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991.
The problem of monitoring of the mesoscale variability of hydrophysical fields in the shelf zone is considered. The usefulness of the data available in regional information centres is discussed. The possibility of monitoring the dynamics of the oceanic fields in the tropical Atlantic encompassing separate observation sites is demonstrated using the oceanographic databank of the scientific research centre (CERESCOR) in Conakry-Rogbane as an example. The results of assimilation of the hydrophysical survey data derived on the shelf in a telescopic model of the region are given.Translated by Mikhail M. Trufanov. 相似文献
992.
993.
Three different barge sizes were tested in uniform current in a tank of limited width. One of the barges was tested with and without bilge keels. Tests were conducted in both deep and shallow water. The barges were placed broadside to the current flow and the lateral forces on the barges were measured. The effect of the tank walls on these forces is clearly shown. 相似文献
994.
The effects of varying intensities of off-road vehicle and pedestrian traffic on vegetation height and percent-cover were investigated at two sites representing pioneer and climax dune shrubland communities in South African dune systems. In all cases, a decreasing trend in vegetation height and percentage cover subsequent to application of the treatments was evident, although this was more clear in the shrub than in the pioneer community. The impact on vegetation variables increased with increasing intensity of vehicle and pedestrian treatments. Vehicles driven along a curved path resulted in greater vegetation destruction than those driven along a straight path. High intensity (single application) treatments resulted in an initial decrease in vegetation height and cover immediately after the impact, which was followed by a further decline over the next 3 months. This two-step response was attributed to the subsequent gradual death of the vegetation which was not evident immediately following the impact. Due to their faster growth rate, pioneer dune communities appear to have the capacity to recover following impacts, while dune shrub communities tend to be more vulnerable, exhibiting signs of damage for longer periods. The results of this study have value for managers of coastal dune systems, particularly those impacted by human recreational activities. 相似文献
995.
Major variations in type and rate of tectonic movement in the southwestern margin of the Ulleung Basin coincide in time with
changes in stratal patterns at succession boundaries, suggesting that the effect of tectonism was dominant for the development
of sequence architecture. During the back-arc opening (16–12 Ma), the rise of relative sea level and the high rate of sediment
supply gave rise to sequences with sigmoid progradational patterns. During the back-arc closing (12–6.5 Ma), fall- and rise-dominated
relative sea-level fluctuations resulted in sequences with varying stratal patterns depending upon changes in deposition rate.
The rise-dominated relative sea level has been prevalent during the later stage (6.5 Ma–Present) with low sedimentation rate.
Received: 16 January 1996 / Revision received: 7 February 1997 相似文献
996.
Geoacoustic and physical properties of carbonate sediments of the Lower Florida Keys 总被引:4,自引:0,他引:4
Near-surface sediment geoacoustic and physical properties were measured from a variety of unconsolidated carbonate sediments
in the Lower Florida Keys. Surficial values of compressional and shear speed correlate with sediment physical properties and
near-surface acoustic reflectivity. Highest speeds (shear 125–150 m s-1; compressional 1670–1725 m s-1) are from sandy sediments near Rebecca Shoal and lowest speeds (shear 40–65 m s-1; compressional 1520–1570 m s-1) are found in soft, silty sediments which collect in sediment ponds in the Southeast Channel of the Dry Tortugas. High compressional
wave attenuation is attributed to scattering of acoustic waves from heterogeneity caused by accumulation of abundant shell
material and other impedance discontinuities rather than high intrinsic attenuation. Compared to siliciclastic sediments,
carbonate sediment shear wave speed is high for comparable values of sediment physical properties. Sediment fabric, rather
than changes due to the effects of biogeochemical processes, is responsible for these differences. 相似文献
997.
The paper considers the application of self-organizing models, specifically, the method of grouped arguments consideration
(MGAC), to forecast short and non-stationary time series of observations in the ocean. A sequence of operations for the treatment
of observational series is suggested. To assess its efficiency, we have used mean monthly oxygen concentration data collected
in the surface and near-bottom layers of the Taganrog Bay. It is shown that the application of the MGAC model allows one to
reduce by two times the root-mean-square error of that of the series prediction by five points, in comparison with the Jenkins-Box
regressional model. It has been concluded that the predictors' non-linear functions may be effectively used in the treatment
of short samplings.
Translated by Vladimir A. Puchkin. 相似文献
998.
999.
1000.