• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2015년도 추계학술대회
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• pp.33-34
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• 2015

북극항로(NSR)를 통항하는 상선과 화물량이 매년 중가추세에 있다. 쇄빙선의 도움을 받아 북극항로를 통항하는 상선의 안전한 항해를 위협하는 가장 큰 요인은 얼음과의 충돌이다. 따라서 선박과 얼음의 충돌 메커니즘을 규명하기 위한 노력이 관련 연구자들에 의해서 활발히 이루어지고 있다. 본 연구에서는 북극항로를 운항하는 내빙선과 유빙의 충돌을 가정한 예인수조실험을 실시하며, 충돌 후 얼음의 운동(속력, 궤적)을 머신비전검사를 통해서 계측한다. 아울러 오차계산을 통해서 머신비전검사 기법의 정밀도를 검증한다.

• 대한조선학회논문집
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• 제48권3호
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• pp.275-280
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• 2011

In the present study, a unified viscoplastic-damage model has been applied in order to describe the mechanical characteristics of fresh water ice such as nonlinear material behavior and volume fraction. The strain softening phenomenon of fresh water ice under quasi-static compressive loading has been evaluated based on unified viscoplastic model. The material degradation such as growth of slip/fraction has quite close relation with material inside damage. The volume fraction phenomenon of fresh water ice has been identified based on volume fraction (nucleation and growth of damage) model. The viscoplastic-damage model has been transformed to the fully implicit formulation and the discretized formulation has been implemented to ABAQUS user defined subroutine (User MATerial: UMAT) for the benefit of application of commercial finite element program. The proposed computational analysis method has been compared to uni-axial compression test of fresh water ice in order to validate the compatibilities, clarities and usefulness.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.228-234
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• 2016

Recent icebreaking ships need to be designed to enhance not only icebreaking capability but also turning ability. For the evaluation of ice resistance induced by an icebreaking hull form, HHI (Hyundai Heavy Industries) has developed the hybrid empirical formulas (Park et al., 2015) by considering the geometrical hull shape features, such as waterline and underwater sections. However, the empirical formulas have inherent limits to the precise estimation of the icebreaking and turning ability because the breaking process and the resulting pattern are ignored. For this reason, numerical calculation in time domain is performed to predict the icebreaking process and pattern. In the simulation, varying crushing stress according to velocity vectors and contact areas between hull and ice is newly introduced. Moreover, the simulation results were verified by comparing them with the model test results for three different bow-first icebreaking models.

• 한국생활과학회지
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• 제23권1호
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• pp.137-148
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• 2014

고지방식이에 의해 경중 정도의 비만과 당뇨가 유발되는 제2형 당뇨동물 모델인 C57BL/6J-ob/ob 마우스에서 콩 이소플라본 단독 또는 콩 이소플라본과 올리고당을 첨가한 우유 아이스크림이 당뇨지표에 미치는 영향을 조사함으로써 콩 이소플라본 첨가 아이스크림의 항당뇨 효능을 조사하였다. 5주령 된 C57BL/6J-ob/ob 수컷 마우스를 1주일간 적응시킨 후 대조군과 설탕 첨가 아이스크림(MS), 콩 이소플라본 첨가 아이스크림(MS-SI), 콩 이소플라본/프럭토올리고당 첨가 아이스크림(MF-SI)을 대조식이에 30% 첨가하여 12주 동안 자유롭게 섭취시켰다. 희생 후 당뇨 지표에 해당하는 경구 당부하 혈당 반응, 공복혈당, 인슐린, C-peptide, $HbA_{1c}$ 및 렙틴 농도와 중성지방, 그리고 비장세포 증식능과 비장세포에서 분비되는 사이토카인인 IL-6과 TNF-${\alpha}$에 미치는 효과를 측정한 결과 군간 유의한 차이를 보이지 않았다. 결론적으로 제2형 당뇨모델 마우스에서 우유 아이스크림에 첨가된 콩 이소플라본이 당뇨 지표에 긍정적인 효과를 나타내지 않았다.

• 한국해양공학회지
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• 제27권5호
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• pp.88-92
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• 2013

The icebreaking research vessel (IBRV) ARAON had her second ice trial in the Arctic Ocean in the summer season of 2010. During the voyage, the local ice loads acting on the bow of the port side were measured using 14 strain gauges. These measurements were carried out in three icebreaking performance tests. To convert the measured strains into the local ice pressures, a finite element model of the instrumented area was developed. The influence coefficient method (ICM), which uses the influence coefficient from the finite element model, and the direct method, which uses the measured strain, were selected as the conversion methods. As a result, the maximum measured pressure was 1.236MPa, and the average difference between ICM and the direct method was about 5% for an area of $0.2m^2$. The pressure-area relationship of the measurement falls below the range of the existing pressure-area curve, which is due to the low ice strength of melted ice in the summer.

• 대한조선학회논문집
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• 제55권6호
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• pp.497-504
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• 2018

Platform Support Vessels operated in the Arctic Ocean support diverse operations of offshore plant in the sea, and the PSV is also needed to support works to exploit the oil and gas in the Arctic Ocean. Both of the ice breaking and the open sea performance have been considered together to secure the enhanced operational performance at the harsh environment in the Arctic Ocean and the open sea as well. In this study, One of the design requirements of a PSV is to guarantee continuous icebreaking performance with 3 knots at 1 m thickness of level ice, where the design draft is 7.5m and the engine power is 13 MW. Three hull forms were designed, and the ice resistance based on empirical formulas was estimated to select the initial hull form having an outstanding performance. The full scale performance of the designed hull forms was predicted by the ice model test conducted in the ice model basin of Korea Research Institute of Ships & Ocean Engineering(KRISO). The analysed results show that the selected hull form satisfies the above design requirement.

• Wind and Structures
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• 제32권3호
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• pp.205-217
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• 2021

Cold regions with high air density and wind speed attract wind energy producers across the globe exhibiting its potential for wind exploitation. However, exposure of wind turbine blades to such cold conditions bring about devastating impacts like aerodynamic degradation, production loss and blade failures etc. A series of wind tunnel tests were performed to investigate the effect of icing on the aerodynamic properties of wind turbine blades. A baseline clean wing configuration along with four different ice accretion geometries were considered in this study. Aerodynamic force coefficients were obtained from the surface pressure measurements made over the test model using MPS4264 Simultaneous pressure scanner. 3D printed Ice templates featuring different ice geometries based on Icing Research Tunnel data is utilized. Aerodynamic characteristics of both the clean wing configuration and Ice accreted geometries were analysed over a wide range of angles of attack (α) ranging from 0° to 24° with an increment of 3° for three different Reynolds number in the order of 105. Results show a decrease in aerodynamic characteristics of the iced aerofoil when compared against the baseline clean wing configuration. The key flow field features such as point of separation, reattachment and formation of Laminar Separation Bubble (LSB) for different icing geometries and its influence on the aerodynamic characteristics are addressed. Additionally, attempts were made to understand the influence of Reynolds number on the iced-aerofoil aerodynamics.

• 대한조선학회논문집
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• 제58권3호
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• pp.158-166
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• 2021

In this paper, a numerical analysis technique using a body force model is investigated to estimate the available net thrust of multi-pod-driven ice-breaking vessels under bollard pull and overload conditions. To employ the body force model in present flow simulations, drag and thrust components acting on the pod unit are calculated by using Propeller Open Water (POW) test data. The available net thrusts according to the direction of operation are evaluated in both bollard pull and overload conditions under deep water. The simulation results are compared with the model test data. The available net thrusts, calculated by the present analysis for ahead operating modes at 3~6 knots which are typical speeds of the target vessel in arctic field, are agreed well with the model test results. It is also found that the present result for astern operating mode appears approximately 6 % larger than the model test result. In addition, the available net thrusts are calculated under the both operating conditions accompanied by shallow water effects, and the main cause of the difference is studied. Based on the result of the present study, it is confirmed that the body force model can be applied to the performance evaluation of multi-pod propulsion system and the main engine selection in early design stage of the vessel.

• 한국항공우주학회지
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• 제46권8호
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• pp.611-620
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• 2018

수치해석을 이용한 항공기 착빙 형상 예측의 정확도 향상을 위하여 거칠기 분포 예측이 가능한 해석적 모델이 개발되고 있다. 그러나 표면의 상태에 대한 정량적인 실험 결과가 거의 없어 해석적 모델을 검증하고, 경험적인 변수를 결정하는데 어려움을 겪고 있다. 이에 본 연구에서는 표면의 상태를 미시적 관점에서 분석하기 위한 실험적 연구를 수행하였다. 우선, 착빙 환경 변수인 온도와 자유류 속도에 따른 매끈한 표면의 넓이의 관계를 정량적으로 파악하였다. 그 결과 대기 온도가 높고 자유류 속도가 증가할수록 매끈한 표면의 넓이가 증가하였다. 그 다음으로 서리 얼음 표면과 유리얼음 표면의 특성을 분석하였다. 서리얼음 조건에서는 불투명한 원뿔 형태의 얼음 요소들이 유동 반대 방향으로 성장하고, 대기 온도가 증가함에 따라 원뿔 얼음 요소들의 길이와 간격이 감소하는 것을 확인하였다. 유리얼음 조건에서는 반투명한 얼음 덩어리를 날개 아랫면에서 관찰할 수 있었다. 이러한 원인은 중력의 영향이 큰 아랫면에서 주로 리블렛이 형성되고, 이와 같이 형성된 리블렛이 집중하여 얼어붙었기 때문이다.

• 한국환경과학회지
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• 제21권11호
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• pp.1395-1406
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• 2012

The purpose of this study is to analyze the hydraulic characteristics of the ice-harbor fishway by considering its geometrical form and utilize such analysis results as the foundational database to be used when establishing fishways in the future. first of all, the study realizes the same form as an ice-harbor fishway that is currently implemented via a FLOW-3D model and estimated the parameters that were optimal to the numerical mock test. Then, this study analyzed the level of sensitivity of the flow conditions which fluctuated due to the changes in geometrical changes by adjusting the inclination and pocket spacing by using the estimated optimal parameters. As a result, the study arrived at the following conclusions. The vortical velocity increased and had a significant effect on the inclination of the fishway. Furthermore, as the velocity within the vorticity increased due to the narrowed vortical area, it was determined that further studies on vorticities or the determination of the design method for the decrease in vortical velocity were imperative.