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Map of Crystal-Field Effects in Correlated Layered t2gn Perovskites

Physical Review Letters 2024年第23期132卷 236505-236505页

作者： Neda Samani Guoren Zhang Eva Pavarini Institute for Advanced Simulation School of Physics and Technology Key Laboratory of Materials Physics Institute of Solid State Physics Forschungszentrum Jülich Germany

Correlated metallic layered t2gn perovskites are intensively studied and yet their low-energy electronic properties remain hotly debated. Important elements of the puzzle, beside the on-site Coulomb repulsion, are the tetragonal crystal-field splitting and the spin-orbit interaction. Here, we show that they control the electronic properties principally via form and occupations of natural orbitals. We discuss consequences for shape and topology of the Fermi surface, effective masses, and metal-insulator transition, building a map of crystal-field effects. The emerging picture captures electronic-structure trends in this family of systems within a single framework.

关键词： Metal-insulator transition Orbital order Spin-orbit coupling Iridates Layered crystals Mott insulators Perovskites Ruthenates Strongly correlated systems Transition metal oxides Crystal-field theory Dynamical mean field theory

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Research on the Configuration and Capacity Calculation of DC Side Dynamic Braking System 6

Research on the Configuration and Capacity Calculation of DC...

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6th International Conference on HVDC, HVDC 2024

作者： Bai, Yu Yang, Yuexi Zhou, Xiao Du, Zhenyu Hu, Yinghong Li, Yu State Grid Smart Grid Research Institute Co. Ltd. National Key Laboratory of Advanced Power Transmission Technology Beijing Key Laboratory of Dc Grid Technology and Simulation Beijing China Electric Power Research Institute State Grid JiBei Electric Power Co. Ltd. Beijing China

ISBN: (纸本)9798350387759

The Flexible DC Transmission technology circumvents the limitation of transmission distance caused by the charging power of AC cables. Additionally, it boasts technical advantages such as effectively isolating the interactions between onshore AC power grids and offshore wind farms, providing stable grid-connected voltage for offshore wind farms, and enabling flexible regulation of system operations. These factors make it the preferred technology for transmitting power from remote offshore wind farms. The offshore wind power flexible grid-connected system incorporates a DC-side dynamic braking system, which functions to absorb excess power injected by the wind farm and prevent system overvoltage when the AC main grid malfunctions, leading to the inability of the onshore converter station to deliver rated power. In this paper, the technical route, configuration scheme and capacity demand of DC side dynamic braking systems are studied, and the DC side dynamic braking system configuration scheme applicable to unipolar and bipolar isolated island new energy transmission flexible system is proposed, and the capacity demand of DC side dynamic braking system is analyzed, and the capacity design scheme of DC side dynamic braking system that conforms to the national calibration and meets the demand of system power balancing and fault ride-through and other requirements under the faulty AC system is proposed. The capacity design scheme of energy consuming devices is proposed in compliance with national calibration and can meet the system power balance and fault ride-through requirements in case of AC system failure and other working conditions. © 2024 IEEE.

关键词： capacity requirements DC side dynamic braking systems flexible DC grid layout design offshore wind power

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NWD-YOLOv5: A YOLOv5 Model for Small Target Detection Based on NWD Loss 6

NWD-YOLOv5: A YOLOv5 Model for Small Target Detection Based ...

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6th International Conference on Robotics, Intelligent Control and Artificial Intelligence, RICAI 2024

作者： Zhou, Liliang Ran, Huaming Xiong, Rongling Tan, Ruijie National Key Laboratory of Complex Aviation System Simulation Chengdu610036 China 10th Research Institute China Electronics Technology Group Corporation Chengdu610036 China School of Mathematics Southwest Jiaotong University Chengdu611756 China

ISBN: (纸本)9798331541699

Target detection technology is vital in modern social management and urban security, with small target detection—accurately identifying tiny objects in large scenes—posing a key challenge for improving surveillance system accuracy and real-time performance. The YOLO series is still the mainstream target detection model, for the YOLOv5 model, as the IoU metric it adopts still uses the geometrical overlap of the detection frame as the basis of the loss calculation, while the experiments have proved that this metric is unable to effectively utilize the small-scale characteristics of small targets. Therefore, improving the loss metric in the existing framework can help the model to pay more attention to the spatial semantic features of small targets in the image in the training phase of the network, respectively, and thus improve the detection effect. In this paper, we propose the NWDYOLOv5 model, i.e., we introduce the NWD loss that measures the difference in the distribution of the detection frames for the existing target detection framework YOLOv5, which ensures that the loss of the small targets is not neglected in the calculation of the forward propagation loss of the model, and we purposefully modify the structure of the feature extraction network in the original framework by adding a feature extraction layer for the detection of the small targets, which enhances the ability of the model to capture the subtle features thus improving the accuracy of small target detection. Through comparative experiments, we evaluated the detection performance of the original YOLOv5 model, the YOLOv5 model using only the NWD loss, the YOLOv5 model with only the additional small-target detection layer, and the full NWD-YOLOv5 model for small-targeted human bodies on the screened COCO2017 public dataset, respectively. The experimental results show that compared to the original YOLOv5 model, the model with only the NWD loss improves the mAP@.5 metrics on small-target detection by 16.5

关键词： Digital elevation model

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Health benefits from the rapid reduction in ambient exposure to air pollutants after China's clean air actions:progress in efficacy and geographic equality

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National Science Review 2024年第2期11卷 103-113页

作者： Tao Xue Ruohan Wang Meng Wang Yanying Wang Dan Tong Xia Meng Conghong Huang Siqi Ai Fangzhou Li Jingyuan Cao Mingkun Tong Xueqiu Ni Hengyi Liu Jianyu Deng Hong Lu Wei Wan Jicheng Gong Shiqiu Zhang Tong Zhu Institute of Reproductive and Child Health National Health Commission Key Laboratory of Reproductive Health/Department of Epidemiology and Biostatistics Ministry of Education Key Laboratory of Epidemiology of Major Diseases(PKU) School of Public Health Peking University Health Science Centre State Environmental Protection Key Laboratory of Atmospheric Exposure and Health Risk Management and Center for Environment and Health Peking University Advanced Institute of Information Technology Peking University Department of Epidemiology and Environmental Health School of Public Health and Health ProfessionsUniversity at Buffalo State Key Joint Laboratory of Environment Simulation and Pollution Control College of Environmental Sciences and EngineeringPeking University Department of Earth System Science Tsinghua University School of Public Health Key Laboratory of Public Health Safety of the Ministry of Education and Key Laboratory of Health Technology Assessment of the Ministry of HealthFudan University College of Land Management Nanjing Agricultural University National&Local Joint Engineering Research Center for Rural Land Resources Use and Consolidation Clean Air Asia

Clean air actions （CAAs） in China have been linked to considerable benefits in public ***,whether the beneficial effects of CAAs are equally distributed geographically is *** high-resolution maps of the distributions of major air pollutants (fine particulate matter[PM2.5]and ozone[O3]) and population,we aimed to track spatiotemporal changes in health impacts from,and geographic inequality embedded in,the reduced exposures to PM2.5and O3from 2013 to *** used a method established by the Global Burden of Diseases *** analyzing the changes in loss of life expectancy（LLE） attributable to PM2.5and O3,we calculated the gain of life expectancy （GLE） to quantify the health benefits of the air-quality ***,we assessed the geographic inequality embedded in the GLE using the Gini index （GI）.Based on risk assessments of PM2.5and O3,during the first stage of CAAs（2013 to 2017）,the mean GLE was 1.87 *** of the sum of the GLE was disproportionally distributed in about one quarter of the population exposed （GI 0.44）.During the second stage of CAAs（2017 to 2020）,the mean GLE increased to 3.94 months and geographic inequality decreased （GI 0.18）.According to our assessments,CAAs were enhanced,from the first to second stages,in terms of not only preventing premature mortality but also ameliorating health *** enhancements were related to increased sensitivity to the health effects of air pollution and synergic control of PM2.5and *** findings will contribute to optimizing future CAAs.

关键词： clean air action public health inequality fine particulate matter ozone

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Effect of Sb-induced oxygen octahedral distortion on piezoelectric performance and thermal stability of Pb(In,Nb)O_(3)-Pb(Hf,Ti)O_(3)ceramics

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Journal of Materials Science & technology 2023年第30期161卷 101-110页

作者： Huanli Shi Mo Zhao Dongyan Zhang Zhimin Li Maolin Zhang Jingya Wang Li Jin Yangxi Yan School of Advanced Materials and Nanotechnology Xidian UniversityXi’an 710071China National Ceramic Industry Design Institute of China Quanzhou 362500China Electronic Materials Research Laboratory Key Laboratory of the Ministry of EducationSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Intense Pulsed Radiation Simulation and Effect(Northwest Institute of Nuclear Technology) Xi’an 710024China Shaanxi Applied Physics and Chemistry Research Institute Xi’an 710061China

The combination of excellent thermal stability and outstanding electrical performance is of great sig-nificance for piezoelectric ***,we have prepared 0.11Pb(In_(0.5)Nb_(0.5))O_(3)-0.89Pb(Hf_(0.47)Ti_(0.53))O_(3)-Sb_(2)O_(5)(PIN-PHT-x Sb)ceramics by solid-phase method and investigated the effect of oxygen octahedral lattice distortion on microstructure and macroscopic electrical *** distortion index of oxygen octahedra is studied by Rietveld refinement,showing that optimal octahedral distortion can soften B-O repulsion,disrupt long-range ordered ferroelectric domains,and enhance local heterogeneities,signifi-cantly increasing piezoelectric ***,outstanding thermal stability and ultrahigh piezo-electric response of PIN-PHT-1.2Sb ceramics are realized under the synergistic influence of octahedral distortion,excellent density,and large grain *** with PIN-PHT ceramics,PIN-PHT-1.2Sb ce-ramics exhibit ultrahigh piezoelectric responses(d_(33)=706 pC/N,k_(p)=0.68,ε_(r)=3244),a high Curie temperature(T C)of 300℃,excellent thermal stability,and anti-fatigue properties.

关键词： Oxygen octahedron Piezoelectric response Thermal stability

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Study on frictional behavior of SiC_(f)/SiC composite clad tube clamping condition under nuclear irradiation

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Friction 2024年第5期12卷 919-938页

作者： Chenglong XIAO Liangliang SHEN Tianqi ZHU Jianbo TANG Ximing XIE Xinyu FAN Jian XU Zhiying REN School of Mechanical Engineering Zhejiang University of TechnologyHangzhou310023China Engineering Laboratory of Advanced Energy Materials Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo315201China State Key Laboratory of Fine Chemicals Liaoning High-Performance Polymer Engineering Research CenterSchool of Chemical EngineeringDalian University of TechnologyDalian116024China School of Mechanical Engineering and Automation Fuzhou UniversityFuzhou350116China School of Computer Science and Technology Shandong UniversityQingdao266237China Aviation Industry Corporation of China Ltd.Beijing100028China

Silicon carbide fiber reinforced silicon carbide matrix(SiC_(f)/SiC)composite is the key cladding material of nuclear fuel,which determines the safety and reliability of nuclear fuel storage and *** replacement of its storage and transportation scenario needs to be completed by the manipulator,but the application of SiC_(f)/SiC wear,fracture,and nuclear leakage in the snatching process of brittle-flexible-rigid contact in the irradiation environment has been seriously restricted due to unclear understanding of the damage ***,the effects of irradiation dose and clamping load on the friction characteristics of the contact interface between SiC_(f)/SiC clad tube are studied in this paper,and the effects of irradiation parameters and clamping force on the static friction coefficient of the contact interface between the clad tube and flexible nitrile are *** on the Greenwood-Williamson tribological model,a numerical model of the shape and structure of the contact micro-convex at the micro-scale of the clamping interface is constructed by introducing the multi-surface integral,and finally verified by *** research results show that there is a unique“Irradiation suppression zone”under the clamping condition of SiC_(f)/SiC cladding tube under the nuclear irradiation environment,and the growth of static friction coefficient slows down until stagnates after irradiation reaches a certain extent(600 kGy),and there will be a decline when the irradiation dose continues to increase,among which the clamping force of 15.2 N within the irradiation interval of 1,000 kGy can meet the safety of nuclear environment *** results of this paper can provide an important theoretical basis and application guidance for the safe operation of SiC_(f)/SiC cladding tubes in the storage and transportation clamping process.

关键词： SiC_(f)/SiC Clad tube nuclear irradiation conditions Greenwood-Williamson tribological model multi-surface integral

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Simultaneously optimizing pore morphology and enhancing mechanical properties of Al-Si alloy composite foams by graphene nanosheets

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Journal of Materials Science & technology 2022年第6期101卷 60-70页

作者： Weiting Li Xudong Yang Kunming Yang Chunnian He Junwei Sha Chunsheng Shi Yunhui Mei Jiajun Li Naiqin Zhao Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and EngineeringTianjin UniversityTianjin 300350China Sino-European Institute of Aviation Engineering Civil Aviation University of ChinaTianjin 300300China Collaborative Innovation Center of Chemical Science and Engineering Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Advanced Joining Technology School of Materials Science and EngineeringTianjin UniversityTianjin 300350China

The integrity and regularity of pore morphology play an important role in determining the mechanical properties of the metallic foam *** conventional methods on refining pore morphology are mainly focused on the optimization of fabrication techniques,however,they are usually inconvenient and ***,incorporating nano reinforcement is considered to be a suitable way to fabricate metallic composite foams accompanied by optimized pore morphology and enhanced mechanical *** this work,through a facile and rapid powder metallurgy foaming method,the aluminum-silicon(Al-Si)alloy composite foams reinforced by graphene nanosheets(GNSs)are successfully *** microstructure analyses reveal that,for the Al-Si alloy foams incorporating the GNSs(GNSs/Al-Si composite foams),the pore size is transformed to be smaller,the pore size distributions become more homogeneous and the pore shape is also refined to a regular and roundish ***,the shape of Si precipitates is found transforming from an irregular long strip(length of~20μm,width of~5μm)to a fine particle state(diameter of~5μm).Moreover,the compressive testing results show that,the 0.4wt%GNSs/Al-Si composite foams own the optimal compression stress of 11.7±0.5 MPa,plateau stress of 10.0±1.0 MPa and energy absorption capacity of 6.8±0.7 MJ/m^(3),which have improvement of 58.1%,53.8%and 51.1%in comparison with the Al-Si alloy foams counterpart,*** present findings may pave a new way for developing new generation of metallic composite foams that with stable microstructure and excellent mechanical performance.

关键词： Metal matrix composites Aluminum foam Graphene Energy absorption

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A Generic Real-Time simulation Modeling Method of Modular DC Chopper for VSC-Based Offshore Wind Farm Connection System 7

A Generic Real-Time Simulation Modeling Method of Modular DC...

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7th International Conference on Power and Energy Engineering, ICPEE 2023

作者： Kou, Longze Gao, Yuqin Gu, Huaiguang Gao, Yang Li, Jin Li, Fangyuan State Grid Smart Grid Research Institute Co. Ltd State Key Laboratory of Advanced Power Transmission Technology Beijing China State Grid Smart Grid Research Institute Co. Ltd Beijing Key Laboratory of DC Grid Technology & Simulation Beijing China

ISBN: (纸本)9798350381146

The DC chopper is a crucial equipment in VSC-based offshore wind farm connection system to dissipate the surplus power during fault scenarios and enhance the system fault ride through capability. The modular DC chopper technology has been used in real engineering project due to its good transient performance. It has numerous SMs stacked in arm bridge with different topologies and thus poses challenges to the electromagnetic modeling, simulation analysis and control system testing of the equipment. This paper proposes a generic electromagnetic modeling method of modular DC chopper, which is especially suitable for the real time simulation. It has both high simulation speed and accuracy and can be used to simulate modular DC chopper with different SM topology. The modeling method is validated and then implemented in real time simulation platform HYPERSIM. Hardware in loop testing of VBC of DC chopper is carried out and the study cases demonstrates that the real time model of modular DC chopper works properly under transient operation conditions. © 2023 IEEE.

关键词： Offshore wind farms

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Enhanced Power Synchronization Based Vector Control with Fault Ride Through for VSC-HVDC 8

Enhanced Power Synchronization Based Vector Control with Fau...

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8th International Conference on Power and Renewable Energy, ICPRE 2023

作者： Pan, Rongcai Li, Chunpeng Yang, Yuexi Zhou, Xiao Research Institute Co. Ltd State Key Laboratory of Advanced Power Transmission Technology State Grid Smart Grid Beijing China Research Institute Co. Ltd Beijing Key Laboratory of DC Grid Technology & Simulation State Grid Smart Grid Beijing China

ISBN: (纸本)9798350328813

The power synchronization based vector control is proposed with the power synchronization controller (PSC) replacing the conventional phase locked loop (PLL) recently. It is reported that the power synchronization unit can have comparable performance of the conventional PLL based vector control. However, the steady state analysis of the PSC control dq frame orientation and the corresponding steady equilibrium points are not discussed. Worse more, fault ride through of the PSC based vector control is not addressed in the related literatures. First, the measurements error on the performance on PSC based vector control is analyzed and the enhanced PSC based vector control is proposed to further reduce the control complexity. Based on the enhanced PSC based vector control, the equilibrium points and the dq frame orientation of PSC based vector control and its comparison with PLL based one are analyzed in the normal operation. After that, the fault ride through strategy is proposed with consideration of equilibrium point. Finally, simulations using PSC based vector control for voltage source converter based high voltage dc transmission station (VSC-HVDC) are carried out to verify the analysis. © 2023 IEEE.

关键词： Fault ride through Phase-locked loop Power synchronization controller Vector control VSC-HVDC

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A new rhombohedral phase and its 48 variants inβtitanium alloy

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Transactions of Nonferrous Metals Society of China 2024年第9期34卷 2849-2863页

作者： Xin-nan WANG Ming HAN Fu-rong ZHANG Guang-ming ZHAO Zhi-shou ZHU Aviation Key Laboratory of Science and Technology on Advanced Titanium Alloys AECC Beijing Institute of Aeronautical MaterialsBeijing 100095China School of Materials Science and Engineering East China Jiaotong UniversityNanchang 330013China

A new rhombohedral phase(termed R′)in a solution-aging-treated titanium alloy(Ti-4.5Al-6.5Mo-2Cr-2Nb-1V-1Sn-1Zr,wt.%)was *** accurate Bravais lattice parameters were determined by a novel unit cell reconstruction method based on conventional selected-area electron diffraction(SAED)*** orientation relationship between R'phase and BCC phase was *** results show that the R′phase is found to have 48crystallographically equivalent variants,resulting in rather complicated SAED patterns with high-order reflections.A series of in-situ SAED patterns were taken along both low-and high-index zone axes,and all weak and strong reflections arising from the 48 variants were properly explained and directly assigned with self-consistent Miller indices,confirming the presence of the rhombohedral ***,some criteria were also proposed for evaluating the indexed results,which together with the Bravais lattice reconstruction method shed light on the microstructure characterization of even unknown phases in other alloys.

关键词： titanium alloy rhombohedral phase Bravais lattice reconstruction variant orientation relationship

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