Consumer memory and price fluctuations in commodity markets: An integrodifferential model

A model for the dynamics of price adjustment in a single commodity market is developed. Nonlinearities in both supply and demand functions are considered explicitly, as are delays due to production lags and storage policies, to yield a nonlinear integrodifferential equation. Conditions for the local stability of the equilibrium price are derived in terms of the elasticities of supply and demand, the supply and demand relaxation times, and the equilibrium production-storage delay. The destabilizing effect of consumer memory on the equilibrium price is analyzed, and the ensuing Hopf bifurcations are described.     

惯性测量系统中实时估计方法的耦合分析与比较

一本文通过对不同精度惯性系统的仿真，根据不同的载体和应用条件，分别实施考虑通道耦合和不考虑通道耦合的实时卡尔曼滤波估计，得到耦合因素对估计误差影响不大的结论。最后利用改装的俄制и－２１惯性系统在北京郊区的实际跑车数据，分别实施卡尔曼滤波和曲线拟合处理，对其估计误差进行了分析和比较。     

Étude des temps de chauffage et de refroidissement des alliages à mémoire de forme (AMF)Heating and cooling time studies of shape memory alloys (SMA)

The knowledge of response times of active material is essential for their efficient use as actuators. In this paper the heating and cooling times of a shape memory alloy wire (NiTi) under a constant load are predicted by the integration of the corresponding heat equation. The comparison with a ‘fictitious’ material with the same material characteristics but without phase transformation shows that the response times are longer for the SMA (around 2.7 times for heating and 1.5 times for cooling). To cite this article: N. Chaillet et al., C. R. Mecanique 332 (2004).     

油水两相渗流压力脉动的实验及数值分析

本文用高精度的压差传感器和高速度的数据采集设备同时测量出油水两相流体在多孔介质流动时产生的较大压力降和微小压力脉动,应用自行研制的大型数据处理软件对恒流速水驱油的两相渗流压力脉动实验数据进行了分析,发现不同阶段压力脉动具有明显的频谱特性和时间相关特性的不同,在第三阶段（油为主,水增加阶段）谱能增加最大,时间正相关程度最强。     

The relaxation of linear flexible polymers which are slightly poly-disperse

The relaxation of slightly poly-disperse linear flexible polymers has been expressed in a simplified blending rule which is presumed to be a weighted linear superposition of the relaxation spectra of mono-disperse components which constitute the blend. Discrete components are characterized by their molecular weight M _i,weight fraction w _i,and relaxation time spectrum H _i(). ). In contrast to broadly distributed blends in which the small molecules mobilize the large ones and vice versa, we introduce the term slightly polydisperse for blends with molecular weight distributions narrow enough to have very little change in the longest relaxation times of each molecular weight component. The properties of this blending rule are analyzed and dynamic data is calculated for slightly poly-disperse polystyrene. As an application, the blending rule is used to determine the characteristic mono-disperse parameters (BSW parameters) of two materials, poly (vinyl methyl ether) and polycarbonate, for which we could not determine their BSW parameters directly since they were not available in nearly monodisperse form. The proposed blending rule can only be applied to systems in which all components are above the entanglement molecular weight, i.e. M _iM _c.Dedicated to the memory of Professor Tasos C. Papanastasiou     

时滞对结构振动半主动控制效果的影响

应用磁流变阻尼器对结构振动进行控制，采用最优控制原理设计了控制器，给出在地震激励下结构半主动控制的仿真计算。研究了时滞对结构振动半主动控制效果的影响。数值结果表明：本文设计的半主动控制策略可有效地减小结构的振动响应，时滞对磁流变半主动控制效果随着时滞的增大而变差，但时滞不会导致该反馈控制系统的失稳。     

位移时空综合分析法及其在边坡工程中的应用

以往对监测位移数据分析方法主要是位移-时间关系分析。但监测数据包含了大量对工程设计和施工都很有用的信息，其中不乏位移-空间方面的信息；另一方面，从工程设计和施工角度看，除需要位移-时间信息外，还需要位移-空间信息。位移时空综合分析法的提出旨在综合位移-时间和位移-空间等两方面的信息，为工程设计和施工服务。该方法依表现形式不同又分为竖线法和曲面法两种。本文将通过五强溪船闸边坡工程实例，来进一步说明位移时空综合分析法的原理及其应用。     

Statistical mechanics of temporary polymer networks I. The equilibrium theory

In part I of this work (the present article) the equilibrium state of temporary polymer networks is treated in the framework of thermodynamics and statistical mechanics. The network is described as an open system. Thereby we use a modified spring-bead model in which the beads represent junctions that decay and reform thus adding a viscous component to the assumed elastic behaviour of the permanent network. The relevant statistical equation — analogous to Liouville's equation — is solved. The grand-canonical probability density function and two of three equations of state are derived. Explicit formulae are given for several relevant probabilities. For instance the probabilityw (z)dz that a network chain connecting two junctions has a contour length betweenz andz +dz is given by the Wien type formulaw(z) =A z ³ exp {–B z} whereA andB do not depend onz.     

空气冲击波在坑道内走时规律的实验研究

介绍了内爆炸试验的发展及现状,通过实验研究建立了可以对高能炸药在坑道内爆炸的空气冲击波到时进行预计的公式。该公式适用于爆点在固定横截面的直通道口外、口内及口部处爆炸的情况。利用该公式可以求出空气冲击波在坑道中传播速度的变化。     

弹性力学的实时神经计算原理与数值仿真

针对现代结构分析的特点，提出了基于神经网络结构的弹性力学分析原理；给出求解该问题的网络———改进的Ｈｏｐｆｉｅｌｄ和ＴＨ网络．提出用ＢＰ网络来实现单元刚度矩阵的实时计算．最后，对两个简单结构的弹性力学神经计算进行了数值仿真