X射线衍射增强成像中的信息分离和信息处理

人们已经利用X射线的高穿透性,发展了较为成熟的X射线成像理论和技术. X射线成像已经广泛应用于众多领域.传统X射线成像受生物样品中组织间吸收系数差别较小和散射噪声较大两个因素的限制,不易利用这种方法获得生物组织的信息. 衍射增强成像方法不但能将有害的散射噪声滤除,而且能利用样品的折射信息, 是一种具有发展潜力的新成像方法. 本文利用衍射增强成像, 通过在摇摆曲线不同部位成像, 然后对信息处理, 得到了清晰的吸收像、消光(小角散射滤除)像、小角散射(角)宽度像和折射像,最后通过一定的算法将各种成分的像合成, 形成细节部位清晰的合成伪彩色像.     

Enhanced resistance switching stability of transparent ITO/TiO2/ITO sandwiches

We report that fully transparent resistive random access memory(TRRAM) devices based on ITO/TiO2/ITO sandwich structure,which are prepared by the method of RF magnetron sputtering,exhibit excellent switching stability.In the visible region(400-800 nm in wavelength) the TRRAM device has a transmittance of more than 80%.The fabricated TRRAM device shows a bipolar resistance switching behaviour at low voltage,while the retention test and rewrite cycles of more than 300,000 indicate the enhancement of switching capability.The mechanism of resistance switching is further explained by the forming and rupture processes of the filament in the TiO 2 layer with the help of more oxygen vacancies which are provided by the transparent ITO electrodes.     

Al、Co和Mn掺杂对LiNiO2结构的影响

本文采用XRD和EXAFS研究Al、Co和Mn原子掺杂对LiNiO₂材料结构的影响。XRD结果表明掺杂材料具有与LiNiO₂相同的晶体结构，都属于R3m点群，但是晶胞略微缩小，LiNiO₂的层状结构得到改善,阳离子有序度增强。从EXAFS数据拟合结果可以看出，引入掺杂原子Al、Co和Mn减弱了Jahn-Teller畸变，使得NiO₆八面对称性提高。掺杂Al和Co使得第一壳层Ni-O配位键长减小，掺杂Mn原子影响不明显。Al、Co和Mn掺杂使第二壳层Ni-Ni配位键长减小，Co和Mn掺杂使得第二壳层局域有序度提高，而Al的引入使得第二壳层局域有序度降低。     

Non-Paraxial Split-Step Semi-Vectorial Finite-Difference Method for Three-Dimensional Wide-Angle Beam Propagation

A wide-angle, split-step finite-difference method with the classical local one-dimensional scheme is presented to analyze the 3-D semi-vectorial wave equation. The method requires only matrix multiplication for beam propagation. To validate the effectiveness, numerical results for the eigen-mode propagation in tilted step-index channel waveguides are studied, and results show that the method has high accuracy and numerical efficiency.     

自旋梯状化合物Sr14(Cu1-y Fey)24O41的拉曼散射谱研究

利用常规的固相合成法制备了三种Sr14(Cu1-y-Fey)24O41(y=.,0.03,0.05)多晶样品,其中y=0.03是单纯Fe3 掺杂,y=0.05是Fe3 和Fe2 混合掺杂.在100-1500 cm-1频移范围内测量了这三种样品的偏振拉曼光谱.首先,通过与同类结构化合物的谱线比较,确定了在由两个子品格组成的简单Fmmm结构样品中,拉曼光谱的测量存在(4Ag 4B1g 3B2gB3G)模式.其次,实验观察到这三种样品都在1170 cm-1附近出现一弱峰,解释为非拉曼散射的红外活性的纵光学声子模,其中峰强的变化反映了空穴在自旋链与自旋梯之间的重新分布.导电性较强的y=0.03样品在1170 Cm-1附近的散射峰强度十分微弱,原因是CuO2自旋链上的空穴转移到了Cu2O3自旋梯上.     

Decomposition of Noncommutative U（1） Gauge Potential

We investigate the decomposition of noncommutative gauge potential Ai, and find that it has inner structure, namely, Ai can be decomposed in two parts, bi and αi, where bi satisfies gauge transformations while αi satisfies adjoint transformations, so dose the Seiberg-Witten mapping of noncommutative U（1） gauge potential. By means of Seiberg-Witten mapping, we construct a mapping of unit vector field between noncommutative space and ordinary space, and find the noncommutative U（1） gauge potential and its gauge field tensor can be expressed in terms of the unit vector field. When the unit vector field has no singularity point, noncommutative gauge potential and gauge field tensor will equal ordinary gauge potential and gauge field tensor     

核物质中五夸克重子态Θ+的有效质量

在相对论平均场框架下, 根据夸克介子耦合模型思想引入密度相关的标量耦合 系数gσN, 计算了密度相关耦合系数下, 核物质标量密度、五夸克重子态Θ⁺有效质量随核物质密度的变化情况, 并与不变耦合系数下情况相比较. 发现在低密度区域, 密度相关的耦合系数对其影响很小, 但在高密区域影响明显. 表明, 在密度相关的耦合系数影响下, 标量介子与重子的相互作用在高密度区域被削弱.     

多孔介质中含溶解反应的互溶驱替过程格子Boltzmann研究

采用格子Boltzmann方法研究了孔隙尺度下多孔介质内含流固溶解反应的互溶驱替过程,重点研究了被驱替流体与驱替流体黏性差异较大的情况下,溶解反应引起的多孔介质内部结构变化对驱替过程的影响;定量分析了不同达姆科勒数及佩克莱数下多孔介质孔隙率和驱替过程驱替效率随时间的演变.研究结果表明:达姆科勒数较大时,溶解反应的发生会在多孔介质内部生成虫洞,导致一部分被驱替流体不能被波及,驱替流体沿虫洞离开多孔介质,造成驱替效率的减少.在此基础上,随着达姆科勒数的增大,孔隙率变化越大,生成的虫洞越宽,最终驱替效率变大,但仍小于无溶解反应时的驱替效率;随着佩克莱数的增大,指进增长速度越快,孔隙率变化越小,驱替效率越小.     

High-Tc ferromagnetism in a Co-doped ZnO system dominated by the formation of a zinc-blende type Co-rich ZnCoO phase

The modulation of the distribution of magnetic ions embedded in the host is crucial for the functionality of dilute magnetic semiconductors. Through an element-specific structural characterization, we observe the formation and enhancement of an unrevealed Co-doped ZnO phase and consequently magnetic properties from paramagnetism to ferromagnetism are controlled by surface-modification.