East European Journal of Physics

FLRW Cosmology with Hybrid Scale Factor in f(R, Lm) Gravity

2023-12-02T13:52:23+00:00

In this paper, we aim to describe the cosmic late-time acceleration of the Universe in f(R,L_m) gravity framework proposed by Harko (2010) with the help of an equation of state for strange quark matter. To achieve this, we adopt a specific form of f(R,L_m) gravity as f(R,L_m) =R/2}+ Lⁿ_m, where n is arbitrary constants. Here we utilize a hybrid scale factor to resolve the modified field equations in the context of f(R,L_m) gravity for an isotropic and homogeneous Friedmann–Lemaître–Robertson–Walker (FLRW) metric in presence of strange quark matter (SQM). Also, we analyze the dynamics of energy density, pressure and the state finder parameters and explained the distinctions between our model and the current dark energy models in the presence of SQM. We observed a transition from an accelerating to a decelerating phase in the Universe, followed by a return to an accelerating phase at late times. Also, we analyzed the state finder diagnostic as well equation of state parameter and found that the model exhibited quintessence-like behavior. The conclusion drawn from our investigation was that the proposed f(R, L_m) cosmological model aligns well with recent observational studies and effectively describes the cosmic acceleration observed during late times.

Spectral and Timing Study of the Newly Detected Ultraluminous X-Ray Sources in NGC 3585 Using Different Chandra Observations.

2023-12-03T10:29:57+00:00

The present work aims to study the previously unstudied Ultraluminous X-ray sources (ULXs) in the galaxy NGC 3585 at its various epochs of Chandra observation. We report here the detection of two new ULXs viz. CXOUJ111306.0-264825 (X-1) and CXOUJ111325.3-264732 (X-2) with their bolometric luminosity > 10³⁹erg s⁻¹ in its various Chandra observations. X-1 was found to be a spectrally hard ULX in both the epochs where it was detected. However in the ULX, X-2, a slight hardening of the spectra was observed within a period of 17 years. Assuming isotropic emission and explained by disk blackbody model, the spectrally softer epoch of X-2 with an inner disk temperature, kTi_n ∼ 0.79 keV and bolometric luminosity ∼ 2.51 × 10³⁹erg s⁻¹ implies for X-2 to be powered by a compact object, necessarily a black hole of mass, M_BH ∼ 44.85^+82.11_−25.92M_⊙ accreting at ∼ 0.42 times the Eddington limit. The Lightcurve of X-1 and X-2 binned at 500s, 1ks, 2ks and 4ks has shown no signature of short-term variability in both the ULXs in kilo-seconds time scales. Overall, both the detected ULXs seem to be almost static sources both in long-term (years) as well as short-term (kilo-seconds) time scales with the presently available Chandra Observations.

Kinematic Calculation of the 16O(γ,4α) Reaction

2023-12-02T13:52:18+00:00

The event distribution over the excitation energy of a system of two α-particles (E_x) is measured for the reaction ¹⁶O(γ,4α). It is found that an intermediate excited ⁸Be nucleus is formed, and the channels of the ⁸Be nucleus ground state (GS) formation are extracted. After the separation of the GS ⁸Be nucleus, a broad maximum with a center at ∼ 3 MeV appears in the distribution of E_x, which may correspond to the first excited state of the ⁸Be nucleus. There are two possible channels for the formation of this state in the reaction - γ + ¹⁶O → α₁ + ¹²C* → α₁ + α₂ + ⁸Be* →α₁ + α₂ + α₃ + α₄ and γ + ¹⁶O → ⁸Be* + ⁸Be* → (α₁ + α₂) + (α₃ + α₄). Each decay mode is reduced to several two-particle systems. For a comprehensive study of the channel for the formation of the first excited state of the ⁸Be nucleus in the ¹⁶O(γ,4α) reaction, a kinematic model for calculating the parameters of α-particles has been developed. The model is based on the assumption of a sequential two-particle decay with the formation of intermediate excited states of ⁸Be and ¹²C nuclei. For the kinematic model of the ¹⁶O(γ,4α) reaction, a graphical application was created in the Python programming language. The matplotlib library is used for data visualization. To generate random values, a set of functions from the standard random library of the Python programming language is used. Monte Carlo simulations of several distributions for one parameter with a given numerical function were performed. Several excited states of the ¹²C and ⁸Be nuclei can contribute to the reaction. The created scheme allows us to choose the relative contribution for each channel of decay, as well as the contribution of a separate level in each channel. To correctly comparison of the experimental data and the results of the kinematic calculation, the α-particles were sorted by energy in such a way that T¹_sort > T²_sort > T³_sort > T⁴_sort. As a result of comparing the experimental and calculated data, it was determined that predominantly occurs the process γ + ¹⁶O → α₁ + ¹²C* → α₁ + α₂ + ⁸Be* → 4α with the formation of the ¹²C nucleus in states with E₀ = 13.3 MeV, E₀ = 15.44 MeV, and the 1st excited state of the ⁸Be nucleus with E₀ = 3.04 MeV. The conditions for the identification of α-particles in the experiment for each decay of the stage are determined.

Estimation of Nuclear Mass Formulas Coefficients Using Least-Squares Method Based on Gauss-Seidel Scheme: A Comparative Study Between Three Models

2023-12-02T13:52:21+00:00

This paper presents the analysis and implementation of the least-squares method based on the Gauss-Seidel scheme for solving nuclear mass formulas. The least-squares method leads to the solution of the system by iterations. The main advantages of the discussed method are simplicity and high accuracy. Moreover, the method enables us to process large data quickly in practice. To demonstrate the effectiveness of the method, implementation using the FORTRAN language is carried out. The steps of the algorithm are detailed. Using 2331 nuclear masses with Z ≥ 8 and N ≥ 8, it was shown that the performance of the liquid drop mass formula with six parameters improved in terms of root mean square (r.m.s. deviation equals 1.28 MeV), compared to the formula of liquid drop mass with six parameters without microscopic energy, deformation energy and congruence energy (r.m.s. deviation equals 2.65 MeV). The nuclear liquid drop model is revisited to make explicit the role of the microscopic corrections (shell and pairing). Deformation energy and the congruence energy estimate have been used to obtain the best fit. It is shown that the performance of the new approach is improved by a model of eight parameters, compared to the previous model of six parameters. The obtained r.m.s. result for the new liquid drop model in terms of masses is equal to 1.05 MeV.

Diffusion of High-Energy Negatively Charged Particles in the Field Atomic Strings of an Oriented Crystal

2023-12-02T13:52:14+00:00

The work analyzes the dependence of the diffusion index of high-energy negatively charged particles on the energy of the transverse motion in oriented crystal. The crystal had an axial orientation relative to the direction of particle incidence. The analysis was carried out using the example of π⁻ mesons with a momentum of 100 GeV/c that impinged on a silicon crystal, which corresponds to the conditions achievable on secondary beam of the the CERN SPS accelerator. The analysis showed that the dependence under consideration is not monotonic. It has a minimum in the energy region slightly exceeding the value of the potential energy of particles at the saddle point of the potential of crystal atomic strings. At higher values of the energy of transverse motion of particles E_⊥, the diffusion index increases with increasing E_⊥, since this increases the average absolute value of the velocity of particle motion in the plane orthogonal to the crystal axis, near which motion takes plase. The increase in the diffusion index at low values of E_⊥ is associated with the manifestation of incoherent scattering of particles on thermal vibrations of crystal atoms. The analysis carried out in the work is of interest both for a deeper understanding of the process of high-energy negatively charged particle beams passage through oriented crystals, and for improving methods for charged particle beams steering with a help of straight and bent oriented crystals.

Instability of Ion Cyclotron Waves (ICWS) at the Expense of Lower Hybrid Drift Waves (LHDWS) Turbulence Energy

2023-12-02T13:52:22+00:00

Instability of ion cyclotron waves(ICWs) is investigated in presence of lower hybrid drift waves(LHDWs) turbulence. Plasma inhomogeneity in the Earth’s magnetopause region supports a range of low frequency drift wave turbulent fields due to gradients in density in different regions of the media. One of these drift phenomena is identified as lower hybrid drift waves (LHDWs) which satisfies resonant conditions ω − k · v = 0. We have considered a nonlinear wave-particle interaction model where the resonant wave that accelerates the particle in magnetopause may transfer its energy to ion cyclotron waves through a modulated field. In spite of the frequency gaps between the two waves, energy can be transferred nonlinearly to generate unstable ion cyclotron waves which always do not satisfy the resonant condition Ω−K · v ≠ 0 and the nonlinear scattering condition Ω − ω − (K − k) · v ̸= 0. Here, ω and Ω are frequencies of the resonant and the nonresonant waves respectively and k and K are the corresponding wave numbers. We have obtained a nonlinear dispersion relation for ion cyclotron waves(ICWs) in presence of lower hybrid drift waves(LHDWs)
turbulence. The growth rate of the ion cyclotron waves using space observational data in the magnetopause region has been estimated.

Numerical Simulation and Analysis of the Modified Burgers' Equation in Dusty Plasmas

2023-12-02T13:52:25+00:00

This paper presents a comprehensive study of the numerical simulation of the one-dimensional modified Burgers' equation in dusty plasmas. The reductive perturbation method is employed to derive the equation, and a numerical solution is obtained using the explicit finite difference technique. The obtained results are extensively compared with analytical solutions, demonstrating a high level of agreement, particularly for lower values of the dissipation coefficient. The accuracy and efficiency of the technique are evaluated based on the absolute error. Additionally, the accuracy and effectiveness of the technique are assessed by plotting L₂ and L_∞ error graphs. The technique's reliability is further confirmed through von Neumann stability analysis, which indicates that the technique is conditionally stable. Overall, the study concludes that the proposed technique is successful and dependable for numerically simulating the modified Burgers' equation in dusty plasmas.

The Effect of Thermal Stratification on Unsteady Parabolic Flow past an Infinite Vertical Plate with Chemical Reaction

2023-12-02T13:52:24+00:00

This research paper investigates the effects of thermal stratification on unsteady parabolic flow past an infinite vertical plate with chemical reaction. Using the Laplace transform method, analytical solutions are derived to simulate the physical process of the flow. The study considers the effects of thermal stratification on the flow field, as well as the effects of chemical reaction on the velocity, and temperature field. The results of the stratification case are then compared to the case of no stratification of a similar flow field. The results of this research can be used to improve understanding of the unsteady parabolic flow in thermal stratified environments and provide valuable insight into the effects of chemical reactions on the temperature field.

Thermal and Mass Stratification Effects on Unsteady Flow Past an Accelerated Infinite Vertical Plate with Variable Temperature and Exponential Mass Diffusion in Porous Medium

2023-12-02T13:52:23+00:00

This study looks at how thermal and mass stratification affect the unsteady flow past an infinitely fast-moving vertical plate when the temperature is changing and there is exponential mass diffusion in a porous medium. By applying the Laplace transformation method, we determine the solutions to the equations that govern the system for the case of unitary Prandtl and Schmidt numbers. Graphical representations of the concentration, temperature, and velocity profiles, as well as the Nusselt Number, Sherwood number, and the Skin friction are provided to facilitate discussion of the cause of the different variables. To see the effects of thermal and mass stratification on the fluid flow, we compare the classical solution (Fluid with out stratification) with the primary solution (Fluid with the stratification) by using graph. The combined effects of the two stratification lead to a quicker approach to steady states. The outcomes can be helpful for heat exchange design and other engineering applications.

Effect of Arrhenius Activation Energy in MHD Micropolar Nanofluid Flow Along a Porous Stretching Sheet with Viscous Dissipation and Heat Source

2023-12-02T13:52:21+00:00

A numerical study of the heat and mass transfer of a micropolar nanofluid flow over a stretching sheet embedded in a porous medium is carried out in this investigation. The main objective of this work is to investigate the influence of Arrhenius activation energy, heat source and viscous dissipation on the fluid velocity, microrotation, temperature, and concentration distribution. The equations governing the flow are transformed into ordinary differential equations using appropriate similarity transformations and solved numerically using bvp4c solver in MATLAB. Graphs are plotted to study the influences of important parameters such as magnetic parameter, porosity parameter, thermophoresis parameter, Brownian motion parameter, activation energy parameter and Lewis number on velocity, microrotation, temperature and concentration distribution. The graphical representation explores that the velocity of the liquid diminishes for increasing values of magnetic parameter, whereas the angular velocity increases with it. This study also reports that an enhancement of temperature and concentration distribution is observed for the higher values of activation energy parameter, whereas the Lewis number shows the opposite behavior. The effects of various pertinent parameters are exposed realistically on skin friction coefficient, Nusselt and Sherwood numbers via tables. A comparison with previous work is conducted, and the results show good agreement.

Analysis of the Heat Transfer Performance of Nanofluids in Micro-Cylinder Groups

2023-12-02T13:52:24+00:00

The objective of this study is to investigate, through numerical simulations, the flow and heat transfer characteristics of Al₂O₃, Cu, TiO_2, and SiC water-based nanofluids flowing over micro-cylinder groups arranged in an inline configuration. The simulations were carried out under laminar flow conditions, and the analysis considered seven different low values of the Reynolds number, with a constant volume fraction of 2%. The aim of this investigation was to determine how nanofluids, i.e., suspensions of nanoparticles in water as the base fluid, can affect the pressure drop and heat transfer performance in micro-cylinder groups. To accomplish this, the finite volume method was employed to evaluate the impact of the nanofluids on pressure drop and heat transfer characteristics in the micro-cylinder groups. The study results demonstrate that, for all the nanofluids studied, the pressure drop and friction factor of the micro-cylinder groups increased with increasing Reynolds number. This behavior can be attributed to the interaction between the nanoparticles and the wall, which results in an increase in friction. Furthermore, the Nusselt number was found to increase with increasing Reynolds number. The SiC/Water nanofluid exhibited the highest Nusselt numbers among the four nanofluids tested, indicating that it provides better heat transfer performance than the other nanofluids. These results are consistent with experimental findings, indicating that the numerical simulations were accurate and reliable.

Impacts of Temperature Dependent Thermal Conductivity and Viscosity on Slipped Flow of Maxwell Nanofluid

2023-12-02T13:52:22+00:00

The mathematical model to inspect the effects of changeable thermo-physical properties such as thermal conduction, slip effects and viscosity on Maxwellian nanofluid is proposed. The thermal conductivity increases rapidly due to presence of nanoparticles such as metals, carbides, oxides etc. in base fluid. The flow occurs from the stagnated point pass a stretched sheet with slipped conditions. The characteristics of the Brownian motion as well as the thermophoresis processes are also taken into consideration. By means of similarity transformations, the ODEs are reduced from the equations influencing the fluid flow. A built-in solver of MATLAB namely bvp4c which is a collocation formula implementing the Lobatto IIIa finite differences numerical method is applied to solve these transformed equations numerically. The graphs of the numerical outcomes representing impacts of variations in different parameters on the fluid movement, transfer of heat along with mass are analyzed. This investigation leads to an important aspect that as the thermal conductivity in the flow is intensified, the temperature of the fluid reduces with high aggregation of the nanoparticles near the sheet’s surface. Also, the rates of heat and mass transferral depletes due to the relaxation of Maxwellian fluid. Furthermore, the effectiveness of the present numerical computations is determined by carrying out comparisons of heat and mass transferred rates against the previous analytical results for several values of thermophoresis and Prandtl parameters. The effectiveness of its outcomes can be applied in nanoscience technology and polymeric industries for their developments.

Synthesis of Pure and Manganese Doped Zinc Oxide Nanoparticles by a Solution Growth Technique: Structural and Optical Investigation

2023-12-02T13:52:21+00:00

Pure and manganese doped zinc oxide nanoparticles have been successfully synthesized over the composition range, Zn_1-xMn_xO (0<x<0.5), by a solution growth process. The effect of Mn doping on the structure, morphology and optical properties were investigated by several techniques. X-Ray diffraction studies confirmed the formation of a single-phase polycrystalline hexagonal wurtzite structure of ZnO within the range, 0 < x < 0.3. No Mn related secondary phases were detected, within this range, which could be attributed to the fact that the dopant atoms had been well incorporated into the ZnO crystal lattice. For Zn_1-xMn_xO (x = 0.5), several low intensity peaks belonging to remnants of Manganese acetate were observed in the diffractogram, establishing a solubility limit for the synthesis technique used. The variation of d-spacing with Mn percent doping showed a very good agreement with Vergard’s law within the range (0<x<0.25). EDAX analysis of the nanoparticles was consistent with the formation of Mn doped ZnO. The optical band gap of the ZnO nanoparticles decreased linearly with increasing Mn percent doping, suggesting the possibility of tuning the band gap of ZnO by doping with Mn.

Design and Simulation of a Triple Absorber Layer Perovskite Solar Cell for High Conversion Efficiency

2023-12-02T13:52:23+00:00

This paper presents a comprehensive simulation study on the influence of a triple absorber layer configuration in a perovskite-based solar cell using the SCAPS-1D software, under AM1.5 illumination. The simulated structure comprises a Cesium Tin-Germanium Triiodide (CsSn_0.5Ge_0.5I3) absorber layer sandwiched between Indium gallium zinc oxide (IGZO) and Cu₂O layers. The main objective of this study is to enhance the power conversion efficiency (PCE) by optimizing the thicknesses of each layer. To validate our simulation results, we compare them with experimental data obtained from existing literature, and we observe a satisfactory agreement between the two. Our findings reveal that the maximum PCE of 28% can be achieved by utilizing specific thickness values for each layer. Specifically, the optimal thicknesses are determined to be 20 nm for the IGZO layer, 200 nm for the Cu₂O layer, and 700 nm for the perovskite layer. These optimized thickness values lead to a significant improvement in the PCE of the solar cell, reaching 29%. This achievement highlights the effectiveness of our proposed triple absorber layer configuration and demonstrates its potential to enhance the overall performance of the perovskite-based solar cell. Overall, this study provides valuable insights into the optimization of the absorber layer configuration in perovskite solar cells, leading to improved power conversion efficiency.

Investigations of Nonlinear Optical Properties of Lithium Niobate Crystals

2023-12-02T13:52:16+00:00

The article is devoted to nonlinear effects in lithium niobate crystals. The possibility of using digital holographic interferograms obtained with the help of laser radiation of different duration at different moments of time for the reconstruction of dynamic phase changes is shown. Holograms were recorded on lithium niobate crystals doped with iron ions in various concentrations using He-Ne and He-Cd lasers, and the diffraction efficiency was calculated. Also, the effect of gamma radiation on the optical properties of LiNbO3 and LiNbO3:Fe crystals was studied. At the same time, it was determined that the band gap of the samples decreases, as a result of which the refractive index, absorption coefficient and photorefractive sensitivity increase several times.

Calculation of the Density of the Distribution of Electronic States in the Conduction Band from the Fundamental Absorption Spectra of Amorphous Semiconductors

2023-12-02T13:52:25+00:00

The region of fundamental absorption in the optical spectra of amorphous semiconductors is theoretically studied using the Davis-Mott approximation according to the Kubo-Greenwood formula. As is known, three types of optical transitions of the electron can be observed in the fundamental absorption region; from the tail of the valence band to the conduction band, from the valence band to the conduction band and from the valence band to the tail of the conduction band. For all these electronic transitions, analytical expressions of the partial absorption spectra are obtained from two different types of the Kubo-Greenwood formula. The width of the optical mobility gap and the proportionality coefficient were determined in the analytical form of the interband absorption spectrum by fitting them to the experimental interband absorption spectrum. A new method is presented for calculating the density of distribution of electronic states in the conduction band of amorphous carbon based on the experimental interband absorption spectrum and the analytical expression of the Kubo-Greenwood formula written for the interband absorption spectrum.

Lateral Photoelectric Effect In Iron-Silicon Dioxide-Compensated Silicon Hybrid Structures

2023-12-02T13:52:22+00:00

This article presents experimental results on the technology of obtaining and studying the lateral photoelectric effect (LPE) in hybrid structures (HS) of the Fe/SiO₂/p-Si<B, Mn> and Fe/SiO₂/n-Si<B, Mn> types. The technology for obtaining such HS consists of two parts: firstly, obtaining compensated (C), highly compensated (HC), and over-compensated (OC) samples of Si <B, Mn>. Secondly, obtaining HS Fe/SiO₂/p-Si<B, Mn> and Fe/SiO₂/n-Si<B, Mn>. Based on the results, it is shown that sufficiently good HS has been obtained. Experiments on the study of LPE have shown that in the studied HS there is a pronounced manifestation of the lateral photoelectric effect, the magnitude and nature of which strongly depend on the type of conductivity and resistivity of the compensated silicon. The observed features are explained by the fact that in С, HC, and OC silicon samples, impurities that create deep levels in the silicon band gap form various multi-charged complexes that modulate the energy band of silicon, which lead to significant changes in its physicochemical and generation-recombination properties, which underlies the observed effects. Based on the LPE studies, depending on the contact distance, it is possible to determine the numerical values of the diffusion lengths of the minor current carriers (L_p and L_n), their lifetimes (τ_p and τ_n), and diffusion coefficients (D_p and D_n) on the substrate material.

Investigation of the Magnetic Properties of Silicon Doped with Rare-Earth Elements

2023-12-02T13:52:25+00:00

This article discusses the electrical properties of silicon doped with rare earth elements (REE). Atoms of rare earth elements (REE) diffused onto the surface of the silicon substrate. To measure the electrical parameters, samples of n-Si, n-Si<Lu>, n-Si<Er> and n-Si<Gd> were prepared and their electrical properties were determined using the Hall effect, four-probe and thermal probe methods. The studies were carried out in the temperature range 77÷300 K. The samples were ohmically contacted using a mixture of 1% Sb + 99% Au for measurement on the HMS500 instrument. The specific resistance of the samples in layers, the concentration of charge carriers, and the mobility of the samples were also studied by the magnetoresistance method. The electrical parameters of the samples were measured on an Ecopia Hall effect measuring system (HMS5000).

Enhancing the Perfection of a Silicon Crystal Doped with Nickel and Zinc Impurities

2023-12-02T13:52:19+00:00

This research paper presents the findings of an investigation into the interaction between zinc (Zn) and nickel (Ni) impurity atoms within a silicon (Si) matrix, which were doped sequentially in various combinations. The characterization techniques employed for this study encompass X-ray diffraction and IR-Fourier spectrometry. It is noteworthy that the degree of crystallinity exhibited by the silicon lattice, subject to the introduction of Zn and Ni impurities, is contingent upon the methodology employed for impurity incorporation. The results of this study reveal a distinctive trend in the optical properties of these doped silicon samples. Specifically, upon the introduction of Zn atoms into silicon that was pre-doped with Ni (Si<Ni, Zn>), there is a concomitant reduction in the concentration of optically active oxygen atoms. Remarkably, this alteration in the dopant composition leads to a marked enhancement in the transparency of the silicon crystal. In stark contrast, when the doping sequence is reversed (Si<Ni, Zn> Ni>), an opposing effect is observed, resulting in a diminishment of crystal transparency. These findings underscore the intricate interplay between the introduced impurity atoms, the dopant sequence, and their collective impact on the optical properties of the silicon matrix. Such insights contribute to our comprehension of the nuanced behavior of doped silicon and have implications for applications requiring tailored optical characteristics in semiconductor materials.

The Mechanism of the Formation of Binary Compounds Between Zn and S Impurity Atoms in Si Crystal Lattice

2023-12-02T13:52:19+00:00

The paper presents the results of an experimental study of surface morphology, elemental composition, electrophysical and optical properties of Si samples earlier doped with impurity atoms of Zn and S. The results of the study revealed a sufficient concentration of Zn and S elements on Si surface after diffusion (3.1% and 2.6% by weight, respectively). After additional thermal treatment at different temperatures, i.e., at 850°C and 875°C, the samples of I group have regained their initial parameters. However, it’s noteworthy that the mobility of charge carriers in group I samples was comparatively lower than that in group II samples allegedly under the influence of Zn and S binary molecules. After additional heat treatment of all samples at a temperature of 875°C, the authors have studied optical absorption coefficients. And their band gap energies were determined using the Tauc Plot method. According to the results of the study, the optical band gaps in group II and III samples were 1.12 eV, whereas the band gap energy in group I samples after additional thermal treatment at a temperature of 875 °C turned out to be 1.31 eV. Having theoretically calculated the band gap by applying Vegard’s law, the authors suggested that the new structure must be of Si_0.92ZnS_0.08 - type.

Evolution of Mechanical Properties of Pb–Sb–Sn–As–Se Grid Alloys for Lead-Acid Batteries During Natural Aging

2023-12-02T13:52:18+00:00

This study is devoted to the investigation of mechanical properties of a series of low-antimony Pb–Sb–Sn–As–Se grid alloys for lead-acid batteries in as-cast condition and after natural aging during storage. Mechanical properties were characterized by ultimate tensile strength, yield strength, elongation, and Young's modulus determined at room temperature using TIRAtest 2300 and P-0.5 universal testing machines. For most investigated as-cast alloys, an increase in ultimate tensile strength is accompanied by an increase in elongation. Within the temperature range between 70 ºС and 150 ºС, higher heating temperature of a casing mold does not markedly affect average elongation but causes the slight decrease (by ~4 %) in average ultimate tensile strength. When aged during storage for 30–33 days, the Pb–Sb–Sn–As–Se grid alloys, attain higher values of ultimate tensile strength, yield strength, and Young's modulus but lower values of elongation. This is due to precipitation of second-phase particles from lead-based solid solution oversaturated by antimony, arsenic, and selenium. The most noticeable effect of strengthening is observed during first five days of natural aging.

Study of the Mobility and Electrical Conductivity of Chromium Silicide

2023-12-02T13:52:15+00:00

The temperature dependence of the mobility in chromium silicides in the temperature range of 80 ÷ 780 K was studied. The mobility gradually increases to a temperature of 350 K, then it saturates in the temperature range of 350 ÷ 450K, then gradually decreases. It is shown that the mobility depends on the scatter of charge of carriers on a crystal lattice, impurity ions, dislocations, and silicide inclusions. The frequency of collisions is proportional to T^3/2, and the mobility varies with temperature as T^-3/2. At high temperatures, phonons may be considered as “frozen” defects and collision frequency with its will proportional to T. The temperature dependences of the electrical conductivity in this temperature range were also studied. Areas with negative and positive temperature coefficients are revealed.

Structure Determination and Defect Analysis n-Si, p-Si Raman Spectrometer Methods

2023-12-02T13:52:24+00:00

In this work, lutetium-doped silicon samples were studied using the Raman scattering method. Registration and identification of both crystalline and amorphous phase components in the samples was carried out. There is some violation in the spectra of Raman scattering of light samples of silicon doped with lutetium in comparison with the original sample. It was found that the intensity of Raman scattering of doped samples is 2-3 times higher than the scattering from silicon. The comparison is carried out for the intensities associated with the intensities of the single-phonon line of the silicon substrate. This effect of the Raman spectra in the range 930 cm^‑1 – 1030 cm^–1 appearing in this range is similar to the data reduction for multiphonon propagation on silicon. For the obtained images (n-Si<Lu> and p-Si<Lu>), the bands in the atomic range of combinatorial scattering have a mixed broad and oval background in the range from 623 cm^-1 to 1400 cm^-1. This background can change the shape of the observed bands.

Influence of silicon characteristics on the parameters of manufactured photonics cells

2023-12-02T13:52:17+00:00

The paper investigates the influence of the electrophysical characteristics of silicon on the final parameters of photoelectronic elements using p-i-n photodiodes as an example. It has been found that photodiode samples made on the basis of silicon with a higher resistivity are more prone to the formation of inversion channels at the oxide-semiconductor interface. Also, the dark current and responsivity of such photodiodes reach saturation at a lower voltage. It has also been shown that silicon-based photodiodes with a longer lifetime of non-basic charge carriers have lower dark current values. It has been shown that products with crystallographic orientation [111] have a much lower density of surface dislocations after technological operations than in the case of silicon with orientation [100]. It was also found that materials with different crystallographic orientations have different phosphorus diffusion coefficients. It has been experimentally established that a silicon oxide film grows faster on the surface of crystallographic orientation silicon [111] than on the surface of crystallographic orientation silicon [100]. This is due to the difference in the surface density of silicon atoms inherent in different crystallographic planes.

On the Properties of the Si-SiO2 Transition Layer in Multilayer Silicon Structures

2023-12-02T13:52:25+00:00

Capacitance spectroscopy was used to study the capacitive-voltage characteristics of multilayer structures with a Si-SiO₂ transition layer in Al-SiO₂-n-Si type samples fabricated by the thermal oxidation of a semiconductor. It is shown that the inhomogeneous distribution of the density of surface states is a localized electroactive center at the very semiconductor-dielectric interface, due to over-barrier charge emission or thermal ionization of impurity centers.

Electronic Structure Calculation of α-Al2X3 System (X = O, S) Based on R++Scan Functional

2023-12-02T13:52:20+00:00

Due to the necessity of reducing the reliance on fossil fuels, several systems are considered to be alternative and/or additional support for the existing battery material. In this report, structural and electronic properties of aluminium oxide (Al₂O₃) and aluminium sulfide (Al₂S₃) with hexagonal symmetry (α-phase), are investigated by utilizing density functional theory technique based on r++SCAN functional. The calculated lattice parameter and insulating gap for both systems are well matched with previous experimental studies and display higher accuracy compared to the results from local density approximation (LDA) and generalized gradient approximation (GGA) studies. The calculated insulating gap values are 10.3 eV and 4.1 eV for α-Al₂O₃ and α-Al₂S₃ respectively. For α-Al₂O₃ system, we observed hybridized s-p-d orbital of Al-O in the conduction states, consistent with the interpretation of past X-ray Absorption Near Edge Structure (XANES) data. Finally, the bulk and young modulus for α-Al₂O₃ are determined to be 251 GPa and 423 GPa which is very close to the known experimental values of 280 GPa and 451 GPa.

Numerical study of T-Gate AlGaN/AlInGaN/GaN MOSHEMT with Single and Double Barrier for THz Frequency Applications

2023-12-02T13:52:19+00:00

This paper presents a comprehensive investigation into the DC analog and AC microwave performance of a state-of-the-art T-gate double barrier AlGaN/AlInGaN/GaN MOSHEMT (Metal Oxide Semiconductor High Electron Mobility Transistor) implemented on a 4H-SiC substrate. The study involves meticulous numerical simulations and an extensive comparison with a single barrier design, utilizing the TCAD-Silvaco software. The observed disparity in performance can be attributed to the utilization of double barrier technology, which enhances electron confinement and current density by augmenting the polarization-induced charge during high-frequency operations. Remarkably, when compared to the single barrier design, the double barrier MOSHEMT exhibits a notable 15% increase in drain current, a 5% increase in transconductance, and an elevated breakdown voltage (VBR) of 140 V in E-mode operation. Furthermore, the radio frequency analysis of the double barrier device showcases exceptional performance, setting new records with a maximum oscillation frequency (fmax) of 1.148 THz and a gain cutoff frequency (ft) of 891 GHz. These impressive results obtained through deck-simulation affirm the immense potential of the proposed double barrier AlGaN/AlInGaN/GaN MOSHEMT for future applications in high-power and terahertz frequency domains.

Simulation of Interaction Processes of C20 Fullerene with Graphene

2023-12-02T13:52:21+00:00

Graphene, a carbon sheet one atom thick, with carbon atoms arranged in a two-dimensional honeycomb configuration, has a number of intriguing properties. Fullerenes are a promising material for creating electro-active elements in solar cells and active layers in thin-film organic transistors. A computer model of the C₂₀ fullerene molecule was constructed using the energy minimization method with the second-generation Brenner potential (REBO). A computer model of "infinite" defect-free graphene was built, designed to consider the process of adsorption of a C₂₀ fullerene molecule on its surface. To study adsorption process computer models of fullerene and "infinite" graphene were approached to the required distance with a different set of geometric arrangement of fullerene with respect to the graphene surface. It has been established that the adsorption of fullerene C₂₀ on the surface of graphene can be carried out in three different ways, differing in the number of interacting fullerene and graphene atoms. The binding energies and adsorption lengths for C₂₀ fullerene molecules adsorbed on the graphene surface in different ways are calculated. The way of adsorption corresponding to the highest binding energy and the shortest adsorption length was revealed.

Ab-Initio Investigation into the Physical Characteristics of CuInSe2 and CuInTe2 Compounds

2023-12-02T13:52:16+00:00

In this study, an analysis of chalcopyrite compounds CuInTe₂ and CuInTe₂ is presented, with a focus on their electronic, structural, optical, and thermal properties. The full-potential linearized augmented plane wave (FP-LAPW) method is employed for the investigation of these properties, based on a first-principles approach rooted in density functional theory (DFT). Two distinct approximations for the exchange and correlation potential, namely the WC-GGA and mBJ-GGA approximations, are considered in our calculations to ensure a robust and accurate examination of the materials under scrutiny. The findings obtained closely align with previously established theoretical and experimental data, thereby validating the reliability of our computational methodology. It is noteworthy that a novel dimension is introduced by this study, as the influence of both pressure and temperature on the thermal parameters of CuInTe₂ and CuInTe₂ compounds is explored. This facet of the research is distinguished by its innovative nature, as there is no prior record, to the best of our knowledge, of a similar analysis in the existing literature. The thermal properties are deemed of paramount significance, particularly in the context of crystal growth process optimization and the prediction of performance under extreme thermodynamic conditions.

Dangerous Bonds Individual of Hydrogenated Amorphous Silicon and Defect Absorption Spectra

2023-12-02T13:52:18+00:00

In this work, defect absorption spectra for defects characteristic of hydrogenated amorphous silicon are theoretically studied. It is shown that in order to determine defect absorption spectra using the Kubo-Greenwood formula, the indefinite integral in this formula must be written in a certain form. It was discovered that electronic transitions involving defect states are divided into two parts depending on the energy of absorbed photons. The values of the partial defect absorption spectrum at low energies of absorbed photons have almost no effect on the overall defect absorption spectrum. It has been established that the main role in determining the defect absorption spectrum is played by partial spectra determined by optical transitions of electrons between allowed bands and defects. It is shown that with a power-law distribution of the density of electronic states in allowed bands, the spectra of optical transitions between them and defects do not depend on the value of this power.

Effect of Compensation Degree and Concentration of Impurity Electroactive Selenium Atoms on Current Auto-Oscillation Parameters in Silicon

2023-12-02T13:52:20+00:00

One of the crucial phenomena is auto-oscillations of current in elementary and binary (A^IIIB^V, A^IIB^VI) semiconductor materials, which allow the creation of solid-state oscillators with a wide frequency range from 10^-3 to 10^-6 Hz. In this paper, we show the results of a study on the effect of the degree of compensation (K) and the concentration of electroactive impurity selenium atoms on the excitation conditions and parameters (amplitude, frequency) of the auto-oscillation current associated with temperature and electrical instability in silicon. In the research, silicon doped with selenium atoms Si<Se> of identical geometrical dimensions has been used. The compensation degree of the initial boron atoms with impurity selenium atoms in the samples is in the range of K = 2N_B/N_Se = 0.94-1.1. It was found that excitation conditions, the amplitude and frequency of auto-oscillation current significantly vary depending on the degree of compensation of selenium atoms with boron atoms in the initial silicon. Obtained experimental results showed that the auto-oscillation current in silicon doped with impurity selenium atoms is characterized by ease of control with stable parameters (amplitude and frequency), which makes it possible based on this unique physical phenomenon to develop and create oscillatory circuits in information technology.

Structure and Physico-Mechanical Properties of Polyelectrolyte Complexes Based on Sodium Carboxymethylcellulose Polysaccharide and Polyacrylamide

2023-12-02T13:52:15+00:00

In this paper, the structure and physico-mechanical properties of films of polyelectrolyte complexes (PEC) based on sodium carboxymethylcellulose (Na-CMC) with linear polyacrylamide (PAA) have been studied. Polyelectrolyte complexes were obtained by mixing aqueous solutions of Na-CMC and PAA components in various ratios of components and pH of the medium. The structure of the obtained products was determined using IR spectroscopy and electron microscopy. IR spectra in the range 400–4000 cm^-1were recorded on NIKOLET Magna-560 IR and Specord-75IR spectrophotometers (Carl Zeiss, GDR). The mechanical properties of films of polyelectrolyte complexes were determined by stretching at a constant speed of movement of the lower clamp, 50 mm/min, on an Instron-1100 automatic dynamometer (England) at room temperature. IR spectroscopic data showed that polyelectrolyte complexes based on Na-CMC and PAA were stabilized due to the cooperative ionic bond between Na-CMC carboxylate anions (-COO^-) and amine groups (-NH₂) of polyacrylamide. It is shown that PEC films with an equimolar ratio of Na-CMC and PAA components have an increased value of mechanical strength (σ_р = 38 MPa), elastic modulus (Е = 73 MPa) and a minimum relative elongation (ε = 0.5%). And in excess of Na-CMC or PAA leads to a decrease in mechanical strength and elastic modulus, which is associated with a decrease in the frequency of intermolecular bonds. It has been ascertained that water-soluble polyelectrolyte complexes based on Na-CMC and PAA with increased strength properties can be obtained from solutions of components taken at an equimolar ratio of interacting components. By changing the ratio of components, properties such as mechanical strength, modulus of elasticity and elongation can be controlled. This can serve as one of the means of controlling the structure and properties of Na-CMC and PAA polyelectrolyte complexes. The regulation of the physico-mechanical properties of PEC films opens up wide opportunities for their use as a soil structure former in agriculture and water management and as the basis for soft drugs in pharmacy.

Microstructure, Nano-, and Macro-Indentation Characterization of AISI 302 Steel After High-Temperatures Aging

2023-12-02T13:52:24+00:00

The structural and mechanical studies of the AISI 302 steel aim to design a correct heat treatment in order to optimize its mechanical properties. In this study, we investigated the influence of temperature and time of aging on the structural and mechanical characteristics of the AISI 302 steel. The steel was aged at temperatures of 1100°C and 1200°C and for times ranging from 0 to 6000 minutes. The structural and mechanical characterization techniques used were the metallurgical microscope, nanoindentation technique, and macro-hardness test. At the microstructural level, an increase in the time or temperature of the aging contributed to an increase in the austenite grains size of AISI 302 steel. This microstructural change led to a decrease in the nanohardness and a drop in the macro-hardness between the unaged and aged conditions of AISI 302 steel.

Influence of Aperture of Radiating Strip Structure on Electrodynamic Characteristics of Patch Antenna

2023-12-02T13:52:22+00:00

The paper presents the results of numerical modeling of the electrodynamic characteristics of a Vivaldi type patch antenna based on a circular disk resonator. The modeling was carried out using the semi-open resonator model by the finite element method (FEM) implemented in the HFFS package. The antenna was fed using a coplanar line segment. The antenna elements were placed over a grounded plane. The influence of design parameters and the function determining the curvature of the exponentially expanding slot discontinuity on the frequency, energy and polarization characteristics was investigated. It was established that with a certain selection of variable parameters, such an antenna can be matched with external circuits in the range from 7.03 GHz to 20 GHz with a level of VSWR values not exceeding 1.92. In the amplitude-frequency characteristic, fairly wide frequency bands with almost perfect matching are observed. The choice of the type of excitation element in the form of a section of the coplanar line made it possible to exclude additional elements inherent in Vivaldi antennas, namely, a section of the auxiliary strip line and a balancing resonator. This kind of antenna allows to form radiation patterns of various shapes from single-sided to cosecant quadrate. At the same time, in some intervals of observation angles, the formed fields turn out to be elliptically polarized with an ellipticity coefficient close to unity. The combination of the obtained results makes it possible to predict the use of this kind of antennas for operation with broadband signals.

The Computer Model of a Thermal Delayed Neutron Fluxes Forming System for Nuclear Medicine

2023-12-02T13:52:17+00:00

In the work the computer model of a cell of a system for generating fluxes of therapeutic beams of delayed neutrons, based on the use of delayed fission neutrons, was developed in the Geant 4 environment. The principle of such a neutron source is that when a powerful electron beam interacts with a combined tungsten target and a target containing fissile material, a fission reaction occurs; as a result of which neutrons are emitted. If we move a target activated in this way several tens of meters into a neutron flux generation system consisting of a heater, protection, collimator and reflector, we will obtain a compact neutron source for nuclear medicine. A significant advantage of such a neutron source is the absence of gamma background from the electron accelerator and the combined target, and a bulky protection system is not required. In the Geant 4 environment, the geometry of this cell was developed and a series of experiments were carried out with 10⁷ neutrons. The QGSP BIC HP physical sheet was used. A study of neutron energy spectra showed that more than half of the neutrons whose fluxes are formed using such a cell of the formation system have an energy <100 keV, which is suitable for use for therapeutic purposes. Analysis of the data obtained in a computer experiment made it possible to develop a modified cell of the system for generating streams of therapeutic beams of delayed neutrons, which differs from the basic one by the presence of a solid polyethylene moderator with holes for activated targets and a graphite reflector. Analysis of the data obtained showed that in this case the number of thermal neutrons hitting the detector increases 10 times compared to the base cell, and the energy of 80% of the particles does not exceed 5 keV, which is much better suited for therapeutic purposes.

Enhanced Heat Transfer Analysis on MHD Hybrid Nanofluid Flow Over a Porous Stretching Surface: An Application to Aerospace Features

2023-12-02T13:52:19+00:00

The advancement of aircraft technology has presented manufacturers with new criteria and problems for the functioning of their devices. It is essential that, in order to guarantee the secure operation of aerospace machinery, the failure mechanisms be identified and the operational durability of critical structural components be improved as quickly as possible. New aviation materials have been developed in modern years. In an aviation engine, engine oil lubricates, cools, washes, maintains against rust, decreases sound, and accelerates. Most important is lubrication. All mechanical components would burn out if not maintained. The aim of this work is to minimize costs by extending the operational life of aircraft components (mechanical and motor parts) and enhancing fuel mileage and flying distance. Based on the importance of the inspiration on magnetohydrodynamic Aluminum Oxide-Cobalt hybrid nanofluid flow over a stretching surface (SS) in the existence of porous medium, and thermal radiation are investigated. In this model we used Engine oil mixed with Aluminum Oxide and Cobalt nanoparticles. By using the suitable self-similarity variables, the PDE is transformed into ODEs. After then, the dimensionless equations are solved by using the Maple built in BVP Midrich scheme. Graphs and tables explain how the operational factors affect fluid flow efficiency. Compared to nanofluids, hybrid nanofluids have a better heat transfer rate.

Surface Electromagnetic TE-Waves Total Internal Reflection

2023-12-02T13:52:14+00:00

We have considered the refraction of surface electromagnetic waves (SEW) at the heterogeneous metasurface. The considered structure consists of three regions: mu-negative metamaterial, ordinary magnetic, and vacuum. The boundaries between considered media are planar. A phenomenological approach was used; media were assumed to be lossless and isotropic. In this paper, we show the possibility of total internal reflection effect for SEW of TE-polarization that can propagate along such heterogeneous metasurface. The value of the angle of total internal reflection decreases for higher frequency waves from the interval under consideration. The presented result may help design both research and industry complex systems.

Optical Parameters of Aluminum Alloy Samples Irradiated by High Current Relativistic Electron Beams

2023-12-02T13:52:15+00:00

The aluminum alloys D16, D16AT are widely used as construction materials in the aircraft industry. Questions connected with the enhancement of the properties of the construction elements made of the alloys through surface modification are of great interest now. The objects of the study in our paper are the samples of the aluminum alloy D16AT subjected to irradiation by high-current relativistic electron beams. Leaving aside the material science aspects, in this work we focused on modeling the optical properties of the samples. The problem is relevant because optical methods for surface analysis have become widespread due to their versatility and efficiency. Through the treatment of the preliminary measured ellipsometry data, we obtain the optical constants of the samples and their dispersion in the visible region of wavelength. The method used consists of an approximation of the reflection coefficient calculated from the ellipsometry data by finding the values of the parameters in the model. The last is performed by the least squares method. The reflection coefficient is assumed to correspond to the semibounded uniaxial medium with the optical axis perpendicular to the interface between the medium and the homogeneous and dielectric ambient medium. The dielectric function of the semibounded medium is approximated by the Drude-Lorentz model. The possibility of birefringence of the samples caused by the irradiation with electron beams is discussed.

Capacitive Spectroscopy of Deep Levels in Silicon with Samarium Impurity

2023-12-02T13:52:14+00:00

The effect of thermal treatment on the behavior of samarium atoms introduced into silicon during the growth process was studied using the method of transient capacitive deep-level spectroscopy (DLTS). It has been shown that various high-temperature treatments lead to the activation of samarium atoms in the bulk of n-Si and the formation of deep levels. The energy spectrum of deep levels arising during heat treatments has been determined. The dependence of the efficiency of formation of these levels in n‑Si<Sm> on the processing temperature has been studied. It was found that the higher the content of samarium atoms in the bulk of silicon at the same high-temperature treatment temperature, the higher the concentration of the deep level E_C–0.39 eV. From this, we can conclude that the EC–0.39 eV level is associated with the activation of samarium atoms in the n-Si<Sm> volume.

To the Theory of Dimensional Quantization in Narrow-Gap Crystals

2023-12-02T13:52:14+00:00

This article discusses studies of size quantization phenomena in zero-, one-, and two-dimensional semiconductor structures. The main attention is paid to the mechanisms of photon-kinetic effects in these structures. Despite many studies of the physical properties of low-dimensional systems of current carriers, the size quantization of energy spectra in narrow-gap semiconductors and the associated photonic-kinetic effects are still insufficiently studied. Therefore, this study focuses on the quantum mechanical study of size quantization in certain cases using Kane's multiband model. The insolvability of the 8×8 matrix Schrödinger equation in the Kane model for a potential well of arbitrary shape is analyzed. The dependence of the energy spectrum on the two-dimensional wave vector is studied for various cases. In particular, the energy spectra for InSb and GaAs semiconductors are considered, depending on the band parameters and the size of the potential well. Conclusions are presented on the analysis of various cases of size quantization in narrow-gap crystals with cubic or tetrahedral symmetry in the three-band approximation. It is shown that the energy spectrum corresponds to a set of size-quantized levels that depend on the Rabi parameter, band gap, and well size. The size-quantized energy spectra of electrons and holes in InSb and GaAs semiconductors are analyzed in a multiband model.

Non-Relativistic Calculation of Excited-State Ionization Potentials for Li-Like Ions Using Weakest Bound Electron Potential Model Theory

2023-12-02T13:52:20+00:00

In this study, a well-known Weakest Bound Electron Potential Model (WBEPM) was used to determine the exited-state ionization potential of lithium-like elements for different iso-spectrum series such as 1s² 2p¹ P_1/2, 1s² 3s² S_1/2 , 1s² 3d² D_1/2, 1s² 4s² S_1/2, 1s² 4p² P_1/2, and 1s² 4d² D_1/2 having nuclear charges from Z = 3 to Z = 18. On the other hand, to utilize relativistic correction, Briet-Pauli approximation has also been applied to the ionization potential using a fourth-order polynomial expression in the nuclear charge Z. The deviation within the range of 0.1% has been observed between estimated and experimental values that are quite remarkable. Furthermore, new ionization potentials were proposed for iso-series with Z ranging from 19 to 30.

Simultaneous Docking of Antiviral Drugs and Cyanine Dyes with Proteins Using Multiple Ligand Approach

2023-12-02T13:52:13+00:00

The protein-based nanosystems for targeted drug delivery of a wide array of substances, ranging from small drugs and therapeutic proteins to nucleic acids and genes, attract increasing attention due to their biocompatibility and biodegradability, extraordinary binding capacity for different ligands, accessibility from natural sources, effective drug protection and gentle encapsulation conditions. Due to the multitude of binding pockets and functional groups on the protein surface, these nanocarriers seem to be highly efficient multifunctional nanotheranostic systems that could incorporate both a therapeutic drug and a visualizing agent. This integration serves multiple purposes, including the regulation of drug release, monitoring the alterations at the target site in response to treatment, and offering crucial insights into the efficacy of the intervention in its early stages. The development of these advanced nanosystems necessitates a thorough comprehension of the potential interactions within these intricate systems. In the present study we assessed the potential of six trimethine and seven pentamethine cyanine dyes to serve as visualizing agents in the drug-protein-dye systems which include functionally significant proteins (cytochrome c, serum albumin, lysozyme and insulin and four antiviral drugs, viz. favipiravir, molnupiravir, nirmatrelvir and ritonavir. The ternary systems with the highest dye-protein surface shape complementarity were established for all groups of the examined cyanine dyes. The influence of the cyanine dye structure on the stability of the drug-protein-dye complexes was assessed. The obtained results indicate that the dye-protein affinity is not solely dependent on the length of the polymethine chain. It was found that the most prospective drug delivery systems containing the trimethines and pentamethines as visualizing agents are AK5-6-, AK5-8- and AK3-11-drug-albumin complexes.

Numerical Investigation of Thermophoresis and Activation Energy Effects on Maxwell Nano Fluid Over an Inclined Magnetic Field Applied to a Disk

2023-12-02T13:52:17+00:00

Numerical model is conducted to investigate the behavior of an incompressible Maxwell nanofluid model flow on a convectively stretched surface, considering the effects of thermophoresis and an inclined magnetic field. The system, originally formulated as a set of partial differential equations, is transformed into a system of ordinary differential equations using similarity transformations. The resulting equations are solved using the Runge-Kutta-Fehlberg method in conjunction with the shooting technique. The obtained physical parameters from the derived system are presented and discussed through graphical representations. The numerical process is assessed by comparing the results with existing literature under various limiting scenarios, demonstrating a high level of proficiency. The key findings of this study indicate that the velocity field decreases as the fluid parameters increase, while the fluid temperature diminishes accordingly. Additionally, the heat transfer rate decreases with increasing fluid and thermophoresis parameters, but it increases with Biot and Prandtl numbers.

Axial Structure of Gas Discharge Sustained by the Eigen Dipolar Wave of The Metal Waveguide with Varying Radius Filled by Magnetized Nonuniform Plasma

2023-12-02T13:52:13+00:00

The article presents the results of the theoretical study of the plasma density axial distribution in a stationary gas discharge sustained by the eigen dipolar wave that propagates in a long cylindrical plasma-metal structure. The discharge structure consists of a column of magnetized non-uniform plasma placed in the metal waveguide of variable radius. The study of the gas discharge is carried out within the framework of the electrodynamic model, in which the main attention is paid to the electrodynamic part of the model. To describe the processes that take place in plasma, the model equations are used. The influence of the metal waveguide inhomogeneity along the structure and the plasma density radial non-uniformity on the phase characteristics of the dipolar wave, its spatial attenuation, the field components radial distribution, the axial distribution of the plasma density sustained by this mode are determined. It is also analysed the condition for the discharge stability and find the regions, where dipolar mode can sustain the stable discharge. The obtained results can be useful for various technological applications.

Cathodic Vacuum ARC Multilayer Coatings (TiZrSiY)N/NbN: Structure and Properties Depending on The Deposition Interval of Alternate Layers

2023-12-03T09:40:25+00:00

Two series of multilayer coatings with different numbers of bilayers (268 and 536, respectively) were synthesised using the cathodic vacuum-arc deposition (CVAD) with the simultaneous sputtering of two different cathodes. The first cathode was made of the multicomponent TiZrSiY material, and the second one was made of technical niobium. The coatings were condensed in a nitrogen atmosphere at a constant negative bias potential applied to the substrate. The resulting coatings have a distinct periodic structure composed of individual layers of (TiZrSiY)N and NbN with the thicknesses determined by the deposition interval (10 or 20 s, respectively). The total thicknesses of the coatings determined by the number of bilayers were 11 and 9 microns, respectively. The formation of polycrystalline TiN and NbN phases with grain size comparable to the size of the layers has been identified for both series of coatings. The layers exhibit a columnar structure growth with a predominant orientation (111). The hardness of the experimental coatings depends on the thickness of the layers and reaches 39.7 GPa for the coating with the smallest layer thickness. The friction coefficient of the obtained coatings varies from 0.512 to 0.498 and also depends on the thickness of the layers. A relatively large value of the friction coefficient is due to high roughness and the presence of a droplet fraction on the surface as well as in the volume of the coatings.

The Contributions to Registration Efficiency of The Fast Neutron Reactions on The Nuclei of The Heavy Oxide Scintillators

2023-12-02T13:52:23+00:00

The results of the study of the contributions of the interaction reactions of fast neutron sources of ²³⁹Pu-Be and ²⁵²Cf to the counting efficiency of registration by oxide scintillators CdWO₄, ZnWO₄, Bi₄Ge₃O₁₂ and Gd₂SiO₅, presented. The amount of gamma quanta per input neutron emitted from final nuclei excited in the reactions of inelastic scattering (n, nʹγ)_in, resonant scattering (n, n)_res and capture (n, γ)_res and radiation capture (n, γ)_cap was measured. PMT R1307 operating in single-electron mode was used as a photodetector, the background rate was ~ 5*10³ s^-¹. The measured efficiency ε for scintillators ø40x40 mm was 752 for ZWO, 532 for CWO, 37 for GSO, and 23 for BGO in "counts/neutron" units, measurement error rate ~ 3-5%. The formation of the detector response is influenced by the parameters of the scintillator nuclei, such as the values of the interaction cross sections in the resonance region, the density of nuclear levels of the final nuclei, the lifetime of excited nuclear states, the upper limit of the resonance region of the cross section, as well as the scintillation time and geometric parameters of the scintillators. A phenomenological model of the response of an oxide scintillator to fast neutrons is proposed.

Assessment of Indoor Radon Gas Concentration in National Open University of Nigeria: A Case Study of Calabar Study Centre

2023-12-03T09:21:28+00:00

The current work deals with indoor radon (²²²Rn) concentrations measurements in the Calabar Study Centre of the National Open University of Nigeria using a Corentium Arthings digital radon detector meter for seven days representing a short–term average measurement of indoor radon gas concentration level. The geographical coordinates were recorded using a hand-held geographical positioning system for the sample point. Measurement were taken for seven days and the following data where obtained 83±2.19 Bq/m³,80±3.69 Bq/m³,86±5.57 Bq/m³,84±1.59 Bq/m³,82±3.59 Bq/m³,81±4.89 Bq/m³ and 85 ±5.59 Bq/m³.The average radon(²²²Rn) concentration level was found to be 83 ± 3.87 Bq/m³with a geometric mean of 82 ± 3.54 Bq/m³. It was observed that the radon concentration was below the reference level of 100 Bq/m³recommended by the World Health Organization (WHO). Although the current exposure of members of the public to natural radiation is not critical, the situation could change abruptly when other activities commenced. The excess life time cancer risk calculated for 70 years, 60 years, 50 years, 40 years and 30 years were 1.72 × 10⁻³,1.65× 10⁻³,1.39× 10⁻³,1.44× 10⁻³ and 0.69× 10⁻³ respectively. The calculated values of the excess life time cancer risk are all higher than the set limit of 0.029 × 10⁻³ by International Commission on Radiological Protection. However, there are no observed cases of lung cancer epidemic in this Centre. Therefore, it is advised to use fans and effective ventilation techniques to reduce radon levels. Identifying the regions of the country where people are most at risk from radon exposure should be the main goal of any national radon policy.

FLRW Universe in f(R,Lm) Gravity with Equation of State Parameter

2023-12-02T13:52:17+00:00

Available observational data regarding current cosmological characteristics suggest that the universe is, to a large extent, both isotropic and homogeneous on a large scale. In this study, our objective is to analyze the Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time using a perfect fluid distribution. We specifically investigate the framework of f(R, L_m) gravity within certain constraints. To accomplish this, we concentrate on a specific nonlinear f(R, L_m) model, represented by f(R, L_m) = R/2 + L^α_m. The field equations are solved using the equation of state parameter of the form of the Chevallier-Polarski-Linder (CPL) parameterization. The deceleration parameter study finds an accelerating universe at late times. The transition redshift is found to be ztr = 0.89 ± 0.25. Also, we discussed the physical and geometrical properties of the model.

Erratum: First-Principles Calculation of Structural, Electronic, and Optical Properties of Cubic Perovskite CsPbF3 [East European Journal Of Physics. 3. 263-270 (2023)]

2023-12-03T09:44:38+00:00

The purpose of this Erratum is to correct a misprint presented in the original article.