Prediction of Static Strength of Tubular T and X Joints Subjected to Axial Compression     

Chen Tieyun  Liu Pu Wang Deyu Professor 《中国海洋工程》1994,(1)

-The formulation of ring analogy method for the prediction of static strength (ductile collapse) of tubular T, X joints under axial compression based on the limit analysis of the ring with some assumptions is presented in this papaer. The regression formula for the effective length of the chord based on test results is established by means of the least square method. The results computed by the present semi-analytic formula are compared with previous results and test data. They are quite close to each other. The accuracy of the present formula depends on the reasonable selection of the effective length of the chord, which requires numerous test data.  相似文献   

海南岛鹿回头水尾岭海滩岩中的微生物岩     

滕建彬  金春花  沈建伟 《海洋地质与第四纪地质》2007,27(3):25-30

在海南岛的海滩岩中首次发现了微生物岩,这是一种发育在珊瑚(碎屑和砾块)骨骼孔穴中,少量在珊瑚碎块表面的微生物碳酸盐沉积,这些微生物碳酸盐沉积呈叠层或包壳状生长,可黏结细小的生物碎屑,具有独特的发育模式。微生物碳酸盐沉积在南海的发现支持海滩岩的胶结物部分是源于微生物成因的假设,进而肯定了微生物在碳酸盐沉积中所起的重要作用。结合海滩岩组分中微钻孔的发育特征和微生物岩发育模式的描述,在一定程度上填补了我国南方海滩岩中发育微生物碳酸盐沉积物的研究空白。  相似文献   

Prediction of geometrical properties of perfect breaking waves on composite breakwaters     

Mevlut Sami Akoz  M. Salih Kirkgoz 《Applied Ocean Research》2011,33(3):178-185

Breaking wave loads on coastal structures depend primarily on the type of wave breaking at the instant of impact. When a wave breaks on a vertical wall with an almost vertical front face called the “perfect breaking”, the greatest impact forces are produced. The correct prediction of impact forces from perfect breaking of waves on seawalls and breakwaters is closely dependent on the accurate determination of their configurations at breaking. The present study is concerned with the determination of the geometrical properties of perfect breaking waves on composite-type breakwaters by employing artificial neural networks. Using a set of laboratory data, the breaker crest height, h_b, breaker height, H_b, and water depth in front of the wall, d_w, from perfect breaking of waves on composite breakwaters are predicted using the artificial neural network technique and the results are compared with those obtained from linear and multi-linear regression models. The comparisons of the predicted results from the present models with measured data show that the h_b, H_b and d_w values, which represent the geometry of waves breaking directly on composite breakwaters, can be predicted more accurately by artificial neural networks compared to linear and multi-linear regressions.  相似文献   

南海大鹏湾盐田海域骨条藻数量的多元分析   总被引：15，自引：3，他引：15  

黄奕华  楚建华  齐雨藻 《海洋与湖沼》1997,28(2):121-127

１９９０年及１９９１年３月３０日－５月３０日，在南海大鹏湾盐田海域设点测定骨条藻数量及各环境要素，以逐步回归，主成分分析及判别分析的方法，分析该海区骨条藻数量与环境因子的关系。１９９０年４、５月与１９９１年４，５月骨条藻数量差异与该期间环境因子值差异显著有关；初步提出用三维主成分分析图及判别分析方程作为盐田海域骨条材料潮预报的方法。  相似文献   

Monthly Variation of Sea-Air Temperature Differences in the Korean Coast     

Hyo?ChoiEmail author  Yuan?Hang?Zhang 《Journal of Oceanography》2005,61(2):359-367

Monthly variations of sensible heat, latent heat and momentum fluxes and the modification of sea temperature to air temperature were examined at four coastal stations—Sokcho, Kangnung, Ulsan and Chungmu in the path of the East Korea Warm Current from the year of 1981 to 1990, which was one of main migration routes of Japanese common squid. The difference between monthly averaged sea surface and air temperatures at the 10 m height above the sea surface mainly became negative values from April through August, while they had positive ones from September through March. Monthly variability of the temperature differences is significant in both summer and winter, while it is generally small in spring and fall. Negative values of sensible heat fluxes, which indicated a heat gain by the sea through heat conduction across the air-sea interface were found at the four coastal stations from April to August. Minimum values of sensible heat fluxes at Sokcho, Kangnung and Chungmu were in June, except for Ulsan in August. To the contrary, positive sensible heat flux implying a heat loss from sea toward atmosphere occurred from October to February with a maximum in December. Latent heat fluxes due to condensation of moist air over sea surface had small magnitudes from April to August and those due to evaporation of water particles from the sea surface into the lower atmosphere had relatively large magnitudes from October to March. Minimum values of latent heat fluxes also occurred in June except for August in Ulsan. Momentum flux was small from June to August under weak wind in summer, but it was large from December to February under strong wind in winter. Regression equations between sea surface temperature and air temperature at the 10 m height above the sea surface had very high correlation coefficients from 0.92-0.98, except for 0.78-0.84 of Ulsan, which was partially affected by upwelling of cool water from the bottom into the sea surface. Similar to the sea surface, correlation coefficients were over 0.83-0.97 except for 0.70-0.79 for Ulsan at the 10 m depth of sea and were over 0.70-0.95 except for 0.59-0.82 for Ulsan at the 20 m depth.  相似文献   

切向流速探头简介     

钱世Rong 《海洋技术学报》1993,12(3):53-71

切向流速探测器是海洋湍流探测中基本的和必要的工具。该探测器可用压电陶瓷双金属片作其传感器。本文介绍了一种目前国际上常用的切向流速探头的结构、制作方法、工作原理、测定其灵敏度的装置、步骤以及在用回归法拟合实验曲线求灵敏度时所用的回归方程。文中还证明了多年来一些海洋学家所采用的拟合函数并非是最佳的。  相似文献   

Second-order ridge axis discontinuities in the south Atlantic: Morphology,structure, and evolution   总被引：1，自引：0，他引：1  

N. R. Grindlay  P. J. Fox  K. C. MacDonald 《Marine Geophysical Researches》1991,13(1):21-49

Continuous along-axis Sea Beam coverage of the slow-intermediate spreading (34–38 mm yr⁻¹ full rate) southern Mid-Atlantic Ridge (25°–27°30′S and 31°–38° S) shows that the ridge axis is segmented by both rigid and non-rigid discontinuities. Following the model of Macdonald et al. (1988b), a hierarchy of four orders is proposed for ridge axis discontinuities based on a continuum of relative age and distance offset across the discontinuites. This paper discusses the characteristics associated with five second-order discontinuities found in the areas surveyed. First-order discontinuities represent rigid offsets, transform faults, whereas non-rigid discontinuities fall into the second, third and fourth orders. Like transform fault boundaries, second-order discontinuities have distinctive morphologic signatures both on and off-axis-discordant zones — and therefore are better defined than third- or fourth-order discontinuities. Second-order discontinuities are offsets that range in distance from less than 10 km to approximately 30 km and vary in age offset from 0.5 to approximately 2.0 m.y. The variable morphotectonic geometries associated with these discontinuities indicate that horizontal shear strains are accommodated by both extensional and strike-slip tectonism and that the geometries are unstable in time. Three characteristic geometries are recognized: (1)en echelon jog in the plate boundary where ridge axis tips overlap slightly, (2)en echelon jog in the plate boundary where ridge axes are separated by an extensional basin whose long axis is oriented parallel to the strike of the adjoining ridge axes, and (3) oblique offset characterized by a large extensional basin that is oriented approximately 45° to the strike of the ridge axes. In the case of the third type, evidence for short strands of strike-slip tectonism that link an obliquely oriented extensional basin flanking ridge tips is often apparent. Analysis of the detailed bathymetric and magnetic data collected over the second-order discontinuities and their off axis terrain out to 5–7 m.y. documents that second-order discontinuities can follow several evolutionary paths: they can evolve from transform fault boundaries through prolonged asymmetric spreading, they may migrate along strike leaving a V-shaped wake, and they may remain in approximately the same position but oscillate slightly back and forth. In addition, a small change in the pole of relative motion occurring 4–5 Ma is thought to have resulted in the initiation of at least one second-order discontinuity in the survey area. A geologic model is proposed which involves the interplay of lithospheric thickness, asymmetric spreading, temporal and spatial variability of along-axis magmatic input and changes in the poles of relative motion to explain the origin, morphology and evolution of second-order ridge axis discontinuities.  相似文献   

Estimating reaction norms for age and size at maturation with reconstructed immature size distributions: a new technique illustrated by application to Northeast Arctic cod   总被引：3，自引：1，他引：3  

Heino  Mikko; Dieckmann  Ulf; Godo  Olav Rune 《ICES Journal of Marine Science》2002,59(3):562-575

  相似文献   

太湖水质参数的遥感监测研究     

汤诗楷  柯长青 《海洋湖沼通报》2007,(2):62-68

以太湖为研究对象,对TM各波段辐射率与水质参数进行拟合,分析了TM各波段经6S模型大气校正和未经校正直接拟合在监测内陆湖泊水质中的可行性。结果表明:TM波段经6S模型校正后能与太湖水质参教进行较好的匹配,同时通过实验得到了太湖地区水质参数的实用性回归公式。  相似文献   

东海陆架冰后期潮流沙脊地貌与内部结构特征   总被引：14，自引：0，他引：14  

印萍 《海洋科学进展》2003,21(2):181-187

东海陆架以宽平的地形、充分的陆源沉积物供应、快速沉降和强动力场为特征，中外陆架发育大规模潮流沙脊地貌。潮流沙脊走向大致为NW—SE向分布，与区域潮流主方向一致或成较小交角。东海陆架冰后期潮流沙脊以不对称横剖面为特征，陡坡倾向SW。沙脊内部发育典型的高角度前积斜层理，倾向与沙脊横剖面陡坡方向一致。这些斜层理可以划分为高达4组不同特征的组合，分别代表潮流沙脊发育的不同阶段，对应于冰后期海平面上升的不同时期。东海陆架潮流沙脊主体形成于冰后期海侵阶段，目前仍然受到陆架潮流场的影响，沙脊顶部为再沉积活动层。  相似文献