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An Algebraic Multigrid-Based Physical Factorization Preconditioner for the Multi-Group Radiation Diffusion Equations in Three Dimensions

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Numerical Mathematics(Theory,Methods and Applications) 2023年第2期16卷 410-432页

作者： Xiaoqiang Yue Zekai Zhang Xiaowen Xu Shuying Zhai Shi Shu National Center for Applied Mathematics in Hunan Key Laboratory of Intelligent Computing&Information Processing of Ministry of EducationHunan Key Laboratory for Computation and Simulation in Science and EngineeringXiangtan UniversityXiangtan 411105China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100094China School of Mathematical Sciences Huaqiao UniversityQuanzhou 362021China.

The paper investigates the robustness and parallel scaling properties of a novel physical factorization preconditioner with algebraic multigrid subsolves in the iterative solution of a cell-centered finite volume discretization of the threedimensional multi-group radiation diffusion *** key idea is to take advantage of a particular kind of block factorization of the resulting system matrix and approximate the left-hand block matrix selectively spurred by parallel processing *** spectral property of the preconditioned matrix is then *** practical strategy is considered sequentially and in ***,numerical results illustrate the numerical robustness,computational efficiency and parallel strong and weak scalabilities over the real-world structured and unstructured coupled problems,showing its competitiveness with many existing block preconditioners.

关键词： Radiation diffusion equations physical factorization preconditioning algebraic multigrid parallel and distributed computing

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Design of Multi-Coupled Laminates with Extension-Twisting Coupling for Application in Adaptive Structures

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Computer Modeling in engineering & sciences 2022年第1期130卷 415-441页

作者： Da Cui Daokui Li Shiming Zhou College of Aerospace Science and Engineering National University of Defense TechnologyChangsha410073China Hunan Key Laboratory of Intelligent Planning and Simulation for AerospaceMissions Changsha410073China

The multiple coupling of composite laminates has a unique advantage in improving the macro mechanical properties of composite structures.A total of three hygro-thermally stablemulti-coupled laminates with extensiontwisting coupling were presented,which were conducive to the formation of passive adaptive ***,the multi-coupled laminates were used to design the bending-twisting coupled box structure,in which the configuration of laminate and box structure could be extended to variable cross-section *** optimal design of stacking sequence was realized,the optimization objectives of which were to maximize bending-twisting coupling of box structure and extension-twisting coupling of laminate,*** effects of multiple coupling on hygro-thermal stability,coupling,failure strength,buckling load,robustness and other comprehensive mechanical properties of laminates and box structures were analyzed by parametric modeling *** results show that the extension-twisting coupling of laminate and the bending-twisting coupling of box structures can be greatly improved by 450%and 260%at maximum,***,it would have a negative impact on the failure strength and buckling load,which,however,can be minimized by a reasonable paving *** laminates have good robustness,and the bending-twisting coupling helps improve ***,the hygro-thermal stability and mechanical properties were verified by numerical simulation with finite element method.

关键词： Multi-coupled laminate passive adaptive structures optimal design mechanical properties numerical simulation

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Shock wave and bubble characteristics of underwater array explosion of charges

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Defence Technology（防务技术） 2022年第8期18卷 1445-1453页

作者： Hong-Wei Hu Pu Song Shuang-feng Guo Hai-yun Feng Dao-kui Li College of Aerospace Science and Engineering National University of Defense TechnologyChangsha410073HunanChina Xi'an Modern Chemistry Research Institute Xi'an710065ShaanxiChina Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Changsha410073HunanChina

In this study, we focused on the effect of the underwater explosion parameters of multi-point array explosion. The shock wave and bubble parameters of aggregate charge, two charges, and four charges were measured through an underwater explosion test, and their influence on the explosion power field of charge quantity and array distance was analyzed. Results show that the multi-shock wave collision of array explosion can be approximated to a linear superposition, and the interaction of delayed shock wave can be deemed as the increase of the shock wave baseline. Shock wave focusing and delayed superposition increase the shock wave peak pressure. Compared with the aggregate charge, the greater the number of array explosion points is, the higher the impulse and the gain of the bubble peak pressure are. At the same array distance, the smaller the charge quantity is, the higher the bubble impulse will be. At the same charge quantity, the smaller the array distance is, the higher the bubble impulse will be. The bubble period decreases gradually with the increase of the charge quantity, but the test orientation has little effect on the bubble period.

关键词： Explosion mechanics Underwater explosion Array explosion Shock waveBubble

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Spectral Galerkin Approximation of Fractional Optimal Control Problems with Fractional Laplacian

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Advances in Applied Mathematics and Mechanics 2023年第6期15卷 1631-1654页

作者： Jiaqi Zhang Yin Yang Zhaojie Zhou School of Mathematics and Computational Science Xiangtan UniversityHunan Key Laboratory for Computation and Simulation in Science and EngineeringKey Laboratory of Intelligent Computing and Information Processing of Ministry of EducationXiangtan 411105HunanChina School of Mathematics and Computational Science Xiangtan UniversityNational Center for Applied Mathematics in HunanHunan International Scientific and Technological Innovation Cooperation Base of Computational ScienceXiangtan 411105HunanChina School of Mathematics and Statistics Shandong Normal UniversityJinan 250014ShandongChina

In this paper spectral Galerkin approximation of optimal control problem governed by fractional elliptic equation is *** deal with the nonlocality of fractional Laplacian operator the Caffarelli-Silvestre extension is *** first order optimality condition of the extended optimal control problem is derived.A spectral Galerkin discrete scheme for the extended problem based on weighted Laguerre polynomials is developed.A priori error estimates for the spectral Galerkin discrete scheme is *** experiments are presented to show the effectiveness of our methods and to verify the theoretical findings.

关键词： Fractional Laplacian optimal control problem Caffarelli-Silvestre extension weighted Laguerre polynomials

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A review of space-object collision probability computation methods

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Astrodynamics 2022年第2期6卷 95-120页

作者： Jia-Sheng Li Zhen Yang Ya-Zhong Luo College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Changsha 410073China

The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision *** works mainly relied on Monte Carlo simulations to predict collision *** such simulations are accurate when a large number of samples are used,these methods are perceived as computationally intensive,which limits their application in *** overcome this limitation,many approximation methods have been developed over the past three *** paper presents a comprehensive review of existing space-object collision probability computation *** advantages and limitations of different methods are analyzed and a systematic comparison is *** regarding how to select a suitable method for different short-term encounter scenarios is then ***,potential future research avenues are discussed.

关键词： collision probability space situational awareness collision avoidance astrodynamics

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A Task Allocation Algorithm of Loitering Munition Group for Regional Blockade Based on Event-Driven 1

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3rd International Conference on Autonomous Unmanned Systems, ICAUS 2023

作者： Zhu, Yunchong Li, Kebo Liu, Yuanhe Liang, Yan’gang College of Aerospace Science and Engineering National University of Defense Technology Changsha410073 China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Mission Changsha410073 China

ISBN: (数字)9789819710874

ISBN: (纸本)9789819710867

Propose an event-driven online task allocation algorithm to solve the problem of online task allocation for the Loitering Munition Group, which has no information about any targets in operational area. Firstly, analyzing the properties of enemy and friendly equipment in typical regional blockade operations and designing the process of unknown regional blockade operations. Secondly, propose the concept of "benefit-cost ratio" to drive the dynamic scrolling of the task allocation window, and achieve a fast response to sudden events such as new target appearance or projectile damage execution, and timely adjust the task allocation plan. Then, construct a simulation system for the Loitering Munition Group's regional blockade operation, conduct Monte Carlo simulation to verify the effectiveness and reliability of the online task allocation method. © Beijing HIWING Scientific and Technological Information Institute 2024.

关键词： Monte Carlo methods

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APF-Based Control for On-Orbit Swarm Guard Against Multiple Threat Targets 7th

APF-Based Control for On-Orbit Swarm Guard Against Multiple ...

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7th Chinese Conference on Swarm Intelligence and Cooperative Control, CCSICC 2023

作者： Wang, Hanwei Zhang, Jiacheng Zhu, Yuehe Luo, Yazhong Jin, Ke Zhang, Yu Fu, Lifeng College of Aerospace Science and Engineering National University of Defense Technology Changsha410073 China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Changsha410073 China

ISBN: (纸本)9789819733279

With the number of satellites and space debris growing fast, it is significant to develop a swarm-to-swarm defense method to protect the on-orbit high value spacecraft. In order to solve the difficulties of swarm assignment combinations, unpredictable threat target maneuvers, non-Euclidean dynamics, and real-time control requirements, a novel method mainly based on Hungarian algorithm and artificial potential fields is proposed. The method involves rapidly searching the one-to-one mission assignment scheme and generating control laws of defenders in real time. Both a positive and a conservative defend strategy are proposed. Case studies show that the computation time of the instantaneous target assignment and control scheme is 0.08 ms. When defenders are not less than threat targets and their maneuverability are the same, the interception number is 100%. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Space debris

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Spring pair method of finding saddle points using the minimum energy path as a compass

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Physical Review E 2024年第6期110卷 064123-064123页

作者： Gang Cui Kai Jiang Hunan Key Laboratory for Computation and Simulation in Science and Engineering Key Laboratory of Intelligent Computing and Information Processing of Ministry of Education School of Mathematics and Computational Science Xiangtan University Xiangtan Hunan 411105 China

Finding index-1 saddle points is crucial for understanding phase transitions. In this work, we propose a simple yet efficient approach, the spring pair method (SPM), to accurately locate saddle points. Without requiring the Hessian information, the SPM evolves a single pair of spring-coupled particles on an energy surface. By designing complementary drifting and climbing dynamics based on gradient decomposition, the spring pair converges onto the minimum energy path (MEP) and spontaneously aligns its orientation with the MEP tangent, providing a reliable ascent direction for efficient convergence to saddle points. The SPM fundamentally differs from traditional surface walking methods that rely on the eigenvectors of the Hessian, which may deviate from the MEP tangent and potentially lead to convergence failure or undesired saddle points. The efficiency of the SPM for finding saddle points is verified by ample examples, including Lennard-Jones clusters, Morse clusters, water clusters, and the Landau energy functional involving quasicrystal phase transitions.

关键词： Lennard-Jones potential

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Divergence-Free Virtual Element Method for the Stokes Equations with Damping on Polygonal Meshes

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Numerical Mathematics(Theory,Methods and Applications) 2024年第1期17卷 210-242页

作者： Yu Xiong Yanping Chen Jianwei Zhou Qin Liang School of Mathematics and Computational Science Hunan Key Laboratory for Computation and Simulation in Science and EngineeringXiangtan UniversityXiangtan 411105P.R.China School of Mathematics and Statistics Linyi University Linyi 276005P.R.China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631P.R.China

In this paper,we construct,analyze,and numerically validate a family of divergence-free virtual elements for Stokes equations with nonlinear damping on polygonal *** virtual element method is H1-conforming and exact *** virtue of these properties and the topological degree argument,we rigorously prove the well-posedness of the proposed discrete *** con-vergence analysis is carried out,which imply that the error estimate for the velocity in energy norm does not explicitly depend on the *** experiments on various polygonal meshes validate the accuracy of the theoretical analysis and the asymptotic pressure robustness of the proposed scheme.

关键词： Optimal error estimates divergence-free virtual element nonlinear damping term.

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A Reinforcement Learning Method to Trajectory Design for Manned Lunar Mission via Reshaping Rewards

A Reinforcement Learning Method to Trajectory Design for Man...

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International Conference on Guidance, Navigation and Control, ICGNC 2022

作者： Yang, Luyi Li, Haiyang Li, Xingyong Li, Zeyue Lu, Lin College of Aerospace Science and Engineering National University of Defense Technology Changsha410073 China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Hunan Changsha410073 China

ISBN: (纸本)9789811966125

This paper applies the reinforcement learning (RL) to multi-stage impulsive trajectory design of the manned lunar mission. The manned spacecraft is modeled as the agent and the nonlinear dynamics in the cislunar space is the interaction environment of the agent. Then the Markov decision model is mathematically built for the spacecraft and the optimization goal is to minimize the total impulses in the whole mission. The Q-learning method is used to learn the optimal policy and to better train the agent to explore and exploit the environment, a reshaping reward is designed to improve the convergency and effectiveness of the algorithm. Numerical results give the integrated designs of the lunar transfer orbit, Earth transfer orbit and three-impulsive lunar injection/ejection orbit. The proposed reshaping reward function shows better performance compared with the non-reshaping reward. The conclusions could provide a reference for China’s future manned lunar project. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Reinforcement learning

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