Stratigraphic analysis and the asymptotic distribution of the coefficient of cross-association     

Miloslav Nosal  Jan Vrbik 《Mathematical Geology》1982,14(1):11-36

The asymptotic distribution of the coefficient of cross-association between two sequences of nominal data is investigated under the assumption of independent random sampling from a multinomial distribution slightly modified to suit geological applications. This modification is due to merging consecutive strata of the same rock type into one lithological unit, and can be described by a simple Markov chain. A distinction is made between the case in which the theoretical frequencies are known, and the situation where these have to be estimated from the observed data.  相似文献   

Middle and late Pleistocene glaciations in the Campo Felice Basin (central Apennines, Italy)   总被引：1，自引：0，他引：1  

Carlo Giraudi  Giulia Bodrato  Nicola Cipriani  Biagio Giaccio 《Quaternary Research》2011,75(1):219-230

The present paper refers to research conducted in the tectonic-karst depression of Campo Felice in the central Apennines (Italy), in which glacial, alluvial and lacustrine sediments have been preserved. Stratigraphic interpretations of sediments underlying the Campo Felice Plain are based on evidence obtained from nine continuous-core boreholes. The boreholes reach a depth of 120 m and provide evidence of five sedimentation cycles separated by erosion surfaces. Each cycle is interpreted as an initial response to a mainly warm stage, characterized by low-energy alluvial and colluvial deposition, pedogenesis, and limited episodes of marsh formation. In turn, a mainly cold stage follows during which a lake formed, and glaciers developed and expanded, leading to deposition of glacial and fluvioglacial deposits. The chronological framework is established by eleven accelerator mass spectrometer ¹⁴C ages and three ³⁹Ar-⁴⁰Ar ages on leucites from interbedded tephra layers. These age determinations indicate five glacial advances that respectively occurred during marine oxygen isotope stages 2, 3-4, 6, 10 and 14.  相似文献   

基于SMS/GPS/GIS地震灾情获取处理技术研究与实现   总被引：3，自引：3，他引：0  

帅向华  郑向  刘钦 《震灾防御技术》2011,6(2):164-171

本文研究了基于Windows Mobile的SMS与GPS的嵌入式集成开发技术,以智能移动终端作为地震现场灾情获取与传输的手段;同时还研究了SMS与GIS的无缝集成技术,实现灾情信息的可视化分析,借助GIS空间分析技术进行地震现场灾情空间分布研究.本文建立了基于SMS、GPS和GIS相结合的地震灾情获取处理模式,并基于GSM移动网关和信息机实现了该方法.该方法的模式可以应用于多种远程信息获取领域.  相似文献   

Bioavailability and toxicity of aluminium in a model planktonic food chain (Chlamydomonas-Daphnia) at neutral pH     

P. Quiroz-Vázquez  K.N. White 《Limnologica》2010,40(3):269-709

Dissolved aluminium (Al) is generally at low concentrations in neutral freshwater due to its insolubility. However, a fall in pH resulting from acid deposition and mining alters the mobility of Al and so entry to adjacent neutral waters. The present study examines the environmental behaviour, cell-associated surface adsorption/absorption and toxicity of Al at neutral pH to the alga Chlamydomonas gigantea in the presence and absence of the key Al-binding ligand silica. We then examined transfer of Al from C. gigantea to the planktonic crustacean Daphnia pulex. Finally, the effect of Al on the elemental composition (and hence nutritional value) of the two organisms was compared to unexposed controls. C. gigantea increased the amount of Al in the algal culture medium. Binding of Al to extracellular glycoprotein is probably the reason why only one-third of the biosorbed Al was absorbed (accumulated) by C. gigantea. Aluminium concentrations between 50 and 500 μg l⁻¹ reduced growth of C. gigantea at 16 days exposure to the metal. Silica reduced biosorption, accumulation and toxicity of Al by C. gigantea. The concentration of Al in D. pulex fed Al-contaminated C. gigantea for 16 days did not differ from those fed alga grown in the absence of added Al. C. gigantea contaminated with Al contained less sulphur, magnesium, potassium and sodium although only sulphur fell in D. pulex subsequently fed the contaminated alga. Chloride, calcium, iron and silicon were significantly higher in D. pulex.  相似文献   

青藏高原新生代形成演化的整合模型——来自火成岩的约束   总被引：28，自引：8，他引：28  

罗照华  莫宣学  侯增谦  邓万明  王江海  赵志丹  喻学惠  李建平 《地学前缘》2006,13(4):196-211

深部过程是青藏高原演化的主导因素,其他地质过程都可以看作是对深部过程的响应。因此,一个构造旋回(阶段)的地球动力学事件链可以概括为深部地质过程—幔源岩浆活动—壳源岩浆活动—陆壳增厚—地表隆升—表层剥蚀与沉积,其中幔源岩浆活动的研究成为追索青藏高原演化历史的关键环节。据此,青藏高原演化的关键性时间坐标为80、45、27、17、9和4Ma。青藏高原新生代火成岩具有三种展布形式:与雅鲁藏布缝合带平行的岩浆带、沿深大断裂展布的岩浆带和藏北离散性岩浆分布区,它们分别受控于大陆碰撞、大规模走滑和岩石圈拆沉构造体制,且都受控于印度—亚洲软流圈汇聚过程。据此,文中提出了一个描述青藏高原演化的整合模型:南北向地幔对流汇聚控制了岩石圈块体的相对运动,并最终导致印度—亚洲大陆的碰撞和沿碰撞带的大规模岩浆活动;碰撞之初(白垩纪末期),大陆岩石圈块体的刚性属性有利于应力的远程传递和块体旋转,沿块体边界分布的大型走滑断裂控制了岩浆活动的发生;随着挤压过程的持续进行,岩石圈块体的受热和变形,高原岩石圈的重力不稳定性增加,最终导致拆沉作用和软流圈物质的大规模上涌以及藏北高原的离散性岩浆活动。在高原演化中,岩石圈拆沉作用具有重要意义,许多地质事件的发生都与此有关。同时,软流圈的汇聚还导致软流圈物质的向东挤出,并因此造成青藏高原岩石圈的向东挤出和晚新生代的伸展构造。  相似文献   

洞庭湖镉迁移转化的马尔可夫模型评价     

张建新  邢旭东 《岩矿测试》2007,26(4):339-342

讨论了在现时泥沙、水体、鱼类、藻类的含镉状态下洞庭湖的输入输出通量；并以其为例，在简要介绍马尔可夫链数学方法的基础上，建立了湖泊生态系统中镉迁移转化的马尔可夫链数学模型，初步评价了当洞庭湖不断有镉加入、系统到达状态稳定时各种介质中的镉总量及镉的迁移转化趋势。  相似文献   

国外灾害风险管理对我国城市洪水保险的启示   总被引：3，自引：0，他引：3  

尚志海 《世界地理研究》2007,16(2):107-111

全球变化和城市化的共同作用将导致城市洪涝灾害加剧，在这一新背景下，结合国外灾害风险管理的研究，对洪水保险进行了有益的探索，针对以前我国洪水保险试点在农村地区失败的原因，提议我国应该从城市开始实施洪水保险计划，认为实施城市洪水保险有必要性和可行性，可以进一步拓展城市洪涝灾害风险管理的渠道。  相似文献   

经济地理学视角下的旅游发展理论演进   总被引：1，自引：0，他引：1  

任瀚 《地域研究与开发》2007,26(6):13-17

经济地理学是一门非常活跃和发展演化很快的学科.近30年来,经济地理学的发展演化带动了旅游发展理论的演变.回顾旅游发展理论研究的进展,依次有依附理论、生命周期理论、社区研究方法、福特主义、弹性专业化和全球商品链理论,这些理论在旅游方面的应用和研究,从时间和数量上都明显滞后于生产实践活动,说明旅游研究还处于经济地理学科"边缘化"的地位.在今天经济全球化的背景下,旅游产业在迅猛发展之时,旅游发展理论的建设更应与经济地理学紧密结合,由"边缘"走向"核心".  相似文献   

Bayesian Spatial Modelling of Gamma Ray Count Data     

Daniela Leonte  David J. Nott 《Mathematical Geology》2006,38(2):135-154

Gamma ray logging is a method routinely employed by geophysicists and environmental engineers in site geology evaluations. Modelling of gamma ray data from individual boreholes assists in the local identification of major lithological changes; modelling these data from a network of boreholes assists with lithological mapping and spatial stratigraphic correlation. In this paper we employ Bayesian spatial partition models to analyse gamma ray data spatially. In particular, a spatial partition is defined via a Voronoi tessellation and the mean intensity is assumed constant in each cell of the partition. The number of vertices generating the tessellation as well as the locations of vertices are assumed unknown, and uncertainty about these quantities is described via a hierarchical prior distribution. We describe the advantages of the spatial partition modelling approach in the context of smoothing gamma ray count data and describe an implementation that may be extended to the fitting of a more general model than a constant mean within each cell of the partition. As an illustration of the methodology we consider a data set collected from a network of eight boreholes, which is part of a geophysical study to assist in mapping the lithology of a site. Gamma ray logs are linked with geological information from cores and the spatial analysis of log data assists with predicting the lithology at unsampled locations.  相似文献   

基于水位和雨量的洪涝受灾面积评估模型研究     

周月华  郭广芬  邵末兰  李竹君 《湖北气象》2007,26(4):323-327

在分析湖北省洪涝灾害孕灾环境和致灾因子的基础上,利用民政部门整理的1951～2000年洪涝受灾面积资料,建立了基于长江中游流域逐月最高水位和湖北省5～10月降水总量的湖北省洪涝灾害受灾面积定性和定量评估模型,并给出了该模型2001～2006年的独立样本检验值,探讨了该模型在年度灾害趋势预估和灾后评估中的应用。  相似文献