随机Petri网应用于马尔可夫预测模型

随机Ｐｅｔｒｉ网和马尔可夫链有着内在的联系,用它来对状态整体的变化规律不十分明确但状态分量的变化规律明确的一类问题建模,为马尔可夫预测模型的应用提供了方便。     

松果采摘对种子库及动物影响的探讨

根据食物链原理和动物与生境密切的关系,探讨了松果采摘对长白山自然保护区动物的影响.认为松果采摘后,一方面松籽没有动物帮助搬运,使红松不能正常天然更新,影响了红松林生态系统正常演替而破坏了动物生境;另一方面使得保护区内以松籽为主要食物来源的动物因缺少食物而发生数量变化,致使食物链遭受破坏,从而导致红松林中动物分布发生变化.     

图书馆纸质文献采访——借阅优化策略分析

书籍随着时间流逝,其无形价值逐渐衰减。与此同时,图书馆因为资金约束,不可能无限制地购置新书。借鉴学者研究产品回收再利用的库存控制方法,以图书馆可服务馆藏与新购在途文献之和作为判断是否达到安全馆藏的依据,采用(s,Q)文献采访策略,以图书的订购、到达、外借、还回、剔旧建立Markov过程,以每一时期图书的新旧程度为读者评价的主要依据,以订购成本、馆藏成本、短缺成本、外借成本、剔旧成本作为系统成本,以读者评价和系统成本作为决策变量,推出图书馆可以获得订购值(Q)和外借期限(Lr)的最优策略。     

沙四下盐湖储层发育控制因素预测研究

盐湖盆地的石油资源勘探,长期以来一直是国际石油界所密切关注、饶有兴趣的一个研究领域。深化东营凹陷膏盐岩的成因分析,通过大量的资料查询、岩芯的详细观察和分析化验资料,搞清楚东营凹陷中泥页岩、膏盐岩以及碎屑砂岩的成因。同时通过大量的岩芯观察利用马尔科夫链的方法建立东营凹陷沙四下亚段盐湖相的沉积序列,并预测储层的有利发育位置,可以为含盐盆地油气成藏规律研究提供很好的沉积学基础。     

基于绿色营销视角的消费者品牌转换成本控制研究

消费者在由非绿色品牌向绿色品牌转换过程中可能会遭遇过高的转换成本,运用价值链成本控制理论能够控制绿色品牌转换成本。消费者品牌转换成本的管理可看作是企业价值链的延伸管理。降低消费者绿色品牌转换成本,需要对整个价值链所涉及成本都加以控制。程序性转换成本的控制应通过建立作业中心来控制企业的售前和售后两部分销售费用;财务性和关系性转换成本的控制则应分析研究竞争对手的价值链和行业价值链．优化企业价值链。     

沪市系统风险β系数实证研究

Beta系数是资本资产定价模型(CAPM)系统风险的量化指标，它揭示了某种证券或者证券组合的风险与市场平均风险的差异．本文在CAPM理论框架下，尝试性地利用带有马尔科夫体制转换的市场模型，对上海股市中的上证30指数的30只组成股票的系统风险beta系数进行动态建模，估计了日收益率度量时限条件下的beta系数，来研究中国股市中系统风险的时变性和体制转换行为，结果发现这30只股票的波动率存在非常强烈的体制转换特征．但是，令人吃惊的是系统风险的时变性比较弱，体制转换行为不明显。     

Graph-based discovery and analysis of atomic-scale one-dimensional materials

Recent decades have witnessed an exponential growth in the discovery of low-dimensional materials (LDMs), benefiting from our unprecedented capabilities in characterizing their structure and chemistry with the aid of advanced computational techniques. Recently, the success of two-dimensional compounds has encouraged extensive research into one-dimensional (1D) atomic chains. Here, we present a methodology for topological classification of structural blocks in bulk crystals based on graph theory, leading to the identification of exfoliable 1D atomic chains and their categorization into a variety of chemical families. A subtle interplay is revealed between the prototypical 1D structural motifs and their chemical space. Leveraging the structure graphs, we elucidate the self-passivation mechanism of 1D compounds imparted by lone electron pairs, and reveal the dependence of the electronic band gap on the cationic percolation network formed by connections between structure units. This graph-theory-based formalism could serve as a source of stimuli for the future design of LDMs.     

Does adding video and subtitles to an audio lesson facilitate its comprehension?

We examined whether adding video and subtitles to an audio lesson facilitates its comprehension and whether the comprehension depends on participants' cognitive abilities, including working memory and executive functions, and where they looked during video viewing. Participants received lessons consisting of statements of facts under four conditions: audio-only, audio with verbatim subtitles, audio with relevant video, and audio with both subtitles and video. Comprehension was assessed as the accuracy in answering multiple-choice questions for content memory. We found that subtitles facilitated comprehension whereas video did not. In addition, comprehension of audio lessons with video depended on participants' cognitive abilities and eye movement pattern: a more centralized (looking mainly at the screen center) eye movement pattern predicted better comprehension as opposed to a distributed pattern (with distributed regions of interest). Thus, whether video facilitates comprehension of audio lessons depends on both learners’ cognitive abilities and where they look during video viewing.     

数字全球价值链：概念、理论框架与未来展望

以数字经济崛起、数字技术发展、数据生产要素涌现为主要特点的新工业革命迫使全球价值链发生颠覆性变革和重构,催生了数字全球价值链。数字全球价值链作为一种新的价值链形式,需要对其属性特征、理论机制和动力机制等问题进行深入研究,以推动进一步发展。首先,系统梳理相关文献,聚焦于已有数字全球价值链的相关概念,并对其进一步拓展和界定,深化对数字全球价值链的理解。其次,通过归纳和提炼现有研究和实践中关于数字全球价值链的活动表现形式,提炼出数字全球价值链的核心特征。在此基础上,对全球数据价值链和全球价值链数字化等相似概念进行辨析。再次,结合数字经济的特点,识别数字全球价值链的投入—产出结构、要素禀赋、治理模式、价值链距离和政策环境五大影响因素。最后,围绕参与主体、动力机制和发展结果搭建数字全球价值链的理论框架。进一步地,围绕这一框架提出数字全球价值链未来亟须探索的三类研究方向。研究有助于提升数字全球价值链研究的系统性,为其后续研究提供参考。