国际化学院的课程体验调查分析

北京航空航天大学中法工程师学院通过中外合作的办学模式以实现国际化人才的培养,其重要途径之一就是通过对课程体系进行的改革,而人才培养的质量很大程度上也取决于所授课程的质量。运用一种在国际上普遍采用的课程质量调查方法———大学生课程体验调查,结合国际化学院的特殊背景修订问卷,对北航中法工程师学院与普通学院的学生进行课程体验的调查。调查发现,北航中法工程师学院学生对课程的满意程度高于普通学院学生,特别在良好教学与资源获取方面明显好于普通学院学生,但在课程收获和学业负担方面仍需改进。     

农村留守儿童心理健康问题及其成因研究

随着我国社会经济的快速发展,越来越多的农村青壮年劳动力走入城市,随之产生的就是一个新的特殊群体——留守儿童.留守儿童是一个需要社会各界予以高度重视的群体,其心理健康问题尤其令人担忧.本文以陕西省户县胡家庄村留守儿童为调查研究的对象,利用青少年心理健康诊断测验(MHT)对胡家庄村留守儿童进行心理测试,结果表明,该村大部分留守儿童有较为严重的孤独倾向、学习焦虑、对人焦虑、自责倾向和身体症状等心理问题,根据总结出的该村留守儿童所存在的具体心理问题及其问题的相关成因,为社会工作介入农村留守儿童心理健康问题提供科学有效的依据.     

自媒体时代历史虚无主义思潮的传播及其反制

历史虚无主义在意识形态层面否定马克思主义的指导地位与唯物史观,歪曲丑化了中国共产党的领导。历史虚无主义思潮借助自媒体平台呈现出的碎片化、隐匿化与庸俗化倾向,在当下自媒体平台肆意传播,在社会上造成了极其恶劣的影响。在此背景下,必须深入分析历史虚无主义思潮在自媒体平台的传播方式及其规律,有针对性地提出相应的反制策略,在重建马克思主义唯物史观的同时,营造健康的网络道德教育环境。     

创投机构声誉、减持退出收益与公司业绩的影响效果——基于我国创业板制造业上市公司的实证分析

本文选取创业板上市公司为样本,实证创投机构声誉、减持退出行为收益与上市公司经营业绩的影响效果。研究发现:有创投参投的上市公司其经营业绩并未能明显优于无创投参投的上市公司,创投减持退出并未造成上市公司业绩显著下滑,创投机构减持行为与参投上市公司的业绩无显著关联;创投机构会发生聪明投资者的择时减持行为,借此获取超额减持收益;不同声誉创投机构退出行为的自我约束效力不同,高声誉创投机构减持退出行为更加理性。?更多还原     

有机硼交联HPG压裂液超低温破胶剂室内研究

对埋藏浅,油层温度低的油藏进行压裂改造,需解决压裂液低温破胶水化的问题。采用活化剂来提高过硫酸铵(APS),酶,胶囊破胶剂的低温破胶能力。通过对有机硼交联的羟丙基瓜胶(HPG)压裂液低温下破胶后粘度损失率的测定,筛选出用于50℃下的APS/活化剂破胶系统及胶囊破胶剂。结果表明:在APS/活化剂破胶系统的作用下,采用有机硼作交联剂的HPG压裂液在较低温度条件下能彻底破胶水化。     

Estimating Abundance from Presence–Absence Maps via a Paired Negative‐Binomial Model

The estimation of abundance from presence–absence data is an intriguing problem in applied statistics. The classical Poisson model makes strong independence and homogeneity assumptions and in practice generally underestimates the true abundance. A controversial ad hoc method based on negative‐binomial counts (Am. Nat.) has been empirically successful but lacks theoretical justification. We first present an alternative estimator of abundance based on a paired negative binomial model that is consistent and asymptotically normally distributed. A quadruple negative binomial extension is also developed, which yields the previous ad hoc approach and resolves the controversy in the literature. We examine the performance of the estimators in a simulation study and estimate the abundance of 44 tree species in a permanent forest plot.     

A Necessary Condition for the Strong Oracle Property

A problem of using a non‐convex penalty for sparse regression is that there are multiple local minima of the penalized sum of squared residuals, and it is not known which one is a good estimator. The aim of this paper is to give a guide to design a non‐convex penalty that has the strong oracle property. Here, the strong oracle property means that the oracle estimator is the unique local minimum of the objective function. We summarize three definitions of the oracle property – the global, weak and strong oracle properties. Then, we give sufficient conditions for the weak oracle property, which means that the oracle estimator becomes a local minimum. We give an example of non‐convex penalties that possess the weak oracle property but not the strong oracle property. Finally, we give a necessary condition for the strong oracle property.     

Combining Inverse Probability Weighting and Multiple Imputation to Improve Robustness of Estimation

Inverse probability weighting (IPW) and multiple imputation are two widely adopted approaches dealing with missing data. The former models the selection probability, and the latter models data distribution. Consistent estimation requires correct specification of corresponding models. Although the augmented IPW method provides an extra layer of protection on consistency, it is usually not sufficient in practice as the true data‐generating process is unknown. This paper proposes a method combining the two approaches in the same spirit of calibration in sampling survey literature. Multiple models for both the selection probability and data distribution can be simultaneously accounted for, and the resulting estimator is consistent if any model is correctly specified. The proposed method is within the framework of estimating equations and is general enough to cover regression analysis with missing outcomes and/or missing covariates. Results on both theoretical and numerical investigation are provided.     

历史地理学研究中GIS的认知过程及其人类因素考量

GIS技术在历史地理学研究领域的引入,为21世纪历史地理学沉淀积累和蓄势待发提供了新的研究视角和路径。随着GIS技术的普遍运用,尤其是在历史自然地理领域的使用,遂成为该研究方向创新和发展的重要因素。不过,GIS技术在人文地理研究领域中的运用情况则略显滞后,其实质在于受人类因素影响下历史文献数据化的标准问题。此外,GIS技术自身定位不再局限于一种研究手段,而是呈现出向新方法和理论高度的认知过程。     

我国农村信贷市场重建的合作制基础

随着新农村建设的深入开展,农村金融发展尤其是农村金融市场建设成为人们关注的焦点。我国农村有普遍的存款服务和汇兑服务,但缺乏有效率和规模的信贷供给。如何重建农村信贷市场成为制约农村金融市场建设的关键因素。通过对农户信贷需求的满足问题的探讨,可以发现,在目前城乡二元经济结构下,小农经济与市场化的矛盾成为制约农户借贷供求的根源。突破这一制约的有效途径是发展合作经济和建立"农民所有"的合作金融。