• 한국정보통신학회논문지
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• 제13권2호
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• pp.376-381
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• 2009

영상의 압축, 인식 그리고 복원 등은 디지털 영상처리 기술의 한 부분으로 영상을 처리하는 가운데 잡음이 발생된다. 발생되는 잡음은 원 영상을 훼손하게 되며, 이러한 잡음으로부터 원 영상을 보존하는 것이 이미지 필터의 사용목적이다. 영상에 사용되는 기본적인 필터는 2차원 필터의 구조를 갖는다. 구현하는 방법에는 1차원 필터를 반복하여 사용하는 방법과 비분리형 2차원 영상 필터를 사용하는 방법이 있고 마스크를 이용하는 공간 영역의 필터 처리법은 후자에 속한다. 이러한 이미지는 기존의 1차 필터와 같이 잡음에 따라 각기 달리 사용되며, 임펄스 잡음 제거하기 위하여서는 다양한 메디안 필터가 사용되고 있다. 본 논문에서는 임펄스 잡음에 강한 변형된 메디안 필터를 제시하였으며, 향상된 성능을 확인하기 위해 기존의 제시된 필터와 비교하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.29-33
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• 2003

The improvement of dimensional accuracy for forged part is one of major goals in cold forging industry. There are many problems in controlling the dimension only by the trial-and-error, especially for a precision forged gear. A FEM analysis has been used in developing the forging technology. However, FE techniques have to be reconfirmed for predicting accurately the dimension of forged part. In this study, the effects of elastic characteristics and temperature changes are investigated by the comparisons between experimental and FEA in cold forging. When FE models related with elastic characteristics are considered as reality, FE results could predict the part dimension within the range of 10 $\mu\textrm{m}$. And if temperature also is considered really, the predicted dimensions are well coincided with the experimental down to about 5$\mu\textrm{m}$.

• Communications for Statistical Applications and Methods
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• 제24권3호
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• pp.303-315
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• 2017

Yoo (2015, Statistics and Probability Letters, 99, 109-113) derives theoretical results in an optimal sufficient dimension reduction with singular inner-product matrix. The results are promising, but Yoo (2015) only presents one simulation study. So, an evaluation of its practical usefulness is necessary based on numerical studies. This paper studies the asymptotic behaviors of Yoo (2015) through various simulation models and presents a real data example that focuses on ordinary least squares. Intensive numerical studies show that the $x^2$ test by Yoo (2015) outperforms the existing optimal sufficient dimension reduction method. The basis estimation by the former can be theoretically sub-optimal; however, there are no notable differences from that by the latter. This investigation confirms the practical usefulness of Yoo (2015).

• 대한치과교정학회지
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• 제14권2호
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• pp.263-272
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• 1984

This study was undertaken to examine the extent to which tooth size and jaw size each contribute to dental crowding. Two groups of dental casts were selected on the basis of dental crowding. One group, consisting of 94 pairs of dental casts (46 males and 48 females) with normal occlusion. A second group, consisting of 84 pairs of dental casts (98 males and 46 females) with crowding. The results were as follows. 1. Means and standard deviations of the two groups were used to compare the two groups. 2. Significant differences were observed between two groups on the basis of tooth size, arch dimension and arch perimeter. 3. Between noncrowded group and crowded group, was crowded group was found to have large troth size than noncrowded group, while smaller arch dimension and perimeter. 4. Significant differences were observed between males and females on the basis of tooth size, arch dimension and arch perimeter. 5. Author found ideal arch shape of normal occlusion.

• 치과방사선
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• 제28권2호
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• pp.339-353
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• 1998

The purpose of this study was to investigate whether a radiographic estimate of osseous fractal dimension and power spectrum of 2D discrete Fourier transform is useful in the characterization of structural changes in bone. Ten specimens of bone were decalcified in fresh 50 ml solutions of 0.1 N hydrochloric acid solution at cummulative timed periods of 0 and 90 minutes. and radiographed from 0 degree projection angle controlled by intraoral parelleling device. I performed one-dimensional variance. fractal analysis of bony profiles and 2D discrete Fourier transform. The results of this study indicate that variance and fractal dimension of scan line pixel intensities decreased significantly in decalcified groups but Fourier spectral analysis didn't discriminate well between control and decalcified specimens.

• 소성∙가공
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• 제13권1호
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• pp.3-8
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• 2004

The improvement of dimensional accuracy for forged part is one of major goals in cold forging industry. There are many problems in controlling the dimension by the trial-and-error, especially for a precision forged gear. A FEM analysis has been used in developing the forging technology. However, FE techniques have to be reconfirmed for predicting accurately the dimension of forged part. In this study, the effects of elastic characteristics and temperature changes are investigated by the comparisons between experimental and FEA in cold forging. When FE models related with elastic characteristics are considered practically, FE results could predict the part dimension within the range of $10\mu\textrm{m}$. And if thermal effects also are considered additionally, the predicted dimensions are well coincided with the experimental down to about $5\mu\textrm{m}$.

• Journal of Information Technology Applications and Management
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• 제9권2호
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• pp.81-106
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• 2002

As more organizations undertake IT-enabled business process reengineering(BPR), IT-enabled BPR projects become a major concern. Especially, one of IT, Enterprise Resource Planning System (ERP) is recognized as a revolution solution. But the success cases of ERP project are rarely reported. In this study, ERP implementation is defined as a IS implementation project based on BPR concepts To explore the issues of implementing ERP systems, a company implementing ERP successfully in Korea is selected. The research framework consists of four components: 1) strategic plan dimension , 2) organizational environment dimension, 3) implementation process dimension, and 4) IT dimension. On this framework, to implement ERP systems successfully, the analysis of the results clearly suggests appropriate planning, top management support, change management, appropriate methodology , ERP specialist commitment, management of standard process and master data, and the extent of IT localization.

• Communications for Statistical Applications and Methods
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• 제29권5호
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• pp.603-614
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• 2022

The naive Bayes classifier is one of the most straightforward classification tools and directly estimates the class probability. However, because it relies on the independent assumption of the predictor, which is rarely satisfied in real-world problems, its application is limited in practice. In this article, we propose employing sufficient dimension reduction (SDR) to substantially improve the performance of the naive Bayes classifier, which is often deteriorated when the number of predictors is not restrictively small. This is not surprising as SDR reduces the predictor dimension without sacrificing classification information, and predictors in the reduced space are constructed to be uncorrelated. Therefore, SDR leads the naive Bayes to no longer be naive. We applied the proposed naive Bayes classifier after SDR to build a recommendation system for the eyewear-frames based on customers' face shape, demonstrating its utility in the top-k classification problem.

• Communications for Statistical Applications and Methods
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• 제29권5호
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• pp.615-627
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• 2022

Principal Fitted Component (PFC) is a semi-parametric sufficient dimension reduction (SDR) method, which is originally proposed in Cook (2007). According to Cook (2007), the PFC has a connection with other usual non-parametric SDR methods. The connection is limited to sliced inverse regression (Li, 1991) and ordinary least squares. Since there is no direct comparison between the two approaches in various forward regressions up to date, a practical guidance between the two approaches is necessary for usual statistical practitioners. To fill this practical necessity, in this paper, we newly derive a connection of the PFC to covariance methods (Yin and Cook, 2002), which is one of the most popular SDR methods. Also, intensive numerical studies have done closely to examine and compare the estimation performances of the semi- and non-parametric SDR methods for various forward regressions. The founding from the numerical studies are confirmed in a real data example.

• Communications for Statistical Applications and Methods
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• 제30권2호
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• pp.179-189
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• 2023

Hybrid sufficient dimension reduction (SDR) methods to a weighted mean of kernel matrices of two different SDR methods by Ye and Weiss (2003) require heavy computation and time consumption due to bootstrapping. To avoid this, Park et al. (2022) recently develop the so-called cross-distance selection (CDS) algorithm. In this paper, two variations of the original CDS algorithm are proposed depending on how well and equally the covk-SAVE is treated in the selection procedure. In one variation, which is called the larger CDS algorithm, the covk-SAVE is equally and fairly utilized with the other two candiates of SIR-SAVE and covk-DR. But, for the final selection, a random selection should be necessary. On the other hand, SIR-SAVE and covk-DR are utilized with completely ruling covk-SAVE out, which is called the smaller CDS algorithm. Numerical studies confirm that the original CDS algorithm is better than or compete quite well to the two proposed variations. A real data example is presented to compare and interpret the decisions by the three CDS algorithms in practice.