ABSTRACT Hu, X.; Wang, Y.; Wu, F., and Huang, A., . Using a new channel estimation algorithm to improve underwater acoustic communication with multiple receivers. Underwater acoustic (UWA) communication with multiple receivers has been developed for underwater wireless data transmission, because the receiving array can improve the reliability of the system by using spatial diversity. In this paper, a channel estimation algorithm is proposed that fully uses UWA channel sparsity for single-input, multiple-output (SIMO) communication. The proposed algorithm integrates L 0 norm into the cost function of the improved proportionate normalized least-mean-square (IPNLMS) algorithm based on L 0 norm. The performance of the L 0 norm–constrained IPNLMS, IPNLMS based on L 0 norm, and the proposed algorithm is studied in terms of normalized misalignment for SIMO UWA channel estimation. In addition, the influence of the number of receivers on channel estimation accuracy is analyzed. Finally, the numerical simulation results demonstrate the superiority of the proposed algorithm in terms of robustness, which achieves the lower normalized misalignment than the other two algorithms in a shallow-water acoustic channel estimation.

ABSTRACT Liu, S.; Ju, Q.; Huang, W.; Hu, X.; Qi, D., and Zhong, G., 2018. Effects of crown wall and berm on wave-overtopping discharge over a seawall. Reliable estimation of wave-overtopping discharge over a seawall is important in the crest-height design and safety assessment of coastal structures. Crown wall and berm have been widely used to reduce the wave overtopping over a seawall. According to recent literature, the influence of crown wall under breaking wave conditions has not been discussed precisely, and the reductive effect of an intermediate berm has not been clarified under nonbreaking wave conditions. In this study, 650 experiments have been conducted to investigate the influence of crown wall in breaking wave conditions and the influence of berm under breaking and nonbreaking wave conditions on the wave-overtopping discharge. New empirical equations have been derived from the analysis of experimental data to provide more accurate estimations of the reduction of wave overtopping on a seawall by crown wall or berm. The formula for crown wall is applicable under breaking waves, and formulas for berm can be applied to both break and nonbreak wave conditions. The empirical equations can be used in coastal seawall design to quantify the effects of sea-wall height, water depth on the berm, and berm width.