Numerical Analysis Techniques Research Articles

VIBRATION PHENOMENA INDUCED BY PULSED LASER HEATING OF MICROMECHANICAL CANTILEVER: INFLUENCE OF LASER-PULSE TEMPORAL SHAPE

Illumination-induced vibrational phenomena can significantly affect the mechanical behavior of micro-mechanical sensors (MEMS) and, consequently, the noise performance of detectors based on these sensors. In this paper, we study thermoelastic deflection induced by photothermal heating of a solid micro-mechanical cantilever illuminated by a short square laser pulse. An analytical-numerical technique based on the Laplace transform is employed to calculate the spectral function of lateral deflection. The results indicate that the profile of laser-induced vibrations depends on the temporal shape of the excitation optical pulse. The square pulse enhances the increasing trend of the high-frequency lateral vibration amplitude peak if cantilever thickness increases suggesting the possibility of size-dependent engineering of the properties of detectors utilizing micro-mechanical cantilevers.

Нестационарные структурные изменения в ВТСП композитах при воздействии фемтосекундных лазерных импульсов высокой интенсивности

The paper presents the results of experimental study and numerical analysis of defect formation processes in superconducting YBa2Cu3O7-x films on Hastelloy substrate under the influence of ultrashort laser radiation. The aim of the work is to develop a technique for numerical analysis and calibration of modes of exposure to high intensity femtosecond laser pulses to create systems of controlled defects in HTS composites. The processes of defect formation under the influence from 1 (single mode) to 20 (multiple mode) laser pulses on one point with a frequency of 10 Hz and duration of 2 ps were considered. The laser beam focusing radii were 1.5 and 3 μm. The dependences of the defect diameter and depth on the laser radiation energy in a wide range have been studied and the peculiarities of defect formation in the multiple mode have been shown. The physical processes occurring under the influence of laser radiation in different focusing modes are demonstrated. The proposed technique in the future can be extended for application in experiments of electron-probe spectroscopy, which will make it possible to study changes in the state of the electron-phonon subsystem of superconductors up to phase transitions associated with melting of the crystal lattice.

Analysis of unsteady heat and mass transfer in rotating MHD convection flow over a porous vertical plate

The aim of this research paper is to investigate the rotational flow of an unsteady magnetohydrodynamic heat and mass transfer flow due to convection over a vertical porous semi-infinite plate. The plate undergoes continuous circular motion, maintaining a constant velocity. To achieve this, we worked on both numerical methods and analytical techniques, particularly utilizing perturbation methods to solve the governing partial differential equations. Consequently, we derive an expression for the Nusselt and Sherwood numbers. We delve into the analysis of the velocity profile, temperature distribution, and concentration variation, exploring their behaviour under different physical parameters, including the magnetic field parameter, Grashof num-ber, Soret number and Schmidt number, as well as the Prandtl number. Our findings reveal that the velocity increases with rising values of Grashof, modified Grashof and Soret numbers, whereas it decreases with declining values of the magnetic field parameter, Prandtl number and Schmidt number. Additionally, as rotation gradually intensifies, the fluid velocity closely follows the boundary and becomes negligible as it moves away from it. To facilitate a comprehensive examination of the fluid flow and heat and mass transfer characteristics, we employ graphical representations. Furthermore, this paper offers an in-depth discussion of the underlying physical aspects and their implications.

Three-dimensional finite-volume theory for elastic stress analysis in solid mechanics

The finite-volume theory is a powerful numerical technique for structural analysis in solid mechanics and has emerged as an alternative to the finite-element method. The finite-volume theory is an equilibrium-based approach that employs surface-averaged tractions and displacements acting on the faces of a subvolume. In addition, this theory employs the equilibrium equations at the subvolume level and continuity conditions between adjacent subvolumes along subvolume faces. The finite-volume theory has been successfully used for two-dimensional structural analyses. However, in the context of three-dimensional solid mechanics analysis, this numerical technique has encountered instability problems related to the interpretation between adjacent subvolumes' faces. These problems result in the singularity of the global stiffness matrix, which has delayed the publication of a three-dimensional version of the finite-volume theory for continuum elastic structures. These numerical instability problems can be solved by employing a modified stiffness matrix, where the Tikhonov regularization method is used to artificially add minimal stiffness in the main diagonal of the global stiffness matrix. This contribution proposes the stress analysis of three-dimensional continuum elastic structures by the finite-volume theory, where problems with analytical solutions are employed for verification.

Machine Learning, Analytical, and Numerical Techniques for Vibration Analysis of Submerged Porous Functional Gradient Piezoelectric Microbeams with Movable Supports

This research numerically and analytically examines the dynamics of underwater movable porous functional gradient (FG) microsize beams integrated with a piezoelectric layer. Also, the efficiency and accuracy of support vector machine (SVM) techniques in the vibration prediction of the microbeam are assessed. The dynamical simulation is conducted by considering the assumptions of Rayleigh beam theory, different porosity distribution models, nonlinear and linear stress–temperature relationships, and modified couple stress theory (MCST). The eigenvalues of the system, critical temperature increment, and critical speed of the microbeam are computed. Comparative studies are carried out, frequency analyses are performed, and stability diagrams are drawn. The impacts of microbeam geometry, fluid mass ratio, piezoelectric voltage, and axial force on stability behavior in variable complex environmental conditions are parametrically inspected. The outcomes revealed that the smaller the contribution of voids on the outer surface of the microbeam, the better the microbeam stability. It is understood that among the utilized regression-based SVMs, the quadratic polynomial and medium Gaussian kernel models have the highest performance and speed, respectively. These research outcomes will be advantageous for designing the next generation of targeted drug delivery devices.

Geometry effects on the pressure-temperature limit curve of small modular reactor vessel

The reactor vessel (RV), recognized as a critical component that ensures the safety of nuclear power plants, is designed and manufactured with sufficient margins in strength and fracture toughness. With the development of small modular reactors (SMRs), RVs include transition regions characterized by geometric discontinuities that limit the application of existing evaluation methods. This study proposes adequate modeling and numerical analysis techniques tailored to assess the different geometries and better understand their impact. A suitable modeling scheme was introduced to consider specific features when evaluating postulated cracks in the RV. Fracture mechanics evaluations using the finite element method were also conducted to examine accurately the cracks and their associated risks. The results from each finite element analysis were utilized to develop pressure-temperature limit curves, providing insight into the operational range of a developing SMR. This framework addresses the unique challenges in RV design and enhances the safety and reliability of SMR operations.

Multistable dynamics and chaos in a system consisting of an inertial neuron coupled to a van der Pol oscillator

Abstract We consider a dynamical system consisting of a van der Pol oscillator linearly coupled to an inertial neuron with two wells potential. Analytical studies are conducted focusing on the energy computation, the dissipation and symmetry, as well as the determination and characterization of the equilibrium points. We define the parameter ranges related to different types of oscillations in the coupled system in order to have an overall idea of the nature of the attractors (hidden or self-excited) that may exist. We apply numerical analysis techniques (2-parameter diagrams, bifurcation analysis, phase portraits, basins of attractions, etc) in accordance with the previous operating range in order to shed light on the plethora of competing dynamics of the model and possible forms of strange attractors as well. Another salient point of this work is the coexistence between five self-excited attractors (limit cycle and chaos) with a hidden attractor (limit cycle). We also examine the impact of symmetry breaking on the system response. An appropriate analog simulator of the coupled system is designed and simulated in PSpice in order to check the results reported during the theoretical analyses. We believe that the results of the present work complement and enrich previously published ones concerning the dynamics of a system composed of a van der pol oscillator coupled to a (non-oscillating) double-well oscillator.

Parameter-dependent fractional boundary value problems: analysis and approximation of solutions

We study a parameter-dependent non-linear fractional differential equation, subject to Dirichlet boundary conditions. Using the fixed point theory, we restrict the parameter values to secure the existence and uniqueness of solutions, and analyse the monotonicity behaviour of the solutions. Additionally, we apply a numerical-analytic technique, coupled with the lower and upper solutions method, to construct a sequence of approximations to the boundary value problem and give conditions for its monotonicity. The theoretical results are confirmed by an example of the Antarctic Circumpolar Current equation in the fractional setting.

Flexural properties and optimisation of hybrid composites reinforced by carbon, glass and flax fibres

This paper presents a study on the flexural properties of hybrid composites (HC) reinforced by carbon, glass, and flax fibres, utilising Finite Element Analysis (FEA). Possible optimal layups are identified through the application of design rules, and regression-based models are developed to predict flexural strength. With the developed models, multi-objective optimisation is done to minimise the cost and weight subjected to a given minimum required flexural strength. By integrating numerical simulation, regression analysis, and optimisation techniques, this research offers a practical approach to the design and fabrication of HC with enhanced mechanical performance and cost-efficiency.

Deep learning-driven predictive tools for damage prediction and optimization in composite hydrogen storage tanks

This research presents a comprehensive framework for predicting the damage in lightweight composite high-pressure hydrogen storage tanks and optimizes their design to prevent failure. By integrating advanced analytical methods, numerical analysis, and deep learning techniques, we introduced a novel approach to enhance design optimization and damage prediction. The framework employs the 3D elasticity anisotropy theory to predict mechanical performance, incorporating failure criteria for accurate damage analysis. A parametric study was conducted to examine the effects of thickness, pressure, and diameter on the behavior of the tank. The analytical results were compared against finite element analysis using the WoundSim software, underscoring the significance of the modeling assumptions. Furthermore, we developed a new framework that combines deep neural networks with differential evolution optimization (DNN-DEO) to predict stress and damage in composite pressure vessels while identifying the optimal design parameters (pressure, radius, and thickness) to minimize failure risks and maintain high performance. A graphical user interface (GUI) was also designed to automate calculations and predictions, providing an intuitive tool for users. This integrated approach offers a powerful solution for optimizing the design and operation of lightweight composite hydrogen storage tanks, ensuring the reliability and efficiency of hydrogen storage systems.

NiCr2−xGdxO4 ceramics’ magnetic, structural and electrical conductivity as well as their activation energy properties

The goal of this work is to synthesize and characterize nanoscale nickel chromites nanoparticles doped with Gd using the economical solution combustion method. Numerous analytical techniques, including energy formation, electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, are used for in-depth characterization. The results show that at low values of coercivity, high values of saturation magnetization, and low values of remnant magnetization, the chromites correspond. The crystalline size of Gd-doped nickel chromites decreases. For the normal spinel structure’s tetrahedral and octahedral coordinated forms, respectively. The present research shows that agglomerated forms and irregular, spherical structures formed by SEM (Scanning Electron Microscope) form regular structures. The present investigation uses a transmission electron microscope (TEM) to illustrate the formation of regular-shaped particles. As demonstrated by Gd-doped NiCr2O4 and pure NiCr2O4, stable interstitial positions are among the typical interstitial positions of the metal oxides. Investigations of magnetic properties from the paramagnetic to the ferromagnetic phase formation. Electrical conductivity and activation energy dropped with Gd doping of nickel chromites and showed an inverse relationship with particle/crystallite sizes. Lastly, applications for NiCr2−x GdxO4 particles were examined and future research directions were also suggested.

Isogeometric topology optimization for maximizing band gap of two-dimensional phononic crystal structures

A smooth and efficient isogeometric topology optimization (ITO) method for maximizing band gaps in two-dimensional phononic crystals is developed in the paper. The band gaps of phononic crystals are computed by the NURBS-based isogeometric analysis, and the material distributions of two-dimensional phononic crystals are represented by the smooth, high-order continuity of the NURBS surface. The densities defined at each control point of the NURBS surface are employed as optimized design variables. The isogeometric analysis optimization using the same spline technique for both geometry and numerical analysis can benefit the optimization procedure and obtain smooth optimized structures, which can be easily used in 3D printing. The maximizing band gaps of phononic crystals for both out-of-plane and in-plane wave modes are obtained here using the present ITO approach. Numerical examples validated the effectiveness and reliability of the ITO method in broadening the band gaps and finding the optimal phononic crystals. And the numerical results show that the smooth optimized structures are obtained with fewer iterations.

Complexes of Copper(II) and Adenine at Various pH: Synthesis and Characterization

The coordination of Cu(II) ion with purine base is pH dependent and versatile. This study describes the synthesis, structuralcomponents and coordination behavior of Cu(II) with adenine. Three complexes of Cu(II) with adenine have been preparedat different pH in aqueous solution and ambient conditions. All synthesized complexes are polycrystalline solids of variouscolors, air-stable and partially soluble in polar solvents. The complexes were characterized by numerous analytical techniques including compositional analyses, Fourier transform infrared and UV-visible analyses, and thermal investigation. The elemental analyses of the complexes established their chemical composition as [Cu(adeninium)Cl3], [Cu(adenine)(H2O)Cl2] and [Cu(H2O)2(adeninato)2]. Analytical results suggest that the adenine nucleobase could act as a cationic (pH: 5), or a neutral (pH: 7), or an anionic (pH: 8) monodentate ligand in pH facilitated aqueous solution. In the structure, the purine moiety, chloride ion and aqua groups are situated around the copper(II) center is basically in a tetrahedral arrangements. Protonation or deprotonation of the adenine and intramolecular interligand hydrogen bond assisted the pH dependent versatile coordinating behavior of purine base. Dhaka Univ. J. Sci. 72(2): 84-90, 2024 (July)

Advances In Celestial Mechanics And Dynamical Astronomy: A Literature Review

This research paper provides a comprehensive examination of recent developments within the realm of celestial mechanics and dynamical astronomy. By conducting an in-depth analysis of existing literature, this study aims to elucidate the pivotal advancements and contributions that have significantly enhanced our understanding of celestial body motion and dynamics. Through a meticulous evaluation of scholarly articles, books, and conference proceedings, this literature review delves into the fundamental concepts and methodologies that underpin celestial mechanics and dynamical astronomy. The paper explores a wide array of topics, encompassing orbital dynamics, dynamical systems, asterodynamics, planetary science, and explanatory systems. By synthesizing the findings of esteemed researchers and scientists, this study reveals the profound impact of novel numerical methods, analytical techniques, and observational discoveries on the field. Furthermore, it identifies areas ripe for future investigation, underscoring the vast potential for continued exploration and innovation within celestial mechanics and dynamical astronomy. Ultimately, this literature review seeks to provide a valuable resource for scholars, researchers, and students seeking insight into the latest advancements and emerging trends in celestial mechanics and dynamical astronomy, while also highlighting the boundless opportunities for future research and discovery.

Effect of Heterojunction Dynamics on Charge Transfer Mechanism in Type-II ZnS/MoS2 Nanocomposite

The development of novel nanocomposites holds immense potential for various applications in optoelectronics, catalysis, energy storage systems and photovoltaic applications. In this manuscript, the synthesis and comprehensive characterization of type-II ZnS/MoS2 nanocomposite synthesized by hydrothermal roue are reported. The synthesized nanocomposite was characterized by numerous analytical techniques to analyse its structural, morphological, optical, and electrochemical properties. XRD analysis revealed the presence of both ZnS and MoS2 phases in the nanocomposite, validating its successful formation. UV-visible spectroscopy (UV) was utilized to study its optical properties which revealed a band gap of 3.2 eV. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging demonstrated the presence of large ZnS sheets with smaller nanoparticles of MoS2 dispersed over the surface, indicating the hierarchical structure of the composites. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to evaluate the electrochemical performance and charge transfer dynamics of the nanocomposite. These techniques facilitated the investigation of their suitability for solar cells. CV analysis displayed prominent reduction peaks, indicating the presence of active electrochemical sites in the nanocomposites. Furthermore, it revealed diffusion-controlled behaviour which indicates the potential of the nanocomposite for efficient solar cells. EIS analysis revealed the presence of Warburg diffusion in the Nyquist plot which indicates the possibility of efficient charge transport and ion diffusion within the nanocomposites. This shows the suitability of nanocomposite material for solar cell applications.

Aero-propulsion coupling effects and installation characteristics of a distributed propulsion system

The ducted fan, as a quintessential propulsion device utilized in Distributed Electric Propulsion (DEP) aircrafts, exhibits a significant influence on the aero-propulsion coupling effects due to its installation characteristics on the wing. In this paper, we employed steady-state numerical analysis techniques in conjunction with actuator disk models and overset mesh to investigate aero-propulsion coupling effects and installation characteristics of a DEP configuration with 5 ducted fans distributed along the wing's trailing edge. We compared various conditions to the wing baseline airfoil under hover condition and cruise condition of the fan tip speed ratio λ from 1.44 to 4.32 and fan installation angle δT from 0 to 90°. The results indicate that DEP system affects the flow over the wing downstream of the maximum thickness point of the baseline airfoil profile at an installation angle of 0. A higher tip speed ratio the flow is accelerated in the upper surface region near the wing's trailing edge, whereas the low energy fluid fails to be accelerated at lower λ, instead forming a local flow blocking. With the increase of the fan installation angle, the overall system lift increases, but the thrust decreases, and both trends increase with the increase of the tip speed ratio. Specifically, the thrust provided by the distributed fans is reduced, and the inlet becomes one of the drag sources when the installation angle is high.

Parameter determination of Johnson–Holmquist–Cook constitutive model and calibration for Indiana Limestone

In this study, a comprehensive parameter determination procedure for the Johnson–Holmquist–Cook (JHC) constitutive model is introduced, including calibration and validation processes for Indiana Limestone rocks. The procedure is conducted utilizing the existing physical and mechanical properties of Indiana Limestone. To obtain an accurate set of parameters for the JHC model for Indiana Limestone, an extensive dataset comprising mechanical and physical properties of Indiana Limestone rocks was initially compiled. The static mechanical tests incorporated uniaxial compression, triaxial compression, direct tensile, and uniaxial strain data, while the dynamic mechanical test data was primarily derived from the Split Hopkinson Pressure Bar experiments. Subsequently, the JHC constitutive model parameters were determined using existing literature data, employing statistical analysis, theoretical derivation, and numerical back analysis techniques. One of the damage parameters was determined through numerical post-peak behavior calibration of triaxial compression strength test results on experimental data. Finally, the accuracy of the determined parameters was validated by comparing the numerical and experimental results of both static and dynamic tests. This study effectively addresses the challenges associated with the numerical method using the JHC material model, such as the complex parameter determination process and the costly required tests, thereby preserving the efficiency and applicability of the numerical method.

A PROJECTION-BASED ERROR ANALYSIS OF HDG METHODS FOR A NONLINEAR SYSTEM: COUPLED IN BOTH DIRECTIONS

A technique for the error analysis of hybrid discontinuous Galerkin methods (HDG) is applied to a coupled problem. The technique relies on the use of a projection whose design is inspired by the numerical traces of the methods. When this technique appeared in the literature (Cockburn et al., 2010), the authors performed an analysis for an elliptical problem. In this work, we will analyze two coupled elliptical subproblems. The main idea is to apply this projection technique, defined based on the shape of the numerical traces, in the numerical analysis of the HDG method for the coupled problem to verify whether this numerical analysis technique still maintains its main characteristics, such as simplicity and consistency, even with this coupling. The analysis of the coupled problem in two directions was carried out following the strategy of first analyzing the partially coupled problem (De Oliveira, 2024), and then the coupled problem in both directions. The differences between both problems were the analytical development of the coupling and the computation of the approximate solution, which in the problem treated here requires a fixed point algorithm. We expect that the orders of convergence for the approximate solutions correspond to theoretical expectations with the approximation spaces used, which are made up of natural polynomials, that is, order k for vector variables and k+1 for scalar variables. All theoretical and and experimental objectives were achieved, i.e., the convergence in the HDG simulations corresponded to what was theoretically expected.

ENTEROBACTER CLOACAE LIPOPOLYSACCHARIDE EXPORT SYSTEM PROTEIN (LPTC) GENE EXPRESSION VARIATION VIA EXPOSE TO BIOSYNTHESIZED ZINC OXIDE NANOPARTICLES

Synthetic nanoparticles (NPs) have become more widely used in the disinfection and health sectors owing to their ability to effectively penetrate biological systems. Recent research has demonstrated the ability of microbial proteins and enzymes to function as reducing agents throughout the NP-production process, providing a different option to chemical and physical techniques. This method not only saves money and is effective, but also has the least possible environmental impact. This work used Lactobacillus spp., as the reducing and capping agent to create zinc oxide nanoparticles, (ZnO NPs). Numerous analytical techniques were employed to examine the generated ZnO NPs; these techniques include ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). As an opportunistic pathogenic bacterium, Enterobacter cloaca possesses several virulence characteristics that enable it to infiltrate target tissues. However, bacteria can become resistant to antibiotics, which in turn makes treating bacterial infections becomes more difficult. With the development of science at the biotechnology level, using zinc oxide ZnO NPs on isolates of Enterobacter cloacae, we conducted research in the promising field of nanotechnology. The impact of three different concentrations of ZnO NPs on the gene expression of Enterobacter cloaca lipopolysaccharide transport (Lpt) proteins in isolates obtained from some patients suffering of various infections was investigated. Bacteria with the highest multidrug resistance were selected for further analysis. Expression of LptC gene was reduced significantly at concentration of 125 mg/mL (P < 0.01) for all the isolate that treated with ZnO NPs.

Adsorption of Eriochrome Black T on Pseudo Boehmite and Gamma Alumina Synthesized from Drinking Water Treatment Sludge: A Waste-to-Recycling Approach

Eriochrome black T is considered as one of the anionic dyes with potential harmful effects on human health and the environment. Among other processes, adsorption can contribute to the removal of these dyes. In the present study, two adsorbent materials, pseudo-boehmite (γ-AlOOH) and gamma alumina (γ-Al2O3), were synthesized and tested in the removal of the Eriochrome black T molecule (EBT). γ-AlOOH and γ-Al2O3 were obtained by precipitation from NaAlO2 solution at pH = 7, at a temperature of 80 °C, and by the thermal transformation of γ-AlOOH at 800 °C, respectively. In order to gain insights into the structural, chemical, thermal and morphological properties of these materials, numerous analytical techniques were involved, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential thermogravimetric–thermal analysis (TGA-DTA), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and specific surface area measurement using the Brunauer–Emmett–Teller (BET) method. Several adsorption parameters were studied, such as the adsorbent dose, initial concentration, pH, contact time and reaction temperature. The kinetic study showed that EBT adsorption follows the pseudo-second-order model. The Langmuir isotherm model revealed a maximum EBT adsorption capacity of 344.44 mg g−1 and 421.94 mg g−1 for γ-AlOOH and γ-Al2O3, respectively. A textural and structural analysis after adsorption highlighted the effective adsorption of the dye.