The crystal chemistry of lithium and Fe3+ in synthetic orthopyroxene     

Fernando Cámara  Gianluca Iezzi  Massimo Tiepolo  Roberta Oberti 《Physics and Chemistry of Minerals》2006,33(7):475-483

Lithian ferrian enstatite with Li₂O = 1.39 wt% and Fe₂O₃ 7.54 wt% was synthesised in the (MgO–Li₂O–FeO–SiO₂–H₂O) system at P = 0.3 GPa, T = 1,000°C, fO₂ = +2 Pbca, and a = 18.2113(7), b = 8.8172(3), c = 5.2050(2) Å, V = 835.79(9) Å³. The composition of the orthopyroxene was determined combining EMP, LA-ICP-MS and single-crystal XRD analysis, yielding the unit formula ^M2(Mg_0.59Fe _0.21 ²⁺ Li_0.20) ^M1(Mg_0.74Fe _0.20 ³⁺ Fe _0.06 ²⁺ ) Si₂O₆. Structure refinements done on crystals obtained from synthesis runs with variable Mg-content show that the orthopyroxene is virtually constant in composition and hence in structure, whereas coexisting clinopyroxenes occurring both as individual grains or thin rims around the orthopyroxene crystals have variable amounts of Li, Fe³⁺ and Mg contents. Structure refinement shows that Li is ordered at the M2 site and Fe³⁺ is ordered at the M1 site of the orthopyroxene, whereas Mg (and Fe²⁺) distributes over both octahedral sites. The main geometrical variations observed for Li-rich samples are actually due to the presence of Fe³⁺, which affects significantly the geometry of the M1 site; changes in the geometry of the M2 site due to the lower coordination of Li are likely to affect both the degree and the kinetics of the non-convergent Fe²⁺-Mg ordering process in octahedral sites.  相似文献   

特征驱动下区实体匹配指标自适应融合技术     

叶亚琴  陈波  万波  周顺平 《测绘科学》2012,37(6):101-103

空间实体匹配过程中多个指标的融合问题是影响匹配效果的关键问题之一。本文针对这一问题,以区实体为例提出了一套基于范例库的解决方案。首先提取出影响实体匹配的数据特征因子并确定了量化方法,其次选取典型的匹配指标,接下来通过建立指标权值范例库确定各指标权值,最后根据权值和数据特征因子调整匹配过程。该方法使得数据具有学习能力,达到了指标权值的自适应性的目标。实验表明该方法可行,并且可以提升空间实体匹配算法的效率、准确度和智能化程度。  相似文献   

WHCORS的技术拓展与应用现状     

黄兵杰  严小平  林科  刘传逢  郭启幼 《地理空间信息》2012,10(4):79-82

介绍了武汉市连续运行卫星定位服务系统(WHCORS)的基本情况和发展现状;对基于WHCORS技术拓展研究的相关情况和WHCORS的应用推广进行了详述,针对具体的关键技术问题提出了较详细的解决方案,对用户有一定的参考和借鉴作用。  相似文献   

环鄱阳湖区农家菜地土壤重金属风险评价及来源分析   总被引：4，自引：0，他引：4  

胡春华  蒋建华  周文斌 《地理科学》2012,(6):771-776

通过评价环鄱阳湖区10个县农家菜地土壤样品重金属的潜在生态风险,分析其与9个社会经济指标间的灰色关联度来探讨重金属的污染来源。结果显示,鄱阳湖区各菜地土壤中Cd的超标情况最严重,超标率达到90%,除部分地区Cu超标外,其余重金属均未超标。鄱阳湖区农家菜地土壤达到轻微生态风险,工业较发达地区重金属生态风险较大于工业落后地区,工业发展情况对湖区的空间污染分异有较大影响。蔬菜产量、工业发展情况、城镇化率、交通业发展情况和菜地土壤不同种重金属具有较高关联度,而地区生产总值、农药使用量对各种重金属含量的影响最弱。  相似文献   

Assessing physical vulnerability for multi-hazards using an indicator-based methodology   总被引：6，自引：0，他引：6  

M.S. Kappes  M. Papathoma-KöhleM. Keiler 《Applied geography (Sevenoaks, England)》2012,32(2):577-590

Globally, many built-up areas are threatened by multiple hazards which pose significant threat to humans, buildings and infrastructure. However, the analysis of the physical vulnerability towards multiple hazards is a field that still receives little attention although vulnerability analysis and assessment can contribute significantly to risk reduction efforts. Indicator-based vulnerability approaches are flexible and can be adjusted to the different hazards as well as to specific user needs. In this paper, an indicator-based vulnerability approach, the PTVA (Papathoma Tsunami Vulnerability Assessment), was further developed to be applicable in a multi-hazard context. The resulting multi-hazard version of the PTVA consists of four steps: the identification of the study area and relevant hazards as well as the acquisition of hazard information, the determination of vulnerability indicators and collection of data, the weighting of factors and vulnerability assessment and finally, the consideration of hazard interactions. After the introduction of the newly developed methodology a pilot application is carried out in the Faucon municipality located in the Barcelonnette basin, Southern French Alps. In this case study the vulnerability of buildings to debris flows, shallow landslides and river flooding for emergency planning and for general risk reduction purposes is assessed. The implementation of the methodology leads to reasonable results indicating the vulnerable buildings and supporting the priority setting of different end-users according to their objectives. The constraints of the presented methodology are: a) the fact that the method is not hazard-intensity specific, thus, vulnerability is measured in a rather qualitative and relative way and b) the high amount of data required for its performance. However, the advantage is that it is a flexible method which can be applied for the vulnerability analysis in a multi-hazard context but also it can be adjusted to the user-specific needs to support decision-making.  相似文献   

精细化气象要素温度指导预报在山西区域的误差及特征   总被引：1，自引：0，他引：1  

张红雨  李毓富  张国勇  赵刚 《气象科技》2012,40(5):778-782

利用2009-2010年山西区域108站共730天精细化气象要素温度指导预报资料,对比日最高气温和日最低气温的预报误差,采用常规统计、EOF分析等方法研究指导预报误差的时间和空间分布特征,结果表明:山西区域的温度预报准确率比较稳定,但有明显的季节特点,夏季最高,秋季次之、冬春季相对偏低,日最高气温年平均正、负误差略高于日最低气温误差,春季大,冬秋次之,夏季小;正负误差值的空间分布与山西地形有一定的联系,日最高气温和日最低气温误差的分布特点具有明显的全区一致性.  相似文献   

GPS-RTK用于矿山高精度沉陷监测的可行性研究     

周锋  刘超 《四川测绘》2012,(1):6-10

针对复杂地表条件下采用水准测量和导线测量等常规方式进行地表变形周期观测、任务量大甚至无法实施等问题,提出了建立研究区域的似大地水准面精化模型,同时采用GPS-RTK技术获取观测站三维空间信息,进而获得概率积分法预计参数。最后以内蒙古准格尔旗某煤矿的生产实践说明该技术的有效性和可行性,极大地提高了工作效率,为保护煤柱的留设提供了科学的依据。  相似文献   

“移去-恢复法”在机场工程大比例尺测图控制网中的应用     

羊远新  戴中东  魏桦 《测绘工程》2012,21(3):44-48

对大地高、正高与正常高的关系进行阐述,对机场工程场址条件较为困难时使用区域似大地水准面精化的方式满足大比例尺测图的可能性进行叙述,对"移去-恢复法"的计算方法、误差来源与精度评定方法进行论述,在实际算例中使用不同的EGM模型、不同的残差拟合方法所得到的结果进行比对,提出适合于机场工程大比例尺测图用控制网点正常高值拟合的方法。  相似文献   

An Adaptive Nonhydrostatic Atmospheric Dynamical Core Using a Multi-Moment Constrained Finite Volume Method     

Pei HUANG  Chungang CHEN  Xingliang LI  Xueshun SHEN  Feng XIAO 《大气科学进展》2022,39(3):487-501

An adaptive 2 D nonhydrostatic dynamical core is proposed by using the multi-moment constrained finite-volume(MCV) scheme and the Berger-Oliger adaptive mesh refinement(AMR) algorithm. The MCV scheme takes several pointwise values within each computational cell as the predicted variables to build high-order schemes based on single-cell reconstruction. Two types of moments, such as the volume-integrated average(VIA) and point value(PV), are defined as constraint conditions to derive the updating formulations of the unknowns, and the constraint condition on VIA guarantees the rigorous conservation of the proposed model. In this study, the MCV scheme is implemented on a height-based, terrainfollowing grid with variable resolution to solve the nonhydrostatic governing equations of atmospheric dynamics. The AMR grid of Berger-Oliger consists of several groups of blocks with different resolutions, where the MCV model developed on a fixed structured mesh can be used directly. Numerical formulations are designed to implement the coarsefine interpolation and the flux correction for properly exchanging the solution information among different blocks. Widely used benchmark tests are carried out to evaluate the proposed model. The numerical experiments on uniform and AMR grids indicate that the adaptive model has promising potential for improving computational efficiency without losing accuracy.  相似文献   

豆荚状铬铁矿床成矿地球化学指标对比和成矿作用讨论     

刘婷  郑有业  王朋冲  杨伟光  郭统军 《矿物岩石地球化学通报》2019,(1):176-183,194

豆荚状铬铁矿主要赋存于地幔橄榄岩中,与方辉橄榄岩密切相关。在全球的分布与蛇绿岩带分布基本一致,但并非所有蛇绿岩体都赋存有铬铁矿,且其中赋存的铬铁矿体规模和分布都是很不规律的。我们对比研究了国内外9个含铬矿和4个不含铬矿蛇绿岩中地幔橄榄岩的地球化学组成,认为含铬矿地幔橄榄岩具有全岩低含量的CaO(<1.91%)和Al_2O_3(<1.76%)、方辉橄榄岩轻稀土元素富集,橄榄石高Fo值(>90),斜方辉石低Al_2O_3含量(<3.8%)以及副矿物铬尖晶石高Cr/Fe值(>1.5)等特征,可以作为该蛇绿岩体含矿评价的地球化学指标。通过这些指标可知豆荚状铬铁矿床是较高程度部分熔融和地幔交代作用的共同结果,结合前人提出的铬铁矿成矿模式,对铬铁矿的成矿过程有了进一步的认识。  相似文献