检索结果-内蒙古大学图书馆

SSRN 2024年

作者： Sun, Shen Liu, Shijie He, Weiwei Zhang, Xuan Tang, Wei Zhou, Liucheng Yi, Min Nanjing210016 China Beijing Aerospace Propulsion Institute Laboratory of Science and Technology on Cryogenic Liquid Propulsion Beijing100076 China National Key Lab of Aerospace Power System and Plasma Technology Air Force Engineering University Xi’an710038 China

Vibration fatigue is a major concern for aeroengine compressor blades under complex cyclic mechanical and aero-dynamic loads, but predicting vibration fatigue behavior of blades remains challenging. Herein, a phase-field fatigue fracture model is applied to simulate the vibration fatigue behavior of the simulated compressor blade. In the phase-field model, a logarithmic degradation function is adopted to describe the fracture toughness decreasing with fatigue cycles. Vibration induced cyclic loads are mimicked by the pressure applied on the blade surface. The three-dimensional (3D) fatigue crack propagation of the simulated blade is simulated. It is found that the fatigue crack initiates at the variable cross-section and propagates horizontally. Laser shock peening (LSP) is further shown to improve the fatigue properties, i.e., LSP induced compressive residual stress results in a 95% increase of fatigue life and notably retards the 3D fatigue crack growth. For the vibration fatigue strength of both the original and LSPed blades, the predictions are within the ±5% error band. The phase-field model here provides a predictive approach for the evaluation of vibration fatigue behavior and shows a great potential in the optimal design of durable and reliable compressor blades. © 2024, The Authors. All rights reserved.

关键词： Fatigue crack propagation

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Experimental Research on Uniaxial Tensile Behavior and Cyclic Deformation Behavior of TA17

Experimental Research on Uniaxial Tensile Behavior and Cycli...

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作者： Du, Juan Shao, Xuejiao Kuang, Linyuan Lu, Yuechuan Yu, Minda Lu, Jiang State Key Laboratory of Reactor System Design Technology Nuclear Power Institute of China Chengdu610213 China

Titanium alloys are widely used in various fields for its high strength, good corrosion resistance and high heat resistance. Many countries in the world have recognized the importance of titanium alloy materials, and have developed and applied them in practice. In order to accurately describe uniaxial tensile behavior and ratcheting behavior of material, a series of experiments of TA17 were conducted at room temperature and 350 ℃, including the uniaxial tensile experiments of TA17 with different processing techniques, the strain controlled cyclic experiments and the stress controlled cyclic experiments. The uniaxial tensile curves of materials with different processing techniques are discussed. The effects of different strain amplitudes of cyclic straining were analyzed. The effects of different combinations of mean stress and stress amplitude were analyzed. Finally, the uniaxial stress and strain curves with different processing techniques, cyclic stress and strain curves under different strain amplitudes and stress amplitude were obtained. The results show that the stress and strain curves of longitudinal plates and forgings are the lowest, while the stress and strain curves of transverse plates and bars are the highest. TA17 exhibited significant cyclic stability under different strain amplitudes and has obvious ratcheting behavior under asymmetric stress control. The obtained conclusions are helpful to improve the mechanical properties of TA17 and establish the cyclic constitutive model in the following work. © Springer Nature Switzerland AG 2020.

关键词： Corrosion resistance

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Microstructure and impact toughness of 16MND5 reactor pressure vessel steel manufactured by electrical additive manufacturing

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Journal of Iron and Steel Research International 2020年第8期27卷 992-1004页

作者： Xi-kou He Chang-sheng Xie Li-jun Xiao Ying Luo Di Lu Zheng-dong Liu Xi-tao Wang Institute for Special Steels China Iron and Steel Research InstituteBeijing 100081China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610041SichuanChina Southern Additive Science and Technology Co. Ltd.Foshan 528225GuangdongChina

Electrical additive manufacturing can improve manufacturing efficiency and reduce the cost of 16MND5 reactor pres-sure vessel steel. Impact tests were conducted to compare the impact toughness of 16MND5 steels manufactured by the electrical additive manufacturing and conventional forging, respectively. It is found that the impact toughness of electrical additive manufacturing specimen was slightly higher than that of conventional forging specimen. The characterizations of microstructure show that there were large ferrites and carbides in electrical additive manufacturing specimen. The fracture mechanisms of electrical additive manufacturing specimen were that microvoids or microcracks were prone to nucleate at the large ferrite/bainite interface and large carbide/bainitic ferrite interface, where the stress concentration was high. In addi-tion, the block size and high-angle grain boundaries played a vital role in hindering crack propagation of electrical additive manufacturing specimen, helping to improve the impact energy and leading to a low ductile–brittle transition temperature. The results suggest that the electrical additive manufacturing technology was an effective method to enhance the impact toughness of 16MND5 steel.

关键词： Electrical additive manufacturing 16MND5 steel Impact toughness Fracture High-angle grain boundary

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Robust Output Synchronization of Discrete-Time Linear-Time-Invariant Multi-Agent systems Using Phase Tool

Robust Output Synchronization of Discrete-Time Linear-Time-I...

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European Control Conference (ECC)

作者： Xin Mao Dan Wang Wei Chen Li Qiu School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen China Division of Decision and Control Systems KTH Royal Institute of Technology Stockholm Sweden Department of Mechanics and Engineering Science State Key Laboratory for Turbulence and Complex Systems Peking University Beijing China Southern University of Science and Technology Shenzhen China Hong Kong University of Science and Technology Hong Kong S.A.R. China

ISBN: (数字)9783907144107

ISBN: (纸本)9798331540920

In this paper, the output synchronization in large-scale discrete-time networks is examined by utilizing the novel phase tool, where the agent dynamics are allowed to be significantly heterogeneous. The synchronization synthesis problem is formulated and thoroughly investigated, with the goal of characterizing the allowable heterogeneity among the agents to ensure synchronization under a uniform controller. The solvability condition is provided in terms of the phases of the residue matrices of the agents at the persistent modes. When the condition is satisfied, a design procedure is given, producing a low-gain synchronizing controller. Numerical examples are given to illustrate the results.

关键词： Sufficient conditions Europe Heterogeneous networks Synchronization Multi-agent systems

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Collaborative Fall Detection and Response using Wi-Fi Sensing and Mobile Companion Robot

arXiv

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arXiv 2024年

作者： Chen, Yunwang Kang, Yaozhong Zhao, Ziqi Hong, Yue Meng, Lingxiao Meng, Max Q.-H. The Shenzhen Key Laboratory of Robotics Perception and Intelligence Southern University of Science and Technology Shenzhen518055 China The Department of Electrical and Electronic Engineering SUSTech Shenzhen China The School of System Design and Intelligent Manufacturing SUSTech Shenzhen China

This paper presents a collaborative fall detection and response system integrating Wi-Fi sensing with robotic assistance. The proposed system leverages channel state information (CSI) disruptions caused by movements to detect falls in non-line-of-sight (NLOS) scenarios, offering non-intrusive monitoring. Besides, a companion robot is utilized to provide assistance capabilities to navigate and respond to incidents autonomously, improving efficiency in providing assistance in various environments. The experimental results demonstrate the effectiveness of the proposed system in detecting falls and responding effectively. Copyright © 2024, The Authors. All rights reserved.

关键词： Fall detection

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Auxiliary Antenna Array Optimization for Mainlobe Interference Suppression systems

Auxiliary Antenna Array Optimization for Mainlobe Interferen...

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International Conference on Microwave and Millimeter Wave technology Proceedings

作者： Jiahao Zhang Jin Meng National Key Laboratory of Science and Technology on Vessel Integrated Power System Naval University of Engineering Wuhan CHINA

ISBN: (纸本)9781665482271

Modern radars are sensitive to the aggressive interference, especially the high-power mainlobe interference. By introducing the auxiliary antenna array, and implementing the spatial domain interference cancellation algorithm, the mainlobe interference can be suppressed, while the signal of interest is reserved. The interference cancellation performance is highly related with the auxiliary array design. In this paper, the location, the element number, and the antenna type of the auxiliary array are investigated. It is found that by adding the number of the auxiliary antenna elements, and optimizing the location of the elements, the mainlobe distortion can be successfully reduced in presence of mainlobe interference. In realistic situations, the omnidirectional auxiliary antenna element is more desired than the directional antenna element, considering the cost and coverage.

关键词： Microwave technology Microwave integrated circuits Interference cancellation Millimeter wave technology Radar Radar antennas Microwave antenna arrays

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Federated Reinforcement Learning for RIS-Aided Non-Orthogonal Multiple Access MEC

Federated Reinforcement Learning for RIS-Aided Non-Orthogona...

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IEEE Conference on Vehicular technology (VTC)

作者： Zhong Yang Yaxing Li Hongbo Liu Fangmin He National Key Laboratory of Science and Technology on Vessel Integrated Power System Naval University of Engineering Wuhan China

ISBN: (纸本)9781665454698

A novel reconfigurable intelligent surface (RIS) aided non-orthogonal multiple access mobile edge computing (NOMA-MEC) framework is proposed to release the heavy transmission delay of the edge devices (EDs) in next-generation wireless communication networks. We formulate a stochastic optimization problem that jointly optimizes the phase-shifter design of the RIS, the task offloading decision and the computing resource allocation of MEC, to minimize the overall transmission delay of all EDs in a long-term manner. The mathematical solution for the formulated optimization problem is a long-term offline policy which is non-trivial for conventional optimization approaches due to high computational complexity and stringent delay constraint. Therefore, we propose a federated reinforcement learning (FRL) approach for the formulated optimization problem to obtain the optimal solution taking advantages of the computing resource of all EDs. Moreover, a reputation-enabled ED selection scheme is proposed in the FRL approach that takes the task offloading history into consideration. The proposed RIS-aided NOMA-MEC framework is capable of outperforming conventional orthogonal multiple access (OMA) enabled RIS-MEC networks. The proposed FRL scheme achieves a near-optimal performance when the computional task is image classification in the MNIST and the IRIS dataset.

关键词： Wireless communication NOMA Vehicular and wireless technologies Reinforcement learning Delays History Task analysis

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Configuration and Motion Analysis of Orthopedic External Fixation Mechanism with Virtual Motion Center

Configuration and Motion Analysis of Orthopedic External Fix...

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International Conference on Mechanical design, ICMD 2021

作者： Su, Peng Li, Shuo Lai, Yuliang Zhang, Li Li, Jian School of Electromechanical Engineering Beijing Information Science and Technology University Beijing100192 China Second Department of Orthopedics The Affiliated Rehabilitation Hospital of National Research Center for Rehabilitation Aids Beijing100176 China Key Laboratory of Rehabilitation Aids Technology and System of the Ministry of Civil Affairs National Research Center for Rehabilitation Technical Aids Beijing100176 China

ISBN: (纸本)9789811673801

Aiming at the surgical requirements of the external fixator for the correction of internal knee varus, there is an urgent clinical need to design a bone external fixation system with precise motion and independently adjustable parameters. Based on the design idea of telecentric mechanism, the orthopaedic mechanism with virtual central motion is innovatively designed based on the theory of rotational volume, and it can rotate around the X and Y axes and move independently along the Z axis, constituting a personalized 2R1T-RCM orthopaedic external fixation robot mechanism. Based on the rotation theory, a modified Kuzbach–Grübler formula is proposed to analyze the degrees of freedom of the mechanism, and determine the motion condition and drive mode of the mechanism. Finally, the virtual central motion characteristics and independent motion function of the mechanism are verified by the motion simulation of the mechanism. The innovative configuration method of the mechanism with medical-industrial integration can meet the requirements of this orthopedic surgery and can also provide a reference for the configuration design of other skeletal orthopedic mechanisms. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Machine design

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A Four-Pronged Defense Against Byzantine Attacks in Federated Learning

arXiv

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arXiv 2023年

作者： Wan, Wei Hu, Shengshan Li, Minghui Lu, Jianrong Zhang, Longling Zhang, Leo Yu Jin, Hai School of Cyber Science and Engineering Huazhong University of Science and Technology China School of Software Engineering Huazhong University of Science and Technology China School of Information and Communication Technology Griffith University Australia School of Computer Science and Technology Huazhong University of Science and Technology China National Engineering Research Center for Big Data Technology and System Services Computing Technology and System Lab Hubei Key Laboratory of Distributed System Security China Hubei Engineering Research Center on Big Data Security China Cluster and Grid Computing Lab

Federated learning (FL) is a nascent distributed learning paradigm to train a shared global model without violating users' privacy. FL has been shown to be vulnerable to various Byzantine attacks, where malicious participants could independently or collusively upload well-crafted updates to deteriorate the performance of the global model. However, existing defenses could only mitigate part of Byzantine attacks, without providing an all-sided shield for FL. It is difficult to simply combine them as they rely on totally contradictory assumptions. In this paper, we propose FPD, a four-pronged defense against both non-colluding and colluding Byzantine attacks. Our main idea is to utilize absolute similarity to filter updates rather than relative similarity used in existingI works. To this end, we first propose a reliable client selection strategy to prevent the majority of threats in the bud. Then we design a simple but effective score-based detection method to mitigate colluding attacks. Third, we construct an enhanced spectral-based outlier detector to accurately discard abnormal updates when the training data is not independent and identically distributed (non-IID). Finally, we design update denoising to rectify the direction of the slightly noisy but harmful updates. The four sequentially combined modules can effectively reconcile the contradiction in addressing non-colluding and colluding Byzantine attacks. Extensive experiments over three benchmark image classification datasets against four state-of-the-art Byzantine attacks demonstrate that FPD drastically outperforms existing defenses in IID and non-IID scenarios (with 30% improvement on model accuracy). © 2023, CC BY.

关键词： Classification (of information)

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Experimental study on the energy loss from flow and electrical of vanadium battery with constant pump frequency 2

Experimental study on the energy loss from flow and electric...

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2023 2nd International Conference on New Energy, Energy Storage and Power Engineering, NESP 2023

作者： Sun, Yanzhao Zou, Tao Li, Dianhong Li, Juntao School of Electrical Engineering and Automation Wuhan University Hubei Wuhan430072 China Big Pawer Electrical Technology Xiangyang Co. Ltd. Hubei Xiangyang441057 China Hubei Key Laboratory of Power System Design and Test for Electrical Vehicle Hubei University of Arts and Science Hubei Xiangyang441053 China Hunan Vanadium Valley New Energy Technology Co. Ltd. Hunan Changsha410116 China

When the vanadium battery was running, pump frequency and current density were two frequently adjusted parameters. When the pump frequency was constant, the main flow-electrical parameter variation needs to be further studied. To this end, a 10 kW vanadium battery was built. When the current density was relatively high during the charge-discharge, the flow-electrical parameters of the cathode and anode including the temperature, flow resistance, turning voltage difference, capacity loss, energy loss and energy efficiency were studied. Besides, the compositions of capacity and energy were introduced, and the loss calculation scheme was proposed. Firstly, in flow analysis, the flow resistance was defined, which represents the flow state of the electrolyte. It was found that the flow resistance was nearly linear with the temperature. Secondly, in electric analysis, the turning voltage difference increased with the current density increasing. For the same current density, the total energy loss of charge was less than the discharge, and the energy loss of bypass was less than the internal resistance. With the current density increasing, the energy efficiency decreased. The research can be provided insight into the optimizing operation for the vanadium battery. © Published under licence by IOP Publishing Ltd.

关键词： Current density

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