Sensitivity analysis of sediment flux derived by laser diffraction and acoustic backscatter within a reservoir     

Stefan Haun  Laura Lizano 《国际泥沙研究》2018,33(1):18-26

A combination of two indirect methods to measure sediment flux is presented in this study to evaluate suspended sediment transport in a hydropower reservoir. The acoustic backscatter signal (ABS) from an Acoustic Doppler Current Profiler (ADCP) is therefore applied in pre-defined transects within the reservoir in combination with a Laser In-Situ Scattering Transmissometry – stream lined device (LISST-SL). The stationary LISST-SL derived suspended sediment concentration (SSC) measurements are used to calibrate the ABS. From the LISST-SL measurements a time series of SSC is obtained. This enables, in addition, a comprehensive data analysis to evaluate the influence of natural fluctuations of the SSC on the calculated sediment flux, which should be taken into account when assessing sediment transport. Furthermore SSC measurements are done with the LISST-SL close to the reservoir bed. In areas close to the bed no information regarding the ABS is available from the ADCP measurements due to the side-lobe interference. In various studies the information from the last three valid cells is used for extrapolation. However, as result of a comparison of the LISST-SL measurements with extrapolated SSC values from the ADCP measurements it can be seen that, especially in deep reservoirs, this method has to be adapted to the in-situ conditions.  相似文献   

分布式超宽带雷达地震被困人员协同探测技术     

孙公德  郭勇  沈建  赵蕾莛  张忠元 《震灾防御技术》2017,12(4):966-977

针对震后在大面积废墟下快速准确检测与定位被困人员的需求,本论文提出了用分布式超宽带雷达探测地震被困人员的技术,主要包括对分布式超宽带雷达协同探测网络构建、超宽带雷达生命迹象探测算法、分布式雷达节点探测数据融合方法等3个方面进行研究,对多雷达干扰抑制、分布式雷达节点自定位、微弱生命迹象稳健探测、废墟穿透定位误差补偿等关键技术难题提供了设计方案,为完成分布式超宽带雷达系统的研制奠定了技术基础。  相似文献   

川东南焦石坝页岩气区现今地温场特征   总被引：2，自引：1，他引：1       下载免费PDF全文

李春荣  饶松  胡圣标  汪集旸  魏志红  黄庆球  胡东风  郭旭升 《地球物理学报》2017,60(2):617-627

四川盆地是我国重要的含油气区,关于盆地现今地温场的工作,前人已经做过一些研究.而对于近年来页岩气勘探取得突破性进展的川东南焦石坝地区,现今地温场的研究工作甚少.本文基于川东南高陡褶皱带焦石坝页岩气区新增的3口钻井的稳态测温数据和118块岩石样品热导率数据,计算了研究区的地温梯度和大地热流值.结合前人的研究成果,编制了研究区大地热流等值线图.结果表明,焦石坝页岩气区地温梯度介于24~34℃/km,大地热流值介于60~70mW·m~(-2)之间,与川中古隆起相似,属于地温高异常区.地温高异常缘于隆起区相对高的岩石热导率引起的浅部热流的重新分配.其次,与位于研究区东侧边界的齐岳山大断裂在燕山和喜山期的构造引起的热液活动有关.焦石坝页岩气区地温高异常对页岩气的解吸附速率具有促进作用,对提高采收率具有一定意义.  相似文献   

古建筑激光点云-模型多层次一体化数据模型     

詹庆明  张海涛  喻亮 《测绘软科学研究》2010,(4):6-11

目前,主流的激光点云数据模型仍以散乱点组织为主,且点云与模型分开组织。本文应古建筑激光点云处理建模的数据组织需要,通过点云、模型的关联组织和古建筑层次编码等方法,创建了古建筑激光点云-模型多层次一体化数据模型。并通过实例应用进行了验证,效果较好,为点云的复杂数据组织提供了借鉴。  相似文献   

Survival of a proto-atmosphere through the stage of giant impacts: the mechanical aspects   总被引：2，自引：0，他引：2  

Hidenori Genda  Yutaka Abe 《Icarus》2003,164(1):149-162

When a giant impact occurs, atmosphere loss may occur due to global ground motion excited by a strong shock wave traveling in the planetary interior. Here, the relations between the ground motion and the amount of the lost atmosphere are systematically investigated through calculations of a spherically one-dimensional atmospheric motion for various initial atmospheric conditions. The fraction of the lost atmosphere to the total mass of the atmosphere is found to be controlled only by the ground velocity and, insensitive to the initial atmospheric conditions. Unlike the previous studies (Ahrens, 1990, Origin of the Earth, H.E. Newson, J.H. Jones (Eds.), pp. 211-227; Ahrens, 1993, Annu. Rev. Earth Planet. Sci. 21, 525-555; Chen and Ahrens, 1997, Phys. Earth Planet. Inter. 100, 21-26); the estimated loss fraction for the giant impact is only 20%. Significant escape occurs only when the ground velocity is close to the escape velocity. Thus, most of the atmosphere should survive the giant impact. The cause of the difference from previous estimates is discussed from energetic and dynamic points of view. Moreover, if our estimates are applied to the atmosphere of the impactor planet, a significant fraction of it is carried to the target planet. Survival of the proto-atmosphere has very important effects on the origin and evolution of the terrestrial planets' volatile budget.  相似文献   

Double-Pulse Laser-Driven Jets on OMEGA     

S. Sublett  J. P. Knauer  I. V. Igumenshchev  A. Frank  D. D. Meyerhofer 《Astrophysics and Space Science》2007,307(1-3):47-50

A double-pulse laser drive is used to create episodic supersonic plasma jets that propagate into a low density ambient medium. These are among the first laser experiments to generate pulsed outflow. The temporal laser-intensity profile consists of two 1-ns square pulses separated by 9.6 ns. The laser is focused on a truncated conical plug made of medium Z material inserted into a high-Z washer. Unloading material from the plug is collimated within the cylindrical washer hole, then propagates into the low-Z foam medium. The resulting jet is denser than the ambient medium. Double-pulse jet evolution is compared to that driven by a single laser pulse. The total drive energy is the same for both jets, as if a source with fixed energy generated a jet from either one or two bursts. Radiographs taken at 100 ns show that a single-pulse jet was broader than the double-pulse jet, as predicted by hydrodynamic simulations. Since the initial shock creating the jet is stronger when all the energy arrives in a single pulse, the jet material impacts the ambient medium with higher initial velocity. Detailed comparisons between single- and double-pulsed jet rheology and shock structure are presented. 2-D hydrodynamic simulations are compared to the experimental radiographs. PACS: 52.30.−q 41.75.Jv 42.62.−b 42.68.Sq 47.40.−x 47.56.+r  相似文献   

Rheological constraints on martian landslides     

Keith P Harrison  Robert E Grimm 《Icarus》2003,163(2):347-362

We use a dynamic finite-difference model to simulate martian landslides in the Valles Marineris canyon system and Olympus Mons aureole using three different modal rheologies: frictional, Bingham, and power law. The frictional and Bingham modes are applied individually. Fluidized rheology is treated as a combination of frictional and power-law modes; general fluidization can include pore pressure contributions, whereas acoustic fluidization does not. We find that general fluidization most often produces slides that best match landslide geometry in the Valles Marineris. This implies that some amount of supporting liquid or gas was present in the material during failure. The profile of the Olympus Mons aureole is not well matched by any landslide model, suggesting an alternative genesis. In contrast, acoustic fluidization produces the best match for a lunar slide, a result anticipated for dry crust with no overlying atmosphere. The presence of pressurized fluid during Valles Marineris landsliding may be due to liquid water beneath a thin cryosphere (<1-2 km) or flash sublimation of CO₂.  相似文献   

CARAIB陆地碳循环模型研究进展及其应用   总被引：1，自引：0，他引：1  

黄康有  郑卓  Cheddadi R.  Laurent J.M.  Fran 《热带地理》2007,27(6):483-488

陆地生态系统碳循环是全球变化研究中的重要组成部分,多种模型已用于陆地生态系统碳循环的模拟。文中着重论述了陆地生物圈碳循环模型CARAIB的原理、方法及其应用和最新进展。CARAIB模型主要是基于叶面光合作用子模型、冠层子模型和木质呼吸作用3个子模型的耦合,应用大气环流模式气候数据模拟出生态系统碳存储量和生物群区分布。介绍了欧洲利用植物数字化地理配准数据库重新划分植物群组(BAGs)的方法,比较BAGs与传统的植物功能型(PFTs)划分在方法上的差异,根据植物群组应用CARAIB模型进行生物群区分布模拟,并提出利用CARAIB模型模拟我国陆地碳循环和生物群区分布的可行性,为研究中国植被对气候变化的响应模型和预测提供区域尺度的新方法。  相似文献   

湖南瑶岗仙钨矿床流体包裹体特征及其意义   总被引：13，自引：5，他引：13  

王巧云胡瑞忠  彭建堂毕献武  武丽艳刘华 苏本勋 《岩石学报》2007,23(9):2263-2273

对瑶岗仙石英脉型钨矿床的石英、萤石和夕卡岩型钨矿床中石榴石流体包裹体的岩相学特征研究表明,与成矿有关的包裹体主要有三类:富液相、富气相和含子晶的多相包裹体。脉型钨矿床中石英包裹体均一温度范围为180℃～300℃,盐度0.88～6.45 wt%NaCl eqv;矽卡岩型钨矿床中石榴石包裹体的均一温度范围为190℃～300℃,盐度0.1～8.95wt%NaCl eqv;成矿溶液的密度为0.81～0.89g/cm~3,表明形成这两种类型矿床的成矿流体均属于中温、低盐度、低密度的流体;成矿压力为120～160MPa,成矿深度约为7～9km,因此该矿床是在中高压力、中深成条件下形成的。激光拉曼探针分析表明,石英中包裹体的气相成分比石榴石中的更富含 CH_4、CO_4和 H_2O 等挥发份,说明流体是一种介于岩浆与热液之间的过渡性流体,具有上部偏液、下部偏浆的特点。由于该区自燕山期以来软流圈上隆,岩石圈经历了强烈的伸展、减薄作用和壳幔相互作用,而 C-H 还原性组分的增加,指示流体很可能来自于深部的地幔过渡带或者软流圈。  相似文献   

利用SLR数据进行广播星历精度评估     

毛悦  贾小林  孙付平 《测绘学院学报》2007,(4)

论述了利用SLR观测数据进行广播星历精度评估的原理、方法及计算模型。通过理论分析及对比试算,得出该方法所能达到的精度为0.03 m,与微波观测数据计算结果存在近50 mm的系统差,验证了方法的可行性。该方法为广播星历精度评估提供了独立的外部检核条件,克服了利用精密星历评估必须事后进行的缺点,达到了实时处理的效果。采用2005年SLR观测数据对GPS 35卫星广播星历精度进行了实测数据评估,给出了有益的结论。  相似文献