A simple model of homophily in social networks

Biases in meeting opportunities have been recently shown to play a key role for the emergence of homophily in social networks (see Currarini et al., 2009). The aim of this paper is to provide a simple microfoundation of these biases in a model where the size and type-composition of the meeting pools are shaped by agents׳ socialization decisions. In particular, agents either inbreed (direct search only to similar types) or outbreed (direct search to population at large). When outbreeding is costly, this is shown to induce stark equilibrium behavior of a threshold type: agents “inbreed” (i.e. mostly meet their own type) if, and only if, their group is above certain size. We show that this threshold equilibrium generates patterns of in-group and cross-group ties that are consistent with empirical evidence of homophily in two paradigmatic instances: high school friendships and interethnic marriages.     

利用Cisco Packet Tracer6.0模拟软件实现交换机VLAN的配置

本文简要介绍了职业院校对非计算机相关专业学生对《计算机网络及应用》实训课程的要求,以交换机VLAN的配置为例,介绍了VLAN的概念和交换机,同时阐述了操作平台Cisco Packet Tracer6.0。     

Opinion dynamics and wisdom under conformity

We study a dynamic model of opinion formation in social networks. In our model, boundedly rational agents update opinions by averaging over their neighbors’ expressed opinions, but may misrepresent their own opinion by conforming or counter-conforming with their neighbors. We show that an agent׳s social influence on the long-run group opinion is increasing in network centrality and decreasing in conformity. Concerning efficiency of information aggregation or “wisdom” of the society, it turns out that misrepresentation of opinions need not undermine wisdom, but may even enhance it. Given the network, we provide the optimal distribution of conformity levels in the society and show which agents should be more conforming in order to increase wisdom.     

Exploring the relationship between multilevel highway networks and local development patterns—a case study of Taiwan

The relationship between local development patterns and highway networks is complicated, as suggested by studies using various analytical methods. The spatial effects of each hierarchical highway network on local development patterns remains unclear. This study combines space syntax and the hierarchical linear model (HLM) within the research framework in a case study of Taiwan. The former is employed to model the topological accessibility of multilevel highway networks, and the latter is applied to handle the hierarchical relationship between multilevel highway networks and local development patterns. Results indicate a high R-squared (R² = 0.803) value, and statistically significant cross-level interactions are observed. The results show the different spatial effects of various highway networks on the scale of local development patterns, and confirm consideration of highway networks with classification in the research design. The implications of the findings may be appropriate for substantive planning and future research approaches.     

The fortunes of air transport gateways

The paper explores the idea that the fortunes of some gateway cities are changing as airlines use modern aircraft to respond to new market opportunities. It uses data on inter-city journeys between Australia and Asia to identify a hierarchy of gateway cities, and then shows how the connections between them has changed over the 2000–2013 period. Results show that secondary, and smaller, gateways in both Australia and Asia have played more important roles in passenger movements over this time. In Melbourne in particular, stronger growth in the demand for international travel in that city along with more use made of the smaller long-haul aircraft by airlines, has strengthened its role as a gateway city relative to Sydney. These results confirm that the geography of inter-continental air networks are changing which may have important implications for the air transport roles of some cities in the immediate future.     

Managing security risks for inter-organisational information systems: a multiagent collaborative model

Information sharing across organisations is critical to effectively managing the security risks of inter-organisational information systems. Nevertheless, few previous studies on information systems security have focused on inter-organisational information sharing, and none have studied the sharing of inferred beliefs versus factual observations. In this article, a multiagent collaborative model (MACM) is proposed as a practical solution to assess the risk level of each allied organisation’s information system and support proactive security treatment by sharing beliefs on event probabilities as well as factual observations. In MACM, for each allied organisation’s information system, we design four types of agents: inspection agent, analysis agent, control agent, and communication agent. By sharing soft findings (beliefs) in addition to hard findings (factual observations) among the organisations, each organisation’s analysis agent is capable of dynamically predicting its security risk level using a Bayesian network. A real-world implementation illustrates how our model can be used to manage security risks in distributed information systems and that sharing soft findings leads to lower expected loss from security risks.     

Efficiency Determinants and Capacity Issues in Angolan Insurance Companies

This paper describes a variety of approaches used to assess the efficiency of a sample of major insurance companies in Angola between 2003 and 2012. Starting out with the bootstrapping technique, several data envelopment analysis (DEA) estimates were generated, allowing the use of confidence intervals and bias correction in central estimates to test for significant differences in efficiency levels and input‐decreasing/output‐increasing potentials. Previous studies have focused on the measurement and explanation of the factors affecting the performance rather than the prediction. The use of neural networks combined with DEA results as part of an attempt to produce a model for insurance companies’ performance with effective predictive ability is investigated. The findings indicate that older insurance companies with Portuguese origin tend to be more efficient. Results also suggest that opportunities for accommodating future demand appear to be scarce.     

Job Search and the Measurement of Unemployment in South Africa

We interrogate the distinction between searching and non‐searching unemployment in South Africa using data from the first national panel survey that tracks the individual. In particular, we test whether the non‐searching unemployed display a weaker commitment to the labour market than the searching unemployed, and we investigate what counts as search activity. We find that over the panel, the search status of the unemployed does not predict their subsequent employment status, a result that is robust also for subsamples that vary by age cohort, gender and location. Moreover, social networks are the most important job‐finding strategy of the employed. These findings challenge the exclusion of the non‐searching unemployed from the measure of “genuine” work seekers.     

A theory of supplier network-based innovation value

To understand how a supplier helps a buying company create value through innovations, studies have focused on a supplier's internal resources or its relationship with a buying company. Building upon this body of literature, we develop a theory of supplier network-based innovation value in this conceptual paper. This theory explains how a supplier's upstream and downstream value network can be a source of competitive advantage for a buying company. Specifically, it proposes that the levels and types of supplier innovation value is contingent on the configuration of a dual-ego value network, characterized by the locus and degree of buyer-supplier structural equivalence. This theory also explains how a supplier's ties with a buying firm's competitors can pose both opportunity and risk to buying company innovation. This theory contributes to the literature by showing when “seemingly undesirable” suppliers, due to a lack of technical capability or strong relationship with a buying company, might still be valuable to a buying company's innovation.     

Analyzing the impact of intermodal-related risk to the design and management of biofuel supply chain

This study presents a mathematical model that designs a reliable multi-modal transportation network for a biofuel supply chain system, where intermodal hubs are subject to site-dependent probabilistic disruptions. The disruption probabilities of intermodal hubs are estimated by using a probabilistic model which is developed using real world data. We developed an accelerated Benders decomposition algorithm to solve this challenging NP-hard problem. Numerical analysis show that the model selects to use intermodal hubs located in areas with low disruption probabilities. In case of a disaster, the reliable solution results in 6.21% savings over the minimum cost solution.