Inductive switching of 4H-SiC gate turn-off thyristors

The high-temperature operation of a silicon carbide gate turn-off thyristor is evaluated for use in inductively loaded switching circuits. Compared to purely resistive load elements, inductive loads subject the switching device to higher internal power dissipation. The ability of silicon carbide components to operate at elevated temperatures and high power dissipations are important factors for their use in future power conversion/control systems. In this work, a maximum current density of 540 A/cm² at 600 V was switched at a frequency of 2 kHz and at several case temperatures up to 150°C. The turn-off and turn-on characteristics of the thyristor are discussed     

Trapped-energy flexural mode filter

An electromechanical filter using trapped-energy flexural modes in a rectangular plate is proposed. The filter is amenable to fabrication by planar techniques and it can operate in the l.f. range, including the voice band. Bandwidth is easily controllable. A considerable gain in size can be obtained with respect to flexural bar filters.     

Investigation of the Possibility of Using UNK Superconducting Dipole Magnets for Producing Rapid-Cycling Magnetic Fields

The superconducting dipoles developed as part of the UNK project have reached a magnetic field 6 T at a rate of up to 0.8 T/sec. Experimental data are presented on the conditioning, rate dependences, and dynamic losses for magnets with two types of superconducting cable (zebra and oxide). Possible ways to decrease the heat release in a dipole operating in rapid-cycling magnetic fields are examined. The results of an analysis of heat release and temperature conditions are presented for a dipole with a winding made of improved current-carrying components.     

Investigation of amorphous Ni0.60Nb0.40 diffusion barriers

Interactions of Ni_0.60Nb_0.40 amorphous alloys with polycrystalline overlayers of gold and copper and single-crystal substrates of silicon. GaAs and GaP were observed with Auger depth profiling. The Ni-Nb layer was deposited by r.f. sputtering and was approximately 5000 Å thick. The overlayers were evaporated to a thickness of 1000 Å. The amorphous metal reacted with the gold overlayers and the GaAs and GaP substrates at temperatures well below the nominal crystallization temperature of 650 °C. The Cu/Ni-Nb/Si system, in contrast, was stable at 600 °C for at least 1 h. Samples were also measured that had been contaminated with approximately 5–10 at.% O. Complete separation of the niobium and nickel into distinct layers was seen. For the samples on silicon substrates this separation was accompanied by the formation of a nickel silicide layer.     

On the mechanisms of adenosine induced pulmonary vasoconstriction in rats

The effect of adenosine on pulmonary vessels was studied in isolated perfused rat lungs. Drugs were administered intra-arterially in a fixed volume of 0.1 ml Krebs solution as bolus injections. Adenosine responses were obtained before and 10 min after drug injections. When applied in logarithmically increasing doses (1-100 micrograms/ml), adenosine caused dose-dependent increases in pulmonary perfusion pressure (e.g. pulmonary vasoconstriction) which were readily reversible. Challenging adenosine with quinidine, dihydroergocristine and cyproheptadine (2 micrograms/ml each) did not significantly alter adenosine responses. Pretreatment of lungs with 0.5 mM theophylline, 10 micrograms/ml indomethacin, 30 micrograms/ml tebokan (a PAF antagonist) or 1 microgram/ml methylene blue for 10 min, however, antagonized the vasoconstrictor effect of the drug significantly. From these experiments, it was concluded that the mechanisms underlying the pulmonary vasoconstrictor action of adenosine are complex, and that both types of purinoceptors, prostaglandins, PAF and other vascular endothelial hormones might be involved.