Recent developments in neural network PID autotuning

PID controllers are widely used in industrial applications. Because the plant can be time variant, methods of autotuning of this type of controllers, are of great economical importance, see (Astrom, 1996). Since 1942, with the work of Ziegler and Nichols (Ziegler and Nichols, 1942), several methods have been proposed in the literature. Recently, a new technique using neural networks was proposed (Ruano et al., 1992). This technique has been shown to produce good tunings as long as certain limitations are met.

Recent developments in the Portuguese nut sector

This work aims to present the main results of an overview study of the nut sector in Portugal. Within the group of horticultural products, different kinds of nuts have been receiving financial supports for several years. The objective was the achievement of a technical recovery and the improvement of commercial organisations. In spite of this help, the sector does not show a clear signal of dynamism. In this study, information has been taken from data series on production, exports and imports and also about empirical approaches on market mechanismsT. hese instruments have helpedt o better identify problems that seemto be responsible for the lack of performance of the Portuguese nut sector in international markets.

Structural issues on the portuguese fig production: recent developments

Fig production evolution registered an enormous decrease in Portugal on the last decades. In what concerns any agricultural production and its evolution we have to look to the structural issues affecting the culture trying to understand what is going on and where to act. This paper will begin to show the decrease on Portuguese fig production, according to FAO statistics. Then, we will look to this evolution in parallel with the evolution of farm structure on the last decades that has been quite strong, in Portugal, even if in what concerns farm area and the distribution of farms among area classes there has been only slight modifications. The population evolution is also a matter of importance and we will try to characterize the Portuguese agricultural population, in what concerns educational level and age and then move to fig producers, trying to understand what is the age and educational level of those who produce rig in Portugal. Finally, we will briefly focus on the economics of production. As a conclusion, there will be some appointments on the fig production future in Portugal.