• Journal of Wind Energy
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• v.14 no.4
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• pp.5-12
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• 2023

In this study, a structural and fatigue strength evaluation of the Fairlead Chain Stopper (FCS) was performed as a part of the development of a disconnectable mooring system to be applied to 10MW floating offshore wind power generation systems. To estimate the load acting on the FCS, a 10 MW semi-submersible floater was designed using the 10 MW wind turbine developed by Technical University of Denmark(DTU). The minimum breaking load (MBL) of the grade R5 and 147mm mooring chain was applied for the FCS strength analysis. The fatigue load was obtained from the coupled analysis results conducted by a collaborating research institute. The structural and fatigue safety of FCS were evaluated in accordance with DNV codes. From the evaluation results, it was confirmed that the FCS satisfies the structural and fatigue safety requirements.

• Ocean Systems Engineering
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• v.9 no.4
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• pp.409-422
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• 2019

Sloshing is a phenomenon which may lead to dynamic stability and damages on the local structure of the tank. Hence, several anti-sloshing devices are introduced in order to reduce the impact pressure and free surface elevation of liquid. A fixed baffle is the most prevailing anti-sloshing mechanism compared to the other methods. However, the additional of the baffle as the internal structure of the LNG tank can lead to frequent damages in long-term usage as this structure absorbs the sloshing loads and thus increases the maintenance cost and downtime. In this paper, a novel type of floating baffle is proposed to suppress the sloshing effect in LNG tank without the need for reconstructing the tank. The sloshing phenomenon in a membrane type LNG tank model was excited under sway motion with 30% and 50% filling condition in the model test. A regular motion by a linear actuator was applied to the tank model at different amplitudes and constant period at 1.1 seconds. Three pressure sensors were installed on the tank wall to measure the impact pressure, and a high-speed camera was utilized to record the sloshing motion. The floater baffle was modeled on the basis of uniform-discretization of domain and tested based on parametric variations. Data of pressure sensors were collected for cases without- and with-floating baffle. The results indicated successful reduction of surface run-up and impulsive pressure by using a floating baffle. The findings are expected to bring significant impacts towards safer sea transportation of LNG.

• New & Renewable Energy
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• v.16 no.3
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• pp.35-41
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• 2020

In this study, a floating LiDAR system (FLS) is investigated through a field test involving two steps. First, correlations among wind speeds, measured using the met mast and two LiDARs, are computed to analyze the acceptance criteria of LiDAR for measuring wind speed. The results of the analysis show that the slopes of single variant regression between mean wind speeds are below 1.03 and the coefficient of determination is above 0.97. Next, correlations among wind speeds measured using the FLS and a fixed LiDAR are determined through a field test carried out in Doomi-doo, Tong-young, Gyeongsangnam-do. The FLS is installed 300 m away from the fixed LiDAR on the ground. The results show that the slope of single variant regression is approximately 1.0275 and the coefficient of determination is above 0.971. According to the IEA/wind 18 recommendation, it is found that the developed FLS measures valid wind speeds to assess wind resources for the development of offshore wind farms.

• Journal of architectural history
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• v.14 no.2 s.42
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• pp.89-101
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• 2005

The bricks in Myung Dong Cathedral Church are now deteriorated by the weather such as temperature, humidity, and winds. Thus it is necessary to replace the old bricks to the restored bricks for the load bearing capacity as well as to prevent the penetrations of rains from outside. However the mortar composition is not well defined at this moment and there are literary about the mortar completions. Thus it is necessary to verify the mortar compactions between old bricks and results to bring the restoring the mortar for the replace of new bricks. The particles of mortar was collected from Myung Dong Cathedral Church and particle size was analyzed by the mortar and pestle and mechanicle floater. The X-ray diffraction and XRF of each particles are analyzed. The quartz and feldspar such as albite, kaolinite are observed in large particles(>1mm). However, the clicite was observed at lower than $43{\mu}m$ particles. In XRF analysis, the $SiO_2\;and\;K_2O$ are observed at large particles$(1mm-208{\mu}m)\;and\;CaCO_3$ is observed at small particles$(208-43{\mu}m)\;and\;CaCO_3$ is observed at small particles($208-43{\mu}m$). This is well coincide with XRD results. The optimum volume ratio of lime mortar would be 1: 2 ($CaO: SiO_2$).

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.5
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• pp.635-644
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• 2012

In order to design a wave energy generating system, a 6-DOF analysis technique is applied to the three-Dimensional CFD analysis on of a floating body and the behavior is interpreted according to the nature of the incoming wave. A wave period of 5.5s & amplitude of 0.57m from Marado is chosen. 12 case of natural pitching period from 1.25 to 2.8s has been modeled. The relation between tuning factor & pitch angle for the waves generated is compared to analyze the effects of energy absorption variables, namely mass moment of inertia, angular velocity and angular acceleration. From the results obtained, we conclude that model L is the maximum power absorbed, 6kW approximately. A maximum pitch angle of 1.91 degree was attained by Model F, and the maximum displacement of nearly 0.7m was attained by Model L among models D, F and L.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.50-56
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• 2012

When a liquid cargo tank is partially filled with fluid, internal impact loads can be occurred from the vessel's motions. In this study, liquid sloshing problems with a thin top layer of particles with a lighter density than water and the coupling effects of the liquid-sloshing/vessel-motion were investigated in order to reduce the sloshing-induced impact loads. The PNU-MPS (Pusan-National-University-modified Moving Particle Simulation) method for solving the liquid motion inside a tank and the CHARM3D BEM (Boundary Element Method) based time-domain ship motion analysis program for vessel-motion simulation were coupled. From the simulation results, we could see that the floaters seemed to be quite effective at reducing the sloshing impact loads in the case of tank-only sloshing problems, but not as much for the coupling problem with vessel motion.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.189-196
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• 1999

In order to verify a numerical model for the calculation of wave motion around an offshore barrier in shallow water, laboratory physical experiments are necessary. In this study, sample experiments are carried out on the wave and wave induced current fields due to a sloping bottom topography and on that due to an isolated structure from the coastline. The water body is divided into 4 levels, in which the current tracking floaters are deployed to measure the wave induced currents. Data measurement was continued using the limited wave gauges and current tracking floaters including a video camera from the top. The wave heights for the preselected surface and time-averaged velocity distributions at each level were measured in detail. The distribution of wave and current fields was analyzed precisely combining the whole measured laboratory data. Moreover, comprehensive analyses were carried out on non-linearity of wave transformation in terms of skewness and atiltness.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.33 no.2
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• pp.1-11
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• 2020

Objectives : The purpose of this study was to analyze and report status of Korean Medicine Ophthalmology patients who did funduscopy examination. Through this, we hope that the development of our diagnosis and treatment. Methods : From June 1, 2010 to May 31, 2019, Based on the electronic medical records of patients who had funduscopy examination at Korean Medicine Ophthalmology, Busan University Korean Medicine Hospital, the gender, age, visiting motives and paths, diagnosis, examination number of years, other eye examinations and treatments method were summarized and analyzed. Results : 463 patients were able to check the electronic medical records. They were 283 females and 180 males. The mean age of the patients was 51.5 years and elderly patients who 50s and 60s were 49.3% of whole patients. The most common motives for Korean Medicine Ophthalmology visitation was 'combination treatment with other department in Korean Medicine Hospital'. Outer eye diseases were 283 cases, inner eye diseases were 198 cases. Dry eye syndrome, asthenopia, visual discomfort, conjunctivitis, and eye discomfort were most common in the outer eye diseases. Cataracts, Vitreous floater, Macular Degeneration, Glaucoma and Ocular Pain were most common in the inner eye disease. The most common parts of outer eye diseases were Conjunctival, lacrimal gland, paralytic, corneal, eyelid and front uveal, scleral disease and then in inner eye diseases parts, Retinal, lens, vitreous, glaucoma, optic nerve, behind uveal, choroid disease were most common. The number of funduscopy examination was ups and downs. Herbal medicine was the most common used. Conclusions : The funduscopy examination is essential for diagnosis and treatment of eye disease. We hope that the use of fundus examination and other ophthalmologic examination will be expanded soon in Korean Medicine Ophthalmology.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.36-41
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• 2014

A floating offshore structure has high tendency to occur the buckling when compressive, bending and shear loads applied. When the buckling is occurred, in-plane stiffness of structure is remarkably decreased. And it has a harmful effect on the local structural strength as well as global structural strength. In the present study, it has been investigated the ultimate strength of tubular members which is located between a floater and a damping plate of the floating pendulum wave energy converter. Nonlinear finite element method is conducted using the initial imperfection according to 1st buckling mode which is obtained from the elastic buckling analysis. It is also noted the ultimate bending strength characteristic varying with a diameter, thickness and stiffeners of the tubular member.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.61-61
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• 2018

본 연구에서는 전자 플로터 시스템의 관한 것으로, 특히 수표면 위에서 작용하는 바람, 파도 등의 영향을 거의 받지 않으면서 물의 흐름방향에 순응하여 이동할 수 있도록 함으로써 정확한 유속 측정이 가능하도록 한 연직 다 지점 GPS 전자 플로터 시스템 및 이를 이용한 유속 측정방법을 제시하였다. 일반적으로 대기나 해양, 하천 등에서 유동 유체의 유동상태를 파악하기 위하여 다양한 연구가 진행되고 있다. 이 같은 연구에서 유체의 유동 특성을 파악하기 위해 시뮬레이션을 통한 모델링을 하는 것이 한 방법이나, 이는 실제 유체가 유동하는 환경에서 발생되는 요인들을 나타내기 위해서는 한계가 있기 때문에 실제 측정을 통한 검증만큼 실제적이진 못하였다. 본 연구의 유속 측정 장치는 GPS 수신기를 탑재한 GPS 전자플로터가 수표면에 부유하고 라인으로 연결된 수중 추진부인 가이드볼, 중량보강부재로 구성되어져 있다. 기존 연구의 GPS 전자플로터는 1구형으로 표면유속만 측정 할 수 있었고 바람, 파도와 같은 외부영향에 대한 단점이 있었다. 이를 보완하기 위해 연직 다 지점 GPS 전자 플로터를 개발하였으며 이는 수표면 위에서 가해지는 바람, 파도 등의 영향을 거의 받지 않고, 하측에서 지지해주는 가이드볼이 물의 흐름에 의해 자연스럽게 자전할 수 있도록 구성되어져 보다 원활하게 물의 흐름에 순응하여 이동하고 수심에 따라 가이드볼 개수를 조절할 수 있기 때문에 대하천에서 운용이 가능하다. 이러한 유속 측정 장치 개발은 접근의 위험성과 안정성이라는 장점을 가지고 있으며 대하천 및 중소하천에서도 다양하게 운용이 가능하다. 또한 화학유출사고와 같은 문제가 많이 발생하는 요즘 화학사고와 관련된 연구들에 많은 도움이 될 것으로 사료된다.