UO2 晶体中低密勒指数晶面表面能的分子动力学模拟

采用基于刚性离子势的分子动力学模拟方法初步计算了UO₂晶体中(100), (110)和(111) 3种低密勒指数晶面在300–1500 K范围内的表面能大小. 结果表明, 3种晶面的表面能大小随温度的升高而降低, 与实验结果趋势一致; 原子排列最紧密的(111)晶面具有最低的表面能, 3种晶面的表面能大小从高到低依次为(100), (110)和(111)晶面; 达到平衡状态下的表面层原子相对于体内原子层在表面的法线方向上发生了明显的压缩并且表面层原子的对称性也降低了, 表面原子的弛豫效应一直影响到了第5层. 计算研究结果将有助于深入认识UO₂燃料中裂变气体气泡的聚集长大以及燃料的辐照肿胀开裂行为. 关键词： 分子动力学 2')" href="#">UO₂ 低密勒指数晶面 表面能     

Pigment identification and decoration analysis of a 5th century Chinese lacquer painting screen: a micro‐Raman and FTIR study

To investigate the pigments and decoration applied to a wood‐based lacquer painting screen from the tomb of Si‐ma Jin‐long, Shanxi Province, central China, made by Chinese craftsmen in the 5th century, a combination of micro‐Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), wavelength dispersive X‐ray fluorescence (WDXRF), and microscopic examination was used. The obtained results are as follows: (1) the black, yellow, and red colors are identified as carbon black, orpiment and realgar, and cinnabar, respectively, by using micro‐Raman spectroscopy. The FTIR result shows that the white pigment filled in the leaves is not lead white, as assumed in the literature, but gypsum. Whether lead white was used at other locations remains unanswered and requires more samples for further work; (2) the thickness of each discernable pigment layer, as observed under the microscope, is approximately equal and the differences among them are small, suggesting a superfine painting skill; besides, a noticeable smooth interface between wood and the red grounding substance indicates that a polishing process might have been applied before the painting; (3) the red background was proved to contain cinnabar, but further FTIR analyses found no evidence for the presence of Chinese wood oil; and (4) the most interesting finding, rarely reported before, is that white grains of different sizes are found in both pigment layers and the grounding substance, which are perhaps an intentional addition. Further, in situ XRF and Raman analyses indicate that they are sourced from hydroxyapatite, coming probably from the intentional addition of animal bone ash to the lacquer. But how such a process could be finished and what purpose it served have not yet been answered. Copyright © 2009 John Wiley & Sons, Ltd.     

Implementation of a multiple round quantum dense coding using nuclear magnetic resonance

~~Implementation of a multiple round quantum dense coding using nuclear magnetic resonance1. Bennett, C. H., Wiesner, S. J., Communication via one- and two-particle operators on Einstein-Podolsky-Rosen states, Phys. Rev. Lett., 1992, 69(20): 2881-2884. 2. Mattle, K., Weinfurter, H., Kwiat, P. G. et al., Dense coding in experimental quantum communication, Phys. Rev. Lett., 1996, 76(25): 4656-4659. 3. Fang, X. M., Zhu, X. W., Feng, M. et al., Experimental implementation of dens…     

潘宁源放电的全三维电磁粒子模拟/蒙特卡罗碰撞数值算法研究

深入研究潘宁放电的物理机制, 研制了全三维高品质算法粒子模拟软件(PIC), 设计并添加了相应物理情景的蒙特卡罗碰撞模块(MCC), 并对电子、氢分子离子(H₂⁺)、氢正离子(H⁺)、氢三正离子(H₃⁺)同时进行了跟踪, 成功研制了全三维电磁PIC/MCC数值算法. 结合国内研究较热的潘宁放电模型, 对该算法进行模拟验证. 模拟结果显示: 采用有效的滤波算法能抑制电磁数值噪声, 电子能量呈麦克斯韦分布, 由于电子的径向漂移和加速导致离子源顶端H₂⁺产量较大. 关键词： 潘宁离子源 高品质算法 粒子模拟/蒙特卡罗     

相关测速声呐阵元坐标估计算法研究

针对相关声呐接收阵元实际坐标与设计坐标不一致引起的测速误差,提出阵元坐标估计算法,以提高相关声呐的测速准确度。基于混响时空相关函数模型,对相关测速声呐时空相关函数特性进行了理论分析,提出了选择用延时0处的数据空间相关函数与理论空间相关函数进行阵元坐标估计的局域最小二乘拟合算法,并采用序列二次规划法解决了阵元坐标估计算法的最优化问题。海上试验数据的处理结果表明,该算法可以对阵元坐标进行有效估计,使用估计的阵元坐标后,相关测速声呐测速准确度提高了67%。     

基于QEPAS技术的乙炔微量气体高灵敏度检测研究

石英增强光声光谱(QEPAS)是近年来发展起来的一种痕量气体探测技术,具有系统体积小、价格低廉、探测灵敏度高等优点。乙炔(C₂H₂)是一种化学性质活泼的有毒气体,对它进行高灵敏度检测在变压器故障诊断、环境监测等领域有着重要的意义,基于此,采用QEPAS技术对C₂H₂微量气体展开高灵敏度检测研究。采用输出波长为1.53 μm的连续波分布反馈半导体激光器作为激发光源。为了提高信噪比和简化数据处理过程,QEPAS传感器系统采用波长调制和2次谐波探测技术。为了提高QEPAS系统信号幅值,相比于常见的共振频率为32.768 kHz的石英音叉,采用了共振频率较低的30.72 kHz石英音叉作为声波传导器,同时还优化了石英音叉与激光束的空间位置、激光波长调制深度,并添加了声波微共振腔,选择的微共振腔长度为4 mm、内径为0.5 mm,最终获得了2.7 ppm的优异检测极限,归一化噪声等效吸收系数为1.3×10-8 cm-1·W·Hz-1/2。     

Formation of long range ordered arrangement of quantum dots with the help of lateral centripetal flow

A simple “chimney” method was used to eliminate the voids in an arrangement of quantum dots sized 2 nm on a solid substrate, which resulted in a large well ordered superlattice of area in the order more than 1 μm². Based on the principle of speeding up the interparticle interaction of nanoparticles to overcome the particle-substrate one, a lateral centripetal force originated from a glass tube acting as a chimney in a simple evaporation device is imposed. This method allows the packing process to be controlled in a mechanical force field, that is, with the same nanogold dispersion different patterns on a substrate—from separate dots to an ordered compact monolayer or even a multilayer structure—could be easily obtained.     

Micromagnetic analysis of transition noise for high-density perpendicular recording

In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated.     

异硫氰酸荧光素标记抗体的固体基质室温磷光性质研究

研究了异硫氰酸荧光素（FITC）标记的羊抗人抗体（GAHAb-FITC)和兔抗羊抗体9RAGAb-FITC)，及其以三种免疫方式与人免疫球蛋白（IgG)反应所得免疫复合物在多种固体薄膜基质上发射室温磷光（RTP）的适宜条件及其光谱，强度和寿命等性质。研究发现，标记抗体及其免疫复合物保留了FITC优良的固体基质室温磷光性质，λ m0643em^(max)=525/650nm，其RTP强度与其浓度线性相关，并有很高的灵敏度，更为重要的是，免疫反应及其RTP检测能结合于同一基质，方便地相继完成，在聚酰胺膜（PM）上，以Pb(Ac)2为重原子微扰剂，稀释比为1：10（ψ）的GAHAb-FITC,RAGAb-FITC及其与人IgG形成的免疫复合物均能发射较强制 RTP信号并有较长的RTP寿命，本结果为建立相应的固体基质室温磷光免疫分析（SS-RTP-IA）新方法奠定了相应的实验基础。