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Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron. Above a critical shock strength, many small close-packed grains nucleate in the shock-compressed body-centered cubic crystal growing on a picosecond time scale to form larger, energetically favored grains. A split two-wave shock structure is observed immediately above this threshold, with an elastic precursor ahead of the lagging transformation wave. For even higher shock strengths, a single, overdriven wave is obtained. The dynamics and orientation of the developing close-packed grains depend on the shock strength and especially on the crystallographic shock direction. Orientational relations between the unshocked and shocked regions are similar to those found for the temperature-driven martensitic transformation in iron and its alloys. 相似文献
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Germann AF 《Science (New York, N.Y.)》1925,61(1568):70-71
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Preferential flow needs self‐dependent fluid mechanical characterization and quantification. A theoretical and experimental approach is presented to describe preferential flow with the three variables volume of flowing water and its kinetic energy and momentum. Two soils were irrigated at rates of 50, 75 and 100 mm hour?1 at one site and three times at 100 mm hour?1 at a second site. The variations of soil water content caused by irrigation were measured at five depths with horizontally installed TDR wave guides at 300‐s intervals. The volume flux densities were calculated from the water balances. The computation of momentum and kinetic energy of preferential flow was based on the velocities of the wetting fronts and the amplitudes of the variations of soil water. Kinetic energy per unit volume of flow in the soil exceeds the one of irrigation by factors between 100 and 1000, which indicates concentration of flow. However, kinetic energy per unit volume of flow in the soil is less by factors of 106 to 108 than the capillary potential of soil water. Kinetic energy per unit volume of flow seems a reasonable variable for discriminating between preferential and ordinary flow at a threshold of 2 × 10?6 Pa. 相似文献
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J Wang Y Yoo C Gao I Takeuchi X Sun H Chang X Xiang PG Schultz 《Science (New York, N.Y.)》1998,279(5357):1712-1714
A quaternary combinatorial masking strategy was used in conjunction with photolithography to generate compositionally diverse thin-film phosphor libraries containing 1024 different compositions on substrates 2.5 centimeters square. A parallel imaging system and scanning spectrophotometer were used to identify and characterize compositions in the library with interesting luminescent behavior. Optimal compositions were identified with the use of gradient libraries, in which the stoichiometry of a material was varied continuously. This process led to the identification of an efficient blue photoluminescent composite material, Gd3Ga5O12/SiO2. Experimental evidence suggests that luminescence in this material may arise from interfacial effects between SiO2 and Gd3Ga5O12. 相似文献
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RC Elphic DJ Lawrence WC Feldman BL Barraclough S Maurice AB Binder PG Lucey 《Science (New York, N.Y.)》1998,281(5382):1493-1496
The Lunar Prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of Clementine spectral reflectance data. With the iron and titanium dependence removed, the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium, incompatible rare earth elements that are enriched in the final phases of magma crystallization. These regions are found mainly around the ramparts of the Imbrium impact basin but not around the other basins, including the much larger and deeper South Pole-Aitken basin. This result confirms the compositional uniqueness of the surface and interior of the Imbrium region. 相似文献
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Daub Matthias Hakl Ulrike Molendijk Leendert PG Schomaker Corrie Been Thomas H van Beers Thea G Jivishova Sevda Jivishov Emil Keusgen Michael Bluemel Roman Fischer Daniel Grundler Florian MW Reuther Marie Cappel Sabrina Bauer Harald Lang Christian Watrin Cliff den Nijs Loes JMF Van Bruggen Anne-Sophie Karssen Gerrit Kiewnick Sebastian Büchler Urs Roth Irma Frey Jürg 《植物病害和植物保护杂志》2015,122(4):189-193
Journal of Plant Diseases and Protection - 相似文献