• Journal of the Korean Applied Science and Technology
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• v.39 no.2
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• pp.161-168
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• 2022

Unmodified castor oil (CO) was used to obtain a castor-based aqueous polyurethane (CPUD) and isophorone diisocyanate (IPDI) was used to obtain a transparent film. The mixing effect of polypropyleneglycole (PPG) was analyzed to increase flexibility. In addition, ethylenediamine (EDA) was used as a chain extender. Tensile strength, elongation, and abrasion resistance were measured according to the change according to the castor oil content and the change in the chain extender, respectively. The tensile strength of the sample containing a lot of castor oil was 1.112 kgf/㎟, and the elongation was 88%. The tensile strength of the sample containing a lot of chain extender was 3.33kgf/㎟, and the elongation was 99%. The surface strength was visually confirmed through SEM. The surface strength was visually confirmed through SEM.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.106-121
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• 2020

In order to make harbor outskirt facilities robust using the reliability-based design, probabilistic models of wave heights at varying stage of shoaling process optimized for Korean sea waves are prerequisite. In this rationale, we numerically simulate the nonlinear shoaling process of random waves over the beach with a sandbar at its foreshore. In doing so, comprehensive numerical models made of spatially filtered Navier-Stokes Eq., LES [Large Eddy Simulation], dynamic Smagorinsky turbulence closure were used. Considering the characteristics of swells observed at the east coast of Korean Peninsula, random waves were simulated using JONSWAP wave spectrum of various peak enhancement coefficients and random phase method. The coefficients of probabilistic models proposed in this study are estimated from the results of frequency analysis of wave crests and its associated trough detected by Wave by Wave Analysis of the time series of numerically simulated free surface displacements based on the threshold crossing method. Numerical results show that Modified Glukhovskiy wave height distribution, the most referred probabilistic models at finite water depth in the literature, over-predicts the occurring probability of relatively large and small wave heights, and under predicts the occurrence rate of waves of moderate heights. On the other hand, probabilistic models developed in this study show vary encouraging agreements. In addition, the discrepancy of the Modified Glukhovskiy distribution from the measured one are most visible over the surf zone, and as a result, the Modified Glukhovskiy distribution should be applied with caution for the reliability-based design of harbor outskirt facilities deployed near the surf-zone.