• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.979-982
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• 2003

In this study, because of change in electromagnetic force, deformation of the free surface motion of a magnetic fluid is changed. Deformation of the free surface motion of a magnetic fluid for the change in electromagnetic force is discussed and carried out theoretically and experimentally on the basis of Rosensweig Ferrohydrodynamic Bernoulli Equation. Objective of this study explicates free surface motion by electromagnetic force and planes to designed controller. To control free surface of magnetic fluid, it embody designed two-dimensional free surface form of magnetic fluid. By using this characteristics, they applied to oscillator for surface control, flow control, boundary layer control. Strength of magnetic field and height of free surface of magnetic fluid measure as a hall-effect sensor. As performing height control of magnetic fluid, the result will be presented possibility of free surface deformation control.

• Journal of the Korean Society of Safety
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• v.12 no.1
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• pp.94-100
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• 1997

The objective of this research is to study the formations of smoke layer in case of several furniture fires such as trashcan, carpet, mattress and wardrobe as a fire starter in a residential room by performing the experimental studies. The uniformly distributed fire in case of carpet showed that the ignition and the initial growth period were relatively short while the fully developed period was considerably long. The concentrated fires such as the trashcan, mattress and wardrobe showed that the ignitions and the initial growth periods were relatively long. The descending speed of the interface height was proportioned to the inflammability of the furniture and the spread of the fire. The time required to come down around 1m was within 1-3 minutes. The Interface heights for the furniture fires were around 1m as the steady state. However, at the time of the maximum temperature, the interface height was lowered to 0.25m-0.75m from the floor. The carbon dioxide concentration reached the highest while the oxygen concentration was minimum.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.494-499
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• 2011

One of the devices to prevent separated flow over a wing or a flap at high angle of attack is a vortex generator. In the present work, we numerically study the flow around a low-profile or micro vortex generator whose height is less than local boundary layer thickness which can delay separation with a minimum drag penalty owing to its very small wetted surface area. As a first step toward a parametric study to efficiently design this MVG flow control system, we simulate the flow around a single MVG on a flat plate. For the simulation, we employ OpenFOAM with Launder-Sharma ${\kappa}$-epsilon model. The analysis results are validated by comparing with experimental results of a rectangular MVG at an angle of attack of 10 degrees whose height is 20% of local boundary layer. Important results and aspects of this numerical study are discussed. We also simulate the flow around rectangular, triangular and trapezoidal MVGs and the results are compared

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1065-1069
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• 2002

The addressing time should be reduced by modifying cell structure and/or driving method in order to replace the dual scan system by single scan and increase the luminance in large ac plasma display panel(PDP). In this paper, the effects of the addressing time was decreased with decreasing thickness of dielectric layer on the front glass and thickness of white dielectric layer on the rear glass. the decreasing rate were 160ns/10$\mu\textrm{m}$ and 270ns/10$\mu\textrm{m}$, respectively Also in case of decreasing the height of barrier rib, addressing time was decreased at the rate of Sons/10$\mu\textrm{m}$.

• Wind and Structures
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• v.15 no.5
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• pp.355-367
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• 2012

Atmospheric boundary layer winds experience two types of effects due to friction at the ground surface. One effect is the increase of the wind speeds with height above the surface. The second effect, called the Ekman layer effect, entails veering - the change of the wind speed direction as a function of height above the surface. In this study a practical procedure is developed within a database-assisted design (DAD) framework that accounts approximately for veering effects on tall building design. The procedure was applied in a case study of a 60-story reinforced concrete building, which also considered the dependence of veering effects on the orientation of the building. Comparisons are presented between response estimates that do not account for veering, and account for veering conservatively. For the case studied in this paper veering effects were found to be small.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.3
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• pp.17-22
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• 2006

Sunroof is getting widely used in automobiles since it maintains, compare to window, better air circulation as well as less noise while driving in high speed. In this study, we consider an electronic control type spoiler sunroof which slides backward after tilting a rear part of a glass. Installing a wind deflector on the sunroof reduces noise much more effectively. The height of the wind deflector is designed using a boundary theory related to incompressible air layer. The developed wind deflector is investigated experimentally by measuring a wind noise. When the height of the wind deflector is designed by a fixed type, the sunroof maintains a very quiet interior noise over a certain driving speed, nevertheless it produces relatively loud noise in low driving speed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.874-878
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• 2001

Solder bump was electroplated on wafer for flip chip application. The process is as follows. Ti/Cu were sputtered and thick PR was formed by several coating PR layer. Fine pitch vias were opened using via mask and then Cu stud and solder bump were electroplated. Finally solder bump was formed by reflow process. In this paper, we opened 40㎛ vias on 57㎛ thick PR layer and electroplated solder bump with 70㎛ height and 40㎛ diameter. After reflow process, we could form solder bump with 53㎛ height and 43㎛ diameter. In plating process, we improved the plating uniformity within 3% by using ring contact instead of conventional multi-point contact.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.765-770
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• 2001

The objective of the present study is to investigate the effects of the various inlet boundary layer thickness on convective heat transfer distribution in a turbine cascade endwall and blade suction surface. In addition, the proper height of the boundary layer fences for various inlet boundary layer thickness were applied to turbine cascade endwall in order to reduce the secondary flow, and to verify its influence on the heat transfer process within the turbine cascade. Convective heat transfer distributions on the experimental regions were measured by the image processing system. The results show that heat transfer coefficients on the blade suction surface were increased with an augmentation of inlet boundary layer thickness. However, in a turbine cascade endwall, magnitude of heat transfer coefficients did not change with variation of inlet boundary layer thickness. The results also present that the boundary layer fence is effective in reducing heat transfer on the suction surface. On the other hand, in the endwall region, boundary layer fence brought about the subsidiary heat transfer increment.

• International Journal of CAD/CAM
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• v.4 no.1
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• pp.33-45
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• 2004

In this work, a rational procedure has been formulated for the selection of points approximating slice contours cut in LOM (Laminated Object manufacturing) with first order approximation. It is suggested that the number of points representing a slice contour can be 'minimised' or 'optmised' by equating the horizontal chordal deviation (HCD) to the user-defined surface form tolerance. It has been shown that such optimization leads to substantial reduction in slice height calculations and NC codes file size for cutting out the slices. Due to optimization, the number of contour points varies from layer to layer, so that points on successive layer contours have to be matched by four sided ruled surface patches and triangular patches. The technological problems associated with the cutting out of triangular patches have been addressed. A robust algorithm has been developed for the determination of slice height for optimum and arbitrary numbers of contour points with different strategies for error calculations. It has been shown that optimisation may even lead to detection and appropriate representation of elusive surface features. An index of optimisation has been defined and calculations of the same have been tabulated.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.146-146
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• 2015

We report the enhanced performance of poly(N-vinylcarbozole) (PVK)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based quantum-dot light-emitting diodes by inserting the polyaniline:poly (p-styrenesulfonic acid) (PANI:PSS) interlayer. The QD-LED with PANI:PSS interlayer exhibited a higher luminance and luminous current efficiency than that without PANI:PSS. Ultraviolet photoelectron spectroscopy results exhibited different electronic energy alignments of QD-LEDs with/without the PANI:PSS interlayer. By inserting the PANI:PSS interlayer, the hole-injection barrier at the QD layer/PVK interface was reduced from 1.45 to 1.23 eV via the energy level down-shift of the PVK layer. The reduced barrier height alleviated the interface carrier charging responsible for the deterioration of the current and luminance efficiency. This suggests that the insertion of PANI:PSS interlayer in QD-LEDs contributed to (i) increase the p-type conductivity and (ii) reduce the hole barrier height of QDs/PVK, which are critical factors leading to improve the efficiency of QD-LEDs.