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求解多约束离散变量结构拓扑优化的序列保守近似整数规划算法
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作者 孙凯 程耿东 +1 位作者 张凯庆 梁缘 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2024年第1期138-154,共17页
序列近似整数规划方法通过求解一系列可分离的近似整数规划子问题成功求解多类大规模拓扑优化问题.然而,这些近似子问题的解析求解依靠正则松弛算法,正则松弛算法要求子问题必须由二次或线性的目标函数以及线性的约束函数构成.同时,序... 序列近似整数规划方法通过求解一系列可分离的近似整数规划子问题成功求解多类大规模拓扑优化问题.然而,这些近似子问题的解析求解依靠正则松弛算法,正则松弛算法要求子问题必须由二次或线性的目标函数以及线性的约束函数构成.同时,序列近似整数规划方法依赖于体分比下降策略,这使得其难以处理不包含体分比约束的拓扑优化问题.为进一步地完善序列近似整数规划算法,我们受移动渐近线方法的启发,引入经典的序列保守近似规划,以获得一系列可行性稳步提升的设计,这个新方法称作序列保守近似整数规划算法.新方法会产生一系列包含倒数设计变量的非线性的近似整数规划子问题,并通过调整渐近线控制子问题的保守性。由于正则松弛算法不能求解非线性子问题,一种基于KKT(Karush-Kuhn-Tucker)条件的简单的设计变量更新准则被给出.基于上述思想,序列保守近似整数规划算法不依靠体分比约束等线性约束就可以获得稳定的优化过程,由此可以用来求解复杂的离散变量拓扑优化问题.多类不同需求的拓扑优化问题被解决,包括考虑等式约束及非等式约束的、以及考虑有效的及无效的体分比约束的问题.数值结果证明,由于保守性的引入,整个优化收敛进程可以自适应地调节无需额外的结构分析. 展开更多
关键词 松弛算法 整数规划 规划算法 拓扑优化 移动渐近线方法 等式约束 方法依赖 线性约束
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Decentralized multi-agent reinforcement learning with networked agents: recent advances 被引量:6
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作者 kaiqing zhang Zhuoran YANG Tamer BAŞAR 《Frontiers of Information Technology & Electronic Engineering》 SCIE EI CSCD 2021年第6期802-814,共13页
Multi-agent reinforcement learning(MARL) has long been a significant research topic in both machine learning and control systems. Recent development of(single-agent) deep reinforcement learning has created a resurgenc... Multi-agent reinforcement learning(MARL) has long been a significant research topic in both machine learning and control systems. Recent development of(single-agent) deep reinforcement learning has created a resurgence of interest in developing new MARL algorithms, especially those founded on theoretical analysis. In this paper, we review recent advances on a sub-area of this topic: decentralized MARL with networked agents.In this scenario, multiple agents perform sequential decision-making in a common environment, and without the coordination of any central controller, while being allowed to exchange information with their neighbors over a communication network. Such a setting finds broad applications in the control and operation of robots, unmanned vehicles, mobile sensor networks, and the smart grid. This review covers several of our research endeavors in this direction, as well as progress made by other researchers along the line. We hope that this review promotes additional research efforts in this exciting yet challenging area. 展开更多
关键词 Reinforcement learning Multi-agent systems Networked systems Consensus optimization Distributed optimization Game theory
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Matching-based two-color X-ray free-electron laser generation utilizing laser-plasma accelerated electron beam
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作者 Tao Liu kaiqing zhang +5 位作者 Zheng Qi Si Chen Chao Feng Haixiao Deng Bo Liu Dong Wang 《High Power Laser Science and Engineering》 SCIE CAS CSCD 2022年第1期1-9,共9页
Laser-plasma accelerators(LPAs)have great potential to realize a compact X-ray free-electron laser(FEL),which is limited by the beam properties currently.Two-color high-intensity X-ray FEL provides a powerful tool for... Laser-plasma accelerators(LPAs)have great potential to realize a compact X-ray free-electron laser(FEL),which is limited by the beam properties currently.Two-color high-intensity X-ray FEL provides a powerful tool for probing ultrafast dynamic systems.In this paper,we present a simple and feasible method to generate a two-color X-ray FEL pulse based on an LPA beam.In this scheme,time-dependent mismatch along the bunch is generated and manipulated by the designed lattice system,enabling FEL lasing at different wavelength within two undulator sections.The time separation between the two pulses can be precisely adjusted by varying the time-delay chicane.Numerical simulations show that two-color soft X-ray FELs with gigawatt-level peak power and femtosecond duration can be generated,which confirm the validity and feasibility of the scheme. 展开更多
关键词 free-electron lasers laser-plasma accelerator two-color X-RAY
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Online single-shot characterization of ultrafast pulses from high-gain free-electron lasers
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作者 Li Zeng Chao Feng +4 位作者 Duan Gu Xiaofan Wang kaiqing zhang Bo Liu Zhentang Zhao 《Fundamental Research》 CAS 2022年第6期929-936,共8页
X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of F... X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas. 展开更多
关键词 X-ray free-electron laser Ultrafast pulses Single-shot characterization Correlation analysis Laser-electron timing feedback
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