Morphological study of thin films: Simulation and experimental insights using horizontal visibility graph

We studied the morphological nature of various thin films such as silicon carbide (SiC), diamond (C), germanium (Ge), and gallium nitride (GaN) on silicon substrate Si(100) using the pulsed laser deposition (PLD) method and Monte Carlo simulation. We, for the first time, systematically employed the visibility algorithm graph to meticulously study the morphological features of various PLD grown thin films. These thin-film morphologies are investigated using random distribution, Gaussian distribution, patterned heights, etc. The nature of the interfacial height of individual surfaces is examined by a horizontal visibility graph (HVG). It demonstrates that the continuous interfacial height of the silicon carbide, diamond, germanium, and gallium nitride films are attributed to random distribution and Gaussian distribution in thin films. However, discrete peaks are obtained in the brush and step-like morphology of germanium thin films. Further, we have experimentally verified the morphological nature of simulated silicon carbide, diamond, germanium, and gallium nitride thin films were grown on Si(100) substrate by pulsed laser deposition (PLD) at elevated temperature. Various characterization techniques have been used to study the morphological, and electrical properties which confirmed the different nature of the deposited films on the Silicon substrate. Decent hysteresis behavior has been confirmed by current-voltage (IV) measurement in all the four deposited films. The highest current has been measured for GaN at ～60 nA and the lowest current in SiC at ～30 nA level which is quite low comparing with the expected signal level (μA). The HVG technique is suitable to understand surface features of thin films which are substantially advantageous for the energy devices, detectors, optoelectronic devices operating at high temperatures.     

基于GPS和WiFi的室内外定位系统的设计与实现

经济和科技高速发展的中国,基于GPS的定位技术和基于WiFi的定位技术已发展成熟。在有14亿人口的中国,人们的思想观念发生了巨大变化,人口老龄化越来越严重,老人和小孩等弱势群体走失事件频发。因此,借助定位技术缓解这种现象十分必要。借助定位信息,不仅可以缓解老人小孩走失问题,而且可以实现前签到等功能。定位技术的应用范围和发展前景非常广阔。     

大采高综放工作面强动压端头顶板控制技术

为了解决大采高综放工作面回风侧端头顶板控制问题,针对马道头矿8211工作面的地质情况,通过对回风顺槽超前注浆加固,提高超前支护范围和支护强度,并对回风侧端头三角区煤壁和顶板进行化学浆加固的技术方案,有效控制了顺槽超前区围岩变形和工作面回风侧端头三角区煤壁片帮,保证了工作面端头区顶板安全。     

北斗三星无源定位技术

介绍了北斗双星定位系统的特点、功能、系统组成和工作原理,说明了北斗有源定位方式在应用方面的局限性。针对北斗有源定位方式不能无线电静默,和人们对具有无线电隐蔽性的卫星定位的需求,详细介绍一种北斗三星无源定位技术:包括工作原理、实现方法、定位精度分析和目前达到的定位精度。阐述了北斗三星无源定位技术的优点和应用形势。     

GPS技术在有线电视线路测绘中的应用

本文简要介绍了GPS的原理。结合目前我国有线网络管理工作的实际。推广这项技术在有线电视工程线路测绘中的应用。并提出了一些具体的实施步骤及经验。     

嵌入式GPS车载系统定位数据压缩算法的实现

根据嵌入式系统的特征，分析数据压缩模型工作原理，结合GPS定位数据的格式和特点，创造性地提出了嵌入式GPS定位数据的实时压缩的新算法，并通过模拟仿真得到验证，效果显著。     

实时GPS定位中的自适应故障检测

给出了一种GPS卡尔曼滤波的自适应方案,该方案能根据GPS导航中变化的动态来估计协方差.当增强卡尔曼滤波器时,方案可得到更精确的定位修正.此外,也可将此估计方法用于完整监测,以增强故障检测的阈值选择.采用模拟数据验证了提出方法的正确性.     

美国GPS系统抗干扰技术的现状与发展

对美国GPS系统抗干扰技术的现状与发展趋势进行了探讨和研究．分析了自适应调零、频域、时域滤波的GPS接收天线，接收P(Y)码，接收M码，伪卫星，GPS与INS组合等先进GPS抗干扰技术的发展及特点．介绍了美国最新研制的GPS接收机及抗干扰设备。概述了美国新一代GPS星座发展计划及对提高未来GPS抗干扰性能的影响．综合探讨了GPS抗干扰技术的发展趋势．     

GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

GPS高程在测量中的应用

通过对高程拟合方案的建立 ,详细分析了拟合点分布不同和一次、二次函数拟合对高程拟合带来的影响 ,并提出了提高水准拟合精度的一些有效措施 ,最后就拟合的精度作了适当的分析