We present a technique for constructing absorbing boundary conditions for diffusion equations from Neumann operators. The symbol of the Neumann operator is approximated by a rational interpolant with symmetric interpolation points. The absorbing boundary ...
National Technical Information Service (NTIS)
... Title : Absorbing Boundary Conditions with Zero Reflection Angles for Compressional and Shear Incident Waves,. Corporate Author : ...
DTIC Science & Technology
... 7 2.3 The Absorbing and Asymptotic Boundary Conditions ..... 14 ... 5.2 Derivation of the Three-Dimensional Asymptotic Boundary Conditions. ...
... prevent rapidly moving waves from ... systems, absorbing boundary conditions, multiple ... WATER WAVES, *BOUNDARIES, *PARTIAL DIFFERENTIAL ...
A uniform approach to construct absorbing artificial boundary conditions for ..... In this section, we will recreate the artificial boundary conditions for ...
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An absorbing non-reflecting boundary condition (NRBC) for practical ...... Two- dimensional Riemann problem with mean and core flows moving at 45O and M ...
... Abstract : The finite element method (FEM) is very ... for arbitrary outer boundaries enables one to ... The asymptotic boundary condition for digital circuit ...
... (Fourier mode) of the Euler equations remains intact across the boundary. ... Non-reflecting boundary condition; Compressible flow. NUMBER OF PAGES: ...
... equation. This methodology is similar to that used by Berenger for the numerical solutions of Maxwell's equations. Specifically ...
Elliptic and hyperbolic problems in unbounded regions are considered. These problems, when one wants
NASA Technical Reports Server (NTRS)
A method is described for generating boundary conditions that can be applied to total fields rather than the usual scattered fields. As compared with the traditional use of absorbing boundary conditions for total-field formulations this method has the adv...
A uniform approach to construct absorbing artificial boundary conditions for second-order linear hyperbolic equations is proposed. The nonlocal boundary condition is given by a pseudodifferential operator that annihilates travelling waves. It is obtained ...
A general expression of an absorbing boundary condition is presented in this paper to model wave propagation in passive microwave integrated-circuits by the finite-difference time-domain method. Unlike previously developed absorbing boundary conditions which can only ...
NASA Astrophysics Data System (ADS)
Many practical problems involve wave propagation through atmosphere, oceans, or terrestrial crust. Modeling and analysis of these problems is usually done in (semi)infinite domains, but numerical calculations obviously impose restriction to finite domains. To mimic the actual behavior in the (semi)infinite medium, artificial absorbing boundary ...
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An absorbing boundary condition is formulated and applied to the one-dimensional open channel flow equations in conjunction with an explicit MacCormack scheme. The physical flow domain has been truncated by introducing an artificial pseudo-boundary. By using an appropriate bounda...
EPA Science Inventory
... Title : Molecular Dynamics Simulations of Shock Waves Using the Absorbing Boundary Condition: A Case Study of Methane. ...
various types of nonreflecting or absorbing boundary ... flat plate computed with the nonreflective characteristic boundary conditions compared with the ...
, 65M10, 86�08. Keywords: absorbing boundary conditions, one� way wave equations, well� fined. To absorb incident waves at the computa� tional boundary one approach uses a damping re� gion for the Absorption of Electromagnetic Waves, J. Comput. Phys, 114, 185�200, 1994. [2] C. ...
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In practical calculations, it is often essential to introduce artificial boundaries to limit the area of computation. Here we develop a systematic method for obtaining a hierarchy of local boundary conditions at these artifical boundaries. These boundary conditions not only ...
PubMed Central
Abstract�We consider in this work the initial value problem for the one dimensional cubic nonlinear Schr�dinger equation. In order to integrate it numerically, one option frequently used, is to impose local absorbing boundary conditions. A finite element discretization in space of the cubic nonlinear Schr�dinger equation is ...
]. Moreover such absorbing boundary conditions appear often in electromagnetic computations where many of electromagnetic waves [1] and many others. In this paper known nonre ecting and re ecting boundary conditions and Fourier series to the two-dimensional wave equation system and derive the ...
In the boundary element (BE) solution of wave propagation, infinite absorbing elements are introduced to minimize diffractions from truncated edges of models. This leads to a significant simplification and reduction of computational effort, especially for 3-D problems. The infinite Be absorbing boundary ...
Energy Citations Database
A boundary condition that absorbs incident stress waves with very little reflection has been implemented in the two-dimensional Eulerian wavecode CSQII. This boundary condition allows inflow or outflow of material, includes the influence of gravity, works with nonlinear materials and includes ...
The numerical solution of the nonlinear wave equation on unbounded spatial domain is considered. The artificial boundary method is introduced to reduce the nonlinear problem on unbounded spatial domain to an initial boundary value problem on a bounded domain. Using the unified approach, which is based on the operator splitting method, we construct the ...
moving wave. We consider a local boundary condition at x = 0 of the form LU = 0 at x = 0.(2.3) Upon is the result of applying the boundary operator L on the left moving wave (moving towards the boundary x = 0) and F2 is the results of applying the boundary operator to the right moving wave ...
In this paper we show boundary observability and boundary stabilizability by linear feedbacks for a class of nonlinear wave equations including the undamped Westervelt model used in nonlinear acoustics. We prove local existence for undamped generalized Westervelt equations with homogeneous Dirichlet boundary ...
A one-way wave equation is a partial differential which, in some approximate sense, behaves like the
... Diefects, oxide layers, etc., tend to trap thc inci- (lent radiatii ... that the radiation is absorbed in a very narrow layer at the ... with the boundary conditions ...
Our main result is a finite time convergence analysis of the Engquist-Majda [B. Engquist and A. Majda, Absorbing boundary conditions for the numerical ...
May 31, 2011 ... Our main result is a finite time convergence analysis of the Engquist-Majda [B. Engquist and A. Majda, Absorbing boundary conditions for the ...
of compu- tational interest. A properly defined PML method absorbs waves propagating into it without measurements by electromagnetic waves. This proposal was validated in experiments at microwave frequencies due. Second-order absorbing boundary conditions for the wave equation: a solution for the corner problem. ...
The positive solutions of a binary reaction-diffusion system of P.D.Es modelling the Schnackenberg chemical autocatalytic reaction are considered. The absorbing sets are obtained.
. Perfectly Matched Layers (PMLs) and an absorbing boundary condition are used to damp waves interacting of the electromagnetic interrogation problems introduced in [3]. Here we use perfectly matched layers (PMLs) as absorbing of interest. We use Perfectly Matched Layers to absorb incident ...
The RAM-6 code for calculation of parameters of the effective logarithmic boundary condition at the absorbent rod surface in reactor is suitably modified to work on IBM PC, the instructions for its usage are presented and capabilities of the personal cpmp...
Based on a recent study of the linearized Bianchi equations by Buchman and Sarbach, we construct and implement a hierarchy of absorbing boundary conditions for the Einstein equations in generalized harmonic gauge. As a test problem, we demonstrate that we can evolve multipolar gravitational waves without any spurious reflections at ...
The temperature field problem described in the paper is analytically solved for the absorber of a new type solar collector. The absorber consists of two plates, one of them being flat and placed on top of the other plate made with a square profile. The temperature field is calculated for four areas using the Laplace equation under stationary ...
The INTERPOL program, written in Autocode for the MERCURY computer, calculates effective boundary conditions at control plate surfaces for use with few group spatial diffusion theory codes. High order spherical harmonic boundary conditions for mono-energetic neutrons are appropriately averaged over a Wigner- ...
A perfectly matched layer (PML) is combined with an absorbing boundary condition (ABC) for mesh truncation in the finite element solution of electromagnetic scattering problems. It is shown by one-, two-, and three-dimensional examples, that the combined PML and ABC has less undesired reflection than the PML or ABC alone. I. ...
Reverse-time migration for post-stack seismic data in anisotropic media is implemented using the finite-element method. As an accurate digital method, the finite-element method is flexible for dealing with complicated geological structures, inner and man-made boundaries despite its intensive computation. Applying it in reverse-time migration may produce accurate images for ...
Diffusion of particles in confined domains with absorbing spots on the otherwise reflecting boundaries is ubiquitous in nature and technology. Because of nonuniform boundary conditions, the problem of finding the mean first passage time (MFPT) of the particle to one of the spots is extremely complicated. We show ...
PubMed
The authors present an energy absorbing non-reflecting boundary condition of Clayton-Engquist type for the elastic wave equation together with a discretization which is stable for any ratio of compressional to shear wave speed. They prove stability for a second order accurate finite-difference discretization of the elastic wave ...
The boundary condition at the hot absorber plate in a solar collector will influence the natural convection in the enclosure. For the isoflux boundary condition and an isothermal cold wall an experimental and numerical study has been made for Ra numbers from 10/sup 5/ to 10/sup 7/ and ...
boundary, it is easily imple� mented in the finite element method as a `natural' boundary condition using of a second�order absorbing boundary condition in a standard semidiscrete finite element method. Multi� plyingA Space�Time Finite Element Method for Structural ...
Abstract�The recently developed multiresolution time-domain technique (MRTD) is applied to the modeling of open microwave circuit problems. Open boundaries are simulated by the use of a novel formulation of the perfect matching layer (PML) absorber. PML is modeled both in split and nonsplit forms and can be brought right on the surface of the planar ...
A new absorbing boundary condition (ABC) is presented for the solution of Maxwell equations in unbounded spaces. Called the Huygens ABC, this condition is a generalization of two previously published ABCs, namely the multiple absorbing surfaces (MAS) and the re-radiating ...
We review the basic scaling laws for Marshak waves and point out the differences in results for wall loss, albedo, and Marshak depth when a constant absorbed flux is considered as opposed to a constant absorbed temperature. Comparisons with LASNEX simulations and with data are presented that imply that a constant absorbed flux is a ...
The problem of the direction of electromagnetic time, i.e., the complete dominance of retarded electromagnetic radiation over advanced radiation in the universe, is considered in the context of a generalized form of the Wheeler--Feynman absorber theory in an open expanding universe with a singularity at T = 0. It is shown that the application of a four-vector reflection ...
A new boundary condition is presented for use in beam propagation calculations that passes outgoing radiation freely with minimum reflection coefficient (as low as 3 {times} 10{sup {minus}8}). In conjunction with a standard Crank-Nicholson finite difference scheme, the assumption that the radiation field behaves as a complex exponential near the ...
A new DSMC boundary condition to model gas flow produced by moving microstructures is presented. The motion is assumed to be quasi-static: the microstructure speed is much smaller than the thermal speed of the molecules. Thus, the gas flow is nearly incompressible and isothermal, and the moving boundary is replaced by a fixed ...
The asymptotic boundary conditions are satisfied at the edge of the .... with asymptotic boundary conditions, a method was developed to eliminate the ...
. Salerno, "Iteratively- improved Robin boundary conditions for the finite element solution of scattering such as the finite element boundary integral method (FEBIM) or incorporate various kinds of absorbing boundary finite element method for the analysis of scattering from a three-dimensional ...
A modification to the Berenger perfectly matched layer (PML) absorbing boundary condition that allows it to be used in particle-in-cell applications where the primary power flow through the boundary is due to electromagnetic radiation is presented. Instead of modeling particles within the PML, a term is introduced ...
In an effort to develop a more efficient time dependent approach for calculating scattering matrix elements, absorbing boundary conditions are combined together with the channel packet method. As an introduction to scattering, scattering matrix elements a...
We prove that the straightforward extension of Berenger's original perfectly matched layer (PML) is not reflectionless at a cylindrical interface in the continuum limit. A quasi-PLM is developed as an absorbing boundary condition (ABC) for the finite-difference time-domain method...
of the external barrier, we employ the method of images to find the Green function of the governing differential valuation of these barrier options. Keywords: Multi�asset options, external barrier, Green's function with the homogeneous Dirichlet boundary condition corresponding to the absorbing barrier. The Green function can
Recently, perfectly matched layer (PML) as an absorbing boundary condition has widespread applications. The idea was first introduced by Berenger for electromagnetic waves computations. In this paper, it is shown that the PML equations for the linearized ...
CONTENTS: Analysis of the Finite Element Radiation Model Cone for Antenna Modeling; Accuracy of the Finite Element Method with Second Order Absorbing Boundary Conditions for the Solution of Aperture Radiation Problems; The FEMAX Finite Element Package for...
We extend Berenger's perfectly matched layers (PML) to conductive media. A finite-difference-time-domain (FDTD) algorithm with PML as an absorbing boundary condition is developed for solutions of Maxwell's equations in inhomogeneous, conductive media. For a perfectly matched laye...
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
nonlocal boundary conditions have proven to be effective in handling acoustic scattering problems developments in fast multipole methods which accelerate the calculation of matrix-vector products in iterative also be 6 #12;derived for acoustic waveguide problems [19, 75, 131]. For absorbing boundary ...
We study E1 resonances, breakup and fusion reactions for weakly bound Be nuclei. The absorbing-boundary condition (ABC) is used to describe both the outgoing and incoming boundary conditions. The neutron continuum plays important roles in response and reaction of neutron drip-line nuclei.
Consider a particle which is randomly accelerated by Gaussian white noise on the line segment 0absorbed as soon as it reaches x=0 or x=1. The mean absorption time T(x,v), where x and v denote the initial position and velocity, was calculated exactly by Masoliver and Porr� in 1995. We consider a more general boundary ...
The present work studies continuous time random walks (CTRWs) in a finite domain. A broad class of boundary conditions, of which absorbing and reflecting boundaries are particular cases, is considered. It is shown how any CTRW in this class can be mapped to a CTRW in an infinite domain. This may allow applying ...
of light leads to the generation of an acoustic wave via the thermoelastic expansion of the absorbing, for acoustic waves, even up to tens of megahertz, the scattering is considerably lower. PAT can therefore com can incorporate absorbing boundary conditions and bulk acoustic absorption. 3455 J. Acoust. Soc. Am
In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modelling domain. The Bayliss, Gunzberger and Turkel (BGT) boundary dampers of first- and second-orders, which require a circular cylindrical truncation boundary in the ...
In the random acceleration process considered here, a point particle is accelerated by Gaussian white noise with zero mean. Early work on first-passage and first-return probabilities and some recent applications are reviewed. Motion on the half line x > 0 and on the finite line 0 < x < 1 is considered, with two types of boundary conditions, ...
The P{sub N} theory has been shown to be an asymptotic limit of transport theory for problems in optically thick planar-geometry media with low adsorption rates and highly anisotropic scattering. In this paper transport problems that lie outside the asymptotic regime of validity of P{sub N} theory are considered. Such problems occur in media that are either optically thin, or contain isotropic or ...
There was some interest in estimating the neutron absorption rate in a composite cylinder consisting of an absorbing and scattering inner region contained by a purely absorbing wall, the cylinder being embedded in a large, predominantly scattering medium containing neutron sources. Results that are basic to the determination of the absorption rate ...
We consider the Helmholtz problem in the context of the evolution of uniform initial distribution of a physical attribute in general porous media subject to a partially absorbing boundary condition. Its spectral property as a reflection of the boundary geometry has been widely exploited, such as in biological and ...
The finite element method is employed to approximate the solutions of the Helmholtz equation for water wave radiation and scattering in an unbounded domain. A discrete, non-local and non-reflecting boundary condition is specified at an artificial external boundary by the DNL method, yielding an equivalent problem that is solved in a ...
A unique and non-negative solution of the radiative transfer equation in two dimensional X-Y geometry in scattering and absorbing media is presented. This solution facilitates asymmetric boundary conditions both in geometry and direction from the two boundaries of geometrical configurations such as stellar ...
We report a method that enables long-time molecular dynamics MD simulations of shock wave loading. The goal is to mitigate the severe interference effects that arise at interfaces or free boundaries when using standard nonequilibrium MD shock wave approac...
elements and Absorbing Boundary Conditions (ABCS) is presented. The ABCS are applied on the outer surface surface was less than half a wavelength from the scatterer. Introduction. The Finite Element Method (FEM on the exterior boundary that truncates the infinite domain) destroys the sparsity of the finite element ...
The key elements of the Muon Ionization Cooling Experiment (MICE) cooling channel are the absorbers that are a part of the MICE absorber focus coil modules (AFC modules). The boundaries of room temperature solid absorbers are well defined. The density of most solid absorber materials is also ...
The Wiener diffusion model (WDM) for 2-alternative tasks assumes that sensory information is integrated over time. Recent neurophysiological studies have found neural correlates of this integration process in certain neuronal populations. This paper analyses the properties of the WDM with two different boundary conditions in decision making tasks in which ...
We consider the diffusion-relaxation dynamics in porous media with partially absorbing boundary conditions. Spectral analysis of Helmholtz equation for the uniform boundary condition has been widely used as a probe of geometry of the medium. The NMR relaxation of the fluid magnetization, for ...
On Boundary Condition Capturing for Multiphase Interfaces ... 4. TITLE AND SUBTITLE On Boundary Condition Capturing for Multiphase Interfaces ...
We present an analytical and numerical study of time dependent diffusion coefficient in systems with partially absorbing boundary condition. We obtain a perturbative expansion for time dependent propagator in terms of volume fraction f of spheres in a dilute suspension of spheres. Exact single sphere t-operator for partially ...
Absorbing boundary conditions in the form of a complex absorbing potential are routinely introduced in the Schr�dinger equation to limit the computational domain or to study reactive scattering events using the multiconfigurational time-dependent Hartree (MCTDH) method. However, it is known that a pure ...
The effects of radiation heat transfer on the soot formation and oxidation process in laminar diffusion flames have been studied experimentally using a �radiation shield� for an ethylene flame and a laser heating technique for propylene flames. The soot volume fraction of ethylene diffusion flames was measured for two different radiation boundary ...
The spatial probability distribution associated with diffusion and attenuation in partially absorbing media is studied. An equivalence is established between a system with free diffusion for x> 0 and partial absorption for x < 0, and a semi-infinite system (x> 0) with a radiation boundary condition at x = 0. By exploiting this ...
A class of Ramified graphs (RG) is introduced as Iterated Function Systems (IFS) to optimally design networks for efficient reverse osmosis desalination in deep seawater. Ramified flow networks of absorbers, ranging from simple structures with constant weights, branch angles, and branch ratios, to fully optimized binary networks are considered. A contracting IFS with fixed ...
A random walk on the set of integers (0,1,2,..., a) with absorbing barriers at 0 and a is considered. The transition times from theintegers z (0 < z < a) are random variables with finite moments. The nth moment of the time to absorption at a, D/sub z,n/, conditioned on the walk starting at z and being absorbed at a, is discussed, ...
The passage of dislocations across grain boundaries in metals has been studied by using the in situ TEM deformation technique. A detailed analysis of the interaction of glissile matrix dislocations with grain-boundary dislocations has been performed. The results show that the dislocations piled-up at the grain boundary can: (1) be ...
The spherical harmonics method is used to obtain solution for the radiative heat transfer equation for a slab with reflective boundaries. An absorbing, emitting, non-isothermal, gray medium is considered with linearly anisotropic scattering. Under the condition of the thermal equilibrium, the slab boundaries are ...
In the context of patient-specific cardiovascular applications, hemodynamics models (going from 3D to 0D) are often limited to a part of the arterial tree. This restriction implies the set up of artificial interfaces with the remaining parts of the cardiovascular system. In particular, the inlet boundary condition is crucial: it supplies the impulsion to ...
This work deals with a numerical investigation on the energy absorbing capability of structural composite components. There are several difficulties associated with the numerical simulation of a composite impact-absorber, such as high geometrical non-linearities, boundary contact conditions, failure criteria, ...
... Title : STUDIES OF THE EFFECTS OF VARIATIONS IN BOUNDARY CONDITIONS ON THE ATMOSPHERIC BOUNDARY LAYER. ...
... Descriptors : *FINITE ELEMENT ANALYSIS, *BOUNDARY VALUE PROBLEMS, BOUNDARIES, PARTIAL DIFFERENTIAL ...
... Title : ASSIGNMENT AND PROGRAM CONTROL OF BOUNDARY CONDITIONS DURING SOLUTION OF NONSTATIONARY BOUNDARY VALUE ...
A theoretical and numerical analysis of Liao's absorbing boundary condition (ABC) is presented. The form of the ABC is related to both space-time polynomial extrapolation and a one-way wave equation. A modification allowing the optimization of the ABC for specific angles of incidence or wave speeds is discussed. The stability of the ...
The path is explored between one-dimensional scattering through Dirac- ? walls and one-dimensional quantum field theories defined on a finite length interval with Dirichlet boundary conditions. It is found that two ?'s are related to the Casimir effect whereas two ?'s plus the first transparent P�sch-Teller well arise in the context of the sine-Gordon ...
The evolution of black holes in �confining boxes� is interesting for a number of reasons, particularly because it mimics the global structure of anti-de Sitter geometries. These are nonglobally hyperbolic space-times and the Cauchy problem may only be well defined if the initial data are supplemented by boundary conditions at the timelike conformal ...
With the ultimate goal of devising effective absorbing boundary conditions (ABCs) for general anisotropic media, we investigate the accuracy aspects of local ABCs designed for the scalar anisotropic wave equation in the frequency domain (time harmonic case). The ABC analyzed in this paper is the perfectly matched discrete layers ...
... (15), corresponding respectively to the equivalent cases of perfectly absorbing boundary, or magnetic confinement (apart from the "pressure ...
In this study we examined an improved reasonable absorbing boundary condition (ABC). We examined ABC on the basis of the algorithm of the constrained interpolation profile (CIP) method for finite-difference time-domain (FDTD) acoustic simulation. Analysis of one-dimensional sound propagation with CIP-ABC was implemented. The results ...
The absorption of moderately and highly soluble vapors into the walls of the conducting airways was previously shown to be a transient process over the timescale of an inhalation cycle. However, a boundary condition to predict the transient wall absorption of vapors in CFD simulations does not exist. The objective of this study was to develop and test a ...
Wall BCs: Moving Wall. The MOVING WALL boundary condition is used at solid boundaries that have uniform translation or rotation. ...
Moving Wall. Boundary conditions for turbulence, chemistry, and MFD equations also. 4. Characteristic Nature at Boundaries. The characteristic (acoustic wave) ...
... Abstract : The purpose of this project was to investigate the artificial boundary conditions which must be imposed at the boundary of a numerical grid ...
A different approach to nonreflective boundary conditions for the Euler equations is presented. This
... The performanes of the oils are discussed in terms of the boundary lubrication conditions of the test. ... under boundary lubrication conditions. ...
... boundary conditions and a comparison of the ... WAVE PROPAGATION, *ACOUSTIC WAVES, EXPERIMENTAL ... Subject Categories : ACOUSTICS. ...
Steady-state planar ablative flow in a laser produced plasma is studied. The calculations relate all steady-state fluid quantities to only three parameters, the material, absorbed irradiance, and laser wavelength. The fluid is divided into three regions; the subcritical expanding plasma, the steady-state ablation front, and the accelerated slab. Boundary ...
The aim of this paper is to compare different ways for truncating unbounded domains for solving general nonlinear one- and two-dimensional Schr�dinger equations. We propose to analyze Complex Absorbing Potentials, Perfectly Matched Layers and Absorbing Boundary Conditions. The time discretization is made by using ...
Exterior complex dilation (ECD) is introduced for the discrete variable representation (DVR) via a general coordinate mapping. The procedure leads to a computationally efficient and easily implemented approach for imposing outgoing boundary conditions, comparable with absorbing potentials in terms of minimizing the grid and parameters ...
We construct exact solutions to the Bianchi equations on a flat spacetime background. When the constraints are satisfied, these solutions represent in- and outgoing linearized gravitational radiation. We then consider the Bianchi equations on a subset of flat spacetime of the form [0, T] � BR, where BR is a ball of radius R, and analyse different kinds of boundary ...
The propagation of sound under water is modeled by the wave equation. Under certain conditions, this equation can be approximated by the parabolic Schroedinger-type equation 2 i k{sub 0} u{sub r} + u{sub zz} + k{sub 0}{sup 2} (n {sup 2} (r,z) - 1)u = 0 where u represents the acoustic pressure at range r and depth z in the ocean. This parabolic equation has been solved ...
The stability of natural circulation flow loop geometry is under investigation in a specific thermo-dynamic region that encompasses the supercritical temperatures and pressures. This flow configuration is pertinent to the design of passive safety systems in some innovative reactor designs proposed for future generations of water-cooled nuclear reactors. Earlier studies employing both transient and ...
This work reports simulation results for a microwave (2.45 GHz) plasma reactor, operated by an axial injection torch (TIA). The study is based on a two-dimensional electromagnetic (EM) and hydrodynamic description of the TIA-reactor system. The EM model [1] solves Maxwell's equations, yielding the distribution of the EM fields and the averaged power absorbed, for a given ...
Questions of flux regulation in biological cells raise a renewed interest in the narrow escape problem. The determination of a higher order asymptotic expansion of the narrow escape time depends on determining the singularity behavior of the Neumann Green's function for the Laplacian in a three-dimensional (3D) domain with a Dirac mass on the boundary. In addition to the usual ...
Minimum-fuel, impulsive, time-fixed extremal solutions are obtained for the problem of orbital rendezvous and interception with path constraints. The coplanar case and a restricted class of path constraints are analyzed. A theory based on the extended problem of Bolza in the calculus of variations was established to determine optimal impulsive trajectories with state variable inequality ...
We consider the numerical scattering of plane waves by a metallic diffraction grating with a single defect. Besides different diffracted orders, a perturbed scattered field with arbitrary reflection direction is generated by the defect. We transform the diffraction grating into a closed waveguide by introducing a perfectly matched layer. The diffracted field is solved by applying pseudoperiodic ...
Band-theoretic methods with periodically repeated supercells have been a powerful approach for ground-state electronic structure calculations, but have not so far been adapted for quantum transport problems with open boundary conditions. Here we introduce a generalized Bloch theorem for complex periodic potentials and use a transfer-matrix formulation to ...
We introduce singular perturbation methods for constructing asymptotic approximations to the mean first passage time for Markov jump processes. Our methods are applied directly to the integral equation for the mean first passage time and do not involve the use of diffusion approximations. An absorbing interval condition is used to properly account for the ...
multiresolution time-domain technique (MRTD) is applied to the modeling of open microwave circuit problems. Open. Krumpholz and L. P. B. Katehi, "MRTD modeling of nonlinear pulse propagation," IEEE Trans. Microwave Theory. The applicability of the MRTD technique to complex geometries with high efficiency and accuracy in computing
A three-dimensional frequency-dependent finite-difference time-domain (FDTD) algorithm with perfectly matched layer (PML) absorbing boundary condition (ABC) and recursive convolution approaches is developed to model plasma-covered open-ended waveguide or cavity-backed slot antenn...
conditions is important for identifying a mechanochemical model of a molecular motor. This efficient method of these events and perform- ing statistical analysis provides insight into the kinetics and mechanochemical is a powerful tool for identifying the mechanochemical model of a molecular motor. The requirement that a single
for the absorption of electromagnetic waves, J. Comput. Phys., 114, 185-200 (1994). [9] J.P. Berenger, Perfectly of electromagnetic waves, J. Comput. Phys., 114, 363-379 (1996). [11] A. Berm�udez, L.M. Hervella-Nieto, A. Prieto. Majda, Absorbing boundary conditions for the numerical simulation of waves, Math. Comp., 31, 629
that the heat flux q is defined as: 21equivalent equivalent 11 withThq e t e t hh ++=�= where h is the heat is the square root of the product of the thermal conductivity, density and heat capacity. The units are a little absorb heat. The effusivity of your hand and the object it touches determines the surface temperature
A realistic model of a nonlinear medium allowing for linear and nonlinear absorption was used to determine the conditions for amplitude and phase bistability of a reflected wave field. The dependence of the phase hysteresis of the reflected wave on the dissipative properties of the boundary of the medium was analyzed. It was noted that these effects may be ...
An electromagnetic method based on rigorous diffraction theory of gratings is applied to the analysis of fields in semiconductor laser cavities. The method is based on the Fourier modal method; it is fully rigorous for infinitely periodic resonators and highly accurate for single resonators when absorbing boundary conditions are ...
Let A be a bounded region in 3D, and let ? A be its surface boundary which we assume to be absorbing. Enclose A and its boundary by a box with sides x = a, x = b, y = c, y = d, z = e, and z = f where a < b, c < d, and e < f. With delta as the step length in the random walk, assume that the intervals [a,b], [c,d], [e,f] ...
We first consider the classical neutral Moran model with two alleles whose fate is either to become extinct or to reach fixation. We study an ergodic version of the Moran model obtained by conditioning it to never hit the boundaries, making use of a Doob transform. We call it the recurrent Moran model. We show that the Siegmund dual of the recurrent Moran ...
The authors report the solution to the coupled nonlinear first-order partial differential equations representing the dynamics of photochemical reactions in systems essentially free from diffusion. No limitation regarding absorption of light by products of inert medium is assumed. These equations have been solved with the boundary condition that the species ...
The products of the corrosion reaction between Zr--2 at.% Sn--2 at.% Nb alloy and high temperature water or steam were an adherent film of ZrO/sub 2/ and H. A portion of this H was absorbed by the alloy. At 600 to 900 deg F in water and steam, the ratio of absorbed H to 0 was 0.01322. This ratio was the same for both the pretransition and ...
This paper describes a model of the absorption process in a falling film Lithium Bromide-Water absorber. Absorption of a gas or vapor into a laminar falling film on the surface of a vertical tube is taken into account. Necessary boundary conditions are provided to solve simultaneous parabolic partial-differential equation which are ...
We consider N vicious walkers moving in one dimension in a one-body potential v(x). Using the backward Fokker-Planck equation we derive exact results for the asymptotic form of the survival probability Q(x, t) of vicious walkers initially located at (x1, ..., xN) = x, when v(x) is an arbitrary attractive potential. Explicit results are given for a square-well potential with ...
Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the boundary of the computational domain. The optimization of the absorption coefficient is not an issue in continuous ...
A key component in an open-cycle solar absorption refrigeration system is the solar collector/regenerator that regenerates the weak absorbent solution. The collector/regenerator can be an open flat-plate solar collector over which the absorbent flows in a thin film. The solution starts at the top as a weak absorbent. Water vapor is ...
We develop and investigate an integral equation connecting the first passage time distribution of a stochastic process in the presence of an absorbing boundary condition and the corresponding Green's function in the absence of the absorbing boundary. Analytical solutions to the integral ...
This paper presents a two-dimensional electromagnetic model for a microwave (2.45 GHz) plasma reactor operated by an axial injection torch. The model solves Maxwell's equations, adopting a harmonic time description and considering the collision dispersion features of the plasma. Perfect-conductor boundary conditions are satisfied at the reactor walls, and ...
A class of Ramified graphs (RG) is introduced as Iterated Function Systems (IFS) to optimally design networks for efficient reverse osmosis desalination in deep seawater. Different forms of the IFS are presented, along with a corresponding contractivity factor sc, in order to identify the attractors of the systems and their fractal dimension. Using the analogy to electrostatics, the diffusion ...
In numerical studies of the dynamics of unbound quantum mechanical systems, absorbing boundary conditions are frequently applied. Although this certainly provides a useful tool in facilitating the description of the system, its applications to systems consisting of more than one particle are problematic. This is due to the fact that ...
The absorbers usually employed in everyday applications and the ultimate layouts recently proposed in the literature and based on unconventional material loading, are usually backed by a metallic plate. The metallic backing plays two main roles. On one hand, it is used to avoid power transmission on the other side of the absorber. On the other hand, it ...
models of the absorbers based on solar abundances severely overpredict the 0 VI columns previously obtained with the Far Ultraviolet Spectrograph, ...
... Abstract : The criticality and distribution conditions of neutron ... thermal-neutron reactor with a system of absorbing ... circle in the core or radial reflector. ...
The problem of determining polynomial spline approximations subject to derivative boundary conditions was considered. It is shown that if B-splines are employed as a basis, the incorporation of a variety of boundary conditions and the solution of the resu...
The boundary conditions at the supply opening have strong influence on the flow in the room and they are therefore very important. It is difficult to measure the profiles at the diffuser and to use them as boundary conditions. The flow in front of the dif...
To obtain a somewhat generic picture of the boundary condition effects, the results for the. classical S2 boundary conditions and the axially ...
ARTIFICIAL BOUNDARY CONDITIONS. 3. (1.5b) fi0(R0) = 0, constitutes ...... Infinite-domain problems, artificial boundary conditions, pseudodifferential ...
Reflection and absorption of an electromagnetic wave by a bounded plasma are studied. Inevitably in considering spatial dispersion, the necessity arises to formulate an additional boundary condition. In macroscopic discussion such conditions must be postulated, but this cannot be regarded as satisfactory. The microscopic ...
The four-state random walk (4RW) model, wherein the particle is endowed with two states of spin and two states of directional motion in each space coordinate, permits a stochastic solution of the Schr�dinger equation (or the equivalent parabolic equation) without resorting to the usual analytical continuation in complex space of the particle trajectories. Analytical expressions are derived here ...
... Keywords: ellipticity, normality, live-boundary condition of traction. ... DEFORMATION, SURFACES, BOUNDARIES, BOUNDARY VALUE PROBLEMS ...
... or Tangential Boundary Conditions in ... Descriptors : *FINITE ELEMENT ANALYSIS, *INCOMPRESSIBLE ... REPRINTS, BOUNDARIES, TANGENTS ...
... Accession Number : AD0771068. Title : On a Numerical Scheme for Solving Nonlinear Boundary Value Problems with Mixed Boundary Conditions. ...
... model in an investigation of the stability of laminar boundary layers in hypersonic ... Boundary layer profile and model surface conditions were ...
In this paper, an exact solution of the gray, scattering, radiative transfer problem in a dynamically evolved thick accretion disk is given. The collimation of the radiation field in the polar regions is demonstrated, and the ratio of radiative to gravitational acceleration is found everywhere. It is shown in detail how these specific dimensionless calculations can be scaled to physical disks of ...
Large-Scale Fluid-Structure Modeling Approaches. Structure. Finite elements. Fluid. Boundary elements; Finite elements with absorbing boundary ...
This invention discloses a shock wave absorber for a piping system carrying liquid. The absorber has a plastically deformable liner defining the normal flow boundary for an axial segment of the piping system, and a nondeformable housing is spaced outwardl...
... Title : The Treatment of Nonhomogeneous Dirichlet Boundary Conditions by the p-Version of the Finite Element Method. ...
The utilization of Langmuir probes in the identification and characterization of plasma boundary conditions is discussed. (C.H.)
... "* no artificial boundary conditions for the vorticity need be introduced at boundaries at which the velocity is specified; and ...
