• ETRI Journal
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• 제31권4호
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• pp.475-477
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• 2009

A balanced dual-band bandpass filter based on ${\lambda}$/2 stepped-impedance resonators and open-loop resonators is proposed in this letter. By employing a type of self-feedback structure, an extra transmission zero is introduced near the common-mode resonance frequency, and the common-mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common-mode suppression is achieved.

• Smart Structures and Systems
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• 제1권3호
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• pp.257-266
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• 2005

In Lamb wave detection of damages in smart structures, the excitation pulse is usually designed as a narrow band burst wave for the convenience of analysis and recognition. However, the wideband excitation can excite more modes in plate/shell structure and thus provides extra information for changes of the structure. This paper presents a method that can extract information in wideband Lamb wave signals. By transforming the detected signals into various sub-frequency band, the measured signal can be converted to its equivalences of narrow band excitations, therefore, the information in different frequency bands can be acquired from a single test and in the same time the complicity of wideband signal can be simplified. Some test results are provided to verify this method.

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.153-158
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• 2012

The hydrogenation of $AlB_2$-type BaGaGe exhibits a metal to insulator (MI) transition, inducing a puckering distortion of the original hexagonal [GaGe] layers. We investigate the electronic structure changes associated with the hydrogen-induced MI transition, using extended H$\ddot{u}$ckel tight-binding band calculations. The results indicate that hydrogen incorporation in the precursor BaGaGe is characterized by an antibonding interaction of $\pi$ on GaGe with hydrogen 1s and the second-order mixing of the singly occupied antibonding $\pi^*$ orbital into it, through Ga-H bond formation. As a result, the fully occupied bonding $\pi$ band in BaGaGe changes to a weakly dispersive band with Ge pz (lone pair) character in the hydride, which becomes located just below the Fermi level. The Ga-Ge bonds within a layered polyanion are slightly weakened by hydrogen incorporation. A rationale for this is given.

• 한국전기전자재료학회논문지
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• 제23권2호
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• pp.137-142
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• 2010

A plane wave expansion method (PWEM) was applied for photonic band structure calculation. We examined zero group velocity modes in photonic crystal. The zero group velocity modes were obtained at the second band along F-K direction. We expanded higher order Brillouin zone (BZ) to find the locations of zero group velocity modes and to investicate their properties. We found twelve locations, inside the first Brillouin zone, where the group velocities became zero. Also, we calculated band structure and group velocity in off-plane configuration.

• Nano
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• 제13권12호
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• pp.1850138.1-1850138.6
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• 2018

Two-dimensional (2D) or layered materials have a great potential for applications in energy storage, catalysis, optoelectronics and gas separation. Fabricating novel 2D or quasi-2D layered materials composed of relatively abundant and inexpensive atomic species is an important issue for practical usage in industry. Here, we suggest the layer-structured AlOOH (Boehmite) as a promising candidate for such applications. Boehmite is a well-known layer-structured material and a single-layer can be exfoliated from the bulk boehmite by breaking the interlayer hydrogen bonding. We study atomic and electronic band structures of both bulk and single-layer boehmite, and also obtain the single-layer exfoliation energy using first-principles calculations.

• 한국ITS학회 논문지
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• 제7권2호
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• pp.50-55
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• 2008

본 논문에서는 단락점과 접지면 사이에 집중형 소자인 인덕터를 이용하여 안테나의 입력 임피던스와 공진주파수 모두를 선택 가능한 다중 대역 내장형 안테나를 제안하였다. 제안된 안테나의 구조는 PIFA (Planar Inverted F Antenna)구조와 반파장 로디드 라인 구조의 합성으로 전체적으로 두 개의 단락점과 하나의 급전점을 가지며 그 중 하나의 단락점을 공유한다. 설계된 안테나의 동작 주파수 대역은 PIFA 구조에서 GSM ($880\;{\sim}\;960MHz$), GPS ($1575{\pm}10MHz$)이며 반파장 로디드 라인 구조에서의 인덕터의 값을 2.2nH, 3.3nH, 4.7nH로 변화시킴에 따라 제안된 안테나는 DCS ($1710{\sim}1880MHz$), US-PCS ($1850{\sim}1990MHz$), 그리고 W-CDMA ($1920{\sim}2170MHz$) 대역에서 동작한다. 공유된 단락점에서의 인덕터 값을 1.2nH, 3.9nH, 6.8nH로 변화시킴으로서 안테나의 입력 임피던스를 변화시켰으며 집중형 소자의 추가로 생기는 안테나의 이득 변화를 최소화하기 위해 사용되는 인덕터의 값을 최대 6.8nH로 제한하였다. 제안된 안테나의 최대 이득은 GSM 대역에서 1.60dBi, GPS 대역에서 -1.16dBi DCS/US-PCS/W-CDMA 대역에서 1.41dBi로 측정되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1536-1538
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• 2000

In this paper, designed and fabricated the 1.9GHz band isolator for wire-less communication base-stations. It was investigated that characteristics of insertion loss and return loss. The characteristic results of dual structure design showed values that insertion loss was about -40dB and return loss was about -23dB at 1.93$\sim$1.99GHz.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.333-335
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• 2016

본 연구에서는 제 1원리 계산을 기반으로 대표적인 p-type TCO 중 하나인 Cu-based delafossite ($CuMO_2$, M=Al, Ga, In, Sc, Y) 의 band structure 및 그에 따른 경향성을 분석하였다. 그 결과, 13족에 속하는 M (Al, Ga, In)은 valence band maximum (VBM)에서 2개의 flat한 line이 나타났고, 3족에 속하는 M (Sc, Y)는 Z point에서도 VBM과 비슷한 값이 나타났다.

• Journal of the Optical Society of Korea
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• 제7권1호
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• pp.7-12
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• 2003

A numerical approach for the analysis of quantum wire structures has been presented using a finite-element method which includes the strain analysis and the band analysis of the Luttinger-Kohn Hamiltonian with the deformation potential. A systematic implementation of the multiband Hamiltonian in the finite-element scheme is outlined and the corresponding variational functional is derived for arbitrarily shaped strained quantum wire arrays. This method is then applied to calculate the band structures of strained quantum wire arrays.

• Journal of applied mathematics & informatics
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• 제12권1_2호
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• pp.261-266
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• 2003

In this paper, we described the structure of coextensions of regular semigroups by rectangular bands.