Doklady Physics最新文献

The magnetism of ZnSe supercells doped with 3d transition metals was investigated using the density functional theory. An analysis of the electronic properties of Zn_1–xMe_xSe systems showed additional peaks at the Fermi level due to Me²⁺ 3d levels. The computed magnetic moments for the Me_xZn_1–xSe supercell systems were found to be 4.0 µ_B for Cr_xZn_1–xSe, Fe_xZn_1–xSe, and Ni_xZn_1–xSe, and the main contribution to the magnetization of these systems is from Me d states. First-principles simulation of total energies for ferromagnetic and antiferromagnetic phases indicated the ferromagnetic phase stability of the Cr_xZn_1–xSe, Fe_xZn_1–xSe, and Ni_xZn_1–xSe systems. Our results demonstrated that the magnetization of Me_xZn_1–xSe supercell systems strongly depends on the Me concentration. In addition, Curie temperatures were estimated for the investigated materials. The Cr_xZn_1–xSe and Ni_xZn_1–xSe systems are half-metallic ferromagnetic materials with higher Curie temperatures. The Cr_xZn_1–xSe and Ni_xZn_1–xSe compounds are promising materials for spintronics and Fe_xZn_1–xSe is a paramagnetic compounds and a useful candidate for optoelectronic devices.

The influence of beam velocity and the kappa distribution function on the growth length of electromagnetic ion cyclotron (EMIC) waves in a multi-ion magnetoplasma is analyzed. EMIC waves, characterized by their transverse nature and frequencies below the proton cyclotron frequency, play a vital role in various space plasma phenomena and laboratory plasma environments. The kappa distribution function (k_p), which accounts for non-Maxwellian plasma characteristics with an enhanced high-energy particle tail, is used to model the energy distribution of plasma particles more realistically. We conduct a comprehensive analysis of the nonlinear variation in growth length as a function of wave vector for different beam velocities (V_Dl) and the parameter ({{k}_{p}}), focusing on a plasma composed of multiple ion species such as H⁺, He⁺, and O⁺. Our results reveal that increasing negative beam velocities significantly enhance the growth length of EMIC waves, indicating stronger beam-driven instabilities and wave–particle interactions. Additionally, the growth length rises exponentially with increasing wave vector, particularly at higher beam velocities. The parameter ({{k}_{p}}) exerts a damping effect, where higher values reduce the growth length, suggesting a potential mechanism for controlling wave growth and stabilizing plasma systems. The study also examines how the ({{k}_{p}}) modifies the dispersion relations, growth rates, and resonance conditions of EMIC waves. The non-Maxwellian energy distribution influences the overall wave behavior, along with the kappa distribution high-energy tail intensifying wave–particle interactions and contributing to the dynamics of wave growth. These findings have significant implications for understanding and controlling plasma instabilities in fusion devices, particle accelerators, and magnetospheric environments. They enhance the modeling of space weather phenomena and provide deeper insight into the interaction between beam velocity and non-Maxwellian plasma distributions, offering valuable contributions to the field of plasma physics and space plasma dynamics.

The development of theoretical methods for calculating the entropy of melting of simple substances is reviewed and an attempt is made to explain positional crystal lattice disordering and the melting entropy growth.

Complex heat transfer in an expanded clay production furnace is simulated by two-dimensional differential equations of energy, radiation transfer, motion, continuity, k–ε-turbulence model, and a two-step methane combustion model. The radiation transfer equation is solved using the discrete ordinate method. A comparison of the obtained calculated data with experimental data of other authors is given.

An intelligent information-measuring system for controlling the thermal characteristics of materials is a relevant topic related to the issue of finding the middle of a thermogram working section using a neural network as an advanced and accurate way of processing experimental results. The object of study is an information-measuring system for nondestructive testing of structural transitions in polymers. The aim of this study was to derive a new regression equation for the middle of the working section of a thermogram, depending on the thermal activity of a material and the specific thermal power of a flat heater, using a neural network. The obtained experimental dependences of the temperatures in the middle of the working section of a thermograms can be used by technologists who deal with the development of new polymers and the use of existing ones. New results have been obtained using a neural network and reliably described by the derived regression equation. Using the results, the regression equation has been refined to determine the middle of the working section in the method for nondestructive testing of structural transitions in polymers. Using the regression equation, one can predict the temperatures in the middle of a thermogram working section, depending on the power of the heater and the coefficient of thermal activity of the material under study.

The paper is devoted to the problems of the immersion (classical) method of electrolytic plasma processing. The immersion method is compared with the jet version. The advantages of the jet version of the plasma electrolytic processing unit are revealed, which, for comparative analysis, was used to polish parts of aircraft engines made of heat-resistant alloys. An alternative version of the plasma electrolytic processing technology showed higher selectivity, versatility, and mitigating of the disadvantages of the classic version.

The article presents the results of heat transfer modeling in the in-cylinder part of a piston combined diesel engine using the AVL BOOST commercial package at the design stage. The calculation results are compared with the results of bench tests of the R6ChN 13.2/15.8 diesel engine. Heat transfer similarity equations for calculating heat loss in the cylinder-piston section of a diesel engine are recommended.

The thermal expansion coefficients of fish oil were measured in a heat-conducting calorimeter in the temperature range of 298–363 K and pressures of 0.098–49 MPa. Based on the obtained values of the coefficients of thermal expansion, the density of fish oil was calculated.

An approach to transparent monolithic polycarbonate fracture diagnostics based on the piezoelectric effect is considered. It was shown that the ΔU/U parameter decreases by at least 10 times before the polycarbonate sample begins to be destroyed. It was shown that the electrodes location influence the changes in the piezoelectric voltage. The location of electrodes along the edge of the sample can provide the best conformity between the piezoelectric voltage and the reaction force of the sample to bending deformation.

The results of an experimental study of the swelling of SEVA-113 and polycarbonate polymers in supercritical carbon dioxide are presented. The effects of temperature and pressure on the character of swelling of the selected polymers in supercritical carbon dioxide has been established. The results of joint dispersion of polymer mixtures of EVA and polycarbonate are presented.