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931.
The stresses generated in the interlock T-junction piles of steel cellular structures used as quays are analysed based on a full scale experimental recording of the stresses in the piles at all stages of construction. Special emphasis is placed on the resonant response of the pile to vibrations of the fill in the interlock cell. Means of stiffening the interlock piles are discussed. A model for the statical behaviour of the interlock pile is postulated and an alternative design for cellular quay construction based on its three-dimensional behaviour rather than the equivalent breadth concept is put forward. This work was instigated by the collapse of three interlock piles during the construction of the deep water quays at Umm Said Port in Qatar. 相似文献
932.
Analysis of microbiological and chitinase activities relative to the white shrimpPenaeus setiferus, and its chitinoclastic endosymbionts, have demonstrated the relevance of total chitinolytic processes in penaeid biology. Microorganisms may serve as a direct source of nutrients for the animal as well as in the elaboration of extracellularin situ chitinase enzymes. The enzyme produced by the predominant gut bacteria,Beneckea neptuna, is a moderately actively inducible chitinase while the shrimp has an indigenous constitutive chitinase and chitobiase system. Factors of temperature, pH, ion inhibition and reducing sugar ratios have been compared for the bacterial and animal enzymes. This dual enzyme system suggests that metabolic chitin transformation may play a vital role in crustacean metabolism. 相似文献
933.
Core 7710, recovered on the George Bligh/Rockall Channel, is composed of fine grained ocher-colored sediments rich in ferriferous smectite (montmorillonite, beidellite). These sediments were deposited during early Eocene in a shallow marine environment. Their mineralogic, chemical and isotopic constituents indicate subaerial weathering of lower Eocene intermediate igneous rocks (ferrodiorite, marscoiite) eroded from the still-emergent George Bligh and Rockall Banks. Lack of any post Eocene Sediments may be due to major morphologic and hydrologic changes forming sedimentation gaps. 相似文献
934.
Mass flux and undertow in a surf zone 总被引:1,自引:0,他引:1
I.A. Svendsen 《Coastal Engineering》1984,8(4):347-365
The mass of water carried shoreward by the breaking waves in a surf zone will, in a two-dimensional situation, be compensated by a seaward return flow, the undertow. It is shown that the undertow is driven by the local difference between radiation stress and the set-up pressure gradient which only balance each other in average over the depth. Turbulent shear stresses are required to maintain a steady situation. Comparison with measurements confirms the theoretical results. 相似文献
935.
Theoretical and laboratory results indicate that bottom velocities within shoaling internal gravity waves intensify upslope approximately inversely proportional to the water depth. The elevated velocities (and bottom stresses) caused by shoaling and, possibly, breaking internal waves might explain the generation and maintenance of near-bottom nepheloid zones and attached turbid plumes that have been observed over certain continental shelves and slopes. This process is proposed as an explanation of zones of relatively low transmissibility that emanate from the upper continental slope near Newport submarine canyon off southern California. 相似文献
936.
937.
Cluster analysis is discussed in the context of its application to map various test areas in the sea. By analysing the correspondence of the identified categories to areas with specific hydrological conditions, an attempt is made to relate the types of fine structure to diverse background conditions. With two test areas mapped, a conclusion is made as to the possible application of cluster analysis to this end.Translated by Vladimir A. Puchkin. 相似文献
938.
The paper is concerned with the evaluation of the drift current parameters derived through the use of an analytical model.
In this model, effective when stratification is stable and indifferent, the vertical turbulence coefficient profile is prescribed
by the power function, and hydrodynamic quantities are prescribed using the external parameters of the problem (wind stress,
the Coriolis parameter, and the dimensionless stratification parameter). Model data are compared with the observations of
the upper mixed layer in the vicinity of the oceanic Station C, conducted during one year. It is shown that, under the spring-summer-time
warming conditions, the model at issue is capable of adequately simulating the upper ocean layer dynamics.
Translated by Vladimir A. Puchkin. 相似文献
939.
Don Maurer Richard T Keck Jeff C Tinsman Wayne A Leathem 《Marine environmental research》1982,6(1):49-68
The survival of benthic invertebrates from dredging and disposal activities is a major environmental concern in such projects. The purpose of the research described in this paper was to determine the ability of benthos (polychaetes, Scoloplos fragilis and Nereis succinea) to migrate vertically in natural and exotic sediments and to determine the survival of benthos when exposed to particular amounts of simulated dredged material.Mortalities generally increased with increased sediment depth, exotic sediment and burial time. Temperature also affected vertical migration and mortalities. These experiments, together with other experiments conducted by us and other workers, indicate that polychaetes in particular, and benthos in general, can survive dredging and disposal projects. Under certain conditions several major taxa (polychaetes, molluscs, crustaceans) can be expected to successfully recolonise disposal sites by vertical migration. 相似文献
940.