Solving a one-dimensional moving boundary problem based on wave digital principles

In this paper, the weighted average-based differential quadrature method is presented for solving one-dimensional homogeneous first-order non-linear parabolic partial differential equation. First, the given solution domain is discretized by using uniform discretization grid point. Next, by using Taylor series expansion we obtain central finite difference discretization of the partial differential equation involving with temporal variable associated with weighted average of partial derivative concerning spatial variable. From this, we obtain the system of nonlinear ordinary differential equations and it is linearized by using the quasilinearization method. Then by using the polynomial-based differential quadrature method for approximating derivative involving with spatial variable at specified grid point, we obtain the system of linear equation. Then they obtained linear system equation is solved by using the LU matrix decomposition method. To validate the applicability of the proposed method, two model examples are considered and solved at each specific grid point on its solution domain. The stability and convergent analysis of the present method is worked by supported the theoretical and mathematical statements and the accuracy of the solution is obtained. The accuracy of the present method has been shown in the sense of root mean square error norm and maximum absolute error norm and the local behavior of the solution is captured exactly. Numerical versus exact solutions and behavior of maximum absolute error between them have been presented in terms of graphs and the corresponding root mean square error norm and maximum absolute error norm presented in tables. The present method approximates the exact solution very well and it is quite efficient and practically well suited for solving the non-linear parabolic equation. The numerical result presented in tables and graphs indicates that the approximate solution is in good agreement with the exact solution.

A new two-step implicit linear Obrechkoff twelfth algebraic order method with vanished phase-lag and its first, second, third and fourth derivatives is constructed in this paper. The purpose of this paper is to develop an efficient algorithm for the approximate solution of the one-dimensional radial Schrodinger equation and related problems. This algorithm belongs in the category of the multistep methods. In order to produce an efficient multistep method the phase-lag property and its derivatives are used. An error analysis and a stability analysis is also investigated and a comparison with other methods is also studied. The efficiency of the new methodology is proved via theoretical analysis and numerical applications.

Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, increasing the size of the MD domain quickly presents intractable computational demands. A robust approach to surmount this computational limitation has been to unite continuum modeling procedures such as the finite element method (FEM) with MD analyses thereby reducing the region of atomic scale refinement. The challenging problem is to seamlessly connect the two inherently different simulation techniques at their interface. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the typical boundary value problem used to define a coupled domain. The method uses statistical averaging of the atomistic MD domain to provide displacement interface boundary conditions to the surrounding continuum FEM region, which, in return, generates interface reaction forces applied as piecewise constant traction boundary conditions to the MD domain. The two systems are computationally disconnected and communicate only through a continuous update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM) as opposed to a direct coupling method where interface atoms and FEM nodes are individually related. The methodology is inherently applicable to three-dimensional domains, avoids discretization of the continuum model down to atomic scales, and permits arbitrary temperatures to be applied.

Linear multistep methods (LMMs) are written as irreducible general linear methods (GLMs). A-stable LMMs are shown to be algebraically stable GLMs for strictly positive definite G-matrices. Optimal order error bounds, independent of stiffness, are derived for A-stable methods, without considering one-leg methods (OLMs). As a GLM, the OLM is shown to be the transpose of the LMM. For A-stable methods, the LMM G-matrix is the inverse of the OLM G-matrix. Examples of G-symplectic LMMs are given.

Liapunov Methods for a One-Dimensional Parabolic Partial Differential Equation

The common basis of the theories of linear cyclic methods and Runge-Kutta methods

This paper focuses on the stability analysis of a general class of linear multistep methods for decoupled forward–backward stochastic differential equations (FBSDEs). The general linear multistep methods we consider contain many well-known linear multistep methods from the ordinary differential equation framework, such as Adams, Nyström, Milne--Simpson and backward differentiation formula methods. Under the classical root condition, we prove that general linear multistep methods are mean-square (zero) stable for decoupled FBSDEs with generator function related to both y and z. Based on the stability result, we further establish a fundamental convergence theorem.

A family of high-order multistep methods with vanished phase-lag and its derivatives for the numerical solution of the Schrödinger equation

ABSTRACTIn this paper, a mesh free algorithm using large pre-solved domain is developed. Using the largest rectangle inside an arbitrary domain, a pre-solved rectangular domain is established using Kronecker product and graph theory rules. This pre-solved domain is efficiently inserted into the mesh free formulation of partial differential equations (PDEs) and engineering problems to reduce the computational complexity and execution time of the solution. The general solution of the pre-solved rectangular domain is formulated for second-order shape functions. The efficiency of the present algorithm depends on the relative size of the large rectangular domain and the main domain; however, the method remains as efficient as a standard method for even small relative sizes. For adaptive procedures with nonuniform density of distributed points in the domain, smaller (e.g. sub-maximal) rectangular domain can be used. The application of the method is demonstrated using some examples.

A family of explicit linear sixth algebraic order six-step methods with vanished phase-lag and its first derivative is obtained in this paper. The investigation of the above family of methods contains: The theoretical study of the above mentioned family of methods contains: The application of the new family of linear six-step sixth algebraic order methods to the resonance problem of the one-dimensional time independent Schrodinger equation is used for the computational study of the new family of methods. The result of the above mentioned theoretical and computational investigation is that the new proposed family of linear explicit schemes are computationally and theoretically more effective than other well known methods for the approximate solution of the radial Schrodinger equation and related initial or boundary value problems with periodic and/or oscillating solutions.

A study on cylindrical moving boundary problem with variable thermal conductivity and convection under the most realistic boundary conditions

Second-order unconditionally stable schemes of linear multi-step methods, and their equivalent single-step methods, are developed in this paper. The parameters of the linear two-, three-, and four-step methods are determined for optimal accuracy, unconditional stability and tunable algorithmic dissipation. The linear three- and four-step schemes are presented for the first time. As an alternative, corresponding single-step methods, spectrally equivalent to the multi-step ones, are developed by introducing the required intermediate variables. Their formulations are equivalent to that of the corresponding multi-step methods; their use is more convenient, owing to being self-starting. Compared with existing second-order methods, the proposed ones, especially the linear four-step method and its alternative single-step one, show higher accuracy for a given degree of algorithmic dissipation. The accuracy advantage and other properties of the newly developed schemes are demonstrated by several illustrative examples.

Plasma equilibrium evolution at the resistive diffusion timescale

Single-chain polymer nanoparticles(SCNPs) obtained through chaincollapse via intramolecular cross-linking are attracting significantinterest for nanomedicine and biomimetic catalysis applications, amongother fields. This interest arises from the possibility to bind activespecies (e.g., drugs and catalysts)—either temporally or permanently—tothe SCNP local pockets formed upon chain collapse. However, directquantification of the size and number of such local domains in solution—even if highly desirable—is currentlyhighly demanding from an experimental point of view because of thesmall size involved (<5 nm). On the basis of a scaling analysis,we establish herein a connection between the global compaction degree(R/R0) and the size (ξ)and number (n) of the “collapsed domains” generated upon SCNP formation at high dilution from a linearsemiflexible precursor polymer. Results from molecular dynamics simulationsand experimental data are used to validate this scaling analysis andto estimate the size and number of local domains in polystyrene SCNPssynthesized through a “click” chemistry procedure, asa representative system, as well as for relevant catalytic SCNPs containingCu, Pt, and Ni atoms. Remarkably, the present work is a first steptoward tuning the local domain size of the next generation of SCNPsfor nanomedicine and bioinspired catalysis applications.

Conjugate symplecticity of second-order linear multi-step methods