InGaAs光纤探测器封装及耦合效率影响因素研究

设计了InGaAs探测器芯片与多模石英光纤的耦合结构,测试了芯片耦合前后的性能变化,并分析了影响耦合效率的因素。结果表明,石英光纤与InGaAs探测器芯片可以较好地耦合。在0．9-1．7um波段,当采用与芯片尺径相当的100um光纤进行无透镜直接耦合时,耦合效率可达30％以上;当采用芯径为500岫的光纤耦合时,耦合效率可达55％以上。多模石英光纤出射端的光强呈高斯分布。随着光纤端面与芯片表面的间距偏差的增加,高斯分布曲线的半宽值增大,光束逐渐发散。芯片与光纤的对准偏差对耦合效率的影响很大,其中对横向偏移量的依赖性最强。     

基于最优控制理论的雷达导引头跟踪速度研究

介绍提高雷达导引头跟踪性能的数学模型及其仿真,给出相应的测试方法.仿真实验结果表明利用kalman输出量形成最佳控制指令进行跟踪能够有效地提高雷达导引头跟踪速度.     

超短环形腔布里渊掺铒光纤激光器

提出了一种超短环形腔布里渊掺铒光纤激光器(BEFL),腔长仅为10m。该BEFL以4m长的普通掺铒光纤(EDF)为激光增益介质,腔外布里渊抽运光和980nm抽运光的注入在掺铒光纤中,分别引入非线性布里渊增益和线性掺铒光纤放大器(EDFA)增益。实验结果表明,BEFL工作在单纵模状态,输出信噪比高(>40dB),抽运阈值低(～20mW),输出功率大(>10mW),且布里渊抽运光不仅决定BEFL的输出波长,更对其抽运阈值和出光功率有重要影响。     

An Investigation of Microstructure and Microhardness of Sn-Cu and Sn-Ag Solders as Functions of Alloy Composition and Cooling Rate

The microstructure and microhardness of Sn-xAg and Sn-xCu solders were investigated as functions of alloy composition and cooling rate. The Ag compositions examined varied from 0.5 wt.% to 3.5 wt.%, while Cu varied from 0.5 wt.% to 2.0 wt.%. Three cooling rates were employed during solidification: 0.02°C/s (furnace cooling), about 10°C/s (air cooling), and 100°C/s or higher (rapid solidification). Sn grain size and orientation were observed by cross-polarization light microscopy and electron-backscattering diffraction (EBSD) techniques. The microhardness was measured to correlate the mechanical properties with alloy compositions and cooling rates. From this study, it was found that both alloy composition and cooling rate can significantly affect the Sn grain size and hardness in Sn-rich solders. The critical factors that affect the microstructure–property relationships of Sn-rich solders are discussed, including grain size, crystal orientation, dendrite cells, twin boundaries, and intermetallic compounds (IMC).     

基于准MMIC技术的12~18GHz宽带VCO

提出了一种基于准MMIC技术的Ku波段宽带压控振荡器.该电路采用MMIC芯片和外加高Q值的超突变结变容管的方式,实现了覆盖整个Ku波段的超宽带的振荡信号输出.通过将MMIC技术与混合集成技术相结合的方法,大大降低了调试难度,更重要的是,克服了通用pHEMT MMIC工艺难于兼容高Q值的变容管对超宽带设计VCO的限制,在相位噪声和调谐频率线性度方面都有较大改善.该方法为微波、毫米波压控振荡器的设计提供了一个新的途径.     

基于主向量分析重建的人脸识别算法研究

提出一种基于主向量分析(PCA)重建的人脸识别方法.传统的特征脸方法是根据PCA投影变换后,利用特征空间的总体散布矩阵最大化的特点进行分类;而本文方法则根据PCA重建误差最小的特点,利用重建误差最小进行人脸的分类.在ORL标准人脸库上的实验结果表明,本文方法优于传统方法,并且具有在增加类别以及增加样本时运算量小的特点,因此具有较好的识别效果及较高的实用性.     

基于MCX314的PCI运动控制卡设计

文中设计了一种基于MCX314的 PCI运动控制卡,其能实现三轴直线、圆弧、位模式的插补运动和四轴位置、速度、加速度控制,并从MCX314控制指令系统、硬件接口电路设计、PCI接口电路设计和驱动程序的开发等方面进行了介绍。该运动控制卡的设计实现了对机电一体化设备的精确控制,降低了设备开发成本,具有一定的应用价值。     

Investigation of Sn Whisker Growth in Electroplated Sn and Sn-Ag as a Function of Plating Variables and Storage Conditions

Sn whiskers are becoming a serious reliability issue in Pb-free electronic packaging applications. Among the numerous Sn whisker mitigation strategies, minor alloying additions to Sn have been proven effective. In this study, several commercial Sn and Sn-Ag baths of low-whisker formulations are evaluated to develop optimum mitigation strategies for electroplated Sn and Sn-Ag. The effects of plating variables and storage conditions, including plating thickness and current density, on Sn whisker growth are investigated for matte Sn, matte Sn-Ag, and bright Sn-Ag electroplated on a Si substrate. Two different storage conditions are applied: an ambient condition (30°C, dry air) and a high-temperature/high-humidity condition (55°C, 85% relative humidity). Scanning electron microscopy is employed to record the Sn whisker growth history of each sample up to 4000 h. Transmission electron microscopy, x-ray diffraction, and focused ion beam techniques are used to understand the microstructure, the formation of intermetallic compounds (IMCs), oxidation, the Sn whisker growth mechanism, and other features. In this study, it is found that whiskers are observed only under ambient conditions for both thin and thick samples regardless of the current density variations for matte Sn. However, whiskers are not observed on Sn-Ag-plated surfaces due to the equiaxed grains and fine Ag₃Sn IMCs located at grain boundaries. In addition, Sn whiskers can be suppressed under the high-temperature/high-humidity conditions due to the random growth of IMCs and the formation of thick oxide layers.     

Synthesis and photoluminescence properties of wash-board belt-like ZnSe nanostructures

Washboard belt-like zinc selenide （ZnSe） nanostructures are successfully prepared by a simple chemical vapor deposi- tion （CVD） technology without catalyst. The phase compositions, morphologies and optical properties of the nanos- tructures are investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high-resolution transmis- sion electron microscopy （HRTEM） and photoluminescence （PL） spectroscop, respectively. A vapor-liquid mecha- nism is proposed for the formation of ZnSe belt-like structures. Strong PL from the ZnSe nanostructure can be tuned from 462 nm to 440 nm with temperature varying from 1000 ℃ to 1200 ℃, and it is demonstrated that the washboard belt-like ZnSe nanostructures have potential applications in optical and sensory nanotechnology. This method is ex- pected to be applied to the synthesis of other II-VI groups or other group＇s semiconducting materials.     

新型预硫化型重整预加氢催化剂的工业应用

根据重整预加氢工业装置及所需催化剂的特点,通过自主研发的器外预硫化工艺及硫化剂配方开发出了新型预硫化型重整预加氢催化剂DZF-1。在国内某炼油厂500 kt/a重整预加氢装置进行工业应用,表明该催化剂具有简化开工程序、可省去干燥脱水过程、节省器内硫化所需的注硫设施、缩短开工时间、减少环境污染及催化剂硫化完全等优点。与氧化型催化剂硫化相比至少节省24 h开工时间,活化开工时催化剂能够逐级释放H_2S,使循环氢中H_2S含量在理想范围内,整个活化开工过程反应器床层最高温升小于15℃。工业运转表明在其他工艺参数相当条件下,与上周期国内某同类型催化剂相比平均反应温度降低10~15℃。