A Caution Regarding Rules of Thumb for Variance Inflation Factors

The Variance Inflation Factor (VIF) and tolerance are both widely used measures of the degree of multi-collinearity of the ith independent variable with the other independent variables in a regression model. Unfortunately, several rules of thumb – most commonly the rule of 10 – associated with VIF are regarded by many practitioners as a sign of severe or serious multi-collinearity (this rule appears in both scholarly articles and advanced statistical textbooks). When VIF reaches these threshold values researchers often attempt to reduce the collinearity by eliminating one or more variables from their analysis; using Ridge Regression to analyze their data; or combining two or more independent variables into a single index. These techniques for curing problems associated with multi-collinearity can create problems more serious than those they solve. Because of this, we examine these rules of thumb and find that threshold values of the VIF (and tolerance) need to be evaluated in the context of several other factors that influence the variance of regression coefficients. Values of the VIF of 10, 20, 40, or even higher do not, by themselves, discount the results of regression analyses, call for the elimination of one or more independent variables from the analysis, suggest the use of ridge regression, or require combining of independent variable into a single index.     

梁位移的有限单元法

介绍了有限元分析法的基本理论和方法,导出梁的形函数、刚度矩阵。用功能强大的数学软件Mathematica计算梁的挠度和转角。     

尾矿植被法治理初探

尾矿作为矿业废弃物,被堆放在尾矿库内．对周围环境造成很大的污染．停用的尾矿库必须进行治理：在几种治理方法中．植被法是一种较为理想的方法．符合我国的国情：主要讨论了利用植被法治理尾矿的具体措施．包括尾矿基质的改良、耐性物种的选择和管理措施的选择等。     

供应链"公差-配合合作伙伴关系"模型

引入公差配合的概念,系统地研究了供应链体系中的配合选择问题,在分析合作伙伴评估因素和供应链结构的基础上,提出了应用“公差-配合合作伙伴关系”模型描述供应链节点企业间匹配关系的方法,并阐述了该模型的应用方法和应用实例。     

On the asynchronous approvals of GM crops: Potential market impacts of a trade disruption of EU soy imports

Due to their high protein content, soybeans are important feedstuffs in the European Union (EU). However, the cultivation of soybeans using genetically modified (GM) varieties in non-EU countries is increasing and the EU authorization of GM products takes longer than in other countries, leading to an asynchronous approval between the EU and non-EU countries that might induce soybean trade disruptions. This paper uses an integrated modelling system to simulate Argentina, Brazil and the United States ending soybean exports to the EU. The impact on world trade and on the EU import prices of soy products is analysed with a computable general equilibrium model. EU soy imports are shown to decline, and the import price of soybeans in the EU increases. The effects on EU agricultural markets are analysed based on a partial equilibrium model. Feed costs in the EU are found to increase with poultry and pork the most affected: production and exports decline and imports increase. However, the effects of a trade ban are found to be less profound than in many other studies due to compensating substitution effects at various market levels: increasing imports from third countries, increasing domestic oilseed production and the use of other protein feeds.     

Explaining changes and trends in the airline industry: Economies of density,multiproduct scale,and spatial scope

Changes in the shape and size of airline networks have not been explained clearly from a cost perspective based on the finding of increasing returns to density for given route structures and constant returns to scale for variable network size. We reassessed the estimates of these economies by using new scale and scope indices, finding savings due to changes in route structures and various types of economies of spatial scope not previously calculated: network size, trunk-local services and domestic-international services. Results contribute new insights on the role of cost incentives in the observed changes and trends in the airline industry.     

新世纪企业组织形式探讨

本文试图从现代企业制度所推崇的有限责任公司的历史发展及科学技术对企业组织形式的推动和变革出发 ,对新世纪中公司的变革作出推断     

基于参数化技术的零件尺寸与尺寸公差集成变型设计方法

文章提出了一种基于参数化技术的零件尺寸公差变型设计方法。对零件参数化模型中的尺寸公差信息表达、提取与标注方法进行了研究,将尺寸公差变型设计方法与尺寸变型设计方法进行集成,实现了零件尺寸与尺寸公差的同步变型设计。利用VC++软件,对三维参数化设计软件SolidWorks进行二次开发,开发了与SolidWorks集成的零件尺寸与尺寸公差集成变型设计插件。以轴类零件为例,对提出的方法和开发的插件进行了应用验证。     

对问题保险公司实施监管干预的国际比较分析——以英国Vehicle和General和中国某财产保险公司为案例

监管机构如何对问题保险公司实施监管干预是一个紧迫的现实问题。在中英两国案例研究的基础上发现:监管干预行动都存在迟滞现象。监管机构给予问题保险公司较高的监管容忍度。原则导向与规则导向方式在监管实务中都是不可或缺的。监督力量在干预行动中发挥着重要作用。应该增加保险保障基金公司的监管权,建立监管干预决策的问责机制,建立及时的市场信息披露制度,激励多种监督力量参与干预行动,建立规则导向与原则导向相互融合的监管模式。     

浅析美发产品品牌文化——以飘柔品牌塑造为例

伴随着我国美发业的发展和强化,各种美发产品的市场竞争也日益激烈,而品牌竞争也成为了新时期美发产品的主要竞争手段。飘柔是宝洁公司美发产品中的佼佼者之一,其依靠品牌能力占领了相当巨大的市场,本文以飘柔为例,通过分析其品牌文化,从而深入了解飘柔这一品牌是如何塑造成功的,并以此作为发展美发产品的成功经验借鉴。