Diffusion of Finite-Mass Particles in a Turbulent Viscous Medium

Based on a Fokker–Planck equation for the Jacobian of mapping of Lagrangian into Eulerian coordinates, derived in this paper, we analyze the process of diffusion of passive-tracer particles in a turbulent viscous medium. Solving this equation allows for studying the effect of finite masses (inertia) of the tracer particles on the appearance of multi-flow motion.     

Statistics of caustics in an underwater sound channel

The numerical-analytical phase screen method is used to analyze the statistics of the density of caustics in an underwater sound channel with large-scale random inhomogeneities. Different cases of wave propagation direction with respect to the channel axis are considered, and the influence of the inhomogeneity correlation radius is investigated.     

Features of diffusion of an incident particle

Mechanisms of turbulent diffusion of particles moving in a turbulent medium under the action of gravity and Stokes forces are studied. It is observed that the velocity variance of particles decreases upon an increase in the inertia of the motion. At the same time, the diffusion coefficients of a particle are independent of its inertia. It is shown that, as the velocity of incidence increases, diffusion in the vertical plane becomes stronger than in the horizontal plane, and the ratio of the horizontal and vertical diffusion coefficients decreases to 1: 2.     

How close to two dimensions does a Lennard-Jones system need to be to produce a hexatic phase?

We report on a computer simulation study of a Lennard-Jones liquid confined in a narrow slit pore with tunable attractive walls. In order to investigate how freezing in this system occurs, we perform an analysis using different order parameters. Although some of the parameters indicate that the system goes through a hexatic phase, other parameters do not. This shows that to be certain whether a system of a finite particle number has a hexatic phase, one needs to study not only a large system, but also several order parameters to check all necessary properties. We find that the Binder cumulant is the most reliable one to prove the existence of a hexatic phase. We observe an intermediate hexatic phase only in a monolayer of particles confined such that the fluctuations in the positions perpendicular to the walls are less than 0.15 particle diameters, i.e., if the system is practically perfectly 2D.     

Localization of an ultrathin buried Fe layer in a multilayer structure Nb/Fe/[Mo/Si]<Subscript>40</Subscript>/SiO<Subscript>2</Subscript> by means of X-ray standing waves

An analysis of the influence of standing waves on the angular dependencies of the fluorescent yield from an ultrathin iron layer buried inside a multilayer structure of Nb(50 nm)/Fe(3.9 nm)/[Si/Mo(6.77 nm)]₄₀/SiO₂ is presented. These angular dependencies of reflectivity and FeK _α-fluorescence yield were measured at the Station for high-precision X-ray optics (HPXO) of the Kurchatov Center for Synchrotron Radiation and Nanotechnology. The measured data was analyzed with the help of our FLUO software package. As a result of the complex treatment of reflectivity and Fe fluorescent yield data, the depth profile for iron atomic density was restored.     

Thermofrictional properties of self-lubricating antifriction plastics

New thermally stable polymers (polyimides, polyarylates, and phenolphthalein-phenolformaldehyde copolymers) were used in a study of the thermofrictional properties of their compositions with molybdenum disulfide. We established the existence of several temperature zones of friction and demonstrated their connection with the changes in the relaxation and autohesion properties of the polymers in these same temperature zones.Institute of Organoelement Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 481–485, May–June, 1970.     

A New Approach to Sampling Petroleum Product Films from Water Surfaces and Their Subsequent Analysis by Gas Chromatography–Mass Spectrometry

Journal of Analytical Chemistry - The capabilities of a new approach to sampling oil product films from water surfaces in order to accurately control the surface area from which the films are taken...     

Angular scattering pattern of waves in the ocean in the presence of anisotropic inhomogeneities

Closed integrodifferential equations are derived for the coherence function and the ray intensity in the ocean. Random inhomogeneities of the medium are assumed to be large-scale and statistically anisotropic. The influence of anisotropy on the angular scattering pattern is analyzed.     

Velocity distribution of Brownian particles at the input of a closed detector

The velocity distribution function of passive-tracer particles in a gas flow on a closed boundary of a given spatial region is found for various relations between the regular drift and diffusion. An example of calculation of the velocity probability density on the boundary of a region comprising a source of particles is given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 1, pp. 86–93, January 2005.