An acoustooptic method for sound velocity measurements in strongly sound-absorbing materials

An acoustooptic method for determining the velocities of longitudinal ultrasonic waves in a 10⁵ to 10⁸-Hz range in strongly absorbing (scattering) materials, when methods based on the sound transmission through a sample are unfit, is described. This method employs the acoustooptic determination of the acoustic impedance of the studied sample by measuring the reflection coefficient from the boundary between two contacting substances, namely, a liquid with the known (or measured) acoustic impedance and the studied solid sample. The method features the following advantages: (i) it is acceptable, when standard methods do not work due to the sound attenuation (scattering); (ii) there is no need for exact knowledge of sample sizes, the operating frequency, and the electromechanical coupling factor, and also for using reference samples; and (iii) the sound attenuation in a liquid and the distance from the sample surface to measurement points (required for calculations of the sound velocity) are easily measured. In this case, the velocity measurement error is usually 5–10%.     

Problem of determining internal boundary conditions in measuring the heat of gas-turbine blades undergoing cooling

This article examines features of the numerical solution of a two-dimensional non-linear inverse problem of heat conduction in a two-layer region with a movable external boundary.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 3, pp. 403–409, September, 1986.     

Magnetic Resonance Force Microscopy of a Permalloy Microstrip Array

The ferromagnetic resonance in an array of permalloy microstrips 3000 × 500 × 30 nm in size ordered on a rectangular grid 3.5 × 6 μm in size has been investigated by magnetic resonance force microscopy. The dependences of magnetic resonance force microscopy spectra of a sample on the probe–sample distance are analyzed. The possibility of detection of a ferromagnetic resonance spectrum of a single microstrip is demonstrated.     

Homo- and Copolymers of N-Acryloylpyrrolidine and N-Vinylpyrrolidone as Kinetic Inhibitors of Hydrate Formation

Two copolymers of N-acryloylpyrrolidine and N-vinylpyrrolidone with a different ratio of monomeric units and two homopolymers; poly-N-acryloylpyrrolidine and poly-N-vinylpyrrolidone, were synthesized to study the effect of the composition of macromolecular compounds (MMC) on their inhibiting power during formation of gas hydrates. The composition of the MMC was confirmed by ¹H and ¹³C NMR spectroscopy and the ratio of monomeric units in the copolymers was determined with the ¹H NMR spectra. The inhibiting power of the synthesized MMC was determined during hydrate formation.     

Molecular dynamics characterization of thermodynamic and mechanical properties of Pu as dependent upon alloying additions and defects concentration. Part I

The paper presents results of molecular dynamics (MD) simulations which were performed to investigate mobility of defects in the δ-PuGa alloy. The defects diffuse through thermal fluctuations and MD results provided parameters for the Arrhenius law describing defect diffusion versus temperature. On the basis of this information a model of radiation defect accumulation allowing for different types of defects and grain size was constructed.The annealing of the defects at elevated temperatures and the effect of accelerated ageing due to adding small quantities of Pu-238 upon defect accumulation were evaluated.     

A study and development of technology for surface induction hardening of railroad rails from low-alloy steel

A technology of heat treatment of railroad rails using induction heating has been developed and installed in the Azovstal' metallurgical works. It provides the requisite combination of properties in the metal of rail heads. However, the metal of the web and the bottom of the rails remains in the initial (unhardened) state. Under severe operational conditions (small-radius curves, high axial loads, and composite configuration of the road) the wear resistance of the head and the structural strength of the web and the bottom not hardened in the plant have to be increased. The properties of the rail steel can be improved by alloying it using the most effective and available elements. Currently, in Ukraine this is manganese. The present paper is devoted to the effect of manganese additives on the phase transformations in induction hardening and the specific features of the formed structure and properties of the rail steel. Optimum parameters for heat treatment of rails are recommended. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 7–10, December, 1998.     

Local heat fluxes on the surfaces of dimples,ditches, and cavities

We present the results from investigating heat transfer at the surface of spherical and asymmetric dimples and in the trails downstream of these dimples on a plate, as well as on the surface of cylindrical and trapezoid ditches and on the plane downstream of them.     

Thermal measurements at the body surface in a supersonic nitrogen flow

Measurements of the heat flux toward the surface of a body of revolution in a supersonic nitrogen flow with Mach number 4 were carried out. Inside the body, an electromagnetic facility is mounted which generates a gas-discharge plasma between electrodes flush-mounted at the body surface. The plasma rotates around the body surface and significantly influences the supersonic flow. During operation of the electromagnetic facility, the heat flux toward the body surface increases and depends on the direction of the electric current flowing through the plasma. The heat flux was measured by fast-response gradient heat flux sensors based on anisotropic bismuth crystals.     

Bismuth-Based Gradient Heat-Flux Sensors in Thermal Experiment

The possibility is examined of using gradient heat-flux sensors made on the basis of 0.9999 pure bismuth in both heat-metering problems and problems associated with the determination of temperature, shear friction stresses, volume flow rate of moving media, thermal characteristics of materials, and emissivity factor of surfaces. The dynamic characteristics of such sensors are determined. Measurement schemes are suggested which significantly extend the information content of experiments without sophistication of the equipment. Examples are given of using gradient sensors in experiments of different scales and technical levels.