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Science china(Physics,mechanics & Astronomy) 2009年第6期52卷 909-918页

作者： SHEN Fang1 & WU WangYi2.1 State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, china 2.State Key Laboratory of Turbulence and Complex Systems & department of {2. and engineering Science, Peking University, Beijing 100871, china 1. State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China 2. State Key Laboratory of Turbulence and Complex Systems & department of mechanics and {2. Science Peking University Beijing 100871 China

Basic function method is developed to treat the incompressible viscous flow. Artificial compressibility coefficient, the technique of flux splitting method and the combination of central and upwind schemes are applied to construct the basic function scheme of trigonometric function type for solving three-dimensional incompressible Navier-Stokes equations numerically. To prove the method, flows in finite-length-pipe are calculated, the velocity and pressure distribution of which solved by our method quite coincide with the exact solutions of Poiseuille flow except in the areas of entrance and exit. After the method is proved elementary, the hemodynamics in two-and three-dimensional aneurysms is researched numerically by using the basic function method of trigonometric function type and unstructured grids generation technique. The distributions of velocity, pressure and shear force in steady flow of aneurysms are calculated, and the influence of the shape of the aneurysms on the hemodynamics is studied.

关键词： basic function unstructured grid aneurysm viscous incompressible flow artificial compressibility flux splitting

Intelligent direct analysis of physical and mechanical parameters of tunnel surrounding rock based on adaptive immunity algorithm and BP neural network

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Journal of Pharmaceutical Analysis 2009年第1期21卷 22-30页

作者： Xiao-rui Wang1,2. Yuan-han Wang1, Xiao-feng Jia31.School of Civil engineering and mechanics,Huazhong University of Science and Technology, Wuhan 430074,{2. 2.department of Civil engineering,Nanyang Institute of Technology,Nanyang 473004,{2. 3.department of Chemistry and Bioengineering,Nanyang Institute of Technology,Nanyang 473004,{2.. School of Civil engineering and mechanics Huazhong University of Science and Technology Wuhan 430074 China department of Civil engineering Nanyang Institute of Technology Nanyang 473004 China department of Chemistry and Bioengineering Nanyang Institute of Technology Nanyang 473004 China

Because of complexity and non-predictability of the tunnel surrounding rock, the problem with the determination of the physical and mechanical parameters of the surrounding rock has become a main obstacle to theoretical research and numerical analysis in tunnel engineering. During design, it is a frequent practice, therefore, to give recommended values by analog based on experience. It is a key point in current research to make use of the displacement back analytic method to comparatively accurately determine the parameters of the surrounding rock whereas artificial intelligence possesses an exceptionally strong capability of identifying, expressing and coping with such complex non-linear relationships. The parameters can be verified by searching the optimal network structure, using back analysis on measured data to search optimal parameters and performing direct computation of the obtained results. In the current paper, the direct analysis is performed with the biological emulation system and the software of Fast Lagrangian Analysis of Continua (FLAC3D. The high non-linearity, network reasoning and coupling ability of the neural network are employed. The output vector required of the training of the neural network is obtained with the numerical analysis software. And the overall space search is conducted by employing the Adaptive Immunity Algorithm. As a result, we are able to avoid the shortcoming that multiple parameters and optimized parameters are easy to fall into a local extremum. At the same time, the computing speed and efficiency are increased as well. Further, in the paper satisfactory conclusions are arrived at through the intelligent direct-back analysis on the monitored and measured data at the Erdaoya tunneling project. The results show that the physical and mechanical parameters obtained by the intelligent direct-back analysis proposed in the current paper have effectively improved the recommended values in the original prospecting data. This is of p

关键词： adaptive immunity algorithm BP neural network physical and mechanical parameters surrounding rock direct-back analysis

On the definition of fractional derivatives in rheology

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Theoretical & Applied mechanics Letters 2011年第1期1卷 62-65页

作者： Fan Yang~(1,2.a)) and Ke-Qin Zhu~(1,b)) 1)department of engineering {2.,Tsinghua University,Beijing 100084,china 2.department of Physics,the Chinese University of Hong Kong,Hong Kong,china department of Physics the Chinese University of Hong Kong Hong Kong China

During the last two decades fractional calculus has been increasingly applied to physics, especially to *** is well known that there are obivious differences between Riemann-Liouville (R-L) definition and Caputo definition,which are the two most commonly used definitions of fractional *** multiple definitions of fractional derivatives have hindered the application of fractional calculus in *** this paper,we clarify that the R-L definition and Caputo definition are both Theologically unreasonable with the help of the mechanical analogues of the fractional element *** also find that to make them more reasonable Theologically,the lower terminals of both definitions should be put to—∞.We further prove that the R-L definition with lower terminal—∞and the Caputo definition with lower terminal—∞are equivalent in the differentiation of functions that are smooth enough and functions that have finite number of singular *** we can define the fractional derivatives in rheology as the R-L derivatives with lower terminal—∞(or,equivalently,the Caputo derivatives with lower terminal—∞) not only for steady-state processes,but also for transient processes.

关键词： fractional derivative Caputo definition Riemann-Liouville definition Scott-Blair model

Tracheal compliance and limit flow rate changes in a murine model of asthma

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Science china(Life Sciences) 2008年第10期51卷 922-931页

作者： TENG ZhongZhao1, WANG YiQin2. LI FuFeng2. YAN HaiXia2.& LIU ZhaoRong3 1 department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA, 01609, USA 2.Syndrome Laboratory of TCM, Shanghai University of Traditional Chinese Medicine, Shanghai 2.12.3, china 3 department of mechanics and engineering Science, Fudan University, Shanghai 2.0433, china 1. department of Mathematical Sciences Worcester Polytechnic Institute Worcester MA 01609 USA 2. Syndrome Laboratory of TCM Shanghai University of Traditional Chinese Medicine Shanghai 201203 China 3. department of mechanics and {2. Science Fudan University Shanghai 200433 China

Trachea is the unique passage for air to flow in and out. Its tone is of importance for the respiration system. However, investigation on how tracheal tone changes due to asthma is limited. Aiming at studying how the mechanical property changes due to asthma as well as the compliance and flow limitation, the following methods are adopted. Static and passive pressure-volume tests of rats' trachea of the asthmatic and control groups are carried out and a new type of tube law is formulated to fit the experimental data, based on which changes of compliance and limit flow rate are investigated. In order to give explanation to such changes, histological examinations with tracheal soft tissues are made. The results show that compliance, limit flow rate and material constants included in the tube law largely depend on the longitudinal stretching ratio. Compared with the control group, the tracheal compliance of asthmatic animals decreases significantly, which results in an increased limit flow rate. Histological studies indicate that asthma can lead to hyperplasia/hypertrophy of smooth muscle cells, and increase elastin and collagen fibres in the muscular membrane. Though decreasing compliance increases sta- bility, during the onset of asthma, limit flow rate is much smaller due to the lower transmural pressure. Asthma leads to a stiffer trachea and the obtained results reveal some aspects relevant to asthma-induced tracheal remodelling.

关键词： trachea asthma collapse tube law compliance limit flow rate remodelling

Optimization design study of low-Reynolds-number high-lift airfoils for the high-efficiency propeller of low-dynamic vehicles in stratosphere

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Science china(Technological Sciences) 2010年第10期53卷 2792-2807页

作者： MA Rong1, ZHONG BoWen2.& LIU PeiQing1 1 Key Laboratory of Fluid mechanics, Ministry of Education, Institute of Fluid mechanics, School of Aeronautical Science and {2., Beijing University of Aeronautics and Astronautics, Beijing 100191, china 2.department of Aerospace Science, School of {2., Cranfield University, MK43 0AL, United Kingdom 1. Key Laboratory of Fluid mechanics Ministry of Education Institute of Fluid Mechanics School of Aeronautical Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China2. Department of Aerospace Science School of Engineering Cranfield University MK43 0AL Cranfield UK

Aerodynamic performance of low-Reynolds-number high-lift airfoil makes a great impact on designing a high-efficiency propeller for low-dynamic vehicles in stratosphere. At high altitude,low-Reynolds-number airfoils are supposed to have high lift-drag ratio or high endurance factor at cruising attack angle along with good stall characteristics. To design such a high-performance low-Reynolds-number high-lift airfoil,the paper established a hierarchical multi-objective optimization platform by combing direct search optimization algorithm EXTREM and airfoil flow field solver XFOIL to automatically and quickly calculate aerodynamic performance function of airfoil by computer. It provides an effective solution to multi-point design problem of low-speed low-Reynolds-number airfoil. It can be seen from the results of three typical optimization examples,the new airfoil E387_OPT2.FX63-137_OPT2.and S12.3_OPT2.based on hot low-Reynolds-number high-lift airfoils (Eppler 387 airfoil,Wortmann FX63-137 airfoil and S12.3 airfoil) can meet the optimization design requirements and have very good aerodynamic characteristics in both design state and non-design state. Thus,the applicability and effectiveness of hierarchical multi-objective optimization platform are verified.

关键词： multi-objective optimization low Reynolds number airfoil EXTREM hierarchical multi-objective optimization

s-ordering operator expansions of quantum-mechanical fundamental representations and their applications

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Science china(Physics,mechanics & Astronomy) 2011年第12期54卷 2150-2154页

作者： FAN HongYi 1,3 , XU YeJun 2.& YUAN HongChun 3,4 1 department of Materials Science and engineering, University of Science and Technology of{2., Hefei 2.002.,{2. 2.department of Physics Electronic and engineering, Chizhou University, Chizhou 2.7000,{2. 3 department of Physics, Shanghai Jiao Tong University, Shanghai 2.0030,{2. 4 College of Optoelectronic engineering, Changzhou Institute of Technology, Changzhou 2.3002.{2. 1. department of Materials Science and engineering University of Science and Technology of China Hefei 230026 China3. Department of Physics Shanghai Jiao Tong University Shanghai 200030 China2. Department of Physics Electronic and Engineering Chizhou University Chizhou 247000 China4. College of Optoelectronic Engineering Changzhou Institute of Technology Changzhou 213002 China

We show that the quantum-mechanical fundamental representations, say, the coordinate representation, the coherent state representation, the Fan-Klauder entangled state representation can be recast into s-ordering operator expansion, which is elegant in form and has many applications in deriving new operator identities. This demonstrates that Dirac's symbolic method can be merged into Newton-Leibniz integration theory in a broad way.

关键词： s-ordering operator expansion operator identities quantum mechanical representation

Optimal motion planning of an underactuated spacecraft using wavelet approximate method

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Progress in Natural Science:Materials International 2006年第8期16卷 868-873页

作者： GE Xinsheng, CHEN Liqun and LIU Yanzhu (Beijing Institute of Machinery, Beijing 100085, china department of {2., Shanghai University, Shanghai 2.0072. china department of engineering {2., Shanghai Jiaotong University, Shanghai 2.0030, china) [a]Beijing Institute of Machiner Beijing China [b]department of mechanics Shanghai University Shanghai China [c]department of engineering {2. Shanghai Jiaotong University Shanghai China

An optimal motion planning scheme using wavelet approximation is proposed for an underactuated spacecraft. The motion planning of an underactuated spacecraft can be formulated as an optimal control of a drift-free system. A cost functional is used to incorporate the control energy and the final state errors. The motion planning is to determine control inputs to minimize the cost functional. Using the method of wavelet, one can transform an infinite-dimensional optimal control problem to a finite-dimensional one and use Gauss-Newton algorithm to solve it for a feasible trajectory which satisfies nonholonomic constraints. The proposed scheme has been applied to a rigid spacecraft with two momentum wheels. The numerical simulation results indicate that optimal control with wavelet approximation is an effective approach to steering an underactuated spacecraft system from the initial configuration to the final configuration.

关键词： underactuated spacecraft motion planning optimal control nonholonomic constraint wavelet analysis.

Multiple time step molecular dynamics simulation for interaction between dislocations and grain boundaries

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Acta Mechanica Sinica 2005年第4期21卷 371-379页

作者： X.Y.Li W.Yang department of engineering {2.,Tsinghua University,Beijing 100084.china department of engineering {2. Tsinghua University Beijing 100084 China

A multiple time step algorithm, called reversible reference system propagator algorithm, is introduced for the long time molecular dynamics simulation. In contrast to the conventional algorithms, the multiple time method has better convergence, stability and efficiency. The method is validated by simulating free relaxation and the hypervelocity impact of nano-clusters. The time efficiency of the multiple time step method enables us to investigate the long time interaction between lattice dislocations and low-angle grain boundaries.

关键词： Multiple time step Molecular dynamics ,Dislocation Grain boundary

WATER ENTRY OF A WEDGE BASED ON SPH MODEL WITH AN IMPROVED BOUNDARY TREATMENT

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Journal of Hydrodynamics 2009年第6期21卷 750-757页

作者： GONG Kai LIU Hua WANG Ben-long department of engineering {2. Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Shanghai 200240 China

The hydrodynamic problem of a two-dimensional wedge entering water is studied based on Smoothed Particle Hydrodynamics （SPH） model. A non-reflection boundary treatment for SPH method is proposed to reduce the reflection of sound waves. The boundary pressure is obtained using an improved coupling boundary treatment approach, which is validated by comparing the simulation results with experimental and analytical results in literature. A series of cases with different initial entering velocities are simulated. The maximum force on the wedge and the corresponding time required to reach it for the different cases of initial entering velocities of the wedge are obained and fitted into formulas against the initial entering velocity of the wedge. The maximum drag coefficients of the wedge for the different cases with Froude number greater than 2.are all near the value of 0.91.

关键词： water entry Smoothed Particle Hydrodynamics (SPH) non-reflection boundary

Stability of core-annular flow of power-law fluids in the presence of interfacial surfactant

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Science china(Physics,mechanics & Astronomy) 2010年第5期53卷 933-943页

作者： SUN XueWei,PENG Jie & ZHU KeQin department of engineering {2.,Tsinghua University,Beijing 100084,china 1. department of engineering {2. Tsinghua University Beijing 100084 China

The shear-thinning influence on the core-annular flow stability of two immiscible power-law fluids is considered by making a linear stability *** flow is driven by an axial pressure gradient in a straight pipe with the interface between the two fluids occupied by an insoluble *** the basic flow for this core-annular arrangement,the analytical solution is obtained with respect to the power-law fluid *** linearized equations for the evolution of infinitesimal disturbances are derived and the stability problem is formulated as a generalized matrix eigenvalue problem,which is solved by using the software package Matlab based on the QZ *** shear-thinning property is found to have marked influence on the power-law fluid core-annular flow stability,which is reflected in various ***,the capillary instability is magnified by the shear-thinning property,which may lead to an essential difference between power-law and Newtonian fluid *** when the interface is close to the pipe wall,the power-law fluid flow may be unstable while the Newtonian fluid flow is ***,under disturbances to the interface a velocity discontinuity at the interface appears which is destabilizing to the *** magnitude of this velocity discontinuity is affected by the power-law index and the flow stability is influenced ***,the shear-thinning property may induce new stability modes which do not appear in the Newtonian fluid *** flow stability shows much dependence on the interface location,the role of which was neglected in most previous *** shear-thinning fluid flow is more unstable to long wave disturbances when the interface is close to the pipe wall,while the Newtonian fluid flow is more unstable when the interface is close to the pipe *** this trend is changed by the addition of interfacial surfactant,for which the power-law fluid flow is more stable no matter where the interface is loca

关键词： core-annular flow power-law fluid interfacial surfactant linear stability analysis