This paper presents a computational method for studying the thermal conductivity of molecular crystals that can be used in the educational course of condensed matter physics. This method is based on the Debye model of thermal conductivity in the approximation of the corresponding relaxation times and allows studying the heat transfer processes features in simple molecular crystals at temperatures close to or above Debye temperature. The thermal conductivity is analysed in the framework of modified Debye model in which heat is transferred by low-frequency phonons and above the phonon mobility edge by “diffusive” modes migrating randomly from site to site. The mobility edge ω0 is found from the condition that the phonon mean-free path cannot become smaller than half the phonon wavelength. The contributions of phonon-phonon, one-, and two-phonon scattering to the total thermal resistance of molecular crystals are calculated under the assumption that the different scattering mechanisms contribute additively. The presented computational method will be useful in pedagogical activities for teaching students of physical faculties.

This article is devoted to the implementation of scientific achievements into the educational process of physics specialties students in the framework of study course “Solid State Physics”. In this work, based on our previous scientific results, we present a quantum-mechanical approach that can adequately describe the temperature dependences of the dielectric crystals thermal conductivity. The basic provisions of quantum-mechanical approach are studied by students in the framework of university study course “Solid State Physics” and are based on Einstein and Debye classical models. This approach is based on the assumption that in dielectric crystals heat is transferred due to the phonons (Debye model) and thermal diffusion between the thermally activated neighboring quantum mechanical oscillators directly from site to site on a time scale of one-half of the oscillation period (Einstein model). In term of this consideration the thermal conductivity of molecular crystals are simulated in the framework of thermal conductivity model where heat is transferred by low-frequency phonons with taking into account phonon–rotation coupling, and above the phonon mobility edge by “diffusive” modes. For this purpose the theoretical temperature dependences of the isochoric thermal conductivity have been calculated numerically in the interval near or over the Debye temperature and compared with experimental results for solid C6H12, CHCl3 and CH2Cl2. Using simple molecular crystals as an example it is shows the dualism of the nature of heat transfer processes in the temperature region of the order of the Debye temperature and above. The obtained results will be useful for implementation in the educational process in the study course “Solid State Physics” in particular for understanding the features of heat transfer in the high-temperature range of dielectric crystals existence.

The article addresses one of the most pressing problems for a trading enterprise, namely the problem of routing logistics flows for efficient enterprise management. To optimize itineraries, we use state-of-the-art electronic navigation and mapping systems that can be implemented in modern computer technology, from online services available on any computer to mobile devices. Navigation and mapping systems are distributed software complexes with an array of information stored in database management systems. They involve millions of static objects and huge amounts of dynamic data around the world. To optimize the logistics flows, an algorithm for an automated routing system is described. This system solves the problems of automatic calculation of the construction and recognition of the optimal route between the specified points of its beginning and the end, tracking of movement on a given route and, in the case of congested roads, redirection of logistics flows. Based on the researches and experiments on the formation of a cognitive map in the human mind and the perception of the route description, an algorithm for storing and displaying route data is considered. This algorithm takes into account the personal psychology of perception of cartographic information. Developing an algorithm for describing the routing of trading enterprise traffic flows is creating a model of automatically found path between the predetermined points of its beginning and end. This mapping information is personalized, easy to read, fast to remember, and insensitive to user errors. The proposed algorithm is universal and can be used to solve a wide range of problems of logistic flows optimization.