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The rangefinder described here is a self-contained instrument for hand-held operation by a diver for searching, tracking, navigation and surveying applications. It has four modes: 1 — to measure range to a passive target directly to ± 1 m; 2 — to measure range to a passive target indirectly to ± 0.1 m; 3 — to measure range to a coded transponder to either ± 1 m or ± 0.1 m; 4 — to indicate the presence of multiple targets downrange where each target occurs in a selected range interval. The pulse echo principle is employed, with pulses typically 250 μs long. The carrier frequency of 300 kHz can be altered easily if required by changing the transducer array. 相似文献
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The plastic deformation of poly-4-methylpentene-1 (P4MP1) crystals on a unidirectionally drawn substrate has been investigated by electron microscopy. In addition to cracks spanned by fibrils and buckling perpendicular to the stretch direction, both features found in deformation studies of other polymers, a unique slip mechanism leading to sectorization of P4MP1 crystals is observed; deformation was also found to occur by means of localized lamellar thinning. The exact type of plastic deformation occurring in P4MP1 crystals is found to depend on the orientation of the lamellae with respect to the tensile axis. Some evidence for a periodicity on the fibrils studied is given. 相似文献
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James F. Woodward André de Klerk Gail Kahler Kathrine Leber Peter Pompei Daniel Schultz Sharon Stern 《Foundations of Physics》1972,2(2-3):241-244
An experiment designed to test the highly speculative hypothesis of photon consciousness was executed. It was found that, within the accuracy attainable with the apparatus, there is no empirical justification for the hypothesis. 相似文献
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By total synthesis, it was shown that the imidazole alkaloids dehydroisolongistrobine and isolongistrobine possess structures 1 and 2, respectively, rather than the structures proposed by Arndt, Eggers and Jordaan in 1969. Reaction of methyl 1-methylimidazole-5-carboxylate with phenylsulfonylmethyl magnesium bromide provided a β-ketosulfone which was alkylated with o-nitrobenzyl bromide to provide 6. In the key step, amino alcohol 10 and tetrahydroquinoline 8 were obtained through aluminum amalgam reduction of 6. 8 was converted to isomacrorine 12. 10 could be converted to 1 by a three-step sequence; 2 was obtained from 10 by acylation with 4-pentenoyl chloride, oxidation, and osmium tetroxide catalyzed periodate cleavage of the vinyl group. Comparison of samples of synthetic alkaloids 1 and 2 with the corresponding alkaloids from natural sources showed that the natural and synthetic samples of each were identical. 相似文献