瞬变电磁法探测公路隧道工程中的不良地质构造     

薛国强  宋建平  武军杰  刘社华 《地球科学与环境学报》2003,25(4):73-75

为了给公路设计部门提供选线依据,运用瞬变电磁法在山西境内的某两条高速公路隧道工程设计线路段上进行探测,以查明下覆不良地质构造的发育情况.通过对瞬变电磁法的探测能力进行理论上的讨论,对不同地电断面情况下的异常体电磁响应的定性分析,得出用瞬变电磁法探测不良地质体的可行性结论.经过资料处理,查出不良地质构造赋存的位置,解释结果与钻探资料完全吻合.  相似文献   

Rapid vegetation change during the early Holocene in the Faroe Islands detected in terrestrial and aquatic ecosystems     

Gina E. Hannon  Richard H. W. Bradshaw  Stefan Wastegrd 《第四纪科学杂志》2003,18(7):615-619

High‐resolution pollen, plant macrofossil and sedimentary analyses from early Holocene lacustrine sediments on the Faroe Islands have detected a significant vegetation perturbation suggesting a rapid change in climate between ca. 10 380 cal. yr BP and the Saksunarvatn ash (10 240±60 cal. yr BP). This episode may be synchronous with the decline in δ¹⁸O values in the Greenland ice‐cores. It also correlates with a short, cold event detected in marine cores from the North Atlantic that has been ascribed to a weakening of thermohaline circulation associated with the sudden drainage of Lake Agassiz into the northwest Atlantic, or, alternatively, a period with distinctly decreased solar forcing. The vegetation sequence begins at ca. 10 500 cal. yr BP with a succession from tundra to shrub‐tundra and increasing lake productivity. Rapid population increases of aquatic plants suggest high summer temperatures between 10 450 and 10 380 cal. yr BP. High pollen percentages, concentrations and influx of Betula, Juniperus and Salix together with macrofossil leaves indicate shrub growth around the site during the initial phases of vegetation colonisation. Unstable conditions followed ca. 10 380 cal. yr BP that changed both the upland vegetation and the aquatic plant communities. A decrease in percentage values of shrub pollen is recorded, with replacement of both aquatics and herbaceous plants by pioneer plant communities. An increase in total pollen accumulation rates not seen in the concentration data suggests increased sediment delivery. The catchment changes are consistent with less seasonal, moister conditions. Subsequent climatic amelioration reinitiated a warmth‐driven succession and catchment stabilisation, but retained high precipitation levels influencing the composition of the post‐event communities. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events     

C. S. M. Turney  K. Van Den Burg  S. Wastegrd  S. M. Davies  N. J. Whitehouse  J. R. Pilcher  C. Callaghan 《第四纪科学杂志》2006,21(4):335-345

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

氢化物发生及其在分析检测领域的应用   总被引：2，自引：2，他引：0  

郑大中  郑若锋  王惠萍 《岩矿测试》2008,27(1):55-59

论述了氢化物发生的条件和普遍性及其在分析检测领域的应用,这些领域包括试样分解,分离富集,容量分析、比色分析、原子荧光光谱、原子吸收光谱、电感耦合等离子体原子发射光谱、电感耦合等离子体质谱等分析测试技术。  相似文献   

纺织品中偶氮染料还原液内芳香胺的电喷雾电离质谱分析   总被引：3，自引：1，他引：2  

吴转璋  丁健桦  赖劲虎  陈焕文 《岩矿测试》2008,27(4):250-254

在优化的条件下,用电喷雾电离质谱(ESI-MS)检测了多种纺织品中由偶氮染料还原获得的芳香胺。当毛细管温度为100℃、鞘气流速为25单位、进样流速为10μL/min、电压为5kV时,信号的总离子流强度高且较稳定。实验分析了19种致癌芳香胺标准溶液的二级质谱,获得了相应物质的特征碎片离子;在此基础上,建立了基于ESI-MS对毛巾、棉布等样品中芳香胺进行快速定性分析的方法,具有灵敏度高、特异性好、检测速度快等优点。  相似文献   

超低频电磁探测信号能量的计算及其地质应用   总被引：1，自引：0，他引：1  

宋本钦李培军  秦其明侯贵廷 《中国地质》2008,35(6):1315-1321

被动式超低频电磁探测技术是一种有效的探测地下地质体和资源的手段,但采用现有的处理方法得到的探测曲线较容易受到各种噪声的干扰,影响了对所获得的探测曲线的解释。笔者将信号能量引入到超低频电磁探测信号的处理中。首先根据信号能量计算原理,计算不同深度的超低频探测信号的能量值．获取能量曲线。同时,根据具体应用目的,分析其曲线特征,并将信号能量曲线与现有的信号曲线,如最大值曲线、最小值曲线等进行对比分析。结果表明,与现有方法相比,笔者所提出的信号能量曲线方法能更准确地反映地下岩层特征,有利于曲线的地质解译。  相似文献   

地下管线内损伤电视检测系统的研制          下载免费PDF全文

张燕  代福仲 《探矿工程》2008,35(7):90-93

介绍了地下管线内损伤电视检测系统的基本结构、工作原理、主要技术参数及其现场试验情况。  相似文献   

钢筋混凝土梁结构断裂损伤诊断方法     

周尚志  王丽华刘瑛 《海洋工程》2005,23(4):47-51

提出一种基于BP神经网络的结构破损诊断方法,该方法以结构破损前后柔度的变化作为破损诊断网络输入,为了解决由于系统响应样本数据空间分布不均匀对网络收敛速度及网络诊断影响问题,对网络训练样本采用广义空间格点进行了交换,模拟算例及应用实例均表明,本文方法能准确诊断结构破损位置与破坏程度,是一种有效的结构破损诊断方法.  相似文献   

A New Probability of Detection Model for Updating Crack Distribution of Offshore Structures     

李典庆  张圣坤  唐文勇 《中国海洋工程》2003,17(3)

1 .IntroductionNondestructiveinspection (NDI)isveryimportantforensuringthereliabilityofoffshorestructuresintheirservicelives (Lauraetal.,1 996 ) .Itiswellknownthatdetectionofflawsinvolvesconsider ablestatisticaluncertainties.Asaresult,theprobabilityofdetection (POD)forallflawsofagivensizehasbeenusedintheliteraturetodefinethecapabilityofaparticularNDItechniqueinagivenen vironment.SincethedataofPODusuallyscatterlargely ,itisdifficulttodeterminewhichmodelfitstheavailabledatabest.Thismodelun…  相似文献   

大黄鱼倍性检测研究     

刘伟斌  谢湘筠  林向阳  曾志南  宋希坤 《台湾海峡》2006,25(1):48-53

于2001—2004年对人工诱导大黄鱼的不同发育阶段和不同组织进行倍性检测，胚胎眼泡期采用染色体计数法测定，鱼苗和成鱼阶段用流式细胞法，结果表明，胚胎染色体数目2n=48条为二倍体，3n=72条为三倍体．采用流式细胞法测定鱼苗和成鱼个体时，若受测样品的DNA相对含量值与已知对照组二倍体的比值约为1．5：1，其个体为三倍体；比值约为1：1，则为二倍体，无论用肌肉或尾鳍组织，皆可检测出其个体的倍性。  相似文献