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LED 광원 크기에 따른 자유 형상 렌즈의 조명 성능 변화와 공차 특성
양재석,김대찬,오범환,박세근,유일현,이승걸,Yang, Jae-Suk,Kim, Dae-Chan,O, Beom-Hoan,Park, Se-Geun,You, Il Hyun,Lee, Seung Gol 한국광학회 2013 한국광학회지 Vol.24 No.1
본 논문에서는 점광원을 기준으로 설계된 자유 형상 렌즈(freeform lens)의 조명 성능과 LED 광원 크기와의 관계 및 공차 특성을 살펴보았다. 비교를 위해 발산 조명 모델(divergent illumination model)을 적용한 두 가지 렌즈와 중첩 조명 모델(overlapped illumination model)을 적용한 한가지 렌즈를 설계하였다. LED 광원이 커짐에 따라 평균 조도에 비해 조도 균일도가 상대적으로 크게 감소하였으며, 정렬 오차에 의한 성능 저하는 거의 발생하지 않았다. 하지만 LED 광원의 방출 특성 변화는 LED 광원 크기에 관계없이 조명 성능에 영향을 미치는 것으로 확인하였다. 발산 조명 모델로 설계된 렌즈가 전반적으로 우수한 성능을 보였지만, LED 방출 특성 변화에 대해서는 중첩 조명 모델로 설계된 렌즈의 성능이 상대적으로 적게 변화함을 알 수 있었다. In this paper, the illumination performances of three freeform lenses optimally designed for a point source were investigated for several LEDs with different source sizes, and also the tolerance characteristics of the lenses were analyzed. For comparison, two lenses with different sizes were designed with a divergent illumination model, and the last one was done with an overlapped illumination model. As the LED source size increased, the illuminance uniformity decreased more strongly, and the influence of a source misalignment on illumination performance became insignificant. However, the variation of LED radiation characteristics had strong effect on the illumination performance, irrespective of LED source size. Even though the lens based on a divergent illumination model showed superior performance compared to the lens based on an overlapped illumination model, the latter was less sensitive to the variation of LED radiation characteristics.
렌즈 최적설계에 있어 Merit Function 구성이 최적화 성능에 미치는 영향
양재석,박혜민,김대찬,오범환,박세근,이일항,이승걸 한국조명·전기설비학회 2012 한국조명·전기설비학회 학술대회논문집 Vol.2012 No.10
In the optimal design of an illumination LED lens with complex type, the influence of merit function on the lens performance was numerically analyzed, and the best merit function for satisfying an illuminance requirement was estimated. The lens was assumed to have freeform surfaces. Simulated annealing method was applied for the optimization, and merit function was composed of an ray arrival rate, a luminous flux efficiency, and an illuminance uniformity. From the analysis it was found that the composition ratio of the illuminance uniformity was the most sensitive to the performance of the optimized lens.
ESL Students’ Vocabulary Learning Strategies in L2 Verbal Skills
양재석 현대영미어문학회 2015 현대영미어문학 Vol.33 No.4
This study investigated vocabulary learning strategies in L2 listening and speaking, drawing on the 432 tertiary level ESL participants. It yielded factors underlying vocabulary learning strategies related to L2 verbal skills. Based on the results of factor analysis, the relationship between the identified factors and vocabulary proficiency level was also examined. The results revealed statistically distinct underlying constructs in strategies for both skill areas. In addition, memory & L1-oriented resource strategies and compensation strategies were employed more frequently in listening by learners with low and mid-level proficiency than by those with high-level. Moreover, in speaking, high proficiency learners used both direct translation & make-up strategies and memory strategies less frequently than did the other two groups. The findings imply that ESL learners ought to be provided with focused training on vocabulary learning strategies tied to listening and speaking, depending on their vocabulary proficiency.
양재석 국제문화기술진흥원 2023 The Journal of the Convergence on Culture Technolo Vol.9 No.1
Pre-service teachers have established and developed their own teaching strategies and professional language teaching skills based on their pedagogical and learning experiences. In this regard, it is conceivable that pre-service teachers' feedback may have distinct viewpoints and focuses. Therefore, the purpose of this study is to analyze pre-service teachers’ feedback to microteaching demonstrations. Participants in the study were 40 prospective elementary school teachers. They were invited to offer feedback on microteachings video-recorded by their peers. According to the findings, we identified a total of 708 comments. The majority of feedback was categorized as teacher talk(40.1%) , followed by teaching and learning activity (20.9%), interaction (12.6%), teaching materials (11.4%), classroom atmosphere and learning environment (8.9%), lesson flow (3.7%), review and evaluation (1.3%), and introduction and objectives (1.1%). The most frequent types of feedback were the teacher's use of appropriate speaking rate, tone, and intonation. This finding reflects the fact that English teachers realize the importance of the teacher's English proficiency, therefore we suggest that teacher education institutions need raise awareness not just of teachers' English skills but also of their diverse perspectives. 우리는 본 연구를 통해 영어 모의 수업시연에 대한 예비교사들의 피드백을 분석함으로써 이들이 수업관찰에 초점을 두는 부분이 무엇인지를 살펴보는 데 목적을 두고 있다. 이를 위해 우리는 국내 교육대학교 1곳에 재학중인 예비 초등학교 교사 40명을 대상으로 모의 수업시연을 실시한 뒤에 관찰하고 이에 대한 동료 피드백을 제공하여 수집된 피드백 내용을 수업관찰 분석 기준에 따라 분류하여 빈도 분석하였다. 분석 결과 총 707개의 피드백이 도출되었으며, 대부분은 교수 언어(40.2%)로 분류되었으며, 교수학습 활동(20.9%), 상호작용(12.6%), 교구재활용(11.5%), 수업 분위기 및 학습환경(8.8%), 수업 흐름(3.7%), 정리 및 평가(1.3%), 도입 및 수업 목표(1.1%) 등이 그 뒤를 이었다. 개별적으로는 교사 영어의 양과 속도, 목소리 크기 및 억양의 적절성에 대한 피드백(16.5%)의 빈도가 가장 높은 것으로 나타났다. 예비교사의 주된 초점이 교사의 말이나 언어 및 영어 유창성에서 비교적 두드러지게 나타났으며, 이는 영어교사로서 영어 능력의 중요성을 인식하고 있다는 점을 알 수 있다. 따라서 우리는 교사교육기관에서 교사의 영어 능력뿐만 아니라 다양한 관점에 대한 인식을 제고할 필요가 있다.
양재석,박재형,오범환,박세근,이승걸 한국광학회 2016 Current Optics and Photonics Vol.20 No.5
In this paper, we propose a novel differential equation method for designing a total internal reflection(TIR) LED lens with double freeform surfaces. A complete set of simultaneous differential equations forthe method is derived from the condition for minimizing the Fresnel loss, illumination models, Snell’sLaw of ray propagation, and a new constraint on the incident angle of a ray on the light-exiting surfaceof the lens. The last constraint is essential to complete the set of simultaneous differential equations. Byadopting the TIR structure and applying the condition for minimizing the Fresnel loss, it is expected thatthe proposed TIR LED lens can have a high luminous flux efficiency, even though its beam-spread angleis narrow. To validate the proposed method, three TIR LED lenses with beam-spread angles of less than22.6° have been designed, and their performances evaluated by ray tracing. Their luminous flux efficienciescould be obviously increased by at least 35% and 5%, compared to conventional LED lenses with a singlefreeform surface and with double freeform surfaces, respectively.