Forced vibration analysis of an offshore tower carrying an eccentric tip mass with rotary inertia due to support excitation     

Jong-Shyong Wu  Chin-Tzu Chen 《Ocean Engineering》2007,34(8-9):1235-1244

Dynamic responses of structures due to earthquake excitation are the important problems in engineering, thus, the information concerned is plenty. However, most of the literature is relating to the discrete methods, particularly to the finite element method (FEM), and the one relating to the method combining both the “continuous” and “discrete” models is rare. The objective of this paper is to provide some information in this respect. First, the analytical solution for the natural frequencies and normal mode shapes of a “continuous” tower, without contacting water (or “dry” tower), carrying an eccentric tip mass possessing rotary inertia is determined. Next, the partial differential equation of motion for the forced vibration of the tower, contacting water (or “wet” tower), subjected to support excitation is transformed into a matrix equation by using the last natural frequencies and normal modes shape of the freely vibrating dry tower. Finally, the numerical integration method is used to solve the matrix equation to yield the seismic response of the wet tower. In theory, the mode superposition method is correct only if the total number of modes considered approaches infinity, however, numerical results of this paper reveal that superposition of only the lowest six modes will yield excellent results to be very close to the corresponding ones obtained from the conventional FEM. For this reason, the CPU time required by the presented approach is less than 5% of that required by the conventional FEM.  相似文献   

福建九龙江口入海泥沙的扩散和河口湾的现代沉积   总被引：15，自引：1，他引：15  

蔡爱智  蔡雄 《海洋地质与第四纪地质》1991,11(1):57-67

本文阐述了40年来九龙江入海泥沙量增加了两倍,入海泥沙在海门岛—鸡屿一带的浅滩区,其年平均淤积8—10cm,一次洪水流域搬来悬浮泥沙,使河口湾新淤积层厚2—3cm.并指出、进入河口湾的三条汉河各有独立的扇形粗粒冲积浅滩;悬移质的粉砂、粘土粒扩散至鼓浪屿以南海域;构成三角洲沉积主体的河口浅滩区的沉积速度由入海泥沙倍增而相应地加快进行.  相似文献   

Design of a sliding mode fuzzy controller for the guidance and control of an autonomous underwater vehicle   总被引：1，自引：0，他引：1  

J. Guo  F. -C. Chiu  C. -C. Huang 《Ocean Engineering》2003,30(16):2137-2155

This work demonstrates the feasibility of applying a sliding mode fuzzy controller to motion control and line of sight guidance of an autonomous underwater vehicle. The design method of the sliding mode fuzzy controller offers a systematical means of constructing a set of shrinking-span and dilating-span membership functions for the controller. Stability and robustness of the control system are guaranteed by properly selecting the shrinking and dilating factors of the fuzzy membership functions. Control parameters selected for a testbed vehicle, AUV-HM1, are evaluated through tank and field experiments. Experimental results indicate the effectiveness of the proposed controller in dealing with model uncertainties, non-linearities of the vehicle dynamics, and environmental disturbances caused by ocean currents and waves.  相似文献   

中国绒扇藻属(钙扇藻科Udoteaceae,绿藻门 Chlorophyta)的新种和新记录     

曾呈奎  董美玲  陆保仁 《海洋科学集刊》2004,46(46):172-180

绒扇藻属(Avrainvillea)藻体广泛分布于热带、亚热带海洋，尤其盛产于珊瑚礁上。因此，该属种类的分布在很大程度上受海区的限制。绒扇藻属的主要特征是藻体深绿色，褐绿色或黑褐色，基部是由假根状丝体相互交织，构成固着器，固着在礁石上。叶柄单生或具有多次分裂。叶片单个或多个，形状不一，多数为扇形，长圆形，肾形到扁压。藻体不钙化，通常黄色或褐色。二叉状分枝，基部常常缢缩，似念珠状或念珠状。皮层丝体无明显分化或具假皮层。关于绒扇藻属海藻的分类研究，至今为止，已发现23个种。 关于中国绒扇藻属的研究，最早是C.K.Tseng(曾呈奎)于1938年在“海南岛海产绿藻研究Ⅱ”中首次报道了两种绒扇藻，即直立绒扇藻Avrainvillea erecta (Berkeley) A. Gepp et E.S.Gepp和裂片绒扇藻A.lacerata J. Agardh，而后在1983年，在曾呈奎主编的《Common Seaweeds of China》一书中，报道了上述种类，并将其产地扩大到西沙群岛。1991年，陆保仁等在“南沙群岛海区的褐藻和绿藻研究I”中，第三次报道了裂片绒扇藻，将其产地扩大到南沙群岛。最近，作者在研究中国绒扇藻属的标本时，除了己经报道的两种外，又发现该属的1个新种(西沙绒扇藻Avrainvillea xishaensis Tseng， Dong et Lu sp. nov.)和3个新记录[模糊绒扇藻A.obscura (C.Agardh)J. Agardh，和氏绒扇藻A.hollenbergii Trono，群栖绒扇藻A.amadelpha (Montagne)A. Gepp et E.S. Gepp。至今共发现了6个种，其标本均存放在中国科学院海洋研究所植物标本室。  相似文献   

相转移催化法制备抗癌新药工艺     

于静  李英霞  孙红艳 《中国海洋大学学报(自然科学版)》1992,(Z1)

提出采用相转移催化法,一步合成了抗癌新药ASF。工艺条件达到最简。利用正交实验法确定了最佳反应条件,通过一系列分析手段确定产物结构。  相似文献   

海洋模态在海洋水声学中的潜在应用前景   总被引：2，自引：0，他引：2  

崔茂常  乔方利  莫军  郭炳火 《海洋学报》2002,24(6):127-134

如同音分五律、光分七色一样,海洋中错综复杂的流速、声速剖面也可以分解成为数不多的经验正交海洋模态(empiricalorthogonaloceanmode)[1～5].以此为基础,20世纪80年代初在着名物理海洋学家Munk和Wunsch的倡导下,美国在大西洋实施了海洋声层析(oceanacoustictomography)实验.声层析技术最主要的潜力在于其观测的积分性质.每秒一次的声层析观测实质上是通过高速传播的声波对长距离内的物理量取积分,因此它能够在较大的时空尺度下求得活跃的中尺度涡旋场的平均值.  相似文献   

Seasonal and Interannual Variability in the Distribution of Surface Nutrients and Dissolved Inorganic Carbon in the Northern North Pacific: Influence of El Niño     

Chi Shing Wong  Nathalie A. D. Waser  Yukihiro Nojiri  Wm. Keith Johnson  Frank A. Whitney  John S. C. Page  Jiye Zeng 《Journal of Oceanography》2002,58(2):227-243

The seasonal and interannual changes in surface nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) were recorded in the North Pacific (30–54°N) from 1995 to 2001. This study focuses on the region north of the subarctic boundary (∼40°N) where there was extensive monthly coverage of surface properties. The nutrient cycles showed large interannual variations in the eastern and western subarctic gyres. In the Alaska Gyre the seasonal depletion of nitrate (ΔNO₃) increased from 8–14 μmol kg⁻¹ in 1995–1999 to 21.5 μmol kg⁻¹ in 2000. In the western subarctic the shifts were similar in amplitude but more frequent. The large ΔNO₃ levels were associated with high silicate depletions, indicating enhanced diatom production. The seasonal DIC:NO₃ drawdown ratios were elevated in the eastern and central subarctic due to calcification. In the western subarctic and the central Bering Sea calcification was significant only during 1997 and/or 1998, two El Ni?o years. Regional C/N stoichiometric molar ratios of 5.7 to 7.0 (>40°N) were determined based on the years with negligible or no calcification. The annual new production (NP_a) based on ΔNO₃ and these C/N ratios showed large interannual variations. NP_a was usually higher in the western than in the eastern subarctic. However, values of 84 gC m⁻²yr⁻¹ were found in the Alaska Gyre in 2000 which is similar to that in the most productive provinces of the northern North Pacific. There were also large increases in NP_a around the Alaska Peninsula in 1997 and 1998. Finally, the net removal of carbon by the biological pump was estimated as 0.72 Gt C yr⁻¹ in the North Pacific (>30°N). This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Size fractionated biomass and productivity of phytoplankton and new production in the Prydz Bay and the adjacent Indian sector of the Southern Ocean during the austral summer 1998/1999     

Cai Yuming  Ning Xiuren  Zhu Genghai  Shi Junxian 《海洋学报(英文版)》2003,22(4):651-670

INTRODUCTIONComparedwithotheroceansintheworld ,thereisrelativelyhigherlevelofnutrients (ni trate ,phosphate ,silicate)intheSouthernOcean .Butprimaryproductivitiesarelow ,andnewproductionisalsoonlyinthemiddlelevelthere .Itiscommonlyconsideredthatthelowerpro ductivitiesintheSouthernOceaniscausedbylowtemperature ,lowlight,lowstabilityofwa ter,scarcityoftraceelementsuchasironandgrazingbyzooplankton (Burkilletal.,1 995) ,etc.ThemostexistedstudiesconcentratedontheAtlanticSectoroftheSouthernO…  相似文献   

Time-series observation of dissolved inorganic carbon and nutrients in the northwestern North Pacific     

Hajime Kawakami  Makio C. Honda  Masahide Wakita  Shuichi Watanabe 《Journal of Oceanography》2007,63(6):967-982

Time-series measurements of dissolved inorganic carbon (DIC) and nutrient concentrations were conducted in the northwestern North Pacific from October 2002 to August 2004. Assuming that data obtained in different years represented time-series seasonal data for a single year, vertical distributions of DIC and nutrients showed large seasonal variabilities in the surface layer (∼100 m). Seasonal variabilities in normalized DIC (nDIC) and nitrate concentrations at the sea surface were estimated to be 81–113 μmol kg⁻¹ and 12.7–15.7 μmol kg⁻¹, respectively, in the Western Subarctic Gyre. The variability in nutrients between May and July was generally at least double that in other seasons. In the Western Subarctic Gyre, estimations based on statistical analyses revealed that seasonal new production was 39–61 gC m⁻² and tended to be higher in the southwestern regions or coastal regions. The seasonal new productions in the northwestern North Pacific were two or more times higher than in the North Pacific subtropical gyre and the northeastern North Pacific. It is likely that this difference is due to spatial variations in the concentrations of trace metals and the species of phytoplankton present. In addition, from estimations of surface pCO₂ it was verified that the Western Subarctic Gyre is a source of atmospheric CO₂ between February and May and a sink for CO₂ between July and October.  相似文献   

海水养殖水体中病害纤毛虫一新种──长拟尾丝虫Parauronema　longum　nov．spec．（纤毛门，盾纤目）     

宋微波 《中国海洋大学学报(自然科学版)》1995,(4)

报道了１９９３—１９９４年采自养殖水体中的一种海洋盾纤类纤毛虫，经鉴定系拟尾丝虫属一新种。文中对其形态学做了综合描述。指出该种可生存于多污低氧环境及贝类外套腔内并可构成对养殖动物的危害。  相似文献