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Influence of Repetitive Impulse Waveforms on Surface Discharge Characteristics and Insulation Life for Polyimide Film

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CSEE Journal of power and {1. Systems 2024年第2期10卷 746-755页

作者： Zhiyun Han Qingmin Li Yujin Guo Tao Liu Guojing Dong Hanwen Ren State key {1. of Alternate Electrical power System with Renewable energy Sources North China Electric Power UniversityBeijing 102206China Electric power Research Institute Beijing 100085China Inner Mongolia Electric Economy and technology Academy Hohhot 010020China

Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics including discharge inception voltage, phase distribution and statistical characteristics on polyimide (PI) surface under different impulse waveforms and the insulation life of PI films are studied in this paper. We carry out experiments based on PD and insulation lifetime test systems, using five different types of repetitive impulses, including three bipolar waves and two unipolar waves. The experimental results show that there is little variation in discharge inception voltage under different waveforms, but great variation in phase distribution and statistical characteristics of PD. In addition, insulation life is approximately the same under different waveforms with the same polarity, and the aging rate under bipolar waveforms is larger than that under unipolar waveforms. We explain the differences between the bipolar and unipolar waveforms on insulation life, which can be concluded that the surface charge under unipolar waveform accumulates more significnatly compared with bipolar waveform and decreases the electric filed strength in discharging the air gap and inhibits surface discharge from occurring.

关键词： Insulation life polyimide film power electronic transformer repetitive impulse surface discharge characteristics

Nanostructured AlFeO_(3) thin films as a novel photoanode for photoelectrochemical water splitting

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Nano Research 2024年第3期17卷 1075-1085页

作者： Xin Sun Min Wang Qi Geng Shuailin Chen Xiaojun Lv Xunlei Ding Meicheng Li State key {1. of Alternate Electrical power System with Renewable energy Sources School of New EnergyNorth China Electric Power UniversityBeijing 102206China School of Mathematics and Physics North China Electric Power UniversityBeijing 102206China

The earth-abundant and robust aluminum ferrite,AlFeO_(3)(AFO),is mainly studied in the context of ***,we demonstrate that AFO can be used as a stable solar absorber in photoelectrochemical cells for solar water splitting,exhibiting attractive *** is the first report on the photoelectrochemical activity of *** thin-film photoelectrodes prepared by solution-processing methods are composed of vertically oriented thin nanosheets,featuring the rhombohedral symmetry(R3c)and n-type *** as-prepared AFO photoanodes generate a photocurrent density of+0.78 mA·cm^(-2) at 1.23 V *** hydrogen electrode(RHE)with the photocurrent _(onset) potential(U_(onset))close to the flat band potential of 0.5 V *** in the presence of hole ***,the U_(onset) of AFO for solar water splitting coincides with the flat band potential as well,which is rare in n-type inorganic *** also report other properties of AFO associated with photoelectrochemical *** films exhibit a band gap energy of 2.31.eV and positive band edges with low ***,the carrier lifetimes in AFO films are up to millisecond timescales under the mediation of defect *** on the photoelectrochemical behavior and optoelectronic properties,we believe that AFO has great potential for application in photoelectrochemical cells.

关键词： AlFeO_(3) photoanode nanosheets photoelectrochemistry onset potential

Effect of Preload Force on Heat Generation of Li(Ni_(0.8)Co_(0.1.Mn_(0.1.)O_(2)/SiO_(x)-C System Batteries:The Discharge Process

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Journal of Thermal Science 2024年第5期33卷 1809-1825页

作者： LIN Chunjing LAI Zhenxing BAI Guangli MA Biao WEI Zhen QI Chuang LIU Shiqiang key {1. of advanced Manufacturing technology for Automobile Parts Ministry of EducationChongqing University of TechnologyChongqing 400054China China Auto Research New energy Vehicle Inspection Center(Tianjin)Co Tianjin 300300China

Lithium-ion batteries(LIBs)undergo various degradation phenomena such as material decomposition,structural change and uneven lithium ion distribution during long-term cycles,which would affect their performance and *** order to improve the performance of the LIBs during their life cycle,preload force is preset when the batteries are *** preload forces will in turn affect the cycle life and heat generation of the *** order to address this issue,this work carries out charge/discharge cycle tests on a NCM81. battery under different preload *** calorimetry tests are performed to investigate the battery heat generation under different states of health(SOHs)and preload *** on the test results,an empirical prediction model for heat generation power as a function of SOH is *** show that when the preload force is 5 N·m,the battery capacity decreases in the slowest rate and the average heat generation power is the *** in peaks of the incremental capacity curve can be used to characterize the loss of lithium at the electrode,which in turn characterizes the change of heat generation power of the *** average heat generation power is mainly affected by the SOH,going through a period of trough with the decrease of the SOH and continuing to increase after crossing the critical *** general,these findings emphasize the relationship between preload force,SOH and heat generation power,which is helpful for the judgment of optimal preload to improve the efficiency of LIBs.

关键词： lithium ion battery cyclic aging preload force heat generation characteristic

Thermal-hydraulic performance analysis and multi-objective optimization of a microchannel with staggered semi-elliptical ribs

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Science China Technological Sciences 2024年第10期67卷 3152-3167页

作者： CUI Pan LIU Wei LIU ZhiChun School of energy and {1. Engineering Huazhong University of Science and Technology

To enhance the cooling capacity of traditional microchannels for high heat flux electronic devices,a microchannel design with staggered semi-elliptical ribs is proposed in this *** numerical simulations,the flow characteristics of the designed microchannel are compared with those of a smooth one,and the effects of rib width（Wr）,rib height（Hr）,and rib length（Lr）,on the thermal-hydraulic performance are investigated under laminar flow *** results show that the periodically arranged ribs induce periodic vortices within the microchannel,effectively promoting fluid mixing and enhancing heat *** Hrhave similar effects on microchannel performance,with an increase in them leading to an enhanced thermal performance at the expense of deteriorated hydraulic ***,Lrhas a comparatively weaker influence,with both the heat transfer and flow resistance initially growing with increasing Lrand then *** strike a balance between the two performances,a multi-objective optimization on the three geometrical parameters is conducted at a Reynolds number（Re） *** with simulation data,artificial neural networks are trained as surrogate models,and a multi-objective genetic algorithm is employed to derive the Pareto *** the TOPSIS decision-making method,an optimal compromise solution is determined as Wr=0.241. mm,Hr=0.0976 mm,and Lr=0.6486 *** testing on the optimized microchannel reveals that it exhibits high heat transfer,middle flow resistance,and excellent overall performance,with the performance evaluation criterion（PEC） falling between 1.572 and 1.723 within the Re range of 220–660.

关键词： heat transfer enhancement microchannel semi-elliptical rib numerical simulation multi-objective optimization

Trial application of the envelope method to the potential ambiguity problem

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Nuclear Science and Techniques 2024年第1期35卷 73-80页

作者： Li-Yuan Hu Yu-Shou Song Fundamental Science on Nuclear Safety and Simulation technology {1. Harbin Engineering UniversityHarbin 150001China College of Nuclear Science and technology Harbin Engineering UniversityHarbin 150001China key {1. of Nuclear Safety and advanced Nuclear energy technology Ministry of Industry and Information TechnologyHarbin 150001China

The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering *** a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering *** contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,***,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity *** this study,we conducted a trial application of the envelope method to the potential ambiguity *** envelope method was improved by including uncertainties in the experimental *** colliding systems of 1.O+28Si at 21..2 MeV and 1.C+1.C at 1.1. MeV were considered in the *** each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is *** calculated angular distributions were decomposed into nearside and farside scattering *** the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside *** capability of the envelope method to analyze the potential ambiguities was also discussed.

关键词： Elastic scattering Optical potential ambiguities Envelope method Nearside/farside decomposition

Light weight design and integrated method for manufacturing hydraulic wheel-legged robots

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第9期25卷 701-715页

作者： Xu LI Haoyang YU Huaizhi ZONG Haibo FENG Yili FU State key {1. of Robotics and System Harbin Institute of TechnologyHarbin 150001China State key {1. of Fluid power and Mechatronic Systems Zhejiang UniversityHangzhou 310058China

Design and manufacturing play pivotal roles in hydraulic-driven robotic ***,previous studies have emphasized mainly results and performance,often overlooking the specifics of the design and manufacturing *** paper introduces a novel approach known as light weight design and integrated manufacturing(LD&IM)for hydraulic wheel-legged *** LD&IM method leverages topology optimization and generative design techniques to achieve a substantial 45%weight reduction,enhancing the robot’s dynamic motion *** innovative design method not only streamlines the design process but also upholds the crucial attributes of light weight construction and high strength essential for hydraulic wheel-legged ***,the integrated manufacturing method,incorporating selective laser melting(SLM)and high-precision subtractive manufacturing(SM)processes,expedites the fabrication of high-quality *** the LD&IM approach,a hydraulic-driven single wheel-legged robot,denoted as WLR-IV,has been successfully *** robot boasts low mass and inertia,high strength,and a simplified component *** assess its dynamic jumping capabilities,the control loop integrates a linear quadratic regulator(LQR)and zero dynamic-based controller,while trajectory planning uses the spring-loaded inverted pendulum(SLIP)*** jumping results confirm the WLR-IV single-legged robot’s exceptional dynamic performance,validating both the effectiveness of the LD&IM method and the rationale behind the control strategy.

关键词： Wheel-legged robot Hydraulic driven Topology optimization Wheel-legged robot Hydraulic driven Topology optimization Additive manufacturing(AM) Jump control

Heterostructure:application of absorption-catalytic center in lithium-sulfur batteries

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Rare Metals 2024年第4期43卷 1461-1487页

作者： Fei Wang Chun-Man Yang Yong-Qi Wang Dan You Wen-Hao Yang Rong-Wei Huang Ji-Yue Hou Qian Wang Ying-Jie Zhang Ying Wang Yue-Jing Zeng Yi-Yong Zhang Xue Li National Local Joint Engineering Research Center for Lithium-Ion Batteries and Materials Preparation technology Key Laboratory of Advanced Batteries Materials of Yunnan ProvinceFaculty of Metallurgical and Energy EngineeringKunming University of Science and TechnologyKunming650093China College of Electrical Information Engineering Panzhihua UniversityPanzhihua617000China State key {1. of Physical Chemistry of Solid Surfaces Collaborative Innovation Centre of Chemistry for Energy MaterialsState-Province Joint Engineering Laboratory of Power Source Technology for New Energy VehicleEngineering Research Center of Electrochemical TechnologyMinistry of EducationCollege of Chemistry and Chemical EngineeringXiamen UniversityXiamen361005China

Due to the high theoretical specific capacity(1.75 mAh·g^(-1.),low cost,and high safety of the sulfur cathodes,they are expected to be one of the most promising rivals for a new generation of energy storage ***,the shuttle effect,low conductivity of sulfur and its discharge products,volume expansion,and other factors hinder the commercialization of lithium-sulfur batteries(LSBs).The development of sulfur-fixing materials and the design of multifunctional materials to enhance the electrochemical performance of LSBs have been the main research priorities in recent *** of the advantages of high conductivity,built-in electric field,and good synergism,more and more researchers have employed heterostructure into sulfur-fixing materials to enhance the catalytic and absorption ability for *** this review,the principle of heterostructure and the mechanism of enhancing the performance of lithium-sulfur batteries are *** applications of heterostructure in cathode and interlayer of LSBs in the latest years are ***,the cutting-edge troubles and possibilities of heterostructures in LSBs are briefly presented.

关键词： Lithium-sulfur batteries(LSBs) Heterostructure Built-in electric field Catalytic Absorption

Coupling effect on the thermal hazard assessment of hazardous chemical materials via calorimetric technologies and simulation approaches

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Defence technology（防务技术） 2024年第2期32卷 644-654页

作者： Yabei Xu Jiankun Shao Wei Wang Shengliang Xu Dongping Chen State key {1. of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China Science and technology on Aerospace Chemical {1. laboratory Hubei Institute of Aerospace ChemotechnologyXiangyang 441003China

The coupling effect of heat absorption and release exists in the thermal decomposition of a few chemical ***,the impact of the above coupling on thermal hazard assessment is not considered in the literature *** this work,nitroguanidine(NQ)and 1.3,5-trinitro-1.3,5-triazine(RDX)are selected as representative materials to explore the influence of the coupling effect on the thermal hazard assessment of chemical *** linear heating experiments of NQ and RDX are carried out by a microcalorimeter and synchronous thermal *** thermal decomposition curves are decoupled by advanced thermokinetics *** thermal decomposition and kinetic parameters before and after decoupling are *** results of TG experiment show that both NQ and RDX began to lose mass during the endothermic *** endothermic melting and exothermic decomposition of NQ and RDX are coupled within this *** coupling effect has different degrees of influence on its initial decomposition temperature and safety *** with the parameters in the coupling state,the initial decomposition temperature and adiabatic induction period after decoupling *** self-accelerating decomposition temperature increases,and internal thermal runaway time *** the thermal hazard assessment of chemical materials with coupling effects,the calculated parameters after decoupling should be taken as an important safety index。

关键词： Calorimetric technologies Kinetics Thermal hazard Phase transformation Thermal decomposition

Distributed and Risk-averse ADP Algorithm for Stochastic Economic Dispatch of power System with Multiple Offshore Wind Farms

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CSEE Journal of power and {1. Systems 2024年第5期10卷 1977-1993页

作者： Xiangyong Feng Shunjiang Lin Yutao Liang Guansheng Fan Mingbo Liu School of Electric power Engineering South China University of TechnologyGuangzhou 510640China Guangdong key {1. of Clean energy technology South China University of TechnologyGuangzhou 511458China Guangzhou power Supply Bureau Guangdong Power Grid Co.Ltd.Guangzhou 510000China

With more and more offshore wind power being increasingly connected to power grids,fluctuations in offshore wind speeds result in risks of high operation *** mitigate this problem,a risk-averse stochastic economic dispatch(ED)model of power system with multiple offshore wind farms(OWFs)is proposed in this *** this model,a novel GlueVaR method is used to measure the tail risk of the probability distribution of operation *** weighted sum of the expected operation cost and the GlueVaR is used to reflect the risk of operation cost,which can consider different risk requirements including risk aversion and risk neutrality flexibly by adjusting ***,a risk-averse approximate dynamic programming(ADP)algorithm is designed for solving the proposed model,in which multi-period ED problem is decoupled into a series of single-period ED ***,GlueVaR is introduced into the approximate value function training process for risk ***,a distributed and risk-averse ADP algorithm is constructed based on the alternating direction method of multipliers,which can further decouple single-period ED between transmission system and multiple OWFs for ensuring information *** studies on the modified IEEE 39-bus system with an OWF and an actual provincial power system with four OWFs demonstrate correctness and efficiency of the proposed model and algorithm.

关键词： Approximate dynamic programming(ADP) alternating direction method of multipliers GlueVaR offshore wind farm risk-averse stochastic optimization