Regularization through variable selection and conditional MLE with application to classification in high dimensions

It is often the case that high-dimensional data consist of only a few informative components. Standard statistical modeling and estimation in such a situation is prone to inaccuracies due to overfitting, unless regularization methods are practiced. In the context of classification, we propose a class of regularization methods through shrinkage estimators. The shrinkage is based on variable selection coupled with conditional maximum likelihood. Using Stein's unbiased estimator of the risk, we derive an estimator for the optimal shrinkage method within a certain class. A comparison of the optimal shrinkage methods in a classification context, with the optimal shrinkage method when estimating a mean vector under a squared loss, is given. The latter problem is extensively studied, but it seems that the results of those studies are not completely relevant for classification. We demonstrate and examine our method on simulated data and compare it to feature annealed independence rule and Fisher's rule.     

The socioeconomic consequences of dropping out of high school: Evidence from an analysis of siblings

There is widespread belief that dropping out of high school leads to economic hardship. This belief rests on tenuous evidence. High school dropouts likely face an increased risk of economic hardship because of differences beyond a high school diploma. In particular, dropouts are more likely to come from disadvantaged backgrounds and thus face an elevated risk of economic hardship. Using data from the National Longitudinal Study of Youth 1979 Cohort, I estimate the consequences of dropping out by comparing dropouts to their siblings who completed high school. I also present OLS regression estimates using the same data. OLS regression estimates are consistently higher than sibling fixed effects estimates with the largest discrepancy occurring between estimates of the effect of dropping out on income-to-poverty ratio. However, the sibling fixed effect estimates reveal that dropping out has an effect on economic hardship net of unobserved background characteristics that are shared by siblings. I conclude with a discussion of how recent policy shifts affect the economic standing of low-ability students and suggest avenues for future research.     

The Generalized Conditional Autoregressive Wishart Model for Multivariate Realized Volatility

It is well known that in finance variances and covariances of asset returns move together over time. Recently, much interest has been aroused by an approach involving the use of the realized covariance (RCOV) matrix constructed from high-frequency returns as the ex-post realization of the covariance matrix of low-frequency returns. For the analysis of dynamics of RCOV matrices, we propose the generalized conditional autoregressive Wishart (GCAW) model. Both the noncentrality matrix and scale matrix of the Wishart distribution are driven by the lagged values of RCOV matrices, and represent two different sources of dynamics, respectively. The GCAW is a generalization of the existing models, and accounts for symmetry and positive definiteness of RCOV matrices without imposing any parametric restriction. Some important properties such as conditional moments, unconditional moments, and stationarity are discussed. Empirical examples including sequences of daily RCOV matrices from the New York Stock Exchange illustrate that our model outperforms the existing models in terms of model fitting and forecasting.     

Vine copula constructions of higher-dimensional dependent reliability systems

Copulas have proved to be very successful tools for the flexible modeling of dependence. Bivariate copulas have been deeply researched in recent years, while building higher-dimensional copulas is still recognized to be a difficult task. In this paper, we study the higher-dimensional dependent reliability systems using a type of decomposition called “vine,” by which a multivariate distribution can be decomposed into a cascade of bivariate copulas. Some equations of system reliability for parallel, series, and k-out-of-n systems are obtained and then decomposed based on C-vine and D-vine copulas. Finally, a shutdown system is considered to illustrate the results obtained in the paper.     

A note on efficient simulation of multidimensional spatial autoregressive processes

In applications of spatial statistics, it is necessary to compute the product of some matrix W of spatial weights and a vector y of observations. The weighting matrix often needs to be adapted to the specific problems, such that the computation of Wy cannot necessarily be done with available R-packages. Hence, this article suggests one possibility treating such issues. The proposed technique avoids the computation of the matrix product by calculating each entry of Wy separately. Initially, a specific spatial autoregressive process is introduced. The performance of the proposed program is briefly compared to a basic program using the matrix multiplication.     

初中起点幼师大学生历史课过度教学现象探析

一般而言,历史课及其任课教师是比较受初中起点幼师大学生欢迎的。与此同时,历史课教学中也时常不经意间在教学内容安排、教学方法运用和教学观点表达等方面出现过度教学现象。学生主体地位的异化,教学过程把控失当和教学反思的缺位,是造成过度教学的主要原因。消除过度教学现象的对策主要是坚持教学过程中学生的主体地位,掌握教学有度的艺术和重视教学反思。     

《高等数学》思想方法在创新教育中的美育价值

培养学生的数学创新能力离不开数学思想方法教学．从创新教育的美育价值角度看,在高师院校的《高等数学》课程中数学思想方法教学是引导学生欣赏美、发现美、创造美的重要工具,并具有推动教学的作用．     

马克思主义政治哲学应当是一种现代政治哲学

侯才从政治哲学的双重维度分析了马克思的政治哲学,他指出,从狭义上讲,马克思政治哲学中包含了一个完整的体系;从广义上讲,整个马克思哲学就是一种地地道道的政治哲学,“实践唯物主义”则是马克思对自己的政治哲学的一种独具特色的表述。李德顺认为,为了卓有成效地发展马克思主义政治哲学,首先应当明确政治哲学本身的基本问题,明确政治哲学在西方及中国兴起的现实原因,从理论基础和现实依据两个方面深入理解马克思主义政治哲学。王南湜认为,当代中国的马克思主义政治哲学应当是一种现代政治哲学,即说明一个正常社会的基本条件。将马克思主义政治哲学归属在现代政治哲学的论域中,则是这项研究当前最迫切和最实际的问题。吴晓明认为,作为近代政治哲学代表的黑格尔哲学揭示了政治事务中的“社会现实”,马克思则批判地拯救了政治哲学通向社会现实的道路,历史唯物主义对“社会现实”的重新发现,并给予今日中国的马克思主义政治哲学研究以重要的启示。     

论北朝西部审美观与盛唐美学思想的展开

我国西部自北朝以来发生的民族大融合及因之形成的西部审美观,已经渗入唐人思想文化风俗习惯亦即唐代社会文化生活的方方面面。盛唐美学思潮的全面展开,与北朝西部审美观的深远影响,有着千丝万缕的内在联系,此乃中国美学主潮在封建社会顶峰形成“盛唐气象”的力量之源。     

包头市中小学教育科研现状的调查分析与策略

以包头市中小学骨干教师为重点调查对象,通过问卷调查,着重从教育科研的意义、基础知识的储备、教科研方法的运用以及科研成果等方面分析,发现包头市中小学教科研现状不容乐观。提出相应策略,以推动包头市中小学教育科研的发展。