• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.114-118
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• 2009

이 논문에서는 울돌목 시험조류발전소에 구축 중인 구조건전성 감시시스템의 계획, 설치 및 활용에 대하여 소개하였다. 현재 시험조류발전소에 설치된 센서로는 전기저항식 변형률계, 광섬유 FBG(Fiber Bragg Grating) 센서, 압전형 MFC(Macro Fiber Composite) 센서, 2축 경사계, 서보형 가속도계 등과 같은 지지구조물의 구조거동을 감시하기 위한 센서와 토크 센서, RPM 센서 등 발전 계통에 대한 감시를 위한 센서, 그리고 H-ADCP(Horizontal Acoustic Doppler Current Profiler)와 같은 외력조건에 대한 계측 장비 등이 있다. 센서 설치 후 현재까지 부분적으로 계측된 자료를 소개하고, 향후 건전성 감시시스템 개선 계획을 소개하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.458-467
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• 2019

The purpose of this study is the suggestion of optimized parameters in OI (Optimal Interpolation) by experimental study. The observation of applying optimal interpolation is ADCP (Acoustic Doppler Current Profiler) data at the southwestern sea of Korea. FVCOM (Finite Volume Coastal Ocean Model) is used for the barotropic model. OI is to the estimation of the gain matrix by a minimum value between the background error covariance and the observation error covariance using the least square method. The scaling factor and correlation radius are very important parameters for OI. It is used to calculate the weight between observation data and model data in the model domain. The optimized parameters from the experiments were found by the Taylor diagram. Constantly each observation point requires optimizing each parameter for the best assimilation. Also, a high accuracy of numerical model means background error covariance is low and then it can decrease all of the parameters in OI. In conclusion, it is expected to have prepared the foundation for research for the selection of ocean observation points and the construction of ocean prediction systems in the future.

• Journal of Environmental Science International
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• v.20 no.1
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• pp.107-118
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• 2011

While the assessment of mean flow field is very important to characterize the hydrodynamic aspect of the flow regime in river, the conventional methodologies have required very time-consuming efforts and cost to obtain the mean flow field. The paper provides an efficient technique to quickly assess mean flow field by developing and applying spatial averaging method utilizing repeatedly surveyed acoustic Doppler current profiler(ADCP)'s cross-sectional measurements. ADCP has been widely used in measuring the detailed velocity and discharge in the last two decades. In order to validate the proposed spatial averaging method, the averaged velocity filed using the spatial averaging was compared with the bench-mark data computed by the time-averaging of the consistent fix-point ADCP measurement, which has been known as a valid but a bit inefficient way to obtain mean velocity field. The comparison showed a good agreement between two methods, which indicates that the spatial averaging method is able to be used as a surrogate way to assess the mean flow field. Bed shear stress distribution, which is a derived hydrodynamic quantity from the mean velocity field, was additionally computed by using both spatial and time-averaging methods, and they were compared each other so as to validate the spatial averaging method. This comparison also gave a good agreement. Therefore, such comparisons proved the validity of the spatial averaging to quickly assess mean flow field. The mean velocity field and its derived riverine quantities can be actively used for characterizing the flow dynamics as well as potentially applicable for validating numerical simulations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.4 s.27
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• pp.285-291
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• 2006

In order to find the current structure between Sori Island and Yokji Island in the South Sea of Korea, water movements were measured in May, June, October and November of 2004 using ADCP(acoustic doppler current profiler). In the southwestern part of Yokji Island, northeastward flow in whole of depth was dominant by mean current The boundary layer between the upper layer and lower layer was formed between 15m and 20m and each layer different flow. The upper and lower layers have a different direction and speed of currents. In the calculated volume transport, the northeastward transport was greater than southwestward.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1946-1950
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• 2010

감조하천은 조석파의 영향으로 자연하천과 달리 매우 복잡하고 다양한 흐름특성을 보인다. 흐름이 하류에서 상류 방향으로 흐르기도 하며, 유속분포는 왜곡되어 수면 근처보다는 하상 근처의 유속이 큰 형태를 보이기도 한다. 또한 만조시 수면경사는 바다의 조위가 하천의 수위보다 높은 역경사를 보이고, 수위변화량은 조위의 변화에 따라 변동하게 되는 복잡한 흐름특성을 보인다. 이와 같은 흐름특성은 감조구간의 하상변동, 생태환경, 수질 등에 큰 영향을 미치게 되기 때문에 조사, 분석이 필요하다. 따라서 본 연구에서는 감조하천 구간에서 3차원 유속측정장비인 ADCP(Acoustic Doppler Current Profiler)로 측정된 자료 및 수위관측소의 수위자료를 활용하여 시간변화에 따른 수위변화량 및 유속분포 특성을 분석하고, 수면경사, 수위변화량 등과 유량과의 관계를 분석함으로서 향후 다양한 연구에 활용할 수 있는 자료를 제공하고자 한다.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.591-597
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• 2013

For Kangjeong stream and Akgeun stream in the central part of the southern Jeju Island, on-site discharge estimation was carried out for approximately 10 months (July 2011-April 2012) twice a month on a regular basis by using ADCP (acoustic doppler current profiler) and long term rate of discharge was calculated by using SWAT (soil and water assessment tool) model. The discharge was $0.28-1.30m^3/sec$ for Kangjeong stream and $0.10-1.54m^3/sec$ for Akgeun stream. It showed the maximum in the summer and the minimum in the winter. As a result of parameter sensitivity analysis of SWAT model, CN (NRCS runoff curve number for moisture condition II), SOL_AWC (available water capacity of the soil layer), and ESCO (soil evaporation compensation factor) showed sensitive responses. By using the result, the model was corrected and the rate of discharge was calculated. As a result, the annual discharge rate was 27.12-31.86(%) at the Akgeun basin and 23.55-28.43(%) at the Kangjeong basin.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.3
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• pp.180-190
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• 2014

It has been customary to exclude top 10-20% of velocity profiles in the Acoustic Doppler Current Profiler (ADCP) measurement due to side lobe effects at the boundary. To better understand the mixing in the Yeongsan estuary, the freshwater advection speed (FAS) was recovered from highly contaminated ADCP data near the surface. The velocity profiles were measured by using ADCP at two stations in the Yeongsan estuary during August 2011: one was located in front of the Yeongsan estuarine dam and the other was deployed near Goha Island. The FAS was recovered from the ADCP data set by applying rigorous post-processing methods and compared with the sediment advection speed (SAS). The SAS was determined by the peak time difference of suspended sediment concentration between two stations in the channel, divided by the distance of two stations. The FAS and the SAS showed very similar value when the freshwater discharge was greater than $2.0{\times}10^7$ ton and the SAS was a bit greater when the freshwater discharge was smaller. Since the FAS was on average about 0.8 m/s greater than the velocity at 0.8 of water depth from the bottom, the net discharge, estimated with recovered FAS and integrated over water depth and tidal cycle, was directed seaward during the high discharge contrary to the onshore direction of the net discharge estimated with 0.8 of water depth from the bottom. Moreover, the velocity shear and Richardson number changed when the FAS was used. Thus, the importance of the true FAS is appreciated in the investigation of the surface layer stability. If currents, temperature and salinity were observed for longer time in the future, it could be possible to more accurately understand the formation and decay of stratification as well as the suspended sediment transport processes.

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.335-346
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• 2018

A vast amount of riverine spatial dataset have recently become available, which include hydrodynamic and morphological survey data by advanced instrumentations such as ADCP (Acoustic Doppler Current Profiler), transect measurements obtained through building various river basic plans, riverine environmental and ecological data, optical images using UAVs, river facilities like multi-purposed weir and hydrophilic sectors. In this regard, a standardized data model has been subsequently required in order to efficiently store, manage, and share riverine spatial dataset. Given that riverine spatial dataset such as river facility, transect measurement, time-varying observed data should be synthetically managed along specified river network, conventional data model showed a tendency to maintain them individually in a form of separate layer corresponding to each theme, which can miss their spatial relationship, thereby resulting in inefficiency to derive synthetic information. Moreover, the data model had to be significantly modified to ingest newly produced data and hampered efficient searches for specific conditions. To avoid such drawbacks for layer-based data model, this research proposed a relational data model in conjunction with river network which could be a backbone to relate additional spatial dataset such as flowline, river facility, transect measurement and surveyed dataset. The new data model contains flexibility to minimize changes of its structure when it deals with any multi-dimensional river data, and assigned reach code for multiple river segments delineated from a river. To realize the newly developed data model, Seom river was applied, where geographic informations related with national and local rivers are available.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.126-132
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• 2011

With the worldwide trend of controlling the utilization fossil fuels inducing global climate change, many efforts will have to be made on securing stable supply of the energy due to UNFCCC. Tidal currents are a concentrated form of gravitational energy. Tidal current resource is significant, but limited locations. Technical and economic feasibility demonstration is the next needed step in the technology development process. So, we investigated overview of tidal in-stream energy in the sea near Wando, and then analytically estimated tidal energy resources and annual energy output of TECS arrays.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.340-343
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• 2008

The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. Seasonal and subinertial variations in the SWC are investigated using data obtained by high-frequency (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly capture the seasonal variations in the surface current fields of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in the summer, and becomes weaker in the winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The almost same seasonal cycle was repeated in the period from August 2003 to March 2007. In addition to the annual variation, the SWC exhibits subinertial variations with a period from 10-15 days. The surface transport by the SWC shows a significant correlation with the sea level difference between the Sea of Japan and Sea of Okhotsk for both of the seasonal and subinertial variations, indicating that the SWC is driven by the sea level difference between the two seas. Generation mechanism of the subinertial variation is discussed using wind data from the European Centre for Medium-range Weather Forecasts (ECMWF) analyses. The subinertial variations in the SWC are significantly correlated with the meridional wind component over the region. The subinertial variations in the sea level difference and surface current delay from the meridional wind variations for one or two days. Continental shelf waves triggered by the meridional wind on the east coast of Sakhalin and west coast of Hokkaido are considered to be a possible generation mechanism for the subinertial variations in the SWC.