Lattice calculations on the spectrum of Dirac and Dirac-K\"ahler operators

We present a matrix technique to obtain the spectrum and the analytical index of some elliptic operators defined on compact Riemannian manifolds. The method uses matrix representations of the derivative which yield exact values for the derivative of a trigonometric polynomial. These matrices can be used to find the exact spectrum of an elliptic operator in particular cases and in general, to give insight into the properties of the solution of the spectral problem. As examples, the analytical index and the eigenvalues of the Dirac operator on the torus and on the sphere are obtained and as an application of this technique, the spectrum of the Dirac-Kahler operator on the sphere is explored.Comment: 11 page

Business Cycle and Speculative Pressures in a Target Zone

In the past time, most economies have suffered cyclical fluctuations in their activity which may influence the optimal use of productive factors in long slow-growth phases or price stability in periods of fast growth. This paper focuses on the possible interrelationship between business cycles and exchange rate ‡uctuations. We have chosen the European Monetary System framework in the nineties, from June 1989 to December 1998, because the Peseta belonged to the EMS during that time. This sample is specially interesting because it includes the worst crisis of the System in 1992-93 and the following ones affecting emerging countries like Mexico, Brazil or Russia at the end of the decade. We use a Binary Dependent Variable Logit Model to estimate the readjustment probability inside a band for two currencies, the Peseta and the french Franc . We calculate the dependent variable values from a Markov-Switching Regime Model with constant transition probabilities. We prove that it is a suitable method and that it allows both real and monetary variables to be identified in order to explain speculative pressures.Readjustment Probability, Speculative Pressures, Economic Fluctuations.

Componentes de la Gramática de la Lengua Española utilizables en la confección de mapas conceptuales

En este artículo se describen y analizan los elementos morfológicos y sintácticos de la gramática de la lengua española; los cuales podrían utilizarse con mayor precisión para representar conceptos y palabras de enlace durante la confección de mapas conceptuales, como herramientas didácticas significativas, colaborativas y constructivistas.In this article, morphological and syntactic elements of the Spanish language grammar are described and analyzed, which could be used to more accurately represent concepts and linking words for conceptual mapping as meaningful teaching collaborative constructive tools

Lexías utilizadas por los estudiantes de noveno año del período lectivo 2009 del Instituto de Educación Integral para referirse a personas homosexuales

Se identifican las lexías utilizadas para referirse a las personas homosexuales por los estudiantes de noveno del período lectivo 2009 del Instituto de Educación Integral de Las Nubes, Coronado, Costa Rica; esto con el fin de determinar la frecuencia de uso, situaciones comunicativas y carácter semántico de estas palabras, según la conceptualización constructivista de esta retícula social cerrada (los adolescentes). A partir de estos datos, se analiza el nivel ideológico de aceptación y rechazo de estos jóvenes hacia la comunidad homosexual en general. Al final, se brindan criterios y recomendaciones a los docentes para el aprovechamiento y discusión sobre el uso de estas palabras en el aula

SOBRE UNA PROPUESTA DE LECTURAS DE DIEZ CUENTOS DE HANS CHRISTIAN ANDERSEN

Se presenta una propuesta metodológica de lecturas de diez cuentos de Hans Christian Andersen, aplicable a una situación de aula de estudiantes de quinto grado de la Escuela de San Rafael de Coronado. Dicho enfoque se orienta desde una perspectiva del valor pragmático de la literatura, en donde el niño y la niña se constituyan a sí mismos como lectores-estudiantesindividuos sociales simultáneamente, a medida que ejecutan su capacidad crítico-analítica, abstracta, simbólica, comparativa, lingüística y representativa sobre la discursividad hegemónica de la identidad y en contra de la dogmática función social del abordaje metodológico cotidiano de los textos literarios aún en las aulas costarricenses. Es por ello que resultan imperativos lecturas y análisis (de)constructivos de textos, literarios propiamente en este caso, los cuales problematicen la institucionalidad del lenguaje en los procesos de enseñanza y aprendizaje

Signalling in voice over IP Networks

Voice signalling protocols have evolved, keeping with the prevalent move from circuit to packet switched networks. Standardization bodies have provided solutions for carrying voice traffic over packet networks while the main manufacturers are already providing products in workgroup, enterprise, or operator portfolio. This trend will accrue in next years due to the evolution of UMTS mobile networks to an “all-IP” environment. In this paper we present the various architectures that are proposed for signalling in VoIP, mainly: H.323, SIP and MGCP. We also include a brief summary about signalling in classical telephone networks and, at the end, we give some ideas about the proposed “all-IP” architectures in UMTS 3G mobile networks.Publicad

Multicast traffic aggregation in MPLS-based VPN networks

This article gives an overview of the current practical approaches under study for a scalable implementation of multicast in layer 2 and 3 VPNs over an IP-MPLS multiservice network. These proposals are based on a well-known technique: the aggregation of traffic into shared trees to manage the forwarding state vs. bandwidth saving trade-off. This sort of traffic engineering mechanism requires methods to estimate the resources needed to set up a multicast shared tree for a set of VPNs. The methodology proposed in this article consists of studying the effect of aggregation obtained by random shared tree allocation on a reference model of a representative network scenario.Publicad

Customer-oriented risk assessment in Network Utilities

For companies that distribute services such as telecommunications, water, energy, gas, etc., quality perceived by the customers has a strong impact on the fulfillment of financial goals, positively increasing the demand and negatively increasing the risk of customer churn (loss of customers). Failures by these companies may cause customer affection in a massive way, augmenting the intention to leave the company. Therefore, maintenance performance and specifically service reliability has a strong influence on financial goals. This paper proposes a methodology to evaluate the contribution of the maintenance department in economic terms, based on service unreliability by network failures. The developed methodology aims to provide an analysis of failures to facilitate decision making about maintenance (preventive/predictive and corrective) costs versus negative impacts in end-customer invoicing based on the probability of losing customers. Survival analysis of recurrent failures with the General Renewal Process distribution is used for this novel purpose with the intention to be applied as a standard procedure to calculate the expected maintenance financial impact, for a given period of time. Also, geographical areas of coverage are distinguished, enabling the comparison of different technical or management alternatives. Two case studies in a telecommunications services company are presented in order to illustrate the applicability of the methodology