直流输电线路对磁测的影响   总被引：3，自引：0，他引：3  

戴琛 《物探与化探》2008,32(4):408-411,416

越来越多的远距离、大容量直流输电线路投入运行对线路附近地区的磁测工作产生了不可忽视的影响。本文阐述了直流输电线路的结构、线路磁场特征及对以地质找矿为目的的磁测工作的影响。对直流输电线路磁场在磁测图中的特点也做了讨论,列举了直流输电线路影响的实例。  相似文献   

基于LSB的遥感图像安全传输模型     

闵连权 《测绘工程》2005,14(1):11-14

互联网在方便人们交流、共享信息的同时,也带来了极大的安全问题.信息隐藏是解决信息安全的一种有效手段,研究采用LSB法实现重要目标遥感图像信息的隐藏,实验证明该方法可以有效地解决网上图像传输出现的安全问题.  相似文献   

扩频通信技术及其在地震台风中的应用试验     

孙宏志  宋绪友等 《东北地震研究》2002,18(1):60-65

扩频通信技术是基于信息容量和信息传输差错概率理论而建立的先进的无线通讯方式、多次野外实地证实它具有抗干扰性强、可实现码分多址等优点。通过分析传输试验数据，我们有理由相信扩频通信技术在遥测地震台风中具有较高的应用和广阔的发展前景。  相似文献   

新疆数字地震前兆台网的数据传输功能分析   总被引：1，自引：0，他引：1  

哈斯高娃  陈勇 《内陆地震》2002,16(3):266-270

为了进一步提高地震前兆数据的传输效率和准确性 ,实现前兆数据采集和管理的自动化 ,对新疆地震局数字化地震前兆台网中心的功能、数据采集原理、数据传输特征进行了分析 ,认为数字化观测技术为地震前兆数据的采集、传输提供了一种高效、可靠的手段  相似文献   

Spatially irregular sedimentation in a small, morphologically complex lake: implications for paleoenvironmental studies     

Robert Gilbert 《Journal of Paleolimnology》2003,29(2):209-220

A sub-bottom acoustic survey of Devil Lake on the Canadian Shield in southern Ontario reveals three acoustic facies: (I) a moderately acoustically transparent, laminated sequence interpreted as a glacilacustrine deposit in glacial Lake Iroquois or a subsequent phase in water depths up to 200 m greater than at present, (II) a transitional more transparent, less layered facies interpreted as being deposited in a more distal glacial lake from erosion of sediment in the watershed exposed by the failure of the ice dam and lowering of the glacial lake before stabilization by the development of forests, and (III) an acoustically transparent facies with similar transmissivity to the water column, interpreted as Holocene gyttja. Each is spatially variable in extent and thickness in response to those processes. There is only a very weak relation between sediment thickness and the water depth in which it was deposited. Wave processes prevent deposition in water depths less than about 6 m and evidence of erosion to the greatest depths of the lake (>40 m) is pervasive. The data demonstrate the value of acoustic survey in assessing lacustrine processes and the history of lakes, and the significance of such documentation in planning a coring program and in interpreting the results.  相似文献   

屏障隔振系统失效机理的探讨          下载免费PDF全文

邱畅  高广运  岳中琦  谭国焕 《地震工程学报》2003,25(3):198-203

屏障隔振是一种用来阻碍或改变外围振波向受保护区(屏蔽区)传播的工程方法，由于其机理的探讨尚不深入，工程实践中常出现隔振系统失效的现象．本假设屏障是埋入土介质的中厚弹性板，采用薄层法分析了该弹性板在振波作用下的振动响应和屏蔽区内位移变化规律；研究了影响屏障隔振效果的主要参量；发现了使屏障隔振效率降低甚至失效的入射波全透射现象．结果表明柔性屏障易发生波的全透射，并指出了避免屏障失效的措施．  相似文献   

加卸载响应比(LURR)理论的实验研究   总被引：13，自引：1，他引：13  

余怀忠  尹祥础  夏蒙棼  梁乃刚  李敏  许昭永  彭克银  Wu Zhishen  Qi Li 《中国地震》2003,19(1):58-66

利用大尺度岩石试件破坏声发射实验，对加卸载响应比(Load/Unload Response Ratio)理论进行了实验研究。实验采用的加载条件力求能够模拟地下岩石的复杂受力过程。在加载过程中，岩石试件内部出现的损伤用声发射技术进行了记录。实验数据经过分析之后所得的结论与加卸载响应比理论预测的结果相符合。把加卸载响应比值Y的变化情况与声发射事件定位的过程相对比，也可以进一步看出岩石材料内部的损伤发展过程与加卸载响应比Y值的变化具有一致性。而高Y值的异常情况出现，又是在材料发生最终破坏之前，所以，可以用加卸载响应比理论定量地分析岩石试件损伤演化情况，从而对岩石材料的破坏及地震做出预测。实验结果再一次验证了加卸载响应比理论。  相似文献   

兰州数字遥测地震台网信号传输方式的设计     

何少林 《地震地磁观测与研究》2003,24(1):60-64

介绍了地震信号传输的常用方式及各自的优缺点，提出了数字遥测地震台网信号传输方式设计的总原则和基本原则。实际应用表明，兰州数字遥测地震台网信号传输方式的是符合要求的，提出的数字遥测地震台网信号传输方式的总原则和基本原则，对数字遥测地震台网建设有直接的借鉴作用。  相似文献   

Acoustic and electromagnetic properties of soils saturated with salt water and NAPL     

Jos M. Carcione  Gza Seriani  Davide Gei 《Journal of Applied Geophysics》2003,52(4):177-191

Electrical, seismic, and electromagnetic methods can be used for noninvasive determination of subsurface physical and chemical properties. In particular, we consider the evaluation of water salinity and the detection of surface contaminants. Most of the relevant properties are represented by electric conductivity, P-wave velocity, and dielectric permittivity. Hence, it is important to obtain relationships between these measurable physical quantities and soil composition, saturation, and frequency. Conductivity in the geoelectric frequency range is obtained with Pride's model for a porous rock. (The model considers salinity and permeability.) White's model of patchy saturation is used to calculate the P-wave velocity and attenuation. Four cases are considered: light nonaqueous phase liquid (LNAPL) pockets in water, dense nonaqueous phase liquid (DNAPL) pockets in water, LNAPL pockets in air, and DNAPL pockets in air. The size of the pockets (or pools), with respect to the signal wavelength, is modeled by the theory. The electromagnetic properties in the GPR frequency range are obtained by using the Hanai–Bruggeman equation for two solids (sand and clay grains) and two fluids (LNAPL or DNAPL in water or air). The Hanai–Bruggeman exponent (1/3 for spherical particles) is used as a fitting parameter and evaluated for a sand/clay mixture saturated with water.Pride's model predicts increasing conductivity for increasing salinity and decreasing permeability. The best-fit exponent of the Hanai–Bruggeman equation for a sand/clay mixture saturated with water is 0.61, indicating that the shape of the grains has a significant influence on the electromagnetic properties. At radar frequencies, it is possible to distinguish between a water-saturated medium and a NAPL-saturated medium, but LNAPL- and DNAPL-saturated media have very similar electromagnetic properties. The type of contaminant can be better distinguished from the acoustic properties. P-wave velocity increases with frequency, and has dissimilar behaviour for wet and dry soils.  相似文献   

气象卫星低分辨率资料传输的数字化          下载免费PDF全文

徐建平  施进明 《气象科技》2003,31(5):289-292

气象卫星低分辨率模拟资料传输WEFAX即将数字化为LRIT，阐述了LRIT(低分辨率信息传输)内容、LRIT数据传输模式和系统结构以及各卫星运行国LRIT传输比较。  相似文献