Prevalent human detection methods are usually applied in cases without rotation angle, and their detection rates are poor when rotation angle varies. In order to solve the issue, an algorithm which could identify human with variable rotation angle was proposed. Firstly, Radial Gradient Transform (RGT) method was adopted to obtain the rotation-invariance gradient. Then, adopting the method similar to the way that blocks were overlapped in the Histogram of Oriented Gradient(HOG) feature, a plurality of descriptors with rotation angle information were obtained and connected linearly into a descriptor group with rotation invariance feature, according to the descriptors' rotation angle. Finally, the human detection algorithm was conducted with the support of a two-level cascaded classifier based on Support Vector Machine (SVM). The recognition rate of the proposed algorithm achieves more than 86% for a human test set with 144 different rotation angles based on the INRIA pedestrian database. In the meantime, the false detection rate is less than 10% for a non-human test set with 144 different rotation angles. The experiments indicate that the proposed algorithm can be used for human detection in an image with arbitrary rotation angle.
To solve the problem in most of conventional multi-task learning algorithms which evaluate risk independently for single task and lack uniform constraint across all tasks, a new hyper-spherical multi-task learning algorithm with adaptive grouping was proposed in this paper. Based on Extreme Learning Machine (ELM) as basic framework, this algorithm introduced hyper-spherical loss function to evaluate the risks of all tasks uniformly, and got decision model via iterative reweighted least squares solution. Furthermore, considering the existence of relatedness between tasks, this paper also constructed regularizer with grouping structure based on the assumption that related tasks had more similar weight vector, which would make the tasks in same group be trained independently. Finally, the optimization object was transformed into a mixed 0-1 programming problem, and a multi-objective method was utilized to identify optimal grouping structure and get model parameters. The simulation results on toy data and cylindrical vibration signal data show that the proposed algorithm outperforms state-of-the-art methods in terms of generalization performance and the ability of identifying inner structure in tasks.
The paper firstly analyzed some security problems in Li-Niu's (LI X, NIU J W, KHAN M K, et al. An enhanced smart card based remote user password authentication scheme[J]. Journal of Network and Computer Applications, 2013, 36(5):1365-1371.) enhanced smart card based remote user password authentication scheme, and then proposed a novel smart-card-based scheme. In new scheme, a self-verified timestamp technique was combined with symmetric encryption methods to solve the problem of implementing clock synchronization in most typical smart-card-based schemes. Compared with Li-Niu's scheme, this scheme can not only provide the users' anonymity, but also resist the impersonation attacks and the privileged insider attacks. The scheme is more secure and efficient for the complicated network environment.