Expanded adaptive fuzzy sliding mode controller using expert knowledge and fuzzy basis function expansion for UFV depth control

Generally, the underwater flight vehicle (UFV) depth control system operates with the following problems: it is a multi-input multi-output (MIMO) system, it requires robustness, a continuous control input, and further, it has the speed dependency of controller parameters. To solve these problems, an expanded adaptive fuzzy sliding mode controller (EAFSMC), which is based on the decomposition method designed by using an expert knowledge and the decoupled sub-controllers and composition method designed by using the fuzzy basis function expansions (FBFEs), is proposed. To verify the performance of the EAFSMC, the depth control of UFV in various operating conditions is performed. Simulation results show that the EAFSMC solves all problems experienced in the UFV depth control system online.     

Application of a two-dimensional depth-averaged hydrodynamic tidal model

A two-dimensional hydrodynamic model application to the San Francisco Bay was performed using the Boundary-Fitted HYDROdynamic model (BFHYDRO). The model forcing functions consist of tidal elevations along the open boundary and fresh water flows from the Delta Outflow. The model-predicted surface elevations compare well with the observed surface elevations at five stations in San Francisco Bay. Mean error in the model predicted surface elevations and currents are less than 7 and 9%, respectively. Correlation coefficients for surface elevations and currents are higher than 0.94 and 0.95, respectively. The amplitudes and phases of the principal tidal constituents at 24 tidal stations in San Francisco Bay, obtained from a harmonic analysis of a 90-day simulation compare well with the observed data. The predicted amplitude and phase of the M₂ tidal constituent at these stations are respectively within 8 cm and 8° of the observed data. Maximum errors in the K₁ harmonic amplitudes and phases are less than 3 cm and 7° respectively. The asymmetric diurnal and semi-diurnal tidal ranges and spring and neap tidal cycles of the surface elevations and currents are well reproduced in the model at all stations.     

双层局部开孔板沉箱对波浪反射的理论研究

提出了一种用于研究由双层开孔板和一个不透水后板的开孔结构对斜向波反射率的理论分析方法。整个流域被分成三个子域，在每个子域内应用特征函数展开法以得到该域内包含未知展开系数的势函数的表达式，在速度势的展开中，考虑了非传播模态波浪的影响。通过匹配开孔板处的边界条件可以求解待定的展开系数，继而求解双层开孔板防波堤结构对斜向波的反射率。数值计算结果与试验结果进行了比较，符合较好。并进一步讨论了几个重要因素对反射系数的影响。     

A Sensitivity Analysis of the Waterline Method of Constructing a Digital Elevation Model for Intertidal Areas in ERS SAR scene of Eastern England

A sensitivity analysis of the waterline method of constructing a Digital Elevation Model (DEM) of an intertidal zone using remote sensing and hydrodynamic modelling is described. Variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ERS Synthetic Aperture Radar (SAR) images of the Humber/Wash area on the English east coast acquired between 1992 and 1994. Waterlines from these images are heighted using a hydrodynamic tide-surge model and interpolated using block kriging. On 1:500 slope beaches, an average block height estimation standard deviation of 18–22 cm is achieved. This rises to 27 cm on 1:100 slope beaches, and 32 cm on 1:30 slope beaches. The average heighting error at different slopes is decomposed into components due to waterline heighting error, inadequate sensor resolution and interpolation inaccuracy. It is shown that, at 1:500 slope, waterline heighting error and interpolation inaccuracy are the main error sources, whilst at 1:30 slope, errors due to inadequate sensor resolution become dominant. The ability of the technique to generate intertidal DEMs for almost the entire coastal zone in a complete ERS SAR scene covering 100×100 km is demonstrated.     

潜艇疲劳载荷的概率模型

探讨了建立潜艇疲劳载荷概率模型的方法，引入了正态分布和两参数威布尔分布两种概率模型。两参数威布尔分布较适合于用来描述潜艇下潜深度分布的概率特征。可根据潜艇的设计参数、任务及航行区域等因素来选取最可能的分布形式获得潜深分布密度函数。潜艇疲劳热点部位的应力(应变)幅值分布，可由应力(应变)和潜深的关系通过相应的变换得到。     

Structural modeling and testing of a concrete canoe

A finite element model is set up and experimental tests are performed to help understand the behavior of a concrete canoe and subsequently optimize its design. First, the performance criteria that must be satisfied to participate at the annual ASCE/Master Builders competition are described. Then, the finite element model and the different loading cases that were studied are presented. Results from these loading cases are discussed and used to optimize the material properties as well as the thickness of the hull and the dimensions of the gunwale and reinforcing ribs. Static and dynamic experimental tests were also conducted to validate the results of the finite element analyses. The results indicate that the main stresses and strains are caused by the static load cases. The additional stresses caused during races are small.     

渤、黄、东海内潮的数值模拟

在全球的海洋中,中国东海和临近海域是最显著的内潮生成地之一。本文采用NODC(Levitus) World Ocean Atlas 1998提供的季平均温、盐资料,计算海水的密度,并计算垂向密度梯度的最大值点,得到一个较符合海水实际的密度分层。使用三维非线性数值模型(将海洋分为2层)研究了潮汐(M2,S2,K1,O1分潮)作用下渤黄东海的内潮,揭示了整个海区内潮起伏的空间分布,结果发现大振幅的波动均发生在台湾东北(冲绳海槽)海域和中国近海地形突变之处,其中前者更显著。对于各分潮模拟得到的表面潮与TOPEX/Poseidon高度计资料基本一致。研究结果表明上层海水的深度和厚度的梯度对内潮有一定的影响;冬季分布区域比夏季小,强度比夏季大。