CdSe薄膜的制备及性能表征

室温下,以CdSO4H1SeO3和Na2SO4为原料,采用二电极体系,利用电化学法在ITO玻璃基底上沉积了CdSe薄膜.采用高分辨x射线衍射仪(HRXRD)、场发射扫描电镜(FESEM)、原子力显微镜(AFM)、紫外.可见.近红外(UV-VIS-NIR)分光光度计、荧光分光光度计(PL)对不同沉积电压下所制备的薄膜的晶体结构、形貌及光学性能进行分析表征.结果表明:所制备的薄膜为立方相CdSe,呈纳米颗粒状,部分粒子表现出不均匀团聚.紫外吸收光谱的吸收峰较体相CdSe有较大的蓝移,且导致禁带宽度发生改变,表现出量子尺寸效应.样品发射光谱表现出荧光现象,且单色性好.适当的沉积电压对CdSe薄膜的形貌和质量起关键作用,同时讨论了其反应机理.     

Early effect modeling of silicon-on-insulator SiGe heterojunction bipolar transistors

Silicon germanium(SiGe) heterojunction bipolar transistor(HBT) on thin silicon-on-insulator(SOI) has recently been demonstrated and integrated into the latest SOI BiCMOS technology.The Early effect of the SOI SiGe HBT is analysed considering vertical and horizontal collector depletion,which is different from that of a bulk counterpart.A new compact formula of the Early voltage is presented and validated by an ISE TCAD simulation.The Early voltage shows a kink with the increase of the reverse base-collector bias.Large differences are observed between SOI devices and their bulk counterparts.The presented Early effect model can be employed for a fast evaluation of the Early voltage and is useful to the design,the simulation and the fabrication of high performance SOI SiGe devices and circuits.     

气相色谱—质谱法测定酒样中多种有机锡化合物

对白酒中的有机锡化合物运用NaBEt4进行衍生,并采用液液萃取和气相色谱—质谱法(GC-MS)对5种衍生物进行分析,建立了5种有机锡同时分析的新方法.选用选择离子扫描模式进行定性和定量分析,实验对影响反应的重要参数进行了优化.在优化条件下,5种有机锡化合物在0.01～4.0 μg·mL-1的线性范围内得获得了较好的线性,检测限,相关系数为0.992 3～0.999 9,检测限为0.4～5.0 μg·L-1.在0.05、0.50和4.0μg·mL-13个添加水平获得了较好的回收率,其相对标准偏差低于13.4％.该方法简便、快速、容易操作,初步运用于检测酒样中的有机锡化合物,取得较满意的结果.     

CdSe/CdS/SiO2复合纳米球的制备及发光性能

采用两相法合成了CdSe/CdS核-壳结构的量子点, 用氨水催化水解正硅酸乙酯制得复合结构的CdSe/CdS/SiO₂发光纳米球. 通过对量子点用量、氨水用量、反应时间及溶剂比例等实验条件的调节, 得到了单分散性较好, 尺寸在23~145 nm的复合发光纳米球. 利用紫外-可见吸收光谱和荧光发射光谱对其发光性能进行了研究, 同时利用透射电镜(TEM)观察复合纳米球的形貌. 结果表明, 复合发光纳米球样品的最高荧光量子产率可达8%.     

快速传递对准用联合强跟踪Kalman滤波器设计与仿真

针对用于快速传递对准的卡尔曼滤波器阶数高,计算量大,滤波更新率低,鲁棒性差及对准精度不高等问题,提出采用联合强跟踪Kalman滤波器进行快速传递对准。文中设计了联合强跟踪Kalman滤波器的结构和算法,同时利用改进的Elman网络进行信息分配系数的自适应调节,以实现融合信息在各子系统中的自适应分配。仿真结果表明,该滤波器不仅提高了解算速度,而且提高了系统鲁棒性和对准精度。     

动力松弛方法中Rayleigh阻尼参数取值分析

论文阐述了动力松弛法计算静力问题的原理,分析了Rayleigh阻尼对计算的影响,提出了一种对质量阻尼和刚度阻尼参数取值的新方法。这种取值方法可以避免计算结果的振荡和过塑性的问题,并利用实例计算进行了对比分析,验证了本文中Rayleigh阻尼取值的合理性。     

Experimental studies of plasma sheath near meshes of different transmissivity

<正>The measurements of the potential distributions in the boundary layer near meshes with different mesh spacing were conducted in weakly collisional plasmas using a fine-structured emissive probe and the results of the sheath thickness and electric field at the sheath-presheath edge were compared with theoretical models of collisional presheath and collisionless sheath.It was shown that,because the meshes are partially transparent to ions,the sheath is thinner and the electric field is stronger for the mesh of higher transmissivity,owing to the increased ion density in the sheath contributed from the ions transmitted from the other side of the mesh.However,the potential profiles in the presheath remain almost the same for different meshes except for the shift of the sheath-presheath edge.The thickness of the sheath decreases while the electric field at the edge increases with the increase of the neutral gas pressure.Furthermore, depending on the pressure,the measured electric fields at the edge are close to that from the models of a transition region.     

Difference-frequency ultrasound generation from microbubbles under dual-frequency excitation

The difference-frequency (DF) ultrasound generated by using parametric effect promises to improve detection depth owing to its low attenuation, which is beneficial for deep tissue imaging. With ultrasound contrast agents infusion, the harmonic components scattered from the microbubbles, including DF, can be generated due to the nonlinear vibration. A theoretical study on the DF generation from microbubbles under the dual-frequency excitation is proposed in formula based on the solution of the RPNNP equation. The optimisation of the DF generation is discussed associated with the applied acoustic pressure, frequency, and the microbubble size. Experiments are performed to validate the theoretical predictions by using a dual-frequency signal to excite microbubbles. Both the numerical and experimental results demonstrate that the optimised DF ultrasound can be achieved as the difference frequency is close to the resonance frequency of the microbubble and improve the contrast-to-tissue ratio in imaging.     

Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

High-quality p-type boron-doped IIb diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K.The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively.The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique.The electrical properties including resistivities,Hall coefficients,Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method.The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized.With the increase of quantity of additive boron,some high-index crystal faces such as {113} gradually disappear,and some stripes and triangle pits occur on the crystal surface.This work is helpful for the further research and application of boron-doped semiconductor diamond.     

Acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction

An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction (MAT-MI) is pro-posed,based on the analyses of one-dimensional tissue vibration,three-dimensional acoustic dipole radiation and acoustic waveform detection with a planar piston transducer.The collected waveforms provide information about the conductiv-ity boundaries in various vibration intensities and phases due to the acoustic dipole radiation pattern.Combined with the simplified back projection algorithm,the conductivity configuration of the measured layer in terms of shape and size can be reconstructed with obvious border stripes.The numerical simulation is performed for a two-layer cylindrical phantom model and it is also verified by the experimental results of MAT-MI for a tissue-like sample phantom.The proposed model suggests a potential application of conductivity differentiation and provides a universal basis for the further study of conductivity reconstruction for MAT-MI.