• Journal of Korea Water Resources Association
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• v.50 no.7
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• pp.455-465
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• 2017

Understanding of the two-dimensional velocity field is crucial in terms of analyzing various hydrodynamic and fluvial processes in the riverine environments. Until recently, many numerical models have played major roles of providing such velocity field instead of in-situ flow measurements, because there were limitations in instruments and methodologies suitable for efficiently measuring in the broad range of river reaches. In the last decades, however, the advent of modernized instrumentations started to revolutionize the flow measurements. Among others, acoustic Doppler current profilers (ADCPs) became very promising especially for accurately assessing streamflow discharge, and they are also able to provide the detailed velocity field very efficiently. Thus it became possible to capture the velocity field only with field observations. Since most of ADCPs measurements have been mostly conducted in the cross-sectional lines despite their capabilities, it is still required to apply appropriate interpolation methods to obtain dense velocity field as likely as results from numerical simulations. However, anisotropic nature of the meandering river channel could have brought in the difficulties for applying simple spatial interpolation methods for handling dynamic flow velocity vector, since the flow direction continuously changes over the curvature of the channel shape. Without considering anisotropic characteristics in terms of the meandering, therefore, conventional interpolation methods such as IDW and Kriging possibly lead to erroneous results, when they dealt with velocity vectors in the meandering channel. Based on the consecutive ADCP cross-sectional measurements in the meandering river channel. For this purpose, the geographic coordinate with the measured ADCP velocity was converted from the conventional Cartesian coordinate (x, y) to a curvilinear coordinate (s, n). The results from application of A-VIM showed significant improvement in accuracy as much as 41.5% in RMSE.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.351-373
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• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.208-225
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• 2019

To understand the mean surface circulation and surface currents in the East Sea, trajectories of surface drifters passed through the East Sea from 1991 to 2017 were analyzed. By analyzing the surface drifter trajectory data, the main paths of surface ocean currents were grouped and the variation in each main current path was investigated. The East Korea Warm Current (EKWC) heading northward separates from the coast at $36{\sim}38^{\circ}N$ and flows to the northeast until $131^{\circ}E$. In the middle (from $131^{\circ}E$ to $137^{\circ}E$) of the East Sea, the average latitude of the currents flowing eastward ranges from 36 to $40^{\circ}N$ and the currents meander with large amplitude. When the average latitude of the surface drifter paths was in the north (south) of $37.5^{\circ}N$, the meandering amplitude was about 50 (100) km. The most frequent route of surface drifters in the middle of the East Sea was the path along $37.5-38.5^{\circ}N$. The surface drifters, which were deployed off the coast of Vladivostok in the north of the East Sea, moved to the southwest along the coast and were separated from the coast to flow southeastward along the cyclonic circulation around the Japan Basin. And, then, the drifters moved to the east along $39-40^{\circ}N$. The mean surface current vector and mean speed were calculated in each lattice with $0.25^{\circ}$ grid spacing using the velocity data of surface drifters which passed through each lattice. The current variance ellipses were calculated with $0.5^{\circ}$ grid spacing. Because the path of the EKWC changes every year in the western part of the Ulleung Basin and the current paths in the Yamato Basin keep changing with many eddies, the current variance ellipses are relatively large in these region. We present a schematic map of the East Sea surface current based on the surface drifter data. The significance of this study is that the surface ocean circulation of the East Sea, which has been mainly studied by numerical model simulations and the sea surface height data obtained from satellite altimeters, was analyzed based on in-situ Lagrangian observational current data.

• (The) Research of the performance art and culture
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• no.23
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• pp.105-158
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• 2011

Due to the system of sending selected hyanggi(local entertaining woman) to the government office in Seoul after the abolition of the system of gyeonggi(entertaining woman in capital area) during the reign of King Injo(1595~1649), the kyobang-jeongjae(local dance performed for the provincial government office) had gotten into the court to be performed at the royal banquet as gungjung-jeongjae(court dance), one of which was seonyurak(dance of boating). It used to be performed for finale of the royal banquet in the late Joseon Dynasty and appeared in several uigwes(record for royal banquet) since its first appearance in the wonhaeng-eulmyo-jeongri-uigwe, documented in 1795, the 19th year of the reign of King Jeongjo. Considering that the yeoggi(female entertainer) responsible for the court dance, seonyurrak was the seonsanggi(selected entertaining woman from provinces) from the northwestern provincial villages such as Euiju, Ahnju, and Seongcheon etc., we can assume that the baettaragi, one of kyobang-jeongjaes whould have been getting into the court to become the seonyurrak as court dance. The baettaragi, kyobang-jeongjae of northwestern province that affected the development of the court dance, seonyurak was created as performance executed by entertaining women of kyobang(local supervisory office for entertaining women) on the basis of the fact that the envoy of Joseon dynasty to the Ming dynasty could not help but taking a sea route when Amaga Aisin Gurun had a grip on the northeastern area of China during the shift of power from Ming to Qing. There had been a lot of banquets for envoys in the northwestern province because of its geographical feature as gateway to trip to China and the baettaragi used to be performed by entertaining women belonged to local provincial office to consolate the sadness of separation with those who destined to depart to China and to hope for their safe return. The kyobang-jeongjae, baettaragi of northwestern province is recorded as performance with sorrowful song to put the pain of parting into work, according to many related documents. It puts together painted boats as props, the march of a couple of dancer dressed up as soldier with marching music called gochiak, the song and musical accompaniment before getting on boat, the dramatic expression of sailing, and the farewell song praying for safe return etc. It turns the situation of dispatching envoys for China by sea into performance with combination of music, song and dance. Created in this way, the kyobang-jeongjae, baettaragi had been performed at the various banquets for envoys departing for China and it affected the formation of court dance or gungjung-jeongjae called seonyurak through the activities of selected local entertaining women. It also exerted influence on other similar performance in provincial area because of the returning home of the selected local entertainers who finished their performance in Seoul and it had been performed with different variation at local banquet including locality in it.

• Korean Journal of Ichthyology
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• v.24 no.3
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• pp.227-229
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• 2012

Based on a single juvenile specimen (20.7 mm SL) collected from Jeju Island, Apogon semiornatus was described as a new Korean record. The species is characterized by having VI-I, 9 dorsal fin rays, 12 pectoral fin rays; II, 8 anal fin rays and two blackish oblique bands on yellowish red body. A new Korean name, "Geom-eun-du-jul-bulg-eun-dong-gal-dom", is proposed.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2003.11a
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• pp.209-216
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• 2003

There are two kinds of controllers in a continuous process system. One is for tension control of a moving web and the other for lateral motion control. The inter-connection between tension and lateral behaivior of web has not yet been considered in the analysis of web dynamics and designing of control stragagies. But the effect of tension variation on the lateral motion of a moving web is observed in the most manufacturing systems. In this paper, experimental studies was carried out to find out the inter-correlation between tension and lateral motion of a web using a 3-span web transport system which consists of two displacement type guiders. As a result, it was found that there are typical operating conditions that tension and lateral motion are correlated each other.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.618-622
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• 2006

충적 선상지(alluvial fan)는 자갈이나 유사가 과도하게 이송되어 부채모양으로 퇴적된 것으로서, 하류로 하폭이 증가하는 곳에서 형성된다. 충적 선상지는 유사가 이송하는 하천, 토석류, 그리고 박층류에 의해 형성된다. 토석류는 자갈에서부터 상대적으로 작은 진흙에 이르기까지 운반하는 밀도체이다. 충적하천의 흐름은 사행하천 및 망상하천에 이르는 흐름을 말하며, 박층류는 기본적으로 비하천 홍수류로서, 한 홍수사상에 대하여 선상지에서 부분분할로 형태로 흐른다. 본 연구에서는 충적 선상지에 대한 공학적인 문제를 검토하기 위한 예비연구로서 유입부에서 유사량의 유입조건에 따른 충적 선상지 델타의 형성 과정을 수치모형을 이용하여 파악하였다. 본 모형은 2차원 모형으로서, 이동경계좌표계를 사용하였고, 수치해석 기법으로는 CIP법이 이용되었으며, wet/dry를 고려하여, 유입 유사량의 변화에 따른 특성을 파악하였다. 초기에는 급격하게 선상지의 높이가 급격하게 증가하며, 유입 유사량의 증가에 따라 선상지의 높이가 평형상태를 유지하는 시간이 짧은 것을 보여주고 있다. 선상지의 면적은 유입 유사량이 적을 경우에는 평형상태가 지속적으로 유지되며, 완만한 증가 현상을 보여주었다. 유입 유사량이 증가할 경우에는 초기에 급격한 상승을 하다가 평형상태가 없이 지속적으로 상승하는 것을 보여주었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.885-889
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• 2009

국가하천 함평천은 전라남도 함평군과 무안군 등 2개 군에 걸쳐 위치하고 있는 영산강의 제1지류로서 동측으로는 고막원천, 서측으로는 서해안, 북측으로는 영광군이 위치하고 있으며, 남측으로는 영산강 본류와 접하고 있다. 전라남도 함평군 함평읍, 엄다면, 학교면 사이에 위치한 함평 세계 나비 곤충 엑스포장 옆의 함평 2지구 하천환경정비사업 구간을 구하도 복원사업 구간으로 설정하였다. 이 연구는 함평 2지구 하천환경정비사업 구간에서 수리학적 영향을 검토할 목적으로 수행하였다. 평면 이차원 모형을 사용하여 흐름 변화를 분석하였다. 흐름 계산은 RMA2 모형을 사용하였으며, 유속과 수위의 평면적 변화를 분석하였다. 또한, 평면 이차원 모형 적용 결과를 통해 하도 폐색 가능성을 분석하였다. 하도의 사행화와 분리하도를 구성하여 다양한 유속 분포를 보였으며, 분리하도 구간은 1 $m^3/s$ 이상의 유량을 유지하고 있어 하도 폐색은 발생하지 않을 것으로 판단되었다. 퇴적 및 침식에 의한 하도의 직선화가 되지 않도록 적절한 재료의 선택하여야 할 것으로 판단된다.

• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.43-50
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• 1991

본 연구에서는 극한 파고를 추정하는 방법을 제시하였다. Type III분포에 근거해서 4가지의 방법들에 의해 분포 함수의 파라미터들을 추정하였다. 실제 자료와 추정된 분포 함수 값의 차이를 다항식을 도입하여 함으로써 그 오차를 줄였다. 이 방법들의 타당성을 보이기 위해 실제 해상의 자료들을 이용하여 분포 함수를 구하고 조우 주기들에 해당하는 극한 파고를 계산하여 보았다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.111-116
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• 2001

In this paper, a simple 2 D.O.F. planar motion model is proposed in order to analyze the snake motion of a machining center cross head assembly, that is travelling on linear guide rails. In the proposed mathematical model, the friction between head and guide ways is neglected, and also the support structures including guide rails, rear- and side-panels of the machining center are assumed to be rigid. The equations of motion of the proposed model are derived and successfully solved to determine vibration responses of the head assembly due to some applied traction forces.