미립화 및 분무장치 1 : 동축형 다공성재분사기의 액체제트분열 및 분무각에 관한 연구

김도헌 ( Do Hun Kim ),손민 ( Min Son ),이인철 ( In Chul Lee ),구자예 ( Ja Ye Koo ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Most of the injectors for mixing and atomizing two phase spray are designed as a coaxial type. The most general form of the coaxial type injector is the liquid-centered coaxial shear injector, which discharges liquid from the center post, and the high speed gas jet from the annular gap disintegrates the liquid core. The outline of a coaxial porous injector is similar to that of the conventional coaxial shear injector, except that the porous cylinder, which discharges gas, encloses the center liquid jet. The center liquid jet passes the radially injecting gas, which develops axially toward the injector tip at the recessed region. The dark core length and the spray angle was measured by pixel classifying technique using Matlab image processing code, and the tendencies along with the geometry of the injector and the spray condition were analysed. As shown in Fig. 1, the dark core length was dramatically decreased by increasing the mass flow rate of the gas jet, which changes both of the radial momentum flux ratio at the recessed region, Jrcs and the axial momentum flux ratio at the injector exit, Jtip. In the condition of the constant Jtip at the injector tip, the shortest dark core length was detected at the middle range of the experimental condition. This tendency is represented in Fig. 2, and it was not shown at the low gas flow rate condition, i.e., the low Jtip. Fig. 3 shows the spatial distribution of the spray, and the spray angle was more sensitive to Jrcs in the higher gas flow rate condition. Especially, the spray from the injector, which has shortest length of the porous element, spread widely at the injector face as the gas flow rate increases

다공성재를 이용한 동축형 분사기의 미립화특성

김도헌 ( Do Hun Kim ),신정환 ( Jeung Hwan Shin ),이인철 ( In Chul Lee ),구자예 ( Ja Ye Koo ) 한국분무공학회 2012 한국액체미립화학회지 Vol.17 No.1

To improve the mixing and atomizing performance at the center region of the conventional coaxial shear injector spray, the concept of a coaxial porous injector was invented. This novel injection concept for liquid rocket engines utilizes the Taylor-Culick flow in the cylindrical porous tube. The 2-dimensional injector, which can be converted in three injection configurations, was fabricated, and several cold flow tests using water-air simulant propellant was performed. The hydraulic characteristics and the effects of a gas flow condition on the spray pattern and the Sauter mean diameter (SMD) was analyzed for each configuration. The atomizing mechanism of coaxial porous injector was different with the coaxial shear injector, and it was explained by the momentum of the gas jet, which is injected normally against the center liquid column, and by the secondary disintegration at the wavy interface of liquid jet, which was generated at the recessed region. The SMD of 2D coaxial porous injector, which has higher gas momentum, was measured and it shows better atomizing performance at the center and outer side of spray than the 2D coaxial shear injector.

사이버가정학습 우수운영사례 질적 연구: 운영유형별 핵심성공요인 분석을 중심으로

김도헌 ( Do Hun Kim ),김영천 ( Young Chun Kim ),이근호 ( Keun Ho Lee ),이현철 ( Hyun Chul Lee ) 한국교육정보미디어학회(구 한국교육정보방송학회) 2007 교육정보미디어연구 Vol.13 No.2

본 연구는 `사이버가정학습 우수 운영사례 및 연구학교의 활용사례`를 중심으로 참여교사들의 운영과정 및 학생들의 학습경험에 대한 질적 연구를 통하여 사이버가정학습 운영유형별로 나타나는 핵심성공요인을 규명하고자 하였다. 이를 위하여 본 연구는 학급지원형, 자율학급형, 학급배정형, 단위학교형, 자율학습형으로 나누어 총 5개의 연구대상 사례를 선정하였다. 연구방법으로는 3개월여에 걸쳐 참여관찰, 심층면담, 내용분석 등의 방법이 활용되어졌다. 핵심성공요인 분석은 최대한 내부자적 관점(emic perspective)에서 규명하고자 하였으며 이에 따라 각 사례별로 참여자의 관점에서 지각된 최소 13개에서 최대 24개의 성공관련 요인들이 도출되었으며 이를 관련영역끼리 범주화하여 각 운영유형별로 3~4개의 핵심성공요인들이 규명, 논의되어졌다. 연구결과를 요약하면 학급지원형, 자율학급형, 학급배정형과 같은 담임형 사이버가정학습 유형에서는 `교사의 헌신과 열정`, `자발적 참여유도전략`, `오프라인 활동과의 연계` 요소들이 핵심성공요인들로 공통적으로 나타나고 있었으며, 단위학교형이나 자율학습형과 같이 학교 또는 시·도 교육청 사이트를 바탕으로 하는 비담임형 사이버가정학습 유형에서는 공통적으로 `콘텐츠의 질`, `학교 또는 운영시스템의 효율적 지원`, `교사 및 운영자의 관심과 노력` 요소들이 핵심성공요인들로 나타나고 있음을 알 수 있었다. This qualitative case study was conducted to 1) understand the inner reality of educational experiences and interaction of teachers and students participated in the best practice cases of cyber home learning system, 2) identify the critical success factors that contributed in making each case a best practice. To archive the goals of study, the total five cases were selected; three cases from 2005 best practice competition awards, one case from u-learning research schools, and one case for peace.com. This study was conducted during three months through in-depth interviews with teachers, students, and parents, participatory observations for schooling and cyberspace activities, and content analysis about the artifacts created by participants for cyber teaching and learning. The research results present the narratives of 5 cases. These narratives include thick descriptions about how cyber teachers implement cyber home learning programs and how teachers and students interact in the cyber space. Based on these narratives, researchers identified the critical success factors influencing to the implementation of successful cyber home learning programs. These critical success factors include effective instructional and learning strategies, interactional strategies, motivational strategies, and other supporting strategies.

젤 추진 연소시험을 위한 비뉴턴 유체 고압공급 시스템의 설계 및 운용기술

김도헌(Do-hun Kim),한승주(Seong-joo Han),박익수(Ik-soo Park),이환규(Hwan-gyu Lee),박재범(Jae-beom Park) 한국추진공학회 2023 한국추진공학회 학술대회논문집 Vol.2023 No.5

테크놀로지 교실 통합을 위한 연구도구로서의 TPACK: 국내 연구동향 분석을 중심으로

김도헌 ( Kim Do Hun ) 한국초등교육학회 2017 초등교육연구 Vol.30 No.4

학교교육은 과학기술 혁명이 가져올 변화의 중심에 서있다. 테크놀로지의 교실통합과 이를 위한 교사교육은 점점 더 중요한 학교교육의 도전과제가 되고 있다. 테크놀로지 교수 내용 지식(TPACK: Technological Pedagogical Contents Knowledge)은 교사들의 테크놀로지 교실 통합에 관한 실천과 연구를 위한 유익한 프레임워크를 제공하여 왔다. 국제적으로 TPACK 프레임워크를 기반으로 한 테크놀로지 교실통합에 관한 연구가 급속히 증가하는 추세에 있으며 최근 들어 국내에서도 TPACK 연구가 활발히 이루어지고 있다. 본 논문은 최근까지 국내에서 이루어진 TPACK 연구들에 대한 문헌분석을 통하여 국내의 연구동향을 탐색하고, 비판적 분석을 통하여 테크놀로지 교실 통합의 연구도구로서 TPACK 연구의 의미 있는 방향성을 논의하고자 하였다. 문헌분석을 위해 35편의 국내 TPACK관련 학술 논문이 RISS등의 데이터베이스 검색을 통하여 규명되었다. 문헌분석은 연구의 방법론적 측면에서 연구접근, 연구방법, 연구대상별로 분류하여 분석하였다. 또한 TPACK 프레임워크에 따라 연구에서 활용된 테크놀로지 영역, 교수적 영역, 교과내용 영역을 분석하였다. 문헌분석 결과를 바탕으로 ‘양적 접근 편향성’, ‘자기보고식 설문조사 측정에 대한 지나친 의존’, ‘TPACK의 본질적 특성과 다른 탈맥락적·가치중립적 접근’등에 대한 비판적 분석과 논의가 이루어졌다. School education has been at the center of changes that technological revolution evokes. Technology integration into classroom and teacher education become more increasingly important challenges for school education. Technological Pedagogical Contents Knowledge(TPACK) have provided an useful framework in guiding practices and researches about teachers’ technology integration into classroom. TPACK-based researches on technology integration have been extended worldwide. In Korea, those researches have been also increased gradually. This study was to explore research trends through the review of research literatures related to TPACK in Korea and discuss the directions for future TPACK research through the critical analysis of literature reviews. 35 journal articles were identified for the literature review using RISS database. Findings of the reviews were presented in two sections: 1) research methodology analyses such as research approaches, research methods, and research participants and 2) contents analyses according to three components of TPACK framework such as technology, content, and pedagogy. From the literature review, this study discussed ‘biased tendency for quantitative research approach’, ‘excessive dependency on self-report survey for TPACK measurement’, and ‘de-contextual and value-neutral research approach’.

한국 사이버가정학습 우수사례 교사들의 실천적 지식 연구

김도헌 ( Do Hun Kim ) 한국교육인류학회 2007 교육인류학연구 Vol.10 No.2

본 연구는 사이버가정학습 우수운영사례를 중심으로 참여교사들의 실천경험 및 운영과정에 대한 질적 연구를 통하여, 우수사례 교사들의 실천활동에 내재되어 있는 실천적 지식의 모습을 규명하고자 하였다. 이를 위하여 2005년도 교육학술정보원이 선정한 우수운영사례 중, 교사의 탁월한 실천력이 돋보이는 3명의 우수사례 교사를 선정하여 3개월에 거쳐 심층면담, 학교현장 및 사이버공간에 대한 참여관찰, 내용분석 등의 연구방법을 활용하였다. 연구결과로서 세 명의 사례교사들에게 나타나는 공통적인 실천 활동의 특질들을 바탕으로 한국 사이버가정학습 우수교사의 실천적 지식을 "사이버세상에서 권위보다 친구 같은 존재감 보여주기", "끊임없는 이벤트와 아이디어 기획하기", "학생과 학부모를 내 편으로 만들기", "교과·사이버·학생의 삼박자 특성에 맞춘 수업전략 운영하기", "학생 스스로의 자발적 운영으로 발전시키기", "감성적이고 신속한 피드백 구사하기", "디지털 첨단과 아날로그 감성 적절히 활용하기"와 같이 7가지 주제영역으로 나누어 14가지의 실천전략들을 심층기술하였다. 이를 바탕으로 사례교사들의 실천적 지식 속에 투영된 포괄적 이미지로서 "종소리 없는 교실의 열정적 헌신 자", "수평적 관계의 눈높이 교사", "변화 추진자로서의 외로운 투쟁자"의 모습에 대하여 논의하였다. This study investigated the practical knowledge embedded in the cyber teaching activities of three teachers who participated in cyber home learning programs. The study was conducted through a qualitative case study to examine their beliefs and experience about cyber-teaching activities during a three-month period. Three teachers were selected from the 10 best teachers as recognized by the Korea Education & Research Information Service (KERIS). Each teacher was also selected from elementary, middle, and high school respectively to represent three formal school systems. The data collection methods were in-depth interviews about teachers` practical experiences, participatory observations about cyber activities, and content analysis about artifacts created by teachers and their students. The results present 14 practical strategies based on 7 practical principles such as "showing friendship rather than authority", "planning various events and ideas continuously", "forming partnership with students and their parents", "balancing instructional strategies with characteristics of teaching subject, students, and cyber environment", "providing emotional and fast feedback", "utilizing high-tech and high-touch adequately". Finally, three images projected in teachers` practical knowledge were discussed in the context of Korea cyber education environment:"passionate devotion", "Noonnoppi teacher" (Noonnoppi means that teachers deal with their students like friends), and "lonely advocate as a change agent".

IgA 신병증에서 혈청 면역글로불린 A 의 유용성

김명성(Myeong Sung Kim),신규태(Gyu Tae Shin),임현이(Hyun Ee Yim),김승정(Seung Jung Kim),신승수(Seung Soo Sheen),마경애(Kyoung Ai Ma),조남한(Nam Han Cho),최영일(Young Il Choi),김흥수(Heung Soo Kim),김도헌(Do Hun Kim) 대한신장학회 2002 Kidney Research and Clinical Practice Vol.21 No.1

배 경 : 면역글로불린 A (Immunoglobulin A, 이하 IgA) 신병증은 가장 흔한 사구체신염으로 알려져 있다. IgA 환자의 30- 50%에서 혈청 IgA 농도가 증가하지만 혈청 IgA 측정이 갖는 IgA 신병증 진단의 유용성에 대해서는 잘 밝혀져 있지 않다. 방 법 : 1994년 6월부터 1998년 12월까지 아주대학교병원에 내원하여 신조직 검사를 시행한 전체환자 333명 중 혈청 IgA 농도를 측정한 270명을 후향적으로 조사하였다. 결 과 : 혈청 IgA 농도의 정상치의 상한 값인 365 ㎎/dL를 초과하는 환자 수는 IgA 신병증 환자들에서는 80명 중에 32.5%인 26명이었으며, 나머지 환자들에서는 190명 중에 8.9%인 17명이 혈청 IgA치가 365 ㎎/dL를 초과하였다(p<0.001). 혈청 IgA 농도 증가에 따라 IgA 신병증 진단에 대한 민감도는 감소하며, 특이도는 증가하는 관계를 나타내었다. 혈청 IgA농도 1 ㎎/dL에 대해 IgA 신병증으로 진단 받을 위험도(Risk ratio)는 1.0025였다(p- value 0.0043). 또한 혈청 보체치가 저하되지 않은 환자만을 대상으로 하였을 경우 이러한 위험도는 1.0079로 더욱 상승하였다. 그러나 혈청 IgA 농도와 신조직 면역형광 소견과는 상관관계가 없는 것으로 나타났다. 결 론 : 혈청 IgA 농도 측정이 IgA 신병증 진단 추정에 유용함을 보여 주었고, 이러한 결과는 특히 신 조직 검사가 적합하지 않은 환자에서, 혈청 IgA 농도, 보체 등을 이용하여 IgA 신병증 진단을 추정하는데 임상적으로 도움을 줄 수 있다. Background : Immunoglogulin A (IgA) nephropathy is the most common primary glomerular disease throughout the world. 30-50% of patients with IgA nephropathy (IgAN) have high serum IgA concentrations. However, we do not know if the degree of elevation in IgA level increases the likelihood of having IgAN. Neither do we know if the IgA level has any association with pathological findings of IgAN. Methods : We analyzed the relationships between IgAN and the levels of serum IgA which has been a routine part of the study in all patients with glomerulonephritis in our institution for the last 4 years. We reviewed 270 patients in whom the pathological diagnosis and the results of their IgA levels were both available. Results : Of 80 patients who were IgA nephropathy, 26 patients (32.5%) had higher than normal cutoff value of serum IgA (385 ㎎/dL). In contrast, 8.9% of patients with other types of glomerulonephropathies showed the values above normal(p<0.0001). The risk ratio for an increase of one unit of the IgA level was 1.0025(logistic regression, p=0.0043), which was increased to 1.0079 when patients with low complement levels were excluded from the analysis. The data were also analyzed according to the immunofluorescence microscopic findings of IgAN, which were found to have no significant correlation with IgA concentrations. Conclusion : The IgA level is a risk factor for IgAN throughout the whole range. However, it does not correlate with the IgA deposition in the renal tissue. We believe that this study will help understanding the interpretation of IgA levels in patients with IgAN.

칼릭스아렌 포로젠을 이용한 다공성 박막의 초기 나노기공 형성과정에 관한 연구

임진형 ( Do Hun Kim ),김도헌 ( Jin Heong Yim ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.5

Fourier Transform Infrared Spectroscopy and in-situ Position Annihilation Lifetime Spectroscopy(PALS) analysis of hybrid film, which consist of silsesquioxane(SSQ) and 4-tert-butyl calix[4]arene-O,O``,O,O``````-tetraacetic acid tetraethyl ester(CA[4]) have been investigated in order to understand initial formation of nanopore in the next generation porous low-k dielectrics(k<2.0). SSQ/CA[4] can provide effective homogeneous thin film having porous structure. The porogen decomposition behavior were completely different in the two kinds of SSQ/CA[4] based hybrid film(i.e. SSQ/CA[4] 10 and SSQ/CA[4] 20%). Relatively small pores(1.5 nm) come from dispersion of uni-molecular CA[4] in the SSQ matrix have been generated at 300 ˚C, while mesopores(2.5~3.0 nm) induced from self assembled CA[4] have been generated at 250 °C. It might be due to highly interconnected structure of SSQ/CA[4] 20% hybrid thin film resulting in facile evacuating of decomposed fragment of CA[4] molecule.

자발 성장법으로 성장된 단결정 Bi 단일 나노선의 정상 자기 저항 특성

심우영,김도헌,이경일,전계진,이우영,장준연,한석희,정원용,Shim, Woo-Young,Kim, Do-Hun,Lee, Kyoung-Il,Jeon, Kye-Jin,Lee, Woo-Young,Chang, Joon-Yeon,Han, Suk-Hee,Jeung, Won-Young,Johnson, Mark 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.4

단결정 Bi단일 나노선의 정상 자기 저항(ordinary magnetoresistance) 특성을 $2{\sim}300K$에서 4 단자법으로 측정하였다. I-V 측정을 통해 전기적 오믹 형성을 확인하였고, 2 K과 300 K에서 비저항이 각각 $1.0{\times}10^{-4}$와 $8.2{\times}10^{-5}{\Omega}{\cdot}cm$으로 측정되었다. 수직(transverse) 및 수평(longitudinal) 자기저항비(MR ratio)가 110 K와 2 K에서 각각 현재까지 보고된 MR 중 가장 큰 2496%와 -38%으로 관찰되었으며, 이 결과는 자발 성장법으로 성장된 Bi 나노선의 결정성이 매우 우수한 단결정임을 증명한다. simple two band(STB) 모델을 통해 Bi 나노선의 수직 및 수평 정상 자기 저항(OMR) 거동이 온도에 따른 페르미 준위(Fermi level)와 밴드 겹침(band overlap)등의 전자 구조 변화 및 운반자 농도 변화로 잘 설명된다. We report the magneto-transport properties of an individual single crystalline Bi nanowire grown by a spontaneous growth method. We have successfully fabricated a four-terminal device based on an individual 400-nm-diameter nanowire using plasma etching technique to remove an oxide layer forming on the outer surface of the nanowire. The transverse MR (2496% at 110 K) and longitudinal MR ratios (38% at 2 K) for the Bi nanowire were found to be the largest known values in Bi nanowires. This result demonstrates that the Bi nanowires grown by the spontaneous growth method are the highest-quality single crystalline in the literatures ever reported. We find that temperature dependence of Fermi energy ($E_F$) and band overlap (${\triangle}_0$) leads to the imbalance between electron concentration ($n_e$) and hole concentration ($n_h$) in the Bi nanowire, which is good agreement with the calculated $n_e\;and\;n_h$ from the respective density of states, N(E), for electrons and holes. We also find that the imbalance of $n_e\;and\;n_h$ plays a crucial role in determining magnetoresistance (MR) at T<75 K for $R_T$ and at T<205 K for $R_L$, while mean-free path is responsible for MR at T>75 K for $R_T$ and T>205 K for $R_L$.

미립화 및 분무장치 1 : 기체 공급 방식에 변화에 따른 2단 공기 보조식 분사기의 분무 분열 및 입도 분포 특성

이인철 ( In Chul Lee ),김도헌 ( Do Hun Kim ),구자예 ( Ja Ye Koo ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Air-blast spray gun can produce homogeneous pattern of droplet distribution, so relatively fine film can be generated at the surfaces. In the spray painting and coating industries, air-blast injector configured with a liquid-centered and 2-stage gas outer nozzle have many advantages which are low paint bounce-back, high transfer efficiency. The experimental investigations are to study liquid column break-up and overspray characteristics. To verify the effect of gas jet, an air-blast injector with a gas post of 2-stages is designed to conduct overall spray characteristics as well as to increase transfer efficiency. Number of droplet distributions is measured by laser diffraction with Mie-scattering methods considering the ratio of refractive indices and absorption coefficient. The experiment results show that the main effect of liquid jet break-up is governed with gas jet of the inner-stage. In the case of inner gas injection, the exit at the inner stage transfer more shear force to center of liquid column. However, because the nozzle exit of outer stage is located to the far from liquid column, shear force to break-up liquid jet do not fully affect liquid column. For the outer-stage gas injection has less shear force to the liquid column than inner-stage gas injection. In case of inner stage gas jet, better atomization qualities can be achieved, however, in case of outer stage gas jet, larger droplet distributions are appeared on the same measurement area. As increase momentum ratio of gas jet, droplet sizes decreased. Additionally, gas jet of the outer-stage also contributes atomization at the far-field spray region and droplet transportation to the object. It was observed that, as the gas jets increase, droplet mean diameters decreased and transfer efficiency increased due to the outer gas post which makes an air-curtain around the spray jets so that impinged droplet cannot overspray to the outer region of the spray jets.