A genetic neuro-model reference adaptive controller for petroleum wells drilling operations

Motivated by rising drilling operation costs, the oil industry has shown a trend towards real-time measurements and control. In this scenario, drilling control becomes a challenging problem for the industry, especially due to the difficulty associated to parameters modeling. One of the drill-bit performance evaluators, the Rate of Penetration (ROP), has been used in the literature as a drilling control parameter. However, the relationships between the operational variables affecting the ROP are complex and not easily modeled. This work presents a neuro-genetic adaptive controller to treat this problem. It is based on the Auto-Regressive with Extra Input Signals model, or ARX model, to accomplish the system identification and on a Genetic Algorithm (GA) to provide a robust control for the ROP. Results of simulations run over a real offshore oil field data, consisted of seven wells drilled with equal diameter bits, are provided. © 2006 IEEE.

Effect of the Rashba and Dresselhaus spin-splitting terms on the electron g factor in semiconductor quantum wells under applied magnetic fields

We use the Ogg-McCombe Hamiltonian together with the Dresselhaus and Rashba spin-splitting terms to find the g factor of conduction electrons in GaAs-(Ga,Al)As semiconductor quantum wells (QWS) (either symmetric or asymmetric) under a magnetic field applied along the growth direction. The combined effects of non-parabolicity, anisotropy and spin-splitting terms are taken into account. Theoretical results are given as functions of the QW width and compared with available experimental data and previous theoretical works. © 2007 Elsevier B.V. All rights reserved.

Anuario estadístico de América Latina y el Caribe, 1987 = Statistical yearbook for Latin America and the Caribbean, 1987

Incluye Bibliografía

Estudio económico de América Latina y el Caribe 1987 = Economic survey of Latin America and the Caribbean 1987

Incluye Bibliografía

Panorama económico de América Latina, 1987 = Economic panorama of Latin America, 1987

Incluye Bibliografía

Evolution of fiscal policy in the Caribbean: based on data for the period 1987-1996

Includes bibliography

Excitons in undoped AlGaAs/GaAs wide parabolic quantum wells

In this work the electronic structure of undoped AlGaAs/GaAs wide parabolic quantum wells (PQWs) with different well widths (1000 and 3000 ) were investigated by means of photoluminescence (PL) measurements. Due to the particular potential shape, the sample structure confines photocreated carriers with almost three-dimensional characteristics. Our data show that depending on the well width thickness it is possible to observe very narrow structures in the PL spectra, which were ascribed to emissions associated to the recombination of confined 1s-excitons of the parabolic potential wells. From our measurements, the exciton binding energies (of a few meV) were estimated. Besides the exciton emission, we have also observed PL emissions associated to electrons in the excited subbands of the PQWs. © 2010 IOP Publishing Ltd.

Escritos de Celso Furtado, 1948-1987: bibliografía existente en la Biblioteca CEPAL

Comprende citas de libros, documentos, artículos de publicaciones periódicas, conferencias, comentarios, etc., publicados entre 1948 y 1987

Escritos de don Norberto González, 1958-1987: bibliografía existente en la Biblioteca CEPAL

Contiene artículos, comentarios, documentos, estudios e informes.

Escritos de Aníbal Pinto Santa Cruz, 1947-1987: bibliografía existente en la Biblioteca CEPAL

Se incluyó además en la investigación la Biblioteca de la Fundación Educacional "Roberto Bellarmino" y la Biblioteca de la Facultad Latinoamericana de Ciencias Sociales (FLACSO)

Ahorro e inversión bajo restricción externa y fiscal: el caso de Chile, 1982-1987

Incluye Bibliografía

Reformas del sistema de salud en Venezuela (1987-1999): balance y perspectivas

Incluye Bibliografía