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High Voltage 2024年第3期9卷 566-580页

作者： Xu Dai yuan yuan Jiang Zhou Guoyong Liu Tao Zhu Huiying Xiang Qi Yu Xue Gao Ruijin Liao State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina College of Materials Science and Engineering Chongqing UniversityChongqingChina Dongfang Electric Machinery Co. LtdDeyangChina

As a typical failure phenomenon in transformers,sulfur corrosion has garnered significant attention in the field of high-voltage *** boundary character distribution(GBCD)copper windings have been introduced to enhance sulfur corrosion resistance by slowing down intergranular *** this study,the sulfur corrosion behaviour and mechanisms of the GBCD copper windings under various temperatures were experi-mentally and theoretically *** show that GBCD can enhance the corrosion resistance of copper in liquid *** the increase in temperatures,the insulating properties of oil and papers in traditional copper windings experience notable degradation,while GBCD copper windings show more stable insulating *** addition,modelling of grain boundary energy indicates that the grain boundary structure of GBCD copper windings has a lower average interface energy of 0.170 eV/Å***-culations of reaction thermodynamics show that GBCD copper windings possess a higher failure temperature(135.2℃)and inhibition degree(activation energy)of the sulfur corrosion(32,557.62 J/mol),revealing the stability and enhanced sulfur corrosion resis-tance at elevated temperatures.

关键词： corrosion grain copper

Chiral thermally activated delayed fluorescence materials for circularly polarized organic light-emitting diodes

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Science China Chemistry 2024年第4期67卷 1097-1116页

作者： Li yuan Yi-Pin Zhang You-Xuan Zheng State Key Laboratory of Coordination Chemistry Collaborative Innovation Center of Advanced MicrostructuresJiangsu Key Laboratory of Advanced Organic MaterialsSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China

Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material *** from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,*** to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical *** ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two *** review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device ***,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.

关键词： chiral thermally activated delayed fluorescence material chiral skeleton circularly polarized luminescence circularly polarized organic light-emitting diodes dissymmetry factor

Methane activation by[LnO]^(+):the 4f orbital matters

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Science China Chemistry 2024年第1期67卷 330-335页

作者： Bowei yuan Jingxiang Zou Mincheng Yu Shaodong Zhou College of Chemical and Biological Engineering Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture TechnologyZhejiang UniversityHangzhou 310027China Zhejiang Provincial Innovation Center of Advanced Chemicals Technology Institute of Zhejiang University–QuzhouQuzhou 324000China Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM) Xiamen 361005China

Gas-phase reactions of[LnO]^(+)with methane have been studied by using inductively coupled plasma-mass spectrometer(ICP-MS)combined with quantum chemical *** indicate that the[LnO]^(+)(Ln=Sm-Lu)ions are able to activate methane to generate methyl *** particular,[EuO]^(+)and[YbO]^(+)exhibit the highest ***,ab initio computations reveal a novel HAT process operating in the absence of a terminal oxygen radical,as mediated by[EuO]^(+)and[YbO]^(+).Such a process diverges from previous findings on the methane activation by metal oxide clusters,not only on the electronic pattern during the course of hydrogen transfer,but also on the important role that 4f electrons *** associated electronic origins have been discussed,and the well-designed 4f electron occupation may turn to be a promising approach in constructing lanthanide involved catalysts.

关键词： lanthanide oxides methane activation 4f orbitals quantum chemical calculation ion-molecule reaction

Performance Assessment and Improvement of Photovoltaic-Thermal System based on Energy,Exergy,Economic and Environment Analysis

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Journal of Thermal Science 2024年第6期33卷 2166-2178页

作者： ZHOU yuan WANG Jiangjiang QIN Yanbo LIU Boxiang Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology North China Electric Power University

A photovoltaic thermal（PV/T） system with parallel cooling channels was designed in this work to decrease the PV panel temperature and improve its photoelectric conversion efficiency.A 4E analysis method（includes energy,exergy,economic,and environmental aspects） was formulated to comprehensively evaluate the performances of the PV/T system,combining experimental and simulation ***,the experiment was performed using water as the cooling *** show that the PV/T system can reduce daily CO2emissions by 1682.47-1705.98 g,and compared to the PV system,the added cooling module can increase electrical efficiency and environmental performance by 12.19% and 6.2%,*** the mass flow of water rose from 0.017 kg/s to 0.023 kg/s,the electrical,thermal,and overall efficiencies were improved by 3.82%,11.36%,and 8.27%,***,a numerical simulation model was constructed based on the experimental results to predict operations of the presented PV/T system using nanofluids as the cooling medium,including Ag,Al2O3,and *** results show that the Al2O3-nanofluid-based PV/T system has a higher application value,enabling an electrical efficiency of up to 15.13%.Its thermal efficiency can be enhanced by5.43% when the volume fraction of Al2O3increases from 1% to 5%.

关键词： 4E analysis method nanofluid numerical analysis parallel cooling channels photovoltaic/thermal system

All-inorganic ultrathin high-sensitivity transparent temperature sensor based on a Mn-Co-Ni-O nanofilm

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Microsystems & Nanoengineering 2024年第3期10卷 195-205页

作者： yuanyuan Cui Mengwei Sun Changbo Liu yuan Deng Research Institute for Frontier Science Beihang UniversityBeijing 100191China School of Materials Science and Engineering Beihang UniversityBeijing 100191China Key Laboratory of Intelligent Sensing Materials and Chip Integration Technology of Zhejiang Province Hangzhou Innovation Institute of Beihang UniversityHangzhou 310051China

The demand for optically transparent temperature sensors in intelligent devices is ***,the performance of these sensors,particularly in terms of their sensitivity and resolution,must be further *** study introduces a novel transparent and highly sensitive temperature sensor characterized by its ultrathin,freestanding design based on a Mn-Co-Ni-O *** Mn-Co-Ni-O-based sensor exhibits remarkable sensitivity,with a temperature coefficient of resistance of−4%℃^(−1),and can detect minuscule temperature fluctuations as small as 0.03℃.Additionally,the freestanding sensor can be transferred onto any substrate for versatile application while maintaining robust structural stability and excellent resistance to interference,indicating its suitability for operation in challenging *** practical utility in monitoring the surface temperature of optical devices is demonstrated through vertical integration of the sensor and a micro light-emitting diode on a polyimide ***,an experiment in which the sensor is implanted in rats confirms its favorable biocompatibility,highlighting the promising applications of the sensor in the biomedical domain.

关键词： transparent sensor versatile

Metarelation2vec:A Metapath-Free Scalable Representation Learning Model for Heterogeneous Networks

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Tsinghua Science and Technology 2024年第2期29卷 553-575页

作者： Lei Chen yuan Li Yong Lei Xingye Deng School of Information and Electrical Engineering Hunan University of Science and TechnologyXiangtan 411201China School of Computer Science and Engineering Hunan University of Science and TechnologyXiangtan 411201China

Metapaths with specific complex semantics are critical to learning diverse semantic and structural information of heterogeneous networks(HNs)for most of the existing representation learning ***,any metapaths consisting of multiple,simple metarelations must be driven by domain *** sensitive,expensive,and limited metapaths severely reduce the flexibility and scalability of the existing models.A metapath-free,scalable representation learning model,called Metarelation2vec,is proposed for HNs with biased joint learning of all metarelations in a bid to address this ***,a metarelation-aware,biased walk strategy is first designed to obtain better training samples by using autogenerating cooperation probabilities for all metarelations rather than using expert-given ***,grouped nodes by the type,a common and shallow skip-gram model is used to separately learn structural proximity for each node ***,grouped links by the type,a novel and shallow model is used to separately learn the semantic proximity for each link ***,supervised by the cooperation probabilities of all meta-words,the biased training samples are thrown into the shallow models to jointly learn the structural and semantic information in the HNs,ensuring the accuracy and scalability of the *** experimental results on three tasks and four open datasets demonstrate the advantages of our proposed model.

关键词： metarelation random walk heterogeneous network metapath representation learning

Boundary Points,Minimal L^(2)Integrals and Concavity PropertyⅢ—Linearity on Riemann Surfaces and Fibrations over Open Riemann Surfaces

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Acta Mathematica Sinica,English Series 2024年第9期40卷 2091-2152页

作者： Qi An GUAN Zhi Tong MI Zheng yuan School of Mathematical Sciences Peking UniversityBeijing 100871P.R.China School of Mathematics and Statistics Beijing Jiaotong UniversityBeijing 100044P.R.China Institute of Mathematics Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190P.R.China

In this article,we consider a modified version of minimal L^(2) integrals on sublevel sets of plurisubharmonic functions related to modules at boundary points,and obtain a concavity property of the modified *** applications,we give characterizations for the concavity degenerating to linearity on open Riemann surfaces and on fibrations over open Riemann surfaces.

关键词： Minimal L^(2)integrals plurisubharmonic functions boundary points weakly pseudoconvex Kähler manifold

Resilience-oriented Transmission Expansion Planning with Optimal Transmission Switching Under Typhoon Weather

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 129-138页

作者： Yang yuan Heng Zhang Haozhong Cheng Zheng Wang Key Laboratory of Control of Power Transmission and Conversion Ministry of EducationElectrical Engineering DepartmentShanghai Jiao Tong UniversityShanghaiChina State Grid East China Branch ShanghaiChina

This paper presents resilience-oriented transmission expansion planning(RTEP)with optimal transmission switching(OTS)model under typhoon *** proposed model carefully considers the uncertainty of component vulnerability by constructing a typhoon-related box uncertainty set where component failure rate varies within a range closely related with typhoon ***,a min-max-min model is developed to enhance transmission network resilience,where the upper level minimizes transmission lines investment,the middle level searches for the probability distribution of failure status leading to max worst-case expected load-shedding(WCEL)under typhoon,and the lower level optimizes WCEL by economic dispatch(ED)and OTS.A nested decomposition algorithm based on benders decomposition is developed to solve the *** studies of modified IEEE 30-bus and 261-bus system of a Chinese region illustrate that:a)the proposed RTEP method can enhance resilience of transmission network with less investment than widely used RTEP method based on attacker and defender(DAD)model,b)the influence of OTS on RTEP is closely related with contingency severity and system scale and c)the RTEP model can be efficiently solved even in a large-scale system.

关键词： Decomposition algorithm optimal transmission switching resilience transmission expansion planning uncertainty vulnerability

Growth process,defects,and dopants of bulkβ-Ga_(2)O_(3)semiconductor single crystals

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China Foundry 2024年第5期21卷 491-506页

作者： Yan-shen Wang Ming-zhi Zhu yuan Liu School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology(Ministry of Education) Beijing 100084China

β-gallium oxide(β-Ga2O3),as the typical representative of the fourth generation of semiconductors,has attracted increasing attention owing to its ultra-wide bandgap,superior optical properties,and excellent tolerance to high temperature and *** to the single crystals of other semiconductors,high-quality and large-sizeβ-Ga_(2)O_(3)single crystals can be grown with low-cost melting methods,making them highly *** this review,the growth process,defects,and dopants ofβ-Ga_(2)O_(3)are primarily ***,the growth process(e.g.,decomposition,crucible corrosion,spiral growth,and development)ofβ-Ga_(2)O_(3)single crystals are summarized and compared in ***,the defects ofβ-Ga_(2)O_(3)single crystals and the influence of defects on Schottky barrier diode(SBD)devices are emphatically ***,the influences of impurities and intrinsic defects on the electronic and optical properties ofβ-Ga_(2)O_(3)are also briefly *** this comprehensive analysis,the article offers a concise summary of the current state,challenges and prospects ofβ-Ga_(2)O_(3)single crystals.

关键词： β-Ga_(2)O_(3) single-crystal growth defects dopants semiconductor

Data-driven discovery of linear dynamical systems from noisy data

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Science China(Technological Sciences) 2024年第1期67卷 121-129页

作者： WANG YaSen yuan Ye FANG HuaZhen DING Han School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China State Key Lab of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China School of Artificial Intelligence and Automation Huazhong University of Science and TechnologyWuhan 430074China Department of Mechanical Engineering University of KansasLawrence 66045USA

In modern science and engineering disciplines,data-driven discovery methods play a fundamental role in system modeling,as data serve as the external representations of the intrinsic mechanisms within ***,empirical data contaminated by process and measurement noise remain a significant obstacle for this type of *** this study,we have developed a data-driven method capable of directly uncovering linear dynamical systems from noisy *** method combines the Kalman smoothing and sparse Bayesian learning to decouple process and measurement noise under the expectation-maximization framework,presenting an analytical method for alternate state estimation and system ***,the discovered model explicitly characterizes the probability distribution of process and measurement noise,as they are essential for filtering,smoothing,and stochastic *** have successfully applied the proposed algorithm to several simulation *** results demonstrate its potential to enable linear dynamical system discovery in practical applications where noise-free data are intractable to capture.

关键词： system identification sparse Bayesian learning Kalman smoothing process and measurement noise