Polymorphic phase transition in Superhydrous Phase B     

M. Koch-Müller  P. Dera  Y. Fei  H. Hellwig  Z. Liu  J. Van Orman  R. Wirth 《Physics and Chemistry of Minerals》2005,32(5-6):349-361

We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction, Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures (down to −180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering occurs not only at the Mg sites but also at the hydrogen sites.  相似文献   

滑坡监测的新方法——PMP测量方法     

孙园  李大心 《中国地质灾害与防治学报》2005,16(B12):15-18

文章从国内外滑坡灾害、滑坡灾害的危害及现有滑坡监测方法等方面，论述了滑坡灾害带来的危害性，从而验证了滑坡监测的重要性。但目前现行的滑坡监测手段各有不足之处。针对这种情况，提出了新的测量方法改进其不足之处。位相测量剖面术的测量原理是将LCD投影仪安装于滑坡体上，在滑坡体外稳定地带放置监测系统，CCD光束中心垂直于滑坡体位移方向，监测系统由望远镜头和CCD组成，CCD输出的视频信号进入计算机。通过软件对图像进行处理，绘制出滑坡整体的三维面貌，并计算出滑动的距离，从而有效的观测滑坡体的运动过程。  相似文献   

Rb2Ca[B4O5(OH)4]2·8H2O溶解及相转化过程的研究   总被引：2，自引：0，他引：2       下载免费PDF全文

王奖  朱黎霞  李淑妮  王波  夏树屏 《盐湖研究》2005,13(1):25-30

利用IR光谱和Raman光谱等实验手段,对25℃时Rb2Ca[B4O5(OH)4]2·8H2O的溶解及相转化过程进行了初步探索,结果表明,Rb2Ca[B4O5(OH)4]2·8H2O溶于水后,硼在溶液中主要以B(OH)3和[B(OH)4]-的形式存在,残留固相由开始的无定形水合三硼酸钙,最终部分转变为Ca2[B3O3(OH)5]2·8H2O晶体。  相似文献   

MODIS多光谱云相态识别技术的应用研究   总被引：1，自引：1，他引：1       下载免费PDF全文

周著华白洁  刘健文纪飞  齐琳琳李玮 《应用气象学报》2005,16(5):678-684

介绍了卫星多光谱云相态识别的基本原理, 并给出了EOS/ MODIS云相态识别的流程。针对简单和复杂云场, 利用个例并结合无线电探空资料与MODI S三通道合成图肯定了多光谱云相态识别的合理性和实际效果。文中对几个特定天气系统(西南涡旋和西太平洋台风)下大面积云场相态分析的结果表明:多光谱云相态识别技术有一定应用价值, 且需要引入可见光技术来减少红外谱段对多层云覆盖和薄卷云的相态分析误差。  相似文献   

基于ASTER影像的近海水产养殖信息自动提取方法   总被引：5，自引：1，他引：5  

周小成  汪小钦  向天梁  江洪 《湿地科学》2006,4(1):64-68

水产养殖地已经成为海洋环境监测的热点目标之一。采用具有高光谱分辨率和较高空间分辨率(15m)的ASTER遥感影像,以九龙江河口地区为研究示范区,进行近海水产养殖信息的自动提取方法研究。结果表明,利用ASTER影像的光谱信息和水产养殖地的纹理结构信息,可以实现近海水产养殖地的自动提取。先利用监督分类方法提取混淆有其他水体的水产养殖信息,采用邻域分析来增强水产养殖地的空间纹理信息。通过综合监督分类和水产养殖地空间纹理增强的结果,在专家决策分类器中建立决策规则,进行水产养殖地的自动提取,提取的精度达93%。  相似文献   

Monte Carlo simulation of mixing in Ca3Fe2Ge3O12–Ca4Ge4O12 garnets and implications for the thermodynamic stability of pyrope–majorite solid solution     

Victor L. Vinograd  Bjoern Winkler  Daniel J. Wilson  Andrew Putnis  Julian D. Gale 《Physics and Chemistry of Minerals》2006,33(8-9):533-544

Static lattice energy calculations, based on empirical pair potentials, were performed for a large set of structures differing in the arrangement of octahedral cations within the garnet 2 × 2 × 2 supercell. The compositions of these structures varied between Ca₃Fe₂Ge₃O₁₂ and Ca₄Ge₄O₁₂. The energies were cluster expanded using pair and quaternary terms. The derived ordering constants were used to constrain Monte Carlo simulations of temperature-dependent mixing properties in the ranges of 1,073–3,673 K and 0–10 GPa. The free energies of mixing were calculated using the method of thermodynamic integration. The calculations predict a wide miscibility gap between Fe-rich (cubic) and Fe-pure (tetragonal) garnets consistent with recent experimental observations of Iezzi et al. (Phys Chem Miner 32:197–207, 2005). It is shown that the miscibility gap arises due to a very strong cation ordering at the Fe-pure composition, driven by the charge difference between Ca²⁺ and Ge⁴⁺ cations. The structural and thermodynamic analogies between Ca–Ge and Mg–Si systems suggest that a similar miscibility gap should exist between pyrope and Mg–Si-majorite.  相似文献   

由三元系相图计算活度的方法Ⅱ.有二元同分熔点化合物的体系          下载免费PDF全文

翟玉春  田彦文 《盐湖研究》2002,10(4):35-37

利用熔化自由能 ,由具有同分熔点二元化合物的三元系相图计算活度。计算的范围遍及三元相图的液相面、液相线、共熔线和三元低共熔点  相似文献   

遥感在新疆淖毛湖戈壁找矿中的应用     

张守林  傅水兴  杨自安 《铀矿地质》2001,17(6):365-367,373

根据不同地质体在不同波段上的光谱特征，选择不同波段的TM数据进行假彩色合成，主成分分析，匹配滤波及多种处理方法，对淖毛湖戈壁琼河坝地区的线环构造特征，赋矿岩层，矿化蚀变等示矿要素进行增强处理和特征提取，取得较好效果，为在戈壁地区快速追踪找矿信息，指导成矿预测提供了重要的基本资料。  相似文献   

Stochastic assessment of GPS carrier phase measurements for precise static relative positioning   总被引：17，自引：11，他引：17  

J. Wang  C. Satirapod  C. Rizos 《Journal of Geodesy》2002,76(2):95-104

 Global positioning system (GPS) carrier phase measurements are used in all precise static relative positioning applications. The GPS carrier phase measurements are generally processed using the least-squares method, for which both functional and stochastic models need to be carefully defined. Whilst the functional model for precise GPS positioning is well documented in the literature, realistic stochastic modelling for the GPS carrier phase measurements is still both a controversial topic and a difficult task to accomplish in practice. The common practice of assuming that the raw GPS measurements are statistically independent in space and time, and have the same accuracy, is certainly not realistic. Any mis-specification in the stochastic model will inevitably lead to unreliable positioning results. A stochastic assessment procedure has been developed to take into account the heteroscedastic, space- and time-correlated error structure of the GPS measurements. Test results indicate that the reliability of the estimated positioning results is improved by applying the developed stochastic assessment procedure. In addition, the quality of ambiguity resolution can be more realistically evaluated. Received: 13 February 2001 / Accepted: 3 September 2001  相似文献   

多级汇水盆地的自动提取   总被引：1，自引：0，他引：1  

余桂贤  孙光耀  郑凯梅  吴磊  余生晨 《物探化探计算技术》2002,24(4):349-351

利用多级汇水盆地在频率城（或波数域）中的频率差异，通过滤波方法逐级分离，并提取它们，实验证明，该方法效果较好。  相似文献