Statistics of closed paths in two-dimensional (2D) systems, which just determines the interference quantum correction to conductivity and anomalous magnetoconductance, has been studied by computer simulation of a particle motion over the plane with randomly distributed scatterers. Both ballistic and diffusion regimes have been considered. The results of simulation have been analyzed in the framework of diffusion approximation. They are used for calculation of the magnetic field dependence of magnetoconductance in the model 2D system. It is shown that the anomalous magnetoconductance can be in principle described by the well known expression, obtained in the diffusion approximation, but with the prefactor less than unity and phase breaking length which differs from true value.

With the advent and rapid growth of massive open online courses (MOOCs) in the world education market in the last decade, online learning technologies are becoming increasingly widespread not only in the non-formal education sector but also in higher and supplementary vocational education. The use of MOOCs for implementing educational programs at the universities opens wide opportunities in terms of expanding the educational choice of students, the development of virtual academic mobility, reducing the cost of educational services, and improving the accessibility of education. However, the effectiveness of using different online learning technologies in the educational process of universities and the consequences of their widespread adoption has not been sufficiently explored.In this research a comparative analysis based on an empirical study of the application of different online-learning models in the educational process within a university was carried out. An experiment was undertaken in which different groups of students of the Ural Federal University were encouraged to master some disciplines in the framework of a blended learning model and an online learning model with tutoring support. The results of the pilot study were compared with the training results of a control group of students who mastered the same disciplines in a traditional taught format. It was shown that both models using MOOCs in the educational process demonstrated greater effectiveness in comparison with the traditional model; both in terms of educational outcomes of students and in terms of their satisfaction with the learning process. For engineering and technical disciplines, there is no statistically significant difference in using blended or online learning technologies, whereas for humanitarian disciplines, where the communicative component of the learning process is significant, the blended learning technology produced better results. Conclusions of the empirical research can be useful for heads of educational organizations and teachers in the modernization of the educational process, improving teaching methods, and increasing the effectiveness of new educational technologies. The results of the research will also be used for implementing the State Priority Project "The Modern Digital Educational Environment of the Russian Federation".

The results of an experimental study of interaction quantum correction to the conductivity of two-dimensional electron gas in A3B5 semiconductor quantum well heterostructures are presented for a wide range of T τ -parameter (T τ ≃ 0.03 − 0.8), where τ is the transport relaxation time. A comprehensive analysis of the magnetic field and temperature dependences of the resistivity and the conductivity tensor components allows us to separate the ballistic and diffusion parts of the correction. It is shown that the ballistic part renormalizes in the main the electron mobility, whereas the diffusion part contributes to the diagonal and does not to the off-diagonal component of the conductivity tensor. We have experimentally found the values of the Fermi-liquid parameters describing the electron-electron contribution to the transport coefficients, which are found in a good agreement with the theoretical results.

The interaction correction to the conductivity of 2D hole gas in strained GaAs/InxGa1−xAs/GaAs quantum well structures was studied. It is shown that the Zeeman splitting, spin relaxation and ballistic contribution should be taking into account for reliable determination of the Fermi-liquid constant F σ 0 . The proper consideration of these effects allows us to describe both th temperature and magnetic field dependences of the conductivity and find the value of F σ 0 .

No abstract