The time dependence of the surface potential of an insulating material is theoretically investigated in the case of simultaneous surface and volume ohmic conduction. When the material presents a constant surface conductivity, the first part of the decrease with time of the surface potential is strongly influenced by the initial distribution of charges and cannot be used to determine the surface conductivity. On the other hand, at rather long times after the surface has been charged, the potential of the surface follows an exponential variation with time, the expression of the corresponding time constant is given in different cases. This model is found in good agreement with experiments performed with photo-oxidized epoxy resins placed in a humid atmosphere.

Calorimetric studies have been made in glassy Se80−xTe20Sbx where 0 ≤ x ≤ 15 with a view to calculate the crystallization kinetic parameters. Multi scan technique has been used to calculate the activation energy of crystallization ΔE and the order parameter (n). The results indicate that ΔE is highly composition dependent in these glasses. A discontinuity in ΔE is observed at 10% of Sb which is explained in terms of mechanically optimised structure at a particular average co-ordination number.

In this work, we study the non–Gaussian dynamic of the magnetic field lines of a plasma confined in a toroidal configuration. We have used the Fourier paths technique in order to calculate the kurtosis of the magnetic field lines. We have also calculate numerically this quantity. The magnetic field lines are described by the standard mapping. A comparison between our analytical and numerical calculations has been done.

The true and apparent temperature of samples during the deposition of III-V layers by molecular beam epitaxy changes as a result of the variation in spectral emissivity ϵ with layer thickness. Taking into account the infrared optical properties of these materials, we modelized the variations of the true sample temperature and the apparent temperature (as determined by pyrometric measurement) during the growth. We limited our study to deposits involving at least one absorbing material (at the pyrometer wavelength), for example GaSb, InAs or InSb. We showed that our simple model can agree reasonably with experiments in the 400−500 °C temperature range.