• Current Optics and Photonics
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• 제2권6호
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• pp.629-634
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• 2018

A broad dual-band terahertz metamaterial filter with sharp out-of-band rejections is designed and demonstrated. The center frequencies of the first and the second bands occur at 0.35 THz and 0.96 THz with 3 dB relative bandwidth of 31% and 17%, respectively. Results are measured using a THz time-domain spectroscopy system that shows agreement with simulations. Physical mechanisms of the broad dual-band resonance are clarified based on transmissions of different structures and surface current density distributions. Influence of structure parameters on the transmission characteristics are discussed. Symmetry of the structure ensures the filter polarization independence at normal incidence. These results supported by the design of the filter could find applications in broad multi-band sensors, terahertz communication systems, and other emerging terahertz technologies.

• 한국정보통신학회논문지
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• 제22권5호
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• pp.787-793
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• 2018

본 논문은 협대역 간섭신호에 대응하기 위한 새로운 SC-FDE 구조를 제안한다. 기존의 SC-FDE구조는 협대역 간섭신호가 발생했을 시 채널 추정이 어려워지고, 그로 인해 데이터 복원이 어려운 상황이 발생한다. 이러한 문제를 해결하기 위해 본 논문에서는 큰 전력의 협대역 간섭신호가 발생했을 때에도 주파수영역 채널추정이 가능한 새로운 SC-FDE 프레임 구조를 제안한다. 구체적으로 기존방식은 시간영역 채널추정을 먼저 수행한 후 푸리에변환을 통해 주파수 영역 채널을 추정하지만 본 논문은 곧바로 수신신호에서 주파수영역에서 채널추정이 가능하도록 새로운 SC-FDE의 구조를 제안하며 제안하는 구조의 성능 향상은 컴퓨터 모의실험을 통해 검증하였다. 모의실험 결과 재머의 크기가 수신신호의 크기와 동일한 환경에서 제안하는 방식은 재머가 없는 경우 대비 약 2 dB 이내의 손실로 수신이 가능하지만 기존의 방식은 통신이 불가능 하다.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.372-378
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• 1996

The phtoreflectance(PR) spectra of B ion implanted semi-insulating(SI) GaAs were studied. Ion implantation was performed by 150keV implantation energy and 1*10/aup 12/-10$^{15}$ ions/c $m^{2}$ doses. Electronic band structure was damaged by ion implantation with above 1*10$^{13}$ ions/c $m^{2}$ dose. When samples were annealed, " peak was observed at 30-40meV below band gap( $E_{g}$). It should be noted that this energy is close to the ionization energies of S $i_{As}$ , and GeAs in G $a_{As}$ which are also found as impurities in LEC GaAs, it is therefore possible that this feature is related to S $i_{As}$ , or G $e_{As}$ and B ions by implanted defect associated with them. From PR spectra of etched samples which is as-implanted by 1*10$^{14}$ and 1*10$^{15}$ ions/c $m^{2}$ dose, the depth of destroyed electronic band structure was from surface to 0.2.mu.m below surface.nic band structure was from surface to 0.2.mu.m below surface.

• Advances in nano research
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• 제9권2호
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• pp.105-112
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• 2020

Silicene is a two-dimensional (2D) derivative of silicon (Si) arranged in honeycomb lattice. It is predicted to be compatible with the present fabrication technology. However, its gapless properties (neglecting the spin-orbiting effect) hinders its application as digital switching devices. Thus, a suitable band gap engineering technique is required. In the present work, the band structure and density of states of uniformly doped silicene are obtained using the nearest neighbour tight-binding (NNTB) model. The results show that uniform substitutional doping using aluminium (Al) has successfully induced band gap in silicene. The band structures of the presented model are in good agreement with published results in terms of the valence band and conduction band. The band gap values extracted from the presented models are 0.39 eV and 0.78 eV for uniformly doped silicene with Al at the doping concentration of 12.5% and 25% respectively. The results show that the engineered band gap values are within the range for electronic switching applications. The conclusions of this study envisage that the uniformly doped silicene with Al can be further explored and applied in the future nanoelectronic devices.

• 한국염색가공학회지
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• 제27권4호
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• pp.270-274
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• 2015

Molecules always show broad absorption band envelopes, and this results from the vibrational properties of bonds. The width of an absorption band can have an important influence on the color of a dye. A narrow band imparts a bright, spectrally pure color to the dye, whereas a broad band can give the same hue, but with a much duller appearance. Typically, half-band widths of cyanine dyes are about 25nm compared to value of over 50nm for typical merocyanine dyes. Thus, cyanine dyes are exceptionally bright. The factors influencing the width of an absorption band can be understood with reference to the Morse curves. The width of the absorption band depends on how closely the bond order of the molecules in the first excited state resembles that in the ground state. We have quantitatively evaluated the "molecular structure-absorption band shape" relationship of dye molecules by means of Pariser-Parr-Pople Molecular Orbital Method(PPP-MO).

• 한국음향학회지
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• 제31권7호
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• pp.472-479
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• 2012

본 논문은 음성과 오디오의 혼합 콘텐츠를 대상으로 하는 9.2 kbps 저 전송률 변환여기 부호화기 설계를 목표로 한다. 저 전송률 환경을 위하여 주파수 영역 신호의 중요도에 따른 Band-Selection 방법과 Gain-Shape 양자화를 이용한 Analysis by Synthesis(AbS) 구조를 이용한다. AbS 구조를 이용하는 과정에서 발생하게 되는 연산량을 감소시키기 위하여 밴드별 IDFT를 취하고 합성하는 방법을 이용한다. 전송 되지 않는 구간에 대하여 Comfort Noise를 삽입함으로써 음질 저하 없이 설계한다. 기존의 TCX모드와 비교하여 저 전송률에서 성능의 저하 없는 부호화기를 제안한다.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.324-329
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• 2015

First-principles investigations on the hybrid one dementional hexagonal hybrboron-nitride nano ribbons (BNNRs) with a armchair graphene nano-ribbons(AGRNRs), are presented. Electronics properties of the mixed armchair BNC nano-ribbon (BNCNRs) structure show control of a band gap on all cases at the special K-point. And we have studied, the band gap is direct in all cases. The band gap of mixed ABNCNRs could be divided into three groups (${\Delta}3p$, ${\Delta}3p+1$ and ${\Delta}3p+2$) and decrease with the increase of the width. Also these results show similar to the AGNRs case. Different from the band gap value ordering of AGNRs (${\Delta}3p+1$ > ${\Delta}3p$ > ${\Delta}3p+2$), the ordering of ABNCNRs is ${\Delta}3p$ > ${\Delta}3p+1$ > ${\Delta}3p+2$. The discrepancy may come from the differences between the edges of AGRNRs and the boundaries of hybrid BNCNRs. In addition, the bandgap of ABNCNRs are much smaller than those of the corresponding AGNRs. Our results show that the origin of band gap for BNCNRs with armchair shaped edges arises from both quantum confinement effect of the edges. These results similar to thecase of AGNRs. These properties of hybrid BN/C nano-ribbon structure may offer suitable bandgap to develop nnanoscale electronics and solar cell beyond individual GNRs and BNNRs.

• Journal of electromagnetic engineering and science
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• 제16권3호
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• pp.159-163
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• 2016

In this paper, a frequency tunable double band-stop resonator (BSR) with voltage control by varactor diodes is suggested. It makes use of a half-wavelength shunt stub as its conventional basic structure, which is replaced by the distributed LC block. Taking advantage of the nonlinear relationship between the frequency and electrical length of the distributed LC block, a dual-band device can be designed easily. With two varactor diodes, the stop-band of the resonator can be easily tuned by controlling the electrical length of the resonator structure. The measurement results show the tuning ranges of the two operating frequencies to be 1.82 GHz to 2.03 GHz and 2.81 GHz to 3.03 GHz, respectively. The entire size of the resonator is $10mm{\times}11mm$, which is very compact.

• Applied Science and Convergence Technology
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• 제26권3호
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• pp.43-46
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• 2017

Aluminum-doped ZnO (AZO) thin films were deposited by atomic layer deposition (ALD) with respect to the Al doping concentrations. In order to explain the chemical stability and electrical properties of the AZO thin films after hydrogen peroxide ($H_2O_2$) solution immersion treatment at room temperature, we investigated correlations between the electrical resistivity and the electronic structure, such as chemical bonding state, conduction band, band edge state below conduction band, and band alignment. Al-doped at ~ 10 at % showed not only a dramatic improvement of the electrical resistivity but also excellent chemical stability, both of which are strongly associated with changes of chemical bonding states and band edge states below the conduction band.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권1호
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• pp.56-65
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• 2007

This paper describes physical meanings of various influences of cavity (or pillar) shape and filling factor of dielectric material on band structures in two-dimensional photonic crystals. Influences of circular and rectangular cross-sections of cavity (or pillar) arrays on photonic band structures are considered theoretically, and significant aspects of square and triangular lattices are compared. It is shown that both averaged dielectric constant of the photonic crystal and distribution profile of photon energy play important roles in designing optical properties. For the triangular lattice, especially, it is shown that cavity array with a rectangular cross-section breaks the band structure symmetry. So, we discuss this point from the band structure and address optical properties of lattice with a circular cross-section cavity.