• Journal of Mechanical Science and Technology
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• v.14 no.1
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• pp.1-10
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• 2000

This work shows that it is possible to obtain information about more than one parameter from acoustic field information. A variety of ultrasonic Lamb wave modes were utilized to reconstruct thickness and density of an isotropic plate. An image reconstruction of one parameter (thickness of a plate) was carried out for four cases, i.e., the lowest symmetrical and anti symmetrical modes, and the fastest symmetrical and anti symmetrical Lamb waves among multiple modes. For two parameter reconstructions (thickness and density), the image processing was performed using the lowest symmetrical and antisymmetrical modes simultaneously. In this work, a modified version of algebraic reconstruction technique (ART), which is a form of finite-series expansion method, was employed to reconstruct the ultrasonically computed tomographic images. Results from several sample geometries are presented.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1123-1128
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• 2008

Marine facilities like buoy, lighthouse are operated with stand alone power supply system. This power system can consist of a stand-alone type power system such as PV(Photovoltaic) system, wave system or hybrid system which is not cooperated with a commercial power system. Generally, PV power system for marine facilities can not supply a sufficient power to buoy, because it is so influenced from weather condition. For solving this problem the hybrid power system with PV and wave is studied on a various area, that is why a hybrid power system is requires to overcome these problems. This paper will describe a generation characteristic of WEC(Wave Energy Converter) for buoy, and an AFS(Anti-Fouling System) influence on WEC.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.347-352
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• 2004

Wave exciting force and moment generate the motions of a ship in waves. Since ship motion exerts the negative influences on a crew's operability, the safety of cargos, passenger's comfort, etc, the anti-rolling devices may be required to reduce such motion In this paper, the dynamics of the anti-rolling devices such as passive and active moving weight stabilizer and anti-rolling tank, and fin stabilizer are mathematically modeled While the effect of the motion of the anti-rolling device on a ship was taken into consideration in roll mode only in the past, the 6 DOF coupled equations of motion between a ship and the anti-rolling devices are constituted Finally the motion of a ship with anti-rolling devices in waves is simulated through the developed simulation program.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1312-1318
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• 2004

Roll stabilization systems for ships are employed to increase comfort for passengers, maintain full working capabilities for members of the crew and prevent cargo damage. In this paper, we have investigated the usefulness of active stabilizing system to reduce ship rolling under disturbances, using varied reaction of the flaps. In the proposed anti-rolling system for a ship, the flaps as the actuator are installed on the stern to reject rolling motion induced by disturbances such as wave. The action induced by flaps depends on power of disturbances and can take the ship balance. Especially, in this study we define the system parameters under the given system structure and design the controller to evaluate the usefulness of the proposed system.

• Korean journal of communication and information
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• v.47
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• pp.120-147
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• 2009

The purpose of this paper is to promote bilateral friendly relations, the elements that hinder Hate Korea wave's(Kenkanryu) status and an analyzation of the characteristics of its causes and solutions for it. The Hate Korea wave is to be discussed in the fountain Hate Korea wave 2ch(2channel, ni channeru) acquaintances of information and representation to analyze the causes of this Japanese anti-Korean thinking. All of society should be aware of the differences and see what we have in common. I researched discussions of 2ch information and the content of other similar media. The expression was very violent. However, there was both general awareness of a gap between criticism and support. The gap was about what is not unusual on the Internet and not to be greatly concerned about. I also compares anti-Korean's awareness to Korea with general Japanese's, and finds that there are gap between them. For example by analyzing general Japanese's awareness we can find 18% of people who criticize the Hate Korea wave or have positive image of Korea. futhermore the proportion of anti-Korean contents in internet is not very high, so we don't have to worrying about the phenomenon seriously. but because of the following three points, there are sufficient needs to concern about the phenomenon constantly. First, sources of Hate Korea wave are traditional media. Second, the consumers of Hate Korea wave are mainly young generation who will make future relation of two countries. And last, Hate Korea wave include potential power to explode when certain conditions are met.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.208-213
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• 2002

A new method is presented for the isolation of resonances from scattered waves for elastic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information is defined. Elastic wave resonance scattering from a water-filled cylindrical cavity imbedded in an aluminum matrix is numerically analyzed. The classical resonance scattering theory and the new method compute different magnitudes and phases of the resonances from each partial wave, and therefore. their total resonance spectra are quite different. The exact $\pi$ - radians phase shifts through the resonance and anti-resonance frequencies show that the proposed method properly extracts the vibrational resonance information of the scatterer compared to resonance scattering theory.

• Journal of Climate Change Research
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• v.9 no.3
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• pp.209-221
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• 2018

The characteristics of heat wave events in Seoul are analyzed using weather station data from Korea Meteorological Administration (KMA) and European Centre for Medium-Range Weather Forecast (ECMWF) ERA-Interim reanalysis data from 1979 to 2016. Heat waves are defined as events in the upper 10th percentile of the daily maximum temperatures. The associated synoptic weather patterns are then classified into six clusters through Self-Organizing Map (SOM) analysis for sea-level pressure anomalies in East Asia. Cluster 1 shows an anti-cyclonic circulation and weak troughs in southeast and west of Korea, respectively. This synoptic pattern leads to southeasterly winds that advect warm and moist air to the Korean Peninsula. Both clusters 2 and 3 are associated with southerly winds formed by an anti-cyclonic circulation over the east of Korea and cyclonic circulation over the west of Korea. Cluster 4 shows a stagnant weather pattern with weak winds and strong insolation. Clusters 5 and 6 are associated with F?hn wind resulting from an anti-cyclonic circulation in the north of the Korean Peninsula. In terms of long-term variations, event frequencies of clusters 4 and 5 show increasing and decreasing trends, respectively. However, other clusters do not show any long-term trends, indicating that the mechanisms that drive heat wave events in Seoul have remained constant over the last four decades.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.559-562
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• 2010

A Lamb wave guided by a plate structure has dispersive characteristics because phase and group velocity change with the variation of frequency and thickness. The Lamb wave has two modes, symmetric and anti-symmetric mode, which propagated symmetrically and non-symmetrically with respect to centerline. In this paper, the Lamb wave velocity variation with respect to direction is investigated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.170-179
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• 2019

In this study, the wave responses in a 'Y'shape water channel resonator for amplifying wave energy of a low density has been investigated. A water channel resonator is composed of the long channel and wave guider installed at the entrance. If the period of the incident waves coincides with the natural period of the fluid in a water channel resonator, resonance occurs and the internal fluid amplifies highly to a standing wave form. In order to analyze the wave response in a water channel resonator, we used the matched asymptotic expansion method and boundary element method. The both results were in good agreement with the results of the model test carried out in the two-dimensional wave tank of Jeju National University. Wave guider has an optimum length and installation angle according to the period of the incident wave, and especially effective in enhancing the amplification factor in a period range deviated from the resonance period. It is expected that the wave energy can be effectively extracted by placing the point absorber wave energy converter at the position of anti-node where the maximum wave height is formed by the internal fluid resonance.

• Journal of KSNVE
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• v.9 no.2
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• pp.409-417
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• 1999

A new method is proposed for the isolation of resonances from scattered waves for the isolaton of resonances from scattered waves for acoustic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information is defined. Acoustic wave scattering from a variety of submerged bodies is numerically analyzed. The classical resonance scattering theory (RST) and the new method compute identical magnitudes of the resonances from each partial wave, however, the phases are significantly different. The exact $\pi$-radians phase shifts through the resonance and anti-resonance frequencies show that the proposed method properly extracts the vibrational resonance information of the scatterer. Due to the differences in phases of the resonances from each partial wave, the new method and RST generate different total resonance spectra.