基于PC机的一种多功能声显微镜及可视化技术的研究

近来研制成功了一种基于ＰＣ机、我们称为“ＴＨＳＡＭＭ”型的多功能声显微镜。在ＰＣ机内插入采样率１ＧＳＰＳ的超高速Ａ／Ｄ卡和信号产生和接收卡,利用软件完成信号检测、处理、显示功能。仪器工作频率为１－１００ＭＨｚ;在检测样品时,同时多层显示Ａ、Ｂ、Ｃ扫描结果。根据声学理论、Ｍａｒｃｈｉｎｇ Ｃｕｂｅ等值面抽取方法和ＯｐｅｎＧＬ技术完成了三维数据的可视化处理,显示样品的内部三维结构。该系统已成功应用于多     

An experimental investigation of high permittivity dielectric resonators for millimeter-wave microstrip components

This paper proposes a new type of high permittivity whispering gallery mode cylindrical dielectric resonators with a geometry which is very suitable for use in microstrip type integrated circuits. These oversized resonators, together with high Q factors and ease of fabrication, are potentially interesting for millimeter wave integrated filters and oscillators. In this paper, we report an experimental investigation of such resonators carried out in Ka band (26.5–40 GHz). Measured results including resonant frequencies and loaded quality factors will be presented. Application to millimeter wave filters will also be demonstrated.     

飞秒脉冲振幅和相位的无干涉条纹重构法测量

对作者所提出的无干涉条纹直接电场重构测量飞秒脉冲的振幅和相位的新方法作出进一步理论分析，并通过实验测量说明该方法的优越性.该方法克服了传统的SPIDER方法的弊病，能得到一组无干涉条纹的图像，排除传统方法必须使用傅里叶变换滤波消除干涉条纹而引进的系统误差，使得该方法能够采用较简便设备且能较准确测量飞秒脉冲强度轮廓和相位.最后给出同一条件下新方法和传统SPIDER方法分别重构的脉冲强度自相关曲线与实验测量结果的比较，以说明新方法的有效性和优越性.     

Tb3+、Yb3+共掺BaGd2ZnO5荧光粉的制备及其近红外量子剪裁研究

采用高温固相法合成了Tb3+、Yb3+共掺杂的BaGd2ZnO5荧光粉。XRD测量数据表明合成的样品为纯相。在Tb3+特征激发(297 nm)下得到了Yb3+的特征发射(977 nm),并且对Tb3+与Yb3+能级图进行分析,证明Tb3+到Yb3+为合作能量传递。测量了不同Yb3+浓度下Tb3+的5D4能级(544 nm)的发光寿命曲线,计算得到Tb3+与Yb3+的能量传递效率和量子效率,最高量子效率为125.5%。Yb3+的发射与硅太阳能电池的吸收匹配,该材料有可能应用于硅太阳能电池以提高其转换效率。     

Spectral Characterization of Nitrogen in Farmland Soil by Laser-Induced Breakdown Spectroscopy

Nitrogen is one of the most important elements in farmland soil, and nitrogen content is one of the evaluation indicators of fertilizers. It is difficult to measure the nitrogen content in farmland soil because the chemical and physical properties of farmland soil are complex. Through the adoption of buffer gases to remove the influence of the nitrogen in air, this paper studied the laser-induced breakdown spectroscopy (LIBS) characteristics of nitrogen in soil to establish a foundation for in situ measurement of nitrogen in farmland soil. Three characteristic spectral lines have been found. Based on the precise controlling of laser power and triggering of delay time between laser generation and spectra collection, we have studied the effects of laser energy on LIBS spectral characteristics and the time evolution characteristics to supply the basis of parameter optimization for the measurement. In addition, we have studied the relationship between nitrogen concentration and LIBS spectral intensity. The results demonstrated that LIBS was an effective measurement method of nitrogen content in farmland soil with simple hardware structure, fast detection, and high precision.     

基于ALOS卫星图像阴影的天津市建筑物高度及分布信息提取

光谱差异是提取建筑物阴影信息的一个重要依据.基于ALOS卫星图像阴影与建筑物高度关系的分析,文章阐述了依据阴影来估算建筑物高度的原理和方法,辅以数据融合的方法,利用多光谱影像中的光谱差异从ALOS全色图像中准确提取阴影信息,从而建立一种基于图像阴影提取城市建筑物高度及分布信息的标准化流程.同时,在天津的城市建筑物高度获取试验中,建筑物高度提取精度的抽样验证率达到87.6%,初步显示出了 ALOS卫星数据在城市建筑物高度测量方面的巨大潜力.     

求任意形状截面无限长直载流螺线管磁场的一种方法

在电磁学中,无限长直载流螺线管的磁场是一个基本与核心的问题,为了得到这一系统的磁场,通常的做法是：先就圆截面情况计算,然后把截面为任意形状无限长直螺线管看成是由无数大大小小的圆截面螺线管叠加而成,由此得到螺线管内的磁场均匀而管外磁场为零的一般结论.这里给出了一种推导截面为任意形状无限长直螺线管内外磁场的直接方法.先计算螺线管表面一窄条的磁场,再算总磁场.这种方法物理图像清楚,数学过程简单,可以在教学中加以应用.     

Effects of an AlN passivation layer on the microstructure and electronic properties of AlGaN/GaN heterostructures

Effects of an AlN passivation layer on the microstructure and electronic properties of AlGaN/GaN heterostructures were investigated by X-ray diffraction and Hall effect measurements. AlN passivation induced an additional compressive stress in an AlGaN barrier layer instead of an additional tensile stress induced by Si₃N₄ passivation. The change of strain after passivation contributes in a relatively small proportion to the variation of the carrier concentration in AlGaN/GaN heterostructures compared with the contribution from passivation of surface traps. The results from Hall effect measurements show that the AlN passivation layer has a better effect on passivation of deep levels than the Si₃N₄ film and also results in a remarkable increase in mobility of the two-dimensional electron gas. PACS 73.40.Kp; 71.55.Eq; 81.65.Rv; 81.05.Ea; 61.05.cp