中子单粒子效应研究现状及进展

回顾了中子单粒子研究的国内外发展情况,介绍了近几年西北核技术研究所在西安脉冲堆开展的低能中子单粒子效应研究进展。比较了稳态与脉冲工况下中子单粒子效应的异同性;分析了含有SRAM结构器件随着特征尺寸的减小,中子单粒子效应敏感性加剧的物理机制。分析认为目前中子单粒子效应已成为小尺寸大规模互补金属氧化物半导体器件的主要中子效应表现;中子辐射效应研究中,除了位移损伤效应以外还必需重视由中子电离造成的中子单粒子效应。     

Realizing variable contrast technique in MRC measuring target using integrating sphere

In order to realize variable contrast in the minimum resolvable contrast (MRC) measuring target in the visible imaging system, a novel technique is presented, which adopts two integrating spheres to illuminate two sides of target respectively and the different contrasts can be achieved by regulating the luminance in two integrating spheres. This technique can make the contrast be regulated more conveniently. Based on this technique, the MRC measuring device is developed. This device can be used in all kinds of trial fields. The expanded uncertainty of measuring MRC is less than 3%.     

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。     

Design and experimental research of angle self-compensation setup for BSDF measurement

When using a single reference to measure the bi-directional scattering distribution function （BSDF）, the incident zenith angle of the tested sample must be identical to that of the reference. In order to get the hemisphere space scattering characteristic on the sample surface, usually a motor drives the sample tilting, then the incident zenith angle is changed and needs to be the compensated by another motor. We mathematically deduce the expression of compensation angle when the incident zenith angle is changed by the rotation of motor. After the incident angle is compensated, the scattering zenith angle and azimuth angle are deduced too. The uncertainty of the system is 0.75%. Scattering measurements are performed on copper sample with visible light under different temperatures.     

Stray light suppression in BRDF measurement infrared optical system

A set of system based on personal computer for the bi-directional reflectance distribution function (BRDF) measurement was developed, whose laser wavelengths cover 0.6328, 1.34, 3.39, and 10.6 μm from visible to infrared. Stray light in BRDF measurement system was analyzed. It can be reduced and suppressed by the design of the system light path in BRDF measurement system, the choice of the measuring scheme, the processing to the optoelectronic signal, and the radiation control of the optical components and mechanical equipments. So the minimum measurable value of BRDF is less than 10-5/sr.     

健康和糖尿病大鼠红细胞荧光光谱非线性程度差异

糖尿病是严重威胁人类健康的慢性疾病之一,对其进行早期诊断尤为重要。由于糖尿病病程的发展会对血液中红细胞的结构和功能产生影响,因此利用红细胞荧光光谱在特征峰位和峰高等方面的差异性,可以对糖尿病状态进行诊断。在选取光谱信号的差异性作为特征向量方面,可以采用荧光光谱信号的非线性程度作为特征向量。为更好地描述荧光光谱信号的非线性,采用延迟向量方差(DVV)法描述信号的非线性程度。采用迭代幅度匹配傅里叶变换(IAAFT)法产生原始数据的替代数据,通过比较原始数据与替代数据的延迟向量方差确定原始数据的非线性特征。以原始数据目标方差为横坐标,以其替代数据目标方差为纵坐标,画出延迟向量方差散布图。健康大鼠红细胞荧光光谱的延迟向量方差散布图与其对角线几乎重合,说明健康大鼠红细胞荧光光谱非线性程度较低;而糖尿病大鼠红细胞荧光光谱的延迟向量方差散布图偏离其对角线,说明糖尿病大鼠红细胞荧光光谱非线性程度较高,并且氨基酸对应的光谱段非线性程度更深。据此,提出健康和糖尿病荧光光谱之间的非线性差异程度可以作为糖尿病早期诊断的特征之一。     

样本空间排序法评价瞬时辐照无失效数据研究

为降低瞬时辐照抽样检验中现行经典非参数法的评价结果的保守性,引入样本空间排序法,从理论和实例两方面计算无失效数据的生存概率置信下限,并与经典非参数法进行对比。结果是,样本空间排序法不仅提高生存概率的置信下限,还增大这些置信限所对应的剂量率范围。该研究结果表明样本空间排序法提高了数据利用率,降低了保守性,可减少试验成本。     

双向反射率测量中锁相放大器的设计

均匀材料表面除镜反射方向的其他散射方向光辐射强度都较微弱.采用信号参量估计中行的最大似然估计,应用相关检测技术,利用被测信号与背景噪声不相关特性,设计了适于微弱光电信号检测的装置--锁相放大器.对金刚砂反射天顶角-55°～55°范围测量的实验结果与双向反射率(BRDF)模型比较显示,在可见光0.632 8 μm波段,误差为3.43%;近红外1.34 μm波段,误差只有0.01%.该锁相放大器适用于材料表面双向反射率的测量.     

基于支持向量机回归的LIBS飞灰含碳量定量分析

采用激光诱导击穿光谱(LIBS)技术对配制的飞灰样品进行实验分析,应用支持向量机回归(SVR)模型对飞灰的含碳量进行预测。运用网格搜索法分别对径向基(RBF)核函数和多项式函数的结构参数进行寻优,然后分别建立基于内标元素特征光谱、全谱和主要元素特征光谱的SVR模型。研究表明,基于RBF和多项式核函数的SVR模型在理想的结构参数下可以取得相同的分析精度,但RBF能较快地完成模型优化并且不易出现欠拟合的现象。基于内标元素特征光谱的SVR模型的分析精度与内标法相当,基于全谱的SVR模型出现明显的过拟合现象。基于主要元素特征光谱的SVR模型的回归系数为0.986,校正均方根误差为1.79%,预测均方根误差为2.57%,说明该模型可以有效避免欠拟合和过拟合。     

基区表面势对栅控横向PNP晶体管中子位移损伤的影响

通过在常规横向PNP晶体管基区表面氧化层上淀积栅电极,制作了可以利用栅极偏置调制基区表面势的栅控横向PNP晶体管。对无栅极偏置电压和偏置电压分别为-10V和10V的栅控横向PNP晶体管,在西安脉冲反应堆上开展注量为2×1012,4×1012,6×1012,8×1012,1×1013 cm-2的中子辐照实验,研究基区表面势的增加和降低对栅控横向PNP晶体管中子位移损伤退化特性的影响。研究结果表明,基区表面势的增加引起栅控横向PNP晶体管共射极电流增益倒数的变化量随辐照中子注量的退化速率增加,基区表面势的降低对位移损伤退化速率无明显影响。