Dependent Boundary Conditions Research Articles

On the Cahn–Hilliard equation with kinetic rate dependent dynamic boundary conditions and non-smooth potentials: Well-posedness and asymptotic limits

We analyze a class of Cahn–Hilliard equations with kinetic rate dependent dynamic boundary conditions that describe possible short-range interactions between the binary mixture and the solid boundary. In the presence of surface diffusion on the boundary, the initial boundary value problem can be viewed as a transmission problem consisting of Cahn–Hilliard-type equations both in the bulk and on the boundary. We first establish the existence, uniqueness, and continuous dependence of global weak solutions. In the construction of weak solutions, an explicit convergence rate in terms of the parameter for the Yosida approximation is obtained. Under some additional assumptions, we further prove the existence and uniqueness of global strong solutions. Next, we study the asymptotic limit as the coefficient of the boundary diffusion goes to zero and show that the limit problem with a forward-backward dynamic boundary condition is well posed in a suitable weak formulation. At last, we investigate the asymptotic limits as the kinetic rate tends to zero and infinity, respectively. Our results are valid for a general class of bulk and boundary potentials with double-well structure, including the physically relevant logarithmic potential and the non-smooth double obstacle potential.

Spectral Properties of the Laplace Operator with Variable Dependent Boundary Conditions in a Disk

In this work, we study the spectral properties of the Laplace operator with variable dependent boundary conditions in a disk. The boundary conditions include periodic and antiperiodic boundary conditions as well as the generalized Samarskii–Ionkin-type boundary conditions. We show eigenfunctions and eigenvalues of these problems in an explicit form. Moreover, the completeness of their eigenfunctions is investigated.

Operator-pencil treatment of multi-interval Sturm-Liouville equation with boundary-transmission conditions

This paper is devoted to a new type of boundary-value problems for Sturm-Liouville equations defined on three disjoint intervals (−π,−π+d),(−π+d,π−d) and (π−d,π) together with eigenparameter dependent boundary conditions and with additional transmission conditions specified at the common end points −π+d and π−d, where 0<d<π. The considered problem cannot be treated by known techniques within the usual framework of classical Sturm-Liouville theory. To establish some important spectral characteristics we introduced the polynomial-operator formulation of the problem. Moreover, we develop a new modification of the Rayleigh method to obtain lower bound of eigenvalues.

Spectral properties for discontinuous Dirac system with eigenparameter‐dependent boundary condition

In this paper, Dirac system with interface conditions and spectral parameter dependent boundary conditions is investigated. By introducing a new Hilbert space, the original problem is transformed into an operator problem. Then the continuity and differentiability of the eigenvalues with respect to the parameters in the problem are showed. In particular, the differential expressions of eigenvalues for each parameter are given. These results would provide theoretical support for the calculation of eigenvalues of the corresponding problems.

Combined effect of temperature dependent material properties and boundary conditions on non-linear thermal stability of porous FG beams

Combined effect of temperature dependent material properties and boundary conditions on non-linear thermal stability of porous FG beams

Hydrodynamic models of pulsation period evolution in R Hydrae

ABSTRACT Pulsation period evolution during the helium–shell flash in the Mira variable R Hya is investigated using consistent stellar evolution and non-linear stellar pulsation computations. The initial and time-dependent inner boundary conditions for the equations of radiation hydrodynamics describing non-linear stellar oscillations were determined using a grid of TP–AGB model sequences with initial masses on the main sequence 1.5M⊙ ≤ MZAMS ≤ 5.0M⊙ and the initial metallicity Z = 0.014. The setup of initial conditions for hydrodynamic models corresponds to ≈100 yr prior to the maximum of the helium–shell luminosity and ensures that the stellar envelope of the evolution model is under both hydrostatic and thermal equilibrium. Solution of the equations of hydrodynamics allowed us to determine the temporal variation of the pulsation period Π(t) during ≈500 yr. Within this time interval R Hya is a fundamental mode pulsator. The period temporal dependencies Π(t) calculated for the AGB star models at the beginning of the third dredge-up phase and with masses $4.4M_{\odot }\lessapprox M\lessapprox 4.5M_{\odot }$ are in agreement with observational estimates of the period of R Hya obtained during last two centuries. The mean radius of R Hya pulsation models at the end of the XX century ($470 R_{\odot }\lessapprox \bar{R}\lessapprox 490 R_{\odot }$) agrees with observational estimates obtained using the interferometric angular diameter measurements.

Inverse problem for Sturm–Liouville operator with complex-valued weight and eigenparameter dependent boundary conditions

Abstract This paper is concerned with discontinuous inverse problem generated by complex-valued weight Sturm–Liouville differential operator with λ-dependent boundary conditions. We establish some properties of spectral characteristic and prove that the potential on the whole interval can be uniquely determined by the Weyl-type function or two spectra.

REGULARIZED TRACE OF OPERATOR WITH UNBOUNDED COEFFICIENT

Abstract. This paper is devoted to the study of the regularized trace formula of an operator generated by a differential expression with operator coefficient and eigenvalue dependent boundary condition.

Sturm-Liouville Problems with Polynomially Eigenparameter Dependent Boundary Conditions

Sturm-Liouville equation on a finite interval together with boundary conditions arises from the infinitesimal, vertical vibrations of a string with the ends subject to various constraints. The coefficient (also called potential) function in the differential equation is in a close relationship with the density of the string. In this sense, the computation of solutions plays a rather important role in both mathematical and physical fields. In this study, asymptotic behaviors of the solutions for Sturm-Liouville problems associated with polynomially eigenparameter dependent boundary conditions are obtained when the potential function is real valued 𝑳𝟏- function on the interval (𝟎, 𝟏). Besides, the asymptotic formulae are given for the derivatives of the solutions.

Massively parallel nodal discontinous Galerkin finite element method simulator for room acoustics

We present a massively parallel and scalable nodal discontinuous Galerkin finite element method (DGFEM) solver for the time-domain linearized acoustic wave equations. The solver is implemented using the libParanumal finite element framework with extensions to handle curvilinear geometries and frequency dependent boundary conditions of relevance in practical room acoustics. The implementation is benchmarked on heterogeneous multi-device many-core computing architectures, and high performance and scalability are demonstrated for a problem that is considered expensive to solve in practical applications. In a benchmark study, scaling tests show that multi-GPU support gives the ability to simulate large rooms, over a broad frequency range, with realistic boundary conditions, both in terms of computing time and memory requirements. Furthermore, numerical simulations on two non-trivial geometries are presented, a star-shaped room with a dome and an auditorium. Overall, this shows the viability of using a multi-device accelerated DGFEM solver to enable realistic large-scale wave-based room acoustics simulations.

An inverse scattering problem for eigenparameter-dependent discrete Dirac system with Levinson formula

In this paper, we have considered an inverse scattering problem for discrete Dirac operator L with eigenparameter dependent boundary condition. At the outset, the Jost solution and the Jost function of L are given. Then the zeros of the Jost function and some properties of the scattering function are examined. After finding the scattering dataset and the main equation for the operator L, the uniqueness of the kernel, continuity of the scattering function and the appropriate Levinson type formula are obtained.

Asymptotics of the eigenvalues of a fourth order differential operator with eigenvalue dependent and periodic boundary conditions

Asymptotics of the eigenvalues of a fourth order differential operator with eigenvalue dependent and periodic boundary conditions

Existence and uniqueness for a convective phase change model with temperature–dependent viscosity

In this article, we consider a class of phase change model with temperature–dependent viscosity, convection and mixed boundary conditions on a bounded domain that reflect melting and solidification in a variety of real-world applications, such as metal casting and crystal growth. The mathematical model, which is based on the enthalpy formulation, takes into consideration the thermophysical differences between the liquid and solid states. The moving liquid-solid interface is explicitly fulfilled as the energy and momentum equations are solved over the full physical domain. Under particular assumptions, we derive various a priori estimates and prove well-posedness results. Numerical simulation of the model employed in the paper is presented as an illustration of an example of a melting problem.

Instability analysis of double diffusive convection under time dependent solute boundary conditions in the presence of internal heat generator

The present study provides heat and mass transport of double-diffusive convective flow of Newtonian fluid with the presence of internal heat source. Here, we have considered two infinite horizontal plates apart from a constant distance under the solutal modulated boundary condition. To obtain the weakly nonlinear instability analysis, we drive Ginzburg–Landau equation. The effects of physical parameters obtained during the study on the Nusselt number and Sherwood number have been examined graphically. The Prandtl number and Richardson number enhance the rate of heat and mass transport, and Lewis number suppressed it. The major finding of the current study is that the internal heat source has a negligible effect on mass transfer, but a significant effect on the heat transfer.

SuSpect3: A C++ code for the supersymmetric and Higgs particle spectrum of the MSSM

We present the program SuSpect3 that calculates the masses and couplings of the Higgs and supersymmetric particles predicted by the Minimal Supersymmetric Standard Model (MSSM). The model is implemented in both its non-constrained version, the MSSM, and its constrained versions, such as the minimal supergravity and the gauge or anomaly mediated supersymmetry breaking models, in which the soft supersymmetry–breaking parameters obey certain universal boundary conditions at the high energy scale. The low energy parameters are then obtained using renormalization group equations and electroweak symmetry breaking, and all the dominant radiative corrections have been consistently implemented. SuSpect3 is a major rewrite, in C++ object oriented programming, of the FORTRAN code SuSpect. It includes all the features of the earlier code in an improved and updated manner, and involves new options such as compressed SUSY scenarios, an MSSM-inflation model and the possibility of using the observed Higgs mass as an input. The main features and the use of the program are explained. Program summaryProgram Title:SuSpect3CPC Library link to program files:https://doi.org/10.17632/55jv4kdrm8.1Developer's repository link:http://suspect.in2p3.frLicensing provisions: GPLv3Programming language:C++, compatible C++98, C++11, C++14, C++17Nature of problem: Supersymmetric models such as the MSSM, mSUGRA, GMSB, AMSB and others have specific parameter sets and boundary conditions. SuSpect3 translates the parameter sets of the models into predictions of the Higgs and supersymmetric particles masses. The mixing matrices of the physical states as well as the mixing angles are calculated in addition to the scale dependent parameters.Solution method: The spectrum of the Higgs and supersymmetric particles depends on the model, its supersymmetric parameter set and the Standard Model parameters. The evolution of the parameters as function of the energy scale is calculated by solving numerically the Renormalization Group Equations. Model dependent boundary conditions are applied at the appropriate scale. Electroweak symmetry breaking is calculated iteratively at the electroweak scale. The application of radiative corrections translate the scale dependent particle masses into the physical pole masses.Additional comments including restrictions and unusual features: The parameters and physical masses are defined to be real. Warnings are issued if intermediate results are unphysical.Compiles with gcc-4.8.5 and later (checked with gcc-8.1.0).

Asymptotic Estimations of Eigenvalues and Eigenfunctions for Nonlocal Boundary Value Problems with Eigenparameter-Dependent Boundary Conditions

The nonlocal boundary value problem with eigenparameter dependent boundary conditions is studied in this work. Firstly, we give the asymptotic expressions of the general solution for the equation corresponding to the initial conditions and prove the simplicity of eigenvalues. Moreover, the general properties of the eigenvalues and eigenfunctions for such a problem are proved. Finally, the asymptotic formulas of eigenvalues and eigenfunctions are obtained under certain mild conditions. Our method is to incorporate the perturbation theory and asymptotic analysis in the framework of classical Sturm-Liouville problems, which provides a different idea for the investigating of the Sturm-Liouville problems with eigenparameter in boundary conditions.

Stability of a flexible missile and asymptotics of the eigenvalues of fourth order boundary value problems

Fourth order problems with the differential equation y^{(4)}-(gy')'=lambda ^2y, where gin C^1[0,a] and a>0, occur in engineering on stability of elastic rods. They occur as well in aeronautics to describe the stability of a flexible missile. Fourth order Birkhoff regular problems with the differential equation y^{(4)}-(gy')'=lambda ^2y and eigenvalue dependent boundary conditions are considered. These problems have quadratic operator representations with non-self-adjoint operators. The first four terms of the asymptotics of the eigenvalues of the problems as well as those of the eigenvalues of the problem describing the stability of a flexible missile are evaluated explicitly.

Reduced order modelling using parameterized non-uniform boundary conditions in room acoustic simulations.

Quick simulations for iterative evaluations of multi-design variables and boundary conditions are essential to find the optimal acoustic conditions in building design. We propose to use the reduced basis method (RBM) for realistic room acoustic scenarios where the surfaces have inhomogeneous acoustic properties, which enables quick evaluations of changing absorption materials for different surfaces in room acoustic simulations. The RBM has shown its benefit to speed up room acoustic simulations by 3 orders of magnitude for uniform boundary conditions. This study investigates the RBM with two main focuses: (1) various source positions in diverse geometries, e.g., square, rectangular, L-shaped, and disproportionate room, (2) two-dimensional and three-dimensional (3D) inhomogeneous surface absorption by parameterizing numerous acoustic parameters of surfaces, e.g., the thickness of a porous material, cavity depth, switching between a frequency independent (e.g., hard surface) and frequency dependent boundary condition. Results of numerical experiments show speedups of more than 2 orders of magnitude compared to a high fidelity numerical solver in a 3D case where reverberation time varies within one just noticeable difference in all the frequency octave bands.

Shear stress regulation in cylindrical arteries through medial growth and nitric oxide release

The mechanisms employed by blood vessels in order to adapt to their hemodynamic environment are important for our general understanding of disease and development. Changes in arterial geometry are generally induced by two effects: vasodilation and/or constriction; and growth and remodeling ("G &R"). The first can occur over short periods of a few minutes, while the second usually occurs over timescales of weeks or months. The free radical Nitric oxide (NO) is one of the few biological signaling molecules that is gaseous. When smooth muscle cells internalize NO, they lengthen and ultimately induce a relaxation of the artery. Platelet-Derived Growth Factor (PDGF) is a growth factor released by smooth muscle cells and platelets that regulates cell growth and division. In this paper we present a single-layered, axisymmetric hyperelastic model for a deforming, growing artery in which the opening angle is regulated by NO and growth is induced by PDGF. Our model describes vasodilation and G &R in a long cylindrical artery regulated by a steady-state Poiseuille flow. The transport of NO released by the endothelium is governed by a diffusion equation with a shear-stress dependent flux boundary condition. Arterial opening angle is assumed to be a Hill function of the wall-averaged NO concentration. We find that both growth and NO help to regulate shear stress with respect to the flow rate, but regulation through growth occurs only at large times. In contrast, regulation through NO is immediate but can only occur as long as the opening angle is able to continually decrease as a function of flow rate. Our model is calibrated using experimental data from ligated, control, and anastomosed carotid arteries of adult and weanling rabbits. Our results generate shear stress/flow rate and lumen radius/flow rate curves that agree with experimental data from control and NO-inhibited rabbit carotid arteries.

Inverse problems for discontinuous Dirac operator with eigenparameter dependent boundary and transmission conditions

AbstractIn this study, we consider the discontinuous Dirac equations system with eigenparameter dependent boundary and finite number of transmission conditions. First, the space that corresponds to problem is introduced, the norm on this space is defined and the operator model that corresponds to the given problem is constructed on this space. Then the integral equations and asymptotics of eigenfunctions of the problem are obtained. The characteristic function is defined and the asymptotic formula of the characteristic function is given by using obtained asymptotics of eigenfunctions. After the Weyl solution and the Weyl function of the problem are formed. Finally, some uniqueness theorems are proved by using Weyl function and some spectral data.