Laplace平滑变换及其在人脸识别中的应用

本文主要研究如何从最优化的角度出发,从图像中提取低频特征.首先,基于图像的局部梯度定义了一种图像频率,并基于这种定义,诱导出Laplace平滑变换(LST),将二维图像映射到一维的向量.然后,将LST与学习算法相结合,提出二步子空间学习算法.所提的基于LST的二步子空间方法,对于光照、表情、姿势具有鲁棒性.实验表明,在ORL,Yale和FERET人脸数据库上,基于LST的人脸识别算法,相对DCT,DWT和PCA等预处理算法,具有更小的识别误差.     

A three-layer back-propagation neural network for spam detection using artificial immune concentration

In this paper, a three-layer back-propagation neural network (BPNN) is employed for spam detection by using a concentration based feature construction (CFC) approach. In the CFC approach, ‘self’ and ‘non-self’ concentrations are constructed through ‘self’ and ‘non-self’ gene libraries, respectively, to form a two-element concentration vector for expressing the e-mail efficiently. A three-layer BPNN with two-element input is then employed to classify e-mails automatically. Comprehensive experiments are conducted on two public benchmark corpora PU1 and Ling to demonstrate that the proposed CFC approach based BPNN classifier not only has a very much fast speed but also achieves 97 and 99% of classification accuracy on corpora PU1 and Ling by just using a two-element concentration feature vector.     

Sparse representation for face recognition by discriminative low-rank matrix recovery

This paper proposes a discriminative low-rank representation (DLRR) method for face recognition in which both the training and test samples are corrupted owing to variations in occlusion and disguise. The proposed method extends the sparse representation-based classification algorithm by incorporating the low-rank structure of data representation. The DLRR algorithm recovers a clean dictionary with enhanced discrimination ability from the corrupted training samples for sparse representation. Simultaneously, it learns a low-rank projection matrix to correct corrupted test samples by projecting them onto their corresponding underlying subspaces. The dictionary elements from different classes are encouraged to be as independent as possible by regularizing the structural incoherence of the original training samples. This leads to a compact representation of a corrected test sample by a linear combination of more dictionary elements from the corrected class. The experimental results on benchmark databases show the effectiveness and robustness of our face recognition technique.     

基于方差及方差梯度的指纹图像自适应分割算法

指纹图像分割指从图像背景中分离出有用的指纹区域的过程.利用图像方差及其梯度的性质提出一种自适应指纹分割算法.首先将待分割的图像分为3×3的块,计算块方差及其梯度,并以两者的乘积作为块特征;然后使用一种自适应的方法设定阈值完成分割;最后利用形态学方法进行后处理得到最终结果.在FVC2002和FVC2004数据库上的实验结果表明,该分割算法快速有效,且有较强的鲁棒性.     

Modeling smooth shape using subdivision on differential coordinates

Traditional subdivision schemes are applied on Euclidean coordinates (the spatial geometry of the control mesh). Although the subdivision limit surfaces are almost everywhere C² continuous, their mean-curvature normals are only C⁰. In order to generate higher quality surfaces with better-distributed mean-curvature normals, we propose a novel framework to apply subdivision for shape modeling, which combines subdivision with differential shape processing. Our framework contains two parts: subdivision on differential coordinates (a kind of differential geometry of the control mesh), and mutual conversions between Euclidean coordinates and differential coordinates. Further discussions about various strategies in both parts include a special subdivision method for mean-curvature normals, additional surface editing options, and a version of our framework for curve design. Finally, we demonstrate the improvement on surface quality by comparing the results between our framework and traditional subdivision methods.     

High-performance textile electrode enhanced by surface modifications of fiberglass cloth with polypyrrole tentacles for flexible supercapacitors

Textile-based flexible supercapacitors have various desirable advantages in practical applications due to their excellent flexibility, ease of large-scale production, and low cost. In this study, a flexible supercapacitor was designed and fabricated using a two-step polymerization method based on fiberglass cloth and unique morphology of polypyrrole (PPy). In this extraordinary nanostructure, not only do PPy tentacles provide high-speed channels for the transfer of electron and ion, but they also create a larger specific surface area, thus enhancing the energy storage. The fabricated PPy/CFC supercapacitor possesses an excellent area-specific capacitance of 549.6 mF cm⁻² and a remarkable energy density of 48.85 μWh cm⁻². Besides, it achieves the high capacitance retention of 92.4% after 10 000 charge and discharge cycles and 96.08% after 1000 bending cycles. Furthermore, it is demonstrated that the PPy/CFC supercapacitor is capable of ensuring a stable power supply for practical applications by driving an LCD electronic watch. The fiberglass cloth-based supercapacitors with PPy tentacles provide a new approach to the practical applications of wearable power supplies.     

Personalized tooth shape estimation from radiograph and cast

Three-dimensional geometric information of teeth is usually needed in pre- and postoperative diagnoses of orthodontic dentistry. The computerized tomography can provide comprehensive 3-D teeth geometries. However, there is still a discussion on computed tomography (CT) as a routine in orthodontic dentistry due to radiation dose. Moreover, the CT is useless when a dentist needs to extract 3-D structures from old archive files with only radiographs and casts, where patient's teeth changed ever since. In this paper, we propose a reconstruction framework for patient-specific teeth based on an integration of 2-D radiographs and digitized casts. The reconstruction is under a template-fitting framework. The shape and orientation of teeth templates are tuned in accordance with patient's radiographs. Specially, the tooth root morphology is controlled by 2-D contours in radiographs. With ray tracing and a contour plane assumption, 2-D root contours in radiographs are projected back to 3-D space, and guide tooth root deformations. Moreover, the template's crown is deformed nonrigidly to fit digitized casts that bear patient's crown details. The system allows 3-D tooth reconstruction with patient-specific geometric details from just casts and 2-D radiographs.     

A facile patterning preparation of barnacle-like polypyrrole on sandpaper for flexible electronics

Journal of Materials Science - The exploration of future energy storage devices with lightweight, flexible, and highly efficient energy management strategy has attracted increased interest in...