• Proceedings of the KSME Conference
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• 2003.04a
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• pp.267-272
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• 2003

In order to investigate the effect of face material on Ti/Al alloy laminates under high velocity impact, a ballistic testing was conducted. Ballistic resistance of these materials was measured by protection ballistic limit($V_{50}$), a statistical velocity with 50% probability penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, were respectfully observed, by $V_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than $V_{50}$. PTP tests were conducted with $0^{\circ}$obliquity at room temperature using 5.56mm ball projectile. $V_{50}$ tests with $0^{\circ}$obliquity were also done with projectiles that were able to achieve near or complete penetration during PTP tests. Resistance to penetration, and penetration modes which face material was Titanium alloy, were compared to those which face material was anodized Al alloy after cold-rolling.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.686-691
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• 2007

The ride comfort is more important according to train speedup. Generally it is defined as the vehicle vibration. There are many studies on evaluation method of ride comfort for railway. In the case of Korean high speed train(HSR 350x), the ride comfort has been assessed by statistical method according to UIC 513R. To verify the design requirements for the performance of HSR 350x, the qualification tests had been conducted from August 19, 2002 to December 2004 and the stabilization and reliability tests are carried out nowadays. Up to December 2006, total test runs and the accumulated milage of the train were 357 times and 164,000km, respectively. A total of 352 ride indices had been acquired through the on-line test from Aug. 2002 to Dec. 2006. In this paper, we have reviewed the characteristics of ride comfort for HSR 350x according to the operational conditions, such as load and track conditions, season and used time, by using the tests data.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.4
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• pp.45-50
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• 2003

In order to investigate the effect of surface treatment (Anodizing) and rolling on AI 5083-H131 alloy, under hyper velocity impact, a ballistic testing was conducted. Ballistic resistance of these materials was measured by a protection ballistic limit ($V_{50}$)' a statistical velocity with 50% probability of penetration. Perforation behavior and ballistic tolerance, described by penetration modes, were respectfully observed, by $V_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than $V_{50}$. PTP tests were conducted with 0$^{\circ}$ obliquity at room temperature using 5.56mm ball projectiles. $V_{50}$ tests with 0$^{\circ}$ obliquity were also done with projectiles that were able to achieve near or complete penetration during PTP tests. Resistance to penetration, and penetration modes of Al 5052-H34 alloy were compared to those of Al 5083-H 131 alloy.

• The Korean Journal of Applied Statistics
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• v.9 no.1
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• pp.139-152
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• 1996

In this paper we propose nonparametric tests using optimal weights for umbrella alternatives in a randomized block design. We obtain the optimal weights by maximizing the asymptotic relative efficiency of the proposed test statistics with respect to Mack and Wolf(1981) type test statistic, and investigate asymptotic relative efficiencies of the proposed test statistics using these optimal weights relative to Mack and Wolfe type statistics and linear rank statistic. Throughout simulations for small samples, the proposed test statistic has good powers rather than the other two tests when the block sizes are different.

• 대한예방의학회:학술대회논문집
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• 1994.02b
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• pp.154-157
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• 1994

The evaluation of diagnostic tests attempts to obtain one or more statistical parameters which can indicate the intrinsic diagnostic utility of a test. Sensitivity. specificity and predictive value are not appropriate for this use. The likelihood ratio has been proposed as a useful measure when using a test to diagnose one of two disease states (e.g. disease present or absent). In this paper, we generalize the likelihood ratio concept to a situation in which the goal is to diagnose one of several non-overlapping disease states. A formula is derived to determine the post-test probability of a specific disease state. The post-test odds are shown to be related to the pre-test odds of a disease and to the usual likelihood ratios derived from considering the diagnosis between the target diagnosis and each alternate in turn. Hence, likelihood ratios derived from comparing pairs of diseases can be used to determine test utility in a multiple disease diagnostic situation.

• Journal of Pharmaceutical Investigation
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• v.39 no.3
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• pp.217-219
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• 2009

There are several approaches to calculate a sample size for bioequivalence test. Among these approaches, sample sizes determination based on Schuirmann's two one-sided tests procedures has been used most popularly in case of 2${\times}$2 bioequivalence study. Here we proposed simple sample size table for conventional 2${\times}$2 bioequivalence test based on Schuirmann's two one-sided tests in accordance with Korean Guidelines for Bioequivalence Test. This table will allow researchers with a little statistical background to calculate the sample size for bioequivalence with easy process.

• The Journal of the Acoustical Society of Korea
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• v.8 no.5
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• pp.78-85
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• 1989

This paper describes a statistical methods and perception test for extracting the parameters to be used for the synthesis-by-rule of Korean plosives. Formant synthesizer is chosen for the synthesis of the phonemes. Speech materials for the analysis consists of 72 CV monosyllables from the single male speaker. The analysis is done mainly focused on the variation of parameters in time and frequency domain, then perception tests are executed to estimate the effects of variations of the formant transitions.

• Journal of the Korean Statistical Society
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• v.30 no.1
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• pp.41-61
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• 2001

The minimum negative exponential disparity estimator(MNEDE), introduced by Lindsay(1994), is an excellenet competitor to the minimum Hellinger distance estimator(Beran 1977) as a robust and yet efficient alternative to the maximum likelihood estimator in parametric models. In this paper we define the negative exponential deviance test(NEDT) as an analog of the likelihood ratio test(LRT), and show that the NEDT is asymptotically equivalent to he LRT at the model and under a sequence of contiguous alternatives. We establish that the asymptotic strong breakdown point for a class of minimum disparity estimators, containing the MNEDE, is at least 1/2 in continuous models. This result leads us to anticipate robustness of the NEDT under data contamination, and we demonstrate it empirically. In fact, in the simulation settings considered here the empirical level of the NEDT show more stability than the Hellinger deviance test(Simpson 1989). The NEDT is illustrated through an example data set. We also define a goodness-of-fit statistic to assess adequacy of a specified parametric model, and establish its asymptotic normality under the null hypothesis.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.5
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• pp.20-27
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• 2001

The purpose of this study is to investigate and compare the validity and the reliability of the visual simulation method using the internet. For this. the evaluation of the artificial and natural landscape through the medium of color slides are compared with the internet survey. Data is analysed through the comparison of t-test between the two media by landscape type, and spatial image is analysed by factor analysis algorithm. Principle component analysis using Varimax Method is applied for extraction and factor rotation respectively. The results of this study can be summarized as follows; There are no statistical differences between the two methods with artificial and natural landscape in the total data that included second tests. Factors covering the spatial image are found to be \`aesthetic\`, \`spatial shape\`, and \`familiarity\`. Total variance is obtained as 66.4%. There are no statistical differences between the two methods in 2/3 of the cases. In the case of far view of artificial landscape, the results of the t-test show that the two methods are exactly the same. Especially in the case of the artificial far landscape shows no difference of all factors between two methods. There are no differences between first and second tests of the same media and the same landscape type. And it shows the reliability of this method. These results suggest that the probability that the internet can be used as a medium of landscape evaluation and gathering information on anyone\`s landscape image. Simulation techniques with the internet survey method should be further developed for practical application.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.360-369
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• 2015

A methodology for determining the design allowables of composite laminates by using lamina level test data and finite element analysis (FEA) is proposed and verified in this paper. An existing method that yields the laminate design allowables by using the complete test results for laminates was improved to reduce the expensive and time-consuming tests. Input property samples for FEA were generated after considering the statistical distribution characteristics of lamina level test data., and design allowables were derived from several FEA analyses of laminates. To apply and verify the proposed method, Hexcel 8552 IM7 test data were used. For both un-notched and open-hole laminate configurations, it was found that the design allowables obtained from the analysis correctly predicted the laminate test data within the confidence interval. The potential of the present simulation to substitute the laminate tests was demonstrated well.