风云二号F星太阳X射线探测器在轨探测初步成果

风云二号系列卫星以自旋稳定方式工作于地球静止轨道,太阳X射线探测器是该系列卫星的重要有效载荷,监测太阳耀斑爆发过程,并对太阳质子事件等灾害性的空间天气事件进行预警.卫星自旋一周,该探测器完成一次全日面观测,记录太阳X射线的能谱与流量.2012年初,太阳活动进入第24周峰年,风云二号卫星太阳X射线探测器的在轨运行取得了良好的观测结果.相比于过去的太阳X射线探测器,风云二号F星的太阳X射线探测器应用了硅漂移探测(Silicon Drift Detector,SDD)技术,对GEO轨道海量的高能带电粒子采取了有效的屏蔽措施,可以对更"软"的X射线进行观测,能谱分辨率本领达到国际先进水平,对太阳耀斑的量化定级精度更高,在轨初步观测结果表明,精确的能谱探测能力可提高太阳质子事件预警能力,能道响应的时间特性比过去的探测数据更准确地反映了太阳耀斑的加热过程和带电粒子加速特性.本文介绍了风云二号F星太阳X射线探测器的设计及其发射前的标定试验结果,并且对发射后在轨运行获得的初步探测成果进行分析和讨论.     

PS转换波界面二次源法射线追踪

界面二次源法是最近提出的一种最小走时射线追踪方法,尤其适合层状介质中走时和射线路径的计算.该方法相对于传统的最小走时树方法（如Moser法）,仅在物性界面上设置二次源,射线路径的方向只在层界面处发生改变,该方法最大程度地消除了射线路径的锯齿状现象,同时也避免了低变速区的射线路径多值现象,因此,它具有更高的追踪精度和效率.本文采用界面二次源法在各向同性介质中实现了PS转换波射线追踪,理论模型的计算证实了界面二次源法追踪PS转换波的准确性和高效性,同时该方法在各向异性介质中也很好地追踪出分离的PSV波和PSH波,因此该方法有利于横波分裂在地震勘探中的研究和应用     

三维地质模型中地震波共轭梯度非线性走时反演

地震体波走时层析成像是探测地球内部速度结构的重要方法之一。基于三维块状建模以及三角形拼接的界面描述方式,结合快速高效的逐段迭代射线追踪方法,获得三维复杂地质模型中的地震射线路径与走时信息,采用共轭梯度非线性反演算法,进行地震波走时反演。实验结果表明共轭梯度反演算法在三维层状模型中具有较高的有效性。     

我国各地膨润土的矿物学性质

运用X射线衍射分析技术对我国不同产地膨润土的矿物学性质进行考察；利用K值法测蒙脱石含量。实验表明，各地膨润土具有蒙脱石的含量较高且均为二八面体的矿物学特点；可能由于所处的矿层或局部地球化学环境不同，使得相同矿床的不同颜色膨润土矿物的蒙脱石含量有所差异。     

Centrifuge model tests on sand specimen under extensional load

The appearance of shear banding in granular materials has been investigated intensively during the last decades and is still of ongoing importance in terms of understanding the stress–strain behaviour of the material, the localization phenomena and the interaction between soil and structure. Only less attention has been paid to the occurrence of systems of shear bands although such systems can be identified in geotechnical structures as well as in geological formations. In this paper we present results of experiments on sand specimens under extensional load in natural gravity as well as in increased gravity in the centrifuge where the influence of the stress level on the geometry of a shear band pattern, specified by the spacing of the shear bands and the angle between failure surfaces and minor stress direction, has been investigated. X‐ray technique has been used to visualize the failure zones inside the specimen, an optical measurement system called Digital Image Correlation has been applied to identify and observe the appearing deformation mechanism on the sides of the specimens in natural gravity as well as during the flight in the centrifuge. It can be shown that the geometry of the shear band pattern is sparsely influenced by the change of the stress level. Copyright © 2004 John Wiley & Sons, Ltd.     

A comparison of grain‐size analysis methods for sand‐dominated fluvial sediments

Grain‐size distribution is a fundamental tool for interpreting sedimentary units within depositional systems. The techniques assessed in this study are commonly used to determine grain‐size distributions for sand‐dominated sediments. However, the degree of consistency and differences in interpretation when using a combination of grain‐size methods have not yet been assessed systematically for sand‐dominated fluvial sediments. Results obtained from laser diffraction, X‐ray attenuation and scanning electron microscopy grain‐size analysis techniques were compared with those obtained from the traditional sieve/hydrometer method. Scanning electron microscopy was shown to provide an inaccurate quantitative analysis of grain‐size distributions because of difficulties in obtaining representative samples for examination. The X‐ray attenuation method is unsuitable for sand‐dominated sediments because of its upper size range of only 300 μm. The consistently strong correlation between the laser diffraction results and the sieve/hydrometer results shows that these methods are comparable for sand‐dominated fluvial sediments. Provided that sample preparation is consistent, the latter two methods can be used together within a study of such sediments while maintaining a high degree of accuracy. These results indicate that data for sand‐dominated fluvial sediments gained from the long‐established sieve/hydrometer method can be compared with confidence to those obtained by modern studies using laser diffraction techniques.     

Chaotic ray behaviour in regional seismology

Rays propagating through strongly laterally varying media exhibit chaotic behaviour. This means that initially close rays diverge exponentially, rather than according to a power law. This chaotic behaviour is especially pronounced if the medium contains laterally varying interfaces. By studying simple 2-D and 3-D versions of models with laterally varying interfaces, the importance of chaotic ray behaviour is determined. A model of the Moho below Germany produces sharp variations with epicentral distance of the number of arrivals. In addition, the number of caustics grows dramatically: up to 1200 caustics are present between a distance of 0 and 800 km. Using the theory of Hamiltonian systems, a more in-depth study of the chaotic character of the ray equations is obtained. It is found that for realistic heterogeneous models most of the relevant rays will exhibit chaotic behaviour. The degree of chaos is quantified in terms of predictability horizons. Beyond the predictability horizons ray tracing cannot be carried out accurately. For the models under consideration, the length from the source to the predictability horizon has an order of magnitude of 1000 km. The chaotic behaviour of the rays makes it necessary to use extensions of asymptotic ray theory, such as Maslov theory, to compute seismic waveforms. It is shown that pseudo-caustics, an important obstacle in computing Maslov synthetics, are a generic feature of the 2-D laterally varying models that are studied. Eventually, the use of asymptotic methods is restricted because of the inaccuracy in the computation of the ray paths.     

溶液结构的X射线衍射──3.粉末衍射仪液体样品池窗口强度校正的相对透明因子

从衍射几何学出发，推导出0－2θ型X射线衍射仪液体样品池窗口强度校正的相对透明因子，解释了由于超厚液体样品池上的窗口的吸收，反射法引起的低角强度损失和透射法引起的高角强度损失，获得了令人满意的的校正结果。     

地震折射波资料解释中射线方法应用的进一步探讨

开鲁陆家堡凹陷内断裂发育、构造复杂,垂直于构造走向跨度30km,凹陷边缘和凹陷内古生界基底顶板埋深分别为1km和5km,在此开展了基底折射波地震勘探。在已知资料基础上,我们用多段倾斜单界面折射波正演理论计算作指导,设计了野外试验和初步的生产观测系统,t_0和差异时距曲线解释方法对于应用于如此复杂的构造地区其准确性和精度受到了限制。因此,我们在解释方法上试做了如下工作:①多段倾斜单界面折射波理论正演走时拟合,给出较有益的反演解释结果;②二维非均匀介质中射线追踪解释方法,提供准确的射线途径给出基底面上下详尽的更为符合实际的二维速度分布信息。     

吸收介质中的Maslov体波理论地震图

本文研究了横向非均匀吸收介质中的Maslov渐近理论地震图方法.对于如何提高计算精度及计算速度作了比较深入的探讨.本方法先计算远场格林函数,由褶积得到一般震源函数的弱吸收理论地震图.对于高Q引起的数值不稳定性,通过引入平滑函数得以解决.由此产生的新的被积函数具有非常好的收敛性,从而提高了计算精度及计算速度.以此理论编写的程序在模拟完全弹性介质以及一维吸收介质时与反射率法作了比较,并取得了令人满意的效果.对于二维横向非均匀吸收介质,计算方法与高斯光束方法作了对比,二者在主要特征上基本一致.数值对比中出现的一些差异也作了必要的讨论及说明.