提高低压DC/DC变换器动态响应的新方案

提出了一种基于负载校正LdCr(olad corrector)的新型低压大电流DC／DC变换器的控制方案,使负载大幅度变化时电压波动保持在一定范围内．有效地提高了DC／DC变换器的动态性能。它相对于开关变换器独立,可设计成即插即拔的辅助电路．并在实验中进行比较,充分证实了它的良好效果。     

自适应光学波前校正器

报告了自适应光学波前校正器——多元分立式压电变形反射镜和两维高速压电倾斜镜的研究工作。讨论了这两类波前校正器的主要性能及其检测方法等，并给出了若干典型的检测结果。研制的１９单元度形镜已成功用于ＩＣＦ驱动器的波前校正，而２１单元变形镜已成功用于天文观测星体成像校正     

On polynomiality of the Mehrotra-type predictor—corrector interior-point algorithms

Recently, Mehrotra [3] proposed a predictor—corrector primal—dual interior-point algorithm for linear programming. At each iteration, this algorithm utilizes a combination of three search directions: the predictor, the corrector and the centering directions, and requires only one matrix factorization. At present, Mehrotra's algorithmic framework is widely regarded as the most practically efficient one and has been implemented in the highly successful interior-point code OB1 [2]. In this paper, we study the theoretical convergence properties of Mehrotra's interior-point algorithmic framework. For generality, we carry out our analysis on a horizontal linear complementarity problem that includes linear and quadratic programming, as well as the standard linear complementarity problem. Under the monotonicity assumption, we establish polynomial complexity bounds for two variants of the Mehrotra-type predictor—corrector interior-point algorithms. These results are summarized in the last section in a table.Research supported in part by NSF DMS-9102761, DOE DE-FG05-91ER25100 and DOE DE-FG02-93ER25171.Corresponding author.     

A finite element approach for analysis and computational modelling of coupled reaction diffusion models

In this article, we establish the existence and uniqueness of solutions to the coupled reaction–diffusion models using Banach fixed point theorem. The Galerkin finite element method is used for the approximation of solutions, and an a priori error estimate is derived for such approximations. A scheme is proposed by combining the Crank–Nicolson and the predictor–corrector methods for the time discretization. Some numerical examples are considered to illustrate the accuracy and efficiency of the proposed scheme. It is found that the scheme is second‐order convergent. In addition, nonuniform grids are used in some cases to enhance the accuracy of the scheme.     

On the numerical solution of the Klein‐Gordon equation

A predictor–corrector (P–C) scheme based on the use of rational approximants of second‐order to the matrix‐exponential term in a three‐time level reccurence relation is applied to the nonlinear Klein‐Gordon equation. This scheme is accelerated by using a modification (MPC) in which the already evaluated values are used for the corrector. Both the predictor and the corrector scheme are analyzed for local truncation error and stability. The proposed method is applied to problems possessing periodic, kinks and single, double‐soliton waves. The accuracy as well as the long time behavior of the proposed scheme is discussed. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009     

无光焦度补偿组与次镜重合的双反射系统设计

叙述无光焦度补偿组与次镜重合时的全球面双反射系统的设计,给出利用PW法求解初始结构的基本理论,阐述应用无光焦度补偿组来平衡球面反射系统像差的方法。通过改变遮拦比K和焦点伸出量进行光线追迹,选择出该类系统K和的最佳组合。给出设计实例:系统工作波段=450 nm～700 nm、焦距f=1 600 mm、相对孔径A=1/8、视场角=05,遮拦比K＝0.35、焦点伸出量＝0.1,系统优化后的球差系数 SⅠ=-0.001 207,彗差系数SⅡ=0.000 192,波像差W=0.043 27。     

Conformal optical system design with a single fixed conic corrector

A conformal optical system refers to the one whose first optical surface conforms to both aerodynamic and imaging requirements. Appropriate correction is required because a conformal dome induces significant aberrations. This paper intends to explain that an effective solution to the easy-fabrication conic surface corrector compensates aberrations induced by a coaxial aspheric dome. A conformal optical system with an ellipsoid MgF₂ conformal dome, which has a fineness ratio of 2.0, is designed as an example. The field of regard angle is pm 30 degrees with a pm 2 degree instantaneous field of view. The system's ultimate value of modulation transfer function is close to the diffraction limit, which indicates that the performance of the conic conformal optical system with a fixed conic corrector meets the imaging requirements.     

共形光学头罩及其像差校正方法研究——综述

为了使高速红外光电制导导弹拥有良好的空气动力学性能,可以采用共形头罩来代替传统的球形头罩。根据共形光学校正元件的不同,归纳整理了七种不同的校正方案。其中,轴向平移相位板、反向旋转相位板、尼克泽楔形板和变形镜属于动态校正;固定式校正和拱形校正属于静态校正;还有一种为静态和动态相结合的校正方案。着重讨论了固定式校正方法,并给出了几种常用的校正表面类型。共形光学是高速红外光电主动制导导弹发展的关键技术之一,对其研究工作具有重要的现实意义。     

双透镜无光焦度校正板和单一反射镜的研究

对双透镜无光焦度校正板和单一反射镜组成的光学系统进行了研究,利用三级像差理论分析了消像差条件,并得出了一组被证明是正确的公式.根据该公式可以求出光学系统的初始结构参量.对于在球面镜反射系统中,基于像差特性分析,得出了系统的最佳结构和双透镜无光焦度校正板中单透镜光焦度的最佳选择.