Doklady Physics最新文献

The present work investigates the influence of indium incorporation on the structural and thermo-physical characteristics of In–Sb–Se chalcogenide glass systems, In_xSb₃₀Se_{70 – x} (x = 0–25), using a theoretical framework. A set of composition-dependent parameters including average coordination number, bond energy, network constraints, heat of atomization, deviation from stoichiometry, and lone-pair electron concentration were evaluated to understand the evolution of network connectivity and thermal stability. The results indicate that increasing indium content leads to enhanced network rigidity, as reflected by higher coordination numbers, increased bond strength, and reduced structural disorder. The decrease in lone-pair electrons and deviation from stoichiometry suggests improved cross-linking within the glassy network, contributing to enhanced thermal stability. In addition, a simple machine-learning-based regression model was employed as a supplementary validation tool to examine correlations between selected structural parameters and the glass transition temperature (T_g). The close agreement between theoretical predictions and regression-based estimates confirms the consistency and robustness of the adopted approach. The present study provides a systematic theoretical understanding of composition-driven trends in In–Sb–Se chalcogenide glasses and offers useful guidance for tailoring their thermo-physical properties.

In this study, we synthesized and investigated the influence of dopant nature on copper oxide nanoparticles (NPs) for four compositions: undoped CuO, Ni-doped CuO (Cu_0.95Ni_0.05O), Mg-doped CuO (Cu_0.95Mg_0.05O), and (Ni,Mg) co-doped CuO (Cu_0.90Ni_0.05Mg_0.05O), using the sol–gel method. Samples were characterized through various characterization techniques and by photocatalytic performance. X-ray diffraction (XRD) analysis confirmed single-phase monoclinic CuO structure. (Ni,Mg) co-doping significantly reduced the average crystallite size from 20.95 to 6.24 nm. Scanning electron microscopy (SEM) demonstrated that the incorporation of Ni and Mg affected the morphology of the CuO NPS. Fourier-transform infrared (FTIR) spectra confirm the formation of CuO NPs. Moreover, (Ni,Mg) co-doping generated a synergistic electronic effect, where Ni narrowed and Mg widened the band gap, yielding an optimized band structure, improved light absorption in both the visible and UV ranges. This tunability is advantageous for photocatalytic applications, as the broader spectral response improves light harvesting and, consequently, photocatalytic efficiency.

The current study investigates nonlinear second harmonic generation of q-Gaussian laser beam in cold quantum plasma. We considered combined action of relativistic and ponderomotive (RP) forces. The electron effective mass varies under combined action of RP forces thereby leading to variation in background plasma density across the beam’s path and causing the beam to self-focus. An electron plasma wave (EPW) is excited at laser’s original frequency due density gradients established in plasma. The nonlinear interaction of EPW with fundamental beam produces second harmonic generation (SHG). In order to explore this process, we have used standard approximations such as WKB approximation and paraxial theory to derive 2nd order ODE denoting the beam waist dynamics with dimensionless propagation distance and efficiency of 2nd harmonic generation. We also explored influence of different laser and plasma parameters on beam’s focusing behavior and the overall SHG efficiency.

This work is aimed to develop a technology for fabrication of high-temperature carbon–ceramic composite materials. The approach includes the following processing stages: the fabrication of filled carbon-fiber blanks, their subsequent carbonization, high-temperature heat treatment, and pyrolytic compaction. A distinctive feature of the technology is the impregnation of particles of refractory component precursors into the interlayer space, that ensures in situ synthesis and subsequent sintering of the ceramic component of the matrix during the carbonization and high-temperature heat treatment stages. This approach has been successfully tested in the fabrication of carbon–ceramic composites in the C_f/C system—carbides and borides of transition metals of IV (Hf, Ti) and V (Nb) groups. The results of gas-dynamic tests of samples of the resulting composites under the influence of high-speed, high-enthalpy flows of oxidizing gases are presented. It is noted that the number of functional layers and their thickness allow to regulate the magnitude of the thermal load by changing the rate of oxidation, ablation and the duration of each mode.

Experimental studies of the process of displacement of industrial oil with a viscosity of 55.2 and 88.3 mPa s from a homogeneous porous medium at pressures in the range of 8–14 MPa and temperatures of 313.333 and 353 K. It is shown that an increase in the dynamic viscosity of hydrocarbons leads to a decrease in the amount of displaced hydrocarbon from the porous medium. It has been suggested that the reduction in the amount of hydrocarbon displaced is due to the low solubility of carbon dioxide in both of the tested hydrocarbons. The dynamic viscosity of industrial oil was calculated in the pressure range of 8–14 MPa on isotherms of 313, 333, and 353 K. It is shown that the dynamic viscosity at pressures of 12 and 14 MPa decreases by 100–150%, which leads to an increase in the mobility of hydrocarbons in a porous medium.

This paper presents the results of an experimental investigation of the normal total emissivity (ε_nt) of EP718 alloy in vacuum within the temperature range of 400–1400 K. The influence of three characteristic surface conditions was systematically studied: polished, as-received (mill-finished), and air-oxidized. It is shown that the surface condition is the determining factor. For the polished and as-received surfaces, good agreement with data for the foreign analogue Inconel 718 is demonstrated. For the oxidized surface, nonmonotonic dependence ε_nt(T) was observed, with a pronounced decrease at temperatures above 1200 K, which is attributed to the high-temperature degradation of the oxide layer in vacuum. The obtained data are of an estimative character and are of interest for the thermal modeling of gas-turbine engine components.

Junctionless field effect transistors heavily rely on control gate engineering to perform. Dielectric material types, scaling of gate oxide, gate metal work, among others all choose the performance of the entire device. This paper simulates and analyses a graphene nanoribbon double gate junctionless tunnel field effect transistor (DG-JL GNR-TFET) using a non-quasi-static small-signal model to investigate its radio frequency properties. The control gate engineering effect, dielectric choice, and oxide scaling has been evaluated in detail with regard to device performance. The experiment shows that as the thickness of the oxide is increased, the efficiency of tunneling increases and the cut-off frequency (f_T) reaches a maximum of 1.01 × 10¹² Hz when the oxide thickness is 1nm thick. Electrostatic control is further enhanced by high-k dielectrics with TiO₂ (2 nm) giving the best trade-off, with current ratio of 2.61 × 10¹², subthreshold swing of 20.75 mV/dec, transconductance of 0.36 mS and gate capacitance of 0.065 fF at 1 V gate and drain voltages. Work function variation reveals an inverse dependence of frequency on work function, with the highest value (5.23 × 10¹¹ Hz) obtained at 4.1 eV. Comparative benchmarking against reported tunnel field effect transistors highlights the superior switching ratio and steep subthreshold swing of the proposed device, confirming its potential for low-power, high-efficiency radio frequency front-end circuits and emerging Internet of Everything applications.

The analytical investigation of q-Gaussian beam propagation in cold quantum plasma with absorption effects is carried out in current study. The nonlinear differential equation showing response of beam waist with dimensionless distance is obtained within framework of Wentzel–Kramers–Brillouin and paraxial theory approaches. The effect of absorption coefficient is also introduced in present study. The nonlinear differential equation is obtained numerically using standard Runge–Kutta method. The key parameters of laser-plasma including beam intensity, plasma density, q-parameter, beam radius and linear absorption coefficient are systematically varied for exploring beam dynamics of q-Gaussian laser profile. The findings of this study are contrasted with corresponding behavior in classical relativistic plasma for highlighting the distinct features arising due to quantum regime.

Laser-plasma interaction-based terahertz (THz) radiation sources are being actively studied due to their tunability and large output potential. In this research, we analyze the theoretical study of THz wave generation driven by two radially polarized q-Gaussian laser beams propagating through a slanting density collisional plasma. A model is formulated to study the effect of plasma density gradient on the nonlinear ponderomotive force. This force is responsible for creating nonlinear current density that emits THz. Factors such as variation in plasma density, density gradient (({{n}_{r}})), background plasma density (({{n}_{0}})), beam radial position ((r)), electron neutral collision frequency (({{nu }_{{{text{en}}}}})) and the q-parameter have been included in the model. A comparison analysis, along with 3D graphical results, indicates that the output of THz enhances in case of positive density gradient but the q-parameter govern the field amplitude. According to these findings, the adjustment of plasma density profile and beam structure allows higher quality and tunable THz generation. The findings provide valuable guidance to developing plasma-based THz sources with efficient and structured plasma waveguides.

Studies have been conducted on how the structural, thermal, morphological, mechanical, and antibacterial properties of PLA polymer are affected by low filling concentrations of ZnO nanoparticles. This study proposes the fabrication of biodegradable PLA–ZnO films with ZnO filling percentages ranging from 2.5 to 40%, utilising a cost-effective process involving solvent casting combined with ultrasonication at room temperature. The films were characterised using XRD, FTIR, SEM, TGA testing, tensile testing, and antibacterial testing against E. coli and S. aureus. The integration of ZnO affects the structural semi-crystallisation of the PLA matrix and prefers an hkl crystallographic orientation as support. SEM images confirmed the efficient dispersion of nanoparticles in all films, which has a direct impact on thermal stability. Regarding mechanical properties, tests conducted according to the ATMD-882 standard demonstrated good properties even at the saturation point of 40%. Ultimately, this study demonstrates that biodegradable films exhibit effective antibacterial activity against E. coli and S. aureus, even at low filling ratios, thereby suggesting their potential applicability in the food packaging sector.