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31.
Introduction and spread of the parasite Myxobolus cerebralis, the causative agent of whirling disease, has contributed to the collapse of wild trout populations throughout the intermountain west. Of concern is the risk the disease may have on conservation and recovery of native cutthroat trout. We employed a Bayesian belief network to assess probability of whirling disease in Colorado River and Rio Grande cutthroat trout (Oncorhynchus clarkii pleuriticus and Oncorhynchus clarkii virginalis, respectively) within their current ranges in the southwest United States. Available habitat (as defined by gradient and elevation) for intermediate oligochaete worm host, Tubifex tubifex, exerted the greatest influence on the likelihood of infection, yet prevalence of stream barriers also affected the risk outcome. Management areas that had the highest likelihood of infected Colorado River cutthroat trout were in the eastern portion of their range, although the probability of infection was highest for populations in the southern, San Juan subbasin. Rio Grande cutthroat trout had a relatively low likelihood of infection, with populations in the southernmost Pecos management area predicted to be at greatest risk. The Bayesian risk assessment model predicted the likelihood of whirling disease infection from its principal transmission vector, fish movement, and suggested that barriers may be effective in reducing risk of exposure to native trout populations. Data gaps, especially with regard to location of spawning, highlighted the importance in developing monitoring plans that support future risk assessments and adaptive management for subspecies of cutthroat trout.  相似文献   
32.
In this paper, we present an access network design problem with end-to-end quality of service (QoS) requirement. The problem can be conceptualized as a two-level hierarchical location-allocation problem on the tree topology with nonlinear side constraints. The objective function of the nonlinear mixed integer programming model minimizes the total cost of switch and fiber cable, while satisfying demand within the prescribed level of QoS. By exploiting the inherent structure of the nonlinear QoS constraints, we develop linearization techniques for finding an optimal solution. Also, we devise an effective exact optimal algorithm within the context of disjunctive constraint generation. We present promising computational results that demonstrate the effectiveness of the proposed solution procedure.  相似文献   
33.
针对大型建筑企业控制力动态协同的定量化仿真问题,基于复杂系统视角,应用自组织理论分析大型建筑企业控制力自组织耦合网络作用关系,选择有效朗之万方程构建大型建筑企业控制力系统的自组织协同进化模型,通过线性近似法的性态稳定求解非线性方程的稳定性,得出大型建筑企业控制力系统协同进化演化过程的四个决定性参数,并通过MATLAB软件进行参数枚举取值,具体分析企业控制力协同演化。案例验证该模型可对大型建筑企业控制力协同演化最佳状态实现更加精确的参数取值,并发现大型建筑企业控制力协同演化最佳状态的充要条件,以及一种新的大型建筑企业控制力协同演化状态。  相似文献   
34.
Upon reviewing the extant literature on determinants of unionism, it becomes clear that many areas that have had a plethora of research attention do not converge upon singularly directional findings. This study explores a potential cause of such an apparent anomaly: nonlinearity of data. An exploratory examination of correlation coefficients among typical union determinant variables seems to show different patterns of relationships at different levels of union demand. Thus, a break from traditional linear data analysis techniques is explored in the interest of explaining more variance with typical, theoretically derived variables by using neural network analysis. Results of analyses on industry level data reveal that using neural network analysis to model union demand explained over four times as much variance as multiple regression analysis.  相似文献   
35.
Regional trade agreements (RTAs) and bilateral investment treaties (BITs) are expected to promote trade and investment relationships. One critical feature of such agreements is the network, so the multiplex coevolution of RTAs and BITs should be captured by the dynamics of their two networks. Although many studies have examined the roles of RTAs and BITs, most studies do not account for crucial network properties. This study explores how RTAs and BITs coevolve by applying a stochastic actor-oriented model of multiplex network evolution. In particular, we examine the roles of (i) cross-network dyadic interinfluences and (ii) within- and cross-network preferential attachments to discuss the dynamic relationships between RTAs and BITs. The results are as follows. First, our estimation supports cross-network dyadic interinfluences. Countries that sign a BIT are willing to establish an RTA, while those that sign an RTA are reluctant to establish a BIT. Second, concerning preferential attachments, countries prefer to sign BITs with partners that have more RTA and BIT links. However, countries tend to form RTAs with partners that have more BIT links but are reluctant to form RTAs with those that have more RTA links. We discuss possible justifications for these results, including arguments regarding the benefits and costs associated with the formation of RTAs and BITs.  相似文献   
36.
数字技术使信息传播渠道从单一向“网络立体化”转变,信息传播主体从“中心化”向“分散化”转变,信息传播环境从“真实化”向“拟态化”转变,信息传播出现了“混沌”与“失序”现象。“坚持人本理念”是网络信息传播秩序重构的基本逻辑,“信息资源与要素的再整合”是网络信息传播秩序重构的基础条件,“智能化信息平台决策机制”是网络信息传播秩序重构的保障。在信息传播秩序重构的过程中,需要强化技术体系与网络体系的链接,搭建多层次信息流动与传播的网络空间;需要加强对社会生活空间与产业的数字化改造,促使现实世界向虚拟世界迁移;需要催生全新的元宇宙信息场域,构建与现实世界映射与交互的虚拟世界。  相似文献   
37.
以CNKI核心论文数据库中的文献为研究对象,梳理网络意识形态安全相关研究成果,可以发现,目前学界对网络意识形态安全的研究成果多以理论分析为主,在研究范式上注重宏观和微观相结合,部分研究成果缺乏精准性和针对性,实证分析较少,研究方法单一,缺乏多学科融合视角。因此,未来应深化研究内容,拓宽研究视角,构建研究话语,以提高研究水平和增加理论供给。  相似文献   
38.
基于2016—2020年我国31个省级行政区的面板数据,考察数字化发展、制度环境与政府舆情治理质量之间的关系。研究发现,数字化发展对政府舆情治理质量具有改善效应;相比制度环境较差的省份,数字化发展对舆情治理质量的改善效应在制度环境较好的省份更为显著。异质性检验表明,数字化发展对政府舆情治理质量的改善效应在数字化水平高的省份、制度环境较好但数字化水平低的省份显著,在制度环境较好的省份、制度环境较差的东部省份显著。研究结论为借助数字化发展改善政府舆情治理质量提供了理论依据。  相似文献   
39.
In this article, the quality of data produced by national statistical institutes and by governmental institutions is considered. In particular, the problem of measurement error is analyzed and an integrated Bayesian network decision support system based on non-parametric Bayesian networks is proposed for its detection and correction. Non-parametric Bayesian networks are graphical models expressing dependence structure via bivariate copulas associated to the edges of the graph. The network structure and the misreport probability are estimated using a validation sample. The Bayesian network model is proposed to decide: (i) which records have to be corrected; (ii) the kind and amount of correction to be adopted. The proposed correction procedure is applied to the Banca d’Italia Survey on Household Income and Wealth and, specifically, the bond amounts are analyzed. Finally, the sensitivity of the conditional distribution of the true value random variable given the observed one to different evidence configurations is studied.  相似文献   
40.
孙怡帆等 《统计研究》2019,36(3):124-128
从大量基因中识别出致病基因是大数据下的一个十分重要的高维统计问题。基因间网络结构的存在使得对于致病基因的识别已从单个基因识别扩展到基因模块识别。从基因网络中挖掘出基因模块就是所谓的社区发现(或节点聚类)问题。绝大多数社区发现方法仅利用网络结构信息,而忽略节点本身的信息。Newman和Clauset于2016年提出了一个将二者有机结合的基于统计推断的社区发现方法(简称为NC方法)。本文以NC方法为案例,介绍统计方法在实际基因网络中的应用和取得的成果,并从统计学角度提出了改进措施。通过对NC方法的分析可以看出对于以基因网络为代表的非结构化数据,统计思想和原理在数据分析中仍然处于核心地位。而相应的统计方法则需要针对数据的特点及关心的问题进行相应的调整和优化。  相似文献   
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