• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.351-359
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• 2006

We investigated subsurface structures of the Bransfield Basin, the Antarctic with AUH (Autonomous Underwater Hydrophne) which was designed to record abyssal T-waves generated from submarine earthquakes. The data obtained from a multi-channel seismic survey and an AUH were used for this study. A seismic reflection method was applied to the multi-channel seismic survey data in order to identify bathymetry and sedimentary structures, and the signals recorded in the AUH were used to obtain deep structures as we applied a seismic refraction method. Even though we couldn’t investigate deeper and detailed structure in study area because of lack of Airgun’s capacity, the AUH showed possibilities for being used for a marine seismic survey. From this experiment, we decided the upper and lower sediment layer velocities, detected irregular basement topography probably caused by submarine volcanic/magmatic activities, and retrieved the velocity of the basement and the depth of the sediment layer/basement boundary.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.523-532
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• 1999

This study is aimed to obtain fundamental knowledge of pulse laser welding phenomena the authors investigated the structure and composition of evaporated particles of Al alloys in air and in the Ar atmosphere during pulsed laser welding. The ultra-fine particles of 5 to 100nm diameter in a globular or irregular shape were formed in laser-induced plasma and the main structure was $MgAl_2O_4$ The composition of particles was ifferent depending on the power density of a laser beam; namely under the low power density conditions magnesium was predominant in the parti-cles while aluminium content increased with an increase in the power density. These results were attributed to evaporation phenomena of metals with different boiling points and latent heats of vaporization. On the other hand the number density of laser-induced plasma species was obtained by Saha's equation. it was confirmed that the number density depends upon the plasma tempera-ture and total pressures.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.316-319
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• 2008

The L-bending of inner-structure bonded sandwich sheet metal is examined by using a bending die attached to the material testing machine. The specimen is composed of top and bottom layers and a middle layer of pyramid-core structure and each layer is bonded by brazing. The variables chosen for experiments were clearance between punch and die, location of bend line on the specimen surface and clamping type of specimen during L-bending. Effects of these variables on deformation of specimen around die-corner radius were investigated. It was shown that the irregular shapes of recess are formed in the inner layer of bended parts and they greatly depend on working conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.128-137
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• 2013

Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.

• Journal of Korean Association for Spatial Structures
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• v.16 no.1
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• pp.105-113
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• 2016

Since the 1980s, the number of large space buildings in Korea has consistently been increasing due to large scale international competitions such as the Olympics and the World Cup, demands for environmental improvement, and development of structural systems. Due to these reasons, this paper conducted a comparative analysis on terrorism risk factors of large space structure and skyscrapers in Korea. The results suggest that the total risk level of high-rise and large space structure was "medium level risk" and that the terrorism risk level for large space structure was as high as that for high-rise buildings. As it relates to the risk levels depending on scenarios, terrorism risks to large space structure were higher than high-rise buildings in the "internal explosion" and "internal intrusion" categories. And the results of analyzing explosion-related scenarios except for CBR suggest that terrorism risks to large space structure were highest when it comes to Internal-Explosive followed by Internal-Intrusion and Explosive-Zone I; and the results showed a regular pattern. On the other hand, in the case of high-rise buildings, terrorism risks were highest in Internal-Explosive followed by Explosive-Zone I and Explosive-Zone II; and the results showed an irregular pattern.

• Journal of Species Research
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• v.9 no.2
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• pp.147-161
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• 2020

Seven new species of two genera Scalarispongia and Smenospongia (Demospongiae: Dictyoceratida: Thorectidae) are described from Gageo Island and Jeju Island, Korea. Five new species of Scalarispongia are compared to nine reported species of the genus by the skeletal structure. Scalarispongia viridis n. sp. has regular ladder-like skeletal pattern arranged throughout the sponge body and has pseudo-tertiary fibres. Scalarispongia favus n. sp. is characterized by the honeycomb shape of the surface and is similar to Sc. flava in skeletal structure, but differs in sponge shape. Scalarispongia lenis n. sp. is similar to Sc. regularis in skeletal structure but has fibers that are smaller in size. Scalarispongia canus n. sp. has irregular skeletal structure in three dimensions and ladder-like which comes out of the surface and choanosome. Scalarispongia subjiensis n. sp. has pseudo-tertiary fibres and its regular ladder-like skeletal pattern occurs at the choanosome. Two new species of Smenospongia are distinguished from the other 19 reported species of the genus by the skeletal structure. Smenospongia aspera n. sp. is similar to Sm. coreana in sponge shape but new species has rarely secondary web and thin and thick bridged fibres at near surface. Smenospongia mureungensis n. sp. has very simple skeletal structure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.1
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• pp.20-35
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• 2017

In the case of the seabed around and under gravity structures such as submerged breakwater is exposed to a large wave action long period, the excess pore pressure will be significantly generated due to pore volume change associated with rearrangement soil grains. This effect will lead a seabed liquefaction around and under structures as a result of the decrease in the effective stress, and eventually the possibility of structure failure will be increased. The study of liquefaction potential for regular waves had already done, and this study considered for irregular waves with the same numerical analysis method used for regular waves. Under the condition of the irregular wave field, the time and spatial series of the deformation of submerged breakwater, the pore water pressure (oscillatory and residual components) and pore water pressure ratio in the seabed were estimated and their results were compared with those of the regular wave field to evaluate the liquefaction potential on the seabed quantitatively. Although present results are based on a limited number of numerical simulations, one of the study's most important findings is that a safer design can be obtained when analyzing case with a regular wave condition corresponding to a significant wave of the irregular wave.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.177-190
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• 2016

In case of the seabed around and under gravity structures such as submerged breakwater is exposed to a large wave action long period, the excess pore pressure will be generated significantly due to pore volume change associated with rearrangement soil grains. This effect will lead a seabed liquefaction around and under structures as a result from decrease in the effective stress. Under the seabed liquefaction occurred and developed, the possibility of structure failure will be increased eventually. Lee et al.(2016) studied for regular waves, and this study considered for irregular waves with the same numerical analysis method used for regular waves. Under the condition of the irregular wave field, the time and spatial series of the deformation of submerged breakwater, the pore water pressure (oscillatory and residual components) and pore water pressure ratio in the seabed were estimated and their results were compared with those of the regular wave field to evaluate the liquefaction potential on the seabed quantitatively. Although present results are based on a limited number of numerical simulations, one of the study's most important findings is that a more safe design can be obtainable when analyzing case with a regular wave condition corresponding to a significant wave of irregular wave.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.41.3-41.3
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• 2015

The supermassive black hole (SMBH) of our Galactic Center is surrounded by the circumnuclear disk (CND) in the radii of about 2-3 pc. New data from the Submillimeter Array and Green Bank Telescope clearly reveal the irregular and clumpy structures of the CND and its surroundings which may be a dynamically evolving integrated system. The CND seems to be the convergence of the various gas streamers inflowing, shaped mostly via local disturbances associated with, rather than a quasi-stationary stable structure.

• Journal of Species Research
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• v.6 no.spc
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• pp.94-109
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• 2017

Eleven new species of two genera, Psammocinia and Ircinia (Demospongiae: Dictyoceratida: Irciniidae) are described from Gageo Island, Ulleung Island and Jeju Island, South Korea. The separation of these two genera was made on basis of morphological evidence, especially skeletal structure with foreign debris. Six new species of Psammocinia and five new species of Ircinia were added to known fauna. All skeletal fibres are very irregular.