• Computers and Concrete
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• 제12권1호
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• pp.37-51
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• 2013

The responses of reinforced concrete slabs subject to an impact loading near the ultimate load range are explored. The analysis is carried out on a simply supported rectangular reinforced concrete slab using a nonlinear explicit dynamic procedure and considering three material models: Drucker-Prager, modified Drucker-Prager, and concrete damaged plasticity, available in the commercial finite element software, ABAQUS/Explicit. For comparison purposes, the impact force-time response, steel reinforcement failure, and concrete perforation pattern are verified against the existing experimental results. Also, the effectiveness of mesh density and damage wave propagation are studied independently. It is shown that the presently adopted finite element procedure is able to simulate and predict fairly accurate the behavior of reinforced concrete slab under impact load. More detailed investigations are however demanded for the justification of effects coming from an imperfect projectile orientation as well as the load and structural surface conditions, including the impulsive contacted state, which are inevitable in an actual impact environment.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.56-56
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• 2010

Using first-principles density-functional theory calculations, we find dramatically different electronic states in the C chains generated on the H-terminated C(111) surface, depending on their length and parity. The infinitely long chain has $\pi$ electrons completely delocalized over the chain, yielding an equal C-C bond length. As the chain length becomes finite, such delocalized $\pi$ electrons are transformed into localized ones. As a result, even-numbered chains exhibit a strong charge-lattice coupling, leading to a bond-alternated structure, while odd-numbered chains show a ferrimagnetic spin ordering with a solitonlike structure. These geometric and electronic features of infinitely and finitely long chains are analogous to those of the closed (benzene) and open (polyacetylene) chains of hydrocarbons, respectively.

• 한국해양환경ㆍ에너지학회지
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• 제19권2호
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• pp.111-119
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• 2016

기체-액체 이상유동의 거동 시뮬레이션을 위해 Lattice Boltzmann방법(LBM)을 이용하였다. 기체-액체사이의 경계면에서 상호포텐셜 모델인 Shen-Chan방식과 Carnahan-Starling 상태방정식을 도입하였다. 또한 외력항의 처리는 Exact Difference Method를 사용하였다. 개발된 코드를 통하여 상태방정식 특성파악, 기체-액체의 상분리, 표면장력 및 기체 액체 경계면 거동 특성, Homogeneous와 Heterogeneous 캐비테이션, 기포 붕괴등의 시뮬레이션을 수행하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.79-81
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• 1988

The capacitance-voltage (C-V) characteristics of poly-Si gate MOS devices fabricated by Low-Pressure Chemical Vapor Deposition (LPCVD) system have been studied. In the case poly-Si gate, work function difference and surface state charge density was found lower than that of Al gate. This fact was identified from the C-V curves that flatband shift was shown small due to the hydrogen gas diffused into oxide in processing of alloy and the annealing effect in processing of poly-Si deposition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.26-26
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• 2000

High quality epitaxial Y2O3 thin films were prepared on Si(111) and (001) substaretes by using ion beam assisted deposition. As a substrate, clean and chemically oxidized Si wafers were used and the effects of surface state on the film crystallinity were investigated. The crystalline quality of the films were estimated by x-ray scattering, rutherford backscattering spectroscopy/channeling, and high-resolution transmission electron microscopy (HRTEM). The interaction between Y and Si atoms interfere the nucleation of Y2O3 at the initial growth stage, it could be suppressed by the interface SiO2 layer. Therefore, SiO2 layer of the 4-6 layers, which have been known for hindering the crystal growth, could rather enhance the nucleation of the Y2O3 , and the high quality epitaxial film could be grown successfully. Electrical properties of Y2O3 films on Si(001) were measured by C-V and I-V, which revealed that the oxide trap charge density of the film was 1.8$\times$10-8C/$\textrm{cm}^2$ and the breakdown field strength was about 10MV/cm.

• Journal of Photoscience
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• 제6권3호
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• pp.103-108
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• 1999

We present recent results on ablation mechanism, single-pulse laser micropatterning , pulsed-laser deposition(PLD) and particulates formation accompanying laser ablation, with special emplasis on polymers, in particular polymide, (PI), and polytetrafluoroethylene, (PTFE). Ablation of polymers is described on the basis of photothermal bond breaking within the bulk material. Here, we assume a first order chemical reaction, which can be described by an Arrhenius law. Ablation starts when the density of broken bonds at the surface reaches a certain critical value. Single-pulse laser ablation of polyimide shows a clear-length dependence of the threshold fluence. This experimental result strongly supports a thermal ablation model. We discuss the various possibilities and drawbacks of PLD and describe the morphology, physical properties and applications of PTFE films.

• 공업화학
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• 제34권4호
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• pp.365-382
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• 2023

A lithium metal anode with high energy density has the potential to revolutionize the field of energy storage systems (ESS) and electric vehicles (EVs) that utilize rechargeable lithium-based batteries. However, the formation of lithium dendrites during cycling reduces the performance of the battery while posing a significant safety risk. In this review, we discuss various strategies for achieving dendrite-free lithium metal anodes, including electrode surface modification, the use of electrolyte additives, and the implementation of protective layers. We analyze the advantages and limitations of each strategy, and provide a critical evaluation of the current state of the art. We also highlight the challenges and opportunities for further research and development in this field. This review aims to provide a comprehensive overview of the different approaches to achieving dendrite-free lithium metal anodes, and to guide future research toward the development of safer and more efficient lithium metal anodes.

• 한국산학기술학회논문지
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• 제10권7호
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• pp.1635-1641
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• 2009

하드코팅에 의해 광변색과 경성의 성질을 갖는 플라스틱 렌즈를 제조하고, 그것들의 광학적 성질과 표면 특성을 평가하였다. 무색 상태의 자외선 스펙트럼과 유색 상태의 가시광선 스펙트럼에서 광변색 효과를 관찰할 수 있었다. 광변색 렌즈의 가시광선 투과율은 무색 상태에서 83.44%(검정)에서 87.15%(청)였으며, 유색 상태에서 71.10%(적)에서 79.98%(황)이었다. 적색 광변색 렌즈는 다른 렌즈에 비해 광학 밀도(${\Delta}$OD)와 색차(${\Delta}$$E^{\ast}_\;{ab}$)가 컸다. 하드코팅을 적용한 광변색 렌즈는 부착성, 내온수성, 내약품성 및 표면 현상이 우수하였으며, 또한 경도와 내마모성은 무코팅 렌즈에 비하여 증가하였다. 따라서 이와 같은 코팅 시스템으로 광변색과 하드코팅 성질과 같은 기능성을 안경렌즈에 부여할 수 있었다.

• 한국세라믹학회지
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• 제36권2호
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• pp.203-209
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• 1999

Si 기판위에 Ba2YCu3O7-$\delta$ 고온초전도체를 응용하기 위해 요구되는 buffer층으로 유망한 재료인 LaAlO3 단일상 분말을 고상반응법과 자발착한 연소반응법으로 제조하였다. 제조된 LaAlO3 분말의 입자형태와 결정상태는 scanning electron microscope (SEM)과 X-ray diffractometer (XRD)를 이용하여 분석하였다. 분말의 비표면적과 소결특성은 각각 Brunauer-Emmett-Teller(BET) 방법과 dilatometer를 측정하였다. 고상반응법으로 LaAlO3 분말을 제조할 때에는 하소온도를 150$0^{\circ}C$까지 높게 하여도 단일상을 얻는 것이 어려웠으나 자발착한 연소반응법에 의한 분말제조는 $650^{\circ}C$의 저온에서 하소하여도 쉽게 얻을 수 있었다. Dilatometer 측정을 통하여 분석해 보면, 고상반응법에 의한 분말보다 자발착한 연소반응법에 의한 분말로 제조된 소결체가 고상반응법에 의한 소결체에 비해 1.4배나 큰 소멸밀도(98.87%)를 가졌다. 이렇게 소결밀도에서 큰 차이가 나는 것은 자발착한 연소방법에 의한 분말의 평균 입자크기가 nano crystal size이고 비표면적 값(56.54 $m^2$/g)이 매우 크기 때문이다. 두가지 방법으로 제조된 분말을 이용, LaAlO3 layer를 스크린 프린팅과 소결법으로 Si 기판상에 제조하였으며 자발착한 연소합성법으로 제조된 분말은 110$0^{\circ}C$에서 우수한 소결특성을 나타내었다.

• 한국수산과학회지
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• 제42권6호
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• pp.621-627
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• 2009

In order to standardize the juvenile abalone rearing technique, we selected sample farms by region in East, West and South coasts of Korea and Jeju island. We also have reviewed previous literature and visited farms to survey on the management of abalone juvenile production, spawning, hatching and so forth. Results of investigation are as follows: The light colors of tanks for larvae breeding are good for a frequent examination of larvae behaviour changes during the breeding period. The tank for the abalone juvenile production is a rectangular form in general and its size should amount to 3.5 m in length and 1.2 m width. It also should be built with proper drainage. The best age and size of adult for juvenile production are 3-6 years old individuals, with 9-12 cm separate burial and 125-150 g average weight. To induce spawning, the use of the exposure on air and ultraviolet ray together was the most effective. The density of larvae by plate should be 150-300 individuals and the proper stocking density was est imated and amount to 10-30 individuals. It has been shown that a correlation between water surface size($X_1$) and number of plates ($Y_1$), when producing abalone juveniles, is quite high and it is described by equation $Y_1=138.88X_1-5,736.8\;(R^2=0.9028)$. In addition, it has also been shown that a correlation between production of abalone juveniles ($Y_2$) and number of plates ($X_2$) is high and it is described by equation $Y_2=4.554X_2+12,493\;(R^2=0.8818)$. In Jindo region where a mass production of juveniles abalone has been done, it was shown, that a correlation between rearing water surface size ($X_3$) and production of juveniles abalone ($Y_3$) is very high and this relationship was described by the equation $Y_3=747.03X_2+94,359(R^2=0.9809)$. It has also been shown that a correlation between water surface size ($X_4$) and production of abalone juveniles ($Y_4$) in nationwide is high and the relationship between this variables was described by equation $Y_4=635.85X_4+99,923\;(R^2=0.9020)$.