• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 춘계학술발표회 논문집
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• pp.45-54
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• 2003

This paper deal with the GPS performance for determining the ocean tidal loading components(M$_2$, N$_2$, S$_2$, K$_2$) and the availability of permanent GPS stations(CHJU, KANR) established in Korea. We determined the ocean tidal loading components from GPS observation by spectrum analysis and compared to that from global ocean tidal models(GOT00.2, FES99, CRS4.0, NAO99). Through this study, we have a sense that amplitude and phase lags of ocean tidal loading components from observed GPS data was almost equal to value calculated in ocean tide models. The diurnal ocean tide loading constituents are not considered, because unmodeled troposhere effects increase the noise level near the diurnal frequency band and prevent us from obtaining significant results.

• 한국측량학회지
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• 제21권4호
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• pp.317-322
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• 2003

본 논문에서는 우리나라 해안에 설치된 GPS상시관측소(제주도, 호미곶, 주문진, 마라도, 팔미도, 울릉도, 영도) 데이터를 사용하여 각 관측소의 상대적 높이차를 구한 후, CLEAN 알고리즘에 의한 스펙트럼 분석을 실시함으로써 해양조석의 부하성분들 중에서 반일분조성분으로 인한 지각의 연직변동량을 추정하고, 이들을 일본과 우리나라 주변에 대하여 지역적으로 개량한 해양조석모델(NAO99jb)로부터 계산된 결과들과 비교$.$분석을 실시하고자 하였다. 그 결과, 총 4개의 반일분조($M_2, N_2, S_2, K_2$) 중 $M_2$와 $N_2$의 부하효과에 의한 부하성분의 진폭 및 위상 차를 결정하였으며, 관측된 부하성분의 진폭과 위상차는 모델에서 구한 부하성분의 진폭과 위상차와 거의 일치되는 양상물을 보이고 있었다. 그러나 주기의 문제로 인해 $S_2$, $K_2$ 반일분조에 대한 부하성분은 산출하지 못하였으며, 또한 일분조(Diurnal) 주기에서는 잡음의 양이 증가함으로 인하여 부하성분을 산출하지 않았다.

• 한국측량학회지
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• 제34권3호
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• pp.299-308
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• 2016

오늘날 우주측지기술은 측위정밀도를 높이고 시간과 비용적 측면에서 효율성을 향상시키는 방향으로 발전되고 있다. 정밀측위를 위하여 지구의 물리적 현상을 보정하는 것은 필수적이며, 그 중 해양조석하중의 보정은 중요한 요소이다. 본 연구에서는 인천과 제주의 조위관측소 GNSS 관측데이터를 이용하여 해양조석하중에 의한 수직지각변위를 산출하고 지각변위를 일으키는 각 분조의 조석성분을 검출하였다. GNSS 측위방법과 자료처리 시간에 따른 해양 조석하중 성분 검출 정확도를 비교하기 위하여 상대측위와 정밀절대측위로 GNSS 데이터를 처리하여 주요 8개 조석성분의 진폭을 산출하고 전지구 해양조석하중 모델의 진폭과 비교하였다. 연구결과 조석분조 진폭 검출에는 2시간 간격의 자료처리와 정밀절대측위 방법이 해양조석하중 분조 검출에 정확한 것으로 나타났다. 추후에는 장기간 자료를 이용하여 장주기 조석성분에 대한 분석도 이루어져야 할 것이다.

• 한국측량학회지
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• 제36권5호
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• pp.343-353
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• 2018

Ocean tides in Antarctica are not well constrained mostly due to the lack of tidal observations. Especially, tides underneath and around ice shelves are uncertain. InSAR (Interferometric Synthetic Aperture Radar) data has been used to observe ice shelf movements primarily caused by ocean tides. Here, we demonstrate that it is possible to estimate tidal constituents underneath the Sulzberger ice shelf, West Antarctica, solely using ERS-1/2 tandem mission DInSAR (differential InSAR) observations. In addition, the tidal constituents can be estimated in a high-resolution (~200 m) grid which is beyond any tidal model resolution. We assume that InSAR observed ocean tidal heights can be derived after correcting the InSAR data for the effect of atmospheric loading using the inverse barometric effect, solid earth tides, and ocean tide loading. The ERS (European Remote Sensing) tandem orbit configuration of a 1-day separation between SAR data takes diminishes the sensitivity to major tidal constituents including $K_1$ and $S_2$. Here, the dominant tidal constituent $O_1$ is estimated using 8 differential interferograms underneath the Sulzberger ice shelf. The resulting tidal constituent is compared with a contemporary regional tide model (CATS2008a) and a global tide model (TPXO7.1). The InSAR estimated tidal amplitude agrees well with both models with RMS (root-mean-square) differences of < 2.2 cm and the phase estimate corroborating both tide models to within $8^{\circ}$. We conclude that fine spatial scale (~200 m) Antarctic ice shelf ocean tide determination is feasible for dominant constituents using C-band ERS-1/2 tandem mission InSAR.

• International Journal of Ocean System Engineering
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• 제3권4호
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• pp.164-168
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• 2013

Tidal-current power is now recognized as a clean power resource. The turbine blade is the fundamental component of a tidal current power turbine. The kinetic energy available within a tidal current can be converted into rotational power by turbine blades. While in service, turbine blades are generally subjected to cyclic fatigue loading due to their rotation and the rotor-tower interaction. Predicting the fatigue life under a hydrodynamic fatigue load is very important to prevent blade failure while in service. To predict the fatigue life, hydrodynamic load data should be acquired. In this study, the vibration characteristics were analyzed based on three-dimensional unsteady simulations to obtain the cyclic fatigue load. Our results can be applied to the fatigue design of horizontal-axis tidal turbines.

• Ocean Systems Engineering
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• 제13권2호
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• pp.147-172
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• 2023

This study investigates the influence of loading and inflow conditions on tidal turbine performance from a hydrodynamic and hydroacoustic point of view. A boundary element method is utilized for the former to investigate turbine performance at various loading conditions under zero/non-zero yaw inflow. The boundary element method is selected as it has been selected, tested, and validated to be computationally efficient and accurate for marine hydrodynamic problems. Once the hydrodynamic solutions are obtained, such as the time-dependent surface pressures and periodic motion of the turbine blade, they are taken as the known noise sources for the subsequence hydroacoustic analysis based on the Ffowcs Williams-Hawkings formulation given in a form proposed by Farassat. This formulation is coupled with the boundary element method to fully consider the three-dimensional shape of the turbine and the speed of sound in the acoustic analysis. For validations, a model turbine is taken from a reference paper, and the comparison between numerical predictions and experimental data reveals satisfactory agreement in hydrodynamic performance. Importantly, this study shows that the noise patterns and sound pressure levels at both the near- and far-field are affected by different loading conditions and sensitive to the inclination imposed in the incoming flow.

• Journal of Astronomy and Space Sciences
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• 제26권4호
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• pp.511-520
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• 2009

이 연구에서는 GPS(Global Positioning System) 정밀단독측위 기법을 이용하여 해양조석하 중(Ocean Tide Loading, OTL) 분조성분을 검출하고, 그 결과를 조석모델에 의한 예측값과 비교하였다. 고정밀 GPS 자료처리 프로그램인 GIPSY를 사용하여 인천, 서산, 제주 GPS 상시관측소를 대상으로 10분 단위의 수직좌표 시계열을 산출하였으며, 시계열의 조석조화분해를 통해 OTL 지각변위를 일으키는 주요 4대 분조($M_2$, $S_2$, $K_1$, $O_1$)의 진폭과 위상을 검출하였다. 조석모델의 예측값을 기준으로 GPS로 산출한 OTL 분조의 정확도를 평가한 결과 진폭은 제주관측소, 위상은 인천관측소에서 가장 높은 정확도를 나타내었다. 주요 11개 분조 중 최대비율을 차지하는 $M_2$분조의 경우 진폭성분에서 평균 23.8%의 상대오차를 보였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.348-353
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• 1996

This study addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements. The marine tidal zone was simulated by alternate filling and draining of the tank (wet and dry cycled), and a galvanostatic corrosion technique to accelerate corrosion of reinforcement was used. Half-cell potentials and changes of crack width were measured periodically during the exposure and followed by ultimate strength testing. The significant findings include adverse effect of fatigue loading, existence of an explicit size effect, poor performance of epoxy coated steel, and negative effect of increasing water/cement ratio.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.18-25
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• 1999

Western coastal ports of Korea experience severe tidal range with up to 9.7 meter between high and low tides. The significant water level variation implicates many operational difficulties during loading and un-loading from cargo ships. To overcome problems due to tide and to secure the continuous loading operation, a new loading system for container cargo called "container pallet system" is developed and introduced in the paper. Three types of structure forms, offshore structural deck, double bottom structural form and the mixed form, are inverstigated with MSC/NASTRAN software. The results prove that the mixed type structure with truss enforcement is found to be the most appropriate for the region.

• Smart Structures and Systems
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• 제23권1호
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• pp.61-69
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• 2019

Offshore structures are generally exposed to harsh environments such as strong tidal currents and wind loadings. Monitoring the structural soundness and integrity of offshore structures is crucial to prevent catastrophic collapses and to prolong their lifetime; however, it is intrinsically challenging because of the difficulties in accessing the critical structural members that are located under water for installing and repairing sensors and data acquisition systems. Virtual sensing technologies have the potential to alleviate such difficulties by estimating the unmeasured structural responses at the desired locations using other measured responses. Despite the usefulness of virtual sensing, its performance and applicability to the structural health monitoring of offshore structures have not been fully studied to date. This study investigates the use of virtual sensing of offshore structures. A Kalman filter based virtual sensing algorithm is developed to estimate responses at the location of interest. Further, this algorithm performs a multi-sensor data fusion to improve the estimation accuracy under non-stationary tidal loading. Numerical analysis and laboratory experiments are conducted to verify the performance of the virtual sensing strategy using a bottom-fixed offshore structural model. Numerical and experimental results show that the unmeasured responses can be reasonably recovered from the measured responses.