利用标志点多视图约束实现结构光扫描高精度粗拼接

在采用标志点拼接的结构光扫描系统中,两两相邻视图拼接存在累积误差,导致拼接精度会随拼接次数下降,为此提出一种利用标志点多视图几何约束的高精度拼接方法.首先利用两两视图拼接的方式在扫描过程中构建标志点多视图网络,并利用光束法平差技术优化多视图网络得到高精度全局控制点;在此过程中保存每个视局部坐标系下三维点云,然后将各局部坐标系下点云和全局控制点进行拼接,得到物体表面完整的三维数据.该方法克服了传统拼接过程中累积误差,提高了多视角三维扫描拼接精度;并通过实验证明了所提出算法的有效性.     

Study on the security of the authentication scheme with key recycling in QKD

In quantum key distribution (QKD), the information theoretically secure authentication is necessary to guarantee the integrity and authenticity of the exchanged information over the classical channel. In order to reduce the key consumption, the authentication scheme with key recycling (KR), in which a secret but fixed hash function is used for multiple messages while each tag is encrypted with a one-time pad (OTP), is preferred in QKD. Based on the assumption that the OTP key is perfect, the security of the authentication scheme has be proved. However, the OTP key of authentication in a practical QKD system is not perfect. How the imperfect OTP affects the security of authentication scheme with KR is analyzed thoroughly in this paper. In a practical QKD, the information of the OTP key resulting from QKD is partially leaked to the adversary. Although the information leakage is usually so little to be neglected, it will lead to the increasing degraded security of the authentication scheme as the system runs continuously. Both our theoretical analysis and simulation results demonstrate that the security level of authentication scheme with KR, mainly indicated by its substitution probability, degrades exponentially in the number of rounds and gradually diminishes to zero.     

Relationship between age differences and display parameters on visual comfort for autostereoscopic display

In order to investigate the age differences for viewing autostereoscopic display, we conduct a 3 × 3 × 3 × 4 mixed design with repeated measurement experiment by using three‐dimensional (3D) video clips. Visual comfort is compared between four age groups with a questionnaire. Results of subjective evaluation are compared through the chi‐square test to check if there is a statistical significance between groups with respect to the distribution of number and proportion according to five levels of visual comfort. Then we examine age differences of visual comfort under three key display parameters including crosstalk, ambient illumination, and disparity. The results indicate that the degree of comfort varies considerably among age groups as the parameters of the display system change. Although the seniors feel most discomfort and the children get best experience in general, there is no statistical difference among the subjects when the ambient illumination is medium or disparity is large. So, it is necessary to take account of the age differences in designing 3D display parameters for enhancing visual comfort.     

固结不排水条件下初始应力各向异性结构性土的力学特性

天然土都具有结构性和各向异性,这使得天然土与重塑土的力学性质有很大区别,对其进行研究可为建筑物的设计和施工提供理论依据。对人工制备的初始应力诱发各向异性结构性土样进行了4组不同围压下的固结不排水三轴压缩试验,并建立了初始应力诱发各向异性结构性土的强度准则。结果表明:(1)结构性土在低围压下结构性较为明显,但是在高围压下由于土的结构性被破坏而表现为接近于重塑土的性质。且初始应力诱发各向异性结构性土的结构性强于初始均质结构性土的结构性;(2)初始应力诱发各向异性结构性土的强度包线呈现非线性,且初始应力诱发各向异性结构性土的抗剪强度要略高于初始均质结构性土的抗剪强度。当应力水平低于结构屈服应力时强度包线呈外凸的曲线,当应力水平较高且超过结构屈服应力时强度包线呈直线;(3)与试验结果的对比表明,本文所建议的初始应力各向异性结构性土的强度准则具有良好的适用性。     

溪洛渡水电站水力发电机磁屏蔽问题研究

针对溪洛渡水电站特大型发电机组热稳定试验期间发电机出口和中性点处电流引线临近的钢构件和部件由于漏磁原因引起发热的现象进行分析和研究,制定出电磁屏蔽解决方法并应用于工程实际。采用热成像仪等设备再次监测短路热稳定试验中的热构件温度。实践证明,由于热点温度大幅度降低,确保了溪洛渡水电站770 MW水力发电机组的可靠运行。此电磁屏蔽方法对于特大型水电站发电机组的安装、调试和水力发电机电磁屏蔽的设计具有参考价值。     

城市雨洪综合模拟方法及应用

为综合模拟城市雨洪和分析其对区域内涝的影响,在Open MI异构模型集成平台上动态耦合河网水文水动力模型和城市排水管网水力模型,以上海14个水利分片之一的淀北片为例,建立了淀北片雨洪耦合模型,并应用此模型分析了不同雨潮组合对淀北片区域内涝的影响。淀北片雨洪综合模拟计算结果表明,雨洪综合模拟较真实地反映了感潮河网城市地区的内涝情况,可为城市防洪除涝工作提供参考。     

基于perl维护网络设备本地认证帐号的方法

大型网络运行着许多网络设备,网管员可以采用本地认证方式来登录到这些设备进行相关操作。对于大量设备和帐号信息,可使用Excel表来管理,但这些帐号信息必须同步到相关设备才有意义,若采用手工方式来同步既繁琐又费时。针对这个问题,借助perl脚本程序,基于该Excel表,对这些网络设备的用户帐号进行维护,不失为一种可行方法。     

薛城电站枢纽布置特点

薛城水电站自2007年12月发电以来,已实际运行2年多时间,特别是经过5.12汶川特大地震后,电站经运行检验,工程基本未受到影响,目前运行正常。简要介绍了电站各建筑物的布置特点及施工过程中的优化设计,以期为今后类似水工建筑物的设计提供借鉴和参考。     

频谱细化在电力谐波分析仪中的应用

论文提出一种基于二段式FFT频谱细化算法,利用了存贮空间中保存的前一次计算的数据,增加了实际计算的数据长度,在运算时间增加不多的情况下,提高了FFT的频率分辨率.并利用谐波分析仪上DSP芯片强大的数字信号处理能力对数据进行分析和处理.该算法作为谐波分析方法用于谐波分析仪中,能提高了谐波分析仪的精确度和快速性.     

经济波动与建筑材料价格相关性分析

经济波动与建筑材料价格的波动存在着一定的相关性,往往经济的增长超前于材料价格的上涨,而材料价格的回落却超前于经济的滑落,不同材料由于各自的特性,与经济波动表现了不同程度的相关关系,而且上涨幅度与回落方式也不同。