通信局房工艺要求设计要点

本文结合未来发展方向和工程设计实例,从局址选择、层高分析、光电缆进局、电缆上线井几个方面对通信机房工艺对土建要求的重点问题进行总结归纳。     

基于Cayley-Menger行列式的高光谱遥感图像端元提取方法

提出了一种基于Cayley-Menger行列式的快速端元提取算法.该算法的目标是寻找包含高光谱数据集的最小体积的单形体.与其它基于单形体几何的算法相比,该方法具有诸多优点.首先,Cayley-Manger行列式的引入使得算法可以便捷地利用Hermite矩阵的特点大大加速搜索过程,进而得到一个稳定的最终解.其次,该算法无须对数据进行降维处理,从而可以避免因数据降维而造成的有用信息的丢失.仿真和实际高光谱数据的实验结果表明,所提出的算法在获得准确解的同时,具有非常快的收敛速度.     

方向自适应的星载光子计数激光测高植被冠层高度估算

星载光子计数激光测高系统具有较高的沿轨距离分辨率,能够探测得到植被冠层和地表的连续高程信息。然而星载植被点云的低点云密度和低信噪比,对植被相对冠层高度的估算方法提出了新的要求。本文提出了一种方向自适应的星载光子计数激光测高植被点云冠高估算方法。首先通过寻找点云高程统计直方图中代表冠层和地面位置的极值进行粗去噪,大致得到信号高程所在的范围,并估算出冠层,地面和噪声点云的平均密度以及地表坡度。随后对粗去噪后的点云进行方向自适应的密度聚类精去噪,其邻域的方向为地表坡度,与密度有关的阈值均根据估算出的点云密度自适应的做出调整。在滤波后,结合点云的密度和高程百分比分别找出地面与树冠顶端的初始点,并通过三角网方法(TIN)扩展初始点以进行分类,最终确定地表与树冠顶端的高程。采用ATLAS星载激光测高仪的植被点云对算法进行了验证,结果表明算法能够正确估算植被冠高,十分适用于坡度较大和叶面积指数较低的地区,其中冠顶与地面的高程和机载LIDAR数据高程的决定系数R~2分别为0.99与0.77,均方根误差RMSE为0.28 m与2.6 m。     

Electrical characteristics of schottky barriers on 4H-SiC: The effects of barrier height nonuniformity

Electrical properties, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics, have been measured on a large number of Ti, Ni, and Pt-based Schottky barrier diodes on 4H-SiC epilayers. Various nonideal behaviors are frequently observed, including ideality factors greater than one, anomalously low I-V barrier heights, and excess leakage currents at low forward bias and in reverse bias. The nonidealities are highly nonuniform across individual wafers and from wafer to wafer. We find a pronounced linear correlation between I-V barrier height and ideality factor for each metal, while C-V barrier heights remain constant. Electron beam induced current (EBIC) imaging strongly suggests that the nonidealities result from localized low barrier height patches. These patches are related to discrete crystal defects, which become visible as recombination centers in the EBIC images. Alternative explanations involving generation-recombination current, uniform interfacial layers, and effects related to the periphery are ruled out.     

碱性抛光液中H_2O_2对铜布线CMP的影响

化学机械平坦化(CMP)过程中,抛光液的化学作用对平坦化效果起着不可替代的作用。介绍了碱性抛光液中氧化剂(H2O2)对铜布线CMP的作用:H2O2对铜的强氧化性可以将铜氧化为离子状态,然后在螯合剂的螯合作用下快速去除铜膜;H2O2对铜的钝化作用可以保护凹处铜膜不被快速去除,从而有效降低高低差。此外,还研究了碱性抛光液中不同H2O2浓度对铜的静态腐蚀速率、动态去除速率及铜布线平坦化结果的影响。研究表明:抛光液对铜的静态腐蚀速率随H2O2浓度的增大逐渐降低然后趋于饱和;铜的动态去除速率随H2O2浓度的增大而逐渐降低;抛光液的平坦化能力随H2O2浓度的增大逐渐增强再趋于稳定。     

NiuPt1-uSivGe1-v/Si0.72Ge0.28界面形貌的改善

针对锗硅在形成金属锗硅化物时存在部分应力释放、界面形貌特性变差的问题,提出了在Si0.72Ge0.28上分别外延薄硅(Si)覆盖层和锗硅(Si072Ge0.28)缓冲层的工艺方案.实验结果表明,通过两步快速热退火,两个方案的工艺条件都能形成低阻的NiuPt1-uSitGe1-v和改善NivPt1-uSitGe./Si0.72Ge0.28的界面形貌.但相比较而言,在Si0.72Ge0.28上外延10 nm Si覆盖层的方案能够形成更好的NiuPt1-uSivGe1-t/Si0.72Ge0.28界面形貌.与没有改进的方案相比,该方案形成的肖特基接触更具有更低的肖特基接触势垒高度,更易形成欧姆接触.     

一种雷达阵地优化的新方法

由于雷达所处的阵地环境各种各样,很容易造成测量高度出现误差,现代雷达要提高不同阵地环境下测高精度。文中分析了测高原理,研究了引起测高误差的因素。根据情报类雷达工作特点,提出利用修正补偿数据方法解决不同阵地环境下测高误差问题,建立了实用的数学模型,给出了准确的算法,并应用于不同阵地的雷达。实践结果表明：应用该方法大大提高了雷达测高的准确度,更加精确获得空中情报信息,且具有通用性,操作简单方便,易掌握。     

Electrical characteristics of Pd Schottky contacts on ZnO films

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φ_b) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.     

三线阵云立体探测技术

根据三线阵立体测绘原理,给出了探测云顶高的三线阵卫星影像模拟方法.提出了改进的SIFT匹配算法,并利用该算法结合前方交会法,获得云顶高度信息.通过实验验证了三线阵卫星影像模拟的正确性,探索了一种获取夜间低照度条件下云顶高参数的新途径.最后,针对测高误差来源,详细分析了三线阵立体探测云顶高的测高误差,并针对云移动给出了一种误差纠正方法.     

基于光纤双波干涉的台阶高度在线高精度测量研究

提出一种基于双波干涉的台阶高度光纤在线干涉测量系统。利用光纤光栅(FBG)只反射布拉格波长的特性,使两个波长同时并独立地工作于同一个光纤干涉测量系统中,每个波长的干涉信号分别并同时被探测,将测量量程扩大为半合成波波长。利用反馈电路补偿环境干扰对光纤干涉测量系统的影响,使光纤干涉测量系统适合于在线测量。本光纤干涉测量系统可测量的最大台阶高度达1mm,测量分辨率小于1nm。