摘要：提出了一种可应用于变形监测的基于三维激光点云的隧道断面连续截取方法。该方法分为点云拼接、中轴线提取和断面截取。隧道中轴线的提取通过随机采样一致性算法和最小二乘平差算法完成;断面截取过程先基于隧道轴线信息调整隧道姿态,再对隧道数据采取局部曲面拟合进行,其中引用了限制最小二乘算法和随机采样一致性算法。采用RIEGL VE-400获取的地铁隧道点云数据进行了验证。实验证明了本文方法在三维激光扫描技术的应用方面具有一定的实践意义。

摘要：利用地基三维激光扫描技术所具有的"形测量"特点,结合高精度、高空间分辨率的多时相点云数据,实现地铁隧道连续形变监测数据处理的软件系统。系统的主要功能包括:点云拼接、隧道中轴线拟合、断面连续截取、形变分析以及成果输出等。结合对上海某地铁隧道的多期激光扫描数据的处理,展示软件的主要功能和技术流程,最后对系统的应用前景进行阐述。

摘要：The development of well-defined TiO2 nanoarchitectures is a versatile strategy to achieve high-efficiency photocatalytic *** this study,mesoporous TiO2 nanofibers consisting of oriented nanocrystals were fabricated by a facile vapothermal-assisted topochemical transformation of preformed H-titanate *** vapothermal temperature is crucial in tuning the microstructures and photocatalytic redox properties of the resulting mesoporous TiO2 *** microstructures were characterized with XRD,TEM,XPS and nitrogen adsorption-desorption isotherms,*** photocatalytic activities were evaluated by photocatalytic oxidation of organic pollutant(Rhodamine B as an example)as well as photocatalytic reduction of water to generate hydrogen(H2).The nanofibers vapothermally treated at 150°C showed the highest photocatalytic activity in both oxidation and reduction reactions,2 times higher than that of *** oriented alignment and suitable mesoporosity in the resulting nanofiber architecture were crucial for enhancing photocatalytic *** oriented alignment of anisotropic anatase nanocrystals shall facilitate faster vectorial charge transportation along the nanofibers ***,the suitable mesoporosity and high surface area would also effectively enhance the mass exchange during photocatalytic *** also demonstrate that efficient energy-recovering photocatalytic water treatments could be accomplished by a cascading oxic-anoxic process where the dye is degraded in the oxic phase and hydrogen is generated in the successive anoxic *** study showcases a novel and facile method to fabricate mesoporous TiO2 nanofibers with high photocatalytic activity for both clean energy production and environmental purification.

摘要：窄线宽激光由于其具有单色性好、稳定度高、相干长度长等优点,广泛应用于光电检测领域,包括相干通信、精密测量、光学频率标准、吸收光谱计量以及光与物质相互作用研究等。目前频率稳定的氦氖激光器线宽可以达到MHz量级,分布反馈式(DFB)光纤激光器线宽可达kHz量级,DFB半导体激光器线宽可以达到MHz量级,然而光栅反馈半导体激光器可以实现百kHz量级线宽的输出。为了进一步压窄各类激光器线宽,需要通过反馈控制技术来锁定激光到某一频率参考。该研究将自行设计的超稳腔作为频率参考,实现了632.8 nm外腔半导体激光器(ECDL)线宽的有效压窄。本窄线宽激光产生系统的研制包括超稳腔设计、光路设计、ECDL频率控制以及系统集成。超稳腔采用两镜法布里-珀罗腔(F-P腔)结构,腔体是膨胀系数约为10^-6K^-1的微晶玻璃,腔镜为一对反射率达99.9885%(±0.0035%)的平面镜和凹面镜。为进一步减小外界环境对F-P腔腔长的影响,需要对腔体进行温度控制,本系统采用四片总功率为96 W的半导体制冷片以及水冷散热设计。同时为了降低声音和空气流动对腔模频率的影响,将F-P腔置于真空度为10-5 torr的真空室中;另外为了有效隔振,腔体与真空室用硅橡胶材料隔离。该系统采用的ECDL为德国Toptica公司的DL pro系列激光器,其具有压电陶瓷(PZT)和电流调制两个频率控制端,响应带宽分别为1 kHz和100 MHz。激光器的频率控制采用了Pound-Drever-Hall(PDH)锁频技术,18 MHz的调制频率加载到激光器的电流调制端,通过对F-P腔的反射信号进行解调获得误差信号,通过两路反馈控制,实现了近1 MHz的锁定带宽。通过对系统的不断优化,最后将自由运转状态下约300 kHz的激光线宽压窄到了10 kHz量级,并且系统运行稳定,连续12小时锁定的频率漂移量约为30 MHz。该研究研制的632.8 nm窄线宽激光源不仅可以应用到吸收光谱计量领域,同时也可以在光学面型精密测量领域发挥重要作用。