Static compression of α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>: linear incompressibility of lattice parameters and high-pressure transformations     

H.?Liu  W. A.?Caldwell  L. R.?Benedetti  W.?Panero  R.?JeanlozEmail author 《Physics and Chemistry of Minerals》2003,30(9):582-588

The high-pressure behavior of x8tf9p4/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Fe₂O₃ has been studied under static compression up to 60 GPa, using a laser-heated diamond anvil cell. Synchrotron-based angular-dispersive X-ray diffraction shows that the sample remains in the corundum structure up to 50 GPa, but with the appearance of coexisting diffraction lines from a high-pressure phase at pressures above 45 GPa. A least-squares fit of low-pressure phase data to an Eulerian finite-strain equation of state yields linear incompressibilities of K _{a 0}=749.5 (± 18.4) GPa and K _{c 0}= 455.7 (± 21.4) GPa, differing by a factor of 1.6 along the two directions. The enhanced compressibility of the c axis may lead to breaking of vertex- or edge-sharing bonds between octahedra, inducing the high-pressure phase transformation at 50 GPa. Analysis of linear compressibilities suggests that the high-pressure phase above 50 GPa is of the Rh₂O₃ (II) structure. Continuous laser heating reveals a new structural phase transformation of x8tf9p4/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Fe₂O₃ at 22 GPa, to an orthorhombic structure with a=7.305(3) Å, b=7.850(3) Å, and c=12.877(14) Å, different from the Rh₂O₃ (II) structure.  相似文献   

龙凤山大气近地层O₃浓度变化及与其它因素的关系   总被引：16，自引：0，他引：16  

徐晓斌  丁国安  李兴生  向荣彪 《气象学报》1998,56(5):560-572

研究首次在龙凤山区域大气本底站测得的地面Ｏ３浓度及其变化的资料表明,中国东北农村地面大气Ｏ３浓度总体水平不很高,但在少数特殊的天气条件下,时均浓度可超过国家二级标准。Ｏ３浓度存在明显的季节和日变化,其月平均浓度１９９５年１月最低（２７．５ｐｐｂ）,１９９４年１１月最高（４３．２ｐｐｂ）。Ｏ３日变化幅度夏季的晴天最大（２８ｐｐｂ）,冬季的阴天最小（８ｐｐｂ）。气象要素（尤其是风速、气温和相对湿度等）和ＮＯｘ与地面Ｏ３浓度有较密切的关系。用多变量分析法探讨了地面Ｏ３各指标随气象因子和ＮＯｘ共同变化的规律,并拟合了寒冷和温暖期里与地面Ｏ３日最高浓度、日最低浓度及日变化幅度有关的方程。  相似文献   

大型水泥厂大气影响预测中污染源简化处理的一种方法     

吴万友  吕小明 《气象与减灾研究》1997,(3)

在大气环境影响评价工作中，对于多源问题通常采用逐个计算叠加的方法。本文介绍了在大型水泥厂大气环境影响预测中，对数量众多的粉尘排放源进行简化处理的一种方法。在瑞昌水泥厂的环境影响评价中，我们采用了这种方法，并对这种方法得到的结果进行了比较验证，讨论了这种方法的合理性和可行性。通过这种简化处理，可以使大气预测工作更简单化，更省时。  相似文献   

计算横向非均匀介质体波理论地震图的Maslov渐近法     

朱良保 《地球物理学报》1989,32(2):163-172

本文运用Maslov渐近理论编写的二维横向非均匀介质中的理论地震图程序,与其它类型算法作了精确对比,结果表明,在层状介质模型中,本程序的结果无论振幅还是波形对比都与反射率法基本相同。对于二维横向非均匀模型,在射线理论的非奇点处,本算法与射线方法基本一致,在射线理论的奇异点处,Maslov方法消除了射线理论所固有奇点,提高了计算精度。  相似文献   

The design of visco‐acoustic weighted L1‐error frequency–space wavefield extrapolators          下载免费PDF全文

Syed Abdul Salam  Wail A. Mousa 《Geophysical Prospecting》2018,66(2):300-310

Seismic imaging is an important step for imaging the subsurface structures of the Earth. One of the attractive domains for seismic imaging is explicit frequency–space (f – x) prestack depth migration. So far, this domain focused on migrating seismic data in acoustic media, but very little work assumed visco‐acoustic media. In reality, seismic exploration data amplitudes suffer from attenuation. To tackle the problem of attenuation, new operators are required, which compensates for it. We propose the weighted L ₁ ‐error minimisation technique to design visco‐acoustic f – x wavefield extrapolators. The L ₁ ‐error wavenumber responses provide superior extrapolator designs as compared with the previously designed equiripple L ₄ ‐norm and L_∞‐norm extrapolation wavenumber responses. To verify the new compensating designs, prestack depth migration is performed on the challenging Marmousi model dataset. A reference migrated section is obtained using non‐compensating f – x extrapolators on an acoustic dataset. Then, both compensating and non‐compensating extrapolators are applied to a visco‐acoustic dataset, and both migrated sections are then compared. The final images show that the proposed weighted L ₁ ‐error method enhances the resolution and results in practically stable images.  相似文献   

The Mel’nikov Subharmonic Function and the Non-existence of Analytic Integrals in Non-autonomous Systems     

Efi Meletlidou 《Celestial Mechanics and Dynamical Astronomy》2000,78(1-4):161-166

We consider a one-dimensional non-degenerate Hamiltonian system perturbed by a periodically time dependent non-Hamiltonian vector field and show that the non-vanishing of the Melx17051258586732r/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">nikov subharmonic function is strongly related to the non-existence of an analytic integral in the perturbed system.  相似文献   

LBS在监外服刑中的应用     

孙海东  禹新辉  张晓波 《地理信息世界》2003,1(3):31-33

移动位置服务在未来几年内将成为移动运营商的主要增值手段,中国联通今年将在CDMA1x网络中启动gpsOne定位业务。通过分析比较各种定位技术,根据监外服刑监管系统的要求,提出采用中国联通的CDMA1x网络和gpsOne定位平台来进行数据传输和位置跟踪的监管系统整体解决方案,并在系统架构、电子镣铐的软硬件设计等方面进行了初步的探讨。  相似文献   

Visualization of geologic geospatial datasets through X3D in the frame of WebGIS     

《International Journal of Digital Earth》2013,6(5):483-503

Abstract

3D geo spatial data have become the normal. However, to view the data, usually expert software is required, which have up to now hindered the wide spread use of 3D scenes for the display of geological data. The internet real time 3D rendering framework X3D is assessed regarding its suitability for building a geological GIS on the internet. Especially important for geological data, 3D rendering enhances the intuitive grasp of the data and enables the user to interactively explore it. It is often necessary to find a solution to distribute this data to a wide range of interested parties, experts and non-experts alike. According to the nature of 3D data, the best technique to display geo-data, the modeling of objects and unresolved issues have to be taken into consideration. The internet is the apparent tool for the public distribution and visualization of 3D data and it was found that through the open ISO-standardized format X3D it offers a multitude of possibilities. A 3D geological interactive map was created with these prerequisites to identify challenges and possibilities through this process. It was found that the use of lead to satisfactory results, that could probably not have been achieved with another technology.  相似文献   

阿西金矿床流体成矿的元素地球化学界面及X荧光测量识别试验   总被引：9，自引：0，他引：9  

膝彦国  倪师军  张成江  赵友清 《矿产与地质》1999,13(5):299-302

阿西金矿床元素地球化学界面的形成,是由区域地球化学高背景场和成矿流体作用的结果,其识别标志有岩石组合标志,构造变异标志和蚀变分带标志,同时,对Ｘ荧光测量方法识别元素地球化学界面的标志进行了有效性试验研究,效果良好。  相似文献   

Generalized ray theory for an Epstein profile     

Guy G. Drijkoningen 《Geophysical Journal International》1991,104(3):469-477

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