• Title, Summary, Keyword: Bowing parameter

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Static Structural Analysis on the Mechanical behavior of the KALIMER Fuel Assembly Duct

  • Kim, Kyung-Gun;Lee, Byoung-Oon;Woan Hwang;Kim, Young ll;Kim, Yong su
    • Nuclear Engineering and Technology
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    • v.33 no.3
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    • pp.298-306
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    • 2001
  • As fuel burnup proceeds, thermal gradients, differential swelling, and inter-assembly loading may induce assembly duct bowing. Since duct bowing affects the reactivity, such as long or short term power-reactivity-decrement variations, handling problem, caused by top end deflection of the bowed assembly duct, and the integrity of the assembly duct itself. Assembly duct bowing were first observed at EBR-ll in 1965, and then several designs of assembly ducts and core restraint system were used to accommodate this problem. In this study, NUBOW-2D KMOD was used to analyze the bowing behavior of the assembly duct under the KALIMER(Korea Advanced Liquid MEtal Reactor) core restraint system conditions. The mechanical behavior of assembly ducts related to several design parameters are evaluated. ACLP(Above Core Load Pad) positions, the gap distance between the ducts, and the gap distance between the duct and restraint ring were selected as the sensitivity parameter for the evaluation of duct deflection.

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Characteristic absorbance of AlGaN epilayers grown on sapphire substrate (사파이어 기판 위에 성장된 AlGaN 에피층의 광 흡수 특성)

  • 김제원;박영균;김용태;최인훈
    • Journal of the Korean Vacuum Society
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    • v.8 no.2
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    • pp.153-157
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    • 1999
  • The dependence of the absorption edge of wurtzite $Al_xGa_{1-x}N$ on alN mole fraction has been studied. The AlN mole fraction was varied from 0 to 1. The absorption coefficients at room temperature were determined by transmission and photothermal deflection spectroscopy. Photothermal deflection spectroscopy can be applied to determine the low absorbance values. From the results, the effective bandgaps of $Al_xGa_{1-x}N$ alloys were determined by choosing corresponding photon energies of the positions of the absorption coefficient of $6.3\times10^4\textrm{cm}^{-1}$ at the absorption curves of the $Al_xGa_{1-x}N$ alloys. From the energy position of the absorption coefficient versus AlN mole fraction, a bowing parameter of 1.3eV was determined. The bowing parameter agreed quite well with the measured effective bandgaps of AlGaN alloys.

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The Calculation of the Energy Band Gaps of Zincblende InAs1-X NX on Temperature and Composition (온도 및 조성비 변화에 따른 질화물계 화합물 반도체 InAs1-X NX의 에너지 밴드갭 계산)

  • Chung, Ho-Yong;Kim, Dae-Ik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.11 no.12
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    • pp.1165-1174
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    • 2016
  • The energy band gaps and the bowing parameters of zincblende InAs1-xN are determined by using an empirical pseudopotential method(EPM) within the improved virtual crystal approximation(VCA), which includes the disorder effect. The direct-band-gap bowing parameter calculated by using the EPM is 4.1eV for InAs1-xNx ($0{\leq}x{\leq}0.05$). The dependences of the band gaps of N-dilute InAs1-xNx on the temperature and composition are calculated by modifying the band anti-crossing(BAC) model. The calculation results are consistent with experimental values, and the coupling parameter CMN of InAs1-xNx is found to be equal to 1.8 by fitting the EPM data.

The Calculation of the Energy Band Gaps of Zincblende GaP1-X NX (질화물계 반도체 GaP1-X NX의 에너지 밴드갭 계산)

  • Chung, Ho-Yong;Kim, Dae-Ik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.12 no.5
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    • pp.783-790
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    • 2017
  • The energy band gaps and the bowing parameters of zincblende GaP1-xNx on the variation of temperature and composition are determined by using an empirical pseudopotential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter calculated is 13.1eV and the energy band gaps are decreased rapidly for GaP1-xNx ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of real dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

The Calculation of the Energy Band Gaps and Optical constants of Zincblende GaAs1-X NX on Temperature and Composition (온도 및 조성비 변화에 따른 질화물계 화합물 반도체 GaAs1-X NX의 에너지 밴드갭과 광학상수 계산)

  • Chung, Ho-Yong;Kim, Dae-Ik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.13 no.6
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    • pp.1213-1222
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    • 2018
  • The energy band gaps and the bowing parameters of zincblende $GaAs_{1-x}N_x$ on the variation of temperature and composition are determined by using an empirical pseudo-potential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter is calculated as 15eV and the energy band gaps are decreasing rapidly in $GaAs_{1-x}N_x$ ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of high-frequency dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

Energy-band-gap Variation of InxGaN1-x Thin Films with Indium Composition (인듐량에 따른 InxGaN1-x 박막의 에너지밴드갭 변화)

  • Park, Ki-Cheol;Ma, Tae-Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.8
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    • pp.677-681
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    • 2009
  • $In_xGa_{1-x}N$ alloys with 20-nm-thickness were deposited onto Mg:GaN/AlN/SiC substrates by MOCVD at $800\;^{\circ}C$. TMGa, TMIn and $NH_3$ were used as the precursor of gallium, indium and nitrogen, respectively. The mole ratio of indium in $In_xGa_{1-x}N$ films varied between 0 and 0.2. The energy-band-gaps of the films were obtained from the photoluminescence and cathodoluminescence peaks. The mole ratios of $In_xGa_{1-x}N$ films were calculated by applying Vegard's law to XRD results. The energy-band-gap versus indium composition plot for $In_xGa_{1-x}N$ alloys were well fit with a bowing parameter of 2.27.

Optical Gap Bowing and Phonon Modes of Amorphous Ge1-x-ySexAsy Thin Films

  • So, Hyeon-Seop;Park, Jun-U;Jeong, Dae-Ho;Lee, Ho-Seon;Sin, Hye-Yeong;Yun, Seok-Hyeon;An, Hyeong-U;Kim, Su-Dong;Lee, Su-Yeon;Jeong, Du-Seok;Jeong, Byeong-Gi
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.288.1-288.1
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    • 2014
  • We investigated the optical properties of Ge1-xSex and Ge1-x-ySexAsy amorphous semiconductor films using spectroscopic ellipsometry and Raman spectroscopy. The dielectric functions and absorption coefficients of the amorphous films were determined from the measured ellipsometric angles. We obtained the optical gap energies and Urbach energies from the absorption coefficients, and found a strong bowing effect in the optical gap energy of Ge1-x-ySexAsy where the endpoint binaries were Ge0.50Se0.50 and Ge0.31As0.69. Based on the correlation between optical gap energies and Urbach energies, the large bowing parameter was attributed to the electronic disorder. We found the composition dependence of several phonon modes using Raman spectroscopy. For Ge1-x-ySexAsy, the D mode (232-267 cm-1) changed from As-As (or As3 pyramid), to As(Se1/2)3 pyramid, and finally to Se clusters, as the Se composition increased. Resonant Raman phenomenon was observed in Ge0.38Se0.62 at a laser excitation of 514 nm (2.41 eV). We verified that this laser energy corresponds to the transition energy of Ge0.38Se0.62 using the second derivative of the dielectric function of Ge0.38Se0.62.

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An Optimum Design of Steel Frames by Second Order Elastic Analysis (2차 탄성해석법에 의한 강뼈대 구조물의 최적설계)

  • Park, Moon-Ho;Jang, Chun-Ho;Kim, Ki-Wook
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.2
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    • pp.123-133
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    • 2006
  • The main objective of this study is to develop an optimization algorithm of framed structures with rigid and various semi-rigid connections using the multilevel dynamic programming and the sequential unconstrained minimization techniques (SUMT). The second-order elastic analysis is performed for steel framed structures. The second order elastic analysis is developed based on nonlinear beam-column theory considering the bowing effect. The following semi-rigid connections are considered; double web angle, top-seat angle and top-seat angle with web angle. We considered the three connection models, such as modified exponential, polynomial and three parameter model. The total weight of the structural steel is used as the objective function in the optimization process. The dimensions of steel cross section are selected as the design variables. The design constraints consist of strength requirements for axial, shear and flexural resistance and serviceability requirements.

The Calculation of the Energy Band Gaps and Optical Constants of Zincblende InyGa1-yAs1-xNx on Composition (조성비 변화에 따른 질화물계 화합물 반도체 InyGa1-yAs1-xNx의 에너지 밴드갭과 광학상수 계산)

  • Chung, Ho-Yong;Kim, Dae-Ik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.14 no.5
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    • pp.877-886
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    • 2019
  • The energy band gaps and optical constants of zincblende $In_yGa_{1-y}As_{1-x}N_x$ on the variation of temperature and composition are determined by using band anticrossing method. The energy band gaps are decreasing continuously in $In_yGa_{1-y}As_{1-x}N_x$ ($0{\leq}x{\leq}0.05$, $0{\leq}y{\leq}1.0$, 300K) and the bowing parameter is calculated as 0.522eV. The calculation results of energy band gaps are consistent with those of other studies. A refractive index n and a high-frequency dielectric constant ${\varepsilon}$ are calculated by a proposed modeling equation using the results of energy band gaps.

A Bifurcation Analysis of Space Structures by Using 3D Beam-Column Element Considering Finite Deformations and Bowing Effect (유한변형과 굽힘효과가 고려된 3차원 보-기둥요소에 의한 공간구조물의 분기좌굴해석)

  • Lee, Kyung-Soo;Han, Sang-Eul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.4
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    • pp.307-314
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    • 2009
  • The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.