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Identification of rural courtyards’utilization status using deep learning and machine learning methods on unmanned aerial vehicle images in north China

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Building Simulation 2024年第5期17卷 799-818页

作者： Maojun Wang Wenyu Xu Guangzhong cao Tao Liu College of Resource Environment and Tourism Capital Normal UniversityBeijing 100048China College of Urban and Environmental Sciences Peking UniversityBeijing 100871China

The issue of unoccupied or abandoned homesteads(courtyards)in China emerges given the increasing aging population,rapid urbanization and massive rural-urban *** the aspect of rural vitalization,land-use planning,and policy making,determining the number of unoccupied courtyards is *** and questionnaire-based surveys were currently the main approaches,but these traditional methods were often expensive and laborious.A new workflow is explored using deep learning and machine learning algorithms on unmanned aerial vehicle(UAV)***,features of the built environment were extracted using deep learning to evaluate the courtyard management,including extracting complete or collapsed farmhouses by Alexnet,detecting solar water heaters by YOLOv5s,calculating green looking ratio(GLR)by *** precisions exceeded 98%.Then,seven machine learning algorithms(Adaboost,binomial logistic regression,neural network,random forest,support vector machine,decision trees,and XGBoost algorithms)were applied to identify the rural courtyards’utilization *** Adaboost algorithm showed the best performance with the comprehensive consideration of most metrics(Accuracy:0.933,Precision:0.932,Recall:0.984,F1-score:0.957).Results showed that identifying the courtyards’utilization statuses based on the courtyard built environment is *** is transferable and cost-effective for large-scale village surveys,and may contribute to the intensive and sustainable approach to rural land use.

关键词： unoccupied homesteads courtyard built environment inner courtyard management GLR solar water heaters machine learning algorithms

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Experimental and Numerical Investigation of Non-synchronous Blade Vibration Excitation in a Transonic Axial Compressor

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Journal of Thermal Science 2024年第2期33卷 602-610页

作者： WANG Songbai WU Yadong CHEN Yong cao Zhipeng School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China AECC Sichuan Gas Turbine Establishment Chengdu610500China

The complex flow phenomenon of rotating instability(RI) and its induced non-synchronous vibration(NSV) have become a significant challenge as they continuously increase aerodynamic *** study aims to provide an understanding of the non-synchronous blade vibration phenomenon caused by the rotating instability of a transonic axial compressor *** this case,blade vibrations and non-synchronous excitation are captured by strain gauges and unsteady wall pressure transducer *** numerical simulations for a full-annulus configuration are used to obtain the non-synchronous flow *** results show that the first-stage rotor blade exhibits an NSV close to the first bending mode;NSV is accompanied by a sharp increase in pressure pulsation;amplitude can reach 20%,and unsteady aerodynamic frequency will lock in a structural mode frequency when the blade vibrates in a large-amplitude *** predicted NSV frequency aligns well with the experimental *** dominant mode of circumferential instability flow structure is approximately 47% of the number blades,and the cell size occupies 2-3 pitches in the circumferential *** full-annulus unsteady simulations demonstrate that the streamwise oscillation of the shedding and reattachment vortex structure is the main cause of NSV owing to the strong interaction between the tip leakage and separation vortices near the suction surface.

关键词： non-synchronous vibration transonic axial compressor rotor blade rotating instabilities unsteady flow

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Non-convex optimization for inverse problem solving in computer-generated holography

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Light(Science & Applications) 2024年第8期13卷 1464-1486页

作者： Xiaomeng Sui Zehao He Daping Chu Liangcai cao Department of Precision Instruments Tsinghua UniversityBeijing 100084China Department of Engineering Centre for Photonic Devices and SensorsUniversity of Cambridge9 JJ Thomson AvenueCambridge CB30FAUK Cambridge University Nanjing Centre of Technology and Innovation 23 Rongyue RoadJiangbei New AreaNanjing 210000China

Computer-generated holography is a promising technique that modulates user-defined wavefronts with digital *** appropriate holograms with faithful reconstructions is not only a problem closely related to the fundamental basis of holography but also a long-standing challenge for researchers in general fields of *** the exact solution of a desired hologram to reconstruct an accurate target object constitutes an ill-posed inverse *** general practice of single-diffraction computation for synthesizing holograms can only provide an approximate answer,which is subject to limitations in numerical *** non-convex optimization algorithms are thus designed to seek an optimal solution by introducing different constraints,frameworks,and ***,we overview the optimization algorithms applied to computer-generated holography,incorporating principles of hologram synthesis based on alternative projections and gradient descent *** is aimed to provide an underlying basis for optimized hologram generation,as well as insights into the cuttingedge developments of this rapidly evolving field for potential applications in virtual reality,augmented reality,head-up display,data encryption,laser fabrication,and metasurface design.

关键词： optimization convex inverse

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H∞ Robustness for Distributed Control in Autonomous Microgrids Considering Cyber Disturbances

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 696-706页

作者： Ge cao Guannan Lou Wei Gu Lina Sheng School of Electrical Engineering Southeast UniversityNanjing 210096China

The physical connections and logical relationships between microgrids and communication networks allow microgrids to develop into typical cyber-physical systems(CPSs).With the extensive use of open communication mechanisms,the impact of cyber disturbances in public communication networks cannot be *** this paper,a parameter optimal method for a distributed secondary controller based on the robust control theory and consensus algorithm is presented to enhance the robustness of a secondary control system under data disturbance,parameter perturbation,and time ***,a distributed secondary control strategy of microgrids is demonstrated that coordinates frequency and voltage restoration and power ***,considering the impact of cyber events on the secondary control,a distributed robust controller gain design method is proposed to satisfy the H∞ performance *** solution of the distributed robust control is transformed into a linear matrix in equation problem and latency margin is simultaneously ***,a test microgrid CPS is simulated with and without time delay to investigate the impact of cyber events on system operational states and the effectiveness and robustness of the proposed method.

关键词： Cyber disturbance cyber-physical lsystem distributed control microgrid robust H∞control

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High-energy-density plasma in femtosecond-laser-irradiated nanowire-array targets for nuclear reactions

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Matter and Radiation at Extremes 2022年第6期7卷 29-40页

作者： Defeng Kong Guoqiang Zhang Yinren Shou Shirui Xu Zhusong Mei zhengxuan cao Zhuo Pan Pengjie Wang Guijun Qi Yao Lou Zhiguo Ma Haoyang Lan Wenzhao Wang Yunhui Li Peter Rubovic Martin Veselsky Aldo Bonasera Jiarui Zhao Yixing Geng Yanying Zhao Changbo Fu Wen Luo Yugang Ma Xueqing Yan Wenjun Ma State Key Laboratory of Nuclear Physics and Technology and Key Laboratory of HEDP of the Ministry of EducationCAPTSchool of PhysicsPeking UniversityBeijing 100871China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Key Laboratory of Nuclear Physics and Ion-Beam Application(MOE) Institute of Modern PhysicsFudan UniversityShanghai 200433China School of Nuclear Science and Technology University of South ChinaHengyang 421001China INPAC and School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Shenzhen Institutes of Advanced Technology Chinese Academy of SciencesShenzhen 518055China Institute of Experimental and Applied Physics Czech Technical University in PragueHusova 240/511000 Prague 1Czech Republic ELI Beamlines Center Institute of Physics of the Czech Academy of Sciences25241 DolníBrezanyCzechia Cyclotron Institute Texas A&M UniversityCollege StationTexas 77843USA Laboratori Nazionali del Sud INFNvia Santa Sofia62Catania 95123Italy Beijing Laser Acceleration Innovation Center HuairouBeijing 101400China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuanShanxi 030006China

In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally *** results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy *** protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that *** give the electron and ion energy densities for broad target parameter *** ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold *** optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) *** the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results *** measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.

关键词： irradiated confined eventually

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Numerical study of the influence of the atmospheric pressure on the thermal environment in the passenger cabin

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Building Simulation 2024年第2期17卷 253-265页

作者： Xin Su Yu Guo Zhengwei Long Yi cao Tianjin Key Lab.of Indoor Air Environmental Quality Control School of Environmental Science and EngineeringTianjin UniversityTianjin300072China Shanghai Aircraft Design and Research Institute Jinke RoadPudong DistrictShanghai201210China

The cabin air pressure remains lower than the horizontal atmospheric pressure when the airplane is in *** pressure is one of the parameters that must be taken into consideration while studying the thermal environment of an airplane *** are still no reference values for aircraft cabins despite the fact that numerous studies on low pressure heat transfer have demonstrated the connection between convective heat transfer coefficient(CHTC)and air *** this paper,a correction method for CHTC under low pressure conditions was established by using the dummy heat dissipation in the low-pressure cabin *** this basis,a thermal environment simulation model was developed,then was applied to the simulation of a seven-row aircraft cabin containing 42 passengers,and the CHTC and heat loss of dummy surface in the cabin were ***,the results of PMV calculated by using heat dissipation and air parameters at sampling points were *** results show that the modified CHTC can accurately reflect the cabin thermal environment under low pressure conditions,and the correction of CHTC can be realized by adjusting the turbulent Prandtl number,which is nonlinear correlated with the *** simulation results of the thermal environment in the seven-row cabin show that the CHTC changes by about 42%before and after *** air pressure decreases during take-off,which reduces the average CHTC of the crew surface from 5.09 W/(m^(2)·K)to 4.56 W/(m^(2)·K),but the air temperature rises by about 0.2°C as a *** deviation of PMV results calculated by using simulated heat loss data and using air parameters of measuring points in space is up to 0.5,but the latter is representative for calculating the thermal comfort level of the whole cabin.

关键词： low pressure aircraft cabin simulation heat dissipation convective heat transfer coefficient

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Distributed Region Tracking and Perimeter Surveillance for Second-Order Multi-Agent Systems in Star-Shaped Sets

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Journal of Systems Science & Complexity 2024年第5期37卷 1995-2020页

作者： SHANG Juan MO Lipo MI Rongxin cao Xianbing School of Mathematics and Statistics Beijing Technology and Business University The Department of Foundation Shijiazhuang Institute of Railway Technology School of Computer and Artificial Intelligence Beijing Technology and Business University Research Centre for Agri-Product Quality Traceability Beijing Technology and Business University Coordination Center of China National Computer Network Emergency Response Technical Team

This paper investigates region tracking and perimeter surveillance of second-order multi-agent systems, where all agents move within a star-shaped set. First, by coordination transformations,the region tracking problem is converted from the star-shaped sets to a circular region. The authors employ communication and collaboration to complete region tracking and perimeter surveillance tasks,and then revert back to the star-shaped set by using inverse transformations. Second, the authors propose a distributed control strategy based on attractive and interaction potential functions, under which all agents can quickly track a given circular region and move around the perimeter. Finally,the authors validate the effectiveness and performance advantages of the proposed method through simulation experiments.

关键词： Distributed control multi-agent systems star-shaped sets target tracking

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Modeling and analysis for material removal and surface roughness in fluid jet polishing of optical glass

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Friction 2024年第7期12卷 1548-1563页

作者： Zhongchen cao Ming WANG Haitao LIU Tian HUANG Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education Tianjin UniversityTianjin 300072China School of Engineering The University of WarwickCoventry CV47ALUK

luid jet polishing(FJP)is a non-contact polishing technology that can fabricate free-form optical surfaces with sub-micron-level form accuracy and nano-level surface roughness,especially for hard and brittle *** surface generation model of FJP can be used to guide the determination and optimization of process parameters and is of great significance for understanding the evolution mechanism of surface ***,predictive models for the microscopic topography of polished surfaces are still *** study established a macroscopic surface profile model for predicting 3D material removal characteristics and surface texture by combining the 3D computer fluid dynamics(CFD)simulation model and single-particle erosion mechanism.A fractal theory-based erosion model has been built to calculate the material removal caused by the erosion of a single abrasive particle on the rough surface;thus,it predicts the micro-topography and surface roughness of the polished samples.A series of polishing experiments were conducted to analyze the feasibility and accuracy of the model quantitatively and study the influence mechanism of process parameters on the material removal characteristics and surface *** indicated that the models could well predict material removal and surface *** prediction accuracy of the surface roughness Ra and maximum removal depth is better than 91.6%and 90%,*** is also found that the material removal rate of FJP could reach 0.517 mm3/min,and the surface roughness convergence rate could reach 62.9%.

关键词： fluid jet polishing(FJP) computational fluid dynamics(CFD) material removal mechanism surface roughness theoretical model

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Fixed-Time Gradient Flows for Solving Constrained Optimization: A Unified Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第8期11卷 1849-1864页

作者： Xinli Shi Xiangping Xu Guanghui Wen Jinde cao School of Cyber Science and Engineering Southeast UniversityNanjing 210096China School of Mathematics Southeast UniversityNanjing 210096China

The accelerated method in solving optimization problems has always been an absorbing *** on the fixedtime(FxT)stability of nonlinear dynamical systems,we provide a unified approach for designing FxT gradient flows(FxTGFs).First,a general class of nonlinear functions in designing FxTGFs is provided.A unified method for designing first-order FxTGFs is shown under Polyak-Łjasiewicz inequality assumption,a weaker condition than strong *** there exist both bounded and vanishing disturbances in the gradient flow,a specific class of nonsmooth robust FxTGFs with disturbance rejection is *** the strict convexity assumption,Newton-based FxTGFs is given and further extended to solve time-varying ***,the proposed FxTGFs are further used for solving equation-constrained ***,an FxT proximal gradient flow with a wide range of parameters is provided for solving nonsmooth composite *** show the effectiveness of various FxTGFs,the static regret analyses for several typical FxTGFs are also provided in ***,the proposed FxTGFs are applied to solve two network problems,i.e.,the network consensus problem and solving a system linear equations,respectively,from the perspective of ***,by choosing component-wisely sign-preserving functions,these problems can be solved in a distributed way,which extends the existing *** accelerated convergence and robustness of the proposed FxTGFs are validated in several numerical examples stemming from practical applications.

关键词： Consensus constrained optimization disturbance rejection linear equations fixed-time gradient flow(FxTGF).

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Quantitative Green's function estimates for lattice quasi-periodic Schrodinger operators

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Science China Mathematics 2024年第5期67卷 1011-1058页

作者： Hongyi cao Yunfeng Shi Zhifei Zhang School of Mathematical Sciences Peking UniversityBeijing 100871China School of Mathematics Sichuan UniversityChengdu 610064China

In this paper,we establish quantitative Green’s function estimates for some higher-dimensional lattice quasi-periodic(QP)Schrodinger *** resonances in the estimates can be described via a pair of symmetric zeros of certain functions,and the estimates apply to the sub-exponential-type non-resonance *** the application of quantitative Green’s function estimates,we prove both the arithmetic version of Anderson localization and the finite volume version of(1/2-)-Holder continuity of the integrated density of states(IDS)for such QP Schrodinger *** gives an affirmative answer to Bourgain’s problem in Bourgain(2000).

关键词： Holder continuity of the IDS quantitative Green's function estimates quasi-periodic Schrodinger operators arithmetic Anderson localization multi-scale analysis

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