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Implementation of dual time-stepping strategy of the gas-kinetic scheme for unsteady flow simulations

Physical Review E 2017年第5期95卷 053307-053307页

作者： Ji Li Chengwen Zhong Yong Wang Congshan Zhuo National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an Shaanxi 710072 China

In our study, the dual time-stepping strategy of the gas-kinetic scheme is constructed and used for the simulation of unsteady flows. In comparison to the previous implicit gas-kinetic scheme, both the inviscid and viscous flux Jacobian are considered in our work, and the linear system of the pseudo-steady-state is solved by applying generalized minimal residual algorithm. The accuracy is validated by several numerical cases, the incompressible flow around blunt bodies (stationary circular cylinder and square cylinder), and the transonic buffet on the NACA0012 airfoil under hybrid mesh. The numerical cases also demonstrate that the present method is applicable to approach the fluid flows from laminar to turbulent and from incompressible to compressible. Finally, the case of acoustic pressure pulse is carried out to evaluate the effects of enlarged time step, and the side effect of enlarged time step is explained. Compared with the explicit gas-kinetic scheme, the proposed scheme can greatly accelerate the computation and reduce the computational costs for unsteady flow simulations.

关键词： Aerodynamics Compressible flows Shock waves

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Development of high-strength,low-cost wrought Mg–2.0 mass% Zn alloy with high Mn content

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Progress in Natural science:Materials International 2016年第6期26卷 630-635页

作者： Fusheng.Pan Jianjun Mao Gen Zhang Aitao Tang Jia She College of Materials Science and Engineering Chongqing University National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing Research Center for Advanced Materials Chongqing Academy of Science and Technology Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China

Mg–Zn–Mn-based alloys have received considerable attention because of their high creep resistance, strength,and good corrosion resistance. The alloying element Mn in Mg–Zn-based alloys is commonly less than 1 wt%. In the present study, the effect of high Mn content(1 wt% and 2 wt%) on the microstructures and mechanical properties of Mg–2Zn–0.3Sr extruded alloy was investigated. The results revealed that the high Mn content significantly increased the ultimate tensile strength, tensile yield strength, compress yield strength, and yield asymmetry of the alloy without affecting its ductility. The dynamically recrystallized(DRXed) grains of Mg–2Zn–0.3Sr were remarkably refined because of the large amount of fine Mn precipitates in the homogenized alloy. The improved strengths were mainly attributed to the fine DRXed grains according to the Hall–Petch effect and to the large amount of spherical and < 0001 > Mn precipitates through the precipitation and dispersion strengthening. The fine DRXed grains and numerous Mn precipitates effectively suppressed the extension twining, substantially enhanced the compress yield strength, and resulted in improved anisotropy.

关键词： Magnesium alloy Mg–Zn alloy Microstructure Ultra-fine grains Second phase Mechanical properties

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Future prospect of solar sails by comparing two light propulsion sailing schemes 21

Future prospect of solar sails by comparing two light propul...

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21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017

作者： Jiang, Li Shi, Aiming Qin, Zhixuan NPU-Duke Joint Research Laboratory for Light Pressure Propulsion Solar Sail-Craft Dynamics National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University National Key Laboratory of Aerodynamic Design and Research Box 114 No.127 West Youyi Road Xi’anShaanxi710072 China

ISBN: (数字)9781624104633

ISBN: (纸本)9781624104633

The concept of solar sailing using sunlight propelling thin membrane structure has been proposed for a long time. The principle of this technology is accumulating velocity to reach a very high speed which may up to 10% speed of light based upon the fact that object could be consistently accelerated even by a tiny force in outer space environment. In 2010, solar sailing was confirmed by IKAROS of JAXA. In this paper, two kinds of propulsive mechanism are mentioned. One propulsive way is based upon the momentum exchange of photons and solar sails. The other propulsive scheme which uses special-made graphene material emitting electrons exhibits a great potential. The former scheme based upon momentum exchange is relatively persistent and stable but requires a large reflecting surface area at the same time. The latter scheme could provide a several orders larger propulsive force although there are engineering difficulties need to be overcome. The values of acceleration due to two propulsive schemes respectively are compared to illustrate the propulsive efficiency. It is believed that if the latter technology matures and these two propulsive ways could be combined comprehensively, a combined light propelling system with better performance would be possible in the future. © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Solar sails

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Soft Robots: Fast‐Response, Stiffness‐Tunable Soft Actuator by Hybrid Multimaterial 3D Printing (Adv. Funct. Mater. 15/2019)

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Advanced Functional Materials 2019年第15期29卷

作者： Yuan‐Fang Zhang Ningbin Zhang Hardik Hingorani Ningyuan Ding Dong Wang Chao Yuan Biao Zhang Guoying Gu Qi Ge Digital Manufacturing and Design Centre Singapore University of Technology and Design Singapore 487372 Singapore Soft Robotics and Biodesign Lab Robotics Institute School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University Shanghai 200240 China Science and Math Cluster Singapore University of Technology and Design Singapore 487372 Singapore

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Scaling analysis and SE simulation of the tilted cylinder-interface capillary interaction

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IOP Conference Series: Materials science and Engineering 2018年第1期372卷

作者： S Q Gao X Y Zhang Y H Zhou National Key Laboratory of Science and Technology on Reactor System Design Technology Nuclear Power Institute of China Chengdu 610041 China Department of Mechanics and Engineering Sciences College of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000 China

The capillary interaction induced by a tilted cylinder and interface is the basic configuration of many complex systems, such as micro-pillar arrays clustering, super-hydrophobicity of hairy surface, water-walking insects, and fiber aggregation. We systematically analyzed the scaling laws of tilt angle, contact angle, and cylinder radius on the contact line shape by SE simulation and experiment. The following in-depth analysis of the characteristic parameters (shift, stretch and distortion) of the deformed contact lines reveals the self-similar shape of contact line. Then a general capillary force scaling law is proposed to incredibly grasp all the simulated and experimental data by a quite straightforward ellipse approximation approach.

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General formation control for multi-agent systems with double-integrator dynamics

arXiv

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arXiv 2018年

作者： Wang, Chen Xia, Weiguo Sun, Jinan Fan, Ruifeng Xie, Guangming State Key Laboratory of Turbulence and Complex Systems Intelligent Biomimetic Design Lab College of Engineering Peking University Beijing100871 China School of Control Science and Engineering Dalian University of Technology Dalian116024 China National Engineering Research Center for Software Engineering Peking University Beijing100871 China

We study the general formation problem for a group of mobile agents in a plane, in which the agents are required to maintain a distribution pattern, as well as to rotate around or remain static relative to a static/moving target. The prescribed distribution pattern is a class of general formations that the distances between neighboring agents or the distances from each agent to the target do not need to be equal. Each agent is modeled as a double integrator and can merely perceive the relative information of the target and its neighbors. A distributed control law is designed using the limit-cycle based idea to solve the problem. One merit of the controller is that it can be implemented by each agent in its Frenet-Serret frame so that only local information is utilized without knowing global information. Theoretical analysis is provided of the equilibrium of the N-agent system and of the convergence of its converging part. Numerical simulations are given to show the effectiveness and performance of the proposed controller. Copyright © 2018, The Authors. All rights reserved.

关键词： Mobile agents

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Semantic-driven method for designing 3D busbars

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Computer Aided Drafting,design and Manufacturing 2017年第2期27卷 16-23页

作者： Shi Kanle Zhu Zixu Wu Zijian Zhang Hui Yong Junhai School of Software Tsinghua University Key Laboratory for Information System Security Ministry of Education of China Tsinghua National Laboratory for Information Science and Technology

Traditional busbar design is inefficient, costly, and error-prone because of frequent changes of requirements. This paper proposes a semantic-driven method for designing 3D busbars to solve this problem. The design process contains two main parts, namely, semantic-driven routing design and automatic routing segmentation. Semantic-driven routing design creates a relation table between electrical semantics and 3D modeling parameters, as well as helps designers create routings efficiently using electrical parameters as input. Automatic routing segmentation can convert routings into busbar segments that also include manufacturing information. Because the design operations are associated with one another, the resulting busbars can automatically be changed in real time when requirements are changed.

关键词： semantic-driven design busbar design busbar segmentation modeling change of requirement

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Automatic wiring method for switchgear design

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Computer Aided Drafting,design and Manufacturing 2017年第2期27卷 32-38页

作者： Shi Kanle Gao Ying Wu Zijian Zhang Hui Yong Junhai School of Software Tsinghua University Key Laboratory for Information System Security Ministry of Education of China Tsinghua National Laboratory for Information Science and Technology

An automatic 3D wiring method for switchgear design is proposed in this paper. First, wiring constraints are created, and a corresponding evaluation model is proposed. Then, based on the structure of the cabinet, we propose a contour expansion scheme to construct rough paths. Different wiring features of the switchgear are used to connect rough local paths. All the paths are represented in a uniform data structure and forma path network. Finally, an improved A* algorithm is used to search the wiring path between the components in the routing network; the evaluation model is considered as heuristic rules for path searching. The result can satisfy the practical requirements of switchgear design. Experimental results are also provided.

关键词： wiring method path searching contour expansion switchgear design A* algorithm

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A B-spline curve extension algorithm

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science china(Information sciences) 2016年第3期59卷 37-45页

作者： Yang LU Kanle SHI Junhai YONG Hejin GU Haichuan SONG School of Software Tsinghua University Department of Computer Science and Technology Tsinghua University Key Laboratory for Information System Security Ministry of Education of China Tsinghua National Laboratory for Information Science and Technology Jiangxi Academy of Science

B-spline curve extension is an important operation in computer aided design systems. In this paper,we present a new extension algorithm for B-spline curves. The algorithm uses curve unclamping to generate a uniform B-spline curve segment from the original curve and gradually extends the segment to pass through every target point. Algorithms of uniform B-spline curves are used such that our algorithm has a low time cost and can easily handle arbitrary-order derivative constraints at the target points. Generalization for non-uniform rational B-spline curve extension is also discussed, and examples show the efficiency of our method.

关键词： curve extension B-spline/NURBS unclamping clamping uniform

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design and Analysis of All-electric Aircraft Nose Wheel Steering system Based on Intelligent Algorithm

Design and Analysis of All-electric Aircraft Nose Wheel Stee...

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2017 2nd International Conference on Applied Mechanics and Mechatronics Engineering(AMME 2017)

作者： Ming ZHANG Meng-jiao LENG Xin WU Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics & Astronautics Aviation Key Laboratory of Science and Technology on Aero Electromechanical System Integration

As all-electric aircraft has many advantages, aircraft nose wheel steering system would be developed to the all-electric direction. Aiming at the control demand of nose wheel steering system, based on the basic principles of nose wheel steering system and the design technique of mechanotronics, an all-electric aircraft nose wheel steering system composed of a nose wheel steering mechanism of two worm gear and a control servo system of fly-by-wire having both steering and anti-shimmy function is designed to meet the demand for operation control in nose wheel steering system. Besides, the fuzzy algorithm and BP neural network algorithm is applied to the control system to explore its algorithm. Then based on Matlab/Simulink and LMS/AMESim software, the united simulation model of the system with fuzzy PID controller is established to make the dynamic simulation analysis for the verification of its steering function, the research results indicate that the nose wheel steering system is reasonable and validated, can meet the requirements of the general project.

关键词： Mechanotronics design United simulation analysis Nose wheel steering system Landing gear

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