Zn∶LiNbO_3晶体倍频性能的研究

在ＬｉＮｂＯ３晶体中掺入ＺｎＯ，生长ＺｎＯ∶ＬｉＮｂＯ３晶体，当ＺｎＯ的掺入浓度高于６ｍｏｌ％时，晶体的抗光损伤能力提高两个数量级，与高掺ＭｇＯ（＞４．６ｍｏｌ％）相似。Ｚｎ∶ＬｉＮｂＯ３的倍频转换效率可达５０％左右，高于Ｍｇ∶ＬｉＮｂＯ３。本文对Ｚｎ∶ＬｉＮｂＯ３晶体中Ｚｎ２＋离子占位以及抗光损伤增强机理进行了初步探讨     

密度泛函方法研究气相胞嘧啶的互变异构化

分别采用7种基组、3种理论方法对胞嘧啶异构体Cyt1的结构进行优化,通过与Cyt1的实验结果进行比较,选取了适合研究胞嘧啶分子的B3LYP/6311+G方法.用该方法对胞嘧啶分子的8种异构体构型进行了充分优化,研究了其中能量较低的6种胞嘧啶异构体的互变异构化过程.对于得到的所有优化构型都进行了频率分析.对于基态构型,所有的频率都是正的;对于过渡态构型,只有一个虚频.同时,做了详尽的内禀反应坐标计算,以保证所得到的过渡态连接相应的始末异构体.所有给出的能量都已做了零点能校正.理论研究结果可以对已有的实验结果给予合理解释.     

CoSi电子结构第一性原理研究

采用基于第一性原理的密度泛函理论全势线性扩展平面波法，首先对CoSi的晶胞参数进行优化计算，CoSi多粒子系统的最低能量为-134684297Ry，此时其晶胞处于最稳态，与最稳态对应的晶胞体积V0等于5899360a.u.3,晶胞参数为a=b=c=04438nm；然后计算了优化后的CoSi的电子结构及Si侧Al掺杂的CoSi075Al025的电子结构并分析了两者的电子结构特征，计算的CoSi电子能态密度与已有的计算结果整体形貌相同，但存在局部差异，Al掺杂后费米面发生了偏移；最后探讨了两者的电子结构对热电性能的影响，Al掺杂可提高CoSi的材料参数B，因此有望提高其热电性能. 关键词： 第一性原理 电子结构 热电性能     

拓扑分子格的S紧性和S次紧性

利用半开元等半拓扑概念在拓扑分子格中引入S紧性与S次紧性，给出了它们的刻画，推广了文[1]中的紧性与次紧性，证明了拓扑分子格的S紧性，S次紧性，STi分离性(i=-1，0，1，2)与STi^*分离性(i=0，1，2)为半拓扑性质。     

Magnetointersubband Oscillations of the Two-Dimensional Electron Gas in AlxGa1-xN／GaN Heterostructures

Shubnikov-de Haas (SdH) measurements are performed over a temperature range of 1.5-20 K in Al0.22 Ga0.78N/GaN heterostructures with two subbands occupied. In addition to an intermodulation between two sets of SdH oscillations from the first and second subbands, a beating in oscillatory magnetoresistance at 12K is observed, due to the mixing of the first subband SdH oscillations and ‘magnetointersubband‘ (MIS) oscillations. A phase shift of π between the SdH and MIS oscillations is also clearly identified. Our experimental results, i.e. that the SdH oscillations dominate at low temperature and MIS oscillations dominate at high temperature, fully comply with the expected behaviour of MIS oscillations.     

飞秒荧光亏蚀光谱技术研究液相体系取向弛豫

溶液中分子的快速弛豫过程直接反映了溶液中溶质和周围溶剂分子间的相互作用[1- 3 ] .在液相体系中分子取向通常是随机分布的 .当溶质分子被线偏振光激发至激发态时 ,其分子取向将由原来各向同性的球形分布瞬间变成各向异性的椭球分布 .由于溶质分子周围大量溶剂分子的存在 ,通过二者之间相互作用 ,激发态溶质分子在一定方向上的取向优势将很快弛豫掉 .这种溶液中的取向弛豫过程通常是几个到几百皮秒[1- 3 ] .飞秒分辨荧光亏蚀光谱原理和实验方法见文献[4 - 7] .当溶液中的溶质分子被线偏振飞秒激光脉冲激发至电子激发态时 ,经过一定的延迟…     

Electron scattering from molecule CH4 at 10-5000eV

Electron scattering from molecules in the intermediate- and high-energy range is investigated employing the developed semi-empirical formula for electron scattering from diatomic molecules. Total cross sections of e-CH4 scattering are obtained over an incident energy range of 10--5000eV. The results agree well with other available experimental and theoretical data. According to our formula, some quantitative information of single Yukawa potential are also obtained.     

浅谈两类基本年金问题的解法和教法

什么是年金？顾名思义，年金就是一年中发生的金额．随着年金问题在经济活动中的广泛应用，年金已泛指业务期中每一期发生的金额．这里的期可以用任何时间为单位，金额可以相等可以不相等．年金问题不同于本金问题，本金问题直接应用单利基本公式［Ｓ＝Ｐ（１＋ｎｒ）］或...     

Dependence of Intrinsic Defects in ZnO Films on Oxygen Fraction Studied by Positron Annihilation

Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetie positron beam technique. The dominate intrinsic defects in these ZnO samples are O vacancies （Vo） and Zn interstitials （Zni） when the oxygen fraction in the O2/Ar feed gas does not exceed 70% in the processing chamber. On the other hand, zinc vacancies are preponderant in the ZnO films fabricated in richer oxygen environment. The concentration of zinc vacancies increases with the increasing O2 fraction. For the oxygen fraction 85%, the number of zinc vacancies that could trap positrons will be smaller. It is speculated that some unknown defects could shield zinc vacancies. The concentration of zinc vacancies in the ZnO films varies with the oxygen fraction in the growth chamber, which is in agreement with the results of photolurninescence spectra.     

过敏性哮喘患者血清中钙镁钡铝锶含量的研究

３４例过敏性哮喘患者血清中钙、镁、钡、铝、锶的含量与对照组比较，结果显示（１）钙的含量明显下降，Ｐ＜０．０１；（２）钡和锶的含量升高，差异有显著性和高度显著性，Ｐ＜０．０５和Ｐ＜０．０１；（３）镁和铝的含量差异无显著性，Ｐ＞０．０５。