A note on global dynamics and imbalance effects in the Lucas-Uzawa model

In the traditional literature on the Lucas-Uzawa model, it is proved that in the neighborhood of the long-run balanced growth path, human capital stock grows at a rate greater than its long-run counterpart when the ratio physical to human capi- tal is above its long run value if and only if the capital share in the production of physical good is lower than the inverse of the elasticity of intertemporal substitution in consumption. We first prove that the claim is true outside the neighborhood of balanced growth paths. More importantly, we identify a crucial asymmetry: what- ever the position of the capital share with respect to the inverse of the elasticity of intertemporal substitution, physical capital stock always grows at a rate lower than its long-run counterpart when the ratio physical to human capital is above its long run value.Lucas-Uzawa, hypergeometric functions, imbalance e®ects, global dynamics.

Selección óptima bajo criterios múltiples de materiales refractarios y aislantes para cazuelas metalúrgicas

ResumenHasta el presente, el problema de la selección de materiales refractarios y aislantes no se ha tratado, en toda su complejidad, como una tarea de optimización bajo criterios múltiples, sino básicamente como un problema de carácter metalúrgico. En este artículo, se expone el modelado matemático de la tarea de selección óptima bajo criterios múltiples y se analiza su complejidad matemática, considerando las dimensiones de los materiales por capas y por zonas, y la interacción entre zonas. La complejidad de la tarea formulada requiere su descomposición en tareas más sencillas, por zonas de la cazuela. Se realiza la validación experimental de los resultados numéricos obtenidos, con lo cual se evidencia la eficiencia y la calidad que se obtienen con los procedimientos utilizados. Estos procedimientos se derivan de la aplicación del método de integración de variables. En particular, se utiliza el operador de búsqueda aleatoria del extremo de una función de un código variable aplicado al problema estudiado.SummaryUntil the present the problem of the refractory and isolating materials selection has not been treated, in all its complexity, as an optimization under multiple criteria task, but basically as a metallurgical problem. In the present article the mathematical modelling of the optimal under multiple criteria task, the analysis of it mathematical complexity, considering the dimensions of the materials by layers and by zones are exposed. The complexity of the formulated task conditions the necessity of its decomposition in simpler tasks by zones of the ladle. The experimental validation of the obtained numeric results, where the efficiency and resulting quality of the used procedures is evidenced. The procedures applied are a part of the Integration of Variables method. Particularly, the Random Search of the Extremes of a Function of a Variable Code operator is applied to the problem studied

Kinematic study of planetary nebulae in NGC 6822

By measuring precise radial velocities of planetary nebulae (which belong to the intermediate age population), H II regions, and A-type supergiant stars (which are members of the young population) in NGC 6822, we aim to determine if both types of population share the kinematics of the disk of H I found in this galaxy. Spectroscopic data for four planetary nebulae were obtained with the high spectral resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) on the Magellan telescope at Las Campanas Observatory. Data for other three PNe and one H II region were obtained from the SPM Catalog of Extragalactic Planetary Nebulae which employed the Manchester Echelle Spectrometer attached to the 2.1m telescope at the Observatorio Astron\'omico Nacional, M\'exico. In the wavelength calibrated spectra, the heliocentric radial velocities were measured with a precision better than 5-6 km s$^{-1}$. Data for three additional H II regions and a couple of A-type supergiant stars were collected from the literature. The heliocentric radial velocities of the different objects were compared to the velocities of the H i disk at the same position. From the analysis of radial velocities it is found that H II regions and A-type supergiants do share the kinematics of the H I disk at the same position, as expected for these young objects. On the contrary, planetary nebula velocities differ significantly from that of the H I at the same position. The kinematics of planetary nebulae is independent from the young population kinematics and it is closer to the behavior shown by carbon stars, which are intermediate-age members of the stellar spheroid existing in this galaxy. Our results are confirming that there are at least two very different kinematical systems in NGC 6822

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

Autopistas de la información. Aplicación en cirugía ortopédica

El término autopistas de información describe los servicios de telecomunicaciones que estarán disponibles dentro de 10-15 años. El embrión de estas autopistas es Internet. Internet ofrece 2 clases de servicios: a) comunicación entre usuarios de todo el mundo, y b) acceso a servicios de información. En el primer grupo de estos servicios encontramos el correo electrónico y los grupos de discusión. En el segundo podemos encontrar servicios como logon remoto, transferencia de ficheros, Gopher o WWW. Describimos cada uno de estos servicios y su aplicación a la ortopedia.Information highway describes the telecomunication services will be working in the next 10-15 years. The embryo of this highway is Internet. Internet offers two kinds of services: a) communication between users around the worid, and b) access to information services. In the first group of this services we can find electronic mail and news group. In the second group we can find services such as telnet, file transfer, Gopher and World Wide Web. We describe each of this kind of services and their applications in orthopaedic surgery

Regresión no lineal mediante la evolución de modelos Híbridos de Redes Neuronales

El presente trabajo es una primera aproximación a la formación de modelos de redes neuronales con unidades ocultas de tipo híbrido (sigmoides, producto) que siendo aproximadores universales, puedan utilizarse como modelos no lineales de regresión cuando las características del espacio de las variables independientes lo aconsejen. Dada la dificultad que presenta la aplicación de algoritmos de aprendizaje de búsqueda local para esta tipología de modelos, se utiliza un algoritmo de programación evolutiva donde se definen operadores de mutación específicos. Los experimentos realizados con cuatro funciones de prueba, las tres funciones de Friedman y una propuesta por los autores, muestran resultados muy prometedores en esta direcció

Revisión taxonómica de Helix zapateri Hidalgo, 1870 (Pulmonata, Trissexodontidae) y su nuevo estatus en la malacofauna ibérica

Alberto Martínez Ortí: [email protected]ón taxonómica de Helix zapateri Hidalgo, 1870 (Pulmonata, Trissexodontidae) y su nuevo estatus en la malacofauna ibérica.— Se realiza la revisión taxonómica y se discute la nueva asignación genérica del taxon ibérico Helix zapateri, mediante la comparación de caracteres conquiológicos con las especies más similares, Hatumia pseudogasulli y Gasullia gasulli, ambas trissexodóntidos. Los estudios conquiológicos nos permiten concluir que Helix zapateri debe ser considerada como una especie válida y designarse como Hatumia zapateri, y que Hatumia pseudogasulli corresponde a un sinónimo posterior de H. zapateri.Taxonomical revision of Helix zapateri Hidalgo, 1870 (Pulmonata, Trissexodontidae) and its new status in the Iberian malacofauna.— A taxonomic revision is made and the new generic assignation of the Iberian taxon Helix zapateri is discussed; its conchological features are compared with the most similar species, Hatumia pseudogasulli and Gasullia gasulli, both trissexodontids. Conchological studies allow us to conclude that Helix zapateri should be considered as a valid species and designated Hatumia zapateri, while H. pseudogasulli is a junior synonym of H. zapateri

Motivation for seeking headship in compulsory education centres: A qualitative approach

Es un hecho constatado que el liderazgo de los directores de los centros educativos es una de las claves del cambio. Su impacto, bien sea de carácter directo o indirecto, ha sido evidenciado en la mejora de los resultados académicos del alumnado, la contribución al desarrollo profesional del equipo docente y la creación y cultivo de comunidades de aprendizaje. Este estudio pretende reconocer cuáles son los motivos que conducen a los directores a acceder al cargo, así como el carácter de su decisión. Para ello, se ha seleccionado de forma intencionada, y con la ayuda de tres inspectores de la Conselleria de Educación, Ciencia y Deporte, a 100 directores de centros de Educación Infantil y Primaria, y Educación Secundaria de la provincia de Alicante. Para la recogida de datos se diseñó una entrevista con preguntas de carácter abierto. Los datos fueron procesados con el programa de análisis cualitativo AQUAD 7. A partir del mismo, se reconoce que la decisión de acceder al cargo es principalmente de carácter individual y que está condicionada fundamentalmente por motivaciones personales. Sin embargo, tales intenciones responden más a una visión institucional y social, que individualista. En relación al perfil de los directores, se aprecia un cariz más social de la decisión de acceso al cargo en las mujeres y los veteranos docentes. Estos datos nos llevan a la conclusión de que conviene prestar atención a las razones que conducen a los directores a acceder al cargo para, desde su reconocimiento, alentar una decisión que cada día menos docentes están dispuestos a tomar.It is a proven fact that the leadership of headteachers is one of the keys to change. Its impact, whether direct or indirect, has been shown to improve the academic performance of students, to contribute to the professional development of the teaching staff and to develop and cultivate learning communities. This study aims to recognise what motivates headteachers to seek office, and the nature of their decision. In order to study this, 100 headteachers of Infant, Primary and Secondary schools in the province of Alicante were intentionally selected with the help of three inspectors from the Regional Ministry of Education, Science and Sport. An open-question interview was designed for the purpose of data collection. Data were processed using AQUAD 7 qualitative analysis programme. It was recognised that the decision to access the position of headteacher was primarily individual in nature and largely influenced by personal motives. But such intentions were found to be the reflection of an institutional and social perspective, rather than of an individualist one. As far as the headteachers’ profile is concerned, it was identified that the decision by female and veteran teachers to seek office had a more social tenor. The data led to the conclusion that the reasons that drive headteachers to take up the position need to be attended to and recognised in order to encourage a decision that fewer and fewer teachers are willing to make

Flamelet structures in spray ignition

In typical liquid-fueled burners the fuel is injected as a high-velocity liquid jet that breaks up to form the spray. The initial heating and vaporization of the liquid fuel rely on the relatively large temperatures of the sourrounding gas, which may include hot combustion products and preheated air. The heat exchange between the liquid and the gas phases is enhanced by droplet dispersion arising from the turbulent motion. Chemical reaction takes place once molecular mixing between the fuel vapor and the oxidizer has occurred in mixing layers separating the spray flow from the hot air stream. Since in most applications the injection velocities are much larger than the premixed-flame propagation velocity, combustion stabilization relies on autoignition of the fuel-oxygen mixture, with the combustion stand-off distance being controlled by the interaction of turbulent transport, droplet heating and vaporization, and gas-phase chemical reactions. In this study, conditions are identified under which analyses of laminar flamelets canshed light on aspects of turbulent spray ignition. This study extends earlier fundamental work by Liñan & Crespo (1976) on ignition in gaseous mixing layers to ignition of sprays. Studies of laminar mixing layers have been found to be instrumental in developing un-derstanding of turbulent combustion (Peters 2000), including the ignition of turbulent gaseous diffusion flames (Mastorakos 2009). For the spray problem at hand, the configuration selected, shown in Figure 1, involves a coflow mixing layer formed between a stream of hot air moving at velocity UA and a monodisperse spray moving at velocity USUA. The boundary-layer approximation will be used below to describe the resulting sl ender flow, which exhibits different igniting behaviors depending on the characteristics of t he fuel. In this approximation, consideration of the case U A = U S enables laminar ignition distances to be related to ignition times of unstrained spray flamelets, thereby pro viding quantitative information of direct applicability in regions of low scala r dissipation-rate in turbulent reactive flows (see the discussion in pp. 181–186 of Peters (2000)) . This report is organized as follows. Effects of droplet dispersion dynamics on ignition of sprays in turbulent mixing layers are discussed in Section 2. The formulation f or ignition in laminar mixing layers is outlined in Sections 3 and 4. The results are presented in Section 5. In Section 6, the mixture-fraction field and associated scalar dissipat ion rates for spray ignition are discussed. Finally, some brief conclusions are drawn in Section 7