基于SoPC的捷联系统硬件平台的设计

为了提高激光陀螺捷联系统的硬件平台集成度并减小其功耗,满足微小型导航系统的要求,在基于Xilinx的Virtex-4 FPGA芯片上,通过SoPC方法设计新一代硬件平台。该硬件平台使用FPGA内嵌的PowerPC405硬核处理器作为功能控制与运算中心,并在FPGA逻辑中设计功能全面的IP核来实现数据采集、数字滤波、串口通信和部分导航解算。从而在保证较高的运算速度和精度的同时,达到了预期的效果。     

太赫兹技术在室内无线通信中的应用

该文通过对太赫兹通信相关器件的总结和相关信道特性的分析,调研了近年来国内外相关实验的结果,对重点实验结果做了着重描述,总结出了未来室内无线通信可能的发展方向和亟待解决的问题。太赫兹波段是介于毫米波与远红外的电磁辐射频段。室内无线局域网的高数据率传输要求通信系统运行于更高的频率以获得更大的带宽。太赫兹频率范围未受军事管制,可实现Gbit/s数据率,并且太赫兹频域不像光频受环境噪声干扰那么严重。全固态室温太赫兹器件的研究为太赫兹无线通信系统奠定了基础。已探明适于未来太赫兹室内通信系统运行的大气窗口。基于飞秒激光门控光导天线的太赫兹通信链路实现了太赫兹波载波音频信号的调制和解调。     

The evaluation of speckle contrast with variable speckle generator

Abstract— While laser projection has many advantages, there is a problem with speckle patterns generated as a result of interference of the laser beam and results in bad effects to observers. In 2010, a variable speckle generator, which produces an angular shift of incident light to the screen and generates variable speckle patterns, was suggested. In this study, the performance of a variable speckle generator by using a volume phase holographic beam shaper and scanning mirror was investigated in detail by evaluating both the objective and subjective speckle contrast. The morphology of the speckle pattern was also investigated when the variable speckle generator was activated. With a scanning VPH beam shaper, the objective speckle was effectively reduced because each point of the VPH beam shaper generated different speckle patterns and coherency among each pattern disappeared by using the scan process. On the other hand, subjective speckle was also dramatically reduced by changing the incident angle on the screen, which resulted in generating variable subjective speckle. It was also shown that the speckle reduction rate by using a variable speckle generator did not depend on the coherent length of a laser by evaluating the normalized speckle contrast against the angular shift on the screen.     

Laser‐irradiated zinc oxide thin‐film transistors fabricated by solution processing

Abstract— This study investigates the effects of subjecting zinc oxide (ZnO) thin films to laser irradiation. The optical, structural, and electrical properties of the as‐deposited and laser‐irradiated films at different laser energies were studied. The transmittances without/with laser irradiation showed a net increase from 85 to 92% (@550 nm) for 250‐nm ZnO films, indicating an improvement in sample crystal linity. In addition, laser treatment decreased the ZnO band gap. Composition structure analysis shows that the crystallinity increased when the laser energy increased. Thin‐film transistors (TFTs) with a ZnO active layer were fabricated. The mobility of as‐deposited ZnO TFT devices (0.19 cm²/V‐sec) increased more than 2.5 times for ZnO of unirradiated laser treatment (0.49 cm²/V‐sec).     

SOM‐based projection module for mobile displays

Abstract— The development of a compact, efficient VGA projection module to be embedded in mobile devices is reported. The design incorporates laser/laser diode (LD) light sources, Schlieren optics, and a one‐dimensional diffractive spatial optical modulator (SOM). During development, the optical parameters were determined and the relationships between the parameters to optimize the optical specifications were derived. The resulting optimized specifications enable us to manufacture two types of optical modu les as compact as 13 cc and with as little as 10% speckle contrast ratio.     

In2O3 + xBaO (x = 0.5-5 at.%) - A novel material for trace level detection of NOx in the ambient

Indium oxide (In₂O₃) doped with 0.5-5 at.% of Ba was examined for their response towards trace levels of NO_x in the ambient. Crystallographic phase studies, electrical conductivity and sensor studies for NO_x with cross interference for hydrogen, petroleum gas (PG) and ammonia were carried out. Bulk compositions with x ≤ 1 at.% of Ba exhibited high response towards NO_x with extremely low cross interference for hydrogen, PG and ammonia, offering high selectivity. Thin films of 0.5 at.% Ba doped In₂O₃ were deposited using pulsed laser deposition technique using an excimer laser (KrF) operating at a wavelength of (λ) 248 nm with a fluence of ∼3 J/cm² and pulsed at 10 Hz. Thin film sensors exhibited better response towards 3 ppm NO_x quite reliably and reproducibly and offer the potential to develop NO_x sensors (Threshold limit value of NO₂ and NO is 3 and 25 ppm, respectively).     

光纤束传感器测量轴系扭转振动的研究

介绍了一种运用光纤束传感器结合双条纹编码盘、测量轴系扭振的系统.论述了该测量系统的实现原理、系统构成、采样时间对扭振测量精度的影响,以及系统误差.将该系统在某型号航空设备上进行模拟实验,验证了该测量系统具备高精度、安装方便、抗干扰能力强等优点,对于回转机械的扭振检测和故障诊断具有很好的实用价值.     

Classifying species of individual trees by intensity and structure features derived from airborne laser scanner data

The objective of this study was to identify candidate features derived from airborne laser scanner (ALS) data suitable to discriminate between coniferous and deciduous tree species. Both features related to structure and intensity were considered. The study was conducted on 197 Norway spruce and 180 birch trees (leaves on conditions) in a boreal forest reserve in Norway. The ALS sensor used was capable of recording multiple echoes. The point density was 6.6 m^− 2. Laser echoes located within the vertical projection of the tree crowns, which were assumed to be circular and defined according to field measurements, were attributed to three categories: “first echoes of many”, “single echoes”, or “last echoes of many echoes”. They were denoted FIRST, SINGLE, and LAST, respectively. In tree species classification using ALS data features should be independent of tree heights. We found that many features were dependent on tree height and that this dependency influenced selection of candidate features. When we accounted for this dependency, it was revealed that FIRST and SINGLE echoes were located higher and LAST echoes lower in the birch crowns than in spruce crowns. The intensity features of the FIRST echoes differed more between species than corresponding features of the other echo categories. For the FIRST echoes the intensity values tended to be higher for birch than spruce. When using the various features for species classification, maximum overall classification accuracies of 77% and 73% were obtained for structural and intensity features, respectively. Combining candidate features related to structure and intensity resulted in an overall classification accuracy of 88%.     

微球探针制备工艺的优化

为了解决现有激光微球探针加工技术中存在的探针尖端微球球心偏离针杆中轴线的问题,提出了一个两步法加工策略.以CO2激光光束为热源,对探针针杆尖端进行加热,使针杆尖端受热融化产生微球.然后将带有微球的探针针杆绕其中轴线旋转180°,再使用CO2激光光束辐照带有微球的探针尖端,对尖端微球偏移量进行补偿.实验结果表明:采用“熔球-旋转再熔球”的两步法加工策略,能明显降低探针尖端微球相对于针杆的弯曲程度,缩小探针尖端球形球心和针杆中心线的偏移距离.     

基于传感器的汽车主动安全设计

从汽车主动安全方面进行研究,通过对车辆道路行驶时关键要素的危险状态识别,实现完善汽车主动安全性能.本设计采取自动控制方法,通过研究汽车防碰撞检测和预防以及偏离车道报警,为汽车安全系统提供信息支持,实现车辆主动避免碰撞危险,减少或避免交通事故发生,大大提高汽车行驶主动安全性.所设计汽车主动安全防撞系统主要包括激光防撞测距、激光车道检测、报警警示系统等.