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83.
探地雷达探测中对媒质相对介电常数的测定 总被引:3,自引:1,他引:2
分别就探地雷达探测中的收发一体式天线、收发分离式天线在实际工作中对媒质相对介电常数的几种主要测定方法:已知目标深度法、点源反射体法、共中心点(CMP)法及层状反射体法,从理论到实例一一做了详细的论述。实践证明,这些方法能够满足生产要求。 相似文献
84.
《水文科学杂志》2013,58(6)
Abstract Abstract Recently, substantial progress has been made in detection and observation of non-aqueous phase liquids (NAPLs) in the subsurface using different experimental techniques. However, there is still a lack of appropriate direct methods to measure the saturation of NAPL (θNAPL). This paper provides a guide for estimating θNAPL and water content (θ w ) in unsaturated and saturated sand based on direct measurements of soil dielectric constant (Ka ) and electrical conductivity (σ a ) using time domain reflectometry (TDR). The results show that the previously used dielectric mixing model fails to predict θNAPL in the case of a four-phase system. A new methodology is suggested and exemplified by showing that the measured Ka gives accurate estimation of θNAPL for a three-phase system while in a four-phase system, both θ a and Ka need to be measured. The results show that using the suggested methodology, accurate predictions of θ w (R 2 = 0.9998) and θNAPL lower than 0.20 m3 m-3 (average R 2 = 0.9756) are possible. 相似文献
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86.
In order to improve the interpretation of the earth system microwave remote sensing, the research of microwavespectrum characteristics of the ground truth (earth objects) was carried out in laboratory. A laboratory formicrowave remote sensing of the earth objects has been constructed to improve the remote sensing level, thelaboratory consists of four parts: the measuring system of dielectric constants, the microwave emissivity meter,the microwave reflectometer and the microwave remote sensing simulation experiment in field. In this paper,the principle of measurement, the correction of near field process, the structure of instrument, the calibrationmethod and the measurement of the earth substances, including soil, water and oil, are discussed. The labora-tory may supply the condition for measuring the parameters of thc earth substance remote sensing and help tointerpret the remote sensing data. 相似文献
87.
The effect of electrical conductivity (EC) of a dielectric material on its TDR-measured dielectric constant εa (called the apparent dielectric constant) was investigated both theoretically and experimentally. The effect of EC on the
apparent dielectric constant εa was more pronounced at low frequency of the electromagnetic pulse applied to measure εa. The assumption of neglecting electrical losses in measuring the dielectric constant by TDR to represent εr was not valid for dielectric materials containing free charges, such as electrolyte solutions, bentonite clay, and saline
soils. A theory is proposed to separate the real part of the dielectric constant εr from the TDR-measured εa in lossy dielectrics. An EC - εr relationship can be developed that would provide εa (=εr) at EC = 0 to be used to determine soil-water contents in conductive soils.
Na-bentonite mixed with distilled water resulted in considerable magnitude of bulk EC due to the adsorbed cations on the surface
of the particles. This EC caused energy loss of the TDR pulse that depended on the length of the probe rod. For a 4.5 cm long
probe, the reflected TDR waveform was completely attenuated for EC between 3.05 dS m−1 and 3.72 dS m−1. The waveforms generated in this range of EC were not suitable for analysis by TDR-support software for dielectric constant.
With the adsorbed cations, Na-bentonite behaved as a lossy or dispersive material.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
从麦克斯韦方程及本构关系出发,导出了频率域中的电磁波动方程。采用有限差分方法,对波动方程求数值解。设计的程序可模拟实际的测井过程。程序执行后给出模拟测井曲线。数值模拟试验表明,多频电磁波测井对区分油水层是成功和有效的。 相似文献
89.
瓦斯突出煤体的介电性质研究 总被引:4,自引:0,他引:4
研究了瓦斯突出煤体和非突出煤体的介电性质,对于探讨电磁波在瓦斯突出煤层中的传播规律和利用电磁方法探测瓦斯突出煤体的分布具有参考价值。 相似文献
90.
微波穿透雷达对月球的观测方式可以分为地基、星载环绕、星地联合以及就位探测等.对比其他探测手段,微波雷达在探测范围和空间分辨率上有很明显的优势,因此在月球和其他行星探测中起着重要的作用.国内外越来越多的深空探测任务已经或准备携带微波雷达,用于探索地外天体的浅表层地质结构,以了解行星地质过程和演化历史.本文综述了我国嫦娥三号和四号月球车玉兔号和玉兔2 号在就位微波雷达(测月雷达)探测月球浅表层地质结构方面所取得的新进展,重点阐述了测月雷达在揭示月壤内部的精细结构、表层与次表层地质结构探测等方面的应用.最后,展望了我国月球微波雷达的发展趋势. 相似文献