• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.203-203
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• 2010

Nano-crystalline Si thin films were deposited on polymer and glass by inductively coupled plasma (ICP) - assisted RF magnetron sputtering at low temperature in an argon and hydrogen atmosphere. Internal ICP coil was installed to increase hydrogen atoms dissociated by the induced magnetic field near the inlet of the working gases. The microstructure of deposited films was investigated with XRD, Raman spectroscopy and TEM. The crystalline volume fraction of the deposited films on polymer was about 70% at magnetron RF power of 600W and ICP RF power of 500W. Crystalline volume fraction was decreased slightly with increasing magnetron RF power due to thermal damage by ion bombardment. The diffraction peak consists of two peaks at $28.18^{\circ}$ and $47.10^{\circ}\;2{\theta}$ at magnetron RF power of 600W and ICP RF power of 500W, which correspond to the (111), (220) planes of crystalline Si, respectively. As magnetron power increase, (220) peak disappeared and a dominant diffraction plane was (111). In case of deposited films on glass, the diffraction peak consists of three peaks, which correspond to the (111), (220) and (311). As the substrate temperature increase, dominant diffraction plane was (220) and the thickness of incubation (amorphous) layer was decreased.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.66.2-66.2
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• 2010

We have studied the properties of interstellar turbulence as observed by Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS). This observation uses 13CO J=$1{\rightarrow}0$ emission with high spectral resolution of 0.21 kms-1 and covers wide galactic plane regions ($18^{\circ}$ < 1 < $55.7^{\circ}$ and -1 < b < $1^{\circ}$). Firstly, we measured the one dimensional power spectrum of 13CO intensity along the galactic longitude and along the galactic latitude. We found the slope of the power spectrum changes around the molecular ring structure and the center of the galactic plane. Secondly, we explored how the power spectral slope is related with the velocity dispersion of supersonic giant molecular clouds in the GRS. Finally, we suggest the turbulent nature of the interstellar medium is connected with star formation activities in spiral arms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.250-257
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• 2011

The power input to an infinite cylindrical shell excited by a point force is investigated. The circumferential direction and axial direction of the cylindrical shell is assumed as a two-dimensional unbounded medium, and the point force is replaced as a periodic array of imaginary sources. The spatial Fourier transform is taken from the equation of motion of the cylindrical shell, which is derived from the static model of Donell-Mushtari-Vlasov. The inverse Fourier transform is taken to derive the vibration responses. Mobility from out-of-plane forces and in-plane forces are derived from the obtained vibration responses. The theory is applied to a cylindrical shell excited by a normal direction of point force.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.335-342
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• 2012

A high-isolation Ka-band WR-28 waveguide power combiner is designed and implemented using a resistive septum. The waveguide power combiner developed here is an E-plane T-junction type with a TaN resistive septum inserted in a slit of waveguide junction. The fabricated waveguide power combiner shows a return loss better than -20 dB and an insertion loss less than 0.1 dB. Also the measurement shows isolation levels of 20 dB or more almost all over the band and in particular 25 dB or more below 37 GHz. The amplitude and phase imbalance are measured to be less than 0.1 dB and $2.5^{\circ}$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.639-643
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• 2018

As electronic systems become smaller and more portable, the need for power conversion continues to increase. In addition, system stability must be ensured from switching noise due to power conversion efficiency and power conversion system miniaturization. Therefore, countermeasures to reduce switching noise during power conversion are essential. In this paper, a DC/DC buck converter circuit is constructed, and the characteristics of switching noise generated when changing the parts layout in a four-layer printed circuit board (PCB) structure with a reference plane are compared and analyzed. In addition, switching noise characteristics were compared and analyzed through simulations when the parts layout was different in a two-layer PCB structure from which the reference planes were removed. As a result, it was confirmed that the radiated emissions characteristic is reduced by 12dB and the conducted emissions characteristic decreased by 7dB to 8dB, according to the current return path in the four-layer PCB structure. Thus, it was confirmed that the noise characteristics can be improved according to the configuration of the current return path when the power conversion circuit is designed.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.5
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• pp.11-17
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• 2016

In this paper, we propose a method of correcting depth image by the plane modeling and then improving the coding performance. We model a plane by using the least squares method to the horizontal and vertical directions including the target pixel, and then determine that the predicted plane is suitable from the estimate error. After that, we correct the target pixel by the plane mode. The proposed method can correct not only the depth image composed the plane but also the complex depth image. From the simulation result that measures the entropy power, which can estimate the coding performance, we can see that the coding performance by the proposed method is improved up to 80.2%.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.295-299
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• 2012

We investigated the crystal and the optical properties of GaN-based blue light emitting diodes (LEDs) which were simultaneously grown on c-plane (0001) and semipolar (11-22) GaN templates by using metal-organic chemical vapor deposition (MOCVD). The X-ray rocking curves (XRCs) full width at half maximums (FWHMs) of c-plane (0001) and semipolar (11-22) GaN templates were 275 and 889 arcsec, respectively. In addition, high-resolution X-ray ω-2θ scan showed that satellite peaks of semipolar (11-22) InGaN quantum-wells (QWs) was weaker and broader than that of c-plane (0001) InGaN QWs, indicating that the interface quality of c-plane (0001) QWs was superior to that of semipolar (11-22) QWs. Photoluminescence (PL) and electroluminescence (EL) results showed that the emission intensity and the FWHMs of polar c-plane (0001) LED were much higher and narrower than those of semipolar (11-22) LED, respectively. From these results, we believed that relative poor crystal quality of semipolar (11-22) GaN template might give rise to the poor interfacial quality of QWs, resulting in lower output power than conventional c-plane (0001) GaN-based LEDs.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1803-1807
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• 2005

The pipe which it uses from the nuclear power plant or factory by a long period use and a corrosive action the inside defect occurs on the inside. abstract here. The ESPI method is in order to investigate the laser light in the measurement object it will be able to measure the wide territory whole in once, does not receive an effect in direction of defect not to be, has the strong point it will be able to measure a change of place arrowhead real-time defect. It measured a inside defect of pressure vessel by using Out of plane ESPI and In plane of ESPI. It compared a each method result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.161-166
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• 2007

In this paper, two 4$\times$4 rectangular patch array antennas operating at 20 GHz are implemented for the satellite communication. The sixteen patch antennas and microstrip feeding line are printed on a single-layered substrate. The design goal is to achieve high directivity and gain by optimizing design parameters through permutations in element spacing. The spacing between the array elements is chosen to be 0.736$\lambda$. Numerical simulation results indicate that the HPBW(Half-Power Beam Width) of the 4$\times$4 patch array antenna is 18.78 degrees in the E-plane and 18.48 degrees in the H-plane with a gain of 17.18 dBi. Numerical simulations of a 4$\times$4 recessed patch array antenna yield a HPBW of 18.71 degrees in the E-plane and 17.82 degrees in the H-plane with a gain of 19.43 dBi.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.239-247
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• 2001

Measured radiative heat fluxes on the furnace exit plane of a heavy duty power boiler of steam output 1650 T/h are discussed. A high-ash pulverized bituminous coal was used. Such measurements are necessary to improve heat fluxes inside a steam boiler furnace was manufactured. An extra small heat radiation sensor was placed in the water cooled head of the probe. The sensor had no direct contact with furnace gases and measured only the radiant energy. There was no exposure to convective heat transfer. With the radiometric probe, one can obtain a spherical indicatrix of radiation intensity as well as hemispherical radiative heat flux incident on any surface passing through a measuring point inside the furnace. Thus, the quantity of radiation energy, passing through the furnace exit plane, to the convective heating surfaces and the quantity of radiation energy going in the opposite direction were measured. A formula for relative radiative heat flux on the furnace exit plane has been proposed.