一种基于GPU和内存映射文件的高分辨率遥感图像快速处理方法

高分辨率遥感图像处理经常面临程序执行时间过长和内存空间不足的问题,虽然并行计算技术可以提高遥感图像的处理速度,但是无法降低算法占用的巨大内存空间。为了解决这一问题,本文提出了一种利用CUDA和内存映射文件的高分辨率遥感图像快速处理方法,并以K-Means算法为例进行了实现。其中,CUDA技术可以有效利用GPU强大的并行计算能力,而内存映射文件技术降低了磁盘I/O速度较慢对算法性能的影响。实验结果表明,本文方法比传统K-Means聚类算法计算速度提高了30倍左右,内存使用量降低了90%以上。     

Efficient joint-probability methods for hurricane surge frequency analysis

The Joint-Probability Method (JPM) was adopted by federal agencies for critical post-Katrina determinations of hurricane surge frequencies. In standard JPM implementations, it is necessary to consider a very large number of combinations of storm parameters, and each such combination (or synthetic storm) requires the simulation of wind, waves, and surge. The tools used to model the wave and surge phenomena have improved greatly in recent years, but this improvement and the use of very large high-resolution grids have made the computations both time-consuming and expensive. In order to ease the computational burden, two independent approaches have been developed to reduce the number of storm surge simulations that are required. Both of these so-called JPM-OS (JPM-Optimal Sampling) methods seek to accurately cover the entire storm parameter space through optimum selection of a small number of parameter values so as to minimize the number of required storm simulations. Tests done for the Mississippi coast showed that the accuracy of the two methods is comparable to that of a full JPM analysis, with a reduction of an order of magnitude or more in the computational effort.     

超长距离跨海二等水准测量的数据处理与应用

为验证改进的精密三角高程法在10 km级超长距离跨海二等水准测量的可行性,参照规范的观测要求和限差规定,采取每时段分组观测的方法,通过合理限制各组间的高差互差值来筛选出合格测段,计算得到跨海段的高差值.以15 km的海湾构成跨海大地四边形进行应用试验,结果表明跨海高差与陆地常规水准高差之间的互差值分别为1.5、0.2、...     

Wavelet analysis for processing of ocean surface wave records

Wavelet analysis is a relatively new technique and in the recent years enormous interest in application of wavelets has been observed. This modern technique is particularly suitable for non-stationary processes as in contrast to the Fourier transform, (FT), the wavelet transform (WT) allows exceptional localization, both in time and frequency domains. The wavelet transform has been successfully implemented in signal and image processing, ordinary and partial differential equation theory, numerical analysis, communication theory and other fields. On the other hand, the application of the WT to ocean engineering and oceanography is rare. In this paper the WTs capability to give a full time–frequency representation of the wave signals is demonstrated. The processing of the time series of the non-stationary deep water waves, waves breaking at the tropical coral reefs and mechanically generated waves in the wave flume demonstrates the ability of the wavelet transform technique to detect a complex variability of these signals in the time–frequency domain. Various spectral representations resulting from the wavelet transform are discussed and their application for wave signals is shown.     

水下光谱吸收衰减仪(ac-s)的使用与数据处理技术

水色遥感的半分析模式是建立在对海洋水体固有光学量的测量数据基础之上,这一数据测量主要用的仪器就是光谱吸收衰减仪(ac-s).根据2006年在东海开展夏季与冬季两个航次的调查情况,介绍了ac-s的软硬件安装、测试、定标技术.详述了仪器清洁、干燥、维护保养等基本方法,针对实测中的注意事项与出现的一些问题作了分析讨论,并介绍了实测结果的数据校正与分析方法,以期对应用这一仪器进行海上实测、深入研究中国近岸二类水体的性质以帮助.     

Digital system for recording fish echoes

A system to record digitised echo information from echo sounders has been developed as part of a project to improve methods of estimating the abundance of fish stocks around New Zealand. The depth of echoes appearing at the echo‐sounder receiver is determined, followed by a sequence of samples of the echo envelope defining its shape. All data are digitised and recorded on a seven‐track digital magnetic tape recorder. The system is designed to preserve as much information about the echoes as possible. In contrast to other published systems designed to either “count” or “integrate” fish echoes, this system allows free choice of methods of analysis.     

半潜型风机浮式基础设计及幅频运动特性研究

针对5MW海上风机,进行了半潜型浮式基础的概念设计,研究了其幅频运动特性。考虑风机浮式基础的稳性和运动要求,对浮式基础的构件进行设计,并进行舱室划分;考虑叶片产生的气动载荷影响以及风载荷作用,计算分析风机浮式基础的完整稳性及破舱稳性;考虑浮式基础构件及压水板的粘性阻尼,计算浮式基础的幅频运动响应特性。计算结果表明,设计的浮式基础运动性能满足风机发电作业的要求。     

Detection and characteristics analysis of the western subarctic front using the high-resolution SST product

Oceanic front plays a significant role in the ocean vertical mixing and the regulation of air-sea interaction, among others. The western branch of the subarctic front(WSAF) located in the Northwest Pacific has attained lots of attention given its strong intensity and widespread influence on this region. In this study, we take advantage of the merged sea surface temperature(SST) at a high spatial resolution of 0.05° to investigate the characteristics of WSAF. The front detection algorithm that co...     

Extending a time/frequency domain hybrid method for riser fatigue analysis

Fully coupled time domain analysis of a floating system is rigorous but time-consuming, thus an efficient hybrid method was developed in a prior work. The method simulates the coupled slow-drift responses in the time domain and analyzes the wave-frequency dynamics in the frequency domain. The hybrid method was shown to compare well with time domain analysis in predicting the mean-square vessel motions and line tensions. In this paper, the hybrid method is extended for the fatigue analysis of moorings and risers. The fatigue damage thus calculated is found to closely agree with the result from time domain analysis in conjunction with rainflow counting. Several spectral fatigue techniques are also compared, and these methods are significantly less accurate, thus attesting to the complexity of the problem.     

香港与珠三角地区海陆联合地震探测的数据处理

介绍了香港与珠三角地区海陆联测地震数据处理的一般流程及方法,讨论了导航数据记录时间存在误差的问题及其解决方法,对数据处理程序进行了改进,使之更加通用化。提出了数据处理中需要改进之处,对较远的地震台站采用滤波、均衡、剪切等处理手段,突出弱震相,压制强噪音。广东和香港地区的大部分固定台站均可清晰识别出有效信号,这是首次利用固定台站记录到远距离海上气枪信号,最远接收距离达到240多公里,获得了较好的观测结果。     

A statistical analysis of low frequency second-order forces and motions

Probability density functions are derived for low frequency second-order forces and motions using a method which represents the random seastate as a sum of regular waves. The method is shown to agree with another recently developed technique and to give a physical insight into the level of approximation which is employed. A convergence check indicates the importance of including a sufficient number of wave components and it is demonstrated that too few components have been considered previously. A method of predicting the extreme value of the response is also presented, and the relationship between the damping coefficient and the response statistics is investigated by considering the response of an example structure.     

基于多源水深数据融合的海底高精度地形重建

本文在研究多源水深数据构建技术的基础上,分析了张力样条插值算法和“移去-恢复”法的多源水深数据融合处理技术,基于该方法选取实验区,利用多波束、单波束、历史海图等多源水深数据进行高精度海底地形融合试验,并针对多源水深融合技术缺少误差评估的现状,利用split-sample方法对融合结果进行水深不确定性评估,形成融合结果的可靠性空间分布。结果表明该方法无论是在数据稀疏区还是高密度区都达到了较好的融合效果,既保留了高分辨率水深数据的细节信息,又较真实的反映了研究区海底地形特征,且构建的海底地形精度可靠,误差百分比集中在0.5%。本文整套数据融合和结果评估方法可为多源水深数据融合的海底高精度地形构建提供借鉴和参考。     

剖面数据的XML格式设计

根据可扩展标记语言(XML)的原理,设计了针对剖面数据的XML存储格式,并给出了一个XBT实测剖面数据的实例。该格式可用于海洋环境要素的剖面数据交换,并可进一步用于断面数据的数据交换。     

近海遥测波浪仪的数据采集与处理

为了解决HBF1-1型近海遥测波浪仪的原始数据保留方式与数据处理能力,本文提出了以IBM/PC微机代替原系统单板机的方法,并设计了“ADL”与“SPE”数据采集与处理程序,经与ENDECO 956浮标观测资料的比较以及1a的海上观测应用,证明该方法所获得的资料是可靠的。     

南沙地块OBS2019-2测线数据处理与震相识别

为揭示南海南部陆缘的地壳结构,研究其张裂-破裂机制,开展共轭陆缘对比,我们在南沙地块礼乐西海槽附近的洋陆转换带上完成了OBS2019-2测线的探测工作。相较于北部陆缘,南部陆缘已有的海底地震仪(ocean bottom seismometer,OBS)测线较少,对深部地壳结构的研究也较少,因此OBS2019-2测线就尤为重要。文章重点阐述了OBS2019-2测线的数据处理工作,包括UKOOA文件制作、数据格式转换、位置校正、单个台站综合地震记录剖面的生成等,然后在剖面图中对各类深部震相(Pg、PcP、PmP、Pn)进行识别追踪,并建立初步的模型;使用Rayinvr软件进行走时试算工作,验证了震相识别的准确性。处理结果显示OBS2019-2测线的深部震相清晰,最远震相可以连续追踪到120km以外,数据整体质量良好,能为后续速度建模和构造解释等工作提供坚实基础。     

Second order frequency domain analysis of moored vessels

A frequency domain analysis method for the dynamic response of a vessel moored in a random sea is presented, in which second order wave forces are included. The non-linearities occurring in the equations of motion of the vessel are accounted for by using the equivalent linearisation technique, leading to an iterative solution scheme for the mean values and covariances of the response. Application of the method to a moored drill ship indicates that the required computer time is relatively low. The method is intended for use in the preliminary stages of design where a parametric study may be required and the costs of a time domain analysis are prohibitive.     

A digitally recording probe for heat-flow measurements in lakes and oceans

Some technical problems commonly encountered in marine heat-flow measurements have been overcome with a digitally recording seabottom probe containing in its pressure case no moving parts except a stepper relay. The probe stores digitally at regular time intervals the resistances of 11 thermistors in a 240-word CMOS memory. After return to the surface, it is connected to a digital printer to read out the measured data. The probe can be reused immediately since it need not be opened or recharged.     

Shear stress statistics and wall similarity analysis in turbulentboundary layers using a high-resolution 3-D ADVP

Three-dimensional (3-D) quasi-instantaneous acoustic Doppler velocity profiles at the center of uniform, turbulent open-channel flow over smooth and rough beds have been analyzed for the dynamics of coherent structures. The qualitative aspects of simultaneously measured Eulerian velocity and shear stress signatures identify coherent structures in the water column. A cumulant discard method is applied to describe the statistical properties of the covariance terms u'w' along the mean flow and v'w' across the mean flow relative to their time means. Conditional statistics and conditional sampling are used to compare the theoretical and experimental relative covariance contributions from the four quadrants in the longitudinal and transverse planes. The results in the (u', w') plane show the dominance of ejections (quadrant 2; u'<0, w'>0) and sweeps (quadrant 4; u'>0, w'<0). In contrast, the distribution of fractional v'w' events in the transverse plane is quasi-uniform over the four quadrants. Based on these experimentally determined statistical properties of the covariance terms in different flow conditions, a simplified form of the vertical turbulent energy flux in the intermediate flow region is given and the concept of wall similarity in turbulent boundary layers is validated. Since the validity of the wall similarity concept over a wide range of bed roughness has been shown, it is proposed to determine the mean bed friction velocity from the evaluation of the vertical turbulent energy flux     

Time and frequency domain coupled analysis of deepwater floating production systems

The dynamic analysis of a deepwater floating structure is complicated by the fact that there can be significant coupling between the dynamics of the floating vessel and the attached risers and mooring lines. Furthermore, there are significant nonlinear effects, such as geometric nonlinearities, drag forces, and second order (slow drift) forces on the vessel, and for this reason the governing equations of motion are normally solved in the time domain. This approach is computationally intensive, and the aim of the present work is to develop and validate a more efficient linearized frequency domain approach. To this end, both time and frequency domain models of a coupled vessel/riser/mooring system are developed, which each incorporate both first and second order motions. It is shown that the frequency domain approach yields very good predictions of the system response when benchmarked against the time domain analysis, and the reasons for this are discussed. It is found that the linearization scheme employed for the drag forces on the risers and mooring lines yields a very good estimate of the resulting contribution to slow drift damping.