逻辑函数绝对最小覆盖的改进算法

逻辑函数的绝对最小化算法存在的主要问题是运行时间过长和需要的存储空间过大,本文提出了一个从给定本源蕴源项集合中抽出一个绝对最小覆盖的算法,而时间空间的需求被大大地缩小了。     

重大突发公共卫生事件中的中小企业多维度社会责任问题探索

企业承担必要的社会责任是企业自身伦理道德的内在要求。肺炎疫情这一重大突发公共卫生事件给中国及世界经济造成了极大的冲击和影响,这就更需要中小企业在这个特殊时期肩负起更大的社会责任。梳理了企业社会责任的相关文献,并从社会、员工、消费者、供应商等维度研究了中小企业在重大突发公共卫生事件时期应当承担的社会责任。     

基于Copula逼近法的股指相依结构研究

Copula在相依结构的研究中具有广泛的应用价值。对传统的Copula模型和Kallenberg提出的Copula逼近法进行了比较,并将其应用于中国股票指数数据的实证分析。结果表明：Copula逼近法可以较大程度地降低模型误差,从而改善Copula模型对中国股指相依结构的拟合效果。     

基于VaR风险控制的半log-最优资产组合模型

通过建立基于VaR风险控制下的单周期半log-最优资产组合数学模型,证明了最优解的存在性与唯一性。利用遗传算法对半log-最优资产组合模型进行了实例计算与分析,并与log-最优资产组合模型进行了比较,结果表明半log-最优资产组合模型具有计算方便的特征。     

Variability explained by covariates in linear mixed‐effect models for longitudinal data

Variability explained by covariates or explained variance is a well‐known concept in assessing the importance of covariates for dependent outcomes. In this paper we study R² statistics of explained variance pertinent to longitudinal data under linear mixed‐effect models, where the R² statistics are computed at two different levels to measure, respectively, within‐ and between‐subject variabilities explained by the covariates. By deriving the limits of R² statistics, we find that the interpretation of explained variance for the existing R² statistics is clear only in the case where the covariance matrix of the outcome vector is compound symmetric. Two new R² statistics are proposed to address the effect of time‐dependent covariate means. In the general case where the outcome covariance matrix is not compound symmetric, we introduce the concept of compound symmetry projection and use it to define level‐one and level‐two R² statistics. Numerical results are provided to support the theoretical findings and demonstrate the performance of the R² statistics. The Canadian Journal of Statistics 38: 352–368; 2010 © 2010 Statistical Society of Canada     

我国区域经济差异的实证分析

改革开放以来,我国经济得到了快速、持续的发展,但同时也出现了地区间经济增长的非均衡现象,地区间经济发展的差异日益显现。本文试图立足于客观,利用多种方法进行分析,以期能够更加系统、科学、全面地分析我国区域间经济发展差异等相关问题。一、我国区域经济发展差异的现状我     

Creating a reference to a complex emergency situation using time series methods: war in Guinea-Bissau 1998-1999

Impacts of complex emergencies or relief interventions have often been evaluated by absolute mortality compared to international standardized mortality rates. A better evaluation would be to compare with local baseline mortality of the affected populations. A projection of population-based survival data into time of emergency or intervention based on information from before the emergency may create a local baseline reference. We find a log-transformed Gaussian time series model where standard errors of the estimated rates are included in the variance to have the best forecasting capacity. However, if time-at-risk during the forecasted period is known then forecasting might be done using a Poisson time series model with overdispersion. Whatever, the standard error of the estimated rates must be included in the variance of the model either in an additive form in a Gaussian model or in a multiplicative form by overdispersion in a Poisson model. Data on which the forecasting is based must be modelled carefully concerning not only calendar-time trends but also periods with excessive frequency of events (epidemics) and seasonal variations to eliminate residual autocorrelation and to make a proper reference for comparison, reflecting changes over time during the emergency. Hence, when modelled properly it is possible to predict a reference to an emergency-affected population based on local conditions. We predicted childhood mortality during the war in Guinea-Bissau 1998-1999. We found an increased mortality in the first half-year of the war and a mortality corresponding to the expected one in the last half-year of the war.     

清代洮河流域水利利用探析

重点探讨了清代洮河流域水利利用及工程建设情况。通过对比分析,发现清代前中期与后期在水利工程建设规模、数量、灌田面积等方面均有较大差别。前中期因政局因素更多表现为大规模与政府主导性,成果较辉煌;后期因政局动乱与民族问题而表现为兴建工程少、泉水灌溉等小规模水利设施兴起、原有水渠部分淤塞等。同时对清代本区的水利利用工具水车与水磨使用情况进行了探讨,认为水利事业的发展与社会的稳定、政府的重视互为因果、相互促进。     

高等教育大众化阶段地方高等院校定位问题分析

伴随大众化高等教育的不断推进,地方高等院校在学校类型、办学层次、人才培养目标、服务面向等出现类型定位趋同、办学层次攀高、人才培养目标模糊和服务面向不明确等问题。这是由于部分地方高等院校主体意识不强,领导者急功近利,办学理念僵化,长期受计划经济体制的影响,地方高等院校缺乏独立自主的办学意识,对当地政府的依赖性过强,造成这些地方高等院校办学定位出现各种问题。因此,地方院校应该改善高等教育的内部环境,各级政府应该优化高等教育的外部环境,在地方高等院校定位问题上中央政府和地方政府应重发挥其统筹规划、评价导向、投资激励的重要作用。整个社会应健全专业人才市场机制,营造良好的社会氛围,培育和完善人才市场体制,发挥产业发展对地方高等院校发展定位的引导作用,从而解决地方高等院校定位趋同、办学层次攀高、人才培养目标模糊和服务面向不明确等问题。