EXTENSION OF THE 1D FOUR-GROUP ANALYTIC NODAL METHOD TO FULL MULTIGROUP
Energy Technology Data Exchange (ETDEWEB)
B. D. Ganapol; D. W. Nigg
2008-09-01
In the mid 80’s, a four-group/two-region, entirely analytical 1D nodal benchmark appeared. It was readily acknowledged that this special case was as far as one could go in terms of group number and still achieve an analytical solution. In this work, we show that by decomposing the solution to the multigroup diffusion equation into homogeneous and particular solutions, extension to any number of groups is a relatively straightforward exercise using the mathematics of linear algebra.
Tominaga, Nozomu; Blinnikov, Sergei I
2015-01-01
We develop a time-dependent multi-group multidimensional relativistic radiative transfer code, which is required to numerically investigate radiation from relativistic fluids involved in, e.g., gamma-ray bursts and active galactic nuclei. The code is based on the spherical harmonic discrete ordinate method (SHDOM) that evaluates a source function including anisotropic scattering in spherical harmonics and implicitly solves the static radiative transfer equation with a ray tracing in discrete ordinates. We implement treatments of time dependence, multi-frequency bins, Lorentz transformation, and elastic Thomson and inelastic Compton scattering to the publicly available SHDOM code. Our code adopts a mixed frame approach; the source function is evaluated in the comoving frame whereas the radiative transfer equation is solved in the laboratory frame. This implementation is validated with various test problems and comparisons with results of a relativistic Monte Carlo code. These validations confirm that the code ...
Time-dependent delta-interactions for 1D Schr\\"odinger Hamiltonians
Hmidi, Taoufik; Nier, Francis
2009-01-01
The non autonomous Cauchy problem for time dependent 1D point interactions is considered. The regularity assumptions for the coupling parameter are accurately analyzed and show that the general results for non autonomous linear evolution equations in Banach spaces are far from being optimal. In the mean time, this article shows an unexpected application of paraproduct techniques, initiated by J.M. Bony for nonlinear partial differential equations, to a classical linear problem.
Livne, E; Walder, R; Lichtenstadt, I; Thompson, T A; Livne, Eli; Burrows, Adam; Walder, Rolf; Lichtenstadt, Itamar; Thompson, Todd A.
2004-01-01
We have developed a time-dependent, multi-energy-group, and multi-angle (S$_n$) Boltzmann transport scheme for radiation hydrodynamics simulations, in one and two spatial dimensions. The implicit transport is coupled to both 1D (spherically-symmetric) and 2D (axially-symmetric) versions of the explicit Newtonian hydrodynamics code VULCAN. The 2D variant, VULCAN/2D, can be operated in general structured or unstructured grids and though the code can address many problems in astrophysics it was constructed specifically to study the core-collapse supernova problem. Furthermore, VULCAN/2D can simulate the radiation/hydrodynamic evolution of differentially rotating bodies. We summarize the equations solved and methods incorporated into the algorithm and present results of a time-dependent 2D test calculation. A more complete description of the algorithm is postponed to another paper. We highlight a 2D test run that follows for 22 milliseconds the immediate post-bounce evolution of a collapsed core. We present the r...
Walder, R; Ott, C D; Livne, E; Jarrah, M
2004-01-01
Using the 2D multi-group, flux-limited diffusion version of the code VULCAN/2D, that also incorporates rotation, we have calculated the collapse, bounce, shock formation, and early post-bounce evolutionary phases of a core-collapse supernova for a variety of initial rotation rates. This is the first series of such multi-group calculations undertaken in supernova theory with fully multi-D tools. We find that though rotation generates pole-to-equator angular anisotropies in the neutrino radiation fields, the magnitude of the asymmetries is not as large as previously estimated. Moreover, we find that the radiation field is always more spherically symmetric than the matter distribution, with its plumes and convective eddies. We present the dependence of the angular anisotropy of the neutrino fields on neutrino species, neutrino energy, and initial rotation rate. Only for our most rapidly rotating model do we start to see qualitatively different hydrodynamics, but for the lower rates consistent with the pre-collap...
Energy Technology Data Exchange (ETDEWEB)
Guasti, M Fernandez [Depto de Fisica, CBI, Universidad A Metropolitana - Iztapalapa, 09340 Mexico, DF, Apdo Postal 55-534 (Mexico); Moya-Cessa, H [INAOE, Coordinacion de Optica, Apdo Postal 51 y 216, 72000 Puebla, Pue. (Mexico)
2003-02-28
An extension of the classical orthogonal functions invariant to the quantum domain is presented. This invariant is expressed in terms of the Hamiltonian. Unitary transformations which involve the auxiliary function of this quantum invariant are used to solve the time-dependent Schroedinger equation for a harmonic oscillator with time-dependent parameter. The solution thus obtained is in agreement with the results derived using other methods which invoke the Lewis invariant in their procedures.
Energy Technology Data Exchange (ETDEWEB)
Petersen, Claudio Z. [Universidade Federal de Pelotas, Capao do Leao (Brazil). Programa de Pos Graduacao em Modelagem Matematica; Bodmann, Bardo E.J.; Vilhena, Marco T. [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Programa de Pos-graduacao em Engenharia Mecanica; Barros, Ricardo C. [Universidade do Estado do Rio de Janeiro, Nova Friburgo, RJ (Brazil). Inst. Politecnico
2014-12-15
In the present work we solve in analytical representation the three dimensional neutron kinetic diffusion problem in rectangular Cartesian geometry for homogeneous and bounded domains for any number of energy groups and precursor concentrations. The solution in analytical representation is constructed using a hierarchical procedure, i.e. the original problem is reduced to a problem previously solved by the authors making use of a combination of the spectral method and a recursive decomposition approach. Time dependent absorption cross sections of the thermal energy group are considered with step, ramp and Chebyshev polynomial variations. For these three cases, we present numerical results and discuss convergence properties and compare our results to those available in the literature.
Energy Technology Data Exchange (ETDEWEB)
Ryu, Eun Hyun; Song, Yong Mann; Park, Joo Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-05-15
If time-dependent equation is solved with the FEM, the limitation of the input geometry will disappear. It has often been pointed out that the numerical methods implemented in the RFSP code are not state-of-the-art. Although an acceleration method such as the Coarse Mesh Finite Difference (CMFD) for Finite Difference Method (FDM) does not exist for the FEM, one should keep in mind that the number of time steps for the transient simulation is not large. The rigorous formulation in this study will richen the theoretical basis of the FEM and lead to an extension of the dynamics code to deal with a more complicated problem. In this study, the formulation for the 1-D, 1-G Time Dependent Neutron Diffusion Equation (TDNDE) without consideration of the delay neutron will first be done. A problem including one multiplying medium will be solved. Also several conclusions from a comparison between the numerical and analytic solutions, a comparison between solutions with various element orders, and a comparison between solutions with different time differencing will be made to be certain about the formulation and FEM solution. By investigating various cases with different values of albedo, theta, and the order of elements, it can be concluded that the finite element solution is agree well with the analytic solution. The higher the element order used, the higher the accuracy improvements are obtained.
Thiery, Thimothée; Le Doussal, Pierre
2017-01-01
We consider the Beta polymer, an exactly solvable model of directed polymer on the square lattice, introduced by Barraquand and Corwin (BC) (2016 Probab. Theory Relat. Fields 1-16). We study the statistical properties of its point to point partition sum. The problem is equivalent to a model of a random walk in a time-dependent (and in general biased) 1D random environment. In this formulation, we study the sample to sample fluctuations of the transition probability distribution function (PDF) of the random walk. Using the Bethe ansatz we obtain exact formulas for the integer moments, and Fredholm determinant formulas for the Laplace transform of the directed polymer partition sum/random walk transition probability. The asymptotic analysis of these formulas at large time t is performed both (i) in a diffusive vicinity, x˜ {{t}1/2} , of the optimal direction (in space-time) chosen by the random walk, where the fluctuations of the PDF are found to be Gamma distributed; (ii) in the large deviations regime, x˜ t , of the random walk, where the fluctuations of the logarithm of the PDF are found to grow with time as t 1/3 and to be distributed according to the Tracy-Widom GUE distribution. Our exact results complement those of BC for the cumulative distribution function of the random walk in regime (ii), and in regime (i) they unveil a novel fluctuation behavior. We also discuss the crossover regime between (i) and (ii), identified as x˜ {{t}3/4} . Our results are confronted to extensive numerical simulations of the model.
Energy Technology Data Exchange (ETDEWEB)
Axness, Carl L.; Keiter, Eric Richard; Kerr, Bert (New Mexico Tech, Socorro, NM)
2011-04-01
Circuit simulation tools (e.g., SPICE) have become invaluable in the development and design of electronic circuits in radiation environments. These codes are often employed to study the effect of many thousands of devices under transient current conditions. Device-scale simulation tools (e.g., MEDICI) are commonly used in the design of individual semiconductor components, but require computing resources that make their incorporation into a circuit code impossible for large-scale circuits. Analytic solutions to the ambipolar diffusion equation, an approximation to the carrier transport equations, may be used to characterize the transient currents at nodes within a circuit simulator. We present new transient 1D excess carrier density and photocurrent density solutions to the ambipolar diffusion equation for low-level radiation pulses that take into account a finite device geometry, ohmic fields outside the depleted region, and an arbitrary change in the carrier lifetime due to neutron irradiation or other effects. The solutions are specifically evaluated for the case of an abrupt change in the carrier lifetime during or after, a step, square, or piecewise linear radiation pulse. Noting slow convergence of the raw Fourier series for certain parameter sets, we use closed-form formulas for some of the infinite sums to produce 'partial closed-form' solutions for the above three cases. These 'partial closed-form' solutions converge with only a few tens of terms, which enables efficient large-scale circuit simulations.
MCNP: Multigroup/adjoint capabilities
Energy Technology Data Exchange (ETDEWEB)
Wagner, J.C.; Redmond, E.L. II; Palmtag, S.P.; Hendricks, J.S.
1994-04-01
This report discusses various aspects related to the use and validity of the general purpose Monte Carlo code MCNP for multigroup/adjoint calculations. The increased desire to perform comparisons between Monte Carlo and deterministic codes, along with the ever-present desire to increase the efficiency of large MCNP calculations has produced a greater user demand for the multigroup/adjoint capabilities. To more fully utilize these capabilities, we review the applications of the Monte Carlo multigroup/adjoint method, describe how to generate multigroup cross sections for MCNP with the auxiliary CRSRD code, describe how to use the multigroup/adjoint capability in MCNP, and provide examples and results indicating the effectiveness and validity of the MCNP multigroup/adjoint treatment. This information should assist users in taking advantage of the MCNP multigroup/adjoint capabilities.
Coupling of Nod1D and HOTCHANNEL: static case; Acoplamiento de Nod1D y HOTCHANNEL: caso estatico
Energy Technology Data Exchange (ETDEWEB)
Gomez T, A.M. [IPN-ESFM, 07738 Mexico D.F. (Mexico); Ovando C, R. [IIE-Gcia. de Energia Nuclear, Cuernavaca, Morelos (Mexico)]. e-mail: rovando@iie.org.mx
2003-07-01
In this work the joining of the programs Nod1D and HOTCHANNEL, developed in the National Polytechnic Institute (IPN) and in the Electrical Research Institute (IIE) respectively is described. The first one allows to study the neutronic of a nuclear reactor and the second one allows to carry out the analysis of hot channel of a Boiling Water Reactor (BWR). Nod1 D is a program that it solves by nodal methods type finite element those diffusion equations in multigroup, and it is the static part of Nod Kin that it solves the diffusion equation in their time dependent part. For another side HOTCHANNEL is based on a mathematical model constituted by four conservation equations (two of mass conservation, one of motion quantity and one of energy), which are solved applying one discretization in implicit finite differences. Both programs have been verified in independent form using diverse test problems. In this work the modifications that were necessary to carry out to both for obtaining a coupled program that it provides the axial distribution of the neutron flux, the power, the burnup and the void fraction, among others parameters as much as neutronic as thermal hydraulics are described. Those are also mentioned limitations, advantages and disadvantages of the final product to which has been designated Nod1 D-HotChn. Diverse results for the Cycle 1 of the Laguna Verde Unit 1 reactor of the Nucleo electric central comparing them with those obtained directly with the CoreMasterPresto code are provided. (Author)
Procedure to Generate the MPACT Multigroup Library
Energy Technology Data Exchange (ETDEWEB)
Kim, Kang Seog [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-12-17
The CASL neutronics simulator MPACT is under development for the neutronics and T-H coupled simulation for the light water reactor. The objective of this document is focused on reviewing the current procedure to generate the MPACT multigroup library. Detailed methodologies and procedures are included in this document for further discussion to improve the MPACT multigroup library.
Ioannidou, Theodora
2016-01-01
An extended version of the BPS Skyrme model that admits time-dependent solutions is discussed. Initially, by introducing a power law at the original potential term of the BPS Skyrme model the existence, stability and structure of the corresponding solutions is investigated. Then, the frequencies and half-lifes of the radial oscillations of the constructed time-dependent solutions are determined.
Time-Dependent Lagrangian Biomechanics
Ivancevic, Tijana T
2009-01-01
In this paper we present the time-dependent generalization of an 'ordinary' autonomous human musculo-skeletal biomechanics. We start with the configuration manifold of human body, given as a set of its all active degrees of freedom (DOF). This is a Riemannian manifold with a material metric tensor given by the total mass-inertia matrix of the human body segments. This is the base manifold for standard autonomous biomechanics. To make its time-dependent generalization, we need to extend it with a real time axis. On this extended configuration space we develop time-dependent biomechanical Lagrangian dynamics, using derived jet spaces of velocities and accelerations, as well as the underlying geometric evolution of the mass-inertia matrix. Keywords: Human time-dependent biomechanics, configuration manifold, jet spaces, geometric evolution
Simulations of protostellar collapse using multigroup radiation hydrodynamics. I. The first collapse
Vaytet, Neil; Chabrier, Gilles; Commercon, Benoit; Masson, Jacques
2012-01-01
Radiative transfer plays a major role in the process of star formation. Many simulations of gravitational collapse of a cold gas cloud followed by the formation of a protostellar core use a grey treatment of radiative transfer coupled to the hydrodynamics. However, dust opacities which dominate extinction show large variations as a function of frequency. In this paper, we used frequency-dependent radiative transfer to investigate the influence of the opacity variations on the properties of Larson's first core. We used a multigroup M1 moment model in a 1D radiation hydrodynamics code to simulate the spherically symmetric collapse of a 1 solar mass cloud core. Monochromatic dust opacities for five different temperature ranges were used to compute Planck and Rosseland means inside each frequency group. The results are very consistent with previous studies and only small differences were observed between the grey and multigroup simulations. For a same central density, the multigroup simulations tend to produce fi...
A numerical model for multigroup radiation hydrodynamics
Vaytet, N M H; Dubroca, B; Delahaye, F
2011-01-01
We present in this paper a multigroup model for radiation hydrodynamics to account for variations of the gas opacity as a function of frequency. The entropy closure model (M1) is applied to multigroup radiation transfer in a radiation hydrodynamics code. In difference from the previous grey model, we are able to reproduce the crucial effects of frequency-variable gas opacities, a situation omnipresent in physics and astrophysics. We also account for the energy exchange between neighbouring groups which is important in flows with strong velocity divergence. These terms were computed using a finite volume method in the frequency domain. The radiative transfer aspect of the method was first tested separately for global consistency (reversion to grey model) and against a well established kinetic model through Marshak wave tests with frequency dependent opacities. Very good agreement between the multigroup M1 and kinetic models was observed in all tests. The successful coupling of the multigroup radiative transfer...
Olson, Gordon L.
2017-03-01
Gray and multigroup radiation is transported through 3D media consisting of spheres randomly placed in a uniform background. Comparisons are made between using constant radii spheres and three different distributions of sphere radii. Because of the computational cost of 3D calculations, only the lowest angle order, n=1, is tested. If the mean chord length is held constant, using different radii distributions makes little difference. This is true for both gray and multigroup solutions. 3D transport solutions are compared to 2D and 1D solutions with the same mean chord lengths. 2D disk and 3D sphere media give solutions that are nearly identical while 1D slab solutions are fundamentally different.
A multigroup radiation diffusion test problem: Comparison of code results with analytic solution
Energy Technology Data Exchange (ETDEWEB)
Shestakov, A I; Harte, J A; Bolstad, J H; Offner, S R
2006-12-21
We consider a 1D, slab-symmetric test problem for the multigroup radiation diffusion and matter energy balance equations. The test simulates diffusion of energy from a hot central region. Opacities vary with the cube of the frequency and radiation emission is given by a Wien spectrum. We compare results from two LLNL codes, Raptor and Lasnex, with tabular data that define the analytic solution.
Time dependence of immersion freezing
Directory of Open Access Journals (Sweden)
A. Welti
2012-05-01
Full Text Available The time dependence of immersion freezing was studied for temperatures between 236 K and 243 K. Droplets with single immersed, size-selected 400 nm and 800 nm kaolinite particles were produced at 300 K, cooled down to supercooled temperatures typical for mixed-phase cloud conditions, and the fraction of frozen droplets with increasing residence time was detected. To simulate the conditions of immersion freezing in mixed-phase clouds we used the Zurich Ice Nucleation Chamber (ZINC and its vertical extension, the Immersion Mode Cooling chAmber (IMCA. We observed that the frozen fraction of droplets increased with increasing residence time in the chamber. This suggests that there is a time dependence of immersion freezing and supports the importance of a stochastic component in the ice nucleation process. The rate at which droplets freeze was observed to decrease towards higher temperatures and smaller particle sizes. Comparison of the laboratory data with four different ice nucleation models, three based on classical nucleation theory with different representations of the particle surface properties and one singular, suggest that the classical, stochastic approach combined with a distribution of contact angles is able to reproduce the ice nucleation observed in these experiments most accurately. Using the models to calculate the increase in frozen fraction at typical mixed-phase cloud temperatures over an extended period of time, yields an equivalent effect of −1 K temperature shift and an increase in time scale by a factor of ~10.
Network-timing-dependent plasticity
Directory of Open Access Journals (Sweden)
Vincent eDelattre
2015-06-01
Full Text Available Bursts of activity in networks of neurons are thought to convey salient information and drive synaptic plasticity. Here we report that network bursts also exert a profound effect on Spike-Timing-Dependent Plasticity (STDP. In acute slices of juvenile rat somatosensory cortex we paired a network burst, which alone induced long-term depression (LTD, with STDP-induced long-term potentiation and depression (LTP and LTD. We observed that STDP-induced LTP was either unaffected, blocked or flipped into LTD by the network burst, and that STDP-induced LTD was either saturated or flipped into LTP, depending on the relative timing of the network burst with respect to spike coincidences of the STDP event. We hypothesized that network bursts flip STDP-induced LTP to LTD by depleting resources needed for LTP and therefore developed a resource-dependent STDP learning rule. In a model neural network under the influence of the proposed resource-dependent STDP rule, we found that excitatory synaptic coupling was homeostatically regulated to produce power law distributed burst amplitudes reflecting self-organized criticality, a state that ensures optimal information coding.
Network-timing-dependent plasticity.
Delattre, Vincent; Keller, Daniel; Perich, Matthew; Markram, Henry; Muller, Eilif B
2015-01-01
Bursts of activity in networks of neurons are thought to convey salient information and drive synaptic plasticity. Here we report that network bursts also exert a profound effect on Spike-Timing-Dependent Plasticity (STDP). In acute slices of juvenile rat somatosensory cortex we paired a network burst, which alone induced long-term depression (LTD), with STDP-induced long-term potentiation (LTP) and LTD. We observed that STDP-induced LTP was either unaffected, blocked or flipped into LTD by the network burst, and that STDP-induced LTD was either saturated or flipped into LTP, depending on the relative timing of the network burst with respect to spike coincidences of the STDP event. We hypothesized that network bursts flip STDP-induced LTP to LTD by depleting resources needed for LTP and therefore developed a resource-dependent STDP learning rule. In a model neural network under the influence of the proposed resource-dependent STDP rule, we found that excitatory synaptic coupling was homeostatically regulated to produce power law distributed burst amplitudes reflecting self-organized criticality, a state that ensures optimal information coding.
Neutron Scattering in Hydrogenous Moderators, Studied by Time Dependent Reaction Rate Method
Energy Technology Data Exchange (ETDEWEB)
Larsson, L.G.; Moeller, E.; Purohit, S.N.
1966-03-15
The moderation and absorption of a neutron burst in water, poisoned with the non-1/v absorbers cadmium and gadolinium, has been followed on the time scale by multigroup calculations, using scattering kernels for the proton gas and the Nelkin model. The time dependent reaction rate curves for each absorber display clear differences for the two models, and the separation between the curves does not depend much on the absorber concentration. An experimental method for the measurement of infinite medium reaction rate curves in a limited geometry has been investigated. This method makes the measurement of the time dependent reaction rate generally useful for thermalization studies in a small geometry of a liquid hydrogenous moderator, provided that the experiment is coupled to programs for the calculation of scattering kernels and time dependent neutron spectra. Good agreement has been found between the reaction rate curve, measured with cadmium in water, and a calculated curve, where the Haywood kernel has been used.
Holographic Complexity for Time-Dependent Backgrounds
Momeni, Davood; Bahamonde, Sebastian; Myrzakulov, Ratbay
2016-01-01
In this paper, we will analyse the holographic complexity for time-dependent asymptotically $AdS$ geometries. We will first use a covariant zero mean curvature slicing of the time-dependent bulk geometries, and then use this co-dimension one spacelike slice of the bulk spacetime to define a co-dimension two minimal surface. The time-dependent holographic complexity will be defined using the volume enclosed by this minimal surface. This time-dependent holographic complexity will reduce to the usual holographic complexity for static geometries. We will analyse the time-dependence as a perturbation of the asymptotically $AdS$ geometries. Thus, we will obtain time-dependent asymptotically $AdS$ geometries, and we will calculate the holographic complexity for such a time-dependent geometries.
A 3D radiative transfer framework. IX. Time dependence
Jack, D.; Hauschildt, P. H.; Baron, E.
2012-10-01
Context. Time-dependent, 3D radiation transfer calculations are important for the modeling of a variety of objects, from supernovae and novae to simulations of stellar variability and activity. Furthermore, time-dependent calculations can be used to obtain a 3D radiative equilibrium model structure via relaxation in time. Aims: We extend our 3D radiative transfer framework to include direct time dependence of the radiation field; i.e., the ∂I/∂t terms are fully considered in the solution of radiative transfer problems. Methods: We build on the framework that we have described in previous papers in this series and develop a subvoxel method for the ∂I/∂t terms. Results: We test the implementation by comparing the 3D results to our well tested 1D time dependent radiative transfer code in spherical symmetry. A simple 3D test model is also presented. Conclusions: The 3D time dependent radiative transfer method is now included in our 3D RT framework and in PHOENIX/3D.
A 3D radiative transfer framework IX. Time dependence
Jack, D; Baron, E
2012-01-01
Context. Time-dependent, 3D radiation transfer calculations are important for the modeling of a variety of objects, from supernovae and novae to simulations of stellar variability and activity. Furthermore, time-dependent calculations can be used to obtain a 3D radiative equilibrium model structure via relaxation in time. Aims. We extend our 3D radiative transfer framework to include direct time dependence of the radiation field; i.e., the $\\partial I/ \\partial t$ terms are fully considered in the solution of radiative transfer problems. Methods. We build on the framework that we have described in previous papers in this series and develop a subvoxel method for the $\\partial I/\\partial t$ terms. Results. We test the implementation by comparing the 3D results to our well tested 1D time dependent radiative transfer code in spherical symmetry. A simple 3D test model is also presented. Conclusions. The 3D time dependent radiative transfer method is now included in our 3D RT framework and in PHOENIX/3D.
Competing risks and time-dependent covariates
DEFF Research Database (Denmark)
Cortese, Giuliana; Andersen, Per K
2010-01-01
Time-dependent covariates are frequently encountered in regression analysis for event history data and competing risks. They are often essential predictors, which cannot be substituted by time-fixed covariates. This study briefly recalls the different types of time-dependent covariates...
Bohr Hamiltonian with time-dependent potential
Naderi, L.; Hassanabadi, H.; Sobhani, H.
2016-04-01
In this paper, Bohr Hamiltonian has been studied with the time-dependent potential. Using the Lewis-Riesenfeld dynamical invariant method appropriate dynamical invariant for this Hamiltonian has been constructed and the exact time-dependent wave functions of such a system have been derived due to this dynamical invariant.
Robertson, Scott; Parentani, Renaud
2016-01-01
We study the spectrum and entanglement of phonons produced by temporal changes in homogeneous one-dimensional atomic condensates. To characterize the experimentally accessible changes, we first consider the dynamics of the condensate when varying the radial trapping frequency, separately studying two regimes: an adiabatic one and an oscillatory one. Working in momentum space, we then show that in situ measurements of the density-density correlation function can be used to assess the nonseparability of the phonon state after such changes. We also study time-of-flight (TOF) measurements, paying particular attention to the role played by the adiabaticity of opening the trap on the nonseparability of the final state of atoms. In both cases, we emphasize that commuting measurements can suffice to assess nonseparability. Some recent observations are analyzed, and we make proposals for future experiments.
Modelling and simulations of macroscopic multi-group pedestrian flow
Mahato, Naveen K; Tiwari, Sudarshan
2016-01-01
We consider a multi-group microscopic model for pedestrian flow describing the behaviour of large groups. It is based on an interacting particle system coupled to an eikonal equation. Hydrodynamic multi-group models are derived from the underlying particle system as well as scalar multi-group models. The eikonal equation is used to compute optimal paths for the pedestrians. Particle methods are used to solve the macroscopic equations. Numerical test cases are investigated and the models and, in particular, the resulting evacuation times are compared for a wide range of different parameters.
Multigroup Free-atom Doppler-broadening Approximation. Theory
Energy Technology Data Exchange (ETDEWEB)
Gray, Mark Girard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-11-06
Multigroup cross sections at a one target temperature can be Doppler-broadened to multigroup cross sections at a higher target temperature by matrix multiplication if the group structure suf- ficiently resolves the original temperature continuous energy cross section. Matrix elements are the higher temperature group weighted averages of the integral over the lower temperature group boundaries of the free-atom Doppler-broadening kernel. The results match theory for constant and 1/v multigroup cross sections at 618 lanl group structure resolution.
A test of time-dependent theories of stellar convection
Gastine, T
2011-01-01
Context: In Cepheids close to the red edge of the classical instability strip, a coupling occurs between the acoustic oscillations and the convective motions close to the surface.The best topical models that account for this coupling rely on 1-D time-dependent convection (TDC) formulations. However, their intrinsic weakness comes from the large number of unconstrained free parameters entering in the description of turbulent convection. Aims: We compare two widely used TDC models with the first two-dimensional nonlinear direct numerical simulations (DNS) of the convection-pulsation coupling in which the acoustic oscillations are self-sustained by the kappa-mechanism. Methods: The free parameters appearing in the Stellingwerf and Kuhfuss TDC recipes are constrained using a chi2-test with the time-dependent convective flux that evolves in nonlinear simulations of highly-compressible convection with kappa-mechanism. Results: This work emphasises some inherent limits of TDC models, that is, the temporal variabilit...
Efficient auxiliary-mode approach for time-dependent nanoelectronics
Popescu, Bogdan Stefan; Croy, Alexander
2016-09-01
A new scheme for numerically solving the equations arising in the time-dependent non-equilibrium Green's function formalism is developed. It is based on an auxiliary-mode expansion of the self-energies which convert the complicated set of integro-differential equations into a set of ordinary differential equations. In the new scheme all auxiliary matrices are replaced by vectors or scalars. This drastically reduces the computational effort and memory requirements of the method, rendering it applicable to topical problems in electron quantum optics and molecular electronics. As an illustrative example we consider the dynamics of a Leviton wave-packet in a 1D wire.
Time-Dependent Transport in Nanoscale Devices
Institute of Scientific and Technical Information of China (English)
CHEN Zhi-Dong; ZHANG Jin-Yu; YU Zhi-Ping
2009-01-01
A method for simulating ballistic time-dependent device transport,which solves the time-dependent SchrSdinger equation using the finite difference time domain (FDTD) method together with Poisson's equation,is described in detail The effective mass SchrSdinger equation is solved. The continuous energy spectrum of the system is discretized using adaptive mesh,resulting in energy levels that sample the density-of-states.By calculating time evolution of wavefunctions at sampled energies,time-dependent transport characteristics such as current and charge density distributions are obtained.Simulation results in a uanowire and a coaxially gated carbon nanotube field-effect transistor (CNTFET) are presented.Transient effects,e.g.,finite rising time,are investigated in these devices.
Investigations of Low Temperature Time Dependent Cracking
Energy Technology Data Exchange (ETDEWEB)
Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J
2002-09-30
The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.
Differential Geometry of Time-Dependent Mechanics
Giachetta, G; Sardanashvily, G
1997-01-01
The usual formulations of time-dependent mechanics start from a given splitting $Y=R\\times M$ of the coordinate bundle $Y\\to R$. From physical viewpoint, this splitting means that a reference frame has been chosen. Obviously, such a splitting is broken under reference frame transformations and time-dependent canonical transformations. Our goal is to formulate time-dependent mechanics in gauge-invariant form, i.e., independently of any reference frame. The main ingredient in this formulation is a connection on the bundle $Y\\to R$ which describes an arbitrary reference frame. We emphasize the following peculiarities of this approach to time-dependent mechanics. A phase space does not admit any canonical contact or presymplectic structure which would be preserved under reference frame transformations, whereas the canonical Poisson structure is degenerate. A Hamiltonian fails to be a function on a phase space. In particular, it can not participate in a Poisson bracket so that the evolution equation is not reduced...
Measurement of the Time Dependence of Neutron Slowing-Down and Therma in Heavy Water
Energy Technology Data Exchange (ETDEWEB)
Moeller, E.
1966-03-15
The behaviour of neutrons during their slowing-down and thermalization in heavy water has been followed on the time scale by measurements of the time-dependent rate of reaction between the flux and the three spectrum indicators indium, cadmium and gadolinium. The space dependence of the reaction rate curves has also been studied. The time-dependent density at 1.46 eV is well reproduced by a function, given by von Dardel, and a time for the maximum density of 7.1 {+-} 0.3 {mu}s has been obtained for this energy in deuterium gas in agreement with the theoretical value of 7.2 {mu}s. The spatial variation of this time is in accord with the calculations by Claesson. The slowing- down time to 0.2 eV has been found to be 16.3 {+-}2.4 {mu}s. The approach to the equilibrium spectrum takes place with a time constant of 33 {+-}4 {mu}s, and the equilibrium has been established after about 200 {mu}s. Comparison of the measured curves for cadmium and gadolinium with multigroup calculations of the time-dependent flux and reaction rate show the superiority of the scattering models for heavy water of Butler and of Brown and St. John over the mass 2 gas model. The experiment has been supplemented with Monte Carlo calculations of the slowing down time.
Time-Dependent Erosion of Ion Optics
Wirz, Richard E.; Anderson, John R.; Katz, Ira; Goebel, Dan M.
2008-01-01
The accurate prediction of thruster life requires time-dependent erosion estimates for the ion optics assembly. Such information is critical to end-of-life mechanisms such as electron backstreaming. CEX2D was recently modified to handle time-dependent erosion, double ions, and multiple throttle conditions in a single run. The modified code is called "CEX2D-t". Comparisons of CEX2D-t results with LDT and ELT post-tests results show good agreement for both screen and accel grid erosion including important erosion features such as chamfering of the downstream end of the accel grid and reduced rate of accel grid aperture enlargement with time.
Time-dependent species sensitivity distributions.
Fox, David R; Billoir, Elise
2013-02-01
Time is a central component of toxicity assessments. However, current ecotoxicological practice marginalizes time in concentration-response (C-R) modeling and species sensitivity distribution (SSD) analyses. For C-R models, time is invariably fixed, and toxicity measures are estimated from a function fitted to the data at that time. The estimated toxicity measures are used as inputs to the SSD modeling phase, which similarly avoids explicit recognition of the temporal component. The present study extends some commonly employed probability models for SSDs to derive theoretical results that characterize the time-dependent nature of hazardous concentration (HCx) values. The authors' results show that even from very simple assumptions, more complex patterns in the SSD time dependency can be revealed.
Transformation of time dependence to linear algebra
Menšík, Miroslav
2005-10-01
Reduced density matrix and memory function in the Nakajima-Zwanzig equation are expanded in properly chosen basis of special functions. This trick completely transforms time dependence to linear algebra. Then, the master equation for memory function is constructed and expanded in the same basis functions. For the model of a simple harmonic oscillator it is shown that this trick introduces infinite partial summation of the memory function in the system-bath interaction.
Time-dependent problems and difference methods
Gustafsson, Bertil; Oliger, Joseph
2013-01-01
Praise for the First Edition "". . . fills a considerable gap in the numerical analysis literature by providing a self-contained treatment . . . this is an important work written in a clear style . . . warmly recommended to any graduate student or researcher in the field of the numerical solution of partial differential equations."" -SIAM Review Time-Dependent Problems and Difference Methods, Second Edition continues to provide guidance for the analysis of difference methods for computing approximate solutions to partial differential equations for time-de
Coasting cosmologies with time dependent cosmological constant
Pimentel, L O; Pimentel, Luis O.
1999-01-01
The effect of a time dependent cosmological constant is considered in a family of scalar tensor theories. Friedmann-Robertson-Walker cosmological models for vacumm and perfect fluid matter are found. They have a linear expansion factor, the so called coasting cosmology, the gravitational "constant" decreace inversely with time; this model satisfy the Dirac hipotesis. The cosmological "constant" decreace inversely with the square of time, therefore we can have a very small value for it at present time.
Dissipative time-dependent quantum transport theory.
Zhang, Yu; Yam, Chi Yung; Chen, GuanHua
2013-04-28
A dissipative time-dependent quantum transport theory is developed to treat the transient current through molecular or nanoscopic devices in presence of electron-phonon interaction. The dissipation via phonon is taken into account by introducing a self-energy for the electron-phonon coupling in addition to the self-energy caused by the electrodes. Based on this, a numerical method is proposed. For practical implementation, the lowest order expansion is employed for the weak electron-phonon coupling case and the wide-band limit approximation is adopted for device and electrodes coupling. The corresponding hierarchical equation of motion is derived, which leads to an efficient and accurate time-dependent treatment of inelastic effect on transport for the weak electron-phonon interaction. The resulting method is applied to a one-level model system and a gold wire described by tight-binding model to demonstrate its validity and the importance of electron-phonon interaction for the quantum transport. As it is based on the effective single-electron model, the method can be readily extended to time-dependent density functional theory.
The Suppression of Energy Discretization Errors in Multigroup Transport Calculations
Energy Technology Data Exchange (ETDEWEB)
Larsen, Edward [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences
2013-06-17
The Objective of this project is to develop, implement, and test new deterministric methods to solve, as efficiently as possible, multigroup neutron transport problems having an extremely large number of groups. Our approach was to (i) use the standard CMFD method to "coarsen" the space-angle grid, yielding a multigroup diffusion equation, and (ii) use a new multigrid-in-space-and-energy technique to efficiently solve the multigroup diffusion problem. The overall strategy of (i) how to coarsen the spatial an energy grids, and (ii) how to navigate through the various grids, has the goal of minimizing the overall computational effort. This approach yields not only the fine-grid solution, but also coarse-group flux-weighted cross sections that can be used for other related problems.
Multigroup Moderation Test in Generalized Structured Component Analysis
Directory of Open Access Journals (Sweden)
Angga Dwi Mulyanto
2016-05-01
Full Text Available Generalized Structured Component Analysis (GSCA is an alternative method in structural modeling using alternating least squares. GSCA can be used for the complex analysis including multigroup. GSCA can be run with a free software called GeSCA, but in GeSCA there is no multigroup moderation test to compare the effect between groups. In this research we propose to use the T test in PLS for testing moderation Multigroup on GSCA. T test only requires sample size, estimate path coefficient, and standard error of each group that are already available on the output of GeSCA and the formula is simple so the user does not need a long time for analysis.
Time-dependent Dyson orbital theory.
Gritsenko, O V; Baerends, E J
2016-08-21
Although time-dependent density functional theory (TDDFT) has become the tool of choice for real-time propagation of the electron density ρ(N)(t) of N-electron systems, it also encounters problems in this application. The first problem is the neglect of memory effects stemming from the, in TDDFT virtually unavoidable, adiabatic approximation, the second problem is the reliable evaluation of the probabilities P(n)(t) of multiple photoinduced ionization, while the third problem (which TDDFT shares with other approaches) is the reliable description of continuum states of the electrons ejected in the process of ionization. In this paper time-dependent Dyson orbital theory (TDDOT) is proposed. Exact TDDOT equations of motion (EOMs) for time-dependent Dyson orbitals are derived, which are linear differential equations with just static, feasible potentials of the electron-electron interaction. No adiabatic approximation is used, which formally resolves the first TDDFT problem. TDDOT offers formally exact expressions for the complete evolution in time of the wavefunction of the outgoing electron. This leads to the correlated probability of single ionization P(1)(t) as well as the probabilities of no ionization (P(0)(t)) and multiple ionization of n electrons, P(n)(t), which formally solves the second problem of TDDFT. For two-electron systems a proper description of the required continuum states appears to be rather straightforward, and both P(1)(t) and P(2)(t) can be calculated. Because of the exact formulation, TDDOT is expected to reproduce a notorious memory effect, the "knee structure" of the non-sequential double ionization of the He atom.
A collisional extension of time-dependent Hartree-Fock
Lacombe, L.; Reinhard, P.-G.; Dinh, P. M.; Suraud, E.
2016-12-01
We propose a collisional extension of time-dependent mean-field theories on the basis of a recently proposed stochastic extension of mean-field dynamics (stochastic time-dependent Hartree-Fock, STDHF). The latter theory is unfortunately too involved to envision practical applications in realistic systems in the near future and is thus bound to model systems. It is also hard to explore moderate to low energies with STDHF, because of vanishing transition probabilities that are impossible to sample properly. For such moderately excited situations covering small fluctuations, we compactify sampling by employing the same average mean field for all STDHF trajectories. The new approach, coined average STDHF (ASTDHF), ignores the fluctuations of the mean field but still accounts correctly for the collisional correlations responsible for dissipative features on top of mean-field dynamics. We detail the main features of the new approach in relation to existing equations, in particular quantum kinetic theories. The new theory is directly connected to STDHF, both formally and practically. We thus discuss in detail how the two approaches are related to each other. We apply the new scheme to illustrative examples taking as benchmark STDHF dynamics in 1D. ASTDHF provides results that are in remarkable agreement with the more elaborate STDHF. It makes it a promising approach to deal with dissipative dynamics in finite quantum systems, because of its moderate cost allowing applications in realistic systems and the possibility of exploring any excitation energy range where collisional correlations are expected to play a role.
Solar Magnetic Flux Tube Simulations with Time-Dependent Ionization
Fawzy, Diaa E; Rammacher, Wolfgang
2012-01-01
In the present work we expand the study of time-dependent ionization previously identified to be of pivotal importance for acoustic waves in solar magnetic flux tube simulations. We focus on longitudinal tube waves (LTW) known to be an important heating agent of solar magnetic regions. Our models also consider new results of wave energy generation as well as an updated determination of the mixing length of convection now identified as 1.8 scale heights in the upper solar convective layers. We present 1-D wave simulations for the solar chromosphere by studying tubes of different spreading as function of height aimed at representing tubes in environments of different magnetic filling factors. Multi-level radiative transfer has been applied to correctly represent the total chromospheric emission function. The effects of time-dependent ionization are significant in all models studied. They are most pronounced behind strong shocks and in low density regions, i.e., the middle and high chromosphere. Concerning our m...
Time-dependent secular evolution in galaxies
Weinberg, M D
2004-01-01
Lynden-Bell & Kalnajs (1972) presented a useful formula for computing the long-range torque between spiral arms and the disk at large. The derivation uses second-order perturbation theory and assumes that the perturbation slowly grows over a very long time: the time-asymptotic limit. This formula has been widely used to predict the angular momentum transport between spiral arms and stellar bars between disks and dark-matter halos. However, this paper shows that the LBK time-asymptotic limit is not appropriate because the characteristic evolution time for galaxies is too close to the relevant dynamical times. We demonstrate that transients, not present in the time-asymptotic formula, can play a major role in the evolution for realistic astronomical time scales. A generalisation for arbitrary time dependence is presented and illustrated by the bar--halo and satellite--halo interaction. The natural time dependence in bar-driven halo evolution causes quantitative differences in the overall torque and qualitat...
The time-dependent Gutzwiller approximation
Fabrizio, Michele
2015-03-01
The time-dependent Gutzwiller Approximation (t-GA) is shown to be capable of tracking the off-equilibrium evolution both of coherent quasiparticles and of incoherent Hubbard bands. The method is used to demonstrate that the sharp dynamical crossover observed by time-dependent DMFT in the quench-dynamics of a half-filled Hubbard model can be identified within the t-GA as a genuine dynamical transition separating two distinct physical phases. This result, strictly variational for lattices of infinite coordination number, is intriguing as it actually questions the occurrence of thermalization. Next, we shall present how t-GA works in a multi-band model for V2O3 that displays a first-order Mott transition. We shall show that a physically accessible excitation pathway is able to collapse the Mott gap down and drive off-equilibrium the insulator into a metastable metal phase. Work supported by the European Union, Seventh Framework Programme, under the project GO FAST, Grant Agreement No. 280555.
Constitutive model with time-dependent deformations
DEFF Research Database (Denmark)
Krogsbøll, Anette
1998-01-01
are common in time as well as size. This problem is adressed by means of a new constitutive model for soils. It is able to describe the behavior of soils at different deformation rates. The model defines time-dependent and stress-related deformations separately. They are related to each other and they occur......In many geological and Engineering problems it is necessary to transform information from one scale to another. Data collected at laboratory scale are often used to evaluate field problems on a much larger scale. This is certainly true for geological problems where extreme scale differences...... simultanelously. The model is based on concepts from elasticity and viscoplasticity theories. In addition to Hooke's law for the elastic behavior, the framework for the viscoplastic behavior consists, in the general case (two-dimensional or three-dimensional), of a yield surface, an associated flow rule...
Time-dependent Cooling in Photoionized Plasma
Gnat, Orly
2017-02-01
I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts (z = 0 ‑ 3), for a range of temperatures (108–104 K), densities (10‑7–103 cm‑3), and metallicities (10‑3–2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibrium (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).
Time dependent friction in a free gas
Fanelli, Cristiano; Sisti, Francesco; Stagno, Gabriele V.
2016-03-01
We consider a body moving in a perfect gas, described by the mean-field approximation and interacting elastically with the body, we study the friction exerted by the gas on the body fixed at constant velocities. The time evolution of the body in this setting was studied in Caprino et al. [Math. Phys. 264, 167-189 (2006)], Caprino et al. [Math. Models Methods Appl. Sci. 17, 1369-1403 (2007)], and Cavallaro [Rend. Mat. Appl. 27, 123-145 (2007)] for object with simple shape; the first study where a simple kind of concavity was considered was in Sisti and Ricciuti [SIAM J. Math. Anal. 46, 3759-3611 (2014)], showing new features in the dynamic but not in the friction term. The case of more general shape of the body was left out for further difficulties, and we believe indeed that there are actually non-trivial issues to be faced for these more general cases. To show this and in the spirit of getting a more realistic perspective in the study of friction problems, in this paper, we focused our attention on the friction term itself, studying its behavior on a body with a more general kind of concavity and fixed at constant velocities. We derive the expression of the friction term for constant velocities, we show how it is time dependent, and we give its exact estimate in time. Finally, we use this result to show the absence of a constant velocity in the actual dynamic of such a body.
Time-dependent correlations in electricity markets
Energy Technology Data Exchange (ETDEWEB)
Alvarez-Ramirez, Jose; Escarela-Perez, Rafael [Departamento de Energia, Universidad Autonoma Metropolitana, Mexico DF, 09340 (Mexico)
2010-03-15
In the last years, many electricity markets were subjected to deregulated operation where prices are set by the action of market participants. In this form, producers and consumers rely on demand and price forecasts to decide their bidding strategies, allocate assets, negotiate bilateral contracts, hedge risks, and plan facility investments. A basic feature of efficient market hypothesis is the absence of correlations between price increments over any time scale leading to random walk-type behavior of prices, so arbitrage is not possible. However, recent studies have suggested that this is not the case and correlations are present in the behavior of diverse electricity markets. In this paper, a temporal quantification of electricity market correlations is made by means of detrended fluctuation and Allan analyses. The approach is applied to two Canadian electricity markets, Ontario and Alberta. The results show the existence of correlations in both demand and prices, exhibiting complex time-dependent behavior with lower correlations in winter while higher in summer. Relatively steady annual cycles in demand but unstable cycles in prices are detected. On the other hand, the more significant nonlinear effects (measured in terms of a multifractality index) are found for winter months, while the converse behavior is displayed during the summer period. In terms of forecasting models, our results suggest that nonlinear recursive models (e.g., feedback NNs) should be used for accurate day-ahead price estimation. In contrast, linear models can suffice for demand forecasting purposes. (author)
Time-dependent Effects in Photospheric-Phase Type II Supernova Spectra
Dessart, Luc
2007-01-01
Spectroscopic modeling of Type II supernovae (SNe) generally assumes steady-state. Following the recent suggestion of Utrobin & Chugai, but using the 1D non-LTE line-blanketed model atmosphere code CMFGEN, we investigate the effects of including time-dependent terms that appear in the statistical and radiative equilibrium equations. We base our discussion on the ejecta properties and the spectroscopic signatures obtained from time-dependent simulations, investigating different ejecta configurations, and covering their evolution from one day to six weeks after shock breakout. Compared to equivalent steady-state models, our time-dependent models produce SN ejecta that are systematically over-ionized, affecting helium at one week after explosion, but ultimately affecting all ions after a few weeks. While the continuum remains essentially unchanged, time-dependence effects on observed spectral lines are large. At the recombination epoch, HI lines and NaID are considerably stronger and broader than in equivale...
Studies of Spuriously Time-dependent Resonances in Time-dependent Density Functional Theory
Luo, Kai; Maitra, Neepa T
2016-01-01
Adiabatic approximations in time-dependent density functional theory (TDDFT) will in general yield unphysical time-dependent shifts in the resonance positions of a system driven far from its ground-state. This spurious time-dependence is rationalized in [J. I. Fuks, K. Luo, E. D. Sandoval and N. T. Maitra, Phys. Rev. Lett. {\\bf 114}, 183002 (2015)] in terms of the violation of an exact condition by the non-equilibrium exchange-correlation kernel of TDDFT. Here we give details on the derivation and discuss reformulations of the exact condition that apply in special cases. In its most general form, the condition states that when a system is left in an arbitrary state, in the absence of time-dependent external fields nor ionic motion, the TDDFT resonance position for a given transition is independent of the state. Special cases include the invariance of TDDFT resonances computed with respect to any reference interacting stationary state of a fixed potential, and with respect to any choice of appropriate stationa...
Time-dependent constrained Hamiltonian systems and Dirac brackets
Energy Technology Data Exchange (ETDEWEB)
Leon, Manuel de [Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Madrid (Spain); Marrero, Juan C. [Departamento de Matematica Fundamental, Facultad de Matematicas, Universidad de La Laguna, La Laguna, Tenerife, Canary Islands (Spain); Martin de Diego, David [Departamento de Economia Aplicada Cuantitativa, Facultad de Ciencias Economicas y Empresariales, UNED, Madrid (Spain)
1996-11-07
In this paper the canonical Dirac formalism for time-dependent constrained Hamiltonian systems is globalized. A time-dependent Dirac bracket which reduces to the usual one for time-independent systems is introduced. (author)
Time dependent deformation of Kilauea Volcano, Hawaii
Montgomery-Brown, Emily Kvietka Desmarais
to a decollement structure 8 km under the south flank, and the locations of the microearthquakes suggest that both occur on the same structure. In 2007, Episode 56 of the Pu'u 'O'o-Kupianaha eruption occurred. This episode was exciting both because it was the largest intrusion in the last decade, and because it occurred concurrently with a flank slow-slip event. The intrusion started on Father's day (June 17th), 2007 with increased seismicity and abrupt tilts at the summit and rift zones. Quasi-static models of the total deformation determined from GPS, tilt, and InSAR indicate that the intrusion occurred on two en echelon dike segments in the upper East Rift Zone along with deformation consistent with slow-slip in the same areas of previous events. The ˜ 2 m maximum opening occurred on the eastern segment near Makaopui crater. Unlike previous intrusions in 1997, 1999, and 2000, the dike model was not sufficient to explain deformation on the western flank. Additionally, a coastal tiltmeter installed in anticipation of a slow-slip event recorded tilts consistent with those observed during the 2005 slow-slip event. These observations led to the conclusion that a concurrent slow-slip event occurred. Geodetic models indicate a similar amount of decollement slip occurred as in previous slow-slip events. Sub-daily GPS positions were used to study the spatio-temporal distribution of the dike intrusion. The time-dependent intrusion model shows that the intrusion began on the western en echelon segment before jumping to the eastern segment, which accumulated the majority of the 2 m of opening. Sub-daily GPS positions limit the number of stations available since there are very few continuous stations north of the East Rift Zone, where coverage is critical for separating the intrusion from the slow-slip. However, an ENVISAT interferogram at 08:22 on June 18, 2007 provides additional spatial coverage of deformation up to that point. Combining this image with the GPS and tilt
Energy Technology Data Exchange (ETDEWEB)
Verley, Jason C.; Axness, Carl L.; Hembree, Charles Edward; Keiter, Eric Richard; Kerr, Bert (New Mexico Institute of Mining and Technology, Socorro, NM)
2012-04-01
Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools such as SPICE [1] can be used to analyze these threats, and typically rely on compact models for individual electrical components such as transistors and diodes. Compact models consist of a handful of differential and/or algebraic equations, and are derived by making simplifying assumptions to any of the many semiconductor transport equations. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of qualitative approximation, rather than mathematically correct solutions to the ambipolar diffusion equation. A practical consequence of this inaccuracy is that a given model calibration is trustworthy over only a narrow range of operating conditions. This report describes work to produce improved compact models for photocurrent. Specifically, an analytic model is developed for epitaxial diode structures that have a highly doped subcollector. The analytic model is compared with both numerical TCAD calculations, as well as the compact model described in reference [2]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the compact model from reference [2].
MUXS: a code to generate multigroup cross sections for sputtering calculations
Energy Technology Data Exchange (ETDEWEB)
Hoffman, T.J.; Robinson, M.T.; Dodds, H.L. Jr.
1982-10-01
This report documents MUXS, a computer code to generate multigroup cross sections for charged particle transport problems. Cross sections generated by MUXS can be used in many multigroup transport codes, with minor modifications to these codes, to calculate sputtering yields, reflection coefficients, penetration distances, etc.
Introduction to numerical methods for time dependent differential equations
Kreiss, Heinz-Otto
2014-01-01
Introduces both the fundamentals of time dependent differential equations and their numerical solutions Introduction to Numerical Methods for Time Dependent Differential Equations delves into the underlying mathematical theory needed to solve time dependent differential equations numerically. Written as a self-contained introduction, the book is divided into two parts to emphasize both ordinary differential equations (ODEs) and partial differential equations (PDEs). Beginning with ODEs and their approximations, the authors provide a crucial presentation of fundamental notions, such as the t
Random Time Dependent Resistance Analysis on Reinforced Concrete Structures
Institute of Scientific and Technical Information of China (English)
GUAN Chang-sheng; WU Ling
2002-01-01
The analysis method on random time dependence of reinforced concrete material is introduced,the effect mechanism on reinforced concrete are discussed, and the random time dependence resistance of reinforced concrete is studied. Furthermore, the corrosion of steel bar in reinforced concrete structures is analyzed. A practical statistical method of evaluating the random time dependent resistance, which includes material, structural size and calculation influence, is also established. In addition, an example of predicting random time dependent resistance of reinforced concrete structural element is given.
Multigroup Equivalence Analysis for High-Dimensional Expression Data
Yang, Celeste; Bartolucci, Alfred A.; Cui, Xiangqin
2015-01-01
Hypothesis tests of equivalence are typically known for their application in bioequivalence studies and acceptance sampling. Their application to gene expression data, in particular high-dimensional gene expression data, has only recently been studied. In this paper, we examine how two multigroup equivalence tests, the F-test and the range test, perform when applied to microarray expression data. We adapted these tests to a well-known equivalence criterion, the difference ratio. Our simulation results showed that both tests can achieve moderate power while controlling the type I error at nominal level for typical expression microarray studies with the benefit of easy-to-interpret equivalence limits. For the range of parameters simulated in this paper, the F-test is more powerful than the range test. However, for comparing three groups, their powers are similar. Finally, the two multigroup tests were applied to a prostate cancer microarray dataset to identify genes whose expression follows a prespecified trajectory across five prostate cancer stages. PMID:26628859
Multigroup Equivalence Analysis for High-Dimensional Expression Data.
Yang, Celeste; Bartolucci, Alfred A; Cui, Xiangqin
2015-01-01
Hypothesis tests of equivalence are typically known for their application in bioequivalence studies and acceptance sampling. Their application to gene expression data, in particular high-dimensional gene expression data, has only recently been studied. In this paper, we examine how two multigroup equivalence tests, the F-test and the range test, perform when applied to microarray expression data. We adapted these tests to a well-known equivalence criterion, the difference ratio. Our simulation results showed that both tests can achieve moderate power while controlling the type I error at nominal level for typical expression microarray studies with the benefit of easy-to-interpret equivalence limits. For the range of parameters simulated in this paper, the F-test is more powerful than the range test. However, for comparing three groups, their powers are similar. Finally, the two multigroup tests were applied to a prostate cancer microarray dataset to identify genes whose expression follows a prespecified trajectory across five prostate cancer stages.
Hoffman, Adam J.; Lee, John C.
2016-02-01
A new time-dependent Method of Characteristics (MOC) formulation for nuclear reactor kinetics was developed utilizing angular flux time-derivative propagation. This method avoids the requirement of storing the angular flux at previous points in time to represent a discretized time derivative; instead, an equation for the angular flux time derivative along 1D spatial characteristics is derived and solved concurrently with the 1D transport characteristic equation. This approach allows the angular flux time derivative to be recast principally in terms of the neutron source time derivatives, which are approximated to high-order accuracy using the backward differentiation formula (BDF). This approach, called Source Derivative Propagation (SDP), drastically reduces the memory requirements of time-dependent MOC relative to methods that require storing the angular flux. An SDP method was developed for 2D and 3D applications and implemented in the computer code DeCART in 2D. DeCART was used to model two reactor transient benchmarks: a modified TWIGL problem and a C5G7 transient. The SDP method accurately and efficiently replicated the solution of the conventional time-dependent MOC method using two orders of magnitude less memory.
Multigroup covariance matrices for fast-reactor studies
Energy Technology Data Exchange (ETDEWEB)
Smith, J.D. III; Broadhead, B.L.
1981-04-01
This report presents the multigroup covariance matrices based on the ENDF/B-V nuclear data evaluations. The materials and reactions have been chosen according to the specifications of ORNL-5517. Several cross section covariances, other than those specified by that report, are included due to the derived nature of the uncertainty files in ENDF/B-V. The materials represented are Ni, Cr, /sup 16/O, /sup 12/C, Fe, Na, /sup 235/U, /sup 238/U, /sup 239/Pu, /sup 240/Pu, /sup 241/Pu, and /sup 10/B (present due to its correlation to /sup 238/U). The data have been originally processed into a 52-group energy structure by PUFF-II and subsequently collapsed to smaller subgroup strutures. The results are illustrated in 52-group correlation matrix plots and tabulated into thirteen groups for convenience.
Multi-group dynamic quantum secret sharing with single photons
Energy Technology Data Exchange (ETDEWEB)
Liu, Hongwei [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Ma, Haiqiang, E-mail: hqma@bupt.edu.cn [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Wei, Kejin [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Yang, Xiuqing [School of Science, Beijing Jiaotong University, Beijing 100044 (China); Qu, Wenxiu; Dou, Tianqi; Chen, Yitian; Li, Ruixue; Zhu, Wu [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)
2016-07-15
In this letter, we propose a novel scheme for the realization of single-photon dynamic quantum secret sharing between a boss and three dynamic agent groups. In our system, the boss can not only choose one of these three groups to share the secret with, but also can share two sets of independent keys with two groups without redistribution. Furthermore, the security of communication is enhanced by using a control mode. Compared with previous schemes, our scheme is more flexible and will contribute to a practical application. - Highlights: • A multi-group dynamic quantum secret sharing with single photons scheme is proposed. • Any one of the groups can be chosen to share secret through controlling the polarization of photons. • Two sets of keys can be shared simultaneously without redistribution.
Jet-Ricci Geometry of Time-Dependent Human Biomechanics
Ivancevic, Tijana T
2009-01-01
We propose the time-dependent generalization of an `ordinary' autonomous human biomechanics, in which total mechanical + biochemical energy is not conserved. We introduce a general framework for time-dependent biomechanics in terms of jet manifolds derived from the extended musculo-skeletal configuration manifold. The corresponding Riemannian geometrical evolution follows the Ricci flow diffusion. In particular, we show that the exponential-like decay of total biomechanical energy (due to exhaustion of biochemical resources) is closely related to the Ricci flow on the biomechanical configuration manifold. Keywords: Time-dependent biomechanics, extended configuration manifold, configuration bundle, jet manifolds, Ricci flow diffusion
Skinner-Rusk approach to time-dependent mechanics
Cortés, Jorge; Martínez, Sonia; Cantrijn, Frans
2002-01-01
The geometric approach to autonomous classical mechanical systems in terms of a canonical first-order system on the Whitney sum of the tangent and cotangent bundle, developed by Skinner and Rusk, is extended to the time-dependent framework.
Time-Dependent Modulation of Cosmic Rays in the Heliosphere
Manuel, Rex; Potgieter, Marius
2013-01-01
The time-dependent modulation of galactic cosmic rays in the heliosphere is studied by computing intensities using a time-dependent modulation model. By introducing recent theoretical advances in the transport coefficients in the model, computed intensities are compared with Voyager 1, International Monitoring Platform (IMP) 8, and Ulysses proton observations in search of compatibility. The effect of different modulation parameters on computed intensities is also illustrated. It is shown that this approach produces, on a global scale, realistic cosmic-ray proton intensities along the Voyager 1 spacecraft trajectory and at Earth upto ~2004, whereafter the computed intensities recovers much slower towards solar minimum than observed in the inner heliosphere. A modified time dependence in the diffusion coefficients is proposed to improve compatibility with the observations at Earth after ~2004. This modified time dependence led to an improved compatibility between computed intensities and the observations along ...
Entanglement Entropy for time dependent two dimensional holographic superconductor
Mazhari, N S; Myrzakulov, Kairat; Myrzakulov, R
2016-01-01
We studied entanglement entropy for a time dependent two dimensional holographic superconductor. We showed that the conserved charge of the system plays the role of the critical parameter to have condensation.
Time-dependent rheological behaviour of bacterial cellulose hydrogel.
Gao, Xing; Shi, Zhijun; Kuśmierczyk, Piotr; Liu, Changqing; Yang, Guang; Sevostianov, Igor; Silberschmidt, Vadim V
2016-01-01
This work focuses on time-dependent rheological behaviour of bacterial cellulose (BC) hydrogel. Due to its ideal biocompatibility, BC hydrogel could be employed in biomedical applications. Considering the complexity of loading conditions in human body environment, time-dependent behaviour under relevant conditions should be understood. BC specimens are produced by Gluconacetobacter xylinus ATCC 53582 at static-culture conditions. Time-dependent behaviour of specimens at several stress levels is experimentally determined by uniaxial tensile creep tests. We use fraction-exponential operators to model the rheological behaviour. Such a representation allows combination of good accuracy in analytical description of viscoelastic behaviour of real materials and simplicity in solving boundary value problems. The obtained material parameters allow us to identify time-dependent behaviour of BC hydrogel at high stress level with sufficient accuracy.
One Dimensional Time-Dependent Tunnelling of Excitons
Kilcullen, Patrick; Salayka-Ladouceur, Logan; Malmgren, Kevin; Reid, Matthew; Shegelski, Mark R. A.
2017-03-01
We study the time-dependent tunnelling of excitons in one dimension using numerical integration based on the Crank-Nicholson method. A complete development of the time-dependent simulator is provided. External barriers studied include single and double delta barriers. We find that the appearance of transmission resonances depends strongly on the dielectric constant, relative effective masses, and initial spatial spread of the wavefunction. A discussion regarding applications to realistic systems is provided.
Multi-configuration time-dependent density-functional theory based on range separation
DEFF Research Database (Denmark)
Fromager, E.; Knecht, S.; Jensen, Hans Jørgen Aagaard
2013-01-01
Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration- Self-Consistent Field (MCSCF) treatment with an adiabatic short...... (srGGA) approximations. As expected, when modeling long-range interactions with the MCSCF model instead of the adiabatic Buijse-Baerends density-matrix functional as recently proposed by Pernal [J. Chem. Phys. 136, 184105 (2012)10.1063/1.4712019], the description of both the 1D doubly-excited state...
Energy Technology Data Exchange (ETDEWEB)
Coste-Delclaux, M
2006-03-15
This document describes the improvements carried out for modelling the self-shielding phenomenon in the multigroup transport code APOLLO2. They concern the space and energy treatment of the slowing-down equation, the setting up of quadrature formulas to calculate reaction rates, the setting-up of a method that treats directly a resonant mixture and the development of a sub-group method. We validate these improvements either in an elementary or in a global way. Now, we obtain, more accurate multigroup reaction rates and we are able to carry out a reference self-shielding calculation on a very fine multigroup mesh. To end, we draw a conclusion and give some prospects on the remaining work. (author)
Jet Methods in Time-Dependent Lagrangian Biomechanics
Ivancevic, Tijana T
2009-01-01
In this paper we propose the time-dependent generalization of an `ordinary' autonomous human biomechanics, in which total mechanical + biochemical energy is not conserved. We introduce a general framework for time-dependent biomechanics in terms of jet manifolds associated to the extended musculo-skeletal configuration manifold, called the configuration bundle. We start with an ordinary configuration manifold of human body motion, given as a set of its all active degrees of freedom (DOF) for a particular movement. This is a Riemannian manifold with a material metric tensor given by the total mass-inertia matrix of the human body segments. This is the base manifold for standard autonomous biomechanics. To make its time-dependent generalization, we need to extend it with a real time axis. By this extension, using techniques from fibre bundles, we defined the biomechanical configuration bundle. On the biomechanical bundle we define vector-fields, differential forms and affine connections, as well as the associat...
Time-dependent density functional theory for quantum transport.
Zheng, Xiao; Chen, GuanHua; Mo, Yan; Koo, SiuKong; Tian, Heng; Yam, ChiYung; Yan, YiJing
2010-09-21
Based on our earlier works [X. Zheng et al., Phys. Rev. B 75, 195127 (2007); J. S. Jin et al., J. Chem. Phys. 128, 234703 (2008)], we propose a rigorous and numerically convenient approach to simulate time-dependent quantum transport from first-principles. The proposed approach combines time-dependent density functional theory with quantum dissipation theory, and results in a useful tool for studying transient dynamics of electronic systems. Within the proposed exact theoretical framework, we construct a number of practical schemes for simulating realistic systems such as nanoscopic electronic devices. Computational cost of each scheme is analyzed, with the expected level of accuracy discussed. As a demonstration, a simulation based on the adiabatic wide-band limit approximation scheme is carried out to characterize the transient current response of a carbon nanotube based electronic device under time-dependent external voltages.
Eigenstates of the time-dependent density-matrix theory
Energy Technology Data Exchange (ETDEWEB)
Tohyama, M. [Kyorin University School of Medicine, 181-8611, Mitaka, Tokyo (Japan); Schuck, P. [Institut de Physique Nucleaire, IN2P3-CNRS, Universite Paris-Sud, F-91406, Orsay Cedex (France)
2004-02-01
An extended time-dependent Hartree-Fock theory, known as the time-dependent density-matrix theory (TDDM), is solved as a time-independent eigenvalue problem for low-lying 2{sup +} states in {sup 24}O to understand the foundation of the rather successful time-dependent approach. It is found that the calculated strength distribution of the 2{sup +} states has physically reasonable behavior and that the strength function is practically positive definite though the non-Hermitian Hamiltonian matrix obtained from TDDM does not guarantee it. A relation to an Extended RPA theory with hermiticity is also investigated. It is found that the density-matrix formalism is a good approximation to the Hermitian Extended RPA theory. (orig.)
Time-dependent stabilization in AdS/CFT
Auzzi, Roberto; Gudnason, Sven Bjarke; Rabinovici, Eliezer
2012-01-01
We consider theories with time-dependent Hamiltonians which alternate between being bounded and unbounded from below. For appropriate frequencies dynamical stabilization can occur rendering the effective potential of the system stable. We first study a free field theory on a torus with a time-dependent mass term, finding that the stability regions are described in terms of the phase diagram of the Mathieu equation. Using number theory we have found a compactification scheme such as to avoid resonances for all momentum modes in the theory. We further consider the gravity dual of a conformal field theory on a sphere in three spacetime dimensions, deformed by a doubletrace operator. The gravity dual of the theory with a constant unbounded potential develops big crunch singularities; we study when such singularities can be cured by dynamical stabilization. We numerically solve the Einstein-scalar equations of motion in the case of a time-dependent doubletrace deformation and find that for sufficiently high freque...
Time-dependent massless Dirac fermions in graphene
Energy Technology Data Exchange (ETDEWEB)
Khantoul, Boubakeur, E-mail: bobphys@gmail.com [Department of Mathematics, City University London, Northampton Square, London EC1V 0HB (United Kingdom); Department of Physics, University of Jijel, BP 98, Ouled Aissa, 18000 Jijel (Algeria); Fring, Andreas, E-mail: a.fring@city.ac.uk [Department of Mathematics, City University London, Northampton Square, London EC1V 0HB (United Kingdom)
2015-10-30
Using the Lewis–Riesenfeld method of invariants we construct explicit analytical solutions for the massless Dirac equation in 2+1 dimensions describing quasi-particles in graphene. The Hamiltonian of the system considered contains some explicit time-dependence in addition to one resulting from being minimally coupled to a time-dependent vector potential. The eigenvalue equations for the two spinor components of the Lewis–Riesenfeld invariant are found to decouple into a pair of supersymmetric invariants in a similar fashion as the known decoupling for the time-independent Dirac Hamiltonians. - Highlights: • An explicit analytical solution for a massless 2+1 dimensional time-dependent Dirac equation is found. • All steps of the Lewis–Riesenfeld method have been carried out.
Time-dependent perturbation theory for inelastic scattering
Cross, R. J.
1982-08-01
We show by numerical integration that the first-order, time-dependent, Magnus approximation agrees with the first-order, exponential, distorted-wave approximation to within a few percent, provided that the trajectory used for the time-dependent calculation is characterized by the arithmetic mean of the initial and final velocities and the arithmetic mean of the initial and final orbital angular momenta. Calculations are done for rotational energy transfer from an exponentially repulsive potential characteristic of He+H2 and for a Lennard-Jones potential characteristic of Ar+N2.
Vacuum radiation induced by time dependent electric field
Zhang, Bo; Zhang, Zhi-meng; Hong, Wei; He, Shu-Kai; Teng, Jian; Gu, Yu-qiu
2017-04-01
Many predictions of new phenomena given by strong field quantum electrodynamics (SFQED) will be tested on next generation multi-petawatt laser facilities in the near future. These new phenomena are basis to understand physics in extremely strong electromagnetic fields therefore have attracted wide research interest. Here we discuss a new SFQED phenomenon that is named as vacuum radiation. In vacuum radiation, a virtual electron loop obtain energy from time dependent external electric field and radiate an entangled photon pair. Features of vacuum radiation in a locally time dependent electric field including spectrum, characteristic temperature, production rate and power are given.
Vacuum radiation induced by time dependent electric field
Directory of Open Access Journals (Sweden)
Bo Zhang
2017-04-01
Full Text Available Many predictions of new phenomena given by strong field quantum electrodynamics (SFQED will be tested on next generation multi-petawatt laser facilities in the near future. These new phenomena are basis to understand physics in extremely strong electromagnetic fields therefore have attracted wide research interest. Here we discuss a new SFQED phenomenon that is named as vacuum radiation. In vacuum radiation, a virtual electron loop obtain energy from time dependent external electric field and radiate an entangled photon pair. Features of vacuum radiation in a locally time dependent electric field including spectrum, characteristic temperature, production rate and power are given.
The time-dependent prize-collecting arc routing problem
DEFF Research Database (Denmark)
Black, Dan; Eglese, Richard; Wøhlk, Sanne
2013-01-01
A new problem is introduced named the Time-Dependent Prize-Collecting Arc Routing Problem (TD-PARP). It is particularly relevant to situations where a transport manager has to choose between a number of full truck load pick-ups and deliveries on a road network where travel times change with the t......A new problem is introduced named the Time-Dependent Prize-Collecting Arc Routing Problem (TD-PARP). It is particularly relevant to situations where a transport manager has to choose between a number of full truck load pick-ups and deliveries on a road network where travel times change...
Exact response functions within the time-dependent Gutzwiller approach
Bünemann, J.; Wasner, S.; Oelsen, E. v.; Seibold, G.
2015-02-01
We investigate the applicability of the two existing versions of a time-dependent Gutzwiller approach (TDGA) beyond the frequently used limit of infinite spatial dimensions. To this end, we study the two-particle response functions of a two-site Hubbard model where we can compare the exact results and those derived from the TDGA. It turns out that only the more recently introduced version of the TDGA can be combined with a diagrammatic approach which allows for the evaluation of Gutzwiller wave functions in finite dimensions. For this TDGA method, we derive the time-dependent Lagrangian for general single-band Hubbard models.
Time-Dependent Collective Neutrino Oscillations in Supernovae
Abbar, Sajad; Duan, Huaiyu
2015-10-01
Neutrinos can experience self-induced flavor conversion in core-collapse supernovae due to neutrino-neutrino forward scattering. Previously a stationary supernova model, the so called ``neutrino bulb model,'' was used exclusively to study collective neutrino oscillations in the core-collapse supernova. We show that even a small time-dependent perturbation in neutrino fluxes on the surface of the proto-neutron star can lead to fast varying collective oscillations at large radii. This result calls for time-dependent supernova models for the study of collective neutrino oscillations. This work was supported by DOE EPSCoR Grant DE-SC0008142 at UNM.
Gao, Fangfang; Zhang, Xiaokang; Pu, Yong; Zhu, Qingjun; Liu, Songlin
2016-08-01
Attaining tritium self-sufficiency is an important mission for the Chinese Fusion Engineering Testing Reactor (CFETR) operating on a Deuterium-Tritium (D-T) fuel cycle. It is necessary to study the tritium breeding ratio (TBR) and breeding tritium inventory variation with operation time so as to provide an accurate data for dynamic modeling and analysis of the tritium fuel cycle. A water cooled ceramic breeder (WCCB) blanket is one candidate of blanket concepts for the CFETR. Based on the detailed 3D neutronics model of CFETR with the WCCB blanket, the time-dependent TBR and tritium surplus were evaluated by a coupling calculation of the Monte Carlo N-Particle Transport Code (MCNP) and the fusion activation code FISPACT-2007. The results indicated that the TBR and tritium surplus of the WCCB blanket were a function of operation time and fusion power due to the Li consumption in breeder and material activation. In addition, by comparison with the results calculated by using the 3D neutronics model and employing the transfer factor constant from 1D to 3D, it is noted that 1D analysis leads to an over-estimation for the time-dependent tritium breeding capability when fusion power is larger than 1000 MW. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB108004, 2015GB108002, and 2014GB119000), and by National Natural Science Foundation of China (No. 11175207)
A time-dependent vector field topology based on streak surfaces.
Uffinger, Markus; Sadlo, Filip; Ertl, Thomas
2013-03-01
It was shown recently how the 2D vector field topology concept, directly applicable to stationary vector fields only, can be generalized to time-dependent vector fields by replacing the role of stream lines by streak lines. The present paper extends this concept to 3D vector fields. In traditional 3D vector field topology separatrices can be obtained by integrating stream lines from 0D seeds corresponding to critical points. We show that in our new concept, in contrast, 1D seeding constructs are required for computing streak-based separatrices. In analogy to the 2D generalization we show that invariant manifolds can be obtained by seeding streak surfaces along distinguished path surfaces emanating from intersection curves between codimension-1 ridges in the forward and reverse finite-time Lyapunov exponent (FTLE) fields. These path surfaces represent a time-dependent generalization of critical points and convey further structure in time-dependent topology of vector fields. Compared to the traditional approach based on FTLE ridges, the resulting streak manifolds ease the analysis of Lagrangian coherent structures (LCS) with respect to visual quality and computational cost, especially when time series of LCS are computed. We exemplify validity and utility of the new approach using both synthetic examples and computational fluid dynamics results.
A Deterministic-Monte Carlo Hybrid Method for Time-Dependent Neutron Transport Problems
Energy Technology Data Exchange (ETDEWEB)
Justin Pounders; Farzad Rahnema
2001-10-01
A new deterministic-Monte Carlo hybrid solution technique is derived for the time-dependent transport equation. This new approach is based on dividing the time domain into a number of coarse intervals and expanding the transport solution in a series of polynomials within each interval. The solutions within each interval can be represented in terms of arbitrary source terms by using precomputed response functions. In the current work, the time-dependent response function computations are performed using the Monte Carlo method, while the global time-step march is performed deterministically. This work extends previous work by coupling the time-dependent expansions to space- and angle-dependent expansions to fully characterize the 1D transport response/solution. More generally, this approach represents and incremental extension of the steady-state coarse-mesh transport method that is based on global-local decompositions of large neutron transport problems. An example of a homogeneous slab is discussed as an example of the new developments.
Effective Maxwell Equations from Time-dependent Density Functional Theory
Institute of Scientific and Technical Information of China (English)
Weinan E; Jianfeng LU; Xu YANG
2011-01-01
The behavior of interacting electrons in a perfect crystal under macroscopic external electric and magnetic fields is studied. Effective Maxwell equations for the macroscopic electric and magnetic fields are derived starting from time-dependent density functional theory. Effective permittivity and permeability coefficients are obtained.
Simulation of time-dependent Heisenberg models in one dimension
DEFF Research Database (Denmark)
Volosniev, A. G.; Hammer, H. -W.; Zinner, N. T.
2016-01-01
In this Letter, we provide a theoretical analysis of strongly interacting quantum systems confined by a time-dependent external potential in one spatial dimension. We show that such systems can be used to simulate spin chains described by Heisenberg Hamiltonians in which the exchange coupling...
Time-dependent exact solutions of the nonlinear Kompaneets equation
Energy Technology Data Exchange (ETDEWEB)
Ibragimov, N H, E-mail: nib@bth.s [Department of Mathematics and Science, Blekinge Institute of Technology, 371 79 Karlskrona (Sweden)
2010-12-17
Time-dependent exact solutions of the Kompaneets photon diffusion equation are obtained for several approximations of this equation. One of the approximations describes the case when the induced scattering is dominant. In this case, the Kompaneets equation has an additional symmetry which is used for constructing some exact solutions as group invariant solutions. (fast track communication)
Noncommutative quantum mechanics in a time-dependent background
Dey, Sanjib; Fring, Andreas
2014-10-01
We investigate a quantum mechanical system on a noncommutative space for which the structure constant is explicitly time dependent. Any autonomous Hamiltonian on such a space acquires a time-dependent form in terms of the conventional canonical variables. We employ the Lewis-Riesenfeld method of invariants to construct explicit analytical solutions for the corresponding time-dependent Schrödinger equation. The eigenfunctions are expressed in terms of the solutions of variants of the nonlinear Ermakov-Pinney equation and discussed in detail for various types of background fields. We utilize the solutions to verify a generalized version of Heisenberg's uncertainty relations for which the lower bound becomes a time-dependent function of the background fields. We study the variance for various states, including standard Glauber coherent states with their squeezed versions and Gaussian Klauder coherent states resembling a quasiclassical behavior. No type of coherent state appears to be optimal in general with regard to achieving minimal uncertainties, as this feature turns out to be background field dependent.
Similarity solutions for radiation in time-dependent relativistic flows
Lucy, L B
2004-01-01
Exact analytic solutions are derived for radiation in time-dependent relativistic flows. The flows are spherically-symmetric homologous explosions or implosions of matter with a grey extinction coefficient. The solutions are suitable for testing numerical transfer codes, and this is illustrated for a fully relativistic Monte Carlo code.
Stability on time-dependent domains: convective and dilution effects
Krechetnikov, R.; Knobloch, E.
2017-03-01
We explore near-critical behavior of spatially extended systems on time-dependent spatial domains with convective and dilution effects due to domain flow. As a paradigm, we use the Swift-Hohenberg equation, which is the simplest nonlinear model with a non-zero critical wavenumber, to study dynamic pattern formation on time-dependent domains. A universal amplitude equation governing weakly nonlinear evolution of patterns on time-dependent domains is derived and proves to be a generalization of the standard Ginzburg-Landau equation. Its key solutions identified here demonstrate a substantial variety-spatially periodic states with a time-dependent wavenumber, steady spatially non-periodic states, and pulse-train solutions-in contrast to extended systems on time-fixed domains. The effects of domain flow, such as bifurcation delay due to domain growth and destabilization due to oscillatory domain flow, on the Eckhaus instability responsible for phase slips in spatially periodic states are analyzed with the help of both local and global stability analyses. A nonlinear phase equation describing the approach to a phase-slip event is derived. Detailed analysis of a phase slip using multiple time scale methods demonstrates different mechanisms governing the wavelength changing process at different stages.
Time dependent solution for acceleration of tau-leaping
Fu, Jin; Wu, Sheng; Petzold, Linda R.
2013-02-01
The tau-leaping method is often effective for speeding up discrete stochastic simulation of chemically reacting systems. However, when fast reactions are involved, the speed-up for this method can be quite limited. One way to address this is to apply a stochastic quasi-steady state assumption. However we must be careful when using this assumption. If the fast subsystem cannot reach a steady distribution fast enough, the quasi-steady-state assumption will propagate error into the simulation. To avoid these errors, we propose to use the time dependent solution rather than the quasi-steady-state. Generally speaking, the time dependent solution is not easy to derive for an arbitrary network. However, for some common motifs we do have time dependent solutions. We derive the time dependent solutions for these motifs, and then show how they can be used with tau-leaping to achieve substantial speed-ups, including for a realistic model of blood coagulation. Although the method is complicated, we have automated it.
Time dependent solution for acceleration of tau-leaping
Energy Technology Data Exchange (ETDEWEB)
Fu, Jin, E-mail: iamfujin@hotmail.com [Department of Computer Science, University of California, Santa Barbara (United States); Wu, Sheng, E-mail: sheng@cs.ucsb.edu [Department of Computer Science, University of California, Santa Barbara (United States); Petzold, Linda R., E-mail: petzold@cs.ucsb.edu [Department of Computer Science, University of California, Santa Barbara (United States)
2013-02-15
The tau-leaping method is often effective for speeding up discrete stochastic simulation of chemically reacting systems. However, when fast reactions are involved, the speed-up for this method can be quite limited. One way to address this is to apply a stochastic quasi-steady state assumption. However we must be careful when using this assumption. If the fast subsystem cannot reach a steady distribution fast enough, the quasi-steady-state assumption will propagate error into the simulation. To avoid these errors, we propose to use the time dependent solution rather than the quasi-steady-state. Generally speaking, the time dependent solution is not easy to derive for an arbitrary network. However, for some common motifs we do have time dependent solutions. We derive the time dependent solutions for these motifs, and then show how they can be used with tau-leaping to achieve substantial speed-ups, including for a realistic model of blood coagulation. Although the method is complicated, we have automated it.
Multicomponent density-functional theory for time-dependent systems
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 ou
PRODUCT FORMULA METHODS FOR TIME-DEPENDENT SCHRODINGER PROBLEMS
HUYGHEBAERT, J; DERAEDT, H
1990-01-01
This paper introduces a family of explicit and unconditionally stable algorithms for solving linear differential equations which contain a time-dependent Hermitian operator. Rigorous upper bounds are derived for two different `time-ordered' approximation schemes and for errors resulting from approxi
Introduction to quantum mechanics a time-dependent perspective
Tannor, David J
2007-01-01
"Introduction to Quantum Mechanics" covers quantum mechanics from a time-dependent perspective in a unified way from beginning to end. Intended for upper-level undergraduate and graduate courses this text will change the way people think about and teach quantum mechanics in chemistry and physics departments.
Dynamic structure evolution of time-dependent network
Zhang, Beibei; Zhou, Yadong; Xu, Xiaoyan; Wang, Dai; Guan, Xiaohong
2016-08-01
In this paper, we research the long-voided problem of formulating the time-dependent network structure evolution scheme, it focus not only on finding new emerging vertices in evolving communities and new emerging communities over the specified time range but also formulating the complex network structure evolution schematic. Previous approaches basically applied to community detection on time static networks and thus failed to consider the potentially crucial and useful information latently embedded in the dynamic structure evolution process of time-dependent network. To address these problems and to tackle the network non-scalability dilemma, we propose the dynamic hierarchical method for detecting and revealing structure evolution schematic of the time-dependent network. In practice and specificity, we propose an explicit hierarchical network evolution uncovering algorithm framework originated from and widely expanded from time-dependent and dynamic spectral optimization theory. Our method yields preferable results compared with previous approaches on a vast variety of test network data, including both real on-line networks and computer generated complex networks.
Linear-response thermal time-dependent density functional theory
Pribram-Jones, Aurora; Burke, Kieron
2015-01-01
The van Leeuwen proof of linear-response time-dependent density functional theory (TDDFT) is generalized to thermal ensembles. This allows generalization to finite temperatures of the Gross-Kohn relation, the exchange-correlation kernel of TDDFT, and fluctuation dissipation theorem for DFT. This produces a natural method for generating new thermal exchange-correlation (XC) approximations.
Student Understanding of Time Dependence in Quantum Mechanics
Emigh, Paul J.; Passante, Gina; Shaffer, Peter S.
2015-01-01
The time evolution of quantum states is arguably one of the more difficult ideas in quantum mechanics. In this article, we report on results from an investigation of student understanding of this topic after lecture instruction. We demonstrate specific problems that students have in applying time dependence to quantum systems and in recognizing…
Numerical analysis of time-dependent Boussinesq models
Houwen, P.J. van der; Mooiman, J.; Wubs, F.W.
1991-01-01
In this paper we analyse numerical models for time-dependent Boussinesq equations. These equations arise when so-called Boussinesq terms are introduced into the shallow water equations. We use the Boussinesq terms proposed by Katapodes and Dingemans. These terms generalize the constant depth terms g
Time-dependent magnetohydrodynamic simulations of the inner heliosphere
Merkin, V. G.; Lyon, J. G.; Lario, D.; Arge, C. N.; Henney, C. J.
2016-04-01
This paper presents results from a simulation study exploring heliospheric consequences of time-dependent changes at the Sun. We selected a 2 month period in the beginning of year 2008 that was characterized by very low solar activity. The heliosphere in the equatorial region was dominated by two coronal holes whose changing structure created temporal variations distorting the classical steady state picture of the heliosphere. We used the Air Force Data Assimilate Photospheric Flux Transport (ADAPT) model to obtain daily updated photospheric magnetograms and drive the Wang-Sheeley-Arge (WSA) model of the corona. This leads to a formulation of a time-dependent boundary condition for our three-dimensional (3-D) magnetohydrodynamic (MHD) model, LFM-helio, which is the heliospheric adaptation of the Lyon-Fedder-Mobarry MHD simulation code. The time-dependent coronal conditions were propagated throughout the inner heliosphere, and the simulation results were compared with the spacecraft located near 1 astronomical unit (AU) heliocentric distance: Advanced Composition Explorer (ACE), Solar Terrestrial Relations Observatory (STEREO-A and STEREO-B), and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft that was in cruise phase measuring the heliospheric magnetic field between 0.35 and 0.6 AU. In addition, during the selected interval MESSENGER and ACE aligned radially allowing minimization of the effects of temporal variation at the Sun versus radial evolution of structures. Our simulations show that time-dependent simulationsreproduce the gross-scale structure of the heliosphere with higher fidelity, while on smaller spatial and faster time scales (e.g., 1 day) they provide important insights for interpretation of the data. The simulations suggest that moving boundaries of slow-fast wind transitions at 0.1 AU may result in the formation of inverted magnetic fields near pseudostreamers which is an intrinsically time-dependent process
Tokamak power reactor ignition and time dependent fractional power operation
Energy Technology Data Exchange (ETDEWEB)
Vold, E.L.; Mau, T.K.; Conn, R.W.
1986-06-01
A flexible time-dependent and zero-dimensional plasma burn code with radial profiles was developed and employed to study the fractional power operation and the thermal burn control options for an INTOR-sized tokamak reactor. The code includes alpha thermalization and a time-dependent transport loss which can be represented by any one of several currently popular scaling laws for energy confinement time. Ignition parameters were found to vary widely in density-temperature (n-T) space for the range of scaling laws examined. Critical ignition issues were found to include the extent of confinement time degradation by alpha heating, the ratio of ion to electron transport power loss, and effect of auxiliary heating on confinement. Feedback control of the auxiliary power and ion fuel sources are shown to provide thermal stability near the ignition curve.
Effective field theory in time-dependent settings
Collins, Hael; Ross, Andreas
2012-01-01
We use the in-in or Schwinger-Keldysh formalism to explore the construction and interpretation of effective field theories for time-dependent systems evolving out of equilibrium. Starting with a simple model consisting of a heavy and a light scalar field taken to be in their free vacuum states at a finite initial time, we study the effects from the heavy field on the dynamics of the light field by analyzing the equation of motion for the expectation value of the light background field. New terms appear which cannot arise from a local action of an effective field theory in terms of the light field, though they disappear in the adiabatic limit. We discuss the origins of these terms as well as their possible implications for time dependent situations such as inflation.
Scintillation time dependence and pulse shape discrimination in liquid argon
Lippincott, W H; Gastler, D; Hime, A; Kearns, E; McKinsey, D N; Nikkel, J A; Stonehill, L C
2008-01-01
Using a single-phase liquid argon detector with a signal yield of 4.85 photoelectrons per keV of electronic-equivalent recoil energy (keVee), we measure the scintillation time dependence of both electronic and nuclear recoils in liquid argon down to 5 keVee. We develop two methods of pulse shape discrimination to distinguish between electronic and nuclear recoils. Using one of these methods, we measure a background and statistics-limited level of electronic recoil contamination to be $7.6\\times10^{-7}$ between 60 and 128 keV of nuclear recoil energy (keVr) for a nuclear recoil acceptance of 50% with no nuclear recoil-like events above 72 keVr. Finally, we develop a maximum likelihood method of pulse shape discrimination using the measured scintillation time dependence and predict the sensitivity to WIMP-nucleon scattering in three configurations of a liquid argon dark matter detector.
Eisenhart lifts and symmetries of time-dependent systems
Cariglia, M; Gibbons, G W; Horvathy, P A
2016-01-01
Certain dissipative systems, such as Caldirola and Kannai's damped simple harmonic oscillator, may be modelled by time-dependent Lagrangian and hence time dependent Hamiltonian systems with $n$ degrees of freedom. In this paper we treat these systems, their projective and conformal symmetries as well as their quantisation from the point of view of the Eisenhart lift to a Bargmann spacetime in $n+2$ dimensions, equipped with its covariantly constant null Killing vector field. Reparametrization of the time variable corresponds to conformal rescalings of the Bargmann metric. We show how the Arnold map lifts to Bargmann spacetime. We contrast the greater generality of the Caldirola-Kannai approach with that of Arnold and Bateman. At the level of quantum mechanics, we are able to show how the relevant Schr\\"odinger equation emerges naturally using the techniques of quantum field theory in curved spacetimes, since a covariantly constant null Killing vector field gives rise to well defined one particle Hilbert space...
Generating time dependent conformally coupled Einstein-scalar solutions
Sultana, Joseph
2015-07-01
Using the correspondence between a minimally coupled scalar field and an effective stiff perfect fluid with or without a cosmological constant, we present a simple method for generating time dependent Einstein-scalar solutions with a conformally coupled scalar field that has vanishing or non-vanishing potential. This is done by using Bekenstein's transformation on Einstein-scalar solutions with minimally coupled massless scalar fields, and its later generalization by Abreu et al. to massive fields. In particular we obtain two new spherically symmetric time dependent solutions to the coupled system of Einstein's and the conformal scalar field equations, with one of the solutions having a Higgs' type potential for the scalar field, and we study their properties.
Characterization of Models for Time-Dependent Behavior of Soils
DEFF Research Database (Denmark)
Liingaard, Morten; Augustesen, Anders; Lade, Poul V.
2004-01-01
. Special attention is paid to elastoviscoplastic models that combine inviscid elastic and time-dependent plastic behavior. Various general elastoviscoplastic models can roughly be divided into two categories: Models based on the concept of overstress and models based on nonstationary flow surface theory...... Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena ~ creep, stress relaxation, and rate effects ! observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part...... is a review of the empirical relations, which apply only to problems of specific boundary conditions and frequently involve natural time alone. The second part deals with different rheological models used for describing the viscous effects in the field of solid mechanics. The rheological models are typically...
Time-Dependent Warping and Non-Singular Bouncing Cosmologies
Balasubramanian, Koushik
2014-01-01
In this note, we construct a family of non-singular time-dependent solutions of a six-dimensional gravitational theory that are warped products of a four dimensional bouncing cosmological solution and a two dimensional internal manifold. The warp factor is time-dependent and breaks translation invariance along one of the internal directions. When the warp factor is periodic in time, the non-compact part of the geometry bounces periodically. The six dimensional geometry is supported by matter that does not violate the null energy condition. We show that this 6D geometry does not admit a closed trapped surface and hence the Hawking-Penrose singularity theorems do not apply to these solutions. We also present examples of singular solutions where the topology of the internal manifold changes dynamically.
Time-dependent density functional theory: Causality and other problems
Energy Technology Data Exchange (ETDEWEB)
Ruggenthaler, Michael; Bauer, Dieter [Max-Planck-Inst. fuer Kernphysik, Heidelberg (Germany)
2007-07-01
Time-dependent density functional theory (TDDFT) is a reformulation of the time dependent many-body problem in quantum mechanics which is capable of reducing the computational cost to calculate, e.g., strongly driven many-electron systems enormously. Recent developments were able to overcome fundamental problems associated with ionization processes. Still vital issues have to be clarified. Besides the construction of the underlying functionals we investigate the causality problem of TDDFT by general considerations and by studying a exactly solvable system of two correlated electrons in an intense laser-pulse. For the latter system, the two alternative approaches to the construction of the action functional or a constrained functional derivative by van Leeuwen and Gal, respectively, are explored.
Time-dependent viscoelastic behavior of an LDPE melt
Institute of Scientific and Technical Information of China (English)
Shuxin Huang; Chuanjing Lu; Yurun Fan
2006-01-01
Two differential constitutive equations,i.e.Giesekus model and Johnson-Segalman model were employed here to predict the time-dependent viscoelastic behavior of an LDPE melt in thixotropy-loop experiments and step shear rate experiment. Multiple relaxation modes were adopted, and the parameters used to describe the nonlinear viscoelasticity in the two models were obtained by fitting the shear-thinning viscosity. The predictions on those transient shear characteristics by the two models are found in qualitative agreement with our previous experiments. Johnson-Segalman model predicts oscillation behavior in the thixotropy-loop and step shear rate experiments, whereas Giesekus model does not. Both models predict higher shear stresses than the experimental data in the case of long time shearing, implying that both models are not able to completely characterize the time-dependent shear stress of the-melt at high shear rate.
Spectral methods for time dependent partial differential equations
Gottlieb, D.; Turkel, E.
1983-01-01
The theory of spectral methods for time dependent partial differential equations is reviewed. When the domain is periodic Fourier methods are presented while for nonperiodic problems both Chebyshev and Legendre methods are discussed. The theory is presented for both hyperbolic and parabolic systems using both Galerkin and collocation procedures. While most of the review considers problems with constant coefficients the extension to nonlinear problems is also discussed. Some results for problems with shocks are presented.
Thermal state of the general time-dependent harmonic oscillator
Indian Academy of Sciences (India)
Jeong-Ryeol Choi
2003-07-01
Taking advantage of dynamical invariant operator, we derived quantum mechanical solution of general time-dependent harmonic oscillator. The uncertainty relation of the system is always larger than ħ=2 not only in number but also in the thermal state as expected. We used the diagonal elements of density operator satisfying Leouville–von Neumann equation to calculate various expectation values in the thermal state. We applied our theory to a special case which is the forced Caldirola–Kanai oscillator.
Time-dependent effects of cardiovascular exercise on memory
DEFF Research Database (Denmark)
Roig, Marc; Thomas, Richard; Mang, Cameron S
2016-01-01
We present new evidence supporting the hypothesis that the effects of cardiovascular exercise on memory can be regulated in a time-dependent manner. When the exercise stimulus is temporally coupled with specific phases of the memory formation process, a single bout of cardiovascular exercise may...... be sufficient to improve memory. SUMMARY: The timing of exercise in relation to the information to be remembered is critical to maximize the effects of acute cardiovascular exercise on memory....
Time dependent density functional calculation of plasmon response in clusters
Institute of Scientific and Technical Information of China (English)
Wang Feng(王锋); Zhang Feng-Shou(张丰收); Eric Suraud
2003-01-01
We have introduced a theoretical scheme for the efficient description of the optical response of a cluster based on the time-dependent density functional theory. The practical implementation is done by means of the fully fledged timedependent local density approximation scheme, which is solved directly in the time domain without any linearization.As an example we consider the simple Na2 cluster and compute its surface plasmon photoabsorption cross section, which is in good agreement with the experiments.
Time-dependent HF approach to SHE dynamics
Umar, A. S.; Oberacker, V. E.
2015-12-01
We employ the time-dependent Hartree-Fock (TDHF) method to study various aspects of the reactions utilized in searches for superheavy elements. These include capture cross-sections, quasifission, prediction of PCN, and other interesting dynamical quantities. We show that the microscopic TDHF approach provides an important tool to shed some light on the nuclear dynamics leading to the formation of superheavy elements.
Tiny graviton matrix theory on time-dependent background
Energy Technology Data Exchange (ETDEWEB)
Chen Bin [Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)], E-mail: bchen01@pku.edu.cn; Liu Xiao [Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)], E-mail: liuxiaoerty@pku.edu.cn
2009-04-11
In this article we construct a tiny graviton matrix model for type IIB string theory on a plane-wave background with null dilaton. For the linear null dilaton case, we analyze its vacuum and the excitation spectrum around the vacuum, and discuss the time-dependent fuzzy three-sphere solutions and their evolution. It turns out that at very late time the non-Abelian fuzzy degrees of freedom disappear, which indicates the appearance of perturbative strings.
Dose and time dependence of box jellyfish antivenom
2014-01-01
Background The effectiveness of the currently available box jellyfish (Chironex fleckeri) antivenom has been subject of debate for many years. To assess whether the box jellyfish antivenom has the ability to attenuate venom-induced damage at cellular level, the present study analyzed the dose and time dependence of the antivenom in a cell-based assay. Methods Different doses of antivenom were added to venom and subsequently administered to cells and the cell index was measured using xCelligen...
Relating Time-Dependent Acceleration and Height Using an Elevator
Kinser, Jason M.
2015-01-01
A simple experiment in relating a time-dependent linear acceleration function to height is explored through the use of a smartphone and an elevator. Given acceleration as a function of time, a(t), the velocity function and position functions are determined through integration as in v(t)=? a(t) dt (1) and x(t)=? v(t) dt. Mobile devices such as…
A time-dependent measuring system for welding deformation
Institute of Scientific and Technical Information of China (English)
蔡志鹏; 赵海燕; 鹿安理; 史清宇; 施光凯
2002-01-01
In this paper the establishment and application of a time-dependent measuring system for welding deformation are presented which is established with high quality sensors shielded from strong welding interference. By using this system, vertical and horizontal displacements of the high temperature area are surveyed at the same time. And this system is also used for monitoring and controlling the deformation of real welded structures.
ARTICLES: Time-Dependent Stokes Shift from Solvent Dielectric Relaxation
Xu, Jing; Wang, Quan-de; Zhu, Quan; Fu, Ke-xiang; He, Fu-cheng; Li, Xiang-yuan
2010-06-01
The Stokes shift response function, which is related to the time dependent solvation energy, is calculated with the dielectric response function and a novel expression of nonequilibrium solvation energy. In the derivation, relationship between the polarization and the dielectric response function is used. With the dipole-in-a-sphere model applied to the system coumarin 343 and water as the solvent, encouraging agreement with the experimental data from Jimenez et al. is obtained [Nature 369, 471 (1994)].
Unique Measure for Time-Dependent Random Dynamical Systems
Varner, Gregory
2016-01-01
This paper proves the uniqueness of measure for the two-dimensional Navier-Stokes equations under a random kick-force and a time-dependent deterministic force. By extending a result for uniqueness of measure for time-homogeneous Markov processes to the time-inhomogeneous case, it is shown that the measures are exponentially mixing for the 2D Navier-Stokes equations on the sphere.
Exact Invariants for a Time-Dependent Hamiltonian System
Institute of Scientific and Technical Information of China (English)
LUO Xiao-Bing
2009-01-01
We have a classical look for a quantum system which is exactly solvable. We construct the invariant manifolds analytically, and then apply the semiclassical quantization rules in a final step to compute the quasienergies. The invariant is obtained by performing a canonical transformation of the initially time-dependent Hamiltonian to a time-independent one. The correspondence between classical and quantum mechanics is elucidated.
Neutrino flavor instabilities in a time-dependent supernova model
Directory of Open Access Journals (Sweden)
Sajad Abbar
2015-12-01
Full Text Available A dense neutrino medium such as that inside a core-collapse supernova can experience collective flavor conversion or oscillations because of the neutral-current weak interaction among the neutrinos. This phenomenon has been studied in a restricted, stationary supernova model which possesses the (spatial spherical symmetry about the center of the supernova and the (directional axial symmetry around the radial direction. Recently it has been shown that these spatial and directional symmetries can be broken spontaneously by collective neutrino oscillations. In this letter we analyze the neutrino flavor instabilities in a time-dependent supernova model. Our results show that collective neutrino oscillations start at approximately the same radius in both the stationary and time-dependent supernova models unless there exist very rapid variations in local physical conditions on timescales of a few microseconds or shorter. Our results also suggest that collective neutrino oscillations can vary rapidly with time in the regimes where they do occur which need to be studied in time-dependent supernova models.
Eisenhart lifts and symmetries of time-dependent systems
Cariglia, M.; Duval, C.; Gibbons, G. W.; Horváthy, P. A.
2016-10-01
Certain dissipative systems, such as Caldirola and Kannai's damped simple harmonic oscillator, may be modelled by time-dependent Lagrangian and hence time dependent Hamiltonian systems with n degrees of freedom. In this paper we treat these systems, their projective and conformal symmetries as well as their quantisation from the point of view of the Eisenhart lift to a Bargmann spacetime in n + 2 dimensions, equipped with its covariantly constant null Killing vector field. Reparametrisation of the time variable corresponds to conformal rescalings of the Bargmann metric. We show how the Arnold map lifts to Bargmann spacetime. We contrast the greater generality of the Caldirola-Kannai approach with that of Arnold and Bateman. At the level of quantum mechanics, we are able to show how the relevant Schrödinger equation emerges naturally using the techniques of quantum field theory in curved spacetimes, since a covariantly constant null Killing vector field gives rise to well defined one particle Hilbert space. Time-dependent Lagrangians arise naturally also in cosmology and give rise to the phenomenon of Hubble friction. We provide an account of this for Friedmann-Lemaître and Bianchi cosmologies and how it fits in with our previous discussion in the non-relativistic limit.
Behaviour of time-dependent materials exposed to periodical loading
Directory of Open Access Journals (Sweden)
Zupancic B.
2010-06-01
Full Text Available Paper presents methodology for analyzing behaviour of time-dependent (viscoelastic materials when exposed to periodical (cyclic loading. Within each loading cycle time-dependent material undergoes a combination of the creep and retardation process. At certain conditions the retardation process between two loading cycles cannot be fully completed to a strain free state. Consequently, strain starts to accumulate, which leads to hardening of the material and ultimately to the failure of polymeric product. Critical frequency of the applied periodical loading depends on the material retardation time (location of mechanical spectrum, while the magnitude of accumulated strain on the strength of corresponding discrete spectrum lines. The shape of mechanical spectrum defines the intensity and the magnitude of accumulated strain. Thus, the mechanical spectrum of time-dependent material is the most important function for predicting durability of dynamically loaded polymeric products. In continuation we present mathematical methodology for predicting durability of periodically loaded polymeric components of drive belt. Methodology includes numerical calculations of accumulated strain as a function of the number of loading cycles and function of loading angular velocity. Based on these calculations we can determine the critical angular velocity area of periodical loading where the strain accumulation is the most intensive.
Progress Report on Alloy 617 Time Dependent Allowables
Energy Technology Data Exchange (ETDEWEB)
Wright, Julie Knibloe [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-06-01
Time dependent allowable stresses are required in the ASME Boiler and Pressure Vessel Code for design of components in the temperature range where time dependent deformation (i.e., creep) is expected to become significant. There are time dependent allowable stresses in Section IID of the Code for use in the non-nuclear construction codes, however, there are additional criteria that must be considered in developing time dependent allowables for nuclear components. These criteria are specified in Section III NH. St is defined as the lesser of three quantities: 100% of the average stress required to obtain a total (elastic, plastic, primary and secondary creep) strain of 1%; 67% of the minimum stress to cause rupture; and 80% of the minimum stress to cause the initiation of tertiary creep. The values are reported for a range of temperatures and for time increments up to 100,000 hours. These values are determined from uniaxial creep tests, which involve the elevated temperature application of a constant load which is relatively small, resulting in deformation over a long time period prior to rupture. The stress which is the minimum resulting from these criteria is the time dependent allowable stress St. In this report data from a large number of creep and creep-rupture tests on Alloy 617 are analyzed using the ASME Section III NH criteria. Data which are used in the analysis are from the ongoing DOE sponsored high temperature materials program, form Korea Atomic Energy Institute through the Generation IV VHTR Materials Program and historical data from previous HTR research and vendor data generated in developing the alloy. It is found that the tertiary creep criterion determines St at highest temperatures, while the stress to cause 1% total strain controls at low temperatures. The ASME Section III Working Group on Allowable Stress Criteria has recommended that the uncertainties associated with determining the onset of tertiary creep and the lack of significant
Solvable time-dependent models in quantum mechanics
Cordero-Soto, Ricardo J.
In the traditional setting of quantum mechanics, the Hamiltonian operator does not depend on time. While some Schrodinger equations with time-dependent Hamiltonians have been solved, explicitly solvable cases are typically scarce. This thesis is a collection of papers in which this first author along with Suslov, Suazo, and Lopez, has worked on solving a series of Schrodinger equations with a time-dependent quadratic Hamiltonian that has applications in problems of quantum electrodynamics, lasers, quantum devices such as quantum dots, and external varying fields. In particular the author discusses a new completely integrable case of the time-dependent Schrodinger equation in Rn with variable coefficients for a modified oscillator, which is dual with respect to the time inversion to a model of the quantum oscillator considered by Meiler, Cordero-Soto, and Suslov. A second pair of dual Hamiltonians is found in the momentum representation. Our examples show that in mathematical physics and quantum mechanics a change in the direction of time may require a total change of the system dynamics in order to return the system back to its original quantum state. The author also considers several models of the damped oscillators in nonrelativistic quantum mechanics in a framework of a general approach to the dynamics of the time-dependent Schrodinger equation with variable quadratic Hamiltonians. The Green functions are explicitly found in terms of elementary functions and the corresponding gauge transformations are discussed. The factorization technique is applied to the case of a shifted harmonic oscillator. The time-evolution of the expectation values of the energy related operators is determined for two models of the quantum damped oscillators under consideration. The classical equations of motion for the damped oscillations are derived for the corresponding expectation values of the position operator. Finally, the author constructs integrals of motion for several models
Development of a Multi-Group Neutron Cross Section Library Generation System for PWR
Energy Technology Data Exchange (ETDEWEB)
Kim, Kang Seog; Hong, Ser Gi; Song, Jae Seung; Lee, Kyung Hoon; Cho, Jin Young; Kim, Ha Yong; Koo, Bon Seung; Shim, Hyung Jin; Park, Sang Yoon
2008-10-15
This report describes a generation system of multi-group cross section library which is used in the KARMA lattice calculation code. In particular, the theoretical methodologies, program structures, and input preparations for the constituent programs of the system are described in detail. The library generation system consists of the following five programs : ANJOY, GREDIT, MERIT, SUBDATA, and LIBGEN. ANJOY generates automatically the NJOY input files and two batch files for automatic NJOY run for all the nuclides considered. The automatic NJOY run gives TAPE 23 (PENDF output file of BROADR module of NJOY) and TAPE24 (GENDF output file of GROUPR module of NJOY) files for each nuclide. GREDIT prepares a formatted multi-group cross section file in which the cross sections are tabulated versus temperature and background cross section after reading the TAPE24 file. MERIT generates the hydrogen equivalence factors and the resonance integral tables by solving the slowing down equation with ultra-fine group cross sections which are prepared with the TAPE 23 file. SUBDATA generates the subgroup data including subgroup levels and weights after reading the MERIT output file. Finally, LIBGEN generates the final multi-group library file by assembling the data prepared in the previous steps and by reading the other data such as fission product yield data and decay data.The multi-group cross section library includes general multi-group cross sections, resonance data, subgroup data, fission product yield data, kappa-values (energy release per fission), and all the data which are required in the depletion calculation. The addition or elimination of the cross sections for some nuclides can be easily done by changing the LIBGEN input file if the general multi-group cross section and the subgroup data files are prepared.
Characterizing time-dependent mechanics in metallic MEMS
Directory of Open Access Journals (Sweden)
Geers M.G.D.
2010-06-01
Full Text Available Experiments for characterization of time-dependent material properties in free-standing metallic microelectromechanical system (MEMS pose challenges: e.g. fabrication and handling (sub-μm sized specimens, control and measurement of sub-μN loads and sub-μm displacements over long periods and various temperatures [1]. A variety of experimental setups have been reported each having their pros and cons. One example is a micro-tensile tester with an ingenious electro-static specimen gripping system [2] aiding simple specimen design giving good results at μN and sub-μm levels, but without in-situ full-field observations. Other progressive examples assimilate the specimen, MEMS actuators and load cells on a single chip [3,4] yielding significant results at nN and nm levels with in-situ TEM/SEM observability, though not without complications: complex load actuator/sensor calibration per chip, measures to reduce fabrication failure and unfeasible cofabrication on wafers with commercial metallic MEMS. This work aims to overcome these drawbacks by developing experimental methods with high sensitivity, precision and in-situ full-field observation capabilities. Moreover, these should be applicable to simple free-standing metallic MEMS that can be co-fabricated with commercial devices. These methods will then serve in systematic studies into size-effects in time-dependent material properties. First a numeric-experimental method is developed. It characterizes bending deformation of onwafer μm-sized aluminum cantilevers. A specially designed micro-clamp is used to mechanically apply a constant precise deflection of the beam (zres <50 nm for a prolonged period, see fig. 1. After this period, the deflection by the micro-clamp is removed. Full-field height maps with the ensuing deformation are measured over time with confocal optical profilometry (COP. This yields the tip deflection as function of time with ~3 nm precision, see fig.2. To extract material
Time-Dependent Neutron and Photon Dose-Field Analysis
Energy Technology Data Exchange (ETDEWEB)
Wooten, Hasani Omar [Georgia Inst. of Technology, Atlanta, GA (United States)
2005-08-01
A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The Pandemonium code, originally designed to determine flux and dose-rates only, is improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. A primary benefit of this work has been an extensive analysis and improvement of the photon model that is not limited to the application described in this thesis. The photon model has been extended in energy range to 10 MeV to include photons from fission and new photon buildup factors have been included that account for the effects of photon buildup at slant-path thicknesses as a function of angle, where the mean free path thickness has been preserved. The overall system of codes is user-friendly and it is directly applicable to facilities such as the plutonium facility at Los Alamos National Laboratory, where high-intensity neutron and photon emitters are regularly used. The codes may be used to determine a priori doses for given work scenarios in an effort to supply dose information to process models which will in turn assist decision makers on ensuring as low as reasonably achievable (ALARA) compliance. In addition, coupling the computational results of these tools with the process model visualization tools will help to increase worker safety and radiological safety awareness.
Time-dependent tomographic reconstruction of the solar corona
Vibert, D.; Peillon, C.; Lamy, P.; Frazin, R. A.; Wojak, J.
2016-10-01
Solar rotational tomography (SRT) applied to white-light coronal images observed at multiple aspect angles has been the preferred approach for determining the three-dimensional (3D) electron density structure of the solar corona. However, it is seriously hampered by the restrictive assumption that the corona is time-invariant which introduces significant errors in the reconstruction. We first explore several methods to mitigate the temporal variation of the corona by decoupling the "fast-varying" inner corona from the "slow-moving" outer corona using multiple masking (either by juxtaposition or recursive combination) and radial weighting. Weighting with a radial exponential profile provides some improvement over a classical reconstruction but only beyond ≈ 3R⊙. We next consider a full time-dependent tomographic reconstruction involving spatio-temporal regularization and further introduce a co-rotating regularization aimed at preventing concentration of reconstructed density in the plane of the sky. Crucial to testing our procedure and properly tuning the regularization parameters is the introduction of a time-dependent MHD model of the corona based on observed magnetograms to build a time-series of synthetic images of the corona. Our procedure, which successfully reproduces the time-varying model corona, is finally applied to a set of 53 LASCO-C2 pB images roughly evenly spaced in time from 15 to 29 March 2009. Our procedure paves the way to a time-dependent tomographic reconstruction of the coronal electron density to the whole set of LASCO-C2 images presently spanning 20 years.
Self-consistent RPA and the time-dependent density matrix approach
Energy Technology Data Exchange (ETDEWEB)
Schuck, P. [Institut de Physique Nucleaire, Orsay (France); CNRS et Universite Joseph Fourier, Laboratoire de Physique et Modelisation des Milieux Condenses, Grenoble (France); Tohyama, M. [Kyorin University School of Medicine, Mitaka, Tokyo (Japan)
2016-10-15
The time-dependent density matrix (TDDM) or BBGKY (Bogoliubov, Born, Green, Kirkwood, Yvon) approach is decoupled and closed at the three-body level in finding a natural representation of the latter in terms of a quadratic form of two-body correlation functions. In the small amplitude limit an extended RPA coupled to an also extended second RPA is obtained. Since including two-body correlations means that the ground state cannot be a Hartree-Fock state, naturally the corresponding RPA is upgraded to Self-Consistent RPA (SCRPA) which was introduced independently earlier and which is built on a correlated ground state. SCRPA conserves all the properties of standard RPA. Applications to the exactly solvable Lipkin and the 1D Hubbard models show good performances of SCRPA and TDDM. (orig.)
Optimal moving grids for time-dependent partial differential equations
Wathen, A. J.
1992-01-01
Various adaptive moving grid techniques for the numerical solution of time-dependent partial differential equations were proposed. The precise criterion for grid motion varies, but most techniques will attempt to give grids on which the solution of the partial differential equation can be well represented. Moving grids are investigated on which the solutions of the linear heat conduction and viscous Burgers' equation in one space dimension are optimally approximated. Precisely, the results of numerical calculations of optimal moving grids for piecewise linear finite element approximation of PDE solutions in the least-squares norm are reported.
The Nonlinear Dynamics of Time Dependent Subcritical Baroclinic Currents
Pedlosky, J.; Flierl, G. R.
2006-12-01
The nonlinear dynamics of baroclinically unstable waves in a time dependent zonal shear flow is considered in the framework of the two-layer Phillips model on the beta plane. In most cases considered in this study the amplitude of the shear is well below the critical value of the steady shear version of the model. Nevertheless, the time dependent problem in which the shear oscillates periodically is unstable, and the unstable waves grow to substantial amplitudes, in some cases with strongly nonlinear and turbulent characteristics. For very small values of the shear amplitude in the presence of dissipation an analytical, asymptotic theory predicts a self-sustained wave whose amplitude undergoes a nonlinear oscillation whose period is amplitude dependent. There is a sensitive amplitude dependence of the wave on the frequency of the oscillating shear when the shear amplitude is small. This behavior is also found in a truncated model of the dynamics, and that model is used to examine larger shear amplitudes. When there is a mean value of the shear in addition to the oscillating component, but such that the total shear is still subcritical, the resulting nonlinear states exhibit a rectified horizontal buoyancy flux with a nonzero time average as a result of the instability of the oscillating shear. For higher, still subcritical, values of the shear we have detected a symmetry breaking in which a second cross-stream mode is generated through an instability of the unstable wave although this second mode would by itself be stable on the basic time dependent current. For shear values that are substantially subcritical but of order of the critical shear, calculations with a full quasi-geostrophic numerical model reveal a turbulent flow generated by the instability. If the beta effect is disregarded the inviscid, linear problem is formally stable. However, our calculations show that a small degree of nonlinearity is enough to destabilize the flow leading to large amplitude
Time-dependent Integrated Predictive Modeling of ITER Plasmas
Institute of Scientific and Technical Information of China (English)
R.V. Budny
2007-01-01
@@ Introduction Modeling burning plasmas is important for speeding progress toward practical Tokamak energy production. Examples of issues that can be elucidated by modelinginclude requirements for heating, fueling, torque, and current drive systems, design of diagnostics, and estimates of the plasma performance (e.g., fusion power production) in various plasma scenarios. The modeling should be time-dependent to demonstrate that burning plasmas can be created, maintained (controlled), and terminated successfully. The modeling also should be integrated to treat self-consistently the nonlinearities and strong coupling between the plasma, heating, current drive, confinement, and control systems.
Time-dependent density-functional theory concepts and applications
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
Time-Dependent Mean-Field Games with Logarithmic Nonlinearities
Gomes, Diogo A.
2015-10-06
In this paper, we prove the existence of classical solutions for time-dependent mean-field games with a logarithmic nonlinearity and subquadratic Hamiltonians. Because the logarithm is unbounded from below, this nonlinearity poses substantial mathematical challenges that have not been addressed in the literature. Our result is proven by recurring to a delicate argument which combines Lipschitz regularity for the Hamilton-Jacobi equation with estimates for the nonlinearity in suitable Lebesgue spaces. Lipschitz estimates follow from an application of the nonlinear adjoint method. These are then combined with a priori bounds for solutions of the Fokker-Planck equation and a concavity argument for the nonlinearity.
Density-functional perturbation theory goes time-dependent
Gebauer, Ralph; Rocca, Dario; Baroni, Stefano
2009-01-01
The scope of time-dependent density-functional theory (TDDFT) is limited to the lowest portion of the spectrum of rather small systems (a few tens of atoms at most). In the static regime, density-functional perturbation theory (DFPT) allows one to calculate response functions of systems as large as currently dealt with in ground-state simulations. In this paper we present an effective way of combining DFPT with TDDFT. The dynamical polarizability is first expressed as an off-diagonal matrix e...
Time-dependent models of dense PDRs with complex molecules
Morata, O.; Herbst, E.
2008-01-01
We present a study of the chemistry of a dense photon-dominated region (PDR) using a time-dependent chemical model. Our major interest is to study the spatial distribution of complex molecules such as hydrocarbons and cyanopolyynes in the cool dense material bordering regions where star formation has taken place. Our standard model uses a homogeneous cloud of density 2x10e4 cm-3 and temperature T=40 K, which is irradiated by a far-ultraviolet radiation field of intermediate intensity, given b...
Time-dependant cosmological interpretation of quantum mechanics
Moulay, Emmanuel
2015-01-01
The aim of this article is to define a time-dependant cosmological interpretation of quantum mechanics in the context of a multiverse coming from eternal inflation. A common notion of time is defined for observers in similar observable universes by using the holographic principle. It is the time elapsed since the post-inflationary epoch. With this improvement, the cosmological interpretation of quantum mechanics becomes a full interpretation of quantum mechanics where the unitary evolution of quantum states is preserved. Moreover, it is well suited for eternal inflation .
Quantifying Time Dependent Moisture Storage and Transport Properties
DEFF Research Database (Denmark)
Peuhkuri, Ruut H
2003-01-01
This paper describes an experimental and numerical approach to quantify the time dependence of sorption mechanisms for some hygroscopic building - mostly insulation - materials. Some investigations of retarded sorption and non-Fickian phenomena, mostly on wood, have given inspiration to the present...... analysis on these other materials. The true moisture capacity of a material can not be described by the slope of the sorption isotherms alone, when the material is exposed to dynamic changes in the moisture conditions. Still, the assumption of an immediate equilibrium is well accepted in the simulation...
Perspective: Fundamental aspects of time-dependent density functional theory
Maitra, Neepa T.
2016-06-01
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.
Time-dependent coupled-cluster method for atomic nuclei
Pigg, D A; Nam, H; Papenbrock, T
2012-01-01
We study time-dependent coupled-cluster theory in the framework of nuclear physics. Based on Kvaal's bi-variational formulation of this method [S. Kvaal, arXiv:1201.5548], we explicitly demonstrate that observables that commute with the Hamiltonian are conserved under time evolution. We explore the role of the energy and of the similarity-transformed Hamiltonian under real and imaginary time evolution and relate the latter to similarity renormalization group transformations. Proof-of-principle computations of He-4 and O-16 in small model spaces, and computations of the Lipkin model illustrate the capabilities of the method.
Kinetic and potential components of the exact time-dependent correlation potential
Luo, Kai; Sandoval, Ernesto D; Elliott, Peter; Maitra, Neepa T
2013-01-01
The exact exchange-correlation (xc) potential of time-dependent density functional theory has been shown to have striking features. For example, step and peak features are generically found when the system is far from its ground-state, and these depend nonlocally on the density in space and time. We analyze the xc potential by decomposing it into kinetic and interaction potential components, and comparing each with their exact-adiabatic counterparts, for a range of dynamical situations in model one-dimensional (1D) two-electron systems. We find that often, but not always, the kinetic contri- bution is mostly responsible for these features, that are missed by the adiabatic approximation. The adiabatic approximation often makes a smaller error for the potential contribution, which we write in two parts, one being the Coulomb potential due to the time-dependent xc hole. These observations also held in non-equilibrium cases we studied where there are large features in the correlation po- tential although no step ...
Time-dependent strains and stresses in a pumpkin balloon
Gerngross, T.; Xu, Y.; Pellegrino, S.
This paper presents a study of pumpkin-shaped superpressure balloons consisting of gores made from a thin polymeric film attached to high stiffness meridional tendons This type of design is being used for the NASA ULDB balloons The gore film shows considerable time-dependent stress relaxation whereas the behaviour of the tendons is essentially time-independent Upon inflation and pressurization the instantaneous i e linear-elastic strain and stress distributions in the film show significantly higher values in the meridional direction However over time and due to the biaxial visco-elastic stress relaxation of the the gore material the em hoop strains increase and the em meridional stresses decrease whereas the em remaining strain and stress components remain substantially unchanged These results are important for a correct assessment of the structural integrity of a pumpkin balloon in a long-duration mission both in terms of the material performance and the overall stability of the shape of the balloon An experimental investigation of the time dependence of the biaxial strain distribution in the film of a 4 m diameter 48 gore pumpkin balloon is presented The inflated shape of selected gores has been measured using photogrammetry and the time variation in strain components at some particular points of these gores has been measured under constant pressure and temperature The results show good correlation with a numerical study using the ABAQUS finite-element package that includes a widely used model of
Characterization of time-dependent anelastic microbeam bending mechanics
Bergers, L. I. J. C.; Hoefnagels, J. P. M.; Geers, M. G. D.
2014-09-01
This paper presents an accurate yet straightforward methodology for characterizing time-dependent anelastic mechanics of thin metal films employed in metalic microelectromechanical systems (MEMS). The deflection of microbeams is controlled with a mechanical micro-clamp, measured with digital holographic microscopy and processed with global digital image correlation (GDIC). The GDIC processing directly incorporates kinematics into the three-dimensional correlation problem, describing drift-induced rigid body motion and the beam deflection. This yields beam curvature measurements with a resolution of <1.5 × 10-6 µm-1, or for films thinner than 5 µm, a strain resolution of <4 μɛ. Using a simple experimental sequence, these curvature measurements are then combined with a linear multi-mode time-dependent anelastic model and a priori knowledge of the Young's modulus. This allows the characterization of the material behaviour in the absence of an additional explicit force measurement, which simplifies the experimental setup. Using this methodology we characterize the anelasticity of 5 µm-thick Al(1 wt%)-Cu microbeams of varying microstructures over relevant timescales of 1 to 1 × 105 s and adequately predict the time and amplitude response of experiments performed for various loading conditions. This demonstrates the validity of the methodology and the suitability for thin film mechanics research for MEMS development.
Time Circular Birefringence in Time-Dependent Magnetoelectric Media
Zhang, Ruo-Yang; Lin, Shi-Rong; Zhao, Qing; Wen, Weijia; Ge, Mo-Lin
2015-01-01
Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking, and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media, and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector $\\mathbf{k}$, and name this effect "time circular birefringence" (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via "time refraction" and "time reflection" of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the "time Faraday effect", namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with n...
Sarstedt, Marko; Henseler, Jörg; Ringle, Christian M.
2011-01-01
Purpose – Partial least squares (PLS) path modeling has become a pivotal empirical research method in international marketing. Owing to group comparisons' important role in research on international marketing, we provide researchers with recommendations on how to conduct multigroup analyses in PLS p
Energy Technology Data Exchange (ETDEWEB)
Chiang, Min-Han; Wang, Jui-Yu [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Sheu, Rong-Jiun, E-mail: rjsheu@mx.nthu.edu.tw [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Department of Engineering System and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Liu, Yen-Wan Hsueh [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Department of Engineering System and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China)
2014-05-01
The High Temperature Engineering Test Reactor (HTTR) in Japan is a helium-cooled graphite-moderated reactor designed and operated for the future development of high-temperature gas-cooled reactors. Two detailed full-core models of HTTR have been established by using SCALE6 and MCNP5/X, respectively, to study its neutronic properties. Several benchmark problems were repeated first to validate the calculation models. Careful code-to-code comparisons were made to ensure that two calculation models are both correct and equivalent. Compared with experimental data, the two models show a consistent bias of approximately 20–30 mk overestimation in effective multiplication factor for a wide range of core states. Most of the bias could be related to the ENDF/B-VII.0 cross-section library or incomplete modeling of impurities in graphite. After that, a series of systematic analyses was performed to investigate the effects of cross sections on the HTTR criticality and burnup calculations, with special interest in the comparison between continuous-energy and multigroup results. Multigroup calculations in this study were carried out in 238-group structure and adopted the SCALE double-heterogeneity treatment for resonance self-shielding. The results show that multigroup calculations tend to underestimate the system eigenvalue by a constant amount of ∼5 mk compared to their continuous-energy counterparts. Further sensitivity studies suggest the differences between multigroup and continuous-energy results appear to be temperature independent and also insensitive to burnup effects.
Time-Dependent Calculations of an Impulsive Impact-Triggered Runaway Greenhouse Atmosphere on Mars
Segura, T. L.; Toon, O. B.; McKay, C. P.
2003-05-01
The existence of a few dozen craters of size 200 km and greater proves that large (30-250 km diameter) impacts were abundant in the early history of Mars. Injected water from three sources (the impactor itself, water innate to the crater, and from melting of the polar caps) provide periods of rain following such impacts. Very hot (> 1600 K), global debris blankets are another consequence of these large impacts, and these layers create a thermal pulse that propagates into the subsurface, melting additional water. Both the melted and precipitated water and debris blanket combine to produce a temporarily altered climate on the planet. This research provides the first time-dependent modeled calcuations of this altered climate, and focuses in particular on a possible "runaway" greenhouse state that might be initiated as a result of the additional heat and a sufficiently rapid supply of the melted and precipitated water to the atmosphere. Our model is a 1-D radiative-convective model coupled to a 1-D model of the regolith to calculate the evolution of the surface and subsurface temperatures. The effects of latent heating, cloud condensation, precipitation, and evaporation are included in the model.
Time-dependent calculations in Potassium mid-infrared wavelengths
Maragakis, P; Lambropoulos, P
1999-01-01
We study the dynamics of the Potassium atom in the mid-infrared, high intensity, short laser pulse regime. We ascertain our numerical convergence by comparing the results of two different propagation methods of the time-dependent Schroedinger equation. We present ionization curves in the 12-, 13-, and 14-photon ionization range for Potassium. The ionization curve of a scaled system, namely Hydrogen starting from the 2s, is compared to the 12-photon results. In the 13-photon regime, a dynamic resonance is observed and analyzed in more detail. The results for all wavelengths and intensities, including the case of Hydrogen, display a clear plateau formation in the peak-heights of the low energy part of the Above Threshold Ionization (ATI) spectrum, which scales with the ponderomotive energy Up, and extends to (2.8 +- 0.5) Up.
Time-dependent density-functional description of nuclear dynamics
Nakatsukasa, Takashi; Matsuo, Masayuki; Yabana, Kazuhiro
2016-01-01
We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of...
Relating Time-Dependent Acceleration and Height Using an Elevator
Kinser, Jason M.
2015-04-01
A simple experiment in relating a time-dependent linear acceleration function to height is explored through the use of a smartphone and an elevator. Given acceleration as a function of time1, a(t), the velocity function and position functions are determined through integration as in v (t ) =∫ a (t ) d t (1) and x (t ) =∫ v (t ) dt. Mobile devices such as smartphones or tablets have accelerometers that capture slowly evolving acceleration with respect to time and can deliver those measurements as a CSV file. A recent example measured the oscillations of the elevator as it starts its motion.2 In the application presented here the mobile device is used to estimate the height of the elevator ride. By estimating the functional form of the acceleration of an elevator ride, it is possible to estimate the height of the ride through Eqs. (1) and (2).
SYMTRAN - A Time-dependent Symmetric Tandem Mirror Transport Code
Energy Technology Data Exchange (ETDEWEB)
Hua, D; Fowler, T
2004-06-15
A time-dependent version of the steady-state radial transport model in symmetric tandem mirrors in Ref. [1] has been coded up and first tests performed. Our code, named SYMTRAN, is an adaptation of the earlier SPHERE code for spheromaks, now modified for tandem mirror physics. Motivated by Post's new concept of kinetic stabilization of symmetric mirrors, it is an extension of the earlier TAMRAC rate-equation code omitting radial transport [2], which successfully accounted for experimental results in TMX. The SYMTRAN code differs from the earlier tandem mirror radial transport code TMT in that our code is focused on axisymmetric tandem mirrors and classical diffusion, whereas TMT emphasized non-ambipolar transport in TMX and MFTF-B due to yin-yang plugs and non-symmetric transitions between the plugs and axisymmetric center cell. Both codes exhibit interesting but different non-linear behavior.
Multiaxial Temperature- and Time-Dependent Failure Model
Richardson, David; McLennan, Michael; Anderson, Gregory; Macon, David; Batista-Rodriquez, Alicia
2003-01-01
A temperature- and time-dependent mathematical model predicts the conditions for failure of a material subjected to multiaxial stress. The model was initially applied to a filled epoxy below its glass-transition temperature, and is expected to be applicable to other materials, at least below their glass-transition temperatures. The model is justified simply by the fact that it closely approximates the experimentally observed failure behavior of this material: The multiaxiality of the model has been confirmed (see figure) and the model has been shown to be applicable at temperatures from -20 to 115 F (-29 to 46 C) and to predict tensile failures of constant-load and constant-load-rate specimens with failure times ranging from minutes to months..
Time-dependent Corotation Resonance in Barred Galaxies
Wu, Yu-Ting; Taam, Ronald E
2016-01-01
The effective potential neighboring the corotation resonance region in barred galaxies is shown to be strongly time-dependent in any rotating frame because of the competition of nearby perturbations of similar strengths with differing rotation speeds. Contrary to the generally adopted assumption, that in the bar rotating frame the corotation region should possess four stationary equilibrium points (Lagrange points), with high quality N-body simulations we localize the instantaneous equilibrium points and find that they circulate or oscillate broadly in azimuth with respect to the pattern speeds of the inner or outer perturbations. This implies that at the particle level the Jacobi integral is not well conserved around the corotation radius. That is, angular momentum exchanges decouple from energy exchanges, enhancing the chaotic diffusion of stars through the corotation region.
Exponential time-dependent perturbation theory in rotationally inelastic scattering
Cross, R. J.
1983-08-01
An exponential form of time-dependent perturbation theory (the Magnus approximation) is developed for rotationally inelastic scattering. A phase-shift matrix is calculated as an integral in time over the anisotropic part of the potential. The trajectory used for this integral is specified by the diagonal part of the potential matrix and the arithmetic average of the initial and final velocities and the average orbital angular momentum. The exponential of the phase-shift matrix gives the scattering matrix and the various cross sections. A special representation is used where the orbital angular momentum is either treated classically or may be frozen out to yield the orbital sudden approximation. Calculations on Ar+N2 and Ar+TIF show that the theory generally gives very good agreement with accurate calculations, even where the orbital sudden approximation (coupled-states) results are seriously in error.
Goal Directed Relative Skyline Queries in Time Dependent Road Networks
Iyer, K B Priya
2012-01-01
The Wireless GIS technology is progressing rapidly in the area of mobile communications. Location-based spatial queries are becoming an integral part of many new mobile applications. The Skyline queries are latest apps under Location-based services. In this paper we introduce Goal Directed Relative Skyline queries on Time dependent (GD-RST) road networks. The algorithm uses travel time as a metric in finding the data object by considering multiple query points (multi-source skyline) relative to user location and in the user direction of travelling. We design an efficient algorithm based on Filter phase, Heap phase and Refine Skyline phases. At the end, we propose a dynamic skyline caching (DSC) mechanism which helps to reduce the computation cost for future skyline queries. The experimental evaluation reflects the performance of GD-RST algorithm over the traditional branch and bound algorithm for skyline queries in real road networks.
Time-dependent reliability analysis and condition assessment of structures
Energy Technology Data Exchange (ETDEWEB)
Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States)
1997-01-01
Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.
Histogram bin width selection for time-dependent Poisson processes
Energy Technology Data Exchange (ETDEWEB)
Koyama, Shinsuke; Shinomoto, Shigeru [Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
2004-07-23
In constructing a time histogram of the event sequences derived from a nonstationary point process, we wish to determine the bin width such that the mean squared error of the histogram from the underlying rate of occurrence is minimized. We find that the optimal bin widths obtained for a doubly stochastic Poisson process and a sinusoidally regulated Poisson process exhibit different scaling relations with respect to the number of sequences, time scale and amplitude of rate modulation, but both diverge under similar parametric conditions. This implies that under these conditions, no determination of the time-dependent rate can be made. We also apply the kernel method to these point processes, and find that the optimal kernels do not exhibit any critical phenomena, unlike the time histogram method.
Histogram bin width selection for time-dependent Poisson processes
Koyama, Shinsuke; Shinomoto, Shigeru
2004-07-01
In constructing a time histogram of the event sequences derived from a nonstationary point process, we wish to determine the bin width such that the mean squared error of the histogram from the underlying rate of occurrence is minimized. We find that the optimal bin widths obtained for a doubly stochastic Poisson process and a sinusoidally regulated Poisson process exhibit different scaling relations with respect to the number of sequences, time scale and amplitude of rate modulation, but both diverge under similar parametric conditions. This implies that under these conditions, no determination of the time-dependent rate can be made. We also apply the kernel method to these point processes, and find that the optimal kernels do not exhibit any critical phenomena, unlike the time histogram method.
Origin of the spike-timing-dependent plasticity rule
Cho, Myoung Won; Choi, M. Y.
2016-08-01
A biological synapse changes its efficacy depending on the difference between pre- and post-synaptic spike timings. Formulating spike-timing-dependent interactions in terms of the path integral, we establish a neural-network model, which makes it possible to predict relevant quantities rigorously by means of standard methods in statistical mechanics and field theory. In particular, the biological synaptic plasticity rule is shown to emerge as the optimal form for minimizing the free energy. It is further revealed that maximization of the entropy of neural activities gives rise to the competitive behavior of biological learning. This demonstrates that statistical mechanics helps to understand rigorously key characteristic behaviors of a neural network, thus providing the possibility of physics serving as a useful and relevant framework for probing life.
Painleve V and time-dependent Jacobi polynomials
Energy Technology Data Exchange (ETDEWEB)
Basor, Estelle [American Institute of Mathematics, Palo Alto, CA 94306 (United States); Chen Yang [Department of Mathematics, Imperial College London, 180 Queen' s Gates, London SW7 2BZ (United Kingdom); Ehrhardt, Torsten [Department of Mathematics, University of California, Santa Cruz, CA 95064 (United States)], E-mail: ebasor@aimath.org, E-mail: ychen@imperial.ac.uk, E-mail: ehrhardt@math.ucsc.edu
2010-01-08
In this paper we study the simplest deformation on a sequence of orthogonal polynomials. This in turn induces a deformation on the moment matrix of the polynomials and associated Hankel determinant. We replace the original (or reference) weight w{sub 0}(x) (supported on R or subsets of R) by w{sub 0}(x) e{sup -tx}. It is a well-known fact that under such a deformation the recurrence coefficients denoted as {alpha}{sub n} and {beta}{sub n} evolve in t according to the Toda equations, giving rise to the time-dependent orthogonal polynomials and time-dependent determinants, using Sogo's terminology. If w{sub 0} is the normal density e{sup -x{sup 2}}, x element of R, or the gamma density x{sup {alpha}} e{sup -x}, x element of R{sub +}, {alpha} > -1, then the initial value problem of the Toda equations can be trivially solved. This is because under elementary scaling and translation the orthogonality relations reduce to the original ones. However, if w{sub 0} is the beta density (1 - x){sup {alpha}}(1 + x){sup {beta}}, x in [ - 1, 1], {alpha}, {beta} > -1, the resulting 'time-dependent' Jacobi polynomials will again satisfy a linear second-order ode, but no longer in the Sturm-Liouville form, which is to be expected. This deformation induces an irregular singular point at infinity in addition to three regular singular points of the hypergeometric equation satisfied by the Jacobi polynomials. We will show that the coefficients of this ode, as well as the Hankel determinant, are intimately related to a particular Painleve V. In particular we show that p{sub 1}(n,t), where p{sub 1}(n,t) is the coefficient of z{sup n-1} of the monic orthogonal polynomials associated with the 'time-dependent' Jacobi weight, satisfies, up to a translation in t, the Jimbo-Miwa {sigma}-form of the same P{sub V}; while a recurrence coefficient {alpha}{sub n}(t) is up to a translation in t and a linear fractional transformation P{sub V}({alpha}{sup 2}/2, - {beta}{sup 2
Study of Time-Dependent Properties of Thermoplastics
Directory of Open Access Journals (Sweden)
Bolchoun A.
2010-06-01
Full Text Available Simple tests carried out with a common tension/compression testing machine are used to obtain timedependent properties of non-reinforced thermoplastics. These tests include ramp loadings as well as relaxation and creep tests. Two materials (PBT Celanex 2002-2 and POM Hostaform C9021, Ticona GmbH, Kelsterbach were taken for the experiments. The experiments show that an adequate description of the long-term material properties can be obtained from the short-time tests, namely from tests with constant traverse speed $L^.$. Below a model for the time-dependent mechanical behavior is presented and fitted to the obtained measured data. For the evaluation of the fitting quality long-term tests are used. Especially creep and relaxation tests with ”jumps”, i.e. rapid change of loading, are important for this purpose.
Spin-orbit torque induced spike-timing dependent plasticity
Energy Technology Data Exchange (ETDEWEB)
Sengupta, Abhronil, E-mail: asengup@purdue.edu; Al Azim, Zubair; Fong, Xuanyao; Roy, Kaushik [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)
2015-03-02
Nanoelectronic devices that mimic the functionality of synapses are a crucial requirement for performing cortical simulations of the brain. In this work, we propose a ferromagnet-heavy metal heterostructure that employs spin-orbit torque to implement spike-timing dependent plasticity. The proposed device offers the advantage of decoupled spike transmission and programming current paths, thereby leading to reliable operation during online learning. Possible arrangement of such devices in a crosspoint architecture can pave the way for ultra-dense neural networks. Simulation studies indicate that the device has the potential of achieving pico-Joule level energy consumption (maximum 2 pJ per synaptic event) which is comparable to the energy consumption for synaptic events in biological synapses.
Time-Dependent Tomographic Reconstruction of the Solar Corona
Vibert, Didier; Lamy, Philippe; Frazin, Richard A; Wojak, Julien
2016-01-01
Solar rotational tomography (SRT) applied to white-light coronal images observed at multiple aspect angles has been the preferred approach for determining the three-dimensional (3D) electron density structure of the solar corona. However, it is seriously hampered by the restrictive assumption that the corona is time-invariant which introduces significant errors in the reconstruction. We first explore several methods to mitigate the temporal variation of the corona by decoupling the "fast-varying" inner corona from the "slow-moving" outer corona using multiple masking (either by juxtaposition or recursive combination) and radial weighting. Weighting with a radial exponential profile provides some improvement over a classical reconstruction but only beyond 3 Rsun. We next consider a full time-dependent tomographic reconstruction involving spatio-temporal regularization and further introduce a co-rotating regularization aimed at preventing concentration of reconstructed density in the plane of the sky. Crucial t...
The time-dependent Aharonov–Casher effect
Directory of Open Access Journals (Sweden)
Douglas Singleton
2016-02-01
Full Text Available In this paper we give a covariant expression for Aharonov–Casher phase. This expression is a combination of the canonical electric field, Aharonov–Casher phase plus a magnetic field phase shift. We use this covariant expression for the Aharonov–Casher phase to investigate the case of a neutral particle with a non-zero magnetic moment moving in the time dependent electric and magnetic fields of a plane electromagnetic wave background. We focus on the case where the magnetic moment of the particle is oriented so that both the electric and magnetic fields lead to non-zero phases, and we look at the interplay between these electric and magnetic phases.
The time-dependent Aharonov-Casher effect
Singleton, Douglas
2015-01-01
In this paper we give a covariant expression for Aharonov-Casher phase. This expression is a combination of the canonical electric field, Aharonov-Casher phase plus a magnetic field phase shift. We use this covariant expression for the Aharonov-Casher phase to investigate the case of a neutral particle with a non-zero magnetic moment moving in the {\\it time dependent} electric and magnetic fields of a plane electromagnetic wave background. We focus on the case where the magnetic moment of the particle is oriented so that both the electric and magnetic field lead to non-zero phases, and we look at the interplay between these electric and magnetic phases.
The time-dependent Aharonov–Casher effect
Energy Technology Data Exchange (ETDEWEB)
Singleton, Douglas, E-mail: dougs@csufresno.edu [Department of Physics, California State University Fresno, Fresno, CA 93740-8031 (United States); ICTP South American Institute for Fundamental Research, UNESP – Univ. Estadual Paulista, Rua Dr. Bento T. Ferraz 271, 01140-070, São Paulo, SP (Brazil); Ulbricht, Jaryd, E-mail: julbrich@ucsc.edu [Physics Department, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Department of Physics, California State University Fresno, Fresno, CA 93740-8031 (United States)
2016-02-10
In this paper we give a covariant expression for Aharonov–Casher phase. This expression is a combination of the canonical electric field, Aharonov–Casher phase plus a magnetic field phase shift. We use this covariant expression for the Aharonov–Casher phase to investigate the case of a neutral particle with a non-zero magnetic moment moving in the time dependent electric and magnetic fields of a plane electromagnetic wave background. We focus on the case where the magnetic moment of the particle is oriented so that both the electric and magnetic fields lead to non-zero phases, and we look at the interplay between these electric and magnetic phases.
The time-dependent Aharonov-Casher effect
Singleton, Douglas; Ulbricht, Jaryd
2016-02-01
In this paper we give a covariant expression for Aharonov-Casher phase. This expression is a combination of the canonical electric field, Aharonov-Casher phase plus a magnetic field phase shift. We use this covariant expression for the Aharonov-Casher phase to investigate the case of a neutral particle with a non-zero magnetic moment moving in the time dependent electric and magnetic fields of a plane electromagnetic wave background. We focus on the case where the magnetic moment of the particle is oriented so that both the electric and magnetic fields lead to non-zero phases, and we look at the interplay between these electric and magnetic phases.
Timing intervals using population synchrony and spike timing dependent plasticity
Directory of Open Access Journals (Sweden)
Wei Xu
2016-12-01
Full Text Available We present a computational model by which ensembles of regularly spiking neurons can encode different time intervals through synchronous firing. We show that a neuron responding to a large population of convergent inputs has the potential to learn to produce an appropriately-timed output via spike-time dependent plasticity. We explain why temporal variability of this population synchrony increases with increasing time intervals. We also show that the scalar property of timing and its violation at short intervals can be explained by the spike-wise accumulation of jitter in the inter-spike intervals of timing neurons. We explore how the challenge of encoding longer time intervals can be overcome and conclude that this may involve a switch to a different population of neurons with lower firing rate, with the added effect of producing an earlier bias in response. Experimental data on human timing performance show features in agreement with the model’s output.
On a time-dependent extra spatial dimension
Kuhfittig, P K F
2006-01-01
In the usual brane-world scenario matter fields are confined to the four-dimensional spacetime, called a 3-brane, embedded in a higher-dimensional space, usually referred to as the bulk spacetime. In this paper we assume that the 3-brane a de Sitter space; there is only one extra spatial dimension, assumed to be time dependent. By using the form of the brane-world energy-momentum tensor suggested by Shiromizu et al. in the five-dimensional Einstein equations, it is shown that whenever the bulk cosmological constant \\Lambda is negative, the extra spatial dimension rapidly shrinks during the inflation of the brane. When \\Lambda>0, on the other hand, the extra spatial dimension either completely follows the cosmological expansion of the brane or completely ignores it. This behavior resembles the all-or-nothing behavior of ordinary systems in an expanding universe, as recently demonstrated by R.H. Price.
Time-dependent particle acceleration in a Fermi reservoir
Litvinenko, Y. E.
2012-08-01
Context. A steady model was presented by Burn, in which energy conservation is used to constrain the parameters of stochastic Fermi acceleration. A steady model, however, is unlikely to be adequate for particle acceleration in impulsive solar flares. Aims: This paper describes a time-dependent model for particle acceleration in a Fermi reservoir Methods: The calculation is based on the original formulation of stochastic acceleration by Fermi, with additional physically motivated assumptions about the turbulent and particle energy densities within the reservoir, that are similar to those of the steady analysis. The problem is reduced to an integro-differential equation that possesses an analytical solution. Results: The model predicts the formation of a power-law differential energy spectrum N(E) ~ E-2, that is observable outside the reservoir. The predicted spectral index is independent of the parameters of the model. The results may help in understanding particle acceleration in solar flares and other astrophysical applications.
On the time dependence of the $h$-index
Mannella, Riccardo
2012-01-01
The time dependence of the $h$-index is analyzed by considering the average behaviour of $h$ as a function of the academic age $A_A$ for about 1400 Italian physicists, with career lengths spanning from 3 to 46 years. The individual $h$-index is strongly correlated with the square root of the total citations $N_C$: $h \\approx 0.53 \\sqrt{N_C}$. For academic ages ranging from 12 to 24 years, the distribution of the time scaled index $h/\\sqrt{A_A}$ is approximately time-independent and it is well described by the Gompertz function. The time scaled index $h/\\sqrt{A_A}$ has an average approximately equal to 3.8 and a standard deviation approximately equal to 1.6. Finally, the time scaled index $h/\\sqrt{A_A}$ appears to be strongly correlated with the contemporary $h$-index $h_c$.
Hamiltonian formulation of time-dependent plausible inference
Davis, Sergio
2014-01-01
Maximization of the path information entropy is a clear prescription for performing time-dependent plausible inference. Here it is shown that, following this prescription under the assumption of arbitrary instantaneous constraints on position and velocity, a Lagrangian emerges which determines the most probable trajectory. Deviations from the probability maximum can be consistently described as slices in time by a Hamiltonian, according to a nonlinear Langevin equation and its associated Fokker-Planck equation. The connections unveiled between the maximization of path entropy and the Langevin/Fokker-Planck equations imply that missing information about the phase space coordinate never decreases in time, a purely information-theoretical version of the Second Law of Thermodynamics. All of these results are independent of any physical assumptions, and thus valid for any generalized coordinate as a function of time, or any other parameter. This reinforces the view that the Second Law is a fundamental property of ...
Time-dependent Corotation Resonance in Barred Galaxies
Wu, Yu-Ting; Pfenniger, Daniel; Taam, Ronald E.
2016-10-01
The effective potential neighboring the corotation resonance region in barred galaxies is shown to be strongly time-dependent in any rotating frame, due to the competition of nearby perturbations of similar strengths with differing rotation speeds. Contrary to the generally adopted assumption that in the bar rotating frame the corotation region should possess four stationary equilibrium points (Lagrange points), with high quality N-body simulations, we localize the instantaneous equilibrium points (EPs) and find that they circulate or oscillate broadly in azimuth with respect to the pattern speeds of the inner or outer perturbations. This implies that at the particle level the Jacobi integral is not well conserved around the corotation radius. That is, angular momentum exchanges decouple from energy exchanges, enhancing the chaotic diffusion of stars through the corotation region.
A gauge invariant theory for time dependent heat current
Chen, Jian; ShangGuan, Minhui; Wang, Jian
2015-05-01
In this work, we develop a general gauge-invariant theory for AC heat current through multi-probe systems. Using the non-equilibrium Green’s function, a general expression for time-dependent electrothermal admittance is obtained where we include the internal potential due to the Coulomb interaction explicitly. We show that the gauge-invariant condition is satisfied for heat current if the self-consistent Coulomb interaction is considered. It is known that the Onsager relation holds for dynamic charge conductance. We show in this work that the Onsager relation for electrothermal admittance is violated, except for a special case of a quantum dot system with a single energy level. We apply our theory to a nano capacitor where the Coulomb interaction plays an essential role. We find that, to the first order in frequency, the heat current is related to the electrochemical capacitance as well as the phase accumulated in the scattering event.
Time-dependent interactions between iboga agents and cocaine.
Maisonneuve, I M; Visker, K E; Mann, G L; Bandarage, U K; Kuehne, M E; Glick, S D
1997-10-08
The purpose of this study was to clarify the effects of iboga agents on cocaine-induced hyperactivity. Both inhibition and enhancement of cocaine-induced activity by ibogaine have been reported. In the present study, rats were treated with either ibogaine (40 mg/kg, i.p.), noribogaine (40 mg/kg, i.p.), 18-methoxycoronaridine (40 mg/kg, i.p.), or saline, 1 or 19 h prior to the administration of cocaine (20 mg/kg, i.p.) or saline. Motor activity was monitored thereafter for 3 h. All three iboga agents had acute inhibitory effects and delayed potentiating effects on cocaine-induced hyperactivity. These time-dependent effects, which could not be attributed to the motor activity induced by the iboga agents alone, account for divergent results reported in the literature.
Large blue isocurvature spectral index signals time-dependent mass
Chung, Daniel J. H.
2016-08-01
We show that if a spectator linear isocurvature dark matter field degree of freedom has a constant mass through its entire evolution history, the maximum measurable isocurvature spectral index that is consistent with the current tensor-to-scalar ratio bound of about r ≲0.1 is about nI≲2.4 , even if experiments can be sensitive to a 10-6 contamination of the predominantly adiabatic power spectrum with an isocurvature power spectrum at the shortest observable length scales. Hence, any foreseeable future measurement of a blue isocurvature spectral index larger than ˜2.4 may provide nontrivial evidence for dynamical degrees of freedom with time-dependent masses during inflation. The bound is not sensitive to the details of the reheating scenario and can be made mildly smaller if r is better constrained in the future.
Translation invariant time-dependent solutions to massive gravity
Energy Technology Data Exchange (ETDEWEB)
Mourad, J.; Steer, D.A., E-mail: mourad@apc.univ-paris7.fr, E-mail: steer@apc.univ-paris7.fr [AstroParticule and Cosmologie (UMR 7164 - APC, Univ Paris Diderot, CNRS/IN2P3, CEA/lrfu, Obs de Paris, Sorbonne Paris Cité, France), 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13 (France)
2013-12-01
Homogeneous time-dependent solutions of massive gravity generalise the plane wave solutions of the linearised Fierz-Pauli equations for a massive spin-two particle, as well as the Kasner solutions of General Relativity. We show that they also allow a clear counting of the degrees of freedom and represent a simplified framework to work out the constraints, the equations of motion and the initial value formulation. We work in the vielbein formulation of massive gravity, find the phase space resulting from the constraints and show that several disconnected sectors of solutions exist some of which are unstable. The initial values determine the sector to which a solution belongs. Classically, the theory is not pathological but quantum mechanically the theory may suffer from instabilities. The latter are not due to an extra ghost-like degree of freedom.
Effects of Temperature on Time Dependent Rheological Characteristics of Koumiss
Directory of Open Access Journals (Sweden)
Serdal Sabancı
2016-04-01
Full Text Available The rheological properties of koumiss were investigated at different temperatures (4, 10, and 20°C. Experimental shear stress–shear rate data were fitted to different rheological models. The consistency of koumiss was predicted by using the power-law model since it described the consistency of koumiss best with highest regression coefficient and lowest errors (root mean square error and chi-square. Koumiss exhibited shear thinning behavior (n<1. The flow activation energy for temperature dependency of consistency was 25.532 kJ/mol, and the frequency constant was 2.18×10-7Pa.sn. As the temperature increased the time dependent thixotropic characteristics of koumiss decreased.
Time-dependent resonant magneto-optical rotation
Dziczek, Dariusz
2015-01-01
Results of a fairly straightforward experiment on resonant magneto-optical rotation by rubidium-87 atoms revealed strong time-dependence of the polarization plane of light emerging from atomic vapors following a sudden irradiation with a laser beam. The rotation of the plane appears as a not direct consequence of the influence of the magnetic field on atoms. Reported measurements conducted using a vapor cell without any buffer gas or an anti-relaxation wall coating show that transmitted light has initially the same (linear) polarization as the incident one. Rotation of the polarization plane caused by an axial magnetic field develops in time scales similar to the pace of establishing the optical pumping/relaxation equilibrium in the atomic ensemble. The traditional passive Faraday rotation picture providing working description for the resonant magneto-optical effects in steady-state conditions does not explain the observed sequence of evolution of the polarization. The picture has to be augmented with analysi...
Translation invariant time-dependent solutions to massive gravity
Mourad, J
2013-01-01
Homogeneous time-dependent solutions of massive gravity generalise the plane wave solutions of the linearised Fierz-Pauli equations for a massive spin-two particle, as well as the Kasner solutions of General Relativity. We show that they also allow a clear counting of the degrees of freedom and represent a simplified framework to work out the constraints, the equations of motion and the initial value formulation. We work in the vielbein formulation of massive gravity, find the phase space resulting from the constraints and show that several disconnected sectors of solutions exist some of which are unstable. The initial values determine the sector to which a solution belongs. Classically, the theory is not pathological but quantum mechanically the theory may suffer from instabilities. The latter are not due to an extra ghost-like degree of freedom.
Time-dependent compaction band formation in sandstone
Heap, Michael J.; Brantut, Nicolas; Baud, Patrick; Meredith, Philip G.
2015-07-01
Compaction bands in sandstone are laterally extensive planar deformation features that are characterized by lower porosity and permeability than the surrounding host rock. As a result, this form of localization has important implications for both strain partitioning and fluid flow in the Earth's upper crust. To better understand the time dependency of compaction band growth, we performed triaxial deformation experiments on water-saturated Bleurswiller sandstone (initial porosity = 0.24) under constant stress (creep) conditions in the compactant regime. Our experiments show that inelastic strain accumulates at a constant stress in the compactant regime, manifest as compaction bands. While creep in the dilatant regime is characterized by an increase in porosity and, ultimately, an acceleration in axial strain rate to shear failure, compaction creep is characterized by a reduction in porosity and a gradual deceleration in axial strain rate. The global decrease in the rates of axial strain, acoustic emission energy, and porosity change during creep compaction is punctuated at intervals by higher rate excursions, interpreted as the formation of compaction bands. The growth rate of compaction bands formed during creep is lower as the applied differential stress, and hence, background creep strain rate, is decreased. However, the inelastic strain associated with the growth of a compaction band remains constant over strain rates spanning several orders of magnitude (from 10-8 to 10-5 s-1). We find that despite the large differences in strain rate and growth rate (from both creep and constant strain rate experiments), the characteristics (geometry and thickness) of the compaction bands remain essentially the same. Several lines of evidence, notably the similarity between the differential stress dependence of creep strain rate in the dilatant and compactant regimes, suggest that as for dilatant creep, subcritical stress corrosion cracking is the mechanism responsible for
New applications with time-dependent thermochemical simulation
Energy Technology Data Exchange (ETDEWEB)
Koukkari, P. [VTT Chemical Technology, Espoo (Finland); Laukkanen, L. [VTT Automation, Espoo (Finland); Penttilae, K. [Kemira Engineering Oy, Helsinki (Finland)
1996-12-31
A new method (RATEMIX) to calculate multicomponent chemical reaction mixtures as a series of sequential thermochemical states was recently introduced. The procedure combines multicomponent thermodynamics with chemical kinetics and may be used to simulate the multicomponent reactors as a thermochemical natural process. The method combines the desired reaction rates sequentially with constrained Gibbs energy minimization. The reactant concentrations are determined by the experimental (Arrhenius) rate laws. During the course of the given reaction the subsequent side reactions are supposed to occur reversibly. At every sequential stage of the given reaction the temperature and composition of the reaction mixture are calculated by a thermodynamic subroutine, which minimizes the Gibbs energy of the system and takes into account the heat transfer between the system and its surroundings. The extents of reaction are included as algorithmic constraints in the Gibbs energy minimization procedure. Initially, the reactants are introduced to the system as inert copies to match both the mass and energy balance of the reactive system. During the calculation the copies are sequentially interchanged to the actual reactants which allows one to simulate the time-dependent reaction route by using the thermochemical procedure. For each intermediate stage, the temperature and composition are calculated and as well numerical estimates of the thermodynamic functions are obtained. The method is applicable in processes where the core thermodynamic and kinetic data of the system are known and the time-dependent heat transfer data can either be measured or estimated by calculation. The method has been used to simulate e.g. high temperature flame reactions, zinc vapour oxidation and a counter-current rotary drum with chemical reactions. The procedure has today been tested with SOLGASMIX, CHEMSAGE and HSC programs. (author)
Time-dependent changes in altruistic punishment following stress.
Vinkers, Christiaan H; Zorn, Jelle V; Cornelisse, Sandra; Koot, Susanne; Houtepen, Lotte C; Olivier, Berend; Verster, Joris C; Kahn, René S; Boks, Marco P M; Kalenscher, Tobias; Joëls, Marian
2013-09-01
Decisions are rarely made in social isolation. One phenomenon often observed in social interactions is altruistic punishment, i.e. the punishment of unfair behavior by others at a personal cost. The tendency for altruistic punishment is altered by affective states including those induced by stress exposure. Stress is thought to exert bi-directional effects on behavior: immediately after stress, reflex-like and habitual behavior is promoted while later on more far-sighted, flexible and goal-directed behavior is enhanced. We hypothesized that such time-dependent effects of stress would also be present in the context of altruistic punishment behavior. Healthy male participants (N=80) were exposed to either a grouped stress test or a control condition. Participants were tested in prosocial decision making tasks either directly after stress or 75 min later. Altruistic punishment was assessed using the Ultimatum Game. General altruism was assessed with a one-shot version of the Dictator Game in which an anonymous donation could be offered to a charitable organization. We found that stress caused a bi-directional effect on altruistic punishment, with decreased rejection rates in the late aftermath of stress in response to ambiguous 30% offers. In the Dictator Game, stressed participants were less generous than controls, but no time-dependent effect was observed, indicating that the general reward sensitivity remained unchanged at various time-points after stress. Overall, during the late aftermath after acute stress exposure (i.e. 75 min later), participants acted more consistent with their own material self-interest, and had a lower propensity for altruistic punishment, possibly through upregulation of cognitive self-control mechanisms. Thus, our findings underscore the importance of time as a factor in simple, real-life economic decisions in a stressful social context.
Spike-timing dependent plasticity in the striatum
Directory of Open Access Journals (Sweden)
Elodie Fino
2010-06-01
Full Text Available The striatum is the major input nucleus of basal ganglia, an ensemble of interconnected sub-cortical nuclei associated with fundamental processes of action-selection and procedural learning and memory. The striatum receives afferents from the cerebral cortex and the thalamus. In turn, it relays the integrated information towards the basal ganglia output nuclei through which it operates a selected activation of behavioral effectors. The striatal output neurons, the GABAergic medium-sized spiny neurons (MSNs, are in charge of the detection and integration of behaviorally relevant information. This property confers to the striatum the ability to extract relevant information from the background noise and select cognitive-motor sequences adapted to environmental stimuli. As long-term synaptic efficacy changes are believed to underlie learning and memory, the corticostriatal long-term plasticity provides a fundamental mechanism for the function of the basal ganglia in procedural learning. Here, we reviewed the different forms of spike-timing dependent plasticity (STDP occurring at corticostriatal synapses. Most of the studies have focused on MSNs and their ability to develop long-term plasticity. Nevertheless, the striatal interneurons (the fast-spiking GABAergic, the NO synthase and cholinergic interneurons also receive monosynaptic afferents from the cortex and tightly regulated corticostriatal information processing. Therefore, it is important to take into account the variety of striatal neurons to fully understand the ability of striatum to develop long-term plasticity. Corticostriatal STDP with various spike-timing dependence have been observed depending on the neuronal sub-populations and experimental conditions. This complexity highlights the extraordinary potentiality in term of plasticity of the corticostriatal pathway.
Nahoon: Time-dependent gas-phase chemical model
Wakelam, V.
2014-09-01
Nahoon is a gas-phase chemical model that computes the chemical evolution in a 1D temperature and density structure. It uses chemical networks downloaded from the KInetic Database for Astrochemistry (KIDA) but the model can be adapted to any network. The program is written in Fortran 90 and uses the DLSODES (double precision) solver from the ODEPACK package to solve the coupled stiff differential equations. The solver computes the chemical evolution of gas-phase species at a fixed temperature and density and can be used in one dimension (1D) if a grid of temperature, density, and visual extinction is provided. Grains, both neutral and negatively charged, and electrons are considered as chemical species and their concentrations are computed at the same time as those of the other species. Nahoon contains a test to check the temperature range of the validity of the rate coefficients and avoid extrapolations outside this range. A test is also included to check for duplication of chemical reactions, defined over complementary ranges of temperature.
Time Dependent Hadronic Modeling of Flat Spectrum Radio Quasars
Diltz, Christopher; Fossati, Giovanni
2015-01-01
We introduce a new time-dependent lepto-hadronic model for blazar emission that takes into account the radiation emitted by secondary particles, such as pions and muons, from photo hadronic interactions. Starting from a baseline parameter set guided by a fit to the spectral energy distribution of the blazar 3C 279, we perform a parameter study to investigate the effects of perturbations of the input parameters to mimic different flaring events to study the resulting lightcurves in the optical, X-ray, high energy (HE: E > 100 MeV) and very-high-energy (VHE: E > 100 GeV) gamma-rays as well as the neutrino emission associated with charged-pion and muon decay. We find that flaring events from an increase in the efficiency of Fermi II acceleration will produce a positive correlation between all bandpasses and a marked plateau in the HE gamma-ray lightcurve. We also predict a distinctive dip in the HE lightcurve for perturbations caused by a change in the proton injection spectral index. These plateaus / dips could...
Time-dependent histamine release from stored human blood products
DEFF Research Database (Denmark)
Nielsen, Hans Jørgen; Edvardsen, L; Vangsgaard, K;
1996-01-01
storage. Whole blood (six units), plasma-reduced whole blood (six units), and plasma- and buffy coat-reduced (saline-adenine-glucose-mannitol) (SAGM) blood (six units) from unpaid healthy donors were stored in the blood bank for 35 days at 4 degrees C. Plasma histamine and total cell-bound histamine......Perioperative transfusion of whole blood has been shown to amplify trauma-induced immunosuppression, which could be attenuated by perioperative administration of histamine2 receptor antagonists. Supernatants from different blood products were, therefore, analysed for histamine content during.......0 (range 176.0-910.0) nmol/l in whole blood and 475.0 (range 360.0-1560.0) nmol/l in plasma-reduced whole blood, while it was undetectable in SAGM blood. Spontaneous histamine release increased in a time-dependent manner from a median of 6.7 (range 2.2-17.4) nmol/l at the time of storage to 175.0 (range 33...
Modeling of time dependent subsidence for coal and ore deposits
Institute of Scientific and Technical Information of China (English)
Ryszard Hejmanowski
2015-01-01
Coal and ore underground mining generates subsidence and deformation of the land surface. Those defor-mations may cause damage to buildings and infrastructures. The environmental impact of subsidence will not be accepted in the future by the society in many countries. Especially there, where the mining regions are densely urbanized, the acceptance of the ground deformations decreases every year. The only solution is to limit the subsidence or its impact on the infrastructure. The first is not rentable for the mining industry, the second depends on the precise subsidence prediction and good preventing management involved in the mining areas. The precision of the subsidence prediction depends strictly on the mathematical model of the deformation phenomenon and on the uncertainty of the input data. The subsidence prediction in the geological conditions of the raw materials used to be made on the basis of numerical modeling or the stochastic models. A modified solution of the stochastic model by Knothe will be presented in the paper. The author focuses on the precise description of the deposit shape and on the time dependent displacements of the rock mass. A two parameters’ time function has been introduced in the algorithm.
Recovery of time-dependent volatility in option pricing model
Deng, Zui-Cha; Hon, Y. C.; Isakov, V.
2016-11-01
In this paper we investigate an inverse problem of determining the time-dependent volatility from observed market prices of options with different strikes. Due to the non linearity and sparsity of observations, an analytical solution to the problem is generally not available. Numerical approximation is also difficult to obtain using most of the existing numerical algorithms. Based on our recent theoretical results, we apply the linearisation technique to convert the problem into an inverse source problem from which recovery of the unknown volatility function can be achieved. Two kinds of strategies, namely, the integral equation method and the Landweber iterations, are adopted to obtain the stable numerical solution to the inverse problem. Both theoretical analysis and numerical examples confirm that the proposed approaches are effective. The work described in this paper was partially supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region (Project No. CityU 101112) and grants from the NNSF of China (Nos. 11261029, 11461039), and NSF grants DMS 10-08902 and 15-14886 and by Emylou Keith and Betty Dutcher Distinguished Professorship at the Wichita State University (USA).
Experimental quantum cosmology in time-dependent optical media
Westerberg, N; Belgiorno, F; Piazza, F Dalla; Faccio, D
2014-01-01
It is possible to construct artificial spacetime geometries for light by using intense laser pulses that modify the spatiotemporal properties of an optical medium. Here we theoretically investigate experimental possibilities for studying spacetime metrics of the form $\\textrm{d}s^2=c^2\\textrm{d}t^2-\\eta(t)^2\\textrm{d}x^2$. By tailoring the laser pulse shape and medium properties, it is possible to create a refractive index variation $n=n(t)$ that can be identified with $\\eta(t)$. Starting from a perturbative solution to a generalised Hopfield model for the medium described by an $n=n(t)$ we provide estimates for the number of photons generated by the time-dependent spacetime. The simplest example is that of a uniformly varying $\\eta(t)$ that therefore describes the Robertson-Walker metric, i.e. a cosmological expansion. The number of photon pairs generated in experimentally feasible conditions appears to be extremely small. However, large photon production can be obtained by periodically modulating the medium...
Time-dependent cavitation in a viscous fluid
Shneidman, Vitaly A.
2016-12-01
Kinetics of nucleation and growth of empty bubbles in a nonvolatile incompressible fluid under negative pressure is considered within the generalized Zeldovich framework. The transient matched asymptotic solution obtained earlier for predominantly viscous nucleation is used to evaluate the distribution of growing cavities over sizes. Inertial effects described by the Rayleigh-Plesset equation are further included. The distributions are used to estimate the volume occupied by cavities, which leads to increase of pressure and eventual self-quenching of nucleation. Numerical solutions are obtained and compared with analytics. Due to rapid expansion of cavities the conventional separation of the nucleation and the growth time scales can be less distinct, which increases the role of transient effects. In particular, in the case of dominant viscosity a typical power-law tail of the quasistationary distribution is replaced by a time-dependent exponential tail. For fluids of the glycerin type such distributions can extend into the micrometer region, while in low-viscosity liquids (water, mercury) exponential distributions are short lived and are restricted to nanometer scales due to inertial effects.
Hot Jupiter Breezes: Time-dependent Outflows from Extrasolar Planets
Owen, James E
2015-01-01
We explore the dynamics of magnetically controlled outflows from Hot Jupiters, where these flows are driven by UV heating from the central star. In these systems, some of the open field lines do not allow the flow to pass smoothly through the sonic point, so that steady-state solutions do not exist in general. This paper focuses on this type of magnetic field configuration, where the resulting flow becomes manifestly time-dependent. We consider the case of both steady heating and time-variable heating, and find the time scales for the corresponding time variations of the outflow. Because the flow cannot pass through the sonic transition, it remains subsonic and leads to so-called breeze solutions. One manifestation of the time variability is that the flow samples a collection of different breeze solutions over time, and the mass outflow rate varies in quasi-periodic fashion. Because the flow is subsonic, information can propagate inward from the outer boundary, which determines, in part, the time scale of the...
Time Dependent Couplings as Observables in de Sitter Space
Kitamoto, Hiroyuki
2014-01-01
We summarize and expand our investigations concerning the soft graviton effects on microscopic matter dynamics in de Sitter space. The physical couplings receive IR logarithmic corrections which are sensitive to the IR cut-off at the one-loop level. The scale invariant spectrum in the gravitational propagator at the super-horizon scale is the source of the de Sitter symmetry breaking. The quartic scalar, Yukawa and gauge couplings become time dependent and diminish with time. In contrast, the Newton's constant increases with time. We clarify the physical mechanism behind these effects in terms of the conformal mode dynamics in analogy with 2d quantum gravity. We show that they are the inevitable consequence of the general covariance and lead to gauge invariant predictions. We construct a simple model in which the cosmological constant is self-tuned to vanish due to UV-IR mixing effect. We also discuss phenomenological implications such as decaying Dark Energy and SUSY breaking at the Inflation era. The quantu...
Nuclear inertia from the time dependent pairing equations
Mirea, M.
2016-10-01
In a dynamical system, the momenta of inertia and the effective masses are not adiabatic quantities, but are dynamical ones that depend on the dissipated energy accumulated during motion. However, these parameters are calculated for adiabatic nuclear systems, leaving no room for dissipated energy. In this work, a formalism is elaborated in order to derive simultaneously the nuclear momenta of inertia and the effective masses by taking into account the appearance of dissipated energy for large amplitude motion of the nuclear system. The expressions that define the inertia are obtained from the variational principle. The same principle manages the time dependent pairing equations, offering estimations of the averaged dissipation energy for large amplitude motions. The model is applied to 232Th fission. The fission barrier was calculated along the least action trajectory. The dissipation energy, effective mass and moment of inertia are determined for different values of the collective velocities. The dissipation increases with the internuclear velocity in binary disintegration processes and modifies the effective mass parameters. We observed that the inertia decreases as long as the collective velocity increases to some moderate values and begins to grow for larger collective velocities. So, a dependence between the cranking mass parameters and the intrinsic excitation energy is evidenced. In order to investigate the overall effect, the half-lives are predicted for adiabatic and dynamics simulations.
Time-dependence of non-planar accretion discs
Energy Technology Data Exchange (ETDEWEB)
Papaloizou, J.C.B. (Queen Mary Coll., London (UK). Dept. of Applied Mathematics); Pringle, J.E. (Amsterdam Univ. (Netherlands). Astronomical Inst.)
1983-03-01
Equations are derived which describe the time-dependence of a viscous, tilted accretion disc subject to external torques. A full hydrodynamical treatment is used and the equations linearized in terms of a small tilt. It is shown that previous attempts at deriving these equations are inadequate due to the inconsistency of some of the assumptions made. The behaviour of a tilted viscous disc is not simple to describe. Viscous forces tend to flatten the disc, but they also produce torques within the disc which induce local precession of disc elements. The main complication is that the horizontal motions induced in the disc by the tilt are resonantly driven so that their magnitude and phase are governed by the viscosity. This leads to the disc being smoothed on a time-scale faster than the usual viscous one. In order to obtain a simple diffusion equation governing the tilt angle ..beta.., it is necessary in a Keplerian disc that the viscosity parameter ..cap alpha.. be greater than the opening angle of the disc (H/R). If this condition is not satisfied consideration must be given to the proper dynamical modes of the disc, and the simple approach to the problem adopted here is inadequate.
Time-dependent radiation dose simulations during interplanetary space flights
Dobynde, Mikhail; Shprits, Yuri; Drozdov, Alexander; Hoffman, Jeffrey; Li, Ju
2016-07-01
Space radiation is one of the main concerns in planning long-term interplanetary human space missions. There are two main types of hazardous radiation - Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR). Their intensities and evolution depend on the solar activity. GCR activity is most enhanced during solar minimum, while the most intense SEPs usually occur during the solar maximum. SEPs are better shielded with thick shields, while GCR dose is less behind think shields. Time and thickness dependences of the intensity of these two components encourage looking for a time window of flight, when radiation intensity and dose of SEP and GCR would be minimized. In this study we combine state-of-the-art space environment models with GEANT4 simulations to determine the optimal shielding, geometry of the spacecraft, and launch time with respect to the phase of the solar cycle. The radiation environment was described by the time-dependent GCR model, and the SEP spectra that were measured during the period from 1990 to 2010. We included gamma rays, electrons, neutrons and 27 fully ionized elements from hydrogen to nickel. We calculated the astronaut's radiation doses during interplanetary flights using the Monte-Carlo code that accounts for the primary and the secondary radiation. We also performed sensitivity simulations for the assumed spacecraft size and thickness to find an optimal shielding. In conclusion, we present the dependences of the radiation dose as a function of launch date from 1990 to 2010, for flight durations of up to 3 years.
Time-dependent models of dense PDRs with complex molecules
Morata, O
2008-01-01
We present a study of the chemistry of a dense photon-dominated region (PDR) using a time-dependent chemical model. Our major interest is to study the spatial distribution of complex molecules such as hydrocarbons and cyanopolyynes in the cool dense material bordering regions where star formation has taken place. Our standard model uses a homogeneous cloud of density 2x10e4 cm-3 and temperature T=40 K, which is irradiated by a far-ultraviolet radiation field of intermediate intensity, given by X=100. We find that over a range of times unsaturated hydrocarbons (e.g., C2H, C4H, C3H2) have relatively high fractional abundances in the more external layers of the PDR, whereas their abundances in the innermost layers are several orders of magnitudes lower. On the other hand, molecules that are typical of late-time chemistry are usually more abundant in the inner parts of the PDR. We also present results for models with different density, temperature, intensity of the radiation field and initial fractional abundance...
Time-dependent effect in green synthesis of silver nanoparticles
Directory of Open Access Journals (Sweden)
Darroudi M
2011-04-01
Full Text Available Majid Darroudi1,2, Mansor Bin Ahmad3, Reza Zamiri4, AK Zak5, Abdul Halim Abdullah1,3, Nor Azowa Ibrahim31Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA, Universiti Putra Malaysia, Selangor, Malaysia; 2Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran; 3Department of Chemistry, 4Department of Physics, Faculty of Science, Universiti Putra Malaysia, Selangor, Malaysia; 5Low Dimensional Materials Research Center, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, MalaysiaAbstract: The application of “green” chemistry rules to nanoscience and nanotechnology is very important in the preparation of various nanomaterials. In this work, we successfully developed an eco-friendly chemistry method for preparing silver nanoparticles (Ag-NPs in natural polymeric media. The colloidal Ag-NPs were synthesized in an aqueous solution using silver nitrate, gelatin, and glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag-NPs were studied at different reaction times. The ultraviolet-visible (UV-vis spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM and their size distributions. The prepared samples were also characterized by X-ray diffraction (XRD and atomic force microscopy (AFM. The use of eco-friendly reagents, such as gelatin and glucose, provides green and economic attributes to this work.Keywords: silver nanoparticles, gelatin, green chemistry, time-dependent effect, ultraviolet-visible spectra
Density-functional perturbation theory goes time-dependent
Directory of Open Access Journals (Sweden)
Gebauer, Ralph
2008-05-01
Full Text Available The scope of time-dependent density-functional theory (TDDFT is limited to the lowest portion of the spectrum of rather small systems (a few tens of atoms at most. In the static regime, density-functional perturbation theory (DFPT allows one to calculate response functions of systems as large as currently dealt with in ground-state simulations. In this paper we present an effective way of combining DFPT with TDDFT. The dynamical polarizability is first expressed as an off-diagonal matrix element of the resolvent of the Kohn-Sham Liouvillian super-operator. A DFPT representation of response functions allows one to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is finally conveniently evaluated using a newly developed non-symmetric Lanczos technique, which allows for the calculation of the entire spectrum with a single Lanczos recursion chain. Each step of the chain essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian or, for that matter, as a single time step of a Car-Parrinello molecular dynamics run. The method will be illustrated with a few case molecular applications.
Translation invariant time-dependent solutions to massive gravity II
Energy Technology Data Exchange (ETDEWEB)
Mourad, J.; Steer, D.A., E-mail: mourad@apc.univ-paris7.fr, E-mail: steer@apc.univ-paris7.fr [AstroParticule and Cosmologie, UMR 7164-CNRS, Université Denis Diderot-Paris 7, CEA, Observatoire de Paris, F-75205 Paris Cedex 13 (France)
2014-06-01
This paper is a sequel to JCAP 12 (2013) 004 and is also devoted to translation-invariant solutions of ghost-free massive gravity in its moving frame formulation. Here we consider a mass term which is linear in the vielbein (corresponding to a β{sub 3} term in the 4D metric formulation) in addition to the cosmological constant. We determine explicitly the constraints, and from the initial value formulation show that the time-dependent solutions can have singularities at a finite time. Although the constraints give, as in the β{sub 1} case, the correct number of degrees of freedom for a massive spin two field, we show that the lapse function can change sign at a finite time causing a singular time evolution. This is very different to the β{sub 1} case where time evolution is always well defined. We conclude that the β{sub 3} mass term can be pathological and should be treated with care.
Translation invariant time-dependent solutions to massive gravity II
Mourad, J
2014-01-01
This paper is a sequel to arXiv:1310.6560 [hep-th] and is also devoted to translation-invariant solutions of ghost-free massive gravity in its moving frame formulation. Here we consider a mass term which is linear in the vielbein (corresponding to a $\\beta_3$ term in the 4D metric formulation) in addition to the cosmological constant. We determine explicitly the constraints, and from the initial value formulation show that the time-dependent solutions can have singularities at a finite time. Although the constraints give, as in the $\\beta_1$ case, the correct number of degrees of freedom for a massive spin two field, we show that the lapse function can change sign at a finite time causing a singular time evolution. This is very different to the $\\beta_1$ case where time evolution is always well defined. We conclude that the $\\beta_3$ mass term can be pathological and should be treated with care.
Gap vortex streets and turbulence in time-dependent streams
Duong, Dan; Tavoularis, Stavros
2016-11-01
Gap vortex streets form in axial flows in highly eccentric annular channels, tightly packed rod bundles and other channels having narrow gap regions flanked by wider ones. The characteristics of these vortices and the flow and turbulence distributions in some of these channels have in the past documented for steady streams; in particular, the vortex generation frequency was found to be proportional to the bulk Reynolds number. The present study extends these findings to both accelerating and decelerating air flows in a large-scale rod bundle, configured as a wind tunnel with a by-pass branch equipped with a controlled movable flap just downstream of the blower. Time-dependent statistical properties in a gap and a subchannel centre were determined by phase-averaging velocity measurements collected with hot-wire anemometers and the time history of the phase-averaged vortex street frequency was determined with the use of a wavelet transform. Contrary to expectations, the results show that deviations of the vortex frequency and other flow characteristics from the corresponding values in steady flows at the same bulk Reynolds number were significant during acceleration and much less so during deceleration. Supported by the Natural Sciences and Engineering Research Council of Canada and the Canadian Nuclear Laboratories.
Distributed energy storage: Time-dependent tree flow design
Bejan, A.; Ziaei, S.; Lorente, S.
2016-05-01
This article proposes "distributed energy storage" as a basic design problem of distributing energy storage material on an area. The energy flows by fluid flow from a concentrated source to points (users) distributed equidistantly on the area. The flow is time-dependent. Several scenarios are analyzed: sensible-heat storage, latent-heat storage, exergy storage vs energy storage, and the distribution of a finite supply of heat transfer surface between the source fluid and the distributed storage material. The chief conclusion is that the finite amount of storage material should be distributed proportionally with the distribution of the flow rate of heating agent arriving on the area. The total time needed by the source stream to "invade" the area is cumulative (the sum of the storage times required at each storage site) and depends on the energy distribution paths and the sequence in which the users are served by the source stream. Directions for future designs of distributed storage and retrieval are outlined in the concluding section.
Stochastic Time-Dependent Current-Density Functional Theory
D'Agosta, Roberto
2008-03-01
Static and dynamical density functional methods have been applied with a certain degree of success to a variety of closed quantum mechanical systems, i.e., systems that can be described via a Hamiltonian dynamics. However, the relevance of open quantum systems - those coupled to external environments, e.g., baths or reservoirs - cannot be overestimated. To investigate open quantum systems with DFT methods we have introduced a new theory, we have named Stochastic Time-Dependent Current Density Functional theory (S-TDCDFT) [1]: starting from a suitable description of the system dynamics via a stochastic Schrödinger equation [2], we have proven that given an initial quantum state and the coupling between the system and the environment, there is a one-to-one correspondence between the ensemble-averaged current density and the external vector potential applied to the system.In this talk, I will introduce the stochastic formalism needed for the description of open quantum systems, discuss in details the theorem of Stochastic TD-CDFT, and provide few examples of its applicability like the dissipative dynamics of excited systems, quantum-measurement theory and other applications relevant to charge and energy transport in nanoscale systems.[1] M. Di Ventra and R. D'Agosta, Physical Review Letters 98, 226403 (2007)[2] N.G. van Kampen, Stochastic processes in Physics and Chemistry, (North Holland, 2001), 2nd ed.
Simple preconditioning for time-dependent density functional perturbation theory
Lehtovaara, Lauri; Marques, Miguel A. L.
2011-07-01
By far, the most common use of time-dependent density functional theory is in the linear-reponse regime, where it provides information about electronic excitations. Ideally, the linear-response equations should be solved by a method that avoids the use of the unoccupied Kohn-Sham states — such as the Sternheimer method — as this reduces the complexity and increases the precision of the calculation. However, the Sternheimer equation becomes ill-conditioned near and indefinite above the first resonant frequency, seriously hindering the use of efficient iterative solution methods. To overcome this serious limitation, and to improve the general convergence properties of the iterative techniques, we propose a simple preconditioning strategy. In our method, the Sternheimer equation is solved directly as a linear equation using an iterative Krylov subspace method, i.e., no self-consistent cycle is required. Furthermore, the preconditioner uses the information of just a few unoccupied states and requires simple and minimal modifications to existing implementations. In this way, convergence can be reached faster and in a considerably wider frequency range than the traditional approach.
Prandtl-Ishlinskii hysteresis models for complex time dependent hysteresis nonlinearities
Al Janaideh, M.; Krejčí, P
2012-01-01
We introduce a new class of time dependent hysteresis models by combining the time dependent Prandtl–Ishlinskii model with functional nonlinearities. This combination improves the capability of the time dependent Prandtl–Ishlinskii model to characterize a class of complex time dependent hysteresis nonlinearities in smart actuators. The analytical inversion for the proposed time dependent hysteresis model is also presented in order to extend the inversion algorithm of the inverse time dependen...
Spike-timing dependent plasticity and the cognitive map
Directory of Open Access Journals (Sweden)
Daniel eBush
2010-10-01
Full Text Available Since the discovery of place cells – single pyramidal neurons that encode spatial location – it has been hypothesised that the hippocampus may act as a cognitive map of known environments. This putative function has been extensively modelled using auto-associative networks, which utilise rate-coded synaptic plasticity rules in order to generate strong bi-directional connections between concurrently active place cells that encode for neighbouring place fields. However, empirical studies using hippocampal cultures have demonstrated that the magnitude and direction of changes in synaptic strength can also be dictated by the relative timing of pre- and post- synaptic firing according to a spike-timing dependent plasticity (STDP rule. Furthermore, electrophysiology studies have identified persistent ‘theta-coded’ temporal correlations in place cell activity in vivo, characterised by phase precession of firing as the corresponding place field is traversed. It is not yet clear if STDP and theta-coded neural dynamics are compatible with cognitive map theory and previous rate-coded models of spatial learning in the hippocampus. Here, we demonstrate that an STDP rule based on empirical data obtained from the hippocampus can mediate rate-coded Hebbian learning when pre- and post- synaptic activity is stochastic and has no persistent sequence bias. We subsequently demonstrate that a spiking recurrent neural network that utilises this STDP rule, alongside theta-coded neural activity, allows the rapid development of a cognitive map during directed or random exploration of an environment of overlapping place fields. Hence, we establish that STDP and phase precession are compatible with rate-coded models of cognitive map development.
Solving the time dependent vehicle routing problem by metaheuristic algorithms
Johar, Farhana; Potts, Chris; Bennell, Julia
2015-02-01
The problem we consider in this study is Time Dependent Vehicle Routing Problem (TDVRP) which has been categorized as non-classical VRP. It is motivated by the fact that multinational companies are currently not only manufacturing the demanded products but also distributing them to the customer location. This implies an efficient synchronization of production and distribution activities. Hence, this study will look into the routing of vehicles which departs from the depot at varies time due to the variation in manufacturing process. We consider a single production line where demanded products are being process one at a time once orders have been received from the customers. It is assumed that order released from the production line will be loaded into scheduled vehicle which ready to be delivered. However, the delivery could only be done once all orders scheduled in the vehicle have been released from the production line. Therefore, there could be lateness on the delivery process from awaiting all customers' order of the route to be released. Our objective is to determine a schedule for vehicle routing that minimizes the solution cost including the travelling and tardiness cost. A mathematical formulation is developed to represent the problem and will be solved by two metaheuristics; Variable Neighborhood Search (VNS) and Tabu Search (TS). These algorithms will be coded in C ++ programming and run using 56's Solomon instances with some modification. The outcome of this experiment can be interpreted as the quality criteria of the different approximation methods. The comparison done shown that VNS gave the better results while consuming reasonable computational efforts.
Time-dependent viscoelastic properties along rat small intestine
Institute of Scientific and Technical Information of China (English)
James B Smith; Jing-Bo Zhao; Yan-Ling Dou; Hans Gregersen
2005-01-01
AIM: To measure the time-dependent (viscoelastic)behavior in the change of the small intestinal opening angle and to test how well the behavior could be described by the Kelvin model for a standard linear solid.METHODS: Segments from the duodenum, jejunum, and ileum were harvested from 10 female Wistar rats and the luminal diameter, wall thickness, and opening angleover time (θ(t)) were measured from rings cut from thesesegments.RESULTS: Morphometric variations were found along thesmall intestine with an increase in luminal area and adecrease in wall thickness from the duodenum to theileum. The opening angle obtained after 60 min washighest in the duodenum (220.8±12.9°) and decreasedalong the length of the intestine to 143.9±8.9° in the jejunum and 151.4±9.4° in the ileum. The change ofopening angle as a function of time, fitted well to theKelvin model using the equation θ(t)/θo = [1-ηexp (-λt)]after the ring was cut. The computed creep rate λ did notdiffer between the segments. Compared to constantcalculated from pig aorta and coronary artery, it showedthat α agreed well (within 5%), η was three times largerthan that for vascular tissue, and λ ranged ±40% from the value of the pig coronary artery and was a third of the value of pig aorta.CONCLUSION: The change of opening angle over timefor all the small intestine segments fits well to the standardlinear spring-dashpot model. This viscoelastic constantof the rat small intestine is fairly homogenous along itslength. The data obtained from this study add to a baseset of biomechanical data on the small intestine andprovide a reference state for comparison to other tissues,diseased intestinal tissue or intestinal tissue exposed todrugs or chemicals.
Time dependent mechanical modeling for polymers based on network theory
Billon, Noëlle
2016-05-01
Despite of a lot of attempts during recent years, complex mechanical behaviour of polymers remains incompletely modelled, making industrial design of structures under complex, cyclic and hard loadings not totally reliable. The non linear and dissipative viscoelastic, viscoplastic behaviour of those materials impose to take into account non linear and combined effects of mechanical and thermal phenomena. In this view, a visco-hyperelastic, viscoplastic model, based on network description of the material has recently been developed and designed in a complete thermodynamic frame in order to take into account those main thermo-mechanical couplings. Also, a way to account for coupled effects of strain-rate and temperature was suggested. First experimental validations conducted in the 1D limit on amorphous rubbery like PMMA in isothermal conditions led to pretty goods results. In this paper a more complete formalism is presented and validated in the case of a semi crystalline polymer, a PA66 and a PET (either amorphous or semi crystalline) are used. Protocol for identification of constitutive parameters is described. It is concluded that this new approach should be the route to accurately model thermo-mechanical behaviour of polymers using a reduced number of parameters of some physicl meaning.
Time-Dependent Moment Tensors of the First Four Source Physics Experiments (SPE) Explosions
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.
One-Dimensional (1-D) Nanoscale Heterostructures
Institute of Scientific and Technical Information of China (English)
Guozhen SHEN; Di CHEN; Yoshio BANDO; Dmitri GOLBERG
2008-01-01
One-dimensional (1-D) nanostructures have been attracted much attention as a result of their exceptional properties, which are different from bulk materials. Among 1-D nanostructures, 1-D heterostructures with modulated compositions and interfaces have recently become of particular interest with respect to potential applications in nanoscale building blocks of future optoelectronic devices and systems. Many kinds of methods have been developed for the synthesis of 1-D nanoscale heterostructures. This article reviews the most recent development, with an emphasize on our own recent efforts, on 1-D nanoscale heterostructures, especially those synthesized from the vapor deposition methods, in which all the reactive precursors are mixed together in the reaction chamber. Three types of 1-D nanoscale heterostructures, defined from their morphologies characteristics, are discussed in detail, which include 1-D co-axial core-shell heterostructures, 1-D segmented heterostructures and hierarchical heterostructures. This article begins with a brief survey of various methods that have been developed for synthesizing 1-D nanoscale heterostructures and then mainly focuses on the synthesis, structures and properties of the above three types of nanoscale heterostructures. Finally, this review concludes with personal views towards the topic of 1-D nanoscale heterostructures.
Plasmon excitations in sodium atomic planes: a time-dependent density functional theory study.
Wang, Bao-Ji; Xu, Yuehua; Ke, San-Huang
2012-08-07
The collective electronic excitation in planar sodium clusters is studied by time-dependent density functional theory calculations. The formation and development of the resonances in photoabsorption spectra are investigated in terms of the shape and size of the two-dimensional (2D) systems. The nature of these resonances is revealed by the frequency-resolved induced charge densities present on a real-space grid. For long double chains, the excitation is similar to that in long single atomic chains, showing longitudinal modes, end and central transverse modes. However, for 2D planes consisting of (n × n) atoms with n being up to 16, new 2D characteristic modes emerge regardless of the symmetries considered. For in-plane excitations, besides the equivalent end mode, mixed modes with contrary polarity occur. The relation between the frequency of the primary modes and the system size is similar to the case of a 2D electron gas but with a correction due to the realistic atomic structure. For excitations perpendicular to the plane there are corner, side center, bulk center, and circuit modes. Our calculation reveals the importance of dimensionality for plasmon excitation and how it evolves from 1D to 2D.
Monte Carlo techniques for time-dependent radiative transfer in 3-D supernovae
Lucy, L B
2004-01-01
Monte Carlo techniques based on indivisible energy packets are described for computing light curves and spectra for 3-D supernovae. The radiative transfer is time-dependent and includes all effects of O(v/c). Monte Carlo quantization is achieved by discretizing the initial distribution of 56Ni into radioactive pellets. Each pellet decays with the emission of a single energy packet comprising gamma-ray photons representing one line from either the 56Ni or the 56Co decay spectrum. Subsequently, these energy packets propagate through the homologously-expanding ejecta with appropriate changes in the nature of their contained energy as they undergo Compton scatterings and pure absorptions. The 3-D code is tested by applying it to a spherically-symmetric SN in which the transfer of optical radiation is treated with a grey absorption coefficient. This 1-D problem is separately solved using Castor's co-moving frame moment equations. Satisfactory agreement is obtained. The Monte Carlo code is a platform onto which mor...
Time dependent non-LTE calculations of ionisation in the early universe
Wehrse, R; Davé, R; Dav\\'e, Romeel
2005-01-01
We present a new implicit numerical algorithm for the calculation of the time dependent non-Local Thermodynamic Equilibrium of a gas in an external radiation field that is accurate, fast and unconditionally stable for all spatial and temporal increments. The method is presented as a backward difference scheme in 1-D but can be readily generalised to 3-D. We apply the method for calculating the evolution of ionisation domains in a hydrogen plasma with plane-parallel Gaussian density enhancements illuminated by sources of UV radiation. We calculate the speed of propagation of ionising fronts through different ambient densities and the interaction of such ionising fronts with density enhancements. We show that for a typical UV source that may be present in the early universe, the introduction of a density enhancement of a factor ~10 above an ambient density 10^{-4} atoms/cm^3 could delay the outward propagation of an ionisation front by millions of years. Our calculations show that within the lifetime of a singl...
Energy Technology Data Exchange (ETDEWEB)
Ford, W.E. III; Roussin, R.W.; Petrie, L.M.; Diggs, B.R.; Comolander, H.E.
1979-01-01
Contents of the IBM version of the APMX system distributed by the Radiation Shielding Information Center (APMX-II) are described. Sample problems which demonstrate the procedure for implementing AMPX-II modules to generate point cross sections; generate multigroup neutron, photon production, and photon interaction cross sections for various transport codes; collapse multigroup cross sections; check, edit, and punch multigroup cross sections; and execute a one-dimensional discrete ordinates transport calculation are detailed. 25 figures, 9 tables.
Energy Technology Data Exchange (ETDEWEB)
Kato, Tsuyoshi; Ide, Yoshihiro; Yamanouchi, Kaoru [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1, Hongo Bunkyo-ku, Tokyo, 113-0033 (Japan)
2015-12-31
We first calculate the ground-state molecular wave function of 1D model H{sub 2} molecule by solving the coupled equations of motion formulated in the extended multi-configuration time-dependent Hartree-Fock (MCTDHF) method by the imaginary time propagation. From the comparisons with the results obtained by the Born-Huang (BH) expansion method as well as with the exact wave function, we observe that the memory size required in the extended MCTDHF method is about two orders of magnitude smaller than in the BH expansion method to achieve the same accuracy for the total energy. Second, in order to provide a theoretical means to understand dynamical behavior of the wave function, we propose to define effective adiabatic potential functions and compare them with the conventional adiabatic electronic potentials, although the notion of the adiabatic potentials is not used in the extended MCTDHF approach. From the comparison, we conclude that by calculating the effective potentials we may be able to predict the energy differences among electronic states even for a time-dependent system, e.g., time-dependent excitation energies, which would be difficult to be estimated within the BH expansion approach.
Propagator for a Time-Dependent Damped Harmonic Oscillator with a Force Quadratic in Velocity
Institute of Scientific and Technical Information of China (English)
HUANG Bo-Wen; GU Zhi-Yu; QIAN Shang-Wu
2003-01-01
The propagator for a time-dependent damped harmonic oscillator with a force quadratic in velocity isobtained by making a specific coordinate transformation and by using the method of time-dependent invariant.
A trapped ion with time-dependent frequency interaction with a laser field
Energy Technology Data Exchange (ETDEWEB)
MartInez, J M Vargas; Moya-Cessa, H [INAOE, Apartado Postal 51 y 216, 72000 Puebla (Mexico)
2004-06-01
We analyse the problem of a trapped ion with time-dependent frequency interacting with a laser field. By using a set of unitary time-dependent transformations we show that this system is equivalent to the interaction between a quantized field and a double level with time-dependent interaction parameters. In passing, we show that in the on-resonance case different vibrational transitions may be achieved by using time-dependent parameters.
Non-Hermitian Swanson model with a time-dependent metric
Fring, Andreas; Moussa, Miled H. Y.
2016-10-01
We provide further nontrivial solutions to the recently proposed time-dependent Dyson and quasi-Hermiticity relation. Here, we solve them for the generalized version of the non-Hermitian Swanson Hamiltonian with time-dependent coefficients. We construct time-dependent solutions by employing the Lewis-Riesenfeld method of invariants and discuss concrete physical applications of our results.
Exact solutions of Feinberg–Horodecki equation for time-dependent anharmonic oscillator
Indian Academy of Sciences (India)
P K Bera; Tapas Sil
2013-01-01
In this work, an alternative treatment known as Nikiforov–Uvarov (NU) method is proposed to find the exact solutions of the Feinberg–Horodecki equation for the time-dependent potentials. The present procedure is illustrated with two examples: (1) time-dependent Wei Hua oscillator, (2) time-dependent Manning–Rosen potential.
Exact solution of a quantum forced time-dependent harmonic oscillator
Yeon, Kyu Hwang; George, Thomas F.; Um, Chung IN
1992-01-01
The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator.
Energy Technology Data Exchange (ETDEWEB)
Bhargava, Kapilesh, E-mail: kapil_66@barc.gov.i [Architecture and Civil Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Mori, Yasuhiro [Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8603 (Japan); Ghosh, A.K. [Reactor Safety Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India)
2011-05-15
This paper forms the third part of a study which addresses time-dependent reliability analyses of reinforced concrete (RC) beams affected by reinforcement corrosion. Parts 1 and 2 of the reliability study are presented in companion papers. Part 1 of the reliability study presents evaluation of probabilistic descriptions for time-dependent strengths of a typical simply supported corrosion-affected RC beam. These probabilistic descriptions, i.e., mean and coefficient of variation (c.o.v.) for the time-dependent strengths are presented for two limit states: (a) flexural failure; and (b) shear failure. Part 2 of the reliability study presents evaluation of time-dependent failure probability for the considered RC beam by utilizing the information on probabilistic descriptions for time-dependent strengths available in Part 1. Evaluation of time-dependent failure probability considering the variability in time-dependent strengths and/or time-dependent degradation functions is also presented. This paper investigates the effects of time to corrosion initiation and its variability on failure probability of the same RC beam presented in companion papers. By considering variability in the identified variables that could affect the expected time of first corrosion, simple estimations are presented for mean time to corrosion initiation and variability associated with time to corrosion initiation. Evaluation of time-dependent failure probability for the beam is presented by considering estimated probabilistic descriptions, i.e., mean and c.o.v. for time to corrosion initiation. Parametric analyses show that failure probability for the beam is sensitive to the mode of strength degradation and time to corrosion initiation.
Attainable conditions and exact invariant for the time-dependent harmonic oscillator
Energy Technology Data Exchange (ETDEWEB)
Guasti, Manuel Fernandez [Lab. de Optica Cuantica, Dep. de Fisica, Universidad A. Metropolitana, Unidad Iztapalapa, Mexico DF, Ap. Post. 55-534 (Mexico)
2006-09-22
The time-dependent oscillator equation is solved numerically for various trajectories in amplitude and phase variables. The solutions exhibit a finite time-dependent parameter whenever the squared amplitude times the derivative of the phase is invariant. If the invariant relationship does not hold, the time-dependent parameter has divergent singularities. These observations lead to the proposition that the harmonic oscillator equation with finite time-dependent parameter must have amplitude and phase solutions fulfilling the invariant relationship. Since the time-dependent parameter or the potential must be finite for any real oscillator implementation, the invariant must hold for any such physically realizable system.
Dembinski, S. T.; Wolniewicz, L.
1996-01-01
It is shown that the 1D Hamiltonian, which is a sum of operators which generate a finite nilpotent Lie algebra and depends explicitly on time existing closed form solutions of the time-dependent Schrödinger equation, cannot fulfil in general boundary and normalization conditions on a positive semi-axis. An explanation of the controversy surrounding the solutions of the quantum bouncer model, which appeared recently in the literature, is given.
Energy Technology Data Exchange (ETDEWEB)
Dembinski, S.T.; Wolniewicz, L. [Institute of Physics, Nicholas Copernicus University, Torun (Poland)
1996-01-21
It is shown that the 1 D Hamiltonian, which is a sum of operators which generate a finite nilpotent Lie algebra and depends explicitly on time existing closed form solutions of the time-dependent Schroedinger equation, cannot fulfil in general boundary and normalization conditions on a positive semi-axis. An explanation of the controversy surrounding the solutions of the quantum bouncer model, which appeared recently in the literature, is given. (author)
Second Quantized Scalar QED in Homogeneous Time-Dependent Electromagnetic Fields
Kim, Sang Pyo
2014-01-01
We formulate the second quantized scalar quantum electrodynamics in homogeneous, time-dependent electromagnetic fields, in which the Hamiltonian for a charged scalar field is an infinite system of decoupled time-dependent oscillators for electric fields but of coupled time-dependent oscillators for magnetic fields. We then employ the quantum invariant method to find various quantum states for the charged field. For time-dependent electric fields, a pair of quantum invariant operators for each oscillator plays the role of the time-dependent annihilation and creation operators, constructs the exact quantum states, and gives the vacuum persistence amplitude as well as the pair-production rate. We also find the quantum invariants for the coupled oscillators for the charged field in time-dependent magnetic fields and advance a perturbation method when the magnetic fields change adiabatically. Finally the quantum state and pair production is discussed when a time-dependent electric field is present in parallel to t...
Measurement invariance via multigroup SEM: Issues and solutions with chi-square-difference tests.
Yuan, Ke-Hai; Chan, Wai
2016-09-01
Multigroup structural equation modeling (SEM) plays a key role in studying measurement invariance and in group comparison. When population covariance matrices are deemed not equal across groups, the next step to substantiate measurement invariance is to see whether the sample covariance matrices in all the groups can be adequately fitted by the same factor model, called configural invariance. After configural invariance is established, cross-group equalities of factor loadings, error variances, and factor variances-covariances are then examined in sequence. With mean structures, cross-group equalities of intercepts and factor means are also examined. The established rule is that if the statistic at the current model is not significant at the level of .05, one then moves on to testing the next more restricted model using a chi-square-difference statistic. This article argues that such an established rule is unable to control either Type I or Type II errors. Analysis, an example, and Monte Carlo results show why and how chi-square-difference tests are easily misused. The fundamental issue is that chi-square-difference tests are developed under the assumption that the base model is sufficiently close to the population, and a nonsignificant chi-square statistic tells little about how good the model is. To overcome this issue, this article further proposes that null hypothesis testing in multigroup SEM be replaced by equivalence testing, which allows researchers to effectively control the size of misspecification before moving on to testing a more restricted model. R code is also provided to facilitate the applications of equivalence testing for multigroup SEM. (PsycINFO Database Record
Asymptotic behavior of stochastic multi-group epidemic models with distributed delays
Liu, Qun; Jiang, Daqing; Shi, Ningzhong; Hayat, Tasawar; Alsaedi, Ahmed
2017-02-01
In this paper, we introduce stochasticity into multi-group epidemic models with distributed delays and general kernel functions. The stochasticity in the model is a standard technique in stochastic population modeling. When the perturbations are small, by using the method of stochastic Lyapunov functions, we carry out a detailed analysis on the asymptotic behavior of the stochastic model regarding of the basic reproduction number R0. If R0 ≤ 1, the solution of the stochastic system oscillates around the disease-free equilibrium E0, while if R0 > 1, the solution of the stochastic model fluctuates around the endemic equilibrium E∗. Moreover, we also establish sufficient conditions of these results.
Multi-group pin power reconstruction method based on colorset form functions
Institute of Scientific and Technical Information of China (English)
HUANG Hao
2009-01-01
A multi-group pin power reconstruction method that fully exploits nodal information obtained from global coarse mesh solution has been developed.It expands the intra-nodal flux distributions into nonseparable semi-analytic basis functions,and a colorset based form function generating method is proposed,which can accurately model the spectral interaction occurring at assembly interface.To demonstrate its accuracy and applicability to realistic problems,the new method is tested against two benchmark problems,including a mixed-oxide fuel problem.The results show that the new method is comparable in accuracy to fine-mesh methods.
Energy Technology Data Exchange (ETDEWEB)
Bhargava, Kapilesh, E-mail: kapilesh_66@yahoo.co.u [Architecture and Civil Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Mori, Yasuhiro [Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8603 (Japan); Ghosh, A.K. [Reactor Safety Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India)
2011-05-15
Research highlights: Predictive models for corrosion-induced damages in RC structures. Formulations for time-dependent flexural and shear strengths of corroded RC beams. Methodology for mean and c.o.v. for time-dependent strengths of corroded RC beams. Simple estimation of mean and c.o.v. for flexural strength with loss of bond. - Abstract: The structural deterioration of reinforced concrete (RC) structures due to reinforcement corrosion is a major worldwide problem. Damages to RC structures due to reinforcement corrosion manifest in the form of expansion, cracking and eventual spalling of the cover concrete; thereby resulting in serviceability and durability degradation of such structures. In addition to loss of cover, RC structure may suffer structural damages due to loss of reinforcement cross-sectional area, and loss of bond between corroded reinforcement and surrounding cracked concrete, sometimes to the extent that the structural failure becomes inevitable. This paper forms the first part of a study which addresses time-dependent reliability analyses of RC beams affected by reinforcement corrosion. In this paper initially the predictive models are presented for the quantitative assessment of time-dependent damages in RC beams, recognized as loss of mass and cross-sectional area of reinforcing bar, loss of concrete section owing to the peeling of cover concrete, and loss of bond between corroded reinforcement and surrounding cracked concrete. Then these models have been used to present analytical formulations for evaluating time-dependent flexural and shear strengths of corroded RC beams, based on the standard composite mechanics expressions for RC sections. Further by considering variability in the identified basic variables that could affect the time-dependent strengths of corrosion-affected RC beams, the estimation of statistical descriptions for the time-dependent strengths is presented for a typical simply supported RC beam. The statistical descriptions
Finite difference approximation of control via the potential in a 1-D Schrodinger equation
Directory of Open Access Journals (Sweden)
K. Kime
2000-04-01
Full Text Available We consider the problem of steering given initial data to given terminal data via a time-dependent potential, the control, in a 1-D Schrodinger equation. We determine a condition for existence of a transferring potential within our approximation. Using Maple, we give equations for the control and also examples in which the potential is restricted to be centralized and to be a step potential.
Development of a hybrid deterministic/stochastic method for 1D nuclear reactor kinetics
Energy Technology Data Exchange (ETDEWEB)
Terlizzi, Stefano; Dulla, Sandra; Ravetto, Piero [Politecnico di Torino, Corso Duca degli Abruzzi, 24 10129, Torino (Italy); Rahnema, Farzad, E-mail: farzad@gatech.edu [Nuclear & Radiological Engineering and Medical Physics Programs, Georgia Institute of Technology, 770 State Street NW, Atlanta, Ga, 30332-0745 (United States); Nuclear & Radiological Engineering and Medical Physics Programs, Georgia Institute of Technology, 770 State Street NW, Atlanta, Ga, 30332-0745 (United States); Zhang, Dingkang [Nuclear & Radiological Engineering and Medical Physics Programs, Georgia Institute of Technology, 770 State Street NW, Atlanta, Ga, 30332-0745 (United States)
2015-12-31
A new method has been implemented for solving the time-dependent neutron transport equation efficiently and accurately. This is accomplished by coupling the hybrid stochastic-deterministic steady-state coarse-mesh radiation transport (COMET) method [1,2] with the new predictor-corrector quasi-static method (PCQM) developed at Politecnico di Torino [3]. In this paper, the coupled method is implemented and tested in 1D slab geometry.
Development of a hybrid deterministic/stochastic method for 1D nuclear reactor kinetics
Terlizzi, Stefano; Rahnema, Farzad; Zhang, Dingkang; Dulla, Sandra; Ravetto, Piero
2015-12-01
A new method has been implemented for solving the time-dependent neutron transport equation efficiently and accurately. This is accomplished by coupling the hybrid stochastic-deterministic steady-state coarse-mesh radiation transport (COMET) method [1,2] with the new predictor-corrector quasi-static method (PCQM) developed at Politecnico di Torino [3]. In this paper, the coupled method is implemented and tested in 1D slab geometry.
Weak approximation of obliquely reflected diffusions in time-dependent domains
Önskog, Thomas; Nyström, Kaj
2010-01-01
In an earlier paper, we proved the existence of solutions to the Skorohod problem with oblique reflection in time-dependent domains and, subsequently, applied this result to the problem of constructing solutions, in time-dependent domains, to stochastic differential equations with oblique reflection. In this paper we use these results to construct weak approximations of solutions to stochastic differential equations with oblique reflection, in time-dependent domains in R^d, by means of a proj...
Numerical modelling of softwood time-dependent behaviour based on microstructure
DEFF Research Database (Denmark)
Engelund, Emil Tang
2010-01-01
by the basic physical mechanism behind the time-dependent behaviour. The mechanism causing time-dependency is thought to be sliding of the microfibrils past each other as a result breaking and re-bonding of hydrogen bonds. This can be incorporated in a numerical model by only allowing time-dependency in shear...... be predicted with the described method of modelling. This is seen by simulating experimental results for both single fibres and tissues in creep and relaxation experiments....
DEFF Research Database (Denmark)
Schnettler, Berta; Miranda, Horacio; Edgardo, Miranda-Zapata
2017-01-01
This study examined longitudinal measurement invariance in the Satisfaction with Food-related Life (SWFL) scale using follow-up data from university students. We examined this measure of the SWFL in different groups of students, separated by various characteristics. Through non-probabilistic long......This study examined longitudinal measurement invariance in the Satisfaction with Food-related Life (SWFL) scale using follow-up data from university students. We examined this measure of the SWFL in different groups of students, separated by various characteristics. Through non...... invariance by time, and second, a multigroup longitudinal invariance by sex, age, socio-economic status and place of residence during the study period. Results showed that the 3-item version of the SWFL exhibited strong longitudinal invariance (equal factor loadings and equal indicator intercepts......). Longitudinal multigroup invariance analysis also showed that the 3-item version of the SWFL displays strong invariance by socio-economic status and place of residence during the study period over time. Nevertheless, it was only possible to demonstrate equivalence of the longitudinal factor structure among...
The group-level consequences of sexual conflict in multigroup populations.
Directory of Open Access Journals (Sweden)
Omar Tonsi Eldakar
Full Text Available In typical sexual conflict scenarios, males best equipped to exploit females are favored locally over more prudent males, despite reducing female fitness. However, local advantage is not the only relevant form of selection. In multigroup populations, groups with less sexual conflict will contribute more offspring to the next generation than higher conflict groups, countering the local advantage of harmful males. Here, we varied male aggression within- and between-groups in a laboratory population of water striders and measured resulting differences in local population growth over a period of three weeks. The overall pool fitness (i.e., adults produced of less aggressive pools exceeded that of high aggression pools by a factor of three, with the high aggression pools essentially experiencing no population growth over the course of the study. When comparing the fitness of individuals across groups, aggression appeared to be under stabilizing selection in the multigroup population. The use of contextual analysis revealed that overall stabilizing selection was a product of selection favoring aggression within groups, but selected against it at the group-level. Therefore, this report provides further evidence to show that what evolves in the total population is not merely an extension of within-group dynamics.
Schnettler, Berta; Miranda, Horacio; Miranda-Zapata, Edgardo; Salinas-Oñate, Natalia; Grunert, Klaus G; Lobos, Germán; Sepúlveda, José; Orellana, Ligia; Hueche, Clementina; Bonilla, Héctor
2017-06-01
This study examined longitudinal measurement invariance in the Satisfaction with Food-related Life (SWFL) scale using follow-up data from university students. We examined this measure of the SWFL in different groups of students, separated by various characteristics. Through non-probabilistic longitudinal sampling, 114 university students (65.8% female, mean age: 22.5) completed the SWFL questionnaire three times, over intervals of approximately one year. Confirmatory factor analysis was used to examine longitudinal measurement invariance. Two types of analysis were conducted: first, a longitudinal invariance by time, and second, a multigroup longitudinal invariance by sex, age, socio-economic status and place of residence during the study period. Results showed that the 3-item version of the SWFL exhibited strong longitudinal invariance (equal factor loadings and equal indicator intercepts). Longitudinal multigroup invariance analysis also showed that the 3-item version of the SWFL displays strong invariance by socio-economic status and place of residence during the study period over time. Nevertheless, it was only possible to demonstrate equivalence of the longitudinal factor structure among students of both sexes, and among those older and younger than 22 years. Generally, these findings suggest that the SWFL scale has satisfactory psychometric properties for longitudinal measurement invariance in university students with similar characteristics as the students that participated in this research. It is also possible to suggest that satisfaction with food-related life is associated with sex and age.
Consistent Multigroup Theory Enabling Accurate Course-Group Simulation of Gen IV Reactors
Energy Technology Data Exchange (ETDEWEB)
Rahnema, Farzad; Haghighat, Alireza; Ougouag, Abderrafi
2013-11-29
The objective of this proposal is the development of a consistent multi-group theory that accurately accounts for the energy-angle coupling associated with collapsed-group cross sections. This will allow for coarse-group transport and diffusion theory calculations that exhibit continuous energy accuracy and implicitly treat cross- section resonances. This is of particular importance when considering the highly heterogeneous and optically thin reactor designs within the Next Generation Nuclear Plant (NGNP) framework. In such reactors, ignoring the influence of anisotropy in the angular flux on the collapsed cross section, especially at the interface between core and reflector near which control rods are located, results in inaccurate estimates of the rod worth, a serious safety concern. The scope of this project will include the development and verification of a new multi-group theory enabling high-fidelity transport and diffusion calculations in coarse groups, as well as a methodology for the implementation of this method in existing codes. This will allow for a higher accuracy solution of reactor problems while using fewer groups and will reduce the computational expense. The proposed research represents a fundamental advancement in the understanding and improvement of multi- group theory for reactor analysis.
Hochstuhl, David
2012-01-01
We introduce the time-dependent restricted active space Configuration Interaction method to solve the time-dependent Schr\\"odinger equation for many-electron atoms, and particularly apply it to the treatment of photoionization processes in atoms. The method is presented in a very general formulation and incorporates a wide range of commonly used approximation schemes, like the single-active electron approximation, time-dependent Configuration Interaction with single-excitations, or the time-dependent R-matrix method. We proof the applicability of the method by calculating the photoionization cross sections of Helium and Beryllium.
Construction of exact Ermakov-Pinney solutions and time-dependent quantum oscillators
Kim, Sang Pyo; Kim, Won
2016-11-01
The harmonic oscillator with a time-dependent frequency has a family of linear quantum invariants for the time-dependent Schrödinger equation, which are determined by any two independent solutions to the classical equation of motion. Ermakov and Pinney have shown that a general solution to the time-dependent oscillator with an inverse cubic term can be expressed in terms of two independent solutions to the time-dependent oscillator. We explore the connection between linear quantum invariants and the Ermakov-Pinney solution for the time-dependent harmonic oscillator. We advance a novel method to construct Ermakov-Pinney solutions to a class of time-dependent oscillators and the wave functions for the time-dependent Schrödinger equation. We further show that the first and the second Pöschl-Teller potentials belong to a special class of exact time-dependent oscillators. A perturbation method is proposed for any slowly-varying time-dependent frequency.
Application de la methode des sous-groupes au calcul Monte-Carlo multigroupe
Martin, Nicolas
This thesis is dedicated to the development of a Monte Carlo neutron transport solver based on the subgroup (or multiband) method. In this formalism, cross sections for resonant isotopes are represented in the form of probability tables on the whole energy spectrum. This study is intended in order to test and validate this approach in lattice physics and criticality-safety applications. The probability table method seems promising since it introduces an alternative computational way between the legacy continuous-energy representation and the multigroup method. In the first case, the amount of data invoked in continuous-energy Monte Carlo calculations can be very important and tend to slow down the overall computational time. In addition, this model preserves the quality of the physical laws present in the ENDF format. Due to its cheap computational cost, the multigroup Monte Carlo way is usually at the basis of production codes in criticality-safety studies. However, the use of a multigroup representation of the cross sections implies a preliminary calculation to take into account self-shielding effects for resonant isotopes. This is generally performed by deterministic lattice codes relying on the collision probability method. Using cross-section probability tables on the whole energy range permits to directly take into account self-shielding effects and can be employed in both lattice physics and criticality-safety calculations. Several aspects have been thoroughly studied: (1) The consistent computation of probability tables with a energy grid comprising only 295 or 361 groups. The CALENDF moment approach conducted to probability tables suitable for a Monte Carlo code. (2) The combination of the probability table sampling for the energy variable with the delta-tracking rejection technique for the space variable, and its impact on the overall efficiency of the proposed Monte Carlo algorithm. (3) The derivation of a model for taking into account anisotropic
Chaplin, Vernon H.; Bellan, Paul M.
2015-12-01
A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne≳ 5 ×1019 m-3 ) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z ,t ) and temperature Te(z ,t ) , and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pA r=30 -60 mTorr . We present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency antenna.
Heat Capacity of 1D Molecular Chains
Bagatskii, M. I.; Barabashko, M. S.; Sumarokov, V. V.; Jeżowski, A.; Stachowiak, P.
2017-04-01
The heat capacity of 1D chains of nitrogen and methane molecules (adsorbed in the outer grooves of bundles of closed-cap single-walled carbon nanotubes) has been studied in the temperature ranges 2-40 and 2-60 K, respectively. The temperature dependence of the heat capacity of 1D chains of nitrogen molecules below 3 K is close to a linear. It was found that the rotational heat capacity of methane molecules is a significant part of the total heat capacity of the chains throughout the whole investigated temperature range, whereas in the case of nitrogen, the librations are significant only above 15 K. The dependence of the heat capacity for methane below 10 K indicates the presence of a Schottky anomaly caused by the tunneling between the lowest energy levels of the CH4 molecule rotational spectra. Characteristic features observed in the temperature dependence of the heat capacity of 1D methane crystals are also discussed.
Social exploration of 1D games
DEFF Research Database (Denmark)
Valente, Andrea; Marchetti, Emanuela
2013-01-01
In this paper the apparently meaningless concept of a 1 dimensional computer game is explored, via netnography. A small number of games was designed and implemented, in close contact with online communities of players and developers, providing evidence that 1 dimension is enough to produce intere...... interesting gameplay, to allow for level design and even to leave room for artistic considerations on 1D rendering. General techniques to re-design classic 2D games into 1D are also emerging from this exploration....
Modelling time-dependent mechanical behaviour of softwood using deformation kinetics
DEFF Research Database (Denmark)
Engelund, Emil Tang; Svensson, Staffan
2010-01-01
The time-dependent mechanical behaviour (TDMB) of softwood is relevant, e.g., when wood is used as building material where the mechanical properties must be predicted for decades ahead. The established mathematical models should be able to predict the time-dependent behaviour. However, these models...
Time-dependent solutions of the spatially implicit neutral model of biodiversity.
Chisholm, Ryan A
2011-09-01
Previous research into the neutral theory of biodiversity has focused mainly on equilibrium solutions rather than time-dependent solutions. Understanding the time-dependent solutions is essential for applying neutral theory to ecosystems in which time-dependent processes, such as succession and invasion, are driving the dynamics. Time-dependent solutions also facilitate tests against data that are stronger than those based on static equilibrium patterns. Here I investigate the time-dependent solutions of the classic spatially implicit neutral model, in which a small local community is coupled to a much larger metacommunity through immigration. I present explicit general formulas for the eigenvalues, left eigenvectors and right eigenvectors of the models's transition matrix. The time-dependent solutions can then be expressed in terms of these eigenvalues and eigenvectors. Some of these results are translated directly from existing results for the classic Moran model of population genetics (the Moran model is equivalent to the spatially implicit neutral model after a reparameterization); others of the results are new. I demonstrate that the asymptotic time-dependent solution corresponding to just these first two eigenvectors can be a good approximation to the full time-dependent solution. I also demonstrate the feasibility of a partial eigendecomposition of the transition matrix, which facilitates direct application of the results to a biologically relevant example in which a newly invading species is initially present in the metacommunity but absent from the local community.
First integrals for time-dependent higher-order Riccati equations by nonholonomic transformation
Guha, Partha; Ghose Choudhury, A.; Khanra, Barun
2011-08-01
We exploit the notion of nonholonomic transformations to deduce a time-dependent first integral for a (generalized) second-order nonautonomous Riccati differential equation. It is further shown that the method can also be used to compute the first integrals of a particular class of third-order time-dependent ordinary differential equations and is therefore quite robust.
Time-dependent transport in interacting and noninteracting resonant-tunneling systems
DEFF Research Database (Denmark)
Jauho, Antti-Pekka; Wingreen, Ned S.; Meir, Yigal
1994-01-01
We consider a mesoscopic region coupled to two leads under the influence of external time-dependent voltages. The time dependence is coupled to source and drain contacts, the gates controlling the tunnel-barrier heights, or to the gates that define the mesoscopic region. We derive, with the Keldy...
Quantum Statistics of a Forced Oscillator with a Time-Dependent Driving Force
Institute of Scientific and Technical Information of China (English)
刘文森
2003-01-01
Quantum statistics of a forced harmonic oscillator acted upon by a time-dependent external force are derived using the Wilcox trick and the time-dependent inhomogeneous Bogoliubov transformation formalism.The internal energy,fluctuation of the particle-number average and entropy of this nonequilibrium system are presented explicitly.
Domínguez, Alvaro
2014-12-01
It has been shown recently that the coefficient of collective diffusion in a colloidal monolayer is divergent due to the hydrodynamic interactions mediated by the ambient fluid in bulk. The analysis is extended to allow for time-dependent hydrodynamic interactions. Observational features specific to this time dependency are predicted. The possible experimental detection in the dynamics of the monolayer is discussed.
Program for quantum wave-packet dynamics with time-dependent potentials
Dion, C M; Rahali, G
2014-01-01
We present a program to simulate the dynamics of a wave packet interacting with a time-dependent potential. The time-dependent Schr\\"odinger equation is solved on a one-, two-, or three-dimensional spatial grid using the split operator method. The program can be compiled for execution either on a single processor or on a distributed-memory parallel computer.
Modified $f(R)$ Gravity and Thermodynamics of Time-Dependent Wormholes at Event Horizon
Saiedi, H
2016-01-01
In the context of modified $f(R)$ gravity theory, we study time-dependent wormhole spacetimes in the radiation background. In this framework, we attempt to generalize the thermodynamic properties of time-dependent wormholes in $f(R)$ gravity. Finally, at event horizon, the rate of change of total entropy has been discussed.
Invariant Hermitian Operator and Density Operator for the Adiabatically Time-Dependent System
Institute of Scientific and Technical Information of China (English)
YAN Feng-Li; YANG Lin-Guang
2001-01-01
The density operator is approximately expressed as a function of the invariant Hermitian operator for the adiabatically time-dependent system. Using this method, the calculation of the density operator for the Heisenberg spin system in a weakly time-dependent magnetic field is exemplified. By virtue of the density operator, we obtain equilibrium.``
Time-Dependence effect in alumite recording media with perpendicular anisotropy
Kim, Phan Le; Lodder, Cock
1999-01-01
In this paper, we will present a study of the time-dependence effect in alumite perpendicular media at different thicknesses. Important parameters of the time-dependence effect such as magnetic viscosity and activation volume are investigated. Viscosity as a function of applied field (viscosity cur
Institute of Scientific and Technical Information of China (English)
Yoshiaki MUROYA; Yoichi ENATSU; Toshikazu KUNIYA
2013-01-01
In this article,we establish the global stability of an endemic equilibrium of multi-group SIR epidemic models,which have not only an exchange of individuals between patches through migration but also cross patch infection between different groups.As a result,we partially generalize the recent result in the article [16].
Investigating Student Difficulties with Time dependence of Expectation Values in Quantum Mechanics
Marshman, Emily
2015-01-01
Quantum mechanics is challenging even for advanced undergraduate and graduate students. In the Schr\\"odinger representation, the wave function evolves in time according to the time dependent Schr\\"odinger equation. The time dependence of the wave function gives rise to time dependence of the expectation value of observables. We have been exploring the difficulties that advanced undergraduate and graduate students have with time dependence of expectation values in quantum mechanics. We have developed and administered conceptual free response and multiple-choice questions to students to investigate these difficulties. We also interviewed 23 students individually using a think-aloud protocol to obtain a better understanding of the rationale behind students' written responses. We find that many students struggle with time dependence of expectation values of observables. We discuss some findings.
Analyzing Density Operator in Thermal State for Complicated Time-Dependent Optical Systems
Directory of Open Access Journals (Sweden)
Jeong Ryeol Choi
2014-01-01
Full Text Available Density operator of oscillatory optical systems with time-dependent parameters is analyzed. In this case, a system is described by a time-dependent Hamiltonian. Invariant operator theory is introduced in order to describe time-varying behavior of the system. Due to the time dependence of parameters, the frequency of oscillation, so-called a modified frequency of the system, is somewhat different from the natural frequency. In general, density operator of a time-dependent optical system is represented in terms of the modified frequency. We showed how to determine density operator of complicated time-dependent optical systems in thermal state. Usually, density operator description of quantum states is more general than the one described in terms of the state vector.
First Observation of Upsilon(1D) States
Csorna, S E; Bonvicini, G; Cinabro, D; Dubrovin, M; McGee, S; Bornheim, A; Lipeles, E; Pappas, S P; Shapiro, A; Sun, W M; Weinstein, A J; Mahapatra, R; Briere, R A; Chen, G P; Ferguson, T; Tatishvili, G T; Vogel, H; Adam, N E; Alexander, J P; Berkelman, K; Boisvert, V; Cassel, David G; Drell, P S; Duboscq, J E; Ecklund, K M; Ehrlich, R; Galik, R S; Gibbons, L; Gittelman, B; Gray, S W; Hartill, D L; Heltsley, B K; Hsu, L; Jones, C D; Kandaswamy, J; Kreinick, D L; Magerkurth, A; Mahlke-Krüger, H; Meyer, T O; Mistry, N B; Nordberg, E; Patterson, J R; Peterson, D; Pivarski, J; Riley, D; Sadoff, A J; Schwarthoff, H; Shepherd, M R; Thayer, J G; Urner, D; Viehhauser, G; Warburton, A; Weinberger, M; Athar, S B; Avery, P; Breva-Newell, L; Potlia, V; Stöck, H; Yelton, J; Brandenburg, G; Kim, D Y J; Wilson, R; Benslama, K; Eisenstein, B I; Ernst, J; Gollin, G D; Hans, R M; Karliner, I; Lowrey, N; Plager, C; Sedlack, C; Selen, M; Thaler, J J; Williams, J; Edwards, K W; Ammar, R; Besson, D; Zhao, X; Anderson, S; Frolov, V V; Kubota, Y; Lee, S J; Li, S Z; Poling, R A; Smith, A; Stepaniak, C J; Urheim, J; Metreveli, Z V; Seth, K K; Tomaradze, A G; Zweber, P; Ahmed, S; Alam, M S; Jian, L; Saleem, M; Wappler, F; Eckhart, E; Gan, K K; Gwon, C; Hart, T; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pedlar, T K; Thayer, J B; Von Törne, E; Wilksen, T; Zoeller, M M; Muramatsu, H; Richichi, S J; Severini, H; Skubic, P L; Dytman, S A; Müller, J A; Nam, S; Savinov, V; Chen, S; Hinson, J W; Lee, J; Miller, D H; Pavlunin, V; Shibata, E I; Shipsey, I P J; Cronin-Hennessy, D; Lyon, A L; Park, C S; Park, W; Thorndike, E H; Coan, T E; Gao, Y S; Liu, F; Maravin, Y; Stroynowski, R; Artuso, M; Boulahouache, C; Bukin, K; Dambasuren, E; Khroustalev, K; Mountain, R; Nandakumar, R; Skwarnicki, T; Stone, S; Wang, J C; Mahmood, A H
2002-01-01
The CLEO III experiment has recently accumulated a large statistics sample of 4.73 x 10^6 Upsilon(3S) decays. We present the first evidence for the production of the triplet Upsilon(1D) states in the four-photon cascade, Upslion(3S) -> gamma chi_b(2P), chi_b(2P) -> gamma Upsilon(1D), Upsilon(1D) -> gamma chi_b(1P), chi_b(1P) -> gamma Upsilon(1S), followed by the Upsilon(1S) annihilation to e+ e- or mu+ mu-. The signal has a significance of 9.7 standard deviations. The measured product branching ratio for these five decays, (3.3 +- 0.6 +- 0.5) x 10^{-5}, is consistent with the theoretical estimates. We see a 6.8 standard deviation signal for a state with a mass of 10162.2 +- 1.6 MeV/c^2, consistent with the Upsilon(1D_2) assignment. We also present improved measurements of the Upsilon(3S) -> pi0 pi0 Upsilon(1S) branching ratio and the associated di-pion mass distribution.
Calibration of a 1D/1D urban flood model using 1D/2D model results in the absence of field data.
Leandro, J; Djordjević, S; Chen, A S; Savić, D A; Stanić, M
2011-01-01
Recently increased flood events have been prompting researchers to improve existing coupled flood-models such as one-dimensional (1D)/1D and 1D/two-dimensional (2D) models. While 1D/1D models simulate sewer and surface networks using a one-dimensional approach, 1D/2D models represent the surface network by a two-dimensional surface grid. However their application raises two issues to urban flood modellers: (1) stormwater systems planning/emergency or risk analysis demands for fast models, and the 1D/2D computational time is prohibitive, (2) and the recognized lack of field data (e.g. Hunter et al. (2008)) causes difficulties for the calibration/validation of 1D/1D models. In this paper we propose to overcome these issues by calibrating a 1D/1D model with the results of a 1D/2D model. The flood-inundation results show that: (1) 1D/2D results can be used to calibrate faster 1D/1D models, (2) the 1D/1D model is able to map the 1D/2D flood maximum extent well, and the flooding limits satisfactorily in each time-step, (3) the 1D/1D model major differences are the instantaneous flow propagation and overestimation of the flood-depths within surface-ponds, (4) the agreement in the volume surcharged by both models is a necessary condition for the 1D surface-network validation and (5) the agreement of the manholes discharge shapes measures the fitness of the calibrated 1D surface-network.
Global dynamics of a novel multi-group model for computer worms
Institute of Scientific and Technical Information of China (English)
Gong Yong-Wang; Song Yu-Rong; Jiang Guo-Ping
2013-01-01
In this paper,we study worm dynamics in computer networks composed of many autonomous systems.A novel multigroup SIQR (susceptible-infected-quarantined-removed) model is proposed for computer worms by explicitly considering anti-virus measures and the network infrastructure.Then,the basic reproduction number of worm R0 is derived and the global dynamics of the model are established.It is shown that if R0 is less than or equal to 1,the disease-free equilibrium is globally asymptotically stable and the worm dies out eventually,whereas,if R0 is greater than 1,one unique endemic equilibrium exists and it is globally asymptotically stable,thus the worm persists in the network.Finally,numerical simulations are given to illustrate the theoretical results.
Validation of the Resilience Scale for Adolescents (READ) in Ireland: a multi-group analysis.
Kelly, Yvonne; Fitzgerald, Amanda; Dooley, Barbara
2016-04-29
Resilience is a process reflecting positive adaptation in the face of adversity. The Resilience Scale for Adolescence (READ) incorporates intrapersonal and interpersonal protective factors mapping onto the three salient domains of resilience, including individual, family and external environment. This study investigated the validity and reliability of the READ by means of factor analysis, multi-group analysis, inter-correlations and internal consistency measures. Participants were 6085 young people in Ireland aged 12-18 years. Participants completed the My World Survey - Second Level (MWS-SL), assessing risk and protective factors of mental health. Confirmatory factor analysis validated the original five-factor structure of the READ including Personal Competence, Social Competence, Structured Style, Family Cohesion, and Social Resources, χ(2) (340) = 6146.02, p resilience factors among adolescents in Ireland, demonstrating its applicability in a different cultural context and with a wider age range of adolescents. Copyright © 2016 John Wiley & Sons, Ltd.
Radiation Transport for Explosive Outflows: A Multigroup Hybrid Monte Carlo Method
Wollaeger, Ryan T; Graziani, Carlo; Couch, Sean M; Jordan, George C; Lamb, Donald Q; Moses, Gregory A
2013-01-01
We explore the application of Implicit Monte Carlo (IMC) and Discrete Diffusion Monte Carlo (DDMC) to radiation transport in strong fluid outflows with structured opacity. The IMC method of Fleck & Cummings is a stochastic computational technique for nonlinear radiation transport. IMC is partially implicit in time and may suffer in efficiency when tracking Monte Carlo particles through optically thick materials. The DDMC method of Densmore accelerates an IMC computation where the domain is diffusive. Recently, Abdikamalov extended IMC and DDMC to multigroup, velocity-dependent neutrino transport with the intent of modeling neutrino dynamics in core-collapse supernovae. Densmore has also formulated a multifrequency extension to the originally grey DDMC method. In this article we rigorously formulate IMC and DDMC over a high-velocity Lagrangian grid for possible application to photon transport in the post-explosion phase of Type Ia supernovae. The method described is suitable for a large variety of non-mono...
SIRIUS - A one-dimensional multigroup analytic nodal diffusion theory code
Energy Technology Data Exchange (ETDEWEB)
Forslund, P. [Westinghouse Atom AB, Vaesteraas (Sweden)
2000-09-01
In order to evaluate relative merits of some proposed intranodal cross sections models, a computer code called Sirius has been developed. Sirius is a one-dimensional, multigroup analytic nodal diffusion theory code with microscopic depletion capability. Sirius provides the possibility of performing a spatial homogenization and energy collapsing of cross sections. In addition a so called pin power reconstruction method is available for the purpose of reconstructing 'heterogeneous' pin qualities. consequently, Sirius has the capability of performing all the calculations (incl. depletion calculations) which are an integral part of the nodal calculation procedure. In this way, an unambiguous numerical analysis of intranodal cross section models is made possible. In this report, the theory of the nodal models implemented in sirius as well as the verification of the most important features of these models are addressed.
Jones, Kelvyn; Johnston, Ron; Manley, David; Owen, Dewi; Charlton, Chris
2015-12-01
We develop and apply a multilevel modeling approach that is simultaneously capable of assessing multigroup and multiscale segregation in the presence of substantial stochastic variation that accompanies ethnicity rates based on small absolute counts. Bayesian MCMC estimation of a log-normal Poisson model allows the calculation of the variance estimates of the degree of segregation in a single overall model, and credible intervals are obtained to provide a measure of uncertainty around those estimates. The procedure partitions the variance at different levels and implicitly models the dependency (or autocorrelation) at each spatial scale below the topmost one. Substantively, we apply the model to 2011 census data for London, one of the world's most ethnically diverse cities. We find that the degree of segregation depends both on scale and group.
Compilation of multigroup cross-section covariance matrices for several important reactor materials
Energy Technology Data Exchange (ETDEWEB)
Drischler, J.D.; Weisbin, C.R.
1977-10-01
Multigroup cross-section covariance matrices are presented for fission in /sup 235/U, /sup 238/U, /sup 239/Pu, and /sup 241/Pu; capture in /sup 235/U, /sup 238/U, /sup 239/Pu, /sup 240/Pu, and /sup 241/Pu; fission neutron yield (anti nu) for /sup 235/U, /sup 238/U, /sup 239/Pu, and /sup 240/Pu; elastic scattering for Na and Fe; non-elastic reactions for Na and Fe; first-level inelastic scattering for /sup 238/U; and all reactions provided in the ENDF/B-IV covariance description of N, O, and C. Other data files generated are included for reference but have not yet been tested. The report presents the nultigroup data in six, ten, and fifteen energy group forms corresponding to weighting of the covariance data with fission (GODIVA), LMFBR (ZPR-6/7) and 1/E spectra, respectively.
Karim, Mohammad Ehsanul; Petkau, John; Gustafson, Paul; Platt, Robert W; Tremlett, Helen
2016-09-21
In longitudinal studies, if the time-dependent covariates are affected by the past treatment, time-dependent confounding may be present. For a time-to-event response, marginal structural Cox models are frequently used to deal with such confounding. To avoid some of the problems of fitting marginal structural Cox model, the sequential Cox approach has been suggested as an alternative. Although the estimation mechanisms are different, both approaches claim to estimate the causal effect of treatment by appropriately adjusting for time-dependent confounding. We carry out simulation studies to assess the suitability of the sequential Cox approach for analyzing time-to-event data in the presence of a time-dependent covariate that may or may not be a time-dependent confounder. Results from these simulations revealed that the sequential Cox approach is not as effective as marginal structural Cox model in addressing the time-dependent confounding. The sequential Cox approach was also found to be inadequate in the presence of a time-dependent covariate. We propose a modified version of the sequential Cox approach that correctly estimates the treatment effect in both of the above scenarios. All approaches are applied to investigate the impact of beta-interferon treatment in delaying disability progression in the British Columbia Multiple Sclerosis cohort (1995-2008).
Second quantized scalar QED in homogeneous time-dependent electromagnetic fields
Kim, Sang Pyo
2014-12-01
We formulate the second quantization of a charged scalar field in homogeneous, time-dependent electromagnetic fields, in which the Hamiltonian is an infinite system of decoupled, time-dependent oscillators for electric fields, but it is another infinite system of coupled, time-dependent oscillators for magnetic fields. We then employ the quantum invariant method to find various quantum states for the charged field. For time-dependent electric fields, a pair of quantum invariant operators for each oscillator with the given momentum plays the role of the time-dependent annihilation and the creation operators, constructs the exact quantum states, and gives the vacuum persistence amplitude as well as the pair-production rate. We also find the quantum invariants for the coupled oscillators for the charged field in time-dependent magnetic fields and advance a perturbation method when the magnetic fields change adiabatically. Finally, the quantum state and the pair production are discussed when a time-dependent electric field is present in parallel to the magnetic field.
Time-Dependent Behaviors of Granite: Loading-Rate Dependence, Creep, and Relaxation
Hashiba, K.; Fukui, K.
2016-07-01
To assess the long-term stability of underground structures, it is important to understand the time-dependent behaviors of rocks, such as their loading-rate dependence, creep, and relaxation. However, there have been fewer studies on crystalline rocks than on tuff, mudstone, and rock salt, because the high strength of crystalline rocks makes the detection of their time-dependent behaviors much more difficult. Moreover, studies on the relaxation, temporal change of stress and strain (TCSS) conditions, and relations between various time-dependent behaviors are scarce for not only granites, but also other rocks. In this study, previous reports on the time-dependent behaviors of granites were reviewed and various laboratory tests were conducted using Toki granite. These tests included an alternating-loading-rate test, creep test, relaxation test, and TCSS test. The results showed that the degree of time dependence of Toki granite is similar to other granites, and that the TCSS resembles the stress-relaxation curve and creep-strain curve. A viscoelastic constitutive model, proposed in a previous study, was modified to investigate the relations between the time-dependent behaviors in the pre- and post-peak regions. The modified model reproduced the stress-strain curve, creep, relaxation, and the results of the TCSS test. Based on a comparison of the results of the laboratory tests and numerical simulations, close relations between the time-dependent behaviors were revealed quantitatively.
Testing a new multigroup inference approach to reconstructing past environmental conditions
Directory of Open Access Journals (Sweden)
Maria RIERADEVALL
2008-08-01
Full Text Available A new, quantitative, inference model for environmental reconstruction (transfer function, based for the first time on the simultaneous analysis of multigroup species, has been developed. Quantitative reconstructions based on palaeoecological transfer functions provide a powerful tool for addressing questions of environmental change in a wide range of environments, from oceans to mountain lakes, and over a range of timescales, from decades to millions of years. Much progress has been made in the development of inferences based on multiple proxies but usually these have been considered separately, and the different numeric reconstructions compared and reconciled post-hoc. This paper presents a new method to combine information from multiple biological groups at the reconstruction stage. The aim of the multigroup work was to test the potential of the new approach to making improved inferences of past environmental change by improving upon current reconstruction methodologies. The taxonomic groups analysed include diatoms, chironomids and chrysophyte cysts. We test the new methodology using two cold-environment training-sets, namely mountain lakes from the Pyrenees and the Alps. The use of multiple groups, as opposed to single groupings, was only found to increase the reconstruction skill slightly, as measured by the root mean square error of prediction (leave-one-out cross-validation, in the case of alkalinity, dissolved inorganic carbon and altitude (a surrogate for air-temperature, but not for pH or dissolved CO2. Reasons why the improvement was less than might have been anticipated are discussed. These can include the different life-forms, environmental responses and reaction times of the groups under study.
A new multigroup method for cross-sections that vary rapidly in energy
Haut, T. S.; Ahrens, C.; Jonko, A.; Lowrie, R.; Till, A.
2017-01-01
We present a numerical method for solving the time-independent thermal radiative transfer (TRT) equation or the neutron transport (NT) equation when the opacity (cross-section) varies rapidly in frequency (energy) on the microscale ε; ε corresponds to the characteristic spacing between absorption lines or resonances, and is much smaller than the macroscopic frequency (energy) variation of interest. The approach is based on a rigorous homogenization of the TRT/NT equation in the frequency (energy) variable. Discretization of the homogenized TRT/NT equation results in a multigroup-type system, and can therefore be solved by standard methods. We demonstrate the accuracy and efficiency of the approach on three model problems. First we consider the Elsasser band model with constant temperature and a line spacing ε =10-4 . Second, we consider a neutron transport application for fast neutrons incident on iron, where the characteristic resonance spacing ε necessitates ≈ 16 , 000 energy discretization parameters if Planck-weighted cross sections are used. Third, we consider an atmospheric TRT problem for an opacity corresponding to water vapor over a frequency range 1000-2000 cm-1, where we take 12 homogeneous layers between 1-15 km, and temperature/pressure values in each layer from the standard US atmosphere. For all three problems, we demonstrate that we can achieve between 0.1 and 1 percent relative error in the solution, and with several orders of magnitude fewer parameters than a standard multigroup formulation using Planck-weighted (source-weighted) opacities for a comparable accuracy.
Comparison between two models of absorption of matter waves by a thin time-dependent barrier
Barbier, Maximilien; Beau, Mathieu; Goussev, Arseni
2015-11-01
We report a quantitative, analytical, and numerical comparison between two models of the interaction of a nonrelativistic quantum particle with a thin time-dependent absorbing barrier. The first model represents the barrier by a set of time-dependent discontinuous matching conditions, which are closely related to Kottler boundary conditions used in stationary-wave optics as a mathematical basis for Kirchhoff diffraction theory. The second model mimics the absorbing barrier with an off-diagonal δ potential with a time-dependent amplitude. We show that the two models of absorption agree in their predictions in a semiclassical regime, the regime readily accessible in modern experiments with ultracold atoms.
Time-Dependant Responses of High-Definition Induction Log and Case Studies
Directory of Open Access Journals (Sweden)
Jianhua Zhang
2014-01-01
Full Text Available The process of drilling mud filtrate invading into a reservoir is time dependant. It causes dynamic invasion profiles of formation parameters such as water saturation, salinity, and formation resistivity. Thus, the responses of a high-definition induction log (HDIL tool are time dependent. The logging time should be considered as an important parameter during logging interpretation for the purposes of determining true formation resistivity, estimating initial water saturation, and evaluating a reservoir. The time-dependent HDIL responses are helpful for log analysts to understand the invasion process physically. Field examples were illustrated for the application of present method.
Analysis of Two-Level Support Systems with Time-Dependent Overflow - A Banking Application
DEFF Research Database (Denmark)
Barth, Wolfgang; Manitz, Michael; Stolletz, Raik
2010-01-01
is available. The analysis of such a system with time-dependent overflow is reduced to the analysis of a continuous-time Markov chain with state-dependent overflow probabilities. To approximate the system with time-dependent overflow, some waiting-based performance measures are modified. Numerical results......In this paper, we analyze the performance of call centers of financial service providers with two levels of support and a time-dependent overflow mechanism. Waiting calls from the front-office queue flow over to the back office if a waiting-time limit is reached and at least one back-office agent...
Effects of Different Time-Dependent Couplings on Two-Atom Entanglement
Institute of Scientific and Technical Information of China (English)
ZHOU Ling; GAO Wen-Bin; YANG Guo-Hui; SONG He-Shan
2007-01-01
The effects of different time-independent and time-dependent couplings on two-atom entanglement are studied. The results show that the effects depend on the initial state. For the initial state |ee0>, it is found that different time-independent couplings make the case without entanglement exhibit entanglement, and time-dependent couplings turn the irregular entanglement regions into regular one. Under the case of decay, for the initial state |eg0>, the different time-dependent couplings have disbenefit.
Davydov-Chaban Hamiltonian in presence of time-dependent potential
Sobhani, Hadi; Hassanabadi, Hassan
2016-09-01
In this article, we have investigated collective effects of atomic nuclei in presence of a time-dependent potential in Davydov-Chaban Hamiltonian. Since such potential has an explicit time-dependency, in order to obtain the wave function of considered system, we should face with time-dependent Schrödinger equation. Obtaining the wave function could be possible using Lewis-Riesenfeld dynamical invariant method. Appropriate dynamical invariant has been constructed after determining the wave functions and values, the wave function will obtain.
Dynamics of a Hogg-Huberman Model with Time Dependent Reevaluation Rates
Tanaka, Toshijiro; Kurihara, Tetsuya; Inoue, Masayoshi
2006-05-01
The dynamical behavior of the Hogg-Huberman model with time-dependent reevaluation rates is studied. The time dependence of the reevaluation rate that agents using one of resources decide to consider their resource choice is obtained in terms of states of the system. It is seen that the change of fraction of agents using one resource is suppressed to be smaller than that in the case of a fixed reevaluation rate and the chaos control in the system associated with time-dependent reevaluation rates can be performed by the system itself.
YORP torques with 1D thermal model
Breiter, Slawomir; Czekaj, Maria
2010-01-01
A numerical model of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect for objects defined in terms of a triangular mesh is described. The algorithm requires that each surface triangle can be handled independently, which implies the use of a 1D thermal model. Insolation of each triangle is determined by an optimized ray-triangle intersection search. Surface temperature is modeled with a spectral approach; imposing a quasi-periodic solution we replace heat conduction equation by the Helmholtz equation. Nonlinear boundary conditions are handled by an iterative, FFT based solver. The results resolve the question of the YORP effect in rotation rate independence on conductivity within the nonlinear 1D thermal model regardless of the accuracy issues and homogeneity assumptions. A seasonal YORP effect in attitude is revealed for objects moving on elliptic orbits when a nonlinear thermal model is used.
Glass-based 1-D dielectric microcavities
Chiasera, Alessandro; Scotognella, Francesco; Valligatla, Sreeramulu; Varas, Stefano; Jasieniak, Jacek; Criante, Luigino; Lukowiak, Anna; Ristic, Davor; Gonçalves, Rogeria Rocha; Taccheo, Stefano; Ivanda, Mile; Righini, Giancarlo C.; Ramponi, Roberta; Martucci, Alessandro; Ferrari, Maurizio
2016-11-01
We have developed a reliable RF sputtering techniques allowing to fabricate glass-based one dimensional microcavities, with high quality factor. This property is strongly related to the modification of the density of states due to the confinement of the gain medium in a photonic band gap structure. In this short review we present some of the more recent results obtained by our team exploiting these 1D microcavities. In particular we present: (1) Er3+ luminescence enhancement of the 4I13/2 → 4I15/2 transition; (2) broad band filters based on disordered 1-D photonic structures; (3) threshold defect-mode lasing action in a hybrid structure.
Sulfur chemistry: 1D modeling in massive dense cores
Wakelam, V; Herpin, F
2011-01-01
The main sulfur-bearing molecules OCS, H2S, SO, SO2, and CS have been observed in four high mass dense cores (W43-MM1, IRAS 18264, IRAS 05358, and IRAS 18162). Our goal is to put some constraints on the relative evolutionary stage of these sources by comparing these observations with time-dependent chemical modeling. We used the chemical model Nahoon, which computes the gas-phase chemistry and gas-grain interactions of depletion and evaporation. Mixing of the different chemical compositions shells in a 1D structure through protostellar envelope has been included since observed lines suggest nonthermal supersonic broadening. Observed radial profiles of the temperature and density are used to compute the chemistry as a function of time. With our model, we underproduce CS by several orders of magnitude compared to the other S-bearing molecules, which seems to contradict observations, although some uncertainties in the CS abundance observed at high temperature remain. The OCS/SO2, SO/SO2, and H2S/SO2 abundance ra...
Aeroelastic response of an aircraft wing with mounted engine subjected to time-dependent thrust
Mazidi, A.; Kalantari, H.; Fazelzadeh, S. A.
2013-05-01
In this paper, the aeroelastic response of a wing containing an engine subjected to different types of time-dependent thrust excitations is presented. In order to precisely consider the spanwise and chordwise locations of the engine and the time-dependent follower force in governing equations, derived through Lagrange's method, the generalized function theory is used. Unsteady aerodynamic lift and moment in the time domain are considered in terms of Wagner's function. Numerical simulations of the aeroelastic response to different types of time-dependent thrust excitation and comparisons with the previously published results are supplied. Effects of the engine mass and location and also the type of time-dependent thrust on the wing aeroelastic response are studied and pertinent conclusions are outlined.
On Noether's Theorem for the Invariant of the Time-Dependent Harmonic Oscillator
Abe, Sumiyoshi; Itto, Yuichi; Matsunaga, Mamoru
2009-01-01
The time-dependent oscillator describing parametric oscillation, the concept of invariant and Noether's theorem are important issues in physics education. Here, it is shown how they can be interconnected in a simple and unified manner.
On Noether's theorem for the invariant of the time-dependent harmonic oscillator
Energy Technology Data Exchange (ETDEWEB)
Abe, Sumiyoshi; Itto, Yuichi; Matsunaga, Mamoru [Department of Physical Engineering, Mie University, Mie 514-8507 (Japan)
2009-11-15
The time-dependent oscillator describing parametric oscillation, the concept of invariant and Noether's theorem are important issues in physics education. Here, it is shown how they can be interconnected in a simple and unified manner.
Branch and price for the time-dependent vehicle routing problem with time windows
DEFF Research Database (Denmark)
Dabia, Said; Van Woensel, Tom; De Kok, Ton
2013-01-01
solution methods to the DM-TDVRPTW are based on (meta-)heuristics. The decomposition of an arc-based formulation leads to a setpartitioning problem as the master problem, and a time-dependent shortest path problem with resource constraints as the pricing problem. The master problem is solved by means...... of column generation, and a tailored labeling algorithm is used to solve the pricing problem. We introduce new dominance criteria that allow more label dominance. For our numerical results, we modified Solomon's data sets by adding time dependency. Our algorithm is able to solve about 63% of the instances......This paper presents a branch-and-price algorithm for the time-dependent vehicle routing problem with time windows (TDVRPTW). We capture road congestion by considering time-dependent travel times, i.e., depending on the departure time to a customer, a different travel time is incurred. We consider...
On the dynamics created by a time--dependent Aharonov-Bohm flux
Asch, J
2007-01-01
We study the dynamics of classical and quantum particles moving in a punctured plane under the influence of a homogeneous magnetic field and driven by a time-dependent singular flux tube through the hole.
Boks, Niels P.; Kaper, Hans J.; Norde, Willem; Busscher, Henk J.; van der Mei, Henny C.
2008-01-01
Adhesion and desorption are simultaneous events during bacterial adhesion to surfaces. although desorption is far less studied than adhesion. Here, desorption of Staphylococcus epidermidis from substratum surfaces is demonstrated to be residence time dependent. Initial desorption rate coefficients w
Energy Technology Data Exchange (ETDEWEB)
Ibarra-Sierra, V.G.; Sandoval-Santana, J.C. [Departamento de Física, Universidad Autónoma Metropolitana Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 México D.F. (Mexico); Cardoso, J.L. [Área de Física Teórica y Materia Condensada, Universidad Autónoma Metropolitana Azcapotzalco, Av. San Pablo 180, Col. Reynosa-Tamaulipas, Azcapotzalco, 02200 México D.F. (Mexico); Kunold, A., E-mail: akb@correo.azc.uam.mx [Área de Física Teórica y Materia Condensada, Universidad Autónoma Metropolitana Azcapotzalco, Av. San Pablo 180, Col. Reynosa-Tamaulipas, Azcapotzalco, 02200 México D.F. (Mexico)
2015-11-15
We discuss the one-dimensional, time-dependent general quadratic Hamiltonian and the bi-dimensional charged particle in time-dependent electromagnetic fields through the Lie algebraic approach. Such method consists in finding a set of generators that form a closed Lie algebra in terms of which it is possible to express a quantum Hamiltonian and therefore the evolution operator. The evolution operator is then the starting point to obtain the propagator as well as the explicit form of the Heisenberg picture position and momentum operators. First, the set of generators forming a closed Lie algebra is identified for the general quadratic Hamiltonian. This algebra is later extended to study the Hamiltonian of a charged particle in electromagnetic fields exploiting the similarities between the terms of these two Hamiltonians. These results are applied to the solution of five different examples: the linear potential which is used to introduce the Lie algebraic method, a radio frequency ion trap, a Kanai–Caldirola-like forced harmonic oscillator, a charged particle in a time dependent magnetic field, and a charged particle in constant magnetic field and oscillating electric field. In particular we present exact analytical expressions that are fitting for the study of a rotating quadrupole field ion trap and magneto-transport in two-dimensional semiconductor heterostructures illuminated by microwave radiation. In these examples we show that this powerful method is suitable to treat quadratic Hamiltonians with time dependent coefficients quite efficiently yielding closed analytical expressions for the propagator and the Heisenberg picture position and momentum operators. -- Highlights: •We deal with the general quadratic Hamiltonian and a particle in electromagnetic fields. •The evolution operator is worked out through the Lie algebraic approach. •We also obtain the propagator and Heisenberg picture position and momentum operators. •Analytical expressions for a
An EOQ model with time dependent Weibull deterioration and ramp type demand ,
Directory of Open Access Journals (Sweden)
Chaitanya Kumar Tripathy
2011-04-01
Full Text Available This paper presents an order level inventory system with time dependent Weibull deterioration and ramp type demand rate where production and demand are time dependent. The proposed model of this paper considers economic order quantity under two different cases. The implementation of the proposed model is illustrated using some numerical examples. Sensitivity analysis is performed to show the effect of changes in the parameters on the optimum solution.
Generalized Sturmians in the time-dependent frame: effect of a fullerene confining potential
Frapiccini, Ana Laura; Gasaneo, Gustavo; Mitnik, Dario M.
2017-02-01
In this work we present a novel implementation of the Generalized Sturmian Functions in the time-dependent frame to numerically solve the time-dependent Schrödinger equation. We study the effect of the confinement of H atom in a fullerene cage for the 1s → 2p resonant transition of the atom interacting with a finite laser pulse, calculating the population of bound states and spectral density.
On the effect of time-dependent inhomogeneous magnetic fields in electron–positron pair production
Directory of Open Access Journals (Sweden)
Christian Kohlfürst
2016-05-01
Full Text Available Electron–positron pair production in space- and time-dependent electromagnetic fields is investigated. Especially, the influence of a time-dependent, inhomogeneous magnetic field on the particle momenta and the total particle yield is analyzed for the first time. The role of the Lorentz invariant E2−B2, including its sign and local values, in the pair creation process is emphasized.
A Realization of a Quasi-Random Walk for Atoms in Time-Dependent Optical Potentials
Directory of Open Access Journals (Sweden)
Torsten Hinkel
2015-09-01
Full Text Available We consider the time dependent dynamics of an atom in a two-color pumped cavity, longitudinally through a side mirror and transversally via direct driving of the atomic dipole. The beating of the two driving frequencies leads to a time dependent effective optical potential that forces the atom into a non-trivial motion, strongly resembling a discrete random walk behavior between lattice sites. We provide both numerical and analytical analysis of such a quasi-random walk behavior.
Propagator for the general time-dependent harmonic oscillator with application to an ion trap
Energy Technology Data Exchange (ETDEWEB)
Harari, Gal; Ben-Aryeh, Yacob; Mann, Ady [Department of Physics, Technion-Israel Institute of Technology, IL-32000 Haifa (Israel)
2011-12-15
We present the simplest possible formula for the propagator of the general time-dependent quadratic Hamiltonian, including linear terms. The method is based on the use of a linear time-dependent invariant and requires only the solution of a linear homogeneous second-order ordinary differential equation corresponding to the classical quadratic Hamiltonian. We give an example for the case of the Paul trap.
2012-05-10
Rheology of polymer solutions/ gels (e.g., hazardous fluids containing thickeners) and biofluids depends on the concen- tration, level of cross-linking...AFRL-RX-TY-TP-2012-0041 MAGNETIC ROTATIONAL SPECTROSCOPY WITH NANORODS TO PROBE TIME-DEPENDENT RHEOLOGY OF MICRODROPLETS (POSTPRINT...Rotational Spectroscopy with Nanorods to Probe Time- Dependent Rheology of Microdroplets (POSTPRINT) FA8650-09-D-5900-0002 QL102011 *Tokarev
Evolution of Arbitrary States under Fock-Darwin Hamiltonian and a Time-Dependent Electric Field
Institute of Scientific and Technical Information of China (English)
徐晓飞; 杨涛; 翟智远; 潘孝胤
2012-01-01
The method of path integral is employed to calculate the time evolution of the eigenstates of a charged particle under the Fock-Darwin （FD） Hamiltonian subjected to a time-dependent electric field in the plane of the system. An exact analytical expression is established for the evolution of the eigenstates. This result then provides a general solution to the time-dependent Schrodinger equation.
Dynamic acoustics for the STAR-100. [computer algorithms for time dependent sound waves in jet
Bayliss, A.; Turkel, E.
1979-01-01
An algorithm is described to compute time dependent acoustic waves in a jet. The method differs from previous methods in that no harmonic time dependence is assumed, thus permitting the study of nonharmonic acoustical behavior. Large grids are required to resolve the acoustic waves. Since the problem is nonstiff, explicit high order schemes can be used. These have been adapted to the STAR-100 with great efficiencies and permitted the efficient solution of problems which would not be feasible on a scalar machine.
Exact expression for decoherence factor in the time-dependent generalized Cini model
Institute of Scientific and Technical Information of China (English)
Jianqi Shen(沈建其); Sanshui Xiao(肖三水); Qiang Wu(武强)
2003-01-01
The present letter finds the complete set of exact solutions of the time-dependent generalized Cini modelby making use of the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformationformulation and, based on this, the general explicit expression for the decoherence factor is thereforeobtained. This study provides us with a useful method to consider the geometric phase and topologicalproperties in the time-dependent quantum decoherence process.
Predicting Sequences of Progressive Events Times with Time-dependent Covariates
Cai, Song; Newlands, Nathaniel
2010-01-01
This paper presents an approach to modeling progressive event-history data when the overall objective is prediction based on time-dependent covariates. This approach does not model the hazard function directly. Instead, it models the process of the state indicators of the event history so that the time-dependent covariates can be incorporated and predictors of the future events easily formulated. Our model can be applied to a range of real-world problems in medical and agricultural science.
Spectral Method for Solving Time Dependent Flow of Upper-Convected Maxwell Fluid in Tube
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The time dependent flow of upper-convected Maxwell fluid in a horizontal circular pipe is studied by spectral method. The time dependent problem is mathematically reduced to a partial differential equation of second order. By using spectral method the partial differential equation can be reduced to a system of ordinary differential equations for different terms of Chebyshev polynomials approximations. The ordinary differential equations are solved by Laplace transform and the eigenvalue method that leads to an analytical form of the solutions.
1-D EQUILIBRIUM DISCRETE DIFFUSION MONTE CARLO
Energy Technology Data Exchange (ETDEWEB)
T. EVANS; ET AL
2000-08-01
We present a new hybrid Monte Carlo method for 1-D equilibrium diffusion problems in which the radiation field coexists with matter in local thermodynamic equilibrium. This method, the Equilibrium Discrete Diffusion Monte Carlo (EqDDMC) method, combines Monte Carlo particles with spatially discrete diffusion solutions. We verify the EqDDMC method with computational results from three slab problems. The EqDDMC method represents an incremental step toward applying this hybrid methodology to non-equilibrium diffusion, where it could be simultaneously coupled to Monte Carlo transport.
Energy Technology Data Exchange (ETDEWEB)
Mosca, P.
2009-12-15
The deterministic transport codes solve the stationary Boltzmann equation in a discretized energy formalism called multigroup. The transformation of continuous data in a multigroup form is obtained by averaging the highly variable cross sections of the resonant isotopes with the solution of the self-shielding models and the remaining ones with the coarse energy spectrum of the reactor type. So far the error of such an approach could only be evaluated retrospectively. To remedy this, we studied in this thesis a set of methods to control a priori the accuracy and the cost of the multigroup transport computation. The energy mesh optimisation is achieved using a two step process: the creation of a reference mesh and its optimized condensation. In the first stage, by refining locally and globally the energy mesh, we seek, on a fine energy mesh with subgroup self-shielding, a solution equivalent to a reference solver (Monte Carlo or pointwise deterministic solver). In the second step, once fixed the number of groups, depending on the acceptable computational cost, and chosen the most appropriate self-shielding models to the reactor type, we look for the best bounds of the reference mesh minimizing reaction rate errors by the particle swarm optimization algorithm. This new approach allows us to define new meshes for fast reactors as accurate as the currently used ones, but with fewer groups. (author)
Energy Technology Data Exchange (ETDEWEB)
Tomaschewski, Fernanda K.; Segatto, Cynthia F., E-mail: fernandasls_89@hotmail.com, E-mail: cynthia.segatto@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Matematica Aplicada; Barros, Ricardo C., E-mail: rcbarros@pq.cnpq.br [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Departamento de Modelagem Computacional
2015-07-01
Presented here is a decomposition method based on series representation of the group angular fluxes and delayed neutron precursors in smoothly continuous functions for energy multigroups, slab-geometry discrete ordinates kinetics equations supplemented with a prescribed number of delayed neutron precursors. Numerical results to a non-reflected sub-critical slab stabilized by steady-state sources are given to illustrate the accuracy and efficiency of the o offered method. (author)
Energy Technology Data Exchange (ETDEWEB)
Smith, L.A.; Gallmeier, F.X. [Oak Ridge Institute for Science and Energy, TN (United States); Gehin, J.C. [Oak Ridge National Lab., TN (United States)] [and others
1995-05-01
The FOEHN critical experiment was analyzed to validate the use of multigroup cross sections and Oak Ridge National Laboratory neutronics computer codes in the design of the Advanced Neutron Source. The ANSL-V 99-group master cross section library was used for all the calculations. Three different critical configurations were evaluated using the multigroup KENO Monte Carlo transport code, the multigroup DORT discrete ordinates transport code, and the multigroup diffusion theory code VENTURE. The simple configuration consists of only the fuel and control elements with the heavy water reflector. The intermediate configuration includes boron endplates at the upper and lower edges of the fuel element. The complex configuration includes both the boron endplates and components in the reflector. Cross sections were processed using modules from the AMPX system. Both 99-group and 20-group cross sections were created and used in two-dimensional models of the FOEHN experiment. KENO calculations were performed using both 99-group and 20-group cross sections. The DORT and VENTURE calculations were performed using 20-group cross sections. Because the simple and intermediate configurations are azimuthally symmetric, these configurations can be explicitly modeled in R-Z geometry. Since the reflector components cannot be modeled explicitly using the current versions of these codes, three reflector component homogenization schemes were developed and evaluated for the complex configuration. Power density distributions were calculated with KENO using 99-group cross sections and with DORT and VENTURE using 20-group cross sections. The average differences between the measured values and the values calculated with the different computer codes range from 2.45 to 5.74%. The maximum differences between the measured and calculated thermal flux values for the simple and intermediate configurations are {approx} 13%, while the average differences are < 8%.
The precise time-dependent solution of the Fokker–Planck equation with anomalous diffusion
Energy Technology Data Exchange (ETDEWEB)
Guo, Ran; Du, Jiulin, E-mail: jiulindu@aliyun.com
2015-08-15
We study the time behavior of the Fokker–Planck equation in Zwanzig’s rule (the backward-Ito’s rule) based on the Langevin equation of Brownian motion with an anomalous diffusion in a complex medium. The diffusion coefficient is a function in momentum space and follows a generalized fluctuation–dissipation relation. We obtain the precise time-dependent analytical solution of the Fokker–Planck equation and at long time the solution approaches to a stationary power-law distribution in nonextensive statistics. As a test, numerically we have demonstrated the accuracy and validity of the time-dependent solution. - Highlights: • The precise time-dependent solution of the Fokker–Planck equation with anomalous diffusion is found. • The anomalous diffusion satisfies a generalized fluctuation–dissipation relation. • At long time the time-dependent solution approaches to a power-law distribution in nonextensive statistics. • Numerically we have demonstrated the accuracy and validity of the time-dependent solution.
Energy Technology Data Exchange (ETDEWEB)
Kapoor, Varun; Brics, Martins; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)
2013-07-01
Autoionizing states are inaccessible to time-dependent density functional theory (TDDFT) using known, adiabatic Kohn-Sham (KS) potentials. We determine the exact KS potential for a numerically exactly solvable model Helium atom interacting with a laser field that is populating an autoionizing state. The exact single-particle density of the population in the autoionizing state corresponds to that of the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose height and width allows for the density to tunnel out and decay with the same rate as in the ab initio time-dependent Schroedinger calculation. However, devising a useful exchange-correlation potential that is capable of governing such a scenario in general and in more complex systems is hopeless. As an improvement over TDDFT, time-dependent reduced density matrix functional theory has been proposed. We are able to obtain for the above described autoionization process the exact time-dependent natural orbitals (i.e., the eigenfunctions of the exact, time-dependent one-body reduced density matrix) and study the potentials that appear in the equations of motion for the natural orbitals and the structure of the two-body density matrix expanded in them.
Energy Technology Data Exchange (ETDEWEB)
Sloan, D.P.
1983-05-01
Morel (1981) has developed multigroup Legendre cross sections suitable for input to standard discrete ordinates transport codes for performing charged-particle Fokker-Planck calculations in one-dimensional slab and spherical geometries. Since the Monte Carlo neutron transport code, MORSE, uses the same multigroup cross section data that discrete ordinates codes use, it was natural to consider whether Fokker-Planck calculations could be performed with MORSE. In order to extend the unique three-dimensional forward or adjoint capability of MORSE to Fokker-Planck calculations, the MORSE code was modified to correctly treat the delta-function scattering of the energy operator, and a new set of physically acceptable cross sections was derived to model the angular operator. Morel (1979) has also developed multigroup Legendre cross sections suitable for input to standard discrete ordinates codes for performing electron Boltzmann calculations. These electron cross sections may be treated in MORSE with the same methods developed to treat the Fokker-Planck cross sections. The large magnitude of the elastic scattering cross section, however, severely increases the computation or run time. It is well-known that approximate elastic cross sections are easily obtained by applying the extended transport (or delta function) correction to the Legendre coefficients of the exact cross section. An exact method for performing the extended transport cross section correction produces cross sections which are physically acceptable. Sample calculations using electron cross sections have demonstrated this new technique to be very effective in decreasing the large magnitude of the cross sections.
Diamond-based 1-D imaging arrays
Energy Technology Data Exchange (ETDEWEB)
Lansley, S.P.; Williams, O.A.; Ye, H. [Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Rizvi, N.; Whitfield, M.D.; Jackman, R.B. [Exitech Limited, Hanborough Park, Long Hanborough, Oxford OX8 8LH (United Kingdom); McKeag, R.D. [Centronic Ltd., Centronic House, King Henry' s Drive, New Addington, Croydon CR9 OBG (United Kingdom)
2002-10-16
Diamond has shown great promise for the fabrication of high sensitivity, low dark current, fast and visible-blind deep UV photodetectors. In addition to careful choice of substrate material, defect passivation treatments applied to the diamond after growth have been found to considerably enhance the detector characteristics achieved. In this paper we report on the first purposefully designed 1-D CVD diamond imaging array for the detection of nanosecond 193 nm excimer laser pulses using this approach. It is shown to perform extremely well, giving less than 2% pixel-to-pixel variation in signal response, and is fast enough to avoid any sign of charge build up during prolonged operation. (Abstract Copyright [2002], Wiley Periodicals, Inc.)
Time-dependent switched discrete-time linear systems control and filtering
Zhang, Lixian; Shi, Peng; Lu, Qiugang
2016-01-01
This book focuses on the basic control and filtering synthesis problems for discrete-time switched linear systems under time-dependent switching signals. Chapter 1, as an introduction of the book, gives the backgrounds and motivations of switched systems, the definitions of the typical time-dependent switching signals, the differences and links to other types of systems with hybrid characteristics and a literature review mainly on the control and filtering for the underlying systems. By summarizing the multiple Lyapunov-like functions (MLFs) approach in which different requirements on comparisons of Lyapunov function values at switching instants, a series of methodologies are developed for the issues on stability and stabilization, and l2-gain performance or tube-based robustness for l∞ disturbance, respectively, in Chapters 2 and 3. Chapters 4 and 5 are devoted to the control and filtering problems for the time-dependent switched linear systems with either polytopic uncertainties or measurable time-varying...
Use and Abuse of a Fractional Fokker-Planck Dynamics for Time-Dependent Driving
Heinsalu, E.; Patriarca, M.; Goychuk, I.; Hänggi, P.
2007-09-01
We investigate a subdiffusive, fractional Fokker-Planck dynamics occurring in time-varying potential landscapes and thereby disclose the failure of the fractional Fokker-Planck equation (FFPE) in its commonly used form when generalized in an ad hoc manner to time-dependent forces. A modified FFPE (MFFPE) is rigorously derived, being valid for a family of dichotomously alternating force fields. This MFFPE is numerically validated for a rectangular time-dependent force with zero average bias. For this case, subdiffusion is shown to become enhanced as compared to the force free case. We question, however, the existence of any physically valid FFPE for arbitrary varying time-dependent fields that differ from this dichotomous varying family.
Probing the noncommutative effects of phase space in the time-dependent Aharonov-Bohm effect
Ma, Kai; Yang, Huan-Xiong
2016-01-01
We study the noncommutative corrections on the time-dependent Aharonov-Bohm effect when both the coordinate-coordinate and momentum-momentum noncommutativities are considered. This study is motivated by the recent observation that there is no net phase shift in the time-dependent AB effect on the ordinary space, and therefore tiny derivation from zero can indicate new physics. The vanishing of the time-dependent AB phase shift on the ordinary space is preserved by the gauge and Lorentz symmetries. However, on the noncomutative phase space, while the ordinary gauge symmetry can be kept by the Seiberg-Witten map, but the Lorentz symmetry is broken. Therefore nontrivial noncommutative corrections are expected. We find there are three kinds of noncommutative corrections in general: 1) $\\xi$-dependent correction which comes from the noncommutativity among momentum operators; 2) momentum-dependent correction which is rooted in the nonlocal interactions in the noncommutative extended model; 3) momentum-independent c...
Intense two-cycle laser pulses induce time-dependent bond hardening in a polyatomic molecule.
Dota, K; Garg, M; Tiwari, A K; Dharmadhikari, J A; Dharmadhikari, A K; Mathur, D
2012-02-17
A time-dependent bond-hardening process is discovered in a polyatomic molecule (tetramethyl silane, TMS) using few-cycle pulses of intense 800 nm light. In conventional mass spectrometry, symmetrical molecules such as TMS do not exhibit a prominent molecular ion (TMS(+)) as unimolecular dissociation into [Si(CH(3))(3)](+) proceeds very fast. Under a strong field and few-cycle conditions, this dissociation channel is defeated by time-dependent bond hardening: a field-induced potential well is created in the TMS(+) potential energy curve that effectively traps a wave packet. The time dependence of this bond-hardening process is verified using longer-duration (≥100 fs) pulses; the relatively slower falloff of optical field in such pulses allows the initially trapped wave packet to leak out, thereby rendering TMS(+) unstable once again.
A theory of time-dependent compaction by fracturing and pressure solution
Keszthelyi, Daniel; Dysthe, Dag Kristian; Jamtveit, Bjørn
2016-04-01
Porous rocks under compressional stress conditions are subject to compaction creep. A previous micromechanical model, dealing with (partially) water-filled carbonates was able to predict strain rates of the compaction at macroscopic level by combining microscopic fracturing and pressure solution at microscopic level and using a statistical upscaling. Building on this model we investigated the time-dependence of the pressure solution and the overall compaction and created a new theory of compaction by developing a statistical theory of time-dependence of pressure solution. Long-term creep experiments on carbonate samples were used to test the model which was able to predict the rate of compaction and its time-dependence in largely different effective stress, temperature and fluid chemistry conditions.
Time-dependent second Born calculations for model atoms and molecules in strong laser fields
Balzer, K; Bonitz, M
2010-01-01
Using the finite-element discrete variable representation of the nonequilibrium Green's function (NEGF) we extend previous work [K.~Balzer et al., Phys. Rev. A \\textbf{81}, 022510 (2010)] to nonequilibrium situations and compute---from the two-time Schwinger-Keldysh-Kadanoff-Baym equations---the response of the helium atom and the heteronuclear molecule lithium hydride to laser fields in the uv and xuv regime. In particular, by comparing the one-electron density and the dipole moment to time-dependent Hartree-Fock results on one hand and the full solution of the time-dependent Schr\\"odinger equation on the other hand, we demonstrate that the time-dependent second Born approximation carries valuable information about electron-electron correlation effects. Also, we outline an efficient distributed memory concept which enables a parallel and well scalable algorithm for computing the NEGF in the two-time domain.
Simulating transient dynamics of the time-dependent time fractional Fokker-Planck systems
Kang, Yan-Mei
2016-09-01
For a physically realistic type of time-dependent time fractional Fokker-Planck (FP) equation, derived as the continuous limit of the continuous time random walk with time-modulated Boltzmann jumping weight, a semi-analytic iteration scheme based on the truncated (generalized) Fourier series is presented to simulate the resultant transient dynamics when the external time modulation is a piece-wise constant signal. At first, the iteration scheme is demonstrated with a simple time-dependent time fractional FP equation on finite interval with two absorbing boundaries, and then it is generalized to the more general time-dependent Smoluchowski-type time fractional Fokker-Planck equation. The numerical examples verify the efficiency and accuracy of the iteration method, and some novel dynamical phenomena including polarized motion orientations and periodic response death are discussed.
On the algebraic approach to the time-dependent quadratic Hamiltonian
Energy Technology Data Exchange (ETDEWEB)
Urdaneta, Ines; Palma, Alejandro [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico); Sandoval, Lourdes, E-mail: urdaneta@sirio.ifuap.buap.m [Facultad de Ciencias de la Computacion, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico)
2010-09-24
The unitary operator V(t) that diagonalizes the time-dependent quadratic Hamiltonian (TDQH) into a time-dependent harmonic oscillator (TDHO) is obtained using a Lie algebra. The method involves a factorization of the TDQH into a TDHO through a unitary Bogoliubov transformation in terms of creation and annihilation operators with time-dependent coefficients. It is shown that this operator can be easily achieved by means of the factorization, together with the commonly known Wei-Norman theorem. We discuss the conditions under which this unitary operator converges to the evolution operator U(t) of the Schroedinger equation for the TDQH, giving then a straightforward calculation of the evolution operator with respect to the procedures published in the literature.
Uniaxial Time-Dependent Ratcheting of SS304 Stainless Steel at High Temperatures
Institute of Scientific and Technical Information of China (English)
KANG Guo-zheng; ZHANG Juan; SUN Ya-fang; KAN Qian-hua
2007-01-01
The uniaxial time-dependent strain cyclic behaviors and ratcheting of SS304 stainless steel were studied at high temperatures (350 ℃ and 700 ℃). The effects of straining and stressing rates, holding time at the peak and/or valley of each cycle in addition to ambient temperature on the cyclic softening/hardening behavior and ratcheting of the material were discussed. It can be seen from experimental results that the material presents remarkable time dependence at 700 ℃, and the ratcheting strain depends greatly on the stressing rate, holding time and ambient temperature. Some significant conclusions are obtained, which are useful to build a constitutive model describing the time-dependent cyclic deformation of the material.
Exact solutions to the supply chain equations for arbitrary, time-dependent demands
DEFF Research Database (Denmark)
Warburton, Roger D.H.; Hodgson, J.P.E.; Nielsen, Erland Hejn
2014-01-01
, so users can determine the inventory behavior to any desired precision. To illustrate, we solve the equations for a non-linear, quadratic time-dependence in the demand. For practical use, only a few terms in the series are required, a proposition illustrated by the For All Practical Purposes (FAPP......We study the impact on inventory of an unexpected, non-linear, time-dependent demand and present the exact solutions over time to the supply chain equations without requiring any approximations. We begin by imposing a boundary condition of stability at infinity, from which we derive expressions...... for the estimated demand and the target work in progress when the demand is time-dependent. The resulting inventory equation is solved in terms of the Lambert modes with all of the demand non-linearities confined to the pre-shape function. The series solution is exact, and all terms are reasonably easy to calculate...
A time-dependent formulation of multi-reference perturbation theory.
Sokolov, Alexander Yu; Chan, Garnet Kin-Lic
2016-02-14
We discuss the time-dependent formulation of perturbation theory in the context of the interacting zeroth-order Hamiltonians that appear in multi-reference situations. As an example, we present a time-dependent formulation and implementation of second-order n-electron valence perturbation theory. The resulting time-dependent n-electron valence second-order perturbation theory (t-NEVPT2) method yields the fully uncontracted n-electron valence perturbation wavefunction and energy, but has a lower computational scaling than the usual contracted variants, and also avoids the construction of high-order density matrices and the diagonalization of metrics. We present results of t-NEVPT2 for the water, nitrogen, carbon, and chromium molecules and outline directions for the future.
Using NIAM to capture time dependencies in a domain of discourse
Energy Technology Data Exchange (ETDEWEB)
Becker, S.D.
1994-07-01
This paper addresses the issues surrounding the use of NIAM to capture time dependencies in a domain of discourse. The NIAM concepts that support capturing time dependencies are in the event and process portions of the NIAM metamodel, which are the portions most poorly supported by a well-established methodology. This lack of methodological support is a potentially serious handicap in any attempt to apply NIAM to a domain of discourse in which time dependencies are a central issue. However, the capability that NIAM provides for validating and verifying the elementary facts in the domain may reduce the magnitude of the event/process-specification task to a level at which it could be effectively handled even without strong methodological support.
Quantum fluctuations in the time-dependent BCS-BEC crossover.
Breid, B M; Anglin, J R
2008-08-28
We describe the time-dependent formation of a molecular Bose-Einstein condensate from a BCS state of fermionic atoms as a result of slow sweeping through a Feshbach resonance. We apply a path integral approach for the molecules, and use two-body adiabatic approximations to solve the atomic evolution in the presence of the classical molecular fields, obtaining an effective action for the molecules. In the narrow resonance limit, the problem becomes semiclassical, and we discuss the growth of the molecular condensate in the saddle point approximation. Considering this time-dependent process as an analogue of the cosmological Zurek scenario, we compare the way condensate growth is driven in this rigorous theory with its phenomenological description via time-dependent Ginzburg-Landau theory.
Directory of Open Access Journals (Sweden)
M. Durga Prasad
2002-05-01
Full Text Available Abstract: A time dependent coupled cluster approach to the calculation of Resonance Raman excitation profiles on general anharmonic surfaces is presented. The vibrational wave functions on the ground electronic surface are obtained by the coupled cluster method (CCM. It is shown that the propagation of the vibrational ground state on the upper surface is equivalent to propagation of the vacuum state by an effective hamiltonian generated by the similarity transformation of the vibrational hamiltonian of that surface by the CCM wave operator of the lower surface up to a normalization constant. This time propagation is carried out by the time-dependent coupled cluster method in a time dependent frame. Numerical studies are presented to asses the validity of the approach.
Closed-orbit theory for photodetachment in a time-dependent electric field
Yang, B C
2016-01-01
The standard closed-orbit theory is extended for the photodetachment of negative ions in a time-dependent electric field. The time-dependent photodetachment rate is specifically studied in the presence of a single-cycle terahertz pulse, based on exact quantum simulations and semiclassical analysis. We find that the photodetachment rate is unaffected by a weak terahertz field, but oscillates complicatedly when the terahertz pulse gets strong enough. Three types of closed classical orbits are identified for the photoelectron motion in a strong single-cycle terahertz pulse, and their connections with the oscillatory photodetachment rate are established quantitatively by generalizing the standard closed-orbit theory to a time-dependent form. By comparing the negative hydrogen and fluorine ions, both the in-phase and antiphase oscillations can be observed, depending on a simple geometry of the contributed closed classical orbits. On account of its generality, the presented theory provides an intuitive understandin...
NATO Advanced Research Workshop on Time-Dependent Quantum Molecular Dynamics : Theory and Experiment
Lathouwers, L
1992-01-01
From March 30th to April 3rd, 1992, a NATO Advanced Research workshop entitled "Time Dependent Quantum Molecular Dynamics: Theory and Experiment" was held at Snowbird, Utah. The organizing committee consisted of J. BROECKHOVE (Antwerp, Belgium), L. CEDERBAUM (Heidelberg, Germany), L. LATHOUWERS (Antwerp, Belgium), N. OHRN (Gainesville, Florida) and J. SIMONS (Salt Lake City, Utah). Fifty-two participants from eleven different countries attended the meeting at which thirty-three talks and one poster session were held. Twenty-eight participants submitted contributions to the proceedings of the meeting, which are reproduced in this volume. The workshop brought together experts in different areas 0 f molecular quantum dynamics, all adhering to the time dependent approach. The aim was to discuss and compare methods and applications. The ~amiliarityo~ the aUdience with the concepts o~ time dependent approaches greatly facilitated topical discussions and probing towards new applications. A broad area of subject matt...
Institute of Scientific and Technical Information of China (English)
陈媚; 谢琼涛
2011-01-01
The new method proposed recently by Friedberg, Lee, and Zhao is extended to obtain an analytic expansion for the ground-state wavefunction of a time-dependent strong-coupling Schroedinger equation. Two different types of the time-dependent harmonic oscillators are considered as examples for application of the time-dependent expansion. It is show that the time-dependent strong-coupling expansion is applicable to the time-dependent harmonic oscillators with a slowly varying time-dependent parameter.
Time-Dependent Mean-Field Games in the Subquadratic Case
Gomes, Diogo A.
2014-10-14
In this paper we consider time-dependent mean-field games with subquadratic Hamiltonians and power-like local dependence on the measure. We establish existence of classical solutions under a certain set of conditions depending on both the growth of the Hamiltonian and the dimension. This is done by combining regularity estimates for the Hamilton-Jacobi equation based on the Gagliardo-Nirenberg interpolation inequality with polynomial estimates for the Fokker-Planck equation. This technique improves substantially the previous results on the regularity of time-dependent mean-field games.
Time-dependent Networks as Models to Achieve Fast Exact Time-table Queries
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Jacob, Rico
2001-01-01
We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....
Time-Dependent Networks as Models to Achieve Fast Exact Time-Table Queries
DEFF Research Database (Denmark)
Brodal, Gert Stølting; Jacob, Rico
2003-01-01
We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....
New estimate for the time-dependent thermal nucleosynthesis of $^{180}$Ta$^m$
Hayakawa, T; Chiba, S; Mathews, G J; 10.1103/PhysRevC.81.052801
2010-01-01
We have made a new time-dependent calculation of the supernova production ratio of the long-lived isomeric state of $^{180}$Ta. Such a time-dependent solution is crucial for understanding the production and survival of this isotope. We include the explicit linking between the isomer and all known excited states.We have also calculated the properties of possible links to a conjectured excited state that might decrease the final isomer residual ratio. We find that the explicit time evolution of the synthesis of $^{180}$Ta using the available nuclear data avoids the overproduction relative to $^{138}$La for a $\
Analysis of time-dependent reliability of degenerated reinforced concrete structure
Directory of Open Access Journals (Sweden)
Zhang Hongping
2016-07-01
Full Text Available Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.
Some Exact Results for the Schroedinger Wave Equation with a Time Dependent Potential
Campbell, Joel
2009-01-01
The time dependent Schroedinger equation with a time dependent delta function potential is solved exactly for many special cases. In all other cases the problem can be reduced to an integral equation of the Volterra type. It is shown that by knowing the wave function at the origin, one may derive the wave function everywhere. Thus, the problem is reduced from a PDE in two variables to an integral equation in one. These results are used to compare adiabatic versus sudden changes in the potential. It is shown that adiabatic changes in the p otential lead to conservation of the normalization of the probability density.
Rüger, Robert; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas
2016-01-01
We report a time-dependent density functional based tight-binding (TD-DFTB) scheme for the calculation of UV/Vis spectra, explicitly taking into account the excitation of nuclear vibrations via the harmonic approximation. The theory of vibrationally resolved UV/Vis spectroscopy is first summarized from the viewpoint of TD-DFTB. The method is benchmarked against time-dependent density functional theory (TD-DFT) calculations for strongly dipole allowed excitations in various aromatic and polar molecules. Using the recent 3ob:freq parameter set of Elstner's group, excellent agreement with TD-DFT calculations using local functionals was achieved.
Singular boundary method using time-dependent fundamental solution for scalar wave equations
Chen, Wen; Li, Junpu; Fu, Zhuojia
2016-11-01
This study makes the first attempt to extend the meshless boundary-discretization singular boundary method (SBM) with time-dependent fundamental solution to two-dimensional and three-dimensional scalar wave equation upon Dirichlet boundary condition. The two empirical formulas are also proposed to determine the source intensity factors. In 2D problems, the fundamental solution integrating along with time is applied. In 3D problems, a time-successive evaluation approach without complicated mathematical transform is proposed. Numerical investigations show that the present SBM methodology produces the accurate results for 2D and 3D time-dependent wave problems with varied velocities c and wave numbers k.
Incompatibility of Time-Dependent Bogoliubov-de-Gennes and Ginzburg-Landau Equations
Frank, Rupert L.; Hainzl, Christian; Schlein, Benjamin; Seiringer, Robert
2016-07-01
We study the time-dependent Bogoliubov-de-Gennes equations for generic translation-invariant fermionic many-body systems. For initial states that are close to thermal equilibrium states at temperatures near the critical temperature, we show that the magnitude of the order parameter stays approximately constant in time and, in particular, does not follow a time-dependent Ginzburg-Landau equation, which is often employed as a phenomenological description and predicts a decay of the order parameter in time. The full non-linear structure of the equations is necessary to understand this behavior.
Direct measurement of time dependent diffusion for Ag and Au under ambient conditions
Yoo, Pil Sun; Jo, Han Yeol; Kim, Taekyeong
2014-12-01
Time-dependent diffusion for Ag and Au metal atoms was measured using the scanning tunneling microscope break-junction technique in ambient conditions. We observed that Ag contacts do not form long single-atomic chains compared to Au contacts during the elongation of each metal electrode, and Ag atoms diffuse more quickly than Au atoms after metal contact rupture. This is consistent with previous results of molecular dynamic simulations. Further, we found a correlation between diffusion length and the evolution time on an atomic scale to reveal the time-dependent diffusion for Ag and Au metal atoms.
Time-dependent Bragg diffraction and short-pulse reflection by one-dimensional photonic crystals
André, Jean-michel
2015-01-01
The time-dependence of the Bragg diffraction by one-dimensional photonic crystals and its influence on the short pulse reflection are studied in the framework of the coupled- wave theory. The indicial response of the photonic crystal is calculated and it appears that it presents a time-delay effect with a transient time conditioned by the extinction length. A numerical simulation is presented for a Bragg mirror in the x-ray domain and a pulse envelope modelled by a sine-squared shape. The potential consequences of the time-delay effect in time-dependent optics of short-pulses are emphasized.
Time-dependent predictors in clinical research, performance of a novel method.
van de Bosch, Joan; Atiqi, Roya; Cleophas, Ton J
2010-01-01
Individual patients' predictors of survival may change across time, because people may change their lifestyles. Standard statistical methods do not allow adjustments for time-dependent predictors. In the past decade, time-dependent factor analysis has been introduced as a novel approach adequate for the purpose. Using examples from survival studies, we assess the performance of the novel method. SPSS statistical software is used (SPSS Inc., Chicago, IL). Cox regression is a major simplification of real life; it assumes that the ratio of the risks of dying in parallel groups is constant over time. It is, therefore, inadequate to analyze, for example, the effect of elevated low-density lipoprotein cholesterol on survival, because the relative hazard of dying is different in the first, second, and third decades. The time-dependent Cox regression model allowing for nonproportional hazards is applied and provides a better precision than the usual Cox regression (P = 0.117 versus 0.0001). Elevated blood pressure produces the highest risk at the time it is highest. An overall analysis of the effect of blood pressure on survival is not significant, but after adjustment for the periods with highest blood pressures using the segmented time-dependent Cox regression method, blood pressure is a significant predictor of survival (P = 0.04). In a long-term therapeutic study, treatment modality is a significant predictor of survival, but after the inclusion of the time-dependent low-density lipoprotein cholesterol variable, the precision of the estimate improves from a P value of 0.02 to 0.0001. Predictors of survival may change across time, e.g., the effect of smoking, cholesterol, and increased blood pressure in cardiovascular research and patients' frailty in oncology research. Analytical models for survival analysis adjusting such changes are welcome. The time-dependent and segmented time-dependent predictors are adequate for the purpose. The usual multiple Cox regression
Wang, Haobin; Thoss, Michael
2016-10-01
The multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method is implemented in the interaction picture to allow a more effective description of correlation effects. It is shown that the artificial correlation present in the original Schrödinger picture can be removed with an appropriate choice of the zeroth-order Hamiltonian. Thereby, operators in the interaction picture are obtained through time-dependent unitary transformations, which have negligible computational cost compared with other parts of the ML-MCTDH algorithm. The efficiency of the method is demonstrated by application to a model of vibrationally coupled charge transport in molecular junctions.
Time-dependent renormalized-natural-orbital theory applied to laser-driven H$_2^+$
Hanusch, A; Brics, M; Bauer, D
2016-01-01
Recently introduced time-dependent renormalized-natural orbital theory (TDRNOT) is extended towards a multi-component approach in order to describe H$_2^+$ beyond the Born-Oppenheimer approximation. Two kinds of natural orbitals, describing the electronic and the nuclear degrees of freedom are introduced, and the exact equations of motion for them are derived. The theory is benchmarked by comparing numerically exact results of the time-dependent Schr\\"odinger equation for a H$_2^+$ model system with the corresponding TDRNOT predictions. Ground state properties, linear response spectra, fragmentation, and high-order harmonic generation are investigated.
VENTURE/PC manual: A multidimensional multigroup neutron diffusion code system
Energy Technology Data Exchange (ETDEWEB)
Shapiro, A.; Huria, H.C.; Cho, K.W. (Cincinnati Univ., OH (United States))
1991-12-01
VENTURE/PC is a recompilation of part of the Oak Ridge BOLD VENTURE code system, which will operate on an IBM PC or compatible computer. Neutron diffusion theory solutions are obtained for multidimensional, multigroup problems. This manual contains information associated with operating the code system. The purpose of the various modules used in the code system, and the input for these modules are discussed. The PC code structure is also given. Version 2 included several enhancements not given in the original version of the code. In particular, flux iterations can be done in core rather than by reading and writing to disk, for problems which allow sufficient memory for such in-core iterations. This speeds up the iteration process. Version 3 does not include any of the special processors used in the previous versions. These special processors utilized formatted input for various elements of the code system. All such input data is now entered through the Input Processor, which produces standard interface files for the various modules in the code system. In addition, a Standard Interface File Handbook is included in the documentation which is distributed with the code, to assist in developing the input for the Input Processor.
VENTURE/PC manual: A multidimensional multigroup neutron diffusion code system. Version 3
Energy Technology Data Exchange (ETDEWEB)
Shapiro, A.; Huria, H.C.; Cho, K.W. [Cincinnati Univ., OH (United States)
1991-12-01
VENTURE/PC is a recompilation of part of the Oak Ridge BOLD VENTURE code system, which will operate on an IBM PC or compatible computer. Neutron diffusion theory solutions are obtained for multidimensional, multigroup problems. This manual contains information associated with operating the code system. The purpose of the various modules used in the code system, and the input for these modules are discussed. The PC code structure is also given. Version 2 included several enhancements not given in the original version of the code. In particular, flux iterations can be done in core rather than by reading and writing to disk, for problems which allow sufficient memory for such in-core iterations. This speeds up the iteration process. Version 3 does not include any of the special processors used in the previous versions. These special processors utilized formatted input for various elements of the code system. All such input data is now entered through the Input Processor, which produces standard interface files for the various modules in the code system. In addition, a Standard Interface File Handbook is included in the documentation which is distributed with the code, to assist in developing the input for the Input Processor.
Non-Regenerative Multi-Antenna Multi-Group Multi-Way Relaying
Directory of Open Access Journals (Sweden)
Klein Anja
2011-01-01
Full Text Available Abstract We consider non-regenerative multi-group multi-way (MGMW relaying. A half-duplex non-regenerative multi-antenna relay station (RS assists multiple communication groups. In each group, multiple half-duplex nodes exchange messages. In our proposal, the required number of communication phases is equal to the maximum number of nodes among the groups. In the first phase, all nodes transmit simultaneously to the RS. Assuming perfect channel state information is available at the RS, in the following broadcast (BC phases the RS applies transceive beamforming to its received signal and transmits simultaneously to all nodes. We propose three BC strategies for the BC phases: unicasting, multicasting and hybrid uni/multicasting. For the multicasting strategy, network coding is applied to maintain the same number of communication phases as for the other strategies. We address transceive beamforming maximising the sum rate of non-regenerative MGMW relaying. Due to the high complexity of finding the optimum transceive beamforming maximising the sum rate, we design generalised low complexity transceive beamforming algorithms for all BC strategies: matched filter, zero forcing, minimisation of mean square error and BC-strategy-aware transceive beamforming. It is shown that the sum rate performance of non-regenerative MGMW relaying depends both on the chosen BC strategies and the applied transceive beamforming at the RS.
Three-dimensional h-adaptivity for the multigroup neutron diffusion equations
Wang, Yaqi
2009-04-01
Adaptive mesh refinement (AMR) has been shown to allow solving partial differential equations to significantly higher accuracy at reduced numerical cost. This paper presents a state-of-the-art AMR algorithm applied to the multigroup neutron diffusion equation for reactor applications. In order to follow the physics closely, energy group-dependent meshes are employed. We present a novel algorithm for assembling the terms coupling shape functions from different meshes and show how it can be made efficient by deriving all meshes from a common coarse mesh by hierarchic refinement. Our methods are formulated using conforming finite elements of any order, for any number of energy groups. The spatial error distribution is assessed with a generalization of an error estimator originally derived for the Poisson equation. Our implementation of this algorithm is based on the widely used Open Source adaptive finite element library deal.II and is made available as part of this library\\'s extensively documented tutorial. We illustrate our methods with results for 2-D and 3-D reactor simulations using 2 and 7 energy groups, and using conforming finite elements of polynomial degree up to 6. © 2008 Elsevier Ltd. All rights reserved.
Multigroup radiation hydrodynamics with flux-limited diffusion and adaptive mesh refinement
González, Matthias; Commerçon, Benoît; Masson, Jacques
2015-01-01
Radiative transfer plays a key role in the star formation process. Due to a high computational cost, radiation-hydrodynamics simulations performed up to now have mainly been carried out in the grey approximation. In recent years, multi-frequency radiation-hydrodynamics models have started to emerge, in an attempt to better account for the large variations of opacities as a function of frequency. We wish to develop an efficient multigroup algorithm for the adaptive mesh refinement code RAMSES which is suited to heavy proto-stellar collapse calculations. Due to prohibitive timestep constraints of an explicit radiative transfer method, we constructed a time-implicit solver based on a stabilised bi-conjugate gradient algorithm, and implemented it in RAMSES under the flux-limited diffusion approximation. We present a series of tests which demonstrate the high performance of our scheme in dealing with frequency-dependent radiation-hydrodynamic flows. We also present a preliminary simulation of a three-dimensional p...
MENDF71x. Multigroup Neutron Cross Section Data Tables Based upon ENDF/B-VII.1
Energy Technology Data Exchange (ETDEWEB)
Conlin, Jeremy Lloyd [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parsons, Donald Kent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gardiner, Steven J. [Univ. of California, Davis, CA (United States); Gray, Mark Girard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lee, Mary Beth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); White, Morgan Curtis [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-12-17
A new multi-group neutron cross section library has been released along with the release of NDI version 2.0.20. The library is named MENDF71x and is based upon the evaluations released in ENDF/B-VII.1 which was made publicly available in December 2011. ENDF/B-VII.1 consists of 423 evaluations of which ten are excited states evaluations and 413 are ground state evaluations. MENDF71x was created by processing the 423 evaluations into 618-group, downscatter only NDI data tables. The ENDF/B evaluation files were processed using NJOY version 99.393 with the exception of ^{35}Cl and ^{233}U. Those two isotopes had unique properties that required that we process the evaluation using NJOY version 2012. The MENDF71x library was only processed to room temperature, i.e., 293.6 K. In the future, we plan on producing a multi-temperature library based on ENDF/B-VII.1 and compatible with MENDF71x.
Vaytet, N; Audit, E; Commercon, B; Masson, J; Ferguson, J; Delahaye, F
2013-01-01
Star formation begins with the gravitational collapse of a dense core inside a molecular cloud. As the collapse progresses, the centre of the core begins to heat up as it becomes optically thick. The temperature and density in the centre eventually reach high enough values where fusion reactions can ignite; the protostar is born. This sequence of events entail many physical processes, of which radiative transfer is of paramount importance. Many simulations of protostellar collapse make use of a grey treatment of radiative transfer coupled to the hydrodynamics. However, interstellar gas and dust opacities present large variations as a function of frequency. In this paper, we follow-up on a previous paper on the collapse and formation of Larson's first core using multigroup radiation hydrodynamics (Paper I) by extending the calculations to the second phase of the collapse and the formation of Larson's second core. We have made the use of a non-ideal gas equation of state as well as an extensive set of spectral ...
Sample-size calculations for multi-group comparison in population pharmacokinetic experiments.
Ogungbenro, Kayode; Aarons, Leon
2010-01-01
This paper describes an approach for calculating sample size for population pharmacokinetic experiments that involve hypothesis testing based on multi-group comparison detecting the difference in parameters between groups under mixed-effects modelling. This approach extends what has been described for generalized linear models and nonlinear population pharmacokinetic models that involve only binary covariates to more complex nonlinear population pharmacokinetic models. The structural nonlinear model is linearized around the random effects to obtain the marginal model and the hypothesis testing involving model parameters is based on Wald's test. This approach provides an efficient and fast method for calculating sample size for hypothesis testing in population pharmacokinetic models. The approach can also handle different design problems such as unequal allocation of subjects to groups and unbalanced sampling times between and within groups. The results obtained following application to a one compartment intravenous bolus dose model that involved three different hypotheses under different scenarios showed good agreement between the power obtained from NONMEM simulations and nominal power.
Stability analysis of multi-group deterministic and stochastic epidemic models with vaccination rate
Wang, Zhi-Gang; Gao, Rui-Mei; Fan, Xiao-Ming; Han, Qi-Xing
2014-09-01
We discuss in this paper a deterministic multi-group MSIR epidemic model with a vaccination rate, the basic reproduction number ℛ0, a key parameter in epidemiology, is a threshold which determines the persistence or extinction of the disease. By using Lyapunov function techniques, we show if ℛ0 is greater than 1 and the deterministic model obeys some conditions, then the disease will prevail, the infective persists and the endemic state is asymptotically stable in a feasible region. If ℛ0 is less than or equal to 1, then the infective disappear so the disease dies out. In addition, stochastic noises around the endemic equilibrium will be added to the deterministic MSIR model in order that the deterministic model is extended to a system of stochastic ordinary differential equations. In the stochastic version, we carry out a detailed analysis on the asymptotic behavior of the stochastic model. In addition, regarding the value of ℛ0, when the stochastic system obeys some conditions and ℛ0 is greater than 1, we deduce the stochastic system is stochastically asymptotically stable. Finally, the deterministic and stochastic model dynamics are illustrated through computer simulations.
A Pareto Improving Strategy for the Time-Dependent Morning Commute Problem
Garcia, Reinaldo Crispiniano
1999-01-01
This dissertation describes a strategy which makes all commuters better off (i.e. a Pareto effecient strategy) for the time-dependent morning commute problem, even if the collected revenues are not returned to the population of commuters. The proposed strategy will apply road pricing as a tool for congestion management, a practice usually called congestion pricing.
Action-angle coordinates for time-dependent completely integrable Hamiltonian systems
Energy Technology Data Exchange (ETDEWEB)
Giachetta, Giovanni; Mangiarotti, Luigi [Department of Mathematics and Physics, University of Camerino, Camerino (Italy)]. E-mails: giovanni.giachetta@unicam.it; luigi.mangiarotti@unicam.it; Sardanashvily, Gennadi [Department of Theoretical Physics, Physics Faculty, Moscow State University, Moscow (Russian Federation)]. E-mail: sard@grav.phys.msu.su
2002-07-26
A time-dependent completely integrable Hamiltonian system is proved to admit the action-angle coordinates around any instantly compact regular invariant manifold. Written relative to these coordinates, its Hamiltonian and first integrals are functions only of action coordinates. (author). Letter-to-the-editor.
Time-adaptive and history-adaptive multicriterion routing in stochastic, time-dependent networks
DEFF Research Database (Denmark)
Pretolani, Daniele; Nielsen, Lars Relund; Andersen, Kim Allan
2009-01-01
We compare two different models for multicriterion routing in stochastic time-dependent networks: the classic "time-adaptive'' model and the more flexible "history-adaptive'' one. We point out several properties of the sets of efficient solutions found under the two models. We also devise a metho...
A marginal structural model for recurrent events in the presence of time-dependent confounding
DEFF Research Database (Denmark)
Jensen, Aksel Karl Georg; Ravn, Henrik; Sorup, S.
2016-01-01
for a time-dependent confounder when studying the effect of a time-varying exposure on a recurrent event based on an analysis in continuous time. Another is to report results via a measure which is easy to interpret and communicate even though quite elaborate treatment regimes are considered. Lastly...
Determination of relaxation modulus of time-dependent materials using neural networks
Aulova, Alexandra; Govekar, Edvard; Emri, Igor
2016-10-01
Health monitoring systems for plastic based structures require the capability of real time tracking of changes in response to the time-dependent behavior of polymer based structures. The paper proposes artificial neural networks as a tool of solving inverse problem appearing within time-dependent material characterization, since the conventional methods are computationally demanding and cannot operate in the real time mode. Abilities of a Multilayer Perceptron (MLP) and a Radial Basis Function Neural Network (RBFN) to solve ill-posed inverse problems on an example of determination of a time-dependent relaxation modulus curve segment from constant strain rate tensile test data are investigated. The required modeling data composed of strain rate, tensile and related relaxation modulus were generated using existing closed-form solution. Several neural networks topologies were tested with respect to the structure of input data, and their performance was compared to an exponential fitting technique. Selected optimal topologies of MLP and RBFN were tested for generalization and robustness on noisy data; performance of all the modeling methods with respect to the number of data points in the input vector was analyzed as well. It was shown that MLP and RBFN are capable of solving inverse problems related to the determination of a time dependent relaxation modulus curve segment. Particular topologies demonstrate good generalization and robustness capabilities, where the topology of RBFN with data provided in parallel proved to be superior compared to other methods.
Return Probability of the Open Quantum Random Walk with Time-Dependence
Institute of Scientific and Technical Information of China (English)
Clement Ampadu
2013-01-01
We study the open quantum random walk (OQRW) with time-dependence on the one-dimensional lattice space and obtain the associated limit distribution.As an application we study the return probability of the OQRW.We also ask,"What is the average time for the return probability of the OQRW?"
Perveaux, A; Lasorne, B; Gatti, F; Robb, M A; Halász, G J; Vibók, Á
2014-01-01
A nonadiabatic scheme for the description of the coupled electron and nuclear motions in the ozone molecule was proposed recently. An initial coherent nonstationary state was prepared as a superposition of the ground state and the excited Hartley band. In this situation neither the electrons nor the nuclei are in a stationary state. The multiconfiguration time dependent Hartree method was used to solve the coupled nuclear quantum dynamics in the framework of the adiabatic separation of the time-dependent Schr\\"odinger equation. The resulting wave packet shows an oscillation of the electron density between the two chemical bonds. As a first step for probing the electronic motion we computed the time-dependent molecular dipole and the Dyson orbitals. The latter play an important role in the explanation of the photoelectron angular distribution. Calculations of the Dyson orbitals are presented both for the time-independent as well as the time-dependent situations. We limited our description of the electronic mot...
The Limit Behavior of a Stochastic Logistic Model with Individual Time-Dependent Rates
Directory of Open Access Journals (Sweden)
Yilun Shang
2013-01-01
Full Text Available We investigate a variant of the stochastic logistic model that allows individual variation and time-dependent infection and recovery rates. The model is described as a heterogeneous density dependent Markov chain. We show that the process can be approximated by a deterministic process defined by an integral equation as the population size grows.
Limit theorem for a time-dependent coined quantum walk on the line
Machida, Takuya
2010-01-01
We study time-dependent discrete-time quantum walks on the one-dimensional lattice. We compute the limit distribution of a two-period quantum walk defined by two orthogonal matrices. For the symmetric case, the distribution is determined by one of two matrices. Moreover, limit theorems for two special cases are presented.
The time-dependent forced anisotropic oscillator in noncommutative phase space
Energy Technology Data Exchange (ETDEWEB)
Liang Mailin; Chen Qian, E-mail: mailinliang@yahoo.com.cn, E-mail: mailinliang@tju.edu.cn [Physics Department, School of Science, Tianjin University, Tianjin 300072 (China)
2011-07-01
Wave functions of the time-dependent forced anisotropic harmonic oscillator in noncommutative phase space are derived using the linear transformation and unitary transformation methods. The energy spectrum is given for the stationary system. Further, quantum fluctuations and the squeezing effect are investigated. It is found that the anisotropic property of the harmonic oscillator in noncommutative space has the squeezing effect.
Time-dependent Aharonov-Bohm effect on the noncommutative space
Ma, Kai; Yang, Huan-Xiong
2016-01-01
We study the time-dependent Aharonov-Bohm effect on the noncommutative space. Because there is no net Aharonov-Bohm phase shift in the time-dependent case on the commutative space, therefore tiny deviation from zero indicates new physics. Based on the Seiberg-Witten map we obtained the gauge invariant and Lorentz covariant Aharonov-Bohm phase shift on noncommutative space in general case. We find there are two kinds of contributions: momentum-dependent and momentum-independent corrections. For the momentum-dependent correction, there is a cancellation between the magnetic and electric phase shifts, just like the case on the commutative space. However, there is a non-trivial contribution in the momentum-independent correction. This is true for both the time-independent and time-dependent Aharonov-Bohm effects on the noncommutative space. However, for the time-dependent Aharonov-Bohm effect, there is no overwhelming background which exists on both commutative and noncommutative space for the time-independent Ah...
Enabling time-dependent uncertain eco-weights for road networks
DEFF Research Database (Denmark)
Hu, Jilin; Yang, Bin; Jensen, Christian Søndergaard;
2017-01-01
dependent and uncertain. We formalize the problem of assigning a time-dependent, uncertain eco-weight to each edge in a road network based on historical GPS records. In particular, a sequence of histograms is employed to describe the uncertain eco-weight of an edge at different time intervals. Compression...
New Unconditionally Stable Algorithms to Solve the Time-Dependent Maxwell Equations
Kole, J.S.; Figge, M.T.; Raedt, H. De
2002-01-01
We present a family of unconditionally stable algorithms, based on the Suzuki product-formula approach, that solve the time-dependent Maxwell equations in systems with spatially varying permittivity and permeability. Salient features of these algorithms are illustrated by computing the density of st
A new approximation method for time-dependent problems in quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima (Mexico)]. E-mail: paolo@ucol.mx; Aranda, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima (Mexico)]. E-mail: fefo@ucol.mx; Fernandez, Francisco M. [INIFTA (Conicet, UNLP), Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)]. E-mail: fernande@quimica.unlp.edu.ar; Jones, Hugh [Department of Physics, Imperial College, London SW7 2AZ (United Kingdom)]. E-mail: h.f.jones@imperial.ac.uk
2005-06-06
We propose an approximate solution of the time-dependent Schroedinger equation using the method of stationary states combined with a variational matrix method for finding the energies and eigenstates. We illustrate the effectiveness of the method by applying it to the time development of the wave-function in the quantum-mechanical version of the inflationary slow-roll transition.
3D time-dependent flow computations using a molecular stress function model with constraint release
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz
2002-01-01
The numerical simulation of time dependent viscoelastic flow (in three dimensions) is of interest in connection with a variety of polymer processing operations. The application of the numerical simulation techniques is in the analysis and design of polymer processing problems. This is operations,...
A time dependent solution for the operation of ion chambers in a high ionization background
Velissaris, C
2005-01-01
We have derived a time dependent solution describing the development of space charge inside an ion chamber subjected to an externally caused ionization rate N. The solution enables the derivation of a formula that the operational parameters of the chamber must satisfy for saturation free operation. This formula contains a correction factor to account for the finite duration of the ionization rate N.
Domain structure and time-dependent properties of a crosslinked urethane elastomer
Energy Technology Data Exchange (ETDEWEB)
Lagasse, R.R.
1977-09-01
The morphology of a chemically crosslinked urethane elastomer is correlated with its time-dependent mechanical properties. Evaluation of this amorphous elastomer by electron microscopy and small-angle x-ray scattering reveals that incompatible chain segments cluster into separate microphases having a periodicity in electron density of about 90 A. This observed domain structure is similar to that seen previously in uncrosslinked, thermoplastic urethane elastomers. As in earlier studies on such linear systems, thermal pretreatment of the crosslinked elastomer causes a time-dependent change in its room temperature modulus. However, the magnitude of this modulus change (about 20%) is generally less than observed previously with the linear systems. Another contrast with previous findings is that this time-dependent phenomenon is apparently not caused by thermally activated changes in microphase segregation. Rather, the observed time dependence in modulus is believed to be caused by molecular relaxation resulting in densification of amorphous packing within the hard-segment domains. The validity of this proposed mechanism is supported by differential scanning calorimetry experiments showing evidence of enthalpy relaxation during room-temperature aging of the elastomer. This relaxation is qualitatively similar to that observed previously during sub-T/sub g/ annealing of single-phase glassy polymers.
Stochastic time-dependent vehicle routing problem: Mathematical models and ant colony algorithm
Directory of Open Access Journals (Sweden)
Zhengyu Duan
2015-11-01
Full Text Available This article addresses the stochastic time-dependent vehicle routing problem. Two mathematical models named robust optimal schedule time model and minimum expected schedule time model are proposed for stochastic time-dependent vehicle routing problem, which can guarantee delivery within the time windows of customers. The robust optimal schedule time model only requires the variation range of link travel time, which can be conveniently derived from historical traffic data. In addition, the robust optimal schedule time model based on robust optimization method can be converted into a time-dependent vehicle routing problem. Moreover, an ant colony optimization algorithm is designed to solve stochastic time-dependent vehicle routing problem. As the improvements in initial solution and transition probability, ant colony optimization algorithm has a good performance in convergence. Through computational instances and Monte Carlo simulation tests, robust optimal schedule time model is proved to be better than minimum expected schedule time model in computational efficiency and coping with the travel time fluctuations. Therefore, robust optimal schedule time model is applicable in real road network.
Two-dimensional time-dependent quantum-mechanical scattering event
Energy Technology Data Exchange (ETDEWEB)
Galbraith, I.; Ching, Y.S.; Abraham, E.
1984-01-01
Nonrelativistic quantum-mechanical scattering in two dimensions is studied numerically by integrating the time-dependent Schroedinger equation. A partial-wave analysis is used to discuss the numerical results. A potential barrier, a square well and a single slit are considered as the scattering potentials.
TIME-DEPENDENT LANDAU SYSTEM AND NON-ADIABATIC BERRY PHASE IN TWO DIMENSIONS
Institute of Scientific and Technical Information of China (English)
Jing Hui; Wu Jian-sheng
2000-01-01
By applying the time-independent unitary transformation, thetime-dependent Landau system is transformed into a product of atime-independent Landau system's Hamiltonian and a factor only dependingon time, which can be solved exactly. Both the invariant operator andthe eigenstate are obtained. In the periodical time-dependent case, thenon-adiabatic Berry's phase is also presented.
A sparse collocation method for solving time-dependent HJB equations using multivariate B-splines
Govindarajan, N.; De Visser, C.C.; Krishnakumar, K.
2014-01-01
This paper presents a sparse collocation method for solving the time-dependent Hamilton–Jacobi–Bellman (HJB) equation associated with the continuous-time optimal control problem on a fixed, finite timehorizon with integral cost functional. Through casting the problem in a recursive framework using t
A time-dependent measurement of charm CP violation at LHCb
Smith, M
2014-01-01
A time dependent analysis of CP violation in charm mesons is presented through the measurement of the observable $A_{\\Gamma}$. This observable involves precise measurements of the D0 lifetime as it decays to a CP eigenstate. The results presented are the most precise to date. No CP violation is observed.
The Time-Dependent Multiple-Vehicle Prize-Collecting Arc Routing Problem
DEFF Research Database (Denmark)
Black, Daniel; Eglese, Richard; Wøhlk, Sanne
2015-01-01
In this paper, we introduce a multi vehicle version of the Time-Dependent Prize-Collecting Arc Routing Problem (TD-MPARP). It is inspired by a situation where a transport manager has to choose between a number of full truck load pick-ups and deliveries to be performed by a fleet of vehicles. Real...
A geometric framework for time-dependent mechanical systems with unilateral constraints
Institute of Scientific and Technical Information of China (English)
Zhang Yi; Mei Feng-Xiang
2006-01-01
The description of modern differential geometry for time-dependent Chetaev nonholonomic mechanical systems with unilateral constraints is studied. By using the structure of exact contact manifold, the geometric framework of timedependent nonholonomic mechanical systems subject to unilateral nonholonomic constraints and unilateral holonomic constraints respectively is presented.
Time-dependent density-functional theory in the projector augmented-wave method
DEFF Research Database (Denmark)
Walter, Michael; Häkkinen, Hannu; Lehtovaara, Lauri
2008-01-01
We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we...
Operation safety risk analysis method of hydropower project considering time-dependent effect
Institute of Scientific and Technical Information of China (English)
Zhang Sherong; Yan Lei
2012-01-01
In order to consider the time-dependent characteristic of risk factors of hydropower project, the method of stochastic process simulating structure resistance and load effect is adopted. On the basis of analyzing the structure characteristics and mode of operation, the operation safety risk rate assessment model of hydropower project is established on the comprehensive application of the improved analytic hierarchy process, the time-dependent reliability theory and the risk rate threshold. A scheme to demonstrate the time-dependent risk rate assessment method for an example of the earth-rock dam is particularly implemented by the proposed approach. The example shows that operation safety risk rate is closely related to both the service period and design standard ; considering the effect of time-dependent, the risk rate increases with time and the intersection of them reflects the technical service life of structures. It could provide scientific basis for the operation safety and risk decision of the hydropower project by predicting the trend of risk rate via this model.
Mixing of photons with light pseudoscalars in time-dependent magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Arias, Paola; Arza, Ariel; Gamboa, Jorge [Universidad de Santiago de Chile, Departmento de Fisica, Santiago (Chile)
2016-11-15
The effects of an external time-dependent magnetic field in the conversion probability of photon- to axion-like particles are studied. Our findings show that for a certain time regime, the amplitude of the produced axion-like field can be enlarged with respect to the static case, thus enhancing the probability of conversion. (orig.)
Parameter and state estimation with a time-dependent adjoint marine ice sheet model
Directory of Open Access Journals (Sweden)
D. N. Goldberg
2013-06-01
Full Text Available To date, assimilation of observations into large-scale ice models has consisted predominantly of time-independent inversions of surface velocities for basal traction, bed elevation, or ice stiffness, and has relied primarily on analytically-derived adjoints of diagnostic ice velocity models. To overcome limitations of such "snapshot" inversions, i.e. their inability to assimilate time-dependent data, or to produce initial states with minimum artificial drift and suitable for time-dependent simulations, we have developed an adjoint of a time-dependent parallel glaciological flow model. The model implements a hybrid shallow shelf-shallow ice stress balance, involves a prognostic equation for ice thickness evolution, and can represent the floating, fast-sliding, and frozen bed regimes of a marine ice sheet. The adjoint is generated by a combination of analytic methods and the use of algorithmic differentiation (AD software. Several experiments are carried out with idealized geometries and synthetic observations, including inversion of time-dependent surface elevations for past thicknesses, and simultaneous retrieval of basal traction and topography from surface data. Flexible generation of the adjoint for a range of independent uncertain variables is exemplified through sensitivity calculations of grounded ice volume to changes in basal melting of floating and basal sliding of grounded ice. The results are encouraging and suggest the feasibility, using real observations, of improved ice sheet state estimation and comprehensive transient sensitivity assessments.
DEFF Research Database (Denmark)
Svendsen, Christian; Mortensen, O. Sonnich; Henriksen, Niels Engholm
1996-01-01
Time-dependent recursion relationships are derived for optical absorption and resonance Raman correlators in the multidimensional harmonic case using a second-quantization formalism. Furthermore, a procedure is given for the calculation of correlators involving a general analytic coordinate depen...... dependence of the transition dipole moment....
Wessling, M.; Huisman, I.; Boomgaard, van den Th.; Smolders, C.A.
1995-01-01
The time-dependent permeation behavior of a glassy polyimide is studied above and below the plasticization pressure with carbon dioxide as the permeating gas. The work particularly focuses on the quantification of the slow increase in permeability at feed pressures above the plasticization pressure.
The Bifurcation of Vortex Current in the Time-Dependent Ginzburg-Landau Model
Institute of Scientific and Technical Information of China (English)
XU Tao; YANG Guo-Hong; DUAN Yi-Shi
2001-01-01
By the method of φ-mapping topological current theory, the bifurcation behavior of the topological current is discussed in detail in the O(n) symmetrical time-dependent Ginzburg-Landau model at the critical points of the order parameter field. The different directions of the branch curves at the critical point have been obtained.
Gauge Invariance of a Time-Dependent Harmonic Oscillator in Magnetic Dipole Approximation
Institute of Scientific and Technical Information of China (English)
WANG Fei; QIAN Shang-Wu; FU Li-Ping; WANG Jing-Shan; GUO Ke-Tao
2008-01-01
A manifestly gauge-invariant formulation of non-relativistic quantum mechanics is applied to the case of time-dependent harmonic oscillator in the magnetic dipole approximation. A genera/ equation for obtaining gauge-invariant transition probability amplitudes is derived.
Mixing of photons with light pseudoscalars in time-dependent magnetic fields
Arias, Paola; Arza, Ariel; Gamboa, Jorge
2016-11-01
The effects of an external time-dependent magnetic field in the conversion probability of photon- to axion-like particles are studied. Our findings show that for a certain time regime, the amplitude of the produced axion-like field can be enlarged with respect to the static case, thus enhancing the probability of conversion.
Mixing of photons with light pseudoscalars in time-dependent magnetic fields
Arias, Paola; Gamboa, Jorge
2016-01-01
The effects of an external time-dependent magnetic field in the conversion probability of photon-to-axion-like particles are studied. Our findings show that for a certain time regime, the amplitude of the produced axion-like field can be enlarged with respect to the static case, thus, enhancing the probability of conversion.
Optimal Preventive Maintenance Schedule based on Lifecycle Cost and Time-Dependent Reliability
2011-11-10
cost PC , the inspection cost IC and an expected variable cost EVC [2, 32]. These costs are a function of quality and reliability. The lifecycle...expected variable cost EVC is a function of the time- dependent reliability which is used to estimate the expected present value of repairing and/or
Time-dependent quantum wave packet dynamics to study charge transfer in heavy particle collisions
Zhang, Song Bin; Wu, Yong; Wang, Jian Guo
2016-12-01
The method of time-dependent quantum wave packet dynamics has been successfully extended to study the charge transfer/exchange process in low energy two-body heavy particle collisions. The collision process is described by coupled-channel equations with diabatic potentials and (radial and rotational) couplings. The time-dependent coupled equations are propagated with the multiconfiguration time-dependent Hartree method and the modulo squares of S-matrix is extracted from the wave packet by the flux operator with complex absorbing potential (FCAP) method. The calculations of the charge transfer process 12Σ+ H-(1s2) +Li(1 s22 s ) →22Σ+ /32 Σ+ /12 Π H(1 s ) +Li-(1s 22 s 2 l ) (l =s ,p ) at the incident energy of about [0.3, 1.3] eV are illustrated as an example. It shows that the calculated reaction probabilities by the present FCAP reproduce that of quantum-mechanical molecular-orbital close-coupling very well, including the peak structures contributed by the resonances. Since time-dependent external interactions can be directly included in the present FCAP calculations, the successful implementation of FCAP provides us a powerful potential tool to study the quantum control of heavy particle collisions by lasers in the near future.
DEFF Research Database (Denmark)
Gillet, N.; Jault, D.; Finlay, Chris
2015-01-01
We report a calculation of time-dependent quasi-geostrophic core flows for 1940–2010. Inverting recursively for an ensemble of solutions, we evaluate the main source of uncertainties, namely, the model errors arising from interactions between unresolved core surface motions and magnetic fields. T...
A Study of Relationship Between Universality in Fractal Colloids Aggregation and Time-dependent SERS
Institute of Scientific and Technical Information of China (English)
张宏光; 刘凡镇; 何天敬; 辛厚文
1994-01-01
The relationship between the rule of time-dependent surface-enhanced Raman scattering (SERS) intensity of adsorbed pyridine in AgBr sol and silver bromide colloidal fractal aggregation is studied in this paper. The experimental results support the view of universality in colloidal aggregation and suggest that SERS may be a useful tool in the study of kinetics of colloidal aggregation.
Emergence of slow collective oscillations in neural networks with spike-timing dependent plasticity
DEFF Research Database (Denmark)
Mikkelsen, Kaare; Imparato, Alberto; Torcini, Alessandro
2013-01-01
The collective dynamics of excitatory pulse coupled neurons with spike timing dependent plasticity (STDP) is studied. The introduction of STDP induces persistent irregular oscillations between strongly and weakly synchronized states, reminiscent of brain activity during slow-wave sleep. We explain...
Unified framework for numerical methods to solve the time-dependent Maxwell equations
De Raedt, H; Kole, JS; Michielsen, KFL; Figge, MT
2003-01-01
We present a comparative study of numerical algorithms to solve the time-dependent Maxwell equations for systems with spatially varying permittivity and permeability. We show that the Lie-Trotter-Suzuki product-formula approach can be used to construct a family of unconditionally stable algorithms,
Extracting molecular Hamiltonian structure from time-dependent fluorescence intensity data
Brif, Constantin; Rabitz, Herschel
2000-01-01
We propose a formalism for extracting molecular Hamiltonian structure from inversion of time-dependent fluorescence intensity data. The proposed method requires a minimum of \\emph{a priori} knowledge about the system and allows for extracting a complete set of information about the Hamiltonian for a pair of molecular electronic surfaces.
Exact solutions to three-dimensional time-dependent Schrödinger equation
Indian Academy of Sciences (India)
Fakir Chand; S C Mishra
2007-06-01
With a view to obtain exact analytic solutions to the time-dependent Schrödinger equation for a few potentials of physical interest in three dimensions, transformation-group method is used. Interestingly, the integrals of motion in the new coordinates turn out to be the desired invariants of the systems.
Institute of Scientific and Technical Information of China (English)
Yong Wu; Siming He
2015-01-01
Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris flow. In the past decades, researches on hydraulic mechanism and time-dependent characteristics of loose deposits failure are frequently reported, however adequate measures for reducing debris flow are not available practically. In this context, a time-dependent model was established to determine the changes of water table of loose deposits using hydraulic and topographic theories. In addition, the variation in water table with elapsed time was analyzed. The formulas for calculating hydrodynamic and hydrostatic pressures on each strip and block unit of deposit were proposed, and the slope stability and failure risk of the loose deposits were assessed based on the time-dependent hydraulic characteristics of established model. Finally, the failure mechanism of deposits based on infinite slope theory was illustrated, with an example, to calculate sliding force, anti-sliding force and residual sliding force applied to each slice. The results indicate that failure of gully deposits under the effect of rainfall is the result of continuously increasing hydraulic pressure and water table. The time-dependent characteristics of loose deposit failure are determined by the factors of hydraulic properties, drainage area of interest, rainfall pattern, rainfall duration and intensity.
Analysis of time-dependent changes in Bitemarks on Styrofoam sheets
Directory of Open Access Journals (Sweden)
Djeapragassam Parimala
2015-01-01
Full Text Available Context: The scope of Bitemarks in forensic dentistry is widening as they help the forensic expert in identifying the perpetuator in medicolegal cases. The greatest challenge in Bitemarks analysis is the time-dependent changes produced in Bitemark patterns on various substrates at the scene of the crime. Aims: To analyze the time-dependent changes in Bitemarks on Styrofoam sheets. Settings and Design: Single centered prospective study. Materials and Methods: Twenty-five subjects were randomly chosen, and dental casts prepared. Then test bites were registered on Styrofoam sheets, overlays prepared from these test bites on subsequent days (day 1, 2, 3, 4 and checked for matching accuracy. Statistical Analysis Used: The data were analyzed using Kruskal-Wallis ANOVA to compare the overlays from dental stone cast with test bites on Styrofoam sheets on subsequent days. Results: The P value was found to be 1 which is statistically not significant implying that there were no significant time-dependent changes in the pattern of Bitemarks. Conclusions: There were no time-dependent changes in the pattern of Bitemarks on Styrofoam sheets hence they serve as better materials than Bitemarks on human skin or food substrates obtained from the scene of the crime.
Finite-difference, spectral and Galerkin methods for time-dependent problems
Tadmor, E.
1983-01-01
Finite difference, spectral and Galerkin methods for the approximate solution of time dependent problems are surveyed. A unified discussion on their accuracy, stability and convergence is given. In particular, the dilemma of high accuracy versus stability is studied in some detail.
Wang, P.; Li, P.
1998-01-01
A high-resolution numerical study on parallel systems is reported on three-dimensional, time-dependent, thermal convective flows. A parallel implentation on the finite volume method with a multigrid scheme is discussed, and a parallel visualization systemm is developed on distributed systems for visualizing the flow.
Coherent states of a time-dependent forced harmomc oscillator and their Aharonov-Anandan phase
Institute of Scientific and Technical Information of China (English)
刘宇峰; 雷奕安; 曾谨言
2000-01-01
A new method to construct coherent states of a time-dependent forced harmonic oscillator was given. The close relation to the classical forced oscillator and the minimum uncertainty relation were investigated. The applied periodic force (off-resonance case), in general, will attenuate the AA phase.
Time-dependent potential through an Ansatz for the Kohn-Sham orbitals
Magyar, R J
2016-01-01
Given the time-evolution of an electron charge density, the local potential in Kohn-Sham time-dependent density functional theory (KS-TDDFT) can be modeled as a sum of instantaneous and dynamic contributions by assuming a certain form of the time-dependent Kohn-Sham (TD-KS) orbitals. The instantaneous part is obtained numerically using methods from ground-state density functional theory (DFT) and the dynamic part is expressed in terms of a velocity potential that depends on the electron current density. The suggested form of the TD-KS orbitals satisfies several known constraints (orthonormality, N-representability, J-representability), and the domain of validity is shown to depend on the evolution of the instantaneous quantities. Through this decomposition, we can relate time-dependent and ground -state V-representability. The resulting potentials are shown numerically to approximate the exact time-dependent Kohn-Sham potentials for a set of 3 non-singlet two-particle systems (a Kohn-mode, a Coulomb explosion...
DEFF Research Database (Denmark)
Rotvig, J.; Smith, H.; Jauho, Antti-Pekka
1996-01-01
We present an analytical study of one-dimensional semiconductor superlattices in external electric fields, which may be time dependent. A number of general results for the (quasi)energies and eigenstates are derived. An equation of motion for the density matrix is obtained for a two-band model an....... 74, 1831 (1995)], where a set of numerical simulations was presented....
The Bloch wave operator: generalizations and applications: II. The time-dependent case
Energy Technology Data Exchange (ETDEWEB)
Jolicard, Georges [Observatoire de Besancon (UMR-CNRS 6091), Universite de Franche-Comte, 41 bis, Avenue de l' Observatoire, 25000 Besancon (France); Killingbeck, John P [Observatoire de Besancon (UMR-CNRS 6091), Universite de Franche-Comte, 41 bis, Avenue de l' Observatoire, 25000 Besancon (France); Mathematics Department, University of Hull, Hull HU6 7RX (United Kingdom)
2003-10-10
Part II of the review shows how the stationary Bloch wave operator of part I can be suitably modified to give a time-dependent wave operator. This operator makes it possible to use a relatively small active space in order to describe the dynamical processes which occur in quantum mechanical systems which have a time-dependent Hamiltonian. A close study is made of the links between the time-dependent and time-independent wave operators at the adiabatic limit; the analysis clarifies the way in which the wave operator formalism allows the time evolution of a system or a wave packet to be described in terms of a fast evolution inside the active space together with weak transitions out of this space which can be treated by perturbation methods. Two alternative wave operator equations of motion are derived and analysed. The first one is a non-linear differential equation in the usual Hilbert space; the second one is a differential equation in an extended Hilbert space with an extra time variable added and becomes equivalent to the usual Bloch equation when the Floquet Hamiltonian is taken in place of the ordinary Hamiltonian. A study is made of the close relationships between the time-dependent wave operator formalism, the Floquet theory and the (t, t') theory. Some original methods of solution of the two forms of wave operator equation are proposed and lead to new techniques of integration for the time-dependent Schroedinger equation (e.g., the generalized Green equation procedure). Mixed procedures involving both the time-independent and time-dependent wave operators are shown to be applicable to the internal eigenstate problem for large complex matrices. A detailed account is given of the description of inelastic and photoreactive processes by means of the time-dependent wave operator formalism, with particular attention to laser-molecule interactions. The emphasis is on projection operator techniques, with special attention being given to the method of selection
Relaxation of a 1-D gravitational system
Valageas, P
2006-01-01
We study the relaxation towards thermodynamical equilibrium of a 1-D gravitational system. This OSC model shows a series of critical energies $E_{cn}$ where new equilibria appear and we focus on the homogeneous ($n=0$), one-peak ($n=\\pm 1$) and two-peak ($n=2$) states. Using numerical simulations we investigate the relaxation to the stable equilibrium $n=\\pm 1$ of this $N-$body system starting from initial conditions defined by equilibria $n=0$ and $n=2$. We find that in a fashion similar to other long-range systems the relaxation involves a fast violent relaxation phase followed by a slow collisional phase as the system goes through a series of quasi-stationary states. Moreover, in cases where this slow second stage leads to a dynamically unstable configuration (two peaks with a high mass ratio) it is followed by a new sequence ``violent relaxation/slow collisional relaxation''. We obtain an analytical estimate of the relaxation time $t_{2\\to \\pm 1}$ through the mean escape time of a particle from its potent...
Time-dependent theoretical treatments of the dynamics of electrons and nuclei in molecular systems
Deumens, E.; Diz, A.; Longo, R.; Öhrn, Y.
1994-07-01
An overview is presented of methods for time-dependent treatments of molecules as systems of electrons and nuclei. The theoretical details of these methods are reviewed and contrasted in the light of a recently developed time-dependent method called electron-nuclear dynamics. Electron-nuclear dynamics (END) is a formulation of the complete dynamics of electrons and nuclei of a molecular system that eliminates the necessity of constructing potential-energy surfaces. Because of its general formulation, it encompasses many aspects found in other formulations and can serve as a didactic device for clarifying many of the principles and approximations relevant in time-dependent treatments of molecular systems. The END equations are derived from the time-dependent variational principle applied to a chosen family of efficiently parametrized approximate state vectors. A detailed analysis of the END equations is given for the case of a single-determinantal state for the electrons and a classical treatment of the nuclei. The approach leads to a simple formulation of the fully nonlinear time-dependent Hartree-Fock theory including nuclear dynamics. The nonlinear END equations with the ab initio Coulomb Hamiltonian have been implemented at this level of theory in a computer program, ENDyne, and have been shown feasible for the study of small molecular systems. Implementation of the Austin Model 1 semiempirical Hamiltonian is discussed as a route to large molecular systems. The linearized END equations at this level of theory are shown to lead to the random-phase approximation for the coupled system of electrons and nuclei. The qualitative features of the general nonlinear solution are analyzed using the results of the linearized equations as a first approximation. Some specific applications of END are presented, and the comparison with experiment and other theoretical approaches is discussed.
Time-dependent Aharonov–Bohm effect on the noncommutative space
Directory of Open Access Journals (Sweden)
Kai Ma
2016-08-01
Full Text Available We study the time-dependent Aharonov–Bohm effect on the noncommutative space. Because there is no net Aharonov–Bohm phase shift in the time-dependent case on the commutative space, therefore, a tiny deviation from zero indicates new physics. Based on the Seiberg–Witten map we obtain the gauge invariant and Lorentz covariant Aharonov–Bohm phase shift in general case on noncommutative space. We find there are two kinds of contribution: momentum-dependent and momentum-independent corrections. For the momentum-dependent correction, there is a cancellation between the magnetic and electric phase shifts, just like the case on the commutative space. However, there is a non-trivial contribution in the momentum-independent correction. This is true for both the time-independent and time-dependent Aharonov–Bohm effects on the noncommutative space. However, for the time-dependent Aharonov–Bohm effect, there is no overwhelming background which exists in the time-independent Aharonov–Bohm effect on both commutative and noncommutative space. Therefore, the time-dependent Aharonov–Bohm can be sensitive to the spatial noncommutativity. The net correction is proportional to the product of the magnetic fluxes through the fundamental area represented by the noncommutative parameter θ, and through the surface enclosed by the trajectory of charged particle. More interestingly, there is an anti-collinear relation between the logarithms of the magnetic field B and the averaged flux Φ/N (N is the number of fringes shifted. This nontrivial relation can also provide a way to test the spatial noncommutativity. For BΦ/N∼1, our estimation on the experimental sensitivity shows that it can reach the 10 GeV scale. This sensitivity can be enhanced by using stronger magnetic field strength, larger magnetic flux, as well as higher experimental precision on the phase shift.
Time-dependent Aharonov-Bohm effect on the noncommutative space
Ma, Kai; Wang, Jian-Hua; Yang, Huan-Xiong
2016-08-01
We study the time-dependent Aharonov-Bohm effect on the noncommutative space. Because there is no net Aharonov-Bohm phase shift in the time-dependent case on the commutative space, therefore, a tiny deviation from zero indicates new physics. Based on the Seiberg-Witten map we obtain the gauge invariant and Lorentz covariant Aharonov-Bohm phase shift in general case on noncommutative space. We find there are two kinds of contribution: momentum-dependent and momentum-independent corrections. For the momentum-dependent correction, there is a cancellation between the magnetic and electric phase shifts, just like the case on the commutative space. However, there is a non-trivial contribution in the momentum-independent correction. This is true for both the time-independent and time-dependent Aharonov-Bohm effects on the noncommutative space. However, for the time-dependent Aharonov-Bohm effect, there is no overwhelming background which exists in the time-independent Aharonov-Bohm effect on both commutative and noncommutative space. Therefore, the time-dependent Aharonov-Bohm can be sensitive to the spatial noncommutativity. The net correction is proportional to the product of the magnetic fluxes through the fundamental area represented by the noncommutative parameter θ, and through the surface enclosed by the trajectory of charged particle. More interestingly, there is an anti-collinear relation between the logarithms of the magnetic field B and the averaged flux Φ / N (N is the number of fringes shifted). This nontrivial relation can also provide a way to test the spatial noncommutativity. For BΦ / N ∼ 1, our estimation on the experimental sensitivity shows that it can reach the 10 GeV scale. This sensitivity can be enhanced by using stronger magnetic field strength, larger magnetic flux, as well as higher experimental precision on the phase shift.
Is the time-dependent behaviour of the aortic valve intrinsically quasi-linear?
Anssari-Benam, Afshin
2014-05-01
The widely popular quasi-linear viscoelasticity (QLV) theory has been employed extensively in the literature for characterising the time-dependent behaviour of many biological tissues, including the aortic valve (AV). However, in contrast to other tissues, application of QLV to AV data has been met with varying success, with studies reporting discrepancies in the values of the associated quantified parameters for data collected from different timescales in experiments. Furthermore, some studies investigating the stress-relaxation phenomenon in valvular tissues have suggested discrete relaxation spectra, as an alternative to the continuous spectrum proposed by the QLV. These indications put forward a more fundamental question: Is the time-dependent behaviour of the aortic valve intrinsically quasi-linear? In other words, can the inherent characteristics of the tissue that govern its biomechanical behaviour facilitate a quasi-linear time-dependent behaviour? This paper attempts to address these questions by presenting a mathematical analysis to derive the expressions for the stress-relaxation G( t) and creep J( t) functions for the AV tissue within the QLV theory. The principal inherent characteristic of the tissue is incorporated into the QLV formulation in the form of the well-established gradual fibre recruitment model, and the corresponding expressions for G( t) and J( t) are derived. The outcomes indicate that the resulting stress-relaxation and creep functions do not appear to voluntarily follow the observed experimental trends reported in previous studies. These results highlight that the time-dependent behaviour of the AV may not be quasi-linear, and more suitable theoretical criteria and models may be required to explain the phenomenon based on tissue's microstructure, and for more accurate estimation of the associated material parameters. In general, these results may further be applicable to other planar soft tissues of the same class, i.e. with the same
Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT.
Podesta, Mark; Nijsten, Sebastiaan M J J G; Persoon, Lucas C G G; Scheib, Stefan G; Baltes, Christof; Verhaegen, Frank
2014-08-21
Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.
Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT
Podesta, Mark; Nijsten, Sebastiaan M. J. J. G.; Persoon, Lucas C. G. G.; Scheib, Stefan G.; Baltes, Christof; Verhaegen, Frank
2014-08-01
Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.
Advanced in Visualization of 3D Time-Dependent CFD Solutions
Lane, David A.; Lasinski, T. A. (Technical Monitor)
1995-01-01
Numerical simulations of complex 3D time-dependent (unsteady) flows are becoming increasingly feasible because of the progress in computing systems. Unfortunately, many existing flow visualization systems were developed for time-independent (steady) solutions and do not adequately depict solutions from unsteady flow simulations. Furthermore, most systems only handle one time step of the solutions individually and do not consider the time-dependent nature of the solutions. For example, instantaneous streamlines are computed by tracking the particles using one time step of the solution. However, for streaklines and timelines, particles need to be tracked through all time steps. Streaklines can reveal quite different information about the flow than those revealed by instantaneous streamlines. Comparisons of instantaneous streamlines with dynamic streaklines are shown. For a complex 3D flow simulation, it is common to generate a grid system with several millions of grid points and to have tens of thousands of time steps. The disk requirement for storing the flow data can easily be tens of gigabytes. Visualizing solutions of this magnitude is a challenging problem with today's computer hardware technology. Even interactive visualization of one time step of the flow data can be a problem for some existing flow visualization systems because of the size of the grid. Current approaches for visualizing complex 3D time-dependent CFD solutions are described. The flow visualization system developed at NASA Ames Research Center to compute time-dependent particle traces from unsteady CFD solutions is described. The system computes particle traces (streaklines) by integrating through the time steps. This system has been used by several NASA scientists to visualize their CFD time-dependent solutions. The flow visualization capabilities of this system are described, and visualization results are shown.
Radiation Transport for Explosive Outflows: A Multigroup Hybrid Monte Carlo Method
Wollaeger, Ryan T.; van Rossum, Daniel R.; Graziani, Carlo; Couch, Sean M.; Jordan, George C., IV; Lamb, Donald Q.; Moses, Gregory A.
2013-12-01
We explore Implicit Monte Carlo (IMC) and discrete diffusion Monte Carlo (DDMC) for radiation transport in high-velocity outflows with structured opacity. The IMC method is a stochastic computational technique for nonlinear radiation transport. IMC is partially implicit in time and may suffer in efficiency when tracking MC particles through optically thick materials. DDMC accelerates IMC in diffusive domains. Abdikamalov extended IMC and DDMC to multigroup, velocity-dependent transport with the intent of modeling neutrino dynamics in core-collapse supernovae. Densmore has also formulated a multifrequency extension to the originally gray DDMC method. We rigorously formulate IMC and DDMC over a high-velocity Lagrangian grid for possible application to photon transport in the post-explosion phase of Type Ia supernovae. This formulation includes an analysis that yields an additional factor in the standard IMC-to-DDMC spatial interface condition. To our knowledge the new boundary condition is distinct from others presented in prior DDMC literature. The method is suitable for a variety of opacity distributions and may be applied to semi-relativistic radiation transport in simple fluids and geometries. Additionally, we test the code, called SuperNu, using an analytic solution having static material, as well as with a manufactured solution for moving material with structured opacities. Finally, we demonstrate with a simple source and 10 group logarithmic wavelength grid that IMC-DDMC performs better than pure IMC in terms of accuracy and speed when there are large disparities between the magnitudes of opacities in adjacent groups. We also present and test our implementation of the new boundary condition.
Symmetry breaking in the opinion dynamics of a multi-group project organization
Institute of Scientific and Technical Information of China (English)
Zhu Zhen-Tao; Zhou Jing; Li Ping; Chen Xing-Guang
2012-01-01
A bounded confidence model of opinion dynamics in multi-group projects is presented in which each group's opinion evolution is driven by two types of forces:(i) the group's cohesive force which tends to restore the opinion back towards the initial status because of its company culture; and (ii) nonlinear coupling forces with other groups which attempt to bring opinions closer due to collaboration willingness.Bifurcation analysis for the case of a two-group project shows a cusp catastrophe phenomenon and three distinctive evolutionary regimes,i.e.,a deadlock regime,a convergence regime,and a bifurcation regime in opinion dynamics.The critical value of initial discord between the two groups is derived to discriminate which regime the opinion evolution belongs to.In the case of a three-group project with a symmetric social network,both bifurcation analysis and simulation results demonstrate that if each pair has a high initial discord,instead of symmetrically converging to consensus with the increase of coupling scale as expected by Gabbay's result (Physica A 378 (2007) p.125 Fig.5),project organization (PO) may be split into two distinct clusters because of the symmetry breaking phenomenon caused by pitchfork bifurcations,which urges that apart from divergence in participants' interests,nonlinear interaction can also make conflict inevitable in the PO.The effects of two asymmetric level parameters are tested in order to explore the ways of inducing dominant opinion in the whole PO.It is found that the strong influence imposed by a leader group with firm faith on the flexible and open minded follower groups can promote the formation of a positive dominant opinion in the PO.
Symmetry breaking in the opinion dynamics of a multi-group project organization
Zhu, Zhen-Tao; Zhou, Jing; Li, Ping; Chen, Xing-Guang
2012-10-01
A bounded confidence model of opinion dynamics in multi-group projects is presented in which each group's opinion evolution is driven by two types of forces: (i) the group's cohesive force which tends to restore the opinion back towards the initial status because of its company culture; and (ii) nonlinear coupling forces with other groups which attempt to bring opinions closer due to collaboration willingness. Bifurcation analysis for the case of a two-group project shows a cusp catastrophe phenomenon and three distinctive evolutionary regimes, i.e., a deadlock regime, a convergence regime, and a bifurcation regime in opinion dynamics. The critical value of initial discord between the two groups is derived to discriminate which regime the opinion evolution belongs to. In the case of a three-group project with a symmetric social network, both bifurcation analysis and simulation results demonstrate that if each pair has a high initial discord, instead of symmetrically converging to consensus with the increase of coupling scale as expected by Gabbay's result (Physica A 378 (2007) p. 125 Fig. 5), project organization (PO) may be split into two distinct clusters because of the symmetry breaking phenomenon caused by pitchfork bifurcations, which urges that apart from divergence in participants' interests, nonlinear interaction can also make conflict inevitable in the PO. The effects of two asymmetric level parameters are tested in order to explore the ways of inducing dominant opinion in the whole PO. It is found that the strong influence imposed by a leader group with firm faith on the flexible and open minded follower groups can promote the formation of a positive dominant opinion in the PO.
1D-1D Coulomb drag in a 6 Million Mobility Bi-layer Heterostructure
Bilodeau, Simon; Laroche, Dominique; Xia, Jian-Sheng; Lilly, Mike; Reno, John; Pfeiffer, Loren; West, Ken; Gervais, Guillaume
We report Coulomb drag measurements in vertically-coupled quantum wires. The wires are fabricated in GaAs/AlGaAs bilayer heterostructures grown from two different MBE chambers: one at Sandia National Laboratories (1.2M mobility), and the other at Princeton University (6M mobility). The previously observed positive and negative drag signals are seen in both types of devices, demonstrating the robustness of the result. However, attempts to determine the temperature dependence of the drag signal in the 1D regime proved challenging in the higher mobility heterostructure (Princeton), in part because of difficulties in aligning the wires within the same transverse subband configuration. Nevertheless, this work, performed at the Microkelvin laboratory of the University of Florida, is an important proof-of-concept for future investigations of the temperature dependence of the 1D-1D drag signal down to a few mK. Such an experiment could confirm the Luttinger charge density wave interlocking predicted to occur in the wires. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL8500.
Fokker-Planck equation with linear and time dependent load forces
Sau Fa, Kwok
2016-11-01
The motion of a particle described by the Fokker-Planck equation with constant diffusion coefficient, linear force (-γ (t)x) and time dependent load force (β (t)) is investigated. The solution for the probability density function is obtained and it has the Gaussian form; it is described by the solution of the linear force with the translation of the position coordinate x. The constant load force preserves the stationary state of the harmonic potential system, however the time dependent load force may not preserve the stationary state of the harmonic potential system. Moreover, the n-moment and variance are also investigated. The solutions are obtained in a direct and pedagogical manner readily understandable by undergraduate and graduate students.
Probing Time-Dependent Molecular Dipoles on the Attosecond Time Scale
Neidel, Ch.; Klei, J.; Yang, C.-H.; Rouzée, A.; Vrakking, M. J. J.; Klünder, K.; Miranda, M.; Arnold, C. L.; Fordell, T.; L'Huillier, A.; Gisselbrecht, M.; Johnsson, P.; Dinh, M. P.; Suraud, E.; Reinhard, P.-G.; Despré, V.; Marques, M. A. L.; Lépine, F.
2013-07-01
Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N2, CO2, and C2H4), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.
Non-Markovian Brownian motion in a magnetic field and time-dependent force fields
Hidalgo-Gonzalez, J. C.; Jiménez-Aquino, J. I.; Romero-Bastida, M.
2016-11-01
This work focuses on the derivation of the velocity and phase-space generalized Fokker-Planck equations for a Brownian charged particle embedded in a memory thermal bath and under the action of force fields: a constant magnetic field and arbitrary time-dependent force fields. To achieve the aforementioned goal we use a Gaussian but non-Markovian generalized Langevin equation with an arbitrary friction memory kernel. In a similar way, the generalized diffusion equation in the zero inertia limit is also derived. Additionally we show, in the absence of the time-dependent external forces, that, if the fluctuation-dissipation relation of the second kind is valid, then the generalized Langevin dynamics associated with the charged particle reaches a stationary state in the large-time limit. The consistency of our theoretical results is also verified when they are compared with those derived in the absence of the force fields and in the Markovian case.
Energy Technology Data Exchange (ETDEWEB)
Tretiak, Sergei [Los Alamos National Laboratory
2008-01-01
Four different numerical algorithms suitable for a linear scaling implementation of time-dependent Hartree-Fock and Kohn-Sham self-consistent field theories are examined. We compare the performance of modified Lanczos, Arooldi, Davidson, and Rayleigh quotient iterative procedures to solve the random-phase approximation (RPA) (non-Hermitian) and Tamm-Dancoff approximation (TDA) (Hermitian) eigenvalue equations in the molecular orbital-free framework. Semiempirical Hamiltonian models are used to numerically benchmark algorithms for the computation of excited states of realistic molecular systems (conjugated polymers and carbon nanotubes). Convergence behavior and stability are tested with respect to a numerical noise imposed to simulate linear scaling conditions. The results single out the most suitable procedures for linear scaling large-scale time-dependent perturbation theory calculations of electronic excitations.
Quantum states with continuous spectrum for a general time-dependent oscillator
Indian Academy of Sciences (India)
Jeong-Ryeol Choi
2005-08-01
We investigated quantum states with continuous spectrum for a general time-dependent oscillator using invariant operator and unitary transformation methods together. The form of the transformed invariant operator by a unitary operator is the same as the Hamiltonian of the simple harmonic oscillator: $\\hat{I'} = \\hat{p}^{2}/2 + ^{2}\\hat{q}^{2}/2$. The fact that 2 of the transformed invariant operator is constant enabled us to investigate the system separately for three cases, where 2 > 0, 2 < 0, and 2 = 0. The eigenstates of the system are discrete for 2 > 0. On the other hand, for 2 ≤ 0, the eigenstates are continuous. The time-dependent oscillators whose spectra of the wave function are continuous are not oscillatory. The wave function for 2 < 0 is expressed in terms of the parabolic cylinder function. We applied our theory to the driven harmonic oscillator with strongly pulsating mass.
Accurate high-harmonic spectra from time-dependent two-particle reduced density matrix theory
Lackner, Fabian; Sato, Takeshi; Ishikawa, Kenichi L; Burgdörfer, Joachim
2016-01-01
The accurate description of the non-linear response of many-electron systems to strong-laser fields remains a major challenge. Methods that bypass the unfavorable exponential scaling with particle number are required to address larger systems. In this paper we present a fully three-dimensional implementation of the time-dependent two-particle reduced density matrix (TD-2RDM) method for many-electron atoms. We benchmark this approach by a comparison with multi-configurational time-dependent Hartree-Fock (MCTDHF) results for the harmonic spectra of beryllium and neon. We show that the TD-2RDM is very well-suited to describe the non-linear atomic response and to reveal the influence of electron-correlation effects.
Babaee, Hessam
2015-01-01
We introduce a variational formulation for the determination of a finite-dimensional, time-dependent, orthonormal basis that captures directions of the phase space associated with transient instabilities. While these instabilities have finite lifetime they can play a crucial role by either altering the system dynamics through the activation of other instabilities, or by creating sudden nonlinear energy transfers that lead to extreme responses. However, their essentially transient character makes their description a particularly challenging task. We develop a variational framework that focuses on the optimal approximation of the system dynamics over finite-time intervals. This variational formulation results in differential equations that evolve a time-dependent basis so that it optimally approximates the most unstable directions over finite times. We demonstrate the capability of the method for two families of problems: i) linear systems including the advection-diffusion operator in a strongly non-normal regi...
Time-dependent tunneling of spin-polarized electrons in coupled quantum wells
Energy Technology Data Exchange (ETDEWEB)
Cruz, H; Luis, D [Departamento de Fisica Basica, Universidad de La Laguna, 38204 La Laguna, Tenerife (Spain)], E-mail: hcruz@ull.es
2008-02-15
We have solved the in-plane momentum-dependent effective-mass nonlinear Schroedinger equation for a spin-polarized electron wave packet in a InAs double quantum well system with an interlayer voltage. Considering a time-dependent Hartree potential, we have calculated the spin-polarized nonlinear electron dynamics between both quantum wells at different in-plane momentum values and applied bias. The spin-splitting caused by the Rashba effect is combined with the level matching between the spin dependent resonant tunneling levels making possible the observed local spin density oscillations which depend on the applied bias value. The filtering efficiency has been studied using time-dependent calculations.
Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm
Energy Technology Data Exchange (ETDEWEB)
Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento, Trento (Italy)
2015-08-07
We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reaction rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.
Multiconfiguration hartree-fock theory for pseudorelativistic systems: The time-dependent case
Hajaiej, Hichem
2014-03-01
In [Setting and analysis of the multi-configuration time-dependent Hartree-Fock equations, Arch. Ration. Mech. Anal. 198 (2010) 273-330] the third author has studied in collaboration with Bardos, Catto and Mauser the nonrelativistic multiconfiguration time-dependent Hartree-Fock system of equations arising in the modeling of molecular dynamics. In this paper, we extend the previous work to the case of pseudorelativistic atoms. We show the existence and the uniqueness of global-in-time solution to the underlying system under technical assumptions on the energy of the initial data and the charge of the nucleus. Moreover, we prove that the result can be extended to the case of neutron stars when the number of electrons is less than a critical number N cr. © 2014 World Scientific Publishing Company.
Searches for Time Dependent Neutrino Sources with IceCube Data from 2008 to 2012
Aartsen, M G; Adams, J; Aguilar, J A; Ahlers, M; Ahrens, M; Altmann, D; Anderson, T; Arguelles, C; Arlen, T C; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beatty, J J; Tjus, J Becker; Becker, K -H; BenZvi, S; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Besson, D Z; Binder, G; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohm, C; Bos, F; Bose, D; Böser, S; Botner, O; Brayeur, L; Bretz, H -P; Brown, A M; Buzinsky, N; Casey, J; Casier, M; Cheung, E; Chirkin, D; Christov, A; Christy, B; Clark, K; Classen, L; Clevermann, F; Coenders, S; Cowen, D F; Silva, A H Cruz; Daughhetee, J; Davis, J C; Day, M; de André, J P A M; De Clercq, C; Dembinski, H; De Ridder, S; Desiati, P; de Vries, K D; de Wasseige, G; de With, M; DeYoung, T; D\\'\\iaz-Vélez, J C; Dumm, J P; Dunkman, M; Eagan, R; Eberhardt, B; Ehrhardt, T; Eichmann, B; Eisch, J; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Felde, J; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Frantzen, K; Fuchs, T; Gaisser, T K; Gaior, R; Gallagher, J; Gerhardt, L; Gier, D; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Gonzalez, J G; Goodman, J A; Góra, D; Grant, D; Gretskov, P; Groh, J C; Groß, A; Ha, C; Haack, C; Ismail, A Haj; Hallen, P; Hallgren, A; Halzen, F; Hanson, K; Hebecker, D; Heereman, D; Heinen, D; Helbing, K; Hellauer, R; Hellwig, D; Hickford, S; Hignight, J; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huang, F; Huelsnitz, W; Hulth, P O; Hultqvist, K; In, S; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jero, K; Jurkovic, M; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kauer, M; Keivani, A; Kelley, J L; Kheirandish, A; Kiryluk, J; Kläs, J; Klein, S R; Köhne, J -H; Kohnen, G; Kolanoski, H; Koob, A; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Kriesten, A; Krings, K; Kroll, G; Kroll, M; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Lanfranchi, J L; Larsen, D T; Larson, M J; Lesiak-Bzdak, M; Leuermann, M; Lünemann, J; Madsen, J; Maggi, G; Mahn, K B M; Maruyama, R; Mase, K; Matis, H S; Maunu, R; McNally, F; Meagher, K; Medici, M; Meli, A; Meures, T; Miarecki, S; Middell, E; Middlemas, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Olivas, A; Omairat, A; O'Murchadha, A; Palczewski, T; Paul, L; Penek, Ö; Pepper, J A; Heros, C Pérez de los; Pfendner, C; Pieloth, D; Pinat, E; Posselt, J; Price, P B; Przybylski, G T; Pütz, J; Quinnan, M; Rädel, L; Rameez, M; Rawlins, K; Redl, P; Rees, I; Reimann, R; Relich, M; Resconi, E; Rhode, W; Richman, M; Riedel, B; Robertson, S; Rodrigues, J P; Rongen, M; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Sander, H -G; Sandroos, J; Santander, M; Sarkar, S; Schatto, K; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Sestayo, Y; Seunarine, S; Shanidze, R; Smith, M W E; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stanisha, N A; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Strotjohann, N L; Sullivan, G W; Sutherland, M; Taavola, H; Taboada, I; Tamburro, A; Ter-Antonyan, S; Terliuk, A; Tešić, G; Tilav, S; Toale, P A; Tobin, M N; Tosi, D; Tselengidou, M; Unger, E; Usner, M; Vallecorsa, S; van Eijndhoven, N; Vandenbroucke, J; van Santen, J; Vanheule, S; Vehring, M; Voge, M; Vraeghe, M; Walck, C; Wallraff, M; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whelan, B J; Whitehorn, N; Wichary, C; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, D L; Xu, X W; Xu, Y; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zoll, M
2015-01-01
In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time integrated searches, where steady emission is assumed, the analyses presented here look for a time dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions as well as neutrino emission following time dependent lightcurves, sporadic emission or periodicities of candidate sources. These include active galactic nuclei, soft $\\gamma$-ray repeaters, supernova remnants hosting pulsars, micro-quasars and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers four years of data from 2008 April 5 to 2012 May 16 including the first year of operation of the completed 86-string detector. The analyses did not find any significant time dependen...
A theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels
Muller, Peter Barkholt
2015-01-01
Based on first- and second-order perturbation theory, we present a numerical study of the temporal build-up and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance wit...
Time-dependent behaviour of high performance concrete: influence of coarse aggregate characteristics
Directory of Open Access Journals (Sweden)
Escadeillas G.
2010-06-01
Full Text Available This paper examines the influence of coarse aggregate characteristics on the time-dependent deformations of High Performances Concretes (HPC. Four concretes made using the same cement paste but incorporating different types of aggregate (rolled siliceous gravel, crushed granite, crushed limestone and crushed siliceous gravels were studied in order to investigate the effect of aggregate properties on the compressive strength, modulus of elasticity, shrinkage and creep. The results indicate that the aggregate type has a significant effect on creep and shrinkage deformations of HPC. An influence of the shape of aggregate on time-dependent deformations has also been observed. On the basis of these results, long-term behaviour seems to be correlated to the characteristics of the Interfacial Transition Zone (ITZ strongly depending on the mineralogical nature and properties of aggregates. The experimental results are compared with the values calculated using the current Eurocode 2 model in order to assess the accuracy of the predictions.
Time-dependent behaviour of high performance concrete: influence of coarse aggregate characteristics
Makani, A.; Vidal, T.; Pons, G.; Escadeillas, G.
2010-06-01
This paper examines the influence of coarse aggregate characteristics on the time-dependent deformations of High Performances Concretes (HPC). Four concretes made using the same cement paste but incorporating different types of aggregate (rolled siliceous gravel, crushed granite, crushed limestone and crushed siliceous gravels) were studied in order to investigate the effect of aggregate properties on the compressive strength, modulus of elasticity, shrinkage and creep. The results indicate that the aggregate type has a significant effect on creep and shrinkage deformations of HPC. An influence of the shape of aggregate on time-dependent deformations has also been observed. On the basis of these results, long-term behaviour seems to be correlated to the characteristics of the Interfacial Transition Zone (ITZ) strongly depending on the mineralogical nature and properties of aggregates. The experimental results are compared with the values calculated using the current Eurocode 2 model in order to assess the accuracy of the predictions.
Numerical modelling of the time-dependent mechanical behaviour of softwood
DEFF Research Database (Denmark)
Engelund, Emil Tang
2010-01-01
When using wood as a structural material it is important to consider its time-dependent mechanical behaviour and to predict this behaviour for decades ahead. For this purpose, several rheological mathematical models, spanning from fairly simple to very complex ones, have been developed over...... the microfibrils. This assumption is incorporated in the numerical model by only allowing non-elastic behaviour in shear deformation modes in the local coordinate system. The rate of shearing is described by deformation kinetics. The results indicate that time-dependent behaviour such as creep and relaxation...... mechanisms causing the observed mechanical behaviour. In this study, the mechanical behaviour of softwood tracheids is described using numerical modelling. The basic composition and orientation of the tracheid constituents is incorporated by establishing a local coordinate system aligned...
Energy Technology Data Exchange (ETDEWEB)
Brantley, P S
2006-09-27
We describe an asymptotic analysis of the coupled nonlinear system of equations describing time-dependent three-dimensional monoenergetic neutron transport and isotopic depletion and radioactive decay. The classic asymptotic diffusion scaling of Larsen and Keller [1], along with a consistent small scaling of the terms describing the radioactive decay of isotopes, is applied to this coupled nonlinear system of equations in a medium of specified initial isotopic composition. The analysis demonstrates that to leading order the neutron transport equation limits to the standard time-dependent neutron diffusion equation with macroscopic cross sections whose number densities are determined by the standard system of ordinary differential equations, the so-called Bateman equations, describing the temporal evolution of the nuclide number densities.
Time-dependent amplitude analysis of $B^0 \\to K^0_S\\pi^ pi^-$
Energy Technology Data Exchange (ETDEWEB)
Aubert, B.
2009-05-26
In this paper we present results from a time-dependent amplitude analysis of the B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decay. In Sec. II we describe the time-dependent DP formalism, and introduce the signal parameters that are extracted in the fit to data. In Sec. III we briefly describe the BABAR detector and the data set. In Sec. IV, we explain the selection requirements used to obtain the signal candidates and suppress backgrounds. In Sec. V we describe the fit method and the approach used to control experimental effects such as resolution. In Sec. VI we present the results of the fit, and extract parameters relevant to the contributing intermediate resonant states. In Sec. VII we discuss systematic uncertainties in the results, and finally we summarize the results in Sec. VIII.
Extended gyrokinetic field theory for time-dependent magnetic confinement fields
Energy Technology Data Exchange (ETDEWEB)
Sugama, H.; Watanabe, T.-H.; Nunami, M. [National Institute for Fusion Science, Toki 509-5292 (Japan)
2014-01-15
A gyrokinetic system of equations for turbulent toroidal plasmas in time-dependent axisymmetric background magnetic fields is derived from the variational principle. Besides governing equations for gyrocenter distribution functions and turbulent electromagnetic fields, the conditions which self-consistently determine the background magnetic fields varying on a transport time scale are obtained by using the Lagrangian, which includes the constraint on the background fields. Conservation laws for energy and toroidal angular momentum of the whole system in the time-dependent background magnetic fields are naturally derived by applying Noether's theorem. It is shown that the ensemble-averaged transport equations of particles, energy, and toroidal momentum given in the present work agree with the results from the conventional recursive formulation with the WKB representation except that collisional effects are disregarded here.
Time-dependent density functional theory quantum transport simulation in non-orthogonal basis.
Kwok, Yan Ho; Xie, Hang; Yam, Chi Yung; Zheng, Xiao; Chen, Guan Hua
2013-12-14
Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining time-dependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.
Time-dependent density-functional theory for open electronic systems
Institute of Scientific and Technical Information of China (English)
ZHENG Xiao; WANG RuLin
2014-01-01
Time-dependent density-functional theory（TDDFT）has been successfully applied to predict excited-state properties of isolated and periodic systems.However,it cannot address a system coupled to an environment or whose number of electrons is not conserved.To tackle these problems,TDDFT needs to be extended to accommodate open systems.This paper provides a comprehensive account of the recent developments of TDDFT for open systems（TDDFT-OS）,including both theoretical and practical aspects.The practicality and accuracy of a latest TDDFT-OS method is demonstrated with two numerical examples：the time-dependent electron transport through a series of quasi-one-dimensional atomic chains,and the real-time electronic dynamics on a two-dimensional graphene surface.The advancement of TDDFT-OS may lead to promising applications in various fields of chemistry,including energy conversion and heterogeneous catalysis.
Zahn, Jochen
2015-01-01
In the framework of quantum electrodynamics (QED) in external potentials, we introduce a method to compute the time-dependence of the expectation value of the current density for time-dependent homogeneous external electric fields. We apply it to the so-called Sauter pulse. For late times, our results agree with the asymptotic value due to electron-positron pair production. For sub-critical peak field strengths, or results agree very well with the general expression derived by Serber for the linearization in the external field. In particular, the expectation value of the current density at intermediate times can be much greater than at asymptotic times. We comment on consequences of these findings for recent proposals to test the Schwinger effect with high intensity lasers using processes at intermediate times.
Time-dependent density functional theory for many-electron systems interacting with cavity photons.
Tokatly, I V
2013-06-07
Time-dependent (current) density functional theory for many-electron systems strongly coupled to quantized electromagnetic modes of a microcavity is proposed. It is shown that the electron-photon wave function is a unique functional of the electronic (current) density and the expectation values of photonic coordinates. The Kohn-Sham system is constructed, which allows us to calculate the above basic variables by solving self-consistent equations for noninteracting particles. We suggest possible approximations for the exchange-correlation potentials and discuss implications of this approach for the theory of open quantum systems. In particular we show that it naturally leads to time-dependent density functional theory for systems coupled to the Caldeira-Leggett bath.
Study of Time-Dependent CP Asymmetries with Partial Reconstruction of B -> D*+ pi-
Aubert, Bernard; Boutigny, D; Gaillard, J M; Hicheur, A; Karyotakis, Yu; Lees, J P; Robbe, P; Tisserand, V; Zghiche, A; Palano, A; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kral, J F; Kukartsev, G; Le Clerc, C; Levi, M E; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Romosan, A; Ronan, Michael T; Shelkov, V G; Telnov, A V; Wenzel, W A; Ford, K; Harrison, T J; Hawkes, C M; Knowles, D J; Morgan, S E; Penny, R C; Watson, A T; Watson, N K; Deppermann, T; Goetzen, K; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schmücker, H; Steinke, M; Barlow, N R; Boyd, J T; Chevalier, N; Cottingham, W N; Kelly, M P; Latham, T E; MacKay, C; Wilson, F F; Abe, K; Çuhadar-Dönszelmann, T; Hearty, C; Mattison, T S; McKenna, J A; Thiessen, D; Kyberd, P; McKemey, A K; Blinov, V E; Bukin, A D; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bruinsma, M; Chao, M; Kirkby, D; Lankford, A J; Mandelkern, M A; Mommsen, R K; Röthel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Shen, B C; Del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, S; Schwanke, U; Sharma, V; Berryhill, J W; Campagnari, C; Dahmes, B; Kuznetsova, N; Levy, S L; Long, O; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Beringer, J; Eisner, A M; Heusch, C A; Lockman, W S; Schalk, T; Schmitz, R E; Schumm, B A; Seiden, A; Turri, M; Walkowiak, W; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S M; Mancinelli, G; Meadows, B T; Sokoloff, M D; Abe, T; Blanc, F; Bloom, P; Chen, S; Clark, P J; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Roy, J; Smith, J G; Van Hoek, W C; Zhang, L; Harton, J L; Hu, T; Soffer, A; Toki, W H; Wilson, R J; Zhang, J; Altenburg, D; Brandt, T; Brose, J; Colberg, T; Dickopp, M; Dubitzky, R S; Hauke, A; Lacker, H M; Maly, E; Müller-Pfefferkorn, R; Nogowski, R; Otto, S; Schubert, J; Schubert, Klaus R; Schwierz, R; Spaan, B; Wilden, L; Bernard, D; Bonneaud, G R; Brochard, F; Cohen-Tanugi, J; Grenier, P; Thiebaux, C; Vasileiadis, G; Verderi, M; Khan, A; Lavin, D; Muheim, F; Playfer, S; Swain, J E; Tinslay, J; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Treadwell, E; Anulli, F; Baldini-Ferroli, R; Biasini, M; Calcaterra, A; De Sangro, R; Falciai, D; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Pioppi, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Crosetti, G; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Morii, M; Won, E; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Eschrich, I; Gaillard, J R; Morton, G W; Nash, J A; Sanders, P; Taylor, G P; Grenier, G J; Lee, S J; Mallik, U; Cochran, J; Crawley, H B; Lamsa, J; Meyer, W T; Prell, S; Rosenberg, E I; Yi, J; Davier, M; Grosdidier, G; Höcker, A; Laplace, S; Le Diberder, F R; Lepeltier, V; Lutz, A M; Petersen, T C; Plaszczynski, S; Schune, M H; Tantot, L; Wormser, G; Brigljevic, V; Cheng, C H; Lange, D J; Wright, D M; Bevan, A J; Coleman, J P; Fry, J R; Gabathuler, Erwin; Gamet, R; Kay, M; Parry, R J; Payne, D J; Sloane, R J; Touramanis, C; Back, J J; Harrison, P F; Shorthouse, H W; Strother, P; Vidal, P B; Brown, C L; Cowan, G; Flack, R L; Flächer, H U; George, S; Green, M G; Kurup, A; Marker, C E; McMahon, T R; Ricciardi, S; Salvatore, F; Vaitsas, G; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, R J; Forti, A C; Hart, P A; Jackson, F; Lafferty, G D; Lyon, A J; Weatherall, J H; Williams, J C; Farbin, A; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Flood, K T; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Stängle, H; Willocq, S; Cowan, R; Sciolla, G; Taylor, F; Yamamoto, R K; Mangeol, D J J; Milek, M; Patel, P M; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L M; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Cote-Ahern, D; Hast, C; Taras, P; Levesque, J A; Nicholson, H; Cartaro, C; Cavallo, N; De Nardo, Gallieno; Fabozzi, F; Gatto, C; Lista, L; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M A; Raven, G; LoSecco, J M; Gabriel, T A; Brau, B; Gan, K K; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pulliam, T; Wong, Q K; Brau, J E; Frey, R; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Tiozzo, G; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; La Vaissière, C de; Del Buono, L; Hamon, O; John, M J J; Leruste, P; Ocariz, J; Pivk, M; Roos, L; Stark, J; T'Jampens, S; Therin, G; Manfredi, P F; Re, V; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Angelini, C; Batignani, G; Bettarini, S; Bondioli, M; Bucci, F; Calderini, G; Carpinelli, M; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Martínez-Vidal, F; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Sandrelli, F; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lü, C; Miftakov, V; Olsen, J; Smith, A J S; Tanaka, H A; Varnes, E W; Bellini, F; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Mazzoni, M A; Morganti, S; Pierini, M; Piredda, G; Safai-Tehrani, F; Voena, C; Christ, S; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B J; Geddes, N I; Gopal, G P; Olaiya, E O; Xella, S M; Aleksan, Roy; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P F; Hamel de Monchenault, G; Kozanecki, Witold; Langer, M; Legendre, M; London, G W; Mayer, B; Schott, G; Vasseur, G; Yéche, C; Zito, M; Purohit, M V; Weidemann, A W; Yumiceva, F X; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmüller, O L; Convery, M R; Coupal, D P; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W M; Field, R C; Glanzman, T; Gowdy, S J; Graugès-Pous, E; Hadig, T; Halyo, V; Hrynóva, T; Innes, W R; Jessop, C P; Kelsey, M H; Kim, P; Kocian, M L; Langenegger, U; Leith, D W G S; Luitz, S; Lüth, V; Lynch, H L; Marsiske, H; Messner, R; Müller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Petrak, S; Ratcliff, B N; Robertson, S H; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Simi, G; Snyder, A; Soha, A; Stelzer, J; Su, D; Sullivan, M K; Vavra, J; Wagner, S R; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wright, D H; Young, C C; Burchat, Patricia R; Edwards, A J; Meyer, T I; Petersen, B A; Roat, C; Ahmed, S; Alam, M S; Ernst, J A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bóna, M; Gallo, F; Gamba, D; Borean, C; Bosisio, L; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Vuagnin, G; Panvini, R S; Banerjee, Sw; Brown, C M; Fortin, D; Jackson, P D; Kowalewski, R V; Roney, J M; Band, H R; Dasu, S; Datta, M; Eichenbaum, A M; Johnson, J R; Kutter, P E; Li, H; Liu, R; Di Lodovico, F; Mihályi, A; Mohapatra, A K; Pan, Y; Prepost, R; Sekula, S J; Von Wimmersperg-Töller, J H; Wu, J; Wu Sau Lan; Yu, Z; Neal, H
2003-01-01
We present a preliminary measurement of the time-dependent CP asymmetries in decays of neutral B mesons to the final states D*pi using approximately 82 million BBbar events collected by the BaBar experiment at the PEPII storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high momentum pion and the low momentum pion from the D* decay are reconstructed. The flavor of the other B meson in the event is tagged using the information from kaon and lepton candidates. We measure the time-dependent CP asymmetry A = -0.063 +/- 0.024 (stat.) +/- 0.017 (syst.). We interpret these results in terms of the angles of the unitarity triangle to set a bound on |sin(2 beta + gamma)|.
Study of time-dependent CP asymmetries with partial reconstruction of B->D*pi
Soffer, A
2003-01-01
The present a preliminary measurement of the time-dependent CP asymmetries in decays of neutral B mesons to the final states D* sup+- pi sup+-, using approximately 82 million B(bar B) events collected by the BABAR experiment at the PEP-II storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high momentum pi sup+- and the low momentum pion from the D* sup+- decay are reconstructed. The flavor of the other B meson in the event is tagged using the information from kaon and lepton candidates. They measure the time-dependent CP asymmetry ALPHA = -0.063 +- 0.024 (stat.) +- 0.017 (syst.). They interpret these results in terms of the angles of the unitarity triangle to set a bound on |sin(2 beta + gamma)|.
Spin interference in Rashba metal ring in a time-dependent magnetic field
Chen, Ji; Abdul Jalil, Mansoor Bin; Ghee Tan, Seng
2013-05-01
We investigate spin transport in a metal square ring with a strong Rashba spin orbit coupling (RSOC) effect, in the presence of a time-dependent magnetic field. We show that RSOC can be regarded as a spin-dependent gauge field which imparts a spin-dependent geometric phase (Aharonov-Casher phase) to conduction electrons in the ring. Combining the Aharonov-Bohm phase due to the time-dependent magnetic field with the able Aharonov-Casher phase due to RSOC, we are able to construct a spin interference condition, which modulates spin transport in the ring. The spin transport in the system is calculated via the tight-binding non-equilibrium Green's function formalism. Based on our transport calculations, we proposed a potential application of the Rashba square ring system as an alternating spin current generator.
Computing Finite-Time Lyapunov Exponents with Optimally Time Dependent Reduction
Babaee, Hessam; Farazmand, Mohammad; Sapsis, Themis; Haller, George
2016-11-01
We present a method to compute Finite-Time Lyapunov Exponents (FTLE) of a dynamical system using Optimally Time-Dependent (OTD) reduction recently introduced by H. Babaee and T. P. Sapsis. The OTD modes are a set of finite-dimensional, time-dependent, orthonormal basis {ui (x , t) } |i=1N that capture the directions associated with transient instabilities. The evolution equation of the OTD modes is derived from a minimization principle that optimally approximates the most unstable directions over finite times. To compute the FTLE, we evolve a single OTD mode along with the nonlinear dynamics. We approximate the FTLE from the reduced system obtained from projecting the instantaneous linearized dynamics onto the OTD mode. This results in a significant reduction in the computational cost compared to conventional methods for computing FTLE. We demonstrate the efficiency of our method for double Gyre and ABC flows. ARO project 66710-EG-YIP.
Stokes phenomenon and schwinger vacuum pair production in time-dependent laser pulses.
Dumlu, Cesim K; Dunne, Gerald V
2010-06-25
Particle production due to external fields (electric, chromoelectric, or gravitational) requires evolving an initial state through an interaction with a time-dependent background, with the rate being computed from a Bogoliubov transformation between the in and out vacua. When the background fields have temporal profiles with substructure, a semiclassical analysis of this problem confronts the full subtlety of the Stokes phenomenon: WKB solutions are only local, while the production rate requires global information. We give a simple quantitative explanation of the recently computed [Phys. Rev. Lett. 102, 150404 (2009)10.1103/PhysRevLett.102.150404] oscillatory momentum spectrum of e^{+}e^{-} pairs produced from vacuum subjected to a time-dependent electric field with subcycle laser pulse structure. This approach also explains naturally why for spinor and scalar QED these oscillations are out of phase.
Rüger, Robert; Niehaus, Thomas; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas
2016-11-01
We report a time-dependent density functional based tight-binding (TD-DFTB) scheme for the calculation of UV/Vis spectra, explicitly taking into account the excitation of nuclear vibrations via the adiabatic Hessian Franck-Condon method with a harmonic approximation for the nuclear wavefunction. The theory of vibrationally resolved UV/Vis spectroscopy is first summarized from the viewpoint of TD-DFTB. The method is benchmarked against time-dependent density functional theory (TD-DFT) calculations for strongly dipole allowed excitations in various aromatic and polar molecules. Using the recent 3ob:freq parameter set of Elstner's group, very good agreement with TD-DFT calculations using local functionals was achieved.
Magnetic circular dichroism in real-time time-dependent density functional theory
Lee, K -M; Bertsch, G F
2010-01-01
We apply the adiabatic time-dependent density functional theory to magnetic ci the real-space, real-time computational method. The standard formulas for the MCD response and its A and B terms are derived from the observables in the time-dependent wave function. We find the real time method is well suited for calculating the overall spectrum, particularly at higher excitation energies where individual excited states are numerous and overlapping. The MCD sum rules are derived and interpreted in the real-time formalism; we find that they are very useful for normalization purposes and assessing the accuracy of the theory. The method is applied to MCD spectrum of C-60 using the adiabatic energy functional from the local density approximation. The theory correctly predicts the signs of the A and B terms for the lowest allowed excitations. However, the magnitudes of the terms only show qualitative agreement with experiment.
Time-dependent Jahn-Teller problem: Phonon-induced relaxation through conical intersection
Energy Technology Data Exchange (ETDEWEB)
Pae, Kaja, E-mail: kaja.pae@gmail.com; Hizhnyakov, Vladimir [Institute of Physics University of Tartu, Tartu (Estonia)
2014-12-21
A theoretical study of time-dependent dynamical Jahn-Teller effect in an impurity center in a solid is presented. We are considering the relaxation of excited states in the E⊗e-problem through the conical intersection of the potential energy. A strict quantum-mechanical treatment of vibronic interactions with both the main Jahn-Teller active vibration and the nontotally symmetric phonons causing the energy loss is given. The applied method enables us to calculate the time-dependence of the distribution function of the basic configurational coordinate. We have performed a series of numerical calculations allowing us, among other relaxation features, to visualise the details of the relaxation through the conical intersection. In particular, we elucidate how the Slonczewski quantization of the states in the conical intersection affects the relaxation.
Ou, Congjie; Chamberlin, Ralph V.; Abe, Sumiyoshi
2017-01-01
The Lindblad equation is widely employed in studies of Markovian quantum open systems. Here, the following question is posed: in a quantum open system with a time-dependent Hamiltonian such as a subsystem in contact with the heat bath, what is the corresponding Lindblad equation for the quantum state that keeps the internal energy of the subsystem constant in time? This issue is of importance in realizing quasi-stationary states of open systems such as quantum circuits and batteries. As an illustrative example, the time-dependent harmonic oscillator is analyzed. It is shown that the Lindbladian operator is uniquely determined with the help of a Lie-algebraic structure, and the time derivative of the von Neumann entropy is shown to be nonnegative if the curvature of the harmonic potential monotonically decreases in time.
Indian Academy of Sciences (India)
Amita Wadehra; B M Deb
2007-09-01
A time-dependent generalized non-linear Schrödinger equation (GNLSE) of motion was earlier derived in our laboratory by combining density functional theory and quantum fluid dynamics in threedimensional space. In continuation of the work reported previously, the GNLSE is applied to provide additional knowledge on the femtosecond dynamics of the electron density in the hydrogen molecule interacting with high-intensity laser fields. For this purpose, the GNLSE is solved numerically for many time-steps over a total interaction time of 100 fs, by employing a finite-difference scheme. Various time-dependent (TD) quantities, namely, electron density, ground-state survival probability and dipole moment have been obtained for two laser wavelengths and four different intensities. The high-order harmonics generation (HHG) is also examined. The present approach goes beyond the linear response formalism and, in principle, calculates the TD electron density to all orders of change.
Directory of Open Access Journals (Sweden)
Ram Paras
2016-01-01
Full Text Available An attempt has been made to describe the effects of geothermal viscosity with viscous dissipation on the three dimensional time dependent boundary layer flow of magnetic nanofluids due to a stretchable rotating plate in the presence of a porous medium. The modelled governing time dependent equations are transformed a from boundary value problem to an initial value problem, and thereafter solved by a fourth order Runge-Kutta method in MATLAB with a shooting technique for the initial guess. The influences of mixed temperature, depth dependent viscosity, and the rotation strength parameter on the flow field and temperature field generated on the plate surface are investigated. The derived results show direct impact in the problems of heat transfer in high speed computer disks (Herrero et al. [1] and turbine rotor systems (Owen and Rogers [2].
Time dependent modelisation of TeV blazars by a stratified jet model
Boutelier, Timothé; Petrucci, Pierre-Olivier
2008-01-01
We present a new time-dependent inhomogeneous jet model of non-thermal blazar emission. Ultra-relativistic leptons are injected at the base of a jet and propagate along it. We assume continuous reacceleration and cooling, producing a relativistic quasi-maxwellian (or "pile-up") particle energy distribution. The synchrotron and Synchrotron-Self Compton jet emissivity are computed at each altitude. Klein-Nishina effects as well as intrinsic gamma-gamma absorption are included in the computation. Due to the pair production optical depth, considerable particle density enhancement can occur, particularly during flaring states.Time-dependent jet emission can be computed by varying the particle injection, but due to the sensitivity of pair production process, only small variations of the injected density are required during the flares. The stratification of the jet emission, together with a pile-up distribution, allows significantly lower bulk Lorentz factors, compared to one-zone models. Applying this model to the ...
Energy Technology Data Exchange (ETDEWEB)
Nascimento, Daniel R.; DePrince, A. Eugene, E-mail: deprince@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390 (United States)
2015-12-07
We present a combined cavity quantum electrodynamics/ab initio electronic structure approach for simulating plasmon-molecule interactions in the time domain. The simple Jaynes-Cummings-type model Hamiltonian typically utilized in such simulations is replaced with one in which the molecular component of the coupled system is treated in a fully ab initio way, resulting in a computationally efficient description of general plasmon-molecule interactions. Mutual polarization effects are easily incorporated within a standard ground-state Hartree-Fock computation, and time-dependent simulations carry the same formal computational scaling as real-time time-dependent Hartree-Fock theory. As a proof of principle, we apply this generalized method to the emergence of a Fano-like resonance in coupled molecule-plasmon systems; this feature is quite sensitive to the nanoparticle-molecule separation and the orientation of the molecule relative to the polarization of the external electric field.
An inverse time-dependent source problem for a time-fractional diffusion equation
Wei, T.; Li, X. L.; Li, Y. S.
2016-08-01
This paper is devoted to identifying a time-dependent source term in a multi-dimensional time-fractional diffusion equation from boundary Cauchy data. The existence and uniqueness of a strong solution for the corresponding direct problem with homogeneous Neumann boundary condition are firstly proved. We provide the uniqueness and a stability estimate for the inverse time-dependent source problem. Then we use the Tikhonov regularization method to solve the inverse source problem and propose a conjugate gradient algorithm to find a good approximation to the minimizer of the Tikhonov regularization functional. Numerical examples in one-dimensional and two-dimensional cases are provided to show the effectiveness of the proposed method. This paper was supported by the NSF of China (11371181) and the Fundamental Research Funds for the Central Universities (lzujbky-2013-k02).
Update of Time-Dependent CP Asymmetry Measurements in b to c-cbar-s Decays
Energy Technology Data Exchange (ETDEWEB)
Aubert, B.
2008-08-20
We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465 {+-} 5) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II B factory. The time-dependent CP asymmetry parameters measured from J/{psi}K{sub S}{sup 0}, J/{psi}K{sub L}{sup 0}, {psi}(2S)K{sub S}{sup 0}, {chi}{sub c1}K{sub S}{sup 0}, {eta}{sub c}K{sub S}{sup 0}, and J/{psi}K*{sup 0} decays are: (1) C{sub f} = 0.026 {+-} 0.020(stat) {+-} 0.016(syst); and (2) S{sub f} = 0.691 {+-} 0.029(stat) {+-} 0.014(syst).
Transient Taylor-Aris dispersion for time-dependent flows in straight channels
DEFF Research Database (Denmark)
Vedel, Søren; Bruus, Henrik
2012-01-01
Taylor–Aris dispersion, the shear-induced enhancement of solute diffusion in the flow direction of the solvent, has been studied intensely in the past half century for the case of steady flow and single-frequency pulsating flows. Here, combining Aris’s method of moments with Dirac’s bra–ket forma......Taylor–Aris dispersion, the shear-induced enhancement of solute diffusion in the flow direction of the solvent, has been studied intensely in the past half century for the case of steady flow and single-frequency pulsating flows. Here, combining Aris’s method of moments with Dirac’s bra......–ket formalism, we derive an expression for the effective solute diffusivity valid for transient Taylor–Aris dispersion in any given time-dependent, multi-frequency solvent flow through straight channels. Our theory shows that the solute dispersion may be greatly enhanced by the time-dependent parts of the flow...
Longitudinal dispersion with time-dependent source concentration in semi-infinite aquifer
Indian Academy of Sciences (India)
Mritunjay Kumar Singh; Nav Kumar Mahato; Premlata Singh
2008-12-01
An analytical solution is obtained to predict the contaminant concentration along unsteady ground-water ﬂow in semi-in ﬁnite aquifer. Initially,the aquifer is not supposed to be solute free ,i.e.,aquifer is not clean.A time-dependent source concentration is considered at the origin of the aquifer and at the other end of the aquifer, it is supposed to be zero. The time-dependent forms of unsteady velocities are considered in which one such form ,i.e., sinusoidal form represents the seasonal pattern in a year in tropical regions. The Laplace Transformation Technique (LTT)is used to get an analytical solution and a graphical representation is made through MATLAB.
Time dependent solitons of noncommutative Chern-Simons theory coupled to scalar fields
Hadasz, L; Rocek, M; Von Unge, R; Hadasz, Leszek; Lindstrom, Ulf; Rocek, Martin; Unge, Rikard von
2003-01-01
We study one- and two-soliton solutions of noncommutative Chern-Simons theory coupled to a nonrelativistic or a relativistic scalar field. In the nonrelativistic case it is not possible to find the dynamics of the solitons using traditional moduli space techniques. To do better we have found exact time dependent one soliton solutions to the full equations of motion. They represent solitons moving in straight lines with constant velocity. Surprisingly we find that the set of allowed velocities is quantized! The allowed velocities are proportional to the square root of an integer. In the relativistic case we find the metric on the two soliton moduli space and using techinques developed in the nonrelativistic case we also find exact time dependent one-soliton solutions. Again the allowed velocities are quantized, though in a slightly more complicated fashion.
Dissociation and dissociative ionization of H2+ using the time-dependent surface flux method
Yue, Lun
2014-01-01
The time-dependent surface flux method developed for the description of electronic spectra [L. Tao and A. Scrinzi, New J. Phys. 14, 013021 (2012); A. Scrinzi, New J. Phys. 14, 085008 (2012)] is extended to treat dissociation and dissociative ionization processes of H2+ interacting with strong laser pulses. By dividing the simulation volume into proper spatial regions associated with the individual reaction channels and monitoring the probability flux, the joint energy spectrum for the dissociative ionization process and the energy spectrum for dissociation is obtained. The methodology is illustrated by solving the time-dependent Schr\\"{o}dinger equation (TDSE) for a collinear one-dimensional model of H2+ with electronic and nuclear motions treated exactly and validated by comparison with published results for dissociative ionization. The results for dissociation are qualitatively explained by analysis based on dressed diabatic Floquet potential energy curves, and the method is used to investigate the breakdow...
How strongly does dating meteorites constrain the time-dependence of the fine-structure constant?
Fujii, Y; Fujii, Yasunori; Iwamoto, Akira
2005-01-01
We review our argument on the nature of the so-called meteorite constraint on the possible time-dependence of the fine-structure constant, emphasizing that dating meteorites at the present time is different in principle from searching directly for the traces in the past, as in the Oklo phenomenon and the QSO absorption lines. In the related literature, we still find some arguments not necessarily consistent with this difference to be taken properly into account. This does not imply that any of the model-dependent approaches are useless in practice, though we cannot help guessing that dating meteorites is no match for the Oklo and the QSO in probing time-dependence of the fine-structure constant, at this moment. Some of the relevance to the QSO data particularly in terms of the scalar field will be discussed.
A time-dependent formulation of multi-reference perturbation theory
Sokolov, Alexander Yu
2016-01-01
We discuss the time-dependent formulation of perturbation theory in the context of the interacting zeroth-order Hamiltonians that appear in multi-reference situations. As an example, we present a time-dependent formulation and implementation of second-order n-electron valence perturbation theory. The resulting t-NEVPT2 method yields the fully uncontracted n-electron valence perturbation wavefunction and energy, but has a lower computational scaling than the usual contracted variants, and also avoids the construction of high-order density matrices and the diagonalization of metrics. We present results of t-NEVPT2 for the water, nitrogen, carbon, and chromium molecules, and outline directions for the future.
Numerical density-to-potential inversions in time-dependent density functional theory.
Jensen, Daniel S; Wasserman, Adam
2016-08-01
We treat the density-to-potential inverse problem of time-dependent density functional theory as an optimization problem with a partial differential equation constraint. The unknown potential is recovered from a target density by applying a multilevel optimization method controlled by error estimates. We employ a classical optimization routine using gradients efficiently computed by the discrete adjoint method. The inverted potential has both a real and imaginary part to reduce reflections at the boundaries and other numerical artifacts. We demonstrate this method on model one-dimensional systems. The method can be straightforwardly extended to a variety of numerical solvers of the time-dependent Kohn-Sham equations and to systems in higher dimensions.
Non-sequential double ionization with time-dependent renormalized natural orbital theory
Brics, M; Bauer, D
2014-01-01
Recently introduced time-dependent renormalized natural orbital theory (TDRNOT) is tested on non-sequential double ionization (NSDI) of a numerically exactly solvable one-dimensional model He atom subject to few-cycle, 800-nm laser pulses. NSDI of atoms in strong laser fields is a prime example of non-perturbative, highly correlated electron dynamics. As such, NSDI is an important "worst-case" benchmark for any time-dependent few and many-body technique beyond linear response. It is found that TDRNOT reproduces the celebrated NSDI "knee," i.e., a many-order-of-magnitude enhancement of the double ionization yield (as compared to purely sequential ionization) with only the ten most significant natural orbitals (NOs) per spin. Correlated photoelectron spectra - as "more differential" observables - require more NOs.
Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels
DEFF Research Database (Denmark)
Muller, Peter Barkholt; Bruus, Henrik
2015-01-01
Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic...... conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated...... in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation...
Chorošajev, Vladimir; Gelzinis, Andrius; Valkunas, Leonas; Abramavicius, Darius
2016-12-01
Time dependent variational approach is a convenient method to characterize the excitation dynamics in molecular aggregates for different strengths of system-bath interaction a, which does not require any additional perturbative schemes. Until recently, however, this method was only applicable in zero temperature case. It has become possible to extend this method for finite temperatures with the introduction of stochastic time dependent variational approach. Here we present a comparison between this approach and the exact hierarchical equations of motion approach for describing excitation dynamics in a broad range of temperatures. We calculate electronic population evolution, absorption and auxiliary time resolved fluorescence spectra in different regimes and find that the stochastic approach shows excellent agreement with the exact approach when the system-bath coupling is sufficiently large and temperatures are high. The differences between the two methods are larger, when temperatures are lower or the system-bath coupling is small.
Institute of Scientific and Technical Information of China (English)
HE Xiang; WANG Fan
2006-01-01
@@ Thioaldehydes and thioketones are candidates of new photoluminescence materials. The time-dependent density functional theory is applied to calculate the absorption and emission wavelengths of ten thiocarbonyl compounds using both B3LYP and PBE0 functionals. The theoretical results are in agreement with the measurable ones.Furthermore, it is found that the maximum absorption and emission wavelengths are linearly correlated to the C-S bond lengths.
Time dependent capacitance voltage measurements on Cu(In,Ga)Se{sub 2} solar cells
Energy Technology Data Exchange (ETDEWEB)
Adler, Tobias; Klein, Andreas [Darmstadt University of Technology, Institute of Materials Science, Petersenstrasse 32, D-64287 Darmstadt (Germany); Witte, Wolfram; Hariskos, Dimitrios [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Industriestrasse 6, D-70565 Stuttgart (Germany)
2011-07-01
Capacitance Voltage (C-V) measurements are widely used to determine the doping density of semiconductor interfaces in dependence on the width of the space charge layer. In Cu(In,Ga)Se{sub 2} (CIGS) solar cells we observe a time dependent capacitance signal, which can be explained by different models like filling and emptying of electronic (metastable) defect states or by the diffusion of copper ions. The observed capacitance transients are compared to the different models.
Phase-Space Explorations in Time-Dependent Density Functional Theory
Rajam, Arun K.; Hessler, Paul; Gaun, Christian; Maitra, Neepa T.
2009-01-01
We discuss two problems which are particularly challenging for approximations in time-dependent density functional theory (TDDFT) to capture: momentum-distributions in ionization processes, and memory-dependence in real-time dynamics. We propose an extension of TDDFT to phase-space densities, discuss some formal aspects of such a "phase-space density functional theory" and explain why it could ameliorate the problems in both cases. For each problem, a two-electron model system is exactly nume...
Nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection
Directory of Open Access Journals (Sweden)
Sonoi Takafumi
2015-01-01
Full Text Available We carry out nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection (TDC. We find that the instability of the modes excited at the Fe bump is weaker with TDC than with frozen-in convection (FC. But the instability still remains with TDC, and could be a possible candidate for the trigger of luminous blue variable (LBV phenomena.
Dynamics of solitons in Bose-Einstein condensate with time-dependent atomic scattering length
Institute of Scientific and Technical Information of China (English)
Li Hua-Mei
2006-01-01
The evolution of solitons in Bose-Einstein condensates (BECs) with time-dependent atomic scattering length in an expulsive parabolic potential is studied. Based on the extended hyperbolic function method, we successfully obtain the bright and dark soliton solutions. In addition, some new soliton solutions in this model are found. The results in this paper include some in the literature (Phys. Rev. Lett. 94 (2005) 050402 and Chin. Phys. Lett. 22 (2005) 1855).
Time-Dependent 2-D Vector Field Topology: An Approach Inspired by Lagrangian Coherent Structures
Sadlo, Filip; Weiskopf, Daniel
2011-01-01
This paper presents an approach to a time-dependent variant of the concept of vector field topology for 2-D vector fields. Vector field topology is defined for steady vector fields and aims at discriminating the domain of a vector field into regions of qualitatively different behaviour. The presented approach represents a generalization for saddle-type critical points and their separatrices to unsteady vector fields based on generalized streak lines, with the classical vector field topology a...
Time dependence of hysteresis loop displacement in hard-soft magnetic systems
Energy Technology Data Exchange (ETDEWEB)
Rivas, Montserrat [Departamento de Fisica de la Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain)]. E-mail: rivas@uniovi.es; Garcia, Jose A. [Departamento de Fisica de la Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Angeles Cerdeira, M. [Departamento de Fisica de la Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Fal-Miyar, Vanessa [Departamento de Fisica de la Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Tejedor, Marcos [Departamento de Fisica de la Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain)
2006-09-15
Time dependence of the hysteresis loop asymmetry observed in partially crystallized Co{sub 66}Si{sub 16}B{sub 12}Fe{sub 4}Mo{sub 2}is here analyzed at room temperature. The results are related to a magnetic aftereffect occurring in the hard crystallites embedded in the residual soft matrix. The coercive field is found to be constant with time, which is explained in terms of the dipolar interaction theory.
LRS Bianchi Type-V Viscous Fluid Universe With a Time Dependent Cosmological Term $\\Lambda$
Pradhan, Anirudh; Singh, C V
2007-01-01
An LRS Bianchi type-V cosmological models representing a viscous fluid distribution with a time dependent cosmological term $\\Lambda$ is investigated. To get a determinate solution, the viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. It turns out that the cosmological term $\\Lambda(t)$ is a decreasing function of time, which is consistent with recent observations of type Ia supernovae. Various physical and kinematic features of these models have also been explored.
Time-dependent cell membrane damage under mechanical tension: Experiments and modeling
Lu, Bo; Chang, Jay Han-Chieh; Tai, Yu-Chong
2011-01-01
This paper reports a study of cancer cell membrane damage during filtration caused by cell membrane tension. The membrane tension was induced when cells were captured on a microfabricated parylene-C filter during the constant-pressure-driven filtration. This work includes both experiments and modeling to explore the underlying biomechanics of the cell membrane damage. The developed model not only agrees with our time-dependent cell damage data, but also fits well with previous results on red ...
Atomic and field dynamics in the time-dependent Jaynes-Cummings model with arbitrary detuning
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
We propose a general numerical method for solving the time -dependent Jaynes-Cummings model with arbitrary detuning by integrating relate d groups of coupled equations using Runge-Kutta numerical technique. The atomic and field dynamics such as evolution of atomic population inversion and second -order correlation function of photons are studied in case of different detunin g. The results show that the field tends to exhibit bunching effect due to the I ncreasing of detuning.
Energy decay of a variable-coefficient wave equation with nonlinear time-dependent localized damping
Directory of Open Access Journals (Sweden)
Jieqiong Wu
2015-09-01
Full Text Available We study the energy decay for the Cauchy problem of the wave equation with nonlinear time-dependent and space-dependent damping. The damping is localized in a bounded domain and near infinity, and the principal part of the wave equation has a variable-coefficient. We apply the multiplier method for variable-coefficient equations, and obtain an energy decay that depends on the property of the coefficient of the damping term.
Time-dependent density functional theory for strong-field ionization by circularly polarized pulses
Chirilă, Ciprian C.; Lein, Manfred
2017-03-01
By applying time-dependent density functional theory to a two-dimensional multielectron atom subject to strong circularly polarized light pulses, we confirm that the ionization of p orbitals with defined angular momentum depends on the sense of rotation of the applied field. A simple ad-hoc modification of the adiabatic local-density exchange-correlation functional is proposed to remedy its unphysical behavior under orbital depletion.
Optical properties of Al nanostructures from time dependent density functional theory
Mokkath, Junais Habeeb
2016-04-05
The optical properties of Al nanostructures are investigated by means of time dependent density functional theory, considering chains of varying length and ladders/stripes of varying aspect ratio. The absorption spectra show redshifting for increasing length and aspect ratio. For the chains the absorption is dominated by HOMO → LUMO transitions, whereas ladders and stripes reveal more complex spectra of plasmonic nature above a specific aspect ratio.
Time-dependent relativistic density functional study of Yb and YbO
Institute of Scientific and Technical Information of China (English)
XU WenHua; ZHANG Yong; LIU WenJian
2009-01-01
The low-lying electronic states of Yb and YbO are investigated by using time-dependent relativistic density functional theory,which is based on the newly developed exact two-component Hamiltonian resulting from symmetrized elimination of the small component.The nature of the excited states is analyzed by using the full molecular symmetry.The calculated results support the previous experimental assignment of the ground and excited states of YbO.
Computation and analysis of time-dependent sensitivities in Generalized Mass Action systems.
Schwacke, John H; Voit, Eberhard O
2005-09-07
Understanding biochemical system dynamics is becoming increasingly important for insights into the functioning of organisms and for biotechnological manipulations, and additional techniques and methods are needed to facilitate investigations of dynamical properties of systems. Extensions to the method of Ingalls and Sauro, addressing time-dependent sensitivity analysis, provide a new tool for executing such investigations. We present here the results of sample analyses using time-dependent sensitivities for three model systems taken from the literature, namely an anaerobic fermentation pathway in yeast, a negative feedback oscillator modeling cell-cycle phenomena, and the Mitogen Activated Protein (MAP) kinase cascade. The power of time-dependent sensitivities is particularly evident in the case of the MAPK cascade. In this example it is possible to identify the emergence of a concentration of MAPKK that provides the best response with respect to rapid and efficient activation of the cascade, while over- and under-expression of MAPKK relative to this concentration have qualitatively different effects on the transient response of the cascade. Also of interest is the quite general observation that phase-plane representations of sensitivities in oscillating systems provide insights into the manner with which perturbations in the envelope of the oscillation result from small changes in initial concentrations of components of the oscillator. In addition to these applied analyses, we present an algorithm for the efficient computation of time-dependent sensitivities for Generalized Mass Action (GMA) systems, the most general of the canonical system representations of Biochemical Systems Theory (BST). The algorithm is shown to be comparable to, or better than, other methods of solution, as exemplified with three biochemical systems taken from the literature.
Dynamics of Periodic Waves in Bose-Einstein Condensate with Time-Dependent Atomic Scattering Length
Institute of Scientific and Technical Information of China (English)
LI Hua-Mei
2007-01-01
Evolution of periodic waves and solitary waves in Bose-Einstein condensates (BECs) with time-dependent atomic scattering length in an expulsive parabolic potential is studied. Based on the mapping deformation method, we successfully obtain periodic wave solutions and solitary wave solutions, including the bright and dark soliton solutions. The results in this paper include some in the literatures [Plys. Rev. Lett. 94 (2005) 050402 and Chin. Phys. Lett. 22(2005) 1855].
Time dependence of piezoelectric d33 coefficient of cellular ferroelectret polypropylene film
Wan, Yongping; Xie, Longtao; Zhang, Xiaoqing; Zhong, Zheng
2011-03-01
Due to the inherent viscosity of polymer, piezoelectric response in the thickness direction (d33) of cellular ferroelectret films usually depends on the time of measurement. In this letter, the micromechanical theory of viscoelastic composite was extended to predict the time dependence of the overall piezoelectric d33 coefficient of voided charged polymer foam. Experiments were carried out to find the time spectra of piezoelectric d33 coefficient of voided charged polypropylene film. Theoretical simulation agrees well with experiment data.
Dynamic behavior of polymer surface and the time dependence of contact angle
Institute of Scientific and Technical Information of China (English)
WANG Xinping; CHEN Zhifang; SHEN Zhiquan
2005-01-01
Time-dependent contact angles were measured by depositing sessile drops of water on the polymer surfaces and monitoring the drop shape as a function of time. It was found that contact angles decreased sharply with contact time and the equilibrium contact angle was finally attained after a certain time. Values of starting (θs) and equilibrium contact angles (θe) obtained by the sessile drop method depend on polymer properties. The Wilhelmy plate technique was used to measure advancing and receding contact angles. The variations of starting (θs) and equilibrium contact angles (θe), advancing (θa) and receding contact angles (θr) have been studied on the oxidized surface of polymers containing polybutadiene block to explore the cause of time-dependence in contact angle measurement and the meaning of θs and θe. The results showed the linear relationships between starting (θs) and advancing contact angles (θa), the equilibrium (θe) and receding contact angles (θr). The similar relationship was also established between the contact angle hysteresis (θa-θr) and differences (θs-θe) in starting contact angles and equilibrium contact angles. Therefore, time-dependence in contact angle measurement was mainly attributed to the surface reconstruction when water drops were deposited on polymer surfaces. The starting contact angle was contributed by the hydrophobic component on polymer surface and the equilibrium contact angle mainly by the hydrophilic component of polymer. These results not only demonstrated the interdependency between two contact angle measurements, the sessile drop method and the Wilhelmy plate technique, but also provided the experimental evidence to explain the cause of time-dependent contact angle. This may also provide a new method to study dynamic behavior of polymer surface.
Multiple time-dependent coefficient identification thermal problems with a free boundary
Hussein, MS; Lesnic, D.; Ivanchov, MI; Snitko, HA
2016-01-01
Multiple time-dependent coefficient identification thermal problems with an unknown free boundary are investigated. The difficulty in solving such inverse and ill-posed free boundary problems is amplified by the fact that several quantities of physical interest (conduction, convection/advection and reaction coefficients) have to be simultaneously identified. The additional measurements which render a unique solution are given by the heat moments of various orders together with a Stefan bounda...
Two Coincidence Detectors for Spike Timing-Dependent Plasticity in Somatosensory Cortex
2006-01-01
Many cortical synapses exhibit spike timing-dependent plasticity (STDP) in which the precise timing of presynaptic and postsynaptic spikes induces synaptic strengthening [long-term potentiation (LTP)] or weakening [long-term depression (LTD)]. Standard models posit a single, postsynaptic, NMDA receptor-based coincidence detector for LTP and LTD components of STDP. We show instead that STDP at layer 4 to layer 2/3 synapses in somatosensory (S1) cortex involves separate calcium sources and coin...
Said-Houari, Belkacem
2012-03-01
In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.
Pricing multi-asset financial derivatives with time-dependent parameters—Lie algebraic approach
Directory of Open Access Journals (Sweden)
C. F. Lo
2002-01-01
Full Text Available We present a Lie algebraic technique for the valuation of multi-asset financial derivatives with time-dependent parameters. Exploiting the dynamical symmetry of the pricing partial differential equations of the financial derivatives, the new method enables us to derive analytical closed-form pricing formulae very straightforwardly. We believe that this new approach will provide an efficient and easy-to-use method for the valuation of financial derivatives.
Constitutive Modeling of Time-Dependent Response of Human Plantar Aponeurosis
Pavan, P. G.; Pachera, P.; Stecco, C.; Natali, A. N.
2014-01-01
The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behav...
Analytical approximation to the dynamics of a binary stars system with time depending mass variation
López, Gustavo V
2016-01-01
We study the classical dynamics of a binary stars when there is an interchange of mass between them. Assuming that one of the star is more massive than the other, the dynamics of the lighter one is analyzed as a function of its time depending mass variation. Within our approximations and models for mass transference, we obtain a general result which establishes that if the lightest star looses mass, its period increases. If the lightest star win mass, its period decreases.
Local regularity for time-dependent tug-of-war games with varying probabilities
Parviainen, Mikko; Ruosteenoja, Eero
2016-07-01
We study local regularity properties of value functions of time-dependent tug-of-war games. For games with constant probabilities we get local Lipschitz continuity. For more general games with probabilities depending on space and time we obtain Hölder and Harnack estimates. The games have a connection to the normalized p (x , t)-parabolic equation ut = Δu + (p (x , t) - 2) Δ∞Nu.
Soliton solutions of some nonlinear evolution equations with time-dependent coefficients
Indian Academy of Sciences (India)
Hitender Kumar; Anand Malik; Fakir Chand
2013-02-01
In this paper, we obtain exact soliton solutions of the modified KdV equation, inho-mogeneous nonlinear Schrödinger equation and (, ) equation with variable coefficients using solitary wave ansatz. The constraint conditions among the time-dependent coefficients turn out as necessary conditions for the solitons to exist. Numerical simulations for dark and bright soliton solutions for the mKdV equation are also given.
D'Angelo, E; Milic-Emili, J; Marazzini, L
1996-11-01
It has been shown that in normal subjects and chronic obstructive pulmonary disease (COPD) patients the maximal expiratory flows and FEV1 are significantly higher if the FVC maneuver is preceded by a rapid inspiration without an end-inspiratory pause (maneuver 1) compared with a slow inspiration with an end-inspiratory pause of approximately 5 s (maneuver 2). This time dependency of FVC was attributed primarily to loss of lung recoil (stress relaxation) during breath-holding at TLC, in association with time constant inequality within the lungs, and changes in bronchomotor tone. To examine the role of bronchomotor tone on time dependency of FVC, 11 COPD and 10 asthmatic patients performed FVC maneuvers 1 and 2 before and after administration of a bronchodilator drug (salbutamol). In addition, using the same approach, the effects of changing airway resistance per se were assessed in another group of 10 COPD patients and 10 normal subjects, while breathing air and after equilibration with 80% helium in oxygen. Main findings were: peak expiratory flow (PEF), FEV1, and maximal midexpiratory flow rate (MMF) were significantly larger with maneuver 1 than 2; after salbutamol administration and during helium-oxygen breathing, all indices increased significantly with both maneuvers but the relative differences between maneuvers 1 and 2 were unchanged. We conclude that time dependency of maximal expiratory flow-volume (MEFV) curves, as indexed by PEF, FEV1, and MMF, is largely independent of bronchomotor tone and gas density, and probably reflects mainly stress relaxation of the respiratory tissues. The relevance of time dependency of FVC maneuver in the assessment of bronchodilator response and density dependence is discussed.
Photodissociation of NaH using time-dependent Fourier grid method
Indian Academy of Sciences (India)
Anindita Bhattacharjee; Krishna Rai Dastidar
2002-03-01
We have solved the time dependent Schrödinger equation by using the Chebyshev polynomial scheme and Fourier grid Hamiltonian method to calculate the dissociation cross section of NaH molecule by 1-photon absorption from the 1+ state to the 1 state. We have found that the results differ signiﬁcantly from an earlier calculation [1] although we have used the same set of potential energy curves [2].
ANGULAR VELOCITY AND CORIOLIS EFFECT IN TIME-DEPENDENT QUANTUM MECHANICAL SU2 ROTATION
Institute of Scientific and Technical Information of China (English)
FAN HONG-YI; SUN MING-ZHAI
2001-01-01
Starting from a time-dependent rotation U (t) in SU2 group element space, we derive its corresponding quantum mechanical dynamic Coriolis term and the relationship between U (t) and rotational angular velocity. Throughout our discussion, the technique of integration within an ordered product of operators is fully used, which has the advantage that the correspondence between the classical rotation and the quantum rotation is in a transparent fashion. A new angular-velocity formula is also derived.
Exact Analytical Solutions in Bose-Einstein Condensates with Time-Dependent Atomic Scattering Length
Institute of Scientific and Technical Information of China (English)
CHEN Yong; LI Biao; ZHENG Yu
2007-01-01
In the paper, the generalized Riccati equation rational expansion method is presented. Making use of the method and symbolic computation, we present three families of exact analytical solutions of Bose-Einstein condensates with the time-dependent interatomic interaction in an expulsive parabolic potential. Then the dynamics of two anlytical solutions are demonstrated by computer simulations under some selectable parameters including the Feshbach-managed nonlinear coefficient and the hyperbolic secant function coefficient.
Time-Dependent AdS Backgrounds from S-Branes
Deger, Nihat Sadik
2016-01-01
We construct time and radial dependent solutions that describe p-branes in chargeless S-brane backgrounds. In particular, there are some new M5- and D3-branes among our solutions which have AdS limits and contain a cosmological singularity as well. We also find a time-dependent version of the dyonic membrane configuration in 11-dimensions by applying a Lunin-Maldacena deformation to our new M5-brane solution.
Time-dependent AdS backgrounds from S-branes
Deger, Nihat Sadik
2016-11-01
We construct time and radial dependent solutions that describe p-branes in chargeless S-brane backgrounds. In particular, there are some new M5- and D3-branes among our solutions which have AdS limits and contain a cosmological singularity as well. We also find a time-dependent version of the dyonic membrane configuration in 11-dimensions by applying a Lunin-Maldacena deformation to our new M5-brane solution.
de Araujo, José C N; Costa, César A
2016-01-01
We study the role of time dependent magnetic ellipticities ($\\epsilon_{B}$) on the calculation of the braking index of pulsars. Moreover, we study the consequences of such a $\\epsilon_{B}$ on the amplitude of gravitational waves (GWs) generated by pulsars with measured braking indices. We show that, since the ellipticity generated by the magnetic dipole is extremely small, the corresponding amplitude of GWs is much smaller than the amplitude obtained via the spindown limit.
An Empirically Driven Time-Dependent Model of the Solar Wind
Linker, Jon A.; Caplan, Ronald M.; Downs, Cooper; Lionello, Roberto; Riley, Pete; Mikic, Zoran; Henney, Carl J.; Arge, Charles N.; Kim, Tae; Pogorelov, Nikolai
2016-05-01
We describe the development and application of a time-dependent model of the solar wind. The model is empirically driven, starting from magnetic maps created with the Air Force Data Assimilative Photospheric flux Transport (ADAPT) model at a daily cadence. Potential field solutions are used to model the coronal magnetic field, and an empirical specification is used to develop boundary conditions for an MHD model of the solar wind. The time-dependent MHD simulation shows classic features of stream structure in the interplanetary medium that are seen in steady-state models; it also shows time evolutionary features that do not appear in a steady-state approach. The model results compare reasonably well with 1 AU OMNI observations. Data gaps when SOLIS magnetograms were unavailable hinder the model performance. The reasonable comparisons with observations suggest that this modeling approach is suitable for driving long term models of the outer heliosphere. Improvements to the ingestion of magnetograms in flux transport models will be necessary to apply this approach in a time-dependent space weather model.
Intense 2-cycle laser pulses induce time-dependent bond-hardening in a polyatomic molecule
Dota, K; Tiwari, A K; Dharmadhikari, J A; Dharmadhikari, A K; Mathur, D
2012-01-01
A time-dependent bond-hardening process is discovered in a polyatomic molecule (tetramethyl silane, TMS) using few-cycle pulses of intense 800 nm light. In conventional mass spectrometry, symmetrical molecules like TMS do not exhibit a prominent molecular ion (TMS$^+$) as unimolecular dissociation into [Si(CH$_3$)$_3]^+$ proceeds very fast. Under strong field and few-cycle conditions, this dissociation channel is defeated by time-dependent bond-hardening: a field-induced potential well is created in the TMS$^+$ potential energy curve that effectively traps a wavepacket. The time-dependence of this bond hardening process is verified using longer-duration ($\\geq$ 100 fs) pulses; the relatively "slower" fall-off of optical field in such pulses allows the initially trapped wavepacket to leak out, thereby rendering TMS$^+$ unstable once again. Our results are significant as they demonstrate (i) optical generation of polyatomic ions that are normally inaccessible and (ii) optical control of dynamics in strong field...
Stimulus-timing dependent multisensory plasticity in the guinea pig dorsal cochlear nucleus.
Directory of Open Access Journals (Sweden)
Seth D Koehler
Full Text Available Multisensory neurons in the dorsal cochlear nucleus (DCN show long-lasting enhancement or suppression of sound-evoked responses when stimulated with combined somatosensory-auditory stimulation. By varying the intervals between sound and somatosensory stimuli we show for the first time in vivo that DCN bimodal responses are influenced by stimulus-timing dependent plasticity. The timing rules and time courses of the observed stimulus-timing dependent plasticity closely mimic those of spike-timing dependent plasticity that have been demonstrated in vitro at parallel-fiber synapses onto DCN principal cells. Furthermore, the degree of inhibition in a neuron influences whether that neuron has Hebbian or anti-Hebbian timing rules. As demonstrated in other cerebellar-like circuits, anti-Hebbian timing rules reflect adaptive filtering, which in the DCN would result in suppression of sound-evoked responses that are predicted by activation of somatosensory inputs, leading to the suppression of body-generated signals such as self-vocalization.
The Time-Dependent Chemistry of Cometary Debris in the Solar Corona
Pesnell, W. D.; Bryans, P.
2015-01-01
Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.