Energy of formation of a tornadolike vortex

The energetic conditions of formation of a tornadolike vortex are studied theoretically and experimentally.     

Visualization of flow structure in a vortex furnace

The spatial structure of a swirling flow in a model vortex furnace with distributed input of fuel-air-mixture jets has been studied. The results of experimental and numerical investigations of a three-dimensional (3D) field of time-averaged velocities in an isothermal laboratory model of a vortex furnace have been used to image the structure of flow. Vortex structures have been identified using λ₂ and Q criteria, as well as the concept of “minimum total pressure.” The vortex core of the flow has a V-shaped 3D structure.     

Fractal vortex structure in a superconductor lattice model

The vortex structure is considered within the framework of a superconductor lattice model with a kinetic term of the Harper type. The problem is reduced to the analysis of discrete maps typical of the theory of fractal structures.     

Special aspects of structure formation of a multicomponent layer in vacuum-arc plasma

A phase boundary is an energy barrier to diffusing atoms. To decrease the diffusion rate, densely packed multicomponent structures were used. The correlation between the methods of obtaining and properties of multicomponent coating formed in a single fabrication cycle upon step-by-step synthesis of carbide of a substrate material and sputter deposition of layers of zirconium and zirconium carbide was investigated.     

Circular vortex formation in a pulsed jet penetrating through a filter layer

A method for the formation of a laminar circular vortex is proposed that excludes the interaction of a pulsed jet with the nozzle edge. Another method is suggested for visualization of the gas flow and measurement of the gas velocity distribution in a jet penetrating through a filter layer. Critical conditions for the formation of a circular vortex are established, determining the jet power as a function of the thickness of a flat filter layer formed by granulated silica gel. It is shown that a mechanism of the laminar circular vortex formation is controlled only by the gas flow acceleration in the jet.     

Molecular-dynamics study of the features of dynamic vortex structure formation in a material with micropores under high-rate deformation conditions

The response of a material containing a system of micropores subjected to high-rate shear deformation has been computer-simulated by methods of molecular dynamics. Deformation of such materials is accompanied by the formation of vortexlike dynamic defects. This process can be divided into three stages. The first stage is characterized by a predominating laminar character of atomic displacements in the regions adjacent to the loaded layers. A special feature of the second stage is the development of a correlated vortexlike motion of atoms in the regions between micropores, with periodic formation and breakage of vortices in a period on the order of several picoseconds. The third stage is related to the loss stability of the atomic structure and the formation of deformation localization bands. This is accompanied by the loss of correlation of the vortexlike motion of atoms in the regions between micropores. The results can be used in analyzing the behavior of materials under conditions involving irradiation.     

The formation of a nondiamond carbon phase in a microwave gas discharge plasma under electron cyclotron resonance conditions

Special features in the nucleation and growth of a nondiamond carbon phase were studied in a microwave plasma of various acetylene-containing gas mixtures.     

Ginzburg-landau equations and vortex structure of a d-wave superconductor

We derive microscopically the Ginzburg-Landau equations of a d-wave superconductor. The structure of a single vortex in such a superconductor is determined by solving these equations. The most interesting feature of the vortex structure is the opposite winding s-wave component induced near the vortex core. Far away from the center of the vortex core, the winding of s-wave component becomes more complicated and the magnitude shows strong anisotropy.     

Reduction of mass bias and matrix effects in inductively coupled plasma mass spectrometry with a supplemental electron source in a negative extraction lens

Electrons from a heated tungsten filament are created inside the extraction lens and driven out toward the skimmer. These electrons move through the ion path and reduce space charge effects between positive ions in the beam. The ion transmission efficiency is improved by factors of two (for Pb+) to 27 (for Li+). The greater sensitivity improvement for low-mass ions leads to a substantial reduction in mass bias. With the additional electrons, MO+/M+ and M2+/M+ abundance ratios increase but can be minimized with a small reduction in aerosol gas flow rate. No new background ions are observed with this technique. Matrix effects can be significantly diminished when the electron source is operated under the high electron current mode. The mass dependence of matrix-induced suppression of analyte signals is essentially eliminated. Using flow injection analysis to minimize solid deposition, the technique can tolerate Na matrix up to 10000 ppm (1%) with only approximately 15% loss of analyte sensitivity.     

Experimental realization of the devil's vortex Fresnel lens with a programmable spatial light modulator

We present a unique method for experimentally generating multiple vortices by way of a devil's vortex lens combined with a Fresnel lens using a spatial light modulator. These lenses have the multifocal properties of fractal zone plates combined with the orbital angular momentum of a spiral phase plate and can be tailored to fit within a small space on an optical bench. Results are presented alongside numerical simulations, demonstrating the robust nature of both the experimental method and the predictive power of the Huygens-Fresnel wavelet theory.     

Experimental determination of the time of tornado-like vortex formation in a closed chamber

The laws of tornado-like vortex formation in a closed chamber have been experimentally studied as dependent on the air volume flow rate and swirl intensity. A physical interpretation of the obtained empirical relationships is proposed.     

The effect of electron density on the kinetics of fullerene formation in carbon plasma

The influence of the carbon cluster charge on their coagulation kinetics has been studied. The equations of kinetics have been solved and it is established that allowance for the cluster charging leads to an increase in the rate of fullerene formation under otherwise equal conditions. In connection with this, the role of minor impurities with a low ionization potential in carbon-containing plasma is discussed.     

The role of a vortex structure in the mechanism maintaining thermal autooscillations

Vortex gas motion accompanying the excitation of thermal autooscillations in a “singing” flame or in a Rijke tube has been studied. A method for measuring the vortex gas flow energy distribution along the resonator tube is proposed. It is established that the vortex motion takes place in the region of a heat source, the size of which does not exceed 3–4 tube diameters. An increase in the resonator tube length increases the relative fraction of the energy of rotational motion in the total mechanical energy of the gas column performing acoustic oscillations.     

Large-scale structure and matter in the Universe

This paper summarizes the physical mechanisms that encode the type and quantity of cosmological matter in the properties of large-scale structure, and reviews the application of such tests to current datasets. The key lengths of the horizon size at matter-radiation equality and at last scattering determine the total matter density and its ratio to the relativistic density; acoustic oscillations can diagnose whether the matter is collisionless, and small-scale structure or its absence can limit the mass of any dark-matter relic particle. The most stringent constraints come from combining data on present-day galaxy clustering with data on CMB anisotropies. Such an analysis breaks the degeneracies inherent in either dataset alone, and proves that the Universe is very close to flat. The matter content is accurately consistent with pure cold dark matter, with ca. 25% of the critical density, and fluctuations that are scalar only, adiabatic and scale invariant. It is demonstrated that these conclusions cannot be evaded by adjusting either the equation of state of the vacuum, or the total relativistic density.     

Near-wall electron instability of a plasma flux

Experimental data are obtained which indicate some characteristic features of the plasma-surface interaction leading to the emission of electrons from the walls of the accelerating channel and the evolution of a specific beam instability of the plasma flux. Pis’ma Zh. Tekh. Fiz. 23, 47–52 (May 26, 1997)     

Producing a compact long-lived plasma formation

A method of producing compact long-lived plasma formations (plasmoids) is described. The method is based on the effect of capture of a high-current relativistic electron beam under conditions of significant overcompensation of space charge of the beam by positive background ions. Requirements are formulated which are placed on the parameters of a plasma-beam system for the realization of this method, and numerical estimates are given of the overall electric charge and energy content of the electron component of a plasmoid. The dynamics of forming a plasmoid are investigated experimentally.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 843–849.Original Russian Text Copyright © 2004 by B. V. Alekhin, A. E. Dubinov, V. S. Zhdanov, V. G Kornilov, K. E. Mikheev, V. D. Selemir, N. V. Stepanov, V. I. Chelpanov, and O. A. Shamro.     

Bicoherent wavelet analysis of the structure formation in an electron beam with virtual cathode

The supercritical electron beam structure formation in a diode gap with inhomogeneous ion background density are analyzed by the bicoherent wavelet transformation method. By studying the wavelet bicoherency of the spatiotemporal data about oscillations in the system, it is possible to effectively reveal and analyze local spatial structures formed in the electron beam.     

Investigation of the processes of periodic plasma structure formation in transverse nanosecond discharge with a slotted cathode

A periodic standing-like plasmic striation in inert gases has been observed and investigated under transversal nanosecond electric discharges. The pressure limits relevant for formation of a periodic plasma structure have been established, and the critical values for the voltage amplitude and discharge current have been found corresponding to the upper boundary of the range in which the plasma structure is formed. The external magnetic field effect on the parameters of the periodic plasma structure has been studied. It is stated that the plasma structure is formed at the stage of steady-state discharge and that the lifetime of the periodic structure considerably increases when the transversal magnetic field is applied.     

Investigation of critical velocity of vortex formation in helium II

It is shown that the critical velocity of vortex formation V _cin helium II, as measured in oscillation experiments, is strongly distorted by the delay effect, the elimination of which removes the dependence of V _con the period, and the increase of V _con approaching the point is changed to a decrease.     

Nanosized structure formation in metals under the action of pulsed electric-explosion-induced plasma jets

A new mechanism is proposed that explains the formation of a thin nanostructural near-surface layer in the alloyed zone formed during the metal surface fusion treatment under the action of a pulsed plasma jet generated by the electric explosion of conductors. The proposed mechanism is based upon the development of the Kelvin-Helmholtz (KH) instability at the plasma-melt interface. A dispersion equation is obtained for the KH problem with allowance for the viscous and capillary stresses in the melt. The dependence of the KH instability increment on the surface perturbation wavelength exhibits a maximum in a nanometer range for the relative velocities of plasma with respect to the melt (within 100–1000 m/s) achieved under real treatment conditions.