The authors present a new approach for affine distorted planar curve matching and exploit it for occluded object recognition. There are two main contributions in the study: First, a novel affine‐invariant curve descriptor (AICD) based on a new‐defined affine‐invariant signature and its unsigned sum is proposed to represent the local shape of a curve with high distinctiveness. Second, a part‐to‐part curve matching algorithm is developed by combining AICD with a curve segmentation strategy based on inflexion points, which can be applied to object recognition under affine distortions and partial occlusions. Experimental results demonstrate that the proposed method exhibits effectiveness in occluded object recognition better than the state‐of‐the‐art partial curve matching methods.
To solve the mis-clusters caused by the traditional information cut algorithm when it is applied to segment images with gray changes, modified information cut in wavelet domain (W-MIC) algorithm is proposed. First, using the gray relevance and space relevance between image pixels, a modified information cut (MIC) is presented, which utilizes a new Parzen windowing function to evaluate probability density functions, and reduces the effect of gray changes to image segmentation; further, considering the difficulties of selecting the optimal parameter in MIC, the proposed W-MIC can reduce the complexity of parameter selection via the smoothing role of wavelet, and improve segmentation results by fusing low frequency information and high frequency information derived from undecimated wavelet decomposition. Segmentation experiments demonstrate that it effectively decreases the influence of parameters selection, and it can not only avoid the mis-clusters caused by gray changes, but also keep image edges.
Narrow available bandwidth, strong multi-path disturbance and serious fading in the long-range channel are main obstacles to the high-rate reliable underwater acoustic communications. In traditional underwater acoustic communication systems, frequency-shift-keying (FSK) and phase-shift-keying (PSK) are typical modulation schemes that are efficient in power and in bandwidth, respectively. But they can't solve effectively the conflicting demands between the high data rate and reliability. A novel self-differential joint frequency and phase modulation (SD-JFPM) approach is presented in this paper, which is well suited in shallow water channels. In SD-JFPM, phase information is transmitted by the difference between initial phases of the former and latter halves of a certain symbol. The theoretical analysis is given, and also the experiments in lake are conducted. The results demonstrate that the SD-JFPM modulation is effective for the multi-path influence in the fading channel, and can overperform single-carrier modulation by increased data rate and communication reliability.
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