检索结果-内蒙古大学图书馆

Martensitic transformation in NiMnGa single crystals:: numerical simulation and experiments

INTERNATIONAL JOURNAL OF PLASTICITY 2006年第10期22卷 1943-1961页

作者： Arndt, M. Griebel, M. Novak, V. Roubicek, T. Sittner, P. Univ Bonn Inst Numer Simulat D-53115 Bonn Germany Acad Sci Czech Republ Inst Phys CZ-18221 Prague 8 Czech Republic Charles Univ Prague Fac Math & Phys CZ-18675 Prague 8 Czech Republic Acad Sci Czech Republ Inst Informat Theory & Automat CZ-18208 Prague 8 Czech Republic

In this article, we develop a continuum mechanical model to simulate deformation and phase transformation processes in shape memory alloys. The model is based on a detailed description of the stored energy. Furthermore, the energy dissipation due to phase transformations is taken into account via the maximum-dissipation principle. The results from the 3D numerical simulations of stress induced transformations from the cubic to the tetragonal phase and martensitic variant reorientations in NiMnGa are compared with laboratory experiments on NiMnGa [001]-oriented single crystals. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： microstructures phase transformation shape memory alloys mechanical testing numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

PolyPole-1: An accurate numerical algorithm for intra-granular fission gas release

引用

JOURNAL OF NUCLEAR MATERIALS 2016年第0期478卷 333-342页

作者： Pizzocri, D. Rabiti, C. Luzzi, L. Barani, T. Van Uffelen, P. Pastore, G. Politecn Milan Dept Energy Nucl Engn Div Via Masa 34 I-20156 Milan Italy Idaho Natl Lab POB 1625 Idaho Falls ID 83415 USA European Commiss Inst Transuranium Elements Joint Res Ctr POB 2340 D-76125 Karlsruhe Germany

The transport of fission gas from within the fuel grains to the grain boundaries (intra-granular fission gas release) is a fundamental controlling mechanism of fission gas release and gaseous swelling in nuclear fuel. Hence, accurate numerical solution of the corresponding mathematical problem needs to be included in fission gas behaviour models used in fuel performance codes. Under the assumption of equilibrium between trapping and resolution, the process can be described mathematically by a single diffusion equation for the gas atom concentration in a grain. In this paper, we propose a new numerical algorithm (PolyPole-1) to efficiently solve the fission gas diffusion equation in time-varying conditions. The PolyPole-1 algorithm is based on the analytic modal solution of the diffusion equation for constant conditions, combined with polynomial corrective terms that embody the information on the deviation from constant conditions. The new algorithm is verified by comparing the results to a finite difference solution over a large number of randomly generated operation histories. Furthermore, comparison to state-of-the-art algorithms used in fuel performance codes demonstrates that the accuracy of PolyPole-1 is superior to other algorithms, with similar computational effort. Finally, the concept of PolyPole-1 may be extended to the solution of the general problem of intra-granular fission gas diffusion during non-equilibrium trapping and resolution, which will be the subject of future work. Published by Elsevier B.V.

关键词： Diffusion Nuclear fuel modelling Intra-granular fission gas release numerical algorithms Modal methods FORMAS URGAS PolyPole

来源：评论

学校读者我要写书评

暂无评论

numerical simulations and modeling of the effective plastic flow surface of a biporous material with pressurized intergranular voids

引用

COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2017年第Aug.15期323卷 174-201页

作者： Boittin, Guylaine Vincent, Pierre-Guy Moulinec, Herve Garajeu, Mihai Inst Radioprotect & Surete Nucl BP 3 F-13115 St Paul Les Durance France Aix Marseille Univ CNRS Cent Marseille LMAUPR 7051 F-13402 Marseille 20 France IRSN CNRS UM Lab Micromecan & Integrite Struct BP 3 F-13115 St Paul Les Durance France

This study is devoted to the effective plastic flow surface of a biporous polycrystalline material, with an intragranular porosity due to spherical voids, and an intergranular porosity due to larger elongated voids along the grain boundaries. These two populations of voids (or bubbles) with well separated scales and shapes are saturated by a fluid and therefore are subjected to internal pressures. The effect of the intragranular voids is modeled through a GTN (Gurson Tvergaard Needleman) criterion in the matrix. numerical simulations are performed with a EFT-based (Fast Fourier Transforms) method. Particular attention is paid to the effect of the distribution of the intergranular bubbles on the effective plastic flow surface. Different microstructures with different volume fractions and sizes for the intergranular bubbles are tested under three loading conditions (the mean size of the grains being fixed). Two main results are exhibited. First, it is shown that the effect of the relative size of the intergranular bubbles on the effective plastic flow surface depends on the loading direction. Secondly, a comparison is made with the analytical model of (Vincent et al., 2014) and a correction of the porosity relative to the intergranular bubbles is introduced in this analytical model in order to take into account the specific distribution of the intergranular bubbles along the grain boundaries. This correction is expressed as a sum of two power law functions, each of them being significant either for low or for large values of the porosity of intergranular bubbles. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Porous materials Effective plastic flow surface Micromechanical models Intergranular cavities Microstructures numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

A DISTRIBUTION FUNCTION FROM POPULATION GENETICS STATISTICS USING STIRLING NUMBERS OF THE FIRST KIND: ASYMPTOTICS, INVERSION AND numerical EVALUATION

引用

MATHEMATICS OF COMPUTATION 2022年第334期91卷 871-885页

作者： Chen, Swaine L. Temme, Nico M. Natl Univ Singapore Yong Loo Bin Sch Med Infect Dis Translat Res Programme Singapore 119228 Singapore Natl Univ Singapore Yong Loo Bin Sch Med Dept Med Div Infect Dis Singapore 119228 Singapore Genome Inst Singapore Lab Bacterial Genom Singapore 138672 Singapore Ctr Wiskunde & Informat CWI Sci Pk 123 NL-1098 XG Amsterdam Netherlands

Stirling numbers of the first kind are common in number theory and combinatorics;through Ewen's sampling formula, these numbers enter into the calculation of several population genetics statistics, such as Fu's F-s. In previous papers we have considered an asymptotic estimator for a finite sum of Stirling numbers, which enables rapid and accurate calculation of Fu's *** sums can also be viewed as cumulative distribution functions, leading directly to the possibility of an inversion function, where, given a value for Fu's F-s, the goal is to solve for one of the input parameters. We solve this inversion using Newton iteration for small parameters. For large parameters, we have to extend our earlier obtained asymptotic results to solve the inversion problem asymptotically. numerical experiments are given to show the efficiency of both solving the inversion problem and the expanded asymptotic estimator for sums of Stirling numbers.

关键词： Stirling numbers of the first kind asymptotic analysis population genetics statistics evolutionary inference from sequence alignments numerical algorithms cumulative distribution function

来源：评论

学校读者我要写书评

暂无评论

numerical INVESTIGATION OF SUBSONIC AND SUPERSONIC ASYMMETRIC VORTICAL FLOW

引用

AIAA JOURNAL 1993年第8期31卷 1377-1383页

作者： VANDEN, KJ BELK, DM Wright Laboratory Armament Directorate Eglin Air Force Base Florida 32542

The high angle of attack flow about a slender body in supersonic and subsonic flow was computed for an angle of attack of 38.5 deg to study the phenomena associated with vortex asymmetry. A laminar thin-layer Navier-Stokes algorithm was used to determine whether vortex asymmetry in numerical computations is the result of a numerically induced perturbation or a property of the governing equations. The fully upwind code used in this study was symmetric in the crossflow plane to 12 orders of magnitude, the level of roundoff error on the Cray Y-MP. It was found that, with a completely symmetric grid and algorithm with respect to the crossflow plane, a bump was needed to perturb the flow to asymmetry. When the bump was taken away, the flow returned to a symmetric state. This corroborates the previous assertion of other investigators that vortex asymmetry at high angles of attack on slender bodies is due lo a convective instability.

关键词： Vortices Angle of Attack Supersonic Flow Computational Fluid Dynamics No Slip Condition Ogive Cylinder Air to Air Missiles Atmospheric Flight Mechanics Finite Volume Formulation numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

numerical Approximations of the Riemann-Liouville and Riesz Fractional Integrals

引用

INFORMATICA 2024年第1期35卷 21-46页

作者： Ciesielski, Mariusz Grodzki, Grzegorz Czestochowa Tech Univ Dept Comp Sci Dabrowskiego 73 PL-42200 Czestochowa Poland

In this paper, the numerical algorithms for calculating the values of the left- and rightsided Riemann-Liouville fractional integrals and the Riesz fractional integral using spline interpolation techniques are derived. The linear, quadratic and three variants of cubic splines are taken into account. The estimation of errors using analytical methods are derived. We show four examples of numerical evaluation of the mentioned fractional integrals and determine the experimental rate of convergence for each derived algorithm. The high -precision calculations are executed using the 128 -bit floating-point numbers and arithmetic routines.

关键词： fractional calculus numerical integration numerical algorithms spline interpolation

来源：评论

学校读者我要写书评

暂无评论

General numerical scheme for heat exchanger thermal analysis and design

引用

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION 1997年第4期5卷 231-242页

作者： Ribando, RJ OLeary, GW CarlsonSkalak, S UNIV VIRGINIA SCH ENGN & APPL SCIDEPT MECH AEROSP & NUCL ENGNCHARLOTTESVILLEVA 22903

This article describes two personal computer-based teaching modules designed to instruct engineering students in the more fundamental thermal aspects of the analysis and design of heat exchangers. One module apples to shell-and-tube exchangers;the other applies to cross-flow types. Enhanced numerical algorithms solve discretized forms of the governing differential energy-conservation equations. Graphical user interfaces display temperature distributions along with traditional design and performance measures. (C) 1997 John Wiley & Sons, Inc.

关键词： heat exchangers engineering education design performance numerical algorithms graphical user interface

来源：评论

学校读者我要写书评

暂无评论

numerical-SOLUTION OF LINEAR LEAST-SQUARES PROBLEMS WITH LINEAR EQUALITY CONSTRAINTS

引用

JOURNAL OF OPTIMIZATION THEORY AND APPLICATIONS 1990年第1期65卷 67-83页

作者： LARATTA, A ZIRONI, F 1. Department of Pure and Applied Mathematics University of Modena Modena Italy 2. Pisa Italy

In Ref. 1, a perturbation theory for the linear least-squares problem with linear equality constraints is presented. In this paper, the condition numbers of a general formula given in Ref. 1 are examined in order to compare them with the condition numbers of the two matrices of the problem. A class of test problems is also defined to study experimentally the numerical stability of three algorithms.

关键词： Least-squares problems numerical algorithms error analysis constrained optimization

来源：评论

学校读者我要写书评

暂无评论

numerical implementation of non-local polycrystal plasticity using fast Fourier transforms

引用

JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2016年 97卷 333-351页

作者： Lebensohn, Ricardo A. Needleman, Alan Los Alamos Natl Lab Mat Sci & Technol Div MS G755 Los Alamos NM 87845 USA Texas A&M Univ Dept Mat Sci & Engn College Stn TX 77843 USA

We present the numerical implementation of a non-local polycrystal plasticity theory using the FFT-based formulation of Suquet and co-workers. Gurtin (2002) non-local formulation, with geometry changes neglected, has been incorporated in the EVP-FFT algorithm of Lebensohn et al. (2012). numerical procedures for the accurate estimation of higher order derivatives of micromechanical fields, required for feedback into single crystal constitutive relations, are identified and applied. A simple case of a periodic laminate made of two fcc crystals with different plastic properties is first used to assess the soundness and numerical stability of the proposed algorithm and to study the influence of different model parameters on the predictions of the non-local model. Different behaviors at grain boundaries are explored, and the one consistent with the micro-clamped condition gives the most pronounced size effect. The formulation is applied next to 3-D fcc polycrystals, illustrating the possibilities offered by the proposed numerical scheme to analyze the mechanical response of polycrystalline aggregates in three dimensions accounting for size dependence arising from plastic strain gradients with reasonable computing times. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Crystal plasticity Non-local plasticity Polycrystalline material Spectral methods numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

Resiliency in numerical algorithm design for extreme scale simulations

引用

INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS 2022年第2期36卷 251-285页

作者： Agullo, Emmanuel Altenbernd, Mirco Anzt, Hartwig Bautista-Gomez, Leonardo Benacchio, Tommaso Bonaventura, Luca Bungartz, Hans-Joachim Chatterjee, Sanjay Ciorba, Florina M. DeBardeleben, Nathan Drzisga, Daniel Eibl, Sebastian Engelmann, Christian Gansterer, Wilfried N. Giraud, Luc Goddeke, Dominik Heisig, Marco Jezequel, Fabienne Kohl, Nils Li, Xiaoye Sherry Lion, Romain Mehl, Miriam Mycek, Paul Obersteiner, Michael Quintana-Orti, Enrique S. Rizzi, Francesco Ruede, Ulrich Schulz, Martin Fung, Fred Speck, Robert Stals, Linda Teranishi, Keita Thibault, Samuel Thoennes, Dominik Wagner, Andreas Wohlmuth, Barbara INRIA Sophia Antipolis France Univ Stuttgart Stuttgart Germany KIT Karlsruher Inst Technol Karlsruhe Germany Barcelona Supercomp Ctr Barcelona Spain Politecn Milan Milan Italy Tech Univ Munich Munich Germany NVIDIA Corp Santa Clara CA USA Univ Basel Basel Switzerland Los Alamos Natl Lab Los Alamos NM USA Univ Erlangen Nurnberg Nurnberg Germany Oak Ridge Natl Lab Oak Ridge TN USA Univ Vienna Vienna Austria Univ Paris 2 Paris France Lawrence Berkeley Natl Lab Berkeley CA USA Univ Bordeaux Bordeaux France CERFACS Toulouse France Univ Politecn Valencia Valencia Spain NexGen Analyt Sheridan WY USA Australian Natl Univ Canberra ACT Australia Forschungszentrum Julich Julich Germany Sandia Natl Labs Livermore CA 94550 USA

This work is based on the seminar titled 'Resiliency in numerical Algorithm Design for Extreme Scale Simulations' held March 1-6, 2020, at Schloss Dagstuhl, that was attended by all the authors. Advanced supercomputing is characterized by very high computation speeds at the cost of involving an enormous amount of resources and costs. A typical large-scale computation running for 48 h on a system consuming 20 MW, as predicted for exascale systems, would consume a million kWh, corresponding to about 100k Euro in energy cost for executing 10(23) floating-point operations. It is clearly unacceptable to lose the whole computation if any of the several million parallel processes fails during the execution. Moreover, if a single operation suffers from a bit-flip error, should the whole computation be declared invalid? What about the notion of reproducibility itself: should this core paradigm of science be revised and refined for results that are obtained by large-scale simulation? Naive versions of conventional resilience techniques will not scale to the exascale regime: with a main memory footprint of tens of Petabytes, synchronously writing checkpoint data all the way to background storage at frequent intervals will create intolerable overheads in runtime and energy consumption. Forecasts show that the mean time between failures could be lower than the time to recover from such a checkpoint, so that large calculations at scale might not make any progress if robust alternatives are not investigated. More advanced resilience techniques must be devised. The key may lie in exploiting both advanced system features as well as specific application knowledge. Research will face two essential questions: (1) what are the reliability requirements for a particular computation and (2) how do we best design the algorithms and software to meet these requirements? While the analysis of use cases can help understand the particular reliability requirements, the construction of remedies is

关键词： numerical algorithms parallel computer architecture fault tolerance resilience

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：