Two models of two-dimensional bandwidth problems

The two-dimensional bandwidth problem is to embed a graph G into an n×n grid in the plane such that the maximum distance between adjacent vertices is as small as possible. Here, the “distance” has two different meanings: the L₁-norm distance and L_∞-norm distance. So we have two models of two-dimensional bandwidth problem. This paper investigates the basic properties and relations of these two models. Some lower bounds, upper bounds, and exact results are presented.     

Lower bounds on the rotation distance of binary trees

The rotation distanced(S,T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S,T)?2n−6, a well-known conjecture states that there are trees for which this bound is sharp for any value of n?11. We are unable to prove the conjecture, but we give here some simple criteria for lower bound evaluation, leading for example to individuate some “regular” tree structures for which d(S,T)=3n/2−O(1), or d(S,T)=5n/3−O(1).     

移动卫星信道中的MPSK网格编码调制特性

基于Rice－Lognormal联合分布的两种信道模型，定性地分析了移动卫星信道中的MP－SK－TCM恃性。推导出了适合这两种模型的Chernoff界和另一种新的特性界表达式，计算了8U-TC－MPSK方案的误比特概率。计算机模拟显示出，本文得到的特性界不仅简单、方便，而且比已有的界紧，能够较好地反应这类信道的TCM特性。     

Computable explicit bounds for the discretization error of variable stepsize multistep methods

This paper deals with the achievement of explicit computable bounds for the global discretization error of variable stepsize multistep methods which are perturbation of strongly stable fixed stepsize methods. The approach is based on the study of the growth of solutions of certain variable coefficient difference equations satisfied by the global discretization error.     

Matrix bounds of the discrete ARE solution

This paper provides new lower and upper matrix bounds of the solution to the discrete algebraic Riccati equation. The lower bound always works if the solution exists. The upper bounds are presented in terms of the solution of the discrete Lyapunov equation and its upper matrix bound. The upper bounds are always calculated if the solution of the Lyapunov equation exists. A numerical example shows that the new bounds are tighter than previous results in many cases.     

THE USE OF A GAS CHROMATOGRAPH TO OBTAIN DRYING RATES DATA THROUGH SIMPLE LABORATORY EXPERIMENTS

Abstract

A method making use of a gas chromatograph was investigated to acquire bound solvent drying rates. The solid to be dried was used as stationary phase in a chromatographic column, and the TCD detector was used to follow the decrease of solvent content of the effluent as inert gas was flown through the column. The measurement of the break-through curve allows the evolution of drying rate with time or solvent content to be obtained. The comparison of the experimental results with numerical simulation leads to the determination, through parametric adjustment, of the internal mass-transfer coefficient as a function of the solvent content during the second stage of bound solvent drying period. This parameter can lead to the value of the diffusivity as a function of solvent content.     

浅谈电熔锆刚玉池壁砖的使用

根据电熔锆刚玉砖的特性,阐述了池壁砖在升温中应注意的事项、池壁在使用中的侵蚀及其维护。     

Comparison of methods to extract an asymmetry parameter from data

Several methods to extract an asymmetry parameter in an event distribution function are discussed and compared in terms of statistical precision and applicability. These methods are: simple counting rate asymmetries, event weighting procedures and the unbinned extended maximum likelihood method. It is known that weighting methods reach the same figure of merit (FOM) as the likelihood method in the limit of vanishing asymmetries. This article presents an improved weighting procedure reaching the FOM of the likelihood method for arbitrary asymmetries. Cases where the maximum likelihood method is not applicable are also discussed.     

基于CV模型的GPS高精度定位方法研究

针对在某些地区GPS卫星可见数目少,定位精度不高的现实,提出一种提高GPS定位精度的新方法。假设目标短时间内常速运动,建立多次采样下的卫星定位模型,对GPS卫星的摄动误差进行消除,并且在模型解算中引入有偏估计,以牺牲无偏性的代价有效的提高估计精度。理论分析和仿真实验表明,该方法能逼近无偏估计的克拉美罗下界,极大的减小定位误差,具有一定工程实用价值。     

基于应力比法的双层网壳结构抗风优化

目前对风敏感结构的抗风优化研究主要集中于高层建筑,而对大跨屋盖结构的抗风优化研究较少.以一实际大跨双层柱面网壳为研究对象,基于Gust Loading Factor (GLF)法构造等效静力风荷载,建立空间桁架结构的应力比法抗风优化设计框架和计算程序.编制计算程序进行数值分析表明,通过优化可使结构总重最多降低约84％,且设定杆件截面积下限后所有杆件应力小于容许应力,因此本文方法用于空间桁架结构的抗风优化中简单有效,容易推广至实际工程设计中.