• 한국도로학회논문집
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• 제7권1호
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• pp.31-38
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• 2005

콘크리트의 타설 직후, 상대적으로 콘크리트는 높은 증기압을 갖게 되며, 주위의 대기는 낮은 증기압을 갖게 된다. 콘크리트와 대기 간의 증기압의 평형을 유지하려는 작용 때문에 콘크리트의 표면에서 대기로 수분이 이동하는 증발이 발생한다. 표면에서 일어나는 증발로 인하여 콘크리트의 내부에서도 증기압의 차이가 발생하며, 이로 인하여 콘크리트 내부의 수분이 서서히 표면으로 이동하는 수분확산이 일어난다 이 수분확산의 속도는 콘크리트의 소성 균열, 수화도, 강도와 같은 요인으로 작용하여 콘크리트의 품질에 크게 영향을 미친다. 본 논문에서는 콘크리트 수분확산의 지배방정식과 실내에서 측정된 콘크리트의 온도와 상대습도를 이용하여 초기재령의 콘크리트의 수분확산도를 역계산하였다. 역계산된 콘크리트의 수분확산도를 이용하여 콘크리트의 수분확산도 모형을 개발하였으며, 이를 입력값으로 사용하여 유한요소법에 의해 콘크리트의 상대습도를 계산하였다. 그 결과로서 계산된 상대습도는 측정된 상대습도와 대체로 일치하였다.

• 한국재료학회지
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• 제14권10호
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• pp.688-695
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• 2004

The capacitor contact barrier(CCB) layers have been introduced in the FeRAM integration to prevent the Pt/Al reaction during the back-end processes. Therefore, the interdiffusion and intermetallic formation in $Pt(1500{\AA})/Al(3000{\AA})$ film stacks were investigated over the annealing temperature range of $100\sim500^{\circ}C$. The interdiffusion in Pt/Al interface started at $300^{\circ}C$ and the stack was completlely intermixed after annealing over $400^{\circ}C$ in nitrogen ambient for 1 hour. Both XRD and SBM analyses revealed that the Pt/Al interdiffusion formed a single phase of $RtAl_2$ intermetallic compound. On the other hand, in the presence of TiN($1000{\AA}$) barrier layer at the Pt/Al interface, the intermetallic formation was completely suppressed even after the annealing at $500^{\circ}C$. These were in good agreement with the predicted effect of the TiN diffusion barrier layer. But the conventional TiN CCB layer could not perfectly block the Pt/Al reaction during the back-end processes of the FeRAM integration with the maximum annealing temperature of $420^{\circ}C$. The difference in the TiN barrier properties could be explained by the voids generated on the Pt electrode surface during the integration. The voids were acted as the starting point of the Pt/Al reaction in real FeRAM structure.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.44-60
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• 2021

In this paper, we validate the decay heat calculation capability via a two-step method to analyze spent nuclear fuel (SNF) discharged from pressurized water reactors (PWRs). The calculation method is implemented with a lattice code STREAM and a nodal diffusion code RAST-K. One of the features of this method is the direct consideration of three-dimensional (3D) core simulation conditions with the advantage of a short simulation time. Other features include the prediction of the isotope inventory by Lagrange non-linear interpolation and the use of power history correction factors. The validation is performed with 58 decay heat measurements of 48 fuel assemblies (FAs) discharged from five PWRs operated in Sweden and the United States. These realistic benchmarks cover the discharge burnup range up to 51 GWd/MTU, 23.2 years of cooling time, and spanning an initial uranium enrichment range of 2.100-4.005 wt percent. The SNF analysis capability of STREAM is also employed in the code-to-code comparison. Compared to the measurements, the validation results of the FA calculation with RAST-K are within ±4%, and the pin-wise results are within ±4.3%. This paper successfully demonstrates that the developed decay heat calculation method can perform SNF back-end cycle analyses.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권7호
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• pp.521-524
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• 1999

Nb silicide was formed on the Si micro-tip arrays in order to improve field emission properties of Si-tip field emitter array. After silicidization of the tips, the etch-back process, by which gate insulator, gate electrode and photoresist were deposited sequentially and gate holes were defined by removing gradually the photoresist by $O_2$ plasma from the surface, was applied. Si nitride film was used as a protective layer in order to prevent oxygen from diffusion into Nb silicide layer and it was identified that the NbSi2 was formed through annealing in $N_2$ ambient at $1100^{\circ}C$ for 1 hour. By the Nb silicide coating on Si tips, the turn-on voltage was decreased from 52.1 V to 32.3 V and average current fluctuation for 1 hour was also reduced from 5% to 2%. Also, the fabricated Nb silicide-coated Si tip FEA emitted electrons toward the phosphor and light emission was obtained at the gate voltage of 40~50 V.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.151-159
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• 2006

A one-dimensional numerical analysis is carried out to investigate the effects of inlet gas humidities, inlet gas pressures, and thicknesses of membrane on the performance of a proton exchange membrane fuel cell. It is found that the relative humidity of inlet gases at anode and cathode sides has a significant effect on the fuel cell performance. Especially, the desirable fuel cell performance occurs at low relative humidity of the cathode side and at high humidity of the anode side. In addition, an increase in the pressure ranging from 1 atm to 4 atm at the cathode side results in a significant improvement in the fuel cell performance due to the convection effect by a pressure gradient toward the anode side, and with decreasing the thickness of membrane, the fuel cell performance is enhanced reasonably.

• International Journal of Automotive Technology
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• 제2권3호
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• pp.109-115
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• 2001

A study has been conducted to clarify the effect of watery vapor concentration in hot ambient on droplet evaporation. Droplets of water, ethanol, n-hexadecaneand n-heptane were used in this experimental study. Ambient conditions are fixed at 470 K in temperature, 0.1 MPa in pressure and 2 m/s in velocity of ambient air. Watery vapor concentration was changed 0%～40% by 10% by add water to air. To obtain the time histories of droplet diameter after exposed in ambient, a suspended droplet in hot and humid ambient stream was synchronized with a back flash light, and enlarged droplet images were taken by a CCD camera. The evaporation rate constant of water droplet decreases slightly with the vapor concentration because diffusion velocity reduction of droplet vapor occurs on the surface. The values of ethanol and n-heptane droplet actively increase by effect that water from condensation of vapor flows into the droplet. The evaporation rate constant of n-hexadecane which has higher boiling point than water increases within around 30% of the concentration.

• 한국도서관정보학회지
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• 제45권3호
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• pp.441-462
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• 2014

본 연구는 최근 문헌정보학에 대두되고 있는 정보코먼스 및 러닝코먼스에 대한 개념과 차이점을 분석하고 일본 공공도서관의 러닝코먼스화 사례연구를 통하여 공공도서관의 러닝코먼스화 방향에 관한 시사점을 얻고자 하였다. 러닝코먼스화 분석을 위해 러닝코먼스의 구성요소를 이론적으로 정리해보고, 공공도서관에 적합한 분석의 틀을 설계하고 일본의 공공도서관에 대한 사례분석을 실시하였다. 사례 분석의 결과, 도서관이 정보의 도구에 의해 주도된 정보 코먼스를 넘어 본연의 학습기능으로 돌아가고 있음을 보여주고 있다. 또한 러닝코먼스를 지향하는 공공도서관이 해야 할 미래 과제에 대한 시사점을 던져주고 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.569-572
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• 2008

본 연구에서는 시멘트와 광물질 혼화재인 고로슬래그미분말과 플라이애시를 미리 혼합한 프리믹스 혼합시멘트와 이들 재료를 각각 투입하여 제작한 콘크리트에 대하여 보통강도 및 고강도 영역에서의 압축강도와 염화물 확산계수를 측정하고 각각에 대한 품질편차를 검토하였다. 검토 결과 프리믹스 혼합시멘트를 사용한 콘크리트가 재료를 각각 투입하여 제조한 콘크리트에 비하여 보통강도 및 고강도 영역 모두에서 압축강도 평균값은 증가하고 표준편차는 감소하는 것으로 나타났으며, 염화물 확산계수의 경우 평균값과 표준편차가 모두 감소하는 경향을 나타냈다. 향후 고강도 영역에서의 압축강도 변동폭 및 보통강도 영역에서의 내구성 변동폭을 감소시키기 위해 프리믹스 혼합시멘트를 사용하는 것이 바람직한 것으로 판단된다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.87-94
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• 2001

Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are useful for a variety of applications, including anti-reflecting coatings in solar cells, passivation layers, dielectric layers in metal/insulator structures, and diffusion masks. PECVD systems are controlled by many operating variables, including RF power, pressure, gas flow rate, reactant composition, and substrate temperature. The wide variety of processing conditions, as well as the complex nature of particle dynamics within a plasma, makes tailoring SiN film properties very challenging, since it is difficult to determine the exact relationship between desired film properties and controllable deposition conditions. In this study, SiN PECVD modeling using optimized neural networks has been investigated. The deposition of SiN was characterized via a central composite experimental design, and data from this experiment was used to train and optimize feed-forward neural networks using the back-propagation algorithm. From these neural process models, the effect of deposition conditions on film properties has been studied. A recipe synthesis (optimization) procedure was then performed using the optimized neural network models to generate the necessary deposition conditions to obtain several novel film qualities including high charge density and long lifetime. This optimization procedure utilized genetic algorithms, hybrid combinations of genetic algorithm and Powells algorithm, and hybrid combinations of genetic algorithm and simplex algorithm. Recipes predicted by these techniques were verified by experiment, and the performance of each optimization method are compared. It was found that the hybrid combinations of genetic algorithm and simplex algorithm generated recipes produced films of superior quality.

• 한국식품영양과학회지
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• 제22권1호
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• pp.91-95
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• 1993

Vibrio vulnificus가 생산하는 용혈독소의 단백화학적, 면역화학적 연구에 이용할 목적으로 이 균의 용혈독소에 대한 항혈청을 간편하게 만드는 방법을 실험한 결과는 다음과 같다. Vibrio vulnificus가 생산하는 조용혈독소를 인위적으로 만든 liposome (cholesterol-phos-phatidyl-liposome)에 혼합하여 반응시킨 결과 분자량 50kD의 단백질인 용혈독소만 선택적으로 liposome에 결합되었다. 그러므로 liposome에 결합시킨 조용혈독소를 면역원으로 하고 이 면역원을 토끼의 등근육에 주사하여 항혈청을 간편하게 만들 수 있었으며 이 항혈청은 용혈독소에 대한 특이성이 높았다. 환자와 환경에서 분리된 Vibrio vulnificus의 용혈독소와 liposome를 이용하여 제조한 항혈청을 gel 내 침강반응으로 확인한 결과 단일 침강선을 형성하였다.