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

The results of computer modeling of heat propagation processes in a multilayer thermoelectric sensor after absorption of single photons of the extreme ultraviolet wavelength range are presented. The sensor consists from a W absorber, a La_0.99Ce_0.01B₆ thermoelectric layer, a Mo heat sink, and an Al₂O₃ dielectric substrate. The optical spectra of tungsten are examined and it is found that a sensor with a W absorber can provide efficient optical coupling with photons of extreme ultraviolet wavelengths. The optimal thickness of the absorber that will provide effective absorption of photons in this region is determined. Computer simulation was performed using the three-dimensional matrix method based on the equation of heat propagation from a limited volume. The temporal dependences of the temperature of different areas of the sensor after absorption of single photons with wavelengths of 55.1, 32.627 and 27.71 nm (22.5, 38 and 44.7 eV) were studied. The obtained results allow calculating the signal/noise ratio of the sensor and determining the efficiency of recording an already absorbed photon. It has been proven that the system efficiency of a thermoelectric sensor with a tungsten absorber can exceed 90% when recording single photons in the extreme ultraviolet range.

Oblivious transfer is a type of message transfer in which a sender transmits one out of many potential pieces of information to the receiver, but she has no knowledge about the actual piece of information being received by the receiver. Oblivious transfer is a deceptively simple scheme that has many possible applications such as secure multiparty computation, private set intersection, federated learning, zero-knowledge proofs, accessing sensitive data etc. Security of most classical oblivious transfer protocols is based upon the unproven assumptions about the computational complexity of certain number theoretic problems such as integer factorization. So, existing classical protocols for oblivious transfer are only computationally secure and not unconditionally secure. Although many quantum oblivious protocols have been proposed lately, they are not simple and easy to implement. In the present work we propose a quantum oblivious transfer protocol that is efficient, simple and easily implementable with the existing quantum technology.

A “hard” four-block Laue-case X-ray interferometer is proposed. The additional block, as compared to the three-block design, enables simultaneous generation of three interferograms from different parts of the interferometer. The rigidity of the interferometer structure ensures the absence of uncontrolled preliminary moiré (at least in the central interferogram), thereby improving measurements.

The optical and electrical properties of silver-doped ZnO (AgZnO) films with Ag concentrations of 0.05 and 0.24 at % were analyzed using XRD, EDS, resistance, transmittance and reflectance measurements. The 0.05 at % AgZnO and as-deposited 0.24 at % AgZnO films exhibited n-type doping, whereas the annealed 0.24 at % AgZnO films showed p-type doping. The crystallite sizes of the 0.05 and 0.24 at % AgZnO films were 24 and 28 nm. The redshift of the band gap was 0.02 eV for 0.24 at % AgZnO. The sample with 0.24 at % Ag exhibits a polaron features in the range 900–3700 cm^–1, and demonstrated a paramagnetic-to-diamagnetic transition. The 0.05 at % AgZnO film showed a negative temperature coefficient of resistivity. These findings suggest that a 0.24 at % Ag concentration is favorable for achieving p-type doping in ZnO and for the formation of polarons, whereas the 0.05 at % AgZnO film could be used for thermal sensing applications.

The current study explores Self-focusing of Cosh–Gaussian (ChG) laser beam through collisional plasma. Here, we have also taken in to account effect of linear absorption. The non-uniform heating in collisional plasma causes carriers redistribution resulting in generation of density gradients in plasma. This density gradient in fact causes self-focusing of beam. The wave equation for electric field vector of laser beam is solved using paraxial approach to obtain 2nd order ODE for beam waist of laser beam. Since, it is not possible to solve this differential equation through direct method. So, this differential equation is numerically solved to investigate the change in beam waist of beam with dimensionless propagation distance. Effect of change in laser intensity, plasma density, decentered parameter and absorption coefficient on laser beam’s waist is also explored.

The dielectric properties of nanocrystalline glass-ceramics based on perlite were investigated in the frequency range of 100 – 1 × 10⁶ Hz and the temperature range of 25–350°C. Relaxation peaks were observed in the temperature dependences of the dielectric permittivity and dielectric losses, shifting toward higher temperatures with increasing frequency, which made it possible to determine the activation energy of the relaxation process. The frequency dependence of the temperature coefficient of dielectric permittivity additionally confirms the relaxation nature of the observed phenomenon. The obtained results are consistent with the Maxwell–Wagner interfacial polarization model, indicating a heterogeneous structure of the material.

A hydrothermal–microwave method has been developed for the synthesis of bismuth metasilicate from water-soluble bismuth compounds and sodium silicate. The bismuth silicate obtained in the form of a nanodispersed powder exhibits high photocatalytic activity and radiation resistance. The characteristics of the synthesized bismuth silicate were determined using differential thermal analysis, X-ray phase analysis, UV–VIS, and IR spectroscopy. In the temperature range of 600–800°C, crystalline phases of bismuth silicates with compositions Bi₂SiO₅, Bi₄Si₂O₁₂, and Bi₂SiO₂₀ are formed. The photocatalytic activity of the samples was studied in the degradation reaction of methylene blue under UV irradiation. Physicochemical studies have shown that the synthesized bismuth silicate is a promising material for various applications as a wide-bandgap semiconductor, photocatalyst, and radiation shielding material. The conducted research demonstrates the efficiency of microwave synthesis of bismuth silicates: the synthesis and heat-treatment times are reduced (by 3–5 times), and energy consumption is lowered (by 70–80%) compared to conventional synthesis methods.

This work presents an experimental investigation into a novel microwave band-pass filter architecture based on interacting conducting ring resonators. Leveraging the inherent resonant behavior of copper rings, the design achieves multiple narrow passbands within the 1–12 GHz frequency range. By systematically varying both the inter-resonator spacing and the number of rings, the study identifies an optimal configuration—particularly at an inter-ring distance of 6.75 mm—that maximizes the quality factor and transmission amplitude. Experimental results reveal distinct resonances at 2.2, 4.2, 6.6, 8.6, and 11.2 ± 0.2 GHz, corresponding to the fundamental and higher-order harmonic modes. The demonstrated filtering mechanism, characterized by compact size, tunable frequency response, and low insertion loss, offers a scalable solution for modern wireless communication systems. These findings indicate significant potential for integration into next-generation 5G and emerging 6G networks, providing a cost-effective alternative to conventional filter designs.

The influence of a black silicon (b-Si) interlayer on the photovoltaic characteristics of tandem perovskite/silicon cells was investigated by numerical modeling in the SCAPS-1D software environment. It is shown that a 640 nm thick nanotextured b-Si interlayer increases the efficiency of the modeled device from 27.17 to 28.97%. The primary contribution to the efficiency gain is attributed to an increase in short-circuit current density, resulting from exceptionally low reflection and enhanced light trapping in the bottom silicon subcell. The qualitative agreement between the simulation results and the experiment, as well as the dominant contribution of optical effects to the observed performance improvement, is demonstrated. Using parametric analysis, the optimal thickness of the b-Si interlayer (∼530 nm) was determined, ensuring current matching between the subcells and a maximum efficiency of 29%.

This paper investigates the nonrelativistic approximation in the first-order 39-component theory for a spin-3/2 particle in curved spacetime under external electromagnetic fields. Starting from the generally covariant matrix equations, generalized via the Weyl-Fock-Ivanenko tetrad method, we employ explicit forms of the four main ({{{Gamma }}^a}) matrices of dimension (16 times 16) within the corresponding first-order system. The analysis is carried out for spacetime metrics that permit the existence of nonrelativistic equations. To separate the large and small components of the complete wave function, three projective operators are constructed from the fourth-order minimal polynomial of the (Gamma _{16 times 16}^0) matrix. The explicit forms of these components are obtained, and the set of independent variables is identified; in particular, only four large components are independent. Following the standard procedure, we derive the nonrelativistic system of equations for a 4-component wave function. The resulting Hamiltonian includes contributions from the electromagnetic field and additional geometric terms expressed through the Ricci rotation coefficients, Ricci scalar R and Ricci tensor ({R_{ab}}). We also isolate the term describing the interaction between the magnetic moment of the spin-3/2 particle and the external magnetic field. This interaction term is expressed via the spin matrices ({S_i}) and the components of the magnetic field vector B.