负权最短路问题的新算法

Bellman-Ford算法自1958年以来一直是负权最短路问题的公认的最好算法之一．1970年,Yen对其进行了改进,理论上可以节省一半的计算量．本文得到了一种比Bellman-Ford算法更加优越的算法．尽管在理论上新算法无法保证完全超越于Yen的改进算法,但在许多情况下需要更少的计算量．     

Structure of a gasdynamic disturbance in a thermodynamically nonequilibrium medium with a power-law relaxation model

The evolution and the steady-state structure of gasdynamic disturbances in a thermodynamically nonequilibrium gas are investigated both analytically and numerically. It is shown that in a medium with negative viscosity steady-state structures different from those in an equilibrium medium can exist. The conditions of existence of stationary shock waves with a discontinuous front and a smooth increase or decrease in the amplitude behind the front, waves with an oscillatory structure, and a stationary self-wave pulse with a power-law trailing front are determined.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 181–191. Original Russian Text Copyright © 2004 by Makaryan and Molevich.     

不同负冲角工况下透平叶栅二次流的数值模拟及分析

本文应用TVD格式和Baldwin－Lomax代数紊流模型求解三维NS方程，对一个透平直列叶栅流场在两个不同的负冲角工况下进行了数值模拟，给出了叶栅马蹄涡及其分离鞍点、通道涡、角涡等二次流涡系的结构及其产生发展过程，并对不同工况下的涡系结构及冲角的影响作了详细的分析和比较．本文结果有助于对叶栅二次流涡系结构的产生发展机制的深入了解，同时表明所用数值求解技术有较高的精度和分辨率。     

PROPERLIES OF ALMOST PERIODIC SOLUTION FOR A KIND OF ECOLOGICAL SYSTEMSWITH TIME DELAY

AMSSubjectClassification34C27Thespatialelementinpopulationbiologyisimportanttounderstandthedynamicsofecologicalsystems.ThetheoreticalworksonthisproblemwerepioneeredbySkellamif]in1951andwerereviewedbyLevin[2]in1974.In12],Levinfirstestablishedthiskindofmode…     

离子色谱法测定碱性溶液中HCOO-时负峰的消除

分析了以Na2CO3-NaHCO3混合溶液为淋洗液，离子色谱法测定碱性样品时，色谱负峰产生的原因。通过计算和试验，采用在样品中加入适量NaHCO3进行中和的方法，解决了负峰影响HCOO^-测定的问题。     

An unconstrained optimization method using nonmonotone second order Goldstein's line search

In this paper,an unconstrained optimization method using the nonmonotone second order Goldstein's line search is proposed.By using the negative curvature information from the Hessian, the sequence generated is shown to converge to a stationary point with the second order optimality conditions.Numerical tests on a set of standard test problems confirm the efficiency of our new method.     

具有缩影的图式流形的分类

在这篇文章中，通过使用扭转运算，我们获得了具有缩影的力图式流形的同胚分类。     

具有正负系数的二阶脉冲中立型方程的振动性

考虑一类具有正负系数的多时滞二阶线性脉冲中立型微分方程,证明了该方程解的振动性等价于一类非脉冲中立型方程解的振动性,得到了方程所有解存在的充分条件.     

Heat capacity calorimetry

Experimental heat capacity measurements of α-ZrW₂O₈, and zeolitic polymorphs of SiO₂, BEA and MFI, have been made from 0.6 to 400 K. Measurements on β-ZrMo₂O₈ have been made from 8 to 400 K. Analysis of the results yields evidence for very low frequency modes in all four materials. These modes are responsible for negative thermal expansion behavior in α-ZrW₂O₈ and β-ZrMo₂O₈. Negative thermal expansion has been observed in some pure SiO₂ zeolites, but no studies have been made to look for it in BEA and MFI. The appearance of low frequency modes in these two zeolites suggests that temperature dependent structural investigations would be worthwhile. These modes are lower in energy than the Boson peak in vitreous silica. This revised version was published online in August 2006 with corrections to the Cover Date.     

非对称开口六边形谐振单环的微波透射特性

受自然界树型结构的启发，设计了分叉树型微结构单元，用电路板刻蚀技术制作了非对称开口六边形谐振单环及其组合结构.采用计算机模拟和实验研究了单个和多个谐振环在微波段(7—12 GHz)的电磁响应行为.研究结果表明：该结构具有负磁导率特性，开口谐振环几何尺寸影响环的磁谐振频率；两环环间距较小时出现二次谐振；带高级分支的辐射状环列相对于不带分支环列透射峰向低频移动.实验和模拟结果相符. 关键词： 负磁导率 开口谐振环 透射率