• 한국진공학회:학술대회논문집
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• 한국진공학회 1997년도 제13회 학술발표회 논문개요집
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• pp.81-82
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• 1997

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제5권1호
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• pp.33-44
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• 1998

This paper is concerned with the existence of mutiple positive solution of (equation omitted) with Dirichlet boundary condition.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 추계학술발표회요약집
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• pp.123-123
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• 1998

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1115-1123
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• 2006

Nuclear fuel rods are exposed to axial flow in a reactor, and flow-induced-vibration due to the flow usually causes damage in the fuel rods. Thus a prior knowledge about dynamic behavior of a fuel rod exposed to the flow condition should be provided. This paper shows that dynamic characteristics of a nuclear fuel rod depend on axial flow velocity. Assuming small lateral displacement, the effects of uniform axial flow are investigated. The analytic results show that axial flow generally reduces fuel rod stiffness and raises its damping in normal condition. Also, the critical axial velocities which make the fuel rod behavior unstable were found. That is, solving generalized eigenvalue equation of the fuel rod dynamic system, the eigenvalues with positive real part are detected. Based on the simulation results, on the other hand, it turns out that the ordinary axial flow in nuclear reactors does not affect to stability of a nuclear fuel rod even in the conservative condition.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.159-163
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• 2014

More accurate CD (Critical Dimension) control is required for the nanometer-scaled devices. However, since the reflectivity between substrate and PR (Photoresist) becomes higher, the CD (Critical Dimension) swing curve was intensified. The higher reflectivity also causes PR notching due to the pattern of sub-layer. For this device requirement, it was optimized for the thickness, refractive index(n) and absorption coefficient(k) in the bottom anti-reflective coating(BARC; SiON) and photoresist with the minimum reflectivity. The computational simulated conditions, which were determined with the thickness of 33 nm, n of 1.89 and k of 0.369 as the optimum condition, were successfully applied to the experiments with no standing wave for the 0.13um-device. At this condition, the lowest reflectivity was 0.44%. This optimum condition for BARC SiON film was applied to the process for 0.13um-device. The optimum SiON film as BARC to PR and sub-layer could be formed with the accurate CD control and no standing waver for the nanometer-scaled semiconductor manufacturing process.

• 열처리공학회지
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• 제32권4호
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• pp.161-167
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• 2019

Impact toughness and fracture behavior were studied in five kinds of non-heat treating steels containing bainite; standard(0.25C-1.5Mn-0.5Cr-0.2Mo-0.15V), high V(0.3V), Ni(0.5Mn-2Ni), W(0.4W instead of Mo), and high C-Ni(0.35C-0.5Mn-2Ni) steels. The good hardness and impact toughness balance was exhibited in the $1100^{\circ}C$-rolled condition, while the impact toughness was deteriorated due to coarse grained microstructure in the $1200^{\circ}C$-rolled condition. The impact toughness decreased with increasing the hardness in all steels studied. The fracture behavior was also basically identical, that is, the fracture area was divided into 3 zones; shear and fibrous zone, fracture transition zone with ductile dimples and cleavage cracks, where the cracks initiate and grow to critical size, unstable cleavage fracture propagation zone. The energy absorbed for the critical crack formation through the plastic deformation inside the plastic zone in front of the notch root contributed to a mostly significant portion of the total impact energy.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제2권10호
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• pp.661-668
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• 2013

Safety Critical 시스템은 시스템의 기능적인 실패 또는 예기치 못한 상황의 발생으로 인해 인명피해, 재산피해, 환경 피해와 같은 치명적인 사고를 초래할 수 있는 시스템을 의미한다. 그러므로 Safety Critical 시스템의 안전을 보장하기 위해서는 시스템 설계 단계에서 시스템에 존재할 수 있는 위험성들이 충분히 고려되어야 하며, 사고가 발생했을 시 피해를 최소화시키기 위한 일련의 예방 동작들이 설계되어야 한다. 현재에는 Safety Critical 시스템의 설계 단계에서 위험성을 식별하고 분석하기 위한 많은 방법들이 연구되었으며, 이 중에는 예기치 못한 사건으로 인한 피해를 예방하는 동작들의 성공 여부를 분석하는 기법도 존재한다. 본 연구에서는 위의 예방 동작들의 성공 여부에 대한 분석뿐만 아니라 기존 연구들에서 언급하지 못한 예방 동작들 간의 충돌과 이로 인해 발생할 수 있는 피해를 분석하는 방법을 제시하고자 한다. 제안한 방법을 통해 Safety Critical 시스템의 안전성이 견고해지고 피해 예방을 위한 동작들의 올바른 설계에 도움이 될 수 있을 것이다.

• 한국세라믹학회지
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• 제55권3호
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• pp.275-284
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• 2018

In the ball milling process of ceramic powders, according to economic considerations for industrial applications, it is very important to quickly determine the optimum process condition with the maximum grinding efficiency. However, it is still difficult to determine the optimum condition for a ball mill with respect to the various process parameters, such as the rotational speed and the milling time. Ball milling was carried out at the same starting conditions with given amounts of alumina powders, balls and water, and was conducted slower or faster or a critical rotational speed was just determined by observing the angular position of the slurry in a semi-translucent polyethylene laboratory container. With respect to the different rotational speeds, which were slower or faster than the critical rotational speed, the particle size distribution of the grained powders and the acoustic intensity caused by cascading of the balls led to various behaviors. From the results of the particle size distribution and the acoustic signal analysis in the ball milling, there was one rotational speed that made the finest milled powder with maximum acoustic intensity. As a result, there was a correlation between the ground particle size and the acoustic intensity, which yields the interpretation that it can be possible in-situ to determine the optimum condition of ball milling by acoustic signal without repeated measurement efforts.

• Advances in nano research
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• 제12권1호
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• pp.81-99
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• 2022

The aim of current work is to evaluate thermo-electrical characteristics of graphene nanoplatelets Reinforced Composite (GNPRC) coupled with magneto-electro-elastic (MEE) face sheet. In this regard, a cylindrical smart nanocomposite made of GNPRC with an external MEE layer is considered. The bonding between the layers are assumed to be perfect. Because of the layer nature of the structure, the material characteristics of the whole structure is regarded as graded. Both mechanical and thermal boundary conditions are applied to this structure. The main objective of this work is to determine critical temperature and critical voltage as a function of thermal condition, support type, GNP weight fraction, and MEE thickness. The governing equation of the multilayer nanocomposites cylindrical shell is derived. The generalized differential quadrature method (GDQM) is employed to numerically solve the differential equations. This method is integrated with Deep Learning Network (DNN) with ADADELTA optimizer to determine the critical conditions of the current sandwich structure. This the first time that effects of several conditions including surrounding temperature, MEE layer thickness, and pattern of the layers of the GNPRC is investigated on two main parameters critical temperature and critical voltage of the nanostructure. Furthermore, Maxwell equation is derived for modeling of the MEE. The outcome reveals that MEE layer, temperature change, GNP weight function, and GNP distribution patterns GNP weight function have significant influence on the critical temperature and voltage of cylindrical shell made from GNP nanocomposites core with MEE face sheet on outer of the shell.

• 한국식품위생안전성학회지
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• 제3권3호
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• pp.117-129
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• 1988

서울·경기지역 도시락 제조업체의 작업환경 및 도시락의 부식인 동태전 생산과정의 위생상태를 위생 점검표 및 미생물 검사를 토대로 분석, 평가한 결과는 다음과 같다. 1) 주방의 위생 상태는 향상 가능성이 있는 보통상태로 나타났고, 종업원의 위생습관은 대·중규모 업체는 향상가능성이 있는 보통상태이었으며 소규모 업체는 위험요인이 존재하는 불량상태로 나타났다. 2) 도시락 제조업체별로 동태전의 생산과정에서 원재료와 전처리 후의 재료는 미생물적인 품질이 낮았다. 3) 조사결과 조리한 음식을 실온에서 보관하는 단계와 출고하기 전까지 조합하고 포장하는 동안 실온에서 방치하는 단계는 온도 및 소요시간이 미생물 증식에 적합한 환경이 되는 위험한 단계이었다. 4) 각 업체에서 사용하는 칼, 도마 ,행주의 미생물 수치가 높아 cross contamination의 가능성이 높았다. 5) 도시락 제조업체에서 동태전의 생산 과정중의 critical control points 는 전처리단계 , 보관단계, 조합과 포장단계 및 기구로 지적되었다.