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应用卫星遥感技术反演浅海水深,对于航运安全、海洋工程、海洋军事等具有重要意义.对IKONOS高分辨率卫星影像数据进行分析处理,提出一种结合主成分分析变换的神经网络水深反演法.通过IKONOS多光谱数 据建立波段比值模型,并对该模型进行主成分分析变换,应用神经网络技术对浅海水深进行定量反演.研究结果表明,这种方法能够很好的建立IKONOS多光谱数据与实测水深数据之间的非线性关系,减少了其他外界环境因素的影响(如海水底质、海水类型等);同时去掉了波段比值模型中线性相关的冗余信息,比传统的线性回归水深反演模型具有更高的可靠性和反演精度. 相似文献
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水体中的泥沙分布非常广泛,它们对进入水环境系统的营养性污染物具有强烈的表面物理、化学和生物等作用,是污染物迁移、转化的主要载体。污染物与泥沙的作用对水体生态环境会产生影响。本文结合国内外研究最新动态,对泥沙及营养性污染物的形态、泥沙与水体水质的关系作了概述,重点对影响营养性污染物释放与吸附的因子作了分析,并对泥沙对营养性污染物吸附与释放存在的问题发表了一些见解。 相似文献
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利用遥感图像反射率和实测水深值之间的相关性,建立了动量BP人工神经网络水深反演模型,对缺失的1995年的水下地形资料进行了插补,并利用插补后的1973~2003年南港水下地形资料计算了南港河段的泥沙冲淤量,分析了南港河段等深线和横断面的变化,结果表明BP人工神经网络水深反演模型能反演出研究区的水深分布情况,特别是对水深浅于-5m区域,模型反演效果更好。 相似文献
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掌握灌河口海域泥沙运动规律是开展灌河口航道整治研究的基础。以现场所取泥沙为研究对象,通过大型波浪水槽试验研究灌河口海域泥沙在不同的水深、不同的波周期和波高条件下的悬浮规律。通过静水沉降试验研究灌河口海域泥沙在不同初始浓度、不同水深下的沉降特性。结果表明,在极限波高情况下,水体上部区域含沙量较小,且沿垂线分布变化较小,但水体底部附近含沙量较大,总体上底部含沙量比上部水体含沙量大0.25~0.96 kg m^3;不同水深以及不同初始含沙量情况下,泥沙沉降速度0.08~0.20 cm s,与单颗粒泥沙沉速在同一量级,灌河口海域泥沙絮凝作用较弱。 相似文献
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浮式生产储油轮(FPSO)是当今海洋石油天然气开发的主要设备之一。针对外输系统作为FPSO重要的一个子系统,但其传统维修策略过于依赖经验的缺陷,从可靠度角度出发,通过对失效模式和失效概率的分析从而确定较为合理的检修周期和大修周期。采取失效模式和效果分析(FMEA)方法确定主要失效模式及其关系,再利用动态故障树分析(DFTA)方法获得最小割集及相应故障时间,最后通过成组维修理论从全局最优化,经济性角度确定大修周期约为3.23年。经过与工程实际数据的对比,验证了该方法的可行性和适用性。 相似文献
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Pigments, size and distribution of Phycoerythrin-containing unicellular cyanobacteria Synechococcus spp. within the euphotic zone were studied for the first time in April–May 1994 in the western and southwestern Black Sea by epifluorescence microscopy and flow-cytometry. Synechococcus was present in varying quantities at every station and depth studied. Surface spatial distribution of Synechococcus revealed that cells were much more abundant in offshore waters than near coastal regions under the direct influence of the Danube river. Minimum and maximum cell concentrations ranged between 9×102 and 1.45×105 cells/ml at the surface, between 2×103 and 1.23×105 cells/ml at the chlorophyll sub-maximum layer, and between 1.3×102 and 3.5×102 at the nitrite maximum layer. Cells at the chlorophyll sub-maximum layer (based on in-situ fluorometer readings) fluoresce brighter and longer than the ones at the surface and lower depths. Spectral properties of chromophore pigment types of total 64 clonal isolates from different depths down to the lower layer of the euphotic zone (60 m) in the southern Black Sea coast revealed that all have type 2 phycoerythrobilin in common, lacking in phycourobilin. In vivo fluorescence emission maxima for the phycoerythrobilin were about the same (578 nm) for all isolates. All isolates examined showed in vivo absorption maxima at between 435 and 442 nm and at about 681 nm due to chlorophyll-a. Based on the flow cytometer mean forward light scatter data for size distribution, it could be concluded that cells at the surface mixed layer (0–10 m) were larger in cell size than the cells at lower depths (20–60 m). 相似文献
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A novel flywheel energy storage(FES) motor/generator(M/G) was proposed for marine systems.The purpose was to improve the power quality of a marine power system(MPS) and strengthen the energy recycle.Two structures including the magnetic or non-magnetic inner-rotor were contrasted in the magnetostatic field by using finite element analysis(FEA).By optimally designing the size parameters,the average speed of FEA results of was 17 200 r/m,and the current was controlled between 62 and 68 A in the transient field.The electrical machine electromagnetism design was further optimized by the FEA in the temperature field,to find the local overheating point under the normal operation condition and provide guidance for the cooling system.Finally,it can be concluded from the comprehensive physical field analysis that the novel redundant structure M/G can improve the efficiency of the M/G and maintain the stability of the MPS. 相似文献
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Deep and narrow channels in Danish Straits are one of the governing factors for the Baltic–North Sea water and salt exchange. The channels have a depth up to 50 m and a horizontal scale of a few hundred meters. The typical horizontal resolution used in current operational three dimensional Baltic–North Sea models is 1 nautical mile (nm) which can not well resolve these deep channels. In this paper, an alternative method is used to generate the 1 nm resolution bathymetry so that the deep channel is well resolved and at the same time the total water volume is roughly conserved. The impact of the new bathymetry on modelling water and salt transports as well as temperature and salinity structure is assessed by comparing a 3-year model run with the adjusted bathymetry and a control run with the averaged bathymetry. Volume and salt transports through the Great Belt are examined in the two runs. The results show that the model ocean is dominated by a typical two-layer transport (i.e., upper brackish Baltic outflow and lower saltier inflow), and the new bathymetry significantly enhances the two-layer transport. The lighter Baltic outflow is increased by 18% in the upper 10 m and saltier deep inflow is increased by 300% (in comparison with the old bathymetry) below 10 m. The total net transport into the Baltic Sea is increased by 13%. The temperature and salinity structure is also significantly influenced by the bathymetry, especially during inflow events. The stratification is strengthened and the bottom salinity is increased in Danish Straits and adjacent waters. The bathymetry impact is found significant through the entire 3-year model run period, and the signal is propagated to a large area covering the Stopple Channel. Comparison with observations show that such changes are positive improvements to the models. The results suggest that the deep channels in the Danish Straits have to be carefully resolved in order to correctly simulate the Baltic–North Sea water exchange. 相似文献
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A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions.The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors(SCFs) at the inner saddle,outer saddle,and crown positions on the central brace.Based on results of finite element(FE) analysis and through nonlinear regression analysis,a new set of SCF parametric equations was established for fatigue design purposes.An assessment study of equations was conducted against the experimental data and original SCF database.The satisfaction of acceptance criteria proposed by the UK Department of Energy(UK DoE) was also checked.Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties.It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results.Hence,it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints.Good results of equation assessment according to UK DoE acceptance criteria,high values of correlation coefficients,and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations.Therefore,the developed equations can be reliably used for fatigue design of offshore structures. 相似文献
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针对航行于海上船舶的横摇运动具有非线性非平稳的特点,探索采用希尔伯特-黄变换(Hilbert-Huang Transform,简称HHT)方法研究船舶在波浪中的非线性横摇运动的响应特性,对几种不同海况下的船舶的典型运动响应,首先通过经验模态分解提取典型横摇响应信号的固有模态函数(Intrinsic Mode Function,简称IMF),再对分解得到的IMF分量进行Hilbert变换,求得典型横摇响应信号的Hilbert谱,通过分析所得谱图的特征,获得船舶非线性横摇运动响应的动力学特性。仿真结果表明,HHT方法在分析船舶非线性横摇运动的动力学特性研究中具有可行性和有效性,从而为船舶运动分析研究提供了一个新的方法。 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