• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.12
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• pp.6043-6062
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• 2019

Low-rank matrix decomposition has shown its capability in many applications such as image in-painting, de-noising, background reconstruction and defect detection etc. In this paper, we consider the texture background of rail track images and the sparse foreground of the defects to construct a low-rank matrix decomposition model with block sparsity for defect inspection of rail tracks, which jointly minimizes the nuclear norm and the 2-1 norm. Similar to ADM, an alternative method is proposed in this study to solve the optimization problem. After image decomposition, the defect areas in the resulting low-rank image will form dark stripes that horizontally cross the entire image, indicating the preciselocations of the defects. Finally, a two-stage defect extraction method is proposed to locate the defect areas. The experimental results of the two datasets show that our algorithm achieved better performance compared with other methods.

• The Pure and Applied Mathematics
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• v.19 no.2
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• pp.199-209
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• 2012

For a locally compact higher rank graph ${\Lambda}$, we construct a two-sided path space ${\Lambda}^{\Delta}$ with shift homeomorphism ${\sigma}$ and its corresponding path groupoid ${\Gamma}$. Then we find equivalent conditions of aperiodicity, cofinality and irreducibility of ${\Lambda}$ in (${\Lambda}^{\Delta}$, ${\sigma}$), ${\Gamma}$, and the groupoid algebra $C^*({\Gamma})$.

• Communications for Statistical Applications and Methods
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• v.24 no.6
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• pp.673-683
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• 2017

The least absolute shrinkage and selection operator (LASSO) has been a popular regression estimator with simultaneous variable selection. However, LASSO does not have the oracle property and its robust version is needed in the case of heavy-tailed errors or serious outliers. We propose a robust penalized regression estimator which provide a simultaneous variable selection and estimator. It is based on the rank regression and the non-convex penalty function, the smoothly clipped absolute deviation (SCAD) function which has the oracle property. The proposed method combines the robustness of the rank regression and the oracle property of the SCAD penalty. We develop an efficient algorithm to compute the proposed estimator that includes a SCAD estimate based on the local linear approximation and the tuning parameter of the penalty function. Our estimate can be obtained by the least absolute deviation method. We used an optimal tuning parameter based on the Bayesian information criterion and the cross validation method. Numerical simulation shows that the proposed estimator is robust and effective to analyze contaminated data.

• Communications for Statistical Applications and Methods
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• v.22 no.4
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• pp.377-387
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• 2015

The area under the ROC curve can be represented by both Mann-Whitney and Wilcoxon rank sum statistics. Consider an ROC surface and manifold equal to three dimensions or more. This paper finds that the volume under the ROC surface (VUS) and the hypervolume under the ROC manifold (HUM) could be derived as functions of both conditional Mann-Whitney statistics and conditional Wilcoxon rank sum statistics. The nullhypothesis equal to three distribution functions or more are identical can be tested using VUS and HUM statistics based on the asymptotic large sample theory of Wilcoxon rank sum statistics. Illustrative examples with three and four random samples show that two approaches give the same VUS and $HUM^4$. The equivalence of several distribution functions is also tested with VUS and $HUM^4$ in terms of conditional Wilcoxon rank sum statistics.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.10 no.2
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• pp.146-151
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• 2010

This paper proposes a rank-based control method of mutation probability for improving the performances of genetic algorithms (GAs). In order to improve the performances of GAs, GAs should not fall into premature convergence phenomena and should also be able to easily get out of the phenomena when GAs fall into the phenomena without destroying good individuals. For this, it is important to keep diversity of individuals and to keep good individuals. If a method for keeping diversity, however, is not elaborately devised, then good individuals are also destroyed. We should devise a method that keeps diversity of individuals and also keeps good individuals at the same time. To achieve these two objectives, we introduce a rank-based control method of mutation probability in this paper. We set high mutation probabilities to lowly ranked individuals not to fall into premature convergence phenomena by keeping diversity and low mutation probabilities to highly ranked individuals not to destroy good individuals. We experimented our method with typical four function optimization problems in order to measure the performances of our method. It was found from extensive experiments that the proposed rank-based control method could accelerate the GAs considerably.

• Journal of Forest and Environmental Science
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• v.23 no.2
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• pp.101-108
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• 2007

This study was to establish the floristic composition of vascular plants of North gate Underground forest Sochunji in Mt. Baekdu. This study was conducted during the period of 27 June ~ 2 July 2007. Vascular plants of Mt. Baekdu were composed of 56 families, 141 genera, 172 species, 34 varieties and 1 formae, totaling 207 taxa; North gate area was 136 taxa, Underground forest area was 71 taxa, Sochunji area was 63 taxa. Among the investigated vascular plants, Korea endemic plants were 4 species, rare and endangered plants were 11 species, naturalized plants were 2 species. The special plants by floristic region were 71 taxa; V rank species in 9 taxa, 8 taxa as IV rank species, 18 taxa as III rank species, 23 taxa as II rank species, and 13 taxa as I rank species.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.1-3
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• 2005

최근 웹 검색 분야에서는 검색 질을 높이기 위한 기법들이 많이 연구되어 왔으며, 대표적인 연구로는 제한 검색, focused crawling, 웹 클러스터링 등이 있다. 그러나 제한 검색은 검색 범위를 의미적으로 관련된 사이트들로 제한할 수 없으며, focused crawling은 질의 시점에 클러스터링하기 때문에 질의 처리 시간이 오래 걸리고, 웹 클러스터링은 많은 웹 페이지들을 대상으로 클러스터링하기 위한 오버헤드가 크다. 본 논문에서는 검색 범위를 특정 커뮤니티로 제한하여 검색 하는 커뮤니티 제한 검색과 커뮤니티를 구하는 방법으로 cluster crawler를 제안하여 이러한 문제점을 해결한다. 또한, 커뮤니티를 이용하여 PageRank를 2단계로 계산하는 방법을 제안한다. 제안된 방법은 첫 번째 과정에서 커뮤니티 단위로 지역적으로 PageRank를 계산한 후, 두 번째 과정에서 이를 바탕으로 전역적으로 PageRank론 계산한다. 제안된 방법은 Wang에 의해 제안된 방법에 비해 PageRank 근사치의 오차를 $59\%$ 정도로 줄일 수 있다.

• Communications for Statistical Applications and Methods
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• v.9 no.3
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• pp.607-618
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• 2002

Crossover design is often used in clinical trials about chronic diseases like hypertension, asthma and arthritis. In this paper, we suggest nonparametric approaches of Friedman-type rank test based on Bernard-van Elteren test and of aligned method keeping the information of blocks based on the AB/BA/AA/BB crossover design. The simulation results are presented to compare experimental error and power of several methods.

• Journal of applied mathematics & informatics
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• v.26 no.3_4
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• pp.643-652
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• 2008

We construct the sets of Boolean matrix pairs, which are naturally occurred at the extreme cases for the Boolean rank inequalities relative to the sums and difference of two Boolean matrices or compared between their Boolean ranks and their real ranks. For these sets, we consider the linear operators that preserve them. We characterize those linear operators as T(X) = PXQ or $T(X)\;=\;PX^tQ$ with appropriate invertible Boolean matrices P and Q.

• Communications for Statistical Applications and Methods
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• v.5 no.3
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• pp.695-706
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• 1998

In this paper we consider the setting where a group of n judges are to independently rank a series of κ objects, but the intended complete rankings are not realized and we are faced with analyzing randomly incomplete rank vectors. We discuss some tests based on Friedman statistics on the designs completed through rank imputation schemes suggested by Lordo and Wolfe (1994) and evaluate them on the basis of simulated power studies, constructing their appropriate null distributions.