• Communications for Statistical Applications and Methods
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• v.26 no.6
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• pp.575-582
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• 2019

The problem of selecting variables in the presence of outliers is considered. Variable selection and outlier detection are not separable problems because each observation affects the fitted regression equation differently and has a different influence on each variable. We suggest a simultaneous method for variable selection and outlier detection in a linear regression model. The suggested procedure uses a sequential method to detect outliers and uses all possible subset regressions for model selections. A simplified version of the procedure is also proposed to reduce the computational burden. The procedures are compared to other variable selection methods using real data sets known to contain outliers. Examples show that the proposed procedures are effective and superior to robust algorithms in selecting the best model.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.361-365
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• 2002

Advancements in silicon phase control (SCR) technologies provide an arc welding power supply that has the capability to allow the alteration of the Alternating Current (AC) welding output. These technologies provide a square wave output involving sixteen frequency selections and multiple balance selections. While an AC out put is known to minimize magnetic disturbances associate with Direct Current (DC), the potentials of a non-sinusoidal waveform have not been explored. The focus of the paper is to determine the effects that the frequency and balance of an AC wave form output will have upon a high speed Submerge Arc (SAW) application. The test matrix of the project includes welding .250" steel plate. Joint type is square groove with a travel speed of 65 IPM. Each of the weld parameters was held constant, only the frequency and/or balance were altered between welds. Each frequency/balance combination involved three-gap spacing. Upon completion of the welds the bead profiles were measured and recorded. A relationships/trends were observed with various frequency and balance values. Optimum frequency and balance values were found for the .250" square groove application which permit consistent weld sizing, ease of slag removal, and minimal plate distortion.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.64-64
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• 2011

We present a new quasi-stellar object (QSO) selection algorithm using a Support Vector Machine, a supervised classification method, on a set of extracted time series features including period, amplitude, color, and autocorrelation value. We train a model that separates QSOs from variable stars, non-variable stars, and microlensing events using 58 known QSOs, 1629 variable stars, and 4288 non-variables in the MAssive Compact Halo Object (MACHO) database as a training set. To estimate the efficiency and the accuracy of the model, we perform a cross-validation test using the training set. The test shows that the model correctly identifies ~80% of known QSOs with a 25% false-positive rate. The majority of the false positives are Be stars. We applied the trained model to the MACHO Large Magellanic Cloud (LMC) data set, which consists of 40 million lightcurves, and found 1620 QSO candidates. During the selection, none of the 33,242 known MACHO variables were misclassified as QSO candidates. In order to estimate the true false-positive rate, we crossmatched the candidates with astronomical catalogs including the Spitzer Surveying the Agents of a Galaxy's Evolution (SAGE) LMC catalog and a few X-ray catalogs. The results further suggest that the majority of the candidates, more than 70%, are QSOs.

• The Korean Journal of Applied Statistics
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• v.29 no.1
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• pp.27-39
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• 2016

This paper considers variable selection in the sparse vector autoregressive (sVAR) model where sparsity comes from setting small coefficients to exact zeros. In the estimation perspective, Davis et al. (2015) showed that the lasso type of regularization method is successful because it provides a simultaneous variable selection and parameter estimation even for time series data. However, their simulations study reports that the regular lasso overestimates the number of non-zero coefficients, hence its finite sample performance needs improvements. In this article, we show that the adaptive lasso significantly improves the performance where the adaptive lasso finds the sparsity patterns superior to the regular lasso. Some tuning parameter selections in the adaptive lasso are also discussed from the simulations study.

• Journal of the Korean Data and Information Science Society
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• v.23 no.4
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• pp.859-866
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• 2012

Some switching properties of multivariate control charts are investigated when the interval between two consecutive sample selections is not fixed but changes according to the result of the previous sample observation. Many articles showed that the performances of variable sampling interval control charts are more efficient than those of fixed sampling interval control charts in terms of average run length (ARL) and average time to signal (ATS). Unfortunately, the ARL and the ATS do not provide any information on how frequent a switch is being made. We evaluate several switching properties of two sampling interval Shewhart and CUSUM procedures for controlling mean vector of correlated quality variables.

• Culinary science and hospitality research
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• v.12 no.4 s.31
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• pp.1-17
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• 2006

The purpose of this study was to find out the impact of a selection attribute on customer satisfaction and customer loyalty in the coffee house industry. Through the preceding research, author chose coffee quality, price value, interior and employee service quality as selection attributes as well as customer loyalty as intent to recommend and to revisit. For this study, data were collected from the pedestrians around Kangnam, Samsung, Seoul national university of education subway stations from July 12 to August 4, 2005. Questionnaires were distributed and, of 314 papers, only 300 were suitable for the statistical analysis. The findings of the research were as follows: First, four selections had an effect on customer satisfaction which influenced customer loyalty. Coffee quality was the most influential variable among the selection attributes, and came price value, and interior and employee service quality in that order. Second, intent to revisit was influenced directly by not only customer satisfaction but also intent to recommend. However, this study had such limitations that data used in this study were limited to relatively narrow area and four attributes were not enough to explain all situations of choosing coffee houses. Consequently, further studies are needed to include more variables and coffee houses' brand images.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.3_4
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• pp.515-526
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• 2002

The purpose of this study will find out the primary element of point make-up image perception, the point make-up image perception by point make-up trend and demographic variables such as sex and age. And this study will show the preferences of the point make-up. This study is based on the quasi-experimental study method with contents analysis method and experimental method. And content ana]isis is primarily based on the color trend and cosmetics colors which were suggested by a fashion magazine. Experiment was conducted by gathering opinions by poll, with the model wearing different make-ups and checking the typical reactions of people. To summarize, sex and age were found out to be influential variable to distinguish color perception abilities. This could verify that point make-up was important factor, influencing on the face image perception. also, face make-up effect could be maximized with Natural or common color groups rather than trend-oriented color group selections. And the polled preferred Natural color group with no point make-up or Classic color group to any other color group.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.552-558
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• 1995

Stereolithography is a process used to rapidly produce polymer components directly from a computer-representation of the part. There are several considerations to be made for the efficient use of te process. Especially, the build-up orientation of part critically affect to the part accuracy, total build time and the volume of support structures. Te purpose of this study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, minimizing total build time, and the volume of supprot structures. The first factor is related to the area of surfaces which have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area with quantifying the process planning errors that the volume of materials is supposed to be removed or added to the part, and the optimal layer thickness for the SLA system whichcan hadle the variable layer thickness in different orientations achieved by rotating the given part to the specified finite directions. So the optimal part orientation is determined based on the user's selections of primary criterion and the optimal thickness of layers is calculated at any part orientations.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.4
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• pp.163-173
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• 1996

Stereolithography is a process used to rapidly produce polymer components directly form a computer representation of the part. There are several considerations to be made for the efficient use of the process. Especially, the build-up orientation of part critically affects the part accuracy, total build time and the volume of support structures. The purpose of tis study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, and minimizing total build time and the volume of support structures. The forst factor is related to the area of surfaces whioch have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area, quantifying the process errors by the volume of materials supposed to be removed or added to the part, and the optimal layer thickness for the SLA system which can handle the variable layer thickness. So the optima l part orientation is determined based on the user's selections of primary criter- ion and the optimal thickness of layers is calculated at any part orientations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.37-49
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• 2000

This paper is for the first essential study on the development of unified finite element formulations for solving problems related to the dynamics/thermoelastics behavior of solids. In the first part of formulations, the finite element method is based on the introduction of a new quantity defined as heat displacement, which allows the heat conduction equations to be written in a form equivalent to the equation of motion, and the equations of coupled thermoelasticity to be written in a unified form. The equations obtained are used to express a variational formulation which, together with the concept of generalized coordinates, yields a set of differential equations with the time as an independent variable. Using the Laplace transform, the resulting finite element equations are described in the transform domain. In the second, the Laplace transform is applied to both the equation of heat conduction derived in the first part and the equations of motions and their corresponding boundary conditions, which is referred to the transformed equation. Selections of interpolation functions dependent on only the space variable and an application of the weighted residual method to the coupled equation result in the necessary finite element matrices in the transformed domain. Finally, to prove the validity of two approaches, a comparison with one finite element equation and the other is made term by term.