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Implementation of an algorithm for general material behavior of steel taking interaction between plasticity and transformation-induced plasticity into account

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INTERNATIONAL JOURNAL FOR numerical METHODS IN ENGINEERING 2011年第12期87卷 1183-1206页

作者： Wolff, Michael Boehm, Michael Mahnken, Rolf Suhr, Bettina Univ Bremen Zentrum Technomath D-2800 Bremen 33 Germany Univ Paderborn Chair Engn Mech Paderborn Germany

In this article a semi-implicit algorithm (predictor-corrector approach) for incorporating the interaction between plasticity and transformation-induced plasticity (TRIP) in steel is developed. Contrary to the usual elasto-plasticity, the underlying model of material behavior of steel is far more complex. The interaction between plasticity and TRIP requires extensions of algorithms developed in Doghri (Int. J. Numer. Meth. Engng 1993;36: 3915-3932) and in Mahnken (Commun. Numer. Meth. Engng 1999;15: 745-754). A particular feature of the algorithm is that the inner iteration can be reduced to a single scalar equation. numerical examples illustrate the algorithm's capabilities. Copyright (C) 2011 John Wiley & Sons, Ltd.

关键词： numerical algorithm steel non-linear isotropic and kinematic hardening interaction between plasticity and TRIP

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The Dissection algorithm for the Second-Born Self-Energy

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PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2019年第7期256卷

作者： Perfetto, Enrico Stefanucci, Gianluca CNR ISM Div Ultrafast Proc Mat FLASHit Area Ric Roma 1 Monterotondo Italy Univ Roma Tor Vergata Dipartimento Fis Via Ricerca Sci I-00133 Rome Italy INFN Sez Roma Tor Vergata Via Ric Sci 1 I-00133 Rome Italy

Here, an algorithm to efficiently compute the second-Born self-energy of many-body perturbation theory is described. The core idea consists in dissecting the set of all four-index Coulomb integrals into properly chosen subsets, thus avoiding to loop over those indices for which the Coulomb integrals are zero or negligible. The scaling properties of the algorithm with the number of basis functions is discussed. The computational gain is demonstrated in the case of one-particle Kohn-Sham basis for organic molecules.

关键词： nonequilibrium Green's functions numerical algorithm second-Born self-energy

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Variational assimilation of observation data in the mathematical model of the Baltic Sea dynamics

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RUSSIAN JOURNAL OF numerical ANALYSIS AND MATHEMATICAL MODELLING 2015年第4期30卷 203-212页

作者： Agoshkov, Valeriy I. Parmuzin, Eugene I. Zalesny, Vladimir B. Shutyaev, Victor P. Gusev, Anatoly V. Zakharova, Natalia B. RAS Inst Numer Math Moscow 119333 Russia

A mathematical model of the dynamics of the Baltic Sea is considered. A problem of variational assimilation of sea surface temperature (SST) data is formulated and studied. Based on variational assimilation of satellite observation data, an algorithm solving the inverse problem of heat flux restoration on the interface of two media is proposed. The results of numerical experiments reconstructing the heat flux functions in the problem of variational assimilation of SST observation data are presented. The influence of SST assimilation on other hydrodynamic parameters of the model is considered.

关键词： Variational assimilation problem numerical algorithm determination of heat flux on the sea surface sea surface temperature

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Optimal control for a singularly perturbed linear stochastic system with multiplicative white noise perturbations and Markovian jumping

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OPTIMAL CONTROL APPLICATIONS & METHODS 2017年第2期38卷 205-228页

作者： Dragan, Vasile Mukaidani, Hiroaki Romanian Acad Inst Math Simion Stoilow Res Unit 2 RO-014700 Bucharest Romania Hiroshima Univ Inst Engn 1-4-1 Kagamiyama Higashihiroshima 7398527 Japan

In this study, we investigate the optimal control of a class of singularly perturbed linear stochastic systems with Markovian jumping parameters. After establishing an asymptotic structure for the stabilizing solution of the coupled stochastic algebraic Riccati equations, a parameter-independent composite controller is derived. Furthermore, the cost degradation in a reduced-order controller is discussed. Thus, the exactness of the proposed approximate control is discussed for the first time. As an additional important contribution, a numerical algorithm for solving the coupled stochastic algebraic Riccati equations is proposed, and the feature of the resulting higher-order controller is shown. Finally, a simple example is presented to demonstrate the validity of the proposed method. Copyright (c) 2016 John Wiley & Sons, Ltd.

关键词： singularly perturbed linear stochastic systems (SPLSS) Markovian jumping parameters coupled stochastic algebraic Riccati equations (CSAREs) linear quadratic optimal control numerical algorithm

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Memory-dependent derivative versus fractional derivative (I): Difference in temporal modeling

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JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2021年 384卷

作者： Wang, Jin-Liang Li, Hui-Feng Qingdao Univ Technol Coll Sci Res Inst ESMD Method & Its Applicat Qingdao 266520 Shandong Peoples R China

Since the memory-dependent derivative (MDD) was developed in 2011, it has become a new branch of Fractional Calculus which is still in the ascendant nowadays. How to understand MDD and fractional derivative (FD)? What are the advantages and disadvantages for them? How do they behave in Modeling? These questions guide going deep into the illustration of memory effect. Though the FD is defined on an interval, it mainly reflects the local change. Relative to the FD, the physical meaning of MDD is much clearer. The time-delay reflects the duration of memory effect, and the kernel function reflects the dependent weight. The results show that the MDD is more suitable for temporal modeling. In addition, a numerical algorithm for MDD is also developed here. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Memory-dependent derivative (MDD) Fractional derivative (FD) Memory effect Logistic model numerical algorithm Time-delay

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Coolant Flow Estimation in Natural Circulation BWR

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ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS 2014年第17期36卷 1949-1957页

作者： Valle-Hernandez, J. Espinosa-Paredes, G. Morales-Sandoval, J. B. Univ Nacl Autonoma Mexico Mexico City 04510 DF Mexico Univ Autonoma Metropolitana Iztapalapa Area Ingn Recursos Energet Mexico City 09340 DF Mexico

This work presents the design and implementation of an advanced controller in real time for the estimation of coolant flows through fuel assemblies about standard neutron flux strings of a boiling water reactor (BWR) reactor core cooled by natural circulating water. During all operations of a natural circulating BWR, the fuel assembly's coolant flow is one of the main variables to consider. The goal of this advanced controller is to reduce penalties associated with operation limits established due to coolant flow uncertainties. The design of the controller was based on the theory of an extended Kalman filter. The estimator flow uses the equivalent electrical model, which was developed from the analogies between electrical current and voltage with coolant flows and pressure drops. Results obtained from computer simulations indicate that the best estimations of the total core flow are possible for the natural circulating BWR.

关键词： coolant flow economic simplified boiling water reactor Kalman filter natural circulation numerical algorithm simulations

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Acceleration of DEM algorithm for quasistatic processes

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INTERNATIONAL JOURNAL FOR numerical METHODS IN ENGINEERING 2011年第7期86卷 816-828页

作者： Padbidri, Jagan M. Mesarovic, Sinisa Dj. Washington State Univ Sch Mech & Mat Engn Pullman WA 99164 USA

The discrete element method (particle dynamics) is an invaluable tool for studying the complex behavior of granular matter. Its main shortcoming is its computational intensity, arising from the vast difference between the integration time scale and the observation time scale (similar to molecular dynamics). This problem is particularly acute for macroscopically quasistatic deformation processes. We first provide the proper definition of macroscopically quasistatic processes, on the basis of dimensional analysis, which reveals that the quasistatic nature of a process is size-dependent. This result sets bounds for application of commonly used method for computational acceleration, based on superficially increased mass of particles. Next, the dimensional analysis of the governing equations motivates the separation of time scales for the numerical integration of rotations and translations. We take advantage of the existence of fast and slow variables (rotations and translations) to develop a two-timescales algorithm based on the concept of inertial manifolds suggested by Gear and Kevrekidis. The algorithm is tested on a 2D problem with axial strain imposed by rigid plates and pressure on lateral boundaries. The benchmarking against the accurate short-time step results confirms the accuracy of the new algorithm for the optimal arrangement of short- and long-time steps. The algorithm provides moderate computational acceleration. Copyright (C) 2010 John Wiley & Sons, Ltd.

关键词： particle dynamics size dependence numerical algorithm dimensional analysis inertial manifold

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Optical Mode Calculation in Large-Area Photonic Crystal Surface-Emitting Lasers

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2024年第2期16卷 1-9页

作者： Radziunas, Mindaugas Kuhn, Eduard Wenzel, Hans King, Ben Crump, Paul Weierstr Inst WIAS D-10117 Berlin Germany Ferdinand Braun Inst FBH D-12489 Berlin Germany

We discuss algorithms and numerical challenges in constructing and resolving spectral problems for photonic crystal surface-emitting lasers (PCSELs) with photonic crystal layers and large (up to several tens of mm(2)) emission areas. We show that finite difference schemes created using coarse numerical meshes provide sufficient accuracy for several major (lowest-threshold) modes of particular device designs. Our technique is applied to the example of large-area all-semiconductor PCSELs, showing how it can be used to optimize device performance.

关键词： Modeling numerical algorithm calculations PCSEL photonic crystal optical modes semiconductor diode surface-emitting laser

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Fast Generation of Attractive Trajectories for a Deficient Satellite. Application to Feedback Control Design

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IFAC Proceedings Volumes 2001年第13期34卷 693-698页

作者： Mazen Alamir Frédéric Boyer Laboratoire d'Automatique de Grenoble UMR 5528 CNRS-INPG-UJF Saint Martin d'Hères France Fax: 04 76 82 63 88 IRCCYN 1 rue de la Noë BP 92 101 44321 Nantes Cedex 3

An algorithm is proposed that enables fast generation of a trajectory that brings the state of a deficient satellite from a given initial position to the neighborhood of a final desired one. The proposed algorithm is then used to design a discrete sampling-based state feedback control. Finally, simulations are done to test the robustness of the closed loop behaviour against several configurations of uncertainties and disturbances.

关键词： Path generation Satellite in failure mode nonlinear discrete control numerical algorithm

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An inverse problem of Bilayer textile thickness determination in dynamic heat and moisture transfer

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APPLICABLE ANALYSIS 2014年第3期93卷 445-465页

作者： Xu, Dinghua Wen, Lei Xu, Boxi Zhejiang Sci Tech Univ Dept Math Zhejiang 310018 Peoples R China Fudan Univ Coll Math Sci Shanghai 200433 Peoples R China

An inverse problem of bilayer textile thickness determination in dynamic heat and moisture transfer is presented satisfying the heat-moisture comfort level of human body. Heat and mass transfer law in bilayer textiles is displayed by proving the existence and uniqueness of solution to the coupled partial differential equations with initial-boundary value conditions. The finite difference method is employed to derive the numerical solution to partial differential equations. The regularized solution of the inverse problem is reformulated into solving function minimum problem through the Tikhonov regularization method. The golden section method is applied to solve the direct search problem and achieve the optimal solution to the inverse problem. numerical algorithm and its numerical results provide theoretical explanation for textile materials research and development.

关键词： inverse problems of thickness determination numerical algorithm well-posedness partial differential equations of parabolic type bilayer textile materials regularized solution

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