基于加权邻域极大边界准则的人脸识别

极大边界准则是近年来提出的一种有监督的线性空间降维方法,该方法通过求解一般的特征方程来获得最优的特征向量,不用计算高维矩阵的逆,克服了特征提取中遇到的小样本问题。然而,极大边界准则只选择数据的全局结构,忽略了数据局部几何结构,而在人脸识别中,数据的局部几何结构起着非常重要的作用。针对极大边界准则这一局限性,提出了一种新的极大边界准则算法。该方法选择数据的邻域点最优重构系数用在目标函数中,保留了数据的局部几何结构,从而在低维空间中提取出更好的分类特征。本文还将该方法用在人脸识别中,通过在两个数据库中的实验,证明了其较主成分分析法,线性判别式方法以及平均邻域极大边界准则算法具有更好的识别性能。

基于加权邻域极大边界判别式嵌入的人脸识别算法

在研究局部极大边界判别式嵌入的基础上,提出加权邻域极大边界判别式嵌入算法。该算法是一种基于流形的特征提取算法,在构建目标函数时采用数据的最优重构系数,能够较好地保留数据的邻域几何结构,且不用计算高维矩阵的逆,克服了特征提取中的小样本问题。在2个通用人脸库上的识别实验结果证明,该算法充分利用了每一个流形的判别信息,在缩小同一类别邻域节点距离的同时增加不同类别邻域节点之间的距离,有效区分了不同的类别,能够获得较好的识别结果。

基于子模式的加权邻域极大边界准则的人脸识别

本文提出了一种基于子模式的加权邻域极大边界准则的人脸识别算法。该方法首先在训练过程中对人脸图像进行子块划分,采用邻接点的类信息自适应地计算每块的权重以提高人脸在姿态、表情以及光照等变化下的鲁棒性。其次,对每块图像采用加权邻域极大边界准则进行特征提取,该准则充分利用了数据的类信息,选择数据的邻域点最优重构系数用在目标函数中,保留了数据的局部几何结构,从而在低维空间中提取出更好的分类特征。最后在识别过程中,融合待识别图像在各子块中与训练图像的相似度进行识别。实验结果表明,本文算法能够有效地提取局部特征,较好地保留原始数据的非线性结构,较其他全局方法如主成分分析方法,线性判别式方法和加权邻域极大边界准则算法具有更好的识别性能。

WIMMC:加权的增量式极大边界准则算法

一些经典降维算法并不是最优的降维策略,它们不再适用于流形式且大尺度的Web文本数据,因此提出了一种加权的增量式有监督的降维算法,称为加权的增量式极大边界准则(Weighted Incremental Maximum Margin Criterion,WIMMC)。WIMMC通过加权得到比传统算法更好的结果,而且可以增量地有监督地处理大尺度的Web文本数据。给出了算法的收敛性证明和一些实验,并从实验结果可以看出,通过WIMMC降维之后的分类效果比其他降维算法更有效。

NO_x Release from Snow and Ice Covered Surface in Polar Regions and the Tibetan Plateau

The exchanges of NOx between snow and air have significant impact on the atmospheric components and photochemical processes in the overlying boundary layer. Such exchanges increase the oxidizing capacity of the atmosphere and may have a crucial impact on the air signals that are retrieved from ice cores. In the recent years, sunlit snow and ice have been demonstrated to be important NOx sources in the polar atmospheric boundary layer. This paper makes a thorough review on the release of NOx from snow and ice, including field observations and experimental evidences, release mechanisms and influential parameters that affect such a release process, polar NOx concentrations and fluxes, and environmental impacts of the chemical processes of NOx in the polar atmospheric boundary layer. In the Tibetan Plateau, the released NOx observed recently in the sunlit snow/ice-cover is 1-order magnitude more than that in polar regions, but further scientific research is still needed to reveal its impact on the atmospheric oxidizing capacity.

Structure of summer atmospheric boundary layer in the center of Arctic Ocean and its relation with sea ice extent change

The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean(80°–88°N) are presented by adopting GPS sounding data obtained by the 4th–6th Arctic expeditions of China and NCEP(National Centre for Environmental Prediction) reanalysis data. Obvious differences are observed regarding the tropopause, boundary layer height, temperature inversion, and vertical structure of wind speed and direction in the center Arctic Ocean in the summer of 2012, 2010, and 2014. These differences can be explained by the relations between temperature and changes in sea ice extent in September from 1979 to 2014. In September 2012, the Arctic sea ice extent decreased by 44% an with obvious warming process. In September 2010 and 2014, it decreased by 22.6% and 17% with an obvious cooling process, respectively. A comparison of the two processes shows that sea ice change has a significant influence on the structure of the atmospheric boundary layer. In the recent 30 years, the temperature changes of 1000 and 850 h Pa in the center of the Arctic Ocean have displayed an obvious warming trend and negative correlation with sea ice extent. These changes indicate that the continuous reduction of Arctic sea ice will continue the warming of the troposphere middle layer.

Existence of solutions for sub-linear or super-linear operator equations

We investigate solutions to superlinear or sublinear operator equations and obtain some abstract existence results by minimax methods. These results apply to superlinear or sublinear Hamiltonian systems satisfying several boundary value conditions including Sturm-Liouville boundary value conditions and generalized periodic boundary value conditions, and yield some new theorems concerning existence of solutions or nontrivial solutions. In particular, some famous results about periodic solutions to superlinear or sublinear Hamiltonian systems by Rabinowitz or Benci and Rabinowitz are special cases of the theorems.