• Title/Summary/Keyword: $E_o-R_e$ Plane

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A Design of the Diplexer for Satellite Transponder using Waveguide E-plane Discontinuities (도파관 전계면 불연속 구조를 이용한 위성 중계기용 다이플렉서의 설계)

  • 최상윤;강우정;이상웅;최성진;라극환
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.30A no.4
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    • pp.1-10
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    • 1993
  • This paper presents the designing/manufacturing scheme of the diplexer for satellite transponder which is composed of 2-channel bandpass filters, coupled with E-plane T-junction, having symmetrical waveguide E-plane step discontinuity structures. The 2-channel bandpass filters of the diplexer are designed by the scheme of connecting ${\lambda}_{g}$/2 shunt stub to the waveguide E-plane, playing the role of heat sinks without attaching a special heat sinks and to give the profitable productivity and allow the low-cost manufacturing at mass production, tuning screws are eliminated which have been used to compensate the operating characteristics of manufactured filters. The 2 channel bandpass filters of manufactured 14/12 GHz diplexer for domestic Ku-band satellite transponder have the return loss of 25 dB, insertion loss of 0.3 dB in passband, and below-50 dB of stopband characteristics (T$_{x}$ : f$_{o}{\pm}$250 MHz, R$_{x}$ : f$_{o}{\pm}$220 MHz) at room temperature.

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Hydrothermal Growth and Characteristics of ZnO Nanorods on R-plane Sapphire Substrates

  • Kim, Min-Su;Kim, So-A-Ram;Nam, Gi-Ung;Park, Hyeong-Gil;Yun, Hyeon-Sik;Im, Jae-Yeong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2012.05a
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    • pp.236-237
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    • 2012
  • ZnO nanorods were grown on R-plane sapphire substrates with the seed layers annealed at different temperature. The effects of annealing temperature for the seed layers on the properties of the ZnO nanorods were investigated by scanning electron microscopy, X-ray diffraction, UV-visible spectroscopy, and photoluminescence. For the as-prepared seed layers, the ZnO nanorods and the ZnO nanosheets were observed. Only the ZnO nanorods were grown as the annealing temperature was above $700^{\circ}C$. The optical transmittance in the UV region was almost zero while that in the visible region was gradually increased as the annealing temperature increased to $700^{\circ}C$. The optical band gap of the ZnO nanorods was increased as the annealing temperature increased to $700^{\circ}C$. In the visible region, the refractive index was decreased with increasing the wavelength, and the extinction coefficient was decreased as the annealing temperature increased to $700^{\circ}C$. The non-linear exciton radiative life time of the FX emission peak was established by cubic equation. The values of Varshni's empirical equation fitting parameters were ${\alpha}=4{\times}10^{-3}eV/K$, ${\beta}=1{\times}10^4K$, and $E_g(0)=3.335eV$ and the activation energy was found to be about 94.6 meV.

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A Simple Parameterization for the Rising Velocity of Bubbles in a Liquid Pool

  • Park, Sung Hoon;Park, Changhwan;Lee, JinYong;Lee, Byungchul
    • Nuclear Engineering and Technology
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    • v.49 no.4
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    • pp.692-699
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    • 2017
  • The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the $E_o-R_e$ plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth.

Investigation of Plane Strain Fatigue Crack Growth Behavior by Using Side-Grooved Specimens (측면홈 시험편을 이용한 평면 변형률 피로 균열 진전에 관한 연구)

  • 김종한;송지호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.1
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    • pp.63-69
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    • 1992
  • Plane-strain fatigue crack growth behavior of 7075-76 aluminium alloy was investigated by using side-grooved through-thickness center cracked tension(CCT) specimens. The effect of side-groove on the stress intensity factor value was examined. The effective thickness expression of $B_{e}$= $B_{o}$-( $B_{o}$-( $B_{ o-B_{n}^{2}}$ $B_{o}$ is the most appropriate to evaluate the stress intensity factor of side-grooved CCT specimen for fatigue testing. Fatigue crack growth rates can be well described by the effective stress intensity factor range based on closure measurements, for both side-grooved and uniform thickness specimens. Provided that the thickness of specimen meets the requirements for valid plane-strain fracture toughness, uniform thickness specimen data may be assumed to approximately represent the plane strain through-thickness crack growth behavior.ehavior.r.

The Rietveld Structure Refinement of Natural Phlogopite Using Neutron Powder Diffraction (중성자분말회절법을 이용한 금운모 결정에 대한 리트벨트 구조분석)

  • 이철규;송윤구;전철민;김신애;성기훈
    • Journal of the Mineralogical Society of Korea
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    • v.16 no.3
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    • pp.215-222
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    • 2003
  • The Rietveld structure refinement for the natural trioctahedral mica, phlogopite-1M (Parker Mine, Quebec, Canada) has been done by high resolution neutron powder diffraction at $25^{\circ}C$ and -263$^{\circ}C$. The structural formula of phlogopite determined by electron probe microanalysis is $K_2$(M $g_{4.46}$F $e_{0.83}$A $l_{0.34}$ $Ti_{0.22}$)(S $i_{5.51}$A $l_{2.49}$) $O_{20}$(O $H_{3.59}$ $F_{0.41}$). Cell parameters are a=5.30∼5.31 $\AA$, b=9.18∼9.20 $\AA$, c=10.18∼10.21 $\AA$, $\beta$=100.06∼100.08$^{\circ}$. Refinements converged to R values in the range of $R_{p}$=2.35%, $R_{wp}$=3.01%, respectively. In this study, the OH bond length is calculated to 0.93 $\AA$ at room temperature and 1.03 $\AA$ at -263$^{\circ}C$, and the angles between OH vector and (001) plane are obtained 93.4$^{\circ}$∼93.6$^{\circ}$. The decrease in the length of OH with the increase in temperature should be due to the hydrogen bonding in the structure of phogopite.e.e.f phogopite.e.e.

Superconductivity and Surface Morphology of YBCO/CeO$_2$ Thin Films on Sapphire Substrate by Pulsed Laser Deposition (사파이어 기판 위에 펄스-증착법으로 성장한 YBCO/CeO2박막의 초전도성과 표면 모폴러지)

  • Kang, Kwang-Yong;J. D. Suh
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.88-91
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    • 2003
  • The crystal structure and properties of YBa$_2$Cu$_3$$O_{7-x}$(YBCO) and CeO$_2$ thin films deposited on r-plane (1(equation omitted)02) sapphire substrate by pulsed- laser deposition(PLD) have been investigated. C-axis oriented epitaxial YBCO thin films with critical temperature (Tc) of 88 K were routinely grown on (200) oriented CeO$_2$ buffer layers with thickness in the range between 20 to 80 nm. When the thickness of the (200)oriented CeO$_2$ buffer layer increases over than 80 nm, the superconducting properties of YBCO thin films on that were deteriorated. The decrease in Tc of YBCO thin films was explained by the microcrack formation in CeO$_2$ buffer layer. These results indicate that the thickness of the (200) oriented CeO$_2$ buffer layer is critical to the epitaxial YBCO thin nim growth on r-plane (1(equation omitted)02) sapphire substrate.e.

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HVPE growth of GaN/InGaN heterostructure on r-plane sapphire substrate (R-plane 사파이어 기판위의 GaN/InGaN 이종접합구조의 HVPE 성장)

  • Jeon, H.S.;Hwang, S.L.;Kim, K.H.;Jang, K.S.;Lee, C.H.;Yang, M.;Ahn, H.S.;Kim, S.W.;Jang, S.H.;Lee, S.M.;Park, G.H.;Koike, M.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.17 no.1
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    • pp.6-10
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    • 2007
  • The a-plane GaN layer on r-plane $Al_2O_3$ substrate is grown by mixed-source hydride vapor phase epitaxy (HVPE). The GaN/InGaN heterostructure is performed by selective area growth (SAG) method. The heterostructure consists of a flown over mixed-sourec are used as gallium (or indium) and nitrogen sources. The gas flow rates of HCl and $NH_3$ are maintained at 10 sccm and 500 sccm, respectively. The temperatures of GaN source zone is $650^{\circ}C$. In case of InGaN, the temperature of source zone is $900^{\circ}C$. The grown temperatures of GaN and InGaN layer are $820^{\circ}C\;and\;850^{\circ}C$, respectively. The EL (electroluminescence) peak of GaN/InGaN heterostructure is at nearly 460 nm and the FWHM (full width at half maximum) is 0.67 eV. These results are demonstrated that the heterostructure of III-nitrides on r-plane sapphire can be successfully grown by mixed-source HVPE with multi-sliding boat system.

Emission and Structural Properties of Titanium Oxide Nanoparticles-coated a-plane (11-20) GaN by Spin Coating Method

  • Kim, Ji-Hoon;Son, Ji-Su;Baik, Kwang-Hyeon;Park, Jung-Ho;Hwang, Sung-Min
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.146-146
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    • 2011
  • The blue light emitting diode (LED) structure based on non-polar a-plane (11-20) GaN which was coated TiO2 nanoparticles using spin coating method was grown on r-plane (1-102) sapphire substrates to improve light extraction efficiency. We report on the emission and structural properties with temperature dependence of photoluminescence (PL) and x-ray rocking curves (XRC). From PL results at 13 K of undoped GaN samples, basal plane stacking fault (BSF) and near band edge (NBE) emission peak were observed at 3.434 eV and 3.484 eV, respectively. We also found the temperature-induced band-gap shrinkage, which was fitted well with empirical Varshini's equation. The PL intensity of TiO2 nanoparticles ?coated multiple quantum well (MQW) sample is decayed slower than that of no coating sample with increasing temperature. The anisotrophic strain and azimuth angle dependence in the films were shown from XRC results. The full width at half maximum (FWHM) along the GaN [11-20] and [1-100] directions were 564.9 arcsec and 490.8 arcsec, respectively. A small deviation of FWHM values at in-plane direction is attributed to uniform in-plane strain.

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RETRIEVAL OF LOCAL INTERPLANETARY DUST EMISSIVITY BY ASTRO-F

  • HONG S. S.;KWON S. M.;PYO J.;UENO M.;ISHIGURO M.;USUI F.;WEINBERG J. L.
    • Journal of The Korean Astronomical Society
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    • v.37 no.4
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    • pp.159-169
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    • 2004
  • This is a proposal to probe local part of the interplanetary dust (IPD) cloud complex and retrieve mean volume emissivity of the local IPDs at mid-infrared wavelengths. This will be done by monitoring, with Infrared Camera (IRC) aboard the ASTRO-F, the annual modulation of the zodiacal emission. In pointing mode of the ASTRO-F mission the spacecraft can make attitude maneuvering over approximately ${\pm}1^{\circ}$ range centered at solar elongation $90^{\circ}$ in the ecliptic plane. The attitude maneuvering combined with high sensitivity of the IRC will provide us with a unique opportunity observationally to take derivatives of the zodiacal emission brightness with respect to the solar elongation. From the resulting differential of the brightness over the ${\pm}1^{\circ}$ range, one can directly determine the mean volume emissivity of the local IPDs with a sufficient accuracy to de-modulate the annual emissivity variations due to the Earth's elliptical motion and the dis-alignment of the maximum IPD density plane with respect to the ecliptic. The non-zero eccentricity ($e_{\oplus}$= 0.0167) of the Earth's orbit combined with the sensitive temperature dependence of the Planck function would bring modulations of amplitude at least $3.34\%$ to the zodiacal emission brightness at mid-infrared wavelengths, with which one may determine the IPD temperature T(r) and mean number density n(r) as functions of heliocentric distance r. This will in turn fix the power-law exponent $\delta$ in the relation $T(r) = T_o(r/r_o)^{-\delta}$ for the dust temperature and v in $n(r) = n_o(r/r_o)^-v$ for the density. We discuss how one may de-couple the notorious degeneracy of cross-section, density, reference temperature $T_o$ and exponent $\delta$.

M.O. Studies of Configuration and Conformation (Part II) Configuration and Conformation of Ketimine isomers

  • Kim, Shi-Choon;Chun, Young-Gu;Lee, Ikchoon
    • Nuclear Engineering and Technology
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    • v.9 no.1
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    • pp.39-44
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    • 1977
  • The configuratior and conformation of N-methyl-C-phenylalkyl-ketimine isomers, Ph-CR=N$CH_3$ (R=H, $CH_3$, $CH_3$CH$_2$), have been studied from extended Huckel molecular orbital calculations. The result shows that the E-configuration of the C=N double bond is favored compared with that of the Z-configuration. The most preferable conformation of the phenyl ring rotamer in N-methyl-C-phenylaldimine and N-methyl-C-phenylmethylketimine are the coplanar forms with regard to the C=N plane, but the conformation of the $CH_3$CH$_2$-rotamer, in N-methyl-C-phenylethyl-ketimine, the gauche form (dihedral angle between C=N and $CH_3$CH$_2$- plane=90$^{\circ}$) is favored.

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