Approximation of the Neutron Diffusion Equation on Hexagonal Geometries

La ecuación de la difusión neutrónica describe la población de neutrones de un reactor nuclear. Este trabajo trata con este modelo para reactores nucleares con geometría hexagonal. En primer lugar se estudia la ecuación de la difusión neutrónica. Este es un problema diferencial de valores propios, llamado problema de los modos Lambda. Para resolver el problema de los modos Lambda se han comparado diferentes métodos en geometrías unidimensionales, resultando como el mejor el método de elementos espectrales. Usando este método discretizamos los operadores en geometrías bidimensiones y tridimensionales, resolviendo el problema algebraica de valores propios resultante con el método de Arnoldi. La distribución de neutrones estado estacionario se utiliza como condición inicial para la integración de la ecuación de la difusión neutrónica dependiente del tiempo. Se utiliza un método de Euler implícito para integrar en el tiempo. Cuando un nodo está parcialmente insertado aparece un comportamiento no físico de la solución, el efecto ``rod cusping'', que se corrige mediante la ponderación de las secciones eficaces con el flujo del paso de tiempo anterior. Cuando la solución de los sistemas algebraicos que surgen en el método hacia atrás, un método de Krylov se utiliza para resolver los sistemas resultantes, y diferentes estrategias de precondicionamiento se evalúan se. La primera consiste en el uso de la estructura de bloque obtenido por los grupos de energía para resolver el sistema por bloques, y diferentes técnicas de aceleración para el esquema iterativo de bloques y un precondicionador utilizando esta estructura de bloque se proponen. Además se estudia un precondicionador espectral, que hace uso de la información en un subespacio de Krylov para precondicionar el siguiente sistema. También se proponen métodos exponenciales de segundo y cuarto orden integrar la ecuación de difusión neutrónica dependiente del tiempo, donde la exponencial de la matriz del sistema tiene quGonzález Pintor, S. (2012). Approximation of the Neutron Diffusion Equation on Hexagonal Geometries [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17829Palanci

Updating the Lambda modes of a nuclear power reactor

[EN] Starting from a steady state configuration of a nuclear power reactor some situations arise in which the reactor configuration is perturbed. The Lambda modes are eigenfunctions associated with a given configuration of the reactor, which have successfully been used to describe unstable events in BWRs. To compute several eigenvalues and its corresponding eigenfunctions for a nuclear reactor is quite expensive from the computational point of view. Krylov subspace methods are efficient methods to compute the dominant Lambda modes associated with a given configuration of the reactor, but if the Lambda modes have to be computed for different perturbed configurations of the reactor more efficient methods can be used. In this paper, different methods for the updating Lambda modes problem will be proposed and compared by computing the dominant Lambda modes of different configurations associated with a Boron injection transient in a typical BWR reactor. (C) 2010 Elsevier Ltd. All rights reserved.This work has been partially supported by the Spanish Ministerio de Educacion y Ciencia under projects ENE2008-02669 and MTM2007-64477-AR07, the Generalitat Valenciana under project ACOMP/2009/058, and the Universidad Politecnica de Valencia under project PAID-05-09-4285.González Pintor, S.; Ginestar Peiro, D.; Verdú Martín, GJ. (2011). Updating the Lambda modes of a nuclear power reactor. Mathematical and Computer Modelling. 54(7):1796-1801. https://doi.org/10.1016/j.mcm.2010.12.013S1796180154

Energías renovables y desarrollo sostenible = Renewable energy and sustainable development

Este trabajo desarrolla diversos puntos relacionados con la energía renovable. En primer lugar desarrolla los principales datos sobre los diferentes tipos de esta tecnología entre los que destacan los más utilizados en España. Desarrolla cada tipo de energía mostrando sus principales usos. A continuación se desarrolla el papel de la Unión Europea en este tipo de energía mostrando los principales datos de cada una de las tecnologías en Europa. Este punto se enlaza con el siguiente, el cual muestra la planificación para las energías renovables, tanto el Plan anterior, como el nuevo Plan de Energías Renovables. El ahorro energético en relación con las energías renovables es también parte de este trabajo, desarrollando aquí las interrelaciones que las mismas tienen tanto con la economía como con diversos factores externos, desarrollando diversas estrategias para este tipo de energía. Por último, se muestra la coyuntura actual de las energías renovables teniendo en cuenta que el desarrollo de las fuentes renovables de energía es uno de los aspectos de la política energética de nuestro país, que deben tenerse en cuenta para el futuro

La motivación en Secundaria. Un estudio empírico

Conocer las motivaciones concretas de nuestros alumnos es el objetivo del presente trabajo. Se pretende contribuir a la necesaria justificación, tanto experimental como teórica, de la práctica docente, desde la perspectiva de la investigación-acción. Las agrupaciones y las relaciones obtenidas en los diversos análisis cuestionan la imagen que alumnos y profesores poseemos de las metas autopropuestas por los estudiantes y su actual cambio.Knowing the our students' specific motivations is the object of the present study. Our aim is to justify in an experimental as theoretical form the docent practice from the research-action perspective. The clusters and relations obtained call into question the image held by students and teachers about the changing and their autoproposed goals

Changes in diadenosine polyphosphates during alignment-fit and orthokeratology rigid gas permeable lens wear

The authors thank Paragon Vision Science (Mesa, AZ), Lenticon SA (Madrid, Spain), and Interlenco SA (Madrid, Spain) for donating the lenses, and Bausch & Lomb (Rochester, NY) for donating the care solutions used in the study.PURPOSE: To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment. METHODS: Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated. RESULTS: Ap(4)A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period. CONCLUSIONS: Daily wear of RGP lenses increased the levels of Ap(4)A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.Supported by Ministerio de Ciencia e Innovacion Grant SAF2010-16024, RETIC Red de Patologia ocular del envejecimiento, calidad visual, y calidad de vida Grant RD07/0062/0004, and BSCHUCM Grant GR58/08

Entornos de verificación de soluciones multi-path BGP

Proceeding of: IX Jornadas de Ingeniería Telemática, JITEL 2010, Valladolid, Spain, 29 de septiembre al 1 de octubre de 2010Actualmente la utilización simultánea de múltiples caminos en redes de comunicaciones tiene el potencial de generar una serie de importantes beneficios como la mejor utilización de los recursos disponibles o la mayor robustez y protección de las transmisiones. Sin embargo, las soluciones existentes hoy en día para dotar a los routers de un paradigma multi-camino no pasan de ser propuestas aisladas o soluciones concretas intra-dominio. Entre otras cosas, esto se debe a las dificultades de probar y validar las diferentes soluciones como a las dificultades de un posterior despliegue. En este artículo se propone un entorno desarrollado para poder verificar soluciones multi-path inter-dominio (BGP) tanto por la vía de la simulación como por la vía de la implementación real de la solución. Se describirá también cómo se ha validado la propuesta con dos soluciones actualmente en desarrollo, habiéndose detectado así en ellas problemas de convergencia.Este artículo ha sido parcialmente financiado por la Comisión Europea a través del proyecto Trilogy (ICT-216372), del VII Programa Marco y por la Cátedra Telefónica-UC3M en Internet del Futuro para la Productividad.European Community's Seventh Framework ProgramNo publicad

Modified Block Newton method for the lambda modes problem

[EN] To study the behaviour of nuclear power reactors it is necessary to solve the time dependent neutron diffusion equation using either a rectangular mesh for PWR and BWR reactors or a hexagonal mesh for VVER reactors. This problem can be solved by means of a modal method, which uses a set of dominant modes to expand the neutron flux. For the transient calculations using the modal method with a moderate number of modes, these modes must be updated each time step to maintain the accuracy of the solution. The updating modes process is also interesting to study perturbed configurations of a reactor. A Modified Block Newton method is studied to update the modes. The performance of the Newton method has been tested for a steady state perturbation analysis of two 2D hexagonal reactors, a perturbed configuration of the IAEA PWR 3D reactor and two configurations associated with a boron dilution transient in a BWR reactor.This work has been partially supported by the Spanish Ministerio de Educación y Ciencia under projects ENE2008-02669 and MTM2007-64477-AR07, the Generalitat Valenciana under project ACOMP/2009/058, and the Universidad Politécnica de Valencia under project PAID-05-09-4285.González Pintor, S.; Ginestar Peiro, D.; Verdú Martín, GJ. (2013). Modified Block Newton method for the lambda modes problem. Nuclear Engineering and Design. 259:230-239. https://doi.org/10.1016/j.nucengdes.2011.06.045S23023925

Moving meshes to solve the time-dependent neutron diffusion equation in hexagonal geometry

To simulate the behaviour of a nuclear power reactor it is necessary to be able to integrate the time-dependent neutron diffusion equation inside the reactor core. Here the spatial discretization of this equation is done using a finite element method that permits h-p refinements for different geometries. This means that the accuracy of the solution can be improved refining the spatial mesh (h-refinement) and also increasing the degree of the polynomial expansions used in the finite element method (p-refinement). Transients involving the movement of the control rod banks have the problem known as the rod-cusping effect. Previous studies have usually approached the problem using a fixed mesh scheme defining averaged material properties. The present work proposes the use of a moving mesh scheme that uses spatial meshes that change with the movement of the control rods avoiding the necessity of using equivalent material cross sections for the partially inserted cells. The performance of the moving mesh scheme is tested studying one-dimensional and three-dimensional benchmark problems. (C) 2015 Elsevier B.V. All rights reserved.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion under project ENE2011-22823, the Generalitat Valenciana under projects II/2014/08 and ACOMP/2013/237, and the Universitat Politecnica de Valencia under project UPPTE/2012/118.Vidal-Ferràndiz, A.; Fayez Moustafa Moawad, R.; Ginestar Peiro, D.; Verdú Martín, GJ. (2016). Moving meshes to solve the time-dependent neutron diffusion equation in hexagonal geometry. Journal of Computational and Applied Mathematics. 291:197-208. https://doi.org/10.1016/j.cam.2015.03.040S19720829

The influence of rigid gas permeable lens wear on the concentrations of dinucleotides in tears and the effect on dry eye signs and symptoms in keratoconus

Purpose: To evaluate the signs and symptoms of dry eye and dinucleotide secretion in tears of keratoconus patients (KC) and the potential effect of rigid gas permeable (RGP) contact lens wear. Methods: Twenty-three KC patients and forty control subjects were enrolled in this study. Signs of dry eye including tear volume, tear stability and corneal staining along with symptoms were assessed using the McMonnies questionnaire. Tears were collected using Schirmer strips, and dinucleotide concentrations in collected tears measured using high pressure liquid chromatography. Values obtained in KC and controls were compared. The effect of contact lens wear in KC was also assessed. Results: KC eyes showed a significantly lower tear volume compared to controls, shorter tear break up time (TBUT), higher corneal staining and higher McMonnies dry eye questionnaire scores (p < 0.05). When compared with non-wearers, KC contact lens wearers showed significantly higher symptoms, lower Schirmer and TBUT values (p < 0.05). Concentration of Ap4A (0.695 ± 0.304 μM vs. 0.185 ± 0.178 μM) and Ap5A (0.132 ± 0.128 μM vs. 0.045 ± 0.036 μM) were higher in KC compared to controls (p < 0.001) and only Ap4A was statistically higher in RGP wearers compared to non-wearers (0.794 ± 0.478 μM vs. 0.417 ± 0.313 μM) (p < 0.05). Conclusion: Signs and symptoms of dry eye as well as concentrations of Ap4A and Ap5A were markedly increased in KC patients compared to controls. Moreover, Ap4A and symptoms of dry eye were statistically higher in RGP wearers compared to non-wearers. This seems to indicate that factors such as RGP contact lens wear might exacerbate the clinical condition of dry eye.This work was supported by grants from the Ministerio de Ciencia e Innovación (SAF2010-16024 and SAF2013-44416-R) and RETICS (RD12/0034/0003). The authors want to thank Thomas Johnson and Vimala Punsammy for helping in the preparation of the manuscript