Technical Physics Letters最新文献

A computational scheme is proposed for the numerical solution of the energy equation by the spline collocation method. The spline collocation method uses the representation of cubic splines through normalized B-splines. The system of linear equations with respect to the spline coefficients is solved by the method of variable directions with a variable iterative parameter.

A method for computational modeling of rapidly developing biophysical processes on the basis of physical analogies and the transient damped oscillation theory has been developed. The relevant phenomena, including invasions of aggressive species, have been discussed and epidemics in the form of a series of peaks in the pathogen activity have been compared. The spread of COVID waves in regions turned out to be difficult to predict using conventional systems of equations of the Kermack–McKendrick theory. A new method for forming modeling structures with the included logic that sets the conditions for redefining the system of equations has been developed. It has been proposed to identify key events for changing the right-hand sides of the system of equations on the basis of tracking the changing evolutionary characteristics and transforming parameters of the interaction between the aggressive agent and the environment. Continuous evolution causes the wave-like dynamics; therefore, repeated virus activity outbreaks have been observed. To model the evolving biophysical processes, several wave equations at once should be used, since the properties of oscillations are not preserved. A hybrid model of wave differential equations has been built from a set of redefined activation and damping functions of oscillations selected according to specified conditions, while the oscillation minima remain positive and the wave maxima do not increase indefinitely. Using a new original method, consequences of the event-driven pathogen evolution has been simulated, which is especially reflected on the characteristics of a new series of COVID wave oscillations. Based on the algorithmic implementation of the structure of transitions between behavioral modes in a series of simulation scenarios for the development of epidemic waves in regions depending on immunization factors and estimated efficiency of anti-epidemic measures, scenarios for the development of the epidemic situation with a change in the dominant strains of coronavirus in five regions have been obtained. The method for organizing hybrid models from variable sets of wave equation forms can be applied to the scenario modeling of many stage oscillatory transient modes that arise both during the formation of new neural connections and in electrical circuits with feedback and trigger switching. The physical, biophysical, and social wave processes have a surprisingly large number of common dynamic aspects. Pulse and rapidly damping phenomena similar to epidemic waves are observed, for example, when waves of negative reactions spread in indignant social networks to information with the deliberate dissemination of shocking content. In social networks, there are groups that actively spread the impact and slow down this indignation, as in physics. The main problem in 2005 is the activity of the group of chronic “Long COVID” spreaders.

In the paper, the application of a high-order approximation scheme in numerical modeling of hemodynamic problems that allows adequate numerical modeling of the change in the volume of the cardiac chamber has been considered. A numerical experiment with the developed software module evaluating the efficiency of the high-order approximation scheme in hemodynamic problems with allowance for their specificity has been performed.

Liquid tin is considered to be a promising plasma-facing material used in intra-chamber components of a stationary fusion reactor. Since corrosion in liquid tin is largely due to dissolution of solid metals in liquid tin, the solubility and thermodynamic activity of the main components of the structural material are key parameters for understanding corrosion processes. The solubility of the transition metals Fe, Cr, Nb, Mo, and W in liquid tin has been theoretically calculated and the results obtained have been compared with the experimental data from the literature. The results of experiments on the compatibility of molybdenum with liquid tin at 1050°C are reported. The results obtained agree well with the computational estimate and provide an optimistic basis for continuing the investigations on a wider time basis under the conditions similar to those for in-chamber tokamak components.

A glow discharge in a supersonic gas flow between the central body (cathode) and nozzle (anode) has been theoretically investigated. Features of a glow discharge in a supersonic gas flow have been taken into account in the theoretical model and distributions of the internal characteristics of the discharge along the electric field lines and along the flow have been calculated. It has been found that the characteristics of the discharge in the spatial localization, radiation intensity, and formation of near-electrode zones depend on the current and geometric parameters of the nozzle and central body. The distribution of the main parameters of the discharge is affected by features of the discharge region geometry. Near the cathode, the field is strong and electrons intensively multiply. Then, the field is almost zero and electrons and ions accumulate in a cloud of electrons and ions. The electrodes absorb this electron and ion cloud. In the distributions, the Faraday dark space can be clearly seen. It extends almost to the anode. The discharge of this type can be used to produce hydrogen by direct pumping of methane through the supersonic nozzle with the central body. Each hydrocarbon molecule will be bombarded by electrons, which will result in decomposition of methane into hydrogen and carbon. The high flow rates and low temperatures will facilitate the long-term operation of the device.

The synthesis of a catalyst carrier precursor by sub- and supercritical water oxidation of metallic aluminum followed by iron oxide deposition has been investigated. The dependences of the physicochemical properties of the samples on temperature, reaction time, and supercritical fluid density have been examined. Conclusions have been drawn about the optimum reaction parameters ensuring the maximum specific surface of the samples.

The radiation patterns of mid-infrared graphene antenna arrays with N = 256 emitters have been simulated in the CST MWS software package at the resonant frequencies of the surface plasmon polariton fundamental mode in micro- and nanosized rectangular graphene elements for different values of the chemical potential. It has been shown that, with an increase in the chemical potential, the operating frequencies are retuned towards higher mid-IR frequencies, the radiation pattern width at the half-power level decreases, and the direction of the main lobe of the radiation pattern changes; i.e., electronic scanning of the main beam of the radiation pattern occurs.

A design of a setup is proposed that allows direct measurements to confirm Einstein’s formula E = mc². The main elements of the setup are a supercapacitor and a mass comparator.

Zinc-oxide nanotubes have been synthesized in an electric arc discharge formed between two graphite electrodes in air at a pressure of 66 kPa. Zinc-oxide nanotubes have been obtained. It has been established that, when appropriate conditions are selected, it is possible to achieve the formation of either nanotubes or nanofilms, depending on the goal setting.