董作宾:乡土研究的先驱

20世纪中国民间文艺学史上存在过多种流派 ,如歌谣研究会、文学人类学派、社会—民族学派、“古史辨”派神话学、民俗学派、俗文学学派、延安学派等。作为第一个流派的歌谣研究会 ,是一个颇松散的团体和流派 ,其中持乡土研究观点的学者 ,如顾颉刚、常惠、董作宾、台静农、钟敬文、罗香林、白启明、刘经等 ,在歌谣研究会流派中占主流地位。本文以董作宾的《看见她》母题研究及其他研究为个例 ,阐明乡土研究思潮是 2 0世纪中国现代民间文艺学的最早的一种研究思潮 ,董作宾 (以及顾颉刚等 )在实践和理论上的成就 ,奠定了中国民间文艺学作为一个独立的人文学科的最初的理论基础。本文从 (1)“母题”的引入和比较研究的实践 ,(2 )家乡歌谣学应时而生 ,(3)考订与考订者 ,(4)综合研究模式的尝试四个方面 ,对董作宾的民间文艺学思想遗产和历史地位作历史的考察。     

A strong law of large numbers for independent random variables under non-additive probabilities

Abstract

Under non‐additive probabilities, cluster points of the empirical average have been proved to quasi-surely fall into the interval constructed by either the lower and upper expectations or the lower and upper Choquet expectations. In this paper, based on the initiated notion of independence, we obtain a different Marcinkiewicz-Zygmund type strong law of large numbers. Then the Kolmogorov type strong law of large numbers can be derived from it directly, stating that the closed interval between the lower and upper expectations is the smallest one that covers cluster points of the empirical average quasi-surely.     

Abundance estimation with a categorical covariate subject to missing in continuous-time capture-recapture studies

Abstract

In continuous-time capture-recapture experiments, individual heterogeneity has a large effect on the capture probability. To account for the heterogeneity, we consider an individual covariate, which is categorical and subject to missing. In this article, we develop a general model to summarize three kinds of missing mechanisms, and propose a maximum likelihood estimator of the abundance. A likelihood ratio confidence interval of the abundance is also proposed. We illustrate the proposed methods by simulation studies and a real data example of a bird species prinia subflava in Hong Kong.     

基于EaR的上市商业银行财务风险评价研究

商业银行在我国经济发展和转型中起着重要作用,近年来随着经济增速放缓、利率市场化和同业竞争加剧的影响,商业银行面临的财务风险也不断加大。为了科学合理地评价商业银行的财务风险,本文从在险价值(VaR)的概念出发引入了在险值的财务风险评价方法对上市商业银行的在险盈余和在险现金流进行测度,实证结果表明目前商业银行总体具有良好的盈利水平,但部分商业银行存在现金流风险。     

没有等价交换,就无法实现市场的双赢——四论商业原则

等价交换原则,是市场经济的基本原则,是商业原则的精髓,也是实现合作共赢的基础.传统的等价交换观念,是按照社会平均必要劳动时间对等来决定商品价格的.然而,社会平均必要劳动时间不仅在实践中无法统计,在理论上也难以对其进行深化、细化地论述.因此,应树立新的等价交换观念,即等价交换的核心是维护买卖双方的基本权益,以达到实现双赢的目的.应注意的是,等价交换不是等量交换,也难以做到等值交换.要以时代的视野、创新的观念,用新的价值观,正确对待交换价值,尽可能做到公平贸易.生财有道是实现等价交换的重要前提,这个道就是商业道德、市场规律、公平竞争和双赢战略.坚持等价交换原则,核心问题要落实一个“真”字,即“真诚待客”“真心服务”“真货经营”和“真价明码”.     

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.     

A combinatorial study of two-periodic random walks

Two-periodic random walks have up-steps and down-steps of one unit as usual, but the probability of an up-step is α after an even number of steps and β = 1 ? α after an odd number of steps, and reversed for down-steps. This concept was studied by Böhm and Hornik^{[2 Böhm, W.; Hornik, K. On two-periodic random walks with boundaries. Stoch. Models 2010, 26, 165–194.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]]}. We complement this analysis by using methods from (analytic) combinatorics. By using two steps at once, we can reduce the analysis to the study of Motzkin paths, with up-steps, down-steps, and level-steps. Using a proper substitution, we get the generating functions of interest in an explicit and neat form. The parameters that are discussed here are the (one-sided) maximum (already studied by Böhm and Hornik^{[2 Böhm, W.; Hornik, K. On two-periodic random walks with boundaries. Stoch. Models 2010, 26, 165–194.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]]}) and the two-sided maximum. For the asymptotic evaluation of the average value of the two-sided maximum after n random steps, more sophisticated methods from complex analysis (Mellin transform, singularity analysis) are required. The approach to transfer the analysis to Motzkin paths is, of course, not restricted to the two parameters under consideration.     

一类含有随机参数的混沌系统的Hopf分岔研究

文章选取随机变量为系统的随机变量研究含有随机参数混沌系统的Hopf分岔,利用Chebyshev正交多项式逼近理论将含有随机变量的系统转化为等价的确定性系统,通过Hopf分岔定理和Lyapunov系数讨论了随机参数系统的Hopf分岔及稳定性,发现随机系统的渐进稳定性参数区间大小不仅和确定性参数有关,还与随机参数有非常密切的关系.     

Linear Increments with Non‐monotone Missing Data and Measurement Error

Linear increments (LI) are used to analyse repeated outcome data with missing values. Previously, two LI methods have been proposed, one allowing non‐monotone missingness but not independent measurement error and one allowing independent measurement error but only monotone missingness. In both, it was suggested that the expected increment could depend on current outcome. We show that LI can allow non‐monotone missingness and either independent measurement error of unknown variance or dependence of expected increment on current outcome but not both. A popular alternative to LI is a multivariate normal model ignoring the missingness pattern. This gives consistent estimation when data are normally distributed and missing at random (MAR). We clarify the relation between MAR and the assumptions of LI and show that for continuous outcomes multivariate normal estimators are also consistent under (non‐MAR and non‐normal) assumptions not much stronger than those of LI. Moreover, when missingness is non‐monotone, they are typically more efficient.