基于光学频率梳的超低噪声微波频率产生

低噪声的微波频率在雷达,长基线干涉仪等领域有重要应用.基于光学频率梳产生的微波信号的相位噪声在1 Hz频偏处低于–100 dBc/Hz,在高频(> 100 kHz)处低于–170 dBc/Hz,是目前所有的微波频率产生技术中噪声最低的.文章介绍了光学频率梳产生微波频率的基本原理,对基于光梳产生的微波频率信号的各类噪声和抑制噪声的技术进行了分析和总结.随后对低噪声的测量方法进行介绍,并展示了几种典型的微波频率产生实验装置和结果.随着光学频率梳和噪声抑制技术的不断提升,基于光梳的极低噪声微波频率源将有更广泛的应用前景和应用领域.     

新一代光谱仪器：Leeman ICP／Echelle

引言自十九世纪中叶火焰光度计面世后,发射光谱便成为一种被普遍采用的分析方法。二十世纪四十年代出现的电弧/火花光电直读光谱仪,提高了分析速度,直至二十世纪七十年代电感耦合等离子体(ICP)激发光源,以其稳定性好、激发温度高,分析浓度范围宽和化学干扰少等优点,开拓了发射光谱分析应用的领域。目前,等离子发射光谱     

钾钠铌酸锶钡晶体作为自泵浦相位共轭镜器件的设计

本文给出了钾钠铌酸锶钡晶体作为自泵浦相位共轭镜器件的设计原理及基本考虑,设计了相应的器件并研究了其基本特性。     

Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer for LiB3O5 crystal

Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer were investigated for LiB3O5 (LBO) substrate. The design was based on the vector method. The thickness of the inserted SiO2 interlayer could be changed in a wide range for the four-layer design with two zeros at 1064 and 532 nm. The coatings without any interlayer and with 0.1 quarter-wave (λ/4), 0.3λ/4, 0.5λ/4 SiO2 interlayer were deposited respectively on LBO by using electron beam evaporation technique. All the prepared coatings with SiO2 interlayer indicated satisfying optical behavior. This expanded our option for the thickness of an interlayer when coating on LBO substrate. The prepared films with SiO2 interlayer showed better adhesion than that without any interlayer. The thickness of the interlayer affected the adhesion, the adhesion for the coating with 0.5λ/4 SiO2 interlayer was not as good as the other two.     

硅钼蓝光度法测定沸石分子筛中的硅

提出沸石分子筛中硅含量测定的硅钼蓝光度法。方法基于盐酸介质中Si（Ⅳ）与钼酸铵形成硅钼黄杂多酸后，用抗坏血酸还原硅钼黄形成硅钼蓝的原理进行硅的测定。本文实验条件下，体系的λmax位于770nm，表观摩尔吸光系数εmax=1.92×10^4L·mol^-1·cm^-1，硅量在0－0.60μg/mL范围内遵守比耳定律。本文提出的新方法已成功地用于某些沸石分子筛中的硅测定。     

伺服台台面与恒温箱间的隔热方法

本文提出了伺服转台台面恒温箱与台面之间的隔热方法，通过理论计算和实验结果证实，隔热效果显著，能够达到理想的技术指标。     

高炉冶炼过程的混沌性解析

根据Grassberger和Procaccia提出的Kolmogorov熵计算方法，以山东莱芜钢铁集团公司1号 高炉和山西临汾钢铁集团公司6号高炉测得的铁水硅含量时间序列为样本，计算了各自的Kol mogorov熵分别为（01453±00151）nats·h-1^-1和（01553±0014 0）nats·h-1^-1，并估计了两座高炉铁水硅含量可预测的时间尺度分别约为6 88和644h.由Kolmogorov熵均为大于零的有限值，定量地说明了这两座高炉 关键词： 混沌 Kolmogorov熵 高炉冶炼过程 铁水硅含量     

ON GENERALIZED LIENARD EQUATION AND THE UNIQUENESS OF LIMIT CYCLES IN GAUSS－TYPE PREDATOR－PREY SYSTEM

ＯＮＧＥＮＥＲＡＬＩＺＥＤＬＩＥＮＡＲＤＥＱＵＡＴＩＯＮＡＮＤＴＨＥＵＮＩＱＵＥＮＥＳＳＯＦＬＩＭＩＴＣＹＣＬＥＳＩＮＧＡＵＳＳ－ＴＹＰＥ　ＰＲＥＤＡＴＯＲ－ＰＲＥＹ　ＳＹＳＴＥＭＳｈａｏＭｉｎｇｈｕａ（邵明华）（ＨａｎｇｚｈｏｕＴｅａｃｈｅｒｓ＇Ｃ...     

Improved Surface Characteristics and Contact Performance of Epitaxial p-AlGaN by a Chemical Treatment Process

The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous peak in the 10 K photoluminescence spectrum is eliminated due to the decrease of surface nitrogen vacancy VN related defective sites, while the surface root-mean-square roughness in atomic force microscopy measurement is decreased from 0.395nm to 0.229nm by such a surface preparation method. Furthermore, the performance of surface contact with Ni/Au bilayer metal fihns is obviously improved with the reduction of the Schottky barrier height of 55meV. The x-ray photoelectron spectroscopy （XPS） results show a notable surface element content change after the treatment which is considered to be the cause of the above-mentioned surface characteristics improvement.