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    2007年 第28卷 第3期    刊出日期:2007-03-25
    论文
    Numerical solutions of linear quadratic control for time-varying systems via symplectic par conservative perturbation
    谭述君;钟万勰
    2007, 28(3):  277-277 .  doi:10.1007,10483-007-0301-1
    摘要 ( 2018 )   PDF (281KB) ( 682 )  
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    Optimal control system of state space is a conservative system, whose approximate method should be symplectic conservation. Based on the precise integration method, an algorithm of symplectic conservative perturbation is presented.It gives a uniform way to solve the linear quadratic control (LQ control) problems for linear time-varying systems accurately and efficiently, whose key points are solutions of differential Riccati equation (DRE) with variable coefficients and the state feedback equation.The method is symplectic conservative and has a good numerical stability and high precision. Numerical examples demonstrate the effectiveness of the proposed method.
    Theoretical research on rotational dispersion coefficient of fiber in turbulent shear flow of fiber suspension
    高振宇;林建忠;李俊
    2007, 28(3):  289-289 .  doi:10.1007,10483-007-0302-1
    摘要 ( 2030 )   PDF (191KB) ( 523 )  
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    The rotational dispersion coefficient of the fiber in the turbulent shear flow of fiber suspension was studied theoretically. The function of correlation moment between the different fluctuating velocity gradients of the flow was built firstly. Then the expression, dependent on the characteristic length, time, velocity and a dimensionless parameter related to the effect of wall, of rotational dispersion coefficient is derived. The derived expression of rotational dispersion coefficient can be employed to the inhomogeneous and non-isotropic turbulent flows.Furthermore it can be expanded to three-dimensional turbulent flows and serves the theoretical basis for solving the turbulent flow of fiber suspension.
    Effective viscoelastic behavior of particulate polymer composites at finite concentration
    李丹;胡更开
    2007, 28(3):  297-297 .  doi:10.1007,10483-007-0303-1
    摘要 ( 2227 )   PDF (375KB) ( 759 )  
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    Polymeric materials usually present some viscoelastic behavior. To improve the mechanical behavior of these materials, ceramics materials are often filled into the polymeric materials in form of fiber or particle. A micromechanical model was proposed to estimate the overall viscoelastic behavior for particulate polymer composites, especially for high volume concentration of filled particles. The method is based on Laplace transform technique and an elastic model including two-particle interaction. The effective creep compliance and the stress and strain relation at a constant loading rate are analyzed. The results show that the proposed method predicts a significant stiffer response than those based on Mori-Tanaka's method at high volume concentration of particles.
    Radiation effect on temperature distribution in three-dimensional Couette flow with suction or injection
    Bhupendra Kumar Sharma;Mamta Agarwal;R. C. Chaudhary
    2007, 28(3):  309-309 .  doi:10.1007,10483-007-0304-z
    摘要 ( 2179 )   PDF (285KB) ( 596 )  
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    A theoretical analysis of three-dimensional Couette flow with radiation effect on temperature distribution has been analysed, when the injection of the fluid at the lower stationary plate is a transverse sinusoidal one and its corresponding removal by constant suction through the upper porous plate is in uniform motion. Due to this type of injection velocity, the flow becomes three-dimensional. The effect of Prandtl number, radiation parameter and injection parameter on rate of heat transfer has been examined by the help of graphs. The Prandtl number has a much greater effect on the temperature distribution than the injection or radiation parameter.
    Analytical investigation on 3D non-Boussinesq mountain wave drag for wind profiles with vertical variations
    唐锦赟;汤杰;王元
    2007, 28(3):  317-317 .  doi:10.1007,10483-007-0305-z
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    A new analytical model was developed to predict the gravity wave drag (GWD) induced by an isolated 3-dimensional mountain, over which a stratified, non-rotating non-Boussinesq sheared flow is impinged. The model is confined to small amplitude motion and assumes the ambient velocity varying slowly with height. The modified Taylor-Goldstein equation with variable coefficients is solved with a Wentzel-Kramers-Brillouin (WKB) approximation, formally valid at high Richardson numbers. With this WKB solution, generic formulae of second order accuracy, for the GWD and surface pressure perturbation (both for hydrostatic and non-hydrostatic flow) are presented, enabling a rigorous treatment on the effects by vertical variations in wind profiles. In an ideal test to the circular bell-shaped mountain, it was found that when the wind is linearly sheared, that the GWD decreases as the Richardson number decreases. However, the GWD for a forward sheared wind (wind increases with height) decreases always faster than that for the backward sheared wind (wind deceases with height). This difference is evident whenever the model is hydrostatic or not.
    Simulation of coupled flowing-reaction-deformation with mass transfer in heap leaching processes
    吴爱祥;刘金枝;唐玲艳
    2007, 28(3):  327-327 .  doi:10.1007,10483-007-0306-1
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    Governing equations for a fully coupled flowing-reaction-deformation behavior with mass transfer in heap leaching are developed. The model equations are solved using an explicit finite difference method under the conditions of invariable application rate and constant hydraulic head. The distribution of the degree of the saturation, as well as the distributions of the concentration of the reagent and the solute is given. A cubic relationship between the mineral recovery and the leaching duration is obtained based on the numerical results. The relationship can be used to predict the recovery percentage of the valuable metal.
    Wave propagation in liquid-saturated porous solid with micropolar elastic skelton at boundary surface
    Rajneesh Kumar;Mahabir Barak
    2007, 28(3):  337-337 .  doi:10.1007,10483-007-0307-z
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    The present study is concerned with the reflection and transmission of plane waves at an interface between homogenous invisicid liquid half space and a micropolar liquid-saturated porous solid half space. The reflection and transmission coefficients of various reflected and transmitted waves with the angle of incident have been obtained. Numerical calculation has been performed for amplitude ratios of various reflected and transmitted waves. Micropolarity and porosity effects on the reflection and transmission coefficients have been depicted graphically. Some particular cases have been deduced from the present formulation.
    Dynamic response of liquid-filled rectangular tank with elastic appendages under pitching excitation
    吕敬;李俊峰;王天舒
    2007, 28(3):  351-351 .  doi:10.1007,10483-007-0308-1
    摘要 ( 2156 )   PDF (404KB) ( 764 )  
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    Nonlinear dynamics of liquid-filled rectangular tank with elastic appendages are studied. Based on the assumption of ideal fluid, the coupling dynamic equations of rigid tank, elastic appendages and liquid fuel are derived using H-O principle. In the case of pitch excitation, the modified potential function and wave height function are introduced to describe the moving boundary of fluid, then Galerkin's method is used to discretize the dynamic equations into ordinary differential equations. The natural frequencies of the coupling system are formulated in liquid depth, the length of the tank, etc. The formulae are confirmed by numerical simulations, which also show that the effects of liquid and elastic appendages on the attitude angular of rigid.
    Global asymptotic stability for Hopfield-type neural networks with diffusion effects
    颜向平;李万同
    2007, 28(3):  361-361 .  doi:10.1007,10483-007-0309-x
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    The existence, uniqueness and global asymptotic stability for the equilibrium of Hopfield-type neural networks with diffusion effects are studied. When the activation functions are monotonously nondecreasing, differentiable, and the interconnected matrix is related to the Lyapunov diagonal stable matrix, the sufficient conditions guaranteeing the existence of the equilibrium of the system are obtained by applying the topological degree theory. By means of constructing the suitable average Lyapunov functions, the global asymptotic stability of the equilibrium of the system is also investigated. It is shown that the equilibrium (if it exists) is globally asymptotically stable and this implies that the equilibrium of the system is unique.
    Axisymmetric free vibrations of infinite micropolar thermoelastic plate
    Rajneesh Kumar;Geeta Partap
    2007, 28(3):  369-369 .  doi:10.1007,10483-007-0310-z
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    The propagation of axisymmetric free vibrations in an infinite homogeneous isotropic micropolar thermoelastic plate without energy dissipation subjected to stress free and rigidly fixed boundary conditions is investigated. The secular equations for homogeneous isotropic micropolar thermoelastic plate without energy dissipation in closed form for symmetric and skew symmetric wave modes of propagation are derived. The different regions of secular equations are obtained. At short wavelength limits, the secular equations for symmetric and skew symmetric modes of wave propagation in a stress free insulated and isothermal plate reduce to Rayleigh surface wave frequency equation. The results for thermoelastic, micropolar elastic and elastic materials are obtained as particular cases from the derived secular equations. The amplitudes of displacement components, microrotation and temperature distribution are also computed during the symmetric and skew symmetric motion of the plate. The dispersion curves for symmetric and skew symmetric modes and amplitudes of displacement components, microrotation and temperature distribution in case of fundamental symmetric and skew symmetric modes are presented graphically. The analytical and numerical results are found to be in close agreement.
    Analytical solution of basic equations set of atmospheric motion
    施惟慧;沈春;王曰朋
    2007, 28(3):  385-385 .  doi:10.1007/s,10483-007-0311-x
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    On condition that the basic equations set of atmospheric motion possesses the best stability in the smooth function classes, the structure of solution space for local analytical solution is discussed, by which the third-class initial value problem with typicality and application is analyzed. The calculational method and concrete expressions of analytical solution about the well-posed initial value problem of the third kind are given in the analytic function classes. Near an appointed point, the relevant theoretical and computational problems about analytical solution of initial value problem are solved completely in the meaning of local solution. Moreover, for other type of problems for determining solution, the computational method and process of their stable analytical solution can be obtained in a similar way given in this paper.
    Galerkin-Petrov least squares mixed element method for stationary incompressible magnetohydrodynamics
    罗振东;毛允魁;朱江
    2007, 28(3):  395-395 .  doi:10.1007/s,10483-007-0312-x
    摘要 ( 2059 )   PDF (190KB) ( 865 )  
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    The Galerkin-Petrov least squares method is combined with the mixed finite element method to deal with the stationary, incompressible magnetohydrodynamics system of equations with viscosity. A Galerkin-Petrov least squares mixed finite element format for the stationary incompressible magnetohydrodynamics equations is presented. And the existence and error estimates of its solution are derived. Through this method,the combination among the mixed finite element spaces does not demand the discrete Babu\v{s}ka-Brezzi stability conditions so that the mixed finite element spaces could be chosen arbitrartily and the error estimates with optimal order could be obtained.
    Risk-sensitive reinforcement learning algorithms with generalized average criterion
    殷苌茗;王汉兴;赵飞
    2007, 28(3):  405-405 .  doi:10.1007/s,10483-007-0313-x
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    A new algorithm is proposed, which immolates the optimality of control policies potentially to obtain the robusticity of solutions. The robusticity of solutions maybe becomes a very important property for a learning system when there exists non-matching between theory models and practical physical system, or the practical system is not static, or the availability of a control action changes along with the variety of time. The main contribution is that a set of approximation algorithms and their convergence results are given. A generalized average operator instead of the general optimal operator max (or min) is applied to study a class of important learning algorithms, dynamic programming algorithms, and discuss their convergences from theoretic point of view. The purpose for this research is to improve the robusticity of reinforcement learning algorithms theoretically.
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