• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.37-44
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• 2001

Ultrasonic testing has a characteristics such as excellent permeability, high-sensitivity to find defect and an almost exact measurement for position. size and direction of inner defect, which differ from other non-destructive testing. In the study, we developed program into optimal testing condition, to distinguish obstacle echo and defect position. This program shows generation and processing of ultrasonic pulse. We compared simulation with ultrasonic test in 45$^\circ$, 60$^\circ$and 70$^\circ$transducer. Test results were in accordance with simulation within 0.1~7.2%.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.501-510
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• 1996

The gas-turbine generator of Seo-Incheon combined-cycle plant was tested for derivation of a model for dynamic analysis. Load rejection and AVR step test was performed to get the dynamic response of generator. The parameters of generator/control system model were determined by these measured data. No-load saturation test was performed for the saturation characteristics of the generator under steady state. V-curve test was also performed so as to find exact generator parameters. Q-axis parameters of generator was derived by measuring power angle. AVR and governor constants have been tuned by their oscillatory period and setting time characteristics. The derived parameters of generator control system is verified by one-machine infinite bus system simulation. (author). 7 refs., 20 figs., 5 tabs.

• Communications for Statistical Applications and Methods
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• v.25 no.1
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• pp.71-78
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• 2018

In this study, we consider the likelihood ratio test for the covariance matrix of the multivariate normal data. For this, we propose a method for obtaining null distributions of the likelihood ratio statistics by the Monte-Carlo approach when it is difficult to derive the exact null distributions theoretically. Then we compare the performance and precision of distributions obtained by the asymptotic normality and the Monte-Carlo method for the likelihood ratio test through a simulation study. Finally we discuss some interesting features related to the likelihood ratio test for the covariance matrix and the Monte-Carlo method for obtaining null distributions for the likelihood ratio statistics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.294-303
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• 2017

As the elderly population increases, the prevalence of various geriatric chronic diseases and dementia diseases is also rapidly increasing; accordingly, dementia is becoming a major concern of our society. In this study, 48 elderly patients with mild cognitive impairment located in K district were selected from a group of experimental groups in one building and a control group in one building and evaluated for blood homocysteine levels and cognitive function changes after 4,8, and 12 weeks of taking vitamin supplements. The Chi-squared test, Fisher's Exact test, independent t-test, repeated measures ANOVA, contrast test, repeated measures ANCOVA, and Wilks' lambda test were utilized to analyze the data. The results revealed that the cognitive function of the experimental group was significantly higher than that of the control group at 12 weeks (p<0.05), and so, the experimental group higher than that of the control group (p<0.01), the effect of taking vitamins was significantly increased, indicating that homocysteine was decreased relative to the control group. Therefore, vitamin supplements may prevent decreases in cognitive functions and dementia among elderly patients with mild cognitive impairment.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.131-138
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• 2004

In the proto design stage of a new car, the performances of an occupant protection system can be evaluated by CAE even though the real test should be carried out. The number of the real test is reduced by the exact predictions followed by the appropriate design recommendation. However, the existing researches using CAE in predicting the performances do not consider the uncertainties of parameters. That often leads to inconsistency between test and CAE. In this research, the robust design of a protection system such as airbag and load limiter is suggested considering the frontal crash. The parameter design scheme of the Taguchi method is introduced to obtain the robust design of arbitrary airbag and load limiter. It is performed based on the frontal crash test condition of US-NCAP with an arbitrary passenger car. The variances of the performances such as HIC, chest acceleration and probability of combined injury are calculated by the outer array and the Taylor series expansion. Through the analysis of the Taguchi method, the robust optimum is determined.

• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.38-42
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• 2004

The cryogenic system for 6.6 kV/200 A inductive superconducting fault current limiter (SFCL) was developed at Yonsei university in 2003. The sub-cooled nitrogen cryogenic system could be applied to not only SFCL but also many other applied high-Tc superconducting (HTS) devices like superconducting motor, superconducting generator and superconducting magnetic energy storage (SMES). Generally, the cooling capacity of GM-cryocooler depends on the load temperature. Therefore it is necessary to perform the cooling capacity test at no load condition to calculate the exact cooling power and heat load of cryogenic system. In this research, the cooling capacity test of GM-cryocooler was executed and the heat load of developed cryogenic system was calculated. The long run operation test results of sub-cooled nitrogen cryogenic system were successful in pressure and temperature condition. Moreover, the design and fabrication method of cryogenic system were introduced and the test results were described.

• Research in Community and Public Health Nursing
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• v.19 no.2
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• pp.280-289
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• 2008

Purpose: This study was carried out to investigate the effects of auricular acupressure therapy on the relief of dysmenorrhea and abdominal pain in female university students. Method: This study was designed as non-equivalent control group research. Data were collected from 44 of the female university students(Exp.: 22, Cont. : 22) from October, 2007 to December, 2007. Collected data were analysed through $x^2test$. Fisher's exact test, Mann-Whitney U test and Wilcoxon signed rank test. Result: Abdominal pain was significantly decreased partially in the experimental group compared to that of the control group(p=.008). Dysmenorrhea was significantly decreased in the experimental group compared to that of the control group(p=.000). Conclusion: It was proven that auricular acupressure therapy was effective for abdominal pain and dysmenorrhea.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.56-58
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• 2003

The Synchronous inductance in Synchronous Reluctance Motor is an element that is proportional to torque. the exact value must be found for controlling and the performance development of motors. In this paper, the inductances that are obtained by the Finite Element Method and AC standstill Test are compared each other. When controlling the direct torque. the fast response characteristics has been carried out with the inductace by the AC stanstill Test. To test the proposal controller, A Synchronous Reluctance Motor has been designed and manufactured and the adequacy of the proposal control are confirmed thought simulations and experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.208-213
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• 2016

In order to detect the exact position of high-speed train, it is necessary to obtain location information from the transponder tag installed along the track. When the transponder tag receives the energizing signal from the train, it sends a telegram to the reader, which includes location information. In high-speed railway environment, this telegram can be corrupted by electromagnetic interference caused by onboard electric train power equipments or wayside devices. In order to assess the performance of transponder system under this harsh environment, we carried out field test using HEMU-430X. Field test results are briefly introduced and discussed for the evaluation of the transponder system under development.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1534-1542
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• 2006

In this paper, the concept of accelerated life test, which is a popular research field nowadays, is applied to the shot peened material. To predict the efficient and exact room temperature fatigue characteristics from the high temperature fatigue data, the adequate accelerated model is investigated. Ono type rotary bending fatigue tester and high temperature chamber were used for the experiment. Room temperature fatigue lives were predicted by applying accelerated models and doing reliability evaluation. Room temperature fatigue tests were accomplished to check the effectiveness of predicted data and the adequate accelerated life test models were presented by considering errors. Experimental result using Arrhenius model, fatigue limit obtain almost 5.45% of error, inverse power law has about 1.36% of error, so we found that inverse power law is applied well to temperature-life relative of shot peened material.