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

Assessment of unintentional islanding operations in distribution networks with large induction motors

This paper is aimed at assessing the impact of unintentional islanding operations (IOs) in the presence of large induction motors (IMs) within distribution networks (DNs). When a fault occurs,followingthecircuitbreaker(CB)faultclearing,theIMsacttransientlyasgenerators,duetoits inertia, until the CB reclosing takes place. The present work is the outcome of a project carried out in a small DN, where ¿eld measurements were recorded over two years. This paper provides a detailed description of the test system, a selected list of ¿eld measurements, and a discussion on modeling guidelinesusedtocreatethemodeloftheactualpowersystem. Themaingoalistovalidatethesystem model by comparing ¿eld measurements with simulation results. The comparison of simulations and ¿eld measurements prove the appropriateness of the modeling guidelines used in this work and highlight the high accuracy achieved in the implemented three-phase Matlab/Simulink modelPostprint (published version

Bistable phase control via rocking in a nonlinear electronic oscillator

We experimentally demonstrate the effective rocking of a nonlinear electronic circuit operating in a periodic regime. Namely, we show that driving a Chua circuit with a periodic signal, whose phase alternates (also periodically) in time, we lock the oscillation frequency of the circuit to that of the driving signal, and its phase to one of two possible values shifted by pi, and lying between the alternating phases of the input signal. In this way, we show that a rocked nonlinear oscillator displays phase bistability. We interpret the experimental results via a theoretical analysis of rocking on a simple oscillator model, based on a normal form description (complex Landau equation) of the rocked Hopf bifurcationComment: 7 pages, 10 figure

Regularization of static self-forces

Various regularization methods have been used to compute the self-force acting on a static particle in a static, curved spacetime. Many of these are based on Hadamard's two-point function in three dimensions. On the other hand, the regularization method that enjoys the best justification is that of Detweiler and Whiting, which is based on a four-dimensional Green's function. We establish the connection between these methods and find that they are all equivalent, in the sense that they all lead to the same static self-force. For general static spacetimes, we compute local expansions of the Green's functions on which the various regularization methods are based. We find that these agree up to a certain high order, and conjecture that they might be equal to all orders. We show that this equivalence is exact in the case of ultrastatic spacetimes. Finally, our computations are exploited to provide regularization parameters for a static particle in a general static and spherically-symmetric spacetime.Comment: 23 pages, no figure

Robustness of the European power grids under intentional attack

The power grid defines one of the most important technological networks of our times and sustains our complex society. It has evolved for more than a century into an extremely huge and seemingly robust and well understood system. But it becomes extremely fragile as well, when unexpected, usually minimal, failures turn into unknown dynamical behaviours leading, for example, to sudden and massive blackouts. Here we explore the fragility of the European power grid under the effect of selective node removal. A mean field analysis of fragility against attacks is presented together with the observed patterns. Deviations from the theoretical conditions for network percolation (and fragmentation) under attacks are analysed and correlated with non topological reliability measures.Comment: 7 pages, 4 figure

L-Citrulline and its effect in endurance sports, a sistematic review

En los últimos años, el estudio del suplemento L-Citrulina ha cobrado importancia debido a sus posibles efectos sobre el rendimiento deportivo. La L-Citrulina es un aminoácido no esencial que se obtiene a través de fuentes tanto vegetales como animales. Es precursor del Óxido Nítrico y de la Arginina, que intervienen de forma protagonista durante el ciclo de la urea. Estos factores presuponen que el consumo de este suplemento podrá tener ciertos beneficios sobre el rendimiento deportivo. Por lo tanto, el objetivo de este estudio fue el de realizar una revisión sistemática con la que comprobar la eficacia de la L-Citrulina o el Malato de L-Citrulina sobre varios parámetros determinantes en el rendimiento deportivo: potencia, resistencia, trabajo, así como en las siguientes otras variables: percepción subjetiva del esfuerzo y factores fisiológicos. El estudió estuvo centrado en deportes de resistencia en concreto. Para ello, se realizó una búsqueda de la literatura existente hasta la fecha de aquellos estudios que analizaban el rendimiento deportivo en deportes de resistencia tras el consumo de L-Citrulina. Se obtuvieron un total de 7 trabajos con los que se realizó esta revisión sistemática. Tras el análisis de los trabajos encontrados, se podría decir que la L-Citrulina o Malato de L-Citrulina tiene un efecto positivo sobre el rendimiento deportivo. Sin embargo, se debería de establecer un consenso en la estandarización de los test realizados en los estudios para poder afirmar con evidencia significativa que este suplemento tiene una afectación clara sobre el rendimiento de los deportistas.In the last years, the study of L-Citrulline as a supplement has been gaining interest due to its possible applications over the performance in sports. L-Citrulline is a non-essential aminoacid which can be obtained from vegetable or animal sources. This supplement is a precursor of Nitric Oxide, Arginine and has a principal role in the urea cycle. These factors presuppose that the consume of this ergogenic aid could have positive effects over the sport performance. The purpose of this study was to make a systematic review with which verify the efficacy of L-Citrulline or Citrulline Malate over various determinants parameters over the sport performance and other variables such as perception of effort and physiological factors in endurance sports. To achieve this objective, a research of the existent studies referred to the analysis of the sport performance after the consumption L-Citrulline was made. Finally, 7 studies were obtained and used to make this systematic review. After the analysis of the collected data it can be said that L-Citrulline or Citrulline Malate might have a positive impact over the sport performance. Nevertheless, a consensus must be made in order to achieve the standardization of the protocols and test used in the different studies to say that this supplement has a significant positive impact over the athletes performance

Pseudognaphalium aldunateoides de nuevo bajo Gnaphalium (Compositae: Gnaphalieae)

Generic classification of some members of the tribe Gnaphalieae (Compositae) and in particular the generic delimitation of the old genus Gnaphalium has been long problematic. The genus Pseudognaphalium was first split from Gnaphalium based on morphology and later supported by molecular phylogenies. However, the generic identity of some species remains doubtful. Here we provide a morphological study of Pseudognaphalium aldunateoides, which is compared with the type species of Gnaphalium (Gnaphalium uliginosum) and Pseudognaphalium (Gnaphalium oxyphyllum). We also include the three species in a nuclear ribosomal DNA (nrDNA) and a plastid (cpDNA) molecular phylogeny of the tribe Gnaphalieae. Our results show that P. aldunateoides has a dimorphic pappus, character not present in the genus Pseudognaphalium but characteristic of the genus Gnaphalium. It also shows a stereome with intermediate features between the undivided stereome typical of Gnaphalium and the fenestrated stereome typical of Pseudognaphalium. In the nrDNA and the cpDNA trees, P. aldunateoides is placed within the Gnaphalium s. str. clade, not closely related to Pseudognaphalium. With all these evidence, we conclude that P. aldunateoides is correctly placed in Gnaphalium.La clasificación genérica de varios miembros de la tribu Gnaphalieae (Compositae) y en particular la delimitación genérica del antiguo género Gnaphalium ha sido problemática durante mucho tiempo. El género Pseudognaphalium fue escindido de Gnaphalium por su morfología lo que después fue apoyado por filogenias moleculares. Sin embargo, la identidad genérica de algunas especies todavía es dudosa. Aquí aportamos un estudio morfológico de Pseudognaphalium aldunateoides, que es comparado con las especies tipo de los géneros Gnaphalium (Gnaphalium uliginosum) y Pseudognaphalium (Gnaphalium oxyphyllum). También hemos incluido estas tres especies en filogenias moleculares de la tribu Gnaphalieae basadas en ADN ribosómico nuclear y ADN cloroplástico. Nuestros resultados muestran que P. aldunateoides tiene el vilano dimórfico, carácter que no está presente en el género Pseudognaphalium pero que, sin embargo, es característico del género Gnaphalium. Además, su estereoma muestra características intermedias entre el estereoma no dividido típico del género Gnaphalium y el estereoma fenestrado típico del género Pseudognaphalium. En ambas filogenias, P. aldunateoides se sitúa dentro del clado Gnaphalium s. str., no próximamente emparentado con Pseudognaphalium. Con todas estas evidencias concluimos que P. aldunateoides se clasifica correctamente dentro de Gnaphalium

Generalization of the equivalence between physical optics and aperture integration for radiation from open-ended structures

The theorem of equivalence between the Kirchhoff aperture integration (AI) and the physical optics (PO) approach applied to the interior walls of a open-ended waveguide is generalized to the case of any open-ended structure (OES).Peer Reviewe

Missing energy in black hole production and decay at the Large Hadron Collider

Black holes could be produced at the Large Hadron Collider in TeV-scale gravity scenarios. We discuss missing energy mechanisms in black hole production and decay in large extra-dimensional models. In particular, we examine how graviton emission into the bulk could give the black hole enough recoil to leave the brane. Such a perturbation would cause an abrupt termination in Hawking emission and result in large missing-energy signatures.Comment: addressed reviewer comments and updated reference