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Safety-Constrained Multi-Agent Reinforcement Learning for Power Quality Control in Distributed Renewable Energy Networks

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Computers, Materials & Continua 2024年第4期79卷 449-471页

作者： yongjiang zhao Haoyi Zhong chang Cyoon Lim Department of Computer Engineering Chonnam National UniversityYeosu59626South Korea

This paper examines the difficulties of managing distributed power systems,notably due to the increasing use of renewable energy sources,and focuses on voltage control challenges exacerbated by their variable nature in modern power *** tackle the unique challenges of voltage control in distributed renewable energy networks,researchers are increasingly turning towards multi-agent reinforcement learning(MARL).However,MARL raises safety concerns due to the unpredictability in agent actions during their exploration *** unpredictability can lead to unsafe control *** mitigate these safety concerns in MARL-based voltage control,our study introduces a novel approach:Safety-ConstrainedMulti-Agent Reinforcement Learning(SC-MARL).This approach incorporates a specialized safety constraint module specifically designed for voltage control within the MARL *** module ensures that the MARL agents carry out voltage control actions *** experiments demonstrate that,in the 33-buses,141-buses,and 322-buses power systems,employing SC-MARL for voltage control resulted in a reduction of the Voltage Out of Control Rate(%***)from0.43,0.24,and 2.95 to 0,0.01,and 0.03,***,the Reactive Power Loss(Q loss)decreased from 0.095,0.547,and 0.017 to 0.062,0.452,and 0.016 in the corresponding systems.

关键词： Power quality control multi-agent reinforcement learning safety-constrained MARL

The Extension Dimension of Subcategories and Recollements of Abelian Categories

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Acta Mathematica Sinica,English Series 2024年第4期40卷 1042-1058页

作者： Xin MA Ye Yang PENG zhao yong HUANG College of Science Henan University of EngineeringZhengzhou 451191P.R.China Department of Mathematics Nanjing UniversityNanjing 210093P.R.China

We investigate the behavior of the extension dimension of subcategories of abelian categories under ***Λ',Λ,Λ"be art in algebras such that(modΛ',mod A,modΛ")is a recollement,and let D'and D"be subcategories of modΛand modΛ"*** any n,m≥0,under some conditions,we get dimΩ^(k)(D)≤dimΩ^(n)(D')+dimΩ^(m)(D")+1,where k=max{m,n}and D is the subcategory of modΛglued by D'and D";moreover,we give a sufficient condition such that the converse inequality holds *** applications,some results for Igusa-Todorov subcategories and syzygy finite sub categories are obtained.

关键词： Recollements extension dimension Igusa–Todorov subcategories syzygy finite subcategories

Abnormal State Detection in Lithium-ion Battery Using Dynamic Frequency Memory and Correlation Attention LSTM Autoencoder

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1757-1781页

作者： Haoyi Zhong yongjiang zhao chang Gyoon Lim Department of Computer Engineering Chonnam National UniversityYeosu59626South Korea

This paper addresses the challenge of identifying abnormal states in Lithium-ion Battery(LiB)time series *** the energy sector increasingly focuses on integrating distributed energy resources,Virtual Power Plants(VPP)have become a vital new framework for energy *** are key in this context,owing to their high-efficiency energy storage capabilities essential for VPP ***,LiBs are prone to various abnormal states like overcharging,over-discharging,and internal short circuits,which impede power transmission *** methods for detecting such abnormalities in LiB are too broad and lack precision for the dynamic and irregular nature of LiB *** response,we introduce an innovative method:a Long Short-Term Memory(LSTM)autoencoder based on Dynamic Frequency Memory and Correlation Attention(DFMCA-LSTM-AE).This unsupervised,end-to-end approach is specifically designed for dynamically monitoring abnormal states in LiB *** method starts with a Dynamic Frequency Fourier Transform module,which dynamically captures the frequency characteristics of time series data across three scales,incorporating a memory mechanism to reduce overgeneralization of abnormal *** is followed by integrating LSTM into both the encoder and decoder,enabling the model to effectively encode and decode the temporal relationships in the time *** tests on a real-world LiB dataset demonstrate that DFMCA-LSTM-AE outperforms existing models,achieving an average Area Under the Curve(AUC)of 90.73%and an F1 score of 83.83%.These results mark significant improvements over existing models,ranging from 2.4%–45.3%for AUC and 1.6%–28.9%for F1 score,showcasing the model’s enhanced accuracy and reliability in detecting abnormal states in LiB data.

关键词： Lithium-ion battery abnormal state detection autoencoder virtual power plants LSTM

Impact of Mo/Ni alloying on microstructural modulation and low-temperature toughness of high-strength low-alloy steel

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Journal of Iron and Steel Research International 2024年第7期31卷 1746-1762页

作者： Wei Liu Hong-li zhao Bing-xing Wang yong Tian State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina

The high-strength low-alloy steel plates with varying Ni/Mo contents were manufactured using the thermos-mechanical control *** investigation was conducted to explore the effect of Ni/Mo microalloying on microstructure evolution and mechanical properties of the *** results revealed that the increase in Ni content from 1 to 2 wt.%reduced the transition temperature of ferrite and the growth range of ferritic grain was narrowed,which promoted grain *** optimized combination of grain size,high-angle grain boundaries(HAGBs),and martensite-austenite(M-A)islands parameter contributed to the excellent impact toughness of S1 steel at-100℃(impact absorbed energy of 218.2 J at-100℃).As the Mo increases from 0 to 2 wt.%,the matrix structure changes from multiphase structure to granular bainite,which increases the average effective grain size to~4.62 pm and reduces HAGBs proportion to~36.22%.With these changes,the low-temperature impact toughness of S3 steel is *** addition,based on the analysis of the characteristics of crack propagation path,it was found that M-A islands with low content(~2.21%)and small size(~1.76 pm)significantly retarded crack propagation,and the fracture model of M-A islands with different morphologies was further ***,correlation between behaviour of delamination and toughness was further analysed by observing delamination size and impact energy parameters.

关键词： High-strength low-alloy steel Microstructural regulation Ni addition Mo addition Crack propagation Low-temperature toughness

A contradictory phenomenon of thicken pericardium and cardiac compression without inferior vena cava dilation:sign of IVC escape

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Journal of Geriatric Cardiology 2024年第5期21卷 583-587页

作者： Tie-Nan CHEN Shuang zhao Shuai QIAO yong-yong HAN Qing LIU chang-Le LIU Guang-Ping LI Tong LIU Hua-Ying FU Department of Cardiovascular Surgery Second Hospital of Tianjin Medical UniversityTianjinChina Department of Cardiology Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular DiseaseTianjin Institute of Cardi-ologyThe Second Hospital of Tianjin Medical UniversityTianjinChina Department of Oncology Second Hospital of Tianjin Medical UniversityTianjinPeople's Republic of China

A 77-year-old female presented with shortness of breath and tightness of chest was *** past medical history included hypertension and she has been taking nifedipine *** years before,she was diagnosed with pericardial effusion(Figure 1)and had pericardiocentesis *** physical examination,her blood pressure was 151/100 mm-Hg and her pulse rate was 91 beats/min.

关键词： admitted cardiac thick

Advanced organic electrode materials for aqueous rechargeable batteries

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Science China Chemistry 2024年第1期67卷 137-164页

作者： Gaojing Yang Yaxun Zhu Qi zhao Zhimeng Hao yong Lu Qing zhao Jun Chen Frontiers Science Center for New Organic Matter Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education)College of ChemistryNankai UniversityTianjin 300071China

Organic electrode materials take advantages of potentially sustainable production and structural tunability compared with present commercial inorganic electrode ***,their applications in traditional rechargeable batteries with nonaqueous electrolytes suffer from the premature failure and safety *** comparison,aqueous rechargeable batteries based on organic electrode materials have received extensive attentions in recent years for low-cost and sustainable energy storage systems due to their inherent *** review aims to provide a comprehensive summary on the recent progress in advanced organic electrode materials for aqueous rechargeable *** start from the overview of working principles and general design strategies of organic electrode materials in aqueous rechargeable *** the research advances of organic electrode materials in various aqueous rechargeable batteries are highlighted in terms of charge carriers(monovalent ions,multivalent ions,and anions).We emphasized the characteristics of organic electrode materials in various charge ***,the critical challenges and future efforts of aqueous organic rechargeable batteries are *** organic electrode materials with better electronic conductivity and fast reaction kinetics are still needed to build advanced aqueous batteries for commercial applications.

关键词： organic electrode materials aqueous batteries organic batteries rechargeable batteries

Environment-adaptive phase-separation-porous fluorofilm for highperformance passive radiation cooling

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Nano Research 2024年第6期17卷 5636-5644页

作者： Weiming Tang yong Li Xue Meng Shutao Wang Ziguang zhao School of Future Technology University of Chinese Academy of SciencesBeijing 100049China CAS Key Laboratory of Bio-inspired Materials and Interfacial Science Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China CAS Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Passive radiative cooling is widely recognized as an environmentally sustainable method for achieving significant cooling ***,the mechanical properties and environmental adaptability of current radiative cooling materials are not sufficient to maintain high cooling performance in external *** we reported an environment-adaptive phase-separation-porous fluorofilm for high-performance passive radiation *** to the homogenous fluoro-porous network with limited scattering efficiencies,we modulated the porous structure of the fluorofilm to achieve a strong emissivity of 95.2%(8-13μm)and a high reflectivity of 97.1%(0.3-2.5μm).The fluorofilm demonstrates a temperature drop of 10.5°C and an average cooling power of 81 W·m^(−2)under a sunlight power of 770 W·m^(−2).The high mechanical performance and environmental adaptability of fluorofilms are also *** its significant radiative cooling capability and robust environmental adaptability,the fluorofilm is expected to have a promising future in radiative temperature regulation.

关键词： fluorofilm passive radiation cooling porous optimization thermal regulation

Global Phase Portraits of Uniform Isochronous Centers System of Degree Six with Polynomial Commutator

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 577-599页

作者： Li-na GUO Ai-yong CHEN Shuai-feng zhao School of Mathematics and Statistics Henan University of Science and TechnologyLuoyang 471023China Department of Mathematics Hunan First Normal UniversityChangsha 410205China School of Mechatronics Engineering Henan University of Science and TechnologyLuoyang 471023China

This paper studies the global phase portraits of uniform isochronous centers system of degree six with polynomial *** systems have the form x=-y+xf(x,y),y=x+yf(x,y),where f(x,y)=a_(1)x+a_(2)xy+a_(3)xy^(2)+a_(4)xy^(3)+a_(5)xy^(4)=xσ(y),and any zero of 1+a_(1)y+a_(2)y^(2)+a_(3)y^(3)+a_(4)y^(4)+a_(5)y^(5),y=y is an invariant straight *** last,all global phase portraits are drawn on the Poincare disk.

关键词： global phase portraits uniform isochronous center polynomial commutator invariant straight lines

Microstructures and mechanical properties of laser-directed energy deposited CrCoNi medium-entropy alloy

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Rare Metals 2024年第7期43卷 3286-3300页

作者： Wen-Jie zhao chang-Yu Liu Peng-Cheng Che Zhi-Liang Ning Hong-Bo Fan Jian-Fei Sun yong-Jiang Huang Alfonso H.W.Ngan National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China Space Environment Simulation Research Infrastructure Harbin Institute of TechnologyHarbin 150001China Department of Mechanical Engineering The University of Hong KongHong Kong 999077China

The distinctive intrinsic heat treatment(IHT)originating from cyclic reheating in the laser-directed energy deposition(LDED) has attracted growing attention in recent *** this investigation,simulations and experimental characterizations were performed to examine the impact of IHT on the micros true ture and mechanical properties of LDED-fabricated CrCoNi medium-entropy alloy(MEA).The results show that the intensity of the IHT is proportional to the utilized laser energy density(LED).As the LED increased,significant dynamic recrystallization and grain refinement occurred within the alloy due to the enhanced intensity of ***,the high LED leads to severe hot cracking within the as-built MEA,resulting in inferior *** decreasing LED,the hot cracking was effectively ***,low LED weakened the intensity of IHT and consequently inhibited kinetic conditions of dynamic recrystallization,resulting in a heterogeneous grain structure characterized by multi-scale-sized *** structure provides significant hetero-deformation-induced hardening during plastic deformation,enabling the alloy to have a sustainable work-hardening *** expect that this work will have implications in taking full advantage of the unique IHT of the LDED process to fabricate ME As with excellent metallurgical quality and mechanical performance.

关键词： Intrinsic heat treatment Laser-directed energy deposition CrCoNi MEA Dynamic recrystallization Heterogeneous grain structure