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Journal of Computational Mathematics 2006年第3期24卷 265-280页

作者： qiang Du Liyong Zhu Department of Mathematics Pennsylvania State University University Park PA 16802 USA ICMSEC Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100080 China ICMSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

In this paper, we study numerical approximations of a recently proposed phase field model for the vesicle membrane deformation governed by the variation of the elastic bending energy. To overcome the challenges of high order nonlinear differential systems and the nonlinear constraints associated with the problem, we present the phase field bending elasticity model in a nested saddle point formulation. A mixed finite element method is then employed to compute the equilibrium configuration of a vesicle membrane with prescribed volume and surface area. Coupling the approximation results for a related linearized problem and the general theory of Brezzi-Rappaz-Raviart, optimal order error estimates for the finite element approximations of the phase field model are obtained. Numerical results are provided to substantiate the derived estimates.

关键词： Bio-membrane Elastic bending energy Phase field Finite element Nestedmixed saddle point formulation Optimal error estimates.

The Complexity and On-Line Algorithm for Automated Storage and Retrieval System with Stacker Cranes on One Rail

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Journal of Systems Science & Complexity 2016年第5期29卷 1302-1319页

作者： GAO qiang LU Xiwen Department of Mathematics East China University of Science and Technology

This paper considers an on-line scheduling and routing problem concerning the automated storage and retrieval system from tobacco industry. In this problem, stacker cranes run on one common rail between two racks. Multiple input/output-points are located at the bottom of the racks. The stacker cranes transport bins between the input/output-points and cells on the racks to complete requests generated over time. Each request should be accomplished within its response time. The objective is to minimize the time by which all the generated requests are completed. Under a given physical layout, the authors study the complexity of the problem and design on-line algorithms for both one-stacker-crane model and two-stacker-crane model. The algorithms axe validated by instances and numerical simulations.

关键词： Automated storage and retrieval system NPohard on-line algorithm routing scheduling.

Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications

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Science China(Physics,Mechanics & Astronomy) 2018年第10期61卷 2-13页

作者： qiang Yuan Lei Feng Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210008China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Center for High Energy Physics Peking UniversityBeijing 100871China

The DArk Matter Particle Explorer （DAMPE） is a satellite-borne, high-energy particle and 3,-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals an interesting spectral softening arount 0.9 TeV and a tentative peak around 1.4 TeV. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.

关键词： dark matter cosmic rays electrons plus positrons pulsars

A new simpler rotation/curvature correction method for Spalart-Allmaras turbulence model

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Chinese Journal of Aeronautics 2013年第2期26卷 326-333页

作者： Zhang qiang Yang Yong National Key Laboratory of Science and Techniques on Aerodynamic Design and Research Northwestern Polytechnical University

A new and much simpler rotation and curvature effects factor, which takes the form of Richardson number suggested by Hellsten originally for SST k-ω model, is presented for Spalart and Shur＇s rotation and curvature correction in the context of Spalart-Allmaras （SA） turbulence model. The new factor excludes the Lagrangian derivative of the strain rate tensor that exists in the SARC model, resulting in a simple, efficient and easy-to-implement approach for SA turbulence model （denoted as SARCM） to account for the effects of system rotation and curvature, techniquely. And then the SARCM is tested through turbulent curved wall flows： one is the flow over a zeropressure-gradient curved wall and the other is the channel flow in a duct with a U-turn. Predictions of the SARCM model are compared with experimental data and with the results obtained using original SA and SARC models. The numerical results show that SARCM can predict the rotation-curvature effects as accurately as SARC, but considerably more efficiently. Additionally, the accuracy of SARCM might strongly depend on the rotation-curvature model constants. Suggesting values for those constants are given, after some trials and errors.

关键词： Accuracy Computation Curvature Improvement Robust Rotation Strain rate tensor Turbulence model

Robust Attitude Control for Reusable Launch Vehicles Based on Fractional Calculus and Pigeon-inspired Optimization

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IEEE/CAA Journal of Automatica Sinica 2017年第1期4卷 89-97页

作者： qiang Xue Haibin Duan Bio-inspired Autonomous Flight Systems(BAFS) Research Group the Science and Technology on Aircraft Control Laboratory School of Automation Science and Electrical Engineering Beihang University (BUAA) IEEE

In this paper, a robust attitude control system based on fractional order sliding mode control and dynamic inversion approach is presented for the reusable launch vehicle RLV during the reentry phase. By introducing the fractional order sliding surface to replace the integer order one, we design robust outer loop controller to compensate the error introduced by inner loop controller designed by dynamic inversion approach. To take the uncertainties of aerodynamic parameters into account, stochastic robustness design approach based on the Monte Carlo simulation and Pigeon-inspired optimization is established to increase the robustness of the controller. Some simulation results are given out which indicate the reliability and effectiveness of the attitude control system. © 2014 Chinese Association of Automation.

关键词： Attitude control Calculations Communication satellites Control systems Intelligent systems Launch vehicles Launching Monte Carlo methods Nonlinear control systems Reusability Reusable rockets Robustness (control systems) Sliding mode control Stochastic systems Vehicles

Coupled Lagrangian impingement spray model for doublet impinging injectors under liquid rocket engine operating conditions

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Chinese Journal of Aeronautics 2017年第4期30卷 1391-1406页

作者： qiang WEI Guozhu LIANG School of Astronautics Beihang University Beoing 100083 China

To predict the effect of the liquid rocket engine combustion chamber conditions on the impingement spray, the conventional uncoupled spray model for impinging injectors is extended by considering the coupling of the jet impingement process and the ambient gas field. The new coupled model consists of the plain-orifice sub-model, the jet-jet impingement sub-model and the droplet collision sub-model. The parameters of the child droplet are determined with the jet-jet impingement sub-model using correlations about the liquid jet parameters and the chamber *** overall model is benchmarked under various impingement angles, jet momentum and offcenter ratios. Agreement with the published experimental data validates the ability of the model to predict the key spray characteristics, such as the mass flux and mixture ratio distributions in quiescent air. Besides, impinging sprays under changing ambient pressure and non-uniform gas flow are investigated to explore the effect of liquid rocket engine chamber conditions. First, a transient impingement spray during engine start-up phase is simulated with prescribed pressure profile. The minimum average droplet diameter is achieved when the orifices work in cavitation state, and is about 30% smaller than the steady single phase state. Second, the effect of non-uniform gas flow produces off-center impingement and the rotated spray fan by 38°. The proposed model suggests more reasonable impingement spray characteristics than the uncoupled one and can be used as the first step in the complex simulation of coupling impingement spray and combustion in liquid rocket engines.

关键词： Combustion chamber Doublet impinging injector Impingement spray model Lagrangian method Liquid rocket engine

Modeling and Analytical Solution of Chatter Stability for T-slot Milling

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Chinese Journal of Mechanical Engineering 2010年第1期23卷 88-93页

作者： LI Zhongqun LIU qiang School of Mechanical Engineering Hunan University of Technology Zhuzhou 412008 China School of Mechanical Engineering and Automation Beihang University Beijing 100191 China

T-slot milling is one of the most common milling processes in industry. Despite recent advances in machining technology, productivity of T-slot milling is usually limited due to the process limitations such as high cutting forces and stability. If cutting conditions are not selected properly the process may result in the poor surface finish of the workpiece and the potential damage to the machine tool. Currently, the predication of chatter stability and determination of optimal cutting conditions based on the modeling of T-slot milling process is an effective way to improve the material removal rate（MRR） of a T-slot milling operation. Based on the geometrical model of the T-slot cutter, the dynamic cutting force model was presented in which the average directional cutting force coefficients were obtained by means of numerical approach, and leads to an analytical determination of stability lobes diagram（SLD） on the axial depth of cut. A new kind of SLD on the radial depth of cut was also created to satisfy the special requirement of T-slot milling. Thereafter, a dynamic simulation model of T-slot milling was implemented using Matlab software. In order to verify the effectiveness of the approach, the transfer functions of a typical cutting system in a vertical CNC machining center were measured in both feed and normal directions by an instrumented hammer and accelerators. Dynamic simulations were conducted to obtain the predicated SLD under specified cutting conditions with both the proposed model and CutPro~. Meanwhile, a set of cutting trials were conducted to reveal whether the cutting process under specified cutting conditions is stable or not. Both the simulation comparison and experimental verification demonstrated that the satisfactory coincidence between the simulated, the predicted and the experimental results. The chatter-free T-slot milling with higher MRR can be achieved under the cutting conditions determined according to the SLD simulation.

关键词： machining dynamics T-slot milling chatter vibration stability lobes diagram

Kinematics-based four-state trajectory tracking control of a spherical mobile robot driven by a 2-DOF pendulum

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Chinese Journal of Aeronautics 2019年第6期32卷 1530-1540页

作者： Wei LI qiang ZHAN Robotics Institute Beihang UniversityBeijing 100083China Ecole Centrale de Pékin Beihang UniversityBeijing 100083China

Spherical mobile robot has compact structure, remarkable stability, and flexible motion,which make it have many advantages over traditional mobile robots when applied in those unmanned environments, such as outer planets. However, spherical mobile robot is a special highly under-actuated nonholonomic system, which cannot be transformed to the classic chained form. At present, there has not been a kinematics-based trajectory tracking controller which could track both the position states and the attitude states of a spherical mobile robot. In this paper, the four-state(two position states and two attitude states) trajectory tracking control of a type of spherical mobile robot driven by a 2-DOF pendulum was studied. A controller based on the shunting model of neurodynamics and the kinematic model was deduced, and its stability was demonstrated with Lyapunov’s direct method. The control priorities of the four states were allocated according to the magnification of each state tracking error in order to firstly ensure the correct tracking of the position states. The outputs(motor speeds) of the controller were regulated according to the maximum speeds and the maximum accelerations of the actuation motors in order to solve the speed jump problem caused by initial state errors, and continuous and bounded outputs were obtained. The effectiveness including the anti-interference ability of the proposed trajectory tracking controller was verified through MATLAB simulations.

关键词： Kinematics Lyapunov methods Neurodynamics Nonholonomic systems Spherical mobile robot Trajectory tracking

Posterior probability calculation procedure for recognition rate comparison

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Journal of Systems Engineering and Electronics 2016年第3期27卷 700-711页

作者： Jun He qiang Fu Science and Technology on Automatic Target Recognition Laboratory College of Electronic Science and EngineeringNational University of Defense Technology

This paper focuses on the recognition rate comparison for competing recognition algorithms, which is a common problem of many pattern recognition research areas. The paper firstly reviews some traditional recognition rate comparison procedures and discusses their limitations. A new method, the posterior probability calculation（PPC） procedure is then proposed based on Bayesian technique. The paper analyzes the basic principle, process steps and computational complexity of the PPC procedure. In the Bayesian view, the posterior probability represents the credible degree（equal to confidence level） of the comparison results. The posterior probability of correctly selecting or sorting the competing recognition algorithms is derived, and the minimum sample size requirement is also pre-estimated and given out by the form of tables. To further illustrate how to use our method, the PPC procedure is used to prove the rationality of the experiential choice in one application and then to calculate the confidence level with the fixed-size datasets in another application. These applications reveal the superiority of the PPC procedure, and the discussions about the stopping rule further explain the underlying statistical causes. Finally we conclude that the PPC procedure achieves all the expected functions and be superior to the traditional methods.

关键词： pattern recognition performance evaluation algorithm uncertainty analysis

Thermal design of a novel heat sink cooled by natural convection with phase transition in the series loop

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Science China(Technological Sciences) 2018年第11期61卷 1732-1744页

作者： CHEN Hao LI qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power Engineering Nanjing University of Science & Technology

In this paper, a novel heat sink, cooled by natural convection, with phase transition in the circulation loop was designed, and the heat sink was applied on averaging temperature and cooling the electronic equipment. The working fluid in the heat sink was driven by the capillary pump. Numerical simulations were performed, to study the heat transfer performance of two systems with various heating power, filling ratios and refrigerants. The influences of above elements on temperature uniformity of two systems were also studied and the thermal performances of two systems were compared. The volume of fluid(VOF) model was utilized to simulate fluid motion in ANSYS FLUENT. The simulation results indicate that the temperature differences of the system comprising two substrates(system 1) are very small under suitable filling ratio conditions, and the thermal performance of system 1 is preferable to the system comprising one substrate(system 2) at the same volume. Besides, the simulation results also show that the system using R245 fa possesses excellent temperature uniformity for the same filling ratio and heating ***, the experiments were investigated and the experimental results proved the correctness of the theoretical model.

关键词： natural convection vapor chamber circulation loop filling ratio temperature difference