AN ANALYSIS OF ACOUSTICAL SCATTERING FROM ELASTIC OBSTACLES BY FINITE AND BOUNDARY ELEMENT COMBINATION APPROACH

A method combining boundary and finite element approaches as well as modal analysis to solve the acoustical scattering from elastic obstacle in infinite fluid is described. An elastic cylinder with finite length immersed in water is chosen as an example for numerical demonstration. The computed frequency response and direction pattern of the backscattering target strength of the cylinder are conformable to those measured.     

机载雷达高度计对海况及海面风速的测量研究

运用我国自行研制的ＺＨＧ－１型Ｘ波段机载雷达高度计于１９９５年４月１３日－４月１８日在青岛附近海域进行的海上飞行实验数据，及导出的均方根波高、有效波高、均方根波陡算法模型，得到了上述海况参数值。     

海带育苗水系微生物的监测与控制

现场及实验室试验表明,近岸水中细菌丰度因时因地有较大差别,近岸水在潮周期中以高潮前后细菌量较低;海水在沉淀贮存过程中细菌丰度有明显变化,且与海水中营养物含量、贮存温度等有关;海水经沙滤后能减少细菌90％左右;回水中脱落苗进入贮水池,是贮水池中细菌数量增长10余倍的主要原因。     

三倍体合浦珠母贝不育性研究

对三倍体合浦珠母贝Ｐｉｎｃｔａｄａｍａｒｔｅｎｓｉｉ（Ｄ．）春、秋两繁殖盛期的生殖腺进行了组织学观察，并对其配子形成及受精、发育进行了研究。结果表明：合浦珠母贝三倍体的生殖腺发育差，生殖细胞数量少，极少个体能见到成熟卵母细胞和精子；三倍体的配子能完成受精作用，能发育至直线铰合期。配子多为非整倍体，其染色体数目多为１４—２８，胚胎染色体数目主要为２８—４２，故胚胎不能正常发育。因此，三倍体合浦珠母贝是不育的．     

大鹏湾夜光藻种群的季节变化和分布特征

于１９９０年３月－１９９２年６月对中国南海大鹏湾盐田附近海域的夜光藻种群动态及时空分布进行了综合调查，结果表明，夜光藻种群的出现期间一般为每年的１－６月，最早是１９９１年的１２月，娄量高峰期为３－５月，种群密度的波动极为显著；调查期间共发生８次赤潮，且都发生在３月初至５月初；大鹏湾夜光藻赤潮的发生特点是，赤潮的发生和消失突然，持续时间短，一般不超过３ｄ。     

Notes Ecological study of macrobenthos in Fuqing Bay

ＮｏｔｅｓＥｃｏｌｏｇｉｃａｌｓｔｕｄｙｏｆｍａｃｒｏｂｅｎｔｈｏｓｉｎＦｕｑｉｎｇＢａｙ￥／／ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｅｃｏｌｏｇｉｃａｌｓｔｕｄｙＯｆｍａｃｒｏｂｅｎｔｈｏｓｈａｓｎｏｔｂｅｅｎｒｅＰＯｒｔｅｄｔｈｏｕｇｈｔｈｅｍａｒｉｎｅ...     

海水硬骨鱼白点病组织病理学研究

在光镜水平下研究了刺激隐核虫寄生黄鳍鲷和真鲷后引起宿主组织病理学的变化。该寄生虫可在宿主皮肤、鳃上皮和舌上皮的组织内寄生。与正常组织相比,被寄生的皮肤表皮层明显增厚、粗糙,其增厚部分主要是粘液细胞层、表皮层与真皮层间的联系被破坏。寄生囊内有较大的空隙。虫体内含有大量的宿主细胞残骸。由于寄生虫的感染,使得非寄生部位的脏器也出现某些病理变化:肝细胞萎缩,窦状隙增大;脾肾内都有颗粒性沉积。本研究结果还与淡水“白点”病引起的病理组织学变化进行了比较。     

FINITE ELEMENT METHOD IN CALCULATION OF KUROSHIO CURRENT

We establish the equations of finite element approximation for three-dimensional ocean current and calculate the Kuroshio current in the eastern sea area off Taiwan Province. The interpolation error of finite element approximation is given as Eq. (3. 14).     

Robust adaptive control of underactuated ships on a linear course with comfort

This paper addresses an important problem in ship control application—the robust stabilization of underactuated ships on a linear course with comfort. Specifically, we develop a multivariable controller to stabilize ocean surface ships without a sway actuator on a linear course and to reduce roll and pitch simultaneously. The controller adapts to unknown parameters of the ship and constant environmental disturbances induced by wave, ocean current and wind. It is also robust to time-varying environmental disturbances, time-varying change in ship parameters and other motions of the ship such as surge and heave. The roll and pitch can be made arbitrarily small while the heading angle and sway are kept to be in reasonably small bounds. The controller development is based on Lyapunov’s direct method and backstepping technique. A Lipschitz continuous projection algorithm is used to update the estimate of the unknown parameters to avoid the parameters’ drift due to time-varying environmental disturbances. Simulations on a full-scale catamaran illustrate the effectiveness of our proposed controller.