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舰船RCS是海上雷达系统探测回波强度的一个重要物理量,受多种因素影响,会呈现不规律的随机起伏。论文主要研究了粗糙海面的起伏特性、不同频率、不同极化方式以及不同入射方向的雷达入射电磁波对舰船RCS特性测量的影响,给出了粗糙海面的统计模型,运用时域有限差分法(FDTD)对舰船的RCS进行了计算仿真,研究结果为海面雷达的侦测提供了理论参考依据。 相似文献
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基于神经网络的海面噪声预测算法 总被引:4,自引:4,他引:0
海面噪声是整个海洋噪声研究领域的重要组成部分,准确预测海面噪声对于船舶探测系统及水声系统性能至关重要。本文对影响海面噪声的信号源特性进行分析,通过统计学方法对噪声源的分布情况及噪声传播条件进行研究,分析传播中的射线原理对噪声的影响。最后利用神经网络算法对简正波模型进行改进,研究小角度范围内噪声场的密度函数,并发散至大广角范围,得到海面噪声以及噪声信道的统计特性函数,并进行了实验。 相似文献
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大连湾溢油动态的监测模式 总被引:1,自引:0,他引:1
应用Fay’s三阶段理论,建立了海面溢油的扩散、蒸发模型,并考虑了风、海流(潮流)影响,对溢油的漂称模式进行了讨论。最后,选择了大庆原油,在大连湾内对上述模型进行了计算,并得到了较为满意的结果。 相似文献
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海面粗糙度对于海洋工程、海气相互作用和军事海洋研究来讲非常重要,但由于海面粗糙度难以直接测量,因此只能通过间接计算得到。随着卫星微波遥感技术的发展,卫星高度计、散射计等为研究海面粗糙度提供了新的研究方法和研究渠道。作者利用T/P星1997-2000年的高度计反演得出的海面风场数据实现了对海面粗糙度的反演,并对太平洋海域(15°-30°N,135°-150°E)海面粗糙度进行研究,同时研究发现太平洋海面粗糙度在El-Nino、La-Nina期间有明显变化。 相似文献
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Region-specific algorithm to derive chlorophyll concentration from Coastal Zone Color Scanner (CZCS) images was adopted following field measurements in the Southeastern Mediterranean Sea, in June 1992. Reflectance in the range 400 to 700 nm, chlorophyll concentration and seston dry weight were measured simultaneously at 21 stations. The optical model used based on algorithm for Case I waters, using shipboard simulation of CZCS channels for adaptation of parameters. The resulting model was validated with an independent data sets from series of cruises in the Southeastern Mediterranean (1981–1984). Concurrent CZCS images were used for retrieval of the radiance ratio Channel 1/Channel 3, for each station. The resulting ratios were then used to calculate chlorophyll concentrations. A comparison between those calculated concentrations and the actual chlorophyll measurements showed that an estimation error of chlorophyll as low as 0.013 mg m−3 was achieved. 相似文献
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Variability of snow and ice thermal, physical and optical properties pertinent to sea ice algae biomass during spring 总被引:6,自引:2,他引:4
Changes in the thermal, physical and optical properties of the snow–sea ice system and feedbacks between various temporal and spatial scales affect accumulation of microalgae at the sea ice bottom and are the focus of this research. During the spring transition period, May 4 to June 9, 2002, we closely monitored atmospheric conditions and properties of the snow–sea ice system, including thermal, physical and optical properties of the snow cover (e.g., temperature, grain size, light attenuation), ice thickness and salinity, and biomass of bottom ice algae. Results show that snowdrift size averaged 31.2 by 10.6 m with a depth range of 2 to 45 cm. Snowpacks also varied in age, distinguished by coincident peaks of snow salinity and grain size and a lower PAR extinction coefficient. Spatial variability of the snowpack was superimposed by temporal variability associated with seasonal snow–ice melt and wind redistribution of snow. Maximum biomass of ice algae was observed under intermediate snow covers. Under thin snow covers, algae biomass declined steadily coincident with seasonal warming and desalination of the ice cover. Under thick snow covers, algae biomass was negatively correlated with snow depth. These results suggest that thin snow covers were associated with a thermal effect causing sloughing of algae, whereas under deep snow, algae were still light limited and thermally insulated from the warming atmosphere. Our results highlight the importance of snow cover history on the sea ice system operating below. Furthermore, in the context of current climate change scenarios, shifts in snow depth would result in decreases of ice algae biomass. 相似文献
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在救灾和战争等非常情况下,利用中小型近海滚装渡轮或改装后的渔轮渡海输送重荷载,具有可征用船只数量多和装卸载不依赖吊装设备等优点。缺乏港口屏蔽的海浪环境中重荷载进行滚动卸载时,必须考虑波浪对船的作用和重荷载与船的相互作用。本文通过对船在波浪中所受表观重力和表观浮力的分析,导出波浪作用力矩的计算公式。运用浮基多体系统动力学方法,建立波浪-浮基-重荷载系统的动力学方程。使用标准的龙格-库塔四阶方法进行数值积分求解。考虑海况、船型和重荷载在船上运动参数等因素,计算了各工况下的横摇运动响应。进而给出了重荷载安全快速卸载的驾驶操作要求及相关运动规律。 相似文献