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

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

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

Of collapses and continuities. A conceptual review on the study of societies in transition

El proceso de estudio de los fenómenos de orden social o natural requiere de categorías analíticas específicas como herramientas destinadas a describir la realidad. Una de las categorías comúnmente utilizadas en la bibliografía es la de colapso. Este artículo persigue dos objetivos fundamentales que convergen en la intención de matizar la definición de este término: (1) se realiza una revisión de su uso a través de la bibliografía que trata casos concretos de sociedades pasadas cuyo destino ha sido directamente relacionado con este fenómeno y (2) se presenta el caso de estudio del colapso de la sociedad argárica, sita en el sudeste peninsular. Finalmente se realiza un ejercicio de correspondencia entre los aspectos destacados en el caso de estudio y los rasgos postulados en la bibliografía acerca del concepto de colapso.El procés de l'estudi dels fenòmens de l'ordre social o natural requereix de categories analítiques especifiques, com eines destinades a descriure la realitat. Una de les categories comunament utilitzades en la bibliografia és el del col·lapse. Aquest article, persegueix dos objectius: (1) es realitza una revisió del seu ús a través de la bibliografia que tracta casos concrets de societats passades en el que el seu destí ha estat directament relacionat amb aquest fenomen i (2) es presenta el cas d'estudi del col·lapse de la societat argàrica, situat en el sud-est peninsular. Finalment, es realitza un exercici de correspondència entre els aspectes destacats en el cas d'estudi i el trets postulats en la bibliografia sobre el concepte de col·lapse.The process of studying social or natural phenomena requires specific analytical categories that serve as tools to describe reality. One of the commonly used categories among the literature is collapse. This article has two main objectives that converge on the intention to refine the definition of the term: (1) a review of its use through the literature dealing with specific instances of past societies whose fate has been directly related to this phenomenon and (2), presents the case study of the collapse of the argaric society, located in southeastern Spain. We carried out an exercise of correspondence between the aspects highlighted in the case study and the features postulated in the literature about the concept of collapse.Peer Reviewe

Factors affecting rework costs in construction

Rework adversely impacts the performance of building projects. In this study, data were analyzed from 788 construction incidents in 40 Spanish building projects to determine the influence of project and managerial characteristics on rework costs. Finally, regression analysis was used to understand the relationship between the contributing factors, and to determine a model for rework prediction.Interestingly, the rework prediction model showed that only the original contract value (OCV) and the project location in relation to the company’s headquarters contribute to the regression model. The Project type, the Type of organization, the Type of contract and the original contract duration (OCD) which represents the magnitude and complexity of a project, were represented by the OCV. This model for rework prediction based on original project conditions enables strategies to be put in place prior to the start of construction, to minimize uncertainties and reduce the impact on project cost and schedule, and thus improve productivity.Peer ReviewedPostprint (author's final draft

Cities and quality of life. Quantitative modeling 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 happiness-related concepts find it difficult to penetrate the planning and design of cities, and 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-occurrence analysis. We identify the main concepts of the “urban happiness” field and their capacity to agglomerate into coherent thematic clusters. We find that while quality of life and well-being are highly interconnected with some well-defined urban categories, other happiness-related concepts, as subjective well-being or happiness itself, are located in peripheral positions where their influence is minimised. We present a one-parameter spatial network model in order to reproduce the changes in the topology of these networks. Results explain the evolution and the level of interpenetration of these two fields as a function of “conceptual” distances, mapped into Euclidean ones. In addition to other approaches (i.e., co-frequency matrix of bibliometric analysis), complex networks science appears as a valid alternative and opens the way for the systematic study of other academic fields in terms of complex evolving networks.Peer ReviewedPostprint (author's final draft