• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.458-466
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• 1993

Natural convection in trapezoidal sections of cavity was numerically investigated using a Finite Volume Method. Temperatures of the upper inclined and lower horizontal walls are constant, with vertical side walls being insulated. When the top wall is hotter than the bottom one, a single cell of stratified flow field is obtained and heat transfer occurs only by conduction. For the colder top wall, bifurcation solutions are obtained for the higher Rayleigh numbers, while unique solutions for lower values. Flow structure is strongly dependent on the configuration and the Rayleigh number.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.207-213
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• 2004

A kinetic theory analysis is used to study the ultra-thin gas flow field in a gas slider bering, The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for a flow in a micro-channel between an inclined slider and a moving disk drive platter. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires much less computational effort.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.354-356
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• 1997

In this paper, we study the distribution of surface charge density on polymer insulators. The electric field of polymer insulators is calculated by axisymetric 3-D FEM with dc source. And the surface charge density is calculated by electric scalar potential and boundary condition for electrostatic fields. Simulation model is the inclined type polymer insulator with a shed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.822-827
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• 2003

Experiments were done for the three dimensional unsteady flow in a counter rotating axial flow fan under stable operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. Swirl velocity, which was generated by the front rotor, was recovered in the form of static pressure rise by the rear rotor except for hub and tip regions.

• Journal of Distribution Science
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• v.12 no.9
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• pp.65-72
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• 2014

Purpose - This study aims to provide a brief understanding of usability and its extended models with TAM as well as identifying additional determinants that had been suggested in previous studies on mobile services. Research design, data, and methodology - Empirical data were collected by conducting a field survey of potential mobile application service users. The call for participation was also made in mobile related application issues, which were widely discussed. Result - The ease of use and usefulness had a significantly positive influence on attitude and intention. It also was revealed that added value services can offer practical value to customers. Thus, positive attitudes toward the adoption of services by customers are present when they perceive higher usefulness and ease of use of mobile application services. Conclusion - It was indicated that customers who are more inclined to try new products or who have a higher demand for new things tend to think about those functionalities and added value mobile application services from the perspective of usefulness and ease of use and operation.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.185-193
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• 2003

Basic flow fields of two dimensional V flames were examined as a preliminary work to study the instability of premixed flame with vorticity generation. Laminar premixed propane and methane flame were anchored by electrically heated wire to make two dimensional V flames. Flow fields were measured mainly by PIV(Particle Image Velocimetray) and the results were compared with those obtained by LDV(Laser Doppler Velocimetry) to confirm their reliability. Because the curvatures of V flames are so small, V flames were locally assumed to be inclined planar flames in gravitational field. The measured flow fields were locally compared with those of analytical solutions, which showed the qualitatively similar results. In downstream region, the vorticity fields were nearly constant except region near the center line, which support the assumption of locally one dimensional flame. Besides it was tried to find experimentally the similarity of flow fields in downstream region. Finally, stability diagram of propane and methane flames were drawn for the equivalence ratio less than one and the wide range of mean velocity.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.448-457
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• 1996

Chemical application is one of the most important field operation in rice production . Rolling of a boom due to local unevenness and softness in fields causes a local under/over-application of spray. This study was conducted to develop a control system for balancing a boom. A boom mounting mechanism was modfied and a control algorithm was developed in the study. The results for testing the performance of the control system showed that the system could balance the boom in flat and inclined fields. This research can contribute to improve spraying uniformity in applying agricultural chemicals with a boom sprayers.

• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.151-162
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• 1997

Chemical application is one of the most important field operation in rice production. Rolling of a boom due to local unevenness and softness in fields causes a local under/over-application of spray. In this study, the vertical movement of boom tips due to unevenness of ground in paddy fields was investigated, and an active pendulum suspension control system was designed and tested for compensating the movement and balancing the boom to the ground. The results for testing the performance of the control system showed that the system could balance the boom both in flat and inclined fields. The active pendulum control system developed in this study could be properly used for improving spraying performance of a boom sprayer.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.316-321
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• 2011

Recently, it has been studied machining of micro parts with increasing demands for ultra precision parts. However, many engineering problems have already begun in polishing of optical parts or lens. As a method to overcome such problems, a new technology for the polishing of the target surface is being studied by controlling abrasives using MR fluids which are sensitive to magnetic fields. Since the current MR polishing system uses a big electromagnet, and is difficult to polish micro parts or spherical lens. Therefore, in this study, a round endmill type MR polishing system was developed to polish a three-dimensional structure which has spherical or inclined plane. And then, series of experiments were performed to verify the polishing performance of the developed round endmill type MR polishing system.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.4
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• pp.388-395
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• 1986

Numerical solutions of two-dimensional, steady, and natural are investigated in a confined rectangular cavity with porous media. The saturated fluid is bounded by two isothermal vertical walls at different temperatures and two adiabatic horizontal walls. Governing equations are numerically solved by finite difference method with the up wind scheme. Distributions of streamline and temperature we. predicted for aspect ratios ranging from 0.1 to 1.0, Rayleigh numbers 50 to $10^4$, and tilt angles $0^{\circ}\;to\;60^{\circ}$. Representative plots of temperature and velocity field according to tilt angle are presented. The effects of aspect ratio, Rayleigh number, and tilt angle on local and average Nusselt numbers are obtained. The optimum conditions for maximum Nusselt number are also presented with tilt angles.