristic.
Time Domain View of Liquid-like Screening and Large Polaron Formation in Lead Halide Perovskites
Joshi, Prakriti Pradhan; Miyata, Kiyoshi; Trinh, M. Tuan; Zhu, Xiaoyang
The structural softness and dynamic disorder of lead halide perovskites contributes to their remarkable optoelectronic properties through efficient charge screening and large polaron formation. Here we provide a direct time-domain view of the liquid-like structural dynamics and polaron formation in single crystal CH3NH3PbBr3 and CsPbBr3 using femtosecond optical Kerr effect spectroscopy in conjunction with transient reflectance spectroscopy. We investigate structural dynamics as function of pump energy, which enables us to examine the dynamics in the absence and presence of charge carriers. In the absence of charge carriers, structural dynamics are dominated by over-damped picosecond motions of the inorganic PbBr3- sub-lattice and these motions are strongly coupled to band-gap electronic transitions. Carrier injection from across-gap optical excitation triggers additional 0.26 ps dynamics in CH3NH3PbBr3 that can be attributed to the formation of large polarons. In comparison, large polaron formation is slower in CsPbBr3 with a time constant of 0.6 ps. We discuss how such dynamic screening protects charge carriers in lead halide perovskites. US Department of Energy, Office of Science - Basic Energy Sciences.
Time coordination of heterogeneous distance protections using a domain specific language
Directory of Open Access Journals (Sweden)
Marcin Kowalski
2012-01-01
Full Text Available BACKGROUND: Distance protections are widely used in protection of energy transmission lines, but their time coordination is still an important and difficult problem. Inappropriate configuration leads to a hazard event: remote circuit breaker tripping provided the local circuit breaker can be opened, which severely impairs power system operation.OBJECTIVE: To describe a method and provide software tools to alleviate the hazard in power systems.METHODS: A domain specific language (DSL for representation of a transmission line with its distance protection schema, and a translation algorithm from the DSL to probabilistic fault trees with time dependencies (PFTTDs are employed.RESULTS: The paper presents software tools that can support power protection experts in time coordination of distance protections. The tools are based upon abstract and concrete syntax of the DSL designed specifically for the purpose of the distance protection time coordination problem. In order to render creation of power line and its protection schema models easier, a DSL-dedicated editor supporting syntax and semantic aspects of the DSL has been developed. Additionally, a translator from the DSL into PFTTD language has been implemented.CONCLUSIONS: Power system experts are enabled to perform hazard probability assessment and sensitivity analysis.LIMITATIONS: Translation supports two types of distance protections, which are: single-system relays with starting elements as well as multi-system relays without starting elements. For the single-system relay, there is one timer per relay. For multi-system relays, there is one timer for each of possibly many protection zones. Other types of protections, e.g. overcurrent are not considered.
Processing grounded-wire TEM signal in time-frequency-pseudo-seismic domain: A new paradigm
Khan, M. Y.; Xue, G. Q.; Chen, W.; Huasen, Z.
2017-12-01
Grounded-wire TEM has received great attention in mineral, hydrocarbon and hydrogeological investigations for the last several years. Conventionally, TEM soundings have been presented as apparent resistivity curves as function of time. With development of sophisticated computational algorithms, it became possible to extract more realistic geoelectric information by applying inversion programs to 1-D & 3-D problems. Here, we analyze grounded-wire TEM data by carrying out analysis in time, frequency and pseudo-seismic domain supported by borehole information. At first, H, K, A & Q type geoelectric models are processed using a proven inversion program (1-D Occam inversion). Second, time-to-frequency transformation is conducted from TEM ρa(t) curves to magneto telluric MT ρa(f) curves for the same models based on all-time apparent resistivity curves. Third, 1-D Bostick's algorithm was applied to the transformed resistivity. Finally, EM diffusion field is transformed into propagating wave field obeying the standard wave equation using wavelet transformation technique and constructed pseudo-seismic section. The transformed seismic-like wave indicates that some reflection and refraction phenomena appear when the EM wave field interacts with geoelectric interface at different depth intervals due to contrast in resistivity. The resolution of the transformed TEM data is significantly improved in comparison to apparent resistivity plots. A case study illustrates the successful hydrogeophysical application of proposed approach in recovering water-filled mined-out area in a coal field located in Ye county, Henan province, China. The results support the introduction of pseudo-seismic imaging technology in short-offset version of TEM which can also be an useful aid if integrated with seismic reflection technique to explore possibilities for high resolution EM imaging in future.
Data Mining and Machine Learning in Time-Domain Discovery and Classification
Bloom, Joshua S.; Richards, Joseph W.
2012-03-01
The changing heavens have played a central role in the scientific effort of astronomers for centuries. Galileo's synoptic observations of the moons of Jupiter and the phases of Venus starting in 1610, provided strong refutation of Ptolemaic cosmology. These observations came soon after the discovery of Kepler's supernova had challenged the notion of an unchanging firmament. In more modern times, the discovery of a relationship between period and luminosity in some pulsational variable stars [41] led to the inference of the size of the Milky way, the distance scale to the nearest galaxies, and the expansion of the Universe (see Ref. [30] for review). Distant explosions of supernovae were used to uncover the existence of dark energy and provide a precise numerical account of dark matter (e.g., [3]). Repeat observations of pulsars [71] and nearby main-sequence stars revealed the presence of the first extrasolar planets [17,35,44,45]. Indeed, time-domain observations of transient events and variable stars, as a technique, influences a broad diversity of pursuits in the entire astronomy endeavor [68]. While, at a fundamental level, the nature of the scientific pursuit remains unchanged, the advent of astronomy as a data-driven discipline presents fundamental challenges to the way in which the scientific process must now be conducted. Digital images (and data cubes) are not only getting larger, there are more of them. On logistical grounds, this taxes storage and transport systems. But it also implies that the intimate connection that astronomers have always enjoyed with their data - from collection to processing to analysis to inference - necessarily must evolve. Figure 6.1 highlights some of the ways that the pathway to scientific inference is now influenced (if not driven by) modern automation processes, computing, data-mining, and machine-learning (ML). The emerging reliance on computation and ML is a general one - a central theme of this book - but the time-domain
The phasor-FLIM fingerprints reveal shifts from OXPHOS to enhanced glycolysis in Huntington Disease
Sameni, Sara; Syed, Adeela; Marsh, J. Lawrence; Digman, Michelle A.
2016-10-01
Huntington disease (HD) is an autosomal neurodegenerative disorder caused by the expansion of Polyglutamine (polyQ) in exon 1 of the Huntingtin protein. Glutamine repeats below 36 are considered normal while repeats above 40 lead to HD. Impairment in energy metabolism is a common trend in Huntington pathogenesis; however, this effect is not fully understood. Here, we used the phasor approach and Fluorescence Lifetime Imaging Microscopy (FLIM) to measure changes between free and bound fractions of NADH as a indirect measure of metabolic alteration in living cells. Using Phasor-FLIM, pixel maps of metabolic alteration in HEK293 cell lines and in transgenic Drosophila expressing expanded and unexpanded polyQ HTT exon1 in the eye disc were developed. We found a significant shift towards increased free NADH, indicating an increased glycolytic state for cells and tissues expressing the expanded polyQ compared to unexpanded control. In the nucleus, a further lifetime shift occurs towards higher free NADH suggesting a possible synergism between metabolic dysfunction and transcriptional regulation. Our results indicate that metabolic dysfunction in HD shifts to increased glycolysis leading to oxidative stress and cell death. This powerful label free method can be used to screen native HD tissue samples and for potential drug screening.
The JWST North Ecliptic Pole Survey Field for Time-domain Studies
Jansen, Rolf A.; Webb Medium Deep Fields IDS GTO Team, the NEPTDS-VLA/VLBA Team, and the NEPTDS-Chandra Team
2017-06-01
The JWST North Ecliptic Pole (NEP) Survey field is located within JWST's northern Continuous Viewing Zone, will span ~14‧ in diameter (~10‧ with NIRISS coverage) and will be roughly circular in shape (initially sampled during Cycle 1 at 4 distinct orientations with JWST/NIRCam's 4.4‧×2.2‧ FoV —the JWST "windmill") and will have NIRISS slitless grism spectroscopy taken in parallel, overlapping an alternate NIRCam orientation. This is the only region in the sky where JWST can observe a clean extragalactic deep survey field (free of bright foreground stars and with low Galactic foreground extinction AV) at arbitrary cadence or at arbitrary orientation. This will crucially enable a wide range of new and exciting time-domain science, including high redshift transient searches and monitoring (e.g., SNe), variability studies from Active Galactic Nuclei to brown dwarf atmospheres, as well as proper motions of extreme scattered Kuiper Belt and Oort Cloud Objects, and of nearby Galactic brown dwarfs, low-mass stars, and ultracool white dwarfs. We therefore welcome and encourage follow-up through GO programs of the initial GTO observations to realize its potential as a JWST time-domain community field. The JWST NEP Survey field was selected from an analysis of WISE 3.4+4.6 μm, 2MASS JHKs, and SDSS ugriz source counts and of Galactic foreground extinction, and is one of very few such ~10‧ fields that are devoid of sources brighter than mAB = 16 mag. We have secured deep (mAB ~ 26 mag) wide-field (~23‧×25‧) Ugrz images of this field and its surroundings with LBT/LBC. We also expect that deep MMT/MMIRS YJHK images, deep 3-4.5 GHz VLA and VLBA radio observations, and possibly HST ACS/WFC and WFC3/UVIS ultraviolet-visible (pending) and Chandra/ACIS X-ray (pending) images will be available before JWST launches in Oct 2018.
Time resolved reversal of spin-spiral domains by an electric field in multiferroic MnWO{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Thielen, Philip; Hoffmann, Tim; Fiebig, Manfred [University Bonn, HISKP (Germany); Becker, Petra; Bohaty, Ladislav [Institut fuer Kristallographie, Universitaet Koeln (Germany)
2011-07-01
The interaction of magnetic and ferroelectric order is intrinsically strong in spin-spiral multiferroics. Here the complex magnetic long range order breaks inversion symmetry and induces a spontaneous electric polarization. The interaction allows for switching of the magnetization by means of an applied electric field and is thus of great interest for possible applications. So far there exists little information on the time scale and dynamics of the actual switching process. Here we report time resolved measurements of the reversal of spin-spiral domains in multiferroic MnWO{sub 4} by optical second harmonic generation. Magnetic single-domain states are created by the application of an electric field. By reversing its polarity, a reversal of the magnetic domain state occurs. The time scale of the dynamic switching process is found to be in the ms region. Images of the domain-reversal process are obtained. The dynamic domain pattern differs substantially from that of quasi-statically switched multi domain structures.