最优Steiner树问题(Steiner tree problem,STP)是一个经典的组合优化问题,许多工程问题都可以归结为最优Steiner树问题。STP被广泛应用于通信网络、电路设计、VLSI设计等领域。然而,STP是典型的NP难问题,还没有多项式时间的精确算法求...最优Steiner树问题(Steiner tree problem,STP)是一个经典的组合优化问题,许多工程问题都可以归结为最优Steiner树问题。STP被广泛应用于通信网络、电路设计、VLSI设计等领域。然而,STP是典型的NP难问题,还没有多项式时间的精确算法求解该问题。目前,求解该问题的算法主要集中在基于启发式的近似算法、智能优化算法、信息传播算法等,并取得了很好的效果。在不同规模的网络中,基于传统遗传算法给出一种叶交叉机制(leaf crossover,LC),使用该机制的算法性能表现更好。通过对这些算法的原理、性能、精度等方面进行梳理,归纳出算法的优缺点,并指出STP的研究方向和算法设计路径,对于相关问题的研究有指导意义。展开更多
针对一类广泛存在的分布式流水线和车辆运输集成调度问题(Distributed Permutation Flow-shop and Vehicle Transportation Integrated Scheduling Problem,DPFVTISP),本文建立问题模型,并提出一种超启发式三维分布估计算法(Hyper-Heuri...针对一类广泛存在的分布式流水线和车辆运输集成调度问题(Distributed Permutation Flow-shop and Vehicle Transportation Integrated Scheduling Problem,DPFVTISP),本文建立问题模型,并提出一种超启发式三维分布估计算法(Hyper-Heuristic three-Dimensional Estimation of Distribution Algorithm,HH3DEDA)进行求解.首先,根据DPFVTISP的问题特性,采用贪婪策略设计一种新颖的编解码规则.其次,为实现对DPFVTISP问题解空间中不同区域的深入搜索,设计10种低层启发式操作(即10种有效的邻域操作),并将其所构成的排列作为高层个体;同时在高层采用三维分布估计算法(three-Dimensional Estimation of Distribution Algorithm,3DEDA)学习和积累优质高层个体中块结构及其位置信息,再通过采样3DEDA中的概率模型生成新的高层个体或排列;进而在低层将高层所生成的每个新个体所表征的一系列有序的启发式操作作为一种新的启发式算法,对问题解空间执行较深入的邻域搜索.最后,通过仿真实验与算法对比验证HH3DEDA可有效求解DPFVTISP.展开更多
By avoiding or reducing the production of waste, waste minimization is an effective approach to solve the pollution problem in chemical industry. Process integration supported by multi-objective optimization provides ...By avoiding or reducing the production of waste, waste minimization is an effective approach to solve the pollution problem in chemical industry. Process integration supported by multi-objective optimization provides a framework for process design or process retrofit by simultaneously optimizing on the aspects of environment and economics. Multi-objective genetic algorithm is applied in this area as the solution approach for the multi-objective optimization problem.展开更多
In the present research, artificial artificial networks hare be applied to establish the constitutive rela- tionship model of Ti - 5Al - 2Sn - 2Zr - 4Mo - 4Cr (wt - % ) alloy. In the first stage of the re- search...In the present research, artificial artificial networks hare be applied to establish the constitutive rela- tionship model of Ti - 5Al - 2Sn - 2Zr - 4Mo - 4Cr (wt - % ) alloy. In the first stage of the re- search, an isothermal compressive experiment using Thermecmastor - Z hot simulator is studied to ac- quire the flow stress at different deformation temperature,equivalent strain and equivalent strain rate. Then,a feed - forward neural network is trained by using the experimental data.After the training process is finished, the neural networks become a knowledge-based constitutive relationship system. Comparison of the predicted and experimental results results shows that the neural network model has good le- arning precision and good generalization.The neural neural network methods are found to show much better agreement than existing methods with the experiment data, and have the advantage of being able to deal with noisy for or data with strong non - linear reationships. At last, this model can be aused to simulate the flow behavior of Ti - 5Al - 2Sn - 2Zr - 4Mo - 4Ca alloy.展开更多
Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is su...Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is suitable for parallel computing. In this paper, a static load balance parallel method is presented by combining Message Passing Interface (MPI) with Adaptively Modified CBFM (AMCBFM). In this method, the object geometry is partitioned into distinct blocks, and the serial number of blocks is sent to related nodes according to a certain rule. Every node only needs to calculate the information on local blocks. The obtained results confirm the accuracy and efficiency of the proposed method in speeding up solving large electrical scale problems.展开更多
In order to ensure the reliability of network-on-chip （NoC） under faulty circumstance, a dynamic fault tolerant routing algorithm is proposed. This algorithm can implement detour routing when there are both static a...In order to ensure the reliability of network-on-chip （NoC） under faulty circumstance, a dynamic fault tolerant routing algorithm is proposed. This algorithm can implement detour routing when there are both static and dynamic permanent faults in the network. That means the packet is able to move around the fanlts to the destination with a non-minimum path. In addition, the multi-level congestion control mechanism gives the algorithm the ability to distribute the load over the whole network and to avoid hotspots around the faults. Simulation results demonstrate the advantage of the proposed routing algorithm in terms of average packet latency and packet loss rate compared with negative-first routing algo- rithm and DyAD routing algorithm in the presence of permanent faults. For the proposed algorithm, it can get much less average packet latency and lead to less than 20% packet loss rate.展开更多
Considering multiplicative Schwarz algorithm for solving algebraic obstacle problems, we show the geometric convergence of the algorithm by the use of discrete maximum principle. We also get a decay rate bound indepen...Considering multiplicative Schwarz algorithm for solving algebraic obstacle problems, we show the geometric convergence of the algorithm by the use of discrete maximum principle. We also get a decay rate bound independent of the meshsize for the iterative error and illustrate the method by some numerical experiments.展开更多
文摘最优Steiner树问题(Steiner tree problem,STP)是一个经典的组合优化问题,许多工程问题都可以归结为最优Steiner树问题。STP被广泛应用于通信网络、电路设计、VLSI设计等领域。然而,STP是典型的NP难问题,还没有多项式时间的精确算法求解该问题。目前,求解该问题的算法主要集中在基于启发式的近似算法、智能优化算法、信息传播算法等,并取得了很好的效果。在不同规模的网络中,基于传统遗传算法给出一种叶交叉机制(leaf crossover,LC),使用该机制的算法性能表现更好。通过对这些算法的原理、性能、精度等方面进行梳理,归纳出算法的优缺点,并指出STP的研究方向和算法设计路径,对于相关问题的研究有指导意义。
文摘针对一类广泛存在的分布式流水线和车辆运输集成调度问题(Distributed Permutation Flow-shop and Vehicle Transportation Integrated Scheduling Problem,DPFVTISP),本文建立问题模型,并提出一种超启发式三维分布估计算法(Hyper-Heuristic three-Dimensional Estimation of Distribution Algorithm,HH3DEDA)进行求解.首先,根据DPFVTISP的问题特性,采用贪婪策略设计一种新颖的编解码规则.其次,为实现对DPFVTISP问题解空间中不同区域的深入搜索,设计10种低层启发式操作(即10种有效的邻域操作),并将其所构成的排列作为高层个体;同时在高层采用三维分布估计算法(three-Dimensional Estimation of Distribution Algorithm,3DEDA)学习和积累优质高层个体中块结构及其位置信息,再通过采样3DEDA中的概率模型生成新的高层个体或排列;进而在低层将高层所生成的每个新个体所表征的一系列有序的启发式操作作为一种新的启发式算法,对问题解空间执行较深入的邻域搜索.最后,通过仿真实验与算法对比验证HH3DEDA可有效求解DPFVTISP.
文摘By avoiding or reducing the production of waste, waste minimization is an effective approach to solve the pollution problem in chemical industry. Process integration supported by multi-objective optimization provides a framework for process design or process retrofit by simultaneously optimizing on the aspects of environment and economics. Multi-objective genetic algorithm is applied in this area as the solution approach for the multi-objective optimization problem.
文摘In the present research, artificial artificial networks hare be applied to establish the constitutive rela- tionship model of Ti - 5Al - 2Sn - 2Zr - 4Mo - 4Cr (wt - % ) alloy. In the first stage of the re- search, an isothermal compressive experiment using Thermecmastor - Z hot simulator is studied to ac- quire the flow stress at different deformation temperature,equivalent strain and equivalent strain rate. Then,a feed - forward neural network is trained by using the experimental data.After the training process is finished, the neural networks become a knowledge-based constitutive relationship system. Comparison of the predicted and experimental results results shows that the neural network model has good le- arning precision and good generalization.The neural neural network methods are found to show much better agreement than existing methods with the experiment data, and have the advantage of being able to deal with noisy for or data with strong non - linear reationships. At last, this model can be aused to simulate the flow behavior of Ti - 5Al - 2Sn - 2Zr - 4Mo - 4Ca alloy.
文摘Characteristic Basis Function Method (CBFM) is a novel approach for analyzing the ElectroMagnetic (EM) scattering from electrically large objects. Based on dividing the studied object into small blocks, the CBFM is suitable for parallel computing. In this paper, a static load balance parallel method is presented by combining Message Passing Interface (MPI) with Adaptively Modified CBFM (AMCBFM). In this method, the object geometry is partitioned into distinct blocks, and the serial number of blocks is sent to related nodes according to a certain rule. Every node only needs to calculate the information on local blocks. The obtained results confirm the accuracy and efficiency of the proposed method in speeding up solving large electrical scale problems.
基金Supported by the National High Technology Research and Development Program of China (863 Program) (2002AA1Z149)
文摘In order to ensure the reliability of network-on-chip （NoC） under faulty circumstance, a dynamic fault tolerant routing algorithm is proposed. This algorithm can implement detour routing when there are both static and dynamic permanent faults in the network. That means the packet is able to move around the fanlts to the destination with a non-minimum path. In addition, the multi-level congestion control mechanism gives the algorithm the ability to distribute the load over the whole network and to avoid hotspots around the faults. Simulation results demonstrate the advantage of the proposed routing algorithm in terms of average packet latency and packet loss rate compared with negative-first routing algo- rithm and DyAD routing algorithm in the presence of permanent faults. For the proposed algorithm, it can get much less average packet latency and lead to less than 20% packet loss rate.
基金This research is supported by the National Natural Science Foundation of China and LSEC.
文摘Considering multiplicative Schwarz algorithm for solving algebraic obstacle problems, we show the geometric convergence of the algorithm by the use of discrete maximum principle. We also get a decay rate bound independent of the meshsize for the iterative error and illustrate the method by some numerical experiments.
