White Emitting ZnS Nanocrystals： Synthesis and Spectrum Characterization

Spherical organic-bonded ZnS nanocrystals with 4.0 4-0.2 nm in diameter are synthesized by a liquid-solid-solution method. The photoluminescence spectrum of sample （[S^2-]/[Zn^2＋] = 1.0） shows a strong white emission with a peak at 490nm and - 170 nm full widths at half maximum. By Gauss fitting, the white emission is attributed to the overlap of a blue emission and a green-yellow emission, originating from electronic transitions from internal S^2- vacancies level to valence band and to the internal Zn^2＋ vacancy level, respectively. After sealingZnS nanocrystals onto InGaN chips, the device shows CIE coordinates of （0.29,0.30）, which indicates their potential applications for white light emitting diodes.     

最大似然法在HL-2A汤姆逊散射中的初步应用

介绍了一种处理HL-2A汤姆逊散射原始实验数据的新方法--最大似然法。该方法用数理统计的手段,通过使理论推导出的数据与实际采集到的散射数据最大可能的一致,得到了较准确的等离子体电子温度T_e和密度n_e。将计算所得的结果与现在汤姆逊散射系统所用的比值法得到的结果相比较,验证了该方法的可适用性,并能够克服比值法的一些缺陷。     

调强放射治疗子野权重优化方法研究

由于子野分割带来的误差, 使得调强放疗(Intensity Modulated Radiation Therapy, 简称IMRT)计划系统所制作的计划往往不能满足临床要求。 本研究将采用基于共轭梯度法的子野权重优化方法来减小此误差, 提高制作计划的效率和效果。 采用共轭梯度法优化子野权重和微调子野形状, 最终使得子野分割前后强度误差最小。 在精确放疗系统中对常见的临床病例（鼻咽癌和周围性肺癌）进行测试, 通过对比靶区和危及器官的剂量体积直方图以及CT片上的等剂量线, 发现子野权重优化后靶区的平均剂量分别从87.0%提高到100.2%和从90.0%提高到98.4%, 更好地满足临床要求。     

非线性元件频率响应

用示波器观测4种二极管对交流信号的响应.为了理解响应图形的含义,对响应信号做了Fourier变换,使学生认识到非线性元件对输入信号能产生高次谐波,即产生倍频和多倍频.在非线性伏安特性测量实验中增加了上述内容,激发了学生的学习兴趣.     

Theoretical study of the electronic ground states and low-lying singlet excited states of thiophene-based spirofluorenes

The electronic structures and optical properties of oligothiophene substituted spirofluorenes are investigated theoretically with semi-empirical quantum chemical calculations. A theoretical investigation of the interaction between two perpendicular π-systems of various oligothiophene substituted spirofluorenes is conducted. The results demonstrate that the interaction between two perpendicular branches is reduced by oligothiophene substitutions. Photoexcitation induced relaxation is mainly located on one of...     

多功能荧光分光计的微机化

本文在原有实验室自制多功能荧光分光计的基础上，通过微机Ａ／Ｄ转换技术的软件设计，实现了光谱的ＣＲＴ显示，分别得到了常规荧光光谱，各种同步荧光光谱及它们的一，二阶导数谱，并且测绘了三维立体荧光光谱和等高图荧光光谱。同时建立了各种光谱及数据处理技术。     

MoSi2能隙的高压调制

 采用LMTO-ASA方法，对过渡金属MoSi₂在高压下的电子结构性质进行了研究，计算中考虑了除自旋-轨道耦合外的所有相对论效应。结果表明：随着压缩度增加，MoSi₂小的能隙变宽，Mo的d电子与Si的p电子杂化增强，原子间相互作用增大，晶体在高压下更加紧密结合。这一能隙随压力增大而增大的结果，与非导体在高压下金属化的特性相反。     

THE ANNEALING FEATURES OF Ta/Si MULTILAYER FILMS

The Ta/Si multilayers on (100) Si substrate have been studied over the annealing temper-ature range from 500 to 900℃ by X-ray diffraction and cross-section transmission electron microscopy. The periodicity of the multilayers becomes worse with increasing annealing tem-perature and disappears at 750℃. At 600℃, two kinds of modulation wavelength coexist because the size of several TaSi₂ grains is larger than the contracted original modulation wavelength. The films are contracted after annealing. The largest contraction, at least 40nm decreasing in thickness, occurs at 600℃. When the annealing temperature is lower than 600℃, h-TaSi₂ grains grow randomly and the growth is not affected by the substrate. At temperatures higher than 750℃, h-TaSi₂ grows preferentially in [001] direction parallel to [100] axis of Si substrate. The appearance of texture depends on whether the atomic diffusion is short range or long range at the corresponding annealing temperature.