Yb~(3+)/Er~(3+)掺杂氟氧化物微晶玻璃的制备与发光性能

采用高温熔融法制备了Yb3+/Er3+掺杂的氟氧化物发光微晶玻璃,确定了最佳熔化温度(1 100℃)和退火温度(440℃,480℃)。测定得到基质玻璃的透过率为85%,掺入稀土后,透过率有所下降,并出现了稀土离子的特征吸收峰。980 nm半导体激光器(LD)激发下样品的上转换发射光谱存在4个明显的发射峰,分别为410,532,546和656 nm,对应于2H9/2→4I15/2,2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2跃迁。研究了不同Yb3+/Er3+(摩尔分数)和Er3+浓度对上转换发光强度的影响,当Yb3+∶Er3+=4∶1、Er3+摩尔分数为1.5%时,上转换发光强度达到最高。根据发光强度与泵浦功率之间的关系,确定了上转换发射均为双光子过程。讨论了Yb3+,Er3+离子间的能量传递,建立了上转换发光机制。     

植被双向反射分布函数的模型及其发展

介绍了双向反射分布函数(BRDF)的概念和反映植被特性的归一化植被指数(NDVI)、增强植被指数(EVI)、差值植被指数(DVI)等一些重要指数参数。评述了近年发展起来的植被BRDF模型的构建方法,例如统计反演方法,MODIS植被指数合成法和集合卡曼滤波法(EnKF)。分析了目标表面BRDF数据的获取方法和改进的驱动核算法。对BRDF模型的发展趋势进行了展望。     

Cosmic ray test for a T0 detector

The endcap of time-of-flight (ETOF) detector in BES (Beijing Spectrometer) III is planned to be upgraded by using multi-gap resistive plate chambers (MRPCs) and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero (T0) detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a T0 detector is built using plastic scintillator tiles (BC420) to couple with four fast phototubes (PMTs, Hamamatsu H6533). The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. T0 detector timing resolutions of ～41-62 ps are achieved, which means that the T0 detector can be used in the MRPC beam test.     

大视场光学遥感器焦平面板的研制

焦平面板作为承载TDICCD器件的部件,其强度、动静态刚度、热稳定性直接影响到遥感器的成像质量.针对目前光学遥感器大视场、宽覆盖的发展趋势,设计了一种新型的焦平面板.选用性能指标优良的高体份SiC/Al复合材料,既满足了结构设计指标的要求,同时又大大降低了产品重量.通过有限元模拟仿真分析和相关试验,验证了设计方案的可行...     

HIRFL-CSRm内靶实验终端CsI(Tl)电磁量能器性能模拟

基于GEANT4模拟了HIRFL CSRm内靶实验终端的CsI(Tl)电磁量能器系统,给出了CsI电磁量能器的最佳设计参数及可能达到的性能.结果表明,设计的CsI(Tl)电磁量能器系统能够满足所研究的物理要求. Based on the GEANT4, the performance of the electromagnetic calorimeter (EMC) of the internal-target detector at HIRFL-CSRm is simulated. The simulation results show that 1.5%—3% of the energy resolution σ_E/E and 2° of the polar angular resolution σ_θ can be obtained. The invariant mass of the π~0 decay can be reconstructed well. The performance can meet the requirement of studying the proposed physics at HIRFL-CSRm.     

氧离子与氦、氖原子碰撞中转移电离过程的研究

采用位置灵敏探测和散射离子-反冲离子飞行时间测量技术,测量了氧离子与氖和氦原子碰撞过程中转移电离截面与单电子俘获截面之比.通过比较发现测量结果与文献结果的趋势一致,并对测量结果进行了讨论.     

稠密气固两相QL-EMMS曳力模型及改进

通过引入颗粒加速度,改进现有EMMS曳力模型中的颗粒受力平衡关系,耦合流动的整体参数、局部参数与曳力,提出了基于流态化多尺度最小能量原理的QL-EMMS曳力模型.实验检验表明,模型精度高,普适性好.进一步采用O-S经验曳力模型的单峰函数,修正了颗粒团直径公式,改进后的QL-EMMSn模型更加合理地体现了非均匀曳力变化的...     

托卡马克微波预电离等离子体

使用回旋管系统产生的电子回旋波段的大功率微波在托卡马克中得到无电流等离子体。其电子密度达8×10¹²cm^-3,电子温度达50eV,粒子约束时间约为0.5ms,加热效率达25％以上。研究了对环向击穿的影响及加热机制。     

等能谷间杂质散射对无序层状系统电导率的影响

本文研究了等能谷间杂质散射对无序层状系统电导率的影响,求得了依赖于平面间耦合t的系统的有效维数的电导率修正。并且发现在计及等能谷间杂质散射时,电导率修正比只考虑谷内杂质散射时小一半,我们研究了层伏系统从二维过渡到三维的跨越维数效应,发现跨越行为依赖于谷间散射时间τ′,当t<1/τ(τ₀/τ′)^1/2时,系统具有二维行为,反之系统具有三维特征。 关键词：     

Ab Initio Comparative Study of Zincblende and Wurtzite ZnO

By employing the first-principles pseudopotential plane-wave method, the physical properties of zincblende ZnO are investigated in comparison with those of the common wurtzite structure. Zincblende ZnO is predicted to be a direct gap semiconductor. Compared to the wurtzite structure, the zincblende ZnO is characterized by smaller bandgap and pressure coefficient, larger electron effective mass, increasing static dielectric constants and more covalent bonding. Furthermore, the optical properties including dielectric function and energy loss function of zincblende ZnO were obtained and analysed with some features. These aspects reveal promising applications of zincblende ZnO in optoelectronic devices.