Multiple partitioning of multiplex signed networks: Application to European parliament votes

For more than a decade, graphs have been used to model the voting behavior taking place in parliaments. However, the methods described in the literature suffer from several limitations. The two main ones are that 1) they rely on some temporal integration of the raw data, which causes some information loss; and/or 2) they identify groups of antagonistic voters, but not the context associated with their occurrence. In this article, we propose a novel method taking advantage of multiplex signed graphs to solve both these issues. It consists in first partitioning separately each layer, before grouping these partitions by similarity. We show the interest of our approach by applying it to a European Parliament dataset.     

Spectral goodness of fit for network models

We introduce a new statistic, ‘spectral goodness of fit’ (SGOF) to measure how well a network model explains the structure of the pattern of ties in an observed network. SGOF provides a measure of fit analogous to the standard R² in linear regression. Additionally, as it takes advantage of the properties of the spectrum of the graph Laplacian, it is suitable for comparing network models of diverse functional forms, including both fitted statistical models and algorithmic generative models of networks. After introducing, defining, and providing guidance for interpreting SGOF, we illustrate the properties of the statistic with a number of examples and comparisons to existing techniques. We show that such a spectral approach to assessing model fit fills gaps left by earlier methods and can be widely applied.     

基于知识图谱分析的国内外智慧教育研究热点

以“智慧教育”和“smart education”为关键词，时间跨度设为2009-2018，分别在中国知网和Web of Science数据库中进行检索，经过筛选后，将所得文献作为研究对象。利用CiteSpaceⅤ软件制作出国内外智慧教育研究高频关键词共现图表，并由此展开分析，总结出国内外智慧教育的研究热点。通过比较分析，获得以下启示：理论与实践并进，共建智慧教育生态系统；立体化与多样化并行，发展混合式动态教学模式；智能技术与深度学习并举，优化智慧教育学习场域；技术与育人并重，重视学习主体情感体验。     

Does biomass energy consumption reduce total energy CO2 emissions in the US?

This study investigates the causal relationship between total biomass energy consumption, total energy CO₂ emissions, and GDP in the United States for the period January 1973–December 2016 by employing a directed acyclic graph (DAG) techniques and the Autoregressive Distributed Lag (ARDL) model. Additionally, this paper examines the existence of the environmental Kuznets curve (EKC) hypothesis. The result of the DAG reveals that total biomass energy consumption and GDP have a unidirectional contemporaneous causal relationship with total energy CO₂ emissions. Based on the results of the ARDL, we find that a 1% increase in per capita total biomass energy consumption causes a 0.65% reduction in per capita total energy CO₂ emissions in the long-run. This finding implies that expanding the usage of biomass is one way to reduce and control greenhouse gases in the US. Moreover, we find that the inverted U-shaped EKC hypothesis is satisfied for the US case. Findings from this study suggest that energy policies should stimulate an increase of biomass production for reducing total energy CO₂.     

Facility Location with Dynamic Distance Functions

Facility location problems have always been studied with theassumption that the edge lengths in the network are static anddo not change over time. The underlying network could be used to model a city street networkfor emergency facility location/hospitals, or an electronic network for locating information centers. In any case, it is clear that due to trafficcongestion the traversal time on links changes with time. Very often, we have estimates as to how the edge lengths change over time, and our objective is to choose a set of locations (vertices) ascenters, such that at every time instant each vertex has a center close to it (clearly, the center close to a vertex may change over time). We also provide approximation algorithms as well as hardness results forthe K-center problem under this model. This is the first comprehensive study regarding approximation algorithmsfor facility location for good time-invariant solutions.     

Likelihood Factorizations for Mixed Discrete and Continuous Variables

Some general remarks are made about likelihood factorizations, distinguishing parameter-based factorizations and concentration-graph factorizations. Two parametric families of distributions for mixed discrete and continuous variables are discussed. Conditions on graphs are given for the circumstances under which their joint analysis can be split into separate analyses, each involving a reduced set of component variables and parameters. The result shows marked differences between the two families although both involve the same necessary condition on prime graphs. This condition is both necessary and sufficient for simplified estimation in Gaussian and for discrete log linear models.     

我国工业污染物的影子价格估计

 污染物的影子价格体现了污染物的边际减排成本。本文采用二次型方向性距离函数和 2003-2008年我国284个地级及以上城市工业部门数据,对废水、SO2和烟尘等三种污染物的影子价格进行了估计。结果发现,2003-2008年期间,废水、SO2、烟尘的影子价格或边际减排成本分别为0.0178万元/吨、5.158万元/吨和4.597万元/吨。SO2排污权交易价格相比污染减排成本偏低,影响了排污权交易市场的有效运作。污染物的影子价格在不同城市具有较大差异,这种差异性能够在一定程度上被污染排放规模、监管强度和污染治理的规模经济性等因素所解释。     

中国省际GDP强影响性特征及其形成机制研究

本文采用最新前沿的宏观经济数据诊断和空间面板模型理论和方法,对我国30个省（西藏除外）1999-2011年的省际GDP强影响性特征进行了实证分析,在此基础上,进一步进行B-N分解深入研究了其形成机制。主要结论表明：我国省际GDP不仅空间关联,而且存在着显著的强影响性特征,每一年样本信息对于样本期内全部信息的影响程度和大小存在着差异。同时,我国省际GDP强影响性特征具有极其显著的形成机制,随机性成分是造成强影响性的主要根源,周期成分也产生较为重要的影响。以上结论对于我国省际GDP强影响性特征判断具有十分重要的政策含义,进一步对于我国政府熨平经济波动、实现宏观经济的平稳较快增长的政策制订和完善等具有十分重要的现实借鉴意义。     

Offshoring and Cross‐Border Interorganizational Relationships: A Justice Model*

In this article, we develop an interorganizational justice model to explain cross‐border interorganizational relationships. The model contends that cultural distance (construed as the cultural differences between offshoring partners) would influence behavioral uncertainty and the boundary spanners' perceptions of justice. Specifically, the model predicts that high levels of behavioral uncertainty are likely to reduce relational commitment, whereas low levels of behavioral uncertainty are likely to enhance relational commitment. However, boundary spanners' perceptions of distributive, procedural, and interactional justice would mitigate the negative impact of behavioral uncertainty on relational commitment. The model also predicts that culturally similar boundary spanners would be more likely to share similar perceptions of distributive, procedural, and interactional justice than culturally dissimilar boundary spanners. This model has implications for further theoretical discussion and empirical research as well as management practice. Managers could use the interorganizational justice model to assess shared perceptions of justice among boundary spanners and develop transcultural justice competencies.     

基于新型图论聚类法的物流系统多设施选址策略研究

提出了一类基于图论的新型聚类算法并将其应用于物流系统中的多设施选址问题。与其他聚类算法相比,该新型算法聚类效率更高且具有更小的聚类树,从而使得有意义的聚类结果更加清晰。比较算例验证了该算法应用于多设施选址问题的高效性和实用性。