P2P环境中k最近邻搜索算法研究

在d维空间n个数据点中,k近邻搜索用于查找给定查询点的k个最近邻居.针对k最近邻搜索算法存在的问题,提出了一种基于P2P的k最近邻自适应搜索算法PKA.探讨了度量空间、相似性查询和GHT*规则,定义了高维数据的相似度函数ESF(X,Y),论述了GHT*中插入算法及范围查找算法和搜索算法.在此基础上,具体给出了PKA算法的实现方法,并验证了其正确性.     

散乱数据点的k近邻搜索算法

文章提出了一种基于八叉树的快速k近邻搜索算法，即通过对点集建立包围盒。利用八叉树记录分割过程，从而使近邻点的搜索只局限于采样点所在包围盒及周围的包围盒，并通过剪枝策略，使搜索范围近一步缩小．提高了搜索的速度，并能对噪声点自动删除。     

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。     

基于LSH的高维大数据k近邻搜索算法

局部敏感哈希(LSH)及其变体是解决高维数据k近邻(kNN)搜索的有效算法.但是,随着数据规模的日趋庞大,传统的集中式LSH算法结构已经不能够满足大数据时代的需求.本文分析传统LSH方案的不足之处,拓展AND-OR结构,提出通过索引而不比较原始数据直接实现高维大数据k近邻搜索算法C2SLSH.理论分析和实验证明,C2SLSH在分布式平台下具有稳定的可扩展性,在保证同等精确率的情况下,处理速度大约是现有方法的3倍.     

基于ISS特征点结合改进ICP的点云配准算法北大核心CSCD

针对点云配准时间长、收敛缓慢、对应点匹配易错等缺点,提出一种基于内部形态描述子(ISS)特征点结合改进迭代最近点(ICP)的点云配准算法。首先采用ISS算法进行点云特征提取,并以快速点特征直方图进行特征描述,然后通过采样一致性算法完成点云的初始配准,使两片不同角度点云获得一个相对较好的初始位姿,最后通过k维树近邻搜索法加速对应点对的查找,以提高点云ICP精细配准效率。实验结果表明,与传统配准算法相比,该算法配准精度高,而且执行速度快。     

基于方向矢量曲率估算的点云精简研究

逆向工程获得的大量散乱点云数据,不利于后续曲面重构工作,因此需要进行点云精简。文章利用包围盒法分割原始点云数据,确定K邻域的中心点并搜索K邻域点,基于方向矢量曲率计算方法估算曲率,并采用曲率精简原则精简点云。实例证明,该方法对于大量点云精简有明显效果。     

应用于无人驾驶车的激光雷达雪天去噪方法研究

针对雪花噪声对激光雷达造成误检的问题,提出了一种基于激光雷达反射强度和邻域搜索算法的综合方法对降雪场景采集的激光雷达点云数据进行去噪处理.首先通过自适应方法统计激光雷达点云数据的反射强度分布,计算点云的动态边界阈值.然后,通过分析点云数据反射强度与邻域搜索算法对雪花噪声进行滤除.本方法对园区降雪天气下的实际激光点云数据...     

基于点云边界质心的粗配准方法

点云配准的质量直接影响着三维重建的质量。针对传统K-4PCS耗时长且易出现错误匹配等问题,文中提出一种基于边界质心的点云粗配准方法。通过对点云进行边界提取,既保留点云外表特征,又减少了点云数据的大小,提高了粗配准速度。为了加快边界点的提取速度,使用K-D tree算法完成对k近邻点的搜索。通过配准边界点的质心,减少点云初始距离并增加重叠度,保证了粗配准的精度。实验结果证明,文中方法在粗配准速度和精度方面都优于传统K-4PCS算法,其速度约为传统K-4PCS算法的2倍,平移和旋转精度也比传统K-4PCS高了40%以上。文中所提方法对提高点云粗配准的速度和精度具有一定的参考价值。     

基于稀疏重建和激光实境复制的电力工程建模方法

由于机载激光雷达生成的原始点云数据存在质量较差且离散点多的问题,故难以直接应用于模型重建与电力工程的管理中。因此,文中基于稀疏-稠密算法和点云数据提出了一种电力工程模型重建算法。利用无人机机载激光雷达来获取多帧输电线路点云数据,并使用索引树近邻搜索法对原始点云数据进行坐标转换及离散数据过滤,进而得到重建的点云数据。通过稀疏重建算法对重建后数据中的框架特征加以提取,同时引入稠密算法进行框架填充,完成输电线路内容的重建。经实验测试表明,所提算法的点云提取误差仅为8.42 cm,在对比算法中性能最优。且重建后的模型可应用于电力工程验收、巡检等实际场景中,具有良好的工程意义。     

一种K值自适应和局部搜索的KNN矩阵修复方法

数据在采集和传输过程中由于多种原因会造成矩阵残缺,因此在数据分析之前需要对残缺矩阵进行修复。常见的KNN修复方法 k值选取不合理,且需在整个矩阵中搜索近邻,影响算法的修复效果。在其基础上提出了一种k值自适应的局部KNN矩阵修复方法,合理考虑了k值的选取和近邻项的搜索范围。实验证明了该方法能有效提高矩阵修复的正确率,且算法的时效性有所提高。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.