Time filter

Source Type

Yan B.,Shandong University of Science and Technology | Liu X.-F.,Hohai University | Liu X.-F.,Changzhou Key Laboratory of Robotics and Intelligent Technology | Yang H.-M.,Shandong University of Science and Technology
Multimedia Tools and Applications | Year: 2015

Localized geometric warping of images is known to be one of the most effective attacks against image watermarking systems. However, the existing local geometrical attacks, when applied to images with regular structures, cause perceptible distortion because they are not adaptive to the content of the images. In this work, we present a multi-scale directional smoothing framework in which local displacement vectors are smoothed by locally adaptive directional kernels. Both the displacement vectors for large structures and those for fine structures are constrained by using a multi-scale pyramid. Subjective tests and objective metrics show that our proposed approach can effectively enhance the perceptual quality of the image after geometric attacks. The test of the attacking effects on two typical watermarking systems demonstrates that our approach does not degrade the attacking effects for Markov random field generated displacement field. © 2015 Springer Science+Business Media New York Source

Su X.,IoT.do - Internet of Things | Su X.,Changzhou Key Laboratory of Robotics and Intelligent Technology | Liu X.,IoT.do - Internet of Things | Liu X.,Changzhou Key Laboratory of Robotics and Intelligent Technology | And 2 more authors.
2016 International Workshop on Antenna Technology, iWAT 2016 | Year: 2016

In conventional design works relevant to antennae transmission, the space-time block coding (STBC) and beamforming (BF) gains could not be achieved at the same time usually. This is mainly due to the STBC performs well under a low correlated channel environment; BF technologies, on the other hand, works efficiently when the multi-input multi-output (MIMO) channels are highly correlated. In order to boost the system performance, in this paper, we propose a novel MIMO architecture to exploit STBC, e.g. Alamouti code, and BF technologies simultaneously. The antenna array systems associated with polarization have potential to obtain gains for both techniques because the cross-branch links in the system usually are not correlated; and the cross-array links could be highly correlated by setting a small array element distance, i.e. equal to or less than a half-wavelength. Finally, the efficiency of our proposed architecture is validated via computer simulations. © 2016 IEEE. Source

Xu N.,Hohai University | Xu N.,Changzhou Key Laboratory of Robotics and Intelligent Technology | Tang Y.,Hohai University | Bao J.,Changzhou Institute of Technology | And 6 more authors.
2015 IEEE International Conference on Consumer Electronics - Taiwan, ICCE-TW 2015 | Year: 2015

In this paper, a computationally efficient voice conversion system has been designed in order to improve the performance in resource-limited scenarios. First, mixtures of Gaus-sians (MoGs) at fixed locations of Mel frequencies have been used to represent the spectrum of STRAIGHT compactly. Second, the key conditional distributions for prediction are approximated by building histograms of aligned features empirically. Experiments have confirmed that our proposed method can obtain fairly good results compared to the traditional method without huge computational costs. © 2015 IEEE. Source

Liu X.,Hohai University | Liu X.,Changzhou Key Laboratory of Robotics and Intelligent Technology | Jiang A.,Hohai University | Jiang A.,Changzhou Key Laboratory of Robotics and Intelligent Technology | And 3 more authors.
Entropy | Year: 2016

Entropy has been a common index to quantify the complexity of time series in a variety of fields. Here, we introduce an increment entropy to measure the complexity of time series in which each increment is mapped onto a word of two letters, one corresponding to the sign and the other corresponding to the magnitude. Increment entropy (IncrEn) is defined as the Shannon entropy of the words. Simulations on synthetic data and tests on epileptic electroencephalogram (EEG) signals demonstrate its ability of detecting abrupt changes, regardless of the energetic (e.g., spikes or bursts) or structural changes. The computation of IncrEn does not make any assumption on time series, and it can be applicable to arbitrary real-world data. © 2015 by the authors. Source

Liu X.,Hohai University | Liu X.,Changzhou Key Laboratory of Robotics and Intelligent Technology | Xu N.,Hohai University | Xu N.,Changzhou Key Laboratory of Robotics and Intelligent Technology | And 2 more authors.
Journal of Theoretical Biology | Year: 2015

The goal of animal movement analysis is to understand how organisms explore and exploit complex and varying environments. Animals usually exhibit varied and complicated movements, from apparently deterministic behaviours to highly random behaviours. It has been a common method to assess movement efficiency and foraging strategies by means of quantifying and analyzing movement trajectories. Here we introduce a tortuosity entropy (TorEn), a simple measure for quantifying the behavioral change in animal movement data. In our approach, the differences between pairwise successive track points are transformed into symbolic sequences, then we map these symbols into a group of pattern vectors and calculate the information entropy of pattern vectors. We test the algorithm on both simulated trajectories and real trajectories to show that it can accurately identify not only the mixed segments in simulated data, but also the different phases in real movement data. Tortuosity entropy can be easily applied to arbitrary real-world data, whether deterministic or stochastic, stationary or non-stationary. It could be a promising tool to reveal behavioral mechanism in movement data. © 2014 Elsevier Ltd. Source

Discover hidden collaborations