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황승노(Seungro Hwang),류기열(Kiyeol Ryu),예홍진(Hongjin Yeh) 한국정보과학회 2003 한국정보과학회 학술발표논문집 Vol.30 No.1A
인터넷에 노출되어 있는 시스템 혹은 내부 네트워크에 대한 해커들의 공격은 날이 갈수록 심각한 상태에 이르고 있으며 이에 따라 이를 방어하기 위한 기법들에 대한 개발도 활발한 상태이다. 아무리 우수한 보안 시스템이라도 이를 어떻게 관리하고 사용하는가에 따라 그 효과가 크게 변한다. 본 논문은 RBAC 모델을 보안 관리에 적용시켜 보안 개체들 간의 효율적 역할 분담 및 상호 견제를 통해 보안 관리 체계를 개선하는 방안을 제안한다.
Lee, Seungro,Shin, Cheol Hee,Choi, Sun,Kwon, Oh Chae Elsevier 2018 ENERGY Vol.164 No.-
<P><B>Abstract</B></P> <P>A computational investigation on the characteristics of nitrogen oxides (NO<SUB>x</SUB>) emissions for counterflow nonpremixed water (H<SUB>2</SUB>O)-laden methane (CH<SUB>4</SUB>)/air flames is conducted since a detailed observation of NO<SUB>x</SUB> formation for fuel having naturally high H<SUB>2</SUB>O vapor content is necessary. Using a detailed kinetic mechanism, NO<SUB>x</SUB> emissions are predicted for low and high flame strain rates (<I>a</I>), and the reaction paths are investigated. With H<SUB>2</SUB>O addition NO<SUB>x</SUB> emissions are reduced due to the chemical process as well as the thermal process such as diluting and cooling effects, the latter is more dominant than the former in NO<SUB>x</SUB> reduction, and the thermal and prompt NO mechanisms become less dominant for the chemical process. With increasing <I>a</I>, NO<SUB>x</SUB> emissions are also reduced, and it is mainly due to the thermal process. Reaction NH + O = NO + H in the prompt pathway is the major reaction step that results in reducing NO emissions via the chemical process due to H<SUB>2</SUB>O addition for both low- and high-stretched flames, though reaction N + OH = NO + H in the thermal pathway is also the major reaction step for the high-stretched flames. In addition, for the high-stretched flames the NO<SUB>2</SUB> pathway in NO production becomes relatively more important with H<SUB>2</SUB>O addition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> With H<SUB>2</SUB>O addition NO<SUB>x</SUB> emissions are reduced mainly due to the thermal effects. </LI> <LI> NH + O = NO + H in the prompt NO pathway becomes less significant with H<SUB>2</SUB>O addition. </LI> <LI> In high-stretched flames N + OH = NO + H is also less significant with H<SUB>2</SUB>O addition. </LI> <LI> In high-stretched, H<SUB>2</SUB>O-added flames the NO<SUB>2</SUB> pathway is relatively important. </LI> <LI> With increasing strain rates, NO<SUB>x</SUB> emissions in H<SUB>2</SUB>O-laden flames are also reduced. </LI> </UL> </P>
Lee, Seungro,Ha, Heonrok,Dunn-Rankin, Derek,Kwon, Oh Chae Pergamon Press 2017 Energy Vol.134 No.-
<P><B>Abstract</B></P> <P>Structure and extinction limits of counterflow nonpremixed water (H<SUB>2</SUB>O)-laden methane (CH<SUB>4</SUB>)/air flames at various pressures are computationally investigated to better understand combustion processes of fuel having naturally high H<SUB>2</SUB>O (vapor) content under elevated pressures. Using a detailed kinetic mechanism and a statistical narrow-band radiation model, the flame structure and extinction limits are predicted for elevated pressures and a wide range of flame strain rates and compared with those at atmospheric pressure. Results show that with increasing pressure the maximum flame temperature increases and the extinction limits are generally extended due to the reduced amount of dissociation and the enhanced radiation reabsorption of H<SUB>2</SUB>O, indicating that flames can sustain more H<SUB>2</SUB>O vapor at elevated pressure. The concentration of active radicals and the flame thickness decrease with increasing pressure. The observed flammable range of the H<SUB>2</SUB>O to CH<SUB>4</SUB> molar ratio at elevated pressures is comparable to that found in self-sustained combustion of CH<SUB>4</SUB> hydrates at atmospheric pressure, and the chemical effects of H<SUB>2</SUB>O addition on flame structure are insignificant. Elevated pressure enhances the formation of soot precursors such as acetylene (C<SUB>2</SUB>H<SUB>2</SUB>), implying an opposite tendency from the water addition effects.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Maximum flame temperature increases with increasing pressure. </LI> <LI> Extinction limits are extended with elevated pressure. </LI> <LI> Enhanced recombination and radiation reabsorption of H<SUB>2</SUB>O cause these tendencies. </LI> <LI> Elevated pressure enhances formation of soot precursor C<SUB>2</SUB>H<SUB>2</SUB>. </LI> <LI> Thermal effect of H<SUB>2</SUB>O addition on flame structure at elevated pressure is dominant. </LI> </UL> </P>
단조 공정의 균일 변형률 분포를 위한 예비성형체 설계 방법
이승로(Seungro Lee),김경민(Kyungmin Kim),김낙수(Naksoo Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Preform design is important for full filling of the die and uniform deformation in forging processes. In this study, a preform design methodology for uniform strain distribution is introduced. The proposed method is based on a convolution neural network (CNN) algorithm. By convolution operation with weight arrays, the model extracts geometrical features of the forging product, forging simulation result, and strain distribution, and connects those features with the corresponding preform. For the different forging products, the saved weight arrays can extract the characteristic features, so that proper preform shape can be easily acquired without any iterations. The proposed design method is utilized for the H-shaped forgings and validated through numerical experiments for rail wheel forging and disk forging. The proposed method has shown to be reliable in preform design procedures, granting uniform deformation with full filling in forging processes.
고압 다이캐스팅 공정에서 제품 결함을 사전 예측하기 위한 기계 학습 기반의 공정관리 방안 연구
이승로 ( Seungro Lee ),이승철 ( Seungcheol Lee ),한도석 ( Dosuck Han ),김낙수 ( Naksoo Kim ) 한국주조공학회 2021 한국주조공학회지 Vol.41 No.6
본 연구는 고압 다이캐스팅 공정에서 제품 결함을 사전에 예측하기 위한 기계 학습 기반의 공정 관리 모델 개발에 관한 연구이다. 모델은 이전 사이클에서의 온도를 입력받고, 사이클에 걸쳐서 나타나는 특징을 인식하여 다음 사이클의 결함 발생 여부를 예측한다. 기어 박스 형상에 대하여 제안된 알고리즘을 적용하여, 3 사이클의 정보를 통해서 9 8 .9%의 정확도와 9 6.8 %의 재현율로 제품 수축 결함을 사전에 예측하였다. This study presents a process management method for the detection of casting defects during in high-pressure die casting based on machine learning. The model predicts the defects of the next cycle by extracting the features appearing over the previous cycles. For design of the gearbox, the proposed model detects shrinkage defects with data from three cycles in advance with 98.9% accuracy and 96.8% recall rates.
EGR 가스의 성층화 조건에 따른 HCCI엔진의 연소 특성
이원준(Wonjun Lee),이승로(Seungro Lee),이창언(Chang-Eon Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Homogeneous charge compression ignition(HCCI) is the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. However HCCI engine’s operation have an excessive rate of pressure rise during combustion. So the purpose of this study solve this problem with EGR gas’s concentration stratification and thermal stratification for reducing the pressure rise in HCCI engine combustion. And we study characteristics of combustion and emissions gas. The reaction mechanism using a this research is diesel surrogate which is composed of heptane/toluene blend fuel.