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《CT理论与应用研究》2000,9(4)
地面电探ＣＴ技术和方法在地下考古探测中的应用为国内外首次。它不仅可以发现原有电探方法难以发现的诸如深埋的前秦时期的土圹墓（目标小且与围体差异甚微）,而且还可以在野外现场随时随地直接出成果图,影像图;繁杂的测量技术方法数据采集,分析处理与成果解释统一由仪器系统自动完成,从而可大大地节省工作量和时间; 钱复业、赵玉林、张洪魁等所研制的地面电探ＣＴ技术ＤＰＡＳ－１００型数采系统达到世界先进水平。探头处数字化,传输过程中不受干扰;应用特殊信号处理技术,使用１６位“工业片”可起到２２位的作用,从而仪器同时… 相似文献
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为了对雷暴云下近地面的电特性进行分析，本文建立了模拟自然尖端所产生的电晕离子演化的一维数值模式。以地面电场为基础，考虑到地面电晕离子的演化，成功地计算了从地面至８００ｍ的空中电场及电荷、电流的时空演变，发现地面电晕离子可解释除雷暴云电荷影响外的空中电场和地面电场的差异，空间电场比地面电场更能反应雷暴电荷所产生的电场。空间电荷层可延伸到８００ｍ的高度上，且电荷密度可高达０．２５ｎＣ／ｍ３，６００ｍ高度上的传导电流密度可达０．１ｎＡ／ｍ２。 相似文献
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《CT理论与应用研究》1996,5(2):1-7
“１９９５年度亚洲ＣＴ科技十大进展及中国ＣＴ科技新进展”评述［本刊讯］在首届“１９９３年度亚洲ＣＴ科技十大进展评选及信息交流会”的基础上，１９９５年３月由地震科学联合基金会、《中国科协报》新闻部、《ＣＴ理论与应用研究》杂志编辑部联合主办了第二届“１９... 相似文献
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Tang Mengxing 《CT理论与应用研究》2001,10(2)
本刊《ＣＴ理论与应用研究》杂志从２０００－２月起，即开始在北京民营科技网上，开辟了“ＣＴ科技进展与科技咨询的网页／ｗｗｗ．Ｍｙｓｔａｒ．ｃｏｍ．ｃｎ／３ＤＣＴ／”登载千禧之年“第七届 １９９９年度亚洲 ＣＴ科技十大进展与中国ＣＴ科技新进展信息交流会”的有关信息和评述．从２０００－０５月起，陆续登载“首届２０００年国际ＣＴ和三维成像会议”的组委会和征文及发奖事项。 本刊从１９９４年起，即向清华大学“国家学学术期刊光盘中心”和“ＣＮＫＩ中国期刊网”提供每期的杂志和相应的文章软磁盘，从２００ｉＮ１０日起… 相似文献
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本文应用我国推广普及型ＣＴ（ＣＴＭＡＸ－Ⅱ），根据世界卫生组织（ＷＨＯ）提出的ＱＡ、ＱＣ体系的原则，制定我院ＣＴ室十个扫描技术规范和ＣＴ诊断技术规范等，和ＣＴ日常维护（ＰＭ）规程和ＣＴ图像考贝后处理等３个规程． 相似文献
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本文选择了云南地区十三个水氡观测点１９９２年９月份以来三年的数据，进行了有关处理，分离出８０－９０天的周期变化，并发现存在地区上的差异，孟连７．３地震及武定６．５地震前，震区周围水氡出现破坏周期性变化的中期异常，时间长达十数个月。 相似文献
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概要回顾了我国金属与非金属矿物探的历史及47年来所经历的四个发展阶段．物探方法由4种增加至40余种，一些已达国际先进水平．47年来，航空物探和区域重力调查基本覆盖了我国陆地面积，提出一大批基础地质和深部地质问题的新认识．物探发现了数以千计的金属与非金属矿的矿床．在技术方面，建立起了第二代航空物探系列、地面高精度重力和磁勘查系列、综合电法系列、综合核物探系列以及地下物探和测井系列．针对固体矿产的勘查任务，提出了物探的发展方向和一些建议． 相似文献
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颅脑肿瘤三维CT的临床应用 总被引：2，自引：0，他引：2
本文通过对９３例颅脑肿瘤病人的三维ＣＴ（３ＤＣＴ）研究，发现①３ＤＣＴ能生动地显示肿瘤的大小、形态、位置及与周围大血管、脑室、小脑幕及大脑镰的立体解剖关系，②能各角度旋转及切割观察，并可进行解剖测量。本文还就其优越性及限度做了探讨。 相似文献
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本文介绍了在ＣＴ引导下，利用激光对原发性肝癌局部进行光动力学疗法（以下简称ＰＤＴ），治疗半月后，进行ＣＴ复查，所有病人肿块中心均出现大小不等的液化坏死区，液化坏死区最大直径３．７ｃｍ，ＣＴ值下降７—４９ＨＵ，经组织学检查治疗区，表明细胞膜严重受损，并可见大量坏死组织，经ＰＤＴ治疗后的病人生存超过半年者达９２．３％，所有随访病例均未发现肿块增大及其它部位转移，有肝区疼痛者，治疗后疼痛消失，同时食欲明显增加，体重有所增长。 相似文献
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Out‐of‐plane effects in 2D borehole‐to‐surface resistivity tomography and applications in mineral exploration 
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下载免费PDF全文 In this paper, we discuss the effects of anomalous out‐of‐plane bodies in two‐dimensional (2D) borehole‐to‐surface electrical resistivity tomography with numerical resistivity modelling and synthetic inversion tests. The results of the two groups of synthetic resistivity model tests illustrate that anomalous bodies out of the plane of interest have an effect on two‐dimensional inversion and that the degree of influence of out‐of‐plane body on inverted images varies. The different influences are derived from two cases. One case is different resistivity models with the same electrode array, and the other case is the same resistivity model with different electrode arrays. Qualitative interpretation based on the inversion tests shows that we cannot find a reasonable electrode array to determine the best inverse solution and reveal the subsurface resistivity distribution for all types of geoelectrical models. Because of the three‐dimensional effect arising from neighbouring anomalous bodies, the qualitative interpretation of inverted images from the two‐dimensional inversion of electrical resistivity tomography data without prior information can be misleading. Two‐dimensional inversion with drilling data can decrease the three‐dimensional effect. We employed two‐ and three‐dimensional borehole‐to‐surface electrical resistivity tomography methods with a pole–pole array and a bipole–bipole array for mineral exploration at Abag Banner and Hexigten Banner in Inner Mongolia, China. Different inverse schemes were carried out for different cases. The subsurface resistivity distribution obtained from the two‐dimensional inversion of the field electrical resistivity tomography data with sufficient prior information, such as drilling data and other non‐electrical data, can better describe the actual geological situation. When there is not enough prior information to carry out constrained two‐dimensional inversion, the three‐dimensional electrical resistivity tomography survey is the better choice. 相似文献
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Flood irrigation is globally one of the most used irrigation methods. Typically, not all water that is applied during flood irrigation is consumed by plants or lost to evaporation. Return flow, the portion of applied water from flood irrigation that returns back to streams either via surface or subsurface flow, can constitute a large part of the water balance. Few studies have addressed the connection between vertical and lateral subsurface flows and its potential role in determining return flow pathways due to the difficulty in observing and quantifying these processes at plot or field scale. We employed a novel approach, combining induced polarization, time‐lapse electrical resistivity tomography, and time‐lapse borehole nuclear magnetic resonance, to identify flow paths and quantify changes in soil hydrological conditions under nonuniform application of flood irrigation water. We developed and tested a new method to track the wetting front in the subsurface using the full range of inverted resistivity values. Antecedent soil moisture conditions did not play an important role in preferential flow path activation. More importantly, boundaries between lithological zones in the soil profile were observed to control preferential flow pathways with subsurface run‐off occurring at these boundaries when saturation occurred. Using the new method to analyse time‐lapse resistivity measurements, we were able to track the wetting front and identify subsurface flow paths. Both uniform infiltration and preferential lateral flows were observed. Combining three geophysical methods, we documented the influence of lithology on subsurface flow processes. This study highlights the importance of characterizing the subsurface when the objective is to identify and quantify subsurface return flow pathways under flood irrigation. 相似文献
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Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. 相似文献
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Induced polarization (IP) 3D tomography with the similar central gradient array combines IP sounding and IP profiling to retrieve 3D resistivity and polarization data rapidly. The method is characterized by high spatial resolution and large probing depth. We discuss data acquisition and 3D IP imaging procedures using the central gradient array with variable electrode distances. A 3D geoelectric model was constructed and then numerically modeled. The data modeling results suggest that this method can capture the features of real geoelectric models. The method was applied to a polymetallic mine in Gansu Province. The results suggest that IP 3D tomography captures the distribution of resistivity and polarization of subsurface media, delineating the extension of abrupt interfaces, and identifies mineralization. 相似文献
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Michel Ritz Jean-Claude Parisot S. Diouf A. Beauvais F. Dione M. Niang 《Journal of Applied Geophysics》1999,41(4):105
The electrical properties of several tens of metres of lateritic weathering mantle were investigated by using electrical resistivity tomography (ERT) in two basement areas of eastern Senegal. The field survey was conducted along two profiles providing continuous coverage. Colour-modulated pseudosections of apparent resistivity vs. pseudo-depth were plotted for all survey lines, giving an approximate image of the subsurface structure. In the area underlain by granitic basement, the pseudosection suggests a very inhomogeneous weathered layer in which the apparent resistivity changes more rapidly than thickness. In the second area, underlain by schists, the lateral changes in electrical properties are less pronounced than those of the granitic area. Interpretation of 2D Wenner resistivity data yielded considerable detail about the regolith, even without pit information. In both areas, the near-surface topsoil comprising undersaturated lateritic material is highly resistive. The intermediate layer with low resistivities (e.g., 20–100 Ωm) contains clays including small quantities of water. The third, highly resistive layer reflects the granitic basement. Comparison of ERT survey results with pit information shows general agreement and suggests that ERT can be used as a fast and efficient exploration tool to map the thick lateritic weathering mantle in tropical basement areas with hard rock geology. 相似文献
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The purpose of geophysical electrical surveys is to determine the subsurface resistivity distribution by making measurements on the ground surface. From these measurements, the true resistivity of the subsurface can be estimated. The ground resistivity is related to various geological parameters, such as the mineral and fluid content, porosity and degree of water saturation in the rock. Electrical resistivity surveys have been used for many decades in hydrogeological, mining and geotechnical investigations. More recently, they have been used for environmental surveys. To obtain a more accurate subsurface model than is possible with a simple 1-D model, a more complex model must be used. In a 2-D model, the resistivity values are allowed to vary in one horizontal direction (usually referred to as the x direction) but are assumed to be constant in the other horizontal (the y) direction. A more realistic model would be a fully 3-D model where the resistivity values are allowed to change in all three directions. In this research, a simulation of the cone penetration test and 2D imaging resistivity are used as tools to simulate the distribution of hydrocarbons in soil. 相似文献
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Ettore Cardarelli Michele Cercato Antonio Cerreto Gerardina Di Filippo 《Geophysical Prospecting》2010,58(4):685-695
Near‐surface cavities can pose serious hazards to human safety, especially in highly urbanized town centres. The location of subsurface voids, the estimation of their size and the evaluation of the overburden thickness are necessary to assess the risk of collapse. In this study, electrical resistivity tomography (ERT) and seismic refraction tomography data are integrated in a joint interpretation process for cavity location in the city of Rome. ERT is a well established and widely employed method for cavity detection. However, additional information provided by seismic refraction tomography is capable of eliminating some potential pitfalls in resistivity data interpretation. We propose that the structure of the cavities defined by ERT can be used as a base to optimize seismic refraction tomography investigations within the framework of a joint interpretation process. Data integration and the insertion of a priori information are key issues for reducing the uncertainties associated with the inversion process and for optimizing both acquisition procedures and computation time. Herein, the two geophysical methods are tested on both synthetic and real data and the integration of the results is found to be successful in detecting isolated cavities and in assessing their geometrical characteristics. The cavity location inferred by geophysical non‐invasive methods has been subsequently confirmed by direct inspection. 相似文献
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A fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer. This technique is based on the smoothness-constrained least-squares method and it produces a two-dimensional subsurface model from the apparent resistivity pseudosection. In the first iteration, a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically. For subsequent iterations, a quasi-Newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times, respectively, compared to the conventional least-squares method. Tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly. This technique takes about one minute to invert a single data set on an 80486DX microcomputer. 相似文献
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The use of electrical resistivity tomography (ERT; non‐intrusive geophysical technique) was assessed to identify the hydrogeological conditions at a surface water/groundwater test site in the southern Black Forest, Germany. A total of 111 ERT transects were measured, which adopted electrode spacings from 0·5 to 5 m as well as using either Wenner or dipole‐dipole electrode arrays. The resulting two‐dimensional (2D) electrical resistivity distributions are related to the structure and water content of the subsurface. The images were interpreted with respect to previous classical hillslope hydrological investigations within the same research basin using both tracer methods and groundwater level observations. A raster‐grid survey provided a quasi 3D resistivity pattern of the floodplain. Strong structural heterogeneity of the subsurface could be demonstrated, and (non)connectivities between surface and subsurface bodies were mapped. Through the spatial identification of likely flow pathways and source areas of runoff, the deep groundwater within the steeper valley slope seems to be much more connected to runoff generation processes within the valley floodplain than commonly credited in such environmental circumstances. Further, there appears to be no direct link between subsurface water‐bodies adjacent to the stream channel. Deep groundwater sources are also able to contribute towards streamflow from exfiltration at the edge of the floodplain as well as through the saturated areas overlying the floodplain itself. Such exfiltrated water then moves towards the stream as channelized surface flow. These findings support previous tracer investigations which showed that groundwater largely dominates the storm hydrograph of the stream, but the source areas of this component were unclear without geophysical measurements. The work highlighted the importance of using information from previous, complementary hydrochemical and hydrometric research campaigns to better interpret the ERT measurements. On the other hand, the ERT can provide a better spatial understanding of existing hydrochemical and hydrometric data. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献