• Journal of Korean Institute of Industrial Engineers
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• v.33 no.1
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• pp.70-75
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• 2007

This paper discusses condition based preventive replacement for deteriorating systems. The system continuouslydeteriorates in time and fails at any deterioration level which is always monitored, It is replaced at failure or atsome deteriorated level preventively before failure. The deterioration process is represented by a Weibulldistribution with a time-linear scale parameter. The cost rate function is formed considering replacement costand opportunity loss cost and deterioration dependent failure distribution, If the system has an increasingdeterioration dependent failure rate, the optimal deterioration level for preventive replacement can be determinedfrom minimizing the cost rate. An illustrative example is given for a Weibull deterioration dependent failuredistribution.

• Journal of Ginseng Research
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• v.42 no.4
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• pp.540-548
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• 2018

Background: Acute hepatic failure is a life-threatening critical condition associated with rapid deterioration of liver function and liver transplantation. Several studies have shown that Panax ginseng Mayer has antidiabetic and hepatoprotective effects. However, the hepatoprotective effect of ginseng berry is still unveiled. In this study, we evaluated the hepatoprotective effects of ultrasonication-processed ginseng berry extract (UGBE) on acute hepatic failure model in rats. Methods: Ginseng berry extract (GBE) was ultrasonically processed. The GBE, silymarin, and UGBE were orally administered to male Sprague-Dawley rats for 4 wk. Twenty-four h after the last administration, rats were challenged with D-galactosamine (D-GalN)/lipopolysaccharide (LPS). Results: After ultrasonication, the component ratio of ginsenosides Rg2, Rg3, Rh1, Rh4, Rk1, Rk3, and F4 in GBE had been elevated. Administration of UGBE significantly increased the survival rate of D-GalN/LPS-challenged rats. Pretreatment with UGBE significantly decreased serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin levels in D-GalN/LPS-challenged rats in a dose-dependent manner. The levels of enzymatic markers for oxidative stress (superoxide dismutase, glutathione peroxidase, catalase, and glutathione) were increased by UGBE treatment in a dose-dependent manner. Tumor necrosis factor alphalevel, inducible nitric oxide synthase activities, and nitric oxide productions were reduced by UGBE treatment. In addition, hemeoxygenase-1 levels in liver were also significantly increased in the UGBE-treated group. The protein expression of toll-like receptor 4 was decreased by UGBE administration. Hematoxylin and eosin staining results also supported the results of this study showing normal appearance of liver histopathology in the UGBE-treated group. Conclusion: UGBE showed a great hepatoprotective effect on D-GalN/LPS-challenged rats via the toll-like receptor 4 signaling pathway.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.109-120
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• 2017

A discounted cost model for preventive maintenance of armor units of rubble-mound breakwaters is mathematically derived by combining the deterioration model based on a discrete-time stochastic process of shock occurrence with the cost model of renewal process together. The discounted cost model of condition-based maintenance proposed in this paper can take into account the nonlinearity of cumulative damage process as well as the discounting effect of cost. By comparing the present results with the previous other results, the verification is carried out satisfactorily. In addition, it is known from the sensitivity analysis on variables related to the model that the more often preventive maintenance should be implemented, the more crucial the level of importance of system is. However, the tendency is shown in reverse as the interest rate is increased. Meanwhile, the present model has been applied to the armor units of rubble-mound breakwaters. The parameters of damage intensity function have been estimated through the time-dependent prediction of the expected cumulative damage level obtained from the sample path method. In particular, it is confirmed that the shock occurrences can be considered to be a discrete-time stochastic process by investigating the effects of uncertainty of the shock occurrences on the expected cumulative damage level with homogeneous Poisson process and doubly stochastic Poisson process that are the continuous-time stochastic processes. It can be also seen that the stochastic process of cumulative damage would depend directly on the design conditions, thus the preventive maintenance would be varied due to those. Finally, the optimal periods and scale for the preventive maintenance of armor units of rubble-mound breakwaters can be quantitatively determined with the failure limits, the levels of importance of structure, and the interest rates.