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21.
More and more researches show that neither the critical downward acceleration nor the critical slope of water waves is a universal constant. On the contrary, they vary with particular wave conditions. This fact moders the models either for the probability of wave breaking B or for the whitecap coverage W based on these criteria difficult to apply. In this paper and the one which follows we seek to develop models for the prediction of both B and W based on the kinematical criterion. First, several joint probabihstic distribution functions (PDFs) of wave characteristics are derived, based on which the breaking properties B and W are estimated. The estimation is made on the assumption that a wave breaks ff the horizontal velocity of water particles at its crest exceeds the local wave celerity, and whitecapping occurs in regions of fluid where water particles travel faster than the waves. The consequent B and W depend on wave spectral moments of orders 0 to 4.Then the JONSWAP spectrum is used to represent the fetch-limited sea waves in deep water, so as to relate the probahility of wave breaking and the whitecap coverage with wind parameters. To this end, the time-averaging technique proposed by Glazman (1986) is applied to the estimation of the spectral moments involved, and furthermore, the theoretical models are compared with available observations collected from published literature. From the comparison, the averaging time scale is determined. The final models show that the probability of wave breaking as well as the whitecap coverage depends on the dimensionless fetch. The agreement between these models and the database is reasonable. 相似文献
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This paper is concerned with the models appropriate for the dynamic assessment of jack-ups, concentrating particularly on the long-term response due to random ocean waves and on work-hardening plasticity models used for spud-can response. A methodology for scaling of short-term statistics, calculated using a Constrained NewWave technique, is shown in a numerical experiment for an example jack-up and central North Sea location. The difference in long-term extreme response statistics due to various footing assumptions is emphasised. Results for two environmental load conditions are described (one excluding and one including wind and current effects) and the role of sea-state severity in the variation of short-term extreme response statistics is also highlighted. 相似文献
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立足样品测试数据,利用空间分析、空间插值、地质统计以及景观生态学方法,深入分析了深圳大鹏湾表层沉积物碎屑矿物的空间分布特征,并使用球状模型对相应半变异函数进行理论建模。结果表明,碎屑矿物分布的Hurst分维数为0.28~0.97,空间几何分维数为1.03~1.72;Moran Ⅰ型空间自相关系数-0.15~0.53。在此基础上,以等值线分布所包围范围作为划分尺度,以Shannon-Wiener信息指数作为度量,得到的矿物分布所反映出的信息量或者富集程度指数为0.88~1.85。 相似文献
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Sylvie Labroue Philippe Gaspar Joel Dorandeu Oz Zanif F. Mertz Patrick Vincent Denis Choquet 《Marine Geodesy》2004,27(3):453-481
The Jason-1 sea state bias (SSB) is analyzed in depth from the first year of GDR products. Compared to previous missions, this work benefits from two aspects of the empirical determination of the SSB from the altimetric data themselves. First, from a methodological point of view, a nonparametric technique (NP) has been developed and largely tested on TOPEX/Poseidon 1, GFO and Envisat data. The NP estimator has proven to be a useful tool in the SSB estimation, and it is now mature enough to be used for a refined analysis. On the other hand, the SSB can be extracted from three different data sets (crossovers, collinear data, and residuals) with different characteristics. It is then possible to cross calibrate various estimations of the SSB models and to determine the most accurate one. A systematic comparison is made between these different estimates for the Jason-1 altimeter. The collinear and crossover data sets yield very similar estimates despite their difference of spatial and temporal distributions. These SSB models assure consistency with the TOPEX mission when comparing Jason-1 and TOPEX residuals during the tandem phase. Thanks to the present work, the impact of the short wavelengths filtering on the SSB estimation is evidenced. More generally, our understanding of potential errors affecting the sea surface height and their impact onto the SSB estimation is also improved. 相似文献
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运用德尔菲调查—灰色统计法确立水库鱼产力综合评价中的指标权重体系 总被引:1,自引:0,他引:1
本文运用德尔菲方法对水库鱼产力综合评价中指标权重的合理分配问题作了专家调查,并采用灰色统计法对调查结果进行归纳处理,从而确立了一个水库鱼产力影响因素诸层次各方面的评价指标权重体系,可供今后的评价工作参考使用。 相似文献
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Two commonly used methods of simulating random time series, given a target power spectrum, are discussed. Wave group statistics, such as the mean length of runs of high waves, produced by the different simulation schemes are compared. The target spectra used are obtained from ocean measurements, and cover a wide range of ocean conditions. For a sufficiently large number of spectral components, no significant differences are found in the wave group statistics produced by the two simulation techniques. 相似文献
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The indicator kriging (IK) is one of the most efficient nonparametric methods in geo-statistics. The order relation problem in the conditional cumulative distribution values obtained by IK is the most severe drawback of it. The correction of order relation deviations is an essential and important part of IK approach. A monotone regression was proposed as a new correction method which could minimize the deviation from original quintiles value, although, ensuring all order relations. 相似文献