在硅晶体中由螺位错引起的电子散射

本文讨论硅晶体中由〈110〉螺位错引起的电子散射,用紧束缚近似只考虑s电子和p电子。用长波近似只考虑Γ附近的电子散射。此散射近似地服从基尔霍夫-惠更斯形式的积分方程。用规范变换和格林函数方法解出了散射方程。确认了在硅复杂能带的情况下也同单一能带的情况一样,在位错的下游侧出现电子波播及不到的影子。 关键词：     

大型FFAG磁铁的2维POISSON设计

 为减小边缘场效应，大型固定磁场交变梯度（FFAG）磁铁的磁场分布由修整线圈和磁极形状两者共同来实现。通过2维POISSON模拟计算，确定了修整线圈电流和位置的分布以及磁极形状, 得到了局域磁场梯度指数与设计值之间的最大差异只有0.5％的磁场分布。为提高POISSON模拟计算的效率，POISSON输入文件中有关线圈电流和位置、磁极形状的输入和调整由程序自动完成。     

掺Eu介质微球腔的荧光光谱研究

原子或离子置于微腔中时其自发辐射速率会由于腔量子电动力学效应而得到大幅提高，这就是Purcell增强效应．如将Eu离子掺入特定的微腔中，因为Eu^3＋的自发辐射荧光线宽比微腔WGM模式的线宽大，其荧光光谱将受到腔模的调制，从而反映出腔模的分布状况。实验上，我们制备了熔融玻璃微球腔，并且在微球的赤道附近沾上一定量的Eu^3＋离子。测量了用395nm半导体激光泵浦时的荧光谱。     

THE POWER SPECTRUM OF THE MASS IN A SANDPILE MODEL WITH STOCHASTIC SLIDE

The power spectrum of the mass in a theoretical sandpile model with stochastic slide is examined. The simulations show that the power spectrum has the form of l/f^α, and the exponent α may vary with the average time interval between the successive events af the sands flowing off the sandpile. The conditions of generating 1/f noise are also discussed.     

碘离子选择电极催化动力学法测定钒(V)的研究

本文介绍用碘离子选择电极催化电势动力学法对测定钒(Ⅴ)进行的研究,发现去氢抗坏血酸是钒(Ⅴ)催化BrO_3-氧化I~-体系的一种良好的活化剂,详细地研究了各种因素对测定的影响,找出了测定钒(Ⅴ)的较佳条件。该法测定钒(Ⅴ)浓度的线性范围很宽,检测限为2×10~(-10)mol/l,灵敏度比文献报道的高3个数量级。对几种离子的干扰进行了试验,柠檬酸可以有效地掩蔽这些离子的干扰。此法曾应用于测定自来水和头发中的钒,得到了较好的结果。     

Synthesis of Schiff Base-type Liquid Crystalline Crown Ethers Containing Dibenzo-18-Crown-6 Unit

The synthesis and characterization of novel Schiff base liquid crystalline crown ethers prepared from the intermediates 4-(4‘-alkoxylbiphenyl-4-carbonyl)benzaldehyde, cis- and trans-4,4‘-diaminodibenzo-18-crown-6 are described. The structure of these compounds have been well characterized by elemental analysis, IR, ^1H NMR and MS spectroscopy. The liquid-crystalline behavior of these compounds was also inverstigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) with a heating stage and polarimetric analysis.     

基于水平集的牙齿牙槽骨图像分割

口腔锥形束计算机断层扫描（Cone Beam Computed Tomography,CBCT）图像中牙齿及牙槽骨的分割对骨性结构的三维重建提供了基础,是实现牙齿牙槽骨三维可视化的必要步骤.本文根据牙齿及牙槽骨特点,将一种改进的势阱函数与水平集模型结合,克服以往势阱函数在部分区域出现“停止演化”或“过快演化”的缺陷,并将其应用在对牙齿牙槽骨的分割当中.采用多次小方差高斯滤波叠加的方式对图像进行序贯滤波预处理,解决单一方差高斯滤波难以有效滤除CBCT图像中噪声的问题,为准确分割提供了条件;基于序列图像相邻两张图片中同一牙齿的轮廓变化不大这一特点,以当前层的分割结果作为下一层曲线演化的初始轮廓,使得用更少的迭代次数得到相同结果,从而提高分割速度.另外,本文还将该算法应用于口腔磁共振图像中,并成功对单颗牙齿进行了分割.     

混凝土构件长期干缩应力的计算

本文用有限元法从砼的水分扩散方程中求出湿度和自由干缩应变场,分别由砼的线性和非线性蠕变理论及拉应变软化模型,推导出计算砼构件的干缩应力的递推公式,并编制了电算程序。计算表明,非线性理论的结果与线性理论的结果相差不大,而拉应变软化模型的结果与前两者有较大差异。     

苯硫酚盐基溶液的可充镁电池电解液

将4-甲基苯硫酚、4-异丙基苯硫酚和4-甲氧基苯硫酚(RSH)分别与格氏试剂C₂H₅MgCl/THF(四氢呋喃)反应制得的苯硫酚氯化镁(RSMgCl)(分别标记为MBMC、IPBMC和MOBMC)/THF和进一步与Lewis 酸AlCl₃反应制得的(RSMgCl)_n-AlCl₃/THF(n=1,1.5,2)苯硫酚盐基溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了电解液的镁沉积-溶出性能和氧化分解电位. 结果表明,苯硫酚上的基团种类和RSMgCl与AlCl₃的比例对其电化学性能有影响. 其中,0.5 mol·L^-1(IPBMC)_1.5-AlCl₃/THF 溶液具有最佳的电化学性能,其氧化分解电位适宜(2.4 V(vs Mg/Mg²⁺)),镁沉积-溶出循环效率稳定,过电位低,电导率较高(2.48 mS·cm^-1),与正极材料Mo₆S₈兼容性良好,且具有一定的空气稳定性,配制方便,有希望应用于实际的可充镁电池体系中.     

Status of CSNS H- ion source

A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source (CSNS). In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.