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김동화,김형순,김영호,Kim, Dong-Hwa,Kim, Hyung-Soon,Kim, Young-Ho 한국음향학회 1997 韓國音響學會誌 Vol.16 No.6
고립단어 음성인식 시스템이 실용적이 되려면 인식 대상 이외의 단어를 거절할 수 있는 기능이 요구된다. 본 논문에서는 집단화된 음소 모델과 likelihood ratio에 의한 후처리 방법을 사용하여 거절기능을 구현하는 방법을 제안하였다. 기본적인 음성인식 시스템은 단어 단위 연속 HMM을 사용하였고, 6개의 집단화된 음소 모델들은 음성학적으로 균형잡힌 음성 데이터베이스를 이용하여 훈련된 45개의 문맥독립 음소 모델들로부터 통계적 방법에 의하여 생성되었다. 22개의 부서 명칭을 대상으로 한 화자독립 고립단어 인식시스템에서 거절성능을 시험하여 본 결과, 가장 높은 확률값과 두 번째 높은 확률값을 가지는 후보단어들 간의 차이값에 의하여 거절기능을 수행하는 기존의 후처리 방법보다 성능이 향상됨을 알 수 있었다. 또한 이 집단화된 음소모델은 인식 대상 어휘가 다른 고립단어 인식 시스템에도 재훈련 없이 그대로 사용될 수 있다. For the practical isolated word recognition system, the ability to reject the out-of -vocabulary(OOV) is required. In this paper, we present a rejection method which uses the clustered phoneme modeling combined with postprocessing by likelihood ratio scoring. Our baseline speech recognition system was based on the whole-word continuous HMM. And 6 clustered phoneme models were generated using statistical method from the 45 context independent phoneme models, which were trained using the phonetically balanced speech database. The test of the rejection performance for speaker independent isolated words recogntion task on the 22 section names shows that our method is superior to the conventional postprocessing method, performing the rejection according to the likelihood difference between the first and second candidates. Furthermore, this clustered phoneme models do not require retraining for the other isolated word recognition system with different vocabulary sets.
3차원 Co-culture 시스템을 통한 BMSC의 NP-like Cell로의 분화
김동화,김수향,허수진,신지원,김영직,박소희,전재우,신정욱,Kim, D.H.,Kim, S.H.,Heo, S.J.,Shin, J.W.,Kim, Y.J.,Park, S.H.,Jun, J.W.,Shin, J.W. 대한의용생체공학회 2008 의공학회지 Vol.29 No.2
The goal of this study is to investigate the effect and potential of three-dimensional Co-culture of BMSCs (bone marrow stromal Cells) and NP (nucleus pulposus) Cells on the differentiation of BMSCs into NP-like Cells. The NP Cells and BMSCs were isolated and cultured from New Zealand White rabbits. The isolated NP Cells and BMSCs were prepared in different alginate beads. Those two types of beads were separated by a track-etched membrane of $3\;{\mu}m$ pore in a 6-well culture plate. No growth factors were used. In addition to these, NP and BMSC were cultured in the beads independently for control. The number of Cells in Co-culturing system was half of those in two control groups. Proliferation and production of glycosaminoglycan (GAG) were evaluated along with histological observation. The GAG production rate(GAG contents/Cell) of Co-cultured BMSCs were much higher than that of BMSCs cultured alone. The total amounts of GAG produced by BMSCs in Co-culturing system were larger than those produced by BMSCs in control group and were comparable with those produced by NP alone even the number of each Cell was half of BMSCs in Co-culturing system. This study showed the potential of differentiation of BMSCs into NP-like Cells through three-dimensional Co-culture system even without any chemical agents.
김동화,이민정,이양,Kim, Dong Hwa,Lee, Min Jung,Lee, Yang 영남수학회 2014 East Asian mathematical journal Vol.30 No.4
Students might find different solutions to the quadratic inequalities according to the range of the number representing the character of the inequalities. They have confusion when the roots of a quadratic inequality are complex numbers since the character of the inequalities generally represents the real number in the mathematics textbooks. Therefore we suggest that we must explain definitely the range of the number representing the character for each inequality question.
김동화,김영아,강주영,Kim, Dong Hwa,Kim, Young A,Kang, Joo Young 영남수학회 2018 East Asian mathematical journal Vol.34 No.4
The purpose of this study is to investigate how the mathematical creativity of middle school mathematical gifted students is represented through the process of problem posing activities. For this goal, they were asked to pose real-world problems similar to the tasks which had been solved together in advance. This study demonstrated that just 2 of 15 pupils showed mathematical giftedness as well as mathematical creativity. And selecting mathematically creative and gifted pupils through creative problem-solving test consisting of problem solving tasks should be conducted very carefully to prevent missing excellent candidates. A couple of pupils who have been exerting their efforts in getting private tutoring seemed not overcoming algorithmic fixation and showed negative attitude in finding new problems and divergent approaches or solutions, though they showed excellence in solving typical mathematics problems. Thus, we conclude that it is necessary to incorporate problem posing tasks as well as multiple solution tasks into both screening process of gifted pupils and mathematics gifted classes for effective assessing and fostering mathematical creativity.
조류 터빈 시스템에서 순시무효전력을 이용한 PMSG의 센서리스 제어와 MPPT 제어
김동화(Dong Hwa Kim),김영조(Young Jo Kim),김영석(Young Seok Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.10
This paper presents the MPPT(Maximum Power Point Tracking) and position sensorless control in the sea flow turbin system. The position sensorless algorithm using an instantaneous reactive power of the PMSM is proposed. In the proposed algorithm, the current observer estimates the line currents and the estimated speed can be yield from the information of speed based on back EMF. Also the proposed MPPT algorithm is controlled by tracking the optimal point, of the generator speed and maximum grid power. Therefore, the vector control of the generator side converter and the grid side converter is controlled respectively to obtain maximum torque and regulate unity power factor. The proposed algorithm is verified by using simulation tool.
면역 알고리즘을 이용한 전동기 제어용 PID 제어기루프의 외란제거 및 최적화 튜닝
김동화(Dong Hwa Kim),조재훈(Jea Hoon Cho) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.11
본 논문에서는 PID제어기를 이용해 외란이 존재하는 2차시스템 특성을 갖는 전동기를 제어하는 경우 외란제거와 최적제어가 동시에 될 수 있는 PID파라메터를 면역알고리즘을 통해 구하였다. 외란제거를 위해 H_∞-norm을 응용하여 제어시스템의 외란제거 조건들을 제시하고 이 조건들을 만족하는 전동기 제어용 PID제어기를 설계하였다. 설계된 PID제어기의 최적 파라메터를 구하기 위해 면역알고리즘을 적용하였고 최적 파라메터를 평가하기 위하여 ITSE(Integral of time weighted squared error)성능지수를 이용하여 만족할 만한 결과를 얻었다.