Ratio Pyrometry를 이용한 매연입자 온도 계측에 대한 고찰

남연우(Youn Woo Nam),이원남(Wonnam Lee),이춘범(Chun Beom Lee) 한국연소학회 2004 KOSCOSYMPOSIUM논문집 Vol.- No.-

ZnO-Bi₂O₃-Mn₃O₄-Co₃O₄ 바리스터의 결함과 전기적 특성

홍연우,이영진,김세기,김진호,Hong, Youn-Woo,Lee, Young-Jin,Kim, Sei-Ki,Kim, Jin-Ho 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.12

In this study, we have investigated the effects of Mn and Co co-doping on defects, J-E curves and grain boundary characteristics of ZnO-$Bi_2O_3$ (ZB) varistor. Admittance spectra and dielectric functions show two bulk defects of $Zn_i^{{\cdot}{\cdot}}$ (0.17~0.18 eV) and $V_o^{\cdot}$ (0.30~0.33 eV). From J-E characteristics the nonlinear coefficient (${\alpha}$) and resistivity (${\rho}_{gb}$) of pre-breakdown region decreased as 30 to 24 and 5.1 to 0.08 $G{\Omega}cm$ with sintering temperature, respectively. The double Schottky barrier of grain boundaries in ZB(MCo) ($ZnO-Bi_2O_3-Mn_3O_4-Co_3O_4$) could be electrochemically single type. However, its thermal stability was slightly disturbed by ambient oxygen because the apparent activation energy of grain boundaries was changed from 0.64 eV at lower temperature to 1.06 eV at higher temperature. It was revealed that a co-doping of Mn and Co in ZB reduced the heterogeneity of the barrier in grain boundaries and stabilized the barrier against an ambient temperature (${\alpha}$-factor= 0.136).

Sb/Bi비가 ZnO-Bi₂O₃-Sb₂O₃-Mn₃O₄-Co₃O₄ 바리스터의 소결과 입계 특성에 미치는 영향

홍연우,이영진,김세기,김진호,Hong, Youn-Woo,Lee, Young-Jin,Kim, Sei-Ki,Kim, Jin-Ho 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.11

In this study we aims to examine the co-doping effects of 1/3 mol% $Mn_3O_4+Co_3O_4$ (1:1) on the reaction, microstructure, and electrical properties such as the bulk defects and grain boundary properties of $ZnO-Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Co-doped ZBS, ZBS(MCo) varistors were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed and promoted densification at lower temperature on heating in Sb/Bi=1.0 by Mn rather than Co. Pyrochlore on cooling was reproduced in all systems however, spinel (${\alpha}$- or ${\beta}$-polymorph) did not formed in Sb/Bi=0.5. More homogeneous microstructure was obtained in $Sb/Bi{\geq}1.0$ In ZBS(MCo), the varistor characteristics were improved drastically (non-linear coefficient, ${\alpha}$=30~49), and seemed to form $Zn_i^{..}$(0.17 eV) and $V_o^{\bullet}$(0.33 eV) as dominant defects. From impedance and modulus spectroscopy (IS & MS), the grain boundaries have divided into two types, i.e. the one is tentatively assign to $ZnO/Bi_2O_3(Mn,Co)/ZnO$ (0.47 eV) and the other ZnO/ZnO (0.80~0.89 eV) homojunctions.

과학 탐구능력 측정을 위한 표준화 검사지 개발 - 중학교 2 학년의 자료 분석과 해석능력을 중심으로 -

이연우(Youne Woo Lee) 한국교원대학교 과학교육연구소 1993 청람과학교육연구논총 Vol.3 No.1

PD 프로그램을 통한 유아교사의 초기 문식성에 대한 인식과 교수 실제 차이

이연우 ( Youn Woo Lee ) 미래유아교육학회 2014 미래유아교육학회지 Vol.21 No.3

본 연구는 유아 교사 훈련 프로그램을 통해 자유놀이 시간 동안 유아 교사의 문식성과 언어 교수에 관한 지각의 정도와 차이에 대해 조사하였다. 본 연구를 위해 작성된 조사지를 만 3-5세 유아 교사들 27명에게 제공하였고, 관련된 교사직업 훈련 (Professional Development Training)을 실시하였다. 언어발달이 지연된 저소득층 유아에게 제공하는 유아 초기 읽기 (Early Reading First) 프로그램에 속해 있는 교사들을 대상으로, 취학전 유아 교사의 조기 문식성 활동과 언어 교수 실제를 높이기 위한 목적의 체계적인 교사 훈련이 실시되었다. 교사 직업 훈련 후, 대부분의 교사들은 자유 놀이 시간 동안 조기 문식성과 언어 교수 인식에 있어서 구체적인 변화를 보였음을 보고하였다. 대부분의 교사들은 자유놀이 시간동안 쓰기나 읽기 중심 교수보다 구어,음운체계 기술 사용이 더 중요함을 보고하었다.특히, 자유놀이 시간 동안 교사의 적절한 구어 사용,음운체계기술,읽기기술 사용의 빈도가 중요함을 보고하였다. 일년 후에 실행된 조사에서도 대부분의 교사들은 자유 놀이 시간 동안 문식성 활동과 언어 교수가 매일 제공되는 것의 중요성을 인식하는 것으로 보고하였다. 또한,조기 문식성 활동이 매일 제공되어야 한다고 보고한 교사들은 다른 기술의 사용보다 구어 중심 교수의 제공이 특히 중요하다고 보고하였다.본 연구는 취학전유아 교사의 초기 문식성과 언어 교수 능력을 향상시키기 위해 실시한 교사 훈련의 효과와 교사 지각능력의 변화에 대한 중요성을 강조함으로써, 저소득층 유아의 초기 문식성과 언어 능력 증진에 대한 여러 시사점을 제공하였다 The purpose of this study was to examine how preschool teachers perceive the importance of teaching early literacy and language skills during center time as a means of determining the influence of professional development on early literacy and language instruction. The self-developed survey about the instruction during center time was provided to teachers prior to and following professional development training. Participants for this study were 27 teachers who were in an intensive professional development program aimed at enhancing teachers`` early literacy and language instruction in daily classroom routines. Results of this study showed that most of the preschool teachers made certain changes in perceiving the importance of providing intensive language and literacy instruction for preschoolers from low-income families. After one-year follow up survey, most teachers especially pointed out the importance of teaching oral language and phonological skills every day during center time. Limitations and implications were also discussed in terms of increasing teachers`` early literacy and language instruction during center time and improving children`s learning outcomes.

Modulated LII 신호와 이색법을 이용한 매연입자 온도 계측

남연우(Youn Woo Nam),이원남(Wonnam Lee) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-

A new measurement technique based on a two-color pyrometry and modulated LⅡ signals to measure local soot particle temperatures has been proposed and examined experimentally. The theoretical review suggests that modulated LⅡ signals of soot particles is suitable for a two-color pyrometry as long as the temperature increase due to laser heating remains relatively small. The modulated LⅡ signals from ethylene and propylene diffusion flames were simultaneously measured at 550 and 750 ㎚ by a dual measurement system that consists of optical fibers, PMT and lock-in amps. The local soot particle temperatures of diffusion flames could be obtained using a two-color pyrometry and modulated LⅡ signal based new technique.

Sb/Bi비에 따른 5원계 바리스터의 소결거동 및 전기적 특성(I) : ZnO-Bi₂O₃-Sb₂O₃-Mn₃O₄-Cr₂O₃

홍연우,이영진,김세기,김진호,Hong, Youn-Woo,Lee, Young-Jin,Kim, Sei-Ki,Kim, Jin-Ho 한국재료학회 2012 한국재료학회지 Vol.22 No.12

We aimed to examine the co-doping effects of 1/6 mol% $Mn_3O_4$ and 1/4 mol% $Cr_2O_3$ (Mn:Cr = 1:1) on the reaction, microstructure, and electrical properties, such as the bulk defects and grain boundary properties, of ZnO-$Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi = 0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Cr-doped ZBS, ZBS(MnCr) varistors were controlled using the Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$), ${\alpha}$-spinel ($Zn_7Sb_2O_{12}$), and ${\delta}-Bi_2O_3$ (also ${\beta}-Bi_2O_3$ at Sb/Bi ${\leq}$ 1.0) were detected for all of the systems. Mn and Cr are involved in the development of each phase. Pyrochlore was decomposed and promoted densification at lower temperature on heating in Sb/Bi = 1.0 system by Mn rather than Cr doping. A more homogeneous microstructure was obtained in all systems affected by ${\alpha}$-spinel. In ZBS(MnCr), the varistor characteristics were improved dramatically (non-linear coefficient, ${\alpha}$ = 40~78), and seemed to form ${V_o}^{\cdot}$(0.33 eV) as a dominant defect. From impedance and modulus spectroscopy, the grain boundaries can be seen to have divided into two types, i.e. one is tentatively assigned to ZnO/$Bi_2O_3$ (Mn,Cr)/ZnO (0.64~1.1 eV) and the other is assigned to the ZnO/ZnO (1.0~1.3 eV) homojunction.

DPF 성능 평가를 위한 Dump Combustor의 활용

남연우(Youn Woo Nam),이원남(Wonnam Lee),오광철(Kwang Chul Oh),이춘범(Chun Beom Lee) 한국연소학회 2007 KOSCOSYMPOSIUM논문집 Vol.- No.-

The number of vehicles employing diesel engines is rapidly rising. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced exhaust regulations. The Diesel Particulate Filter (DPF) system is considered as the most efficient method to reduce particulate matter (PM), but the improvement of a regeneration performance at any engine operation point presents a considerable challenge by itself. Temperature, gas compostion and flow rate of exhaust gas are important parameters in DPF evaluation, especially regeneration process. Engine dynamometer and degment tester are generally used in DPF evaluation so far. But these test method couldn't reveal the effect of various parameters on real DPF, such as O2 concentration, amount of soot and exhaust gas temperature. This research has studied the possibility using dump combustor that used to take an approach lean premixed combustion in gas turbine for a DPF power and optimized. It is possible that utilize the system as DOC (Diesel Oxidation Catalyst) and SCR(Selective Catalytic Reduction) assessments test as well as DPF evaluation

소결온도가 ZnO-Co3O4-Cr2O3의 결함과 전기적 특성에 미치는 영향

홍연우 ( Youn Woo Hong ),김유비 ( You Bi Kim ),이영진 ( Young Jin Lee ),김세기 ( Sei Ki Kim ),백종우 ( Jong Hoo Paik ),조만호 ( Man Ho Jo ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.12

The defects and origin of the good varistor properties in the ZnO-Co3O4-Cr2O3 system were investigated by admittance spectroscopy, I-V characteristics, and impedance and modulus spectroscopy. Two kinds of defects were detected, but (0.27 eV) was identified as a major donor level by admittance spectroscopy. The ZnO grain resistivity of ~0.4 Ωcm was calculated but somewhat increased with sintering temperature. J-E characteristics with varistor behavior was seen in this system while the nonlinear coefficient α changed from 9 to 92 with sintering temperature. The single potential barrier of 0.64-1.01 eV at the grain boundary region was confirmed by impedance and modulus spectroscopy. The origin of a good varistor behavior in ZnO-Co3O4-Cr2O3 would be due to the formation and stabilization of a double Schottky barrier by the redox reaction of Co ions and the existence of small Cr ions in the grain boundaries.

저소득층 장애위험 유아의 발달특성 및 교사교육 프로그램에 관한 유아교사 인식

이연우 ( Lee Youn-woo ),최지영 ( Choi Ji-young ) 대구대학교 한국특수교육문제연구소 2017 특수교육저널 : 이론과 실천 Vol.18 No.3

본 연구는 저소득층 장애위험 유아의 발달특성과 교사교육 프로그램의 개발 및 실행에 대한 유아교사의 인식 조사를 목적으로 하였다. 이를 위해 대전·대구·부산 지역의 어린이집 및 유치원에 근무하는 유아교사 228명을 대상으로 설문조사를 실시한 후 장애위험 유아 교육경험이 있는 교사와 없는 교사 집단으로 구분하여 수집된 자료를 분석하였다. 이에 따른 연구결과는 다음과 같다. 첫째, 저소득층 장애위험 유아의 대표적인 특성으로 이상하고 돌출된 행동을 보인다고 인식한 응답이 41.2%로 가장 높게 나타났으며 또래 유아들보다 중점을 두어야할 발달 영역에서는 사회·정서적 발달이 64.9%로 가장 높게 나타났다. 둘째, 저소득층 장애위험 유아를 위한 교사교육 프로그램의 필요성에 대해 거의 대부분의 교사들(98.7%)이 필요하다고 응답하였으며, 프로그램의 주요내용으로 의사소통 훈련과 적응행동 향상 훈련의 필요성에 대해 각각 36.8%의 응답을 나타냈다. 또한, 프로그램의 실행에 있어서 대그룹과 소그룹을 혼용하고 영상과 토론을 함께 사용하며 한 학기에 1∼2번 실행하여 총 5∼10시간 정도로 제공하는 것을 가장 적합하게 인식하였다. 셋째, 장애위험 유아 교육 시 중점을 두어야 할 영역과 발달 영역별 특성에 대한 인식에서 장애위험 유아 교육경험이 있는 교사와 없는 교사 간에 유의미한 차이를 보였다. 이러한 연구결과를 바탕으로 저소득층 장애위험 유아를 위한 교사교육 프로그램 개발 및 실행을 위한 논의점과 제언을 제시하였다. The purpose of this study was to investigate the preschool teachers` perceptions about developmental characteristics and in-service program for at-risk young children from low Income families. For the purpose, the modified questionnaire was distributed to teachers working in day care centers or kindergarten located in Daejun, Daegu, and Busan cities. A total of 228 questionnaires were used for data analysis by dividing teachers with two groups according to their teaching experiences in at-risk young children. Results of this study are as follows. First, less than half of teachers(41.2%) responded that main characteristics of at-risk young children from low income families is related to show odd behavior, and social-emotional development was perceived as the developmental area to focus on. Second, most of teachers(98.7%) perceived on the necessity of the in-service program and responded on the need of communication training and adaptive behavior training for the main contents of the program. Third, group differences were found in the developmental area to focus and the developmental characteristics of at-risk young children from low income families. Based on the results, discussion and implication were suggested in terms of developing and implementing in-service program for at-risk young children from low income families.