Unsupervised SAR Image Segmentation Based on a Hierarchical TMF Model in the Discrete Wavelet Domain for Sea Area Detection

Unsupervised synthetic aperture radar (SAR) image segmentation is a fundamental preliminary processing step required for sea area detection in military applications. The purpose of this step is to classify large image areas into different segments to assist with identification of the sea area and the ship target within the image. The recently proposed triplet Markov field (TMF) model has been successfully used for segmentation of nonstationary SAR images. This letter presents a hierarchical TMF model in the discrete wavelet domain of unsupervised SAR image segmentation for sea area detection, which we have named the wavelet hierarchical TMF (WHTMF) model. The WHTMF model can precisely capture the global and local image characteristics in the two-pass computation of posterior distribution. The multiscale likelihood and the multiscale energy function are constructed to capture the intrascale and intrascale dependencies in a random field (X,U). To model the SAR data related to radar backscattering sources, the Gaussian distribution is utilized. The effectiveness of the proposed model for SAR image segmentation is evaluated using synthesized and real SAR data

Calculation of Blade-profile Icing and Analysis of Flow Field

The icing of the blade will change its original aerodynamic shape and affect its aerodynamic characteristics. The FENSAP-ICE software is used to compare and verify the numerical calculation results of icing on NACA0012 airfoil with the experimental results. The two-dimensional icing calculation of the compressor inlet guide vane profile is carried out, and the numerical calculation results of flow field are analyzed. The results show that the aerodynamic effect of glaze ice on the blade profile is greater than that of rime ice, the aerodynamic characteristics of the blade profile are mainly affected by the upper separation vortex in the separation zone, the upturned glaze ice on the leading edge of blade profile causes the tailing separation area to expand, and the strong separation vortex can increase the pressure loss of the icing blade profile