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유효 주파수 선택과 선형판별분석기법을 이용한 유도전동기 고장진단 시스템
이대종(Dae-Jong Lee),조재훈(Jae-Hoon Cho),윤종환(Jong Hwan Yoon),전명근(Myung-Geun Chun) 한국지능시스템학회 2010 한국지능시스템학회논문지 Vol.20 No.3
본 논문에서는 3상 유도전동기의 고장진단을 수행하기 위해 상호정보량과 선형판별분석기법에 기반을 둔 진단 알고리즘을 제안한다. 실험 장치는 유도전동기 구동의 기계적 모듈과 고장신호를 구하기 위한 데이터 획득 모듈로 구성하였다. 제안된 방법은 취득된 전류신호를 DFT에 의해 주파수 영역으로 변환한 후 분산정보를 이용하여 고장상태별로 차별성이 큰 순서대로 유효 주파수 성분을 추출한다. 다음 단계로 선택된 주파수 성분에 대해서 선형판별분석기법을 적용하여 고장상태별 특징들을 추출한 후 k-NN 분류기에 의해 유도전동기의 상태를 진단하게 된다. 제안된 방법의 타당성을 보이기 위해 다양한 조건하에서 실험한 결과 기존방법에 비하여 우수한 결과를 나타냈다. For the fault diagnosis of three-phase induction motors, we propose a diagnosis algorithm based on mutual information and linear discriminant analysis (LDA). The experimental unit consists of machinery module for induction motor drive and data acquisition module to obtain the fault signal. As the first step for diagnosis procedure, DFT is performed to transform the acquired current signal into frequency domain. And then, frequency components are selected according to discriminate order calculated by mutual information As the next step, feature extraction is performed by LDA, and then diagnosis is evaluated by k-NN classifier. The results to verify the usability of the proposed algorithm showed better performance than various conventional methods.
이대식(Daesik Lee),구영완(Youngwan Goo),이성훈(Seong-Hoon Lee) 한국경제연구학회 2009 한국경제연구 Vol.26 No.-
2000~2005년 사이 한국항공우주산업(KAI) 등 미국 및 유럽의 10개 업체를 대상으로 자료표락분석모형과 Malmquist 생산성지수를 이용하여 상대적인 효율성과 생산성을 분석하였다. 효율성은 미국 기업이 전반적으로 유럽과 한국보다 높은 것으로 측정되었으며, 한국의 경우에는 현재의 규모에서 순수기술적인 측면에서 최고의 효율성을 나타내고 있는 것으로 분석되었다. 비효율의 원인으로는 전반적으로 순수기술적인 측면보다는 규모적인 측면에 기인한 것으로 나타났다. 특히, 한국은 규모의 비효율이 가장 큰 것으로 측정되었다. 생산성 변화는 전체적으로 평균생산성은 증가한 것으로 나타났는데 역시 미국 기업이 더 높은 것으로 평가되었다. 기술진보는 꾸준하게 일어났지만, 규모효율성 변화가 낮았기 때문에 생산성 변화를 저하시키는 것으로 확인되었다. 한국은 규모효율성 변화가 가장 낮은 것으로 측정되었으며, 규모의 비효율을 줄이기 위해서는 규모확장 등을 통하여 그 비효율을 줄일 수 있을 것으로 분석된다. This paper analyzed relative efficiency and productivity of 10 military plane manufacturing firms in U.S., Europe and Korea, including Korea Aerospace Industries (KAI), by using DEA model and Malmquist productivity index for the period 2000~2005. Efficiency was, in general, higher in U.S. firms than in European and Korean firms. KAI showed the highest pure technical efficiency at current scale among the firms. Inefficiency in the firms, in general, was due to scale rather than pure technical inefficiency. Especially, KAI was the highest in scale inefficiency among the firms. Average productivity increased over time with U.S. firms highest among the firms. There was a steady technological progress in all firms but the scale inefficiency lowered the productivity change. Therefore, the scale inefficiency in KAI can be improved by expanding the manufacturing scale.
이대일,남하경,이미화,곽민정,이현정,이수배,홍광선,Lee, Dae-Il,Nam, Ha-Gyeong,Lee, Mi-Hwa,Gwak, Min-Jeong,Lee, Hyeon-Jeong,Lee, Su-Bae,Hong, Gwang-Seon 한국건강관리협회 2006 한국건강관리협회지 Vol.4 No.1
Background : Osteoporosis and atrophic cell pattern in Pap smear are frequent findings In postmenopausal women due to loss of ovarian function, The present study attempted to find out possible correlation between morphologic characteristics of Pap smear and osteoporosis. Material & methods: The subjects were 825 women(age from 35 to 80) who had undergone Pap smear and bone mineral density(BMD) at The Korea Association of Health Promotion, Seoul Branch, from March 8 to May 10, 2005. Pap smears from 825 women were reviewed and classified either mature cell pattern or atrophic cell pattern by their cytologic patterns, BMD were measured using LUNAR DPX MdIQ(Minster, Ohio, USA). BMD value of lumbar spine(Ll, L2,L3 and L4) were measured from 825 women and BMD value of proximal region off emur(neck NK, Wards triangle WT, and trochanter TR) were measured from 818 women and their bone status were classified as normal( T-sore:>-1.0), osteopenia (T-score: -l~<-2,5) and osteoporosis(T-score: ≤ -2.5). And age distribution of Pap smear, average T-value andfrequency ofsteoporo-sis of each region of the bone, percentage of osteoporosis of each boneregion by age group and changing pattern of percentage of osteopenia and osteoporosis in certain postmenopausal period were compared between mature and atrophic cell pattern. Results: Pap smears revealed total mature cell pattern 53,9%(445/825) and total atrophic cell pattern 46.1%(380/825), Percentage of mature cell pattern decreased from 98.2%(168/171)under 44 age group to 13,3%(17/128) over 65 age group and mature cell pattern increased from 1.8%(3/171) under 44 age group to 86.7%(111/128) oyer 65 age group. Mean T-value of each region of lumbar spine and femur of mature cell pattern were lower than that of atrophic cell pattern about -1,5. And osteoporosis has noted in atrophic cell pattern showing odds ratio Ll 13.9, L2 15.3, L3 12.0, L4 10,4, UK 6.7, WT 10.9 and TR 4.1.Atrophic cell pattern started to increase after 45 years of age and osteoporosis of a trophic cell pattern started after 55 years of age. During 50 to 64 years of age period, L3, L4 and WT revealed parallel increased of osteopenia and osteoporosis and Ll, L2 revealed decreased of osteopenia and increased of osteoporosis. nia Conclusion: Above findings suggest that atrophic cell pattern of Pap smear precedes osteoporosis about 10 years and one of predictor of osteoporosis.