陕西潼关-河南灵宝蛭石定向晶片X射线衍射研究

采用定向晶片法对陕西潼关一河南灵宝蛭石进行了X射线研究，结果表明河南灵宝石板沟和陕西潼关李家乡蛭石矿“蛭石”的矿物组成主要为金云母．蛭石的规则或不规则间层矿物；程村藏马峪“蛭石”的矿物组成主要为罕见的大片状绿泥石．蛭石的间层矿物。对比样品的定向晶片法与粉末法的X射线衍射谱可以发现，定向晶片法更能揭示晶片中不同晶层的间层结构特点，特别是对于分结型间层矿物，可以从衍射谱图上直接确定分结型间层的组元。     

多钙钾石膏（Gorgeyite）晶体结构的精确修正

本文利用直接法和富利叶合成侧定了产于我国四川省三叠系蒸发岩里的多钙钾石膏 的晶体结构，结构参数经最小二乘法修正后，,R = 0.084。结构分析表明，多钙钾石膏属单斜晶系，空间群C2/c, a = 17.462 (8)A，b=6.828(2)A，c=18.219(9)A，β=113.45(4)º。，V=1992(1)A3, Z=4, Dm=2,91, Dx=2.90(3)。三个硫酸根四面体各自的平均S-O键长为1,467、 1.464 和1.478A。有三套Ca原子，其中Ca1在二次对称轴上。Ca原子的配位数为9，各自的平均Ca-O键 长为2.516、 2,515和2.459A。K原子的配位数为8。首次测定了矿一物中氢原子的位置，证实矿物含1个结晶水，而不是含1.5个结晶水。晶体化学式为K2Ca5 (SO4)6.H2O。     

Nd3+ :Gd3 Sc2 Al3 O12 晶场能级及拟合

Nd³⁺ :GSAG是性能优良的942 nm激光晶体.用提拉法成功生长Nd³⁺ :GSAG单晶,研究其室温透射光谱,辨认位置高达29967 cm^-1的68个Nd³⁺晶场能级.对这些能级拟合了自由离子及晶场Hamilton参量,拟合标准偏差为16.7 cm^-1,表明实验与计算能级符合很好.获得的Hamilton参量可用于计算Nd³⁺ :GSAG中Nd³⁺的     

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor core-shell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence (PL) measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.     

石英道芬双晶对晶格优选取向及变形机制的贡献和意义

矿物是岩石圈最基本的物质组成,其变形行为、特性和物理/化学过程直接影响着大陆岩石圈的力学强度和流变学性质。石英是地壳主要的组成矿物之一,对其变形机理及制约因素的研究,是理解地壳流变学性质的关键。石英中的道芬双晶在晶体形态上表现出沿c轴方向的6次对称,早期研究认为其只能形成于α-和β-石英的相变过程中,越来越多的研究发现,机械应力诱发的道芬双晶对温度和应力具有一定的依赖性。通过对高黎贡剪切带内变形石英的EBSD组构分析并结合前人的研究,发现石英道芬双晶对晶内塑性应变的分布及其不同滑移系的激活起着重要作用。α-石英晶体中菱面方向比方向具有更高柔度,即更适应变形。在外力作用下,石英道芬双晶通过菱面和上的弹性性质差异,即相比方向,在压缩方向(σ₁)上代表晶面方向的极点更多地聚集在方向,形成一种较为少见的菱面晶格优选取向。由此可见,道芬双晶是石英塑性变形过程中的一种特殊的流变弱化机制,其不仅使得晶体发生可恢复的结构弱化,还通过动态重结晶作用和颗粒边界...     

Determination and interpretation of preferred orientation with texture goniometry: An application of indicators to maximum entropy pole- to orientation-density inversion

The probability density function of orientations of crystals generally cannot be measured directly without destruction of the specimen. Therefore it is usual practice to sample pole density functions of several crystal forms in diffraction experiments with a texture goniometer. Determining a reasonable orientation density function from experimental pole density functions is then the crucial prerequisite of quantitative texture analysis. This mathematical problem may be addressed as a tomographic inversion problem specified by the crystal and statistical specimen symmetries and the properties of the diffraction experiment. Its solution with maximum entropy preferred orientation portion and maximum uniform portion is proposed because it yields the most conservative orientation density function with systematically reduced correlation effects, thus avoiding artificial texture ghost≓ components caused by the specific properties of the diffraction experiment.     

场分立体显示系统的硬件实现

根据双摄像机的几何模型,提出了一套双眼立体显示系统的设计方案——场分立体视觉系统。硬件采用流行的ＰＣＩ总线与计算机相连,能够实时获取２个摄像机图像,并能按双眼成像要求的频率工作,产生一个增强的三维世界。     

Average ice crystal size and bulk short-wave single-scattering properties of cirrus clouds

The bulk single-scattering properties of cirrus clouds required for driving the radiation scheme in large-scale climate models are computed with respect to various size distributions and ice crystal shapes. It is shown that the average ice crystal size, defined as the ratio of total volume to the total projected area, can well-characterize the effect of various size distributions in determining the bulk radiative properties of cirrus clouds. Details of the size distributions are not significant in specifying the radiative properties of these clouds if the effective average size is thus defined. Therefore, the ratio of the total volume to the total projected area is an ideal parameter for describing the bulk single-scattering properties. The effect of ice crystal shape is not critical in the parameterization of the extinction coefficient and single-scattering albedo. However, the various crystal habits must be accounted for in the parameterization of the asymmetry parameter. The resulting parameterization is intended for radiative transfer calculations involving cirrus clouds in large-scale models.     

南极拉斯曼丘陵长英质片麻岩中夕线石的出溶现象

南极拉斯曼丘陵长英质片麻岩中的粗粒夕线石可能有内部出溶现象,出溶形成的矿物有磁铁矿、钛铁矿-赤铁矿和石英出溶矿物条纹,并有少量的斜方辉石.电子探针成分分析表明,本区夕线石高温结晶时不仅有Fe3 ,可能还有Fe2 、Mg2 和Ti4 的替换,铁氧化物质量分数可高达2.9%;随着温度的不断降低,固溶体互溶度也不断减小,大部分微量组分从夕线石中析出形成出溶结构,而且低温变体中稳定的替换元素以Fd3 为主.铁组分的类质同像替换对物理化学计算和夕线石矿化环境均有所影响,对夕线石晶胞参数a的影响很小,而对b,尤其对c的影响较大,与前人的结论有所不同.     

Mg—Al水滑石纳米晶热分解行为的TG—MS研究

利用热重-质谱联用仪(TG-MS)和多晶XRD对水热法制备的Mg-Al水滑石纳米晶的热分解行为进行表征研究表明:Mg-Al水滑石的热性能与其晶体化学特征有密切的关系。Mg-Al水滑石的热分解过程可分为4个阶段:①T≤280℃时,失层间H2O;②T=280℃~380℃时,失层板中[Mg—OH—Al]结构单元OH-;③T=380℃~580℃时,失层板中[Mg—OH—Mg]结构单元的OH-;④T=395℃~580℃时,层间CO32-逸出。后两个阶段有较大重叠性。[Mg—OH—Mg]中OH-和CO32-最大逸出量对应的温度明显不一致。[Mg—OH—Mg]中OH-的逸出是导致层状结构破坏的诱因,热分解的阶段性随升温速率提高而表现得明显。Mg-Al水滑石的热分解行为受扩散控制。