The 2017 North Korea M6 seismic sequence: moment tensor, source time function, and aftershocks

Science.gov (United States)

Ni, S.; Zhan, Z.; Chu, R.; He, X.

2017-12-01

On September 3rd, 2017, an M6 seismic event occurred in North Korea, with location near previous nuclear test sites. The event features strong P waves and short period Rayleigh waves are observed in contrast to weak S waves, suggesting mostly explosion mechanism. We performed joint inversion for moment tensor and depth with both local and teleseismic waveforms, and find that the event is shallow with mostly isotropic yet substantial non-isotropic components. Deconvolution of seismic waveforms of this event with respect to previous nuclear test events shows clues of complexity in source time function. The event is followed by smaller earthquakes, as early as 8.5 minutes and lasted at least to October. The later events occurred in a compact region, and show clear S waves, suggesting double couple focal mechanism. Via analyzing Rayleigh wave spectrum, these smaller events are found to be shallow. Relative locations, difference in waveforms of the events are used to infer their possible links and generation mechanism.

The recovery of a time-dependent point source in a linear transport equation: application to surface water pollution

International Nuclear Information System (INIS)

Hamdi, Adel

2009-01-01

The aim of this paper is to localize the position of a point source and recover the history of its time-dependent intensity function that is both unknown and constitutes the right-hand side of a 1D linear transport equation. Assuming that the source intensity function vanishes before reaching the final control time, we prove that recording the state with respect to the time at two observation points framing the source region leads to the identification of the source position and the recovery of its intensity function in a unique manner. Note that at least one of the two observation points should be strategic. We establish an identification method that determines quasi-explicitly the source position and transforms the task of recovering its intensity function into solving directly a well-conditioned linear system. Some numerical experiments done on a variant of the water pollution BOD model are presented

Blind source separation problem in GPS time series

Science.gov (United States)

Gualandi, A.; Serpelloni, E.; Belardinelli, M. E.

2016-04-01

A critical point in the analysis of ground displacement time series, as those recorded by space geodetic techniques, is the development of data-driven methods that allow the different sources of deformation to be discerned and characterized in the space and time domains. Multivariate statistic includes several approaches that can be considered as a part of data-driven methods. A widely used technique is the principal component analysis (PCA), which allows us to reduce the dimensionality of the data space while maintaining most of the variance of the dataset explained. However, PCA does not perform well in finding the solution to the so-called blind source separation (BSS) problem, i.e., in recovering and separating the original sources that generate the observed data. This is mainly due to the fact that PCA minimizes the misfit calculated using an L2 norm (χ 2), looking for a new Euclidean space where the projected data are uncorrelated. The independent component analysis (ICA) is a popular technique adopted to approach the BSS problem. However, the independence condition is not easy to impose, and it is often necessary to introduce some approximations. To work around this problem, we test the use of a modified variational Bayesian ICA (vbICA) method to recover the multiple sources of ground deformation even in the presence of missing data. The vbICA method models the probability density function (pdf) of each source signal using a mix of Gaussian distributions, allowing for more flexibility in the description of the pdf of the sources with respect to standard ICA, and giving a more reliable estimate of them. Here we present its application to synthetic global positioning system (GPS) position time series, generated by simulating deformation near an active fault, including inter-seismic, co-seismic, and post-seismic signals, plus seasonal signals and noise, and an additional time-dependent volcanic source. We evaluate the ability of the PCA and ICA decomposition

Time-lapse controlled-source electromagnetics using interferometry

NARCIS (Netherlands)

Hunziker, J.W.; Slob, E.C.; Wapenaar, C.P.A.

In time-lapse controlled-source electromagnetics, it is crucial that the source and the receivers are positioned at exactly the same location at all times of measurement. We use interferometry by multidimensional deconvolution (MDD) to overcome problems in repeatability of the source location.

Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

International Nuclear Information System (INIS)

Zhang, Chi; Xu, Yiqing; Wei, Xiaoming; Tsia, Kevin K.; Wong, Kenneth K. Y.

2014-01-01

Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated by a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier

Time functions revisited

Science.gov (United States)

Fathi, Albert

2015-07-01

In this paper we revisit our joint work with Antonio Siconolfi on time functions. We will give a brief introduction to the subject. We will then show how to construct a Lipschitz time function in a simplified setting. We will end with a new result showing that the Aubry set is not an artifact of our proof of existence of time functions for stably causal manifolds.

Fission-neutrons source with fast neutron-emission timing

Energy Technology Data Exchange (ETDEWEB)

Rusev, G., E-mail: rusev@lanl.gov; Baramsai, B.; Bond, E.M.; Jandel, M.

2016-05-01

A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of {sup 252}Cf. The time is provided by registering the fission fragments in a layer of a thin scintillation film with a signal rise time of 1 ns. The scintillation light output is measured by two silicon photomultipliers with rise time of 0.5 ns. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements using it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.

Source-independent time-domain waveform inversion using convolved wavefields: Application to the encoded multisource waveform inversion

KAUST Repository

Choi, Yun Seok

2011-09-01

Full waveform inversion requires a good estimation of the source wavelet to improve our chances of a successful inversion. This is especially true for an encoded multisource time-domain implementation, which, conventionally, requires separate-source modeling, as well as the Fourier transform of wavefields. As an alternative, we have developed the source-independent time-domain waveform inversion using convolved wavefields. Specifically, the misfit function consists of the convolution of the observed wavefields with a reference trace from the modeled wavefield, plus the convolution of the modeled wavefields with a reference trace from the observed wavefield. In this case, the source wavelet of the observed and the modeled wavefields are equally convolved with both terms in the misfit function, and thus, the effects of the source wavelets are eliminated. Furthermore, because the modeled wavefields play a role of low-pass filtering, the observed wavefields in the misfit function, the frequency-selection strategy from low to high can be easily adopted just by setting the maximum frequency of the source wavelet of the modeled wavefields; and thus, no filtering is required. The gradient of the misfit function is computed by back-propagating the new residual seismograms and applying the imaging condition, similar to reverse-time migration. In the synthetic data evaluations, our waveform inversion yields inverted models that are close to the true model, but demonstrates, as predicted, some limitations when random noise is added to the synthetic data. We also realized that an average of traces is a better choice for the reference trace than using a single trace. © 2011 Society of Exploration Geophysicists.

Time Functions as Utilities

Science.gov (United States)

Minguzzi, E.

2010-09-01

Every time function on spacetime gives a (continuous) total preordering of the spacetime events which respects the notion of causal precedence. The problem of the existence of a (semi-)time function on spacetime and the problem of recovering the causal structure starting from the set of time functions are studied. It is pointed out that these problems have an analog in the field of microeconomics known as utility theory. In a chronological spacetime the semi-time functions correspond to the utilities for the chronological relation, while in a K-causal (stably causal) spacetime the time functions correspond to the utilities for the K + relation (Seifert’s relation). By exploiting this analogy, we are able to import some mathematical results, most notably Peleg’s and Levin’s theorems, to the spacetime framework. As a consequence, we prove that a K-causal (i.e. stably causal) spacetime admits a time function and that the time or temporal functions can be used to recover the K + (or Seifert) relation which indeed turns out to be the intersection of the time or temporal orderings. This result tells us in which circumstances it is possible to recover the chronological or causal relation starting from the set of time or temporal functions allowed by the spacetime. Moreover, it is proved that a chronological spacetime in which the closure of the causal relation is transitive (for instance a reflective spacetime) admits a semi-time function. Along the way a new proof avoiding smoothing techniques is given that the existence of a time function implies stable causality, and a new short proof of the equivalence between K-causality and stable causality is given which takes advantage of Levin’s theorem and smoothing techniques.

Source modeling and inversion with near real-time GPS: a GITEWS perspective for Indonesia

Science.gov (United States)

Babeyko, A. Y.; Hoechner, A.; Sobolev, S. V.

2010-07-01

We present the GITEWS approach to source modeling for the tsunami early warning in Indonesia. Near-field tsunami implies special requirements to both warning time and details of source characterization. To meet these requirements, we employ geophysical and geological information to predefine a maximum number of rupture parameters. We discretize the tsunamigenic Sunda plate interface into an ordered grid of patches (150×25) and employ the concept of Green's functions for forward and inverse rupture modeling. Rupture Generator, a forward modeling tool, additionally employs different scaling laws and slip shape functions to construct physically reasonable source models using basic seismic information only (magnitude and epicenter location). GITEWS runs a library of semi- and fully-synthetic scenarios to be extensively employed by system testing as well as by warning center personnel teaching and training. Near real-time GPS observations are a very valuable complement to the local tsunami warning system. Their inversion provides quick (within a few minutes on an event) estimation of the earthquake magnitude, rupture position and, in case of sufficient station coverage, details of slip distribution.

Moving source localization with a single hydrophone using multipath time delays in the deep ocean.

Science.gov (United States)

Duan, Rui; Yang, Kunde; Ma, Yuanliang; Yang, Qiulong; Li, Hui

2014-08-01

Localizing a source of radial movement at moderate range using a single hydrophone can be achieved in the reliable acoustic path by tracking the time delays between the direct and surface-reflected arrivals (D-SR time delays). The problem is defined as a joint estimation of the depth, initial range, and speed of the source, which are the state parameters for the extended Kalman filter (EKF). The D-SR time delays extracted from the autocorrelation functions are the measurements for the EKF. Experimental results using pseudorandom signals show that accurate localization results are achieved by offline iteration of the EKF.

Electron energy distributions and electron impact source functions in Ar/N{sub 2} inductively coupled plasmas using pulsed power

Energy Technology Data Exchange (ETDEWEB)

Logue, Michael D., E-mail: mdlogue@umich.edu; Kushner, Mark J., E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109-2122 (United States)

2015-01-28

In plasma materials processing, such as plasma etching, control of the time-averaged electron energy distributions (EEDs) in the plasma allows for control of the time-averaged electron impact source functions of reactive species in the plasma and their fluxes to surfaces. One potential method for refining the control of EEDs is through the use of pulsed power. Inductively coupled plasmas (ICPs) are attractive for using pulsed power in this manner because the EEDs are dominantly controlled by the ICP power as opposed to the bias power applied to the substrate. In this paper, we discuss results from a computational investigation of EEDs and electron impact source functions in low pressure (5–50 mTorr) ICPs sustained in Ar/N{sub 2} for various duty cycles. We find there is an ability to control EEDs, and thus source functions, by pulsing the ICP power, with the greatest variability of the EEDs located within the skin depth of the electromagnetic field. The transit time of hot electrons produced in the skin depth at the onset of pulse power produces a delay in the response of the EEDs as a function of distance from the coils. The choice of ICP pressure has a large impact on the dynamics of the EEDs, whereas duty cycle has a small influence on time-averaged EEDs and source functions.

Functionality of Sea Ice Data Sources on the NSR

Directory of Open Access Journals (Sweden)

Tadeusz Pastusiak

2016-09-01

Full Text Available The functionality of available official sources of sea ice data for the Northern Sea Route to date is low. In recent years a large number of new publicly available sources have appeared. Their functionality for purposes of route planning has yet to be evaluated. This study presents results of qualitative and expert analyses of various sources. It is proposed to use new indicators to enable comparison of functionality of data sources. New sources provide the technical progress that is instrumental in reducing the amount of effort and influence of the human factor in the decision-making system. The study also presents solutions to the problem of limited bandwidth available at high latitudes with Iridium satellite system. Presented solutions can be used on any vessel by any company or navigator to implement or design the decision support system related to route planning in ice in accordance with the requirements of the ISM Code and concept of e-Navigation.

Comparison of source moment tensor recovered by diffraction stacking migration and source time reversal imaging

Science.gov (United States)

Zhang, Q.; Zhang, W.

2017-12-01

Diffraction stacking migration is an automatic location methods and widely used in microseismic monitoring of the hydraulic fracturing. It utilizes the stacking of thousands waveform to enhance signal-to-noise ratio of weak events. For surface monitoring, the diffraction stacking method is suffered from polarity reverse among receivers due to radiation pattern of moment source. Joint determination of location and source mechanism has been proposed to overcome the polarity problem but needs significantly increased computational calculations. As an effective method to recover source moment tensor, time reversal imaging based on wave equation can locate microseismic event by using interferometry on the image to extract source position. However, the time reversal imaging is very time consuming compared to the diffraction stacking location because of wave-equation simulation.In this study, we compare the image from diffraction stacking and time reversal imaging to check if the diffraction stacking can obtain similar moment tensor as time reversal imaging. We found that image produced by taking the largest imaging value at each point along time axis does not exhibit the radiation pattern, while with the same level of calculation efficiency, the image produced for each trial origin time can generate radiation pattern similar to time reversal imaging procedure. Thus it is potential to locate the source position by the diffraction stacking method for general moment tensor sources.

Acoustic wavefield evolution as a function of source location perturbation

KAUST Repository

Alkhalifah, Tariq Ali

2010-12-01

The wavefield is typically simulated for seismic exploration applications through solving the wave equation for a specific seismic source location. The direct relation between the form (or shape) of the wavefield and the source location can provide insights useful for velocity estimation and interpolation. As a result, I derive partial differential equations that relate changes in the wavefield shape to perturbations in the source location, especially along the Earth\\'s surface. These partial differential equations have the same structure as the wave equation with a source function that depends on the background (original source) wavefield. The similarity in form implies that we can use familiar numerical methods to solve the perturbation equations, including finite difference and downward continuation. In fact, we can use the same Green\\'s function to solve the wave equation and its source perturbations by simply incorporating source functions derived from the background field. The solutions of the perturbation equations represent the coefficients of a Taylor\\'s series type expansion of the wavefield as a function of source location. As a result, we can speed up the wavefield calculation as we approximate the wavefield shape for sources in the vicinity of the original source. The new formula introduces changes to the background wavefield only in the presence of lateral velocity variation or in general terms velocity variations in the perturbation direction. The approach is demonstrated on the smoothed Marmousi model.

Loading functions for assessment of water pollution from nonpoint sources

International Nuclear Information System (INIS)

McElroy, A.D.; Chiu, S.Y.; Nebgen, J.W.; Aleti, A.; Bennett, F.W.

1976-05-01

Methods for evaluating the quantity of water pollutants generated from nonpoint sources including agriculture, silviculture, construction, mining, runoff from urban areas and rural roads, and terrestrial disposal are developed and compiled for use in water quality planning. The loading functions, plus in some instances emission values, permit calculation of nonpoint source pollutants from available data and information. Natural background was considered to be a source and loading functions were presented to estimate natural or background loads of pollutants. Loading functions/values are presented for average conditions, i.e., annual average loads expressed as metric tons/hectare/year (tons/acre/year). Procedures for estimating seasonal or 30-day maximum and minimum loads are also presented. In addition, a wide variety of required data inputs to loading functions, and delineation of sources of additional information are included in the report. The report also presents an evaluation of limitations and constraints of various methodologies which will enable the user to employ the functions realistically

Dependence of Au- production upon the target work function in a plasma-sputter-type negative ion source

International Nuclear Information System (INIS)

Okabe, Yushirou; Sasao, Mamiko; Fujita, Junji; Yamaoka, Hitoshi; Wada, Motoi.

1991-01-01

A method to measure the work function of the target surface in a plasma-sputter-type negative ion source has been developed. The method can determine the work function by measuring the photoelectric current induced by two lasers (He-Ne, Ar + laser). The dependence of Au - production upon the work function of the target surface in the ion source was studied using this method. The time variation of the target work function and Au - production rate were measured during the cesium coverage decrease due to the plasma ion sputtering. The observed minimum work function of a cesiated gold surface in an Ar plasma was 1.3 eV. At the same time, the negative ion production rate (Au - current/target current) took the maximum value. The negative ion production rate indicated the same dependence on the incident ion energy as that of the sputtering rate when the work function was constant. (author)

Understanding handpump sustainability: Determinants of rural water source functionality in the Greater Afram Plains region of Ghana.

Science.gov (United States)

Fisher, Michael B; Shields, Katherine F; Chan, Terence U; Christenson, Elizabeth; Cronk, Ryan D; Leker, Hannah; Samani, Destina; Apoya, Patrick; Lutz, Alexandra; Bartram, Jamie

2015-10-01

Safe drinking water is critical to human health and development. In rural sub-Saharan Africa, most improved water sources are boreholes with handpumps; studies suggest that up to one third of these handpumps are nonfunctional at any given time. This work presents findings from a secondary analysis of cross-sectional data from 1509 water sources in 570 communities in the rural Greater Afram Plains (GAP) region of Ghana; one of the largest studies of its kind. 79.4% of enumerated water sources were functional when visited; in multivariable regressions, functionality depended on source age, management, tariff collection, the number of other sources in the community, and the district. A Bayesian network (BN) model developed using the same data set found strong dependencies of functionality on implementer, pump type, management, and the availability of tools, with synergistic effects from management determinants on functionality, increasing the likelihood of a source being functional from a baseline of 72% to more than 97% with optimal management and available tools. We suggest that functionality may be a dynamic equilibrium between regular breakdowns and repairs, with management a key determinant of repair rate. Management variables may interact synergistically in ways better captured by BN analysis than by logistic regressions. These qualitative findings may prove generalizable beyond the study area, and may offer new approaches to understanding and increasing handpump functionality and safe water access.

Identification of a time-varying point source in a system of two coupled linear diffusion-advection- reaction equations: application to surface water pollution

International Nuclear Information System (INIS)

Hamdi, Adel

2009-01-01

This paper deals with the identification of a point source (localization of its position and recovering the history of its time-varying intensity function) that constitutes the right-hand side of the first equation in a system of two coupled 1D linear transport equations. Assuming that the source intensity function vanishes before reaching the final control time, we prove the identifiability of the sought point source from recording the state relative to the second coupled transport equation at two observation points framing the source region. Note that at least one of the two observation points should be strategic. We establish an identification method that uses these records to identify the source position as the root of a continuous and strictly monotonic function. Whereas the source intensity function is recovered using a recursive formula without any need of an iterative process. Some numerical experiments on a variant of the surface water pollution BOD–OD coupled model are presented

A method for untriggered time-dependent searches for multiple flares from neutrino point sources

International Nuclear Information System (INIS)

Gora, D.; Bernardini, E.; Cruz Silva, A.H.

2011-04-01

A method for a time-dependent search for flaring astrophysical sources which can be potentially detected by large neutrino experiments is presented. The method uses a time-clustering algorithm combined with an unbinned likelihood procedure. By including in the likelihood function a signal term which describes the contribution of many small clusters of signal-like events, this method provides an effective way for looking for weak neutrino flares over different time-scales. The method is sensitive to an overall excess of events distributed over several flares which are not individually detectable. For standard cases (one flare) the discovery potential of the method is worse than a standard time-dependent point source analysis with unknown duration of the flare by a factor depending on the signal-to-background level. However, for flares sufficiently shorter than the total observation period, the method is more sensitive than a time-integrated analysis. (orig.)

A method for untriggered time-dependent searches for multiple flares from neutrino point sources

Energy Technology Data Exchange (ETDEWEB)

Gora, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Institute of Nuclear Physics PAN, Cracow (Poland); Bernardini, E.; Cruz Silva, A.H. [Institute of Nuclear Physics PAN, Cracow (Poland)

2011-04-15

A method for a time-dependent search for flaring astrophysical sources which can be potentially detected by large neutrino experiments is presented. The method uses a time-clustering algorithm combined with an unbinned likelihood procedure. By including in the likelihood function a signal term which describes the contribution of many small clusters of signal-like events, this method provides an effective way for looking for weak neutrino flares over different time-scales. The method is sensitive to an overall excess of events distributed over several flares which are not individually detectable. For standard cases (one flare) the discovery potential of the method is worse than a standard time-dependent point source analysis with unknown duration of the flare by a factor depending on the signal-to-background level. However, for flares sufficiently shorter than the total observation period, the method is more sensitive than a time-integrated analysis. (orig.)

Source-Free Exchange-Correlation Magnetic Fields in Density Functional Theory.

Science.gov (United States)

Sharma, S; Gross, E K U; Sanna, A; Dewhurst, J K

2018-03-13

Spin-dependent exchange-correlation energy functionals in use today depend on the charge density and the magnetization density: E xc [ρ, m]. However, it is also correct to define the functional in terms of the curl of m for physical external fields: E xc [ρ,∇ × m]. The exchange-correlation magnetic field, B xc , then becomes source-free. We study this variation of the theory by uniquely removing the source term from local and generalized gradient approximations to the functional. By doing so, the total Kohn-Sham moments are improved for a wide range of materials for both functionals. Significantly, the moments for the pnictides are now in good agreement with experiment. This source-free method is simple to implement in all existing density functional theory codes.

Time-dependent source model of the Lusi mud volcano

Science.gov (United States)

Shirzaei, M.; Rudolph, M. L.; Manga, M.

2014-12-01

The Lusi mud eruption, near Sidoarjo, East Java, Indonesia, began erupting in May 2006 and continues to erupt today. Previous analyses of surface deformation data suggested an exponential decay of the pressure in the mud source, but did not constrain the geometry and evolution of the source(s) from which the erupting mud and fluids ascend. To understand the spatiotemporal evolution of the mud and fluid sources, we apply a time-dependent inversion scheme to a densely populated InSAR time series of the surface deformation at Lusi. The SAR data set includes 50 images acquired on 3 overlapping tracks of the ALOS L-band satellite between May 2006 and April 2011. Following multitemporal analysis of this data set, the obtained surface deformation time series is inverted in a time-dependent framework to solve for the volume changes of distributed point sources in the subsurface. The volume change distribution resulting from this modeling scheme shows two zones of high volume change underneath Lusi at 0.5-1.5 km and 4-5.5km depth as well as another shallow zone, 7 km to the west of Lusi and underneath the Wunut gas field. The cumulative volume change within the shallow source beneath Lusi is ~2-4 times larger than that of the deep source, whilst the ratio of the Lusi shallow source volume change to that of Wunut gas field is ~1. This observation and model suggest that the Lusi shallow source played a key role in eruption process and mud supply, but that additional fluids do ascend from depths >4 km on eruptive timescales.

Separation of non-stationary multi-source sound field based on the interpolated time-domain equivalent source method

Science.gov (United States)

Bi, Chuan-Xing; Geng, Lin; Zhang, Xiao-Zheng

2016-05-01

In the sound field with multiple non-stationary sources, the measured pressure is the sum of the pressures generated by all sources, and thus cannot be used directly for studying the vibration and sound radiation characteristics of every source alone. This paper proposes a separation model based on the interpolated time-domain equivalent source method (ITDESM) to separate the pressure field belonging to every source from the non-stationary multi-source sound field. In the proposed method, ITDESM is first extended to establish the relationship between the mixed time-dependent pressure and all the equivalent sources distributed on every source with known location and geometry information, and all the equivalent source strengths at each time step are solved by an iterative solving process; then, the corresponding equivalent source strengths of one interested source are used to calculate the pressure field generated by that source alone. Numerical simulation of two baffled circular pistons demonstrates that the proposed method can be effective in separating the non-stationary pressure generated by every source alone in both time and space domains. An experiment with two speakers in a semi-anechoic chamber further evidences the effectiveness of the proposed method.

[The Performance Analysis for Lighting Sources in Highway Tunnel Based on Visual Function].

Science.gov (United States)

Yang, Yong; Han, Wen-yuan; Yan, Ming; Jiang, Hai-feng; Zhu, Li-wei

2015-10-01

Under the condition of mesopic vision, the spectral luminous efficiency function is shown as a series of curves. Its peak wavelength and intensity are affected by light spectrum, background brightness and other aspects. The impact of light source to lighting visibility could not be carried out via a single optical parametric characterization. The reaction time of visual cognition is regard as evaluating indexes in this experiment. Under the condition of different speed and luminous environment, testing visual cognition based on vision function method. The light sources include high pressure sodium, electrodeless fluorescent lamp and white LED with three kinds of color temperature (the range of color temperature is from 1 958 to 5 537 K). The background brightness value is used for basic section of highway tunnel illumination and general outdoor illumination, its range is between 1 and 5 cd x m(-)2. All values are in the scope of mesopic vision. Test results show that: under the same condition of speed and luminance, the reaction time of visual cognition that corresponding to high color temperature of light source is shorter than it corresponding to low color temperature; the reaction time corresponding to visual target in high speed is shorter than it in low speed. At the end moment, however, the visual angle of target in observer's visual field that corresponding to low speed was larger than it corresponding to high speed. Based on MOVE model, calculating the equivalent luminance of human mesopic vision, which is on condition of different emission spectrum and background brightness that formed by test lighting sources. Compared with photopic vision result, the standard deviation (CV) of time-reaction curve corresponding to equivalent brightness of mesopic vision is smaller. Under the condition of mesopic vision, the discrepancy between equivalent brightness of different lighting source and photopic vision, that is one of the main reasons for causing the

Compilation of Instantaneous Source Functions for Varying ...

African Journals Online (AJOL)

Compilation of Instantaneous Source Functions for Varying Architecture of a Layered Reservoir with Mixed Boundaries and Horizontal Well Completion Part IV: Normal and Inverted Letter 'h' and 'H' Architecture.

Multiple time-reversed guide-sources in shallow water

Science.gov (United States)

Gaumond, Charles F.; Fromm, David M.; Lingevitch, Joseph F.; Gauss, Roger C.; Menis, Richard

2003-10-01

Detection in a monostatic, broadband, active sonar system in shallow water is degraded by propagation-induced spreading. The detection improvement from multiple spatially separated guide sources (GSs) is presented as a method to mitigate this degradation. The improvement of detection by using information in a set of one-way transmissions from a variety of positions is shown using sea data. The experimental area is south of the Hudson Canyon off the coast of New Jersey. The data were taken using five elements of a time-reversing VLA. The five elements were contiguous and at midwater depth. The target and guide source was an echo repeater positioned at various ranges and at middepth. The transmitted signals were 3.0- to 3.5-kHz LFMs. The data are analyzed to show the amount of information present in the collection, a baseline probability of detection (PD) not using the collection of GS signals, the improvement in PD from the use of various sets of GS signals. The dependence of the improvement as a function of range is also shown. [The authors acknowledge support from Dr. Jeffrey Simmen, ONR321OS, and the chief scientist Dr. Charles Holland. Work supported by ONR.

Modeling the NPE with finite sources and empirical Green`s functions

Energy Technology Data Exchange (ETDEWEB)

Hutchings, L.; Kasameyer, P.; Goldstein, P. [Lawrence Livermore National Lab., CA (United States)] [and others

1994-12-31

In order to better understand the source characteristics of both nuclear and chemical explosions for purposes of discrimination, we have modeled the NPE chemical explosion as a finite source and with empirical Green`s functions. Seismograms are synthesized at four sties to test the validity of source models. We use a smaller chemical explosion detonated in the vicinity of the working point to obtain empirical Green`s functions. Empirical Green`s functions contain all the linear information of the geology along the propagation path and recording site, which are identical for chemical or nuclear explosions, and therefore reduce the variability in modeling the source of the larger event. We further constrain the solution to have the overall source duration obtained from point-source deconvolution results. In modeling the source, we consider both an elastic source on a spherical surface and an inelastic expanding spherical volume source. We found that the spherical volume solution provides better fits to observed seismograms. The potential to identify secondary sources was examined, but the resolution is too poor to be definitive.

Time-Dependent Moment Tensors of the First Four Source Physics Experiments (SPE) Explosions

Science.gov (United States)

Yang, X.

2015-12-01

We use mainly vertical-component geophone data within 2 km from the epicenter to invert for time-dependent moment tensors of the first four SPE explosions: SPE-1, SPE-2, SPE-3 and SPE-4Prime. We employ a one-dimensional (1D) velocity model developed from P- and Rg-wave travel times for Green's function calculations. The attenuation structure of the model is developed from P- and Rg-wave amplitudes. We select data for the inversion based on the criterion that they show consistent travel times and amplitude behavior as those predicted by the 1D model. Due to limited azimuthal coverage of the sources and the mostly vertical-component-only nature of the dataset, only long-period, diagonal components of the moment tensors are well constrained. Nevertheless, the moment tensors, particularly their isotropic components, provide reasonable estimates of the long-period source amplitudes as well as estimates of corner frequencies, albeit with larger uncertainties. The estimated corner frequencies, however, are consistent with estimates from ratios of seismogram spectra from different explosions. These long-period source amplitudes and corner frequencies cannot be fit by classical P-wave explosion source models. The results motivate the development of new P-wave source models suitable for these chemical explosions. To that end, we fit inverted moment-tensor spectra by modifying the classical explosion model using regressions of estimated source parameters. Although the number of data points used in the regression is small, the approach suggests a way for the new-model development when more data are collected.

Compilation of Instantaneous Source Functions for Varying ...

African Journals Online (AJOL)

Compilation of Instantaneous Source Functions for Varying Architecture of a Layered Reservoir with Mixed Boundaries and Horizontal Well Completion Part III: B-Shaped Architecture with Vertical Well in the Upper Layer.

A single-sided homogeneous Green's function representation for holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval

Science.gov (United States)

Wapenaar, Kees; Thorbecke, Jan; van der Neut, Joost

2016-04-01

Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the right-hand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate single-sided representation of the homogeneous Green's function. This single-sided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the first-order scattering approximation breaks down.

Impact parameter and source selected correlation functions with a 4π multidetector

International Nuclear Information System (INIS)

Gourio, D.; Reposeur, T.; Assenard, M.; Germain, M.; Ardouin, D.; Eudes, P.; Lautridou, P.; Laville, J.L.; Lebrun, C.; Metivier, V.

1997-01-01

For the first time in the domain of (light charged) particle interferometry in nuclear physics, a complete study of proton an deuteron correlation functions is presented with both impact parameter and emission source selections. The correlations were determined for the system 129 Xe + nat Sn at 45 and 50 AMeV using the 4π multidetector INDRA at GANIL as an event selector as well as a particle correlator. Very short emission times are found for all the selections indicating possible contributions from a fast and preequilibrium process. (author)

Collective Odor Source Estimation and Search in Time-Variant Airflow Environments Using Mobile Robots

Science.gov (United States)

Meng, Qing-Hao; Yang, Wei-Xing; Wang, Yang; Zeng, Ming

2011-01-01

This paper addresses the collective odor source localization (OSL) problem in a time-varying airflow environment using mobile robots. A novel OSL methodology which combines odor-source probability estimation and multiple robots’ search is proposed. The estimation phase consists of two steps: firstly, the separate probability-distribution map of odor source is estimated via Bayesian rules and fuzzy inference based on a single robot’s detection events; secondly, the separate maps estimated by different robots at different times are fused into a combined map by way of distance based superposition. The multi-robot search behaviors are coordinated via a particle swarm optimization algorithm, where the estimated odor-source probability distribution is used to express the fitness functions. In the process of OSL, the estimation phase provides the prior knowledge for the searching while the searching verifies the estimation results, and both phases are implemented iteratively. The results of simulations for large-scale advection–diffusion plume environments and experiments using real robots in an indoor airflow environment validate the feasibility and robustness of the proposed OSL method. PMID:22346650

A Derivation of Source-based Kinetics Equation with Time Dependent Fission Kernel for Reactor Transient Analyses

International Nuclear Information System (INIS)

Kim, Song Hyun; Woo, Myeong Hyun; Shin, Chang Ho; Pyeon, Cheol Ho

2015-01-01

In this study, a new balance equation to overcome the problems generated by the previous methods is proposed using source-based balance equation. And then, a simple problem is analyzed with the proposed method. In this study, a source-based balance equation with the time dependent fission kernel was derived to simplify the kinetics equation. To analyze the partial variations of reactor characteristics, two representative methods were introduced in previous studies; (1) quasi-statics method and (2) multipoint technique. The main idea of quasistatics method is to use a low-order approximation for large integration times. To realize the quasi-statics method, first, time dependent flux is separated into the shape and amplitude functions, and shape function is calculated. It is noted that the method has a good accuracy; however, it can be expensive as a calculation cost aspect because the shape function should be fully recalculated to obtain accurate results. To improve the calculation efficiency, multipoint method was proposed. The multipoint method is based on the classic kinetics equation with using Green's function to analyze the flight probability from region r' to r. Those previous methods have been used to analyze the reactor kinetics analysis; however, the previous methods can have some limitations. First, three group variables (r g , E g , t g ) should be considered to solve the time dependent balance equation. This leads a big limitation to apply large system problem with good accuracy. Second, the energy group neutrons should be used to analyze reactor kinetics problems. In time dependent problem, neutron energy distribution can be changed at different time. It can affect the change of the group cross section; therefore, it can lead the accuracy problem. Third, the neutrons in a space-time region continually affect the other space-time regions; however, it is not properly considered in the previous method. Using birth history of the neutron sources

Watching proteins function with time-resolved x-ray crystallography

Science.gov (United States)

Šrajer, Vukica; Schmidt, Marius

2017-09-01

Macromolecular crystallography was immensely successful in the last two decades. To a large degree this success resulted from use of powerful third generation synchrotron x-ray sources. An expansive database of more than 100 000 protein structures, of which many were determined at resolution better than 2 Å, is available today. With this achievement, the spotlight in structural biology is shifting from determination of static structures to elucidating dynamic aspects of protein function. A powerful tool for addressing these aspects is time-resolved crystallography, where a genuine biological function is triggered in the crystal with a goal of capturing molecules in action and determining protein kinetics and structures of intermediates (Schmidt et al 2005a Methods Mol. Biol. 305 115-54, Schmidt 2008 Ultrashort Laser Pulses in Biology and Medicine (Berlin: Springer) pp 201-41, Neutze and Moffat 2012 Curr. Opin. Struct. Biol. 22 651-9, Šrajer 2014 The Future of Dynamic Structural Science (Berlin: Springer) pp 237-51). In this approach, short and intense x-ray pulses are used to probe intermediates in real time and at room temperature, in an ongoing reaction that is initiated synchronously and rapidly in the crystal. Time-resolved macromolecular crystallography with 100 ps time resolution at synchrotron x-ray sources is in its mature phase today, particularly for studies of reversible, light-initiated reactions. The advent of the new free electron lasers for hard x-rays (XFELs; 5-20 keV), which provide exceptionally intense, femtosecond x-ray pulses, marks a new frontier for time-resolved crystallography. The exploration of ultra-fast events becomes possible in high-resolution structural detail, on sub-picosecond time scales (Tenboer et al 2014 Science 346 1242-6, Barends et al 2015 Science 350 445-50, Pande et al 2016 Science 352 725-9). We review here state-of-the-art time-resolved crystallographic experiments both at synchrotrons and XFELs. We also outline

Cross-functional Sourcing Teams – A Purchasing and Supply Management Literature Review

DEFF Research Database (Denmark)

Hansen, Anders Peder Lysholm

2014-01-01

This paper presents a systematic literature review of scientific papers on cross-functional sourcing teams in top journals within Purchasing and Supply Management. The review identifies four common research topics within the field; Determining factors of sourcing team success, Performance...... management/goals of sourcing teams, Behavior and decisions in sourcing teams and Involvement of purchasing in sourcing teams. Further research on Performance Management and how to create a holistic, teams based perspective in cross-functional sourcing teams is suggested....

TEMPS, 1-Group Time-Dependent Pulsed Source Neutron Transport

International Nuclear Information System (INIS)

Ganapol, B.D.

1988-01-01

1 - Description of program or function: TEMPS numerically determines the scalar flux as given by the one-group neutron transport equation with a pulsed source in an infinite medium. Standard plane, point, and line sources are considered as well as a volume source in the negative half-space in plane geometry. The angular distribution of emitted neutrons can either be isotropic or mono-directional (beam) in plane geometry and isotropic in spherical and cylindrical geometry. A general anisotropic scattering Kernel represented in terms of Legendre polynomials can be accommodated with a time- dependent number of secondaries given by c(t)=c 0 (t/t 0 ) β , where β is greater than -1 and less than infinity. TEMPS is designed to provide the flux to a high degree of accuracy (4-5 digits) for use as a benchmark to which results from other numerical solutions or approximations can be compared. 2 - Method of solution: A semi-analytic Method of solution is followed. The main feature of this approach is that no discretization of the transport or scattering operators is employed. The numerical solution involves the evaluation of an analytical representation of the solution by standard numerical techniques. The transport equation is first reformulated in terms of multiple collisions with the flux represented by an infinite series of collisional components. Each component is then represented by an orthogonal Legendre series expansion in the variable x/t where the distance x and time t are measured in terms of mean free path and mean free time, respectively. The moments in the Legendre reconstruction are found from an algebraic recursion relation obtained from Legendre expansion in the direction variable mu. The multiple collision series is evaluated first to a prescribed relative error determined by the number of digits desired in the scalar flux. If the Legendre series fails to converge in the plane or point source case, an accelerative transformation, based on removing the

3D Multi‐source Least‐squares Reverse Time Migration

KAUST Repository

Dai, Wei; Boonyasiriwat, Chaiwoot; Schuster, Gerard T.

2010-01-01

: random time shift, random source polarity and random source location selected from a pre‐designed table. Numerical tests for the 3D SEG/EAGE Overthrust model show that multi‐source LSRTM can suppress migration artifacts in the migration image and remove

Source-based neurofeedback methods using EEG recordings: training altered brain activity in a functional brain source derived from blind source separation

Science.gov (United States)

White, David J.; Congedo, Marco; Ciorciari, Joseph

2014-01-01

A developing literature explores the use of neurofeedback in the treatment of a range of clinical conditions, particularly ADHD and epilepsy, whilst neurofeedback also provides an experimental tool for studying the functional significance of endogenous brain activity. A critical component of any neurofeedback method is the underlying physiological signal which forms the basis for the feedback. While the past decade has seen the emergence of fMRI-based protocols training spatially confined BOLD activity, traditional neurofeedback has utilized a small number of electrode sites on the scalp. As scalp EEG at a given electrode site reflects a linear mixture of activity from multiple brain sources and artifacts, efforts to successfully acquire some level of control over the signal may be confounded by these extraneous sources. Further, in the event of successful training, these traditional neurofeedback methods are likely influencing multiple brain regions and processes. The present work describes the use of source-based signal processing methods in EEG neurofeedback. The feasibility and potential utility of such methods were explored in an experiment training increased theta oscillatory activity in a source derived from Blind Source Separation (BSS) of EEG data obtained during completion of a complex cognitive task (spatial navigation). Learned increases in theta activity were observed in two of the four participants to complete 20 sessions of neurofeedback targeting this individually defined functional brain source. Source-based EEG neurofeedback methods using BSS may offer important advantages over traditional neurofeedback, by targeting the desired physiological signal in a more functionally and spatially specific manner. Having provided preliminary evidence of the feasibility of these methods, future work may study a range of clinically and experimentally relevant brain processes where individual brain sources may be targeted by source-based EEG neurofeedback. PMID

Wind wave source functions in opposing seas

KAUST Repository

Langodan, Sabique; Cavaleri, Luigi; Viswanadhapalli, Yesubabu; Hoteit, Ibrahim

2015-01-01

that the currently available wave model source functions may not properly represent the evolution of the local fields that appear to be characterized by a less effective wind input and an enhanced white-capping. We propose and test a possible simple solution

A Derivation of Source-based Kinetics Equation with Time Dependent Fission Kernel for Reactor Transient Analyses

Energy Technology Data Exchange (ETDEWEB)

Kim, Song Hyun; Woo, Myeong Hyun; Shin, Chang Ho [Hanyang University, Seoul (Korea, Republic of); Pyeon, Cheol Ho [Kyoto University, Osaka (Japan)

2015-10-15

In this study, a new balance equation to overcome the problems generated by the previous methods is proposed using source-based balance equation. And then, a simple problem is analyzed with the proposed method. In this study, a source-based balance equation with the time dependent fission kernel was derived to simplify the kinetics equation. To analyze the partial variations of reactor characteristics, two representative methods were introduced in previous studies; (1) quasi-statics method and (2) multipoint technique. The main idea of quasistatics method is to use a low-order approximation for large integration times. To realize the quasi-statics method, first, time dependent flux is separated into the shape and amplitude functions, and shape function is calculated. It is noted that the method has a good accuracy; however, it can be expensive as a calculation cost aspect because the shape function should be fully recalculated to obtain accurate results. To improve the calculation efficiency, multipoint method was proposed. The multipoint method is based on the classic kinetics equation with using Green's function to analyze the flight probability from region r' to r. Those previous methods have been used to analyze the reactor kinetics analysis; however, the previous methods can have some limitations. First, three group variables (r{sub g}, E{sub g}, t{sub g}) should be considered to solve the time dependent balance equation. This leads a big limitation to apply large system problem with good accuracy. Second, the energy group neutrons should be used to analyze reactor kinetics problems. In time dependent problem, neutron energy distribution can be changed at different time. It can affect the change of the group cross section; therefore, it can lead the accuracy problem. Third, the neutrons in a space-time region continually affect the other space-time regions; however, it is not properly considered in the previous method. Using birth history of the

An ion source for radiofrequency-pulsed glow discharge time-of-flight mass spectrometry

International Nuclear Information System (INIS)

González Gago, C.; Lobo, L.; Pisonero, J.; Bordel, N.; Pereiro, R.; Sanz-Medel, A.

2012-01-01

A Grimm-type glow discharge (GD) has been designed and constructed as an ion source for pulsed radiofrequency GD spectrometry when coupled to an orthogonal time of flight mass spectrometer. Pulse shapes of argon species and analytes were studied as a function of the discharge conditions using a new in-house ion source (UNIOVI GD) and results have been compared with a previous design (PROTOTYPE GD). Different behavior and shapes of the pulse profiles have been observed for the two sources evaluated, particularly for the plasma gas ionic species detected. In the more analytically relevant region (afterglow), signals for 40 Ar + with this new design were negligible, while maximum intensity was reached earlier in time for 41 (ArH) + than when using the PROTOTYPE GD. Moreover, while maximum 40 Ar + signals measured along the pulse period were similar in both sources, 41 (ArH) + and 80 (Ar 2 ) + signals tend to be noticeable higher using the PROTOTYPE chamber. The UNIOVI GD design was shown to be adequate for sensitive direct analysis of solid samples, offering linear calibration graphs and good crater shapes. Limits of detection (LODs) are in the same order of magnitude for both sources, although the UNIOVI source provides slightly better LODs for those analytes with masses slightly higher than 41 (ArH) + . - Highlights: ► A new RF-pulsed GD ion source (UNIOVI GD) coupled to TOFMS has been characterized. ► Linear calibration graphs and LODs in the low ppm range are achieved. ► Craters with flat bottoms and vertical walls are obtained. ► UNIOVI source can be easily cleaned as it does not require flow tube. ► UNIOVI GD has a simple design and thus its manufacture is easy and cheap.

Advanced RF and microwave functions based on an integrated optical frequency comb source.

Science.gov (United States)

Xu, Xingyuan; Wu, Jiayang; Nguyen, Thach G; Shoeiby, Mehrdad; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

2018-02-05

We demonstrate advanced transversal radio frequency (RF) and microwave functions based on a Kerr optical comb source generated by an integrated micro-ring resonator. We achieve extremely high performance for an optical true time delay aimed at tunable phased array antenna applications, as well as reconfigurable microwave photonic filters. Our results agree well with theory. We show that our true time delay would yield a phased array antenna with features that include high angular resolution and a wide range of beam steering angles, while the microwave photonic filters feature high Q factors, wideband tunability, and highly reconfigurable filtering shapes. These results show that our approach is a competitive solution to implementing reconfigurable, high performance and potentially low cost RF and microwave signal processing functions for applications including radar and communication systems.

Watching proteins function with time-resolved x-ray crystallography

Energy Technology Data Exchange (ETDEWEB)

Šrajer, Vukica; Schmidt, Marius

2017-08-22

Macromolecular crystallography was immensely successful in the last two decades. To a large degree this success resulted from use of powerful third generation synchrotron x-ray sources. An expansive database of more than 100 000 protein structures, of which many were determined at resolution better than 2 Å, is available today. With this achievement, the spotlight in structural biology is shifting from determination of static structures to elucidating dynamic aspects of protein function. A powerful tool for addressing these aspects is time-resolved crystallography, where a genuine biological function is triggered in the crystal with a goal of capturing molecules in action and determining protein kinetics and structures of intermediates (Schmidt et al 2005a Methods Mol. Biol. 305 115–54, Schmidt 2008 Ultrashort Laser Pulses in Biology and Medicine (Berlin: Springer) pp 201–41, Neutze and Moffat 2012 Curr. Opin. Struct. Biol. 22 651–9, Šrajer 2014 The Future of Dynamic Structural Science (Berlin: Springer) pp 237–51). In this approach, short and intense x-ray pulses are used to probe intermediates in real time and at room temperature, in an ongoing reaction that is initiated synchronously and rapidly in the crystal. Time-resolved macromolecular crystallography with 100 ps time resolution at synchrotron x-ray sources is in its mature phase today, particularly for studies of reversible, light-initiated reactions. The advent of the new free electron lasers for hard x-rays (XFELs; 5–20 keV), which provide exceptionally intense, femtosecond x-ray pulses, marks a new frontier for time-resolved crystallography. The exploration of ultra-fast events becomes possible in high-resolution structural detail, on sub-picosecond time scales (Tenboer et al 2014 Science 346 1242–6, Barends et al 2015 Science 350 445–50, Pande et al 2016 Science 352 725–9). We review here state-of-the-art time-resolved crystallographic experiments both at synchrotrons and XFELs. We

Watching proteins function with time-resolved x-ray crystallography

International Nuclear Information System (INIS)

Šrajer, Vukica; Schmidt, Marius

2017-01-01

Macromolecular crystallography was immensely successful in the last two decades. To a large degree this success resulted from use of powerful third generation synchrotron x-ray sources. An expansive database of more than 100 000 protein structures, of which many were determined at resolution better than 2 Å, is available today. With this achievement, the spotlight in structural biology is shifting from determination of static structures to elucidating dynamic aspects of protein function. A powerful tool for addressing these aspects is time-resolved crystallography, where a genuine biological function is triggered in the crystal with a goal of capturing molecules in action and determining protein kinetics and structures of intermediates (Schmidt et al 2005a Methods Mol. Biol . 305 115–54, Schmidt 2008 Ultrashort Laser Pulses in Biology and Medicine (Berlin: Springer) pp 201–41, Neutze and Moffat 2012 Curr. Opin. Struct. Biol . 22 651–9, Šrajer 2014 The Future of Dynamic Structural Science (Berlin: Springer) pp 237–51). In this approach, short and intense x-ray pulses are used to probe intermediates in real time and at room temperature, in an ongoing reaction that is initiated synchronously and rapidly in the crystal. Time-resolved macromolecular crystallography with 100 ps time resolution at synchrotron x-ray sources is in its mature phase today, particularly for studies of reversible, light-initiated reactions. The advent of the new free electron lasers for hard x-rays (XFELs; 5–20 keV), which provide exceptionally intense, femtosecond x-ray pulses, marks a new frontier for time-resolved crystallography. The exploration of ultra-fast events becomes possible in high-resolution structural detail, on sub-picosecond time scales (Tenboer et al 2014 Science 346 1242–6, Barends et al 2015 Science 350 445–50, Pande et al 2016 Science 352 725–9). We review here state-of-the-art time-resolved crystallographic experiments both at synchrotrons and XFELs

Loading functions for assessment of water pollution from nonpoint sources. Final report

International Nuclear Information System (INIS)

McElroy, A.D.; Chiu, S.Y.; Nebgen, J.W.; Aleti, A.; Bennett, F.W.

1976-05-01

Methods for evaluating the quantity of water pollutants generated from nonpoint sources including agriculture, silviculture, construction, mining, runoff from urban areas and rural roads, and terrestrial disposal are developed and compiled for use in water quality planning. The loading functions, plus in some instances emission values, permit calculation of nonpoint source pollutants from available data and information. Natural background was considered to be a source and loading functions were presented to estimate natural or background loads of pollutants. Loading functions/values are presented for average conditions, i.e., annual average loads expressed as metric tons/hectare/year (tons/acre/year). Procedures for estimating seasonal or 30-day maximum and minimum loads are also presented. In addition, a wide variety of required data inputs to loading functions, and delineation of sources of additional information are included in the report. The report also presents an evaluation of limitations and constraints of various methodologies which will enable the user to employ the functions realistically

Time-frequency analysis and harmonic Gaussian functions

International Nuclear Information System (INIS)

Ranaivoson, R.T.R; Raoelina Andriambololona; Hanitriarivo, R.

2013-01-01

A method for time-frequency analysis is given. The approach utilizes properties of Gaussian distribution, properties of Hermite polynomials and Fourier analysis. We begin by the definitions of a set of functions called Harmonic Gaussian Functions. Then these functions are used to define a set of transformations, noted Τ n , which associate to a function ψ, of the time variable t, a set of functions Ψ n which depend on time, frequency and frequency (or time) standard deviation. Some properties of the transformations Τ n and the functions Ψ n are given. It is proved in particular that the square of the modulus of each function Ψ n can be interpreted as a representation of the energy distribution of the signal, represented by the function ψ, in the time-frequency plane for a given value of the frequency (or time) standard deviation. It is also shown that the function ψ can be recovered from the functions Ψ n .

Nonadiabatic Dynamics in Single-Electron Tunneling Devices with Time-Dependent Density-Functional Theory

Science.gov (United States)

Dittmann, Niklas; Splettstoesser, Janine; Helbig, Nicole

2018-04-01

We simulate the dynamics of a single-electron source, modeled as a quantum dot with on-site Coulomb interaction and tunnel coupling to an adjacent lead in time-dependent density-functional theory. Based on this system, we develop a time-nonlocal exchange-correlation potential by exploiting analogies with quantum-transport theory. The time nonlocality manifests itself in a dynamical potential step. We explicitly link the time evolution of the dynamical step to physical relaxation timescales of the electron dynamics. Finally, we discuss prospects for simulations of larger mesoscopic systems.

Acoustic wavefield evolution as a function of source location perturbation

KAUST Repository

Alkhalifah, Tariq Ali

2010-01-01

differential equations have the same structure as the wave equation with a source function that depends on the background (original source) wavefield. The similarity in form implies that we can use familiar numerical methods to solve the perturbation equations

Investigation of the ion beam of the Titan source by the time-of-flight mass spectrometer

International Nuclear Information System (INIS)

Bugaev, A.S.; Gushenets, V.V.; Nikolaev, A.G.; Yushkov, G.Yu.

2000-01-01

The Titan ion source generates wide-aperture beams of both gaseous and metal ions of various materials. The above possibility is realized on the account of combining two types of arc discharge with cold cathodes in the source discharge system. The vacuum arc, initiated between the cathode accomplished from the ion forming material, and hollow anode, is used for obtaining the metal ions. The pinch-effect low pressure arc discharge, ignited on the same hollow anode, is used for obtaining gaseous ions. The composition of ion beams, generated by the Titan source through the specially designed time-of-flight spectrometer, is studied. The spectrometer design and principle pf operation are presented. The physical peculiarities of the source functioning, influencing the ion beam composition, are discussed [ru

Real-time monitoring and massive inversion of source parameters of very long period seismic signals: An application to Stromboli Volcano, Italy

Science.gov (United States)

Auger, E.; D'Auria, L.; Martini, M.; Chouet, B.; Dawson, P.

2006-01-01

We present a comprehensive processing tool for the real-time analysis of the source mechanism of very long period (VLP) seismic data based on waveform inversions performed in the frequency domain for a point source. A search for the source providing the best-fitting solution is conducted over a three-dimensional grid of assumed source locations, in which the Green's functions associated with each point source are calculated by finite differences using the reciprocal relation between source and receiver. Tests performed on 62 nodes of a Linux cluster indicate that the waveform inversion and search for the best-fitting signal over 100,000 point sources require roughly 30 s of processing time for a 2-min-long record. The procedure is applied to post-processing of a data archive and to continuous automatic inversion of real-time data at Stromboli, providing insights into different modes of degassing at this volcano. Copyright 2006 by the American Geophysical Union.

The role of executive function in children's source monitoring with varying retrieval strategies

Science.gov (United States)

Earhart, Becky; Roberts, Kim P.

2014-01-01

Previous research on the relationship between executive function and source monitoring in young children has been inconclusive, with studies finding conflicting results about whether working memory and inhibitory control are related to source-monitoring ability. In this study, the role of working memory and inhibitory control in recognition memory and source monitoring with two different retrieval strategies were examined. Children (N = 263) aged 4–8 participated in science activities with two sources. They were later given a recognition and source-monitoring test, and completed measures of working memory and inhibitory control. During the source-monitoring test, half of the participants were asked about sources serially (one after the other) whereas the other half of the children were asked about sources in parallel (considering both sources simultaneously). Results demonstrated that working memory was a predictor of source-monitoring accuracy in both conditions, but inhibitory control was only related to source accuracy in the parallel condition. When age was controlled these relationships were no longer significant, suggesting that a more general cognitive development factor is a stronger predictor of source monitoring than executive function alone. Interestingly, the children aged 4–6 years made more accurate source decisions in the parallel condition than in the serial condition. The older children (aged 7–8) were overall more accurate than the younger children, and their accuracy did not differ as a function of interview condition. Suggestions are provided to guide further research in this area that will clarify the diverse results of previous studies examining whether executive function is a cognitive prerequisite for effective source monitoring. PMID:24847302

Time domain localization technique with sparsity constraint for imaging acoustic sources

Science.gov (United States)

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.

Three-dimensional localization of low activity gamma-ray sources in real-time scenarios

Energy Technology Data Exchange (ETDEWEB)

Sharma, Manish K., E-mail: mksrkf@mst.edu; Alajo, Ayodeji B.; Lee, Hyoung K.

2016-03-21

Radioactive source localization plays an important role in tracking radiation threats in homeland security tasks. Its real-time application requires computationally efficient and reasonably accurate algorithms even with limited data to support detection with minimum uncertainty. This paper describes a statistic-based grid-refinement method for backtracing the position of a gamma-ray source in a three-dimensional domain in real-time. The developed algorithm used measurements from various known detector positions to localize the source. This algorithm is based on an inverse-square relationship between source intensity at a detector and the distance from the source to the detector. The domain discretization was developed and implemented in MATLAB. The algorithm was tested and verified from simulation results of an ideal case of a point source in non-attenuating medium. Subsequently, an experimental validation of the algorithm was performed to determine the suitability of deploying this scheme in real-time scenarios. Using the measurements from five known detector positions and for a measurement time of 3 min, the source position was estimated with an accuracy of approximately 53 cm. The accuracy improved and stabilized to approximately 25 cm for higher measurement times. It was concluded that the error in source localization was primarily due to detection uncertainties. In verification and experimental validation of the algorithm, the distance between {sup 137}Cs source and any detector position was between 0.84 m and 1.77 m. The results were also compared with the least squares method. Since the discretization algorithm was validated with a weak source, it is expected that it can localize the source of higher activity in real-time. It is believed that for the same physical placement of source and detectors, a source of approximate activity 0.61–0.92 mCi can be localized in real-time with 1 s of measurement time and same accuracy. The accuracy and computational

The Functions of Sourcing Intermediaries in Global Supply Risk Management

DEFF Research Database (Denmark)

Vedel, Mette; Ellegaard, Chris

The aim of this work-in-progress paper is to uncover the supply risk management functions performed by sourcing intermediaries. The purchasing and supply chain management literature, including the part of it concerned with supply risk, pays little attention to sourcing intermediaries....... But the fields of marketing and international business have investigated the intermediary including its high supply risk reducing potentials, suggesting that this supply chain entity may be highly relevant to supply risk management. In order to get a better understanding of the supply risk reducing properties...... of sourcing intermediaries, we perform a study of the Danish clothing industry. The study incorporate interviews across a range of functions and companies in this industry including retailers, producers, suppliers, and various types of intermediaries. We contribute by coupling the supply risk management...

Recursive evaluation of space-time lattice Green's functions

International Nuclear Information System (INIS)

De Hon, Bastiaan P; Arnold, John M

2012-01-01

Up to a multiplicative constant, the lattice Green's function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z-domain counterpart of the finite-difference time-domain Green's function (GF) on a lattice. Expansion of a well-known integral representation for the LGF on a ν-dimensional hyper-cubic lattice in powers of Z −1 and application of the Chu–Vandermonde identity results in ν − 1 nested finite-sum representations for discrete space-time GFs. Due to severe numerical cancellations, these nested finite sums are of little practical use. For ν = 2, the finite sum may be evaluated in closed form in terms of a generalized hypergeometric function. For special lattice points, that representation simplifies considerably, while on the other hand the finite-difference stencil may be used to derive single-lattice-point second-order recurrence schemes for generating 2D discrete space-time GF time sequences on the fly. For arbitrary symbolic lattice points, Zeilberger's algorithm produces a third-order recurrence operator with polynomial coefficients of the sixth degree. The corresponding recurrence scheme constitutes the most efficient numerical method for the majority of lattice points, in spite of the fact that for explicit numeric lattice points the associated third-order recurrence operator is not the minimum recurrence operator. As regards the asymptotic bounds for the possible solutions to the recurrence scheme, Perron's theorem precludes factorial or exponential growth. Along horizontal lattices directions, rapid initial growth does occur, but poses no problems in augmented dynamic-range fixed precision arithmetic. By analysing long-distance wave propagation along a horizontal lattice direction, we have concluded that the chirp-up oscillations of the discrete space-time GF are the root cause of grid dispersion anisotropy. With each factor of ten increase in the lattice distance, one would have to roughly

Photodetection-induced relative timing jitter in synchronized time-lens source for coherent Raman scattering microscopy

Directory of Open Access Journals (Sweden)

Jiaqi Wang

2017-09-01

Full Text Available Synchronized time-lens source is a novel method to generate synchronized optical pulses to mode-locked lasers, and has found widespread applications in coherent Raman scattering microscopy. Relative timing jitter between the mode-locked laser and the synchronized time-lens source is a key parameter for evaluating the synchronization performance of such synchronized laser systems. However, the origins of the relative timing jitter in such systems are not fully determined, which in turn prevents the experimental efforts to optimize the synchronization performance. Here, we demonstrate, through theoretical modeling and numerical simulation, that the photodetection could be one physical origin of the relative timing jitter. Comparison with relative timing jitter due to the intrinsic timing jitter of the mode-locked laser is also demonstrated, revealing different qualitative and quantitative behaviors. Based on the nature of this photodetection-induced timing jitter, we further propose several strategies to reduce the relative timing jitter. Our theoretical results will provide guidelines for optimizing synchronization performance in experiments.

Insulin in the brain: sources, localization and functions.

Science.gov (United States)

Ghasemi, Rasoul; Haeri, Ali; Dargahi, Leila; Mohamed, Zahurin; Ahmadiani, Abolhassan

2013-02-01

Historically, insulin is best known for its role in peripheral glucose homeostasis, and insulin signaling in the brain has received less attention. Insulin-independent brain glucose uptake has been the main reason for considering the brain as an insulin-insensitive organ. However, recent findings showing a high concentration of insulin in brain extracts, and expression of insulin receptors (IRs) in central nervous system tissues have gathered considerable attention over the sources, localization, and functions of insulin in the brain. This review summarizes the current status of knowledge of the peripheral and central sources of insulin in the brain, site-specific expression of IRs, and also neurophysiological functions of insulin including the regulation of food intake, weight control, reproduction, and cognition and memory formation. This review also considers the neuromodulatory and neurotrophic effects of insulin, resulting in proliferation, differentiation, and neurite outgrowth, introducing insulin as an attractive tool for neuroprotection against apoptosis, oxidative stress, beta amyloid toxicity, and brain ischemia.

Time-correlated neutron analysis of a multiplying HEU source

Energy Technology Data Exchange (ETDEWEB)

Miller, E.C., E-mail: Eric.Miller@jhuapl.edu [Johns Hopkins University Applied Physics Laboratory, Laurel, MD (United States); Kalter, J.M.; Lavelle, C.M. [Johns Hopkins University Applied Physics Laboratory, Laurel, MD (United States); Watson, S.M.; Kinlaw, M.T.; Chichester, D.L. [Idaho National Laboratory, Idaho Falls, ID (United States); Noonan, W.A. [Johns Hopkins University Applied Physics Laboratory, Laurel, MD (United States)

2015-06-01

The ability to quickly identify and characterize special nuclear material remains a national security challenge. In counter-proliferation applications, identifying the neutron multiplication of a sample can be a good indication of the level of threat. Currently neutron multiplicity measurements are performed with moderated {sup 3}He proportional counters. These systems rely on the detection of thermalized neutrons, a process which obscures both energy and time information from the source. Fast neutron detectors, such as liquid scintillators, have the ability to detect events on nanosecond time scales, providing more information on the temporal structure of the arriving signal, and provide an alternative method for extracting information from the source. To explore this possibility, a series of measurements were performed on the Idaho National Laboratory's MARVEL assembly, a configurable HEU source. The source assembly was measured in a variety of different HEU configurations and with different reflectors, covering a range of neutron multiplications from 2 to 8. The data was collected with liquid scintillator detectors and digitized for offline analysis. A gap based approach for identifying the bursts of detected neutrons associated with the same fission chain was used. Using this approach, we are able to study various statistical properties of individual fission chains. One of these properties is the distribution of neutron arrival times within a given burst. We have observed two interesting empirical trends. First, this distribution exhibits a weak, but definite, dependence on source multiplication. Second, there are distinctive differences in the distribution depending on the presence and type of reflector. Both of these phenomena might prove to be useful when assessing an unknown source. The physical origins of these phenomena can be illuminated with help of MCNPX-PoliMi simulations.

Time-correlated neutron analysis of a multiplying HEU source

Science.gov (United States)

Miller, E. C.; Kalter, J. M.; Lavelle, C. M.; Watson, S. M.; Kinlaw, M. T.; Chichester, D. L.; Noonan, W. A.

2015-06-01

The ability to quickly identify and characterize special nuclear material remains a national security challenge. In counter-proliferation applications, identifying the neutron multiplication of a sample can be a good indication of the level of threat. Currently neutron multiplicity measurements are performed with moderated 3He proportional counters. These systems rely on the detection of thermalized neutrons, a process which obscures both energy and time information from the source. Fast neutron detectors, such as liquid scintillators, have the ability to detect events on nanosecond time scales, providing more information on the temporal structure of the arriving signal, and provide an alternative method for extracting information from the source. To explore this possibility, a series of measurements were performed on the Idaho National Laboratory's MARVEL assembly, a configurable HEU source. The source assembly was measured in a variety of different HEU configurations and with different reflectors, covering a range of neutron multiplications from 2 to 8. The data was collected with liquid scintillator detectors and digitized for offline analysis. A gap based approach for identifying the bursts of detected neutrons associated with the same fission chain was used. Using this approach, we are able to study various statistical properties of individual fission chains. One of these properties is the distribution of neutron arrival times within a given burst. We have observed two interesting empirical trends. First, this distribution exhibits a weak, but definite, dependence on source multiplication. Second, there are distinctive differences in the distribution depending on the presence and type of reflector. Both of these phenomena might prove to be useful when assessing an unknown source. The physical origins of these phenomena can be illuminated with help of MCNPX-PoliMi simulations.

Time-correlated neutron analysis of a multiplying HEU source

International Nuclear Information System (INIS)

Miller, E.C.; Kalter, J.M.; Lavelle, C.M.; Watson, S.M.; Kinlaw, M.T.; Chichester, D.L.; Noonan, W.A.

2015-01-01

The ability to quickly identify and characterize special nuclear material remains a national security challenge. In counter-proliferation applications, identifying the neutron multiplication of a sample can be a good indication of the level of threat. Currently neutron multiplicity measurements are performed with moderated 3 He proportional counters. These systems rely on the detection of thermalized neutrons, a process which obscures both energy and time information from the source. Fast neutron detectors, such as liquid scintillators, have the ability to detect events on nanosecond time scales, providing more information on the temporal structure of the arriving signal, and provide an alternative method for extracting information from the source. To explore this possibility, a series of measurements were performed on the Idaho National Laboratory's MARVEL assembly, a configurable HEU source. The source assembly was measured in a variety of different HEU configurations and with different reflectors, covering a range of neutron multiplications from 2 to 8. The data was collected with liquid scintillator detectors and digitized for offline analysis. A gap based approach for identifying the bursts of detected neutrons associated with the same fission chain was used. Using this approach, we are able to study various statistical properties of individual fission chains. One of these properties is the distribution of neutron arrival times within a given burst. We have observed two interesting empirical trends. First, this distribution exhibits a weak, but definite, dependence on source multiplication. Second, there are distinctive differences in the distribution depending on the presence and type of reflector. Both of these phenomena might prove to be useful when assessing an unknown source. The physical origins of these phenomena can be illuminated with help of MCNPX-PoliMi simulations

SIMULATION OF SURFACE HEATING FOR ARBITRARY SHAPE’S MOVING BODIES/SOURCES BY USING R-FUNCTIONS

Directory of Open Access Journals (Sweden)

Sergiy Plankovskyy

2016-12-01

Full Text Available The purpose of this article is to propose an efficient algorithm for determining the place of an action of a heat source with a given motion law for a body of an arbitrary shape using methods of analytical geometry. The solution to this problem is an important part of a modeling of a laser, plasma, ion beam treatment. In addition, it can also be used for mass transfer problems, such as simulation of coating, sputtering, painting etc. The problem is solved by the method of R-functions to define the shape of the test body and the heat source and the analytical determination zone shadowing. As an example, we consider the problem of using the method of ion cleaning parameters optimization considering temperature limitations. Application of the R-functions can significantly reduce the amount of computation with usage of the ray tracing algorithm. The numerical realization of the proposed method requires an accurate creation of a numerical mesh. The best results in terms of accuracy of determination the scope of the source can be expected when applying adaptive tunable meshes. In case of integration of the R-functions into the CAD system, the use of the proposed method would be simple enough. The proposed method allows to determine the range of the source by the expression, which is constructed only once for the body and the source of arbitrary geometric shapes moving in any law. This distinguishes the proposed approach against all known algorithms for ray tracing. The proposed method can also be used for time-dependent multisource with arbitrary shapes, which move in different directions.

Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

Directory of Open Access Journals (Sweden)

S. C. Stähler

2014-11-01

Full Text Available Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Seismic source Mechanisms (PRISM that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 source time functions (STFs by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits propagating these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

Time evolution of distribution functions in dissipative environments

International Nuclear Information System (INIS)

Hu Li-Yun; Chen Fei; Wang Zi-Sheng; Fan Hong-Yi

2011-01-01

By introducing the thermal entangled state representation, we investigate the time evolution of distribution functions in the dissipative channels by bridging the relation between the initial distribution function and the any time distribution function. We find that most of them are expressed as such integrations over the Laguerre—Gaussian function. Furthermore, as applications, we derive the time evolution of photon-counting distribution by bridging the relation between the initial distribution function and the any time photon-counting distribution, and the time evolution of R-function characteristic of nonclassicality depth. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

SCARDEC: a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body-wave deconvolution

Science.gov (United States)

Vallée, M.; Charléty, J.; Ferreira, A. M. G.; Delouis, B.; Vergoz, J.

2011-01-01

Accurate and fast magnitude determination for large, shallow earthquakes is of key importance for post-seismic response and tsumami alert purposes. When no local real-time data are available, which is today the case for most subduction earthquakes, the first information comes from teleseismic body waves. Standard body-wave methods give accurate magnitudes for earthquakes up to Mw= 7-7.5. For larger earthquakes, the analysis is more complex, because of the non-validity of the point-source approximation and of the interaction between direct and surface-reflected phases. The latter effect acts as a strong high-pass filter, which complicates the magnitude determination. We here propose an automated deconvolutive approach, which does not impose any simplifying assumptions about the rupture process, thus being well adapted to large earthquakes. We first determine the source duration based on the length of the high frequency (1-3 Hz) signal content. The deconvolution of synthetic double-couple point source signals—depending on the four earthquake parameters strike, dip, rake and depth—from the windowed real data body-wave signals (including P, PcP, PP, SH and ScS waves) gives the apparent source time function (STF). We search the optimal combination of these four parameters that respects the physical features of any STF: causality, positivity and stability of the seismic moment at all stations. Once this combination is retrieved, the integration of the STFs gives directly the moment magnitude. We apply this new approach, referred as the SCARDEC method, to most of the major subduction earthquakes in the period 1990-2010. Magnitude differences between the Global Centroid Moment Tensor (CMT) and the SCARDEC method may reach 0.2, but values are found consistent if we take into account that the Global CMT solutions for large, shallow earthquakes suffer from a known trade-off between dip and seismic moment. We show by modelling long-period surface waves of these events that

Automatic classification of time-variable X-ray sources

Energy Technology Data Exchange (ETDEWEB)

Lo, Kitty K.; Farrell, Sean; Murphy, Tara; Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia)

2014-05-01

To maximize the discovery potential of future synoptic surveys, especially in the field of transient science, it will be necessary to use automatic classification to identify some of the astronomical sources. The data mining technique of supervised classification is suitable for this problem. Here, we present a supervised learning method to automatically classify variable X-ray sources in the Second XMM-Newton Serendipitous Source Catalog (2XMMi-DR2). Random Forest is our classifier of choice since it is one of the most accurate learning algorithms available. Our training set consists of 873 variable sources and their features are derived from time series, spectra, and other multi-wavelength contextual information. The 10 fold cross validation accuracy of the training data is ∼97% on a 7 class data set. We applied the trained classification model to 411 unknown variable 2XMM sources to produce a probabilistically classified catalog. Using the classification margin and the Random Forest derived outlier measure, we identified 12 anomalous sources, of which 2XMM J180658.7–500250 appears to be the most unusual source in the sample. Its X-ray spectra is suggestive of a ultraluminous X-ray source but its variability makes it highly unusual. Machine-learned classification and anomaly detection will facilitate scientific discoveries in the era of all-sky surveys.

Automatic classification of time-variable X-ray sources

International Nuclear Information System (INIS)

Lo, Kitty K.; Farrell, Sean; Murphy, Tara; Gaensler, B. M.

2014-01-01

To maximize the discovery potential of future synoptic surveys, especially in the field of transient science, it will be necessary to use automatic classification to identify some of the astronomical sources. The data mining technique of supervised classification is suitable for this problem. Here, we present a supervised learning method to automatically classify variable X-ray sources in the Second XMM-Newton Serendipitous Source Catalog (2XMMi-DR2). Random Forest is our classifier of choice since it is one of the most accurate learning algorithms available. Our training set consists of 873 variable sources and their features are derived from time series, spectra, and other multi-wavelength contextual information. The 10 fold cross validation accuracy of the training data is ∼97% on a 7 class data set. We applied the trained classification model to 411 unknown variable 2XMM sources to produce a probabilistically classified catalog. Using the classification margin and the Random Forest derived outlier measure, we identified 12 anomalous sources, of which 2XMM J180658.7–500250 appears to be the most unusual source in the sample. Its X-ray spectra is suggestive of a ultraluminous X-ray source but its variability makes it highly unusual. Machine-learned classification and anomaly detection will facilitate scientific discoveries in the era of all-sky surveys.

Pulsar timing residuals due to individual non-evolving gravitational wave sources

International Nuclear Information System (INIS)

Tong Ming-Lei; Zhao Cheng-Shi; Yan Bao-Rong; Yang Ting-Gao; Gao Yu-Ping

2014-01-01

The pulsar timing residuals induced by gravitational waves from non-evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The orbits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities

Time-resolved X-ray studies using third generation synchrotron radiation sources

International Nuclear Information System (INIS)

Mills, D.M.

1991-10-01

The third generation, high-brilliance, hard x-ray, synchrotron radiation (SR) sources currently under construction (ESRF at Grenoble, France; APS at Argonne, Illinois; and SPring-8 at Harima, Japan) will usher in a new era of x-ray experimentation for both physical and biological sciences. One of the most exciting areas of experimentation will be the extension of x-ray scattering and diffraction techniques to the study of transient or time-evolving systems. The high repetition rate, short-pulse duration, high brilliance, and variable spectral bandwidth of these sources make them ideal for x-ray time-resolved studies. The temporal properties (bunch length, interpulse period, etc.) of these new sources will be summarized. Finally, the scientific potential and the technological challenges of time-resolved x-ray scattering from these new sources will be described. 13 refs., 4 figs

Time-dependent potential-functional embedding theory

International Nuclear Information System (INIS)

Huang, Chen; Libisch, Florian; Peng, Qing; Carter, Emily A.

2014-01-01

We introduce a time-dependent potential-functional embedding theory (TD-PFET), in which atoms are grouped into subsystems. In TD-PFET, subsystems can be propagated by different suitable time-dependent quantum mechanical methods and their interactions can be treated in a seamless, first-principles manner. TD-PFET is formulated based on the time-dependent quantum mechanics variational principle. The action of the total quantum system is written as a functional of the time-dependent embedding potential, i.e., a potential-functional formulation. By exploiting the Runge-Gross theorem, we prove the uniqueness of the time-dependent embedding potential under the constraint that all subsystems share a common embedding potential. We derive the integral equation that such an embedding potential needs to satisfy. As proof-of-principle, we demonstrate TD-PFET for a Na 4 cluster, in which each Na atom is treated as one subsystem and propagated by time-dependent Kohn-Sham density functional theory (TDDFT) using the adiabatic local density approximation (ALDA). Our results agree well with a direct TDDFT calculation on the whole Na 4 cluster using ALDA. We envision that TD-PFET will ultimately be useful for studying ultrafast quantum dynamics in condensed matter, where key regions are solved by highly accurate time-dependent quantum mechanics methods, and unimportant regions are solved by faster, less accurate methods

A FOURIER-TRANSFORMED BREMSSTRAHLUNG FLASH MODEL FOR THE PRODUCTION OF X-RAY TIME LAGS IN ACCRETING BLACK HOLE SOURCES

International Nuclear Information System (INIS)

Kroon, John J.; Becker, Peter A.

2014-01-01

Accreting black hole sources show a wide variety of rapid time variability, including the manifestation of time lags during X-ray transients, in which a delay (phase shift) is observed between the Fourier components of the hard and soft spectra. Despite a large body of observational evidence for time lags, no fundamental physical explanation for the origin of this phenomenon has been presented. We develop a new theoretical model for the production of X-ray time lags based on an exact analytical solution for the Fourier transform describing the diffusion and Comptonization of seed photons propagating through a spherical corona. The resulting Green's function can be convolved with any source distribution to compute the associated Fourier transform and time lags, hence allowing us to explore a wide variety of injection scenarios. We show that thermal Comptonization is able to self-consistently explain both the X-ray time lags and the steady-state (quiescent) X-ray spectrum observed in the low-hard state of Cyg X-1. The reprocessing of bremsstrahlung seed photons produces X-ray time lags that diminish with increasing Fourier frequency, in agreement with the observations for a wide range of sources

General post-Minkowskian expansion of time transfer functions

Energy Technology Data Exchange (ETDEWEB)

Teyssandier, Pierre; Poncin-Lafitte, Christophe Le [Departement Systemes de Reference Temps et Espace, CNRS/UMR 8630, Observatoire de Paris, 61 avenue de l' Observatoire, F-75014 Paris (France)

2008-07-21

Modeling most of the tests of general relativity requires us to know the function relating light travel time to the coordinate time of reception and to the spatial coordinates of the emitter and the receiver. We call such a function the reception time transfer function. Of course, an emission time transfer function may as well be considered. We present here a recursive procedure enabling us to expand each time transfer function into a perturbative series of ascending powers of the Newtonian gravitational constant G (general post-Minkowskian expansion). Our method is self-sufficient in the sense that neither the integration of null geodesic equations nor the determination of Synge's world function is necessary. To illustrate the method, the time transfer function of a three-parameter family of static, spherically symmetric metrics is derived within the post-linear approximation.

General post-Minkowskian expansion of time transfer functions

International Nuclear Information System (INIS)

Teyssandier, Pierre; Poncin-Lafitte, Christophe Le

2008-01-01

Modeling most of the tests of general relativity requires us to know the function relating light travel time to the coordinate time of reception and to the spatial coordinates of the emitter and the receiver. We call such a function the reception time transfer function. Of course, an emission time transfer function may as well be considered. We present here a recursive procedure enabling us to expand each time transfer function into a perturbative series of ascending powers of the Newtonian gravitational constant G (general post-Minkowskian expansion). Our method is self-sufficient in the sense that neither the integration of null geodesic equations nor the determination of Synge's world function is necessary. To illustrate the method, the time transfer function of a three-parameter family of static, spherically symmetric metrics is derived within the post-linear approximation

Time-dependent anisotropic external sources in transient 3-D transport code TORT-TD

International Nuclear Information System (INIS)

Seubert, A.; Pautz, A.; Becker, M.; Dagan, R.

2009-01-01

This paper describes the implementation of a time-dependent distributed external source in TORT-TD by explicitly considering the external source in the ''fixed-source'' term of the implicitly time-discretised 3-D discrete ordinates transport equation. Anisotropy of the external source is represented by a spherical harmonics series expansion similar to the angular fluxes. The YALINA-Thermal subcritical assembly serves as a test case. The configuration with 280 fuel rods has been analysed with TORT-TD using cross sections in 18 energy groups and P1 scattering order generated by the KAPROS code system. Good agreement is achieved concerning the multiplication factor. The response of the system to an artificial time-dependent source consisting of two square-wave pulses demonstrates the time-dependent external source capability of TORT-TD. The result is physically plausible as judged from validation calculations. (orig.)

The Electromagnetic Field of Elementary Time-Dependent Toroidal Sources

International Nuclear Information System (INIS)

Afanas'ev, G.N.; Stepanovskij, Yu.P.

1994-01-01

The radiation field of toroidal-like time-dependent current configurations is investigated. Time-dependent charge-current sources are found outside which the electromagnetic strengths disappear but the potentials survive. This can be used to carry out time-dependent Aharonov-Bohm-like experiments and the information transfer. Using the Neumann-Helmholtz parametrization of the current density we present the time-dependent electromagnetic field in a form convenient for applications. 17 refs

Time-resolved materials science opportunities using synchrotron x-ray sources

International Nuclear Information System (INIS)

Larson, B.C.; Tischler, J.Z.

1995-06-01

The high brightness, high intensity, and pulsed time-structure of synchrotron sources provide new opportunities for time-resolved x-ray diffraction investigations. With third generation synchrotron sources coming on line, high brilliance and high brightness are now available in x-ray beams with the highest flux. In addition to the high average flux, the instantaneous flux available in synchrotron beams is greatly enhanced by the pulsed time structure, which consists of short bursts of x-rays that are separated by ∼tens to hundreds of nanoseconds. Time-resolved one- and two-dimensional position sensitive detection techniques that take advantage of synchrotron radiation for materials science x-ray diffraction investigations are presented, and time resolved materials science applications are discussed in terms of recent diffraction and spectroscopy results and materials research opportunities

Locating single-point sources from arrival times containing large picking errors (LPEs): the virtual field optimization method (VFOM)

Science.gov (United States)

Li, Xi-Bing; Wang, Ze-Wei; Dong, Long-Jun

2016-01-01

Microseismic monitoring systems using local location techniques tend to be timely, automatic and stable. One basic requirement of these systems is the automatic picking of arrival times. However, arrival times generated by automated techniques always contain large picking errors (LPEs), which may make the location solution unreliable and cause the integrated system to be unstable. To overcome the LPE issue, we propose the virtual field optimization method (VFOM) for locating single-point sources. In contrast to existing approaches, the VFOM optimizes a continuous and virtually established objective function to search the space for the common intersection of the hyperboloids, which is determined by sensor pairs other than the least residual between the model-calculated and measured arrivals. The results of numerical examples and in-site blasts show that the VFOM can obtain more precise and stable solutions than traditional methods when the input data contain LPEs. Furthermore, we discuss the impact of LPEs on objective functions to determine the LPE-tolerant mechanism, velocity sensitivity and stopping criteria of the VFOM. The proposed method is also capable of locating acoustic sources using passive techniques such as passive sonar detection and acoustic emission.

Inverse source problems in elastodynamics

Science.gov (United States)

Bao, Gang; Hu, Guanghui; Kian, Yavar; Yin, Tao

2018-04-01

We are concerned with time-dependent inverse source problems in elastodynamics. The source term is supposed to be the product of a spatial function and a temporal function with compact support. We present frequency-domain and time-domain approaches to show uniqueness in determining the spatial function from wave fields on a large sphere over a finite time interval. The stability estimate of the temporal function from the data of one receiver and the uniqueness result using partial boundary data are proved. Our arguments rely heavily on the use of the Fourier transform, which motivates inversion schemes that can be easily implemented. A Landweber iterative algorithm for recovering the spatial function and a non-iterative inversion scheme based on the uniqueness proof for recovering the temporal function are proposed. Numerical examples are demonstrated in both two and three dimensions.

A Green's function solution for a rectangular heat source on an infinite plate

International Nuclear Information System (INIS)

Bainbridge, B.L.

1989-01-01

The applications associated with a rectangular heat source on an infinite plate range from integrated circuits to thin film heat flux sensors on thin substrates. The particular problem from which the solution is developed concerns the use of a resistive strip for monitoring currents generated in circuits exposed to electromagnetic fields. The Green's function formulation is solved by using early and late time approximations for which analytical solutions can be derived. In this paper expressions are developed for three sets of boundary conditions and compared to the experimental performance of a physical device

Blind Separation of Nonstationary Sources Based on Spatial Time-Frequency Distributions

Directory of Open Access Journals (Sweden)

Zhang Yimin

2006-01-01

Full Text Available Blind source separation (BSS based on spatial time-frequency distributions (STFDs provides improved performance over blind source separation methods based on second-order statistics, when dealing with signals that are localized in the time-frequency (t-f domain. In this paper, we propose the use of STFD matrices for both whitening and recovery of the mixing matrix, which are two stages commonly required in many BSS methods, to provide robust BSS performance to noise. In addition, a simple method is proposed to select the auto- and cross-term regions of time-frequency distribution (TFD. To further improve the BSS performance, t-f grouping techniques are introduced to reduce the number of signals under consideration, and to allow the receiver array to separate more sources than the number of array sensors, provided that the sources have disjoint t-f signatures. With the use of one or more techniques proposed in this paper, improved performance of blind separation of nonstationary signals can be achieved.

Supply risk management functions of sourcing intermediaries – an investigation of the clothing industry

DEFF Research Database (Denmark)

Vedel, Mette; Ellegaard, Chris

2013-01-01

Purpose: The purpose of this research is to uncover how buying companies use sourcing intermediaries to manage supply risks in global sourcing. Design/methodology/approach: We carry out an explorative qualitative study of the clothing industry, interviewing key respondents that occupy different...... intermediary types, characterised by the set of functions they handle. Research limitations/implications: By analysing a limited set of in-depth interviews in one industry we have traded off broader analytical generalization for in-depth exploration and theory building. Therefore, future research should test...... by identifying the supply risk management functions that sourcing intermediaries carry out for buying companies. We also contribute by uncovering different types of sourcing intermediaries, determined by the collection of functions handled....

Optimization of NANOGrav's time allocation for maximum sensitivity to single sources

International Nuclear Information System (INIS)

Christy, Brian; Anella, Ryan; Lommen, Andrea; Camuccio, Richard; Handzo, Emma; Finn, Lee Samuel

2014-01-01

Pulsar timing arrays (PTAs) are a collection of precisely timed millisecond pulsars (MSPs) that can search for gravitational waves (GWs) in the nanohertz frequency range by observing characteristic signatures in the timing residuals. The sensitivity of a PTA depends on the direction of the propagating GW source, the timing accuracy of the pulsars, and the allocation of the available observing time. The goal of this paper is to determine the optimal time allocation strategy among the MSPs in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) for a single source of GW under a particular set of assumptions. We consider both an isotropic distribution of sources across the sky and a specific source in the Virgo cluster. This work improves on previous efforts by modeling the effect of intrinsic spin noise for each pulsar. We find that, in general, the array is optimized by maximizing time spent on the best-timed pulsars, with sensitivity improvements typically ranging from a factor of 1.5 to 4.

Time-dependent friction and solvation time correlation function

International Nuclear Information System (INIS)

Samanta, Alok; Ali, Sk Musharaf; Ghosh, Swapan K

2005-01-01

We have derived a new relation between the time-dependent friction and solvation time correlation function (STCF) for non-polar fluids. The friction values calculated using this relation and simulation results on STCF for a Lennard-Jones fluid are shown to have excellent agreement with the same obtained through mode-coupling theory. Also derived is a relation between the time-dependent dielectric friction and STCF for polar fluids. Routes are thus provided to obtain the time-dependent friction (non-polar as well as dielectric) from an experimentally measured quantity like STCF, even if the interparticle interaction potential is not known

About the Modeling of Radio Source Time Series as Linear Splines

Science.gov (United States)

Karbon, Maria; Heinkelmann, Robert; Mora-Diaz, Julian; Xu, Minghui; Nilsson, Tobias; Schuh, Harald

2016-12-01

Many of the time series of radio sources observed in geodetic VLBI show variations, caused mainly by changes in source structure. However, until now it has been common practice to consider source positions as invariant, or to exclude known misbehaving sources from the datum conditions. This may lead to a degradation of the estimated parameters, as unmodeled apparent source position variations can propagate to the other parameters through the least squares adjustment. In this paper we will introduce an automated algorithm capable of parameterizing the radio source coordinates as linear splines.

The Advanced Photon Source injection timing system

International Nuclear Information System (INIS)

Lenkszus, F.R.; Laird, R.

1995-01-01

The Advanced Photon Source consists of five accelerators. The injection timing system provides the signals required to cause a bunch emitted from the electron gun to navigate through intermediate accelerators to a specific bucket (1 out of 1296) within the storage ring. Two linacs and a positron accumulator ring operate at 60Hz while a booster synchrotron ramps and injects into the storage ring at 2Hz. The distributed, modular VME/VXI-based injection timing system is controlled by two EPICS-based input/output controllers (IOCs). Over 40 VME/VXI cards have been developed to implement the system. Card types range from 352MHz VXI timing modules to VME-based fiber optic fanouts and logic translators/drivers. All timing is distributed with fiber optics. Timing references are derived directly from machine low-level rf of 9.77MHz and 352MHz. The timing references provide triggers to programmable delay generators. Three grades of timing are provided. Precision timing is derived from commercial digital delay generators, intermediate precision timing is obtained from VXI 8-channel digital delay generators which provide timing with 25ns peak-to-peak jitter, and modest precision timing is provided by the APS event system. The timing system is fully integrated into the APS EPICS-based control system

NNLO time-like splitting functions in QCD

International Nuclear Information System (INIS)

Moch, S.; Vogt, A.

2008-07-01

We review the status of the calculation of the time-like splitting functions for the evolution of fragmentation functions to the next-to-next-to-leading order in perturbative QCD. By employing relations between space-like and time-like deep-inelastic processes, all quark-quark and the gluon-gluon time-like splitting functions have been obtained to three loops. The corresponding quantities for the quark-gluon and gluon-quark splitting at this order are presently still unknown except for their second Mellin moments. (orig.)

Real-time digital signal recovery for a multi-pole low-pass transfer function system.

Science.gov (United States)

Lee, Jhinhwan

2017-08-01

In order to solve the problems of waveform distortion and signal delay by many physical and electrical systems with multi-pole linear low-pass transfer characteristics, a simple digital-signal-processing (DSP)-based method of real-time recovery of the original source waveform from the distorted output waveform is proposed. A mathematical analysis on the convolution kernel representation of the single-pole low-pass transfer function shows that the original source waveform can be accurately recovered in real time using a particular moving average algorithm applied on the input stream of the distorted waveform, which can also significantly reduce the overall delay time constant. This method is generalized for multi-pole low-pass systems and has noise characteristics of the inverse of the low-pass filter characteristics. This method can be applied to most sensors and amplifiers operating close to their frequency response limits to improve the overall performance of data acquisition systems and digital feedback control systems.

Timing jitter measurements at the SLC electron source

International Nuclear Information System (INIS)

Sodja, J.; Browne, M.J.; Clendenin, J.E.

1989-03-01

The SLC thermionic gun and electron source produce a beam of up to 15 /times/ 10 10 /sub e//minus/ in a single S-band bunch. A 170 keV, 2 ns FWHM pulse out of the gun is compressed by means of two subharmonic buncher cavities followed by an S-band buncher and a standard SLAC accelerating section. Ceramic gaps in the beam pipe at the output of the gun allow a measure of the beam intensity and timing. A measurement at these gaps of the timing jitter, with a resolution of <10 ps, is described. 3 refs., 5 figs

An Open Source-Based Real-Time Data Processing Architecture Framework for Manufacturing Sustainability

Directory of Open Access Journals (Sweden)

Muhammad Syafrudin

2017-11-01

Full Text Available Currently, the manufacturing industry is experiencing a data-driven revolution. There are multiple processes in the manufacturing industry and will eventually generate a large amount of data. Collecting, analyzing and storing a large amount of data are one of key elements of the smart manufacturing industry. To ensure that all processes within the manufacturing industry are functioning smoothly, the big data processing is needed. Thus, in this study an open source-based real-time data processing (OSRDP architecture framework was proposed. OSRDP architecture framework consists of several open sources technologies, including Apache Kafka, Apache Storm and NoSQL MongoDB that are effective and cost efficient for real-time data processing. Several experiments and impact analysis for manufacturing sustainability are provided. The results showed that the proposed system is capable of processing a massive sensor data efficiently when the number of sensors data and devices increases. In addition, the data mining based on Random Forest is presented to predict the quality of products given the sensor data as the input. The Random Forest successfully classifies the defect and non-defect products, and generates high accuracy compared to other data mining algorithms. This study is expected to support the management in their decision-making for product quality inspection and support manufacturing sustainability.

Wave function for time-dependent harmonically confined electrons in a time-dependent electric field.

Science.gov (United States)

Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht

2013-09-21

The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential.

Single sources in the low-frequency gravitational wave sky: properties and time to detection by pulsar timing arrays

Science.gov (United States)

Kelley, Luke Zoltan; Blecha, Laura; Hernquist, Lars; Sesana, Alberto; Taylor, Stephen R.

2018-06-01

We calculate the properties, occurrence rates and detection prospects of individually resolvable `single sources' in the low-frequency gravitational wave (GW) spectrum. Our simulations use the population of galaxies and massive black hole binaries from the Illustris cosmological hydrodynamic simulations, coupled to comprehensive semi-analytic models of the binary merger process. Using mock pulsar timing arrays (PTA) with, for the first time, varying red-noise models, we calculate plausible detection prospects for GW single sources and the stochastic GW background (GWB). Contrary to previous results, we find that single sources are at least as detectable as the GW background. Using mock PTA, we find that these `foreground' sources (also `deterministic'/`continuous') are likely to be detected with ˜20 yr total observing baselines. Detection prospects, and indeed the overall properties of single sources, are only moderately sensitive to binary evolution parameters - namely eccentricity and environmental coupling, which can lead to differences of ˜5 yr in times to detection. Red noise has a stronger effect, roughly doubling the time to detection of the foreground between a white-noise only model (˜10-15 yr) and severe red noise (˜20-30 yr). The effect of red noise on the GWB is even stronger, suggesting that single source detections may be more robust. We find that typical signal-to-noise ratios for the foreground peak near f = 0.1 yr-1, and are much less sensitive to the continued addition of new pulsars to PTA.

Radiation Tolerant Low Power Precision Time Source, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The availability of small, low power atomic clocks is now a reality for ground-based and airborne navigation systems. Kernco's Low Power Precision Time Source...

Statistical measurement of the gamma-ray source-count distribution as a function of energy

Science.gov (United States)

Zechlin, H.-S.; Cuoco, A.; Donato, F.; Fornengo, N.; Regis, M.

2017-01-01

Photon counts statistics have recently been proven to provide a sensitive observable for characterizing gamma-ray source populations and for measuring the composition of the gamma-ray sky. In this work, we generalize the use of the standard 1-point probability distribution function (1pPDF) to decompose the high-latitude gamma-ray emission observed with Fermi-LAT into: (i) point-source contributions, (ii) the Galactic foreground contribution, and (iii) a diffuse isotropic background contribution. We analyze gamma-ray data in five adjacent energy bands between 1 and 171 GeV. We measure the source-count distribution dN/dS as a function of energy, and demonstrate that our results extend current measurements from source catalogs to the regime of so far undetected sources. Our method improves the sensitivity for resolving point-source populations by about one order of magnitude in flux. The dN/dS distribution as a function of flux is found to be compatible with a broken power law. We derive upper limits on further possible breaks as well as the angular power of unresolved sources. We discuss the composition of the gamma-ray sky and capabilities of the 1pPDF method.

Time-ordered products and Schwinger functions

International Nuclear Information System (INIS)

Eckmann, J.P.; Epstein, H.

1979-01-01

It is shown that every system of time-ordered products for a local field theory determines a related system of Schwinger functions possessing an extended form of Osterwalder-Schrader positivity and that the converse is true provided certain growth conditions are satisfied. This is applied to the phi 3 4 theory and it is shown that the time-ordered functions and S-matrix elements admit the standard perturbation series as asymptotic expansions. (orig.) [de

Sources of variability and systematic error in mouse timing behavior.

Science.gov (United States)

Gallistel, C R; King, Adam; McDonald, Robert

2004-01-01

In the peak procedure, starts and stops in responding bracket the target time at which food is expected. The variability in start and stop times is proportional to the target time (scalar variability), as is the systematic error in the mean center (scalar error). The authors investigated the source of the error and the variability, using head poking in the mouse, with target intervals of 5 s, 15 s, and 45 s, in the standard procedure, and in a variant with 3 different target intervals at 3 different locations in a single trial. The authors conclude that the systematic error is due to the asymmetric location of start and stop decision criteria, and the scalar variability derives primarily from sources other than memory.

Real time source term and dose assessment

International Nuclear Information System (INIS)

Breznik, B.; Kovac, A.; Mlakar, P.

2001-01-01

The Dose Projection Programme is a tool for decision making in case of nuclear emergency. The essential input data for quick emergency evaluation in the case of hypothetical pressurised water reactor accident are following: source term, core damage assessment, fission product radioactivity, release source term and critical exposure pathways for an early phase of the release. A reduced number of radio-nuclides and simplified calculations can be used in dose calculation algorithm. Simple expert system personal computer programme has been developed for the Krsko Nuclear Power Plant for dose projection within the radius of few kilometers from the pressurised water reactor in early phase of an accident. The input data are instantaneous data of core activity, core damage indicators, release fractions, reduction factor of the release pathways, spray operation, release timing, and dispersion coefficient. Main dose projection steps are: accurate in-core radioactivity determination using reactor power input; core damage and in-containment source term assessment based on quick indications of instrumentation or on activity analysis data; user defines release pathway for typical PWR accident scenarius; dose calculation is performed only for exposure pathway critical for decision about evacuation or sheltering in early phase of an accident.(author)

Wave resistance calculation method combining Green functions based on Rankine and Kelvin source

Directory of Open Access Journals (Sweden)

LI Jingyu

2017-12-01

Full Text Available [Ojectives] At present, the Boundary Element Method(BEM of wave-making resistance mostly uses a model in which the velocity distribution near the hull is solved first, and the pressure integral is then calculated using the Bernoulli equation. However,the process of this model of wave-making resistance is complex and has low accuracy.[Methods] To address this problem, the present paper deduces a compound method for the quick calculation of ship wave resistance using the Rankine source Green function to solve the hull surface's source density, and combining the Lagally theorem concerning source point force calculation based on the Kelvin source Green function so as to solve the wave resistance. A case for the Wigley model is given.[Results] The results show that in contrast to the thin ship method of the linear wave resistance theorem, this method has higher precision, and in contrast to the method which completely uses the Kelvin source Green function, this method has better computational efficiency.[Conclusions] In general, the algorithm in this paper provides a compromise between precision and efficiency in wave-making resistance calculation.

Time-Reversal Study of the Hemet (CA) Tremor Source

Science.gov (United States)

Larmat, C. S.; Johnson, P. A.; Guyer, R. A.

2010-12-01

Since its first observation by Nadeau & Dolenc (2005) and Gomberg et al. (2008), tremor along the San Andreas fault system is thought to be a probe into the frictional state of the deep part of the fault (e.g. Shelly et al., 2007). Tremor is associated with slow, otherwise deep, aseismic slip events that may be triggered by faint signals such as passing waves from remote earthquakes or solid Earth tides.Well resolved tremor source location is key to constrain frictional models of the fault. However, tremor source location is challenging because of the high-frequency and highly-scattered nature of tremor signal characterized by the lack of isolated phase arrivals. Time Reversal (TR) methods are emerging as a useful tool for location. The unique requirement is a good velocity model for the different time-reversed phases to arrive coherently onto the source point. We present results of location for a tremor source near the town of Hemet, CA, which was triggered by the 2002 M 7.9 Denali Fault earthquake (Gomberg et al., 2008) and by the 2009 M 6.9 Gulf of California earthquake. We performed TR in a volume model of 88 (N-S) x 70 (W-E) x 60 km (Z) using the full-wave 3D wave-propagation package SPECFEM3D (Komatitsch et al., 2002). The results for the 2009 episode indicate a deep source (at about 22km) which is about 4km SW the fault surface scarp. We perform STA/SLA and correlation analysis in order to have independent confirmation of the Hemet tremor source. We gratefully acknowledge the support of the U. S. Department of Energy through the LANL/LDRD Program for this work.

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Dron, J.; El Haddad, I.; Temime-Roussel, B.; Wortham, H.; Marchand, N. [Univ Aix Marseille, CNRS, Lab Chim Provence, Equipe Instrumentat and React Atmospher, UMR 6264, F-13331 Marseille 3 (France); Jaffrezo, J.L. [Univ Grenoble 1, CNRS, UMR 5183, Lab Glaciol and Geophys Environm, F-38402 St Martin Dheres (France)

2010-07-01

The functional group composition of various organic aerosols (OA) is investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCIMS/MS). The determinations of three functional groups contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups, R-COOH and R-CO-R' respectively) and precursor ion (nitro groups, R-NO{sub 2}) scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA) produced through photooxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounts for 1.7% (vehicular) to 13.5% (o-xylene photooxidation) of the organic carbon. Diagnostic functional group ratios are then used to tentatively discriminate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France) during a strong winter pollution event. The three functional groups under study account for a total functionalization rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to discriminate sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assess a wood burning organic carbon contribution of about 60%. Finally, examples of functional

Transforming the autocorrelation function of a time series to detect land cover change

CSIR Research Space (South Africa)

Salmon

2015-07-01

Full Text Available stream_source_info Salmon_2016.pdf.txt stream_content_type text/plain stream_size 1090 Content-Encoding ISO-8859-1 stream_name Salmon_2016.pdf.txt Content-Type text/plain; charset=ISO-8859-1 International Geoscience... and Remote Sensing Symposium (IEEE IGARSS), 10-15 July 2016, Beijing Transforming the autocorrelation function of a time series to detect land cover change Salmon, B.P., Kleynhans, W., Olivier, J.C. and Schwegmann, C.P. ABSTRACT Regional...

Covariant Density Functionals: time-odd channel investigated

International Nuclear Information System (INIS)

Afanasjev, A. V.; Abusara, H.

2009-01-01

The description of exotic nuclear systems and phenomena requires a detailed understanding of all channels of density functional theories. The role of time-odd mean fields, their evidence in experiment, and an accurate description of these fields are subject of current interest. Recent studies advanced the understanding of these fields in energy density functional theories based on the Skyrme force [1,2]. Time-odd mean fields are related to nuclear magnetism in covariant density functional (CDF) theories [3]. They arise from space-like components of vector mesons and Lorentz invariance requires that their coupling strengths are identical to that of time-like components. There were only few limited efforts to understand the role of time-odd mean fields in covariant density functional theory [4,5]. For example, the microscopic role of nuclear magnetism and its impact on rotational properties of nuclei has been studied in Ref. [5]. It is known that time-odd mean fields modify the angular momentum content of the single-particle orbitals and thus the moments of inertia, effective alignments, alignment gains at the band crossings and other physical observables. We aim on more detailed and systematic understanding of the role of time-odd mean fields in covariant density functional theory. This investigation covers both rotating and non-rotating systems. It is shown that contrary to the Skyrme energy density functionals time-odd mean fields of CDF theory always provide additional binding in the systems with broken time-reversal symmetry (rotating nuclei, odd mass nuclei). This additional binding increases with spin and has its maximum exactly at the terminating state [6], where it can reach several MeV. The impact of time-odd mean fields on the properties of rotating systems has been studied in a systematic way (as a function of particle number and deformation) across the nuclear chart [7]. In addition, this contribution extends these studies to non-rotating systems such as

Positivity of time-frequency distribution functions

NARCIS (Netherlands)

Janssen, A.J.E.M.

1988-01-01

This paper deals with the question how various 'natural' conditions posed on time-frequency distribution functions prevent them to be nonnegative everywhere for all signals. The attention is restricted mainly to distribution functions that involve the signal bilinearly. This paper summarizes and

Advances in high-order harmonic generation sources for time-resolved investigations

Energy Technology Data Exchange (ETDEWEB)

Reduzzi, Maurizio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Carpeggiani, Paolo [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Kühn, Sergei [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Calegari, Francesca [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Nisoli, Mauro; Stagira, Salvatore [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Vozzi, Caterina [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Dombi, Peter [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Wigner Research Center for Physics, 1121 Budapest (Hungary); Kahaly, Subhendu [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Tzallas, Paris; Charalambidis, Dimitris [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Foundation for Research and Technology – Hellas, Institute of Electronic Structure and Lasers, P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Varju, Katalin [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, 6720 Szeged (Hungary); Osvay, Karoly [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); and others

2015-10-15

We review the main research directions ongoing in the development of extreme ultraviolet sources based on high-harmonic generation for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

Advances in high-order harmonic generation sources for time-resolved investigations

International Nuclear Information System (INIS)

Reduzzi, Maurizio; Carpeggiani, Paolo; Kühn, Sergei; Calegari, Francesca; Nisoli, Mauro; Stagira, Salvatore; Vozzi, Caterina; Dombi, Peter; Kahaly, Subhendu; Tzallas, Paris; Charalambidis, Dimitris; Varju, Katalin; Osvay, Karoly

2015-01-01

We review the main research directions ongoing in the development of extreme ultraviolet sources based on high-harmonic generation for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

Directory of Open Access Journals (Sweden)

L. Miaja-Avila

2015-03-01

Full Text Available We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

A new time-space accounting scheme to predict stream water residence time and hydrograph source components at the watershed scale

Science.gov (United States)

Takahiro Sayama; Jeffrey J. McDonnell

2009-01-01

Hydrograph source components and stream water residence time are fundamental behavioral descriptors of watersheds but, as yet, are poorly represented in most rainfall-runoff models. We present a new time-space accounting scheme (T-SAS) to simulate the pre-event and event water fractions, mean residence time, and spatial source of streamflow at the watershed scale. We...

Evaluation of TG-43 recommended 2D-anisotropy function for elongated brachytherapy sources

International Nuclear Information System (INIS)

Awan, Shahid B.; Meigooni, Ali S.; Mokhberiosgouei, Ramin; Hussain, Manzoor

2006-01-01

The original and updated protocols recommended by Task Group 43 from the American Association of Physicists in Medicine (i.e., TG-43 and TG-43U1, respectively), have been introduced to unify brachytherapy source dosimetry around the world. Both of these protocols are based on experiences with sources less than 1.0 cm in length. TG-43U1 recommends that for 103 Pd sources, 2D anisotropy function F(r,θ), should be tabulated at a minimum for radial distances of 0.5, 1.0, 2.0, 3.0, and 5.0 cm. Anisotropy functions defined in these protocols are only valid when the point of calculation does not fall on the active length of the source. However, for elongated brachytherapy sources (active length >1 cm), some of the calculation points with r 103 Pd source at radial distances of 2.5, 3.0, and 4.0 cm were 2.95, 1.74, and 1.19, respectively, with differences up to about a factor of 3. Therefore, the validity of the linear interpolation technique for an elongated brachytherapy source with such a large variation in F(r,θ) needs to be investigated. In this project, application of the TG-43U1 formalism for dose calculation around an elongated RadioCoil trade mark sign 103 Pd brachytherapy source has been investigated. In addition, the linear interpolation techniques as described in TG-43U1 for seed type sources have been evaluated for a 5.0 cm long RadioCoil trade mark sign 103 Pd brachytherapy source. Application of a polynomial fit to F(r,θ) has also been investigated as an alternate approach to the linear interpolation technique. The results of these investigations indicate that the TG-43U1 formalism can be extended for elongated brachytherapy sources, if the two-dimensional (2D) anisotropy function is tabulated at a minimum for radial distances of 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 cm, L/2, and L/2±0.2 cm. Moreover, with the addition of recommended radial distances for 2D anisotropy functions, the linear interpolation technique more closely replicates

Microseismic imaging using a source-independent full-waveform inversion method

KAUST Repository

Wang, Hanchen

2016-09-06

Using full waveform inversion (FWI) to locate microseismic and image microseismic events allows for an automatic process (free of picking) that utilizes the full wavefield. However, waveform inversion of microseismic events faces incredible nonlinearity due to the unknown source location (space) and function (time). We develop a source independent FWI of microseismic events to invert for the source image, source function and the velocity model. It is based on convolving reference traces with the observed and modeled data to mitigate the effect of an unknown source ignition time. The adjoint-state method is used to derive the gradient for the source image, source function and velocity updates. The extended image for source wavelet in z axis is extracted to check the accuracy of the inverted source image and velocity model. Also the angle gather is calculated to see if the velocity model is correct. By inverting for all the source image, source wavelet and the velocity model, the proposed method produces good estimates of the source location, ignition time and the background velocity for part of the SEG overthrust model.

Microseismic imaging using a source-independent full-waveform inversion method

KAUST Repository

Wang, Hanchen

2016-01-01

Using full waveform inversion (FWI) to locate microseismic and image microseismic events allows for an automatic process (free of picking) that utilizes the full wavefield. However, waveform inversion of microseismic events faces incredible nonlinearity due to the unknown source location (space) and function (time). We develop a source independent FWI of microseismic events to invert for the source image, source function and the velocity model. It is based on convolving reference traces with the observed and modeled data to mitigate the effect of an unknown source ignition time. The adjoint-state method is used to derive the gradient for the source image, source function and velocity updates. The extended image for source wavelet in z axis is extracted to check the accuracy of the inverted source image and velocity model. Also the angle gather is calculated to see if the velocity model is correct. By inverting for all the source image, source wavelet and the velocity model, the proposed method produces good estimates of the source location, ignition time and the background velocity for part of the SEG overthrust model.

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry

Directory of Open Access Journals (Sweden)

J. Dron

2010-08-01

Full Text Available The functional group composition of various organic aerosols (OA is investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCI-MS/MS. The determinations of three functional groups contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups, R-COOH and R-CO-R´ respectively and precursor ion (nitro groups, R-NO₂ scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA produced through photooxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounts for 1.7% (vehicular to 13.5% (o-xylene photooxidation of the organic carbon. Diagnostic functional group ratios are then used to tentatively discriminate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France during a strong winter pollution event. The three functional groups under study account for a total functionalisation rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to discriminate sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assess a wood burning organic carbon contribution of about 60

Probing Motion of Fast Radio Burst Sources by Timing Strongly Lensed Repeaters

Science.gov (United States)

Dai, Liang; Lu, Wenbin

2017-09-01

Given the possible repetitive nature of fast radio bursts (FRBs), their cosmological origin, and their high occurrence, detection of strongly lensed sources due to intervening galaxy lenses is possible with forthcoming radio surveys. We show that if multiple images of a repeating source are resolved with VLBI, using a method independent of lens modeling, accurate timing could reveal non-uniform motion, either physical or apparent, of the emission spot. This can probe the physical nature of FRBs and their surrounding environments, constraining scenarios including orbital motion around a stellar companion if FRBs require a compact star in a special system, and jet-medium interactions for which the location of the emission spot may randomly vary. The high timing precision possible for FRBs (˜ms) compared with the typical time delays between images in galaxy lensing (≳10 days) enables the measurement of tiny fractional changes in the delays (˜ {10}-9) and hence the detection of time-delay variations induced by relative motions between the source, the lens, and the Earth. We show that uniform cosmic peculiar velocities only cause the delay time to drift linearly, and that the effect from the Earth’s orbital motion can be accurately subtracted, thus enabling a search for non-trivial source motion. For a timing accuracy of ˜1 ms and a repetition rate (of detected bursts) of ˜0.05 per day of a single FRB source, non-uniform displacement ≳0.1-1 au of the emission spot perpendicular to the line of sight is detectable if repetitions are seen over a period of hundreds of days.

Modulating Function-Based Method for Parameter and Source Estimation of Partial Differential Equations

KAUST Repository

Asiri, Sharefa M.

2017-10-08

Partial Differential Equations (PDEs) are commonly used to model complex systems that arise for example in biology, engineering, chemistry, and elsewhere. The parameters (or coefficients) and the source of PDE models are often unknown and are estimated from available measurements. Despite its importance, solving the estimation problem is mathematically and numerically challenging and especially when the measurements are corrupted by noise, which is often the case. Various methods have been proposed to solve estimation problems in PDEs which can be classified into optimization methods and recursive methods. The optimization methods are usually heavy computationally, especially when the number of unknowns is large. In addition, they are sensitive to the initial guess and stop condition, and they suffer from the lack of robustness to noise. Recursive methods, such as observer-based approaches, are limited by their dependence on some structural properties such as observability and identifiability which might be lost when approximating the PDE numerically. Moreover, most of these methods provide asymptotic estimates which might not be useful for control applications for example. An alternative non-asymptotic approach with less computational burden has been proposed in engineering fields based on the so-called modulating functions. In this dissertation, we propose to mathematically and numerically analyze the modulating functions based approaches. We also propose to extend these approaches to different situations. The contributions of this thesis are as follows. (i) Provide a mathematical analysis of the modulating function-based method (MFBM) which includes: its well-posedness, statistical properties, and estimation errors. (ii) Provide a numerical analysis of the MFBM through some estimation problems, and study the sensitivity of the method to the modulating functions\\' parameters. (iii) Propose an effective algorithm for selecting the method\\'s design parameters

Extracting Date/Time Expressions in Super-Function Based Japanese-English Machine Translation

Science.gov (United States)

Sasayama, Manabu; Kuroiwa, Shingo; Ren, Fuji

Super-Function Based Machine Translation(SFBMT) which is a type of Example-Based Machine Translation has a feature which makes it possible to expand the coverage of examples by changing nouns into variables, however, there were problems extracting entire date/time expressions containing parts-of-speech other than nouns, because only nouns/numbers were changed into variables. We describe a method for extracting date/time expressions for SFBMT. SFBMT uses noun determination rules to extract nouns and a bilingual dictionary to obtain correspondence of the extracted nouns between the source and the target languages. In this method, we add a rule to extract date/time expressions and then extract date/time expressions from a Japanese-English bilingual corpus. The evaluation results shows that the precision of this method for Japanese sentences is 96.7%, with a recall of 98.2% and the precision for English sentences is 94.7%, with a recall of 92.7%.

Functional groups in North Chilean desert shrub species, based on the water sources used

International Nuclear Information System (INIS)

Squeo, Francisco A; Olivares, Nancy; Olivares, Sandra; Jorquera, Carmen; Pollastri, Alberto; Aguirre, Evelyn; Aravena, Ramon; Ehleringer, James R

1999-01-01

Primary productivity and vegetation structure in arid ecosystems are determined by water availability. In studies conducted in the coastal dry land of North Central Chile (29 degrees 43'S; 71degrees 14'0, 300m), the mechanisms to use different water sources by shrubs species, in two contrasting rainfall years were compared. Information on pheno logical studies, root architecture and water sources used by shrubs through the use of stable isotopes is are discussed. Six functional groups based on water uptake and water use are recognized. The functional groups were defined based on their habits (deciduous and evergreen), their root systems, (shallow, dimorphic and deep), and their ability to use different water sources (surficial and/or deep). Because of the differential impact of the goat overgrazing on different functional groups, this would result on a lower utilization of surficial waters. A management and/or restoration plan should maximize the use of all water sources available to recover the primary productivity and the system stability

Time-dependent anisotropic distributed source capability in transient 3-d transport code tort-TD

International Nuclear Information System (INIS)

Seubert, A.; Pautz, A.; Becker, M.; Dagan, R.

2009-01-01

The transient 3-D discrete ordinates transport code TORT-TD has been extended to account for time-dependent anisotropic distributed external sources. The extension aims at the simulation of the pulsed neutron source in the YALINA-Thermal subcritical assembly. Since feedback effects are not relevant in this zero-power configuration, this offers a unique opportunity to validate the time-dependent neutron kinetics of TORT-TD with experimental data. The extensions made in TORT-TD to incorporate a time-dependent anisotropic external source are described. The steady state of the YALINA-Thermal assembly and its response to an artificial square-wave source pulse sequence have been analysed with TORT-TD using pin-wise homogenised cross sections in 18 prompt energy groups with P 1 scattering order and 8 delayed neutron groups. The results demonstrate the applicability of TORT-TD to subcritical problems with a time-dependent external source. (authors)

Improving wheat productivity through source and timing of nitrogen fertilization

International Nuclear Information System (INIS)

Jan, M.T.; Khan, A.; Afridi, M.Z.; Arif, M.; Khan, M.J.; Farhatullah; Jan, D.; Saeed, M.

2011-01-01

Efficient nitrogen (N) fertilizer management is critical for the improved production of wheat (Triticum aestivum L.) and can be achieved through source and timing of N application. Thus, an experiment was carried out at the Research Farm of KPK Agricultural University Peshawar during 2005-06 to test the effects of sources and timing of N application on yield and yield components of wheat. Nitrogen sources were ammonium (NH/sub 4/) and nitrate (NO/sub 3/) applied at the rate of 100 kg ha/sup -1/ at three different stages i.e., at sowing (S1), tillering (S2) and boot stage (S3). Ammonium N increased yield component but did not affect the final grain yield. Split N application at sowing, tillering and boot stages had increased productive tillers m-2, and thousand grains weight, whereas grain yield was higher when N was applied at tillering and boot stages. Nitrogen fertilization increased 20% grain yield compared to control regardless of N application time. It was concluded from the experiment that split application of NH/sub 4/-N performed better than full dose application and/or NO/sub 3/-N for improved wheat productivity and thus, is recommended for general practice in agro-climatic conditions of Peshawar. (author)

The Contribution of Executive Function to Source Memory Development in Early Childhood

Science.gov (United States)

Rajan, Vinaya; Cuevas, Kimberly; Bell, Martha Ann

2014-01-01

Age-related differences in episodic memory judgments assessing recall of fact information and the source of this information were examined. The role of executive function (EF) in supporting early episodic memory ability was also explored. Four- and 6-year-old children were taught 10 novel facts from two different sources (experimenter or puppet),…

Almost Automorphic Functions on the Quantum Time Scale and Applications

Directory of Open Access Journals (Sweden)

Yongkun Li

2017-01-01

Full Text Available We first propose two types of concepts of almost automorphic functions on the quantum time scale. Secondly, we study some basic properties of almost automorphic functions on the quantum time scale. Then, we introduce a transformation between functions defined on the quantum time scale and functions defined on the set of generalized integer numbers; by using this transformation we give equivalent definitions of almost automorphic functions on the quantum time scale; following the idea of the transformation, we also give a concept of almost automorphic functions on more general time scales that can unify the concepts of almost automorphic functions on almost periodic time scales and on the quantum time scale. Finally, as an application of our results, we establish the existence of almost automorphic solutions of linear and semilinear dynamic equations on the quantum time scale.

Non-linear shape functions over time in the space-time finite element method

Directory of Open Access Journals (Sweden)

Kacprzyk Zbigniew

2017-01-01

Full Text Available This work presents a generalisation of the space-time finite element method proposed by Kączkowski in his seminal of 1970’s and early 1980’s works. Kączkowski used linear shape functions in time. The recurrence formula obtained by Kączkowski was conditionally stable. In this paper, non-linear shape functions in time are proposed.

Disrupting gatekeeping practices: Journalists' source selection in times of crisis.

Science.gov (United States)

van der Meer, Toni G L A; Verhoeven, Piet; Beentjes, Johannes W J; Vliegenthart, Rens

2017-10-01

As gatekeepers, journalists have the power to select the sources that get a voice in crisis coverage. The aim of this study is to find out how journalists select sources during a crisis. In a survey, journalists were asked how they assess the following sources during an organizational crisis: news agencies, an organization undergoing a crisis, and the general public. The sample consisted of 214 Dutch experienced journalists who at least once covered a crisis. Using structural equation modeling, sources' likelihood of being included in the news was predicted using five source characteristics: credibility, knowledge, willingness, timeliness, and the relationship with the journalist. Findings indicated that during a crisis, news agencies are most likely to be included in the news, followed by the public, and finally the organization. The significance of the five source characteristics is dependent on source type. For example, to be used in the news, news agencies and organizations should be mainly evaluated as knowledgeable, whereas information from the public should be both credible and timely. In addition, organizations should not be seen as too willing or too eager to communicate. The findings imply that, during a crisis, journalists remain critical gatekeepers; however, they rely mainly on familiar sources.

Time-dependent density functional methods for Raman spectra in open-shell systems.

Science.gov (United States)

Aquino, Fredy W; Schatz, George C

2014-01-16

We present an implementation of a time-dependent density functional theory (TD-DFT) linear response module in NWChem for unrestricted DFT calculations and apply it to the calculation of resonant Raman spectra in open-shell molecular systems using the short-time approximation. The new source code was validated and applied to simulate Raman spectra on several doublet organic radicals (e.g., benzyl, benzosemiquinone, TMPD, trans-stilbene anion and cation, and methyl viologen) and the metal complex copper phthalocyanine. We also introduce a divide-and-conquer approach for the evaluation of polarizabilities in relatively large systems (e.g., copper phthalocyanine). The implemented tool gives comparisons with experiment that are similar to what is commonly found for closed-shell systems, with good agreement for most features except for small frequency shifts, and occasionally large deviations for some modes that depend on the molecular system studied, experimental conditions not being accounted in the modeling such as solvation effects and extra solvent-based peaks, and approximations in the underlying theory. The approximations used in the quantum chemical modeling include (i) choice of exchange-correlation functional and basis set; (ii) harmonic approximation used in the frequency analysis to determine vibrational normal modes; and (iii) short-time approximation (omission of nuclear motion effects) used in calculating resonant Raman spectra.

The relationship between sources and functions of social support and dimensions of child- and parent-related stress.

Science.gov (United States)

Guralnick, M J; Hammond, M A; Neville, B; Connor, R T

2008-12-01

In this longitudinal study, we examined the relationship between the sources and functions of social support and dimensions of child- and parent-related stress for mothers of young children with mild developmental delays. Sixty-three mothers completed assessments of stress and support at two time points. Multiple regression analyses revealed that parenting support during the early childhood period (i.e. advice on problems specific to their child and assistance with child care responsibilities), irrespective of source, consistently predicted most dimensions of parent stress assessed during the early elementary years and contributed unique variance. General support (i.e. primarily emotional support and validation) from various sources had other, less widespread effects on parental stress. The multidimensional perspective of the construct of social support that emerged suggested mechanisms mediating the relationship between support and stress and provided a framework for intervention.

Addendum to foundations of multidimensional wave field signal theory: Gaussian source function

Directory of Open Access Journals (Sweden)

Natalie Baddour

2018-02-01

Full Text Available Many important physical phenomena are described by wave or diffusion-wave type equations. Recent work has shown that a transform domain signal description from linear system theory can give meaningful insight to multi-dimensional wave fields. In N. Baddour [AIP Adv. 1, 022120 (2011], certain results were derived that are mathematically useful for the inversion of multi-dimensional Fourier transforms, but more importantly provide useful insight into how source functions are related to the resulting wave field. In this short addendum to that work, it is shown that these results can be applied with a Gaussian source function, which is often useful for modelling various physical phenomena.

Addendum to foundations of multidimensional wave field signal theory: Gaussian source function

Science.gov (United States)

Baddour, Natalie

2018-02-01

Many important physical phenomena are described by wave or diffusion-wave type equations. Recent work has shown that a transform domain signal description from linear system theory can give meaningful insight to multi-dimensional wave fields. In N. Baddour [AIP Adv. 1, 022120 (2011)], certain results were derived that are mathematically useful for the inversion of multi-dimensional Fourier transforms, but more importantly provide useful insight into how source functions are related to the resulting wave field. In this short addendum to that work, it is shown that these results can be applied with a Gaussian source function, which is often useful for modelling various physical phenomena.

Attenuation of contaminant plumes in homogeneous aquifers: Sensitivity to source function at moderate to large peclet numbers

International Nuclear Information System (INIS)

Selander, W.N.; Lane, F.E.; Rowat, J.H.

1995-05-01

A groundwater mass transfer calculation is an essential part of the performance assessment for radioactive waste disposal facilities. AECL's IRUS (Intrusion Resistant Underground Structure) facility, which is designed for the near-surface disposal of low-level radioactive waste (LLRW), is to be situated in the sandy overburden at AECL's Chalk River Laboratories. Flow in the sandy aquifers at the proposed IRUS site is relatively homogeneous and advection-dominated (large Peclet numbers). Mass transfer along the mean direction of flow from the IRUS site may be described using the one-dimensional advection-dispersion equation, for which a Green's function representation of downstream radionuclide flux is convenient. This report shows that in advection-dominated aquifers, dispersive attenuation of initial contaminant releases depends principally on two time scales: the source duration and the pulse breakthrough time. Numerical investigation shows further that the maximum downstream flux or concentration depends on these time scales in a simple characteristic way that is minimally sensitive to the shape of the initial source pulse. (author). 11 refs., 2 tabs., 3 figs

Time-domain representation of frequency-dependent foundation impedance functions

Science.gov (United States)

Safak, E.

2006-01-01

Foundation impedance functions provide a simple means to account for soil-structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.

Extracting functional components of neural dynamics with Independent Component Analysis and inverse Current Source Density.

Science.gov (United States)

Lęski, Szymon; Kublik, Ewa; Swiejkowski, Daniel A; Wróbel, Andrzej; Wójcik, Daniel K

2010-12-01

Local field potentials have good temporal resolution but are blurred due to the slow spatial decay of the electric field. For simultaneous recordings on regular grids one can reconstruct efficiently the current sources (CSD) using the inverse Current Source Density method (iCSD). It is possible to decompose the resultant spatiotemporal information about the current dynamics into functional components using Independent Component Analysis (ICA). We show on test data modeling recordings of evoked potentials on a grid of 4 × 5 × 7 points that meaningful results are obtained with spatial ICA decomposition of reconstructed CSD. The components obtained through decomposition of CSD are better defined and allow easier physiological interpretation than the results of similar analysis of corresponding evoked potentials in the thalamus. We show that spatiotemporal ICA decompositions can perform better for certain types of sources but it does not seem to be the case for the experimental data studied. Having found the appropriate approach to decomposing neural dynamics into functional components we use the technique to study the somatosensory evoked potentials recorded on a grid spanning a large part of the forebrain. We discuss two example components associated with the first waves of activation of the somatosensory thalamus. We show that the proposed method brings up new, more detailed information on the time and spatial location of specific activity conveyed through various parts of the somatosensory thalamus in the rat.

Disrupting gatekeeping practices: Journalists’ source selection in times of crisis

Science.gov (United States)

van der Meer, Toni G.L.A.; Verhoeven, Piet; Beentjes, Johannes W.J.; Vliegenthart, Rens

2016-01-01

As gatekeepers, journalists have the power to select the sources that get a voice in crisis coverage. The aim of this study is to find out how journalists select sources during a crisis. In a survey, journalists were asked how they assess the following sources during an organizational crisis: news agencies, an organization undergoing a crisis, and the general public. The sample consisted of 214 Dutch experienced journalists who at least once covered a crisis. Using structural equation modeling, sources’ likelihood of being included in the news was predicted using five source characteristics: credibility, knowledge, willingness, timeliness, and the relationship with the journalist. Findings indicated that during a crisis, news agencies are most likely to be included in the news, followed by the public, and finally the organization. The significance of the five source characteristics is dependent on source type. For example, to be used in the news, news agencies and organizations should be mainly evaluated as knowledgeable, whereas information from the public should be both credible and timely. In addition, organizations should not be seen as too willing or too eager to communicate. The findings imply that, during a crisis, journalists remain critical gatekeepers; however, they rely mainly on familiar sources. PMID:29278263

Developmental changes in fact and source recall: Contributions from executive function and brain electrical activity

Directory of Open Access Journals (Sweden)

Vinaya Rajan

2015-04-01

Full Text Available Source memory involves recollecting the contextual details surrounding a memory episode. When source information is bound together, it makes a memory episodic in nature. Unfortunately, very little is known about the factors that contribute to its formation in early development. This study examined the development of source memory in middle childhood. Measures of executive function were examined as potential sources of variation in fact and source recall. Continuous electroencephalogram (EEG measures were collected during baseline and fact and source retrieval in order to examine memory-related changes in EEG power. Six and 8-year-old children were taught 10 novel facts from two different sources and recall for fact and source information was later tested. Older children were better on fact recall, but both ages were comparable on source recall. However, source recall performance was poor at both ages, suggesting that this ability continues to develop beyond middle childhood. Regression analyses revealed that executive function uniquely predicted variance in source recall performance. Task-related increases in theta power were observed at frontal, temporal and parietal electrode sites during fact and source retrieval. This investigation contributes to our understanding of age-related differences in source memory processing in middle childhood.

Overcomplete Blind Source Separation by Combining ICA and Binary Time-Frequency Masking

DEFF Research Database (Denmark)

Pedersen, Michael Syskind; Wang, DeLiang; Larsen, Jan

2005-01-01

a novel method for over-complete blind source separation. Two powerful source separation techniques have been combined, independent component analysis and binary time-frequency masking. Hereby, it is possible to iteratively extract each speech signal from the mixture. By using merely two microphones we...

Functional food awareness and perceptions in relation to information sources in older adults.

Science.gov (United States)

Vella, Meagan N; Stratton, Laura M; Sheeshka, Judy; Duncan, Alison M

2014-05-17

The functional food industry has experienced innovative and economic expansion, yet research into consumer perceptions of functional foods and their associated health claims is limited. Among consumers, older adults could benefit from functional foods due to age-related issues pertaining to food and health. The purpose of this research was to identify the need for information related to functional foods among older adults (≥60 years old) and to assess awareness and perceptions of health claims on functional food packages. Community-dwelling older adults (n = 200) completed a researcher administered questionnaire designed to collect information about functional foods including current consumption, motivating factors for consumption, perceived need for information, sources of information for functional foods and awareness of health claims. Prevalence of functional food consumption among participants was 93.0%. Increased awareness and knowledge was the most commonly reported factor that would promote functional food consumption (85.5%) and 63.5% of participants wanted more information about functional foods with preferred sources being newspapers/magazines/books (68.5%) and food labels (66.1%). Participants were predominately (93.5%) aware of health claims on functional foods and those with more education were more likely to report being aware of health claims (p = 0.045). Although functional food consumption among older adults in this sample is high, there is a need for further information regarding functional foods. These results inform stakeholders regarding the potential for information to influence functional food acceptance among older adult consumers.

An open-source framework for analyzing N-electron dynamics. II. Hybrid density functional theory/configuration interaction methodology.

Science.gov (United States)

Hermann, Gunter; Pohl, Vincent; Tremblay, Jean Christophe

2017-10-30

In this contribution, we extend our framework for analyzing and visualizing correlated many-electron dynamics to non-variational, highly scalable electronic structure method. Specifically, an explicitly time-dependent electronic wave packet is written as a linear combination of N-electron wave functions at the configuration interaction singles (CIS) level, which are obtained from a reference time-dependent density functional theory (TDDFT) calculation. The procedure is implemented in the open-source Python program detCI@ORBKIT, which extends the capabilities of our recently published post-processing toolbox (Hermann et al., J. Comput. Chem. 2016, 37, 1511). From the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions, the framework exploits the multideterminental structure of the hybrid TDDFT/CIS wave packet to compute fundamental one-electron quantities such as difference electronic densities, transient electronic flux densities, and transition dipole moments. The hybrid scheme is benchmarked against wave function data for the laser-driven state selective excitation in LiH. It is shown that all features of the electron dynamics are in good quantitative agreement with the higher-level method provided a judicious choice of functional is made. Broadband excitation of a medium-sized organic chromophore further demonstrates the scalability of the method. In addition, the time-dependent flux densities unravel the mechanistic details of the simulated charge migration process at a glance. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Finite element approximation for time-dependent diffusion with measure-valued source

Czech Academy of Sciences Publication Activity Database

Seidman, T.; Gobbert, M.; Trott, D.; Kružík, Martin

2012-01-01

Roč. 122, č. 4 (2012), s. 709-723 ISSN 0029-599X R&D Projects: GA AV ČR IAA100750802 Institutional support: RVO:67985556 Keywords : measure-valued source * diffusion equation Subject RIV: BA - General Mathematics Impact factor: 1.329, year: 2012 http://library.utia.cas.cz/separaty/2012/MTR/kruzik-finite element approximation for time - dependent diffusion with measure-valued source.pdf

Design of the Advanced Light Source timing system

International Nuclear Information System (INIS)

Fahmie, M.

1993-05-01

The Advanced Light Source (ALS) is a third generation synchrotron radiation facility, and as such, has several unique timing requirements. Arbitrary Storage Ring filling patterns and high single bunch purity requirements demand a highly stable, low jitter timing system with the flexibility to reconfigure on a pulse-to-pulse basis. This modular system utilizes a highly linear Gauss Clock with ''on the fly'' programmable setpoints to track a free-running Booster ramping magnet and provides digitally programmable sequencing and delay for Electron Gun, Linac, Booster Ring, and Storage Ring RF, Pulsed Magnet, and Instrumentation systems. It has proven itself over the last year of accelerator operation to be reliable and rock solid

Source Estimation by Full Wave Form Inversion

Energy Technology Data Exchange (ETDEWEB)

Sjögreen, Björn [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing; Petersson, N. Anders [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing

2013-08-07

Given time-dependent ground motion recordings at a number of receiver stations, we solve the inverse problem for estimating the parameters of the seismic source. The source is modeled as a point moment tensor source, characterized by its location, moment tensor components, the start time, and frequency parameter (rise time) of its source time function. In total, there are 11 unknown parameters. We use a non-linear conjugate gradient algorithm to minimize the full waveform misfit between observed and computed ground motions at the receiver stations. An important underlying assumption of the minimization problem is that the wave propagation is accurately described by the elastic wave equation in a heterogeneous isotropic material. We use a fourth order accurate finite difference method, developed in [12], to evolve the waves forwards in time. The adjoint wave equation corresponding to the discretized elastic wave equation is used to compute the gradient of the misfit, which is needed by the non-linear conjugated minimization algorithm. A new source point moment source discretization is derived that guarantees that the Hessian of the misfit is a continuous function of the source location. An efficient approach for calculating the Hessian is also presented. We show how the Hessian can be used to scale the problem to improve the convergence of the non-linear conjugated gradient algorithm. Numerical experiments are presented for estimating the source parameters from synthetic data in a layer over half-space problem (LOH.1), illustrating rapid convergence of the proposed approach.

Characterization of Ground Displacement Sources from Variational Bayesian Independent Component Analysis of Space Geodetic Time Series

Science.gov (United States)

Gualandi, Adriano; Serpelloni, Enrico; Elina Belardinelli, Maria; Bonafede, Maurizio; Pezzo, Giuseppe; Tolomei, Cristiano

2015-04-01

A critical point in the analysis of ground displacement time series, as those measured by modern space geodetic techniques (primarly continuous GPS/GNSS and InSAR) is the development of data driven methods that allow to discern and characterize the different sources that generate the observed displacements. A widely used multivariate statistical technique is the Principal Component Analysis (PCA), which allows to reduce the dimensionality of the data space maintaining most of the variance of the dataset explained. It reproduces the original data using a limited number of Principal Components, but it also shows some deficiencies, since PCA does not perform well in finding the solution to the so-called Blind Source Separation (BSS) problem. The recovering and separation of the different sources that generate the observed ground deformation is a fundamental task in order to provide a physical meaning to the possible different sources. PCA fails in the BSS problem since it looks for a new Euclidean space where the projected data are uncorrelated. Usually, the uncorrelation condition is not strong enough and it has been proven that the BSS problem can be tackled imposing on the components to be independent. The Independent Component Analysis (ICA) is, in fact, another popular technique adopted to approach this problem, and it can be used in all those fields where PCA is also applied. An ICA approach enables us to explain the displacement time series imposing a fewer number of constraints on the model, and to reveal anomalies in the data such as transient deformation signals. However, the independence condition is not easy to impose, and it is often necessary to introduce some approximations. To work around this problem, we use a variational bayesian ICA (vbICA) method, which models the probability density function (pdf) of each source signal using a mix of Gaussian distributions. This technique allows for more flexibility in the description of the pdf of the sources

Time collimation for elastic neutron scattering instrument at a pulsed source

International Nuclear Information System (INIS)

Aksenov, V.L.; Nikitenko, Yu.V.

1996-01-01

Conditions for carrying out elastic neutron scattering experiments using the time-of-flight technique are considered. It is shown that the employment of time dependent neutron beam collimation in the source-sample flight path increases the luminosity of the spectrometer under certain resolution restrictions. 3 refs., 8 figs

SLStudio: Open-source framework for real-time structured light

DEFF Research Database (Denmark)

Wilm, Jakob; Olesen, Oline Vinter; Larsen, Rasmus

2014-01-01

that this software makes real-time 3D scene capture more widely accessible and serves as a foundation for new structured light scanners operating in real-time, e.g. 20 depth images per second and more. The use cases for such scanners are plentyfull, however due to the computational constraints, all public......An open-source framework for real-time structured light is presented. It is called “SLStudio”, and enables real-time capture of metric depth images. The framework is modular, and extensible to support new algorithms for scene encoding/decoding, triangulation, and aquisition hardware. It is the aim...... implementations so far are limited to offline processing. With “SLStudio”, we are making a platform available which enables researchers from many different fields to build application specific real time 3D scanners. The software is hosted at http://compute.dtu.dk/~jakw/slstudio....

Disentangling the major source areas for an intense aerosol advection in the Central Mediterranean on the basis of Potential Source Contribution Function modeling of chemical and size distribution measurements

Science.gov (United States)

Petroselli, Chiara; Crocchianti, Stefano; Moroni, Beatrice; Castellini, Silvia; Selvaggi, Roberta; Nava, Silvia; Calzolai, Giulia; Lucarelli, Franco; Cappelletti, David

2018-05-01

In this paper, we combined a Potential Source Contribution Function (PSCF) analysis of daily chemical aerosol composition data with hourly aerosol size distributions with the aim to disentangle the major source areas during a complex and fast modulating advection event impacting on Central Italy in 2013. Chemical data include an ample set of metals obtained by Proton Induced X-ray Emission (PIXE), main soluble ions from ionic chromatography and elemental and organic carbon (EC, OC) obtained by thermo-optical measurements. Size distributions have been recorded with an optical particle counter for eight calibrated size classes in the 0.27-10 μm range. We demonstrated the usefulness of the approach by the positive identification of two very different source areas impacting during the transport event. In particular, biomass burning from Eastern Europe and desert dust from Sahara sources have been discriminated based on both chemistry and size distribution time evolution. Hourly BT provided the best results in comparison to 6 h or 24 h based calculations.

Time-dependent importance sampling in semiclassical initial value representation calculations for time correlation functions.

Science.gov (United States)

Tao, Guohua; Miller, William H

2011-07-14

An efficient time-dependent importance sampling method is developed for the Monte Carlo calculation of time correlation functions via the initial value representation (IVR) of semiclassical (SC) theory. A prefactor-free time-dependent sampling function weights the importance of a trajectory based on the magnitude of its contribution to the time correlation function, and global trial moves are used to facilitate the efficient sampling the phase space of initial conditions. The method can be generally applied to sampling rare events efficiently while avoiding being trapped in a local region of the phase space. Results presented in the paper for two system-bath models demonstrate the efficiency of this new importance sampling method for full SC-IVR calculations.

Measurement of emission diameter as a function of time on foam z- pinch plasmas

International Nuclear Information System (INIS)

Lazier, S.E.; Barber, T.L.; Derzon, M.S.; Kellogg, J.W.

1996-01-01

We have developed a streaked imaging capability to make time-resolved measurements of the emission size for low density foam z-pinches. By lens coupling visible emission from the z-pinch target to an array of fiber optics we obtained the emission profile in the visible as a function of time with radial resolution of 300 μm. To measure the emission at temperatures greater than ∼40 eV the source was slit-imaged or pin-hole imaged onto an x-ray filtered scintillator. Non-uniformities in both visible and x-ray emission were observed. We describe the diagnostics, the image unfold process, and results from the instrument for both visible and x-ray measurements

OpenNFT: An open-source Python/Matlab framework for real-time fMRI neurofeedback training based on activity, connectivity and multivariate pattern analysis.

Science.gov (United States)

Koush, Yury; Ashburner, John; Prilepin, Evgeny; Sladky, Ronald; Zeidman, Peter; Bibikov, Sergei; Scharnowski, Frank; Nikonorov, Artem; De Ville, Dimitri Van

2017-08-01

Neurofeedback based on real-time functional magnetic resonance imaging (rt-fMRI) is a novel and rapidly developing research field. It allows for training of voluntary control over localized brain activity and connectivity and has demonstrated promising clinical applications. Because of the rapid technical developments of MRI techniques and the availability of high-performance computing, new methodological advances in rt-fMRI neurofeedback become possible. Here we outline the core components of a novel open-source neurofeedback framework, termed Open NeuroFeedback Training (OpenNFT), which efficiently integrates these new developments. This framework is implemented using Python and Matlab source code to allow for diverse functionality, high modularity, and rapid extendibility of the software depending on the user's needs. In addition, it provides an easy interface to the functionality of Statistical Parametric Mapping (SPM) that is also open-source and one of the most widely used fMRI data analysis software. We demonstrate the functionality of our new framework by describing case studies that include neurofeedback protocols based on brain activity levels, effective connectivity models, and pattern classification approaches. This open-source initiative provides a suitable framework to actively engage in the development of novel neurofeedback approaches, so that local methodological developments can be easily made accessible to a wider range of users. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Origin of the tail in Green's functions in odd-dimensional space-times

Science.gov (United States)

Dai, De-Chang; Stojkovic, Dejan

2013-10-01

It is well known that the scalar field Green's function in odd dimensions has a tail, i.e. a non-zero support inside the light cone, which in turn implies that the Huygens' principle is violated. However, the reason behind this behavior is still not quite clear. In this paper we shed more light on the physical origin of the tail by regularizing the term which is usually ignored in the literature since it vanishes due to the action of the delta function. With this extra term the Green's function does not satisfy the source-free wave equation (in the region outside of the source). We show that this term corresponds to a charge imprinted on the light-cone shell. Unlike the vector field charge, a moving scalar field charge is not Lorentz invariant and is contracted by a factor. If a scalar charge is moving at the speed of light, it appears to be zero in the static (with respect to the original physical charge) observer's frame. However, the field it sources is not entirely on the light cone. Thus, it is likely that this hidden charge sources the mysterious tail in odd dimensions.

Blind Time-Frequency Analysis for Source Discrimination in Multisensor Array Processing

National Research Council Canada - National Science Library

Amin, Moeness

1999-01-01

.... We have clearly demonstrated, through analysis and simulations, the offerings of time-frequency distributions in solving key problems in sensor array processing, including direction finding, source...

Determination of noise sources and space-dependent reactor transfer functions from measured output signals only

Energy Technology Data Exchange (ETDEWEB)

Hoogenboom, J.E.; van Dam, H.; Kleiss, E.B.J.; van Uitert, G.C.; Veldhuis, D.

1982-01-01

The measured cross power spectral densities of the signals from three neutron detectors and the displacement of the control rod of the 2 MW research reactor HOR at Delft have been used to determine the space-dependent reactor transfer function, the transfer function of the automatic reactor control system and the noise sources influencing the measured signals. From a block diagram of the reactor with control system and noise sources expressions were derived for the measured cross power spectral densities, which were adjusted to satisfy the requirements following from the adopted model. Then for each frequency point the required transfer functions and noise sources could be derived. The results are in agreement with those of autoregressive modelling of the reactor control feed-back loop. A method has been developed to determine the non-linear characteristics of the automatic reactor control system by analysing the non-gaussian probability density function of the power fluctuations.

Determination of noise sources and space-dependent reactor transfer functions from measured output signals only

International Nuclear Information System (INIS)

Hoogenboom, J.E.

1982-01-01

The measured cross power spectral densities of the signals from three neutron detectors and the displacement of the control rod of the 2 MW research reactor HOR at Delft have been used to determine the space-dependent reactor transfer function, the transfer function of the automatic reactor control system and the noise sources influencing the measured signals. From a block diagram of the reactor with control system and noise sources expressions were derived for the measured cross power spectral densities, which were adjusted to satisfy the requirements following from the adopted model. Then for each frequency point the required transfer functions and noise sources could be derived. The results are in agreement with those of autoregressive modelling of the reactor control feed-back loop. A method has been developed to determine the non-linear characteristics of the automatic reactor control system by analysing the non-gaussian probability density function of the power fluctuations. (author)

Functional food awareness and perceptions in relation to information sources in older adults

Science.gov (United States)

2014-01-01

Background The functional food industry has experienced innovative and economic expansion, yet research into consumer perceptions of functional foods and their associated health claims is limited. Among consumers, older adults could benefit from functional foods due to age-related issues pertaining to food and health. The purpose of this research was to identify the need for information related to functional foods among older adults (≥60 years old) and to assess awareness and perceptions of health claims on functional food packages. Methods Community-dwelling older adults (n = 200) completed a researcher administered questionnaire designed to collect information about functional foods including current consumption, motivating factors for consumption, perceived need for information, sources of information for functional foods and awareness of health claims. Results Prevalence of functional food consumption among participants was 93.0%. Increased awareness and knowledge was the most commonly reported factor that would promote functional food consumption (85.5%) and 63.5% of participants wanted more information about functional foods with preferred sources being newspapers/magazines/books (68.5%) and food labels (66.1%). Participants were predominately (93.5%) aware of health claims on functional foods and those with more education were more likely to report being aware of health claims (p = 0.045). Conclusions Although functional food consumption among older adults in this sample is high, there is a need for further information regarding functional foods. These results inform stakeholders regarding the potential for information to influence functional food acceptance among older adult consumers. PMID:24886306

A compact time-of-flight mass spectrometer for ion source characterization

International Nuclear Information System (INIS)

Chen, L.; Wan, X.; Jin, D. Z.; Tan, X. H.; Huang, Z. X.; Tan, G. B.

2015-01-01

A compact time-of-flight mass spectrometer with overall dimension of about 413 × 250 × 414 mm based on orthogonal injection and angle reflection has been developed for ion source characterization. Configuration and principle of the time-of-flight mass spectrometer are introduced in this paper. The mass resolution is optimized to be about 1690 (FWHM), and the ion energy detection range is tested to be between about 3 and 163 eV with the help of electron impact ion source. High mass resolution and compact configuration make this spectrometer useful to provide a valuable diagnostic for ion spectra fundamental research and study the mass to charge composition of plasma with wide range of parameters

Measurement and simulation of the time-dependent behavior of the UMER source

International Nuclear Information System (INIS)

Haber, I.; Feldman, D.; Fiorito, R.; Friedman, A.; Grote, D.P.; Kishek, R.A.; Quinn, B.; Reiser, M.; Rodgers, J.; O'Shea, P.G.; Stratakis, D.; Tian, K.; Vay, J.-L.; Walter, M.

2007-01-01

Control of the time-dependent characteristics of the beam pulse, beginning when it is born from the source, is important for obtaining adequate beam intensity on a target. Recent experimental measurements combined with the new mesh-refinement capability in WARP have improved the understanding of time-dependent beam characteristics beginning at the source, as well as the predictive ability of the simulation codes. The University of Maryland Electron Ring (UMER), because of its ease of operation and flexible diagnostics has proved particularly useful for benchmarking WARP by comparing simulation to measurement. One source of significant agreement has been in the ability of three-dimensional WARP simulations to predict the onset of virtual cathode oscillations in the vicinity of the cathode grid in the UMER gun, and the subsequent measurement of the predicted oscillations

Non-uniform dwell times in line source high dose rate brachytherapy: physical and radiobiological considerations

International Nuclear Information System (INIS)

Jones, B.; Tan, L.T.; Freestone, G.; Bleasdale, C.; Myint, S.; Littler, J.

1994-01-01

The ability to vary source dwell times in high dose rate (HDR) brachytherapy allows for the use of non-uniform dwell times along a line source. This may have advantages in the radical treatment of tumours depending on individual tumour geometry. This study investigates the potential improvements in local tumour control relative to adjacent normal tissue isoeffects when intratumour source dwell times are increased along the central portion of a line source (technique A) in radiotherapy schedules which include a relatively small component of HDR brachytherapy. Such a technique is predicted to increase the local control for tumours of diameters ranging between 2 cm and 4 cm by up to 11% compared with a technique in which there are uniform dwell times along the line source (technique B). There is no difference in the local control rates for the two techniques when used to treat smaller tumours. Normal tissue doses are also modified by the technique used. Technique A produces higher normal tissue doses at points perpendicular to the centre of the line source and lower dose at points nearer the ends of the line source if the prescription point is not in the central plane of the line source. Alternatively, if the dose is prescribed at a point in the central plane of the line source, the dose at all the normal tissue points are lower when technique A is used. (author)

Three-Dimensional Passive-Source Reverse-Time Migration of Converted Waves: The Method

Science.gov (United States)

Li, Jiahang; Shen, Yang; Zhang, Wei

2018-02-01

At seismic discontinuities in the crust and mantle, part of the compressional wave energy converts to shear wave, and vice versa. These converted waves have been widely used in receiver function (RF) studies to image discontinuity structures in the Earth. While generally successful, the conventional RF method has its limitations and is suited mostly to flat or gently dipping structures. Among the efforts to overcome the limitations of the conventional RF method is the development of the wave-theory-based, passive-source reverse-time migration (PS-RTM) for imaging complex seismic discontinuities and scatters. To date, PS-RTM has been implemented only in 2D in the Cartesian coordinate for local problems and thus has limited applicability. In this paper, we introduce a 3D PS-RTM approach in the spherical coordinate, which is better suited for regional and global problems. New computational procedures are developed to reduce artifacts and enhance migrated images, including back-propagating the main arrival and the coda containing the converted waves separately, using a modified Helmholtz decomposition operator to separate the P and S modes in the back-propagated wavefields, and applying an imaging condition that maintains a consistent polarity for a given velocity contrast. Our new approach allows us to use migration velocity models with realistic velocity discontinuities, improving accuracy of the migrated images. We present several synthetic experiments to demonstrate the method, using regional and teleseismic sources. The results show that both regional and teleseismic sources can illuminate complex structures and this method is well suited for imaging dipping interfaces and sharp lateral changes in discontinuity structures.

Development of computer-based function to estimate radioactive source term by coupling atmospheric model with monitoring data

International Nuclear Information System (INIS)

Akiko, Furuno; Hideyuki, Kitabata

2003-01-01

Full text: The importance of computer-based decision support systems for local and regional scale accidents has been recognized by many countries with the experiences of accidental atmospheric releases of radionuclides at Chernobyl in 1986 in the former Soviet Union. The recent increase of nuclear power plants in the Asian region also necessitates an emergency response system for Japan to predict the long-range atmospheric dispersion of radionuclides due to overseas accident. On the basis of these backgrounds, WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information) at Japan Atomic Energy Research Institute is developed to forecast long-range atmospheric dispersions of radionuclides during nuclear emergency. Although the source condition is critical parameter for accurate prediction, it is rarely that the condition can be acquired in the early stage of overseas accident. Thus, we have been developing a computer-based function to estimate radioactive source term, e.g. the release point, time and amount, as a part of WSPEEDI. This function consists of atmospheric transport simulations and statistical analysis for the prediction and monitoring of air dose rates. Atmospheric transport simulations are carried out for the matrix of possible release points in Eastern Asia and possible release times. The simulation results of air dose rates are compared with monitoring data and the best fitted release condition is defined as source term. This paper describes the source term estimation method and the application to Eastern Asia. The latest version of WSPEEDI accommodates following two models: an atmospheric meteorological model MM5 and a particle random walk model GEARN. MM5 is a non-hydrostatic meteorological model developed by the Pennsylvania State University and the National Center for Atmospheric Research (NCAR). MM5 physically calculates more than 40 meteorological parameters with high resolution in time and space based an

Prediction of broadband ground-motion time histories: Hybrid low/high-frequency method with correlated random source parameters

Science.gov (United States)

Liu, P.; Archuleta, R.J.; Hartzell, S.H.

2006-01-01

We present a new method for calculating broadband time histories of ground motion based on a hybrid low-frequency/high-frequency approach with correlated source parameters. Using a finite-difference method we calculate low- frequency synthetics (structure. We also compute broadband synthetics in a 1D velocity model using a frequency-wavenumber method. The low frequencies from the 3D calculation are combined with the high frequencies from the 1D calculation by using matched filtering at a crossover frequency of 1 Hz. The source description, common to both the 1D and 3D synthetics, is based on correlated random distributions for the slip amplitude, rupture velocity, and rise time on the fault. This source description allows for the specification of source parameters independent of any a priori inversion results. In our broadband modeling we include correlation between slip amplitude, rupture velocity, and rise time, as suggested by dynamic fault modeling. The method of using correlated random source parameters is flexible and can be easily modified to adjust to our changing understanding of earthquake ruptures. A realistic attenuation model is common to both the 3D and 1D calculations that form the low- and high-frequency components of the broadband synthetics. The value of Q is a function of the local shear-wave velocity. To produce more accurate high-frequency amplitudes and durations, the 1D synthetics are corrected with a randomized, frequency-dependent radiation pattern. The 1D synthetics are further corrected for local site and nonlinear soil effects by using a 1D nonlinear propagation code and generic velocity structure appropriate for the site’s National Earthquake Hazards Reduction Program (NEHRP) site classification. The entire procedure is validated by comparison with the 1994 Northridge, California, strong ground motion data set. The bias and error found here for response spectral acceleration are similar to the best results that have been published by

Unified functional network and nonlinear time series analysis for complex systems science: The pyunicorn package

Science.gov (United States)

Donges, Jonathan; Heitzig, Jobst; Beronov, Boyan; Wiedermann, Marc; Runge, Jakob; Feng, Qing Yi; Tupikina, Liubov; Stolbova, Veronika; Donner, Reik; Marwan, Norbert; Dijkstra, Henk; Kurths, Jürgen

2016-04-01

We introduce the pyunicorn (Pythonic unified complex network and recurrence analysis toolbox) open source software package for applying and combining modern methods of data analysis and modeling from complex network theory and nonlinear time series analysis. pyunicorn is a fully object-oriented and easily parallelizable package written in the language Python. It allows for the construction of functional networks such as climate networks in climatology or functional brain networks in neuroscience representing the structure of statistical interrelationships in large data sets of time series and, subsequently, investigating this structure using advanced methods of complex network theory such as measures and models for spatial networks, networks of interacting networks, node-weighted statistics, or network surrogates. Additionally, pyunicorn provides insights into the nonlinear dynamics of complex systems as recorded in uni- and multivariate time series from a non-traditional perspective by means of recurrence quantification analysis, recurrence networks, visibility graphs, and construction of surrogate time series. The range of possible applications of the library is outlined, drawing on several examples mainly from the field of climatology. pyunicorn is available online at https://github.com/pik-copan/pyunicorn. Reference: J.F. Donges, J. Heitzig, B. Beronov, M. Wiedermann, J. Runge, Q.-Y. Feng, L. Tupikina, V. Stolbova, R.V. Donner, N. Marwan, H.A. Dijkstra, and J. Kurths, Unified functional network and nonlinear time series analysis for complex systems science: The pyunicorn package, Chaos 25, 113101 (2015), DOI: 10.1063/1.4934554, Preprint: arxiv.org:1507.01571 [physics.data-an].

Long-time tails of correlation and memory functions

Science.gov (United States)

Sawada, Isao

2002-11-01

We review the generalized Langevin equation, which is a transformation and reformulation of equation of motion, from the two viewpoints: the projection operator method developed by Mori and the recurrence relations method developed by Lee. The fluctuating forces acting on the Bloch electrons’ current are clarified the strongly colored quantum fluctuations with the spontaneous interband transitions leading to a long-time tail of 1/ t for the envelope of the memory function. The velocity autocorrelation functions in the coupled harmonic oscillator on the Bethe lattice have a long-time tail of 1/t t. The oscillation and the form of decay found in correlation functions affect transport coefficients given by the integrated intensity up to infinity. We also study the force-force correlation functions often used as an approximation to the memory function.

Impact source identification in finite isotropic plates using a time-reversal method: theoretical study

International Nuclear Information System (INIS)

Chen, Chunlin; Yuan, Fuh-Gwo

2010-01-01

This paper aims to identify impact sources on plate-like structures based on the synthetic time-reversal (T-R) concept using an array of sensors. The impact source characteristics, namely, impact location and impact loading time history, are reconstructed using the invariance of time-reversal concept, reciprocal theory, and signal processing algorithms. Numerical verification for two finite isotropic plates under low and high velocity impacts is performed to demonstrate the versatility of the synthetic T-R method for impact source identification. The results show that the impact location and time history of the impact force with various shapes and frequency bands can be readily obtained with only four sensors distributed around the impact location. The effects of time duration and the inaccuracy in the estimated impact location on the accuracy of the time history of the impact force using the T-R method are investigated. Since the T-R technique retraces all the multi-paths of reflected waves from the geometrical boundaries back to the impact location, it is well suited for quantifying the impact characteristics for complex structures. In addition, this method is robust against noise and it is suggested that a small number of sensors is sufficient to quantify the impact source characteristics through simple computation; thus it holds promise for the development of passive structural health monitoring (SHM) systems for impact monitoring in near real-time

[Cortical functional connectivity during retention of affective pictures in working memory: EEG-source theta coherence analysis].

Science.gov (United States)

Machinskaya, R I; Rozovskaya, R I; Kurgansky, A V; Pechenkova, E V

2016-01-01

A pattern of cortical functional connectivity in the source space was studied in a group of right-handed adult participants (N = 44:17 women, 27 men, aged M = 29.61 ± 6.45 years) who retained in their working memory (WM) traces of realistic pictures of positive, neutral, and negative emotional valence while in their working memory (WM) while performing same different task in which participants had to compare an etalon picture against a target picture that followed after a specified delay. A coherence (COH) between pairs of cortical sources chosen in advance according to fMRI data was estimated in the theta frequency range for the period of time preceding the etalon stimulus, distinct sets of functional links are found. The links of the first type that presumably reflect the involvement of sustained attention were between the dorsal anterior cingulate cortex, the prefrontal areas, and temporal areas of the right hemispheres. When compared to the rest period, links of this type showed strengthening not only during the retention period but also during the period preceding the etalon picture. The links of the second type presumably reflecting a progressive neocortex-to-hippocampus functional integration with increasing memory load and strengthened exclusively during retention period. Those links were between parietal, temporal and prefrontal cortices in the lateral surface of both hemispheres with the additional inclusion of the posterior cingulate cortex and the medial parietal cortex in the left hemisphere. An impact of emotional valence onto the strength and topography of the functional links of the second type was found. In the left hemisphere, an increase in the strength of cortical interaction was more pronounced for pictures of positive valence than for pictures of either neutral or negative valences. When compared to the pictures of neutral valence, the retention of pictorial information of both positive and negative valence showed some extraneous integration

Relation between equal-time and light-front wave functions

International Nuclear Information System (INIS)

Miller, Gerald A.; Tiburzi, Brian C.

2010-01-01

The relation between equal-time and light-front wave functions is studied using models for which the four-dimensional solution of the Bethe-Salpeter wave function can be obtained. The popular prescription of defining the longitudinal momentum fraction using the instant-form free kinetic energy and third component of momentum is found to be incorrect except in the nonrelativistic limit. One may obtain light-front wave functions from rest-frame, instant-form wave functions by boosting the latter wave functions to the infinite momentum frame. Despite this difficulty, we prove a relation between certain integrals of the equal-time and light-front wave functions.

Time dependence of energy spectra of brachytherapy sources and its impact on the half and the tenth value layers

International Nuclear Information System (INIS)

Yue, Ning J.; Chen Zhe; Hearn, Robert A.; Rodgers, Joseph J.; Nath, Ravinder

2009-01-01

Purpose: Several factors including radionuclide purity influence the photon energy spectra from sealed brachytherapy sources. The existence of impurities and trace elements in radioactive materials as well as the substrate and encapsulation may not only alter the spectrum at a given time but also cause change in the spectra as a function of time. The purpose of this study is to utilize a semiempirical formalism, which quantitatively incorporates this time dependence, to calculate and evaluate the shielding requirement impacts introduced by this time dependence for a 103 Pd source. Methods: The formalism was used to calculate the NthVL thicknesses in lead for a 103 Pd model 200 seed. Prior to 2005, the 103 Pd in this source was purified to a level better than 0.006% of the total 103 Pd activity, the key trace impurity consisting of 65 Zn. Because 65 Zn emits higher energy photons and has a much longer half-life of 244 days compared to 103 Pd, its presence in 103 Pd seeds led to a time dependence of the photon spectrum and other related physical quantities. This study focuses on the time dependence of the NthVL and the analysis of the corresponding shielding requirements. Results: The results indicate that the first HVL and the first TVL in lead steadily increased with time for about 200 days and then reached a plateau. The increases at plateau were more than 1000 times compared to the corresponding values on the zeroth day. The second and third TVLs in lead reached their plateaus in about 100 and 60 days, respectively, and the increases were about 19 and 2.33 times the corresponding values on the zeroth day, respectively. All the TVLs demonstrated a similar time dependence pattern, with substantial increases and eventual approach to a plateau. Conclusions: The authors conclude that the time dependence of the emitted photon spectra from brachytherapy sources can introduce substantial variations in the values of the NthVL with time if certain impurities are present

Identification of long-range transport of air pollutants using a Potential Source Contribution Function in Baengyeong Island, Korea

Science.gov (United States)

Ban, J.; Park, T.; Atwood, S. A.; Soo, C. J.; Ahn, J.; Lee, T.

2017-12-01

To understand the influence of long-range transport, Potential Source Contribution Function (PSCF) analysis is widely used in many studies. PSCF is a region containing a source for a particular constituent estimated by looking at the percentage of back-trajectories that pass over that region which contain high concentrations of the constituent. Aerosol concentration, wind direction, wind speed and back trajectory from NOAA HYSPLIT model in Baengyeong Island were used as input data for PSCF to consider the retention time of aerosol. Non-refractory PM1 (NR-PM1) concentrations were measured by an Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and meteorological variables were also measured in Baengnyeong Island, Korea during 2013 to 2015. We will investigate the influence of long-range transport and compare with AMS data from eastern China in November 2013. It will be provided the overview of long-range transport of NR-PM1 including inorganics and organics species to South Korea.

Estimating the Seasonal Importance of Precipitation to Plant Source Water over Time and Space with Water Isotopes

Science.gov (United States)

Nelson, D. B.; Kahmen, A.

2017-12-01

The stable isotopic composition of hydrogen and oxygen are physical properties of water molecules that can carry information on their sources or transport histories. This provides a useful tool for assessing the importance of rainfall at different times of the year for plant growth, provided that rainwater values vary over time and that waters do not partially evaporate after deposition. We tested the viability of this approach using data from samples collected at nineteen sites throughout Europe at monthly intervals over two consecutive growing seasons in 2014 and 2015. We compared isotope measurements of plant xylem water with soil water from multiple depths, and measured and modeled precipitation isotope values. Paired analyses of oxygen and hydrogen isotope values were used to screen out a limited number of water samples that were influenced by evaporation, with the majority of all water samples indicating meteoric sources. The isotopic composition of soil and xylem waters varied over the course of an individual growing season, with many trending towards more enriched values, suggesting integration of the plant-relevant water pool at a timescale shorter than the annual mean. We then quantified how soil water residence times varied at each site by calculating the interval between measured xylem water and the most recently preceding match in modeled precipitation isotope values. Results suggest a generally increasing interval between rainfall and plant uptake throughout each year, with source water corresponding to dates in the spring, likely reflecting a combination of spring rain, and mixing with winter and summer precipitation. The seasonally evolving spatial distribution of source water-precipitation lag values was then modeled as a function of location and climatology to develop continental-scale predictions. This spatial portrait of the average date for filling the plant source water pool provides insights on the seasonal importance of rainfall for plant

Detection and Characterization of Ground Displacement Sources from Variational Bayesian Independent Component Analysis of GPS Time Series

Science.gov (United States)

Gualandi, A.; Serpelloni, E.; Belardinelli, M. E.

2014-12-01

A critical point in the analysis of ground displacements time series is the development of data driven methods that allow to discern and characterize the different sources that generate the observed displacements. A widely used multivariate statistical technique is the Principal Component Analysis (PCA), which allows to reduce the dimensionality of the data space maintaining most of the variance of the dataset explained. It reproduces the original data using a limited number of Principal Components, but it also shows some deficiencies. Indeed, PCA does not perform well in finding the solution to the so-called Blind Source Separation (BSS) problem, i.e. in recovering and separating the original sources that generated the observed data. This is mainly due to the assumptions on which PCA relies: it looks for a new Euclidean space where the projected data are uncorrelated. Usually, the uncorrelation condition is not strong enough and it has been proven that the BSS problem can be tackled imposing on the components to be independent. The Independent Component Analysis (ICA) is, in fact, another popular technique adopted to approach this problem, and it can be used in all those fields where PCA is also applied. An ICA approach enables us to explain the time series imposing a fewer number of constraints on the model, and to reveal anomalies in the data such as transient signals. However, the independence condition is not easy to impose, and it is often necessary to introduce some approximations. To work around this problem, we use a variational bayesian ICA (vbICA) method, which models the probability density function (pdf) of each source signal using a mix of Gaussian distributions. This technique allows for more flexibility in the description of the pdf of the sources, giving a more reliable estimate of them. Here we present the application of the vbICA technique to GPS position time series. First, we use vbICA on synthetic data that simulate a seismic cycle

Algorithm for removing scalp signals from functional near-infrared spectroscopy signals in real time using multidistance optodes.

Science.gov (United States)

Kiguchi, Masashi; Funane, Tsukasa

2014-11-01

A real-time algorithm for removing scalp-blood signals from functional near-infrared spectroscopy signals is proposed. Scalp and deep signals have different dependencies on the source-detector distance. These signals were separated using this characteristic. The algorithm was validated through an experiment using a dynamic phantom in which shallow and deep absorptions were independently changed. The algorithm for measurement of oxygenated and deoxygenated hemoglobins using two wavelengths was explicitly obtained. This algorithm is potentially useful for real-time systems, e.g., brain-computer interfaces and neuro-feedback systems.

Time dependence of the field energy densities surrounding sources: Application to scalar mesons near point sources and to electromagnetic fields near molecules

International Nuclear Information System (INIS)

Persico, F.; Power, E.A.

1987-01-01

The time dependence of the dressing-undressing process, i.e., the acquiring or losing by a source of a boson field intensity and hence of a field energy density in its neighborhood, is considered by examining some simple soluble models. First, the loss of the virtual field is followed in time when a point source is suddenly decoupled from a neutral scalar meson field. Second, an initially bare point source acquires a virtual meson cloud as the coupling is switched on. The third example is that of an initially bare molecule interacting with the vacuum of the electromagnetic field to acquire a virtual photon cloud. In all three cases the dressing-undressing is shown to take place within an expanding sphere of radius r = ct centered at the source. At each point in space the energy density tends, for large times, to that of the ground state of the total system. Differences in the time dependence of the dressing between the massive scalar field and the massless electromagnetic field are discussed. The results are also briefly discussed in the light of Feinberg's ideas on the nature of half-dressed states in quantum field theory

Decentralized and Real-Time Power Dispatch Control for an Islanded Microgrid Supported by Distributed Power Sources

Directory of Open Access Journals (Sweden)

Changsun Ahn

2013-12-01

Full Text Available Microgrids can deploy traditional and/or renewable power sources to support remote sites. Utilizing renewable power sources requires more complicated control strategies to achieve acceptable power quality and maintain grid stability. In this research, we assume that the grid stability problem is already solved. As a next step, we focus on how the power can be dispatched from multiple power sources for improved grid efficiency. Isolated microgrids frequently require reconfigurations because of the grid expansion or component failures. Therefore, the control strategies ideally should be implemented in a plug-and-play fashion. Moreover, these strategies ideally require no pre-knowledge of the grid structure, and as little communication with neighboring power sources as possible. The control objective is to minimize a cost function that can be adjusted to reflect the desire to minimize energy cost and/or losses. An algorithm is designed to satisfy a derived necessary condition of function optimality. Such conditions are obtained by formulating Lagrange functions. An equivalent grid model approximates the grid structure which was later confirmed to represent the grid behavior adequately. For decentralized operations, we execute the distributed control sequentially using a simple token communication protocol. The performance of the combined system identification-Lagrange function minimization algorithm is demonstrated through simulations.

Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

International Nuclear Information System (INIS)

David, W.I.F.; Jorgensen, J.D.

1990-10-01

The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs

Evaluated Rayleigh integrals for pulsed planar expanding ring sources

International Nuclear Information System (INIS)

Warshaw, S.I.

1985-01-01

Time-domain analytic and semianalytic pressure fields acoustically radiated from expanding pulsed ring sources imbedded in a planar rigid baffle have been calculated. The source functions are radially symmetric delta-function distributions whose amplitude and argument have simple functional dependencies on radius and time. Certain cases yield closed analytic results, while others result in elliptic integrals, which are evaluated to high accuracy by Gauss-Chebyshev and modified Gauss-Legendre quadrature. These results are of value for calibrating computer simulations and convolution procedures, and estimating fields from more complex planar radiators. 3 refs., 4 figs

Effects of source and receiver locations in predicting room transfer functions by a phased beam tracing method

DEFF Research Database (Denmark)

Jeong, Cheol-Ho; Ih, Jeong-Guon

2012-01-01

The accuracy of a phased beam tracing method in predicting transfer functions is investigated with a special focus on the positions of the source and receiver. Simulated transfer functions for various source-receiver pairs using the phased beam tracing method were compared with analytical Green’s...

OpenPSTD : The open source implementation of the pseudospectral time-domain method

NARCIS (Netherlands)

Krijnen, T.; Hornikx, M.C.J.; Borkowski, B.

2014-01-01

An open source implementation of the pseudospectral time-domain method for the propagation of sound is presented, which is geared towards applications in the built environment. Being a wavebased method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory

Alkali suppression within laser ion-source cavities and time structure of the laser ionized ion-bunches

CERN Document Server

Lettry, Jacques; Köster, U; Georg, U; Jonsson, O; Marzari, S; Fedosseev, V

2003-01-01

The chemical selectivity of the target and ion-source production system is an asset for Radioactive Ion-Beam (RIB) facilities equipped with mass separators. Ionization via laser induced multiple resonant steps Ionization has such selectivity. However, the selectivity of the ISOLDE Resonant Ionization Laser Ion-Source (RILIS), where ionization takes place within high temperature refractory metal cavities, suffers from unwanted surface ionization of low ionization potential alkalis. In order to reduce this type of isobaric contaminant, surface ionization within the target vessel was used. On-line measurements of the efficiency of this method is reported, suppression factors of alkalis up to an order of magnitude were measured as a function of their ionization potential. The time distribution of the ion bunches produced with the RILIS was measured for a variety of elements and high temperature cavity materials. While all ions are produced within a few nanoseconds, the ion bunch sometimes spreads over more than 1...

Invited Article: Characterization of background sources in space-based time-of-flight mass spectrometers

International Nuclear Information System (INIS)

Gilbert, J. A.; Gershman, D. J.; Gloeckler, G.; Lundgren, R. A.; Zurbuchen, T. H.; Orlando, T. M.; McLain, J.; Steiger, R. von

2014-01-01

For instruments that use time-of-flight techniques to measure space plasma, there are common sources of background signals that evidence themselves in the data. The background from these sources may increase the complexity of data analysis and reduce the signal-to-noise response of the instrument, thereby diminishing the science value or usefulness of the data. This paper reviews several sources of background commonly found in time-of-flight mass spectrometers and illustrates their effect in actual data using examples from ACE-SWICS and MESSENGER-FIPS. Sources include penetrating particles and radiation, UV photons, energy straggling and angular scattering, electron stimulated desorption of ions, ion-induced electron emission, accidental coincidence events, and noise signatures from instrument electronics. Data signatures of these sources are shown, as well as mitigation strategies and design considerations for future instruments

Continuous time random walk model with asymptotical probability density of waiting times via inverse Mittag-Leffler function

Science.gov (United States)

Liang, Yingjie; Chen, Wen

2018-04-01

The mean squared displacement (MSD) of the traditional ultraslow diffusion is a logarithmic function of time. Recently, the continuous time random walk model is employed to characterize this ultraslow diffusion dynamics by connecting the heavy-tailed logarithmic function and its variation as the asymptotical waiting time density. In this study we investigate the limiting waiting time density of a general ultraslow diffusion model via the inverse Mittag-Leffler function, whose special case includes the traditional logarithmic ultraslow diffusion model. The MSD of the general ultraslow diffusion model is analytically derived as an inverse Mittag-Leffler function, and is observed to increase even more slowly than that of the logarithmic function model. The occurrence of very long waiting time in the case of the inverse Mittag-Leffler function has the largest probability compared with the power law model and the logarithmic function model. The Monte Carlo simulations of one dimensional sample path of a single particle are also performed. The results show that the inverse Mittag-Leffler waiting time density is effective in depicting the general ultraslow random motion.

A 1.5 GeV high brilliance synchrotron light source with combined function lattice

International Nuclear Information System (INIS)

Eriksson, M.; Lindgren, L.J.; Andersson, Aa.; Roejsel, P.; Werin, S.

1988-01-01

A 1.5 GeV synchrotron light source with a combined function lattice is studied. The light source will offer X-ray radiation with λc=1.0 angstrom from a superconducting wiggler and high brilliance VUV-radiation from undulators. The magnet lattice, magnet design and ring performance is discussed. (authors)

MEG/EEG source reconstruction, statistical evaluation, and visualization with NUTMEG.

Science.gov (United States)

Dalal, Sarang S; Zumer, Johanna M; Guggisberg, Adrian G; Trumpis, Michael; Wong, Daniel D E; Sekihara, Kensuke; Nagarajan, Srikantan S

2011-01-01

NUTMEG is a source analysis toolbox geared towards cognitive neuroscience researchers using MEG and EEG, including intracranial recordings. Evoked and unaveraged data can be imported to the toolbox for source analysis in either the time or time-frequency domains. NUTMEG offers several variants of adaptive beamformers, probabilistic reconstruction algorithms, as well as minimum-norm techniques to generate functional maps of spatiotemporal neural source activity. Lead fields can be calculated from single and overlapping sphere head models or imported from other software. Group averages and statistics can be calculated as well. In addition to data analysis tools, NUTMEG provides a unique and intuitive graphical interface for visualization of results. Source analyses can be superimposed onto a structural MRI or headshape to provide a convenient visual correspondence to anatomy. These results can also be navigated interactively, with the spatial maps and source time series or spectrogram linked accordingly. Animations can be generated to view the evolution of neural activity over time. NUTMEG can also display brain renderings and perform spatial normalization of functional maps using SPM's engine. As a MATLAB package, the end user may easily link with other toolboxes or add customized functions.

Digital time stamping system based on open source technologies.

Science.gov (United States)

Miskinis, Rimantas; Smirnov, Dmitrij; Urba, Emilis; Burokas, Andrius; Malysko, Bogdan; Laud, Peeter; Zuliani, Francesco

2010-03-01

A digital time stamping system based on open source technologies (LINUX-UBUNTU, OpenTSA, OpenSSL, MySQL) is described in detail, including all important testing results. The system, called BALTICTIME, was developed under a project sponsored by the European Commission under the Program FP 6. It was designed to meet the requirements posed to the systems of legal and accountable time stamping and to be applicable to the hardware commonly used by the national time metrology laboratories. The BALTICTIME system is intended for the use of governmental and other institutions as well as personal bodies. Testing results demonstrate that the time stamps issued to the user by BALTICTIME and saved in BALTICTIME's archives (which implies that the time stamps are accountable) meet all the regulatory requirements. Moreover, the BALTICTIME in its present implementation is able to issue more than 10 digital time stamps per second. The system can be enhanced if needed. The test version of the BALTICTIME service is free and available at http://baltictime. pfi.lt:8080/btws/ and http://baltictime.lnmc.lv:8080/btws/.

Space-time structure of neutron and X-ray sources in a plasma focus

International Nuclear Information System (INIS)

Bostick, W.H.; Nardi, V.; Prior, W.

1977-01-01

Systematic measurements with paraffin collimators of the neutron emission intensity have been completed on a plasma focus with a 15-20 kV capacitor bank (hollow centre electrode; discharge period T approximately 8 μs; D 2 filling at 4-8 torr). The space resolution was 1 cm or better. These data indicate that at least 70% of the total neutron yield originates within hot-plasma regions where electron beams and high-energy D beams (approximately > 0.1-1 MeV) are produced. The neutron source is composed of several (approximately > 1-10) space-localized sources of different intensity, each with a duration approximately less than 5 ns (FWHM). Localized neutron sources and hard (approximately > 100 keV) X-ray sources have the same time multiplicity and are usually distributed in two groups over a time interval 40-400 ns long. By the mode of operation used by the authors one group of localized sources (Burst II) is observed 200-400 ns after the other group (Burst I) and its space distribution is broader than for Burst I. The maximum intensity of a localized source of neutrons in Burst I is much higher than the maximum intensity in Burst II. Secondary reactions T(D,n) 4 He (from the tritium produced only by primary reactions in the same discharge; no tritium was used in filling the discharge chamber) are observed in a time coincidence with the strongest D-D neutron pulse of Burst I. The neutron signal from a localized source with high intensity has a relatively long tail of small amplitude (area tail approximately less than 0.2 X area peak). This tail can be generated by the D-D reactions of the unconfined part of an ion beam in the cold plasma. Complete elimination of scattered neutrons on the detector was achieved in these measurements. (author)

Neutron generators with size scalability, ease of fabrication and multiple ion source functionalities

Science.gov (United States)

Elizondo-Decanini, Juan M

2014-11-18

A neutron generator is provided with a flat, rectilinear geometry and surface mounted metallizations. This construction provides scalability and ease of fabrication, and permits multiple ion source functionalities.

Real-time control using open source RTOS

Science.gov (United States)

Irwin, Philip C.; Johnson, Richard L., Jr.

2002-12-01

Complex telescope systems such as interferometers tend to rely heavily on hard real-time operating systems (RTOS). It has been standard practice at NASA's Jet Propulsion Laboratory (JPL) and many other institutions to use costly commercial RTOSs and hardware. After developing a real-time toolkit for VxWorks on the PowerPC platform (dubbed RTC), the interferometry group at JPL is porting this code to the real-time Application Interface (RTAI), an open source RTOS that is essentially an extension to the Linux kernel. This port has the potential to reduce software and hardware costs for future projects, while increasing the level of performance. The goals of this paper are to briefly describe the RTC toolkit, highlight the successes and pitfalls of porting the toolkit from VxWorks to Linux-RTAI, and to discuss future enhancements that will be implemented as a direct result of this port. The first port of any body of code is always the most difficult since it uncovers the OS-specific calls and forces "red flags" into those portions of the code. For this reason, It has also been a huge benefit that the project chose a generic, platform independent OS extension, ACE, and its CORBA counterpart, TAO. This port of RTC will pave the way for conversions to other environments, the most interesting of which is a non-real-time simulation environment, currently being considered by the Space Interferometry Mission (SIM) and the Terrestrial Planet Finder (TPF) Projects.

Time Reversal Migration for Passive Sources Using a Maximum Variance Imaging Condition

KAUST Repository

Wang, H.; Alkhalifah, Tariq Ali

2017-01-01

The conventional time-reversal imaging approach for micro-seismic or passive source location is based on focusing the back-propagated wavefields from each recorded trace in a source image. It suffers from strong background noise and limited acquisition aperture, which may create unexpected artifacts and cause error in the source location. To overcome such a problem, we propose a new imaging condition for microseismic imaging, which is based on comparing the amplitude variance in certain windows, and use it to suppress the artifacts as well as find the right location for passive sources. Instead of simply searching for the maximum energy point in the back-propagated wavefield, we calculate the amplitude variances over a window moving in both space and time axis to create a highly resolved passive event image. The variance operation has negligible cost compared with the forward/backward modeling operations, which reveals that the maximum variance imaging condition is efficient and effective. We test our approach numerically on a simple three-layer model and on a piece of the Marmousi model as well, both of which have shown reasonably good results.

Time Reversal Migration for Passive Sources Using a Maximum Variance Imaging Condition

KAUST Repository

Wang, H.

2017-05-26

The conventional time-reversal imaging approach for micro-seismic or passive source location is based on focusing the back-propagated wavefields from each recorded trace in a source image. It suffers from strong background noise and limited acquisition aperture, which may create unexpected artifacts and cause error in the source location. To overcome such a problem, we propose a new imaging condition for microseismic imaging, which is based on comparing the amplitude variance in certain windows, and use it to suppress the artifacts as well as find the right location for passive sources. Instead of simply searching for the maximum energy point in the back-propagated wavefield, we calculate the amplitude variances over a window moving in both space and time axis to create a highly resolved passive event image. The variance operation has negligible cost compared with the forward/backward modeling operations, which reveals that the maximum variance imaging condition is efficient and effective. We test our approach numerically on a simple three-layer model and on a piece of the Marmousi model as well, both of which have shown reasonably good results.

Evaluating four-dimensional time-lapse electrical resistivity tomography for monitoring DNAPL source zone remediation.

Science.gov (United States)

Power, Christopher; Gerhard, Jason I; Karaoulis, Marios; Tsourlos, Panagiotis; Giannopoulos, Antonios

2014-07-01

Practical, non-invasive tools do not currently exist for mapping the remediation of dense non-aqueous phase liquids (DNAPLs). Electrical resistivity tomography (ERT) exhibits significant potential but has not yet become a practitioner's tool due to challenges in interpreting the survey results at real sites. This study explores the effectiveness of recently developed four-dimensional (4D, i.e., 3D space plus time) time-lapse surface ERT to monitor DNAPL source zone remediation. A laboratory experiment demonstrated the approach for mapping a changing NAPL distribution over time. A recently developed DNAPL-ERT numerical model was then employed to independently simulate the experiment, providing confidence that the DNAPL-ERT model is a reliable tool for simulating real systems. The numerical model was then used to evaluate the potential for this approach at the field scale. Four DNAPL source zones, exhibiting a range of complexity, were initially simulated, followed by modeled time-lapse ERT monitoring of complete DNAPL remediation by enhanced dissolution. 4D ERT inversion provided estimates of the regions of the source zone experiencing mass reduction with time. Results show that 4D time-lapse ERT has significant potential to map both the outline and the center of mass of the evolving treated portion of the source zone to within a few meters in each direction. In addition, the technique can provide a reasonable, albeit conservative, estimate of the DNAPL volume remediated with time: 25% underestimation in the upper 2m and up to 50% underestimation at late time between 2 and 4m depth. The technique is less reliable for identifying cleanup of DNAPL stringers outside the main DNAPL body. Overall, this study demonstrates that 4D time-lapse ERT has potential for mapping where and how quickly DNAPL mass changes in real time during site remediation. Copyright © 2014 Elsevier B.V. All rights reserved.

Time domain functional NIRS imaging for human brain mapping.

Science.gov (United States)

Torricelli, Alessandro; Contini, Davide; Pifferi, Antonio; Caffini, Matteo; Re, Rebecca; Zucchelli, Lucia; Spinelli, Lorenzo

2014-01-15

This review is aimed at presenting the state-of-the-art of time domain (TD) functional near-infrared spectroscopy (fNIRS). We first introduce the physical principles, the basics of modeling and data analysis. Basic instrumentation components (light sources, detection techniques, and delivery and collection systems) of a TD fNIRS system are described. A survey of past, existing and next generation TD fNIRS systems used for research and clinical studies is presented. Performance assessment of TD fNIRS systems and standardization issues are also discussed. Main strengths and weakness of TD fNIRS are highlighted, also in comparison with continuous wave (CW) fNIRS. Issues like quantification of the hemodynamic response, penetration depth, depth selectivity, spatial resolution and contrast-to-noise ratio are critically examined, with the help of experimental results performed on phantoms or in vivo. Finally we give an account on the technological developments that would pave the way for a broader use of TD fNIRS in the neuroimaging community. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Time course of effects of emotion on item memory and source memory for Chinese words.

Science.gov (United States)

Wang, Bo; Fu, Xiaolan

2011-05-01

Although many studies have investigated the effect of emotion on memory, it is unclear whether the effect of emotion extends to all aspects of an event. In addition, it is poorly understood how effects of emotion on item memory and source memory change over time. This study examined the time course of effects of emotion on item memory and source memory. Participants learned intentionally a list of neutral, positive, and negative Chinese words, which were presented twice, and then took test of free recall, followed by recognition and source memory tests, at one of eight delayed points of time. The main findings are (within the time frame of 2 weeks): (1) Negative emotion enhances free recall, whereas there is only a trend that positive emotion enhances free recall. In addition, negative and positive emotions have different points of time at which their effects on free recall reach the greatest magnitude. (2) Negative emotion reduces recognition, whereas positive emotion has no effect on recognition. (3) Neither positive nor negative emotion has any effect on source memory. The above findings indicate that effect of emotion does not necessarily extend to all aspects of an event and that valence is a critical modulating factor in effect of emotion on item memory. Furthermore, emotion does not affect the time course of item memory and source memory, at least with a time frame of 2 weeks. This study has implications for establishing the theoretical model regarding the effect of emotion on memory. Copyright © 2011 Elsevier Inc. All rights reserved.

Generator of an exponential function with respect to time

International Nuclear Information System (INIS)

Janin, Paul; Puyal, Claude.

1981-01-01

This invention deals with an exponential function generator, and an application of this generator to simulating the criticality of a nuclear reactor for reactimeter calibration purposes. This generator, which is particularly suitable for simulating the criticality of a nuclear reactor to calibrate a reactimeter, can also be used in any field of application necessitating the generation of an exponential function in real time. In certain fields of thermodynamics, it is necessary to represent temperature gradients as a function of time. The generator might find applications here. Another application is nuclear physics where it is necessary to represent the attenuation of a neutron flux density with respect to time [fr

Real-time tunability of chip-based light source enabled by microfluidic mixing

DEFF Research Database (Denmark)

Olsen, Brian Bilenberg; Rasmussen, Torben; Balslev, Søren

2006-01-01

We demonstrate real-time tunability of a chip-based liquid light source enabled by microfluidic mixing. The mixer and light source are fabricated in SU-8 which is suitable for integration in SU-8-based laboratory-on-a-chip microsystems. The tunability of the light source is achieved by changing...... the concentration of rhodamine 6G dye inside two integrated vertical resonators, since both the refractive index and the gain profile are influenced by the dye concentration. The effect on the refractive index and the gain profile of rhodamine 6G in ethanol is investigated and the continuous tuning of the laser...

Multiscale time-dependent density functional theory: Demonstration for plasmons.

Science.gov (United States)

Jiang, Jiajian; Abi Mansour, Andrew; Ortoleva, Peter J

2017-08-07

Plasmon properties are of significant interest in pure and applied nanoscience. While time-dependent density functional theory (TDDFT) can be used to study plasmons, it becomes impractical for elucidating the effect of size, geometric arrangement, and dimensionality in complex nanosystems. In this study, a new multiscale formalism that addresses this challenge is proposed. This formalism is based on Trotter factorization and the explicit introduction of a coarse-grained (CG) structure function constructed as the Weierstrass transform of the electron wavefunction. This CG structure function is shown to vary on a time scale much longer than that of the latter. A multiscale propagator that coevolves both the CG structure function and the electron wavefunction is shown to bring substantial efficiency over classical propagators used in TDDFT. This efficiency follows from the enhanced numerical stability of the multiscale method and the consequence of larger time steps that can be used in a discrete time evolution. The multiscale algorithm is demonstrated for plasmons in a group of interacting sodium nanoparticles (15-240 atoms), and it achieves improved efficiency over TDDFT without significant loss of accuracy or space-time resolution.

Multi-source least-squares migration of marine data

KAUST Repository

Wang, Xin; Schuster, Gerard T.

2012-01-01

Kirchhoff based multi-source least-squares migration (MSLSM) is applied to marine streamer data. To suppress the crosstalk noise from the excitation of multiple sources, a dynamic encoding function (including both time-shifts and polarity changes

Lead-acid batteries life time prolongation in renewable energy source plants

Directory of Open Access Journals (Sweden)

Костянтин Ігорович Ткаченко

2015-11-01

Full Text Available Charge controllers with microprocessor control are recognized to be almost optimal process control devices for collecting and storing energy in batteries in power systems with renewable energy sources such as solar photoelectric batteries, wind electrogenerators and others. The task of the controller is charging process control, that is such as charging and discharging the batteries while providing maximum charging speed and battery saving parameters that characterize the state of the battery, within certain limits, preventing overcharging, overheating and the batteries deep discharge. The possibility of archiving data that keeps the battery parameters time dependance is also important. Thus, the concept of a charge controller with Texas Instruments microcontroller device MSP430G2553 was introduced in the study. The program saved in the ROM microcontroller provides for: charge regime(with a particular algorithm; control and training cycle followed by charging; continuous charge-discharge regime to restore the battery or the study of charge regime algorithms influence on repair effectiveness. The device can perform its functions without being connected to a personal computer, but this connection makes it possible to observe in real time the characteristics of a number of discharge and charge regimes parameters, as well as reading the stored data from microcontroller flash memory and storing these data on the PC hard disk for further analysis. A four stages charging algorithm with reverse charging regime was offered by the author and correctness of algorithm was proved

Travel-time source-specific station correction improves location accuracy

Science.gov (United States)

Giuntini, Alessandra; Materni, Valerio; Chiappini, Stefano; Carluccio, Roberto; Console, Rodolfo; Chiappini, Massimo

2013-04-01

Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. The consequences of large mislocations of seismic events in the context of the CTBT verification is particularly critical in order to trigger a possible On Site Inspection (OSI). In fact, the Treaty establishes that an OSI area cannot be larger than 1000 km2, and its larger linear dimension cannot be larger than 50 km. Moreover, depth accuracy is crucial for the application of the depth event screening criterion. In the present study, we develop a method of source-specific travel times corrections based on a set of well located events recorded by dense national seismic networks in seismically active regions. The applications concern seismic sequences recorded in Japan, Iran and Italy. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying source-specific station corrections.

High-resolution and super stacking of time-reversal mirrors in locating seismic sources

KAUST Repository

Cao, Weiping; Hanafy, Sherif M.; Schuster, Gerard T.; Zhan, Ge; Boonyasiriwat, Chaiwoot

2011-01-01

Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors

Multi-source least-squares reverse time migration

KAUST Repository

Dai, Wei

2012-06-15

Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.

Multi-source least-squares reverse time migration

KAUST Repository

Dai, Wei; Fowler, Paul J.; Schuster, Gerard T.

2012-01-01

Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.

Photon statistics characterization of a single-photon source

International Nuclear Information System (INIS)

Alleaume, R; Treussart, F; Courty, J-M; Roch, J-F

2004-01-01

In a recent experiment, we reported the time-domain intensity noise measurement of a single-photon source relying on single-molecule fluorescence control. In this paper, we present data processing starting from photocount timestamps. The theoretical analytical expression of the time-dependent Mandel parameter Q(T) of an intermittent single-photon source is derived from ON↔OFF dynamics. Finally, source intensity noise analysis, using the Mandel parameter, is quantitatively compared with the usual approach relying on the time autocorrelation function, both methods yielding the same molecular dynamical parameters

Two Functionally Distinct Sources of Actin Monomers Supply the Leading Edge of Lamellipodia

Science.gov (United States)

Vitriol, Eric A.; McMillen, Laura M.; Kapustina, Maryna; Gomez, Shawn M.; Vavylonis, Dimitrios; Zheng, James Q.

2015-01-01

Summary Lamellipodia, the sheet-like protrusions of motile cells, consist of networks of actin filaments (F-actin) regulated by the ordered assembly from and disassembly into actin monomers (G-actin). Traditionally, G-actin is thought to exist as a homogeneous pool. Here, we show that there are two functionally and molecularly distinct sources of G-actin that supply lamellipodial actin networks. G-actin originating from the cytosolic pool requires the monomer binding protein thymosin β4 (Tβ4) for optimal leading edge localization, is targeted to formins, and is responsible for creating an elevated G/F-actin ratio that promotes membrane protrusion. The second source of G-actin comes from recycled lamellipodia F-actin. Recycling occurs independently of Tβ4 and appears to regulate lamellipodia homeostasis. Tβ4-bound G-actin specifically localizes to the leading edge because it doesn’t interact with Arp2/3-mediated polymerization sites found throughout the lamellipodia. These findings demonstrate that actin networks can be constructed from multiple sources of monomers with discrete spatiotemporal functions. PMID:25865895

Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

Science.gov (United States)

Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

2017-06-01

Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

Time Series Analysis of Monte Carlo Fission Sources - I: Dominance Ratio Computation

International Nuclear Information System (INIS)

Ueki, Taro; Brown, Forrest B.; Parsons, D. Kent; Warsa, James S.

2004-01-01

In the nuclear engineering community, the error propagation of the Monte Carlo fission source distribution through cycles is known to be a linear Markov process when the number of histories per cycle is sufficiently large. In the statistics community, linear Markov processes with linear observation functions are known to have an autoregressive moving average (ARMA) representation of orders p and p - 1. Therefore, one can perform ARMA fitting of the binned Monte Carlo fission source in order to compute physical and statistical quantities relevant to nuclear criticality analysis. In this work, the ARMA fitting of a binary Monte Carlo fission source has been successfully developed as a method to compute the dominance ratio, i.e., the ratio of the second-largest to the largest eigenvalues. The method is free of binning mesh refinement and does not require the alteration of the basic source iteration cycle algorithm. Numerical results are presented for problems with one-group isotropic, two-group linearly anisotropic, and continuous-energy cross sections. Also, a strategy for the analysis of eigenmodes higher than the second-largest eigenvalue is demonstrated numerically

The effect of interaural-time-difference fluctuations on apparent source width

DEFF Research Database (Denmark)

Käsbach, Johannes; May, Tobias; Oskarsdottir, Gudrun

2014-01-01

For the perception of spaciousness, the temporal fluctuations of the interaural time differences (ITDs) and interaural level differences (ILDs) provide important binaural cues. One major characteristic of spatial perception is apparent source width (ASW), which describes the perceived width of a ...

openPSTD: The open source pseudospectral time-domain method for acoustic propagation

Science.gov (United States)

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.

Signal Processing for Time-Series Functions on a Graph

Science.gov (United States)

2018-02-01

Figures Fig. 1 Time -series function on a fixed graph.............................................2 iv Approved for public release; distribution is...φi〉`2(V)φi (39) 6= f̄ (40) Instead, we simply recover the average of f over time . 13 Approved for public release; distribution is unlimited. This...ARL-TR-8276• FEB 2018 US Army Research Laboratory Signal Processing for Time -Series Functions on a Graph by Humberto Muñoz-Barona, Jean Vettel, and

Measurement of Neutron Energy Spectrum Emitted by Cf-252 Source Using Time-of-Flight Method

Energy Technology Data Exchange (ETDEWEB)

Lee, Cheol Ho; Son, Jaebum; Kim, Tae Hoon; Lee, Sangmin; Kim, Yong-Kyun [Hanyang University, Seoul (Korea, Republic of)

2016-10-15

The techniques proposed to detect the neutrons usually require the detection of a secondary recoiling nucleus in a scintillator (or other type of detector) to indicate the rare collision of a neutron with a nucleus. This is the same basic technique, in this case detection of a recoil proton that was used by Chadwick in the 1930 s to discover and identify the neutron and determine its mass. It is primary technique still used today for detection of fast neutron, which typically involves the use of a hydrogen based organic plastic or liquid scintillator coupled to a photo-multiplier tube. The light output from such scintillators is a function of the cross section and nuclear kinematics of the n + nucleus collision. With the exception of deuterated scintillators, the scintillator signal does not necessarily produce a distinct peak in the scintillator spectrum directly related to the incident neutron energy. Instead neutron time-of-flight (TOF) often must be utilized to determine the neutron energy, which requires generation of a prompt start signal from the nuclear source emitting the neutrons. This method takes advantage of the high number of prompt gamma rays. The Time-of-Flight method was used to measure neutron energy spectrum emitted by the Cf-252 neutron source. Plastic scintillator that has a superior discrimination ability of neutron and gamma-ray was used as a stop signal detector and liquid scintillator was used as a stat signal detector. In experiment, neutron and gamma-ray spectrum was firstly measured and discriminated using the TOF method. Secondly, neutron energy spectrum was obtained through spectrum analysis. Equation of neutron energy spectrum that was emitted by Cf-252 source using the Gaussian fitting was obtained.

High-resolution and super stacking of time-reversal mirrors in locating seismic sources

KAUST Repository

Cao, Weiping

2011-07-08

Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors have been previously verified with computer simulations and laboratory experiments but not with exploration-scale seismic data. We now demonstrate the high-resolution and the super-stacking properties in locating seismic sources with field seismic data that include multiple scattering. Tests on both synthetic data and field data show that a time reversal mirror has the potential to exceed the Rayleigh resolution limit by factors of 4 or more. Results also show that a time reversal mirror has a significant resilience to strong Gaussian noise and that accurate imaging of source locations from passive seismic data can be accomplished with traces having signal-to-noise ratios as low as 0.001. Synthetic tests also demonstrate that time reversal mirrors can sometimes enhance the signal by a factor proportional to the square root of the product of the number of traces, denoted as N and the number of events in the traces. This enhancement property is denoted as super-stacking and greatly exceeds the classical signal-to-noise enhancement factor of. High-resolution and super-stacking are properties also enjoyed by seismic interferometry and reverse-time migration with the exact velocity model. © 2011 European Association of Geoscientists & Engineers.

Real-time implementation of logo detection on open source BeagleBoard

Science.gov (United States)

George, M.; Kehtarnavaz, N.; Estevez, L.

2011-03-01

This paper presents the real-time implementation of our previously developed logo detection and tracking algorithm on the open source BeagleBoard mobile platform. This platform has an OMAP processor that incorporates an ARM Cortex processor. The algorithm combines Scale Invariant Feature Transform (SIFT) with k-means clustering, online color calibration and moment invariants to robustly detect and track logos in video. Various optimization steps that are carried out to allow the real-time execution of the algorithm on BeagleBoard are discussed. The results obtained are compared to the PC real-time implementation results.

Real-time software for multi-isotopic source term estimation

International Nuclear Information System (INIS)

Goloubenkov, A.; Borodin, R.; Sohier, A.

1996-01-01

Consideration is given to development of software for one of crucial components of the RODOS - assessment of the source rate (SR) from indirect measurements. Four components of the software are described in the paper. First component is a GRID system, which allow to prepare stochastic meteorological and radioactivity fields using measured data. Second part is a model of atmospheric transport which can be adapted for emulation of practically any gamma dose/spectrum detectors. The third one is a method which allows space-time and quantitative discrepancies in measured and modelled data to be taken into account simultaneously. It bases on the preference scheme selected by an expert. Last component is a special optimization method for calculation of multi-isotopic SR and its uncertainties. Results of a validation of the software using tracer experiments data and Chernobyl source estimation for main dose-forming isotopes are enclosed in the paper

Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size

International Nuclear Information System (INIS)

Jacob, J; Ong, M; Wargo, P

2005-01-01

Lawrence Livermore National Laboratory (LLNL) is currently investigating various approaches to minimize the x-ray source size on the Flash X-Ray (FXR) linear induction accelerator in order to improve x-ray flux and increase resolution for hydrodynamic radiography experiments. In order to effectively gauge improvements to final x-ray source size, a fast, robust, and accurate system for measuring the spot size is required. Timely feedback on x-ray source size allows new and improved accelerator tunes to be deployed and optimized within the limited run-time constraints of a production facility with a busy experimental schedule; in addition, time-resolved measurement capability allows the investigation of not only the time-averaged source size, but also the evolution of the source size, centroid position, and x-ray dose throughout the 70 ns beam pulse. Combined with time-resolved measurements of electron beam parameters such as emittance, energy, and current, key limiting factors can be identified, modeled, and optimized for the best possible spot size. Roll-bar techniques are a widely used method for x-ray source size measurement, and have been the method of choice at FXR for many years. A thick bar of tungsten or other dense metal with a sharp edge is inserted into the path of the x-ray beam so as to heavily attenuate the lower half of the beam, resulting in a half-light, half-dark image as seen downstream of the roll-bar; by measuring the width of the transition from light to dark across the edge of the roll-bar, the source size can be deduced. For many years, film has been the imaging medium of choice for roll-bar measurements thanks to its high resolution, linear response, and excellent contrast ratio. Film measurements, however, are fairly cumbersome and require considerable setup and analysis time; moreover, with the continuing trend towards all-electronic measurement systems, film is becoming increasingly difficult and expensive to procure. Here, we shall

Using recruitment source timing and diagnosticity to enhance applicants' occupation-specific human capital.

Science.gov (United States)

Campion, Michael C; Ployhart, Robert E; Campion, Michael A

2017-05-01

[Correction Notice: An Erratum for this article was reported in Vol 102(5) of Journal of Applied Psychology (see record 2017-14296-001). In the article, the following headings were inadvertently set at the wrong level: Method, Participants and Procedure, Measures, Occupation specific human capital, Symbolic jobs, Relevant majors, Occupation-specific capital hotspots, Source timing, Source diagnosticity, Results, and Discussion. All versions of this article have been corrected.] This study proposes that reaching applicants through more diagnostic recruitment sources earlier in their educational development (e.g., in high school) can lead them to invest more in their occupation-specific human capital (OSHC), thereby making them higher quality candidates. Using a sample of 78,157 applicants applying for jobs within a desirable professional occupation in the public sector, results indicate that applicants who report hearing about the occupation earlier, and applicants who report hearing about the occupation through more diagnostic sources, have higher levels of OSHC upon application. Additionally, source timing and diagnosticity affect the likelihood of candidates applying for jobs symbolic of the occupation, selecting relevant majors, and attending educational institutions with top programs related to the occupation. These findings suggest a firm's recruiting efforts may influence applicants' OSHC investment strategies. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Estimation of functional preparedness of young handballers in setup time

Directory of Open Access Journals (Sweden)

Favoritоv V.N.

2012-11-01

Full Text Available The dynamics of level of functional preparedness of young handballers in setup time is shown. It was foreseen to make alteration in educational-training process with the purpose of optimization of their functional preparedness. 11 youths were plugged in research, calendar age 14 - 15 years. For determination of level of their functional preparedness the computer program "SVSM" was applied. It is set that at the beginning of setup time of 18,18% of all respondent functional preparedness is characterized by a "middle" level, 27,27% - below the "average", 54,54% - "above" the average. At the end of setup time among sportsmen representatives prevailed with the level of functional preparedness "above" average - 63,63%, with level "high" - 27,27%, sportsmen with level below the average were not observed. Efficiency of the offered system of trainings employments for optimization of functional preparedness of young handballers is well-proven.

Wind wave source functions in opposing seas

KAUST Repository

Langodan, Sabique

2015-08-26

The Red Sea is a challenge for wave modeling because of its unique two opposed wave systems, forced by opposite winds and converging at its center. We investigate the different physical aspects of wave evolution and propagation in the convergence zone. The two opposing wave systems have similar amplitude and frequency, each driven by the action of its own wind. Wave patterns at the centre of the Red Sea, as derived from extensive tests and intercomparison between model and measured data, suggest that the currently available wave model source functions may not properly represent the evolution of the local fields that appear to be characterized by a less effective wind input and an enhanced white-capping. We propose and test a possible simple solution to improve the wave-model simulation under opposing winds and waves condition. This article is protected by copyright. All rights reserved.

Recursive evaluation of space-time lattice Green's functions

NARCIS (Netherlands)

Hon, de B.P.; Arnold, J.M.

2012-01-01

Up to a multiplicative constant, the lattice Green’s function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z- domain counterpart of the finite-difference time-domain Green’s function (GF) on a lattice. Expansion of a well-known integral

Influence of starch source in the required hydrolysis time for the ...

African Journals Online (AJOL)

Influence of starch source in the required hydrolysis time for the production of maltodextrins with different dextrose equivalent. José Luis Montañez Soto, Luis Medina García, José Venegas González, Aurea Bernardino Nicanor, Leopoldo González Cruz ...

Efficient quantum algorithm for computing n-time correlation functions.

Science.gov (United States)

Pedernales, J S; Di Candia, R; Egusquiza, I L; Casanova, J; Solano, E

2014-07-11

We propose a method for computing n-time correlation functions of arbitrary spinorial, fermionic, and bosonic operators, consisting of an efficient quantum algorithm that encodes these correlations in an initially added ancillary qubit for probe and control tasks. For spinorial and fermionic systems, the reconstruction of arbitrary n-time correlation functions requires the measurement of two ancilla observables, while for bosonic variables time derivatives of the same observables are needed. Finally, we provide examples applicable to different quantum platforms in the frame of the linear response theory.

Effects of detector–source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors

International Nuclear Information System (INIS)

Ermis, E.E.; Celiktas, C.

2012-01-01

Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. 133 Ba and 207 Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. - Highlights: ► Effect of the source-detector distance on time spectra was investigated. ► Effect of the detector bias voltage variations on time spectra was examined. ► Optimum detector–source distance was determined for the best time resolution. ► Optimum detector bias voltage was determined for the best time resolution. ► 133 Ba and 207 Bi radioisotopes were used.

Time-resolved far-infrared experiments at the National Synchrotron Light Source. Final report

International Nuclear Information System (INIS)

Tanner, D.B.; Reitze, D.H.; Carr, G.L.

1999-01-01

A facility for time-resolved infrared and far-infrared spectroscopy has been built and commissioned at the National Synchrotron Light Source. This facility permits the study of time dependent phenomena over a frequency range from 2-8000cm -1 (0.25 meV-1 eV). Temporal resolution is approximately 200 psec and time dependent phenomena in the time range out to 100 nsec can be investigated

Soil Monitor: an open source web application for real-time soil sealing monitoring and assessment

Science.gov (United States)

Langella, Giuliano; Basile, Angelo; Giannecchini, Simone; Iamarino, Michela; Munafò, Michele; Terribile, Fabio

2016-04-01

Soil sealing is one of the most important causes of land degradation and desertification. In Europe, soil covered by impermeable materials has increased by about 80% from the Second World War till nowadays, while population has only grown by one third. There is an increasing concern at the high political levels about the need to attenuate imperviousness itself and its effects on soil functions. European Commission promulgated a roadmap (COM(2011) 571) by which the net land take would be zero by 2050. Furthermore, European Commission also published a report in 2011 providing best practices and guidelines for limiting soil sealing and imperviousness. In this scenario, we developed an open source and an open source based Soil Sealing Geospatial Cyber Infrastructure (SS-GCI) named as "Soil Monitor". This tool merges a webGIS with parallel geospatial computation in a fast and dynamic fashion in order to provide real-time assessments of soil sealing at high spatial resolution (20 meters and below) over the whole Italy. Common open source webGIS packages are used to implement both the data management and visualization infrastructures, such as GeoServer and MapStore. The high-speed geospatial computation is ensured by a GPU parallelism using the CUDA (Computing Unified Device Architecture) framework by NVIDIA®. This kind of parallelism required the writing - from scratch - all codes needed to fulfil the geospatial computation built behind the soil sealing toolbox. The combination of GPU computing with webGIS infrastructures is relatively novel and required particular attention at the Java-CUDA programming interface. As a result, Soil Monitor is smart because it can perform very high time-consuming calculations (querying for instance an Italian administrative region as area of interest) in less than one minute. The web application is embedded in a web browser and nothing must be installed before using it. Potentially everybody can use it, but the main targets are the

Influence of meat source, pH and production time on zinc protoporphyrin IX formation as natural colouring agent in nitrite-free dry fermented sausages.

Science.gov (United States)

De Maere, Hannelore; Chollet, Sylvie; De Brabanter, Jos; Michiels, Chris; Paelinck, Hubert; Fraeye, Ilse

2018-01-01

Nitrite is commonly used in meat products due to its plural technological advantages. However, it is controversial because of its detrimental side effects on health. Within the context of nitrite reduction, zinc protoporphyrin IX (Zn(II)PPIX) formation in meat products as natural red colouring agent has been suggested. This investigation presents the evaluation of naturally occurring pigments, namely Zn(II)PPIX, protoporphyrin IX (PPIX) and heme in nitrite-free dry fermented sausages in function of time, meat source (pork, horsemeat and a combination of both meat sources) and pH condition. In function of time, Zn(II)PPIX and PPIX were formed and heme content decreased. Higher pH conditions promoted Zn(II)PPIX and PPIX formation, whereas the influence of pH on heme was less clear. The use of horsemeat also promoted Zn(II)PPIX formation. Moreover, even similar amounts were formed when it was combined with pork. Product redness, however, could not be related to Zn(II)PPIX formation. Copyright © 2017 Elsevier Ltd. All rights reserved.

The algorithms for calculating synthetic seismograms from a dipole source using the derivatives of Green's function

Science.gov (United States)

Pavlov, V. M.

2017-07-01

The problem of calculating complete synthetic seismograms from a point dipole with an arbitrary seismic moment tensor in a plane parallel medium composed of homogeneous elastic isotropic layers is considered. It is established that the solutions of the system of ordinary differential equations for the motion-stress vector have a reciprocity property, which allows obtaining a compact formula for the derivative of the motion vector with respect to the source depth. The reciprocity theorem for Green's functions with respect to the interchange of the source and receiver is obtained for a medium with cylindrical boundary. The differentiation of Green's functions with respect to the coordinates of the source leads to the same calculation formulas as the algorithm developed in the previous work (Pavlov, 2013). A new algorithm appears when the derivatives with respect to the horizontal coordinates of the source is replaced by the derivatives with respect to the horizontal coordinates of the receiver (with the minus sign). This algorithm is more transparent, compact, and economic than the previous one. It requires calculating the wavenumbers associated with Bessel function's roots of order 0 and order 1, whereas the previous algorithm additionally requires the second order roots.

Time-of-flight diffraction at pulsed neutron sources: An introduction to the symposium

International Nuclear Information System (INIS)

Jorgensen, J.D.

1994-01-01

In the 25 years since the first low-power demonstration experiments, pulsed neutron sources have become as productive as reactor sources for many types of diffraction experiments. The pulsed neutron sources presently operating in the United States, England, and Japan offer state of the art instruments for powder and single crystal diffraction, small angle scattering, and such specialized techniques as grazing-incidence neutron reflection, as well as quasielastic and inelastic scattering. In this symposium, speakers review the latest advances in diffraction instrumentation for pulsed neutron sources and give examples of some of the important science presently being done. In this introduction to the symposium, I briefly define the basic principles of pulsed neutron sources, review their development, comment in general terms on the development of time-of-flight diffraction instrumentation for these sources, and project how this field will develop in the next ten years

System of delay difference equations with continuous time with lag function between two known functions

Directory of Open Access Journals (Sweden)

Hajnalka Péics

2016-08-01

Full Text Available The asymptotic behavior of solutions of the system of difference equations with continuous time and lag function between two known real functions is studied. The cases when the lag function is between two linear delay functions, between two power delay functions and between two constant delay functions are observed and illustrated by examples. The asymptotic estimates of solutions of the considered system are obtained.

Quantifying effects of biodiversity on ecosystem functioning across times and places†

Science.gov (United States)

Isbell, Forest; Cowles, Jane; Dee, Laura E.; Loreau, Michel; Reich, Peter B.; Gonzalez, Andrew; Hector, Andy; Schmid, Bernhard

2018-01-01

Biodiversity loss decreases ecosystem functioning at the local scales at which species interact, but it remains unclear how biodiversity loss affects ecosystem functioning at the larger scales of space and time that are most relevant to biodiversity conservation and policy. Theory predicts that additional insurance effects of biodiversity on ecosystem functioning could emerge across time and space if species respond asynchronously to environmental variation and if species become increasingly dominant when and where they are most productive. Even if only a few dominant species maintain ecosystem functioning within a particular time and place, ecosystem functioning may be enhanced by many different species across many times and places (β-diversity). Here, we develop and apply a new approach to estimate these previously unquantified insurance effects of biodiversity on ecosystem functioning that arise due to species turnover across times and places. In a long-term (18-year) grassland plant diversity experiment, we find that total insurance effects are positive in sign and substantial in magnitude, amounting to 19% of the net biodiversity effect, mostly due to temporal insurance effects. Species loss can therefore reduce ecosystem functioning both locally and by eliminating species that would otherwise enhance ecosystem functioning across temporally fluctuating and spatially heterogeneous environments. PMID:29493062

Algebraic relaxation of a time correlation function

International Nuclear Information System (INIS)

Srivastava, S.; Kumar, C.N.; Tankeshwar, K.

2004-06-01

A second order non-linear differential equation obtained from Mori's integro- differential equation is shown to transform to another form which provides algebraic decay to a time correlation function. Involved parameters in algebraic formula are related to exact properties of the corresponding correlation function. The model has been used to study a sol-gel system which is known, experimentally, to exhibit a power law decay to stress auto-correlation function. The expression obtained for the viscosity shows a logarithmic divergence at some critical value of the parameter. Some features of the model have also been tested using available information about Lennard-Jones fluids. (author)

Fast Bayesian optimal experimental design for seismic source inversion

KAUST Repository

Long, Quan

2015-07-01

We develop a fast method for optimally designing experiments in the context of statistical seismic source inversion. In particular, we efficiently compute the optimal number and locations of the receivers or seismographs. The seismic source is modeled by a point moment tensor multiplied by a time-dependent function. The parameters include the source location, moment tensor components, and start time and frequency in the time function. The forward problem is modeled by elastodynamic wave equations. We show that the Hessian of the cost functional, which is usually defined as the square of the weighted L2 norm of the difference between the experimental data and the simulated data, is proportional to the measurement time and the number of receivers. Consequently, the posterior distribution of the parameters, in a Bayesian setting, concentrates around the "true" parameters, and we can employ Laplace approximation and speed up the estimation of the expected Kullback-Leibler divergence (expected information gain), the optimality criterion in the experimental design procedure. Since the source parameters span several magnitudes, we use a scaling matrix for efficient control of the condition number of the original Hessian matrix. We use a second-order accurate finite difference method to compute the Hessian matrix and either sparse quadrature or Monte Carlo sampling to carry out numerical integration. We demonstrate the efficiency, accuracy, and applicability of our method on a two-dimensional seismic source inversion problem. © 2015 Elsevier B.V.

Fast Bayesian Optimal Experimental Design for Seismic Source Inversion

KAUST Repository

Long, Quan

2016-01-06

We develop a fast method for optimally designing experiments [1] in the context of statistical seismic source inversion [2]. In particular, we efficiently compute the optimal number and locations of the receivers or seismographs. The seismic source is modeled by a point moment tensor multiplied by a time-dependent function. The parameters include the source location, moment tensor components, and start time and frequency in the time function. The forward problem is modeled by the elastic wave equations. We show that the Hessian of the cost functional, which is usually defined as the square of the weighted L2 norm of the difference between the experimental data and the simulated data, is proportional to the measurement time and the number of receivers. Consequently, the posterior distribution of the parameters, in a Bayesian setting, concentrates around the true parameters, and we can employ Laplace approximation and speed up the estimation of the expected Kullback-Leibler divergence (expected information gain), the optimality criterion in the experimental design procedure. Since the source parameters span several magnitudes, we use a scaling matrix for efficient control of the condition number of the original Hessian matrix. We use a second-order accurate finite difference method to compute the Hessian matrix and either sparse quadrature or Monte Carlo sampling to carry out numerical integration. We demonstrate the efficiency, accuracy, and applicability of our method on a two-dimensional seismic source inversion problem.

Fast Bayesian Optimal Experimental Design for Seismic Source Inversion

KAUST Repository

Long, Quan; Motamed, Mohammad; Tempone, Raul

2016-01-01

We develop a fast method for optimally designing experiments [1] in the context of statistical seismic source inversion [2]. In particular, we efficiently compute the optimal number and locations of the receivers or seismographs. The seismic source is modeled by a point moment tensor multiplied by a time-dependent function. The parameters include the source location, moment tensor components, and start time and frequency in the time function. The forward problem is modeled by the elastic wave equations. We show that the Hessian of the cost functional, which is usually defined as the square of the weighted L2 norm of the difference between the experimental data and the simulated data, is proportional to the measurement time and the number of receivers. Consequently, the posterior distribution of the parameters, in a Bayesian setting, concentrates around the true parameters, and we can employ Laplace approximation and speed up the estimation of the expected Kullback-Leibler divergence (expected information gain), the optimality criterion in the experimental design procedure. Since the source parameters span several magnitudes, we use a scaling matrix for efficient control of the condition number of the original Hessian matrix. We use a second-order accurate finite difference method to compute the Hessian matrix and either sparse quadrature or Monte Carlo sampling to carry out numerical integration. We demonstrate the efficiency, accuracy, and applicability of our method on a two-dimensional seismic source inversion problem.

Proper-time resolution function for measurement of time evolution of B mesons at the KEK B-Factory

International Nuclear Information System (INIS)

Tajima, H.; Aihara, H.; Higuchi, T.; Kawai, H.; Nakadaira, T.; Tanaka, J.; Tomura, T.; Yokoyama, M.; Hazumi, M.; Sakai, Y.; Sumisawa, K.; Kawasaki, T.

2004-01-01

The proper-time resolution function for the measurement of the time evolution of B mesons with the Belle detector at KEKB is studied in detail. The obtained resolution function is applied to the measurement of B meson lifetimes, the B0B-bar 0 oscillation frequency and time-dependent CP asymmetries

Natural excitation orbitals from linear response theories : Time-dependent density functional theory, time-dependent Hartree-Fock, and time-dependent natural orbital functional theory

NARCIS (Netherlands)

Van Meer, R.; Gritsenko, O. V.; Baerends, E. J.

2017-01-01

Straightforward interpretation of excitations is possible if they can be described as simple single orbital-to-orbital (or double, etc.) transitions. In linear response time-dependent density functional theory (LR-TDDFT), the (ground state) Kohn-Sham orbitals prove to be such an orbital basis. In

Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

International Nuclear Information System (INIS)

Rutherford, Michael E.; Chapman, David J.; White, Thomas G.; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E.

2016-01-01

Scintillator performance in time-resolved, hard, indirect detection X-ray studies on the sub-microsecond timescale at synchrotron light sources is reviewed, modelled and examined experimentally. LYSO:Ce is found to be the only commercially available crystal suitable for these experiments. The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits)

Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

Energy Technology Data Exchange (ETDEWEB)

Rutherford, Michael E.; Chapman, David J.; White, Thomas G. [Imperial College London, London (United Kingdom); Drakopoulos, Michael [Diamond Light Source, I12 Joint Engineering, Environmental, Processing (JEEP) Beamline, Didcot, Oxfordshire (United Kingdom); Rack, Alexander [European Synchrotron Radiation Facility, Grenoble (France); Eakins, Daniel E., E-mail: d.eakins@imperial.ac.uk [Imperial College London, London (United Kingdom)

2016-03-24

Scintillator performance in time-resolved, hard, indirect detection X-ray studies on the sub-microsecond timescale at synchrotron light sources is reviewed, modelled and examined experimentally. LYSO:Ce is found to be the only commercially available crystal suitable for these experiments. The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits)

Time-resolved hard x-ray studies using third-generation synchrotron radiation sources (abstract)

International Nuclear Information System (INIS)

Mills, D.M.

1992-01-01

The third-generation, high-brilliance, synchrotron radiation sources currently under construction will usher in a new era of x-ray research in the physical, chemical, and biological sciences. One of the most exciting areas of experimentation will be the extension of static x-ray scattering and diffraction techniques to the study of transient or time-evolving systems. The high repetition rate, short-pulse duration, high-brilliance, variable spectral bandwidth, and large particle beam energies of these sources make them ideal for hard x-ray, time-resolved studies. The primary focus of this presentation will be on the novel instrumentation required for time-resolved studies such as optics which can increase the flux on the sample or disperse the x-ray beam, detectors and electronics for parallel data collection, and methods for altering the natural time structure of the radiation. This work is supported by the U.S. Department of Energy, BES-Materials Science, under Contract No. W-31-109-ENG-38

Lyapunov Functions to Caputo Fractional Neural Networks with Time-Varying Delays

Directory of Open Access Journals (Sweden)

Ravi Agarwal

2018-05-01

Full Text Available One of the main properties of solutions of nonlinear Caputo fractional neural networks is stability and often the direct Lyapunov method is used to study stability properties (usually these Lyapunov functions do not depend on the time variable. In connection with the Lyapunov fractional method we present a brief overview of the most popular fractional order derivatives of Lyapunov functions among Caputo fractional delay differential equations. These derivatives are applied to various types of neural networks with variable coefficients and time-varying delays. We show that quadratic Lyapunov functions and their Caputo fractional derivatives are not applicable in some cases when one studies stability properties. Some sufficient conditions for stability of equilibrium of nonlinear Caputo fractional neural networks with time dependent transmission delays, time varying self-regulating parameters of all units and time varying functions of the connection between two neurons in the network are obtained. The cases of time varying Lipschitz coefficients as well as nonLipschitz activation functions are studied. We illustrate our theory on particular nonlinear Caputo fractional neural networks.

Real-time scintillation probe measurement of left ventricular function

International Nuclear Information System (INIS)

Green, M.V.; Ostrow, H.G.; Bacharach, S.L.; Allen, S.I.; Bonow, R.O.; Johnston, G.S.

1981-01-01

The micro-processor based system described in this report was designed for maximum flexibility and utility. While the principle function of the system is to acquire, create, analyze and display (in real-time) left ventricular time activity (or volume) curves, provision is also made to acquire additional physiologic signals (e.g., ECG, flowmeter, etc.) and to calculate and display relationships between these various data. The system was designed for interactive use so that the system user can alter the course of a series of measurements based on previous results. These general capabilities are illustrated with several examples. In the first, LV function was measured continuously in a subject from (supine) rest through exercise and recovery. The second example illustrates the use of the system in acquiring (LV) pressure-volume loops. Several technical problems, such as correction for LV background radiation, appear at present to limit the probes applicability. Even now, however, probe systems are demonstrably useful in the study of global left ventricular function when this function is changing rapidly with time in response to various interventions. (orig.) [de

Contributed Review: Source-localization algorithms and applications using time of arrival and time difference of arrival measurements

Science.gov (United States)

Li, Xinya; Deng, Zhiqun Daniel; Rauchenstein, Lynn T.; Carlson, Thomas J.

2016-04-01

Locating the position of fixed or mobile sources (i.e., transmitters) based on measurements obtained from sensors (i.e., receivers) is an important research area that is attracting much interest. In this paper, we review several representative localization algorithms that use time of arrivals (TOAs) and time difference of arrivals (TDOAs) to achieve high signal source position estimation accuracy when a transmitter is in the line-of-sight of a receiver. Circular (TOA) and hyperbolic (TDOA) position estimation approaches both use nonlinear equations that relate the known locations of receivers and unknown locations of transmitters. Estimation of the location of transmitters using the standard nonlinear equations may not be very accurate because of receiver location errors, receiver measurement errors, and computational efficiency challenges that result in high computational burdens. Least squares and maximum likelihood based algorithms have become the most popular computational approaches to transmitter location estimation. In this paper, we summarize the computational characteristics and position estimation accuracies of various positioning algorithms. By improving methods for estimating the time-of-arrival of transmissions at receivers and transmitter location estimation algorithms, transmitter location estimation may be applied across a range of applications and technologies such as radar, sonar, the Global Positioning System, wireless sensor networks, underwater animal tracking, mobile communications, and multimedia.

Time Eigenstates for Potential Functions without Extremal Points

Directory of Open Access Journals (Sweden)

Gabino Torres-Vega

2013-09-01

Full Text Available In a previous paper, we introduced a way to generate a time coordinate system for classical and quantum systems when the potential function has extremal points. In this paper, we deal with the case in which the potential function has no extremal points at all, and we illustrate the method with the harmonic and linear potentials.

Assessing the contribution of binaural cues for apparent source width perception via a functional model

DEFF Research Database (Denmark)

Käsbach, Johannes; Hahmann, Manuel; May, Tobias

2016-01-01

In echoic conditions, sound sources are not perceived as point sources but appear to be expanded. The expansion in the horizontal dimension is referred to as apparent source width (ASW). To elicit this perception, the auditory system has access to fluctuations of binaural cues, the interaural time...... a statistical representation of ITDs and ILDs based on percentiles integrated over time and frequency. The model’s performance was evaluated against psychoacoustic data obtained with noise, speech and music signals in loudspeakerbased experiments. A robust model prediction of ASW was achieved using a cross...

Double point source W-phase inversion: Real-time implementation and automated model selection

Science.gov (United States)

Nealy, Jennifer; Hayes, Gavin

2015-01-01

Rapid and accurate characterization of an earthquake source is an extremely important and ever evolving field of research. Within this field, source inversion of the W-phase has recently been shown to be an effective technique, which can be efficiently implemented in real-time. An extension to the W-phase source inversion is presented in which two point sources are derived to better characterize complex earthquakes. A single source inversion followed by a double point source inversion with centroid locations fixed at the single source solution location can be efficiently run as part of earthquake monitoring network operational procedures. In order to determine the most appropriate solution, i.e., whether an earthquake is most appropriately described by a single source or a double source, an Akaike information criterion (AIC) test is performed. Analyses of all earthquakes of magnitude 7.5 and greater occurring since January 2000 were performed with extended analyses of the September 29, 2009 magnitude 8.1 Samoa earthquake and the April 19, 2014 magnitude 7.5 Papua New Guinea earthquake. The AIC test is shown to be able to accurately select the most appropriate model and the selected W-phase inversion is shown to yield reliable solutions that match published analyses of the same events.

Biodegradable triboelectric nanogenerator as a life-time designed implantable power source.

Science.gov (United States)

Zheng, Qiang; Zou, Yang; Zhang, Yalan; Liu, Zhuo; Shi, Bojing; Wang, Xinxin; Jin, Yiming; Ouyang, Han; Li, Zhou; Wang, Zhong Lin

2016-03-01

Transient electronics built with degradable organic and inorganic materials is an emerging area and has shown great potential for in vivo sensors and therapeutic devices. However, most of these devices require external power sources to function, which may limit their applications for in vivo cases. We report a biodegradable triboelectric nanogenerator (BD-TENG) for in vivo biomechanical energy harvesting, which can be degraded and resorbed in an animal body after completing its work cycle without any adverse long-term effects. Tunable electrical output capabilities and degradation features were achieved by fabricated BD-TENG using different materials. When applying BD-TENG to power two complementary micrograting electrodes, a DC-pulsed electrical field was generated, and the nerve cell growth was successfully orientated, showing its feasibility for neuron-repairing process. Our work demonstrates the potential of BD-TENG as a power source for transient medical devices.

New Insights on the Uncertainties in Finite-Fault Earthquake Source Inversion

KAUST Repository

Razafindrakoto, Hoby

2015-04-01

New Insights on the Uncertainties in Finite-Fault Earthquake Source Inversion Hoby Njara Tendrisoa Razafindrakoto Earthquake source inversion is a non-linear problem that leads to non-unique solutions. The aim of this dissertation is to understand the uncertainty and reliability in earthquake source inversion, as well as to quantify variability in earthquake rupture models. The source inversion is performed using a Bayesian inference. This technique augments optimization approaches through its ability to image the entire solution space which is consistent with the data and prior information. In this study, the uncertainty related to the choice of source-time function and crustal structure is investigated. Three predefined analytical source-time functions are analyzed; isosceles triangle, Yoffe with acceleration time of 0.1 and 0.3 s. The use of the isosceles triangle as source-time function is found to bias the finite-fault source inversion results. It accelerates the rupture to propagate faster compared to that of the Yoffe function. Moreover, it generates an artificial linear correlation between parameters that does not exist for the Yoffe source-time functions. The effect of inadequate knowledge of Earth’s crustal structure in earthquake rupture models is subsequently investigated. The results show that one-dimensional structure variability leads to parameters resolution changes, with a broadening of the posterior 5 PDFs and shifts in the peak location. These changes in the PDFs of kinematic parameters are associated with the blurring effect of using incorrect Earth structure. As an application to real earthquake, finite-fault source models for the 2009 L’Aquila earthquake are examined using one- and three-dimensional crustal structures. One- dimensional structure is found to degrade the data fitting. However, there is no significant effect on the rupture parameters aside from differences in the spatial slip extension. Stable features are maintained for both

Real-time particle monitor calibration factors and PM2.5 emission factors for multiple indoor sources.

Science.gov (United States)

Dacunto, Philip J; Cheng, Kai-Chung; Acevedo-Bolton, Viviana; Jiang, Ruo-Ting; Klepeis, Neil E; Repace, James L; Ott, Wayne R; Hildemann, Lynn M

2013-08-01

Indoor sources can greatly contribute to personal exposure to particulate matter less than 2.5 μm in diameter (PM2.5). To accurately assess PM2.5 mass emission factors and concentrations, real-time particle monitors must be calibrated for individual sources. Sixty-six experiments were conducted with a common, real-time laser photometer (TSI SidePak™ Model AM510 Personal Aerosol Monitor) and a filter-based PM2.5 gravimetric sampler to quantify the monitor calibration factors (CFs), and to estimate emission factors for common indoor sources including cigarettes, incense, cooking, candles, and fireplaces. Calibration factors for these indoor sources were all significantly less than the factory-set CF of 1.0, ranging from 0.32 (cigarette smoke) to 0.70 (hamburger). Stick incense had a CF of 0.35, while fireplace emissions ranged from 0.44-0.47. Cooking source CFs ranged from 0.41 (fried bacon) to 0.65-0.70 (fried pork chops, salmon, and hamburger). The CFs of combined sources (e.g., cooking and cigarette emissions mixed) were linear combinations of the CFs of the component sources. The highest PM2.5 emission factors per time period were from burned foods and fireplaces (15-16 mg min(-1)), and the lowest from cooking foods such as pizza and ground beef (0.1-0.2 mg min(-1)).

A program PULSYN01 for wide-band simulation of source radiation from a finite earthquake source/fault

International Nuclear Information System (INIS)

Gusev, A.A.

2001-12-01

The purpose of the program PULSYN01 is to apply a realistic wideband source-side input for calculation of earthquake ground motion. The source is represented as a grid of point subsources, and their seismic moment rate time functions are generated considering each of them as realizations (sample functions) of a non-stationary random process. The model is intended for use at receiver-to fault distances from far field to as small as 10-20% of the fault width. Combined with an adequate Green's function synthesizer, PULSUNT01 can be used for assessment of possible ground motion and seismic hazard in many ways, including scenario event simulation, parametric studies, and eventually stochastic hazard calculations

Radial dose functions for 103Pd, 125I, 169Yb and 192Ir brachytherapy sources: an EGS4 Monte Carlo study

International Nuclear Information System (INIS)

Mainegra, E.

2000-01-01

Radial dose functions g(r) in water around 103 Pd, 125 I, 169 Yb and 192 Ir brachytherapy sources were estimated by means of the EGS4 simulation system and extensively compared with experimental as well as with theoretical results. The DLC-136/PHOTX cross section library, water molecular form factors, bound Compton scattering and Doppler broadening of the Compton-scattered photon energy were considered in the calculations. Use of the point source approach produces reasonably accurate values of the radial dose function only at distances beyond 0.5 cm for 103 Pd sources. It is shown that binding corrections for Compton scattering have a negligible effect on radial dose function for 169 Yb and 192 Ir seeds and for 103 Pd seeds under 5.0 cm from the source centre and for the 125 I seed model 6702 under 8.0 cm. Beyond those limits there is an increasing influence of binding corrections on radial dose function for 103 Pd and 125 I sources. Results in solid water medium underestimate radial dose function for low-energy sources by as much as 6% for 103 Pd and 2.5% for 125 I already at 2 cm from source centre resulting in a direct underestimation of absolute dose rate values. It was found necessary to consider medium boundaries when comparing results for the radial dose function of 169 Yb and 192 Ir sources to avoid discrepancies due to the backscattering contribution in the phantom medium. Values of g(r) for all source types studied are presented. Uncertainties lie under 1% within one standard deviation. (author)

Integrator drawer with pre-adjusted time for the study of decay of very low activity sources; Tiroir integrateur a temps preregle pour l'etude de decroissance des sources de tres faible activite

Energy Technology Data Exchange (ETDEWEB)

Couly, J. P.

1962-07-01

The author presents a drawer which can be adapted on standard counting assemblies to control the decay of very low activity sources such as samples aimed at atmospheric control. The operation principle relies on charging a tank capacitor with pulses received from a sensor. The resulting voltage is measured by a high input resistance circuit, and then recorded. The tank capacitor is periodically discharged by pulses from a time base circuit. The recording appears under the form of rays. Their length corresponds to the counting rate and the extremity envelope represents the source activity decay curve as a function of time [French] Ce tiroir, pouvant s'adapter sur les ensembles de comptage standards, permet de suivre la decroissance de sources radioactives de tres faible activite (de l'ordre de 10{sup -9} curie) tels que les prelevements de controle atmospherique. Le principe de fonctionnement consiste a charger un condensateur reservoir avec les impulsions recues du detecteur, et prealablement mises en forme. La tension resultante est mesuree par un circuit a grande resistance d'entree puis enregistree a l'aide d'un enregistreur MECI monovoie. Le condensateur reservoir est decharge periodiquement par des impulsions provenant d'un circuit de base de temps. L'enregistrement apparait sous la forme de traits, leur longueur correspond au taux de comptage et l'enveloppe de leur extremite represente la courbe de decroissance de l'activite de la source en fonction du temps. (auteur)

Numerical simulation of electromagnetic waves in Schwarzschild space-time by finite difference time domain method and Green function method

Science.gov (United States)

Jia, Shouqing; La, Dongsheng; Ma, Xuelian

2018-04-01

The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.

The dislocation distribution function near a crack tip generated by external sources

International Nuclear Information System (INIS)

Lung, C.W.; Deng, K.M.

1988-06-01

The dislocation distribution function near a crack tip generated by external sources is calculated. It is similar to the shape of curves calculated for the crack tip emission case but the quantative difference is quite large. The image forces enlarges the negative dislocation zone but does not change the form of the curve. (author). 10 refs, 3 figs

Real-time Inversion of Tsunami Source from GNSS Ground Deformation Observations and Tide Gauges.

Science.gov (United States)

Arcas, D.; Wei, Y.

2017-12-01

Over the last decade, the NOAA Center for Tsunami Research (NCTR) has developed an inversion technique to constrain tsunami sources based on the use of Green's functions in combination with data reported by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART®) systems. The system has consistently proven effective in providing highly accurate tsunami forecasts of wave amplitude throughout an entire basin. However, improvement is necessary in two critical areas: reduction of data latency for near-field tsunami predictions and reduction of maintenance cost of the network. Two types of sensors have been proposed as supplementary to the existing network of DART®systems: Global Navigation Satellite System (GNSS) stations and coastal tide gauges. The use GNSS stations to provide autonomous geo-spatial positioning at specific sites during an earthquake has been proposed in recent years to supplement the DART® array in tsunami source inversion. GNSS technology has the potential to provide substantial contributions in the two critical areas of DART® technology where improvement is most necessary. The present study uses GNSS ground displacement observations of the 2011 Tohoku-Oki earthquake in combination with NCTR operational database of Green's functions, to produce a rapid estimate of tsunami source based on GNSS observations alone. The solution is then compared with that obtained via DART® data inversion and the difficulties in obtaining an accurate GNSS-based solution are underlined. The study also identifies the set of conditions required for source inversion from coastal tide-gauges using the degree of nonlinearity of the signal as a primary criteria. We then proceed to identify the conditions and scenarios under which a particular gage could be used to invert a tsunami source.

Time-dependent density functional theory for multi-component systems

International Nuclear Information System (INIS)

Tiecheng Li; Peiqing Tong

1985-10-01

The Runge-Gross version of Hohenberg-Kohn-Sham's density functional theory is generalized to multi-component systems, both for arbitrary time-dependent pure states and for arbitrary time-dependent ensembles. (author)

Analysis of positron annihilation lifetime data by numerical Laplace inversion: Corrections for source terms and zero-time shift errors

International Nuclear Information System (INIS)

Gregory, R.B.

1991-01-01

We have recently described modifications to the program CONTIN for the solution of Fredholm integral equations with convoluted kernels of the type that occur in the analysis of positron annihilation lifetime data. In this article, modifications to the program to correct for source terms in the sample and reference decay curves and for shifts in the position of the zero-time channel of the sample and reference data are described. Unwanted source components, expressed as a discrete sum of exponentials, may be removed from both the sample and reference data by modification of the sample data alone, without the need for direct knowledge of the instrument resolution function. Shifts in the position of the zero-time channel of up to half the channel width of the multichannel analyzer can be corrected. Analyses of computer-simulated test data indicate that the quality of the reconstructed annihilation rate probability density functions is improved by employing a refernce material with a short lifetime and indicate that reference materials which generate free positrons by quenching positronium formation (i.e. strong oxidizing agents) have lifetimes that are too long (400-450 ps) to provide reliable estimates of the lifetime parameters for the shortlived components with the methods described here. Well-annealed single crystals of metals with lifetimes less than 200 ps, such as molybdenum (123 ps) and aluminium (166 ps) do not introduce significant errors in estimates of the lifetime parameters and are to be preferred as reference materials. The performance of our modified version of CONTIN is illustrated by application to positron annihilation in polytetrafluoroethylene. (orig.)

Design, development and testing of real time control and data acquisition system for R&D IC H&CD source

Energy Technology Data Exchange (ETDEWEB)

Rajnish, Kumar, E-mail: krajnish@iter-india.org [ITER-India, Institute for Plasma Research, Gandhinagar, Gujarat (India); Soni, Dipal; Verma, Sriprakash; Patel, Hriday; Trivedi, Rajesh; Singh, Raghuraj; Patel, Manoj; Mukherjee, Aparajita [ITER-India, Institute for Plasma Research, Gandhinagar, Gujarat (India); Makadia, Keyur [Optimized Solutions Pvt. Ltd., Ahmedabad, Gujarat (India)

2016-11-15

Highlights: • Application program of LCU is developed using LabVIEW™ to operate megawatt RF source. • PXI 6133 module is used for acquiring data with 1 MHz sampling frequency in trigger mode. • PXI 6255 is used for continuous acquisition with 1 KHz sampling frequency. • PXI 7841 R is used for hard wired fast protection function and for real time control loop. • Schneider PLC is used to develop sequence control system. - Abstract: One of the important auxiliary heating and current drive systems for ITER experiment is Ion Cyclotron Heating & Current Drive (IC H&CD) system. ITER requires 1 prototype and 8 independent RF Sources, each having capability to deliver constant output power of 2.5 MW at VSWR 2 in the frequency range of 35–65 MHz. To meet the ITER requirement, an R&D program has been launched to identify the final stage tube (Tetrode/Diacrode) for MW level RF amplifier, along with other critical components. Under this R&D program, single chain of RF cascaded amplifiers, consisting of low & high power RF sections, auxiliary power supply, Anode power supply and test bench simulating ITER requirement, are being developed. To ensure reliable and safe operation of the entire system, PLC/PXI based Local Control Unit (LCU) is developed. PLC based sequential control system is developed for sequential biasing of electrodes of high power vacuum tubes (Tetrode/Diacrode). To protect the RF Source against critical fault condition, local protection logic is developed using PXI-7841R, which will ensure fast shut off (<10 μs) of RF and power supplies. Constant and stable power output even with variable load condition (up to VSWR 2) is achieved by employing two real time feedback control loops-one for making constant output power and the other one for optimizing anode & screen grid dissipation. For fault/offline analysis, event based acquisition and logging functionality is provided that acquires and logs data at 1 μs sampling rate for 100 ms pre and post time

Higher time derivatives of the generalized Liapunov function

International Nuclear Information System (INIS)

Schieve, W.C.; Bulsara, A.R.

1975-01-01

Using the generalized N-body expression for a Liapunov functional developed by Prigogine and coworkers, a condition is obtained whereby the successive time derivatives of this function alternate in sign for weakly coupled systems. This generalized Liapunov function contains contributions from the diagonal as well as off-diagonal (correlation) components of the density matrix. The alternating sign condition is applied (and seen to hold true) for the cases of elastic phonon scattering in a lattice, three-phonon scattering (the anharmonic lattice), and the quantum electron gas. It is also proved simply for the Friedrichs model

OpenPSTD : The open source pseudospectral time-domain method for acoustic propagation

NARCIS (Netherlands)

Hornikx, M.C.J.; Krijnen, T.F.; van Harten, L.

2016-01-01

An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in

Experimental investigation of statistical density function of decaying radioactive sources

International Nuclear Information System (INIS)

Salma, I.; Zemplen-Papp, E.

1991-01-01

The validity of the Poisson and the λ P(k) modified Poisson statistical density functions of observing k events in a short time interval is investigated experimentally in radioactive decay detection for various measuring times. The experiments to measure radioactive decay were performed with 89m Y, using a multichannel analyzer. According to the results, Poisson statistics adequately describes the counting experiment for short measuring times. (author) 13 refs.; 4 figs

[Multiple time scales analysis of spatial differentiation characteristics of non-point source nitrogen loss within watershed].

Science.gov (United States)

Liu, Mei-bing; Chen, Xing-wei; Chen, Ying

2015-07-01

Identification of the critical source areas of non-point source pollution is an important means to control the non-point source pollution within the watershed. In order to further reveal the impact of multiple time scales on the spatial differentiation characteristics of non-point source nitrogen loss, a SWAT model of Shanmei Reservoir watershed was developed. Based on the simulation of total nitrogen (TN) loss intensity of all 38 subbasins, spatial distribution characteristics of nitrogen loss and critical source areas were analyzed at three time scales of yearly average, monthly average and rainstorms flood process, respectively. Furthermore, multiple linear correlation analysis was conducted to analyze the contribution of natural environment and anthropogenic disturbance on nitrogen loss. The results showed that there were significant spatial differences of TN loss in Shanmei Reservoir watershed at different time scales, and the spatial differentiation degree of nitrogen loss was in the order of monthly average > yearly average > rainstorms flood process. TN loss load mainly came from upland Taoxi subbasin, which was identified as the critical source area. At different time scales, land use types (such as farmland and forest) were always the dominant factor affecting the spatial distribution of nitrogen loss, while the effect of precipitation and runoff on the nitrogen loss was only taken in no fertilization month and several processes of storm flood at no fertilization date. This was mainly due to the significant spatial variation of land use and fertilization, as well as the low spatial variability of precipitation and runoff.

Monopoly models with time-varying demand function

Science.gov (United States)

Cavalli, Fausto; Naimzada, Ahmad

2018-05-01

We study a family of monopoly models for markets characterized by time-varying demand functions, in which a boundedly rational agent chooses output levels on the basis of a gradient adjustment mechanism. After presenting the model for a generic framework, we analytically study the case of cyclically alternating demand functions. We show that both the perturbation size and the agent's reactivity to profitability variation signals can have counterintuitive roles on the resulting period-2 cycles and on their stability. In particular, increasing the perturbation size can have both a destabilizing and a stabilizing effect on the resulting dynamics. Moreover, in contrast with the case of time-constant demand functions, the agent's reactivity is not just destabilizing, but can improve stability, too. This means that a less cautious behavior can provide better performance, both with respect to stability and to achieved profits. We show that, even if the decision mechanism is very simple and is not able to always provide the optimal production decisions, achieved profits are very close to those optimal. Finally, we show that in agreement with the existing empirical literature, the price series obtained simulating the proposed model exhibit a significant deviation from normality and large volatility, in particular when underlying deterministic dynamics become unstable and complex.

Functional development of fronto-striato-parietal networks associated with time perception

Directory of Open Access Journals (Sweden)

Anna eSmith

2011-11-01

Full Text Available Compared to our understanding of the functional maturation of executive functions, little is known about the neurofunctional development of perceptive functions. Time perception develops during late adolescence, underpinning many functions including motor and verbal processing, as well as late maturing higher order cognitive skills such as forward planning and future-related decision-making. Nothing, however, is known about the neurofunctional changes associated with time perception from childhood to adulthood. Using functional magnetic resonance imaging we explored the effects of age on the brain activation and functional connectivity of 32 male participants from 10 to 53 years of age during a time discrimination task that required the discrimination of temporal intervals of seconds differing by several hundred milliseconds. Increasing development was associated with progressive activation increases within left lateralised dorsolateral and inferior fronto-parieto-striato-thalamic brain regions. Furthermore, despite comparable task performance, adults showed increased functional connectivity between inferior/dorsolateral interhemispheric fronto-frontal activation as well as between inferior fronto-parietal regions compared with adolescents. Activation in caudate, specifically, was associated with both increasing age and better temporal discrimination. Progressive decreases in activation with age were observed in ventromedial prefrontal cortex, limbic regions and cerebellum. The findings demonstrate age-dependent developmentally dissociated neural networks for time discrimination. With increasing age there is progressive recruitment of later maturing left hemispheric and lateralised fronto-parieto-striato-thalamic networks, known to mediate time discrimination in adults, while earlier developing brain regions such as ventromedial prefrontal cortex, limbic and paralimbic areas and cerebellum subserve fine-temporal processing functions in children

Time-domain single-source integral equations for analyzing scattering from homogeneous penetrable objects

KAUST Repository

Valdé s, Felipe; Andriulli, Francesco P.; Bagci, Hakan; Michielssen, Eric

2013-01-01

Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis

Optimization of Excitation in FDTD Method and Corresponding Source Modeling

Directory of Open Access Journals (Sweden)

B. Dimitrijevic

2015-04-01

Full Text Available Source and excitation modeling in FDTD formulation has a significant impact on the method performance and the required simulation time. Since the abrupt source introduction yields intensive numerical variations in whole computational domain, a generally accepted solution is to slowly introduce the source, using appropriate shaping functions in time. The main goal of the optimization presented in this paper is to find balance between two opposite demands: minimal required computation time and acceptable degradation of simulation performance. Reducing the time necessary for source activation and deactivation is an important issue, especially in design of microwave structures, when the simulation is intensively repeated in the process of device parameter optimization. Here proposed optimized source models are realized and tested within an own developed FDTD simulation environment.

The importance of source and cue type in time-based everyday prospective memory.

Science.gov (United States)

Oates, Joyce M; Peynircioğlu, Zehra F

2014-01-01

We examined the effects of the source of a prospective memory task (provided or generated) and the type of cue (specific or general) triggering that task in everyday settings. Participants were asked to complete both generated and experimenter-provided tasks and to send a text message when each task was completed. The cue/context for the to-be-completed tasks was either a specific time or a general deadline (time-based cue), and the cue/context for the texting task was the completion of the task itself (activity-based cue). Although generated tasks were completed more often, generated cues/contexts were no more effective than provided ones in triggering the intention. Furthermore, generated tasks were completed more often when the cue/context comprised a specific time, whereas provided tasks were completed more often when the cue/context comprised a general deadline. However, texting was unaffected by the source of the cue/context. Finally, emotion modulated the effects. Results are discussed within a process-driven framework.

On the Relationship Between Transfer Function-derived Response Times and Hydrograph Analysis Timing Parameters: Are there Similarities?

Science.gov (United States)

Bansah, S.; Ali, G.; Haque, M. A.; Tang, V.

2017-12-01

The proportion of precipitation that becomes streamflow is a function of internal catchment characteristics - which include geology, landscape characteristics and vegetation - and influence overall storage dynamics. The timing and quantity of water discharged by a catchment are indeed embedded in event hydrographs. Event hydrograph timing parameters, such as the response lag and time of concentration, are important descriptors of how long it takes the catchment to respond to input precipitation and how long it takes the latter to filter through the catchment. However, the extent to which hydrograph timing parameters relate to average response times derived from fitting transfer functions to annual hydrographs is unknown. In this study, we used a gamma transfer function to determine catchment average response times as well as event-specific hydrograph parameters across a network of eight nested watersheds ranging from 0.19 km2 to 74.6 km2 prairie catchments located in south central Manitoba (Canada). Various statistical analyses were then performed to correlate average response times - estimated using the parameters of the fitted gamma transfer function - to event-specific hydrograph parameters. Preliminary results show significant interannual variations in response times and hydrograph timing parameters: the former were in the order of a few hours to days, while the latter ranged from a few days to weeks. Some statistically significant relationships were detected between response times and event-specific hydrograph parameters. Future analyses will involve the comparison of statistical distributions of event-specific hydrograph parameters with that of runoff response times and baseflow transit times in order to quantity catchment storage dynamics across a range of temporal scales.

eBooking of beam-time over internet for beamlines of Indus synchrotron radiation sources

International Nuclear Information System (INIS)

Jain, Alok; Verma, Rajesh; Rajan, Alpana; Modi, M.H.; Rawat, Anil

2015-01-01

Users from various research labs and academic institutes carry out experiments on beamlines of two Synchrotron Radiation Sources Indus-1 and Indus-2 available at RRCAT, Indore. To carry out experimental work on beamlines of both synchrotron radiation sources, beam-time is booked over Internet by the users of beamlines using user portal designed, developed and deployed over Internet. This portal has made the process of beamtime booking fast, hassle free and paperless as manual booking of beam-time for carrying out experiment on a particular beamline is cumbersome. The portal facilitates in-charge of Indus-1 and Indus-2 beamlines to keep track of users' records, work progress and other activities linked to experiments carried on beamlines. It is important to keep record and provide statistics about the usage of the beam lines from time-to-time. The user portal for e-booking of beam-time has been developed in-house using open source software development tools. Multi-step activities of users and beamline administrators are workflow based with seamless flow of information across various modules and fully authenticated using role based mechanism for different roles of software usage. The software is in regular use since November 2013 and has helped beamline in- charges in efficiently managing various activities related to user registration, booking of beam-time, booking of Guest House, Generation of Security permits, User feedback etc. Design concept, role based authentication mechanism and features provided by the web portal are discussed in detail in this paper. (author)

In vivo time-gated diffuse correlation spectroscopy at quasi-null source-detector separation.

Science.gov (United States)

Pagliazzi, M; Sekar, S Konugolu Venkata; Di Sieno, L; Colombo, L; Durduran, T; Contini, D; Torricelli, A; Pifferi, A; Mora, A Dalla

2018-06-01

We demonstrate time domain diffuse correlation spectroscopy at quasi-null source-detector separation by using a fast time-gated single-photon avalanche diode without the need of time-tagging electronics. This approach allows for increased photon collection, simplified real-time instrumentation, and reduced probe dimensions. Depth discriminating, quasi-null distance measurement of blood flow in a human subject is presented. We envision the miniaturization and integration of matrices of optical sensors of increased spatial resolution and the enhancement of the contrast of local blood flow changes.

Dispersion and betatron function correction in the Advanced Photon Source storage ring using singular value decomposition

International Nuclear Information System (INIS)

Emery, L.

1999-01-01

Magnet errors and off-center orbits through sextuples perturb the dispersion and beta functions in a storage ring (SR), which affects machine performance. In a large ring such as the Advanced Photon Source (APS), the magnet errors are difficult to determine with beam-based methods. Also the non-zero orbit through sextuples result from user requests for steering at light source points. For expediency, a singular value decomposition (SVD) matrix method analogous to orbit correction was adopted to make global corrections to these functions using strengths of several quadrupoles as correcting elements. The direct response matrix is calculated from the model of the perfect lattice. The inverse is calculated by SVD with a selected number of singular vectors. Resulting improvement in the lattice functions and machine performance will be presented

Selective Attention, Working Memory, and Executive Function as Potential Independent Sources of Cognitive Dysfunction in Schizophrenia.

Science.gov (United States)

Gold, James M; Robinson, Benjamin; Leonard, Carly J; Hahn, Britta; Chen, Shuo; McMahon, Robert P; Luck, Steven J

2017-11-11

People with schizophrenia demonstrate impairments in selective attention, working memory, and executive function. Given the overlap in these constructs, it is unclear if these represent distinct impairments or different manifestations of one higher-order impairment. To examine this question, we administered tasks from the basic cognitive neuroscience literature to measure visual selective attention, working memory capacity, and executive function in 126 people with schizophrenia and 122 healthy volunteers. Patients demonstrated deficits on all tasks with the exception of selective attention guided by strong bottom-up inputs. Although the measures of top-down control of selective attention, working memory, and executive function were all intercorrelated, several sources of evidence indicate that working memory and executive function are separate sources of variance. Specifically, both working memory and executive function independently contributed to the discrimination of group status and independently accounted for variance in overall general cognitive ability as assessed by the MATRICS battery. These two cognitive functions appear to be separable features of the cognitive impairments observed in schizophrenia. © The Author 2017. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

The Source of Time-Correlated Photons at 1.064 μm and its Applications

Directory of Open Access Journals (Sweden)

Gostev P.P.

2015-01-01

Full Text Available The source of time-correlated photon-pairs at 1064 nm is described. The source consists of the spontaneous parametric down-conversion (SPDC generator, pumped by cw laser operating at 532 nm, and the measuring and control appliances. One of the main parts of the electronic systems is the “time-to-digital converter” which is designed and built by our group. The system allows to create and detect correlation of photon pairs with resolution better than 1 ns. We adduce the results of a quantum key distribution through open air. The key length was about 5000 bits and the accuracy ~0.1%.

New results for time reversed symplectic dynamic systems and quadratic functionals

Directory of Open Access Journals (Sweden)

Roman Simon Hilscher

2012-05-01

Full Text Available In this paper, we examine time scale symplectic (or Hamiltonian systems and the associated quadratic functionals which contain a forward shift in the time variable. Such systems and functionals have a close connection to Jacobi systems for calculus of variations and optimal control problems on time scales. Our results, among which we consider the Reid roundabout theorem, generalize the corresponding classical theory for time reversed discrete symplectic systems, as well as they complete the recently developed theory of time scale symplectic systems.

BLUES function method in computational physics

Science.gov (United States)

Indekeu, Joseph O.; Müller-Nedebock, Kristian K.

2018-04-01

We introduce a computational method in physics that goes ‘beyond linear use of equation superposition’ (BLUES). A BLUES function is defined as a solution of a nonlinear differential equation (DE) with a delta source that is at the same time a Green’s function for a related linear DE. For an arbitrary source, the BLUES function can be used to construct an exact solution to the nonlinear DE with a different, but related source. Alternatively, the BLUES function can be used to construct an approximate piecewise analytical solution to the nonlinear DE with an arbitrary source. For this alternative use the related linear DE need not be known. The method is illustrated in a few examples using analytical calculations and numerical computations. Areas for further applications are suggested.

Effects of detector-source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors.

Science.gov (United States)

Ermis, E E; Celiktas, C

2012-12-01

Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. (133)Ba and (207)Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Time-dependent importance sampling in semiclassical initial value representation calculations for time correlation functions. II. A simplified implementation.

Science.gov (United States)

Tao, Guohua; Miller, William H

2012-09-28

An efficient time-dependent (TD) Monte Carlo (MC) importance sampling method has recently been developed [G. Tao and W. H. Miller, J. Chem. Phys. 135, 024104 (2011)] for the evaluation of time correlation functions using the semiclassical (SC) initial value representation (IVR) methodology. In this TD-SC-IVR method, the MC sampling uses information from both time-evolved phase points as well as their initial values, and only the "important" trajectories are sampled frequently. Even though the TD-SC-IVR was shown in some benchmark examples to be much more efficient than the traditional time-independent sampling method (which uses only initial conditions), the calculation of the SC prefactor-which is computationally expensive, especially for large systems-is still required for accepted trajectories. In the present work, we present an approximate implementation of the TD-SC-IVR method that is completely prefactor-free; it gives the time correlation function as a classical-like magnitude function multiplied by a phase function. Application of this approach to flux-flux correlation functions (which yield reaction rate constants) for the benchmark H + H(2) system shows very good agreement with exact quantum results. Limitations of the approximate approach are also discussed.

An automated multi-scale network-based scheme for detection and location of seismic sources

Science.gov (United States)

Poiata, N.; Aden-Antoniow, F.; Satriano, C.; Bernard, P.; Vilotte, J. P.; Obara, K.

2017-12-01

We present a recently developed method - BackTrackBB (Poiata et al. 2016) - allowing to image energy radiation from different seismic sources (e.g., earthquakes, LFEs, tremors) in different tectonic environments using continuous seismic records. The method exploits multi-scale frequency-selective coherence in the wave field, recorded by regional seismic networks or local arrays. The detection and location scheme is based on space-time reconstruction of the seismic sources through an imaging function built from the sum of station-pair time-delay likelihood functions, projected onto theoretical 3D time-delay grids. This imaging function is interpreted as the location likelihood of the seismic source. A signal pre-processing step constructs a multi-band statistical representation of the non stationary signal, i.e. time series, by means of higher-order statistics or energy envelope characteristic functions. Such signal-processing is designed to detect in time signal transients - of different scales and a priori unknown predominant frequency - potentially associated with a variety of sources (e.g., earthquakes, LFE, tremors), and to improve the performance and the robustness of the detection-and-location location step. The initial detection-location, based on a single phase analysis with the P- or S-phase only, can then be improved recursively in a station selection scheme. This scheme - exploiting the 3-component records - makes use of P- and S-phase characteristic functions, extracted after a polarization analysis of the event waveforms, and combines the single phase imaging functions with the S-P differential imaging functions. The performance of the method is demonstrated here in different tectonic environments: (1) analysis of the one year long precursory phase of 2014 Iquique earthquake in Chile; (2) detection and location of tectonic tremor sources and low-frequency earthquakes during the multiple episodes of tectonic tremor activity in southwestern Japan.

Estimates of Imaging Times for Conventional and Synchrotron X-Ray Sources

CERN Document Server

Kinney, J

2003-01-01

The following notes are to be taken as estimates of the time requirements for imaging NIF targets in three-dimensions with absorption contrast. The estimates ignore target geometry and detector inefficiency, and focus only on the statistical question of detecting compositional (structural) differences between adjacent volume elements in the presence of noise. The basic equations, from the classic reference by Grodzins, consider imaging times in terms of the required number of photons necessary to provide an image with given resolution and noise. The time estimates, therefore, have been based on the calculated x-ray fluxes from the proposed Advanced Light Source (ALS) imaging beamline, and from the calculated flux for a tungsten anode x-ray generator operated in a point focus mode.

Transfer functions of double- and multiple-cavity Fabry-Perot filters driven by Lorentzian sources.

Science.gov (United States)

Marti, J; Capmany, J

1996-12-20

We derive expressions for the transfer functions of double- and multiple-cavity Fabry-Perot filters driven by laser sources with Lorentzian spectrum. These are of interest because of their applications in sensing and channel filtering in optical frequency-division multiplexing networks.

3-D time-domain induced polarization tomography: a new approach based on a source current density formulation

Science.gov (United States)

Soueid Ahmed, A.; Revil, A.

2018-04-01

Induced polarization (IP) of porous rocks can be associated with a secondary source current density, which is proportional to both the intrinsic chargeability and the primary (applied) current density. This gives the possibility of reformulating the time domain induced polarization (TDIP) problem as a time-dependent self-potential-type problem. This new approach implies a change of strategy regarding data acquisition and inversion, allowing major time savings for both. For inverting TDIP data, we first retrieve the electrical resistivity distribution. Then, we use this electrical resistivity distribution to reconstruct the primary current density during the injection/retrieval of the (primary) current between the current electrodes A and B. The time-lapse secondary source current density distribution is determined given the primary source current density and a distribution of chargeability (forward modelling step). The inverse problem is linear between the secondary voltages (measured at all the electrodes) and the computed secondary source current density. A kernel matrix relating the secondary observed voltages data to the source current density model is computed once (using the electrical conductivity distribution), and then used throughout the inversion process. This recovered source current density model is in turn used to estimate the time-dependent chargeability (normalized voltages) in each cell of the domain of interest. Assuming a Cole-Cole model for simplicity, we can reconstruct the 3-D distributions of the relaxation time τ and the Cole-Cole exponent c by fitting the intrinsic chargeability decay curve to a Cole-Cole relaxation model for each cell. Two simple cases are studied in details to explain this new approach. In the first case, we estimate the Cole-Cole parameters as well as the source current density field from a synthetic TDIP data set. Our approach is successfully able to reveal the presence of the anomaly and to invert its Cole

Source amplitudes for active exterior cloaking

International Nuclear Information System (INIS)

Norris, Andrew N; Amirkulova, Feruza A; Parnell, William J

2012-01-01

The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources. (paper)

Equilibrium arrival times to queues with general service times and non-linear utility functions

DEFF Research Database (Denmark)

Breinbjerg, Jesper

2017-01-01

by a general utility function which is decreasing in the waiting time and service completion time of each customer. Applications of such queueing games range from people choosing when to arrive at a grand opening sale to travellers choosing when to line up at the gate when boarding an airplane. We develop...

X-ray absorption in insulators with non-Hermitian real-time time-dependent density functional theory.

Science.gov (United States)

Fernando, Ranelka G; Balhoff, Mary C; Lopata, Kenneth

2015-02-10

Non-Hermitian real-time time-dependent density functional theory was used to compute the Si L-edge X-ray absorption spectrum of α-quartz using an embedded finite cluster model and atom-centered basis sets. Using tuned range-separated functionals and molecular orbital-based imaginary absorbing potentials, the excited states spanning the pre-edge to ∼20 eV above the ionization edge were obtained in good agreement with experimental data. This approach is generalizable to TDDFT studies of core-level spectroscopy and dynamics in a wide range of materials.

Correlations in Many-Body systems from two-time Greens functions

International Nuclear Information System (INIS)

Morawetz, K.; Kohler, H.S.

2000-01-01

The Kadanoff-Baym (KB) equations are solved numerically for infinite nuclear matter. In particular we calculate correlation energies and correlation times. Approximating the Green's functions in the KB collision kernel by the free Green's functions the Levinson equation is obtained. This approximation is valid for weak interactions and/or low densities. It relates to the extended quasi-particle approximation for the spectral function. The Levinson correlation energy reduces for large times to a second order Born approximation for the energy. Comparing the Levinson, Born and KB calculations allows for an estimate of higher order spectral corrections to the correlations. (authors)

Exact Time-Dependent Wave Functions of a Confined Time-Dependent Harmonic Oscillator with Two Moving Boundaries

International Nuclear Information System (INIS)

Lo, C.F.

2009-01-01

By applying the standard analytical techniques of solving partial differential equations, we have obtained the exact solution in terms of the Fourier sine series to the time-dependent Schroedinger equation describing a quantum one-dimensional harmonic oscillator of time-dependent frequency confined in an infinite square well with the two walls moving along some parametric trajectories. Based upon the orthonormal basis of quasi-stationary wave functions, the exact propagator of the system has also been analytically derived. Special cases like (i) a confined free particle, (ii) a confined time-independent harmonic oscillator, and (iii) an aging oscillator are examined, and the corresponding time-dependent wave functions are explicitly determined. Besides, the approach has been extended to solve the case of a confined generalized time-dependent harmonic oscillator for some parametric moving boundaries as well. (general)

Functional localization of a "Time Keeper" function separate from attentional resources and task strategy.

Science.gov (United States)

Tracy, J I; Faro, S H; Mohamed, F B; Pinsk, M; Pinus, A

2000-03-01

The functional neuroanatomy of time estimation has not been well-documented. This research investigated the fMRI measured brain response to an explicit, prospective time interval production (TIP) task. The study tested for the presence of brain activity reflecting a primary time keeper function, distinct from the brain systems involved either in conscious strategies to monitor time or attentional resource and other cognitive processes to accomplish the task. In the TIP task participants were given a time interval and asked to indicate when it elapsed. Two control tasks (counting forwards, backwards) were administered, in addition to a dual task format of the TIP task. Whole brain images were collected at 1.5 Tesla. Analyses (n = 6) yielded a statistical parametric map (SPM ¿z¿) reflecting time keeping and not strategy (counting, number manipulation) or attention resource utilization. Additional SPM ¿z¿s involving activation associated with the accuracy and magnitude the of time estimation response are presented. Results revealed lateral cerebellar and inferior temporal lobe activation were associated with primary time keeping. Behavioral data provided evidence that the procedures for the explicit time judgements did not occur automatically and utilized controlled processes. Activation sites associated with accuracy, magnitude, and the dual task provided indications of the other structures involved in time estimation that implemented task components related to controlled processing. The data are consistent with prior proposals that the cerebellum is a repository of codes for time processing, but also implicate temporal lobe structures for this type of time estimation task. Copyright 2000 Academic Press.

Bayesian Nonparametric Mixture Estimation for Time-Indexed Functional Data in R

Directory of Open Access Journals (Sweden)

Terrance D. Savitsky

2016-08-01

Full Text Available We present growfunctions for R that offers Bayesian nonparametric estimation models for analysis of dependent, noisy time series data indexed by a collection of domains. This data structure arises from combining periodically published government survey statistics, such as are reported in the Current Population Study (CPS. The CPS publishes monthly, by-state estimates of employment levels, where each state expresses a noisy time series. Published state-level estimates from the CPS are composed from household survey responses in a model-free manner and express high levels of volatility due to insufficient sample sizes. Existing software solutions borrow information over a modeled time-based dependence to extract a de-noised time series for each domain. These solutions, however, ignore the dependence among the domains that may be additionally leveraged to improve estimation efficiency. The growfunctions package offers two fully nonparametric mixture models that simultaneously estimate both a time and domain-indexed dependence structure for a collection of time series: (1 A Gaussian process (GP construction, which is parameterized through the covariance matrix, estimates a latent function for each domain. The covariance parameters of the latent functions are indexed by domain under a Dirichlet process prior that permits estimation of the dependence among functions across the domains: (2 An intrinsic Gaussian Markov random field prior construction provides an alternative to the GP that expresses different computation and estimation properties. In addition to performing denoised estimation of latent functions from published domain estimates, growfunctions allows estimation of collections of functions for observation units (e.g., households, rather than aggregated domains, by accounting for an informative sampling design under which the probabilities for inclusion of observation units are related to the response variable. growfunctions includes plot

Time-of-flight small-angle scattering spectrometers on pulsed neutron sources

International Nuclear Information System (INIS)

Ostanevich, Yu.M.

1987-01-01

The operation principles, constructions, advantages and shortcomings of known time-of-flight small angle neutron scattering (TOF SANS) spectrometers built up with pulsed neutron sources are reviewed. The most important characteristics of TOF SANS apparatuses are rather a high luminosity and the possibility for the measurement in an extremely wide range of scattering vector at a single exposure. This is achieved by simultaneous employment of white beam, TOF technique for wave length-scan and the commonly known angle-scan. However, the electronic equipment, data-matching programs, and the measurement procedure, necessary for accurate normalization of experimental data and their transformation into absolute cross-section scale, they all become more complex, as compared with those for SANS apparatuses operating on steady-state neutron sources, where only angle-scan is used

Technical Note: A novel approach to estimation of time-variable surface sources and sinks of carbon dioxide using empirical orthogonal functions and the Kalman filter

Directory of Open Access Journals (Sweden)

R. Zhuravlev

2011-10-01

Full Text Available In this work we propose an approach to solving a source estimation problem based on representation of carbon dioxide surface emissions as a linear combination of a finite number of pre-computed empirical orthogonal functions (EOFs. We used National Institute for Environmental Studies (NIES transport model for computing response functions and Kalman filter for estimating carbon dioxide emissions. Our approach produces results similar to these of other models participating in the TransCom3 experiment.

Using the EOFs we can estimate surface fluxes at higher spatial resolution, while keeping the dimensionality of the problem comparable with that in the regions approach. This also allows us to avoid potentially artificial sharp gradients in the fluxes in between pre-defined regions. EOF results generally match observations more closely given the same error structure as the traditional method.

Additionally, the proposed approach does not require additional effort of defining independent self-contained emission regions.

Real-time source deformation modeling through GNSS permanent stations at Merapi volcano (Indonesia

Science.gov (United States)

Beauducel, F.; Nurnaning, A.; Iguchi, M.; Fahmi, A. A.; Nandaka, M. A.; Sumarti, S.; Subandriyo, S.; Metaxian, J. P.

2014-12-01

Mt. Merapi (Java, Indonesia) is one of the most active and dangerous volcano in the world. A first GPS repetition network was setup and periodically measured since 1993, allowing detecting a deep magma reservoir, quantifying magma flux in conduit and identifying shallow discontinuities around the former crater (Beauducel and Cornet, 1999;Beauducel et al., 2000, 2006). After the 2010 centennial eruption, when this network was almost completely destroyed, Indonesian and Japanese teams installed a new continuous GPS network for monitoring purpose (Iguchi et al., 2011), consisting of 3 stations located at the volcano flanks, plus a reference station at the Yogyakarta Observatory (BPPTKG).In the framework of DOMERAPI project (2013-2016) we have completed this network with 5 additional stations, which are located on the summit area and volcano surrounding. The new stations are 1-Hz sampling, GNSS (GPS + GLONASS) receivers, and near real-time data streaming to the Observatory. An automatic processing has been developed and included in the WEBOBS system (Beauducel et al., 2010) based on GIPSY software computing precise daily moving solutions every hour, and for different time scales (2 months, 1 and 5 years), time series and velocity vectors. A real-time source modeling estimation has also been implemented. It uses the depth-varying point source solution (Mogi, 1958; Williams and Wadge, 1998) in a systematic inverse problem model exploration that displays location, volume variation and 3-D probability map.The operational system should be able to better detect and estimate the location and volume variations of possible magma sources, and to follow magma transfer towards the surface. This should help monitoring and contribute to decision making during future unrest or eruption.

Decreasing Computational Time for VBBinaryLensing by Point Source Approximation

Science.gov (United States)

Tirrell, Bethany M.; Visgaitis, Tiffany A.; Bozza, Valerio

2018-01-01

The gravitational lens of a binary system produces a magnification map that is more intricate than a single object lens. This map cannot be calculated analytically and one must rely on computational methods to resolve. There are generally two methods of computing the microlensed flux of a source. One is based on ray-shooting maps (Kayser, Refsdal, & Stabell 1986), while the other method is based on an application of Green’s theorem. This second method finds the area of an image by calculating a Riemann integral along the image contour. VBBinaryLensing is a C++ contour integration code developed by Valerio Bozza, which utilizes this method. The parameters at which the source object could be treated as a point source, or in other words, when the source is far enough from the caustic, was of interest to substantially decrease the computational time. The maximum and minimum values of the caustic curves produced, were examined to determine the boundaries for which this simplification could be made. The code was then run for a number of different maps, with separation values and accuracies ranging from 10-1 to 10-3, to test the theoretical model and determine a safe buffer for which minimal error could be made for the approximation. The determined buffer was 1.5+5q, with q being the mass ratio. The theoretical model and the calculated points worked for all combinations of the separation values and different accuracies except the map with accuracy and separation equal to 10-3 for y1 max. An alternative approach has to be found in order to accommodate a wider range of parameters.

Separation of source and propagation effects at regional distances

Energy Technology Data Exchange (ETDEWEB)

Goldstein, P.; Jarpe, S.; Mayeda, K. [Lawrence Livermore National Lab., CA (United States)] [and others

1994-12-31

Improved estimates of the contributions of source and propagation effects to regional seismic signals are needed to explain the performance of existing discriminants and to help develop more robust methods for identifying underground explosions. In this paper, we use close-in, local, and regional estimates of explosion source time functions to remove source effects from regional recordings of the Non-Proliferation Experiment (NPE), a one kiloton chemical explosion in N-tunnel at Rainier Mesa on the Nevada Test Site, and nearby nuclear explosions and earthquakes. Using source corrected regional waveforms, we find that regional Pg and Lg spectra of shallow explosions have significant low frequency ({approximately}1Hz) enhancements when compared to normal depth earthquakes. Data and simulations suggest that such enhancements are most sensitive to source depth, but may also be a function of mechanism, source receiver distance, and regional structure.

Locating the source of diffusion in complex networks by time-reversal backward spreading

Science.gov (United States)

Shen, Zhesi; Cao, Shinan; Wang, Wen-Xu; Di, Zengru; Stanley, H. Eugene

2016-03-01

Locating the source that triggers a dynamical process is a fundamental but challenging problem in complex networks, ranging from epidemic spreading in society and on the Internet to cancer metastasis in the human body. An accurate localization of the source is inherently limited by our ability to simultaneously access the information of all nodes in a large-scale complex network. This thus raises two critical questions: how do we locate the source from incomplete information and can we achieve full localization of sources at any possible location from a given set of observable nodes. Here we develop a time-reversal backward spreading algorithm to locate the source of a diffusion-like process efficiently and propose a general locatability condition. We test the algorithm by employing epidemic spreading and consensus dynamics as typical dynamical processes and apply it to the H1N1 pandemic in China. We find that the sources can be precisely located in arbitrary networks insofar as the locatability condition is assured. Our tools greatly improve our ability to locate the source of diffusion in complex networks based on limited accessibility of nodal information. Moreover, they have implications for controlling a variety of dynamical processes taking place on complex networks, such as inhibiting epidemics, slowing the spread of rumors, pollution control, and environmental protection.

Computing the real-time Green's Functions of large Hamiltonian matrices

OpenAIRE

Iitaka, Toshiaki

1998-01-01

A numerical method is developed for calculating the real time Green's functions of very large sparse Hamiltonian matrices, which exploits the numerical solution of the inhomogeneous time-dependent Schroedinger equation. The method has a clear-cut structure reflecting the most naive definition of the Green's functions, and is very suitable to parallel and vector supercomputers. The effectiveness of the method is illustrated by applying it to simple lattice models. An application of this method...

Fundamentals of time-dependent density functional theory

International Nuclear Information System (INIS)

Marques, Miguel A.L.; Rubio, Angel

2012-01-01

There have been many significant advances in time-dependent density functional theory over recent years, both in enlightening the fundamental theoretical basis of the theory, as well as in computational algorithms and applications. This book, as successor to the highly successful volume Time-Dependent Density Functional Theory (Lect. Notes Phys. 706, 2006) brings together for the first time all recent developments in a systematic and coherent way. First, a thorough pedagogical presentation of the fundamental theory is given, clarifying aspects of the original proofs and theorems, as well as presenting fresh developments that extend the theory into new realms such as alternative proofs of the original Runge-Gross theorem, open quantum systems, and dispersion forces to name but a few. Next, all of the basic concepts are introduced sequentially and building in complexity, eventually reaching the level of open problems of interest. Contemporary applications of the theory are discussed, from real-time coupled-electron-ion dynamics, to excited-state dynamics and molecular transport. Last but not least, the authors introduce and review recent advances in computational implementation, including massively parallel architectures and graphical processing units. Special care has been taken in editing this volume as a multi-author textbook, following a coherent line of thought, and making all the relevant connections between chapters and concepts consistent throughout. As such it will prove to be the text of reference in this field, both for beginners as well as expert researchers and lecturers teaching advanced quantum mechanical methods to model complex physical systems, from molecules to nanostructures, from biocomplexes to surfaces, solids and liquids. (orig.)

Normalization methods in time series of platelet function assays

Science.gov (United States)

Van Poucke, Sven; Zhang, Zhongheng; Roest, Mark; Vukicevic, Milan; Beran, Maud; Lauwereins, Bart; Zheng, Ming-Hua; Henskens, Yvonne; Lancé, Marcus; Marcus, Abraham

2016-01-01

Abstract Platelet function can be quantitatively assessed by specific assays such as light-transmission aggregometry, multiple-electrode aggregometry measuring the response to adenosine diphosphate (ADP), arachidonic acid, collagen, and thrombin-receptor activating peptide and viscoelastic tests such as rotational thromboelastometry (ROTEM). The task of extracting meaningful statistical and clinical information from high-dimensional data spaces in temporal multivariate clinical data represented in multivariate time series is complex. Building insightful visualizations for multivariate time series demands adequate usage of normalization techniques. In this article, various methods for data normalization (z-transformation, range transformation, proportion transformation, and interquartile range) are presented and visualized discussing the most suited approach for platelet function data series. Normalization was calculated per assay (test) for all time points and per time point for all tests. Interquartile range, range transformation, and z-transformation demonstrated the correlation as calculated by the Spearman correlation test, when normalized per assay (test) for all time points. When normalizing per time point for all tests, no correlation could be abstracted from the charts as was the case when using all data as 1 dataset for normalization. PMID:27428217

Long-time tails of the heat-conductivity time correlation functions for a magnetized plasma - a kinetic theory approach

NARCIS (Netherlands)

Schoolderman, A.J.; Suttorp, L.G.

1989-01-01

The long-time behaviour of the longitudinal and the transverse heat conductivity time correlation functions for a magnetized one-component plasma is studied by means of kinetic theory. To that end these correlation functions, which are defined as the inverse Laplace transforms of the dynamic heat

Identification of fractional-order systems with time delays using block pulse functions

Science.gov (United States)

Tang, Yinggan; Li, Ning; Liu, Minmin; Lu, Yao; Wang, Weiwei

2017-07-01

In this paper, a novel method based on block pulse functions is proposed to identify continuous-time fractional-order systems with time delays. First, the operational matrices of block pulse functions for fractional integral operator and time delay operator are derived. Then, these operational matrices are applied to convert the continuous-time fractional-order systems with time delays to an algebraic equation. Finally, the system's parameters along with the differentiation orders and the time delays are all simultaneously estimated through minimizing a quadric error function. The proposed method reduces the computation complexity of the identification process, and also it does not require the system's differentiation orders to be commensurate. The effectiveness of the proposed method are demonstrated by several numerical examples.

Time-limited effects of emotional arousal on item and source memory.

Science.gov (United States)

Wang, Bo; Sun, Bukuan

2015-01-01

Two experiments investigated the time-limited effects of emotional arousal on consolidation of item and source memory. In Experiment 1, participants memorized words (items) and the corresponding speakers (sources) and then took an immediate free recall test. Then they watched a neutral, positive, or negative video 5, 35, or 50 min after learning, and 24 hours later they took surprise memory tests. Experiment 2 was similar to Experiment 1 except that (a) a reality monitoring task was used; (b) elicitation delays of 5, 30, and 45 min were used; and (c) delayed memory tests were given 60 min after learning. Both experiments showed that, regardless of elicitation delay, emotional arousal did not enhance item recall memory. Second, both experiments showed that negative arousal enhanced delayed item recognition memory only at the medium elicitation delay, but not in the shorter or longer delays. Positive arousal enhanced performance only in Experiment 1. Third, regardless of elicitation delay, emotional arousal had little effect on source memory. These findings have implications for theories of emotion and memory, suggesting that emotion effects are contingent upon the nature of the memory task and elicitation delay.

Short time propagation of a singular wave function: Some surprising results

Science.gov (United States)

Marchewka, A.; Granot, E.; Schuss, Z.

2007-08-01

The Schrödinger evolution of an initially singular wave function was investigated. First it was shown that a wide range of physical problems can be described by initially singular wave function. Then it was demonstrated that outside the support of the initial wave function the time evolution is governed to leading order by the values of the wave function and its derivatives at the singular points. Short-time universality appears where it depends only on a single parameter—the value at the singular point (not even on its derivatives). It was also demonstrated that the short-time evolution in the presence of an absorptive potential is different than in the presence of a nonabsorptive one. Therefore, this dynamics can be harnessed to the determination whether a potential is absorptive or not simply by measuring only the transmitted particles density.

An open source/real-time atomic force microscope architecture to perform customizable force spectroscopy experiments.

Science.gov (United States)

Materassi, Donatello; Baschieri, Paolo; Tiribilli, Bruno; Zuccheri, Giampaolo; Samorì, Bruno

2009-08-01

We describe the realization of an atomic force microscope architecture designed to perform customizable experiments in a flexible and automatic way. Novel technological contributions are given by the software implementation platform (RTAI-LINUX), which is free and open source, and from a functional point of view, by the implementation of hard real-time control algorithms. Some other technical solutions such as a new way to estimate the optical lever constant are described as well. The adoption of this architecture provides many degrees of freedom in the device behavior and, furthermore, allows one to obtain a flexible experimental instrument at a relatively low cost. In particular, we show how such a system has been employed to obtain measures in sophisticated single-molecule force spectroscopy experiments [Fernandez and Li, Science 303, 1674 (2004)]. Experimental results on proteins already studied using the same methodologies are provided in order to show the reliability of the measure system.

Modal parameter identification based on combining transmissibility functions and blind source separation techniques

Science.gov (United States)

Araújo, Iván Gómez; Sánchez, Jesús Antonio García; Andersen, Palle

2018-05-01

Transmissibility-based operational modal analysis is a recent and alternative approach used to identify the modal parameters of structures under operational conditions. This approach is advantageous compared with traditional operational modal analysis because it does not make any assumptions about the excitation spectrum (i.e., white noise with a flat spectrum). However, common methodologies do not include a procedure to extract closely spaced modes with low signal-to-noise ratios. This issue is relevant when considering that engineering structures generally have closely spaced modes and that their measured responses present high levels of noise. Therefore, to overcome these problems, a new combined method for modal parameter identification is proposed in this work. The proposed method combines blind source separation (BSS) techniques and transmissibility-based methods. Here, BSS techniques were used to recover source signals, and transmissibility-based methods were applied to estimate modal information from the recovered source signals. To achieve this combination, a new method to define a transmissibility function was proposed. The suggested transmissibility function is based on the relationship between the power spectral density (PSD) of mixed signals and the PSD of signals from a single source. The numerical responses of a truss structure with high levels of added noise and very closely spaced modes were processed using the proposed combined method to evaluate its ability to identify modal parameters in these conditions. Colored and white noise excitations were used for the numerical example. The proposed combined method was also used to evaluate the modal parameters of an experimental test on a structure containing closely spaced modes. The results showed that the proposed combined method is capable of identifying very closely spaced modes in the presence of noise and, thus, may be potentially applied to improve the identification of damping ratios.

Electrophysiological Source Imaging: A Noninvasive Window to Brain Dynamics.

Science.gov (United States)

He, Bin; Sohrabpour, Abbas; Brown, Emery; Liu, Zhongming

2018-06-04

Brain activity and connectivity are distributed in the three-dimensional space and evolve in time. It is important to image brain dynamics with high spatial and temporal resolution. Electroencephalography (EEG) and magnetoencephalography (MEG) are noninvasive measurements associated with complex neural activations and interactions that encode brain functions. Electrophysiological source imaging estimates the underlying brain electrical sources from EEG and MEG measurements. It offers increasingly improved spatial resolution and intrinsically high temporal resolution for imaging large-scale brain activity and connectivity on a wide range of timescales. Integration of electrophysiological source imaging and functional magnetic resonance imaging could further enhance spatiotemporal resolution and specificity to an extent that is not attainable with either technique alone. We review methodological developments in electrophysiological source imaging over the past three decades and envision its future advancement into a powerful functional neuroimaging technology for basic and clinical neuroscience applications.

Oxygenated organic functional groups and their sources in single and submicron organic particles in MILAGRO 2006 campaign

Directory of Open Access Journals (Sweden)

S. Liu

2009-09-01

Full Text Available Fourier Transform Infrared (FTIR and X-ray Fluorescence (XRF were used to measure organic functional groups and elements of submicron particles collected during MILAGRO in March 2006 on three platforms: the Mexico City urban area (SIMAT, the high altitude site at 4010 m (Altzomoni, and the NCAR C130 aircraft. Scanning Transmission X-ray Microscopy (STXM and Near-Edge X-ray Absorption Fine Structure (NEXAFS were applied to single particle organic functional group abundance analysis of particles simultaneously collected at SIMAT and C130. Correlations of elemental concentrations showed different groups of source-related elements at SIMAT, Altzomoni, and C130, suggesting different processes affecting the air masses sampled at the three platforms. Cluster analysis resulted in seven distinct clusters of FTIR spectra, with the last three clusters consisting of spectra collected almost exclusively on the C130 platform, reflecting the variety of sources contributing to C130 samples. Positive Matrix Factorization (PMF of STXM-NEXAFS spectra identified three main factors representing soot, secondary, and biomass burning type spectra. PMF of FTIR spectra resulted in two fossil fuel combustion factors and one biomass burning factor, the former representative of source regions to the northeast and southwest of SIMAT. Alkane, carboxylic acid, amine, and alcohol functional groups were mainly associated with combustion related sources, while non-acid carbonyl groups were likely from biomass burning events. The majority of OM and O/C was attributed to combustion sources, although no distinction between direct emissions and atmospherically processed OM could be identified.

Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources.

Science.gov (United States)

Rutherford, Michael E; Chapman, David J; White, Thomas G; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E

2016-05-01

The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).

Acoustic emission source location in plates using wavelet analysis and cross time frequency spectrum.

Science.gov (United States)

Mostafapour, A; Davoodi, S; Ghareaghaji, M

2014-12-01

In this study, the theories of wavelet transform and cross-time frequency spectrum (CTFS) are used to locate AE source with frequency-varying wave velocity in plate-type structures. A rectangular array of four sensors is installed on the plate. When an impact is generated by an artificial AE source such as Hsu-Nielsen method of pencil lead breaking (PLB) at any position of the plate, the AE signals will be detected by four sensors at different times. By wavelet packet decomposition, a packet of signals with frequency range of 0.125-0.25MHz is selected. The CTFS is calculated by the short-time Fourier transform of the cross-correlation between considered packets captured by AE sensors. The time delay is calculated when the CTFS reaches the maximum value and the corresponding frequency is extracted per this maximum value. The resulting frequency is used to calculate the group velocity of wave velocity in combination with dispersive curve. The resulted locating error shows the high precision of proposed algorithm. Copyright © 2014 Elsevier B.V. All rights reserved.

Global sourcing - performance and integration : reflections on performance, implications from cross-functional and external integration

NARCIS (Netherlands)

Horn, Philipp

2013-01-01

Despite the fact that firms and individuals have been sourcing on a global basis since ancient times, global sourcing as a topic has received considerable attention from managers and scholars in recent years. Global business has been reported to be growing considerably during the last decades and

Existence of time-dependent density-functional theory for open electronic systems: time-dependent holographic electron density theorem.

Science.gov (United States)

Zheng, Xiao; Yam, ChiYung; Wang, Fan; Chen, GuanHua

2011-08-28

We present the time-dependent holographic electron density theorem (TD-HEDT), which lays the foundation of time-dependent density-functional theory (TDDFT) for open electronic systems. For any finite electronic system, the TD-HEDT formally establishes a one-to-one correspondence between the electron density inside any finite subsystem and the time-dependent external potential. As a result, any electronic property of an open system in principle can be determined uniquely by the electron density function inside the open region. Implications of the TD-HEDT on the practicality of TDDFT are also discussed.

Assessing the Financial Benefits of Faster Development Times: The Case of Single-source Versus Multi-vendor Outsourced Biopharmaceutical Manufacturing.

Science.gov (United States)

DiMasi, Joseph A; Smith, Zachary; Getz, Kenneth A

2018-05-10

The extent to which new drug developers can benefit financially from shorter development times has implications for development efficiency and innovation incentives. We provided a real-world example of such gains by using recent estimates of drug development costs and returns. Time and fee data were obtained on 5 single-source manufacturing projects. Time and fees were modeled for these projects as if the drug substance and drug product processes had been contracted separately from 2 vendors. The multi-vendor model was taken as the base case, and financial impacts from single-source contracting were determined relative to the base case. The mean and median after-tax financial benefits of shorter development times from single-source contracting were $44.7 million and $34.9 million, respectively (2016 dollars). The after-tax increases in sponsor fees from single-source contracting were small in comparison (mean and median of $0.65 million and $0.25 million). For the data we examined, single-source contracting yielded substantial financial benefits over multi-source contracting, even after accounting for somewhat higher sponsor fees. Copyright © 2018 Elsevier HS Journals, Inc. All rights reserved.

Micro-seismic Imaging Using a Source Independent Waveform Inversion Method

KAUST Repository

Wang, Hanchen

2016-04-18

Micro-seismology is attracting more and more attention in the exploration seismology community. The main goal in micro-seismic imaging is to find the source location and the ignition time in order to track the fracture expansion, which will help engineers monitor the reservoirs. Conventional imaging methods work fine in this field but there are many limitations such as manual picking, incorrect migration velocity and low signal to noise ratio (S/N). In traditional surface survey imaging, full waveform inversion (FWI) is widely used. The FWI method updates the velocity model by minimizing the misfit between the observed data and the predicted data. Using FWI to locate and image microseismic events allows for an automatic process (free of picking) that utilizes the full wavefield. Use the FWI technique, and overcomes the difficulties of manual pickings and incorrect velocity model for migration. However, the technique of waveform inversion of micro-seismic events faces its own problems. There is significant nonlinearity due to the unknown source location (space) and function (time). We have developed a source independent FWI of micro-seismic events to simultaneously invert for the source image, source function and velocity model. It is based on convolving reference traces with the observed and modeled data to mitigate the effect of an unknown source ignition time. The adjoint-state method is used to derive the gradient for the source image, source function and velocity updates. To examine the accuracy of the inverted source image and velocity model the extended image for source wavelet in z-axis is extracted. Also the angle gather is calculated to check the applicability of the migration velocity. By inverting for the source image, source wavelet and the velocity model simultaneously, the proposed method produces good estimates of the source location, ignition time and the background velocity in the synthetic experiments with both parts of the Marmousi and the SEG

An Open-Source Sandbox for Increasing the Accessibility of Functional Programming to the Bioinformatics and Scientific Communities.

Science.gov (United States)

Fenwick, Matthew; Sesanker, Colbert; Schiller, Martin R; Ellis, Heidi Jc; Hinman, M Lee; Vyas, Jay; Gryk, Michael R

2012-01-01

Scientists are continually faced with the need to express complex mathematical notions in code. The renaissance of functional languages such as LISP and Haskell is often credited to their ability to implement complex data operations and mathematical constructs in an expressive and natural idiom. The slow adoption of functional computing in the scientific community does not, however, reflect the congeniality of these fields. Unfortunately, the learning curve for adoption of functional programming techniques is steeper than that for more traditional languages in the scientific community, such as Python and Java, and this is partially due to the relative sparseness of available learning resources. To fill this gap, we demonstrate and provide applied, scientifically substantial examples of functional programming, We present a multi-language source-code repository for software integration and algorithm development, which generally focuses on the fields of machine learning, data processing, bioinformatics. We encourage scientists who are interested in learning the basics of functional programming to adopt, reuse, and learn from these examples. The source code is available at: https://github.com/CONNJUR/CONNJUR-Sandbox (see also http://www.connjur.org).

Source size and time dependence of multifragmentation induced by GeV 3He beams

International Nuclear Information System (INIS)

Wang, G.; Kwiatkowski, K.; Bracken, D.S.; Renshaw Foxford, E.; Hsi, W.; Morley, K.B.; Viola, V.E.; Yoder, N.R.; Volant, C.; Legrain, R.; Pollacco, E.C.; Korteling, R.G.; Botvina, A.; Brzychczyk, J.; Breuer, H.

1999-01-01

To investigate the source size and time dependence of multifragmentation reactions, small- and large-angle relative velocity correlations between coincident complex fragments have been measured for the 1.8 - 4.8 GeV 3 He+ nat Ag, 197 Au systems. The results support an evolutionary scenario for the fragment emission process in which lighter IMFs (Z approx-lt 6) are emitted from a hot, more dense source prior to breakup of an expanded residue. For the most highly excited residues, for which there is a significant yield of fragments with very soft energy spectra (E/A≤3 MeV), comparisons with an N-body simulation suggest a breakup time of τ∼50 fm/c for the expanded residue. Comparison of these data with both the evolutionary expanding emitting source model and the Copenhagen statistical multifragmentation model shows good agreement for heavier IMF close-quote s formed in the final breakup stage, but only the evolutionary model is successful in accounting for the lighter IMFs. copyright 1999 The American Physical Society

NNLO splitting and coefficient functions with time-like kinematics

International Nuclear Information System (INIS)

Mitov, A.; Moch, S.; Vogt, A.; Liverpool Univ.

2006-09-01

We discuss recent results on the three-loop (next-to-next-to-leading order, NNLO) time-like splitting functions of QCD and the two-loop (NNLO) coefficient functions in one-particle inclusive e + e - -annihilation. These results form the basis for extracting fragmentation functions for light and heavy flavors with NNLO accuracy that will be needed at the LHC and ILC. The two-loop calculations have been performed in Mellin space bases on a new method, the main features of which we also describe briefly. (orig.)

astroplan: An Open Source Observation Planning Package in Python

Science.gov (United States)

Morris, Brett M.; Tollerud, Erik; Sipőcz, Brigitta; Deil, Christoph; Douglas, Stephanie T.; Berlanga Medina, Jazmin; Vyhmeister, Karl; Smith, Toby R.; Littlefair, Stuart; Price-Whelan, Adrian M.; Gee, Wilfred T.; Jeschke, Eric

2018-03-01

We present astroplan—an open source, open development, Astropy affiliated package for ground-based observation planning and scheduling in Python. astroplan is designed to provide efficient access to common observational quantities such as celestial rise, set, and meridian transit times and simple transformations from sky coordinates to altitude-azimuth coordinates without requiring a detailed understanding of astropy’s implementation of coordinate systems. astroplan provides convenience functions to generate common observational plots such as airmass and parallactic angle as a function of time, along with basic sky (finder) charts. Users can determine whether or not a target is observable given a variety of observing constraints, such as airmass limits, time ranges, Moon illumination/separation ranges, and more. A selection of observation schedulers are included that divide observing time among a list of targets, given observing constraints on those targets. Contributions to the source code from the community are welcome.

Nucleon structure functions in noncommutative space-time

Energy Technology Data Exchange (ETDEWEB)

Rafiei, A.; Rezaei, Z.; Mirjalili, A. [Yazd University, Physics Department, Yazd (Iran, Islamic Republic of)

2017-05-15

In the context of noncommutative space-time we investigate the nucleon structure functions which play an important role in identifying the internal structure of nucleons. We use the corrected vertices and employ new vertices that appear in two approaches of noncommutativity and calculate the proton structure functions in terms of the noncommutative tensor θ{sub μν}. To check our results we plot the nucleon structure function (NSF), F{sub 2}(x), and compare it with experimental data and the results from the GRV, GJR and CT10 parametrization models. We show that with the new vertex that arises the noncommutativity correction will lead to a better consistency between theoretical results and experimental data for the NSF. This consistency will be better for small values of the Bjorken variable x. To indicate and confirm the validity of our calculations we also act conversely. We obtain a lower bound for the numerical values of Λ{sub NC} scale which correspond to recent reports. (orig.)

Dynamical equations for time-ordered Green’s functions: from the Keldysh time-loop contour to equilibrium at finite and zero temperature

International Nuclear Information System (INIS)

Ness, H; Dash, L K

2012-01-01

We study the dynamical equation of the time-ordered Green’s function at finite temperature. We show that the time-ordered Green’s function obeys a conventional Dyson equation only at equilibrium and in the limit of zero temperature. In all other cases, i.e. finite temperature at equilibrium or non-equilibrium, the time-ordered Green’s function obeys instead a modified Dyson equation. The derivation of this result is obtained from the general formalism of the non-equilibrium Green’s functions on the Keldysh time-loop contour. At equilibrium, our result is fully consistent with the Matsubara temperature Green’s function formalism and also justifies rigorously the correction terms introduced in an ad hoc way with Hedin and Lundqvist. Our results show that one should use the appropriate dynamical equation for the time-ordered Green’s function when working beyond the equilibrium zero-temperature limit.

Generalised time functions and finiteness of the Lorentzian distance

OpenAIRE

Rennie, Adam; Whale, Ben E.

2014-01-01

We show that finiteness of the Lorentzian distance is equivalent to the existence of generalised time functions with gradient uniformly bounded away from light cones. To derive this result we introduce new techniques to construct and manipulate achronal sets. As a consequence of these techniques we obtain a functional description of the Lorentzian distance extending the work of Franco and Moretti.

Effects of electron scattering on the oscillations of an X-ray source

International Nuclear Information System (INIS)

Kylafis, N.D.; Klimis, G.S.

1987-01-01

The time variability observed at infinity due to a variable point source at the center of a spherical cloud of radius R and optical depth to electron scattering tau is analytically determined. The emissin pattern of the source and its time variability are assumed to be of the following three forms: (1) isotropic emission with intensity varying sinusoidally in time with angular frequency Omega(L), (2) emission in the form of a delta-function beam rotating with angular frequency Omega(R) about a fixed axis and with intensity constant in time, and (3) emission in the form of a delta-function beam rotating with angular frequency Omega(R) about a fixed axis and with intensity varying sinusoidally in time with angular frequency Omega(L). More complicated source emissions and variabilities are studied by superposing the above forms. The results of our calculations reveal the conditions under which quasi-periodic oscillations can be observed from X-ray sources, while periodic oscillations are completely smeared out. Furthermore, these results can be used to study the X-ray oscillations of such sources as Her X-1, Cyg X-3, and the Vela pulsar, which are believed to be embedded in scattering clouds. 35 references

Bird functional diversity decreases with time since disturbance: Does patchy prescribed fire enhance ecosystem function?.

Science.gov (United States)

Sitters, Holly; Di Stefano, Julian; Christie, Fiona; Swan, Matthew; York, Alan

2016-01-01

Animal species diversity is often associated with time since disturbance, but the effects of disturbances such as fire on functional diversity are unknown. Functional diversity measures the range, abundance, and distribution of trait values in a community, and links changes in species composition with the consequences for ecosystem function. Improved understanding of the relationship between time since fire (TSF) and functional diversity is critical given that the frequency of both prescribed fire and wildfire is expected to increase. To address this knowledge gap, we examined responses of avian functional diversity to TSF and two direct measures of environmental heterogeneity, plant diversity, and structural heterogeneity. We surveyed birds across a 70-year chronosequence spanning four vegetation types in southeast Australia. Six bird functional traits were used to derive four functional diversity indices (richness, evenness, divergence, and dispersion) and the effects of TSF, plant diversity and structural heterogeneity on species richness and the functional diversity indices were examined using mixed models. We used a regression tree method to identify traits associated with species more common in young vegetation. Functional richness and dispersion were negatively associated with TSF in all vegetation types, suggesting that recent prescribed fire generates heterogeneous vegetation and provides greater opportunities for resource partitioning. Species richness was not significantly associated with TSF, and is probably an unreliable surrogate for functional diversity in fire-prone systems. A positive, relationship between functional evenness and structural heterogeneity was comnon to all vegetation types, suggesting that fine-scale (tens of meters) structural variation can enhance ecosystem function. Species more common in young vegetation were primarily linked by their specialist diets, indicating that ecosystem services such as seed dispersal and insect control

Modeling multivariate time series on manifolds with skew radial basis functions.

Science.gov (United States)

Jamshidi, Arta A; Kirby, Michael J

2011-01-01

We present an approach for constructing nonlinear empirical mappings from high-dimensional domains to multivariate ranges. We employ radial basis functions and skew radial basis functions for constructing a model using data that are potentially scattered or sparse. The algorithm progresses iteratively, adding a new function at each step to refine the model. The placement of the functions is driven by a statistical hypothesis test that accounts for correlation in the multivariate range variables. The test is applied on training and validation data and reveals nonstatistical or geometric structure when it fails. At each step, the added function is fit to data contained in a spatiotemporally defined local region to determine the parameters--in particular, the scale of the local model. The scale of the function is determined by the zero crossings of the autocorrelation function of the residuals. The model parameters and the number of basis functions are determined automatically from the given data, and there is no need to initialize any ad hoc parameters save for the selection of the skew radial basis functions. Compactly supported skew radial basis functions are employed to improve model accuracy, order, and convergence properties. The extension of the algorithm to higher-dimensional ranges produces reduced-order models by exploiting the existence of correlation in the range variable data. Structure is tested not just in a single time series but between all pairs of time series. We illustrate the new methodologies using several illustrative problems, including modeling data on manifolds and the prediction of chaotic time series.

HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE

International Nuclear Information System (INIS)

SHAPIRO, S.M.; ZALIZNYAK, I.A.

2002-01-01

This document lays out a proposal by the Instrument Development Team (IDT) composed of scientists from leading Universities and National Laboratories to design and build a conceptually new high-flux inelastic neutron spectrometer at the pulsed Spallation Neutron Source (SNS) at Oak Ridge. This instrument is intended to supply users of the SNS and scientific community, of which the IDT is an integral part, with a platform for ground-breaking investigations of the low-energy atomic-scale dynamical properties of crystalline solids. It is also planned that the proposed instrument will be equipped with a polarization analysis capability, therefore becoming the first polarized beam inelastic spectrometer in the SNS instrument suite, and the first successful polarized beam inelastic instrument at a pulsed spallation source worldwide. The proposed instrument is designed primarily for inelastic and elastic neutron spectroscopy of single crystals. In fact, the most informative neutron scattering studies of the dynamical properties of solids nearly always require single crystal samples, and they are almost invariably flux-limited. In addition, in measurements with polarization analysis the available flux is reduced through selection of the particular neutron polarization, which puts even more stringent limits on the feasibility of a particular experiment. To date, these investigations have mostly been carried out on crystal spectrometers at high-flux reactors, which usually employ focusing Bragg optics to concentrate the neutron beam on a typically small sample. Construction at Oak Ridge of the high-luminosity spallation neutron source, which will provide intense pulsed neutron beams with time-averaged fluxes equal to those at medium-flux reactors, opens entirely new opportunities for single crystal neutron spectroscopy. Drawing upon experience acquired during decades of studies with both crystal and time-of-flight (TOF) spectrometers, the IDT has developed a conceptual

HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE.

Energy Technology Data Exchange (ETDEWEB)

SHAPIRO,S.M.; ZALIZNYAK,I.A.

2002-12-30

This document lays out a proposal by the Instrument Development Team (IDT) composed of scientists from leading Universities and National Laboratories to design and build a conceptually new high-flux inelastic neutron spectrometer at the pulsed Spallation Neutron Source (SNS) at Oak Ridge. This instrument is intended to supply users of the SNS and scientific community, of which the IDT is an integral part, with a platform for ground-breaking investigations of the low-energy atomic-scale dynamical properties of crystalline solids. It is also planned that the proposed instrument will be equipped with a polarization analysis capability, therefore becoming the first polarized beam inelastic spectrometer in the SNS instrument suite, and the first successful polarized beam inelastic instrument at a pulsed spallation source worldwide. The proposed instrument is designed primarily for inelastic and elastic neutron spectroscopy of single crystals. In fact, the most informative neutron scattering studies of the dynamical properties of solids nearly always require single crystal samples, and they are almost invariably flux-limited. In addition, in measurements with polarization analysis the available flux is reduced through selection of the particular neutron polarization, which puts even more stringent limits on the feasibility of a particular experiment. To date, these investigations have mostly been carried out on crystal spectrometers at high-flux reactors, which usually employ focusing Bragg optics to concentrate the neutron beam on a typically small sample. Construction at Oak Ridge of the high-luminosity spallation neutron source, which will provide intense pulsed neutron beams with time-averaged fluxes equal to those at medium-flux reactors, opens entirely new opportunities for single crystal neutron spectroscopy. Drawing upon experience acquired during decades of studies with both crystal and time-of-flight (TOF) spectrometers, the IDT has developed a conceptual

Lifetime information from correlation functions selected by directional cuts

International Nuclear Information System (INIS)

Gelbke, C.K.

1995-01-01

Two-particle correlation functions provide information on the space-time characteristics of the emitting source. In many cases, ambiguities of the relative magnitudes of source radius and lifetime can be reduced by analysis of correlation functions evaluated for specific directional cuts on the relative velocity of the coincident particle pair. Information on non-spherical breakup geometries is more difficult to extract. Examples of two-proton correlation functions in which directional cuts are employed to reduce existing space-time ambiguities for the emitting system are presented. (author). 50 refs., 10 figs

Comparison of the hypothetical (57)Co brachytherapy source with the (192)Ir source.

Science.gov (United States)

Toossi, Mohammad Taghi Bahreyni; Ghorbani, Mahdi; Rostami, Atefeh; Khosroabadi, Mohsen; Khademi, Sara; Knaup, Courtney

2016-01-01

The (57)Co radioisotope has recently been proposed as a hypothetical brachytherapy source due to its high specific activity, appropriate half-life (272 days) and medium energy photons (114.17 keV on average). In this study, Task Group No. 43 dosimetric parameters were calculated and reported for a hypothetical (57)Co source. A hypothetical (57)Co source was simulated in MCNPX, consisting of an active cylinder with 3.5 mm length and 0.6 mm radius encapsulated in a stainless steel capsule. Three photon energies were utilized (136 keV [10.68%], 122 keV [85.60%], 14 keV [9.16%]) for the (57)Co source. Air kerma strength, dose rate constant, radial dose function, anisotropy function, and isodose curves for the source were calculated and compared to the corresponding data for a (192)Ir source. The results are presented as tables and figures. Air kerma strength per 1 mCi activity for the (57)Co source was 0.46 cGyh(-1) cm 2 mCi(-1). The dose rate constant for the (57)Co source was determined to be 1.215 cGyh(-1)U(-1). The radial dose function for the (57)Co source has an increasing trend due to multiple scattering of low energy photons. The anisotropy function for the (57)Co source at various distances from the source is more isotropic than the (192)Ir source. The (57)Co source has advantages over (192)Ir due to its lower energy photons, longer half-life, higher dose rate constant and more isotropic anisotropic function. However, the (192)Ir source has a higher initial air kerma strength and more uniform radial dose function. These properties make (57)Co a suitable source for use in brachytherapy applications.

Time-resolved X-ray scattering program at the Advanced Photon Source

International Nuclear Information System (INIS)

Rodricks, B.

1994-01-01

The Time-Resolved Scattering Program's goal is the development of instruments and techniques for time-resolved studies. This entails the development of wide bandpass and focusing optics, high-speed detectors, mechanical choppers, and components for the measurement and creation of changes in samples. Techniques being developed are pump-probe experiments, single-bunch scattering experiments, high-speed white and pink beam Laue scattering, and nanosecond to microsecond synchronization of instruments. This program will be carried out primarily from a white-beam, bend-magnet source, experimental station, 1-BM-B, that immediately follows the first optics enclosure (1-BM-A). This paper will describe the experimental station and instruments under development to carry out the program

Lambda-lifting in Quadratic Time

DEFF Research Database (Denmark)

Danvy, O.; Schultz, U.P.

2004-01-01

-lifting transforms a block-structured program into a set of recursive equations, one for each local function in the source program. Each equation carries extra parameters to account for the free variables of the corresponding local function and of all its callees. It is the search for these extra parameters......Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda...... that yields the cubic factor in the traditional formulation of lambda-lifting, which is due to Johnsson. This search is carried out by computing a transitive closure. To reduce the complexity of lambda-lifting, we partition the call graph of the source program into strongly connected components, based...

Adaptive Control and Function Projective Synchronization in 2D Discrete-Time Chaotic Systems

International Nuclear Information System (INIS)

Li Yin; Chen Yong; Li Biao

2009-01-01

This study addresses the adaptive control and function projective synchronization problems between 2D Rulkov discrete-time system and Network discrete-time system. Based on backstepping design with three controllers, a systematic, concrete and automatic scheme is developed to investigate the function projective synchronization of discrete-time chaotic systems. In addition, the adaptive control function is applied to achieve the state synchronization of two discrete-time systems. Numerical results demonstrate the effectiveness of the proposed control scheme.

Bifurcations in a discrete time model composed of Beverton-Holt function and Ricker function.

Science.gov (United States)

Shang, Jin; Li, Bingtuan; Barnard, Michael R

2015-05-01

We provide rigorous analysis for a discrete-time model composed of the Ricker function and Beverton-Holt function. This model was proposed by Lewis and Li [Bull. Math. Biol. 74 (2012) 2383-2402] in the study of a population in which reproduction occurs at a discrete instant of time whereas death and competition take place continuously during the season. We show analytically that there exists a period-doubling bifurcation curve in the model. The bifurcation curve divides the parameter space into the region of stability and the region of instability. We demonstrate through numerical bifurcation diagrams that the regions of periodic cycles are intermixed with the regions of chaos. We also study the global stability of the model. Copyright © 2015 Elsevier Inc. All rights reserved.

Probability density function modeling of scalar mixing from concentrated sources in turbulent channel flow

Science.gov (United States)

Bakosi, J.; Franzese, P.; Boybeyi, Z.

2007-11-01

Dispersion of a passive scalar from concentrated sources in fully developed turbulent channel flow is studied with the probability density function (PDF) method. The joint PDF of velocity, turbulent frequency and scalar concentration is represented by a large number of Lagrangian particles. A stochastic near-wall PDF model combines the generalized Langevin model of Haworth and Pope [Phys. Fluids 29, 387 (1986)] with Durbin's [J. Fluid Mech. 249, 465 (1993)] method of elliptic relaxation to provide a mathematically exact treatment of convective and viscous transport with a nonlocal representation of the near-wall Reynolds stress anisotropy. The presence of walls is incorporated through the imposition of no-slip and impermeability conditions on particles without the use of damping or wall-functions. Information on the turbulent time scale is supplied by the gamma-distribution model of van Slooten et al. [Phys. Fluids 10, 246 (1998)]. Two different micromixing models are compared that incorporate the effect of small scale mixing on the transported scalar: the widely used interaction by exchange with the mean and the interaction by exchange with the conditional mean model. Single-point velocity and concentration statistics are compared to direct numerical simulation and experimental data at Reτ=1080 based on the friction velocity and the channel half width. The joint model accurately reproduces a wide variety of conditional and unconditional statistics in both physical and composition space.

Perspective: Fundamental aspects of time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Maitra, Neepa T. [Department of Physics and Astronomy, Hunter College and the Physics Program at the Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States)

2016-06-14

In the thirty-two years since the birth of the foundational theorems, time-dependent density functional theory has had a tremendous impact on calculations of electronic spectra and dynamics in chemistry, biology, solid-state physics, and materials science. Alongside the wide-ranging applications, there has been much progress in understanding fundamental aspects of the functionals and the theory itself. This Perspective looks back to some of these developments, reports on some recent progress and current challenges for functionals, and speculates on future directions to improve the accuracy of approximations used in this relatively young theory.

Wave Functions for Time-Dependent Dirac Equation under GUP

Science.gov (United States)

Zhang, Meng-Yao; Long, Chao-Yun; Long, Zheng-Wen

2018-04-01

In this work, the time-dependent Dirac equation is investigated under generalized uncertainty principle (GUP) framework. It is possible to construct the exact solutions of Dirac equation when the time-dependent potentials satisfied the proper conditions. In (1+1) dimensions, the analytical wave functions of the Dirac equation under GUP have been obtained for the two kinds time-dependent potentials. Supported by the National Natural Science Foundation of China under Grant No. 11565009

Functional swept source optical coherence tomography

International Nuclear Information System (INIS)

Blatter, C.

2013-01-01

Optical coherence tomography (OCT) is a non-invasive imaging modality capable of providing information about a sample structure along the three spatial dimensions with micrometer scale resolution. A new chapter opened with the development of functional OCT that provides additional information to the standard structural imaging. Among those extensions is Doppler OCT (D-OCT) that yields knowledge about the motion of the sample and/or its substructure. Its main application in biomedical imaging is the assessment of blood flow. D-OCT is therefore often associated with blood velocity measurement and recently with the visualization of the vascular network. Blood flow and vasculature are important markers of tissue health. Their assessment provides crucial information for diagnostics, treatment planning and monitoring. OCT is in a good position, as a non-invasive technique, to become an alternative to current fluorescence based techniques, allowing thereby also more frequent examination and broader screenings and, as a high resolution modality, to give insight into potential changes at the capillary level. An important challenge of in vivo imaging is patient motion that decreases the quality of acquisitions. One solution to that issue is high-speed imaging. Recently swept source OCT (SSOCT) revealed to be an efficient technology to achieve high-speed. This thesis investigates the use of swept sources for qualitative and quantitative vasculature imaging. It is presented via five journal papers that form its backbone. Prior to that, main concepts of FDOCT, D-OCT and SS systems are presented. The first paper reports a SSOCT system for skin imaging. In standard OCT systems, improving the lateral resolution comes at a cost of reduced depth of focus. This should be avoided in order to be able to assess different vascular beds in depth while keeping the speed advantage of FDOCT. Employing a Bessel beam for illumination of the sample allows circumventing this issue. The image

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.

Space-time quantitative source apportionment of soil heavy metal concentration increments.

Science.gov (United States)

Yang, Yong; Christakos, George; Guo, Mingwu; Xiao, Lu; Huang, Wei

2017-04-01

Assessing the space-time trends and detecting the sources of heavy metal accumulation in soils have important consequences in the prevention and treatment of soil heavy metal pollution. In this study, we collected soil samples in the eastern part of the Qingshan district, Wuhan city, Hubei Province, China, during the period 2010-2014. The Cd, Cu, Pb and Zn concentrations in soils exhibited a significant accumulation during 2010-2014. The spatiotemporal Kriging technique, based on a quantitative characterization of soil heavy metal concentration variations in terms of non-separable variogram models, was employed to estimate the spatiotemporal soil heavy metal distribution in the study region. Our findings showed that the Cd, Cu, and Zn concentrations have an obvious incremental tendency from the southwestern to the central part of the study region. However, the Pb concentrations exhibited an obvious tendency from the northern part to the central part of the region. Then, spatial overlay analysis was used to obtain absolute and relative concentration increments of adjacent 1- or 5-year periods during 2010-2014. The spatial distribution of soil heavy metal concentration increments showed that the larger increments occurred in the center of the study region. Lastly, the principal component analysis combined with the multiple linear regression method were employed to quantify the source apportionment of the soil heavy metal concentration increments in the region. Our results led to the conclusion that the sources of soil heavy metal concentration increments should be ascribed to industry, agriculture and traffic. In particular, 82.5% of soil heavy metal concentration increment during 2010-2014 was ascribed to industrial/agricultural activities sources. Using STK and SOA to obtain the spatial distribution of heavy metal concentration increments in soils. Using PCA-MLR to quantify the source apportionment of soil heavy metal concentration increments. Copyright © 2017

Time-dependent density-functional theory concepts and applications

CERN Document Server

Ullrich, Carsten A

2011-01-01

Time-dependent density-functional theory (TDDFT) describes the quantum dynamics of interacting electronic many-body systems formally exactly and in a practical and efficient manner. TDDFT has become the leading method for calculating excitation energies and optical properties of large molecules, with accuracies that rival traditional wave-function based methods, but at a fraction of the computational cost.This book is the first graduate-level text on the concepts and applications of TDDFT, including many examples and exercises, and extensive coverage of the literature. The book begins with a s

Decay of Complex-Time Determinantal and Pfaffian Correlation Functionals in Lattices

Science.gov (United States)

Aza, N. J. B.; Bru, J.-B.; de Siqueira Pedra, W.

2018-06-01

We supplement the determinantal and Pfaffian bounds of Sims and Warzel (Commun Math Phys 347:903-931, 2016) for many-body localization of quasi-free fermions, by considering the high dimensional case and complex-time correlations. Our proof uses the analyticity of correlation functions via the Hadamard three-line theorem. We show that the dynamical localization for the one-particle system yields the dynamical localization for the many-point fermionic correlation functions, with respect to the Hausdorff distance in the determinantal case. In Sims and Warzel (2016), a stronger notion of decay for many-particle configurations was used but only at dimension one and for real times. Considering determinantal and Pfaffian correlation functionals for complex times is important in the study of weakly interacting fermions.

Decay of Complex-Time Determinantal and Pfaffian Correlation Functionals in Lattices

Science.gov (United States)

Aza, N. J. B.; Bru, J.-B.; de Siqueira Pedra, W.

2018-04-01

We supplement the determinantal and Pfaffian bounds of Sims and Warzel (Commun Math Phys 347:903-931, 2016) for many-body localization of quasi-free fermions, by considering the high dimensional case and complex-time correlations. Our proof uses the analyticity of correlation functions via the Hadamard three-line theorem. We show that the dynamical localization for the one-particle system yields the dynamical localization for the many-point fermionic correlation functions, with respect to the Hausdorff distance in the determinantal case. In Sims and Warzel (2016), a stronger notion of decay for many-particle configurations was used but only at dimension one and for real times. Considering determinantal and Pfaffian correlation functionals for complex times is important in the study of weakly interacting fermions.

Infrasound Predictions Using the Weather Research and Forecasting Model: Atmospheric Green's Functions for the Source Physics Experiments 1-6.

Energy Technology Data Exchange (ETDEWEB)

Poppeliers, Christian; Aur, Katherine Anderson; Preston, Leiph

2018-03-01

This report shows the results of constructing predictive atmospheric models for the Source Physics Experiments 1-6. Historic atmospheric data are combined with topography to construct an atmo- spheric model that corresponds to the predicted (or actual) time of a given SPE event. The models are ultimately used to construct atmospheric Green's functions to be used for subsequent analysis. We present three atmospheric models for each SPE event: an average model based on ten one- hour snap shots of the atmosphere and two extrema models corresponding to the warmest, coolest, windiest, etc. atmospheric snap shots. The atmospheric snap shots consist of wind, temperature, and pressure profiles of the atmosphere for a one-hour time window centered at the time of the predicted SPE event, as well as nine additional snap shots for each of the nine preceding years, centered at the time and day of the SPE event.

Social Functioning and Adjustment in Chinese Children: The Imprint of Historical Time

Science.gov (United States)

Chen, Xinyin; Cen, Guozhen; Li, Dan; He, Yunfeng

2005-01-01

This study examined, in 3 cohorts (1990, 1998, and 2002) of elementary school children (M age10 years), relations between social functioning and adjustment in different phases of the societal transition in China. Data were obtained from multiple sources. The results indicate that sociability-cooperation was associated with peer acceptance and…

Exactly solvable model for the time response function of RPCs

International Nuclear Information System (INIS)

Mangiarotti, A.; Fonte, P.; Gobbi, A.

2004-01-01

The fluctuation theory for the growth of several avalanches is briefly summarized and extended to include the case of electronegative gas mixtures. Based on such physical picture, the intrinsic time response function of an RPC can be calculated in a closed form and its average and rms extracted from series representations. The corresponding timing resolution, expressed in units of 1/((α-η)vd), is a universal function of the mean number of 'effective' clusters n0 reduced by electron attachment: n0(1-η/α). A comparison to a few selected good-quality experimental data is attempted for the timing resolution of both 1-gap and 4-gaps RPCs, finding a reasonable agreement

Groundwater Pollution Source Identification using Linked ANN-Optimization Model

Science.gov (United States)

Ayaz, Md; Srivastava, Rajesh; Jain, Ashu

2014-05-01

Groundwater is the principal source of drinking water in several parts of the world. Contamination of groundwater has become a serious health and environmental problem today. Human activities including industrial and agricultural activities are generally responsible for this contamination. Identification of groundwater pollution source is a major step in groundwater pollution remediation. Complete knowledge of pollution source in terms of its source characteristics is essential to adopt an effective remediation strategy. Groundwater pollution source is said to be identified completely when the source characteristics - location, strength and release period - are known. Identification of unknown groundwater pollution source is an ill-posed inverse problem. It becomes more difficult for real field conditions, when the lag time between the first reading at observation well and the time at which the source becomes active is not known. We developed a linked ANN-Optimization model for complete identification of an unknown groundwater pollution source. The model comprises two parts- an optimization model and an ANN model. Decision variables of linked ANN-Optimization model contain source location and release period of pollution source. An objective function is formulated using the spatial and temporal data of observed and simulated concentrations, and then minimized to identify the pollution source parameters. In the formulation of the objective function, we require the lag time which is not known. An ANN model with one hidden layer is trained using Levenberg-Marquardt algorithm to find the lag time. Different combinations of source locations and release periods are used as inputs and lag time is obtained as the output. Performance of the proposed model is evaluated for two and three dimensional case with error-free and erroneous data. Erroneous data was generated by adding uniformly distributed random error (error level 0-10%) to the analytically computed concentration

Winter Annual Weed Response to Nitrogen Sources and Application Timings prior to a Burndown Corn Herbicide

Directory of Open Access Journals (Sweden)

Kelly A. Nelson

2015-01-01

Full Text Available Autumn and early preplant N applications, sources, and placement may affect winter annual weed growth. Field research evaluated (1 the effect of different nitrogen sources in autumn and early preplant on total winter annual weed growth (2006–2010, and (2 strip-till and broadcast no-till N applied in autumn and early preplant on henbit (Lamium amplexicaule L. growth (2008–2010 prior to a burndown herbicide application. Total winter annual weed biomass was greater than the nontreated control when applying certain N sources in autumn or early preplant for no-till corn. Anhydrous ammonia had the lowest average weed density (95 weeds m−2, though results were inconsistent over the years. Winter annual weed biomass was lowest (43 g m−2 when applying 32% urea ammonium nitrate in autumn and was similar to applying anhydrous ammonia in autumn or early preplant and the nontreated control. Henbit biomass was 28% greater when applying N in the autumn compared to an early preplant application timing. Nitrogen placement along with associated tillage with strip-till placement was important in reducing henbit biomass. Nitrogen source selection, application timing, and placement affected the impact of N on winter annual weed growth and should be considered when recommending a burndown herbicide application timing.

Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows

Science.gov (United States)

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.

Moving-Horizon Modulating Functions-Based Algorithm for Online Source Estimation in a First Order Hyperbolic PDE

KAUST Repository

Asiri, Sharefa M.; Elmetennani, Shahrazed; Laleg-Kirati, Taous-Meriem

2017-01-01

In this paper, an on-line estimation algorithm of the source term in a first order hyperbolic PDE is proposed. This equation describes heat transport dynamics in concentrated solar collectors where the source term represents the received energy. This energy depends on the solar irradiance intensity and the collector characteristics affected by the environmental changes. Control strategies are usually used to enhance the efficiency of heat production; however, these strategies often depend on the source term which is highly affected by the external working conditions. Hence, efficient source estimation methods are required. The proposed algorithm is based on modulating functions method where a moving horizon strategy is introduced. Numerical results are provided to illustrate the performance of the proposed estimator in open and closed loops.

Moving-Horizon Modulating Functions-Based Algorithm for Online Source Estimation in a First Order Hyperbolic PDE

KAUST Repository

Asiri, Sharefa M.

2017-08-22

In this paper, an on-line estimation algorithm of the source term in a first order hyperbolic PDE is proposed. This equation describes heat transport dynamics in concentrated solar collectors where the source term represents the received energy. This energy depends on the solar irradiance intensity and the collector characteristics affected by the environmental changes. Control strategies are usually used to enhance the efficiency of heat production; however, these strategies often depend on the source term which is highly affected by the external working conditions. Hence, efficient source estimation methods are required. The proposed algorithm is based on modulating functions method where a moving horizon strategy is introduced. Numerical results are provided to illustrate the performance of the proposed estimator in open and closed loops.

Source detection at 100 meter standoff with a time-encoded imaging system

International Nuclear Information System (INIS)

Brennan, J.; Brubaker, E.; Gerling, M.; Marleau, P.; Monterial, M.

2017-01-01

Here, we present the design, characterization, and testing of a laboratory prototype radiological search and localization system. The system, based on time-encoded imaging, uses the attenuation signature of neutrons in time, induced by the geometrical layout and motion of the system. We have demonstrated the ability to detect a ~1 mCi 252 Cf radiological source at 100 m standoff with 90% detection efficiency and 10% false positives against background in 12 min. As a result, this same detection efficiency is met at 15 s for a 40 m standoff, and 1.2 s for a 20 m standoff.

Seasonal variations and source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons in a mixed multi-function area of Hangzhou, China.

Science.gov (United States)

Lu, Hao; Wang, Shengsheng; Li, Yun; Gong, Hui; Han, Jingyi; Wu, Zuliang; Yao, Shuiliang; Zhang, Xuming; Tang, Xiujuan; Jiang, Boqiong

2017-07-01

To reveal the seasonal variations and sources of PM 2.5 -bound polycyclic aromatic hydrocarbons (PAHs) during haze and non-haze episodes, daily PM 2.5 samples were collected from March 2015 to February 2016 in a mixed multi-function area in Hangzhou, China. Ambient concentrations of 16 priority-controlled PAHs were determined. The sums of PM 2.5 -bound PAH concentrations during the haze episodes were 4.52 ± 3.32 and 13.6 ± 6.29 ng m -3 in warm and cold seasons, respectively, which were 1.99 and 1.49 times those during the non-haze episodes. Four PAH sources were identified using the positive matrix factorization model and conditional probability function, which were vehicular emissions (45%), heavy oil combustion (23%), coal and natural gas combustion (22%), and biomass combustion (10%). The four source concentrations of PAHs consistently showed higher levels in the cold season, compared with those in the warm season. Vehicular emissions were the most considerable sources that result in the increase of PM 2.5 -bound PAH levels during the haze episodes, and heavy oil combustion played an important role in the aggravation of haze pollution. The analysis of air mass back trajectories indicated that air mass transport had an influence on the PM 2.5 -bound PAH pollution, especially on the increased contributions from coal combustion and vehicular emissions in the cold season.

Real-time analysis, visualization, and steering of microtomography experiments at photon sources

International Nuclear Information System (INIS)

Laszeski, G. von; Insley, J.A.; Foster, I.; Bresnahan, J.; Kesselman, C.; Su, M.; Thiebaux, M.; Rivers, M.L.; Wang, S.; Tieman, B.; McNulty, I.

2000-01-01

A new generation of specialized scientific instruments called synchrotron light sources allow the imaging of materials at very fine scales. However, in contrast to a traditional microscope, interactive use has not previously been possible because of the large amounts of data generated and the considerable computation required translating this data into a useful image. The authors describe a new software architecture that uses high-speed networks and supercomputers to enable quasi-real-time and hence interactive analysis of synchrotron light source data. This architecture uses technologies provided by the Globus computational grid toolkit to allow dynamic creation of a reconstruction pipeline that transfers data from a synchrotron source beamline to a preprocessing station, next to a parallel reconstruction system, and then to multiple visualization stations. Collaborative analysis tools allow multiple users to control data visualization. As a result, local and remote scientists can see and discuss preliminary results just minutes after data collection starts. The implications for more efficient use of this scarce resource and for more effective science appear tremendous

Multicomponent density-functional theory for time-dependent systems

NARCIS (Netherlands)

Butriy, O.; Ebadi, H.; de Boeij, P. L.; van Leeuwen, R.; Gross, E. K. U.

2007-01-01

We derive the basic formalism of density functional theory for time-dependent electron-nuclear systems. The basic variables of this theory are the electron density in body-fixed frame coordinates and the diagonal of the nuclear N-body density matrix. The body-fixed frame transformation is carried

An elementary solution of the Maxwell equations for a time-dependent source

International Nuclear Information System (INIS)

Rivera, R; Villarroel, D

2002-01-01

We present an elementary solution of the Maxwell equations for a time-dependent source consisting of an infinite solenoid with a current density that increases linearly with time. The geometrical symmetries and the time dependence of the current density make possible a mathematical treatment that does not involve the usual technical difficulties, thus making this presentation suitable for students that are taking a first course in electromagnetism. We also show that the electric field generated by the solenoid can be used to construct an exact solution of the relativistic equation of motion of the electron that takes into account the effect of the radiation. In particular, we derive, in an almost trivial way, the formula for the radiation rate of an electron in circular motion

Passive Detection of Narrowband Sources Using a Sensor Array

Energy Technology Data Exchange (ETDEWEB)

Chambers, D H; Candy, J V; Guidry, B L

2007-10-24

In this report we derive a model for a highly scattering medium, implemented as a set of MATLAB functions. This model is used to analyze an approach for using time-reversal to enhance the detection of a single frequency source in a highly scattering medium. The basic approach is to apply the singular value decomposition to the multistatic response matrix for a time-reversal array system. We then use the array in a purely passive mode, measuring the response to the presence of a source. The measured response is projected onto the singular vectors, creating a time-reversal pseudo-spectrum. We can then apply standard detection techniques to the pseudo-spectrum to determine the presence of a source. If the source is close to a particular scatterer in the medium, then we would expect an enhancement of the inner product between the array response to the source with the singular vector associated with that scatterer. In this note we begin by deriving the Foldy-Lax model of a highly scattering medium, calculate both the field emitted by the source and the multistatic response matrix of a time-reversal array system in the medium, then describe the initial analysis approach.

Quantal density functional theory

CERN Document Server

Sahni, Viraht

2016-01-01

This book deals with quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The treated time-independent QDFT constitutes a special case. In the 2nd edition, the theory is extended to include the presence of external magnetostatic fields. The theory is a description of matter based on the ‘quantal Newtonian’ first and second laws which is in terms of “classical” fields that pervade all space, and their quantal sources. The fields, which are explicitly defined, are separately representative of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, correlation-kinetic, correlation-current-density, and correlation-magnetic effects. The book further describes Schrödinger theory from the new physical perspective of fields and quantal sources. It also describes traditional Hohenberg-Kohn-Sham DFT, and explains via QDFT the physics underlying the various energy functionals and functional derivatives o...

Tow efficiency correction functions of source self-absorption of an HPGe detector

International Nuclear Information System (INIS)

Gao Zheng; Ma Yusheng; Luo Jianghua; Chen Luning

2007-01-01

The efficiency correction function of source absorption of an HPGe γ detector is determined by experiment in energy range from 59.5 keV to 1408 keV and density range from 0.3 g/cm 3 to 2.0 g/cm 3 . Fit Polynomial and fit Sigmoidal are compared. The results show that fit Sigmoidal is better than fit polynomial, and the detection efficiency at any points of energy and density could be conveniently calculated with it in calibrated range. (authors)

Feel the Time. Time Perception as a Function of Interoceptive Processing

Directory of Open Access Journals (Sweden)

Daniele Di Lernia

2018-03-01

Full Text Available The nature of time is rooted in our body. Constellations of impulses arising from the flesh constantly create our interoceptive perception and, in turn, the unfolding of these perceptions defines human awareness of time. This study explored the connection between time perception and interoception and proposes the Interoceptive Buffer saturation (IBs index. IBs evaluates subjects’ ability to process salient stimuli from the body by measuring subjective distortions of interoceptive time perception, i.e., the estimated duration of tactile interoceptive stimulations. Thirty female healthy subjects were recruited through consecutive sampling and assessed for common variables related to interoceptive alterations: depressive symptoms (Beck Depression Inventory, BDI-II, eating disorders (EDI-3 risk, and anxiety levels (State Trait Anxiety Inventory, STAI. Interoceptive cardiac accuracy (IAc was assessed as well. Subjects performed verbal time estimation of interoceptive stimuli (IBs delivered using a specifically designed interoceptive tactile stimulator, as well as verbal time estimation of visual and auditory stimuli. Results showed that IBs index positively correlated with IAc, and negatively with EDI-3 Drive for Thinness (DT risk subscale. Moreover, IBs index was positively predicted by IAc, and negatively predicted by DT and somatic factors of depression. Our results suggest that underestimations in interoceptive time perception are connected to different psychological conditions characterized by a diminished processing of high salience stimuli from the body. Conversely, overestimations of the duration of interoceptive stimuli appear to be function of subjects’ ability to correctly perceive their own bodily information. Evidence supported IBs index, fostering the concept of interoceptive treatments for clinical purposes.

Towards three-loop QCD corrections to the time-like splitting functions

International Nuclear Information System (INIS)

Gituliar, O.; Moch, S.

2015-05-01

We report on the status of a direct computation of the time-like splitting functions at next-to-next-to-leading order in QCD. Time-like splitting functions govern the collinear kinematics of inclusive hadron production and the evolution of the parton fragmentation distributions. Current knowledge about them at three loops has been inferred by means of crossing symmetry from their related space-like counterparts, which has left certain parts of the off-diagonal quark-gluon splitting function undetermined. This motivates an independent calculation from first principles. We review the tools and methods which are applied to attack the problem.

An Open-Source Sandbox for Increasing the Accessibility of Functional Programming to the Bioinformatics and Scientific Communities

Science.gov (United States)

Fenwick, Matthew; Sesanker, Colbert; Schiller, Martin R.; Ellis, Heidi JC; Hinman, M. Lee; Vyas, Jay; Gryk, Michael R.

2012-01-01

Scientists are continually faced with the need to express complex mathematical notions in code. The renaissance of functional languages such as LISP and Haskell is often credited to their ability to implement complex data operations and mathematical constructs in an expressive and natural idiom. The slow adoption of functional computing in the scientific community does not, however, reflect the congeniality of these fields. Unfortunately, the learning curve for adoption of functional programming techniques is steeper than that for more traditional languages in the scientific community, such as Python and Java, and this is partially due to the relative sparseness of available learning resources. To fill this gap, we demonstrate and provide applied, scientifically substantial examples of functional programming, We present a multi-language source-code repository for software integration and algorithm development, which generally focuses on the fields of machine learning, data processing, bioinformatics. We encourage scientists who are interested in learning the basics of functional programming to adopt, reuse, and learn from these examples. The source code is available at: https://github.com/CONNJUR/CONNJUR-Sandbox (see also http://www.connjur.org). PMID:25328913

2D CFT partition functions at late times

Science.gov (United States)

Dyer, Ethan; Gur-Ari, Guy

2017-08-01

We consider the late time behavior of the analytically continued partition function Z( β + it) Z( β - it) in holographic 2 d CFTs. This is a probe of information loss in such theories and in their holographic duals. We show that each Virasoro character decays in time, and so information is not restored at the level of individual characters. We identify a universal decaying contribution at late times, and conjecture that it describes the behavior of generic chaotic 2 d CFTs out to times that are exponentially large in the central charge. It was recently suggested that at sufficiently late times one expects a crossover to random matrix behavior. We estimate an upper bound on the crossover time, which suggests that the decay is followed by a parametrically long period of late time growth. Finally, we discuss gravitationally-motivated integrable theories and show how information is restored at late times by a series of characters. This hints at a possible bulk mechanism, where information is restored by an infinite sum over non-perturbative saddles.

A new quantum statistical evaluation method for time correlation functions

International Nuclear Information System (INIS)

Loss, D.; Schoeller, H.

1989-01-01

Considering a system of N identical interacting particles, which obey Fermi-Dirac or Bose-Einstein statistics, the authors derive new formulas for correlation functions of the type C(t) = i= 1 N A i (t) Σ j=1 N B j > (where B j is diagonal in the free-particle states) in the thermodynamic limit. Thereby they apply and extend a superoperator formalism, recently developed for the derivation of long-time tails in semiclassical systems. As an illustrative application, the Boltzmann equation value of the time-integrated correlation function C(t) is derived in a straight-forward manner. Due to exchange effects, the obtained t-matrix and the resulting scattering cross section, which occurs in the Boltzmann collision operator, are now functionals of the Fermi-Dirac or Bose-Einstein distribution

Isotope source apportionment of carbonaceous aerosol as a function of particle size and thermal refractiveness

Science.gov (United States)

Masalaite, Agne; Holzinger, Rupert; Remeikis, Vidmantas; Röckmann, Thomas; Dusek, Ulrike

2016-04-01

The stable carbon isotopes can be used to get information about sources and processing of carbonaceous aerosol. We will present results from source apportionment of carbonaceous aerosol as a function of particle size thermal refractiveness. Separate source apportionment for particles smaller than 200 nm and for different carbon volatility classes are rarely reported and give new insights into aerosol sources in the urban environment. Stable carbon isotope ratios were measured for the organic carbon (OC) fraction and total carbon (TC) of MOUDI impactor samples that were collected on a coastal site (Lithuania) during the winter 2012 and in the city of Vilnius (Lithuania) during the winter of 2009. The 11 impactor stages spanned a size range from 0.056 to 18 μm, but only the 6 stages in the submicron range were analysed. The δ13C values of bulk total carbon (δ13CTC) were determined with an elemental analyser (Flash EA 1112) coupled with an isotope ratio mass spectrometer (Thermo Finnigan Delta Plus Advantage) (EA - IRMS). Meanwhile δ13COC was measured using thermal-desorption isotope ratio mass spectrometry (IRMS) system. This allows a rough separation of the more volatile OC fraction (desorbed in the oven of IRMS up to 250 0C) from the more refractory fraction (desorbed up to 400 0C). In this study we investigated the composition of organic aerosol desorbed from filter samples at different temperatures using the thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) technique. During winter-time in Lithuania we expect photochemistry and biogenic emissions to be of minor importance. The main sources of aerosol carbon should be fossil fuel and biomass combustion. In both sites, the coastal and the urban site, δ13C measurements give a clear indication that the source contributions differ for small and large particles. Small particles < 200 nm are depleted in 13C with respect to larger particles by 1 - 2 ‰Ṫhis shows that OC in small particle

Fitting a function to time-dependent ensemble averaged data.

Science.gov (United States)

Fogelmark, Karl; Lomholt, Michael A; Irbäck, Anders; Ambjörnsson, Tobias

2018-05-03

Time-dependent ensemble averages, i.e., trajectory-based averages of some observable, are of importance in many fields of science. A crucial objective when interpreting such data is to fit these averages (for instance, squared displacements) with a function and extract parameters (such as diffusion constants). A commonly overlooked challenge in such function fitting procedures is that fluctuations around mean values, by construction, exhibit temporal correlations. We show that the only available general purpose function fitting methods, correlated chi-square method and the weighted least squares method (which neglects correlation), fail at either robust parameter estimation or accurate error estimation. We remedy this by deriving a new closed-form error estimation formula for weighted least square fitting. The new formula uses the full covariance matrix, i.e., rigorously includes temporal correlations, but is free of the robustness issues, inherent to the correlated chi-square method. We demonstrate its accuracy in four examples of importance in many fields: Brownian motion, damped harmonic oscillation, fractional Brownian motion and continuous time random walks. We also successfully apply our method, weighted least squares including correlation in error estimation (WLS-ICE), to particle tracking data. The WLS-ICE method is applicable to arbitrary fit functions, and we provide a publically available WLS-ICE software.

The first synchrotron infrared beamlines at the Advanced Light Source: Microspectroscopy and fast timing

International Nuclear Information System (INIS)

Martin, M.C.; McKinney, W.R.

1998-05-01

A set of new infrared (IR) beamlines on the 1.4 bending magnet port at the Advanced Light Source, LBNL, are described. Using a synchrotron as an IR source provides considerable brightness advantages, which manifests itself most beneficially when performing spectroscopy on a microscopic length scale. Beamline (BL) 1.4.3 is a dedicated microspectroscopy beamline, where the much smaller focused spot size using the synchrotron source is utilized. This enables an entirely new set of experiments to be performed where spectroscopy on a truly microscopic scale is now possible. BL 1.4.2 consists of a vacuum FTIR bench with a wide spectral range and step-scan capabilities. The fast timing is demonstrated by observing the synchrotron electron storage pattern at the ALS

Less-structured time in children's daily lives predicts self-directed executive functioning.

Science.gov (United States)

Barker, Jane E; Semenov, Andrei D; Michaelson, Laura; Provan, Lindsay S; Snyder, Hannah R; Munakata, Yuko

2014-01-01

Executive functions (EFs) in childhood predict important life outcomes. Thus, there is great interest in attempts to improve EFs early in life. Many interventions are led by trained adults, including structured training activities in the lab, and less-structured activities implemented in schools. Such programs have yielded gains in children's externally-driven executive functioning, where they are instructed on what goal-directed actions to carry out and when. However, it is less clear how children's experiences relate to their development of self-directed executive functioning, where they must determine on their own what goal-directed actions to carry out and when. We hypothesized that time spent in less-structured activities would give children opportunities to practice self-directed executive functioning, and lead to benefits. To investigate this possibility, we collected information from parents about their 6-7 year-old children's daily, annual, and typical schedules. We categorized children's activities as "structured" or "less-structured" based on categorization schemes from prior studies on child leisure time use. We assessed children's self-directed executive functioning using a well-established verbal fluency task, in which children generate members of a category and can decide on their own when to switch from one subcategory to another. The more time that children spent in less-structured activities, the better their self-directed executive functioning. The opposite was true of structured activities, which predicted poorer self-directed executive functioning. These relationships were robust (holding across increasingly strict classifications of structured and less-structured time) and specific (time use did not predict externally-driven executive functioning). We discuss implications, caveats, and ways in which potential interpretations can be distinguished in future work, to advance an understanding of this fundamental aspect of growing up.

Predicting kidney graft failure using time-dependent renal function covariates

NARCIS (Netherlands)

de Bruijne, Mattheus H. J.; Sijpkens, Yvo W. J.; Paul, Leendert C.; Westendorp, Rudi G. J.; van Houwelingen, Hans C.; Zwinderman, Aeilko H.

2003-01-01

Chronic rejection and recurrent disease are the major causes of late graft failure in renal transplantation. To assess outcome, most researchers use Cox proportional hazard analysis with time-fixed covariates. We developed a model adding time-dependent renal function covariates to improve the

Real-time earthquake source imaging: An offline test for the 2011 Tohoku earthquake

Science.gov (United States)

Zhang, Yong; Wang, Rongjiang; Zschau, Jochen; Parolai, Stefano; Dahm, Torsten

2014-05-01

In recent decades, great efforts have been expended in real-time seismology aiming at earthquake and tsunami early warning. One of the most important issues is the real-time assessment of earthquake rupture processes using near-field seismogeodetic networks. Currently, earthquake early warning systems are mostly based on the rapid estimate of P-wave magnitude, which contains generally large uncertainties and the known saturation problem. In the case of the 2011 Mw9.0 Tohoku earthquake, JMA (Japan Meteorological Agency) released the first warning of the event with M7.2 after 25 s. The following updates of the magnitude even decreased to M6.3-6.6. Finally, the magnitude estimate stabilized at M8.1 after about two minutes. This led consequently to the underestimated tsunami heights. By using the newly developed Iterative Deconvolution and Stacking (IDS) method for automatic source imaging, we demonstrate an offline test for the real-time analysis of the strong-motion and GPS seismograms of the 2011 Tohoku earthquake. The results show that we had been theoretically able to image the complex rupture process of the 2011 Tohoku earthquake automatically soon after or even during the rupture process. In general, what had happened on the fault could be robustly imaged with a time delay of about 30 s by using either the strong-motion (KiK-net) or the GPS (GEONET) real-time data. This implies that the new real-time source imaging technique is helpful to reduce false and missing warnings, and therefore should play an important role in future tsunami early warning and earthquake rapid response systems.

Source-Sink Mismatch Causing Functional Conduction Block in Re-Entrant Ventricular Tachycardia.

Science.gov (United States)

Ciaccio, Edward J; Coromilas, James; Wit, Andrew L; Peters, Nicholas S; Garan, Hasan

2018-01-01

Ventricular tachycardia (VT) caused by a re-entrant circuit is a life-threatening arrhythmia that at present cannot always be treated adequately. A realistic model of re-entry would be helpful to accurately guide catheter ablation for interruption of the circuit. In this review, models of electrical activation wavefront propagation during onset and maintenance of re-entrant VT are discussed. In particular, the relationship between activation mapping and maps of transition in infarct border zone thickness, which results in source-sink mismatch, is considered in detail and supplemented with additional data. Based on source-sink mismatch, the re-entry isthmus can be modeled from its boundary properties. Isthmus boundary segments with large transitions in infarct border zone thickness have large source-sink mismatch, and functional block forms there during VT. These alternate with segments having lesser thickness change and therefore lesser source-sink mismatch, which act as gaps, or entrance and exit points, to the isthmus during VT. Besides post-infarction substrates, the source-sink model is likely applicable to other types of volumetric changes in the myocardial conducting medium, such as when there is presence of fibrosis or dissociation of muscle fibers. Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Trans-Z-source Neutral Point Clamped inverter

DEFF Research Database (Denmark)

Mo, W.; Loh, P. C.; Li, D.

2012-01-01

Transformer based Z-source (trans-Z-source) inverters are recently proposed by extending the traditional Z-source inverter with higher buck-boost capability as well as reducing the passive components at the same time. Multi-Level Z-source inverters are single-stage topological solutions used...... for buck-boost energy conversion with all the favourable advantages of multi-level switching retained. This paper presents three-level trans-Z-source Neutral Point Clamped (NPC) inverter topology, which achieves both the advantages of trans-Z-source and three-level NPC inverter configuration. With proper...... modulation scheme, the three-level trans-Z-source inverter can function with minimum of six device commutations per half carrier cycle (same as the traditional buck NPC inverter), while maintaining to produce the designed volt-sec average and inductive voltage boosting at ac output terminals. The designed...

Development of the work function monitoring method for a converter of a negative ion source

International Nuclear Information System (INIS)

Yamaoka, Hitoshi; Sasao, Mamiko; Wada, Motoi; Ramos, H.J.

1988-07-01

A method to monitor the change in the work function of the converter surface in a self-extraction negative ion source is developed. The photoelectron emission from the Cs-Mo surface in a plasma is detected by irradiating surface with laser lights. Negative ions produced at the surface shows a strong correlation with the photoelectron current from the surface in hydrogen and helium discharges. The photoelectron current induced by the Ar + laser is used to detect the change in the cesium coverage, or the work function, while that by the dye laser is found to be suitable to confirm the region of the work function minimum. (author)

The space-time outside a source of gravitational radiation: the axially symmetric null fluid

Energy Technology Data Exchange (ETDEWEB)

Herrera, L. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Universidad de Salamanca, Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain); Di Prisco, A. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Ospino, J. [Universidad de Salamanca, Departamento de Matematica Aplicada and Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain)

2016-11-15

We carry out a study of the exterior of an axially and reflection symmetric source of gravitational radiation. The exterior of such a source is filled with a null fluid produced by the dissipative processes inherent to the emission of gravitational radiation, thereby representing a generalization of the Vaidya metric for axially and reflection symmetric space-times. The role of the vorticity, and its relationship with the presence of gravitational radiation is put in evidence. The spherically symmetric case (Vaidya) is, asymptotically, recovered within the context of the 1 + 3 formalism. (orig.)

Optical Absorption in Molecular Crystals from Time-Dependent Density Functional Theory

Science.gov (United States)

2017-04-23

Our approach represents a full solid-state calculation, allowing for polarization ef- fects while still capable of capturing inter-molecular dis...AFRL-AFOSR-UK-TR-2017-0030 Optical absorption in molecular crystals from time-dependent density functional theory Leeor Kronik WEIZMANN INSTITUTE OF...from time-dependent density functional theory 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-15-1-0290 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S

The Space-, Time-, and Energy-distribution of Neutrons from a Pulsed Plane Source

Energy Technology Data Exchange (ETDEWEB)

Claesson, Arne

1962-05-15

The space-, time- and energy-distribution of neutrons from a pulsed, plane, high energy source in an infinite medium is determined in a diffusion approximation. For simplicity the moderator is first assumed to be hydrogen gas but it is also shown that the method can be used for a moderator of arbitrary mass.

Calibration of time of flight detectors using laser-driven neutron source

Energy Technology Data Exchange (ETDEWEB)

Mirfayzi, S. R.; Kar, S., E-mail: s.kar@qub.ac.uk; Ahmed, H.; Green, A.; Alejo, A.; Jung, D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom); Krygier, A. G.; Freeman, R. R. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Clarke, R. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom); Fuchs, J.; Vassura, L. [LULI, Ecole Polytechnique, CNRS, Route de Saclay, 91128 Palaiseau Cedex (France); Kleinschmidt, A.; Roth, M. [Institut für Kernphysik, Technische Universität Darmstadt, Schloßgartenstrasse 9, D-64289 Darmstadt,Germany (Germany); Morrison, J. T. [Propulsion Systems Directorate, Air Force Research Lab, Wright Patterson Air Force Base, Ohio 45433 (United States); Najmudin, Z.; Nakamura, H. [Blackett Laboratory, Department of Physics, Imperial College, London SW7 2AZ (United Kingdom); Norreys, P. [Central Laser Facility, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom); Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Oliver, M. [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Zepf, M. [Centre for Plasma Physics, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom); Helmholtz Institut Jena, D-07743 Jena (Germany); Borghesi, M. [Centre for Plasma Physics, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom); Institute of Physics of the ASCR, ELI-Beamlines Project, Na Slovance 2, 18221 Prague (Czech Republic)

2015-07-15

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

Calibration of time of flight detectors using laser-driven neutron source

Science.gov (United States)

Mirfayzi, S. R.; Kar, S.; Ahmed, H.; Krygier, A. G.; Green, A.; Alejo, A.; Clarke, R.; Freeman, R. R.; Fuchs, J.; Jung, D.; Kleinschmidt, A.; Morrison, J. T.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.

2015-07-01

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

Calibration of time of flight detectors using laser-driven neutron source

International Nuclear Information System (INIS)

Mirfayzi, S. R.; Kar, S.; Ahmed, H.; Green, A.; Alejo, A.; Jung, D.; Krygier, A. G.; Freeman, R. R.; Clarke, R.; Fuchs, J.; Vassura, L.; Kleinschmidt, A.; Roth, M.; Morrison, J. T.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Oliver, M.; Zepf, M.; Borghesi, M.

2015-01-01

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil

On the zero temperature limit of the Kubo-transformed quantum time correlation function

Science.gov (United States)

Hernández de la Peña, Lisandro

2014-04-01

The zero temperature limit of several quantum time correlation functions is analysed. It is shown that while the canonical quantum time correlation function retains the full dynamical information as temperature approaches zero, the Kubo-transformed and the thermally symmetrised quantum time correlation functions lose all dynamical information at this limit. This is shown to be a consequence of the projection onto the ground state, via the limiting process of the quantities ? and ?, either together as a product, or separately. Although these findings would seem to suggest that finite-temperature methods commonly used to estimate Kubo correlation functions would be incapable of retaining any ground state dynamics, we propose a route for recovering in principle all dynamical information at the ground state. It is first shown that the usual frequency space relation between canonical and Kubo correlation functions also holds for microcanonical time correlation functions. Since the Kubo-transformed microcanonical correlation function can be obtained from the usual finite-temperature function by including a projection onto the corresponding microcanonical ensemble, finite-temperature methods, properly modified to incorporate such a constraint, can be used to capture full quantum dynamics at any arbitrary energy state, including the ground state. This approach is illustrated with the application of centroid dynamics to the ground state dynamics of the harmonic oscillator.

Assessment of Real-Time Time-Dependent Density Functional Theory (RT-TDDFT) in Radiation Chemistry: Ionized Water Dimer.

Science.gov (United States)

Chalabala, Jan; Uhlig, Frank; Slavíček, Petr

2018-03-29

Ionization in the condensed phase and molecular clusters leads to a complicated chain of processes with coupled electron-nuclear dynamics. It is difficult to describe such dynamics with conventional nonadiabatic molecular dynamics schemes since the number of states swiftly increases as the molecular system grows. It is therefore attractive to use a direct electron and nuclear propagation such as the real-time time-dependent density functional theory (RT-TDDFT). Here we report a RT-TDDFT benchmark study on simulations of singly and doubly ionized states of a water monomer and dimer as a prototype for more complex processes in a condensed phase. We employed the RT-TDDFT based Ehrenfest molecular dynamics with a generalized gradient approximate (GGA) functional and compared it with wave-function-based surface hopping (SH) simulations. We found that the initial dynamics of a singly HOMO ionized water dimer is similar for both the RT-TDDFT/GGA and the SH simulations but leads to completely different reaction channels on a longer time scale. This failure is attributed to the self-interaction error in the GGA functionals and it can be avoided by using hybrid functionals with large fraction of exact exchange (represented here by the BHandHLYP functional). The simulations of doubly ionized states are reasonably described already at the GGA level. This suggests that the RT-TDDFT/GGA method could describe processes following the autoionization processes such as Auger emission, while its applicability to more complex processes such as intermolecular Coulombic decay remains limited.

Examining Multiple Sources of Differential Item Functioning on the Clinician & Group CAHPS® Survey

Science.gov (United States)

Rodriguez, Hector P; Crane, Paul K

2011-01-01

Objective To evaluate psychometric properties of a widely used patient experience survey. Data Sources English-language responses to the Clinician & Group Consumer Assessment of Healthcare Providers and Systems (CG-CAHPS®) survey (n = 12,244) from a 2008 quality improvement initiative involving eight southern California medical groups. Methods We used an iterative hybrid ordinal logistic regression/item response theory differential item functioning (DIF) algorithm to identify items with DIF related to patient sociodemographic characteristics, duration of the physician–patient relationship, number of physician visits, and self-rated physical and mental health. We accounted for all sources of DIF and determined its cumulative impact. Principal Findings The upper end of the CG-CAHPS® performance range is measured with low precision. With sensitive settings, some items were found to have DIF. However, overall DIF impact was negligible, as 0.14 percent of participants had salient DIF impact. Latinos who spoke predominantly English at home had the highest prevalence of salient DIF impact at 0.26 percent. Conclusions The CG-CAHPS® functions similarly across commercially insured respondents from diverse backgrounds. Consequently, previously documented racial and ethnic group differences likely reflect true differences rather than measurement bias. The impact of low precision at the upper end of the scale should be clarified. PMID:22092021

Dynamics of Gaussian Wigner functions derived from a time-dependent variational principle

Directory of Open Access Journals (Sweden)

Jens Aage Poulsen

2017-11-01

Full Text Available By using a time-dependent variational principle formulated for Wigner phase-space functions, we obtain the optimal time-evolution for two classes of Gaussian Wigner functions, namely those of either thawed real-valued or frozen but complex Gaussians. It is shown that tunneling effects are approximately included in both schemes.

Time correlation functions and transport coefficients in a dilute superfluid

International Nuclear Information System (INIS)

Kirkpatrick, T.R.; Dorfman, J.R.

1985-01-01

Time correlation functions for the transport coefficients in the linear Landau-Khalatnikov equations are derived on the basis of a formal theory. These Green--Kubo expressions are then explicitly evaluated for a dilute superfluid and the resulting transport coefficiencts are shown to be identical to those obtained previously by using a distribution function method