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Analytical inverse model with flexible parameters for dynamic hysteresis loops modelling

Nova I., Zemanek I.

Przegląd Elektrotechniczny

2011

R. 87, nr 9b

89-92

Analytical inverse model was proposed to find simple mathematical approximation of dynamic hysteresis loops of soft magnetic materials. It consists of dynamic loop construction from three components by means of mathematical functions. Favourable mimicking coefficients were searched, which depend on excitation amplitude and frequency. The nature of its behaviour was studied in order to be able to predict the loop shape. The model was tested for opened specimen of classic silicon electrical steel at sinusoidal excitation, measured by compensation ferrometer.

Zaproponowano inwersyjny model analityczny do opisu matematycznego dynamicznej pętli histerezy materiałów magnetycznie miękkich. Model był sprawdzony dla próbki otwartej klasycznej blachy elektrotechnicznej przy sinusoidalnym magnesowaniu.

Determination of the geometry function for a brachytherapy seed, comparing MCNP results with TG-43U1 analytical approximations

Raisali G., Ghonchehnazi M. G., Shokrani P., Sadeghi M.

Nukleonika

2008

Vol. 53, No. 2

45-49

Geometry function is the only dosimetry parameter of a brachytherapy source seed, introduced in TG-43U1 protocol which is determined using calculational methods rather than physical measurement. In order to evaluate the accuracy of point and line source approximations, for calculation of the geometry function, the MCNP computer code has been used for a typical brachytherapy seed and the results have been compared. The MCNP has been used to simulate the geometry and activity distribution of a Pd-103 seed in order to calculate the geometry function for various angles and distances from the source. The comparison of results shows that at distances close to the source, the values predicted with different methods are not in agreement. The difference between the MCNP calculations and line approximation for small angles from ? = 0 to 15° is about 27% at 0.25 cm from the seed center. This difference is so much higher for point source approximation (up to a factor of 3) even up to distances of 0.5 cm from the source. As ? increases, the difference between MCNP and approximate methods is reduced. Therefore, for small distances from brachytherapy seeds, it is recommended to calculate the geometry function using more detailed methods instead of point and linear source approximations. This will provide more accurate results for other TG-43U1 dosimetry parameters such as radial dose function or anisotropy function which for some points are calculated via interpolation or extrapolation of the available discrete dosimetry data.