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971.
ABSTRACTIntegrated two-dimensional electrical resistivity imaging (ERI) and hydrochemical surveys were used to investigate the groundwater alluvial aquifer in Kuala Langat, Malaysia. The study in the Langat basin considered the thickness of the aquifer, the depth of the bedrock, the regions influenced by seawater intrusion, and the monitoring of water levels. The resistivity imaging results show that the upper layer consists of clay, while the second layer is an aquifer whose thickness varies mostly in the range of 10–30 m, and in some cases extends to 40 m. The bedrock depth varies from 30 to 65 m. The chemical analyses were carried out on groundwater samples from nine boreholes collected between 2008 and 2012. The analyses indicate that the total dissolved solids (TDS) exceed 1000 mg L-1 near the coastal area and are often less than 500 mg L-1 further inland. The ERI and hydrochemical analyses reveal that groundwater in the study area, especially towards the coast, is a mixture of brackish and fresh waters.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR M.D. Fidelibus 相似文献
972.
973.
目的:探讨使用320排螺旋CT前瞻性心电门控窄窗采集技术,在降低辐射剂量方面的应用。方法:研究组50例采用前瞻性心电门控技术,对照组50例患者采用回顾性心电门控技术,分别测量两组间图像质量以及辐射剂量。结果:两组数据比较,患者的基本情况如年龄、心率、体重和体重指数以及图像质量差异无统计学意义(P〉0.05),有效放射剂量两组间的差异有统计学意义(P=0.0001),前瞻性心电门控组辐射剂量(8.80±2.78)mSv显著低于回顾心电门控组(25.82±8.84)mSv。结论:前瞻性心电门控窄窗采集技术在确保图像质量的同时可以降低辐射剂量。 相似文献
974.
目的:探讨动态增强MRI对乳腺钼靶上含钙化占位性病变的诊断价值。资料与方法:回顾性分析101例乳腺含钙化占位性病变的钼靶及MRI检查资料。其中,乳腺恶性占位性病变56例,包括浸润性导管癌46例,导管原位癌3例,小叶原位癌2例,粘液腺癌3例,基底细胞癌1例,肌上皮癌1例;乳腺良性占位性病变45例,包括乳腺纤维腺瘤39例,乳腺囊肿4例,乳腺纤维囊性增生2例。根据钼靶上钙化形态对于良恶性病变的判断标准,将钙化分为典型良性、可疑恶性、高度可能恶性三类。将钼靶和MRI的诊断结果与病理诊断结果进行对照。以病理结果为金标准,对钼靶与MRI的诊断结果进行配对四格表χ2检验统计学分析。结果:本组85例患者(84.2%)根据钼靶所见做出正确诊断。16例患者(15.8%)钼靶提示可疑恶性钙化但未能确诊或误诊,其中14例在MRI检查后做出正确诊断。MRI检查做出正确诊断99例(98.0%)。钼靶和MRI检查对本组含钙化乳腺占位性病变的诊断准确率差异有统计学意义(P=0.0005,P<0.O5)。结论:当钼靶上钙化信息不能明确乳腺占位性病变的性质,特别在钙化归为BI-RADS3和BI-RADS4级乳腺疾病时,动态增强MRI可以提高诊断准确性。 相似文献
975.
中心回线式直升机TEM资料的电导率-深度成像方法 总被引:1,自引:0,他引:1
毛立峰 《CT理论与应用研究》2013,(3):429-437
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?的数据函数?(?)的变换公式,由此建立数据表???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10-4~102S/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。 相似文献
976.
TOBIAS H. KURZ JULIE DEWIT SIMON J. BUCKLEY JOHN B. THURMOND DAVID W. HUNT RUDY SWENNEN 《Sedimentology》2012,59(2):623-645
Ground‐based hyperspectral imaging combined with terrestrial lidar scanning is a novel technique for outcrop analysis, which has been applied to Early and Late Albian carbonates of the Pozalagua Quarry (Cantabrian Mountains, Spain). An image processing workflow has been developed for differentiating limestone from dolomite, providing additional sedimentary and diagenetic information, and the possibility to quantitatively delineate diagenetic phases in an accurate way. Spectral absorption signatures can be linked to specific sedimentary or diagenetic products, such as recent and palaeokarst, hydrothermal karst, (solution enlarged) fractures and different dolomite types. Some of the spectral signatures are related to iron, manganese, organic matter, clay and/or water content. Ground‐truthing accessible parts of the quarry showed that the classification based on hyperspectral image interpretation was very accurate. This technique opens the possibility for quantitative data evaluation on sedimentary and diagenetic features in inaccessible outcrops. This study demonstrates the potential of ground‐based imaging spectroscopy to provide information about the chemical–mineralogical distribution in outcrops, which could otherwise not be established using conventional field methods. 相似文献
977.
Michael Wiedenbeck Roxana Bugoi M. John M. Duke Tibor Dunai Jacinta Enzweiler Mary Horan Klaus Peter Jochum Kathryn Linge Jan Košler Silke Merchel Luiz F.G. Morales Lutz Nasdala Roland Stalder Paul Sylvester Ulrike Weis Arnaud Zoubir 《Geostandards and Geoanalytical Research》2012,36(4):337-398
Advances in the chemical and isotopic characterisation of geological and environmental materials can often be ascribed to technological improvements in analytical hardware. Equally, the creation of novel methods of data acquisition and interpretation, including access to better reference materials, can also be crucial components enabling important breakthroughs. This biennial review highlights key advances in either instrumentation or data acquisition and treatment, which have appeared since January 2010. This review is based on the assessments by scientists prominent in each of the given analytical fields; it is not intended as an exhaustive summary, but rather provides insight from experts of the most significant advances and trends in their given field of expertise. In contrast to earlier reviews, this presentation has been formulated into a unified work, providing a single source covering a broad spectrum of geoanalytical techniques. Additionally, some themes that were not previously emphasised, in particular thermal ionisation mass spectrometry, accelerator‐based methods and vibrational spectroscopy, are also presented in detail. 相似文献
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980.