Efficiency of aerosol particle collection with filtering materials containing dispersed inclusions

During the flow around spherical inclusions in a homogeneous porous medium, the gas flow field is calculated using the Brinkman equation. The expression is derived for the effective permeability of the porous medium containing the rarefied ensemble of randomly arranged dispersed spherical particles of arbitrary sizes. It is shown that the Darcy approximation is applicable to the large-size inclusions. The influence of dispersed inclusions of spheroidal shape on both the pressure drop and the efficiency of aerosol particle collection with a filter is studied in the Darcy approximation. It is shown that dispersed inclusions can both increase and decrease the quality criterion of a filter depending on the values of parameters.     

Fluctuation Flows in Random Fibrous Media and Their Influence on the Efficiency of Aerosol Particle Deposition

The distribution function of random velocities in the fibrous medium of parallel fibers and the generating functional of correlation functions in a 3D fibrous medium are calculated. It is shown that the velocity fluctuations are Gaussian in the rarefied medium at a small packing density. The influence of 3D fluctuation hydrodynamic gas flows on the efficiency of aerosol particle deposition is studied.     

Monolithic white LEDs: Approaches, technology, design

The results of investigations of monolithic white InGaAlN LEDs with an active region containing several thin InGaN layers, emitting in the range from blue to yellow-green, and separated by short-period InGaN/GaN superlattices, are presented. The influence of the growth conditions and layer sequence in the active region on the optical properties of monolithic white LEDs was studied with the aim of controlling their color parameters.     

The effect of diffusion on nanoaerosol filtration through porous materials with allowance for desorption processes

The effects of the finite residence time of aerosol particles in the bound state and their detachment due to thermal fluctuations on the filtration efficiency of porous and fibrous materials have been investigated with allowance for longitudinal diffusion in a flow. It has been shown that the desorption of particles affects the filtration efficiency even at times shorter than residence time τ_d of the particles in the bound state, while, at t ? τ_d, filtration stops. Allowance for the diffusion of aerosol particles in the flow leads to a decrease in the filtration efficiency as compared with the calculations performed without taking into account the longitudinal diffusion.     

Efficiency of inertial deposition of aerosol particles in fibrous filters with regard to particle rebounds from fibers

The inertial deposition of submicron aerosol nanoparticles onto fibers during gas filtration through fine-fiber filters is considered. It is shown that there is critical filtration velocity U* below which the energy loss upon collisions has no influence on the filtration efficiency. Above this critical velocity, the filtration efficiency depends on the mechanism of the inelastic energy loss and can be noticeably lower than the result of its estimation with no allowance for the particle rebound. For a rather dense fibrous medium, when not all particles that have rebounded from a fiber have time to attain the flow velocity before the next collision with another fiber, the filtration efficiency depends on the velocity distribution of the rebounding particles. It is shown that, in this case, the filtration efficiency must increase with the packing density of a filter.     

Explicit Semi-invariants and Integrals of the Full Symmetric {\mathfrak{sl}_n} Toda Lattice

We show how to construct semi-invariants and integrals of the full symmetric \({\mathfrak{sl}_n}\) Toda lattice for all n. Using the Toda equations for the Lax eigenvector matrix we prove the existence of semi-invariants which are homogeneous coordinates in the corresponding projective spaces. Then we use these semi-invariants to construct the integrals. The existence of additional integrals which constitute a full set of independent non-involutive integrals was known but the chopping and Kostant procedures have crucial computational complexities already for low-rank Lax matrices and are practically not applicable for higher ranks. Our new approach solves this problem and results in simple explicit formulae for the full set of independent semi-invariants and integrals expressed in terms of the Lax matrix and its eigenvectors, and of eigenvalue matrices for the full symmetric \({\mathfrak{sl}_n}\) Toda lattice.     

Theory of plasticity and creep taking account of microstrains

A relationship between the theories of plasticity and creep of the type /1, 2/ and theories based on the concept of slip is set up. A most logical structure is proposed for the constitutive equations of the theory which is convenient for engineering calculations.

It has been shown /3/ that the theory of slip /4/ results from the theories /1, 2/. However, it remains unclear whether a deeper connection exists between these theories. Moreover, the connection between creep theories constructed using the approach in /1, 2/ and creep theories based on the slip concept was not generally examined. A survey of the development of polycrystalline strain theory /5/ yields a complete representation of the state of matters in plasticity and creep theories.     

The Influence of Fluctuations on the Efficiency of Aerosol Particle Collection with Fibrous Filters

The influence of fluctuations on the filtration efficiency was studied. In the case of arbitrary random macroscopic inhomogeneities in the packing density and fluctuations in the filter surface form, the expressions were derived for the pressure drop and the penetration of aerosol particle, expressed via the correlation functions of fluctuating parameters. For the high degrees of cleaning, the probabilistic approach was developed, which takes into account the discreteness of the number of aerosol particles deposited on filter fibers.     

Pressure Drop and Aerosol-Particle-Collection Efficiency of Polydisperse Fibrous Filters

The effect of the polydispersity of fibrous materials on the viscous drag and the efficiency of gas filtration has been studied. The dependence of the Brinkman constant on parameter β_g, which characterizes the variance of the lognormal function of fiber-length distribution over fiber radii, has been calculated for equations describing the hydrodynamics of a gas in a porous medium. The dependences of the effective aerosol- particle-collection efficiency on the packing density, dispersion of fiber-size scatter, and average fiber radius have been investigated. Quality parameters of filters with different degrees of polydispersity have been compared. Results of calculations have been compared with experimental data.     

Some problems of the theory of plasticity for metals with strength differential

Within the framework of the problem of describing the plastic deformation of polycrystalline metals with strength differential, we consider problems of selection of universal constants and functions of the material that control the influence of the first and third invariants of the stress tensor. The possibility of using different types of experiments for the determination of these constants and verification of the theory is analyzed. It is shown that the traditionally used combined tension–torsion experiments on a thin-walled tube do not enable one to distinguish the influence of hydrostatic pressure and the Lode angle. The expedience of using biaxial tension and other experiments on simple and complex loading of a thin-walled tube by an axial force and internal pressure is justified.