Electrodynamic approach for description of mass transfer phenomena

Based on the equations of macroscopic electrodynamics, the article considers the most important consequences from the point of view of practical application for condensed matter. It has been theoretically shown that a virtual molecular filter with a fairly high degree of selectivity can be used for them. The theoretical substantiation of mass transfer processes in condensed systems is presented for cases of external influence on them when solving problems of technological change of macroscopic properties of a molecular system. Monitoring problems are indicated when moving the minimum amount of substance in the case of mass transfer for processes: diffusion, adsorption, capillary filtration. The functioning of the filter is based on the theory of macroscopic electrodynamics, namely, on how the space charge density is distributed in the sample under study. The results obtained make it possible to evaluate the physicochemical changes that occur in a condensed medium under external technological influence. The presented theoretical research results can serve as the basis for improving the methods of electrometric monitoring of gaseous and liquid media of unknown qualitative and quantitative composition.

High-performance Planar Thermal Diode with Wickless Components

The characterization "thermal diode" has been used to portray systems that spread heat very efficiently in a specific direction but obstruct it from flowing in the opposite direction. In this study, a planar vapor chamber with a wickless, wettability-patterned condenser is fabricated and tested as a thermal diode. When the chamber operates in the forward mode, heat is naturally driven away from the heat source; in the reverse mode, the system blocks heat backflow, thus working as a thermal diode. The low-profile assembly takes advantage of the phase-changing properties of water inside a closed loop comprised of a classical thin-wick evaporator opposing a wickless wettability-patterned condenser, when the chamber operates in the forward (heat-transporting) mode. The wettability patterned plate -when on the cooled side- enables spatial controlled dropwise and filmwise condensation and offers an efficient transport mechanism of the condensed medium on superhydrophilic wedge tracks by way of capillary forces. The same chamber acts as a thermal blocker when the opposing wick-covered plate is on the cool side, trapping the liquid in the pores and blocking heat flow. With this system, thermal diodicities exceeding 20 have been achieved, and are tunable by altering the wettability pattern as needed for different purposes. The present vapor chamber - thermal diode design could be well-suited for an extensive range of thermal-management applications, ranging from aerospace, spacecraft, and construction building materials, to electronics protection, electronics packaging, refrigeration, thermal control during energy harvesting, thermal isolation, etc.

О возможности использования спектрального анализа для исследования структуры линии сигнала ядерного магнитного резонанса

The necessity of recording the spectrum of nuclear magnetic resonance in a weak field from a condensed medium with express control of its state is substantiated. The conditions are established that allow the registration of nuclear magnetic resonance spectra in a weak field. A new design of a small-sized nuclear magnetic spectrometer for recording the NMR spectrum in a weak magnetic field from a volume of a condensed medium of about 3.0 ml has been developed. The results of experimental studies of various media are presented.

On the influence of clustering processes in the liquid structure on Raman scattering

A mathematical relation has been obtained that makes it possible to calculate the polarizability of a polyatomic molecule in the structure of a cluster. It is shown that the scattered frequencies in the Raman effect are proportional to the square root of the number of particles in the most probable (or average) cluster in the liquid structure. The appearance of frequencies in the far part of the Raman spectrum region is caused by the processes of intermolecular interactions in clusters and the processes of disintegration or formation of cluster systems in the structure of disordered condensed media. According to the proposed model and experimental data in the frequency range 20–1300 cm-1, it has been carried out the comparison of the values of the calculated frequencies of the Raman spectrum and their mutual position, which has shown the adequacy of the proposed model. The cluster model of liquid structure and the methods of mathematical statistics and statistical thermodynamics make it possible to expand the capabilities of the classical theory of Raman scattering in liquids and to predict the position of spectral bands in Raman spectra in the far long-wavelength region of the spectrum. It is revealed that the formation and breakdown of the most probable clusters is associated with the correlations of the most stable clusters (in terms of the number of particles) in a condensed medium with the Fibonacci numbers.

Casimir Force between Two Vortices in a Turbulent Bose–Einstein Condensate

We consider the Casimir force between two vortices due to the presence of density fluctuations induced by turbulent modes in a Bose–Einstein condensate. We discuss the cases of unbounded and finite condensates. Turbulence is described as a superposition of elementary excitations (phonons or BdG modes) in the medium. Expressions for the Casimir force between two identical vortex lines are derived, assuming that the vortices behave as point particles. Our analytical model of the Casimir force is confirmed by numerical simulations of the Gross–Pitaevskii equation, where the finite size of the vortices is retained. Our results are valid in the mean-field description of the turbulent medium. However, the Casimir force due to quantum fluctuations can also be estimated, assuming the particular case where the occupation number of the phonon modes in the condensed medium is reduced to zero and only zero-point fluctuations remain.

Study of corrosion of gas production infrastructure objects in the presence of CO2 by the methods of analytical control

Promising domestic gas and gas condensate fields are characterized by the presence of CO2 in the composition of the extracted raw materials which (in combination with moisture condensation and a number of other factors) stimulates the intensive development of local corrosion processes). The paper presents the results of studying corrosion of gas production objects using methods of analytical control (gas chromatography with mass spectrometry, X-ray fluorescence spectrometry, X-ray diffraction). It is shown that key parameters (CO2 partial pressure, mineralization, pH factor, total pressure, etc.) should be considered with allowance for their expected changes during the life cycle of the field and production facilities. To determine the ultimate local corrosion rates, corrosion tests were carried out under conditions of moisture condensation. The corrosion development under CO2 conditions is shown to depend on the amount of moisture formed during condensation on metal surfaces, composition and content of the condensate in the vapor phase. Monoethylene (MEG) glycol which is used in gas production as a hydrate formation inhibitor can be also present in the condensed medium. MEG concentration also significantly contributes to the rate of corrosion processes Local carbon dioxide corrosion rate can attain several millimeters per year. Analytical methods can be successfully used in combination with other control methods to predict and monitor a corrosion situation (content of a corrosion inhibitor, presence of the corrosion products or deposits, etc.) at gas production facilities.

ON THE NEW EXPLICIT SOLUTIONS OF THE FRACTIONAL NONLINEAR SPACE-TIME NUCLEAR MODEL

In this research, the analytical and numerical solutions of the fractional nonlinear space-time Phi-four model are investigated by employing two systematic schemes and the B-spline schemes. A new fractional operator definition is applied to this model to convert the model from its fractional formula to an integer-order nonlinear ordinary differential equation. The considered model is of major interest for studying the nuclear interaction, elementary particles in a condensed medium, and propagation of dislocations in crystals. Explicit wave solutions are obtained.

Особенности регистрации спектра ядерного магнитного резонанса конденсированной среды при экспресс-контроле ее состояния

The necessity of recording the spectrum of nuclear magnetic resonance in a weak field from a condensed medium during express control of its state is substantiated. The conditions are established that allow realizing the registration of nuclear magnetic resonance spectra in a weak field. A new design of a small-sized nuclear magnetic spectrometer has been developed for recording the NMR spectrum in a weak magnetic field from the volume of the condensed medium of the order of 3.0 ml. The results of experimental studies of various environments are presented.