• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1511-1520
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• 2004

A flow visualization of the two-dimensional rigid fling-clap motions of the flat-plate wing are performed to gain knowledge of butterfly mechanisms that might be employed by butterflies during flight. In this numerical visualization, the time-dependent Navier-Stokes equations are solved for cyclic fling and clap types of wing motion. The separation vortex pair that is developed in the fling phase of the cyclic fling and clap motion is observed to be stronger than those of the fling followed by clap and pause motion(1st cycle motion). This stronger separation vortex pair in the fling phase is attributable to the separation vortex pair of the outside space developed in the clap phase as it moves into the opening in the following fling phase. Accordingly, higher lift and power expenditure coefficients in the fling after clap phase is caused by the stronger separation vortex pair.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.999-1004
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• 2002

This paper presents the color displays using more than three primary colors, for the reproduction of wider color gamut, and high-fidelity color reproduction. First, Natural Vision system, which is currently under development for the natural color reproduction in visual telecommunication applications, is introduced, The natural vision is based on spectrum instead of trichromatic color space, and enables high-fidelity color reproduction using multispectral and multiprimary technologies. Then, sixprimary color projection displays using LCD and DLP, and a four-primary color flat panel display are shown. It is experimentally demonstrated that the color gamut becomes much larger than conventional RGB-based display. In addition, it is proved that the spectral color reproduction using multiprimary display suppresses the influence of observer metamerism, and as a result, the color matching between the display and the real object is well improved.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.95-99
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• 2008

Applications of composite materials in various engineering fields have been extended significantly. For being useful composite materials, we could modify the rigidity and strength characteristics of composite material according to structures and material direction. In this study, CFRP, which has been widely used in space leisure and general structural applications due to the weight, elasticity coefficient, high fatigue strength and lower thermal transformation ect, was selected. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of CFRP fiat and CFEP square members. It's different on the each result of strength and rigidity of CFRP flat and CFRP square members.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.469-470
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• 2006

Piezoelectric transformers based on lead zirconate titanate(PZT) have been received considerable interest because of their wide potential applications in transformer, oscillator, resonance sensor, actuator, acoustic transducer, as well as active slider for hard disk drives. However, for the applications which need a small power supply such as thin and flat displays, micro-robot, micro-system, it is especially necessary to integrate the passive components because they typically need more than 2/3 of the space of the conventional circuit. So, we have fabricated the piezoelectric micro-transformer to supply energy for micro-systems using PZT thin films and MEMS technologies.

• Journal of electromagnetic engineering and science
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• v.6 no.3
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• pp.176-181
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• 2006

Signal distortion due to the path loss, shadow, and multi-path fading is very serious in radio channel. In this paper, we propose CDMA-OFDM cooperative communication system based on DFP(Decode and Forward Protocol) to overcome these phenomena using spread spectrum technique, orthogonal sub-carrier, and the space diversity. We simulated proposed system under Rayleigh flat fading channel environment. A variety of simulation results reveal the cooperation can provide performance gain of up to 12 dB over direct communications in ideal inter-user case at BER of $10^{-3}$. And we can also confirm variation of diversity effect as channel environment changes.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.79-87
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• 2011

In this paper, suggested is a hybrid-type visual alignment system to align mask and panel in 3-D space, where mask and panel are to be controlled independently by two individual positioning mechanisms in order to compensate for spatial misalignments. In the hybrid visual alignment system, the below 4-PPR parallel mechanism provides in-plain motions to pattern mask like the other conventional alignment systems while the above 4-RPS parallel mechanism is to move glass panel to achieve a complete spatial alignment. For the control of the hybrid alignment system, first, inverse kinematic solutions for the parallel mechanisms are given to determine the driving distance of each active joint, and also an efficient way to determine the spatial alignment error is developed by exploiting three in-plane cameras.

• ETRI Journal
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• v.33 no.4
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• pp.645-647
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• 2011

In this study, a microcapillary pumped loop (MCPL) that can be used as a cooling device for small electronic and telecommunications equipment has been developed. For thin devices such as an MCPL, securing a vapor flow space is a critical issue for enhancing the thermal performance. In this letter, such enhancement in thermal performance was accomplished by eliminating condensed droplets from the vapor line. By fabricating the grooves in the vapor line to eliminate droplets, a decrease in thermal resistance of about 63.7% was achieved.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.150-151
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• 2013

Recently, the internal space organization of the building changes to the frame construction and flat slab construction in the wall type structure. And the use of light weight panel changing the internal joint use easily is increased. Therefore, in this research, the length change characteristic that the magnesium chloride addition rate reaches to the magnesium curing body tries to be studied. It could confirm according to the length change specific result that the magnesium chloride amount of addition reaches to the magnesium oxide curing body to expand. And the thing described below was the large-scale expansion the magnesium oxide addition rate 60%. And it showed up as 50, 40, 30, 20, and order of 10s (%). It could look at to form the hydrate of the SEM picture result needle-shaped of the Hardened.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1251-1253
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• 1996

The vision processing system for mobile robots requires real time processing and reliability for the purpose of safe navigation. But, general types of vision systems are not appropriate owing to the correspondence problem which correlates the points out of two images. To determine the obstacle area, we use correspondences of line segments between two perspective images sequentially acquired by camera. To simplify the correspondence, the matching of line segments are performed in the navigation space, based on the assumption that mobile robot should be navigated in the flat surface and the motion of mobile robot between two frames should be approximately known.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.924-927
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• 2004

Measurements of fluctuating wall pressures were made with a linear array of 16 piezo-electric transducers beneath a fully-developed turbulent boundary layer. The piezoelectric bimorph actuator applied in this experiment has bonding structures of each polarity to make out-of-plane displacements rather than in-plane ones by using piezoelectric effect To specify the boundary layer characteristics at the location where the actuation was applied, the wall friction coefficients and $Re_\theta$ were measured by using the CPM method. The actuating frequency for the bimorph film was determined according to the priori bursting frequency from boundary layer parameters. The reduction of convecting energies in wave-number space was clearly observed at the specified actuating frequencies.