Energy Technology Data Exchange (ETDEWEB)
Shih, H.R. [Jackson State Univ., MS (United States); Duffield, R.C.; Lin, J. [Univ. of Missouri, Columbia, MO (United States)
1996-10-01
An integral equation formulation and a numerical procedure for a boundary-finite element technique are developed for the static analysis of a stiffened plate with eccentric stiffeners. This formulation employs the fundamental solution associated with unstiffened plate bending and plane stress problems. With this approach, the resulting integral equation not only contained integrals along the perimeter of the stiffened but additional integrals along the stiffeners and the interface between the plate and its stiffeners. Thus the domain of the plate has to be divided into zones between the stiffeners. Each zone is modeled by boundary elements and stiffeners by finite elements. In this paper, the boundary element solution procedures for plate bending and in-plane problems are presented. The zone technique which permits coupling of unstiffened plate boundary element with stiffener finite elements is presented as well. Numerical example is given to demonstrate the effectiveness of this approach.
Boundary integral equation formulations for free-surface flow problems in two and three dimensions
Romate, J.E.; Zandbergen, P.J.
1989-01-01
To compute the transient solution of free-surface flow problems in two and three dimensions boundary integral equation formulations are considered. Consistent lower and higher order approximations based on small curvature expansions are compared and applied to a time-dependent, linear free-surface wave problem.
Energy Technology Data Exchange (ETDEWEB)
Corcelli, S.A.; Kress, J.D.; Pratt, L.R.
1995-08-07
This paper develops and characterizes mixed direct-iterative methods for boundary integral formulations of continuum dielectric solvation models. We give an example, the Ca{sup ++}{hor_ellipsis}Cl{sup {minus}} pair potential of mean force in aqueous solution, for which a direct solution at thermal accuracy is difficult and, thus for which mixed direct-iterative methods seem necessary to obtain the required high resolution. For the simplest such formulations, Gauss-Seidel iteration diverges in rare cases. This difficulty is analyzed by obtaining the eigenvalues and the spectral radius of the non-symmetric iteration matrix. This establishes that those divergences are due to inaccuracies of the asymptotic approximations used in evaluation of the matrix elements corresponding to accidental close encounters of boundary elements on different atomic spheres. The spectral radii are then greater than one for those diverging cases. This problem is cured by checking for boundary element pairs closer than the typical spatial extent of the boundary elements and for those cases performing an ``in-line`` Monte Carlo integration to evaluate the required matrix elements. These difficulties are not expected and have not been observed for the thoroughly coarsened equations obtained when only a direct solution is sought. Finally, we give an example application of hybrid quantum-classical methods to deprotonation of orthosilicic acid in water.
Solving the hypersingular boundary integral equation for the Burton and Miller formulation.
Langrenne, Christophe; Garcia, Alexandre; Bonnet, Marc
2015-11-01
This paper presents an easy numerical implementation of the Burton and Miller (BM) formulation, where the hypersingular Helmholtz integral is regularized by identities from the associated Laplace equation and thus needing only the evaluation of weakly singular integrals. The Helmholtz equation and its normal derivative are combined directly with combinations at edge or corner collocation nodes not used when the surface is not smooth. The hypersingular operators arising in this process are regularized and then evaluated by an indirect procedure based on discretized versions of the Calderón identities linking the integral operators for associated Laplace problems. The method is valid for acoustic radiation and scattering problems involving arbitrarily shaped three-dimensional bodies. Unlike other approaches using direct evaluation of hypersingular integrals, collocation points still coincide with mesh nodes, as is usual when using conforming elements. Using higher-order shape functions (with the boundary element method model size kept fixed) reduces the overall numerical integration effort while increasing the solution accuracy. To reduce the condition number of the resulting BM formulation at low frequencies, a regularized version α = ik/(k(2 )+ λ) of the classical BM coupling factor α = i/k is proposed. Comparisons with the combined Helmholtz integral equation Formulation method of Schenck are made for four example configurations, two of them featuring non-smooth surfaces. PMID:26627805
Institute of Scientific and Technical Information of China (English)
丁皓江; 江爱民
2003-01-01
To obtain the fundamental solutions for computation of magneto-electro-elastic media by the boundary element method, the general solutions in the case of distinct eigenvalues are derived and expressed in five harmonic functions from the governing equations and the strict differential operator theorem. On the basis of these general solutions, the fundamental solution of infinite magneto-electro-elastic solid are obtained with the method of trial-and-error. Finally, the boundary integral formulation is derived and the corresponding boundary element method program is implemented to perform two numerical calculations(a column under uni-axial tension, uniform electric displacement or uniform magnetic induction, an annular plate simply-supported on outer and inner surfaces under axial loads). The numerical results agree well with the analytical ones.
Institute of Scientific and Technical Information of China (English)
马杭; 黄兴
2003-01-01
Based on the fact that the singular boundary integrals in the sense of Cauchy principal value can be represented approxi-mately by the mean values of two companion nearly singular boundary integrals, a vary general approach was developed in the paper.In the approach, the approximate formulation before discretization was constructed to cope with the difficulties encountered in the cor-ner treatment in the formulations of hypersingular boundary integral equations. This makes it possible to solve the hypersingularboundary integral equation numerically in a non-regularized form and in a local manner by using conforming C0 quadratic boundary ele-ments and standard Gaussian quadratures similar to those employed in the conventional displacement-BIE formulations. The approxi-mate formulation is very convenient to use because the corner information is comprised naturally in the representations of those ap-proximate integrals. Numerical examples in plane elasticity show that with the present approach, the compatible or better results canbe achieved in comparison with those of the conventional BIE formulations.
Natarajan, Sundararajan; Ooi, Ean Tat; Chiong, Irene; Song, Chongmin
2013-01-01
Three different displacement based finite element formulations over arbitrary polygons are studied in this paper. The formulations considered are: the conventional polygonal finite element method (FEM) with Laplace interpolants, the cell-based smoothed polygonal FEM with simple averaging technique and the scaled boundary polygon formulation. For the purpose of numerical integration, we employ the sub-traingulation for the polygonal FEM and classical Gaussian quadrature for the smoothed FEM an...
A NOVEL BOUNDARY INTEGRAL EQUATION METHOD FOR LINEAR ELASTICITY--NATURAL BOUNDARY INTEGRAL EQUATION
Institute of Scientific and Technical Information of China (English)
Niu Zhongrong; Wang Xiuxi; Zhou Huanlin; Zhang Chenli
2001-01-01
The boundary integral equation (BIE) of displacement derivatives is put at a disadvantage for the difficulty involved in the evaluation of the hypersingular integrals. In this paper, the operators δij and εij are used to act on the derivative BIE. The boundary displacements, tractions and displacement derivatives are transformed into a set of new boundary tensors as boundary variables. A new BIE formulation termed natural boundary integral equation (NBIE) is obtained. The NBIE is applied to solving two-dimensional elasticity problems. In the NBIE only the strongly singular integrals are contained. The Cauchy principal value integrals occurring in the NBIE are evaluated. A combination of the NBIE and displacement BIE can be used to directly calculate the boundary stresses. The numerical results of several examples demonstrate the accuracy of the NBIE.
Path Integral Formulation of Noncommutative Quantum Mechanics
Acatrinei, C S
2001-01-01
We propose a phase-space path integral formulation of noncommutative quantum mechanics, and prove its equivalence to the operatorial formulation. As an illustration, the partition function of a noncommutative two-dimensional harmonic oscillator is calculated.
Completed Beltrami-Michell formulation for analyzing mixed boundary value problems in elasticity
Patnaik, Surya N.; Kaljevic, Igor; Hopkins, Dale A.; Saigal, Sunil
1995-01-01
In elasticity, the method of forces, wherein stress parameters are considered as the primary unknowns, is known as the Beltrami-Michell formulation (BMF). The existing BMF can only solve stress boundary value problems; it cannot handle the more prevalent displacement of mixed boundary value problems of elasticity. Therefore, this formulation, which has restricted application, could not become a true alternative to the Navier's displacement method, which can solve all three types of boundary value problems. The restrictions in the BMF have been alleviated by augmenting the classical formulation with a novel set of conditions identified as the boundary compatibility conditions. This new method, which completes the classical force formulation, has been termed the completed Beltrami-Michell formulation (CBMF). The CBMF can solve general elasticity problems with stress, displacement, and mixed boundary conditions in terms of stresses as the primary unknowns. The CBMF is derived from the stationary condition of the variational functional of the integrated force method. In the CBMF, stresses for kinematically stable structures can be obtained without any reference to the displacements either in the field or on the boundary. This paper presents the CBMF and its derivation from the variational functional of the integrated force method. Several examples are presented to demonstrate the applicability of the completed formulation for analyzing mixed boundary value problems under thermomechanical loads. Selected example problems include a cylindrical shell wherein membrane and bending responses are coupled, and a composite circular plate.
Directory of Open Access Journals (Sweden)
A. Tadeu
2012-01-01
Full Text Available The evaluation of the singular and hypersingular integrals that appear in three-dimensional boundary element formulations for heat diffusion, in the frequency domain, is presented in analytical form. This improves computational efficiency and accuracy. Numerical integrations using existing techniques based on standard Gaussian integration schemes that incorporate an enormous amount of sampling points are used to verify the solutions of singular integrals. For the hypersingular integrals the comparison is evaluated by making use of an analytical solution that is valid for circular domains, combined with a standard Gaussian integration scheme for the remaining boundary element domain. Closed form solutions for cylindrical inclusions (with null temperatures and null heat fluxes prescribed on the boundary are then derived and used to validate the three-dimensional boundary element formulations.
Spectral integration of linear boundary value problems
Viswanath, Divakar
2012-01-01
Spectral integration is a method for solving linear boundary value problems which uses the Chebyshev series representation of functions to avoid the numerical discretization of derivatives. It is occasionally attributed to Zebib (J. of Computational Physics vol. 53 (1984), p. 443-455) and more often to Greengard (SIAM J. on Numerical Analysis vol. 28 (1991), p. 1071-1080). Its advantage is believed to be its relative immunity to errors that arise when nearby grid points are used to approximate derivatives. In this paper, we reformulate the method of spectral integration by changing it in four different ways. The changes consist of a more convenient integral formulation, a different way to treat and interpret boundary conditions, treatment of higher order problems in factored form, and the use of piecewise Chebyshev grid points. Our formulation of spectral integration is more flexible and powerful as show by its ability to solve a problem that would otherwise take 8192 grid points using only 96 grid points. So...
Critical Review of Path Integral Formulation
Fujita, Takehisa
2008-01-01
The path integral formulation in quantum mechanics corresponds to the first quantization since it is just to rewrite the quantum mechanical amplitude into many dimensional integrations over discretized coordinates $x_n$. However, the path integral expression cannot be connected to the dynamics of classical mechanics, even though, superficially, there is some similarity between them. Further, the field theory path integral in terms of many dimensional integrations over fields does not correspo...
International Nuclear Information System (INIS)
The reflection equation algebra of Sklyanin is extended to the supersymmetric case. A graded reflection equation algebra is proposed and the corresponding graded (supersymmetric) boundary quantum inverse scattering method (QISM) is formulated. As an application, integrable open-boundary conditions for the doped spin-1 chain of the supersymmetric t-J model are studied in the framework of the boundary QISM. Diagonal boundary K-matrices are found and four classes of integrable boundary terms are determined. (author)
Galerkin Boundary Integral Analysis for the 3D Helmholtz Equation
Energy Technology Data Exchange (ETDEWEB)
Swager, Melissa [Emporia State University; Gray, Leonard J [ORNL; Nintcheu Fata, Sylvain [ORNL
2010-01-01
A linear element Galerkin boundary integral analysis for the three-dimensional Helmholtz equation is presented. The emphasis is on solving acoustic scattering by an open (crack) surface, and to this end both a dual equation formulation and a symmetric hypersingular formulation have been developed. All singular integrals are defined and evaluated via a boundary limit process, facilitating the evaluation of the (finite) hypersingular Galerkin integral. This limit process is also the basis for the algorithm for post-processing of the surface gradient. The analytic integrations required by the limit process are carried out by employing a Taylor series expansion for the exponential factor in the Helmholtz fundamental solutions. For the open surface, the implementations are validated by comparing the numerical results obtained by using the two different methods.
A positive formalism for quantum theory in the general boundary formulation
Oeckl, Robert
2012-01-01
We introduce a new "positive formalism" for encoding quantum theories in the general boundary formulation, somewhat analogous to the mixed state formalism of the standard formulation. This makes the probability interpretation more natural and elegant, eliminates operationally irrelevant structure and opens the general boundary formulation to quantum information theory.
A Advanced Boundary Element Formulation for Acoustic Radiation and Scattering in Three Dimensions.
Soenarko, Benjamin
A computational method is presented for determining acoustic fields produced by arbitrary shaped three-dimensional bodies. The formulation includes both radiation and scattering problems. In particular an isoparametric element formulation is introduced in which both the surface geometry and the acoustic variables on the surface of the body are represented by second order shape functions within the local coordinate system. A general result for the surface velocity potential and the exterior field is derived. This result is applicable to non-smooth bodies, i.e. it includes the case where the surface may have a non-unique normal (e.g. at the edge of a cube). Test cases are shown involving spherical, cylindrical and cubical geometry for both radiation and scattering problems. The present formulation is also extended to include half-space problems in which the effect of the reflected wave from an infinite plane is taken into account. By selecting an appropriate Green's function, the surface integral over the plane is nullified; thus all the computational efforts can be performed only on the radiating or scattering body at issue and thereby greatly simplify the solution. A special formulation involving axisymmetric bodies and boundary conditions is also presented. For this special case, the surface integrals are reduced to line integrals and an integral over the angle of revolution. The integration over the angle is performed partly analytically in terms of elliptic integrals and partly numerically using simple Gaussian quadrature formula. Since the rest of the integrals involve only line integrals along the generator of the body, any discretization scheme can be easily obtained to achieve a desired degree of accuracy in evaluating these integrals.
Adjoint Formulation for an Embedded-Boundary Cartesian Method
Nemec, Marian; Aftosmis, Michael J.; Murman, Scott M.; Pulliam, Thomas H.
2004-01-01
, which is based on the full-potential equation with viscous corrections. More recently, Dadone and Grossman presented an adjoint formulation for the Euler equations. In both approaches, a boundary condition is introduced to approximate the effects of the evolving surface shape that results in accurate gradient computation.
Boundary integral methods for microfluidic problems
Burbidge, Adam
2015-01-01
Microscale experiments of reduced complexity allow one to tease out and examine some of the interesting phenomena that manifest in large hierarchically structured materials which are of general interest across many industries. Recent advances in high speed imaging techniques and post-processing allow experiments to yield small scale information which was previously unavailable, or extremely difficult to obtain. This additional information provides new challenges in terms of theoretical understanding and prediction that requires new tools. We discuss generalised weighted residual numerical methods as a means of solving physically derived systems of PDEs, using the steady Stokes equation as an example. These formulations require integration of arbitrary functions of submanifolds which often will have a lower dimensionality than the parent manifold, leading to cumbersome calculations of the Jacobian determinant. We provide a tensorial view of the transformation, in which the natural element coordinate system is a non-orthogonal frame, and derive an expression for the Jacobian factor in terms of the contravariant metric tensor gij. This approach has the additional advantage that it can be extended to yield the local surface curvature, which will be essential for correct implementation of free surface boundaries.
Bugeanu, Monica; Di Remigio, Roberto; Mozgawa, Krzysztof; Reine, Simen Sommerfelt; Harbrecht, Helmut; Frediani, Luca
2015-12-21
The simplicity of dielectric continuum models has made them a standard tool in almost any Quantum Chemistry (QC) package. Despite being intuitive from a physical point of view, the actual electrostatic problem at the cavity boundary is challenging: the underlying boundary integral equations depend on singular, long-range operators. The parametrization of the cavity boundary should be molecular-shaped, smooth and differentiable. Even the most advanced implementations, based on the integral equation formulation (IEF) of the polarizable continuum model (PCM), generally lead to working equations which do not guarantee convergence to the exact solution and/or might become numerically unstable in the limit of large refinement of the molecular cavity (small tesserae). This is because they generally make use of a surface parametrization with cusps (interlocking spheres) and employ collocation methods for the discretization (point charges). Wavelets on a smooth cavity are an attractive alternative to consider: for the operators involved, they lead to highly sparse matrices and precise error control. Moreover, by making use of a bilinear basis for the representation of operators and functions on the cavity boundary, all equations can be differentiated to enable the computation of geometrical derivatives. In this contribution, we present our implementation of the IEFPCM with bilinear wavelets on a smooth cavity boundary. The implementation has been carried out in our module PCMSolver and interfaced with LSDalton, demonstrating the accuracy of the method both for the electrostatic solvation energy and for linear response properties. In addition, the implementation in a module makes our framework readily available to any QC software with minimal effort. PMID:26256401
Perturbation theory and importance functions in integral transport formulations
International Nuclear Information System (INIS)
Perturbation theory expressions for the static reactivity derived from the flux, collision density, birth-rate density, and fission-neutron density formulations of integral transport theory, and from the integro-differential formulation, are intercompared. The physical meaning and relation of the adjoint functions corresponding to each of the five formulations are established. It is found that the first-order approximation of the perturbation expressions depends on the transport theory formulation and on the adjoint function used. The approximations of the integro-differential formulation corresponding to different first-order approximations of the integral transport theory formulations are identified. It is found that the accuracy of all first-order approximations of the integral transport formulations examined is superior to the accuracy of first-order integro-differential perturbation theory
PROBLEM WITH INTEGRAL BOUNDARY CONDITIONS INVOLVING PETTIS INTEGRAL
Institute of Scientific and Technical Information of China (English)
Hussein A.H. Salem
2011-01-01
In this article, we investigate the existence of Pseudo solutions for some frac- tional order boundary value problem with integral boundary conditions in the Banach space of continuous function equipped with its weak topology. The class of such problems constitute a very interesting and important class of problems. They include two, three, multi-point and nonlocal boundary-value problems as special cases. In our investigation, the right hand side of the above problem is assumed to be Pettis integrable function. To encompass the full scope of this article, we give an example illustrating the main result.
An integral formulation for wave propagation on weakly non-uniform potential flows
Mancini, Simone; Sinayoko, Samuel; Gabard, Gwenael; Tournour, Michel
2015-01-01
An integral formulation for acoustic radiation in moving flows is presented. It is based on a potential formulation for acoustic radiation on weakly non-uniform subsonic mean flows. This work is motivated by the absence of suitable kernels for wave propagation on non-uniform flow. The integral solution is formulated using a Green's function obtained by combining the Taylor and Lorentz transformations. Although most conventional approaches based on either transform solve the Helmholtz problem in a transformed domain, the current Green's function and associated integral equation are derived in the physical space. A dimensional error analysis is developed to identify the limitations of the current formulation. Numerical applications are performed to assess the accuracy of the integral solution. It is tested as a means of extrapolating a numerical solution available on the outer boundary of a domain to the far field, and as a means of solving scattering problems by rigid surfaces in non-uniform flows. The results...
Geometric Phase and Chiral Anomaly in Path Integral Formulation
Fujikawa, Kazuo
2007-01-01
All the geometric phases, adiabatic and non-adiabatic, are formulated in a unified manner in the second quantized path integral formulation. The exact hidden local symmetry inherent in the Schr\\"{o}dinger equation defines the holonomy. All the geometric phases are shown to be topologically trivial. The geometric phases are briefly compared to the chiral anomaly which is naturally formulated in the path integral.
A Boundary Integral Equation Approach for Boundary Problem of Laplace Equation
Institute of Scientific and Technical Information of China (English)
SUNJian-she; YELiu-qing
2003-01-01
Using the second Green formula, the boundary problem of Laplace equation satisfied by potential function of static electric field is transformed to the problem of the boundary integral equation,and then a boundary integral equation approach is established by partitioning boundary using linear boundary element.
The initial boundary value problem for free-evolution formulations of General Relativity
Hilditch, David
2016-01-01
We consider the initial boundary value problem for free-evolution formulations of general relativity coupled to a parametrized family of coordinate conditions that includes both the moving puncture and harmonic gauges. We concentrate primarily on boundaries that are geometrically determined by the outermost normal observer to spacelike slices of the foliation. We present high-order-derivative boundary conditions for the gauge, constraint violating and gravitational wave degrees of freedom of the formulation. Second order derivative boundary conditions are presented in terms of the conformal variables used in numerical relativity simulations. Using Kreiss-Agranovich-Metivier theory we demonstrate, in the frozen coefficient approximation, that with sufficiently high order derivative boundary conditions the initial boundary value problem can be rendered boundary stable. The precise number of derivatives required depends on the gauge. For a choice of the gauge condition that renders the system strongly hyperbolic...
Numerical analysis of Weyl's method for integrating boundary layer equations
Najfeld, I.
1982-01-01
A fast method for accurate numerical integration of Blasius equation is proposed. It is based on the limit interchange in Weyl's fixed point method formulated as an iterated limit process. Each inner limit represents convergence to a discrete solution. It is shown that the error in a discrete solution admits asymptotic expansion in even powers of step size. An extrapolation process is set up to operate on a sequence of discrete solutions to reach the outer limit. Finally, this method is extended to related boundary layer equations.
Iterative solution of Hermite boundary integral equations
Energy Technology Data Exchange (ETDEWEB)
Gray, Leonard J [ORNL; Nintcheu Fata, Sylvain [ORNL; Ma, Ding [ORNL
2008-01-01
An efficient iterative method for the solution of the linear equations arising from a Hermite boundary integral approximation has been developed. Along with equations for the boundary unknowns, the Hermite system incorporates equations for the first-order surface derivatives (gradient) of the potential, and is therefore substantially larger than the matrix for a corresponding linear approximation. However, by exploiting the structure of the Hermite matrix, a two-level iterative algorithm has been shown to provide a very efficient solution algorithm. In this approach, the boundary function unknowns are treated separately from the gradient, taking advantage of the sparsity and near-positive definiteness of the gradient equations. In test problems, the new algorithm significantly reduced computation time compared to iterative solution applied to the full matrix. This approach should prove to be even more effective for the larger systems encountered in three-dimensional analysis, and increased efficiency should come from pre-conditioning of the non-sparse matrix component.
Boundary conditions for the Einstein-Christoffel formulation of Einstein's equations
Arnold, Douglas N.; Nicolae Tarfulea
2007-01-01
Specifying boundary conditions continues to be a challenge in numerical relativity in order to obtain a long time convergent numerical simulation of Einstein's equations in domains with artificial boundaries. In this paper, we address this problem for the Einstein--Christoffel (EC) symmetric hyperbolic formulation of Einstein's equations linearized around flat spacetime. First, we prescribe simple boundary conditions that make the problem well posed and preserve the constraints. Next, we indi...
RADIATION BOUNDARY CONDITIONS FOR MAXWELL'S EQUATIONS: A REVIEW OF ACCURATE TIME-DOMAIN FORMULATIONS
Institute of Scientific and Technical Information of China (English)
Thomas Hagstrom; Stephen Lau
2007-01-01
We review time-domain formulations of radiation boundary conditions for Maxwell's equations, focusing on methods which can deliver arbitrary accuracy at acceptable computational cost. Examples include fast evaluations of nonlocal conditions on symmetric and general boundaries, methods based on identifying and evaluating equivalent sources, and local approximations such as the perfectly matched layer and sequences of local boundary conditions. Complexity estimates are derived to assess work and storage requirements as a function of wavelength and simulation time.
NATURAL BOUNDARY INTEGRAL METHOD AND ITS NEW DEVELOPMENT
Institute of Scientific and Technical Information of China (English)
De-hao Yu
2004-01-01
In this paper, the natural boundary integral method, and some related methods, including coupling method of the natural boundary elements and finite elements, which is also called DtN method or the method with exact artificial boundary conditions, domain decomposition methods based on the natural boundary reduction, and the adaptive boundary element method with hyper-singular a posteriori error estimates, are discussed.
A finite element-boundary integral method for cavities in a circular cylinder
Kempel, Leo C.; Volakis, John L.
1992-01-01
Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. However, due to a lack of rigorous mathematical models for conformal antenna arrays, antenna designers resort to measurement and planar antenna concepts for designing non-planar conformal antennas. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. We extend this formulation to conformal arrays on large metallic cylinders. In this report, we develop the mathematical formulation. In particular, we discuss the shape functions, the resulting finite elements and the boundary integral equations, and the solution of the conformal finite element-boundary integral system. Some validation results are presented and we further show how this formulation can be applied with minimal computational and memory resources.
Energy Technology Data Exchange (ETDEWEB)
Kempka, S.N.; Strickland, J.H.; Glass, M.W.; Peery, J.S. [Sandia National Labs., Albuquerque, NM (United States); Ingber, M.S. [Univ. of New Mexico, Albuquerque, NM (United States)
1995-04-01
formulation to satisfy velocity boundary conditions for the vorticity form of the incompressible, viscous fluid momentum equations is presented. The tangential and normal components of the velocity boundary condition are satisfied simultaneously by creating vorticity adjacent to boundaries. The newly created vorticity is determined using a kinematical formulation which is a generalization of Helmholtz` decomposition of a vector field. Though it has not been generally recognized, these formulations resolve the over-specification issue associated with creating voracity to satisfy velocity boundary conditions. The generalized decomposition has not been widely used, apparently due to a lack of a useful physical interpretation. An analysis is presented which shows that the generalized decomposition has a relatively simple physical interpretation which facilitates its numerical implementation. The implementation of the generalized decomposition is discussed in detail. As an example the flow in a two-dimensional lid-driven cavity is simulated. The solution technique is based on a Lagrangian transport algorithm in the hydrocode ALEGRA. ALEGRA`s Lagrangian transport algorithm has been modified to solve the vorticity transport equation and the generalized decomposition, thus providing a new, accurate method to simulate incompressible flows. This numerical implementation and the new boundary condition formulation allow vorticity-based formulations to be used in a wider range of engineering problems.
An Explicit Time-Domain Hybrid Formulation Based on the Unified Boundary Condition
Energy Technology Data Exchange (ETDEWEB)
Madsen, N; Fasenfest, B J; White, D; Stowell, M; Jandhyala, V; Pingenot, J; Champagne, N J; Rockway, J D
2007-02-28
An approach to stabilize the two-surface, time domain FEM/BI hybrid by means of a unified boundary condition is presented. The first-order symplectic finite element formulation [1] is used along with a version of the unified boundary condition of Jin [2] reformulated for Maxwell's first-order equations in time to provide both stability and accuracy over the first-order ABC. Several results are presented to validate the numerical solutions. In particular the dipole in a free-space box is analyzed and compared to the Dirchlet boundary condition of Ziolkowski and Madsen [3] and to a Neuman boundary condition approach.
Exact Boundary Derivative Formulation for Numerical Conformal Mapping Method
Wei-Lin Lo; Nan-Jing Wu; Chuin-Shan Chen; Ting-Kuei Tsay
2016-01-01
Conformal mapping is a useful technique for handling irregular geometries when applying the finite difference method to solve partial differential equations. When the mapping is from a hyperrectangular region onto a rectangular region, a specific length-to-width ratio of the rectangular region that fitted the Cauchy-Riemann equations must be satisfied. In this research, a numerical integral method is proposed to find the specific length-to-width ratio. It is conventional to employ the boundar...
Canonical formulation and path integral for local vacuum energy sequestering
Bufalo, R.; Klusoň, J.; Oksanen, M.
2016-01-01
We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity...
Tezduyar, T. E.; Liou, J.
1991-01-01
Downstream boundary conditions equivalent to the homogeneous form of the natural boundary conditions associated with the velocity-pressure formulation of the Navier-Stokes equations are derived for the vorticity-stream function formulation of two-dimensional incompressible flows. Of particular interest are the zero normal and shear stress conditions at a downstream boundary.
De Corato, M.; Slot, J. J. M.; Hütter, M.; D'Avino, G.; Maffettone, P. L.; Hulsen, M. A.
2016-07-01
In this paper, we present a finite element implementation of fluctuating hydrodynamics with a moving boundary fitted mesh for treating the suspended particles. The thermal fluctuations are incorporated into the continuum equations using the Landau and Lifshitz approach [1]. The proposed implementation fulfills the fluctuation-dissipation theorem exactly at the discrete level. Since we restrict the equations to the creeping flow case, this takes the form of a relation between the diffusion coefficient matrix and friction matrix both at the particle and nodal level of the finite elements. Brownian motion of arbitrarily shaped particles in complex confinements can be considered within the present formulation. A multi-step time integration scheme is developed to correctly capture the drift term required in the stochastic differential equation (SDE) describing the evolution of the positions of the particles. The proposed approach is validated by simulating the Brownian motion of a sphere between two parallel plates and the motion of a spherical particle in a cylindrical cavity. The time integration algorithm and the fluctuating hydrodynamics implementation are then applied to study the diffusion and the equilibrium probability distribution of a confined circle under an external harmonic potential.
Boundary integral method applied in chaotic quantum billiards
Li, B; Li, Baowen; Robnik, Marko
1995-01-01
The boundary integral method (BIM) is a formulation of Helmholtz equation in the form of an integral equation suitable for numerical discretization to solve the quantum billiard. This paper is an extensive numerical survey of BIM in a variety of quantum billiards, integrable (circle, rectangle), KAM systems (Robnik billiard) and fully chaotic (ergodic, such as stadium, Sinai billiard and cardioid billiard). On the theoretical side we point out some serious flaws in the derivation of BIM in the literature and show how the final formula (which nevertheless was correct) should be derived in a sound way and we also argue that a simple minded application of BIM in nonconvex geometries presents serious difficulties or even fails. On the numerical side we have analyzed the scaling of the averaged absolute value of the systematic error \\Delta E of the eigenenergy in units of mean level spacing with the density of discretization (b = number of numerical nodes on the boundary within one de Broglie wavelength), and we f...
Cleansing Formulations That Respect Skin Barrier Integrity
Directory of Open Access Journals (Sweden)
Russel M. Walters
2012-01-01
Full Text Available Surfactants in skin cleansers interact with the skin in several manners. In addition to the desired benefit of providing skin hygiene, surfactants also extract skin components during cleansing and remain in the stratum corneum (SC after rinsing. These side effects disrupt SC structure and degrade its barrier properties. Recent applications of vibrational spectroscopy and two-photon microscopy in skin research have provided molecular-level information to facilitate our understanding of the interaction between skin and surfactant. In the arena of commercial skin cleansers, technologies have been developed to produce cleansers that both cleanse and respect skin barrier. The main approach is to minimize surfactant interaction with skin through altering its solution properties. Recently, hydrophobically modified polymers (HMPs have been introduced to create skin compatible cleansing systems. At the presence of HMP, surfactants assemble into larger, more stable structures. These structures are less likely to penetrate the skin, thereby resulting in less aggressive cleansers and the integrity of the skin barrier is maintained. In this paper, we reviewed our recent findings on surfactant and SC interactions at molecular level and provided an overview of the HM technology for developing cleansers that respect skin barrier.
Energy Technology Data Exchange (ETDEWEB)
Bendapudi, Satyam [United Technologies Research Center, East Hartford, CT (United States); Braun, James E.; Groll, Eckhard A. [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)
2008-12-15
Dynamic models of vapor compression systems are useful tools in developing feedback controllers and are gaining increasing attention in recent years. The dominant dynamics are typically those of the evaporator and condenser, which are difficult to model. Accuracy and execution speed of system models therefore are highly dependent on the modeling approach of the heat exchangers. The two common approaches are the finite-volume (FV) and the moving-boundary (MB) methods. Both have been used successfully and reported in the literature, but there is little discussion presented for either choice. This paper presents the development and comparative study of shell-and-tube heat exchanger dynamic models using both the FV and the MB approaches. Detailed model formulations are provided and stability is demonstrated as components and within a complete centrifugal chiller system model. The system models are validated using data from a 300 kW R134a centrifugal chiller test stand. The FV formulation is found to be more robust through start-up and all load-change transients, but executes slower. The moving-boundary method can handle all load-change transients but start-up stability is more sensitive to compressor and expansion valve formulations. The moving-boundary formulation also executes about three times faster than the finite-volume while maintaining nearly identical accuracy. With the homogenous two-phase assumption, charge prediction is seen to be less accurate in the moving-boundary approach. (author)
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Juhl, Peter Møller
2013-01-01
The formulation presented in this paper is based on the Boundary Element Method (BEM) and implements Kirchhoff’s decomposition into viscous, thermal and acoustic components, which can be treated independently everywhere in the domain except on the boundaries. The acoustic variables with losses...... are solved using extended boundary conditions that account for: i) negligible temperature fluctuations at the boundary, and ii) normal and tangential matching of the boundary’s particle velocity. The proposed model does not require constructing a special mesh for the viscous and thermal boundary layers...... as is the case with the existing Finite Element Method (FEM) implementations with losses. The suitability of this approach is demonstrated using an axisymmetrical BEM and two test cases where the numerical results are compared with analytical solutions....
Thermal momentum distribution from path integrals with shifted boundary conditions
Giusti, Leonardo
2011-01-01
For a thermal field theory formulated in the grand canonical ensemble, the distribution of the total momentum is an observable characterizing the thermal state. We show that its cumulants are related to thermodynamic potentials. In a relativistic system for instance, the thermal variance of the total momentum is a direct measure of the enthalpy. We relate the generating function of the cumulants to the ratio of (a) a partition function expressed as a Matsubara path integral with shifted boundary conditions in the compact direction, and (b) the ordinary partition function. In this form the generating function is well suited for Monte-Carlo evaluation, and the cumulants can be extracted straightforwardly. We test the method in the SU(3) Yang-Mills theory and obtain the entropy density at three different temperatures.
Canonical formulation and path integral for local vacuum energy sequestering
Bufalo, R; Oksanen, M
2016-01-01
We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity. It is argued to imply a relation between the fraction of the most likely values of the gravitational and cosmological constants and the average values of the energy density and pressure of matter over spacetime. Finally, we construct and analyze a BRST-exact formulation of the theory, which can be considered as a topological field theory.
Canonical formulation and path integral for local vacuum energy sequestering
Bufalo, R.; KlusoÅ, J.; Oksanen, M.
2016-08-01
We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the Universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity. It is argued to imply a relation between the fraction of the most likely values of the gravitational and cosmological constants and the average values of the energy density and pressure of matter over spacetime. Finally, we construct and analyze a Becchi-Rouet-Stora-Tyutin-exact formulation of the theory, which can be considered as a topological field theory.
Second-order domain derivative of normal-dependent boundary integrals
Balzer, Jonathan
2010-03-17
Numerous reconstruction tasks in (optical) surface metrology allow for a variational formulation. The occurring boundary integrals may be interpreted as shape functions. The paper is concerned with the second-order analysis of such functions. Shape Hessians of boundary integrals are considered difficult to find analytically because they correspond to third-order derivatives of an, in a sense equivalent, domain integral. We complement previous results by considering cost functions depending explicitly on the surface normal. The correctness and practicability of our calculations are verified in the context of a Newton-type shape reconstruction method. © 2010 Birkhäuser / Springer Basel AG.
Integrated watershed planning across jurisdictional boundaries
Watts, A. W.; Roseen, R.; Stacey, P.; Bourdeau, R.
2014-12-01
We will present the foundation for an Coastal Watershed Integrated Plan for three communities in southern New Hampshire. Small communities are often challenged by complex regulatory requirements and limited resources, but are wary of perceived risks in engaging in collaborative projects with other communities. Potential concerns include loss of control, lack of resources to engage in collaboration, technical complexity, and unclear benefits. This project explores a multi-town subwatershed application of integrated planning across jurisdictional boundaries that addresses some of today's highest priority water quality issues: wastewater treatment plant upgrades for nutrient removal; green infrastructure stormwater management for developing and re-developing areas; and regional monitoring of ecosystem indicators in support of adaptive management to achieve nutrient reduction and other water quality goals in local and downstream waters. The project outcome is a collaboratively-developed inter-municipal integrated plan, and a monitoring framework to support cross jurisdictional planning and assess attainment of water quality management goals. This research project has several primary components: 1) assessment of initial conditions, including both the pollutant load inputs and the political, economic and regulatory status within each community, 2) a pollutant load model for point and non-point sources, 3) multi-criteria evaluation of load reduction alternatives 4) a watershed management plan optimized for each community, and for Subwatersheds combining multiple communities. The final plan will quantify the financial and other benefits/drawbacks to each community for both inter municipal and individual pollution control approaches. We will discuss both the technical and collaborative aspects of the work, with lessons learned regarding science to action, incorporation of social, economic and water quality assessment parameters, and stakeholder/researcher interaction.
Geometric formulations and variational integrators of discrete autonomous Birkhoff systems
International Nuclear Information System (INIS)
The variational integrators of autonomous Birkhoff systems are obtained by the discrete variational principle. The geometric structure of the discrete autonomous Birkhoff system is formulated. The discretization of mathematical pendulum shows that the discrete variational method is as effective as symplectic scheme for the autonomous Birkhoff systems. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Geometric formulations and variational integrators of discrete autonomous Birkhoff systems
Institute of Scientific and Technical Information of China (English)
Liu Shi-Xing; Liu Chang; Guo Yong-Xin
2011-01-01
The variational integrators of autonomous Birkhoff systems are obtained by the discrete variational principle. The geometric structure of the discrete autonomous Birkhoff system is formulated. The discretization of mathematical pendulum shows that the discrete variational method is as effective as symplectic scheme for the autonomous Birkhoff systems.
Argeso, Hakan; Mengi, Yalcin
2014-02-01
A unified formulation is presented, based on the boundary element method, to perform the interaction analysis for the problems involving poroviscoelastic media. The proposed formulation permits the evaluation of all the elements of impedance and input motion matrices at a single step in terms of system matrices of boundary element method without solving any special problem, such as, unit displacement or load problem, as required by conventional methods. It further eliminates the complicated procedure and the need for using scattering analysis in the evaluation of input motion functions. The formulation is explained by considering a simple interaction problem involving an inclusion embedded in an infinite poroviscoelastic medium, which is under the influence of a dynamic excitation induced by seismic waves. In the formulation, an impedance relation is established for this interaction problem, suitable for performing the interaction analysis by substructure method, which permits carrying out the analysis for inclusion and its surrounding medium separately. The inclusion is first treated as poroviscoelastic, then viscoelastic and finally rigid, where the formulation in each of these cases is obtained consecutively as a special case of the previous one. It is remarkable to note that, a cavity problem where there is a hole in place of inclusion can be also considered within the framework of the present formulation. The formulation is assessed by applying it to some sample problems. The extension of the formulation to other types of interaction problems, such as, multi-inclusion problems, the analyses of foundations supported by a poroviscoelastic medium, etc., will be the subject of a separate study.
A finite element-boundary integral method for conformal antenna arrays on a circular cylinder
Kempel, Leo C.; Volakis, John L.
1992-01-01
Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. In the past, antenna designers have had to resort to expensive measurements in order to develop a conformal array design. This was due to the lack of rigorous mathematical models for conformal antenna arrays. As a result, the design of conformal arrays was primarily based on planar antenna design concepts. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. We are extending this formulation to conformal arrays on large metallic cylinders. In doing so, we will develop a mathematical formulation. In particular, we discuss the finite element equations, the shape elements, and the boundary integral evaluation. It is shown how this formulation can be applied with minimal computation and memory requirements.
BOUNDARY INTEGRAL FORMULA OF ELASTIC PROBLEMS IN CIRCLE PLANE
Institute of Scientific and Technical Information of China (English)
DONG Zheng-zhu; LI Shun-cai; YU De-hao
2005-01-01
By bianalytic functions, the boundary integral formula of the stress function for the elastic problem in a circle plane is developed. But this integral formula includes a strongly singular integral and can not be directly calculated. After the stress function is expounded to Fourier series, making use of some formulas in generalized functions to the convolutions, the boundary integral formula which does not include strongly singular integral is derived further. Then the stress function can be got simply by the integration of the values of the stress function and its derivative on the boundary. Some examples are given. It shows that the boundary integral formula of the stress function for the elastic problem is convenient.
Perfectly-matched-layer boundary integral equation method for wave scattering in a layered medium
Lu, Wangtao; Qian, Jianliang
2016-01-01
For scattering problems of time-harmonic waves, the boundary integral equation (BIE) methods are highly competitive, since they are formulated on lower-dimension boundaries or interfaces, and can automatically satisfy outgoing radiation conditions. For scattering problems in a layered medium, standard BIE methods based on the Green's function of the background medium must evaluate the expensive Sommefeld integrals. Alternative BIE methods based on the free-space Green's function give rise to integral equations on unbounded interfaces which are not easy to truncate, since the wave fields on these interfaces decay very slowly. We develop a BIE method based on the perfectly matched layer (PML) technique. The PMLs are widely used to suppress outgoing waves in numerical methods that directly discretize the physical space. Our PML-based BIE method uses the Green's function of the PML-transformed free space to define the boundary integral operators. The method is efficient, since the Green's function of the PML-tran...
Accurate computation of Galerkin double surface integrals in the 3-D boundary element method
Adelman, Ross; Duraiswami, Ramani
2015-01-01
Many boundary element integral equation kernels are based on the Green's functions of the Laplace and Helmholtz equations in three dimensions. These include, for example, the Laplace, Helmholtz, elasticity, Stokes, and Maxwell's equations. Integral equation formulations lead to more compact, but dense linear systems. These dense systems are often solved iteratively via Krylov subspace methods, which may be accelerated via the fast multipole method. There are advantages to Galerkin formulations for such integral equations, as they treat problems associated with kernel singularity, and lead to symmetric and better conditioned matrices. However, the Galerkin method requires each entry in the system matrix to be created via the computation of a double surface integral over one or more pairs of triangles. There are a number of semi-analytical methods to treat these integrals, which all have some issues, and are discussed in this paper. We present novel methods to compute all the integrals that arise in Galerkin fo...
Quantum Brans-Dicke Gravity in Euclidean Path Integral Formulation
Kim, Hongsu
1997-01-01
The conformal structure of Brans-Dicke gravity action is carefully studied. It is discussed that Brans-Dicke gravity action has definitely no conformal invariance. It is shown, however, that this lack of conformal invariance enables us to demonstrate that Brans-Dicke theory appears to have a better short-distance behavior than Einstein gravity as far as Euclidean path integral formulation for quantum gravity is concerned.
A spectral boundary integral equation method for the 2D Helmholtz equation
International Nuclear Information System (INIS)
In this paper, we present a new numerical formulation of solving the boundary integral equations reformulated from the Helmholtz equation. The boundaries of the problems are assumed to be smooth closed contours. The solution on the boundary is treated as a periodic function, which is in turn approximated by a truncated Fourier series. A Fourier collocation method is followed in which the boundary integral equation is transformed into a system of algebraic equations. It is shown that in order to achieve spectral accuracy for the numerical formulation, the non-smoothness of the integral kernels, associated with the Helmholtz equation, must be carefully removed. The emphasis of the paper is on investigating the essential elements of removing the non-smoothness of the integral kernels in the spectral implementation. The present method is robust for a general smooth boundary contour. Aspects of efficient implementation of the method using FFT are also discussed. Numerical examples of wave scattering are given in which the exponential accuracy of the present numerical method is demonstrated. 15 refs., 3 figs., 4 tabs
Treatment of domain integrals in boundary element methods
Energy Technology Data Exchange (ETDEWEB)
Nintcheu Fata, Sylvain [ORNL
2012-01-01
A systematic and rigorous technique to calculate domain integrals without a volume-fitted mesh has been developed and validated in the context of a boundary element approximation. In the proposed approach, a domain integral involving a continuous or weakly-singular integrand is first converted into a surface integral by means of straight-path integrals that intersect the underlying domain. Then, the resulting surface integral is carried out either via analytic integration over boundary elements or by use of standard quadrature rules. This domain-to-boundary integral transformation is derived from an extension of the fundamental theorem of calculus to higher dimension, and the divergence theorem. In establishing the method, it is shown that the higher-dimensional version of the first fundamental theorem of calculus corresponds to the well-known Poincare lemma. The proposed technique can be employed to evaluate integrals defined over simply- or multiply-connected domains with Lipschitz boundaries which are embedded in an Euclidean space of arbitrary but finite dimension. Combined with the singular treatment of surface integrals that is widely available in the literature, this approach can also be utilized to effectively deal with boundary-value problems involving non-homogeneous source terms by way of a collocation or a Galerkin boundary integral equation method using only the prescribed surface discretization. Sample problems associated with the three-dimensional Poisson equation and featuring the Newton potential are successfully solved by a constant element collocation method to validate this study.
International Nuclear Information System (INIS)
The collisional plasma transport problem is formulated as an initial boundary value problem for general characteristic boundary conditions. Starting from the full set of hydrodynamic and electrodynamic equations an expansion in the electron-ion mass ratio together with a multiple timescale method yields simplified equations on each timescale. On timescales where many collisions have taken place for the simplified equations the initial boundary value problem is formulated. Through the introduction of potentials a two-dimensional scalar formulation in terms of quasi-linear integro-differential equations of second order for a domain consisting of plasma and vacuum sub-domains is obtained. (Auth.)
Boundary Integral Solutions to Three-Dimensional Unconfined Darcy's Flow
Lennon, Gerard P.; Liu, Philip L.-F.; Liggett, James A.
1980-08-01
The boundary integral equation method (BIEM) is used to solve three-dimensional potential flow problems in porous media. The problems considered here are time dependent and have a nonlinear boundary condition on the free surface. The entire boundary, including the moving free surface, discretized into linear finite elements for the purpose of evaluating the boundary integrals. The technique allows transient, three-dimensional problems to be solved with reasonable computational costs. Numerical examples include recharge through rectangular and circular areas and seepage flow from a surface pond. The examples are used to illustrate the method and show the nonlinear effects.
Discrete holomorphicity and integrability in loop models with open boundaries
de Gier, Jan; Rasmussen, Jorgen
2012-01-01
We consider boundary conditions compatible with discrete holomorphicity for the dilute O(n) and C_2^(1) loop models. In each model, for a general set of boundary plaquettes, multiple types of loops can appear. A generalisation of Smirnov's parafermionic observable is therefore required in order to maintain the discrete holomorphicity property in the bulk. We show that there exist natural boundary conditions for this observable which are consistent with integrability, that is to say that, by imposing certain boundary conditions, we obtain a set of linear equations whose solutions also satisfy the corresponding reflection equation. In both loop models, several new sets of integrable weights are found using this approach.
Ivanyshyn Yaman, Olha; Le Louër, Frédérique
2016-09-01
This paper deals with the material derivative analysis of the boundary integral operators arising from the scattering theory of time-harmonic electromagnetic waves and its application to inverse problems. We present new results using the Piola transform of the boundary parametrisation to transport the integral operators on a fixed reference boundary. The transported integral operators are infinitely differentiable with respect to the parametrisations and simplified expressions of the material derivatives are obtained. Using these results, we extend a nonlinear integral equations approach developed for solving acoustic inverse obstacle scattering problems to electromagnetism. The inverse problem is formulated as a pair of nonlinear and ill-posed integral equations for the unknown boundary representing the boundary condition and the measurements, for which the iteratively regularized Gauss-Newton method can be applied. The algorithm has the interesting feature that it avoids the numerous numerical solution of boundary value problems at each iteration step. Numerical experiments are presented in the special case of star-shaped obstacles.
On the formulation of open boundary conditions at the mouth of a bay
Greatbatch, Richard J.; Otterson, Timm
1991-10-01
We describe our experience in formulating open boundary conditions to apply at the mouth of a reduced-gravity model of a bay. Our objective is to find a way to calculate the response of the bay to wind forcing over the bay itself, without being concerned about the influence of regions beyond. We show that open boundaries from which Kelvin waves can propagate along the coast into the model domain ("upstream" boundaries) must be treated with care. We begin by considering an "upstream" boundary which runs perpendicular to the coast. We find that if a radiation condition is applied on such a boundary, then spurious Kelvin waves of near-inertial period can propagate in from the boundary and contaminate the solution in the interior of the model domain. Also, if there is Ekman transport at the "upstream" boundary away from (toward) the coast, then upwelling (downwelling) will occur indefinitely and completely swamp the model solution in the bay. This is similar to the solution we expect when the coastline is straight and extends to infinity in the "upstream" direction. However, it is not the same, since the rate of upwelling (downwelling) is roughly half the theoretical value for that case. For the problem of a bay we suggest that the way to deal with this is to extend the coastline out to sea on the "upstream" side of the mouth and apply a condition on the artificial stretch of the boundary which suppresses Kelvin wave propagation but is also not prohibitively reflective to outgoing Poincaré waves. For our problem a condition of zero normal gradient in interface displacement seems to be sufficient. This condition also captures reasonably well the near-inertial Kelvin waves that are generated by the northwest corner of the bay (which are a genuine part of the solution) as long as the other boundaries are sufficiently far from the bay. We have also experimented with using sponge layers rather than radiation conditions on the other boundaries. We find that sponging only
Dault, Daniel Lawrence
The moment method is the predominant approach for the solution of electromagnetic boundary integral equations. Traditional moment method discretizations rely on the projection of solution currents onto basis sets that must satisfy strict continuity properties to model physical currents. The choice of basis sets is further restricted by the tight coupling of traditional functional descriptions to the underlying geometrical approximation of the scattering or radiating body. As a result, the choice of approximation function spaces and geometry discretizations for a given boundary integral equation is significantly limited. A quasi-meshless partition of unity based method called the Generalized Method of Moments (GMM) was recently introduced to overcome some of these limitations. The GMM partition of unity scheme affords automatic continuity of solution currents, and therefore permits the use of a much wider range of basis functions than traditional moment methods. However, prior to the work in this thesis, GMM was limited in practical applicability because it was only formulated for a few geometry types, could not be accurately applied to arbitrary scatterers, e.g. those with mixtures of geometrical features, and was not amenable to traditional acceleration methodologies that would permit its application to electrically large problems. The primary contribution of this thesis is to introduce several new GMM formulations that significantly expand the capabilities of the method to make it a practical, broadly applicable approach for solving boundary integral equations and overcoming the limitations inherent in traditional moment method discretizations. Additionally, several of the topics covered address continuing open problems in electromagnetic boundary integral equations with applicability beyond GMM. The work comprises five broad contributions. The first is a new GMM formulation capable of mixing both GMM-type basis sets and traditional basis sets in the same
Analytical Solution of Boundary Integral Equations for 2-D Steady Linear Wave Problems
Institute of Scientific and Technical Information of China (English)
J.M. Chuang
2005-01-01
Based on the Fourier transform, the analytical solution of boundary integral equations formulated for the complex velocity of a 2-D steady linear surface flow is derived. It has been found that before the radiation condition is imposed,free waves appear both far upstream and downstream. In order to cancel the free waves in far upstream regions, the eigensolution of a specific eigenvalue, which satisfies the homogeneous boundary integral equation, is found and superposed to the analytical solution. An example, a submerged vortex, is used to demonstrate the derived analytical solution. Furthermore,an analytical approach to imposing the radiation condition in the numerical solution of boundary integral equations for 2-D steady linear wave problems is proposed.
Boundary Integral Equations and A Posteriori Error Estimates
Institute of Scientific and Technical Information of China (English)
YU Dehao; ZHAO Longhua
2005-01-01
Adaptive methods have been rapidly developed and applied in many fields of scientific and engineering computing. Reliable and efficient a posteriori error estimates play key roles for both adaptive finite element and boundary element methods. The aim of this paper is to develop a posteriori error estimates for boundary element methods. The standard a posteriori error estimates for boundary element methods are obtained from the classical boundary integral equations. This paper presents hyper-singular a posteriori error estimates based on the hyper-singular integral equations. Three kinds of residuals are used as the estimates for boundary element errors. The theoretical analysis and numerical examples show that the hyper-singular residuals are good a posteriori error indicators in many adaptive boundary element computations.
Mitharwal, Rajendra
2015-01-01
This work presents a Boundary Element Method (BEM) formulation for contactless electromagnetic field assessments. The new scheme is based on a regularized BEM approach that requires the use of electric measurements only. The regularization is obtained by leveraging on an extension of Calderon techniques to rectangular systems leading to well-conditioned problems independent of the discretization density. This enables the use of highly discretized Huygens surfaces that can be consequently placed very near to the radiating source. In addition, the new regularized scheme is hybridized with both surfacic homogeneous and volumetric inhomogeneous forward BEM solvers accelerated with fast matrix-vector multiplication schemes. This allows for rapid and effective dosimetric assessments and permits the use of inhomogeneous and realistic head phantoms. Numerical results corroborate the theory and confirms the practical effectiveness of all newly proposed formulations.
Two-point boundary value and Cauchy formulations in an axisymmetrical MHD equilibrium problem
International Nuclear Information System (INIS)
In this paper we present two equilibrium solvers for axisymmetrical toroidal configurations, both based on the expansion in poloidal angle method. The first one has been conceived as a two-point boundary value solver in a system of coordinates with straight field lines, while the second one uses a well-conditioned Cauchy formulation of the problem in a general curvilinear coordinate system. In order to check the capability of our moment methods to describe equilibrium accurately, a comparison of the moment solutions with analytical solutions obtained for a Solov'ev equilibrium has been performed. (author)
Integrability of the Inozemtsev Spin Chain with Open Boundary Conditions
Institute of Scientific and Technical Information of China (English)
XUE Wei-Xing; WANG Yu-Peng
2004-01-01
@@ A long range interacting quantum spin chain with open boundary conditions is proposed. By constructing the reflection spin-Dunkl operators, the integrability of the model is proven. The model is therefore exactly solvable via the asymptotic Bethe ansatz method and falls into the universal class of the usual Heisenberg spin chain with boundary fields.
APPLICATION OF BOUNDARY INTEGRAL EQUATION METHOD FOR THERMOELASTICITY PROBLEMS
Vorona Yu.V.; Kara I.D.
2015-01-01
Boundary Integral Equation Method is used for solving analytically the problems of coupled thermoelastic spherical wave propagation. The resulting mathematical expressions coincide with the solutions obtained in a conventional manner.
APPLICATION OF BOUNDARY INTEGRAL EQUATION METHOD FOR THERMOELASTICITY PROBLEMS
Directory of Open Access Journals (Sweden)
Vorona Yu.V.
2015-12-01
Full Text Available Boundary Integral Equation Method is used for solving analytically the problems of coupled thermoelastic spherical wave propagation. The resulting mathematical expressions coincide with the solutions obtained in a conventional manner.
Gomez-Sousa, Hipolito; Martinez-Lorenzo, Jose Angel
2015-01-01
The electromagnetic behavior of plasmonic structures can be predicted after discretizing and solving a linear system of equations, derived from a continuous surface integral equation (SIE) and the appropriate boundary conditions, using a method of moments (MoM) methodology. In realistic large-scale optical problems, a direct inversion of the SIE-MoM matrix cannot be performed due to its large size, and an iterative solver must be used instead. This paper investigates the performance of four iterative solvers (GMRES, TFQMR, CGS, and BICGSTAB) for five different SIE-MoM formulations (PMCHWT, JMCFIE, CTF, CNF, and MNMF). Moreover, under this plasmonic context, a set of suggested guidelines are provided to choose a suitable SIE formulation and iterative solver depending on the desired simulation error and available runtime resources.
Numerical solution of multiple hole problem by using boundary integral equation
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
This paper studies a numerical solution of multiple hole problem by using a boundary integral equation.The studied problem can be considered as a supposition of many single hole problems.After considering the interaction among holes,an algebraic equation is formulated,which is then solved by using an iteration technique.The hoop stress around holes can be finally determined. One numerical example is provided to check its accuracy.
The functional integral formulation of the Schrieffer–Wolff transformation
Zamani, Farzaneh; Ribeiro, Pedro; Kirchner, Stefan
2016-06-01
We revisit the Schrieffer–Wolff transformation and present a path integral version of this important canonical transformation. The equivalence between the low-energy sector of the Anderson model in the so-called local moment regime and the spin-isotropic Kondo model is usually established via a canonical transformation performed on the Hamiltonian, followed by a projection. Here we present a path integral formulation of the Schrieffer–Wolff transformation which relates the functional integral form of the partition function of the Anderson model to that of its effective low-energy model. The resulting functional integral assumes the form of a spin path integral and includes a geometric phase factor, i.e. a Berry phase. Our approach stresses the underlying symmetries of the model and allows for a straightforward generalization of the transformation to more involved models. It thus not only sheds new light on a classic problem, it also offers a systematic route of obtaining effective low-energy models and higher order corrections. This is demonstrated by obtaining the effective low-energy model of a quantum dot attached to two ferromagnetic leads.
On approximation of nonlinear boundary integral equations for the combined method
Energy Technology Data Exchange (ETDEWEB)
Gregus, M.; Khoromsky, B.N.; Mazurkevich, G.E.; Zhidkov, E.P.
1989-09-22
The nonlinear boundary integral equations that arise in research of nonlinear magnetostatic problems are investigated in combined formulation on an unbounded domain. Approximations of the derived operator equations are studied based on the Galerkin method. The investigated boundary operators are strongly monotone, Lipschitz-continuous, potential and have a symmetrical Gateaux derivative. The error estimates of the Galerkin's approximation in Sobolev spaces of fractional powers are obtained using the above-mentioned properties of the operators, too. The problem has been studied on surfaces in two and three-dimensional spaces. We answer also some questions on convergence connected with the discretized systems of equations. 21 refs.
Formulation of fields in terms of path-integrals
Vatsya, S R
2014-01-01
Path-integral formulation of quantum mechanics defines the amplitude, or wavefunction, as a sum of the phase-factors over trajectories in a base manifold, which is taken here to be a general Riemannian space with trajectories parameterized by their arclengths. Generalized Klein-Gordon equation, deducible from the path-integral representation, provides the quantum mechanical description of a particle. Phase-factors are periodic functions of the classical action. Periodicity of the phase-factors with respect to action is shown in this article to impart corresponding periodicity to one parameter family of amplitudes generated by the translations of arclength. The translation parameter is also identified with arclength that can be adjoined to the base space to obtain an extended manifold, which is endowed with a Riemannian structure induced in it by trajectories in the base. Further, periodicity of the family of amplitudes with respect to the translation parameter together with the solutions of the Klein-Gordon e...
Hu, Fang Q.; Pizzo, Michelle E.; Nark, Douglas M.
2016-01-01
Based on the time domain boundary integral equation formulation of the linear convective wave equation, a computational tool dubbed Time Domain Fast Acoustic Scattering Toolkit (TD-FAST) has recently been under development. The time domain approach has a distinct advantage that the solutions at all frequencies are obtained in a single computation. In this paper, the formulation of the integral equation, as well as its stabilization by the Burton-Miller type reformulation, is extended to cases of a constant mean flow in an arbitrary direction. In addition, a "Source Surface" is also introduced in the formulation that can be employed to encapsulate regions of noise sources and to facilitate coupling with CFD simulations. This is particularly useful for applications where the noise sources are not easily described by analytical source terms. Numerical examples are presented to assess the accuracy of the formulation, including a computation of noise shielding by a thin barrier motivated by recent Historical Baseline F31A31 open rotor noise shielding experiments. Furthermore, spatial resolution requirements of the time domain boundary element method are also assessed using point per wavelength metrics. It is found that, using only constant basis functions and high-order quadrature for surface integration, relative errors of less than 2% may be obtained when the surface spatial resolution is 5 points-per-wavelength (PPW) or 25 points-per-wavelength squared (PPW2).
A simple boundary element formulation for shape optimization of 2D continuous structures
International Nuclear Information System (INIS)
For the design of nuclear equipment like pressure vessels, steam generators, and pipelines, among others, it is very important to optimize the shape of the structural systems to withstand prescribed loads such as internal pressures and prescribed or limiting referential values such as stress or strain. In the literature, shape optimization of frame structural systems is commonly found but the same is not true for continuous structural systems. In this work, the Boundary Element Method (BEM) is applied to simple problems of shape optimization of 2D continuous structural systems. The proposed formulation is based on the BEM and on deterministic optimization methods of zero and first order such as Powell's, Conjugate Gradient, and BFGS methods. Optimal characterization for the geometric configuration of 2D structure is obtained with the minimization of an objective function. Such function is written in terms of referential values (such as loads, stresses, strains or deformations) prescribed at few points inside or at the boundary of the structure. The use of the BEM for shape optimization of continuous structures is attractive compared to other methods that discretized the whole continuous. Several numerical examples of the application of the proposed formulation to simple engineering problems are presented. (authors)
On the Implementation of 3D Galerkin Boundary Integral Equations
Energy Technology Data Exchange (ETDEWEB)
Nintcheu Fata, Sylvain [ORNL; Gray, Leonard J [ORNL
2010-01-01
In this article, a reverse contribution technique is proposed to accelerate the construction of the dense influence matrices associated with a Galerkin approximation of singular and hypersingular boundary integral equations of mixed-type in potential theory. In addition, a general-purpose sparse preconditioner for boundary element methods has also been developed to successfully deal with ill-conditioned linear systems arising from the discretization of mixed boundary-value problems on non-smooth surfaces. The proposed preconditioner, which originates from the precorrected-FFT method, is sparse, easy to generate and apply in a Krylov subspace iterative solution of discretized boundary integral equations. Moreover, an approximate inverse of the preconditioner is implicitly built by employing an incomplete LU factorization. Numerical experiments involving mixed boundary-value problems for the Laplace equation are included to illustrate the performance and validity of the proposed techniques.
Calculation of Turbulent Boundary Layers Using the Dissipation Integral Method
Institute of Scientific and Technical Information of China (English)
MatthiasBuschmann
1999-01-01
This paper gives an introduction into the dissipation integral method.The general integral equations for the three-dimensional case are derved.It is found that for a practical calculation algorithm the integral monentum equation and the integral energy equation are msot useful.Using Two different sets of mean velocity profiles the hyperbolical character of a dissipation integral method is shown.Test cases for two-and three-dimensional boundary layers are analysed and discussed.The paper concludes with a discussion of the advantages and limits of dissipation integral methods.
Explicit Expressions for 3D Boundary Integrals in Potential Theory
Energy Technology Data Exchange (ETDEWEB)
Nintcheu Fata, Sylvain [ORNL
2009-01-01
On employing isoparametric, piecewise linear shape functions over a flat triangular domain, exact expressions are derived for all surface potentials involved in the numerical solution of three-dimensional singular and hyper-singular boundary integral equations of potential theory. These formulae, which are valid for an arbitrary source point in space, are represented as analytic expressions over the edges of the integration triangle. They can be used to solve integral equations defined on polygonal boundaries via the collocation method or may be utilized as analytic expressions for the inner integrals in the Galerkin technique. Also, the constant element approximation can be directly obtained with no extra effort. Sample problems solved by the collocation boundary element method for the Laplace equation are included to validate the proposed formulae.
Diffraction of Elastic Waves in Fluid-Layered Solid Interfaces by an Integral Formulation
Directory of Open Access Journals (Sweden)
J. E. Basaldúa-Sánchez
2013-01-01
Full Text Available In the present communication, scattering of elastic waves in fluid-layered solid interfaces is studied. The indirect boundary element method is used to deal with this wave propagation phenomenon in 2D fluid-layered solid models. The source is represented by Hankel’s function of second kind and this is always applied in the fluid. Our method is an approximate boundary integral technique which is based upon an integral representation for scattered elastic waves using single-layer boundary sources. This approach is typically called indirect because the sources’ strengths are calculated as an intermediate step. In addition, this formulation is regarded as a realization of Huygens’ principle. The results are presented in frequency and time domains. Various aspects related to the different wave types that emerge from this kind of problems are emphasized. A near interface pulse generates changes in the pressure field and can be registered by receivers located in the fluid. In order to show the accuracy of our method, we validated the results with those obtained by the discrete wave number applied to a fluid-solid interface joining two half-spaces, one fluid and the other an elastic solid.
Cai, Jian; Roy, Somesh; Modest, Michael F.
2016-10-01
In simulations of periodic or symmetric geometries, computational domains are reduced by imaginary boundaries that exploit the symmetry conditions. Two boundary conditions are proposed for Discrete Ordinate Methods to solve axisymmetric radiation problems. Firstly, a specularly reflective boundary condition similar to that is used in Photon Monte Carlo methods is developed for Discrete Ordinate Methods. Secondly, the rotational invariant formulation is revisited for axisymmetric wedge geometries. Correspondingly, a new rotationally invariant boundary condition specially designed for axisymmetric problems on wedge shape is proposed to enforce the rotational invariance properties possessed by the radiative transfer equation (RTE) but violated by three-dimensional conventional Discrete Ordinate Methods. Both boundary conditions have the advantage that the discretization and linear equation solution procedures of conventional three-dimensional DOM are not affected by changing to a reduced geometry. Consistency, accuracy and efficiency of the new boundary conditions are demonstrated by multiple numerical examples involving periodic symmetry and axisymmetry. A comparison between specularly reflective boundary conditions and the rotationally invariant formulation shows that the latter offers several advantages for wedge geometries. In other symmetry conditions, when the rotational invariant formulation is not applicable, specular reflective boundary conditions are still effective.
Boundary integral solution of potential problems arising in the modelling of electrified oil films
Chappell, David J
2014-01-01
We consider a class of potential problems on a periodic half-space for the modelling of electrified oil films, which are used in the development of novel switchable liquid optical devices (diffraction gratings). A boundary integral formulation which reduces the problem to the study of the oil-air interface alone is derived and solved in a highly efficient manner using the Nystr\\"{o}m method. The oil films encountered experimentally are typically very thin and thus an interface-only integral representation is important for avoiding the near-singularity problems associated with boundary integral methods for long slender domains. The super-algebraic convergence of the proposed methods is discussed and demonstrated via appropriate numerical experiments.
NOVEL REGULARIZED BOUNDARY INTEGRAL EQUATIONS FOR POTENTIAL PLANE PROBLEMS
Institute of Scientific and Technical Information of China (English)
ZHANG Yao-ming; L(U) He-xiang; WANG Li-min
2006-01-01
The universal practices have been centralizing on the research of regularization to the direct boundary integal equations (DBIEs). The character is elimination of singularities by using the simple solutions. However, up to now the research of regularization to the first kind integral equations for plane potential problems has never been found in previous literatures. The presentation is mainly devoted to the research on the regularization of the singular boundaryintegral equations with indirect unknowns. A novel view and idea is presented herein, in which the regularized boundary integral equations with indirect unknowns without including the Cauchy principal value (CPV) and Hadamard-finite-part (HFP) integrals are established for the plane potential problems.With some numerical results, it is shown that the better accuracy and higher efficiency,especially on the boundary, can be achieved by the present system.
Spatial integration of boundaries in a 3D virtual environment.
Bouchekioua, Youcef; Miller, Holly C; Craddock, Paul; Blaisdell, Aaron P; Molet, Mikael
2013-10-01
Prior research, using two- and three-dimensional environments, has found that when both human and nonhuman animals independently acquire two associations between landmarks with a common landmark (e.g., LM1-LM2 and LM2-LM3), each with its own spatial relationship, they behave as if the two unique LMs have a known spatial relationship despite their never having been paired. Seemingly, they have integrated the two associations to create a third association with its own spatial relationship (LM1-LM3). Using sensory preconditioning (Experiment 1) and second-order conditioning (Experiment 2) procedures, we found that human participants integrated information about the boundaries of pathways to locate a goal within a three-dimensional virtual environment in the absence of any relevant landmarks. Spatial integration depended on the participant experiencing a common boundary feature with which to link the pathways. These results suggest that the principles of associative learning also apply to the boundaries of an environment.
A GPU-accelerated Direct-sum Boundary Integral Poisson-Boltzmann Solver
Geng, Weihua
2013-01-01
In this paper, we present a GPU-accelerated direct-sum boundary integral method to solve the linear Poisson-Boltzmann (PB) equation. In our method, a well-posed boundary integral formulation is used to ensure the fast convergence of Krylov subspace based linear algebraic solver such as the GMRES. The molecular surfaces are discretized with flat triangles and centroid collocation. To speed up our method, we take advantage of the parallel nature of the boundary integral formulation and parallelize the schemes within CUDA shared memory architecture on GPU. The schemes use only $11N+6N_c$ size-of-double device memory for a biomolecule with $N$ triangular surface elements and $N_c$ partial charges. Numerical tests of these schemes show well-maintained accuracy and fast convergence. The GPU implementation using one GPU card (Nvidia Tesla M2070) achieves 120-150X speed-up to the implementation using one CPU (Intel L5640 2.27GHz). With our approach, solving PB equations on well-discretized molecular surfaces with up ...
The integrated Earth System Model Version 1: formulation and functionality
Energy Technology Data Exchange (ETDEWEB)
Collins, William D.; Craig, Anthony P.; Truesdale, John E.; Di Vittorio, Alan; Jones, Andrew D.; Bond-Lamberty, Benjamin; Calvin, Katherine V.; Edmonds, James A.; Kim, Son H.; Thomson, Allison M.; Patel, Pralit L.; Zhou, Yuyu; Mao, Jiafu; Shi, Xiaoying; Thornton, Peter E.; Chini, Louise M.; Hurtt, George C.
2015-07-23
The integrated Earth System Model (iESM) has been developed as a new tool for pro- jecting the joint human/climate system. The iESM is based upon coupling an Integrated Assessment Model (IAM) and an Earth System Model (ESM) into a common modeling in- frastructure. IAMs are the primary tool for describing the human–Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species, land use and land cover change, and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. The iESM project integrates the economic and human dimension modeling of an IAM and a fully coupled ESM within a sin- gle simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore- omitted feedbacks between natural and societal drivers, we can improve scientific under- standing of the human–Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper de- scribes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
Advanced applications of boundary-integral equation methods
International Nuclear Information System (INIS)
The BIE (boundary integral equation) method is based on the numerical solution of a set of integral constraint equations which couple boundary tractions (stresses) to boundary displacements. Thus the dimensionality of the problem is reduced by one; only boundary geometry and data are discretized. Stresses at any set of selected interior points are computed following the boundary solution without any further numerical approximations. Thus, the BIE method has inherently greater resolution capability for stress gradients than does the finite element method. Conversely, the BIE method is not efficient for problems involving significant inhomogeneity such as in multi-thin-layered materials, or in elastoplasticity. Some progress in applyiing the BIE method to the latter problem has been made but much more work remains. Further, the BIE method is only optional for problems with significant stress risers, and only when boundary stresses are most important. Interior stress calculations are expensive, per point, and can drive the solution costs up rapidly. The current report summarizes some of the advanced elastic applications of fracture mechanics and three-dimensional stress analysis, while referencing some of the much broader developmental effort. Future emphasis is needed to exploit the BIE method in conjunction with other techniques such as the finite element method through the creation of hybrid stress analysis methods
Advanced applications of boundary-integral equation methods
International Nuclear Information System (INIS)
Numerical analysis has become the basic tool for both design and research problems in solid mechanics. The boundary-integral equation (BIE) method is based on classical mathematical techniques but is finding new life as a basic stress analysis tool for engineering applications. The BIE method is based on the numerical solution of a set of integral constraint equations which couple boundary tractions (stresses) to boundary displacements. Thus the dimensionality of the problem is reduced by one; only boundary geometry and data are discretized. Stresses at any set of selected interior points are computed following the boundary solution without any further numerical approximations. Thus, the BIE method has inherently greater resolution capability for stress gradients than does the finite element method. Conversely, the BIE method is not efficient for problems involving significant inhomogeneity such as in multi-thin-layered materials, or in elastoplasticity. Some progress in applying the BIE method to the latter problem has been made but much more work remains. Further, the BIE method is only optional for problems with significant stress risers, and only when boundary stresses are more important. Interior stress calculations are expensive, per point, and can drive the solution costs up rapidly. The current report summarizes some of the advanced elastic applications of fracture mechanics and three-dimensional stress analysis, while referring some of the much broader developmental effort. (Auth.)
Analytical Nonlocal Electrostatics Using Eigenfunction Expansions of Boundary-Integral Operators
Bardhan, Jaydeep P; Brune, Peter R
2012-01-01
In this paper, we present an analytical solution to nonlocal continuum electrostatics for an arbitrary charge distribution in a spherical solute. Our approach relies on two key steps: (1) re-formulating the PDE problem using boundary-integral equations, and (2) diagonalizing the boundary-integral operators using the fact their eigenfunctions are the surface spherical harmonics. To introduce this uncommon approach for analytical calculations in separable geometries, we rederive Kirkwood's classic results for a protein surrounded concentrically by a pure-water ion-exclusion layer and then a dilute electrolyte (modeled with the linearized Poisson--Boltzmann equation). Our main result, however, is an analytical method for calculating the reaction potential in a protein embedded in a nonlocal-dielectric solvent, the Lorentz model studied by Dogonadze and Kornyshev. The analytical method enables biophysicists to study the new nonlocal theory in a simple, computationally fast way; an open-source MATLAB implementatio...
Study of flow and mass transport in multilayered aquifers using boundary integral method
Energy Technology Data Exchange (ETDEWEB)
Zakikhani, M.
1988-01-01
In recent years, the boundary integral element method (BIEM) has been widely used in the area of ground-water modeling. This method, based on Green's theorem, has a variety of advantages over domain methods. Earlier applications of the BIEM to multilayer aquifer problems were restricted to steady-state flows. In these applications, layered aquifer systems were solved iteratively using the Bessel function as the principal Green function. In this formulation, the argument of the Bessel function is a function of hydraulic properties of the aquifer-aquitard system. Such an approach reduces the efficiency of the computations and yields less accurate numerical results. In the study presented here, a non-iterative boundary integral equation formulation (NIBIEM) for multilayer aquifer systems with or without a well network is developed. In this procedure, the coefficients of the singular points associated with pumping or recharge wells are included in the analysis in an analytic sense. This improves the efficiency and the accuracy of the computation. The formulation presented is developed for three different phases of flow.
Optimal control problems for impulsive systems with integral boundary conditions
Directory of Open Access Journals (Sweden)
Allaberen Ashyralyev
2013-03-01
Full Text Available In this article, the optimal control problem is considered when the state of the system is described by the impulsive differential equations with integral boundary conditions. Applying the Banach contraction principle the existence and uniqueness of the solution is proved for the corresponding boundary problem by the fixed admissible control. The first and second variation of the functional is calculated. Various necessary conditions of optimality of the first and second order are obtained by the help of the variation of the controls.
An integrated approach to marketing strategy formulation and implementation
Akroush, Mamoun Nadim Awwad
2003-01-01
The overall aim of the thesis was to address the issues involved in marketing strategy formulation, implementation and company performance by developing a framework for the marketing of insurance services in Jordan. In order to achieve this aim the research developed a comprehensive framework involving three parts; marketing strategy formulation components, marketing strategy implementation, and company performance. The research population included all the insurance companies t...
Free boson formulation of boundary states in W_3 minimal models and the critical Potts model
Caldeira, A F; Wheater, J F; Caldeira, Alexandre F.; Kawai, Shinsuke; Wheater, John F.
2003-01-01
We develop a Coulomb gas formalism for boundary conformal field theory having a $W$ symmetry and illustrate its operation using the three state Potts model. We find that there are free-field representations for six $W$ conserving boundary states, which yield the fixed and mixed physical boundary conditions, and two $W$ violating boundary states which yield the free and new boundary conditions. Other $W$ violating boundary states can be constructed but they decouple from the rest of the theory. Thus we have a complete free-field realization of the known boundary states of the three state Potts model. We then use the formalism to calculate boundary correlation functions in various cases. We find that the conformal blocks arising when the two point function of $\\phi_{2,3}$ is calculated in the presence of free and new boundary conditions are indeed the last two solutions of the sixth order differential equation generated by the singular vector.
Surface integrals approach to solution of some free boundary problems
Directory of Open Access Journals (Sweden)
Igor Malyshev
1988-01-01
Full Text Available Inverse problems in which it is required to determine the coefficients of an equation belong to the important class of ill-posed problems. Among these, of increasing significance, are problems with free boundaries. They can be found in a wide range of disciplines including medicine, materials engineering, control theory, etc. We apply the integral equations techniques, typical for parabolic inverse problems, to the solution of a generalized Stefan problem. The regularization of the corresponding system of nonlinear integral Volterra equations, as well as local existence, uniqueness, continuation of its solution, and several numerical experiments are discussed.
Leise, Tanya L.
2009-08-19
We consider the problem of the dynamic, transient propagation of a semi-infinite, mode I crack in an infinite elastic body with a nonlinear, viscoelastic cohesize zone. Our problem formulation includes boundary conditions that preclude crack face interpenetration, in contrast to the usual mode I boundary conditions that assume all unloaded crack faces are stress-free. The nonlinear viscoelastic cohesive zone behavior is motivated by dynamic fracture in brittle polymers in which crack propagation is preceeded by significant crazing in a thin region surrounding the crack tip. We present a combined analytical/numerical solution method that involves reducing the problem to a Dirichlet-to-Neumann map along the crack face plane, resulting in a differo-integral equation relating the displacement and stress along the crack faces and within the cohesive zone. © 2009 Springer Science+Business Media B.V.
International Nuclear Information System (INIS)
Highlights: •Dispersive properties of viscoelastic waveguides and cavities are computed using a regularized 2.5D BEM. •Linear viscoelasticity is introduced at the constitutive level by means of frequency dependent complex moduli. •A contour integral algorithm is used to solve the nonlinear eigenvalue problem. •The Sommerfeld radiation condition is used to select the permissible Riemann sheets. •Attenuation of surface waves in cavities approaches the attenuation of Rayleigh waves. -- Abstract: A regularized 2.5D boundary element method (BEM) is proposed to predict the dispersion properties of damped stress guided waves in waveguides and cavities of arbitrary cross-section. The wave attenuation, induced by material damping, is introduced using linear viscoelastic constitutive relations and described in a spatial manner by the imaginary component of the axial wavenumber. The discretized dispersive wave equation results in a nonlinear eigenvalue problem, which is solved obtaining complex axial wavenumbers for a fixed frequency using a contour integral algorithm. Due to the singular characteristics and the multivalued feature of the wave equation, the requirement of holomorphicity inside the contour region over the complex wavenumber plane is fulfilled by the introduction of the Sommerfeld branch cuts and by the choice of the permissible Riemann sheets. A post processing analysis is developed for the extraction of the energy velocity of propagative guided waves. The reliability of the method is demonstrated by comparing the results obtained for a rail and a bar with square cross-section with those obtained from a 2.5D Finite Element formulation also known in literature as Semi Analytical Finite Element (SAFE) method. Next, to show the potential of the proposed numerical framework, dispersion properties are predicted for surface waves propagating along cylindrical cavities of arbitrary cross-section. It is demonstrated that the attenuation of surface waves
Institute of Scientific and Technical Information of China (English)
Zhigang WANG; Yachun LI
2012-01-01
The authors are concerned with a zero-flux type initial boundary value problem for scalar conservation laws.Firstly,a kinetic formulation of entropy solutions is established.Secondly,by using the kinetic formulation and kinetic techniques,the uniqueness of entropy solutions is obtained.Finally,the parabolic approximation is studied and an error estimate of order η1/3 between the entropy solution and the viscous approximate solutions is established by using kinetic techniques,where ris the size of artificial viscosity.
Farhat, Charbel; Lakshminarayan, Vinod K.
2014-04-01
Embedded Boundary Methods (EBMs) for Computational Fluid Dynamics (CFD) are usually constructed in the Eulerian setting. They are particularly attractive for complex Fluid-Structure Interaction (FSI) problems characterized by large structural motions and deformations. They are also critical for flow problems with topological changes and FSI problems with cracking. For all of these problems, the alternative Arbitrary Lagrangian-Eulerian (ALE) methods are often unfeasible because of the issue of mesh crossovers. However for viscous flows, Eulerian EBMs for CFD do not track the boundary layers around dynamic rigid or flexible bodies. Consequently, the application of these methods to viscous FSI problems requires either a high mesh resolution in a large part of the computational fluid domain, or adaptive mesh refinement. Unfortunately, the first option is computationally inefficient, and the second one is labor intensive. For these reasons, an alternative approach is proposed in this paper for maintaining all moving boundary layers resolved during the simulation of a turbulent FSI problem using an EBM for CFD. In this approach, which is simple and computationally reasonable, the underlying non-body-fitted mesh is rigidly translated and/or rotated in order to track the rigid component of the motion of the dynamic obstacle. Then, the flow computations away from the embedded surface are performed using the ALE framework, and the wall boundary conditions are treated by the chosen Eulerian EBM for CFD. Hence, the solution of the boundary layer tracking problem proposed in this paper can be described as an ALE implementation of a given EBM for CFD. Its basic features are illustrated with the Large Eddy Simulation using a non-body-fitted mesh of a turbulent flow past an airfoil in heaving motion. Its strong potential for the solution of challenging FSI problems at reasonable computational costs is also demonstrated with the simulation of turbulent flows past a family of
Integrated care in the daily work: coordination beyond organisational boundaries
Directory of Open Access Journals (Sweden)
Alexandra Petrakou
2009-07-01
Full Text Available Objectives: In this paper, integrated care in an inter-organisational cooperative setting of in-home elderly care is studied. The aim is to explore how home care workers coordinate their daily work, identify coordination issues in situ and discuss possible actions for supporting seamless and integrated elderly care at home. Method: The empirical findings are drawn from an ethnographic workplace study of the cooperation and coordination taking place between home care workers in a Swedish county. Data were collected through observational studies, interviews and group discussions. Findings: The paper identifies a need to support two core issues. Firstly, it must be made clear how the care interventions that are currently defined as ‘self-treatment’ by the home health care should be divided. Secondly, the distributed and asynchronous coordination between all care workers involved, regardless of organisational belonging must be better supported. Conclusion: Integrated care needs to be developed between organisations as well as within each organisation. As a matter of fact, integrated care needs to be built up beyond organisational boundaries. Organisational boundaries affect the planning of the division of care interventions, but not the coordination during the home care process. During the home care process, the main challenge is the coordination difficulties that arise from the fact that workers are distributed in time and/or space, regardless of organisational belonging. A core subject for future practice and research is to develop IT tools that reach beyond formal organisational boundaries and processes while remaining adaptable in view of future structure changes.
Energy Technology Data Exchange (ETDEWEB)
Pereira, Luis Carlos Martins
1998-06-15
New Petrov-Galerkin formulations on the finite element methods for convection-diffusion problems with boundary layers are presented. Such formulations are based on a consistent new theory on discontinuous finite element methods. Existence and uniqueness of solutions for these problems in the new finite element spaces are demonstrated. Some numerical experiments shows how the new formulation operate and also their efficacy. (author)
An Integrated Methodology for Emulsified Formulated Product Design
DEFF Research Database (Denmark)
Mattei, Michele
The consumer oriented chemical based products are used every day by millions of people. They are structured products constituted of numerous chemicals, and many of them, especially household and personal care products, are emulsions where active ingredients, solvents, additives and surfactants...... consists of three stages: the problem definition stage, the model - based design stage, and the experiment - based verification stage. In the probl em definition stage, the consumer needs are trans- lated into a set of target thermo - physical properties and into a list of categories of ingre- dients...... formulation are measured by means of tailor - made exp eriments. The formulation is then validated or, if necessary, re- fined thanks to a systematic list of action. The problem definition stage relies on a robust knowledge base, which needs to system- atically generate quantitative, useful input information...
Revisit boundary conditions for the self-adjoint angular flux formulation
Energy Technology Data Exchange (ETDEWEB)
Wang, Yaqi [Idaho National Lab. (INL), Idaho Falls, ID (United States); Gleicher, Frederick N. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-03-01
We revisit the boundary conditions for SAAF. We derived the equivalent parity variational form ready for coding up. The more rigorous approach of evaluating odd parity should be solving the odd parity equation coupled with the even parity. We proposed a symmetric reflecting boundary condition although neither positive definiteness nor even-odd decoupling is achieved. A simple numerical test verifies the validity of these boundary conditions.
Tokamak plasma shape identification based on the boundary integral equations
International Nuclear Information System (INIS)
A necessary condition for tokamak plasma shape identification is discussed and a new identification method is proposed in this article. This method is based on the boundary integral equations governing a vacuum region around a plasma with only the measurement of either magnetic fluxes or magnetic flux intensities. It can identify various plasmas with low to high ellipticities with the precision determined by the number of the magnetic sensors. This method is applicable to real-time control and visualization using a 'table-look-up' procedure. (author)
A boundary integral formalism for stochastic ray tracing in billiards
Chappell, David J
2014-01-01
Determining the flow of rays or particles driven by a force or velocity field is fundamental to modelling many physical processes, including weather forecasting and the simulation of molecular dynamics. High frequency wave energy distributions can also be approximated using flow or transport equations. Applications arise in underwater and room acoustics, vibro-acoustics, seismology, electromagnetics, quantum mechanics and in producing computer generated imagery. In many practical applications, the driving field is not known exactly and the dynamics are determined only up to a degree of uncertainty. This paper presents a boundary integral framework for propagating flows including uncertainties, which is shown to systematically interpolate between a deterministic and a completely random description of the trajectory propagation. A simple but efficient discretisation approach is applied to model uncertain billiard dynamics in an integrable rectangular domain.
A boundary integral formalism for stochastic ray tracing in billiards
Energy Technology Data Exchange (ETDEWEB)
Chappell, David J. [School of Science and Technology, Nottingham Trent University, Clifton Campus, Nottingham NG11 8NS (United Kingdom); Tanner, Gregor [School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
2014-12-15
Determining the flow of rays or non-interacting particles driven by a force or velocity field is fundamental to modelling many physical processes. These include particle flows arising in fluid mechanics and ray flows arising in the geometrical optics limit of linear wave equations. In many practical applications, the driving field is not known exactly and the dynamics are determined only up to a degree of uncertainty. This paper presents a boundary integral framework for propagating flows including uncertainties, which is shown to systematically interpolate between a deterministic and a completely random description of the trajectory propagation. A simple but efficient discretisation approach is applied to model uncertain billiard dynamics in an integrable rectangular domain.
A hybrid formulation to suppress the numerical oscillations caused by immersed moving boundaries
Luo, Haoxiang; Dai, Hu; Ferreira de Sousa, Paulo
2009-11-01
A family of immersed-boundary methods, based on the sharp-interface representation of the boundary and local interpolation/extrapolation, has been recently developed to handle complex and moving boundary problems encountered in biological flows. Implemented typically on structured meshes, these methods save the computational cost of grid generation and take advantage of efficient computations on structured grids. However, since some of the nodes near the immersed boundary do not have the regular finite-difference stencil available for discretizing the Navier-Stokes equation, a local interpolation or extrapolation scheme is often used to reconstruct the flow field around the nodes. The drawback of this approach is that when a non-stationary boundary moves across the mesh points, the change of the stencil for the solution reconstruction causes artificial oscillations in the pressure. To suppress the oscillations, we have introduced a set of hybrid nodes on which both the Navier-Stokes solution and flow reconstruction are sought, and they are weighted according to the distance to the immersed boundary. The method has been implemented in both two- and three-dimensional solvers to handle a class of biological locomotion problems including flow-structure interaction. The accuracy and capability of the solvers will be demonstrated.
Integrability + Supersymmetry + Boundary: Life on the edge is not so dull after all!
Nepomechie, R I
2004-01-01
After a brief review of integrability, first in the absence and then in the presence of a boundary, I outline the construction of actions for the N=1 and N=2 boundary sine-Gordon models. The key point is to introduce Fermionic boundary degrees of freedom in the boundary actions.
Intrinsic Formulation of Geometric Integrability and Generation of Conservation Laws
Bracken, Paul
2007-01-01
An intrinsic version of the integrability theorem for the classical Backlund theorem is presented. It is characterized by a one-form which can be put in the form of a Riccati system. It is shown how this system can be linearized. Based on this, a procedure for generating an infinite number of conservation laws is given.
Advanced applications of boundary-integral equation methods
International Nuclear Information System (INIS)
Numerical analysis has become the basic tool for both design and research problems in solid mechanics. The need for accuracy and detail, plus the availablity of the high speed computer has led to the development of many new modeling methods ranging from general purpose structural analysis finite element programs to special purpose research programs. The boundary-integral equation (BIE) method is based on classical mathematical techniques but is finding new life as a basic stress analysis tool for engineering applications. The paper summarizes some advanced elastic applications of fracture mechanics and three-dimensional stress analysis, while referencing some of the much broader developmental effort. Future emphasis is needed to exploit the BIE method in conjunction with other techniques such as the finite element method through the creation of hybrid stress analysis methods. (Auth.)
DEFF Research Database (Denmark)
Keck, Rolf-Erik; Veldkamp, Dick; Wedel-Heinen, Jens Jakob;
This thesis describes the further development and validation of the dynamic meandering wake model for simulating the flow field and power production of wind farms operating in the atmospheric boundary layer (ABL). The overall objective of the conducted research is to improve the modelling...... by an actuator line model. As a consequence, part of the research also targets the performance of the actuator line model when generating wind turbine wakes in the atmospheric boundary layer. Highlights of the conducted research: 1. A description is given for using the dynamic wake meandering model....... 2. The EllipSys3D actuator line model, including the synthetic methods used to model atmospheric boundary layer shear and turbulence, is verified for modelling the evolution of wind turbine wake turbulence by comparison to field data and wind tunnel experiments. 3. A two-dimensional eddy viscosity...
Pun, Kit Fai
2003-01-01
Performance measurement quantifies the efficiency and effectiveness of action that helps organisations translate their strategies into results and fixes accountability to improve performance. This research identifies two problem statements: First, can integrating strategy formulation with measurement initiatives safeguard the performance goals in manufacturing enterprises? And second, how can manufacturing enterprises derive an integrated approach that meet their requirements and needs for ...
A coupled finite-element, boundary-integral method for simulating ultrasonic flowmeters.
Bezdĕk, Michal; Landes, Hermann; Rieder, Alfred; Lerch, Reinhard
2007-03-01
Today's most popular technology of ultrasonic flow measurement is based on the transit-time principle. In this paper, a numerical simulation technique applicable to the analysis of transit-time flowmeters is presented. A flowmeter represents a large simulation problem that also requires computation of acoustic fields in moving media. For this purpose, a novel boundary integral method, the Helmholtz integral-ray tracing method (HIRM), is derived and validated. HIRM is applicable to acoustic radiation problems in arbitrary mean flows at low Mach numbers and significantly reduces the memory demands in comparison with the finite-element method (FEM). It relies on an approximate free-space Green's function which makes use of the ray tracing technique. For simulation of practical acoustic devices, a hybrid simulation scheme consisting of FEM and HIRM is proposed. The coupling of FEM and HIRM is facilitated by means of absorbing boundaries in combination with a new, reflection-free, acoustic-source formulation. Using the coupled FEM-HIRM scheme, a full three-dimensional (3-D) simulation of a complete transit-time flowmeter is performed for the first time. The obtained simulation results are in good agreement with measurements both at zero flow and under flow conditions. PMID:17375833
Influence of the plasma boundary on the line-integrated emissivity
International Nuclear Information System (INIS)
In tokamak plasma radiation diagnostics, if the width of a detected plasma chord is comparable with the plasma minor radius, the plasma boundary may influence the line-integrated emissivity considerably and make it a weighted integral of the width-averaged emissivity. The explicit formula for the line-integrated emissivity with taking into account the plasma boundary effect is presented
Radiolysis Model Formulation for Integration with the Mixed Potential Model
Energy Technology Data Exchange (ETDEWEB)
Buck, Edgar C.; Wittman, Richard S.
2014-07-10
The U.S. Department of Energy Office of Nuclear Energy (DOE-NE), Office of Fuel Cycle Technology has established the Used Fuel Disposition Campaign (UFDC) to conduct the research and development activities related to storage, transportation, and disposal of used nuclear fuel (UNF) and high-level radioactive waste. Within the UFDC, the components for a general system model of the degradation and subsequent transport of UNF is being developed to analyze the performance of disposal options [Sassani et al., 2012]. Two model components of the near-field part of the problem are the ANL Mixed Potential Model and the PNNL Radiolysis Model. This report is in response to the desire to integrate the two models as outlined in [Buck, E.C, J.L. Jerden, W.L. Ebert, R.S. Wittman, (2013) “Coupling the Mixed Potential and Radiolysis Models for Used Fuel Degradation,” FCRD-UFD-2013-000290, M3FT-PN0806058
Boundary conditions and the generalized metric formulation of the double sigma model
Ma, Chen-Te
2015-09-01
Double sigma model with strong constraints is equivalent to the ordinary sigma model by imposing a self-duality relation. The gauge symmetries are the diffeomorphism and one-form gauge transformation with the strong constraints. We consider boundary conditions in the double sigma model from three ways. The first way is to modify the Dirichlet and Neumann boundary conditions with a fully O (D, D) description from double gauge fields. We perform the one-loop β function for the constant background fields to find low-energy effective theory without using the strong constraints. The low-energy theory can also have O (D, D) invariance as the double sigma model. The second way is to construct different boundary conditions from the projectors. The third way is to combine the antisymmetric background field with field strength to redefine an O (D, D) generalized metric. We use this generalized metric to reconstruct a consistent double sigma model with the classical and quantum equivalence.
Directory of Open Access Journals (Sweden)
Nahed S. Hussein
2014-01-01
Full Text Available A numerical boundary integral scheme is proposed for the solution to the system of eld equations of plane. The stresses are prescribed on one-half of the circle, while the displacements are given. The considered problem with mixed boundary conditions in the circle is replaced by two problems with homogeneous boundary conditions, one of each type, having a common solution. The equations are reduced to a system of boundary integral equations, which is then discretized in the usual way, and the problem at this stage is reduced to the solution to a rectangular linear system of algebraic equations. The unknowns in this system of equations are the boundary values of four harmonic functions which define the full elastic solution and the unknown boundary values of stresses or displacements on proper parts of the boundary. On the basis of the obtained results, it is inferred that a stress component has a singularity at each of the two separation points, thought to be of logarithmic type. The results are discussed and boundary plots are given. We have also calculated the unknown functions in the bulk directly from the given boundary conditions using the boundary collocation method. The obtained results in the bulk are discussed and three-dimensional plots are given. A tentative form for the singular solution is proposed and the corresponding singular stresses and displacements are plotted in the bulk. The form of the singular tangential stress is seen to be compatible with the boundary values obtained earlier. The efficiency of the used numerical schemes is discussed.
Stenroos, Matti
2016-01-01
Boundary element methods (BEM) are used for forward computation of bioelectromagnetic fields in multi-compartment volume conductor models. Most BEM approaches assume that each compartment is in contact with at most one external compartment. In this work, I present a general surface integral equation and BEM discretization that remove this limitation and allow BEM modeling of general piecewise-homogeneous medium. The new integral equation allows positioning of field points at junctioned boundary of more than two compartments, enabling the use of linear collocation BEM in such a complex geometry. A modular BEM implementation is presented for linear collocation and Galerkin approaches, starting from standard formulation. The approach and resulting solver are verified in three ways, including comparison to finite element method (FEM). In a two-compartment split-sphere model with two spaced monopoles, the results obtained with high-resolution FEM and the BEMs were almost identical (relative difference < 0.003).
Boundary Conditions and the Generalized Metric Formulation of the Double Sigma Model
Ma, Chen-Te
2015-01-01
Double sigma model with the strong constraints is equivalent to the normal sigma model by imposing the self-duality relation. The gauge symmetries are the diffeomorphism and one-form gauge transformation with the strong constraints. We modify the Dirichlet and Neumann boundary conditions with the fully $O(D, D)$ description from the doubled gauge fields. We perform the one-loop $\\beta$ function for the constant background fields to find low energy effective theory without using the strong constraints. The low energy theory can also be $O(D,D)$ invariant as the double sigma model. We use the other one way to construct different boundary conditions from the projectors. Finally, we combine the antisymmetric background field with the field strength to redefine a different $O(D, D)$ generalized metric. We use this generalized metric to construct a consistent double sigma model with the classical and quantum equivalence. We show the one-loop $\\beta$ function for the constant background fields and obtain the normal ...
Coarse projective kMC integration: forward/reverse initial and boundary value problems
International Nuclear Information System (INIS)
In 'equation-free' multiscale computation a dynamic model is given at a fine, microscopic level; yet we believe that its coarse-grained, macroscopic dynamics can be described by closed equations involving only coarse variables. These variables are typically various low-order moments of the distributions evolved through the microscopic model. We consider the problem of integrating these unavailable equations by acting directly on kinetic Monte Carlo microscopic simulators, thus circumventing their derivation in closed form. In particular, we use projective multi-step integration to solve the coarse initial value problem forward in time as well as backward in time (under certain conditions). Macroscopic trajectories are thus traced back to unstable, source-type, and even sometimes saddle-like stationary points, even though the microscopic simulator only evolves forward in time. We also demonstrate the use of such projective integrators in a shooting boundary value problem formulation for the computation of 'coarse limit cycles' of the macroscopic behavior, and the approximation of their stability through estimates of the leading 'coarse Floquet multipliers'
BOUNDARY INTEGRAL FORMULAS FOR ELASTIC PLANE PROBLEM OF EXTERIOR CIRCULAR DOMAIN
Institute of Scientific and Technical Information of China (English)
DONG Zheng-zhu; LI Shun-cai; YU De-hao
2006-01-01
After the stress function and the normal derivative on the boundary for the plane problem of exterior circular domain are expanded into Laurent series, comparing them with the Laurent series of the complex stress function and making use of some formulas in Fourier series and the convolutions, the boundary integral formula of the stress function is derived further. Then the stress function can be obtained directly by the integration of the stress function and its normal derivative on the boundary. Some examples are given. It shows that the boundary integral formula of the stress function is convenient to be used for solving the elastic plane problem of exterior circular domain.
High Order Projection Plane Method for Evaluation of Supersingular Curved Boundary Integrals in BEM
Miao Cui; Wei-zhe Feng; Xiao-wei Gao; Kai Yang
2016-01-01
Boundary element method (BEM) is a very promising approach for solving various engineering problems, in which accurate evaluation of boundary integrals is required. In the present work, the direct method for evaluating singular curved boundary integrals is developed by considering the third-order derivatives in the projection plane method when expanding the geometry quantities at the field point as Taylor series. New analytical formulas are derived for geometry quantities defined on the curve...
Piloting and Path Integration within and across Boundaries
Mou, Weimin; Wang, Lin
2015-01-01
Three experiments investigated whether navigation is less efficient across boundaries than within boundaries. In an immersive virtual environment, participants learned objects' locations in a large room or a small room. Participants then pointed to the objects' original locations after physically walking a circuitous path without vision.…
The impact of a boundary layer height formulation on the GEOS-5 model climate
McGrath-Spangler, E. L.
2016-04-01
Planetary boundary layer (PBL) processes are important for the estimation of surface-atmosphere exchanges that impact global climate. One way of characterizing the strength of these processes is the PBL depth. In the Goddard Earth Observing System (GEOS-5) atmospheric general circulation model, the PBL depth is also used in calculating the turbulent length scale, which, in turn, is used in estimating the turbulence and vertical mixing within the model. Therefore, changing the PBL depth definition directly affects the model climate. This study evaluates the climatological model response of two long-term simulations using different PBL depth definitions. The first definition is based on a bulk Richardson number; the second uses a combination of the same bulk Richardson number definition over land plus a definition based on the turbulent eddy diffusion coefficient over water. The two simulations produce different spatiotemporal patterns of temperature, specific humidity, and wind speed related to the differences in turbulence. The largest differences, as expected, are present over water. Due to differences in atmospheric stability, the relationship between the two PBL depth estimates differ among the majority of the oceans and off the west coasts of continents, affecting the climatic response. Due to its optimization of the climatic response while maintaining a realistic diurnal cycle of PBL depth, the mixed PBL depth configuration is preferred.
Hanasoge, S M; Gizon, L
2010-01-01
Perfectly matched layers are a very efficient and accurate way to absorb waves in media. We present a stable convolutional unsplit perfectly matched formulation designed for the linearized stratified Euler equations. However, the technique as applied to the Magneto-hydrodynamic (MHD) equations requires the use of a sponge, which, despite placing the perfectly matched status in question, is still highly efficient at absorbing outgoing waves. We study solutions of the equations in the backdrop of models of linearized wave propagation in the Sun. We test the numerical stability of the schemes by integrating the equations over a large number of wave periods.
Atluri, Satya N.; Shen, Shengping
2002-01-01
In this paper, a very simple method is used to derive the weakly singular traction boundary integral equation based on the integral relationships for displacement gradients. The concept of the MLPG method is employed to solve the integral equations, especially those arising in solid mechanics. A moving Least Squares (MLS) interpolation is selected to approximate the trial functions in this paper. Five boundary integral Solution methods are introduced: direct solution method; displacement boundary-value problem; traction boundary-value problem; mixed boundary-value problem; and boundary variational principle. Based on the local weak form of the BIE, four different nodal-based local test functions are selected, leading to four different MLPG methods for each BIE solution method. These methods combine the advantages of the MLPG method and the boundary element method.
Signatures of chaos and non-integrability in two-dimensional gravity with dynamical boundary
Directory of Open Access Journals (Sweden)
Fitkevich Maxim
2016-01-01
Full Text Available We propose a model of two-dimensional dilaton gravity with a boundary. In the bulk our model coincides with the classically integrable CGHS model; the dynamical boundary cuts of the CGHS strong-coupling region. As a result, classical dynamics in our model reminds that in the spherically-symmetric gravity: wave packets of matter fields either reflect from the boundary or form black holes. We find large integrable sector of multisoliton solutions in this model. At the same time, we argue that the model is globally non-integrable because solutions at the verge of black hole formation display chaotic properties.
Algebraic Bethe Ansatz for O(2N) sigma models with integrable diagonal boundaries
Gombor, Tamas
2015-01-01
The finite volume problem of O(2N) sigma models with integrable diagonal boundaries on a finite interval is investigated. The double row transfer matrix is diagonalized by Algebraic Bethe Ansatz. The boundary Bethe Yang equations for the particle rapidities and the accompanying Bethe Ansatz equations are derived.
Multiple integral representation for the trigonometric SOS model with domain wall boundaries
Galleas, W
2011-01-01
Using the dynamical Yang-Baxter algebra we derive a functional equation for the partition function of the trigonometric SOS model with domain wall boundary conditions. The solution of the equation is given in terms of a multiple contour integral.
Isolation, Integration, and Ethnic Boundaries in Rural Guatemala
Pebley, Anne R.; Goldman, Noreen; Robles, Arodys
2002-01-01
The Guatemalan Indigenous population is engaged in a process of ethnic reorganization that closely parallels that of contemporary American Indians. We investigate the consequences of this process on the use of two key ethnic boundary markers for women -- dress and language use – using data from a 1995 social survey. The results show that social isolation and education are key factors in knowledge and use of Indigenous languages. By contrast, use of Indigenous dress does not vary substantially...
Topology and boundary shape optimization as an integrated design tool
Bendsoe, Martin Philip; Rodrigues, Helder Carrico
1990-01-01
The optimal topology of a two dimensional linear elastic body can be computed by regarding the body as a domain of the plane with a high density of material. Such an optimal topology can then be used as the basis for a shape optimization method that computes the optimal form of the boundary curves of the body. This results in an efficient and reliable design tool, which can be implemented via common FEM mesh generator and CAD type input-output facilities.
Gomez, Alejandro De La Rosa; Regelskis, Vidas
2016-01-01
We present a general method of folding an integrable spin chain, defined on a line, to obtain an integrable open spin chain, defined on a half-line. We illustrate our method through two fundamental models with sl(2) Lie algebra symmetry: the Heisenberg XXX and the Inozemtsev hyperbolic spin chains. We obtain new long-range boundary Hamiltonians and demonstrate that they exhibit Yangian symmetries, thus ensuring integrability of the models we obtain. The method presented provides a "bottom-up" approach for constructing integrable boundaries and can be applied to any spin chain model.
Energy Technology Data Exchange (ETDEWEB)
Reinhardt, Hugo [Tuebingen Univ. (Germany). Inst. fuer Theoretische Physik
2012-11-01
The first volume of this two-volume textbook gives a modern introduction to the quantum theory, which connects Feynman's path-integral formulation with the traditional operator formalism. In easily understandable form starting from the double-slit experiment the characteristic features and foundations of quantum theory are made accessible by means of the functional-integral approach. Just this approach makes a ''derivation'' of the Schroedinger equation from the principle of the interfering alternatives possible. In the following the author developes the traditional operator formulation of quantum mechanics, which is better suited for practical solution of elementary problems. However he then refers to the functional-integral approach, when this contributes to a better understanding. A further advance of this concept: The functional-integral approach facilitates essentially the later access to quantum field theory. The work is in like manner suited for the self-study as for the deepening accompanying of the course.
On the Structure of QFT in the Particle Picture of the Path Integral Formulation
Jackson, D M; Morales, A
2008-01-01
In quantum field theory the path integral is usually formulated in the wave picture, i.e., as a sum over field evolutions. This path integral is difficult to define rigorously because of analytic problems whose resolution may ultimately require knowledge of non-perturbative or even Planck scale physics. Alternatively, QFT can be formulated directly in the particle picture, namely as a sum over all multi-particle paths, i.e., over Feynman graphs. This path integral is well-defined, as a map between rings of formal power series. This suggests a program for determining which structures of QFT are provable for this path integral and thus are combinatorial in nature, and which structures are actually sensitive to analytic issues. For a start, we show that the fact that the Legendre transform of the sum of connected graphs yields the effective action is indeed combinatorial in nature and is thus independent of analytic assumptions. Our proof also leads to new methods for the efficient decomposition of Feynman graph...
Young, D. L.; Tsai, C. H.; Wu, C. S.
2015-11-01
An alternative vector potential formulation is used to solve the Navier-Stokes (N-S) equations in 3D incompressible viscous flow problems with and without through-flow boundaries. Difficulties of the vector potential formulation include the implementation of boundary conditions for through-flow boundaries and the numerical treatment of fourth-order partial differential equations. The advantages on the other hand are the automatic satisfaction of the continuity equation; and pressure is decoupled from the velocity. The objective of this paper is to introduce the appropriate gauge and boundary conditions on the vector potential formulation by a localized meshless method. To handle the divergence-free property, a Coulomb gauge condition is enforced on the vector potential to ensure its existence and uniqueness mathematically. We further improve the algorithm to through-flow problems for the boundary conditions of vector potential by introducing the concept of Stokes' theorem. Based on this innovation, there is no need to include an additional variable to tackle the through-flow fields. This process will greatly simplify the imposition of boundary conditions by the vector potential approach. Under certain conditions, the coupled fourth-order partial differential equations can be easily solved by using this meshless local differential quadrature (LDQ) method. Due to the LDQ capability to deal with the high order differential equations, this algorithm is very attractive to solve this fourth-order vector potential formulation for the N-S equations as comparing to the conventional numerical schemes such as finite element or finite difference methods. The proposed vector potential formulation is simpler and has improved accuracy and efficiency compared to other pressure-free or pressure-coupled algorithms. This investigation can be regarded as the first complete study to obtain the N-S solutions by vector potential formulation through a LDQ method. Two classic 3D benchmark
WODC
2007-01-01
The project's aim is to contribute to the building of a common system of indicators to measure immigrant integration in Europe, providing the input of states, countries and affected groups: immigrants (and women in particular in this group) as well as the host population. The responsibility of this project is in the hands of the General Directorate for Immigrant Integration of the Ministry of Labour and Social Affairs in Spain. It has been supported by a transnational network involving the pa...
Classical Mechanics in Hilbert Space: Path Integral Formulation, and a Quantum Correction
Shee, James
2015-01-01
While it is well-known that quantum mechanics can be reformulated in terms of a path integral representation, it will be shown that such a formulation is also possible in the case of classical mechanics. From Koopman-von Neumann theory, which recasts classical mechanics in terms of a Hilbert space wherein the Liouville operator acts as the generator of motion, we derive a path integral representation of the classical propagator and suggest an efficient numerical implementation using fast fourier transform techniques. We then include a first quantum correction to derive a revealing expression for the semi-classical path integral, which augments the classical picture of a single trajectory through phase space with additional wave-like spreading.
Jokela, Niko; Kytölä, Kalle
2013-01-01
We study the probabilities with which chordal Schramm-Loewner Evolutions (SLE) visit small neighborhoods of boundary points. We find explicit formulas for general chordal SLE boundary visiting probability amplitudes, also known as SLE boundary zig-zags or order refined SLE multi-point Green's functions on the boundary. Remarkably, an exact answer can be found to this important SLE question for an arbitrarily large number of marked points. The main technique employed is a spin chain - Coulomb gas correspondence between tensor product representations of a quantum group and functions given by Dotsenko-Fateev type integrals. We show how to express these integral formulas in terms of regularized real integrals, and we discuss their numerical evaluation. The results are universal in the sense that apart from an overall multiplicative constant the same formula gives the amplitude for many different formulations of the SLE boundary visit problem. The formula also applies to renormalized boundary visit probabilities f...
Shape integral method for magnetospheric shapes. [boundary layer calculations
Michel, F. C.
1979-01-01
A method is developed for calculating the shape of any magnetopause to arbitrarily high precision. The method uses an integral equation which is evaluated for a trial shape. The resulting values of the integral equation as a function of auxiliary variables indicate how close one is to the desired solution. A variational method can then be used to improve the trial shape. Some potential applications are briefly mentioned.
High Order Projection Plane Method for Evaluation of Supersingular Curved Boundary Integrals in BEM
Directory of Open Access Journals (Sweden)
Miao Cui
2016-01-01
Full Text Available Boundary element method (BEM is a very promising approach for solving various engineering problems, in which accurate evaluation of boundary integrals is required. In the present work, the direct method for evaluating singular curved boundary integrals is developed by considering the third-order derivatives in the projection plane method when expanding the geometry quantities at the field point as Taylor series. New analytical formulas are derived for geometry quantities defined on the curved line/plane, and unified expressions are obtained for both two-dimensional and three-dimensional problems. For the two-dimensional boundary integrals, analytical expressions for the third-order derivatives are derived and are employed to verify the complex-variable-differentiation method (CVDM which is used to evaluate the high order derivatives for three-dimensional problems. A few numerical examples are given to show the effectiveness and the accuracy of the present method.
Li, Yuan; Dang, HuaYang; Xu, GuangTao; Fan, CuiYing; Zhao, MingHao
2016-08-01
The extended displacement discontinuity boundary integral equation (EDDBIE) and boundary element method is developed for the analysis of planar cracks of arbitrary shape in the isotropic plane of three-dimensional (3D) transversely isotropic thermo-magneto-electro-elastic (TMEE) media. The extended displacement discontinuities (EDDs) include conventional displacement discontinuity, electric potential discontinuity, magnetic potential discontinuity, as well as temperature discontinuity across crack faces; correspondingly, the extended stresses represent conventional stress, electric displacement, magnetic induction and heat flux. Employing a Hankel transformation, the fundamental solutions for unit point EDDs in 3D transversely isotropic TMEE media are derived. The EDDBIEs for a planar crack of arbitrary shape in the isotropic plane of a 3D transversely isotropic TMEE medium are then established. Using the boundary integral equation method, the singularities of near-crack border fields are obtained and the extended stress field intensity factors are expressed in terms of the EDDs on crack faces. According to the analogy between the EDDBIEs for an isotropic thermoelastic material and TMEE medium, an analogical solution method for crack problems of a TMEE medium is proposed for coupled multi-field loadings. Employing constant triangular elements, the EDDBIEs are discretized and numerically solved. As an application, the problems of an elliptical crack subjected to combined mechanical-electric-magnetic-thermal loadings are investigated.
Directory of Open Access Journals (Sweden)
Christophe Prud'homme
2006-01-01
Full Text Available In this article, we present a domain specific embedded language in C++ that can be used in various contexts such as numerical projection onto a functional space, numerical integration, variational formulations and automatic differentiation. Albeit these tools operate in different ways, the language overcomes this difficulty by decoupling expression constructions from evaluation. The language is implemented using expression templates and meta-programming techniques and uses various Boost libraries. The language is exercised on a number of non-trivial examples and a benchmark presents the performance behavior on a few test problems.
The Brown-Henneaux's central charge from the path-integral boundary condition
Terashima, Hiroaki
2000-01-01
We derive Brown-Henneaux's commutation relation and central charge in the framework of the path integral. If we use the leading part of the asymptotic symmetry to derive the Ward-Takahashi identity, we can see the central charge arises from the fact that the boundary condition of the path integral is not invariant under the transformation.
RESTRICTED NONLINEAR APPROXIMATION AND SINGULAR SOLUTIONS OF BOUNDARY INTEGRAL EQUATIONS
Institute of Scientific and Technical Information of China (English)
Reinhard Hochmuth
2002-01-01
This paper studies several problems, which are potentially relevant for the construction of adaptive numerical schemes. First, biorthogonal spline wavelets on [0,1 ] are chosen as a starting point for characterizations of functions in Besov spaces B , (0,1) with 0＜σ＜∞ and (1+σ)-1＜τ＜∞. Such function spaces are known to be related to nonlinear approximation. Then so called restricted nonlinear approximation procedures with respect to Sobolev space norms are considered. Besides characterization results Jackson type estimates for various tree-type and tresholding algorithms are investigated. Finally known approximation results for geometry induced singularity functions of boundary integeral equations are combined with the characterization results for restricted nonlinear approximation to show Besov space regularity results.
Gomez-Sousa, Hipolito; Martinez-Lorenzo, Jose Angel; Arias-Acuña, Marcos
2015-01-01
This paper presents a new method, based on the well-known method of moments (MoM), for the numerical electromagnetic analysis of scattering and radiation from metallic or dielectric structures, or both structure types in the same simulation, that are in contact with other metallic or dielectric structures. The proposed method for solving the MoM junction problem consists of two separate algorithms, one of which comprises a generalization for bodies in contact of the surface integral equation (SIE) formulations. Unlike some other published SIE generalizations in the field of computational electromagnetics, this generalization does not require duplicating unknowns on the dielectric separation surfaces. Additionally, this generalization is applicable to any ordinary single-scatterer SIE formulations employed as baseline. The other algorithm deals with enforcing boundary conditions and Kirchhoff's Law, relating the surface current flow across a junction edge. Two important features inherent to this latter algorit...
Boundary integral equation Neumann-to-Dirichlet map method for gratings in conical diffraction.
Wu, Yumao; Lu, Ya Yan
2011-06-01
Boundary integral equation methods for diffraction gratings are particularly suitable for gratings with complicated material interfaces but are difficult to implement due to the quasi-periodic Green's function and the singular integrals at the corners. In this paper, the boundary integral equation Neumann-to-Dirichlet map method for in-plane diffraction problems of gratings [Y. Wu and Y. Y. Lu, J. Opt. Soc. Am. A26, 2444 (2009)] is extended to conical diffraction problems. The method uses boundary integral equations to calculate the so-called Neumann-to-Dirichlet maps for homogeneous subdomains of the grating, so that the quasi-periodic Green's functions can be avoided. Since wave field components are coupled on material interfaces with the involvement of tangential derivatives, a least squares polynomial approximation technique is developed to evaluate tangential derivatives along these interfaces for conical diffraction problems. Numerical examples indicate that the method performs equally well for dielectric or metallic gratings. PMID:21643404
An, Hongli; Fan, Engui; Zhu, Haixing
2015-01-01
The 2+1-dimensional compressible Euler equations are investigated here. A power-type elliptic vortex ansatz is introduced and thereby reduction obtains to an eight-dimensional nonlinear dynamical system. The latter is shown to have an underlying integral Ermakov-Ray-Reid structure of Hamiltonian type. It is of interest to notice that such an integrable Ermakov structure exists not only in the density representations but also in the velocity components. A class of typical elliptical vortex solutions termed pulsrodons corresponding to warm-core eddy theory is isolated and its behavior is simulated. In addition, a Lax pair formulation is constructed and the connection with stationary nonlinear cubic Schrödinger equations is established.
Hijazzi, Norshamirra; Thiruchelvam, Sivadass; Sabri Muda, Rahsidi; Nasharuddin Mustapha, Kamal; Che Muda, Zakaria; Ghazali, Azrul; Kamal Kadir, Ahmad; Hakimie, Hazlinda; Sahari, Khairul Salleh Mohamed; Hasini, Hasril; Mohd Sidek, Lariyah; Itam, Zarina; Fadhli Mohamad, Mohd; Razad, Azwin Zailti Abdul
2016-03-01
Dams, however significant their contributions are to the society, are not immune to failures and diminishing lifespan not unlike other structural elements in our infrastructure. Despite continuing efforts on design, construction, operation, and maintenance of dams to improve the safety of the dams, the possibility of unforeseen events of dam failures is still possible. Seeing that dams are usually integrated into close approximities with the community, dam failures may consequent in tremendous loss of lives and properties. The aims of formulation of Integrated Community Based Disaster Management (ICBDM) is to simulate evacuation modelling and emergency planning in order to minimize loss of life and property damages in the event of a dam-related disaster. To achieve the aim above, five main pillars have been identified for the formulation of ICBDM. A series of well-defined program inclusive of hydrological 2-D modelling, life safety modelling, community based EWS and CBTAP will be conducted. Finally, multiple parties’ engagement is to be carried out in the form of table top exercise to measure the readiness of emergency plans and response capabilities of key players during the state of a crisis.
Tetervin, Neal; Lin, Chia Chiao
1951-01-01
A general integral form of the boundary-layer equation, valid for either laminar or turbulent incompressible boundary-layer flow, is derived. By using the experimental finding that all velocity profiles of the turbulent boundary layer form essentially a single-parameter family, the general equation is changed to an equation for the space rate of change of the velocity-profile shape parameter. The lack of precise knowledge concerning the surface shear and the distribution of the shearing stress across turbulent boundary layers prevented the attainment of a reliable method for calculating the behavior of turbulent boundary layers.
Behavior of boundary string field theory associated with integrable massless flow.
Fujii, A; Itoyama, H
2001-06-01
We put forward an idea that the boundary entropy associated with integrable massless flow of thermodynamic Bethe ansatz (TBA) is identified with tachyon action of boundary string field theory. We show that the temperature parametrizing a massless flow in the TBA formalism can be identified with tachyon energy for the classical action at least near the ultraviolet fixed point, i.e., the open string vacuum.
Integrity of fuelling machine pressure boundary under flow reversal during defuelling
Energy Technology Data Exchange (ETDEWEB)
Wahba, N.N.; Bayoumi, M.H. [Ontario Power Generation, Inc., Nuclear Safety Analysis Division, Fuel and Fuel Channel Analysis Dept., Toronto, Ontario (Canada)
2002-07-01
This paper documents the calculated loads and stresses of various components of the fuelling machine pressure boundary, pressure tube and fixed-end positioning-assembly stud due to reverse flow bundle impact if an inlet feeder break is postulated to occur during flow defuelling. The information was required to support pressure tube inspection during outage for Darlington NGS. The results indicate that the integrity of the pressure boundary is maintained under the postulated scenario. (author)
International Nuclear Information System (INIS)
This report deals with the formulation and numerical integration of constitutive models in the framework of finite deformation thermomechanics. Based on the concept of dual variables, plasticity and viscoplasticity models exhibiting nonlinear kinematic hardening as well as nonlinear isotropic hardening rules are presented. Care is taken that the evolution equations governing the hardening response fulfill the intrinsic dissipation inequality in every admissible process. In view of the development of an efficient numerical integration procedure, simplified versions of these constitutive models are supposed. In these versions, the thermoelastic strains are assumed to be small and a simplified kinematic hardening rule is considered. Additionally, in view of an implementation into the ABAQUS finite element code, the elasticity law is approximated by a hypoelasticity law. For the simplified onstitutive models, an implicit time-integration algorithm is developed. First, in order to obtain a numerical objective integration scheme, use is made of the HUGHES-WINGET-Algorithm. In the resulting system of ordinary differential equations, it can be distinguished between three differential operators representing different physical effects. The structure of this system of differential equations allows to apply an operator split scheme, which leads to an efficient integration scheme for the constitutive equations. By linearizing the integration algorithm the consistent tangent modulus is derived. In this way, the quadratic convergence of Newton's method used to solve the basic finite element equations (i.e. the finite element discretization of the governing thermomechanical field equations) is preserved. The resulting integration scheme is implemented as a user subroutine UMAT in ABAQUS. The properties of the applied algorithm are first examined by test calculations on a single element under tension-compression-loading. For demonstrating the capabilities of the constitutive theory
[Boundaries and integrity in the "Social Contract for Spanish Science", 1907-1939].
Gómez, Amparo
2014-01-01
This article analyzes the relationship between science and politics in Spain in the early 20th century from the perspective of the Social Contract for Science. The article shows that a genuine social contract for science was instituted in Spain during this period, although some boundary and integrity problems emerged. These problems are analyzed, showing that the boundary problems were a product of the conservative viewpoint on the relationship between science and politics, while the integrity problems involved the activation of networks of influence in the awarding of scholarships to study abroad. Finally, the analysis reveals that these problems did not invalidate the Spanish social contract for science.
Exact solution of the open XXZ chain with general integrable boundary terms at roots of unity
Murgan, R; Shi, C; Murgan, Rajan; Nepomechie, Rafael I.; Shi, Chi
2006-01-01
We propose a Bethe-Ansatz-type solution of the open spin-1/2 integrable XXZ quantum spin chain with general integrable boundary terms and bulk anisotropy values i \\pi/(p+1), where p is a positive integer. All six boundary parameters are arbitrary, and need not satisfy any constraint. The solution is in terms of generalized T - Q equations, having more than one Q function. We find numerical evidence that this solution gives the complete set of 2^N transfer matrix eigenvalues, where N is the number of spins.
Reid, M T Homer; White, Jacob K
2013-01-01
We present a generic technique, automated by computer-algebra systems and available as open-source software \\cite{scuff-em}, for efficient numerical evaluation of a large family of singular and nonsingular 4-dimensional integrals over triangle-product domains, such as those arising in the boundary-element method (BEM) of computational electromagnetism. To date, practical implementation of BEM solvers has often required the aggregation of multiple disparate integral-evaluation schemes to treat all of the distinct types of integrals needed for a given BEM formulation; in contrast, our technique allows many different types of integrals to be handled by the \\emph{same} algorithm and the same code implementation. Our method is a significant generalization of the Taylor--Duffy approach \\cite{Taylor2003,Duffy1982}, which was originally presented for just a single type of integrand; in addition to generalizing this technique to a broad class of integrands, we also achieve a significant improvement in its efficiency b...
DEFF Research Database (Denmark)
Cutanda Henríquez, Vicente; Juhl, Peter Møller
2008-01-01
It is well known that the Boundary Element Method (BEM) in its standard version cannot readily handle situations where the calculation point is very close to a surface. These problems are found: i) when two boundary surfaces are very close together, such as in narrow gaps and thin bodies, and ii)...
Integrating Sustainability into the Curriculum: Crossing Disciplinary Boundaries
Pushnik, J.
2012-12-01
The next generation will confront an increased number of global issues that interface the complexities of socioeconomic perspectives, environmental stability, poverty and development. Recently California State University Chico undertook a general education reform, providing a unique opportunity to craft a general education pathway to prepare students for these challenges by focusing a curriculum on sustainability. The Sustainability Pathway emphasizes a system thinking approach to help students understand and be able to address a set of problems involving the biosphere processes, human institutions and the economic vitality. The curriculum intentionally integrates courses from across the disciplines of natural sciences, social sciences, agriculture, engineering, economics, arts and humanities into a central focused theme of sustainability. The diverse backgrounds and academic focus of the participating faculty has necessitate the development of a common language and a cohesion within the curriculum. To address these needs a faculty learning community (FLC) was established to build on a common set of case studies. Three regional environmental water related issues were selected that had demonstrable socioeconomic, equity/ethical dimensions and environmental consequences. These case studies are Klamath River basin in northern California, the Bay-Delta project in the central part of the state and the Sultan Sea in southern California. Members of the FLC has contributed a perspective from their academic discipline which includes proposed reading lists, web based resources and PowerPoint presentations which are housed in common web- based resource repository. The pedagogical rational is to create linkages and cohesion among the courses in the curriculum by iteratively examining these case studies as basis for development of a multidisciplinary perspective as students progress through their general education.
Correct Path-Integral Formulation of Quantum Thermal Field Theory in Coherent State Representation
Institute of Scientific and Technical Information of China (English)
SU Jun-Chen; ZHENG Fu-Hou
2005-01-01
The path-integral quantization of thermal scalar, vector, and spinor fields is performed newly in the coherent-state representation. In doing this, we choose the thermal electrodynamics and ψ4 theory as examples. By this quantization, correct expressions of the partition functions and the generating functionals for the quantum thermal electrodynamics and ψ4 theory are obtained in the coherent-state representation. These expressions allow us to perform analytical calculations of the partition functions and generating functionals and therefore are useful in practical applications. Especially, the perturbative expansions of the generating functionals are derived specifically by virtue of the stationary-phase method. The generating functionals formulated in the position space are re-derived from the ones given in the coherent-state representation.
Integral equation solution for truncated slab structures by using a fringe current formulation
DEFF Research Database (Denmark)
Jørgensen, Erik; Toccafondi, A.; Maci, S.
1999-01-01
Full-wave solutions of truncated dielectric slab problems are interesting for a variety of engineering applications, in particular patch antennas on finite ground planes. For this application a canonical reference solution is that of a semi-infinite slab illuminated by a line source. Standard...... integral equation (IE) techniques are not easily applied to this problem, since unknown equivalent currents have to be distributed on a semi-infinite domain. In this paper we present a surface/surface approach, applied to an IE which is based on a non-conventional formulation. More precise, the unknowns of...... this IE are the difference between the actual currents and the currents of the infinite structure (without truncation)...
Explicit expressions for three-dimensional boundary integrals in linear elasticity
Energy Technology Data Exchange (ETDEWEB)
Nintcheu Fata, Sylvain [ORNL
2011-01-01
On employing isoparametric, piecewise linear shape functions over a flat triangle, exact formulae are derived for all surface potentials involved in the numerical treatment of three-dimensional singular and hyper-singular boundary integral equations in linear elasticity. These formulae are valid for an arbitrary source point in space and are represented as analytical expressions along the edges of the integration triangle. They can be employed to solve integral equations defined on triangulated surfaces via a collocation method or may be utilized as analytical expressions for the inner integrals in a Galerkin technique. A numerical example involving a unit triangle and a source point located at various distances above it, as well as sample problems solved by a collocation boundary element method for the Lame equation are included to validate the proposed formulae.
Integration of the SL(2,R)/U(1) Gauged WZNW Model with Periodic Boundary Conditions
Mueller, Uwe; Weigt, Gerhard
1999-01-01
Gauged WZNW models are integrable conformal field theories. We integrate the classical \\slu{} theory with periodic boundary conditions, which describes closed strings moving in a curved target-space geometry. We calculate its Poisson bracket structure by solving an initial state problem. The results differ from previous field-theoretic calculations due to zero modes. For a future exact canonical quantization the physical fields are (non-locally) transformed onto canonical free fields.
Integration of the SL(2,(R/U(1)) gauged WZNW model with periodic boundary conditions
Energy Technology Data Exchange (ETDEWEB)
Mueller, Uwe; Weigt, Gerhard
2000-02-28
Gauged WZNW models are integrable conformal field theories. We integrate the classical SL(2,R/U(1)) theory with periodic boundary conditions, which describes closed strings moving in a curved target-space geometry. We calculate its Poisson bracket structure by solving an initial state problem. The results differ from previous field-theoretic calculations due to zero-modes. For a future exact canonical quantization the physical fields are (non-locally) transformed onto canonical free fields.
Histone crosstalk directed by H2B ubiquitination is required for chromatin boundary integrity.
Directory of Open Access Journals (Sweden)
Meiji Kit-Wan Ma
2011-07-01
Full Text Available Genomic maps of chromatin modifications have provided evidence for the partitioning of genomes into domains of distinct chromatin states, which assist coordinated gene regulation. The maintenance of chromatin domain integrity can require the setting of boundaries. The HS4 insulator element marks the 3' boundary of a heterochromatin region located upstream of the chicken β-globin gene cluster. Here we show that HS4 recruits the E3 ligase RNF20/BRE1A to mediate H2B mono-ubiquitination (H2Bub1 at this insulator. Knockdown experiments show that RNF20 is required for H2Bub1 and processive H3K4 methylation. Depletion of RNF20 results in a collapse of the active histone modification signature at the HS4 chromatin boundary, where H2Bub1, H3K4 methylation, and hyperacetylation of H3, H4, and H2A.Z are rapidly lost. A remarkably similar set of events occurs at the HSA/HSB regulatory elements of the FOLR1 gene, which mark the 5' boundary of the same heterochromatin region. We find that persistent H2Bub1 at the HSA/HSB and HS4 elements is required for chromatin boundary integrity. The loss of boundary function leads to the sequential spreading of H3K9me2, H3K9me3, and H4K20me3 over the entire 50 kb FOLR1 and β-globin region and silencing of FOLR1 expression. These findings show that the HSA/HSB and HS4 boundary elements direct a cascade of active histone modifications that defend the FOLR1 and β-globin gene loci from the pervasive encroachment of an adjacent heterochromatin domain. We propose that many gene loci employ H2Bub1-dependent boundaries to prevent heterochromatin spreading.
Energy Technology Data Exchange (ETDEWEB)
Chen, Ke [Univ. of Liverpool (United Kingdom)
1996-12-31
We study various preconditioning techniques for the iterative solution of boundary integral equations, and aim to provide a theory for a class of sparse preconditioners. Two related ideas are explored here: singularity separation and inverse approximation. Our preliminary conclusion is that singularity separation based preconditioners perform better than approximate inverse based while it is desirable to have both features.
2012-01-01
This thesis explores Norwegian majority members’ role in incorporating and integrating immigrant minorities from a broad social psychological perspective on intergroup relations. It consists of four studies which investigate changing symbolic boundaries of immigrants and the majority as reflected in media discourse, and majority members’ attitudes toward proactively incorporating immigrant minorities. These different studies aim to develop better understandings of how immigrant minorities may...
A well-conditioned boundary integral equation for transmission problems of electromagnetism
Levadoux, David; Millot, Florence; Pernet, Sébastien
2015-01-01
We propose a new well-conditioned boundary integral equation to solve transmission problems of electromagnetism. This equation is well posed and appears as a compact perturbation of the identity leading to fast iterative solutions without the help of any preconditioner. Some numerical experiments confirm this result.
Kao, Gloria Yi-Ming; Lin, Sunny S. J.; Sun, Chuen-Tsai
2008-01-01
The authors address the role of computer support for building conceptual self-awareness--that is, enabling students to think outside of concept boundaries in hope of enhancing creative potential. Based on meta-cognition theory, we developed an integrated concept mapping system (ICMSys) to improve users' conceptual self-awareness in addition to…
International Nuclear Information System (INIS)
The thesis addresses the numerical simulation of non-destructive testing (NDT) using eddy currents, and more precisely the computation of induced electromagnetic fields by a transmitter sensor in a healthy part. This calculation is the first step of the modeling of a complete control process in the CIVA software platform developed at CEA LIST. Currently, models integrated in CIVA are restricted to canonical (modal computation) or axially-symmetric geometries. The need for more diverse and complex configurations requires the introduction of new numerical modeling tools. In practice the sensor may be composed of elements with different shapes and physical properties. The inspected parts are conductive and may contain dielectric or magnetic elements. Due to the cohabitation of different materials in one configuration, different regimes (static, quasi-static or dynamic) may coexist. Under the assumption of linear, isotropic and piecewise homogeneous material properties, the surface integral equation (SIE) approach allows to reduce a volume-based problem to an equivalent surface-based problem. However, the usual SIE formulations for the Maxwell's problem generally suffer from numerical noise in asymptotic situations, and especially at low frequencies. The objective of this study is to determine a version that is stable for a range of physical parameters typical of eddy-current NDT applications. In this context, a block-iterative scheme based on a physical decomposition is proposed for the computation of primary fields. This scheme is accurate and well-conditioned. An asymptotic study of the integral Maxwell's problem at low frequencies is also performed, allowing to establish the eddy-current integral problem as an asymptotic case of the corresponding Maxwell problem. (author)
N{sup ±}-integrals and boundary values of Cauchy-type integrals of finite measures
Energy Technology Data Exchange (ETDEWEB)
Aliev, R. A., E-mail: aliyevrashid@hotmail.ru, E-mail: alievrashid@box.az [Baku State University (Azerbaijan)
2014-07-31
Let Γ be a simple closed Lyapunov contour with finite complex measure ν, and let G{sup +} be the bounded and G{sup −} the unbounded domains with boundary Γ. Using new notions (so-called N-integration and N{sup +}- and N{sup −}-integrals), we prove that the Cauchy-type integrals F{sup +}(z), z∈G{sup +}, and F{sup −}(z), z∈G{sup −}, of ν are Cauchy N{sup +}- and N{sup −}-integrals, respectively. In the proof of the corresponding results, the additivity property and the validity of the change-of-variable formula for the N{sup +}- and N{sup −}-integrals play an essential role. Bibliography: 21 titles. (paper)
$A_n^{(1)}$ affine Toda field theories with integrable boundary conditions revisited
Doikou, Anastasia
2008-01-01
Generic classically integrable boundary conditions for the $A_{n}^{(1)}$ affine Toda field theories (ATFT) are investigated. The present analysis relies primarily on the underlying algebra, defined by the classical version of the reflection equation. We use as a prototype example the first non-trivial model of the hierarchy i.e. the $A_2^{(1)}$ ATFT, however our results may be generalized for any $A_{n}^{(1)}$ ($n>1$). We assume here two distinct types of boundary conditions called some times soliton preserving (SP), and soliton non-preserving (SNP) associated to two distinct algebras, i.e. the reflection algebra and the ($q$) twisted Yangian respectively. The boundary local integrals of motion are then systematically extracted from the asymptotic expansion of the associated transfer matrix. In the case of SNP boundary conditions we recover previously known results. The other type of boundary conditions (SP), associated to the reflection algebra, are novel in this context and lead to a different set of conser...
Directory of Open Access Journals (Sweden)
Sulym Heorhiy
2016-03-01
Full Text Available This paper studies a thermoelastic anisotropic bimaterial with thermally imperfect interface and internal inhomogeneities. Based on the complex variable calculus and the extended Stroh formalism a new approach is proposed for obtaining the Somigliana type integral formulae and corresponding boundary integral equations for a thermoelastic bimaterial consisting of two half-spaces with different thermal and mechanical properties. The half-spaces are bonded together with mechanically perfect and thermally imperfect interface, which model interfacial adhesive layers present in bimaterial solids. Obtained integral equations are introduced into the modified boundary element method that allows solving arbitrary 2D thermoelacticity problems for anisotropic bimaterial solids with imperfect thin thermo-resistant inter-facial layer, which half-spaces contain cracks and thin inclusions. Presented numerical examples show the effect of thermal resistance of the bimaterial interface on the stress intensity factors at thin inhomogeneities.
Fisher, Travis C.; Carpenter, Mark H.; Nordstroem, Jan; Yamaleev, Nail K.; Swanson, R. Charles
2011-01-01
Simulations of nonlinear conservation laws that admit discontinuous solutions are typically restricted to discretizations of equations that are explicitly written in divergence form. This restriction is, however, unnecessary. Herein, linear combinations of divergence and product rule forms that have been discretized using diagonal-norm skew-symmetric summation-by-parts (SBP) operators, are shown to satisfy the sufficient conditions of the Lax-Wendroff theorem and thus are appropriate for simulations of discontinuous physical phenomena. Furthermore, special treatments are not required at the points that are near physical boundaries (i.e., discrete conservation is achieved throughout the entire computational domain, including the boundaries). Examples are presented of a fourth-order, SBP finite-difference operator with second-order boundary closures. Sixth- and eighth-order constructions are derived, and included in E. Narrow-stencil difference operators for linear viscous terms are also derived; these guarantee the conservative form of the combined operator.
POSITIVE SOLUTIONS OF A NONLINEAR THREE-POINT EIGENVALUE PROBLEM WITH INTEGRAL BOUNDARY CONDITIONS
Directory of Open Access Journals (Sweden)
FAOUZI HADDOUCHI
2015-11-01
Full Text Available In this paper, we study the existence of positive solutions of a three-point integral boundary value problem (BVP for the following second-order differential equation u''(t + \\lambda a(tf(u(t = 0; 0 0 is a parameter, 0 <\\eta < 1, 0 <\\alpha < 1/{\\eta}. . By using the properties of the Green's function and Krasnoselskii's fixed point theorem on cones, the eigenvalue intervals of the nonlinear boundary value problem are considered, some sufficient conditions for the existence of at least one positive solutions are established.
Boundary integral equation methods in eigenvalue problems of elastodynamics and thin plates
Kitahara, M
1985-01-01
The boundary integral equation (BIE) method has been used more and more in the last 20 years for solving various engineering problems. It has important advantages over other techniques for numerical treatment of a wide class of boundary value problems and is now regarded as an indispensable tool for potential problems, electromagnetism problems, heat transfer, fluid flow, elastostatics, stress concentration and fracture problems, geomechanical problems, and steady-state and transient electrodynamics.In this book, the author gives a complete, thorough and detailed survey of the method. It pro
Institute of Scientific and Technical Information of China (English)
Gao－LianLiu
1996-01-01
By introducing an image plane,the inverse heat conduction problem with free boundary is transformed into one with completely known boundary,which is much simpler to handle,as a by-product ,the classical Krichhoff's transformation for accounting for varialble conductivity is rederived and an invariance proerty of the inverse problem solution with respect to variable conductivity is indicated.Then a pair of complementary extremum principles are established on the image plane.providing a sound theoretical foundation for the Ritz's method and finite element method (FEM),An example solved by FEM is also given.
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
International Nuclear Information System (INIS)
With the adoption of the Kyoto Protocol in 1997 national leaders have started investigating options for reducing carbon emissions within national borders. Despite confronting similar energy issues, every country that adopted the Kyoto Protocol has a unique energy strategy - being characterized by a different context, social, economic or environmental that influences the way different nations deal with climate change and other energy-related issues. Finding that currently available energy models are often too detailed or narrowly focused to inform longer-term policy formulation and evaluation holistically, the present study proposes the utilization of an integrated cross-sectoral medium to longer-term research and modeling approach, incorporating various methodologies to minimize exogenous assumptions and endogenously represent the key drivers of the system analyzed. The framework proposed includes feedback, delays and non-linearity and focuses on structure, scenarios and policies, requires a profound customization of the model that goes beyond a new parameterization. The inclusion of social and environmental factors, in addition to economic ones, all unique to the geographical area analyzed, allows for a wider analysis of the implication of policies by identifying potential side effect or longer-term bottlenecks for socio-economic development and environmental preservation arising from cross-sectoral relations. (author)
Field, J. H.
2011-01-01
It is shown how the time-dependent Schrodinger equation may be simply derived from the dynamical postulate of Feynman's path integral formulation of quantum mechanics and the Hamilton-Jacobi equation of classical mechanics. Schrodinger's own published derivations of quantum wave equations, the first of which was also based on the Hamilton-Jacobi…
Regularized boundary integral representations for dislocations and cracks in smart media
International Nuclear Information System (INIS)
This paper presents a complete set of singularity-reduced boundary integral relations for isolated discontinuities embedded in three-dimensional infinite media. The development is carried out within a broad context that allows the treatment of a well-known class of smart media such as linear piezoelectric, linear piezomagnetic and linear piezoelectromagnetic materials. In addition, resulting boundary integral representations are applicable to general discontinuities of arbitrary geometry and possessing a general jump distribution. The latter aspect allows the treatment of two special kinds of discontinuities: dislocations and cracks. The most attractive feature of the current development is that all integral relations for field quantities such as state variables and their gradients, the body flux, and the generalized interaction energy produced by dislocations are expressed only in terms of line integrals over the dislocation loops and, for cracks, the key governing boundary integral equation is established in a symmetric weak form and contains only weakly singular kernels of O(1/r). Results for the former case are fundamental and useful in the context of dislocation mechanics and modeling while the resulting weakly singular, weak form integral equation constitutes a basis for the development of a well-known numerical technique, called a symmetric Galerkin boundary element method (SGBEM), for analysis of cracked bodies. The weakly singular nature of such an integral equation allows low order interpolations to be used in the numerical approximation. The key ingredient for achieving such development of integral representations is the use of certain special decompositions in the derivative-transferring process via Stokes's theorem. Existence of such decompositions is ensured by a careful consideration of the singularity nature of the kernels, and a particular solution of the weakly singular functions involved is obtained by solving a system of partial differential
The Prediction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method
Farassat, F.; Dunn, M. H.; Tweed, J.
1996-01-01
A computationally efficient Boundary Integral Equation Method (BIEM) for the prediction of ducted fan engine noise is presented. The key features of the BIEM are its versatility and the ability to compute rapidly any portion of the sound field without the need to compute the entire field. Governing equations for the BIEM are based on the assumptions that all acoustic processes are linear, generate spinning modes, and occur in a uniform flow field. An exterior boundary value problem (BVP) is defined that describes the scattering of incident sound by an engine duct with arbitrary profile. Boundary conditions on the duct walls are derived that allow for passive noise control treatment. The BVP is recast as a system of hypersingular boundary integral equations for the unknown duct surface quantities. BIEM solution methodology is demonstrated for the scattering of incident sound by a thin cylindrical duct with hard walls. Numerical studies are conducted for various engine parameters and continuous portions of the total pressure field are computed. Radiation and duct propagation results obtained are in agreement with the classical results of spinning mode theory for infinite ducts.
Goza, Andres
2016-01-01
We present a strongly-coupled immersed-boundary method for flow-structure interaction problems involving thin deforming bodies. The method is stable for arbitrary choices of solid-to-fluid mass ratios and for large body motions. As with many strongly-coupled immersed-boundary methods, our method requires the solution of a nonlinear algebraic system at each time step. The system is solved through iteration, where the iterates are obtained by linearizing the system and performing a block LU factorization. This restricts all iterations to small-dimensional subsystems that scale with the number of discretization points on the immersed surface, rather than on the entire flow domain. Moreover, the iteration procedure we propose does not involve heuristic regularization parameters, and has converged in a small number of iterations for all problems we have considered. We derive our method for general deforming surfaces, and verify the method with two-dimensional test problems of geometrically nonlinear beams undergoi...
Retarded potentials and time domain boundary integral equations a road map
Sayas, Francisco-Javier
2016-01-01
This book offers a thorough and self-contained exposition of the mathematics of time-domain boundary integral equations associated to the wave equation, including applications to scattering of acoustic and elastic waves. The book offers two different approaches for the analysis of these integral equations, including a systematic treatment of their numerical discretization using Galerkin (Boundary Element) methods in the space variables and Convolution Quadrature in the time variable. The first approach follows classical work started in the late eighties, based on Laplace transforms estimates. This approach has been refined and made more accessible by tailoring the necessary mathematical tools, avoiding an excess of generality. A second approach contains a novel point of view that the author and some of his collaborators have been developing in recent years, using the semigroup theory of evolution equations to obtain improved results. The extension to electromagnetic waves is explained in one of the appendices...
Institute of Scientific and Technical Information of China (English)
Pan Xiaomin; Sheng Xinqing
2008-01-01
A general and efficient parallel approach is proposed for the first time to parallelize the hybrid finite-element-boundary-integral-multi-level fast multipole algorithm (FE-BI-MLFMA). Among many algorithms of FE-BI-MLFMA, the decomposition algorithm (DA) is chosen as a basis for the parallelization of FE-BI-MLFMA because of its distinct numerical characteristics suitable for parallelization. On the basis of the DA, the parallelization of FE-BI-MLFMA is carried out by employing the parallelized multi-frontal method for the matrix from the finite-element method and the parallelized MLFMA for the matrix from the boundary integral method respectively. The programming and numerical experiments of the proposed parallel approach are carried out in the high perfor-mance computing platform CEMS-Liuhui. Numerical experiments demonstrate that FE-BI-MLFMA is efficiently parallelized and its computational capacity is greatly improved without losing accuracy, efficiency, and generality.
Edwards, S.; Reuther, J.; Chattot, J. J.
The objective of this paper is to present a control theory approach for the design of airfoils in the presence of viscous compressible flows. A coupled system of the integral boundary layer and the Euler equations is solved to provide rapid flow simulations. An adjoint approach consistent with the complete coupled state equations is employed to obtain the sensitivities needed to drive a numerical optimization algorithm. Design to a target pressure distribution is demonstrated on an RAE 2822 airfoil at transonic speeds.
The Reduction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method
Tweed, John
2000-01-01
Engineering studies for reducing ducted fan engine noise were conducted using the noise prediction code TBIEM3D. To conduct parametric noise reduction calculations, it was necessary to advance certain theoretical and computational aspects of the boundary integral equation method (BIEM) described in and implemented in TBIEM3D. Also, enhancements and upgrades to TBIEM3D were made for facilitating the code's use in this research and by the aeroacoustics engineering community.
Pai, Ravindra
1991-01-01
A numerical method has been developed for computing the steady state flow about arbitrary shaped three dimensional bodies on or below the free surface using a Boundary Integral Element Method ( Panel Method). The method uses a singularity distribution over the body surface and the free surface. The method can solve for the potential distribution as well as the source density distribution. In this study a constant source distribution is assumed on each panel. The free surface bo...
Fatma Kanca
2013-01-01
This paper investigates the inverse problem of finding a time-dependent diffusion coefficient in a parabolic equation with the periodic boundary and integral overdetermination conditions. Under some assumption on the data, the existence, uniqueness, and continuous dependence on the data of the solution are shown by using the generalized Fourier method. The accuracy and computational efficiency of the proposed method are verified with the help of the numerical examples.
Epitaxial integration of a nanoscale BiFeO3 phase boundary with silicon.
Liang, Wen-I; Peng, Chun-Yen; Huang, Rong; Kuo, Wei-Cheng; Huang, Yen-Chin; Adamo, Carolina; Chen, Yi-Chun; Chang, Li; Juang, Jenh-Yih; Schlom, Darrel G; Chu, Ying-Hao
2016-01-21
The successful integration of the strain-driven nanoscale phase boundary of BiFeO3 onto a silicon substrate is demonstrated with extraordinary ferroelectricity and ferromagnetism. The detailed strain history is delineated through a reciprocal space mapping technique. We have found that a distorted monoclinic phase forms prior to a tetragonal-like phase, a phenomenon which may correlates with the thermal strain induced during the growth process.
Muskhelishvili, N I
2011-01-01
Singular integral equations play important roles in physics and theoretical mechanics, particularly in the areas of elasticity, aerodynamics, and unsteady aerofoil theory. They are highly effective in solving boundary problems occurring in the theory of functions of a complex variable, potential theory, the theory of elasticity, and the theory of fluid mechanics.This high-level treatment by a noted mathematician considers one-dimensional singular integral equations involving Cauchy principal values. Its coverage includes such topics as the Hölder condition, Hilbert and Riemann-Hilbert problem
The Application of a Boundary Integral Equation Method to the Prediction of Ducted Fan Engine Noise
Dunn, M. H.; Tweed, J.; Farassat, F.
1999-01-01
The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally reacting liner on the duct interior. Using potential theory, the BVP is recast as a system of hypersingular boundary integral equations with subsidiary conditions. We describe the integral equation derivation and solution procedure in detail. The development of the computationally efficient ducted fan noise prediction program TBIEM3D, which implements the BIEM, and its utility in conducting parametric noise reduction studies are discussed. Unlike prediction methods based on spinning mode eigenfunction expansions, the BIEM does not require the decomposition of the interior acoustic field into its radial and axial components which, for the liner case, avoids the solution of a difficult complex eigenvalue problem. Numerical spectral studies are presented to illustrate the nexus between the eigenfunction expansion representation and BIEM results. We demonstrate BIEM liner capability by examining radiation patterns for several cases of practical interest.
Conservation laws in field dynamics or why boundary motion is exactly integrable?
Mineev-Weinstein, M B
1995-01-01
An infinite number of conserved quantities in the field dynamics \\phi_t = L\\,U(\\phi) + \\rho for a linear Hermitian (or anti-Hermitian) operator L, an arbitrary function U and a given source \\rho are presented. These integrals of motion are the multipole moments of the potential created by \\phi in the far-field. In the singular limit of a bistable scalar field \\phi = \\phi_{\\pm} (i.e. Ising limit) this theory describes a dissipative boundary motion (such as Stefan or Saffman-Taylor problem that is the continuous limit of the DLA-fractal growth) and can be exactly integrable. These conserved quantities are the polynomial conservation laws attributed to the integrability. The criterion for integrability is the uniqueness of the inverse potential problem's solution.
Maintaining a cognitive map in darkness: the need to fuse boundary knowledge with path integration.
Directory of Open Access Journals (Sweden)
Allen Cheung
Full Text Available Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's "cognitive map", or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark information. In vivo recordings demonstrate that the rodent head direction (HD system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and--we conjecture--necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation
Maintaining a cognitive map in darkness: the need to fuse boundary knowledge with path integration.
Cheung, Allen; Ball, David; Milford, Michael; Wyeth, Gordon; Wiles, Janet
2012-01-01
Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's "cognitive map", or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and--we conjecture--necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and elaborate on
Integrity of the reactor coolant boundary of the European pressurized water reactor (EPR)
Energy Technology Data Exchange (ETDEWEB)
Goetsch, D.; Bieniussa, K.; Schulz, H.; Jalouneix, J.
1997-04-01
This paper is an abstract of the work performed in the frame of the development of the IPSN/GRS approach in view of the EPR conceptual safety features. EPR is a pressurized water reactor which will be based on the experience gained by utilities and designers in France and in Germany. The reactor coolant boundary of a PWR includes the reactor pressure vessel (RPV), those parts of the steam generators (SGs) which contain primary coolant, the pressurizer (PSR), the reactor coolant pumps (RCPs), the main coolant lines (MCLs) with their branches as well as the other connecting pipes and all branching pipes including the second isolation valves. The present work covering the integrity of the reactor coolant boundary is mainly restricted to the integrity of the main coolant lines (MCLs) and reflects the design requirements for the main components of the reactor coolant boundary. In the following the conceptual aspects, i.e. design, manufacture, construction and operation, will be assessed. A main aspect is the definition of break postulates regarding overall safety implications.
A time-domain finite element boundary integration method for ultrasonic nondestructive evaluation.
Shi, Fan; Choi, Wonjae; Skelton, Elizabeth A; Lowe, Michael J S; Craster, Richard V
2014-12-01
A 2-D and 3-D numerical modeling approach for calculating the elastic wave scattering signals from complex stress-free defects is evaluated. In this method, efficient boundary integration across the complex boundary of the defect is coupled with a time-domain finite element (FE) solver. The model is designed to simulate time-domain ultrasonic nondestructive evaluation in bulk media. This approach makes use of the hybrid concept of linking a local numerical model to compute the near-field scattering behavior and theoretical mathematical formulas for postprocessing to calculate the received signals. It minimizes the number of monitoring signals from the FE calculation so that the computation effort in postprocessing decreases significantly. In addition, by neglecting the conventional regular monitoring box, the region for FE calculation can be made smaller. In this paper, the boundary integral method is implemented in a commercial FE code, and it is validated by comparing the scattering signals with results from corresponding full FE models. The coupled method is then implemented in real inspection scenarios in both 2-D and 3-D, and the accuracy and the efficiency are demonstrated. The limitations of the proposed model and future works are also discussed. PMID:25474780
Anti-Periodic Boundary Conditions in Supersymmetric DLCQ
Pinsky, S.; Trittmann, U.
2000-01-01
It is of considerable importance to have a numerical method for solving supersymmetric theories that can support a non-zero central charge. The central charge in supersymmetric theories is in general a boundary integral and therefore vanishes when one uses periodic boundary conditions. One is therefore prevented from studying BPS states in the standard supersymmetric formulation of DLCQ (SDLCQ). We present a novel formulation of SDLCQ where the fields satisfy anti-periodic boundary conditions...
Kitanine, N; Niccoli, G
2014-01-01
We solve the longstanding problem to define a functional characterization of the spectrum of the transfer matrix associated to the most general spin-1/2 representations of the 6-vertex reflection algebra for general inhomogeneous chains. The corresponding homogeneous limit reproduces the spectrum of the Hamiltonian of the spin-1/2 open XXZ and XXX quantum chains with the most general integrable boundaries. The spectrum is characterized by a second order finite difference functional equation of Baxter type with an inhomogeneous term which vanishes only for some special but yet interesting non-diagonal boundary conditions. This functional equation is shown to be equivalent to the known separation of variable (SOV) representation hence proving that it defines a complete characterization of the transfer matrix spectrum. The polynomial character of the Q-function allows us then to show that a finite system of equations of generalized Bethe type can be similarly used to describe the complete transfer matrix spectru...
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper investigates the existence and multiplicity of nonnegative solutions to a singular nonlinear boundary value problem of second order differential equations with integral boundary conditions in a Banach space. The arguments are based on the construction of a nonempty bounded open convex set and fixed point index theory. Our nonlinearity possesses singularity and first derivative which makes it different with that in [10].
Om, D.; Childs, M. E.
1983-01-01
An approximate integral viscous-inviscid interaction method is presented for calculating the development of a turbulent boundary layer subjected to a normal shock wave induced adverse pressure gradient in an internal axisymmetric flow. The inflow conditions and the downstream pressure are provided for the computation. In the supersonic region of shock pressure rise, the Prandtl-Meyer function is used to couple the viscous and inviscid flows. An analytical model for the coupling process is postulated and appropriate equations are defined. Downstream of the sonic point, one-dimensional inviscid flow is assumed for coupling with the viscous flow. The turbulent boundary layer is calculated using Green's integral lag-entrainment method. Comparisons of the solutions with the experimental data are made for interactions which are unseparated, near separation and separated. For comparison purposes, solutions to the time-dependent, mass-averaged, Navier-Stokes equations incorporating a two-equation, Wilcox-Rubesin turbulence model are also shown. The computed results from the integral method show good agreement with experimental data for unseparated interactions and reasonable agreement with the trend of the viscous effects when the interaction becomes increasingly separated.
A Fast Spectral Galerkin Method for Hypersingular Boundary Integral Equations in Potential Theory
Energy Technology Data Exchange (ETDEWEB)
Nintcheu Fata, Sylvain [ORNL; Gray, Leonard J [ORNL
2009-01-01
This research is focused on the development of a fast spectral method to accelerate the solution of three-dimensional hypersingular boundary integral equations of potential theory. Based on a Galerkin approximation, the Fast Fourier Transform and local interpolation operators, the proposed method is a generalization of the Precorrected-FFT technique to deal with double-layer potential kernels, hypersingular kernels and higher-order basis functions. Numerical examples utilizing piecewise linear shape functions are included to illustrate the performance of the method.
TIME–HARMONIC BEHAVIOUR OF CRACKED PIEZOELECTRIC SOLID BY BOUNDARY INTEGRAL EQUATION METHOD
Directory of Open Access Journals (Sweden)
Rangelov Tsviatko
2014-03-01
Full Text Available Anti-plane cracked functionally graded finite piezoelectric solid under time-harmonic elecromechanical load is studied by a non-hypersingular traction boundary integral equation method (BIEM. Exponentially varying material properties are considered. Numerical solutions are obtained by using Mathematica. The dependance of the intensity factors (IF - mechanical stress intensity factor (SIF and electrical field intensity factor (FIF on the inhomogeneous material parameters, on the type and frequency of the dynamic load and on the crack position are analyzed by numerical illustrative examples
Pinckney, John
2010-01-01
With the advent of high speed computing Monte Carlo ray tracing techniques has become the preferred method for evaluating spacecraft orbital heats. Monte Carlo has its greatest advantage where there are many interacting surfaces. However Monte Carlo programs are specialized programs that suffer from some inaccuracy, long calculation times and high purchase cost. A general orbital heating integral is presented here that is accurate, fast and runs on MathCad, a generally available engineering mathematics program. The integral is easy to read, understand and alter. The integral can be applied to unshaded primitive surfaces at any orientation. The method is limited to direct heating calculations. This integral formulation can be used for quick orbit evaluations and spot checking Monte Carlo results.
Institute of Scientific and Technical Information of China (English)
龙述尧; 熊渊博
2004-01-01
The meshless local boundary integral equation method is a currently developed numerical method, which combines the advantageous features of Galerkin finite element method(GFEM), boundary element method(BEM) and element free Galerkin method(EFGM), and is a truly meshless method possessing wide prospects in engineering applications.The companion solution and all the other formulas required in the meshless local boundary integral equation for a thin plate were presented, in order to make this method apply to solve the thin plate problem.
Young, D. P.; Woo, A. C.; Bussoletti, J. E.; Johnson, F. T.
1986-01-01
A general method is developed combining fast direct methods and boundary integral equation methods to solve Poisson's equation on irregular exterior regions. The method requires O(N log N) operations where N is the number of grid points. Error estimates are given that hold for regions with corners and other boundary irregularities. Computational results are given in the context of computational aerodynamics for a two-dimensional lifting airfoil. Solutions of boundary integral equations for lifting and nonlifting aerodynamic configurations using preconditioned conjugate gradient are examined for varying degrees of thinness.
Boundary integral equation methods and numerical solutions thin plates on an elastic foundation
Constanda, Christian; Hamill, William
2016-01-01
This book presents and explains a general, efficient, and elegant method for solving the Dirichlet, Neumann, and Robin boundary value problems for the extensional deformation of a thin plate on an elastic foundation. The solutions of these problems are obtained both analytically—by means of direct and indirect boundary integral equation methods (BIEMs)—and numerically, through the application of a boundary element technique. The text discusses the methodology for constructing a BIEM, deriving all the attending mathematical properties with full rigor. The model investigated in the book can serve as a template for the study of any linear elliptic two-dimensional problem with constant coefficients. The representation of the solution in terms of single-layer and double-layer potentials is pivotal in the development of a BIEM, which, in turn, forms the basis for the second part of the book, where approximate solutions are computed with a high degree of accuracy. The book is intended for graduate students and r...
Integration of Image Data for Refining Building Boundaries Derived from Point Clouds
Perera, S. N.; Hetti Arachchige, N.; Schneider, D.
2014-08-01
Geometrically and topologically correct 3D building models are required to satisfy with new demands such as 3D cadastre, map updating, and decision making. More attention on building reconstruction has been paid using Airborne Laser Scanning (ALS) point cloud data. The planimetric accuracy of roof outlines, including step-edges is questionable in building models derived from only point clouds. This paper presents a new approach for the detection of accurate building boundaries by merging point clouds acquired by ALS and aerial photographs. It comprises two major parts: reconstruction of initial roof models from point clouds only, and refinement of their boundaries. A shortest closed circle (graph) analysis method is employed to generate building models in the first step. Having the advantages of high reliability, this method provides reconstruction without prior knowledge of primitive building types even when complex height jumps and various types of building roof are available. The accurate position of boundaries of the initial models is determined by the integration of the edges extracted from aerial photographs. In this process, scene constraints defined based on the initial roof models are introduced as the initial roof models are representing explicit unambiguous geometries about the scene. Experiments were conducted using the ISPRS benchmark test data. Based on test results, we show that the proposed approach can reconstruct 3D building models with higher geometrical (planimetry and vertical) and topological accuracy.
Boundary integral equation method for added mass in arrays of cylinders
International Nuclear Information System (INIS)
The dynamic behavior of a group of cylinders in fluid, such as heat exchanger tubes and nuclear fuel assemblies, is strongly influenced by the surrounding fluid. Although, the added mass of such clusters of cylinders has been studied by many researchers with various analytical methods and numerical methods, no attempt has been made so far to analyze these problems by the Boundary Integral Equation Method (BIEM). This paper presents a BIEM model simulating the added mass arising when clusters of cylinders vibrate in an inviscid and incompressible fluid. In this model, perturbed fluid pressure is described by a two- dimensional Laplace equation. The primary advantage of this approach compared with other numerical methods, e.g., the finite element method (FEM), is that the integration and discretization of the model are only needed on boundary rather than in whole domain. Therefore, the proposed approach is much more economical than the finite element method. Various numerical examples are subsequently presented in this paper to illustrate the methodology and to demonstrate its accuracy
Directory of Open Access Journals (Sweden)
S. Bonafede
2007-01-01
Full Text Available We study qualitative properties of minimizers for a class of integral functionals, defined in a weighted space. In particular we obtain Hölder regularity up to the boundary for the minimizers of an integral functional of high order by using an interior local regularity result and a modified Moser method with special test function.
Energy Technology Data Exchange (ETDEWEB)
Bammann, Douglas J.; Johnson, G. C. (University of California, Berkeley, CA); Marin, Esteban B.; Regueiro, Richard A. (University of Colorado, Boulder, CO)
2006-01-01
In this report we present the formulation of the physically-based Evolving Microstructural Model of Inelasticity (EMMI) . The specific version of the model treated here describes the plasticity and isotropic damage of metals as being currently applied to model the ductile failure process in structural components of the W80 program . The formulation of the EMMI constitutive equations is framed in the context of the large deformation kinematics of solids and the thermodynamics of internal state variables . This formulation is focused first on developing the plasticity equations in both the relaxed (unloaded) and current configurations. The equations in the current configuration, expressed in non-dimensional form, are used to devise the identification procedure for the plasticity parameters. The model is then extended to include a porosity-based isotropic damage state variable to describe the progressive deterioration of the strength and mechanical properties of metals induced by deformation . The numerical treatment of these coupled plasticity-damage constitutive equations is explained in detail. A number of examples are solved to validate the numerical implementation of the model.
De Hoop, A.T.; Abubakar, A.; Habashy, T.M.
2009-01-01
The contrast-source stress-velocity integral-equation formulation of three-dimensional time-domain elastodynamic scattering problems is discussed. A novel feature of the formulation is a tensor partitioning of the relevant dynamic stress and the contrast source volume density of deformation rate. Th
Multigrid solution of a path integral formulation for the hydrogen atom
Bai, D
2004-01-01
An efficient multigrid Monte-Carlo algorithm for calculating the ground state of the hydrogen atom using path integral is presented. The algorithm uses a unigrid approach. The action integral near r=0 is modified so that the correct values of observables are obtained. It is demonstrated that the critical slow down (CSD) is eliminated. Finally, the algorithm is compared to the staging algorithm.
Liou, Luen-Woei; Ray, Asok
1991-01-01
A state feedback control law for integrated communication and control systems (ICCS) is formulated by using the dynamic programming and optimality principle on a finite-time horizon. The control law is derived on the basis of a stochastic model of the plant which is augmented in state space to allow for the effects of randomly varying delays in the feedback loop. A numerical procedure for synthesizing the control parameters is then presented, and the performance of the control law is evaluated by simulating the flight dynamics model of an advanced aircraft. Finally, recommendations for future work are made.
Advances in the study of boundary value problems for nonlinear integrable PDEs
Pelloni, Beatrice
2015-02-01
In this review I summarize some of the most significant advances of the last decade in the analysis and solution of boundary value problems for integrable partial differential equations (PDEs) in two independent variables. These equations arise widely in mathematical physics, and in order to model realistic applications, it is essential to consider bounded domain and inhomogeneous boundary conditions. I focus specifically on a general and widely applicable approach, usually referred to as the unified transform or Fokas transform, that provides a substantial generalization of the classical inverse scattering transform. This approach preserves the conceptual efficiency and aesthetic appeal of the more classical transform approaches, but presents a distinctive and important difference. While the inverse scattering transform follows the ‘separation of variables’ philosophy, albeit in a nonlinear setting, the unified transform is based on the idea of synthesis, rather than separation, of variables. I will outline the main ideas in the case of linear evolution equations, and then illustrate their generalization to certain nonlinear cases of particular significance.
Advanced Amine Solvent Formulations and Process Integration for Near-Term CO2 Capture Success
Energy Technology Data Exchange (ETDEWEB)
Fisher, Kevin S.; Searcy, Katherine; Rochelle, Gary T.; Ziaii, Sepideh; Schubert, Craig
2007-06-28
This Phase I SBIR project investigated the economic and technical feasibility of advanced amine scrubbing systems for post-combustion CO2 capture at coal-fired power plants. Numerous combinations of advanced solvent formulations and process configurations were screened for energy requirements, and three cases were selected for detailed analysis: a monoethanolamine (MEA) base case and two “advanced” cases: an MEA/Piperazine (PZ) case, and a methyldiethanolamine (MDEA) / PZ case. The MEA/PZ and MDEA/PZ cases employed an advanced “double matrix” stripper configuration. The basis for calculations was a model plant with a gross capacity of 500 MWe. Results indicated that CO2 capture increased the base cost of electricity from 5 cents/kWh to 10.7 c/kWh for the MEA base case, 10.1 c/kWh for the MEA / PZ double matrix, and 9.7 c/kWh for the MDEA / PZ double matrix. The corresponding cost per metric tonne CO2 avoided was 67.20 $/tonne CO2, 60.19 $/tonne CO2, and 55.05 $/tonne CO2, respectively. Derated capacities, including base plant auxiliary load of 29 MWe, were 339 MWe for the base case, 356 MWe for the MEA/PZ double matrix, and 378 MWe for the MDEA / PZ double matrix. When compared to the base case, systems employing advanced solvent formulations and process configurations were estimated to reduce reboiler steam requirements by 20 to 44%, to reduce derating due to CO2 capture by 13 to 30%, and to reduce the cost of CO2 avoided by 10 to 18%. These results demonstrate the potential for significant improvements in the overall economics of CO2 capture via advanced solvent formulations and process configurations.
Connectivity as an alternative to boundary integral equations: Construction of bases
Herrera, Ismael; Sabina, Federico J.
1978-01-01
In previous papers Herrera developed a theory of connectivity that is applicable to the problem of connecting solutions defined in different regions, which occurs when solving partial differential equations and many problems of mechanics. In this paper we explain how complete connectivity conditions can be used to replace boundary integral equations in many situations. We show that completeness is satisfied not only in steady-state problems such as potential, reduced wave equation and static and quasi-static elasticity, but also in time-dependent problems such as heat and wave equations and dynamical elasticity. A method to obtain bases of connectivity conditions, which are independent of the regions considered, is also presented. PMID:16592522
Yang, Zhiguo; Rong, Zhijian; Wang, Bo; Zhang, Baile
2015-01-01
In this paper, we present an efficient spectral-element method (SEM) for solving general two-dimensional Helmholtz equations in anisotropic media, with particular applications in accurate simulation of polygonal invisibility cloaks, concentrators and circular rotators arisen from the field of transformation electromagnetics (TE). In practice, we adopt a transparent boundary condition (TBC) characterized by the Dirichlet-to-Neumann (DtN) map to reduce wave propagation in an unbounded domain to a bounded domain. We then introduce a semi-analytic technique to integrate the global TBC with local curvilinear elements seamlessly, which is accomplished by using a novel elemental mapping and analytic formulas for evaluating global Fourier coefficients on spectral-element grids exactly. From the perspective of TE, an invisibility cloak is devised by a singular coordinate transformation of Maxwell's equations that leads to anisotropic materials coating the cloaked region to render any object inside invisible to observe...
A Family of Well-Clear Boundary Models for the Integration of UAS in the NAS
Munoz, Cesar A.; Narkawicz, Anthony; Chamberlain, James; Consiglio, Maria; Upchurch, Jason
2014-01-01
The FAA-sponsored Sense and Avoid Workshop for Unmanned Aircraft Systems (UAS) defines the concept of sense and avoid for remote pilots as "the capability of a UAS to remain well clear from and avoid collisions with other airborne traffic." Hence, a rigorous definition of well clear is fundamental to any separation assurance concept for the integration of UAS into civil airspace. This paper presents a family of well-clear boundary models based on the TCAS II Resolution Advisory logic. For these models, algorithms that predict well-clear violations along aircraft current trajectories are provided. These algorithms are analogous to conflict detection algorithms but instead of predicting loss of separation, they predict whether well-clear violations will occur during a given lookahead time interval. Analytical techniques are used to study the properties and relationships satisfied by the models.
Boundary integral equation method calculations of surface regression effects in flame spreading
Altenkirch, R. A.; Rezayat, M.; Eichhorn, R.; Rizzo, F. J.
1982-01-01
A solid-phase conduction problem that is a modified version of one that has been treated previously in the literature and is applicable to flame spreading over a pyrolyzing fuel is solved using a boundary integral equation (BIE) method. Results are compared to surface temperature measurements that can be found in the literature. In addition, the heat conducted through the solid forward of the flame, the heat transfer responsible for sustaining the flame, is also computed in terms of the Peclet number based on a heated layer depth using the BIE method and approximate methods based on asymptotic expansions. Agreement between computed and experimental results is quite good as is agreement between the BIE and the approximate results.
Directory of Open Access Journals (Sweden)
Jingfu Jin
2012-04-01
Full Text Available This article shows the existence of a positive solution for the singular fractional differential equation with integral boundary condition $$displaylines{ {}^C!D^p u(t=lambda h(tf(t, u(t, quad tin(0, 1, cr u(0-au(1=int^1_0g_0(su(s,ds, cr u'(0-b,{}^C!D^qu(1=int^1_0g_1(su(s,ds, cr u''(0=u'''(0=dots =u^{(n-1}(0=0, }$$ where $lambda $ is a parameter and the nonlinear term is allowed to be singular at $t=0, 1$ and $u=0$. We obtain an explicit interval for $lambda$ such that for any $lambda$ in this interval, existence of at least one positive solution is guaranteed. Our approach is by a fixed point theory in cones combined with linear operator theory.
Bhattacharya, Amitabh
2013-11-01
An efficient algorithm for simulating Stokes flow around particles is presented here, in which a second order Finite Difference method (FDM) is coupled to a Boundary Integral method (BIM). This method utilizes the strong points of FDM (i.e. localized stencil) and BIM (i.e. accurate representation of particle surface). Specifically, in each iteration, the flow field away from the particles is solved on a Cartesian FDM grid, while the traction on the particle surface (given the the velocity of the particle) is solved using BIM. The two schemes are coupled by matching the solution in an intermediate region between the particle and surrounding fluid. We validate this method by solving for flow around an array of cylinders, and find good agreement with Hasimoto's (J. Fluid Mech. 1959) analytical results.
Furukawa, Hideaki; Miyazawa, Takaya; Wada, Naoya; Harai, Hiroaki
2014-01-13
Optical packet and circuit integrated (OPCI) networks provide both optical packet switching (OPS) and optical circuit switching (OCS) links on the same physical infrastructure using a wavelength multiplexing technique in order to deal with best-effort services and quality-guaranteed services. To immediately respond to changes in user demand for OPS and OCS links, OPCI networks should dynamically adjust the amount of wavelength resources for each link. We propose a resource-adjustable hybrid optical packet/circuit switch and transponder. We also verify that distributed control of resource adjustments can be applied to the OPCI ring network testbed we developed. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we demonstrate that automatically allocating a shared resource and moving the wavelength resource boundary between OPS and OCS links can be successfully executed, depending on the number of optical paths in use.
Institute of Scientific and Technical Information of China (English)
PAN Zhong-liang; CHEN Ling
2009-01-01
The integrated circuit chip with high performance has a high sensitivity to the defects in manufacturing environments. When there are defects on a wafer, the defects may lead to the degradation of chip performance. It is necessary to design effective detection approaches for the defects in order to ensure the reliability of wafer. In this paper, a new method based on image boundary extraction is presented for the detection of defects on a wafer. The method uses island model genetic algorithms to perform the segmentation of wafer images, and gets the optimal threshold values. The island model genetic algorithm uses two distinct subpopulations, it is a coarse grain parallel model. The individuals migration can occur between the two subpopulations to share genetic materials. A lot of experimental results show that the defect detection method proposed in this paper can obtain the features of defects effectively.
Prediction of metallic nano-optical trapping forces by finite element-boundary integral method.
Pan, Xiao-Min; Xu, Kai-Jiang; Yang, Ming-Lin; Sheng, Xin-Qing
2015-03-01
The hybrid of finite element and boundary integral (FE-BI) method is employed to predict nano-optical trapping forces of arbitrarily shaped metallic nanostructures. A preconditioning strategy is proposed to improve the convergence of the iterative solution. Skeletonization is employed to speed up the design and optimization where iteration has to be repeated for each beam configuration. The radiation pressure force (RPF) is computed by vector flux of the Maxwell's stress tensor. Numerical simulations are performed to validate the developed method in analyzing the plasmonic effects as well as the optical trapping forces. It is shown that the proposed method is capable of predicting the trapping forces of complex metallic nanostructures accurately and efficiently.
Directory of Open Access Journals (Sweden)
Mojtaba Biglar
2014-01-01
Full Text Available This study addresses new formulation for active vibration control of plates by optimal locations of attached piezotransducers. Free vibrations are solved by Rayleigh-Ritz and transient by assumed modes methods. Optimal orientations of patches are determined by spatial controllability/observability, as well as residual modes to reduce spillover. These criteria are used to achieve optimal fitness function defined for genetic algorithm to find optimal locations. To control vibrations, negative velocity feedback control is designed. Results indicate that, by locating piezopatches at optimal positions, depreciation rate increases and amplitudes of vibrations reduce effectively. The effect of number of piezodevices is analyzed.
Directory of Open Access Journals (Sweden)
Alsaedi Ahmed
2009-01-01
Full Text Available A generalized quasilinearization technique is developed to obtain a sequence of approximate solutions converging monotonically and quadratically to a unique solution of a boundary value problem involving Duffing type nonlinear integro-differential equation with integral boundary conditions. The convergence of order for the sequence of iterates is also established. It is found that the work presented in this paper not only produces new results but also yields several old results in certain limits.
International Nuclear Information System (INIS)
The formalism of Martin, Siggia and Rose is utilized to write a functional-integral representation for generating functionals in plasma transport theory, following Nakayama and Dawson. Parallel treatments of Navier-Stokes turbulence (attempted by Rosen) and of critical dynamics, by Kawasaki, are compared to illustrate the application of common field-theory techniques, such as the effective action. Quasi-classical methods for functional integrals are discussed
跨共振的周期-积分边值问题%Periodic-Integral Boundary Value Problems across Resonance
Institute of Scientific and Technical Information of China (English)
宋新; 杨雪
2011-01-01
研究二阶微分方程周期-积分边值问题,应用最优控制理论给出了跨多个共振情形下的二阶微分方程周期-积分边值问题唯一可解的最优条件.%The periodic-integral boundary value problems for second order differential equations were considered. On the basis of optimal control theory method, we gave an optimal condition of the unique solvability to the periodic-integral boundary value problems for second order differential equations across multiple resonance.
Directory of Open Access Journals (Sweden)
Mooranian A
2014-09-01
Full Text Available Armin Mooranian,1 Rebecca Negrulj,1 Nigel Chen-Tan,2 Gerald F Watts,3 Frank Arfuso,4 Hani Al-Salami11Biotechnology and Drug Development Research Laboratory, School of Pharmacy, Curtin Health Innovation Research Institute, Biosciences Research Precinct, Curtin University, 2Faculty of Science and Engineering, Curtin University, 3School of Medicine and Pharmacology, Royal Perth Hospital, University of Western Australia, 4School of Biomedical Science, Curtin Health Innovation Research Institute, Biosciences Research Precinct, Curtin University, Perth, AustraliaAbstract: The authors have previously designed, developed, and characterized a novel microencapsulated formulation as a platform for the targeted delivery of therapeutics in an animal model of type 2 diabetes, using the drug probucol (PB. The aim of this study was to optimize PB microcapsules by incorporating the bile acid deoxycholic acid (DCA, which has good permeation-enhancing properties, and to examine its effect on microcapsules’ morphology, rheology, structural and surface characteristics, and excipients’ chemical and thermal compatibilities. Microencapsulation was carried out using a BÜCHI-based microencapsulating system established in the authors’ laboratory. Using the polymer sodium alginate (SA, two microencapsulated formulations were prepared: PB-SA (control and PB-DCA-SA (test at a constant ratio (1:30 and 1:3:30, respectively. Complete characterization of the microcapsules was carried out. The incorporation of DCA resulted in better structural and surface characteristics, uniform morphology, and stable chemical and thermal profiles, while size and rheological parameters remained similar to control. In addition, PB-DCA-SA microcapsules showed good excipients’ compatibilities, which were supported by data from differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray studies, suggesting
On the determination of phase boundaries via thermodynamic integration across coexistence regions
Energy Technology Data Exchange (ETDEWEB)
Abramo, Maria Concetta, E-mail: mcabramo@unime.it; Caccamo, Carlo, E-mail: caccamo@unime.it; Costa, Dino, E-mail: dcosta@unime.it; Giaquinta, Paolo V., E-mail: paolo.giaquinta@unime.it; Malescio, Gianpietro, E-mail: malescio@unime.it; Munaò, Gianmarco, E-mail: gmunao@unime.it [Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina (Italy); Prestipino, Santi, E-mail: sprestipino@unime.it [Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina (Italy); CNR-IPCF, Viale F. Stagno d’Alcontres 37, I-98158 Messina (Italy)
2015-06-07
Specialized Monte Carlo methods are nowadays routinely employed, in combination with thermodynamic integration (TI), to locate phase boundaries of classical many-particle systems. This is especially useful for the fluid-solid transition, where a critical point does not exist and both phases may notoriously go deeply metastable. Using the Lennard-Jones model for demonstration, we hereby investigate on the alternate possibility of tracing reasonably accurate transition lines directly by integrating the pressure equation of state computed in a canonical-ensemble simulation with local moves. The recourse to this method would become a necessity when the stable crystal structure is not known. We show that, rather counterintuitively, metastability problems can be alleviated by reducing (rather than increasing) the size of the system. In particular, the location of liquid-vapor coexistence can exactly be predicted by just TI. On the contrary, TI badly fails in the solid-liquid region, where a better assessment (to within 10% accuracy) of the coexistence pressure can be made by following the expansion, until melting, of the defective solid which has previously emerged from the decay of the metastable liquid.
Preconditioning first and second kind integral formulations of the capacitance problem
Energy Technology Data Exchange (ETDEWEB)
Tausch, J.; White, J.
1996-12-31
Engineering programs which compute electrostatic capacitances for complicated arrangements of conductors commonly set up the electrostatic potential u as a superposition of surface carges {sigma} u(x) = {integral}{sub s}G(x, y){sigma}(y) dS(y). Where G(x, y) = {1/4}{pi}{vert_bar}x - y{vert_bar} is the Green`s function for the Laplacian in the three-space. For a specified potential on the conductor surface(s) S, this approach leads to an integral equation of the first kind on S for the charge density {sigma}. The capacitance is the net-charge on the conductors and is given by the surface integral of {sigma}.
Bracken, Paul
An intrinsic version of the integrability theorem for the classical Backlund theorem is presented. It is characterized by a one-form which can be put in the form of a Riccati system. It is shown how this system can be linearized. Based on this, a procedure for generating an infinite number of conservation laws is given.
Institute of Scientific and Technical Information of China (English)
ZHAO Ming-hao; LI Dong-xia; SHEN Ya-peng
2005-01-01
The integral-differential equations for three-dimensional planar interfacial cracks of arbitrary shape in transversely isotropic bimaterials were derived by virtue of the Somigliana identity and the fundamental solutions, in which the displacement discontinuities across the crack faces are the unknowns to be determined. The interface is parallel to both the planes of isotropy. The singular behaviors of displacement and stress near the crack border were analyzed and the stress singularity indexes were obtained by integral equation method. The stress intensity factors were expressed in terms of the displacement discontinuities. In the non-oscillatory case, the hyper-singular boundary integral-differential equations were reduced to hyper-singular boundary integral equations similar to those of homogeneously isotropie materials.
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2016-01-01
A new technique for estimating the impedance frequency bandwidth of electrically small antennas loaded with magneto-dielectric material from a single-frequency simulation in a surface integral equation solver is presented. The estimate is based on the inverse of the radiation Q computed using newly...... derived expressions for the stored energy and the radiated power of arbitrary coupled electric and magnetic currents in free space....
Parsonage, Catherine; Fadnes, Petter Frost; Taylor, James
2007-01-01
Academic study has become a more significant part of a conservatoire education in recent times, but it has not always informed performance as effectively as it might. There is a need for further development of an academic curriculum that is specifically relevant to performers, in which the links between theory and practice are made explicit rather than expecting students to construct these for themselves. This article reports on research into the integration of theory and practice at Leeds Co...
Directory of Open Access Journals (Sweden)
Nittaya Pongarm
2013-01-01
Full Text Available This paper studies sufficient conditions for the existence of solutions to the problem of sequential derivatives of nonlinear q-difference equations with three-point q-integral boundary conditions. Our results are concerned with several quantum numbers of derivatives and integrals. By using Banach's contraction mapping, Krasnoselskii's fixed-point theorem, and Leray-Schauder degree theory, some new existence results are obtained. Two examples illustrate our results.
Friedrich, Johannes; Fetzer, Ingo; Cornell, Sarah
2016-04-01
The planetary boundaries framework is an approach to global sustainability that emphasises non-linear threshold behavior in anthropogenically perturbed Earth system processes. However, knowledge about the characteristics and positions of thresholds, and the scope for management of the boundaries is not well established. Global integrated models can help to improve this understanding, by reflecting the complex feedbacks between human and environmental systems. This study analyses the current state of integrated models with regard to the main processes identified as 'critical Earth system processes' in the planetary boundaries framework, and identifies gaps and suggests priorities for future improvements. Our approach involves creating a common ontology of model descriptions, and performing a network analysis on the state of system integration in models. The distinct clusters of specific biophysical and social-economic systems obviously has enabled progress in those specific areas of global change, but it now constrains analysis of important human-driven Earth system dynamics. The modeling process therefore has to be improved through technical integration, scientific gap-filling, and also changes in scientific institutional dynamics. Combined, this can advance model potentials that may help us to find sustainable pathways within planetary boundaries.
Directory of Open Access Journals (Sweden)
Chatthai Thaiprayoon
2014-01-01
Full Text Available By developing a new comparison result and using the monotone iterative technique, we are able to obtain existence of minimal and maximal solutions of periodic boundary value problems for first-order impulsive functional integrodifferential equations with integral-jump conditions. An example is also given to illustrate our results.
Chang, Ruinan
The ability to have a good understanding of and to manipulate electromagnetic elds has been increasingly important for many hardware technologies. There is a strong need for advanced numeric algorithms that yield fast and accuracy controllable solvers for electromagnetic and micromagnetic simulations. The first part of the dissertation presents methods constituting the core of the high-performance simulator FastMag. FastMag derives its high speed from three aspects. First, it leverages the state-of-the-art graphics processing unit computational architectures, which can be hundreds of times faster than a single central processing unit. Moreover, ecient and and accurate implementations of numeric quadrature was invoked. Thirdly, we provide an analytic method for Jacobian vector products. Some advanced features are provided in FastMag. Quadratic basis functions are used to provide better accuracy. Hexahedral elements were also implemented because they are more accurate, consume less memory. The second part of the dissertation is devoted to electromagnetic scattering problems. We developed new algorithms that signicantly improved the traditional methods. First of all, potential volume integral equations were implemented, where the potential quantities (vector and scalar potential). Another important contribution of this disertation is quadrilateral barycentric basis functions (QBBFs). The QBBFs can serve as a fundamental block for primary basis functions (PBFs) and dual basis functions (DBFs). The PBFs and DBFs, when applied in combination into traditional electric and magnetic eld integral equations (EFIE and MFIE), give rise to accurate and robust results. Moreover, the DBFs make the famous Calderon preconditioner multiplicative.
Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope
Kotko, P.; Serino, M.; Stasto, A. M.
2016-08-01
One of the methods to calculate tree-level multi-gluon scattering amplitudes is to use the Berends-Giele recursion relation involving off-shell currents or off-shell amplitudes, if working in the light cone gauge. As shown in recent works using the light-front perturbation theory, solutions to these recursions naturally collapse into gauge invariant and gauge-dependent components, at least for some helicity configurations. In this work, we show that such structure is helicity independent and emerges from analytic properties of matrix elements of Wilson line operators, where the slope of the straight gauge path is shifted in a certain complex direction. This is similar to the procedure leading to the Britto-Cachazo-Feng-Witten (BCFW) recursion, however we apply a complex shift to the Wilson line slope instead of the external momenta. While in the original BCFW procedure the boundary integrals over the complex shift vanish for certain deformations, here they are non-zero and are equal to the off-shell amplitudes. The main result can thus be summarized as follows: we derive a decomposition of a helicity-fixed off-shell current into gauge invariant component given by a matrix element of a straight Wilson line plus a reminder given by a sum of products of gauge invariant and gauge dependent quantities. We give several examples realizing this relation, including the five-point next-to-MHV helicity configuration.
A hybrid boundary-integral/thin-sheet equation for subduction modelling
Xu, Bingrui; Ribe, Neil M.
2016-09-01
Subducting oceanic lithosphere is an example of a thin sheet-like object whose characteristic lateral dimension greatly exceeds its thickness. Here we exploit this property to derive a new hybrid boundary-integral/thin sheet (BITS) representation of subduction that combines in a single equation all the forces acting on the sheet: gravity, internal resistance to bending and stretching, and the tractions exerted by the ambient mantle. For simplicity, we limit ourselves to 2-D. We solve the BITS equations using a discrete Lagrangian approach in which the sheet is represented by a set of vertices connected by edges. Instantaneous solutions for the sinking speed of a slab attached to a trailing flat sheet obey a scaling law of the form V/VStokes = fct(St), where VStokes is a characteristic Stokes sinking speed and St is the sheet's flexural stiffness. Time-dependent solutions for the evolution of the sheet's shape and thickness show that these are controlled by the viscosity ratio between the sheet and its surroundings. An important advantage of the BITS approach is the possibility of generalizing the sheet's rheology, either to a viscosity that varies along the sheet or to a non-Newtonian shear-thinning rheology.
Energy Technology Data Exchange (ETDEWEB)
T.F. Eibert; J.L. Volakis; Y.E. Erdemli
2002-03-03
Hybrid finite element (FE)--boundary integral (BI) analysis of infinite periodic arrays is extended to include planar multilayered Green's functions. In this manner, a portion of the volumetric dielectric region can be modeled via the finite element method whereas uniform multilayered regions can be modeled using a multilayered Green's function. As such, thick uniform substrates can be modeled without loss of efficiency and accuracy. The multilayered Green's function is analytically computed in the spectral domain and the resulting BI matrix-vector products are evaluated via the fast spectral domain algorithm (FSDA). As a result, the computational cost of the matrix-vector products is kept at O(N). Furthermore, the number of Floquet modes in the expansion are kept very few by placing the BI surfaces within the computational unit cell. Examples of frequency selective surface (FSS) arrays are analyzed with this method to demonstrate the accuracy and capability of the approach. One example involves complicated multilayered substrates above and below an inhomogeneous filter element and the other is an optical ring-slot array on a substrate several hundred wavelengths in thickness. Comparisons with measurements are included.
Yuan, Zhengwen; Xiao, Hong; Xie, Hongbiao
2014-02-01
Precise strip-shape control theory is significant to improve rolled strip quality, and roll flattening theory is a primary part of the strip-shape theory. To improve the accuracy of roll flattening calculation based on semi-infinite body model, a new and more accurate roll flattening model is proposed in this paper, which is derived based on boundary integral equation method. The displacement fields of the finite length semi-infinite body on left and right sides are simulated by using finite element method (FEM) and displacement decay functions on left and right sides are established. Based on the new roll flattening model, a new 4Hi mill deformation model is established and verified by FEM. The new model is compared with Foppl formula and semi-infinite body model in different strip width, roll shifting value and bending force. The results show that the pressure and flattening between rolls calculated by the new model are more precise than other two models, especially near the two roll barrel edges.
Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope
Kotko, Piotr; Stasto, Anna M
2016-01-01
One of the methods to calculate tree-level multi-gluon scattering amplitudes is to use the Berends-Giele recursion relation involving off-shell currents or off-shell amplitudes. As shown in recent works using for example the light-front perturbation theory, solutions to these recursions naturally collapse into gauge invariant and gauge-dependent components, at least for some helicity configurations. In this work, we show that such structure is helicity independent and emerges from analytic properties of matrix elements of Wilson line operators, where the slope of the straight gauge path is shifted in certain complex direction. This is similar to the procedure leading to the Britto-Cachazo-Feng-Witten (BCFW) recursion, however we apply a complex shift of the Wilson line slope instead of shifting an external momentum. While the boundary integrals over the complex shift in BCFW procedure vanish for certain deformations, here they are non-zero and are equal to the off-shell amplitudes.
The influence of a scaled boundary response on integral system transient behavior
International Nuclear Information System (INIS)
Scaling relationships associated with the thermal-hydraulic response of a closed-loop system are applied to a calculational assessment of a feed-and-bleed recovery in a nuclear reactor integral effects test. The analysis demonstrates both the influence of scale on the system response and the ability of the thermal-hydraulics code to represent those effects. The qualitative response of the fluid is shown to be coupled to the behavior of the bounding walls through the energy equation. The results of the analysis described in this paper influence the determination of computer code applicability. The sensitivity of the code response to scaling variations introduced in the analysis is found to be appropriate with respect to scaling criteria determined from the scaling literature. Differences in the system response associated with different scaling criteria are found to be plausible and easily explained using well-known principles of heat transfer. Therefore, it is concluded that RELAP5/MOD2 can adequately represent the scaled effects of heat transfer boundary conditions of the thermal-hydraulic calculations through the mechanism of communicating walls. The results of the analysis also serve to clarify certain aspects of experiment and facility design
Moving Towards Integrated Policy Formulation and Evaluation: The Green Economy Model
Bassi, Andrea M.
2015-12-01
The mainstreaming of concepts related to the Green Economy, an action-oriented approach to reach sustainable development, has increased demands for integrated models that can shed light on the complex relations existing across social, economic and environmental indicators. A gap exists, whereby our thinking is rapidly evolving, but the tools available are still in the vast majority of cases sectorial, leading to planning processes taking place in silos. To avoid the emergence of side effects, and anticipate future threats and opportunities, a more systemic approach is needed. The Green Economy Model (GEM) was created taking into account four main capitals and their interconnections: physical capital, human capital, social capital and natural capital. The application of GEM in 10 countries has shown its capability to coherently represent reality and generate results that can more effectively inform decision making.
Moving Towards Integrated Policy Formulation and Evaluation: The Green Economy Model
Directory of Open Access Journals (Sweden)
Bassi Andrea M.
2015-12-01
Full Text Available The mainstreaming of concepts related to the Green Economy, an action-oriented approach to reach sustainable development, has increased demands for integrated models that can shed light on the complex relations existing across social, economic and environmental indicators. A gap exists, whereby our thinking is rapidly evolving, but the tools available are still in the vast majority of cases sectorial, leading to planning processes taking place in silos. To avoid the emergence of side effects, and anticipate future threats and opportunities, a more systemic approach is needed. The Green Economy Model (GEM was created taking into account four main capitals and their interconnections: physical capital, human capital, social capital and natural capital. The application of GEM in 10 countries has shown its capability to coherently represent reality and generate results that can more effectively inform decision making.
The Pressure Boundary Conditions for the Incompressible Navier—Stokes Equations Computation
Institute of Scientific and Technical Information of China (English)
YaosongCHEN; TaoJIANG
1996-01-01
This article devotes to the correct formulation of the pressure boundary conditions for the incompressible Navier-Stokes equation and gives the method of integration.The example has been shown for its feasibility.
Zeng, Y. Y.; Guo, J. Y.; Shang, K.; Shum, C. K.; Yu, J. H.
2015-09-01
Two methods for computing gravitational potential difference (GPD) between the GRACE satellites using orbit data have been formulated based on energy integral; one in geocentric inertial frame (GIF) and another in Earth fixed frame (EFF). Here we present a rigorous theoretical formulation in EFF with particular emphasis on necessary approximations, provide a computational approach to mitigate the approximations to negligible level, and verify our approach using simulations. We conclude that a term neglected or ignored in all former work without verification should be retained. In our simulations, 2 cycle per revolution (CPR) errors are present in the GPD computed using our formulation, and empirical removal of the 2 CPR and lower frequency errors can improve the precisions of Stokes coefficients (SCs) of degree 3 and above by 1-2 orders of magnitudes. This is despite of the fact that the result without removing these errors is already accurate enough. Furthermore, the relation between data errors and their influences on GPD is analysed, and a formal examination is made on the possible precision that real GRACE data may attain. The result of removing 2 CPR errors may imply that, if not taken care of properly, the values of SCs computed by means of the energy integral method using real GRACE data may be seriously corrupted by aliasing errors from possibly very large 2 CPR errors based on two facts: (1) errors of bar C_{2,0} manifest as 2 CPR errors in GPD and (2) errors of bar C_{2,0} in GRACE data-the differences between the CSR monthly values of bar C_{2,0} independently determined using GRACE and SLR are a reasonable measure of their magnitude-are very large. Our simulations show that, if 2 CPR errors in GPD vary from day to day as much as those corresponding to errors of bar C_{2,0} from month to month, the aliasing errors of degree 15 and above SCs computed using a month's GPD data may attain a level comparable to the magnitude of gravitational potential
Abarbanel, Saul; Gottlieb, David; Carpenter, Mark H.
1994-01-01
It has been previously shown that the temporal integration of hyperbolic partial differential equations (PDE's) may, because of boundary conditions, lead to deterioration of accuracy of the solution. A procedure for removal of this error in the linear case has been established previously. In the present paper we consider hyperbolic (PDE's) (linear and non-linear) whose boundary treatment is done via the SAT-procedure. A methodology is present for recovery of the full order of accuracy, and has been applied to the case of a 4th order explicit finite difference scheme.
Formulation of an Integrated Model for Freshwater Resources Policy Evaluation in Jordan
Gorelick, S.; Yoon, J.; Gawel, E.; Klauer, B.; Klassert, C. J. A.; Sigel, K.; Tilmant, A.; Lachaut, T.; Avisse, N.; Harou, J. J.; Padula, S.; Mustafa, D.
2014-12-01
Jordan is one of the four water poorest countries in the world. It is a highly vulnerable arid region whose freshwater system is at a tipping point due to the confluence of severely limited water supplies, rapid population growth, refugee influxes, climate change and variability, internal and transboundary competition for shared freshwater resources, and institutional impediments. Our team is engaged in an interdisciplinary effort aimed at developing a new approach to evaluate policies that enhance sustainability of freshwater resource systems. Our work adopts a multi-agent modeling framework that incorporates institutional complexity to evaluate policy instruments for improving water security in Jordan. We are developing this model using a modular approach, integrating biophysical modules that simulate natural and engineered phenomena (e.g., groundwater-surface water flow, reservoir storage, network routing, salt balance, and crop yield) with human modules that represent behavior at multiple scales of decision making. The human modules adopt a multi-agent simulation approach, defining agents as autonomous decision-makers at the government, administrative, organizational, and user levels. Our goal is to construct a suite of policy intervention scenarios that will form the basis for analysis of freshwater sustainability. This work has benefitted from a strong working relationship with leaders of the water sector in Jordan. Our approach and the merit of the policy interventions should have significant transfer value to other water-stressed regions.
Institute of Scientific and Technical Information of China (English)
ZHANG Min; YUAN Tao; BAI Lu; LI Le-Wei; WU Zhen-Sen
2005-01-01
@@ We present an effective technique for mixed potential integral equation formulations in multilayered media. In terms of the dipole source method, the formulations of Green functions in spectral domain are restructured concisely, a proper integration path is chosen to straightforwardly apply the two-level discrete complex image method and the high order Sommerfeld identities yield very accurate results of Green functions in the spatial domain for general electric and magnetic sources in three-dimensional multilayered media. Finally, it is used to design a realistic low temperature co-fired ceramic aperture coupled antenna with vertical via-holes connected at the Ka band.
Directory of Open Access Journals (Sweden)
TIAN Jialei
2015-11-01
Full Text Available By using the ground as the boundary, Molodensky problem usually gets the solution in form of series. Higher order terms reflect the correction between a smooth surface and the ground boundary. Application difficulties arise from not only computational complexity and stability maintenance, but also data-intensiveness. Therefore, in this paper, starting from the application of external gravity disturbance, Green formula is used on digital terrain surface. In the case of ignoring the influence of horizontal component of the integral, the expression formula of external disturbance potential determined by boundary value consisted of ground gravity anomalies and height anomaly difference are obtained, whose kernel function is reciprocal of distance and Poisson core respectively. With this method, there is no need of continuation of ground data. And kernel function is concise, and suitable for the stochastic computation of external disturbing gravity field.
Integral method for the calculation of three-dimensional, laminar and turbulent boundary layers
Stock, H. W.
1978-01-01
The method for turbulent flows is a further development of an existing method; profile families with two parameters and a lag entrainment method replace the simple entrainment method and power profiles with one parameter. The method for laminar flows is a new development. Moment of momentum equations were used for the solution of the problem, the profile families were derived from similar solutions of boundary layer equations. Laminar and turbulent flows at the wings were calculated. The influence of wing tapering on the boundary layer development was shown. The turbulent boundary layer for a revolution ellipsoid is calculated for 0 deg and 10 deg incidence angles.
REDUCING DIMENSIONS OF DOMAIN INTEGRATION IN BOUNDARY ELEMENT METHOD%边界元法中区域积分的降维计算方法
Institute of Scientific and Technical Information of China (English)
袁政强; 祝家麟
2002-01-01
The main advantage of Boundary Element Method (BEM) is reducing the dimensions by one in performing calculation.When inhomogeneous term appears in the governing equation of the problem,the domain integral is inevitable excepting some special cases.The common way to perform the domain integral involves subdividing the domain into a series of subdomains over which a numberical integration formula or an analytical quadrature can be applied.This paper presents an alternative way to transform the domain integral over subdomains into equivalent boundary integrals on the boundary of each subdomain,so that all the integrals are performed on the boundary case.It makes the whole calculation of BEM reduced by one dimension really.
Directory of Open Access Journals (Sweden)
Ying Wang
2014-01-01
Full Text Available We study the positive solutions of the (n-1,1-type fractional differential system with coupled integral boundary conditions. The conditions for the existence of positive solutions to the system are established. In addition, we derive explicit formulae for the estimation of the positive solutions and obtain the unique positive solution when certain additional conditions hold. An example is then given to demonstrate the validity of our main results.
Consistent multi-time-point brain atrophy estimation from the boundary shift integral.
Leung, Kelvin K; Ridgway, Gerard R; Ourselin, Sébastien; Fox, Nick C
2012-02-15
Brain atrophy measurement is increasingly important in studies of neurodegenerative diseases such as Alzheimer's disease (AD), with particular relevance to trials of potential disease-modifying drugs. Automated registration-based methods such as the boundary shift integral (BSI) have been developed to provide more precise measures of change from a pair of serial MR scans. However, when a method treats one image of the pair (typically the baseline) as the reference to which the other is compared, this systematic asymmetry risks introducing bias into the measurement. Recent concern about potential biases in longitudinal studies has led to several suggestions to use symmetric image registration, though some of these methods are limited to two time-points per subject. Therapeutic trials and natural history studies increasingly involve several serial scans, it would therefore be useful to have a method that can consistently estimate brain atrophy over multiple time-points. Here, we use the log-Euclidean concept of a within-subject average to develop affine registration and differential bias correction methods suitable for any number of time-points, yielding a longitudinally consistent multi-time-point BSI technique. Baseline, 12-month and 24-month MR scans of healthy controls, subjects with mild cognitive impairment and AD patients from the Alzheimer's Disease Neuroimaging Initiative are used for testing the bias in processing scans with different amounts of atrophy. Four tests are used to assess bias in brain volume loss from BSI: (a) inverse consistency with respect to ordering of pairs of scans 12 months apart; (b) transitivity consistency over three time-points; (c) randomly ordered back-to-back scans, expected to show no consistent change over subjects; and (d) linear regression of the atrophy rates calculated from the baseline and 12-month scans and the baseline and 24-month scans, where any additive bias should be indicated by a non-zero intercept. Results
A robust and accurate formulation of molecular and colloidal electrostatics
Sun, Qiang; Klaseboer, Evert; Chan, Derek Y. C.
2016-08-01
This paper presents a re-formulation of the boundary integral method for the Debye-Hückel model of molecular and colloidal electrostatics that removes the mathematical singularities that have to date been accepted as an intrinsic part of the conventional boundary integral equation method. The essence of the present boundary regularized integral equation formulation consists of subtracting a known solution from the conventional boundary integral method in such a way as to cancel out the singularities associated with the Green's function. This approach better reflects the non-singular physical behavior of the systems on boundaries with the benefits of the following: (i) the surface integrals can be evaluated accurately using quadrature without any need to devise special numerical integration procedures, (ii) being able to use quadratic or spline function surface elements to represent the surface more accurately and the variation of the functions within each element is represented to a consistent level of precision by appropriate interpolation functions, (iii) being able to calculate electric fields, even at boundaries, accurately and directly from the potential without having to solve hypersingular integral equations and this imparts high precision in calculating the Maxwell stress tensor and consequently, intermolecular or colloidal forces, (iv) a reliable way to handle geometric configurations in which different parts of the boundary can be very close together without being affected by numerical instabilities, therefore potentials, fields, and forces between surfaces can be found accurately at surface separations down to near contact, and (v) having the simplicity of a formulation that does not require complex algorithms to handle singularities will result in significant savings in coding effort and in the reduction of opportunities for coding errors. These advantages are illustrated using examples drawn from molecular and colloidal electrostatics.
Bagci, Hakan
2010-05-01
A hierarchically regularized coupled set of time-domain surface and volume electric field integral-equations (TD-S-EFIE and TD-V-EFIE) for analyzing electromagnetic wave interactions with electrically small and geometrically intricate composite structures comprising perfect electrically conducting surfaces and finite dielectric volumes is presented. A classically formulated coupled set of TD-S- and V-EFIEs is shown to be ill-conditioned at low frequencies owing to the hypersingular nature of the TD-S-EFIE. To eliminate low-frequency breakdown in marching-on-in-time solvers for these coupled equations, a hierarchical regularizer leveraging generalized RaoWiltonGlisson functions is applied to the TD-S-EFIE; no regularization is applied to the TD-V-EFIE as it is protected from low-frequency breakdown by an identity term. The resulting hierarchically regularized hybrid TD-S- and V-EFIE solver is applicable to the analysis of wave interactions with electrically small and densely meshed structures of arbitrary topology. The accuracy, efficiency, and applicability of the proposed solver are demonstrated by analyzing crosstalk in a six-port transmission line, radiation from a miniature radio-frequency identification antenna, and, plane-wave coupling onto a partially-shielded and fully loaded two-layer computer board. © 2006 IEEE.
Directory of Open Access Journals (Sweden)
Akimov Pavel Alekseevich
2012-10-01
Full Text Available The proposed paper covers the operator-related formulation of the eigenvalue problem of analysis of a three-dimensional structure that has piecewise-constant physical and geometrical parameters alongside the so-called basic direction within the framework of a discrete-continual approach (a discrete-continual finite element method, a discrete-continual variation method. Generally, discrete-continual formulations represent contemporary mathematical models that become available for computer implementation. They make it possible for a researcher to consider the boundary effects whenever particular components of the solution represent rapidly varying functions. Another feature of discrete-continual methods is the absence of any limitations imposed on lengths of structures. The three-dimensional problem of elasticity is used as the design model of a structure. In accordance with the so-called method of extended domain, the domain in question is embordered by an extended one of an arbitrary shape. At the stage of numerical implementation, relative key features of discrete-continual methods include convenient mathematical formulas, effective computational patterns and algorithms, simple data processing, etc. The authors present their formulation of the problem in question for an isotropic medium with allowance for supports restrained by elastic elements while standard boundary conditions are also taken into consideration.
On the boundaries of quantum integrability for the spin-1/2 Richardson–Gaudin system
International Nuclear Information System (INIS)
We discuss a generalised version of Sklyanin's Boundary Quantum Inverse Scattering Method applied to the spin-1/2, trigonometric sl(2) case, for which both the twisted-periodic and boundary constructions are obtained as limiting cases. We then investigate the quasi-classical limit of this approach leading to a set of mutually commuting conserved operators which we refer to as the trigonometric, spin-1/2 Richardson–Gaudin system. We prove that the rational limit of the set of conserved operators for the trigonometric system is equivalent, through a change of variables, rescaling, and a basis transformation, to the original set of trigonometric conserved operators. Moreover, we prove that the twisted-periodic and boundary constructions are equivalent in the trigonometric case, but not in the rational limit
Allen, Davina
2014-07-01
This article examines the translation of a clinical governance concept - integrated care pathways (ICPs)--into an infrastructural technology. Building on previous work, the application of boundary object theory is extended in this article to argue that stakeholder enrolment in pathway methodology may be less thoroughgoing than originally assumed. Pathways have effectively aligned management and nursing interests around a quality agenda and nurses have emerged as the leaders in this field, but doctors have rather lower levels of engagement. It is suggested that the contradictory logics inherent in pathway philosophy (primarily as these relate to 'evidence') and the social organisation of ICP development foster a transformation of the concept when this is translated into the technology, creating a negative boundary object from the perspective of doctors. Medicine is a powerful actor in health care, which is consequential for whether pathways, as designated boundary objects, become boundary objects-in-use. It also has implications for the diffusion of the concept as a mechanism of clinical governance and the credibility of nurses as emergent leaders in this field. Qualitative case studies of ICP development processes undertaken in the UK National Health Service and ethnographic research on the ICP community provide the empirical foundations for the analysis. PMID:24635748
边界元计算中一种新的积分方法%A NEW INTEGRATION APPROACH IN BOUNDARY ELEMENT METHOD
Institute of Scientific and Technical Information of China (English)
侯劲松; 王泽毅
1999-01-01
In three dimensional boundary element calculation, the boundaryintegration is the most time-consuming work. In this paper, a newapproach called parameterized integration method is presented. Itcalculates values of a multivariate function instead of traditionalGauss integral and saves integral time.
Bethe States of the integrable spin-s chain with generic open boundaries
Yang, Lijun; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2015-01-01
Based on the inhomogeneous T-Q relation and the associated Bethe Ansatz equations obtained via the off-diagonal Bethe Ansatz, we construct the Bethe-type eigenstates of the SU(2)-invariant spin-s chain with generic non-diagonal boundaries by employing certain orthogonal basis of the Hilbert space.
Boundary bootstrap principle in two-dimensional integrable quantum field theories
Riva, Valentina
2001-01-01
We study the reflection amplitudes of affine Toda field theories with boundary, following the ideas developed by Fring and Koberle and focusing our attention on the $E_{n}$ series elements, because of their interesting structure of higher order poles. We also investigate the corresponding minimal reflection matrices, finding, with respect to the bulk case, a more complicated relation between the spectra of bound states associated to the minimal and to the ''dressed'' amplitudes.
Significance of Strain in Formulation in Theory of Solid Mechanics
Patnaik, Surya N.; Coroneos, Rula M.; Hopkins, Dale A.
2003-01-01
The basic theory of solid mechanics was deemed complete circa 1860 when St. Venant provided the strain formulation or the field compatibility condition. The strain formulation was incomplete. The missing portion has been formulated and identified as the boundary compatibility condition (BCC). The BCC, derived through a variational formulation, has been verified through integral theorem and solution of problems. The BCC, unlike the field counterpart, do not trivialize when expressed in displacements. Navier s method and the stiffness formulation have to account for the extra conditions especially at the inter-element boundaries in a finite element model. Completion of the strain formulation has led to the revival of the direct force calculation methods: the Integrated Force Method (IFM) and its dual (IFMD) for finite element analysis, and the completed Beltrami-Michell formulation (CBMF) in elasticity. The benefits from the new methods in elasticity, in finite element analysis, and in design optimization are discussed. Existing solutions and computer codes may have to be adjusted for the compliance of the new conditions. Complacency because the discipline is over a century old and computer codes have been developed for half a century can lead to stagnation of the discipline.
A Collocation Method for Volterra Integral Equations with Diagonal and Boundary Singularities
Kolk, Marek; Pedas, Arvet; Vainikko, Gennadi
2009-08-01
We propose a smoothing technique associated with piecewise polynomial collocation methods for solving linear weakly singular Volterra integral equations of the second kind with kernels which, in addition to a diagonal singularity, may have a singularity at the initial point of the interval of integration.
Quantum Group Invariant Integrable n-State Vertex Models with Periodic Boundary Conditions
Karowski, M.; Zapletal, A.
1993-01-01
An $U_q(sl(n))$ invariant transfer matrix with periodic boundary conditions is analysed by means of the algebraic nested Bethe ansatz for the case of $q$ being a root of unity. The transfer matrix corresponds to a 2-dimensional vertex model on a torus with topological interaction w.r.t. the 3-dimensional interior of the torus. By means of finite size analysis we find the central charge of the corresponding Virasoro algebra as $c=(n-1) \\left[1-n(n+1)/(r(r-1))\\right] $.
DEFF Research Database (Denmark)
Zølner, Mette
in the period of post-acquisition when their organization is being integrated into the acquiring MNC. The paper contributes to the literature on boundary spanning in three ways: First, by illustrating that boundary spanning is performed by numerous organizational actors in a variety of positions in MNCs......, inclusively by locals in subsidiaries. Second, by showing that boundary spanning is ‘situated’ in the sense that its result depends on the kind of knowledge to be transmitted and the attitude of the receivers. A third contribution is methodological. The study illustrates that combining bottom-up grounded...
The Blurred Boundaries and Multiple Effects of European Integration and Globalisation
DEFF Research Database (Denmark)
Lynggaard, Kennet
2015-01-01
This chapter presents analytical strategies for the study of European integration and Globalisation in concert. This is an increasingly important as well as a highly diverse field of inquiry. The chapter presents a series of research clusters in various ways concerned with the fundamental questions...... of how European integration contribute to, and are effected by, globalisation. By means of concrete research examples the chapter discusses the advantages of the research strategies and tools typically applied on the area and the challenges we face in this regard. This includes discussions of top...
Tello-Leal, Edgar; Chiotti, Omar; Villarreal, Pablo David
2012-12-01
The paper presents a methodology that follows a top-down approach based on a Model-Driven Architecture for integrating and coordinating healthcare services through cross-organizational processes to enable organizations providing high quality healthcare services and continuous process improvements. The methodology provides a modeling language that enables organizations conceptualizing an integration agreement, and identifying and designing cross-organizational process models. These models are used for the automatic generation of: the private view of processes each organization should perform to fulfill its role in cross-organizational processes, and Colored Petri Net specifications to implement these processes. A multi-agent system platform provides agents able to interpret Colored Petri-Nets to enable the communication between the Healthcare Information Systems for executing the cross-organizational processes. Clinical documents are defined using the HL7 Clinical Document Architecture. This methodology guarantees that important requirements for healthcare services integration and coordination are fulfilled: interoperability between heterogeneous Healthcare Information Systems; ability to cope with changes in cross-organizational processes; guarantee of alignment between the integrated healthcare service solution defined at the organizational level and the solution defined at technological level; and the distributed execution of cross-organizational processes keeping the organizations autonomy. PMID:22434534
Directory of Open Access Journals (Sweden)
Aldawsari HM
2015-01-01
Full Text Available Hibah M Aldawsari,1 Shaimaa M Badr-Eldin,1,2 Gihan S Labib,1,3 Amal H El-Kamel3 1Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia; 2Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Cairo University, Cairo, Egypt; 3Department of Pharmaceutics, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt Abstract: Lemongrass oil (LGO is a volatile oil extracted from the leaves of Cymbopogon citratus that has become one of the most important natural oils in the pharmaceutical industry because of its diverse pharmacologic and clinical effects. However, LGO suffers from low aqueous solubility, which could lead to a reduced effect. Moreover, the instability of its major active constituent, citral, could lead to volatilization, reaction with other formulation ingredients, and consequently, skin irritation. To surmount these problems, this research aims to formulate lemongrass-loaded ethyl cellulose nanosponges with a topical hydrogel with an enhanced antifungal effect and decreased irritation. The minimal inhibitory concentration and minimal fungicidal concentration of LGO against Candida albicans strain ATC 100231, determined using the broth macrodilution method, were found to be 2 and 8 µL/mL, respectively. The emulsion solvent evaporation technique was used for the preparation of the nanosponges. The nanosponge dispersions were then integrated into carbopol hydrogels (0.4%. Nine formulations were prepared based on a 32 full factorial design employing the ethyl cellulose:polyvinyl alcohol ratio and stirring rate as independent variables. The prepared formulations were evaluated for particle size, citral content, and in vitro release. Results revealed that all the nanosponge dispersions were nanosized, with satisfactory citral content and sustained release profiles. Statistical analysis revealed that both ethyl cellulose:polyvinyl alcohol ratio and
On the Vilenkin boundary condition proposal in anisotropic universes
Energy Technology Data Exchange (ETDEWEB)
Louko, J.; Vachaspati, T.
1989-06-01
We show that the Vilenkin boundary condition proposal, as formulated in terms of the Klein-Gordon type current, does not specify a unique wave function in the vacuum minisuperspace models of the Kantowski-Sachs type and the locally rotationally symmetric Bianchi type III. The underlying reasons are directly in the classical dynamics of the models. We also discuss the suggestion of relating the Vilenkin proposal to a lorentzian path integral with the causal boundary condition advocated by Teitelboim.
A LOCAL BOUNDARY INTEGRAL EQUATION[1mm］METHOD FOR THE ELASTICITY PROBLEM%弹性力学问题的局部边界积分方程方法
Institute of Scientific and Technical Information of China (English)
龙述尧; 许敬晓
2000-01-01
The basic concept and numerical implementation of a local boundaryintegral equation formulation for solving the elasticity problem havebeen presented in the present paper. It is a new truly meshless method,because the numerical implementation of the method leads to an efficientmeshless discrete model. The concept of a companion solution isintroduced, such that the traction terms would not appear in theintegrals over the local boundary after the modified integral kernel isused for all nodes whose local boundary s falls within theglobal boundary of the given problem; it uses the moving leastsquare approximations, and involves only boundary integration over alocal boundary centered at the node in question. It poses nodifficulties in satisfying essential boundary conditions, and leads to abanded and sparse system matrix. The undependence of the solution onthe size of the integral local boundary provides a great flexibilityin dealing with the numerical model of the elastic plane problems undervarious boundary conditions with arbitrary shapes. Convergence studiesin the numerical examples show that the present method possesses anexcellent rate of convergence and reasonably accurate results for boththe unknown displacement and strain energy, as the originalapproximated trial solutions have nice continuity and smoothness. Thenumerical results also show that using both linear and quadratic basesas well as spline and Gaussian weight functions in approximationfunctions can give quite accurate numerical results. Compared with the conventional boundary element method based on the globalboundary integral equations, the present method is advantageous in thefollowing aspects: i) No boundary and domain element needed to be constructed in the presentmethod, while it is necessary to discretize both the entire domain andits boundary for the conventional boundary element method in general. Thevolume and boundary integrals in the present method are evaluated onlyover small
Half-Baked Logo Microworlds as Boundary Objects in Integrated Design
Directory of Open Access Journals (Sweden)
Chronis KYNIGOS
2007-10-01
Full Text Available The paper addresses the problem of fragmentation of the communities involved in the design of digital media for education. It draws on the experience gained at the Educational Technology Lab in the design of Logo-based microworlds with three different platforms respectively based on component computing, 3D game engines and 3D navigation with a GIS. In this paper I use the term half-baked to describe a microworld which is explicitly designed to engage its users with changing it as the main aspect of their activity. I discuss this kind of microworld as a tool for integrated design involving people with diverse expertise and/or roles to communicate. These kinds of microworlds implicitly exist within the community, but they can be explicitly designed mediated and put to use in the role of facilitators for integrated design and development to enable a growing communication amongst researchers, technicians, teachers and students. A template for presenting microworlds which was constructed through the experience with four such integrated communities is used to describe for each respective case the design principles, the affordances, the histories of development and the variety of emergent microworlds.
Directory of Open Access Journals (Sweden)
Noella J. Gray
2016-08-01
Full Text Available Marine protected areas (MPAs are an increasingly popular tool for management of the marine commons. Effective governance is essential if MPAs are to achieve their objectives, yet many MPAs face conflicts and governance challenges, including lack of trust and knowledge integration between fishers, scientists, and policy makers. This paper considers the role of a boundary organization in facilitating knowledge integration in a co-managed MPA, the Gladden Spit and Silk Cayes Marine Reserve in Belize. Boundary organizations can play an important role in resource management, by bridging the science-policy divide, facilitating knowledge integration, and enabling communication in conditions of uncertainty. Drawing on ethnographic research conducted in Belize, the paper identifies four challenges for knowledge integration. First, actors have divergent perspectives on whether and how knowledge is being integrated. Second, actors disagree on resource conditions within the MPA and how these should be understood. Third, in order to maintain accountability with multiple actors, including fishers, government, and funders, the boundary organization has promoted the importance of different types of knowledge for different purposes (science and fishers’ knowledge, rather than the integration of these. Finally, a lack of trust and uneven power relations make it difficult to separate knowledge claims from political claims. However, even if knowledge integration proves difficult, boundary organizations may still play an important role by maintaining accountability, providing space for conflicting understandings to co-exist, and ultimately for governance institutions to evolve.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
There is now solid evidence that cell-to-cell trafficking of certain proteins and RNAs plays a critical role in trans-cellular regulation of gene expression to coordinate cellular differentiation and development. Such trafficking also is critical for viral infection and plant defense. The mechanisms of trafficking remain poorly understood. Although some proteins may move between cells by diffusion, many proteins and RNAs move in a highly regulated fashion. Regulation is likely achieved through interactions between distinct protein or RNA motifs and cellular factors. Some motifs and factors have been identified. One of the major focuses for future studies is to identify all motifs and their cognate factors and further elucidate their roles in trafficking between specific cells. With increasing information from such studies, we should be able to develop an understanding of the mechanisms that regulate trafficking of various proteins and RNAs across all and specific cellular boundaries. On the basis of such mechanistic knowledge, we can further investigate how the trafficking machinery has evolved to regulate developmental and physiological processes in a plant, how pathogens have co-evolved to use this machinery for systemic spread in a plant, and how plants use this machinery for counterdefense.
Institute of Scientific and Technical Information of China (English)
刘志芳; 罗远新; 严兴春; 王勇勤
2015-01-01
Leveler is widely used to improve the quality of defective mild steel plates. Its typical ranges of the leveling capacity are constrained by three criteria, namely the maximum stroke of rollers, allowable total leveling force and motor power. In this work, an optimization model with equality and inequality constraints was built for the maximum yield stress search of each thickness of plates. The corresponding search procedure with three loops was given. The approximate range by the simplification model could be used as the initial value for the actual range search of the leveling capacity. Therefore, the search speed could be accelerated compared with a global search. The consistency of the analytical results and field data demonstrates the reliability of the proposed model and procedure. The typical ranges of the leveling capacity are expressed by several boundary curves which are helpful to judge whether the incoming plate can be leveled quickly or not. Also, these curves can be used to find the maximum yield stress for a specific thickness or the maximum thickness for a yield stress for plates.
Bardhan, Jaydeep P; Knepley, Matthew G
2011-09-28
We analyze the mathematically rigorous BIBEE (boundary-integral based electrostatics estimation) approximation of the mixed-dielectric continuum model of molecular electrostatics, using the analytically solvable case of a spherical solute containing an arbitrary charge distribution. Our analysis, which builds on Kirkwood's solution using spherical harmonics, clarifies important aspects of the approximation and its relationship to generalized Born models. First, our results suggest a new perspective for analyzing fast electrostatic models: the separation of variables between material properties (the dielectric constants) and geometry (the solute dielectric boundary and charge distribution). Second, we find that the eigenfunctions of the reaction-potential operator are exactly preserved in the BIBEE model for the sphere, which supports the use of this approximation for analyzing charge-charge interactions in molecular binding. Third, a comparison of BIBEE to the recent GBε theory suggests a modified BIBEE model capable of predicting electrostatic solvation free energies to within 4% of a full numerical Poisson calculation. This modified model leads to a projection-framework understanding of BIBEE and suggests opportunities for future improvements.
Shea, Munyi; Yang, Lawrence H.; Leong, Frederick T. L.
2010-01-01
Culture shapes the nature, experience, and expression of psychopathology and help-seeking behavior across ethnically diverse groups. Although the study of psychopathology among Asian Americans has advanced, clinicians remain in need of culturally appropriate tools for the assessment and diagnosis of severe mental disorders including psychotic symptoms among Asian Americans. In this article, we present a brief overview of two culturally relevant conceptual tools: a) the Cultural Formulation Mo...
Four formulations of noncommutative quantum mechanics
Gouba, Laure
2016-01-01
Four formulations of noncommutative quantum mechanics are reviewed. These are the canonical, path-integral, Weyl-Wigner and systematic formulations. The four formulations are charaterized by a deformed Heisenberg algebra but differ in mathematical and conceptual overview.
The influence of a scaled boundary response on integral system transient behavior
International Nuclear Information System (INIS)
In this paper, scaling relationships associated with the thermal-hydraulic response of a closed loop system are applied to a calculational assessment of a feed-and-bleed recovery in a nuclear reactor integral effects test. The analysis demonstrates both the influence of scale on the system response and the ability of the thermal-hydraulics code to represent those effects. The qualitative response of the fluid is shown to be coupled to the behavior of the bounding walls through the energy equation. A variety of scaling relationships associated with an integral system test facility are applied to computer models representing a feed and bleed transient in a nuclear reactor. the difference in scaled behavior between the solid walls and the two-phase fluid is shown to have a significant impact on the qualitative nature of the results, both in the calculations and in the experiment. The principal effect for the transient addressed is shown to be the behavior of the pressurizer walls. The energy transfer rate from the walls to the fluid has a direct influence on the mass discharge rate from the primary system
Self-Trail, J. M.; Robinson, M. M.; Edwards, L. E.; Powars, D. S.; Wandless, G. A.; Willard, D. A.
2013-12-01
An exceptional Paleocene-Eocene boundary section occurs in a cluster of six short (Marlboro Clay. Sediment samples were analyzed for carbon and oxygen isotopes, percent calcium carbonate, calcareous nannofossils, planktic and benthic foraminifera, dinoflagellates, pollen, and lithology. A well-defined carbon isotope excursion (CIE) documents a gradual negative shift in δ13C values that starts below the lithologic break between the Aquia Formation and the Marlboro Clay. A benthic foraminifer extinction event, reduction of calcareous nannofossil assemblages, and change in core color from gray to alternating gray and pink also occurs within the CIE transition. These alternating changes in color coincide with cyclic peaks in the carbon isotope and percent calcium carbonate curves, where gray color corresponds to a positive shift in carbon isotope values and to a corresponding increase in percent benthic and planktic foraminifera. The upper third of the Marlboro Clay is barren of all calcareous microfossil material, although the presence of foraminiferal molds and linings proves that deposition occurred in a marine environment. Co-occurrence of the dinoflagellates Apectodinium augustum and Phthanoperidinium crenulatum at the top of the Marlboro Clay suggests that the Marlboro Clay at Mattawoman Creek is truncated. This is corroborated by the absence in the Marlboro of specimens of the calcareous nannofossil Rhomboaster-Discoaster assemblage, which is restricted to early Eocene Zone NP9b. Based on planktic/benthic foraminifera ratios, deposition of sediments at Mattawoman Creek occurred predominantly in an inner neritic environment, at water depths between 25-50 m. Occasional deepening to approximately 75m (middle neritic environment) occurred in the early Eocene, as represented by the basal Marlboro Clay. The planktic/benthic ratio, however, could also be affected by surface productivity and/or river runoff. The gradual shift up-section in core color from gray to
Boundary Element Method with Non—overlapping Domain Decomposition for Diffusion Equation
Institute of Scientific and Technical Information of China (English)
ZHUJialin; ZHANGTaiping
2002-01-01
A boundary element method based on non-overlapping domain decomposition method to solve the time-dependent diffusion equations is presented.The time-dependent fundamental solution is used in the formulation of boundary integrals and the time integratioin process always restarts from the initial time condition.The process of replacing the interface values,which needs a summation of boundary integrals related to the boundary values at previous time steps can be treated in parallel parallel iterative procedure,Numerical experiments demonstrate that the implementation of the present alogrithm is efficient.
Rahmouni, Lyes; Cools, Kristof; Andriulli, Francesco P
2016-01-01
In this paper we present a new discretization strategy for the boundary element formulation of the Electroencephalography (EEG) forward problem. Boundary integral formulations, classically solved with the Boundary Element Method (BEM), are widely used in high resolution EEG imaging because of their recognized advantages in several real case scenarios. Unfortunately however, it is widely reported that the accuracy of standard BEM schemes is limited, especially when the current source density is dipolar and its location approaches one of the brain boundary surfaces. This is a particularly limiting problem given that during an high-resolution EEG imaging procedure, several EEG forward problem solutions are required for which the source currents are near or on top of a boundary surface. This work will first present an analysis of standardly discretized EEG forward problems, reporting on a theoretical issue of some of the formulations that have been used so far in the community. We report on the fact that several ...
DEFF Research Database (Denmark)
Arsalis, Alexandros; Nielsen, Mads Pagh; Kær, Søren Knudsen
2013-01-01
. It consists of a fuel cell stack, a fuel processing subsystem, heat exchangers, and balance-of-plant components. The optimization methodology involves system optimization attempting to maximize the net electrical efficiency, and then by use of a mixed integer nonlinear programming (MINLP) problem formulation......, the heat exchange network (HEN) annual cost is minimized. The results show the high potential of the proposed model since high efficiencies are accomplished. The net electrical efficiency and total system efficiency, based on lower heating value (LHV), are 35.2% and 91.1%, respectively. The minimized total...
Monitoring the northern Chile megathrust with the Integrated Plate boundary Observatory Chile (IPOC)
Schurr, Bernd; Asch, Günter; Cailleau, Beatrice; Diaz, Guillermo Chong; Barrientos, Sergio; Vilotte, Jean-Pierre; Oncken, Onno
2010-05-01
thousand aftershocks during the following week using waveform cross-correlation and the double-difference algorithm. Aftershocks reveal that rupture during this earthquake was confined to the deeper part (35 - 55 km depth) of the seismogenic coupling zone, except near the Mejillones peninsula that marks rupture termination in the south. Here earthquake activity reaches to depths of 20 km and even shallower, possibly indicating upper plate activation. The sequence also features an M 6.8 earthquake that broke the oceanic slab on an almost vertical plane at the down-dip end of the megathrust rupture. Confrontation with the aftershock distribution of the 1995 M 8.0 Antofagasta earthquake on the adjoining southern segment reveals an intriguing mirror symmetry with an axis crossing the Mejillones peninsula, emphasizing the penisula's significance as a segment boundary. Since then activity inside the remaining seismic gap to the north picked up with three earthquakes exceeding magnitude 6, maybe heralding the next great rupture.
International Nuclear Information System (INIS)
We present three families of integrable models for Bose–Einstein condensates in a double-well potential which are based on the combination, two by two, of three algebraic realizations of the Lax operator: the bosonic realization and the su(2) and su(1, 1) Holstein–Primakoff realizations. The families of Hamiltonians describe Josephson tunneling between two condensates in a double-well potential with boson distribution dependence in the tunneling term. Two families describe models with interacting bosons and the other does not. The integrability is shown by using the quantum inverse scattering method and algebraic Bethe ansatz. The energy eigenvalues and the Bethe ansatz equations are obtained for each model proposed. In the end, we use the energy gap as a testing function to compare the proposed integrable models with the well-known integrable two-site Bose–Hubbard model to show the effect of the boson distribution in the tunneling. (paper)
Fractional Extensions of some Boundary Value Problems in Oil Strata
Indian Academy of Sciences (India)
Mridula Garg; Alka Rao
2007-05-01
In the present paper, we solve three boundary value problems related to the temperature field in oil strata - the fractional extensions of the incomplete lumped formulation and lumped formulation in the linear case and the fractional generalization of the incomplete lumped formulation in the radial case. By using the Caputo differintegral operator and the Laplace transform, the solutions are obtained in integral forms where the integrand is expressed in terms of the convolution of some auxiliary functions of Wright function type. A generalization of the Laplace transform convolution theorem, known as Efros’ theorem is widely used.
Inoue, Junko; Doi, Shinji
2007-01-01
After the report of Softky and Koch [Softky, W.R., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13, 334-350], leaky integrate-and-fire models have been investigated to explain high coefficient of variation (CV) of interspike intervals (ISIs) at high firing rates observed in the cortex. The purpose of this paper is to study the effect of the position of a lower boundary of membrane potential on the possible value of CV of ISIs based on the diffusional leaky integrate-and-fire models with and without reversal potentials. Our result shows that the irregularity of ISIs for the diffusional leaky integrate-and-fire neuron significantly changes by imposing a lower boundary of membrane potential, which suggests the importance of the position of the lower boundary as well as that of the firing threshold when we study the statistical properties of leaky integrate-and-fire neuron models. It is worth pointing out that the mean-CV plot of ISIs for the diffusional leaky integrate-and-fire neuron with reversal potentials shows a close similarity to the experimental result obtained in Softky and Koch [Softky, W.R., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13, 334-350].
Indian Academy of Sciences (India)
Denny P Alappattu; D Bala Subrahamanyam; P K Kunhikrishnan; K M Somayaji; G S Bhat; R Venkatesan; C B S Dutt; A Bagavath Singh; V K Soni; A S Tripathi
2008-07-01
Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail.
Ho, Hsuan-Fu; Hung, Chia-Chi
2008-01-01
Purpose: The purpose of this paper is to examine how a graduate institute at National Chiayi University (NCYU), by using a model that integrates analytic hierarchy process, cluster analysis and correspondence analysis, can develop effective marketing strategies. Design/methodology/approach: This is primarily a quantitative study aimed at…
Energy Technology Data Exchange (ETDEWEB)
Kolk, K.
2005-07-15
This is an important contribution to reliable simulation of stable fatigue crack growth in real 3D problems under complex loads. The nonlinear crack propagation process requires an incremental solution algorithm. Each increment starts with a load analysis of the current crack configuration using the fast dual boundary element method. The potential of this method is more fully utilized with a fast boundary element formulation. Afater this, a real 3D crack propagation criterion is evaluated which is based on experimental findings and is realized within a preditor-corrector method. Finally, the numeric model is generated for the next increment. This generation is made automatically using a local renetworking algorithm. With the crack propagation module thus developed, complex components, e.g. motor car components, can be analyzed fracture-mechanically on a standard PC. (orig.) [German] Die vorliegende Arbeit leistet einen wesentlichen Beitrag zur zuverlaessigen Simulation des stabilen Ermuedungsrisswachstums in realen 3D-Problemen unter komplexen Belastungen. Der nichtlineare Vorgang des Risswachstums erfordert einen inkrementellen Loesungsalgorithmus. In jedem Inkrement wird zunaechst eine Beanspruchungsanalyse der aktuellen Risskonfiguration mit der leistungsstarken dualen Randelementmethode durchgefuehrt. Das Potenzial dieser Methode wird mit einer schnellen Randelementformulierung weiter ausgeschoepft. Anschliessend wird ein echtes 3D-Rissfortschrittskriterium ausgewertet, welches auf experimentellen Erkenntnissen beruht und innerhalb eines Praediktor-Korrektor-Verfahrens realisiert ist. Abschliessend wird das numerische Modell fuer das naechste Inkrement generiert. Diese Generierung erfolgt automatisch mit einem lokalen Neuvernetzungsalgorithmus. Mit dem entwickelten Rissfortschrittsmodul koennen komplexe Bauteile, z.B. aus dem Automobilbau, erfolgreich auf einem Standard-PC bruchmechanisch analysiert werden.
Rasmussen, Jorgen
2011-01-01
We construct new Yang-Baxter integrable boundary conditions in the lattice approach to the logarithmic minimal model WLM(1,p) giving rise to reducible yet indecomposable representations of rank 1 in the continuum scaling limit. We interpret these W-extended Kac representations as finitely-generated W-extended Feigin-Fuchs modules over the triplet W-algebra W(p). The W-extended fusion rules of these representations are inferred from the recently conjectured Virasoro fusion rules of the Kac representations in the underlying logarithmic minimal model LM(1,p). We also introduce the modules contragredient to the W-extended Kac modules and work out the correspondingly-extended fusion algebra. Our results are in accordance with the Kazhdan-Lusztig dual of tensor products of modules over the restricted quantum universal enveloping algebra $\\bar{U}_q(sl_2)$ at $q=e^{\\pi i/p}$. Finally, polynomial fusion rings isomorphic with the various fusion algebras are determined, and the corresponding Grothendieck ring of charact...
Institute of Scientific and Technical Information of China (English)
LongShuyao; HuDe'an
2003-01-01
The meshless method is a new numerical technique presented in recent years .It uses the moving least square (MLS) approximation as a shape function . The smoothness of the MLS approximation is determined by that of the basic function and of the weight function, and is mainly determined by that of the weight function. Therefore, the weight function greatly affects the accuracy of results obtained. Different kinds of weight functions, such as the spline function, the Gauss function and so on, are proposed recently by many researchers. In the present work, the features of various weight functions are illustrated through solving elasto-static problems using the local boundary integral equation method. The effect of various weight functions on the accuracy, convergence and stability of results obtained is also discussed. Examples show that the weight function proposed by Zhou Weiyuan and Gauss and the quartic spline weight function are better than the others if parameters c and a in Gauss and exponential weight functions are in the range of reasonable values, respectively, and the higher the smoothness of the weight function, the better the features of the solutions.
Balcão, Victor M; Glasser, Cássia A; Chaud, Marco V; del Fiol, Fernando S; Tubino, Matthieu; Vila, Marta M D C
2014-11-01
The emergence of antibiotic-resistant bacterial strains and the weak penetration of antibiotics into bacterial biofilms put an emphasis in the need for safe and effective alternatives for antimicrobial treatments. The application of strictly lytic bacteriophages (or phages) has been proposed as an alternative (or complement) to conventional antibiotics, allowing release of the natural predators of bacteria directly to the site of infection. In the present research effort, production of bacteriophage derivatives (starting from lytic phage particle isolates), encompassing full stabilization of their three-dimensional structure, has been attempted via housing said bacteriophage particles within lipid nanovesicles integrating a multiple water-in-oil-in-water (W/O/W) emulsion. As a proof-of-concept for the aforementioned strategy, bacteriophage particles with broad lytic spectrum were entrapped within the aqueous core of lipid nanoballoons integrating a W/O/W multiple emulsion. Long-term storage of the multiple emulsions produced did not lead to leaching of phage particles, thus proving the effectiveness of the encapsulation procedure.
Bonfiglio, Paolo; Pompoli, Francesco; Lionti, Riccardo
2016-04-01
The transfer matrix method is a well-established prediction tool for the simulation of sound transmission loss and the sound absorption coefficient of flat multilayer systems. Much research has been dedicated to enhancing the accuracy of the method by introducing a finite size effect of the structure to be simulated. The aim of this paper is to present a reduced-order integral formulation to predict radiation efficiency and radiation impedance for a panel with equal lateral dimensions. The results are presented and discussed for different materials in terms of radiation efficiency, sound transmission loss, and the sound absorption coefficient. Finally, the application of the proposed methodology for rectangular multilayer systems is also investigated and validated against experimental data.
Terraneo, Tullia Isotta
2015-12-01
In the present study the species boundaries of the scleractinian coral genus Goniopora from the Saudi Arabian Red Sea were investigated. An integrated morpho-molecular approach was used to better clarify the complex scenario derived from traditional classification efforts based on skeletal morphology. Traditional taxonomy of this genus considers skeletal morphology first and polyp morphology as a secondary discriminating character. This leads to potential complication due to plasticity in skeletal features within a species. To address this issue, molecular analyses of evolutionary relationships between nine traditional morphospecies of Goniopora from the Red Sea were performed and were used to re-evaluate the informativeness of macromorphological and micromorphological features. Between four and six putative molecular lineages were identified within Goniopora samples from the Saudi Arabian Red Sea on the basis of four molecular markers: the mitochondrial intergenic spacer between Cytochrome b and the NADH dehydrogenase subunit 2, the entire nuclear ribosomal internal transcribed spacer region, the ATP synthase subunit β gene, and a portion of the Calmodulin gene. The results were strongly corroborated by three distinct analyses of species delimitation. Subsequent analyses of micromorphological and microstructural skeletal features identified the presence of distinctive characters in each of the molecular clades. Unique in vivo morphologies were associated with the genetic-delimited lineages, further supporting the molecular findings. The proposed re-organization of Goniopora will resolve several taxonomic problems in this genus while reconciling molecular and morphological evidence. Reliable species-level identification of Goniopora spp. can be achieved with polyp morphology under the proposed revision.
An inverse problem by boundary element method
Energy Technology Data Exchange (ETDEWEB)
Tran-Cong, T.; Nguyen-Thien, T. [University of Southern Queensland, Toowoomba, QLD (Australia); Graham, A.L. [Los Alamos National Lab., NM (United States)
1996-02-01
Boundary Element Methods (BEM) have been established as useful and powerful tools in a wide range of engineering applications, e.g. Brebbia et al. In this paper, we report a particular three dimensional implementation of a direct boundary integral equation (BIE) formulation and its application to numerical simulations of practical polymer processing operations. In particular, we will focus on the application of the present boundary element technology to simulate an inverse problem in plastics processing.by extrusion. The task is to design profile extrusion dies for plastics. The problem is highly non-linear due to material viscoelastic behaviours as well as unknown free surface conditions. As an example, the technique is shown to be effective in obtaining the die profiles corresponding to a square viscoelastic extrudate under different processing conditions. To further illustrate the capability of the method, examples of other non-trivial extrudate profiles and processing conditions are also given.
Periodic Time-Domain Nonlocal Nonreflecting Boundary Conditions for Duct Acoustics
Watson, Willie R.; Zorumski, William E.
1996-01-01
Periodic time-domain boundary conditions are formulated for direct numerical simulation of acoustic waves in ducts without flow. Well-developed frequency-domain boundary conditions are transformed into the time domain. The formulation is presented here in one space dimension and time; however, this formulation has an advantage in that its extension to variable-area, higher dimensional, and acoustically treated ducts is rigorous and straightforward. The boundary condition simulates a nonreflecting wave field in an infinite uniform duct and is implemented by impulse-response operators that are applied at the boundary of the computational domain. These operators are generated by convolution integrals of the corresponding frequency-domain operators. The acoustic solution is obtained by advancing the Euler equations to a periodic state with the MacCormack scheme. The MacCormack scheme utilizes the boundary condition to limit the computational space and preserve the radiation boundary condition. The success of the boundary condition is attributed to the fact that it is nonreflecting to periodic acoustic waves. In addition, transient waves can pass rapidly out of the solution domain. The boundary condition is tested for a pure tone and a multitone source in a linear setting. The effects of various initial conditions are assessed. Computational solutions with the boundary condition are consistent with the known solutions for nonreflecting wave fields in an infinite uniform duct.
Institute of Scientific and Technical Information of China (English)
毛文贵; 韩旭; 刘桂萍
2015-01-01
In order to eliminate the numerical instability of transfer matrix method and to build a transfer matrix of nonlinear elements(bearings),the Riccati transfer matrix method was extended to the transient analysis of nonlinear rotor-bearing systems.In the method,the transfer matrix was obtained with the aid of the Newmark acceleration formulation,the deflections and velocities at the stations containing nonlinear element (bearings)were predicted by Taylor series,and then the deflections,velocities and accelerations at all stations were solved by using the Riccati transfer matrix method combined with the Newmark acceleration formulation integration according to the boundary conditions.An example of single disc rotor system was presented and the results were compared with those by a transient analysis considering linear perturbation and linear oil film force to verify the effectiveness of the proposed method.%为克服传递矩阵法数值不稳定及非线性瞬态响应分析中滑动轴承矩阵建立困难问题，提出 Riccati-New-mark 加速度传递矩阵法。借助 Newmark 加速度法建立传递矩阵，采用 Taylor 级数预估滑动轴承轴心下一时刻位移、速度建立滑动轴承矩阵；据边界条件用 Riccati 传递矩阵法求滑动轴承－转子系统非线性瞬态响应，提高数值稳定性。以单圆盘转子系统为例，与传统轴颈下一时刻位移、速度近似线性扰动处理的瞬态响应对比分析，验证此方法的有效性；讨论不同转速下线性、非线性油膜力的瞬态轨迹。
Meshfree analysis with the aid of NURBS boundary
Chi, Sheng-Wei; Lin, Shih-Po
2016-05-01
We present a meshfree analysis framework to integrate the geometric exactness of non-uniform rational B-splines (NURBS)-based isogeometric analysis (IGA) (Hughes et al., Comput Methods Appl Mech Eng 194:4135-4195, 2005) with the flexibility of meshfree approximations. In the framework, only the NURBS boundary surface immediately available from CAD tools is used to describe the exact problem domain, and meshfree particles are inserted inside the boundary surface, in a flexible manner, for construction of the approximation for analysis. Nitche's method is employed for imposing essential boundary conditions and the domain integration in the Galerkin formulation is performed based on variationally consistent integration (VCI) to recover integration exactness. The NURBS boundary surface from CAD serves as an aid in selecting particle distributions and as the integration net for the boundary integration required both for the Nitche's method and the VCI. As shown in numerical studies, the VCI is essential for the solution accuracy of the method. Several benchmarks are tested to examine the effectiveness of the proposed framework and numerical results are compared with those obtained by the IGA.
Meshfree analysis with the aid of NURBS boundary
Chi, Sheng-Wei; Lin, Shih-Po
2016-09-01
We present a meshfree analysis framework to integrate the geometric exactness of non-uniform rational B-splines (NURBS)-based isogeometric analysis (IGA) (Hughes et al., Comput Methods Appl Mech Eng 194:4135-4195, 2005) with the flexibility of meshfree approximations. In the framework, only the NURBS boundary surface immediately available from CAD tools is used to describe the exact problem domain, and meshfree particles are inserted inside the boundary surface, in a flexible manner, for construction of the approximation for analysis. Nitche's method is employed for imposing essential boundary conditions and the domain integration in the Galerkin formulation is performed based on variationally consistent integration (VCI) to recover integration exactness. The NURBS boundary surface from CAD serves as an aid in selecting particle distributions and as the integration net for the boundary integration required both for the Nitche's method and the VCI. As shown in numerical studies, the VCI is essential for the solution accuracy of the method. Several benchmarks are tested to examine the effectiveness of the proposed framework and numerical results are compared with those obtained by the IGA.
Directory of Open Access Journals (Sweden)
GIULIO PAVIA
2004-03-01
Full Text Available This paper deals with a definition of the lower boundary stratotype of the Tithonian Stage in the Upper Jurassic succession of Monte Inici, Western Sicily. The upper member of the Rosso Ammonitico Fm. is 27 m thick and shows a typical nodular-calcareous lithofacies; its lower beds have been sampled for biostratigraphic and paleomagnetic purposes. Though the succession is affected by high stratigraphic condensation, the resulting hiatuses have been shown to be below biochronological resolution and thus do not hinder any biostratigraphic definition. The biostratigraphic analysis has been based on the rich ammonite assemblages in which the common genus Hybonoticeras is the index-key for characterizing the Kimmeridgian-Tithonian boundary. Four ammonite biozones have been identified; the basal Tithonian one is defined by the assemblage of Hybonoticeras gr. hybonotum and Haploceras staszycii. The recorded calcareous nannofossil bioevents allow recognition of the V. stradneri and C. mexicana Zones, whose boundary is located a little below the identified Tithonian lower boundary. The paleomagnetic record shows normal polarity in the S. darwini/V. albertinum Zone and mainly reverse polarity in the H. beckeri and H. hybonotum Zones, with three minor normal polarity intervals; the lower boundary of the Tithonian falls in the oldest of these intervals. The integrated multidisciplinary stratigraphic information gathered from the Contrada Fornazzo section defines the lower boundary of the H. hybonotum Zone at the base of Bed 110, and supplies elements of chrono-correlation sufficient to regard this section as a possible G.S.S.P. of the Tithonian Stage.
Assessment of strategy formulation
DEFF Research Database (Denmark)
Acur, Nuran; Englyst, Linda
2006-01-01
Purpose – Today, industrial firms need to cope with competitive challenges related to innovation, dynamic responses, knowledge sharing, etc. by means of effective and dynamic strategy formulation. In light of these challenges, the purpose of the paper is to present and evaluate an assessment tool...... for strategy formulation processes that ensures high quality in process and outcome. Design/methodology/approach – A literature review was conducted to identify success criteria for strategy formulation processes. Then, a simple questionnaire and assessment tool was developed and used to test the validity...... of the success criteria through face-to-face interviews with 46 managers, workshops involving 40 managers, and two in-depth case studies. The success criteria have been slightly modified due to the empirical results, to yield the assessment tool. Findings – The resulting assessment tool integrates three generic...
Measurement and analysis of grain boundary grooving by volume diffusion
Hardy, S. C.; Mcfadden, G. B.; Coriell, S. R.; Voorhees, P. W.; Sekerka, R. F.
1991-01-01
Experimental measurements of isothermal grain boundary grooving by volume diffusion are carried out for Sn bicrystals in the Sn-Pb system near the eutectic temperature. The dimensions of the groove increase with a temporal exponent of 1/3, and measurement of the associated rate constant allows the determination of the product of the liquid diffusion coefficient D and the capillarity length Gamma associated with the interfacial free energy of the crystal-melt interface. The small-slope theory of Mullins is generalized to the entire range of dihedral angles by using a boundary integral formulation of the associated free boundary problem, and excellent agreement with experimental groove shapes is obtained. By using the diffusivity measured by Jordon and Hunt, the present measured values of Gamma are found to agree to within 5 percent with the values obtained from experiments by Gunduz and Hunt on grain boundary grooving in a temperature gradient.
Dal Poz, A. P.; Fazan, Antonio J.
2014-10-01
This paper presents a semiautomatic method for rectilinear building roof boundary extraction, based on the integration of high-resolution aerial image and LiDAR (Light Detection and Ranging) data. The proposed method is formulated as an optimization problem, in which a snakes-based objective function is developed to represent the building roof boundaries in an object-space coordinate system. Three-dimensional polylines representing building roof boundaries are obtained by optimizing the objective function using the dynamic programming optimization technique. The results of our experiments showed that the proposed method satisfactorily performed the task of extracting different building roof boundaries from aerial image and LiDAR data.
On fictitious domain formulations for Maxwell's equations
DEFF Research Database (Denmark)
Dahmen, W.; Jensen, Torben Klint; Urban, K.
2003-01-01
We consider fictitious domain-Lagrange multiplier formulations for variational problems in the space H(curl: Omega) derived from Maxwell's equations. Boundary conditions and the divergence constraint are imposed weakly by using Lagrange multipliers. Both the time dependent and time harmonic...... formulations of the Maxwell's equations are considered. and we derive well-posed formulations for both cases. The variational problem that arises can be discretized by functions that do not satisfy an a-priori divergence constraint....
Modeling the urban boundary layer
Bergstrom, R. W., Jr.
1976-01-01
A summary and evaluation is given of the Workshop on Modeling the Urban Boundary Layer; held in Las Vegas on May 5, 1975. Edited summaries from each of the session chairpersons are also given. The sessions were: (1) formulation and solution techniques, (2) K-theory versus higher order closure, (3) surface heat and moisture balance, (4) initialization and boundary problems, (5) nocturnal boundary layer, and (6) verification of models.
$\\mathcal{N}=2$ supersymmetric field theories on 3-manifolds with A-type boundaries
Aprile, Francesco
2016-01-01
General half-BPS A-type boundary conditions are formulated for N=2 supersymmetric field theories on compact 3-manifolds with boundary. We observe that under suitable conditions manifolds of the real A-type admitting two complex supersymmetries (related by charge conjugation) possess, besides a contact structure, a natural integrable toric foliation. A boundary, or a general co-dimension-1 defect, can be inserted along any leaf of this preferred foliation to produce manifolds with boundary that have the topology of a solid torus. We show that supersymmetric field theories on such manifolds can be endowed with half-BPS A-type boundary conditions. We specify the natural curved space generalization of the A-type projection of bulk supersymmetries and analyze the resulting A-type boundary conditions in generic 3d non-linear sigma models and YM/CS-matter theories.
Boundary conditions for the gravitational field
International Nuclear Information System (INIS)
A review of the treatment of boundaries in general relativity is presented with the emphasis on application to the formulations of Einstein's equations used in numerical relativity. At present, it is known how to treat boundaries in the harmonic formulation of Einstein's equations and a tetrad formulation of the Einstein-Bianchi system. However, a universal approach valid for other formulations is not in hand. In particular, there is no satisfactory boundary theory for the 3+1 formulations which have been highly successful in binary black hole simulation. I discuss the underlying problems that make the initial-boundary-value problem much more complicated than the Cauchy problem. I review the progress that has been made and the important open questions that remain. Science is a differential equation. Religion is a boundary condition. (Alan Turing, quoted in J D Barrow, 'Theories of Everything') (topical review)
Kuhn, G. D.
1971-01-01
A computer program was developed to do the calculations for two-dimensional or axisymmetric configurations from low speeds to hypersonic speeds with arbitrary streamwise pressure, temperature, and Mach number distributions. Options are provided for obtaining initial conditions either from experimental information or from a theoretical similarity solution. The transition region can be described either by an arbitrary distribution of intermittency or by a function based on Emmons' probability theory. Correlations were developed for use in estimating the parameters of the theoretical intermittency function. Correlations obtained from other sources are used for estimating the transition point. Comparisons were made between calculated and measured boundary layer quantities for laminar, transitional, and turbulent flows on flat plates, cones, cone flares, and a waisted body of revolution. Excellent agreement was obtained between the present theory and two other theories based on the method of finite differences. The intermittency required to reproduce some experimental heat transfer results in hypersonic flow was found to be quite different from the theoretical function. It is suggested that the simple probability theory of Emmons may not be valid for representing the intermittency of hypersonic transitional boundary layers and that the program could be useful as a tool for detailed study of the intermittency of the transition region.
Vahidinia, Mohammad; Youssef, Mohamed; Shafiee Ardestani, Meysam; Sadeghi, Abbas; Dochev, Docho
2014-02-01
The foraminiferal content of the well-known, foraminifera-rich Abderaz Formation of the Kopeh-Dagh basin in northeastern Iran was analyzed to determine biostratigraphy, age dating, chronostratigraphy and evolutionary trends. The Abderaz Formation was sampled at the following four sections: the Qarehso section, the Abderaz village section, the Muzduran section and the Shorab section. The Qarehso section is approximately 540 m thick and consists of 77 planktonic foraminifera species belonging to 18 genera in 5 biozones, 10 echinoid species belonging to 4 genera and 8 inoceramid species belonging to 5 genera. Based on this fossil content, the Qarehso section was dated to the lowermost Turonian to the upper Santonian. Based on the first occurrence datums of Cremnoceramus walterdorfensis walterdorfensis and Cremnoceramus deformis deformis and on the FODs of Micraster cortestudinarium and Dicarinella concavata, the Turonian-Conician boundary was detected in this section. In addition, based on the FODs of Echinocorys gr. scutata forma vulgaris, Echinocorys gr. scutata forma vulgaris-planodama and Di. Asymetrica, the base of the Santonian stage was also detected in the Qarehso section. The Abderaz village section is 556.5 m thick and contains 17 genera and 68 species of planktonic foraminifera that have been identified in 9 biozones and 7 genera and 15 species of invertebrates. The lowermost Turonian to the lowermost Campanian ages have been established in the Abderaz Formation. In the Abderaz village section, 3 boundaries were identified. Based on the FODs of Cremnoceramus walterdorfensis walterdorfensis, C. deformis deformis and C. crassus crassus and on the FODs of Contusotruncana fornicata and C. pateliformis, the base of the Coniacian stage was identified. Based on the FODs of Di. asymetrica and Macroglobigerinelloides alvarezi, the Coniacian-Santonian boundary was identified. Additionally, based on the extinction of the Marginotruncanid group and on the LOD of
A variational formulation of electrodynamics
De Nicola, Antonio
2007-01-01
We present a variational formulation of electrodynamics using de Rham even and odd differential forms. Our formulation relies on a variational principle more complete than the Hamilton principle and thus leads to field equations with external sources and permits the derivation of the constitutive relations. We interpret a domain in space-time as an odd de Rham 4-current. This permits a treatment of different types of boundary problems in an unified way. In particular we obtain a smooth transition to the infinitesimal version by using a current with a one point support.
A Curved, Elastostatic Boundary Element for Plane Anisotropic Structures
Smeltzer, Stanley S.; Klang, Eric C.
2001-01-01
The plane-stress equations of linear elasticity are used in conjunction with those of the boundary element method to develop a novel curved, quadratic boundary element applicable to structures composed of anisotropic materials in a state of plane stress or plane strain. The curved boundary element is developed to solve two-dimensional, elastostatic problems of arbitrary shape, connectivity, and material type. As a result of the anisotropy, complex variables are employed in the fundamental solution derivations for a concentrated unit-magnitude force in an infinite elastic anisotropic medium. Once known, the fundamental solutions are evaluated numerically by using the known displacement and traction boundary values in an integral formulation with Gaussian quadrature. All the integral equations of the boundary element method are evaluated using one of two methods: either regular Gaussian quadrature or a combination of regular and logarithmic Gaussian quadrature. The regular Gaussian quadrature is used to evaluate most of the integrals along the boundary, and the combined scheme is employed for integrals that are singular. Individual element contributions are assembled into the global matrices of the standard boundary element method, manipulated to form a system of linear equations, and the resulting system is solved. The interior displacements and stresses are found through a separate set of auxiliary equations that are derived using an Airy-type stress function in terms of complex variables. The capabilities and accuracy of this method are demonstrated for a laminated-composite plate with a central, elliptical cutout that is subjected to uniform tension along one of the straight edges of the plate. Comparison of the boundary element results for this problem with corresponding results from an analytical model show a difference of less than 1%.
Petrizzo, Maria Rose
2014-05-01
Planktonic foraminifera are marine protozoans characterized by an excellent geological record and by high morphological diversification and speciation rates. For these reasons, they have been widely used in biostratigraphy and strongly contributed to the multi-disciplinary efforts to improve Cretaceous chronostratigraphy in pelagic settings. A critical time is the Albian to Santonian interval for which a high-resolution multiple bio-, geochemical and physical integrated stratigraphy framework exportable worldwide is still needed. This is partially because a consistent correlation of the planktonic foraminifera bioevents and calibration against other stratigraphic tools often lacks in accuracy, resolution and reproducibility of the data. At present the GSSPs for the base of the Cenomanian (Mt Risou, SE France), the base of the Turonian (Pueblo, Colorado) and the base of the Santonian (Olazagutia, N Spain) stages have been established and ratified by IUGS. Planktonic foraminifera bioevents are primary defining criteria for the Albian/Cenomanian boundary (appearance level of Thalmanninella globotruncanoides), and secondary defining criteria for the Cenomanian/Turonian (appearance level of Helvetoglobotruncana helvetica) and Coniacian/Santonian (appearance level of Globotruncana linneiana) boundaries. However, the identifications of the foraminiferal index species across those boundaries have been reported to be sometimes difficult or unreliable from a number of localities worldwide either because of their rarity or uncertainty in the taxonomic identifications. Reasons rely on many factors, such as poor sampling resolution, incomplete exposure, facies differences, fossil preservation quality, diachronous taxa occurrences, and regional/provincial distribution of the index species. Often, discrepancies pertain to taxonomic inconsistencies, species misidentifications and different species concepts that accumulate over time in the literature. Nevertheless, biostratigraphy
Toose, E.M.; Geurts, B.J.; Kuerten, J.G.M.
1999-01-01
The boundary integral formulation of the solution to the Stokes equations is used to describe the deformation of small compound non-Newtonian axisymmetric drops suspended in a Newtonian fluid that is subjected to an axisymmetric flow field. The non-Newtonian stress is treated as a source term in the
Non-singular field-only surface integral equations for electromagnetic scattering
Klaseboer, Evert; Chan, Derek Y C
2016-01-01
A boundary integral formulation of electromagnetics that involves only the components of E and H is derived without the use of surface currents that appear in the classical PMCHWT formulation. The kernels of the boundary integral equations for E and H are non-singular so that all field quantities at the surface can be determined to high precision and also geometries with closely spaced surfaces present no numerical difficulties. Quadratic elements can readily be used to represent the surfaces so that the surface integrals can be calculated to higher numerical precision than using planar elements for the same numbers of degrees of freedom.
International Nuclear Information System (INIS)
The trans-boundary area between Northern China, Mongolia and eastern Siberia of Russia is a continuous geographical area located in north eastern Asia. Many common issues in this region need to be addressed based on a uniform resources and environmental data warehouse. Based on the practice of joint scientific expedition, the paper presented a data integration solution including 3 steps, i.e., data collection standards and specifications making, data reorganization and process, data warehouse design and development. A series of data collection standards and specifications were drawn up firstly covering more than 10 domains. According to the uniform standard, 20 resources and environmental survey databases in regional scale, and 11 in-situ observation databases were reorganized and integrated. North East Asia Resources and Environmental Data Warehouse was designed, which included 4 layers, i.e., resources layer, core business logic layer, internet interoperation layer, and web portal layer. The data warehouse prototype was developed and deployed initially. All the integrated data in this area can be accessed online
Wang, J.; Song, J.; Gao, M.; Zhu, L.
2014-02-01
The trans-boundary area between Northern China, Mongolia and eastern Siberia of Russia is a continuous geographical area located in north eastern Asia. Many common issues in this region need to be addressed based on a uniform resources and environmental data warehouse. Based on the practice of joint scientific expedition, the paper presented a data integration solution including 3 steps, i.e., data collection standards and specifications making, data reorganization and process, data warehouse design and development. A series of data collection standards and specifications were drawn up firstly covering more than 10 domains. According to the uniform standard, 20 resources and environmental survey databases in regional scale, and 11 in-situ observation databases were reorganized and integrated. North East Asia Resources and Environmental Data Warehouse was designed, which included 4 layers, i.e., resources layer, core business logic layer, internet interoperation layer, and web portal layer. The data warehouse prototype was developed and deployed initially. All the integrated data in this area can be accessed online.
Morduchow, Morris
1955-01-01
A survey of integral methods in laminar-boundary-layer analysis is first given. A simple and sufficiently accurate method for practical purposes of calculating the properties (including stability) of the laminar compressible boundary layer in an axial pressure gradient with heat transfer at the wall is presented. For flow over a flat plate, the method is applicable for an arbitrarily prescribed distribution of temperature along the surface and for any given constant Prandtl number close to unity. For flow in a pressure gradient, the method is based on a Prandtl number of unity and a uniform wall temperature. A simple and accurate method of determining the separation point in a compressible flow with an adverse pressure gradient over a surface at a given uniform wall temperature is developed. The analysis is based on an extension of the Karman-Pohlhausen method to the momentum and the thermal energy equations in conjunction with fourth- and especially higher degree velocity and stagnation-enthalpy profiles.
Boundary transfer matrices and boundary quantum KZ equations
Energy Technology Data Exchange (ETDEWEB)
Vlaar, Bart, E-mail: Bart.Vlaar@nottingham.ac.uk [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
2015-07-15
A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.
Directory of Open Access Journals (Sweden)
Aimé Lachal
2011-01-01
Full Text Available Let ((∈[0,1] be the linear Brownian motion and ((∈[0,1] the (−1-fold integral of Brownian motion, with being a positive integer: ∫(=0((−−1/(−1!d( for any ∈[0,1]. In this paper we construct several bridges between times 0 and 1 of the process ((∈[0,1] involving conditions on the successive derivatives of at times 0 and 1. For this family of bridges, we make a correspondence with certain boundary value problems related to the one-dimensional polyharmonic operator. We also study the classical problem of prediction. Our results involve various Hermite interpolation polynomials.
Chen, D. S.; Cheng, S. Y.; Liu, L.; Chen, T.; Guo, X. R.
In this paper, an integrated MM5-CMAQ modeling approach was employed to investigate the PM 10 air pollution issue in Beijing, China, with a focus on assessing pollution contributions from surrounding provinces. A 2-level-nested grid domain with spatial resolutions of 36 and 12 km was designed for the study region. Seven monitoring stations across Beijing municipality were selected to provide hourly PM 10 measurement data. The months of January, April, July and October in 2002 were taken as target periods for model performance evaluation. Five emission scenarios were designed and run in order to quantitatively assess the trans-boundary PM 10 contributions. The results show that, while Beijing needs to take positive steps to reduce its own pollution emissions, much effort should also be placed on demanding more pollution reduction and better environmental performance from surrounding provinces.
Dash, Rajendra Narayan; Mohammed, Habibuddin; Humaira, Touseef
2016-01-01
We studied the application of Taguchi orthogonal array (TOA) design during the development of an isocratic stability indicating HPLC method for glimepiride as per TOA design; twenty-seven experiments were conducted by varying six chromatographic factors. Percentage of organic phase was the most significant (p glimepiride from a novel supersaturatable self-nanoemulsifying formulation. PMID:26903773
Gopurenko, David; Bellis, Glenn Adam; Yanase, Tohru; Wardhana, April Hari; Thepparat, Arunrat; Wang, Jinglin; Cai, Ducheng; Mitchell, Andrew
2015-01-01
In this study, species boundaries were examined for 15 described and 2 undescribed species within the economically important Culicoides subg. Avaritia Fox from Australasia and Eastern Asia. We used an integrative taxonomic approach incorporating DNA barcoding, nuclear gene sequencing, and retrospective morphological analyses. Some arbovirus vector species such as Culicoides fulvus Sen and Das Gupta and Culicoides wadai Kitaoka were genetically and morphologically uniform across sampled distributions, but others including Culicoides actoni Smith and Culicoides brevipalpis Delfinado contained 2 or more genetically independent populations of 'cryptic species' that in some cases were sympatric. Some of these 'cryptic species' exhibited consistent morphological differences, while differences are yet to be found for others species. Additionally, an undescribed species, C. Avaritia sp. No. 3, was found to be synonymous with C. fulvus. These results refine our understanding of the distribution of individual species of C. subg. Avaritia and demonstrate that species descriptions and distribution records need revision for part of the Culicoides fauna. Furthermore, because vector competence studies for most of these species are based entirely on Australian populations, the competence of the putative cryptic species identified elsewhere will require independent assessment. Finally, integrative taxonomic assessment requires genetic and morphological assessment of material from the type localities in order to clarify the status and distribution of species, especially for clades containing cryptic species. International collaboration is needed to facilitate this research. PMID:26741249
Shapiro-Ilan, David I; Morales-Ramos, Juan A; Rojas, Maria G; Tedders, Walker L
2010-02-01
An alternative approach to applying entomopathogenic nematodes entails the distribution of nematodes in their infected insect hosts. Protection of the infected host from rupturing, and improving ease of handling, may be necessary to facilitate application. In this study our objective was to test the potential of a new method of formulating the infected hosts, i.e., enclosing the infected host in masking tape. Tenebrio molitor L. cadavers infected with Heterorhabditis indica Poinar, Karunakar and David or Steinernema carpocapsae (Weiser) were wrapped in tape using an automatic packaging machine; the machine was developed to reduce labor and to standardize the final product. The effects of the tape formulation on the ability to protect the cadavers from mechanical damage, nematode yield, and pest control efficacy were tested. After exposure to mechanical agitation at 7-d-post-infection, S. carpocapsae cadavers in tape were more resistant to rupture than cadavers without tape, yet H. indica cadavers 7-d-post-infection were not affected by mechanical agitation (with or without tape), nor was either nematode affected when 4-d-old cadavers were tested. Experiments indicated that infective juvenile yield was not affected by the tape formulation. Laboratory experiments were conducted measuring survival of the root weevil, Diaprepes abbreviatus (L.), or the small hive beetle, Aethina tumida Murray, after the application of two H. indica-infected hosts with or without tape per 15 cm pot (filled with soil). A greenhouse experiment was also conducted in a similar manner measuring survival of D. abbreviatus. In all experiments, both the tape and no-tape treatments caused significant reductions in insect survival relative to the control, and no differences were detected between the nematode treatments. Fifteen days post-application, the infected host treatments caused up to 78% control in A. tumida, 91% control in D. abbreviatus in the lab, and 75% in the greenhouse. These
Shapiro-Ilan, David I; Morales-Ramos, Juan A; Rojas, Maria G; Tedders, Walker L
2010-02-01
An alternative approach to applying entomopathogenic nematodes entails the distribution of nematodes in their infected insect hosts. Protection of the infected host from rupturing, and improving ease of handling, may be necessary to facilitate application. In this study our objective was to test the potential of a new method of formulating the infected hosts, i.e., enclosing the infected host in masking tape. Tenebrio molitor L. cadavers infected with Heterorhabditis indica Poinar, Karunakar and David or Steinernema carpocapsae (Weiser) were wrapped in tape using an automatic packaging machine; the machine was developed to reduce labor and to standardize the final product. The effects of the tape formulation on the ability to protect the cadavers from mechanical damage, nematode yield, and pest control efficacy were tested. After exposure to mechanical agitation at 7-d-post-infection, S. carpocapsae cadavers in tape were more resistant to rupture than cadavers without tape, yet H. indica cadavers 7-d-post-infection were not affected by mechanical agitation (with or without tape), nor was either nematode affected when 4-d-old cadavers were tested. Experiments indicated that infective juvenile yield was not affected by the tape formulation. Laboratory experiments were conducted measuring survival of the root weevil, Diaprepes abbreviatus (L.), or the small hive beetle, Aethina tumida Murray, after the application of two H. indica-infected hosts with or without tape per 15 cm pot (filled with soil). A greenhouse experiment was also conducted in a similar manner measuring survival of D. abbreviatus. In all experiments, both the tape and no-tape treatments caused significant reductions in insect survival relative to the control, and no differences were detected between the nematode treatments. Fifteen days post-application, the infected host treatments caused up to 78% control in A. tumida, 91% control in D. abbreviatus in the lab, and 75% in the greenhouse. These
An integral equation representation approach for valuing Russian options with a finite time horizon
Jeon, Junkee; Han, Heejae; Kim, Hyeonuk; Kang, Myungjoo
2016-07-01
In this paper, we first describe a general solution for the inhomogeneous Black-Scholes partial differential equation with mixed boundary conditions using Mellin transform techniques. Since Russian options with a finite time horizon are usually formulated into the inhomogeneous free-boundary Black-Scholes partial differential equation with a mixed boundary condition, we apply our method to Russian options and derive an integral equation satisfied by Russian options with a finite time horizon. Furthermore, we present some numerical solutions and plots of the integral equation using recursive integration methods and demonstrate the computational accuracy and efficiency of our method compared to other competing approaches.
Crystallization Formulation Lab
Federal Laboratory Consortium — The Crystallization Formulation Lab fills a critical need in the process development and optimization of current and new explosives and energetic formulations. The...
Compatibility of DLC coatings with formulated oils
Sedlaček, Marko; PODGORNIK, Bojan; Vižintin, Jože
2015-01-01
In the present study, the tribological performance and compatibility of hydrogenated amorphous carbon coating (a-C:H) and metal-doped diamond-like carbon (DLC) coating (Me-C:H) with formulated oils under the boundary lubrication regime was investigated. The investigation employed ball-on-flat contact geometry in reciprocating sliding motion and six formulated oils (manual gearbox oil, automatic gearbox oil, hydraulic oil, compressor oil, andnormal and high performance motor oil), with pure po...
Three dimensional boundary element solutions for eddy current nondestructive evaluation
Yang, Ming; Song, Jiming; Nakagawa, Norio
2014-02-01
The boundary integral equations (BIE) method is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations. It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, and fracture mechanics. The eddy current problem is formulated by the BIE and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The three dimensional arbitrarily shaped objects are described by a number of triangular patches. The Stratton-Chu formulation is specialized for the conductive medium. The equivalent electric and magnetic surface currents are expanded in terms of Rao-Wilton-Glisson (RWG) vector basis function while the normal component of magnetic field is expanded in terms of the pulse basis function. Also, a low frequency approximation is applied in the external medium. Additionally, we introduce Auld's impedance formulas to calculate impedance variation. There are very good agreements between numerical results and those from theory and/or experiments for a finite cross-section above a wedge.
The Unified Method: II NLS on the Half-Line with $t$-Periodic Boundary Conditions
Lenells, J.; Fokas, A. S.
2011-01-01
Boundary value problems for integrable nonlinear evolution PDEs formulated on the half-line can be analyzed by the unified method introduced by one of the authors and used extensively in the literature. The implementation of this general method to this particular class of problems yields the solution in terms of the unique solution of a matrix Riemann-Hilbert problem formulated in the complex $k$-plane (the Fourier plane), which has a jump matrix with explicit $(x,t)$-dependence involving fou...
Application of impedance boundary conditions to numerical solution of corrugated circular horns
DEFF Research Database (Denmark)
Iskander, K; Shafai, L; Frandsen, Aksel;
1982-01-01
An integral equation method is used to formulate the problem of scattering by rotationally symmetric horn antennas. The excitation is assumed to be due to an infinitesimal dipole antenna, while the secondary field is obtained by assuming anisotropic impedance boundary conditions on the horn surface...... surface at the inner-end wall of the horn antenna, which is illuminated by an axially incident plane wave....
An extension of the transpired skin-friction equation to compressible turbulent boundary layers
Silva-Freire, Atila P.
1988-11-01
A skin-friction equation for transpired incompressible turbulent boundary layer, proposed in a previous paper (Silva-Freire, 1988), is extended to compressible flow. The expression derived here is simple and gives more consistent results than the momentum-integral equation. The difficulty with the present formulation, however, is that the wake profile parameter due to injection has to be carefully determined in order to obtain good results.
Energy Technology Data Exchange (ETDEWEB)
Orlowska, S [Ecole Centrale de Lyon, Centre de Genie Electrique de Lyon, CNRS UMR 5005, 69134 Ecully (France); Beroual, A [Ecole Centrale de Lyon, Centre de Genie Electrique de Lyon, CNRS UMR 5005, 69134 Ecully (France); Fleszynski, J [Institute of Fundamental Electrotechnics and Electrotechnology, University of Technology of Wroclaw, Wroclaw (Poland)
2002-10-21
The heterogeneous mixture properties depend on its constituents' characteristics. We examine the effective permittivity of a two-phase composite material made of epoxy resin host matrix and barium titanate (BaTiO{sub 3}) filler for different volume fractions in the matrix. The task we undertake consists in finding a model of BaTiO{sub 3} particles through the computer simulations executed in PHI3D-electric field calculating package, based on the resolution of the Laplace equation using boundary integral equation method. With this aim in view we compare the measured results of the effective permittivity of the BaTiO{sub 3}-epoxy resin composite samples with the simulation results for different BaTiO{sub 3} particle geometric models and for the same experimental conditions, with regard to the given volume fraction of the powder in the matrix. The experimental results are obtained through the measurements with an impedance meter in the range of frequencies from 50 Hz to 1 MHz.
BRST formulation of 4-monopoles
Gianvittorio, R; Restuccia, A
1996-01-01
A supersymmetric gauge invariant action is constructed over any 4-dimensional Riemannian manifold describing Witten's theory of 4-monopoles. The topological supersymmetric algebra closes off-shell. The multiplets include the auxiliary fields and the Wess-Zumino fields in an unusual way, arising naturally from BRST gauge fixing. A new canonical approach over Riemann manifolds is followed, using a Morse function as an euclidean time and taking into account the BRST boundary conditions that come from the BFV formulation. This allows a construction of the effective action starting from gauge principles.
XFEM simulation of a quenched cracked glass plate with moving convective boundaries
Ghaffari, Diyako; Rash Ahmadi, Samrand; Shabani, Farzin
2016-02-01
A moving quenched soda-lime glass plate with an initial edge crack is modeled, applying the eXtended finite-element method (XFEM) in order to investigate the stress field components and Von Mises stress around the crack. The convective heat with moving boundaries is considered in thermal formulation. The Crank-Nicolson time integration scheme is reformed and adjusted with a view to accurately solving the system of transient heat conduction matrix equations. In order to simulate the whole stages of the problem formulation, MATLAB XFEM (MXFEM) codes are written and employed. The stress distribution contours are plotted in detail and the stress fields around the crack tip are compared quantitatively. The variations of stress intensity factors (SIFs) during crack propagation are obtained through the calculation of the domain form of the interaction integral. In order to verify the procedure and display the ability of the developed formulation, the results are compared with experimental outputs from the literature.
Three-dimensional shape optimization using the boundary element method
Yamazaki, Koetsu; Sakamoto, Jiro; Kitano, Masami
1994-06-01
A practical design sensitivity calculation technique of displacements and stresses for three-dimensional bodies based on the direct differentiation method of discrete boundary integral equations is formulated in detail. Then the sensitivity calculation technique is applied to determine optimum shapes of minimum weight subjected to stress constraints, where an approximated subproblem is constructed repeatedly and solved sequentially by the mathematical programming method. The shape optimization technique suggested here is applied to determine optimum shapes of a cavity in a cube and a connecting rod.
Three-dimensional shape optimization using boundary element method
Yamazaki, Koetsu; Sakamoto, Jiro; Kitano, Masami
1993-04-01
A practical design sensitivity calculation technique of displacements and stresses for three-dimensional bodies based on the direct differentiation method of discrete boundary integral equations is formulated in detail. Then, the sensitivity calculation technique is applied to determine optimum shapes of minimum weight subjected to stress constraints, where an approximated subproblem is constructed repeatedly and solved sequentially by the mathematical programming method. The shape optimization technique suggested here is applied to determine optimum shapes of a cavity shape in a cube and a connecting rod.
Spin Observables and Path Integrals
López, J A
2000-01-01
We discuss the formulation of spin observables associated to a non-relativistic spinning particles in terms of grassmanian differential operators. We use as configuration space variables for the pseudo-classical description of this system the positions $x$ and a Grassmanian vector quantum amplitudes as path integrals in this superspace. We compute the quantum action necessary for this description including an explicit expression for the boundary terms. Finally we shown how for simple examples, the path integral may be performed in the semi-classical approximation, leading to the correct quantum propagator.
Guo, L.; Gao, R.; Meng, X.; Zhang, J.; Wang, H.; Liu, Y.
2013-12-01
analysis on them. Seismic reflection profiles focus on fine lithosphere structure vertically along the profile, while gravity and magnetic methods are beneficial to reveal regional tectonic features laterally. The integrate study of seismic, gravity and magnetic data will play the advantages of various methods and constraint and confirm each other. Hence, we did the interpretation of gravity and magnetic data with constraints of the newly seismic reflection profile. Based on the above studies, we traced the boundaries of tectonic units in the SCC from Meso-Neoproterozoic to early Paleozoic, and formed a certain understanding of the tectonic evolution in the SCC before the late Paleozoic. Acknowledgment: We acknowledge the financial support of the SinoProbe-02-01 and SinoProbe-01-05 projects, and the Fundamental Research Funds for the Central Universities.
The unified method: II. NLS on the half-line with t-periodic boundary conditions
Lenells, J.; Fokas, A. S.
2012-05-01
Boundary value problems for integrable nonlinear evolution PDEs formulated on the half-line can be analyzed by the unified method introduced by one of the authors and used extensively in the literature. The implementation of this general method to this particular class of problems yields the solution in terms of the unique solution of a matrix Riemann-Hilbert problem formulated in the complex k-plane (the Fourier plane), which has a jump matrix with explicit (x, t)-dependence involving four scalar functions of k, called spectral functions. Two of these functions depend on the initial data, whereas the other two depend on all boundary values. The most difficult step of the new method is the characterization of the latter two spectral functions in terms of the given initial and boundary data, i.e. the elimination of the unknown boundary values. For certain boundary conditions, called linearizable, this can be achieved by simply using algebraic manipulations. Here, we first present an effective characterization of the spectral functions in terms of the given initial and boundary data for the general case of non-linearizable boundary conditions. This characterization is based on the analysis of the so-called global relation and on the introduction of the so-called Gelfand-Levitan-Marchenko representations of the eigenfunctions defining the spectral functions. We then concentrate on the physically significant case of t-periodic Dirichlet boundary data. After presenting certain heuristic arguments which suggest that the Neumann boundary values become periodic as t → ∞, we show that for the case of the NLS with a sine-wave as Dirichlet data, the asymptotics of the Neumann boundary values can be computed explicitly at least up to third order in a perturbative expansion and indeed at least up to this order are asymptotically periodic.
Energy Technology Data Exchange (ETDEWEB)
Jo, Jong Chull; Shin, Won Ky [Korea Institute of Nuclear Safety, Taejon (Korea, Republic of)
1997-12-31
This paper presents an effective and simple procedure for the simulation of the motion of the solid-liquid interfacial boundary and the transient temperature field during phase change process. To accomplish this purpose, an iterative implicit solution algorithm has been developed by employing the dual reciprocity boundary element method. The dual reciprocity boundary element approach provided in this paper is much simpler than the usual boundary element method applying a reciprocity principle and an available technique for dealing with domain integral of boundary element formulation simultaneously. The effectiveness of the present analysis method have been illustrated through comparisons of the calculation results of an example with its semi-analytical or other numerical solutions where available. 22 refs., 3 figs. (Author)
IT Supporting Strategy Formulation
Achterbergh, J.M.I.M.
2005-01-01
This overview approaches information and communication technology (ICT) for competitive intelligence from the perspective of strategy formulation. It provides an ICT architecture for supporting the knowledge processes producing relevant knowledge for strategy formulation. To determine what this arch
Phase Boundaries in Algebraic Conformal QFT
Bischoff, Marcel; Kawahigashi, Yasuyuki; Longo, Roberto; Rehren, Karl-Henning
2016-02-01
We study the structure of local algebras in relativistic conformal quantum field theory with phase boundaries. Phase boundaries are instances of a more general notion of boundaries that give rise to a variety of algebraic structures. These can be formulated in a common framework originating in Algebraic QFT, with the principle of Einstein Causality playing a prominent role. We classify the phase boundary conditions by the centre of a certain universal construction, which produces a reducible representation in which all possible boundary conditions are realized. For a large class of models, the classification reproduces results obtained in a different approach by Fuchs et al. before.
IT Supporting Strategy Formulation
Achterbergh, J.M.I.M.
2005-01-01
This overview approaches information and communication technology (ICT) for competitive intelligence from the perspective of strategy formulation. It provides an ICT architecture for supporting the knowledge processes producing relevant knowledge for strategy formulation. To determine what this architecture looks like, we first examine the process of strategy formulation and determine the knowledge required in the process of strategy formulation. To this purpose, we use Beer’s viable system m...
Boundary Conditions in an Electric Current Contact
Titov, O. Yu.; Giraldo, J.; Gurevich, Yu. G.
2002-01-01
In most electronic devices, electric current of both types (electrons and holes) flows through a junction. Usually the boundary conditions have been formulated exclusively for open circuit. The boundary conditions proposed here bypass this limitation by the first time, as far as we are aware. Besides, these new boundary conditions correctly describe current flow in a circuit, i.e., closed circuit conditions, which are the usual operation conditions for electronic devices and for the measureme...
Hybrid Finite Element and Volume Integral Methods for Scattering Using Parametric Geometry
DEFF Research Database (Denmark)
Volakis, John L.; Sertel, Kubilay; Jørgensen, Erik;
2004-01-01
n this paper we address several topics relating to the development and implementation of volume integral and hybrid finite element methods for electromagnetic modeling. Comparisons of volume integral equation formulations with the finite element-boundary integral method are given in terms of...... accuracy and computing resources. We also discuss preconditioning and parallelization of the multilevel fast multipole method, and propose higher-order basis functions for curvilinear quadrilaterals and volumetric basis functions for curvilinear hexahedra. The latter have the desirable property of...
DEFF Research Database (Denmark)
Emerek, Ruth
2004-01-01
Bidraget diskuterer de forskellige intergrationsopfattelse i Danmark - og hvad der kan forstås ved vellykket integration......Bidraget diskuterer de forskellige intergrationsopfattelse i Danmark - og hvad der kan forstås ved vellykket integration...
DEFF Research Database (Denmark)
Løvschal, Mette
2014-01-01
and formalization. These principles are then used to argue the case for socioconceptual emergence and causality between the lines. This causality appears only in a long-term perspective and implies that, although the development of these boundaries was chronologically displaced across northwestern......This article proposes a processual ontology for the emergence of man-made, linear boundaries across northwestern Europe, particularly in the first millennium BC. Over a significant period of time, these boundaries became new ways of organizing the landscape and settlements—a phenomenon that has...... Europe, elements of this phenomenon emerged along equivalent trajectories. At the same time, variation in the regional incorporation of these linear phenomena points toward situation-specific applications and independent development....
Institute of Scientific and Technical Information of China (English)
王家玉; 陈金兰
2001-01-01
By using the concept of abstract cone,improved comparable theoremand fixed point theorem of nonlinear operator and by discussing the periodic boundary condition of nonlinear integral-differential equation in Banach spaces,this paper gave two monotonic iterative sequences,also verified the minimum and maximum theorem for nonlinear integral-differential equation with periodic boundary condition in Banach spaces.%本文考虑Banach空间中非线性积分－微分方程的周期边值问题，利用抽象锥、推广了的比较定理及非线性算子的不动点定理，构造出两个单调迭代序列，证明了Banach空间中非线性积分－微分方程具有周期边值的最小解、最大解存在定理。
DEFF Research Database (Denmark)
Brodkin, Evelyn; Larsen, Flemming
2013-01-01
In recent decades, workfare-style policies have become part of the institutional architecture of welfare and labor market arrangements around the world. In this article, we offer a comparative, historical view of workfare´s advance. Our analysis recognizes the complexity and diversity of what we...... project that is altering the boundary between the democratic welfare state and the market economy. We see workfare policies as boundary-changing with potentially profound implications both for individuals disadvantaged by market arrangements and for societies seeking to grapple with the increasing...
International Nuclear Information System (INIS)
In this paper we study path integral for a single spinless particle on a star graph with N edges, whose vertex is known to be described by U(N) family of boundary conditions. After carefully studying the free particle case, both at the critical and off-critical levels, we propose a new path integral formulation that correctly captures all the scale-invariant subfamily of boundary conditions realized at fixed points of boundary renormalization group flow. Our proposal is based on the folding trick, which maps a scalar-valued wave function on star graph to an N-component vector-valued wave function on half-line. All the parameters of scale-invariant subfamily of boundary conditions are encoded into the momentum independent weight factors, which appear to be associated with the two distinct path classes on half-line that form the cyclic group Z2. We show that, when bulk interactions are edge-independent, these weight factors are generally given by an N-dimensional unitary representation of Z2. Generalization to momentum dependent weight factors and applications to worldline formalism are briefly discussed. - Highlights: ► We propose the new path integral formulation on star graph with N edges. ►U(N) family of boundary conditions is well-described by weight factors. ► The scale-invariant weight factor is given by N-dimensional unitary representation of Z2. ► Generalization to momentum dependent weight factors is briefly discussed.
Energy Technology Data Exchange (ETDEWEB)
Yokoi, T. [Building Research Institute, Tokyo (Japan); Sanchez-Sesma, F. [Universidad National Autonoma de Mexico, (Mexico). Institute de Ingenieria
1997-05-27
Formulation is introduced for discretizing a boundary integral equation into an indirect boundary element method for the solution of 3-dimensional topographic problems. Yokoi and Takenaka propose an analytical solution-capable reference solution (solution for the half space elastic body with flat free surface) to problems of topographic response to seismic motion in a 2-dimensional in-plane field. That is to say, they propose a boundary integral equation capable of effectively suppressing the non-physical waves that emerge in the result of computation in the wake of the truncation of the discretized ground surface making use of the wave field in a semi-infinite elastic body with flat free surface. They apply the proposed boundary integral equation discretized into the indirect boundary element method to solve some examples, and succeed in proving its validity. In this report, the equation is expanded to deal with 3-dimensional topographic problems. A problem of a P-wave vertically landing on a flat and free surface is solved by the conventional boundary integral equation and the proposed boundary integral equation, and the solutions are compared with each other. It is found that the new method, different from the conventional one, can delete non-physical waves from the analytical result. 4 figs.
DEFF Research Database (Denmark)
Aarhus, Rikke; Ballegaard, Stinne Aaløkke
2010-01-01
To move treatment successfully from the hospital to that of technology assisted self-care at home, it is vital in the design of such technologies to understand the setting in which the health IT should be used. Based on qualitative studies we find that people engage in elaborate boundary work...
DEFF Research Database (Denmark)
Neergaard, Ulla; Nielsen, Ruth
2010-01-01
; and 3) Services of general interest. In the Blurring Boundaries project, three aspects of the European Social Model have been particularly highlighted: the constitutionalisation of the European Social Model, its multi-level legal character, and the clash between market access justice at EU level...... and distributive justice at national level....
A comparative review of four formulations of noncommutative quantum mechanics
Gouba, Laure
2016-07-01
Four formulations of quantum mechanics on noncommutative Moyal phase spaces are reviewed. These are the canonical, path-integral, Weyl-Wigner and systematic formulations. Although all these formulations represent quantum mechanics on a phase space with the same deformed Heisenberg algebra, there are mathematical and conceptual differences which we discuss.
Explicit boundary form factors: The scaling Lee–Yang model
Energy Technology Data Exchange (ETDEWEB)
Hollo, L. [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary); Laczko, Z.B. [Roland Eötvös University, Pázmány Péter sétány 1/A, 1117 Budapest (Hungary); Bajnok, Z. [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary)
2014-09-15
We provide explicit expressions for boundary form factors in the boundary scaling Lee–Yang model for operators with the mildest ultraviolet behavior for all integrable boundary conditions. The form factors of the boundary stress tensor take a determinant form, while the form factors of the boundary primary field contain additional explicit polynomials.
He, Lianyi
2016-10-01
We present a standard field theoretical derivation of the dynamic density and spin linear response functions of a dilute superfluid Fermi gas in the BCS-BEC crossover in both three and two dimensions. The derivation of the response functions is based on the elegant functional path integral approach which allows us to calculate the density-density and spin-spin correlation functions by introducing the external sources for the density and the spin density. Since the generating functional cannot be evaluated exactly, we consider two gapless approximations which ensure a gapless collective mode (Goldstone mode) in the superfluid state: the BCS-Leggett mean-field theory and the Gaussian-pair-fluctuation (GPF) theory. In the mean-field theory, our results of the response functions agree with the known results from the random phase approximation. We further consider the pair fluctuation effects and establish a theoretical framework for the dynamic responses within the GPF theory. We show that the GPF response theory naturally recovers three kinds of famous diagrammatic contributions: the Self-Energy contribution, the Aslamazov-Lakin contribution, and the Maki-Thompson contribution. We also show that unlike the equilibrium state, in evaluating the response functions, the linear (first-order) terms in the external sources as well as the induced order parameter perturbations should be treated carefully. In the superfluid state, there is an additional order parameter contribution which ensures that in the static and long wavelength limit, the density response function recovers the result of the compressibility (compressibility sum rule). We expect that the f-sum rule is manifested by the full number equation which includes the contribution from the Gaussian pair fluctuations. The dynamic density and spin response functions in the normal phase (above the superfluid critical temperature) are also derived within the Nozières-Schmitt-Rink (NSR) theory.
Directory of Open Access Journals (Sweden)
D. Diederen
2015-06-01
Full Text Available We present a new equation describing the hydrodynamics in infinitely long tidal channels (i.e., no reflection under the influence of oceanic forcing. The proposed equation is a simple relationship between partial derivatives of water level and velocity. It is formally derived for a progressive wave in a frictionless, prismatic, tidal channel with a horizontal bed. Assessment of a large number of numerical simulations, where an open boundary condition is posed at a certain distance landward, suggests that it can also be considered accurate in the more natural case of converging estuaries with nonlinear friction and a bed slope. The equation follows from the open boundary condition and is therefore a part of the problem formulation for an infinite tidal channel. This finding provides a practical tool for evaluating tidal wave dynamics, by reconstructing the temporal variation of the velocity based on local observations of the water level, providing a fully local open boundary condition and allowing for local friction calibration.
Spherical gravitational curvature boundary-value problem
Šprlák, Michal; Novák, Pavel
2016-08-01
Values of scalar, vector and second-order tensor parameters of the Earth's gravitational field have been collected by various sensors in geodesy and geophysics. Such observables have been widely exploited in different parametrization methods for the gravitational field modelling. Moreover, theoretical aspects of these quantities have extensively been studied and well understood. On the other hand, new sensors for observing gravitational curvatures, i.e., components of the third-order gravitational tensor, are currently under development. As the gravitational curvatures represent new types of observables, their exploitation for modelling of the Earth's gravitational field is a subject of this study. Firstly, the gravitational curvature tensor is decomposed into six parts which are expanded in terms of third-order tensor spherical harmonics. Secondly, gravitational curvature boundary-value problems defined for four combinations of the gravitational curvatures are formulated and solved in spectral and spatial domains. Thirdly, properties of the corresponding sub-integral kernels are investigated. The presented mathematical formulations reveal some important properties of the gravitational curvatures and extend the so-called Meissl scheme, i.e., an important theoretical framework that relates various parameters of the Earth's gravitational field.
Peters, Arne
2016-01-01
The enduring stages of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis are infective juveniles, which require a high humidity and sufficient ventilation for survival. Formulations must account for these requirements. Nematodes may be formulated inside the insects in which they reproduced or they need to be cleaned and mixed with a suitable binder to maintain humidity but allowing for gas exchange. Another method for formulation is the encapsulation in beads of Ca-alginate. Generic procedures for these formulation techniques are described. PMID:27565496
Dynamic Stationary Response of Reinforced Plates by the Boundary Element Method
Directory of Open Access Journals (Sweden)
Luiz Carlos Facundo Sanches
2007-01-01
Full Text Available A direct version of the boundary element method (BEM is developed to model the stationary dynamic response of reinforced plate structures, such as reinforced panels in buildings, automobiles, and airplanes. The dynamic stationary fundamental solutions of thin plates and plane stress state are used to transform the governing partial differential equations into boundary integral equations (BIEs. Two sets of uncoupled BIEs are formulated, respectively, for the in-plane state (membrane and for the out-of-plane state (bending. These uncoupled systems are joined to form a macro-element, in which membrane and bending effects are present. The association of these macro-elements is able to simulate thin-walled structures, including reinforced plate structures. In the present formulation, the BIE is discretized by continuous and/or discontinuous linear elements. Four displacement integral equations are written for every boundary node. Modal data, that is, natural frequencies and the corresponding mode shapes of reinforced plates, are obtained from information contained in the frequency response functions (FRFs. A specific example is presented to illustrate the versatility of the proposed methodology. Different configurations of the reinforcements are used to simulate simply supported and clamped boundary conditions for the plate structures. The procedure is validated by comparison with results determined by the finite element method (FEM.
Knowlton, Kelly; Andrews, Jane C.
2006-01-01
(Ozone Monitoring Instrument) and TES (Tropospheric Emission Spectrometer) air quality data for the RPOs by comparing OMI and TES data with ground-based data that are acquired during identified episodes of air pollution. The air quality data from OMI and TES are of different spectral ranges than data from satellites currently included in FASTNET, giving them potential advantages over the existing satellites. If the OMI and TES data are shown to be useful to the RPOs, they would then be integrated into the FASTNET DST for use on an operational basis.
Thermal field theories and shifted boundary conditions
Giusti, Leonardo
2013-01-01
The analytic continuation to an imaginary velocity of the canonical partition function of a thermal system expressed in a moving frame has a natural implementation in the Euclidean path-integral formulation in terms of shifted boundary conditions. The Poincare' invariance underlying a relativistic theory implies a dependence of the free-energy on the compact length L_0 and the shift xi only through the combination beta=L_0(1+xi^2)^(1/2). This in turn implies that the energy and the momentum distributions of the thermal theory are related, a fact which is encoded in a set of Ward identities among the correlators of the energy-momentum tensor. The latter have interesting applications in lattice field theory: they offer novel ways to compute thermodynamic potentials, and a set of identities to renormalize non-perturbatively the energy-momentum tensor. At fixed bare parameters the shifted boundary conditions also provide a simple method to vary the temperature in much smaller steps than with the standard procedur...
Dirichlet-Neumann bracketing for boundary-value problems on graphs
Directory of Open Access Journals (Sweden)
Sonja Currie
2005-08-01
Full Text Available We consider the spectral structure of second order boundary-value problems on graphs. A variational formulation for boundary-value problems on graphs is given. As a consequence we can formulate an analogue of Dirichlet-Neumann bracketing for boundary-value problems on graphs. This in turn gives rise to eigenvalue and eigenfunction asymptotic approximations.
Townsend, Alan R.; Porder, Stephen
2011-03-01
What is our point of no return? Caesar proclaimed 'the die is cast' while crossing the Rubicon, but rarely does modern society find so visible a threshold in our continued degradation of ecosystems and the services they provide. Humans have always used their surroundings to make a living— sometimes successfully, sometimes not (Diamond 2005)—and we intuitively know that there are boundaries to our exploitation. But defining these boundaries has been a challenge since Malthus first prophesied that nature would limit the human population (Malthus 1798). In 2009, Rockström and colleagues tried to quantify what the 6.8 billion (and counting) of us could continue to get away with, and what we couldn't (Rockström et al 2009). In selecting ten 'planetary boundaries', the authors contend that a sustainable human enterprise requires treating a number of environmental thresholds as points of no return. They suggest we breach these Rubicons at our own peril, and that we've already crossed three: biodiversity loss, atmospheric CO2, and disruption of the global nitrogen (N) cycle. As they clearly hoped, the very act of setting targets has provoked scientific inquiry about their accuracy, and about the value of hard targets in the first place (Schlesinger 2009). Such debate is a good thing. Despite recent emphasis on the science of human-ecosystem interactions, understanding of our planetary boundaries is still in its infancy, and controversy can speed scientific progress (Engelhardt and Caplan 1987). A few weeks ago in this journal, Carpenter and Bennett (2011) took aim at one of the more controversial boundaries in the Rockström analysis: that for human alteration of the global phosphorus (P) cycle. Rockström's group chose riverine P export as the key indicator, suggesting that humans should not exceed a value that could trigger widespread marine anoxic events—and asserting that we have not yet crossed this threshold. There are defensible reasons for a marine
2003-01-01
MGS MOC Release No. MOC2-510, 11 October 2003The sharp, nearly straight line that runs diagonally across the center of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an albedo boundary. Albedois a term that refers to reflectance of sunlight. A surface with a low albedo is one that appears dark because it reflects less light than a high albedo (bright) surface. On Mars, albedo boundaries occur between two materials of differing texture, particle size, or composition, or some combination of these three factors. The boundary shown here is remarkable because it is so sharp and straight. This is caused by wind. Most likely, the entire surface was once covered with the lower-albedo (darker) material that is now seen in the upper half of the image. At some later time, wind stripped away this darker material from the surfaces in the lower half of the image. The difference in albedo here might be related to composition, and possibly particle size. This picture is located near the southwest rim of Schiaparelli Basin at 5.5oS, 345.9oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.
Institute of Scientific and Technical Information of China (English)
王训练
2002-01-01
The steps and methods for the establishment of the global boundary stratotype section and point (GSSP) are summed up briefly as follows. (i) Select rock sequences of approximately the same age duration in a region, make a thorough study of their properties or attributes in order to establish the high-resolution stratigraphic units reflecting the natural rhythms in Earth's history, and proceed by multidisciplinary comprehensive studies to reveal the relationship, including time-space relation and possible mutual causality, among the various stratigraphic units and the different natural rhythms established. (ii) Seek for the "natural break" that represents the "major natural changes in the historical development of the Earth" in shallow marine facies areas, which is frequently the third-order sequence boundaries. (iii) Trace from shallow marine facies areas toward the continental slope and bathyal areas to seek for a continuous depositional sequence that corresponds in time span to the "natural break" of shallow marine facies areas. (iv) Seek for a horizon within the continuous depositional sequence that approximately coincides with the maximum regressive point in the "natural break". This horizon is commonly within a lowerstand systems tract (LST) or a shelf margin systems tract (SMST) of the relevant third-order sequence. (v) Seek immediately above this horizon of maximum marine regression for an organic radiation or explosion event closely related to the natural boundary, which is generally the first flooding surface (FFS) of the relevant third-order sequence. (vi) Select within the organic event deposits closely related to the FFS the base boundary of a fossil taxon with widest geographical range as the Leading Group biozone for designation of the stratigraphic boundary. (vii) Select from among the sections with continuous depositional sequence formed under similar sedimentary palaeogeographic background (in general continental slope or bathyal environments) the
Formulations in first encounters
A. Hak (Tony); F. de Boer (Fijgje)
1994-01-01
markdownabstractThe paper describes and compares the use and function of the formulation--decision pair in three types of diagnostic interviewing. The investigatory type of interviewing, which typically occurs in the medical interview, is characterized by the absence of formulations. In the explora
Alves, I. P.; Degrazia, G. A.; Buske, D.; Vilhena, M. T.; Moraes, O. L. L.; Acevedo, O. C.
2012-12-01
In this study an integral and an algebraic formulation for the eddy diffusivities in a shear driven planetary boundary layer are derived for pollutant dispersion applications. The expressions depend on the turbulence properties and on the distance from the source. They are based on the turbulent kinetic energy spectra, Taylor’s statistical diffusion theory and measured turbulent characteristics during intense wind events. The good agreement between the algebraic and the integral formulation for the eddy diffusivities corroborate the hypothesis that using an algebraic formulation as a surrogate for the eddy diffusivities in the neutral planetary boundary layer is valid. As a consequence, the vertical eddy diffusivity provided by the algebraic formulation and its asymptotic limit for large time (diffusion time much larger than the Lagrangian integral time scale), were introduced into an analytical air pollution model and validated against data from the classic Prairie Grass project. A statistical analysis, employing specific indices shows that the results are in good agreement with the observations. Furthermore, this study suggests that the inclusion of the memory effect, which is important in regions near to a continuous point source, improves the description of the turbulent transport process of atmospheric contaminants. Therefore, the major finding of this paper is the necessity of including the downwind distance-dependent eddy diffusivity for low continuous point sources in air quality modeling studies.
Rankin, Pressley Robinson, IV
2013-01-01
How individuals manage work/life boundaries when they live at the place they work, as opposed to working from home, is a gap in both work/life literature and in higher education literature. An obvious example from higher education is the resident life professional that lives in the residential facility that she or he oversees. Living in a…
Post-buckling analysis of composite beams: A simple intuitive formulation
Indian Academy of Sciences (India)
Jagadish Babu Gunda; G Venkateswara Rao
2013-06-01
Post-buckling analysis of composite beams with axially immovable ends is investigated using an Intuitive formulation. Intuitive formulation uses two parameters namely critical buckling load and axial stretching force developed in the post-buckled domain of composite beam. Geometric nonlinearity of von-Karman type is taken into consideration which accounts for membrane stretching action of the beam. Axial stretching force developed in post-buckled domain of composite beam is evaluated by using an axial governing equation and is expressed either in terms of lateral displacement function as an integrated value, or as a function of both axial and lateral displacement functions at any discrete location of the beam. The available expressions of critical buckling load and derived expressions of axial stretching force developed in the beam are used for obtaining an approximate closed-form expressions for the post-buckling loads of various beam boundary conditions. Numerical accuracy of the proposed analytical closed-form expressions obtained from the intuitive formulation are compared to the available ﬁnite element solutions for symmetric and asymmetric lay-up schemes of laminated composite beam. Effect of central amplitude ratio and lay-up orientation on post-buckling load variation is brieﬂy discussed for various beam boundary conditions considered in this study.
Energy Technology Data Exchange (ETDEWEB)
Lim, T.
2011-04-28
To simulate numerically a non-destructive by eddy current testing (NDT-CF), the sensor response can be modeled through a semi-analytical approach by volume integral equations. Faster than the finite element method, this approach is however restricted to the study of plane or cylindrical parts (without taking into account the edge effects) because of the complexity of the expression of the dyadic Green function for more general configurations. However, there is an industrial demand to extend the capabilities of the CF model in complex configurations (deformed plates, edges effects...). We were thus brought to formulate the electromagnetic problem differently, by setting ourselves the goal of maintaining a semi-analytical approach. The surface integral equation (SIE) expresses the volume problem by an equivalent transmission one at the interfaces (2D) between homogeneous sub-domains. This problem is approached by a linear system (by the method of moments), whose number of unknowns is reduced due to the nature of the surfacic mesh. Therefore, this system can be solved by a direct solver for small configurations. That enabled us to treat several various positions of the sensor for only one inversion of the impedance matrix. The numerical results obtained using this formulation involve plates with consideration of edge effects such as edge and corner. They are consistent with results obtained by the finite element method. For larger configurations, we conducted a preliminary study for the adaptation of an acceleration method of the matrix vector product involved in an iterative solver (fast multipole method or FMM) to define the conditions under which the FMM calculation works correctly (accuracy, convergence...) in the NDT's domain. A special attention has been given to the choice of basis functions (which have to satisfy an Hdiv conforming property) and on the evaluation of near interactions (which are weakly singular). (author) [French] Pour simuler
Directory of Open Access Journals (Sweden)
Mehmet Camurdan
1998-01-01
are coupled by appropriate trace operators. This overall model differs from those previously studied in the literature in that the elastic chamber floor is here more realistically modeled by a hyperbolic Kirchoff equation, rather than by a parabolic Euler-Bernoulli equation with Kelvin-Voight structural damping, as in past literature. Thus, the hyperbolic/parabolic coupled system of past literature is replaced here by a hyperbolic/hyperbolic coupled model. The main result of this paper is a uniform stabilization of the coupled PDE system by a (physically appealing boundary dissipation.
Riemann Boundary Value Problems for Koch Curve
Directory of Open Access Journals (Sweden)
Zhengshun Ruanand
2012-11-01
Full Text Available In this study, when L is substituted for Koch curve, Riemann boundary value problems was defined, but generally speaking, Cauchy-type integral is meaningless on Koch curve. When some analytic conditions are attached to functions G (z and g (z, through the limit function of a sequence of Cauchytype integrals, the homogeneous and non-homogeneous Riemann boundary problems on Koch curve are introduced, some similar results was attained like the classical boundary value problems for analytic functions.
An Axisymmetrical Acoustic BEM Formulation Including Visco-Thermal Losses
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Juhl, Peter Møller
2011-01-01
Sound waves in air experience losses due to viscous friction and thermal exchange, which become particularly relevant in a thin boundary layer over the domain boundaries. The lossless wave equation can still be used when the thickness of the boundary layer is small as compared with the setup...... dimensions. However, this is not usually true for small devices such as microphones, hearing aids, couplers, MEMS devices, mobile phones, etc., and then the losses need to be modeled. In this paper a numerical implementation of the Boundary Element Method (BEM) which includes visco-thermal losses...... is presented. The formulation is based on the Kirchoff method, where acoustic, thermal and viscous effects are decoupled everywhere except at the boundaries. This BEM formulation does not impose geometrical restrictions to the setup and can be applied to any axisymmetrical object, as long as the division...
Audits of radiopharmaceutical formulations
International Nuclear Information System (INIS)
A procedure for auditing radiopharmaceutical formulations is described. To meet FDA guidelines regarding the quality of radiopharmaceuticals, institutional radioactive drug research committees perform audits when such drugs are formulated away from an institutional pharmacy. All principal investigators who formulate drugs outside institutional pharmacies must pass these audits before they can obtain a radiopharmaceutical investigation permit. The audit team meets with the individual who performs the formulation at the site of drug preparation to verify that drug formulations meet identity, strength, quality, and purity standards; are uniform and reproducible; and are sterile and pyrogen free. This team must contain an expert knowledgeable in the preparation of radioactive drugs; a radiopharmacist is the most qualified person for this role. Problems that have been identified by audits include lack of sterility and apyrogenicity testing, formulations that are open to the laboratory environment, failure to use pharmaceutical-grade chemicals, inadequate quality control methods or records, inadequate training of the person preparing the drug, and improper unit dose preparation. Investigational radiopharmaceutical formulations, including nonradiolabeled drugs, must be audited before they are administered to humans. A properly trained pharmacist should be a member of the audit team
Audits of radiopharmaceutical formulations.
Castronovo, F P
1992-03-01
A procedure for auditing radiopharmaceutical formulations is described. To meet FDA guidelines regarding the quality of radiopharmaceuticals, institutional radioactive drug research committees perform audits when such drugs are formulated away from an institutional pharmacy. All principal investigators who formulate drugs outside institutional pharmacies must pass these audits before they can obtain a radiopharmaceutical investigation permit. The audit team meets with the individual who performs the formulation at the site of drug preparation to verify that drug formulations meet identity, strength, quality, and purity standards; are uniform and reproducible; and are sterile and pyrogen free. This team must contain an expert knowledgeable in the preparation of radioactive drugs; a radiopharmacist is the most qualified person for this role. Problems that have been identified by audits include lack of sterility and apyrogenicity testing, formulations that are open to the laboratory environment, failure to use pharmaceutical-grade chemicals, inadequate quality control methods or records, inadequate training of the person preparing the drug, and improper unit dose preparation. Investigational radiopharmaceutical formulations, including nonradiolabeled drugs, must be audited before they are administered to humans. A properly trained pharmacist should be a member of the audit team. PMID:1598931
Random Matrices, Boundaries and Branes
Niedner, Benjamin
2016-01-01
This thesis is devoted to the application of random matrix theory to the study of random surfaces, both discrete and continuous; special emphasis is placed on surface boundaries and the associated boundary conditions in this formalism. In particular, using a multi-matrix integral with permutation symmetry, we are able to calculate the partition function of the Potts model on a random planar lattice with various boundary conditions imposed. We proceed to investigate the correspondence between the critical points in the phase diagram of this model and two-dimensional Liouville theory coupled to conformal field theories with global $\\mathcal{W}$-symmetry. In this context, each boundary condition can be interpreted as the description of a brane in a family of bosonic string backgrounds. This investigation suggests that a spectrum of initially distinct boundary conditions of a given system may become degenerate when the latter is placed on a random surface of bounded genus, effectively leaving a smaller set of ind...
Gravitational action with null boundaries
Lehner, Luis; Poisson, Eric; Sorkin, Rafael D
2016-01-01
We present a complete discussion of the boundary term in the action functional of general relativity when the boundary includes null segments in addition to the more usual timelike and spacelike segments. We confirm that ambiguities appear in the contribution from a null segment, because it depends on an arbitrary choice of parametrization for the generators. We also show that similar ambiguities appear in the contribution from a codimension-two surface at which a null segment is joined to another (spacelike, timelike, or null) segment. The parametrization ambiguity can be tamed by insisting that the null generators be affinely parametrized; this forces each null contribution to the boundary action to vanish, but leaves intact the fredom to rescale the affine parameter by a constant factor on each generator. Once a choice of parametrization is made, the ambiguity in the joint contributions can be eliminated by formulating well-motivated rules that ensure the additivity of the gravitational action. Enforcing t...
Conjugate boundary condition, hidden matters, and gauge-Higgs inflation
Abe, Yugo; Kawamura, Yoshiharu; Nishikawa, Yasunari
2016-01-01
We propose an idea that hidden matters can be separated according to gauge quantum numbers from the visible ones by the difference of boundary conditions on extra dimensions. We formulate 5-dimensional gauge theories yielding conjugate boundary conditions besides ordinary ones on $S^1/Z_2$, and examine physical implications concerning hidden matters on an extension of the standard model coexisting different types of boundary conditions. A model with conjugate boundary conditions is applied on a gauge-Higgs inflation scenario.
Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan; Illangasekare, Tissa
2013-04-01
The study of the interaction between the land and atmosphere is paramount to our understanding of many emerging problems to include climate change, the movement of green house gases such as possible leaking of sequestered CO2 and the accurate detection of buried objects such as landmines. Soil moisture distribution in the shallow subsurface becomes a critical factor in all these problems. The heat and mass flux in the form of soil evaporation across the land surface couples the atmospheric boundary layer to the shallow subsurface. The coupling between land and the atmosphere leads to highly dynamic interactions between the porous media properties, transport processes and boundary conditions, resulting in dynamic evaporative behavior. However, the coupling at the land-atmospheric interface is rarely considered in most current models and their validation for practical applications. This is due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining coupled energy and mass transfer theories. In most efforts to compute evaporation from soil, only indirect coupling is provided to characterize the interaction between non-isothermal multiphase flows under realistic atmospheric conditions even though heat and mass flux are controlled by the coupled dynamics of the land and the atmospheric boundary layer. In earlier drying modeling concepts, imposing evaporation flux (kinetic of relative humidity) and temperature as surface boundary condition is often needed. With the goal of improving our understanding of the land/atmospheric coupling, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model consists of the coupled equations of mass conservation for the liquid phase (water) and gas phase (water vapor and air) in porous medium with gas phase (water vapor and air) in free flow domain under non-isothermal, non-equilibrium conditions. The boundary
DEFF Research Database (Denmark)
Olwig, Karen Fog
2011-01-01
, while the countries have adopted disparate policies and ideologies, differences in the actual treatment and attitudes towards immigrants and refugees in everyday life are less clear, due to parallel integration programmes based on strong similarities in the welfare systems and in cultural notions of...
Biondini, Gino; Fagerstrom, Emily; Prinari, Barbara
2016-10-01
We formulate the inverse scattering transform (IST) for the defocusing nonlinear Schrödinger (NLS) equation with fully asymmetric non-zero boundary conditions (i.e., when the limiting values of the solution at space infinities have different non-zero moduli). The theory is formulated without making use of Riemann surfaces, and instead by dealing explicitly with the branched nature of the eigenvalues of the associated scattering problem. For the direct problem, we give explicit single-valued definitions of the Jost eigenfunctions and scattering coefficients over the whole complex plane, and we characterize their discontinuous behavior across the branch cut arising from the square root behavior of the corresponding eigenvalues. We pose the inverse problem as a Riemann-Hilbert Problem on an open contour, and we reduce the problem to a standard set of linear integral equations. Finally, for comparison purposes, we present the single-sheet, branch cut formulation of the inverse scattering transform for the initial value problem with symmetric (equimodular) non-zero boundary conditions, as well as for the initial value problem with one-sided non-zero boundary conditions, and we also briefly describe the formulation of the inverse scattering transform when a different choice is made for the location of the branch cuts.
A generalized anisotropic deformation formulation for geomaterials
Lei, Z.; Rougier, Esteban; Knight, E. E.; Munjiza, A.; Viswanathan, H.
2016-04-01
In this paper, the combined finite-discrete element method (FDEM) has been applied to analyze the deformation of anisotropic geomaterials. In the most general case geomaterials are both non-homogeneous and non-isotropic. With the aim of addressing anisotropic material problems, improved 2D FDEM formulations have been developed. These formulations feature the unified hypo-hyper elastic approach combined with a multiplicative decomposition-based selective integration for volumetric and shear deformation modes. This approach is significantly different from the co-rotational formulations typically encountered in finite element codes. Unlike the co-rotational formulation, the multiplicative decomposition-based formulation naturally decomposes deformation into translation, rotation, plastic stretches, elastic stretches, volumetric stretches, shear stretches, etc. This approach can be implemented for a whole family of finite elements from solids to shells and membranes. This novel 2D FDEM based material formulation was designed in such a way that the anisotropic properties of the solid can be specified in a cell by cell basis, therefore enabling the user to seed these anisotropic properties following any type of spatial variation, for example, following a curvilinear path. In addition, due to the selective integration, there are no problems with volumetric or shear locking with any type of finite element employed.
Testing outer boundary treatments for the Einstein equations
Rinne, Oliver; Scheel, Mark A
2007-01-01
Various methods of treating outer boundaries in numerical relativity are compared using a simple test problem: a Schwarzschild black hole with an outgoing gravitational wave perturbation. Numerical solutions computed using different boundary treatments are compared to a `reference' numerical solution obtained by placing the outer boundary at a very large radius. For each boundary treatment, the full solutions including constraint violations and extracted gravitational waves are compared to those of the reference solution, thereby assessing the reflections caused by the artificial boundary. These tests use a first-order generalized harmonic formulation of the Einstein equations. Constraint-preserving boundary conditions for this system are reviewed, and an improved boundary condition on the gauge degrees of freedom is presented. Alternate boundary conditions evaluated here include freezing the incoming characteristic fields, Sommerfeld boundary conditions, and the constraint-preserving boundary conditions of K...
Element free Galerkin formulation of composite beam with longitudinal slip
Energy Technology Data Exchange (ETDEWEB)
Ahmad, Dzulkarnain; Mokhtaram, Mokhtazul Haizad [Department of Civil Engineering, Universiti Selangor, Bestari Jaya, Selangor (Malaysia); Badli, Mohd Iqbal; Yassin, Airil Y. Mohd [Faculty of Civil Engineering, Universiti Teknologi Malaysia, Skudai, Johor (Malaysia)
2015-05-15
Behaviour between two materials in composite beam is assumed partially interact when longitudinal slip at its interfacial surfaces is considered. Commonly analysed by the mesh-based formulation, this study used meshless formulation known as Element Free Galerkin (EFG) method in the beam partial interaction analysis, numerically. As meshless formulation implies that the problem domain is discretised only by nodes, the EFG method is based on Moving Least Square (MLS) approach for shape functions formulation with its weak form is developed using variational method. The essential boundary conditions are enforced by Langrange multipliers. The proposed EFG formulation gives comparable results, after been verified by analytical solution, thus signify its application in partial interaction problems. Based on numerical test results, the Cubic Spline and Quartic Spline weight functions yield better accuracy for the EFG formulation, compares to other proposed weight functions.
Hydrodynamic structure of the boundary layers in a rotating cylindrical cavity with radial inflow
Herrmann-Priesnitz, Benjamín; Calderón-Muñoz, Williams R.; Salas, Eduardo A.; Vargas-Uscategui, Alejandro; Duarte-Mermoud, Manuel A.; Torres, Diego A.
2016-03-01
A flow model is formulated to investigate the hydrodynamic structure of the boundary layers of incompressible fluid in a rotating cylindrical cavity with steady radial inflow. The model considers mass and momentum transfer coupled between boundary layers and an inviscid core region. Dimensionless equations of motion are solved using integral methods and a space-marching technique. As the fluid moves radially inward, entraining boundary layers develop which can either meet or become non-entraining. Pressure and wall shear stress distributions, as well as velocity profiles predicted by the model, are compared to numerical simulations using the software OpenFOAM. Hydrodynamic structure of the boundary layers is governed by a Reynolds number, Re, a Rossby number, Ro, and the dimensionless radial velocity component at the periphery of the cavity, Uo. Results show that boundary layers merge for Re > 0.1, and boundary layers become predominantly non-entraining for low Ro, low Re, and high Uo. Results may contribute to improve the design of technology, such as heat exchange devices, and turbomachinery.
Brain response to prosodic boundary cues depends on boundary position
Directory of Open Access Journals (Sweden)
Julia eHolzgrefe
2013-07-01
Full Text Available Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer’s syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name as compared to later in the utterance (i.e., after the second name. A closure positive shift (CPS — marking the processing of a prosodic phrase boundary — was elicited only for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context.
Logarithmic minimal models with Robin boundary conditions
Bourgine, Jean-Emile; Pearce, Paul A.; Tartaglia, Elena
2016-06-01
We consider general logarithmic minimal models LM≤ft( p,{{p}\\prime}\\right) , with p,{{p}\\prime} coprime, on a strip of N columns with the (r, s) Robin boundary conditions introduced by Pearce, Rasmussen and Tipunin. On the lattice, these models are Yang–Baxter integrable loop models that are described algebraically by the one-boundary Temperley–Lieb algebra. The (r, s) Robin boundary conditions are a class of integrable boundary conditions satisfying the boundary Yang–Baxter equations which allow loop segments to either reflect or terminate on the boundary. The associated conformal boundary conditions are organized into infinitely extended Kac tables labelled by the Kac labels r\\in {Z} and s\\in {N} . The Robin vacuum boundary condition, labelled by ≤ft(r,s-\\frac{1}{2}\\right)=≤ft(0,\\frac{1}{2}\\right) , is given as a linear combination of Neumann and Dirichlet boundary conditions. The general (r, s) Robin boundary conditions are constructed, using fusion, by acting on the Robin vacuum boundary with an (r, s)-type seam consisting of an r-type seam of width w columns and an s-type seam of width d = s ‑ 1 columns. The r-type seam admits an arbitrary boundary field which we fix to the special value ξ =-\\fracλ{2} where λ =\\frac≤ft( {{p}\\prime}-p\\right)π{{{p}\\prime}} is the crossing parameter. The s-type boundary introduces d defects into the bulk. We consider the commuting double-row transfer matrices and their associated quantum Hamiltonians and calculate analytically the boundary free energies of the (r, s) Robin boundary conditions. Using finite-size corrections and sequence extrapolation out to system sizes N+w+d≤slant 26 , the conformal spectrum of boundary operators is accessible by numerical diagonalization of the Hamiltonians. Fixing the parity of N for r\
Formulation of Automotive Lubricants
Atkinson, D.; Brown, A. J.; Jilbert, D.; Lamb, G.
The formulation of lubricants for current light- and heavy-duty vehicles (passenger cars and trucks) and also motorcycles/small engines is described in terms of engine types and meeting European, US and Japanese emission control requirements. Trends in the formulation of lubricants are discussed and the importance of high and low 'SAPS' for future developments emphasised. Specification and evaluation of lubricant performance for light-vehicle gasoline and diesel, and also heavy-duty diesel engines are described. Emphasis is given to diesel engine cleanliness by soot and deposit control and the effect of emission controls on lubricant formulation. The lubricant requirements for motorcycle and small engines, primarily two-stroke cycle, and their specifications are described.
Parenteral formulation of zopiclone
Directory of Open Access Journals (Sweden)
Swamy P
2008-01-01
Full Text Available The present study was undertaken with an intention to develop a stable and effective parenteral formulation, containing the drug zopiclone. Since zopiclone is a water insoluble drug, various methods such as co-solvency, pH control and hydrotrophy have been tried in order to enhance its solubility. When all these methods could not give adequate solubility enhancement of the drug, a hydrochloride salt was prepared, and it was found to be thermostable. Various batches of zopiclone hydrochloride injection formulation were prepared in order to assess the influence of light, atmospheric oxygen and antioxidant on the stability of the drug and the formulations were also subjected to accelerated stability testing in order to predict approximate shelf-life of the product.
Energy Technology Data Exchange (ETDEWEB)
GHARAKHANI,ADRIN; WOLFE,WALTER P.
1999-10-01
the collocation points. Unfortunately, the development of elements with C{sup 1} continuity for the potential jumps is quite complicated in 3-D. To this end, the application of Galerkin ''smoothing'' to the boundary integral equations removes the singularity at the collocation points; thus allowing the use of C{sup o} elements and potential jump distributions [4]. Successful implementations of the Galerkin Boundary Element Method to 2-D conduction [4] and elastostatic [5] problems have been reported in the literature. Thus far, the singularity removal algorithms have been based on a posterior and mathematically complex reasoning, which have required Taylor series expansion and limit processes. The application of these strategies to 3-D is expected to be significantly more complicated. In this report, we develop the formulation for a ''Regularized'' Galerkin Boundary Element Method (RGBEM). The regularization procedure involves simple manipulations using vector calculus to reduce the singularity of the hypersingular boundary integral equation by two orders for C{sup o} elements. For the case of linear potential jump distributions over plane triangles the regularized integral is simplified considerably to a double surface integral of the Green function. This is the case implemented and tested in this report. Using the example problem of flow normal to a square flat plate, the linear RGBEM predictions are demonstrated here to be more accurate, to converge faster, and to be significantly less spiked than the solutions obtained by the vortex loop method.
Unified formulation of radiation conditions for the wave equation
DEFF Research Database (Denmark)
Krenk, Steen
2002-01-01
A family of radiation conditions for the wave equation is derived by truncating a rational function approxiamtion of the corresponding plane wave representation, and it is demonstrated how these boundary conditions can be formulated in terms of fictitious surface densities, governed by second......-order wave equations on the radiating surface. Several well-established radiation boundary conditions appear as special cases, corresponding to different choice of the coefficients in the rational approximation. The relation between these choices is established, and an explicit formulation in terms...
Boundary Conditions at Infinity for Physical Theories
Trautman, Andrzej
2016-01-01
The Sommerfeld boundary conditions, imposed on hyperbolic differential equations to obtain solutions in the form of outgoing waves, are formulated here so as to make explicit the role of an appropriate null vector field. When applied to the scalar and Maxwell equations, they lead to the asymptotic form of the energy-momentum tensor representing radiation as a null, perfect dust.
Analytical model for intergrain expansion and cleavage: random grain boundaries
International Nuclear Information System (INIS)
A description of rigid-body grain boundary relaxation and cleavage in tungsten is performed using a pair-wise Morse interatomic potential in real and reciprocal spaces. Cleavage energies and grain boundary dilatation of random grain boundaries were formulated and computed using atomic layer interaction energies. These values were determined using a model for a relaxed random grain boundary that consists of rigid grains on either side of the boundary plane that are allowed to float to reach the equilibrium position. Expressions are given that describe in real space the energy of interatomic interaction on random grain boundaries with twist orientation. It was shown that grain-boundary expansion and cleavage energies of the most widespread random grain boundaries are mainly determined by grain boundary atomic density
Reis, Tim
2012-01-01
We present lattice Boltzmann simulations of rarefied flows driven by pressure drops along two-dimensional microchannels. Rarefied effects lead to non-zero cross-channel velocities, nonlinear variations in the pressure along the channel. Both effects are absent in flows driven by uniform body forces. We obtain second-order accuracy for the two components of velocity the pressure relative to asymptotic solutions of the compressible Navier-Stokes equations with slip boundary conditions. Since the common lattice Boltzmann formulations cannot capture Knudsen boundary layers, we replace the usual discrete analogs of the specular diffuse reflection conditions from continuous kinetic theory with a moment-based implementation of the first-order Navier-Maxwell slip boundary conditions that relate the tangential velocity to the strain rate at the boundary. We use these conditions to solve for the unknown distribution functions that propagate into the domain across the boundary. We achieve second-order accuracy by reformulating these conditions for the second set of distribution functions that arise in the derivation of the lattice Boltzmann method by an integration along characteristics. Our moment formalism is also valuable for analysing the existing boundary conditions. It reveals the origin of numerical slip in the bounce-back other common boundary conditions that impose conditions on the higher moments, not on the local tangential velocity itself. © 2012 American Institute of Physics.
DEFF Research Database (Denmark)
Bødker, Susanne; Kristensen, Jannie Friis; Nielsen, Christina;
2003-01-01
This paper presents a study of an organisation, which is undergoing a process transforming organisational and technological boundaries. In particular, we shall look at three kinds of boundaries: the work to maintain and change the boundary between the organisation and its customers; boundaries.......After analysing the history and the current boundary work, the paper will propose new technological support for boundary work. In particular the paper will suggest means of supporting boundaries when these are productive and for changing boundaries when this seems more appropriate. In total, flexible technologies...... seem a core issue when dealing with technology for boundaries....
9th International Conference on Boundary Elements
Wendland, W; Kuhn, G
1987-01-01
This book contains the edited versions of most of the papers presented at the 9th International Conference on Boundary Elements held at the University of Stuttgart, Germany from August 31st to September 4th, 1987, which was organized in co-operation with the Computational Mechanics Institute and GAMM (Society for Applied Mathematics and Mechanics). This Conference, as the previous ones, aimed to review the latest developments in technique and theory and point out new advanced future trends. The emphasis of the meeting was on the engineering advances versus mathematical formulations, in an effort to consolidate the basis of many new applications. Recently engineers have proposed different techniques to solve non-linear and time dependent problems and many of these formulations needed a better mathematical understanding. Furthermore, new approximate formulations have been proposed for boundary elements which appeared to work in engineering practice, but did not have a proper theoretical background. The Conferen...
Dishron, Joseph B.
2011-12-01
The Delaware Basin of the Permian Basin is a classic intra-cratonic basin of West Texas and Southeast New Mexico. Hydrocarbon exploration and production have occurred in the region since the early 1920s, and, as a result, the formations related to these oil and gas reserves have been studied in great detail. Some formations in the Delaware Basin, however, have not been studied in such detail, and this thesis examines one, lesser-known unit that could have economic potential. The Lamar Limestone (Lamar Lime) of the Bell Canyon Formation has commonly been dismissed as a production interval; rather, it has been described as a source and seal rock for the Ramsey Sand of the lower Bell Canyon Formation. However, recent studies found that the Lamar Lime was contributing to production, and it has been described by Trentham (2006) as a potentia "mini Barnett" reservoir. The depths of these deposits are in a range that is ideal for oil accumulation. This study made use of data from wells and test holes drilled in the western Delaware Basin, Culberson County, Texas. Many oil and gas wells have been drilled in the western Delaware Basin, but they are concentrated in the north and east portions of Culberson County. In addition, sulfur wells were drilled in the area in the late 1960s and early 1970s. Analyses of the well logs of these wells and of core and outcrop studies were completed to gain a better understanding of the distribution and economic potential of the Lamar. Both datasets were combined to provide information not readily available in the oil and gas dataset. The Lamar Lime is an excellent marker bed because it underlies thick evaporites. The evaporite sequences are Ochoan in age, and, therefore, the contact of the Lamar Lime (Bell Canyon Formation) and the Castile Formation is the approximate boundary for the Guadalupian-Ochoan Series. The Castile Formation, the Salado Formation, and the Rustler Formation (from oldest to youngest) are the evaporite units that
Lamellar eutectic growth with anisotropic interphase boundaries
Akamatsu, Silvère; Bottin-Rousseau, Sabine; Faivre, G.; Ghosh, S.; Plapp, M.
2015-01-01
We present a numerical study of the effect of a free-energy anisotropy of the solid- solid interphase boundaries on the formation of tilted lamellar microstructures during directional solidification of nonfaceted binary eutectic alloys. We used two different methods - phase-field (PF) and dynamic boundary-integral (BI) - to simulate the growth of periodic eutectic patterns in two dimensions. For a given Wulff plot of the interphase boundary, which characterizes a eutectic grain with a given r...
Tatyana Darienko; Lydia Gustavs; Anja Eggert; Wiebke Wolf; Thomas Pröschold
2015-01-01
Integrative taxonomy is an approach for defining species and genera by taking phylogenetic, morphological, physiological, and ecological data into account. This approach is appropriate for microalgae, where morphological convergence and high levels of morphological plasticity complicate the application of the traditional classification. Although DNA barcode markers are well-established for animals, fungi, and higher plants, there is an ongoing discussion about suitable markers for microalgae ...
Spinor Formulations for Gravitational Energy-Momentum
Chen, C M; Tung, R S; Chen, Chiang-Mei; Nester, James M.; Tung, Roh-Suan
2004-01-01
We first describe a class of spinor-curvature identities (SCI) which have gravitational applications. Then we sketch the topic of gravitational energy-momentum, its connection with Hamiltonian boundary terms and the issues of positivity and (quasi)localization. Using certain SCIs several spinor expressions for the Hamiltonian have been constructed. One SCI leads to the celebrated Witten positive energy proof and the Dougan-Mason quasilocalization. We found two other SCIs which give alternate positive energy proofs and quasilocalizations. In each case the spinor field has a different role. These neat expressions for gravitational energy-momentum have much appeal. However it seems that such spinor formulations just have no room for angular momentum; which leads us to doubt that spinor formulations can really correctly capture the elusive gravitational energy-momentum.
ABSORBING BOUNDARY TECHNIQUE FOR OPEN CHANNEL FLOWS. (R825200)
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...
Optimal boundary conditions at the staircase-shaped coastlines
Kazantsev, Eugene
2014-01-01
A 4D-Var data assimilation technique is applied to the rectangular-box configuration of the NEMO in order to identify the optimal parametrization of boundary conditions at lateral boundaries. The case of the staircase-shaped coastlines is studied by rotating the model grid around the center of the box. It is shown that, in some cases, the formulation of the boundary conditions at the exact boundary leads to appearance of exponentially growing modes while optimal boundary conditions allow to correct the errors induced by the staircase-like appriximation of the coastline.
Recent advances in boundary element methods
Manolis, GD
2009-01-01
Addresses the needs of the computational mechanics research community in terms of information on boundary integral equation-based methods and techniques applied to a variety of fields. This book collects both original and review articles on contemporary Boundary Element Methods (BEM) as well as on the Mesh Reduction Methods (MRM).
Magnetohydrodynamic cross-field boundary layer flow
Directory of Open Access Journals (Sweden)
D. B. Ingham
1982-01-01
Full Text Available The Blasius boundary layer on a flat plate in the presence of a constant ambient magnetic field is examined. A numerical integration of the MHD boundary layer equations from the leading edge is presented showing how the asymptotic solution described by Sears is approached.
International Nuclear Information System (INIS)
Highlights: • We develop a new formulation between the yield stress and Young’s modulus of bone. • We validate the optimized formulation for cortical and trabecular bone. • We integrate the reliability analysis into artificially hip replacement design. - Abstract: Using classical design optimization methods for implant-bone studies does not completely guarantee a safety and satisfactory performance, due in part to the randomness of bone properties and loading. Here, the material properties of the different bone layers are considered as uncertain parameters. So their corresponding yield stress values will not be deterministic, that leads to integrate variable limitations into the optimization process. Here there is a strong need to find a reliable mathematical relationship between yield stress and material properties of the different bone layers. In this work, a new optimized formulation for yield stress against elasticity modulus relationship is first developed. This model is based on some experimental results. A validation of the proposed formulation is next carried out to show its accuracy for both bone layers (cortical and cancellous). A probabilistic sensitivity analysis is then carried out to show the role of each input parameter with respect to the limit state function. The new optimized formulation is next integrated into a reliability analysis problem in order to assess the reliability level of the stem–bone study where we deal with variable boundary limitations. An illustrative application is considered as a bi-dimensional example (contains only two variables) in order to present the results in an illustrative 2D space. Finally, a multi-variable problem considering several daily loading cases on a hip prosthesis shows the applicability of the proposed strategy
Directory of Open Access Journals (Sweden)
Tatyana Darienko
Full Text Available Integrative taxonomy is an approach for defining species and genera by taking phylogenetic, morphological, physiological, and ecological data into account. This approach is appropriate for microalgae, where morphological convergence and high levels of morphological plasticity complicate the application of the traditional classification. Although DNA barcode markers are well-established for animals, fungi, and higher plants, there is an ongoing discussion about suitable markers for microalgae and protists because these organisms are genetically more diverse compared to the former groups. To solve these problems, we assess the usage of a polyphasic approach combining phenotypic and genetic parameters for species and generic characterization. The application of barcode markers for database queries further allows conclusions about the 'coverage' of culture-based approaches in biodiversity studies and integrates additional aspects into modern taxonomic concepts. Although the culture-dependent approach revealed three new lineages, which are described as new species in this paper, the culture-independent analyses discovered additional putative new species. We evaluated three barcode markers (V4, V9 and ITS-2 regions, nuclear ribosomal operon and studied the morphological and physiological plasticity of Coccomyxa, which became a model organism because its whole genome sequence has been published. In addition, several biotechnological patents have been registered for Coccomyxa. Coccomyxa representatives are distributed worldwide, are free-living or in symbioses, and colonize terrestrial and aquatic habitats. We investigated more than 40 strains and reviewed the biodiversity and biogeographical distribution of Coccomyxa species using DNA barcoding. The genus Coccomyxa formed a monophyletic group within the Trebouxiophyceae separated into seven independent phylogenetic lineages representing species. Summarizing, the combination of different characteristics
Darienko, Tatyana; Gustavs, Lydia; Eggert, Anja; Wolf, Wiebke; Pröschold, Thomas
2015-01-01
Integrative taxonomy is an approach for defining species and genera by taking phylogenetic, morphological, physiological, and ecological data into account. This approach is appropriate for microalgae, where morphological convergence and high levels of morphological plasticity complicate the application of the traditional classification. Although DNA barcode markers are well-established for animals, fungi, and higher plants, there is an ongoing discussion about suitable markers for microalgae and protists because these organisms are genetically more diverse compared to the former groups. To solve these problems, we assess the usage of a polyphasic approach combining phenotypic and genetic parameters for species and generic characterization. The application of barcode markers for database queries further allows conclusions about the 'coverage' of culture-based approaches in biodiversity studies and integrates additional aspects into modern taxonomic concepts. Although the culture-dependent approach revealed three new lineages, which are described as new species in this paper, the culture-independent analyses discovered additional putative new species. We evaluated three barcode markers (V4, V9 and ITS-2 regions, nuclear ribosomal operon) and studied the morphological and physiological plasticity of Coccomyxa, which became a model organism because its whole genome sequence has been published. In addition, several biotechnological patents have been registered for Coccomyxa. Coccomyxa representatives are distributed worldwide, are free-living or in symbioses, and colonize terrestrial and aquatic habitats. We investigated more than 40 strains and reviewed the biodiversity and biogeographical distribution of Coccomyxa species using DNA barcoding. The genus Coccomyxa formed a monophyletic group within the Trebouxiophyceae separated into seven independent phylogenetic lineages representing species. Summarizing, the combination of different characteristics in an integrative
Directory of Open Access Journals (Sweden)
Lorenzo Piccoli
2013-02-01
Full Text Available Following the research agenda introduced by Will Kymlicka, this qualitative study offers an interpretation of how the sub-national elites of Québec and South Tyrol police the integration of immigrants. For these national minority groups, which are constantly undergoing a process of redefinition of their collective identities by differentiating themselves from the Others who do not belong to the in-group, immigrants have progressively become the most significant Others as they are not part of the original system of compromises. This article questions how sub-national elites are handling this relatively new kind of ethnocultural diversity brought about by large-scale permanent immigration on two levels: first, the political narrative of the ruling sub-national parties, their electoral appeals, manifestos and speeches; second, the policy arrangements for the integration of immigrants in education, language and social policy. The initial approach of the article is pessimistic, as it assumes that sub-national elites will marginalize immigrants to please core nationalist supporters. In fact, the hypotheses to be tested are whether the national minority groups of Québec and South Tyrol engage in a process of reconstruction of their ethnic identity bounded by opposition to real or imagined Others – the newcomers; and whether they adopt practical measures that force newcomers to be assimilated into the group or to be marginalized. The comparison between Québec and South Tyrol provides a basic understanding of the impact of immigration in two sub-national polities that are very different, but still adopt similar political narratives and policy strategies with regard to the integration of newcomers.
Liposomal formulations for inhalation.
Cipolla, David; Gonda, Igor; Chan, Hak-Kim
2013-08-01
No marketed inhaled products currently use sustained release formulations such as liposomes to enhance drug disposition in the lung, but that may soon change. This review focuses on the interaction between liposomal formulations and the inhalation technology used to deliver them as aerosols. There have been a number of dated reviews evaluating nebulization of liposomes. While the information they shared is still accurate, this paper incorporates data from more recent publications to review the factors that affect aerosol performance. Recent reviews have comprehensively covered the development of dry powder liposomes for aerosolization and only the key aspects of those technologies will be summarized. There are now at least two inhaled liposomal products in late-stage clinical development: ARIKACE(®) (Insmed, NJ, USA), a liposomal amikacin, and Pulmaquin™ (Aradigm Corp., CA, USA), a liposomal ciprofloxacin, both of which treat a variety of patient populations with lung infections. This review also highlights the safety of inhaled liposomes and summarizes the clinical experience with liposomal formulations for pulmonary application. PMID:23919478
On Consistent Boundary Conditions for c=1 String Theory
O'Loughlin, Martin
1995-01-01
We introduce a new parametrisation for the Fermi sea of the $c = 1$ matrix model. This leads to a simple derivation of the scattering matrix, and a calculation of boundary corrections in the corresponding $1+1$--dimensional string theory. The new parametrisation involves relativistic chiral fields, rather than the non-relativistic fields of the usual formulations. The calculation of the boundary corrections, following recent work of Polchinski, allows us to place restrictions on the boundary ...
Sogachev, Andrey; Kelly, Mark
2016-03-01
Displacement height ( d) is an important parameter in the simple modelling of wind speed and vertical fluxes above vegetative canopies, such as forests. Here we show that, aside from implicit definition through a (displaced) logarithmic profile, accepted formulations for d do not consistently predict flow properties above a forest. Turbulent transport can affect the displacement height, and is an integral part of what is called the roughness sublayer. We develop a more general approach for estimation of d, through production of turbulent kinetic energy and turbulent transport, and show how previous stress-based formulations for displacement height can be seen as simplified cases of a more general definition including turbulent transport. Further, we also give a simplified and practical form for d that is in agreement with the general approach, exploiting the concept of vortex thickness scale from mixing-layer theory. We assess the new and previous displacement height formulations by using flow statistics derived from the atmospheric boundary-layer Reynolds-averaged Navier-Stokes model SCADIS as well as from wind-tunnel observations, for different vegetation types and flow regimes in neutral conditions. The new formulations tend to produce smaller d than stress-based forms, falling closer to the classic logarithmically-defined displacement height. The new, more generally defined, displacement height appears to be more compatible with profiles of components of the turbulent kinetic energy budget, accounting for the combined effects of turbulent transport and shear production. The Coriolis force also plays a role, introducing wind-speed dependence into the behaviour of the roughness sublayer; this affects the turbulent transport, shear production, stress, and wind speed, as well as the displacement height, depending on the character of the forest. We further show how our practical (`mixing-layer') form for d matches the new turbulence-based relation, as well as
Uzawa Type Algorithm Based on Dual Mixed Variational Formulation
Institute of Scientific and Technical Information of China (English)
王光辉; 王烈衡
2002-01-01
Based on the dual mixed variational formulation with three variants (stress,displacement, displacement on contact boundary ) and the unilateral beaming problem of finite element discretization, an Uzawa type iterative algorithm is presented. The convergence of this iterative algorithm is proved, and then the efficiency of the algorithm is tested by a numerical example.
Differential and Integral Models of TOKAMAK
Directory of Open Access Journals (Sweden)
Ivo Dolezel
2004-01-01
Full Text Available Modeling of 3D electromagnetic phenomena in TOKAMAK with typically distributed main and additional coils is not an easy business. Evaluated must be not only distribution of the magnetic field, but also forces acting in particular coils. Use of differential methods (such as FDM or FEM for this purpose may be complicated because of geometrical incommensurability of particular subregions in the investigated area or problems with the boundary conditions. That is why integral formulation of the problem may sometimes be an advantages. The theoretical analysis is illustrated on an example processed by both methods, whose results are compared and discussed.
Rasheed, Arun; Naik, Madhu; Mohammed-Haneefa, Kotappadath Pillanayil; Arun-Kumar, Raveendran Pillai; Azeem, Abdul Kharim
2014-07-01
Bhasmas are unique Ayurvedic-metallic preparations with herbal juices/fruits, widely recommended to treat variety of chronic ailments. Trivanga bhasma, a calcinated preparation, is used to treat Diabetes mellitus and as Diuretic. In the present research an attempt has been made to carry out a comparative standardization of formulated Trivanga bhasma (TB1) prepared as per Ayurvedic formulary and marketed Trivanga bhasma (TB2) integrating conventional and modern analytical tools. The formulations were evaluated for physical properties, chemical characterization using FTIR, AAS, SEM, TGA, XRD and AFM along with anti-diabetic, diuretic and toxicology studies. The X-ray Diffraction analysis of both formulations exhibited crystalline nature and nano-sized particles by Scherrer's equation. In SEM studies, Lead, zinc and tin oxides show well-defined plate like structures while TB1 showed spongy, relatively compact microcrystalline aggregates with loss of grain boundaries. AFM analysis confirmed the spherical morphology of TB1 and TB2 with an average particle size of 500 nm. The present study is the first report of fingerprinting of Trivanga bhasma using sophisticated analytical techniques. In vivo pharmacological screening revealed that both TB1 and TBK2 possess anti-diabetic and diuretic activity and less toxicity, thereby facilitating standardization of Trivanga bhasma. PMID:25015442
Knowledge Sharing Across Global-Local Boundaries
DEFF Research Database (Denmark)
Zølner, Mette
in the period of post-acquisition when their organization is being integrated into the acquiring MNC. The paper contributes to the literature on boundary spanning in three ways: First, by illustrating that boundary spanning is performed by numerous organizational actors in a variety of positions in MNCs......The paper explores how locals span boundaries between corporate and local levels. The aim is to better comprehend potentialities and challenges when MNCs draws on locals’ culture specific knowledge. The study is based on an in-depth, interpretive case study of boundary spanning by local actors...
DEFF Research Database (Denmark)
Plummer, Ruth; Swaisland, Helen; Leunen, Karin;
2015-01-01
BACKGROUND: The oral PARP inhibitor olaparib has shown efficacy in patients with BRCA-mutated cancer. This Phase I, open-label, three-part study (Parts A-C) in patients with advanced solid tumours evaluated the effect of food on the pharmacokinetics (PK) of olaparib when administered in tablet...... formulation. METHODS: PK data were obtained in Part A using a two-treatment period crossover design; single-dose olaparib 300 mg (two 150 mg tablets) was administered in two prandial states: fasted and fed. In Part B, patients received olaparib tablets (300 mg bid) for 5 days under fasting conditions; in Part...
Systematic Equation Formulation
DEFF Research Database (Denmark)
Lindberg, Erik
2007-01-01
A tutorial giving a very simple introduction to the set-up of the equations used as a model for an electrical/electronic circuit. The aim is to find a method which is as simple and general as possible with respect to implementation in a computer program. The “Modified Nodal Approach”, MNA, and th......, and the “Controlled Source Approach”, CSA, for systematic equation formulation are investigated. It is suggested that the kernel of the P Spice program based on MNA is reprogrammed....
New Boundaries for the B-Model
Bergman, Aaron
2008-01-01
Witten couples the open topological B-model to a holomorphic vector bundle by adding to the boundary of the worldsheet a Wilson loop for an integrable connection on the bundle. Using the descent procedure for boundary vertex operators in this context, I generalize this construction to write a worldsheet coupling for a graded vector bundle with an integrable superconnection. I then compute the open string vertex operators between two such boundaries. A theorem of J. Block gives that this is equivalent to coupling the B-model to an arbitrary object in the derived category.
Skin moisturizing effects of panthenol-based formulations.
Camargo, Flávio B; Gaspar, Lorena R; Maia Campos, Patrícia M B G
2011-01-01
This study aims to evaluate the skin moisturizing efficacy of formulations containing different concentrations of panthenol. Formulations supplemented with or without 0.5%, 1.0%, or 5.0% panthenol were applied daily to the forearms of healthy subjects. Skin conditions in terms of moisture and transepidermal water loss (TEWL) were analyzed before and after 15- and 30-day periods of application. The formulations were also applied after skin washing with sodium laureth sulphate (SLES) to evaluate the immediate effects on TEWL and skin moisture. Panthenol-containing formulations (1.0% and 5.0%) produced significant decreases in TEWL after 30-day applications. In skin washed with SLES, significant reduction of TEWL was evident two hours after application of formulations loaded with panthenol when compared with control and vehicle. It is concluded that skin integrity is maintained by the improved protective effect of 1.0% panthenol added to the formulation. PMID:21982351
Distributed Tuning of Boundary Resources
DEFF Research Database (Denmark)
Eaton, Ben; Elaluf-Calderwood, Silvia; Sørensen, Carsten;
2015-01-01
The digital age has seen the rise of service systems involving highly distributed, heterogeneous, and resource-integrating actors whose relationships are governed by shared institutional logics, standards, and digital technology. The cocreation of service within these service systems takes place...... resources within Apple’s iOS service system. We conduct an embedded case study of Apple’s iOS service system with an in-depth analysis of 4,664 blog articles concerned with 30 boundary resources covering 6 distinct themes. Our analysis reveals that boundary resources of service systems enabled by digital...... in the context of a paradoxical tension between the logic of generative and democratic innovations and the logic of infrastructural control. Boundary resources play a critical role in managing the tension as a firm that owns the infrastructure can secure its control over the service system while independent...
Institute of Scientific and Technical Information of China (English)
S.E.SADIQUE; S.; RAMAKRISHNA; S.BASRI; S.M.SAPUAN; M.M.HMEGATAHMED
2001-01-01
The contact characteristics of rigid cylinders lubricated by Newtonian liquids are inves-tigated in this paper using hard elastohydrodynamic lubrication (EHL) theory. Numerical modelingis formulated for the coupled set of generalized pressure and plane strain elasticity equations for afinite plane model and a circular representation of the junction under a pure hard rolling line con-tact using boundary element method (BEM). Also a numerical routine is developed to compute filmthickness and pressure profiles and the results are evaluated for a range of possible dimen-sionless parameters such as speed and load. The hydrodynamic equation is also transformed intoa form of boundary integral equation, which is solved by Simpson’s rule. The elasticity equationwith boundary conditions was solved by constant and quadratic elements based on an iterativeprocedure by assuming an initial film thickness. From the comparative study between the presentNewtonian model and the previously published results proved to be very effective and efficient andhigh precision is easily achieved for such rolling elements as well. The computed results areshown to be amenable to standard boundary element formulation of EHL problem in the contactregion and show that speed and load have influential effects on the lubricating film shape.
Time-Discrete Higher-Order ALE Formulations: Stability
Bonito, Andrea
2013-01-01
Arbitrary Lagrangian Eulerian (ALE) formulations deal with PDEs on deformable domains upon extending the domain velocity from the boundary into the bulk with the purpose of keeping mesh regularity. This arbitrary extension has no effect on the stability of the PDE but may influence that of a discrete scheme. We examine this critical issue for higher-order time stepping without space discretization. We propose time-discrete discontinuous Galerkin (dG) numerical schemes of any order for a time-dependent advection-diffusion-model problem in moving domains, and study their stability properties. The analysis hinges on the validity of the Reynold\\'s identity for dG. Exploiting the variational structure and assuming exact integration, we prove that our conservative and nonconservative dG schemes are equivalent and unconditionally stable. The same results remain true for piecewise polynomial ALE maps of any degree and suitable quadrature that guarantees the validity of the Reynold\\'s identity. This approach generalizes the so-called geometric conservation law to higher-order methods. We also prove that simpler Runge-Kutta-Radau methods of any order are conditionally stable, that is, subject to a mild ALE constraint on the time steps. Numerical experiments corroborate and complement our theoretical results. © 2013 Society for Industrial and Applied Mathematics.
Honti, Mark; Schuwirth, Nele; Rieckermann, Jörg; Ghielmetti, Nico; Stamm, Christian
2014-05-01
Catchments are complex systems where water quantity, quality and the ecological services provided are determined by interacting physical, chemical, biological, economical and social factors. The realization of these interactions led to the prevailing catchment management paradigm: Integrated Water Resources Management (IWRM). IWRM requires considering all these aspects during the design of sustainable resource utilization. Due to the complexity of this task, mathematical modeling plays a key role in IWRM, namely in the evaluation of the impacts of hypothetical scenarios and management measures. Toxicity is a key determinant of the ecological state and as such a focal point in IWRM, but we still have significant knowledge gaps about the diffuse loads of organic micropollutants (OMP) that leak from both urban and agricultural areas. Most European catchments possess mixed land use, containing rural (natural and agricultural) landscapes and settlements in varying proportions. Thus, a catchment model supporting IWRM must be able to cope with both classes. However, the majority of existing catchment models is dedicated to either rural or urban areas, while the minority capable of simulating both contain overly simplified descriptions for either land use category. We applied a conceptual model that describes all major land use classes for assessing the impacts of climate change, socio-economic development and management alternatives on diffuse OMP loads. We simulated the loads of 12 compounds (agricultural and urban pesticides and urban biocides) with daily resolution at 11 locations in the stream network of a small catchment (46 km2) in Switzerland. The model considers all important diffuse transport pathways separately, but each with a simple empirical process rate. Consequently, some site-specific observations were required to calibrate rate parameters. We assessed uncertainty during both calibration and prediction phases. Predictions indicated that future OMP loads
ICM: an Integrated Compartment Method for numerically solving partial differential equations
International Nuclear Information System (INIS)
An integrated compartment method (ICM) is proposed to construct a set of algebraic equations from a system of partial differential equations. The ICM combines the utility of integral formulation of finite element approach, the simplicity of interpolation of finite difference approximation, and the flexibility of compartment analyses. The integral formulation eases the treatment of boundary conditions, in particular, the Neumann-type boundary conditions. The simplicity of interpolation provides great economy in computation. The flexibility of discretization with irregular compartments of various shapes and sizes offers advantages in resolving complex boundaries enclosing compound regions of interest. The basic procedures of ICM are first to discretize the region of interest into compartments, then to apply three integral theorems of vectors to transform the volume integral to the surface integral, and finally to use interpolation to relate the interfacial values in terms of compartment values to close the system. The Navier-Stokes equations are used as an example of how to derive the corresponding ICM alogrithm for a given set of partial differential equations. Because of the structure of the algorithm, the basic computer program remains the same for cases in one-, two-, or three-dimensional problems
ICM: an Integrated Compartment Method for numerically solving partial differential equations
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.
1981-05-01
An integrated compartment method (ICM) is proposed to construct a set of algebraic equations from a system of partial differential equations. The ICM combines the utility of integral formulation of finite element approach, the simplicity of interpolation of finite difference approximation, and the flexibility of compartment analyses. The integral formulation eases the treatment of boundary conditions, in particular, the Neumann-type boundary conditions. The simplicity of interpolation provides great economy in computation. The flexibility of discretization with irregular compartments of various shapes and sizes offers advantages in resolving complex boundaries enclosing compound regions of interest. The basic procedures of ICM are first to discretize the region of interest into compartments, then to apply three integral theorems of vectors to transform the volume integral to the surface integral, and finally to use interpolation to relate the interfacial values in terms of compartment values to close the system. The Navier-Stokes equations are used as an example of how to derive the corresponding ICM alogrithm for a given set of partial differential equations. Because of the structure of the algorithm, the basic computer program remains the same for cases in one-, two-, or three-dimensional problems.
Variable thickness transient ground-water flow model. Volume 1. Formulation
International Nuclear Information System (INIS)
Mathematical formulation for the variable thickness transient (VTT) model of an aquifer system is presented. The basic assumptions are described. Specific data requirements for the physical parameters are discussed. The boundary definitions and solution techniques of the numerical formulation of the system of equations are presented
Lagrangian formulation of the one-dimensional Vlasov equation. [in plasma physics
Lewak, G. J.
1974-01-01
A new formulation of the one-dimensional Vlasov equation is derived which is analogous to the Kalman-transformed cold-plasma equations. The equations are shown to yield nonsecular, nonlinear approximations to a source or boundary-value problem. It is suggested that the formulation may have other applications in nonlinear plasma theory.
Institute of Scientific and Technical Information of China (English)
赖格英; 潘瑞鑫; 黄小红
2011-01-01
method on computational fluid dynamics. Thereby, an integrated method to deal with complicated moving boundary due to high amplitudes of water level changes was presented for shallow lakes. In order to develop Poyang Lake hydrodynamic modeling system, an algorithm based on the open-source component of MapWinGIS for the boundary fitted orthogonal curvilinear grid of each morphological structure and hydrological characteristics pattern was developed for the needs of hydrodynamic simulation and results visualization. Two main modules of Poyang Lake hydrodynamic modeling system, the module of data pro-post processing and data interaction and the module of hydrodynamic numerical simulation were integrated in the form of loose coupling using the programming platforms of Visual C# and Visual Fortran. In order to verify the simulation effect and precision, an experimental simulation for Poyang Lake with gauged data in December 6-14, 1999 was carried out using developed Poyang Lake hydrodynamic modeling system. The simulated results show that not only the simulation time is obviously shorted but also the simulated effects, which include lake water boundary, water level, depth and current, are better because of the use of integrated moving boundary method.
An Inverse Stefan Problem Relevant to Boilover: Heat Balance Integral Solutions and Analysis
Hristov, Jordan
2010-01-01
Stefan problems relevant to burning oil-water systems are formulated. Two moving boundary sub-problems are defined: burning liquid surface and formation of a distillation ("hot zone") layer beneath it. The basic model considers a heat transfer equation with internal heat generation due to radiation flux absorbed in the fuel depth. In verse Stefan problem corresponding to the first case solved by the heat balance integral method and dimensionless scaling of semi-analytical solutions are at issue.
Boundary states and finite size effects in sine-Gordon model with Neumann boundary condition
Bajnok, Z.; Palla, L.; Takacs, G.
2001-01-01
The sine-Gordon model with Neumann boundary condition is investigated. Using the bootstrap principle the spectrum of boundary bound states is established. Somewhat surprisingly it is found that Coleman-Thun diagrams and bound state creation may coexist. A framework to describe finite size effects in boundary integrable theories is developed and used together with the truncated conformal space approach to confirm the bound states and reflection factors derived by bootstrap.
Using reciprocity in Boundary Element Calculations
DEFF Research Database (Denmark)
Juhl, Peter Møller; Cutanda Henriquez, Vicente
2010-01-01
as the reciprocal radiation problem. The present paper concerns the situation of having a point source (which is reciprocal to a point receiver) at or near a discretized boundary element surface. The accuracy of the original and the reciprocal problem is compared in a test case for which an analytical solution......The concept of reciprocity is widely used in both theoretical and experimental work. In Boundary Element calculations reciprocity is sometimes employed in the solution of computationally expensive scattering problems, which sometimes can be more efficiently dealt with when formulated...
A SYSTEMATIC FORMULATION OF THE CONTINUOUS ADJOINT METHOD APPLIED TO VISCOUS AERODYNAMIC DESIGN
Directory of Open Access Journals (Sweden)
C. Castro*, C. Lozano**, F. Palacios*** and E. Zuazua****
2009-01-01
Full Text Available A continuous adjoint approach to aerodynamic design for viscous compressible flows on unstructuredgrids is developed, and three important problems raised in the continuous adjoint literature are solved. First, using tools of shape deformation of boundary integrals a generic adjoint formulation is developed withindependence of the kind of mesh used. Then, a systematic way of reducing the 2nd order derivative terms which arise is presented which avoids the need of using higher order numerical solvers to obtain accurateapproximations of the 2nd order derivatives. And finally, the class of admissible optimization functionals isclarified. Several remarks are made concerning the longstanding discrete vs. continuous adjoint dichotomy, with the emphasis not on the advantages or disadvantages of each method, but rather on the well-posedness of the approaches. The accuracy of the sensitivity derivatives is assessed by comparison with finite-difference computations, and the validity of the overall methodology is illustrated with design examples under demanding subsonic conditions.
Beauchamp, Catherine; Beauchamp, Miriam H.
2013-01-01
Within the emerging field of educational neuroscience, concerns exist that the impact of neuroscience research on education has been less effective than hoped. In seeking a way forward, it may be useful to consider the problems of integrating two complex fields in the context of disciplinary boundaries. Here, a boundary perspective is used as a…
Fabris, Clara; Ouédraogo, Robert Kossivi; Coppellotti, Olimpia; Dabiré, Roch K; Diabaté, Abdoulaye; Di Martino, Piera; Guidolin, Laura; Jori, Giulio; Lucantoni, Leonardo; Lupidi, Giulio; Martena, Valentina; Sawadogo, Simon P; Soncin, Marina; Habluetzel, Annette
2012-09-01
Biolarvicides, such as microbial formulations based on Bacillus thuringiensis and B. sphaericus, have been found to be highly effective against mosquito larvae and are currently employed as eco-friendly alternatives to synthetic chemical insecticides for vector control. Recently, a porphyrin of natural origin has been suggested as a sunlight-activatable larvicide against the dengue vector Aedes aegypti. In order to validate the approach for the control of the malaria vector, we tested the photo-larvicidal activity of a novel porphyrin, namely meso-tri(N-methyl-pyridyl), mono(N-dodecyl-pyridyl)porphine, C12, associated with two specifically selected carriers, against Anopheles gambiae s.s. and An. arabiensis larvae, both laboratory reared and collected from malaria endemic sites in Burkina Faso. Both C12-porphyrin formulates, when administered to larvae at a 50μM porphyrin dose, were accumulated in the alimentary canal. Subsequent exposure of the porphyrin-loaded larvae to sunlight for short times (0.5-3h) led to a complete mortality. The high efficacy exhibited by a "foodstuff" porphyrin formulate also in the presence of typical larval food particles opens promising perspectives for the development of an effective photocidal larvicide.
The Effect of Recessions on Firms’ Boundaries
DEFF Research Database (Denmark)
Knudsen, Eirik Sjåholm; Foss, Kirsten
2014-01-01
The economic theory of the firm offers conflicting predictions of how the two major effects of recessions, changes in demand and access to credit, affect firm boundaries. Using data on Norwegian firms in the recent recession, we find support for both increased and reduced vertical integration...... explanation for the conflicting theoretical predictions regarding vertical integration in response to demand and credit shocks....
Allegheny County Municipal Boundaries
Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset demarcates the municipal boundaries in Allegheny County. Data was created to portray the boundaries of the 130 Municipalities in Allegheny County the...
County Political Boundaries (National)
Department of Transportation — County boundaries with political limit - boundaries extending into the ocean (NTAD 2015). The TIGER/Line shapefiles and related database files (.dbf) are an extract...
Department of Housing and Urban Development — The HUD GIS Boundary Files are intended to supplement boundary files available from the U.S. Census Bureau. The files are for community planners interested in...
State Agency Administrative Boundaries
Kansas Data Access and Support Center — This database comprises 28 State agency boundaries and point of contact. The Kansas Geological Survey collected legal descriptions of the boundaries for various...
Plutonium Immobilization Project Baseline Formulation
Energy Technology Data Exchange (ETDEWEB)
Ebbinghaus, B.
1999-02-01
A key milestone for the Immobilization Project (AOP Milestone 3.2a) in Fiscal Year 1998 (FY98) is the definition of the baseline composition or formulation for the plutonium ceramic form. The baseline formulation for the plutonium ceramic product must be finalized before the repository- and plant-related process specifications can be determined. The baseline formulation that is currently specified is given in Table 1.1. In addition to the baseline formulation specification, this report provides specifications for two alternative formulations, related compositional specifications (e.g., precursor compositions and mixing recipes), and other preliminary form and process specifications that are linked to the baseline formulation. The preliminary specifications, when finalized, are not expected to vary tremendously from the preliminary values given.
Compatibility assessment of thermoplastic formulations
D. McAteer; Weaver, M.; Blair, L H; Flood, N; Gaulter, S E
2016-01-01
Prior to the large-scale preparation of any new chemical formulation an assessment of the potential reactivity between the components must be carried out. This practice, which is common to many fields including pharmaceutical science, is particularly essential in the case of energetic formulations whose chemical incompatibility may result in an unexpected and potentially explosive decomposition. The common method used to investigate incompatibility is to heat 1:1 (w/w) formulations and eva...
Explosive Formulation Code Naming SOP
Energy Technology Data Exchange (ETDEWEB)
Martz, H. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2014-09-19
The purpose of this SOP is to provide a procedure for giving individual HME formulations code names. A code name for an individual HME formulation consists of an explosive family code, given by the classified guide, followed by a dash, -, and a number. If the formulation requires preparation such as packing or aging, these add additional groups of symbols to the X-ray specimen name.
Baseline LAW Glass Formulation Testing
Energy Technology Data Exchange (ETDEWEB)
Kruger, Albert A. [USDOE Office of River Protection, Richland, WA (United States); Mooers, Cavin [The Catholic University of America, Washington, DC (United States). Vitreous State Lab.; Bazemore, Gina [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Pegg, Ian L. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Hight, Kenneth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Lai, Shan Tao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Buechele, Andrew [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Rielley, Elizabeth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Gan, Hao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Muller, Isabelle S. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Cecil, Richard [The Catholic University of America, Washington, DC (United States). Vitreous State Lab
2013-06-13
The major objective of the baseline glass formulation work was to develop and select glass formulations that are compliant with contractual and processing requirements for each of the LAW waste streams. Other objectives of the work included preparation and characterization of glasses with respect to the properties of interest, optimization of sulfate loading in the glasses, evaluation of ability to achieve waste loading limits, testing to demonstrate compatibility of glass melts with melter materials of construction, development of glass formulations to support ILAW qualification activities, and identification of glass formulation issues with respect to contract specifications and processing requirements.
On supersymmetry, boundary actions and brane charges
Di Pietro, Lorenzo; Klinghoffer, Nizan; Shamir, Itamar
2016-02-01
Supersymmetry transformations change the Lagrangian [InlineMediaObject not available: see fulltext.] into a total derivative [InlineMediaObject not available: see fulltext.]. On manifolds with boundaries the total derivative term is an obstruction to preserving supersymmetry. Such total derivative terms can be canceled by a boundary action without specifying boundary conditions, but only for a subalgebra of supersymmetry. We study compensating boundary actions for {N}=1 supersymmetry in 4d, and show that they are determined independently of the details of the theory and of the boundary conditions. Two distinct classes of boundary actions exist, which correspond to preserving either a linear combination of supercharges of opposite chirality (called A-type) or supercharges of opposite chirality independently (B-type). The first option preserves a subalgebra isomorphic to {N}=1 in 3d, while the second preserves only a 2d subgroup of the Lorentz symmetry and a subalgebra isomorphic to {N}=(0,2) in 2d. These subalgebras are in one to one correspondence with half-BPS objects: the A-type corresponds to domain walls while the B-type corresponds to strings. We show that integrating the full current algebra and taking into account boundary contributions leads to an energy-momentum tensor which contains the boundary terms. The boundary terms come from the domain wall and string currents in the two respective cases.
A Neumann Boundary Term for Gravity
Krishnan, Chethan
2016-01-01
The Gibbons-Hawking-York (GHY) boundary term makes the Dirichlet problem for gravity well defined, but no such general term seems to be known for Neumann boundary conditions. In this paper, we view Neumann {\\em not} as fixing the normal derivative of the metric ("velocity") at the boundary, but as fixing the functional derivative of the action with respect to the boundary metric ("momentum"). This leads directly to a new boundary term for gravity: the trace of the extrinsic curvature with a specific dimension-dependent coefficient. In three dimensions this boundary term reduces to a "one-half" GHY term noted in the literature previously, and we observe that our action translates precisely to the Chern-Simons action with no extra boundary terms. In four dimensions the boundary term vanishes, giving a natural Neumann interpretation to the standard Einstein-Hilbert action without boundary terms. We argue that in light of AdS/CFT, ours is a natural approach for defining a "microcanonical" path integral for gravit...
Watershed Boundaries - Watershed Boundary Database for Montana
NSGIC GIS Inventory (aka Ramona) — This data set is a complete digital hydrologic unit boundary layer of the Subbasins (8-digit), Watersheds (10-digit), and Subwatersheds (12-digit) for Montana. This...
Energy Technology Data Exchange (ETDEWEB)
Kamphuis, E. [ETC Nederland, Leusden (Netherlands); Permana, I. [Technical Education Development Centre TEDC, Bandung (Indonesia)
2011-11-15
The overall objective of the CASINDO programme is to establish a self-sustaining and self-developing structure at both the national and regional level to build and strengthen human capacity to enable the provinces of North Sumatra, Yogyakarta, Central Java, West Nusa Tenggara and Papua to formulate sound policies for renewable energy and energy efficiency and to develop and implement sustainable energy projects. This report focuses on the achievements for settling a national curriculum for Renewable Energy Technologies (RET) within the framework of national programme SPECTRUM, which includes all curricula of the medium technical schools in Indonesia.
Moiseiwitsch, B L
2005-01-01
Two distinct but related approaches hold the solutions to many mathematical problems--the forms of expression known as differential and integral equations. The method employed by the integral equation approach specifically includes the boundary conditions, which confers a valuable advantage. In addition, the integral equation approach leads naturally to the solution of the problem--under suitable conditions--in the form of an infinite series.Geared toward upper-level undergraduate students, this text focuses chiefly upon linear integral equations. It begins with a straightforward account, acco
Formulation and Evaluation of Coprocessed Excipient for Mouth Dissolving Formulation
Directory of Open Access Journals (Sweden)
Gandhi PP and Mundada AS
2016-03-01
Full Text Available In the present study an attempt has been made to evaluate Ocimum bascilium mucilage coprocessed with Mannitol as a novel super disintegrant. Coprocessed excipients were prepared by solvent evaporation method and evaluated in the formulation of mouth dissolving tablets of Terbutaline sulphate. Formulated mouth dissolving tablets were characterised for physicochemical parameters like hardness, friability, weight variation, disintegration time, drug content and in vitro drug release behaviour. The outcomes of physicochemical evaluation of formulations showed that all developed formulations had desirable features. The coprocessed mucilage (Mannitol: Mucilage exhibited disintegration within 8 sec at the concentration of 1 gm: 65 mg as compared to the coprocessed Mannitol: SSG which disintegrated within 11 sec at the concentration of 1 gm: 85 mg. The developed excipient showed improvement in parent excipient functionalities and proving coprocessed mucilage of Ocimum bascilium to be an excellent novel superdisintegrant in mouth dissolving formulation and thus it can be exploited commercially.
Saltstone Clean Cap Formulation
Energy Technology Data Exchange (ETDEWEB)
Langton, C
2005-04-22
The current operation strategy for using Saltstone Vault 4 to receive 0.2 Ci/gallon salt solution waste involves pouring a clean grout layer over the radioactive grout prior to initiating pour into another cell. This will minimize the radiating surface area and reduce the dose rate at the vault and surrounding area. The Clean Cap will be used to shield about four feet of Saltstone poured into a Z-Area vault cell prior to moving to another cell. The minimum thickness of the Clean Cap layer will be determined by the cesium concentration and resulting dose levels and it is expected to be about one foot thick based on current calculations for 0.1 Ci Saltstone that is produced in the Saltstone process by stabilization of 0.2 Ci salt solution. This report documents experiments performed to identify a formulation for the Clean Cap. Thermal transient calculations, adiabatic temperature rise measurements, pour height, time between pour calculations and shielding calculations were beyond the scope and time limitations of this study. However, data required for shielding calculations (composition and specific gravity) are provided for shielding calculations. The approach used to design a Clean Cap formulation was to produce a slurry from the reference premix (10/45/45 weight percent cement/slag/fly ash) and domestic water that resembled as closely as possible the properties of the Saltstone slurry. In addition, options were investigated that may offer advantages such as less bleed water and less heat generation. The options with less bleed water required addition of dispersants. The options with lower heat contained more fly ash and less slag. A mix containing 10/45/45 weight percent cement/slag/fly ash with a water to premix ratio of 0.60 is recommended for the Clean Cap. Although this mix may generate more than 3 volume percent standing water (bleed water), it has rheological, mixing and flow properties that are similar to previously processed Saltstone. The recommended
Mackenzie, S G; Leinonen, I; Ferguson, N; Kyriazakis, I
2016-05-28
The objective of this study was to develop a novel methodology that enables pig diets to be formulated explicitly for environmental impact objectives using a Life Cycle Assessment (LCA) approach. To achieve this, the following methodological issues had to be addressed: (1) account for environmental impacts caused by both ingredient choice and nutrient excretion, (2) formulate diets for multiple environmental impact objectives and (3) allow flexibility to identify the optimal nutritional composition for each environmental impact objective. An LCA model based on Canadian pig farms was integrated into a diet formulation tool to compare the use of different ingredients in Eastern and Western Canada. By allowing the feed energy content to vary, it was possible to identify the optimum energy density for different environmental impact objectives, while accounting for the expected effect of energy density on feed intake. A least-cost diet was compared with diets formulated to minimise the following objectives: non-renewable resource use, acidification potential, eutrophication potential, global warming potential and a combined environmental impact score (using these four categories). The resulting environmental impacts were compared using parallel Monte Carlo simulations to account for shared uncertainty. When optimising diets to minimise a single environmental impact category, reductions in the said category were observed in all cases. However, this was at the expense of increasing the impact in other categories and higher dietary costs. The methodology can identify nutritional strategies to minimise environmental impacts, such as increasing the nutritional density of the diets, compared with the least-cost formulation.
Mackenzie, S G; Leinonen, I; Ferguson, N; Kyriazakis, I
2016-05-28
The objective of this study was to develop a novel methodology that enables pig diets to be formulated explicitly for environmental impact objectives using a Life Cycle Assessment (LCA) approach. To achieve this, the following methodological issues had to be addressed: (1) account for environmental impacts caused by both ingredient choice and nutrient excretion, (2) formulate diets for multiple environmental impact objectives and (3) allow flexibility to identify the optimal nutritional composition for each environmental impact objective. An LCA model based on Canadian pig farms was integrated into a diet formulation tool to compare the use of different ingredients in Eastern and Western Canada. By allowing the feed energy content to vary, it was possible to identify the optimum energy density for different environmental impact objectives, while accounting for the expected effect of energy density on feed intake. A least-cost diet was compared with diets formulated to minimise the following objectives: non-renewable resource use, acidification potential, eutrophication potential, global warming potential and a combined environmental impact score (using these four categories). The resulting environmental impacts were compared using parallel Monte Carlo simulations to account for shared uncertainty. When optimising diets to minimise a single environmental impact category, reductions in the said category were observed in all cases. However, this was at the expense of increasing the impact in other categories and higher dietary costs. The methodology can identify nutritional strategies to minimise environmental impacts, such as increasing the nutritional density of the diets, compared with the least-cost formulation. PMID:26987378
Novak, Jerome; Bonazzola, Silvano
2002-01-01
We present a new formulation of the multipolar expansion of an exact boundary condition for the wave equation, which is truncated at the quadrupolar order. Using an auxiliary function, that is the solution of a wave equation on the sphere defining the outer boundary of the numerical grid, the absorbing boundary condition is simply written as a perturbation of the usual Sommerfeld radiation boundary condition. It is very easily implemented using spectral methods in spherical coordinates. Numer...
Institute of Scientific and Technical Information of China (English)
WEN Lihua; ZAHNG Jingmei; SUN Jincai
2002-01-01
The application of wavelets is explored to solve acoustic radiation and scattering problems. A new wavelet approach is presented for solving two-dimensional and axisymmetric acoustic problems. It is different from the previous methods in which Galerkin formulation or wavelet matrix transform approach is used. The boundary quantities are expended in terms of a basis of the periodic, orthogonal wavelets on the interval. Using wavelet transform leads a highly sparse matrix system. It can avoid an additional integration in Galerkin formulation,which may be very computationally expensive. The techniques of the singular integrals in two-dimensional and axisymmetric wavelet formulation are proposed. The new method can solve the boundary value problems with Dirichlet, Neumann and mixed conditions and treat axisymmetric bodies with arbitrary boundary conditions. It can be suitable for the solution at large wave numbers. A series of numerical examples are given. The comparisons of the results from new approach with those from boundary element method and analytical solutions demonstrate that the new technique has a fast convergence and high accuracy.
Calculation methods for compressible turbulent boundary layers
Bushnell, D. M.; Cary, A. M., Jr.; Harris, J. E.
1976-01-01
Calculation procedures for non-reacting compressible two- and three-dimensional turbulent boundary layers were reviewed. Integral, transformation and correlation methods, as well as finite difference solutions of the complete boundary layer equations summarized. Alternative numerical solution procedures were examined, and both mean field and mean turbulence field closure models were considered. Physics and related calculation problems peculiar to compressible turbulent boundary layers are described. A catalog of available solution procedures of the finite difference, finite element, and method of weighted residuals genre is included. Influence of compressibility, low Reynolds number, wall blowing, and pressure gradient upon mean field closure constants are reported.
Comment on the uncertainty relation with periodic boundary conditions
Fujikawa, Kazuo
2010-01-01
The Kennard-type uncertainty relation $\\Delta x\\Delta p >\\frac{\\hbar}{2}$ is formulated for a free particle with given momentum $ inside a box with periodic boundary conditions in the large box limit. Our construction of a free particle state is analogous to that of the Bloch wave in a periodic potential. A simple Robertson-type relation, which minimizes the effect of the box boundary and may be useful in some practical applications, is also presented.
Indian Academy of Sciences (India)
Ramesh Chander; S K Tomar
2014-10-01
A concentrated load with step-function time behaviour is placed normal to the planar, pervious boundary of a porous elastic half space (PEHS) with compressible constituents. A planar fault exists in the PEHS in such a way that the poroelastic behaviour of the medium is unhindered. We derive an approximate but integral-free expression for CFSCPP, i.e., changes in fault stability due to changes in pore pressure, at a point not too far off the line along which the load acts. But, in the interest of simplicity, the main discussion is focussed on a consideration of CFSCPP at a point located on the fault at depth directly beneath the load. It is convenient to introduce dimensionless time directly proportional to real time . The constant of proportionality is 4c/z2, where is hydraulic diffusivity. The derived approximate expression gives results with an accuracy of greater than 99% for limited values of after the load is imposed. We learn from the derived expression that, for a given , fault stability undergoes an initial sudden decrease commensurate with the undrained pore pressure induced in the PEHS. This is followed by a more gradual decrease in fault stability with increasing until a minimum is reached. The real time to minimum fault stability increases with . The magnitude of CFSCPP decreases with as −2 for a given in the permissible range. The derived expression and the inferences based on it should be useful during earth science investigations of the possible hazards due to reactivation of a pre-existing shallow fault when a civil engineering project involving imposition of a heavy load on the earth’s surface is to be executed nearby. They should be useful also for investigations if a shallow earthquake occurs near such a project soon after its execution.
Formulation of elastic multi-structures
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Based on the creative and groundbreaking work done by Feng and Shi, some further work has been carried out comprehensively by the first author on the formulation of elastic multi-structures. The main contribution of this paper can be summarized as follows: The work of Feng and Shi has been extended to an elastic multi-structures with nonlinear structural element: shell in both linear and nonlinear case. Three general combinations of multi-structures have been formulated, that is, Case 1: linear elements of 3-D body, 1-D bar/beam, 2-D plates and 2-D shell; Case 2: nonlinear elements of 3-D body, 1-D bar/beam, 2-D plates and 2-D shell; and Case 3: the linear-nonlinear mix problem of 3-D body (nonlinear), 1-D bar/beam (linear), 2-D plates (linear) and 2-D shell (linear). From the investigation, it has proved that the higher dimensional element will have a strong influence on the lower one with the inner linkage boundaries, and also proved that solution uniqueness of elastic multi-structures is different from a single 3-D body.
Optimal boundaries for decisions
Directory of Open Access Journals (Sweden)
Carfi', David
2008-01-01
Full Text Available In this paper we state and prove some new results on the optimal boundaries. These boundaries (called Pareto boundaries too are of increasing importance in the applications to Decision Theory. First of all the Pareto boundaries are the first and most important generalization of the concept of optimum; on the other hand, if f is a real functional defined on a non empty set X and K is a part of X, the determination of the optimal boundaries of the part K with respect to some preorder of X for which f is strictly increasing permits to reduce the optimization problem (f, K, inf (or (f, K, sup to the problem (f, minP(K, inf (resp. (f, maxP(K, sup, where by minP(K we denoted the minimal boundary of K (that in general is greatly smoller than K.
An Alternate Path Integral for Quantum Gravity
Krishnan, Chethan; Raju, Avinash
2016-01-01
We define a (semi-classical) path integral for gravity with Neumann boundary conditions in $D$ dimensions, and show how to relate this new partition function to the usual picture of Euclidean quantum gravity. We also write down the action in ADM Hamiltonian formulation and use it to reproduce the entropy of black holes and cosmological horizons. A comparison between the (background-subtracted) covariant and Hamiltonian ways of semi-classically evaluating this path integral in flat space reproduces the generalized Smarr formula and the first law. This "Neumann ensemble" perspective on gravitational thermodynamics is parallel to the canonical (Dirichlet) ensemble of Gibbons-Hawking and the microcanonical approach of Brown-York.
An alternative path integral for quantum gravity
Krishnan, Chethan; Kumar, K. V. Pavan; Raju, Avinash
2016-10-01
We define a (semi-classical) path integral for gravity with Neumann boundary conditions in D dimensions, and show how to relate this new partition function to the usual picture of Euclidean quantum gravity. We also write down the action in ADM Hamiltonian formulation and use it to reproduce the entropy of black holes and cosmological horizons. A comparison between the (background-subtracted) covariant and Hamiltonian ways of semi-classically evaluating this path integral in flat space reproduces the generalized Smarr formula and the first law. This "Neumann ensemble" perspective on gravitational thermodynamics is parallel to the canonical (Dirichlet) ensemble of Gibbons-Hawking and the microcanonical approach of Brown-York.
Novel Formulations for Antimicrobial Peptides
Directory of Open Access Journals (Sweden)
Ana Maria Carmona-Ribeiro
2014-10-01
Full Text Available Peptides in general hold much promise as a major ingredient in novel supramolecular assemblies. They may become essential in vaccine design, antimicrobial chemotherapy, cancer immunotherapy, food preservation, organs transplants, design of novel materials for dentistry, formulations against diabetes and other important strategical applications. This review discusses how novel formulations may improve the therapeutic index of antimicrobial peptides by protecting their activity and improving their bioavailability. The diversity of novel formulations using lipids, liposomes, nanoparticles, polymers, micelles, etc., within the limits of nanotechnology may also provide novel applications going beyond antimicrobial chemotherapy.
Wittenberg, Ralf W.
2008-01-01
We investigate the influence of the thermal properties of the boundaries in turbulent Rayleigh-Benard convection on analytical bounds on convective heat transport. Using the Doering-Constantin background flow method, we systematically formulate a bounding principle on the Nusselt-Rayleigh number relationship for general mixed thermal boundary conditions of constant Biot number \\eta which continuously interpolates between the previously studied fixed temperature ($\\eta = 0$) and fixed flux ($\\...
Kanguzhin, Baltabek; Tokmagambetov, Niyaz
2016-08-01
In this work, we research a boundary inverse problem of spectral analysis of a differential operator with integral boundary conditions in the functional space L2(0, b) where b operator by its spectrum and some additional data.
A fast integral equation method for solid particles in viscous flow using quadrature by expansion
Klinteberg, Ludvig af
2016-01-01
Boundary integral methods are advantageous when simulating viscous flow around rigid particles, due to the reduction in number of unknowns and straightforward handling of the geometry. In this work we present a fast and accurate framework for simulating spheroids in periodic Stokes flow, which is based on the completed double layer boundary integral formulation. The framework implements a new method known as quadrature by expansion (QBX), which uses surrogate local expansions of the layer potential to evaluate it to very high accuracy both on and off the particle surfaces. This quadrature method is accelerated through a newly developed precomputation scheme. The long range interactions are computed using the spectral Ewald (SE) fast summation method, which after integration with QBX allows the resulting system to be solved in M log M time, where M is the number of particles. This framework is suitable for simulations of large particle systems, and can be used for studying e.g. porous media models.
Relativistic formulation of quark model
International Nuclear Information System (INIS)
A relativistic model, which describes spin-orbital excitations of quark-antiquark bound system, is proposed. A formulation of the model provides the meson classification established in frame of the nonrelativistic quark model. 3 refs
Numerical Solution for the Helmholtz Equation with Mixed Boundary Condition
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
We consider the numerical solution for the Helmholtz equation in R2 with mixed boundary conditions. The solvability of this mixed boundary value problem is established by the boundary integral equation method. Based on the Green formula, we express the solution in terms of the boundary data. The key to the numerical realization of this method is the computation of weakly singular integrals. Numerical performances show the validity and feasibility of our method. The numerical schemes proposed in this paper have been applied in the realization of probe method for inverse scattering problems.
Directory of Open Access Journals (Sweden)
J. Callies
2011-08-01
Full Text Available A simple model of the thermohaline circulation (THC is formulated, with the objective to represent explicitly the geostrophic force balance of the basinwide THC. The model comprises advective-diffusive density balances in two meridional-vertical planes located at the eastern and the western walls of a hemispheric sector basin. Boundary mixing constrains vertical motion to lateral boundary layers along these walls. Interior, along-boundary, and zonally integrated meridional flows are in thermal-wind balance. Rossby waves and the absence of interior mixing render isopycnals zonally flat except near the western boundary, constraining meridional flow to the western boundary layer. The model is forced by a prescribed meridional surface density profile.
This two-plane model reproduces both steady-state density and steady-state THC structures of a primitive-equation model. The solution shows narrow deep sinking at the eastern high latitudes, distributed upwelling at both boundaries, and a western boundary current with poleward surface and equatorward deep flow. The overturning strength has a 2/3-power-law dependence on vertical diffusivity and a 1/3-power-law dependence on the imposed meridional surface density difference. Convective mixing plays an essential role in the two-plane model, ensuring that deep sinking is located at high latitudes. This role of convective mixing is consistent with that in three-dimensional models and marks a~sharp contrast with previous two-dimensional models.
Overall, the two-plane model reproduces crucial features of the THC as simulated in simple-geometry three-dimensional models. At the same time, the model self-consistently makes quantitative a conceptual picture of the three-dimensional THC that hitherto has been expressed either purely qualitatively or not self-consistently.
Directory of Open Access Journals (Sweden)
J. Callies
2012-01-01
Full Text Available A simple model of the thermohaline circulation (THC is formulated, with the objective to represent explicitly the geostrophic force balance of the basinwide THC. The model comprises advective-diffusive density balances in two meridional-vertical planes located at the eastern and the western walls of a hemispheric sector basin. Boundary mixing constrains vertical motion to lateral boundary layers along these walls. Interior, along-boundary, and zonally integrated meridional flows are in thermal-wind balance. Rossby waves and the absence of interior mixing render isopycnals zonally flat except near the western boundary, constraining meridional flow to the western boundary layer. The model is forced by a prescribed meridional surface density profile.
This two-plane model reproduces both steady-state density and steady-state THC structures of a primitive-equation model. The solution shows narrow deep sinking at the eastern high latitudes, distributed upwelling at both boundaries, and a western boundary current with poleward surface and equatorward deep flow. The overturning strength has a 2/3-power-law dependence on vertical diffusivity and a 1/3-power-law dependence on the imposed meridional surface density difference. Convective mixing plays an essential role in the two-plane model, ensuring that deep sinking is located at high latitudes. This role of convective mixing is consistent with that in three-dimensional models and marks a sharp contrast with previous two-dimensional models.
Overall, the two-plane model reproduces crucial features of the THC as simulated in simple-geometry three-dimensional models. At the same time, the model self-consistently makes quantitative a conceptual picture of the three-dimensional THC that hitherto has been expressed either purely qualitatively or not self-consistently.
Regular and Irregular Boundary Conditions in the AdS/CFT Correspondence
Mück, W
1999-01-01
We expand on Klebanov and Witten's recent proposal for formulating the AdS/CFT correspondence using irregular boundary conditions. The proposal is shown to be correct to any order in perturbation theory.
Otelbaev, Mukhtarbay; Koshanov, Bakytbek D.
2016-08-01
This paper describes the correct narrowing of the Navier-Stokes equations in a stationary three-dimensional cube and clarified the correct formulation of the boundary conditions for the pressure in the environment.
Formulation Optimization of Arecoline Patches
Directory of Open Access Journals (Sweden)
Pao-Chu Wu
2014-01-01
Full Text Available The response surface methodology (RSM including polynomial equations has been used to design an optimal patch formulation with appropriate adhesion and flux. The patch formulations were composed of different polymers, including Eudragit RS 100 (ERS, Eudragit RL 100 (ERL and polyvinylpyrrolidone K30 (PVP, plasticizers (PEG 400, and drug. In addition, using terpenes as enhancers could increase the flux of the drug. Menthol showed the highest enhancement effect on the flux of arecoline.
Integrable discretisations for a class of nonlinear Schrödinger equations on Grassmann algebras
Energy Technology Data Exchange (ETDEWEB)
Grahovski, Georgi G., E-mail: G.Grahovski@leeds.ac.uk [Department of Applied Mathematics, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT (United Kingdom); Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tsarigradsko chausee, Sofia 1784 (Bulgaria); Mikhailov, Alexander V., E-mail: A.V.Mikhailov@leeds.ac.uk [Department of Applied Mathematics, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT (United Kingdom)
2013-12-17
Integrable discretisations for a class of coupled (super) nonlinear Schrödinger (NLS) type of equations are presented. The class corresponds to a Lax operator with entries in a Grassmann algebra. Elementary Darboux transformations are constructed. As a result, Grassmann generalisations of the Toda lattice and the NLS dressing chain are obtained. The compatibility (Bianchi commutativity) of these Darboux transformations leads to integrable Grassmann generalisations of the difference Toda and NLS equations. The resulting systems will have discrete Lax representations provided by the set of two consistent elementary Darboux transformations. For the two discrete systems obtained, initial value and initial-boundary problems are formulated.
Niosomal Formulation Of Orlistat: Formulation And In-Vitro Evaluation
Directory of Open Access Journals (Sweden)
SAMYUKTHA RANI. B
2011-06-01
Full Text Available The purpose of the research was to prepare Orlistat niosomes from proniosome to improve its poor and variable oral bioavailability. The non-ionic surfactant vesicles are prepared by the reverse phase evaporation technique (slurry method. The slurry of - Cyclodextrin and Span 60 was dried to form a free flowing powder in rotary flash evaporator which could be rehydrated by addition of buffer (0.5% NaCl with 3% SLS at pH 6.0. The lipid mixture consisted of cholesterol, Span 60 and - Cyclodextrin carrier in molar ratios of (0.1:0.9:1 to 0.9:0.1:1 respectively. The niosomal formulations were evaluated for particle size, entrapment efficiency, in-vitro drug release, release kinetics, Interactions and compatibility (FT-IR, surface morphology (SEM, stability studies, conductivity and sedimentation rate, pH density, viscosity. The formulation OT9 which showed higher entrapment efficiency of 44.09% and invitro releases of 94.59% at the end of 12hrs was found to be best among all the 9 formulations. Release was best fitted with Hixson kinetics and it shows that the drug release may follow diffusion mechanism. FT-IR data revealed that, compatible and there were no interactions between the drug and excipients added in the formulation. SEM images of niosomes with various magnifications revealed the mean size of the niosomes were 100 nm with smooth surface. Niosome formulation has showed appropriate stability for 90 days by storing the formulation at room temperature. Thus the niosomal formulations could be a promising delivery system for Orlistat with improved oral bioavailability, stability and for sustained drug release.
DEFF Research Database (Denmark)
Gorm Hansen, Birgitte
2012-01-01
Whether celebratory or critical, STS research on science-industry relations has focused on the blurring of boundaries and hybridization of codes and practices. However, the vocabulary of boundary and hybrid tends to reify science and industry as separate in the attempt to map their relation. Draw...
DEFF Research Database (Denmark)
Gorm Hansen, Birgitte
2011-01-01
Whether celebratory or critical, STS research on science-industry relations has focused on the blurring of boundaries and hybridization of codes and practices. However, the vocabulary of boundary and hybrid tends to reify science and industry as separate in the attempt to map their relation. Draw...
Behaviour of boundary functions for quantum billiards
International Nuclear Information System (INIS)
We study the behaviour of the normal derivative of eigenfunctions of the Helmholtz equation inside billiards with Dirichlet boundary condition. These boundary functions are of particular importance because they uniquely determine the eigenfunctions inside the billiard and also other physical quantities of interest. Therefore, they form a reduced representation of the quantum system, analogous to the Poincare section of the classical system. For the normal derivatives we introduce an equivalent to the standard Green function and derive an integral equation on the boundary. Based on this integral equation we compute the first two terms of the mean asymptotic behaviour of the boundary functions for large energies. The first term is universal and independent of the shape of the billiard. The second one is proportional to the curvature of the boundary. The asymptotic behaviour is compared with numerical results for the stadium billiard, different limacon billiards and the circle billiard, and good agreement is found. Furthermore, we derive an asymptotic completeness relation for the boundary functions
Coleman-Gurtin type equations with dynamic boundary conditions
Gal, Ciprian G.; Shomberg, Joseph L.
2015-02-01
We present a new formulation and generalization of the classical theory of heat conduction with or without fading memory. As a special case, we investigate the well-posedness of systems which consist of Coleman-Gurtin type equations subject to dynamic boundary conditions, also with memory. Nonlinear terms are defined on the interior of the domain and on the boundary and subject to either classical dissipation assumptions, or to a nonlinear balance condition in the sense of Gal (2012). Additionally, we do not assume that the interior and the boundary share the same memory kernel.
A simple method to determine evaporation duct height in the sea surface boundary layer
Musson-Genon, Luc; Gauthier, Sylvie; Bruth, Eric
1992-09-01
A formulation to determine the evaporation duct height in the sea surface boundary layer is presented. This formulation is based upon the theory of similarity of Monin Obukhov by using analytical solutions currently used in the field of numerical weather prediction. The proposed solution is simple, coherent with the surface boundary layer parameterization used in the Meteo France and European Centre for Medium-Range Weather Forecasts weather prediction models and gives good results when compared to more traditional methods.
Paint and Click: Unified Interactions for Image Boundaries
Energy Technology Data Exchange (ETDEWEB)
Summa, B. [Univ. of Utah, Salt Lake City, UT (United States). Scientific Computing and Imaging (SCI) Inst.; Gooch, A. A. [Univ. of Utah, Salt Lake City, UT (United States). Scientific Computing and Imaging (SCI) Inst.; Scorzelli, G. [Univ. of Utah, Salt Lake City, UT (United States). Scientific Computing and Imaging (SCI) Inst.; Pascucci, V. [Univ. of Utah, Salt Lake City, UT (United States). Scientific Computing and Imaging (SCI) Inst.
2015-06-22
Image boundaries are a fundamental component of many interactive digital photography techniques, enabling applications such as segmentation, panoramas, and seamless image composition. Interactions for image boundaries often rely on two complementary but separate approaches: editing via painting or clicking constraints. In this work, we provide a novel, unified approach for interactive editing of pairwise image boundaries that combines the ease of painting with the direct control of constraints. Rather than a sequential coupling, this new formulation allows full use of both interactions simultaneously, giving users unprecedented flexibility for fast boundary editing. To enable this new approach, we provide technical advancements. In particular, we detail a reformulation of image boundaries as a problem of finding cycles, expanding and correcting limitations of the previous work. Our new formulation provides boundary solutions for painted regions with performance on par with state-of-the-art specialized, paint-only techniques. In addition, we provide instantaneous exploration of the boundary solution space with user constraints. Finally, we provide examples of common graphics applications impacted by our new approach.
Social Groupwork. A Model for Goal Formulation.
Tompkins, Rosamond P.; Gallo, Frank T.
1978-01-01
A conceptual model for goal formulation in social groupwork, discussion of existing models and their limitations, and an attempt to formulate an encompassing groupwork model that facilitates goal formulation. (Author/PD)
Molecular Dynamics ofa Coulomb System with Deformable Periodic Boundary Conditions
Totsuji, Hiroo; Shirokoshi, Hideki; Nara, Shigetoshi
1991-01-01
Variable shape molecular dynamics is formulated for the one-component plasma and the structural transition from the fcc lattice to the bcc lattice has been observed. It is emphasized that the condition of constant volume should be imposed when deformations of periodic boundary conditions are taken into account.
On the algebraic Bethe ansatz: Periodic boundary conditions
Lima-Santos, A.
2006-01-01
In this paper, the algebraic Bethe ansatz with periodic boundary conditions is used to investigate trigonometric vertex models associated with the fundamental representations of the non-exceptional Lie algebras. This formulation allow us to present explicit expressions for the eigenvectors and eigenvalues of the respective transfer matrices.
Level set formulation of two-dimensional Lagrangian vortex detection methods
Hadjighasem, Alireza
2016-01-01
We propose here the use of the variational level set methodology to capture Lagrangian vortex boundaries in 2D unsteady velocity fields. This method reformulates earlier approaches that seek material vortex boundaries as extremum solutions of variational problems. We demonstrate the performance of this technique for two different variational formulations built upon different notions of coherence. The first formulation uses an energy functional that penalizes the deviation of a closed material line from piecewise uniform stretching [Haller and Beron-Vera, J. Fluid Mech. 731, R4 (2013)]. The second energy function is derived for a graph-based approach to vortex boundary detection [Hadjighasem et al., Phys. Rev. E 93, 063107 (2016)]. Our level-set formulation captures an a priori unknown number of vortices simultaneously at relatively low computational cost. We illustrate the approach by identifying vortices from different coherence principles in several examples.
On consistent boundary conditions for c = 1 string theory
O'Loughlin, M H
1995-01-01
We introduce a new parametrisation for the Fermi sea of the c = 1 matrix model. This leads to a simple derivation of the scattering matrix, and a calculation of boundary corrections in the corresponding 1+1--dimensional string theory. The new parametrisation involves relativistic chiral fields, rather than the non-relativistic fields of the usual formulations. The calculation of the boundary corrections, following recent work of Polchinski, allows us to place restrictions on the boundary conditions in the matrix model. We provide a consistent set of boundary conditions, but believe that they need to be supplemented by some more subtle relationship between the space-time and matrix model. Inspired by these boundary conditions, some thoughts on the black hole in c=1 string theory are presented.
Equivariant preconditioners for boundary element methods
Energy Technology Data Exchange (ETDEWEB)
Tausch, J. [Colorado State Univ., Fort Collins, CO (United States)
1994-12-31
In this paper the author proposes and discusses two preconditioners for boundary integral equations on domains which are nearly symmetric. The preconditioners under consideration are equivariant, that is, they commute with a group of permutation matrices. Numerical experiments demonstrate their efficiency for the GMRES method.
Secure Supply Chains: Design Restrictions & Organizational Boundaries
Ludema, M.W.
2009-01-01
An important issue in the design of secure supply chains is the understanding of the relation between supply chains and the organizational responsibility of specific parts of these supply chains. Organizational boundaries change over time by means of vertical and/or horizontal (des)-integration and
Effective boundary action in fermion string theory
International Nuclear Information System (INIS)
Continual Polyakov integral for the Neveu-Schwarz-Ramon (NSR) type fermion string is calculated on the Riemann Surface with special choice of local boundary conditions for the fermion fields. The derived expressions are used when studying behaviour of the string Green function in configurational space. Generalization of the effective fermion action for the case of non-Archimedean strings is discussed. 11 refs
Numerical solution of the exterior oblique derivative BVP using the direct BEM formulation
Čunderlík, Róbert; Špir, Róbert; Mikula, Karol
2016-04-01
The fixed gravimetric boundary value problem (FGBVP) represents an exterior oblique derivative problem for the Laplace equation. A direct formulation of the boundary element method (BEM) for the Laplace equation leads to a boundary integral equation (BIE) where a harmonic function is represented as a superposition of the single-layer and double-layer potential. Such a potential representation is applied to obtain a numerical solution of FGBVP. The oblique derivative problem is treated by a decomposition of the gradient of the unknown disturbing potential into its normal and tangential components. Our numerical scheme uses the collocation with linear basis functions. It involves a triangulated discretization of the Earth's surface as our computational domain considering its complicated topography. To achieve high-resolution numerical solutions, parallel implementations using the MPI subroutines as well as an iterative elimination of far zones' contributions are performed. Numerical experiments present a reconstruction of a harmonic function above the Earth's topography given by the spherical harmonic approach, namely by the EGM2008 geopotential model up to degree 2160. The SRTM30 global topography model is used to approximate the Earth's surface by the triangulated discretization. The obtained BEM solution with the resolution 0.05 deg (12,960,002 nodes) is compared with EGM2008. The standard deviation of residuals 5.6 cm indicates a good agreement. The largest residuals are obviously in high mountainous regions. They are negative reaching up to -0.7 m in Himalayas and about -0.3 m in Andes and Rocky Mountains. A local refinement in the area of Slovakia confirms an improvement of the numerical solution in this mountainous region despite of the fact that the Earth's topography is here considered in more details.
Stress Wave Propagation in Soils Modelled by the Boundary Element Method
DEFF Research Database (Denmark)
Rasmussen, K. M.
This thesis deals with different aspects of the boundary element method (BEM) applied to stress wave propagation problems in soils. Among other things BEM formulations for coupled FEM and BEM, moving loads, direct BEM and indirect BEM are presented. For all the formulations both analytical expres...
Boundary-value problems for x-analytical functions with weighted boundary conditions
Energy Technology Data Exchange (ETDEWEB)
Kapshivyi, A.A. [Kiev Univ. (Ukraine)
1994-11-10
We consider boundary-value problems for x-analytical functions of a complex variable z = x + iy in a number of domains. Limit values with the weight (ln x){sup {minus}1} are given for the real part of the x-analytical function on the sections of the boundary that follow the imaginary axis, and simple limits are given for the real part of the x-analytical functions on the part of the boundary outside the imaginary axis. The apparatus of integral representations of x-analytical functions is applied to obtain a solution of the problem in quadratures.
Integral equations for the electromagnetic field in dielectrics
Mostowski, Jan; Załuska-Kotur, Magdalena A.
2016-09-01
We study static the electric field and electromagnetic waves in dielectric media. In contrast to the standard approach, we use, formulate and solve integral equations for the field. We discuss the case of an electrostatic field of a point charge placed inside a dielectric; the integral equation approach allows us to find and interpret the dielectric constant in terms of molecular polarizability. Next we discuss propagation of electromagnetic waves using the same integral equation approach. We derive the dispersion relation and find the reflection and transmission coefficients at the boundary between the vacuum and the dielectric. The present approach supplements the standard approach based on macroscopic Maxwell equations and contributes to better a understanding of some electromagnetic effects.
New Formulation of Weyl Quantization Scheme in Coherent State Representation*
Institute of Scientific and Technical Information of China (English)
LIU Tang-Kun; FAN Hong-Yi
2011-01-01
By virtue of the technique of integration within an ordered product of operators we present a new formulation of the Weyl quantization scheme in the coherent state representation, which not only brings convenience for calculating the Weyl correspondence of normally ordered operators, but also directly leads us to find both the coherent state representation and the Weyl ordering representation of the Wigner operator.
Boundary conditions for the Pauli equation: application to photodetachment of Cs-.
Bahrim, C; Fabrikant, I I; Thumm, U
2001-09-17
We formulate the boundary conditions near the atomic nucleus for solving the Pauli equation, based on the analytic solution of the Dirac equation for a Coulomb potential. We then integrate the Pauli equation using an effective potential that is adjusted to reproduce Dirac R-matrix scattering phase shifts, and find the (3)P(o)(1) resonance contribution to the photodetachment cross section of Cs-. Our photodetachment cross sections agree with recent experiments by Scheer et al. [Phys. Rev. Lett. 80, 684 (1998)] after tuning the resonance position by 2.4 meV. We also provide angle-differential photodetachment cross sections and the corresponding asymmetry parameter beta near the Cs(6s) threshold. PMID:11580504
Yang, Pengliang; Brossier, Romain; Métivier, Ludovic; Virieux, Jean
2016-10-01
In this paper, we study 3-D multiparameter full waveform inversion (FWI) in viscoelastic media based on the generalized Maxwell/Zener body including arbitrary number of attenuation mechanisms. We present a frequency-domain energy analysis to establish the stability condition of a full anisotropic viscoelastic system, according to zero-valued boundary condition and the elastic-viscoelastic correspondence principle: the real-valued stiffness matrix becomes a complex-valued one in Fourier domain when seismic attenuation is taken into account. We develop a least-squares optimization approach to linearly relate the quality factor with the anelastic coefficients by estimating a set of constants which are independent of the spatial coordinates, which supplies an explicit incorporation of the parameter Q in the general viscoelastic wave equation. By introducing the Lagrangian multipliers into the matrix expression of the wave equation with implicit time integration, we build a systematic formulation of multiparameter FWI for full anisotropic viscoelastic wave equation, while the equivalent form of the state and adjoint equation with explicit time integration is available to be resolved efficiently. In particular, this formulation lays the foundation for the inversion of the parameter Q in the time domain with full anisotropic viscoelastic properties. In the 3-D isotropic viscoelastic settings, the anelastic coefficients and the quality factors using bulk and shear moduli parametrization can be related to the counterparts using P and S velocity. Gradients with respect to any other parameter of interest can be found by chain rule. Pioneering numerical validations as well as the real applications of this most generic framework will be carried out to disclose the potential of viscoelastic FWI when adequate high-performance computing resources and the field data are available.