Advances in Complex Systems

To what extent does joint membership in intergovernmental organizations (IGOs) matter for bilateral trade? How and under what conditions do the various types of IGOs — economic, socio-cultural and general purpose — influence bilateral trade between their members? How do complex interdependencies in world trade matter? Existing research tends to examine aggregate joint IGO memberships and has done little to analyze how specific types of IGO membership matter in trade. Using a detailed IGO dataset and a novel network analysis approach called the temporal exponential random graph model, I assess the importance of three main IGO types — economic, socio-cultural and general purpose — in helping members to establish major trading ties. The results provide support for general purpose and socio-cultural IGOs and point to the importance of network phenomena such as popularity, activity and transitivity effects. Moreover, joint economic IGO memberships exhibit slightly more complex relations with bilateral trade. A robustness test reveals that preferential trade agreements are significant in fostering trade, while the World Trade Organization and other economic IGOs such as development banks are not. This paper presents a nuanced way of analyzing IGOs and provides the impetus for the study of complex interdependencies in international trade.

Statistical properties of software networks have been extensively studied. However, in the previous works, software networks are usually considered as a single-layer network, which cannot capture the authentic characteristics of software since software in its nature should be multilayer. In this paper, we explore the structural properties of the multilayer software network at the class level by progressively merging layers together, where each coupling type such as inheritance, implements, and method call defines a specific layer. A case study in software Tomcat is conducted using a set of 10 measures widely used in complex network literatures. The results show that some structural properties that are widely observed in software network researches can only emerge when several layers are merged together, such as high clustering coefficient, small value of average shortest path length, and high global efficiency. Our study highlights the importance of taking into consideration the multilayer nature of software systems. The results we found can provide valuable insights to our understanding and modeling of the dynamical processes taking place in the design and development of software systems.

In this paper, we explore the relationship between Minimum Feedbackability Set (MFS) and Feedbackability Set (FS) of complex networks and use simulated annealing algorithm to obtain a relatively fast and reliable estimation of the MFS. Then, we implement this method to estimate the MFS of some real-world networks and explore whether the topological features influence the size of MFS. Additionally, we propose an optimal perturbation strategy to enhance the feedbackability of complex networks. Finally, we also research the intricate relationship between the structural properties and the feedbackability of various networks perturbed by optimal and random perturbation strategies.

Since all the existing real world networks are evolving, the study of traffic dynamics is a challenging task. Avoidance of traffic congestion, system utility maximization and enhancement of network capacity are prominent issues. Network capacity may be improved either by optimizing network topology or enhancing in routing approach. In this context, we propose and design a model of the time-varying data communication networks (TVCN) based on the dynamics of inflowing links. Traffic congestion can be avoided by using a suitable centrality measure, especially betweenness and Eigen vector centralities. If the nodes coming in user’s route are most betweenness central, then that route will be highly congested. Eigen vector centrality is used to find the influence of a node on others. If a node is most influential, then it will be highly congested and considered as least reputed. For that reason, routes are chosen such that the sum of the centralities of the nodes coming in user’s route should be minimum. Furthermore, Kelly’s optimization formulation for a rate allocation problem is used for obtaining optimal rates of distinct users at different time instants and it is found that the user’s path with lowest betweenness centrality and highest reputation will always give maximum rate at the stable point.