一种使用灰度梯度提取合成孔径雷达图像灰度边界的方法

在合成孔径雷达数字成像的多级成像和合成孔径雷达图像的许多应用中,往往需要提取合成孔径雷达图像的灰度边界特征。人们对于由可见光或红外成像系统获得的普通图像的灰度边界提取已经进行了很多研究。使用灰度梯度提取普通图像的灰度边界非常有效,得到了广泛的应用.但由于在合成孔径雷达图像中存在严重的相干斑噪声,有人认为使用灰度梯度提取合成孔径雷达图像的灰度边界得不到好的结果。在本文中,我们考虑到合成孔径雷达图像的特性,给出了一种比较理想的提取合成孔径雷达图像的灰度边界的方法。这种方法使用相对平均灰度梯度,并且把检测与跟踪结合起来。     

What do we want specifically from the cell phone? An age related study

This study investigated the evolution of specific cell phone feature preferences among high school, undergraduate and graduate college students in Finland. Following the relevant literature review, the paper analyzed the responses of 118 high school, 268 undergraduate and 84 graduate students from educational institutions located in the metropolitan area of Tampere, Finland. The results indicate that the students in Finland appreciate the specific feature “clock”, “phone”, “high battery life”, “alarm”, and “calendar” as very important, and the specific features “TV connectivity”, “joystick”, “live TV”, “Twitter”, and “small screen size” as unimportant features. There were also significant differences in the specific feature preferences between the students between high school, undergraduate and graduate students. In addition there were differences in the way the respondents conceptualize the specific feature preferences of the cell phone. The paper concludes with a discussion regarding the academic and managerial implications.     

纹理分析窗大小的高斯-马尔可夫随机场模型估计方法

在纹理分析中,窗口大小的选择对所提取特征的有效性及计算速度等有很大影响。文中利用高斯－马尔可夫随机场（ＧＭＲＦ）模型对纹理进行描述,采用最小平方误差估计获取纹理图像的随机场参数,并证明了这种估计的一致性。针对估计式在某些情况下可能无解,对该式作了改进,使其在实际应用中总能有解。利用估计的一致性,提出了一种系统估计纹理分析窗口大小的方法,实验表明了这种方法的有效性。     

基于分水岭分割和尺度不变特征点的多目标全自主跟踪算法

该文针对多目标的鲁棒跟踪问题,设计了一种基于图像分水岭分割和尺度不变特征变换(SIFT)特征点的多目标全自主跟踪算法。为规避图像平坦区域,提出在原图上叠加规则坡度图的思想,并在浮点域进行一定尺度高斯模糊处理,将区域极小值点作为种子点完成分水岭分割,并将极值点作为目标特征点,通过前后帧分水岭映射生成特征点短时轨迹,自动检测运动目标。之后依据目标所处状态(是否发生遮挡)和分水岭分割图建立、更新目标SIFT特征池,结合分水岭映射、SIFT特征池匹配完成对目标的鲁棒跟踪。实验结果表明,该算法能有效完成视频中多目标的持续跟踪,并对目标遮挡有较好的鲁棒性。     

分布式压缩感知实现联合信道估计的方法

针对无线通信中多个信道之间存在相关性的现象,本文研究了基于压缩感知的联合信道估计。通过选取多个节点与簇头之间的信道为研究背景,本文建立了多信道下的联合信道估计模型,推导了判决门限与信噪比之间的关系,提出了基于门限自适应-正交匹配追踪联合重构技术(TA-SOMP)的信道估计算法,并进行了相应的仿真实验。仿真结果表明:与经典的正交匹配追踪(OMP)算法相比,本文算法所重构的信道与原始信道之间的均方误差(MSE)更小,传输信号误比特率(BER)更低;在相同信噪比环境下,TA-SOMP算法所需导频数量更少,频带利用率更高。      

Stereo matching cost computation based on nonsubsampled contourlet transform

A new matching cost computation method based on nonsubsampled contourlet transform (NSCT) for stereo image matching is proposed in this paper. Firstly, stereo image is decomposed into high frequency sub-band images at different scales and along different directions by NSCT. Secondly, by utilizing coefficients in high frequency domain and grayscales in RGB color space, the computation model of weighted matching cost between two pixels is designed based on the gestalt laws. Lastly, two types of experiments are carried out with standard stereopairs in the Middlebury benchmark. One of the experiments is to confirm optimum values of NSCT scale and direction parameters, and the other is to compare proposed matching cost with nine known matching costs. Experimental results show that the optimum values of scale and direction parameters are respectively 2 and 3, and the matching accuracy of the proposed matching cost is twice higher than that of traditional NCC cost.     

适用于GSM900/GPS系统的双频段低噪声放大器设计

基于SMIC 0.18μm CMOS工艺,设计了一个适用于GSM900和GPS系统的并行式双频段低噪声放大器.电路采用1.8V电源供电,考虑到两级之间的匹配特性,运用了级间电感技术.介绍了输入、输出匹配电路的具体设计方法.运用Cadence中的SpectreRF软件进行仿真,结果表明,增益特性S21在两个频段均大于10...     

一种面向信号分类的匹配追踪新方法

匹配追踪(MP)的主要策略是通过每次迭代时选择一个局部最优解,从而逐步逼近原始信号。然而传统的MP系列算法进行原子匹配时,各类原子集间存在交集,从而影响了原子的表示能力以及相应的分类效果。基于此,该文提出一种适用于信号监督分类的匹配追踪新算法。其原子挑选的准则为：同类信号采用相同的原子集匹配,获取相同的类内表示结构;异类信号选择不同的原子集匹配,从而增强信号的类间差异。示例分析表明,使原子集间相互独立,能够减少异类信号间的共性因素,强化信号间的区分度,从而有利于提升分类识别效果。通过在标准图像库和实测雷达辐射源信号集上的实验表明,较之传统的MP系列方法,所提算法对噪声和遮挡具有更强的鲁棒性。     

Feature Selection with Data Field

A new feature selection method is proposed for high-dimensional data clustering on the basis of data field. With the potential entropy to evaluate the importance of feature subsets, features are filtered by removing unimportant features or noises from the original datasets. Experiments show that the proposed method can sharply reduce the number of dimensions and effectively improve the clustering performance on WDBC dataset.     

基于Blob-Harris特征区域和NSCT-Zernike的鲁棒水印算法

为了有效抵抗水印图像的几何攻击,该文提出了一种基于Blob-Harris特征区域和非下采样轮廓波变换(NSCT)和伪Zernike矩的鲁棒水印算法。首先原始图像进行两层非下采样Contourlet变换后提取其低频图像,然后利用Blob-Harris检测算子对低频图像进行特征点提取,根据各个特征点的特征尺度确定其特征区域,优化筛选出稳定且互不重叠的特征区域并将其四周补零,得到稳定的互不重叠的方形特征区域作为水印嵌入区域,最后计算每一个方形特征区域的Zernike矩,将水印信息嵌入在量化调制正则化Zernike矩的幅值当中。实验结果表明,Lena图峰值信噪比达到40 dB以上时,本文算法对常规图像处理以及缩放、旋转、剪切等几何攻击和组合攻击都有相对较强的鲁棒性。