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SSRN 2022年

作者： Qu, Wenhai Xie, Hao Shen, Danhong Wang, Zefeng Xiong, Jinbiao School of Nuclear Science and Engineering Shanghai Jiao Tong University Shanghai China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

Experimental study of coherent structures downstream of a spacer grid with different inclination angles of mixing vanes in a 5×5 rod bundle was conducted by TR-PIV under four Reynolds *** coherent structures downstream of spacer grid change with several patterns. The developments of lateral time-averaged velocity, Reynolds stress, dominant frequency, integral spatial length scales and integral temporal length scales are determined by coherent structures. Smaller coherent structures are generated with Reynolds number increasing, and time-averaged velocity, Reynolds stress, St numbers, spatial and temporal length scales decrease. Larger inclination angle generates larger coherent structures, and spatial and temporal length scales increase with inclination angle increasing. The coherent structures indicate strong anisotropy of turbulent flow in rod *** experimental findings provide valuable information for understanding sub-channel mixing phenomena caused by mixing vaned spacer grids. The experimental data can be used for sub-channel mixing model developments and validations of turbulent models. © 2022, The Authors. All rights reserved.

关键词： Reynolds number

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Development, Validation and Application of Sub-Channel Thermal-Hydraulic Analysis Code for Liquid Metal Cooled reactor

SSRN

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SSRN 2024年

作者： Wang, Jinshun Chen, Ronghua Liang, Yu Gui, Minyang Zhu, Xinyang Tian, Wenxi Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China College of Nuclear Science and Technology Harbin Engineering University Harbin150001 China

The liquid metal reactor, specifically the lead-based fast reactor and the sodium-cooled fast reactor, are generally recognized as the most significant representatives of the Gen IV reactors due to their sustainability, economy, security and reliability. In order to conduct thermal-hydraulic safety analysis for liquid metal cooled fast reactors, adaptive improvements are made to the model and solution algorithms based on the sub-channel analysis method, and a Sub-channel Analysis Code Of Safety for Liquid Metal cooled reactor (SACOS-LMR) is developed. The validation of SACOS-LMR is conducted using classic experimental data of liquid metal. The results show that the dimensionless temperature deviations of ORNL 19-pin test and Toshiba 37-pin test are within 10%, and the relative temperature deviations of KIT-KALLA 19-pin test are within 25%. These findings confirm the accuracy and reliability of SACOS-LMR in predicting the temperature distribution of liquid metal reactors. Ultimately, calculations conducted on the ALFRED lead-cooled fast reactor demonstrated the practical utility of the code and have certain guiding significance for its subsequent design and development. © 2024, The Authors. All rights reserved.

关键词： Liquid metals

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Experimental Study of Coherent Structures Downstream Mixing Vaned Spacer Grid of Different Inclination Angles in a 5×5 Rod Bundle by Tr-Piv

SSRN

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SSRN 2022年

关键词： Reynolds number

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Dual-State-Driven Evolutionary Optimization for Expensive Optimization Problems with Continuous and Categorical Variables

Dual-State-Driven Evolutionary Optimization for Expensive Op...

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Data-driven Optimization of Complex systems (DOCS), International Conference on

作者： Lindong Xie Genghui Li Kangnian Lin Zhenkun Wang School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen P.R. China Department of Computer Science and Engineering School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen P.R. China

The surrogate-assisted evolutionary algorithm (SAEA) is one of the most efficient approaches for addressing expensive continuous or combinatorial optimization problems. However, it encounters significant challenges in expensive mixed-variable optimization problems (EMVOPs). To overcome this limitation, a dual-state-driven evolutionary optimization (called DSDEO), integrating a surrogate-assisted mixed-variable evolutionary optimization stage (MVEOS) and a surrogate-assisted continuous-variable evolutionary optimization stage (CVEOS), is proposed in this paper. Specifically, MVEOS employs global and local search to enhance the exploration and exploitation of the mixed-variable space. Global and local searches are alternately executed if one search fails to yield a better solution. CVEOS utilizes a continuous-improvement strategy to refine the continuous variables of the best solution obtained so far. Experimental results demonstrate the advantages of DSDEO compared to some state-of-the-art SAEAs on many benchmark problems.

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Understanding the Importance of Evolutionary Search in Automated Heuristic design with Large Language Models

arXiv

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arXiv 2024年

作者： Zhang, Rui Liu, Fei Lin, Xi Wang, Zhenkun Lu, Zhichao Zhang, Qingfu Department of Computer Science City University of Hong Kong Hong Kong School of System Design and Intelligent Manufacturing Southern University of Science and Technology China

Automated heuristic design (AHD) has gained considerable attention for its potential to automate the development of effective heuristics. The recent advent of large language models (LLMs) has paved a new avenue for AHD, with initial efforts focusing on framing AHD as an evolutionary program search (EPS) problem. However, inconsistent benchmark settings, inadequate baselines, and a lack of detailed component analysis have left the necessity of integrating LLMs with search strategies and the true progress achieved by existing LLM-based EPS methods to be inadequately justified. This work seeks to fulfill these research queries by conducting a large-scale benchmark comprising four LLM-based EPS methods and four AHD problems across nine LLMs and five independent runs. Our extensive experiments yield meaningful insights, providing empirical grounding for the importance of evolutionary search in LLM-based AHD approaches, while also contributing to the advancement of future EPS algorithmic development. To foster accessibility and reproducibility, we have fully open-sourced our benchmark and corresponding results. Copyright © 2024, The Authors. All rights reserved.

关键词： Heuristic methods

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Intelligent Hybrid Resource Allocation in MEC-assisted RAN Slicing Network

arXiv

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arXiv 2024年

作者： Zheng, Chong Huang, Yongming Zhang, Cheng Quek, Tony Q.S. The School of Information Science and Engineering Southeast University Nanjing210096 China Purple Mountain Laboratories Nanjing211111 China The Information System Technology and Design Pillar Singapore University of Technology and Design Singapore487372 Singapore

Mobile edge computing (MEC) combining radio access network (RAN) slicing shows tremendous potential in satisfying diverse service level agreement (SLA) demands in future wireless communications. Since the limited computing capacities of MEC servers as well as the limited transmission capacities of wireless communication links, efficient hybrid resource allocation (RA) from the perspective of computing and transmission resources is crucial to maintain high SLA satisfaction rate (SSR). However, in cooperative multi-node MEC-assisted RAN slicing systems, the complexity of the multi-node cooperation in spatial dimension as well as the contextual correlation of system state in time dimension pose significant challenges to the hybrid RA policy optimization. In this paper, we aim to maximize the SSR for heterogeneous service demands in the cooperative MEC-assisted RAN slicing system by jointly considering the multi-node computing resources cooperation and allocation, the transmission resource blocks (RBs) allocation, and the time-varying dynamicity of the system. To this end, we abstract the system into a weighted undirected topology graph and, then propose a recurrent graph reinforcement learning (RGRL) algorithm to intelligently learn the optimal hybrid RA policy. Therein, the graph neural network (GCN) and the deep deterministic policy gradient (DDPG) is combined to effectively extract spatial features from the equivalent topology graph. Furthermore, a novel time recurrent reinforcement learning framework is designed in the proposed RGRL algorithm by incorporating the action output of the policy network at the previous moment into the state input of the policy network at the subsequent moment, so as to cope with the time-varying and contextual network environment. In addition, we explore two use case scenarios to discuss the universal superiority of the proposed RGRL algorithm. Simulation results demonstrate the superiority of the proposed algorithm in terms of the aver

关键词： Resource allocation

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Real-Time Status Update system in a Parallel Blocking Queue

IEEE Open Journal of the Communications Society

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IEEE Open Journal of the Communications Society 2025年 6卷 4608-4623页

作者： Zhengchuan Chen Junyao Zhu Nikolaos Pappas Lyutianyang Zhang Min Wang Chaowei Tang Tony Q. S. Quek School of Microelectronics and Communication Engineering Chongqing University Chongqing China The Department of Computer and Information Science Linköping University Linköping Sweden School of Optoelectronics Engineering Chongqing University of Posts and Telecommunications Chongqing China Information System Technology and Design Pillar Singapore University of Technology and Design Tampines Singapore

Multi-path transmission is promising in improving the freshness of information received in status-updating systems. However, multi-path transmission results in out-of-order arrivals at the monitoring point, which poses significant challenges to the analysis of freshness. This work analyzes the age of information (AoI) of a multi-path transmission non-preemptive system where multiple servers can deliver the information generated from a source to a common monitor. Two systems are considered: the homogeneous M/M/n/n non-preemptive system, where the arrival rates and service rates are identical across servers, and the heterogeneous M/M/2/2 non-preemptive system, where the service rates of all servers are different. We employ the stochastic hybrid systems (SHS) approach to characterize the average AoI of the systems and derive an explicit expression for the average AoI in both homogeneous and heterogeneous cases. Numerical results verify the effectiveness of the analysis. It is shown that when the number of servers increases in powers of 2, the most significant reduction in the average AoI occurs when the number of servers changes from 1 to 2. Besides, the numerical results confirm that the M/M/2/2 non-preemptive system is superior to the M/M/1/1 dual-queue system in terms of average AoI.

关键词： Servers Monitoring Queueing analysis Real-time systems Information age Receivers Out of order Measurement Transportation Mathematical models

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Dynamic area coverage for Multi-USV with fully connected constraint based on game theory

Dynamic area coverage for Multi-USV with fully connected con...

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2022 Chinese Automation Congress, CAC 2022

作者： Han, Xiao Chen, Huan Gao, Yufeng Ma, Guangfu Wu, Shuanghong Hao, Wenxin Harbin Institute of Technology Department of Control Science and Engineering Harbin China China Ship Development and Design Center Wuhan China China Academy of Space Technology The Beijing Institute of Spacecraft System Engineering Beijing China

ISBN: (纸本)9781665465335

This paper proposes a novel method to solve the problem of regional surveys on the ocean in a complex environment. In order to solve this challenging regional survey problem considering fully connected, a new method combined artificial potential field and game theory is designed to maximize the coverage ratio. This paper gives the mathematical model of information transfer between two unmanned surface vehicles(USVs), and then the motion strategy of USVs is given based on the idea of game theory. The area coverage task of the multi-USV system is realized by a control method similar to the artificial potential field method. © 2022 IEEE.

关键词： Game theory

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Effect of rotationally accelerated shot peening on the microstructure and mechanical behavior of a metastableβtitanium alloy

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Journal of Materials science & technology 2021年第16期75卷 27-38页

作者： Xinkai Ma Zhuo Chen Dongling Zhong SNLuo Lei Xiao Wenjie Lu Shanglin Zhang Key Laboratory of Advanced Technologies of Materials(Ministry of Education) School of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China National Key Laboratory of Reactor System Design Technology Nuclear Power Institute of ChinaChengdu 610041China

Microstructural evolution and deformation mechanism of a metastableβalloy(Ti-10 V-2 Fe-3 Al)processed by rotationally accelerated shot peening(RASP)were systematically investigated with optical microscopy,X-ray diffraction,electron backscatter diffraction and transmission electron *** gradient hierarchical microstructures(gradients inα″martensite andβphase,and hierarchical twins range from the nanoscale to microscale)can be fabricated by RASP via changing the shot peening *** hardening behavior and tensile mechanical properties of gradient hierarchical microstructure were systematically *** deformation twinning systems of{112}α″and{130}<310>α″in the kinkedα″martensite were revealed during the tensile *** was found that stress-induced martensitic transformation,twinnedα″martensite and the related dynamic grain refinement contribute to hardness and work hardening *** improvement of strength and ductility of the metastableα″titanium alloy can be achieved by introducing a gradient hierarchical microstructure.

关键词： Titanium alloys Gradient hierarchical microstructure α″martensite Rotationally accelerated shot peening Mechanical behavior

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UDC: a unified neural divide-and-conquer framework for large-scale combinatorial optimization problems 24

UDC: a unified neural divide-and-conquer framework for large...

引用

Proceedings of the 38th International Conference on Neural Information Processing systems

作者： Zhi Zheng Changliang Zhou Xialiang Tong Mingxuan Yuan Zhenkun Wang School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen China Huawei Noah's Ark Lab Shenzhen China

ISBN: (纸本)9798331314385

Single-stage neural combinatorial optimization solvers have achieved near-optimal results on various small-scale combinatorial optimization (CO) problems without requiring expert knowledge. However, these solvers exhibit significant performance degradation when applied to large-scale CO problems. Recently, two-stage neural methods motivated by divide-and-conquer strategies have shown efficiency in addressing large-scale CO problems. Nevertheless, the performance of these methods highly relies on problem-specific heuristics in either the dividing or the conquering procedure, which limits their applicability to general CO problems. Moreover, these methods employ separate training schemes and ignore the interdependencies between the dividing and conquering strategies, often leading to sub-optimal solutions. To tackle these drawbacks, this article develops a unified neural divide-and-conquer framework (i.e., UDC) for solving general large-scale CO problems. UDC offers a Divide-Conquer-Reunion (DCR) training method to eliminate the negative impact of a sub-optimal dividing policy. Employing a high-efficiency Graph Neural Network (GNN) for global instance dividing and a fixed-length sub-path solver for conquering divided sub-problems, the proposed UDC framework demonstrates extensive applicability, achieving superior performance in 10 representative large-scale CO problems. The code is available at https://***/CIAM-Group/NCO_code/tree/main/single_objective/UDC-Large-scale-CO-master

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