• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.1
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• pp.11-23
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• 1989

A computer code has been developed to simulate three-dimensional viscous flows over a ship-stern. Semi-elliptic forms of Reynolds equations are adopted and numerically generated body-fitted coordinate systems are used to resolve complex geometries of the ship-hull. A standard form of $k-\varepsilon$ turbulence model is adopted for evaluation of the Reynolds stresses. Turbulent flows on a model with 3:1 elliptic sections and the SSPA-720 container ship model are predicted by using the code. Calculated pressure distributions of hull-surfaces and mean velocity distributions are generally in good agreements with measured values in wind-tunnels. But turbulent kinetic energies tend to be over-estimated near the stern in comparison with measured data.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.29-42
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• 1992

A potential based panel method is used to predict the open water characteristics of spade-type rudders. The inflow velocity is assumed to be constant in lime and uniform in space. Source and dipole are distributed on the rudder surface. It is assumed that the wake surface is streaming from trailing edge and it is represented by dipole distribution. In this paper, wake geometry is assumed by imposing appropriate conditions at the trailing edge and far from the body. The effects of wake geometry are studied. The pressure Kutta condition is applied at the trailing edge, the effects of which are compared with those of two-dimensional Kutta condition. The results of calculations for a spade-type rudder are compared with published results. It is concluded that this approach shows fairly good agreement with experimental results and can be used in the initial design stage of a rudder.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.1
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• pp.73-79
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• 2016

In this paper a cervical rehabilitation robot for Mckenzie exercises to be effective to neck pain relief is proposed. The robot has two degrees of freedom (DOF) for Lateral flexion and extension, Dorsal and Vental flexion which enable user to perform cervical stretching and isometric exercises for neck muscles. The mechanical parts of the cervical rehabilitation robot can be mounted on a back- or head-rest of chair, and user can perform the Mckenzie exercise with seated. In experiments we measured the range of motion of cervical part, EMG signals from neck muscles and the contact forces of a head bracket fixing the head part of user, and then evaluated their performances. From the experimental results, we showed a feasibility of the cervical rehabilitation robot proposed in this study.

• Journal of the Korean Chemical Society
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• v.38 no.3
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• pp.214-220
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• 1994

A glow discharge atomic absorption system for the direct analysis of conducting solid samples has been designed and constructed. An arrestor made of machinable ceramic which is a main component for confining the discharge between cathode and anode is modified to have a better stability in discharge. Discharge voltage or current, shape of arrestor, pressure, and gas flow rate can be controlled by an ADC/DAC board with a personal computer. The effect of discharge parameters such as discharge voltage, pressure, and gas flow rate on the sample loss rate, absorbance, and the surface morphology of sample by SEM has been studied to find optimum discharge conditions.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.79-82
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• 2015

The design parameter study about the magnetic pulse forming is performed using finite element analysis with MAXWELL. The first case of design parameters is about the initial charging voltage and the capacitance and the second case of design parameters are about the winding turns and the spacing of electromagnetic coil. The 3D finite element model of electromagnetic forming system is created and the magnetic force is calculated. The effects of design parameters on the magnetic forming force are investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.116-122
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• 1988

Interfacial shear stresses have been determined for countercurrent stratified flow of air and water in a nearly-horizontal rectangular channel, based upon measurements of pressure drop, gas velocity profiles and mean film thickness. A dimensionless correlation for the interfacial friction factor has been developed as a function of the gas and liquid Reynolds numbers. Equivalent surface roughnesses for the interfacial friction factor have been calculated using the Nikuradse correlation and have been compared with the intensity of the wave height fluctuation on the interface. The results show that the interfacial shear stress is mainly affected by turbulent mixing near the interface due to the wave motion rather than by the roughened surface.

• Fire Science and Engineering
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• v.23 no.5
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• pp.50-56
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• 2009

Explosion limit and autoignition temperature are the major properties used to determine the fire and explosion hazards of the flammable substances. Explosion limit and autoignition temperature for safe handling of ethylene were investigated. By using the literatures data, the lower and upper explosion limits of ethylene recommended 2.6vol% and 36vol%, respectively. Also autoignition temperatures of ethylene with ignition sources recommended $420^{\circ}C$ at the electrically heated crucible furnace (the whole surface heating) and recommended about $800^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosion limits for ethylene are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.3
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• pp.41-47
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• 2002

Turbulent wake behind a ship propeller has been investigated using the adaptive hybrid 2-frame PTV(Particle Tracking Velocimetry). 400 instantaneous velocity fields were measured according to 4 different blade phases and ensemble-averaged to investigate the spatial evolution of the vortical structure of near wake within one propeller diameter downstream. The phase averaged mean velocity fields show the potential wake and the viscous wake formed by the boundary layers developed on the blade surfaces. As the tip vortex evolves downstream, the slipstream is contracted and the turbulent intensity is decreased with viscous dissipation and turbulent diffusion.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.61-64
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• 2008

Reinforced Concrete structures are constructed under the basic assumption of perfect bonding between steel and concrete. The corrosion of steel in the reinforced concrete columns results in the excessive cracks and gradual deterioration of concrete between steel and concrete. The cyclic loading test was conducted with the three corrosion rates in the laboratory. Throughout this test, it is investigated a bond behavior of reinforced concrete columns under a steel corrosion. Main variables of the test are a corrosion of steel reinforcement and a level of stress.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.6
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• pp.41-47
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• 2009

This paper presents the spray characteristics of the simplex fuel nozzle with different working fluids for the gas turbine engine. Spray characteristics can be changed with viscosity, surface tension and density. In this research, water and test fluid type 2 which has similar characteristics of the kerosene are used as a working fluid. Spray visualization was performed by using ND-Yag laser and droplet size was measured by using PDPA(Phase doppler particle analyzer) system. The test results show that spray shapes and SMD distributions of two working fluids are similar at main spray region.