• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.23 no.2
• /
• pp.186-195
• /
• 2010

Objective : This study was performed to prove the effect of the oriental medical treatments like acupuncture, moxibustion, herbal medicine on macular edema resulted from branch retinal vein occlusion which could lead to terrible result like permanent visual loss at worst. Methods : The patient was treated 62 times, from July 15th, 2009 through May 12th, 2010. We used fundus photography and Dr. Hann's standard test chart for 5m to examinate the patient's eyesight. We used acupuncture, electropuncture, moxibustion and herbal medicine to treat the patient. We considered visual field, scotoma, metamorphopsia and vitreous floater to measure the effect of treatment. Results : After about 10 months of treatment, the eyesight of Rt eye was improved from 0.8 to 0.9, Lt. eye from zero to 0.3. The visual field turbidity were absolutely cleared. The scotomas in Lt. eye were reduced from 5 to 2. The metamorphopsia were improved. The vitreous floaters in Rt. eye were decreased from 5~6 to 1~2. Conclusion : These results show that the oriental medical treatment can be conservative measure to the macular edema resulted from branch retinal vein occlusion.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.3 no.2
• /
• pp.185-201
• /
• 1993

The objectives of this study are to identify the physical, chemical and microstructural properties of coal fly ash and to increase the industrial use of coal fly ash. Experimental results show that 3 major constituents of coal fly ash are $SiO_2$, $Al_2O_3$ and coal fly ash includes the crystalline of Quartz and Mullite. Coal fly ash are classified into 7 groups based on the type of microstructure. Cenosphere is divided into floater and dry separated cenosphere which are consist mainly of $SiO_2$ and $Al_2O_3$. Cenosphere segregations are formed by adsorption and neck growth of the smaller sized cenosphere particles on the condition of the high temperature and air pressure.

• Ocean Systems Engineering
• /
• v.8 no.1
• /
• pp.79-99
• /
• 2018

The effects of BPC (blade pitch control) on FOWT (floating offshore wind turbine) motions and generated power are investigated by using a fully-coupled turbine-floater-mooring simulation program. In this regard, two example FOWTs, OC4-5MW semi-submersible FOWT and KRISO four-3MW-units FOWT, are selected since the numerical simulations of those two FOWTs have been verified against experiments in authors' previous studies. Various simulations are performed changing BPC natural frequency (BPCNF), BPC damping ratio (BPCDR), and wind speeds. Through the numerical simulations, it was demonstrated that negative damping can happen for platform pitch motions and its influences are affected by BPCNF, BPCDR, and wind speeds. If BPCNF is significantly larger than platform-pitch natural frequency, the pitch resonance can be very serious due to the BPC-induced negative-damping effects, which should be avoided in the FOWT design. If wind speed is significantly higher than the rated wind velocity, the negative damping effects start to become reduced. Other important findings are also given through systematic sensitivity investigations.

• Journal of the Society of Naval Architects of Korea
• /
• v.56 no.3
• /
• pp.211-216
• /
• 2019

In order to utilize the marine environment in various fields such as renewable energy and offshore plant, it is necessary to utilize the far and deep ocean. However, there is still a limit to overcome and utilize the extreme deep-sea environment. Currently, the mooring system, which is the representative position control method of floating structure, has a structural and economic limit to expand the installation range to extreme deep-sea environment. Research has been conducted to utilize wave energy by developing floater using flapping foil as an alternative for station keeping in the deep sea by University of Ulsan. Based on the research, a model test was conducted for application to actual structures. In this study, we investigate how the floating body with passive flapping foils move in regular waves with different periods and study the condition of the model that can maintain its position within a certain range by overcoming the movement.

• Ocean Systems Engineering
• /
• v.11 no.4
• /
• pp.313-330
• /
• 2021

In this study, the dynamic interaction between an Arctic Spar and drifting level ice is examined in time domain using the newly developed ice-hull-mooring coupled dynamics program. The in-house program, CHARM3D, which is the hull-riser-mooring coupled dynamic simulator is extended by coupling with the open-source discrete element method (DEM) simulator, LIGGGHTS. In the LIGGGHTS module, the parallel-bonding method is implemented to model the level ice using an assembly of multiple bonded spherical particles. As a case study, a spread-moored Artic Spar platform, whose hull surface near waterline is the inverted conical shape, is chosen. To determine the breaking-related DEM parameter (the critical bonding strength), the four-point numerical bending test is used. A series of numerical simulations is systematically performed under the various ice conditions including ice drift velocity, flexural strength, and thickness. Then, the effects of these parameters on the ice force, platform motions, and mooring tensions are discussed. The simulations reveal various features of dynamic interactions between the drifting ice and moored platform for various ice conditions including the novel synchronous resonance at low ice speed. The newly developed simulator is promising and can repeatedly be used for the future design and analysis including ice-floater-mooring coupled dynamics.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.7 no.2
• /
• pp.156-162
• /
• 1995

A numerical method for a 2-D oil boom model considering the flexibility of skirt has been developed The neater is assumed rigid and the skirt is tensioned membrane having a point mass at its end The fluid motion is potential. The kinematic condition which demands the continuity of the displacement is imposed at the joint between the floater and the skirt. The dynamic condition for the point mass is imposed at the bottom end of the skirt. The numerical method is based on the Green's function method in the frame of linear potential theory. It finds it's solution simultaneously from the total system of three equations, integral equation, the equation of motion of the floater and the equilibrium equation of the deformation of the skirt. Integral equation is derived by applying the Green's theorem to radiation potential and Green's function. Proper descretization of those three equations leads to the system of a linear algebraic equation. Due to the flexibility of skirt the motion of floater can be diminished in some range of wave frequency and furthermore the mechanism of resonance of the oil boom can be changed. The motion responses of various oil booms have been compared varying the length of the skirt and the point mass. The numerical method has been validated indirectly from the good correspondence between the motion responses of the flexible skirt model and the rigid skirt model in low frequency limit.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.5B
• /
• pp.479-486
• /
• 2010

Reliable hydrologic data acquisition is the basic and essential requirement for efficient water management. Especially the acquisition of various stream data in a certain location is very important to construct on alarm system to response an urban flood which occurs frequently due to the effect of climate change. Although the frequency of stream inundation flood occurrence becomes low owing to the consistent stream improvement, the urban flood due to the drainage system problems such as deterioration and bad management occurs continuously. The consistent management and current status understanding of the urban drainage system is essential to reduce the urban flood. The purpose of this study is to develop the urban runoff network flow velocity monitoring system which has the capability of collecting stream data whenever, wherever and to whomever without expert knowledge using Code Division Multiple Access technique and Bluetooth near-distance wireless communication technique. The urban runoff network flow velocity monitoring system consists of three stages. In the first stage, the stream information obtained by using ubiquitous floater is transferred to the server computer. In the second stage, the current state of the urban drainage system is assessed through the server computer. In the last stage, the information is provided to the user through a GUI. As a result of applying, the developed urban runoff network flow velocity monitoring system to Woncheon-Stream in Suwon, the information necessary for urban drainage management can be managed in real time.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.5
• /
• pp.632-639
• /
• 2011

In order to design a wave energy generate system, a 6-Degree of freedom motion analysis technique was applied to the three-Dimensional CFD analysis on two floating body and the behavior was interpreted according to the nature of the incoming wave. The waves are generated by the same type of wave in the model of tank using the piston type, but due to the shallow water that is generated from the bottom of the wave energy is attenuated by Ekman boundary layer. According to the wavelength of waves generated by the result of evaluating the behavior of floating body, it is concluded that 0.3m is the maximum amplitude of wavelength of 5m, and 0.15m is the minimum amplitude of wavelength of 1m. 1.06m is the maximum distance between the two floaters of wavelength of 6m.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.99-110
• /
• 2017

This paper presents the study of the bending behavior of mooring chain links for keeping the position of the offshore floating structures. In general, chain links have been thought as the axial members due to the fundamental boundary condition. But, the flexural stiffness can be induced to the contact surface between chain links when friction occurs at the surface of the chain links due to high tensile force. Especially, the mooring chains for offshore floating platforms are highly tensioned. If the floater suffers rotational motion and the mooring chain links are highly tensioned, the rotation between contact links, induced by the floater rotation, generates the bending moment and relevant stresses due to the unexpected bending stiffness. In 2005, the mooring chain links for the Girassol Buoy Platform were failed after just 5 months after facility installation, and the accident investigation research concluded the chain failure was mainly caused by the fatigue due to the unexpected bending stress fluctuation. This study investigates the pattern of the induced bending stiffness and stresses of the highly tensioned chain links by nonlinear finite element analysis.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.9 no.3
• /
• pp.141-147
• /
• 2006

A newly designed floating breakwater made of Polyethylene with considering the introduction of new material for being harmony with environment and stability of the floater is developed for a marine ranching. In this study, the new concept in which incident wave dissipates its energy due to the vortex shedding by passing through the pipes and sheets is selected for wave breaking mechanism. Model experiment in order to te st its capability is performed for the regular and irregular waves in ocean engineering basin. Good capability to break the incident wave within the 6 seconds of period and 1 m of height is shown. Breaking efficiency for long period wave is not so good in regular and irregular wave. The results of this study will contribute to the design and construction of the floating breakwater.