Investigation of the dynamics of radiative micropinch discharges

The dynamics of plasma cylinder compression by current pulses with a rise time of ∼100 nsec in the Z-pinch geometry has been considered. The numerical simulation has been performed in the approximation of one-dimensional magnetic radiation gas dynamics. In the calculations, real thermodynamic, transport, and optical properties of the plasma have been used. The radiation transfer is described in the multigroup approximation by the photon energy. The calculations have been performed for a pinch in xenon (radius ∼0.5 cm, energy E₀ = 10–30 J, maximum current ∼30 kA). A detailed pattern of the dynamics of pinches has been investigated and the energy-to-radiation conversion efficiency has been determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 2, pp. 216–222, March–April, 2008.     

Investigation of the restrictions on the shape of the radiation pattern of an adaptive antenna array

An algorithm for adapting the radiation pattern of an antenna array to the jamming conditions is described, based on direct inversion of the covariance matrix of the input signals, with a new method of restricting the shape of the radiation pattern for this algorithm. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 44–46, October, 1997.     

Lower frequency of free-field calibration of hydrophones in emission of tonal signals in a non-anechoic water tank

An approach to estimation of the lower free-field calibration frequency as well as the required magnitude of the water tank for calibration of hydrophones in a specified frequency range from the cepstrum of a segment of the amplitude response of the electroacoustic system, projector – hydrophone – non-anechoic water tank – measurement path of standard facility, is proposed. Estimates of the lower calibration frequency of hydrophones in a water tank with minimal dimension of 6 m in the case of radiation of quadrature-added harmonic signals are presented.     

Temperature dependence of the intensity and phase of reflected light in a liquid-crystal structure with surface plasmons

The results of a theoretical calculation of the temperature dependence of the amplitude coefficient and phase of reflected radiation with wavelength λ=6328 Å in a liquid-crystal structure with surface plasmons are reported for the first time. The computational results could be helpful for developing temperature sensors and optically coupled thermal imagers based on liquid-crystal structures with surface plasmons. Pis’ma Zh. Tekh. Fiz. 23, 11–15 (September 12, 1997)     

Anomalous backscattering of high-power laser radiation by the flat surface of a solid

Results of measurements of the backscattering characteristics of high-power laser radiation at flat randomly rough surfaces of various materials are described for a wide range of radiation and surface parameters. It is observed that for probe radiation intensities in the range ∼10³–10⁷ W/cm² and a pulse duration of ∼10⁻⁸ s the scattering pattern becomes anomalous under various additional conditions. The results are analyzed in accordance with the laws of structural conditionality, the qualitative boundary, abnormality, and alternation of nonequilibrium. Possible practical applications of the observed effect are discussed. Pis’ma Zh. Tekh. Fiz. 25, 29–38 (August 26, 1999)     

LEDs based on InAs/InAsSb heterostructures for CO<Subscript>2</Subscript> spectroscopy (λ = 4.3 μm)

Light-emitting diodes (LEDs) operating in a 4.1–4.3 μm wavelength range have been created on the basis of InAs/InAsSb heterostructures grown by metalorganic vapor-phase epitaxy. The output radiation power of LEDs is increased using flip-chip design. Investigation of the electrolumuinescent properties of LEDs with smooth and profiled output edge surface showed that the latter LEDs possess a greater efficiency, which is related to an increase in the radiation yield due to multiply repeated reflection from the curved surface. The output power of LED operating in a quasi-continuous wave mode was 30 μW at a current of 200 mA and that in a pulse mode was 0.6 mW at a current pulse amplitude of 2 A.     

Mathematical model of an angular velocity transducer utilizing a laser with a fiber-optic ring resonator

An angular velocity transducer based on a laser with a fiber-optic ring resonator is considered. A relationship is obtained linking the amplitude and phase characteristics of the radiation with the parameters of the resonator and the rotational velocity of the transducer. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 6–8, March, 1996.     

Voltage dependences of the amplitude and phase of reflected radiation in liquid-crystal structures with surface plasmons

The results of a theoretical calculation of the amplitude and phase of p-polarized monochromatic radiation reflected from layered liquid-crystal structures with surface plasmons as a function of the external voltage applied to the structure (in the Kretschmann geometry) are reported. Pis’ma Zh. Tekh. Fiz. 23, 75–80 (September 26, 1997)     

A method of determining the spatial position of the phase center of log-periodic antennas

A method of estimating the position of the phase center of log-periodic antennas from the phase radiation pattern in the intermediate zone is proposed. __________ Translated from Metrologiya, No. 4, pp. 39–43, April, 2008.     

Multi-scale Modeling of Radiation Heat Transfer through Nanoporous Superinsulating Materials

In this contribution, the extraordinarily high level of thermal insulation produced by nanoporous materials, which can achieve thermal conductivities down to a few mW·m⁻¹·K⁻¹ when they are evacuated to a primary vacuum, is highlighted. The objective here is to quantify the level of radiation heat transfer traveling through a nanoporous material in relation with its composition. The model used here is based on the “non-gray anisotropically scattering Rosseland approximation,” which allows the definition of a “radiation thermal conductivity” expressed as a function of the optical properties (complex optical index spectra), mean sizes and volume fractions of the different populations of particles constituting the material. With the help of this simple model, one can draw interesting conclusions concerning the impacts of different parameters related to the microstructure of the nanoporous material on the amplitude of the radiation heat transfer. In the future, this model should help to orient the formulation of new nanoporous materials with optimized radiative properties. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Flexural vibrations of semiconductor wafers in the presence of a pulsed thermal excitation source

An analysis is made of the action of current pulses on a metal film lying on a semiconductor wafer. It is shown that the passage of current pulses of amplitude (1–7)×10¹⁰ A/m² and duration 50–200 μs across aluminum tracks excites sound. Experimental dependences of the energy of the flexural vibrations as a function of the duration and amplitude of the pulsed action were obtained. It was observed for the first time that the melting of a metal-semiconductor contact is accompanied by an abrupt increase in the energy of the flexural vibrations of the wafer. Pis’ma Zh. Tekh. Fiz. 25, 57–63 (March 12, 1999)     

Diffraction of SH-waves on interface cracks under the action of concentrated forces

In the mathematically rigorous statement, we solve the problem of diffraction of elastic SH-waves on a finite (semiinfinite) crack located on the plane boundary of two perfectly joined materials. As a sounding field, we consider the field of a point source. The problem is reduced to the Wiener – Hopf functional equation, which is solved by the method of factorization. An approximate solution of this equation is obtained. We numerically study the distribution of the field in the radiation zone and the distinctive features of its formation depending on the location of the source of radiation. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 6, pp. 67–77, November–December, 2008.     

Operation of an electron interferometer with photon illumination of the biprism tip

A study is made of electron diffraction by an optical fiber, which plays the role of the electrode of a Fresnel-Mollenstedt biprism. Irradiation of the electrode with the radiation from a lowpower laser causes a change in the diffraction pattern. A tentative explanation for this effect is proposed. Pis’ma Zh. Tekh. Fiz. 23, 7–10 (February 26, 1997)     

The effect of the horizontal vibrations on natural heat transfer from an isothermal array of cylinders

A numerical investigation is carried out to study an unsteady laminar natural convection heat transfer caused by an array of isothermal oscillating circular cylinders. Under oscillating conditions, flow and thermal fields are categorized into a class of moving boundary problems. In this study, the moving interfaces between the fluid and cylinders have been considered. The numerical model used in the present paper, is based on a 2D Navier–Stokes momentum and energy equations for an incompressible flow solver on an unstructured grid. Discretization of the governing equations including continuity, momentum and energy equations is achieved through a finite element scheme based on characteristic based split algorithm using the arbitrary Lagrangian–Eulerian approach to satisfy boundary movement. Besides a dual time stepping method is employed to capture unsteady flow and thermal characteristics. The working fluid is designated a Prandtl number of 0.71(air) and assumed to be incompressible with constant physical properties. The radiation, viscous dissipation and pressure work are also assumed to be negligible throughout this investigation. Fluid flow and heat transfer characteristics are examined in the domain of the Rayleigh number, cylinders spacing, amplitude, and frequency of oscillations such that: 10³ ≤ Ra ≤ 10⁵, 2 ≤ s/d ≤ 4, 0.5 ≤ l ≤ 2, and 0.1 ≤ f ≤ 0.4. The obtained results reveal that increment of Rayleigh number and cylinders’ spacing augment the average Nusselt of each cylinder as well as higher oscillation amplitude and frequency. Moreover, it was found that horizontal vibration makes vortices appear in the left and right area of the cylinders. These vortices reduce heat transfer from two upper cylinders.     

Effect of the transparency of the skeleton on parameters of an axisymmetric cylindrical filtration combustion heater

Numerical simulation with a differential approximation of radiation transfer was carried out to study the effect of the partial transparency of the porous skeleton on the radiant efficiency, the maximum temperature, and the localization of the combustion front in an cylindrical axisymmetric filtration combustion heater. It is shown that the partial transparency of amorphous quartz grains for radiation provides a 2–5% increase in the radiant efficiency in comparison with nontransparent materials under the simulated conditions. It is shown that use of transparent fillings can both decrease and increase the skeleton temperature, depending on the size of the system and other parameters. Optical characteristics of porous fillings and models of radiation transfer in isotropic porous media are discussed. Translated from Inzhenerno-Fizcheskii Zhurnal, Vol. 71, No. 1, pp. 62–69, January–February, 1998.     

Mathematical modeling of the damage threshold of cornea tissues by short IR laser pulses

A series of experimental data on threshold energy levels of cornea damage by IR radiation pulses with duration shorter than 1 μs is generalized. Mathematical modeling of the radiation energy thresholds is based on the concept of the removal of a surface layer of the cornea tissue without a phase transition as a result of the work of pressure forces. Academic Scientific Complex “A. V. Luikov Institute of Heat and Mass Transfer, Academy of Sciences of Belarus”, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 3, pp. 424–427, May–June, 1996.     

State Primary Standards in the Area of Radiometry of Ultraviolet Radiation

The present article describes the system used for assurance of the uniformity of measurements of the characteristics of ultraviolet radiation in the wavelength band 0.03–0.40 μm for radiation sources and receivers based on the State Primary Standards of the unit of spectral density of radiance as well as the unit of radiant flux and unit of irradiance. __________ Translated from Izmeritel'naya Tekhnika, No. 11, pp. 17–20, November, 2005.     

The influence of longitudinal magnetic field on recombination radiation of low-pressure glow discharge in hydrogen and helium

We study the influence of longitudinal magnetic field on the radiation of low-pressure glow discharges in hydrogen and helium. We conducted experiments under a pressure in a discharge chamber of 10–20 Pa and a discharge current of 10–20 mA. A 0–1600 G magnetic field influenced only the cathode parts of the discharge, negative glow, and the dark Faraday space. The electron temperature and density were measured by the two-probe method as a function of magnetic field. We studied the dependence of the intensity of radiation in the spectral lines and continuous spectrum on magnetic field induction. We discovered that, under the action of magnetic field, discharge in hydrogen and helium is compressed and its glow volume increases by a factor of 20–25. In contrast, the radiation intensity in the lines and continuous spectrum increase by a factor of 100–200. We found a strong discrepancy in the measured intensity of the continuous spectrum into spectral ranges with calculation of electron-ion recombination.     

On the absorptivity of a limited volume of blood subjected to extracorporeal ultraviolet irradiation

A method and results of calculations of the absorptivity of a limited volume of blood under the conditions of ultraviolet irradiation in extracorporeal-type apparatuses up to practical use in clinics are presented. The method is based on an approximate analytical solution of the equation of radiation transfer in the 3D geometry for a disperse medium that models blood in a chamber for irradiation. For the given shape of the chamber with relative dimensions 5 × 3 × 1, data on the density of multiply scattered ultraviolet radiation formed at each point of the medium have been obtained. The spectra of the absorptivity, the values of the radiation energy absorbed by the irradiated volume of blood and issuing from the medium through the chamber walls, as well as the volumes of the zones of effective irradiation of erythrocytes for the whole and diluted blood have been calculated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 6, pp. 1170–1177, November–December, 2008.     

Effect of UV radiation on the relaxation characteristics of ferroelectric thin-film capacitors

The effect of UV radiation with a wavelength near the fundamental absorption edge on the relaxation characteristics of ferroelectric capacitors based on thin (Ba,Sr)TiO₃ (BSTO) films has been studied. The absorption spectra of BSTO films with thicknesses up to 1 μm obtained by RF magnetron sputtering on sapphire substrates have been measured in a 300–600 nm wavelength range, the UV radiation penetration depth in this material was determined, and the optical bandgap width was evaluated. It is established that UV irradiation leads to a significant decrease in the relaxation time of the residual capacitance of BSTO-film-based structures. A minimum relaxation time is achieved upon the irradiation in a 350–360 nm wavelength interval.