Search results for "distribution function"

Finite-size-scaling study of the simple cubic three-state Potts glass: Possible lower critical dimension d=3.

1990

For small lattices with linear dimension L ranging from L=3 to L=8 we obtain the distribution function P(q) of the overlap q between two real replicas of the three-state Potts-glass model with symmetric nearest-neighbor interaction with a Gaussian distribution. A finite-size-scaling analysis suggests a zero-temperature transition to occur with an exponentially diverging correlation length ${\ensuremath{\xi}}_{\mathrm{SG}}$\ensuremath{\sim}exp(C/${\mathit{T}}^{\mathrm{\ensuremath{\sigma}}}$). This implies that d=3 is the lower critical dimension.

Exact results for the homogeneous cooling state of an inelastic hard-sphere gas

1998

The infinite set of moments of the two-particle distribution function is found exactly for the uniform cooling state of a hard-sphere gas with inelastic collisions. Their form shows that velocity correlations cannot be neglected, and consequently the 'molecular chaos' hypothesis leading to the inelastic Boltzmann and Enskog kinetic equations must be questioned. © 1998 Cambridge University Press.

2012

We study the Wigner function for a quantum system with a discrete, infinite dimensional Hilbert space, such as a spinless particle moving on a one dimensional infinite lattice. We discuss the peculiarities of this scenario and of the associated phase space construction, propose a meaningful definition of the Wigner function in this case, and characterize the set of pure states for which it is non-negative. We propose a measure of non-classicality for states in this system which is consistent with the continuum limit. The prescriptions introduced here are illustrated by applying them to localized and Gaussian states, and to their superpositions.

Kinetic model for steady heat flow

1986

We construct a consistent solution of the Bhatnagar-Gross-Krook (BGK) model kinetic equation describing a system in a steady state with constant pressure and nonuniform temperature. The thermal profile is not linear and depends on the interaction potential. All the moments of the distribution function are given as polynomials in the local thermal gradient. In particular, the heat flux always obeys the (linear) Fourier law.

A dynamic model for hysteresis in magnetostrictive devices

2014

In this paper, a dynamic model for the description and design of hysteresis in magnetostrictive devices is presented. The model is based on Preisach theory and its dynamic extension. A procedure for determining the Preisach distribution function is given. This procedure is based on neural networks. The model is able to reconstruct both the magnetization relation and the field-strain relation. The model is validated through comparison and prediction of data collected from a typical Terfenol-D sample and a novel experimental technique dedicated to the validation of dynamic models is proposed.

A Novel Neural Approach to the Determination of the Distribution Function in Magnetic Preisach Systems

2004

This paper presents a novel method to identify both the functional dependence of the Preisach function as well as its numerical parameters on the basis of some known magnetic behavior. In this paper, the identification of the Preisach function of a material is performed by using a neural network trained by a collection of hysteresis curves, whose Preisach functions are known. When a new hysteresis curve is given as input to this neural network, it is able to give as output both the functional dependence of the Preisach function as well as its numerical parameters.

Multiplication of distributions in any dimension: Applications to δ-function and its derivatives

2009

In two previous papers the author introduced a multiplication of distributions in one dimension and he proved that two one-dimensional Dirac delta functions and their derivatives can be multiplied, at least under certain conditions. Here, mainly motivated by some engineering applications in the analysis of the structures, we propose a different definition of multiplication of distributions which can be easily extended to any spatial dimension. In particular we prove that with this new definition delta functions and their derivatives can still be multiplied.

Structure and dynamics of polymer brushes near the Θ point: A Monte Carlo simulation

1992

Grafted polymer layers under variable solvent conditions are studied by Monte Carlo simulations using the bond fluctuation model. Structural information such as monomer density profiles, brush thickness, mean‐square displacement of monomers, and positions of the monomers along the chain are obtained for temperatures above, at, and below the Θ point. In particular, the scaling of the brush thickness is formulated and verified by the simulation data. At the Θ point, more extensive simulations are performed to investigate the structural and dynamical properties. While the brush thickness at the Θ point agrees very well with the scaling and self‐consistent field predictions, the latter deviate …

Iterative integral equation methods for structural coarse-graining

2021

In this paper, new Newton and Gauss-Newton methods for iterative coarse-graining based on integral equation theory are evaluated and extended. In these methods, the potential update is calculated from the current and target radial distribution function, similar to iterative Boltzmann inversion, but gives a potential update of quality comparable with inverse Monte Carlo. This works well for the coarse-graining of molecules to single beads, which we demonstrate for water. We also extend the methods to systems that include coarse-grained bonded interactions and examine their convergence behavior. Finally, using the Gauss-Newton method with constraints, we derive a model for single bead methano…

Measurement of transverse single-spin asymmetries forJ/ψproduction in polarizedp+pcollisions ats=200  GeV

2010

We report the first measurement of transverse single-spin asymmetries in J/psi production from transversely polarized p + p collisions at root s = 200 GeV with data taken by the PHENIX experiment in 2006 and 2008. The measurement was performed over the rapidity ranges 1.2 < vertical bar y vertical bar < 2.2 and vertical bar y vertical bar < 0.35 for transverse momenta up to 6 GeV/c. J/psi production at the Relativistic Heavy Ion Collider is dominated by processes involving initial-state gluons, and transverse single-spin asymmetries of the J/psi can provide access to gluon dynamics within the nucleon. Such asymmetries may also shed light on the long-standing question in QCD of the J/psi pro…