面向售后服务的汽车备品需求预测研究

根据面向售后服务的汽车备品需求特点的差异,本文将其分为专用配件和通用配件并分别选用不同的预测模型.对专用配件,采用基于时间序列相关的线性回归模型,并运用加权最小二乘法（WLS）估计参数.对通用配件,选用GM（1,1）模型进行需求预测.     

上市公司财务困境的回归预测

在合理选择财务指标的基础上,利用因子分析计算个体综合因子得分,并在综合因子得分与财务指标之间建立回归预测模型;最后,择取2003年“财务状况异常”的上市公司来检验模型的合理性,证明了模型对陷入财务困境的公司有较高的预测准确性。判断财务困境的回归模型引入和其较方便的操作性,可以使证券市场及时发现财务失败公司,市场监管者可以减少公司违规、违法的监督成本,证券投资者可以缩小择股范围、加大投资的准确性。同时,通过上市来融资的股份公司也可以利用其预警作用,提前采取对策,防止出现因财务进一步恶化而被退市的命运。     

谈高压配网输变电工程可研阶段系统规划设计收资

文章就高压配网输变电工程可研阶段的系统规划设计收资情况作简要的分析,并通过工程实例,罗列出进行系统规划设计前所需要收集的大量数据及收资方法,以供同行参考。     

我国通信企业客户流失预测研究综述

客户流失问题是全球电信企业面临的一个严峻问题。我国通信市场经过快速发展,市场容量已经接近饱和,客户流失成为我国各通信运营商面临的严重问题。文章综述了客户流失的影响因素及其预测模型和方法,以期为深入研究客户流失问题提供参考。     

对口援疆背景下的新疆入境旅游发展研究

利用年际变动指数、地理集中指数对新疆入境旅游时空演变特征进行定量分析。研究表明:入境旅游呈现人数波动式增长,入境游客中外国游客占主导;入境旅游年际变化较大,客源市场不稳定。利用灰色系统模型GM(1,1)模型对新疆未来五年入境旅游指标进行预测,以期为新疆旅游管理部门和旅游企业提供参考。     

基于LVQ神经网络的电信企业客户流失预测模型研究

随着人工智能的快速发展,人工神经网络被广泛地运用到分类预测领域。文章首先明确了客户流失的定义及其分类,然后分析了LVQ神经网络的基本原理,最后从研究样本的确定、预测变量的选取、模型的训练及评估三个方面构建了基于LVQ神经网络的电信企业客户流失预测模型,以期为电信企业客户流失预测模型的设计提供一定的借鉴意义。     

基于灰色聚类的珠三角区域物流竞争能力分析

建立区域物流能力指标体系,收集相关数据,应用灰色定权聚类分析法,对珠三角各个城市物流能力各项指标定量分析。依据结果,判断各个城市属于哪个类别,分析各个城市的物流发展潜力并提出相关建议。     

钢筋混凝土叠合梁的斜截面承载力灰关联分析

为了经济合理地设计叠合梁,应用灰色系统理论,对均布荷载下钢筋混凝土叠合梁的斜截面积承载力及其关联因素进行关联度分析。结果表明,对叠合梁斜截面承载力影响最大的是预制梁混凝土强度等级,其次是叠合层混凝土强度等级、叠合特征参数αｈ,影响最小的是叠合特征参数αｍ。     

Random Effects Misspecification Can Have Severe Consequences for Random Effects Inference in Linear Mixed Models

There has been considerable and controversial research over the past two decades into how successfully random effects misspecification in mixed models (i.e. assuming normality for the random effects when the true distribution is non‐normal) can be diagnosed and what its impacts are on estimation and inference. However, much of this research has focused on fixed effects inference in generalised linear mixed models. In this article, motivated by the increasing number of applications of mixed models where interest is on the variance components, we study the effects of random effects misspecification on random effects inference in linear mixed models, for which there is considerably less literature. Our findings are surprising and contrary to general belief: for point estimation, maximum likelihood estimation of the variance components under misspecification is consistent, although in finite samples, both the bias and mean squared error can be substantial. For inference, we show through theory and simulation that under misspecification, standard likelihood ratio tests of truly non‐zero variance components can suffer from severely inflated type I errors, and confidence intervals for the variance components can exhibit considerable under coverage. Furthermore, neither of these problems vanish asymptotically with increasing the number of clusters or cluster size. These results have major implications for random effects inference, especially if the true random effects distribution is heavier tailed than the normal. Fortunately, simple graphical and goodness‐of‐fit measures of the random effects predictions appear to have reasonable power at detecting misspecification. We apply linear mixed models to a survey of more than 4 000 high school students within 100 schools and analyse how mathematics achievement scores vary with student attributes and across different schools. The application demonstrates the sensitivity of mixed model inference to the true but unknown random effects distribution.     

航班计划优化研究概述

从航班计划优化的不同时间阶段分析,可以将航班计划优化分为航班计划静态编排优化、基于航班延误预测的航班计划动态反馈优化和基于机场协同决策(A-CDM)的航班计划动态调整角度三类;进而从航班时刻、机型指派、航班频率等编制环节分析了航班计划静态编排优化;随后利用延误波及预测与数据挖掘预测的优化方法分析了基于航班延误预测的航班计划动态反馈优化的相关研究。最后,根据航班计划优化复杂性分析,给出了航班计划优化的发展趋势和未来研究方向。