Transformation of the bridge during drop separation

The geometry of flows during separation of pendant drops of liquids with significantly different physical properties (alcohol, water, glycerin, oil) has been studied by high-speed video recording. The dynamics of the processes involving the formation of bridges of two characteristic shapes—slightly nonuniform in thickness and with thinning of the upper and lower ends—has been investigated. It has been shown that the shape change of the separated bridge has a number of stages determined by the properties of the liquid. As a result, the bridge is transformed into a small drop—a satellite drop.     

Pressure Dependences of Elastic Constants of AMg6 Aluminum–Magnesium Alloy and n-AMg6/С60 Nanocomposite Alloy

The ultrasonic study results for dependence of the elastic wave velocities and second-order elasticity coefficients of the polycrystalline aluminum alloy AMg6 and its nanocomposite n-AMg6/C₆₀ on hydrostatic pressure up to 1.6 GPa have been described. The ultrasonic research has been carried out using a highpressure ultrasonic piezometer based on the piston-cylinder device. The pressure derivatives of the secondorder elastic constants of these materials established in the present study have been compared with the results of the third-order elastic constants measurements of the test alloys using the Thurston–Brugger method. Involving available literature data, we determined the relationships between the pressure derivatives of the second-order elastic constants of the AMg6 alloy and the Mg-content and nanostructuring.

     

Study of the breakup of liquid droplets in the vortex wake behind pylon at high airspeeds

The study is devoted to the establishment of regularities in the process of liquid-droplet breakup in the vortex wake behind pylon at high subsonic airspeeds. The article describes the laboratory setup, the diagnostic tools, and the experimental procedure. Structure of the unsteady gas flow behind pylon was examined, and the main characteristics of the generated vortex wake were evaluated. Experimental data concerning the variation of droplet diameters in the gas-dynamic fractionation process versus the flow conditions and liquid injection regimes were obtained. Typical distribu-tions of droplet diameters and velocities in the vortex wake behind pylon are reported. A comparison of experimental data on the rate of the gas-dynamic fractionation process with calculations made using previously developed evaluation procedures was performed. The results of the study may prove useful when choosing the configuration of systems for implementation of liquid injection into a high-speed flow and, also, for validation of mathematical models intended for calculation of parameters of two-phase flows.     

Dynamic magnetic hysteresis in a liquid suspension of acicular maghemite particles

This paper presents theoretical and experimental studies on the magnetodynamics and energy absorption in a dilute suspension of small ferromagnetic particles with magnetic hysteresis and mechanical mobility in an AC magnetic field. Experiments with 0.1% suspensions of acicular particles of gamma ferric oxide in solid and liquid matrices, subjected to a 430 Hz magnetic field with an intensity of up to 1200 Oe, revealed important role of particle mobility. The main qualitative and quantitative features of the phenomenon are in agreement with a model of joint magneto-mechanical dynamics of particles with a chain-of-spheres mode of incoherent magnetic reversal.     

Methods of terahertz-subterahertz BWO spectroscopy of conducting materials

This paper considers present spectroscopic methods developed for measurement of dielectric response (conductivity and permittivity spectra) of condensed media in the terahertz-subterahertz spectral regions. The techniques based on the use of BWO spectrometers and designed for direct quantitative measurements (without invoking the Kramers-Kronig relations) in the terahertz-subterahertz frequency range (0.03–1.45 THz) of the conductivity σ(ν) and permittivity ?′(ν) spectra of conducting and absorbing materials are described. The techniques are based on measuring the amplitude and phase of the transmission coefficient of film samples on dielectric substrates and the reflection coefficient of a reference plane-parallel dielectric plate contacting the surface of the sample under study. The use of these techniques in measurement of the σ(ν)) and ?′(ν) spectra of conductors and superconductors is illustrated with examples.     

Pulse acoustic microscopy characterization of the elastic properties of nanostructured metal-nanocarbon composites (Declercq/ICU'07)

New metal-nanocarbon composites were obtained by high-energy (ball milling) pre-treatment of the powder mixture followed by high-pressure/high-temperature treatment. Acoustic microscopy was used to study elastic properties and bulk irregularities of the samples.     

IR spectroscopy of diamondlike silicon-carbon films

IR spectra of metal-containing diamondlike silicon-carbon films are taken for the first time. It is shown that the optical response from the subsystem of free charge carriers in chromium-containing films can be described in terms of a simple model that deals with carriers localized inside clusters several nanometers in size. The data obtained indicate that the electric and dielectric properties of the films can be controlled by technological means during their synthesis and by varying the size, concentration, and conductivity of metallic nanoclusters.     

Evaluation of Limiting Characteristics of Laser Separation of Silicon Isotopes

Isotopically selective photoionization of silicon atoms by laser radiation using tunable dye lasers is considered. The scheme of atomic ionization with two-photon excitation via the resonance level of one of the high states with subsequent excitation of the autoionization state is proposed. The calculations carried out show that the up-to-date development of laser facilities allows one to evaluate the ultimate production of the highly enriched ²⁸Si isotope at a level of 0.1 g/h at a radiating power of 1 W for each wavelength. The excitation selectivity appears to be high (about 100) within the framework of the radiation problem and is actually defined by the conditions of ion extraction, background atom concentration, charge exchange, and so on rather than by the radiation processes.