点云边界快速精确提取算法

点云边界提取是点云三维重建中极其关键的一步, 现有的边界提取算法大多采用一种 判别准则进行边界点提取,导致提取的效率低或者提取效果不理想。针对上述问题,本文提 出一种快速精确的点云边界提取算法,其包括粗提取与精提取两个步骤。粗提取中对任意点 ,利用Kdtree搜索其近邻点,对该点与其近邻点构成的单位法向量进行叠加,依据叠加后 向量的模长与近邻数的比值粗提取出边界点;精提取中对于粗提取出的边界点,搜索其近邻 点并依据近邻点拟合成平面,再将近邻点投影到该平面上,根据判断点的投影点与近邻点的 投影点连线间的最大夹角精确提取出边界点。使用地面与机载两类不同的点云数据验证本算 法,实验结果表明:本算法均可以准确提取出这两种点云的边界点,同时在提取机载点云边 界上效率提高了6.8倍,在地面点云中提高了2倍。本文算法可用于快 速提取边界点,有利用后续点云重建。     

一种针对大规模场景的点云匹配算法

针对大规模点云匹配时传统算法速度慢和匹配结果不一致的问题,提出一种新的点云匹配方法。该方法首先利用KD树找到点云中深度最小的点并以该点作为种子点,然后通过在深度信息和曲率两个方面做以改进的区域生长分割算法提取出点云上表面区域,并在该区域提取点云边界。最后使用改进的点对特征完成点云匹配算法验证。实验结果表明,相比传统算法,该方法在匹配速度以及匹配结果的一致性方面得到了显著的提升,在处理大规模点云匹配上具有实际应用价值。     

提取桥梁点云的组合滤波算法

在土木桥梁施工场景中，点云数据包含大量植被、地面和桥梁建筑点云。现有滤波算法对桥梁建筑的提取完整度仍存在一些问题，因此提出一种基于组合滤波的桥梁点云提取算法。首先，该算法根据植被点云分布发散这一特征运用分散度法对植被进行粗滤除；其次，基于半径滤波与充分利用颜色与高程特征思想进行半径滤波算法的改进，对剩余植被点云进行精细滤除；最后，利用法向滤波模型对地面点云进行滤除。实验结果表明，所提算法提取桥梁点云的完整率为99.3%，误差为0.73%，对比现有滤波算法，可更完整地提取桥梁点云，准确率更高。     

改进的SUSAN角点提取算法

采用了一种改进的SUSAN角点提取算法。SUSAN角点提取算法主要利用了角点周边的纹理分布特性,即在角点的某个区域内的像素灰度与角点的相似性来完成角点的提取。在此理论基础上,研究了一种新的基于SUSAN理论的改进的SUSAN角点提取算法,该算法利用了角点附近像素灰度的纹理特征来完成角点的提取,即通过控制与核心点相似的点的连通性与数量来确定该点是否为角点。并且针对阈值T固定选取的问题,采用了一种自动选取阈值的新方法。为了进一步验证所提取角点的实用性,利用特征点匹配对其进行了匹配验证。并通过仿真实验对其进行了检验。     

基于曲线拟合的棋盘角点提取算法

由于环境及相机拍摄效果的影响,导致对棋盘格进行角点提取时出现许多错误和冗余的角点,为此提出了一种基于曲线拟合的棋盘角点提取算法。该算法是在Harris角点检测算法的基础上,将多项式曲线拟合应用到提取的结果中,更加精确地提取出亚像素角点,实验结果表明该算法是有效可行的。     

一种基于Zernike矩的直线提取算法

提出了一种新颖的基于Zernike矩(ZMs)的直线提取算法。该算法首先是利用ZMs在局部坐标系中计算边缘点所在直线方程，然后通过坐标变换将直线方程变换到图像坐标系中，从而建立了边缘点和所在直线参数之间的一一映射关系，最后对于所求出的直线参数在参数空间对参数单元投票取阈值提取直线。实验表明，该算法速度快、精度高和抗干扰性强。     

一种基于特征点过程的遥感影像道路中心线提取算法

针对现有的道路提取算法提取速率低和完整度低等问题，提出了一种基于特征点过程的遥感影像道路中心线提取算法。根据道路区域的光谱性构建特征点过程，并利用线(表征道路段)连接特征点构成初始的网络结构；根据道路的连接性、弯曲性等特点对网络结构进行约束，同时，根据道路光谱性构建了学生-检验光谱测度约束模型；结合以上模型构建道路提取模型，并设计相关的模拟算法求解提取模型，在最大化后验概率准则下获得最优的道路中心线。以Ikonos, GeoEye-1,Gaofen-2卫星影像为实验对象验证和比较了提出算法和对比算法，利用缓冲区评价法对实验结果进行了定性和定量评价。结果表明，提出算法提取道路中心线的速率和完整度有显著提高，证明了该算法的有效性。     

一种针对民航通信信号的解调算法

针对民航通信信号的调制方式,介绍了该信号的传统解调算法,同时指出了传统算法存在的缺陷。针对传统算法存在的不足,提出了一种新的信号解调算法,即在最小频移键控(MSK)信号解调中,先进行码元同步,进而提取出每一个码元周期内的采样点序列,然后根据采样点序列的特征完成每一个码元的符号映射,从而实现解调。该算法很好地解决了传统算法存在的问题,并且在性能上也优于传统算法。     

基于激光雷达的室内玻璃三维重建算法

针对激光雷达在室内地图重建过程中,扫描不到透明玻璃的问题,文章提出了一种玻璃检测三维重建算法,实现了三维地图中玻璃的重建。该方法将三维激光雷达扫描的点云经过点云滤波、分割、聚类以及运动匹配,提取出感兴趣的透明玻璃上的点云,从而识别出室内场景中的透明玻璃。实验结果显示,该算法能有效地使用激光雷达数据检测玻璃并进行三维地图重建。     

基于单目视觉的无人机障碍探测算法研究

针对低空飞行无人机的避障问题,研究了一种基于单目视觉的障碍物深度提取算法。在无人机前视摄像机获取的图像中,通过Harris角点检测算法提取角点作为特征点,使用归一化互相关算法进行角点的匹配,根据图像序列中特征点间距离的变化和无人机的运动计算障碍物的深度。对用于单个障碍物深度计算方法进行了改进,使用RANSAC算法区分不同深度的障碍物。仿真表明,该算法可以有效发现并区分不同深度的障碍物。     

ITO阻值的精确计算及影响因素

论述了ITO、方块电阻的定义及ITO阻值的精确计算，并结合实际应用讨论了影响ITO阻值的因素，对版图设计和LCD生产的过程控制有一定的借鉴意义。     

Characteristics of surface film on slip-ring in the low atmosphericpressure

The surface him of slip-ring is important for good sliding contact of brush and slip-ring. This film formation is influenced by the brush material, the atmospheric temperature, humidity and atmospheric pressure. The condition of sliding contact and surface film can be estimated by the measurement of contact voltage drops. The contact resistance is classified into constriction resistance and film resistance. From the results of this paper, in the low atmospheric pressure, the oxidized film scarcely grew on the slip-ring surface, so the contact resistance is thought to be generated mainly by the current constriction. Further, it can be found that the resistance in the low atmospheric pressure was only constriction resistance, and that the resistance in the air was composed of the constriction resistance and him resistance. The wear length of the test brushes at reduced atmospheric pressure, depending upon the brush grade, was many times larger than the wear in the air     

提高压电换能器导纳圆测量精度的方法研究

不同压电换能器的动态电阻、电容、电感和静态电阻、电容的值不同,这些参数均可从其对应的导纳圆中得到.分析了导纳圆测量中的两个重要影响因素:A/D转换器的量化误差、测量电阻.为提高导纳圆的测量精度,量化误差不变时不同的压电换能器需选择不同的测量电阻以保证所测量的两路正弦信号有适当的幅值比和相位差.测量电阻的值为压电换能器动态电阻值的0.15～3.5倍时,导纳圆半径的相对误差小于0.5％,测量电阻为动态电阻的0.7倍时导纳圆的相对误差最小.     

ESD对RuO2厚膜电阻阻值的影响

采用静电放电(Electrostatic discharge,ESD)发生器对RuO2厚膜电阻直接放电,研究了电阻阻值变化率与电阻尺寸、阻值和ESD条件的关系。结果表明:厚膜电阻阻值受ESD作用而下降;相同ESD及阻值条件下的阻值变化率随电阻尺寸的增大而减小;相同电阻的阻值变化率随ESD电压的增大而增大;10kΩ左右的厚膜电阻在ESD作用下的阻值变化率最大,阻值变化率随着阻值的减小和增大而呈减小趋势;对10kΩ厚膜电阻反复施加不断增大的ESD电压,除宽度尺寸为0.45mm的电阻阻值在8～10kV之间出现一次回升外,电阻阻值逐步下降。     

Analysis of the Constriction Resistance in an ACF Bond

The standard model for electrical resistance of an anisotropic conducting film (ACF) bond has been analyzed for the case that includes both constriction resistance and a film resistance between the conducting particle and the bond pad. The electrical circuit for the bond resistance is divided into its different geometric regions for analysis. Evidence is give against the prevailing practice of equating the apparent physical area of contact between the conducting particle and the bond pad to the real area of electrical contact. A calculation evaluates the resistance of an ACF bond versus electrical current. This analysis shows that the constriction resistance for the ACF bond can be determined from the slope of the resistance versus current squared plot. Previous calculations for separable contact that extract the constriction resistance from the resistance versus current relationship have been carried out only for conductors that obey the Wiedemann–Franz law. Calculations in this work have extended the results to materials used in ACF bonds. Finally, it is argued that higher than expected contact resistance in anisotropic conducting adhesive bonds is likely due to a high resistivity temperature independent film resistance.     

Electrodepositing amorphous Ni-W alloys for MEMS

The wearing resistance and corrosion resistance of Ni-W alloy films is more excellent than that of Ni film. As a contrast, wearing resistance and corrosion resistance of Ni and NiW films are investigated in this paper. The results show that electrodeposited amorphous Ni-W alloy films have good wearing resistance and excellent corrosion resistance compared with electrodeposited Ni films. Moreover, the Ni-W alloy films still had good properties after heat treatment. The good wearing resistance and corrosion resistance of amorphous Ni-W alloy films are associated with crystal structure. The micro-spinneret is fabricated successfully with amorphous Ni-W alloys by UV-LIGA technology.     

梯形网络等效电阻的计算机辅助分析

本文简要介绍了梯形电阻网络的概念,对梯形电阻网络等效电阻的求解从理论上进行了分析,并应用Visual Basic 6．0编制了梯形电阻网络的等效电阻分析程序,由分析程序可方便求出在R1、R2、R3、R0、n取不同值时梯形网络的等效电阻。同时得出了无穷梯形电阻网络的等效电阻存在一个定值R（N0）等重要结论。     

Optimization of the thermal contact resistance within press pack IGBTs

The research of thermal contact resistance between multi-layers within press pack IGBTs (PP IGBTs) is significant for optimizing the PP IGBTs' thermal resistance to improve reliability, as the thermal contact resistance accounts for approximately 50% of the total thermal resistance of PP IGBTs. In this paper, thermal contact resistance between multi-layers is analysed via a finite element model (FEM) of a single fast recovery diode (FRD) submodule. Most importantly, the influence of temperature and clamping force on the thermal contact resistance is also discussed, and findings are verified by submodule thermal resistance experiments. Based on the FEM and experimental results, nanosilver sintering technology is proposed to fill the gap between the contact interfaces to reduce thermal contact resistance. The fabrication of a sintered single FRD submodule is also investigated in this paper, and the results of the sintered sample indicate that the thermal resistance is reduced by approximately 18.8% compared to a direct contact sample.     

High-Q GaAs varactor diodes

A double epitaxial gallium arsenide tuning diode has been developed for TV varactor tuners. The capacitance variation ratio is 6.0 and is large enough to cover the UHF TV broadcasting band. Diode series resistance is 0.18 Ω (Q = 200) at 470 MHz, and at a capacitance of 9 pF. This resistance is 4.4 times smaller than Si diodes in its mean value. Contribution of each resistance component to the total diode resistance was studied. The result shows that package loss is 0.11 Ω, RF skin-effect resistance is 0.05 Ω, and the undepleted epitaxial layer resistance is 0.048 Ω. Therefore, a diode with a 0.075-Ω (Q = 480) series resistance at 470 MHz could be developed, if package loss and RF skin-effect resistance are improved.     

对负电阻及其应用的研究

负电阻在电路分析、电工学、电子技术中应用广泛，本文通过运算放大器实现了负电阻，画出了负电阻的伏安特性曲线，讨论了负电阻与负电阻的串并联关系，负电阻与正电阻的串并联关系，得出结论：它们的串并联关系遵守串并联法则，遵守欧姆定律。但负电阻的串并联能改变它们的正负关系。负电阻既可吸收功率．又可释放功率，但负电阻不能单独作用。