We investigated a parametric kernel-driven active contour (PKAC) model, which implicitly transfers kernel mapping and piecewise constant to modeling the image data via kernel function. The proposed model consists of curve evolution functional with three terms: global kernel-driven and local kernel-driven terms, which evaluate the deviation of the mapped image data within each region from the piecewise constant model, and a regularization term expressed as the length of the evolution curves. In the local kernel-driven term, the proposed model can effectively segment images with intensity inhomogeneity by incorporating the local image information. By balancing the weight between the global kernel-driven term and the local kerneldriven term, the proposed model can segment the images with either intensity homogeneity or intensity inhomogeneity. To ensure the smoothness of the level set function and reduce the computational cost, the distance regularizing term is applied to penalize the deviation of the level set function and eliminate the requirement of reinitialization. Compared with the local image fitting model and local binary fitting model, experimental results show the advantages of the proposed method in terms of computational efficiency and accuracy.
Based on the Sino-European cooperation in the Galileo satellite navigation system Search And Rescue(SAR) service, a multi-channel distress beacon signal simulator is presented here. The mathematic model and spectrum analysis of current 406 MHz distress beacons signals is presented which includes Emergency Position Indicating Radio Beacons (EPIRB) for Maritime, Personal Locator Beacons (PLB) for land (road and rail), and Emergency Locator Transmitter (ELT) for aeronautical applications. Based on Software Defined Radio (SDR) and digital IF techniques, the design of a SAR Signal Simulator (SAR-SS) is proposed, which can generate no less than 20 distress signals simultaneously. The Doppler shift and space propagation effect such as ionosphere delay, free space attenuation and etc, are simulated in SAR-SS, which provided a significant test and evaluation capability for SAR/Galileo project. The performance of SAR-SS is more accurate and stabile than the Cospas-Sarsat(C-S) requirement. SAR-SS will be a significant instrument for the Galileo system search and rescue project ground test.
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