共查询到20条相似文献，搜索用时 46 毫秒
1.
By means of X-ray fluorescence with synchroton radiation (XRF-SR), the contents of all 14 rare-earth elements (REEs) and that of Y were determined in 12 monazite samples from different veins in the Ilmen’ Reserve (South Urals). It was found that, in anphibole-micaceous-carbonate mineralized zones within metabasites, monazites were pronouncedly depleted in middle and, especially, in heavy rare-earth elements (HREEs) (from 0.25% and below for Sm, 0.08% or below for Gd, 0.03% for Dy, 0.01% for Er and Tm, below 0.005% for Yb, trace amounts of other odd HREEs, at a Y content of 0.1% or below). Monazites from the veins of granitic pegmatites were characterized by vastly decreased La contents (4–8 compared to 11–13% for the group above), at high values for Pr (to 3%), Nd (to 8%), Sm (to 1.3%), Gd (to 1.1%), Dy (to 0.9%), Er (to 0.2%), Yb (to 0.05%), and Y (from 0.2 to 1.7%). Here, the values for odd REEs are also quite high compared to the group above (to 0.2% for Tb, to 0.08% for Ho, and to 0.1% for Tm).
相似文献2.
Developments in information and communication technologies offer new opportunities to use and integrate scientific data that have been collected by researchers and scholars from diverse fields of inquiry. Data archives and digital repository systems are being developed to preserve current and legacy scientific data and technical information for use by others. However, capabilities are needed for data producers of various disciplines to easily and efficiently submit their data into archival systems for preservation. Analysis of digital preservation requirements has identified the requirements for services to support the submission and review of scientific data for preservation. Data submission and review processes are segmented into services, which are defined to support efficient preparation of scientific data for ingest into an archive or digital repository system. A model is proposed to inform the design of submission and workflow services for preserving interdisciplinary scientific data. Recommendations are offered for improving the design and evaluation of systems and services to prepare and preserve scientific data for new uses by interdisciplinary communities of users in the future. Improving the infrastructure that enables members of the scientific community to submit their data for archiving contributes to the scientific data stewardship and data curation capabilities needed to preserve scientific data for future generations of users. 相似文献
3.
Risk-targeted seismic design maps for mainland France 总被引：3，自引：2，他引：1
In this article, the recently proposed approach known as ‘risk targeting’ for the development of national seismic design maps is investigated for mainland France. Risk targeting leads to ground-motion maps that, if used for design purposes, would lead to a uniform level of risk nationally. The Eurocode 8 design loads currently in force for France are used as the basis of this study. Because risk targeting requires various choices on, for example, the level of acceptable risk to be made a priori and these choices are not solely engineering decisions but involve input from decision makers we undertake sensitivity tests to study their influence. It is found that, in contrast to applications of this methodology for US cities, risk targeting does not lead to large modifications with respect to the national seismic hazard map nor to changes in the relative ranking of cities with respect to their design ground motions. This is because the hazard curves for French cities are almost parallel. In addition, we find that using a target annual collapse probability of about 10?5 for seismically designed buildings and a probability of collapse when subjected to the design PGA of 10?5 leads to reasonable results. This is again in contrast to US studies that have adopted much higher values for both these probabilities. 相似文献
4.
项目国家审计是一种执法监督活动,设计方满足审计要求是必不可少的义务和职责。通过铁路建设项目国家审计,初步分析国家审计对设计方要求,提出设计方满足项目国家审计要求的措施,为设计方适应国家投资市场规则及其变化趋势,规避设计风险,拓展设计方生存空间提供思路。 相似文献
5.
This paper investigates use of inventories, or checklists of activities, as an emergency management tool to motivate preparedness action in individuals. It develops the inventory concept to provide the foundation for a more targeted approach to storm preparation communication and community engagement. It also examines the potential efficacy of alternatives to paper-based checklists, such as web or smartphone applications. Academic and grey literature was reviewed to collect activities for a storm inventory for emergency agencies to measure individual preparedness and for individuals to measure their preparation progress. The resulting master list was refined for application and tested for useability in a pilot study of semi-structured interviews in a storm-susceptible community in Queensland, Australia. Also, clustering items by type of preparedness activity reveal where strengths and weaknesses exist in individual preparedness. For instance, preparation for leaving and safety planning were shown to be the areas of weakest activity in the pilot sample, while preparation of the house for a storm was the strongest area. In addition, behaviour change literature shows potential for effective use of an inventory-based smartphone application in motivating preparation activity. Data collected by a storm preparedness smartphone application could show where a communication or engagement program for targeted communities should be focused. It is supported by health literature that identifies preferences of individuals to make progress on complex tasks in stages, the value of lists to achievement of goals and demonstrated increase in uptake of activities prompted by smartphone applications over web or paper-based diaries.
相似文献6.
7.
根据浙江293个有开采价值的中生代热液萤石、金、银和铅锌矿床数据,在矿床地质研究基础上探讨了这些矿床的空间和储量分形问题。研究表明,在两个尺度范围内,矿床在空间上呈分形分布,其中群集分布的分维数D分别为0.1405-0.3778(1-20km)和0.7168-1.1851(20-750km);密度分布的分维数D分别为0.294-1.1242(1-40km)和0.135-0.252(40-750km)。研究还发现矿床的频度-大小分布也是分形的,其储量分形分布的分维数为萤石(浙江)D=2.34萤石(中国)D=2.13:铅锌(浙江)D=2.27;银(浙江)D=1.63:金(浙江)D=1.09。 相似文献
8.
福建省大田县土地利用适宜性评价 总被引：5，自引：0，他引：5
新修订的《中华人民共和国土地管理法》已于１９９９年元旦实施,其重要特点之一是实行土地用途管理,限制农用地转为非农建设用地,确保耕地动态平衡,因此,必面编制土地利用总体规划,而土地适宜性评价是“规划”编制的基础,也是各级政府土地利用决策的依据之一。我们在编制大田县土地利用总体规划中,对该县建设用地,水域,裸岩地以外的大部分土地作了适宜性评价,划分了宜耕,宜园,宜林地和暂不适宜土地,并进一步划定了适宜 相似文献
9.
《Chemical Geology》2007,236(3-4):247-265
A knowledge of the processes involved in streamflow generation are critical to an understanding of solute transport and weathering rates in upland catchments. The determination of specific flow pathways and the formulation of process-based models have proved difficult in such terrains, largely due to the heterogeneous nature of catchments and the necessary limitations of bulked parameter models. Natural geochemical tracers have proved invaluable in developing conceptual models of catchment functioning and for constraining weathering processes and geochemical cycling. Strontium isotopes have been used as a natural tracer to calculate weathering rates for Sr and Ca, and to constrain the dominant flow pathways in two upland forested sub-catchments (Afon Hafren and Afon Hore) of the River Severn at Plynlimon in Central Wales. The dominant source of Sr in the catchments is considered to be from the weathering of silicate minerals. Weathering rates for Sr and Ca in the Afon Hafren, calculated using Sr isotopes, were similar to those derived from mass balance studies. The rates for the Afon Hore were similar for Ca, but significantly different for Sr. The reason for the difference is unclear, but may be due to additional sources (calcite) in the catchment. Strontium isotope ratios for different input sources and compartments within the catchment were characterised and helped to identify potential flow pathways. The data suggest an important role for groundwater inputs in contrast to previous models which indicated a dominant role for soil waters. 相似文献
10.
分期设计洪水标准计算方法研究 总被引：3，自引：0，他引：3
针对水库分期设计和调度运用所涉及的分期情况下如何定义水库防洪标准,以及如何在不突破水库防洪标准的前提下合理确定分期设计洪水标准等关键问题,本文基于概率论中独立事件的概率组合原理,提出了水库分期运用情况下的水库防洪标准的等价表达形式,并以一个水库作为分析案例,在确保水库分期运用情况下的等价防洪标准不突破水库防洪标准的前提下,分别确定了各个分期设计洪水标准以及相应的汛限水位。 相似文献
11.
This paper gathered available flow and transport solutions and used them for two composite liners, consisting of geomembrane
(GM) overlying either a compacted clay liner (CCL) or a geosynthetic clay liner (GCL). Its aim is to provide a guiding framework
for the possible choices of (a) approaches to bottom liner design, (b) respective analytical solutions to flow and transport
equations, as well as (c) parameters required for each type of solution. On the basis of the obtained results, the following
recommendations are made. When the goal of analysis is to determine material equivalency, leachate flow rate is an adequate
key parameter for GM-CCL composite liners. For GM-GCL composite liners, it is necessary to compute contaminant concentration
or mass flux, considering (a) transport through defects for inorganic contaminants and (b) diffusion and the contribution
of any available attenuation layer for organic contaminants. When the goal of analysis is to assess impact to groundwater,
it is advised to calculate both discharge rate and contaminant mass flux regardless of liner type. The critical parameter
for the transport calculations is the retardation factor of the contaminant, for the case of CCLs, while the results for GCLs
are much less sensitive to this parameter. 相似文献
12.
基于多沙河流"多来多排"输沙基本公式,建立了考虑上站来沙量、前期累计淤积量、临界输沙水量及干支流泥沙粒径影响的输沙量一般表达式。进而根据黄河内蒙古河段1953—2010年实测水沙资料,得到了内蒙古巴彦高勒—头道拐全河段及巴彦高勒—三湖河口和三湖河口—头道拐分河段的年输沙量公式,并根据输沙率法采用建立的输沙量公式计算了各河段1953—2010年的逐年冲淤量。选取三湖河口—头道拐河段的计算结果分析表明,在输沙基本公式基础上增加前期累计淤积量、临界输沙水量及干支流泥沙粒径参数,所得公式计算的年冲淤量与实测值之间的相关系数R2由基本公式的0.41依次提高到0.50、0.75和0.80,说明在基本公式基础上进一步考虑这些参数的必要性。此外,全河及分河段输沙公式计算所得输沙量及各河段冲淤量和累计淤积量与实测值的符合程度均较好,表明建立的输沙公式能够用于不同水沙条件下的输沙量和冲淤量计算,可为分析内蒙古河段的输沙特性和长期淤积趋势提供参考。 相似文献
13.
新疆东天山康古尔剪切带西段金矿床的成矿流体特征及其地质意义 总被引：2，自引：2，他引：0
东天山觉罗塔格地区沿着康古尔韧性剪切带发育众多金矿床,已经成为新疆重要的黄金产地之一。文章对位于该剪切带西段储量较大、勘查程度较高的红石、康古尔和马头滩3个金矿床进行了地质特征、流体包裹体和氢氧同位素研究,结果表明,这3个矿床含矿石英脉流体包裹体的均一温度分别为294.4~468.0℃(红石)、236.9~441.0℃(康古尔)、150.9~444.7℃(马头滩);盐度w(NaCleq)分别2.7%~10.5%(红石)、4.2%~9.1%(康古尔)和6.4%~8.4%(马头滩);密度分别为0.54~0.83 g/cm3(红石)、0.80~0.86 g/cm3(康古尔)和0.57~0.80 g/cm3(马头滩)。本文和前人数据表明,这3个矿床的δDSMOW值分别为-104‰~-63‰(红石)、-72‰~-45‰(康古尔)和-55‰~-45‰(马头滩),与石英相平衡的水的δ18OH2O值分别为-1.7‰~7.4‰(红石)、-8.3‰~5.0‰(康古尔)和2.5‰~2.6‰(马头滩)。以上特征表明,红石、康古尔和马头滩金矿床成矿流体具有中-高温、低盐度、较高CO2含量,其中红石金矿床的成矿流体中岩浆水比例比康古尔和马头滩两个矿床相对要高。综合地质、流体和年代学特征表明,沿康古尔韧性剪切带分布的金矿床可能具有较为一致的成因,可能是295~280 Ma和260~240Ma两个成矿期叠加作用的产物,分别与早二叠世拉张背景下的中-酸性岩浆的侵入和晚二叠世—早三叠世(260~240 Ma)挤压背景下康古尔剪切带的韧性剪切变形及抬升作用相对应。 相似文献
14.
A Reflection on Mg, Cd, Ca, Li and Si Isotopic Measurements and Related Reference Materials 总被引：6，自引：1，他引：6
Jean Carignan Damien Cardinal Anton Eisenhauer Albert Galy Mark Rehkamper Frank Wombacher Nathalie Vigier 《Geostandards and Geoanalytical Research》2004,28(1):139-148
This contribution aims to report the reflections we had with the scientific community during two international workshops on reference materials for stable isotopes in Davos (2002) and Nice (2003). After evaluating the isotopic homogeneity of some existing reference materials, based on either certificates, literature data or specific inter-laboratory rounds, we confirm these as primary reference materials or propose new ones relative to which stable isotope compositions should be reported. We propose DSM-3 for Mg, NIST SRM 915a for Ca, L-SVEC for Li and NBS28 for Si. Cadmium does not yet have a well identified delta zero material, although three commercial mono-elemental Cd solutions have yielded the same isotopic composition relative to one another. In order to scale the linearity of any mass spectrometer, some secondary reference materials are also proposed: Cambridge-1 solution for Mg, the "Münster-Cd" and JEPPIM Cd solutions for Cd and the "Big Batch" silicate for Si. The team from Nancy propose to prepare a mixed spike solution for Li isotopes. Well-characterised natural samples such as ocean or continental waters, diatoms, sponges, rocks and minerals are needed to validate the entire analytical procedure, particularly to take into account the effect of sample mineralisation and of chemical manipulations for elemental separation prior to analysis. 相似文献
15.
迎接新形势 将物探推进到一个新阶段 总被引：1，自引：0，他引：1
近年来,随着整个地质工作任务和布局的调整,贯彻以地质一找矿为中心的方针,综合物探(指除专业石油物探队伍以外的所有物探)工作有了很大的发展,主要是工作领域和工作方面有所扩大,所采用的方法也有所增加,新研制的仪器陆续投入生产,地质效果也日益明显,方法技术有较大进步。 相似文献
16.
Methods are presented for analysing earth structures subjected to tensile stresses that may produce cracking. The linear elastic fracture mechanics approach is emphasized. Methods of solution are proposed for cracking of a clay layer above the water table due to desiccation; cracking of layered earth structures subjected to external loads; cracking of clay caps for landfills due to differential settlement; and radial cracking in pressurized boreholes. Causes and mechanisms of cracking are discussed for each problem and models pertinent to each problem are proposed. Solutions have been developed by synthesizing analytical and numerical methods. Published experimental data have been incorporated in modelling matric suction and cracked beams on elastic foundations. Finite element analyses were employed to obtain solutions for cracking due to differential settlement and radial cracking in boreholes. The solutions presented herein can be used to assess the soundness of existing structures or to assess the risk of cracking for the design of new structures. 相似文献
17.
Graciela Salinas de Salmuni Inés Velasco Mirta Fresina Alberto L. Flores 《GeoJournal》2007,70(4):273-279
Much of the central-western region of Argentina, where San Juan Province is located, experiences arid to semi-arid climatic
conditions with low average annual rainfall accompanied by substantial evapotranspiration. Consequently, a viable crop industry
depends to a large extent upon irrigation from major river systems. Increasing demand for water in the lower basin of the
San Juan River is emphasizing the need for more accurate estimates of water used for irrigation. Since the water demand for
a particular crop is very closely related to crop area, monitoring the area of crop under irrigation is considered a proxy
for the amount of water used. Landsat 5 imagery for the growing season, field data and aerial photographs were used to evaluate
crop area. 相似文献
18.
在河流排污引起的污染物扩散计算中,不同河流宽度类别对应不同的移流扩散解析解算式,但缺少具体的河流宽度分类判别准则,给实际应用带来很大困难。按照河流污染物扩散受边界反射影响程度的不同,从移流扩散解析解算式的简化条件出发,提出了宽阔、中宽、窄小的分类方法和定义;根据二维可忽略边界反射的条件和达到全断面均匀混合距离小于等于河流宽度的条件,分别求解了河流宽阔与中宽窄小的分区临界关系线和中宽与窄小的分区临界关系线,提出了相应判据的数学表达式;给出了河流宽阔、中宽、窄小的分类判别准则以及各类别河流移流扩散解析解算式的对应关系。最后指出基于环境扩散条件的河流宽阔、中宽、窄小分区是相对的,对于同一河流在不同水力要素、扩散系数、排污强度和允许浓度升高值等条件下,可以得到不同的分区结果。 相似文献
19.
异常查证是加速矿产普查的进程,是发现新矿产地的一条捷径。新一轮国土资源大调查对异常查证提出了新的更高的要求。本文总结了物探、化探异常查证找矿效果,分析了目前异常查证中存在的主要问题,强调了异常查证的重要性和必要性,提出了强化异常查证思考要点及主要途径。 相似文献
20.
T. M. Rachkovskaya 《Astronomy Reports》2000,44(4):227-234
Using high-resolution spectra, we have determined the abundances of carbon (logε(C)), nitrogen (logε(N)), oxygen (logε(O)), silicon (logε(Si)), sulphur (logε(S)), and some other elements for three δ Scuti stars. Logε(C) for all three stars and logε(N) for δ Sct and HD 127986 are close to the solar values, while there appears to be a slight (0.15 dex) nitrogen deficiency for 14 Aur. The logε(O) values correspond to a 0.30-dex deficiency for 14 Aur and δ Sct and a 0.20-dex deficiency for HD 127986. The values of logε(Si) for the three stars are close to solar, and the logε(S) values indicate a slight deficiency (0.10 dex) for 14 Aur and HD 127986 and a 0.20-dex excess for δ Sct. Comparison of the elemental abundances for seven δ Scuti stars with those for Am stars shows that the mean deficiencies of C, N, and O are smaller for pulsating δ Scuti stars than for Am stars with similar effective temperatures. The sulphur abundances are virtually the same for both types of stars. 相似文献