Ion-acoustic shocks with reflected ions: modeling and PIC simulations

Non-relativistic collisionless shock waves are widespread in space and astrophysical plasmas and are known as efficient particle accelerators. However, our understanding of collisionless shocks, including their structure and the mechanisms whereby they accelerate particles remains incomplete. We present here the results of numerical modeling of an ion-acoustic collisionless shock based on one-dimensional (1D) kinetic approximation both for electrons and ions with a real mass ratio. Special emphasis is made on the shock-reflected ions as the main driver of shock dissipation. The reflection efficiency, velocity distribution of reflected particles and the shock electrostatic structure are studied in terms of the shock parameters. Applications to particle acceleration in geophysical and astrophysical shocks are discussed.Comment: 6 pages, 7 figures, International Workshop "Complex Plasma Phenomena in the Laboratory and in the Universe", January 19-20, 2015, Rome, Ital

Magnetorheology of Polymer Systems

The results of researches of a magnetic field effect on rheological properties of both paramagnetic, and diamagnetic polymer systems are described. Influence of intensity and the direction of power lines of the magnetic field on the viscosity of magnetic liquids and magnetorheological suspensions is analyzed. Results of theoretical researches of the magnetic field effect on the diamagnetic macromolecule orientation in solutions are discussed. The data on the influence of the magnetic field on rheological parameters of cellulose ether solutions are generalized and analyzed. The rheological parameters are compared with a change of studied system structure under magnetic field. The concentration dependences of viscosity and the sizes of supramolecular particles in solutions are compared. The rheological behavior of systems in a region of phase transitions is considered. Concentration dependences of the viscosity are described by curves with a maximum which concentration corresponds to a phase transition concentration

Phase equilibrium, structure, and rheological properties of the carboxymethyl cellulose-water system

The phase transitions, structure, and rheological properties of the carboxymethyl cellulose-water system were studied via the turbidity-point method, viscometry, polarization microscopy, and the turbidityspectrum method as well as with a polarization photoelectric unit. The regions of existence of the isotropic and anisotropic phases, the gel point, and the concentration dependence of the supramolecular-particle size were determined. Magnetic-field application results in a gain in the viscosities of carboxymethyl cellulose solutions. © 2013 Pleiades Publishing, Ltd

Three approaches to evaluate of the heat dissipated during fatigue crack propagation experiments

This work is devoted to the comparative analysis of three techniques for measurement of energy dissipation in metals under fatigue crack propagation: original contact heat flux sensor, post-processing of the infrared thermography data and lock-in thermography. The contact heat flux sensor allows real-time recording of the heat source value. Non-contact temperature measurements by infrared thermography techniques allows one to calculate the heat source field on the specimen surface using the solution of heat conductivity equation. Lock-in thermography is a well-established technique for measuring of the dissipated energy under cyclic loading based on the analysis of the second harmonic amplitude of the thermal signal. This paper deals with the V-notched flat specimens made of stainless steel AISE 304 subjected to cyclic loading. It was shown that the dissipated energy values estimated by different techniques have a good qualitative agreement. Contact and non-contact measurements can be used for investigation on energy dissipation either in combination or separately. The measured values allows one to propose a relation between the fatigue crack growth rate and dissipated heat near the crack tip

The effect of fatigue crack rate on the heat dissipation in metals under mixed-mode loading

The monitoring of a heat dissipation process can give an important information about kinetics of deformation process and current crack propagation rate. The work is devoted to the theoretical and experimental study of the problem. The estimation of the heat sources during the mechanical test was carried out based on infrared temperature measurements combined with an additional system for direct monitoring of a heat flow. To propose the phenomenological description of evolution of plastic work (energy dissipation) at the crack tip under arbitrary loading conditions we used a relations introduced by Dixon in 1965. To illustrate the abilities of the proposed approximation we compare the derived equation with the results of fatigue crack propagation test in flat titanium Grade 2 specimens. The theoretical and experimental results give a good quantitative agreement

Heat dissipation and fatigue crack kinetic features of titanium alloy Grade 2 after laser shock peening

The work is devoted to experimental investigation of the laser shock peening (LSP) effect on fatigue crack propagation rate and heat dissipation at the crack tip in specimens made of titanium alloy Grade 2 with a stress concentrator. It is shown that the LSP can leads both to positive and negative effect on fatigue lifetime. The effective processing scheme, which includes stress concentrator zone, was proposed. This type of treatment forms an optimal residual stress field, which slows down the crack initiation and propagation processes. The effective LSP processing scheme reduces the value of the stress intensity factor and, as a consequence, effects on an intensity of plastic deformation at the crack tip. This effect can be visualised by measurement of heat flux from the crack tip area. Both heat flux from the crack tip and crack rate are less in the LSP processed specimens. Structural investigations of LSP treated material near fatigue crack path have shown that structural defects (twins) that appear on the surface of the material as a result of LSP do not have a significant effect on the fatigue crack propagation, and the configuration of the residual stresses field created by LSP plays a decisive role

SYNTHESIS OF 2-(2-NITROBENZYL)FURANS AND INVESTIGATION OF THEIR REACTIVITY

This work was supported by Russian Science Foundation (project № 21-73-10063)