• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1430-1436
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• 2007

A principal components analysis (PCA) of the median head-related impulse responses (HRIRs) in the CIPIC HRTF database reveals that the individual HRIRs can be adequately reconstructed by a linear combination of 12 orthonormal basis functions. These basis functions can be used generally to model arbitrary HRIRs, which are not included in the process to obtain the basis functions. To clarify whether these basis functions can be used to model other set of arbitrary HRIRs, an numerical error analysis for modeling and a series of subjective listening tests were carried out using the measured and modeled HRIRs. The results showed that the set of individual HRIRs, which were measured in our lab using different measurement conditions, techniques, and source positions, can be well modeled with reasonable accuracy. Furthermore, all subjects reported not only the accurate vertical perception but also the front-back discrimination with the modeled HRIRs based on 12 basis functions. However, as less basis functions were used for HRIR modeling, the modeling accuracy and localization performance deteriorated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.448-457
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• 2008

A principal components analysis (PCA) of the median-plane head-related impulse responses (HRIRs) in the CIPIC HRTF database reveals that the individual HRIRs in the median plane can be adequately reconstructed by a linear combination of 12 orthonormal basis functions. These basis functions can be used to model arbitrary median-plane HRIRs, which are not included in the process to obtain the basis functions. Memory size can be reduced up to 5-fold depending on the number of HRIRs to be modeled. To clarify whether these basis functions can be used to model other set of arbitrary median plane HRIRs, a numerical error analysis for modeling and a series of subjective listening tests were carried out using the measured and modeled HRIRs. The results showed that the set of individual HRIRs in the median plane, which were measured in our lab using different measurement conditions, techniques, and source positions, can be modeled with reasonable accuracy. All subjects, involved in the subjective listening test, reported not only the accurate vertical perception but also the front-back discrimination with the modeled HRIRs based on 12 basis functions.

• Journal of IKEEE
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• v.22 no.3
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• pp.816-821
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• 2018

Recently, machine learning algorithms based on artificial neural networks started to be used widely as classifiers in the field of EEG research for emotion analysis and disease diagnosis. When a machine learning model is used to classify EEG data, if training data is composed of only data having similar characteristics, classification performance may be deteriorated when applied to data of another group. In this paper, we propose a method to construct training data set by selecting several groups of data using semi-supervised learning algorithm to improve these problems. We then compared the performance of the two models by training the model with a training data set consisting of data with similar characteristics to the training data set constructed using the proposed method.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.202-211
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• 2014

Pairs trading is a type of arbitrage investment strategy that buys an underpriced security and simultaneously sells an overpriced security. Since the 1980s, investors have recognized pairs trading as a promising arbitrage strategy that pursues absolute returns rather than relative profits. Thus, individual and institutional traders, as well as hedge fund traders in the financial markets, have an interest in developing a pairs trading strategy. This study proposes pairs trading rules (PTRs) created from a price ratio between securities (i.e., stock index futures) using rough set analysis. The price ratio involves calculating the closing price of one security and dividing it by the closing price of another security and generating Buy or Sell signals according to whether the ratio is increasing or decreasing. In this empirical study, we generate PTRs through rough set analysis applied to various technical indicators derived from the price ratio between KOSPI 200 and S&P 500 index futures. The proposed trading rules for pairs trading indicate high profits in the futures market.

• Communications for Statistical Applications and Methods
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• v.29 no.5
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• pp.591-601
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• 2022

In gene set analysis with microarray expression data, a group of genes such as a gene regulatory pathway and a signaling pathway is often tested if there exists either differentially expressed (DE) or differentially co-expressed (DC) genes between two biological conditions. Recently, a statistical test based on covariance estimation have been proposed in order to identify DC genes. In particular, covariance regularization by hard thresholding indeed improved the power of the test when the proportion of DC genes within a biological pathway is relatively small. In this article, we compare covariance thresholding methods using four different regularization penalties such as lasso, hard, smoothly clipped absolute deviation (SCAD), and minimax concave plus (MCP) penalties. In our extensive simulation studies, we found that both SCAD and MCP thresholding methods can outperform the hard thresholding method when the proportion of DC genes is extremely small and the number of genes in a biological pathway is much greater than a sample size. We also applied four thresholding methods to 3 different microarray gene expression data sets related with mutant p53 transcriptional activity, and epithelium and stroma breast cancer to compare genetic pathways identified by each method.

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.136-145
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• 2014

This article has compared the level of activities of occupational safety and health in workplace among sub-sectors of manufacturing industry in order to set the priority for policy intervention. Data of manufacturing industry in the survey on the current status of occupational safety and health was used with factor analysis and radar graphic method. Authors have categorized sub-sectors of manufacturing industry into four categories, attained group, active group, neglected group, and passive group based on injury rate, level of safety and health activities. The neglected group may be the first target group for occupational safety and health policy guiding some detailed occupational safety and health activities. Limitation of this study is that cross sectional data was analyzed. The long term effect could not be analyzed.

• Korea Journal of Hospital Management
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• v.14 no.2
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• pp.21-40
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• 2009

The importance-performance analysis (IPA) is a widely used analytical technique that produces a priority of managerial attention for the customer satisfaction. This study attempted to compare various different approaches of IPA such as direct and indirect measurement of importance, and traditional four quadrants grid model and diagonal grid model of IPA. Data on 17 inpatient service quality attributes were collected from 234 inpatients of a general hospital. Eight IPA grids were produced to compare the result of each model. Based on the study results the strength and weakness of each model were discussed, and a set of recommendations for practical application of the IPA in hospital settings was suggested.

• Structural Engineering and Mechanics
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• v.7 no.3
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• pp.241-257
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• 1999

This paper presents a procedure to minimize the cost of materials of cable-stayed bridges with composite box girder and concrete tower. Two sets of iterations are included in the proposed procedure. The first set of iteration performs the structural analysis for a cable-stayed bridge. The second set of iteration performs the optimization process. The design is formulated as a general mathematical problem with the cost of the bridge as the objective function and bending forces, shear forces, fatigue stresses, buckling and deflection as constraints. The constraints are developed based on the Canadian National Standard CAN/CSA-S6-88. The finite element method is employed to perform the complicated nonlinear structural analysis of the cable-stayed bridges. The internal penalty function method is used in the optimization process. The limit states design method is used to determine the load capacity of the bridge. A computer program written in FORTRAN 77 is developed and its validity is verified by several practical-sized designs.

• Journal of the Ergonomics Society of Korea
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• v.14 no.2
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• pp.63-73
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• 1995

An approach to quantitative evaluation of product usability during the design and implementation phases of the product life cycle is presented. The evaluation starts by defining a set of usability characteristics, viz. physical, cognitive and affective characteristic. Each of these characteristics is assessed by a set of usability criteria, such as functionality, visual clarity, learmability, etc. The usability criterion is then evaluated by a checklist consisting of a detailed questionnaire. The fuzzy weighted-checklist method with linguistic variables is used for quantitative analysis. Also, the method for quantifying usability improve- ments in iterative design processes is considered. This analysis procides a quantit- ative measure, which reflects the degree of excellence of product usability during the design and development phases.

• Journal of Conservation Science
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• v.27 no.2
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• pp.135-144
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• 2011

When metal artifacts have to undergo conservation treatment, the person in charge of the treatment selects and uses various coating mixtures based on his judgment regarding their condition, material, or environment. Since the kinds of coating mixtures or solvents make a difference in the set time of cyanoacrylate adhesives, they have something to do with the efficiency of the conservation treatment. This study examines the effects and causes that affect the set time of cyanoacrylate adhesives according to the kinds of coating mixtures and solvents and suggests ways to increase the set time. As a result, it is thought that as the surface roughness gets flatter, the wettability of adhesive is improved further, which increases the set time. Moreover, the C-F binding of V-Flon, C-O-C absorption peak, molecular weight of the coating mixtures, and glass transition temperature (Tg) were the factors that significantly affected the set time. According to the result of measuring the set time based on the result of superficial and chemical analysis, relative difference was shown according to the kind and viscosity of adhesive, but all the adhesives indicated the following order of the set time: V-Flon > Paraloid B-72 (in xylene) > Paraloid NAD-10 > Paraloid B-72 (in acetone).