Key Engineering Materials Vol. 1029

Abstract: The solution of the time-dependent Schrödinger equation for the helium atom in double excited states using the time-dependent Hartree-Fock (TDHF) equation is outlined in this work. Schwartz interpolation is used to derive grid representations that are particularly suitable for problems involving the Coulomb potential. This method allows a non-uniform spatial discretization of grid and provides an accurate description of the excited states, eigenvalues and wave functions with a few numbers of grid points. We have introduced the solution using the Coulomb Wave Function Discrete Variable Representation (CWDVR) which is an economical and promising step towards a more efficient treatment of many-electron systems. The equation is transformed into a diffusion type equation by an imaginary-time evolution method and the solution is obtained numerically. The asymptotic solution of these equations leads to definite energy double excited states. We have shown that the calculated electronic energies for the helium atom agree well with the best available values.

Abstract: This study examines the phenomenon of electron ionization induced by the excitation of hydrogen atoms using a short laser pulse. We determined the temporal probability density distribution of electrons ejected from the atom and scattered in the continuum upon ionization of an atom by a short laser pulse, demonstrating that the electron probability density has increased radially. Based on Born's interpolation and Kemble's imaging theorem , the photoelectron momentum distribution found by square rooting the wave function's modulus matches the results found using the ionization amplitude, which is a standard method in quantum mechanics. We show that we can directly determine the differential ionization cross-section for the time-dependent one-electron wave function without considering spatial integrals for finding the ionization amplitude. It makes the work easier because it gets rid of the need to create a scattered wave function, which is needed to figure out the results that show how atomic and molecular photoelectron momentum is spread out in modern labs.

Abstract: This paper aims to show that the fully differential ionization cross section when an antiproton collision with a hydrogen atom can be directly expressed as a time-dependent wave function. For the projectile, wave function corresponding to the specific scattering angle was converted by two-dimensional Fourier transform from the wave functions of corresponding to impact parameters. This wave function shows how the ejected electron probability density distribution varies with time. We are shown that the calculation of the fully differential cross section of ionization can be directly determined by the local value of the wave function without the need to calculate the spatial integral for calculating the transition amplitude. It has been shown that the direct determination of the fully differential cross section by this time-dependent wave function is in good agreement with the results of determined the traditional method is by the transition amplitude.

Abstract: The crystal structure, electronic and optical properties of organic molecular crystal Trans-4-(trifluoromethyl) cinnamic acid (4-TFMCA, C₁₀H₇F₃O₂) were studied using the density functional theory (DFT). Since 4-TFMCA undergoes solid-state photodimerization under an external light source (UV), the optical properties were a subject of interest. In the calculations, experimental lattice parameters were obtained from previous studies and used as an initial geometry. Structural optimization was achieved using the vdW-DF2 functional with norm-conserving pseudopotentials (NCPP). To optimize the crystal structure, the Birch-Murnaghan equation of state (EOS) was used, and the total volume showed a decrease of 2%. The electronic band structure of the 4-TFMCA crystal was first calculated. The electronic and optical band gaps were predicted, and an artificial acceptor level, attributed to the unsaturated carbon and hydrogen atoms in the molecule, was observed. Additionally, optical properties such as the dielectric function, reflectivity, loss function, refractive index, and absorption coefficient were computed.

Abstract: This paper deals with the problem of visualization of the widely known and of considerable practical value problem of sound wave propagation in a liquid medium containing gas bubbles. The study was carried out using modern methods of computer simulation in the COMSOL Multiphysics software environment, which provides extensive opportunities for numerical analysis of complex physical processes. In the course of the study, a set of calculations was performed, which made it possible to obtain a series of illustrative images reflecting the distribution of acoustic and sound pressure both in the volume of the water medium and on the boundary surfaces at different sound frequencies. The constructed model demonstrated its efficiency, allowing to identify areas with increased and decreased acoustic pressure formed on the surface of air bubbles under the influence of sound waves. Visualization of these processes opens up opportunities for analysis and optimization of acoustic systems operating in the presence of gas inclusions in the liquid.

Abstract: In this study, we used a linear regression machine learning model to predict the stress-strain curve of AZ91/graphene composites. The proposed model successfully made predictions with an accuracy of approximately 0.99 (99%) and a small error. The mechanical properties obtained from the curves, such as the yield and ultimate tensile strength, were in excellent agreement with the actual and predicted values. This linear regression model is also well-suited for predicting the stress-strain curve of composites.

Abstract: This research aims to design and develop honeycomb structures for sandwich structures, focusing on enhancing the strength and reducing the weight of the components compared to the prototype. The research began with creating test models using a 3D printer and tensile testing with a Tensile Testing Machine. The data obtained from the tests were analyzed using SolidWorks software to adjust the material properties to align with the experimental results. The experimental design was conducted through the Response Surface Methodology (RSM), resulting in nine test model designs. These models were fabricated using a 3D printer, and their strength was analyzed with SolidWorks and validated through tensile testing. The experimental results revealed that six models exhibited a 133.655% increase in strength and a 7.568% reduction in weight compared to the prototype.

Abstract: This research presents a numerical study on the Equal Channel Angular Pressing (ECAP) process using AA6061 aluminum alloy, employing Finite Element Analysis (FEA) with ABAQUS/Explicit software. The primary objective is to simulate the deformation behavior of AA6061 under different die angles (60°, 90°, and 120°) and evaluate the simulation results by comparing them to experimental findings. The study focuses on stress distribution, plastic strain, and deformation patterns during the ECAP process to identify the optimal processing conditions. The results provide insights into the effects of die angle on the material's deformation behavior and mechanical properties, offering a foundation for optimizing the ECAP process for AA6061.

Abstract: The paper presents a study of the behavior of particles of different sizes in a medium, focusing on their settling rate, hardness and elastic modulus. The settling rate was calculated using Stokes’ law, which shows a quadratic dependence on the particle radius. The results demonstrate that particles with a diameter of 100 μm settle significantly faster compared to smaller particles (1 μm and 10 μm), while the latter remain suspended for a long time due to the significant influence of viscosity. Mechanical properties of particles, such as hardness and elastic modulus, exhibit size dependence: hardness decreases with decreasing particle size, making smaller particles more vulnerable to mechanical stress. The elastic modulus shows a weak decrease for small particles, which may affect their resistance to deformation during collisions. The results obtained are important for the practical use of particles in various technological processes, such as liquid purification, development of nanomaterials, transport of solid particles in liquid or gas flows. The study emphasizes the need to consider the relationships between the physical, mechanical and dynamic characteristics of particles for optimizing technological processes and developing new materials.