A parallel variable-metric dynamic programming algorithm

This paper presents a potentially parallel iterative algorithm for the solution of the unconstrainedN-stage decision problem of dynamic programming. The basis of the algorithm is the use of variable-metric minimization techniques to develop a quadratic approximation to the cost function at each stage. The algorithm is applied to various problems, and comparisons with other algorithms are made.This research forms part of the author's PhD program, and is supported by the Department of Scientific and Industrial Research of the New Zealand Government. The author is indebted to Dr. B. A. Murtagh, PhD supervisor, for his encouragement and support during the preparation of this paper.     

New strain standards for glass-ware stress photoelastic evaluation

Strain viewers are used for residual strain evaluation and assessment of glassware. Most viewers are the crossed-nicol type photoelastic apparatus with tint plates, in which the tint colour in the field of view changes with the insertion of strained glassware. Strain standards, which give known or predetermined optical path differences, are necessary for qualitative evaluation of residual internal stress in glassware. Two types of new strain standards, namely rotary-plate type and film-array type, are proposed and presented in detail.     

Cofolga: a genetic algorithm for finding the common folding of two RNAs

In order to predict non-coding RNA genes and functions on the basis of genome sequences, accurate secondary structure prediction is useful. Although single-sequence folding programs such as mfold have been successful, it is of great importance to develop a novel approach for further improvement of the prediction performance. In the present paper, a secondary structure prediction method based on genetic algorithm, Cofolga, is proposed. The program developed performs folding and alignment of two homologous RNAs simultaneously. Cofolga was tested with a dataset composed of 13 tRNAs, seven 5S rRNAs, five RNase P RNAs, and five SRP RNAs; as a result, it turned out that the average prediction accuracies for the tRNAs, 5S rRNAs, RNase P RNAs, and SRP RNAs obtained by Cofolga with an optimal weight factor and default parameters were 83.6, 81.8, 73.5, and 67.7%, respectively. These results were superior to those obtained by a single-sequence folding based on free-energy minimization in which corresponding average prediction accuracies were 52.4, 47.4, 57.7, and 52.3%, respectively. Cofolga has a post-processing in which a single-sequence folding is performed after fixation of a predicted common structure; this post-processing enables Cofolga to predict a structure that is present in one of two RNAs alone. The executable files of Cofolga (for Windows/Unix/Mac) can be obtained by an e-mail request.     

Dynamic Behavior of Rigid–Plastic Sector Plates

The paper studies the dynamic behavior of perfect rigid-plastic plates in the form of a sector with hinged or clamped sides under short-term intensive loads. Two dynamic deformation mechanisms are demonstrated. The dynamic equation is derived for each of the mechanisms. The realization conditions for the mechanisms are analyzed. Analytical expressions are derived for the ultimate (high) loads and the maximum residual deflection. Numerical examples are given     

计算机辅助彩色立体图像生成中的误差分析与处理

柱透镜光栅的计算机辅助立体成像的基本原理是将二维序列图像进行切分和重组,使之以三维模型的形式展现,使合成的图像在柱透镜光栅下观察时具有"纵深感"。该项技术在广告、摄影、电影制作中具有广泛的应用。但是长期以来,在图像切分时并不能保证像素一定被整除,这意味着剩余像素的出现,合成的立体图像必然存在误差。如何处理剩余像素的问题一直是个难题,阻碍了该技术的推广。针对立体图像生成方法中的剩余像素问题,详尽地分析了误差的形成,并提出了强行取整算法和误差分散算法两种误差处理方法。实验表明,这两种算法能较好的处理剩余像素,增强了合成图像的立体效果,这将有助于立体成像技术的进一步推广。     

Hilbert Functions, Residual Intersections, and Residually S2 Ideals

Let R be a homogeneous ring over an infinite field, IR a homogeneous ideal, and I an ideal generated by s forms of degrees d ₁,...,d _s so that codim( :I)s. We give broad conditions for when the Hilbert function of R/ or of R/( :I) is determined by I and the degrees d ₁,...,d _s . These conditions are expressed in terms of residual intersections of I, culminating in the notion of residually S ₂ ideals. We prove that the residually S ₂ property is implied by the vanishing of certain Ext modules and deduce that generic projections tend to produce ideals with this property.     

On Convergence of Minimization Methods: Attraction, Repulsion, and Selection

In this paper, we revisit the convergence properties of the iterationprocess x^k+1=x^k–(x^k)B(x^k)^–1f(x^k)for minimizing a function f(x). After reviewing some classic results andintroducing the notion of strong attraction, we give necessary andsufficient conditions for a stationary point of f(x) to be a point of strongattraction for the iteration process. Not only this result gives a newalgorithmic interpretation to the classic Ostrowski theorem, but alsoprovides insight into the interesting phenomenon called selectiveminimization. We present also illustrative numerical examples for nonlinearleast squares problems.     

基于XRD的镀锌钝化膜残余应力试验研究

利用XRD技术测试了镀锌钝化膜结合界面的残余应力，同时通过电解抛光法检测了其厚度方向残余应力的分布规律，分析了残余应力对镀锌钝化膜结合强度的影响. 试验结果表明，镀锌钝化膜的残余应力均表现为压应力，并随着基体表面残余应力的增大而减小；钝化膜在2—10μm厚度方向的残应力为-274.5—-428.3MPa，其应力为梯度分布；镀锌钝化膜与基体的界面结合强度与其残余应力成反比，减小薄膜残余应力，有利于提高镀锌钝化膜与基体的结合强度. 关键词： X射线衍射法(XRD) 镀锌钝化膜 结合强度 残余应力     

基于双核模型对超重元素合成机制的研究

在双核模型基础上，考虑了熔合与准裂变的竞争，通过数值法求解主方程，计算了⁵⁰Ti，⁵⁸Fe+²⁰⁸Pb，²⁰⁹Bi这4个反应系统通过冷熔合反应合成超重元素的激发函数，得到了与实验比较符合的结果.计算了不同入射能量时各角动量分波对熔合概率和超重核存活概率的影响以及对蒸发剩余截面的贡献.这些结果对进一步理解超重核的合成机制有重要意义. 关键词： 超重元素 双核模型 熔合反应 蒸发剩余截面     

NaI闪烁探测器测量感生放射性及其蒙特卡罗模拟

描述了如何使用蒙特卡罗方法评估产生在加速器屏蔽混凝土中的感生放射性. 使用EGS4程序模拟了NaI闪烁探测器测量屏蔽混凝土块表面剂量率时, 对于半径和厚度的响应. 结果发现,在屏蔽混凝土块半径和厚度分别达到40cm和30cm时, 表面剂量率达到饱和. 研究了东京大学SF回旋加速器北墙位置8和位置9的表面剂量率, 并和使用NaI闪烁探测器的测量结果进行了对比, 发现模拟和实验结果符合很好. 并且, 获得了表面剂量和表面感生放射性之间的转换系数, 对于⁶⁰Co转换系数为0.90(Bq·g^－1)·(μSv·h^－1)^－1, 对于¹⁵²Eu转换系数为1.26(Bq·g^－1)·(μSv·h^－1)^－1. 这样, 就可以通过NaI闪烁探测器表面剂量的测量结果简单评估加速器设备屏蔽混凝土中的感生放射性.