Blocked-Error-R 2: A Conceptually Improved Definition of the Proportion of Explained Variance in Models Containing Loops or Correlated Residuals

Bentler and Raykov (2000, Journal of Applied Psychology 85: 125–131), and Jöreskog (1999a, http://www.ssicentral.com/lisrel/column3.htm, 1999b http://www.ssicentral. com/lisrel/column5.htm) proposed procedures for calculating R ² for dependent variables involved in loops or possessing correlated errors. This article demonstrates that Bentler and Raykov’s procedure can not be routinely interpreted as a “proportion” of explained variance, while Jöreskog’s reduced-form calculation is unnecessarily restrictive. The new blocked-error-R ² (beR ²) uses a minimal hypothetical causal intervention to resolve the variance-partitioning ambiguities created by loops and correlated errors. Hayduk (1996) discussed how stabilising feedback models – models capable of counteracting external perturbations – can result in an acceptable error variance which exceeds the variance of the dependent variable to which that error is attached. For variables included within loops, whether stabilising or not, beR ² provides the same value as Hayduk’s (1996) loop-adjusted-R ². For variables not involved in loops and not displaying correlated residuals, beR ² reports the same value as the traditional regression R ². Thus, beR ² provides a conceptualisation of the proportion of explained variance that spans both recursive and nonrecursive structural equation models. A procedure for calculating beR ² in any SEM program is provided.     

探析C2C电子商务物流新模式

针对现在C2C电子商务发展的迅猛势头,分析了目前存在于其中的物流问题。通过整合社会和第三方物流公司资源,结合C2C平台自身的优势,对如何解决C2C电子商务物流的问题提出一定的建议和意见。探析了建立自营模式、物流联盟模式、指定或推荐物流模式和基于便利店支持下的电子商务物流模式的可行性。从而解决困扰电子商务交易中的物流瓶颈问题。     

基于J2EE的学校后勤管理系统关键技术研究

针对桂林电子科技大学现有后勤管理系统相对落后的问题,采用B/S架构,运用开源框架Struts-Spring-Hibernate构建基于J2EE的高校后勤管理系统。该系统将开源框架与Ajax技术相结合,可实现系统的异步提交,减轻网络通信和服务器端的负担;以后勤管理数据为研究对象,通过数据仓库、OLAP、数据挖掘技术的综合运用发现后勤管理系统中的有用信息,为管理高层提供辅助决策支持,具有较强的实用价值。     

Multi-scale tests for serial correlation

This paper introduces a new family of portmanteau tests for serial correlation. Using the wavelet transform, we decompose the variance of the underlying process into the variance of its low frequency and of its high frequency components and we design a variance ratio test of no serial correlation in the presence of dependence. Such decomposition can be carried out iteratively, each wavelet filter leading to a rich family of tests whose joint limiting null distribution is a multivariate normal. We illustrate the size and power properties of the proposed tests through Monte Carlo simulations.     

B2B电子商务企业价值链研究

电子商务使传统的价值链发生了很大的变化,缩短了企业价值链环节,提供了价值链创新的平台,影响到价值链活动的各个方面。电子商务的发展使商务价值越来越建立在数据、信息和知识的基础上,从而由传统价值链中分化出虚拟价值链。虚拟价值链与物理价值链既有区别又有联系,对于B2B电子商务企业具有十分重要的作用。本文分析了B2B电子商务对传统价值链的影响、虚拟价值链理论及其对B2B电子商务企业的作用,并对B2B电子商务企业虚拟价值链建设进行了讨论,以期为B2B电子商务企业构筑竞争优势提供有益的参考。     

论我国B2C电子商务企业物流经营之路

阐述了我国B2C电子商务企业的物流经营现状,主要分析了B2C电子商务企业在物流经营模式上可以选择的物流外包和战略联盟两种方案,指出我国B2C电子商务企业的物流经营之路。     

A note on the projection properties of Hadamard matrices obtained by the first Payley construction

We show that the projections on four factors of an arbitrary orthogonal array of strength 2 allow the estimation of main effects and two-factor interactions when all other effects are assumed to be zero, if those projections satisfy the bounds given by Weils theorem. The only exceptions are the Hadamard matrices of orders 16 and 24. A consequence is again the estimability of main effects and two-factor interactions for the projections on four factors of the first Payley construction for arbitrary run size.     

“智能+”时代背景下跨学科应用型物流人才培养模式探究

通过对“智能+”时代背景下应用型物流人才社会需求变化的调查分析,提出对现有物流专业在知识、能力、素质结构体系方面的调整建议,围绕“课程体系改革”及“教学工作改革”两个重点领域,依托“四个平台”,对构建创新型“智慧物流”专业的“ILTTM2+4”培养机制进行了深入探讨。     

百龙滩水电站船闸二期工程施工导流设计

文章介绍百龙滩水电站船闸二期工程施工导流方隶、导流标准的选定及导流建筑物设计。     

越南昆江2水电站埋藏式压力钢管设计

越南昆江2水电站二级电站为典型的高水头水电站,其埋藏式压力钢管段是该电站设计施工重点部位.文章就管径管材选用、高压管道钢衬起点位置、抗内外压力稳定以及灌浆排水等方面进行了计算分析。