Journal of Contemporary Physics (Armenian Academy of Sciences)最新文献

The results of the ten years of diamond synthesis from graphite in industrial volumes (2 × 10⁸ carats) based on the PA “Almaz”, Yerevan, Armenia are analyzed. Theoretical studies are used in the physics of first-order phase transitions. The process of diamond growth is described within the frames of the transition state model using the Fokker-Planck and Zeldovich–Frenkel equations. The formation of a diamond carbon phase nucleus is the result of a direct graphite-diamond phase transition under high pressures and temperatures.

The magnetic size effects of single-domain nickel nanoparticles encapsulated in a graphite-like carbon shell (Ni@C nanocomposites) have been studied. Along with ferro- and superparamagnetic characteristics, the samples exhibit paramagnetism due to surface nickel ions formed through charge transfer from the carbon matrix. A detailed analysis of the total curves of magnetization M(H) and coercivity at 10 K was carried out and the corresponding magnetic parameters were determined.

Single crystals of YAlO₃-Er (YAP:Er) are grown by the Bridgman method from melts with different Y/Al ratio. The structural defects and color centers are compared for Y/Al = 1 and Y/Al > 1, as well as formed in the processes of gamma-irradiation and thermal treatment. Based on the obtained data, the growth conditions of YAP:Er crystals free of color centers and twins are determined. Spectral-luminescent properties of crystals are investigated: the absorption and luminescent spectra are registered in the polarized light, the luminescence kinetics is investigated and the lifetime of the ⁴I_13/2 level of Er³⁺ ion is determined.

The results of modeling the electrophysical characteristics of reusable capacitive immunosensors based on the electrolyte-insulator-semiconductor (EIS) structure are presented. Electrophysical and geometrical data on the most common viruses are collected and classified from a unified point of view. The results of theoretical computations of the capacitance and capacitive sensitivity of multiple-use EIS immunosensors for COVID-19 viruses are presented and analyzed.

We study an analytically solvable pseudoscalar interaction potential for the one-dimensional stationary Dirac equation, which consists of power terms proportional to ({{x}^{{ - 1}}}), ({{x}^{{ - 1/3}}}), and ({{x}^{{1/3}}}). This potential is classified as conditionally exactly solvable due to the fixed strength of the first term at a specific constant. We present the general solution to the Dirac equation in terms of non-integer index Hermite functions, which are distinct from the conventional integer index Hermite polynomials. We analyze the energy spectrum of the bound states and the eigenfunctions and compare the results with the case without the ({{x}^{{ - 1/3}}}) term.

Within the framework of a three-dimensional model, the burnup process of the core of the WWER-440 reactor was studied using measurements of the operating cycles of the Armenian NPP (ANPP). Simulation results showed that a model study that takes into account only the temperature dependence of the thermal conductivity of the PATHS (PARCS Advanced Thermal Hydraulic Solver) fuel leads to discrepancies with the measured values of the boron concentration as the cycle time increases. However, taking into account the dependence of thermal conductivity on burnup significantly improved the agreement between the results of PARCS–PATHS (Purdue Advanced Reactor Core Simulator) and measurements. Taking into account the heat transfer of the fuel rod gap further improved the agreement between the simulation and measurement results. For the non-peripheral fuel assemblies, the relative difference between the predicted PARCS–PATHS and measured thermocouple results meet the acceptance criteria (≤10%). For peripheral assemblies that are in contact with the reflector by three faces, the relative error exceeds the acceptance criteria (15%) by 1–2%.

The influence of external factors on the process of low-temperature propane oxidation in the presence of vacuum ultraviolet (UV) radiation (λ = 100–200 nm) and mercury vapor was studied. The modeling of the process of low-temperature propane oxidation taking into account the above external factors was carried out within the framework of the mathematical theory of a point explosion in gases, which allowed consideration of the possibilities for the formation of shock fronts. For numerical computations, the computer program PTS Mathcad Prime 3.1 was used. The results obtained show the possibility of the formation of shock fronts because of the initiation of the process when the reaction medium is exposed to the vacuum UV radiation and mercury vapor and at a certain symmetry of the reaction vessel. The reflection of thermal radiation of the reaction medium and active particles by mercury atoms (vapors) because of their neutrality and focusing of thermal radiation to the center of the reactor because of the symmetry of the reaction vessel, allows one to apply the theory of thermal development of a chain process and to determine the values of parameters for the point explosion. The phenomenon is explained as the formation of a flame front during initiation in the center of the reaction vessel, and mercury vapor reflects the thermal radiation of the reaction to the center of the vessel. When the amount of energy is sufficient for a point explosion, a shock front is generated.

The effect of lithium impurity on the dielectric characteristics and the mechanism of conductivity of zinc oxide thin films obtained by the electron beam deposition method was studied. At low frequencies, a strong dispersion of permittivity constants associated with interfacial polarization at grain boundaries was found. It was shown that the frequency dependencies of the conductivity are well described by the Mott theory. It has been established that the mechanism of ac conductivity undergoes qualitative changes with increasing lithium concentration: hopping conductivity is replaced by correlated hops through the barrier and tunneling of small radius polarons. The characteristics of the obtained films indicate the possibility of using them to create a capacitive memory element and a channel of a field-effect transistor.

The ITO/ZnO and ITO/ZnO:Mg bilayer structures were fabricated by the sol-gel method and their structural and photoelectric properties were experimentally studied. It is shown that, compared with ZnO and ZnO:Mg films without an ITO sublayer, the morphology changes noticeably and the band gap decreases. The I–V characteristics of obtained structures were analyzed in the dark and under the influence of optical radiation of different wavelengths. Using artificial neural networks, their spectral photosensitivity was modeled.