Electrical conductivity of ferroelectric sodium vanadate,rubidium vanadate,cesium vanadate and their solid solutions

The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO₃, RbVO₃ and CsVO₃, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric state and depends upon sodium concentration.     

Strength of small-scale spherical shells formed from pressed glass elements

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Sumy Branch, Khar'kov Polytechnic Institute. Translated from Problemy Prochnosti, No. 8, pp. 102–104, August, 1989.     

Indoor body-area channel model for narrowband communications

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described.     

Surface barrier diode based on zinc selenide with a passivating zinc oxide film

We propose a method of fabricating surface barrier diodes with overlapped metal junction, which provides for a significant decrease in the reverse currents and an increase in the breakdown voltage.     

Modelling induction skull melting design modifications

Induction Skull Melting (ISM) is used for heating, melting, mixing and, possibly, evaporating reactive liquid metals at high temperatures when a minimum contact at solid walls is required. The numerical model presented here involves the complete time dependent process analysis based on the coupled electromagnetic, temperature and turbulent velocity fields during the melting and liquid shape changes. The simulation is validated against measurements of liquid metal height, temperature and heat losses in a commercial size ISM furnace. The often observed limiting temperature plateau for ever increasing electrical power input is explained by the turbulent convective heat losses. Various methods to increase the superheat within the liquid melt, the process energy efficiency and stability are proposed.     

Surface Activation of Diamond Particles in the Process of Chemical Coppering

The effect of the composition of sensitizing–activating solutions on the activation efficiency and the chemical coppering of diamond powders is studied. The results demonstrate that stabilizing additives improve the stability of the solutions, influence the average coppering rate, and play a key role in determining the morphology and quality of the resultant coatings. The most effective stabilizing additive is synthamid-10, which ensures the deposition of high-quality copper coatings.     

Thermodynamic Properties of Alloys and Phase Equilibria in the In–Sb System

New thermodynamic data for the In–Sb system are obtained and compared with calculation results available in the literature. An isothermal vacuum cell and a procedure for electrolyte preparation are described which ensure high measurement accuracy.     

High-strain-rate superplasticity of nanocrystalline aluminum alloy 1570

The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10^?3 to 1 s^?1.