【正文】 文 (設(shè)計 ) 30 致 謝 本論文是在我的導(dǎo)師段清明老師的悉心指導(dǎo)下完成的。在本論文課題進(jìn)行過程中，段老師不但 給予了我全面的技術(shù)指導(dǎo)，還幫我們買材料，尋找緊缺電子元器件，花費 了很 多心血。在做畢業(yè)設(shè)計的三個月中，段老師不但把把他淵博的知識傳授給我，而且他嚴(yán)謹(jǐn)?shù)膶W(xué)術(shù)作風(fēng)，精益求精的科研和工作態(tài)度以及敢于創(chuàng)新的精神更使我欽佩不已。在此，謹(jǐn)向段老師表示最真摯的敬意和感謝！ 在課題進(jìn)行過程中，得到了各位老師、師兄、師姐的幫助，在此我要感謝王應(yīng)吉老師、孫淑琴老師對我課題研究的幫助和支持；感謝 榮 亮亮師兄、易曉峰師兄、吳海燕師姐、王中興師兄、尚新磊師兄在項目開發(fā)中的給予的幫助；感謝實驗室的劉漢北師兄、田瑜娟師姐、李曉明師兄、賈曉晨師兄、對我的關(guān)心與支持，是他們的幫助使我順利而愉快的完成了畢業(yè)設(shè)計。 感謝我的父親、母親謹(jǐn)以此文獻(xiàn)給他們，謝謝他們無私的愛和無盡的支持。最后感謝所有幫助和理解我的人。 吉林大學(xué)本科畢業(yè)論文 (設(shè)計 ) 31 附錄 A 弱信號放大器增益表 表 1 表 2 G 1 2 3 4 5 6 7 8 增益 (dB) 0 G 9 10 11 12 13 14 15 16 增益 (dB) 表 3 程控放大器倍數(shù) G（倍） 前放低增益總增益 (dB) 前放低增益總增益 (倍 ) 前放高增益總增益 (dB) 前放高增益總增益 (倍 ) 1 3728 169604 2 7389 336171 3 10620 483209 4 14156 644095 5 17389 791198 6 20789 945878 7 25276 1150006 8 29028 1320718 9 31053 1412879 項目 增益 前放低 增益 (dB) 前放高 增益 (dB) 帶通濾波器 增益 (dB) 開關(guān)濾波器 增益 (dB) Gain 吉林大學(xué)本科畢業(yè)論文 (設(shè)計 ) 32 程控放大器倍數(shù) G（倍） 前放低增益總增益 (dB) 前放低增益總增益 (倍 ) 前放高增益總增益 (dB) 前放高增益總增益 (倍 ) 10 35478 1614191 11 39084 1778279 12 42104 1915667 13 44450 2022437 14 49720 2262221 15 53062 2414238 16 56624 2576321 吉林大學(xué)本科畢業(yè)論文 (設(shè)計 ) 33 英文原文 ： Imaging of groundwater with nuclear magic resonance Marian Hertrich The method of surface nuclear magic resonance (SNMR) is a relatively new geophysical technique that exploits the NMRphenomenon for a quantitative determination of the subsurface distribution of hydrogen protons, . water molecules of groundwater resources, by nonintrusive means. The idea to employ NMR techniques within the Earth’s magic field to derive subsurface water contents was first proposed by Varian. It was not until the late 1970s that a group of Russian scientists took up the idea and developed the first fieldready prototype of surface NMR equipment in the 1980s. It allowed for the first time the recording of NMR signals from groundwater at considerable depths in the Earth. Numerous field applications with the Russian Hydroscopeequipment encouraged the ongoing technical developments for about a decade. They were supported by several studies on the modeling, inversion and processing of surface NMR data. Surface NMR became better known to western scientists when the first mercial equipment was launched by Iris Instruments (France) in 1996. A few groups worldwide actively pursued the fundamentalresearch and applications of surface NMR. Over the past decade the continuous progress and experience has been reported at periodic international workshops (Berlin 1999, Orleans 2021, Madrid 2021), and followedup publishing special issues of peer reviewed journals devoted to surface NMR. Continuous technical development of surface NMR measurements has been carried out and, recently, two new suites of surface NMR hardware have been made 吉林大學(xué)本科畢業(yè)論文 (設(shè)計 ) 34 mercially available. The new systems extend the available technical possibilities towards improved noise mitigation schemes and multichannel recording. Major advances in the development of surface NMR were triggered by a revision of the fundamental equations proposed byWeichman et al. The improved formulation allows the correct calculation of plexvalued signals of measurements on conductive ground and the calculation of surface NMR signals with separated transmitter and receiver loops. The latter feature has been studied in detail by Hertrich and coworkers which revealed that a series of measurements at multiple offsets along a profile provides sufficient sensitivity to allow for high resolution tomographic inversion. A fast and efficient tomographic inversion scheme has been developed that provides the correct imaging of 2D subsurface structures from a series of surface measurements. Various geophysical techniques, like geoelectrics, electromagics,georadar and seismics, are routinely used in a structural mapping sense in hydrogeology, to delineate bedrock and sometimes determine depth of the water table and other major geological boundaries. But surface NMR is the only technique that allows a quantitative determination of the actual water content distribution in the subsurface. Near surface aquifers are the major source of drinking water worldwide. Additionally, these aquifers might be substantially affected by cultural pollution, mismanagement and natural retreat in the ongoing climate change. But also in many other environmental problems groundwater plays a key role. Examples are unstable permafrost and hillslope stability in the progressive global warming or dynamics of glaciers and icesheets. For those issues surface NMR may provide essential information in high resolution imaging of the subsurface water content distribution and monitoring of groundwater dynamics. 吉林大學(xué)本科畢業(yè)論文 (設(shè)計 ) 35 In conventional NMR applications (. spectroscopy,medical imaging, nondestructive material testing) the excitation of the spin magization is in most cases induced and recorded by uniform secondary magic fields such that the recorded signal amplitude can be calibrated by samples of known spin density and the experiment can be designed such that perfectly controlled flip angles are obtained. By contrast, in surface NMR none of these requirements can be met and the amplitude of the recorded signal has to be quantitatively derived for nonuniform fields and the resulting arbitrary flip angles. Therefore, in this review article, a prehensive derivation of the surface NMR signal is given and the formulations of the problem for 1D and 2D conditions are presented. Stateoftheart inversion techniques are needed to derive subsurface models of water content distribution from measured field data stateoftheart inversion techniques are needed and are applied with appropriate estimates of the reliability of those models given. The ob