Numerical time integration for air pollution models
J.G. Verwer (Jan); W. Hundsdorfer (Willem); J.G. Blom (Joke)
1998-01-01
textabstractDue to the large number of chemical species and the three space dimensions, off-the-shelf stiff ODE integrators are not feasible for the numerical time integration of stiff systems of advection-diffusion-reaction equations [ fracpar{c{t + nabla cdot left( vu{u c right) = nabla cdot left(
Numerical counting ratemeter with variable time constant and integrated circuits
International Nuclear Information System (INIS)
Kaiser, J.; Fuan, J.
1967-01-01
We present here the prototype of a numerical counting ratemeter which is a special version of variable time-constant frequency meter (1). The originality of this work lies in the fact that the change in the time constant is carried out automatically. Since the criterion for this change is the accuracy in the annunciated result, the integration time is varied as a function of the frequency. For the prototype described in this report, the time constant varies from 1 sec to 1 millisec. for frequencies in the range 10 Hz to 10 MHz. This prototype is built entirely of MECL-type integrated circuits from Motorola and is thus contained in two relatively small boxes. (authors) [fr
Exploiting natural scale separation with efficient asynchronous numerical time integration
Rubel, Michael; Leonard, Anthony
2002-11-01
The systems of ordinary differential equations that arise in problems of computational fluid mechanics often exhibit time-scale separation in addition to being stiff: each solution variable acts at a small range of time scales relative to the problem as a whole. When only a small fraction of the solution variables act at the fastest scales, conventional timestepping algorithms waste a great deal of effort over-resolving the slow variables. In this talk, I will discuss numerical strategies to take advantage of time-scale separation for more efficient computing. In particular, results from the dead-reckoning algorithm will be presented.
DEFF Research Database (Denmark)
Cook, Gerald; Lin, Ching-Fang
1980-01-01
The local linearization algorithm is presented as a possible numerical integration scheme to be used in real-time simulation. A second-order nonlinear example problem is solved using different methods. The local linearization approach is shown to require less computing time and give significant...... improvement in accuracy over the classical second-order integration methods....
Wang, Jinting; Lu, Liqiao; Zhu, Fei
2018-01-01
Finite element (FE) is a powerful tool and has been applied by investigators to real-time hybrid simulations (RTHSs). This study focuses on the computational efficiency, including the computational time and accuracy, of numerical integrations in solving FE numerical substructure in RTHSs. First, sparse matrix storage schemes are adopted to decrease the computational time of FE numerical substructure. In this way, the task execution time (TET) decreases such that the scale of the numerical substructure model increases. Subsequently, several commonly used explicit numerical integration algorithms, including the central difference method (CDM), the Newmark explicit method, the Chang method and the Gui-λ method, are comprehensively compared to evaluate their computational time in solving FE numerical substructure. CDM is better than the other explicit integration algorithms when the damping matrix is diagonal, while the Gui-λ (λ = 4) method is advantageous when the damping matrix is non-diagonal. Finally, the effect of time delay on the computational accuracy of RTHSs is investigated by simulating structure-foundation systems. Simulation results show that the influences of time delay on the displacement response become obvious with the mass ratio increasing, and delay compensation methods may reduce the relative error of the displacement peak value to less than 5% even under the large time-step and large time delay.
Loureiro, F. S.; Mansur, Webe Joao
2009-09-01
This paper is concerned with the formulation and numerical implementation of a new class of time integration schemes applied to linear heat conduction problems. The temperature field at any time level is calculated in terms of the numerical Green’s function matrix of the model problem by considering an analytical time integral equation. After spatial discretization by the finite element method, the Green’s function matrix which transfers solution from t to t + Δ t is explicitly computed in nodal coordinates using efficient implicit and explicit Runge-Kutta methods. It is shown that the stability and the accuracy of the proposed method are highly improved when a sub-step procedure is used to calculate recursively the Green’s function matrix at the end of the first time step. As a result, with a suitable choice of the number of sub-steps, large time steps can be used without degenerating the numerical solution. Finally, the effectiveness of the present methodology is demonstrated by analyzing two numerical examples.
Time transformations and Cowell's method. [for numerical integration of satellite motion equations
Velez, C. E.; Hilinski, S.
1978-01-01
The precise numerical integration of Cowell's equations of satellite motion is frequently performed with an independent variable s defined by an equation of the form dt = cr to the n-th power ds, where t represents time, r the radial distance from the center of attraction, c is a constant, and n is a parameter. This has been primarily motivated by the 'uniformizing' effects of such a transformation resulting in desirable 'analytic' stepsize control for elliptical orbits. This report discusses the 'proper' choice of the parameter n defining the independent variable s for various types of orbits and perturbation models, and develops a criterion for its selection.
An accurate real-time model of maglev planar motor based on compound Simpson numerical integration
Kou, Baoquan; Xing, Feng; Zhang, Lu; Zhou, Yiheng; Liu, Jiaqi
2017-05-01
To realize the high-speed and precise control of the maglev planar motor, a more accurate real-time electromagnetic model, which considers the influence of the coil corners, is proposed in this paper. Three coordinate systems for the stator, mover and corner coil are established. The coil is divided into two segments, the straight coil segment and the corner coil segment, in order to obtain a complete electromagnetic model. When only take the first harmonic of the flux density distribution of a Halbach magnet array into account, the integration method can be carried out towards the two segments according to Lorenz force law. The force and torque analysis formula of the straight coil segment can be derived directly from Newton-Leibniz formula, however, this is not applicable to the corner coil segment. Therefore, Compound Simpson numerical integration method is proposed in this paper to solve the corner segment. With the validation of simulation and experiment, the proposed model has high accuracy and can realize practical application easily.
An accurate real-time model of maglev planar motor based on compound Simpson numerical integration
Directory of Open Access Journals (Sweden)
Baoquan Kou
2017-05-01
Full Text Available To realize the high-speed and precise control of the maglev planar motor, a more accurate real-time electromagnetic model, which considers the influence of the coil corners, is proposed in this paper. Three coordinate systems for the stator, mover and corner coil are established. The coil is divided into two segments, the straight coil segment and the corner coil segment, in order to obtain a complete electromagnetic model. When only take the first harmonic of the flux density distribution of a Halbach magnet array into account, the integration method can be carried out towards the two segments according to Lorenz force law. The force and torque analysis formula of the straight coil segment can be derived directly from Newton-Leibniz formula, however, this is not applicable to the corner coil segment. Therefore, Compound Simpson numerical integration method is proposed in this paper to solve the corner segment. With the validation of simulation and experiment, the proposed model has high accuracy and can realize practical application easily.
Directory of Open Access Journals (Sweden)
Hussein Rappel
2014-01-01
integration technique (EFIT as well as its validation with analytical results. Lamb wave method is a long range inspection technique which is considered to have unique future in the field of structural health monitoring. One of the main problems facing the lamb wave method is how to choose the most appropriate frequency to generate the waves for adequate transmission capable of properly propagating in the material, interfering with defects/damages, and being received in good conditions. Modern simulation tools based on numerical methods such as finite integration technique (FIT, finite element method (FEM, and boundary element method (BEM may be used for modeling. In this paper, two sets of simulation are performed. In the first set, group velocities of lamb wave in a steel plate are obtained numerically. Results are then compared with analytical results to validate the simulation. In the second set, EFIT is employed to study fundamental symmetric mode interaction with a surface braking defect.
Energy conservation and high-frequency damping in numerical time-integration
DEFF Research Database (Denmark)
Krenk, Steen
2007-01-01
Momentum and energy conserving time integration procedures are receiving increased interest due to the central role of conservation properties in relation to the problems under investigation. However, most problems in structural dynamics are based on models that are first discretized in space, en...... to introduce so-called alpha-damping, and an improved form leading only to high-frequency damping can be obtained by suitable averaging of the equilibrium equation at consecutive time steps. Conservative time integration algorithms are obtained by use of an integral of the equation of motion......, or by introducing additional variables to represent damping. In the present paper it is demonstrated, how damping equivalent to the alpha-damping of the Newmark algorithm can be introduced directly via displacement and velocity dependent terms. It is furthermore shown, how this damping can be improved...
Numerical Time Integration Methods for a Point Absorber Wave Energy Converter
DEFF Research Database (Denmark)
Zurkinden, Andrew Stephen; Kramer, Morten
2012-01-01
function of the radiation force and the unknown body velocity due to an external force. The convolution integral can be seen as a memory effect where the system response in the past affects the response in the future. Two different time-domain models will be presented. The first one is based...
Energy conservation and high-frequency damping in numerical time integration
DEFF Research Database (Denmark)
Krenk, Steen
2008-01-01
this often leads to a fairly large number of high-frequency modes, that are not represented well – and occasionally directly erroneously – by the model. It is desirable to cure this problem by devising algorithms that include the possibility of introducing algorithmic energy dissipation of the high-frequency...... to introduce so-called α-damping, and an improved form leading only to high-frequency damping can be obtained by suitable averaging of the equilibrium equation at onsecutive time steps. Conservative time integration algorithms are obtained by use of an integral of the equation of motion and the acceleration...... of variables related to the displacement and velocity vectors by a suitable first order filter with scalar coefficients. By this device an algorithmic damping can be obtained that is of third order in the low-frequency regime. It is an important feature of both algorithms that they can be arranged to require...
International Nuclear Information System (INIS)
Aviles, B.N.; Sutton, T.M.; Kelly, D.J. III.
1991-09-01
A generalized Runge-Kutta method has been employed in the numerical integration of the stiff space-time diffusion equations. The method is fourth-order accurate, using an embedded third-order solution to arrive at an estimate of the truncation error for automatic timestep control. The efficiency of the Runge-Kutta method is enhanced by a block-factorization technique that exploits the sparse structure of the matrix system resulting from the space and energy discretized form of the time-dependent neutron diffusion equations. Preliminary numerical evaluation using a one-dimensional finite difference code shows the sparse matrix implementation of the generalized Runge-Kutta method to be highly accurate and efficient when compared to an optimized iterative theta method. 12 refs., 5 figs., 4 tabs
Numerical Contour Integration for Loop Integrals
Kurihara, Y.; Kaneko, T.
2005-01-01
A fully numerical method to calculate loop integrals, a numerical contour-integration method, is proposed. Loop integrals can be interpreted as a contour integral in a complex plane for an integrand with multi-poles in the plane. Stable and efficient numerical integrations an along appropriate contour can be performed for tensor integrals as well as for scalar ones appearing in loop calculations of the standard model. Examples of 3- and 4-point diagrams in 1-loop integrals and 2- and 3-point ...
Numerical integration of variational equations.
Skokos, Ch; Gerlach, E
2010-09-01
We present and compare different numerical schemes for the integration of the variational equations of autonomous Hamiltonian systems whose kinetic energy is quadratic in the generalized momenta and whose potential is a function of the generalized positions. We apply these techniques to Hamiltonian systems of various degrees of freedom and investigate their efficiency in accurately reproducing well-known properties of chaos indicators such as the Lyapunov characteristic exponents and the generalized alignment indices. We find that the best numerical performance is exhibited by the "tangent map method," a scheme based on symplectic integration techniques which proves to be optimal in speed and accuracy. According to this method, a symplectic integrator is used to approximate the solution of the Hamilton equations of motion by the repeated action of a symplectic map S , while the corresponding tangent map TS is used for the integration of the variational equations. A simple and systematic technique to construct TS is also presented.
Cuba: Multidimensional numerical integration library
Hahn, Thomas
2016-08-01
The Cuba library offers four independent routines for multidimensional numerical integration: Vegas, Suave, Divonne, and Cuhre. The four algorithms work by very different methods, and can integrate vector integrands and have very similar Fortran, C/C++, and Mathematica interfaces. Their invocation is very similar, making it easy to cross-check by substituting one method by another. For further safeguarding, the output is supplemented by a chi-square probability which quantifies the reliability of the error estimate.
International Nuclear Information System (INIS)
Fota, C.
1996-12-01
This work is part of an evaluation of a high resolution time encoder implemented as a circular vernier. Two integrated technologies have been used, silicon CMOS and GaAs HEMT. After a short survey of the existing time encoding techniques, we propose a digital method using a circular time vernier built around two ring oscillators. We present the benefits of such a technique, a detailed analysis of the vernier, and simulation results. Technological spreads that are critical for such a time encoder have been measured on a silicon ship with 0.8 micron gate length CMOS technology. The achievable resolution is derived from the results. The frequencies dictated by the circular vernier architecture reach a few hundred Megahertz, the chip layout is thus critical, as showed from the measurements on a 0.3 micron GaAs HEMT chip. Measurements are compared with simulations for each chip. Several other circular vernier layouts are proposed in order to improve the results. A mathematical model of a calibration phase lock loop of the ring oscillators on a reference clock is also presented. (author)
Numerical Quadrature of Periodic Singular Integral Equations
DEFF Research Database (Denmark)
Krenk, Steen
1978-01-01
This paper presents quadrature formulae for the numerical integration of a singular integral equation with Hilbert kernel. The formulae are based on trigonometric interpolation. By integration a quadrature formula for an integral with a logarithmic singularity is obtained. Finally it is demonstra......This paper presents quadrature formulae for the numerical integration of a singular integral equation with Hilbert kernel. The formulae are based on trigonometric interpolation. By integration a quadrature formula for an integral with a logarithmic singularity is obtained. Finally...... it is demonstrated how a singular integral equation with infinite support can be solved by use of the preceding formulae....
Time's arrow: A numerical experiment
Fowles, G. Richard
1994-04-01
The dependence of time's arrow on initial conditions is illustrated by a numerical example in which plane waves produced by an initial pressure pulse are followed as they are multiply reflected at internal interfaces of a layered medium. Wave interactions at interfaces are shown to be analogous to the retarded and advanced waves of point sources. The model is linear and the calculation is exact and demonstrably time reversible; nevertheless the results show most of the features expected of a macroscopically irreversible system, including the approach to the Maxwell-Boltzmann distribution, ergodicity, and concomitant entropy increase.
Applying recursive numerical integration techniques for solving high dimensional integrals
Energy Technology Data Exchange (ETDEWEB)
Ammon, Andreas [IVU Traffic Technologies AG, Berlin (Germany); Genz, Alan [Washington State Univ., Pullman, WA (United States). Dept. of Mathematics; Hartung, Tobias [King' s College, London (United Kingdom). Dept. of Mathematics; Jansen, Karl; Volmer, Julia [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Leoevey, Hernan [Humboldt Univ. Berlin (Germany). Inst. fuer Mathematik
2016-11-15
The error scaling for Markov-Chain Monte Carlo techniques (MCMC) with N samples behaves like 1/√(N). This scaling makes it often very time intensive to reduce the error of computed observables, in particular for applications in lattice QCD. It is therefore highly desirable to have alternative methods at hand which show an improved error scaling. One candidate for such an alternative integration technique is the method of recursive numerical integration (RNI). The basic idea of this method is to use an efficient low-dimensional quadrature rule (usually of Gaussian type) and apply it iteratively to integrate over high-dimensional observables and Boltzmann weights. We present the application of such an algorithm to the topological rotor and the anharmonic oscillator and compare the error scaling to MCMC results. In particular, we demonstrate that the RNI technique shows an error scaling in the number of integration points m that is at least exponential.
Applying recursive numerical integration techniques for solving high dimensional integrals
International Nuclear Information System (INIS)
Ammon, Andreas; Genz, Alan; Hartung, Tobias; Jansen, Karl; Volmer, Julia; Leoevey, Hernan
2016-11-01
The error scaling for Markov-Chain Monte Carlo techniques (MCMC) with N samples behaves like 1/√(N). This scaling makes it often very time intensive to reduce the error of computed observables, in particular for applications in lattice QCD. It is therefore highly desirable to have alternative methods at hand which show an improved error scaling. One candidate for such an alternative integration technique is the method of recursive numerical integration (RNI). The basic idea of this method is to use an efficient low-dimensional quadrature rule (usually of Gaussian type) and apply it iteratively to integrate over high-dimensional observables and Boltzmann weights. We present the application of such an algorithm to the topological rotor and the anharmonic oscillator and compare the error scaling to MCMC results. In particular, we demonstrate that the RNI technique shows an error scaling in the number of integration points m that is at least exponential.
A numerical method for resonance integral calculations
International Nuclear Information System (INIS)
Tanbay, Tayfun; Ozgener, Bilge
2013-01-01
A numerical method has been proposed for resonance integral calculations and a cubic fit based on least squares approximation to compute the optimum Bell factor is given. The numerical method is based on the discretization of the neutron slowing down equation. The scattering integral is approximated by taking into account the location of the upper limit in energy domain. The accuracy of the method has been tested by performing computations of resonance integrals for uranium dioxide isolated rods and comparing the results with empirical values. (orig.)
Spatiotemporal feature integration shapes approximate numerical processing.
Fornaciai, Michele; Park, Joonkoo
2017-11-01
Numerosity perception involves a complex cascade of processing stages comprising an early sensory representation stage followed by a later stage providing a conceptual representation of numerical magnitude. While much recent work has focused on understanding how nonnumerical spatial features (e.g., density, area) influence numerosity perception in this processing cascade, little is known about how the spatiotemporal properties of the stimuli affect numerosity processing. Whether numerosity information is integrated over space and time in the processing cascade is an important question as it can provide insights into how the system dedicated for numerosity interacts with other perceptual systems. To address these issues, in four independent experiments, we asked participants to judge the numerosities of various different kinds of dynamically presented dot arrays, such as dots randomly changing in their locations, moving in smooth trajectories, or flickering on and off. The results revealed a systematic overestimation of dynamically presented dot arrays, which implicates the existence of spatiotemporal integration mechanisms, both at the early sensory representation stage and the later conceptual representation stage. The results also revealed the influence of motion and color processing areas on numerosity processing. The findings thus provide empirical evidence that numerosity perception arises from a complex interaction between multiple perceptual mechanisms in the visual stream, and that it is shaped by the integration of spatiotemporal properties of visual stimuli.
Fibonacci numerical integration on a sphere
International Nuclear Information System (INIS)
Hannay, J H; Nye, J F
2004-01-01
For elementary numerical integration on a sphere, there is a distinct advantage in using an oblique array of integration sampling points based on a chosen pair of successive Fibonacci numbers. The pattern has a familiar appearance of intersecting spirals, avoiding the local anisotropy of a conventional latitude-longitude array. Besides the oblique Fibonacci array, the prescription we give is also based on a non-uniform scaling used for one-dimensional numerical integration, and indeed achieves the same order of accuracy as for one dimension: error ∼N -6 for N points. This benefit of Fibonacci is not shared by domains of integration with boundaries (e.g., a square, for which it was originally proposed); with non-uniform scaling the error goes as N -3 , with or without Fibonacci. For experimental measurements over a sphere our prescription is realized by a non-uniform Fibonacci array of weighted sampling points
The dynamical systems approach to numerical integration
Wisdom, Jack
2018-03-01
The dynamical systems approach to numerical integration is reviewed and extended. The new method is compared to some alternative methods based on the Lie series approach. The test problem is the motion of the outer planets. The algorithms developed using the dynamical systems approach perform well.
Automatic numerical integration methods for Feynman integrals through 3-loop
International Nuclear Information System (INIS)
De Doncker, E; Olagbemi, O; Yuasa, F; Ishikawa, T; Kato, K
2015-01-01
We give numerical integration results for Feynman loop diagrams through 3-loop such as those covered by Laporta [1]. The methods are based on automatic adaptive integration, using iterated integration and extrapolation with programs from the QUADPACK package, or multivariate techniques from the ParInt package. The Dqags algorithm from QuadPack accommodates boundary singularities of fairly general types. PARINT is a package for multivariate integration layered over MPI (Message Passing Interface), which runs on clusters and incorporates advanced parallel/distributed techniques such as load balancing among processes that may be distributed over a network of nodes. Results are included for 3-loop self-energy diagrams without IR (infra-red) or UV (ultra-violet) singularities. A procedure based on iterated integration and extrapolation yields a novel method of numerical regularization for integrals with UV terms, and is applied to a set of 2-loop self-energy diagrams with UV singularities. (paper)
An integrated numerical protection system (SPIN)
International Nuclear Information System (INIS)
Savornin, J.L.; Bouchet, J.M.; Furet, J.L.; Jover, P.; Sala, A.
1978-01-01
Developments in technology have now made it possible to perform more sophisticated protection functions which follow more closely the physical phenomena to be monitored. For this reason the Commissariat a l'energie atomique, Merlin-Gerin, Cerci and Framatome have embarked on the joint development of an Integrated Numerical Protection System (SPIN) which will fulfil this objective and will improve the safety and availability of power stations. The system described involves the use of programmed numerical techniques and a structure based on multiprocessors. The architecture has a redundancy of four. Throughout the development of the project the validity of the studies was confirmed by experiments. A first numerical model of a protection function was tested in the laboratory and is now in operation in a power station. A set of models was then introduced for checking the main components of the equipment finally chosen prior to building and testing a prototype. (author)
Notes on the integration of numerical relativity waveforms
Energy Technology Data Exchange (ETDEWEB)
Reisswig, Christian [Theoretical Astrophysics Including Relativity, California Institute of Technology, Pasadena, CA 91125 (United States); Pollney, Denis, E-mail: reisswig@tapir.caltech.edu [Departament de Fisica, Universitat de les Illes Balears, Palma de Mallorca E-07122 (Spain)
2011-10-01
The primary goal of numerical relativity is to provide estimates of the wave strain, h, from strong gravitational wave sources, to be used in detector templates. The simulations, however, typically measure waves in terms of the Weyl curvature component, {psi}{sub 4}. Assuming Bondi gauge, transforming to the strain h reduces to integration of {psi}{sub 4} twice in time. Integrations performed in either the time or frequency domain, however, lead to secular nonlinear drifts in the resulting strain h. These nonlinear drifts are not explained by the two unknown integration constants which can at most result in linear drifts. We identify a number of fundamental difficulties which can arise from integrating finite length, discretely sampled and noisy data streams. These issues are an artifact of post-processing data. They are independent of the characteristics of the original simulation, such as gauge or numerical method used. We suggest, however, a simple procedure for integrating numerical waveforms in the frequency domain, which is effective at strongly reducing spurious secular nonlinear drifts in the resulting strain.
Numerical integration of massive two-loop Mellin-Barnes integrals in Minkowskian regions
International Nuclear Information System (INIS)
Dubovyk, Ievgen
2016-07-01
Mellin-Barnes (MB) techniques applied to integrals emerging in particle physics perturbative calculations are summarized. New versions of AMBRE packages which construct planar and nonplanar MB representations are shortly discussed. The numerical package MBnumerics.m is presented for the first time which is able to calculate with a high precision multidimensional MB integrals in Minkowskian regions. Examples are given for massive vertex integrals which include threshold effects and several scale parameters.
Numerical Differentiation and Integration through Aitken-Neville Schemes
Directory of Open Access Journals (Sweden)
Ramesh Kumar Muthumalai
2013-09-01
Full Text Available Some new formulas are given to approximate higher order derivatives and integrals through Aitken-Neville iterative schemes for arbitrary spaced grids. An algorithm is given in MATLAB for numerical differentiation. Also, numerical examples are provided to study error analysis of new formulas for numerical differentiation and integration.
Numerical treatments for solving nonlinear mixed integral equation
Directory of Open Access Journals (Sweden)
M.A. Abdou
2016-12-01
Full Text Available We consider a mixed type of nonlinear integral equation (MNLIE of the second kind in the space C[0,T]×L2(Ω,T<1. The Volterra integral terms (VITs are considered in time with continuous kernels, while the Fredholm integral term (FIT is considered in position with singular general kernel. Using the quadratic method and separation of variables method, we obtain a nonlinear system of Fredholm integral equations (NLSFIEs with singular kernel. A Toeplitz matrix method, in each case, is then used to obtain a nonlinear algebraic system. Numerical results are calculated when the kernels take a logarithmic form or Carleman function. Moreover, the error estimates, in each case, are then computed.
Time-symmetric integration in astrophysics
Hernandez, David M.; Bertschinger, Edmund
2018-04-01
Calculating the long-term solution of ordinary differential equations, such as those of the N-body problem, is central to understanding a wide range of dynamics in astrophysics, from galaxy formation to planetary chaos. Because generally no analytic solution exists to these equations, researchers rely on numerical methods that are prone to various errors. In an effort to mitigate these errors, powerful symplectic integrators have been employed. But symplectic integrators can be severely limited because they are not compatible with adaptive stepping and thus they have difficulty in accommodating changing time and length scales. A promising alternative is time-reversible integration, which can handle adaptive time-stepping, but the errors due to time-reversible integration in astrophysics are less understood. The goal of this work is to study analytically and numerically the errors caused by time-reversible integration, with and without adaptive stepping. We derive the modified differential equations of these integrators to perform the error analysis. As an example, we consider the trapezoidal rule, a reversible non-symplectic integrator, and show that it gives secular energy error increase for a pendulum problem and for a Hénon-Heiles orbit. We conclude that using reversible integration does not guarantee good energy conservation and that, when possible, use of symplectic integrators is favoured. We also show that time-symmetry and time-reversibility are properties that are distinct for an integrator.
Time-symmetric integration in astrophysics
Hernandez, David M.; Bertschinger, Edmund
2018-01-01
Calculating the long term solution of ordinary differential equations, such as those of the N-body problem, is central to understanding a wide range of dynamics in astrophysics, from galaxy formation to planetary chaos. Because generally no analytic solution exists to these equations, researchers rely on numerical methods which are prone to various errors. In an effort to mitigate these errors, powerful symplectic integrators have been employed. But symplectic integrators can be severely limited because they are not compatible with adaptive stepping and thus they have difficulty accommodating changing time and length scales. A promising alternative is time-reversible integration, which can handle adaptive time stepping, but the errors due to time-reversible integration in astrophysics are less understood. The goal of this work is to study analytically and numerically the errors caused by time-reversible integration, with and without adaptive stepping. We derive the modified differential equations of these integrators to perform the error analysis. As an example, we consider the trapezoidal rule, a reversible non-symplectic integrator, and show it gives secular energy error increase for a pendulum problem and for a Hénon-Heiles orbit. We conclude that using reversible integration does not guarantee good energy conservation and that, when possible, use of symplectic integrators is favored. We also show that time-symmetry and time-reversibility are properties that are distinct for an integrator.
An efficient numerical integral in three-dimensional electromagnetic field computations
Whetten, Frank L.; Liu, Kefeng; Balanis, Constantine A.
1990-01-01
An improved algorithm for efficiently computing a sinusoid and an exponential integral commonly encountered in method-of-moments solutions is presented. The new algorithm has been tested for accuracy and computer execution time against both numerical integration and other existing numerical algorithms, and has outperformed them. Typical execution time comparisons on several computers are given.
A Generalized Technique in Numerical Integration
Safouhi, Hassan
2018-02-01
Integration by parts is one of the most popular techniques in the analysis of integrals and is one of the simplest methods to generate asymptotic expansions of integral representations. The product of the technique is usually a divergent series formed from evaluating boundary terms; however, sometimes the remaining integral is also evaluated. Due to the successive differentiation and anti-differentiation required to form the series or the remaining integral, the technique is difficult to apply to problems more complicated than the simplest. In this contribution, we explore a generalized and formalized integration by parts to create equivalent representations to some challenging integrals. As a demonstrative archetype, we examine Bessel integrals, Fresnel integrals and Airy functions.
Numerical studies of time-independent and time-dependent scattering by several elliptical cylinders
Nigsch, Martin
2007-07-01
A numerical solution to the problem of time-dependent scattering by an array of elliptical cylinders with parallel axes is presented. The solution is an exact one, based on the separation-of-variables technique in the elliptical coordinate system, the addition theorem for Mathieu functions, and numerical integration. Time-independent solutions are described by a system of linear equations of infinite order which are truncated for numerical computations. Time-dependent solutions are obtained by numerical integration involving a large number of these solutions. First results of a software package generating these solutions are presented: wave propagation around three impenetrable elliptical scatterers. As far as we know, this method described has never been used for time-dependent multiple scattering.
DEFF Research Database (Denmark)
Val, Maria Rosa Rovira; Lehmann, Martin; Zinenko, Anna
dramatically with many of the world’s economies facing downturn and a looming possible recession; and the global economic and political balance changing; (ii) most larger companies and quite a few SMEs now have a mature knowledge of these standards; and (iii) some standards are advocating for integration...... procedures, such as cases of for example ISO integrated management systems, mutual equivalences recognition of Global Compact-GRI-ISO26000, or the case of IIRC initiative to develop integrated reporting on an organization’s Financial, Environmental, Social and Governance performance. This paper focuses...
Numerical integration and optimization of motions for multibody dynamic systems
Aguilar Mayans, Joan
This thesis considers the optimization and simulation of motions involving rigid body systems. It does so in three distinct parts, with the following topics: optimization and analysis of human high-diving motions, efficient numerical integration of rigid body dynamics with contacts, and motion optimization of a two-link robot arm using Finite-Time Lyapunov Analysis. The first part introduces the concept of eigenpostures, which we use to simulate and analyze human high-diving motions. Eigenpostures are used in two different ways: first, to reduce the complexity of the optimal control problem that we solve to obtain such motions, and second, to generate an eigenposture space to which we map existing real world motions to better analyze them. The benefits of using eigenpostures are showcased through different examples. The second part reviews an extensive list of integration algorithms used for the integration of rigid body dynamics. We analyze the accuracy and stability of the different integrators in the three-dimensional space and the rotation space SO(3). Integrators with an accuracy higher than first order perform more efficiently than integrators with first order accuracy, even in the presence of contacts. The third part uses Finite-time Lyapunov Analysis to optimize motions for a two-link robot arm. Finite-Time Lyapunov Analysis diagnoses the presence of time-scale separation in the dynamics of the optimized motion and provides the information and methodology for obtaining an accurate approximation to the optimal solution, avoiding the complications that timescale separation causes for alternative solution methods.
Numerical simulations of time-resolved quantum electronics
International Nuclear Information System (INIS)
Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier
2014-01-01
Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects–mathematical and numerical–associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation
DEFF Research Database (Denmark)
Ding, Yi; Nyeng, Preben; Ostergaard, Jacob
2012-01-01
This paper provides an overview of the Ecogrid EU project, which is a large-scale demonstration project on the Danish island Bornholm. It provides Europe a fast track evolution towards smart grid dissemination and deployment in the distribution network. Objective of Ecogrid EU is to illustrate th...... customers will be equipped with demand response devices with smart controllers and smart meters, allowing them to respond to real-time prices based on their pre-programmed demand-response preferences.......This paper provides an overview of the Ecogrid EU project, which is a large-scale demonstration project on the Danish island Bornholm. It provides Europe a fast track evolution towards smart grid dissemination and deployment in the distribution network. Objective of Ecogrid EU is to illustrate...
Integrating spatial and numerical structure in mathematical patterning
Ni’mah, K.; Purwanto; Irawan, E. B.; Hidayanto, E.
2018-03-01
This paper reports a study monitoring the integrating spatial and numerical structure in mathematical patterning skills of 30 students grade 7th of junior high school. The purpose of this research is to clarify the processes by which learners construct new knowledge in mathematical patterning. Findings indicate that: (1) students are unable to organize the structure of spatial and numerical, (2) students were only able to organize the spatial structure, but the numerical structure is still incorrect, (3) students were only able to organize numerical structure, but its spatial structure is still incorrect, (4) students were able to organize both of the spatial and numerical structure.
Parallel time integration software
Energy Technology Data Exchange (ETDEWEB)
2014-07-01
This package implements an optimal-scaling multigrid solver for the (non) linear systems that arise from the discretization of problems with evolutionary behavior. Typically, solution algorithms for evolution equations are based on a time-marching approach, solving sequentially for one time step after the other. Parallelism in these traditional time-integrarion techniques is limited to spatial parallelism. However, current trends in computer architectures are leading twards system with more, but not faster. processors. Therefore, faster compute speeds must come from greater parallelism. One approach to achieve parallelism in time is with multigrid, but extending classical multigrid methods for elliptic poerators to this setting is a significant achievement. In this software, we implement a non-intrusive, optimal-scaling time-parallel method based on multigrid reduction techniques. The examples in the package demonstrate optimality of our multigrid-reduction-in-time algorithm (MGRIT) for solving a variety of parabolic equations in two and three sparial dimensions. These examples can also be used to show that MGRIT can achieve significant speedup in comparison to sequential time marching on modern architectures.
Parallel Algorithm for Adaptive Numerical Integration
International Nuclear Information System (INIS)
Sujatmiko, M.; Basarudin, T.
1997-01-01
This paper presents an automation algorithm for integration using adaptive trapezoidal method. The interval is adaptively divided where the width of sub interval are different and fit to the behavior of its function. For a function f, an integration on interval [a,b] can be obtained, with maximum tolerance ε, using estimation (f, a, b, ε). The estimated solution is valid if the error is still in a reasonable range, fulfil certain criteria. If the error is big, however, the problem is solved by dividing it into to similar and independent sub problem on to separate [a, (a+b)/2] and [(a+b)/2, b] interval, i. e. ( f, a, (a+b)/2, ε/2) and (f, (a+b)/2, b, ε/2) estimations. The problems are solved in two different kinds of processor, root processor and worker processor. Root processor function ti divide a main problem into sub problems and distribute them to worker processor. The division mechanism may go further until all of the sub problem are resolved. The solution of each sub problem is then submitted to the root processor such that the solution for the main problem can be obtained. The algorithm is implemented on C-programming-base distributed computer networking system under parallel virtual machine platform
Case studies in the numerical solution of oscillatory integrals
International Nuclear Information System (INIS)
Adam, G.
1992-06-01
A numerical solution of a number of 53,249 test integrals belonging to nine parametric classes was attempted by two computer codes: EAQWOM (Adam and Nobile, IMA Journ. Numer. Anal. (1991) 11, 271-296) and DO1ANF (Mark 13, 1988) from the NAG library software. For the considered test integrals, EAQWOM was found to be superior to DO1ANF as it concerns robustness, reliability, and friendly user information in case of failure. (author). 9 refs, 3 tabs
Numerical integrators for Stiff and Stiff oscillatory First Order initial ...
African Journals Online (AJOL)
Numerical integrators for Stiff and Stiff oscillatory First Order initial value problems. ... Journal of the Nigerian Association of Mathematical Physics ... In this paper, efforts are geared towards the numerical solution of the first order initial value problem (I.V.P) of the form Y\\' = F(X,Y), X∈[ a, b] , Y(a) = Y0, where Y\\' is the total ...
SNS Diagnostics Timing Integration
Long, Cary D; Murphy, Darryl J; Pogge, James; Purcell, John D; Sundaram, Madhan
2005-01-01
The Spallation Neutron Source (SNS) accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The SNS diagnostics platform is PC-based running Windows XP Embedded for its OS and LabVIEW as its programming language. Coordinating timing among the various diagnostics instruments with the generation of the beam pulse is a challenging task that we have chosen to divide into three phases. First, timing was derived from VME based systems. In the second phase, described in this paper, timing pulses are generated by an in house designed PCI timing card installed in ten diagnostics PCs. Using fan-out modules, enough triggers were generated for all instruments. This paper describes how the Timing NAD (Network Attached Device) was rapidly developed using our NAD template, LabVIEW's PCI driver wizard, and LabVIEW Channel Access library. The NAD...
Translation and integration of numerical atomic orbitals in linear molecules
International Nuclear Information System (INIS)
Heinäsmäki, Sami
2014-01-01
We present algorithms for translation and integration of atomic orbitals for LCAO calculations in linear molecules. The method applies to arbitrary radial functions given on a numerical mesh. The algorithms are based on pseudospectral differentiation matrices in two dimensions and the corresponding two-dimensional Gaussian quadratures. As a result, multicenter overlap and Coulomb integrals can be evaluated effectively
Translation and integration of numerical atomic orbitals in linear molecules
Energy Technology Data Exchange (ETDEWEB)
Heinäsmäki, Sami, E-mail: sami.heinasmaki@gmail.com [Department of Physics, University of Oulu, FIN-90014, Oulu (Finland)
2014-02-14
We present algorithms for translation and integration of atomic orbitals for LCAO calculations in linear molecules. The method applies to arbitrary radial functions given on a numerical mesh. The algorithms are based on pseudospectral differentiation matrices in two dimensions and the corresponding two-dimensional Gaussian quadratures. As a result, multicenter overlap and Coulomb integrals can be evaluated effectively.
Translation and integration of numerical atomic orbitals in linear molecules.
Heinäsmäki, Sami
2014-02-14
We present algorithms for translation and integration of atomic orbitals for LCAO calculations in linear molecules. The method applies to arbitrary radial functions given on a numerical mesh. The algorithms are based on pseudospectral differentiation matrices in two dimensions and the corresponding two-dimensional Gaussian quadratures. As a result, multicenter overlap and Coulomb integrals can be evaluated effectively.
Translation and integration of numerical atomic orbitals in linear molecules
Heinäsmäki, Sami
2014-02-01
We present algorithms for translation and integration of atomic orbitals for LCAO calculations in linear molecules. The method applies to arbitrary radial functions given on a numerical mesh. The algorithms are based on pseudospectral differentiation matrices in two dimensions and the corresponding two-dimensional Gaussian quadratures. As a result, multicenter overlap and Coulomb integrals can be evaluated effectively.
Canonical algorithms for numerical integration of charged particle motion equations
Efimov, I. N.; Morozov, E. A.; Morozova, A. R.
2017-02-01
A technique for numerically integrating the equation of charged particle motion in a magnetic field is considered. It is based on the canonical transformations of the phase space in Hamiltonian mechanics. The canonical transformations make the integration process stable against counting error accumulation. The integration algorithms contain a minimum possible amount of arithmetics and can be used to design accelerators and devices of electron and ion optics.
Numerical Integration of the Transport Equation For Infinite Homogeneous Media
Energy Technology Data Exchange (ETDEWEB)
Haakansson, Rune
1962-01-15
The transport equation for neutrons in infinite homogeneous media is solved by direct numerical integration. Accounts are taken to the anisotropy and the inelastic scattering. The integration has been performed by means of the trapezoidal rule and the length of the energy intervals are constant in lethargy scale. The machine used is a Ferranti Mercury computer. Results are given for water, heavy water, aluminium water mixture and iron-aluminium-water mixture.
Conservation properties of numerical integrators for highly oscillatory Hamiltonian systems
Cohen, David
2017-01-01
Modulated Fourier expansion is used to show long-time near-conservation of the total and oscillatory energies of numerical methods for Hamiltonian systems with highly oscillatory solutions. The numerical methods considered are an extension of the trigonometric methods. A brief discussion of conservation properties in the continuous problem and in the multi-frequency case is also given
International Nuclear Information System (INIS)
Witkowski, W.R.; Eldred, M.S.; Harding, D.C.
1994-01-01
The use of state-of-the-art numerical analysis tools to determine the optimal design of a radioactive material (RAM) transportation container is investigated. The design of a RAM package's components involves a complex coupling of structural, thermal, and radioactive shielding analyses. The final design must adhere to very strict design constraints. The current technique used by cask designers is uncoupled and involves designing each component separately with respect to its driving constraint. With the use of numerical optimization schemes, the complex couplings can be considered directly, and the performance of the integrated package can be maximized with respect to the analysis conditions. This can lead to more efficient package designs. Thermal and structural accident conditions are analyzed in the shape optimization of a simplified cask design. In this paper, details of the integration of numerical analysis tools, development of a process model, nonsmoothness difficulties with the optimization of the cask, and preliminary results are discussed
Monograph - The Numerical Integration of Ordinary Differential Equations.
Hull, T. E.
The materials presented in this monograph are intended to be included in a course on ordinary differential equations at the upper division level in a college mathematics program. These materials provide an introduction to the numerical integration of ordinary differential equations, and they can be used to supplement a regular text on this…
Symplectic integrators with adaptive time steps
Richardson, A. S.; Finn, J. M.
2012-01-01
In recent decades, there have been many attempts to construct symplectic integrators with variable time steps, with rather disappointing results. In this paper, we identify the causes for this lack of performance, and find that they fall into two categories. In the first, the time step is considered a function of time alone, Δ = Δ(t). In this case, backward error analysis shows that while the algorithms remain symplectic, parametric instabilities may arise because of resonance between oscillations of Δ(t) and the orbital motion. In the second category the time step is a function of phase space variables Δ = Δ(q, p). In this case, the system of equations to be solved is analyzed by introducing a new time variable τ with dt = Δ(q, p) dτ. The transformed equations are no longer in Hamiltonian form, and thus do not benefit from integration methods which would be symplectic for Hamiltonian systems. We analyze two methods for integrating the transformed equations which do, however, preserve the structure of the original equations. The first is an extended phase space method, which has been successfully used in previous studies of adaptive time step symplectic integrators. The second, novel, method is based on a non-canonical mixed-variable generating function. Numerical trials for both of these methods show good results, without parametric instabilities or spurious growth or damping. It is then shown how to adapt the time step to an error estimate found by backward error analysis, in order to optimize the time-stepping scheme. Numerical results are obtained using this formulation and compared with other time-stepping schemes for the extended phase space symplectic method.
Preserving Simplecticity in the Numerical Integration of Linear Beam Optics
Energy Technology Data Exchange (ETDEWEB)
Allen, Christopher K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2017-07-01
Presented are mathematical tools and methods for the development of numerical integration techniques that preserve the symplectic condition inherent to mechanics. The intended audience is for beam physicists with backgrounds in numerical modeling and simulation with particular attention to beam optics applications. The paper focuses on Lie methods that are inherently symplectic regardless of the integration accuracy order. Section 2 provides the mathematically tools used in the sequel and necessary for the reader to extend the covered techniques. Section 3 places those tools in the context of charged-particle beam optics; in particular linear beam optics is presented in terms of a Lie algebraic matrix representation. Section 4 presents numerical stepping techniques with particular emphasis on a third-order leapfrog method. Section 5 discusses the modeling of field imperfections with particular attention to the fringe fields of quadrupole focusing magnets. The direct computation of a third order transfer matrix for a fringe field is shown.
Numerical integration of discontinuous functions: moment fitting and smart octree
Hubrich, Simeon; Di Stolfo, Paolo; Kudela, László; Kollmannsberger, Stefan; Rank, Ernst; Schröder, Andreas; Düster, Alexander
2017-11-01
A fast and simple grid generation can be achieved by non-standard discretization methods where the mesh does not conform to the boundary or the internal interfaces of the problem. However, this simplification leads to discontinuous integrands for intersected elements and, therefore, standard quadrature rules do not perform well anymore. Consequently, special methods are required for the numerical integration. To this end, we present two approaches to obtain quadrature rules for arbitrary domains. The first approach is based on an extension of the moment fitting method combined with an optimization strategy for the position and weights of the quadrature points. In the second approach, we apply the smart octree, which generates curved sub-cells for the integration mesh. To demonstrate the performance of the proposed methods, we consider several numerical examples, showing that the methods lead to efficient quadrature rules, resulting in less integration points and in high accuracy.
Symbolic-Numeric Integration of the Dynamical Cosserat Equations
Lyakhov, Dmitry A.
2017-08-29
We devise a symbolic-numeric approach to the integration of the dynamical part of the Cosserat equations, a system of nonlinear partial differential equations describing the mechanical behavior of slender structures, like fibers and rods. This is based on our previous results on the construction of a closed form general solution to the kinematic part of the Cosserat system. Our approach combines methods of numerical exponential integration and symbolic integration of the intermediate system of nonlinear ordinary differential equations describing the dynamics of one of the arbitrary vector-functions in the general solution of the kinematic part in terms of the module of the twist vector-function. We present an experimental comparison with the well-established generalized \\\\alpha -method illustrating the computational efficiency of our approach for problems in structural mechanics.
ARABIC NUMERAL TIME ACCUMULATOR FOR SOMTER PLAYBACK SYSTEM MOD 2
The SOMTER Arabic Numeral Time Accululator (SANTA) is an electronic counter scaled in time units, with a capacity of twenty days. Input may be in...signals suitable for printing of its contents in Arabic numeral format with a digital recorder with a single row of electric stili. The logical design, circuit design, and output voltage waveforms of SANTA are discussed. (Author)
Producing complex spoken numerals for time and space
Meeuwissen, M.H.W.
2004-01-01
This thesis addressed the spoken production of complex numerals for time and space. The production of complex numerical expressions like those involved in telling time (e.g., 'quarter to four') or producing house numbers (e.g., 'two hundred forty-five') has been almost completely ignored. Yet, adult
Numerical solution of nonlinear Hammerstein fuzzy functional integral equations
Enkov, Svetoslav; Georgieva, Atanaska; Nikolla, Renato
2016-12-01
In this work we investigate nonlinear Hammerstein fuzzy functional integral equation. Our aim is to provide an efficient iterative method of successive approximations by optimal quadrature formula for classes of fuzzy number-valued functions of Lipschitz type to approximate the solution. We prove the convergence of the method by Banach's fixed point theorem and investigate the numerical stability of the presented method with respect to the choice of the first iteration. Finally, illustrative numerical experiment demonstrate the accuracy and the convergence of the proposed method.
Numerical Integration with Graphical Processing Unit for QKD Simulation
2014-03-27
33 NUMERICAL INTEGRATION WITH GRAPHICAL PROCESSING UNIT FOR QKD SIMULATION Virginia R. Garrett, B.S.E.E. Captain, USAF Approved: //signed// Douglas ...17] B. Nelson, R. Kirby , and R. Haimes, “Gpu-based volume visualization from high- order finite element fields,” IEEE Transactions on Visualization and...Intel i7-3610QM CPU. 15. SUBJECT TERMS Software Engineering, GPU Programming, Numerical Methods, Quantum Key Distribution U U U UU 74 Dr. Douglas Hodson, AFIT/ENG (937) 785-3636 x4719
International Nuclear Information System (INIS)
Friedman, A.; Auerbach, S.P.
1988-01-01
In a one-dimensional anharmonic potential well, the period of an orbit is a function of its energy. The true motion in such a well is regular, since energy conservation constrains the velocity at each value of the coordinate. Nontheless, when the orbit is computed numerically, stochastic behavior can result. The phenomenon of numerically induced stochasticity has significance in several contexts. Firstly, a numerical investigation of the regions of phase space accessible to an orbit may lead to erroneous results, if the timestep is too large or the mover inappropriate. Furthermore, conclusions about orbital stability based on numerical integrations may be erroneous, since neighboring chaotic orbits diverge exponentially, even if the chaos is numerically induced. When studying the dynamics of a physical system, one should demonstrate that any chaos observed is not numerically induced. Also, linearized simulations of collective phenomena must avoid numerically induced stochasticity, since the zero-order and perturbed trajectories are 'neighboring'. Finally, trajectory crossings in PIC simulations can lead to enhanced noise and other errors. In addition to these investigations, an analysis is also made of the long-term behavior of numerical trajectories (small ΔT analysis). (Nogami, K.)
Long Pulse Integrator of Variable Integral Time Constant
International Nuclear Information System (INIS)
Wang Yong; Ji Zhenshan; Du Xiaoying; Wu Yichun; Li Shi; Luo Jiarong
2010-01-01
A kind of new long pulse integrator was designed based on the method of variable integral time constant and deducting integral drift by drift slope. The integral time constant can be changed by choosing different integral resistors, in order to improve the signal-to-noise ratio, and avoid output saturation; the slope of integral drift of a certain period of time can be calculated by digital signal processing, which can be used to deduct the drift of original integral signal in real time to reduce the integral drift. The tests show that this kind of long pulse integrator is good at reducing integral drift, which also can eliminate the effects of changing integral time constant. According to experiments, the integral time constant can be changed by remote control and manual adjustment of integral drift is avoided, which can improve the experiment efficiency greatly and can be used for electromagnetic measurement in Tokamak experiment. (authors)
GHOLAMI, SAEID; BABOLIAN, ESMAIL; JAVIDI, MOHAMMAD
2016-01-01
This paper presents a new numerical approach to solve single and multiterm time fractional diffusion equations. In this work, the space dimension is discretized to the Gauss$-$Lobatto points. We use the normalized Grunwald approximation for the time dimension and a pseudospectral successive integration matrix for the space dimension. This approach shows that with fewer numbers of points, we can approximate the solution with more accuracy. Some examples with numerical results in tables and fig...
A comparison of the efficiency of numerical methods for integrating chemical kinetic rate equations
Radhakrishnan, K.
1984-01-01
The efficiency of several algorithms used for numerical integration of stiff ordinary differential equations was compared. The methods examined included two general purpose codes EPISODE and LSODE and three codes (CHEMEQ, CREK1D and GCKP84) developed specifically to integrate chemical kinetic rate equations. The codes were applied to two test problems drawn from combustion kinetics. The comparisons show that LSODE is the fastest code available for the integration of combustion kinetic rate equations. It is shown that an iterative solution of the algebraic energy conservation equation to compute the temperature can be more efficient then evaluating the temperature by integrating its time-derivative.
International Nuclear Information System (INIS)
Chernyshenko, Dmitri; Fangohr, Hans
2015-01-01
In the finite difference method which is commonly used in computational micromagnetics, the demagnetizing field is usually computed as a convolution of the magnetization vector field with the demagnetizing tensor that describes the magnetostatic field of a cuboidal cell with constant magnetization. An analytical expression for the demagnetizing tensor is available, however at distances far from the cuboidal cell, the numerical evaluation of the analytical expression can be very inaccurate. Due to this large-distance inaccuracy numerical packages such as OOMMF compute the demagnetizing tensor using the explicit formula at distances close to the originating cell, but at distances far from the originating cell a formula based on an asymptotic expansion has to be used. In this work, we describe a method to calculate the demagnetizing field by numerical evaluation of the multidimensional integral in the demagnetizing tensor terms using a sparse grid integration scheme. This method improves the accuracy of computation at intermediate distances from the origin. We compute and report the accuracy of (i) the numerical evaluation of the exact tensor expression which is best for short distances, (ii) the asymptotic expansion best suited for large distances, and (iii) the new method based on numerical integration, which is superior to methods (i) and (ii) for intermediate distances. For all three methods, we show the measurements of accuracy and execution time as a function of distance, for calculations using single precision (4-byte) and double precision (8-byte) floating point arithmetic. We make recommendations for the choice of scheme order and integrating coefficients for the numerical integration method (iii). - Highlights: • We study the accuracy of demagnetization in finite difference micromagnetics. • We introduce a new sparse integration method to compute the tensor more accurately. • Newell, sparse integration and asymptotic method are compared for all ranges
Numerical solution of time dependent neutron transport equation. An application
International Nuclear Information System (INIS)
Barroso, Dalton Ellery Girao
2000-01-01
In this work we show a simple method to solve numerically the time-dependent neutron transport equation which is a simple extension of the numerical methods used to solve the time-independent static transport equation. This is possible because the time-discretized transport equation has the same form as the time-independent transport equation, with only some additional terms. A general outline of the method is given and used to evaluate the neutron flux in a microexplosion calculation of a highly compressed micro fissile system composed by DT-Pu-Be microsphere. (author)
Singularity Preserving Numerical Methods for Boundary Integral Equations
Kaneko, Hideaki (Principal Investigator)
1996-01-01
In the past twelve months (May 8, 1995 - May 8, 1996), under the cooperative agreement with Division of Multidisciplinary Optimization at NASA Langley, we have accomplished the following five projects: a note on the finite element method with singular basis functions; numerical quadrature for weakly singular integrals; superconvergence of degenerate kernel method; superconvergence of the iterated collocation method for Hammersteion equations; and singularity preserving Galerkin method for Hammerstein equations with logarithmic kernel. This final report consists of five papers describing these projects. Each project is preceeded by a brief abstract.
Steffensen's Integral Inequality on Time Scales
Directory of Open Access Journals (Sweden)
Ozkan Umut Mutlu
2007-01-01
Full Text Available We establish generalizations of Steffensen's integral inequality on time scales via the diamond- dynamic integral, which is defined as a linear combination of the delta and nabla integrals.
Integrated numerical modeling of a laser gun injector
International Nuclear Information System (INIS)
Liu, H.; Benson, S.; Bisognano, J.; Liger, P.; Neil, G.; Neuffer, D.; Sinclair, C.; Yunn, B.
1993-01-01
CEBAF is planning to incorporate a laser gun injector into the linac front end as a high-charge cw source for a high-power free electron laser and nuclear physics. This injector consists of a DC laser gun, a buncher, a cryounit and a chicane. The performance of the injector is predicted based on integrated numerical modeling using POISSON, SUPERFISH and PARMELA. The point-by-point method incorporated into PARMELA by McDonald is chosen for space charge treatment. The concept of open-quotes conditioning for final bunchingclose quotes is employed to vary several crucial parameters of the system for achieving highest peak current while maintaining low emittance and low energy spread. Extensive parameter variation studies show that the design will perform better than the specifications for FEL operations aimed at industrial applications and fundamental scientific research. The calculation also shows that the injector will perform as an extremely bright cw electron source
Comparison of four stable numerical methods for Abel's integral equation
Murio, Diego A.; Mejia, Carlos E.
1991-01-01
The 3-D image reconstruction from cone-beam projections in computerized tomography leads naturally, in the case of radial symmetry, to the study of Abel-type integral equations. If the experimental information is obtained from measured data, on a discrete set of points, special methods are needed in order to restore continuity with respect to the data. A new combined Regularized-Adjoint-Conjugate Gradient algorithm, together with two different implementations of the Mollification Method (one based on a data filtering technique and the other on the mollification of the kernal function) and a regularization by truncation method (initially proposed for 2-D ray sample schemes and more recently extended to 3-D cone-beam image reconstruction) are extensively tested and compared for accuracy and numerical stability as functions of the level of noise in the data.
Integrated numerical modeling of a laser gun injector
International Nuclear Information System (INIS)
Liu, H.; Benson, S.; Bisognano, J.; Liger, P.; Neil, G.; Neuffer, D.; Sinclair, C.; Yunn, B.
1993-06-01
CEBAF is planning to incorporate a laser gun injector into the linac front end as a high-charge cw source for a high-power free electron laser and nuclear physics. This injector consists of a DC laser gun, a buncher, a cryounit and a chicane. The performance of the injector is predicted based on integrated numerical modeling using POISSON, SUPERFISH and PARMELA. The point-by-point method incorporated into PARMELA by McDonald is chosen for space charge treatment. The concept of ''conditioning for final bunching'' is employed to vary several crucial parameters of the system for achieving highest peak current while maintaining low emittance and low energy spread. Extensive parameter variation studies show that the design will perform beyond the specifications for FEL operations aimed at industrial applications and fundamental scientific research. The calculation also shows that the injector will perform as an extremely bright cw electron source
Dose calculation using a numerical method based on Haar wavelets integration
Energy Technology Data Exchange (ETDEWEB)
Belkadhi, K., E-mail: khaled.belkadhi@ult-tunisie.com [Unité de Recherche de Physique Nucléaire et des Hautes Énergies, Faculté des Sciences de Tunis, Université Tunis El-Manar (Tunisia); Manai, K. [Unité de Recherche de Physique Nucléaire et des Hautes Énergies, Faculté des Sciences de Tunis, Université Tunis El-Manar (Tunisia); College of Science and Arts, University of Bisha, Bisha (Saudi Arabia)
2016-03-11
This paper deals with the calculation of the absorbed dose in an irradiation cell of gamma rays. Direct measurement and simulation have shown that they are expensive and time consuming. An alternative to these two operations is numerical methods, a quick and efficient way can furnish an estimation of the absorbed dose by giving an approximation of the photon flux at a specific point of space. To validate the numerical integration method based on the Haar wavelet for absorbed dose estimation, a study with many configurations was performed. The obtained results with the Haar wavelet method showed a very good agreement with the simulation highlighting good efficacy and acceptable accuracy. - Highlights: • A numerical integration method using Haar wavelets is detailed. • Absorbed dose is estimated with Haar wavelets method. • Calculated absorbed dose using Haar wavelets and Monte Carlo simulation using Geant4 are compared.
Numerical simulation of a cabin ventilation subsystem in a space station oriented real-time system
Directory of Open Access Journals (Sweden)
Zezheng QIU
2017-12-01
Full Text Available An environment control and life support system (ECLSS is an important system in a space station. The ECLSS is a typical complex system, and the real-time simulation technology can help to accelerate its research process by using distributed hardware in a loop simulation system. An implicit fixed time step numerical integration method is recommended for a real-time simulation system with time-varying parameters. However, its computational efficiency is too low to satisfy the real-time data interaction, especially for the complex ECLSS system running on a PC cluster. The instability problem of an explicit method strongly limits its application in the ECLSS real-time simulation although it has a high computational efficiency. This paper proposes an improved numerical simulation method to overcome the instability problem based on the explicit Euler method. A temperature and humidity control subsystem (THCS is firstly established, and its numerical stability is analyzed by using the eigenvalue estimation theory. Furthermore, an adaptive operator is proposed to avoid the potential instability problem. The stability and accuracy of the proposed method are investigated carefully. Simulation results show that this proposed method can provide a good way for some complex time-variant systems to run their real-time simulation on a PC cluster. Keywords: Numerical integration method, Real-time simulation, Stability, THCS, Time-variant system
Time delay systems theory, numerics, applications, and experiments
Ersal, Tulga; Orosz, Gábor
2017-01-01
This volume collects contributions related to selected presentations from the 12th IFAC Workshop on Time Delay Systems, Ann Arbor, June 28-30, 2015. The included papers present novel techniques and new results of delayed dynamical systems. The topical spectrum covers control theory, numerical analysis, engineering and biological applications as well as experiments and case studies. The target audience primarily comprises research experts in the field of time delay systems, but the book may also be beneficial for graduate students alike. .
Advances in Integrated Vehicle Thermal Management and Numerical Simulation
Directory of Open Access Journals (Sweden)
Yan Wang
2017-10-01
Full Text Available With the increasing demands for vehicle dynamic performance, economy, safety and comfort, and with ever stricter laws concerning energy conservation and emissions, vehicle power systems are becoming much more complex. To pursue high efficiency and light weight in automobile design, the power system and its vehicle integrated thermal management (VITM system have attracted widespread attention as the major components of modern vehicle technology. Regarding the internal combustion engine vehicle (ICEV, its integrated thermal management (ITM mainly contains internal combustion engine (ICE cooling, turbo-charged cooling, exhaust gas recirculation (EGR cooling, lubrication cooling and air conditioning (AC or heat pump (HP. As for electric vehicles (EVs, the ITM mainly includes battery cooling/preheating, electric machines (EM cooling and AC or HP. With the rational effective and comprehensive control over the mentioned dynamic devices and thermal components, the modern VITM can realize collaborative optimization of multiple thermodynamic processes from the aspect of system integration. Furthermore, the computer-aided calculation and numerical simulation have been the significant design methods, especially for complex VITM. The 1D programming can correlate multi-thermal components and the 3D simulating can develop structuralized and modularized design. Additionally, co-simulations can virtualize simulation of various thermo-hydraulic behaviors under the vehicle transient operational conditions. This article reviews relevant researching work and current advances in the ever broadening field of modern vehicle thermal management (VTM. Based on the systematic summaries of the design methods and applications of ITM, future tasks and proposals are presented. This article aims to promote innovation of ITM, strengthen the precise control and the performance predictable ability, furthermore, to enhance the level of research and development (R&D.
An integral equation-based numerical solver for Taylor states in toroidal geometries
O'Neil, Michael; Cerfon, Antoine J.
2018-04-01
We present an algorithm for the numerical calculation of Taylor states in toroidal and toroidal-shell geometries using an analytical framework developed for the solution to the time-harmonic Maxwell equations. Taylor states are a special case of what are known as Beltrami fields, or linear force-free fields. The scheme of this work relies on the generalized Debye source representation of Maxwell fields and an integral representation of Beltrami fields which immediately yields a well-conditioned second-kind integral equation. This integral equation has a unique solution whenever the Beltrami parameter λ is not a member of a discrete, countable set of resonances which physically correspond to spontaneous symmetry breaking. Several numerical examples relevant to magnetohydrodynamic equilibria calculations are provided. Lastly, our approach easily generalizes to arbitrary geometries, both bounded and unbounded, and of varying genus.
Directory of Open Access Journals (Sweden)
Suresh Thenozhi
2012-01-01
Full Text Available An important objective of health monitoring systems for tall buildings is to diagnose the state of the building and to evaluate its possible damage. In this paper, we use our prototype to evaluate our data-mining approach for the fault monitoring. The offset cancellation and high-pass filtering techniques are combined effectively to solve common problems in numerical integration of acceleration signals in real-time applications. The integration accuracy is improved compared with other numerical integrators. Then we introduce a novel method for support vector machine (SVM classification, called convex-concave hull. We use the Jarvis march method to decide the concave (nonconvex hull for the inseparable points. Finally the vertices of the convex-concave hull are applied for SVM training.
Optimal integration time in OCT imaging
Martin, Lorenz; Gräub, Stephan; Meier, Christoph
2015-07-01
When measuring static objects with 3D OCT, two opposing trends occur: If the integration time is too short, the measurement is noisy resulting in granulated textures on measured objects. If the integration time is too long, drifts e.g. due to thermal effects or unstable laser sources lead to blurred images. The Allan variance is a scheme to find the optimal integration time in terms of reducing noise without picking up signal drift. A long-term measurement with short integration time of a reference target under realistic conditions is needed to obtain the database for the calculation of the Allan variance. Longer integration times are simulated by taking averages of subsequent samples. The Allan variance being the mean of the squared differences between two consecutive averages is calculated for different integration times. The optimal integration time is achieved for minimal Allan variance. First, the scheme is explained and discussed with simulated data. Then, reference measurements of layers of adhesive tape made with a 3D OCT device are analysed to find the optimal integration time of the device. Finally, the findings are applied to the detection of water inclusions in calcite. With too short integration time the water inclusions appear with a stained surface. With the integration time increased towards the optimal time, the surfaces of the water inclusions get smoother and easier to discriminate from the background. Ready-to-use Octave code for the computation of the Allan variance is provided.
How to integrate divergent integrals: a pure numerical approach to complex loop calculations
International Nuclear Information System (INIS)
Caravaglios, F.
2000-01-01
Loop calculations involve the evaluation of divergent integrals. Usually [G. 't Hooft, M. Veltman, Nucl. Phys. B 44 (1972) 189] one computes them in a number of dimensions different than four where the integral is convergent and then one performs the analytical continuation and considers the Laurent expansion in powers of ε=n-4. In this paper we discuss a method to extract directly all coefficients of this expansion by means of concrete and well defined integrals in a five-dimensional space. We by-pass the formal and symbolic procedure of analytic continuation; instead we can numerically compute the integrals to extract directly both the coefficient of the pole 1/ε and the finite part
International Nuclear Information System (INIS)
Furukawa, Masaru; Ohkawa, Yushiro; Matsuyama, Akinobu
2016-01-01
A high-accuracy numerical integration algorithm for a charged particle motion is developed. The algorithm is based on the Hamiltonian mechanics and the operator decomposition. The algorithm is made to be time-reversal symmetric, and its order of accuracy can be increased to any order by using a recurrence formula. One of the advantages is that it is an explicit method. An effective way to decompose the time evolution operator is examined; the Poisson tensor is decomposed and non-canonical variables are adopted. The algorithm is extended to a time dependent fields' case by introducing the extended phase space. Numerical tests showing the performance of the algorithm are presented. One is the pure cyclotron motion for a long time period, and the other is a charged particle motion in a rapidly oscillating field. (author)
Directory of Open Access Journals (Sweden)
Nikesh S. Dattani
2012-03-01
Full Text Available One of the most successful methods for calculating reduced density operator dynamics in open quantum systems, that can give numerically exact results, uses Feynman integrals. However, when simulating the dynamics for a given amount of time, the number of time steps that can realistically be used with this method is always limited, therefore one often obtains an approximation of the reduced density operator at a sparse grid of points in time. Instead of relying only on ad hoc interpolation methods (such as splines to estimate the system density operator in between these points, I propose a method that uses physical information to assist with this interpolation. This method is tested on a physically significant system, on which its use allows important qualitative features of the density operator dynamics to be captured with as little as two time steps in the Feynman integral. This method allows for an enormous reduction in the amount of memory and CPU time required for approximating density operator dynamics within a desired accuracy. Since this method does not change the way the Feynman integral itself is calculated, the value of the density operator approximation at the points in time used to discretize the Feynamn integral will be the same whether or not this method is used, but its approximation in between these points in time is considerably improved by this method. A list of ways in which this proposed method can be further improved is presented in the last section of the article.
A numerical integration approach suitable for simulating PWR dynamics using a microcomputer system
International Nuclear Information System (INIS)
Zhiwei, L.; Kerlin, T.W.
1983-01-01
It is attractive to use microcomputer systems to simulate nuclear power plant dynamics for the purpose of teaching and/or control system design. An analysis and a comparison of feasibility of existing numerical integration methods have been made. The criteria for choosing the integration step using various numerical integration methods including the matrix exponential method are derived. In order to speed up the simulation, an approach is presented using the Newton recursion calculus which can avoid convergence limitations in choosing the integration step size. The accuracy consideration will dominate the integration step limited. The advantages of this method have been demonstrated through a case study using CBM model 8032 microcomputer to simulate a reduced order linear PWR model under various perturbations. It has been proven theoretically and practically that the Runge-Kutta method and Adams-Moulton method are not feasible. The matrix exponential method is good at accuracy and fairly good at speed. The Newton recursion method can save 3/4 to 4/5 time compared to the matrix exponential method with reasonable accuracy. Vertical Barhis method can be expanded to deal with nonlinear nuclear power plant models and higher order models as well
Integrating Numerical Computation into the Modeling Instruction Curriculum
Caballero, Marcos D.; Burk, John B.; Aiken, John M.; Thoms, Brian D.; Douglas, Scott S.; Scanlon, Erin M.; Schatz, Michael F.
2014-01-01
Numerical computation (the use of a computer to solve, simulate, or visualize a physical problem) has fundamentally changed the way scientific research is done. Systems that are too difficult to solve in closed form are probed using computation. Experiments that are impossible to perform in the laboratory are studied numerically. Consequently, in…
Numerical Integration of the Vlasov Equation of Two Colliding Beams
Zorzano-Mier, M P
2000-01-01
In a circular collider the motion of particles of one beam is strongly perturbed at the interaction points by the electro-magnetic field associated with the counter-rotating beam. For any two arbitrary initial particle distributions the time evolution of the two beams can be known by solving the coupled system of two Vlasov equations. This collective description is mandatory when the two beams have similar strengths, as in the case of LEP or LHC. The coherent modes excited by this beam-beam interaction can be a strong limitation for the operation of LHC. In this work, the coupled Vlasov equations of two colliding flat beams are solved numerically using a finite difference scheme. The results suggest that, for the collision of beams with equal tunes, the tune shift between the $\\sigma$- and $\\pi$- coherent dipole mode depends on the unperturbed tune $q$ because of the deformation that the so-called dynamic beta effect induces on the beam distribution. Only when the unperturbed tune $q\\rightarrow 0.25$ this tun...
Numerical evaluation of integrals containing a spherical Bessel function by product integration
International Nuclear Information System (INIS)
Lehman, D.R.; Parke, W.C.; Maximon, L.C.
1981-01-01
A method is developed for numerical evaluation of integrals with k-integration range from 0 to infinity that contain a spherical Bessel function j/sub l/(kr) explicitly. The required quadrature weights are easily calculated and the rate of convergence is rapid: only a relatively small number of quadrature points is needed: for an accurate evaluation even when r is large. The quadrature rule is obtained by the method of product integration. With the abscissas chosen to be those of Clenshaw--Curtis and the Chebyshev polynomials as the interpolating polynomials, quadrature weights are obtained that depend on the spherical Bessel function. An inhomogenous recurrence relation is derived from which the weights can be calculated without accumulation of roundoff error. The procedure is summarized as an easily implementable algorithm. Questions of convergence are discussed and the rate of convergence demonstrated for several test integrals. Alternative procedures are given for generating the integration weights and an error analysis of the method is presented
Numerical Integration with GeoGebra in High School
Herceg, Dorde; Herceg, Dragoslav
2010-01-01
The concept of definite integral is almost always introduced as the Riemann integral, which is defined in terms of the Riemann sum, and its geometric interpretation. This definition is hard to understand for high school students. With the aid of mathematical software for visualisation and computation of approximate integrals, the notion of…
Numerical investigation of the late-time Kerr tails
International Nuclear Information System (INIS)
Racz, Istvan; Toth, Gabor Zs
2011-01-01
The late-time behavior of a scalar field on fixed Kerr background is examined in a numerical framework incorporating the techniques of conformal compactification and hyperbolic initial value formulation. The applied code is 1+(1+2) as it is based on the use of the spectral method in the angular directions while in the time-radial section fourth order finite differencing, along with the method of lines, is applied. The evolution of various types of stationary and non-stationary pure multipole initial states are investigated. The asymptotic decay rates are determined not only in the domain of outer communication but along the event horizon and at future null infinity as well. The decay rates are found to be different for stationary and non-stationary initial data, and they also depend on the fall off properties of the initial data toward future null infinity. The energy and angular momentum transfers are found to show significantly different behavior in the initial phase of the time evolution. The quasinormal ringing phase and the tail phase are also investigated. In the tail phase, the decay exponents for the energy and angular momentum losses at I + are found to be smaller than at the horizon which is in accordance with the behavior of the field itself and it means that at late times the energy and angular momentum falling into the black hole become negligible in comparison with the energy and angular momentum radiated toward I + . The energy and angular momentum balances are used as additional verifications of the reliability of our numerical method.
Non-deteriorating time domain numerical algorithms for Maxwell's electrodynamics
Petropavlovsky, S.; Tsynkov, S.
2017-05-01
The Huygens' principle and lacunae can help construct efficient far-field closures for the numerical simulation of unsteady waves propagating over unbounded regions. Those closures can be either standalone or combined with other techniques for the treatment of artificial outer boundaries. A standalone lacunae-based closure can be thought of as a special artificial boundary condition (ABC) that is provably free from any error associated with the domain truncation. If combined with a different type of ABC or a perfectly matched layer (PML), a lacunae-based approach can help remove any long-time deterioration (e.g., instability) that arises at the outer boundary regardless of why it occurs in the first place. A specific difficulty associated with Maxwell's equations of electromagnetism is that in general their solutions do not have classical lacunae and rather have quasi-lacunae. Unlike in the classical case, the field inside the quasi-lacunae is not zero; instead, there is an electrostatic solution driven by the electric charges that accumulate over time. In our previous work [23], we have shown that quasi-lacunae can also be used for building the far-field closures. However, for achieving a provably non-deteriorating performance over arbitrarily long time intervals, the accumulated charges need to be known ahead of time. The main contribution of the current paper is that we remove this limitation and modify the algorithm in such a way that one can rather avoid the accumulation of charge all together. Accordingly, the field inside the quasi-lacunae becomes equal to zero, which facilitates obtaining the temporally uniform error estimates as in the case of classical lacunae. The performance of the modified algorithm is corroborated by a series of numerical simulations. The range of problems that the new method can address includes important combined formulations, for which the interior subproblem may be non-Huygens', and only the exterior subproblem, i.e., the far
Liu, Meilin
2011-07-01
A discontinuous Galerkin finite element method (DG-FEM) with a highly-accurate time integration scheme is presented. The scheme achieves its high accuracy using numerically constructed predictor-corrector integration coefficients. Numerical results show that this new time integration scheme uses considerably larger time steps than the fourth-order Runge-Kutta method when combined with a DG-FEM using higher-order spatial discretization/basis functions for high accuracy. © 2011 IEEE.
Numerical modeling in photonic crystals integrated technology: the COPERNICUS Project
DEFF Research Database (Denmark)
Malaguti, Stefania; Armaroli, Andrea; Bellanca, Gaetano
2011-01-01
Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project.......Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project....
Exact numerical calculation of fixation probability and time on graphs.
Hindersin, Laura; Möller, Marius; Traulsen, Arne; Bauer, Benedikt
2016-12-01
The Moran process on graphs is a popular model to study the dynamics of evolution in a spatially structured population. Exact analytical solutions for the fixation probability and time of a new mutant have been found for only a few classes of graphs so far. Simulations are time-expensive and many realizations are necessary, as the variance of the fixation times is high. We present an algorithm that numerically computes these quantities for arbitrary small graphs by an approach based on the transition matrix. The advantage over simulations is that the calculation has to be executed only once. Building the transition matrix is automated by our algorithm. This enables a fast and interactive study of different graph structures and their effect on fixation probability and time. We provide a fast implementation in C with this note (Hindersin et al., 2016). Our code is very flexible, as it can handle two different update mechanisms (Birth-death or death-Birth), as well as arbitrary directed or undirected graphs. Copyright Â© 2016 Elsevier Ireland Ltd. All rights reserved.
Fauzi, Ahmad
2017-11-01
Numerical computation has many pedagogical advantages: it develops analytical skills and problem-solving skills, helps to learn through visualization, and enhances physics education. Unfortunately, numerical computation is not taught to undergraduate education physics students in Indonesia. Incorporate numerical computation into the undergraduate education physics curriculum presents many challenges. The main challenges are the dense curriculum that makes difficult to put new numerical computation course and most students have no programming experience. In this research, we used case study to review how to integrate numerical computation into undergraduate education physics curriculum. The participants of this research were 54 students of the fourth semester of physics education department. As a result, we concluded that numerical computation could be integrated into undergraduate education physics curriculum using spreadsheet excel combined with another course. The results of this research become complements of the study on how to integrate numerical computation in learning physics using spreadsheet excel.
Integration of the time-dependent heat equation in the fuel rod performance program IAMBUS
International Nuclear Information System (INIS)
West, G.
1982-01-01
An iterative numerical method for integration of the time-dependent heat equation is described. No presuppositions are made for the dependency of the thermal conductivity and heat capacity on space, time and temperature. (orig.) [de
Monolithic Time Delay Integrated APD Arrays Project
National Aeronautics and Space Administration — The overall goal of the proposed program by Epitaxial Technologies is to develop monolithic time delay integrated avalanche photodiode (APD) arrays with sensitivity...
Baczewski, Andrew D.; Bond, Stephen D.
2013-07-01
Generalized Langevin dynamics (GLD) arise in the modeling of a number of systems, ranging from structured fluids that exhibit a viscoelastic mechanical response, to biological systems, and other media that exhibit anomalous diffusive phenomena. Molecular dynamics (MD) simulations that include GLD in conjunction with external and/or pairwise forces require the development of numerical integrators that are efficient, stable, and have known convergence properties. In this article, we derive a family of extended variable integrators for the Generalized Langevin equation with a positive Prony series memory kernel. Using stability and error analysis, we identify a superlative choice of parameters and implement the corresponding numerical algorithm in the LAMMPS MD software package. Salient features of the algorithm include exact conservation of the first and second moments of the equilibrium velocity distribution in some important cases, stable behavior in the limit of conventional Langevin dynamics, and the use of a convolution-free formalism that obviates the need for explicit storage of the time history of particle velocities. Capability is demonstrated with respect to accuracy in numerous canonical examples, stability in certain limits, and an exemplary application in which the effect of a harmonic confining potential is mapped onto a memory kernel.
Directory of Open Access Journals (Sweden)
Jin-Xiu Hu
2014-01-01
Full Text Available A new approach is presented for the numerical evaluation of arbitrary singular domain integrals. In this method, singular domain integrals are transformed into a boundary integral and a radial integral which contains singularities by using the radial integration method. The analytical elimination of singularities condensed in the radial integral formulas can be accomplished by expressing the nonsingular part of the integration kernels as a series of cubic B-spline basis functions of the distance r and using the intrinsic features of the radial integral. In the proposed method, singularities involved in the domain integrals are explicitly transformed to the boundary integrals, so no singularities exist at internal points. A few numerical examples are provided to verify the correctness and robustness of the presented method.
Real-time numerical simulation of the Carnot cycle
International Nuclear Information System (INIS)
Hurkala, J; Gall, M; Kutner, R; Maciejczyk, M
2005-01-01
We developed a highly interactive, multi-windows Java applet which made it possible to simulate and visualize within any platform and internet the Carnot cycle (or engine) in a real-time computer experiment. We extended our previous model and algorithm (Galant et al 2003 Heat Transfer, Newton's Law of Cooling and the Law of Entropy Increase Simulated by the Real-Time Computer Experiments in Java (Lecture Notes in Computer Science vol 2657) pp 45-53, Gall and Kutner 2005 Molecular mechanisms of heat transfer: Debye relaxation versus power-law Physica A 352 347-78) to simulate not only the heat flow but also the macroscopic movement of the piston. Since in reality it is impossible to construct a reversible Carnot engine, the question arises whether it is possible to simulate it at least in a numerical experiment? The positive answer to this question which we found is related to our model and algorithm which make it possible to omit the many-body problem arising when many gas particles simultaneously interact with the mobile piston. As usual, the considerations of phenomenological thermodynamics began with a study of the basic properties of heat engines, hence our approach, besides intrinsic physical significance, is also important from the educational, technological and even environmental points of view
Towards time symmetric N-body integration
Dehnen, Walter
2017-11-01
Computational efficiency demands discretized, hierarchically organized and individually adaptive time-step sizes (known as the block-step scheme) for the time integration of N-body models. However, most existing N-body codes adapt individual step sizes in a way that violates time symmetry (and symplecticity), resulting in artificial secular dissipation (and often secular growth of energy errors). Using single-orbit integrations, I investigate various possibilities to reduce or eliminate irreversibility from the time-stepping scheme. Significant improvements over the standard approach are possible at little extra effort. However, in order to reduce irreversible step-size changes to negligible amounts, such as suitable for long-term integrations of planetary systems, more computational effort is needed, while exact time reversibility appears elusive for discretized individual step sizes.
Real time wave forecasting using wind time history and numerical model
Jain, Pooja; Deo, M. C.; Latha, G.; Rajendran, V.
Operational activities in the ocean like planning for structural repairs or fishing expeditions require real time prediction of waves over typical time duration of say a few hours. Such predictions can be made by using a numerical model or a time series model employing continuously recorded waves. This paper presents another option to do so and it is based on a different time series approach in which the input is in the form of preceding wind speed and wind direction observations. This would be useful for those stations where the costly wave buoys are not deployed and instead only meteorological buoys measuring wind are moored. The technique employs alternative artificial intelligence approaches of an artificial neural network (ANN), genetic programming (GP) and model tree (MT) to carry out the time series modeling of wind to obtain waves. Wind observations at four offshore sites along the east coast of India were used. For calibration purpose the wave data was generated using a numerical model. The predicted waves obtained using the proposed time series models when compared with the numerically generated waves showed good resemblance in terms of the selected error criteria. Large differences across the chosen techniques of ANN, GP, MT were not noticed. Wave hindcasting at the same time step and the predictions over shorter lead times were better than the predictions over longer lead times. The proposed method is a cost effective and convenient option when a site-specific information is desired.
Explicit solution of Calderon preconditioned time domain integral equations
Ulku, Huseyin Arda
2013-07-01
An explicit marching on-in-time (MOT) scheme for solving Calderon-preconditioned time domain integral equations is proposed. The scheme uses Rao-Wilton-Glisson and Buffa-Christiansen functions to discretize the domain and range of the integral operators and a PE(CE)m type linear multistep to march on in time. Unlike its implicit counterpart, the proposed explicit solver requires the solution of an MOT system with a Gram matrix that is sparse and well-conditioned independent of the time step size. Numerical results demonstrate that the explicit solver maintains its accuracy and stability even when the time step size is chosen as large as that typically used by an implicit solver. © 2013 IEEE.
Numerical Integration of Stiff System of Ordinary Differential ...
African Journals Online (AJOL)
The goal of this work is to develop, analyse and implement a K-step Implicit Rational Runge-Kutta schemes for Integration of Stiff system of Ordinary differential Equations. Its development adopted Taylor and Binomial series expansion Techniques to generate its parameters. The analysis of its basic properties adopted ...
Numerical calculation of path integrals : The small-polaron model
Raedt, Hans De; Lagendijk, Ad
1983-01-01
The thermodynamic properties of the small-polaron model are studied by means of a discrete version of the Feynman path-integral representation of the partition function. This lattice model describes a fermion interacting with a boson field. The bosons are treated analytically, the fermion
Integrated numerical methods for hypersonic aircraft cooling systems analysis
Petley, Dennis H.; Jones, Stuart C.; Dziedzic, William M.
1992-01-01
Numerical methods have been developed for the analysis of hypersonic aircraft cooling systems. A general purpose finite difference thermal analysis code is used to determine areas which must be cooled. Complex cooling networks of series and parallel flow can be analyzed using a finite difference computer program. Both internal fluid flow and heat transfer are analyzed, because increased heat flow causes a decrease in the flow of the coolant. The steady state solution is a successive point iterative method. The transient analysis uses implicit forward-backward differencing. Several examples of the use of the program in studies of hypersonic aircraft and rockets are provided.
Banyukevich, A.; Ziolkovski, K.
1975-01-01
A number of hybrid methods for solving Cauchy problems are described on the basis of an evaluation of advantages of single and multiple-point numerical integration methods. The selection criterion is the principle of minimizing computer time. The methods discussed include the Nordsieck method, the Bulirsch-Stoer extrapolation method, and the method of recursive Taylor-Steffensen power series.
GENERIC Integrators: Structure Preserving Time Integration for Thermodynamic Systems
Öttinger, Hans Christian
2018-04-01
Thermodynamically admissible evolution equations for non-equilibrium systems are known to possess a distinct mathematical structure. Within the GENERIC (general equation for the non-equilibrium reversible-irreversible coupling) framework of non-equilibrium thermodynamics, which is based on continuous time evolution, we investigate the possibility of preserving all the structural elements in time-discretized equations. Our approach, which follows Moser's [1] construction of symplectic integrators for Hamiltonian systems, is illustrated for the damped harmonic oscillator. Alternative approaches are sketched.
Numerical Integration Techniques for Curved-Element Discretizations of Molecule–Solvent Interfaces
Bardhan, Jaydeep P.; Altman, Michael D.; Willis, David J.; Lippow, Shaun M.; Tidor, Bruce; White, Jacob K.
2012-01-01
Surface formulations of biophysical modeling problems offer attractive theoretical and computational properties. Numerical simulations based on these formulations usually begin with discretization of the surface under consideration; often, the surface is curved, possessing complicated structure and possibly singularities. Numerical simulations commonly are based on approximate, rather than exact, discretizations of these surfaces. To assess the strength of the dependence of simulation accuracy on the fidelity of surface representation, we have developed methods to model several important surface formulations using exact surface discretizations. Following and refining Zauhar’s work (J. Comp.-Aid. Mol. Des. 9:149-159, 1995), we define two classes of curved elements that can exactly discretize the van der Waals, solvent-accessible, and solvent-excluded (molecular) surfaces. We then present numerical integration techniques that can accurately evaluate nonsingular and singular integrals over these curved surfaces. After validating the exactness of the surface discretizations and demonstrating the correctness of the presented integration methods, we present a set of calculations that compare the accuracy of approximate, planar-triangle-based discretizations and exact, curved-element-based simulations of surface-generalized-Born (sGB), surface-continuum van der Waals (scvdW), and boundary-element method (BEM) electrostatics problems. Results demonstrate that continuum electrostatic calculations with BEM using curved elements, piecewise-constant basis functions, and centroid collocation are nearly ten times more accurate than planartriangle BEM for basis sets of comparable size. The sGB and scvdW calculations give exceptional accuracy even for the coarsest obtainable discretized surfaces. The extra accuracy is attributed to the exact representation of the solute–solvent interface; in contrast, commonly used planar-triangle discretizations can only offer improved
International Nuclear Information System (INIS)
Liu, Fang; Lin, Lin; Vigil-Fowler, Derek; Lischner, Johannes; Kemper, Alexander F.; Sharifzadeh, Sahar; Jornada, Felipe H. da; Deslippe, Jack; Yang, Chao
2015-01-01
We present a numerical integration scheme for evaluating the convolution of a Green's function with a screened Coulomb potential on the real axis in the GW approximation of the self energy. Our scheme takes the zero broadening limit in Green's function first, replaces the numerator of the integrand with a piecewise polynomial approximation, and performs principal value integration on subintervals analytically. We give the error bound of our numerical integration scheme and show by numerical examples that it is more reliable and accurate than the standard quadrature rules such as the composite trapezoidal rule. We also discuss the benefit of using different self energy expressions to perform the numerical convolution at different frequencies
Advanced Numerical Integration Techniques for HighFidelity SDE Spacecraft Simulation
National Aeronautics and Space Administration — Classic numerical integration techniques, such as the ones at the heart of several NASA GSFC analysis tools, are known to work well for deterministic differential...
Numerical Evaluation of Stress Intensity Factors (Ki) J-Integral Approach
National Research Council Canada - National Science Library
Riveros, Guillermo A
2006-01-01
The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to describe the numerical evaluation of the stress intensity factors using the J-integral approach (Rice 1968a, 1968b...
Shi, Yifei
2013-08-01
Internal resonant modes are always observed in the marching-on-in-time (MOT) solution of the time domain electric field integral equation (EFIE), although \\'relaxed initial conditions,\\' which are enforced at the beginning of time marching, should in theory prevent these spurious modes from appearing. It has been conjectured that, numerical errors built up during time marching establish the necessary initial conditions and induce the internal resonant modes. However, this conjecture has never been proved by systematic numerical experiments. Our numerical results in this communication demonstrate that, the internal resonant modes\\' amplitudes are indeed dictated by the numerical errors. Additionally, it is shown that in a few cases, the internal resonant modes can be made \\'invisible\\' by significantly suppressing the numerical errors. These tests prove the conjecture that the internal resonant modes are induced by numerical errors when the time domain EFIE is solved by the MOT method. © 2013 IEEE.
Numerical Solution of The Linear Fredholm Integral Equations of the Second Kind
Directory of Open Access Journals (Sweden)
N. Parandin
2010-03-01
Full Text Available The theory of integral equation is one of the major topics of applied mathematics. The main purpose of this paper is to introduce a numerical method based on the interpolation for approximating the solution of the second kind linear Fredholm integral equation. In this case, the divided differences method is applied. At last, two numerical examples are presented to show the accuracy of the proposed method
Geometric numerical integration applied to the elastic pendulum at higher order resonance
Tuwankotta, J.M.; Quispel, G.R.W.
2000-01-01
In this paper we study the performance of a symplectic numerical integrator based on the splitting method This method is applied to a subtle problem ie higher order resonance of the elastic pendulum In order to numerically study the phase space of the elastic pendulum at higher order resonance a
Kelly, N. M.; Marchi, S.; Mojzsis, S. J.; Flowers, R. M.; Metcalf, J. R.; Bottke, W. F., Jr.
2017-12-01
Impacts have a significant physical and chemical influence on the surface conditions of a planet. The cratering record is used to understand a wide array of impact processes, such as the evolution of the impact flux through time. However, the relationship between impactor size and a resulting impact crater remains controversial (e.g., Bottke et al., 2016). Likewise, small variations in the impact velocity are known to significantly affect the thermal-mechanical disturbances in the aftermath of a collision. Development of more robust numerical models for impact cratering has implications for how we evaluate the disruptive capabilities of impact events, including the extent and duration of thermal anomalies, the volume of ejected material, and the resulting landscape of impacted environments. To address uncertainties in crater scaling relationships, we present an approach and methodology that integrates numerical modeling of the thermal evolution of terrestrial impact craters with low-temperature, (U-Th)/He thermochronometry. The approach uses time-temperature (t-T) paths of crust within an impact crater, generated from numerical simulations of an impact. These t-T paths are then used in forward models to predict the resetting behavior of (U-Th)/He ages in the mineral chronometers apatite and zircon. Differences between the predicted and measured (U-Th)/He ages from a modeled terrestrial impact crater can then be used to evaluate parameters in the original numerical simulations, and refine the crater scaling relationships. We expect our methodology to additionally inform our interpretation of impact products, such as lunar impact breccias and meteorites, providing robust constraints on their thermal histories. In addition, the method is ideal for sample return mission planning - robust "prediction" of ages we expect from a given impact environment enhances our ability to target sampling sites on the Moon, Mars or other solar system bodies where impacts have strongly
High speed numerical integration algorithm using FPGA | Razak ...
African Journals Online (AJOL)
RRS), Middle Riemann Sum (MRS) and Trapezoidal Sum (TS) algorithms. The system performance is evaluated based on target chip Altera Cyclone IV FPGA in the metrics of resources utilization, clock latency, execution time, power consumption ...
Numerical method for solving integral equations of neutron transport. II
International Nuclear Information System (INIS)
Loyalka, S.K.; Tsai, R.W.
1975-01-01
In a recent paper it was pointed out that the weakly singular integral equations of neutron transport can be quite conveniently solved by a method based on subtraction of singularity. This previous paper was devoted entirely to the consideration of simple one-dimensional isotropic-scattering and one-group problems. The present paper constitutes interesting extensions of the previous work in that in addition to a typical two-group anisotropic-scattering albedo problem in the slab geometry, the method is also applied to an isotropic-scattering problem in the x-y geometry. These results are compared with discrete S/sub N/ (ANISN or TWOTRAN-II) results, and for the problems considered here, the proposed method is found to be quite effective. Thus, the method appears to hold considerable potential for future applications. (auth)
Optimal stability polynomials for numerical integration of initial value problems
Ketcheson, David I.
2013-01-08
We consider the problem of finding optimally stable polynomial approximations to the exponential for application to one-step integration of initial value ordinary and partial differential equations. The objective is to find the largest stable step size and corresponding method for a given problem when the spectrum of the initial value problem is known. The problem is expressed in terms of a general least deviation feasibility problem. Its solution is obtained by a new fast, accurate, and robust algorithm based on convex optimization techniques. Global convergence of the algorithm is proven in the case that the order of approximation is one and in the case that the spectrum encloses a starlike region. Examples demonstrate the effectiveness of the proposed algorithm even when these conditions are not satisfied.
Some Nonlinear Integral Inequalities on Time Scales
Directory of Open Access Journals (Sweden)
Li Wei Nian
2007-01-01
Full Text Available The purpose of this paper is to investigate some nonlinear integral inequalities on time scales. Our results unify and extend some continuous inequalities and their corresponding discrete analogues. The theoretical results are illustrated by a simple example at the end of this paper.
Energy drift in reversible time integration
International Nuclear Information System (INIS)
McLachlan, R I; Perlmutter, M
2004-01-01
Energy drift is commonly observed in reversible integrations of systems of molecular dynamics. We show that this drift can be modelled as a diffusion and that the typical energy error after time T is O(√T). (letter to the editor)
Mixed time integration methods for transient thermal analysis of structures
Liu, W. K.
1983-01-01
The computational methods used to predict and optimize the thermal-structural behavior of aerospace vehicle structures are reviewed. In general, two classes of algorithms, implicit and explicit, are used in transient thermal analysis of structures. Each of these two methods has its own merits. Due to the different time scales of the mechanical and thermal responses, the selection of a time integration method can be a difficult yet critical factor in the efficient solution of such problems. Therefore mixed time integration methods for transient thermal analysis of structures are being developed. The computer implementation aspects and numerical evaluation of these mixed time implicit-explicit algorithms in thermal analysis of structures are presented. A computationally-useful method of estimating the critical time step for linear quadrilateral element is also given. Numerical tests confirm the stability criterion and accuracy characteristics of the methods. The superiority of these mixed time methods to the fully implicit method or the fully explicit method is also demonstrated.
Hippocampal “Time Cells”: Time versus Path Integration
Kraus, Benjamin J.; Robinson, Robert J.; White, John A.; Eichenbaum, Howard; Hasselmo, Michael E.
2014-01-01
SUMMARY Recent studies have reported the existence of hippocampal “time cells,” neurons that fire at particular moments during periods when behavior and location are relatively constant. However, an alternative explanation of apparent time coding is that hippocampal neurons “path integrate” to encode the distance an animal has traveled. Here, we examined hippocampal neuronal firing patterns as rats ran in place on a treadmill, thus “clamping” behavior and location, while we varied the treadmill speed to distinguish time elapsed from distance traveled. Hippocampal neurons were strongly influenced by time and distance, and less so by minor variations in location. Furthermore, the activity of different neurons reflected integration over time and distance to varying extents, with most neurons strongly influenced by both factors and some significantly influenced by only time or distance. Thus, hippocampal neuronal networks captured both the organization of time and distance in a situation where these dimensions dominated an ongoing experience. PMID:23707613
The Crank Nicolson Time Integrator for EMPHASIS.
Energy Technology Data Exchange (ETDEWEB)
McGregor, Duncan Alisdair Odum; Love, Edward; Kramer, Richard Michael Jack
2018-03-01
We investigate the use of implicit time integrators for finite element time domain approxi- mations of Maxwell's equations in vacuum. We discretize Maxwell's equations in time using Crank-Nicolson and in 3D space using compatible finite elements. We solve the system by taking a single step of Newton's method and inverting the Eddy-Current Schur complement allowing for the use of standard preconditioning techniques. This approach also generalizes to more complex material models that can include the Unsplit PML. We present verification results and demonstrate performance at CFL numbers up to 1000.
Numerical integration of the equations of relativistic hydrodynamics
International Nuclear Information System (INIS)
Wilson, J.R.
1977-01-01
The gravitational field equations are solved by starting with the '3+1' approach. The freedom to choose coordinates is used to reduce Einstein's field equations to a set of elliptic type quations which have no time derivatives and a set of first order (hyperbolic) time evolution equations for the true gravitational degrees of freedom only. In a spherically symmetric system there are no gravitational degrees of gravitational freedom. In an axially symmetric (nonrotating) there is one degree of gravitational freedom. Computer programs have only been written for spherical and axial symmetry so far, but the same approach should easily work for the full non symmetric systems. The axymmetriy so far, but the same approach should easily work for the full non symmetric systems. The axially symmetric case will be discussed in detail below since it best illustrates the method. The equations for spherical symmetry will be given along with some results of computer calcualtions. Some results will be given for the axial symmetric program, but these results are very preliminary at this point and since the computer program has not been well checked and probably still has errors, these problems only illustrate that the method seems to work well. (orig.) [de
Sphaleron transitions and baryon asymmetry: A numerical, real time analysis
International Nuclear Information System (INIS)
Ambjoern, J.; Askgaard, T.; Porter, H.; Shaposhnikov, M.E.
1990-08-01
We estimate by numerical simulations the rate Γ of sphaleron-like transitions in the electroweak theory in the phase with restored symmetry. There is no suppression and Γ=κ(α W T) 4 with κ ≅ 0.1-1.0. We further address the question of a spontaneous CP-breaking in this phase of the electroweak theory, but have not yet found any evidence in this direction. (orig.)
Ramo, Nicole L.; Puttlitz, Christian M.
2018-01-01
Compelling evidence that many biological soft tissues display both strain- and time-dependent behavior has led to the development of fully non-linear viscoelastic modeling techniques to represent the tissue’s mechanical response under dynamic conditions. Since the current stress state of a viscoelastic material is dependent on all previous loading events, numerical analyses are complicated by the requirement of computing and storing the stress at each step throughout the load history. This requirement quickly becomes computationally expensive, and in some cases intractable, for finite element models. Therefore, we have developed a strain-dependent numerical integration approach for capturing non-linear viscoelasticity that enables calculation of the current stress from a strain-dependent history state variable stored from the preceding time step only, which improves both fitting efficiency and computational tractability. This methodology was validated based on its ability to recover non-linear viscoelastic coefficients from simulated stress-relaxation (six strain levels) and dynamic cyclic (three frequencies) experimental stress-strain data. The model successfully fit each data set with average errors in recovered coefficients of 0.3% for stress-relaxation fits and 0.1% for cyclic. The results support the use of the presented methodology to develop linear or non-linear viscoelastic models from stress-relaxation or cyclic experimental data of biological soft tissues. PMID:29293558
Sendur, Kürşat
2009-04-27
To address the large number of parameters involved in nano-optical problems, a more efficient computational method is necessary. An integral equation based numerical solution is developed when the particles are illuminated with collimated and focused incident beams. The solution procedure uses the method of weighted residuals, in which the integral equation is reduced to a matrix equation and then solved for the unknown electric field distribution. In the solution procedure, the effects of the surrounding medium and boundaries are taken into account using a Green's function formulation. Therefore, there is no additional error due to artificial boundary conditions unlike differential equation based techniques, such as finite difference time domain and finite element method. In this formulation, only the scattering nano-particle is discretized. Such an approach results in a lesser number of unknowns in the resulting matrix equation. The results are compared to the analytical Mie series solution for spherical particles, as well as to the finite element method for rectangular metallic particles. The Richards-Wolf vector field equations are combined with the integral equation based formulation to model the interaction of nanoparticles with linearly and radially polarized incident focused beams.
Numerical integration of detector response functions via Monte Carlo simulations
Kelly, K. J.; O'Donnell, J. M.; Gomez, J. A.; Taddeucci, T. N.; Devlin, M.; Haight, R. C.; White, M. C.; Mosby, S. M.; Neudecker, D.; Buckner, M. Q.; Wu, C. Y.; Lee, H. Y.
2017-09-01
Calculations of detector response functions are complicated because they include the intricacies of signal creation from the detector itself as well as a complex interplay between the detector, the particle-emitting target, and the entire experimental environment. As such, these functions are typically only accessible through time-consuming Monte Carlo simulations. Furthermore, the output of thousands of Monte Carlo simulations can be necessary in order to extract a physics result from a single experiment. Here we describe a method to obtain a full description of the detector response function using Monte Carlo simulations. We also show that a response function calculated in this way can be used to create Monte Carlo simulation output spectra a factor of ∼ 1000 × faster than running a new Monte Carlo simulation. A detailed discussion of the proper treatment of uncertainties when using this and other similar methods is provided as well. This method is demonstrated and tested using simulated data from the Chi-Nu experiment, which measures prompt fission neutron spectra at the Los Alamos Neutron Science Center.
Aspects for Run-time Component Integration
DEFF Research Database (Denmark)
Truyen, Eddy; Jørgensen, Bo Nørregaard; Joosen, Wouter
2000-01-01
Component framework technology has become the cornerstone of building a family of systems and applications. A component framework defines a generic architecture into which specialized components can be plugged. As such, the component framework leverages the glue that connects the different inserted...... to dynamically integrate into the architecture of middleware systems new services that support non-functional aspects such as security, transactions, real-time....
Analysis of thermal-plastic response of shells of revolution by numerical integration
International Nuclear Information System (INIS)
Leonard, J.W.
1975-01-01
An economic technique for the numerical analysis of the elasto-plastic behaviour of shells of revolution would be of considerable value in the nuclear reactor industry. A numerical method based on the numerical integration of the governing shell equations has been shown, for elastic cases, to be more efficient than the finite element method when applied to shells of revolution. In the numerical integration method, the governing differential equations of motion are converted into a set of initial-value problems. Each initial-value problem is integrated numerically between meridional boundary points and recombined so as to satisfy boundary conditions. For large-deflection elasto-plastic behaviour, the equations are nonlinear and, hence, are recombined in an iterative manner using the Newton-Raphson procedure. Suppression techniques are incorporated in order to eliminate extraneous solutions within the numerical integration procedure. The Reissner-Meissner shell theory for shells of revolution is adopted to account for large deflection and higher-order rotation effects. The computer modelling of the equations is quite general in that specific shell segment geometries, e.g. cylindrical, spherical, toroidal, conical segments, and any combinations thereof can be handled easily. (Auth.)
Characteristic times in the English Channel from numerical modelling: supporting decision-making
Energy Technology Data Exchange (ETDEWEB)
Perianez, R [Departamento de Fisica Aplicada 1, Universidad de Sevilla, EUITA, Carretera Utrera km 1, 41013 Sevilla (Spain); Miro, C [Departamento de Fisica Aplicada, Facultad de Veterinaria, Universidad de Extremadura, Avenida de la Universidad s/n, 10071 Caceres (Spain)], E-mail: rperianez@us.es, E-mail: cmiro@unex.es
2009-06-15
A numerical model that simulates the dispersion of radionuclides in the English Channel has been applied to study the dispersion of conservative and non-conservative radionuclides released from the La Hague nuclear fuel reprocessing plant. The model is based upon previous work and now is able to simulate dispersion over long timescales (decades), explicitly including transport by instantaneous tidal currents and variable wind conditions. Wind conditions are obtained from meteorological statistics using a stochastic method. Outputs from the model are treated using time-series analysis techniques. These techniques allow the determination of characteristic times of the system, transport velocities and dispersion factors. This information may be very useful to support the decision-making process after an emergency situation. Thus, we are proposing that time-series analysis can be integrated with numerical modelling for helping decision-making in response to an accident. The model is first validated through its application to actual releases of {sup 99}Tc and {sup 125}Sb, comparing measured and computed concentrations, and characteristic times for three radionuclides are given next: a perfectly conservative one, a very reactive one ({sup 239,240}Pu) and {sup 137}Cs, which has an intermediate behaviour. Characteristic transport velocities and dispersion factors have been calculated as well. Model results are supported by experimental evidence.
Numerical path integral solution to strong Coulomb correlation in one dimensional Hooke's atom
Ruokosenmäki, Ilkka; Gholizade, Hossein; Kylänpää, Ilkka; Rantala, Tapio T.
2017-01-01
We present a new approach based on real time domain Feynman path integrals (RTPI) for electronic structure calculations and quantum dynamics, which includes correlations between particles exactly but within the numerical accuracy. We demonstrate that incoherent propagation by keeping the wave function real is a novel method for finding and simulation of the ground state, similar to Diffusion Monte Carlo (DMC) method, but introducing new useful tools lacking in DMC. We use 1D Hooke's atom, a two-electron system with very strong correlation, as our test case, which we solve with incoherent RTPI (iRTPI) and compare against DMC. This system provides an excellent test case due to exact solutions for some confinements and because in 1D the Coulomb singularity is stronger than in two or three dimensional space. The use of Monte Carlo grid is shown to be efficient for which we determine useful numerical parameters. Furthermore, we discuss another novel approach achieved by combining the strengths of iRTPI and DMC. We also show usefulness of the perturbation theory for analytical approximates in case of strong confinements.
Numerical integration methods and layout improvements in the context of dynamic RNA visualization.
Shabash, Boris; Wiese, Kay C
2017-05-30
RNA visualization software tools have traditionally presented a static visualization of RNA molecules with limited ability for users to interact with the resulting image once it is complete. Only a few tools allowed for dynamic structures. One such tool is jViz.RNA. Currently, jViz.RNA employs a unique method for the creation of the RNA molecule layout by mapping the RNA nucleotides into vertexes in a graph, which we call the detailed graph, and then utilizes a Newtonian mechanics inspired system of forces to calculate a layout for the RNA molecule. The work presented here focuses on improvements to jViz.RNA that allow the drawing of RNA secondary structures according to common drawing conventions, as well as dramatic run-time performance improvements. This is done first by presenting an alternative method for mapping the RNA molecule into a graph, which we call the compressed graph, and then employing advanced numerical integration methods for the compressed graph representation. Comparing the compressed graph and detailed graph implementations, we find that the compressed graph produces results more consistent with RNA drawing conventions. However, we also find that employing the compressed graph method requires a more sophisticated initial layout to produce visualizations that would require minimal user interference. Comparing the two numerical integration methods demonstrates the higher stability of the Backward Euler method, and its resulting ability to handle much larger time steps, a high priority feature for any software which entails user interaction. The work in this manuscript presents the preferred use of compressed graphs to detailed ones, as well as the advantages of employing the Backward Euler method over the Forward Euler method. These improvements produce more stable as well as visually aesthetic representations of the RNA secondary structures. The results presented demonstrate that both the compressed graph representation, as well as the Backward
Time-Lapse Measurement of Wellbore Integrity
Duguid, A.
2017-12-01
Well integrity is becoming more important as wells are used longer or repurposed. For CO2, shale gas, and other projects it has become apparent that wells represent the most likely unintended migration pathway for fluids out of the reservoir. Comprehensive logging programs have been employed to determine the condition of legacy wells in North America. These studies provide examples of assessment technologies. Logging programs have included pulsed neutron logging, ultrasonic well mapping, and cement bond logging. While these studies provide examples of what can be measured, they have only conducted a single round of logging and cannot show if the well has changed over time. Recent experience with time-lapse logging of three monitoring wells at a US Department of Energy sponsored CO2 project has shown the full value of similar tools. Time-lapse logging has shown that well integrity changes over time can be identified. It has also shown that the inclusion of and location of monitoring technologies in the well and the choice of construction materials must be carefully considered. Two of the wells were approximately eight years old at the time of study; they were constructed with steel and fiberglass casing sections and had lines on the outside of the casing running to the surface. The third well was 68 years old when it was studied and was originally constructed as a production well. Repeat logs were collected six or eight years after initial logging. Time-lapse logging showed the evolution of the wells. The results identified locations where cement degraded over time and locations that showed little change. The ultrasonic well maps show clearly that the lines used to connect the monitoring technology to the surface are visible and have a local effect on cement isolation. Testing and sampling was conducted along with logging. It provided insight into changes identified in the time-lapse log results. Point permeability testing was used to provide an in-situ point
Montagna, Chiara; Perugini, Diego; De Campos, Christina; Longo, Antonella; Dingwell, Donald Bruce; Papale, Paolo
2015-04-01
Arrival of magma from depth into shallow reservoirs and associated mixing processes have been documented as possible triggers of explosive eruptions. Quantifying the timing from beginning of mixing to eruption is of fundamental importance in volcanology in order to put constraints about the possible onset of a new eruption. Here we integrate numerical simulations and high-temperature experiment performed with natural melts with the aim to attempt identifying the mixing-to-eruption timescales. We performed two-dimensional numerical simulations of the arrival of gas-rich magmas into shallow reservoirs. We solve the fluid dynamics for the two interacting magmas evaluating the space-time evolution of the physical properties of the mixture. Convection and mingling develop quickly into the chamber and feeding conduit/dyke. Over time scales of hours, the magmas in the reservoir appear to have mingled throughout, and convective patterns become harder to identify. High-temperature magma mixing experiments have been performed using a centrifuge and using basaltic and phonolitic melts from Campi Flegrei (Italy) as initial end-members. Concentration Variance Decay (CVD), an inevitable consequence of magma mixing, is exponential with time. The rate of CVD is a powerful new geochronometer for the time from mixing to eruption/quenching. The mingling-to-eruption time of three explosive volcanic eruptions from Campi Flegrei (Italy) yield durations on the order of tens of minutes. These results are in perfect agreement with the numerical simulations that suggest a maximum mixing time of a few hours to obtain a hybrid mixture. We show that integration of numerical simulation and high-temperature experiments can provide unprecedented results about mixing processes in volcanic systems. The combined application of numerical simulations and CVD geochronometer to the eruptive products of active volcanoes could be decisive for the preparation of hazard mitigation during volcanic unrest.
Wang, Yi
2016-07-21
Velocity of fluid flow in underground porous media is 6~12 orders of magnitudes lower than that in pipelines. If numerical errors are not carefully controlled in this kind of simulations, high distortion of the final results may occur [1-4]. To fit the high accuracy demands of fluid flow simulations in porous media, traditional finite difference methods and numerical integration methods are discussed and corresponding high-accurate methods are developed. When applied to the direct calculation of full-tensor permeability for underground flow, the high-accurate finite difference method is confirmed to have numerical error as low as 10-5% while the high-accurate numerical integration method has numerical error around 0%. Thus, the approach combining the high-accurate finite difference and numerical integration methods is a reliable way to efficiently determine the characteristics of general full-tensor permeability such as maximum and minimum permeability components, principal direction and anisotropic ratio. Copyright © Global-Science Press 2016.
Analysis of thermal-plastic response of shells of revolution by numerical integration
International Nuclear Information System (INIS)
Leonard, J.W.
1975-01-01
A numerical method based instead on the numerical integration of the governing shell equations has been shown, for elastic cases, to be more efficient than the finite element method when applied to shells of revolution. In the numerical integration method, the governing differential equations of motions are converted into a set of initial-value problems. Each initial-value problem is integrated numerically between meridional boundary points and recombined so as to satisfy boundary conditions. For large-deflection elasto-plastic behavior, the equations are nonlinear and, hence, are recombined in an iterative manner using the Newton-Raphson procedure. Suppression techniques are incorporated in order to eliminate extraneous solutions within the numerical integration procedure. The Reissner-Meissner shell theory for shells of revolution is adopted to account for large deflection and higher-order rotation effects. The computer modelling of the equations is quite general in that specific shell segment geometries, e.g. cylindrical, spherical, toroidal, conical segments, and any combinations thereof can be handled easily. The elasto-plastic constitutive relations adopted are in accordance with currently recommended constitutive equations for inelastic design analysis of FFTF Components. The Von Mises yield criteria and associated flow rule is used and the kinematic hardening law is followed. Examples are considered in which stainless steels common to LMFBR application are used
Directory of Open Access Journals (Sweden)
Yan Nan
2017-01-01
Full Text Available In order to calculate the dynamometer card of oil well using acceleration sensor, the algorithm which combined by Kalman filter and discrete numerical integration is proposed. It can be applied to calculate the displacement and precipitation displacement period of oil well dynamometer card. The Kalman filter not only filters out the noise of the acceleration signal, but also maintains the original shape feature. The accurate precipitation of the displacement period ensures the correctness of displacement. The discrete numerical integration algorithm can make the relative error of displacement measurement less than 1%, which meets the requirement for dynamometer card accuracy. It is suitable for different types of oil wells.
pySecDec: A toolbox for the numerical evaluation of multi-scale integrals
Borowka, S.; Heinrich, G.; Jahn, S.; Jones, S. P.; Kerner, M.; Schlenk, J.; Zirke, T.
2018-01-01
We present pySECDEC, a new version of the program SECDEC, which performs the factorization of dimensionally regulated poles in parametric integrals, and the subsequent numerical evaluation of the finite coefficients. The algebraic part of the program is now written in the form of python modules, which allow a very flexible usage. The optimization of the C++ code, generated using FORM, is improved, leading to a faster numerical convergence. The new version also creates a library of the integrand functions, such that it can be linked to user-specific codes for the evaluation of matrix elements in a way similar to analytic integral libraries.
Numerical solution of nonlinear Urisohn-Volterra fuzzy functional integral equations
Georgieva, Atanaska; Naydenova, Iva
2017-12-01
In the present paper, we propose an efficient iterative numerical method of successive approximations to approximate solution of nonlinear Urisohn-Volterra fuzzy functional integral equations by fuzzy trapezoidal quadrature formula for classes of fuzzy-number-valued functions of Lipschitz type. We prove the convergence of the method and investigate the numerical stability of the present method with respect to the choice of the first iteration. The convergence of the method is tested through a numerical experiment, that confirms the obtained theoretical results.
On the initial condition problem of the time domain PMCHWT surface integral equation
Uysal, Ismail Enes
2017-05-13
Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced properly. This problem can be remedied by solving the time integral of the surface integral for auxiliary currents that are defined to be the time derivatives of the equivalent currents. Then the equivalent currents are obtained by numerically differentiating the auxiliary ones. In this work, this approach is applied to the marching on-in-time solution of the time domain Poggio-Miller-Chan-Harrington-Wu-Tsai surface integral equation enforced on dispersive/plasmonic scatterers. Accuracy of the proposed method is demonstrated by a numerical example.
Penenko, Vladimir; Tsvetova, Elena; Penenko, Alexey
2015-04-01
The proposed method is considered on an example of hydrothermodynamics and atmospheric chemistry models [1,2]. In the development of the existing methods for constructing numerical schemes possessing the properties of total approximation for operators of multiscale process models, we have developed a new variational technique, which uses the concept of adjoint integrating factors. The technique is as follows. First, a basic functional of the variational principle (the integral identity that unites the model equations, initial and boundary conditions) is transformed using Lagrange's identity and the second Green's formula. As a result, the action of the operators of main problem in the space of state functions is transferred to the adjoint operators defined in the space of sufficiently smooth adjoint functions. By the choice of adjoint functions the order of the derivatives becomes lower by one than those in the original equations. We obtain a set of new balance relationships that take into account the sources and boundary conditions. Next, we introduce the decomposition of the model domain into a set of finite volumes. For multi-dimensional non-stationary problems, this technique is applied in the framework of the variational principle and schemes of decomposition and splitting on the set of physical processes for each coordinate directions successively at each time step. For each direction within the finite volume, the analytical solutions of one-dimensional homogeneous adjoint equations are constructed. In this case, the solutions of adjoint equations serve as integrating factors. The results are the hybrid discrete-analytical schemes. They have the properties of stability, approximation and unconditional monotony for convection-diffusion operators. These schemes are discrete in time and analytic in the spatial variables. They are exact in case of piecewise-constant coefficients within the finite volume and along the coordinate lines of the grid area in each
Numerical treatment of Faddeev integral equations for non-separable potentials
International Nuclear Information System (INIS)
Eyre, D.
1986-10-01
A finite element method is used to solve the three-body problem for bound states. Two-dimensional integral equations are approximated in a trial space of piecewise quadratic polynomials. Approximate solutions are obtained for a model problem of three spinless bosons interacting via the sum of S-wave Yukawa potentials. Numerical estimates for rates of convergence of the method are obtained
Numerical solutions of integral and integro-differential equations using Legendre polynomials
Khater, A.; Shamardan, A.; Callebaut, D.; Sakran, M.
2007-11-01
In this paper, a finite Legendre expansion is developed to solve singularly perturbed integral equations, first order integro-differential equations of Volterra type arising in fluid dynamics and Volterra delay integro-differential equations. The error analysis is derived. Numerical results and comparisons with other methods in literature are considered.
Stable unitary integrators for the numerical implementation of continuous unitary transformations
Savitz, Samuel; Refael, Gil
2017-09-01
The technique of continuous unitary transformations has recently been used to provide physical insight into a diverse array of quantum mechanical systems. However, the question of how to best numerically implement the flow equations has received little attention. The most immediately apparent approach, using standard Runge-Kutta numerical integration algorithms, suffers from both severe inefficiency due to stiffness and the loss of unitarity. After reviewing the formalism of continuous unitary transformations and Wegner's original choice for the infinitesimal generator of the flow, we present a number of approaches to resolving these issues including a choice of generator which induces what we call the "uniform tangent decay flow" and three numerical integrators specifically designed to perform continuous unitary transformations efficiently while preserving the unitarity of flow. We conclude by applying one of the flow algorithms to a simple calculation that visually demonstrates the many-body localization transition.
Towards a stable numerical time scale for the early Paleogene
Hilgen, Frederik; Kuiper, Klaudia; Sierro, Francisco J.; Wotzlaw, Jorn; Schaltegger, Urs; Sahy, Diana; Condon, Daniel
2014-05-01
The construction of an astronomical time scale for the early Paleogene is hampered by ambiguities in the number, correlation and tuning of 405-kyr eccentricity related cycles in deep marine records from ODP cores and land-based sections. The two most competing age models result in astronomical ages for the K/Pg boundary that differ by ~750 kyr (~66.0 Ma of Vandenberghe et al. (2012) versus 65.25 Ma of Westerhold et al. (2012); these ages in turn are consistent with proposed ages for the Fish Canyon sanidine (FCs) that differ by ~300 kyr (28.201 Ma of Kuiper et al. (2008) versus 27.89 Ma of Westerhold et al. (2012)); an even older age of 28.294 Ma is proposed based on a statistical optimization model (Renne et al., 2011). The astronomically calibrated FCs age of 28.201 ± 0.046 Ma of Kuiper et al. (2008), which is consistent with the astronomical age of ~66.0 Ma for the K/Pg boundary, is currently adopted in the standard geological time scale (GTS2012). Here we combine new and published data in an attempt to solve the controversy and arrive at a stable nuemrical time scale for the early Paleogene. Supporting their younger age model, Westerhold et al. (2012) argue that the tuning of Miocene sections in the Mediterranean, which underlie the older FCs age of Kuiper et al. (2008) and, hence, the coupled older early Paleogene age model of Vandenberghe et al. (2012), might be too old by three precession cycles. We thoroughly rechecked this tuning; distinctive cycle patterns related to eccentricity and precession-obliquity interference make a younger tuning that would be consistent with the younger astronomical age of 27.89 Ma for the FCs of Westerhold et al. (2012) challenging. Next we compared youngest U/Pb zircon and astronomical ages for a number of ash beds in the tuned Miocene section of Monte dei Corvi. These ages are indistinguishable, indicating that the two independent dating methods yield the same age when the same event is dated. This is consistent with results
Numerical path integration technique for the calculation of transport properties of proteins.
Kang, Eun-Hee; Mansfield, Marc L; Douglas, Jack F
2004-03-01
We present a new technique for the computation of both the translational diffusivity and the intrinsic viscosity of macromolecules, and apply it here to proteins. Traditional techniques employ finite element representations of the surface of the macromolecule, taking the surface to be a union of spheres or of polygons, and have computation times that are O(m(3)) where m is the number of finite elements. The new technique, a numerical path integration method, has computation times that are only O(m). We have applied the technique to approximately 1000 different protein structures. The computed translational diffusivities and intrinsic viscosities are, to lowest order, proportional respectively to N(-1/3)(R) and N(0)(R), where N(R) is the number of amino acid residues in the protein. Our calculations also show some correlation with the shape of the molecule, as represented by the ratio m(2)/m(3), where m(2) and m(3) are, respectively, the middle and the smallest of the three principal moments of inertia. Comparisons with a number of experimental results are also performed, with results generally consistent to within experimental error.
A variable step method for the numerical integration of the one-dimensional Schroedinger equation
International Nuclear Information System (INIS)
Raptis, A.D.; Cash, J.R.
1985-01-01
Most numerical methods which have been proposed for the approximate integration of the one-dimensional Schroedinger equation use a fixed step length of integration. Such an approach can of course result in gross inefficiency since the small step length which must normally be used in the initial part of the range of integration to obtain the desired accuracy must then be used throughout the integration. In this paper we consider the method of embedding, which is widely used with explicit Runge-Kutta methods for the solution of first order initial value problems, for use with the special formulae used to integrate the Schroedinger equation. By adopting this technique we have available at each step an estimate of the local truncation error and this estimate can be used to automatically control the step length of integration. Also considered is the problem of estimating the global truncation error at the end of the range of integration. The power of the approaches considered is illustrated by means of some numerical examples. (orig.)
Keslerová, R.; Kozel, K.
2014-03-01
This work deals with the numerical solution of viscous and viscoelastic fluids flow. The governing system of equations is based on the system of balance laws for mass and momentum for incompressible laminar fluids. Different models for the stress tensor are considered. For viscous fluids flow Newtonian model is used. For the describing of the behaviour of the mixture of viscous and viscoelastic fluids Oldroyd-B model is used. Numerical solution of the described models is based on cell-centered finite volume method in conjunction with artificial compressibility method. For time integration an explicit multistage Runge-Kutta scheme is used. In the case of unsteady computation dual-time stepping method is considered. The principle of dual-time stepping method is following. The artificial time is introduced and the artificial compressibility method in the artificial time is applied.
Conservative fourth-order time integration of non-linear dynamic systems
DEFF Research Database (Denmark)
Krenk, Steen
2015-01-01
the resulting time integrals of the inertia and stiffness terms via integration by parts. This process introduces the time derivatives of the state space variables, and these are then substituted from the original state-space differential equations. The resulting discrete form of the state-space equations......An energy conserving time integration algorithm with fourth-order accuracy is developed for dynamic systems with nonlinear stiffness. The discrete formulation is derived by integrating the differential state-space equations of motion over the integration time increment, and then evaluating...... integration of oscillatory systems with only a few integration points per period. Three numerical examples demonstrate the high accuracy of the algorithm. (C) 2015 Elsevier B.V. All rights reserved....
Bogner, Christian; Schweitzer, Armin; Weinzierl, Stefan
2017-09-01
We study the analytic continuation of Feynman integrals from the kite family, expressed in terms of elliptic generalisations of (multiple) polylogarithms. Expressed in this way, the Feynman integrals are functions of two periods of an elliptic curve. We show that all what is required is just the analytic continuation of these two periods. We present an explicit formula for the two periods for all values of t ∈ R. Furthermore, the nome q of the elliptic curve satisfies over the complete range in t the inequality | q | ≤ 1, where | q | = 1 is attained only at the singular points t ∈ {m2 , 9m2 , ∞ }. This ensures the convergence of the q-series expansion of the ELi-functions and provides a fast and efficient evaluation of these Feynman integrals.
Examination of Numerical Integration Accuracy and Modeling for GRACE-FO and GRACE-II
McCullough, C.; Bettadpur, S.
2012-12-01
As technological advances throughout the field of satellite geodesy improve the accuracy of satellite measurements, numerical methods and algorithms must be able to keep pace. Currently, the Gravity Recovery and Climate Experiment's (GRACE) dual one-way microwave ranging system can determine changes in inter-satellite range to a precision of a few microns; however, with the advent of laser measurement systems nanometer precision ranging is a realistic possibility. With this increase in measurement accuracy, a reevaluation of the accuracy inherent in the linear multi-step numerical integration methods is necessary. Two areas where this can be a primary concern are the ability of the numerical integration methods to accurately predict the satellite's state in the presence of numerous small accelerations due to operation of the spacecraft attitude control thrusters, and due to small, point-mass anomalies on the surface of the Earth. This study attempts to quantify and minimize these numerical errors in an effort to improve the accuracy of modeling and propagation of these perturbations; helping to provide further insight into the behavior and evolution of the Earth's gravity field from the more capable gravity missions in the future.
Rosenbaum, J. S.
1976-01-01
If a system of ordinary differential equations represents a property conserving system that can be expressed linearly (e.g., conservation of mass), it is then desirable that the numerical integration method used conserve the same quantity. It is shown that both linear multistep methods and Runge-Kutta methods are 'conservative' and that Newton-type methods used to solve the implicit equations preserve the inherent conservation of the numerical method. It is further shown that a method used by several authors is not conservative.
Projector methods applied to numerical integration of the SN transport equation
International Nuclear Information System (INIS)
Hristea, V.; Covaci, St.
2003-01-01
We are developing two methods of integration for the S N transport equation in x - y geometry, methods based on projector technique. By cellularization of the phase space and by choosing a finite basis of orthogonal functions, which characterize the angular flux, the non-selfadjoint transport equation is reduced to a cellular automaton. This automaton is completely described by the transition Matrix T. Within this paper two distinct methods of projection are described. One of them uses the transversal integration technique. As an alternative to this we applied the method of the projectors for the integral S N transport equation. We show that the constant spatial approximation of the integral S N transport equation does not lead to negative fluxes. One of the problems with the projector method, namely the appearance of numerical instability for small intervals is solved by the Pade representation of the elements for Matrix T. Numerical tests here presented compare the numerical performances of the algorithms obtained by the two projection methods. The Pade representation was also taken into account for these two algorithm types. (authors)
Parareal algorithms with local time-integrators for time fractional differential equations
Wu, Shu-Lin; Zhou, Tao
2018-04-01
It is challenge work to design parareal algorithms for time-fractional differential equations due to the historical effect of the fractional operator. A direct extension of the classical parareal method to such equations will lead to unbalance computational time in each process. In this work, we present an efficient parareal iteration scheme to overcome this issue, by adopting two recently developed local time-integrators for time fractional operators. In both approaches, one introduces auxiliary variables to localized the fractional operator. To this end, we propose a new strategy to perform the coarse grid correction so that the auxiliary variables and the solution variable are corrected separately in a mixed pattern. It is shown that the proposed parareal algorithm admits robust rate of convergence. Numerical examples are presented to support our conclusions.
A numerical solution for a class of time fractional diffusion equations with delay
Directory of Open Access Journals (Sweden)
Pimenov Vladimir G.
2017-09-01
Full Text Available This paper describes a numerical scheme for a class of fractional diffusion equations with fixed time delay. The study focuses on the uniqueness, convergence and stability of the resulting numerical solution by means of the discrete energy method. The derivation of a linearized difference scheme with convergence order O(τ2−α+ h4 in L∞-norm is the main purpose of this study. Numerical experiments are carried out to support the obtained theoretical results.
Evaluation of time integration methods for transient response analysis of nonlinear structures
International Nuclear Information System (INIS)
Park, K.C.
1975-01-01
Recent developments in the evaluation of direct time integration methods for the transient response analysis of nonlinear structures are presented. These developments, which are based on local stability considerations of an integrator, show that the interaction between temporal step size and nonlinearities of structural systems has a pronounced effect on both accuracy and stability of a given time integration method. The resulting evaluation technique is applied to a model nonlinear problem, in order to: 1) demonstrate that it eliminates the present costly process of evaluating time integrator for nonlinear structural systems via extensive numerical experiments; 2) identify the desirable characteristics of time integration methods for nonlinear structural problems; 3) develop improved stiffly-stable methods for application to nonlinear structures. Extension of the methodology for examination of the interaction between a time integrator and the approximate treatment of nonlinearities (such as due to pseudo-force or incremental solution procedures) is also discussed. (Auth.)
Rößler, Thomas; Stein, Olaf; Heng, Yi; Baumeister, Paul; Hoffmann, Lars
2018-02-01
The accuracy of trajectory calculations performed by Lagrangian particle dispersion models (LPDMs) depends on various factors. The optimization of numerical integration schemes used to solve the trajectory equation helps to maximize the computational efficiency of large-scale LPDM simulations. We analyzed global truncation errors of six explicit integration schemes of the Runge-Kutta family, which we implemented in the Massive-Parallel Trajectory Calculations (MPTRAC) advection module. The simulations were driven by wind fields from operational analysis and forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) at T1279L137 spatial resolution and 3 h temporal sampling. We defined separate test cases for 15 distinct regions of the atmosphere, covering the polar regions, the midlatitudes, and the tropics in the free troposphere, in the upper troposphere and lower stratosphere (UT/LS) region, and in the middle stratosphere. In total, more than 5000 different transport simulations were performed, covering the months of January, April, July, and October for the years 2014 and 2015. We quantified the accuracy of the trajectories by calculating transport deviations with respect to reference simulations using a fourth-order Runge-Kutta integration scheme with a sufficiently fine time step. Transport deviations were assessed with respect to error limits based on turbulent diffusion. Independent of the numerical scheme, the global truncation errors vary significantly between the different regions. Horizontal transport deviations in the stratosphere are typically an order of magnitude smaller compared with the free troposphere. We found that the truncation errors of the six numerical schemes fall into three distinct groups, which mostly depend on the numerical order of the scheme. Schemes of the same order differ little in accuracy, but some methods need less computational time, which gives them an advantage in efficiency. The selection of the integration
Directory of Open Access Journals (Sweden)
T. Rößler
2018-02-01
Full Text Available The accuracy of trajectory calculations performed by Lagrangian particle dispersion models (LPDMs depends on various factors. The optimization of numerical integration schemes used to solve the trajectory equation helps to maximize the computational efficiency of large-scale LPDM simulations. We analyzed global truncation errors of six explicit integration schemes of the Runge–Kutta family, which we implemented in the Massive-Parallel Trajectory Calculations (MPTRAC advection module. The simulations were driven by wind fields from operational analysis and forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF at T1279L137 spatial resolution and 3 h temporal sampling. We defined separate test cases for 15 distinct regions of the atmosphere, covering the polar regions, the midlatitudes, and the tropics in the free troposphere, in the upper troposphere and lower stratosphere (UT/LS region, and in the middle stratosphere. In total, more than 5000 different transport simulations were performed, covering the months of January, April, July, and October for the years 2014 and 2015. We quantified the accuracy of the trajectories by calculating transport deviations with respect to reference simulations using a fourth-order Runge–Kutta integration scheme with a sufficiently fine time step. Transport deviations were assessed with respect to error limits based on turbulent diffusion. Independent of the numerical scheme, the global truncation errors vary significantly between the different regions. Horizontal transport deviations in the stratosphere are typically an order of magnitude smaller compared with the free troposphere. We found that the truncation errors of the six numerical schemes fall into three distinct groups, which mostly depend on the numerical order of the scheme. Schemes of the same order differ little in accuracy, but some methods need less computational time, which gives them an advantage in efficiency. The
A chaos detectable and time step-size adaptive numerical scheme for nonlinear dynamical systems
Chen, Yung-Wei; Liu, Chein-Shan; Chang, Jiang-Ren
2007-02-01
The first step in investigation the dynamics of a continuous time system described by ordinary differential equations is to integrate them to obtain trajectories. In this paper, we convert the group-preserving scheme (GPS) developed by Liu [International Journal of Non-Linear Mechanics 36 (2001) 1047-1068] to a time step-size adaptive scheme, x=x+hf(x,t), where x∈R is the system variables we are concerned with, and f(x,t)∈R is a time-varying vector field. The scheme has the form similar to the Euler scheme, x=x+Δtf(x,t), but our step-size h is adaptive automatically. Very interestingly, the ratio h/Δt, which we call the adaptive factor, can forecast the appearance of chaos if the considered dynamical system becomes chaotical. The numerical examples of the Duffing equation, the Lorenz equation and the Rossler equation, which may exhibit chaotic behaviors under certain parameters values, are used to demonstrate these phenomena. Two other non-chaotic examples are included to compare the performance of the GPS and the adaptive one.
Numerical Study of Two-Dimensional Volterra Integral Equations by RDTM and Comparison with DTM
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Reza Abazari
2013-01-01
Full Text Available The two-dimensional Volterra integral equations are solved using more recent semianalytic method, the reduced differential transform method (the so-called RDTM, and compared with the differential transform method (DTM. The concepts of DTM and RDTM are briefly explained, and their application to the two-dimensional Volterra integral equations is studied. The results obtained by DTM and RDTM together are compared with exact solution. As an important result, it is depicted that the RDTM results are more accurate in comparison with those obtained by DTM applied to the same Volterra integral equations. The numerical results reveal that the RDTM is very effective, convenient, and quite accurate compared to the other kind of nonlinear integral equations. It is predicted that the RDTM can be found widely applicable in engineering sciences.
Voytishek, Anton V.; Shipilov, Nikolay M.
2017-11-01
In this paper, the systematization of numerical (implemented on a computer) randomized functional algorithms for approximation of a solution of Fredholm integral equation of the second kind is carried out. Wherein, three types of such algorithms are distinguished: the projection, the mesh and the projection-mesh methods. The possibilities for usage of these algorithms for solution of practically important problems is investigated in detail. The disadvantages of the mesh algorithms, related to the necessity of calculation values of the kernels of integral equations in fixed points, are identified. On practice, these kernels have integrated singularities, and calculation of their values is impossible. Thus, for applied problems, related to solving Fredholm integral equation of the second kind, it is expedient to use not mesh, but the projection and the projection-mesh randomized algorithms.
Integrating Orthographic Information Across Time and Space.
Snell, Joshua; Bertrand, Daisy; Meeter, Martijn; Grainger, Jonathan
2018-01-01
Research has suggested that the word recognition process is influenced by the integration of orthographic information across words. The precise nature of this integration process may vary, however, depending on whether words are in temporal or spatial proximity. Here we present a lexical decision experiment, designed to compare temporal and spatial integration processes more directly. Masked priming was used to reveal effects of temporal integration, while the flanker paradigm was used to reveal effects of spatial integration. Primes/flankers were high-frequency orthographic neighbors of the target (blue-blur) or unrelated control words (head-blur). We replicated prior observations of inhibition in trials where the neighbor was used as a masked prime, while facilitation was observed in trials where the neighbor was presented as flanker. We conclude that sub-lexical orthographic information is integrated both temporally and spatially, but that spatial information is used to segregate lexical representations activated by spatially distinct sources.
Chebyshev Wavelet Method for Numerical Solution of Fredholm Integral Equations of the First Kind
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Hojatollah Adibi
2010-01-01
Full Text Available A computational method for solving Fredholm integral equations of the first kind is presented. The method utilizes Chebyshev wavelets constructed on the unit interval as basis in Galerkin method and reduces solving the integral equation to solving a system of algebraic equations. The properties of Chebyshev wavelets are used to make the wavelet coefficient matrices sparse which eventually leads to the sparsity of the coefficients matrix of obtained system. Finally, numerical examples are presented to show the validity and efficiency of the technique.
Directory of Open Access Journals (Sweden)
Mohamed Ali
2017-10-01
Full Text Available This work, Bernoulli wavelet method is formed to solve nonlinear fuzzy Volterra-Fredholm integral equations. Bernoulli wavelets have been Created by dilation and translation of Bernoulli polynomials. First we introduce properties of Bernoulli wavelets and Bernoulli polynomials, and then we used it to transform the integral equations to the system of algebraic equations. We compared the result of the proposed method with the exact solution to show the convergence and advantages of the new method. The results got by present wavelet method are compared with that of by collocation method based on radial basis functions method. Finally, the numerical examples explain the accuracy of this method.
Numerical simulation and experimental research of the integrated high-power LED radiator
Xiang, J. H.; Zhang, C. L.; Gan, Z. J.; Zhou, C.; Chen, C. G.; Chen, S.
2017-01-01
The thermal management has become an urgent problem to be solved with the increasing power and the improving integration of the LED (light emitting diode) chip. In order to eliminate the contact resistance of the radiator, this paper presented an integrated high-power LED radiator based on phase-change heat transfer, which realized the seamless connection between the vapor chamber and the cooling fins. The radiator was optimized by combining the numerical simulation and the experimental research. The effects of the chamber diameter and the parameters of fin on the heat dissipation performance were analyzed. The numerical simulation results were compared with the measured values by experiment. The results showed that the fin thickness, the fin number, the fin height and the chamber diameter were the factors which affected the performance of radiator from primary to secondary.
Fourth-Order Method for Numerical Integration of Age- and Size-Structured Population Models
Energy Technology Data Exchange (ETDEWEB)
Iannelli, M; Kostova, T; Milner, F A
2008-01-08
In many applications of age- and size-structured population models, there is an interest in obtaining good approximations of total population numbers rather than of their densities. Therefore, it is reasonable in such cases to solve numerically not the PDE model equations themselves, but rather their integral equivalents. For this purpose quadrature formulae are used in place of the integrals. Because quadratures can be designed with any order of accuracy, one can obtain numerical approximations of the solutions with very fast convergence. In this article, we present a general framework and a specific example of a fourth-order method based on composite Newton-Cotes quadratures for a size-structured population model.
Zhang, ShangHong; Xia, ZhongXi; Wang, TaiWei
2013-06-01
Decision support systems based on a virtual environment (VE) are becoming a popular platform in watershed simulation and management. Simulation speed and data visualization is of great significance to decision making, especially in urgent events. Real-time interaction during the simulation process is also very important for dealing with different conditions and for making timely decisions. In this study, a VE-based real-time interactive simulation framework (VERTISF) is developed and applied to simulation and management of the Dujiangyan Project in China. In VERTISF development, a virtual reality platform and numerical models were hosted on different computers and connected by a network to improve simulation speed. Different types of numerical models were generalized in a unified architecture based on time step, and interactive control was realized by modifying model boundary conditions at each time step. The "instruction-response" method and data interpolation were used to synchronize virtual environment visualization and numerical model calculation. Implementation of the framework was based on modular software design; various computer languages can be used to develop the appropriate module. Since only slight modification was needed for current numerical model integration in the framework, VERTISF was easy to extend. Results showed that VERTISF could take full advantage of hardware development, and it was a simple and effective solution for complex watershed simulation.
International Nuclear Information System (INIS)
Adler, A.; Fuchs, B.; Thielheim, K.O.
1977-01-01
The longitudinal development of electromagnetic cascades in air, copper, iron, and lead is studied on the basis of results derived recently by numerical integration of the cascade equations applying rather accurate expressions for the cross-sections involved with the interactions of high energy electrons, positrons, and photons in electromagnetic cascades. Special attention is given to scaling properties of transition curves. It is demonstrated that a good scaling may be achieved by means of the depth of maximum cascade development. (author)
Directory of Open Access Journals (Sweden)
Guliar O.
2015-12-01
Full Text Available On the basis of virtual work variations a new finite element with a variable crosssectional area along a generation, which due to numerical integration takes into account the variability of mechanical and geometrical parameters in cross-section was developed. In the process of test problem solving the correctness of the results, which allows to get this version of FE, was confirmed.
Discounting model selection with area-based measures: A case for numerical integration.
Gilroy, Shawn P; Hantula, Donald A
2018-03-01
A novel method for analyzing delay discounting data is proposed. This newer metric, a model-based Area Under Curve (AUC) combining approximate Bayesian model selection and numerical integration, was compared to the point-based AUC methods developed by Myerson, Green, and Warusawitharana (2001) and extended by Borges, Kuang, Milhorn, and Yi (2016). Using data from computer simulation and a published study, comparisons of these methods indicated that a model-based form of AUC offered a more consistent and statistically robust measurement of area than provided by using point-based methods alone. Beyond providing a form of AUC directly from a discounting model, numerical integration methods permitted a general calculation in cases when the Effective Delay 50 (ED50) measure could not be calculated. This allowed discounting model selection to proceed in conditions where data are traditionally more challenging to model and measure, a situation where point-based AUC methods are often enlisted. Results from simulation and existing data indicated that numerical integration methods extended both the area-based interpretation of delay discounting as well as the discounting model selection approach. Limitations of point-based AUC as a first-line analysis of discounting and additional extensions of discounting model selection were also discussed. © 2018 Society for the Experimental Analysis of Behavior.
Evans, Tanya M; Kochalka, John; Ngoon, Tricia J; Wu, Sarah S; Qin, Shaozheng; Battista, Christian; Menon, Vinod
2015-08-19
Early numerical proficiency lays the foundation for acquiring quantitative skills essential in today's technological society. Identification of cognitive and brain markers associated with long-term growth of children's basic numerical computation abilities is therefore of utmost importance. Previous attempts to relate brain structure and function to numerical competency have focused on behavioral measures from a single time point. Thus, little is known about the brain predictors of individual differences in growth trajectories of numerical abilities. Using a longitudinal design, with multimodal imaging and machine-learning algorithms, we investigated whether brain structure and intrinsic connectivity in early childhood are predictive of 6 year outcomes in numerical abilities spanning childhood and adolescence. Gray matter volume at age 8 in distributed brain regions, including the ventrotemporal occipital cortex (VTOC), the posterior parietal cortex, and the prefrontal cortex, predicted longitudinal gains in numerical, but not reading, abilities. Remarkably, intrinsic connectivity analysis revealed that the strength of functional coupling among these regions also predicted gains in numerical abilities, providing novel evidence for a network of brain regions that works in concert to promote numerical skill acquisition. VTOC connectivity with posterior parietal, anterior temporal, and dorsolateral prefrontal cortices emerged as the most extensive network predicting individual gains in numerical abilities. Crucially, behavioral measures of mathematics, IQ, working memory, and reading did not predict children's gains in numerical abilities. Our study identifies, for the first time, functional circuits in the human brain that scaffold the development of numerical skills, and highlights potential biomarkers for identifying children at risk for learning difficulties. Children show substantial individual differences in math abilities and ease of math learning. Early
Xing, Yanyuan; Yan, Yubin
2018-03-01
Gao et al. [11] (2014) introduced a numerical scheme to approximate the Caputo fractional derivative with the convergence rate O (k 3 - α), 0 definition of the Caputo fractional derivative, see also Lv and Xu [20] (2016), where k is the time step size. Under the assumption that the solution of the time fractional partial differential equation is sufficiently smooth, Lv and Xu [20] (2016) proved by using energy method that the corresponding numerical method for solving time fractional partial differential equation has the convergence rate O (k 3 - α), 0 time variable t. However, in general the solution of the time fractional partial differential equation has low regularity and in this case the numerical method fails to have the convergence rate O (k 3 - α), 0 time variable t. In this paper, we first obtain a similar approximation scheme to the Riemann-Liouville fractional derivative with the convergence rate O (k 3 - α), 0 time discretization scheme to approximate the time fractional partial differential equation and show by using Laplace transform methods that the time discretization scheme has the convergence rate O (k 3 - α), 0 0 for smooth and nonsmooth data in both homogeneous and inhomogeneous cases. Numerical examples are given to show that the theoretical results are consistent with the numerical results.
Numerical calculation of a class of highly oscillatory integrals with the Mathieu function
International Nuclear Information System (INIS)
Long Yongxing
1992-01-01
The author describes a method for computing highly oscillatory integrals with the Mathieu function. The practice proves that not only the results are highly satisfactory, but also the method is time-saving
Ellmer, Matthias; Mayer-Gürr, Torsten
2016-04-01
Future gravity missions like GRACE-FO and beyond will deliver low-low satellite-to-satellite (ll-sst) ranging measurements of much increased precision. This necessitates a re-evaluation of the processes used in gravity field determination with an eye to numerical stability. When computing gravity fields from ll-sst data, precise positions of both satellites are needed in the setup of the observation equations. These positions thus have an immediate effect on the sought-after gravity field parameters. We use reduced-dynamic orbits which are computed through integration of all accelerations experienced by the satellite, as determined through a priori models and observed through the accelerometer. Our simulations showed that computing the orbit of the satellite through complete integration of all acting forces leads to numeric instabilities magnitudes larger than the expected ranging accuracy. We introduce a numerically stable approach employing a best-fit keplerian reference orbit based on Encke's method. Our investigations revealed that using canonical formulations for the evaluation of the reference keplerian orbit and accelerations lead to insufficient precision, necessitating an alternative formulation like the equinoctial elements.
International Nuclear Information System (INIS)
Kiefer, B; Bartel, T; Menzel, A
2012-01-01
Several constitutive models for magnetic shape memory alloys (MSMAs) have been proposed in the literature. The implementation of numerical integration schemes, which allow the prediction of constitutive response for general loading cases and ultimately the incorporation of MSMA response into numerical solution algorithms for fully coupled magneto-mechanical boundary value problems, however, has received only very limited attention. In this work, we establish two algorithmic implementations of the internal variable model for MSMAs proposed in (Kiefer and Lagoudas 2005 Phil. Mag. Spec. Issue: Recent Adv. Theor. Mech. 85 4289–329, Kiefer and Lagoudas 2009 J. Intell. Mater. Syst. 20 143–70), where we restrict our attention to pure martensitic variant reorientation to limit complexity. The first updating scheme is based on the numerical integration of the reorientation strain evolution equation and represents a classical predictor–corrector-type general return mapping algorithm. In the second approach, the inequality-constrained optimization problem associated with internal variable evolution is converted into an unconstrained problem via Fischer–Burmeister complementarity functions and then iteratively solved in standard Newton–Raphson format. Simulations are verified by comparison to closed-form solutions for experimentally relevant loading cases. (paper)
The numerical analysis of functional integral and integro-differential equations of Volterra type
Brunner, Hermann
The qualitative and quantitative analysis of numerical methods for delay differential equations is now quite well understood, as reflected in the recent monograph by Bellen and Zennaro (2003). This is in remarkable contrast to the situation in the numerical analysis of functional equations, in which delays occur in connection with memory terms described by Volterra integral operators. The complexity of the convergence and asymptotic stability analyses has its roots in new `dimensions' not present in DDEs: the problems have distributed delays; kernels in the Volterra operators may be weakly singular; a second discretization step (approximation of the memory term by feasible quadrature processes) will in general be necessary before solution approximations can be computed.The purpose of this review is to introduce the reader to functional integral and integro-differential equations of Volterra type and their discretization, focusing on collocation techniques; to describe the `state of the art' in the numerical analysis of such problems; and to show that - especially for many `classical' equations whose analysis dates back more than 100 years - we still have a long way to go before we reach a level of insight into their discretized versions to compare with that achieved for DDEs.
Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model
Energy Technology Data Exchange (ETDEWEB)
Baudron, Anne-Marie, E-mail: anne-marie.baudron@cea.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CEA-DRN/DMT/SERMA, CEN-Saclay, 91191 Gif sur Yvette Cedex (France); Lautard, Jean-Jacques, E-mail: jean-jacques.lautard@cea.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CEA-DRN/DMT/SERMA, CEN-Saclay, 91191 Gif sur Yvette Cedex (France); Maday, Yvon, E-mail: maday@ann.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7598, Laboratoire Jacques-Louis Lions and Institut Universitaire de France, F-75005, Paris (France); Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); Brown Univ, Division of Applied Maths, Providence, RI (United States); Riahi, Mohamed Kamel, E-mail: riahi@cmap.polytechnique.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CMAP, Inria-Saclay and X-Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Salomon, Julien, E-mail: salomon@ceremade.dauphine.fr [CEREMADE, Univ Paris-Dauphine, Pl. du Mal. de Lattre de Tassigny, F-75016, Paris (France)
2014-12-15
In this paper we present a time-parallel algorithm for the 3D neutrons calculation of a transient model in a nuclear reactor core. The neutrons calculation consists in numerically solving the time dependent diffusion approximation equation, which is a simplified transport equation. The numerical resolution is done with finite elements method based on a tetrahedral meshing of the computational domain, representing the reactor core, and time discretization is achieved using a θ-scheme. The transient model presents moving control rods during the time of the reaction. Therefore, cross-sections (piecewise constants) are taken into account by interpolations with respect to the velocity of the control rods. The parallelism across the time is achieved by an adequate use of the parareal in time algorithm to the handled problem. This parallel method is a predictor corrector scheme that iteratively combines the use of two kinds of numerical propagators, one coarse and one fine. Our method is made efficient by means of a coarse solver defined with large time step and fixed position control rods model, while the fine propagator is assumed to be a high order numerical approximation of the full model. The parallel implementation of our method provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch–Maurer–Werner benchmark.
Numerical integration and FEM-implementation of a viscoplastic Chaboche-model with static recovery
Kullig, E.; Wippler, S.
2006-11-01
This paper is concerned with the implementation of a viscoplastic material model of the Chaboche type in the framework of the finite element method (FEM). The equations of the used constitutive law, that incorporates isotropic hardening, back stress evolution with static recovery terms and drag stress evolution, are introduced. A representation of their numerical integration using the implicit backward Euler method under the assumption of small deformations and an isothermal formulation follows. The use of the backward Euler method leads to a nonlinear algebraic system of three equations, which is solved by a combination of the Pegasus method and a fixed-point iteration. After considering the accuracy of the presented integration algorithm in form of iso-error maps, the derivation of the consistent viscoplastic tangent operator is shown. The integration scheme and the calculation of the consistent viscoplastic tangent operator are implemented in the commercial finite element code ABAQUS, using the possibility of the user-defined material subroutine (UMAT). Finally a numerical example in form of a notched bar under tension is presented.
On the numerical evaluation of algebro-geometric solutions to integrable equations
International Nuclear Information System (INIS)
Kalla, C; Klein, C
2012-01-01
Physically meaningful periodic solutions to certain integrable partial differential equations are given in terms of multi-dimensional theta functions associated with real Riemann surfaces. Typical analytical problems in the numerical evaluation of these solutions are studied. In the case of hyperelliptic surfaces efficient algorithms exist even for almost degenerate surfaces. This allows the numerical study of solitonic limits. For general real Riemann surfaces, the choice of a homology basis adapted to the anti-holomorphic involution is important for a convenient formulation of the solutions and smoothness conditions. Since existing algorithms for algebraic curves produce a homology basis not related to automorphisms of the curve, we study symplectic transformations to an adapted basis and give explicit formulae for M-curves. As examples we discuss solutions of the Davey–Stewartson and the multi-component nonlinear Schrödinger equations
Numerical Modeling of an Integrated Vehicle Fluids System Loop for Pressurizing a Cryogenic Tank
LeClair, A. C.; Hedayat, A.; Majumdar, A. K.
2017-01-01
This paper presents a numerical model of the pressurization loop of the Integrated Vehicle Fluids (IVF) system using the Generalized Fluid System Simulation Program (GFSSP). The IVF propulsion system, being developed by United Launch Alliance to reduce system weight and enhance reliability, uses boiloff propellants to drive thrusters for the reaction control system as well as to run internal combustion engines to develop power and drive compressors to pressurize propellant tanks. NASA Marshall Space Flight Center (MSFC) conducted tests to verify the functioning of the IVF system using a flight-like tank. GFSSP, a finite volume based flow network analysis software developed at MSFC, has been used to support the test program. This paper presents the simulation of three different test series, comparison of numerical prediction and test data and a novel method of presenting data in a dimensionless form. The paper also presents a methodology of implementing a compressor map in a system level code.
Numerical time-domain modelling of hoof-ground interaction during the stance phase.
Behnke, R
2017-11-09
Hoof-ground interaction impacts on the health and performance characteristics of horses. Due to complex interactions between hoof and ground during the stance phase, previous experimentally dominated studies concentrated on subproblems of the phenomena observed. A multidisciplinary methodology with mathematical modelling, material testing and in vivo experimental measurements seems promising. With the help of a mathematical approach, this contribution aims to explain from a biomechanical point of view the phenomena observed during experimental investigations (hoof acceleration, interacting forces) and aims to contribute to an overall experimental-mathematical multidisciplinary approach. In silico modelling of hoof-ground interaction (limb, hoof and horizontally unbounded ground). Hoof-ground interaction is represented by a time-domain finite element model including the limb, the hoof and the unbounded representation of the ground via the scaled boundary finite element method to capture radiation damping during the stance phase. Motoric forces (driving forces) of the horse during locomotion are included. Numerical model results for acceleration-time relations (hoof) at different trotting velocities are compared with previously published acceleration-time relations and show qualitative agreement. From the model approach, power loss due to different ground properties and ground damping is computed in combination with the maximum limb force during the stance phase. Intentionally, a simplified model approach for the material and structural representation of the limb, the hoof and the ground in terms of material features and spatial resolution has been used for this study, which might be the basis for a model refinement in terms of contact properties as well as the integration of bone and joint structures. The comparison to experimentally obtained results demonstrates the applicability of the model, which, in turn, enables an insight into the processes taking place
Numerical evaluation of Feynman loop integrals by reduction to tree graphs
Energy Technology Data Exchange (ETDEWEB)
Kleinschmidt, T.
2007-12-15
We present a method for the numerical evaluation of loop integrals, based on the Feynman Tree Theorem. This states that loop graphs can be expressed as a sum of tree graphs with additional external on-shell particles. The original loop integral is replaced by a phase space integration over the additional particles. In cross section calculations and for event generation, this phase space can be sampled simultaneously with the phase space of the original external particles. Since very sophisticated matrix element generators for tree graph amplitudes exist and phase space integrations are generically well understood, this method is suited for a future implementation in a fully automated Monte Carlo event generator. A scheme for renormalization and regularization is presented. We show the construction of subtraction graphs which cancel ultraviolet divergences and present a method to cancel internal on-shell singularities. Real emission graphs can be naturally included in the phase space integral of the additional on-shell particles to cancel infrared divergences. As a proof of concept, we apply this method to NLO Bhabha scattering in QED. Cross sections are calculated and are in agreement with results from conventional methods. We also construct a Monte Carlo event generator and present results. (orig.)
Chan, William M.
1992-01-01
This project forms part of the long term computational effort to simulate the time dependent flow over the integrated Space Shuttle vehicle (orbiter, solid rocket boosters (SRB's), external tank (ET), and attach hardware) during its ascent mode for various nominal and abort flight conditions. Due to the limitations of experimental data such as wind tunnel wall effects and the difficulty of safely obtaining valid flight data, numerical simulations are undertaken to supplement the existing data base. This data can then be used to predict the aerodynamic behavior over a wide range of flight conditions. Existing computational results show relatively good overall comparison with experiments but further refinement is required to reduce numerical errors and to obtain finer agreements over a larger parameter space. One of the important goals of this project is to obtain better comparisons between numerical simulations and experiments. In the simulations performed so far, the geometry has been simplified in various ways to reduce the complexity so that useful results can be obtained in a reasonable time frame due to limitations in computer resources. In this project, the finer details of the major components of the Space Shuttle are modeled better by including more complexity in the geometry definition. Smaller components not included in early Space Shuttle simulations will now be modeled and gridded.
Ryabinkin, Ilya G; Nagesh, Jayashree; Izmaylov, Artur F
2015-11-05
We have developed a numerical differentiation scheme that eliminates evaluation of overlap determinants in calculating the time-derivative nonadiabatic couplings (TDNACs). Evaluation of these determinants was the bottleneck in previous implementations of mixed quantum-classical methods using numerical differentiation of electronic wave functions in the Slater determinant representation. The central idea of our approach is, first, to reduce the analytic time derivatives of Slater determinants to time derivatives of molecular orbitals and then to apply a finite-difference formula. Benchmark calculations prove the efficiency of the proposed scheme showing impressive several-order-of-magnitude speedups of the TDNAC calculation step for midsize molecules.
NUMERICAL METHODS FOR SOLVING THE MULTI-TERM TIME-FRACTIONAL WAVE-DIFFUSION EQUATION
Liu, F.; Meerschaert, M.M.; McGough, R.J.; Zhuang, P.; Liu, Q.
2013-01-01
In this paper, the multi-term time-fractional wave-diffusion equations are considered. The multi-term time fractional derivatives are defined in the Caputo sense, whose orders belong to the intervals [0,1], [1,2), [0,2), [0,3), [2,3) and [2,4), respectively. Some computationally effective numerical methods are proposed for simulating the multi-term time-fractional wave-diffusion equations. The numerical results demonstrate the effectiveness of theoretical analysis. These methods and technique...
Numerical analysis of diffuse ceiling ventilation and its integration with a radiant ceiling system
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per Kvols; Chen, Qingyan
2017-01-01
A novel system combining diffuse ceiling ventilation and radiant ceiling was proposed recently, with the aim of providing energy efficient and comfort environment to office buildings. Designing of such a system is challenging because of complex interactions between the two subsystems and a large...... number of design parameters encountered in practice. This study aimed to develop a numerical model that can reliably predict the airflow and thermal performance of the integrated system during the design stage. The model was validated by experiments under different operating conditions. The validated...
Majumdar, Alok K.; LeClair, Andre C.; Hedayat, Ali
2016-01-01
This paper presents a numerical model of pressurization of a cryogenic propellant tank for the Integrated Vehicle Fluid (IVF) system using the Generalized Fluid System Simulation Program (GFSSP). The IVF propulsion system, being developed by United Launch Alliance, uses boiloff propellants to drive thrusters for the reaction control system as well as to run internal combustion engines to develop power and drive compressors to pressurize propellant tanks. NASA Marshall Space Flight Center (MSFC) has been running tests to verify the functioning of the IVF system using a flight tank. GFSSP, a finite volume based flow network analysis software developed at MSFC, has been used to develop an integrated model of the tank and the pressurization system. This paper presents an iterative algorithm for converging the interface boundary conditions between different component models of a large system model. The model results have been compared with test data.
Ulku, Huseyin Arda
2012-09-01
An explicit yet stable marching-on-in-time (MOT) scheme for solving the time domain magnetic field integral equation (TD-MFIE) is presented. The stability of the explicit scheme is achieved via (i) accurate evaluation of the MOT matrix elements using closed form expressions and (ii) a PE(CE) m type linear multistep method for time marching. Numerical results demonstrate the accuracy and stability of the proposed explicit MOT-TD-MFIE solver. © 2012 IEEE.
A stable numerical inversion of Abel's integral equation using almost Bernstein operational matrix
International Nuclear Information System (INIS)
Singh, Om P.; Singh, Vineet K.; Pandey, Rajesh K.
2010-01-01
Many problems in physics like reconstruction of the radially distributed emissivity from the line-of-sight projected intensity, the 3-D image reconstruction from cone-beam projections in computerized tomography, etc. lead naturally, in the case of radial symmetry, to the study of Abel's type integral equation. The aim of this communication is to modify the stable algorithm proposed in [Singh VK, Pandey RK, Singh OP. New stable numerical solution of singular integral equations of Abel type by using normalized Bernstein polynomials. Applied Mathematical Sciences 2009;3(5):241-255] which is based on normalized Bernstein polynomial approximation of the projected intensity profile. So, first we construct an orthonormal family {b i5 } i=0 5 of polynomials of degree 5 from the 5th degree Bernstein polynomials B i5 and use them as a basis to approximate the projected intensity profile. Then, a 6x6 matrix P, named as almost Bernstein operational matrix of integration is constructed and used to reduce the integral equation to a system of algebraic equation which can be solved easily. The method is quite accurate and stable even though the approximations are performed by polynomials of degree 5, as illustrated by applying the method to intensity data with and without random noise to invert and compare it with those obtained by the other methods or with the known analytical inverse. Thus it is good method for applying to experimental intensities distorted by noise.
Ecotoxicology and macroecology--time for integration.
Beketov, Mikhail A; Liess, Matthias
2012-03-01
Despite considerable progress in ecotoxicology, it has become clear that this discipline cannot answer its central questions, such as, "What are the effects of toxicants on biodiversity?" and "How the ecosystem functions and services are affected by the toxicants?". We argue that if such questions are to be answered, a paradigm shift is needed. The current bottom-up approach of ecotoxicology that implies the use of small-scale experiments to predict effects on the entire ecosystems and landscapes should be merged with a top-down macroecological approach that is directly focused on ecological effects at large spatial scales and consider ecological systems as integral entities. Analysis of the existing methods in ecotoxicology, ecology, and environmental chemistry shows that such integration is currently possible. Therefore, we conclude that to tackle the current pressing challenges, ecotoxicology has to progress using both the bottom-up and top-down approaches, similar to digging a tunnel from both ends at once. Copyright © 2011 Elsevier Ltd. All rights reserved.
Szerszeń, Krzysztof; Zieniuk, Eugeniusz
2016-06-01
The paper presents a strategy for numerical solving of parametric integral equation system (PIES) for 2D potential problems without explicit calculation of singular integrals. The values of these integrals will be expressed indirectly in terms of easy to compute non-singular integrals. The effectiveness of the proposed strategy is investigated with the example of potential problem modeled by the Laplace equation. The strategy simplifies the structure of the program with good the accuracy of the obtained solutions.
Numerical Modelling of Mechanical Integrity of the Copper-Cast Iron Canister. A Literature Review
International Nuclear Information System (INIS)
Lanru Jing
2004-04-01
This review article presents a summary of the research works on the numerical modelling of the mechanical integrity of the composite copper-cast iron canisters for the final disposal of Swedish nuclear wastes, conducted by SKB and SKI since 1992. The objective of the review is to evaluate the outstanding issues existing today about the basic design concepts and premises, fundamental issues on processes, properties and parameters considered for the functions and requirements of canisters under the conditions of a deep geological repository. The focus is placed on the adequacy of numerical modelling approaches adopted in regards to the overall mechanical integrity of the canisters, especially the initial state of canisters regarding defects and the consequences of their evolution under external and internal loading mechanisms adopted in the design premises. The emphasis is the stress-strain behaviour and failure/strength, with creep and plasticity involved. Corrosion, although one of the major concerns in the field of canister safety, was not included
Ulku, Huseyin Arda
2013-08-01
An explicit marching on-in-time (MOT) scheme for solving the time-domain magnetic field integral equation (TD-MFIE) is presented. The proposed MOT-TD-MFIE solver uses Rao-Wilton-Glisson basis functions for spatial discretization and a PE(CE)m-type linear multistep method for time marching. Unlike previous explicit MOT-TD-MFIE solvers, the time step size can be chosen as large as that of the implicit MOT-TD-MFIE solvers without adversely affecting accuracy or stability. An algebraic stability analysis demonstrates the stability of the proposed explicit solver; its accuracy and efficiency are established via numerical examples. © 1963-2012 IEEE.
Želi, Velibor; Zorica, Dušan
2018-02-01
Generalization of the heat conduction equation is obtained by considering the system of equations consisting of the energy balance equation and fractional-order constitutive heat conduction law, assumed in the form of the distributed-order Cattaneo type. The Cauchy problem for system of energy balance equation and constitutive heat conduction law is treated analytically through Fourier and Laplace integral transform methods, as well as numerically by the method of finite differences through Adams-Bashforth and Grünwald-Letnikov schemes for approximation derivatives in temporal domain and leap frog scheme for spatial derivatives. Numerical examples, showing time evolution of temperature and heat flux spatial profiles, demonstrate applicability and good agreement of both methods in cases of multi-term and power-type distributed-order heat conduction laws.
Global integration in times of crisis
DEFF Research Database (Denmark)
Jensen, Camilla
Past research suggests that a financial crisis event has a dual and ambiguous effect on the exporting strategy of subsidiaries of multinational firms in a value chain and offshoring perspective. From a total volume perspective exports are expected to contract due to a decline in demand (demand...... to reconcile these findings by testing a number of hypothesis about global integration strategies in the context of the global financial crisis and how it affected exporting among multinational subsidiaries operating out of Turkey. Controlling for the impact that depreciations and exchange rate volatility has...... on firm-level exports the study shows that the particular global event studied only had a positive effect (if any) on individual firms' exports. Since multinational subsidiaries are insulated from these effects as documented in this study they are able to expand rather than contract their global...
Guevara Hidalgo, Esteban; Nemoto, Takahiro; Lecomte, Vivien
Rare trajectories of stochastic systems are important to understand because of their potential impact. However, their properties are by definition difficult to sample directly. Population dynamics provide a numerical tool allowing their study, by means of simulating a large number of copies of the system, which are subjected to a selection rule that favors the rare trajectories of interest. However, such algorithms are plagued by finite simulation time- and finite population size- effects that can render their use delicate. Using the continuous-time cloning algorithm, we analyze the finite-time and finite-size scalings of estimators of the large deviation functions associated to the distribution of the rare trajectories. We use these scalings in order to propose a numerical approach which allows to extract the infinite-time and infinite-size limit of these estimators.
International Nuclear Information System (INIS)
Takeda, H.; Isha, H.
1981-01-01
The paper is concerned with the displacement-assumed-finite elements by applying the reduced numerical integration technique in structural problems. The first part is a general consideration on the technique. Its purpose is to examine a variational interpretation of the finite element displacement formulation with the reduced integration technique in structural problems. The formulation is critically studied from a standpoint of the natural stiffness approach. It is shown that these types of elements are equivalent to a certain type of displacement and stress assumed mixed elements. The rank deficiency of the stiffness matrix of these elements is interpreted as a problem in the transformation from the natural system to a Cartesian system. It will be shown that a variational basis of the equivalent mixed formulation is closely related to the Hellinger-Reissner's functional. It is presented that for simple elements, e.g. bilinear quadrilateral plane stress and plate bending there are corresponding mixed elements from the functional. For relatively complex types of these elements, it is shown that they are equivalent to localized mixed elements from the Hellinger-Reissner's functional. In the second part, typical finite elements with the reduced integration technique are studied to demonstrate this equivalence. A bilinear displacement and rotation assumed shear beam element, a bilinear displacement assumed quadrilateral plane stress element and a bilinear deflection and rotation assumed quadrilateral plate bending element are examined to present equivalent mixed elements. Not only the theoretical consideration is presented but numerical studies are shown to demonstrate the effectiveness of these elements in practical analysis. (orig.)
International Nuclear Information System (INIS)
Pujols, Agnes
1991-01-01
We prove that the scattering operator for the wave equation in the exterior of an non-homogeneous obstacle exists. Its distribution kernel is represented by a time-dependent boundary integral equation. A space-time integral variational formulation is developed for determining the current induced by the scattering of an electromagnetic wave by an homogeneous object. The discrete approximation of the variational problem using a finite element method in both space and time leads to stable convergent schemes, giving a numerical code for perfectly conducting cylinders. (author) [fr
Experimental and numerical investigations of the energy confinement times in the stellarator TJ-K
Energy Technology Data Exchange (ETDEWEB)
Ali, Ahmed; Koehn, Alf; Munoz, Alejandro; Holzhauer, Eberhard; Ramisch, Mirko [Institute of Interfacial Process Engineering and Plasma Technology IGVP, Uni Stuttgart, Stuttgart (Germany); Birkenmeier, Gregor [Max-Planck Institute fuer Plasmaphysik, Garching (Germany)
2015-05-01
A particle and power balance model has been employed to numerically simulate and qualitatively understand transport processes, which determine equilibrium density and temperature profiles in the stellarator TJ-K. To quantify losses by these processes, the e-folding time of density and energy after switching off the heating source is used as a measure of the corresponding confinement times. For comparison with numerical simulation, both quantities are investigated experimentally in TJ-K. The particle confinement can be directly deduced from an interferometer or from Langmuir probes measuring the ion-saturation current. A commercial satellite receiver is used to measure the emitted radiation around 12 GHz, which is assumed to be dominated by Bremsstrahlung. In addition, the signal from a fast diode, which is sensitive in the visible range of light, is used. Results of the comparative numerical and experimental studies are presented.
International Nuclear Information System (INIS)
Bechlars, J.
1978-12-01
1) Integrable (L 1 ) singularities, occuring on the boundary or along the diagonal direction, and jumps along the diagonal direction do not disturb the compactness of otherwise continuous integral operator kernels. So the theory of compact operators can be applied for solving the integral equation. 2) Provided the regular parts of the kernel are sufficiently differentiable, the continuous differentiability (Cn) of the right hand side is transposed to the solution, if the kernel has no singularities or no singularities on the boundary and no jump. In the case of singularities in connection with a jump examples show, that this result is not valid in general. Therefore a second definition of smoothness has been introduced (Csup((n,α)) : continuous differentiability in the interior and 'limitation of derivatives') which can be applied in such cases and on the other side shows satisfactory error behaviour during interpolation and includes singularities from logarithms and negative powers. Provided diagonal singularities or singularities on the boundary can be asigned to Csup((n+1,α-1)) (0 2 also Csup((2,α)) (0 -2 ). This is confirmed by numerical examples. (orig./HSI) [de
Laboratory and Numerical Investigations of Residence Time Distribution of Fluids in Laminar Flow Stirred Annular PhotoreactorE. Sahle-Demessie1, Siefu Bekele2, U. R. Pillai11U.S. EPA, National Risk Management Research LaboratorySustainable Technology Division,...
International Nuclear Information System (INIS)
Lee, W.W.
2003-01-01
Particle simulation has played an important role for the recent investigations on turbulence in magnetically confined plasmas. In this paper, theoretical and numerical properties of a gyrokinetic plasma as well as its relationship with magnetohydrodynamics (MHD) are discussed with the ultimate aim of simulating microturbulence in transport time scale using massively parallel computers
New numerical methods for solving the time-dependent Maxwell equations
De Raedt, H; Kole, JS; Michielsen, KFL; Figge, MT; Berz, M; Makino, K
2005-01-01
We review some recent developments in numerical algorithms to solve the time-dependent Maxwell equations for systems with spatially varying permittivity and permeabilitly. We show that the Suzuki product-formula approach can be used to construct a family of unconditionally stable algorithms, the
International Nuclear Information System (INIS)
Tong, S.S.; Powell, D.; Goel, S.
1992-02-01
A new software system called Engineous combines artificial intelligence and numerical methods for the design and optimization of complex aerospace systems. Engineous combines the advanced computational techniques of genetic algorithms, expert systems, and object-oriented programming with the conventional methods of numerical optimization and simulated annealing to create a design optimization environment that can be applied to computational models in various disciplines. Engineous has produced designs with higher predicted performance gains that current manual design processes - on average a 10-to-1 reduction of turnaround time - and has yielded new insights into product design. It has been applied to the aerodynamic preliminary design of an aircraft engine turbine, concurrent aerodynamic and mechanical preliminary design of an aircraft engine turbine blade and disk, a space superconductor generator, a satellite power converter, and a nuclear-powered satellite reactor and shield. 23 refs
Ubiquitous time variability of integrated stellar populations
Conroy, Charlie; van Dokkum, Pieter G.; Choi, Jieun
2015-11-01
Long-period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to about 1,000 days and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode, which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population. The overall number of long-period variables in a population is directly related to their lifetimes, which is difficult to predict from first principles because of uncertainties associated with stellar mass-loss and convective mixing. The time variability of these stars has not previously been taken into account when modelling the spectral energy distributions of galaxies. Here we construct time-dependent stellar population models that include the effects of long-period variable stars, and report the ubiquitous detection of this expected ‘pixel shimmer’ in the massive metal-rich galaxy M87. The pixel light curves display a variety of behaviours. The observed variation of 0.1 to 1 per cent is very well matched to the predictions of our models. The data provide a strong constraint on the properties of variable stars in an old and metal-rich stellar population, and we infer that the lifetime of long-period variables in M87 is shorter by approximately 30 per cent compared to predictions from the latest stellar evolution models.
Numerical modeling of wind turbine aerodynamic noise in the time domain.
Lee, Seunghoon; Lee, Seungmin; Lee, Soogab
2013-02-01
Aerodynamic noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge noise model is used to determine the unsteady pressure on the blade surface. The far-field noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine noise can be quite different with respect to the distance and direction from the wind turbine.
On-the-fly Numerical Surface Integration for Finite-Difference Poisson-Boltzmann Methods.
Cai, Qin; Ye, Xiang; Wang, Jun; Luo, Ray
2011-11-01
Most implicit solvation models require the definition of a molecular surface as the interface that separates the solute in atomic detail from the solvent approximated as a continuous medium. Commonly used surface definitions include the solvent accessible surface (SAS), the solvent excluded surface (SES), and the van der Waals surface. In this study, we present an efficient numerical algorithm to compute the SES and SAS areas to facilitate the applications of finite-difference Poisson-Boltzmann methods in biomolecular simulations. Different from previous numerical approaches, our algorithm is physics-inspired and intimately coupled to the finite-difference Poisson-Boltzmann methods to fully take advantage of its existing data structures. Our analysis shows that the algorithm can achieve very good agreement with the analytical method in the calculation of the SES and SAS areas. Specifically, in our comprehensive test of 1,555 molecules, the average unsigned relative error is 0.27% in the SES area calculations and 1.05% in the SAS area calculations at the grid spacing of 1/2Å. In addition, a systematic correction analysis can be used to improve the accuracy for the coarse-grid SES area calculations, with the average unsigned relative error in the SES areas reduced to 0.13%. These validation studies indicate that the proposed algorithm can be applied to biomolecules over a broad range of sizes and structures. Finally, the numerical algorithm can also be adapted to evaluate the surface integral of either a vector field or a scalar field defined on the molecular surface for additional solvation energetics and force calculations.
McBeck, Jessica A.; Cooke, Michele L.; Herbert, Justin W.; Maillot, Bertrand; Souloumiac, Pauline
2017-09-01
We employ work optimization to predict the geometry of frontal thrusts at two stages of an evolving physical accretion experiment. Faults that produce the largest gains in efficiency, or change in external work per new fault area, ΔWext/ΔA, are considered most likely to develop. The predicted thrust geometry matches within 1 mm of the observed position and within a few degrees of the observed fault dip, for both the first forethrust and backthrust when the observed forethrust is active. The positions of the second backthrust and forethrust that produce >90% of the maximum ΔWext/ΔA also overlap the observed thrusts. The work optimal fault dips are within a few degrees of the fault dips that maximize the average Coulomb stress. Slip gradients along the detachment produce local elevated shear stresses and high strain energy density regions that promote thrust initiation near the detachment. The mechanical efficiency (Wext) of the system decreases at each of the two simulated stages of faulting and resembles the evolution of experimental force. The higher ΔWext/ΔA due to the development of the first pair relative to the second pair indicates that the development of new thrusts may lead to diminishing efficiency gains as the wedge evolves. The numerical estimates of work consumed by fault propagation overlap the range calculated from experimental force data and crustal faults. The integration of numerical and physical experiments provides a powerful approach that demonstrates the utility of work optimization to predict the development of faults.
Numerical analysis of effects of measurement errors on ultrasonic-measurement-integrated simulation.
Funamoto, Kenichi; Hayase, Toshiyuki; Saijo, Yoshifumi; Yambe, Tomoyuki
2011-03-01
Ultrasonic-measurement-integrated (UMI) simulation, in which feedback signals are applied to the governing equations based on errors between ultrasonic measurement and numerical simulation, has been investigated for reproduction of the blood flow field. However, ultrasonic measurement data inherently include some errors. In this study, the effects of four major measurement errors, namely, errors due to gaussian noise, aliasing, wall filter, and lack of data, on UMI simulation were examined by a numerical experiment dealing with the blood flow field in the descending aorta with an aneurysm, the same as in our previous study. While solving the governing equations in UMI simulation, gaussian noise did not prevent the UMI simulation from effectively reproducing the blood flow field. In contrast, aliasing caused significant errors in UMI simulation. Effects of wall filter and lack of data appeared in diastole and in the whole period, respectively. By detecting significantly large feedback signals as a sign of aliasing and by not adding feedback signals where measured Doppler velocities were aliasing or zero, the computational accuracy substantially improved, alleviating the effects of measurement errors. Through these considerations, UMI simulation can provide accurate and detailed information on hemodynamics with suppression of four major measurement errors.
Improving Music Genre Classification by Short-Time Feature Integration
DEFF Research Database (Denmark)
Meng, Anders; Ahrendt, Peter; Larsen, Jan
2005-01-01
Many different short-time features, using time windows in the size of 10-30 ms, have been proposed for music segmentation, retrieval and genre classification. However, often the available time frame of the music to make the actual decision or comparison (the decision time horizon) is in the range...... of seconds instead of milliseconds. The problem of making new features on the larger time scale from the short-time features (feature integration) has only received little attention. This paper investigates different methods for feature integration and late information fusion for music genre classification...
Energy Technology Data Exchange (ETDEWEB)
Hurd, J.V.
1986-01-01
One of the elements of the 750-keV polarized H/sup -/ injection transport at LAMPF is a Wien (E x B) filter. The Wien filter is used to process the spin of the polarized H/sup -/ ions to the appropriate orientation needed by the experiments. The proton-spin orientation is changed several times during a production cycle. At each new setting of the Wien filter, the beam is focused differently and the beam transport must be returned for an optimum match into the linac. The transport is tuned interactively using the first-order optics code TRACE. The first-order transformation matrix for a simple Wien filter is developed for use in TRACE and the transformation is compared to results of numerical integration to determine the validity of the first-order approximation.
An integrated numerical and physical modeling system for an enhanced in situ bioremediation process
International Nuclear Information System (INIS)
Huang, Y.F.; Huang, G.H.; Wang, G.Q.; Lin, Q.G.; Chakma, A.
2006-01-01
Groundwater contamination due to releases of petroleum products is a major environmental concern in many urban districts and industrial zones. Over the past years, a few studies were undertaken to address in situ bioremediation processes coupled with contaminant transport in two- or three-dimensional domains. However, they were concentrated on natural attenuation processes for petroleum contaminants or enhanced in situ bioremediation processes in laboratory columns. In this study, an integrated numerical and physical modeling system is developed for simulating an enhanced in situ biodegradation (EISB) process coupled with three-dimensional multiphase multicomponent flow and transport simulation in a multi-dimensional pilot-scale physical model. The designed pilot-scale physical model is effective in tackling natural attenuation and EISB processes for site remediation. The simulation results demonstrate that the developed system is effective in modeling the EISB process, and can thus be used for investigating the effects of various uncertainties. - An integrated modeling system was developed to enhance in situ bioremediation processes
Numerical relativity for D dimensional axially symmetric space-times: Formalism and code tests
Zilhão, Miguel; Witek, Helvi; Sperhake, Ulrich; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Nerozzi, Andrea
2010-04-01
The numerical evolution of Einstein’s field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modeling black hole production in TeV gravity scenarios, to analysis of the stability of exact solutions, and to tests of cosmic censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D≥5, or SO(D-3) for D≥6. Performing a dimensional reduction on a (D-4) sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata, and Nakamura formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the Lean code and perform a variety of simulations of nonspinning black hole space-times. Specifically, we present a modified moving puncture gauge, which facilitates long-term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5, 6.
Numerical modeling for saturated-zone groundwater travel time analysis at Yucca Mountain
International Nuclear Information System (INIS)
Arnold, B.W.; Barr, G.E.
1996-01-01
A three-dimensional, site-scale numerical model of groundwater flow in the saturated zone at Yucca Mountain was constructed and linked to particle tracking simulations to produce an estimate of the distribution of groundwater travel times from the potential repository to the boundary of the accessible environment. This effort and associated modeling of groundwater travel times in the unsaturated zone were undertaken to aid in the evaluation of compliance of the site with 10CFR960. These regulations stipulate that pre-waste-emplacement groundwater travel time to the accessible environment shall exceed 1,000 years along any path of likely and significant radionuclide travel
International Nuclear Information System (INIS)
Zhurina, M.I.; Zatekin, V.V.; Popova, A.M.
1981-01-01
The collocation method of numerical solution of singular integral equations for partial scattering amplitudes in the three nucleon system using Tschebyscheff first kind polynomials as basis expansion functions is proposed. The selection of Tchebishev polynomials is due to the fact that the Fourier series on Tschebyscheff polynomials comerge much faster than, for instance the Taylor series and their convergence field is wider. Recurrent formulas for Tschebyscheff polynomials are most simple as compared with the corresponding formulas for other orthogonal polynomials and therefore most economical in the sence of count time. The Tschebyscheff polynomials are successfuly applied for integral equations solution in mathematical physics with singular nuclei. As example integral equations for amplitudes of the process of inelastic neutron scattering on deuteron are considered. The numerical solution method is demonstrated on the example of the separable Yamaguchi potential but this method can be simply generalized for other form separable potentials [ru
Time resolved spectroscopy of GRB 030501 using INTEGRAL
DEFF Research Database (Denmark)
Beckmann, V.; Borkowski, J.; Courvoisier, T.J.L.
2003-01-01
The gamma-ray instruments on-board INTEGRAL offer an unique opportunity to perform time resolved analysis on GRBs. The imager IBIS allows accurate positioning of GRBs and broad band spectral analysis, while SPI provides high resolution spectroscopy. GRB 030501 was discovered by the INTEGRAL Burst...... the Ulysses and RHESSI experiments....
Path integral solution for some time-dependent potential
International Nuclear Information System (INIS)
Storchak, S.N.
1989-12-01
The quantum-mechanical problem with a time-dependent potential is solved by the path integral method. The solution is obtained by the application of the previously derived general formula for rheonomic homogeneous point transformation and reparametrization in the path integral. (author). 4 refs
Time Varying Market Integration and Expected Rteurns in Emerging Markets
de Jong, F.C.J.M.; de Roon, F.A.
2001-01-01
We use a simple model in which the expected returns in emerging markets depend on their systematic risk as measured by their beta relative to the world portfolio as well as on the level of integration in that market.The level of integration is a time-varying variable that depends on the market value
Space-time transformations in radial path integrals
International Nuclear Information System (INIS)
Steiner, F.
1984-09-01
Nonlinear space-time transformations in the radial path integral are discussed. A transformation formula is derived, which relates the original path integral to the Green's function of a new quantum system with an effective potential containing an observable quantum correction proportional(h/2π) 2 . As an example the formula is applied to spherical Brownian motion. (orig.)
Integration of numerical modeling and observations for the Gulf of Naples monitoring network
Iermano, I.; Uttieri, M.; Zambianchi, E.; Buonocore, B.; Cianelli, D.; Falco, P.; Zambardino, G.
2012-04-01
Lethal effects of mineral oils on fragile marine and coastal ecosystems are now well known. Risks and damages caused by a maritime accident can be reduced with the help of better forecasts and efficient monitoring systems. The MED project TOSCA (Tracking Oil Spills and Coastal Awareness Network), which gathers 13 partners from 4 Mediterranean countries, has been designed to help create a better response system to maritime accidents. Through the construction of an observational network, based on state of the art technology (HF radars and drifters), TOSCA provides real-time observations and forecasts of the Mediterranean coastal marine environmental conditions. The system is installed and assessed in five test sites on the coastal areas of oil spill outlets (Eastern Mediterranean) and on high traffic areas (Western Mediterranean). The Gulf of Naples, a small semi-closed basin opening to the Tyrrhenian Sea is one of the five test-sites. It is of particular interest from both the environmental point of view, due to peculiar ecosystem properties in the area, and because it sustains important touristic and commercial activities. Currently the Gulf of Naples monitoring network is represented by five automatic weather stations distributed along the coasts of the Gulf, one weather radar, two tide gauges, one waverider buoy, and moored physical, chemical and bio-optical instrumentation. In addition, a CODAR-SeaSonde HF coastal radar system composed of three antennas is located in Portici, Massa Lubrense and Castellammare. The system provides hourly data of surface currents over the entire Gulf with a 1km spatial resolution. A numerical modeling implementation based on Regional Ocean Modeling System (ROMS) is actually integrated in the Gulf of Naples monitoring network. ROMS is a 3-D, free-surface, hydrostatic, primitive equation, finite difference ocean model. In our configuration, the model has high horizontal resolution (250m), and 30 sigma levels in the vertical. Thanks
Connection between Feynman integrals having different values of the space-time dimension
International Nuclear Information System (INIS)
Tarasov, O.V.
1996-05-01
A systematic algorithm for obtaining recurrence relations for dimensionally regularized Feynman integrals w.r.t. the space-time dimension d is proposed. The relation between d and d-2 dimensional integrals is given in terms of a differential operator for which an explicit formula can be obtained for each Feynman diagram. We show how the method works for one-, two- and three-loop integrals. The new recurrence relations w.r.t. d are complementary to the recurrence relations which derive from the method of integration by parts. We find that the problem of the irreducible numerators in Feynman integrals can be naturally solved in the framework of the proposed generalized recurrence relations. (orig.)
Comment on ``Nonexistence of the final first integral in the Zipoy-Voorhees space-time''
Lukes-Gerakopoulos, Georgios
2013-11-01
The accuracy of the numerical findings of [G. Lukes-Gerakopoulos, Phys. Rev. D 86, 044013 (2012)], regarding the existence of additional first integrals in the Zipoy-Voorhees space-time, was recently questioned [A. J. Maciejewski, M. Przybylska, and T. Stachowiak, Phys. Rev. D 88, 064003 (2013)PRVDAQ1550-799810.1103/PhysRevD.88.064003]. In this Comment, it is shown that the discrepancy between the results of Lukes-Gerakopoulos; Maciejewski et al. is not due to issues related to numerical accuracy, as claimed in Maciejewski et al., but due to a different choice of coordinates used in Maciejewski et al.
An extended Halanay inequality of integral type on time scales
Directory of Open Access Journals (Sweden)
Boqun Ou
2015-07-01
Full Text Available In this paper, we obtain a Halanay-type inequality of integral type on time scales which improves and extends some earlier results for both the continuous and discrete cases. Several illustrative examples are also given.
Statistics of Extreme Time-Integrated Geomagnetic Activity
Mourenas, D.; Artemyev, A. V.; Zhang, X.-J.
2018-01-01
A statistical analysis of the time-integrated Dst index is performed over 1958-2007. The tail of the probability distribution of extreme time-integrated Dst events, which occur during strong geomagnetic storms, can be precisely fitted by a power law function with upper cutoff, apparently not exceeded even by the 1859 Carrington event. This time-integrated Dst is expected to be a reasonable proxy for maximum densities of MeV electrons in the heart of the outer radiation belt, which are known to pose a serious threat to satellites. During such strong events, a correlation is found between the time-integrated levels of various physical quantities, such as interplanetary magnetic field Bz, particle energy fluxes measured during injections in the magnetotail, geosynchronous ULF wave index, and geomagnetic activity in the inner magnetosphere, suggesting cumulative effects from successive disturbances.
Safety analytics for integrating crash frequency and real-time risk modeling for expressways.
Wang, Ling; Abdel-Aty, Mohamed; Lee, Jaeyoung
2017-07-01
To find crash contributing factors, there have been numerous crash frequency and real-time safety studies, but such studies have been conducted independently. Until this point, no researcher has simultaneously analyzed crash frequency and real-time crash risk to test whether integrating them could better explain crash occurrence. Therefore, this study aims at integrating crash frequency and real-time safety analyses using expressway data. A Bayesian integrated model and a non-integrated model were built: the integrated model linked the crash frequency and the real-time models by adding the logarithm of the estimated expected crash frequency in the real-time model; the non-integrated model independently estimated the crash frequency and the real-time crash risk. The results showed that the integrated model outperformed the non-integrated model, as it provided much better model results for both the crash frequency and the real-time models. This result indicated that the added component, the logarithm of the expected crash frequency, successfully linked and provided useful information to the two models. This study uncovered few variables that are not typically included in the crash frequency analysis. For example, the average daily standard deviation of speed, which was aggregated based on speed at 1-min intervals, had a positive effect on crash frequency. In conclusion, this study suggested a methodology to improve the crash frequency and real-time models by integrating them, and it might inspire future researchers to understand crash mechanisms better. Copyright © 2017 Elsevier Ltd. All rights reserved.
Ni, Xiao-Ting; Wu, Xin
2014-10-01
The time-transformed leapfrog scheme of Mikkola & Aarseth was specifically designed for a second-order differential equation with two individually separable forms of positions and velocities. It can have good numerical accuracy for extremely close two-body encounters in gravitating few-body systems with large mass ratios, but the non-time-transformed one does not work well. Following this idea, we develop a new explicit symplectic integrator with an adaptive time step that can be applied to a time-dependent Hamiltonian. Our method relies on a time step function having two distinct but equivalent forms and on the inclusion of two pairs of new canonical conjugate variables in the extended phase space. In addition, the Hamiltonian must be modified to be a new time-transformed Hamiltonian with three integrable parts. When this method is applied to the elliptic restricted three-body problem, its numerical precision is explicitly higher by several orders of magnitude than the nonadaptive one's, and its numerical stability is also better. In particular, it can eliminate the overestimation of Lyapunov exponents and suppress the spurious rapid growth of fast Lyapunov indicators for high-eccentricity orbits of a massless third body. The present technique will be useful for conservative systems including N-body problems in the Jacobian coordinates in the the field of solar system dynamics, and nonconservative systems such as a time-dependent barred galaxy model in a rotating coordinate system.
Application of modified integration rule to time-domain finite-element acoustic simulation of rooms.
Okuzono, Takeshi; Otsuru, Toru; Tomiku, Reiji; Okamoto, Noriko
2012-08-01
The applicability of the modified integration rule for time-domain finite-element analysis is tested in sound field analysis of rooms involving rectangular elements, distorted elements, and finite impedance boundary conditions. Dispersion error analysis in three dimensions is conducted to evaluate the dispersion error in time-domain finite-element analysis using eight-node hexahedral elements. The results of analysis confirmed that fourth-order accuracy with respect to dispersion error is obtainable using the Fox-Goodwin method (FG) with a modified integration rule, even for rectangular elements. The stability condition in three-dimensional analysis using the modified integration rule is also presented. Numerical experiments demonstrate that FG with a modified integration rule performs much better than FG with the conventional integration rule for problems with rectangular elements, distorted elements, and with finite impedance boundary conditions. Further, as another advantage, numerical results revealed that the use of modified integration rule engenders faster convergence of the iterative solver than a conventional rule for problems with the same degrees of freedom.
Variable time-stepping in the pathwise numerical solution of the chemical Langevin equation
Ilie, Silvana
2012-12-01
Stochastic modeling is essential for an accurate description of the biochemical network dynamics at the level of a single cell. Biochemically reacting systems often evolve on multiple time-scales, thus their stochastic mathematical models manifest stiffness. Stochastic models which, in addition, are stiff and computationally very challenging, therefore the need for developing effective and accurate numerical methods for approximating their solution. An important stochastic model of well-stirred biochemical systems is the chemical Langevin Equation. The chemical Langevin equation is a system of stochastic differential equation with multidimensional non-commutative noise. This model is valid in the regime of large molecular populations, far from the thermodynamic limit. In this paper, we propose a variable time-stepping strategy for the numerical solution of a general chemical Langevin equation, which applies for any level of randomness in the system. Our variable stepsize method allows arbitrary values of the time-step. Numerical results on several models arising in applications show significant improvement in accuracy and efficiency of the proposed adaptive scheme over the existing methods, the strategies based on halving/doubling of the stepsize and the fixed step-size ones.
Precise digital integration in wide time range: theory and realization
International Nuclear Information System (INIS)
Batrakov, A.M.; Pavlenko, A.V.
2017-01-01
The digital integration method based on using high-speed precision analog-to-digital converters (ADC) has become widely used over the recent years. The paper analyzes the limitations of this method that are caused by the signal properties, ADC sampling rate and noise spectral density of the ADC signal path. This analysis allowed creating digital integrators with accurate synchronization and achieving an integration error of less than 10 −5 in the time range from microseconds to tens of seconds. The structure of the integrator is described and its basic parameters are presented. The possibilities of different ADC chips in terms of their applicability to digital integrators are discussed. A comparison with other integrating devices is presented.
Simulating variable-density flows with time-consistent integration of Navier-Stokes equations
Lu, Xiaoyi; Pantano, Carlos
2017-11-01
In this talk, we present several features of a high-order semi-implicit variable-density low-Mach Navier-Stokes solver. A new formulation to solve pressure Poisson-like equation of variable-density flows is highlighted. With this formulation of the numerical method, we are able to solve all variables with a uniform order of accuracy in time (consistent with the time integrator being used). The solver is primarily designed to perform direct numerical simulations for turbulent premixed flames. Therefore, we also address other important elements, such as energy-stable boundary conditions, synthetic turbulence generation, and flame anchoring method. Numerical examples include classical non-reacting constant/variable-density flows, as well as turbulent premixed flames.
Sotiropoulos, F.; Kang, S.; Chamorro, L. P.; Hill, C.
2011-12-01
The field of MHK energy is still in its infancy lagging approximately a decade or more behind the technology and development progress made in wind energy engineering. Marine environments are characterized by complex topography and three-dimensional (3D) turbulent flows, which can greatly affect the performance and structural integrity of MHK devices and impact the Levelized Cost of Energy (LCoE). Since the deployment of multi-turbine arrays is envisioned for field applications, turbine-to-turbine interactions and turbine-bathymetry interactions need to be understood and properly modeled so that MHK arrays can be optimized on a site specific basis. Furthermore, turbulence induced by MHK turbines alters and interacts with the nearby ecosystem and could potentially impact aquatic habitats. Increased turbulence in the wake of MHK devices can also change the shear stress imposed on the bed ultimately affecting the sediment transport and suspension processes in the wake of these structures. Such effects, however, remain today largely unexplored. In this work a science-based approach integrating state-of-the-art experimentation with high-resolution computational fluid dynamics is proposed as a powerful strategy for optimizing the performance of MHK devices and assessing environmental impacts. A novel numerical framework is developed for carrying out Large-Eddy Simulation (LES) in arbitrarily complex domains with embedded MHK devices. The model is able to resolve the geometrical complexity of real-life MHK devices using the Curvilinear Immersed Boundary (CURVIB) method along with a wall model for handling the flow near solid surfaces. Calculations are carried out for an axial flow hydrokinetic turbine mounted on the bed of rectangular open channel on a grid with nearly 200 million grid nodes. The approach flow corresponds to fully developed turbulent open channel flow and is obtained from a separate LES calculation. The specific case corresponds to that studied
Time domain numerical calculations of the short electron bunch wakefields in resistive structures
International Nuclear Information System (INIS)
Tsakanian, Andranik
2010-10-01
The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of structures are performed
Time domain numerical calculations of the short electron bunch wakefields in resistive structures
Energy Technology Data Exchange (ETDEWEB)
Tsakanian, Andranik
2010-10-15
The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of
Combined Effects of Numerical Method Type and Time Step on Water Stressed Actual Crop ET
Directory of Open Access Journals (Sweden)
B. Ghahraman
2016-02-01
Full Text Available Introduction: Actual crop evapotranspiration (Eta is important in hydrologic modeling and irrigation water management issues. Actual ET depends on an estimation of a water stress index and average soil water at crop root zone, and so depends on a chosen numerical method and adapted time step. During periods with no rainfall and/or irrigation, actual ET can be computed analytically or by using different numerical methods. Overal, there are many factors that influence actual evapotranspiration. These factors are crop potential evapotranspiration, available root zone water content, time step, crop sensitivity, and soil. In this paper different numerical methods are compared for different soil textures and different crops sensitivities. Materials and Methods: During a specific time step with no rainfall or irrigation, change in soil water content would be equal to evapotranspiration, ET. In this approach, however, deep percolation is generally ignored due to deep water table and negligible unsaturated hydraulic conductivity below rooting depth. This differential equation may be solved analytically or numerically considering different algorithms. We adapted four different numerical methods, as explicit, implicit, and modified Euler, midpoint method, and 3-rd order Heun method to approximate the differential equation. Three general soil types of sand, silt, and clay, and three different crop types of sensitive, moderate, and resistant under Nishaboor plain were used. Standard soil fraction depletion (corresponding to ETc=5 mm.d-1, pstd, below which crop faces water stress is adopted for crop sensitivity. Three values for pstd were considered in this study to cover the common crops in the area, including winter wheat and barley, cotton, alfalfa, sugar beet, saffron, among the others. Based on this parameter, three classes for crop sensitivity was considered, sensitive crops with pstd=0.2, moderate crops with pstd=0.5, and resistive crops with pstd=0
A new heterogeneous asynchronous explicit-implicit time integrator for nonsmooth dynamics
Fekak, Fatima-Ezzahra; Brun, Michael; Gravouil, Anthony; Depale, Bruno
2017-07-01
In computational structural dynamics, particularly in the presence of nonsmooth behavior, the choice of the time-step and the time integrator has a critical impact on the feasibility of the simulation. Furthermore, in some cases, as in the case of a bridge crane under seismic loading, multiple time-scales coexist in the same problem. In that case, the use of multi-time scale methods is suitable. Here, we propose a new explicit-implicit heterogeneous asynchronous time integrator (HATI) for nonsmooth transient dynamics with frictionless unilateral contacts and impacts. Furthermore, we present a new explicit time integrator for contact/impact problems where the contact constraints are enforced using a Lagrange multiplier method. In other words, the aim of this paper consists in using an explicit time integrator with a fine time scale in the contact area for reproducing high frequency phenomena, while an implicit time integrator is adopted in the other parts in order to reproduce much low frequency phenomena and to optimize the CPU time. In a first step, the explicit time integrator is tested on a one-dimensional example and compared to Moreau-Jean's event-capturing schemes. The explicit algorithm is found to be very accurate and the scheme has generally a higher order of convergence than Moreau-Jean's schemes and provides also an excellent energy behavior. Then, the two time scales explicit-implicit HATI is applied to the numerical example of a bridge crane under seismic loading. The results are validated in comparison to a fine scale full explicit computation. The energy dissipated in the implicit-explicit interface is well controlled and the computational time is lower than a full-explicit simulation.
Numerical Methods for Pricing American Options with Time-Fractional PDE Models
Directory of Open Access Journals (Sweden)
Zhiqiang Zhou
2016-01-01
Full Text Available In this paper we develop a Laplace transform method and a finite difference method for solving American option pricing problem when the change of the option price with time is considered as a fractal transmission system. In this scenario, the option price is governed by a time-fractional partial differential equation (PDE with free boundary. The Laplace transform method is applied to the time-fractional PDE. It then leads to a nonlinear equation for the free boundary (i.e., optimal early exercise boundary function in Laplace space. After numerically finding the solution of the nonlinear equation, the Laplace inversion is used to transform the approximate early exercise boundary into the time space. Finally the approximate price of the American option is obtained. A boundary-searching finite difference method is also proposed to solve the free-boundary time-fractional PDEs for pricing the American options. Numerical examples are carried out to compare the Laplace approach with the finite difference method and it is confirmed that the former approach is much faster than the latter one.
Hu, Shaoxing; Xu, Shike; Wang, Duhu; Zhang, Aiwu
2015-11-11
Aiming at addressing the problem of high computational cost of the traditional Kalman filter in SINS/GPS, a practical optimization algorithm with offline-derivation and parallel processing methods based on the numerical characteristics of the system is presented in this paper. The algorithm exploits the sparseness and/or symmetry of matrices to simplify the computational procedure. Thus plenty of invalid operations can be avoided by offline derivation using a block matrix technique. For enhanced efficiency, a new parallel computational mechanism is established by subdividing and restructuring calculation processes after analyzing the extracted "useful" data. As a result, the algorithm saves about 90% of the CPU processing time and 66% of the memory usage needed in a classical Kalman filter. Meanwhile, the method as a numerical approach needs no precise-loss transformation/approximation of system modules and the accuracy suffers little in comparison with the filter before computational optimization. Furthermore, since no complicated matrix theories are needed, the algorithm can be easily transplanted into other modified filters as a secondary optimization method to achieve further efficiency.
The time-dependent simplified P2 equations: Asymptotic analyses and numerical experiments
International Nuclear Information System (INIS)
Shin, U.; Miller, W.F. Jr.
1998-01-01
Using an asymptotic expansion, the authors found that the modified time-dependent simplified P 2 (SP 2 ) equations are robust, high-order, asymptotic approximations to the time-dependent transport equation in a physical regime in which the conventional time-dependent diffusion equation is the leading-order approximation. Using diffusion limit analysis, they also asymptotically compared three competitive time-dependent equations (the telegrapher's equation, the time-dependent SP 2 equations, and the time-dependent simplified even-parity equation). As a result, they found that the time-dependent SP 2 equations contain higher-order asymptotic approximations to the time-dependent transport equation than the other competitive equations. The numerical results confirm that, in the vast majority of cases, the time-dependent SP 2 solutions are significantly more accurate than the time-dependent diffusion and the telegrapher's solutions. They have also shown that the time-dependent SP 2 equations have excellent characteristics such as rotational invariance (which means no ray effect), good diffusion limit behavior, guaranteed positivity in diffusive regimes, and significant accuracy, even in deep-penetration problems. Through computer-running-time tests, they have shown that the time-dependent SP 2 equations can be solved with significantly less computational effort than the conventionally used, time-dependent S N equations (for N > 2) and almost as fast as the time-dependent diffusion equation. From all these results, they conclude that the time-dependent SP 2 equations should be considered as an important competitor for an improved approximately transport equations solver. Such computationally efficient time-dependent transport models are important for problems requiring enhanced computational efficiency, such as neutronics/fluid-dynamics coupled problems that arise in the analyses of hypothetical nuclear reactor accidents
Efficient Simulation of Compressible, Viscous Fluids using Multi-rate Time Integration
Mikida, Cory; Kloeckner, Andreas; Bodony, Daniel
2017-11-01
In the numerical simulation of problems of compressible, viscous fluids with single-rate time integrators, the global timestep used is limited to that of the finest mesh point or fastest physical process. This talk discusses the application of multi-rate Adams-Bashforth (MRAB) integrators to an overset mesh framework to solve compressible viscous fluid problems of varying scale with improved efficiency, with emphasis on the strategy of timescale separation and the application of the resulting numerical method to two sample problems: subsonic viscous flow over a cylinder and a viscous jet in crossflow. The results presented indicate the numerical efficacy of MRAB integrators, outline a number of outstanding code challenges, demonstrate the expected reduction in time enabled by MRAB, and emphasize the need for proper load balancing through spatial decomposition in order for parallel runs to achieve the predicted time-saving benefit. This material is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.
Directory of Open Access Journals (Sweden)
Poruba Z.
2009-06-01
Full Text Available For the numerical solution of elasto-plastic problems with use of Newton-Raphson method in global equilibrium equation it is necessary to determine the tangent modulus in each integration point. To reach the parabolic convergence of Newton-Raphson method it is convenient to use so called algorithmic tangent modulus which is consistent with used integration scheme. For more simple models for example Chaboche combined hardening model it is possible to determine it in analytical way. In case of more robust macroscopic models it is in many cases necessary to use the approximation approach. This possibility is presented in this contribution for radial return method on Chaboche model. An example solved in software Ansys corresponds to line contact problem with assumption of Coulomb's friction. The study shows at the end that the number of iteration of N-R method is higher in case of continuum tangent modulus and many times higher with use of modified N-R method, initial stiffness method.
Numerical Studies on Time Resolution of Micro-Pattern Gaseous Detectors
Bhattacharya, Purba; Majumdar, Nayana; Mukhopadhyay, Supratik; Bhattacharya, Sudeb
2018-02-01
The Micro-Pattern Gaseous Detectors offer excellent spatial and temporal resolution in harsh radiation environments of high-luminosity colliders. In this work, an attempt has been made to establish an algorithm for estimating the time resolution of different MPGDs. It has been estimated numerically on the basis of two aspects, statistics and distribution of primary electrons and their diffusion in gas medium, while ignoring their multiplication. The effect of detector design parameters, field configuration and the composition of gas mixture on the resolution have also been investigated. Finally, a modification in the numerical approach considering the threshold limit of detecting the signal has been done and tested for the RPC detector for its future implementation in case of MPGDs.
Numerical solution of continuous-time DSGE models under Poisson uncertainty
DEFF Research Database (Denmark)
Posch, Olaf; Trimborn, Timo
We propose a simple and powerful method for determining the transition process in continuous-time DSGE models under Poisson uncertainty numerically. The idea is to transform the system of stochastic differential equations into a system of functional differential equations of the retarded type. We...... then use the Waveform Relaxation algorithm to provide a guess of the policy function and solve the resulting system of ordinary differential equations by standard methods and fix-point iteration. Analytical solutions are provided as a benchmark from which our numerical method can be used to explore broader...... classes of models. We illustrate the algorithm simulating both the stochastic neoclassical growth model and the Lucas model under Poisson uncertainty which is motivated by the Barro-Rietz rare disaster hypothesis. We find that, even for non-linear policy functions, the maximum (absolute) error is very...
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...... 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...... originates from simple physical processes. However, the interaction between the sliding of the microfibrils on the microscale (local coordinate system) and the orientation of the microfibrils in the tracheid becomes complex on the macroscale. An example of the simplicity of the current numerical model...
An Integrated Numerical Hydrodynamic Shallow Flow-Solute Transport Model for Urban Area
Alias, N. A.; Mohd Sidek, L.
2016-03-01
The rapidly changing on land profiles in the some urban areas in Malaysia led to the increasing of flood risk. Extensive developments on densely populated area and urbanization worsen the flood scenario. An early warning system is really important and the popular method is by numerically simulating the river and flood flows. There are lots of two-dimensional (2D) flood model predicting the flood level but in some circumstances, still it is difficult to resolve the river reach in a 2D manner. A systematic early warning system requires a precisely prediction of flow depth. Hence a reliable one-dimensional (1D) model that provides accurate description of the flow is essential. Research also aims to resolve some of raised issues such as the fate of pollutant in river reach by developing the integrated hydrodynamic shallow flow-solute transport model. Presented in this paper are results on flow prediction for Sungai Penchala and the convection-diffusion of solute transports simulated by the developed model.
Boundary integral equation methods and numerical solutions thin plates on an elastic foundation
Constanda, Christian; Hamill, William
2016-01-01
This book presents and explains a general, efficient, and elegant method for solving the Dirichlet, Neumann, and Robin boundary value problems for the extensional deformation of a thin plate on an elastic foundation. The solutions of these problems are obtained both analytically—by means of direct and indirect boundary integral equation methods (BIEMs)—and numerically, through the application of a boundary element technique. The text discusses the methodology for constructing a BIEM, deriving all the attending mathematical properties with full rigor. The model investigated in the book can serve as a template for the study of any linear elliptic two-dimensional problem with constant coefficients. The representation of the solution in terms of single-layer and double-layer potentials is pivotal in the development of a BIEM, which, in turn, forms the basis for the second part of the book, where approximate solutions are computed with a high degree of accuracy. The book is intended for graduate students and r...
Galvín, P.; Romero, A.
2014-05-01
This paper presents a numerical method based on a three dimensional boundary element-finite element (BEM-FEM) coupled formulation in the time domain. The proposed model allows studying soil-structure interaction problems. The soil is modelled with the BEM, where the radiation condition is implicitly satisfied in the fundamental solution. Half-space Green's function including internal soil damping is considered as the fundamental solution. An effective treatment based on the integration into a complex Jordan path is proposed to avoid the singularities at the arrival time of the Rayleigh waves. The efficiency of the BEM is improved taking into account the spatial symmetry and the invariance of the fundamental solution when it is expressed in a dimensionless form. The FEM is used to represent the structure. The proposed method is validated by comparison with analytical solutions and numerical results presented in the literature. Finally, a soil-structure interaction problem concerning with a building subjected to different incident wave fields is studied.
International Nuclear Information System (INIS)
Lau, Stephen R
2004-01-01
For scalar, electromagnetic, or gravitational wave propagation on a fixed Schwarzschild black hole background, we consider the exact nonlocal radiation outer boundary conditions (ROBC) appropriate for a spherical outer boundary of finite radius enclosing the black hole. Such boundary conditions feature temporal integral convolution between each spherical harmonic mode of the wave field and a time-domain radiation kernel (TDRK). For each orbital angular integer l the associated TDRK is the inverse Laplace transform of a frequency-domain radiation kernel (FDRK). Drawing upon theory and numerical methods developed in a previous article, we numerically implement the ROBC via a rapid algorithm involving approximation of the FDRK by a rational function. Such an approximation is tailored to have relative error ε uniformly along the axis of imaginary Laplace frequency. Theoretically, ε is also a long-time bound on the relative convolution error. Via study of one-dimensional radial evolutions, we demonstrate that the ROBC capture the phenomena of quasinormal ringing and decay tails. We also consider a three-dimensional evolution based on a spectral code, one showing that the ROBC yield accurate results for the scenario of a wave packet striking the boundary at an angle. Our work is a partial generalization to Schwarzschild wave propagation and Heun functions of the methods developed for flatspace wave propagation and Bessel functions by Alpert, Greengard, and Hagstrom
Emerging opportunities in enterprise integration with open architecture computer numerical controls
Hudson, Christopher A.
1997-01-01
The shift to open-architecture machine tool computer numerical controls is providing new opportunities for metal working oriented manufacturers to streamline the entire 'art to part' process. Production cycle times, accuracy, consistency, predictability and process reliability are just some of the factors that can be improved, leading to better manufactured product at lower costs. Open architecture controllers are allowing manufacturers to apply general purpose software and hardware tools increase where previous approaches relied on proprietary and unique hardware and software. This includes DNC, SCADA, CAD, and CAM, where the increasing use of general purpose components is leading to lower cost system that are also more reliable and robust than the past proprietary approaches. In addition, a number of new opportunities exist, which in the past were likely impractical due to cost or performance constraints.
Al Jarro, Ahmed
2012-11-01
An explicit marching-on-in-time (MOT) scheme for solving the time domain volume integral equation is presented. The proposed method achieves its stability by employing, at each time step, a corrector scheme, which updates/corrects fields computed by the explicit predictor scheme. The proposedmethod is computationally more efficient when compared to the existing filtering techniques used for the stabilization of explicit MOT schemes. Numerical results presented in this paper demonstrate that the proposed method maintains its stability even when applied to the analysis of electromagnetic wave interactions with electrically large structures meshed using approximately half a million discretization elements.
A numerical study of the integral equations for the laser fields in free-electron lasers
International Nuclear Information System (INIS)
Yoo, J. G.; Park, S. H.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.
2004-01-01
The dynamics of the radiation fields in free-electron lasers is investigated on the basis of the integro-differential equations in the one-dimensional formulation. For simple cases we solved the integro-differential equations analytically and numerically to test our numerical procedures developed on the basis of the Filon method. The numerical results showed good agreement with the analytical solutions. To confirm the legitimacy of the numerical package, we carried out numerical studies on the inhomogeneous broadening effects, where no analytic solutions are available, due to the energy spread and the emittance of the electron beam.
El-Tom, M E A
1974-01-01
A procedure, using spine functions of degree m, deficiency k-1, for obtaining approximate solutions to nonlinear Volterra integral equations of the second kind is presented. The paper is an investigation of the numerical stability of the procedure for various values of m and k. (5 refs).
Bonotto, C.
1995-01-01
Attempted to verify knowledge regarding decimal and rational numbers in children ages 10-14. Discusses how pupils can receive and assimilate extensions of the number system from natural numbers to decimals and fractions and later can integrate this extension into a single and coherent numerical structure. (Author/MKR)
International Nuclear Information System (INIS)
Vlasov, M.N.; Korsun, A.S.; Maslov, Yu.A.; Merinov, I.G.; Kharitonov, V.S.
2013-01-01
Systematic numerical calculations have been performed for studying the longitudinal flow past an array of rods with a corridor or chess-board packing in a broad range of flow Reynolds numbers. Structures with the porosity varied in a broad range have been studied and the main parameters of the proposed integral model of turbulence are determined [ru
National Research Council Canada - National Science Library
Mitchell, Jason
2002-01-01
A method is presented for the generation of exact numerical coefficients found in two families of implicit Chebyshev methods for the numerical integration of first- and second-order ordinary differential equations...
Directory of Open Access Journals (Sweden)
Jinfeng Wang
2014-01-01
Full Text Available We discuss and analyze an H1-Galerkin mixed finite element (H1-GMFE method to look for the numerical solution of time fractional telegraph equation. We introduce an auxiliary variable to reduce the original equation into lower-order coupled equations and then formulate an H1-GMFE scheme with two important variables. We discretize the Caputo time fractional derivatives using the finite difference methods and approximate the spatial direction by applying the H1-GMFE method. Based on the discussion on the theoretical error analysis in L2-norm for the scalar unknown and its gradient in one dimensional case, we obtain the optimal order of convergence in space-time direction. Further, we also derive the optimal error results for the scalar unknown in H1-norm. Moreover, we derive and analyze the stability of H1-GMFE scheme and give the results of a priori error estimates in two- or three-dimensional cases. In order to verify our theoretical analysis, we give some results of numerical calculation by using the Matlab procedure.
Wang, Jinfeng; Zhao, Meng; Zhang, Min; Liu, Yang; Li, Hong
2014-01-01
We discuss and analyze an H 1-Galerkin mixed finite element (H 1-GMFE) method to look for the numerical solution of time fractional telegraph equation. We introduce an auxiliary variable to reduce the original equation into lower-order coupled equations and then formulate an H 1-GMFE scheme with two important variables. We discretize the Caputo time fractional derivatives using the finite difference methods and approximate the spatial direction by applying the H 1-GMFE method. Based on the discussion on the theoretical error analysis in L 2-norm for the scalar unknown and its gradient in one dimensional case, we obtain the optimal order of convergence in space-time direction. Further, we also derive the optimal error results for the scalar unknown in H 1-norm. Moreover, we derive and analyze the stability of H 1-GMFE scheme and give the results of a priori error estimates in two- or three-dimensional cases. In order to verify our theoretical analysis, we give some results of numerical calculation by using the Matlab procedure. PMID:25184148
Numerical analysis of the photo-injection time-of-flight curves in molecularly doped polymers
Tyutnev, A. P.; Ikhsanov, R. Sh.; Saenko, V. S.; Nikerov, D. V.
2018-03-01
We have performed numerical analysis of the charge carrier transport in a specific molecularly doped polymer using the multiple trapping model. The computations covered a wide range of applied electric fields, temperatures and most importantly, of the initial energies of photo injected one-sign carriers (in our case, holes). Special attention has been given to comparison of time of flight curves measured by the photo-injection and radiation-induced techniques which has led to a problematic situation concerning an interpretation of the experimental data. Computational results have been compared with both analytical and experimental results available in literature.
DEFF Research Database (Denmark)
Pedersen, Jonas Wied; Courdent, Vianney Augustin Thomas; Vezzaro, Luca
2017-01-01
Numerical Weather Predictions (NWP) can be used to forecast urban runoff with long lead times. However, NWP exhibit large spatial uncertainties and using forecasted precipitation directly above the catchment might therefore not be an ideal approach in an online setup. We use the Danish...... Meteorological Institute’s NWP ensemble and investigate a large spatial neighborhood around the catchment over a two-year period. When compared against in-sewer observations, runoff forecasts forced with precipitation from north-east of the catchment are most skillful. This highlights spatial biases...... in the coupled hydro-meteorological setup, which a forecaster should be aware of....
Li, Zhichen; Bai, Yan; Huang, Congzhi; Yan, Huaicheng
2017-05-01
This paper investigates the stability and stabilization problems for interval time-delay systems. By introducing a new delay partitioning approach, various Lyapunov-Krasovskii functionals with triple-integral terms are established to make full use of system information. In order to reduce the conservatism, improved integral inequalities are developed for estimation of double integrals, which show remarkable outperformance over the Jensen and Wirtinger ones. Particularly, the relationship between the time-delay and each subinterval is taken into consideration. The resulting stability criteria are less conservative than some recent methods. Based on the derived condition, the state-feedback controller design approach is also given. Finally, the numerical examples and the application to inverted pendulum system are provided to illustrate the effectiveness of the proposed approaches. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Goorjian, Peter M.; Silberberg, Yaron; Kwak, Dochan (Technical Monitor)
1995-01-01
This paper will present results in computational nonlinear optics. An algorithm will be described that solves the full vector nonlinear Maxwell's equations exactly without the approximations that we currently made. Present methods solve a reduced scalar wave equation, namely the nonlinear Schrodinger equation, and neglect the optical carrier. Also, results will be shown of calculations of 2-D electromagnetic nonlinear waves computed by directly integrating in time the nonlinear vector Maxwell's equations. The results will include simulations of 'light bullet' like pulses. Here diffraction and dispersion will be counteracted by nonlinear effects. The time integration efficiently implements linear and nonlinear convolutions for the electric polarization, and can take into account such quantum effects as Karr and Raman interactions. The present approach is robust and should permit modeling 2-D and 3-D optical soliton propagation, scattering, and switching directly from the full-vector Maxwell's equations.
An efficient explicit marching on in time solver for magnetic field volume integral equation
Sayed, Sadeed Bin
2015-07-25
An efficient explicit marching on in time (MOT) scheme for solving the magnetic field volume integral equation is proposed. The MOT system is cast in the form of an ordinary differential equation and is integrated in time using a PE(CE)m multistep scheme. At each time step, a system with a Gram matrix is solved for the predicted/corrected field expansion coefficients. Depending on the type of spatial testing scheme Gram matrix is sparse or consists of blocks with only diagonal entries regardless of the time step size. Consequently, the resulting MOT scheme is more efficient than its implicit counterparts, which call for inversion of fuller matrix system at lower frequencies. Numerical results, which demonstrate the efficiency, accuracy, and stability of the proposed MOT scheme, are presented.
Contour Integration over Time: Psychophysical and fMRI Evidence.
Kuai, Shu-Guang; Li, Wu; Yu, Cong; Kourtzi, Zoe
2017-05-01
The brain integrates discrete but collinear stimuli to perceive global contours. Previous contour integration (CI) studies mainly focus on integration over space, and CI is attributed to either V1 long-range connections or contour processing in high-visual areas that top-down modulate V1 responses. Here, we show that CI also occurs over time in a design that minimizes the roles of V1 long-range interactions. We use tilted contours embedded in random orientation noise and moving horizontally behind a fixed vertical slit. Individual contour elements traveling up/down within the slit would be encoded over time by parallel, rather than aligned, V1 neurons. However, we find robust contour detection even when the slit permits only one viewable contour element. Similar to CI over space, CI over time also obeys the rule of collinearity. fMRI evidence shows that while CI over space engages visual areas as early as V1, CI over time mainly engages higher dorsal and ventral visual areas involved in shape processing, as well as posterior parietal regions involved in visual memory that can represent the orientation of temporally integrated contours. These results suggest at least partially dissociable mechanisms for implementing the Gestalt rule of continuity in CI over space and time. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Real-time 3-D space numerical shake prediction for earthquake early warning
Wang, Tianyun; Jin, Xing; Huang, Yandan; Wei, Yongxiang
2017-12-01
In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.
Velocity-gauge real-time TDDFT within a numerical atomic orbital basis set
Pemmaraju, C. D.; Vila, F. D.; Kas, J. J.; Sato, S. A.; Rehr, J. J.; Yabana, K.; Prendergast, David
2018-05-01
The interaction of laser fields with solid-state systems can be modeled efficiently within the velocity-gauge formalism of real-time time dependent density functional theory (RT-TDDFT). In this article, we discuss the implementation of the velocity-gauge RT-TDDFT equations for electron dynamics within a linear combination of atomic orbitals (LCAO) basis set framework. Numerical results obtained from our LCAO implementation, for the electronic response of periodic systems to both weak and intense laser fields, are compared to those obtained from established real-space grid and Full-Potential Linearized Augmented Planewave approaches. Potential applications of the LCAO based scheme in the context of extreme ultra-violet and soft X-ray spectroscopies involving core-electronic excitations are discussed.
Bohlen, Thomas; Wittkamp, Florian
2016-03-01
We analyse the performance of a higher order accurate staggered viscoelastic time-domain finite-difference method, in which the staggered Adams-Bashforth (ABS) third-order and fourth-order accurate time integrators are used for temporal discretization. ABS is a multistep method that uses previously calculated wavefields to increase the order of accuracy in time. The analysis shows that the numerical dispersion is much lower than that of the widely used second-order leapfrog method. Numerical dissipation is introduced by the ABS method which is significantly smaller for fourth-order than third-order accuracy. In 1-D and 3-D simulation experiments, we verify the convincing improvements of simulation accuracy of the fourth-order ABS method. In a realistic elastic 3-D scenario, the computing time reduces by a factor of approximately 2.4, whereas the memory requirements increase by approximately a factor of 2.2. The ABS method thus provides an alternative strategy to increase the simulation accuracy in time by investing computer memory instead of computing time.
A New time Integration Scheme for Cahn-hilliard Equations
Schaefer, R.
2015-06-01
In this paper we present a new integration scheme that can be applied to solving difficult non-stationary non-linear problems. It is obtained by a successive linearization of the Crank- Nicolson scheme, that is unconditionally stable, but requires solving non-linear equation at each time step. We applied our linearized scheme for the time integration of the challenging Cahn-Hilliard equation, modeling the phase separation in fluids. At each time step the resulting variational equation is solved using higher-order isogeometric finite element method, with B- spline basis functions. The method was implemented in the PETIGA framework interfaced via the PETSc toolkit. The GMRES iterative solver was utilized for the solution of a resulting linear system at every time step. We also apply a simple adaptivity rule, which increases the time step size when the number of GMRES iterations is lower than 30. We compared our method with a non-linear, two stage predictor-multicorrector scheme, utilizing a sophisticated step length adaptivity. We controlled the stability of our simulations by monitoring the Ginzburg-Landau free energy functional. The proposed integration scheme outperforms the two-stage competitor in terms of the execution time, at the same time having a similar evolution of the free energy functional.
Integral equation approach to time-dependent kinematic dynamos in finite domains
International Nuclear Information System (INIS)
Xu Mingtian; Stefani, Frank; Gerbeth, Gunter
2004-01-01
The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of the Biot-Savart law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos, with stationary dynamo sources, in finite domains. The time dependence is restricted to the magnetic field, whereas the velocity or corresponding mean-field sources of dynamo action are supposed to be stationary. For the spherically symmetric α 2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and toroidal field components. The integral equation formulation for spherical dynamos with general stationary velocity fields is also derived. Two numerical examples - the α 2 dynamo model with radially varying α and the Bullard-Gellman model - illustrate the equivalence of the approach with the usual differential equation method. The main advantage of the method is exemplified by the treatment of an α 2 dynamo in rectangular domains
On the mixed discretization of the time domain magnetic field integral equation
Ulku, Huseyin Arda
2012-09-01
Time domain magnetic field integral equation (MFIE) is discretized using divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming Buffa-Christiansen (BC) functions as spatial basis and testing functions, respectively. The resulting mixed discretization scheme, unlike the classical scheme which uses RWG functions as both basis and testing functions, is proper: Testing functions belong to dual space of the basis functions. Numerical results demonstrate that the marching on-in-time (MOT) solution of the mixed discretized MFIE yields more accurate results than that of classically discretized MFIE. © 2012 IEEE.
High-Order Calderón Preconditioned Time Domain Integral Equation Solvers
Valdes, Felipe
2013-05-01
Two high-order accurate Calderón preconditioned time domain electric field integral equation (TDEFIE) solvers are presented. In contrast to existing Calderón preconditioned time domain solvers, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of fully-localized high-order div-and quasi curl-conforming (DQCC) basis functions. Numerical results demonstrate that the linear systems of equations obtained using the proposed basis functions converge rapidly, regardless of the mesh density and of the order of the current expansion. © 1963-2012 IEEE.
On the solution of high order stable time integration methods
Czech Academy of Sciences Publication Activity Database
Axelsson, Owe; Blaheta, Radim; Sysala, Stanislav; Ahmad, B.
2013-01-01
Roč. 108, č. 1 (2013), s. 1-22 ISSN 1687-2770 Institutional support: RVO:68145535 Keywords : evolution equations * preconditioners for quadratic matrix polynomials * a stiffly stable time integration method Subject RIV: BA - General Mathematics Impact factor: 0.836, year: 2013 http://www.boundaryvalueproblems.com/content/2013/1/108
Models and numerical methods for time- and energy-dependent particle transport
Energy Technology Data Exchange (ETDEWEB)
Olbrant, Edgar
2012-04-13
Particles passing through a medium can be described by the Boltzmann transport equation. Therein, all physical interactions of particles with matter are given by cross sections. We compare different analytical models of cross sections for photons, electrons and protons to state-of-the-art databases. The large dimensionality of the transport equation and its integro-differential form make it analytically difficult and computationally costly to solve. In this work, we focus on the following approximative models to the linear Boltzmann equation: (i) the time-dependent simplified P{sub N} (SP{sub N}) equations, (ii) the M{sub 1} model derived from entropy-based closures and (iii) a new perturbed M{sub 1} model derived from a perturbative entropy closure. In particular, an asymptotic analysis for SP{sub N} equations is presented and confirmed by numerical computations in 2D. Moreover, we design an explicit Runge-Kutta discontinuous Galerkin (RKDG) method to the M{sub 1} model of radiative transfer in slab geometry and construct a scheme ensuring the realizability of the moment variables. Among other things, M{sub 1} numerical results are compared with an analytical solution in a Riemann problem and the Marshak wave problem is considered. Additionally, we rigorously derive a new hierarchy of kinetic moment models in the context of grey photon transport in one spatial dimension. For the perturbed M{sub 1} model, we present numerical results known as the two beam instability or the analytical benchmark due to Su and Olson and compare them to the standard M{sub 1} as well as transport solutions.
Broek, P.L.C. van den; Egmond, J. van; Rijn, C.M. van; Takens, F.; Coenen, A.M.L.; Booij, L.H.D.J.
2005-01-01
This study assessed the feasibility of online calculation of the correlation integral (C(r)) aiming to apply C(r)-derived statistics. For real-time application it is important to reduce calculation time. It is shown how our method works for EEG time series. Methods: To achieve online calculation of
van den Broek, PLC; van Egmond, J; van Rijn, CM; Takens, F; Coenen, AML; Booij, LHDJ
2005-01-01
Background: This study assessed the feasibility of online calculation of the correlation integral (C(r)) aiming to apply C(r)derived statistics. For real-time application it is important to reduce calculation time. It is shown how our method works for EEG time series. Methods: To achieve online
Tang, H.; Sun, W.
2016-12-01
The theoretical computation of dislocation theory in a given earth model is necessary in the explanation of observations of the co- and post-seismic deformation of earthquakes. For this purpose, computation theories based on layered or pure half space [Okada, 1985; Okubo, 1992; Wang et al., 2006] and on spherically symmetric earth [Piersanti et al., 1995; Pollitz, 1997; Sabadini & Vermeersen, 1997; Wang, 1999] have been proposed. It is indicated that the compressibility, curvature and the continuous variation of the radial structure of Earth should be simultaneously taken into account for modern high precision displacement-based observations like GPS. Therefore, Tanaka et al. [2006; 2007] computed global displacement and gravity variation by combining the reciprocity theorem (RPT) [Okubo, 1993] and numerical inverse Laplace integration (NIL) instead of the normal mode method [Peltier, 1974]. Without using RPT, we follow the straightforward numerical integration of co-seismic deformation given by Sun et al. [1996] to present a straightforward numerical inverse Laplace integration method (SNIL). This method is used to compute the co- and post-seismic displacement of point dislocations buried in a spherically symmetric, self-gravitating viscoelastic and multilayered earth model and is easy to extended to the application of geoid and gravity. Comparing with pre-existing method, this method is relatively more straightforward and time-saving, mainly because we sum associated Legendre polynomials and dislocation love numbers before using Riemann-Merlin formula to implement SNIL.
Becker, A.; Hansen, V.
2003-05-01
In this paper a hybrid method combining the FDTD/FIT with a Time Domain Boundary-Integral Marching-on-in-Time Algorithm (TD-BIM) is presented. Inhomogeneous regions are modelled with the FIT-method, an alternative formulation of the FDTD. Homogeneous regions (which is in the presented numerical example the open space) are modelled using a TD-BIM with equivalent electric and magnetic currents flowing on the boundary between the inhomogeneous and the homogeneous regions. The regions are coupled by the tangential magnetic fields just outside the inhomogeneous regions. These fields are calculated by making use of a Mixed Potential Integral Formulation for the magnetic field. The latter consists of equivalent electric and magnetic currents on the boundary plane between the homogeneous and the inhomogeneous region. The magnetic currents result directly from the electric fields of the Yee lattice. Electric currents in the same plane are calculated by making use of the TD-BIM and using the electric field of the Yee lattice as boundary condition. The presented hybrid method only needs the interpolations inherent in FIT and no additional interpolation. A numerical result is compared to a calculation that models both regions with FDTD.
Directory of Open Access Journals (Sweden)
A. Becker
2003-01-01
Full Text Available In this paper a hybrid method combining the FDTD/FIT with a Time Domain Boundary-Integral Marching-on-in-Time Algorithm (TD-BIM is presented. Inhomogeneous regions are modelled with the FIT-method, an alternative formulation of the FDTD. Homogeneous regions (which is in the presented numerical example the open space are modelled using a TD-BIM with equivalent electric and magnetic currents flowing on the boundary between the inhomogeneous and the homogeneous regions. The regions are coupled by the tangential magnetic fields just outside the inhomogeneous regions. These fields are calculated by making use of a Mixed Potential Integral Formulation for the magnetic field. The latter consists of equivalent electric and magnetic currents on the boundary plane between the homogeneous and the inhomogeneous region. The magnetic currents result directly from the electric fields of the Yee lattice. Electric currents in the same plane are calculated by making use of the TD-BIM and using the electric field of the Yee lattice as boundary condition. The presented hybrid method only needs the interpolations inherent in FIT and no additional interpolation. A numerical result is compared to a calculation that models both regions with FDTD.
Directory of Open Access Journals (Sweden)
J. Schmidt
2008-04-01
Full Text Available A project established at the National Institute of Water and Atmospheric Research (NIWA in New Zealand is aimed at developing a prototype of a real-time landslide forecasting system. The objective is to predict temporal changes in landslide probability for shallow, rainfall-triggered landslides, based on quantitative weather forecasts from numerical weather prediction models. Global weather forecasts from the United Kingdom Met Office (MO Numerical Weather Prediction model (NWP are coupled with a regional data assimilating NWP model (New Zealand Limited Area Model, NZLAM to forecast atmospheric variables such as precipitation and temperature up to 48 h ahead for all of New Zealand. The weather forecasts are fed into a hydrologic model to predict development of soil moisture and groundwater levels. The forecasted catchment-scale patterns in soil moisture and soil saturation are then downscaled using topographic indices to predict soil moisture status at the local scale, and an infinite slope stability model is applied to determine the triggering soil water threshold at a local scale. The model uses uncertainty of soil parameters to produce probabilistic forecasts of spatio-temporal landslide occurrence 48~h ahead. The system was evaluated for a damaging landslide event in New Zealand. Comparison with landslide densities estimated from satellite imagery resulted in hit rates of 70–90%.
Directory of Open Access Journals (Sweden)
Benjamin M. Cowan
2013-04-01
Full Text Available We describe a modification to the finite-difference time-domain algorithm for electromagnetics on a Cartesian grid which eliminates numerical dispersion error in vacuum for waves propagating along a grid axis. We provide details of the algorithm, which generalizes previous work by allowing 3D operation with a wide choice of aspect ratio, and give conditions to eliminate dispersive errors along one or more of the coordinate axes. We discuss the algorithm in the context of laser-plasma acceleration simulation, showing significant reduction—up to a factor of 280, at a plasma density of 10^{23} m^{-3}—of the dispersion error of a linear laser pulse in a plasma channel. We then compare the new algorithm with the standard electromagnetic update for laser-plasma accelerator stage simulations, demonstrating that by controlling numerical dispersion, the new algorithm allows more accurate simulation than is otherwise obtained. We also show that the algorithm can be used to overcome the critical but difficult challenge of consistent initialization of a relativistic particle beam and its fields in an accelerator simulation.
Directory of Open Access Journals (Sweden)
L. Malgaca
2009-01-01
Full Text Available Piezoelectric smart structures can be modeled using commercial finite element packages. Integration of control actions into the finite element model solutions (ICFES can be done in ANSYS by using parametric design language. Simulation results can be obtained easily in smart structures by this method. In this work, cantilever smart structures consisting of aluminum beams and lead-zirconate-titanate (PZT patches are considered. Two cases are studied numerically and experimentally in parallel. In the first case, a smart structure with a single PZT patch is used for the free vibration control under an initial tip displacement. In the second case, a smart structure with two PZT patches is used for the forced vibration control under harmonic excitation, where one of the PZT patches is used as vibration generating shaker while the other is used as vibration controlling actuator. For the two cases, modal analyses are done using chirp signals; Control OFF and Control ON responses in the time domain are obtained for various controller gains. A non-contact laser displacement sensor and strain gauges are utilized for the feedback signals. It is observed that all the simulation results agree with the experimental results.
International Nuclear Information System (INIS)
Ohwada, Hiroshi; Ishihara, Yasutoshi
2010-01-01
To improve the efficacy of hyperthermia treatment, a novel method of noninvasive measurement of body temperature change is proposed. The proposed technology, thermometry, is based on changes in the electromagnetic field distribution inside the heating applicator with temperature changes and the temperature dependence of the dielectric constant. In addition, an image of the temperature change distribution inside a body is reconstructed by applying a computed tomography (CT) algorithm. The proposed thermometry method can serve as a possible noninvasive method to monitor the temperature change distribution inside the body without the use of enormous thermometers such as in the case of magnetic resonance imaging (MRI). Furthermore, this temperature monitoring method can be easily combined with a heating applicator based on a cavity resonator, and the novel integrated treatment system can possibly be used to treat cancer effectively while noninvasively monitoring the heating effect. In this paper, the phase change distributions of the electromagnetic field with temperature changes are simulated by numerical analysis using the finite difference time domain (FDTD) method. Moreover, to estimate the phase change distributions inside a target body, the phase change distributions with temperature changes are reconstructed by a filtered back-projection. In addition, the reconstruction accuracy of the converted temperature change distribution from the phase change is evaluated. (author)
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Numerical simulation of homogenization time measurement by probes with different volume size
International Nuclear Information System (INIS)
Thyn, J.; Novy, M.; Zitny, R.; Mostek, M.; Jahoda, M.
2004-01-01
Results of continuous homogenization time measurement of liquid in a stirred tank depend on the scale of scrutiny. Experimental techniques use a probe, which is situated inside as a conductivity method, or outside of the tank as in the case of gamma-radiotracer methods. Expected value of homogenization time evaluated for a given degree of homogenization is higher when using the conductivity method because the conductivity probe measures relatively small volume in contrast to application of radiotracer, when the volume is much greater. Measurement through the wall of tank is a great advantage of radiotracer application but a comparison of the results with another method supposes a determination of measured volume, which is not easy. Simulation of measurement by CFD code can help to solve the problem. Methodology for CFD simulation of radiotracer experiments was suggested. Commercial software was used for simulation of liquid homogenization in mixed vessel with Rushton turbine. Numerical simulation of liquid homogenization time by CFD for different values of detected volume was confronted with measurement of homogenization time with conductivity probe and with different radioisotopes 198 Au, 82 Br and 24 Na. Detected size of the tank volume was affected by different energy of radioisotope used. (author)
Uncoupled continuous-time random walk model: Analytical and numerical solutions
Fa, Kwok Sau
2014-05-01
Solutions for the continuous-time random walk (CTRW) model are known in few cases. In this work, the uncoupled CTRW model is investigated analytically and numerically. In particular, the probability density function (PDF) and n-moment are obtained and analyzed. Exponential and Gaussian functions are used for the jump length PDF, whereas the Mittag-Leffler function and a combination of exponential and power-laws function is used for the waiting time PDF. The exponential and Gaussian jump length PDFs have finite jump length variances and they give the same second moment; however, their distribution functions present different behaviors near the origin. The combination of exponential and power-law function for the waiting time PDF can generate a crossover from anomalous regime to normal regime. Moreover, the parameter of the exponential jump length PDF does not change the behavior of the n-moment for all time intervals, and for the Gaussian jump length PDF the n-moment also indicates a similar behavior.
A revised method to calculate the concentration time integral of atmospheric pollutants
International Nuclear Information System (INIS)
Voelz, E.; Schultz, H.
1980-01-01
It is possible to calculate the spreading of a plume in the atmosphere under nonstationary and nonhomogeneous conditions by introducing the ''particle-in-cell'' method (PIC). This is a numerical method by which the transport of and the diffusion in the plume is reproduced in such a way, that particles representing the concentration are moved time step-wise in restricted regions (cells) and separately with the advection velocity and the diffusion velocity. This has a systematical advantage over the steady state Gaussian plume model usually used. The fixed-point concentration time integral is calculated directly instead of being substituted by the locally integrated concentration at a constant time as is done in the Gaussian model. In this way inaccuracies due to the above mentioned computational techniques may be avoided for short-time emissions, as may be seen by the fact that both integrals do not lead to the same results. Also the PIC method enables one to consider the height-dependent wind speed and its variations while the Gaussian model can be used only with averaged wind data. The concentration time integral calculated by the PIC method results in higher maximum values in shorter distances to the source. This is an effect often observed in measurements. (author)
Optimal Real-time Dispatch for Integrated Energy Systems
DEFF Research Database (Denmark)
Anvari-Moghaddam, Amjad; Guerrero, Josep M.; Rahimi-Kian, Ashkan
2016-01-01
into a cohesive, networked package that fully utilizes smart energy-efficient end-use devices, advanced building control/automation systems, and integrated communications architectures, it is possible to efficiently manage energy and comfort at the end-use location. In this paper, an ontology-driven multi......-agent control system with intelligent optimizers is proposed for optimal real-time dispatch of an integrated building and microgrid system considering coordinated demand response (DR) and DERs management. The optimal dispatch problem is formulated as a mixed integer nonlinear programing problem (MINLP...
PBO Integrated Real-Time Observing Sites at Volcanic Sites
Mencin, D.; Jackson, M.; Borsa, A.; Feaux, K.; Smith, S.
2009-05-01
The Plate Boundary Observatory, an element of NSF's EarthScope program, has six integrated observatories in Yellowstone and four on Mt St Helens. These observatories consist of some combination of borehole strainmeters, borehole seismometers, GPS, tiltmeters, pore pressure, thermal measurements and meteorological data. Data from all these instruments have highly variable data rates and formats, all synchronized to GPS time which can cause significant congestion of precious communication resources. PBO has been experimenting with integrating these data streams to both maximize efficiency and minimize latency through the use of software that combines the streams, like Antelope, and VPN technologies.
Chang, Sin-Chung; To, Wai-Ming
1991-01-01
A new numerical framework for solving conservation laws is being developed. It employs: (1) a nontraditional formulation of the conservation laws in which space and time are treated on the same footing, and (2) a nontraditional use of discrete variables such as numerical marching can be carried out by using a set of relations that represents both local and global flux conservation.
Multisensory integration: the case of a time window of gesture-speech integration.
Obermeier, Christian; Gunter, Thomas C
2015-02-01
This experiment investigates the integration of gesture and speech from a multisensory perspective. In a disambiguation paradigm, participants were presented with short videos of an actress uttering sentences like "She was impressed by the BALL, because the GAME/DANCE...." The ambiguous noun (BALL) was accompanied by an iconic gesture fragment containing information to disambiguate the noun toward its dominant or subordinate meaning. We used four different temporal alignments between noun and gesture fragment: the identification point (IP) of the noun was either prior to (+120 msec), synchronous with (0 msec), or lagging behind the end of the gesture fragment (-200 and -600 msec). ERPs triggered to the IP of the noun showed significant differences for the integration of dominant and subordinate gesture fragments in the -200, 0, and +120 msec conditions. The outcome of this integration was revealed at the target words. These data suggest a time window for direct semantic gesture-speech integration ranging from at least -200 up to +120 msec. Although the -600 msec condition did not show any signs of direct integration at the homonym, significant disambiguation was found at the target word. An explorative analysis suggested that gesture information was directly integrated at the verb, indicating that there are multiple positions in a sentence where direct gesture-speech integration takes place. Ultimately, this would implicate that in natural communication, where a gesture lasts for some time, several aspects of that gesture will have their specific and possibly distinct impact on different positions in an utterance.
Time-integrated directional detection of dark matter
O'Hare, Ciaran A. J.; Kavanagh, Bradley J.; Green, Anne M.
2017-10-01
The analysis of signals in directional dark matter (DM) detectors typically assumes that the directions of nuclear recoils can be measured in the Galactic rest frame. However, this is not possible with all directional detection technologies. In nuclear emulsions, for example, the recoil events must be detected and measured after the exposure time of the experiment. Unless the entire detector is mounted and rotated with the sidereal day, the recoils cannot be reoriented in the Galactic rest frame. We examine the effect of this "time integration" on the primary goals of directional detection, namely: (1) confirming that the recoils are anisotropic; (2) measuring the median recoil direction to confirm their Galactic origin; and (3) probing below the neutrino floor. We show that after time integration the DM recoil distribution retains a preferred direction and is distinct from that of Solar neutrino-induced recoils. Many of the advantages of directional detection are therefore preserved and it is not crucial to mount and rotate the detector. Rejecting isotropic backgrounds requires a factor of 2 more signal events compared with an experiment with event time information, whereas a factor of 1.5-3 more events are needed to measure a median direction in agreement with the expectation for DM. We also find that there is still effectively no neutrino floor in a time-integrated directional experiment. However to reach a cross section an order of magnitude below the floor, a factor of ˜8 larger exposure is required than with a conventional directional experiment. We also examine how the sensitivity is affected for detectors with only 2D recoil track readout, and/or no head-tail measurement. As for non-time-integrated experiments, 2D readout is not a major disadvantage, though a lack of head-tail sensitivity is.
International Nuclear Information System (INIS)
Hathaway, D.H.; Somerville, R.C.J.; National Solar Observatory, Sunspot, NM; California Univ., La Jolla)
1985-01-01
Three-dimensional, time-dependent convection in a plane layer of fluid, uniformly heated from below and subject to vertical shear and to rotation about an axis tilted from the vertical, was simulated by the numerical solution of the Boussinesq equations, including all Coriolis terms. Rotation about a vertical axis produces smaller convection cells with diminished heat fluxes and considerable vorticity. When the rotation axis is tilted from the vertical to represent tropical latitudes, the convection cells become elongated in a N-S direction. Imposed flows with constant vertical shear produce convective rolls aligned with the mean flow. When the rotation vector is tilted from the vertical, the competing effects due to rotation and shear can stabilize the convective motions. 15 references
Numerical investigation of time-dependent cloud cavitating flow around a hydrofoil
Directory of Open Access Journals (Sweden)
Zhang De-Sheng
2016-01-01
Full Text Available Time-dependent cloud cavitation around the 2-D Clark-Y hydrofoil was investigated in this paper based on an improved filter based model and a density correction method. The filter-scale in filter based model simulation was discussed and validated according to the grid size. Numerical results show that in the transition from sheet cavitation to cloud cavitation, the sheet cavity grows slowly to the maximum length during the re-entrant jet develops. The mild shedding bubble cluster convects downwards the hydrofoil and continues to grow up after detaching from the suction surface of hydrofoil, and a bubble cluster introduced at the rear part of hydrofoil. While the sheet cavity generates, the bubble cluster breakups.
Directory of Open Access Journals (Sweden)
M Vijayashree
2015-05-01
Full Text Available The purpose of this article is to investigate a two-echelon supply chain inventory problem consisting of a single-vendor and a single-buyer with controllable lead time and investment for quality improvements. This paper presents an integrated vendor-buyer inventory model in order to minimize the sum of the ordering cost, holding cost, setup cost, investment for quality improvement and crashing cost by simultaneously optimizing the optimal order quantity, process quality, lead time and number of deliveries the vendor to the buyer in one production run with the objective of minimizing total relevant cost. Here the lead-time crashing cost has been assumed to be an exponentially function of the lead-time length. The main contribution of proposed model is an efficient iterative algorithm developed to minimize integrated total relevant cost for the single vendor and the single buyer systems with controllable lead time reduction and investment for quality improvements. Graphical representation is also presented to illustrate the proposed model. Numerical examples are presented to illustrate the procedures and results of the proposed algorithm. Matlab coding is also developed to derive the optimal solution and present numerical examples to illustrate the model.
Integral-Value Models for Outcomes over Continuous Time
DEFF Research Database (Denmark)
Harvey, Charles M.; Østerdal, Lars Peter
Models of preferences between outcomes over continuous time are important for individual, corporate, and social decision making, e.g., medical treatment, infrastructure development, and environmental regulation. This paper presents a foundation for such models. It shows that conditions on prefere...... on preferences between real- or vector-valued outcomes over continuous time are satisfied if and only if the preferences are represented by a value function having an integral form......Models of preferences between outcomes over continuous time are important for individual, corporate, and social decision making, e.g., medical treatment, infrastructure development, and environmental regulation. This paper presents a foundation for such models. It shows that conditions...
A path-integral approach to the problem of time
Amaral, M. M.; Bojowald, Martin
2018-01-01
Quantum transition amplitudes are formulated for model systems with local internal time, using intuition from path integrals. The amplitudes are shown to be more regular near a turning point of internal time than could be expected based on existing canonical treatments. In particular, a successful transition through a turning point is provided in the model systems, together with a new definition of such a transition in general terms. Some of the results rely on a fruitful relation between the problem of time and general Gribov problems.
A Digitally Programmable Differential Integrator with Enlarged Time Constant
Directory of Open Access Journals (Sweden)
S. K. Debroy
1994-12-01
Full Text Available A new Operational Amplifier (OA-RC integrator network is described. The novelties of the design are used of single grounded capacitor, ideal integration function realization with dual-input capability and design flexibility for extremely large time constant involving an enlargement factor (K using product of resistor ratios. The aspect of the digital control of K through a programmable resistor array (PRA controlled by a microprocessor has also been implemented. The effect of the OA-poles has been analyzed which indicates degradation of the integrator-Q at higher frequencies. An appropriate Q-compensation design scheme exhibiting 1 : |A|2 order of Q-improvement has been proposed with supporting experimental observations.
Energy conservation in Newmark based time integration algorithms
DEFF Research Database (Denmark)
Krenk, Steen
2006-01-01
Energy balance equations are established for the Newmark time integration algorithm, and for the derived algorithms with algorithmic damping introduced via averaging, the so-called a-methods. The energy balance equations form a sequence applicable to: Newmark integration of the undamped equations...... by the algorithm. The magnitude and character of these terms as well as the associated damping terms are discussed in relation to energy conservation and stability of the algorithms. It is demonstrated that the additional terms in the energy lead to periodic fluctuations of the mechanical energy and are the cause......, and that energy fluctuations take place for integration intervals close to the stability limit. (c) 2006 Elsevier B.V. All rights reserved....
Directory of Open Access Journals (Sweden)
Mehriban Imanova Natiq
2012-03-01
Full Text Available Normal 0 false false false EN-US X-NONE X-NONE As is known, many problems of natural science are reduced mainly to the solution of nonlinear Volterra integral equations. The method of quadratures that was first applied by Volterra to solving variable boundary integral equations is popular among numerical methods for the solution of such equations. At present, there are different modifications of the method of quadratures that have bounded accuracies. Here we suggest a second derivative multistep method for constructing more exact methods.
DEFF Research Database (Denmark)
Elarga, Hagar; Fantucci, Stefano; Serra, Valentina
2017-01-01
The study investigates the thermal performances of Phase Change Materials (PCM) integrated in a roof space to be used as a residential attic in Torino, Italy. Three different solutions were applied to a roof continuously monitored under summer climatic conditions. The roof was divided into three...... portions, one, the bare roof, representing the reference case without PCMs, the other two integrating two PCM's typologies with different melting/solidification temperatures range. A numerical model was furthermore developed implementing the equivalent capacitance numerical method to describe the substance...... phase transition and the measured data set were used for its validation. The study demonstrates that PCM-enhanced components are a promising solution toward a higher thermal performance efficiency in roof attic spaces during the summer season. Experimental results showed a reduction of the ongoing heat...
Numerical dispersion and stability characteristics of time-domain methods on nonorthogonal meshes
International Nuclear Information System (INIS)
Ray, S.L.
1993-01-01
The familiar finite-difference, time-domain method for discretizing Maxwell's curl equations on orthogonal grids has been extended to nonorthogonal grids by a number of researchers. While it is difficult to determine the dispersion and stability characteristics of these methods when applied on arbitrary grids, analysis of the idealized but representative case of a uniform skewed mesh proves to be quite tractable in 2-D. This analysis demonstrates that numerical dispersion errors are small for well-resolved spatial wavelengths and that these methods converge to the continuous-space solution in the limit as the cell and time step sizes vanish. Grid anisotropy (variations in wave propagation speed as a function of the propagation angle relative to the mesh coordinates) increases as the mesh is skewed. In spite of this, there exist some angles where waves propagate through the skewed mesh with virtually no dispersion. This analysis also provides a stability limit for the time step size in terms of geometrical mesh quantities
International Nuclear Information System (INIS)
Cash, J.R.; Raptis, A.D.; Simos, T.E.
1990-01-01
An efficient algorithm is described for the accurate numerical integration of the one-dimensional Schroedinger equation. This algorithm uses a high-order, variable step Runge-Kutta like method in the region where the potential term dominates, and an exponential or Bessel fitted method in the asymptotic region. This approach can be used to compute scattering phase shifts in an efficient and reliable manner. A Fortran program which implements this algorithm is provided and some test results are given. (orig.)
International Nuclear Information System (INIS)
Kalogiratou, Z.; Monovasilis, Th.; Psihoyios, G.; Simos, T.E.
2014-01-01
In this work we review single step methods of the Runge–Kutta type with special properties. Among them are methods specially tuned to integrate problems that exhibit a pronounced oscillatory character and such problems arise often in celestial mechanics and quantum mechanics. Symplectic methods, exponentially and trigonometrically fitted methods, minimum phase-lag and phase-fitted methods are presented. These are Runge–Kutta, Runge–Kutta–Nyström and Partitioned Runge–Kutta methods. The theory of constructing such methods is given as well as several specific methods. In order to present the performance of the methods we have tested 58 methods from all categories. We consider the two dimensional harmonic oscillator, the two body problem, the pendulum problem and the orbital problem studied by Stiefel and Bettis. Also we have tested the methods on the computation of the eigenvalues of the one dimensional time independent Schrödinger equation with the harmonic oscillator, the doubly anharmonic oscillator and the exponential potentials
A Time Marching Scheme for Solving Volume Integral Equations on Nonlinear Scatterers
Bagci, Hakan
2015-01-07
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are oftentimes solved using marchingon-in-time (MOT) schemes. Unlike finite difference and finite element schemes, MOT-TDVIE solvers require discretization of only the scatterers, do not call for artificial absorbing boundary conditions, and are more robust to numerical phase dispersion. On the other hand, their computational cost is high, they suffer from late-time instabilities, and their implicit nature makes incorporation of nonlinear constitutive relations more difficult. Development of plane-wave time-domain (PWTD) and FFT-based schemes has significantly reduced the computational cost of the MOT-TDVIE solvers. Additionally, latetime instability problem has been alleviated for all practical purposes with the development of accurate integration schemes and specially designed temporal basis functions. Addressing the third challenge is the topic of this presentation. I will talk about an explicit MOT scheme developed for solving the TDVIE on scatterers with nonlinear material properties. The proposed scheme separately discretizes the TDVIE and the nonlinear constitutive relation between electric field intensity and flux density. The unknown field intensity and flux density are expanded using half and full Schaubert-Wilton-Glisson (SWG) basis functions in space and polynomial temporal interpolators in time. The resulting coupled system of the discretized TDVIE and constitutive relation is integrated in time using an explicit P E(CE) m scheme to yield the unknown expansion coefficients. Explicitness of time marching allows for straightforward incorporation of the nonlinearity as a function evaluation on the right hand side of the coupled system of equations. Consequently, the resulting MOT scheme does not call for a Newton-like nonlinear solver. Numerical examples, which demonstrate the applicability
Retarded potentials and time domain boundary integral equations a road map
Sayas, Francisco-Javier
2016-01-01
This book offers a thorough and self-contained exposition of the mathematics of time-domain boundary integral equations associated to the wave equation, including applications to scattering of acoustic and elastic waves. The book offers two different approaches for the analysis of these integral equations, including a systematic treatment of their numerical discretization using Galerkin (Boundary Element) methods in the space variables and Convolution Quadrature in the time variable. The first approach follows classical work started in the late eighties, based on Laplace transforms estimates. This approach has been refined and made more accessible by tailoring the necessary mathematical tools, avoiding an excess of generality. A second approach contains a novel point of view that the author and some of his collaborators have been developing in recent years, using the semigroup theory of evolution equations to obtain improved results. The extension to electromagnetic waves is explained in one of the appendices...
Modeling the Evolution of Galaxy Properties across Cosmic Time with Numerical Simulations
Torrey, Paul A.
We present a series of numerical galaxy formation studies which apply new numerical methods to produce increasingly realistic galaxy formation models. We first investigate the metallicity evolution of a large set of idealized hydrodynamical galaxy merger simulations of colliding galaxies. We find that inflows of metal-poor interstellar gas triggered by galaxy tidal interactions can account for the systematically lower central oxygen abundances observed in local interacting galaxies. We show the central metallicity evolution during merger events is determined by a competition between the inflow of low-metallicity gas and enrichment from star formation. We find a time-averaged depression in the galactic nuclear metallicity of ~0.07 dex for gas-poor disk-disk interactions, which explains the observed close pair mass-metallicity and separation-metallicity relationships. We then pioneer the impact of a novel hydro solver in our understanding of galaxy gas disk assembly by comparing the structural properties of galaxies formed in cosmological simulations using the smoothed particle hydrodynamics (SPH) code GADGET with those using the moving-mesh code AREPO. We find that the cold gas disks formed using the moving mesh approach have systematically larger disk scale lengths and higher specific angular momenta than their GADGET counterparts across a wide range in halo masses. We articulate the numerical origins of these differences, and discuss the impact on large body of galaxy formation literature. We explore the performance of a recently implemented feedback model in AREPO which includes primordial and metal line radiative cooling with self-shielding corrections; stellar evolution with associated mass loss and chemical enrichment; feedback by stellar winds; black hole seeding, growth and merging; and AGN quasar- and radio-mode heating with a phenomenological prescription for AGN electro-magnetic feedback. We demonstrate that our feedback scheme is capable of producing
An energy-stable time-integrator for phase-field models
Vignal, Philippe
2016-12-27
We introduce a provably energy-stable time-integration method for general classes of phase-field models with polynomial potentials. We demonstrate how Taylor series expansions of the nonlinear terms present in the partial differential equations of these models can lead to expressions that guarantee energy-stability implicitly, which are second-order accurate in time. The spatial discretization relies on a mixed finite element formulation and isogeometric analysis. We also propose an adaptive time-stepping discretization that relies on a first-order backward approximation to give an error-estimator. This error estimator is accurate, robust, and does not require the computation of extra solutions to estimate the error. This methodology can be applied to any second-order accurate time-integration scheme. We present numerical examples in two and three spatial dimensions, which confirm the stability and robustness of the method. The implementation of the numerical schemes is done in PetIGA, a high-performance isogeometric analysis framework.
Pandey, Rishi Kumar; Mishra, Hradyesh Kumar
2017-11-01
In this paper, the semi-analytic numerical technique for the solution of time-space fractional telegraph equation is applied. This numerical technique is based on coupling of the homotopy analysis method and sumudu transform. It shows the clear advantage with mess methods like finite difference method and also with polynomial methods similar to perturbation and Adomian decomposition methods. It is easily transform the complex fractional order derivatives in simple time domain and interpret the results in same meaning.
Liu, Changying; Iserles, Arieh; Wu, Xinyuan
2018-03-01
The Klein-Gordon equation with nonlinear potential occurs in a wide range of application areas in science and engineering. Its computation represents a major challenge. The main theme of this paper is the construction of symmetric and arbitrarily high-order time integrators for the nonlinear Klein-Gordon equation by integrating Birkhoff-Hermite interpolation polynomials. To this end, under the assumption of periodic boundary conditions, we begin with the formulation of the nonlinear Klein-Gordon equation as an abstract second-order ordinary differential equation (ODE) and its operator-variation-of-constants formula. We then derive a symmetric and arbitrarily high-order Birkhoff-Hermite time integration formula for the nonlinear abstract ODE. Accordingly, the stability, convergence and long-time behaviour are rigorously analysed once the spatial differential operator is approximated by an appropriate positive semi-definite matrix, subject to suitable temporal and spatial smoothness. A remarkable characteristic of this new approach is that the requirement of temporal smoothness is reduced compared with the traditional numerical methods for PDEs in the literature. Numerical results demonstrate the advantage and efficiency of our time integrators in comparison with the existing numerical approaches.
Adaptive time-stepping Monte Carlo integration of Coulomb collisions
Särkimäki, K.; Hirvijoki, E.; Terävä, J.
2018-01-01
We report an accessible and robust tool for evaluating the effects of Coulomb collisions on a test particle in a plasma that obeys Maxwell-Jüttner statistics. The implementation is based on the Beliaev-Budker collision integral which allows both the test particle and the background plasma to be relativistic. The integration method supports adaptive time stepping, which is shown to greatly improve the computational efficiency. The Monte Carlo method is implemented for both the three-dimensional particle momentum space and the five-dimensional guiding center phase space. Detailed description is provided for both the physics and implementation of the operator. The focus is in adaptive integration of stochastic differential equations, which is an overlooked aspect among existing Monte Carlo implementations of Coulomb collision operators. We verify that our operator converges to known analytical results and demonstrate that careless implementation of the adaptive time step can lead to severely erroneous results. The operator is provided as a self-contained Fortran 95 module and can be included into existing orbit-following tools that trace either the full Larmor motion or the guiding center dynamics. The adaptive time-stepping algorithm is expected to be useful in situations where the collision frequencies vary greatly over the course of a simulation. Examples include the slowing-down of fusion products or other fast ions, and the Dreicer generation of runaway electrons as well as the generation of fast ions or electrons with ion or electron cyclotron resonance heating.
Block-pulse functions approach to numerical solution of Abel’s integral equation
Directory of Open Access Journals (Sweden)
Monireh Nosrati Sahlan
2015-12-01
Full Text Available This study aims to present a computational method for solving Abel’s integral equation of the second kind. The introduced method is based on the use of Block-pulse functions (BPFs via collocation method. Abel’s integral equations as singular Volterra integral equations are hard and heavy in computation, but because of the properties of BPFs, as is reported in examples, this method is more efficient and more accurate than some other methods for solving this class of integral equations. On the other hand, the benefit of this method is low cost of computing operations. The applied method transforms the singular integral equation into triangular linear algebraic system that can be solved easily. An error analysis is worked out and applications are demonstrated through illustrative examples.
Real-time numerical shake prediction and updating for earthquake early warning
Wang, Tianyun; Jin, Xing; Wei, Yongxiang; Huang, Yandan
2017-12-01
Ground motion prediction is important for earthquake early warning systems, because the region's peak ground motion indicates the potential disaster. In order to predict the peak ground motion quickly and precisely with limited station wave records, we propose a real-time numerical shake prediction and updating method. Our method first predicts the ground motion based on the ground motion prediction equation after P waves detection of several stations, denoted as the initial prediction. In order to correct the prediction error of the initial prediction, an updating scheme based on real-time simulation of wave propagation is designed. Data assimilation technique is incorporated to predict the distribution of seismic wave energy precisely. Radiative transfer theory and Monte Carlo simulation are used for modeling wave propagation in 2-D space, and the peak ground motion is calculated as quickly as possible. Our method has potential to predict shakemap, making the potential disaster be predicted before the real disaster happens. 2008 M S8.0 Wenchuan earthquake is studied as an example to show the validity of the proposed method.
A numerical dispersion compensation technique for time recompression of Lamb wave signals.
Sicard, René; Goyette, Jacques; Zellouf, Djamel
2002-05-01
A Fourier domain numerical reconstruction technique has been created in order to eliminate the time spread of Lamb wave signals caused by their dispersive nature. This method allows a good time compaction of the echoes obtained from a Lamb wave inspection. In a pulse-echo setup, reflection peaks coming from targets located close one from each other that could not be separated or seen within raw signals are identified using this procedure. The utility of this new technique goes from simple signal analysis to imaging purposes such as the improvement of B-scan images or SAFT processing. It has been tested in three different situations with the S0 mode generated in a frequency bandwidth where it is highly dispersive. The reconstruction of a pure reflection coming from the edge of a plate, the separation of the echoes resulting from reflections on two targets near one each other and the effects of the presence of an obstacle between the emitter and the receiver are treated. Good results are obtained for every case studied.
Integration of Real-Time Data Into Building Automation Systems
Energy Technology Data Exchange (ETDEWEB)
Mark J. Stunder; Perry Sebastian; Brenda A. Chube; Michael D. Koontz
2003-04-16
The project goal was to investigate the possibility of using predictive real-time information from the Internet as an input to building management system algorithms. The objectives were to identify the types of information most valuable to commercial and residential building owners, managers, and system designers. To comprehensively investigate and document currently available electronic real-time information suitable for use in building management systems. Verify the reliability of the information and recommend accreditation methods for data and providers. Assess methodologies to automatically retrieve and utilize the information. Characterize equipment required to implement automated integration. Demonstrate the feasibility and benefits of using the information in building management systems. Identify evolutionary control strategies.
Evaluation of the filtered leapfrog-trapezoidal time integration method
International Nuclear Information System (INIS)
Roache, P.J.; Dietrich, D.E.
1988-01-01
An analysis and evaluation are presented for a new method of time integration for fluid dynamic proposed by Dietrich. The method, called the filtered leapfrog-trapezoidal (FLT) scheme, is analyzed for the one-dimensional constant-coefficient advection equation and is shown to have some advantages for quasi-steady flows. A modification (FLTW) using a weighted combination of FLT and leapfrog is developed which retains the advantages for steady flows, increases accuracy for time-dependent flows, and involves little coding effort. Merits and applicability are discussed
On Tuning PI Controllers for Integrating Plus Time Delay Systems
Directory of Open Access Journals (Sweden)
David Di Ruscio
2010-10-01
Full Text Available Some analytical results concerning PI controller tuning based on integrator plus time delay models are worked out and presented. A method for obtaining PI controller parameters, Kp=alpha/(k*tau, and, Ti=beta*tau, which ensures a given prescribed maximum time delay error, dtau_max, to time delay, tau, ratio parameter delta=dau_max/tau, is presented. The corner stone in this method, is a method product parameter, c=alpha*beta. Analytical relations between the PI controller parameters, Ti, and, Kp, and the time delay error parameter, delta, is presented, and we propose the setting, beta=c/a*(delta+1, and, alpha=a/(delta+1, which gives, Ti=c/a*(delta+1*tau, and Kp=a/((delta+1*k*tau, where the parameter, a, is constant in the method product parameter, c=alpha*beta. It also turns out that the integral time, Ti, is linear in, delta, and the proportional gain, Kp, inversely proportional to, delta+1. For the original Ziegler Nichols (ZN method this parameter is approximately, c=2.38, and the presented method may e.g., be used to obtain new modified ZN parameters with increased robustness margins, also documented in the paper.
Improved integration time estimation of endogenous retroviruses with phylogenetic data.
Directory of Open Access Journals (Sweden)
Hugo Martins
2011-03-01
Full Text Available Endogenous retroviruses (ERVs are genetic fossils of ancient retroviral integrations that remain in the genome of many organisms. Most loci are rendered non-functional by mutations, but several intact retroviral genes are known in mammalian genomes. Some have been adopted by the host species, while the beneficial roles of others remain unclear. Besides the obvious possible immunogenic impact from transcribing intact viral genes, endogenous retroviruses have also become an interesting and useful tool to study phylogenetic relationships. The determination of the integration time of these viruses has been based upon the assumption that both 5' and 3' Long Terminal Repeats (LTRs sequences are identical at the time of integration, but evolve separately afterwards. Similar approaches have been using either a constant evolutionary rate or a range of rates for these viral loci, and only single species data. Here we show the advantages of using different approaches.We show that there are strong advantages in using multiple species data and state-of-the-art phylogenetic analysis. We incorporate both simple phylogenetic information and Monte Carlo Markov Chain (MCMC methods to date the integrations of these viruses based on a relaxed molecular clock approach over a Bayesian phylogeny model and applied them to several selected ERV sequences in primates. These methods treat each ERV locus as having a distinct evolutionary rate for each LTR, and make use of consensual speciation time intervals between primates to calibrate the relaxed molecular clocks.The use of a fixed rate produces results that vary considerably with ERV family and the actual evolutionary rate of the sequence, and should be avoided whenever multi-species phylogenetic data are available. For genome-wide studies, the simple phylogenetic approach constitutes a better alternative, while still being computationally feasible.
Rigorous time slicing approach to Feynman path integrals
Fujiwara, Daisuke
2017-01-01
This book proves that Feynman's original definition of the path integral actually converges to the fundamental solution of the Schrödinger equation at least in the short term if the potential is differentiable sufficiently many times and its derivatives of order equal to or higher than two are bounded. The semi-classical asymptotic formula up to the second term of the fundamental solution is also proved by a method different from that of Birkhoff. A bound of the remainder term is also proved. The Feynman path integral is a method of quantization using the Lagrangian function, whereas Schrödinger's quantization uses the Hamiltonian function. These two methods are believed to be equivalent. But equivalence is not fully proved mathematically, because, compared with Schrödinger's method, there is still much to be done concerning rigorous mathematical treatment of Feynman's method. Feynman himself defined a path integral as the limit of a sequence of integrals over finite-dimensional spaces which is obtained by...
Signal integral for optimizing the timing of defibrillation.
Wu, Xiaobo; Bisera, Joe; Tang, Wanchun
2013-12-01
The possibility of successful defibrillation decreases with an increased duration of ventricular fibrillation (VF). Futile electrical shocks are inversely correlated with myocardial contractile function and long-term survival. Previous studies have demonstrated that various ECG waveform analyses predict the success of defibrillation. This study investigated whether the absolute amplitude of pre-shock VF waveform is likely to predict the success of defibrillation. ECG recordings of 350 out-of-hospital cardiac arrest (OOHCA) patients were obtained from the automated external defibrillator (AED) and analyzed by the method of signal integral. Successful defibrillation was defined as organized rhythm with heart rate ≥40beat/min commencing within one min of post-shock period and persisting for a minimum of 30s. Signal integral was significantly greater in successful defibrillation than unsuccessful defibrillation (81.76±32.3mV vs. 34.9±15.33mV, pdefibrillation were 90%, 86%, 80% and 93%, respectively. The receiver operator curve further revealed that signal integral predicted the likelihood of successful defibrillation (area under the curve=0.949). Signal integral predicted successful electrical shocks on patients with ventricular fibrillation and have potential to optimize the timing of defibrillation and reduce the number of electrical shocks. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Fundamental aspects of the integration of seismic monitoring with numerical modelling.
CSIR Research Space (South Africa)
Mendecki, AJ
2001-06-01
Full Text Available Numerical modelling of rock-mass response to underground excavations is of vital importance for the decision-making process in designing and running a mine. Likewise, seismic monitoring with state-of-the-art local seismic systems is indispensable...
A Numerical Methods Course Based on B-Learning: Integrated Learning Design and Follow Up
Cepeda, Francisco Javier Delgado
2013-01-01
Information and communication technologies advance continuously, providing a real support for learning processes. Learning technologies address areas which previously have corresponded to face-to-face learning, while mobile resources are having a growing impact on education. Numerical Methods is a discipline and profession based on technology. In…
Two-step rational cononical function in the numerical integration of ...
African Journals Online (AJOL)
By collocation, an explicit nonlinerar two-step scheme is obtained. Numerical examples are provided to demonstrate the performance of the scheme. The results obtained were found to be quite comparable with those by existing schemes. Key Words: Collocation two-step scheme. [Global Jnl Mathematical Sci Vol.2(1) 2003: ...
Tuning of IMC based PID controllers for integrating systems with time delay.
Kumar, D B Santosh; Padma Sree, R
2016-07-01
Design of Proportional Integral and Derivative (PID) controllers based on IMC principles for various types of integrating systems with time delay is proposed. PID parameters are given in terms of process model parameters and a tuning parameter. The tuning parameter is IMC filter time constant. In the present work, the IMC filter (Q) is chosen in such a manner that the order of the denominator of IMC controller is one less than the order of the numerator. The IMC filter time constant (λ) is tuned in such a way that a good compromise is made between performance and robustness for both servo and regulatory problems. To improve servo response of the controller a set point filter is designed such that the closed loop response is similar to that of first order plus time delay system. The proposed controller design method is applied to various transfer function models and to the non-linear model equations of jacketed CSTR to demonstrate its applicability and effectiveness. The performance of the proposed controller is compared with the recently reported methods in terms of IAE and ITAE. The smooth functioning of the controller is determined in terms of total variation and compared with recently reported methods. Simulation studies are carried out on various integrating systems with time delay to show the effectiveness and superiority of the proposed controllers. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Pablo Dolado
2015-10-01
Full Text Available A novel technique of design of experiments applied to numerical simulations is proposed in this paper as a methodology for the sizing and design of thermal storage equipment integrated in any specific application. The technique is carried out through the response surfaces in order to limit the number of simulation runs required to achieve an appropriate solution. Thus, there are significant savings on the time spent on the design as well as a potential cost saving on the experimentation if similarity relationships between the prototype and the model are met. The technique is applied here to a previously developed and validated numerical model that simulates the thermal behavior of a phase change material-air heat exchanger. The incorporation of the thermal energy storage unit is analyzed in the case of a solar cooling application, improving the system coefficient of performance. The economic viability is mainly conditioned by the price of the macroencapsulated phase change material.
An arbitrary-order staggered time integrator for the linear acoustic wave equation
Lee, Jaejoon; Park, Hyunseo; Park, Yoonseo; Shin, Changsoo
2018-02-01
We suggest a staggered time integrator whose order of accuracy can arbitrarily be extended to solve the linear acoustic wave equation. A strategy to select the appropriate order of accuracy is also proposed based on the error analysis that quantitatively predicts the truncation error of the numerical solution. This strategy not only reduces the computational cost several times, but also allows us to flexibly set the modelling parameters such as the time step length, grid interval and P-wave speed. It is demonstrated that the proposed method can almost eliminate temporal dispersive errors during long term simulations regardless of the heterogeneity of the media and time step lengths. The method can also be successfully applied to the source problem with an absorbing boundary condition, which is frequently encountered in the practical usage for the imaging algorithms or the inverse problems.
CSIR Research Space (South Africa)
Long, CS
2009-01-01
Full Text Available The effects of selected planar finite element formulations, and their associated integration schemes, on the stiffness of a checkerboard material layout are investigated. Standard 4-node bilinear elements, 8- and 9-node quadratic elements, as well...
DEFF Research Database (Denmark)
Saraswathi, Ananthavel; Sanjeevikumar, Padmanaban; Shanmugham, Sutha
2016-01-01
on generation, transmission and distribution etc. This paper exploited the integration of static synchronous compensator (STATCOM) and superconducting magnetic energy storage (SMES) which is then connected to existing power transmission line for enhancing the available power transfer capacity (ATC). STATCOMis...
Altürk, Ahmet
2016-01-01
Mean value theorems for both derivatives and integrals are very useful tools in mathematics. They can be used to obtain very important inequalities and to prove basic theorems of mathematical analysis. In this article, a semi-analytical method that is based on weighted mean-value theorem for obtaining solutions for a wide class of Fredholm integral equations of the second kind is introduced. Illustrative examples are provided to show the significant advantage of the proposed method over some existing techniques.
ICM: an Integrated Compartment Method for numerically solving partial differential equations
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.
1981-05-01
An integrated compartment method (ICM) is proposed to construct a set of algebraic equations from a system of partial differential equations. The ICM combines the utility of integral formulation of finite element approach, the simplicity of interpolation of finite difference approximation, and the flexibility of compartment analyses. The integral formulation eases the treatment of boundary conditions, in particular, the Neumann-type boundary conditions. The simplicity of interpolation provides great economy in computation. The flexibility of discretization with irregular compartments of various shapes and sizes offers advantages in resolving complex boundaries enclosing compound regions of interest. The basic procedures of ICM are first to discretize the region of interest into compartments, then to apply three integral theorems of vectors to transform the volume integral to the surface integral, and finally to use interpolation to relate the interfacial values in terms of compartment values to close the system. The Navier-Stokes equations are used as an example of how to derive the corresponding ICM alogrithm for a given set of partial differential equations. Because of the structure of the algorithm, the basic computer program remains the same for cases in one-, two-, or three-dimensional problems.
Development of visuo-auditory integration in space and time.
Gori, Monica; Sandini, Giulio; Burr, David
2012-01-01
Adults integrate multisensory information optimally (e.g., Ernst and Banks, 2002) while children do not integrate multisensory visual-haptic cues until 8-10 years of age (e.g., Gori et al., 2008). Before that age strong unisensory dominance occurs for size and orientation visual-haptic judgments, possibly reflecting a process of cross-sensory calibration between modalities. It is widely recognized that audition dominates time perception, while vision dominates space perception. Within the framework of the cross-sensory calibration hypothesis, we investigate visual-auditory integration in both space and time with child-friendly spatial and temporal bisection tasks. Unimodal and bimodal (conflictual and not) audio-visual thresholds and PSEs were measured and compared with the Bayesian predictions. In the temporal domain, we found that both in children and adults, audition dominates the bimodal visuo-auditory task both in perceived time and precision thresholds. On the contrary, in the visual-auditory spatial task, children younger than 12 years of age show clear visual dominance (for PSEs), and bimodal thresholds higher than the Bayesian prediction. Only in the adult group did bimodal thresholds become optimal. In agreement with previous studies, our results suggest that also visual-auditory adult-like behavior develops late. We suggest that the visual dominance for space and the auditory dominance for time could reflect a cross-sensory comparison of vision in the spatial visuo-audio task and a cross-sensory comparison of audition in the temporal visuo-audio task.
Wildfire Disturbance and Sediment Transfers over Millennial Time Scales: A Numerical Modelling Study
Martin, Y.
2003-12-01
Wildfire may lead to accelerated soil erosion, debris flow and shallow landsliding activity in the years following disturbance. This study focuses on coastal drainage basins in British Columbia over millennial time scales, for which accelerated rates of shallow landsliding following wildfire may be of particular significance. An algorithm for wildfire occurrence, based on lake and sediment charcoal studies undertaken in coastal British Columbia and western Washington over millennial time scales (for example, Gavin et al., 2003), is incorporated into a numerical model of sediment routing over these same time scales. A stochastic rule set for wildfire frequency, based on a Weibull distribution of fire return intervals, assigns years of fire occurrence in the model. In terms of location, south-facing aspects are assigned a 25 times greater susceptibility to wildfire than north-facing aspects. As a first-order approximation, it is supposed that loss of tree root strength resulting from stand-replacing wildfires is comparable in its effects to clearcut logging. Therefore, documentation of increased shallow landslide activity associated with logging is used to adjust landsliding transport equations for the years following wildfire disturbance. Thereafter, landsliding rates are returned to pre-disturbance values. Fire return intervals, particularly those on north-facing aspects, can be relatively long in coastal British Columbia when compared to return intervals typically found in drier mountain ranges. This study investigates the degree to which wildfire disturbance affects sediment routing and delivery to channels over millennial time scales in coastal British Columbia. Sensitivity to model parameters is evaluated. Further investigations of wildfire effects on geomorphic process operation will lead to improved understanding of natural disturbance regimes to which ecosystems adjust over both the short and long term. Such information can be used to evaluate possible
Long linear arrays with time delay integration and element deselection
Arthurs, C. P.
1997-08-01
GEC-Marconi infra-red has developed a sensor technology based on lateral collection CdHgTe photodiode arrays mounted on custom designed CMOS multiplexer integrated circuits. The availability of submicron silicon processes has enabled a very high degree of functionality to be integrated within the detector thereby simplifying the overall system design. This paper describes a generic architecture that finds particular application for advanced infrared search-and-track, surveillance and high performance imaging applications. These applications require the highest possible performance and are therefore based on time-delay and integration (TDI) to enhance the signal-to-noise ratio, and detector element redundancy with defective element deselection (DED) to give resultant arrays with no dropouts. The detectors have fully variable integration period control, selectable integration capacitors, and a signal-to-noise enhancement capability at low infrared flux levels. The overall power consumption is low rendering the detectors suitable for engine cooling. The architecture is based on a number of unit cell designs and is readily adaptable to a wide range of configurations. The unit capacitor sizes within the design being rescaled to accommodate the required signal levels. In this way the numbers of elements in TDI and the number of TDI channels can be matched to the end application requirements. The architecture is applicable to both long and medium wave detectors. TDI channels are typically composed of 8 or 10 elements and in excess of 700 channels have been demonstrated. The results obtained from a number of prototype detectors are presented.
Hedayatrasa, Saeid; Bui, Tinh Quoc; Zhang, Chuanzeng; Lim, Chee Wah
2014-02-01
Numerical modeling of the Lamb wave propagation in functionally graded materials (FGMs) by a two-dimensional time-domain spectral finite element method (SpFEM) is presented. The high-order Chebyshev polynomials as approximation functions are used in the present formulation, which provides the capability to take into account the through thickness variation of the material properties. The efficiency and accuracy of the present model with one and two layers of 5th order spectral elements in modeling wave propagation in FGM plates are analyzed. Different excitation frequencies in a wide range of 28-350 kHz are investigated, and the dispersion properties obtained by the present model are verified by reference results. The through thickness wave structure of two principal Lamb modes are extracted and analyzed by the symmetry and relative amplitude of the vertical and horizontal oscillations. The differences with respect to Lamb modes generated in homogeneous plates are explained. Zero-crossing and wavelet signal processing-spectrum decomposition procedures are implemented to obtain phase and group velocities and their dispersion properties. So it is attested how this approach can be practically employed for simulation, calibration and optimization of Lamb wave based nondestructive evaluation techniques for the FGMs. The capability of modeling stress wave propagation through the thickness of an FGM specimen subjected to impact load is also investigated, which shows that the present method is highly accurate as compared with other existing reference data.
Liang, Fayun; Chen, Haibing; Huang, Maosong
2017-07-01
To provide appropriate uses of nonlinear ground response analysis for engineering practice, a three-dimensional soil column with a distributed mass system and a time domain numerical analysis were implemented on the OpenSees simulation platform. The standard mesh of a three-dimensional soil column was suggested to be satisfied with the specified maximum frequency. The layered soil column was divided into multiple sub-soils with a different viscous damping matrix according to the shear velocities as the soil properties were significantly different. It was necessary to use a combination of other one-dimensional or three-dimensional nonlinear seismic ground analysis programs to confirm the applicability of nonlinear seismic ground motion response analysis procedures in soft soil or for strong earthquakes. The accuracy of the three-dimensional soil column finite element method was verified by dynamic centrifuge model testing under different peak accelerations of the earthquake. As a result, nonlinear seismic ground motion response analysis procedures were improved in this study. The accuracy and efficiency of the three-dimensional seismic ground response analysis can be adapted to the requirements of engineering practice.
Stroe, Gabriela; Andrei, Irina-Carmen; Frunzulica, Florin
2017-01-01
The objectives of this paper are the study and the implementation of both aerodynamic and propulsion models, as linear interpolations using look-up tables in a database. The aerodynamic and propulsion dependencies on state and control variable have been described by analytic polynomial models. Some simplifying hypotheses were made in the development of the nonlinear aircraft simulations. The choice of a certain technique to use depends on the desired accuracy of the solution and the computational effort to be expended. Each nonlinear simulation includes the full nonlinear dynamics of the bare airframe, with a scaled direct connection from pilot inputs to control surface deflections to provide adequate pilot control. The engine power dynamic response was modeled with an additional state equation as first order lag in the actual power level response to commanded power level was computed as a function of throttle position. The number of control inputs and engine power states varied depending on the number of control surfaces and aircraft engines. The set of coupled, nonlinear, first-order ordinary differential equations that comprise the simulation model can be represented by the vector differential equation. A linear time-invariant (LTI) system representing aircraft dynamics for small perturbations about a reference trim condition is given by the state and output equations present. The gradients are obtained numerically by perturbing each state and control input independently and recording the changes in the trimmed state and output equations. This is done using the numerical technique of central finite differences, including the perturbations of the state and control variables. For a reference trim condition of straight and level flight, linearization results in two decoupled sets of linear, constant-coefficient differential equations for longitudinal and lateral / directional motion. The linearization is valid for small perturbations about the reference trim
Integral Time and the Varieties of Post-Mortem Survival
Directory of Open Access Journals (Sweden)
Sean M. Kelly
2008-06-01
Full Text Available While the question of survival of bodily death is usually approached by focusing on the mind/body relation (and often with the idea of the soul as a special kind of substance, this paper explores the issue in the context of our understanding of time. The argument of the paper is woven around the central intuition of time as an “ever-living present.” The development of this intuition allows for a more integral or “complex-holistic” theory of time, the soul, and the question of survival. Following the introductory matter, the first section proposes a re-interpretation of Nietzsche’s doctrine of eternal recurrence in terms of moments and lives as “eternally occurring.” The next section is a treatment of Julian Barbour’s neo-Machian model of instants of time as configurations in the n-dimensional phase-space he calls “Platonia.” While rejecting his claim to have done away with time, I do find his model suggestive of the idea of moments and lives as eternally occurring. The following section begins with Fechner’s visionary ideas of the nature of the soul and its survival of bodily death, with particular attention to the notion of holonic inclusion and the central analogy of the transition from perception to memory. I turn next to Whitehead’s equally holonic notions of prehension and the concrescence of actual occasions. From his epochal theory of time and certain ambiguities in his reflections on the “divine antinomies,” we are brought to the threshold of a potentially more integral or “complex-holistic” theory of time and survival, which is treated in the last section. This section draws from my earlier work on Hegel, Jung, and Edgar Morin, as well as from key insights of Jean Gebser, for an interpretation of Sri Aurobindo’s inspired but cryptic description of the “Supramental Time Vision.” This interpretation leads to an alternative understanding of reincarnation—and to the possibility of its reconciliation
Integral Time and the Varieties of Post-Mortem Survival
Directory of Open Access Journals (Sweden)
Sean M. Kelly
2008-06-01
Full Text Available While the question of survival of bodily death is usually approached byfocusing on the mind/body relation (and often with the idea of the soul as a special kindof substance, this paper explores the issue in the context of our understanding of time.The argument of the paper is woven around the central intuition of time as an “everlivingpresent.” The development of this intuition allows for a more integral or “complexholistic”theory of time, the soul, and the question of survival. Following the introductorymatter, the first section proposes a re-interpretation of Nietzsche’s doctrine of eternalrecurrence in terms of moments and lives as “eternally occurring.” The next section is atreatment of Julian Barbour’s neo-Machian model of instants of time as configurations inthe n-dimensional phase-space he calls “Platonia.” While rejecting his claim to have doneaway with time, I do find his model suggestive of the idea of moments and lives aseternally occurring. The following section begins with Fechner’s visionary ideas of thenature of the soul and its survival of bodily death, with particular attention to the notionof holonic inclusion and the central analogy of the transition from perception to memory.I turn next to Whitehead’s equally holonic notions of prehension and the concrescence ofactual occasions. From his epochal theory of time and certain ambiguities in hisreflections on the “divine antinomies,” we are brought to the threshold of a potentiallymore integral or “complex-holistic” theory of time and survival, which is treated in thelast section. This section draws from my earlier work on Hegel, Jung, and Edgar Morin,as well as from key insights of Jean Gebser, for an interpretation of Sri Aurobindo’sinspired but cryptic description of the “Supramental Time Vision.” This interpretationleads to an alternative understanding of reincarnation—and to the possibility of itsreconciliation with the once-only view
Morrison, Abigail; Straube, Sirko; Plesser, Hans Ekkehard; Diesmann, Markus
2007-01-01
Very large networks of spiking neurons can be simulated efficiently in parallel under the constraint that spike times are bound to an equidistant time grid. Within this scheme, the subthreshold dynamics of a wide class of integrate-and-fire-type neuron models can be integrated exactly from one grid point to the next. However, the loss in accuracy caused by restricting spike times to the grid can have undesirable consequences, which has led to interest in interpolating spike times between the grid points to retrieve an adequate representation of network dynamics. We demonstrate that the exact integration scheme can be combined naturally with off-grid spike events found by interpolation. We show that by exploiting the existence of a minimal synaptic propagation delay, the need for a central event queue is removed, so that the precision of event-driven simulation on the level of single neurons is combined with the efficiency of time-driven global scheduling. Further, for neuron models with linear subthreshold dynamics, even local event queuing can be avoided, resulting in much greater efficiency on the single-neuron level. These ideas are exemplified by two implementations of a widely used neuron model. We present a measure for the efficiency of network simulations in terms of their integration error and show that for a wide range of input spike rates, the novel techniques we present are both more accurate and faster than standard techniques.
EVALUATION OF THE POUNDING FORCES DURING EARTHQUAKE USING EXPLICIT DYNAMIC TIME INTEGRATION METHOD
Directory of Open Access Journals (Sweden)
Nica George Bogdan
2017-09-01
Full Text Available Pounding effects during earthquake is a subject of high significance for structural engineers performing in the urban areas. In this paper, two ways to account for structural pounding are used in a MATLAB code, namely classical stereomechanics approach and nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures acted by ELCentro recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion are numerical integrated using central finite difference method, an explicit method, having the main advantage that in the displacement at the ith+1 step is calculated based on the loads from the ith step. Thus, the collision is checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. First, a comparison is done using available data in the literature. Both linear and nonlinear behavior of the structures during earthquake is further investigated. Several layout scenarios are also investigated, in which one or more weak buildings are adjacent to a stiffer building. One of the main findings in this paper is related to the behavior of a weak structure located between two stiff structures.
Gutman, S. I.; Bock, Y.
2007-12-01
The accurate characterization of atmospheric moisture fields (including water vapor and clouds) is essential for improved weather forecasting and climate monitoring. Despite its importance, the ability to do so under all weather conditions has been a continuing problem for atmospheric scientists. The principle reason why this problem has been so difficult to solve is related to the high temporal and spatial variability of water in the free atmosphere. Under certain circumstances the distribution of moisture in the atmosphere can change abruptly over short distances, and this causes it to be under-observed using conventional weather observing systems. As water vapor, temperature and pressure change in the atmosphere, the refractivity of the troposphere changes accordingly and GNSS accuracy can suffer if the hydrostatic and wet signal delays are mismodeled. Recognizing this, the geodetic community developed techniques to treat the signal delays caused by the neutral atmosphere as nuisance parameters and remove them for high accuracy positioning applications. In ground-based GNSS/GPS Meteorology at NOAA, the tropospheric signal delay is estimated in near real-time from a network of about 400 continuously operating reference stations distributed across the U.S. using an 8-hr sliding window technique. Estimates of tropospheric refractivity (and/or integrated precipitable water vapor retrieved from these delays) have been assimilated into numerical weather prediction models in the U.S., Canada, Europe and Japan with exceptionally good results. Based on these and other findings, GNSS/GPS-Met is scheduled to transition from NOAA Research into operational use in NOAA's National Weather Service starting in 2009. Recognizing the need for improved ways to mitigate tropospheric effects on GNSS accuracy, especially for applications requiring low-latency measurements of height, scientists at NOAA's Earth System Research Laboratory began to investigate the feasibility of using
Numerical Integration of the Master Equation in Some Models of Stochastic Epidemiology
Jenkinson, Garrett; Goutsias, John
2012-01-01
The processes by which disease spreads in a population of individuals are inherently stochastic. The master equation has proven to be a useful tool for modeling such processes. Unfortunately, solving the master equation analytically is possible only in limited cases (e.g., when the model is linear), and thus numerical procedures or approximation methods must be employed. Available approximation methods, such as the system size expansion method of van Kampen, may fail to provide reliable solutions, whereas current numerical approaches can induce appreciable computational cost. In this paper, we propose a new numerical technique for solving the master equation. Our method is based on a more informative stochastic process than the population process commonly used in the literature. By exploiting the structure of the master equation governing this process, we develop a novel technique for calculating the exact solution of the master equation – up to a desired precision – in certain models of stochastic epidemiology. We demonstrate the potential of our method by solving the master equation associated with the stochastic SIR epidemic model. MATLAB software that implements the methods discussed in this paper is freely available as Supporting Information S1. PMID:22615755
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.
2014-12-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method\\'s efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
Development of visuo-auditory integration in space and time
Directory of Open Access Journals (Sweden)
Monica eGori
2012-09-01
Full Text Available Adults integrate multisensory information optimally (e.g. Ernst & Banks, 2002 while children are not able to integrate multisensory visual haptic cues until 8-10 years of age (e.g. Gori, Del Viva, Sandini, & Burr, 2008. Before that age strong unisensory dominance is present for size and orientation visual-haptic judgments maybe reflecting a process of cross-sensory calibration between modalities. It is widely recognized that audition dominates time perception, while vision dominates space perception. If the cross sensory calibration process is necessary for development, then the auditory modality should calibrate vision in a bimodal temporal task, and the visual modality should calibrate audition in a bimodal spatial task. Here we measured visual-auditory integration in both the temporal and the spatial domains reproducing for the spatial task a child-friendly version of the ventriloquist stimuli used by Alais and Burr (2004 and for the temporal task a child-friendly version of the stimulus used by Burr, Banks and Morrone (2009. Unimodal and bimodal (conflictual or not conflictual audio-visual thresholds and PSEs were measured and compared with the Bayesian predictions. In the temporal domain, we found that both in children and adults, audition dominates the bimodal visuo-auditory task both in perceived time and precision thresholds. Contrarily, in the visual-auditory spatial task, children younger than 12 years of age show clear visual dominance (on PSEs and bimodal thresholds higher than the Bayesian prediction. Only in the adult group bimodal thresholds become optimal. In agreement with previous studies, our results suggest that also visual-auditory adult-like behaviour develops late. Interestingly, the visual dominance for space and the auditory dominance for time that we found might suggest a cross-sensory comparison of vision in a spatial visuo-audio task and a cross-sensory comparison of audition in a temporal visuo-audio task.
Further triple integral approach to mixed-delay-dependent stability of time-delay neutral systems.
Wang, Ting; Li, Tao; Zhang, Guobao; Fei, Shumin
2017-09-01
This paper studies the asymptotic stability for a class of neutral systems with mixed time-varying delays. Through utilizing some Wirtinger-based integral inequalities and extending the convex combination technique, the upper bound on derivative of Lyapunov-Krasovskii (L-K) functional can be estimated more tightly and three mixed-delay-dependent criteria are proposed in terms of linear matrix inequalities (LMIs), in which the nonlinearity and parameter uncertainties are also involved, respectively. Different from those existent works, based on the interconnected relationship between neutral delay and state one, some novel triple integral functional terms are constructed and the conservatism can be effectively reduced. Finally, two numerical examples are given to show the benefits of the proposed criteria. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Algorithmic properties of the midpoint predictor-corrector time integrator.
Energy Technology Data Exchange (ETDEWEB)
Rider, William J.; Love, Edward; Scovazzi, Guglielmo
2009-03-01
Algorithmic properties of the midpoint predictor-corrector time integration algorithm are examined. In the case of a finite number of iterations, the errors in angular momentum conservation and incremental objectivity are controlled by the number of iterations performed. Exact angular momentum conservation and exact incremental objectivity are achieved in the limit of an infinite number of iterations. A complete stability and dispersion analysis of the linearized algorithm is detailed. The main observation is that stability depends critically on the number of iterations performed.
Integrated real time bowel sound detector for artificial pancreas systems
Directory of Open Access Journals (Sweden)
Khandaker A. Al Mamun
2016-03-01
Full Text Available This paper reports an ultra-low power real time bowel sound detector with integrated feature extractor for physiologic measure of meal instances in artificial pancreas devices. The system can aid in improving long term diabetic patient care and consists of a front end detector and signal processing unit. The front end detector transduces the initial bowel sound recorded from a piezoelectric sensor into a voltage signal. The signal processor uses a feature extractor to determine whether a bowel sound is detected. The feature extractor consists of a low noise, low power signal front-end, peak and trough locator, signal slope and width detector, digitizer, and bowel pulse locator. The system was fabricated in a standard 0.18 μm CMOS process, and the bowel sound detection system was characterized and verified with experimentally recorded bowel sounds. The integrated instrument consumes 53 μW of power from a 1 V supply in a 0.96 mm2 area, and is suitable for integration with portable devices. Keywords: Bowel sound, Artificial pancreas, Glucose monitoring, Feature extractor, Charge amplifier, Piezoelectric sensor
Linear Time Invariant Models for Integrated Flight and Rotor Control
Olcer, Fahri Ersel
2011-12-01
Recent developments on individual blade control (IBC) and physics based reduced order models of various on-blade control (OBC) actuation concepts are opening up opportunities to explore innovative rotor control strategies for improved rotor aerodynamic performance, reduced vibration and BVI noise, and improved rotor stability, etc. Further, recent developments in computationally efficient algorithms for the extraction of Linear Time Invariant (LTI) models are providing a convenient framework for exploring integrated flight and rotor control, while accounting for the important couplings that exist between body and low frequency rotor response and high frequency rotor response. Formulation of linear time invariant (LTI) models of a nonlinear system about a periodic equilibrium using the harmonic domain representation of LTI model states has been studied in the literature. This thesis presents an alternative method and a computationally efficient scheme for implementation of the developed method for extraction of linear time invariant (LTI) models from a helicopter nonlinear model in forward flight. The fidelity of the extracted LTI models is evaluated using response comparisons between the extracted LTI models and the nonlinear model in both time and frequency domains. Moreover, the fidelity of stability properties is studied through the eigenvalue and eigenvector comparisons between LTI and LTP models by making use of the Floquet Transition Matrix. For time domain evaluations, individual blade control (IBC) and On-Blade Control (OBC) inputs that have been tried in the literature for vibration and noise control studies are used. For frequency domain evaluations, frequency sweep inputs are used to obtain frequency responses of fixed system hub loads to a single blade IBC input. The evaluation results demonstrate the fidelity of the extracted LTI models, and thus, establish the validity of the LTI model extraction process for use in integrated flight and rotor control
An integrated numerical model for the prediction of Gaussian and billet shapes
DEFF Research Database (Denmark)
Hattel, Jesper; Pryds, Nini; Pedersen, Trine Bjerre
2004-01-01
Separate models for the atomisation and the deposition stages were recently integrated by the authors to form a unified model describing the entire spray-forming process. In the present paper, the focus is on describing the shape of the deposited material during the spray-forming process, obtaine...
Optimization of Nordsieck's Method for the Numerical Integration of Ordinary Differential Equations
Gmelig, R.H.J.; Traas, C.R.
1984-01-01
Stability and accuracy of Nordsieck's integration method can be improved by choosing the zero-positions of the extraneous roots of the characteristic equation in a suitable way. Optimum zero-positions have been found by minimizing the lower bound of the interval of absolute stability and the
A time-domain finite element boundary integration method for ultrasonic nondestructive evaluation.
Shi, Fan; Choi, Wonjae; Skelton, Elizabeth A; Lowe, Michael J S; Craster, Richard V
2014-12-01
A 2-D and 3-D numerical modeling approach for calculating the elastic wave scattering signals from complex stress-free defects is evaluated. In this method, efficient boundary integration across the complex boundary of the defect is coupled with a time-domain finite element (FE) solver. The model is designed to simulate time-domain ultrasonic nondestructive evaluation in bulk media. This approach makes use of the hybrid concept of linking a local numerical model to compute the near-field scattering behavior and theoretical mathematical formulas for postprocessing to calculate the received signals. It minimizes the number of monitoring signals from the FE calculation so that the computation effort in postprocessing decreases significantly. In addition, by neglecting the conventional regular monitoring box, the region for FE calculation can be made smaller. In this paper, the boundary integral method is implemented in a commercial FE code, and it is validated by comparing the scattering signals with results from corresponding full FE models. The coupled method is then implemented in real inspection scenarios in both 2-D and 3-D, and the accuracy and the efficiency are demonstrated. The limitations of the proposed model and future works are also discussed.
Integral ceramic superstructure evaluation using time domain optical coherence tomography
Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.
2014-02-01
Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.
Želi, Velibor; Zorica, Dušan
2017-01-01
Generalization of the heat conduction equation is obtained by considering the system of equations consisting of the energy balance equation and fractional-order constitutive heat conduction law, assumed in the form of the distributed-order Cattaneo type. The Cauchy problem for system of energy balance equation and constitutive heat conduction law is treated analytically through Fourier and Laplace integral transform methods, as well as numerically by the method of finite differences through A...
Sathyachandran, S. K.; Roy, D. P.; Boschetti, L.
2014-12-01
The Fire Radiative Power (FRP) [MW] is a measure of the rate of biomass combustion and can be retrieved from ground based and satellite observations using middle infra-red measurements. The temporal integral of FRP is the Fire Radiative Energy (FRE) [MJ] and is related linearly to the total biomass consumption and so pyrogenic emissions. Satellite derived biomass consumption and emissions estimates have been derived conventionally by computing the summed total FRP, or the average FRP (arithmetic average of FRP retrievals), over spatial geographic grids for fixed time periods. These two methods are prone to estimation bias, especially under irregular sampling conditions such as provided by polar-orbiting satellites, because the FRP can vary rapidly in space and time as a function of the fire behavior. Linear temporal integration of FRP taking into account when the FRP values were observed and using the trapezoidal rule for numerical integration has been suggested as an alternate FRE estimation method. In this study FRP data measured rapidly with a dual-band radiometer over eight prescribed fires are used to compute eight FRE values using the sum, mean and trapezoidal estimation approaches under a variety of simulated irregular sampling conditions. The estimated values are compared to biomass consumed measurements for each of the eight fires to provide insights into which method provides more accurate and precise biomass consumption estimates. The three methods are also applied to continental MODIS FRP data to study their differences using polar orbiting satellite data. The research findings indicate that trapezoidal FRP numerical integration provides the most reliable estimator.
Energy Technology Data Exchange (ETDEWEB)
Hurd, J.W.
1987-08-15
The first-order transformation matrix is derived for a simple Wien filter. The Wien filter is approximated by square-edged, homogeneous, transverse E and B fields. The results are compared to results of numerical integration through a Wien filter with and without fringe fields. The derived transformation matrix is presently used in the first-order optics code TRACE to tune the 750 keV polarized proton injection transport at LAMPF. The Wien filter is used to precess the spin of the polarized proton beam.
Hurd, James W.
1987-08-01
The first-order transformation matrix is derived for a simple Wien filter. The Wien filter is approximated by square-edged homogeneous, transverse E and B fields. The results are compared to results of numerical integration through a Wien filter with and without fringe fields. The derived transformation matrix is presently used in the first-order optics code TRACE to tune the 750 keV polarized proton injection transport at LAMPF. The Wien filter is used to precess the spin of the polarized proton beam.
Integrative real-time geographic visualization of energy resources
International Nuclear Information System (INIS)
Sorokine, A.; Shankar, M.; Stovall, J.; Bhaduri, B.; King, T.; Fernandez, S.; Datar, N.; Omitaomu, O.
2009-01-01
'Full text:' Several models forecast that climatic changes will increase the frequency of disastrous events like droughts, hurricanes, and snow storms. Responding to these events and also to power outages caused by system errors such as the 2003 North American blackout require an interconnect-wide real-time monitoring system for various energy resources. Such a system should be capable of providing situational awareness to its users in the government and energy utilities by dynamically visualizing the status of the elements of the energy grid infrastructure and supply chain in geographic contexts. We demonstrate an approach that relies on Google Earth and similar standard-based platforms as client-side geographic viewers with a data-dependent server component. The users of the system can view status information in spatial and temporal contexts. These data can be integrated with a wide range of geographic sources including all standard Google Earth layers and a large number of energy and environmental data feeds. In addition, we show a real-time spatio-temporal data sharing capability across the users of the system, novel methods for visualizing dynamic network data, and a fine-grain access to very large multi-resolution geographic datasets for faster delivery of the data. The system can be extended to integrate contingency analysis results and other grid models to assess recovery and repair scenarios in the case of major disruption. (author)
Energy Technology Data Exchange (ETDEWEB)
Bammann, Douglas J.; Johnson, G. C. (University of California, Berkeley, CA); Marin, Esteban B.; Regueiro, Richard A. (University of Colorado, Boulder, CO)
2006-01-01
In this report we present the formulation of the physically-based Evolving Microstructural Model of Inelasticity (EMMI) . The specific version of the model treated here describes the plasticity and isotropic damage of metals as being currently applied to model the ductile failure process in structural components of the W80 program . The formulation of the EMMI constitutive equations is framed in the context of the large deformation kinematics of solids and the thermodynamics of internal state variables . This formulation is focused first on developing the plasticity equations in both the relaxed (unloaded) and current configurations. The equations in the current configuration, expressed in non-dimensional form, are used to devise the identification procedure for the plasticity parameters. The model is then extended to include a porosity-based isotropic damage state variable to describe the progressive deterioration of the strength and mechanical properties of metals induced by deformation . The numerical treatment of these coupled plasticity-damage constitutive equations is explained in detail. A number of examples are solved to validate the numerical implementation of the model.
Gocad2OGS: Workflow to Integrate Geo-structural Information into Numerical Simulation Models
Fischer, Thomas; Walther, Marc; Naumov, Dmitri; Sattler, Sabine; Kolditz, Olaf
2015-04-01
The investigation of fluid circulation in the Thuringian syncline is one of the INFLUINS project's targets. A 3D geo-structural model including 12 stratigraphic layers and 54 fault zones is created by geologists in the first step using the Gocad software. Within the INFLUINS project a ground-water flow simulation is used to check existing hypotheses and to gain new ideas of the underground fluid flow behaviour. We used the scientific, platform independent, open source software OpenGeoSys that implements the finite element method to solve the governing equations describing fluid flow in porous media. The geo-structural Gocad model is not suitable for the FEM numerical analysis. Therefore it is converted into an unstructured grid satisfying all mesh quality criteria required for the ground-water flow simulation. The resulting grid is stored in an open data format given by the Visualization Toolkit (vtk). In this work we present a workflow to convert geological structural models, created using the Gocad software, into a simulation model that is easy to use from numerical simulation software. We tested our workflow with the 3D geo-structural model of the Thuringian syncline and were able to setup and to evaluate a hydrogeological simulation model successfully.
International Nuclear Information System (INIS)
Glouannec, Patrick; Michel, Benoit; Delamarre, Guillaume; Grohens, Yves
2014-01-01
This paper presents an experimental and numerical design study of an insulation wall for refrigerated vans. The thermophysical properties of the insulating multilayer panel, the external environment impact (solar irradiation, temperature, etc.) and durability are taken into account. Different tools are used to characterize the thermal performances of the insulation walls and the thermal properties of the insulation materials are measured. In addition, an experiment at the wall scale is carried out and a 2D FEM model of heat and mass transfer within the wall is formulated. Three configurations are studied with this design approach. Multilayer insulation walls containing reflective multi-foil insulation, aerogel and phase change materials (PCM) are tested. Promising results are obtained with these materials, especially the reduction of peak heat transfer and energy consumption during the daytime period. Furthermore, the major influence of solar irradiation is highlighted as it can increase the peak heat transfer crossing the insulation wall by up to 43%. Nevertheless, we showed that the use of reflective multi-foil insulation and aerogel layers allowed decreasing this impact by 27%. - Highlights: • A design study of an insulation wall for a refrigerated van is carried out. • Experimental and numerical studies of multilayer insulation walls are performed. • The major influence of solar irradiation is highlighted. • New insulation materials (reflective multi-foil, aerogel and PCM) are tested
Cloud-Based Numerical Weather Prediction for Near Real-Time Forecasting and Disaster Response
Molthan, Andrew; Case, Jonathan; Venners, Jason; Schroeder, Richard; Checchi, Milton; Zavodsky, Bradley; Limaye, Ashutosh; O'Brien, Raymond
2015-01-01
activities in environmental monitoring and prediction across a growing number of regional hubs throughout the world. Capacity-building applications that extend numerical weather prediction to developing countries are intended to provide near real-time applications to benefit public health, safety, and economic interests, but may have a greater impact during disaster events by providing a source for local predictions of weather-related hazards, or impacts that local weather events may have during the recovery phase.
Siegler, Robert S.; Braithwaite, David W.
2016-01-01
In this review, we attempt to integrate two crucial aspects of numerical development: learning the magnitudes of individual numbers and learning arithmetic. Numerical magnitude development involves gaining increasingly precise knowledge of increasing ranges and types of numbers: from non-symbolic to small symbolic numbers, from smaller to larger…
On the Numerical Solution of the Integral Equation Formulation for Transient Structural Synthesis
2014-09-01
Keenan L. Coleman Lieutenant, United States Navy B.S., University of Arizona, 2007 Submitted in partial fulfillment of the requirements for...history of integral equations dates back to the early nineteenth century when the profound mathematical insights of Newton and Leibniz were being...Neta for their guidance and patience during this process. Finally, I would like to thank Dr. Richard Feynman, whose marriage of genius and common
Cao, Xinhua; Xu, Xiaoyin; Voss, Stephan
2017-03-01
In this paper, we describe an enhanced DICOM Secondary Capture (SC) that integrates Image Quantification (IQ) results, Regions of Interest (ROIs), and Time Activity Curves (TACs) with screen shots by embedding extra medical imaging information into a standard DICOM header. A software toolkit of DICOM IQSC has been developed to implement the SC-centered information integration of quantitative analysis for routine practice of nuclear medicine. Primary experiments show that the DICOM IQSC method is simple and easy to implement seamlessly integrating post-processing workstations with PACS for archiving and retrieving IQ information. Additional DICOM IQSC applications in routine nuclear medicine and clinic research are also discussed.
Park, Sang-Uk; Kim, Jun-Mo; Kihm, Jung-Hwi
2014-05-01
A series of numerical simulations was performed using a multiphase thermo-hydro-chemical numerical model to predict integratedly and evaluate quantitatively thermo-hydro-chemical phenomena due to heat generation associated with geologic disposal of high-level radioactive waste. The average mineralogical composition of the fifteen unweathered igneous rock bodies, which were classified as granite, in Republic of Korea was adopted as an initial (primary) mineralogical composition of the host rock of the repository of high-level radioactive waste in the numerical simulations. The numerical simulation results show that temperature rises and thus convective groundwater flow occurs near the repository due to heat generation associated with geologic disposal of high-level radioactive waste. Under these circumstances, a series of water-rock interactions take place. As a result, among the primary minerals, quartz, plagioclase (albite), biotite (annite), and muscovite are dissolved. However, orthoclase is initially precipitated and is then dissolved, whereas microcline is initially dissolved and is then precipitated. On the other hand, the secondary minerals such as kaolinite, Na-smectite, chlorite, and hematite are precipitated and are then partly dissolved. In addition, such dissolution and precipitation of the primary and secondary minerals change groundwater chemistry (quality) and induce reactive chemical transport. As a result, in groundwater, Na+, Fe2+, and HCO3- concentrations initially decrease, whereas K+, AlO2-, and aqueous SiO2 concentrations initially increase. On the other hand, H+ concentration initially increases and thus pH initially decreases due to dissociation of groundwater in order to provide OH-, which is essential in precipitation of Na-smectite and chlorite. Thus, the above-mentioned numerical simulation results suggest that thermo-hydro-chemical numerical simulation can provide a better understanding of heat transport, groundwater flow, and reactive
Valdés, Felipe
2013-03-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis functions and a collocation testing procedure, thus allowing for a marching-on-in-time (MOT) solution scheme. Unlike dual-source formulations, single-source equations involve space-time domain operator products, for which spatial discretization techniques developed for standalone operators do not apply. Here, the spatial discretization of the single-source time-domain integral equations is achieved by using the high-order divergence-conforming basis functions developed by Graglia alongside the high-order divergence-and quasi curl-conforming (DQCC) basis functions of Valdés The combination of these two sets allows for a well-conditioned mapping from div-to curl-conforming function spaces that fully respects the space-mapping properties of the space-time operators involved. Numerical results corroborate the fact that the proposed procedure guarantees accuracy and stability of the MOT scheme. © 2012 IEEE.
Directory of Open Access Journals (Sweden)
Naumenko Mikhail
2018-01-01
Full Text Available Modern parallel computing algorithm has been applied to the solution of the few-body problem. The approach is based on Feynman’s continual integrals method implemented in C++ programming language using NVIDIA CUDA technology. A wide range of 3-body and 4-body bound systems has been considered including nuclei described as consisting of protons and neutrons (e.g., 3,4He and nuclei described as consisting of clusters and nucleons (e.g., 6He. The correctness of the results was checked by the comparison with the exactly solvable 4-body oscillatory system and experimental data.
Naumenko, Mikhail; Samarin, Viacheslav
2018-02-01
Modern parallel computing algorithm has been applied to the solution of the few-body problem. The approach is based on Feynman's continual integrals method implemented in C++ programming language using NVIDIA CUDA technology. A wide range of 3-body and 4-body bound systems has been considered including nuclei described as consisting of protons and neutrons (e.g., 3,4He) and nuclei described as consisting of clusters and nucleons (e.g., 6He). The correctness of the results was checked by the comparison with the exactly solvable 4-body oscillatory system and experimental data.
Numerical Simulation of Fluidized Bed Gasifier for Integrated Gasification Combined Cycle
Directory of Open Access Journals (Sweden)
CHEN Ju-hui
2017-06-01
Full Text Available The overall thermal efficiency of the integrated gasification combined cycle ( IGCC has not been sufficiently improved. In order to achieve higher power generation efficiency，the advanced technology of IGCC has been developed which is on the basis of the concept of exergy recovery. IGCC systems and devices from the overall structure of opinion，this technology will generate electricity for the integration of advanced technology together，the current utilization of power generation technology and by endothermic reaction of steam in the gasifier，a gas turbine exhaust heat recovery or the solid oxide fuel cell. It is estimated that such the use of exergy recycling has the advantage of being easy to use，separating，collecting fixed CO2，making it very attractive，and can increase the overall efficiency by 10% or more. The characteristics of fluidized bed gasifier，one of the core equipment of the IGCC system，and its effect on the whole system were studied.
Cendagorta, Joseph R; Bačić, Zlatko; Tuckerman, Mark E
2018-03-14
We introduce a scheme for approximating quantum time correlation functions numerically within the Feynman path integral formulation. Starting with the symmetrized version of the correlation function expressed as a discretized path integral, we introduce a change of integration variables often used in the derivation of trajectory-based semiclassical methods. In particular, we transform to sum and difference variables between forward and backward complex-time propagation paths. Once the transformation is performed, the potential energy is expanded in powers of the difference variables, which allows us to perform the integrals over these variables analytically. The manner in which this procedure is carried out results in an open-chain path integral (in the remaining sum variables) with a modified potential that is evaluated using imaginary-time path-integral sampling rather than requiring the generation of a large ensemble of trajectories. Consequently, any number of path integral sampling schemes can be employed to compute the remaining path integral, including Monte Carlo, path-integral molecular dynamics, or enhanced path-integral molecular dynamics. We believe that this approach constitutes a different perspective in semiclassical-type approximations to quantum time correlation functions. Importantly, we argue that our approximation can be systematically improved within a cumulant expansion formalism. We test this approximation on a set of one-dimensional problems that are commonly used to benchmark approximate quantum dynamical schemes. We show that the method is at least as accurate as the popular ring-polymer molecular dynamics technique and linearized semiclassical initial value representation for correlation functions of linear operators in most of these examples and improves the accuracy of correlation functions of nonlinear operators.
Cendagorta, Joseph R.; Bačić, Zlatko; Tuckerman, Mark E.
2018-03-01
We introduce a scheme for approximating quantum time correlation functions numerically within the Feynman path integral formulation. Starting with the symmetrized version of the correlation function expressed as a discretized path integral, we introduce a change of integration variables often used in the derivation of trajectory-based semiclassical methods. In particular, we transform to sum and difference variables between forward and backward complex-time propagation paths. Once the transformation is performed, the potential energy is expanded in powers of the difference variables, which allows us to perform the integrals over these variables analytically. The manner in which this procedure is carried out results in an open-chain path integral (in the remaining sum variables) with a modified potential that is evaluated using imaginary-time path-integral sampling rather than requiring the generation of a large ensemble of trajectories. Consequently, any number of path integral sampling schemes can be employed to compute the remaining path integral, including Monte Carlo, path-integral molecular dynamics, or enhanced path-integral molecular dynamics. We believe that this approach constitutes a different perspective in semiclassical-type approximations to quantum time correlation functions. Importantly, we argue that our approximation can be systematically improved within a cumulant expansion formalism. We test this approximation on a set of one-dimensional problems that are commonly used to benchmark approximate quantum dynamical schemes. We show that the method is at least as accurate as the popular ring-polymer molecular dynamics technique and linearized semiclassical initial value representation for correlation functions of linear operators in most of these examples and improves the accuracy of correlation functions of nonlinear operators.
Ying, Wenjun; Henriquez, Craig S
2015-01-01
A both space and time adaptive algorithm is presented for simulating electrical wave propagation in the Purkinje system of the heart. The equations governing the distribution of electric potential over the system are solved in time with the method of lines. At each timestep, by an operator splitting technique, the space-dependent but linear diffusion part and the nonlinear but space-independent reactions part in the partial differential equations are integrated separately with implicit schemes, which have better stability and allow larger timesteps than explicit ones. The linear diffusion equation on each edge of the system is spatially discretized with the continuous piecewise linear finite element method. The adaptive algorithm can automatically recognize when and where the electrical wave starts to leave or enter the computational domain due to external current/voltage stimulation, self-excitation, or local change of membrane properties. Numerical examples demonstrating efficiency and accuracy of the adaptive algorithm are presented.
Directory of Open Access Journals (Sweden)
Wenjun Ying
2015-01-01
Full Text Available A both space and time adaptive algorithm is presented for simulating electrical wave propagation in the Purkinje system of the heart. The equations governing the distribution of electric potential over the system are solved in time with the method of lines. At each timestep, by an operator splitting technique, the space-dependent but linear diffusion part and the nonlinear but space-independent reactions part in the partial differential equations are integrated separately with implicit schemes, which have better stability and allow larger timesteps than explicit ones. The linear diffusion equation on each edge of the system is spatially discretized with the continuous piecewise linear finite element method. The adaptive algorithm can automatically recognize when and where the electrical wave starts to leave or enter the computational domain due to external current/voltage stimulation, self-excitation, or local change of membrane properties. Numerical examples demonstrating efficiency and accuracy of the adaptive algorithm are presented.
International Nuclear Information System (INIS)
Jamali, J.; Aghajafari, R.; Moini, R.; Sadeghi, H.
2002-01-01
A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper
The TIME Model: Time to Make a Change to Integrate Technology
Directory of Open Access Journals (Sweden)
Debby Mitchell
2004-06-01
Full Text Available The purpose of this article is to report the successful creation and implementation of an instructional model designed to assist educators in infusing technology into the curriculum while at the same time create opportunities for faculty to learn, become more proficient,and successful at integrating technology into their own classroom curriculum.The model was successfully tested and implemented with faculty, inservice and preservice teachers at the University of Central Florida (UCF. Faculty, inservice, and preservice teachers were successfully trained to integrate technology using a theme based curriculum with an instructional model called the TIME model which consists of twelve elements that include: Vision, Incentives, Personalization, Awareness, Learning Communities, Action Plan, Research, Development of Modules, Skills, Implementation, Evidence of Change, and Evaluation/Reflection.
Liao, Feng; Zhang, Luming; Wang, Shanshan
2018-02-01
In this article, we formulate an efficient and accurate numerical method for approximations of the coupled Schrödinger-Boussinesq (SBq) system. The main features of our method are based on: (i) the applications of a time-splitting Fourier spectral method for Schrödinger-like equation in SBq system, (ii) the utilizations of exponential wave integrator Fourier pseudospectral for spatial derivatives in the Boussinesq-like equation. The scheme is fully explicit and efficient due to fast Fourier transform. The numerical examples are presented to show the efficiency and accuracy of our method.
Time series Analysis of Integrateds Building System Variables
Georgiev, Tz.; Jonkov, T.; Yonchev, E.
2010-10-01
This article deals with time series analysis of indoor and outdoor variables of the integrated building system. The kernel of these systems is heating, ventilation and air conditioning (HVAC) problems. Important outdoor and indoor variables are: air temperature, global and diffuse radiations, wind speed and direction, temperature, relative humidity, mean radiant temperature, and so on. The aim of this article is TO select the structure and investigation of a linear auto—regressive (AR) and auto—regressive with external inputs (ARX) models. The investigation of obtained models is based on real—live data. All researches are derived in MATLAB environment. The further research will focus on synthesis of robust energy saving control algorithms.
Orthogonally referenced integrated ensemble for navigation and timing
Smith, Stephen Fulton; Moore, James Anthony
2014-04-01
An orthogonally referenced integrated ensemble for navigation and timing includes a dual-polyhedral oscillator array, including an outer sensing array of oscillators and an inner clock array of oscillators situated inside the outer sensing array. The outer sensing array includes a first pair of sensing oscillators situated along a first axis of the outer sensing array, a second pair of sensing oscillators situated along a second axis of the outer sensing array, and a third pair of sensing oscillators situated along a third axis of the outer sensing array. The inner clock array of oscillators includes a first pair of clock oscillators situated along a first axis of the inner clock array, a second pair of clock oscillators situated along a second axis of the inner clock array, and a third pair of clock oscillators situated along a third axis of the inner clock array.
Global Format for Conservative Time Integration in Nonlinear Dynamics
DEFF Research Database (Denmark)
Krenk, Steen
2014-01-01
in the new generation of energy conserving algorithms developed over the last two decades. However, the conservative algorithms typically rely on the special structure of the problem to be solved and require intermediate calculations using a mean state. This seems to have limited their use outside academia......The widely used classic collocation-based time integration procedures like Newmark, Generalized-alpha etc. generally work well within a framework of linear problems, but typically may encounter problems, when used in connection with essentially nonlinear structures. These problems are overcome...... equivalent static load steps, easily implemented in existing computer codes. The paper considers two aspects: representation of nonlinear internal forces in a form that implies energy conservation, and the option of an algorithmic damping with the purpose of extracting energy from undesirable high...
Pneumatic oscillator circuits for timing and control of integrated microfluidics.
Duncan, Philip N; Nguyen, Transon V; Hui, Elliot E
2013-11-05
Frequency references are fundamental to most digital systems, providing the basis for process synchronization, timing of outputs, and waveform synthesis. Recently, there has been growing interest in digital logic systems that are constructed out of microfluidics rather than electronics, as a possible means toward fully integrated laboratory-on-a-chip systems that do not require any external control apparatus. However, the full realization of this goal has not been possible due to the lack of on-chip frequency references, thus requiring timing signals to be provided from off-chip. Although microfluidic oscillators have been demonstrated, there have been no reported efforts to characterize, model, or optimize timing accuracy, which is the fundamental metric of a clock. Here, we report pneumatic ring oscillator circuits built from microfluidic valves and channels. Further, we present a compressible-flow analysis that differs fundamentally from conventional circuit theory, and we show the utility of this physically based model for the optimization of oscillator stability. Finally, we leverage microfluidic clocks to demonstrate circuits for the generation of phase-shifted waveforms, self-driving peristaltic pumps, and frequency division. Thus, pneumatic oscillators can serve as on-chip frequency references for microfluidic digital logic circuits. On-chip clocks and pumps both constitute critical building blocks on the path toward achieving autonomous laboratory-on-a-chip devices.
Czech Academy of Sciences Publication Activity Database
Minster, Jiří; Micka, Michal
2012-01-01
Roč. 2, č. 1 (2012), s. 81-89 ISSN 2161-6221 R&D Projects: GA AV ČR(CZ) IAA200710801 Institutional support: RVO:68378297 Keywords : microindentation * numerical simulation * viscoelastic characteristics Subject RIV: JJ - Other Materials
International Nuclear Information System (INIS)
Qin, H.; Guan, X.
2008-01-01
A variational symplectic integrator for the guiding-center motion of charged particles in general magnetic fields is developed for long-time simulation studies of magnetized plasmas. Instead of discretizing the differential equations of the guiding-center motion, the action of the guiding-center motion is discretized and minimized to obtain the iteration rules for advancing the dynamics. The variational symplectic integrator conserves exactly a discrete Lagrangian symplectic structure, and has better numerical properties over long integration time, compared with standard integrators, such as the standard and variable time-step fourth order Runge-Kutta methods.
Yee, H. C.; Sweby, P. K.
1995-01-01
The global asymptotic nonlinear behavior of 1 1 explicit and implicit time discretizations for four 2 x 2 systems of first-order autonomous nonlinear ordinary differential equations (ODES) is analyzed. The objectives are to gain a basic understanding of the difference in the dynamics of numerics between the scalars and systems of nonlinear autonomous ODEs and to set a baseline global asymptotic solution behavior of these schemes for practical computations in computational fluid dynamics. We show how 'numerical' basins of attraction can complement the bifurcation diagrams in gaining more detailed global asymptotic behavior of time discretizations for nonlinear differential equations (DEs). We show how in the presence of spurious asymptotes the basins of the true stable steady states can be segmented by the basins of the spurious stable and unstable asymptotes. One major consequence of this phenomenon which is not commonly known is that this spurious behavior can result in a dramatic distortion and, in most cases, a dramatic shrinkage and segmentation of the basin of attraction of the true solution for finite time steps. Such distortion, shrinkage and segmentation of the numerical basins of attraction will occur regardless of the stability of the spurious asymptotes, and will occur for unconditionally stable implicit linear multistep methods. In other words, for the same (common) steady-state solution the associated basin of attraction of the DE might be very different from the discretized counterparts and the numerical basin of attraction can be very different from numerical method to numerical method. The results can be used as an explanation for possible causes of error, and slow convergence and nonconvergence of steady-state numerical solutions when using the time-dependent approach for nonlinear hyperbolic or parabolic PDES.
International Nuclear Information System (INIS)
Egorov, Alexander A
2012-01-01
We consider theoretical and numerical methods for studying propagation and scattering of laser radiation of eigenmodes and non-eigenmodes in an irregular integrated-optical waveguide. Scattering of non-eigenmodes in an irregular integratedoptical waveguide is investigated for the first time. We present the calculated dispersion curves for TE and TM eigenmodes and TE non-eigenmodes. For the leaky TE 0 modes we plot the dependence of the complex dispersion relation and show the vertical complex profile of the field. The dependence of the scattered laser radiation field on the effective refractive index is obtained for the given parameters of the waveguide. We compare for the first time the calculated complex scattering diagram of laser radiation outside the waveguide layer in the plane, perpendicular to the plane of incidence, for the leaky and guided TE 0 modes.
Directory of Open Access Journals (Sweden)
Sheam-Chyun Lin
2014-02-01
Full Text Available Since the inlet and outlet of hidden ceiling fan are almost located at the same Plane; thus, an improper housing may cause inhale-return phenomenon which significantly affects its power consumption and performance. In this study, a comprehensive investigation by numerical and experimental techniques was used to predict and identify the flow pattern, airflow rate, efficiency, and noise for ceiling fans with different design parameters. The results showed that the unique inhale-return phenomenon happens for an inappropriate housing. Several key parameters, such as fan guard, housing ring, inlet-to-outlet area ratio, and blockage height, are evaluated for finding out the criterion to avoid the inhale-return flow. Consequently the study finds that fan guard changes the airflow to a wider distribution with a lower velocity. A minimum blockage distance and a maximum height of ring-plate are set at 80 mm and 30 mm, respectively. Also, it is suggested that the inlet area must be bigger than the outlet area. Moreover, all the parameters show the same trend under various rotational speeds. In conclusion, this systematic investigation not only provides the fan engineer's design ability to avoid the inhale-return phenomenon, but also the predicting capability on its aerodynamic and acoustic performances.
Energy Technology Data Exchange (ETDEWEB)
Patrignani, L.; Losurdo, M.; Bruno, C. [Sapienza Univ. de Roma, Rome (Italy)
2010-09-15
Exhaust emissions from furnace burners can be reduced by premixing reactants with combustion products. This paper discussed the use of a trapped vortex combustor (TVC) as a very promising technology for gas turbines. The TVC can reduce emissions and ensure that the temperature is uniform in the exhaust products, which is a key aspect for certain types of heat treatments, such as in steel rolling mills. The TVC for gas turbines is configured to mix air, fuel and hot products at turbulent scales fine enough to render the combustion mode flameless, or close to flameless. The vortex ensures a high recirculation factor between hot combustion products and reactants, and ultimately flame stability. In this study, the TVC configuration for an existing gas turbine was numerically investigated by means of RANS and LES. According to preliminary results of the fast-flameless combustion (FFC) strategy, the proposed TVC is a suitable candidate to reduce nitrogen oxide (NOx) emissions while keeping the pressure drop below 1 per cent. Both RANS and LES show that too much fuel burns along the main duct. Better fuel splitting or a different position for the injectors may enhance combustion inside the recirculation zone. Behaviour of the main vortices showed that a more accurate design of the internal shape of the combustor is needed to prevent excessive velocity fluctuation or vortex instabilities and therefore emissions. 13 refs., 9 figs.
Doubenskaia, M.; Smurov, I.; Nagulin, K. Yu.
2016-04-01
Complimentary optical diagnostic tools are applied to provide comprehensive analysis of thermal phenomena in millisecond Nd:YAG laser irradiation of steel substrates. The following optical devices are employed: (a) infrared camera FLIR Phoenix RDASTM equipped by InSb sensor with 3 to 5 µm band pass arranged on 320 × 256 pixels array, (b) ultra-rapid camera Phantom V7.1 with SR-CMOS monochrome sensor in the visible spectral range, up to 105 frames per second for 64 × 88 pixels array, (c) original multi-wavelength pyrometer in the near-infrared range (1.370-1.531 µm). The following laser radiation parameters are applied: variation of energy per pulse in the range 15-30 J at a constant pulse duration of 10 ms with and without application of protective gas (Ar). The evolution of true temperature is restored based on the method of multi-colour pyrometry; by this way, melting/solidification dynamics is analysed. Emissivity variation with temperature is studied, and hysteresis type functional dependence is found. Variation of intensity of surface evaporation visualised by the camera Phantom V7.1 is registered and linked with the surface temperature evolution, different surface roughness and influence of protective gas atmosphere. Determination of the vapour plume temperature based on relatively intensities of spectral lines is done. The numerical simulation is carried out applying the thermal model with phase transitions taken into account.
Nagar, Swati; Jones, Jeffrey P.
2014-01-01
Inhibition of cytochromes P450 by time-dependent inhibitors (TDI) is a major cause of clinical drug-drug interactions. It is often difficult to predict in vivo drug interactions based on in vitro TDI data. In part 1 of these manuscripts, we describe a numerical method that can directly estimate TDI parameters for a number of kinetic schemes. Datasets were simulated for Michaelis-Menten (MM) and several atypical kinetic schemes. Ordinary differential equations were solved directly to parameterize kinetic constants. For MM kinetics, much better estimates of KI can be obtained with the numerical method, and even IC50 shift data can provide meaningful estimates of TDI kinetic parameters. The standard replot method can be modified to fit non-MM data, but normal experimental error precludes this approach. Non-MM kinetic schemes can be easily incorporated into the numerical method, and the numerical method consistently predicts the correct model at errors of 10% or less. Quasi-irreversible inactivation and partial inactivation can be modeled easily with the numerical method. The utility of the numerical method for the analyses of experimental TDI data is provided in our companion manuscript in this issue of Drug Metabolism and Disposition (Korzekwa et al., 2014b). PMID:24939654
Digging Back In Time: Integrating Historical Data Into an Operational Ocean Observing System
McCammon, M.
2016-02-01
Modern technologies allow reporting and display of data near real-time from in situ instrumentation live on the internet. This has given users fast access to critical information for scientific applications, marine safety, planning, and numerous other activities. Equally as valuable is having access to historical data sets. However, it is challenging to identify sources and access of historical data of interest as it exists in many different locations, depending on the funding source and provider. Also, time-varying formats can make it difficult to data-mine and display historical data. There is also the issue of data quality, and having a systematic means of assessing credibility of historical data sets. The Alaska Ocean Observing System (AOOS) data management system demonstrates the successful ingestion of historical data, both old and new (as recent as yesterday) and has integrated numerous historical data streams into user friendly data portals, available for data upload and display on the AOOS Website. An example is the inclusion of non-real-time (e.g. day old) AIS (Automatic Identification System) ship tracking data, important for scientists working in marine mammal migration regions. Other examples include historical sea ice data, and various data streams from previous research projects (e.g. moored time series, HF Radar surface currents, weather, shipboard CTD). Most program or project websites only offer access to data specific to their agency or project alone, but do not have the capacity to provide access to the plethora of other data that might be available for the region and be useful for integration, comparison and synthesis. AOOS offers end users access to a one stop-shop for data in the area they want to research, helping them identify other sources of information and access. Demonstrations of data portals using historical data illustrate these benefits.
Integrating Real-time Earthquakes into Natural Hazard Courses
Furlong, K. P.; Benz, H. M.; Whitlock, J. S.; Bittenbinder, A. N.; Bogaert, B. B.
2001-12-01
Natural hazard courses are playing an increasingly important role in college and university earth science curricula. Students' intrinsic curiosity about the subject and the potential to make the course relevant to the interests of both science and non-science students make natural hazards courses popular additions to a department's offerings. However, one vital aspect of "real-life" natural hazard management that has not translated well into the classroom is the real-time nature of both events and response. The lack of a way to entrain students into the event/response mode has made implementing such real-time activities into classroom activities problematic. Although a variety of web sites provide near real-time postings of natural hazards, students essentially learn of the event after the fact. This is particularly true for earthquakes and other events with few precursors. As a result, the "time factor" and personal responsibility associated with natural hazard response is lost to the students. We have integrated the real-time aspects of earthquake response into two natural hazard courses at Penn State (a 'general education' course for non-science majors, and an upper-level course for science majors) by implementing a modification of the USGS Earthworm system. The Earthworm Database Management System (E-DBMS) catalogs current global seismic activity. It provides earthquake professionals with real-time email/cell phone alerts of global seismic activity and access to the data for review/revision purposes. We have modified this system so that real-time response can be used to address specific scientific, policy, and social questions in our classes. As a prototype of using the E-DBMS in courses, we have established an Earthworm server at Penn State. This server receives national and global seismic network data and, in turn, transmits the tailored alerts to "on-duty" students (e-mail, pager/cell phone notification). These students are responsible to react to the alarm
Yaros, Steven F.; Carlson, John R.; Chandrasekaran, Balasubramanyan
1986-01-01
An effort has been undertaken at the NASA Langley Research Center to assess the capabilities of available computational methods for use in propulsion integration design studies of transonic transport aircraft, particularly of pylon/nacelle combinations which exhibit essentially no interference drag. The three computer codes selected represent state-of-the-art computational methods for analyzing complex configurations at subsonic and transonic flight conditions. These are: EULER, a finite volume solution of the Euler equation; VSAERO, a panel solution of the Laplace equation; and PPW, a finite difference solution of the small disturbance transonic equations. In general, all three codes have certain capabilities that allow them to be of some value in predicting the flows about transport configurations, but all have limitations. Until more accurate methods are available, careful application and interpretation of the results of these codes are needed.
Yaros, S. F.; Carlson, J. R.; Chandrasekaran, B.
1986-01-01
An effort has been undertaken at the NASA Langley Research Center to assess the capabilities of available computational methods for use in propulsion integration design studies of transonic transport aircraft, particularly of pylon/nacelle combinations which exhibit essentially no interference drag. The three computer codes selected represent state-of-the-art computational methods for analyzing complex configurations at subsonic and transonic flight conditions. These are: EULER, a finitie volume solution of the Euler equation; VSAERO, a panel solution of the Laplace equation; and PPW, a finite difference solution of the small disturbance transonic equations. In general, all three codes have certain capabilities that allow them to be of some value in predicting the flows about transport configurations, but all have limitations. Until more accurate methods are available, careful application and interpretation of the results of these codes are needed.
DEFF Research Database (Denmark)
Wang, Y.; Chen, H.; Rosbjerg, Dan
2013-01-01
In reservoir operation improvement of the accuracy of forecast flood inflow and extension of forecast lead-time can effectively be achieved by using rainfall forecasts from numerical weather predictions with a hydrological catchment model. In this study, the Regional Spectrum Model (RSM), which i...
He, Yong; Ji, Meng-Di; Zhang, Chuan-Ke; Wu, Min
2016-05-01
This paper is concerned with global exponential stability problem for a class of neural networks with time-varying delays. Using a new proposed inequality called free-matrix-based integral inequality, a less conservative criterion is proposed, which is expressed by linear matrix inequalities. Two numerical examples are given to show the effectiveness and superiority of the obtained criterion. Copyright © 2016 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Mahmoud Paripour
2014-08-01
Full Text Available In this paper, the Bernstein polynomials are used to approximatethe solutions of linear integral equations with multiple time lags (IEMTL through expansion methods (collocation method, partition method, Galerkin method. The method is discussed in detail and illustrated by solving some numerical examples. Comparison between the exact and approximated results obtained from these methods is carried out
Numerical simulation of time-dependent deformations under hygral and thermal transient conditions
International Nuclear Information System (INIS)
Roelfstra, P.E.
1987-01-01
Some basic concepts of numerical simulation of the formation of the microstructure of HCP are outlined. The aim is to replace arbitrary terms like aging by more realistic terms like bond density in the xerogel and bonds between hydrating particles of HCP. Actual state parameters such as temperature, humidity and degree of hydration can be determined under transient hygral and thermal conditions by solving numerically a series of appropriate coupled differential equations with given boundary conditions. Shrinkage of a composite structure without crack formation, based on calculated moisture distributions, has been determined with numerical concrete codes. The influence of crack formation, tensile strain-hardening and softening on the total deformation of a quasi-homogeneous drying material has been studied by means of model based on FEM. The difference between shrinkage without crack formation and shrinkage with crack formation can be quantified. Drying shrinkage and creep of concrete cannot be separated. The total deformation depends on the superimposed stress fields. Transient hygral deformation can be realistically predicted if the concept of point properties is applied rigorously. Transient thermal deformation has to be dealt with in the same way. (orig./HP)
Energy Technology Data Exchange (ETDEWEB)
Chen, Xiangyi; Suh, Kune Y. [KAERI, Daejeon (Korea, Republic of)
2016-05-15
In this work, this benchmark problem is conducted to assess the precision of the upgraded in-house code MINA. Comparison of the results from different best estimate codes employed by various grid spacer pressure drop correlations is carried out to suggest the best one. By modifying In's method, it presents good agreement with the experiment data which is shown in Figure 7. The reason for the failure of the prediction in previous work is caused by the utilization of Rehme's method which is categorized into four groups according to different fitting strategy. Through comparison of drag coefficients calculated by four groups of Rheme's method, equivalent drag coefficient calculated by In's method and experiment data shown in Figure 8, we can conclude that Rehme's method considerably underestimate the drag coefficients in grid spacers used in HELIOS and In's method give a reasonable prediction. Starting from the core inlet, the accumulated pressure losses are presented in figure 9 along the accumulated length of the forced convection flow path; the good agreement of the prediction from MINA with the experiment result shows MINA has very good capability in integrated momentum analysis makes it robust in the future design scoping method development of LFR.
Woźniak, M.
2016-06-02
We study the features of a new mixed integration scheme dedicated to solving the non-stationary variational problems. The scheme is composed of the FEM approximation with respect to the space variable coupled with a 3-leveled time integration scheme with a linearized right-hand side operator. It was applied in solving the Cahn-Hilliard parabolic equation with a nonlinear, fourth-order elliptic part. The second order of the approximation along the time variable was proven. Moreover, the good scalability of the software based on this scheme was confirmed during simulations. We verify the proposed time integration scheme by monitoring the Ginzburg-Landau free energy. The numerical simulations are performed by using a parallel multi-frontal direct solver executed over STAMPEDE Linux cluster. Its scalability was compared to the results of the three direct solvers, including MUMPS, SuperLU and PaSTiX.
Integration of Infrasound Propagation Models and Near-Real-Time Atmospheric Characterizations
National Research Council Canada - National Science Library
Gibson, Robert G; Norris, David E
2004-01-01
.... Near-real-time atmospheric updates, such as the output from numerical weather prediction models, supplement the baseline climatological characterization of temperature, wind and air composition...
Ulku, Huseyin Arda
2014-07-06
and full Schubert-Wilton-Glisson (SWG) functions, respectively. Equations are Galerkin tested in space and the resulting semi-discrete system is integrated in time for the unknown expansion coefficients using the aforementioned predictor-corrector scheme. The explicitness of the MOT scheme allows for incorporation of the nonlinearities as simple discretized function evaluations on the right hand side of the system. Numerical results that demonstrate the accuracy, efficiency, and applicability of the proposed nonlinear MOT-TDVIE solver will be presented.
International Nuclear Information System (INIS)
Kouri, D.J.; Huang, Y.; Hoffman, D.K.
1995-01-01
The distributed approximating functional-path integral is formulated as an iterated sequence of d-dimensional integrals, where d is the intrinsic number of degrees of freedom for the system under consideration. This is made practical for larger values of d by evaluating these integrals using average-case complexity integration techniques, based on deterministic ''low discrepancy sequences,'' as opposed to products of one-dimensional quadratures or basis functions. The integration converges as (logP) d-1 /P, where P is the number of sample points used, and the dimensionality of the integral does not increase with the number of time slices required
Matlaga, David P; da S L Sternberg, Leonel
2009-02-01
A major advantage of clonal growth forms is the intergenerational transfer of resources through vascular connections (clonal integration). Connections linking ramets can be persistent or ephemeral. For species with ephemeral connections, whether the extent of clonal integration changes over time is unclear. To address this issue, we tracked water movement using an isotopic label and assessed the demographic performance of parent and offspring ramets over time in a severing experiment. Our study system was the understory herb Calathea marantifolia, which has parent ramets that produce vegetative bulbils (clonal offspring) that pass through distinct pre- and post-rooting stages. Little water was transported between parents and offspring, and the direction of movement was primarily from parent to pre-rooting offspring. Anatomical observations of inter-ramet connections showed that vascular bundles were twice as abundant in parent stems compared to inter-ramet connections. Severing inter-ramet connections reduced the growth of offspring ramets but not parents. Survival of pre-rooting offspring was reduced by 10% due to severing, but post-rooting offspring were not affected. Our results suggest that offspring ramets of C. marantifolia are weaned from their parent as they progress from pre- to post-rooting stages.
Zhao, Tingting; He, Xianyou; Zhao, Xueru; Huang, Jianrui; Zhang, Wei; Wu, Shuang; Chen, Qi
2017-10-17
The Spatial Numerical/Temporal Association of Response Codes (SNARC/STEARC) effects are considered evidence of the association between number or time and space, respectively. As the SNARC effect was proposed by Dehaene, Bossini, and Giraux in 1993, several studies have suggested that different tasks and cultural factors can affect the flexibility of the SNARC effect. This study explored the influence of time units on the flexibility of the SNARC effect via materials with Arabic numbers, which were suffixed with time units and subjected to magnitude comparison tasks. Experiment 1 replicated the SNARC effect for numbers and the STEARC effect for time units. Experiment 2 explored the flexibility of the SNARC effect when numbers were attached to time units, which either conflicted with the numerical magnitude or in which the time units were the same or different. Experiment 3 explored whether the SNARC effect of numbers was stable when numbers were near the transition of two adjacent time units. The results indicate that the SNARC effect was flexible when the numbers were suffixed with time units: Time units influenced the direction of the SNARC effect in a way which could not be accounted for by the mathematical differences between the time units and numbers. This suggests that the SNARC effect is not obligatory and can be easily adapted or inhibited based on the current context. © 2017 The Authors. British Journal of Psychology published by John Wiley & Sons Ltd on behalf of British Psychological Society.
Directory of Open Access Journals (Sweden)
Timchenko V.
2015-01-01
Full Text Available Numerical and experimental investigations of the flow and heat transfer in open-ended channel formed by the double skin façade have been undertaken in order to improve understanding of the phenomena and to apply it to passive cooling of building integrated photovoltaic systems. Both uniform heating and non-uniform heating configurations in which heat sources alternated with unheated zones on both skins were studied. Different periodic and asymmetric heating modes have been considered for the same aspect ratio 1/15 of wall distance to wall height and for periodicity 1/15 and 4/15 of heated/unheated zones and heat input, 220 W/m2. In computational study three dimensional transient LES simulation was carried out. It is shown that in comparison to uniformly heating configuration, non-uniformly heating configuration enhances both convective heat transfer and chimney effect.
DEFF Research Database (Denmark)
Courdent, Vianney Augustin Thomas
to evaluate when acting on the forecast is beneficial or not. Rainfall forecasts are extremely valuable for estimating near future storm-water-related impacts on the IUDWS. Therefore, weather radar extrapolation “nowcasts” provide valuable predictions for RTC. However, radar nowcasts are limited...... by their prediction horizon of 1 to 2 hours and RTC of IUDWS could benefit from longer forecast horizons. The development of NWP models in parallel to the increase in computational power has led to limited area models (LAM) with increasingly finer spatial-temporal resolution, opening the possibility to use...... such weather forecast products in urban water management. NWPs are complementary to radar forecasts, providing predictions on a longer time scale (days). However, atmospheric motions are chaotic and highly nonlinear. Applying NWP to urban catchments, which often have a similar size to a single NWP grid cell...
Numerical integration of a relativistic two-body problem via a multiple scales method
Abouelmagd, Elbaz I.; Elshaboury, S. M.; Selim, H. H.
2016-01-01
We offer an analytical study on the dynamics of a two-body problem perturbed by small post-Newtonian relativistic term. We prove that, while the angular momentum is not conserved, the motion is planar. We also show that the energy is subject to small changes due to the relativistic effect. We also offer a periodic solution to this problem, obtained by a method based on the separation of time scales. We demonstrate that our solution is more general than the method developed in the book by Brumberg (Essential Relativistic Celestial Mechanics, Hilger, Bristol, 1991). The practical applicability of this model may be in studies of the long-term evolution of relativistic binaries (neutron stars or black holes).
Schmidt, R. F.
1971-01-01
Some results obtained with a digital computer program written at Goddard Space Flight Center to obtain electromagnetic fields scattered by perfectly reflecting surfaces are presented. For purposes of illustration a paraboloidal reflector was illuminated at radio frequencies in the simulation for both receiving and transmitting modes of operation. Fields were computed in the Fresnel and Fraunhofer regions. A dual-reflector system (Cassegrain) was also simulated for the transmitting case, and fields were computed in the Fraunhofer region. Appended results include derivations which show that the vector Kirchhoff-Kottler formulation has an equivalent form requiring only incident magnetic fields as a driving function. Satisfaction of the radiation conditions at infinity by the equivalent form is demonstrated by a conversion from Cartesian to spherical vector operators. A subsequent development presents the formulation by which Fresnel or Fraunhofer patterns are obtainable for dual-reflector systems. A discussion of the time-average Poynting vector is also appended.
Classifying terrestrial surface water systems using integrated residence time
Jones, Allan; Hodges, Ben; McClelland, James; Hardison, Amber; Moffett, Kevan
2017-04-01
Linkages between ecology and hydrology in terrestrial surface water often invoke a discussion of lentic (reservoir) vs. lotic (riverine) system behaviors. However, the literature shows a wide range of thresholds separating lentic/lotic regimes and little agreement on a quantitative, repeatable classification metric that can be broadly and reliably applied across a range of systems hosting various flow regimes and suspended/benthic taxa. We propose an integrated Residence Time (iTR) metric as part of a new Freshwater Continuum Classification (FCC) to address this issue. The iTR is computed as the transit time of a water parcel across a system given observed temporal variations in discharge and volume, which creates a temporally-varying metric applicable across a defined system length. This approach avoids problems associated with instantaneous residence times or average residence times that can lead to misleading characterizations in seasonally- or episodically-dynamic systems. The iTR can be directly related to critical flow thresholds and timescales of ecology (e.g., zooplankton growth). The FCC approach considers lentic and lotic to be opposing end-members of a classification continuum and also defines intermediate regimes that blur the line between the two ends of the spectrum due to more complex hydrological system dynamics. We also discover the potential for "oscillic" behavior, where a system switches between lentic and lotic classifications either episodically or regularly (e.g., seasonally). Oscillic behavior is difficult to diagnose with prior lentic/lotic classification schemes, but can be readily identified using iTR. The FCC approach was used to analyze 15 tidally-influenced river segments along the Texas (USA) coast of the Gulf of Mexico. The results agreed with lentic/lotic designations using prior approaches, but also identified more nuanced intermediate and oscillic regimes. Within this set of systems, the oscillic nature of some of the river
Hofmeister, Richard; Lemmen, Carsten; Nasermoaddeli, Hassan; Klingbeil, Knut; Wirtz, Kai
2015-04-01
Data and models for describing coastal systems span a diversity of disciplines, communities, ecosystems, regions and techniques. Previous attempts of unifying data exchange, coupling interfaces, or metadata information have not been successful. We introduce the new Modular System for Shelves and Coasts (MOSSCO, http://www.mossco.de), a novel coupling framework that enables the integration of a diverse array of models and data from different disciplines relating to coastal research. In the MOSSCO concept, the integrating framework imposes very few restrictions on contributed data or models; in fact, there is no distinction made between data and models. The few requirements are: (1) principle coupleability, i.e. access to I/O and timing information in submodels, which has recently been referred to as the Basic Model Interface (BMI) (2) open source/open data access and licencing and (3) communication of metadata, such as spatiotemporal information, naming conventions, and physical units. These requirements suffice to integrate different models and data sets into the MOSSCO infrastructure and subsequently built a modular integrated modeling tool that can span a diversity of processes and domains. We demonstrate how diverse coastal system constituents were integrated into this modular framework and how we deal with the diverging development of constituent data sets and models at external institutions. Finally, we show results from simulations with the fully coupled system using OGC WebServices in the WiMo geoportal (http://kofserver3.hzg.de/wimo), from where stakeholders can view the simulation results for further dissemination.
Shi, Yifei
2014-01-01
When marching-on-in-time (MOT) method is applied to solve the time-domain electric field integral equation, spurious internal resonant and static loop modes are always observed in the solution. The internal resonant modes have recently been studied by the authors; this letter investigates the static loop modes. Like internal resonant modes, static loop modes, in theory, should not be observed in the MOT solution since they do not satisfy the zero initial conditions; their appearance is attributed to numerical errors. It is discussed in this letter that the dependence of spurious static loop modes on numerical errors is substantially different from that of spurious internal resonant modes. More specifically, when Rao-Wilton-Glisson functions and Lagrange interpolation functions are used as spatial and temporal basis functions, respectively, errors due to space-time discretization have no discernible impact on spurious static loop modes. Numerical experiments indeed support this discussion and demonstrate that the numerical errors due to the approximate solution of the MOT matrix system have dominant impact on spurious static loop modes in the MOT solution. © 2014 IEEE.
Optimal Real-time Dispatch for Integrated Energy Systems
Energy Technology Data Exchange (ETDEWEB)
Firestone, Ryan Michael [Univ. of California, Berkeley, CA (United States)
2007-05-31
This report describes the development and application of a dispatch optimization algorithm for integrated energy systems (IES) comprised of on-site cogeneration of heat and electricity, energy storage devices, and demand response opportunities. This work is intended to aid commercial and industrial sites in making use of modern computing power and optimization algorithms to make informed, near-optimal decisions under significant uncertainty and complex objective functions. The optimization algorithm uses a finite set of randomly generated future scenarios to approximate the true, stochastic future; constraints are included that prevent solutions to this approximate problem from deviating from solutions to the actual problem. The algorithm is then expressed as a mixed integer linear program, to which a powerful commercial solver is applied. A case study of United States Postal Service Processing and Distribution Centers (P&DC) in four cities and under three different electricity tariff structures is conducted to (1) determine the added value of optimal control to a cogeneration system over current, heuristic control strategies; (2) determine the value of limited electric load curtailment opportunities, with and without cogeneration; and (3) determine the trade-off between least-cost and least-carbon operations of a cogeneration system. Key results for the P&DC sites studied include (1) in locations where the average electricity and natural gas prices suggest a marginally profitable cogeneration system, optimal control can add up to 67% to the value of the cogeneration system; optimal control adds less value in locations where cogeneration is more clearly profitable; (2) optimal control under real-time pricing is (a) more complicated than under typical time-of-use tariffs and (b) at times necessary to make cogeneration economic at all; (3) limited electric load curtailment opportunities can be more valuable as a compliment to the cogeneration system than alone; and
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz
2000-01-01
A new technique for the numerical 3D simulation of time dependent flow of viscoelastic fluid is presented. The technique is based on a Lagrangian kinematics description of the fluid flow. The fluid is described by the Rivlin Sawyer integral constitutive equation. The method (referred to as the 3D...... Lagrangian Integral Method) is a finite element method where Galerkons method is used for solving the governing equation in rectangular coordinates numerically. In the present implementation the velocity and pressure fields are approximated with tri-linear and constant shape functions, respectivly.The 3D LIM......) and polymeric solutions. Secondly, the 3D-LIM has also been applied to calculate the inflation of a thick sheet of a polymeric melt into a elliptic cylinder. These problems all include free surfaces. As the governing equations are solved for the particle positions, the motion of surfaces can be followed easily...
Energy Technology Data Exchange (ETDEWEB)
Chen, Guangye [Los Alamos National Laboratory; Chacon, Luis [Los Alamos National Laboratory; Knoll, Dana Alan [Los Alamos National Laboratory; Barnes, Daniel C [Coronado Consulting
2015-07-31
A multi-rate PIC formulation was developed that employs large timesteps for slow field evolution, and small (adaptive) timesteps for particle orbit integrations. Implementation is based on a JFNK solver with nonlinear elimination and moment preconditioning. The approach is free of numerical instabilities (ω_{pe}Δt >>1, and Δx >> λ_{D}), and requires many fewer dofs (vs. explicit PIC) for comparable accuracy in challenging problems. Significant gains (vs. conventional explicit PIC) may be possible for large scale simulations. The paper is organized as follows: Vlasov-Maxwell Particle-in-cell (PIC) methods for plasmas; Explicit, semi-implicit, and implicit time integrations; Implicit PIC formulation (Jacobian-Free Newton-Krylov (JFNK) with nonlinear elimination allows different treatments of disparate scales, discrete conservation properties (energy, charge, canonical momentum, etc.)); Some numerical examples; and Summary.
Numerical and experimental analysis of time-dependent load transfer in reinforced concrete columns
Directory of Open Access Journals (Sweden)
L. T. Kataoka
Full Text Available A study was conducted to assess the influence of the steel reinforcement ratio in concrete columns on their properties of creep and shrinkage. Experimental tests and three-dimensional finite element-based simulations of the experimental curves from plain concrete cylinders and plain concrete columns derived by curve fitting were performed using the ACI 209 model available in DIANA 9.3. Columns with longitudinal reinforcement ratios of 0%, 1.4% and 2.8%, loaded to 30% and 40% of their 7-day compressive strength, were investigated. The results indicated that numerical simulation does not predict experimental data for a long period. However, simulations fitted with experimental curves derived from plain concrete columns presented values close to those of experimental data for 91 days.
Deep Time Data Infrastructure: Integrating Our Current Geologic and Biologic Databases
Kolankowski, S. M.; Fox, P. A.; Ma, X.; Prabhu, A.
2016-12-01
As our knowledge of Earth's geologic and mineralogical history grows, we require more efficient methods of sharing immense amounts of data. Databases across numerous disciplines have been utilized to offer extensive information on very specific Epochs of Earth's history up to its current state, i.e. Fossil record, rock composition, proteins, etc. These databases could be a powerful force in identifying previously unseen correlations such as relationships between minerals and proteins. Creating a unifying site that provides a portal to these databases will aid in our ability as a collaborative scientific community to utilize our findings more effectively. The Deep-Time Data Infrastructure (DTDI) is currently being defined as part of a larger effort to accomplish this goal. DTDI will not be a new database, but an integration of existing resources. Current geologic and related databases were identified, documentation of their schema was established and will be presented as a stage by stage progression. Through conceptual modeling focused around variables from their combined records, we will determine the best way to integrate these databases using common factors. The Deep-Time Data Infrastructure will allow geoscientists to bridge gaps in data and further our understanding of our Earth's history.
Guevara Hidalgo, Esteban; Nemoto, Takahiro; Lecomte, Vivien
2017-06-01
Rare trajectories of stochastic systems are important to understand because of their potential impact. However, their properties are by definition difficult to sample directly. Population dynamics provides a numerical tool allowing their study, by means of simulating a large number of copies of the system, which are subjected to selection rules that favor the rare trajectories of interest. Such algorithms are plagued by finite simulation time and finite population size, effects that can render their use delicate. In this paper, we present a numerical approach which uses the finite-time and finite-size scalings of estimators of the large deviation functions associated to the distribution of rare trajectories. The method we propose allows one to extract the infinite-time and infinite-size limit of these estimators, which—as shown on the contact process—provides a significant improvement of the large deviation function estimators compared to the standard one.
Guevara Hidalgo, Esteban; Nemoto, Takahiro; Lecomte, Vivien
2017-06-01
Rare trajectories of stochastic systems are important to understand because of their potential impact. However, their properties are by definition difficult to sample directly. Population dynamics provides a numerical tool allowing their study, by means of simulating a large number of copies of the system, which are subjected to selection rules that favor the rare trajectories of interest. Such algorithms are plagued by finite simulation time and finite population size, effects that can render their use delicate. In this paper, we present a numerical approach which uses the finite-time and finite-size scalings of estimators of the large deviation functions associated to the distribution of rare trajectories. The method we propose allows one to extract the infinite-time and infinite-size limit of these estimators, which-as shown on the contact process-provides a significant improvement of the large deviation function estimators compared to the standard one.
Recent advances in marching-on-in-time schemes for solving time domain volume integral equations
Sayed, Sadeed Bin
2015-05-16
Transient electromagnetic field interactions on inhomogeneous penetrable scatterers can be analyzed by solving time domain volume integral equations (TDVIEs). TDVIEs are constructed by setting the summation of the incident and scattered field intensities to the total field intensity on the volumetric support of the scatterer. The unknown can be the field intensity or flux/current density. Representing the total field intensity in terms of the unknown using the relevant constitutive relation and the scattered field intensity in terms of the spatiotemporal convolution of the unknown with the Green function yield the final form of the TDVIE. The unknown is expanded in terms of local spatial and temporal basis functions. Inserting this expansion into the TDVIE and testing the resulting equation at discrete times yield a system of equations that is solved by the marching on-in-time (MOT) scheme. At each time step, a smaller system of equations, termed MOT system is solved for the coefficients of the expansion. The right-hand side of this system consists of the tested incident field and discretized spatio-temporal convolution of the unknown samples computed at the previous time steps with the Green function.
Uysal, Ismail Enes
2016-10-01
Plasmonic structures are utilized in many applications ranging from bio-medicine to solar energy generation and transfer. Numerical schemes capable of solving equations of classical electrodynamics have been the method of choice for characterizing scattering properties of such structures. However, as dimensions of these plasmonic structures reduce to nanometer scale, quantum mechanical effects start to appear. These effects cannot be accurately modeled by available classical numerical methods. One of these quantum effects is the tunneling, which is observed when two structures are located within a sub-nanometer distance of each other. At these small distances electrons “jump" from one structure to another and introduce a path for electric current to flow. Classical equations of electrodynamics and the schemes used for solving them do not account for this additional current path. This limitation can be lifted by introducing an auxiliary tunnel with material properties obtained using quantum models and applying a classical solver to the structures connected by this auxiliary tunnel. Early work on this topic focused on quantum models that are generated using a simple one-dimensional wave function to find the tunneling probability and assume a simple Drude model for the permittivity of the tunnel. These tunnel models are then used together with a classical frequency domain solver. In this thesis, a time domain surface integral equation solver for quantum corrected analysis of transient plasmonic interactions is proposed. This solver has several advantages: (i) As opposed to frequency domain solvers, it provides results at a broad band of frequencies with a single simulation. (ii) As opposed to differential equation solvers, it only discretizes surfaces (reducing number of unknowns), enforces the radiation condition implicitly (increasing the accuracy), and allows for time step selection independent of spatial discretization (increasing efficiency). The quantum model
Neuromuscular fatigue following isometric contractions with similar torque time integral.
Rozand, V; Cattagni, T; Theurel, J; Martin, A; Lepers, R
2015-01-01
Torque time integral (TTI) is the combination of intensity and duration of a contraction. The aim of this study was to compare neuromuscular alterations following different isometric sub-maximal contractions of the knee extensor muscles but with similar TTI. Sixteen participants performed 3 sustained contractions at different intensities (25%, 50%, and 75% of Maximal Voluntary Contraction (MVC) torque) with different durations (68.5±33.4 s, 35.1±16.8 s and 24.8±12.9 s, respectively) but similar TTI value. MVC torque, maximal voluntary activation level (VAL), M-wave characteristics and potentiated doublet amplitude were assessed before and immediately after the sustained contractions. EMG activity of the vastus lateralis (VL) and -rectus femoris (RF) muscles was recorded during the sustained contractions. MVC torque reduction was similar in the 3 conditions after the exercise (-23.4±2.7%). VAL decreased significantly in a similar extent (-3.1±1.3%) after the 3 sustained contractions. Potentiated doublet amplitude was similarly reduced in the 3 conditions (-19.7±1.5%), but VL and RF M-wave amplitudes remained unchanged. EMG activity of VL and RF muscles increased in the same extent during the 3 contractions (VL: 54.5±40.4%; RF: 53.1±48.7%). These results suggest that central and peripheral alterations accounting for muscle fatigue are similar following isometric contractions with similar TTI. TTI should be considered in the exploration of muscle fatigue during sustained isometric contractions. © Georg Thieme Verlag KG Stuttgart · New York.
International Nuclear Information System (INIS)
Bernardin, B.; Le Guillou, G.; Parcy, JP.
1981-04-01
Usual spectral methods, based on temperature fluctuation analysis, aiming at thermocouple time constant identification are using an equipment too much sophisticated for on-line application. It is shown that numerical filtering is optimal for this application, the equipment is simpler than for spectral methods and less samples of signals are needed for the same accuracy. The method is described and a parametric study was performed using a temperature noise simulator [fr
Asghari, Mohammad H; Park, Yongwoo; Azaña, José
2011-01-17
We propose and experimentally prove a novel design for implementing photonic temporal integrators simultaneously offering a high processing bandwidth and a long operation time window, namely a large time-bandwidth product. The proposed scheme is based on concatenating in series a time-limited ultrafast photonic temporal integrator, e.g. implemented using a fiber Bragg grating (FBG), with a discrete-time (bandwidth limited) optical integrator, e.g. implemented using an optical resonant cavity. This design combines the advantages of these two previously demonstrated photonic integrator solutions, providing a processing speed as high as that of the time-limited ultrafast integrator and an operation time window fixed by the discrete-time integrator. Proof-of-concept experiments are reported using a uniform fiber Bragg grating (as the original time-limited integrator) connected in series with a bulk-optics coherent interferometers' system (as a passive 4-points discrete-time photonic temporal integrator). Using this setup, we demonstrate accurate temporal integration of complex-field optical signals with time-features as fast as ~6 ps, only limited by the processing bandwidth of the FBG integrator, over time durations as long as ~200 ps, which represents a 4-fold improvement over the operation time window (~50 ps) of the original FBG integrator.
Numerical modelling of softwood time-dependent behaviour based on microstructure
DEFF Research Database (Denmark)
Engelund, Emil Tang
2010-01-01
The time-dependent mechanical behaviour of softwood such as creep or relaxation can be predicted, from knowledge of the microstructural arrangement of the cell wall, by applying deformation kinetics. This has been done several times before; however, often without considering the constraints defined...
Estimation of flushing time in a monsoonal estuary using observational and numerical approaches
Digital Repository Service at National Institute of Oceanography (India)
Manoj, N.T.
Estimation of flushing time (T sub(F)) in an estuary is important for water quality analysis, and it is one of the major transport time scales used in estuaries to quantify the hydrodynamic processes and for water resources management strategies...
Rao, G Shanker
2006-01-01
About the Book: This book provides an introduction to Numerical Analysis for the students of Mathematics and Engineering. The book is designed in accordance with the common core syllabus of Numerical Analysis of Universities of Andhra Pradesh and also the syllabus prescribed in most of the Indian Universities. Salient features: Approximate and Numerical Solutions of Algebraic and Transcendental Equation Interpolation of Functions Numerical Differentiation and Integration and Numerical Solution of Ordinary Differential Equations The last three chapters deal with Curve Fitting, Eigen Values and Eigen Vectors of a Matrix and Regression Analysis. Each chapter is supplemented with a number of worked-out examples as well as number of problems to be solved by the students. This would help in the better understanding of the subject. Contents: Errors Solution of Algebraic and Transcendental Equations Finite Differences Interpolation with Equal Intervals Interpolation with Unequal Int...
Numerical results for near surface time domain electromagnetic exploration: a full waveform approach
Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.
2015-12-01
Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two
Stochastic integrated vendor–buyer model with unstable lead time and setup cost
Directory of Open Access Journals (Sweden)
Chandra K. Jaggi
2011-01-01
Full Text Available This paper presents a new vendor-buyer system where there are different objectives for both sides. The proposed method of this paper is different from the other previously published works since it considers different objectives for both sides. In this paper, the vendor’s emphasis is on the crashing of the setup cost, which not only helps him compete in the market but also provides better services to his customers; and the buyer’s aim is to reduce the lead time, which not only facilitates the buyer to fulfill the customers’ demand on time but also enables him to earn a good reputation in the market or vice versa. In the light of the above stated facts, an integrated vendor-buyer stochastic inventory model is also developed. The propsed model considers two cases for demand during lead time: Case (i Complete demand information, Case (ii Partial demand information. The proposed model jointly optimizes the buyer’s ordered quantity and lead time along with vendor’s setup cost and the number of shipments. The results are demonstrated with the help of numerical examples.
A numerical analysis of time focusing of crystal analyzer spectrometers on pulsed sources
International Nuclear Information System (INIS)
Zsigmond, G.; Carpenter, J.M.
2005-01-01
We have carried out Monte Carlo simulations that support the linear analytical theory of time-focusing on crystal analyzer instruments and provide further interesting details on the time-of-flight signals obtained for different geometries. Important non-linear effects are revealed close to the time-focusing conditions. Calculations for realistic sizes of spectrometer elements indicate an elastic-scattering time-of-flight spread σ t /t approximately 7.9x10 -5 , far less than the conventional (and incorrect) ΔΘcotΘ estimate for such type of instrument. The aim is to provide a basis for design of spectrometers of the highest possible resolution with the highest possible counting rates, meanwhile to reveal new flexibilities for the design e.g. tunable analyzer energy
Numerical test for hyperbolicity in chaotic systems with multiple time delays
Kuptsov, Pavel V.; Kuznetsov, Sergey P.
2018-03-01
We develop an extension of the fast method of angles for hyperbolicity verification in chaotic systems with an arbitrary number of time-delay feedback loops. The adopted method is based on the theory of covariant Lyapunov vectors and provides an efficient algorithm applicable for systems with high-dimensional phase space. Three particular examples of time-delay systems are analyzed and in all cases the expected hyperbolicity is confirmed.
Starn, J. J.; Belitz, K.; Carlson, C.
2017-12-01
Groundwater residence-time distributions (RTDs) are critical for assessing susceptibility of water resources to contamination. This novel approach for estimating regional RTDs was to first simulate groundwater flow using existing regional digital data sets in 13 intermediate size watersheds (each an average of 7,000 square kilometers) that are representative of a wide range of glacial systems. RTDs were simulated with particle tracking. We refer to these models as "general models" because they are based on regional, as opposed to site-specific, digital data. Parametric RTDs were created from particle RTDs by fitting 1- and 2-component Weibull, gamma, and inverse Gaussian distributions, thus reducing a large number of particle travel times to 3 to 7 parameters (shape, location, and scale for each component plus a mixing fraction) for each modeled area. The scale parameter of these distributions is related to the mean exponential age; the shape parameter controls departure from the ideal exponential distribution and is partly a function of interaction with bedrock and with drainage density. Given the flexible shape and mathematical similarity of these distributions, any of them are potentially a good fit to particle RTDs. The 1-component gamma distribution provided a good fit to basin-wide particle RTDs. RTDs at monitoring wells and streams often have more complicated shapes than basin-wide RTDs, caused in part by heterogeneity in the model, and generally require 2-component distributions. A machine learning model was trained on the RTD parameters using features derived from regionally available watershed characteristics such as recharge rate, material thickness, and stream density. RTDs appeared to vary systematically across the landscape in relation to watershed features. This relation was used to produce maps of useful metrics with respect to risk-based thresholds, such as the time to first exceedance, time to maximum concentration, time above the threshold
Shen, H. M.; Li, W. B.; Wang, X. M.; Li, W. B.
2017-09-01
To study the application of multi-point initiation technology on shaped charge warhead, numerically simulated the influence of initiating delay time of different charge caliber on detonation wave and performance forming of penetrator. The study found that as charge caliber increased, the allowable initiating delay time also increased. For the commonly used small and medium-charge caliber shaped charge warhead, the charge caliber(Dk ) and the delay time (σ) presented a linear relationship σ = -12.79+1.25Dk . As charge caliber continue increasing, the initiating allowable delay time started to increase exponentially. The study reveals the matching law between charge caliber, initiating delay time and performance forming of penetrator, and it offers guidance for the design of multi-point initiation network for shaped charge.
International Nuclear Information System (INIS)
Bindel, Laurent; Gamess, Andre; Jasserand, Frederic; Laporte, Sebastien
2003-01-01
This paper present a modern numerical method, implemented in a TUI-code named MacDSP, for solving any set of differential equations and in particular phenomenological accidental dynamic calculations. The speed efficiency of such an approach, thanks to the use of the hybrid-level power offered by C++ and an ad-hoc design, make it possible to construct the first kid of a family of real time simulator employing the video games technology DirectX TM : Lady Godiva Real Time Simulator. (author)
Buša, Ján; Kocur, Dušan; Švecová, Mária
2018-02-01
UWB radar technologies enable localization of moving persons (targets) situated behind nonmetallic obstacles. Under exact knowledge of the propagation times, from the transmitting to the receiving antennas, of the radar emitted electromagnetic wave (time of arrival, TOA), a highly accurate target localization can be achieved. Since TOA estimates only are available, their use for target localization may result in a sizeable target localization error. In this paper we study the influence of TOA quantization on the point target localization accuracy using numerical simulation methods.
Estimating Travel Time in Bank Filtration Systems from a Numerical Model Based on DTS Measurements.
des Tombe, Bas F; Bakker, Mark; Schaars, Frans; van der Made, Kees-Jan
2018-03-01
An approach is presented to determine the seasonal variations in travel time in a bank filtration system using a passive heat tracer test. The temperature in the aquifer varies seasonally because of temperature variations of the infiltrating surface water and at the soil surface. Temperature was measured with distributed temperature sensing along fiber optic cables that were inserted vertically into the aquifer with direct push equipment. The approach was applied to a bank filtration system consisting of a sequence of alternating, elongated recharge basins and rows of recovery wells. A SEAWAT model was developed to simulate coupled flow and heat transport. The model of a two-dimensional vertical cross section is able to simulate the temperature of the water at the well and the measured vertical temperature profiles reasonably well. MODPATH was used to compute flowpaths and the travel time distribution. At the study site, temporal variation of the pumping discharge was the dominant factor influencing the travel time distribution. For an equivalent system with a constant pumping rate, variations in the travel time distribution are caused by variations in the temperature-dependent viscosity. As a result, travel times increase in the winter, when a larger fraction of the water travels through the warmer, lower part of the aquifer, and decrease in the summer, when the upper part of the aquifer is warmer. © 2017 The Authors. Groundwater published by Wiley Periodicals, Inc. on behalf of National Ground Water Association.
National Ignition Facility sub-system design requirements integrated timing system SSDR 1.5.3
International Nuclear Information System (INIS)
Wiedwald, J.; Van Aersau, P.; Bliss, E.
1996-01-01
This System Design Requirement document establishes the performance, design, development, and test requirements for the Integrated Timing System, WBS 1.5.3 which is part of the NIF Integrated Computer Control System (ICCS). The Integrated Timing System provides all temporally-critical hardware triggers to components and equipment in other NIF systems
Numerical Simulation of Real-Time Trajectory Optimization for Helicopter Noise Abatement
Ikaida, Hiroshi; Tsuchiya, Takeshi; Ishii, Hirokazu; Gomi, Hiromi; Okuno, Yoshinori
This study was an attempt to obtain optimal landing approaches for helicopters to reduce ground noise impact. Simulations and real flight tests in our previous study confirmed that flights along pre-calculated optimal trajectories resulted in lower noise levels than flights along conventional approach paths. However, some experiments did not show the expected optimization effects because of unforeseen disturbances. This paper therefore improves the algorithms in order to realize practical real-time optimization, which can involve external disturbances. To validate the effect of the new method, various computer simulations were conducted under real flight experimental scenarios. The obtained optimal solutions were characterized by steep flight path angles, which can avoid the generation of loud noise, the avoidance of noise sensitive points, and short flight times. These are different from conventional landing approaches. The optimal trajectories resulted in noise reduction on the ground, which shows the effectiveness and potential of the proposed real-time trajectory optimization method.
Performance Analysis of High-Order Numerical Methods for Time-Dependent Acoustic Field Modeling
Moy, Pedro Henrique Rocha
2012-07-01
The discretization of time-dependent wave propagation is plagued with dispersion in which the wavefield is perceived to travel with an erroneous velocity. To remediate the problem, simulations are run on dense and computationally expensive grids yielding plausible approximate solutions. This work introduces an error analysis tool which can be used to obtain optimal simulation parameters that account for mesh size, orders of spatial and temporal discretizations, angles of propagation, temporal stability conditions (usually referred to as CFL conditions), and time of propagation. The classical criteria of 10-15 nodes per wavelength for second-order finite differences, and 4-5 nodes per wavelength for fourth-order spectral elements are shown to be unrealistic and overly-optimistic simulation parameters for different propagation times. This work analyzes finite differences, spectral elements, optimally-blended spectral elements, and isogeometric analysis.
Real-time terahertz material characterization by numerical three-dimensional optimization.
Scheller, Maik
2011-05-23
Terahertz time domain spectroscopy allows for characterization of dielectrics even in cases where the samples thickness is unknown. However, a parameter extraction over a broad frequency range with simultaneous thickness determination is time consuming using conventional algorithms due to the large number of optimization steps. In this paper we present a novel method to extract the data. By employing a three dimensional optimization algorithm the calculation effort is significantly reduced while preserving the same accuracy level as conventional approaches. The presented method is even fast enough to be used in imaging applications.
Lutsenko, N. A.; Fetsov, S. S.
2017-10-01
Mathematical model and numerical method are proposed for investigating the one-dimensional time-dependent gas flows through a packed bed of encapsulated Phase Change Material (PCM). The model is based on the assumption of interacting interpenetrating continua and includes equations of state, continuity, momentum conservation and energy for PCM and gas. The advantage of the method is that it does not require predicting the location of phase transition zone and can define it automatically as in a usual shock-capturing method. One of the applications of the developed numerical model is the simulation of novel Adiabatic Compressed Air Energy Storage system (A-CAES) with Thermal Energy Storage subsystem (TES) based on using the encapsulated PCM in packed bed. Preliminary test calculations give hope that the method can be effectively applied in the future for modelling the charge and discharge processes in such TES with PCM.
Schenker, M C; Pourquié, M J B M; Eskin, D G; Boersma, B J
2013-01-01
The flow in a confined container induced by an ultrasonic horn is measured by Particle Image Velocimetry (PIV). This flow is caused by acoustic streaming and highly influenced by the presence of cavitation. The jet-like experimentally observed flow is compared with the available theoretical solution for a turbulent free round jet. The similarity between both flows enables a simplified numerical model to be made, whilst the phenomenon is very difficult to simulate otherwise. The numerical model requires only two parameters, i.e. the flow momentum and turbulent kinetic energy at the position of the horn tip. The simulated flow is used as a basis for the calculation of the time required for the entire liquid volume to pass through the active cavitation region. Copyright © 2012 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Kotler, Z.; Neria, E.; Nitzan, A.
1991-01-01
The use of the time-dependent self-consistent field approximation (TDSCF) in the numerical solution of quantum curve crossing and tunneling dynamical problems is investigated. Particular emphasis is given to multiconfiguration TDSCF (MCTDSCF) approximations, which are shown to perform considerably better with only a small increase in computational effort. We investigate a number of simple models in which a 'system' characterized by two electronic potential surfaces evolves while interacting with a 'bath' mode described by an harmonic oscillator, and compare exact numerical solutions to one- and two-configuration TDSCF approximations. We also introduce and investigate a semiclassical approximation in which the 'bath' mode is described by semiclassical wavepackets (one for each electronic state) and show that for all models investigated this scheme works very well in comparison with the fully quantum MCTDSCF approximation. This provides a potentially very useful method to simulate strongly quantum systems coupled to an essentially classical environment. (orig.)
Numerical study of the time evolution of a wave packet in quantum mechanics
International Nuclear Information System (INIS)
Segura, J.; Fernandez de Cordoba, P.
1993-01-01
We solve the Schrodinger equation in order to study the time evolution of a wave packet in different situations of physical interest. This work illustrates, with pedagogical aim, some quantum phenomena which shock our classical conception of the universe: propagation in classically forbidden regions, energy quantization. (Author)
On the relationship between supplier integration and time-to-market
Perols, J.; Zimmermann, C.; Kortmann, S.
2013-01-01
Recent operations management and innovation management research emphasizes the importance of supplier integration. However, the empirical results as to the relationship between supplier integration and time-to-market are ambivalent. To understand this important relationship, we incorporate two major
Oskouie, M. Faraji; Ansari, R.; Rouhi, H.
2018-04-01
Eringen's nonlocal elasticity theory is extensively employed for the analysis of nanostructures because it is able to capture nanoscale effects. Previous studies have revealed that using the differential form of the strain-driven version of this theory leads to paradoxical results in some cases, such as bending analysis of cantilevers, and recourse must be made to the integral version. In this article, a novel numerical approach is developed for the bending analysis of Euler-Bernoulli nanobeams in the context of strain- and stress-driven integral nonlocal models. This numerical approach is proposed for the direct solution to bypass the difficulties related to converting the integral governing equation into a differential equation. First, the governing equation is derived based on both strain-driven and stress-driven nonlocal models by means of the minimum total potential energy. Also, in each case, the governing equation is obtained in both strong and weak forms. To solve numerically the derived equations, matrix differential and integral operators are constructed based upon the finite difference technique and trapezoidal integration rule. It is shown that the proposed numerical approach can be efficiently applied to the strain-driven nonlocal model with the aim of resolving the mentioned paradoxes. Also, it is able to solve the problem based on the strain-driven model without inconsistencies of the application of this model that are reported in the literature.
A comparison of numerical methods for the solution of continuous-time DSGE models
DEFF Research Database (Denmark)
Parra-Alvarez, Juan Carlos
This paper evaluates the accuracy of a set of techniques that approximate the solution of continuous-time DSGE models. Using the neoclassical growth model I compare linear-quadratic, perturbation and projection methods. All techniques are applied to the HJB equation and the optimality conditions...... parameters of the model and suggest the use of projection methods when a high degree of accuracy is required....
Ranjbar, Mohammad Hassan; Hadjizadeh Zaker, Nasser
2018-01-01
Gorgan Bay is a semi-enclosed basin located in the southeast of the Caspian Sea, Iran. The bay is recognized as a resting place for migratory birds as well as a spawning habitat for native fish. However, apparently, no detailed research on its physical processes has previously been conducted. In this study, a 3D coupled hydrodynamic and solute transport model was used to investigate general circulation, thermohaline structure, and residence time in Gorgan Bay. Model outputs were validated against a set of field observations. Bottom friction and attenuation coefficient of light intensity were tuned in order to achieve optimum agreement with the observations. Results revealed that, due to the interaction between bathymetry and prevailing winds, a barotropic double-gyre circulation, dominating the general circulation, existed during all seasons in Gorgan Bay. Furthermore, temperature and salinity fluctuations in the bay were seasonal, due to the seasonal variability of atmospheric fluxes. Results also indicated that under the prevailing winds, the domain-averaged residence time in Gorgan Bay would be approximately 95 days. The rivers discharging into Gorgan Bay are considered as the main sources of nutrients in the bay. Since their mouths are located in the area with a residence time of over 100 days, Gorgan Bay could be at risk of eutrophication; it is necessary to adopt preventive measures against water quality degradation.
Real-time numerical evaluation of dynamic tests with sudden closing of valves in piping systems
International Nuclear Information System (INIS)
Geidel, W.; Leimbach, K.R.
1979-01-01
The sudden closing of a valve in a piping system causes a build-up of pressure which, in turn, causes severe vibrations of the structural system. The licensing procedure calls for on-site tests to determine the dynamic effects of such closing of valves, and to check the stresses and displacements against the allowable ones. The measurements include time histories of displacements, accelerations and internal pressure. The computer program KWUROHR for the static and dynamic analysis of piping systems has been used by KWU and several subcontractors during the past four vears. This program has been extended by adding a subroutine package which computes time histories of displacements, accelerations and stresses resulting from the input of measured time histories of internal pressures at selected locations. The computer algorithm establishes the topological connectivity between the internal pressure measuring locations, to set up a logic for linear pressure interpolation between these points and pressure steps at reducers and valves. A minimum number of input points is required to give realistic results. (orig.)
Fully Integrated SAW-Less Discrete-Time Superheterodyne Receiver
Madadi, I.
2015-01-01
There are nowadays strong business and technical demands to integrate radio- frequency (RF) receivers (RX) into a complete system-on-chip (SoC) realized in scaled digital processes technology. As a consequence, the RF circuitry has to function well in face of reduced power supply ( V DD ) while the
International Nuclear Information System (INIS)
Kim, K. S.; Ju, H. G.; Jeon, T. H. and others
2005-03-01
A comprehensive high fidelity reactor core modeling capability has been developed for detailed analysis of current and advanced reactor designs as part of a US-ROK collaborative I-NERI project. High fidelity was accomplished by integrating highly refined solution modules for the coupled neutronic, thermal-hydraulic, and thermo-mechanical phenomena. Each solution module employs methods and models that are formulated faithfully to the first-principles governing the physics, real geometry, and constituents. Specifically, the critical analysis elements that are incorporated in the coupled code capability are whole-core neutron transport solution, ultra-fine-mesh computational fluid dynamics/heat transfer solution, and finite-element-based thermo-mechanics solution, all obtained with explicit (fuel pin cell level) heterogeneous representations of the components of the core. The vast computational problem resulting from such highly refined modeling is solved on massively parallel computers, and serves as the 'numerical nuclear reactor'. Relaxation of modeling parameters were also pursued to make problems run on clusters of workstations and PCs for smaller scale applications as well
Energy Technology Data Exchange (ETDEWEB)
Azadeh, A.; Amalnick, M.S.; Ghaderi, S.F.; Asadzadeh, S.M. [Department of Industrial Engineering, Faculty of Engineering, Center of Excellence for Intelligent Experimental Mechanics, Research Institute of Energy Management and Planning, P.O. Box 14178-43111, University of Tehran (Iran); Department of Engineering Optimization Research, Faculty of Engineering, Center of Excellence for Intelligent Experimental Mechanics, Research Institute of Energy Management and Planning, P.O. Box 14178-43111, University of Tehran (Iran)
2007-07-15
This paper introduces an integrated approach based on data envelopment analysis (DEA), principal component analysis (PCA) and numerical taxonomy (NT) for total energy efficiency assessment and optimization in energy intensive manufacturing sectors. Total energy efficiency assessment and optimization of the proposed approach considers structural indicators in addition conventional consumption and manufacturing sector output indicators. The validity of the DEA model is verified and validated by PCA and NT through Spearman correlation experiment. Moreover, the proposed approach uses the measure-specific super-efficiency DEA model for sensitivity analysis to determine the critical energy carriers. Four energy intensive manufacturing sectors are discussed in this paper: iron and steel, pulp and paper, petroleum refining and cement manufacturing sectors. To show superiority and applicability, the proposed approach has been applied to refinery sub-sectors of some OECD (Organization for Economic Cooperation and Development) countries. This study has several unique features which are: (1) a total approach which considers structural indicators in addition to conventional energy efficiency indicators; (2) a verification and validation mechanism for DEA by PCA and NT and (3) utilization of DEA for total energy efficiency assessment and consumption optimization of energy intensive manufacturing sectors. (author)
Energy Technology Data Exchange (ETDEWEB)
Kim, K. S.; Ju, H. G.; Jeon, T. H. and others
2005-03-15
A comprehensive high fidelity reactor core modeling capability has been developed for detailed analysis of current and advanced reactor designs as part of a US-ROK collaborative I-NERI project. High fidelity was accomplished by integrating highly refined solution modules for the coupled neutronic, thermal-hydraulic, and thermo-mechanical phenomena. Each solution module employs methods and models that are formulated faithfully to the first-principles governing the physics, real geometry, and constituents. Specifically, the critical analysis elements that are incorporated in the coupled code capability are whole-core neutron transport solution, ultra-fine-mesh computational fluid dynamics/heat transfer solution, and finite-element-based thermo-mechanics solution, all obtained with explicit (fuel pin cell level) heterogeneous representations of the components of the core. The vast computational problem resulting from such highly refined modeling is solved on massively parallel computers, and serves as the 'numerical nuclear reactor'. Relaxation of modeling parameters were also pursued to make problems run on clusters of workstations and PCs for smaller scale applications as well.
International Nuclear Information System (INIS)
Azadeh, A.; Amalnick, M.S.; Ghaderi, S.F.; Asadzadeh, S.M.
2007-01-01
This paper introduces an integrated approach based on data envelopment analysis (DEA), principal component analysis (PCA) and numerical taxonomy (NT) for total energy efficiency assessment and optimization in energy intensive manufacturing sectors. Total energy efficiency assessment and optimization of the proposed approach considers structural indicators in addition conventional consumption and manufacturing sector output indicators. The validity of the DEA model is verified and validated by PCA and NT through Spearman correlation experiment. Moreover, the proposed approach uses the measure-specific super-efficiency DEA model for sensitivity analysis to determine the critical energy carriers. Four energy intensive manufacturing sectors are discussed in this paper: iron and steel, pulp and paper, petroleum refining and cement manufacturing sectors. To show superiority and applicability, the proposed approach has been applied to refinery sub-sectors of some OECD (Organization for Economic Cooperation and Development) countries. This study has several unique features which are: (1) a total approach which considers structural indicators in addition to conventional energy efficiency indicators; (2) a verification and validation mechanism for DEA by PCA and NT and (3) utilization of DEA for total energy efficiency assessment and consumption optimization of energy intensive manufacturing sectors
Trzcina, Estera; Rohm, Witold; Dymarska, Natalia
2017-04-01
GNSS tropospheric tomography is a technique that aims to obtain spatial distribution of wet refractivity in the lower atmosphere based on satellite signal delay. These estimates, strictly related to the water vapor amount in atmosphere, can be assimilated in Numerical Weather Prediction (NWP) models. These observations are very valuable for the weather prediction process. Water vapor amount in the troposphere is one of the most important factors forming weather conditions. Moreover it is highly variable in time and space, thus should be monitored with high spatio-temporal resolution. Vertical distribution of the water vapor in the atmosphere is usually obtained by balloon-based radiosonde sounding. This approach is very common, but also expensive. Spatial and temporal resolutions of these measurements are rather poor in comparison to the NWP models. In contrast, resolution of the GNSS tomography can be similar to the NWP models with no additional costs, especially on the areas equipped with well-developed GNSS stations networks. Previous studies on GNSS tomography indicates that the accuracy of the results is satisfactory and might be applied in meteorology. Tropospheric tomography is a very promising technique for the weather prediction because of the slant satellite observations utilization - Slant Wet Delays (SWD) or Slant Integrated Water Vapor (SIWV). Due to the slant trajectories of the GNSS signals crossing atmosphere and tomography inverse processing the vertical profiles of humidity can be estimated. In this study an effort was made to meet two major preconditions for tomographic data assimilation in NWP: 1) adjusting tomography model to near-real time (NRT) observation and 2) reaching required accuracy of the solution. Moreover the first attempt of assimilation tomographic data in NWP model was made using refractivity profile operator (GPS_REF). GNSS tomography model TOMO2 was adjusted to use NRT troposphere observation by using predicted orbits, ZTDs and
Integration of neutron time-of-flight single-crystal Bragg peaks in reciprocal space
Energy Technology Data Exchange (ETDEWEB)
Schultz, Arthur J [ORNL; Joergensen, Mads [ORNL; Wang, Xiaoping [ORNL; Mikkelson, Ruth L [ORNL; Mikkelson, Dennis J [ORNL; Lynch, Vickie E [ORNL; Peterson, Peter F [ORNL; Green, Mark L [ORNL; Hoffmann, Christina [ORNL
2014-01-01
The intensity of single crystal Bragg peaks obtained by mapping neutron time-of-flight event data into reciprocal space and integrating in various ways are compared. These include spherical integration with a fixed radius, ellipsoid fitting and integrating of the peak intensity and one-dimensional peak profile fitting. In comparison to intensities obtained by integrating in real detector histogram space, the data integrated in reciprocal space results in better agreement factors and more accurate atomic parameters. Furthermore, structure refinement using integrated intensities from one-dimensional profile fitting is demonstrated to be more accurate than simple peak-minus-background integration.
Directory of Open Access Journals (Sweden)
Simon D Angus
Full Text Available Multi-dose radiotherapy protocols (fraction dose and timing currently used in the clinic are the product of human selection based on habit, received wisdom, physician experience and intra-day patient timetabling. However, due to combinatorial considerations, the potential treatment protocol space for a given total dose or treatment length is enormous, even for relatively coarse search; well beyond the capacity of traditional in-vitro methods. In constrast, high fidelity numerical simulation of tumor development is well suited to the challenge. Building on our previous single-dose numerical simulation model of EMT6/Ro spheroids, a multi-dose irradiation response module is added and calibrated to the effective dose arising from 18 independent multi-dose treatment programs available in the experimental literature. With the developed model a constrained, non-linear, search for better performing cadidate protocols is conducted within the vicinity of two benchmarks by genetic algorithm (GA techniques. After evaluating less than 0.01% of the potential benchmark protocol space, candidate protocols were identified by the GA which conferred an average of 9.4% (max benefit 16.5% and 7.1% (13.3% improvement (reduction on tumour cell count compared to the two benchmarks, respectively. Noticing that a convergent phenomenon of the top performing protocols was their temporal synchronicity, a further series of numerical experiments was conducted with periodic time-gap protocols (10 h to 23 h, leading to the discovery that the performance of the GA search candidates could be replicated by 17-18 h periodic candidates. Further dynamic irradiation-response cell-phase analysis revealed that such periodicity cohered with latent EMT6/Ro cell-phase temporal patterning. Taken together, this study provides powerful evidence towards the hypothesis that even simple inter-fraction timing variations for a given fractional dose program may present a facile, and highly cost
Angus, Simon D; Piotrowska, Monika Joanna
2014-01-01
Multi-dose radiotherapy protocols (fraction dose and timing) currently used in the clinic are the product of human selection based on habit, received wisdom, physician experience and intra-day patient timetabling. However, due to combinatorial considerations, the potential treatment protocol space for a given total dose or treatment length is enormous, even for relatively coarse search; well beyond the capacity of traditional in-vitro methods. In constrast, high fidelity numerical simulation of tumor development is well suited to the challenge. Building on our previous single-dose numerical simulation model of EMT6/Ro spheroids, a multi-dose irradiation response module is added and calibrated to the effective dose arising from 18 independent multi-dose treatment programs available in the experimental literature. With the developed model a constrained, non-linear, search for better performing cadidate protocols is conducted within the vicinity of two benchmarks by genetic algorithm (GA) techniques. After evaluating less than 0.01% of the potential benchmark protocol space, candidate protocols were identified by the GA which conferred an average of 9.4% (max benefit 16.5%) and 7.1% (13.3%) improvement (reduction) on tumour cell count compared to the two benchmarks, respectively. Noticing that a convergent phenomenon of the top performing protocols was their temporal synchronicity, a further series of numerical experiments was conducted with periodic time-gap protocols (10 h to 23 h), leading to the discovery that the performance of the GA search candidates could be replicated by 17-18 h periodic candidates. Further dynamic irradiation-response cell-phase analysis revealed that such periodicity cohered with latent EMT6/Ro cell-phase temporal patterning. Taken together, this study provides powerful evidence towards the hypothesis that even simple inter-fraction timing variations for a given fractional dose program may present a facile, and highly cost-effecitive means
Numerical simulation of time-invariant error and its effect on planetary gearbox dynamics
Directory of Open Access Journals (Sweden)
Venkataram Nithin
2018-01-01
Full Text Available Planetary gearbox is used in high precision applications such as robotic arm, control system of antenna, positioning and radar tracking systems. Planetary gearbox have high torque-to-weight ratio, high degree of control over the speed range and better efficiency. Most of the literatures assume that the gearbox are free from errors. Errors significantly affect the dynamic characteristics of the gearbox. The major challenge is to model these errors and study its behaviour under dynamic condition. The simulation results of time domain signal when converted to frequency domain signal, it shows the presence of error in the gearbox. Also, simulation result indicates a non-uniform motion of planetary gearbox in the presence of errors.
Numerical Context and Time Perception: Contrast Effects and the Perceived Duration of Numbers.
Alards-Tomalin, Doug; Walker, Alexander C; Kravetz, Alexa; Leboe-McGowan, Launa C
2016-01-01
In the current study, we examined how the contextual repetition of magnitude information presented in either symbolic (Arabic digits) or nonsymbolic (numerosities) formats impacted on the perceived duration of a later occurring target number. The results of the current study demonstrated a time-magnitude bias in which, on average, large magnitude target numbers were judged to last for longer durations relative to small magnitude target numbers, regardless of notation (symbolic number and numerosity). Furthermore, context effects were found, in which a greater discrepancy in the target's magnitude from the initial context led to longer perceived duration ratings. However, this was found to be asymmetrical, occurring only for large magnitude targets. Additionally, the type of context effect was shown to be determined by whether the context was presented in the same notation as the target or a different notation. © The Author(s) 2015.
Przekwas, A. J.; Athavale, M. M.; Hendricks, R. C.; Steinetz, B. M.
2006-01-01
Detailed information of the flow-fields in the secondary flowpaths and their interaction with the primary flows in gas turbine engines is necessary for successful designs with optimized secondary flow streams. Present work is focused on the development of a simulation methodology for coupled time-accurate solutions of the two flowpaths. The secondary flowstream is treated using SCISEAL, an unstructured adaptive Cartesian grid code developed for secondary flows and seals, while the mainpath flow is solved using TURBO, a density based code with capability of resolving rotor-stator interaction in multi-stage machines. An interface is being tested that links the two codes at the rim seal to allow data exchange between the two codes for parallel, coupled execution. A description of the coupling methodology and the current status of the interface development is presented. Representative steady-state solutions of the secondary flow in the UTRC HP Rig disc cavity are also presented.
Numerical study of fourth-harmonic generation of a picosecond laser pulse with time predelay
Energy Technology Data Exchange (ETDEWEB)
Zhang, T.; Kato, Y.; Daido, H. [Institute of Laser Engineering, Osaka University, Yamada-oka 2-6, Suita, Osaka 565 (Japan)
1996-06-01
We describe fourth-harmonic generation of a picosecond laser pulse with KDP crystals. The coupled nonlinear equations for the parametric process including the third-order nonlinear susceptibility have been solved. Applying a time predelay in the doubling crystal between the extraordinary and the ordinary waves of the fundamental pulse causes the group-velocity mismatch and the nonlinear phase shift in the doubling crystal to be compensated for each other, resulting in pulse duration compression at the fourth-harmonic wavelength. It is shown that the reduction from a 1-ps fundamental pulse to a 0.25-ps fourth-harmonic pulse can be achieved at an incident intensity of 50 GW/cm{sup 2}. {copyright} {ital 1996 Optical Society of America.}
Improving Music Genre Classification by Short Time Feature Integration
DEFF Research Database (Denmark)
Meng, Anders; Ahrendt, Peter; Larsen, Jan
Many different short-time features (derived from 10-30ms of audio) have been proposed for music segmentation, retrieval and genre classification. Often the available time frame of the music to make a decision (the decision time horizon) is in the range of seconds instead of milliseconds...... or decisions from the classifier, e.g. majority voting) for music genre classification....
Integrating Security in Real-Time Embedded Systems
2017-04-26
integration 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF a. REPORT b. ABSTRACT c. THIS PAGE ABSTRACT u u u SAR 18. NUMBER OF PAGES 12 19a. NAME... REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1...Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arl ington, VA 22202-4302. Respondents should be aware that
Knowledge Representation and Management, It's Time to Integrate!
Dhombres, F; Charlet, J
2017-08-01
Objectives: To select, present, and summarize the best papers published in 2016 in the field of Knowledge Representation and Management (KRM). Methods: A comprehensive and standardized review of the medical informatics literature was performed based on a PubMed query. Results: Among the 1,421 retrieved papers, the review process resulted in the selection of four best papers focused on the integration of heterogeneous data via the development and the alignment of terminological resources. In the first article, the authors provide a curated and standardized version of the publicly available US FDA Adverse Event Reporting System. Such a resource will improve the quality of the underlying data, and enable standardized analyses using common vocabularies. The second article describes a project developed in order to facilitate heterogeneous data integration in the i2b2 framework. The originality is to allow users integrate the data described in different terminologies and to build a new repository, with a unique model able to support the representation of the various data. The third paper is dedicated to model the association between multiple phenotypic traits described within the Human Phenotype Ontology (HPO) and the corresponding genotype in the specific context of rare diseases (rare variants). Finally, the fourth paper presents solutions to annotation-ontology mapping in genome-scale data. Of particular interest in this work is the Experimental Factor Ontology (EFO) and its generic association model, the Ontology of Biomedical AssociatioN (OBAN). Conclusion: Ontologies have started to show their efficiency to integrate medical data for various tasks in medical informatics: electronic health records data management, clinical research, and knowledge-based systems development. Georg Thieme Verlag KG Stuttgart.
Browning, G. L.; Tzur, I.; Roble, R. G.
1987-01-01
A time-dependent model is introduced that can be used to simulate the interaction of a thunderstorm with its global electrical environment. The model solves the continuity equation of the Maxwell current, which is assumed to be composed of the conduction, displacement, and source currents. Boundary conditions which can be used in conjunction with the continuity equation to form a well-posed initial-boundary value problem are determined. Properties of various components of solutions of the initial-boundary value problem are analytically determined. The results indicate that the problem has two time scales, one determined by the background electrical conductivity and the other by the time variation of the source function. A numerical method for obtaining quantitative results is introduced, and its properties are studied. Some simulation results on the evolution of the displacement and conduction currents during the electrification of a storm are presented.
DEFF Research Database (Denmark)
Wang, Y.; Chen, H.; Rosbjerg, Dan
2013-01-01
In reservoir operation improvement of the accuracy of forecast flood inflow and extension of forecast lead-time can effectively be achieved by using rainfall forecasts from numerical weather predictions with a hydrological catchment model. In this study, the Regional Spectrum Model (RSM), which...... is developed by the Japan Meteorological Agency, was used to forecast rainfall with 5 days lead-time in the upper region of the Three Gorges Reservoir (TGR). A conceptual hydrological model, the Xinanjiang Model, has been set up to forecast the inflow flood of TGR by the Ministry of Water Resources Information...... Center. Here, the flood forecast model coupled with the rainfall forecast from RSM has been employed to carry out real-time dynamic control of the Flood Limiting Water Level (FLWL) of TGR in order to improve the hydropower generation without increasing the flood risk. Taking the flood events of the flood...
Hu, Fang Q; Pizzo, Michelle E; Nark, Douglas M
2017-12-01
It has been well-known that under the assumption of a uniform mean flow, the acoustic wave propagation equation can be formulated as a boundary integral equation. However, the constant mean flow assumption, while convenient for formulating the integral equation, does not satisfy the solid wall boundary condition wherever the body surface is not aligned with the assumed uniform flow. A customary boundary condition for rigid surfaces is that the normal acoustic velocity be zero. In this paper, a careful study of the acoustic energy conservation equation is presented that shows such a boundary condition would in fact lead to source or sink points on solid surfaces. An alternative solid wall boundary condition, termed zero energy flux boundary condition, is proposed that conserves the acoustic energy and a time domain boundary integral equation is derived. Furthermore, stabilization of the integral equation by Burton-Miller type reformulation is presented. The stability is studied theoretically as well as numerically by an eigenvalue analysis. Numerical solutions are also presented that demonstrate the stability of the current formulation.
International Nuclear Information System (INIS)
Prij, J.; Vons, L.H.
1984-01-01
Results are presented of in-situ measurements, performed in a 300 m deep dry-drilled borehole, in the ASSE-mine. Convergence measurements at ambient as well as elevated temperatures and pressure measurements at elevated temperatures are discussed. Creep equations derived from these experiments are used for the numerical analysis of the time dependent behavior of a salt dome with a HLW repository. The analyses show that the total stresses in the salt remain compressive with deviatoric components smaller than 3 MPa. 9 references, 6 figures, 1 table
Lv, Xueming; Pan, Yunxiang; Jia, Zhichao; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu
2017-05-01
Time-resolved surface temperature of single crystal silicon was measured by an infrared radiation pyrometer. The silicon sample was irradiated by two pulsed Nd:YAG lasers with pulse duration of 1ms superposed by 7ns pulses, referred to as combined pulse laser (CPL). The change of the damage radius with the millisecond (ms) laser energy density was studied, and then compared with that of single ms laser irradiation. An axisymmetric numerical model was established for calculation of the temperature field distribution while silicon was irradiated by single ms laser and CPL, respectively. Compared with experimental results, the CPL-silicon damage mechanism was discussed.
Energy Technology Data Exchange (ETDEWEB)
Baczewski, Andrew David; Shulenburger, Luke; Desjarlais, Michael Paul; Magyar, Rudolph J.
2014-02-01
In recent years, DFT-MD has been shown to be a useful computational tool for exploring the properties of WDM. These calculations achieve excellent agreement with shock compression experiments, which probe the thermodynamic parameters of the Hugoniot state. New X-ray Thomson Scattering diagnostics promise to deliver independent measurements of electronic density and temperature, as well as structural information in shocked systems. However, they require the development of new levels of theory for computing the associated observables within a DFT framework. The experimentally observable x-ray scattering cross section is related to the electronic density-density response function, which is obtainable using TDDFT - a formally exact extension of conventional DFT that describes electron dynamics and excited states. In order to develop a capability for modeling XRTS data and, more generally, to establish a predictive capability for rst principles simulations of matter in extreme conditions, real-time TDDFT with Ehrenfest dynamics has been implemented in an existing PAW code for DFT-MD calculations. The purpose of this report is to record implementation details and benchmarks as the project advances from software development to delivering novel scienti c results. Results range from tests that establish the accuracy, e ciency, and scalability of our implementation, to calculations that are veri ed against accepted results in the literature. Aside from the primary XRTS goal, we identify other more general areas where this new capability will be useful, including stopping power calculations and electron-ion equilibration.
International Nuclear Information System (INIS)
Heintze, E.
1993-01-01
The aim of this report is to validate the program MAX3D built up from the discretization of the formulation (FB) established in part 1. A qualitative and quantitative analysis is carried out on numerical results obtained with various test cases of which, for most of them, analytical solutions are known. 32 figs., 3 refs
International Nuclear Information System (INIS)
Kostroun, V.O.
1980-01-01
Theoretical expressions for the angular and spectral distributions of synchrotron radiation involve modified Bessel functions of fractional order and the integral ∫sup(infinitely)sub(x)Ksub(ν)(eta)d eta. A simple series expression for these quantities which can be evaluated numerically with hand-held programmable calculators is presented. (orig.)
Corver, M.P.; Doust, H.; van Wees, J.D.A.M.; Cloetingh, S.A.P.L.
2011-01-01
We present the results of an integrated analogue and numerical modeling study with a focus on structural, stratigraphic and thermal differences between symmetric and asymmetric grabens. These models enable fault interpretation and subsidence analyses in studies of active rifting and graben
Time variability of X-ray binaries: observations with INTEGRAL. Modeling
International Nuclear Information System (INIS)
Cabanac, Clement
2007-01-01
The exact origin of the observed X and Gamma ray variability in X-ray binaries is still an open debate in high energy astrophysics. Among others, these objects are showing aperiodic and quasi-periodic luminosity variations on timescales as small as the millisecond. This erratic behavior must put constraints on the proposed emission processes occurring in the vicinity of the neutrons star or the stellar mass black-hole held by these objects. We propose here to study their behavior following 3 different ways: first we examine the evolution of a particular X-ray source discovered by INTEGRAL, IGR J19140+0951. Using timing and spectral data given by different instruments, we show that the source type is plausibly consistent with a High Mass X-ray Binary hosting a neutrons star. Subsequently, we propose a new method dedicated to the study of timing data coming from coded mask aperture instruments. Using it on INTEGRAL/ISGRI real data, we detect the presence of periodic and quasi-periodic features in some pulsars and micro-quasars at energies as high as a hundred keV. Finally, we suggest a model designed to describe the low frequency variability of X-ray binaries in their hardest state. This model is based on thermal comptonization of soft photons by a warm corona in which a pressure wave is propagating in cylindrical geometry. By computing both numerical simulations and analytical solution, we show that this model should be suitable to describe some of the typical features observed in X-ray binaries power spectra in their hard state and their evolution such as aperiodic noise and low frequency quasi-periodic oscillations. (author) [fr
Campbell, Kyle K; Braile, Thomas; Winker, Kevin
2016-01-01
The Philippine Islands are one of the most biologically diverse archipelagoes in the world. Current taxonomy, however, may underestimate levels of avian diversity and endemism in these islands. Although species limits can be difficult to determine among allopatric populations, quantitative methods for comparing phenotypic and genotypic data can provide useful metrics of divergence among populations and identify those that merit consideration for elevation to full species status. Using a conceptual approach that integrates genetic and phenotypic data, we compared populations among 48 species, estimating genetic divergence (p-distance) using the mtDNA marker ND2 and comparing plumage and morphometrics of museum study skins. Using conservative speciation thresholds, pairwise comparisons of genetic and phenotypic divergence suggested possible species-level divergences in more than half of the species studied (25 out of 48). In speciation process space, divergence routes were heterogeneous among taxa. Nearly all populations that surpassed high genotypic divergence thresholds were Passeriformes, and non-Passeriformes populations surpassed high phenotypic divergence thresholds more commonly than expected by chance. Overall, there was an apparent logarithmic increase in phenotypic divergence with respect to genetic divergence, suggesting the possibility that divergence among these lineages may initially be driven by divergent selection in this allopatric system. Also, genetic endemism was high among sampled islands. Higher taxonomy affected divergence in genotype and phenotype. Although broader lineage, genetic, phenotypic, and numeric sampling is needed to further explore heterogeneity among divergence processes and to accurately assess species-level diversity in these taxa, our results support the need for substantial taxonomic revisions among Philippine birds. The conservation implications are profound.
Kwong-Wong-type integral equation on time scales
Directory of Open Access Journals (Sweden)
Baoguo Jia
2011-09-01
Full Text Available Consider the second-order nonlinear dynamic equation $$ [r(tx^Delta(ho(t]^Delta+p(tf(x(t=0, $$ where $p(t$ is the backward jump operator. We obtain a Kwong-Wong-type integral equation, that is: If $x(t$ is a nonoscillatory solution of the above equation on $[T_0,infty$, then the integral equation $$ frac{r^sigma(tx^Delta(t}{f(x^sigma(t} =P^sigma(t+int^infty_{sigma(t}frac{r^sigma(s [int^1_0f'(x_h(sdh][x^Delta(s]^2}{f(x(s f(x^sigma(s}Delta s $$ is satisfied for $tgeq T_0$, where $P^sigma(t=int^infty_{sigma(t}p(sDelta s$, and $x_h(s=x(s+hmu(sx^Delta(s$. As an application, we show that the superlinear dynamic equation $$ [r(tx^{Delta}(ho(t]^Delta+p(tf(x(t=0, $$ is oscillatory, under certain conditions.
Guillaume, G; Gauvreau, B; L'Hermite, P
2015-01-01
Given a constantly increasing urban population, the mitigation of environmental impacts caused by urbanization has become a critical concern. Sprawling cities accelerate the phenomenon of soil sealing, whose impacts relative to climatology, water cycle and ecology are substantial. The "VegDUD" project, which provides the framework for the present paper, lays out a possible alternative for limiting these deleterious effects through focusing on the role of vegetation in promoting sustainable urban development. The study presented herein addresses the beneficial effect of greening building facades and rooftops in terms of both acoustic level and sound-decay time indicators at low frequency third-octave bands. This is carried out through numerical simulations in the time-domain of sound propagation in a canyon street of infinite length for various scenarios of surface vegetalization. Numerical predictions show a more significant effect in the upper part and outside the street, depending on the location of the vegetalized surfaces, frequency bands and number of reflections on the treated materials. Copyright © 2014 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Dasgupta, I.
1998-01-01
We discuss new bounce-like (but non-time-reversal-invariant) solutions to Euclidean equations of motion, which we dub boomerons. In the Euclidean path integral approach to quantum theories, boomerons make an imaginary contribution to the vacuum energy. The fake vacuum instability can be removed by cancelling boomeron contributions against contributions from time reversed boomerons (anti-boomerons). The cancellation rests on a sign choice whose significance is not completely understood in the path integral method. (orig.)
Brezinski, C
2012-01-01
Numerical analysis has witnessed many significant developments in the 20th century. This book brings together 16 papers dealing with historical developments, survey papers and papers on recent trends in selected areas of numerical analysis, such as: approximation and interpolation, solution of linear systems and eigenvalue problems, iterative methods, quadrature rules, solution of ordinary-, partial- and integral equations. The papers are reprinted from the 7-volume project of the Journal of Computational and Applied Mathematics on '/homepage/sac/cam/na2000/index.html<
Saylor, Rick D.; Ford, Gregory D.
The integration of systems of ordinary differential equations (ODEs) that arise in atmospheric photochemistry is of significant concern to tropospheric and stratospheric chemistry modelers. As a consequence of the stiff nature of these ODE systems, their solution requires a large fraction of the total computational effort in three-dimensional chemical model simulations. Several integration techniques have been proposed and utilized over the years in an attempt to provide computationally efficient, yet accurate, solutions to chemical kinetics ODES. In this work, we present a comparison of some of these techniques and argue that valid comparisons of ODE solvers must take into account the trade-off between solution accuracy and computational efficiency. Misleading comparison results can be obtained by neglecting the fact that any ODE solution method can be made faster or slower by manipulation of the appropriate error tolerances or time steps. Comparisons among ODE solution techniques should therefore attempt to identify which technique can provide the most accurate solution with the least computational effort over the entire range of behavior of each technique. We present here a procedure by which ODE solver comparisons can achieve this goal. Using this methodology, we compare a variety of integration techniques, including methods proposed by Hesstvedt et al. (1978, Int. J. Chem. Kinet.10, 971-994), Gong and Cho (1993, Atmospheric Environment27A, 2147-2160), Young and Boris (1977, J. phys. Chem.81, 2424-2427) and Hindmarsh (1983, In Scientific Computing (edited by Stepleman R. S. et al.), pp. 55-64. North-Holland, Amsterdam). We find that Gear-type solvers such as the Livermore Solver for ordinary differential equations (LSODE) and the sparse-matrix version of LSODE (LSODES) provide the most accurate solution of our test problems with the least computational effort.
Khan, M O; Valen-Sendstad, K; Steinman, D A
2015-07-01
Recent high-resolution computational fluid dynamics studies have uncovered the presence of laminar flow instabilities and possible transitional or turbulent flow in some intracranial aneurysms. The purpose of this study was to elucidate requirements for computational fluid dynamics to detect these complex flows, and, in particular, to discriminate the impact of solver numerics versus mesh and time-step resolution. We focused on 3 MCA aneurysms, exemplifying highly unstable, mildly unstable, or stable flow phenotypes, respectively. For each, the number of mesh elements was varied by 320× and the number of time-steps by 25×. Computational fluid dynamics simulations were performed by using an optimized second-order, minimally dissipative solver, and a more typical first-order, stabilized solver. With the optimized solver and settings, qualitative differences in flow and wall shear stress patterns were negligible for models down to ∼800,000 tetrahedra and ∼5000 time-steps per cardiac cycle and could be solved within clinically acceptable timeframes. At the same model resolutions, however, the stabilized solver had poorer accuracy and completely suppressed flow instabilities for the 2 unstable flow cases. These findings were verified by using the popular commercial computational fluid dynamics solver, Fluent. Solver numerics must be considered at least as important as mesh and time-step resolution in determining the quality of aneurysm computational fluid dynamics simulations. Proper computational fluid dynamics verification studies, and not just superficial grid refinements, are therefore required to avoid overlooking potentially clinically and biologically relevant flow features. © 2015 by American Journal of Neuroradiology.
Space Time Adaptive Processing and Clutter Classification Integration and Evaluation
National Research Council Canada - National Science Library
Jensen, Nathan
2002-01-01
.... Current radar technologies suffer from jamming and clutter limitations. STAP is a statistical method to remove this noise, however it is extremely computationally intensive, and presents several real time processing hurdles...
Computational morphodynamics of plants: integrating development over space and time.
Roeder, Adrienne H K; Tarr, Paul T; Tobin, Cory; Zhang, Xiaolan; Chickarmane, Vijay; Cunha, Alexandre; Meyerowitz, Elliot M
2011-04-01
The emerging field of computational morphodynamics aims to understand the changes that occur in space and time during development by combining three technical strategies: live imaging to observe development as it happens; image processing and analysis to extract quantitative information; and computational modelling to express and test time-dependent hypotheses. The strength of the field comes from the iterative and combined use of these techniques, which has provided important insights into plant development.
SEASONAL AUTOREGRESSIVE INTEGRATED MOVING AVERAGE MODEL FOR PRECIPITATION TIME SERIES
Yan Wang; Meng Gao; Xinghua Chang; Xiyong Hou
2012-01-01
Predicting the trend of precipitation is a difficult task in meteorology and environmental sciences. Statistical approaches from time series analysis provide an alternative way for precipitation prediction. The ARIMA model incorporating seasonal characteristics, which is referred to as seasonal ARIMA model was presented. The time series data is the monthly precipitation data in Yantai, China and the period is from 1961 to 2011. The model was denoted as SARIMA (1, 0, 1) (0, 1, 1)12 in this stu...
Time, dynamics and chaos. Integrating Poincare's "non-integrable systems"
Energy Technology Data Exchange (ETDEWEB)
Prigogine, I.
1990-01-01
This report discusses the nature of time. The author attempts to resolve the conflict between the concept of time reversibility in classical and quantum mechanics with the macroscopic world's irreversibility of time. (LSP)
An integration time adaptive control method for atmospheric composition detection of occultation
Ding, Lin; Hou, Shuai; Yu, Fei; Liu, Cheng; Li, Chao; Zhe, Lin
2018-01-01
When sun is used as the light source for atmospheric composition detection, it is necessary to image sun for accurate identification and stable tracking. In the course of 180 second of the occultation, the magnitude of sun light intensity through the atmosphere changes greatly. It is nearly 1100 times illumination change between the maximum atmospheric and the minimum atmospheric. And the process of light change is so severe that 2.9 times per second of light change can be reached. Therefore, it is difficult to control the integration time of sun image camera. In this paper, a novel adaptive integration time control method for occultation is presented. In this method, with the distribution of gray value in the image as the reference variable, and the concepts of speed integral PID control, the integration time adaptive control problem of high frequency imaging. The large dynamic range integration time automatic control in the occultation can be achieved.
Energy Technology Data Exchange (ETDEWEB)
Finn, John M., E-mail: finn@lanl.gov [T-5, Applied Mathematics and Plasma Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2015-03-15
Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a “special divergence-free” (SDF) property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Feng and Shang [Numer. Math. 71, 451 (1995)], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Richardson and Finn [Plasma Phys. Controlled Fusion 54, 014004 (2012
Real-Time Integrated Re-scheduling for Tramway Operations
Cheung, Kam-Fung; Kuo, Yong-Hong; Lai, S.W.; Leung, Janny M.Y.
2018-01-01
Our work aims to develop practical solution approaches for real-time dispatch of crews and vehicles for disruption management. The practical motivation for our research arose from the operations of a public tramway system in Hong Kong. The tram system shares the road with other vehicular traffic in
Representing real time semantics for distributed application integration
Poon, P.M.S.; Dillon, T.S.; Chang, E.; Feng, L.
Traditional real time system design and development are driven by technological requirements. With the ever growing complexity of requirements and the advances in software design, the alignment of focus has gradually been shifted to the perspective of business and industrial needs. This paper
Integrated Formal Analysis of Timed-Triggered Ethernet
Dutertre, Bruno; Shankar, Nstarajan; Owre, Sam
2012-01-01
We present new results related to the verification of the Timed-Triggered Ethernet (TTE) clock synchronization protocol. This work extends previous verification of TTE based on model checking. We identify a suboptimal design choice in a compression function used in clock synchronization, and propose an improvement. We compare the original design and the improved definition using the SAL model checker.
Amasia, Mary; Kang, Seok-Won; Banerjee, Debjyoti; Madou, Marc
2013-01-01
A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of
Sayed, Sadeed Bin
2015-05-05
A time domain electric field volume integral equation (TD-EFVIE) solver is proposed for characterizing transient electromagnetic wave interactions on high-contrast dielectric scatterers. The TD-EFVIE is discretized using the Schaubert- Wilton-Glisson (SWG) and approximate prolate spherical wave (APSW) functions in space and time, respectively. The resulting system of equations can not be solved by a straightforward application of the marching on-in-time (MOT) scheme since the two-sided APSW interpolation functions require the knowledge of unknown “future” field samples during time marching. Causality of the MOT scheme is restored using an extrapolation technique that predicts the future samples from known “past” ones. Unlike the extrapolation techniques developed for MOT schemes that are used in solving time domain surface integral equations, this scheme trains the extrapolation coefficients using samples of exponentials with exponents on the complex frequency plane. This increases the stability of the MOT-TD-EFVIE solver significantly, since the temporal behavior of decaying and oscillating electromagnetic modes induced inside the scatterers is very accurately taken into account by this new extrapolation scheme. Numerical results demonstrate that the proposed MOT solver maintains its stability even when applied to analyzing wave interactions on high-contrast scatterers.
Electric vehicle integration in a real-time market
DEFF Research Database (Denmark)
Pedersen, Anders Bro
with an externally simulated model of the power grid, it is be possible, in real-time, to simulate the impact of EV charging and help to identify bottlenecks in the system. In EDISON the vehicles are aggregated using an entity called a Virtual Power Plant (VPP); a central server monitoring and controlling...... the distributed energy resources registered with it, in order to make them appear as a single producer in the eyes of the market. Although the concept of a VPP is used within the EcoGrid EU project, the idea of more individual control is introduced through a new proposed real-time electricity market, where...... the consumers will have direct access to the current price. As opposed to the hourly spot-price market of today, the real-time market see price updates as often as every couple of minutes. To allow the individual resources to react to these changes, independent of each other, so called “smart controllers...
Doummar, J.; Kassem, A.; Gurdak, J. J.
2017-12-01
In the framework of a three-year USAID/NSF- funded PEER Science project, flow in a karst system in Lebanon (Assal Spring; discharge 0.2-2.5 m3/s yearly volume of 22-30 Mm3) dominated by snow and semi arid conditions was simulated using an integrated numerical model (Mike She 2016). The calibrated model (Nash-Sutcliffe coefficient of 0.77) is based on high resolution input data (2014-2017) and detailed catchment characterization. The approach is to assess the influence of various model parameters on recharge signals in the different hydrological karst compartments (Atmosphere, unsaturated zone, and saturated zone) based on an integrated numerical model. These parameters include precipitation intensity and magnitude, temperature, snow-melt parameters, in addition to karst specific spatially distributed features such as fast infiltration points, soil properties and thickness, topographical slopes, Epikarst and thickness of unsaturated zone, and hydraulic conductivity among others. Moreover, the model is currently simulated forward using various scenarios for future climate (Global Climate Models GCM; daily downscaled temperature and precipitation time series for Lebanon 2020-2045) in order to depict the flow rates expected in the future and the effect of climate change on hydrographs recession coefficients, discharge maxima and minima, and total spring discharge volume . Additionally, a sensitivity analysis of individual or coupled major parameters allows quantifying their impact on recharge or indirectly on the vulnerability of the system (soil thickness, soil and rock hydraulic conductivity appear to be amongst the highly sensitive parameters). This study particularly unravels the normalized single effect of rain magnitude and intensity, snow, and temperature change on the flow rate (e.g., a change of temperature of 3° on the catchment yields a Residual Mean Square Error RMSE of 0.15 m3/s in the spring discharge and a 16% error in the total annual volume with
International Nuclear Information System (INIS)
Bae, D.S.; Kim, C.S.; Koh, Y.K.; Kim, K.S.; Song, M.Y.
1997-01-01
The prediction of groundwater flow affecting the migration of radionuclides is an important component of the performance assessment of radioactive waste disposal. Groundwater flow in fractured rock mass is controlled by fracture networks, transmissivity and hydraulic gradient. Furthermore the scale-dependent and anisotropic properties of hydraulic parameters are resulted mainly from irregular patterns of fracture system, which are very complex to evaluate properly with the current techniques available. For the purpose of characterizing a groundwater flow in fractured rock mass, the discrete fracture network (DFN) concept is available on the basis of assumptions of groundwater flowing only along fractures and flowpaths in rock mass formed by interconnected fractures. To increase the reliability of assessment in groundwater flow phenomena, numerical groundwater flow model and isotopic techniques were applied. Fracture mapping, borehole acoustic scanning were performed to identify conductive fractures in gneissic terrane. Tracer techniques, using deuterium, oxygen-18 and tritium were applied to evaluate the recharge area and groundwater residence time
Dzierzbicka-Głowacka, Lidia
2005-01-01
A nutrient-phytoplankton-zooplankton-detritus (1D-NPZD) `phytoplankton {Phyt} and Pseudocalanus elongatus {Zoop} dynamics in the spring bloom time in the Gdańsk Gulf. The 1D-NPZD model consists of three coupled, partial second-order differential equations of the diffusion type for phytoplankton {Phyt}, zooplankton {Zoop}, nutrients {Nutr} and one ordinary first-order differential equation for benthic detritus pool {Detr}, together with initial and boundary conditions. In this model, the {Zoop} is presented by only one species of copepod ( P. elongatus) and {Zoop} is composed of six cohorts of copepods with weights ( Wi) and numbers ( Zi); where Zoop= limit∑i=16W iZ i. The calculations were made for 90 days (March, April, May) for two stations at Gdańsk Gulf with a vertical space step of 0.5m and a time step of 900 s. The flow field and water temperature used as the inputs in the biological model 1D-NPZD were reproduced by the prognostic numerical simulation technique using hydrographic climatological data. The results of the numerical investigations described here were compared with the mean observed values of surface chlorophyll- a and depth integrated P. elongatus biomass for 10 years, 1980-1990. The slight differences between the calculated and mean observed values of surface chlorophyll- a and zooplankton biomass are ca. 10-60 mg C m -3 and ca. 5-23 mg C m -2, respectively, depending on the location of the hydrographic station. The 1D-NPZD model with a high-resolution zooplankton module for P. elongatus can be used to describe the temporal patterns for phytoplankton biomass and P. elongatus in the centre of the Gdańsk Gulf.
Khabarov, Nikolay; Huggel, Christian; Obersteiner, Michael; Ramírez, Juan Manuel
2010-05-01
Mountain regions are typically characterized by rugged terrain which is susceptible to different types of landslides during high-intensity precipitation. Landslides account for billions of dollars of damage and many casualties, and are expected to increase in frequency in the future due to a projected increase of precipitation intensity. Early warning systems (EWS) are thought to be a primary tool for related disaster risk reduction and climate change adaptation to extreme climatic events and hydro-meteorological hazards, including landslides. An EWS for hazards such as landslides consist of different components, including environmental monitoring instruments (e.g. rainfall or flow sensors), physical or empirical process models to support decision-making (warnings, evacuation), data and voice communication, organization and logistics-related procedures, and population response. Considering this broad range, EWS are highly complex systems, and it is therefore difficult to understand the effect of the different components and changing conditions on the overall performance, ultimately being expressed as human lives saved or structural damage reduced. In this contribution we present a further development of our approach to assess a landslide EWS in an integral way, both at the system and component level. We utilize a numerical model using 6 hour rainfall data as basic input. A threshold function based on a rainfall-intensity/duration relation was applied as a decision criterion for evacuation. Damage to infrastructure and human lives was defined as a linear function of landslide magnitude, with the magnitude modelled using a power function of landslide frequency. Correct evacuation was assessed with a ‘true' reference rainfall dataset versus a dataset of artificially reduced quality imitating the observation system component. Performance of the EWS using these rainfall datasets was expressed in monetary terms (i.e. damage related to false and correct evacuation). We
High resolution time integration for Sn radiation transport
International Nuclear Information System (INIS)
Thoreson, Greg; McClarren, Ryan G.; Chang, Jae H.
2008-01-01
First order, second order and high resolution time discretization schemes are implemented and studied for the S n equations. The high resolution method employs a rate of convergence better than first order, but also suppresses artificial oscillations introduced by second order schemes in hyperbolic differential equations. All three methods were compared for accuracy and convergence rates. For non-absorbing problems, both second order and high resolution converged to the same solution as the first order with better convergence rates. High resolution is more accurate than first order and matches or exceeds the second order method. (authors)
He, M.; Hardin, D. M.; Goodman, M.; Blakeslee, R.
2008-05-01
The Real Time Mission Monitor (RTMM) is an interactive visualization application based on Google Earth, that provides situational awareness and field asset management during NASA field campaigns. The RTMM can integrate data and imagery from numerous sources including GOES-12, GOES-10, and TRMM satellites. Simultaneously, it can display data and imagery from surface observations including Nexrad, NPOL and SMART- R radars. In addition to all these it can display output from models and real-time flight tracks of all aircraft involved in the experiment. In some instances the RTMM can also display measurements from scientific instruments as they are being flown. All data are recorded and archived in an on-line system enabling playback and review of all sorties. This is invaluable in preparing for future deployments and in exercising case studies. The RTMM facilitates pre-flight planning, in-flight monitoring, development of adaptive flight strategies and post- flight data analyses and assessments. Since the RTMM is available via the internet - during the actual experiment - project managers, scientists and mission planners can collaborate no matter where they are located as long as they have a viable internet connection. In addition, the system is open so that the general public can also view the experiment, in-progress, with Google Earth. Predecessors of RTMM were originally deployed in 2002 as part of the Altus Cumulus Electrification Study (ACES) to monitor uninhabited aerial vehicles near thunderstorms. In 2005 an interactive Java-based web prototype supported the airborne Lightning Instrument Package (LIP) during the Tropical Cloud Systems and Processes (TCSP) experiment. In 2006 the technology was adapted to the 3D Google Earth virtual globe and in 2007 its capabilities were extended to support multiple NASA aircraft (ER-2, WB-57, DC-8) during Tropical Composition, Clouds and Climate Coupling (TC4) experiment and 2007 Summer Aerosonde field study. In April 2008
Multi-channel time-division integrator in HL-2A
International Nuclear Information System (INIS)
Yan Ji
2008-01-01
HL-2A is China's first Tokamak device with divertor configuration (magnetic confinement controlled nuclear fusion device). To find out the details of on-going fusion reaction at different times is of important significance in achieving controlled nuclear fusion. We developed a new type multi-channel time-division integrator for HL-2A. It has functions of automatic cutting off negative pulse of the input signals, optional integrating time division spacing 0.2-1 ms, TTL starting trigger signal, automatic regularly work 20 s, and integrating 10 channel at the same time. (authors)