• Journal of the Korean Data and Information Science Society
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• v.18 no.1
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• pp.195-210
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• 2007

This paper develops a consistent nonparametric test for Granger causality in the context of strong-mixing process, which covers a large class of stationary processes including ARMA and ARCH models. The previously proposed tests require absolute regularity ($\beta$-mixing) more stringent than the strong-mixing condition. We prove the consistency of the test under a high level assumption on the approximation error of U statistic by its projection. Due to the sample splitting, the test statistic we propose is asymptotically normally distributed under the null.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.288-295
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• 1995

In this paper a hypotheses test procedure based on the least absolute deviation estimators for the unknown parameters in nonlinear regression models is investigated. The asymptotic distribution of the proposed likelihood ratio test statistic are established voth under the null hypotheses and a sequence of local alternative hypotheses. The asymptotic relative efficiency of the proposed test with classical test based on the least squares estimator is also discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.596-601
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• 1990

When using robot manipulator to carry out autonomous tasks, the positioning accuracy of the robot manipulator relative to a reference coordinate frame is of greate importance. The task program, which is generated by off-line CAD-system and used in actual robot positioning, may cause serious amount of the absolute positioning error of the robot manipulator. In this study, a robot performance test and calibration algorithms are proposed in order to improve the absolute positioning accuracy of the robot end effector. Experiments were also carried out by utilizing the HYUNDAI Robot AE 7601 and KIM2-Tester, a three dimensional measurement system, which is developed in Robotics & Fluid Power Control Lab. at Korea Institute of Science and Technology.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.153-159
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• 2008

We have developed an absolute evaluation method to obtain the ratio error and phase displacement of a current transformer (CT) without any precise standard CT by measuring four parameters in a CT equivalent circuit. The excitation admittance in the CT equivalent circuit can be obtained by employing standard resistors with negligible reactive component. The secondary leakage impedance in the CT equivalent circuit can be measured using a universal impedance bridge. The method was applied to CTs under test with the wide current ratios in the range of 5 A / 5 A - 5,000 A / 5 A and 5 A / 1 A - 5,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Canada using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.2
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• pp.201-211
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• 2014

PURPOSE: The purpose of this study was to investigate the inter-rater absolute reliability and the concurrent validity of the Tinetti-gait scale that was translated into Korean for chronic stroke patients. METHODS: Fifty-two patients with post-stroke participated in this study. Inter-rater reliability was analyzed by Intraclass Correlation Coefficient ($ICC_{3,1}$) and Kappa coefficient, and absolute reliability was analyzed by the Standard Error of Measurement (SEM), and the Minimal Detectable Change (MDC). Concurrent validity was analyzed by correlating between the Tinetti-gait scale and physical functions. The physical functions were measured by using the Dynamic Gait Index(DGI), 10m walking test(10WT), One Leg Standing Test of affected/non-affected side(OLST), Sit to Stand test(STS), (Fugl Meyer assessment of Lower Extremity(FM-LE). RESULTS: The inter-rater reliability of the Tinetti-gait scale was high; $ICC_{(3,1)}=.91$ (95% CI=.85~.95) (very reliable), the range of Kappa coefficient were .73~.92 (substantial~good). The inter-rater agreement of the each item in Tinetti-gait scale ranged from .74 to .92 (95 % CI=.59~.95) (reliable~very reliable). The SEM and MDC were .56 and 1.55, respectively. In the results of concurrent validity, there were moderate positive correlation between Tinetti-gait scale and DGI (r=.78), 10WT (r=.74), OLST (r=.65~.73), FM-LE (r=67). And there was moderate negative correlation between Tinetti-gait scale and STS (r=-79) (p<.01). CONCLUSION: The Tinetti-gait scale(Korean version) was a reliable and valid tool to measure gait ability in patients with chronic stroke. Thus, it could be a useful tool for examining a gait ability of post-stroke patients. Further study should be conducted to investigate the usability to predict fall risk of post-stroke patients of the Tinetti-gait scale.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.41-50
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• 2019

Purpose : The goal of this descriptive research study was to identify the relationship between t relative deprivation, absolute deprivation, self-esteem, self-efficacy, and social support of university students and their show-off behavior on social network services (SNSs), as well as to identify the influencing factors. Methods : The research tools consisted of 8 items for general characteristics, a measure of deprivation (9 items for relative deprivation and 8 items for absolute deprivation), 15 items for show-off behavior on SNSs, 10 items for self-esteem, 25 items for social support, and 20 items for self-efficacy. Data analysis was performed using the SPSS 22.0 program for the descriptive statistics, t-test, ANOVA, Pearson's correlation, and stepwise multiple regression. Results : The results showed relative deprivation (B=.102, t=4.060, p<.001) was the most important factor in show-off behavior on SNSs for university students. Furthermore, social support (B=-.178, t=-3.099, p=.002), absolute deprivation (B=-.175, t=-4.284, p<.001), and self-esteem (B=-.212, t=-2.490, p=.014) accounted for 21.5% of the explanatory power (F=14.215, p<.001). Conclusion : The study findings revealed that relative deprivation is the most important factor in the show-off behavior of university students on SNSs. Social support, absolute deprivation, and self-esteem were also identified as factors that affect their show-off behavior on such services. This study aims to contribute to the effective program progress by providing basic data for the development of the show-off behavior on SNSs intervention and prevention programs to reduce the side effects of various the show-off behaviors on SNSs of university students.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.10
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• pp.1062-1072
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• 2008

When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the traversabilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm's feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed. And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.

• Communications of the Korean Mathematical Society
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• v.20 no.1
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• pp.145-159
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• 2005

In this paper we consider the problem of testing statistical hypotheses for unknown parameters in nonlinear regression models and propose three asymptotically equivalent tests based on regression quantiles estimators, which are Wald test, Lagrange Multiplier test and Likelihood Ratio test. We also derive the asymptotic distributions of the three test statistics both under the null hypotheses and under a sequence of local alternatives and verify that the asymptotic relative efficiency of the proposed test statistics with classical test based on least squares depends on the error distributions of the regression models. We give some examples to illustrate that the test based on the regression quantiles estimators performs better than the test based on the least squares estimators of the least absolute deviation estimators when the disturbance has asymmetric and heavy-tailed distribution.

• Journal of Nutrition and Health
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• v.35 no.2
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• pp.250-262
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• 2002

This study was conducted to develop a simple flood frequency questionnaire (FFQ) based on the results of contributions of specific floods to absolute intake and between-person variance in nutrients using semi-quantitative FFQ with 93 flood items. The subjects were 554 healthy adults for development of a simple FFQ, and 37 students for a validation test of a developed simple FFQ. The contribution of specific floods to 80% absolute nutrient intake was measured by assessing their percentage in total consumption of a nutrient. To assess the contributions of floods to the between-person variance in the intake of each specific nutrient, stepwise multiple regressions were performed. The number of floods necessary to account for the respective 80% of absolute intake was 11-36, depending on the nutrient, while flower floods (5-16 floods) were required for the corresponding percentage of between-person variation for all nutrients. Important floods for between-person variance include Tangsuyuk (pork) and snacks for energy and fat, fish for protein and polyunsaturated fatty acids (PUFA) and snacks for carbohydrates. Spearman correlation coefficients between 93-itemed FFQ and 63-itemed FFQ ranged from 0.91 for vitamin A to 0.99 for fat in the population data used in developing a simple FFQ. Also, the correlation coefficients between the two FFQs were 0.82-7.92 in the population for the validation test. This study suggests that useful information on dietary intake could be obtained using a simple semi-quantitative FFQ in a large-scale dietary survey in Korea.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.2
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• pp.53-62
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• 2020

This study is to evaluate the accuracy of the meteorological information provided for the aircraft operating at low altitude. At first, it is necessary to identify crucial elements of weather information closely related to flight safety during low altitude flights. The study conducted a survey of pilots of low altitude aircraft, divided into pre-flight and in-flight phases, and reached an opinion that wind direction, wind speed, cloud coverage and ceiling and visibility are important items. Related to these items, we compared and calculated the accuracy of TAFs and METARs from Taean Airfield, Seosan Airport and Gunsan Airport because of their high number of domestic low-altitude flights. Accuracy analysis evaluated the accuracy of two numerical variables, Mean Absolute Error(MAE) and Root Mean Square Error(RMSE), and the cloud coverage which is categorical variable was calculated and compared by accuracy. For numeric variables, one-way ANOVA, which is a parameter-test, was approached to identify differences between actual forecast values and observations based on absolute errors for each item derived from the results of MAE and RMSE accuracy analyses. To determine the satisfaction of both normality assumptions and equivalence variability assumptions, the Shapiro-Wilk test was performed to verify that they do not have a normality distribution for numerical variables, and for the non-parametric test, Kruscal-Wallis test was conducted to determine whether or not they are satisfied.