• ETRI Journal
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• 제32권2호
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• pp.265-272
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• 2010

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band's lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains.

• 한국전자파학회논문지
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• 제15권11호
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• pp.1019-1025
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• 2004

직각 도파관 내의 주 모드인 TE$_{10}$ 모드의 필드 분포를 기준으로 만든 전송선 등가 모델을 바탕으로 슬롯 결합의 결합을 통해 급전하는 도파관 슬롯 배열 안테나를 설계하였다. 이를 위해 도파관 중심에 위치한 기울어진 슬롯(결합 슬롯)의 적절한 각도와 도파관 축 방향 슬롯(방사 슬롯)의 이격거리를 구해낸 후, 이를 EM 시뮬레이션을 통해 전자기적 특성을 파악하고 특성을 분석하였으며 실제 제작품 측정 결과 비교하였다. 측정된 반사손실 대역폭은 중심주파수 9.15 GHz에서 180 MHz, 부엽레벨은 -25 dB 이하, 반 전력 빔폭은 약 9$^{\circ}$, 이득은 25.5 dB이며 이러한 결과는 시뮬레이션 데이터와 유사하다.

• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.139-142
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• 2013

Silicon nanowire (SiNW) silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices were fabricated and their electrical characteristics were analyzed. Compared to planar SONOS devices, these SiNW SONOS devices have good program/erase (P/E) characteristics and a large threshold voltage ($V_T$) shift of 2.5 V in 1ms using a gate pulse of +14 V. The devices also show excellent immunity to short channel effects (SCEs) due to enhanced gate controllability, which becomes more apparent as the nanowire width decreases. This is attributed to the fully depleted mode operation as the nanowire becomes narrower. 3D TCAD simulations of both devices show that the electric field of the junction area is significantly reduced in the SiNW structure.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1611-1618
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• 2017

This paper presents a compact reconfigurable printed monopole antenna, operating in three different frequency bands (2.45 GHz, 3 GHz and 5.2 GHz), depending upon the state of the lumped element switch. The proposed multiband reconfigurable antenna is designed and fabricated on a 1.6 mm thicker FR-4 substrate having a relative permittivity of 4.4. When the switch is turned ON, the antenna operates in a dual band frequency mode, i.e. WiFi at 2.45 GHz (2.06-3.14 GHz) and WLAN at 5.4 GHz (5.11-5.66 GHz). When the switch is turned OFF, it operates only at 3 GHz (2.44-3.66 GHz). The antenna radiates omni-directionally in these bands with an adequate, bandwidth (>10 %), efficiency (>90 %), gain (>1.2 dB), directivity (>1.7 dBi) and VSWR (<2). The fabricated antenna is tested in the laboratory to validate the simulated results. The antenna, due to its reasonably compact size ($39{\times}37mm^2$), can be used in portable devices such as laptops and iPads.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.517-529
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• 2009

A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic cross-section, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.150-155
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• 2006

Carbon nanotubes backlight unit (CNT-BLU) that lightened by field emission was developed into practicability. According to our novel structure, AC mode circuit design and simple printing process, CNT-BLU could achieve 85% of uniformity, 8000 nits of brightness and low material and fabrication cost. Based on these performances, this new planar backlight technology has chances to proceed to mass production and has the potential to replace traditional backlight technology because of its good properties, like the simple processes, easy to large scale, low surface temperature, low power consumption, optical film-free and Hg-free, etc.

• 한국전기전자재료학회논문지
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• 제33권2호
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• pp.109-113
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• 2020

A power device is a component used as a switch or rectifier in power electronics to control high voltages. Consequently, power devices are used to improve the efficiency of electric-vehicle (EV) chargers, new energy generators, welders, and switched-mode power supplies (SMPS). Power device designs, which require high voltage, high efficiency, and high reliability, are typically based on MOSFET (metal-oxide-semiconductor field-effect transistor) and IGBT (insulated-gate bipolar transistor) structures. As a unipolar device, a MOSFET has the advantage of relatively fast switching and low tail current at turn-off compared to IGBT-based devices, which are built on bipolar structures. A superjunction structure adds a p-base region to allow a higher yield voltage due to lower R_DS (on) and field dispersion than previous p-base components, significantly reducing the total gate charge. To verify the basic characteristics of the superjunction, we worked with a planar type MOSFET and Synopsys' process simulation T-CAD tool. A basic structure of the superjunction MOSFET was produced and its changing electrical characteristics, tested under a number of environmental variables, were analyzed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.179.1-179.1
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• 2014

Si nanowires have exhibited unique optical characteristics, including nano-antenna effects due to the guided mode resonance, significant optical absorption enhancement in wide wavelength and incident angle range due to resonant optical modes, graded refractive index, and scattering. Since Si poor optical absorption coefficient due to indirect bandgap, all such properties have stimulated proposal of new optoelectronic devices whose performance can surpass that of conventional planar devices. We have carried out finite-difference time-domain simulation studies to design optimal Si nanowire array for solar cell applications. Optical reflectance, transmission, and absorption can be calculated for nanowire arrays with various diameter, length, and period. From the absorption, maximum achievable photocurrent can be estimated. In real devices, serious recombination loss occurring at the surface states is known to limit the photovoltaic performance of the nanowire-based solar cells. In order to address such issue, we will discuss how the geometric parameters of the array can influence the spatial distribution of the optical field (resulting optical generation rate) in the nanowires.

• 한국전자파학회논문지
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• 제14권8호
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• pp.878-883
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• 2003

본 논문에서는 평판형 마이크로스트립 공진기를 위한 선형 및 지수형 테이퍼 라인을 이용한 급전선 구조를 제안하였다. 제안된 테이퍼 급전선(Tapered Feedline: TFL)은 결합 효율 증가에 의해 공진기 설계시 발생하는 결합 손실과 임피던스 부정합의 문제를 해결하였다. 제안된 구조의 급전각에 따른 삽입 손실 및 대역폭 변화에 대한 특성이 평가되었으며, ${\lambda}_{g}$/2의 최적 급전선 길이가 제시되었다. 제안된 테이퍼 급전선 구조를 마이크로스트립 링 공진기/여파기와 패치 안테나에 적용하였으며, 공진기/여파기 구조에서는 약 7 dB의 삽입 손실 이득을 얻었으며, 패치 안테나에서는 우수한 정합 특성과 왜곡 없는 방사 패턴 등을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2895-2899
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• 2013

Direction of intercalation to DNA of the planar dipyrido[3,2-a:2',3'-c]phenazine ligands (dppz) of a bis-Ru(II) complex namely, $[Ru(1,10-phenanthroline)_2dipyrido[3,2-a:2^{\prime},3^{\prime}-c]phenazine]^{2+}$ linkered by a 1,3-bis(4-pyridyl)propane, was investigated by probing the behavior of 4',6-diamidino-2-phenylindole (DAPI) that bound deep in the minor groove. Bis-intercalation of DPPZ resulted in a little blue shift and hyperchromism in DAPI absorption band, and a large decrease in DAPI fluorescence intensity which accompined by an increase in the dppz emission intensity. Diminishing the intenisty of the positive induced circular dichroism (CD) and linear dichroism (LD) were also observed. These spectral changes indicated that insertion of dppz ligand caused the change of the binding mode of DAPI, which probably moved to the exterior of DNA from the minor groove and interacted with the phospghate groups of DNA by electrostatic interaction. At the surface of DNA, DAPI binds at the phosphate groups of DNA by electrostatic attraction. Consequently, this observation indicated that the dppz ligand intercalated from the minor groove.