• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.273-286
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• 2021

In recent years, as human casualties and property damage caused by hazardous waves have increased in the East Sea, precise wave prediction skills have become necessary. In this study, the Simulating WAves Nearshore (SWAN) third-generation numerical wave model was calibrated and optimized to enhance the accuracy of winter storm wave prediction in the East Sea. We used Source Term 6 (ST6) and physical observations from a large-scale experiment conducted in Australia and compared its results to Komen's formula, a default in SWAN. As input wind data, we used Korean Meteorological Agency's (KMA's) operational meteorological model called Regional Data Assimilation and Prediction System (RDAPS), the European Centre for Medium Range Weather Forecasts' newest 5th generation re-analysis data (ERA5), and Japanese Meteorological Agency's (JMA's) meso-scale forecasting data. We analyzed the accuracy of each model's results by comparing them to observation data. For quantitative analysis and assessment, the observed wave data for 6 locations from KMA and Korea Hydrographic and Oceanographic Agency (KHOA) were used, and statistical analysis was conducted to assess model accuracy. As a result, ST6 models had a smaller root mean square error and higher correlation coefficient than the default model in significant wave height prediction. However, for peak wave period simulation, the results were incoherent among each model and location. In simulations with different wind data, the simulation using ERA5 for input wind datashowed the most accurate results overall but underestimated the wave height in predicting high wave events compared to the simulation using RDAPS and JMA meso-scale model. In addition, it showed that the spatial resolution of wind plays a more significant role in predicting high wave events. Nevertheless, the numerical model optimized in this study highlighted some limitations in predicting high waves that rise rapidly in time caused by meteorological events. This suggests that further research is necessary to enhance the accuracy of wave prediction in various climate conditions, such as extreme weather.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.220-226
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• 2007

The two major objectives of acoustical measurements in a cavitation tunnel are measuring the noise levels generated by rotating propellers behind a hull and localizing possible noise sources in order to reduce noise levels. Propeller noise measurement experiments were performed in MOERI cavitation tunnel at December, 2006. In order to put the propeller into cavitating conditions, a wake-generating dummy body was devised. In addition, ten hydrophones are put inside a wing-shaped casing in order to minimize the unexpected flow induced self noise around hydrophone itself. After measuring both of the noises of the rotating propeller behind the dummy body and signals generated by a virtual source, respectively the data were matched field processed using the frequency incoherent Bartlett processor to localize noises on the propeller plane. In this paper, we presented the measured noise analysis and the localization results.

• Journal of Korean Philosophical Society
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• v.141
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• pp.63-84
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• 2017

In the twentieth century Anscombe's 1958 article "Modern Moral Philosophy" argued that duty-based conceptions of morality are conceptually incoherent for they are based on the idea of a "law without a lawgiver". Concepts such as "morally ought", "morally obligated", and "morally right" require a legislator as the source of moral authority. In the past God occupied the role, but systems that dispense with God are lacking the proper foundation for meaningful employment of those concepts. Aristotle's virtue ethics can do so without appealing to any such lawgiver, and ground morality in the well being of human moral agents. Therefore Anscombe recommends a return to the eudaimonistic ethical theories of the ancients as secular approaches. Eudaimonia is a central concept in Aristotelian ethics, along with the terms "aret?"(translated as virtue or excellence) and "phronesis"(translated as practical wisdom). In Aristotle's works, eudaimonia was used as the term for the highest human good, and so it is the aim of practical philosophy to consider what it really is and how it can be achieved. Eudaimonia is a Greek word commonly translated as well-being, happiness, welfare or "human flourishing". As Aristotle points out, saying that eudaimon life is a life which is objectively desirable, and means living well. Everyone wants to be eudaimon. And everyone agrees that being eudaimon is related to faring well and to an individual's well being. But the really difficult question is to specify just what sort of activities enable one to live well. Aristotle says that the eudaimon life is one of "virtuous activity in accordance with reason," this is a necessary condition of eudaimonia, the pleasure accompanied by virtuous activities is a sufficient condition. Hence we have a more accurate translation of eudaimonia with a review the practical meaning of eudaimonia, and the correlation between eudaimonia and arete, pleasure.