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적응적 학습방법과 초기값의 개선에 의한 신경망 모형을 이용한 시계열 예측
윤여창(Yoon Yeo Chang),이성덕(Lee Sung Duck) 한국정보처리학회 1998 정보처리학회논문지 Vol.5 No.10
In this work, we consider the forecasting performance between neural network and Box-Jenkins method for time series data. A modified learning process is developed for neural approach at time series data, ie. properly adaptive learning rates selecting by orthogonal arrays and dynamic selecting of initial values using Easton's controller box. We can obtain good starting points with dynamic graphics approach. We use real data sets for this study : the Wolf yearly sunspot numbers between 1700 and 1988.
SiCp / Mg-Al 복합재료의 조직에 미치는 용융가공의 영향
윤여창,최정철,남태운,박익민 ( Yeo Chang Yoon,Jeong Cheol Choi,Tae Woon Nam,Ik Min Park ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.4
N/A Mg-9wt.%Al and Mg-9wt.%-1.6wt%Zn/SiCp(particle size 40㎛) metal-matrix-composite specimens were manufactured by rheo-compocasting method, known for its effect of improving the wettability. The ceramic reinforcement particles(SiCp) were dispersed in the semi-solid magnesium alloy matrix slurry being vigorously stirred in a high frequency induction furnace under inert atmosphere. A microstructural study of the dispersed particles in the specimens, prepared under different conditions as regards the time(10min, 20min, 30min) and temperature of the stirring, was made with the aid of optical microscope and SEM. The effect of superheating was also observed. It is revealed that 30 minutes` stirring time of the semi-solid at 40% solid fraction temperature(Mg-9wt.%Al : 590℃, AZ91 : 576℃), as determined by the lever rule, gives a satisfactorily uniform distribution of the particles. The superheating is observed to enhance further the uniformity.
Rheocompocasting 한 Al-Cu-Ti / SiCp 복합재료의 조직
윤여창,최정철,홍성길 ( Yeo Chang Yoon,Jung Chul Choe,Sung Kil Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.4
N/A An Al-composite material was fabricated with using the rheocompocasting process and the microstructure, of the Al-Cu/SiCp composite material was investigated depending on the stirring times and the amount of Ti additions. The distribution of SiC dispersion shows the good result at the stirring time of 30 min. The degree of microdistribution of the Al₂Cu and SiC_p is improved when the amount of Ti addition is increased. At the compositon of 0.3%Ti, the primary solid is the compound of Al₃Ti and no exist of the SiC_p and Al₂Cu phase around the primary Al₃Ti. In the process of compositization, .SiC_p is found at the primary and final solid parts and is found at the final solid part after remelting. Al₂Cu and SiC_p are distributed around and outside of dendrite or independently after remelting, which is different from the process of compositization.
$2{\times}2$ 분할표에서 동적 그래픽스로 구현된 겹쳐진 모자익 그림을 이용한 범주형 자료의 연관성 측정
윤여창,오민권,Yoon, Yeo-Chang,Oh, Min-Gweon 한국데이터정보과학회 1999 한국데이터정보과학회지 Vol.10 No.2
Hartigan과 Kleiner(1981)는 분할표 자료에서 주변합의 비율에 대한 각 칸의 관측도수의 비율을 사각형의 면적으로 표현한 모자익 그림을 제안하였는데, 본 연구에서는 $2{\times}2$ 분할표에서 관측도수와 기대도수에 대한 두 개의 모자익 그림을 겹쳐서 나타낸 겹쳐진 모자익 그림을 이용한 범주형 자료의 연관성을 측정하고자 한다. 동적 그래픽스기법으로 개선시킨 겹쳐진 모자익 그림을 이용하면 범주형 변수의 연관성을 시각적으로 쉽게 파악할 수 있는데, 이러한 그림은 자료분석이나 통계 패키지에서 제공되고 있지 않다. 겹쳐진 모자익 그림은 변수들의 종속성 여부, 관측도수와 기대도수의 차이등을 제시된 통계량과 함께 시각적으로 파악할 수 있기 때문에 모형 설정시 매우 유용한 정보를 얻을 수 있다. In this paper, we propose an overlapped mosaic plot which proposed by Hartigan and Kleiner(1981) represents the counts in $2{\times}2$ contingency table directly by tiles whose area is proportional to the cell frequency. Overlapped mosaic plot provides some measurements of association including dynamic graphics for mosaic plots. Dynamic graphics for mosaic plots give some useful informations when one gets some measurements of association and selects a model, and current statistical software does not provide this feature. We can see the deviations between observation and estimate of independence from overlapped mosaic plot. This dynamic graphics give some useful informations how far this data are apart from independence.
2 × 2 분할표에서 동적 그래픽스로 구현된 겹쳐진 모자익 그림을 이용한 범주형 자료의 연관성 측정
윤여창(Yeo Chang Yoon),오민권(Min Gweon Oh) 한국데이터정보과학회 1999 한국데이터정보과학회지 Vol.10 No.2
Hartigan과 kleiner(1981)는 분할표 자료에서 주변합의 비율에 대한 각 칸의 관측도수의 비율을 사각형의 면적으로 표현한 모자익 그림을 제안하였는데, 본 연구에서는 2 x 2 분할표에서 관측도수와 기대도수에 대한 두 개의 모자익 그림을 겹쳐서 나타낸 겹쳐진 모자익 그림을 이용한 범주형 자료의 연관성을 측정하고자 한다. 동적 그래픽스기법으로 개선시킨 겹쳐진 모자익 그림을 이용하면 범주형 변수의 연관성을 시각적으로 쉽게 파악할 수 있는데, 이러한 그림은 자료분석이나 통계 패키지에서 제공되고 있지 않다. 겹쳐진 모자익 그림은 변수들의 종속성 여부, 관측도수와 기대도수의 차이 등을 제시된 통계량과 함께 시각적으로 파악할 수 있기 때문에 모형 설정시 매우 유용한 정보를 얻을 수 있다. In this paper, we propose an overlapped mosaic plot which proposed by Hartigan and Kleiner(1981) represents the counts in 2 x 2 contingency table directly by tiles whose area is proportional to the cell frequency. Overlapped mosaic plot provides some measurements of association including dynamic graphics for mosaic plots. Dynamic graphics for mosaic plots give some useful informations when one gets some measurements of association and selects a model, and current statistical software does not provide this feature. We can see the deviations between observation and estimate of independence from overlapped mosaic plot. This dynamic graphics give some useful informations how far this data are apart from independence.
지속가능한 산지개발을 위한 환경기준 설정에 관한 연구 (
윤여창(Yeo Chang Youn),김상윤(Sang Yoon Kim),권태호(Tae Ho Kwon),이창석(Chang Suk Lee) 한국환경영향평가학회 1999 환경영향평가 Vol.8 No.2
This study aims to develop a set off criteria for evaluating the sustainability of forest landuse, which could facilitate the environmentally friendly development of forest lands in Korea. The concept of sustainable development in forest landuse was reviewed from literature and by interviews with experts in forest-related fields. Delphi technique was employed for gathering experts` opinions. According to the results of Delphi test, the concept of sustainable development in forest landuse was confirmed as Use of forest lands in a lasting manner within the carrying rapacity of the ecosystem involved. There are 16 factors which should be considered with care when the development of forest lands is planned. They include the ratio of forest cover left undeveloped, ecological stability, and landscape naturalness. Among them are the ecological factors rated most important. The experts emphasized the importance of local characteristics in setting up the criteria for sustainable forestland development. The study did not attempted to apply the criteria to real settings. Therefore, before applications in real situations, further case studies should be made for the criteria to be safely used in landuse planning.