可压缩混合层光学传输效应理论分析与实验研究

利用量级分析和风洞实验研究了可压缩混合层流动第二发展阶段气动光学效应的规律性.理论分析主要针对二维大尺度结构存在时视线误差(boresight error,BSE)与混合层流场及其特征参数之间的关系进行了讨论.研究结果表明:在混合层发展的第二阶段,时均BSE与对流马赫数呈现出复杂的非线性关系;同时还发现流场中的湍动能和混合层界面处的雷诺应力分布也是影响时均BSE的重要因素;采用细光束穿越混合层流场的风洞试验结果主要证实了时均BSE与对流马赫数之间的非线性关系.     

Computer-assisted Modelling and Analysis of Linear Programming Problems: Towards a Unified Framework

A framework for model formulation and analysis to support operationsand management of large-scale linear programs is developed fromthe combined capabilities of CAMPS and ANALYZE. Both the systemsare reviewed briefly and the interface which integrates thetwo systems is then described. The model formulation, matrixgeneration, and model management capability of CAMPS and thecomplementary model and solution analysis capability of ANALYZEare presented within a unified framework. Relevant generic functionsare highlighted, and an example is presented in detail to illustratethe level of integration achieved in the current prototype system.Some new results on discourse models and model management supportare given in a framework designed to move toward an ‘intelligent’system for linear programming modelling and analysis.     

Data parallel computing for network-structured optimization problems

Data level parallelism is a type of parallelism whereby operations are performed on many data elements concurrently, by many processors. These operations are (more or less) identical, and are executed in a synchronous, orderly fashion. This type of parallelism is used by massively parallel SIMD (i.e., Single Instruction, Multiple Data) architectures, like the Connection Machine CM-2, the AMT DAP and Masspar, and MIMD (i.e., Multiple Instruction, Multiple Data) architectures, like the Connection Machine CM-5. Data parallelism can also be described by a theoretical model of computation: the Vector-Random Access Machine (V-RAM).In this paper we discuss practical approaches to the data-parallel solution of large scale optimization problems with network—or embedded-network—structures. The following issues are addressed: (1) The concept of dataparallelism, (2) algorithmic principles that lead to data-parallel decomposition of optimization problems with network—or embedded-network—structures, (3) specific algorithms for several network problems, (4) data-structures needed for efficient implementations of the algorithms, and (5) empirical results that highlight the performance of the algorithms on a data-parallel computer, the Connection Machine CM-2.     

低速热射流剪切层光学性质主动控制研究

分别对稳定、基波和亚谐波周期扰动入口边界条件的二维欧拉方程进行了数值模拟,得出了射流剪切层中大涡结构的空间演化特征,计算了不同入口边界条件时的流向斯特列尔比,从而提出了对流场进行主动控制的光学意义。     

Global convergence of SSM for minimizing a quadratic over a sphere

In an earlier paper [Minimizing a quadratic over a sphere, SIAM J. Optim., 12 (2001), 188-208], we presented the sequential subspace method (SSM) for minimizing a quadratic over a sphere. This method generates approximations to a minimizer by carrying out the minimization over a sequence of subspaces that are adjusted after each iterate is computed. We showed in this earlier paper that when the subspace contains a vector obtained by applying one step of Newton's method to the first-order optimality system, SSM is locally, quadratically convergent, even when the original problem is degenerate with multiple solutions and with a singular Jacobian in the optimality system. In this paper, we prove (nonlocal) convergence of SSM to a global minimizer whenever each SSM subspace contains the following three vectors: (i) the current iterate, (ii) the gradient of the cost function evaluated at the current iterate, and (iii) an eigenvector associated with the smallest eigenvalue of the cost function Hessian. For nondegenerate problems, the convergence rate is at least linear when vectors (i)-(iii) are included in the SSM subspace.

     

Relativistic Kinematic Honeycombs

In this paper, we study the honeycombs of the relativistic velocities space using the fact that this space has a hyperbolic space structure. For the three-dimensional case there are only four of these honeycombs with bounded cells and, since in this space there is a characteristic length, the cells have a fixed size. This fact, strongly limit the possible relative velocities between the vertices of the honeycombs. We consider as a possible application to cosmology the interpretation of these honeycombs as discrete large scale mass distribution.     

Feasible Interior Methods Using Slacks for Nonlinear Optimization

A slack-based feasible interior point method is described which can be derived as a modification of infeasible methods. The modification is minor for most line search methods, but trust region methods require special attention. It is shown how the Cauchy point, which is often computed in trust region methods, must be modified so that the feasible method is effective for problems containing both equality and inequality constraints. The relationship between slack-based methods and traditional feasible methods is discussed. Numerical results using the KNITRO package show the relative performance of feasible versus infeasible interior point methods.     

大型仪器公共技术服务中心管理经验介绍

结合中国科学院长春应用化学研究所公共技术服务中心建设情况,从运行管理模式、大型仪器设备共享措施、科技支撑队伍建设等方面介绍了中心如何推动大型仪器设备开放共享工作.     

An Optimal Extension of the Polak–Ribière–Polyak Conjugate Gradient Method

Based on a singular value analysis on an extension of the Polak–Ribière–Polyak method, a nonlinear conjugate gradient method with the following two optimal features is proposed: the condition number of its search direction matrix is minimum and also, the distance of its search direction from the search direction of a descent nonlinear conjugate gradient method proposed by Zhang et al. is minimum. Under proper conditions, global convergence of the method can be achieved. To enhance e?ciency of the proposed method, Powell’s truncation of the conjugate gradient parameters is used. The method is computationally compared with the nonlinear conjugate gradient method proposed by Zhang et al. and a modified Polak–Ribière–Polyak method proposed by Yuan. Results of numerical comparisons show e?ciency of the proposed method in the sense of the Dolan–Moré performance profile.