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Prediction methods for thermophysical properties of metals and alloys such as emissivity are of great interest not only for science but also for the metal working industry as time-consuming and often expensive measurements may not be required. As recent results have shown, an assumed Hagen-Rubens relation for the prediction of emissivity based on electrical resistivity results was not found in the visible spectra. Within this work normal spectral emissivity results obtained with two complete different techniques are presented. On one hand, a multi-wavelength-pyrometry (MWLP) approach has been used to obtain emissivity as a function of temperature at 684.5, 902, and 1570 nm, and on the other hand, a radiance-comparison method was used to obtain emissivity isotherms as a function of wavelength for a range starting from 1 to 24 µm. From results of the radiance-comparison measurements an intersection of the isotherms, often referred to as the emissivity x-point, was found for both investigated materials, tungsten and molybdenum. According to these results, the x-point wavelengths are given by λ x = 1.41 µm for tungsten and λ x = 1.55 µm for molybdenum. Based on these x-points and the MWLP measurements, a new prediction method for the liquid-phase behavior of emissivity is developed and discussed.

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This paper is concerned with the optimization of base load production of hydro energy storage plants within a given time interval at a varying tariff rate. For three real world storage plants in Austria, each of them presenting some characteristic difficulty we discuss both mathematical models and numerical techniques. Beside classical techniques as Dynamic Programming and Simulation two newly developed nonlinear optimization methods were used.The first combines the Homotopy method with the active index set strategy, the second technique is based on decomposition and is strongly directed to the special structure of the problems.