Search results for "boundary"
showing 10 items of 1626 documents
Phase transitions in thin films with competing surface fields and gradients.
2011
As a generic model for phase equilibria under confinement in a thin-film geometry in the presence of a gradient in the field conjugate to the order parameter, an Ising-lattice gas system is studied by both Monte Carlo simulations and a phenomenological theory. Choosing an $L\ifmmode\times\else\texttimes\fi{}L\ifmmode\times\else\texttimes\fi{}D$ geometry with $L\ensuremath{\gg}D$ and periodic boundary conditions in the $x,y$ directions, we place competing surface fields on the two $L\ifmmode\times\else\texttimes\fi{}L$ surfaces. In addition, a field gradient $g$ is present in the $z$ direction across the film, in competition with the surface fields. At temperatures $T$ exceeding the critical…
Absence of hyperscaling violations for phase transitions with positive specific heat exponent
1994
Finite size scaling theory and hyperscaling are analyzed in the ensemble limit which differs from the finite size scaling limit. Different scaling limits are discussed. Hyperscaling relations are related to the identification of thermodynamics as the infinite volume limit of statistical mechanics. This identification combined with finite ensemble scaling leads to the conclusion that hyperscaling relations cannot be violated for phase transitions with strictly positive specific heat exponent. The ensemble limit allows to derive analytical expressions for the universal part of the finite size scaling functions at the critical point. The analytical expressions are given in terms of generalH-fu…
Three-dimensional scattering of dielectric gratings under plane-wave excitation
2003
The problem of scattering of electromagnetic plane waves by one-dimensional (1D) periodic dielectric gratings, under the most general condition of oblique incidence (3D incidence), is rigorously solved. A recently developed vectorial modal method for obtaining the modal spectrum of 1D dielectric periodic guiding media has been extended to consider 3D incidence. Polarization coupling effects are included in the analysis, just demonstrating the impossibility of the separation between the transverse electric and transverse magnetic polarizations traditionally employed in the two-dimensional (2D) case. A study of the scattering parameters of a multilayered dielectric periodic structure is accom…
Numerical simulation of a wawe generator: A case of study
2013
The aim of present work is the numerical simulation of a linear generator, capable of directly converting the kinetic energy, available by the wave, into electrical energy, through the device linear motion (up and down). In this paper, we intend to propose a numerical simulation approach to immersed devices by applying the Immersed Boundary Method. The Theory of linear wave is used to study and reproduce sea conditions and the computational domain is created based on observations available for the site in which it is envisaged the positioning of the device.
Multicanonical Monte Carlo study and analysis of tails for the order-parameter distribution of the two-dimensional Ising model.
2003
The tails of the critical order-parameter distribution of the two-dimensional Ising model are investigated through extensive multicanonical Monte Carlo simulations. Results for fixed boundary conditions are reported here, and compared with known results for periodic boundary conditions. Clear numerical evidence for ‘‘fat’’ stretched exponential tails exists below the critical temperature, indicating the possible presence of fat tails at the critical temperature. Our work suggests that the true order-parameter distribution at the critical temperature must be considered to be unknown at present.
Manifestation of Hamiltonian Monodromy in Nonlinear Wave Systems
2011
International audience; We show that the concept of dynamical monodromy plays a natural fundamental role in the spatiotemporal dynamics of counterpropagating nonlinear wave systems. By means of an adiabatic change of the boundary conditions imposed to the wave system, we show that Hamiltonian monodromy manifests itself through the spontaneous formation of a topological phase singularity (2 - or -phase defect) in the nonlinear waves. This manifestation of dynamical Hamiltonian monodromy is illustrated by generic nonlinear wave models. In particular, we predict that its measurement can be realized in a direct way in the framework of a nonlinear optics experiment.
High-order simulation scheme for active particles driven by stress boundary conditions
2020
Abstract We study the dynamics and interactions of elliptic active particles in a two dimensional solvent. The particles are self-propelled through prescribing a fluid stress at one half of the fluid-particle boundary. The fluid is treated explicitly solving the Stokes equation through a discontinuous Galerkin scheme, which allows to simulate strictly incompressible fluids. We present numerical results for a single particle and give an outlook on how to treat suspensions of interacting active particles.
Displacement measurements in structural elements by optical techniques
2000
Speckle metrology and holographic interferometry (HI) have been used in several civil engineering applications. We present the results obtained by applying speckle photography (SP) to the study of two quadratic shearwalls with different boundary conditions, and the potential of the technique in the study of this kind of structures is described. The analysis of Young's fringes obtained with this technique at certain points on each shearwall provides the whole field of displacement measurements. HI has been used to measure the three components of absolute displacement, verifying that the bulging phenomenon does not affect the in-plane components when the applied load remains on the same plane…
The Ground State of the 2-Dimensional Potts Glass
1992
We study the ground state of the 3-state Potts glass in 2 dimensions with a Gaussian distribution of couplings by domain wall renormalization group techniques. We find that the glass correlation function decays to a finite value within a distance of about 2.4 lattice spacings. Thus, there is long-range order in the ground state even though, as found earlier, there is a finite zero-point entropy.
Heat Conduction Problem for Double-Layered Ball
2014
Heat conduction models for double layered spherical sample are developed. Parabolic (classic, based on Fourier’s Law) and hyperbolic (based on Modified Fourier’s Law) heat conduction equations are used to describe processes in the sample during Intensive Quenching. Solution and numerical results are obtained for 1D model using Conservative Averaging method and transforming the original problem for a sphere to a new problem for a slab, with non classic boundary condition. Models include boundary conditions of third kind and non-linear BC case. Numerical results are presented for several relaxation time and initial heat flux values.