• 한국진공학회지
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• 제17권5호
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• pp.461-465
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• 2008

적층 박막 내에서의 상변화는 주변 층에 영향을 준다. 결정화가 게이트 절연층에 주는 영향이 제거된 선결정화법(precrystallization)이 금속 유도 일측면 결정화(metal-induced unilateral crystallization)에 의해 제작된 다결정 실리콘 박막 트랜지스터 소자 및 회로의 전기적 특성에 미치는 영향에 대하여 연구하였다. 이 방법으로 만들어진 소자는 일반적인 후 결정화(postcrystallization) 소자에 비하여 높은 전류 구동력을 보였다. 여기에 본 연구는 DC bias에 의한 ring oscillator의 특성 변화를 연구하였다. 선결정화된 실리콘 박막을 이용하여 제작한 PMOS inverter는 후결정화된 실리콘 박막을 이용하여 제작한 inverter에 비하여 매우 동적(dynamic)이고도 안정적인 특성을 보였다.

• 한국재료학회지
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• 제22권8호
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• pp.409-415
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• 2012

$TiO_2$ thin films for high energy density capacitors were prepared by r.f. magnetron sputtering at room temperature. Flexible PET (Polyethylene terephtalate) substrate was used to maintain the structure of the commercial film capacitors. The effects of deposition pressure on the crystallization and electrical properties of $TiO_2$ films were investigated. The crystal structure of $TiO_2$ films deposited on PET substrate at room temperature was unrelated to deposition pressure and showed an amorphous structure unlike that of films on Si substrate. The grain size and surface roughness of films decreased with increasing deposition pressure due to the difference of mean free path. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of chemically stable $TiO_2$ films. The dielectric constant of $TiO_2$ films was significantly changed with deposition pressure. $TiO_2$ films deposited at low pressure showed high dissipation factor due to the surface microstructure. The dielectric constant and dissipation factor of films deposited at 70 mTorr were found to be 100~120 and 0.83 at 1 kHz, respectively. The temperature dependence of the capacitance of $TiO_2$ films showed the properties of class I ceramic capacitors. $TiO_2$ films deposited at 10~30 mTorr showed dielectric breakdown at applied voltage of 7 V. However, the films of 500~300 nm thickness deposited at 50 and 70 mTorr showed a leakage current of ${\sim}10^{-8}{\sim}10^{-9}$ A at 100 V.

• 분석과학
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• 제8권4호
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• pp.675-682
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• 1995

Thin films of buckminsterfullerene($C_{60}$) formed by solution drop casting on Pt foil electrode surfaces were studied by cyclic voltammetry(CV) in acetonitrile(MeCN) containing quaternary ammonium or alkali-metal salts as supporting electrolyte. The electrochemical behaviors of $C_{60}$ films are found to be strongly dependent on the nature of the supporting electrolytes, especially with tetrabutyl ammonium perchlorate (TBAP, $NBu_4ClO_4$), and tetrabutyl ammonium tetrafluoroborate ($TBABF_4$, $NBu_4BF_4$). Reasonably stable films are formed into which electrons can be injected. The interaction of $C_{60}$ film with the quaternary ammonium cation may produce the fulleride salts $(TBA^+)(C{_{60}}^-)$ and $(TBA^+)_2(C{_{60}}^{2-})$. The bulk electroreduction with a controlled potential to generate the soluble $C{_{60}}^{3-}$ anions(dark red-brown color) is followed by electrooxidative deposition to produce a neutral $C_{60}$ film on the surface. The peak currents($I_{pc}$ and $I_{pa}$) of these thin film were dramatically decreased with repetitive potential scanning. These results could be explained by the adsorption-desorption phenomena and ion pairing interaction of reduced species($C{_{60}}^-$, and $C{_{60}}^{2-}$) onto the electrode surface. The peak current changes and peak potential shifts of the thin $C_{60}$ film in cyclic voltammograms formed from solution were observed by varying scan rates.

• 지질공학
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• 제16권3호
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• pp.255-263
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• 2006

지표가 불규칙한 지형에서 경사시추공을 이용한 단극-쌍극자 배열 전기비저항 토모그래피 탐사를 보면, 우리는 시추공안에 있는 전류원과 지표의 지형기복 사이의 최단거리에 위치한 전위전극에서의 극성변화, 지형기복에 따른 거리계수와 포텐셜의 변화 및 모델링에서 경사 시추공에 위치한 전극과 절점의 공간적인 불일치 등을 고려할 수 있다. 요소분할 방법은 시추공이 곡선이거나 경사져 있을 경우와 하나의 요소에 여러 개의 전극이 있을 때 각 전극에 대한 절점 좌표를 지정할 수 있기 때문에 매우 효과적인 방법이라고 본다. 시추공과 지형기복이 동일한 경사를 갖는 경우에서의 역산 결과는 매우 좋은 영상으로 나타났으며 최소자승근의 오차가 안정적으로 수렴되는 경향을 보였다.

• 센서학회지
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• 제4권1호
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• pp.3-8
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• 1995

ITO(indium tin oxide)와 PSL(porous silicon layer)을 이용하여 n-ITO/p-PSL 이종접합형 광검출 소자를 실리콘 기판상에 제조하였다. 실리콘 질화막과 Ni-Cr/Au를 이용하여 선택적으로 양극반응을 시켰으며, 각 소자를 메사구조로 정의하여 소자간을 격리하였고 ITO를 이용하여 소자의 열화문제를 억제시켰다. 제조된 소자에 백색광을 $0{\sim}3000Lux$까지 변화시키면서 얻은 I-V 특성으로부터 광전류가 입사된 광량에 선형적으로 비례함을 알았다. 제조된 소자는 약 -40V의 역방향 바이어스까지 안정되게 동작하였으며 암전류 밀도가 약 $40nA/mm^{2}$로 나타났다. Xe램프를 이용하여 $400nm{\sim}1100nm$까지 파장을 변화시키면서 측정한 결과 $600nm{\sim}700nm$사이에서 약 0.6A/W의 광응답을 나타내었다. 또한 제조된 소자는 3주 경과 후에도 거의 특성의 변화가 관찰되지 않았다.

• 한국환경복원기술학회지
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• 제14권3호
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• pp.157-168
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• 2011

In order to promote efficiency of upstream and downstream migration of fishes, this study has developed a combined fishway of herring-bone bottom baffle type and brush type fishways. The results obtained are as follows : 1. In a channel with constant incline, the velocity of current generally shows a distinct tendency of acceleration as it goes down the stream. But in the hydraulic experiment of herring-bone bottom baffle type fishway, the velocity reached its maximum only at 0.4m/sec, and it tended to be stable without any acceleration. 2. The velocity in the brush type fishway showed a distinct tendency of acceleration as the discharge increased. But its greatest velocity was only 0.3m/sec, and its velocity change according to the discharge increase was only 0.15m/sec at maximum. 3. The maximum velocity in the combined type fishway was less than half of the blast speed of the poorest swimmer, the juvenile eel with 90mm of body length. So any species of fishes are supposed to be able to migrate upstream from the estuary through this combined type fishway. 4. The field experiment of upstream migration showed that the combined type fishway can promote efficiency of upstream and downstream migration of any species of fishes.

• 인터넷정보학회논문지
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• 제17권3호
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• pp.25-32
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• 2016

본 논문에서는 에지를 사용한 관측 모델과 파티클 필터를 이용하여 실시간으로 객체를 추적하는 방법을 제안한다. 논문에서 제안하는 방법은 먼저, 초기 프레임에서 추적하고자 하는 객체를 지정한다. 지정된 객체에 대해 에지 관측 모델과 N개의 파티클 필터 집합을 생성한다. 에지 관측 모델과 파티클의 8방향 에지 모델의 중간 거리 평균을 비교하여 가중치를 계산하고, 계산된 값으로 가중치를 업데이트한다. 업데이트된 가중치를 이용해 파티클들을 리샘플링한 후, 추적 객체의 상태인 현재 위치를 추정할 수 있다. 마지막으로 본 논문에서 제안하는 방법은 여러 실험 데이터를 이용하여 기존의 방법과의 비교분석을 통해 안정적인 추적에 대한 성능을 입증한다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.129-129
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• 2018

Hard coating application is effective way of cutting tool for hard-to-machine materials such as Inconel, Ti and composite materials focused on high-tech industries which are widely employed in aerospace, automobile and the medical device industry also Information Technology. In cutting tool for hard-to-machine materials, high hardness is one of necessary condition along with high temperature stability and wear resistance. In recent years, high-entropy alloys (HEAs) which consist of five or more principal elements having an equi-atomic percentage were reported by Yeh. The main features of novel HEAs reveal thermodynamically stable, high strength, corrosion resistance and wear resistance by four characteristic features called high entropy, sluggish diffusion, several-lattice distortion and cocktail effect. It can be possible to significantly extend the field of application such as cutting tool for difficult-to-machine materials in extreme conditions. Base on this understanding, surface coatings using HEAs more recently have been developed with considerable interest due to their useful properties such as high hardness and phase transformation stability of high temperature. In present study, the nanocomposite coating layers with high hardness on WC substrate are investigated using high entropy alloy target made a powder metallurgy. Among the many surface coating methods, reactive magnetron sputtering is considered to be a proper process because of homogeneity of microstructure, improvement of productivity and simplicity of independent control for several critical deposition parameters. The N2 is applied to reactive gas to make nitride system with transition metals which is much harder than only alloy systems. The acceleration voltage from 100W to 300W is controlled by direct current power with various deposition times. The coating layers are systemically investigated by structural identification (XRD), evaluation of microstructure (FE-SEM, TEM) and mechanical properties (Nano-indenter).

• 센서학회지
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• 제7권2호
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• pp.97-102
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• 1998

PPV(poly(p-phenylenevinylene))를 발광체로 이용한 유기 박막 EL 소자를 다양한 구조와 조건으로 제작하였으며, 그 전기-광학적 특성을 평가하였다. 제작된 EL 소자는 단층구조(ITO(indium tin oxide)PPV/Mg), 이층구조 (ITO/PVK(poly(N-vinylcarbazole))/PPV)Mg와 ITO/PPV/Polymer matrix+PBD/Mg) 그리고 삼층구조 (ITO/PVK/PPV/PS(polystyrene)+PBD(butyl-2-(4-biphenyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole))/Mg)를 가지며, 그들의 전기광학적 특성을 상호 비교하였다. 이층구조(ITO/PPV)Polymer matrix+PBD/Mg)에서는 PMMA (poly(methyl methacrylate)), PC(polycarbonate) PS 와 MCH(side chain liquid crystalline homopolymer)를 고분자 메트릭스로 사용하였으며, 특히, PS 고분자 메트 릭스를 전자수송층으로 사용하는 경우에 전자수송제인 PBD의 농도에 따른 발광휘도 특성을 구하였다. 제작된 소자의 인가전압에 따른 전류, 휘도특성을 분석한 결과 터널링효과를 나타내었고 안정된 발광특성을 가진다는 것을 알 수 있었다.

• 보건행정학회지
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• 제18권2호
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• pp.19-38
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• 2008

Financial ratios are key indicators of an organization's financial and business conditions. Among various financial indicators, profitability, financial structure, financial activity and liquidity ratios are frequently used and analyzed. Using the structural equation modeling(SEM) technique, this study examines the structural causal relationships among key financial indicators. Data for this study are taken from complete financial statements from 142 hospitals that passed the standardization audit undertaken by the Korean Hospital Association from 1998 to 2001 for the purpose of accrediting teaching hospitals. In order to improve comparability, ratio values are standardized using the Blom's normal distribution. The final model of the SEM has four latent constructs: financial activity(total asset turnover, fixed asset turnover), liquidity(current ratio, quick ratio, collection period), financial structure(total debt to equity, long-term debt to equity, fixed assets to fund balance), and profitability(return on assets, normal profit to total assets, operating margin to gross revenue, normal profit to gross revenue). While examining several model fit indices(Chi-square (df) = 178.661 (40), likelihood ratio=4.467, RMR=.11, GFI=.849, RMSEA=.157), the final SEM we employed shows a relatively good fit. After examining the path coefficient of the constructs, the financial structure of the hospital affects the hospital's profitability in a statistically significant way. A hospital which utilizes its liabilities, more specifically fixed liabilities, and makes a stable investment decision for fixed assets was found to have a higher profitability than other hospitals. Then, the standard path coefficients were examined to directly compare the influence of variables. It was found that there were no statistically significant path coefficients among constructs. When it comes to variables, however, statistically significant relationships were found. between. financial activity and. fixed. asset turnover, and between profitability and normal profit to gross revenue. These results show that the observed variables of fixed asset turnover and normal profit to gross revenue can be used as indicators representing financial activity and profitability.