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531.
We study the time decay of surges of a liquid in a round shallow-water basin of variable depth. The dependence of the logarithmic
decrement of oscillations on the bottom topography and wind velocity is analyzed. The role of convective acceleration and
bottom friction in the formation of both the level of vertical displacement of the surface of the basin and the velocity field
of horizontal wave currents is estimated.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 3–11, March–April, 2006. 相似文献
532.
533.
This work aims at contributing to improve knowledge on transient asymmetric flooding through theoretical and experimental research. First, a time domain theoretical model of ship motions and flooding is described. Results from experimental work are presented evidencing that transient asymmetric flooding may cause the capsizing of a Ro-Ro shaped barge. The theoretical model is used to predict the capsize of the Ro-Ro shaped barge. Reasonable agreement between experimental and theoretical results was found. Finally, a review of the European Gateway accident is given and the theoretical model is applied to the study of this type of accident. The conclusion is that this theoretical model, together with an accurate modelling of the flooding of machinery compartments, reproduces successfully the capsizing of the European Gateway due to transient asymmetric flooding. Therefore, the internal arrangement of Ro-Ro ships should be carefully studied at the design stage in order to avoid this phenomenon. 相似文献
534.
E. D. Golubeva 《Oceanology》2006,46(5):672-682
Based on the summarized geological and petrogeochemical information on the basaltic magmatism on the Pacific Ocean floor, the formation-geochemical rock types, their associations in the oceanic morpho-structures, and petrological provinces were distinguished. The features of the composition variations of the rocks presented mainly by magno-and ferrotholeiites in mid-oceanic ridges and by their petrological analogues at the plates (Fenner trend) were examined. The increase in the silica acidity and alkalinity of the rocks (Bowen trend) is moderately manifested in the eastern provinces of the ocean and is much more pronounced in the western areas (including the formation of complexes constituted by significant volumes of alkaline rocks). 相似文献
535.
From 1988 to 1993, 23 satellite-tracked drifting buoys entered the Kamchatka Current. The buoy trajectories showed a well-formed, high-speed current that originated near Shirshov Ridge, and flowed southward through Kamchatka Strait. During some years, the buoys turned eastward at 50°N, while in other years they were transported as far south as Japan (40°N). Only one buoy entered the Sea of Okhotsk. Eddies were evident in many of the buoy trajectories. Greatest maximum daily velocities (>100 cm s–1) were observed south of Kamchatka Strait, with 50–60 cm s–1 being more common. 相似文献
536.
Early life stages of Spisula solidissima (1-, 4-, 8- and 12-h post-fertilization) were exposed to various concentrations of silver in solution (0, 4, 8, 24, 44, 124 and 278 μg liter?1) for 1 h. An additional group of 1-h post-fertilized eggs was treated with 0, 4, 11 and 24 μg liter?1 silver continuously for 48h. Results indicate that younger embryos are more susceptible to Ag. Exposure of one-hour-old embryos to silver for only 1 h gives results similar to a continuous 48-h exposure to the same concentration of Ag. The calculated EC50 for 48-h continuously exposed embryos was similar to the EC50 for 1-h post-fertilized embryos that were exposed to silver for only 1 h. 相似文献
537.
The structure and functioning of nanoplanktonic assemblages in coastal upwelling areas have usually been overlooked in explorations of the productivity of these areas. As part of a multidisciplinary, time-series station in the coastal area off Concepción, seasonal variations (upwelling and non-upwelling) in the abundance and biomass of these assemblages were investigated. Hydrographic measurements and biological samples were taken monthly over a 2-year period (18 August 2004-28 July 2006). Nanoflagellates dominated the total integrated abundance (3-317 × 109 cells m−2; 0-80 m). Diatoms and dinoflagellates usually contributed to a lesser degree (<20%) but sporadically made important contributions to the total integrated nanoplankton biomass (0.02-10.6 g C m−2). Most of the nanoplankton was concentrated in surface waters (<30 m) during all the samplings and no seasonal differences in abundance or biomass were found in this layer, although the mean values and dispersions around them were highest during the upwelling period along with maximum integrated (0-80 m) chlorophyll-a values, as total or in the <20 μm fraction. Changes in nanoplankton abundance were significantly but weakly (r < 0.4) correlated with changes in the hydrographic variables; the highest correlation values were positive for temperature and oxygen, factors that varied with depth and date. The potential grazing rates of heterotrophic nano-predators (flagellates and dinoflagellates) on prokaryotic prey, estimated with a generic model, ranged from 3 to 242 bacterioplankton predator−1 h−1 and from 0.1 to 14 cyanobacteria predator−1 h−1. Our results imply a small impact of seasonal hydrographic variability on the abundance and biomass of nanoplanktonic assemblages and suggest that grazing by nanoheterotrophs might control the prokaryotic picoplankton populations in the upwelling area off Concepción. 相似文献
538.
Rates for nitrification, phytoplankton uptake of ammonium, and regeneration of ammonium were measured in the Delaware River as functions of irradiance and nutrient concentrations, using 15N labeling methods. Phytoplankton uptake increased and nitrification rates declined with increased light intensity. The irradiance level required for maximum uptake by phytoplankton was similar to that for maximal inhibition of nitrification (about 300μEm−2 s−1). Daily, water-column averaged rates, calculated by integration of the observed rate-intensity relationships, indicate that light plays a key role in regulating the balance between oxidation of NH4+ by bacteria and assimilation by phytoplankton in the Delaware. The results show that uptake of ammonium by phytoplankton in the dark may exceed uptake in the light in optically thick systems. 相似文献
539.
Arnold H. Bouma James M. Coleman Charles E. Stelting Barry Kohl 《Geo-Marine Letters》1989,9(3):161-170
A conceptual sea-level-driven depositional model for individual fanlobes (channel-overbank systems) of the Mississippi Fan
does not permit direct application of the sequence stratigraphic principles of Vail and colleagues. Deep Sea Drilling Project
Leg 96 results suggest that, during initial relative lowering of sea level, the canyon and upper fan channel were formed;
excavated fine-grained slope sediments may have formed a debris flow deposit base for the fanlobe. Continued lowering produced
constructional channel-levee-overbank deposits. Rising relative sea level inhibited input of coarse clastics, and channel
depressions filled with muds. A blanket of (hemi)pelagics represents relative high sea level stand. 相似文献
540.