矩阵方程XA＝B的亚（半）正定自共轭四元数矩阵解

给出了四元数体Ｑ上ｎ×ｎ分块矩阵为亚（半）正定自共轭矩阵的一个充要条件，进而给出了Ｑ上矩阵方程ＸＡｎｍ＝Ｂｎｍ有亚（半）正定自共轭四元数矩阵解的充要条件及解集合的显式表示，从而推广改进了数城上线性方程组的反问题及矩阵反问题的相应结果．     

一类二阶中立型时滞差分方程的振动定理

研究了一类具有变系数的二阶中立型时滞差分方程的振动性,得到了该类方程振动及差分算子△振动的一个充分条件.     

Efficient Estimation of a Distribution Function under Quadrant Dependence

LetX₁,X₂, ..., be real-valued random variables forming a strictly stationary sequence, and satisfying the basic requirement of being either pairwise positively quadrant dependent or pairwise negatively quadrant dependent. LetF^ be the marginal distribution function of theX_ips, which is estimated by the empirical distribution functionF_n and also by a smooth kernel-type estimateF_n, by means of the segmentX₁, ...,X_n. These estimates are compared on the basis of their mean squared errors (MSE). The main results of this paper are the following. Under certain regularity conditions, the optimal bandwidth (in the MSE sense) is determined, and is found to be the same as that in the independent identically distributed case. It is also shown thatn MSE(F_n(t)) andnMSE (F^_n(t)) tend to the same constant, asn→∞ so that one can not discriminate be tween the two estimates on the basis of the MSE. Next, ifi(n) = min {k∈{1, 2, ...}; MSE (F_k(t)) ≤ MSE (F_n(t))}, then it is proved thati(n)/n tends to 1, asn→∞. Thus, once again, one can not choose one estimate over the other in terms of their asymptotic relative efficiency. If, however, the squared bias ofF^_n(t) tends to 0 sufficiently fast, or equivalently, the bandwidthh_n satisfies the requirement thatnh³_n→ 0, asn→∞, it is shown that, for a suitable choice of the kernel, (i(n) ?n)/(nh_n) tends to a positive number, asn→∞ It follows that the deficiency ofF_n(t) with respect toF^_n(t),i(n) ?n, is substantial, and, actually, tends to ∞, asn→∞. In terms of deficiency, the smooth estimateF^_n(t) is preferable to the empirical distribution functionF_n(t)     

Approach and Positive Affect in Toddlerhood Predict Early Childhood Behavior Problems

The aim of the study was to examine the moderating role of positive affect on the relation between approach behaviors and adjustment outcomes. One hundred eleven toddlers participated in a laboratory assessment of approach and positive affect at 24 months. Behavior problems were reported by a parent in the fall of the child's kindergarten year. Results supported our hypotheses that children who displayed high approach and high positive affect in both non‐threat and low‐threat contexts were rated as higher in externalizing behavior problems. On the other hand, for children showing low positive affect, increases in approach in a moderate‐threat context lowered the risk of developing internalizing behavior problems. Implications for these findings are discussed, including methodological considerations of differences among eliciting contexts and advantages of separating positive affect and approach.     

Multivariate normal estimation: the case (n < p)

Estimation in the multivariate context when the number of observations available is less than the number of variables is a classical theoretical problem. In order to ensure estimability, one has to assume certain constraints on the parameters. A method for maximum likelihood estimation under constraints is proposed to solve this problem. Even in the extreme case where only a single multivariate observation is available, this may provide a feasible solution. It simultaneously provides a simple, straightforward methodology to allow for specific structures within and between covariance matrices of several populations. This methodology yields exact maximum likelihood estimates.     

A qualitative study on participants’ perceptions of child development accounts in Korea

ABSTRACT

In 2007, Korea implemented Child Development Accounts (CDAs) for institutionalised children in child welfare systems. Since then, the target group and a matching cap of CDAs in Korea have evolved. The target group expanded to include poor children receiving welfare, whereas the matching cap increased from KRW 30,000 (US$26.53) to KRW 40,000 (US$35.38), which is matched at a 1:1 rate. Despite the expansion, there is little empirical evidence examining the extent to which CDAs have influenced the life of participants. Using a content analysis method with a sample (N = 22), this study examines how CDAs have changed children’s mindsets, saving habits, education, future planning and sponsorship. The findings suggest that CDAs have multiple positive influences on children. This study concludes with policy implications for the inclusive and progressive development of CDAs in Korea.     

Double shrinkage estimators for large sparse covariance matrices

Covariance matrices play an important role in many multivariate techniques and hence a good covariance estimation is crucial in this kind of analysis. In many applications a sparse covariance matrix is expected due to the nature of the data or for simple interpretation. Hard thresholding, soft thresholding, and generalized thresholding were therefore developed to this end. However, these estimators do not always yield well-conditioned covariance estimates. To have sparse and well-conditioned estimates, we propose doubly shrinkage estimators: shrinking small covariances towards zero and then shrinking covariance matrix towards a diagonal matrix. Additionally, a richness index is defined to evaluate how rich a covariance matrix is. According to our simulations, the richness index serves as a good indicator to choose relevant covariance estimator.     

积极心理学视域下的环境美德伦理探究

环境伦理学自诞生以来,一直以构建客观的自然价值和自然权利为主要任务,忽略了作为道德行为主体的人。面对这种人未到场的环境伦理学现状,学者们开始从美德视角研究环境伦理学。积极心理学是一种研究人类的积极力量和美德的心理学思潮,对伦理学研究产生了重要影响。通过借鉴积极心理学的最新研究成果,环境美德伦理强调发挥环境保护中的积极因素,特别是积极的人格品质,从而鼓励和影响人对环境的友好行为。     

积极心理学在大学生思想政治教育应用中的思考

积极心理学致力于研究人的积极品质和积极力量,与大学生思想政治教育在培养“人”的积极品质;追求个人的自我价 值和社会价值的统一;预防大学生思想意识淡薄;激发个体积极力量等方面有着契合点。这为大学生思想政治教育借鉴和批 判性吸收积极心理学成果提供了可能,但应寻求科学合理有效的方式和方法,将其研究成果应用到大学生思想政治教育中。     

西利亚·撒克斯特作品中灾难书写的美学意蕴

西利亚·撒克斯特是19世纪美国女作家,其作品以其所居住的海岛为背景,记录了她在岛上的生活以及周围的自然景色。她在作品中表达了对自然之美的无尽热爱,这份热爱不仅局限于传统的田园牧歌式的自然景致,也延伸到了神秘而令人胆怯的荒野之中。本文结合当代环境美学家关于“非美自然”的论述,并参考康德对于纯粹审美判断的阐释,从“距离”与“道德”两个角度对西利亚作品中关于灾难性自然景观的言说进行审美意义上诠释。西利亚坚持以自然的名义欣赏自然,希望借助康德式的纯粹审美还原审美自然灾难的合理性。此外,她选择成为灾难的“旁观者”而非“参与者”,克服了“恐惧”对于审美自然灾难所产生的阻碍,证明了欣赏自然灾难的可行性。分析西利亚作品中所体现的自然审美思想,不仅是对自然文学研究领域的进一步延伸,也是对当代环境美学理论的一次反哺与验证。西利亚对自然灾难的审美言说是一次勇敢的尝试,不仅为人类积极地理解自然灾难提供了一种可能性,也扩宽了“非美自然”的审美疆域。