检索结果-南通市图书馆

The Active Compensation Technique for Large Reflector Antennas Based on Quadratic Curve Fitting

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第7期24卷 226-234页

作者： Tian-Xiang Zheng Bin-Bin Xiang Han-Wei Cui Wei Wang Pei-Yuan Lian shang-Ming Lin Yang Zhang Jian-ping Zhou Kai Li School of Mechanical Engineering Xinjiang UniversityUrumqi 830017China School of Mechano-Electronic Engineering Xidian UniversityXi’an 710017China Xi’an Institute of Optics and Precision Mechanics Chinese Academy of SciencesXi’an 710119China

Active reflectors are often used to compensate the surface distortion caused by environmental factors that degrade the electromagnetic performance of large high-frequency reflector *** is crucial for maintaining high gain operation in antennas.A distortion compensation method for the active reflector of a large dual-reflector antenna is proposed.A relationship is established between the surface deformation and the optical path difference for the primary reflector by geometric ***,employing finite element analysis,a polynomial fitting approach is used to describe the impact of adjusting points on the reflector surface based on the coordinates of each *** standardizing the positions of various panels on the reflector,the fitting ns can be applied to the reflector panels of similar ***,based on the distribution characteristics of the primary reflector panels,the adjustment equation for the actuators is derived by the influence matrix *** can be used to determine the adjustment amount of actuators to reduce the rms of the optical path ***,the least squares method is employed to resolve the matrix *** example of a 110 m aperture dual-reflector antenna is carried out by finite element analysis and the proposed *** results show that the optical path difference is reduced significantly at various elevation cases,which indicates that the proposed method is effective.

关键词： Methods analytical-Methods numerical-Telescopes

Dynamic modeling and RBF neural network compensation control for space flexible manipulator with an underactuated hand

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第3期37卷 417-439页

作者： Dongyang shang Xiaopeng LI Meng YIN Fanjie LI School of Mechanical Engineering and Automation Northeastern UniversityShenyang 110819China Shenzhen Institute of Advanced Technology Chinese Academy of SciencesShenzhen 518055China

In space operation,flexible manipulators and gripper mechanisms have been widely used because of light weight and ***,the vibration caused by slender structures in manipulators and the parameter perturbation caused by the uncertainty derived from grasping mass variation cannot be *** existence of vibration and parameter perturbation makes the rotation control of flexible manipulators difficult,which seriously affects the operation accuracy of ***’s more,the complex dynamic coupling brings great challenges to the dynamics modeling and vibration *** solve this problem,this paper takes the space flexible manipulator with an underactuated hand(SFMUH)as the research *** dynamics model considering flexibility,multiple nonlinear elements and disturbance torque is established by the assumed modal method(AMM)and Hamilton’s principle.A dynamic modeling simplification method is proposed by analyzing the nonlinear ***’s more,a sliding mode control(SMC)method combined with the radial basis function(RBF)neural network compensation is ***,the control law is designed using a saturation function in the control method to weaken the chatter *** the help of neural networks to identify the uncertainty composition in the SFMUH,the tracking accuracy is *** results of ground control experiments verify the advantages of the control method for vibration suppression of the SFMUH.

关键词： Space flexible manipulator RBF neural network Underactuated hand Dynamic models Model simplification

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

在线全文

学校读者我要写书评

暂无评论

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 UniversityBeijing 100048China The Department of Foundation Shijiazhuang Institute of Railway TechnologyShijiazhuang 050041China School of Computer and Artificial Intelligence Beijing Technology and Business UniversityBeijing 100048China Research Centre for Agri-Product Quality Traceability Beijing Technology and Business UniversityBeijing 100048China Coordination Center of China National Computer Network Emergency Response Technical TeamBeijing 100029China

This paper investigates region tracking and perimeter surveillance of second-order multiagent systems,where all agents move within a star-shaped ***,by coordination transformations,the region tracking problem is converted from the star-shaped sets to a circular *** 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 ***,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 ***,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

Recent progress in visualization and digitization of coherent transformation structures and application in high-strength steel

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1298-1310页

作者： Xuelin Wang Zhenjia Xie Xiucheng Li Chengjia shang Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Yangjiang Branch Guangdong Laboratory for Materials Science and Technology(Yangjiang Advanced Alloys Laboratory)Yangjiang 529500China

High-strength steels are mainly composed of medium-or low-temperature microstructures,such as bainite or martensite,with coherent transformation *** type of microstructure has a high density of dislocations and fine crystallographic structural units,which ease the coordinated matching of high strength,toughness,and ***,given its excellent welding perform-ance,high-strength steel has been widely used in major engineering constructions,such as pipelines,ships,and ***,visual-ization and digitization of the effective units of these coherent transformation structures using traditional methods(optical microscopy and scanning electron microscopy)is difficult due to their complex ***,the establishment of quantitative relationships with macroscopic mechanical properties and key process parameters presents additional *** article reviews the latest progress in microstructural visualization and digitization of high-strength steel,with a focus on the application of crystallographic methods in the development of high-strength steel plates and *** obtained the crystallographic data(Euler angle)of the transformed microstruc-tures through electron back-scattering diffraction and combined them with the calculation of inverse transformation from bainite or martensite to austenite to determine the reconstruction of high-temperature parent austenite and orientation relationship(OR)during con-tinuous cooling ***,visualization of crystallographic packets,blocks,and variants based on actual OR and digit-ization of various grain boundaries can be effectively completed to establish quantitative relationships with alloy composition and key process parameters,thereby providing reverse design guidance for the development of high-strength steel.

关键词： high-strength steel microstructure visualization digitization quantification mechanical properties

Energy harvesting technology for AC overhead insulated transmission line based on electric field induction

在线全文

学校读者我要写书评

暂无评论

High Voltage 2024年第4期9卷 816-825页

作者： Le Zhou Hongwei Liu Kun Zuo Kuo shang School of Electrical and Electronic Engineering North China Electric Power UniversityBeijingChina Electric Power Company of Sichuan Province Tianfu Power Supply Company ChengduSichuanChina Changde Power Supply Branch State Grid Hunan Electric Power Company LimitedChangdeHunanChina

To solve the problem of the energy harvesting(EEH)effect of the condition monitoring devices power supply on the transmission line is not *** authors designed three kinds of EEH schemes based on AC electric field induction,which can effectively improve the output power of load power *** EEH principle of each scheme was analysed in detail,and the influence factors such as the shape of outer energy harvester,capacitance compensation and impedance matching characteristics were ***,the experiment showed that 140.9 mW of power was obtained in direct-mode field EEH when the line voltage level was 10 *** high-potential field EEH mode obtained 4.1 mW of *** harvesting effect of the inner energy harvester with the same potential as the aluminium wire was obviously better,and 30.7 mW of power was ***,based on the third mode,when the load resistance was 2200Ω,the rectifier received 23.7 mW DC *** experimental results are in agreement with the theoretical analysis,which verifies the effectiveness of the electric field induction power supply technology.

关键词： field harvesting mode

Vibration suppression for rotating space slender flexible structures based on novel deformation description and NNSMC controller with hyperbolic tangent function

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第10期37卷 339-364页

作者： Dongyang shang Xiaopeng LI Men YIN Sainan ZHOU School of Mechanical Engineering and Automation Northeastern UniversityShenyang 110819China Shenzhen Institute of Advanced Technology Chinese Academy of SciencesShenzhen 518055China

Rotating Space Slender Flexible Structures(RSSFS)are extensively utilized in space operations because of their light weight,mobility,and low energy *** realize the accurate space operation of the RSSFS,it is necessary to establish a precise mechanical model and develop a control algorithm with high ***,with the application of traditional control strategies,the RSSFS often suffers from the chattering phenomenon,which will aggravate structure *** this paper,novel deformation description is put forward to balance modeling accuracy and computational efficiency of the RSSFS,which is better appropriate for real-time ***,the Neural Network Sliding Mode Control(NNSMC)strategy modified by the hyperbolic tangent(tanh)function is put forward to compensate for modeling errors and reduce the chattering phenomenon,thereby improving the trajectory tracking accuracy of the ***,a mathematical model for the RSSFS is developed according to the novel deformation description and the vibration theory of flexible *** of the deformation accuracy between different models proves that the novel modeling method proposed has high modeling ***,the universal approximation property of the Radial Basis Function(RBF)neural network is put forward to determine and compensate for modeling errors,which consist of higher-order modes and the uncertainties of external *** addition,the tanh function is proposed as the reaching law in the conventional NNSMC strategy to suppress driving torque *** control law of modified NNSMC strategy and the adaptive law of weight coefficients are developed according to the Lyapunov theorem to guarantee the RSSFS ***,the simulation and physical experimental tests of the RSSFS with different control strategies are *** results show that the control law according to the novel deformation description and the modified NNSMC strategy can obta

关键词： Space slender flexible structure Novel deformation description RBF neural network Vibration suppression Hyperbolic tangent function

Energy-Function Based Pilot Protection Scheme for Hybrid UHVDC Transmission Applying Improved Hausdorff Distance

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2024年第3期10卷 891-902页

作者： Zijiang Wang Youping Fan Ben shang Yinbiao Shu School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Institute of Next Generation Power Systems&International Standards Wuhan UniversityWuhan 430072China CSEE IEEE

A hybrid UHVDC transmission system applying LCC as the rectifier and MMC as the inverter combines the advantages of both converter types,which makes this protection scheme more complicated.A new pilot protection scheme for a three-terminal hybrid DC transmission system applying energy functions is *** energy function for LCC is applied to MMC to derive the energy level of the hybrid ***,an improved Hausdorff distance(IHD)algorithm is proposed to detect the difference in energy levels between the normal and fault *** abrupt change in energy level is characterized by IHD change *** points at which the IHD change rate exceeds the threshold at converter stations are applied to determine the fault line and to estimate the fault *** proposed protection scheme is then verified by a simulation model of the Wudongde±800 kV three-terminal hybrid UHVDC transmission *** appropriate sampling frequency is selected for a real-time calculation,and the threshold is selected considering the effect of *** show the proposed scheme can identify and trip fault lines quickly and effectively,even for a 600Ωgrounding *** waveshape similarity algorithms are compared and *** with existing protection schemes,the proposed scheme transmits less data to improve communication speed and reliability.

关键词： Energy function Hausdorff distance pilot protection UHVDC transmission

Plant-derived nanovesicles as an emerging platform for cancer therapy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Pharmaceutica Sinica B 2024年第1期14卷 133-154页

作者： Hanzhe Liu Guo-Feng Luo Zhengjun shang The State Key Laboratory Breeding Base of Basic Science of Stomatology(Hubei-MOST)&Key Laboratory of Oral Biomedicine Ministry of Education School and Hospital of StomatologyWuhan UniversityWuhan 430079China

Plant-derived nanovesicles(PDNVs)derived from natural green products have emerged as an attractive nanoplatform in biomedical *** are usually characterized by unique structural and biological functions,such as the bioactive lipids/proteins/nucleic acids as therapeutics and targeting groups,immune-modulation,and long-term *** the rapid development of nanotechnology,materials,and synthetic chemistry,PDNVs can be engineered with multiple functions for efficient drug delivery and specific killing of diseased cells,which represent an innovative biomaterial with high biocompatibility for fighting against *** this review,we provide an overview of the state-of-theart studies concerning the development of PDNVs for cancer *** original sources,methods for obtaining PDNVs,composition and structure are introduced *** an emphasis on the featured application,the inherent anticancer properties of PDNVs as well as the strategies in constructing multifunctional PDNVs-based nanomaterials will be discussed in ***,some scientific issues and technical challenges of PDNVs as promising options in improving anticancer therapy will be discussed,which are expected to promote the further development of PDNVs in clinical translation.

关键词： Naturally occurring nanovesicles Plant Nanotechnology Drug delivery Cancer therapy

Novel de novo TRPV4 mutation identified in a Chinese family with metatropic dysplasia inhibits chondrogenic differentiation

在线全文

学校读者我要写书评

暂无评论

Genes & Diseases 2024年第3期11卷 83-86页

作者： ping Wei Weizhe Shi Tianying Nong Caixia Xian Xia Li Zhaohui Li Xin Li Jianping Wu Liyuan shang Fulong Xu Yibo Xu Hongwen Xu Mingwei Zhu guangzhou Institute of Pediatrics Guangzhou Women and Children's Medical CenterGuangzhou Medical UniversityGuangdong Provincial Clinical Research Center for Child HealthGuangzhouGuangdong 510623China Department of Pediatric Orthopedics Guangzhou Women and Children's Medical CenterGuangzhou Medical UniversityGuangdong Provincial Clinical Research Center for Child HealthGuangzhouGuangdong 510623China

Metatropicdysplasia(MD,MIM156530)is a rare congenital bone dysplasia primarily characterized by severe platyspondyly with long and wide vertebral bodies and dumbbell deformity of the tubular *** can be caused by heterozygous mutations in the gene encoding transient receptor potential vanilloid family member 4(TRPV4).We identifieda novel de novo mutation,c.2353T>C,in the TRPV4 gene,in a Chinese family with mild MD.

关键词： TRPV4 dysplasia congenital