Local reduction in physics

A conventional wisdom about the progress of physics holds that successive theories wholly encompass the domains of their predecessors through a process that is often called “reduction.” While certain influential accounts of inter-theory reduction in physics take reduction to require a single “global” derivation of one theory׳s laws from those of another, I show that global reductions are not available in all cases where the conventional wisdom requires reduction to hold. However, I argue that a weaker “local” form of reduction, which defines reduction between theories in terms of a more fundamental notion of reduction between models of a single fixed system, is available in such cases and moreover suffices to uphold the conventional wisdom. To illustrate the sort of fixed-system, inter-model reduction that grounds inter-theoretic reduction on this picture, I specialize to a particular class of cases in which both models are dynamical systems. I show that reduction in these cases is underwritten by a mathematical relationship that follows a certain liberalized construal of Nagel/Schaffner reduction, and support this claim with several examples. Moreover, I show that this broadly Nagelian analysis of inter-model reduction encompasses several cases that are sometimes cited as instances of the “physicist׳s” limit-based notion of reduction.     

汇文系统下的合订本期刊价格管理

介绍了在汇文系统环境下,如何对合订本期刊价格进行管理的几种方法。     

改善分支限界法求解旅行商问题效率的策略

叙述了NP完全问题的复杂性及分支限界法求解问题最优解的策略,分析了利用分支限界法求解旅行商问题过程中影响算法求解效率的主要原因。针对欧氏空间的旅行商问题求解,提出了通过化简初始边集的策略,改善算法的求解效率,通过实验说明了该策略的有效性。该策略可应用到求解旅行商问题的其他算法中。     

Her X-1是中子星吗?

本文通过对Her X-1的X-ray观测结果和其他中子星X-ray时间变化特征和X-ray谱特征分析,对Her X-1是中子星提出质疑.并根据"电子-离子束缚态及其引发核过程"(简称:电子-离子束缚态)假说,时照太阳耀斑机制,认为Her X-1的辐射可能是它的伴星HZ-Her的耀斑.     

具有较小最大度的临界图边数的下界

运用Discharge法给出了不含2点和3点的6临界图及不含4点和5点的7临界图边数的下界．     

基于单粒子的量子投票方案

提出了一个量子投票方案。投票者利用局域幺正操作进行投票，计票员可根据测量的结果计算出投票的结果。通过对方案的正确性和秘密性进行分析，表明该方案是安全的。而且，与采用Ⅳ维量子纠缠态的量子投票方案相比，该方案只涉及二维量子态，测量较为简单，这在现有的技术条件下是更易于实现的。     

板端砌体局压应力分布研究综述

对混合结构房屋中砌体局部受压的特点进行了介绍。从国外和国内对板端砌体应力分布理论研究、试验研究方面进行了论述。对研究中应进行的相关问题进行了分析。     

A NOTE ON THE PAPER “UNIFORM PERSISTENCE IN DISCRETE SEMIDYNAMICAL SYSTEM AND ITS APPLICATION”

1.IntroductionAsweknow,theresearchonthepersistenceofnonautonomousKolmogorovspeciessystems:isallalongaveryimportantsllbjectinthetheoryofmathematicalbiology.But,sofar,theworkonitisnotenough.ThemainresultsachievedarealmostconcernedwiththeLotka-Volterrasystems.Recently,in[l]theauthorshavehadahelpfultryonthestudyofuniformpersistenceoftwodimensionalperiodicKolmogorovsystem:Unfortunately,thereisamistakeintheproofofthemainTheorem3.3in[1].Themistakemakestheconclusionofthistheoremdoubtful.Asanimprov…