Automation of Thermotechnical Machinery in Glass Production

The operating principles of automated control system for glass-melting furnaces and drums for drying sand and dolomite are described.__________Translated from Steklo i Keramika, No. 4, pp. 20 – 22, April, 2005.     

Metal oxide bicrystal Josephson junctions of a new type with high critical parameters

Film bicrystal Josephson junctions of a new type based on a metal oxide high-T _c superconductor of the YBa₂Cu₃O_7−x (YBCO) system are suggested and studied. In junctions of the new type, in contrast to the known ones, the working surfaces situated on the opposite sides of the bicrystal interface have different crystal orientations: one is (001)YBCO, and the other is rotated (misoriented) relative to it by an asymmetric bicrystal angle around a certain axis lying in the substrate plane. The main electrical and dynamic (microwave) characteristics have been determined for junctions of the new type based on NdGaO₃ bicrystal substrates with the misorientation angle varying from 13° to 28°. These junctions exhibit high values of the critical parameters at T=77 K, including the critical current density I _C= (2–5)×10⁵ A/cm² and the characteristic voltage V _C=I _C R _N=0.6–0.9 mV. Advantages of the bicrystal Josephson junctions of the new type over the known junctions are considered.     

A speckle-interferometric setup for contactless measurements of the velocity of rayleigh ultrasonic waves

The velocity of a Rayleigh wave was determined by measuring its propagation time between two Iaser-illuminated small areas of a rough surface. It is sh own that, if a Rayleigh wave passes over these areas, a photodiode twice detects signals proportional to the surface displacement in the speckle overlap region. In contrast to the previous variant, signal-distorting reflections are eliminated in the instrument. A sample holder excluding adjustment of the interferometer upon a change in the object size has been manufactured. A new technique for determining the time interval between two signals is used. The instrument operates at a frequency of 5 MHz, and the distance between the areas is adjusted in the range 5–100 mm. The rms deviation of the velocity from the average value for ten measurements is 8 × 10–4.     

Adaptive control system for a tool drive in machining

An adaptive control system for a tool drive is outlined, along with the corresponding algorithm and practical results.