Special Features of Thermal and Stress Hysteresis of B2–R–B19' Martensitic Transformations in Aged [001]-Oriented Ti–50.6 at.% Ni Single Crystals

Russian Physics Journal - Stress-induced and thermal-induced martensitic transformations (MTs) in compression were investigated in [001]-oriented Ti–50.6 at.% Ni single crystals aged at 573 K...     

Investigation into transmission of complex sound signals in the human respiratory system

Lumen probing of human lungs with complex acoustic signals in the frequency band from 100 to 1000 Hz made it possible for the first time to explicitly confirm the concurrent existence of two mechanisms differing in propagation velocity behind the transmission of acoustic vibrations from the oral cavity to the thoracic cage surface. The numerical values of propagation time lags allowed one of these mechanisms to be associated with combined aerial-structural transmission and the other, with purely structural transmission.     

Regression Modeling of the Acousto-Biomechanical Characteristics of Wheezes during Human Forced Expiration

Within the framework of a specified acousto-biomechanical model, a possibility of explaining wheezes during forced expiration on the basis of a vortex separation mechanism is tested and the localization of the zones in the bronchial tree where forced expiratory wheezes are generated is refined. As an experimental model, a group of 18 healthy volunteers from 18 to 44 years old (median is equal 19) was used. On the basis of linear regression modeling the relationship between the principal spectral frequency of medium-frequency forced expiratory wheezes (400–600 Hz) recorded on the trachea and the standard volume flow-rates of expired air measured in computer spirometry is analyzed. The data obtained show that vortex separation in the air flow at the bronchial tree bifurcations (where a stepwise increase in the cross-section area takes place) is a probable mechanism of medium-frequency forced expiratory wheeze generation and that during the forced expiratory maneuver the vortex separation zone tends to be displaced deeper into the bronchial tree.     

Effect of ultrasonic oscillations on the fluidity of heavy oil products at low temperatures

We develop a laboratory setup to estimate the force of rotation of a metal branch pipe in a viscoelastic medium. We show that 2-min action of shearing ultrasonic oscillations (frequency, 32.5 kHz; specific power, no more than 0.008 W/cm²) reduces by 17% the static limit of fluidity brought to an initial temperature of ì-100 fuel oil cooled to −15°C in the wall layer of a rotating branch pipe. We obtain a linear regression dependence between the ratio of the threshold force of the onset of branch pipe motion to the consumption current of the ultrasonic transducer and the fuel temperature.     

Flow noise of an underwater vector sensor embedded in a flexible towed array

The objective of this work is to simulate the flow noise of a vector sensor embedded in a flexible towed array. The mathematical model developed, based on long-wavelength analysis of the inner space of a cylindrical multipole source, predicts the reduction of the flow noise of a vector sensor embedded in an underwater flexible towed array by means of intensimetric processing (cross-spectral density calculation of oscillatory velocity and sound-pressure-sensor responses). It is found experimentally that intensimetric processing results in flow noise reduction by 12-25 dB at mean levels and by 10-30 dB in fluctuations compared to a squared oscillatory velocity channel. The effect of flow noise suppression in the intensimetry channel relative to a squared sound pressure channel is observed, but only for frequencies above the threshold. These suppression values are 10-15 dB at mean noise levels and 3-6 dB in fluctuations. At towing velocities of 1.5-3 ms(-1) and an accumulation time of 98.3 s, the threshold frequency in fluctuations is between 30 and 45 Hz.     

Special Features of Functional Properties of Heterophase High-Strength Ni50.2Ti37.3Hf12.5 Polycrystals and Single Crystals

Russian Physics Journal - Stress-induced B2–B19' martensitic transformations (MTs) in Ni50.2Ti37.3Hf12.5 (at.%) alloy aged at 773 K, 3 h are studied. Single crystals have lower (by 100 K)...     

A two-jet plasmatron for the spectrochemical analysis of geological samples

The analytical possibilities with a two-jet plasmatron with non-consumable electrodes have been investigated. Large amounts of easily ionised additives present in the plasma enhance atom line intensities of trace elements, the effect being greater the lower the ionisation potential of the element but the effect on ion line intensities is not significant. The temperature of the plasma is only slightly affected by the ionisation potential of the substance introduced into the plasma.Analytical errors caused by variations in the matrix and mineralogical composition of samples are of the same order as the random error of analysis. The analysis of different types of rock samples can be made using a single standard procedure giving a relative standard deviation of 4–6 % and detection limits between 10^?5 and 10^?7 %. A feature of the analytical method is the direct analysis of solid samples.     

Effect of High Temperature and High Stress-Assisted Austenite Aging on Martensitic Transformations in High-Strength Ti – 51.8 ат.% Ni Single Crystals

Russian Physics Journal - High-strength materials containing dispersed Ti3Ni4 particles (d ~ 800 nm) and exhibiting superelasticity (SE) in a wide temperature range from 200 to 450 K were designed...