• Title/Summary/Keyword: Density of states

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Interfacial Electronic Structure of Bathocuproine and Al: Theoretical Study and Photoemission Spectroscopy

  • Lee, Jeihyun;Kim, Hyein;Shin, Dongguen;Lee, Younjoo;Park, Soohyung;Yoo, Jisu;Jeong, Junkyeong;Hyun, Gyeongho;Jeong, Kwangho;Yi, Yeonjin
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.169-169
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    • 2014
  • Interfacial electronic structure of bathocuproine and Al was investigated using in-situ photoemission spectroscopy and density functional theory (DFT) calculations. Bathocuproine is used for exciton blocking and electron transport material in organic photovoltaics and Al is typical cathode material. When thin thickness of Al was thermally evaporated on BCP, gap states were observed by ultraviolet photoemission spectroscopy. The closest gap state yielded below 0.3 eV from Fermi level. By x-ray photoemission spectroscopy, interaction of Al with nitrogen of BCP was observed. To understand the origin of gap states, DFT calculation was carried out and gap states was verified with successive calculation of interaction of Al and nitrogen of BCP. Furthermore, emergency of another state above Fermi level was observed. Remarkable reduction of electron injection barrier between Al and BCP, therefore, is possible.

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Investigation of the Electronic Structure of Mn12 Molecular Magnet Using Synchrotron Radiation

  • Kang, J.S.;Kim, J. H.;Kim, Yoo-Jin;Jeon, Won-Suk;Jung, Duk-Young;Han, S.W.;Kim, K.H.;Kim, K.J.;Kim, B.S.;Shim, J.H.;Min, B.I.
    • Journal of Magnetics
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    • v.8 no.4
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    • pp.149-152
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    • 2003
  • The electronic structure of Mn12-Ac molecular magnet has been investigated using synchrotron radiation. The valence-band photoemission spectroscopy (PES) measurement reveals that Mn 3d states are located near the top of the valence band. The trend in the measured valence-band PES spectra is found to be consistent with that in the calculated local density of states. The Mn 2p x-ray absorption spectroscopy (XAS) measurement provides evidence for the Mn$^{3+}$-Mn$^{4+}$ mixed-valent states.

A Structural Compendium on Perceptual Displays of Rural India towards the Role and Impact of ICT

  • Potluri, Rajasekhara Mouly;Potluri, Lohith Sekhar
    • The Journal of Asian Finance, Economics and Business
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    • v.3 no.4
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    • pp.81-90
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    • 2016
  • The core purpose of the paper is to explore perceptual displays of rural India towards the role and impact of ICT in transforming the lives through education and telecommunications. After meticulous review of pertinent literature on ICT, and its policy framework, the researcher administers both quantitative and qualitative field data collected from the villages of Andhra Pradesh, Karnataka, Kerala, and Tamil Nadu with a sample of 250 from each state. More than 90 percent of respondents from the four southern states in India clearly thought that the role and impact of ICT is very momentous. Predominantly, cent percent respondents from Kerala evinced that ICT is the major reason for achieving the tag of "100% Literacy State". And also in the remaining three states viz., Andhra Pradesh, Karnataka, and Tamil Nadu, the literacy rate has crossed mind-boggling figures only because of ICT's reinforcement. Even in the arena of telecommunications, these four states average telecom density is more than the country's average. The paper concentrated only on how ICT function empirically to build human capacity in rural south-India through the sectors of only education and telecom. This study is first of its kind and precious to all stakeholders of the ICT sector like educational institutional, telecom firms, customers, employees, and governments, etc.

A Study on the Electronic Structures of Li Intercalated Vanadium Sulfide and Oxide (Li의 첨가에 따른 Vanadium의 유화물과 산화물의 전자상태계산에 관한 연구)

  • Jung, Hyun-Chul;Kim, Hui-Jin;Won, Dae-Hee;Yoon, Dong-Joo;Kim, Yang-Soo;Kim, Byung-Il
    • Korean Journal of Metals and Materials
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    • v.46 no.9
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    • pp.604-608
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    • 2008
  • The layered compounds vanadium disulfide($VS_2$) and vanadium dioxide($VO_2$) intercalated with Li are investigated for using the Discrete Variational $(DV)-X{\alpha}$ molecular orbital method. The chemical bonding properties of the atoms were examined by bond overlap population of electronic states. The plot of density of states supports the covalent bonding properties by showing the overlap between the atoms. There is a strong tendency of covalent bonding between V-S and V-O. The intensity of covalent bonding of $VS_2$ is stronger than $VO_2$. The net charge of $LiVO_2$ is higher than that of $LiVS_2$. This results of the calculation of $VO_2$ and $VS_2$ indicate that $(DV)-X{\alpha}$ method can be widely applied in the new practical materials.

A Study of Nitric Oxide Oxidation Catalyst Using Non-noble Metals (비귀금속계 금속을 이용한 일산화질소 산화 촉매 연구)

  • Shin, JungHun;Hong, SungChang
    • Applied Chemistry for Engineering
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    • v.32 no.4
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    • pp.385-392
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    • 2021
  • In this study, impact of Co proportion and calcination temperature of ceria on the Co/CeO2 was analyzed by comparing nitrogen monoxide oxidation performance of various catalysts and their physico-chemical properties. The structural properties of each catalyst were studied by XRD and BET analysis, and the surface crystal states of cobalt were proposed according to the surface density. Oxidation states of elements were observed through Raman and XPS analysis, and the relationship between typical oxidation states and nitrogen monoxide oxidation performance was designed. Through H2-TPR, oxygen-transferring capacity due to changes in the characteristics of catalysts were identified, and activation sites (Co3+) for oxidation were suggested.

Quantitative Comparison of Packing States of Various Press Scraps (다양한 생압고철 충전 상태의 정량적 비교)

  • Sang-Hwan Lee
    • Journal of Korea Foundry Society
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    • v.42 no.6
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    • pp.358-368
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    • 2022
  • In this study, visual simulations were performed on the packing behaviors of various press scraps. The packing states after the initial charging step were quantitatively compared. The comparison targets were 300mm cubic press scraps, customized cubic press scraps, customized octagonal prism press scraps and customized cylinder press scraps. The customized press scraps were designed in customized sizes for furnaces with melting capacities of 1, 1.5, 2, 3, 4, 5 and 6t/h. The packing states such as the initial charging number, the additional charging weight percentage, the packing density and the gap volume percentage were comparatively evaluated.

Surface Relaxation Effect on the Magnetism of Fe Overlayer on Cr (001)

  • Kim, I.G.;Lee, J.I.;Jang, Y.R.;Hong, C.S
    • Journal of Magnetics
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    • v.1 no.1
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    • pp.9-13
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    • 1996
  • The effects of surface relaxation on surface and interface magnetism in Fe/Cr (001) are investigated using the highly precise all-electron total-energy full-potential linearized augmented plane wave method. The Fe-Cr interlayer spacing is deter-mined by total-energy calculation and it is found to be relaxed downward by 18%. For the relaxed system, the magnetic moment of surface Fe is highly suppressed to be $1.72\mu_B$compared to the unrelaxed case ($2.39\mu_B$). This reduction of magnetic moment is considered as a result of the enhanced hybridization between Fe-d and Cr-d states, which can be seen from the calculated density of states. This work suggests the importance of effect of relaxation to the surface and interface magnetism in Fe/Cr system.

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Cost Effectiveness of Bse-Isolation for Bridges in Low and Moderate Seismic Region (중저진 지역에서의 지진격리교량의 경제적 효율성에 관한 연구)

  • 고현무
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1999.04a
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    • pp.178-185
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    • 1999
  • Minimum life-cycle cost helps to evaluate cost effectiveness of base-isolated bridges under specific condition. Life-cycle cost mainly consists of the initial construction cost and the expected damage cost. Damage cost estimation needs proper model of input ground motion failure probability evaluation method and limit states definition. We model the input ground motion as spectral density function compatible with the response spectra defined at each seismicity and site condition. Spectrum analysis and crossing theory is suitable for reseating calculation of failure probabilities in the process of cost minimization. Limit states of base-isolated bridges re defined for superstructure isolator and pier respectively The method is applied to both base-isolated bridges and conventional bridges under the same conditions to investigate cost effectiveness of base isolation in low and moderate seismic region. the results show that base-isolation of bridges are more effective in low and moderate seismic region and that the site effects on the economical efficiency may not be negligible in such a region.

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ELECTRONIC STRUCTURES AND MAGNETIC PROPERTIES OF HEUSLER COMPOUNDS: XMnSb (X=Ni, Pd, and Pt)

  • Youn, S.J.;Min, B.I.;Jang, Y.R.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.749-752
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    • 1995
  • Electronic structures of the Heusler compounds, XMnSb (X=Ni, Pd, and Pt) are investigated systematically by using the linearized muffiu-tin orbital (LMTO) band method. LMTO band calculations yield that, by including the spinorbit interactions, the NiMnSb and PtMnSb are half-metallic, while PdMnSb is normal metallic at the experimental lattice constant. The effect of the spin-orbit interaction is substantial in PtMnSb, in contrast to NiMnSb and PdMnSb. The calculated X d and Mn 3d angular momentum projected local density of states's reveal that the hybridization between the Mn 3d X d states increases from X = Pt to Pd and Ni.

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EMTDC Modeling Method of Resistive type Superconducting Fault Current Limiter

  • Taejeon Huh;Lee, Jaedeuk;Park, Minwon;Yu, In-Keun
    • Progress in Superconductivity and Cryogenics
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    • v.5 no.1
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    • pp.60-65
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    • 2003
  • An effective modeling and simulation scheme of a resistive type Superconducting fault Current Limiter (SFCL) using PSCAD/EMTDC is proposed in this paper. In case of High Temperature Superconducting (HTS) resistive type fault current limiter current limiting is implemented by the ultra-fast transition characteristics from the superconducting (non-resistive) state to the normal (resistive) state by overstepping the critical current density. The states can generally be divided into three sub-states: the superconducting state the quench state and the recovery state respectively. In order to provide alternative application schemes of a resistive type SFCL, an effective modeling and simulation method of the SFCL is necessary. For that purpose, in this study, an actual experiment based component model is developed and applied for the simulation of the real resistive type SFCL using PSCAD/EMTDC. The proposed simulation scheme can be implemented to the grid system readily under various system conditions including sort of faults and the system capacity as well. The simulation results demonstrate the effectiveness of the proposed model and simulation scheme.