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Predicting Reverse Flow Characteristics in Equal-Height-Difference Passive Heat Removal system for Ocean Nuclear Power

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SSRN 2022年

作者： Wang, Zhiwei He, Yanping Duan, Zhongdi Huang, Chao Li, Mingzhi Liu, Shiwen Hao, Chengming State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai200240 China Institute of Marine Equipment Shanghai Jiao Tong University Shanghai200240 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China

The equal-height-difference passive heat removal system (EHDPHRS) via natural circulation driving and utilizes ocean as infinite heat sink for heat dissipation, showing broad application prospect in ocean nuclear power field;but the heat removal pipe normally encounters the reverse flow of the cold seawater into the pipe, leading to operation instability and even condensation-induced water hammer. In this study, the integration of the volume of fluid model and the condensation model based on surface renewal theory is used to simulate the reverse flow characteristics in heat removal pipe under single-and two-phase natural circulation conditions. The interfacial heat and mass transfer are calculated by user-defined functions. The numerical results reveal that the buoyancy force ( [[EQUATION]] ) and condensation driving force ( [[EQUATION]] ) both accelerate the reverse flow, while the inertial force ( [[EQUATION]] ) restrains the reverse flow;the reverse flow length presents monotonous decrease with increasing flow velocity under single-phase conditions and parabolic-like trend for two-phase flow. A prediction correlation for reverse length is developed using dimensionless Reynolds number, Grashof number and vapor volume fraction, covering single- and two-phase conditions. The predicted reverse length by the correlation agrees with 94% of the results within deviations of [[EQUATION]] 15%. © 2022, The Authors. All rights reserved.

关键词： Forecasting

Effect of residual pore on the performance of UN kernel TRISO particle fuel 14

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Effect of residual pore on the performance of UN kernel TRIS...

14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water reactor Fuel Performance Conference, TOP FUEL 2019

作者： Liu, Shichao Chen, Ping Zhou, Yi Pang, Hua Xi, Yong Tang, Changbing Zhao, Yanli Qiu, Xi Guo, Zixuan Nuclear power institute of China Science and Technology on Reactor System Design Technology Laboratory Changshun Stress No.1 Chengdu Sichuan610200 China

The thermal-mechanical performance of uranium nitride (UN) tri-isotropic (TRISO) particle with residual pore used in Light Water reactor (LWR) was investigated. The effect of pore size and location on the performance of inner dense pyrolytic carbon (IPyC) layer, SiC layer and outer dense pyrolytic carbon (OPyC) layer was studied. The dimensional changes, fission gas release and internal pressure of the fuel particle layers were calculated. Residual pore size can affect the stress distribution of coated layers obviously. The residual pore especially the big ones may be the source of cracks on the SiC layer, which can break or loss the capacity of SiC layer. Residual pore location has little influence on the stress distribution of the coated layer. In order to maintain the fission retention capacity of TRISO particle, the big residual pore should be avoided during fabrication process. Copyright © GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water reactor Fuel Performance *** rights reserved.

关键词： Silicon carbide

Anti-Fatigue Nanomechanics in the Pre-Cracked Graphene-Copper Artificial Nacre Under Cyclic Tension

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SSRN 2023年

作者： Liu, Xiaoyi Xu, Yunfei Shi, Jinchun Zhu, YinBo Zhang, Sen Wu, HengAn Mechanics+X Laboratory Chengdu Development Center of Science and Technology China Academy of Engineering Physics Chengdu610200 China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China Hefei230027 China

The fatigue performance of pre-cracked graphene-copper artificial nacre (GrCu nacre) under cyclic tensile loading is investigated using theoretical analysis and molecular dynamics (MD) simulations. Mechanical models are proposed to describe the fatigue performance of GrCu nacre, which agree well with MD simulations. Compared with nanocomposites consisting of large graphene sheets, graphene fragments cannot improve the ultimate strength of GrCu nacre, but significantly improve its fatigue limit. This anti-fatigue effect is dominated by the graphene-copper interfaces with van der Waals interactions, which can be adjusted by tailoring the architectural parameters of GrCu nacre. The ultimate strength of nacre decreases as the volume fraction of graphene increases. The fatigue limit of GrCu nacre decreases as the length of graphene fragments increases, and can be approximately described by a quadratic function of interlayer repeat spacing. An anomalous weakening effect occurs when the in-plane distance between graphene fragments is less than 2 nm, while this effect can be ignored when it is higher than 2 nm. The fatigue ratio of common metals is ~0.4, whereas that of GrCu nacre is generally higher than 0.9. These underlying mechanisms and theoretical models can improve the fundamental understanding of the fatigue performance of composites with incoherent interfaces, as well as the bottom-up design of graphene-metal nanocomposites. © 2023, The Authors. All rights reserved.

关键词： Molecular dynamics

A transient fiuid–structure interaction analysis strategy and validation of a pressurized reactor with regard to loss-ofcoolant accidents

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Nuclear science and Techniques 2020年第6期31卷 11-21页

作者： Ying-Chao Ma Xie-Lin Zhao Xian-Hui Ye Nai-Bin Jiang Jin-Xiong Zhou State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China Key Laboratory of Nuclear Reactor System Design Technology Nuclear Power Institute of ChinaChengdu 610200China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen UniversityZhuhai 519082China

A loss-of-coolant accident(LOCA)is one of the basic design considerations for nuclear reactor safety analysis.A LOCA induces propagation of a depressurization wave in the coolant,exerting hydrodynamic forces on structures viafiuid–structure interaction(FSI).The analysis of hydrodynamic forces on the core structures during a LOCA process is *** describe the implementation of a numerical strategy for prestressed *** consists of an initialization and a restarted transient analysis process,all implemented via the ANSYS Workbench by system coupling of ANSYS and *** strategy is validated by making extensive comparisons of the pressures,displacements,and strains on various locations between the simulation and reported *** approach is appealing for dynamic analysis of other prestressed structures,owing to the good popularity and acknowledgement of ANSYS and Fluent in both academia and industry.

关键词： Loss-of-coolant accident(LOCA) Fluid–structure interaction(FSI) Finite element method Prestressed structure Structural dynamics

Mixture of Experts for Network Optimization: A Large Language Model-enabled Approach

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arXiv

arXiv 2024年

作者： Du, Hongyang Liu, Guangyuan Lin, Yijing Niyato, Dusit Kang, Jiawen Xiong, Zehui Kim, Dong In The School of Computer Science and Engineering Nanyang Technological University Singapore639798 Singapore The State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing100876 China The School of Automation Guangdong University of Technology Key Laboratory of Intelligent Information Processing and System Integration of IoT Ministry of Education Guangzhou510006 China Guangdong-HongKong-Macao Joint Laboratory for Smart Discrete Manufacturing Guangzhou510006 China The Pillar of Information Systems Technology and Design Singapore University of Technology and Design Singapore487372 Singapore The Department of Electrical and Computer Engineering Sungkyunkwan University Suwon16419 Korea Republic of

Optimizing various wireless user tasks poses a significant challenge for networking systems because of the expanding range of user requirements. Despite advancements in Deep Reinforcement Learning (DRL), the need for customized optimization tasks for individual users complicates developing and applying numerous DRL models, leading to substantial computation resource and energy consumption and can lead to inconsistent outcomes. To address this issue, we propose a novel approach utilizing a Mixture of Experts (MoE) framework, augmented with Large Language Models (LLMs), to analyze user objectives and constraints effectively, select specialized DRL experts, and weigh each decision from the participating experts. Specifically, we develop a gate network to oversee the expert models, allowing a collective of experts to tackle a wide array of new tasks. Furthermore, we innovatively substitute the traditional gate network with an LLM, leveraging its advanced reasoning capabilities to manage expert model selection for joint decisions. Our proposed method reduces the need to train new DRL models for each unique optimization problem, decreasing energy consumption and AI model implementation costs. The LLM-enabled MoE approach is validated through a general maze navigation task and a specific network service provider utility maximization task, demonstrating its effectiveness and practical applicability in optimizing complex networking systems. © 2024, CC BY.

关键词： Reinforcement learning

Effect of the Graphene Oxide Incorporation on the Morphology, Corrosion Resistance And Fatigue Performance Of Micro-Arc Oxidation Coating on Mg Alloy

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SSRN 2024年

作者： Tan, Yansong Liu, Xin Sun, Xiaohao Gao, Lilan Liu, Debao Zhang, Chunqiu Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Cont rol School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineerin g Education Tianjin University of Technology Tianjin300384 China School of Materials Science and Engineering Tianjin University of Technology Tianjin300384 China

Mg alloy has great potential in biomedical applications, but the rapid corrosion rate which mismatches with bone reconstruction rate limits its clinical use. A protective oxide coating layer can be generated on the surface of Mg alloy by micro-arc oxidation (MAO) technique, aiming to improve the corrosion performance and long-term structural integrity of Mg alloy. In this study, the MAO coating layer of Mg alloy was improved by adding appropriate content of graphene oxide (GO) into electrolyte solution. GO has excellent adsorption property and plays a role in the MAO process, reducing the intermolecular gap, thereby improving the densification and obturation of the coating surface. With the increase of GO content, the surface morphology of the MAO coating initially has improved, then later deteriorated, and the best surface morphology has achieved at a GO content of 0.4 g/L. When the GO content increases from 0 g/L to 0.4 g/L, the corrosion current density reduces to 5.226 μA/cm2, with a reduction two orders in magnitude;in addition, at a stress amplitude of 140 MPa and a frequency of 4 Hz, the fatigue life increases from 9261 cycles to 13887 cycles without corrosion, and from 2042 cycles to 2759 cycles after pre-corrosion. This study provided a promising approach to ameliorate the morphology, corrosion resistance and fatigue performance of MAO coating on Mg alloy by elaborately configuring the electrolyte solution and customizing the process parameters. © 2024, The Authors. All rights reserved.

关键词： Corrosion resistance

Effect of the Graphene Oxide Incorporation on the Morphology, Corrosion Resistance and Fatigue Performance of Micro-Arc Oxidation Coating on Magnesium Alloy

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SSRN 2024年

Magnesium (Mg) alloy has great potential in biomedical applications, but the rapid corrosion rate which mismatches with bone reconstruction rate limits its clinical use. In this study, the graphene oxides (GO) were added into alkaline electrolyte solution during micro-arc oxidation (MAO) process, aiming to form a corrosion resistant surface coating on Mg alloy. By changing the concentration of GO, the coatings' morphology, composition, corrosion resistance, and fatigue property were compared to reveal the strengthening mechanism and find out the optimal graphene concentration. The results show that the MAO coating is composed of MgO, Mg2SiO4, Mg3(PO4)2 and GO. The added GO exhibits excellent adsorption property in the MAO process, reducing the intermolecular gap, thereby improving densification and obturation of the MAO coating. The surface morphology of MAO coating initially improves with increasing GO content, but then deteriorates, reaching its best quality at 0.4 g/L. Compared to MAO samples without GO, the samples with 0.4g/L GO not only have lower corrosion current density of 5.226 μA/cm2, but also show higher fatigue lives both before and after pre-corrosion. This study offers a promising approach to enhance the corrosion resistance and fatigue performance of Mg alloy by applying a GO-strengthened MAO coating onto its surface. © 2024, The Authors. All rights reserved.

关键词： Magnesium alloys

Bioinspired hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers

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National science Review 2020年第1期7卷 73-83页

作者： Huai-Ling Gao Ran Zhao Chen Cui Yin-Bo Zhu Si-Ming Chen Zhao Pan Yu-Feng Meng Shao-Meng Wen Chuang Liu Heng-An Wu Shu-Hong Yu Division of Nanomaterials & Chemistry Hefei National Laboratory for Physical Sciences at the Microscale CAS Center for Excellence in Nanoscience Hefei Science Center of CAS Department of Chemistry University of Science and Technology of China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China

Bio-sourced nanocellulosic materials are promising candidates for spinning high-performance sustainable macrofibers for advanced applications. Various strategies have been pursued to gain nanocellulose-based macrofibers with improved strength. However, nearly all of them have been achieved at the expense of their elongation and toughness. Inspired by the widely existed hierarchical helical and nanocomposite structural features in biosynthesized fibers exhibiting exceptional combinations of strength and toughness, we report a design strategy to make nanocellulose-based macrofibers with similar characteristics. By combining a facile wet-spinning process with a subsequent multiple wet-twisting procedure, we successfully obtain biomimetic hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers, realizing impressive improvement in their tensile strength, elongation and toughness simultaneously. The achievement certifies the validity of the bioinspired hierarchical helical and nanocomposite structural design proposed here. This bioinspired design strategy provides a potential platform for further optimizing or creating many more strong and tough nanocomposite fiber materials for diverse applications.

关键词： bioinspired nanocomposite hierarchical helical macrofibers strength and toughness bacterial cellulose

Cover Picture: Materials and Corrosion. 11/2024

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Materials and Corrosion 2024年第11期75卷 1399-1399页

作者： Wei Zhang Mingyang Zhou Huifang Yue Danmin Peng Xi Qiu Jijun Yang Key Laboratory of Radiation Physics and Technology of Ministry of Education Institute of Nuclear Science and Technology Sichuan University Chengdu China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China