Boundary Conditions Research Articles

Finite element analysis of a generalized rotating FGM vessel subjected to thermo-mechanical loadings: Effect of Poisson ratio and inhomogeneity parameters.

Cylinders and thick walled cylindrical shells are commonly utilized in several industries to transport and store fluids under certain pressure and temperature conditions. In the present paper, a numerical solution is developed in order to investigate displacement, temperature and stress fields in a rotating pressure vessel made of generalized functionally graded material (FGM) subjected to different thermo-mechanical boundary conditions. The aim is to investigate the effect of Poisson ratio, internal pressure and temperature and inhomogeneity parameters on the stress and deformation distributions of the rotating pressure vessel. The material is considered isotropic nonhomogeneous and linearly elastic with its properties varying along the radial direction. Additionally, certain conditions, such as exterior or interior problems where r → ∞ or r → 0, respectively, are impossible to resolve using the variation of attributes as a power-law distribution. An approach to the spatial Young modulus distribution that is more broad has been suggested in the literature which can be applied to such physical challenges. The rotation of the pressure vessel is considered in the analysis, and the temperature distribution is assumed to be non-uniform. Since an analytical solution to the differential equation is not accessible, the conventional Galerkin discretization approach of the Finite Element Method (FEM) is applied, nowadays is considered one of the main numerical tools for solving Boundary Value Problems (BVP). It is addressed how stress, strain, and displacement are affected by the inhomogeneity parameter, rotation speed, pressure, temperature, and Poisson ratio. The examination of the various findings indicates that changes in the temperature profile, rotation, and inhomogeneity parameter on the thermoelastic field have a substantial impact on the stress and strain in the FGM cylinder. The findings indicate that the Poisson ratio and inhomogeneity parameters have a significant impact on the stress and deformation distributions. According to the results, the above-mentioned parameters can be adapted to control the thermoelastic filed in a FGM cylinder. The present research offers significant perspectives on the development and enhancement of rotating FGM pressure vessels intended for high-temperature applications.

Analytical formulation for the study of the effect of shear deformations on beam-columns and piles: Engesser and Haringx theories

This paper presents a novel analytical formulation to study the impact of shear deformations on beam-columns and piles by means of the Timoshenko-Engesser’s and Timoshenko-Haringx’s theories. The proposed solution enables the analysis of lateral deformation or buckling, while considering the effect of shear deformations. It offers the flexibility to i) incorporate different boundary conditions at the ends of the element (e.g., semi-rigid connections and lateral transverse springs) and ii) consider an inhomogeneous elastic foundation. When certain variables are disregarded, the proposed GDE can capture particular cases of GDEs found in the literature for beam-columns and piles. Examples are provided to demonstrate the simplicity and practicality of the proposed method, and its accuracy is validated against available analytical or numerical methods. The influence of the shear effects, as computed from Engesser’s and Haringx’s methods, on the lateral and buckling responses of beam-column and pile elements is discussed.

Comparing sensitivities of groundwater head to variations in hydraulic parameters under boundary conditions of river stage rise and tidal variation

The sensitivity of hydraulic head responses to spatially distributed hydraulic parameters is essential for uncertainty analysis, inverse modeling, and parameter estimation and interpretation. This study formulates the Fréchet sensitivity kernel of hydraulic head responses to a suddenly rising boundary and a sinusoidal head fluctuation boundary to variation of spatially distributed hydraulic parameters in a semi-infinite, one-dimensional (1-D), confined aquifer, and it then derives analytical solutions. Different from previous studies that derived expressions for Fréchet kernels in the time domain for a 2-D pumping test, this study is the first to derive the closed-form Fréchet kernels in time and frequency domains for a semi-infinite, 1-D, confined aquifer. This study uses the Fréchet kernels to investigate the nature of singularities in the spatial sensitivity functions around the observation location and boundary. The information content revealed by observation of head change or head fluctuation amplitude at a given specified location and time (or frequency) under the above two boundary conditions is different. When comparing Fréchet sensitivity kernels across various times or periods, multi-frequency information, much like multi-time information, can be instrumental for hydrogeological parameter inversion. The explicit-form Fréchet sensitivity kernels also identify the optimal time or period for obtaining measurements.

Analytical solution for simplifying the pile-soil interaction to a spring-damping system under horizontal vibration

An analytical solution is developed to investigate the model of simplifying the pile-soil interaction to a spring-damping system when the horizontal earthquake input or the top of the model is subjected to horizontal dynamic load. Based on Euler-Bernoulli theory, the dynamic equilibrium equations of pile in soil and air are established, respectively. Then, utilizing the corresponding boundary conditions, potential function decomposition, and transfer matrix method, the analytical expression of impedance at the pile head whether the horizontal earthquake input or the top of the system is subjected to horizontal dynamic load can be presented. Furthermore, the model of the pile-soil complex interaction can be simplified as a spring-damping system according to the stress equilibrium at the pile bottom in the air. Moreover, the rationality of the present solution (without simplification) is verified by comparison with existing methods, and then the difference between the present solution (without simplification) and the spring-damping system (simplification) is also compared. Finally, the influence of the parameter variation in the pile buried in the soil and soil free-field on the simplified model are discussed. The research results will be instructive for the simplification of numerical model for pile-soil interaction.

The mediated and moderated effects of IEO on international performance: An investigation of emerging market SMEs

Mixed and inconsistent research results linking International Entrepreneurial Orientation (IEO) to international performance have led to controversies about the value of IEO as a determinant of international performance. Our research proposes a new model that considers international dynamic capabilities (IDCs) as a mediator between IEO and international performance. Cultural and institutional distance are considered as boundary conditions. Using multi-country, multi-informant, and multi-source data collected from 303 SMEs in China and Tunisia, we find that IDCs mediate the effect of SMEs' IEO on international performance, but the impacts of three IEO dimensions on IDCs vary under different institutional and cultural contexts.

Analysis of surimi extrusion behavior during 3D printing by modified Computational Fluid Dynamics (CFD) and quick prediction of printability using machine learning based on texture data

The purpose of this study was to develop a modifying Computational Fluid Dynamics (CFD) model for precise analysis of surimi extrusion behavior and establish a machine learning method for quickly prediction of surimi printability. The 2D rotational axisymmetric model used in this study to replace the 3D/4D physical model, which could improve the simulation efficiency. To improve the accuracy of the CFD simulations, the wall “no-slip” boundary condition assumed in the textbook was replaced with a boundary condition of wall slip. This reduced the error between the simulated results and the measured ones to <1%, and thus calculated required extrusion pressure below 17,034 Pa for printability. The CFD calculation efficiency was improved 33 times than the previously reports by the modifying CFD model, and the simulated results for the required extrusion pressure of inks could be obtained within 10 s. Additionally, a machine-learning method (partial least squares regression model) based on texture data was proposed to quickly predict the required extrusion pressure of surimi to assessed printability. The machine learning model showed a good performance with an R2 > 0.95.

The influence of heterogeneous catalytic processes on the heat flux to the surface and the chemical composition of the shock layer at high-speed flow around blunt bodies

Numerical modeling of the high-speed flow of a multicomponent dissociated gas around a blunt body was carried out for the flow regime corresponding to the thermally stressed point of the gliding trajectory of entry into the Earth's atmosphere in the surface temperature range of 800–2000 K. As boundary conditions, a stage-by-stage model of heterogeneous catalysis of the interaction of dissociated air with the thermal protection material SiO2 was used, previously developed by the authors on the basis of transition state theory and quantum mechanical calculations. The dependence of the modes of heterogeneous chemical reactions on the surface temperature and the density of surface adsorption centers and their influence on the chemical composition of the shock layer and the convective heat flux to the streamlined surface are analyzed. The contributions of individual mechanisms of heterogeneous recombination to the total rate of formation of molecules on the surface are estimated. The possibility of using the density of adsorption sites as an effective parameter when setting boundary conditions on a real thermal protection surface in flow problems is shown.

A Reduced Order Schwarz Method for Nonlinear Multiscale Elliptic Equations Based on Two-Layer Neural Networks

Neural networks are powerful tools for approximating high dimensional data that have been used in many contexts, including solution of partial differential equations (PDEs). We describe a solver for multiscale fully nonlinear elliptic equations that makes use of domain decomposition, an accelerated Schwarz framework, and two-layer neural networks to approximate the boundary-to-boundary map for the subdomains, which is the key step in the Schwarz procedure. Conventionally, the boundary-to-boundary map requires solution of boundary-value elliptic problems on each subdomain. By leveraging the compressibility of multiscale problems, our approach trains the neural network offline to serve as a surrogate for the usual implementation of the boundary-to-boundary map. Our method is applied to a multiscale semilinear elliptic equation and a multiscale $p$-Laplace equation. In both cases we demonstrate significant improvement in efficiency as well as good accuracy and generalization performance.

Periodic Boundary Value problem for the Dynamical system with neutral integro-differential equation on time scales

Examining the results of existence and Ulam stability in a fractional dynamic system, including a neutral integro-differential equation that incorporates periodic boundary conditions on time scales and the Caputo fractional nabla derivative, is the main objective of the study. Standard fixed-point techniques are applied to obtain the results. Additionally, controllability and Ulam stability results are included. The application of the theoretical results is illustrated with a suitable example.

An Efficient Finite Difference Method for Stochastic Linear Second-Order Boundary-Value Problems Driven by Additive White Noises

An Efficient Finite Difference Method for Stochastic Linear Second-Order Boundary-Value Problems Driven by Additive White Noises

A Direct Discontinuous Galerkin Method for Time Fractional Diffusion Equations with Fractional Dynamic Boundary Conditions

A Direct Discontinuous Galerkin Method for Time Fractional Diffusion Equations with Fractional Dynamic Boundary Conditions

Multiple Pole Solutions of the Hirota Equation Under Nonzero Boundary Conditions by Inverse Scattering Method

Multiple Pole Solutions of the Hirota Equation Under Nonzero Boundary Conditions by Inverse Scattering Method

A Semianalytical Solution for the Transient Response of One-Dimensional Unsaturated Single-Layer Porous Media with General Boundary Conditions

A Semianalytical Solution for the Transient Response of One-Dimensional Unsaturated Single-Layer Porous Media with General Boundary Conditions

Application of 2-D GDQ Method to Analysis a Thick FG Rotating Disk with Arbitrarily Variable Thickness and Non-Uniform Boundary Conditions

Application of 2-D GDQ Method to Analysis a Thick FG Rotating Disk with Arbitrarily Variable Thickness and Non-Uniform Boundary Conditions

Coupled surface-internal deformation monitoring in three-dimensional space for freezing-thawing soil

Soil frost deformation significantly influences engineering projects in cold regions. The anisotropic behavior of soil, involving surface and internal deformation in three dimensions (3D), introduces inaccuracies in evaluating freeze–thaw geological hazards. To explore the relationship between internal strain and surface displacement of soil in a 3D space during the freezing-thawing process, a platform for monitoring coupled surface-internal deformation in 3D were developed using binocular recognition technology and a novel 3D strain rosette. Subsequently, a freezing-thawing model test of soil in Dalian Offshore Airport filling is conducted using the platform. The results show that, the internal strain of soil is closely associated with the boundary conditions of the test unit. During freezing test, the vertical strain exhibits a more significant increase in comparison to the horizontal strain. Surface displacements in soil primarily occur during the initial freezing and thawing stages. The variation of surface horizontal displacement in each direction is minimal throughout the freezing-thawing process. A surface freezing boundary leads to an increment in internal strain, while the deep frozen stress relief causes the soil surface expand during thawing. This study provides a suggestion for the control of the cold source in cold region engineering.

Optimizing launch window opportunities for ESA's comet Interceptor mission using primer vector theory

Comet Interceptor (Comet-I) was selected in June 2019 as the first ESA F-Class mission and aims to explore a pristine comet, which will visit the inner Solar System for the first time. Comet-I will hitch a ride to a Sun-Earth L2 quasi-halo orbit, as a co-passenger in ESA's M4 ARIEL's launch. At the time of writing, this is scheduled for 2029. It will then remain there awaiting the right departure conditions to leave definitively and intercept a newly discovered comet. Comet-I will be the first mission to be designed and launched without an already identified target. Given the latter, the Comet-I Target Identification Working Group is tasked with the continuous follow-up of newly discovered comets, to analyse their characteristics as virtual targets for Comet-I. The goal of the paper is to inform the decision-making process that will eventually be necessary to commit Comet-I spacecraft to its final target.Within this context, this paper presents a trajectory optimization process based on Primer Vector theory that considers intercept trajectories with multiple revolutions and multiple deep space manoeuvres (DSM). The process is applied to 21 long period comets, which were discovered since July 1,1st July 2020 and whose characteristics are of interest for the Comet-I mission. In fact, one of the latest of these recently discovered comets, C/2023 H2, is the most accessible virtual target discovered at the time of writing, with delta-V intercept costs well within Comet-I capabilities. A complete launch window analysis is thus presented for C/2023 H2, which accounts not only for the most optimal delta-V intercept transfer, but also considers all launch options that satisfy all Comet-I's current boundary conditions and flyby constraints. A systematic launch window analysis is made possible by a grid search approach on which departure and fly-by dates are fixed and the remaining design variables, including the times for manoeuvres and their Δv impulse vector, are optimized via Primer Vector theory. This allows to understand the latest possible departure date, but also the sensitivity to departure and arrival dates of key encounter characteristics such as relative fly-by speed, the solar aspect angle and the Earth distance.

On nonlinear buckling of microshells

Investigation of the geometrical nonlinear action of doubly curved shell panels (DCSPs) in micro scale is the main target of this paper. The proposed microshell panels (MSPs) are assumed to be made of an auxetic honeycomb core (AHOC), leading to negative magnitudes of Poisson's ratio, covered by two nanocomposite enriched coating layers (NCECLs). To conduct the size-dependent nonlinear analysis and achieve the corresponding nonlinear equilibrium path (EQP) of the proposed MSPs, the nonlocal strain gradient theory (NLSGT) is utilized. The governing equations containing the equilibrium and compatibility nonlinear partial differential equations in terms of the deformation components are analytically solved based on the Galerkin technique for different types of simply-supported panels. The achieved results of the present solution exhibit the fact that nonlocal and material length scale parameters significantly affect the EQP of the proposed MSPs especially at their post-buckling stage during their snap-through instability. By solving several numerical examples, the effects of various parameters on the size-dependent EQP of the proposed MSPs are investigated. The results indicate that the influences of size-dependency are significantly affected by the curvature and also boundary conditions of the microshells.

Should I do this? Incongruence in the face of conflicting moral and role expectations

Moral incongruence—a misalignment between professional role expectations and personal moral values—is an important phenomenon in modern organizations. Though scholarly work has provided us with insights into broad forms of role incongruence, much less is known about the distinct characteristics of moral incongruence. Moreover, we lack understanding of how moral incongruence may shape employee attitudes and behaviors. Drawing on deonance theory and socio-cognitive theory, we develop a model explaining the role of moral incongruence in promoting employee prohibitive voice, withdrawal, and unethical role behavior through the mechanisms of moral outrage and moral disengagement. Examining potential boundary conditions, we also consider the roles of moral identity, self-interest, moral intensity, unethical climate, ethical leadership, and organizational identification. Given the ethical implications of moral incongruence and the significance of the phenomenon for organizations, this work has implications for both theory and practice.

Inverse source problem for two-term time-fractional diffusion equation with nonlocal boundary conditions

This paper explores an inverse source problem related to the heat equation, incorporating nonlocal boundary conditions and featuring two-term time-fractional derivatives. The task is to identify a source term that is independent of the spatial variable, as well as to define the temperature distribution based on energy measurements. Since the stated problem cannot be solved by direct use of the generalized Fourier method, we divide the problem into two sub-problems. The well-posedness of each problem is established through the application of the generalized Fourier method.

Взаимосвязь окружной скорости и потерь энергии в проточной части центростремительной турбины с частичным облопачиванием рабочего колеса

Low-consumption turbomachines are devices that play an important role in the drive of various units in the field of shipbuilding, aircraft engineering and other branches of heavy engineering. They have some advantages over a high-average power turbine. The largest number of low-consumption turbomachines are made partial, i.e. with partial intake. The principle of a turbine with partial flapping of the impeller is considered as one of the types of partial turbomachines. The influence of the main velocity characteristic of the turbine stage on the loss of kinetic energy in the stage is investigated. The simulation of gas dynamic processes occurring in the turbine stage was carried out using the ANSYS Workbench software package. With the help of this complex, a three-dimensional geometric model of the turbine stage with varying degrees of impeller damping was created. By applying the finite element method, a computational grid, a computational model are generated, and boundary conditions of a numerical experiment are set. The result of the numerical experiment is graphs of the dependence of kinetic energy loss on the circumferential velocity (speed characteristics of the turbine stage). This dependence can be represented not only graphically, but also with the help of mathematical apparatus. An example of such an apparatus is the polynomial dependence. The considered mathematical design can be used in order to optimize mathematical models of gas flow in the flow part of a low-flow turbine. Cubic two-parameter polynomials of kinetic energy losses in the flow part of the nozzle and impeller are obtained, and an assessment of its applicability in the current mathematical model is given.