• Journal of the Korean Society for Railway
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• v.3 no.1
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• pp.1-11
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• 2000

In this paper, the IGBT VVVF inverter for 1C4M propulsion system of railway traction is studied. The inverter is consisted of IGBT stacks, a DB unit, and a control unit. The test results of the combined system is given, which shows an excellent performance of the overall system.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.580-584
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• 2002

This paper proposes an experimental study on the traction system of rubber tired AGT (Automated Guideway Transit). IGBT VVVF inverter is developed for 1C2M propulsion system of AGT, and it consists of inverter stack, gate control unit, control unit, and interface unit. The combination test was carried out to prove the performance of inverter, and test results show that the developed inverter is excellent.

• Communications for Statistical Applications and Methods
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• v.17 no.2
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• pp.223-229
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• 2010

We consider the asymptotic results of the variance ratio statistic when the underlying processes have moving average(MA) unit roots. This degenerate situation of zero spectral density near the origin cause the limit of the variance ratio to become zero. Its asymptotic behaviors are different from non-degenerating case, where the convergence rate of the variance ratio statistic is formally derived.

• Journal of the Korean Institute of Oriental Medical Informatics
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• v.22 no.1
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• pp.27-36
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• 2016

Purpose: The purpose of this study was to compare the level of job stress, burn-out and job satisfaction between intensive care unit nurses and general unit nurses. Methods: The subjects of this study were 100 intensive care unit nurses and 100 general unit nurses in university's hospitals. The data were collected using self-report questionnaires. The data were analyzed by descriptive statistics, -test, ANCOVA, t-test, ANOVA, and Pearson correlation coefficient by using the SPSS WIN 20.0 program. Results: There were significantly negative correlation in the score of job stress and job satisfaction in both groups of nurses. Job stress of intensive care unit nurses was significantly differences according to department satisfaction. Burn-out of intensive care unit nurses was significantly differences according to position, department satisfaction. Job satisfaction of intensive care nurses unit was significantly differences according to department satisfaction. Job stress of general unit nurses unit was significantly differences according to department satisfaction. Burn-out of general unit nurses was significantly differences according to clinical experience, position, department satisfaction. Job satisfaction of general unit nurses was significantly differences according to clinical experience, department satisfaction. Conclusions: The appropriate rewards for intensive care nurses and general unit nurses to decrease their job stress will be needed in hospital settings. In addition, a plan for systemic nurse training program is needed to provide high quality nursing education for each unit nurses effectively.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.1-10
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• 2016

The purpose of this study was to examine the effect of aroma inhalation on stress, anxiety and depression in coronary care unit patients. The study was a nonequivalent control group non-synchronized design. Participants were thirty patients for the experimental group, and thirty-three patients for the control group. The instruments were VAS, the equipment, developed by Spielberger(1972) and adapted by Kim & Shin(1978), Beck Depression Inventory-II(BDI-II). Data were collected from 25 February, 2015 to 8 May, 2015. The data were analyzed number and percentage, $x^2$-test, t-test, paired t-test. There were no statistically significant effects of aroma inhalation treatment for patients in coronary care unit on the stress, anxiety, and depression. Therefore, it is required follow-up studies that it is tried in a variety of ways for reducing the stress, anxiety, and depression in coronary care unit patients,

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.2
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• pp.1-7
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• 2005

For the reliability evaluation of the track drive unit(TDU), firstly, we analyzed the major failure modes through FMEA(failure mode & effects analysis), FTA(failure tree analysis), and 2-stage QFD(quality function deployment), and then quantitatively determined the priority order of test items. The Minitab analysis was also performed for prediction of life distribution and parameters of TDU by use of field failure data collected from 430 excavators for two years. In addition, we converted the fluctuation load in field conditions into the equivalent load, and for evaluation of the accelerated lift by the cumulative fatigues, the equivalent load is again divided into the fluctuation load by reference of test time. And then, by use of the test method in this paper, the acceleration factor(AF) of needle bearing inside planetary gear which is the most weakly designed part of TDU is achieved as 5.3. This paper presents the quantitative selection method of test items for reliability evaluation, the determination method of the accelerated life test time, and the method of non-failure test time based on a few of samples. And, we proved the propriety of the proposed methods by experiments using a TDU for a 30 ton excavator.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.137.2-137
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• 2001

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.208-213
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• 2008

In order to assess the reliability of the electronics control unit for vehicles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows : i) the main failure mechanism is degradation failure that is, junction destruction of a semiconductor resin by high temperature. ii) the life distribution of the electronics control unit for vehicles is fitted well to Weibull life distribution and the accelerated life model of that is fitted well to Arrhenius model. iii) at the result of the life distribution, accelerated life test method is developed, and test time for life assessment will be shortened by 5,000 hours by this test method.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.101-114
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• 1995

In this paper we consider the multiple unit root tests both for the regular and seasonal unit roots based on the Lagrange Multiplier(LM) principle. Unlike Li(1991)'s method, by plugging the restricted maximum likelihood estimates of the nuisance parameters in the model, we propose a Lagrange multiplier test which does not depend on the existence of the nuisance parameters. The asymptotic distribution of the proposed statistic is derived and empirical percentiles of the test statistic for selected seasonal periods are provided. The power and size of the test statistic for examined for finite samples through a Monte Carlo simularion.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.4
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• pp.86-92
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• 2008

This paper is to investigate the behavior of linear static structure stress, the fatigue and experimental shock fracture far engine base in the Auxiliary Power Unit to resolve its restricted electrical power problem. The shock fracture test was experimentally made under MIL standard criteria. The numerical results by finite element method had a good agreement with those from the shock test. The design data of predicting the fracture at the initial crack and the damage behavior of structure with shock and vibration load in the battle field can be obtained from shock test. In the functional shock test, the crack at the side parts of the engine base was found at peak acceleration of 40g.