主动声纳恒包络波形设计及其性能分析

为了解决伪随机编码调相信号峰均比过高问题,为主动声纳设计恒包络的伪随机编码MSK调制波形。通过分析MSK信号表达式,得到波形的复包络信号。使用遗传算法优化伪随机序列,降低波形的自相关旁瓣,可减小声纳的虚警概率。通过优化复包络信号的自相关函数旁瓣值和互相关函数值,得到自相关性能和正交性能优良的恒包络波形,可以缓解多部声纳间的同频干扰。通过仿真分析波形的模糊度图可知,波形具有良好的频率分辨率和距离分辨率。该波形设计可以取代峰均比过高的编码调相信号,满足主动声纳对运动目标的探测需求。     

主动声呐恒包络波形设计及其性能分析

为主动声呐设计恒包络的伪随机编码MSK调制波形。通过分析MSK信号表达式,得到波形的复包络信号。使用遗传算法优化伪随机序列,降低波形的自相关旁瓣,可减小声呐的虚警概率。通过优化复包络信号的自相关函数旁瓣值和互相关函数值,得到自相关性能和正交性能优良的恒包络波形,可以缓解多部声呐间的同频干扰。通过仿真分析波形的模糊度图,波形具有良好的频率分辨率和距离分辨率,可以取代峰均比过高的编码调相信号,满足主动声呐对运动目标的探测需求。     

距离无关的高精度混沌激光测距

研究了利用类噪声混沌激光的相关特性实现目标距离的测定方法.数值分析了混沌激光自相关曲线的半峰全宽和旁瓣水平与表征其混沌状态的最大李雅普诺夫指数及关联维数的关系.同时,模拟研究了波形误差对混沌激光测距的影响,并分析了不同混沌态的波形误差的临界值.结果表明,具有窄半峰全宽和低旁瓣水平的自相关曲线的高维混沌激光序列是理想的测距激光,其测量分辨率可达1.5 cm以下,且波形误差容忍度大,测量范围大.在测量范围内,精度与距离无关.     

利用Ce:KNSBN光折变晶体提高光学图像相关模式识别鉴别率

给出了在相干匹配滤波系统中利用Ce:KNSBN光折变晶体非线性特性实现图像边缘增强光学相关模式识别的理论分析和实验结果。实验中自相关峰半最大值宽度降低了75％，自相关峰与互相关峰的强度比增强了近一倍，自相关峰的边瓣强度和互相关峰的强度得到抑制，系统的信噪比和相关鉴别率得到显著提高。     

相位光时域反射计瑞利散射波形特性研究

采用单模光纤后向瑞利散射的一维脉冲响应模型,数值模拟了相位光时域反射计(OTDR)中80 m探测光纤对1550 nm波长的纳秒激光脉冲的瑞利散射波形特性.模拟给出了影响波形的各种物理参数(折射率、激光频率和脉宽等)变化时的相应瑞利散射波形,理论分析得到了这些参数影响瑞利散射波形变化规律:随着光纤折射率逐渐增大,第一峰漂...     

F—P滤波窗在半导体光孤子源中的作用

利用光谱窗滤波法对增益开关半导体激光器输出光脉冲消啁啾进行了理论分析，在线性啁啾近似下得到了啁啾光脉冲经Ｆ－Ｐ后的谱宽表达式，给出了经Ｆ－Ｐ后光脉冲的宽度，波形以及自相关测量时的波形因子与Ｆ－Ｐ参数的关和纱曲线，实验结果与理论分析基本一致。     

相关峰细化的精确时延估计快速算法研究

研究精确计算相关峰的方法,提高时延估计精度,改进传统的CZT算法,计算细化的频谱,降低了标准FFT计算带来的栅栏效应,利用互谱的前后两段计算相关函数的主峰波形,并建立了新的快速变换算法(FICP),相关峰可以任意“插值”而不增加计算量。采用该方法和模型,可以有针对性地利用有限范围频谱,抑制宽带噪声对时延估计的影响,提高相关峰的检测精度。     

基于电光采样的超快脉冲波形参数实验研究

针对NTN技术的脉冲波形参数国家基准已无法完全满足目前超高速电脉冲波形测量和校准的现状,构建了基于电光采样技术的脉冲波形参数测量系统,自主设计并制备了钽酸锂基共面波导结构的高频电光调制器,通过网络分析系统测量得到了其3dB频率响应可达100GHz。以高速光电探测器输出的电脉冲波形作为待测信号,对系统参数进行了详细的分析和优化。在优化完善的基础上,最终实现了对70GHz高速光电探测器输出电脉冲波形的精密测量,获得的波形的上升时间和半峰全宽分别为4.6ps和5.0ps,这将为我国基于电光采样技术脉冲波形参数国家基准的建立和持续提升提供参考。     

利用染料片吸收控制受激布里渊散射功率限幅波形

理论研究了受激布里渊散射过程中功率限幅响应特性.采用高斯型入射脉冲，数值模拟了抽运参数(抽运峰值功率密度、抽运脉冲宽度)，介质参数(增益系数、声子寿命)和结构参数(聚焦透镜焦距、介质池长)等物理参数影响限幅输出波形中剩余峰的特性规律.对如何控制剩余峰进行了理论分析.研究表明，声子寿命较小、增益系数大的布里渊介质光限幅响应较好，声子寿命较大、增益系数小的布里渊介质光限幅响应较差；无法单纯通过控制布里渊介质参数来完全消除剩余峰.实验上采用染料片吸收剩余峰，获得接近平顶的限幅输出波形.     

感应叠加过程行波分析和模拟

 采用变换矩阵为研究工具对感应叠加过程中行波的传播、透射、反射进行了分析，得到了和集中参数分析一致的稳定解，给出了电压随时间变化的细节。建立了3.5 MeV注入器脉冲功率源和感应叠加结构的电路模型，得到的感应腔压模拟波形和实验波形基本一致，结合行波分析法基本解释了腔压波形和Blumlein线输出波形之间较大差异的成因，阴极叠加电压的模拟也反映了实验中主脉冲后的反射波形。     

融合检测机制的鲁棒相关滤波视觉跟踪算法

为了解决相关滤波视觉跟踪算法在复杂场景中产生的跟踪漂移问题, 提出一种融合检测机制的相关滤波跟踪框架。利用时空正则化滤波器作为跟踪器, 同时使用线性核相关滤波器作为检测器。当跟踪器与目标进行相关计算得到的响应图为多个峰值时, 激活检测器, 对多个峰值进行相关匹配, 获得重检测结果; 同时, 使用平均峰值相关能量的滤波器模型更新策略得到更加可靠的检测器, 以达到提高跟踪精度和算法鲁棒性的目的。在OTB2015、Temple color 128和VOT2016数据平台上的实验结果表明, 与近年提出的性能较出色的跟踪算法相比, 本文算法在目标运动模糊、相似背景干扰和光照变化等复杂场景中具有更好的鲁棒性和准确性, 且跟踪精度和成功率上均有提高。     

BP神经网络在光学相关器相关峰识别中的应用

光学相关识别是图像识别的重要方法，有效识别相关器输出平面的相关峰信号是保证光学相关器图像识别准确性的关键。由于激光器输出功率的波动、光学系统本身的误差以及SLM器件本身带来的噪声，采用一般的阈值方法很难达到理想的效果。该文提出对相关器的输出平面进行预处理，充分考虑相关信号的形状信息，提取感兴趣区域(ROI)，采用BP神经网络对输入矢量进行计算，可达到对相关峰信号和噪声的有效分类识别，从而提高了光学相关器识别的可靠性，降低了误判的概率。     

Matched Spatial Filtering by Primitive Reference Patterns and Correlation Diagrams for Shape Invariant Pattern Recognition

In this paper, twelve linear primitive reference patterns are proposed for synthesizing a matched spatial filter, known as a shape invariant filter, which can recognize all patterns with various shapes. Furthermore, reprocessed data, given by correlation between the input object of the system and the reference patterns “correlation diagrams” are introduced for processing peak signals in a digital system. By correlating the diagram from the input object with the standard diagrams, the 26 of the alphabet letters were recognized in the experiment. Moreover, feasibility of the rotational invariance of the filter was suggested by the computer simulation.     

基于投票加权累积度量的模板匹配算法

从点集相关性的角度提出了一种新的模板边缘图像匹配度量——投票加权累积度量(WVAM),在该度量中融入了抗几何畸变以及抗杂点与相似区域干扰的机制,能够实现异源情况下模板边缘图像的匹配定位。为了进一步提高WVAM匹配的单相关峰特性,转换点的坐标投票为局部结构信息投票,形成了融入局部结构相似性的投票加权累积度量(LSS-WVAM),该度量能够表征模板边缘图像与待匹配区域的整体结构相似性,更具有稳健性。在仿真实验中利用全局与局部度量信噪比作为评价指标,证明了WVAM具有比LTS-HD(Least trimmed square Hausdorff distance)更好的全局单峰与局部梯度特性。与WVAM相比,LSS-WVAM在全局和局部性能上约提高30%和4%。     

点源信标相关哈特曼-夏克波前传感器光斑偏移测量误差分析

在基于哈特曼-夏克波前传感器(SH-WFS)的自适应光学系统中,通常采用质心算法探测点源信标的子孔径光斑偏移量.然而质心算法探测精度受到诸如减阈值等因素的影响,在低信噪比(SNR )时不能准确估计光斑质心位置,而相关哈特曼算法不需要减阈值,具有更好的鲁棒性.本文在介绍相关SH-WFS基本原理的基础上,通过建立基于点源信标探测的相关SH-WFS算法的随机噪声模型,推导了光斑偏移测量误差表达式,系统分析了光子噪声、CCD读出噪声、背景光子噪声等因素对相关SH-WFS测量误差的影响.并进行了数值仿真及实验,仿真 关键词： 相关哈特曼-夏克波前传感器 相关哈特曼算法 质心算法 测量误差     

One-dimensional DOSY.

A new NMR experiment for correlating diffusion coefficients and chemical shifts is presented. This experiment provides the same information as the conventional DOSY experiment, but only requires a single dimension because a nonuniform magnetic field gradient is used to encode the diffusion information into the lineshapes of the peaks in the chemical shift dimension. By fitting the resulting lineshapes, the diffusion coefficient for each peak in the spectrum can be extracted. Using this experiment, a qualitative DOSY spectrum can be generated using the results from a single one-dimensional experiment. Quantitative results can be determined with the use of reference experiments.     

Scattering noise and measurement artifacts in a single-shot cross-correlator and their suppression

We studied the optical scattering noise, measurement artifacts, and their suppression in single-shot measurements of prepulse contrast. The measurement noise due to air scattering and the two kinds of measurement artifacts resulting from multiple reflections of the generated correlation signal and correlation between the pulse under test and the internally reflected sampling pulse were experimentally explored. The scattering noise and measurement artifacts significantly degrade the measurement fidelity. We demonstrate the clean measurement of prepulse contrast in a single-shot cross-correlator by attenuating the main peak of the correlation beam with a dot mirror and designing the correlating process based on a periodically-poled lithium niobate crystal embedded in an unpoled wafer. The standard time-scanning measurements of pulse contrast are also performed to confirm the experimental results of our single-shot measurement.     

基于紫外吸收的烟气中NO和NO2成分浓度的同时测量

利用高分辨率光栅单色仪测量到的不同浓度的NO和NO2混合气体综合紫外吸收光学厚度,将光学厚度中的快变离散吸收与NO浓度相关,将慢变连续吸收与NO2浓度相关,同时反演NO和NO2的摩尔浓度。研究结果表明:(1)当气体总压接近一个大气压时,NO2反映出很强的转换为N2O4的倾向,转化率R最大值约为22.5%,远大于低气压下的R值,导致NO2吸收截面主要取决于N2O4的吸收特性,表现为慢变的连续吸收特征;(2)离散吸收截面随NO分压增大产生谱线增宽现象,吸收截面在增宽区域的积分值和NO浓度的线性相关性优于吸收截面峰值。测量和反演结果表明:当NO2分压在17～100Pa范围变化时,NO2摩尔浓度反演的平均相对误差为11.7%。当NO分压在63.8～181.62Pa范围变化时,基于积分法的NO浓度反演的最大相对误差为16.9%,平均相对误差为9.6%,而基于峰值法的NO浓度反演的最大相对误差为38.2%,平均相对误差为14.4%。因此,积分法反演较峰值反演具有更好的线性度和更高的精确度。利用上述测量技术,采用相对简单的测试装备,实现了NO和NO2多种成分浓度的同时测量。     

A novel image encryption scheme based on improved hyperchaotic sequences

This paper proposes a novel image encryption scheme based on the improved hyperchaotic sequences. Firstly, the hyperchaotic sequences are modified to generate chaotic key stream that is more suitable for image encryption. Secondly, the final encryption key stream is generated by correlating the chaotic key stream and plaintext which result in both key sensitivity and plaintext sensitivity. The scheme can achieve high key sensitivity and high plaintext sensitivity through only two rounds diffusion operation. The performance test and security analysis has been performed using the histograms, correlation coefficients, information entropy, peak signal-to-noise ratio, key sensitivity analysis, differential analysis, key space analysis, decryption quality and speed analysis. Results suggest that the proposed image encryption scheme is secure and reliable, with high potential to be adopted for the secure image communication applications.     

Correlation of the Radially Integrated Properties of Gas Blast Arc Discharges

Extensive experimental results for the properties of the arc thermal region and local electrical conductances have been reported in the literature for both peak current and current zero phases of orifice air flow arcs. The present paper is concerned with interpreting these results in terms of boundary layer integral analysis concepts. "Characteristic area" and "shape factor" values are presented for orifice flow arcs and methods of correlating these parameters for different arcing conditions are examined. The results show that within experimental accuracy unique relationships exist between various shape factors and correlation parameters, over a wide range of arcing conditions including the current zero period of an ac waveform. The resulting correlation curves, therefore, form the basis for predictive calculations of arc behavior under different gas blast conditions. Finally, an illustration is presented of the manner in which the shape factor correlations may be used for determining the relative importance of various fundamental processes during the current zero period of a gas blast circuit breaker arc.