一阶线性非齐次微分方程求解方法的讨论和一个简化的求解方法

本文证明了一阶线性非齐次微分方程y＇+P(x)·y=f(x)三个求解方法:参数变易法、积分公式、积分因子法之间的等同关系.从参数变易法中引出一个简化的积分公式.事实上此公式恰是对用参数变易法解高阶线性非齐次微分方程时对n=1的拓广.最后以实例验证此公式的简易.     

Functional magnetic resonance imaging of amphetamine craving

The aim of this study is to identify the brain activity associated with amphetamine craving for understanding the neurobiology of addiction by watching pictures of happy, sad or amphetamine. Brain activity was measured in 12 amphetamine addicts and 12 healthy subjects by fMRI while the subjects watched pictures designed to elicit happy feelings, sad feelings, or the desire to use amphetamine. The result demonstrated that amphetamine cues led to abnormally high cingulate and low frontal lobe activation in amphetamine addicts, who showed abnormalities in affect-related brain activation.     

Heterostructure in ZnO Nano-Tetrapods

1 Introduction 　　Nanoscale science and technology have attracted greatattention since the novel properties become dominant for well-known materials as their sizes reduced to some critical dimension. These properties frequently originate in lattice distortions, structure transformations etc[1]. The variations of size and structure ofnanocrystals lead to the change of their electronic structures. Very recently, nanoscale materials with different electronic structures were utilized in fabricating nanoscale junctions[2]. 　　……     

我国城市水价改革研究

文章分析了目前我国城市水价存在的主要问题为：总体水价偏低，水价计价和构成不合理，合理的水价应包括资源水价，工程水价和环境水价三个部分，本文讨论了水价三个构成部分的内涵和机制成因。最后，文章讨论了我国城市水价改革应遵循的原则和应采取的对策。     

Which survey indicators are useful for monitoring consumption? Evidence from European countries

This paper assesses the information content of two survey indicators for consumption developments in the near future for eight European countries in the period 1985–1998. Empirical work on this topic typically focuses on consumer confidence, the perceptions of buyers of consumption goods. This paper examines whether perceptions of sellers of consumption goods, measured by retail trade surveys, may also improve short‐term monitoring of consumption. We find that both consumer confidence and retailer confidence embody valuable information, when analysed in isolation. For France, Italy and Spain we conclude that adding retail confidence does not improve the indicator model once consumer confidence has been included. For the UK the reverse case is obtained. For the remaining four countries we show that combining consumer sentiment and retail trade confidence into a composite indicator leads to optimal results. Our results suggest that incorporating information from retail trade surveys may offer significant benefits for the analysis of short‐term prospects of consumption. Copyright © 2004 John Wiley & Sons, Ltd.     

带参模糊关系合成

该文对广义λ-并算子的性质作了进一步的研究,利用该算子对通常的模糊关系合成进行了推广,提出一种带参的模糊关系合成,并给出了它的若干性质。     

变速齿轮传动系统最佳轴向结构布局智能设计的推理机制

本文通过对变速齿轮传动系统轴向结构布局设计规律的研究,提出了一种适合于该类问题的知识表达方式,将改进后的带有启发函数的最佳优先搜索方法引入到该问题的求解中,使得含有多重搜索空间以及带有一定约束的设计问题统一在同一搜索策略下。根据本文提出的方法,用PROLOG语言建造的推理机,通过对实际问题的考证,证明该方法在解决传动结构自动设计上是行之有效的,并且在推理机制上成功地体现了设计过程中反复设计与优化设计的功能特征.     

Estimation and testing of time-varying coefficient regression models in the presence of linear restrictions

A linear regression model with random walk coefficients is extended to allow for linear restrictions between the coefficients to be satisfied at each point in time. Estimation in this model is shown to be no more involved than estimation in the standard model. It is also demonstrated how, after a slight modification to the testing problem, classical test procedures may be applied to the problem of testing for such restrictions. The performance of the Lagrange Multiplier test for a variety of different restrictions is then investigated via simulation. An empirical application involving testing for homogeneity in a random walk coefficient version of the AIDS model is given.