• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.141-147
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• 2016

Background: A project for building a neutron time-of-flight (nTOF) facility is progressing. We expect that the construction will start in early 2016. Before that, a detailed simulation based on the current architectural drawings was performed to optimize the performance of our facility. Materials and Methods: Currently, several parts had been modified or changed from the original design to reflect requirements such as the layout of the electron beam line, shape of the vacuum chamber producing a neutron beam, and the underground layout of the nTOF facility. Detailed analysis for these modifications has been done with MCNP simulation. Results and Discussion: An overview of our photo-neutron source and KAERI nTOF facility were introduced. The numerical simulations for heat deposition, source term, and radiation shielding of KAERI nTOF facility were performed and the results are discussed. Conclusion: We are expecting that the construction of the KAERI nTOF facility will start in early 2016, and these results will be used as basic data.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.562-565
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• 1996

The photoreactivity of twelve anthraquinone derivatives was examined to evaluate its usefulness as a photo-reagent for the analysis of ginsenosides using photoreduction fluorescence (PRF) detection method. Among the tested compounds, 2-tert-butylandthraquinone (TBAQ), 2-chloroanthraquinone (CAQ) and anthraquinone (AQ) showed good characteristics as photoreagents. The detection limits of ginsenoside $Rg_{1}$PRF-HPLC method using TBAQ, CAQ or AQ as a photo-reagent were found to be ca. 35 ng, 50 ng and 50 ng, respectively.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.469-476
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• 2022

A mathematical model of Lord-Shulman photo-thermal theorem induced by pulse heat flux is presented to study the propagations waves for plasma, thermal and elastic in two-dimensional semiconductor materials. The medium is assumed initially quiescent. By using Laplace-Fourier transforms with the eigenvalue method, the variables are obtained analytically. A semiconductor medium such as silicon is investigated. The displacements, stresses, the carrier density and temperature distributions are calculated numerically and clarified graphically. The outcomes show that thermal relaxation time has varying degrees of effects on the studying fields.

• 한국안전학회지
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• 제28권2호
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• pp.26-30
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• 2013

The purpose of this study is to find risk factors by analyzing the operation principle of a photo coupler (P/C) used to remove the noise of electronic devices and establish a base for the performance improvement of developed products. It was found from the P/C circuit analysis of normal products that they were equipped with an electrolytic condenser of $0.1{\mu}F$ to smooth system signals. Due to the epoxy resin packing the external part of the P/C, this study experienced a limit to visually examine the damage to it. It could be seen from the analysis of electric characteristics of the P/C that the forward voltage ($V_f$) and reverse current ($I_r$) were 1.3 V and 10 uA, respectively. In addition, it is required that the breakdown voltage (VCE) between the collector (C) and emitter (E) be maintained at less than 35 V. The and of the damaged product #1 were comparatively good. However, the measurement of was 100.0 uA. From this, it is thought that a short circuit occurred to the internal circuit. Moreover, from the fact that the of the damaged product #2 was open circuit and the measurement of was 0.0 uA, it is thought that the collector and emitter was separated or insulation resistance was significantly high. Furthermore, from the fact that the of the damaged product #3 was open circuit and the measurement of was 0.0 uA, it is thought that the space between the collector (C) and emitter (E) failed to meet the design standard or that they were separated. Therefore, it is thought that fabricating the P/C by increasing the reverse current 10 mA to 50 mA will prevent its malfunction.

• 대한지구과학교육학회지
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• 제13권2호
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• pp.134-146
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• 2020

이 연구의 목적은 초등 예비교사들은 '과학'에 대해 어떻게 이해하고 있는지를 알아보기 위한 것이다. 특히 이번 연구에서는 초등 예비교사들의 '과학'에 대한 이해를 구체적으로 알아보기 위해 포토 내러티브의 방법을 이용하였다. 포토 내러티브는 연구참여자가 이야기하고자 하는 것을 사진을 찍어 설명하는 방법을 말한다. 연구참여자는 초등 예비교사 66명이었다. 연구 결과, 첫째, 초등 예비교사들은 과학을 설명하기 위해 현상, 원리와 같은 과학적 용어뿐만 아니라, 사람, 생활, 일상과 같은 단어를 많이 사용하였다. 둘째, 초등 예비교사들이 과학을 설명하기 위해 사용한 사진에는 생활용품, 자연현상, 첨단기기, 생물 등이 있었다. 셋째, 초등 예비교사들은 과학을 학문과 지식, 탐구, 편리함, 과학의 본성 등으로 설명하고 있었다. 이러한 결과를 통해 초등 예비교사들이 과학을 생활과 밀접하고 필요한 학문으로 인식하고 있음을 알게 되었으며, 이번 연구결과가 앞으로 초중등 과학교육의 교육과정 구성 및 교과 내용 편성은 물론 교사양성을 위한 교육과정 편성에도 도움을 줄 수 있을 것이라 생각된다.

• 전기전자학회논문지
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• 제26권3호
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• pp.373-379
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• 2022

LTV(Light to Voltage) 변환을 위한 APD(Avalanche Photo Diode)는 다른 PD(Photo Diode)와 다르게 높은전압의 동작영역을 사용하므로 TIA(Transimpedance Amplifier) 사용시 과전류 방지를 위해 Quenching 저항을 직렬로 연결하여야 한다. 그러한 경우 Quenching 저항이 TIA 전달함수에 영향을 미쳐 안정도에 심각한 결과를 초래할 수 있다. 본 논문에서는 APD Quenching 저항이 TIA의 전압과 전류 루프 전달함수에 미치는 영향을 분석하여 안정도 개선을 위한 Quenching 저항 값 결정 방법을 제안하고자 한다. 제안된 방법에 의하여 Quenching 저항을 가지는 TIA 회로를 설계하여 시뮬레이션 및 칩 제작을 통하여 동작의 안정도를 검증하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.109.2-109.2
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• 2015

Graphene, as a single layer of $sp^2$-bonded carbon atoms packed into a 2D honeycomb crystal lattice, has attracted much attention due to its outstanding properties such as high carrier mobility, chemical stability, and optical transparency. In order to synthesize high quality graphene, transition metals, such as nickel and copper, have been widely employed as catalysts, which need transfer to desired substrates for various applications. However, the transfer steps inevitably induce defects, impurities, wrinkles, and cracks of graphene. Here, we report a facile transfer-free graphene synthesis method through nickel and carbon co-deposited layer, which does not require separately deposited catalytic nickel and carbon source layers. The 100 nm NiC layer was deposited on the top of $SiO_2/Si$ substrates by nickel and carbon co-deposition. When the sample was annealed at $1000^{\circ}C$, the carbon atoms diffused through the NiC layer and deposited on both sides of the layer to form graphene upon cooling. The remained NiC layer was removed by using nickel etchant, and graphene was then directly obtained on $SiO_2/Si$ without any transfer process. Raman spectroscopy was carried out to confirm the quality of resulted graphene layer. Raman spectra revealed that the resulted graphene was at high quality with low degree of $sp^3$-type structural defects. Furthermore, the Raman analysis results also demonstrated that gas flow ratio (Ar : $CH_4$) during the NiC deposition and annealing temperature significantly influence not only the number of graphene layers but also structural defects. This facile non-transfer process would consequently facilitate the future graphene research and industrial applications.

• 한국측량학회지
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• 제23권3호
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• pp.323-330
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• 2005

현재 Direct Georeferencing은 지난 10여년 적용되어오던 GPS-항측의 단점인 항공사진의 6개 외부표정요소중 단지 투영중심의 위치만 제공하던 약점을 극복하고 실무에 보편적으로 적용되고 있는 실정이다. 이의 가장 큰 장점은 지상기준점 측량작업의 절감내지는 이를 완전히 생략할 수 있다는 점이다. 본 본문은 상용의 GPS/IMU 를 이용하여 외부표정요소 결정에 대한 실힘 결과를 소개하였다. 실힘을 위하여 사진축척 1:5,000의 대축척과 1:20,000의 중축척으로 촬영한 관측자료를 처리하여 사진축척의 변화를 고려한 외부표정요소 결정의 정확도 및 결합블럭조정의 특성 등 다양하고 의미 있는 결과들을 도출하였다.

• 한국광학회지
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• 제15권2호
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• pp.109-113
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• 2004

광섬유와 평면도파로 결합기의 소산장 결합을 이용하여 디아릴에텐 유도체 DM-BTE(1,2-bis[2,5-dimethylthio-phen-3-yl]-hexafluorocyclopentene)의 광유도 굴절률 변화(photo-induced refractive index change)에 관하여 그 특성을 평가하였다. DM-BTE가 분산된 평면도 파로는 자외선과 가시광선(λ＞450 nm)의 조사에 의해 광변색 반응이 가역적으로 진행되었으며 굴절률변화에 의한 공명 파장 또한 가역적으로 이동하였다. 광변색 반응이 진행되는 동안 평면도 파로의 결정상태(crystal shape)는 일정한 형태를 유지하였으며, 자외선 조사시간에 대한 소자의 파장응답은 0.057 nm/sec 이었고 포화시간은 60 sec로 나타났으며, 가시광선이 다시 조사될 때의 공명파장의 변화는 0.028 nm/sec 이었고, 복귀시간은 140 sec로 측정되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.471.2-471.2
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• 2014

We demonstrate here that an improvement in precursor film density (green density) leads to a great enhancement in the photovoltaic performance of CuInSe2 (CISe) thin film solar cells fabricated with Cu-In nanoparticle precursor films via chemical solution deposition. A cold-isostatic pressing (CIP) technique was applied to uniformly compress the precursor film over the entire surface (measuring 3~4 cm2) and was found to increase its relative density (particle packing density) by ca. 20%, which resulted in an appreciable improvement in the microstructural features of the sintered CISe film in terms of lower porosity, reduced grain boundaries, and a more uniform surface morphology. The low-bandgap (Eg=1.0 eV) CISe PV devices with the CIP-treated film exhibited greatly enhanced open-circuit voltage (VOC, from 0.265 V to 0.413 V) and fill factor (FF, from 0.34 to 0.55), as compared to the control devices. As a consequence, an almost 3-fold increase in the average power conversion efficiency, 3.0 to 8.2% (with the highest value of 9.02%), was realized without an anti-reflection coating. A diode analysis revealed that the enhanced VOC and FF were essentially attributed to the reduced reverse saturation current density (j0) and diode ideality factor (n). This is associated with the suppressed recombination, likely due to the reduction in recombination sites such as grain/air surfaces (pores), inter-granular interfaces, and defective CISe/CdS junctions in the CIP-treated device. From the temperature dependences of VOC, it was confirmed that the CIP-treated devices suffer less from interface recombination.