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921.
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A comprehensive study of undisturbed, mostly silty clay samples, taken from large-diameter surface cores collected in the North Atlantic and its bordering seas, shows that measurement of the Atterberg limits, water content, specific gravity of grains and grain-size distribution can provide the basis for predicting many seabed geotechnical and geophysical properties which can lead to a quick assessment of environmental conditions. Thus, the sediment compression curve can be reconstructed, acoustic properties assessed, electrical and thermal resistivities deduced and an indication of the shearing forces, which have affected the sediment, inferred. 相似文献
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Video assessment of environmental impacts of salmon farms 总被引:1,自引:0,他引:1
927.
This article presents a comparative study of the breathing resistance and clearing characteristics of several types of commercially available snorkels in an attempt to device quantitative means that enable the divers to select the best snorkel and the designers to see the possible directions and modifications necessary for improving the performance of such important life support devices.Two test stands have therefore been built, the first to measure the breathing resistance and the second to monitor the clearing efficiency and speed of some of the commonly used snorkels.The tested snorkels varied from the simple J-type to the sophisticated wrap-around snorkels with convoluted flexible hoses and flared ends.The results obtained show that large diameter snorkels of the wrap-around design with sweeping barrels and flared ends (as the AMF Swimmaster snorkel number 2S55) offer the least breathing resistance. As for the clearing characteristics snorkels with small diameters and of the simple J-type (as the Spanish Aquasub snorkel: The Canarias) or with large diameters and sweeping barrels (as the Power Tuned snorkel of U.S. divers) possess the best clearing figure of merit. 相似文献
928.
Measurements of 226Ra and 210Pb in barite samples separated from different depths of a piston core from the eastern equatorial Pacific are reported. 226Ra is enriched in the barite as would be expected from the chemistries of Ra and Ba; the ratio centers around 1.5 · 1014 atoms/mole. The results suggest that barite is concentrating Ra at a rate comparable to its decay rate, viz. 5.78 · 10?3 yr?1. The gross 210Pb depletion with respect to 226Ra is indicative of 222Rn loss due to the smallness of the barite crystals. 相似文献
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