• The Korean Journal of Applied Statistics
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• v.15 no.1
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• pp.45-55
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• 2002

The 2-level rotation design based on 3 rotation groups is discussed in view of Monthly Retail Trade Survey conducted by the Bureau of Census in U.S., and composite estimators for population characteristics are concerned. The generalized composite estimators and the recursive composite estimators are presented at 2-level rotation design with design gap and variance formulas for the composite estimators are provided. Also under the response variability related with covariance structure and correlation structure from repeated response, relative efficiencies of the composite estimators are compared.

• The Korean Journal of Applied Statistics
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• v.32 no.3
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• pp.331-348
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• 2019

Understanding the tumor heterogeneity due to differences in the growth pattern of metastatic tumors and rate of change is important for understanding the sensitivity of tumor cells to drugs and finding appropriate therapies. It is often possible to test for differences in population means using t-test or ANOVA when the group of N samples is distinct. However, these statistical methods can not be used unless the groups are distinguished as the data covered in this paper. Statistical methods have been studied to test heterogeneity between samples. The minimum combination t-test method is one of them. In this paper, we propose a maximum combinatorial t-test method that takes into account combinations that bisect data at different ratios. Also we propose a method based on the idea that examining the heterogeneity of a sample is equivalent to testing whether the number of optimal clusters is one in the cluster analysis. We verified that the proposed methods, maximum combination t-test method and gap statistic, have better type-I error and power than the previously proposed method based on simulation study and obtained the results through real data analysis.

• The Journal of the Korea Contents Association
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• v.19 no.4
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• pp.682-689
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• 2019

This study aims to spatialize the gap between obesity levels through the body mass index, an objective indicator of the level of health among vulnerable people. Thus, areas where the BMI showed cluster patterns with spatial high and low values were extracted and the characteristics of the region were analyzed. The analysis showed that the I statistics for the obesity rate were 0.07 and the z-score was 4.39, confirming spatial autocorrelation. For z-score, it was much larger than the maximum threshold of 2.57. This means that the rate of obesity among the socially vulnerable is regional, and this gap is spatially significant. The results of comparing and analyzing the local environment for these areas of obesity and health care were found to be areas with poor public transportation, less readily available parks, and a concentration of single and multi-generation housing. The analysis results of this study are meaningful in that they provide spatial implications for the health of the socially vulnerable class that previous studies have neglected.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.856-866
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• 1987

In the present paper a statistical method using probability density function has been applied to investigate experimentally the flow patterns and fluctuations of time-averaged local void fraction in air-water two-phase mixtures which flow vertically upwards in concentric annuli. This study was carried out using three vertical concentric annuli. The annular test section consists of a lucite outer tube whose inside diameter is 38mm and a stainless steel inner rod. The rod diameter is either 12mm, 16mm or 20mm. The two-phase flow patterns observed in the experiment were bubbly, slug, annular and each transition patterns. It was first demonstrated that the variance, coefficients of skewness and kurtosis calculated from probability density function on time-averaged local void fraction can be used to identify the flow patterns in the annular passage, and the fluctuation of time-averaged local void fraction varies with the radial position in annular gap and the flow pattern.

• Journal of the Korea Society of Computer and Information
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• v.25 no.11
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• pp.27-40
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• 2020

In this paper, we investigate the correlation between the amount of English sentences that Korean English learners (L2ers) are exposed to and their sentence processing patterns by examining what Long Short-Term Memory (LSTM) language models (LMs) can learn about implicit syntactic relationship: that is, the filler-gap dependency. The filler-gap dependency refers to a relationship between a (wh-)filler, which is a wh-phrase like 'what' or 'who' overtly in clause-peripheral position, and its gap in clause-internal position, which is an invisible, empty syntactic position to be filled by the (wh-)filler for proper interpretation. Here to implement L2ers' English learning, we build LSTM LMs that in turn learn a subset of the known restrictions on the filler-gap dependency from English sentences in the L2 corpus that L2ers can potentially encounter in their English learning. Examining LSTM LMs' behaviors on controlled sentences designed with the filler-gap dependency, we show the characteristics of L2ers' sentence processing using the information-theoretic metric of surprisal that quantifies violations of the filler-gap dependency or wh-licensing interaction effects. Furthermore, comparing L2ers' LMs with native speakers' LM in light of processing the filler-gap dependency, we not only note that in their sentence processing both L2ers' LM and native speakers' LM can track abstract syntactic structures involved in the filler-gap dependency, but also show using linear mixed-effects regression models that there exist significant differences between them in processing such a dependency.

• The Korean Journal of Financial Management
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• v.10 no.1
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• pp.97-123
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• 1993

본 연구는 소속부 변경이 주가, 주가변동성 및 유동성에 미치는 영향을 최근 7년간의 표본을 이용하여 실증분석하였다. 이는 소속부 변경이 주식시장에 미치는 영향에 관한 최초의 연구로 다음과 같은 결과를 얻을 수 있었다. 첫째, 시장 제1부로의 승격은 변경일 이전에 통계적으로 유의적인 양의 초과수익률을 야기시키며, 시장 제2부로의 탈락은 통계적으로는 비유의적이나 음의 초과수익률을 가져온다. 둘째, 소속부 변경 일을 전후로 한 주가변동성은 ARCH 및 GARCH 모형에 의해 설명될 수 있으며, 변경일 이전에 주가변동성은 증가하는 경향이 있음을 알 수 있었다. 세째, 유동성 측면에서는 시장 제1부 승격과 시장 제2부 탈락의 모든 경우에 있어서 변경전보다 변경후에 거래량이 감소함을 발견 하였다.

• The Korean Journal of Applied Statistics
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• v.23 no.4
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• pp.715-724
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• 2010

Recurrent event data occurs when a subject experience the event of interest several times and has been found in biomedical studies, sociology and engineering. Several diverse approaches have been applied to analyze the recurrent events (Cook and Lawless, 2007). In this study, we analyzed the YTOP(Young Traffic Offenders Program) dataset which consists of 192 drivers with conviction dates by speeding violation and traffic rule violation. We consider a subject-specific effect, frailty, to reflect the individual's driving behavior and extend to time-varying frailty effect. Another feature of this study is about the redefinition of risk set. During the study, subject may be under suspension and this period is regarded as non-risk period. Thus the risk variables are reformatted according to suspension and termination time.

• Journal of Korean Society of Transportation
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• v.20 no.6
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• pp.115-128
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• 2002

Traffic engineers have developed and implemented various microscopic simulation models to verify the traffic performance and to prevent the expected problems. The existing microscopic simulation models categorize drivers into several types to reflect various drivers' driving patterns but miss the dynamics of drivers' behavior changed based upon the traffic conditions. It was found from the field data collected from two different merging sections on an urban freeway in Seoul, Korea, that the drivers' critical gap distributions are changed based on (1) the traffic density on the adjacent lane to the acceleration lane and (2) the opportunities left to merge in terms of distance to the end of acceleration lane. It was also found from the study that the drivers' critical gap distributions follow the Normal distribution. and its mean and variance change while a vehicle progresses on an acceleration lane. This paper proposes a new gap-acceptance model developed based on a set of drivers' critical gap distributions from each segment on the acceleration lanes. Through the comparison study between the field data and the results from the simulation utilizing the proposed model, it was verified that (1) the distribution of merging points on an acceleration lane to the adjacent main lane at different density levels, (2) the size of the gap accepted for merging and (3) the speed difference between the merging vehicle and the trailing vehicle at the time of merging are statistically identical to the field data at 95% confidence level.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.281-286
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• 2010

Purpose: This research provided basic data for refraction by comparing the corrected diopter of trial lens and phoropter. Methods: We compared the corrected diopter of trial lens and phoropter, and analyzed statistical significance and relations of the spherical lens corrected diopter and cylindrical lens corrected diopter according to the types (trial lens and phoropter) of subjective refractive instruments. Also we analyzed statistical significance and relations between cylindrical lens corrected diopter at the astigmatism and the types (trial lens and phoropter) of subjective refractory instruments. Results: When we measured the corrected diopter of simple myopia, the mean value for corrected diopter was S-2.74D using the trial lens and S-2.65D using the phoropter. So the corrected diopter was 0.09D smaller when measured by phoropter. The degree of astigmatism was measured C-0.81D using the trial lens and C-0.77D using the phoropter which showed that the measured value was 0.04D smaller using the phoropter. On correlation analysis between the refractive instruments (trial lens and phoropter) and the corrected diopter, there was significant (p<0.01) strong correlation between refractory machine and corrected spherical diopter (r=0.996) and the correlation between refractory machine and corrected cylindrical diopter was r=0.986 and was also significant (p<0.01). Conclusions: The use of phoropter than trial lens was more desirable when performing refraction on high myopia (simple refractive error, high astigmatism), and when using trial lens, you should consider the vertex distance and the gap between overlapped lenses before prescription.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.401-410
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• 2023

A radiographer is a job in charge of diagnostic imaging equipment, and must contribute to the promotion of public health by suggesting an appropriate level of work. To this end, we intend to present an appropriate level of work through evaluation of human harm according to work, statistical evaluation through questionnaires, and domestic and international trends. In the case of human harm evaluation, considering radiation exposure, 42.6%, shield work, 69.7%, and in the case of magnetic resonance imaging, the maximum length of stay in the examination room should be adjusted to 15 minutes and not exceed 30 times. According to the survey statistics, it was confirmed that the physical and mental burden increased due to the high workload and difficulty compared to working hours. Based on domestic and international trends, it is necessary to adjust the examination standards for domestic radiographers to 36.8% to promote national health through qualitative improvement of radiological examinations. something to do.