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21.
A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection 总被引:1,自引:0,他引:1
To dates,most ship detection approaches for single-pol synthetic aperture radar(SAR) imagery try to ensure a constant false-alarm rate(CFAR).A high performance ship detector relies on two key components:an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm.First,a novel nonparametric sea surface distribution estimation method is developed based on n-order Bézier curve.To estimate the sea surface distribution using n-order Bézier curve,an explicit analytical solution is derived based on a least square optimization,and the optimal selection also is presented to two essential parameters,the order n of Bézier curve and the number m of sample points.Next,to validate the ship detection performance of the estimated sea surface distribution,the estimated sea surface distribution by n-order Bézier curve is combined with a cell averaging CFAR(CA-CFAR).To eliminate the possible interfering ship targets in background window,an improved automatic censoring method is applied.Comprehensive experiments prove that in terms of sea surface estimation performance,the proposed method is as good as a traditional nonparametric Parzen window kernel method,and in most cases,outperforms two widely used parametric methods,K and G0 models.In terms of computation speed,a major advantage of the proposed estimation method is the time consuming only depended on the number m of sample points while independent of imagery size,which makes it can achieve a significant speed improvement to the Parzen window kernel method,and in some cases,it is even faster than two parametric methods.In terms of ship detection performance,the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors,resolutions and sea surface homogeneities and obtains a leading performance on the test dataset. 相似文献
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The case of a freak wave collision with the ship in the Agulhas current is described. The explanation of the appearance of the freak wave as a result of wind-wave transformation in the Agulhas current is given. Swell is captured and intensified by the counter-current and is located in the neighbourhood of the maximum value of the current velocity, as a result of which there is a great concentration of wave-energy density. The superposition of wind and sea with swell transformed by the current promotes the formation of the freak waves. Using a simple mathematical analysis, an optimal ship track is proposed which could reduce the risk of collision with a freak wave. 相似文献
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The topic of ship recycling has obtained considerable attention during the last two decades for a variety of reasons with the likelihood of the adoption of a new international convention under the auspices of the International Maritime Organization (IMO). This study applies econometric modeling to a unique data set to provide insight into the dynamics of the ship recycling market. The data set contains information on 51,112 ships over 100 gt and includes 748,621 events over a period of 29 years. The analysis confirms a negative relationship of earnings and a positive relationship of scrap prices for all locations while Bangladesh seems to be more sensitive to changes in earnings than the other locations and more likely demolishes larger and older vessels. The results for flag and ownership vary across scrapping locations with Malta and Cyprus indicating potential importance from a registry perspective. The overall safety profile of a vessel seems to be less important towards the probability of a ship being scrapped. Possible implementation of the convention at EU level will mostly likely affect Turkey while non-ratification of one of the major flags will most likely affect China or Bangladesh. 相似文献
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提出一种基于北斗卫星导航系统(BDS)的油电混合动力推进系统,柴油机和电动机采取PTH驱动方式,采用燃油和电能混合提供推进动力,可以依据BDS导航的航行区域以及航行速度选择不同动力源输出.经过燃油经济性和效益分析,与传统推进系统相比,应用基于BDS的混合动力推进系统,公务船运营成本降低26%,增加的初始建造投资成本3年内可以收回;金枪鱼延绳钓船综合节油15%~20%,通过节油方式可在4年内收回初始建造投资成本.基于BDS的混合动力系统可以增加推进冗余度,提高船舶安全性,具有良好的节能减排和节约运营成本的效果. 相似文献
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《海洋技术学报》2024,(1)
作为当今世界上最先进的测流仪器,水平式声学多普勒流速剖面仪(Horizontal Acoustic Doppler Current Profiler,H-ADCP) 因其精度高、速度快等突出优势在河流中的应用越来越广泛,但在航运业发达地区,由于受船行波的影响,很难得到稳定可靠的流速数据,阻碍了H-ADCP在平原河网地区的应用和推广。目前技术上很难做到完全消除船行波的影响,本文将H-ADCP应用在平原河网地区对流速进行测量,并分析了船行波对测量精度的影响。从H-ADCP设备选型、测量和安装方式、测量预处理、数据后处理等多方面入手,可以有效消减船行波对H-ADCP 的影响,从而提高测流精度。同时,通过实验测量断面一天内平均流速变化情况,得到受船行波影响后的流速波形,然后采用数据处理手段,验证了所提方法的可行性。 相似文献
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简要介绍了Google Maps JavaScript API技术,并着重阐述了其作为主流的WebGIS技术在船舶自动气象站监控页面设计中的应用,包括:通过JavaScript和AJAX技术请求远程数据服务器获取气象数据、状态数据及GIS信息等,并将返回的JOSN格式数据加载到Google Map上,同时通过Google Maps JavaScript定制化船舶图标并对加载的船舶轨迹进行渲染,使用户需要的监控信息更加直观地显示在监控页面上。本文结果已成功应用到广东省气象局设备全网监控系统之中。 相似文献
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