Marine tether dynamics: retrieval and deployment from a heaving platform     

R. E. Baddour  W. Raman-Nair 《Ocean Engineering》2002,29(13):550-1661

A tether management system of a winch module in a marine environment is proposed. For the purpose of this study the subsea body is considered as a mass attached at the free end of a long tether which is wrapped around a circular drum controlled by an external torque. The winch is considered mounted on a heaving platform. The effect of the heaving platform on the motions of the drum, tether and attached mass are studied with respect to the longitudinal vibrations of the tether in one dimension. The hydrodynamic effects are considered on the deployed portion of the tether and the tethered mass, both of which are assumed submerged in otherwise still water. The resulting nonlinear system of equations of motion is developed and solved numerically for an example of a marine tether system. The effect of the tether extensibility on the operation threshold of the system is identified. Comparison with an inextensible tether case is provided. The numerical results and their analysis for the retrieval/deployment of the system are presented.  相似文献   

盐碱水NaCl浓度和碱度对银鲫(Carassius auratus gibelio)幼鱼毒性的初步研究   总被引：2，自引：0，他引：2  

郑伟刚  张兆琪  张美昭  董双林 《中国海洋大学学报(自然科学版)》2001,31(4):513-517

通过对银鲫(Carassiusauratusgibelio)幼鱼(L=3.56±0.28cm)的NaCl浓度(pH=8.80±0.10)及碱度(pH=8.84±0.26)的急性毒性试验，用概率单位法求得其24，48，96h的半致死浓度(LC50值)NaCl浓度分别为11.53、10.77、8.58g/L；碱度分别为98.74、79.49、64.19mmol/L。在此基础上采用水生毒理联合效应相加指数法进行了氯化钠与碳酸氢钠浓度的联合毒性实验(浓度=11)，结果在96h内二者的关系全部为协同作用,且其协同性逐渐减弱并趋向于相加作用。  相似文献   

细菌对海水中各形态氮的影响   总被引：1，自引：0，他引：1  

王江涛  赵春霞  尹晓楠  王秋璐 《中国海洋大学学报(自然科学版)》2006,36(3):468-472

海洋细菌生长过程中,不但能利用体系中的有机物质,而且也能利用无机营养盐。本论文通过小麦岛细菌接种实验发现,细菌大量繁殖时吸收利用体系中的营养物质,生成颗粒态氮(PN)和溶解有机氮(DON),体系中溶解无机氮(DIN)、总溶解氮(TDN)降低至最低值。进入细菌指数生长期和稳定期后,颗粒态和有机态氮不断降解向体系中释放出无机营养盐,DIN和TDN呈现回升趋势,颗粒氮(PN)与细菌数量变化正相关。体系中,初始氮源的量决定了细菌体内POC/PN的比值,氮源充足,细菌繁殖数量多,POC/PN值低,氮源不足,细菌数量相对较少,POC/PN比值高。  相似文献   

Evaluation of long-term extreme response statistics of jack-up platforms   总被引：1，自引：0，他引：1  

M. J. Cassidy  P. H. Taylor  R. Eatock Taylor  G. T. Houlsby 《Ocean Engineering》2002,29(13):1603-1631

This paper is concerned with the models appropriate for the dynamic assessment of jack-ups, concentrating particularly on the long-term response due to random ocean waves and on work-hardening plasticity models used for spud-can response. A methodology for scaling of short-term statistics, calculated using a Constrained NewWave technique, is shown in a numerical experiment for an example jack-up and central North Sea location. The difference in long-term extreme response statistics due to various footing assumptions is emphasised. Results for two environmental load conditions are described (one excluding and one including wind and current effects) and the role of sea-state severity in the variation of short-term extreme response statistics is also highlighted.  相似文献   

Lower Cd/P ratio in settling particles than in surface seawater in the Okinawa Trough     

Kazuo Abe  Kazuo Iseki  Kazumaro Okamura  Yoko Kiyomoto 《Journal of Oceanography》2006,62(5):745-752

The characteristics of the ratios between cadmium (Cd) and phosphorus (P) in settling particles collected from the Okinawa Trough in the East China Sea were examined using a sediment trap, moored at a depth of 811 m for one year. The Cd/P ratios varied within a narrow range throughout the year, in spite of the large seasonal change in the total dry mass, Cd, and P fluxes. The average Cd/P ratio of settling particles was 0.062 (nmol/μmol), which was obviously lower than that of surface seawater around the study site (0.16). This lower ratio in the Okinawa Trough particles collected using the 811 m-moored trap certainly reflected the mixture of biologically produced organic matter around the study site and other components that were mainly transported as lateral flux from the shelf edge and slope area of the East China Sea.  相似文献   

Long-term changes in the fish community structure from the Tsushima warm current region of the Japan/East Sea with an emphasis on the impacts of fishing and climate regime shift over the last four decades     

Yongjun Tian  Hideaki Kidokoro  Tatsuro Watanabe 《Progress in Oceanography》2006,68(2-4):217

Japanese fisheries production in the Japan/East Sea between 1958 and 2003 increased to their peak (1.76 million tons) in the late 1980s and decreased abruptly with the collapse of Japanese sardine. Catch results for 58 fisheries and various environmental time-series data sets and community indices, including mean trophic level (MTL) and Simpson’s diversity index (DI), were used to investigate the impacts of fishing and climate changes on the structure of the fish community in the Tsushima warm current (TWC) region of the Japan/East Sea. The long-term trend in fisheries production was largely dependent on the Japanese sardine that, as a single species, contributed up to 60% of the total production in the Japanese waters of the Japan/East Sea during the late 1980s. Excluding Japanese sardine, production of the small pelagic species was higher during 1960s and 1990s but lower during 1970s and 1980s. This variation pattern generally corresponds with the trend in water temperature, warmer before early 1960s and after 1990s but colder during 1970s and 1980s. The warm-water, large predatory fishes and cold water demersal species show opposite responses to the water temperature in the TWC region, indicating the significant impact of oceanic conditions on fisheries production of the Japan/East Sea. Declines in demersal fishes and invertebrates during 1970s and 1980s suggested some impact of fishing. MTL and DI show a similar variation pattern: higher during 1960s and 1990s but lower during 1970s and 1980s. In particular, the sharp decline during the 1980s resulted from the abundant sardine catches, suggesting that dominant species have a large effect on the structure of the fish community in the Japan/East Sea. Principal component analysis for 58 time-series data sets of fisheries catches suggested that the fish community varied on inter-annual to inter-decadal scales; the abrupt changes that occurred in the mid-1970s and late 1980s seemed to correspond closely with the climatic regime shifts in the North Pacific. These results strongly suggest that the structure of the fish community in the Japan/East Sea was largely affected by climatic and oceanic regime shifts rather than by fishing. There is no evidence showing “fishing down food webs” in the Japan/East Sea. However, in addition to the impacts of abrupt shifts that occurred in the late 1980s, the large predatory and demersal fishes seem to be facing stronger fishing pressure with the collapse of the Japanese sardine.  相似文献   

海浪日最大波高序列的一种标度性质   总被引：1，自引：0，他引：1  

尉华  沈正 《海洋湖沼通报》1994,(4):1-8

应用重标度分析方法研究小麦岛海洋观测站１９６１－１９８０年二十年海浪日最大波高序列时发现，该序列并不是相互独立的，而是具有记忆性和持久性，详细的论证表明分式布朗运动模型是描述海浪日最大波高序列的一个较好的模型，同时，应用分式布朗运动模型我们找到了存在于海浪日最大波高序列中的一种标度性质－累积离差（ｔ）的统计自仿射性。  相似文献   

Effect of enriched rotifers on growth, survival, and composition of larval Atlantic cod (Gadus morhua)   总被引：1，自引：0，他引：1  

Park  Heum Gi; Puvanendran  Velmurugu; Kellett  Anne; Parrish  Christopher C.; Brown  Joseph A. 《ICES Journal of Marine Science》2006,63(2):285-295

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Application of hermite polynomial to wave and wave force statistics     

Yeli Yuan  C.C. Tung   《Ocean Engineering》1984,11(6):593-607

This paper discusses the use of Hermite polynomial in the derivation of statistical properties of waves, wave field kinematics and dynamics and wave forces under various conditions. Specifically, covariance functions and approximate spectra are obtained for (1) wave force on vertical cylinder according to Morison's formula, (2) horizontal fluid particle velocity considering the effects of free surface fluctuations, and (3) elevation of breaking waves.  相似文献   

2001-2002年天目湖(沙河水库)浮游植物的生态学研究   总被引：7，自引：0，他引：7  

张运林  陈伟民  周万平  杨顶田  江晶 《海洋湖沼通报》2006,(2):31-37

2001年6月~2002年5月,对天目湖进行的浮游植物周年调查表明,天目湖共有浮游植物7门75属,其中年平均丰度为5026.20×104个/L,以蓝藻为主,占总丰度的54.45%;而年平均生物量为(15.364±9.103)mg/L,其中硅藻居首位,为6.634 mg/L,占浮游植物年平均生物量的43.18%;其周年变化是丰度和生物量最高值均出现在5月,丰度在5月和9月出现2个峰值,而生物量则在5、7、10月出现3个峰值。浮游植物丰度从大坝处1#点到河流入湖口的9#、10#点变化不明显但略有增加,而生物量则呈明显增加。通过对水温、透明度、营养盐与浮游植物丰度和生物量的线性回归分析发现,浮游植物丰度、生物量与水温、TP存在显著的正相关,而与N/P比、透明度存在显著性负相关,与TN相关性不是很明显。  相似文献