• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.6
• /
• pp.558-562
• /
• 1999

For 6H-SiC crystals which was obtained by sublimation growth, the formation of micropipes and internal planar defects was discussed in consideration of the inter-relationship between mass adsorption behavior and the defects origin on the growth interface on the basis of KSV theory and the the step growth pattern on the vicinal plane. Micropipes and planar defects was formed in the region which the step could not be grown by impurities impinging. It was realized that the internal defects formation was related to the crystallographic step planes formed on the growth interface and the migration of the molecules adsorbed on it.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1770-1771
• /
• 2011

In mission planning of UAV applications, especially for the missions requiring height transitions, it is required to generate reference flight trajectories considering the performances of the engine installed in the UAV. Even though the vertical line following guidance based height transition trajectory generation method has been developed to build reference height transition trajectories easily, it is not adequate for considering engine performances effectively since many engine characteristics and performances have conventionally been described in the V-H(speed-height) plane which is not the very space where the UAVs are actually flying. In this paper, we derive the trajectories in V-H plane for the vertical line following flights. And based on the results, a new algorithm to design the reference height transition trajectories for UAV applicaions. Simulation results demonstrate that the proposed algorithm is very effective and easily applicable.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.5
• /
• pp.47-52
• /
• 2004

In this paper we fabricated microchip antenna operating in bluetooth frequency bands(2.402∼2.4800㎓). The antenna has a size of about 54mm${\times}$19mm${\times}$0.8mm giving a total bluetooth PCB for suuort and chip of about 11mm${\times}$4mm${\times}$1.6mm. Bandwidth of the designed and fabricated chip antenna for bruetooth is 10.71% at the resonated frequency of 2.45㎓ and the resonant frequency and bandwidth versus change of my arbitrary fled point is observed. also, E-plane and H-plane in the Measured radiation pattern characteristic of chip antenna is compared and analyzed.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.10
• /
• pp.57-68
• /
• 1995

An upper bound elemental technique (UBET) program has been developed to predict forging load, die-cavity filling, preform in non-axisymmetric forging. To analyze the process easily, it is suggested that the deformation is divided into two different parts. Those are axisymmetric part in corner, plane-strain part in lateral. The plane-strain and axisymmetric parts are combined by building block method. And the total energy is computed through combination of three deformation parts. A dumbbell-type preform has been obtained from height and volumetric compensations of the billet based on the backward simulation. Experimetns have been carried out with pure plasticine at room temperature. Theoretical predictions are in good agreement with expereimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.359-360
• /
• 2006

Recently, a lot of work and interest has been devoted to the development of multiaxial fatigue parameters for fretting fatigue life prediction. Many of these parameters have been reviewed in the literature for simple geometries like a cylinder-on-flat contact configuration. The purpose of this study was to estimate fretting fatigue life using critical plane approach which is one of the multiaxial fatigue theories.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.27-28
• /
• 2006

This study performs to investigate deformation of wall thinning pipe and to find out the position of the internal thinning defect by shearography. Shearography is one of optical methods those have applied to nondestructive testing (NDT) and the strain/stress analysis. This technique has the merit of the directly measuring the first derivative of displacement, sensitivity of which can be adjusted by the handling of optical component in interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and developed the nondestructive out-of-plane deformation analysis technique fur internal thinning defect of elbow by shearography. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.13 no.2
• /
• pp.285-289
• /
• 1995

This paper describes the determination of geoid using height data measured by GPS and Spirit Levelling. The GPS data of the 88 stations were used to determine the geoid undulation (N) which can be easily obtained by subtracting the orthometric height(H) from the ellipsoidal height(h). From the geoid undulation (N) calculated at each station mentioned above, geoid plots with a contour interval of 0.25 m were drawn using two interpolation methods. The following interpolation methods were applied and compared with each other: Minimum Curvature Method and Least Squares Fitted Plane. Comparison between geometric geoid and gravimetric geoid undulation by FFT technique was carried out.

• Journal of Magnetics
• /
• v.11 no.3
• /
• pp.143-146
• /
• 2006

We attempted to fabricate a new type of magneto optic spatial light modulator (MO-SLM) for multiple-tone modulation by using in-plane magnetization. In the MO-SLM, magnetic property of magneto-optical layer was modified to be suitable for multiple-tone expression by substituting Al in Bi:YIG film. At a driving current to 28 mA in an electrode of the fabricated MO-SLM, changes in brightness of pixels were observed using a polarization microscope.

• Journal of ILASS-Korea
• /
• v.4 no.4
• /
• pp.38-45
• /
• 1999

The near field structure of round turbulent jets with initially asymmetric velocity distribution is investigated experimentally. Experiments were carried out using a constant temperature hot-wire anemometry system to measure streamwise velocity in the jets. The measurements were undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distribution of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stress. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend at the upstream of the exit. Three pipes were used for this study: A straight pipe, 90 and 160 degree-bended pipes. Therefore, at the upstream of the pipe exit, the secondary flow through the bend and the mean streamwise velocity distribution could be controlled by changing the curvature of pipes.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.6
• /
• pp.15-23
• /
• 1998

A three dimensional simulation of the fluid flow in an automotive torque converter was conducted adopting the mixing plane model implemented in the computational fluid dynamics program CFD-ACE. The present numerical results for performance characteristics showed a good agreement with the experimental results. In the flow of the torque converter, recirculating flow regimes were found mostly at the suction side of each element, which caused the performance decrease. The recirculating flow can be minimized by the optimization of the blade geometries.