Three-dimensional numerical simulations of free convection in a layered porous enclosure

Three-dimensional numerical simulations are carried out for the study of free convection in a layered porous enclosure heated from below and cooled from the top. The system is defined as a cubic porous enclosure comprising three layers, of which the external ones share constant physical properties and the internal layer is allowed to vary in both permeability and thermal conductivity. The model is based on Darcy's law and the Boussinesq approximation. A parametric study to evaluate the sensitivity of the Nusselt number to a decrease in the permeability of the internal layer shows that strong permeability contrasts are required to observe an appreciable drop in the Nusselt number. If additionally the thickness of the internal layer is increased, a further decrease in the Nusselt number is observed as long as the convective modes remain the same, if the convective modes change the Nusselt number may increase. Decreasing the thermal conductivity of the middle layer causes first an increment in the Nusselt number and then a drop. On the other hand, the Nusselt number decreases in an approximately linear trend when the thermal conductivity of the layer is increased

Cladobotryum mycophilum as Potential Biocontrol Agent

A study was conducted to explore the efficacy of potential biocontrol agent Cladobotryum mycophilum against different phytopathogenic fungi. The growth rates of 24 isolates of C. mycophilum were determined, and their antagonistic activity was analysed in vitro and in vivo against Botrytis cinerea, Fusarium oxysporum f. sp. radicis-lycopersici, Fusarium oxysporum f.sp. cucumerinum, Fusarium solani, Phytophthora parasitica, Phytophthora capsici, Pythium aphanidermatum and Mycosphaerella melonis. Most isolates grow rapidly, reaching the opposite end of the Petri dish within 72–96 h. Under dual-culture assays, C. mycophilum showed antagonistic activity in vitro against all phytopathogenic fungi tested, with mycelial growth inhibition ranging from 30 to 90% against all the different phytopathogens tested. Similarly, of all the selected isolates, CL60A, CL17A and CL18A significantly (p < 0.05) reduced the disease incidence and severity in the plant assays compared to the controls for the different pathosystems studied. Based on these results, we conclude that C. mycophilum can be considered as a potential biological control agent in agriculture. This is the first study of Cladobotryum mycophilum as a biological control agent for different diseases caused by highly relevant phytopathogens in horticultur

Materias primas de la Luna para emprender la colonización espacial

1 página.-- Reportaje.Peer reviewe

Enhancement of the magnetic anisotropy of Co clusters by Au capping

et al.We study the magnetic properties of Co nanoparticles, prepared by sputtering, with diameters ranging from 1 to 3.5 nm. The effective anisotropy, which determines the activation energy for the magnetization reversal, increases with decreasing particle's size, showing the dominant role played by surface atoms. We find that the superparamagnetic blocking temperature and the coercive field are significatively enhanced when the clusters are capped by a thin Au layer. This enhancement is probably caused by the bonding or hybridization of Co and Au atoms at the interface between the two metals. It provides thus a method to modify the magnetic anisotropy, which can be of interest for the applications of magnetic nanoparticles.Peer reviewe

careers and incentives

En primer lugar se caracterizan los arreglos institucionales que rigen los contratos y la movilidad de los docentes. Se describe luego la condición social de la fuerza de trabajo para examinar el atractivo de la ocupación para quienes la ejercen. Se examina la evolución histórica de la matrícula de los centros de formación docente. La tercera parte examina el impacto de programas especiales sobre la movilidad. La cuarta sección trata el perfil de los cuerpos docentes según tipos de escuela. La quinta sección considera la medición del desempeño docente a través de variables sociodemográficas y actitudinales

VNUML vs GNS3 en el desarrollo de laboratorios de redes virtuales

El aprendizaje práctico de redes de computadores es reconocido como un proceso crítico que permite a los estudiantes consolidar los conceptos introducidos en las lecciones teóricas. En este sentido, las tecnologías de virtualización están adquiriendo gran relevancia debido a que permiten desarrollar laboratorios de redes de computadores con un reducido coste de despliegue y gestión. Este artículo presenta un análisis comparativo entre GNS3 y VNUML, que son herramientas de virtualización open-source que han sido empleadas para el desarrollo de laboratorios de red virtuales para llevar a cabo el proceso de enseñanza-aprendizaje en las asignaturas Arquitectura de Redes y Arquitectura de Redes Avanzadas del Grado en Ingeniería Informática impartido en la Universidad de Murcia. El estudio presenta las principales ventajas y/o deficiencias de cada herramienta tanto para profesores como alumnos y se identifican los escenarios en los que parece más adecuada su utilización.SUMMARY -- The practical learning of computer networks is known to be a critical process in order to allow students to consolidate the concepts introduced in theoretical lessons. In this sense, virtualization technologies are becoming popular since they allow to set up a computer network laboratory with a reduced deployment and management cost. This paper presents a comparative analysis performed between GNS3 and VNUML, which are open-source tools for virtualization that have been used for developing virtual network laboratories that support the teaching-learning process in the Networks Architecture and Advanced Networks Architecture subjects of the Computer Engineering degree at the University of Murcia. The study presents the main advantages and/or deficiencies of each tool not only for professors but also for students and identifies the scenarios where the use of each tool seems to be more appropriate.Peer Reviewe

Mode locking in discrete solition dynamics under ac forces

We present here analytical arguments and numerical evidence for the existence of net directional motion of highly discrete sine-Gordon kinks under ac forces of zero average. We have also characterized the depinning of the oscillating kink under those circumstances, and analyzed the instability mechanisms of the phase-locked running solutions. Possible experimental relevance of this phenomenon in circular arrays of Josephson junctions is discussed.Financial support from DGES (PB95-0797) and CICYT (MAT95-0325)Publicad

Generación de piloto automático difuso para maniobras de embarcaciones

This paper introduces a method to generate autopilots for ship headings by using issues from the observation of control actions performed by human operators. The controller is designed based on fuzzy logic and uses triangular membership functions for the antecedent and consequent functions for Singleton type. For an automatic adjustment of the consequential, the recursive least squares method was used. This method is used to generate and validate the course driver of a 350-m tanker, at different load conditions.Este documento presenta un método para generar pilotos automáticos para rumbo de embarcación mediante el uso de asuntos provenientes de la observación de acciones de control realizadas por operadores humanos. El controlador está diseñado basado en lógica difusa (fuzzy logic) y utiliza funciones de pertenencia triangular para las funciones antecedentes y consecuentes para tipo Singleton. Para un ajuste automático de la consecuente, se utilizó el método de mínimos cuadrados recursivos. Este método es utilizado para generar y validar el conductor de curso de un buque cisterna de 350 m, en diferentes condiciones de carga

Adaptive Function and Brain Evolution

Contains fulltext : 108558.pdf (publisher's version ) (Open Access