Marine debris collects within the North Pacific Subtropical Convergence Zone   总被引：1，自引：0，他引：1  

Pichel WG  Churnside JH  Veenstra TS  Foley DG  Friedman KS  Brainard RE  Nicoll JB  Zheng Q  Clemente-Colón P 《Marine pollution bulletin》2007,54(8):1207-1211

Floating marine debris, particularly derelict fishing gear, is a hazard to fish, marine mammals, turtles, sea birds, coral reefs, and even human activities. To ameliorate the economic and environmental impact of marine debris, we need to efficiently locate and retrieve dangerous debris at sea. Guided by satellite-derived information, we made four flights north of Hawaii in March and April 2005. During these aerial surveys, we observed over 1800 individual pieces of debris, including 122 derelict fishing nets. The largest debris concentrations were found just north of the North Pacific Transition Zone Chlorophyll Front (TZCF) within the North Pacific Subtropical Convergence Zone (STCZ). Debris densities were significantly correlated with sea-surface temperature (SST), chlorophyll-a concentration (Chla), and the gradient of Chla. A Debris Estimated Likelihood Index (DELI) was developed to predict where high concentrations of debris would be most likely in the North Pacific during spring and early summer.  相似文献   

大跨径钢索塔斜拉桥钢箱梁施工测量技术     

孙景领  赵显富  王新志 《东北测绘》2012,(2):196-198

南京长江三桥是我国首座主塔采用钢结构形式的特大型斜拉桥,主梁为正交异性板流线型扁平式钢箱梁。文章介绍了钢箱粱安装的精度要求,以及分步骤建立施工控制网的方法,并详细阐述了不同梁段施工测量的技术和方法,结果表明成桥后的钢箱梁线型符合设计要求。  相似文献   

大巴山弧形构造带中段渔渡地区侏罗纪叠加变形研究     

武国利  陈虹  田密  施炜  高卫 《西安地质学院学报》2010,(2):130-136,148

大巴山构造带是秦岭造山带南部发育的一个以逆冲推覆构造为特征的构造带。通过在大巴山弧形构造带中段渔渡地区进行的详细构造解析发现,大巴山构造带在侏罗纪以来经历了至少两期变形叠加,变形地层三叠系嘉陵江组—侏罗系沙溪庙组。早期变形以与滑脱构造相关的轴向北西—北北西向箱状或隔挡状褶皱为主,并在深部发育顺层滑脱构造,变形时代为晚侏罗世到早白垩世。晚期变形与北侧逆冲相关,导致右行走滑变形,主要形成右行走滑断层和北西—北北西向紧闭褶皱,变形时代比第一期稍晚,为晚侏罗世之后到早白垩世。两期变形形成的褶皱延伸方向一致,与区域构造线的方向协调,而且在远离北侧镇巴断裂的地区变形强度有减弱的趋势,两期变形叠加形成共轴或斜交叠加构造。研究表明,变形与大巴山冲断—推覆构造带向南逆冲有关。  相似文献   

地表几何形态对冲断带构造特征影响的物理模拟实验研究          下载免费PDF全文

谢玉华  赵坤  周建勋  王利  王雪芹 《沉积与特提斯地质》2010,30(1):89-92

设计了基底均匀的水平砂层单测挤压砂箱模型,包括水平砂层上无砂丘以及砂丘分别位于距左侧活动挡板5 cm、10 cm、15 cm、20 cm、25 cm、30 cm时的7组实验,通过实验着重对水平砂层在受单侧挤压时不同位置砂丘对冲断带的影响问题进行研究。实验结果表明,砂丘在不同位置时,冲断带的形成规模、几何形状都发生相应变化:砂丘距左侧活动挡板10～25 cm时,冲起构造发育,且冲断带的构造特征明显;而砂丘距左铡活动档板5 cm、30 cm时不发育冲起构造,主要发育逆冲断层。  相似文献   

On Outflow Passages in the South China Sea   总被引：2，自引：0，他引：2  

DONG Danpeng  ZHOU Weidong  YANG Yang  DU Yan 《大气科学进展》2010,27(1):60-68

Both box and inverse methods are used to study the relative importance of outflow passages of the South China Sea.The physical meaning of the box model is described in detail,and its optimization is based on the most efficient way to remove the warm and fresh water in terms of the heat and salt budgets.The box model results suggest that the Kalimantan Strait is the main outflow passage,because the water near the Kalimantan is the warmest and freshest.The system of the South China Sea advects the warmest and...  相似文献   

Gray box identification of flexible structures: application to robust active vibration suppression control     

A. Forrai  S. Hashimoto  A. Isojima  H. Funato  K. Kamiyama 《地震工程与结构动力学》2001,30(8):1203-1220

The paper deals with gray box identification of flexible structures and active vibration suppression from a robust control perspective. First, the linearized mathematical model of an N‐storey flexible structure is presented. Next, the generalized mathematical model is particularized for the investigated three‐storey flexible structure. The considered flexible structure is identified based on black box and gray box identification methods and the model's parametric uncertainties are deduced. Furthermore, control constraints are presented for the design problem, in case of velocity as well as acceleration feedback, from a robust control perspective. Finally, the effectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record). Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

An index for describing the core-stone shape in weathered columnar joints     

Z. Y. Yang  T. J. Wu 《Geotechnical and Geological Engineering》2006,24(5):1349-1363

The shape of core-stones remained in the weathering basalt column is an index to classify its weathered degree. In this paper, a roundness index (RI) like the box dimension using in fractal theory, was employed to quantitatively measure the shape of core-stone in various weathering grades. The rounded core-stone that is weathered seriously has a smaller RI value. According to the value of RI, the five classes shown in the Russell–Taylor–Pettijohn chart for visually classifying grain shape is available to approximately determine the weathered grades of core-stones remained in the basalt column in Taiwan. A slump test is preliminarily tested to show the difference in repose angle of a stability slope assembled by the grains in a similar shape. The collection of angular core-stones those are less weathered (with a higher RI value) indeed reveals a greater repose angle.  相似文献   

箱涵顶进工艺在玄武湖水底交通隧道方案中的应用   总被引：2，自引：0，他引：2       下载免费PDF全文

王国权  罗国煜  李晓昭 《探矿工程》1998,(5):50-51

在玄武湖水底交通隧道筑堤开槽埋管方案中,为确保古城墙的安全,可采用箱涵顶进工艺穿越古城墙基础。介绍了箱涵顶进工艺的结构设计及实用前景。  相似文献   

连续箱梁高架桥横向动力分析   总被引：4，自引：0，他引：4  

陈淮  曾庆元 《地震工程与工程振动》1996,16(3):114-121

本文提出了可以考虑箱形梁弯曲、扭转、畸变多种因素的梁－墩系统横向振动的动力分析模型。  相似文献   

钻井过程中钻具吸附卡钻事故成因与处理技术          下载免费PDF全文

卢予北  刘志国  程存平  吴青松 《探矿工程》2004,31(12):33-35

针对钻井过程中常遇的吸附卡钻事故，就其成因、产生条件及处理技术方法进行了较为详细的论述。结合工程实例对新研制的XS-1型解卡剂作用机理进行了分析、应用并提出了具体的操作规程和注意事项。  相似文献