宏观尺寸弯曲石英管对中低能电子束的导向作用

研究了宏观尺寸的弯曲圆柱形石英管对 1 100, 1 300和1 500 eV 3种能量电子束的导向作用, 并对实验结果与相同材质和尺寸的直管的情形进行了分析对比。 实验中利用一个位置灵敏法拉第筒对从石英管出射的电子束进行探测, 获得从管道中出射的电子束流强度在位置灵敏法拉第筒各道上的分布, 其结果显示宏观尺寸石英管对电子束存在导向作用。 与慢速高电荷态离子和绝缘毛细管相互作用的物理过程类似, 这种导向效应是由电荷在管壁内表面自组织充电引起的。 实验还发现, 入射电子束流的强度越强, 其导向作用越明显, 这与微观尺寸毛细管对慢速高电荷态离子的导向作用不同。 石英管导向能力与管的尺寸、 形状及材料之间的关系还有待进一步的系统研究。 It was inevstigated in the experiment that the guiding effect of electron beam with energy of 1 100, 1 300 and 1 500 eV through a bended cylindrical quartz tube with macro sized. A position sensitive Faraday cup was developed and used to detect the electron beam transmitted through the quartz tube, and the distribution of transmitted beam current on each channel of the Faraday cup was acquired. Results indicate the existence of guiding effect which is due to the self organized charge up in the inner wall of the quartz tube similar to that of the highly charged ions. We also found that the guiding ability of the tube is related to the incident beam intensity. The relationship between the guiding ability and the material as well as the size of the tube is to be studied in the near future.     

Sinusoidal Steady State Analysis on 4H--SiC Buried Channel MOSFETs

With the combined use of the drift-diffusion （DD） model, experiment measured parameters and small-signal sinusoidM steady-state analysis, we extract the Y-parameters for 4H-SiC buried-channel metal oxide semicon- ductor field effect transistors （BCMOSFETs）. Output short-circuit current gain G and Mason＇s invariant U are cMculated for extrapolating unity current gain frequency in the common-source configuration fT and the maximum frequency of oscillation fmax, respectively. Here fT = 800 MHz and fmax= 5 GHz are extracted for the 4H-SiC BCMOSFETs, while the field effect mobility reaches its peak value 87cm2/Vs when VGs = 4.5 V. Simulation results clearly show that the characteristic frequency of 4H-SiC BCMOSFETs and field effect mobility are superior, due to the novel structure, compared with conventional MOSFETs.     

Amorphization Induced High Magneto-Caloric Effect of Gd55Al20Ni25 Ternary Alloy

We report the amorphization induced high magneto-caloric effect （MCE） of recently developed Gd55Al15Ni30 bulk metallic glass （BMG）. The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55Al15Ni30 bulk metallic glass.     

Temperature Dependence of Photoluminescence from Single and Ensemble InAs/GaAs Quantum Dots

We investigate the temperature dependence of photoluminescence from single and ensemble InAs/GaAs quantum dots systematically. As temperature increases, the exciton emission peak for single quantum dot shows broadening and redshift. For ensemble quantum dots, however, the exciton emission peak shows narrowing and fast redshift. We use a simple steady-state rate equation model to simulate the experimental data of photoluminescence spectra. It is confirmed that carrier-phonon scattering gives the broadening of the exciton emission peak in single quantum dots while the effects of carrier thermal escape and retrapping play an important role in the narrowing and fast redshift of the exciton emission peak in ensemble quantum dots.     

采用显微图像测量系统实现人体组织典型参数测量

人体组织典型参数的获取对于各类疾病的诊断和治疗有着极其重要的作用。采用高性能显微图像测量系统实现人体组织典型参数在体测量, 对系统研制过程中所涉及的基本原理, 以及图像采集系统、成像系统与图像处理软件等关键性技术问题作了阐述。该显微图像测量系统能快速、有效地完成对人体组织典型图像指标的直接测取和定量分析, 基本实现了人体组织典型参数图像观测的数字化与检测的高智能化。实验结果表明, 采用该系统在体观测人体组织典型参数, 可以实时观测人体组织显微图像, 计算并保存毛细血管网络形态学参数和微血流动力学的各项参数, 同时具有快速简单、精确度高等特点, 可作为医学研究的重要手段之一。     

电场喷射活细胞

一般人使用喷墨打印机来打印文件和图片＋这种技术将细小的彩色墨滴从喷嘴中挤压出来．然而，在电子学和医学中正越来越多地用这种技术产生小体积的液滴．例如，使用压电晶体从一根针头中挤压出含有细胞的溶液，产生活细胞的二维和三维图像．但是细胞液滴的大小受到针头直径大小的限制＋因而这种方法不能产生小于100μm同左右的液滴．这意味着很难制成带有细微特征的小的生物组织．     

变频率压缩态光场与原子的相互作用

研究了频率随时间变化的压缩态光场与二能级原子的相互作用，主要讨论了光场频率随时间作正弦调制和脉冲调制两种典型情况下，原子布居数反转随时间的演化特性。当光场频率随时间作正弦调制时，不仅光场频率调制，而且压缩态的压缩系数和压缩相位均对原子布居数反转的崩塌—回复过程有影响。当光场频率随时间作脉冲调制时，在原子布居数反转随时间演化过程中诱导出新的崩塌—回复过程，尤其在脉冲出现的区间内，原子布居数反转表现出持续的小幅快速振荡，这与压缩态的压缩系数无关。     

聚变堆用结构材料CLF-1研究进展

本文报道了我院近半年来低活性铁素体／马氏体钢CLF-1的研究进展。通过微观组织观察和室温拉伸性能测试，证明该钢已具有优于Eurofer97的室温拉伸性能，而且得到了全马氏体的微观组织。     

Molecular dynamics study of ice structural evolution

Molecular dynamics simulation is employed to study the structural evolution of low density amorphous ice during its compression from one atmosphere to 2.5 GPa. Calculated results show that high density amorphous ice is formed at an intermediate pressure of -1.0 GPa; the O-O-O bond angle ranges from 83° to 113°, and the O-H… O bond is bent from 112° to 160°. Very high density amorphous ice is obtained by quenching to 80 K and decompressing the ice to ambient pressure from 160 K/1.3 GPa or 160 K/1.7 GPa; and the next-nearest O-O length is found to be 0.310 nm, just 0.035 nm beyond the nearest O-O distance of 0.275 nm.     

轴流透平与排汽系统间流场相互作用研究

为了研究轴流透平与非轴对称排汽系统流场间的相互作用,对带有单级透平的300/600MW汽轮机排汽系统模型内流场进了模型实验,并用商用软件CFX数值计算了实验工况下带有全周叶栅通道的单级透平与排汽系统内的耦合流场.对比实验与数值模拟结果,二者吻合较好.通过对实验和数值结果分析发现,排汽系统内的非轴对称流场使透平叶栅通道内流动沿周向发生变化,扩压器内出现大的流动分离,排汽系统内总压损失增大,静压恢复系数为负.