Browsing by Issue Date, starting with "2008-11"
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- Conforto Térmico em Meio HospitalarPublication . Alberto Alves Carvalhais, Carlos; Neves, Paula; Lourenço, Irina; Torres Costa, JoséComunicação apresentada no 7º Congresso Nacional de Saúde Ocupacional. Introdução e Objectivos: A atmosfera do local de trabalho deve garantir a saúde e o bem estar dos trabalhadores. Os parámetros especificados na legislação nacional que dizem respeito ao ambiente térmico, cingem-se aos valores de temperatura e humidade do ar preconizados pelo DLn 243/86 de 20 de Agosto. Para além da conformidade legal dos parámetros legislados, este trabalho objectivou a determinação de indices de conforto térmico e as sensações e preferências térmicas, a partir de um estudo de campo efectuado em meio hospitalar, durante os meses de Maio e Junho de 2008.
- Possible Adaptive Control by Tangent Hyperbolic Fixed Point Transformations Used for Controlling the Φ6-Type Van der Pol OscillatorPublication . Tar, József K.; Bitó, János F.; Rudas, Imre J.; Kozłowski, Krzysztof R.; Tenreiro Machado, J. A.In this paper a further step towards a novel approach to adaptive nonlinear control developed at Budapest Tech in the past few years is reported. Its main advantage in comparison with the complicated Lyapunov function based techniques is that its fundament is some simple geometric consideration allowing to formulate the control task as a Fixed Point Problem for the solution of which various Contractive Mappings can be created that generate Iterative Cauchy Sequences for Single Input - Single Output (SISO) systems. These sequences can converge to the fixed points that are the solutions of the control tasks. Recently alternative potential solutions were proposed and sketched by the use of special functions built up of the “response function” of the excited system under control. These functions have almost constant values apart from a finite region in which they have a “wrinkle” in the vicinity of the desired solution that is the “proper” fixed point of these functions. It was shown that at one of their sides these fixed points were repulsive, while at the opposite side they were attractive. It was shown, too, that at the repulsive side another, so called “false” fixed points were present that were globally attractive, with the exception of the basins of attraction of the “proper” ones. This structure seemed to be advantageous because no divergences could occur in the iterations, the convergence to the “false” values could easily be detected, and by using some ancillary tricks in the most of the cases the solutions could be kicked from the wrong fixed points into the basins of attraction of the “proper ones”. It was expected that via adding simple rules to the application of these transformations good adaptive control can be developed. However, due to certain specialties of these functions practical problems arose. In the present paper novel transformations are presented that seem to evade these difficulties. Their applicability is illustrated via simulations in the adaptive control of the popular nonlinear paradigm, the Φ6 Van der Pol oscillator.
- Application of Fractional Calculus in Engineering SciencesPublication . Tenreiro Machado, J. A.The Fractional Calculus (FC) goes back to the beginning of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades, due to the progress in the area of chaos and nonlinear dynamics that revealed subtle relationships with the FC concepts. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. Having these ideas in mind, the paper discusses the application of FC in engineering sciences.
- A Survey of Technologies for Climbing Robots Adhesion to SurfacesPublication . Silva, Manuel F.; Tenreiro Machado, J. A.; Tar, József K.Climbing robots are being developed for applications ranging from cleaning to inspection of dif cult to reach constructions. These machines should be capable of travelling on different types of surfaces (such as oors, walls, ceilings) and to walk between such surfaces. Furthermore, these machines should adapt and recon gure for various environment conditions and should be self-contained. Regarding the adhesion to the surface, they should be able to produce a secure gripping force using a light-weight mechanism. Bearing these facts in mind, this paper presents a survey of different technologies used for climbing robots adhesion to surfaces.
- Fractional Control of Two Cooperating ManipulatorsPublication . Ferreira, N. M. Fonseca; Tenreiro Machado, J. A.; Tar, József K.This paper analyzes the dynamic performance of two cooperative robot manipulators. It is studied the implementation of fractional-order algorithms in the position/force control of two cooperating robotic manipulators holding an object. The simulations reveal that fractional algorithms lead to performances superior to classical integer-order controllers.
- Photodynamic inactivation of recombinant bioluminescent Escherichia coli by cationic porphyrins under artificial and solar irradiationPublication . Alves, Eliana; Carvalho, Carla M. B.; Tomé, João P. C.; Faustino, Maria A. F.; Neves, Maria G. P. M. S.; Tomé, Augusto C.; Cavaleiro, João A. S.; Cunha, Ângela; Mendo, Sónia; Almeida, AdelaideA faster and simpler method to monitor the photoinactivation process of Escherichia coli involving the use of recombinant bioluminescent bacteria is described here. Escherichia coli cells were transformed with luxCDABE genes from the marine bioluminescent bacterium Vibrio fischeri and the recombinant bioluminescent indicator strain was used to assess, in real time, the effect of three cationic meso-substituted porphyrin derivatives on their metabolic activity, under artificial (40 W m−2) and solar irradiation (≈620 W m−2). The photoinactivation of bioluminescent E. coli is effective (>4 log bioluminescence decrease) with the three porphyrins used, the tricationic porphyrin Tri-Py+-Me-PF being the most efficient compound. The photoinactivation process is efficient both with solar and artificial light, for the three porphyrins tested. The results show that bioluminescence analysis is an efficient and sensitive approach being, in addition, more affordable, faster, cheaper and much less laborious than conventional methods. This approach can be used as a screening method for bacterial photoinactivation studies in vitro and also for the monitoring of the efficiency of novel photosensitizer molecules. As far as we know, this is the first study involving the use of bioluminescent bacteria to monitor the antibacterial activity of porphyrins under environmental conditions.