Continuous Boundary Conditions Research Articles

High gain boost DC-DC converters with minimized switch stress for renewable energy applications

Abstract This paper introduces a new series of non-isolated boost DC-DC converters, showcasing a novel high step-up switching cell integrated into a basic boost converter to form a new transformerless converter design. The primary focus is on achieving significant voltage gains with moderate duty cycles while minimizing the stress on semiconductor devices. Comprehensive comparative analyses underline the new converter’s advantages over existing models regarding voltage and current stresses, component count, and performance metrics. Additionally, the converter’s design simplifies transistor driving by utilizing a single switch, enhancing operational ease. Detailed theoretical explanations are provided for continuous conduction mode (CCM), discontinuous mode (DCM), and boundary condition mode (BCM), including equations for voltages and currents. The proposed converter’s effectiveness is examined through simulation and experimental validation. A 260-watt PV panel supplied by the proposed converter prototype demonstrates the converter’s impressive boosting capability and high efficiency across 0.5 a duty cycle with a constant input voltage, providing solid proof of concept for the proposed designs. These findings promise substantial advancements in designing and applying high-gain boost converters in various electronic, industrial, and renewable energy applications.

Vibration analysis of piping system coupled with conical-cylindrical combined shells

Fluid-filled piping system are widely used in power cooling, fuel transportation and underwater vessel, which not only produce vibration along the system, but also transmit to the connecting structure to generate noise in ambient environment. Most investigations have concentrated on either the vibration characteristics of piping systems or of combined shells separately. In this work, an analytical impedance synthesis method (ISM) is proposed to analyze the vibration characteristics of a pipe-hull coupled system, in which the hull can be simplified to a combined conical-stiffened cylindrical-hemisphere shell. The piping system is modeled by fluid-filled beams in three-dimensional configuration. Wave function and power series solution are used to describe the displacements of cylindrical and conical shell respectively. Based on exact analytical solutions, the impedance matrix of each segment is established separately and assembled in the global coordinate by displacement continuity and force balance boundary conditions. Forced responses are compared with the experimental results to verify the correctness of the method.

A two-level semi-hybrid-mixed model for Stokes–Brinkman flows with divergence-compatible velocity–pressure elements

A two-level semi-hybrid-mixed model for Stokes–Brinkman flows with divergence-compatible velocity–pressure elements

An insight on local defect resonance based on modal decomposition analysis: A two-dimensional case

An insight on local defect resonance based on modal decomposition analysis: A two-dimensional case

Plane SV-waves scattering by seawater convex surface topography and underlying lined tunnel in a saturated half-space

Plane SV-waves scattering by seawater convex surface topography and underlying lined tunnel in a saturated half-space

Remarks on analytical solutions to compressible Navier–Stokes equations with free boundaries

Abstract In this paper, we consider the free boundary problem of the radially symmetric compressible Navier–Stokes equations with viscosity coefficients of the form μ(ρ) = ρ θ , λ(ρ) = (θ − 1)ρ θ in R N ${\mathbb{R}}^{N}$ . Under the continuous density boundary condition, we correct some errors in (Z. H. Guo and Z. P. Xin, “Analytical solutions to the compressible Navier–Stokes equations with density-dependent viscosity coefficients and free boundaries,” J. Differ. Equ., vol. 253, no. 1, pp. 1–19, 2012) for N = 3, θ = γ > 1 and improve the spreading rate of the free boundary, where γ is the adiabatic exponent. Moreover, we construct an analytical solution for θ = 2 3 $\theta =\frac{2}{3}$ , N = 3 and γ > 1, and we prove that the free boundary grows linearly in time by using some new techniques. When θ = 1, under the stress free boundary condition, we construct some analytical solutions for N = 2, γ = 2 and N = 3, γ = 5 3 $\gamma =\frac{5}{3}$ , respectively.

Stability and dynamic analyses of hybrid laminates using refined higher-order zigzag theory

This article presents a comparative study on the stability and dynamic response of hybrid laminated composite plates over monolithically produced laminated composite plates. A Refined Higher-order Zigzag Theory (RHZT) is formulated and implemented using finite element method for the analysis of hybrid laminates. This formulation considers both the interlaminar shear stress continuity and shear-free boundary conditions at surfaces of the plates. The numerical implementation employs C 0 continuous eight-noded isoparametric plate elements considering geometric nonlinearity. The element stiffness matrix is formulated to consider both the linear and nonlinear terms of the strain-displacement equations. Derivation of the consistent mass matrix for a plate element is presented following the approximation of total kinetic energy and utilising Hamilton’s principle. Numerical examples are provided to demonstrate buckling and free vibration analyses (as eigenvalue problems). The results are numerically verified and validated using data from published literature. Finally, parametric studies are presented to demonstrate the effectiveness of fibre hybridisation approach on the buckling and free vibration behaviour of laminated composites.

Double Drainage Consolidation Theory of Vertical Drains Based on Continuous Drainage Boundary Conditions

Double Drainage Consolidation Theory of Vertical Drains Based on Continuous Drainage Boundary Conditions

Finch–Skea Stellar structures obeying Karmarkar condition in modified [formula omitted] gravity

Finch–Skea Stellar structures obeying Karmarkar condition in modified [formula omitted] gravity

Online Magneto-Thermal Coupled Model of PMECCs Using Measured Boundaries

Online modeling of the magneto-thermal coupled field (MCF) in permanent magnet eddy current couplings (PMECCs) has long been challenging since it exists in the copper layer and cannot be directly measured. This article proposes an online magneto-thermal coupled model (OMCM) to reconstruct the MCF using measured boundaries. The magnetic field (MF), eddy current field (ECF), and temperature field (TF) in the MCF are coupled in an identical space-time united discretization system. Virtual boundary nodes are added to the system, which can adapt to different boundary conditions in electromagnetic and thermal analysis. The measured data of single-point sensors are spanned to continuous boundary conditions. An approximate solution of the MCF is derived based on the measured boundaries and the general solutions of Laplace's equation and Poisson's equation in magneto-thermal analysis. The three-dimensional distribution of the MF, ECF, and TF at each spatial node and time segment can be simultaneously calculated in matrix form by the OMCM. Furthermore, the output torque is estimated and compared with the conventional methods. A verification process is carried out to assess the reconstructed results, showing that the OMCM can yield results close to the verification sensors for various slips and air gaps.

Nonlinear consolidation finite element analysis of a layered soft soil foundation under multistage loading based on the continuous drainage boundary

Nonlinear consolidation finite element analysis of a layered soft soil foundation under multistage loading based on the continuous drainage boundary

Propagation Behavior of P1-Wave Passing through Fluid-Saturated Porous Continuous Barrier in Layered Saturated Soil

The fluid-saturated porous continuous barrier has a better vibration isolation effect than the single-phase solid continuous barrier, and layer-forming saturated soils will have an impact on the vibration isolation effect of the barriers due to their irregular layer-forming distribution. Based on Biot’s theory of saturated porous media and Snell’s law, a dynamic model of a fluid-saturated porous continuous barrier in layered saturated soil is established in this study. By introducing the potential function and using the continuous boundary condition of the interface between the saturated soil and the barrier, the analytical solution of the inverse transmission amplitude ratio of a P1-wave passing through the fluid-saturated porous continuous barrier in stratified saturated soil is obtained. The rationality of the proposed method is verified by comparing the solution of the P-wave model at the interface between the elastic medium and the saturated coarse particle interlayer. The differences in the propagation characteristics of fluid-saturated porous continuous barriers in layered saturated soils, homogeneous saturated soils, and layered single-phase soils are analyzed via numerical examples, and the influence of changes in the physical and mechanical parameters of the fluid-saturated porous continuous barriers on the reflectance amplitude ratios under the conditions of a layered saturated soil foundation are also analyzed. The results show that the presence of fluid in the stratified saturated soil model changes the trend of the reflection amplitude ratio with the incidence angle. The reflection amplitude ratio of the P2-wave and the SV-wave increases first and then decreases with the increase in the incident angle, while the reflection amplitude ratio of P1-wave decreases first and then increases. Barrier thickness and porosity change the energy distribution relationship at the interface; a relatively thicker barrier thickness and a higher porosity would result in a higher amplitude of barrier reflections.

Three-dimensional Finite Element Model of Three-phase Contact Line Dynamics and Dynamic Contact Angle

An unconventional model of three-phase contact liny dynamics is suggested for the numerical solution of the boundary value problem of dipping and spreading. The numerical modeling is conducted with the use of the finite-element method in Lagrange variables. The mathematical model of the process is described by the equation of motion, continuity, and natural boundary conditions on the free surface. To exclude the ity of viscous stresses in the mathematical model on three-phase contact lines (TPCL) there was suggested a gridded model of gliding that takes into consideration peculiarities of dissipative processes in the neighborhood of TPCL at the microlevel. To reduce oscillations of pressure in the neighborhood of TPCL, a finite element is used. The suggested method allows for natural monitoring of free surface and TPCL with an unconventional model for dynamic contact micro-angle. A stable convergent algorithm is suggested that is not dependent on the grid step size and that is tested through the example of a three-dimensional semispherical drop and a drop in the form of a cube. The investigations obtained are compared to well-known experimental and analytical results demonstrating a high efficiency of the suggested model of TPCL dynamics at small values of capillary number.

Nonlinear consolidation of arbitrary layered soil with continuous drainage boundary: An approximate closed-form solution

Nonlinear consolidation of arbitrary layered soil with continuous drainage boundary: An approximate closed-form solution

Analytical solution for dynamic responses of offshore wind turbines supported by pipe pile in radially heterogeneous soil

Analytical solution for dynamic responses of offshore wind turbines supported by pipe pile in radially heterogeneous soil

DETECTING MOISTURE IN BAUXITE USING MICROWAVES

AbstractMathematical modelling of microwaves travelling through bauxite ore provides a way to compute moisture content in the free space transmission method given data on signal attenuation, phase shift and variable bauxite depth. We extend a recently developed four-layer model that uses coupled ordinary differential wave equations for the electric field together with continuity boundary conditions at interfaces between ore, air and antenna to find a solution that incorporates multiple internal reflections in ore and air. The model provides good fits to data, depending on ore permittivity and conductivity.Our extensions are to use effective medium models to obtain electromagnetic properties of the ore mixture from moisture content and to incorporate the damping effects of scattering from the ore surface. Our model leads to a formula for the received signal showing how signal strengths SS and phase shifts depend on the moisture content of the bauxite ore, through the effects of moisture on permittivity and conductivity. We show that SS may be noninvertible, indicating that attenuation data alone cannot be used to infer moisture content. Combining with phase data typically corrects the noninvertibility. Reducing the operating frequency dramatically improves the usefulness of signal strength data for inferring moisture content.

Using artificial intelligence algorithms to reconstruct the heat transfer coefficient during heat conduction modeling

The article shows the usage of swarming algorithms for reconstructing the heat transfer coefficient regarding the continuity boundary condition. Numerical calculations were performed using the authors’ own application software with classical forms of swarm algorithms implemented. A functional determining error of the approximate solution was used during the numerical calculations. It was minimized using the artificial bee colony algorithm (ABC) and ant colony optimization algorithm (ACO). The considered in paper geometry comprised a square (the cast) in a square (the casting mold) separated by a heat-conducting layer with the coefficient kappa . Due to the symmetry of that geometry, for calculations, only a quarter of the cast-mold system was considered. A Robin’s boundary condition was assumed outside the casting mold. Both regions’ inside boundaries were insulated, but between the regions, a continuity boundary condition with nonideal contact was assumed. The coefficient of the thermally conductive layer was restored using the swarm algorithms in the interval 900{-}1500 ; [mathrm{W/m}^{2}textrm{K} ] and compared with a reference value. Calculations were carried out using two finite element meshes, one with 111 nodes and the other with 576 nodes. Simulations were conducted using 15, 17, and 20 individuals in a population with 2 and 6 iterations, respectively. In addition, each scenario also considered disturbances at 0%, 1%, 2%, and 5% of the reference values. The tables and figures present the reconstructed value of the kappa coefficient for ABC and ACO algorithms, respectively. The results show high satisfaction and close agreement with the predicted values of the kappa coefficient. The numerical experiment results indicate significant potential for using artificial intelligence algorithms in the context of optimization production processes, analyze data, and make data-driven decisions.

Study of SH-wave in a pre-stressed anisotropic magnetoelastic layer sandwich by heterogeneous semi-infinite media

Study of SH-wave in a pre-stressed anisotropic magnetoelastic layer sandwich by heterogeneous semi-infinite media

Nonlinear consolidation analysis of saturated multi‐layered soil with continuous drainage boundary

AbstractContinuous drainage boundary is widely accepted to overcome the shortcoming of the traditional assumption of fully permeable or impermeable drainage boundary in consolidation theories. This study presents an analytical solution for one‐dimensional small‐strain nonlinear consolidation of saturated multi‐layered soil with constant consolidation coefficients under continuous drainage boundary condition. The proposed solution is validated by comparison with the existing solutions in literature, which shows that the existing solutions are special cases of this solution. A parametric study performed on saturated four‐layered soil with continuous drainage boundary indicates that the interface parameter and the loading stress ratio have great influences on the nonlinear consolidation of saturated multi‐layered soil. The present solution can be effectively applied to provide more reasonable design for soil foundation.

Correction: Effects of continuous and discrete boundary conditions on the movement of upper-convected maxwell and Newtonian mucus layers in coughing and sneezing

Correction: Effects of continuous and discrete boundary conditions on the movement of upper-convected maxwell and Newtonian mucus layers in coughing and sneezing