试论石柱县人口的发展变化

本文叙述了建国后石柱县各阶段人口发展的情形以及目前石柱县的人口生育模式等人口状况。研究分析表明,影响石柱县人口发展变化的主要因素是经济和政策因素;在不同时期,这两种因素所起的作用是不同的;而在现今的石柱县,政策因素对人口发展的影响占据着主导地位。     

Approximation strategy-proof mechanisms for obnoxious facility location on a line

In the facility location game on a line, there are some agents who have fixed locations on the line where an obnoxious facility will be placed. The objective is to maximize the social welfare, e.g., the sum of distances from the facility to all agents. On collecting location information, agents may misreport the locations so as to stay far away from the obnoxious facility. In this paper, strategy-proof mechanisms are designed and the approximation ratio is used to measure the performances of the strategy-proof mechanisms. Two objective functions, maximizing the sum of squares of distances (maxSOS) and maximizing the sum of distances (maxSum), have been considered. For maxSOS, a randomized 5/3-approximated strategy-proof mechanism is proposed, and the lower bound of the approximation ratio is proved to be at least 1.042. For maxSum, the lower bound of the approximation ratio of the randomized strategy-proof mechanism is proved to be 1.077. Moreover, a general model is considered that each agent may have multiple locations on the line. For the objective functions maxSum and maxSOS, both deterministic and randomized strategy-proof mechanisms are investigated, and the deterministic mechanisms are shown to be best possible.     

A simpler PTAS for connected <Emphasis Type="Italic">k</Emphasis>-path vertex cover in homogeneous wireless sensor network

Because of its application in the field of security in wireless sensor networks, k-path vertex cover (\(\hbox {VCP}_k\)) has received a lot of attention in recent years. Given a graph \(G=(V,E)\), a vertex set \(C\subseteq V\) is a k-path vertex cover (\(\hbox {VCP}_k\)) of G if every path on k vertices has at least one vertex in C, and C is a connected k-path vertex cover of G (\(\hbox {CVCP}_k\)) if furthermore the subgraph of G induced by C is connected. A homogeneous wireless sensor network can be modeled as a unit disk graph. This paper presents a new PTAS for \(\hbox {MinCVCP}_k\) on unit disk graphs. Compared with previous PTAS given by Liu et al., our method not only simplifies the algorithm and reduces the time-complexity, but also simplifies the analysis by a large amount.     

Asymptotically optimal policy for stochastic job shop scheduling problem to minimize makespan

This paper studies the large-scale stochastic job shop scheduling problem with general number of similar jobs, where the processing times of the same step are independently drawn from a known probability distribution, and the objective is to minimize the makespan. For the stochastic problem, we introduce the fluid relaxation of its deterministic counterpart, and define a fluid schedule for the fluid relaxation. By tracking the fluid schedule, a policy is proposed for the stochastic job shop scheduling problem. The expected value of the gap between the solution produced by the policy and the optimal solution is proved to be O(1), which indicates the policy is asymptotically optimal in expectation.     

An $$O(|E(G)|^2)$$ algorithm for recognizing Pfaffian graphs of a type of bipartite graphs

A graph \(G=(V,E)\) with even number vertices is called Pfaffian if it has a Pfaffian orientation, namely it admits an orientation such that the number of edges of any M-alternating cycle which have the same direction as the traversal direction is odd for some perfect matching M of the graph G. In this paper, we obtain a necessary and sufficient condition of Pfaffian graphs in a type of bipartite graphs. Then, we design an \(O(|E(G)|^2)\) algorithm for recognizing Pfaffian graphs in this class and constructs a Pfaffian orientation if the graph is Pfaffian. The results improve and generalize some known results.     

A continuous characterization of the maximum vertex-weighted clique in hypergraphs

For a simple graph G on n vertices with adjacency matrix A, Motzkin and Strauss established a remarkable connection between the clique number and the global maximum value of the quadratic programm: \(\textit{max}\{ \mathbf {x}^T A \mathbf {x}\}\) on the standard simplex: \(\{\sum _{i=1}^{n} x_i =1, x_i \ge 0 \}\). In Gibbons et al. (Math Oper Res 122:754–768, 1997), an extension of the Motzkin–Straus formulation was provided for the vertex-weighted clique number of a graph. In this paper, we provide a continuous characterization of the maximum vertex-weighted clique problem for vertex-weighted uniform hypergraphs.     

信息技术背景下教育教学多维度创新体系研究

“互联网+”、3D打印技术为代表的信息化浪潮已经到来,创新创业教育的已经在全国展开,这既是高等教育教学的挑战,更是不可多得的机遇。为适应信息技术的需求,高等院校要未雨绸缪,及时应对,从创新体系构建信息技术要先行、教育教学创新体系构建要结合学科、专业特点进行、二级学院联动、对教师要求及激励等多个方面探讨信息技术背景下教育教学多维度创新体系。     

Co-Occurring Psychosocial Problems and Multiple Sexual Partners among Men Who Have Sex with Men in Shanghai,China: A Syndemic Approach

We aimed to apply syndemic theory to verify the association and reinforcing effects between psychosocial problems and multiple sexual partners (MSP) of men who have sex with men (MSM) in Shanghai, China. A cross-sectional study was conducted among 547 MSM in Shanghai, China using a face-to-face survey. Sociodemographic and psychosocial data were collected, as well as information on MSP and condomless anal sex. In the 6 months prior to the survey, 54.3% of the MSM sample had had MSP. Univariate analysis showed that self-esteem, depression, loneliness, sexual compulsivity, and involuntary subordination (IS) were associated with MSP. Sexual compulsivity (multivariate odds ratio [ORm] = 2.94, 95% CI = 1.76–4.91) and IS (ORm = 1.79, 95% CI = 1.14–2.81) remained significant in multivariate analysis. MSM with five or more psychosocial problems had greater odds of (adjusted odds ratios = 3.06, 95% CI = 1.49–6.25) having MSP in the previous 6 months than the non-syndemic group. Our findings provide preliminary confirmation of the additive relationship of syndemic psychosocial health conditions and MSP among MSM in Shanghai, China. An integrated intervention with special focus on sexual compulsivity and IS is needed.     

思想史叙事中的范式性遮蔽——智者学派何以在政治哲学史中消失

苏格拉底及其弟子在学术界被很多人看成是古希腊自然哲学转向政治哲学的标志。这种看法虽然也有一定的依据,但在今天人们对理性主义政治学的反思中,它却多少是坚持理性主义认知范式的结果。除去这种范式所带有的特定遮蔽,我们可以看到古希腊政治哲学发展史的另一幅画面:智者学派具有自己特点鲜明的政治哲学思想,它全面参与了政治哲学转向的过程。当今时代变革催生的"认知范式"转换正颠覆着理性主义政治哲学史的解释框架。     

命名的故事:“底层”,还是“新左翼”?——大陆新世纪文学新潮的内在困境

近年来,大陆文坛兴起了一个"底层文学"思潮,主要表现下岗工人和进城打工农民的生活、命运与抗争。其中一些启用传统社会主义思想资源的作品(如《那儿》、《问苍茫》)又被命名为"新左翼文学"。这些作品及相关评论既包含一些新的因素,如从前国家意识形态里汲取抗争性资源,又往往非历史、非逻辑地解释中国左翼文化传统,导致"新左翼"命题未能释放出应有的涵义和广阔的阐释空间,反而使之狭义化。但使"新左翼"狭义化的还有对"左翼"价值持怀疑、否定的论者,在他们的意识里,阶级论和阶级分析本身就是虚幻而荒谬的,结果不仅使他们放过了对以"社会主义"之名长期存在的"身份制"等级社会分析的契机,又以一种"西方的今天就是我们的明天"的历史幻觉,面对非规则变动着的当代中国,并衍生出包括"纯文学"在内的各种新意识形态观念。随着所有制改革、政府减轻财政负担的政策调整,以及全球化背景下中国经济的高速增长,中国社会急剧分化,贫富差距日益加大,旧的身份制社会尚未改变,一个庞大的底层社会业已形成。这给已经习惯于"纯文学"写作的文学界带来道德压力,也使与"纯文学"观相悖的"底层文学"应运而生。但"底层文学"从一开始就陷入争议,其本身在创作和理论上也问题多多,无论是"底层",还是"新左翼"都很快沦为没有生长性的命题。或许,不是从文坛既有问题,而是从"底层"、"新左翼"所黏合的"问题状况"着眼,新的可能性才会被发现。