Modeling dispersion of partial discharges due to propagation velocity variation in power cables

Existing models for partial discharge (PD) propagation based on a single attenuation constant are unable to explain how each frequency component travels with a different propagation velocity. This paper proposes a new model based on a complex propagation term whose real component does not depend on the frequency ($f$), and whose imaginary part is modeled with a second order polynomial in $f$. The proposed model explains how the PD is attenuated, delayed, and dispersed due to the fact that each frequency component is differently delayed. A closed-form expression is proposed for the PD peak value and width, and a method to derive the model parameters from a reference model existing in the bibliography. Simulation results show that the peak value and width of the propagated PD pulse are similar to those obtained with the proposed model. Additionally, the proposed model provides the velocity of each PD frequency component, which is crucial to get an accurate estimation of the PD source location. The parameters of the proposed model have been estimated using a vector network analyzer for a XLPE cable. These results have been compared to the measurement obtained in a medium voltage test bench where intentionally induced PDs have been captured and processed, confirming the results of attenuation, delay and dispersion predicted by the proposed model

School Choice with Transferable Students Characteristics

We consider a school choice problem where schools' priorities depend on transferable students' characteristics. A school choice algorithm selects for each profile of students' preferences over schools an assignment of students to schools and a final allocation of characteristics (an extended matching). We define the Student Exchange with Transferable Characteristics (SETC) class of algorithms. Each SETC always selects a constrained efficient extended matching. That is an extended matching that i) is stable according to the priorities generated by the final allocation of characteristics and ii) is not Pareto dominated by another stable extended matching. Every constrained efficient extended matching that Pareto improves upon a stable extended matching can be obtained via an algorithm in the SETC class. When students' characteristics are fully transferable, a specific algorithm in the SETC family is equivalent to the application of the Top Trade Cycle Algorithm starting from the Student Optimal Stable Matching

Anonymizing cybersecurity data in critical infrastructures: the CIPSEC approach

Cybersecurity logs are permanently generated by network devices to describe security incidents. With modern computing technology, such logs can be exploited to counter threats in real time or before they gain a foothold. To improve these capabilities, logs are usually shared with external entities. However, since cybersecurity logs might contain sensitive data, serious privacy concerns arise, even more when critical infrastructures (CI), handling strategic data, are involved. We propose a tool to protect privacy by anonymizing sensitive data included in cybersecurity logs. We implement anonymization mechanisms grouped through the definition of a privacy policy. We adapt said approach to the context of the EU project CIPSEC that builds a unified security framework to orchestrate security products, thus offering better protection to a group of CIs. Since this framework collects and processes security-related data from multiple devices of CIs, our work is devoted to protecting privacy by integrating our anonymization approach.Peer ReviewedPostprint (published version

Modelo de gerencia estratégica como elemento de mejora de la gestión habitacional en el estado Lara (Venezuela)

Tesis de Maestría en Gestión y Desarrollo Habitacional (MGDH)Frente a la limitada capacidad de los Institutos Públicos de Vivienda en la provincia de Lara (Venezuela) para ofrecer soluciones efectivas a la creciente demanda de la población por hábitat y vivienda, se desarrolla el presente trabajo, en el que se constata la necesidad de proveerles de un direccionamiento y adecuadas estrategias para asegurar el futuro inmediato en su prestación pública. La metodología empleada obedece a un proyecto factible basado en un estudio de campo descriptivo. Se evalúa de manera integral las unidades gerenciales que conforman estas instituciones (10 organizaciones en total con distintas competencias en la provincia), efectuandose para ello, un diagnóstico organizacional de sus entornos (interno y externo) y del tipo de gestión habitacional prestada. Las conclusiones apuntan a que la gestión habitacional que prestan las instituciones de viviendas es un proceso que en buena parte depende de aspectos endógenos y exógenos al ámbito de éstas, que requiere necesariamente de nuevos modos de pensar, gestionar y producir el hábitat y vivienda para superar las desigualdades espaciales y sociales existentes. El proyecto constituye una propuesta derivada del diagnóstico estratégico efectuado y del análisis crítico de teorías organizacionales, adecuado a la realidad factual bajo la coordinación de expertos en el área. También se proponen un conjunto de medidas generales como aportes del autor para complementar la mejora que se persigue

Time domain analysis of partial discharges envelope in medium voltage XLPE cables

Partial discharge (PD) analysis has been widely used to detect premature degradation of power cables. Although there are recognized techniques for PD analysis, there is still lack of knowledge about measuring and modeling this phenomenon. This paper proposes a new model based on time domain parameters of the PD signal envelope. The proposed variables (time duration, and rising and falling slopes of the envelopes), together with conventional PD analyses focused on PD amplitude and phase resolved patterns, will provide a better understanding of this phenomenon. Based on this model, a new technique to reshape the PD signal envelope is also proposed that compensates the negative effect of dispersion in the location techniques that estimate the time of arrival (TOA). Experimental results were obtained in the lab, where a power cable has been artificially damaged in order to produce PD. To this end, a specific PD on-line acquisition system has been developed. In the first set of experiments, we illustrate how the cable attenuates and disperses the PD signal envelope. In the second one, we show how the proposed variables are useful to distinguish among different types of PD sources. Finally, an accurate estimation of the PD source location is achieved by measuring the time of arrival of the PD signal envelopes at both cable ends, and reshaping one of the signals captured. This technique improves the accuracy of the estimated location of the PD sources, both in simulation and in experimental results

Experimental and numerical analysis of the influence of drill point angle when drilling biocomposites

Biocomposites are promising materials for traditional composites replacement in specific applications due to their interesting properties and sustainability. Although the composite components are manufactured near net shape, some machining operations, commonly drilling, are commonly required prior to mechanical joining of the components. Tool geometry, mainly the point angle of the drill, strongly affects the performance of the drilling process of composites in terms of machining induced damage. The aim of this work is analyzing the influence of the point angle of the drill on the damage generated during drilling of 100% biodegradable composite, using both numerical and experimental approaches. The novelty of the work relies on the lack of studies of drilling 100% biodegradable composites. The influence of the point angle on the thrust forces and hence in the machining induced damage was demonstrated.The authors acknowledge the financial support to the Ministry of Economy and Competitiveness of Spain and FEDER program through the projects DPI2017-89197-C2-1-R and DPI2017-89197-C2-2-R

Novel Findings about Double-Loaded Curcumin-in-HPβcyclodextrin-in Liposomes: Effects on the Lipid Bilayer and Drug Release

In this study, the encapsulation of curcumin (Cur) in “drug-in-cyclodextrin-in-liposomes (DCL)” by following the double-loading technique (DL) was proposed, giving rise to DCL–DL. The aim was to analyze the effect of cyclodextrin (CD) on the physicochemical, stability, and drug-release properties of liposomes. After selecting didodecyldimethylammonium bromide (DDAB) as the cationic lipid, DCL–DL was formulated by adding 2-hydroxypropyl-α/β/γ-CD (HPβCD)–Cur complexes into the aqueous phase. A competitive effect of cholesterol (Cho) for the CD cavity was found, so cholesteryl hemisuccinate (Chems) was used. The optimal composition of the DCL–DL bilayer was obtained by applying Taguchi methodology and regression analysis. Vesicles showed a lower drug encapsulation efficiency compared to conventional liposomes (CL) and CL containing HPβCD in the aqueous phase. However, the presence of HPβCD significantly increased vesicle deformability and Cur antioxidant activity over time. In addition, drug release profiles showed a sustained release after an initial burst effect, fitting to the Korsmeyer-Peppas kinetic model. Moreover, a direct correlation between the area under the curve (AUC) of dissolution profiles and flexibility of liposomes was obtained. It can be concluded that these “drug-in-cyclodextrin-in-deformable” liposomes in the presence of HPβCD may be a promising carrier for increasing the entrapment efficiency and stability of Cur without compromising the integrity of the liposome bilayer

Effects of Dispersion and Multi-Path Propagation in Partial Discharges Location

Article number 9281048Dispersion and multi-path propagation distort partial discharge (PD) pulses that travel along power cables. This article proposes a theoretical framework that models the PD source location error owing to these effects. Regarding dispersion a closed-form expression is proposed to estimate the PD bandwidth reduction at the cable ends as well as the expected location error due to propagation velocity variation. A new expression is proposed for the difference of times of arrival (TOAs) which exhibits dependence with frequency. Multi-path propagation also introduces a non-linear dependence with frequency in the TOAs which leads to location errors when the echo is very close to the main PD signal. Three location algorithms (based on cross-correlation phase increment and energy criterion) are investigated under noise dispersion and multi-path conditions. Simulation results show that the energy criterion algorithm is very sensitive to dispersion but it is robust to multi-path propagation. The algorithm based on phase increments is the most sensitive to noise. Finally the best location method for noisy highly dispersive multi-path propagation is the one based on cross-correlation.Laboratorio de Ingeniería en Energía y Sostenibilidad Ambiental de la Universidad de Sevilla VI Plan Propio de Investigació

Sobre la región de accesibilidad de ciertas iteraciones de tercer orden

La región de accesibilidad de los procesos iterativos cuando se aplican a la resolución de ecuaciones no lineales adquiere cierto interés a la hora de elegir un proceso iterativo. Sabemos, a priori, que cuanto mayor es el orden de convergencia de los procesos iterativos, menor es su región de accesibilidad. Nosotros aquí presentamos una simple modificación de las iteraciones clásicas de tercer orden de manera que podamos considerar, para cada una de ellas, la misma región de accesibilidad que para el método de segundo orden más conocido, el método de Newton