• Journal of Korean Ophthalmic Optics Society
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• 제20권3호
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• pp.349-354
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• 2015

Purpose: To investigate the changes of corrective values of astigmatism caused by the position of circle of least confusion on retina in refining astigmatic test using cross cylinder. Methods: 62 subjects (115 eyes) aged $22.24{\pm}2.48$ years participated for this study. After astigmatic test using a radial chart, refining test was performed using a cross cylinder in a condition of maximum plus to maximum visual acuity (MPMVA). Astigmatic refining test was repeatedly performed in each condition of which S+0.75 D, S+0.50 D, S+0.25 D, S-0.25 D, S-0.50 D, and S-0.75 D are added to spherical lenses of MPMVA. The measured values were compared with the values in MPMVA condition. Results: As compared with values in condition of MPMVA, change of astigmatic axis was increased with add the power of (+) spherical lenses and (-) spherical lenses. In same spherical condition, change of astigmatic axis was decreased with increment of astigmatic power (p<0.05). The corrective power of astigmatism was reduced with increment of (+) spherical lenses (p<0.05), and was raised with increment of (-) spherical lenses compared with the power in MPMVA condition. In case of adding (+) spherical lenses, difference of astigmatic power increased with increment of corrective astigmatism power in same test condition. Conclusions: In order to obtain a proper values for corrective astigmatism, position of circle of least confusion should be accurately adjusted before the performing an astigmatism's refining test.

• Journal of Preventive Medicine and Public Health
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• 제37권4호
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• pp.366-372
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• 2004

Objectives : This study was conducted to propose a new transmission/disequilibrium test(TDT) to test the linkage between genetic markers and disease-susceptibility genes based on haplotypes. Simulation studies were performed to compare the proposed method with that of Zhao et al. in terms of type I error probability and powers. Methods : We estimated the haplotype frequencies using the expectation-maximization(EM) algorithm with parents genotypes taken from a trio dataset, and then constructed a two-way contingency table containing estimated frequencies to all possible pairs of parents haplotypes. We proposed a score test based on differences between column marginals and their corresponding row marginals. The test also involved a covariance structure of marginal differences and their variances. In simulation, we considered a coalescent model with three genetic markers of biallele to investigate the performance of the proposed test under six different configurations. Results : The haplotype-based TDT statistics, our test and Zhao et al.'s test satisfied a type I error probability, but the TDT test based on single locus showed a conservative trend. As expected, the tests based on haplotypes also had better powers than those based on single locus. Our test and that of Zhao et al. were comparable in powers. Conclusion : We proposed a TDT statistic based on haplotypes and showed through simulations that our test was more powerful than the single locus-based test. We will extend our method to multiplex data with affected and/or unaffected sibling(s) or simplex data having only one parent s genotype.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1261-1262
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• 2013

• Journal of the Korean Data and Information Science Society
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• 제18권3호
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• pp.697-704
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• 2007

It is common in financial time series that volatility(conditional variance) as a measure of risk exhibits asymmetry in such a manner that positive and negative values of return rates of the series tend to provide different contributions to the volatility. We are concerned with asymmetric conditional variances for Korean financial time series especially during the time span of 2000-2001. Notice that these periods suffer from 9-11 disaster in US and collapses of stock prices of dot-companies in Korea. Threshold-ARCH models are considered and a Wald test of asymmetry is suggested. News impact curves are illustrated for graphical representations of leverage effects inherent in various Korean financial time series.

• Journal of Applied Reliability
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• 제14권2호
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• pp.93-96
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• 2014

RFID (Radio Frequency IDentification) system is recognition technology which can maintain various object's information. Reliability of RFID tags is the most important factor in RFID system. In this paper, we proposed ALT (Accelerated Life Test) method for UHF RFID tags. Temperature and humidity were adopted as stress factors and the accelerated life tests were conducted in three different conditions. We performed failure analysis for identifying failure mechanism and statistical analysis of test data. In the statistical analysis, we employed Inverse Power law for relationship between tag's life and stress. Through the statistical analysis, we proposed acceleration factor for several levels of temperature-humidity. The reliability qualification test plans were also designed for the tag's target reliability.

• Journal of the Korea Institute of Military Science and Technology
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• 제22권6호
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• pp.784-796
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• 2019

As the size and complexity of software increases, it is important to ensure the quality of software through testing. Many organizations refer to international standards or test process models to improve the quality of software through establishing a systematic test process. However, these standards and process models provide general processes that do not reflect the characteristics of the domain or the organization's test policies and strategies. To establish a test process that reflects the characteristics of the organization, test policies and strategies based on the organization's quality objectives and the organizational and domain characteristics should be reflected. This study proposes specific methods for eliciting activities and information to establish organizational software test policies and strategies that are essential to establishing a test process that reflects the characteristics of the organization and the system.

• Journal of the Institute of Electronics Engineers of Korea SP
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• 제38권1호
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• pp.69-78
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• 2001

MPEG-4 visual conformance standard specifies methods to verify whether bitstreams and decoders meet the requirements at the specified profile and level. The test of decoders can be divided into two parts: the static test and the dynamic test. The static test can be performed by examining the decoder output with that of a reference decoder. This paper proposes design methods of test bitstreams for static test of texture decoding, and shows the test results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.242-242
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• 2007

To verify the applicability of High Temperature Superconducting (HTS) cable system into the real grid, the HTS cable system with the specification of 22.9 kV, 1250 A, 100 m long was installed in the second quarter of 2006, and the long term field test has been in progress at the KEPCO's Gochang power testing yard. Apart from the conventional power cable, HTS cable system requires sufficient thermo-mechanical strength to endure a large temperature difference. To date, the KEPCO HTS cable system was cooled down and warmed to the room temperature several times to investigate the influence of thermal cycles experimentally. Dielectric properties, critical current dependance and heat losses were evaluated at each step of thermal cycle. The test results showed that thermal cycle did not induce the degradation of dielectric properties, and the critical current decreased to 5 % of the initial value.

• Journal of radiological science and technology
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• 제35권1호
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• pp.35-44
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• 2012

The goal of this study is to awaken about risk occurred by CT examination. For radio-technologists working at 'S medical center' located in Seoul, we investigated a recognition about dose and risk CT and normal X-ray examination according by working experience in hospital, experience about CT examination and radiation source. For subjects of investigation, radio-technologists working at 'S medical center' located in Seoul helped us. We collected 131 questionnaires for a test of hypothesis. Cronbach @ coefficients of questionnaires were 0.825988 and 0.767161 and a rejection rate of p-value was below 0.05. SAS 9.1(SAS Institute Inc., Cary, NC, USA.) statistic package was used for hypothesis test. We used Mann-Whitney test, Kruskai-Wallis test, Two sample T-test, Two sample T-test with Bonferroni's Correction and One-way ANOVA methods. P-values of hypothesis about dose of CT and normal X-ray examination were 0.2291 ~ 0.9663. p-values of hypothesis about risk were 0.1924 ~ 1.0000. All of hypothesis is over rejection rate(<0.05). This study shows that radio-technologists of S medical center recognized that CT has higher dose and risk than general X-ray examination.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제34권1호
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• pp.62-66
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• 1998

The maneuverabilities of the training ship M.S. HEUIMANGBONG were studied, based on the data obtained from her Z test. The results obtained were summerized as follows: 1. The maneuvering indices K' and T'of the M.S. HEUIMANGBONG were 0.542, 1.305 at 10$^{\circ}$Z Test and 0.433, 1.351 at 20$^{\circ}$Z test and 0.442, 1.388 at 30$^{\circ}$Z test respectively. The above calculated values K', T' showed that her maneuverabilities were more effective when her rudder was used to small angle than to large angle. 2. As the overshoot angles of the starbord side of the M.S. HEUIMANGBONG were larger than those of port side at 10$^{\circ}$, 20$^{\circ}$and 30$^{\circ}$Z test, her maneuverabilities in port turning were found to be higher than in starbord turning. 3. The running distance of a turn at her 10$^{\circ}$Z test was about 9.9 times her own length and she was considered to have a good maneuverabilities synthetically