• 한국음향학회지
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• 제40권2호
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• pp.99-108
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• 2021

본 논문에서는 수괴가 능동소나에서 허위표적으로 오인 탐지 될 수 있는지에 대한 여부를 시각적으로 확인하기 위해 시간영역에 대한 음파 전달 수치 실험을 수행하였다. 수치 실험을 위해 무한영역에 과장된 수괴를 표적으로 구성하였으며 불연속 경계에 대해 개발된 시간영역 유사스펙트럴 모델을 이용하여 산란신호를 계산하고 해석해와 비교하였다. 또한, 시간에 따른 음파전달양상을 모의하였다. 이를 통해 수괴 자체가 허위표적으로 탐지 될 수 없음을 확인하였다.

• Ocean and Polar Research
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• 제27권3호
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• pp.277-288
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• 2005

Spatial distribution and vertical structures of water masses around the Antarctic continental margin are described using synthesized hydrographic data. Antarctic Surface Water (AASW) over the shelf regime is distinguished from underlying other water masses by the cut-off salinity, varying from approximately 34.35 to 34.45 around Antarctica. Shelf water, characterized by salinity greater than the cut-off salinity and potential temperature less than $-17^{\circ}C$, is observed on the Ross Sea, off George V Land, off Wilkes Land, the Amery Basin, and the Weddell Sea, but in some shelves AASW occupies the entire shelf. Lower Circumpolar Deep Water is present everywhere around the Antarctic oceanic regime and in some places it mixes with Shelf Water, producing Antarctic Slope Front Water (ASFW). ASFW, characterized by potential temperature less than about $0^{\circ}C$ and greater than $-17^{\circ}C$, and salinity greater than the cut-off salinity, is found everywhere around Antarctica except in the Bellingshausen-Amundsen sector. The presence of different water masses over the Antarctic shelves and shelf edges produces mainly three types of water mass stratifications: no significant meridional property gradient in the Bellingshausen and Amundsen Seas, single property gradient where ASFW presents, and a V-shaped front where Shelf Water exists.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.285-289
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• 2004

Oceanographic observation and qualitative analysis for deep ocean water in the East Sea were carried out from January 2003 to January 2004, in order to understand the characteristics of deep sea water in the East Sea. Temporal and spatial variation of water masses were discussed from survey of the study area including the coastal sea of Kwangwon province in where the polar front mixing cold and warm water masses were formed. On the basis of the vertical profiles of temperature, salinity and dissolved oxygen, water masses in the study area were divided into 5 major groups; (1) Low Saline Surface Water (LSSW) (2) Tsushima Surface water (TSW) (3) Tsushima Middle Water (TMW) (4) North Korea Cold Water (NKCW) and (5) East Sea Proper Water (ESPW). In winter, surface water in coastal sea of Kwangwaan Kosung region were dominated by North Korean Cold Water (NKCW). As Tsushima warm current were enforced in summer, various water masses were vertically emerged in study area, in order of TSW, TMW, NKCW and ESPW. It is highly possible that the LSSW which occurred at surface water of september is originated from influx of fresh water due to the seasonal rainy spell. Nevertheless water masses existed within surface water were seasonally varied, water quality characteristics of East Sea Proper Water (ESPW) under 300 m did not changed all the seasons of the year.

• Ocean and Polar Research
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• 제26권1호
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• pp.65-75
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• 2004

In order to understand the water masses and their distribution in the eastern Yellow Sea from winter to spring, a cluster analysis was applied to the temperature and salinity data of Korea Oceanographic Data Center from 1970 to 1990. From December to April, Yellow Sea Cold Water (YSCW) dominates the eastern Yellow Sea, whereas Eastern Yellow Sea Mixed Water (MW) and Yellow Sea Warm Water (YSWW) are found in the southern part of the eastern Yellow Sea. MW appears at the frontal region around $34^{\circ}N$ between YSCW in the north and YSWW in the south. On the other hand, Tshushima Warm Water (TWW) is found around Jeju Island and the South Sea of Korea. These water masses are relatively well-mixed throughout the water column due to the winter monsoon. However, the water column begins to be stratified in spring due to increased solar heating, the diminishing winds and fresh water discharge, and the water masses in June may be separated into surface, intermediate and bottom layers of the water column. YSWW advances northwestward from December to February and retreats southeastward from February to April. This suggests a periodic movement of water masses in the southern part of the eastern Yellow Sea from winter to spring. YSWW may continue to move eastward with the prevailing eastward current to the South Sea from April to June. Also, the front relaxes in June, but the mixed water advances to the north, increasing salinity. The salinity is also higher in the nearshore region than offshore. This indicates an influx of oceanic water to the north in the nearshore region of the eastern Yellow Sea in spring in the form of mixed water.

• 해양환경안전학회지
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• 제22권3호
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• pp.286-295
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• 2016

With the results of observations in 2013 and 2014 including ocean buoys, in-situ investigations and wind data, we examined the spatio-temporal variation of cold water masses along the eastern coast of Korea. Usually, a cold water mass first appears along the northern part of the eastern coast from May to July, and then along the southern part of the eastern coast from late June to mid-August. Cold water masses appear 3~5 times a year and remain for 5~20 days in the southwestern part of the East Sea. A distinctive cold water mass appeared usually in mid-July in this area, the surface temperature of which was below $10^{\circ}C$ in some cases. During the appearance of a cold water mass in the southwestern part of the East Sea, the horizontal temperature gradient was large at the surface and a significant low water temperature below $8^{\circ}C$ appeared at the bottom level. This appearance of cold water masses clearly corresponded to southwesterly winds, which generated coastal upwelling.

• Ocean and Polar Research
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• 제38권2호
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• pp.161-169
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• 2016

The interannual variability of the water masses was analyzed from the CTD data measured in the tropical northwestern Pacific from 2006 to 2014. There are two typical water masses NPTW and NPIW that reveal the interannual variability in the survey area, in addition to two other water masses; the surface water mass TSW with a large seasonal variability and the deep water mass AACDW with a constant temperature-salinity characteristic at the depths deeper than 2,000 meters. In 2012 and 2014 NPTW was the most widely extended horizontally and thicker than 100 meters vertically, which was found over the entire survey area. However, NPTW was reduced and became much narrower in 2009 than in the other years. NPIW seemed to expand southwards from the north of $21^{\circ}N$ to $15^{\circ}N$ in 2008 and in 2012, which showed the salinity minimum in 2013 (< 34.15 psu). The sea surface height estimated by Absolute Dynamic Topography (ADT) approximately along $135^{\circ}E$ section showed the high peaks (> $1.45dyn{\cdot}m$) between $16^{\circ}N$ and $18^{\circ}N$ during the periods between 2007 and 2009 and between 2012 and 2013; the former peak lasted wider and longer in latitude and time (about three times) than the latter. The vertical section of the geostrophic currents in the upper 1,000 meters shows that there was a mesoscale pattern of repeated eastward and westward flows a few times in some years (2010 and 2014), which seemed to disappear in some other years (2008 and 2012); the former was closely related to the mesoscale eddies and the latter implied the pattern with the permanent currents. The persistent eastward flow between $17^{\circ}N$ and $19^{\circ}N$ seems to be related to the Subtropical Countercurrent (STCC).

• Korean Journal of Hydrosciences
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• 제3권
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• pp.1-9
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• 1992

The effects of fractures in rock masses on the groundwater flow and the groundwater flow system in the volcanic rocks are analyzed by GFFP-WT model, which allows more realistic analysis of groundwater system by considering the fractures in rock masses. The evaluation of the effects of fractures in rock masses on the groundwater flow has been carried out in the 2nd Yeonwha and resulted in that the fractures mostly influence flow time because of hydraulic head distribution change. The results of the groundwater flow system analysis in the volcanic rocks are as follows. Most of groundwater once flowed in Lapilli tuff flowed out through Lappilli tuff layer. But only a small fraction of water flowed out through crystal tuff layer.

• Geomechanics and Engineering
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• 제18권6호
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• pp.627-638
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• 2019

Estimation of representative elementary volume (REV) of jointed rock masses is critical to predict the mechanical behavior of field-scale rock masses. The REV of jointed rock masses at site is strongly influenced by stress state. The paper proposed a method to systematically studied the influence of confining stress on the REV of jointed rock masses with various strengths (weak, medium and strong), which were sourced from the water inlet slope of Xiaowan Hydropower Station, China. A finite element method considering material heterogeneity was employed, a series of two-dimensional (2D) models was established based on the Monte-Carlo method and a lot of biaxial compressive tests were conducted. Numerical results showed that the REV of jointed rock masses presented a step-like reduction as the normalized confining stress increased. Confining stress weakened the size effect of jointed rock masses, indicating that the REV determined under uniaxial compression test can be reasonably taken as the REV of jointed rock masses under complexed in-situ stress environment.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2001년도 춘계 수산관련학회 공동학술대회발표요지집
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• pp.242-243
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• 2001

Tsushima Warm Current(WD entering into the East Sea through the Korean Strait flows northeastward and during this travel it shows complicated movement like meandering and eddy. It is considered that these variations of TWC are important causes making water masses unstable and also have influence on biological and chemical properties of water masses. Lee and Cho(2000) suggested that meandering of TWC in adjacent waters of Noto peninsula has much influence on fluctuation of current structure. (omitted)

• Geomechanics and Engineering
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• 제23권2호
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• pp.151-163
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• 2020

Grouting method is an effective way of reinforcing cracked rock masses and plugging water gushing. Current grouting diffusion models are generally developed for horizontal cracks, which is contradictory to the fact that the crack generally occurs in rock masses with irregular spatial distribution characteristics in real underground environments. To solve this problem, this study selected a cement-sodium silicate slurry (C-S slurry) generally used in engineering as a fast-curing grouting material and regarded the C-S slurry as a Bingham fluid with time-varying viscosity for analysis. Based on the theory of fluid mechanics, and by simultaneously considering the deadweight of slurry and characteristics of non-uniform spatial distribution of viscosity of fast-curing grouts, a theoretical model of slurry diffusion in an oblique crack in rock masses at constant grouting rate was established. Moreover, the viscosity and pressure distribution equations in the slurry diffusion zone were deduced, thus quantifying the relationship between grouting pressure, grouting time, and slurry diffusion distance. On this basis, by using a 3-d finite element program in multi-field coupled software Comsol, the numerical simulation results were compared with theoretical calculation values, further verifying the effectiveness of the theoretical model. In addition, through the analysis of two engineering case studies, the theoretical calculations and measured slurry diffusion radius were compared, to evaluate the application effects of the model in engineering practice. Finally, by using the established theoretical model, the influence of cracking in rock masses on the diffusion characteristics of slurry was analysed. The results demonstrate that the inclination angle of the crack in rock masses and azimuth angle of slurry diffusion affect slurry diffusion characteristics. More attention should be paid to the actual grouting process. The results can provide references for determining grouting parameters of fast-curing grouts in engineering practice.