Variability of sediment diatom assemblages in an upland,wind-stressed lake (Loch Fleet,Galloway, S.W. Scotland)     

N. J. Anderson 《Journal of Paleolimnology》1990,4(1):43-59

The variability of diatom distribution in an acidified, upland wind-stressed lake (Loch Fleet, Galloway, S. W. Scotland) was assessed by analysis of 28 surface sediment samples and 11 cores. Correspondence analysis (CA) and cluster analysis were used to illustrate the variability of the surface sediment and core samples. There was reasonable uniformity of taxa in most of the surface sediment samples, although 7 samples, as indicated by both CA and cluster analyses were atypical. Most cores recorded clearly the acidification of the lake, although percentages of individual taxa varied up to 20% between cores. Two cores had old, preacidification diatom assemblages (of indeterminate age) close to the sediment surface. These old sediments were probably the source of the re-worked diatoms found in the atypical surface sediment assemblages. Diatom trends, as CA ordinations and pH profiles, were less variable than the surface sediment assemblages. It is argued that non-uniform sediment accumulation rates and diatom deposition cause variability in surface sediment diatom samples. This variability may be reduced in core profiles by homogenization during further resuspension/deposition cycles and burial. Cores, and the associated time component they offer, may be useful in assessing the variability of surface sediment assemblages.  相似文献   

The Earth's decelerated rotation and regularities in orientation of its surface lineaments and faults     

Lev A. Maslov  Vladimir A. Anokhin 《Planetary and Space Science》2006,54(2):216-218

The Earth's crust faults and lineaments group in clusters with predominant N-S and E-W (System I) and NW-SE and NE-SW (System II) directions. The earthquake epicenters of the Benioff seismofocal zones follow the same regularities. In other words, seismofocal zones (epicenters of earthquakes) constitute a part of the regular network of the Earth's crust and lithosphere faults and lineaments. Mathematical modeling of stress distribution in the lithosphere due to a change of the Earth's ellipsoid compression showed that the principal stresses σ₁ and σ₂ are oriented in N-S and E-W directions, while corresponding shear stresses τ are oriented in NE-SW and NW-SE directions. It is shown that the secular deceleration of the Earth's rotation can be a reasonable mechanism for the change of Earth's ellipsoid compression and, consequently, for the origin of the regular system of faults and lineaments described above.  相似文献   

频率可切换的矩形缝隙环频率选择表面     

廖翔宇  李亚鹏  杜国宏 《成都信息工程学院学报》2015,30(2)

基于金属屏上周期排列的缝隙单元结构的通带特性,提出矩形缝隙环(Rectangular Slot Ring,RSR)加载短路线的单元结构实现频率可调频率选择表面(Frequency Selective Surface,FSS).谐振缝隙单元开路与短路时相对应的谐振频率分别为13 GHz和15 GHz.RSR-FSS选用Rogers RO4003介质作为基板,按照12×12的方阵进行周期排列,利用全波电磁仿真软件CST对其进行了电磁传输特性仿真.最终,通过实验验证了该频率选择表面在Ku波段通过连通和断开短路线可以进行频率的切换.  相似文献   

Reliability analysis of H-infinity control for a container ship in way-point tracking     

《Applied Ocean Research》2015

Efficient control of ships in a designed trajectory is always a significant charge for ship maneuverings. The purpose of this paper is to design a robust H_∞ controller and a reliability analysis for a container ship in a way-point tracking. First, the H_∞ controller is designed for a container ship because of model parameters’ uncertainties and external disturbances such as waves, winds and ocean currents. Then, to evaluate the reliability of the designed controller, a well-known reliability analysis technique is employed to achieve the predefined heading angle overshoot (that is less than 20%) in way-point tracking. To do this, three random variables including wind speed, wind direction and wave direction are considered as the inputs due to their significant effect on overshoot, compared to other variables. The results demonstrate the capability of the designed H_∞ controller against modeling uncertainties and external disturbances in way point tracking control.  相似文献   

Application of an improved semi-Lagrangian procedure to fully-nonlinear simulation of sloshing in non-wall-sided tanks     

《Applied Ocean Research》2015

The semi-Lagrangian procedure is widely used for updating the fully-nonlinear free surface in the time domain. However, this procedure is only available to cases when the body surface is vertical near the waterline. Present study introduces an improved semi-Lagrangian procedure which removes this ‘vertical-wall’ limitation. Coupling with the boundary element method, the improved semi-Lagrangian procedure is applied to the simulation of fully-nonlinear sloshing waves in non-wall-sided tanks. From the result comparison with the open source CFD software OpenFOAM, it is confirmed that this numerical scheme could guarantee a sufficient accuracy. Further series studies on 2D and 3D fully-nonlinear sloshing waves in wedged tanks are performed. Featured phenomena are observed which are distinct from those in wall-sided tanks.  相似文献   

基于不同权重的栖息地指数模型预报阿根廷滑柔鱼中心渔场   总被引：12，自引：3，他引：9  

胡贯宇  陈新军  汪金涛 《海洋学报》2015,37(8):88-95

本文根据2003-2009年1-5月和2011年1-5月西南大西洋海域阿根廷滑柔鱼(Illex argentinus)的生产数据,结合遥感获得的海表面温度(SST)和海表面高度(SSH)数据,利用不同权重的栖息地指数模型来预报阿根廷滑柔鱼的中心渔场。采用外包络法,利用作业次数与SST、SSH建立适应性指数(SI)模型,依据作业次数比重和产量比重来比较不同权重的算术加权模型(AWM),从而筛选出最佳模型,并对最佳模型进行验证。结果显示,确定AWM(a=0.3,SST权重为0.3,SSH的权重为0.7)为最佳模型,当栖息地适应性指数(HSI)大于0.6时,作业次数的比重为93.23%,产量比重为89.28%,当HSI小于0.4时,作业次数的比重为2.12%,产量比重为3.35%。利用2011年1-5月的生产数据和环境数据对AWM(a=0.3)进行验证,结果显示,在HSI大于0.6的海域,各月作业次数比重均在91%以上,产量比重均在95%以上。研究表明,在阿根廷滑柔鱼渔场形成中SSH比SST更为重要,基于SST和SSH的AWM(a=0.3)能够较好地预测西南大西洋阿根廷滑柔鱼的中心渔场。  相似文献   

南极半岛东北海域表层沉积有机质来源及其沉积环境     

韩喜彬  赵军  初凤友  潘建明  唐灵刚  许冬  边叶萍  葛倩 《海洋学报》2015,37(8):26-38

采用气相色谱-质谱技术对南极半岛东北海域海底表层沉积物的总有机碳、有机质碳同位素(δ13 Corg)和生物标志化合物等进行了测试分析。研究区表层沉积物总有机碳TOC平均值高于现代深海沉积物中的平均含量。δ13 Corg的变化说明该海域有机碳来源呈海洋水生生物来源和陆源混合的特征。正构烷烃的峰型分布、主峰碳、饱和烃轻重比C-21/C+22和(C21+C22)/(C28+C29)、甾烷组合和藿烷组合证实研究区西部表层沉积物有机质来源以陆源高等植物为主,其陆源可能来自于附近的南极半岛和南舍得兰群岛;研究区东部表层沉积物有机质来源偏以海源为主,且以低等浮游生物、藻类及细菌生物等海源输入为主。碳优势指数(Carbon preference index,CPI)、奇偶优势指数(Odd-even Predominance,OEP)和甾烷C29ααα20S/(20S+20R)比值显示研究区D1-7站位和D5-9沉积物有机质演化程度较高,D5-2和D2-4站位的有机质演化程度低,其他站位介于中间状态。饱和烃中姥鲛烷、植烷及其比值(Pr/Ph)等组合显示研究区西部以氧化-弱还原的沉积环境为主,其可能是受高温低盐别林斯高晋海水流和附近火山喷发的影响所致;研究区东部以还原—强还原沉积环境为主,可能是受低温高盐的威德尔底层水(WSBW)和威德尔海深层水(WSDW)影响所致。  相似文献   

北极海冰的年代际转型与中国冻雨年代际变化的关系   总被引：1，自引：0，他引：1  

牛璐  黄菲  周晓 《海洋学报》2015,37(11):105-117

基于1961-2013年HadISST海冰密集度资料,定义了北极海冰的季节性融冰指数,结果显示近几十年来北极季节性融冰范围呈显著的上升趋势,并分别在20世纪70年代末和90年代中期存在显著的年代际转型,相应地,中国冻雨发生频数总体上呈现出显著的减少趋势,但也存在显著的年代际转型。在20世纪70年代末之前,北极季节性融冰范围较小但显著增长,中国冻雨频数年际变化振幅较大,且主要受巴伦支海、喀拉海海冰的影响;20世纪70年代末至90年代中期北极季节性融冰范围维持振荡特征,没有显著的线性趋势,中国冻雨频数变化振幅减小,与北极海冰相关较弱,主要相关因子为北大西洋及北太平洋海表温度变化;而90年代中期以后,北极海冰融化加快,特别是2007年以后,季节性融冰范围大大增加,而中国冻雨频数处于低发时段,其变化与太平洋扇区海冰及堪察加半岛附近海温呈显著负相关,季节性融冰的显著区域也从东西伯利亚海逆时针旋转向波弗特海-加拿大群岛北部扩张,同时向北极中央区扩张。不同年代影响冻雨的海温或海冰关键海区不同,产生特定的大气环流异常响应,进而影响到我国冻雨。  相似文献   

便携式高频地波雷达台湾海峡浪高观测   总被引：2，自引：1，他引：1  

ZHOU Hao  ROARTY Hugh  WEN Biyang 《海洋学报(英文版)》2015,34(1):73-78

As an important equipment for sea state remote sensing, high frequency surface wave radar(HFSWR) has received more and more attention. The conventional method for wave height inversion is based on the ratio of the integration of the second-order spectral continuum to that of the first-order region, where the strong external noise and the incorrect delineation of the first- and second-order Doppler spectral regions due to spectral aliasing are two major sources of errors in the wave height. To account for these factors, two more indices are introduced to the wave height estimation, i.e., the ratio of the maximum power of the second-order continuum to that of the Bragg spectral region(RSCB) and the ratio of the power of the second harmonic peak to that of the Bragg peak(RSHB). Both indices also have a strong correlation with the underlying wave height. On the basis of all these indices an empirical model is proposed to estimate the wave height. This method has been used in a three-months long experiment of the ocean state measuring and analyzing radar, type S(OSMAR-S), which is a portable HFSWR with compact cross-loop/monopole receive antennas developed by Wuhan University since 2006. During the experiment in the Taiwan Strait, the significant wave height varied from 0 to 5 m. The significant wave heights estimated by the OSMAR-S correlate well with the data provided by the Oceanweather Inc. for comparison, with a correlation coefficient of 0.74 and a root mean square error(RMSE) of 0.77 m. The proposed method has made an effective improvement to the wave height estimation and thus a further step toward operational use of the OSMAR-S in the wave height extraction.  相似文献   

南海海面高度变化及其与太平洋上涛动信号的关系   总被引：1，自引：1，他引：0  

PEI Yuhu  ZHANG Rong-Hu  ZHANG Xiangming  JIANG Lianghong  WEI Yanzhou 《海洋学报(英文版)》2015,34(12):80-92

本文使用循环平稳经验正交函数(CSEOF)方法分析了南海海面高度(SCS-SSH)的时空变化模态,并对它们与太平洋海盆尺度振荡的关系进行了探讨分析。结果表明,SCS-SSH的第一个CSEOF模态是季节变化模态,其变化强度受到一个与厄尔尼诺-南方涛动(ENSO)有关的低频信号的调制,即在厄尔尼诺期间季节变化的幅度减弱(最大可降低30%,1997/98)而在拉尼娜期间季节变化增强。SCS-SSH的第二个CSEOF模态是年际-年代际尺度的低频变化模态,其空间模态的月与月之间的差异微弱,而时间模态和太平洋年代际振荡(PDO)指数高度相关。然后,我们使用独立成分分析(ICA)方法提取了太平洋中的五个主要振荡成分,并检验了它们对SCS-SSH变化的各自影响。分析表明,纯粹的ENSO模态(类似于太平洋东部型ENSO)对SCS-SSH的低频变化的影响比较微弱,而ENSO的红化模态(类似于太平洋中部型ENSO)对SCS-SSH的低频变化具有明显影响。由于ENSO的红化模态是PDO信号的一个主要成分,这一结果解释了为什么在影响SCS-SSH的低频变化上PDO比ENSO更重要。径向鞍型振荡模态、黑潮延伸体处的增温模态、以及赤道的降温模态也由ICA方法提取出来,但它们对SCS-SSH低频变异的影响微弱。进一步的分析表明,太平洋的涛动信号可能以不同的方式来影响南海海面高度变化和海表温度变化。  相似文献