DELPH2X── 一种双频双道高分辨率数字地震探测系统     

梁瑞才  吴金龙  秦亚金 《海洋科学进展》1999,(2)

Ｄｅｌｐｈ２ｘ是一套双频、双道地震探测系统,该系统由单道地震和剖面仪２套设备组合而成,在Ｄｅｌｐｈ２ｘ软件的控制下同步采集来自２套独立系统的资料。本系统具有以下特点：同时获得双频、双道信号,可以获得不同的勘探深度和分辨率;可以采用多种震源组合,以适应不同的勘探目的;具有较强的数字后处理功能,大大改善剖面质量;具有适应范围广和较强抗干扰能力。/关键词##4地震探测;;双频双道;;分辨率;;剖面;;地层  相似文献   

宁波舟山港主通道混凝土结构耐久性评估与维护技术     

李乐  方明山  王俊杰  李全旺  李克非 《海洋工程》2023,41(4):168-177

系统阐述宁波舟山港主通道跨海工程混凝土结构耐久性评估与维护技术。首先介绍宁波舟山港主通道工程概况及100年使用年限的总体要求;确定耐久性极限状态为海洋氯离子侵入引起的钢筋表面脱钝。针对此极限状态,建立了氯离子侵入过程的耐久性评估模型,确定了不同暴露条件下模型参数的统计规律;根据混凝土保护层厚度的现场实测数据和修正的暴露条件下氯离子扩散系数,对模型参数进行了更新;考虑施工阶段混凝土构件的耐久性附加措施,以某标段非通航孔桥为例,使用全概率方法计算了各类混凝土桥梁构件的失效概率和可靠指标;最终在混凝土构件耐久性评估的基础上,提出了某标段非通航孔桥各类混凝土构件的基本维护制度和维护周期。  相似文献   

LiDAR-based fluvial remote sensing to assess 50–100-year human-driven channel changes at a regional level: The case of the Piedmont Region,Italy     

S. Bizzi  H. Piégay  L. Demarchi  W. Van de Bund  C.J. Weissteiner  F. Gob 《地球表面变化过程与地形》2019,44(2):471-489

Remote Sensing (RS) technology has recently offered new and promising opportunities to analyze river systems. In this paper, we present a calibration of characteristic Hydraulic Scaling Law (HSL) using a regional database of river geomorphic features. We consistently linked discharge with channel geometry features for estimated Bankfull Channel Depth (eBCD), Active Channel Width (ACW), and Low Flow water Channel Width (LFCW), which are continuously available from RS data along the river course. We then used historical information and external sources of information on channel reaches that were relatively unaffected by human pressure over periods ranging from a few decades to a century (measured in comparable geographical areas) to infer relatively Unaltered HSLs (rUHSLs). Adopting rUHSL validated with available local historical evidence on channel geometry, we were able to assess historical changes in channel geometry consistently over the entire region and within the studied temporal window. The case study was conducted for the Po basin in the Piedmont Region, north-west Italy. From our analysis, it emerges that regionally 74% of the river network has riverbed incisions exceeding 1 m, while 66% of channels have halved their historical widths with a total of 617 ha of land subtracted from the active channel. LFCW is, on average, wider in Alpine rivers compared with those located in the North Apennines. Although it is currently not possible to measure the accuracy of these estimates, the evidence generated is coherent with available historical information, characteristic hydraulic scaling laws, evidence from relatively unaltered reaches and the available literature on local fluvial systems. This methodology provides robust, novel and quantitative information regarding decadal to secular channel changes that have occurred on a regional scale. This new layer of information enriches our ability to rationally address assessments of large-scale past and future channel trajectories. © 2018 John Wiley & Sons, Ltd.  相似文献   

地震废墟环境下Wi-Fi无线信号传播模型参数测量     

武有文  洪利  姚振静  韩智明  李亚南 《震灾防御技术》2017,12(1):210-219

本文主要针对地震废墟下手机Wi-Fi无线定位,分析实际废墟环境下Wi-Fi 2.4G无线信号的传播特性。通过对废墟结构的分析,使用矢量网络分析仪进行信道测量,对大尺度和小尺度衰减两种特性进行信道分析。采取理论预测和实际测量分析相结合的方法,对2008年5·12汶川地震的极重灾区遗址进行了废墟实地测量。对大尺度衰减进行路径损耗和钢筋混凝土吸收损耗分析,对小尺度衰减进行了平均超量时延和均方根时延分析,利用加窗、计算滑动均值,得到废墟下2.4G无线信号的传播规律,为下一步定位工作提供理论基础。  相似文献   

Review on Subaqueous Sediment Gravity Flow and Submarine Fan     

Hanpu Fu  Qun Liu  Xiumian Hu 《地球科学进展》2020,35(2):124-136

Subaqueous sediment gravity flow is the volumetrically most important process transporting sediment across our planet, which forms its largest sediment accumulations (submarine fan). Based on the previous studies, we tried to clear up the concept, classification and identification of subaqueous sediment gravity flow, and introduced the progress of modern direct observation and submarine fan model. Turbidity current and debris flow are two of the most important parts of the gravity flow, the former deposits layer by layer with normal gradation while the latter is en masse settling with chaotic disorder. The turbidity current transformed into the debris flow during the transportation is called hybrid flow. The hyperpycnal flow is the turbidity current formed by flood discharges into the ocean/lake. Modern direct observations show that the turbidity current can contain dense basal layers and last for a week. The structure of turbidity current can be different from those surge-like turbidity current observed in laboratory. Submarine fans are mainly composed of channel, levee, lobe, background deposits and mass transport deposits, which should be studied by architecture analysis and hierarchical classification. The channel deposits extend narrowly with abundant erosion structures; levee deposits are composed of thin layer mud-silty turbidites, wedge thinning laterally; the lobe deposits extend well laterally with narrow range of grain size. The hierarchy of channel deposits is channel unit, channel complex and channel complex system. The hierarchy of lobe deposits is bed, lobe element, lobe and lobe complex.  相似文献   

近半个世纪长江口九段沙湿地的冲淤演变   总被引：24，自引：6，他引：18  

杨世伦  杜景龙  郜昂  李鹏  李明  赵华云 《地理科学》2006,26(3):335-339

根据1958~2004年的系列地形图,在地理信息系统软件ArcGis8.2的支持下,探讨近半个世纪九段沙湿地演变过程。研究表明:九段沙在长期的自然淤积过程中既具有趋势性的渐变,又存在非趋势性的突变,北槽深水航道工程改变了九段沙的自然冲淤模式,使九段沙顶端至江亚南沙大片区域显著淤积,工程后期,淤积速率回落,九段沙形态稳定。  相似文献   

LIVE-BED SCOUR IN LONG CONTRACTIONS   总被引：1，自引：0，他引：1  

Subhasish DEY Rajkumar V. RAIKAR 《国际泥沙研究》2006,21(2):166-170

1 INTRODUCTION Scour within a channel contraction occurs where the waterway is restricted by the foundations or road approach embankments of a bridge. Alternately, contraction scour takes place when a bridge is located at a natural contraction in the rive…  相似文献   

Timing of Cadomian and Variscan tectonothermal activity,La Hague and Alderney,North Armorican Massif: Evidence from 40Ar/39Ar mineral ages     

R. D. Dallmeyer  R. S. D'Lemos  R. A. Strachan 《Geological Journal》1994,29(1):29-44

The La Hague region of northwest France exposes Palaeo-Proterozoic Icartian gneisses which were reworked and intruded by calc-alkaline plutonic rocks during the Cadomian Orogeny (about 700–500 Ma). ⁴⁰Ar/³⁹Ar mineral cooling ages have been determined to clarify the timing of the regional metamorphism of orthogneisses and the emplacement of quartz diorite plutons in this region. Metamorphic amphiboles within Icartian gneisses display discordant ⁴⁰Ar/³⁹Ar apparent age spectra interpreted to result from limited Variscan (about 350–300 Ma) overprinting of intracrystalline argon systems which initially cooled through post-metamorphic hornblende closure temperatures during the Cadomian at about 600 Ma. Igneous hornblendes from the weakly foliated Jardeheu and Moulinet quartz diorites record isotope correlation ages of 599 ± 2 and 561 ± 2 Ma, respectively. Igneous hornblende and biotite from foliated quartz diorite on the nearby Channel Island of Alderney record isotope correlation ages of about 560 Ma. The results imply that metamorphic and plutonic events in the La Hague-Alderney region were approximately contemporaneous with those recorded on Guernsey and Sark, which are thus likely to have formed part of the same tectonic block during the Cadomian Orogeny.  相似文献   

黄土丘陵沟壑区沟谷网络自动制图技术研究   总被引：32，自引：1，他引：31  

闾国年  钱亚东  陈钟明 《测绘学报》1998,27(2):131-137

黄土丘陵沟壑区沟谷网络自动制图技术的核心是沟谷网络的自动提取技术。本文基于沟谷网络和汇流网络的差别,提出了形态学方法和水文学方法相结合自动提取沟谷网络的新技术,设计了完整的基于栅格数字高程数据的提取算法,并给出了典型黄土沟壑丘陵区山西离石王家沟小流域的运行结果。提取得到的沟谷网络与实际情况相符。  相似文献   

中国江心洲河型的地域分布特征   总被引：2，自引：0，他引：2  

许炯心 《云南地理环境研究》1992,4(2):46-55

本文将江心洲河型在某一地域的出现作为或然率问题来处理,提出了江心洲河型频度的概念,作出了我国江心洲河型频度随纬度分布的曲线,并从不同自然带的自然地理因子的组合所决定的水沙因子的特定组合关系对这一分布曲线的形成机理进行了解释。  相似文献