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In this paper, the transport characteristics of two-dimensional systems has been investigated. Modeling by means of the Yukawa potential, in a wide range of values of the nonideality parameter, has been carried out. The Yukawa potential was chosen because of its wide applicability in the description of screened interactions in plasmas and other systems. A molecular dynamics method was used to determine the transport characteristics. The study was carried out with the aim of expanding the knowledge of heat transfer in two-dimensional systems. The paper presented the results of numerical experiments in which the dependences of the heat transfer and viscosity coefficients on the screening and non-ideality parameters in systems with Yukawa potential were studied. The obtained data can also serve as a basis for further theoretical and experimental studies in the field of transport characteristics of two-dimensional systems. These data not only expand the understanding of the peculiarities of two-dimensional systems, but also can be useful in the design and analysis of nanostructures and various microdevices. [ABSTRACT FROM AUTHOR]

This paper presents a study of the temperature distribution on a universal cryogenic surface when it is cooled to nitrogen temperatures. Using computer simulation methods, in particular the finite element method, it was possible to determine the temperature-time dependences that occur during the cooling of a surface using the heat exchange tubes of different diameters located inside the surface at equal distances from each other. By varying the diameter of the heat exchange tubes, its effect on the cooling intensity was revealed when examining the volumetric temperature distribution: a larger diameter of the heat exchange tube yields a more uniform cooling of the surface. Besides, a larger orifice diameter leads to reaching thermal equilibrium quicker over the entire surface examined. By using a 7 mm orifice diameter, thermal equilibrium was reached 70 seconds after the start of cooling while 5 mm and 3 mm orifice diameters reached temperature equilibrium after 90 and 100 seconds respectively. The results obtained will make it possible to produce cooling of higher quality when designing universal cryogenic surfaces by using heat exchange tubes with certain geometric parameters. [ABSTRACT FROM AUTHOR]

The paper presents the results of study of the effect of irradiation with heavy Ar8+, Kr15+ and Xe22+ ions with energies of 70, 150 and 230 MeV, respectively, on the stability of mechanical properties, in particular, hardness and wear resistance, as well as thermal conductivity, depending on irradiation fluence. The interest in this research topic is due to the wide prospects for the use of nitride ceramics as the basis for structural materials for nuclear and thermonuclear energy, exposed to ionizing radiation, in particular, particles -- fragments of fission of uranium nuclei. During the experiments, dose dependences of changes in strength, mechanical and heat-thermal conductive properties were obtained. It has been established that the decrease in thermal conductivity has a pronounced dependence on both the energy of incident ions and the radiation dose. The obtained dependencies can later be used in the forecasting and design of nuclear power plants, in which it is planned to replace traditional materials with new classes, including ceramics or composite structures. [ABSTRACT FROM AUTHOR]

Utilization of the thermoelectric materials in cooling/heating, converting used heat into electrical energy becomes the crucial phenomenal investigation, which new thermoelectric materials have been discovered every day. Thermoelectric materials often require a description of the electrical conductivity and thermoelectric power of the sample from room temperature to 900 K. This paper is presented the study results in thermal conductivity and heat capacity of nanocrystalline copper sulfides K0.01Cu1.85S and K0.04Cu1.85S at the temperature range between 300 K and 700 K. As well as, this work shows the figures of X-ray phase analysis, differential scanning calorimetry (DSC) and differential thermal analysis of alloys. In the investigated temperature range Zeebeck coefficient α for K0,01Cu1,85S fluctuate all around the period, but the figures for K0.04Cu1.85S increase to reaching a pick of around 1.96 mV/K, before falling to around 0.32 mV/K. For the studied alloys, a strong contrast in electronic conductivity in both components of the alloy was observed and a dramatic decrease in thermal conductivity (from 2.0 to 0.5 W ∙ m-1 ∙ K-1), leading to the very high local peak value of the dimensionless thermoelectric figure of merit ZT = 9.67, which is important for possible technical applications. We compared and analyzed obtained data with previous materials and focused on the estimation of the thermoelectric figure of merit of the nanocrystalline copper sulfides. [ABSTRACT FROM AUTHOR]