利用~3He中子监测仪对中子管产额进行实验监测

以自主研制的ZFD-1型中子发生器为例,研究了在不同加速高压下D-D型中子管中子的轴向分布情况,以及影响3He中子监测仪探测性能的一些主要因素.根据所得实验数据拟合图线,可对中子管产生中子的轴向分布进行标定.     

空间相机调焦机构的设计与分析

设计了一种用于空间相机的调焦机构,该机构采用步进电机带动的精密步进谐波传动。波发生器由椭圆凸轮与套在其上的柔性轴承组成,输出端连接滚珠丝杠将旋转运动转化为直线运动,带动调焦镜沿直线导轨往复运动,其中输出刚轮与绝对式编码器相连,检测调焦移动位移。该机构具有传动比大、精度高、结构紧凑、效率高、运转平稳等特点。针对该机构在空间相机的实际应用,推导出了调焦机构位移与焦面移动的位置关系,并对该调焦机构进行了误差分析,用闭环控制的方式对其精度进行了检测。试验数据表明,该调焦机构传动比为1：70,重复定位精度为2μm,满足空间相机使用要求。     

Simulation of growing GaN in vertical HVPE reactor

The paper reports the setting up of a model of fluid dynamic for GaN HVPE system and the simulation. It is found that when the direction of gravity is opposite to the direction of GaCl flow inlet,there exits a distance at which the uniformity of the deposition is optimal. Here the good uniformity of the deposition is obtained when the distance between the substrate and GaCl inlet is 5 cm. The parameters of gas flow used in growing GaN are also optimized. In addition, the influence of gravity and buoyancy on...     

Determination of the ~(12)C(p, γ)~(13)N reaction rates fromthe ~(12)C(~7Li,~6He)~(13)N reaction

The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance.     

星载成像光谱仪杂散光检测技术

介绍了星载成像光谱仪杂散光检测技术在国内外的发展状况,阐述了成像光谱仪杂散光的定义、来源和危害,分析了杂散光检测的必要性。通过截止滤光片法、光谱法、谱杂散光系数法、级数透过率法、氧气吸收光谱及参数拟合法、卷积计算法和矩阵修正法等7种光谱仪器杂散光检测方法优缺点的对比,给出了星载成像光谱仪杂散光检测技术的具体要求和发展趋势,认为单一的检测技术很难满足工程研制的实际需要,针对各研制阶段的组合检测技术将是星载成像光谱仪杂光检测的发展方向。     

相位延迟器在四频激光陀螺中的应用研究

介绍了典型相位延迟器1／4波片和90°相位延迟膜的工作原理,定义了四频激光陀螺输出信号解调信噪比,分析了相位延迟量对其造成的影响,并就此结果进行了MATLAB仿真。从两种相位延迟器的工作原理出发,阐述了温度、入射角、入射光波长等因素对两者相位延迟量的影响。结合激光陀螺在实际应用中的要求,对两者进行了比较,并得出结论：90°相位延迟膜更适合作为四频激光陀螺输出解调系统中的相位延迟器。     

Ab initio investigation of boron nanodevices: conductances of the different geometric conformations

Conductances of different geometric conformations of boron ribbon devices are calculated by the ab initio method. The I-V characteristics of three devices are rather different due to the difference in structure. The current of the hexagonal boron device is the largest and increases nonlinearly. The current of the hybrid hexagon-triangle boron device displays a large low-bias current and saturates at a value of about 5.2 μA. The current of the flat triangular boron flake exhibits a voltage gap at low bias and rises sharply with increasing voltage. The flat triangular boron device can be either conducting or insulating, depending on the field.     

On the number of matchings of graphs formed by a graph operation

Let G be a simple graph. Define R(G) to be the graph obtained from G by adding a new vertex e* corresponding to each edge e = (a,b) of G and by joining each new vertex e* to the end vertices a and b of the edge e corresponding to it. In this paper, we prove that the number of matchings of R(G) is completely determined by the degree sequence of vertices of G.     

向量组的极小生成组

分析了线性相关概念的教学难点.引入了向量组的生成组和极小生成组的概念.由此给出了线性相关和极大线性无关组的刻画.     

Invariants of Multi-Component Ermakov Systems

It is shown that certain multi-component Ermakov systems admit Lewis-Ray-Reid invariants. This extends the result to the two-component Ermakov system.