Variance estimation based on blocked 3×2 cross-validation in high-dimensional linear regression

In high-dimensional linear regression, the dimension of variables is always greater than the sample size. In this situation, the traditional variance estimation technique based on ordinary least squares constantly exhibits a high bias even under sparsity assumption. One of the major reasons is the high spurious correlation between unobserved realized noise and several predictors. To alleviate this problem, a refitted cross-validation (RCV) method has been proposed in the literature. However, for a complicated model, the RCV exhibits a lower probability that the selected model includes the true model in case of finite samples. This phenomenon may easily result in a large bias of variance estimation. Thus, a model selection method based on the ranks of the frequency of occurrences in six votes from a blocked 3×2 cross-validation is proposed in this study. The proposed method has a considerably larger probability of including the true model in practice than the RCV method. The variance estimation obtained using the model selected by the proposed method also shows a lower bias and a smaller variance. Furthermore, theoretical analysis proves the asymptotic normality property of the proposed variance estimation.     

L2句子加工心理机制的ERPs研究及问题思考

国内外对L2句子加工的研究存在着较大区别。国外偏重于探讨句子加工的心理机制本身,而国内不仅探讨句子加工的心理机制本身,而且还注重探讨句子加工的心理机制所说明的问题,分析L2句子加工是否接近或相似于L1句子加工。目前,该领域的研究主要存在三种主要流派:模块说、交互说和平行说。多数学者认为L2句子加工是句法和语义加工交织的过程,即多数人接受了交互说。少数学者认为语义加工优先于句法加工。至于平行说,最近L2句子加工研究鲜有成果支持此理论。     

网络舆情评估EHA三维指标体系的构建

随着网络在我国的兴起和发展,网络舆情的评估已经成为评价和预警社会形势的重要指标.通过对现有舆情研究的调研和分析,得出由舆情要素、舆情热度和舆情活性3个一级指标、7个二级指标以及14个三级指标共同构建的网络舆情评估的EHA三维指标体系,并对各级指标给出了详尽的分析和阐述.     

P2P技术与网络传播的未来

伴随着P2P技术和商业应用的发展,P2P技术对于未来网络传播可能产生的影响也成为一个令 人关注的问题。从目前来看,P2P技术对于网络传播的影响主要包括以下几方面:网络信息共享与 利用的方式与程度将进一步改变;围绕P2P技术思想展开的软件与信息产品开发,将在一定程度上 决定作为媒体的网络的未来面貌;P2P带来的去中心化特点将使互联网管理的难度进一步增加; P2P可能成为媒体间的交流与合作的新平台,也可能加速媒体形态的演化。从总体看,P2P技术未 来的社会影响程度,取决于政治、经济等各种力量的博弈结果,而这也将最终影响着互联网的未来。     

“双碳”目标下农业生态效率测度及影响因素分析

农业生态效率是农业经济和生态环保协调发展的重要体现。文章首先引入农业碳汇效应,构建农业生态效率测度指标体系;其次,基于2010—2019年中国31个省市面板数据,运用熵权法改进的超效率SBM测算各地区农业生态效率;然后运用面板Tobit模型探究农业生态效率影响因素。结果发现：2010—2019年中国农业生态效率总体呈现平稳上升态势,空间上呈现东北地区最高、东部次之、西部较低、中部最低的分布格局;财政支农程度、工业化程度、农业自然环境、农业机械密度对农业生态效率产生负向影响;农业环境规制、科技支持力度、农业资源禀赋、农业人力资本和农业生产能力对农业生态效率产生正向影响。最后,提出合理投入农业要素资源;促进农业生产增长;加大农业科技研发和推广力度;提高农业劳动力素质等建议。     

Lower bound of average centered L2-discrepancy for U-type designs

Uniform designs are widely used in various scientific investigations and industrial applications. By considering all possible level permutation of the factors, a connection between average centered L₂-discrepancy and generalized wordlength pattern for asymmetrical fractional factorial designs is derived. Moreover, we present new lower bounds to the average centered L₂-discrepancy for symmetrical and asymmetrical U-type designs. For illustration of the theoretical results, the lower bounds for symmetrical and asymmetrical U-type designs are tabulated, and numerical results indicate that our lower bounds behave well and can be recommended for use in practice.     

On Hotelling’s T2 test in a special paired sample case

In a special paired sample case, Hotelling’s T² test based on the differences of the paired random vectors is the likelihood ratio test for testing the hypothesis that the paired random vectors have the same mean; with respect to a special group of affine linear transformations it is the uniformly most powerful invariant test for the general alternative of a difference in mean. We present an elementary straightforward proof of this result. The likelihood ratio test for testing the hypothesis that the covariance structure is of the assumed special form is derived and discussed. Applications to real data are given.     

论促进山东半岛蓝色经济区建设的财产权路径——以温室气体排放权交易为视角

温室气体排放权是在指定时期内排放一定数量温室气体的权利,它也是一项财产权。温室气体排放权交易分为总量控制型交易与基线和信用型交易两类。温室气体排放权交易不仅可以有效地降低碳减排的成本,还可以催生新的经济增长点——碳汇经济。在山东半岛蓝色经济区推行温室气体排放权交易,既可以引导产业结构向低碳转型,又可以创新海洋经济的发展模式,应选择基线和信用型交易的模式。通过创建温室气体排放权交易市场,为山东半岛蓝色经济区海洋碳汇经济的发展提供平台。     

几种典型的烟气脱硫技术

烟气脱硫是控制二氧化硫污染的常用方法,我国的烟气脱硫技术研究从19世纪五十年代开始,目前已形成较多的应用技术。文中对国内几种典型的烟气脱硫技术的工艺流程、特点、应用情况及其发展做了介绍。     

技术进步、生产方式转型与中国生猪养殖温室气体减排

基于技术水平和规模化水平时空差异,收集不同养殖模式生长周期、出栏量等关键数据,对全国和各省生猪养殖碳排放量进行估算。结果表明,1998-2015年,全国生猪养殖碳排放量呈震荡上升趋势,从1.08亿吨CO2当量增加到1.33亿吨 CO2当量;规模化养殖逐渐取代散养成为碳排放主体,2015年其排放量占比达到73.57%;四川、湖南、河南、山东等生猪主产省份碳排放量居全国前列;LMDI模型的分解结果表明,生猪产量扩张是碳排放增长的主要驱动力,推动碳排放量增长43.93%,技术进步和养殖规模化则将碳排放增长削减了近一半。因此,提高养殖技术、推动规模化养殖、应用沼气池处理粪污将是重要的温室气体减排措施。