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Kernel Estimation of Hazard Ratio Based on Censored Data
최명희,이인석,송재기,Choi, Myong-Hui,Lee, In-Suk,Song, Jae-Kee The Korean Data and Information Science Society 2001 한국데이터정보과학회지 Vol.12 No.2
We, in this paper, propose a kernel estimator of hazard ratio with censored survival data. The uniform consistency and asymptotic normality of the proposed estimator are proved by using counting process approach. In order to assess the performance of the proposed estimator, we compare the kernel estimator with Cox estimator and the generalized rank estimators of hazard ratio in terms of MSE by Monte Carlo simulation. Two examples are illustrated for our results.
A Kernel Estimator of Hazard Ratio
최명희,이인석,송재기,Choi, Myong-Hui,Lee, In-Suk,Song, Jae-Kee Korean Data and Information Science Society 1992 한국데이터정보과학회지 Vol.3 No.1
We consider hazard ratio as a descriptive measure to compare the hazard experience of a treatment group with that of a control group with censored survival data. In this paper, we propose a kernel estimator of hazard ratio. The uniform consistency and asymptotic normality of a kernel estimator are proved by using counting process approach via martingale theory and stochastic integrals.
칼라 에지 검출을 위한 Van der Waerden 검정 통계 기법
최명희 ( Myong Hui Choi ),경왕준 ( Wang Jun Kyung ),하영호 ( Yeong Ho Ha ) 한국화상학회 2010 한국화상학회지 Vol.16 No.4
This paper proposes an efficient edge detection using statistical tests under YCbCr model in color images. We propose an efficient edge detection based on Van der Waerden statistic using the threshold determined by specifying significance level and an edge-height parameter under YCbCr in various color images. We describe a nonparametric Wilcoxon test and T test based on statistical hypothesis testing for the detection of edges. Comparison with our statistical tests and the differential operator with sobel shows that Van der Waerden method performs more effectively under YCbCr model in various color images.
모바일 디스플레이의 장치 출력 영상 분석을 통한 인지 화질 평가의 정량화
최봉석 ( Bong Seok Choi ),이철희 ( Cheol Hee Lee ),최명희 ( Myong Hui Choi ),하영호 ( Yeong Ho Ha ) 한국화상학회 2014 한국화상학회지 Vol.20 No.4
Display image quality evaluation methods are generally divided into objective and subjective evaluations. Physical display characteristics are evaluated in objective evaluation. On the other hand, subjective evaluation method evaluate the display image quality based on observer``s opinions. Objective evaluation method is hard to consider subjective evaluation factors of observer``s viewing condition, emotion, and region of interest. Meanwhile, in subjective evaluation method, much time for experiments are required and their results are hard to quantify. In display image quality assessment to exactly evaluate, analysis of human visual characteristics and quantification thereof are needed. In this paper, we proposed perceived image quality evaluation method with perceived color representation by using perceived whiteness and color representation. we used subjective evaluation method to find preferred color axis about preferred white point and preferred color for 11 primary colors. To quantization of perceived image quality assessment, we are measured distance between display characterized image and preferred white and 11 color points.
김대철 ( Dae Chul Kim ),최봉석 ( Bong Seok Choi ),최명희 ( Myong Hui Choi ),하영호 ( Yeong Ho Ha ) 한국화상학회 2013 한국화상학회지 Vol.19 No.4
Digital still camera generally uses optical low-pass filter (OLPF) to enhance its image quality because it removes high spatial frequencies causing aliasing. However, sometimes manufactures want to use no OLPF with the reason of saving manufacturing cost. When image is captured without OLPF, the color smear is generally existed in high spatial frequency region of an image. Then, color smear reduction method is needed to reduce the moire after capturing the image. Therefore, in this paper, color smear region is detected by using color variation ratio for each channel of RGB and corrected by multiplying the chromaticity ratio. Through the experimental results, it is shown that the proposed method can achieve color smear reduction of both luminance and color channels with preserving the detail.
색 공간 기반의 피부색 검출 방법과 관심 영역을 이용한 피부색 검출 기법
김대철 ( Dae Chul Kim ),이철희 ( Cheol Hee Lee ),최명희 ( Myong Hui Choi ),하영호 ( Yeong Ho Haa ) 한국화상학회 2012 한국화상학회지 Vol.18 No.4
Skin color information is an important feature for skin region detection in color image. Generally, skin region is detected by using statistical skin color model. however, statistical model has an inaccurate performance in color image including skin color in background. Therefore, this paper proposes skin detection method to detect skin region correctly in various color images which other complexion part is included. First, candidate skin region is set by applying skin detection rates to RGB, YCbCr, HSI skin color models. after that we find region of interest to remove noise part and non-skin region in color image. Then, skin region is detected by using candidate skin region and region of interest. the proposed method is capable of distinguishing skin region from extremely similar skin colors in background. In experimental results, proposed method gives better skin detection than the previous methods.
최명희 대구산업정보대학 2002 논문집 Vol.16 No.-
The edges of an image hold much of the information in that image. The edges tell where objects are, their shape and size, and something about their texture. An edge is where the intensity of an image moves from a low value to a high value. We propose an efficient edge detection using Van der Waerden's statistic using the threshold determined by specifying significance level and an edge-height parameter in images. We describe a nonparametric Wilcoxon test based on statistical hypothesis testing for the detection of edges. Comparison with our statistical test and the differential operator with Sobel operator shows that Van der Waerden method performs more effectively in both noisy and noise-free images.