西晋玄风与咏鸟赋的意象创造

谈玄之风始于正始年间,持续至东晋末期。玄风对两晋文学产生了重要的影响。受玄风影响,西晋时期咏鸟赋的创作较为繁荣,其意象类型主要有:"玄鸟"意象、"逸鸟"意象、"儒鸟"意象等。三种鸟意象的出现显示出西晋时期的咏鸟赋创作既与政治密切相关,也与当时玄学风气密不可分。     

Conditional entropy,entropy density,and strong law of large numbers for generalized controlled tree-indexed Markov chains

In this paper, we first introduces a tree model without degree boundedness restriction namely generalized controlled tree T, which is an extension of some known tree models, such as homogeneous tree model, uniformly bounded degree tree model, controlled tree model, etc. Then some limit properties including strong law of large numbers for generalized controlled tree-indexed non homogeneous Markov chain are obtained. Finally, we establish some entropy density properties, monotonicity of conditional entropy, and entropy properties for generalized controlled tree-indexed Markov chains.     

在丛生的意象群落中呈现诗魂--读段光安的诗

段光安是对诗的创作规律有深切领悟的一位中年诗人，把强大的生命之火注入到丛生的意象之中，使意象成为诗人主观情思的对应物，这是段光安诗性思维的明显特征。丰富的生活积累，勤奋的艺术追求，对诗歌把握世界的方式的独特见解，感受着诗歌这一崇高的生命形式的呼唤，使他的眼前展开一道通向诗歌天国的云梯。     

Adaptive stochastic gradient boosting tree with composite criterion

ABSTRACT

In this paper, we propose an adaptive stochastic gradient boosting tree for classification studies with imbalanced data. The adjustment of cost-sensitivity and the predictive threshold are integrated together with a composite criterion into the original stochastic gradient boosting tree to deal with the issues of the imbalanced data structure. Numerical study shows that the proposed method can significantly enhance the classification accuracy for the minority class with only a small loss in the true negative rate for the majority class. We discuss the relation of the cost-sensitivity to the threshold manipulation using simulations. An illustrative example of the analysis of suboptimal health-state data in traditional Chinese medicine is discussed.     

人性与自由情感——兼论奥斯卡影像美学

人类存在着两类不同性质的情感：自由情感和必然情感。所谓自由情感指的是刺激源和这种情感对象之间没有任何直接的利害关系条件下所产生的情感。美的本质就在于自由情感。奥斯卡艺术堪称电影艺术中的经典。奥斯卡奖近百年的评奖历史证明人性是社会大众和奥斯卡奖评委共同的最好的审美趣味激发源。其中爱情、亲情、友情是奥斯卡影像中最浓墨重彩的人性主题，是自由情感的主要源泉，也是奥斯卡影像美学的核心。     

Variable Selection via Regression Trees in the Presence of Irrelevant Variables

Many tree algorithms have been developed for regression problems. Although they are regarded as good algorithms, most of them suffer from loss of prediction accuracy when there are many irrelevant variables and the number of predictors exceeds the number of observations. We propose the multistep regression tree with adaptive variable selection to handle this problem. The variable selection step and the fitting step comprise the multistep method.

The multistep generalized unbiased interaction detection and estimation (GUIDE) with adaptive forward selection (fg) algorithm, as a variable selection tool, performs better than some of the well-known variable selection algorithms such as efficacy adaptive regression tube hunting (EARTH), FSR (false selection rate), LSCV (least squares cross-validation), and LASSO (least absolute shrinkage and selection operator) for the regression problem. The results based on simulation study show that fg outperforms other algorithms in terms of selection result and computation time. It generally selects the important variables correctly with relatively few irrelevant variables, which gives good prediction accuracy with less computation time.     

A Research on the Social Role and Status of Tibetan Females as they Appear in Internet Images

Previous research on Tibetan women’s identity and status are mainly concentrat-ed in the role and function of women in the family, production,labor,work and religious affairs within Tibetan society. Ho...     

“木精为青牛”考释

植物精怪的动物化是一种世界性民俗现象,在中国古代则有“木精为青牛”的说法。究其原因,这一观念的出现大约有三方面的影响因素:一是古代神话中植物神祗动物形貌的遗存;二是秦汉时期有“出土牛迎春”的礼俗,土牛、青牛与春天、树木关联在一起;三是中国古代有源远流长的青牛信仰,在魏晋南北朝时期尤为突出,这是“木精为青牛”说的民俗背景。      

Throughput and delay analysis of an opportunistic tree algorithm

Tree algorithms are a well-known class of random access algorithms with a provable maximum stable throughput under the infinite population model (as opposed to ALOHA or the binary exponential backoff algorithm). In this article, we propose a tree algorithm for opportunistic spectrum usage in cognitive radio networks. A channel in such a network is shared among so-called primary and secondary users, where the secondary users are allowed to use the channel only if there is no primary user activity. The tree algorithm designed in this article can be used by the secondary users to share the channel capacity left by the primary users.

We analyze the maximum stable throughput and mean packet delay of the secondary users by developing a tree structured Quasi-Birth Death Markov chain under the assumption that the primary user activity can be modeled by means of a finite state Markov chain and that packets lengths follow a discrete phase-type distribution.

Numerical experiments provide insight on the effect of various system parameters and indicate that the proposed algorithm is able to make good use of the bandwidth left by the primary users.