Ciencias Economicas Y Empresariales

Desarrollo de ejercicio práctico del registro de las operaciones de una institución gubernamental en El Salvador; acorde al manual de contabilidad gubernamental de acuerdo a las normas para su registro y el manual dado para el registro de dichas operaciones en El Salvador.

In recent years, the unregulated increase of the population in coastal areas of developing countries has become source of concern for both water supply and quality control. In the region of Dakar (Senegal), approximately 80% of water resources come from groundwater reservoirs, which are increasingly affected by anthropogenic pressures. The identification of the main sources of pollution, and thus the aquifer vulnerability, is essential to provide a sound basis for the implementation of long-term geochemically based water management plans in this sub-Saharan area. With this aim, a hydrochemical and isotopic survey on 26 wells was performed in the so-called Peninsula of Cap-Vert. Results show that seawater intrusion represents the main process affecting groundwater chemical characteristics. Nitrates often exceed the World Health Organization drinking water limits: stable isotopes of dissolved nitrate ( $\updelta ^{15}$ N and $\updelta ^{18}$ O) indicate urban sewage and fertilizers as a major source of contamination. Results depict a complex situation in which groundwater is affected by direct and indirect infiltration of effluents, mixing with seawater and freshening processes from below. Besides the relevance of the investigation at a regional level, it represents a basis for decision-making processes in an integrated water resources management and in the planning of similar monitoring strategies for other urban coastal regions.

A finite element method to approximate the vibration modes of a structure in contact with an incompressible fluid is analyzed in this paper. The effect of the fluid is taken into account by means of an added mass formulation, which is one of the most usual procedures in engineering practice. Gravity waves on the free surface of the liquid are also considered in the model. Piecewise linear continuous elements are used to discretize the solid displacements, the variables to compute the added mass terms and the vertical displacement of the free surface, yielding a non conforming method for the spectral coupled problem. Error estimates are settled for approximate eigenfunctions and eigenfrequencies. Implementation issues are discussed and numerical experiments are reported. In particular the method is compared with other numerical scheme, based on a pure displacement formulation, which has been recently analyzed.

This paper addresses the problem of assessing the quality of an a posteriori error estimate of a finite element solution. An error estimate based on local L2-projections is analysed in the case of translation-invariant meshes. It is shown that for general meshes this technique does not lead to an asymptotically exact estimator. The problem is analysed in detail in the one-dimensional setting. It is shown that an asymptotically exact estimator is not the optimal one when the solution is not sufficiently smooth. An optimal estimator for adaptively constructed meshes is given. Finally, a general mathematical framework for the quality assessment of estimators is introduced.