Static and dynamic frictional phenomena at the interface with random impurities are investigated in a two-chain model with incommensurate structure. Static frictional force is caused by the impurity pinning and/or by the pinning due to the regular potential, which is responsible for the breaking of analyticity transition for impurity-free cases. It is confirmed that the static frictional force ...

The present paper—a continuation of our recent series of papers on Casimir friction for a pair of particles at low relative particle velocity—extends the analysis, so as to include dense media. The situation becomes, in this case, more complex, due to induced dipolar correlations, both within planes and between planes. We show that the structure of the problem can be simplified by regarding the...

This paper addresses entropy generation in the flow of an electrically-conducting couple stress nanofluid through a vertical porous channel subjected to constant heat flux. By using the Buongiorno model, equations for momentum, energy, and nanofluid concentration are modelled, solved using homotopy analysis and furthermore, solved numerically. The variations of significant fluid parameters with...

This paper deals with the problem of describing spatially inhomogeneous gases by applying model Boltzmann equations. A plane discrete velocity model is presented, capable of describing a gas of particles with internal degrees of freedom. The number of particle speeds is variable. All possible collisions, both elastic and inelastic, are calculated. The corresponding equation system for 2L+1 spee...

We present and analyze a penalization method which extends the the method of [2] to the case of a rigid body moving freely in an incompressible fluid. The fluid-solid system is viewed as a single variable density flow. The interface is captured by a color function satisfying a transport equation. The solid velocity is computed by averaging at every time the flow velocity in the solid phase. Thi...

We present a method to compute surface expansion rates from sequences of range data. Towards this end the 3D velocity field (range flow) is extracted first and then used in a second step to estimate the local area expansion. A detailed performance analysis is presented and the method is applied on two real examples.

In this paper, we consider optimal resolution of air traffic (AT) conflicts. Aircraft are assumed to cruise within a given altitude layer and are modeled as a kinematic system with constant velocity and curvature bounds. Aircraft cannot get closer to each other than a predefined safety distance. For such system of multiple aircraft, we consider the problem of planning optimal paths among given ...

We present an approach based on clustering to segment renal arteries from 2D PC Cine MR images to measure blood velocity and flow. Such information are important in grading renal artery stenosis and support the decision on surgical interventions like percutan transluminal angioplasty. Results show that the renal arteries could be extracted automatically and the corresponding velocity profiles c...

We study the problem of homogenization for inertial particles moving in a time dependent random velocity field and subject to molecular diffusion. We show that, under appropriate assumptions on the velocity field, the large–scale, long–time behavior of the inertial particles is governed by an effective diffusion equation for the position variable alone. This is achieved by the use of a formal m...

This paper deals with the numerical simulations of the 2D generalized quasi geostrophic equation, where the velocity field is related to the solution θ by a rotation of Riesz transforms. Depending on the parameters of the problem, we present numerical evidences for long time behavior of the solution such as global existence effects or blow up in finite time.