Robustness and Closeness Centrality for Self-Organized and Planned Cities

Street networks are important infrastructural transportation systems that cover a great part of the planet. It is now widely accepted that transportation properties of street networks are better understood in the interplay between the street network itself and the so called \textit{information} or \textit{dual network}, which embeds the topology of the street network navigation system. In this work, we present a novel robustness analysis, based on the interaction between the primal and the dual transportation layer for two large metropolis, London and Chicago, thus considering the structural differences to intentional attacks for \textit{self-organized} and planned cities. We elaborate the results through an accurate closeness centrality analysis in the Euclidean space and in the relationship between primal and dual space. Interestingly enough, we find that even if the considered planar graphs display very distinct properties, the information space induce them to converge toward systems which are similar in terms of transportation properties

A formal approach to the specification of hierarchical multi-agent systems

Este trabajo presenta una aproximación formal para crear especificaciones de sistemas de agentes jerarquizados. El funcionamiento permite una automatización de las tareas, a las que el usuario del sistema accederá a través de peticiones. De manera general, lo que se hace es definir los elementos básicos del sistema, los agentes atómicos que son los que están a cargo de realizar las transformaciones de los recursos,y el sistema recompondrá estos últimos para crear agentes complejos, que actúan como intermediarios entre los agentes atómicos y el usuario. Los agentes se localizan en una estructura conforme el sistema. [ABSTRACT] This Master´s Thesis provides a formal approach to create specifications of hierarchical systems of agents. The inner working of the system allows for an automatization of the tasks, that will be accessed by the user through the use of petitions. We will first define the actual transformations of resources, and the system will recompose the latter to create complez agents, that will act as mediators in between the hierarchical stratificacion. The cells conform a tree structure, and this structure conforms the system

Microfinance institutions and efficiency

Microfinance Institutions (MFIs) are special financial institutions. They have both a social nature and a for-profit nature. Their performance has been traditionally measured by means of financial ratios. The paper uses a Data Envelopment Analysis (DEA) approach to efficiency to show that ratio analysis does not capture DEA efficiency.Special care is taken in the specification of the DEA model. We take a methodological approach based on multivariate analysis. We rank DEA efficiencies under different models and specifications; e.g., particular sets of inputs and outputs. This serves to explore what is behind a DEA score. The results show that we can explain MFIs efficiency by means of four principal components of efficiency, and this way we are able to understand differences between DEA scores. It is shown that there are country effects on efficiency; and effects that depend on Non-governmental Organization (NGO)/non-NGO status of the MFI

Seasonal changes in the population dynamics of Aurelia aurita in Thau lagoon

Seasonal dynamics of the scyphomedusae, Aurelia aurita, was investigated twice a month from January 2010 to June 2011 and related to environmental conditions in Thau lagoon, southwestern Mediterranean Sea. Strobilation, indicated by the presence of 1 mm ephyrae, occurred from November to the middle of April. Maximum abundances up to 330 ind.100 m-3 were reached in May 2011, few weeks after the last ephyrae release. The population declines afterwards steadily until disappearing from the water column. Concurrent with increased water temperature and mesozooplankton predation during May, growth rates increased from 0.04 mm.day-1 to a peak of 4.5 mm.day-1, with a maximum bell diameter of 11.3 cm reached on the 7th May. During the study period, there was no advection of A. aurita between Thau lagoon and the coastal waters

Modelling the multi-scalar effect of commuting on exposure to diversity

Urban systems are primarily relational. The uneven intensities and distribution of flows between systems of cities results in hierarchically organised complex networks of urban exchange. Distinct urban spatial structures reflect the diversity of functional and social patterns which vary or remain constant across multiple scales. In this work, we examine the impact of commuting on the potential accessibility to spatial and social diversity, and the scalar relations that may exist. We first define relational scales by conducting a process of percolation on the commuting network, as a hierarchical clustering algorithm. This gives rise to a nested structure of urban clusters based on flow connectivity. For each cluster at each scale, we compute measures of commuting structural and social diversity by examining the spatial distribution of origin-destination pairs, and the distribution of workers' skills and occupations. To do this, we make use of global entropy measures allowing us to quantitatively analyse the reachable diversity across scales. Applying this methodology to Chile, we observe that the hierarchical accessibility to the wider system of cities and the patterns of spatial interaction, significantly influence the degree of exposure to diversity within urban systems. This framework examines connectivity-based diversity at multiple scales, and allows for the classification of cities and systems of cities according to the spatial and social dimensions of commuting dispersion. Such insights could contribute to the planning of infrastructural projects connecting the urban system at different scales, while also guiding a strategic relocation and redistribution of economic activities at regional levels