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141.
An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials 总被引:2,自引:0,他引:2
Kenneth W.W. Sims James B. Gill Anthony Dosseto Dirk L. Hoffmann Craig C. Lundstrom Ross W. Williams Lary Ball Darren Tollstrup Simon Turner Julie Prytulak Justin J.G. Glessner J.J. Standish Tim Elliott 《Geostandards and Geoanalytical Research》2008,32(1):65-91
We present a concerted international effort to cross-calibrate five synthetic Th isotope reference materials (UCSC Th "A", OU Th "U", WUN, IRMM-35 and IRMM-36), and six rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2, USGS BHVO-2, LV18) using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We then compare our new values with a compilation of literature mass spectrometric data for these reference materials and derive recommended "consensus"230 Th/232 Th values for each. We also present isotope dilution U and Th concentration data for four rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2). 相似文献
142.
李莹 《广东海洋大学学报》2006,26(2):135-138
随着科技的不断进步,跨文化交际日益频繁,如何在外语教学中培养学习者的跨文化意识已成为外语教育者研究的新课题。试从文化的核心———价值观入手,以文化语言融合教学观为理论基础,提出价值观与语言相融合的文化教学新模式,以期培养学习者的跨文化意识。 相似文献
143.
F. Lorenzo A. Alonso M. J. Pellicer J. L. Pagés M. Pérez-Arlucea 《Environmental Geology》2007,52(4):789-802
This research focuses on the development of metal pollution in sediment cores from three estuaries in Northwest Spain: Viveiro,
Ortigueira and Barqueiro. Pb, Cu, Co, Cr, Cd and Zn and total organic carbon were assessed using principal component analysis
(PCA) in order to obtain background values, measure pollution levels and identify pollution sources. Results were interpreted
by considering the local industrial history, grain size and C/N relationship. The pollution levels obtained bear a strong
resemblance to those documented for of a moderately industrialised area. PCA identifies factors that reflect mainly temporal
associations with metals. Sedimentation rates between 0.9 and 1.1 cm/year were determined. In Viveiro core levels of Cr pollution
are associated with tanneries. In Ortigueira, high core levels of Cu and Co are linked to mining, and Cr levels to adjacent
ultramafic rocks. Erosion of Holocene sediment causes high values of Co and Cr in the Barqueiro core. Cu increase in the three
estuaries is related to fungicide use since 1910. Sea level rise appears to be affecting the marine characteristics of the
sediments in Barqueiro. In Viveiro, the nature of the sediment reflects engineering work and land reclamation. 相似文献
144.
The International Organisation for Standardisation (ISO) has published many guides, or technical standards, of great value to analytical geochemists. Two of particular importance are Guide 33 (Uses of Certified Reference Materials) and Guide 35 (Certification of Reference Materials). Both were first developed in the 1980s and undergo regular review and updating by the Reference Materials Committee (REMCO) that operates within ISO. Recent revisions have focused on adding statistical rigour to both guides. Although this offers significant advantages for use by professional metrologists, there are consequent issues of comprehension by the analytical chemists who in fact have the greatest need of them. A major focus of Guide 35 is the development of reference material uncertainties that are in full compliance with the Guide on Measurement Uncertainty (GUM), jointly issued by ISO, IUPAC and others. Guide 35 details handling of uncertainty due to (1) degradation on the shelf and in transport, (2) sample heterogeneity and (3) inter‐method and inter‐laboratory bias, as well as within‐laboratory repeatability. The International Association of Geoanalysts has developed a protocol for reference material certification that applies Guide 35 to the specific needs of the geoanalytical community. The approach being taken by the IAG in developing GUM‐compliant uncertainties for its certified values is presented. Recommendations made in Guide 33 for how a laboratory should compare its own results with certified values in assessing laboratory accuracy are outlined. Additionally, the subject of misusing reference materials is discussed. The apparent misuse occurs because so few CRMs exist that meet critical measurement needs of geoanalytical laboratories and that also meet the rigorous metrological demands of the latest editions of the ISO Guides. All of the focus of the IAG certification programme has been to undertake certifications that would fill gaps in CRM availability and thus serve to limit this misuse. 相似文献
145.
This paper describes an improved algorithm for fuzzyc-means clustering of remotely sensed data, by which the degree of fuzziness of the resultant classification is decreased as
comparing with that by a conventional algorithm: that is, the classification accuracy is increased. This is achieved by incorporating
covariance matrices at the level of individual classes rather than assuming a global one. Empirical results from a fuzzy classification
of an Edinburgh suburban land cover confirmed the improved performance of the new algorithm for fuzzyc-means clustering, in particular when fuzziness is also accommodated in the assumed reference data. 相似文献
146.
多维分形模型不仅采用常规的低阶矩统计, 而且采用高阶矩统计对多维分形分布进行度量, 从而能较细致地刻划正常值以及异常值.地球化学元素的正常值往往服从统计学中的大数定量, 即满足正态分布或对数正态分布, 然而异常值会服从分形分布(Preato).介绍了多维分形领域中的最新发展以及在地球化学研究中特别是研究超常元素空间分布和富集规律中的应用.结果表明, 通常的统计方法只对应于多维分形围绕均值周围的局部特征.为了有效地研究异常值的分布和富集规律, 建议采用高阶矩统计方法和多维分形方法, 并给出了两种分析地球化学元素, 并突出异常值贡献的方法.这些方法不仅可应用于研究微量元素的空间分布和富集规律, 而且可以区分地球化学背景与矿化有关的异常值.还介绍了该方法在对加拿大B.C.省西北部Mitchell-Sulphurets地区金铜矿化蚀变带研究中的应用. 相似文献
147.
A synthetic Earth for use in geodesy 总被引:1,自引:0,他引:1
R. Haagmans 《Journal of Geodesy》2000,74(7-8):503-511
A synthetic Earth and its gravity field that can be represented at different resolutions for testing and comparing existing
and new methods used for global gravity-field determination are created. Both the boundary and boundary values of the gravity
potential can be generated. The approach chosen also allows observables to be generated at aircraft flight height or at satellite
altitude. The generation of the synthetic Earth shape (SES) and gravity-field quantities is based upon spherical harmonic
expansions of the isostatically compensated equivalent rock topography and the EGM96 global geopotential model. Spherical
harmonic models are developed for both the synthetic Earth topography (SET) and the synthetic Earth potential (SEP) up to
degree and order 2160 corresponding to a 5′×5′ resolution. Various sets of SET, SES and SEP with boundary geometry and boundary
values at different resolutions can be generated using low-pass filters applied to the expansions. The representation is achieved
in point sets based upon refined triangulation of a octahedral geometry projected onto the chosen reference ellipsoid. The
filter cut-offs relate to the sampling pattern in order to avoid aliasing effects. Examples of the SET and its gravity field
are shown for a resolution with a Nyquist sampling rate of 8.27 degrees.
Received: 6 August 1999 / Accepted: 26 April 2000 相似文献
148.
干旱区典型山地绿洲荒漠系统中绿洲土地利用/覆盖变化对生态系统服务价值的影响 总被引:26,自引:7,他引:19
研究土地利用/覆盖变化对区域生态系统服务价值的影响具有重要意义。对处于干旱区典型MODS(Mountain-Oasis-Desert System)系统中的新疆南部且末绿洲1989年Landsat TM 影像及2004年的CBERS遥感影像进行处理,分析且末绿洲15 a来的土地利用/覆盖变化。在此基础上,采用中国陆地生态系统服务价值的测算方法,评估且末绿洲土地利用/覆盖变化引起的生态系统服务价值的变化。结果表明,1989-2004年,且末绿洲减少的土地面积有林地、戈壁沙地和盐碱地,增加的土地面积有水域、建筑用地和耕地。林地减少了41.73%,耕地增加了58.04%。1989年且末绿洲生态系统服务价值总额为184 349.88万元,2004年为176 970.72万元,15 a间,生态系统服务价值损失了7 379.16万元。林地面积的减少是生态系统服务价值减少的主要原因。保护区域生态环境,恢复和提高区域生态系统服务功能是该区域生态环境建设的重要任务。 相似文献
149.
150.
国外城市轨道交通对房地产价值的影响研究 总被引:13,自引:0,他引:13
从区域的角度分析北美洲、欧洲和东亚的城市轨道交通与房地产价值的相关研究成果,论述轨道交通所带来的巨大的经济、社会和环境效应.国外关于城市轨道交通对商业物业价值的研究较少,这是值得开辟的研究视角;城市轨道交通对房地产价值的影响具有区域性和时效性;对城市轨道交通与房地产价值的研究非常强调定性与定量的结合.这些成果对我国关于城市轨道交通对房地产价值影响研究具有一定的借鉴意义. 相似文献