On the finite displacement problem of a hollow sphere under internal and external pressures

Taking advantage of successive approximations the present boundary-value problemis solved.We find the first-order and second-order solutions,and there fore we obtain theformulae in the second approximatior for the displacement,strain,and stress fields.     

NON-INTERIOR SMOOTHING ALGORITHM FOR FRICTIONAL CONTACT PROBLEMS

A new algorithm for solving the three-dimensional elastic contact problem with friction is presented. The algorithm is a non-interior smoothing algorithm based on an NCP-function. The parametric variational principle and parametric quadratic programming method were applied to the analysis of three-dimensional frictional contact problem. The solution of the contact problem was finally reduced to a linear complementarity problem, which was reformulated as a system of nonsmooth equations via an NCP-function. A smoothing approximation to the nonsmooth equations was given by the aggregate function. A Newton method was used to solve the resulting smoothing nonlinear equations. The algorithm presented is easy to understand and implement. The reliability and efficiency of this algorithm are demonstrated both by the numerical experiments of LCP in mathematical way and the examples of contact problems in mechanics.     

A positive interior-point algorithm for nonlinear complementarity problems

1　ＩｎｔｒｏｄｕｃｔｉｏｎａｎｄＡｌｇｏｒｉｔｈｍＧｉｖｅｎａｆｕｎｃｔｉｏｎｆ:Ｒｎ→Ｒｎ,ｗｈｉｃｈｉｓａｓｓｕｍｅｄｔｏｂｅｃｏｎｔｉｎｕｏｕｓｌｙｄｉｆｆｅｒｅｎｔｉａｂｌｅｉｎａｎｏｐｅｎｓｅｔｃｏｎｔａｉｎｉｎｇＲｎ+,ｔｈｅｎｏｎｌｉｎｅａｒｃｏｍｐｌｅｍｅｎｔａｒｉｔｙｐｒｏｂｌｅｍ ,ｄｅｎｏｔｅｄＮＣＰ (ｆ) ,ｉｓｔｏｆｉｎｄａｖｅｃｔｏｒｘ∈Ｒｎｓｕｃｈｔｈａｔｘ≥ 0 ,　ｆ(ｘ) ≥ 0 ,　ｘＴｆ(ｘ) =0 ,Ｃｌｅａｒｌｙ ,ｔｈｅＮＣＰ (ｆ)ｉｓｅｑｕｉｖａｌｅｎｔｔｏｔｈｅｆｏｌｌｏｗ…     

A new smoothing technique for mathematical programs with equilibrium constraints

A kind of mathematical programs with equilibrium constraints(MPEC)is studied.By using the idea of successive approximation,a smoothing nonlinear program- ming,which is equivalent to the MPEC problem,is proposed.Thereby,it is ensured that some classical optimization methods can be applied for the MPEC problem.In the end, two algorithm models are proposed with the detail analysis of the global convergence.     

接触问题的互补变分原理及非线性互补模型

给出了接触问题的互补虚功原理,互补能量原理及变分不等式等变分提法,并讨论了三类提法的关系。其此建立了有限维非线性互补模型并给出解的存在唯一性定理。文中还阐明了有,无摩擦接触问题之间以及二维和三维有摩擦接触问题之间的本质区别。     

接触问题的非线性互补－接触柔度法

基于势能互补原理，不引入额外松弛变量，对库仑摩擦定律未做预先线性化近似，提出了三维弹性摩擦接触问题的非线性互补－接触柔度法，收敛性和收敛速率得到了严格理论保证。数值实验结果表明方法可靠、有效、低存储量、高精度     

RECURRENT NEURAL NETWORK MODEL BASED ON PROJECTIVE OPERATOR AND ITS APPLICATION TO OPTIMIZATION PROBLEMS

The recurrent neural network (RNN) model based on projective operator was studied. Different from the former study, the value region of projective operator in the neural network in this paper is a general closed convex subset of n-dimensional Euclidean space and it is not a compact convex set in general, that is, the value region of projective operator is probably unbounded. It was proved that the network has a global solution and its solution trajectory converges to some equilibrium set whenever objective function satisfies some conditions. After that, the model was applied to continuously differentiable optimization and nonlinear or implicit complementarity problems. In addition, simulation experiments confirm the efficiency of the RNN.     

Mixed energy method for solution of quadratic programming problems and elastic-plastic analysis of truss structures

A new algorithm for the solution of quadratic programming problems is put forward in terms of the mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures. The method proposed is different from the traditional one, for which the unknown variables are selected just in one class such as displacements or stresses. The present method selects the variables in the mixed form with both displacement and stress. As the method is established in the hybrid space, the information found in the previous incremental step can be used for the solution of the present step, making the algorithm highly efficient in the numerical solution process of quadratic programming problems. The results obained in the examples of the elastic-plastic solution of the truss structures verify what has been predicted in the theoretical analysis. Project supported by the National Natural Science Foundation of China (No. 50178916, No. 19732020 and No. 19872016), the National Key Basic Research Special Foundation (No. G1999032805), the Special Funds for Major State Basic Research Projects and the Foundation for University Key Teachers by the Ministry of Education of China.     

Convergence of a Modified SLP Algorithm for the Extended Linear Complementarity Problem

ＩｎｔｒｏｄｕｃｔｉｏｎＷｅｃｏｎｓｉｄｅｒｔｈｅｅｘｔｅｎｄｅｄｌｉｎｅａｒｃｏｍｐｌｅｍｅｎｔａｒｉｔｙｐｒｏｂｌｅｍ (ＸＬＣＰ)ｉｎｔｒｏｄｕｃｅｄｂｙＭａｎｇａｓａｒｉａｎａｎｄＰａｎｇ[1](ａｌｓｏｓｅｅＹｅ[2 ]) :Ｆｉｎｄａｖｅｃｔｏｒ(ｘ ,ｙ) ∈Ｒ2ｎｓｕｃｈｔｈａｔＭｘ-Ｎｙ∈Ｋ ,ｘＴｙ=0 ,　ｘ≥ 0 ,ｙ≥ 0 ,( 1 )ｗｈｅｒｅＭ ,Ｎ ∈Ｒｍ×ｎａｒｅｇｉｖｅｎ ,ａｎｄＫｉｓａｐｏｌｙｈｅｄｒａｌｓｅｔｉｎＲｍｄｅｆｉｎｅｄｂｙＫ :=ｕ∈Ｒｍ｜Ｇｕ≥ｇ ,　　Ｇ∈Ｒｌ×ｍ,ｇ∈Ｒｌ.Ｔｈｉｓｐｒｏ…     

A linear complementarity model for multibody systems with frictional unilateral and bilateral constraints

The Lagrange-I equations and measure differential equations for multibody systems with unilateral and bilateral constraints are constructed.For bilateral constraints,frictional forces and their impulses contain the products of the filled-in relay function induced by Coulomb friction and the absolute values of normal constraint reactions.With the time-stepping impulse-velocity scheme,the measure differential equations are discretized.The equations of horizontal linear complementarity problems(HLCPs),which are used to compute the impulses,are constructed by decomposing the absolute function and the filled-in relay function.These HLCP equations degenerate into equations of LCPs for frictional unilateral constraints,or HLCPs for frictional bilateral constraints.Finally,a numerical simulation for multibody systems with both unilateral and bilateral constraints is presented.     

A Newton type iterative inverse method for heat-conduction problems

An inverse problem for identification of the coefficient in heat-conduction equation is considered. After reducing the problem to a nonlinear ill-posed operator equation, Newton type iterative methods are considered. The implicit iterative method is applied to the linearized Newton equation, and the key step in the process is that a new reasonable a posteriori stopping rule for the inner iteration is presented. Numerical experiments for the new method as well as for Tikhonov method and Bakushikskii method are given, and these results show the obvious advantages of the new method over the other ones.     

A Newton type iterative method for heat-conduction inverse problems

An inverse problem for identification of the coefficient in heat-conduction equation is considered. After reducing the problem to a nonlinear ill-posed operator equation, Newton type iterative methods are considered. The implicit iterative method is applied to the linearized Newton equation, and the key step in the process is that a new reasonable a posteriori stopping rule for the inner iteration is presented. Numerical experiments for the new method as well as for Tikhonov method and Bakushikskii method are given, and these results show the obvious advantages of the new method over the other ones.     

非线性方程组的二次规划解法和应用

给出了非线性方程组的二次规划解法和应用 ,几个算例表明按拟牛顿法出现病态而不收敛 ,采用本法收敛极快。     

三维接触问题的非光滑算法

给出了一种非光滑算法直接用于求解三维摩擦接触问题的不可微非线性互补模型,不再对模型进行光滑化处理,使算法更加简单。文中对非光滑算法的收敛性给出了严格的数学证明,数值实验表明该算法列式简单,但与光滑化算法同样有效。     

Preconditioned iterative methods for solving weighted linear least squares problems

A class of preconditioned iterative methods,i.e.,preconditioned generalized accelerated overrelaxation(GAOR) methods,is proposed to solve linear systems based on a class of weighted linear least squares problems.The convergence and comparison results are obtained.The comparison results show that the convergence rate of the preconditioned iterative methods is better than that of the original methods.Furthermore,the effectiveness of the proposed methods is shown in the numerical experiment.     

Stochastic level-value approximation for quadratic integer convex programming

We propose a stochastic level value approximation method for a quadratic integer convex minimizing problem in this paper. This method applies an importance sampling technique, and make use of the cross-entropy method to update the sample density functions. We also prove the asymptotic convergence of this algorithm, and report some numerical results to illuminate its effectiveness.     

Modified integral-level set method for the constrained solving Global Optimization

The constrained global optimization problem being considered, a modified integral-level set method was illustrated based on Chew-Zheng‘s paper on Integral Global Optimizationand Wu‘s paper on Implementable Algorithm Convergence of Mottled Integral-Level SetMethod for Global Optimization Problem. It has two characters : 1 ) Each phase must constructa new function which has the same global optimal value as that of primitive objective function ;2) Comparing it with Zheng‘s method, solving level set procedure is avoided. Animplementable algorithm also is given and it is proved that this algorithm is convergent.     

Numerical solutions of linear quadratic control for time-varying systems via symplectic conservative perturbation

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.     

Numerical simulation of contact problems in vane machinery by a parametric quadratic programming method

Interference fits are widely used for connecting impeller and shaft assembly that are forced together slowly by pressing. The interference fit design ensures stable balance behavior and allows for positive contact between the impeller and shaft assembly throughout the range of operating speeds. In addition to maintaining radial contact, sufficient net radial interface pressure must remain in order to transmit torque when the rotational speed is very high. Therefore, the interference fit between the impeller and the shaft assembly is one of the most important factors influencing the performance of the turbo unit in the design of turbocharger compressor. A suitable fit tolerance needs to be considered in the structural design. A locomotive-type turbocharger compressor with 24 blades under combined centrifugal and interference fit loading is used for the analysis. The finite-element (FE) parametric quadratic programming (PQP) method developed based on the parametric variational principle (PVP) is used for the analysis of the stress distribution in the three-dimensional (3D) contact problem of impeller. The advantages of the parametric programming method compared with conventional approaches are that the penalty factors can be canceled and that solutions can be obtained directly without tedious iterative procedures such as the general incremental iterative method. To save time in the computation, a~multi-substructure technique is adopted for structural modeling. This not only simplifies the calculation, but also provides a convenient service for process computer-aided design (CAD) by means of FE simulation. The effects of the fit tolerance, coefficient of friction and rotational speed (centrifugal force), wall thickness of the shaft sleeve and the contact stress on the interference-fitting surfaces are studied in detail in the numerical computation. It is found that a nonuniform initial amount of interference in the structural design avoids the relative displacement generated and ensures uniformity of the contact stress. To assure quality of press-fitting, the amount of interference between the shaft sleeve and shaft should be strictly controlled to avoid the rapid increase of the contact stress. The numerical results demonstrate the high accuracy and good convergence of the algorithm presented here, which provides an effective approach that achieves more-reliable interference-fitted connections and more-precise assembly accuracy with lower manufacturing cost in the structural design.     

Numerical solutions of linear quadratic control for time-varying systems via symplectic par conservative perturbation

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.