Mass Boundary Conditions Research Articles

Modeling and Simulation of the Impact Behavior of a Sports Knee Joint Protector Using the Preparation Method of Ferroelectric Photovoltaic Thin Film

This article analyzed the preparation methods of ferroelectric photovoltaic thin films. This article analyzed the modeling of impact mechanics, including mass distribution, boundary conditions, and loading conditions, to ensure appropriate load transfer and joint stability; in the simulation, it was found that the material properties included photovoltaic and ferroelectric properties, which were suitable for the production of knee joint protectors. From these data, it could be found that the deformation of protector 2 was smaller than that of protector 1, indicating that the PZT material in protector 2 could better fix the protector and prevent significant deformation due to impact behavior. It had a higher hardness value, representing higher wear performance. The results of this article highlighted that sports knee joint protectors based on PZT materials could better cope with impact behavior, extend the lifespan of the protector, and protect the wearer’s knee joint.

Ultrafast field-driven valley polarization of transition metal dichalcogenide quantum dots

We study theoretically the electron dynamics of transition metal dichalcogenide (TMDC) quantum dots (QDs) in the field of an ultrashort and ultrafast circularly polarized optical pulse. The QDs have the shape of a disk and their electron systems are described within an effective model with infinite mass boundary conditions. Similar to TMDC monolayers, a circularly polarized pulse generates ultrafast valley polarization of such QDs. The dependence of the valley polarization on the size of the dot is sensitive to the dot material and, for different materials, show both monotonic increase with the dot radius and nonmonotonic behavior with a local maximum at a finite dot radius.

Experimental study on a cable-stayed bridge isolated with the combination of elastoplastic cables and fluid viscous dampers in the transverse direction

It is usually challenging to design an effective transverse isolation strategy that needs both large restoring force and large deformation capacity for cable-stayed bridges to meet the requirements under regular operation and earthquakes. The authors proposed a novel transverse isolation device that combines elastoplastic cables and fluid viscous dampers (FVDs) to address this challenge. The elastoplastic cables are adopted to control the relative displacements at the girder-pylon connections in the transverse direction under both regular operation and earthquakes. FVDs are responsible for dissipating input seismic energy. To further validate the effectiveness of the proposed isolation system under both far and near-fault ground motions, shake table tests were conducted for a cable-stayed bridge with a scale ratio of 1/20. Details of the scaled model for the isolated and fixed systems, including dimensions of the components, additional mass arrangement, instrumentations, and boundary conditions, are briefly described. Seismic responses are recorded for each test case, such as accelerations and displacements of the pylons and girder, hysteretic responses of the combined devices, and strain responses of the pylon rebars. The experimental results indicate that the transverse boundary conditions have significant effects on the seismic responses of the girder, and the high-mode content of ground motions mainly dominates the seismic responses of the pylons. In addition, the isolated system effectively reduces the seismic responses at the bottom of the pylons, and the effectiveness of the isolation is becoming more evident with an increase in the PGA of the ground motions.

Heat Gneration on Three Dimensional Casson Nanofluid Motion with Arrhenius Activation Energy Effect Via Stretching Sheet

The current study Arrhenius activation energy effect on 3D porous Casson nanofluid (NFs) motion via stretching sheet (SS) is explored in this study using numerical process based on Runge Kutta Fehlberg (R-K-F). To provide useful visions into the physical and dynamic examinations of this study, convective heat and mass boundary conditions are used. The established of nonlinear partial differential equations (PDEs) has been transported into ordinary differential equations (ODEs) by helping suitable similarity transformations. The translated ODEs are computed by help of shooting iterative approach. The outcomes of this study are validated with previous investigations, and get excellent agreements. The behaviour of different physical parameters is analysed. It is observed that, the heat transfer rate is high in presence of Activation energy for large values Prandtl number and mass transfer rate decline low in presence of Activation energy for numerical values of Lewis number.

Effect of Torso Boundary Conditions on Spine Kinematic and Injury Responses in Head-First Impact Assessed with a 50th Percentile Male Human Body Model

<div>Computational and experimental studies have been undertaken to investigate injurious head-first impacts (HFI), which can occur during automotive rollovers. Recent studies assume a torso surrogate mass (TSM) boundary condition, wherein the first or first two thoracic vertebrae are potted and constrained to only move in the vertical loading direction. The TSM boundary condition has not been compared with a full body (FB) model computationally or experimentally for HFI. In this study, the Global Human Body Models Consortium 50th percentile male detailed human body model (M50-O, Version 6.0) was applied to compare the kinematic, kinetic, and injury response of an HFI with a TSM boundary condition (M50-TSM), and a full body boundary condition (M50-FB). Impacts (to M50-TSM and M50-FB) were simulated between the head and a rigid plate using a commercial FE code (LS-DYNA). The impact velocity of 3.1 m/s corresponded to the onset of spinal injury in diving reconstructions, and the impact velocity reported in experiments. The TSM boundary condition was simulated by applying a mass of 16 kg to the first thoracic vertebra (T1), and constraining motion to only the vertical direction. A quantitative comparison of the head and spine impact forces, spine kinematics, and prediction of hard tissue fracture was reported. The M50-TSM model demonstrated a 53.4% lower (straighter) spinal curvature 10 ms after impact, compared to the M50-FB. The lower curvature of the M50-TSM resulted in higher neck loads during that timeframe (2.26 kN M50-TSM, 1.44 kN M50-FB). The resulting hard tissue fracture in M50-TSM was attributed to direct compression at an early time (<5 ms) in the impact, while M50-FB demonstrated compression-extension fractures later (>16 ms) in the simulation. It was concluded that kinematics, kinetics, and injury response differed for the TSM and FB boundary conditions, and therefore these conditions are critical to consider when investigating HFI.</div>

Convective heat and mass transfer rate on 3D Williamson nanofluid flow via linear stretching sheet with thermal radiation and heat absorption

A mathematical analysis is communicated to the thermal radiation and heat absorption effects on 3D MHD Williamson nanoliquid (NFs) motion via stretching sheet. The convective heat and mass boundary conditions are taken in sheet when liquid is motion. As a novelty, the effects of thermal radiation, heat absorption and heat and mass convection are incorporated. The aim is to develop heat transfer. Williamson NFs are most important source of heat absorption, it having many significant applications in “energy generation, HT, aircraft, missiles, electronic cooling systems, gas turbines” etc. The suitable similarity transformations have been utilized for reduce basic governing P.D. E’s into coupled nonlinear system of O.D. E’s. Obtained O.D. Es are calculated by help of R–K–F (“Runge–Kutta–Fehlberg”)4th order procedure with shooting technique in MATLAB programming. We noticed that, the skin friction coefficient is more effective in Williamson liquid motion when compared with NFs motion with higher numerical values of stretching ratio parameter, Williamson liquid motion is high when compared to NFs motion for large values of magnetic field. We compared with present results into previous results for various conditions. Finally, in the present result is good invention of previous results.

Effects of Environmental and Operational Conditions on Structural Health Monitoring and Non-Destructive Testing: A Systematic Review

The development of Structural Health Monitoring (SHM) and Non-Destructive Testing (NDT) techniques has rapidly evolved and matured over the past few decades. Advances in sensor technology have facilitated deploying SHM systems for large-scale structures and local NDT of structural members. Although both methods have been successfully applied to identify structural damage in various systems, Environmental and Operational Condition (EOC) variations can influence sensor measurements and mask damage signatures in the structural response. EOCs include environmental conditions, such as temperature, humidity, and wind, as well as operational conditions, such as mass loading, vibration, and boundary conditions. The effect of EOCs can significantly undermine the reliability and robustness of damage assessment technologies and limit their performance. Thus, successful SHM and NDT systems can compensate for changing EOCs. This paper provides a state-of-the-art review of the effects of EOCs on SHM and NDT systems. It presents recent developments in advanced sensing technology, signal processing, and analysis techniques that aim to eliminate the masking effect of EOC variations and increase the damage sensitivity and performance of SHM and NDT systems. The paper concludes with current research challenges, trends, and recommendations for future research directions.

Natural Frequencies of a Viscoelastic Supported Axially Functionally Graded Bar With Tip Masses

The frequency parameters of an Axially Functionally Graded (AFG) bar for viscoelastic and point mass boundary conditions are studied in this paper. The structures with functionally graded materials under axial loads can be modelled as AFG bars. Those may be considered as support elements with spring and dashpot in the vibration isolation. Keeping the ratio of force frequency and natural frequency at a certain level is ensured to control the natural frequency therefore dynamic amplification factor with different material combinations. Various boundary conditions are attained by changing the spring and damping coefficients of viscoelastic support elements and the ratio of rod mass to tip mass. Researchers assume that the beam material properties in directions of length and thickness change exponentially, individually, or both in their studies. There are a few studies on the AFG rods in the existing studies. Analysis is carried out via the finite element method for the non-dimensional frequency parameters of the bar in MATLAB. The energy equations of the motion are obtained in the frame of axial bar theory considering the material properties of the bar vary longitudinally according to the power-law distribution. The effects of material distribution, spring, damping and tip mass values on the bar's frequency parameters and structural behaviour have been extensively investigated.

Bulk–edge correspondence for unbounded Dirac–Landau operators

We consider two-dimensional unbounded magnetic Dirac operators, either defined on the whole plane or with infinite mass boundary conditions on a half-plane. Our main results use techniques from elliptic PDEs and integral operators, while their topological consequences are presented as corollaries of some more general identities involving magnetic derivatives of local traces of fast decaying functions of the bulk and edge operators. One of these corollaries leads to the so-called Středa formula: if the bulk operator has an isolated compact spectral island, then the integrated density of states of the corresponding bulk spectral projection varies linearly with the magnetic field as long as the gaps between the spectral island and the rest of the spectrum are not closed, and the slope of this variation is given by the Chern character of the projection. The same bulk Chern character is related to the number of edge states that appear in the gaps of the bulk operator.

Ultrafast valley polarization of graphene nanorings

We study theoretically electron dynamics of a graphene nanoring placed in the field of an ultrashort optical pulse. We describe the graphene nanoring within an effective model with infinite mass boundary conditions. For an optical pulse with a duration of just a few femtoseconds, the electron dynamics is coherent and is described by a time-dependent Schr\"odinger equation. If the optical pulse is circularly polarized, then two valleys of graphene are populated differently, resulting in a finite valley polarization of the system after the pulse. Such a valley polarization is a unique property of graphene nanoscale systems, while for a graphene monolayer, a circularly polarized pulse does not produce any valley polarization. The valley polarization of the graphene nanoring depends on parameters of the system, such as inner and outer radii. With the system's size increasing, the valley polarization monotonically decreases, converging to its zero value for the infinite graphene monolayer.

Dynamics of longitudinal impact in uniform and composite rods with effects of various support conditions

A finite element formulation is developed in this paper to analyze impact-induced waves in a rod collide with a striking mass. The formulation is established based on St. Venant's contact theory. Effects of mass ratios and boundary conditions, whether fixed, free, or elastic, are investigated. Both uniform rods and composite rods are considered. A shortcoming in traditional finite element models is to consider the rod and the struck mass as separate identities that gives inaccurate results for the discontinuity at the arrival of the impact wave. Instead, the proposed model considers the rod and the struck mass as one system that gives extremely accurate corresponding results. Wave propagation, transmission, and reflection from the constraint end and at the discontinuous interface are thoroughly analyzed. Succession collision that may occur between the struck mass and the rod is also investigated. Whenever it is possible, the finite element results are compared with analytical solutions. The analytical solutions are obtained with either the direct mode superposition method (DMSM) or wave theory. The proposed model can be used to model many systems that are subjected to longitudinal impact loadings and for crack detection. The model has the potential to be extended to perform simulation and analysis for many practical applications, like nanostructures under impact loads.

Thermosolutal natural convection cooling process of a thermal source inside a partially porous cavity

This work deals with the numerical study of the thermosolutal natural convection from a heat source immerged in a porous layer, which is placed vertically inside a square cavity. All walls of the cavity are thermally insulated, except the right wall, which is maintained at cold temperature. For the mass boundary conditions, the vertical walls are subjected to a gradient of concentration, whereas the horizontal walls and the part of the left wall that contacts with the heat source are impermeable. The finite volume method and the SIMPLER algorithm are employed to solve the mathematical equations. The effects of several geometrical and physical parameters are analyzed, such as vertical heat source positions (0 ≤ Yp ≤ 0.8), the porous layer thickness (0 ≤ Xp ≤ 1), the thermal conductivity ratio (1 ≤ Kr ≤ 100), Darcy number (10−6 ≤ Da ≤ 10−2), Rayleigh number (104 ≤ Ra ≤ 106), Lewis number (0.1 ≤ Le ≤ 10), and the buoyancy ratio (-5 ≤ N ≤ 5). The results indicate that the best cooling of the heat source is observed when the Yp is located between 0.38 and 0.55. Moreover, the case of coupling heat and mass transfer (N ≠ 0) offers low maximum heat source temperature compared to that of the classical natural convection (N = 0), especially with an increase in the Ra number and N and/or a decrease in the Le number. In addition, an increase in the thermal conductivity ratio and the permeability of the porous layer (Da) enhances the cooling process of the thermal source.

Dirac–Coulomb operators with infinite mass boundary conditions in sectors

We investigate the properties of self-adjointness of a two-dimensional Dirac operator on an infinite sector with infinite mass boundary conditions and in the presence of a Coulomb-type potential with the singularity placed on the vertex. In the general case, we prove the appropriate Dirac–Hardy inequality and exploit the Kato–Rellich theory. In the explicit case of a Coulomb potential, we describe the self-adjoint extensions for all the intensities of the potential relying on a radial decomposition in partial wave subspaces adapted to the infinite-mass boundary conditions. Finally, we integrate our results, giving a description of the spectrum of these operators.

Spectral Properties of Relativistic Quantum Waveguides

We make a spectral analysis of the massive Dirac operator in a tubular neighborhood of an unbounded planar curve,subject to infinite mass boundary conditions. Under general assumptions on the curvature, we locate the essential spectrum and derive an effective Hamiltonian on the base curve which approximates the original operator in the thin-strip limit. We also investigate the existence of bound states in the non-relativistic limit and give a geometric quantitative condition for the bound states to exist.

Characterization of MHD convective flow of Jeffrey nanofluid driven by a curved stretching surface by employing Darcy–Forchheimer law of porosity

The mathematical modeling of Jeffrey nanofluid flow driven by a curved stretching sheet, by employing Darcy–Forchheimer law of porosity with thermal radiation, chemical reaction and convective heat, and mass boundary conditions, has been made. The flow anchored partial differential equations are dealt with similarity variables to switch them to simple ordinary differential equations. Runge–Kutta–Fehlberg 45th-order method, a viable numerical tactic, was availed to extract numerical solutions for the considered problem. While performing a numerical procedure to obtain numerical solutions for all flow fields against concerning parameters, all other parameters have been fixed to their standard values. Furthermore, to discuss the results obtained, various plots are drawn using numerical extractions. Here, the study reveals that an enhancement in Deborah number increases velocity panel, whereas upliftment in relaxation time to retardation time ratio shows opposite behavior. Also, with an increase in Forchheimer’s number, the velocity panel decreases. Furthermore, the Biot numbers have an increasing influence on thermal and concentration fields, respectively. Schmidt number () and chemical reaction parameter () increase, then the concentration panel () declines.

Implementing the Vieta–Lucas Collocation Optimization Method for MHD Casson and Williamson Model under the Effects of Heat Generation and Viscous Dissipation

Theoretical investigation of magnetohydrodynamics (MHD) Casson and Williamson fluid flow and heat and mass transfer in laminar flow through a stretching sheet in the presence of heat generation is carried out in this study. The convective wall temperature and convective wall mass boundary condition are taken into account in this study. A study is also provided, which looks into the impact of viscous dissipation. Except for a temperature‐dependent thermal conductivity, all properties of the proposed model are assumed to be constants in the study. The spectral collocation method based on the shifted Vieta–Lucas polynomials is used to give an approximate formula for the n‐order derivative and solve numerically the coupled momentum, energy, and mass equations. This method is used to convert the problem’s system of ordinary differential equations (ODEs) into a nonlinear system of algebraic equations. This system is built as a restricted optimization problem and optimized to obtain the series solution’s unknown coefficients. Some theorems are provided to investigate the method’s convergence. The statistics, which are given visually, were compared to the results of other researchers’ theoretical analysis.

Analytical simulation of time dependent electromagneto-hydrodynamic flow of Williamson fluid due to oscillatory curved convectively heated Riga surface with variable thermal conductivity and diffusivity

The main objective of the present article is to provide an analytical simulation for time dependent boundary layer flow of non-Newtonian Williamson fluid due to stretchable curved oscillatory Riga surface. Also the characteristics of heat and mass transport are studied under the influence of variable thermal conductivity and diffusivity along with convective heat and mass boundary conditions. Additionally, energy equation is also characterized with the impact of heat production. Curvilinear coordinate scheme is followed to attain the boundary layer expressions for the flow model. The governing nonlinear partial differential equations are solved analytically via homotopy analysis method (HAM). Graphs are plotted to examine comprehensively the consequences of various concerned parameters like modified magnetic parameter and radius of curvature, Williamson fluid parameter, relation of the surface's oscillating frequency to its stretching rate constant, Prandtl number, variable conductivity and heat production parameters, Schmidt number and variable diffusivity parameter on concentration, temperature, pressure and velocity profile. Also the outcomes of afore said variables on surface drag force, rate of temperature and mass transmission (Nusselt and Sherwood numbers) are shown in tabular form. The liquid velocity amplitude is enhanced with modified magnetic parameter and shows opposite behavior for Williamson fluid parameter.

Computational Study on Three-Dimensional Convective Casson Nanofluid Flow past a Stretching Sheet with Arrhenius Activation Energy and Exponential Heat Source Effects

The effective applications of Casson fluid in drilling processes, biological treatments, food processing, and bio-engineering activities have caught the interest of a wide range of researchers. The suitable knowledge of heat transfer via non-Newtonian fluid is essential for the achievement of best quality products in industry. Thus, the three-dimensional Casson nanofluid flow over a stretching sheet with Arrhenius activation energy and exponential heat source effects is investigated in this paper using a computational process based on iterative power series (IPS) method. To provide useful insights into the physical and dynamic examinations of this topic, convective heat and convective mass boundary conditions are used. The developed model of nonlinear partial differential equations (PDEs) has been transformed into ordinary differential equations (ODEs) using similarity transformations. The numerical solution of the transformed ODEs is obtained by employing the IPS technique combined with shooting iteration approach. The results of this study are validated with the previous studies, and excellent agreements have been obtained. The behavior of various capable physical parameters is analyzed. It is observed that the thermal and concentration fields show an enhancement with respect to the exponential heat source parameter and thermal and concentration Biot numbers. Further, the Arrhenius activation energy parameter has shown a significant effect on the concentration field.

Computational analysis of thermal and mass transmit in a hydromagnetic hybrid nanofluid flow over a slippery curved surface

This study addresses a steady, incompressible and electrically conducting hybrid-nanofluid flow through a stretching curved surface. The consequences of velocity slip, convective heat and mass boundary conditions have been included in the study. We have opted for water as a base fluid and Molybdenum Disulphide for a nanofluid and Silver for a hybrid-nanofluid. In the cooling practice, the proficiency of a hybrid-nanofluid compared to a nanofluid is accomplished in detail. Through a similar transformation, we obtain non-linear ODEs from PDEs and solve subsequent equations numerically by employing the RK-4 shooting practice. An incitement of inspiring flow-factors on flow specific is accomplished precisely through figures and charts. The result shows that thermal plus concentration outlines have a linear relationship with thermal and concentration Biot numbers, and it discloses a reverse relationship with curvature factor. The outcomes certify that the highest rate of heat transport is enhanced by 85.27% and 99.62% for a hybrid-nanofluid and a nanofluid, respectively. No such research works were done before. Henceforth, consequences are unique and novel.

Nonlinear vibration and instability of a randomly distributed CNT-reinforced composite plate subjected to localized in-plane parametric excitation

This study presents a semi-analytical formulation for the nonlinear vibration and dynamic instability of a randomly distributed carbon nanotube-reinforced composite (RD-CNTRC) plate. Three cases of localized in-plane periodic loadings are studied. The analytical stress fields within the RD-CNTRC plate for all the in-plane stress components (σij, (i, j = x, y)) are developed by solving the in-plane elastic problem using Airy's stress approach. The effective mechanical properties of the RD-CNTRC plate are evaluated by the Eshelby-Mori-Tanaka technique. The plate is modeled based on higher-order shear deformation theory (HSDT) in conjunction with the von-Kármán nonlinearity. Using Hamilton's principle, the governing partial differential equations (PDEs) are derived, whose approximate solution is sought, referring to the Galerkin method. The resulting nonlinear ODEs are solved using the Incremental Harmonic Balance (IHB) Method to compute the nonlinear vibration response of the RD-CNTRC plate. Further dropping the nonlinear terms, these ODEs are solved by Bolotin's method to trace the instability region. The proposed semi-analytical method is an effective strategy for studying the influence of different parameters such as agglomeration models, CNT mass fraction, pre-loading, and boundary conditions on the nonlinear vibration and dynamic instability characteristics of the RD-CNTRC plates. The reduced computational effort allows the design phase to be supported in selecting parameters when designing RD-CNTRC plates with stability and vibration requirements.