• 대한조선학회논문집
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• 제54권3호
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• pp.227-241
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• 2017

In this study, a Volterra system for the variations of metacentric height (GM) in waves is employed to simulate the parametric roll phenomena of ships in head sea condition. Using the present Volterra system, the transfer function of each harmonic component in the GM variation is computed for different ship models, including mathematical models and a real containership, and the results are validated through the comparison with the values obtained using the direct calculations based on a weakly nonlinear time-domain method. Then, a semi-analytic approach employing a 1-degree of freedom equation for roll motion is developed to simulate the parametric roll motions in irregular waves. In the derived approach, the nonlinear and time-varying restoring forces in the waves are approximated using the Volterra system. Through simulations of the parametric roll for different sea states, the effects of the 1st and 2nd-order harmonic components of the variations in the occurrence and amplitude of the parametric roll motions are investigated. Because of the strong nonlinearities in the phenomena, a stochastic analysis is conducted to examine the statistical properties of the roll motions in consideration of the sensitivities and uncertainties in the computations.

• Natural Product Sciences
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• 제9권1호
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• pp.13-17
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• 2003

The hepatoprotective effect of the ethanolic extract of Coccinia indica fruits in rats treated with carbon tetrachloride. In hepatotoxic rats, liver damage was studied by assessing parameters such as aspartate aminotransferase (AST), alanine aminotransferase (AlT), alkaline phosphatase (AIP) and gamma glutamyl transpeptidase (GGT) in serum, and concentrations of total proteins, total lipids, phospholipids, triglycerides and cholesterol in both serum and liver. The effect of co-administration of ethanolic extract on the above parameters was further investigated. Histopathological study of the liver in experimental animals was also undertaken. Hepatic damage as evidenced by a rise in the levels of AST, AIT, AIP and GGT in serum, and also changes observed in other biochemical parameters In serum and liver showed a tendency to attain near normalcy in animals co-administered with the extract. The normal values for AST (IU/L), AIP (IU/I), protein (g/100 ml) and total lipids (mg/100 ml) in serum (i.e.,20.24, 70.04, 5.72 and 135.54 respectively) were found to alter towards values 32.61, 127.11, 3.83 and 265.91 in hepatotoxic rats. These parameters Attained near normal values (I.e.,22.82, 79.30, 5.22 and 151.24 for AST, AIP protein and total lipids respectively) in ethanolic extract co-administered rats. Profound steatosis, ballooning degeneration and nodule formation observed in the hepatic architecture of $CCl_4$ treated rats were found to acquire near-normalcy in drug co-administered rats, thus corroborating the biochemical observations. Thus the study substantiates the hepatoprotective potential of ethanolic extract of Coccinia indica fruits.