Modeling on discharge characteristics of helicon plasmas

Suwon Cho 한국진공학회 2000 한국진공학회 학술발표회초록집 Vol.- No.-

Formulation of a Wave Equation for ECR plasmas in Inhomogeneous Magnetic fields

Cho, Suwon 경기대학교연구교류처 1993 論文集 Vol.33 No.-

Helicon and Trivelpiece-Gould Eigenmodes in Helicon Plasmas

Suwon Cho 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.6

The eigenmode dispersion relation of the helicon and the Trivelpiece-Gould modes are studied for helicon plasmas. The condition of the Trivelpiece-Gould modes is found to be valid only in the limited region that is opaque to the fast helicon wave. The approximation neglecting the electron's inertia is not good when compared with the exact results. However, it roughly yields a linear relation between the density and the magnetic field, according which particular eigenmodes are most strongly excited. The eigenmode dispersion relation of the helicon and the Trivelpiece-Gould modes are studied for helicon plasmas. The condition of the Trivelpiece-Gould modes is found to be valid only in the limited region that is opaque to the fast helicon wave. The approximation neglecting the electron's inertia is not good when compared with the exact results. However, it roughly yields a linear relation between the density and the magnetic field, according which particular eigenmodes are most strongly excited.

휠 베어링 씰 적용을 위한 라비린스 씰 구조 개발

조수원(Suwon Cho),백길호(Gilho Baek),안대철(Daecheol Ahn),김하영(Hayoung Kim),김세훈(Sehoon Kim) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11

헬리콘 플라즈마메서 이온 펌핑 효과의 영향에 대한 수치적 해석 연구

조수원(Suwon Cho),박인호(Inho Park),최성을(S.E. Choi),권명회(M.H. Kwon) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.3(2)

시간 변화를 고려한 출력 및 입자의 전체 균형 모델(global balance model)을 적용하여 헬리콘 플라즈마에서의 전자 밀도 및 온도와 중성 밀도의 시간에 따른 변화를 연구하였다. 출력 흡수량은 맥쓰웰 방정식으로 부터 계산하여 균형 방정식에 이용하였으며, 플라즈마 변수와 출력 흡수 및 손실을 self-consistent하게 구하였다. 계산 결과를 이용하여 헬리콘 플라즈마에서 관찰되는 이온 펌핑 효과와 펄스 방전에서 나다나는 두가지 방전 모드의 존재를 설명하였으며, 중성 기체의 유량, 압력 등이 플라즈마 변수 변화에 미치는 효과를 분석하였다. 그리고 낮은 압력에서 전자 밀도는 자기장에 관계없이 중성 밀도에 좌우되나, 이온 펌핑 효과가 무시될 수 있는 압력 이상에서는 전자 밀도가 자기장이 커짐에 따라 증가하는 결과를 얻었다. The global balance model is applied to investigate the transient behavior of the electron density and temperature in helicon plasmas. The power absorption calculated from the solutions of the Maxwell equations is used in solving the power balance equation. A balance model for the neutral gas is also considered to find its density self-consistently. It is turned out that the numerical results reasonably explain consequences of the ion pumping effect including the occurrence of two distinct modes of pulsed helicon discharge which have been observed experimentally. The behavior of the discharge parameters are found to be primarily dependent on the power absorption and the gas flow rate, but the pressure controls the electron density and temperature of the final steady state as well as the transient state even with the same flow rate. Finally, it is shown that the electron density virtually remains constant as the magnetic field varies when the pressure is lower than a certain value and that the linear relationship between the density and the magnetic field is retained for a higher pressure when the effect of the ion pumping is negligible.

Comparisons of Lepidoptera Species Assemblages among the Different Plant Communities within the Long Term Ecological Research Sites in 2007 in Korea

Hoonbok Yi,Suwon Cho,Se-woong Choi,Moonki Bak,Byung In Sohn,Hyun Jung Kim 한국응용곤충학회 2009 한국응용곤충학회 학술대회논문집 Vol.2009 No.05

Moths were caught by using two 22W UV black light traps per treatment during May, June, August and September in 2007 from our study sites. Our study areas of the Korea Long Term Ecological Research (KLTER) sites were Mt. Nam with two plant communities (Quercus mongolica, Pinus densiflora), Mt. Jiri with three plant communities (Q. mongolica, P. densiflora, Abies koreana), Mt. Wolak with three plant communities (Q. mongolica, P. densiflora, Q. variabilis), and Mt. Jumbong with t재 plant communities (Q. mongolica, P. densiflora). The purpose of this study was to compare the species diversity of major plant feeders, Lepidopteran species (moths) at each forest type of the regional KLTER sites. Overall, the total numbers of moth species we’ve collected from the all KLTER sites in 2007 were 670 species. For the three plant communities, Mt.Jiri (11 family, 259 species, 2372 individuals) was the highest site and Mt. Wolak (7 family, 401 species, 2243 individuals) was the next highest. For the two plant communities, Mt. Jumbong (14 family, 166 species, 1750 individuals) was highest and Mt Nam (4 family, 21 species, 142 individuals) was very few. The ordination analyses, Nonmetric multidimensional scaling (NMS) and cluster analysis, showed distinct clusters separating the assemblages of moth found at each site and each plant community of the KLTER sites (P<0.05 from MRPP). Therefore, we suggest that our sustainable monitoring will verify the distinct cluster with the forest type at each site with many replications.

Pythagorean Hodograph 곡선을 이용한 무추력 비행체 비행경로 설계

이수원(Suwon Lee),조남훈(Namhoon Cho),김유단(Youdan Kim) 한국항공우주학회 2017 한국항공우주학회 학술발표회 논문집 Vol.2017 No.11

초등학교 블렌디드 러닝에서 맞춤형 학습을 위한 학습자 군집 탐색

이수원 ( Suwon Lee ),한예진 ( Ye Jin Han ),이승민 ( Seungmin Lee ),조영환 ( Young Hoan Cho ) 한국교육공학회 2022 교육공학연구 Vol.38 No.1

최근 코로나19 팬데믹으로 서로 다른 수업방법과 교육매체를 통합하는 블렌디드 러닝(blended learning)의 중요성이 초등학교에서 증가하고 있다. 블렌디드 러닝에 대한 관심이 증가하고 있지만, 교사가 학습자의 온라인 활동을 관찰하기 어렵고 학습자의 다양한 특성을 종합적으로 판단하기 어렵다는 제한점이 있다. 교사가 학습자의 요구를 쉽게 파악하고 맞춤형 학습지원을 효과적으로 제공할 수 있도록 학습자를 군집으로 구분하고 각 군집에 필요한 학습자료와 스캐폴딩을 제공할 필요가 있다. 본 연구는 블렌디드 러닝에서 온라인과 면대면 학습 데이터를 활용하여 초등학생의 군집을 탐색하고 군집 간 차이점을 비교하였다. 한 달 동안 초등학교 4학년 학생들(n=70)의 수학학습 데이터를 수집하였으며, 블렌디드 러닝에서 활용된 학습관리시스템에서 온라인 학습 데이터를 수집하고, 면대면 수업에서 수학 성취도 평가 점수와 동기, 성취정서, 자기효능감, 자기조절학습에 대한 설문조사 자료를 수집하였다. 수집된 데이터에 대한 군집분석을 실시한 결과, (1) 통합 지원이 필요한 군집, (2) 온라인 학습참여와 성적이 높은 군집, (3) 긍정정서를 가지고 있으며 자기조절학습 능력이 높은 군집으로 구분되었다. 그리고 담임교사 4명을 대상으로 학습자 군집의 유용성에 대한 면담을 실시하였다. 교사들은 군집분석 결과가 자신이 인지하지 못한 학습자들의 특성을 보여주고 학습자를 종합적으로 이해하는 것을 돕기 때문에 블렌디드 러닝에서 맞춤형 학습을 지원하는 데 유용하다고 인식했다. 향후 우리나라 학습자들의 고유한 특성을 다각도로 이해하고 다양한 학습자를 위한 맞춤형 학습환경을 개발하기 위해 군집분석을 체계적으로 실시할 필요가 있다. During the COVID-19 pandemic, teachers have emphasized the importance of blended learning in elementary schools by integrating different instructional methods and educational media. Despite the growing interest in blended learning, teachers have difficulties in observing online learning activities and understanding students’ characteristics comprehensively. To identify students’ needs easily and provide effective personalized learning support, it is essential for teachers to identify a few clusters of learners and provide learning materials and necessary support for each cluster. In this study, clusters of elementary school students were explored by employing blended learning data of achievements, affective characteristics, self-regulated learning skills, and online learning participation. We collected fourth graders’ mathematics learning data (n=70) for a month. The data included online learning data collected from a learning management system and face-to-face learning data such as assessment scores and surveys of motivation, achievement emotion, self-efficacy, and self-regulated learning. Cluster analysis revealed three clusters of elementary school students: (1) those who needed integrated support, (2) those with positive affective characteristics and high-level self-regulated learning skills, and (3) those with high-level online learning participation and achievement. Interviews with four homeroom teachers revealed that the clusters may be beneficial in understanding learners comprehensively and supporting personalized learning in blended learning. It is recommended that future research should conduct cluster analysis to explore Korean learners’ unique characteristics and develop personalized learning environments for a diverse group of students.

자연환기 및 공기청정기 가동에 따른 실내공기질 분석

송수원(Suwon Song),유정연(JungYeon Yu),조정식(ChungSik Cho),이윤규(YunGyu Lee) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-

This study analyzed the concentration reduction effects of particulate matters (e.g., PM10 and PM2.5) and indoor air pollutants (e.g., CO2, TVOC, Radon) according to the operation conditions of an air-cleaner and natural ventilation through windows in a small office. As results, the daily average concentrations of PM10 and PM2.5 decreased into 0.2 μg/m3 from 1.6 μg/㎥ when the air-cleaner was in operation along with all windows closed during holidays. Under the conditions of natural ventilation with the windows opened during weekdays, the concentrations of Radon significantly decreased up to 0.2 pCi/ℓfrom 3.7 pCi/ℓ. However, the daily average concentrations of PM10 increased almost double up to 74.7 μg/㎥ from 30.5 μg/㎥ and PM2.5 increased up to 40.9 μg/㎥ from 21.5 μg/㎥ as well even though the air-cleaner was in operation. Consequently, when it comes to improving indoor air quality, it is important to timely operate ventilation (natural or mechanical) systems as well as air-cleaner(s) depending on the concentrations of measured indoor and outdoor air pollutants.

RRT 기법을 이용한 무추력 비행체의 궤적 보정

이수원(Suwon Lee),조남훈(Namhoon Cho),홍유경(Youkyung Hong),김유단(Youdan Kim) 한국항공우주학회 2016 한국항공우주학회 학술발표회 논문집 Vol.2016 No.11