On the evolution of cooling cores in X-ray galaxy clusters     

S. Ettori  F. Brighenti 《Monthly notices of the Royal Astronomical Society》2008,387(2):631-638

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Crystal Size Distributions Derived from 3D Datasets: Sample Size Versus Uncertainties   总被引：4，自引：1，他引：3  

GUALDA  GUILHERME A. R. 《Journal of Petrology》2006,47(6):1245-1254

Crystal size distributions (CSD) are the most commonly studiedcharacter in quantitative textural investigations of igneousrocks. The quality of CSD depends fundamentally on the samplesize (i.e. total number of crystals). Here we use 3D X-ray tomographicdatasets of two early erupted Bishop Tuff pumice clasts (comprising849 and 446 quartz crystals) to investigate the effect of samplesize on the quality of the quartz size distributions. BecauseCSD are obtained using a counting procedure, uncertainties relatedto counting statistics can be used as minimum estimates of error.Given that most natural samples are characterized by a decreasingnumber of crystals with increasing crystal size, uncertaintiestend to increase markedly with crystal size, and the numberof small crystals to be counted grows very quickly with increasingsample size. Accordingly, with as few as 100 crystals in total,it is possible to properly estimate the population densitiesfor small size bins (20–80 µm). However, to obtainmeaningful estimates across four bin sizes (20–320 µm),at least 250 crystals, but preferably >400 crystals are needed.To minimize the total number of crystals counted, and keep theuncertainties on the larger size ranges within reasonable values,it becomes necessary to study multiple volumes at variable spatialresolution. KEY WORDS: crystal size distributions; quantitative petrography; texture; X-ray tomography  相似文献   

沉积物岩芯X光片图像灰度数值及其影响因素     

张喜林  范德江  刘明  王亮 《沉积学报》2012,30(2):318-324

沉积体的X光影像包含了沉积物密度、结构、构造等众多信息,对X光影像进行数字图像分析可快速提取这些信息,成为进行沉积记录和古环境演变研究的有力手段。基于长江水下三角洲沉积物岩芯的X光影像,利用Matlab软件平台把X光影像转换成数字灰度图像,进而提取了岩芯灰度值;结合该岩芯的粒度等沉积学属性,探讨了灰度图像的影响因素。结果表明:沉积物岩芯的X光图像灰度值是沉积物组成、结构和构造的综合反映,其中粒度对灰度值起到控制性的影响。平均粒径与灰度值之间为良好的线性关系;砂粒级、粉砂粒级含量与灰度之间存在较好的正相关,而黏土粒级含量与灰度存在很好的负相关。沉积物岩芯X光图像的灰度值可以作为该岩芯的粒度的良好替代性指标。  相似文献   

便携式X荧光分析仪在萤石矿勘查中的应用   总被引：1，自引：0，他引：1  

张鹏  张寿庭  邹灏  方乙  曹华文  高永璋  马永非 《物探与化探》2012,(5):718-722

在赤峰市林西县水头萤石矿区,利用便携式X荧光分析仪对第四系浅覆盖区进行隐伏萤石矿体探测的有效性试验。通过测量数据分析及与已知矿体的对比证明,在浅覆盖区利用X荧光分析仪勘查隐伏萤石体是有效的。该结论为便携式X荧光仪在勘查隐伏萤石矿体中的应用提供了重要依据。  相似文献   

Illite Crystallinity Mapping of Very Low Grade Metamorphism of Triassic Metapelites in the Zoig(e) Area,Western China     

TANG Yan  SANG Longkang  YUAN Yanming  YU Jishun  ZHANG Yunpeng  QI Xianmao  YANG Yunlong 《《地质学报》英文版》2012,86(1)

X-ray diffraction methods for estimating the metamorphic grade of diagenetic,anchizone and epizone in metapelites are reviewed and applied to samples from a 7000 m+ borehole in western China and surfac...  相似文献   

Algorithm Analysis of Autonomous Navigation of Spacecraft Based on X-ray Pulsars     

Chong-Xia Zhong  Li Zhang  Feng Nian  Jun Yang 《Chinese Astronomy and Astrophysics》2012

A pulsar has the very stable rotation and can be used as the time standard. The astrometric parameters and astrophysical parameters of many pulsars, such as the spatial position, proper motion, distance, rotation period and its derivative, etc., can be all accurately determined. Since the pulsar can provide the time signal and the coordinates of its spatial position simultaneously, the pulsar navigation system installed on a spacecraft enables the autonomous navigation of the spacecraft to be realized. Firstly, the position of the spacecraft is predicted based on the equation of orbit dynamics of the spacecraft and then the Kalman filtering is applied to calculating the estimation error of the spacecraft position through the difference between the pulse arrival time observed on the spacecraft and the predicted pulse arrival time, thereby modifying the position of the spacecraft. Finally, the effects of the initial error, measuring accuracy of the pulse arrival time and number of pulsars on the navigation accuracy are analyzed.  相似文献   

Morphology,Trace, and Rare Earth Elements of Detrital Zircon of Kayamkulam,Thottappally Placers,South West India—Implications for Provenance     

Babu Nallusamy 《Marine Georesources & Geotechnology》2013,31(5):437-446

Detrital zircon crystals from beach and were subjected to morphology and Inductively coupled plasma mass spectrometry (ICPMS) analysis to assess the efficacy of the zircon composition as a provenance indicator. The inclusions of rutile and sillimanite in the lattice of the zircon support metamorphic growth. Zircon grains from relatively dry alkalic and igneous rocks tend to be dominated by {100} and {101} forms, whereas those from aluminous to calc-alkaline rocks exhibit various combinations of forms, with a predominance of {211}, and those from water-rich granites and pegmatites tend to have {110} and {101} as their dominant forms. Prismatic faces develop from zircon mainly due to the temperature of the crystallisation, but the pyramidal faces were linked to chemical factors. Light group Rare Earth Element (LREE) is enriched relative to Heavy group Rare Earth Element (HREE) in zircon. It shows significant negative anomalies in Eu, Co, Rb, and Cs and positive anomalies in V, Zn, Sr, Y, Nb, and Ba. The negative anomaly of Eu is maybe due to the redox condition operative at the time of zircon crystallisation from magma, where most of the Eu could be in Eu²⁺ state. The ratio of the Zr/Hf in detrital zircon shows a range of values between 6.56 and 6.25%. This supports the idea of the role ascribed to mafic rocks for the parentage of southwest coastal placer deposits.  相似文献   

High-mass X-ray binaries and recent star formation history of the Small Magellanic Cloud     

P. E. Shtykovskiy  M. R. Gilfanov 《Astronomy Letters》2007,33(7):437-454

We study the relation between high-mass X-ray binary (HMXB) population and recent star formation history (SFH) for the Small Magellanic Cloud (SMC). Using archival optical SMC observations, we have approximated the color-magnitude diagrams of the stellar population by model stellar populations and, in this way, reconstructed the spatially resolved SFH of the galaxy over the past 100 Myr. We analyze the errors and stability of this method for determining the recent SFH and show that uncertainties in the models of massive stars at late evolutionary stages are the main factor that limits its accuracy. By combining the SFH with the spatial distribution of HMXBs obtained from XMM-Newton observations, we have derived the dependence of the HMXB number on the time elapsed since the star formation event. The number of young systems with ages ? 10 Myr is shown to be smaller than the prediction based on the type-II supernova rate. The HMXB number reaches its maximum ～20–50 Myr after the star formation event. This may be attributable, at least partly, to a low luminosity threshold in the population of X-ray sources studied, L _min ～ 10³⁴ erg s^?1. Be/X systems make a dominant contribution to this population, while the contribution from HMXBs with black holes is relatively small.  相似文献   

爽身粉中石棉鉴定方法的研究          下载免费PDF全文

封亚辉  程薇  张梅  卢志刚  赵伟  郑建明  许新春 《江苏地质》2009,33(4):417-419

利用X射线衍射分析结合偏光显微镜观察,通过特征衍射峰和纤维形态可以判断试样中石棉的存在,并可判断石棉类型。该方法用于爽身粉中石棉的鉴定得到满意的结果。  相似文献   

变形监测中GPS信号衍射误差的环境建模法   总被引：1，自引：0，他引：1  

熊永良  丁晓利 《测绘学报》2005,34(4):283-287

信号衍射是GPS结构变形监测的重要误差源之一.GPS天线周围的建筑物是常见的信号衍射体.针对在变形监测中观测环境相对固定之特点,提出一种基于环境模型的衍射误差建模算法.若干试验表明所提方法能有效检测并削弱衍射误差对变形监测结果的影响.  相似文献