An Experimental Study of Several Special Issues Regarding the Ice Force on Conical Structures

The effect of the cone spacing of a conieal structure on the ice force is studied by model experiments. The ice force reduction coefficient presented in this paper expresses the relationship between the ice force and the arrangement of cones. The experiments prove that the mode of the ice failure before the boundary of upward-downward bending cone (UDBC) is crushing. A conclusion can also be drawn from the experiments that the ice force on the boundary of UDBC is by far less than that on a vertical pile with the same diameter. Moreover, the ice force frequencies on upright and inve-rted cones are obtained under the field condition of the platform JZ20-2, respectively. The results show that the alterna-tion of the ice force on UDBC can hardly induce resonance of platform JZ20-2.     

海南九孔鲍养成技术

自１９９３年我国皱纹盘鲍苗种及成体发生大规模死亡以来 ,北方鲍鱼产量一直处于低谷阶段 ,鲍鱼人工育苗及养殖严重受阻 ;１９９６年开始增产 ,但速度缓慢 ,生产极不稳定。南方福建东山一带 ,目前发生鲍鱼大规模死亡现象 ,并有向南方拓展之势 ,如广东湛江、汕头、汕尾也发生鲍鱼大规模死亡现象。海南省政府决定 ,今后几年内全省计划大力发展鲍类养殖 ,全省计划几年内发展网箱养鲍１０×１０５箱 ,许多企业大力开展工厂化养鲍。本文针对海南养殖九孔鲍的独特特点 ,从养殖模式及养成技术的操作和管理 ,以及养殖过程中存在的诸多问题作一简要的…     

Integration of a Multi-Stage Bulk Materials Acquisition System from the Viewpoint of Dock Operations

A multi-stage bulk materials acquisition system is examined from the viewpoint of dock operations. The whole process can be divided into four stages and treated as four subsystems: ships scheduling planning, material yard planning, dock arrangement, and material discharging. Since the structure and the complexity of each subsystem is different, the solution approaches applied are also different with respect to each. To increase operations efficiency and data consistency, an integration of the subsystems by coordinating the operations sequence and data communications for the four subsystems is discussed. The four subsystems are illustrated by using the material docks of China Steel Corporation, and the models developed in this research are also validated. The results indicate that the models developed are capable of deriving solutions better than the existing ones. Although the discussions are confined to China Steel Corporation, the models can be applied to other companies with similar operations.     

Model Test Study of Dynamic Ice Force on Compliant Conical Structures

To study ice-induced vibration of a compliant conical structure,a series of model tests were performed from 2004 to 2005.In the tests,the ice sheet before the compliant conical structure was found to fail in two-time breaking.From 2005 to 2006,this type of ice failure was studied through more groups of tests.The tests show that two-time breaking is the typical failure of ice before steep conical structures,and is controlled by other factors at the same time,such as ice speed and the angle of the cone.     

Effects of tributyltin at environmental levels on monooxygenase system of digestive gland in hard clam Meretrix meretrix

The effects on ethoxyresorufin O-deethylase （EROD）, NADPH-cytochrome c reductase and NADH cytochrorne b5 reductase activities of digestive gland in Meretrix meretrix exposed to tributyltin （TBT） at environmental levels （0.1,1.0,10.0 ng/dm as stannum concentration）,in experimental condition, were evaluated. The EROD, NADH cytochrorne b5 reductase activities were significantly inhibited after exposure to 10.0 ng/dm^3 TBT for 8 and 20 d, the NADPH cytochrorne c reductase activities were significantly inhibited after exposure to 0.1,1.0 and 10.0 ng/dm TBT for 8 d and to 1.0 and 10.0 ng/dm for 20 d, as compared with the matched control, while NADH cytochrorne b5 reductases and NADPH cytochrome c reductase activities were induced after exposure to 10.0 ng/dm^3 TBT for 2 d. The EROD activity in the 10 ng/dm^3 group,and the NADH cytochrome b5 reductases activities in 1.0 and 10.0 ng/dm groups, were significantly induced when transferred to clean recovery tanks for 7 d. The three enzymic activities in the clams exposed to TBT were recovered to the level corresponding to that of the control group after transfer to clean recovery tanks for 20 d. NADPH cytochrome c reductase activity in Meretrix meretrix seems to be more sensitive to exposure of TBT than that of the EROD and NADH cytochrome b5 reductases. The results suggest that induction and inhibition by TBT to the monooxygenase system enzymic activity in Meretrix meretrix would simultaneously exist. The enzymic activities were inhibited by exposure for a long time. The results suggest that inhibition of the monooxygenase system should be an indication of the exposure to environmentally relevant concentrations of TBT for a long time.     

九龙江河口区表层水铀同位素的粒级分布

利用微滤和超滤技术研究了九龙江河口区表层水中铀及其同位素组成的粒级分布和地球化学行为.结果表明,溶解态(<0.4μm)中低分子量组分(<10 000 u)占主要份额,胶体态(10 000 u~0.4μm)238U所占比例不足1%,且随盐度的增加其所占份额逐渐降低.溶解态、低分子量组分和胶体态238U的比活度与盐度之间存在良好的线性正相关关系,证实它们在九龙江河口区呈现保守行为.在颗粒态(>0.4μm)中,各粒级组分238U所占份额主要受控于相应颗粒物的浓度,在盐度小于20的区域,各粒级颗粒组分238U占颗粒态的份额有如下变化次序:10~53μm>2~10μm>0.4~2μm>大于53μm,而在盐度大于30的近外海站位,该次序发生一些变化:0.4~2μm>10~53μm>2~10μm>大于53μm,最小粒级颗粒组分238U的贡献有所增加,反映了自生铀贡献的加强.九龙江河口区表层水中溶解态(包括低分子量组分和胶体态)的234U/238U)_A.R.均大于1,显示出234U过剩的特征,而各粒级颗粒组分中的234U/238U)_A.R.则接近于平衡值(1.0).这一现象与陆地岩石风化过程中水体对铀的淋滤释出量及234U的优先浸出有关.对232Th/238U质量比的研究显示,溶解态及其所包括的低分子量组分和胶体态的232Th/238U质量比均小于1,而颗粒态及其所包括的4个粒级组分中的232Th/238U质量比均大于1,反映了向外海输送过程中铀、钍地球化学行为的差异.     

罗非鱼、南美白对虾对重金属富集的研究

对广东省养殖的罗非鱼Oreochromis niloticus及南美白对虾Litopeneaus vannamei体内Pb、Cd、Hg、As 4种重金属富集及分布状况进行研究。比较了不同规格罗非鱼及南美白对虾体内重金属差异。分析重金属在罗非鱼及南美白对虾不同部位的分布状况。结果表明,罗非鱼及南美白对虾体内Pb、Cd、Hg、As均有不同程度的检出,但含量均低于国家限定标准(NY5125-2002);其中Pb的含量最高,罗非鱼和南美白对虾体内Pb含量最高值分别为限量的39.32%和42.18%;重金属含量因其规格大小及部位而异,趋势为大规格样品重金属含量相对较高,重金属含量在罗非鱼及南美白对虾体内的增长情况与其体重具有正相关性;罗非鱼内脏重金属含量明显高于肌肉组织,虾头为虾重金属富集的主要部位。     

围垦的社会经济价值及其对海洋环境影响的评估

从围垦滩涂与保护湿地的关系着手,针对浙江省的滩涂围垦现状,讨论了沿海滩涂实施围垦工程所创造的社会经济价值,分析了湿地生态的环境特征及其对自然界的贡献,指出并探讨了海岸带资源开发与海岸工程建设所带来的问题,从湿地保护和经济可持续发展的角度提出了相关的建议。     

A comparison of several wave spectra for the random wave diffraction by a semi-infinite breakwater

A comparison of the diffraction of multidirectional random waves using several selected wave spectrum models is presented in this paper. Six wave spectrum models, Bretschneider, Pierson–Moskowitz, ISSC, ITTC, Mitsuyasu, and JONSWAP spectrum, are considered. A discrete form for each of the given spectrum models is used to specify the incident wave conditions. Analytical solutions based on both the Fresnel integrals and polynomial approximations of the Fresnel integrals and numerical solutions of a boundary integral approach have been used to obtain the two-dimensional wave diffraction by a semi-infinite breakwater at uniform water depth. The diffraction of random waves is based on the cumulative superposition of linear diffraction solution. The results of predicted random wave diffraction for each of the given spectrum models are compared with those of the published physical model presented by Briggs et al. [1995. Wave diffraction around breakwater. Journal of Waterway, Port, Coastal and Ocean Engineering—ASCE 121(1), 23–35]. Reasonable agreement is obtained in all cases. The effect of the directional spreading function is also examined from the results of the random wave diffraction. Based on these comparisons, the present model for the analysis of various wave spectra is found to be an accurate and efficient tool for predicting the random wave field around a semi-infinite breakwater or inside a harbor of arbitrary geometry in practical applications.     

A General Linear Wave Theory for Water Waves Propagating over Uneven Porous Bottoms

Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green‘s scond identity. This theory can be reduced to a number of the most typical mild-slope equations curreutly in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms.