仿生复眼测量系统中全景图生成的研究

模仿昆虫复眼结构形状,设计了一种仿生复眼测量系统.该系统由七个CCD摄像机按照复眼最小单元排列组成,利用多个DSP处理板对七路视频信号进行同步处理,模拟实现了复眼的功能.与传统的视觉测量系统相比,该系统具有更宽的视场和更高的运动灵敏度.本文利用改进的相关性方法实现视频图像的拼接,生成全景图,并提出了新的方法,较好地消除了因图像局部不齐和图像灰度不一致带来的人为拼接痕迹.     

Multiple-Tone Signals and Detection Probabillities

An analysis technique is presented for multiple-tone signals insystems employing noncoherent integration of a square-law detectoroutput. It is shown how the characteristic function for the teststatistic can be found from the easily determined "coherent"characteristic function defined in the two-dimensional signal space.This result is applied to two detection problems, the detection of multiple-tone signals in Gaussian noise and the detection of a Gaussian signal in multiple-tone plus Gaussian noise interference.The detection curves are compared to an approximation that is often used in practice to estimate performance. It is found that detection performance in the presence of multiple-tone interferences can be significantly different from that in the presence of Gaussian noise alone.     

基于灵敏度的可靠性优化解耦方法

针对航空结构可靠性优化设计问题,提出了一种基于灵敏度的可靠性优化(RBO)解耦方法。首先将高效求解的可靠性灵敏度用于失效概率函数(FPF)的快速构建,其优点在于仅需要一次可靠性分析即可得到失效概率函数的局部近似,克服了常规求解方法中需要多次可靠性分析的缺点;然后将得出的FPF近似代入RBO模型中,将原问题解耦成确定性优化子问题,可用常规优化方法来求解。另外,采用了序列近似优化策略来保证可靠性优化解的正确性。文中给出了复合材料梁和机翼三盒段结构的优化求解算例来说明本文方法的可行性和正确性。     

Sensitivity Study and Optimization of Predictive Systems for Transmission of Video Signals

A method is proposed to optimize the prediction coefficient of a first order predictor. The optimization is with respect to the sensitivity of variations in statistics of the video signal. Given the characteristics of human vision, it has been shown that the DPCM is not worse than the PCM with respect to the sensitivity to variations in the input video signal statistics, but is even better than the PCM. Also, the following point is made clear. If an encoding system is designed with a = as (?Mo) providing the satisfactory quality for the picture with ? = ?Mo, this system will yield picture of better or equal quality as for ? = ?Mo for any other picture.     

数字视频总线在综合航电系统中的应用研究

针对现有机载视频传输系统存在的不足,提出了基于光纤通道FC的数字视频传输系统硬件架构,介绍了现有数字视频传输协议,比较分析了基于光纤通道-音频视频协议FC-AV的视频帧传输模式和基于航电数字视频总线的视频行传输模式下的传输协议设计及其对硬件设计的影响。     

航空电子系统中的FC-AV技术研究

航电系统中的高速数字视频传输技术是一项有待解决的关键技术。FC-AV是FC的一个子集,提供数字音、视频至FC的映射格式,可实现航电系统中传感器和显示器网络的视频传输。本文讨论了FC-AV的层次结构、容器系统、帧头控制协议、简单内容移动架构;并针对航电系统的需求,提出了一种采用FC-AV的视频传输方案。     

基于自适应插值算法的视频图像缩放技术及其FPGA实现

介绍了一种基于自适应插值算法的视频图像缩放技术;重点阐述了采用FPGA芯片实现该算法的原理和具体结构。经实验验证,该算法及其FPGA实现能有效消除传统插值算法在物体边缘部分出现的锯齿,提高图像经过缩放后的视觉质量,同时具有较低的复杂度,适用于实时图像处理。     

基于改进POCET技术的通导一体化信号设计

随着低轨卫星组网的发展,结合我国北斗三号全球卫星导航系统的全面建成,研究兼容北斗的通信导航一体化技术日益迫切。为使卫星上的高功率放大器工作在非线性饱和区,以达到较高的发射功率效率,需要保证合成信号的恒包络特性。考虑北斗导航信号与低轨卫星通信信号频点不同,且待复用信号分量较多,以相位优化恒包络发射(POCET)技术为基础,提出了一种改进的多频点多非独立信号分量恒包络复用技术,对七路信号进行复用,利用罚函数进行目标函数优化得到最优解。通过分析其信号特性,表明该方法具有较高的复用效率,并能有效抑制非独立分量造成的波形畸变,从而实现通信导航一体化信号设计,为未来基于低轨卫星的通信导航一体化波形设计提供了思路。     

Low altitude target model for radar simulation

A simulation model of antenna array signals from a low altitude target is considered. Explicit expressions for statistical and spectral characteristics of the scattered signals are obtained in the Kirchhoff approximation. The model permits to evaluate the efficiency of different techniques of low altitude target tracking. It benefits the comprehension of the influence of multipath propagation on tracking radars     

基于改进POCET技术的通导一体化信号设计

随着低轨卫星组网的发展,结合我国北斗三号全球卫星导航系统的全面建成,研究兼容北斗的通信导航一体化技术日益迫切。为使卫星上的高功率放大器工作在非线性饱和区,以达到较高的发射功率效率,需要保证合成信号的恒包络特性。考虑北斗导航信号与低轨卫星通信信号频点不同,且待复用信号分量较多,以相位优化恒包络发射（POCET）技术为基础,提出了一种改进的多频点多非独立信号分量恒包络复用技术,对七路信号进行复用,利用罚函数进行目标函数优化得到最优解。通过分析其信号特性,表明该方法具有较高的复用效率,并能有效抑制非独立分量造成的波形畸变,从而实现通信导航一体化信号设计,为未来基于低轨卫星的通信导航一体化波形设计提供了思路。     

An adaptive array detector with mismatched signal rejection

An adaptive detection algorithm with a sensibility parameter for rejecting unwanted signals is presented. This algorithm is a simple modification of the generalized likelihood ratio (GLR) detector (or test) for detecting a signal in zero mean Gaussian noise with unknown correlation matrix. Specifically, the adaptive detection algorithm is obtained by introducing an arbitrary positive scalar, which is called the sensitivity parameter, into the GLR detector as a multiplier of an already existing quadratic term. The GLR detector then becomes a special case of this detector for the unity sensitivity parameter. It is shown that the sensitivity parameter controls the degree to which unwanted signals are rejected. From numerical examples, it is demonstrated how the sensitivity parameter can be chosen such that unwanted signals, can be rejected while maintaining acceptable detection loss for slightly mismatched signals. Further insight into previous work on adaptive detection is also given     

Video watermarking synchronization based on profile statistics

A novel temporal synchronization method for video watermarking by matching the profile statistics. The profile statistics, represented by the characteristic parameters such as position mean and variance in the x-and y-directions, of a frame in a video sequence can easily be calculated and sent as side information to the receiver. At the receiving end, temporal attacks such as transposition, dropping, and insertion can be detected by comparing side information and characteristic parameters calculated from the received video. The simulation results show that the proposed method can successfully re-synchronize the attacked video back to the original format with accuracy from 72.41% to 98.15% for various video sequences based on single frame matching. After the voting process, the GOP detection accuracy can be improved to the range of from 96.30% to 100%.     

民航卫星通信网可视通信图像压缩编码方法研究

对民航卫星通信网进行可视通信图像压缩编码方法进行了研究。通过在多媒体计算机上进行模拟实验表明，将视频信息及语音信息压缩为64kbps通过TES卫星网传输方案是可行的。     

基于传动误差设计的弧齿锥齿轮啮合分析

 提出了基于传动误差设计的弧齿锥齿轮啮合质量控制的新概念。首先分析了传动误差所反映的弧齿锥齿轮传动的动态特性、强度性能等众多信息,包括设计重合度、实际重合度、振动激励、边缘接触、载荷齿间分配和齿面印痕相对于误差的敏感性。在此基础上,提出了高重合度传动误差曲线的设计,通过齿面接触路径方向的倾斜,重合度能够高至 2.0～ 3.0,有效地改善了齿轮动态特性,提高了强度。进一步又提出了几何传动误差曲线幅值的设计,结合承载传动误差,使齿轮在不同载荷条件下既能具有高的重合度,又保证了相对低的误差敏感性。其后提出的四阶传动误差曲线的设计,除上述优点外,还改进了齿轮的轻载振动和噪声。最后论述了基于传动误差设计的弧齿锥齿轮的相应制造方法。该研究为高性能弧齿锥齿轮的开发开辟了途径。     

A Method for Selection of an Optimum Communication Link

A method is presented for the selection of a communication system based upon optimization of both frequency-dependent and frequency independent parameters. The indicator of quality used is the effective radiated power per cycle per second of information bandwidth. The method involves consideration of the frequency-dependent qualities such as system temperature and propagation losses independently from the frequency-independent quantities such as modulation loss, signal-to-noise ratio, performance margin, etc. Except for temperature and propagation loss effects, the method is made frequency-independent by considering the spacecraft antenna in terms of area while the ground terminal antenna is treated in terms of gain, thus removing wavelength from the transmission equation. An example is presented of the application of the method to the selection of a system for transmission of wide-band video signals over a satellite to earth link. The example illustrates the exchanges that can be made between the frequency-dependent and -independent quantities in order to arrive at an optimum system.     

基于形态分量分析与阶次跟踪的齿轮箱复合故障诊断方法

针对变转速下齿轮箱复合故障的故障特征提取,提出了基于形态分量分析与阶次跟踪的齿轮箱复合故障诊断方法.该方法根据齿轮箱复合故障振动信号中齿轮和滚动轴承故障成分的形态差异性,先用形态分量分析将其分解为包含齿轮局部故障信息的谐振分量、包含滚动轴承局部故障信息的冲击分量和随机噪声分量,再根据实测转速信号分别对谐振分量和冲击分量进行包络阶次分析,根据各包络阶次谱诊断齿轮箱复合故障.算法仿真和应用实例表明:该方法能有效分离变转速下齿轮和滚动轴承的故障特征,且其故障特征提取效果要优于传统的包络阶次谱方法.      

基于ASM实现视频中物体的定位

对目标进行有效跟踪是目前许多国家获取信息的重要手段,主动形状模型(ASM)主要应用于灰度图像中物体的跟踪与定位,本文针对Koschan等提出的结合金字塔模型的ASM方法作进一步改进,使之应用于视频(本文视频采用MPEG数字视频压缩编码标准)中物体的定位:首先将视频解码还原成图像序列,从人眼视觉特征出发,将RGB颜色模型转换为HSV颜色模型,用色调信息取代灰度信息进行物体定位;并研究图像序列帧之间物体的重合度对提高定位效率的作用.实验结果说明在ASM中使用色调信息能有效地实现视频中的物体定位.     

绕水翼空化非定常动力特性的时频分析

为了解绕水翼附着空化的流体动力特性,用实验方法研究了绕水翼的空化流动现象。实验在空化水洞中完成,采用高速摄像技术观测了不同空化阶段的空穴形态,并测量了水翼所受的升阻力。利用时频分析中的Choi-Williams变换和小波变换对水翼升力信号进行了分析处理,得到了水翼升力信号在不同空化阶段的时频特征。结果表明：在不同的空化阶段,对应于各种不同的空化形态,其流体动力的频谱特性也表现了不同的特点。在没有空化产生时,水翼升力的时频无规则,升力随时间的变化不存在周期性;在片状空化阶段,升力信号变化的频率随着空化数的减小而减小;在云状空化阶段,空穴波动增强,升力信号的周期性更加显著,而此时频率基本不随时间和空化数变化。     

Optimal Digital Beam Splitting for Radar Beacon Systems

Beam splitting for a radar beacon system that scans in azimuth is investigated from a theoretical viewpoint. The video output is quantized into two levels corresponding to a detection and no detection. Further, the antenna sensitivity profile is described by sin ?/?. For this system, a digital method of beam splitting that minimizes angular error is developed. Prior information about the probable location of targets can be included. Both Bayesian and minimax approaches are developed. The minimax estimate of the target azimuth is the average of the angles at which beacon signals are detected. The antenna beam can be interpolated by a factor of 10 when the signal power is 3 dB above the noise and without prior azimuth information The interaction of beam splitting and detection is discussed.     

Multi-resolution Analysis of Density Fluctuation of Coherent Structures About Supersonic Flow over VG

The density field around a vortex generator (VG) in supersonic flow is studied with a nanoparticle-based planar laser scattering (NPLS) method. Based on the calibration, i.e., the density distribution of the supersonic flow around a wedge, the density field of a supersonic VG is measured. According to movement characteristics of coherent structure in VG’s flow fields and the basic concepts of wavelet, the density fluctuating signals and multi-resolution characteristics of density field images are studied. The multi-resolution characteristics of density fluctuation can be analyzed with wavelet transformation of NPLS images. The wavelet approximate coefficients of density fluctuating signals exhibit their characteristics at different scales, and the corresponding detail coefficients show the difference of diverse layer smooth approximation in some way. Based on 2D wavelet decomposition and reconstruction of density field images, the approximate and detail signals at different scales are studied, and the coherent structures at different scales are extracted and analyzed.