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Ocean waves are abundant in energy; however, they also cause ships to sway and can disrupt the operation of precision equipment. Harvesting energy from ocean waves and isolating vibrations in marine precision equipment have long posed significant challenges due to the inherently low-frequency nature of ocean waves. This study proposes a dynamic-constrained nonlinear (DCN) stiffness method for low-frequency energy harvesting and vibration isolation. A generalized mathematical model of the DCN stiffness system is established, and its semi-analytical solution is derived using the harmonic balance method and the arc-length extension method. Finally, various application scenarios for energy harvesting and vibration isolation using the nonlinear stiffness method are explored. The results demonstrate that the DCN stiffness method can significantly enhance the performance of low-frequency wave energy, capture and provide excellent low-frequency vibration isolation. Notably, this method exhibits a strong adaptive capability to excitation compared to traditional nonlinear stiffness methods.

The influence of global climate change due to green house effects on the earth environment will be required impact assessment, mitigation and adaptation strategies for future our society. This study predicts future ocean wave climate in comparison with present wave climate based on the atmospheric general circulation model and global wave model. The annual averaged and extreme sea surface winds and waves are analyzed in detail. There are clear regional dependence of annual average and extreme value from present to future climate. The wind speeds and wave heights of future climate are increased in middle latitudes and the Antarctic ocean, and these are decreased in the equator. The annual averaged winds and waves are decreased off coast of Japan but their maxima are increased than those of present climate.