CT理论与应用研究
CT理論與應用研究
CT이론여응용연구
COMPUTERIZED TOMOGRAPHY THEORY AND APPLICATIONS
2013年
3期
429-437
,共9页
直升机航空瞬变电磁%电导率-深度成像%中心回线%视电导率%视深度
直升機航空瞬變電磁%電導率-深度成像%中心迴線%視電導率%視深度
직승궤항공순변전자%전도솔-심도성상%중심회선%시전도솔%시심도
helicopter airborne TEM%conductivity-depth imaging%central-loop%apparent conductivity%apparent depth
以理论上的中心回线式直升机航空瞬变电磁系统为例，提出一种快速的电导率-深度成像方法，将感生电动势瞬变响应数据变换为地下介质电导率-深度断面。该方法针对成像计算中视电导率非唯一性问题和成像深度难以确定的困难，首先给出一个关于均匀半空间模型电导率s的数据函数()bs的变换公式，由此建立数据表sb-来查询视电导率值，可以得到可靠的视电导率值。其次用均匀半空间中的感应电场最大幅值对应深度值来定义视深度，建立视电导率-视深度的数据表，并在2个相邻时间道期间的最大电场深度变化的基础上定义成像深度，从而导出 CDI 结果。该方法的特点是理论简单、物理意义明确，且利用了数据表查询技术大大提高了计算速度，使得实时 CDI 处理成为可能。最后用理论模型进行试算，结果表明，电导率值的查询范围宽至10-4～102 S/m 时，高阻薄层、低阻薄层及二维目标体模型均有较好的成像效果。
以理論上的中心迴線式直升機航空瞬變電磁繫統為例，提齣一種快速的電導率-深度成像方法，將感生電動勢瞬變響應數據變換為地下介質電導率-深度斷麵。該方法針對成像計算中視電導率非唯一性問題和成像深度難以確定的睏難，首先給齣一箇關于均勻半空間模型電導率s的數據函數()bs的變換公式，由此建立數據錶sb-來查詢視電導率值，可以得到可靠的視電導率值。其次用均勻半空間中的感應電場最大幅值對應深度值來定義視深度，建立視電導率-視深度的數據錶，併在2箇相鄰時間道期間的最大電場深度變化的基礎上定義成像深度，從而導齣 CDI 結果。該方法的特點是理論簡單、物理意義明確，且利用瞭數據錶查詢技術大大提高瞭計算速度，使得實時 CDI 處理成為可能。最後用理論模型進行試算，結果錶明，電導率值的查詢範圍寬至10-4～102 S/m 時，高阻薄層、低阻薄層及二維目標體模型均有較好的成像效果。
이이론상적중심회선식직승궤항공순변전자계통위례，제출일충쾌속적전도솔-심도성상방법，장감생전동세순변향응수거변환위지하개질전도솔-심도단면。해방법침대성상계산중시전도솔비유일성문제화성상심도난이학정적곤난，수선급출일개관우균균반공간모형전도솔s적수거함수()bs적변환공식，유차건립수거표sb-래사순시전도솔치，가이득도가고적시전도솔치。기차용균균반공간중적감응전장최대폭치대응심도치래정의시심도，건립시전도솔-시심도적수거표，병재2개상린시간도기간적최대전장심도변화적기출상정의성상심도，종이도출 CDI 결과。해방법적특점시이론간단、물리의의명학，차이용료수거표사순기술대대제고료계산속도，사득실시 CDI 처리성위가능。최후용이론모형진행시산，결과표명，전도솔치적사순범위관지10-4～102 S/m 시，고조박층、저조박층급이유목표체모형균유교호적성상효과。
A Conductivity-Depth Imaging (CDI) algorithm is presented for a central-loop helicopter airborne system as an example in this paper, to transform the transient induced electromotive force response data into a conductivity-depth section very quickly. The method aimed at the non-uniqueness problem of the apparent conductivity and the difficulties to obtain the imaging depth in the imaging method, and is successfully developed according to the following steps: firstly, a transformation formula of the data function ( )b s about the conductivity of homogeneous half-space model s is presented, and then a table of the data function relationship with the conductivity is built to search the apparent conductivity value. This method can overcome the problem of the non-unique value of the apparent conductivity. Secondly, the apparent depth is approximated using the depth of the maximum induced electric field in the homogeneous half-space earth, and a data table about apparent conductivity and apparent depth is established to accelerate computing. Finally, the imaging depth is determined based on the depth change of the maximum electric field at the two adjacent delay time and then the CDI result is obtained consequently. The advantage of the method is that its high-efficiency of the table lookup technique can make the real-time CDI possible. Using a table lookup with a large conductivity range from 10-4 S/m to 102 S/m, tests on synthetic data demonstrate that the algorithm does a good job of solving conductive or resistive thin layers and 2D object.
