Simulation of Helium Behaviour in Titanium Crystals Using Molecular Dynamics

The behaviour of helium in Ti crystals at 300 K has been investigated by means of the molecular dynamics. The study is focused on the influences of He-Ti interaction on the aggregation of helium atoms in the substrate. When a Born-Mayer potential is used to describe the He-Ti interaction, the He atoms are unable to cluster with each other due to the weak bridge barrier that cannot trap the helium atoms, Whereas using a He-Ti potential that is constructed by fitting the ab initio pairwise He-Ti potential, the clustering of He atoms can be observed. The results indicate that suitable He-Ti potential plays an important role in the formation of He clusters in metals. Moreover, it is noted that the shape of the formed He cluster is irregular, and the produced defect prefers to congregating on one side of the He cluster rather than spreading symmetrically around it.     

Block Entanglement in the Single-Hole Hubbard Model

We investigate the distribution of the entanglement of the one-dimensional single-hole Hubbard model （HM） and study the relationship between the entanglement and quantum phase transition in the model. The von Neumann entropy of a block with neighbouring spins L for a single-hole HM is calculated using the densitymatrix renormalization group. The distributions of the entanglement entropy in the ground state, as a function of block length, show a dramatic effect, i.e. effectively decoupling with the centres, no matter how the Coulomb interaction u 〉0 or u 〈0. Contrarily, for the Coulomb interaction u = 0 or close to zero, the entanglement entropy in the single-hole model reaches a saturation value for a certain block size. For a fixed size L = 40, the ground state entanglement entropy measure, as a function of u1 shows a peak corresponding to the critical quantum phase transition.     

Effect of Alumina and Chromium Interlayers on Microstructures and Optical Properties of Thin Ag Films on Glass Substrates

Effects of alumina and chromium interlayers on the microstructure and optical properties of thin Ag films are investigated by using spectrophotometry, x-ray diffraction and AFM. The characteristics of Ag films in Ag/glass, Ag/l2O3/glass and Ag/Cr/glass stacks are analysed. The results indicate that the insertion of an Al2O3 or Cr layer decreases the grains and influences the reflectance of Ag films. The reflectance of the Ag film can be increased by controlling the thickness of alumina interlayer. The stability of Ag films is improved and the adhesion of Ag films on glass substrates is enhanced by alumina as an interlayer.     

条件非线性最优扰动方法在陆面过程模式参数优化中的扩展应用初探

本文旨在探讨条件非线性最优扰动(CNOP)方法在陆面过程模式的参数优化工作方面的扩展应用.使用通用陆面模式(CoLM)和CEOP地面基准站——吉林通榆站退化草地2006年生长季的资料,针对土壤颜色、砂土比例和叶面积指数等关键模式参数,使用感热通量、潜热通量和浅层土壤温湿度作为检测变量,设计了单参数和多参数优化试验.结果表明,CONP扩展方法得到的优化参数提高了CoLM对检测变量的模拟能力,并且多参数的优化结果明显优于单参数的优化结果,在模式模拟偏差较大的土壤湿度方面改进尤为显著,此外,使用了差异进化算法( 关键词： 条件非线性最优扰动(CNOP) 陆面过程模式 参数优化     

飞秒激光低压N2等离子体特性的实验研究

在低于一个标准大气压的条件下对飞秒激光产生的N₂等离子体光谱进行了实验研究.结果表明, 各种样品气压下的激光N₂等离子体光谱均表现为连续谱和线状谱的叠加.随着样品气压的降低, 连续谱和原子谱线的强度经历了由缓慢增强发展为缓慢降低再到迅速降低的过程, 而正一价离子谱线强度呈现逐步增强的特征.在气压低于0.3 atm (1 atm=101325 Pa)时, 出现了正二价态的离子谱线. 给出了低压N₂等离子体对于飞秒激光传输和能量吸收的物理特性, 并初步讨论了低压等离子体通道特性.这些结果有助于加深了解飞秒激光等离子体的特性和机理, 特别是给出了在实验上测量不同价态离子光谱的条件, 为今后的研究提供了有益的实验依据. 关键词： 飞秒激光 气压 等离子体光谱 激光传输     

基于太赫兹光谱的固体片剂孔隙率研究

内部孔隙影响着药片的崩解特性,进而影响药效的发挥,但目前鲜有关于药片孔隙率有效检测手段的报道。基于太赫兹脉冲的飞行时间测量原理,利用太赫兹时域光谱技术研究了微晶纤维素和吲哚美辛混合片剂的孔隙率与折射率、吲哚美辛质量分数之间的定量关系;建立了三者关系的数学计算模型,通过实际测试固体样品片剂的太赫兹时域光谱,计算了片剂的孔隙率、折射率。结果表明:片剂的孔隙率与折射率、不同成分质量分数间存在线性关系,与建立的数学计算模型相符。利用太赫兹光谱法测得的孔隙率与采用气体置换法测量的孔隙率的平均相对误差为6.0%,与采用密度法计算的孔隙率的平均相对误差为8.9%,表明利用太赫兹光谱法测量片剂孔隙率具有可行性,能够成为药物片剂质量监测的补充手段。     

高压拉曼光谱方法研究卟啉J-聚集体

本文利用金刚石对顶砧(DAC)和拉曼光谱技术,测量了四苯基卟啉J聚集体在13GPa内的高压拉曼光谱,根据各个拉曼谱带的频移-压强变化曲线得出在13GPa内Tpp J聚集体无相变发生,并且高波数(1010～1600cm-1)和低波数(230～330cm-1)区的斜率要远大于中等波数(380～1000cm-1)区,这表明对应于高波数和低波数区的化学键比中等波数区更具有易压缩性,并对体积的减小起着重要的作用。根据苯环ψ3C-C面内伸缩振动模式强度逐渐增强的现象提出了分子弹簧垫圈模型。此外,这种分子弹簧垫圈的劲度系数可以通过中位取代基团调控。     

Angular distributions of CH3I fragment ions under the irradiation of a single pulse and trains of ultrashort laser pulses

The angular distribution of CH3I is investigated experimentally using a single Fourier transform-limited laser pulse and a pulse train, where a 90-fs 800-nm linearly polarized laser field with a moderate intensity of 2.8×1013 W/cm2 is used. The dynamic alignment is demonstrated in a single pulse experiment. Moreover, a pulse train is used to optimize the molecular alignment, and the alignment degree is almost identical to that with the single pulse. The results are analysed by using chirped femtosecond laser pulses, and it demonstrates that the structure of pulse train rather than its effective duration is crucial to the molecular alignment.     

光学元件损伤在线检测图像处理技术

针对光学元件损伤图像中损伤区域的高精度检测问题,对内全反射照明下光学元件损伤图像的处理技术进行了研究。根据在线检测图像中损伤区域中心峰值的信号强度高于局部背景的信号强度这一特点,利用高斯滤波器生成待检测图像的局部信号强度比图像,实现了对损伤区域的低漏检率自动定位;根据CCD的成像原理,利用辐射标定的方法建立起损伤区域的尺寸与其在图像中总灰度的关系方程,实现了损伤区域的亚像素高精度尺寸测量。实验结果表明,与传统的光学元件损伤图像处理算法相比,本文提出的算法在保持低漏检率的同时大大提高了损伤区域的测量精度。     

用正四棱锥形阵对声目标定位研究

文章结合声阵列在智能雷系统中的应用，提出了用立体五元声阵列对声目标进行定位，将智能雷中用于预警的传感器也参与到定位阵列中来，这样就在不增加传感器的条件下实现了市体阵列对声目标的定位。文章推导了定位公式和误差公式，并对结果进行仿真分析，与平面阵相比取得了较好的效果。不但提高了精度还降低了声阵列的盲区。