Ethnic segregation of friendship networks in school: Testing a rational-choice argument of differences in ethnic homophily between classroom- and grade-level networks

Adolescents’ school-based friendship networks tend to be segregated along ethnic lines. But few studies have examined whether variation in network boundaries affects the degree of ethnic friendship segregation. We use rational-choice theory to argue that ethnic homophily is more pronounced for friendships between classrooms than for those within classrooms. We empirically test this hypothesis using two-wave German panel data (N = 1258) and stochastic actor-oriented models (RSiena). In line with our theoretical argument, we find that the tendency to form same-ethnic friendships is indeed stronger at the grade level, which translates into stronger ethnic segregation in friendship networks at the grade level than at the classroom level. Implications for research on ethnic segregation in school-based friendship networks are discussed.     

How social exclusion distorts social network perceptions

In two studies we investigate whether social exclusion—a well-studied, common and quite painful social experience-influences people's perceptions of novel social networks. In a first study, exclusion experiences led people to report that novel networks were more dense relative to those who had not been excluded. As predicted, this was true only for social networks; exclusion had no impact on perceptions when networks were described as geographical. In a follow-up experiment, participants watched a custom-created video, depicting avatars interacting in social scenes and they were asked to report the ties among the avatars in the video. Exclusion experiences led people to see network ties where none exist (i.e., false positives), though there was no effect for exclusion (versus inclusion) on reports of false negatives. Results indicate that common social experiences systematically shape network perceptions, leading people to seeing novel social networks as more densely connected than they are.     

中国商贸物流企业海外物流节点选择策略研究

基于国家节点的拓扑结构和经济属性,构建"一带一路"沿线国家的拓扑重要性与经济重要性评价指标体系,运用熵权-TOPSIS法对国家节点的重要性进行综合评估。研究表明:俄罗斯、印度、马来西亚、新加坡、阿联酋等国的拓扑重要性与经济重要性排名均靠前,地理位置与战略地位十分重要,投资与建设环境稳定,是我国商贸物流企业"走出去"优先选择的投资建设重点;哈萨克斯坦、蒙古、塞尔维亚、老挝等国,拓扑重要性排名靠后,其物流市场和基础设施建设空间很大,是潜在的投资建设区域;伊拉克、阿富汗、巴勒斯坦等国拓扑重要性与经济重要性排名均靠后,地缘政治复杂,投资与营商环境不稳定,有着较高的投资建设风险。     

国际生产网络视角下的增加值贸易结构分析与主导因素识别——以中美双边贸易为例

本文利用世界投入产出表测度了2001—2014年中美双边增加值贸易结构。结果表明,中国在双边贸易中的单位出口获利能力低于美国,国际分工地位的差异使得两国的贸易结构显示出较强的互补性。在对增加值贸易构成分解的基础上,本文识别并分析了国际生产网络体系下影响出口国内增加值的主导因素及其作用机制。研究发现,网络外最终需求、生产网络上游因素分别是推动中国和美国出口国内增加值扩大的主导因素。此外,产业层面的研究结果显示,中国高技术制造业出口国内增加值的扩大主要是由生产网络上游因素驱动的,生产网络外最终需求则是中国传统制造业出口国内增加值扩张的重要推动力。中国在扩大对外开放的同时应与国际生产网络中的上下游经济体形成多元化匹配,进而加快形成以国内大循环为主体、国内国际双循环相互促进的新发展格局。     

城市网络位置与疫情风险

作为重大突发公共卫生事件,传染病疫情风险是一个值得关注的前沿新论题。本文从一个较新的网络拓扑视角,以新冠肺炎疫情为例,构建了一个由病毒感染人群流动形成的城市间疫情关联网络,并探讨了城市在疫情关联网络中的位置对其疫情风险的影响。研究发现,城市之间的传染病疫情呈现出紧密的网络关联性;疫情的风险程度与城市在疫情关联网络中的位置密切相关,处在网络重要位置的城市与其他城市关联度较高,从而面临更大的疫情风险,这一点在针对城市群和交通枢纽聚集性感染风险研究中尤为突出。拓展分析表明,城市网络中心度具有疫情扩散风险放大效应,关闭离汉通道措施有助于降低城市在疫情关联网络中的核心位置对本城市疫情风险的影响。     

Hierarchical production planning for multi-product lines in the beverage industry¶

Multi-commodity production and distribution scheduling is one of the most complex and crucial problems facing many manufacturing companies. For a major European manufacturer specialising in bottling juices and drinks, we have designed and developed a hierarchical decomposition approach to the solution of the multi-commodity production planning problem. In this paper we focus our attention on the coarsest decomposition level, called multi-commodity aggregate production planning (MCAP). It concerns the choice of the best feasible production plan for a set of products (commodities) over an extended time horizon so as to meet forecast aggregate demands throughout the horizon. At this level, the problem constraints include hard constraints (such as production lines having a maximum capacity and products having short life-times), and soft constraints (budgetary concerns.) The objective is to determine the production plan that covers each period's demands as best as possible, while minimizing all relevant costs. Our method for solving MCAP produces optimal plans in negligible times in commodity PC workstations.     

Risk management and managerial efficiency in Chinese banks: A network DEA framework

Risk management in Chinese banks has traditionally been the Cinderella of its internal functions. Political stricture and developmental imperative have often overridden standard practice of risk management resulting in large non-performing loan (NPL) ratios. The training and practice of risk managers remain second class compared with foreign banks operating in China. This paper surveys Chinese bank risk managers and constructs metrics of risk management practice and risk management organisation. The metrics are used as intermediate inputs in a Network DEA framework to produce a measure of income efficiency. A statistical test is carried out to assess the importance of the risk metrics in evaluating bank income efficiency.     

经济网络化下的企业组织结构创新

网络经济时代,企业的交易成本大为降低,交易费用作为企业替代市场的前提被削弱,从而降低了对企业内部纵向一体化的要求。网络型企业组织既利用了市场的价格机制,又利用了企业的行政管理协调机制,具有无论是单个企业还是整个市场都不具备的效率优势,既能保证分工与专业化的效率机制,还可以获得一种成本最低的制度安排。创新企业组织结构,培育网络型企业组织是经济网络化快速发展的内在要求。     

非计算机专业"计算机网络"教学改革实践

文章讨论了非计算机专业“计算机网络”教学的一些教学改革措施。提出了从教育观念与教学顺序上的逆向法应用、多种教学手段与方法的协调、最终质量评价依据的多样性方面进行教学改革的探索。从而有利于把人才培养模式从注重知识传授转向知识传授与素质培养并重。     

基于ASP技术的网上考试系统的设计

文章介绍了一个基于ASP技术的网上考试系统的设计方案,对系统的功能作了说明,并给出部分关键技术的具体实现方法。