Selection of the relevant information set for predictive relationships analysis between time series

In time series analysis, a vector Y is often called causal for another vector X if the former helps to improve the k‐step‐ahead forecast of the latter. If this holds for k=1, vector Y is commonly called Granger‐causal for X . It has been shown in several studies that the finding of causality between two (vectors of) variables is not robust to changes of the information set. In this paper, using the concept of Hilbert spaces, we derive a condition under which the predictive relationships between two vectors are invariant to the selection of a bivariate or trivariate framework. In more detail, we provide a condition under which the finding of causality (improved predictability at forecast horizon 1) respectively non‐causality of Y for X is unaffected if the information set is either enlarged or reduced by the information in a third vector Z . This result has a practical usefulness since it provides a guidance to validate the choice of the bivariate system { X , Y } in place of { X , Y , Z }. In fact, to test the ‘goodness’ of { X , Y } we should test whether Z Granger cause X not requiring the joint analysis of all variables in { X , Y , Z }. Copyright © 2002 John Wiley & Sons, Ltd.     

产生式系统与神经元网络的结合

提出了产生式系统和神经元网络相结合的方法,研究了从推理网络转换到神经元网络的途径,研究了从神经元网络权矩阵转换到产生式规则的方法,从而使产生式系统能自动修正规则和获取规则.还提出了一种由二次型阈值元件组成的神经元网络,给出了它的学习算法,并严格证明了它的收敛性.     

在培养应用型人才中看高等数学教学的改革

本文从培养应用型人才出发,研究了高等数学教学方法的改革,强调了教学内容的直观引入,以达到把教学方法灵活地运用到解决实际问题。     

现代英语词汇的新变化

语言是社会交际的工具。它随时都在适应社会的需要,反映社会的变化。语言这种适应社会和反映社会的过程,就是语言本身的发展过程。在当代,英、美社会的急剧变化和科学技术的飞速发展使得现代英语的词汇有了不少新的变化。尤其是美国英语的兴起,对整个现代英语的发展影响很大,不可忽视。掌握现代英语词汇变化的新情况,跟上它的发展步伐,对于我们学习和使用这种语言是十分必要的。     

关于整函数级的思考

文章对整函数级定义进行了分析,给出了几种定义方式,对这些方式作了比较并得出了一些结论。     

神经网络推理机制的电机调整设计专家系统

针对传统电机调整设计专家系统的缺陷,提出一种新型的,基于神经网络推理机制的电机调整设计专家系统模型．该模型将神经网络技术与专家系统技术、优化技术紧密结合,采用并行推理策略,能够有效提高推理效率,解决调整设计过程中调整力度难以确定的问题．     

复杂系统的定性表示与推理

基于人工智能中树图推理的思想,提出一种对复杂系统进行定性描述和推理的方法.该方法基于图论把一般的定性约束方程转化为一种约束图的表示形式,并在虚拟因果理论基础上,得到描述系统波动演化的各关键变量的约束影响图形式.最后,比较了Kuipers的QSIM和本文发展出的方法,表明采用图形化的方式来表征系统各变量之间所存在的约束关系,可以得到和原系统等价的但变量数大大减少的约束影响图形式.这种处理可以推动定性推理的研究从QSIM的实验室阶段走向实际应用领域.     

基于聚类算法的神经模糊推理系统结构和参数的优化

根据社会网络与模糊逻辑系统的各自特性，在分析了扩展RBF网络与T－S型模糊逻辑系统功能等价性的基础之上，提出了扩展RBF网络与T－S型模糊逻辑系统相互融合的一种新的自适应模糊逻辑系统，考察了系统现有的结构和参数优化方法，提出了采用基于山峰函数的减法聚类算法与由梯度下降算法和最小二乘算法所组成的混合学习算法来对模糊推理系统进行训练，从而优化自适应模糊推理系统的结构和参数，最后，针对一非线性函数逼近问题进行了验证，仿真取得了很好的效果。系统的逼近精度和收敛速度获得了明显的提高，从而表明本文提出的算法是有效性和可行性。     

Pascal定理的初等证明及初等推论

给出了高等几何中的Ｐａｓｃａｌ定理的初等证明及５个初等推论。     

Self-organised criticality—what it is and what it isn’t

The last decade and a half has seen an ardent development of self-organised criticality (SOC), a new approach to complex systems, which has become important in many domains of natural as well as social science, such as geology, biology, astronomy, and economics, to mention just a few. This has led many to adopt a generalist stance towards SOC, which is now repeatedly claimed to be a universal theory of complex behaviour. The aim of this paper is twofold. First, I provide a brief and non-technical introduction to SOC. Second, I critically discuss the various bold claims that have been made in connection with it. Throughout, I will adopt a rather sober attitude and argue that some people have been too readily carried away by fancy contentions. My overall conclusion will be that none of these bold claims can be maintained. Nevertheless, stripped of exaggerated expectations and daring assertions, many SOC models are interesting vehicles for promising scientific research.