基于需求预测技术弱化牛鞭效应影响研究

研究了供应链系统中的牛鞭效应.不同于通常研究采用的量化公式模型,建立计算机模型模拟当供应链成员采用需求预测技术进行订货决策时的订货过程.利用模拟过程产生的数据进行研究分析,比较不同需求预测方法下产生的牛鞭效应.并得出与指数平滑法比,最小均方差法对抑制牛鞭效应更有效,在某些情况下,采用最小均方差法可以消除牛鞭效应.     

Reliability analysis of a two-dependent-unit parallel system with a standby unit

A parallel system with two active components and a cold standby unit is studied in this paper. The two simultaneously working components are dependent and the copula function is used to model their dependence. An explicit expression is obtained for the mean time to failure of the system in terms of the copula function and marginal lifetime distributions in two different cases As an application, numerical calculations are presented corresponding to two different copula functions and marginal lifetime distributions.     

探讨石油价格、粮食价格及汇率难经济成长率的影响分析

粮食与石油是人类生存与发展的基本资源,粮食危机与能源危机都将对经济成长有相当的影响。汇率升贬值亦面临物价稳定与经济成长之抉择。不同于过去文献大多探讨单一因素对经济成长率的影响,同时探讨实质油价、粮食价格及汇率对经济成长率的关系,分别探讨对于高收入与低收入不同经济结构的国家是否会有不同的影响。由实证结果得知,较多的分析采用PMG估计法较为有效。实质油价、汇率、粮食价格对经济成长率存在长期关系,且长期、短期的结果在影响的方向上有差异。若未同时考虑油价、粮食价格及汇率对经济成长率的影响,其所得到的结果将会产生偏差;且不同的经济体结构其实质油价、粮食价格与汇率对经济成长率的反应亦有所差异。故在探讨此议题时应同时考虑实质油价、粮食价格及汇率对经济成长率的影响,亦应对不同经济结构分别探讨其间的关系,始能得到更正确的分析。     

Detecting Misspecification in Mean Structures for Growth Curve Models: Performance of Pseudo R 2s and Concordance Correlation Coefficients

This study examined the performance of 4 correlation-based fit indexes (marginal and conditional pseudo R ²s; average and conditional concordance correlations) in detecting misspecification in mean structures in growth curve models. Their performance was also compared to that of 4 traditional SEM fit indexes. We found that the marginal pseudo R ² and average concordance correlation were able to detect misspecification in the marginal mean structure (average change trajectory). The conditional pseudo R ² and concordance correlation could detect misspecification when it occurred in the conditional mean structure (individual change trajectory) or in both mean structures. Compared to the SEM fit indexes, the correlation-based fit indexes were more robust to sample size but were less robust to data properties such as magnitude of population mean and measurement error. Theoretical and practical implications of the results and directions for future research are discussed.     

残差性质的探究

残差是回归分析中的重要概念。本文对残差的分布、性质做了一定研究,得出了其期望和方差,并否定了一种关于残差的分布的假定。     

对数幂平均

在这编文章中,我们定义了两相异正数的对数幂平均,并从它的分解式得到对数平均分隔幂平均的不等式.     

几何中的比例中项问题

以“问题解决”理论为依据,对一类比例中项问题进行提炼,得到一种具有一般意义的模型,它含有某种模式,只要搞清题设、图形和结论之间的联系,或许会使解题思路更加清晰．     

导函数的一个重要性质的证明

本文根据微分中值定理及间断点的定义证明导函数若有间断点,则该间断点只可能是第二类间断点。     

不同时代的盗火者--中庸的孔子与尖刻的鲁迅

本文试图在一个较大的可包容的空间内，以历史的纵深感和横向的视点游移性，来探求两住文化英雄——孔子和鲁迅的异同。通过对他们人生经历、处世态度、革新思想、毕生追求等方面的对比，来揭示他们对自身及民族命运的自觉．他们主动担当起重建文化秩序的重任，努力寻找着一条文化的超越之路，昭示出历史不同时代的最大机遇。     

Differentials in Mathematics Achievement among Eighth-Grade Students in Malaysia

This paper examines differences in mathematics achievement among eighth-grade students using a secondary analysis of the data. The students, who are from Malaysia, had participated in the Trend International Mathematics and Science Study (TIMSS) 1999. A series of school, home, demographic and socio-economic variables were used to investigate the differences in the mean student mathematics scores. Evidence from the data shows that gender, the language spoken at home, expected educational level, family background, and home educational resources and aids have a significant influence on the students’ level of mathematics achievement.