海上孤立混凝土构筑物的爆破拆除

在海洋工程中,采用爆破手段拆除海上孤立混凝土构筑物或清理孤立大块石是一种快速、有效的方法。文中详细介绍了爆破方案的确定、爆破孔网参数的设计、爆破药量的计算以及安全防护措施,对于类似工程的实施具有重要的参考价值。     

动态水平-海面辐照度测量的新理念

目前海面辐照度的测量,在消除天空光影响的同时,却引入了仪器接收面倾斜的误差。作者经过多年的实践,提出动态水平的理念和一整套技术方法,解决了这一问题。动态水平技术的应用,需应用最新技术的发展,而且必然引起海洋光学测量仪器、特别是海洋光学浮标的一系列变革,对海洋水色遥感具有重要的意义和影响。     

三亚湾浮游动物数量分布及群落特征的季节变化

根据三亚湾2005年春、夏、秋和冬季航次的调查资料,分析了这4个季度的浮游动物的种类组成、优势种、群落结构、丰度和生物量的时空变化。经过鉴定共有终生性浮游动物125种,阶段性浮游动物17种,其中毛颚类幼虫和短尾溞状幼虫是各个季度都出现的优势种。三亚湾的浮游动物可以分为河口类群、暖水沿岸类群和广布暖水外海类群。全年浮游动物平均丰度为95.91ind·m-3,浮游动物平均生物量为69.22mg·m-3;浮游动物丰度的季节分布是夏>秋>春>冬,平均生物量的季节分布是秋>夏>春>冬,总体上一般是夏秋季高于冬春季。冬季浮游动物丰度与浮游植物细胞总密度之间没有相关性。     

南海北部藻类粒级结构及色素成分对浮游植物吸收系数的影响

在珠江口、广东沿岸及南海北部三个航次生物-光学数据的基础上,研究了色素打包效应和色素成分的变化对浮游植物吸收系数的影响,结果表明,两种因素对吸收系数都有较大的贡献,但在不同的水体它们的影响程度各有不同.对网采浮游植物含量较高的珠江口和广东沿岸的水体而言,色素打包效应较强,对675 nm处比吸收系数的贡献平均分别为40%和20%;对微型浮游植物占主导地位的南海北部航次的水体,打包效应较弱,对675 nm处比吸收系数的影响平均仅为6%.采用多元线性回归的方法对吸收光谱进行分析,发现除叶绿素a之外的辅助色素对吸收系数的贡献主要表现在蓝绿光波段,三个航次440 nm波长处对总吸收的贡献平均分别为44%,43%和53%,其中对珠江口和广东沿岸航次的水体主要是光合类胡萝卜素的吸收贡献,而对南海北部航次的水体除了光合类胡萝卜素以外还要受到光保护类胡萝卜素的影响.由于河口、近岸和外海水体藻类粒级结构和辅助色素成分对浮游植物吸收系数的贡献有明显的差异,在南海北部水体建立比较精确的生物光学模型时,需考虑藻类粒级结构及色素成分对浮游植物吸收系数的影响.     

南黄海和东海毛颚类生态特征的研究Ⅱ.群落特征

在对南黄海和东海毛颚类生态特征的研究数量分布特征后的续篇.重点探讨调查区毛颚类群落性质和群落结构的特征及与海区环境因子的相关性.结果表明,本区共记录毛颚类28种,种类季节变化不明显,周年共有种达64.3%;但群落优势种则有季节差异与区域差异.毛颚类群落多样性指数(H')和均匀度(J')年均值分别为1.68和0.64.H'的平面分布表现出外部海区大于近岸海区的分布格局.在群落中存在4个生态类群,其中近海暖温带类群和广盐暖水类群可分别指示黄海水、浙江沿岸流和东海陆架混合水在南黄海和东海这两个海区的相互推移和消长过程.此外,从不同侧面的计算分析也表明,影响群落特征值(H')的主要因子是温度和盐度.群落性质是以近岸暖温带低盐种和暖水广布种为主,近岸暖水种和大洋暖水种占一定比例的暖温带-亚热带群落结构的特点.     

A time-dependent numerical model of the mild-slope equation

On the basis of the previous studies, the simplest hyperbolic mild-slope equation has been gained and the linear time-dependent numerical model for the water wave propagation has been established combined with different boundary conditions. Through computing the effective surface displacement and transforming into the real transient wave motion, related wave factors will be calculated. Compared with Lin’s model, analysis shows that calculation stability of the present model is enhanced efficiently, because the truncation errors of this model are only contributed by the dissipation terms, but those of Lin’s model are induced by the convection terms, dissipation terms and source terms. The tests show that the present model succeeds the merit in Lin’s model and the computational program is simpler, the computational time is shorter, and the computational stability is enhanced efficiently. The present model has the capability of simulating transient wave motion by correctly predicting at the speed of wave propagation, which is important for the real-time forecast of the arrival time of surface waves generated in the deep sea. The model is validated against analytical solution for wave diffraction and experimental data for combined wave refraction and diffraction over a submerged elliptic shoal on a slope. Good agreements are obtained. The model can be applied to the theory research an d engineering applications about the wave propagation in a biggish area.     

鄂尔多斯地块周缘三维地壳速度结构研究

鄂尔多斯地块及周缘位于青藏高原与华北地块之间,其内部无大断裂分布,而周缘却由活跃的地震带——活动断陷带和弧形断裂带包围.因此,鄂尔多斯地块内部无6级以上大地震分布,而周缘地震活动则频度高、强度大(图1),历史上发生多次破坏性大地震,如:1654 年天水南8.0 级、1879 年武都南8.0级、1920 年宁夏海原81/...     

Risk assessment of a vertical breakwater using possibility and evidence theories

This paper proposes a preliminary investigation of possibility and evidence theories in a risk analysis of a vertical breakwater. The results obtained from both theories are presented and compared to the Monte Carlo simulations. This study indicates that the evidence theory approach is more flexible than the possibility theory approach and may provide a useful tool for a joint handling of variability and imprecision in the computation of risk. On the other hand, the possibility theory approach may have a good potential to be used for risk assessment of coastal structures, when sufficient data are not available.     

Application of a vanishing, quasi-sigma, vertical coordinate for simulation of high-speed, deep currents over the Sigsbee Escarpment in the Gulf of Mexico

Recent observations over the Sigsbee Escarpment in the Gulf of Mexico have revealed extremely energetic deep currents (near 1 m s⁻¹), which are trapped along the escarpment. Both scientific interest and engineering needs demand dynamical understanding of these extreme events, and can benefit from a numerical model designed to complement observational and theoretical investigations in this region of complicated topography. The primary objective of this study is to develop a modeling methodology capable of simulating these physical processes and apply the model to the Sigsbee Escarpment region. The very steep slope of the Sigsbee Escarpment (0.05–0.1) limits the application of ocean models with traditional terrain-following (sigma) vertical coordinates, which may represent the very complicated topography in the region adequately, can result in large truncation errors during calculation of the horizontal pressure gradient. A new vertical coordinate system, termed a vanishing quasi-sigma coordinate, is implemented in the Navy Coastal Ocean Model for application to the Sigsbee Escarpment region. Vertical coordinate surfaces for this grid have noticeably gentler slopes than a traditional sigma grid, while still following the terrain near the ocean bottom. The new vertical grid is tested with a suite of numerical experiments and compared to a classical sigma-layer model. The numerical error is substantially reduced in the model with the new vertical grid. A one-year, realistic, numerical simulation is performed to simulate strong, deep currents over the Escarpment using a very-high-resolution nested modeling approach. The model results are analyzed to demonstrate that the deep-ocean currents in the simulation replicate the prominent dynamical features of the observed intense currents in the region.     

误差椭圆在精密工程测量中的应用研究

进行精密工程测量时,要根据工程的要求和现场的具体条件,通过精度分析拟定切实可行的观测方案,采用合适的测量方法来获得最可靠的成果。据此探讨了误差椭圆在精密工程测量中的应用。