Control of multi-terminal HVDC networks towards wind power integration: A review

© 2015 Elsevier Ltd. More interconnections among countries and synchronous areas are foreseen in order to fulfil the EU 2050 target on the renewable generation share. One proposal to accomplish this challenging objective is the development of the so-called European SuperGrid. Multi-terminal HVDC networks are emerging as the most promising technologies to develop such a concept. Moreover, multi-terminal HVDC grids are based on highly controllable devices, which may allow not only transmitting power, but also supporting the AC grids to ensure a secure and stable operation. This paper aims to present an overview of different control schemes for multi-terminal HVDC grids, including the control of the power converters and the controls for power sharing and the provision of ancillary services. This paper also analyses the proposed modifications of the existing control schemes to manage high participation shares of wind power generation in multi-terminal grids.Postprint (author's final draft

Osteoma osteoide a nivel de una falange proximal de la mano

El osteoma osteoide es un tumor óseo benigno que aparece fundamentalmente en adolescentes, y aunque con menor frecuencia, también en adultos jóvenes. El fémur y la tibia son las localizaciones más frecuentes, hallándose raramente a nivel de la mano. Presentamos un caso de osteoma osteoide de la localización infrecuente sobre la primera falange del 4º dedo de la mano derecha en un paciente de 22 años de edad. El paciente presentaba dolor y tumefacción de dos meses de evolución en la base del 4º dedo que aumentaban progresivamente. Tras las pruebas complementarias se diagnosticó un osteoma osteoide yuxtacortical que se trató mediante resección en bloque y autoinjerto.Osteoid osteoma is a benign bone tumour that appears most frequently in adolescents. The tibia and femur are the most frequent locations, and the hand is very uncommon. We present the case of a 22 year-old-man, without relevant antecedents, who presented in the base of the 4th finger. Bye means of complementary tests, juxtacortical osteoid osteoma was diagnosed. The treatment consisted in surgical resection in bloc and bone graft

Estudio epidemiológico de terceros molares superiores retenidos, en relación a la biotipología cráneo-facial, en pacientes dentados de entre 18 y 40 años de edad, en la ciudad de Córdoba (República Argentina).

Considerando los accidentes y complicaciones producto de la retención de los terceros molares superiores, los cuales se hacen evidentes en un alto porcentaje estadístico en pacientes cuyo promedio de edad es de 23 años para el sexo femenino y de 25 años para el masculino, es por ello que se ha realizado el presente trabajo epidemiológico, para tener conocimiento de la forma en que se impacta en la población de la Ciudad de Córdoba (República Argentina). Para esto se relacionó el tipo de retención (según la clasificación de Winter) en correspondencia al sexo, índice craneofacial y la sintomatología clínica que presentaran. El presente trabajo de investigación se realizó en una población de 47 pacientes, en la cual se seleccionó un rango de edad la cual oscilara entre los 18 y 40 años, además debían presentar todos los elementos dentarios en el maxilar superior. Los pacientes fueron 28 del sexo femenino y 19 del sexo masculino, con un total de 77 terceros molares superiores retenidos. Se realizaron Ortopantomografías y Telerradiografía de Perfil, sobre las que se realizaron calcos cefalométricos. Los resultados obtenidos nos indicaron que en la población de Córdoba (República Argentina) es más frecuente la retención en el caso del elemento dentario 18 en los mesofaciales, encontrandose con mayor frecuencia en posición vertical. El elemento denyario 28, presenta un predominio en la retención en braquifaciales y, su posición más frecuente es la distoangular. Respecto de la sintomatología que producen estos elementos dentarios retenidos, se observó en relación al sexo y la biotipología, el siguiente resultado obtenido: El sexo femenino, presentó predominio de pacientes braquifaciales asintomáticos y mesofaciales sintomáticos. El sexo masculino, presentó predominio de pacientes braquifaciales asintomáticos y dolicofaciales sintomáticos. Basándonos en los resultados obtenidos del presente trabajo de investigación, creemos de suma importancia efectuar estudios clínicos radiográficos en pacientes de entre 23 y 25 años de edad de los cuales nos permitan evaluar el riesgo-beneficio, para realizar la toma de decisión respecto de la extracción o no de este elemento dentario

Tracking the dynamic nature of learner individual differences: Initial results from a longitudinal study

Individual differences (IDs) have long been considered one of the most important factors explaining variable rates and outcomes in second language acquisition (Dewaele, 2013). While traditional operationalizations of IDs have, explicitly or implicitly, assumed that IDs are static traits that are stable through time, more recent research inspired by complex dynamic systems theory (Larsen-Freeman, 1997, 2020) demonstrates that many IDs are dynamic and variable through time and across contexts, a theme echoed throughout the current issue. This study reports the initial semester of a diachronic project investigating the dynamicity of four learner IDs: motivation, personality, learning and cognitive styles, and working memory. In the initial semester, data from 323 participants in their first year of university-level Spanish were collected and analyzed to determine what type of variability may be present across learners with respect to the four IDs studied at one time point and to discern possible learner profiles in the data or patterns via which the data may be otherwise meaningfully described. The results revealed four types of learner profiles present in the dataset

A new neural network technique for the design of multilayered microwave shielded bandpass filters

In this work, we propose a novel technique based on neural networks, for the design of microwave filters in shielded printed technology. The technique uses radial basis function neural networks to represent the non linear relations between the quality factors and coupling coefficients, with the geometrical dimensions of the resonators. The radial basis function neural networks are employed for the first time in the design task of shielded printed filters, and permit a fast and precise operation with only a limited set of training data. Thanks to a new cascade configuration, a set of two neural networks provide the dimensions of the complete filter in a fast and accurate way. To improve the calculation of the geometrical dimensions, the neural networks can take as inputs both electrical parameters and physical dimensions computed by other neural networks. The neural network technique is combined with gradient based optimization methods to further improve the response of the filters. Results are presented to demonstrate the usefulness of the proposed technique for the design of practical microwave printed coupled line and hairpin filters

Efficient integral equation formulation for inductive waveguide components with posts touching the waveguide walls

In this paper a surface integral equation technique is employed for the analysis of inductive waveguide problems containing metallic or dielectric objects of arbitrary shape, focusing on the case where these objects are connected to the waveguide walls. Using the extinction theorem, the main problem is split into two problems. In the first one the parallel plate waveguide Green’s functions are used. Because of the choice of these functions, the side of the object touching the waveguide wall is not considered for discretization in a method of moments analysis. The second problem is applied inside the dielectric object, and uses the free space Green’s functions. It is shown that an additional spatial image is needed to impose the proper boundary conditions for the fields on the side touching the waveguide wall in the original problem. Results show the importance of including this additional image in the formulation for the correct behavior of the fields. With the proposed technique, the paper explores some alternatives for designing specific filter responses using dielectric posts inside cavity filters. Comparisons with a commercial finite elements tool demonstrate the accuracy of the proposed integral equation formulation.This work has been developed with support from the Spanish National Project (CICYT) with Ref TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with Ref 02972/PI/05

On reducible non-Weierstrass semigroups

Weierstrass semigroups are well known along the literature. We present a new family of non- Weierstrass semigroups which can be written as an intersection of Weierstrass semigroups. In addition, we provide methods for computing non-Weierstrass semigroups with genus as large as desired.Funding information: Part of this paper was written during a visit of Fernando Torres to the Universidad de Cadiz (Spain) ; his visit was partially supported by Ayudas para Estancias Cortas de Investigadores (EST2018-R0, Programa de Fomento e Impulso de la Investigacion y la Transferencia en la Universidad de Cadiz) . Fernando Torres was partially supported by CNPq/Brazil (Grant 310623/2017-0) . Juan Ignacio Garcia-Garcia, Daniel Marin-Aragon, and Alberto Vigneron-Tenorio were partially supported by Junta de Andalucia research groups FQM-343 and FQM-366, and by the project MTM2017-84890-P (MINECO/FEDER, UE)

Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method

IIn this paper, a spatial image technique is used to efficiently calculate the mixed potential Green’s functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are thencalculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.This work has been developed with support from the Spanish National Project (CICYT) with reference TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with reference 02972/PI/0

Un Simulador empresarial como herramienta práctica para la asignatura de Aprendizaje Automático

En este artículo se plantea el uso de un simulador empresarial (SIMBA) como dominio de aplicación de las prácticas de la asignatura de Aprendizaje Automático (AA). El objetivo principal es que los alumnos se enfrenten a un entorno realista en el que tengan que plantear y ofrecer soluciones basadas en AA. El contexto de la toma de decisiones empresarial ofrece un amplio abanico de aplicaciones, desde el análisis de datos (predicción de resultados empresariales, análisis de perfiles de decisión, etc.) hasta el aprendizaje de comportamientos (soporte a la toma de decisión). Esto permite configurar la parte práctica de la asignatura mediante prácticas solapadas con un matiz mucho más realista que el que se conseguía en años anteriores, a la vez que se cubren gran parte de los contenidos teóricos de la asignatura. La iniciativa se aplicó el curso 2008-2009 con resultados satisfactorios y forma parte de un proyecto de innovación docente que se está realizando en el curso 2009-2010.Peer Reviewe