• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.221-223
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• 2013

Self-assembly of the molecular system of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) and the amide analogue (PTCDI) is of potential importance for organic semiconductor devices. Therefore we studied the density of states (DOS), the charge densities, and intermolacular bond lengths for PTCDA and PTCDI using the density functional theory calculations.

• Fibers and Polymers
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• 제7권4호
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• pp.424-431
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• 2006

Roll drafting, a mechanical operation attenuating fiber bundles to an appropriate thickness, is an important operation unit for manufacturing staple yams. It influences not only the linear density regularity of the slivers or staple yams that are produced, but also the quality of the textile product and the efficiency of the thereafter processes. In this research, the dynamic states of the fiber bundle in the roll drafting zone were analyzed by simulation, based on the mathematical model that describes the dynamic behavior of the flowing bundle. The state variables are the linear density and velocity of the fiber bundles and we simulated the dynamics states of the bundle flow, e.g., the profiles of the linear density and velocity in the draft zone for various values of the model parameters and boundary conditions, including the initial conditions to obtain their influence on the dynamic state. Results showed that the mean velocity profile of the fiber bundle was strongly influenced by draft ratio and process speed, while the input sliver linear density has hardly affected the process dynamics. Velocity variance of individual fibers that could be supposed to be a disturbing factor in drafting was also influenced by the process speed. But the major disturbance occurred due to the velocity slope discontinuity at the front roll, which was strongly influenced by the process speed. Thickness of input sliver didn't play any important role in the process dynamics.

• EDISON SW 활용 경진대회 논문집
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• 제3회(2014년)
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• pp.475-477
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• 2014

Self-assembly of the molecular system of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) is of such potential importance for organic semiconductor devices that PTCDA molecule on a variety of substrates has been extensively studied. Therefore we studied the density of states (DOS), the charge densities, and intermolacular bond lengths for PTCDA, and investigated PTCDA absorptioni sites on Si(111)In-$8{\times}8$ at room temperature using the density functional theory calculations.

• Bulletin of the Korean Chemical Society
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• 제22권5호
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• pp.499-502
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• 2001

Unexpectedly, the brightest row was known to represents the lowest lying Te atoms in the STM image of NbTe2. Projected density of states and crystal orbital overlap population show that the 5pz orbital of the lowest lying Te(2) atom doe s not interact with the 4d orbital of Nb strongly so that the 5pz band remains in the vicinity of the Fermi energy. Consequently the lowest lying Te(2) atoms contribute higher electron density near the Fermi energy which in turn exhibits brightest image in the STM experiments.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.775-782
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• 2014

The importance of including spin-orbit interactions for the correct description of structures and vibrational frequencies of haloiodomethanes is demonstrated by density functional theory calculations with spin-orbit relativistic effective core potentials (SO-DFT). The vibrational frequencies and the molecular geometries obtained by SO-DFT calculations do not match with the experimental results as well as for other cations without significant relativistic effects. In this sense, the present data can be considered as a guideline in the development of the relativistic quantum chemical methods. The influence of spin-orbit effects on the bending frequency of the cation could well be recognized by comparing the experimental and calculated results for $CH_2BrI$ and $CH_2ClI$ cations. Spin-orbit effects on the geometries and vibrational frequencies of $CH_2XI$ (X=F, Cl, Br, and I) neutral are negligible except that C-I bond lengths of haloiodomethane neutral is slightly increased by the inclusion of spin-orbit effects. The $^2A^{\prime}$ and $^2A^{{\prime}{\prime}}$ states were found in the cations of haloiodomethanes and mix due to the spin-orbit interactions and generate two $^2E_{1/2}$ fine-structure states. The geometries of $CH_2XI^+$ (X=F and Cl) from SO-DFT calculations are roughly in the middle of two cation geometries from DFT calculations since two cation states of $CH_2XI$ (X=F and Cl) from DFT calculations are energetically close enough to mix two cation states. The geometries of $CH_2XI^+$ (X=Br and I) from SO-DFT calculations are close to that of the most stable cation from DFT calculations since two cation states of $CH_2XI$(X=Br and I) from DFT calculations are energetically well separated near the fine-structure state minimum.

• 대한의용생체공학회:의공학회지
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• 제39권3호
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• pp.124-133
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• 2018

We tried to investigate the changes in cortical activities according to emotional valence states during watching video clips. We examined the neural basis of two emotional states (positive and negative) using spectral power analysis and brain functional connectivity analysis of cortical current density time-series reconstructed from high-density electroencephalograms (EEGs). Fifteen healthy participants viewed a series of thirty-two 2 min emotional video clips. Sixty-four channel EEGs were recorded. Distributed cortical sources were reconstructed using weighted minimum norm estimation. The temporal and spatial characteristics of spectral source powers showing significant differences between positive and negative emotion were examined. Also, correlations between gamma-band activities and affective valence ratings were determined. We observed the changes of cortical current density time-series according to emotional states modulated by video clip. Gamma-band activities showed significant difference between emotional states for thirty seconds at the middle and the latter half of the video clip, mainly in prefrontal area. It was also significantly anti-correlated with the self-ratings of emotional valence. In addition, the gamma-band activities in frontal and temporal areas were strongly phase-synchronized, more strongly for negative emotional states. Cortical activities in frontal and temporal areas showed high spectral power and inter-regional phase synchronization in gamma-band during negative emotional states. It is inferred that the higher amygdala activation induced by negative stimuli resulted in strong emotional effects and caused strong local and global synchronization of neural activities in gamma-band in frontal and temporal areas.

• Journal of Magnetics
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• 제12권2호
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• pp.68-71
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• 2007

Even a pure bulk Fe has a complicated magnetic phase and its magnetism is still needed to be clarified. In this study we investigated the magnetism of bcc and fcc bulk Fe with total energy calculations as functions of atomic volume. The full-potential linearized augmented plane wave method was adopted within a generalized gradient approximation. The ground state of bulk Fe is confirmed to be of ferromagnetic (FM) bcc. For fcc structured Fe an antiferromagnetic (AFM) state is more stable compared to FM states which exist as low spin and high spin states. The stable AFM states were found to accompany a tetragonal distortion, while the FM states remained in a cubic symmetry. At an expanded lattice constant a high spin FM state was calculated to be able to be stabilized with significant enhanced magnetic moment compared to the value of the ground state, bcc FM.

• 센서학회지
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• 제5권6호
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• pp.60-67
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• 1996

저온 remote PECVD $SiO_{2}$막을 이용하여 제조된 InSb MIS구조에서의 계면의 전기적 특성에 대하여 연구하였다. $105^{\circ}C$에서 증착시킨 $SiO_{2}$막을 이용한 MIS구조의 중간 에너지 대역폭에서의 계면상태밀도가 $1{\sim}2{\times}10^{11}\;cm^{-2}eV^{-1}$으로 평가되었다. 그러나, $105^{\circ}C$이상의 고온에서 제조된 MIS소자의 계면에는 다량의 계면준위 및 트랩 준위가 존재하였다. G-V측정으로부터 계산된 계면준위들의 시상수는 $10^{-4}{\sim}10^{-5}\;sec$였으며, 증착온도가 증가할수록 트랩밀도가 증가하여 C-V특성곡선의 이력특성이 증대되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1016-1018
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• 1995

In this paper, we studied the electrical and the microwave properties of the amorphous $As_{10}Ge_{15}Te_{75}$ thin film. The electrical properties of a-$As_{10}Ge_{15}Te_{75}$ thin film were examined d.c. and a.c. bias with annealing condition. As the result of the electrical properties, we observed the physical characteristics of a-$As_{10}Ge_{15}Te_{75}$ thin film such as the density of defect states, characteristic relaxation time, localized density of states, and localized wave function by using CBH and QMT model. We also examined the microwave conduction properties before and after d.e. switching.

• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.238-239
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• 2013

We studied the thermal and electron properties of covalent one-dimensional (1D) monatomic linear chains of carbon, particularly carbyne. We found the ${\alpha}$-carbyne (Polyyne, alternating single and triple C-C bond co-existing) is more stable than ${\beta}$-carbyne (Equally-spaced based on C-C double bond) energetically. As investigation of electron density of states (EDOS), polyyne and cumulene had different electronic characteristic, which corresponding metallic and semiconducting respectively. We also calculate the phonon dispersion, phonon density of states (PDOS) and phonon transmission of carbynes.