Social Security and the search behaviour of workers approaching retirement

This paper explores the links between unemployment, retirement and their associated public insurance programs. It is a contribution to a growing body of literature focused on a better understanding of the labor behavior of advanced-age workers, which has gained importance as the pension crisis looms. It also contributes to the literature of optimal unemployment insurance by exploring the interaction of unemployment benefits and retirement pensions. The analysis combines the development of a new theoretical model and a detailed exploration of the empirical regularities using the Spanish Muestra Continua de Vidas Laborales (MCVL) dataset. The model is an extension of the standard search model, designed to reproduce the non-stationary environment faced by workers of advanced ages (in the age range 50/65). Via calibrated simulations we show that the basic empirical re-employment and retirement patterns can be considered as rational responses to both the labor market conditions and the institutional incentives. Generous Unemployment Benefits (for durations of up to two years) together with very significant early retirement penalties, make optimal to stay unemployed without searching for large groups of unemployed workers. This moral hazard problem can be substantially alleviated through institutional reform. We explore several potential reforms and find that changing the details of early retirement pensions seems more promising than changing the Unemployment Benefit system.Unemployment, Retirement, Search models

Contribution of reversible processes to the non-linear dielectric response in hard lead zirconate titanate ceramics

Se estudia la dependencia entre la constante dieléctrica y las pérdidas con el campo eléctrico aplicado, así como entre la constante dieléctrica y las pérdidas dieléctricas. Los resultados muestran que las cerámicas PZT duras no pueden ser decritas por el modelo de Rayleigh, pues la respuesta histerética de estos materiales no puede ser atribuida exclusivamente a la contribución de procesos irreversibles. Las medidas experimentales muestran la existencia de procesos reversibles, relacionados con movimientos de arqueo de dominios que contribuyen a la constante dieléctrica sin producir pérdidas. Esta contribución reversible es independiente del envejecimiento de la cerámica.Peer Reviewe

Retirement incentives, individual heterogeneity and labour transitions of employed and unemployed workers

In this paper we analyze the sensitivity of the labour market decisions of workers close to retirement with respect to the incentives created by public regulations. We improve upon the extensive prior literature on the effect of pension incentives on retirement in two ways. First, by modeling the transitions between employment, unemployment and retirement in a simultaneous manner, paying special attention to the transition from unemployment to retirement (which is particularly important in Spain). Second, by considering the influence of unobserved heterogeneity in the estimation of the effect of our (carefully constructed) incentive variables. Using administrative data, we find that, when properly defined, economic incentives have a strong impact on labour market decisions in Spain. Unemployment regulations are shown to be particularly influential for retirement behaviour, along with the more traditional determinants linked to the pension system. Pension variables also have a major bearing on both workers’ reemployment decisions and on the strategic actions of employers. The quantitative impact of the incentives, however, is greatly affected by the existence of unobserved heterogeneity among workers. Its omission leads to sizable biases in the assessment of the sensitivity to economic incentives, a finding that has clear consequences for the credibility of any model-based policy analysis. We confirm the importance of this potential problem in one especially interesting instance: the reform of early retirement provisions undertaken in Spain in 2002. We use a difference-in-difference approach to measure the behavioural reaction to this change, finding a large overestimation when unobserved heterogeneity is not taken into account.Retirement, unemployment, incentives, Pension system, Unobserved, heterogeneity, Spain.

análisis de la red subterránea de distribución eléctrica de la Zona Centro de Pereira

La importancia de este trabajo radica en que permite identificar las anomalías en la red subterránea de distribución de la zona centro de la ciudad de Pereira (delimitada por la calle 12 y la calle 28 entre carreras 4ª y 10ª), permite analizar el estado actual de la red subterránea, determinar las falencias de la red ante la normatividad vigente y comparar la norma actual con las normas de otras empresas de energía de la región. Por otra parte este trabajo estimula el desarrollo de habilidades y competencias en el diagnóstico de redes subterráneas por parte de los estudiantes, además de ayudar a la EEP a tomar medidas correctivas con relación a las anomalías encontradas. Como antecedentes teóricos en la Universidad Tecnológica de Pereira, solo se tiene el trabajo de grado "sistemas eléctricos de transmisión bajo tierra" [5], en el cual se trató el tema de una manera más general enfocado hacia el cálculo de parámetros de las redes. En la Universidad Tecnológica de Pereira no se encontraron antecedentes prácticos sobre este tipo de trabajo. Objetivos buscados con la realización del trabajo. "objetivo general. Analizar el estado actual de la red subterránea eléctrica en una parte de la zona "centro" de la ciudad de Pereira. "Objetivos específicos. - Recopilar información del estado de la red. - Identificar problemas de la red. - Buscar la normatividad vigente de la red subterránea. - Analizar las falencias de la red ante la normatividad vigente. - Comparar la normatividad vigente de las EEP con normas existentes de otras empresas de la región. En la realización de este trabajo se procedió a destapar cárcamos, caminar por ductos verificando el estado actual de la red subterránea y de esta manera identificar las diferentes anomalías

Nonlinear behavior in a piezoelectric resonator: a method of analysis

Theories used for understanding nonlinear behavior of piezoelectric resonators are usually only valid for a given range of amplitudes. Thus, important discrepancies can sometimes be observed between theory and experiment. In this work, a simplified model of the resonator is assumed in order to extend the analysis of nonlinear behavior to any kind of nonlinear function, without a significant increase of mathematical complexity. Nevertheless, nonlinearities are considered to be weak enough to be taken as perturbations. An asymptotic method is used to obtain the first and second order perturbations of the response to an harmonic excitation applied to the system, and each one is separated into Fourier series. Nonlinearity is described by two functions-/spl Phi/, (S,D,S/spl dot/,D/spl dot/) and /spl Psi/ (S,D,S/spl dot/,D/spl dot/)-that must be added to the constitutive equations that give T and E as functions of S and D. These functions can be split into their symmetrical and antisymmetrical parts, which have different incidence over the perturbation terms. In order to simplify the problem, no mechanical excitation is considered, the electrical one is taken as strictly harmonic, and the current rather than the e.m.f. is taken as initial data. As an application example, this method is applied in order to find the second harmonic generation for a particular kind of nonlinearity.Peer ReviewedPostprint (published version

Multiprocessing for the particle tracking model MODPATH

Particle tracking has several important applications for solute transport studies in aquifer systems. Travel time distribution at observation points, particle coordinates in time and streamlines are some practical results providing information of expected transport patterns and interaction with boundary conditions. However, flow model complexity and simultaneous displacement of multiple particle groups leads to rapid increase of computational requirements. MODPATH is a particle tracking engine for MODFLOW models and source code displays potential for parallel processing of particles. This article addresses the implementation of this feature with the OpenMP library. Two synthetic aquifer applications are employed for performance tests on a desktop computer with increasing number of particles. Speed up analysis shows that dynamic thread scheduling is preferable for highly heterogeneous flows, providing processing adaptivity to the presence of slow particles. In simulations writing particles position in time, thread exclusive output files lead to higher speed up factors. Results show that above a threshold number of particles, simulation runtimes become independent of flow model grid complexity and are controlled by the large number of particles, then parallel processing reduces simulation runtimes for the particle tracking model MODPATH.Peer ReviewedPostprint (published version

Problemas de decisión Bayesiana no paramétrica : aproximación lineal

Tesis Univ. Compl. de Madrid. Dpto. de Estadística operativa. Dir. por. Vicente Quesada Paloma, leída en Madrid el 27 de enero de 1982.Depto. de Estadística e Investigación OperativaFac. de Ciencias MatemáticasTRUEProQuestpu

Extrinsic behaviour of PZT ceramics near the morphotropic phase transition

The aim of this work is to study the dependence of the linear and non-linear dielectric, piezoelectric and mechanical coefficients on the Ti fraction in PZT ceramic compositions near the morphotropic phase boundary. The dependence of these coefficients with the defect concentration is also analysed. Special attention is given to the extrinsic piezoelectric measurements related to the domain wall movement. Since the non-linear behaviour is produced by the extrinsic phenomenon, the non-linear measurements provide a good extrinsic characterization of materials. In all cases the physical explanation of the behaviour is sought.Peer Reviewe