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The effect of two salinity concentrations (35 and 40 ‰) on the daily feeding and burrowing activities of the sea cucumber, Holothuria parva was investigated, using the nutritional parameters (intestinal  indices, organic materials, and the absorption efficiency). Although no significant difference between the initial and final sections of the intestinal gut of sea cucumbers in two saline conditions was found, the maximum level of intestinal indices, organic material and absorption efficiency was associated with the 40‰ salinity. The survey results displayed that sea cucumber had better feeding activity in 40‰ than 35‰ salinity.  

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In this study, the performance of a cylinder absorbing wave energy from irregular incident waves, as one of the renewable energy systems, is investigated numerically using complete solution of the Navier-Stokes equations. For this purpose, the control volume approach in conjunction with the fictitious domain method, for modeling the solid object motions inside fluid, are used where a two-step projection method is used to solve the governing equations. The results show that despite the cylinder absorbs energy in two main directions, its energy absorption efficiency in irregular waves is about 8%. Due to the employed spring and damper in these devices, the system has only one natural frequency which is the reason for its low efficiency at irregular waves. Results also show that for steep waves at deep waters, the maximum efficiency occurs at larger spring coefficient and smaller damping coefficients, while at moderate water depths and wave steepness, the maximum efficiency occurs at smaller spring coefficients and larger damping coefficients. Therefore, to reach maximum energy absorption efficiency at irregular waves, not only these coefficient has to be adjusted carefully, but also it is recommended to use multi-resonance systems or several cylinders with different natural frequencies.