A temperature predicting model for manufacturing processes requiring coiling

A model for predicting temperature evolution for automatic controling systems in manufacturing processes requiring the coiling of bars in the transfer table is presented. Although the method is of a general nature, the presentation in this work refers to the manufacturing of steel plates in hot rolling mills. The predicting strategy is based on a mathematical model of the evolution of temperature in a coiling and uncoiling bar and is presented in the form of a parabolic partial differential equation for a shape changing domain. The mathematical model is solved numerically by a space discretization via geometrically adaptive finite elements which accomodate the change in shape of the domain, using a computationally novel treatment of the resulting thermal contact problem due to coiling. Time is discretized according to a Crank-Nicolson scheme. Since the actual physical process takes less time than the time required by the process controlling computer to solve the full mathematical model, a special predictive device was developed, in the form of a set of least squares polynomials, based on the off-line numerical solution of the mathematical model.

Avaliação do potencial alelopático de genótipos de aveia no final do ciclo

Em sistemas de cultivo em semeadura direta, a aveia é uma das culturas de inverno mais importantes entre as que são utilizadas para formação de cobertura morta. Nos tecidos da aveia existem aleloquímicos, o que torna importante o entendimento deste fenômeno nesta cultura. Através da análise da palha de resíduos de genótipos de aveia, bem como dos seus aleloquímicos, poder-se-á obter uma avaliação ampla do seu potencial alelopático. Nesta análise, pode-se verificar que os genótipos de aveia mantém o potencial alelopático no final do ciclo de vida, revelando-se com maior efeito alelopático UFRGS 6, UFRGS 9, UFRGS 10 e UPF 13. Ao mesmo tempo, os genótipos que exibem menor efeito alelopático são UFRGS 12, UFRGS 17, UFRGS 884077 e UPF 12. Os efeitos produzidos por compostos aleloquímicos (ácidos fenólicos) são similares aos provocados pelos extratos dos genótipos de aveia, mostrando uma relação entre o efeito alelopático dessas substâncias e os genótipos testados. Os aleloquímicos apresentam maior fitotoxicidade para as infestantes do que para as culturas, assim como ocorre com os resíduos de genótipos de aveia.

Measuring higher order optical aberrations of the human eye: techniques and applications

In the present paper we discuss the development of "wave-front", an instrument for determining the lower and higher optical aberrations of the human eye. We also discuss the advantages that such instrumentation and techniques might bring to the ophthalmology professional of the 21st century. By shining a small light spot on the retina of subjects and observing the light that is reflected back from within the eye, we are able to quantitatively determine the amount of lower order aberrations (astigmatism, myopia, hyperopia) and higher order aberrations (coma, spherical aberration, etc.). We have measured artificial eyes with calibrated ametropia ranging from +5 to -5 D, with and without 2 D astigmatism with axis at 45º and 90º. We used a device known as the Hartmann-Shack (HS) sensor, originally developed for measuring the optical aberrations of optical instruments and general refracting surfaces in astronomical telescopes. The HS sensor sends information to a computer software for decomposition of wave-front aberrations into a set of Zernike polynomials. These polynomials have special mathematical properties and are more suitable in this case than the traditional Seidel polynomials. We have demonstrated that this technique is more precise than conventional autorefraction, with a root mean square error (RMSE) of less than 0.1 µm for a 4-mm diameter pupil. In terms of dioptric power this represents an RMSE error of less than 0.04 D and 5º for the axis. This precision is sufficient for customized corneal ablations, among other applications.