Engineering topics

Szalay, A.

Publications and source records attributed to Szalay, A..

2 records

NASA NTRS1995

Effect of particle size and particle size distribution on physical characteristics, morphology and crystal structure of explosively compacted high-T(sub c) superconductors

A superconductor, of composition Y(Ba,K,Na)2Cu3O(x)/F(y) and a composite of composition Y(Ba,K,Na)2Cu3O(x)/F(y) + Ag, with changing K, Na and F content but a constant silver content (Ag = 10 mass%) was prepared using a single heat treatment. the resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 micron, 0-63 micron and 63-900 micron and explosively compacted, using an explosive pressure of 10(exp 4) MPa and a subsequent heat treatment. Best results were obtained with the 63-900 micron fraction of composition Y(Ba(1.95) K(0.01)Cu3O(x)F(0),(05)/Ag: porosity less than 0.01 cu cm/g and current density 2800 A/sq cm at 77K.

Kotsis, I.↗

NASA NTRS1986

Quasars as indicators of galactic ages

Theoretical models of QSO evolution and their use in estimating the ages of galaxies containing QSOs are discussed, with a focus on the problems involved in extrapolating from statistical data on relatively nearby objects (z less than 2) to characterize distant objects. Graphs and histograms are provided, and it is concluded that the sharp decrease in the number of QSOs between z = 2 and z =3, if not the result of obscuration or some other selection effect, makes it probable that the galaxy-formation processes which led to the formation of the QSOs occurred at z greater than 5. In that case, the QSOs would be one of the only observational probes of these processes. Mechanisms which could account for the time delay between galaxy formation and QSO turn-on are considered.

Cavaliere, A.↗