The authors report on and analyze a survey of practices and experiences with time-delay back-up protection associated with unit-connected generators, predominantly rated 100 MVA and above. In addition, application and setting considerations are discussed. The survey covered large unit-connected installations, involving 47 respondents and 6698 unit-years of experience. Phase back-up, negative-sequence overcurrent, and high-side neutral overcurrent protection were considered. The majority of respondents were found to apply all three classes of back-up protection: phase, negative-sequence, and high-side neutral overcurrent

Measurements of critical currents using a four-point direct current (dc) method and an alternating magnetic field method have been performed on several superconducting YBa2Cu3O7 ceramics at 77 K. In the presence of a constant magnetic field, the critical currents obtained with the alternating field method are several orders of magnitude larger than the critical currents measured by the dc method. Also, we observed a minimum in the dc critical current as a function of applied transverse magnetic field. Several authors have suggested that these ceramics behave as individual superconducting grains coupled by Josephson junctions. In this paper, we explain the two observations above using that model.

The transport critical current density, Jc, and the ac susceptibility have been measured for 28 YBa2Cu3O7, ceramic samples. It is observed that a Silsbee-like rule relates Jc to the alternating magnetic fields at which the ceramics begin to show a reduced Meissner effect.

Experimental results are presented for the stress required to cause quenching during successive runs when bare fibers of Nb-Ti are carrying subcritical currents with no cross field. The data fall into two distinct regimes attributed to regions of magnetic flux stability and instability. Microplastic deformation is believed to supply the energy to initiate the flux jump process in the magnetic instability regime, and is the only source of heat available for triggering a quench when the fiber is magnetically stable. In both cases, quenching is observed at stresses well below the mechanically observed elastic limit. Simple techniques for “one-step” training and “detraining” are also described.

The mechanical behavior of Nb-46.5% wt Ti in the form of single fibers of 53 µm diameter, chemically extracted from a superconducting composite, has been studied at 4.2 K and room temperature. It is established that the fiber itself is in both radial and longitudinal compressive residual stress in the core and longitudinal tensile stress in the outside layers. These are a consequence of the manufacturing process. Twinning and Lüdering behavior is observed in both temperature ranges and a mechanism involving adiabatic behavior in small crystallite regions is used to account for the 4.2 K results. This paper attempts to establish the nature of stress changes on the dislocation network, since we believe that these are fundamental in defining the stability of the fluxoid network.

Tensile stress experiments were made on single Ti 39.5 at % Nb fibers, 18.3 µm in diameter, and fiber bundles chemically extracted from a commercial superconducting composite. As the temperature decreases, the fracture stress increases, as does the fracture elongation. This abnormal behavior argues for either a very fine-scale structural change or microdeformation. Load-strain serrations, previously reported, were not observed in these small-diameter fibers.

Eastern gamagrass, Tripsacum dactyloides (L.) L., may have potential for use as a grazed or stored forage if problems with establishment and stand persistence can be reduced and if its nutritive value is high enough to justify the relatively intense management that will likely be necessary for sustained production. In 1979 and 1981, 51 gamagrass accessions, primarily from Texas and Oklahoma were studied in detail near Perkins, Okla. in order to characterize the magnitude of phenotypic variability among them for several agronomic and morphological traits. Most of the accessions had been collected in Texas and Oklahoma. The traits studied were: spring vigor, anthesis date, leaf width, plant height, percent seed set, regrowth vigor, and percent in vitro dry matter digestibility (IVDMD). The IVDMD determinations were made for four sampling dates in 1979 and one sampling date in 1981. The first three 1979 samplings were at intervals of 4 weeks on progressively older plants. The fourth sampling in 1979 and the 1981 sampling were of 5‐week old regrowth following a uniform mowing of the nursery. There were highly significant differences (P < 0.01) among the accessions for all traits during each of the 2 years. Years constituted a significant source of variation (P < 0.01) for spring vigor, anthesis date, regrowth vigor, and IVDMD of regrowth forage. Accessions differed significantly (P< 0.01) in IVDMD at each of the four sampling dates in 1979 and the accession by sampling date interaction for IVDMD was also significant(P < 0.01). Accession by year interactions were significant (P < 0.01) for spring vigor, anthesis date, percent seed set, and regrowth vigor. The only partial correlation coefficients that were significantly different from zero were those for vigor of spring growth vs. vigor of regrowth (during both years and for the 2‐year mean), and vigor of spring growth vs. plant height (in 1979 and for the 2‐ year mean). The magnitudes of the ranges among accessions were relatively large for all the traits studied, indicating a wide array of variability that might be used in the genetic manipulation of the species.

The specific heat of cold-rolled Nb-25% Zr has been measured from 2 to 11.6 K in zero magnetic field. The transition temperature has been found to be 10.9±0.05 K and the specific heat below the transition temperature is reasonably well represented by C=1954 exp(−1.874Tc/T) +0.16T3 mJ/mole K.

rently on the problems of sex education for the normal adolescent, but relatively few studies on sexual behavior in the adolescent retardate have been reported. Nevertheless, the sexual maturation of the retarded adolescent always creates apprehension and often precipitates emotional crises in their families during this period. For example, with the 44 non-institutionalized adolescent retardates reviewed by Hammar and Barnard,5 fears of sexual misbehavior and pregnancy were the primary concerns of parents which motivated them to seek professional help. In the past, the recourse for allaying anxiety and solving such critical family situations