基于激光雷达的移动机器人动态障碍检测

动态环境下运动物体的检测是移动机器人研究的难点问题之一。以未知环境为研究背景,提出了一种基于激光雷达的自主动态障碍检测方法。通过k-近邻方法对激光雷达测距数据进行了空间障碍聚类,在此基础上分析了聚类障碍的特征参数,例如区域、质心,利用聚类障碍数据的时间关联性分析并确定了障碍的类型,并采用模糊地图匹配的策略实现了地图匹配和更新。在所研制的移动机器人上进行了实验,实验结果验证了方法的有效性。     

基于深度聚类的目标细粒度分类方法北大核心CSCD

为提高光电系统对弱小目标的识别和分类能力,降低算法对硬件平台和数据的依赖,提出一种无监督分类方法−基于目标深度特征聚类的细粒度分类方法。该方法通过轮廓、颜色、对比度等浅层特征提取提示目标,经超分辨处理后,利用卷积神经网络对目标的深层特征进行编码,进一步采用基于注意机制的主成分分析方法进行降维生成表征矩阵,最后利用聚类的方式实现目标细粒度分类。实验验证了基于不同神经网络的深度聚类方法在不同数据集上的分类性能,其中采用ResNet-34聚类方法在CIFAR-10测试集上细粒度分类性能达92.71%,结果表明,基于深度聚类的目标细粒度方法能够取得与强监督学习方法相当的目标分类效果。此外,还可以根据不同簇数和聚类等级的选择实现不同细粒度的分类效果。     

基于SOM和PSO的云计算异构资源聚类MPI并行算法

针对云计算环境下大量用户请求同时到来造成的短暂峰值,使得用户的QOS服务需求不能得到有效保证,设计了一种基于MPI并行计算模型和SOM的异构资源聚类方法;首先,设计了一种改进的MPI的树状层次结构模型,然后,定义了基于SOM自组织映射的资源聚类算法,为了提高资源聚类精度,将PSO算法用于SOM的参数优化中,使得SOM在初始时刻就具有一个较好的连接结构;最后,为了充分满足用户请求的QOS需求,将MPI树状层次结构与基于PSO的SOM资源聚类算法相结合,并提出了具体的基于MPI的SOM资源聚类算法;为了验证文中方法,在Matlab仿真环境中进行测试,实验结果表明文中方法聚类精度为100%,且与其它方法比较,具有较高的聚类精度和较少的执行时间,是一种云计算环境下的可行资源聚类方法。     

基于AR模型的人体脉象信号模糊聚类研究

根据一种新的模糊聚类方法－F－PFSR（Fuzzy Pseudo F-Statistic Ratio)聚类法,对人体脉搏声信号（脉象信号）进行了聚类识别研究。首先对脉搏声信号作8阶AR模型拟合,模型系数构成信号的特征集,其次采用K－L变换对特征集进行了压缩,最后对临床实测脉象信号进行了聚类分析。实验结果表明,本文的聚类方法是可行和有效的。     

采用时序多谱段信号分析的空间目标运动状态辨识EI北大核心CSCD

为表征在轨卫星的自旋稳定、三轴稳定和"翻滚"三种运动状态,提出了一种基于可见光时序多谱段信号分析的目标运动状态辨识方法,分析了目标运动状态与观测星探测视场内时变的目标表面材料间的对应关系,以及材料属性/种类与时序双色比聚类信息之间的关联性。提出了基于时序双色比特征高斯混合聚类的目标表面材料种类判别算法以及目标运动状态辨识算法。综合考虑卫星的背景特性、材料特性、结构特性、轨道特性,对三种运动状态卫星的多谱段信号进行了数学仿真,对目标运动状态辨识算法进行了验证,证明了所提出算法的有效性。     

采用时序多谱段信号分析的空间目标运动状态辨识

为表征在轨卫星的自旋稳定、三轴稳定和"翻滚"三种运动状态,提出了一种基于可见光时序多谱段信号分析的目标运动状态辨识方法,分析了目标运动状态与观测星探测视场内时变的目标表面材料间的对应关系,以及材料属性/种类与时序双色比聚类信息之间的关联性。提出了基于时序双色比特征高斯混合聚类的目标表面材料种类判别算法以及目标运动状态辨识算法。综合考虑卫星的背景特性、材料特性、结构特性、轨道特性,对三种运动状态卫星的多谱段信号进行了数学仿真,对目标运动状态辨识算法进行了验证,证明了所提出算法的有效性。     

基于鲁棒模糊聚类的混沌时间序列预测

采用一种基于鲁棒模糊聚类算法的模糊辨识方法,通过引入局部划分关联度因子,增强了系统辨识的抗干扰能力,提高了系统辨识的鲁棒性.首先用最近邻模糊聚类法划分初始输入空间,得到模糊规则数及初始聚类中心;然后用鲁棒模糊聚类算法求解并优化模糊隶属度和聚类中心,建立高精度的T-S模糊模型;最后利用最小二乘法辨识模型的初始结论参数,进一步利用带遗忘因子的递推最小二乘法优化结论参数.采用该方法对Mackey-Glass混沌时间序列进行建模和预测,仿真结果表明利用本方法可以进行准确建模和预测,验证了本方法的鲁棒性、有效性和实 关键词： 最近邻模糊聚类 鲁棒模糊聚类 混沌时间序列 最小二乘法     

基于聚类技术的三维舰船模型特征库研究

存贮目标所有的视点图像,建立完备的特征库,或者提取能够抵抗视点变化的不变特征,是三维目标识别的常用方法。这两种方案都存在不足:要么特征库规模庞大,识别过程计算量大,识别效率低;要么难以找到鲁棒的识别特征。结合两种方案研究了基于聚类技术建立三维舰船模型特征库的方法。利用仿射传播聚类方法无需事先指定聚类中心的优点,将其应用于两型舰船模型的视点空间聚类。通过提取视点图像的Hu矩特征,进行了仿真实验,给出了聚类结果的有效性分析。     

基于音色单元分布的音乐结构分析

音乐的结构是音乐作品表达作者思想的一种重要形式,也是听众理解音乐作品内涵的有效途径。本文研究了基于音乐特征的音色单元建模方法,研究了在Fisher准则下,根据局部范围音色单元的分布,采用非监督聚类方法分析音乐的结构。实验结果证明了基于离散余弦变换的音色特征,用音色单元分布聚类算法进行音乐结构分析的有效性。      

基于核独立成分分析和聚类中值的水下传感器故障诊断

水下传感器所处环境的开放性以及其长期处于无人值守状态,极易收到环境作用而发生破坏,传统分簇式的分布式故障诊断方法无法有效对其进行故障诊断,因此,提出了一种基于核主成分分析和聚类中值的故障诊断方法。首先,设计了水下传感器节点故障诊断的模型,然后采用核主成分分析方法对节点采集的数据和来自邻居节点发送的数据进行数据降维,得到具有最小属性集的数据集,然后对节点的邻居节点集进行聚类,选出具有最多元素的聚类,并将聚类的中值作为参考数据,将各节点与其对应的参考数据进行比较从而确定节点是否发生故障,最后定义了基于核独立成分分析和聚类中值的传感器节点故障诊断算法。仿真实验证明了文中方法能有效地对水下传感器进行故障诊断,且与其它方法相比,具有误差检测率高和误检率低的优点。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.