共查询到19条相似文献,搜索用时 500 毫秒
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利用核磁共振方法探查岩溶水 总被引:19,自引:4,他引:15
核磁共振(NMR)找水方法是目前唯一直接找水的物探新方法,该方法可以探查各种类型的地下水。本文仅论述了在岩溶发育区常规电阻率方法找水时遇到的地质干扰。NMR找水方法的原理,仪器的组成,并以实例说明了NMR找水方法探查岩溶水的效果。 相似文献
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利用核磁共振方法探查基岩裂隙水 总被引:10,自引:0,他引:10
基岩裂隙水是我国分布最为广泛的地下水类型之一。本文阐述了基岩裂隙水的特点:含水层产状不规则、其赋存空间介质不均匀、同一含水层埋深不同、地下水运动状态复杂等。这些特殊的地质、地球物理特征,给常用的物探找水方法带来许多困难。本文通过对直接找水的新方法一核磁共振(NuclearMagnetic Resonance,缩写为NMR)测深与间接找水的电阻率测深的对比分析,论述了NMR测深直接找水的实质。并以实例说明了NMR测深在探查基岩裂隙水中的应用效果。 相似文献
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目的 医学核磁共振与地面核磁共振找水是核磁共振技术应用的不同领域。本文通过对二者在方法原理、技术、应用等方面的对比研究,提出了地面核磁共振找水工作建议。 相似文献
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地面核磁共振找水仪及其在水文地质调查工作中的应用研究 总被引:6,自引:0,他引:6
本文概要介绍了地面核磁共振找水方法的原理和世界上最新的直接探查地下水的仪器设备--地面核磁感应系统的特点,并以实例说明了NMR找水方法的应用效果,提出了关于提高NUMIS系统抗干扰能力、完善解释方法、研制系列仪器等方面的建议. 相似文献
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利用核磁共振(NuclearMagneticResonance缩写为NMR)技术探查地下水仅有二十多年的历史,文中简要介绍了NMR找水方法的发展状况,原理和方法特点,重点介绍了中国地质大学(武汉)利用NMR找水方法在中国一些地区找水取得的成效,最后指出了NMR找水方法的发展趋势。 相似文献
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近20多年来,用核磁共振(Nuclear Magnetic Resonance,NMR)方法形成的一种直接非侵害性的探测地下水的地球物理新技术,与传统的地球物理探测地下水的方法相比具有高分辨力、高效率、信息量丰富和解的唯一性等优点,是一种很有发展前景的找水方法技术.我国的水资源短缺,对地下水资源的勘探、开发与利用十分重视,已将核磁共振找水技术研究列入国家十一五科技支撑计划.本文在广泛收集迄今为止的国内外大量资料的基础上,并根据作者近年来有关核磁共振找水技术的研究经历,综述了核磁共振找水技术的发展历史、现状和发展趋势,以推进我国核磁共振找水技术的发展. 相似文献
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地面磁共振是一种新的地球物理探测方法,能够通过探测地下水中氢质子丰度获取地下水含量、孔隙度等水文地质信息.然而,磁共振信号甚为微弱,仅达到纳伏级(10~(-9)V),极易受到噪声干扰.其中,尖峰噪声对磁共振信号影响最为严重,亟待研究有效的噪声抑制方法.小波多尺度分解硬阈值是近两年国际磁共振领域专家提出的尖峰噪声有效消除方法,但硬阈值算法设定阈值的固有缺陷会引发信号震荡,出现伪吉布斯效应,导致信号损失.基于此,本文提出压缩小波变换(Synchrosqueezing Wavelet Transform,SWT)和非线性國值处理(Nonlinear Thresholding,NT)算法联合消除磁共振信号尖峰噪声干扰.首先选择Morlet小波作为基小波,使得信号与噪声数据具有更高的时频集中性,利于尖峰噪声消除.其次,基于压缩小波系数进行非线性处理,可以弥补利用硬阈值和软阈值进行噪声消除时所引起的信号损失.仿真数据和实际数据结果表明,SWT联合NT方法可以利用单次采集数据有效消除尖峰噪声干扰并还原信号.本文提出的消噪方法将为磁共振数据后续反演解释,如多指数弛豫反演,奠定坚实的基础. 相似文献
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The surface nuclear magnetic resonance (SNMR) method has been tested at a site in Haldensleben, northern Germany, to assess the suitability of this new method for groundwater exploration and environmental investigations. More information is obtained by SNMR, particularly with respect to aquifer parameters, than with other geophysical techniques. SNMR measurements were carried out at three borehole locations, together with 2D and 1D direct current geoelectrics, as well as ground-penetrating radar, and well logging (induction log, gamma-ray log and pulsed neutron-gamma log). Permeabilities were calculated from the grain-size distributions of core material determined in the laboratory. It is demonstrated that the SNMR method is able to detect groundwater and the results are in good agreement with other geophysical and hydrogeological data. Using the SNMR method, the water content of the unsaturated and saturated zones (i.e. porosity of an aquifer) can be reliably determined. This information and resistivity data permit in situ determination of other aquifer parameters. Comparison of the SNMR results with borehole data clearly shows that the water content determined by SNMR is the free or mobile water in the pores. The permeabilities estimated from the SNMR decay times are similar to those derived from sieve analysis of core material. Thus, the combination of SNMR with geoelectric methods promises to be a powerful tool for studying aquifer properties. 相似文献
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The surface nuclear magnetic resonance (SNMR) method is widely used in groundwater detection because of its sensitivity to hydrogen in water and direct water detection. However, low signal-to-noise ratios (SNRs) restrict the development of this technique. An optimum pulse sequence is designed according to correspondence between the pulse moment strength and its best detection depth. Because only selection of the pulse intensity distribution according to the target aquifer depth is required and the “on-resonance” pulse pattern is still employed, this pulse sequence emission can be easily achieved using existing SNMR instrumentation. Numerical simulation results and field experiments show that, compared with traditional exponential growth pulses, the optimum pulse sequence effectively improves the SNR of the SNMR method. The aquifer boundary, water content, and pore characteristics of the inversion result are thus more consistent with characteristics of underground structures. Additionally, because the optimum pulse sequence focuses most of the pulse moments in the target depth range, in situations where two aquifers are separated by a relatively narrow aquitard, it is better able to resolve the individual aquifers than the traditional pulses. Optimum pulse moments improve the SNR by enhancing the signal amplitude, compared with various filtering methods, and obtain a better detection effect. This kind of pulse sequence can be used as an alternative pulse sequence form of the SNMR method. 相似文献
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在多孔隙含水层中地面磁共振(surface nuclear magnetic resonance,SNMR)信号呈现多弛豫衰减特性,常规盲源分离方法和单指数拟合方法引起信号严重失真和信息缺失等问题.本文提出了基于稀疏表示的随机噪声背景下多弛豫SNMR信号的提取方法.根据SNMR信号的衰减特征,设计了精确刻画SNMR信号且与随机噪声不相关的离散衰减余弦冗余字典.其次,针对多弛豫SNMR信号稀疏度未知的问题,通过设置合理的残差比阈值控制迭代次数,改进了广义正交匹配追踪(generalized orthogonal matching pursuit,gOMP)算法,使得该方法应用于SNMR信号的提取时,具有更好的自适应性和普适性.再次,鉴于SNMR测量数据为多次独立重复采集的结果,提出了基于数据流的SNMR信号提取策略,在提高算法鲁棒性的同时,保证了信号提取结果的唯一性.最后,通过仿真和实测数据证明了基于gOMP算法的稀疏表示方法可以显著地提升多弛豫SNMR信号的提取质量,降低随机噪声对含水层反演结果的影响,提高SNMR探测能力. 相似文献
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瞬变电磁法在地下水勘查中的应用综述 总被引:13,自引:3,他引:10
水是地球上最重要的天然资源,供人类需要的淡水有95%以上取自地下水,地下水在人类经济活动中发挥着重要的作用.传统的地球物理方法在地下水勘查工作中得到应用的同时,新的更先进的物探方法不断涌现.近年来,瞬变电磁法在国内外的应用得到迅速发展,在地下水勘查领域的应用也得到拓展.与其它电探方法相比,利用瞬变电磁法进行地下水勘查具有明显优势。 相似文献
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一种应用于三峡滑坡探测的新方法-SNMR法 总被引:4,自引:0,他引:4
三峡库区蓄水后,由于水位上升滑坡地区的软弱层遇到水就会变软并引起滑塌。核磁共振是当今世界尖端技术之一,我们首先将该技术应用于滑坡探查。本文探讨了用SNMR探查滑坡的方法技术以及通过SNMR实测数据求取与滑坡稳定性有关的水文地质参数,通过一个三峡的实例说明了该方法是一种快速有效的探测滑坡的方法。 相似文献
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Currently, surface nuclear magnetic resonance (SNMR) method is the only geophysical method that detects groundwater directly. In this paper, we investigate the effect of elliptical polarization in the perpendicular excitation magnetic field. The effect of elliptical polarization is clearly visible in our ellipticity calculation and it can cause strong distortion to the excitation field in the presence of high subsurface conductivities. By examining the co-rotating and counter-rotating components of the field, we show that elliptical polarization affects transmitting and receiving processes differently and that a clear phase lag exists between transmitter loop and receiver loop. Finally, we derive the response function of coincident loops and calculate proton tip angles, the kernel function and SNMR response curves of a 1D aquifer model. Based on the simulations, we conclude that the elliptical polarization and phase lag can significantly affect SNMR response and it is essential to include elliptical polarization in SNMR modeling and data interpretation. 相似文献