Unveiling connectivity patterns of categories in complex systems: an application to human needs in urban places

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of mathematical sociology on 06/09/2016, available online: http://www.tandfonline.com/doi/full/10.1080/0022250X.2016.1219855We present a methodology based on weighted networks and dependence coefficients aimed at revealing connectivity patterns between categories. As a case study, it is applied to an urban place and at two spatial levels—neighborhood and square—where categories correspond to human needs. Our results show that diverse spatial levels present different and nontrivial patterns of need emergence. A numerical model indicates that these patterns depend on the probability distribution of weights. We suggest that this way of analyzing the connectivity of categories (human needs in our case study) in social and ecological systems can be used to define new strategies to cope with complex processes, such as those related to transition management and governance, urban-making, and integrated planning.Peer ReviewedPostprint (author's final draft

Network hierarchy evolution and system vulnerability in power grids

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The seldom addressed network hierarchy property and its relationship with vulnerability analysis for power transmission grids from a complex-systems point of view are given in this paper. We analyze and compare the evolution of network hierarchy for the dynamic vulnerability evaluation of four different power transmission grids of real cases. Several meaningful results suggest that the vulnerability of power grids can be assessed by means of a network hierarchy evolution analysis. First, the network hierarchy evolution may be used as a novel measurement to quantify the robustness of power grids. Second, an antipyramidal structure appears in the most robust network when quantifying cascading failures by the proposed hierarchy metric. Furthermore, the analysis results are also validated and proved by empirical reliability data. We show that our proposed hierarchy evolution analysis methodology could be used to assess the vulnerability of power grids or even other networks from a complex-systems point of view.Peer ReviewedPostprint (author's final draft

Computing and visualizing informative trajectories in temporaly annotated data

2n premi en la 3a edició dels Big Data Talent AwardsA trajectory in the medical world, is the sequence of events that occur during the life of a patient. In the recent years, these trajectories have been stored in the Electronical Health Records and many of the health organizations have databases with the clinical history of all their patients. The trajectories can be summarized in a trajectory graph which shows the different paths the trajectory of a patient may take. The graph contains events on its nodes and the edges contain the temporal relations. Previous works focused in the exploration of trajectory graphs only allow one event at each node, thus losing information and potentially mixing different groups of patients. In this work, we have developed a new procedure to extract the trajectory graphs that allows having several events in a single node of the graph. This procedure has been tested in two real world datasets: one related to diagnostics at hospital admissions, and the other on prescriptions in intensive care units.Award-winnin

Spatial and performance optimality in power distribution networks

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Complex network theory has been widely used in vulnerability analysis of power networks, especially for power transmission ones. With the development of the smart grid concept, power distribution networks are becoming increasingly relevant. In this paper, we model power distribution systems as spatial networks. Topological and spatial properties of 14 European power distribution networks are analyzed, together with the relationship between geographical constraints and performance optimization, taking into account economic and vulnerability issues. Supported by empirical reliability data, our results suggest that power distribution networks are influenced by spatial constraints which clearly affect their overall performance.Peer ReviewedPostprint (author's final draft

A simple spatiotemporal evolution model of a transmission power grid

In this paper, we present a model for the spatial and temporal evolution of a particularly large human-made network: the 400-kV French transmission power grid. This is based on 1) an attachment procedure that diminishes the connection probability between two nodes as the network grows and 2) a coupled cost function characterizing the available budget at every time step. Two differentiated and consecutive processes can be distinguished: a first global space-filling process and a secondary local meshing process that increases connectivity at a local level. Results show that even without power system engineering design constraints (i.e., population and energy demand), the evolution of a transmission network can be remarkably explained by means of a simple attachment procedure. Given a distribution of resources and a time span, the model can also be used to generate the probability distribution of cable lengths at every time step, thus facilitating network planning. Implications for network's fragility are suggested as a starting point for new design perspectives in this kind of infrastructures.Peer ReviewedPostprint (author's final draft

Transport energy consumption in mountainous roads. A comparative case study for internal combustion engines and electric vehicles in Andorra

This paper analyses transport energy consumption of conventional and electric vehicles in mountainous roads. A standard round trip in Andorra has been modelled in order to characterise vehicle dynamics in hilly regions. Two conventional diesel vehicles and their electric-equivalent models have been simulated and their performances have been compared. Six scenarios have been simulated to study the effects of factors such as orography, traffic congestion and driving style. The European fuel consumption and emissions test and Artemis urban driving cycles, representative of European driving cycles, have also been included in the comparative analysis. The results show that road grade has a major impact on fuel economy, although it affects consumption in different levels depending on the technology analysed. Electric vehicles are less affected by this factor as opposed to conventional vehicles, increasing the potential energy savings in a hypothetical electrification of the car fleet. However, electric vehicle range in mountainous terrains is lower compared to that estimated by manufacturers, a fact that could adversely affect a massive adoption of electric cars in the short term.Peer ReviewedPostprint (author’s final draft

Sustainability study for wheat straw torrefaction technology

The aim of this article is to examine the torrefaction production technology placed in two power plant environment (Rankine-Clausius, and Organic Rankine-Clausius circular procedures). The torrefaction is a heat treatment process at 280 – 300 °C obturated from oxygen, this heat treatment effectively changing the structure of the material, and the feedstock’s heating value improves. Our study is restricted is wheat pallet because we conducted the laboratory experiments with material. In Hungary the agricultural industry produces raw materials in big amounts (mainly combustibles that is energetically renewables) which are at the moment, mixed with nitrogen-based fertilizers and biodegradable anaerobe bacteria ploughed back into the tillage as a form of nutrient supply. It takes 9 months to become nutriment from this inorganic material. The object of our study is the key equipment of a production technology which continuously works, double-jacketed, and can be subjected to vacuuming. This equipment is a cylindrical furnace in which the torrefaction is realized.Peer ReviewedPostprint (published version

Post-handover housing defects: sources and origins

In Spain, the high levels of inexperienced workers and the long chains of subcontracting contribute to the poor quality of dwellings. Althoughthe Ley reguladora de la subcontratación en el Sector de la Construcción (subcontracting law) has established quality measures, the number of customer complaints is still increasing. In this paper, a total of 2,351 posthandover defects derived from four Spanish builders and seven residential developments are classi fi ed according to their source and origin. The research reveals that the most common defects identi fi ed by customers at posthandover were derived from bad workmanship and were related to construction errors and omissions. Typical defects were foundtoincludeincorrectinstallation,appearancedefects,andmissinganitemortaskmainlyrelatedto fi nishingandconsideredtobeminor.No defects were caused by poor design because they are mainly detected and resolved during construction or become apparent after some years of use. This study demonstrates the negative impact of redoing defective work during the fi nal stages of construction and provides knowledge to de fi ne measures to improve the quality of the fi nished buildings, such as understanding customer expectations and preferences, training programs for workers, specialization of subcontractors, and tightening external controls prior to handover.Postprint (author's final draft

Cities and quality of life. Quantitative modelling of the emergence of the happiness field in urban studies

Where we live affects all aspects of our life and thus our happiness. In recent years, and now for more than half of the population of the Earth, our place of residence or activity has been increasingly transformed into an urban one. However, while the impact of happiness studies has grown in importance during the last twenty years, we note that concepts like subjective well-being or happiness itself find it difficult to penetrate the planning and design of cities and truly affect the field of urban studies. In this paper we map the temporal evolution of the fields of happiness and urban studies into dynamic networks obtained by paper keywords co-word analysis. In order to reproduce the changes in its topology, a one-parameter spatial network model is presented. The results suggest an explanation for the level of penetration of these two fields in particular, but they also explain how different related academic or scientific fields evolve and pervade each other as a function of “conceptual distances” which in this case are mapped into Euclidean ones. The results and methodologies developed in the context of the happiness and urban studies keyword network could be useful for a systematic study of other complex evolving networks.Preprin