Dmitry Strunin

COUPLED THERMOMECHANICAL WAVES IN HYPERBOLIC THERMOELASTICITY

Using models incorporating a thermal relaxation time (hyperbolic models), we study the properties of spatially periodic thermoelastic waves propagating in an infinite rod. Analyzing the Lord-Schulman and Green-Lindsay linear models, we reveal dependencies of decay rates and frequency shifts of temperature and displacement upon the wave number for the case of weak thermoelastic coupling. We explore numerically a general nonlinear hyperbolic model, describing the time evolution of initially sinusoidal distributions of displacement and temperature. Mechanisms of nonlinear interaction between thermal and mechanical fields are qualitatively analyzed. It is demonstrated that larger relaxation times may provide smoother temperature profiles at an intermediate stage of the dynamics.Using models incorporating a thermal relaxation time (hyperbolic models), we study the properties of spatially periodic thermoelastic waves propagating in an infinite rod. Analyzing the Lord-Schulman and Green-Lindsay linear models, we reveal dependencies of decay rates and frequency shifts of temperature and displacement upon the wave number for the case of weak thermoelastic coupling. We explore numerically a general nonlinear hyperbolic model, describing the time evolution of initially sinusoidal distributions of displacement and temperature. Mechanisms of nonlinear interaction between thermal and mechanical fields are qualitatively analyzed. It is demonstrated that larger relaxation times may provide smoother temperature profiles at an intermediate stage of the dynamics.

Nonlinear analysis of rubber-based polymeric materials with thermal relaxation models

ABSTRACT Using mathematical modeling and computer simulation, nonlinear dynamics of rubber-based polymers has been studied with due regard for the effect of thermal relaxation. Main results have been obtained for the case of elongational oscillations of a ring-shaped body subjected to periodic (“internal”)boundary conditions. Particular emphasis has been placed on high-frequency and short spatial variations of temperature and displacement, in which the role of nonlinearities in the dynamics of the material and their close connection with the effect of thermal relaxation time can be best appreciated. It is shown how the vanishing relaxation time can lead to an attenuation of nonlinear effects in the thermomechanical system.

Effect of canine hyperimmune plasma on TNFα and inflammatory cell levels in a lipopolysaccharide-mediated rat air pouch model of inflammation

The purpose of this study was to test the effect of canine hyperimmune frozen plasma (HFP), which is known to contain elevated levels of soluble TNFα receptor 1 (sTNFR1), on TNFα and inflammatory cell levels in a LPS-mediated rat air pouch model of inflammation. There appears to be a correlation between elevated levels of sTNFR1 and depression of TNFα and neutrophil levels in the pouch fluid of HFP dosed rats (r = -0.73, P < 0.0001). The data suggest that canine HFP, which has been demonstrated to contain elevated levels of sTNFR1 compared with FFP, has a direct effect on depressing TNFα levels and neutrophil sequestration in the rat air pouch model of inflammation. These data suggest that HFP may be worthy of further investigation to determine whether such preparations have a therapeutic potential for treatment of acute inflammatory diseases in which TNFα is implicated.

Computations of auto-solitary structures modeling extended elementary particles

Abstract The classical Hamilton–Jacobi (HJ) equation for the action function leads to a blow-up of disturbances of a free-particle solution. We propose an extension of the HJ equation, which prevents the blow-up. Within this extension, any perturbation evolves into a stable soliton, which we associate with an extended elementary particle. We determine numerically a continuous range of coefficients of the equation, that guarantees the solitons existence.

A transfer of a tracer in decaying turbulent layer

A mixing of a passive tracer inside a turbulent layer generated by a localized short-time perturbation is studied numerically. Two cases of initial distribution of the tracer are considered: two-layer and continuous with constant gradient. It is shown that, regardless of details of initial fields of a turbulent energy and dissipation in the layer, a tracer concentration goes with time to self-similar regimes. Distributions of the concentration inside the layer are found to be substantially nonuniform, with a ratio of concentration gradient in the middle of the layer to initial gradient about 0.5.