• Journal of the Korean Data and Information Science Society
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• v.15 no.3
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• pp.585-592
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• 2004

This study detects Korea economic crisis of 1997 using various change-point detection methods and then compares their performance. In change-point detection method, there are three major categories: (1) the parametric approach, (2) the nonparametric approach, and (3) the model-based approach. Through the application to Korea foreign exchange rate during her economic crisis, we compare the employed change-point detection methods and, furthermore, determine which of them performs better.

• Communications for Statistical Applications and Methods
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• v.15 no.3
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• pp.421-427
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• 2008

This paper deals with the problem of testing for the existence of change in mean and estimating the change-point when the data are from the exponential distributions. The likelihood ratio test statistic and Gombay and Horvath (1990) test statistic are compared in a power study when there exists one change-point in the exponential means. Also the change-point estimator using the likelihood ratio and the change-point estimators based on Gombay and Horvath (1990) statistic are compared for their detecting capability via simulation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.371-382
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• 2008

The objective of this study is to develop the laboratory testing method for evaluating the loading capacity of lattice girder used for support in tunnel structure. 3-point flexible strength test and 4-point flexible strength test were performed on three types of lattice girder, such as $LG-50{\times}20{\times}30$, $LG-70{\times}20{\times}30$, and $LG-95{\times}22{\times}32$, mainly used in Korea. Two types of loading position for each flexible strength test were used to analyze the behavior of load-deformation. The loading distribution in the lattice girder was analyzed by means of strains measured by strain gauges attached on chords and diagonal bars. In 3-point flexible strength test, the difference of the average of maximum flexible strength according to loading position had the range from 10% to 33%. In 4-point flexible strength test, the average of maximum flexible strength according to loading position was almost no difference. The difference between the average of maximum flexible strengths obtained from 3-point and 4-point flexible strength tests was from 13.56 to 31.55%. The load applied on the lattice girder was concentrated to the main chord in 3-point flexible strength test. The load applied on the lattice girder in 4-point flexible strength test was distributed to three chords and diagonal bars.

• Communications for Statistical Applications and Methods
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• v.13 no.3
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• pp.607-619
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• 2006

We consider the problem of testing the existence of change in mean and estimating the change-point when the data are from the normal distribution. A change-point estimator using the likelihood ratio test statistic, Gombay and Horvath (1990) test statistic, and nonparametric change-point estimator using Carlstein (1988) empirical distribution are studied when there exists one change-point in the mean. A power study is done to compare the change test statistics. And a comparison study of change-point estimators for estimation capability is done via simulations with S-plus software.

• Physical Therapy Korea
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• v.26 no.3
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• pp.76-83
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• 2019

Background: The hyoid bone is the only non-jointed structure among the skeletal tissues of the head and neck region, and its movement and posture depend on the attached muscle, ligament, and fascia. The location of the hyoid bone is important for airway maintenance, vocalization, chewing, swallowing, breathing, and head and scapular position. In general, the location of the hyoid bone is measured using radiographs and 3D computed tomography, and no studies have reported on clinical measurement methods. Objects: This study was performed to suggest clinical measurement methods for lateral deviation of the hyoid bone and to evaluate their reliability. Methods: In this study, 24 healthy volunteers (12 males, 12 females) in Cheongju-si participated. Two examiners performed the center point test and lateral motion test twice each to measure the lateral displacement of the hyoid bone. The reliability of the center point test was analyzed using intra-class correlation coefficients (ICC), and the reliability of the lateral motion test was analyzed using Cohen's kappa coefficient. Results: The intra-rater reliability of the center point test was good, and the inter-rater reliability was moderate. The intra- and inter-rater reliability of the lateral motion test showed substantial reliability. Conclusion: Based on these results, the center point test and the lateral motion test can be used as an alternative methods of the measurement of lateral deviation of the hyoid bone for people who have musculoskeletal disorders of the head, neck, and scapula.

• Journal of the Korean Statistical Society
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• v.25 no.1
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• pp.123-131
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• 1996

The problerm of testing for a constant mean is considered. A Kolmogorov-Smirnov type test using the sample Fourier coefficients is suggested and its asymptotic distribution is derived. A simulation study shows that the proposed test is more powerful than the cusum type test when there is more than one change-point or there is a cyclic change.

• The Korean Journal of Nuclear Medicine Technology
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• v.20 no.2
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• pp.75-79
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• 2016

Purpose The ASAN Medical Center, Nuclear Medicine performs TSH (Thyroid stimulating hormone) and FT4 (Free Thyroxine) tests 8 times per day. Accordingly, 70 ~ 80 kit tubes are consumed every day for the measurements and the time consumed for reagent dispensing averages over 170 seconds, where the TAT (turnaround time) may be effected when the number of test samples is larger than expected. Therefore, the following test was conducted with the purpose to reduce the number of kit tubes consumed, and reduce the time for reagent dispensing. Materials and Methods The test is based on applying the same reagent for tests where the number of samples is 30 or less. The test for TSH was conducted 9 times from July $1^{st}$ 2015 to July $10^{th}$ 2015. The test for FT4 was conducted 4 times from June $18^{th}$ 2015 to June $22^{nd}$, 2015. Standard Solution No.2 (0.153 uU/mL) and No.5 (4.96 uU/mL) was selected as the two-point standards for the TSH test, and Standard Solution No.3 (0.777 ng/dL) and No.4 (2.044 ng/dL) was selected as the two-point standards for the FT4 test. 38 test samples were subject to correlation analysis. Results For TSH, the result of the normal test shows ranges of 0.20 ~ 0.37 uU/mL for Control1, 0.53 ~ 0.71 uU/mL for Control2, and 6.77 ~ 7.94uU/mL for Control3, while the result of two-point calibration curve test shows ranges of 0.18 ~ 0.27 uU/mL for Control1, 0.53 ~ 0.71 uU/mL for Control2, and 7.30 ~ 8.52 uU/mL for Control3. For FT4, the result of the normal test shows ranges of 0.85 ~ 0.94 ng/dL for Control1 and 4.23 ~ 4.57 ng/dL for Control2, while the result of two-point calibration curve test shows ranges of 0.61 ~ 0.75 ng/dL for Control1 and 3.88 ~ 5.71 ng/dL for Control2. For TSH, the CV% of the normal test for Control1, Control2 and Control3 are 10.5, 3.3 and 3.6 respectively, while the CV% of the two-point calibration curve test for Control1 and Control1 are 12.4, 8.2 and 5.1 respectively. The result shows an outstanding correlation of TSH: y = 0.9985x - 0.0459 $R^2=0.9986$. For FT4, the CV% of the normal test for Control1 and Control2 are 0.70 and 0.71 respectively, while the CV% of the two-point calibration curve test for Control1 and Control1 are 8.7 and 16.2 respectively. The result shows an outstanding correlation of FT4: y = 1.2674x - 0.1133 $R^2=0.9824$. Conclusion The two-point calibration curve can be efficiently applied for TSH in cases where the number of test samples is not large, since the number of samples to be re-tested increases when the result is abnormal from the calibration curve. The two-point calibration curve test should not be applied for FT4 where the results do not consistently comply with the quality assessment range. Depending on how the two-point calibration curve is applied, up to 5 test tubes can be conserved per test, and the reduced time for reagent dispensing is anticipated to have a positive effect on the TAT (turnaround time).

• Journal of Korean Society for Quality Management
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• v.30 no.3
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• pp.195-202
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• 2002

The problem of trend change in the mean residual life is great Interest in the reliability and survival analysis. In this paper, a new test statistic for testing whether or not the mean residual life changes its trend Is developed. It is assumed that neither the change point nor the proportion at which the trend change occurs is known. The asymptotic null distribution of test statistic is established and asymptotic critical values of the asymptotic null distribution is obtained. Monte Carlo simulation is used to compare the proposed test with previously known tests.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.241-245
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• 2012

Categorical data collected based on complex sample design is not proper for the standard Pearson multinomial-based chi-squared test because the observations are not independent and identically distributed. This study investigates effects of bias of point estimator of population proportion and its variance estimator to the standard Pearson chi-squared test statistics when the sample is collected based on complex sampling scheme. This study examines the effect under two population homogeneity test. The standard Pearson test statistic can be partitioned into two parts; the first part is the weighted sum of ${\chi}^2_1$ with eigenvalues of design matrix as their weights, and the additional second part which is added due to the biases of the point estimator and its variance estimator. Our empirical analysis shows that even though the bias of point estimator is small, Pearson test statistic is very much inflated due to underestimate the variance of point estimator. In the connection of design-based variance estimator and its design matrix, the bigger the average of eigenvalues of design matrix is, the larger relative size of which the first component part to Pearson test statistic is taking.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.128-136
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• 2020

In the present experimental study, the effect of water-based iron(III) oxide nanofluid on the MFB(Minimum Film Boiling) point during quenching was investigated. As the highly heated test specimen, the cylindrical stainless steel rod was used, and as the test fluids, the water-based iron(III) oxide nanofluids of 0.001 and 0.01 vol% concentrations were prepared with the pure water. To examine the effect of location in the test specimen, the thermocouples were installed at the bottom and middle of wall, and center in the test specimen. Through a series of experiments, the experimental data about the influences of nanofluid concentrations, the number of repeated experiments, and locations in the test specimen on the reaching time to MFB point, MFBT(Minimum Film Boiling Temperature), and MHF(Minimum Heat Flux) were obtained. As a result, with increasing the concentration of nanofluid and the number of repeated experiments, the reaching time to MFB point was reduced, but the MFBT and MHF were increased. In addition, it was found that the effect of water-based iron(III) oxide nanofluid on the MFB point at the bottom of wall in the test specimen was observed to be greater than that at the middle of wall and center. In the present experimental ranges, as compared with the pure water, the water-based iron(III) oxide nanofluid showed that the maximum reduction of reaching time to MFB point was about 53.6%, and the maximum enhancements of MFBT and MHF were about 31.1% and 73.4%, respectively.