The research article deals with the study of a thermoelastic double porosity layer of width h with an internal heat source overlying an elastic halfspace. The equations of motion are solved analytically to obtain the expressions of displacement, stress, temperature distribution and pressure in macro and micro pores. The analytical results are then complemented with a numerical example to show the variation of these quantities with horizontal distance. The effect of width of the layer and internal heat source on the quantities is shown by the graphical representations.
In this paper, the losses of kinetic energy in big band saw machines are examined. Expressions have been obtained to calculate the kinetic energy of the mechanical system in the ideal and the real case. With the help of these expressions, the final dependencies for determining the energy losses for the studied class of machines were obtained. These dependences show the influence of linear and angular inaccuracies, i.e. of the parameters e and alpha. A number of optimization solutions have been proposed that allow the values of both parameters to be calculated so that energy losses are minimal. The proposed approach can be used in the design of other classes of woodworking machines, as well as in the study of energy losses for this class of machines.
This study analyzes the influence of finite-length effects on thermally induced flow in a rarefied monatomic gas between two stationary coaxial cylinders. Using the Direct Simulation Monte Carlo method, thermoacoustic waves induced by a sudden inner-cylinder temperature shock are examined under four axial boundary conditions: diffuse, adiabatic, symmetric, and periodic. Results reveal a transient regime, where thermoacoustic waves propagate and reflect depending on boundary type, and a steady-state regime, where temperature, density, and velocity profiles stabilize. Axial boundaries significantly affect wave dynamics, dissipation, and flow structure, particularly at intermediate and radial positions. The findings emphasize the importance of accurate boundary modeling in rarefied gas dynamics for applications in microscale devices, vacuum systems, and aerospace technologies.
In this paper, the influence of material composition on free vibration of bidirectional functionally graded beam using a quasi-3D theory is investigated. The material properties are assumed to be graded in both the thickness and longitudinal directions by power gradation laws and four different distribution patterns are considered. Equations of motion based on a quasi-3D model that contains undetermined integral forms and involves few unknowns to derive, are obtained from Hamilton's principle. The problem is solved using the Navier solution for a simply supported beam. The accuracy of the present solution is demonstrated by comparing it with some results available in the literature and a good agreement is showed. The effects of the type of material distribution, power-law indexes, and the aspect ratio on the fundamental frequencies are examined and highlighted.
In the present paper, a closed form solution of transverse Stokes rarefied slip fluid flow past axially symmetric bodies is being considered. The transverse Stokes drag is evaluated for axially symmetric bodies in the slip-flow regime and which is valid for Knudsen numbers, Kn <= 0.1. The extension of Stokes drag on micro-axially symmetric particles from no-slip boundary conditions to slip boundary conditions has been given. It has been concluded in the end that transverse Stokes drag on the micro-axially symmetric particles is equivalent to Stokes solution for continuum flows multiplied by a rarefaction coefficient which is dependent upon the Knudsen number. The author proposed a new approach of providing analytic closed form drag formula for transverse Stokes slip flow past axially symmetric bodies for rarefied gas.
Coastal vegetation provides critical wave attenuation for shoreline protection, but existing models are computationally prohibitive or lack educational transparency. We present wave-attenuation-1d, an open-source Python package implementing linearized shallow water equations with vegetation-induced drag. The model uses fourth-order Runge-Kutta integration on a staggered grid, achieving unconditional stability through implicit treatment of the drag term. Numerical experiments with monochromatic waves through 40-meter vegetation patches demonstrate transmission coefficients from 0.655 (sparse) to 0.010 (dense vegetation), corresponding to 34.5% and 99.0% wave height reductions. While the one-dimensional framework simplifies threedimensional flows and flexible vegetation dynamics, it provides a computationally efficient baseline for understanding wave-vegetation interactions. The package features standardized NetCDF output and modular architecture, bridging research-grade simulations and accessible educational tools for exploring nature-based coastal protection solutions.
The problem under consideration involves identifying the coefficients of a partial sum of a Fourier series used to approximate the effect of an external periodic force on a Lienard oscillator. A method for constructing a nonlinear identifier is proposed, enabling the real-time asymptotical estimation of the oscillator velocity and coefficients of a partial sum of a Fourier series by means of displacement measurements. This method is based on the synthesis of invariant relations that make it possible to interrelate the variables of a special extended dynamic system and determine unknown variables as functions of known ones. The asymptotic convergence of estimates of unknowns to their true values is proven. The results of numerical simulation of the proposed method for the Duffing oscillator are presented.
This article presents a study on the behavior of rectangular functionally graded plates under thermo-mechanical bending conditions. The study employs a finite element method to analyze these plates, consisting of functionally graded face sheets and core. Validating the proposed model's accuracy through comparisons with existing literature, the investigation explores the effects of key parameters thermal load, geometric factors, and volume fraction distribution on thermo-mechanical bending behavior. The study includes a thorough parametric analysis to identify significant factors impacting normal stresses and deflection of functionally graded plates. The findings offer valuable insights for designing functionally graded plates subjected to combined thermal and mechanical loads. With its simplicity and potential for future advancements, the suggested method proves highly suitable for addressing these problems.
This study presents new insights into structures of magnetohydrodynamics flow in a double lid-driven L-shaped cavity under an oriented magnetic field. The governing equations are presented using the stream functionvorticity approach and solved numerically. Radial basis function-finite difference method utilizing polyharmonic splines is proposed to achieve local refinement. Flow topologies are examined for problem parameters, including the inclination angle, Hartmann number, and Reynolds number. The results indicate that as the strength of the magnetic field increases, the Lorentz force becomes the dominant factor, making the impact of the Reynolds number on flow negligible. The strength and inclination angle of the magnetic field play crucial roles in influencing the flow structure by altering the number, position, and type of critical points.
This paper provides an overview of research in arterial solid mechanics for readers who may not have expertise in the field of biomechanics. The review explores whether a healthy artery functions as an "intelligent" organ. A brief description of the biological and mechanical processes that govern arterial performance is followed by an overview of typical experimental findings and mathematical models describing the passive, active, and remodeling behavior of healthy arteries. The review includes critical commentary based on the author's perspective. The term "Bulgarian imprint" highlights the significant contributions of Bulgarian scientists, frequently in collaboration with international partners, to arterial biomechanics. When cited, the corresponding papers are denoted in the reference list by an asterisk.
This study explores how bed roughness affects the length of hydraulic jumps in a rectangular compound channel under zero slope. Experiments were done in a 10 m flume with a compound cross-section (minor bed: 14.4 cm, major bed: 25 cm), using plastic roughness elements (epsilon = 6-12 mm). Different flow rates and upstream depths were tested. Results show that increased roughness shortens jump length (Lj) by enhancing turbulence and momentum transfer. The minor bed's relative roughness (epsilon/b) had the strongest effect. Dimensionless equations were developed linking Lj/h1 with the Froude number (F1) and roughness. Findings underline the role of bed roughness in managing jumps, with implications for energy dissipation and flood control systems.
In this study, a three-dimensional simulation was conducted to examine the effect of rib integration on the heat transfer characteristics in Taylor-Couette-Poiseuille flow (TCPF). The ribs are fixed to the periphery of the inner cylinder of the system studied. Three cases were analyzed: 4, 8, and 16 ribs. Initially, the study considers purely axial flow with a stationary inner cylinder, while the next phase evaluates the combined influence of axial flow and cylinder rotation. The findings reveal that the configuration with four ribs achieves the most significant heat transfer improvement, with an increase of up to 312% at higher Reeff values and approximately 103.6% at lower Reeff values.
This paper considers the problem of inviscid and incompressible flow with a free surface over sinusoidal obstacles of finite length placed in the bottom with finite length. The flow is considered by neglecting the gravity effect, but we take into account the surface tension effect. Applying the first order perturbation technique in conjunction with the Hilbert transformation, we provide an approximate solution to the boundary value problem with mixed boundary conditions arising from the flow problem. The unknown free-surface profiles are established for each large value of the Weber number. The obtained results reveal the simplicity of the used method; they also provide approximate solutions to these kinds of problems.
This study performs a computational fluid dynamics (CFD) anal ysis of a solar air collector (SAC) under natural and forced circulation, vali dated against experimental data. A 2D ANSYS Fluent model with a structured mesh simulated thermo-hydraulic behavior, including Boussinesq buoyancy and transient solar loading. In natural circulation, outlet temperatures peaked at 355 K around 13:00-14:00, with < 3% deviation from experiments. Ver tical gradients of triangle T approximate to 30 K indicated buoyancy-driven flow. Under forced circulation, the outlet temperature peaked earlier at 333.51 K, showing better thermal uniformity due to a thinner boundary layer. Forced convection im proved thermal efficiency by 39% over natural circulation but required addi tional pumping. CFD proves valuable for optimizing SAC designs, balancing efficiency, simplicity, and operational costs
A monitoring of liver elasticity is important in managing viral hepatitis because liver damage leads to hepatocellular carcinoma. The prospective study was conducted over a 24 month period among newly diagnosed patients with viral hepatitis B (HBV) and C (HCV). The aim of the study was to predict the cases of hepatocellular carcinoma (HCC) according to liver elasticity and age of the patients. The patients in risk are those whose liver stiffness (LS) is over 13 kPa and was established that they are between 18-25%. The results showed that hepatitis C and age over 50 yrs. leads to high level of liver stiffness. The patients over 50 yrs have 3.25 times higher odds of increased LS compared to those under 50 in case of HCV and 2.15 times higher odds in case of HBV.
In this manuscript, two modified truncated expansion methods (i.e MTEM-I and MTEM-II) are built up to obtain analytical solution (i.e so called traveling wave solutions) for triple (1+1) dimensional nonlinear partial differential equations (NLPDEs)such as Sawada-Kotera equation (SKE), generalized Korteweg-de Vries equation (GKdVE) and Kaup-Kuperschmidt equation (KKE), which have been widely used in mathematical physics. The present topic minimizes the complex nature and non-integrable characteristics to obtain solution of NLPDEs. To demonstrate the influence of the parameters, 3D plots are surfed for triple NLPDEs. certification.
This study explores the validation process of a drop test virtual FEM experiment of a complex structure-battery pack. A physical prototype has been manufactured and subjected to drop tests, where its impact behavior has been examined through the use of high-speed imaging and visual tracking software. Different indicators have been used in order to validate the virtual analysis through adjusting materials, boundary conditions and analysis settings. A validated virtual analysis gives an insight of the deformations and stresses in different areas of the tested assembly that can be used for further geometry optimization and/or certification.
This study investigates the effects of artificial thermal aging on the mechanical properties of 30% glass fiber-reinforced Polyamide 11 (PA11-GF30). Tensile and compression tests were conducted on specimens aged at 125 degrees C, 150 degrees C, and 175 degrees C for up to 4152 hours. The results indicate a progressive decline in mechanical properties, with tensile strength decreasing from an initial 104.6 MPa to 92.63 MPa (12.4% reduction) at 125 degrees C, 73.96 MPa (34.3% reduction) at 150 degrees C, and 74.36 MPa (33.8% reduction) at 175 degrees C. Similarly, compressive strength declined from 135.59 MPa to 122.81 MPa (9.4% reduction) at 125 degrees C, 124.28 MPa (8.3% reduction) at 150 degrees C, and 104.76 MPa (22.7% reduction) at 175 degrees C. Notably, an initial strengthening phase was observed due to post-crystallization, particularly at lower temperatures. Elongation at break exhibited a sharp decline, confirming the transition from ductile to brittle behavior, with samples at 150 degrees C and 175 degrees C reaching the 5% brittleness threshold after 2016 hours and 1344 hours, respectively. These findings provide critical insights for the design and application of PA11-GF30 in high-temperature environments, supporting its use in automotive, aerospace, and industrial sectors requiring durable polymer-based components.
The dynamics is investigated for an axially moving immersed plate subjected to time-dependent tension and follower force. The study is focused on simultaneous resonant cases i.e. principal parametric resonance and subharmonic resonance. Based on von Karman plate theory and D'Alambert's principle, the vibration equations of the plate are derived. Employing the method of multiple scales, simultaneous resonance is discussed. Stability of periodic solutions of the system is examined by Lyapunov's stability theory. By analyzing the influence of follower load amplitude and tuning parameter on the steady-state periodic motion of simultaneous resonances, the system displays complex and variable dynamical behaviors. Furthermore, the approximate analytical results are verified by using the Runge-Kutta method.
This research investigates the effects of regime flow in recess on the pressure distribution within a hydrostatic bearing flat pad supplied by an orifice restrictor. The validation of the findings is conducted using Reynolds' analytical method, which demonstrates a strong correlation with computational fluid dynamics (CFD) simulations, particularly when the Reynolds number in the recess is maintained below 1000. The simulations were carried out using the SST-k omega turbulence model. The results reveal that a reduction in viscosity has a pronounced effect on lubrication efficiency. Furthermore, it was observed that deeper recesses yield a more uniform pressure distribution in contrast to shallower recesses, and an increase in the eccentricity ratio results in the presence of the Rayleigh step throughout the entire pressure supply spectrum.
