回弹模拟精度的主要影响因素

板料成形过程中普遍存在着回弹问题,特别在弯曲和浅拉深过程中回弹现象更严重,在板料成形领域,回弹已成为模具设计中要考虑的关键问题。本文从成形过程模拟和回弹过程模拟两方面对影响回弹模拟精度的主要因素进行了研究,指出限制回弹模拟精度提高的重要因素和提高回弹模拟精度的主要措施。     

基于ECM的团购网站继续使用行为实证研究

当今网络团购已成为电子商务的新兴力量,大量团购网站涌现。以团购网站为研究对象,基于期望证实模型(ECM)构建了影响团购网站继续使用行为的因素研究模型(该模型包含感知有用、感知经济性、感知愉悦、信任、满意、证实、继续使用意愿等7个因素),并对用户使用团购网站后影响其继续使用行为的因素进行了实证分析和验证。结果显示:用户的预期感受与实际使用后的证实程度对感知经济性、感知有用、满意有显著影响;感知经济性、感知有用、满意等3个因素对用户的继续使用意愿有显著影响,而信任因素对使用意愿的影响不显著。     

湿空气热力参数的计算方程

本文通过对有关文献提供的干空气和水蒸汽热力参数的准确值进行的拟合,在宽广的参数范围内给出了湿空气热力参数的计算方程。为制冷、空调、干燥和采暖通风等技术中湿空气的热力性质和热力过程的计算,提供了方便条件。     

关于数论函数方程δ（x^2＋y）＋δ（x＋y^2）=2ψ（x^3＋y^3）

对于正整数k，设δ（k）和ψ（k）分别是k的约数和函数和Dedekind函数．该文证明了：方程仅有正整数解（x,y）=（1，1）．     

浅谈矩阵特征值的估计

矩阵的特征值问题是矩阵计算的一个重要方向,在众多的领域中都得到了应用。在这样的大背景下,有必要深入地研究矩阵的特征值的估计问题。基于此,本文将结合国内外对于矩阵的特征值的估计方面的研究,以及一些具体的应用实例,来深入地探索矩阵的特征值的估计问题。     

二维奇异非稳态问题有限元解的误差估计

二维奇异问题的有限元方法是实际中经常会遇到的一类问题,对其解决有重要意义.本文讨论二维奇异非稳态问题的有限元方法,证明了弱解的存在唯一性,并给出有限元解的加权L2-模估计.     

Estimation of odds ratios under order restrictions

A new method for estimating a set of odds ratios under an order restriction based on estimating equations is proposed. The method is applied to those of the conditional maximum likelihood estimators and the Mantel-Haenszel estimators. The estimators derived from the conditional likelihood estimating equations are shown to maximize the conditional likelihoods. It is also seen that the restricted estimators converge almost surely to the respective odds ratios when the respective sample sizes become large regularly. The restricted estimators are compared with the unrestricted maximum likelihood estimators by a Monte Carlo simulation. The simulation studies show that the restricted estimates improve the mean squared errors remarkably, while the Mantel-Haenszel type estimates are competitive with the conditional maximum likelihood estimates, being slightly worse.     

An additive subdistribution hazard model for competing risks data

The cumulative incidence function plays an important role in assessing its treatment and covariate effects with competing risks data. In this article, we consider an additive hazard model allowing the time-varying covariate effects for the subdistribution and propose the weighted estimating equation under the covariate-dependent censoring by fitting the Cox-type hazard model for the censoring distribution. When there exists some association between the censoring time and the covariates, the proposed coefficients’ estimations are unbiased and the large-sample properties are established. The finite-sample properties of the proposed estimators are examined in the simulation study. The proposed Cox-weighted method is applied to a competing risks dataset from a Hodgkin's disease study.     

Concept mapping as an approach for expert-guided model building: The example of health literacy

Concept mapping served as the starting point for the aim of capturing the comprehensive structure of the construct of ‘health literacy.’ Ideas about health literacy were generated by 99 experts and resulted in 105 statements that were subsequently organized by 27 experts in an unstructured card sorting. Multidimensional scaling was applied to the sorting data and a two and three-dimensional solution was computed. The three dimensional solution was used in subsequent cluster analysis and resulted in a concept map of nine “clusters”: (1) self-regulation, (2) self-perception, (3) proactive approach to health, (4) basic literacy and numeracy skills, (5) information appraisal, (6) information search, (7) health care system knowledge and acting, (8) communication and cooperation, and (9) beneficial personality traits. Subsequently, this concept map served as a starting point for developing a “qualitative” structural model of health literacy and a questionnaire for the measurement of health literacy. On the basis of questionnaire data, a “quantitative” structural model was created by first applying exploratory factor analyses (EFA) and then cross-validating the model with confirmatory factor analyses (CFA). Concept mapping proved to be a highly valuable tool for the process of model building up to translational research in the “real world”.     

Universal versus contextual effects on TQM: a triangulation study using neural networks

The objective of this study is to extend previous research on total quality management (TQM)-context-performance relationships and ‘fit’ using multiple methods. We combine artificial neural networks (ANNs) with structural equation modelling (SEM) to analyse several hypotheses and propositions. This is the first study in this area of research that utilises ANNs and a triangulation technique in the presence of several contextual factors. The SEM analyses suggest that company size and industry type may have contingency effects on some of the TQM practices and/or TQM-performance relationships. However, the ANN models have shown that these two contingency factors do not moderate TQM outcomes, implying that all organisations can benefit from TQM regardless of size and type. As well, these models show that formal TQM implementation and/or ISO certifications do not add any predictive power to the ANN models except in one case: TQM implementation and/or ISO certification added to organisational effectiveness and customer results to predict financial and market (F&M) results. The results further indicate that even though implementing TQM alone has a bigger impact on F&M results than obtaining ISO certification alone, combining the two will have an even greater impact on these results. Joint implementation leads to greater improvements in organisational effectiveness, which, in turn, has a positive effect on customer results and consequently F&M results. This is a unique finding within the context of moderator effects on TQM-performance relationships.