A note on the minimum size of an orthogonal array

It is an elementary fact that the size of an orthogonal array of strength t on k factors must be a multiple of a certain number, say L_t, that depends on the orders of the factors. Thus L_t is a lower bound on the size of arrays of strength t on those factors, and is no larger than L_k, the size of the complete factorial design. We investigate the relationship between the numbers L_t, and two questions in particular: For what t is L_t < L_k? And when L_t = L_k, is the complete factorial design the only array of that size and strength t? Arrays are assumed to be mixed-level.

We refer to an array of size less than L_k as a proper fraction. Guided by our main result, we construct a variety of mixed-level proper fractions of strength k ? 1 that also satisfy a certain group-theoretic condition.     

基于AHP与FCE方法的企业间竞争合作关系强度识别模型

企业间竞争与合作关系并非是对立的,而是统一的,竞争与合作具有"同素异相"的特性,是企业间的关系在不同外部约束及内部动力下所表现出的不同的强度。企业间竞争合作关系强度(SCCR)从最紧密的一体化关系到竞争最激励的敌对关系形成了一个谱系。文章从承诺效度、互动强度、资源依赖(竞争)强度、情感深度、收益强度五个维度构建了SCCR评判指标体系,并基于AHP(层次分析法)和FCE(模糊综合评判方法)建立了SCCR识别模型。同时,运用此模型对某汽车零部件企业和其供应商间的SCCR进行了识别。     

泥浆滤液侵入对岩石物性及电性影响的实验研究

评价工作液俊入所造成的地层报害是保护储层的钻井完井技术的基拙工作.本丈应用高泥高压多点长宕心摘害评价系统,对西那某油田休罗系若心进行了泥浆泌液任入实脸研究.所获得的涟液设入深度、摘害深度,很害程度及宕心含油饱和度变化千方面的结果,在理论上和实际应用上有-定价值.     

School as haven: Transforming school environments into welcoming learning communities

This study investigated school factors that impact attendance. Interviews and focus groups with over 60 key stakeholders from five Maryland counties were conducted. Respondents indicated that despite individual, family, and community factors that contribute to non-attendance, students will attend a school that is intentional about creating a welcoming climate that is supportive and academically stimulating. Attendance can be improved when schools evaluated policies that may unintentionally deter student attendance, when students feel heard by school personnel, and when students are given opportunities to establish supportive relationships with caring adults in and out of the classroom.     

Power Ratings for NCAA Division II Football

ABSTRACT

There is an abundance of entities that disseminate power ratings for NCAA Division I-A and I-AA football teams. This is not true for the NCAA Division II level. Statistical data on all NCAA Divisions II football games for two years were examined to develop a rating system. Several statistical techniques were performed on the data. Ultimately, the ratings were based on won-lost percentage, margin of victory, strength of schedule, and quality wins. Results are given for the 2001 and 2002 seasons. Ratings for the 2002 season for Divisions I-A and I-AA are also given using the techniques developed.     

Lower confidence bounds for percentiles of weibull and birnbaum-saunders distributions

Approximate lower confidence bounds on percentiles of the Weibull and the Birnbaum-Saunders distributions are investigated. Asymptotic lower confidence bounds based on Bonferroni's inequality and the Fisher information are discussed, and parametric bootstrap methods to provide better bounds are considered. Since the standard percentile bootstrap method typically does not perform well for confidence bounds on quantiles, several other bootstrap procedures are studied via extensive computer simulations. Results of the simulations indicate that the bootstrap methods generally give sharper lower bounds than the Bonferroni bounds but with coverages still near the nominal confidence level. Two illustrative examples are also presented, one for tensile strength of carbon micro-composite specimens and the other for cycles-to-failure data.     

The performance of standard and hybrid em algorithms for ml estimates of the normal mixture model with censoring

Many studies have been made of the performance of standard algorithms used to estimate the parameters of a mixture density, where data arise from two or more underlying populations. While these studies examine uncensored data, many mixture processes are right-censored. Therefore, this paper addresses the accuracy and efficiency of standard and hybrid algorithms under different degrees of right-censored data. While a common belief is that the EM algorithm is slow and inaccurate, we find that the EM generally exhibits excellent efficiency and accuracy. While extreme right censoring causes the EM to frequently fail to converge, a hybrid-EM algorithm is found to be superior at all levels of right-censoring.s     

企业营销竞争力的自测与分析

本文论述了企业营销竞争力的内涵、自测模型及企业营销竞争力下降时出现的征兆,并分析了企业营销竞争力下降的一般原因。     

基于COSMOSWORKS悬臂主轴的力学性能分析研究

采用Solidworks Cosmosworks有限元方法,对掘进机悬臂主轴进行静态分析、校核强度并进行疲劳寿命分析。与传统的零件强度校核方法比较,有限元方法更准确、更符合实际,得到的分析结果可以为产品的设计、改进提供参考,也可以为掘进机的动态性能分析打下基础。