• Macromolecular Research
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• 제12권3호
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• pp.276-281
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• 2004

In this study we investigated the spectral properties, including electric absorption, circular and linear dichroism (CD and LD), and fluorescence emission, of DNA in a DNA-branched polyethyleneimine (BPEI) polyplex at various polymer molecular weights (M$\_$w/) and BPEI-amine-to-DNA-phosphate ratios (N/P ratios). All BPEIs exhibited a common N/P dependence in their absorption and CD spectra. At N/P ratios ＜ 1.0, we observed some hyperchromism in the absorption spectrum, red-shifts in CD bands, and decreases in LD intensity and fluorescence intensity of intercalated ethidium. At intermediate N/P ratios, complete collapse of all spectra occurred. As the N/P ratio increased further, the polyplex dissolved in water. From its characteristic CD spectrum obtained under these conditions, we conclude that the DNA exists in a B-like form. The fluorescence and LD intensities never recovered even at high N/P ratios- which indicates that the dissolved polyplex possesses positive charges and the DNA in the polyplex is condensed despite its B-form CD spectrum. The N/P range in which the absorption and CD signals collapsed was wider when the BPEIs M$\_$w/ decreased. In the case where the BPEIs M$\_$w/ was 0.8 k, recovery of the absorption and CD spectral properties at a high N/P ratio was never achieved, which suggests that the molecular weight of the polymer plays an important role in its dissolution at a high N/P ratio.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.231-237
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• 2018

In this study, two important requirements for the home production of a robot to detect and remove improvised explosive devices (IEDs) are presented in terms of the total cost for robot system development and the performance improvement of the mine detection technology. Firstly, cost analyses were performed in order to provide a reasonable solution following an engineering estimate method. As a result, the total cost for a mass production system without the mine detection system was estimated to be approximately 396 million won. For the case including the mine detection system, the total cost was estimated to be approximately 411 million won, in which labor costs and overhead charges were slightly increased and the material costs for the mine detection system were negligible. Secondly, a method for fabricating the carbon nanotube (CNT) based gas detection sensor was studied. The detection electrodes were formed by a photolithography process using a photosensitive CNT paste. As a result, this method was shown to be a scalable and expandable technology for producing excellent mine detection sensors. In particular, it was found that surface treatments by using adhesive taping or ion beam bombardment methods are effective for exposing the CNTs to the ambient air environment. Fowler-Nordheim (F-N) plots were obtained from the electron-emission characteristics of the surface treated CNT paste. The F-N plot suggests that sufficient electrons are available for transport between CNT surfaces and chemical molecules, which will make an effective chemiresistive sensor for the advanced IED detection system.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.263-272
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• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.

• 한국기후변화학회지
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• 제1권3호
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• pp.205-210
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• 2010

LED 조명이 기존 조명 대비 80% 이상의 에너지 절감 효과 및 환경 친화적 특성 등 다양한 장점을 가지고 있으면서도, 높은 가격으로 인해 시장이 제대로 형성되지 못하고 있다. 이에 본 논문은 공공부문의 기존 백열 전구를 LED 조명으로의 교체로 인한 에너지 절감 및 유지 보수 측면에서의 효율성을 분석하기 위해 LED 조명에 대한 경제성 평가를 통해 보급 확대에 대한 타당성을 논하였다. 분석대상은 에너지관리공단에서 시행한 "퇴출관리시스템"을 바탕으로 지식경제부에서 발표한 '백열 전구 현황 및 퇴출실적'을 이용하였다. 공공기관의 백열 전구의 LED 조명 교체에 대한 타당성 분석을 위해서 교체 비용, 연간 절전량 및 전기요금 절감액, 유지보수 비용, $CO_2$ 저감량, 탄소배출권 판매수익을 고려하였다. 경제성 분석 결과, 기존의 백열 전구를 LED 조명으로 교체 시 할인율이 3.26%일 때, 8,648.4백만원으로 NPV가 '양(+)'의 값을 가지는 것으로 분석되어 수익성이 있는 것으로 나타났다.