The present work deals with the multi-objective optimization of an industrial Isoprene production unit by using Genetic Algorithm (GA). The chemical process consists basically of a dimerization reactor and a separation column train. The GA-search was chosen as an optimization tool because of their successful application in many industrial optimization problems Laquerbe et al., 2001;Pibouleau et al., 1999). Then, the aim of this paper is to present and discuss the applicability of a GA as an alternative procedure for a multi-objective optimization of an industrial process that may be difficult to handle by classical methods. In this case the optimization of the entire plant involves 21 variables to be optimized. So, in order to decrease the dimensionality of the problem, the global model was divided into three sections and each one was optimized separately, but sequentially, by using the optimal conditions from previous optimization section procedure. For this, a multi-objective genetic algorithm (MOGA) based on a Pareto sort (PS) procedure was implemented to manage this specific problem.
The number of papers published by the Brazilian scientific community in all fields and indexed by the ISI (Institute of Scientific Information, Philadelphia, USA) has steadily increased since 1981. It is of interest to compare the evolution of the number of publications for different countries and in different fields. For this purpose, the ISI's National Science Indicators Database -NSI was used. The NSI is a database of summary publication and citation statistics for the period 1981-2002 that reflects research performance in over 170 countries classified into 105 separate fields in the sciences, social sciences, arts and humanities.Brazil's share of world science papers has grown from less than 0.50 % of ISI-indexed papers published during 1981 to 1985 -or roughly 11,100 papers -to 1.32 % of the database, or about 48,500 papers, in the most recent 5 year period (1998)(1999)(2000)(2001)(2002). Thus, Brazil has increased its position in the world publication statistics from 28 th to 18 th place in 21 years. If we consider the growth rate in the period 1981-2002 for the 22 countries that had a greater than 1 % share in the most recent 5 year period, Brazil's performance is even more outstanding. Brazil's 4.4 fold growth rate is the fifth largest, exceeded only by South Korea (33.1), Taiwan (13.6), China (8.9) and Spain (4.7). The need to sustain and, if possible, increase this effort is obvious considering the figures presented here.Another interesting aspect is the contribution of each field within the countries. Of the five countries above with the fastest growth rate, the profiles of Brazil and Spain are the most similar to the average world distribution. South Korea, China and Taiwan, in contrast, have above average contributions from fields like engineering, chemistry and materials science relative to the world average.Within a country, the evolution of the various fields can be assessed by comparison of the relative growth rate of the field. In the case of Brazil, the growth rate of 30.2 for chemical engineering is by far the highest.
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