• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.1-4
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• 2015

The study analyses secondary damage of surrounding facilities from the fire accident by Unloading of LPG Bulk Lorry. Potential risk and extent of damage from jet flame and radiation heat is estimated with PHAST-RISK v6.7 program of DNV. According to above study, supplies can predict the damage range from gas release by Unloading, and be able to respond quickly.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.279-282
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• 2006

Experiments in low strain rate methane-air counterflow diffusion flames diluted with $CO_2$ have been conducted to investigate the flame extinction behavior and edge flame oscillation The critical mole fraction at flame extinction is examined in terms of velocity ratio and global strain rate. Onset conditions of the edge flame oscillation and the relevant modes are also provided with global strain rate. It is observed that flame length is intimately relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation considerably. Edge flame oscillations are categorized into three: a growing-, a decaying-, and a harmonic-oscillation mode.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.181-188
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• 2012

The present study on nitrogen-diluted non-premixed counterflow flames with finite burner diameters experimentally investigates the important role of the outer edge flame in flame extinction. Flame stability diagrams mapping the flame extinction response of nitrogen-diluted non-premixed counterflow flames to varying global strain rates in terms of the burner diameter, burner gap, and velocity ratio are explored. There exists a critical nitrogen mole fraction beyond which the flame cannot be sustained, and also the curves of the critical nitrogen mole fraction versus the global strain rate have C-shapes in terms of burner diameter, burner gap, and velocity ratio. In flames with sufficiently high strain rates, the curves of the critical nitrogen mole fractions versus global strain rate collapse into one curve, and the flames can have the 1-D flame response of typical diffusion flames. Three flame extinction modes are identified: flame extinctions through the shrinkage of the outer edge flame with and without an oscillation of the outer edge flame prior to the extinction and flame extinction through a flame hole at the flame center. The measured flame surface temperature and a numerical evaluation of the fractional contribution of each term in the energy equation show that the radial conductive heat loss at the flame edge destabilizes the outer edge flame, and the conductive and convection heat addition to the outer edge from the trailing diffusion flame stabilizes the outer edge flame. The radial conductive heat loss at the flame edge is the dominant extinction mechanism acting through the shrinkage of the outer edge flame.

• Journal of Korea Water Resources Association
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• v.30 no.2
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• pp.119-129
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• 1997

A three-dimensional numerical model for the simulation of meso-scale local circulation is developed and it is applied to the land and sea breezes which take place around Ulsan. The surface temperature and moisture on the land are determined by means of the surface heat budget with a layer of vegetation considered. The vertical diffusion coefficients of momentum, heat and specific humidity at the surface layer are obtained by the lever-2 model of the turbulence closure proposed by Yamada (1982). This model proved to be effective in simulating the structure of the land and sea breezes around Ulsan.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.869-872
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• 2018

온라인 뉴스 소비의 확산과 함께 댓글은 여론 형성에 큰 역할을 담당한다. 그러나 아직 댓글에 영향을 미치는 형식 요소에 대한 실증 데이터 기반의 연구는 미흡하다. 본 연구는 이의 시작으로 온라인 뉴스 기사 소비의 두 가지 중요 요소 즉, 헤드라인과 댓글의 관계에 대해 다루고자 한다. 이를 위해, 헤드라인의 논조 유무에 따른 댓글의 논쟁 활성화 정도 차를 확인하고자 댓글의 수와 길이를 분석하였다. '이세돌, 알파고 바둑대결', '최저임금', '북미회담' 기사로 총 537건의 해드라인과 약 85만개의 댓글을 수집하였다. 그 결과 논쟁 활성화 측면에서 논조가 있는 헤드라인일때 댓글의 수가 많고 길이가 길어 논쟁이 더 활발한 것을 할 수 있었다. 또, 댓글의 논쟁 주제도 차이가 있어 헤드라인의 논조가 있는 경우에 의견이나 감정을 표출하는 토픽이 더 많았다. 본 연구는 실증 데이터를 통해, 헤드라인의 논조 유무가 댓글의 논쟁의 활성화 정도와 주제에 영향을 주는 요소임을 밝힘으로써 댓글 소비에 대한 새로운 관점을 제시하고, 헤드라인의 형식 요소의 연구의 중요성을 확인한 데 그 의의가 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.307-314
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• 1998

PZT thin films were fabricated by the Sol-gel method. Starting materials used for the preparation of the stock solution were Pb-acetate trihydrate, Zr-normal propoxide and Ti-isopropoxide. 2-Methoxyethanol and iso-propanol were used for solution. For studying the diffusion of Pb ion into the substrates. We used bare Si substrate, $SiO_2/Si$ substrates which was produced by thermal oxidation and $TiO_2/SiO_2/Si$ which was mad by Sol-gel method. Densification and adhesion of thin films were observed by SEM. Phase formation of thin films and diffusion of Pb ion into the substrate were examined by XRD and ESCA, respectively. In the case of bare Si and $SiO_2/Si$ substrate, we obtained the perovskite phase at $700^{\circ}C$ and restricted a little the diffusion of Si ion into the film with $SiO_2$ buffer layer. In the case of $TiO_2/SiO_2/Si$, perovskite phase were obtained at $500^{\circ}C$ and the diffusion of Pb ion and Si ion were restriced.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.807-815
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• 2013

A numerical study on soot formation in a laminar ethylene diffusion flame at atmospheric pressure was conducted to obtain a better understanding of the effects of buoyancy on sooting flames under 0g and 1g using a gas-phase reaction mechanism and thermal and transport properties. A simple model was employed to predict soot formation, growth and oxidation with interactions between the gas phase chemistry and the soot chemistry taken into account. Results showed that the flames in 0g are much wider than that of 1g because of the thicker diffusion layer and reduction in axial velocity. The reduction in the axial velocity in 0g results in longer residence times, and resulting in greatly enhanced soot volume fraction. And, under zero-gravity, due to the lack of a buoyancy-induced instability, flame instability disappears.

• Korean Journal of Food Science and Technology
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• v.22 no.1
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• pp.1-6
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• 1990

The thermal diffusivity of defatted and nondefatted starches were measured on the basis of one dimensional semi-infinitive theory. Differential scanning calorymetry was used to study the effects of cooling rate, fat and water contents on the enthalpy and entropy changes with the cooling rate of $-2.5{\sim}10^{\circ}C/min$. Thermal diffusivity of defatted and nondefatted straches were determined to be $4.14{\times}10^{-4}{\sim}4.96{\times}10^{-4}(m^2/h),\;4.09{\times}10^{-4}{\sim}4.81{\times}10^{-4}(m^2/h)$ in unfrozen state, and $2.78{\times}10^{-3}{\sim}3.91{\times}10^{-3}(m^2/h),\;2.26{\times}10^{-3}{\sim}3.57{\times}1-^{-3}(m^2/h)$ in frozen state respectively. On decreasing temperatures in frozen state, thermal diffusivities of starches were increased and entropy and enthalpy were decreased, and more rapid cooling rates resulted in a decrease in entropy. A linear relation was observed between enthropy, enthaly and water content. Thermal diffusivity was decreased, and entropy was increasing fat content. With water content ranging from 35 to 90%, enthalpy and entropy of straches were found to be $107{\sim}216 (kcal /moi),\;0.45{\sim}0.94(kcal/mol.\;K)$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3647-3653
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• 2010

An experimental investigation of the flame appearance and heat transfer characteristics in both unexcited and excited impinging inverse diffusion flames with a loud speaker has been performed. The flame is found to become broader and shorter (in length) with acoustic excitation. The heat flux at the stagnation point is increased with the acoustic excitation. The acoustic excitation is more effective in lean conditions than in rich conditions. The reasons for these behaviors are that acoustic excitation improves the entrainment of surrounding air into the jet. From this study, it is found that the maximum increase of 57% in the total heat flux is obtained at the stagnation point of $\Phi$=0.8. Therefore, it is ascertained that the excitation combustion can be adopted with effective instruments as a method for improving heat transfer in impinging jet flames.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.61-61
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• 2021

온도 성층화는 많은 저수지와 댐에서 흔히 발생하는 현상으로 호수나 저수지의 표면 온도가 바닥보다 상대적으로 높아 깊이에 따른 열 구배를 나타낸다. 이러한 온도 성층화 현상은 여름철과 같이 상부와 하부의 온도 차가 클수록 안정적이게 나타나며 이러한 층화 현상으로 수직 확산이 제어되어 수질에 영향을 미친다고 알려져 있다. 따라서 댐이나 호수 등 층화 현상이 심한 유체 내부 바닥에 물순환장치를 설치하여 외부로부터 공기를 끌어와 하부에서 공기를 분출하여 온도 성층을 약화시키기도 한다. 물순환 장치를 설비하면 수체의 혼합이 용이해지며 물질전달이 개선되어 수질이 향상된다. 국내의 경우 대청댐, 보령댐, 영주 댐 등 많은 국내 댐 내부에 물순환장치가 설비되어있다. 본 연구에서 댐의 물순환장치의 성능을 파악하기 위해 산기식 물순환 장비가 설치되어있는 영주댐을 연구 대상 지역으로 잡았다. 연구지역의 계절별 성층구조 및 특성을 조사하기 위해, 봄, 여름, 가을 영주댐에 방문하여 관측 자료를 취득하였으며 물순환 장치는 봄철의 경우만 가동하였다. 봄철의 물순환 장치 가동 전후 관측 데이터를 바탕으로 수치모형실험을 실행하여 관측 결과와 비교 및 검증하였다. 이를 바탕으로 여름, 가을에 물순환장치를 가동하였을 경우 댐 내부 수체의 혼합과정을 살펴보는 연구를 진행하였다. 본 연구는 CFD (Computational Fluid Dynamic) 시뮬레이션을 수행하기 위해 오픈 소스 소프트웨어 OpenFOAM(version 4.0)에서 열 전달이 포함되어있는 비압축성 VOF 솔버를 사용하였다. 본 솔버는 물과 공기를 동시에 나타낼 수 있으며 온도의 확산 방정식을 포함하고 있다. 또한 유동해석 수행 시 사용한 물순환장치의 효울은 실제 장치의 효율과 동일하다. 본 연구의 목표는 다음과 같다. (1) 관측만으로 파악하기 어려운 수체의 혼합거동을 유동해석 자료를 통해 면밀히 살펴보고 (2) 봄철 물순환 장치가 작동하기 전후 자료를 바탕으로 여름 및 가을철 물순환장치 가동 전후 데이터를 유동해석 자료로 취득한다. (3) 또한 물순환장치 가동 전후 데이터를 통해 계절별 혼합 효율을 취득한다.