基于图像处理的异重流与系泊结构物作用模型试验研究

异重流广泛存在于江河入海口附近,速度快、破坏力强,给近海工程的施工作业带来不小的难度。为了研究系泊结构物在异重流作用下的运动响应,基于图像处理技术,采用开闸式异重流模型试验方法,将异重流和结构物作为研究对象。利用图像处理技术处理由高速摄像机拍摄的结构物运动图片,从而获得结构物运动的时历曲线。对比讨论了不同密度比的异重流对结构物运动的影响,同一密度比的异重流对处于不同深度结构物运动的影响。研究结果表明：结构物运动受异重流密度的影响较大,结构物的运动幅值随着密度的增大而增大。处于高密度流体非混合层的结构物受到异重流的作用会产生大幅度的顺时针旋转和正x方向偏移;位置较高的方柱受到淡水的主导作用,会产生逆时针旋转和负x方向偏移。位于盐水与淡水剧烈混合区域的方柱并不会产生单一方向的偏移,而是在平衡位置附近波动。     

验证法处理密立根油滴实验探讨

为了更好、更快地进行密立根油滴实验,减小实验中的误差,对常规处理密立根油滴实验数据的验证法进行分析研究,用分析后的结果反过来指导实验。通过适当选取密立根油滴实验中的平衡电压和下落时间,可以在一定范围内减小实验误差,有利于尽快锁定平衡电压,快速准确的完成实验的测量,节约实验时间。     

Interspecies competition for nutrients between Prorocentrum donghaiense Lu and Skeletonema costatum (Grev.) Cleve in mesocosm experiments

Three mesocosm experiments were conducted in the East China Sea during blooms of Prorocentrum donghaiense Lu in May of 1998, 2002 and 2003 to examine the role of nutrients in the formation of these harmful algae blooms (HABs). The results showed that there was interspecies competition between P. donghaiense and Skeletonema costatum (Grev.) Cleve. The cell number of P. donghaiense and S. costatum accounted for about 85% and 11% of the total cell number of phytoplankton respectively at the beginning of the experiment in May 1998. In May 2002, at the beginning of the experiment, the cell number of P. donghaiense accounted for 55%—66% of the total and S. costatum accounted for 32%—42%. The density of P. donghaiense and S. costatum was over 95% and 1%—5% respectively in May 2003. The results of these three mesocosm experiments showed that the dominant species in this specific community varied with different nutrient availability. Under lowphosphate conditions, the dominant species was P. donghaiense, while S. costatum became dominant in phosphatereplete cases. The average growth rate (1.08 d-1) of S. costatum in exponential growth phase was higher than that (0.39 d-1) of P. donghaiense. In the mesocosm, S. costatum predominated in the mesocosm by its rapid growth. When phosphorus was depleted, the cell number of S. costatum dropped rapidly, while P. donghaiense Lu decreased more slowly. The results from mesocosm experiment may explain why: (1) P. donghaiense bloom usually occurs in May, when phosphate concentration is low; (2) the bloom of S. costatum appears in early spring and summer time, when nutrients increase with increasing Changjiang River (Yangtze River) runoff; (3) the bloom of S. costatum is short and that of P. donghaiense Lu can last more than a month in the East China Sea.     

Iron geochemistry under mussel rafts in the Galician ria system (Galicia-NW Spain)

The intensive mussel culture carried out in the past 40 years in the Rias of Vigo and Arousa (Galicia-NW Spain) has led to substantial changes in the ecology and geochemistry of the seabed in these areas. Organic C enrichment of the seabed has generated strongly reducing conditions that directly affect the geochemistry of Fe and S. In the present study a total of six sediment cores were collected from the seabed under mussel rafts, and two different layers were distinguished: the biodeposit generated by the mussels, and the sediment situated immediately below this. Samples of each were analyzed to determine the pH, redox potential, sulphate and chloride in the interstitial water, as well as total percentage of organic C (TOC), N and S. Sequential extraction of the samples differentiated six fractions of Fe: exchangeable, carbonate, ferrihydrite, lepidocrocite, goethite and pyrite. The contents of total Fe, Fe associated with silicates, Fe soluble in 1 M HCl and AVS-Fe were also determined. In general, both the biodeposit and the sediment were anoxic (Eh < 100 mV) and there were no significant differences between the two in the total Fe or in the Fe associated with silicates, which appears to indicate that the input of Fe to the system did not vary greatly. However, there were significant differences between the sediment and the biodeposit in terms of the forms of Fe in each layer. The concentrations of pyrite in the biodeposit (0.37 ± 0.25 μmol g⁻¹) were high but significantly lower than in the sediment (1.10 ± 0.20 μmol g⁻¹), and there remained large quantities of reactive-Fe that were susceptible to pyritisation. In contrast, in the sediment, the reactive-Fe was intensively pyritised, and judging from the ratio of TOC–DOP, it limited synthesis of pyrite. Furthermore, a plot of the concentration of pyrite-S against TOC revealed an excess of ∼15% of pyrite-S, which is explained by the partial decoupling of pyrite formation from organic matter accumulation, caused by the formation of pyrite from the H₂S generated by the anaerobic oxidation of methane. The latter process also appears to favour, although to a lesser extent, the precipitation of Ca carbonate, with incorporation of Fe.     

Single particle analysis of oceanic suspended matter during the SEEDS II iron fertilization experiment

Suspended particles collected from surface seawater during the SEEDS II (Subarctic Iron Experiment for Ecosystem and Dynamics Study II) experiment were analyzed individually using an electron probe X-ray micro analyzer and characterized by size and elemental composition. Their numbers, relative abundances, and relative particle volume all showed clear differences between samples collected inside vs. outside the phytoplankton bloom that developed following the addition of iron. Throughout the study, Si-rich, Ca-rich and Organic particles were dominant and their number increased inside the fertilized patch; these particles accounted for 21%, 13% and 58% of the particles examined, respectively. Si-rich or Ca-rich particles commonly consisted of fragments of diatom frustules and coccolithophorids. There was consistently greater percentage of Ca-rich particles and lower percentage of Si-rich particles inside the patch than outside of it in number, but both types of these particles apparently occupied a larger volume inside the patch than outside of it. Organic particles, that showed having peaks in smaller diameter particles, increased apparently inside the patch with time after iron fertilization. The Organic particles had a more diverse mixture of both bio-related and crustal trace elements than the other types of particles. These results suggest that the increase in suspended particles following the iron enrichment was due to a combination of detrital material and live phytoplankton.     

热带太平洋对风应力拖曳系数响应的敏感性试验

为了检验一个准全球的海洋环流模式中热带太平洋对风应力变化的响应,使用NCEP月平均再分析资料计算的强迫场强迫该模式进行控制试验,在(10.5°S～9.5°N,159.75°E～110.25°W)的区域增大或减小风应力拖曳系数进行敏感性试验,并把试验结果与同时段的SODA资料进行分析比较.该模式基本能模拟出海洋环流的基本气候态,但是对一些细节描述还不够准确.试验结果表明,风应力减小时可以改善模式对热带东太平洋冷舌的模拟,而对次表层温度和流场的刻画能力较弱.增大风应力则对次表层温度和流场的模拟有所改善.通过对模式中热量收支的分析可知,平流过程、扩散过程对热带太平洋海表温度的变化起到了重要的作用;海表面热交换可以促使海温距平向相反的方向发展.垂直输送对赤道中东太平洋表层的降温起重要作用,抑制了次表层的增暖,水平平流过程则促进了赤道太平洋次表层的增暖.     

垂向动载荷下桶形基础响应实验研究

对垂向动载荷作用下吸力式桶形基础(简称桶基)响应进行离心机实验模拟.结果表明,在垂向动载荷作用下,当载荷幅值超过一定值时,桶基周围砂土软化甚至液化,发生明显的沉降.桶基周围土体的沉降随着载荷幅值的增加而增加.由于液化区的滤波和对动载的衰减作用,发生沉降的范围有限,离桶壁约一倍桶高距离.超孔隙水压从桶基边沿水平向逐渐衰减,从土面开始往下逐渐衰减到零.桶基周围砂土完全液化的厚度随载荷幅值的增加而增加,最大值约为桶高的40%.     

机载激光扫描测距(LIDAR)系统的应用试验

机载激光扫描测距技术,使传统的摄影测量技术发生了质的飞跃。本文在介绍机载激光扫描测距原理、系统组成、技术特点的基础上,对机载激光扫描测距系统进行了试验性研究,并得出了机载激光扫描测距系统的试验精度。     

Investigation of Hydroelastic Ship Responses of An ULOC in Head Seas

Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed.