• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.299-315
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• 2016

In this work, a strategy for passive vibration control of periodic structures is proposed which involves adding a periodic array of simple resonant devices for creating band gaps. It is shown that such band gaps can be generated at low frequencies as opposed to the well known Bragg scattering effects when the wavelengths have to meet the length of the elementary cell of a periodic structure. For computational purposes, the wave finite element (WFE) method is investigated, which provides a straightforward and fast numerical means for identifying band gaps through the analysis of dispersion curves. Also, the WFE method constitutes an efficient and fast numerical means for analyzing the impact of band gaps in the attenuation of the frequency response functions of periodic structures. In order to highlight the relevance of the proposed approach, numerical experiments are carried out on a 1D academic rod and a 3D aircraft fuselage-like structure.

• 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.

• Structural Engineering and Mechanics
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• v.40 no.3
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• pp.373-392
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• 2011

Periodic and quasi-periodic Timoshenko beams on Pasternak foundation are investigated using the differential quadrature method. Not only band gaps in the beams but also the dynamic response of them is analyzed. Numerical results show that vibration in periodic beams can be dramatically attenuated when the exciting frequency falls into band gaps. Different from the band structures of periodic beams without foundation, the so-called critical frequency was found because of the Pasternak foundation. Its physical meaning was explained in detail and a useful formula was given to calculate the critical frequency. Additionally, a comprehensive parameter study is conducted to highlight the influence of foundation modulus on the band gaps.

• 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 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.

• 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.

• Bulletin of the Korean Chemical Society
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• v.22 no.7
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• pp.743-747
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• 2001

New azomethine metal complexes were synthesized systematically and characterized. Beryllium, magnesium, or zinc ions were used as a central metal cation and aromatic azomethines (L1-L4) were employed as a chelating anionic ligand. Emission peaks o f the complexes in both solution and solid states were observed mostly at the region of 400-500 nm in the luminescence spectra, where blue light was emitted. Three of them (BeL1 (Ⅰ), ZnL2 (Ⅱ), and ZnL3 (Ⅲ)) were sublimable and thus were applied to the organic light-emitting devices (OLED) as an emitting layer, respectively. The device including the emitting layer of Ⅰ exhibited white emission with the broad luminescence spectral range. The device with the emitting layer of Ⅱ showed blue luminescence with the maximum emission peak at 460 nm. Their ionization potentials, electron affinities, and electrochemical band gaps were investigated with cyclic voltammetry. The electrochemical gaps of 2.98 for I, 2.70 for Ⅱ, and 2.63 eV for Ⅲ were found to be consistent with their respective optical band gaps of 3.01, 2.95 and 2.61 eV within an experimental error. The structure of OLED manufactured in this study reveals that these complexes can work as electron transporting materials as well.

• Journal of the Korean Ceramic Society
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• v.47 no.4
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• pp.353-356
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• 2010

Zinc oxide (ZnO) thin films were deposited using atomic layer deposition. The electrical and optical properties were characterized using Hall measurements, spectroscopic ellipsometry and UV-visible spectrophotometry. The electronic concentration and the mobility were found to be critically dependent on the deposition temperature, exhibiting increased resistivity and reduced electronic mobility at low temperature. The corresponding optical properties were measured as a function of photon energy ranging from 1.5 to 5.0 eV. The simulated extinction coefficients allowed the determination of optical band gaps, i.e., ranging from 3.36 to 3.41 eV. The electronic carrier concentration appears to be related to the reduction in the corresponding band gap in ZnO thin films.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.253-256
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• 2012

The rugate porous silicons containing multiple photonic band gaps have been generated by applying a composite waveform summed three computer-generated pseudo-sinusoidal current waveforms and exhibit three sharp photonic band gaps in the optical reflectivity spectrum. Generated multiple rugate porous silicons display three rugate peaks corresponding to the each of the sine components varied from 0.42, 0.36, and 0.30 Hz, with a spacing of 0.06 Hz between each sine component. The resulting rugate PSi films have been removed from the silicon substrate by applying an lift-off current and are then made into particles by ultrasono-method in a organic solution. The sensing experiments using these particles for organic solvents such as toluene, hexane, acetone, and methanol have been achieved. Condensing of organic vapors in the pores increases the refractive indices of entire particle which results a red shift in the photonic peaks.

• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.76-82
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• 2002

For dielectric gratings on a flat metal surface, photonic band gaps created by Brags scattering of surface plasmon polaritons are observed. The observation result that directly images this gap is compared with that predicted by a numerical model based on a plane wave expansion. Consistency between the experimental and numerical results is also confirmed by comparison with the well-known calculation method of diffraction, the rigorous coupled wave analysis method.