• Korean Journal of Digital Imaging in Medicine
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• v.12 no.1
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• pp.59-64
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• 2010

We examined the accuracy and efficiency of phantom by applying the designed phantom in order to check daily quality assurance easily by objective criteria and to confirm daily quality assurance of linear accelerator, simulator, and CT-simulator. The results of 10 weeks of linear accelerator output dose using American Association of Physicists in Medicine(AAPM) daily quality assurance guide were measured within ${\pm}1%$ of error. Mechanical check of laser alignment, optical distance indicator(ODI), CT scanner laser and alignment of gantry lasers with the center of imaging plane were measured within ${\pm}1mm$. Daily average working time for daily quality assurance of radiation therapy equipments was 38 minutes. The designed phantom was easy to install and daily quality assurance was possible with only one installation. The aspects reproducibility and efficiency as well as accuracy of quality assurance were excellent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.357-358
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• 2006

Accurate calibration matching for maladjusted stereo cameras with calibrated pixel distance parameter is presented. The camera calibration is a necessary procedure for stereo vision-based depth computation. Intra and extra parameters should be obtain to determine the relation between image and world coordination through experiment. One difficulty is in camera alignment for parallel installation: placing two CCD arrays in a plane. No effective methods for such alignment have been presented before. Some amount of depth error caused from such non-parallel installation of cameras is inevitable. If the pixel distance parameter which is one of Intra parameter is calibrated with known points, such error can be compensated in some amount and showed the variable experiments for accurate effects.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.177-182
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• 2010

The pentacene-based organic thin film transistors(OTFTs) using polyvinylalcohol(PVA) alignment layer were fabricated on the $SiO_2$ evaporated to n-type (111) Si substrates. The pentacene film was deposited by thermally evaporated at $10^{-7}$ torr. X-ray diffraction (XRD) and atomic force microscope(AFM) measurement showed pentacene film which deposited on rubbed PVA layers were partially crystallized at (001) plane. The pentacene OTFTs with PVA layers rubbed perpendicular to the direction of current flow was shown to align better orientation than parallel rubbed case and thus to enhance the mobility and saturation current by a factor of 2.3 respectively. We obtained mobility by 0.026 $cm^2$/Vs and on-off current ratio by ${\sim}10^8$.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2313-2316
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• 2004

Accurate calibration effect for maladjusted stereo cameras with calibrated pixel distance parameter is presented. The camera calibration is a necessary procedure for stereo vision-based depth computation. Intra and extra parameters should be obtain to determine the relation between image and world coordination through experiment. One difficulty is in camera alignment for parallel installation: placing two CCD arrays in a plane. No effective methods for such alignment have been presented before. Some amount of depth error caused from such non-parallel installation of cameras is inevitable. If the pixel distance parameter which is one of intra parameter is calibrated with known points, such error can be compensated in some amount and showed the variable experiments for accurate effects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.109-114
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• 2003

Depth error correction effect for maladjusted stereo cameras with calibrated pixel distance parameter is presented. The camera calibration is a necessary procedure for stereo vision-based depth computation. Intra and extra parameters should be obtain to determine the relation between image and world coordination through experiment. One difficulty is in camera alignment for parallel installation: placing two CCD arrays in a plane. No effective methods for such alignment have been presented before. Some amount of depth error caused from such non-parallel installation of cameras is inevitable. If the pixel distance parameter which is one of intra parameter is calibrated with known points, such error can be compensated in some amount. Such error compensation effect with the calibrated pixel distance parameter is demonstrated with various experimental results.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.107-112
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• 2003

The alignment effect of liquid crystals on Polyimide surfaces bombarded by a low energy argon ion beam and the effect of pretilt angle on viewing characteristics of an LCD cell are discussed. The unidirectional out-of-plane liquid crystal tilt angle is varied with various ion beam irradiation conditions, such as the energy of the incident ions, the angle of incidence and exposure time. As low pretilt angle is profitable for wider viewing property, LCD cell with ion beam modified Polyimide layer show wider viewing characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.306-313
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• 1998

To elucidate the liquid crystal(LC) molecules alignment mechanism, it is important to determine the molecular orientation of the rubbed polymer surface molecules that directly contact with LC molecules. In this work, the molecular orientation on a rubbed surface of polyimide (SE-3310, Nissan) film has been studied by polarized FTIR absorption spectroscopy. It has been found that molecular chain on the rubbed surface of polymide film are oriented along the rubbing direction and are tilted up on an average by 5.0$^{\circ}$. In the SHG(Second Harmonic Generation) measurement, the pretilt angle of molecular chain on the poylmide fim was 4.6$^{\circ}$ fro, the surface plane. And the pedit angle of liquid crystal (ZLI-2293, Merck) molecules measured by crystal rotation method was 5.4$^{\circ}$in the same rubbing condition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.2
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• pp.56-62
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• 2003

Epitaxial $Bi_4Ti_3O_{12}$ films on $SrTiO_3$(100), L$aA1O_3$(100) and MgO(100) were prepared by sol-gel process using metal naphthenate as a starting material. As-deposited films were pyrolyzed at $500^{\circ}C$ for 10 min In air and annealed at $750^{\circ}C$ for 30 min in air. Crystallinity and in-plane alignment of the film were investigated by X-ray diffraction $\theta$-2$\theta$ scan and P scanning. A field emission-scanning electron microscope and an atomic force microscope were used for characterizing the surface morphology and the surface roughness of the film. The film prepared on MgO(100) showed the most poor crystallinity and in-plane alignment, compared to those on the other substrates. While the films on $LaA1O_3$(100) and $SrTiO_3$(100) having high crystallinity and in-plane alignment showed the form of columnar grain growth, the film on MgO(100) which had poor crystallinity showed the form of acicula grain growth.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.792-795
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• 2006

In-plane-switching (IPS)-mode LCD is one of the most useful technologies for a broad range of viewing angles. To apply for IPS-LCDs, we synthesized novel homogeneous alignment materials, changing dianhydrides (BTDA and BPDA) and bridged diamines (ODA and PACM). We measured their pre-tilt angles using the crystal rotation method with positive LC and their surface properties.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.27.1-27.1
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• 2009

In recent years, ZnO nanostructures have drawn considerable attentions for the development of futuristic electronic devices due to their superior structural and optical properties. As the growth of ZnO nanowires by MOCVD is a bottom-up technique, the nature of substrates has a vital role for the dimension and alignment of the nanowires. However, in the pursuit of next generation ZnO based nanodevices, it would be highly preferred if well-ordered ZnO nanowires could be obtained on various substrates like sapphire, silicon, glass etc. Vertically aligned nanowires were grown on A and C-plane sapphire substrates, where as nanopencils were obtained on R-plane sapphire substrates. In addition, C-axis oriented vertical nanowires were also found using an interfacial layer(aluminum nitride film) on silicon substrates. On the other hand, long nanowires were found on Ga-doped ZnO film on glass substrates. Structural and optical properties of the ZnO nanowires on various substrates were also investigated.