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Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni(3)Al and Ni(3)V-Co(3)V-Fe(3)V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed. 相似文献
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T. C. Carter 《British poultry science》1977,18(2):205-211
1. The mean energy, Ef, required for fracture of an egg shell at its equator by a flat plate is known to depend on shell compression speed, vm, for speeds in the range 20 μm/s to 2.lb5 mm/s; analysis of published data shows that Ef bears a linear relationship to log (vm ) throughout the industrially important speed range from 20 μm/s to 1.lb1 m/s, increasing from 1.lb3 to 5.lb0 mJ.
2. At lower speeds down to 2 μm/s Ef is constant.
3. Ef is reduced if the flat plate is replaced by a sphere or cylinder; the greater its curvature, the smaller Ef.
4. Ef for the narrow pole is greater and for the broad pole smaller than that for the equator but these differences may be due in part to . systematic differences in shell thickness as well as curvature. 相似文献
337.
Samples and observations under 420 meters of ice and 430 kilometers from the open sea on the Ross Ice Shelf at a water depth of 597 meters revealed an unusual assemblage of benthic organisms. Scavenging amphipods, an isopod, and fish were present but a living infauna was absent. The observations may be accounted for by sampling or spatial bias, or by extremely low or fluctuating trophic resources. 相似文献
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Hayes ET 《Science (New York, N.Y.)》1979,203(4377):233-239
Energy and the gross national product have grown hand in hand at 3 to 3(1/2) percent a year for almost 40 years. Our energy growth is slowing down and will sentially level off in the 1990's. Our production of oil and gas passed a peak in the early 1970's, and there is no resource base to justify predictions of increased yields. Coal is the only fossil fuel capable of increased production. There are serious doubts that our uranium resources can support a large light-water reactor program. Finding rates for petroleum, natural gas, and uranium are less than half of what they were 20 years ago. 相似文献
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