法向承力锚极限抗拔力特性     

刘海笑  杨晓亮 《海洋工程》2006,24(4):8-14

法向承力锚是一种新型的适用于深海工程的系泊基础,其极限抗拔力是锚在工程应用中的关键指标。尝试用两种不同的方法评估法向承力锚的极限抗拔力,其一是基于塑性上限分析理论;其二是运用非线性有限元数值方法。与已有的经验公式相比,所建立的计算模型不仅可考虑海床土性质,还能反映锚板定位(嵌入深度及角度)以及系缆力角度对锚极限抗拔力的影响。在与已有评估方法进行比较的基础上,还特别对锚板的嵌入深度、角度以及系缆力角度变化对极限抗拔力的影响规律进行了分析,对三种方法的适用性进行了评述。  相似文献   

微齿喜马拉雅低额溞生长及种群增长的研究     

施心路  于丽杰  张大维  史新柏 《海洋与湖沼》1997,28(3):262-270

于1990年6月在哈尔滨市东北林业大学实验林场一水池中采到微齿喜马拉雅低额溞，根据实验结果应用生物统计学方法对它的生长和种群增长进行研究。结果表明，在不同温度条件下性成熟时间与水温的关系为，雌性（10-30°C）：h=8072t^-1.313（r=0.985, P＜0.01）；雄性（5-25°C）：h=1074t^-0.855（r=0.9844，P＜0.01）。在20±1°C条件下，其体长增长模型为：l_t=3.334-2.7345e^-0.1117t。龄期（x）与年龄（t，d）的关系为：雌体：t=0.07169x²＋1.3808x-1.7361；雄体：t=0.8425x²＋2.534x-1.8600。内禀增长率（r_m）为0.4076。种群增长呈“logistic”型，其方程式为：y=3625/[1+e^{(3.848-0.164t)}]。  相似文献   

Spatial and temporal variability in coccolithophore abundance and production of PIC and POC in the NE subarctic Pacific during El Niño (1998), La Niña (1999) and 2000     

M.S. Lipsen  D.W. Crawford  P.J. Harrison 《Progress in Oceanography》2007,75(2):304-325

Seasonal variations in coccolithophore abundance, chlorophyll, nutrients and production of particulate organic and inorganic carbon (POC and PIC) were determined along a coastal to oceanic east-west transect (Line P) culminating at Ocean Station Papa in the northeastern subarctic Pacific between 1998 and 2000. Offshore stations generally exhibited low seasonality in chlorophyll concentrations, with moderate seasonality in POC production. Near shelf stations showed a similar pattern to offshore stations, but were also characterized by sporadic events of higher POC productivity. During the 1998 El Niño, June was characterized by low chlorophyll and POC productivity along the transect, presumably as a result of depleted surface nitrate. In contrast, during the 1999 La Niña, and in 2000, higher POC productivity and surface nitrate occurred along the transect in June. Chlorophyll and POC productivity were similar in late summer in all 3 years. The coccolithophore population was usually numerically dominated by Emiliania huxleyi, particularly in June. Along the transect, abundance of coccolithophores was much higher in June during the 1998 El Niño (mean of 221 cells ml⁻¹) than in the 1999 La Niña (mean of 40 cells ml⁻¹), with their abundance in late summers of both years being very low. Abundances were even higher along the transect in June and the late summer of 2000 with sporadic ‘blooms’ of >1000 cells ml⁻¹ at some stations (cruise averages 395 and 552 cell ml⁻¹, respectively). Production rates of PIC did not consistently correlate with areas of high coccolithophore abundance. PIC production was high (100-250 mg C m⁻² d⁻¹) along the transect during June 1998, and low (1-40 mg C m⁻² d⁻¹) during both winters, June 1999 and during late summers of 1998 and 1999. The year 2000 was more complicated, with high rates of PIC production accompanying high abundance of coccolithophores in late summer, but lower rates of PIC production accompanying high coccolithophore numbers in June. Our data suggest that the abundance of coccolithophores and the production rates of PIC in the subarctic are higher than previously thought. Occasional PIC:POC production ratios of 1 or greater in 1998 and 2000 suggest that coccolithophores in this region could have a significant impact on the efficiency of the biological carbon pump.  相似文献   

Experimental Study of Factors Controlling Sorption of Heavy Metals on Ariake Clay and Implication for Practice     

Y. J. Du  S. Hayashi 《Marine Georesources & Geotechnology》2006,24(2):103-118

A series of batch tests have been presented to investigate the effects of solid-solution contact time, solid:solution ratio, and pH of solution on sorption of Cd²⁺ and Pb²⁺ on Ariake clay from Kyushu region of Japan. The results show that, among the three investigated factors, solid:solution ratio (SD/SN) seems to be the crucial controlling factor. The Freundlich sorption parameters determined from the batch tests were applied to a typical field landfill in which the Ariake clay was used as soil barrier. The impacts of the landfill were assessed by numerical analysis. Based on the analysis result, the significance of selecting proper solid:solution ratio for determining sorption parameters from batch test has been discussed.  相似文献   

Stable isotope analysis of Pacific salmon: insight into trophic status and oceanographic conditions over the last 30 years     

Franklin R. Satterfield  IV  Bruce P. Finney   《Progress in Oceanography》2002,53(2-4)

Food web interactions and the response of Pacific salmon to physical processes in the North Pacific Ocean over interannual and interdecadal timescales are explored using naturally occurring stable isotope ratios of carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N). Stable isotope analyses of five species of sexually mature North Pacific salmon from Alaska (Oncorhynchus spp.) cluster into three groups: chinook salmon (O. tshawytscha) have the highest values, followed by coho (O. kisutch), with chum (O. keta), sockeye (O. nerka), and pink (O. gorbuscha) together having the lowest values. Although detailed isotopic data on salmon prey are lacking, there are limited data on relevant prey items from areas in which they are found in high abundance. These data suggest that the characteristics of the sockeye, pink and chum we have analyzed are compatible with their diets including open ocean squid and zooplankton, which are in general agreement with stomach content analyses. Isotope relationships between muscle and scale show consistent relationships for both δ¹³C (R²=0.98) and δ¹⁵N (R²=0.90). Thus, scales, which have been routinely archived for many systems, can be used for retrospective analyses. Archived sockeye salmon scales spanning 1966–1999 from Red Lake, Kodiak Island, Alaska were analyzed for their stable isotope ratios of carbon and nitrogen. The δ¹⁵N record displays a decreasing trend of ˜3‰ from 1969–1982 and an increasing trend of ˜3‰ from 1982–1992, while the variations in δ¹³C are relatively minor. These trends may result from factors such as shifts in trophic level of feeding and/or feeding location, or may originate at the base of the food web via changes in processes such as nutrient cycling or primary productivity. Detailed studies on prey isotopic variability and its controls are needed to distinguish between these factors, and thus to improve the use of stable isotope analysis as a tool to learn more about present and past ecosystem change in the North Pacific and its relation to climatic change.  相似文献   

Station Papa Time Series: Insights into Ecosystem Dynamics     

Paul J. Harrison 《Journal of Oceanography》2002,58(2):259-264

The Northeast Pacific has one of the longest time series of any open ocean station, primarily as a result of the weathership station at Station P from the 1950s to 1981. This review summarizes our understanding of the plankton ecosystem for this station and examines interannual variability for the primary producers. The weathership era characterized a period of high temporal sampling resolution with a limited number of parameters being measured. In contrast, the post-weathership period focussed on seasonal sampling (usually three times per year), but a wider range of parameters were measured and sediment traps were deployed to estimate carbon and opal flux rates. The mixed layer depth is shallow compared to the Atlantic Ocean, ranging from 40 to 120 m in late summer and winter respectively. Nitrate, silicate and phosphate are saturating year round with only a few exceptions in the 1970s. Winter and summer Si:N ratios are the same (1.5:1). Ammonium and urea are 0.5 uM in winter and near detection limits (∼0.1 uM) in late summer. Iron is limiting (∼0.05 nM) in late spring and summer for the growth of large diatoms, but iron is co-limiting with irradiance in winter. Chlorophyll and primary productivity are low and show little seasonal variation (about 2 times). Summer chl is about 20 mg m⁻² while primary productivity ranges from 400–850 mg C m⁻²d⁻¹. The f-ratio of 0.25 does not vary with seasons and indicates that primary productivity is fueled by regenerated nitrogen (e.g. NH₄ and urea). Small cells (<5 um) are normally abundant and they utilize regenerated nitrogen produced by the micrograzers; they do not appear to be Fe-limited, but rather controlled by the micrograzers. Shipboard carboy experiments indicate that large diatoms become dominant when iron is added. Therefore top down control is exerted by the micrograzers on the small cells, while there is bottom up control of the large phytoplankton due to low Fe concentrations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

三江平原湿地植物群落P、K的积累、动态及其生物循环   总被引：9，自引：0，他引：9  

何太蓉  杨永兴 《海洋与湖沼》2006,37(2):178-183

在三江平原湿地植物生长季节里,选择该区分布最广、面积最大且最具有代表性的毛果苔草(Carexlasioncarpa)-狭叶甜茅(Glyceria spiculosa)群落和小叶章(Deyeuxia angustifo-lia)群落为研究对象,逐月测定两类湿地群落生物量,并对植物样品分别用钼锑抗比色法和原子吸收法测定其P、K含量。在此基础上,探讨了两类湿地群落的P、K积累量及其生物循环特征。结果表明,三江平原不同的植物群落以及同一群落的不同器官,其P、K元素积累量不同,而且都有明显的季节变化。根是群落中P、K元素的最大贮存器官,其P、K积累量占总量的80%左右。湿地群落中K的吸收量、归还量、存留量、现存量和表土贮量都大于P的对应值,同时K的利用系数和循环系数均大于P,毛果苔草-狭叶甜茅群落K的吸收系数大于P,而小叶章群落K的吸收系数小于P。  相似文献   

伶仃洋N,P静态环境容量的研究     

饶开燕  古秋森  黎夏  万肇忠 《海洋科学》1991,15(3):49-52

本文利用陆地卫星影象具有水陆边界清晰和多时相等优点,计算出伶仃洋枯、平、丰水期的水容量。结合实地采样分析,推算出伶仃洋从上界各口门排入的N,P输送量,和从伶仃洋输出南海的N,P通量;估算出伶仃洋的N,P静态容量,为伶仃洋水环境的治理和资源开发利用的环境保护规划提供了科学依据。  相似文献   

闽南-台湾浅滩海域鱼类资源生产量   总被引：8，自引：0，他引：8  

卢振彬  戴泉水  肖方森 《热带海洋学报》2005,24(1):60-66

以海洋生态系统营养动力学为理论依据,根据调查所获得的有关闽南-台湾浅滩海域的初级生产力资料,检测了该海域的浮游植物有机碳含量,测算了生态效率,检测了52种主要经济鱼类营养级及其有机碳含量.采用营养动态模型和Cushing模型估算了该海域生态系统中鱼类资源的生产量(自然生产量),同时采用Cadima模式和MSY简单模式估算鱼类资源最大可持续开发量.估算结果如下鱼类资源生产量为98.63×104t,最大可持续开发量为 48.35×104t.1997年以来实际年渔获量为48.64×104t -53.83×104t,超过了鱼类资源的最大可持续开发量,呈现过度捕捞态势.还讨论了加强该渔场渔业资源管理的7项重要措施,以促进鱼类资源的较快恢复.  相似文献   

P/E界线全球事件在西藏定日地区的响应     

李祥辉  胡修棉  王成善  包向农  万晓樵  范善发 《海洋地质与第四纪地质》2002,22(1):69-74

生物群、沉积物和有机地球化学变化显示，古新统－始新统（P／E）界线全球事件在西藏南部定日（东特提期残留海低纬度浅水）地区存在明显响应：古新统宗浦组顶部有孔虫动物群的属、种绝灭率分别为87％和94％，始新统遮普惹组底部有孔虫属、种新生率分别达80％和69％；岩层以（生物滩相）薄－中层向厚层－块状生物灰岩转化，泥质含量增加；典型生物标志经合物参数变化明显，Pr／17比值平均从0．365增加到0．86，Ph／18由0．56变为0．92，β／17由12．843剧增到123．17，γ／17由2．46突变为29．5。结合西藏及邻区岩相分布、接触关系后认为，这种全球地质事件的响应在研究区可能是一种古海洋事件，可能由大洋环流（古水团）变化引起。  相似文献