On the Ginzburg-Landau Analysis of the Upper Critical Field Hc2 in MgB2

Temperature dependence of the upper critical field Hc2 (T) for the superconducting magnesium diboride, MgB2, is studied in the vicinity of Tc by using a two-band Ginzburg-Landau (G-L) theory. The temperature dependence of Hc2 (T) near Tc exhibits a positive curvature. In addition, the calculated temperature dependence and its higher order derivatives are also shown to be in a good agreement with the experimental data. In analogy with the multi-band character of Eliashberg microscopic theory, the positive curvature of Hc2 (T) is described reasonably by solving the two-band of G-L theory.Comment: 14 pages, 2 figures, submitted to SUST November 200

Anisotropy of the upper critical field in superconductors with anisotropic gaps. Anisotropy parameters of MgB2

The upper critical field Hc2 is evaluated for weakly-coupled two-band superconductors. By modeling the actual bands and the gap distribution of MgB2 by two Fermi surface spheroids with average parameters of the real material, we show that H_{c2,ab}/H_{c2,c} increases with decreasing temperature in agreement with available data.Comment: 4 pages, 2 figure

Temperature dependence of critical currents of two-gap superconductors

In this paper, we consider the two-gap Ginzburg-Landau (G-L) free energy functional including the interactions, and obtain a very simple and explicit formula which presents the relation between the critical current density and temperature. The result shows that the temperature dependence of critical current density of a two-gap superconductor is of the form Jc ∝ (Tc* − T)1/2 at low temperatures and Jc ∝ (Tc* − T)3/2 near the critical temperature. Our critical current density expression is in accord with the previous theoretical work and experimental data

A Data Science Study For Determining Food Quality: An Application To Wine

In this paper, wine quality is investigated based on physicochemical ingredients which include fixed acidity, volatile acidity, citric acid, residual sugar, chloride, free sulfur dioxide, total sulfur dioxide, density, pH, sulphate and alcohol, by ANFIS (Adaptive Neuro Fuzzy Inference System) method and by random forest algorithm which is a powerful classification algorithm. Although this study specifically investigate the relation between physicochemical ingredients and the quality of wine, the results can be adaped to determination of the quality of any food product in terms of the ingredients.Wo