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1.
本文利用一些复随机变量的分布和统计推断理论，导出了向量过程的正旋谱、负旋谱、谱差、总谱、外自谱、频域外自相关函数、外自谱的位相函数等估计量的渐近分布以及它们的置信区间，并简略地讨论了所得置信区间的最优性。最后用锚系海流计资料实例说明了所得置信区间公式在海流资料分析中的应用。 相似文献
2.
海流矢量时间序列旋转谱估计及其应用实例 总被引：1，自引：0，他引：1
本文扼要叙述了海流矢量旋转谱估计的数学背景和有关的旋转不变量,概括介绍了目前矢量旋转谱估计置信区间方面的一些研究成果.在此基础上,借鉴和利用标量谱估计的某些假设和结果,推导出了矢量旋转谱自谱估计的期望和方差表达式,进而给出了矢量旋转谱自谱估计的置信区间,最后列举了矢量旋转谱估计的计算实例. 相似文献
3.
本文对北部湾内一个连续7d的海流观测站的资料进行旋转谱分析。结果表明,该海区潮流属于不正规全日潮,全日周期分量的谱能量与半日周期分量的谱能量的比值为1.7。全日周期分量的椭圆主轴方向为341°,且椭圆主轴方向较稳定。整个流场基本上受顺时针旋转流所控制。总的趋势,在低频段海流的北分量自谱能量远比东分量自谱大。东分量谱相对北分量有一个较短的时间滞后,且北分量与东分量相关性较好。分析结果与以往对测站所在海区观测的潮流准调和分析结果相吻合。 相似文献
4.
本文利用大亚湾大鹏(?)1989年7～8月海流连续观测资料,用黄金分割法逐步逼近威布尔分布参数的改进适线法,拟合出该湾流速三参数威布尔分布函数。流速良好地服从三参数威布尔分布,文中还探讨了资料的代表性对所求分布函数的影响。 相似文献
5.
南海北部大陆坡区斜压海流的垂向结构 总被引：6，自引：0，他引：6
对南海北部陆坡区一定点站连续28.6d的27个等间隔水层(11,15,…,115m)的ADCP海流观测资料进行正压海流、斜压海流分解, 运用调和分析、功率谱分析和能量计算等方法着重对观测点各水层的斜压海流的时间序列进行研究.得到如下结果:(1)斜压海流向岸分量平均值、斜压海流两分量样本标准差、斜压海流K1分潮流振幅、斜压海流的平均涡动动能以及斜压海流向岸分量功率谱显著的谱峰值的垂向分布均随深度的增加由大变小再变大.(2)斜压海流的日周期显著, 斜压海流的日分潮流的椭圆长轴方向偏NW-SE向, 日分潮流作顺时针方向旋转;斜压海流的日分潮流迟角的垂向分布是:约以67m为界,界面附近水层的迟角变化较大,远离界面的水层的迟角分布较稳定,界面上、下水体的迟角反向;67m层以浅水层, 相对集中在300°附近,67m以深水层,主要分布在120°周围.(3)斜压海流的平均涡动动能较大,约占实测海流平均动能的41%,其向岸分量大于沿岸分量, 且其大小与日分潮流椭圆的长短轴分布相对应.(4)斜压海流功率谱峰值显著周期在24h左右;19与99m层相同,为23.6h,55m层为24.4h;斜压海流向岸分量与沿岸分量功率谱的显著谱峰值的垂向分布有所不同, 前者随深度增加由大变小再变大,后者则随深度增加而减小. 相似文献
6.
依据波浪力成因和作用效果的不同,将波浪力分为两部分(Morisson 波浪力和 Inundation波浪力)讨论.对于两种波浪力中的非线性拖曳力项,采用高次多项式逼近,结合高斯型统计量高阶矩计算原理、相关函数、变换法和单输入多输出系统的互谱关系,预测海流海浪联合作用下的海洋平台响应谱的理论形式,求得总波浪力谱以及平台响应谱.在Inundation模态力的相关函数推导过程中,考虑海流影响时,惯性力项与拖曳力项的相关函数总和为0,这一结果与不考虑海流影响时的结果相同. 相似文献
7.
1982年2—3月“南海暖流动力学实验”结果表明:南海东北部深水区域冬季流场以斜压性流为主要分量。据此,本文重新分析了1966—1968及1975年冬季在南海北部观测所得的温度断面资料以探索这支逆风海流的分布变化特征。分析表明,东北向逆风海流以汕头外海为最稳定和强大,海南岛东南方的也相当稳定。在这两断面上,东北向流的存在时间尺度可达4—6个月以上。冬季东-西向的空间尺度有时可达6个经度。但这些断面上的热结构与相应的海流结构在水平及垂直方向上都很复杂。除南海东北部外,逆风海流很不稳定。这支海流与副热带逆流颇为类似。 相似文献
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10.
海流谱分析是近十年来引进的新方法,它从海水运动的内部结构——谐波组成来阐眀海流速度的时空变化特性,因而这种方法在分析流场的运动学和动力学特性以及流场之间的相互关系等方面颇有成效。在国外,海流谱分析方法已经广泛应用于研究风生流,内波,惯性运动,中尺度涡以及沿岸上升流等方面。随着浮标测流技术在我国的普遍推广,适用于长期连续测流资料的谱分析方法将得到日益广泛的应用。
海流是一矢量,相对标量而言,矢量谱的计算要比标量谱复杂一些。另外,由于科氏力的影响,海洋中的流动现象大都具有旋转性质。因此,在对海流时间系列作谱分析时，为了阐明海流运动的旋转性质,引人与海流的旋转特性相联系的旋转谱(rotary spectrum),要比单纯采用两个正交方向上的谱,如东分量谱和北分量谱更为恰当。利用旋转谱,一方面可以消除定位方向不准所产生的误差;另一方面,常常可以使海流的谱结构显得更加简洁,从而简化海流的动力学分析手续。
二维矢量的旋转谱分析方法在海流资料分析中的应用,较早可见于Perkins和 Gonella的论文。尔后, Moores系统地阐明了二维矢量谱的分析方法。 Calman把这一方法推广到三维情况,并把旋转谱推广到经验本征谱( Empirical eigenmode spectra);此外,他还阐明了谱分析方法在海流动力学分析中的若干应用。
一九七九年四月下旬,我们用测流浮标在青岛近海取得了持续四天的流速时间系列(采样间隔为十分钟或十五分钟)本文即试图采用二维矢量的旋转谱分析方法来处理这些观测数据,并由此得到该区海流的某些运动学特征。 相似文献
11.
Stan E. Dosso Charles W. Holland 《Oceanic Engineering, IEEE Journal of》2006,31(3):657-671
This paper applies nonlinear Bayesian inversion to seabed reflection data to estimate viscoelastic parameters of the upper sediments. The inversion provides maximum a posteriori probability (MAP) parameter estimates with uncertainties quantified in terms of marginal probability distributions, variances, and credibility intervals; interparameter relationships are quantified by correlations and joint marginal distributions. The inversion is applied to high-resolution reflectivity data from two sites in the Strait of Sicily. One site is characterized by low-speed sediments, resulting in data with a well-defined angle of intromission; the second is characterized by high-speed sediments, resulting in a critical angle. Data uncertainties are quantified using several approaches, including maximum-likelihood (ML) estimation, treating uncertainties as nuisance parameters in the inversion, and analysis of experimental errors. Statistical tests are applied to the data residuals to validate the assumed uncertainty distributions. Excellent results (i.e., small uncertainties) are obtained for sediment compressional-wave speed, compressional attenuation, and density; shear parameters are less well determined although low shear-wave speeds are indicated. The Bayesian analysis provides a quantitative comparison of inversion results for the two sites in terms of the resolution of specific geoacoustic parameters, and indicates that the geoacoustic information content is significantly higher for intromission data 相似文献
12.
Based on the second-order random wave solutions of water wave equations in tinite water depth, statistical distributions of the depth-integrated local horizontal momentum components are derived by use of the characteristic function expansion method. The parameters involved in the distributions can be all detemained by the water depth and the wavenumber spectrum of ocean waves. As an illustrative example, a fully developed wind-generated sea is considered and the parameters are calculated for typical wind speeds and water depths by means of the Donelan and Pierson spectrum. The effects of nonlinearity and water depth on the distributions are also investigated. 相似文献
13.
本文基于Longuet-Higgins随机波浪模型和JONSWAP谱,进行了大量深水随机波的模拟,获取了畸形波发生概率稳定的随机波列,并对随机波列中的畸形波进行了分析。结果表明,畸形波发生的概率小于基于Rayleigh分布预测结果,且随谱宽的减小而增大。在固定时间段内,畸形波发生的频次服从泊松分布,时间间隔服从指数分布,且随着谱宽的增大,畸形波的发生频次减小,相邻畸形波的发生时间间隔增加。通过小波变换方法分离随机波中的波群,研究了出现畸形波的波群特征,发现一个波群中最多会出现4个畸形波,但是在发生畸形波的波群中,单个畸形波的概率最大。随着谱宽减小,一个波群中包含多个畸形波的概率增加。另外,出现畸形波的波群时间长度服从广义极值分布,随着谱宽减小,畸形波波群的时间跨度增加。 相似文献
14.
《Oceanic Engineering, IEEE Journal of》1996,21(4):537-544
The acoustic spectrum of a transiting aircraft, when received by a hydrophone located beneath the sea surface, changes with time due to the acoustical Doppler effect. The traditional method for analysing signals whose frequency content changes with time is the short-time Fourier transform that selects only a short segment of the signal (or window of data) for spectral analysis at any one time. The short-time Fourier transform requires the frequency content of the signal to be stationary during the analysis window, otherwise the frequency information will be smeared by the transformation. Recently, joint time-frequency distributions, which highlight the temporal localisation of a signal's spectral components, have been used to analyse nonstationary signals whose spectra are time dependent. In this paper, the short-time Fourier transform and the Wigner-Ville time-frequency distribution are applied to time-series data from a hydrophone so that the instantaneous frequency of the propeller blade rate of a turbo-prop aircraft can be estimated at short time intervals during the aircraft's transit over the hydrophone. The variation with time of the estimates of the Doppler-shifted blade rate is then compared with the corresponding temporal variation predicted using a model that assumes the sound propagates from the airborne acoustic source to the subsurface receiver through two distinct isospeed media (air and water) separated by a plane boundary (the air-sea interface). The results for five transits are presented in which the altitude of the aircraft ranged from 350 to 6050 ft with the speed of the aircraft varying from 232 to 245 kn 相似文献
15.
On the calculation of extreme wave heights: A review 总被引：2，自引：0，他引：2
Over the past two decades there has been a great deal of interest in calculating design waves for offshore structures. This paper reviews the data limitations, statistical assumptions, distributions, fitting methods, and statistical tests used to determine confidence intervals and goodness of fit. Use is made of an illustrative example from the Grand Banks of Canada to indicate how a design wave could be calculated. It is concluded that no single method will be entirely suitable for all data sets. 相似文献
16.
Knowledge on intermittency of wave breaking is so far limited to a few summary statistics, while the probability distribution of time interval between breaking events can provide a full view of intermittency. Based on a series of experiments on wind wave breaking, such probability distributions are investigated. Breaking waves within a wave group were taken as a single breaking event according to recent studies. Interval between successive wave groups with breaker is the focus of this paper. For intervals in our experiments with different fetch and wind conditions, their distributions are all skewed and weighted on small intervals. Results of Kolmogorov-Smirnov tests on time series of these intervals indicate that they all follow gamma distribution, and some are even exponential type. Average breaking-group-interval decreases with friction velocity and significant steepness until the wind is strong enough;most of them are more than 10 times the dominant wave period. Group breaking probability proposed by Babanin recently and the average number of breaking waves in wave groups are also discussed, and they are seemingly more reasonable and sensitive than traditional breaking probability defined in terms of single wave. 相似文献
17.
R.J. Sobey 《Ocean Engineering》1992,19(2)
Existing theoretical distributions of wave height and period do not reflect measured joint distributions from field data. A simulation methodology is introduced to retain the essential features of the theoretical background in Gaussian random noise but to avoid further compromising assumptions in the interpretation of height and period in the amplitude domain. A joint distribution can be associated directly with an empirical or measured variance spectrum. Spectral shape appears to dominate the detail of predicted joint distributions. There is generally a much sharper decay in probability levels at higher periods than is predicted by theoretical models. For Jonswap spectra, there is a dominant central ridge and a distinct bimodal structure in the joint distribution, features that are not evident in symmetric Gaussian spectral forms. The wave height distributions for Jonswap spectra differ little from the Rayleigh distribution, except at extreme wave heights where Rayleigh overpredicts. The period distributions are strongly sensitive to spectral shape. In the conditional distribution of periods, given the height, the asymptotic median period at extreme wave heights is significantly longer than the mean period for Jonswap spectra, but not for symmetric Gaussian forms. 相似文献
18.
Fluvial sands host excellent oil and gas reservoirs in various fields throughout the world. However, the lateral heterogeneity of reservoir properties within these reservoirs can be significant and determining the distribution of good reservoirs is a challenge. This study attempts to predict sand distribution within fluvial depositional systems by applying the Continuous Wavelet Transformation technique of spectral decomposition along with full spectrum seismic attributes, to a 3D seismic data set in the Pattani Basin, Gulf of Thailand. Full spectrum seismic attributes such as root mean square and coherency help to effectively map fluvial systems down to certain depth below which imaging is difficult in the intervals of interest in this study. However, continuous wavelet transform used in conjunction with other attributes by applying visualization techniques of transparency and RGB can be used at greater depths to extract from 3D seismic data useful information of fluvial depositional elements. This workflow may help to identify different reservoir compartments within the fluvial systems of the Gulf of Thailand. 相似文献
19.
New version of SWAN model includes the wave diffraction effect which is the main improvement compared with the previous versions.Experimental data collected in the wave basin of the University of Delaware were used to test its performance.Wave heights were compared in the four cases(with different wave energies and directional spreading spectra).The results agreed well with the measurements,especially for the broad directional spectra cases.The effect of wave diffraction was analyzed by switching on/off the corresponding term.By introducing the diffraction term,the distributions of wave height and wave direction were smoothed,especially obvious for the narrow spectrum cases.Compared with the calculations without diffraction,the model with diffraction effect gave better results. 相似文献
20.
Ying-guang Wang 《中国海洋工程》2018,32(6):655-664
This paper first proposes a new approach for predicting the nonlinear wave trough distributions by utilizing a transformed linear simulation method. The linear simulation method is transformed based on a Hermite transformation model where the transformation is chosen to be a monotonic cubic polynomial and calibrated such that the first four moments of the transformed model match the moments of the true process. The proposed new approach is applied for calculating the wave trough distributions of a nonlinear sea state with the surface elevation data measured at the coast of Yura in the Japan Sea, and its accuracy and efficiency are convincingly validated by comparisons with the results from two theoretical distribution models, from a linear simulation model and a second-order nonlinear simulation model. Finally, it is further demonstrated in this paper that the new approach can be applied to all the situations characterized by similar nondimensional spectrum. 相似文献