基于同步挤压小波变换的烃类识别技术          下载免费PDF全文

潘晓  曹思远  徐彦凯  孙晓明  陈思远 《地球物理学报》1954,63(11):4176-4187

利用频谱分解得到的频率能量数据体进行属性提取,是烃类检测的常用手段之一.同步挤压小波变换能够提供高分辨率的时频谱,具有较好的应用潜力.本文以同步挤压小波变换为基础,提出了一套烃类检测方法,包括低频阴影检测、流体流动性估计以及高频能量衰减等,通过自适应选取优势频段,实现了多属性联合高精度刻画烃类的分布范围.实际资料处理结果与现有钻井情况吻合,具有较好的实用性,实现了对储层位置的高精度描述,对指导油气田开发具有重要的理论意义和实用价值.  相似文献   

Detrital and authigenic(?) baddeleyite (ZrO2) in ferromanganese nodules of Central Indian Ocean Basin     

Bibhuranjan Nayak  Swapan Kumar Das  Kalyan Kumar Bhattacharyya 《地学前缘(英文版)》2011,2(4):571-576

Occurrence of baddeleyite (ZrO2) which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin (CIOB). The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals (<3 mm) within ferromanganese concretionary growth bands. The mode of occurrence, textural features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite. For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in the form of baddeleyite within manganese nodules under oxic to sub-oxic conditions.  相似文献   

Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh   总被引：1，自引：0，他引：1  

M. Aziz Hasan  Mattias von Br?mssen  Prosun Bhattacharya  Kazi Matin Ahmed  Arif Mohiuddin Sikder  Gunnar Jacks  Ondra Sracek 《Environmental Geology》2009,57(3):499-511

The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements determined by X-ray fluorescence (XRF) show that iron (Fe₂O₃), aluminum (Al₂O₃) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO₃ ⁻, SO₄ ²⁻ and NO₃ ⁻ in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment. Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic pyrite in the dark grey sediment indicates active reduction in the aquifer.  相似文献   

上海市居民居住迁移的区位选择及其影响因素研究     

崔璨  穆学英  常鹤影  李佳怡  王丰龙 《地理科学进展》2021,40(3):422-432

随着中国住房改革的推进,城市居民通过居住迁移进行住房调整的行为日趋频繁。居住迁移作为城市空间分异和重构的微观机制在城市地理学、住房研究中得到了广泛关注,然而现有研究主要考察居住迁移的发生概率和驱动因素,较少论及居住迁移中的区位选择。论文基于2018年“上海市居民住房和生活空间调查”问卷,采用生命历程和时间地理学视角,刻画居民居住迁移的时空轨迹,并使用多项逻辑斯蒂回归模型探究居住迁移前后居住区位变化的影响因素。研究发现,上海市居民居住迁移的主要区位选择为跨环线向外迁移,但不同世代、不同户口、不同住房产权的居民的居住区位选择有较大差异。生命历程中的年龄、可达性中的工作单位区位以及住房属性中的产权性质都是影响居住迁移区位选择的重要因素。  相似文献   

生命历程视角下的广州市居民居住迁移的时空路径   总被引：4，自引：3，他引：1  

古杰  周素红  闫小培 《地理研究》2013,32(1):157-165

转型与重构是现阶段中国城市发展的主旋律,在这一背景下,从个体生命历程的视角研究居住迁移的时空规律和影响因素有助于从深层次理解城市空间结构重构的内置机制,同时,对公共服务设施供给和提高居民生活质量等有一定的现实意义。以2007年进行的一次入户调查资料作为基础,研究了广州市居民居住迁移时空路径的生命历程特征。结果显示,广州市居民居住迁移的时空路径呈现出年龄偏好和空间偏好两个基本规律,这两个规律可以用“N”形曲线和“微笑曲线”来表达。“N”形曲线揭示了居住迁移率随年龄变化呈现出先上升后下降最后再上升的规律。微笑曲线则揭示了老人与孩子的居住迁移的方向较为集中而中年人的居住迁移方向较为离散的特点。文章据此从不同生命历程居民居住偏好的角度分析了产生上述居住迁移宏观规律的原因。从而证实了广州市居民居住迁移的时空路径具有若干生命历程的特征,对转型期广州市住房的供给与公共设施和服务的空间配置有着积极的意义。  相似文献   

Transformation from Permian to Quaternary bauxite in southwestern South China Block driven by superimposed orogeny: A case study from Sanhe ore deposit     

《Ore Geology Reviews》2017

Permian karstic bauxite and its Quaternary derivative, in western Guangxi, southwestern, South China Block, possess a total tonnage greater than 0.5 billion tons. The primary late Permian karstic bauxite formed in reduced environment in the background of Tethyan accretionary orogenesis. And as one consequence of Cenozoic convergence of the Indian and Eurasia continents, the primary orebody was uplifted, eroded and re-sedimented within Quaternary laterite. The geochemical variation and its controls during the ore transformation from Permian to Quaternary remain poorly understood. Quaternary ore blocks comprise an inner zone of fresh ore, and then it gradually transited through a middle zone to a margin with extensive weathering. One such bauxite block was selected and further subdivided into twenty-three samples for geochemical and mineralogical analysis. The inner and middle zones contain similar mineralogical compositions, dominated by diaspore and amesite, with minor illite, anatase, goethite, pyrite, zircon, and rutile. The margin is composed of diaspore, with small amounts of amesite, boehmite, illite, goethite, anatase, kaolinite, zircon, rutile, and barite. Bauxite in all three zones is composed of mainly Al, Si, Fe, and Ti, and high contents of Zr, Cr, Li, F, S, Zn, V, Sr, Nb, Ba, and REE. Variations in Fe²⁺ and Fe³⁺ between the three zones were observed. The elements Si, Al, Fe²⁺, Mg, Ba, Cr, F, Li, Ni, Zn, and REE decrease from the core of the ore block outwards, corresponding to an increase in S and Fe³⁺. Depletions in Si, Al, Fe²⁺, Mg, Ba, and Cr were caused by the dissolution of amesite. Most of the Al and Si in amesite were lost during the weathering, and minor retained to form kaolinite. Depletions in Li, Ni, and Zn resulted from changes in the depositional environment between the late Permian and Quaternary. Dissolution of REE-bearing fluorocarbonates resulted in depletions of REE and F. The enrichment of Fe³⁺ and S was related to the precipitation of goethite, hematite, and barite in an oxidizing environment, while local enrichment of Ce resulted from the redox change of Ce³⁺ → Ce⁴⁺ under the same condition. This shows that the chemical composition of laterite enwrapping the bauxite also took part in Quaternary bauxite transformation. This study shows that the elements migrations during bauxite transformation were influenced by multiple independent factors except for the elemental attributes.  相似文献   

Job-related mobility and plant performance in Sweden     

《Geoforum》2017

This paper uses a Swedish micro-dataset containing 2,696,909 hires during the period 2002–2006 to assess the impact of job-related mobility on plant-level performance. The analysis classifies new recruits according to their work experience and level of formal qualification, as well as by the region of origin and of destination. New hires are divided into graduates and experienced workers and between high- and low-educated. The results point towards the importance of acknowledging both the experience and the skills of new recruits. The greatest benefits are related to hiring new workers from outside the region where the plant is located. The analysis also stresses the importance of geography, with plants in metropolitan regions gaining the most from labour mobility, while the benefits of mobility for plants in smaller, more peripheral regions are more diverse and dependent on both the type and origin of new workers.  相似文献   

Distinctive and comparative places: Alternative narratives of distinction within international student mobility     

《Geoforum》2017

Moving beyond the ‘world-class’ institutional model of international student mobility, this paper examines alternative narratives of distinction relating to place of study. Drawing on semi-structured interviews with international students at universities in the UK, Austria and Latvia, we illustrate how students inside and outside mainstream reputable higher education institutions narrate and reconfigure markers of distinction to validate their international mobility and location of study, in part to compete with peers at other (more prestigious) institutions. We demonstrate the importance of lifestyle and experiential places within a global differentiated higher education landscape and argue that many students engage in comparative narratives of place of study to authorise the symbolic capital associated with international education. The findings also consider how experiential places and mobility capital are used for distinction not only during educational mobility but within post-study aspirations.  相似文献   

防水措施对堤坝地震液化影响的数值分析     

夏志凡  叶冠林  王建华  叶斌  张锋 《岩土力学》2010,31(8):2682-2688

通过基于有效应力的完全耦合动力分析方法,研究了混凝土面板坝在地震作用下的动力响应,详细地讨论了堤坝迎水面斜坡上铺设的防水毯对堤坝地震液化的影响。计算中土体采用Cyclic mobility本构模型,该模型通过在修正剑桥模型上增加应力诱导各向异性、超固结和结构性的概念及其相关发展准则,可以很好地描述可液化土体的动力特性。计算结果表明防水毯的存在可以有效降低坝体的地下水位浸润线,增加坝基的初始有效应力,从而降低坝基地震液化发生的可能性,同时坝体的变形明显减小。  相似文献   

建议纳入地下水调查指标体系的有机污染物——基于迁移性和致病风险的分析          下载免费PDF全文

王昭  石建省张兆吉费宇红李亚松张凤娥 《中国地质》2009,36(5):1175-1178

在地下水有机污染调查中,如何准确地选择测试项目,对于正确认识和评价地下水的污染状况是十分必要的.本文通过参照不同标准或规范中所选择的有机指标,依据它们的迁移性和致病风险,从258种有机物中遴选出了29种"地下水污染调查评价规范"(2006)中尚未包括的有机物(主要是除草剂和杀虫剂).建议在进行地下水有机污染调查时,依据当地的污染源情况,增加相应的监测指标,特别是要加强对致病风险高和迁移性较高有机物的重视.  相似文献