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Theoretical analyses of mechanical performance of higher-order vertex-based hierarchical square cell structure subjected to compression

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Journal of Physics: Conference Series 2019年第5期1213卷 052116-052116页

作者： Shi, Chong Wang, Zhonggang School of Traffic & Transportation engineering Central South University Changsha Hunan China Key Laboratory of Traffic Safety on Track Ministry of Education Changsha Hunan China Joint International Research Laboratory of Key Technology for Rail Traffic Safety Changsha Hunan China National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle Changsha Hunan China

Hierarchical structure has gained great popularity in recent years, due to its significant promotion on structural strength and stiffness. In this study, the concept of high-order vertex-based hierarchy structure (VHS) was incorporated based on the new-rising multi-cell square tubes by replacing every vertex with scaled itself, layer by layer. The theoretical solution of VHS structure subjected to static compression has been conducted, based on the classical Super Folding Element. Mean crushing force ( MCF, P ) and energy absorption E have been calculated theoretically. The innovative finding lies that the relationship of the mean load between case lever i to lever i+1 has been determined. The relationship of the mean load between case lever i to lever i+1 mainly related to the cell number and length scale. All these achievements shield a light in aid to design novel thin-walled and light-weight energy absorption device.

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Self-ordering induces multiple topological transitions for in-plane bulk waves in solid phononic crystals

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Physical Review B 2018年第1期98卷 014302-014302页

作者： Jiujiu Chen Hongbo Huang Shaoyong Huo Zhuhua Tan Xiaoping Xie Jianchun Cheng Guo-liang Huang State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha 410082 China School of Mechanical Engineering Hebei University of Technology Tianjin 300401 China Department of Physics Nanjing University Nanjing 210093 China Department of Mechanical and Aerospace Engineering University of Missouri Columbia Missouri 65211 USA

Topological defects with symmetry-breaking phase transitions have captured much attention. A vortex generated by topological defects exhibits exotic properties, and its flow direction can be switched by altering the spin configurations. Contrary to electromagnetic and acoustic domains, the topological transport of in-plane bulk waves in periodic structures with topological defects is not well explored due to the mode conversion between longitudinal and transverse modes. Here, we propose an elastic topological insulator with spontaneously broken symmetry based on the topological theory of defects and homotopy theory. Multiple topological transitions for in-plane bulk waves are achieved by topologically modifying the ellipse orientation in a triangular lattice of elliptical cylinders. The solid system, independent of the number of molecules in order-parameter space, breaks through the limit of point-group symmetry to emulate elastic pseudospin-orbit coupling. The transport robustness of the edge states is experimentally demonstrated. Our approach provides new possibilities for controlling and transporting in-plane bulk waves.

关键词： Acoustic metamaterials Edge states Bloch-Floquet theorem Ultrasound techniques

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Adaptive operation strategy for voltage stability enhancement in active DMFCs

arXiv

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arXiv 2018年

作者： Yang, Qin-Wen Hu, Xu-Qu Lei, Xiu-Cheng Zhu, Ying Wang, Xing-Yi Ji, Sheng-Cheng State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China Beijing Aeronautical Science & Technology Research Institute of COMAC Beijing102211 China

An adaptive operation strategy for on-demand control of active direct methanol fuel cells (DMFCs) is proposed as an alternative method to enhance the voltage stability. A simplified semi-empirical model is firstly developed to describe I-V relationships based on uniform-designed experiments. It is then embedded into multi-objective optimizations to construct the adaptive operation strategy. Experimental studies are implemented on different DMFC systems to validate the proposed semi-empirical model, control strategy and system response to operational adjustments. Numerical simulations are also performed to investigate the underlying mechanisms of the proposed adaptive operation strategy. The results show that the adaptive operation strategy provides possibilities for voltage stability enhancement without the sacrifice of energy conversion efficiency. The adaptive operations are also found to be able to extend the range of operating current density or to decrease the voltage deviation according to ones Copyright © 2018, The Authors. All rights reserved.

关键词： Direct methanol fuel cells (DMFC)

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Experimental study on the energy flow of a gasoline-powered vehicle under the NEDC of cold starting

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Applied Thermal engineering 2017年 115卷 1173-1186页

作者： Duan, Xiongbo Fu, Jianqin Zhang, Zhizhong Liu, Jingping Zhao, Dan Zhu, Guohui State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha410082 China Research Center for Advanced Powertrain Technology Hunan University Changsha410082 China Division of Aerospace Engineering College of Engineering Nanyang Technological University Singapore639798 Singapore

In order to evaluate and improve the fuel utilization efficiency of gasoline-powered vehicle, the vehicle energy flow test was conducted on chassis dynamometer under the NEDC of cold starting. Based on the tested data, the vehicle energy balance was built under the whole NEDC. Research results show that the distributions of various kinds of energy flow were largely influenced by vehicle operating conditions. Apart from idling conditions, the brake thermal efficiency of internal combustion engine (ICE) is mainly between 10% and 35%. At the initial stage of NEDC, the brake thermal efficiency is very low due to the cold starting. Under urban driving cycle (UDC), the percentage of pumping loss is usually below 10%, and under extra urban driving cycle (EUDC), it further decreases and even approaches to zero. The exhaust gas energy flow is mainly influenced by the mass flow rate of exhaust gas, while its percentage in total fuel energy depends largely on exhaust gas temperature. In general, the coolant energy flow is less sensitive to the ICE operating conditions, but its percentage fluctuates wildly under the transient conditions of NEDC. In most cases, the percentage of ICE coolant energy flow is between 13% and 35% with dramatic fluctuations, and the sudden deceleration of vehicle causes the generation of sharp peaks of the percentages of pumping loss and coolant energy flow. © 2016 Elsevier Ltd

关键词： Internal combustion engines

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Improved Wavelet Denoising by Penalty Function and Regularization Parameter

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Journal of Physics: Conference Series 2019年第2期1345卷

作者： Wanhui Wei Wei Zhou Yongjun Wu School of Traffic & Transportation engineering Central South University Changsha Hunan 410083 China Key Laboratory of Traffic Safety on Track Ministry of Education Joint International Research Laboratory of Key Technology for Rail Traffic Safety Changsha Hunan 410083 China National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle Changsha Hunan 410083 China Changsha Hunan 410083 China

Wavelet-based convex optimization in sparse signal processing has attracted extensive research interest in recent years. Research demonstrates that the penalty function promotes the sparsity and improves the accuracy better than L1 norm method in dealing with convex and sparse signal reconstruction issues. This paper presents an improved denoising model which utilizes a penalty function to induce stronger sparsity in wavelet domain. In this paper, we have redefined the relationship model between signal noise levels and the regularization parameter to enhance sparsity caused by penalty functions in a wavelet domain. And three penalty functions are employed for wavelet coefficients to induce strong sparse wavelet coefficients under the wavelet domain. We then apply the improved wavelet denoising algorithm for image denoising to get the values of the PSNR are analysed under different noise level conditions. Experimental results clearly show that the improved wavelet denoising model is strength in terms of both quantitative measure and structural similarity quality, and outperforms many widely used denoising algorithms.

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Fault-Tolerant Flight Control for an Air-breathing Hypersonic vehicle Using Multivariable Sliding Mode and Neural Network 36

Fault-Tolerant Flight Control for an Air-breathing Hypersoni...

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第36届中国控制会议

作者： Peng Li Xiang Yu Jianjun Ma Zhiqiang Zheng College of Mechatronics Engineering and Automation National University of Defense Technology Department of Mechanical and Industrial Engineering Concordia University State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University

ISBN: (纸本)9781538629185

This paper presents a fault-tolerant control(FTC) with integration of neural network(NN) and multivariable sliding mode approaches for an air-breathing hypersonic vehicle(AHV),where both partial loss of effectiveness faults and bias faults in actuators are considered.A radial bias function NN(RBFNN) is derived using on-line updating law to approximate the lumped uncertainties,which consists of actuator faults and system uncertainties.A finite-time convergent multivariable sliding mode control(SMC) is developed against system uncertainties and actuator *** results of a generic AHV are provided to demonstrate the effectiveness of the proposed FTC scheme.

关键词： Fault-tolerant control multivariable sliding mode neural network air-breathing hypersonic vehicle

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Self-ordering induces multiple topological transitions for elastic waves in phononic crystals

arXiv

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arXiv 2018年

作者： Chen, Jiujiu Huang, Hongbo Huo, Shaoyong Tan, Zhuhua Xie, Xiaoping Cheng, Jianchun State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China School of Mechanical Engineering Hebei University of Technology Tianjin300401 China Department of Physics Nanjing University Nanjing210093 China

Topological defects with symmetry-breaking phase transitions have captured much attention. Vortex generated by topological defects exhibits exotic properties and its flow direction can be switched by altering the spin configurations. Contrary to electromagnetic and acoustic domains, the topological transport of elastic waves in periodic structures with topological defects is not well explored due to the mode conversion between the longitudinal and transverse modes. Here, we propose an elastic topological insulator with spontaneously broken symmetry based on the topological theory of defects and homotopy theory. Multiple topological transitions for elastic waves are achieved by topologically modifying the ellipse orientation in a triangular lattice of elliptical cylinders. The solid system, independent of the number of molecules in order parameter space, breaks through the limit of the point-group symmetry to emulate elastic pseudospin-orbit coupling. The transport robustness of the edge states is experimentally demonstrated. Our approach provides new possibilities for controlling and transporting elastic waves. Copyright © 2018, The Authors. All rights reserved.

关键词： Elastic waves

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Simulation Analysis of Flow Field in Engine Compartment of a Rear-Mounted Exhaust

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IOP Conference Series: Materials Science and engineering 2019年第1期562卷

作者： Y Y Xie L Q Zhang Y L Yan S W Qiu C Z Tan Mechanical and Electrical Engineering Institute Central South University of Forestry and Technology Changsha 410000 Hunan China State Key Laboratory of Advanced Design and Manufacture for Vehicle Body Hunan University Changsha 410082 Hunan China Changan Oushang Automotive Research Institute Chongqing 400023 China

The numerical simulation of the flow field in the engine compartment of a car is the basis for the evaluation and research of the air flow characteristics in the engine compartment. In this paper, the computational fluid simulation software STAR-CCM+ was applied to simplify the vehicle model of a rear-mounted exhaust. The surface wrapper and surface remesher were used to obtain the whole vehicle surface mesh. Combining with the vehicle wind tunnel model was generated the volume mesh based on Trim mesh sub-regional method. Then, the finite element model of the car engine compartment was established. Three-dimensional flow field in engine compartment was analyzed under reasonable boundary conditions, and found the reflow at climbing is more apparent as compared with that at high constant speed. Then the flow rate experiment of the whole vehicle was obtained wind speed value of the windward surface of the radiator. The error between the simulated value and the experimental value is within 10%, indicating that the simulation model established in this paper is reliable and possesses high simulating accuracy.

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The real-time shortest path algorithm with a consideration of traffic-light

The real-time shortest path algorithm with a consideration o...

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作者： Hu, Lin Yang, Jia Huang, Jing School of Automotive and Mechanical Engineering Changsha University of Science and Technology Changsha China Hunan Province Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle Changsha University of Science and Technology Changsha China State Key Laboratory of Advanced Design and Manufacture for Vehicle Body Hunan University Changsha China

In urban area, the delay due to the traffic-light should be taken into considerable when searching for the optimal path. So this paper presents an algorithm for find the real-time shortest path in urban area with traffic-light. The core of the algorithm is a translation module which can translate the delay due to the traffic-light(a quantity about time) into length (a quantity about space). In this way to simplify the calculation difficulty and combine the influence due to time delay as well as length simultaneously. Then, this module was added into the heuristic function of A∗ algorithm to get the improved algorithm. Finally, the simple simulation of the algorithm shown that it can save 5.8 time even when driving more 10 distances. In conclusion, the algorithm is very suitable for the urban traffic and the longer the distance, the more obvious effects it would be. © 2016 - IOS Press and the authors.

关键词： Heuristic algorithms

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Human motion data editing based on a convolutional automatic encoder and manifold learning

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Entertainment Computing 2019年 30卷

作者： Dongsheng Zhou Xinzhu Feng Xin Yang Qiang Zhang Xiaopeng Wei Xiaoyong Fang Deyun Yang Key Laboratory of Advanced Design and Intelligent Computing (Dalian University) Ministry of Education Dalian 116622 China College of Computer Science and Technology Dalian University of Technology Dalian 116024 China Research Institute of Human Factors and Safety Engineering Hunan Institute of Technology Hengyang Hunan Province 421002 China School of Information Science and Technology Taishan University Tai’an Shandong Province 271000 China

technology of human motion capture has been widely used in digital entertainment field. Editing the existing large amount of human motion capture data, correcting and eliminating motion distortion caused by noise and other defects have important value and significance for data reuse. In this paper, data processing is carried out based on convolutional automatic encoder and manifold learning. The popular structure of human motion data was learned by a one-dimensional time domain convolution automatic encoder, in which the hidden unit of the automatic encoder represents motion data. Three constraints were used to overcome the problem that the hidden unit has too much motion editing range. The data to be processed in this paper has no limit on the number of motions. The proposed method can process large data sets in parallel and automatically perform manifold learning without manual labelling and segmentation. In the final, comparative experiments based on a variety of damaged motion data have been carried out. The results showed that the proposed method can effectively reduce the error of the original motion data, and has achieved good results in both objective evaluation and subjective evaluation.

关键词： Human motion data Convolution automatic encoder Manifold learning Motion editing

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