Characteristic ichthyoplankton taxa in the separation zone of the East Australian Current: Larval assemblages as tracers of coastal mixing     

Augy Syahailatua  Moninya Roughan  Iain M. Suthers 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(5):678-690

Ichthyoplankton assemblages were compared between regions dominated by the oligotrophic East Australian Current (EAC) and the inner-shelf waters off southeastern Australia, to determine if the early life history of fish was related to the separation of the EAC from the coast, producing different water masses as well as characteristic taxa. Samples were collected at the surface and in sub-surface waters, at 50 and 100 m isobath stations, during two summer research voyages in November 1998 and January 1999. On both voyages the study region was characterized by coastal and EAC waters in the north (∼31°S), and in the south by topographically induced upwelling (∼31°S), associated with narrowing of the continental shelf and separation of the EAC from the coast. Among the 111 families of larval fish, we observed distinctive assemblages of ichthyoplankton associated with the two different water masses. A greater abundance of the Carangidae, Labridae, Lutjanidae, Microcanthidae, Myctophidae and Scombridae was associated with the nutrient poor EAC water mass, while the Callionymidae, Clupeidae, Platycephalidae and Sillaginidae were mostly found in the cooler and/or fresher inner-shelf water mass. We assessed these patterns with opportunistic samples from an unusual, wind-driven upwelling event in the north (∼31°S) earlier in the November voyage. The relative abundance of these 10 characteristic families distinguished this wind-driven upwelling event from the subsequent relaxation and predominance of the EAC assemblage at this location just 6 d later. Distinctive and abundant families such as larval clupeids, relative to larval carangids, could be a useful marker of inner-shelf, EAC and mixed water masses in the absence of robust hydrographic data. This and related studies indicate contrast in early life histories of Sardinops sagax and Trachurus spp., which appear to spawn respectively in the inner-shelf and outer-shelf waters. The post-flexion stages of S. sagax predominate in the outer-shelf and Tasman Front, while post-flexion Trachurus spp. predominate in inner-shelf water masses.  相似文献   

FoxPro事件驱动程序设计     

任瑞英 《成都信息工程学院学报》1997,(3)

作者叙述了事件驱动程序设计的基本概念及事件管理、捕获事件、窗口管理的基本方法。  相似文献   

An analytical solution for a jointed shield‐driven tunnel lining     

K. M. Lee  X. Y. Hou  X. W. Ge  Y. Tang 《国际地质力学数值与分析法杂志》2001,25(4):365-390

This paper presents an analytical solution for the prediction of internal forces and displacements of a jointed segmental precast circular tunnel lining. The effects of joint stiffness on the performance of the tunnel lining are discussed. The ‘force method’ is used to determine the internal forces and displacements of jointed tunnel lining. Five shield‐driven tunnel cases are adopted to study the effects of joint stiffness, soil resistance, joint distribution and joint number on the internal forces and displacements of circular tunnels. Laboratory model tests are conducted to verify the proposed analytical solution. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

线性Radon域地震干涉层间多次波预测方法     

孙宇  王德利  胡斌 《世界地质》2018,37(1):267-275

为避免时空域地震干涉技术预测层间多次波过程中出现假象干扰,影响地震资料处理。笔者结合线性Radon变换与地震干涉技术,在线性Radon域中利用地震干涉技术预测层间多次波。通过数值模拟验证了线性Radon域地震干涉层间多次波预测方法的有效性,并将该方法应用到复杂速度模型中。结果表明,线性Radon域地震干涉技术可以有效减少时空域地震干涉技术预测层间多次波存在的假象,压缩数据体积大小,提高计算效率,并能够适用于复杂地质环境。  相似文献   

Subspace system identification of support‐excited structures—part I: theory and black‐box system identification     

Junhee Kim  Jerome P. Lynch 《地震工程与结构动力学》2012,41(15):2235-2251

This paper reviews the theoretical principles of subspace system identification as applied to the problem of estimating black‐box state‐space models of support‐excited structures (e.g., structures exposed to earthquakes). The work distinguishes itself from past studies by providing readers with a powerful geometric interpretation of subspace operations that relates directly to theoretical structural dynamics. To validate the performance of subspace system identification, a series of experiments are conducted on a multistory steel frame structure exposed to moderate seismic ground motions; structural response data is used off‐line to estimate black‐box state‐space models. Ground motions and structural response measurements are used by the subspace system identification method to derive a complete input–output state‐space model of the steel frame system. The modal parameters of the structure are extracted from the estimated input–output state‐space model. With the use of only structural response data, output‐only state‐space models of the system are also estimated by subspace system identification. The paper concludes with a comparison study of the modal parameters extracted from the input–output and output‐only state‐space models in order to quantify the uncertainties present in modal parameters extracted from output‐only models. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Drift currents in the southern New Zealand region as derived from Lagrangian measurements and the remote sensing of sea‐surface temperature distributions     

W. N. Jenks  J. Grindrod  J. A. Peterson 《新西兰海洋与淡水研究杂志》2013,47(3-4):359-371

Four drift bottles, cast adrift south of the Subtropical Convergence at 48°S, 156°E in November 1980, landed within 123 days of release at a short stretch of coast north of Banks Peninsula. A high degree of coherence in the responsible drift pattern is indicated. The contemporary surface circulation inferred from satellite‐derived sea‐surface temperature distributions indicates that the bottles were entrained in a meridionally‐converging flow after drifting across the southern Tasman Sea without crossing the Convergence. They were prevented from further eastward drifting because of a marked southward flexing of the Convergence east of the Southland Current during February 1981. Because of local weather and tide effects, the bottles finally beached in Pegasus Bay.  相似文献   

Solving density driven flow problems with efficient spatial discretizations and higher-order time integration methods     

Anis Younes  Marwan FahsSelim Ahmed 《Advances in water resources》2009

Modelling density driven flow problems requires an excessive computational time and/or heavy equipments due to the non-linear coupling between flow and transport equations. In this work, we develop a robust numerical model with efficient advanced approximations for both spatial and temporal discretizations in order to reduce the excessive computational requirement while maintaining accuracy.  相似文献   

The importance of missing strain in Deep Water Fold and Thrust Belts     

《Marine and Petroleum Geology》2017

Deep water fold and thrust belts (DWFTBs) are sedimentary wedges that accommodate plate-scale deformation on both active and passive continental margins. Internally, these wedges consist of individual structures that strongly influence sediment dispersal, bathymetry and fluid migration. Most DWFTB studies investigate basin- and intra-wedge- scale processes using seismic reflection profiles, yet are inherently limited by seismic resolution. Of critical importance is strain distribution and its accommodation on discrete faults compared to distributed deformation. Recent studies have considered strain distribution by investigating regional reflection DWFTBs profiles within coupled systems, which contain down-dip compression and up-dip extension. There is broad agreement of a mis-balance in compression versus extension, with ∼5% excess in the latter associated with horizontal compaction, yet this remains unproven.Using two exceptionally well exposed outcrops in the Spanish Pyrenees we consider deformation of DWFTB at a scale comparable to, and beyond, seismic resolution for the first time. By coupling outcrop observations (decametre to hectometre scale) with a re-evaluation of seismic profiles from the Orange Basin, South Africa, which contains one of the best imaged DWFTBs globally, we provide a unique insight into the deformation from metre to margin scale. Our observations reveal hitherto unrecognised second order structures that account for the majority of the previously recognised missing strain. This re-evaluation implies that ∼5% missing strain should be accounted for in all DWFTBs, therefore existing studies using restorations of the sediment wedge will have underestimated crustal shortening in active margins, or sedimentary shortening in gravity driven systems by this amount. In contrast to previous studies, our observations imply that the majority of this strain is accommodated on discrete fault surfaces and this can explain the occurrence and location of a range of intra-wedge processes that are intimately linked to structures including sediment dispersal, fluid migration pathways and reservoir compartmentalisation.  相似文献   

盾构法开挖隧道对桩基础影响的有限元分析     

王丽  郑刚 《岩土力学》2011,32(Z1):704-0712

利用有限元软件ABAQUS,采用对隧道洞室周边及开挖面的土体施加由盾构机引起的各种荷载的方法模拟天津市地铁1号线盾构施工。计算结果表明,有限元模型能够很好地模拟盾构施工过程。利用此模型研究隧道开挖对桩基础的影响。隧道开挖引起的桩顶沉降、桩身侧移主要发生在盾构机推进面逐渐接近桩的过程中,当盾构机推进面通过桩所在的位置后桩顶沉降、桩身侧移增加不明显;与隧道水平距离相同时,由于长桩能够充分发挥桩身下部的侧摩阻力,隧道开挖引起的长桩的桩顶沉降小于短桩的桩顶沉降;隧道开挖过程中12 m长桩的桩身发生了整体倾斜,16、19 m长桩的桩身出现了弯曲变形,16、19 m长桩的桩身最大弯矩发生在地面下12～13 m之间,即在隧道轴线附近;开挖过程中桩顶出现沿隧道推进方向的往复位移;桩顶作用的竖向荷载越大,由隧道开挖引起的桩顶沉降越大  相似文献   

汶川地震强余震的电磁同震效应   总被引：8，自引：3，他引：5       下载免费PDF全文

汤吉  詹艳  王立凤  董泽义  赵国泽  徐建郎 《地球物理学报》2010,53(3):526-534

汶川5.12大地震发生后,在武都汉王地震台及其附近地区布置了2个大地电磁测深点,进行了两期余震序列的地震电磁效应连续监测,共观测到M_s4.0及以上的余震事件35次.通过与汉王强震台的地震记录数据中15个强震记录比较发现,与地震波相对应的地震同震电磁信号存在于所有的电场和磁场记录分量中,它们与地震波到达同步.地震破裂发生时的电磁辐射信号在记录数据中相比地震波达到观测点的电磁信号幅度要小得多,无法从观测数据识别出来.通过分析对比地震位移和同震电磁信号的关系,提出了地震电磁同震信号产生的地震波驱动机理,认为观测系统在地球基本磁场中随地面运动产生了地震同震电磁信号,并从观测的地震振动位移和电磁信号进行了验证.  相似文献