• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2238-2246
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• 2012

Molecular dynamics simulations have been performed to investigate hydrogen bonding characteristics of hydroxyl groups in glucose aqueous solutions with different concentrations. The hydrogen bonding abilities and strength of different O and H atom types have been calculated and compared. The acceptor/donor efficiencies have been predicted and it has been found that: (1) O2-HO2 and O3-HO3 are more efficient intramolecular hydrogen bonding acceptors than donors; (2) O1-HO1, O4-HO4 and O6-HO6 are more efficient intramolecular hydrogen bonding donors than acceptors; (5) O1-HO1 and O6-HO6 are more efficient intermolecular hydrogen bonding acceptors than donors while hydroxyl groups O2-HO2 and O4-HO4 are more efficient intermolecular hydrogen bonding donors than acceptors. The hydrogen bonding abilities of hydroxyl groups revealed that: (1) the hydrogen bonding ability of OH2-$H_w$ is larger than that of hydroxyl groups in glucose; (2) among the hydroxyl groups in glucose, the hydrogen bonding ability of O6-HO6 is the largest and the hydrogen bonding ability of O4-HO4 is the smallest; (3) the intermolecular hydrogen bonding ability of O6-HO6 is the largest; (4) the order for intramolecular hydrogen bonding abilities (from large to small) is O2-HO2, O1-HO1, O3-HO3, O6-HO6 and O4-HO4.

• 한국해양공학회지
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• 제27권3호
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• pp.67-72
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• 2013

In this study, numerical analyses that considered the dynamic interaction effects between the flow and a turbine were carried out to investigate the power output performance of an H-type Darrieus turbine rotor, which is one of the representative lifting-type vertical-axis tidal-current turbines. For this purpose, a commercial CFD code, Star-CCM+, was utilized for an example three-bladed turbine with a rotor diameter of 3.5 m, a solidity of 0.13, and the blade shape of an NACA0020 airfoil, and the optimal tip speed ratio (TSR) and corresponding maximum power coefficient were evaluated through exhaustive simulations with different sets of flow speed and external torque conditions. The optimal TSR and maximum power coefficient were found to be approximately 1.84 and 48%, respectively. The torque and angular velocity pulsations were also investigated, and it was found that the pulsation ratios for the torque and angular velocity were gradually increased and decreased with an increase in TSR, respectively.

• 한국해양공학회지
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• 제27권3호
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• pp.73-78
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• 2013

CFD (computational fluid dynamics) analyses that considered the dynamic interaction effects between the flow and a turbine were performed to evaluate the power output characteristics of two representative vertical-axis tidal-current turbines: an H-type Darrieus turbine and Gorlov helical turbine (GHT). For this purpose, a commercial CFD code, Star-CCM+, was utilized, and the power output characteristic were investigated in relation to the scale ratio using the relation between the Reynolds number and the lift-to-drag ratio. It was found that the power coefficients were significantly reduced when the scaled model turbine was used, especially when the Reynolds number was lower than $10^5$. The power output characteristics of GHT in relation to the twisting angle were also investigated using a three-dimensional CFD analysis, and it was found that the power coefficient was maximized for the case of a Darrieus turbine, i.e., a twisting angle of $0^{\circ}$, and the torque pulsation ratio was minimized when the blade covered $360^{\circ}$ for the case of a turbine with a twisting angle of $120^{\circ}$.

• Journal of Advanced Marine Engineering and Technology
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• 제35권8호
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• pp.1028-1034
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• 2011

본 논문에서는 파도의 상하운동에너지의 이용효율을 높이기 위해서 부양체와 2 D.O.F.(자유도) 진동발전시스템을 일체로 구성한 파력진동발전시스템을 제안한다. 파도가 갖는 상하운동 주파수 중 속도 에너지가 큰 주요 주파수 ${\omega}_1$, ${\omega}_2$을 선정하고, 2 D.O.F. 파력진동발전시스템의 고유진동수와 선정된 주파수들을 일치시킨다. 그러면 공진효과에 의해 각각의 질량과 권선사이의 상대속도가 파도의 상하운동속도보다 커진다. 또한 2 D.O.F. 진동시스템의 연성효과로 인한 1 D.O.F. 파력진동발전시스템보다 더 많은 전기에너지를 얻을 수 있다. 따라서 본 논문에서 제안한 2 D.O.F. 파력 발전시스템은 파도가 갖는 에너지를 더 많이 이용할 뿐만 아니라 더 많은 전기에너지를 얻을 수 있는 장점을 가짐을 알 수 있었다.

• Wind and Structures
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• 제18권2호
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• pp.195-213
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• 2014

Recently, the horizontal axis rotor performance optimizer (HARP_Opt) tool was developed in the National Renewable Energy Laboratory, USA. This innovative tool is becoming more popular in the wind turbine industry and in the field of academic research. HARP_Optwas developed on the basis of two fundamental modules, namely, WT_Perf, a performance evaluator computer code using the blade element momentum theory; and a genetic algorithm module, which is used as an optimizer. A pattern search algorithm was more recently incorporated to enhance the optimization capability, especially the calculation time and consistency of the solutions. The blade optimization is an aspect that is highly dependent on experience and requires significant consideration on rotor control strategies, wind data, and generator type. In this study, the effects of rotor control strategies including fixed speed and fixed pitch, variable speed and fixed pitch, fixed speed and variable pitch, and variable speed and variable pitch algorithms on optimal blade shapes and rotor performance are investigated using optimized blade designs. The effects of environmental wind data and the objective functions used for optimization are also quantitatively evaluated using the HARP_Opt tool. Performance indices such as annual energy production, thrust, torque, and roof-flap moment forces are compared.

• 한국해양공학회지
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• 제29권1호
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• pp.100-110
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• 2015

To meet the increasing demand for energy around the world, offshore and subsea energy development is constantly being conducted. This trend is accompanied by an increasing demand for pipeline installation, which brings numerous problems, including those related to accessibility, high pressure, and corrosion. Among these, corrosion is a primary factor in pipeline fractures, and can cause severe environmental and industrial damage. Hence, accurate corrosion assessment for corroded pipelines is very important. For this reason, the present study investigated the mechanical behavior of an idealized corroded subsea pipeline with an internal/external pressure load using the commercial FEA code ABAQUS. Then, the analysis result was compared with corrosion assessment codes such as ASME B31G, DNV RP F101, ABS. Finally, a fitness-for-service assessment was conducted.

• 한국측량학회지
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• 제39권2호
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• pp.73-79
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• 2021

Recently there are growing interests on the energy conservation and emission reduction. In the fields of architecture and civil engineering, the energy monitoring of structures is required to response the energy issues. In perspective of thermal monitoring, thermal images gains popularity for their rich visual information. With the rapid development of the drone platform, aerial thermal images acquired using drone can be used to monitor not only a part of structure, but wider coverage. In addition, the stereo photogrammetric process is expected to generate 3D point cloud with thermal information. However thermal images show very poor in resolution with narrow field of view that limit the use of drone-based thermal photogrammety. In the study, we aimed to generate 3D thermal point cloud using visible and thermal images. The visible images show high spatial resolution being able to generate precise and dense point clouds. Then we extract thermal information from thermal images to assign them onto the point clouds by precisely establishing photogrammetric collinearity between the point clouds and thermal images. From the experiment, we successfully generate dense 3D thermal point cloud showing 3D thermal distribution over the building structure.

• Journal of Magnetics
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• 제17권1호
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• pp.19-26
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• 2012

This paper deals with the performance analysis and estimation of the electrical parameters of a permanent magnet synchronous generator (PMSG) for hydrokinetic energy conversion applications using vortex induced vibration (VIV). The analytical solutions for the magnetic fields produced by permanent magnets (PMs) and stator winding currents are obtained using a 2D polar coordinate system and a magnetic vector potential. An analytical expression for the 2D permeance is also derived, which takes into account stator skew effects. Based on these magnetic field solutions and the 2D permeance function, electrical circuit parameters such as the backemf constant and the air-gap inductance are obtained analytically. The performances of the PMSG are investigated using the estimated electrical circuit parameters and an equivalent circuit (EC). All analytical results are validated extensively using 2D finite element (FE) analyses. Experimental measurements for parameters such as the back-emf and inductance are also presented to confirm the analyses.

• 한국해안·해양공학회논문집
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• 제22권4호
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• pp.235-240
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• 2010

발전소 배수로에서 방류되는 냉각수에 의하여 발생하는 거품은 시각적인 공해를 유발하여 인근 주민들의 민원 소지가 되고 있다. 본 연구에서는 배수로에서 발생하는 거품발생량을 저감하기 위한 효과적인 방안을 제안하기 위하여 테트라포드(TTP)를 배수로 경사면에 배치하여 수리모형실험을 실시하였다. 수리모형실험의 주요 결과를 실제 발전소 배수로 현장에 적용하여 정성적인 거품발생량 저감 효과가 있음을 확인하였다.

• Journal of Ship and Ocean Technology
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• 제1권1호
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• pp.48-56
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• 1997

This paper deals with the energy dissipation of ductile metal plate due to cutting. By using nondimensional analysis, we present that the dissipation energy of tearing behaviour can be formulated as a function of slenderness ratio expressed by cutting length, yield stress, plate thickness and elastic modulus. The validity of the proposed formula for Al-alloy, copper and mild steel is demonstrated by comparing the proposed formula with experimental results, which are shown in good agreements except for thick mild steel plate.