Teachers’ collaborative inquiry through professional study group

Youngjoo Bang 한국외국어교육학회 2010 Foreign languages education Vol.17 No.2

The purpose of this study is to explore the nature of the professional study group as a tool of teacher development, examining how teachers reflect upon their learning experiences in the study group. The study was conducted at a private elementary school in Seoul during the fall semester of 2009. Seven EFL teachers at the school, 4 males and 3 females, ranging in age from 25 to 41 years, were involved in this study. This study was a qualitative research. The data were collected through semi-structured interviews, audio-taped dialogues, observations, and researcher field notes. Using these data, the study analyzes teachers’ perceptions towards professional study group. The results of the study highlighted the followings as its positive effects: creating a supportive learning community; exploiting the critical reflections from colleagues; increasing collaboration and communication among teachers; improving self-efficacy in regard to individual’s teaching behaviors; changing teachers’ ideas of, and raising awareness in, their own beliefs and instructions. In addition, the study showed the benefits and the challenges of creating an environment that supports a collegial learning community, identifying some major themes that the participants discussed during the meetings. The study will help inform ESL/EFL teachers and teacher educators of how reflective teaching through professional study group may support teachers’ in-depth exploration of their professional thinking and practice.

효율적인 원어민 영어교사 자질에 대한 인식

방영주 ( Bang Youngjoo ) 현대영어교육학회 2007 현대영어교육 Vol.8 No.3

The purpose of this study is to provide a selective but representative review of empirical research on teacher effectiveness of native speakers of English teaching at college and university. A close investigation of students’ and teachers' perceptions of teacher effectiveness entails clear implications for improvement of teaching. For this study, 237 students and 50 teachers from several universities participated. The data collection was a questionnaire. The questionnaire with 40 items consists of questions regarding knowledge of English, instruction skill, evaluation, interaction skill, personality of the teacher. The findings showed significant differences in 21 items out of 40 between teacher and student group. In addition, the results indicated that the teachers and the students had different opinions and attitudes towards the characteristics of effective teachers. The findings might help the upgrading of English teacher training programs for the benefit of prospective teachers and students.

교사-학생간의 홈페이지를 활용한 자기주도적 학습의 효과

방영주(Bang Youngjoo) 한국영어어문교육학회 2006 영어어문교육 Vol.12 No.3

  This study aims to investigate the effects of the implementation of self-directed learning through the homepage between the teacher and the students for English reading classes. The study focuses on the questions of whether the self-directed learning through the homepage, compared to the teacher-centered learning, would enable a significantly positive change in the students" achievements and of what their responses to this new learning method are. 72 students were grouped into an experimental and a control group, and then each group was subdivided into three levels(high, medium, low) of proficiency. Findings demonstrate that the experimental group showed statistically more significant increases in their scores of reading proficiency test than the control group. For the question of students" responses to the learning experience, the three groups within the experimental group responded to a questionnaire survey with regard to the positive attitude of learning, the effectiveness of self-directed learning and its learning materials, and usability of the homepage. In general, the experimental group considered the experience satisfactory, although the degree of positive responses varied according to the proficiency level of the group. This suggests the importance and effectiveness of self-directed learning using the computer and internet as a supplementary learning tool.

Visual Target Tracking and Relative Navigation for Unmanned Aerial Vehicles in a GPS - Denied Environment

Youngjoo Kim,Wooyoung Jung,Hyochoong Bang 한국항공우주학회 2014 International Journal of Aeronautical and Space Sc Vol.15 No.3

We present a system for the real-time visual relative navigation of a fixed-wing unmanned aerial vehicle in a GPS-denied environment. An extended Kalman filter is used to construct a vision-aided navigation system by fusing the image processing results with barometer and inertial sensor measurements. Using a mean-shift object tracking algorithm, an onboard vision system provides pixel measurements to the navigation filter. The filter is slightly modified to deal with delayed measurements from the vision system. The image processing algorithm and the navigation filter are verified by flight tests. The results show that the proposed aerial system is able to maintain circling around a target without using GPS data.

Ad-hoc Network for Inter-Vehicle Communication of Multiple UAVs

Youngjoo Kim,Hyochoong bang 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10

This paper addresses a method to implement an ad-hoc network for inter-vehicle communication of multiple UAVs. During cooperative missions, it is essential to share information between different UAVs. The ad-hoc network provides greater autonomy to the team of UAVs because it is free of intervention of ground stations. The challenges we consider for implementing inter-vehicle communication are including increased data amount, distinguishing data, and system complexity. This paper provides the solutions to these problems in terms of hardware and software.

무인항공기 공중 급유를 위한 INS/Vision 상대 항법

김영주(Youngjoo Kim),정우영(Wooyoung Jung),방효충(Hyochoong Bang) 한국항공우주학회 2017 한국항공우주학회 학술발표회 논문집 Vol.2017 No.11

유도포탄 저속 회전 시 안정성 분석

김영주(Youngjoo Kim),방효충(Hyochoong Bang),서송원(Songwon Seo),박장호(Chang-Ho Pak),김진원(Jin-Won Kim),서일원(Ilwon Seo) 한국항공우주학회 2018 韓國航空宇宙學會誌 Vol.46 No.9

본 논문에서는 비선형 모델 시뮬레이션을 통해 저속 회전 중인 유도포탄의 비행 모습을 확인하고 외란으로써 여러 가지 방향과 크기의 돌풍을 작용하여 유도포탄의 비행 안정성을 분석한 방법과 결과를 소개한다. 돌풍은 3m/s, 7m/s, 10m/s, 15m/s 네 가지의 속력을 가지고 26가지의 방향에서 탄도 정점 부근부터 작용하도록 설정하였다. 초당 1회전 및 3회전으로 회전하는 경우에 대해 총 208회의 시뮬레이션을 수행한 결과를 분석하였다. 초당 3회전으로 회전할 때는 탄체가 전복되지 않았지만, 초당 1회전으로 회전할 때는 7m/s 이상의 돌풍이 작용할 때 비행 후반부에 탄체가 전복되는 경우가 발견되었다. 탄체 비행 방향 반대쪽으로 작용하여 비행 방향 대기속도를 증가하는 돌풍은 해로운 영향을 주지 않았다. 탄체전복은 모두 탄체가 하강하는 후반부에 발생하였으며, 탄도 정점 부근에서는 자세가 크게 진동하거나 탄체가 전복되지 않았다. This paper presents methods and results of nonlinear simulations for a guided munition for verifying stability at slow spin. The munition is launched by an artillery and it deploys the rear fins to reduce its spin. While the spin speed command is set to 1 rps and 3 rps, wind gusts of 3m/s, 7m/s, 10m/s, and 15m/s in amplitude, and 26 different directions were generated as disturbance for each simulation run. Whereas the munition with the spin speed of 3 rps didn’t flip, that with 1-rps spin flipped under some gusts. However, the gusts which increase airspeed in the flight direction didn’t introduce harmful effect. Most importantly, all the flips of the munition was observed near the end of the simulation where the munition is going down. No problem was observed near the summit of trajectory.

Utilizing Out-of-Sequence Measurement for Ambiguous Update in Particle Filtering

Kim, Youngjoo,Hong, Kyungwoo,Bang, Hyochoong IEEE 2018 IEEE transactions on aerospace and electronic syst Vol.54 No.1

<P>This paper proposes a novel method to cope with local measurement ambiguity problem in particle filtering. The ambiguity of the measurement has been attributed as a crucial cause of filter degradation and divergence. Given the observation that the ambiguous measurement update is contributed by not only the shape of the measurement model but also the prior distribution of the filter estimate, we adopt a solution to the out-of-sequence measurement problem on the framework of the particle filter with sequential importance resampling. Once an ambiguous measurement update is detected, the proposed method skips the measurement update at the time step and utilizes the measurement later when the particle distribution becomes adequate for the measurement update. This strategy provides a remedy to the ambiguity problem to obtain accurate current position estimate with lower covariance. Numerical simulation is presented to demonstrate effectiveness and performance of the proposed method. Compared to other methods, such as the standard particle filter, the auxiliary particle filter, the mixture particle filter, and the receding-horizon Kalman filter, the proposed method shows better performance in terms of root-mean-square error and estimated covariance.</P>

표적 추적 성능 최적화 및 충돌 회피를 위한 다수 에이전트 분산 제어

김영주(Youngjoo Kim),방효충(Hyochoong Bang) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.9

A decentralized control method is proposed to enable a group of robots to achieve maximum performance in multisensory target tracking while avoiding collision with the target. The decentralized control was designed based on navigation function formalism. The study showed that the multiple agent system converged to the positions providing the maximum performance by the decentralized controller, based on Lyapunov and Hessian theory. An exemplary simulation was given for a multiple agent system tracking a stationary target.

비행 실험을 통한 유도형 탄약 항법 시스템 검증

김영주(Youngjoo Kim),임승한(Seunghan Lim),방효충(Hyochoong Bang),김재호(Jaeho Kim),박장호(Changho Pak) 한국항공우주학회 2016 韓國航空宇宙學會誌 Vol.44 No.11

유도형 탄약은 비행속도 증가를 이용한 기존의 사거리 증가 방식과 다르게 정밀 유도제어를 사거리 연장 및 정밀 타격하는 기술을 기반으로 한다. 고회전으로 상승하는 탄은 탄도 정점에서 후미 날개를 전개하여 회전을 감소하고, 최종적으로 회전을 제거한 후 비행하게 된다. 주 날개 전개 전 탄체 뒤집힘 감지를 위하여 자세 추정이 요구되는데, 회전 감속 중에서는 일정한 회전을 가정한 기존의 유도무기 자세 추정 기법을 사용할 수 없다. 또한, 비행 시에는 횡축 가속도를 제어하기 때문에 중력 가속도 성분을 기반으로 하는 일반적인 무인기의 자세추정 기법은 큰 오차를 발생한다. 이러한 문제를 해결하기 위해 본 논문에서는 저속 회전 및 비행 중 자세추정기법을 제시하고, 무인기에 탑재하여 비행 실험을 통해 검증하였다. 저속 회전 중 자세 추정 기법은 롤 각을 상태변수로 갖는 칼만 필터 형태로 구성하였다. 비행 시 자세 추정 기법은 사원수를 이용한 곱연산 확장형 칼만 필터를 기반으로 하며, 가속도 측정치가 중력 가속도뿐만 아니라 선회에 의한 구심력을 포함하도록 측정 모델을 개선하였다. This paper presents results of flight experiments on a navigation algorithm including multiplicative extended Kalman filter for estimating attitude of the guided munition. The filter describes orientation of aircraft by data fusion with low-cost sensors where measurement update is done by multiplication, rather than addition, which is suitable for quaternion representation. In determining attitude from vector observations, the existing approach utilizes a 3-axis accelerometer as a 2-axis inclinometer by measuring gravity to estimate pitch and roll angles, while GNSS velocity is used to derive heading of the vehicle. However, during accelerated maneuvers such as coordinated flight, the accelerometer provides inadequate inclinometer measurements. In this paper, the measurement update process is newly defined to complement the vulnerability by using different vector observations. The acceleration measurement is considered as a result of a centrifugal force and gravity during turning maneuvers and used to estimate roll angle. The effectiveness of the proposed method is verified through flight experiments.