The thermodynamic and kinetic behavior of both the 85and 110-K superconducting phases during the crystallization annealing process has been observed and analyzed using x-ray diAraction, magnetic shielding, and resistivity measurements in crystallized Bi-Sr-Ca-Cu-0 glasses with nominal compositions Bi2Sr2Ca2Cu30 (2:2:2:3), Bi2Sr2Ca3Cu40"(2:2:3:4),and BiqSrqCa4-Cu50"(2:2:4:5).A single superconducting transition near 110 K has been observed in both resistive and magnetization shielding experiments for crystallized samples with 2:2:3:4 and 2:2:4:5 nominal compositions.Eutectic crystallization occurs during annealing of rapidly solidified glass samples. Both the 85-K and Ca2Cu03 phases cooperatively nucleate and grow from the amorphous matrix. The 110-K phase subsequently forms at the interfaces between the eutectic products, controlled by calcium and copper diff'usion. A phase-change cycling has been observed, during which the 110-K phase increases in volume percent with increasing annealing time at 870 C in calciumand copper-rich samples. It then vanishes as annealing is prolonged at the same temperature. This behavior also occurs with diA'erent time periods depending on the initial calcium and copper composition of the samples. Microstructural changes associated with such cycling have also been observed. Also discussed are crystallization mechanisms, diAusion phenomena, and related superconducting properties.
We apply the phase portrait analysis to semiconductor lasers with Auger recombination and extend the analysis to high modulation frequency ωm. On the two-dimensional bifurcation diagram of modulation depth and modulation frequency, there are seven regions: digital pulsing regions, analog modulation region, period doubling regions, chaos regions, and one multiloop region. It is found that Auger recombination tends to suppress chaos for ωm<ωr, the relaxation frequency. However, for ωm>ωr, chaotic behavior becomes prominent. Furthermore, in the pulsing region, the maximum pulsation frequency is limited to a value around ωr even though ωm may be twice or three times ωr. A normalized two-dimensional bifurcation diagram defining the digital pulse region and the analog modulation region is presented for the purpose of locating the suitable region for analog and digital operation of semiconductor lasers.
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