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191.
中国"数字国土"工程的方法论研究 总被引:7,自引:1,他引:7
“数字国土”是新世纪的一项宏伟工程,也是对“数字地球”和“数字中国”战略计划的响应,其核心问题是分布式点源空间数据库和属性数据库建设。分布式主题数据库建模,“多S”结合与集成,三级网络结构,信息标准化体系,海量数据入库,计算机辅助设计等关键技术的攻克,是实现区域地质调查了与矿产资源的信息化前提,而信息安全是“数字国土”的保障,作为合理而完善的解决方案,除了制定总体规划和系统结构外,还应当制定切实可行的对策和实施步骤,这需要借鉴国际上国土资源信息系统建设和地球信息科学方向发展和最新成果,并根据我国国土资源勘查与管理的特殊布局,通过周密的系统分析和系统设计来制定。 相似文献
192.
美国犹他州中西部、北美下-中奥陶统之交重要剖面上的遗迹沉积学证据表明,在奥陶纪生物爆发的重要时期─早、中奥陶世之交和重要生态领域─陆架区,存在持续3.4 Ma、周期性的陆架缺氧事件。主要的遗迹沉积学证据包括:低的遗迹化石分异度,非常浅的生物扰动层厚度和潜穴深度(小于4 cm, 现代陆架区大于20 cm),稀少的居住滤食迹,遗迹化石和遗迹组构的分布与风暴事件层密切相关;细小的Chondrites 阶层占据较浅或最浅的生态阶层 (中生代以来,细小的Chondrites 阶层总是占据最深的生态阶层);地层序列具轨道旋回地层结构,并且富含呈黄铁矿假象的褐铁矿结核。早古生代较低的大气氧水平,快速和高幅度的奥陶纪耗氧生物大辐射,早、中奥陶世之交陆架区快速和高幅度的海进和温暖的陆架环境可能是导致早、中奥陶世之交陆架环境周期性缺氧的主要原因。轨道旋回地层的研究表明,这次周期性缺氧事件始于473.27 Ma, 结束于 469.87 Ma,持续时间约3.4 Ma,如果早、中奥陶世之交的同位素年龄值为473.0 Ma。早、中奥陶世之交陆架环境周期性缺氧事件的发现,给正确认识奥陶纪生物辐射、古生代演化生物群起源环境和显生宙生物集群绝灭与缺氧关系增添了新资料。 相似文献
193.
虢国墓地位于河南省三门峡市区上村岭,于1956年被发现,经历过20世纪50年代和90年代两次大规模发掘,共发掘墓葬250多座,出土了33000余件(套)珍贵文物。本研究对象是出自M2011太子墓的380余件精美玉(石)器。采用宝玉石学和岩石学的研究思路和无损鉴定方法对M2011(太子墓)出土玉(石)器的玉质进行了详细的研究,结果表明肉眼观察颜色和不同程度受沁的26件出土玉(石)器中23件为软玉,3件为细砂岩。严重受沁会影响出土玉(石)器的材质鉴别,用强透射光观察受沁玉器玉质,部分能够看到沁色的深度,反映出本来的颜色和质地。大型仪器测试可以很好的反映出土玉器的材质与结构特征及成分的变化,弥补了肉眼观察的局限。本研究丰富了三门峡虢国博物馆出土文物的研究内容,提高了出土玉器研究的科技含量,有助于出土玉器的分类命名以及文物等级的确定。 相似文献
194.
195.
The paper presents the results of field measurements of critical conditions for bedload motion conducted in the Rio Cordon, a steep boulder‐bed stream in the Italian Alps, under conditions of high Reynolds numbers and low relative submergence poorly explored before. Two methods have been used to determine threshold of motion: the displacement of marked clasts and the flow competence approach, which uses the largest grain size diameter transported by each flood event. The high values of confirm the great relevance of non‐bedload effective shear stresses in step–pool streams given by the additional form drag associated with this morphology. Relative submergence effects on the dimensionless critical shear stress have been quantified by considering the relative submergence ratio Rh/D84, and the major effect of relative size on the mobility of each particle in steep, widely graded bed mixtures has been evaluated. Finally, the dimensionless critical unit discharge has also been adopted in the regression equations as the critical hydraulic parameter, because it may represent an easier parameter to use than the critical shear stress for steep, rough mountain rivers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
196.
The use of geoprocessing to assess vulnerability on the east coast aquifers of Rio de Janeiro State,Brazil 总被引:1,自引:0,他引:1
Vinicius Silva Seabra Gerson Cardoso da SilvaJr Carla Bernadete Madureira Cruz 《Environmental Geology》2009,57(3):665-674
The east coast of Rio de Janeiro State, Brazil, shows a worrying overlap between areas with intrinsic groundwater vulnerability
and the most significant urban expansion zones. It experienced a rapid population growth in recent years, mainly due to the
tourism industry, resulting in a significant pressure on drinking groundwater resources. In this regard, development and use
of techniques to control and protect areas susceptible to contamination is crucial. The elaboration of aquifer vulnerability
maps is thus extremely helpful to support water resources management. The aim of the work is to present the methodological
approach in the use of Geoprocessing techniques to obtain a suitable groundwater vulnerability model in Rio de Janeiro east
coast. Considering the existing problems and the current land use and characteristics of the study region, it is clear that
the most vulnerable areas (that is, “extreme” and “very high” vulnerability areas), coincide with the most significant zones
of urban occupation, corresponding to 11% of the total study area, demanding adoption of urgent measures in the near future.
Geoprocessing tools and remote sensing for characterization of Rio de Janeiro’s east coast aquifer vulnerability gave good
results, representing a satisfactory method for management actions at low cost. 相似文献
197.
Geographical distribution of arsenic in sediments within the Rio Conchos Basin,Mexico 总被引:1,自引:0,他引:1
Melida Gutierrez M. Teresa Alarcón-Herrera Lucy M. Camacho 《Environmental Geology》2009,57(4):929-935
Arsenic (As) content of sediments from the Rio Conchos and Rio San Pedro in northern Mexico were measured to determine if
this toxic metalloid had accumulated to unsafe levels to humans and aquatic life. The spatial distribution of As in each of
the six clusters of river and arroyo sediments was analyzed to determine variations with respect to background levels and
to infer about potential As sources and sinks. In the northern part of the study area, background concentrations varied little
throughout the area and concentrations in river sediments were close to background levels. In the southern part, however,
the content of As in arroyo sediment contained a wider range of values and anomalous concentrations. The latter could be traced
in part to the presence of mine tailings. As concentrations were below the limit in all studied river stretches and thus do
not pose an immediate threat to the river environment, but As content in reservoir sediments exceeded the guideline values.
Reservoirs seem to act as a sink for As, warranting closer observation and monitoring. 相似文献
198.
Children and youth are a key target group for interventions to address southern Africa’s AIDS pandemic. Such interventions are frequently implemented through schools, and are often complex products of negotiation between a range of institutional actors including international agencies, NGOs, government departments and individual schools. These institutions not only stand in different (horizontally scaled) spatial relationships to students in schools; they also appear to operate at different hierarchical levels. Empirical research with policy makers and practitioners in Lesotho, however, reveals how interventions are produced through flows of knowledge, funding and personnel within and between institutions that make it difficult to assert that any intervention is manifestly more international or more local than any other. Scale theory offers the metaphor of a network or web which usefully serves to move attention away from discrete organisations, sectors and scalar positionings and onto the relationships and flows between them. Nevertheless, organisations and development interventions are often partly structured in scalar hierarchical ways that express substantive power differentials and shape the forms of interaction that take place, albeit not binding them to strict binaries or nested hierarchies. A modified network metaphor is useful in aiding understanding of how particular interventions are produced through intermeshing scales and diverse fluid interactions, and why they take the form they do. 相似文献
199.
Soft-sediment clasts composed of silt and clay are contained within glacial outwash sands in the Puget Sound, Washington State, USA. The outwash was deposited during ice retreat of the Cordilleran ice sheet around 17 cal kyr BP. The soft-sediment clasts have a distinctive and consistent morphology and disposition within the sand beds. The sedimentology, sedimentary structures and presence of soft-sediment clasts suggest sand was deposited as proglacial outwash with silts and clays deposited in meltwater pools. Following drying-out of the pools and subaerial cracking, lumps of silt and clay were excavated by meltwater and transported distally as soft-sediment clasts within high-density flows. The most likely final depositional setting is as a Salisbury-type ‘delta’ in which subaqueous outwash grades distally into deeper water. This interpretation shows the power of soft-sediment clasts to inform on past processes and palaeogeography for which there is often little evidence in the geologic record. 相似文献
200.
Rio Marina mining district (Elba Island) is characterised by hematite + pyrite ore association and was exploited for iron till 1981, leaving waste rock dumps of several millions m3. The effect of open pit mining activity in this site is to produce acid mine drainage (AMD) processes leading to environmental pollution, testified by all the sampled waters (Giove stream, drainage channels, superficial pools and settling basin) which have pH values ranging from 2.08 to 3.35 and heavy metal concentrations that reach 903.16 mg/l for Fe, 45.02 mg/l for Mn, 10.08 mg/l for Zn and 1.75 mg/l for Cu. In the present work a space and time related approach to geochemical hazard evaluation was applied. The geochemical hazard is mainly related to high heavy metal concentration, acid mine drainage processes development and topographic setting. As all these parameters are related in space, hazard evaluation was performed by geostatistical methods. Fifty-four earth material samples (residual soils, waste rocks or debris materials) were collected in a central aligned 100 m mesh square grid. These were analysed for major elements by XRF, for Cu, Pb, Zn by ICP-AES and for AMD potential following the AMIRA procedure. The concentration of heavy metals was compared with Italian law limits. The overlap of Cu, Pb and Zn content maps show that at least one of these heavy metals exceed law limits in all the area. The AMD test results show that more than 50% of samples have a positive NAPP (Net Acid Producing Potential) that could reach 258.9 kg H2SO4/t. According to the obtained data, three main geochemical hazard classes were established and their distribution in the mining area was assessed. About 51% of the mining area surface belongs to the major hazard class, where AMD process occurs, about 49% belongs to an intermediate hazard class, where AMD process could occur only if certain conditions are met. Finally, the persistence of the AMD process in the Rio Marina area was evaluated on the basis of yearly rainfall, mining waters pH and NAPP values. A complete leaching of the first 0.25 m of the earth materials can retain the current environmental conditions for several centuries. 相似文献