• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.3-9
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• 2001

In this paper, a random number generator for simulation of speech-waveform coders was designed. A random number generator having a desired probability density function and a desired power spectral density is discussed and experimental results are presented. The technique is based on Sondhi algorithm which consists of a linear filter and a memoryless nonlinearity. Several methods of obtaining memoryless nonlinearities for some typical continuous distributions are discussed. Sondhi algorithm is analyzed in the time domain using the diagonal expansion of the bivariate Gaussian probability density function. It is shown that the Sondhi algorithm gives satisfactory results when the memoryless nonlinearity is given in an antisymmetric form as in uniform, Cauchy, binary and gamma distribution. It is shown that the Sondhi algorithm does not perform well when the corresponding memoryless nonlinearity cannot be obtained analytically as in Student-t and F distributions, and when the memoryless nonlinearity can not be expressed in an antisymmetric form as in chi-squared and lognormal distributions.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.2
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• pp.32-46
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• 2017

Recent rapid urban expansion and crowding of various industrial facilities has affected the features of a significant part of downtown area, resulting in areas having buildings with a wide range of height and the foothills. To compute a velocity pressure exposure coefficient, namely the design wind speed factor, this study defines ground surface roughness by utilizing concentration analysis for the height of each building. After obtaining spatial data by extracting a building layer from digital maps, the study area was partitioned for the concentration analysis and to allow investigation of the frequency distribution of building heights. Concentration analysis by building height was determined with the Variation-to-Means Ratio (VMR) and Poisson distribution analysis using a buildings distribution chart, with statistical significance determined using Chi-square verification. Applying geographic information systems (GIS) with the architectural information made it possible to estimate a velocity pressure exposure coefficient factor more quantitatively and objectively, by including geographic features, as compared to current methods. Thus, this method is expected to eliminate inaccuracies that arise when building designers calculate the velocity pressure exposure coefficient in subjective way, and to help increase the wind resistance of buildings in a more logical and cost-effective way.

• Journal of the Korean Data and Information Science Society
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• v.24 no.4
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• pp.825-833
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• 2013

An estimation of confidence intervals is essential to calculate uncertainty for greenhouse gases inventory. It is generally assumed that the population has a normal distribution for the confidence interval of parameters. However, in case data distribution is asymmetric, like nonnormal distribution or positively skewness distribution, the traditional estimation method of confidence intervals is not adequate. This study compares two estimation methods of confidence interval; parametric and non-parametric method for exponential distribution as an asymmetric distribution. In simulation study, coverage probability, confidence interval length, and relative bias for the evaluation of the computed confidence intervals. As a result, the chi-square method and the standardized t-bootstrap method are better methods in parametric methods and non-parametric methods respectively.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.933-936
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• 2011

이 연구는 2008년 9월부터 11월까지 3개월에 걸쳐 대전광역시에 거주하는 19세 이상 주민들 2,947명을 대상으로 대면면접에 의한 간접 기입식 설문조사 방법으로 시행되었으며 일반적 특성과 건강행태가 교통안전 미 실천과 관련성이 있는지를 살펴보고자 하였다. 수집된 자료는 SPSS 14.0을 활용하여 카이제곱 검정과 다중 로지스틱 회귀 분석을 실시하였다. 그 결과를 요약하면 다음과 같다. 첫째, 연구대상자는 일반적 특성 중 교육수준, 배우자 유무, 월 가구소득, 직업, 가구 소유 유무와 같이 사회 문화적인 부분에 있어서는 성별 분포가 통계적으로 유의한 차이를 보였다. 둘째, 운전 시 안전벨트 미착용이라는 교통안전 미 실천에 관련하여 30대와 40대는 운전 시 안전벨트를 더 많이 착용하였고 스트레스를 대단히 많이 느끼는 사람은 더 많이 미 실천하였다. 셋째, 음주운전은 30대와 40대, 기타 및 농어업 종사자, 고위험음주를 한 적이 있는 사람, 현재 흡연 중인 사람이 더 많이 하였고 반면 가구를 1채 소유한 사람은 음주운전을 더 적게 하였다. 음주운전과 안전벨트 미착용은 치명적 교통사고의 큰 원인이 되는 한편 예방이 가능한 원인이라는 점에서 예방을 하기 위해 미 실천 집단을 파악하고 교육을 시행하거나 원인을 제거하는 등의 예방사업을 통해서 대비할 수 있다. 본 연구에서는 미 실천 빈도가 높은 집단이 통계적으로 유의한 수준으로 있음을 확인하였으며 원인 분석 및 분석을 통한 해결책 마련을 위한 추가적인 연구가 필요하리라 사료된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.625-629
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• 2015

In this study, we develop a prognostic method of assessing the stator windings of power generators against water absorption through statistical data analysis and degradation modeling. The 42 windings of the generator are divided into two groups: the absorption and normal groups. A degradation model of a winding is constructed using Fick's second law to predict the level of absorption. By analyzing data from the normal group, we can determine the distribution of the data of normal windings. The health index of a winding is estimated using the directional Mahalanobis distance (DMD) method. Finally, the probability distributions of the failure time of the windings are determined.

• The Korean Journal of Applied Statistics
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• v.18 no.3
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• pp.583-595
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• 2005

Contingency tables are used to compare counts of n-grams to determine if the n-gram is a true collocation, meaning that the words that make up the n-gram are highly associated in the text. Some statistical methods for identifying collocation are used. They are Kulczinsky coefficient, Ochiai coefficient, Frager and McGowan coefficient, Yule coefficient, mutual information, and chi-square, and so on. But the main problem is that these measures are based ell the assumption of a nor-mal or approximately normal distribution of the variables being sampled. While this assumption is valid in most instances, it is not valid when comparing the rates of occurrence of rare events, and texts are composed mostly of rare events. In this paper we have simply reviewed some statistics about testing association of two words. Some randomization tests to evaluate the significance level in analyzing collocation in large corpora are proposed. A related graph can be used to compare different lest statistics that ran be used to analyze the same contingency table.

• Journal of KIISE:Software and Applications
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• v.30 no.11
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• pp.1062-1071
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• 2003

A genre-based classification means classifying documents by the purpose for which they were written, not by the semantics or subject areas. Most genre classifying methods in the past were based on the existing documents categorization algorithms and ineffective for feature selections, resulting in low quality classification results. In this research, we propose a new method for automatic classification of digital documents by genre. The genre classifier we developed uses the deviation statistic between the genre-revealing term frequencies and between the subject-revealing term frequencies within a genre. We collected Web documents to evaluate the proposed genre classification method. The experimental results show that the proposed method outperforms a direct application of a kai-square feature selection and bayesian classifier often used for subject classification by proving an excellent accuracy of about 30 percent.

• The Journal of the Korea Contents Association
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• v.21 no.11
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• pp.426-435
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• 2021

This study aims to functionally classify lexical bundles appearing in academic papers on nuclear science and engineering written in English and then analyze the lexical bundles' characteristics compared to those appearing in general academic papers. To this end, the texts of nuclear science and engineering papers were collected and produced as a corpus(c. 1 mil. tokens). Then they were statistically compared through Chi-square tests and standardized residuals with the corpus of general academic papers(c. 750,000 tokens). The results revealed that, compared to general academic papers, the bundles in the stance lexical bundle category were mainly used among the functional lexical bundle in nuclear science and engineering. The use of the lexical bundles lacked much variety. The same type of lexical bundles was 're-used' and 'recycled'. Based on these research results, educational implications for English for Academic Purposes and the further direction of follow-up research were discussed and suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.955-963
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• 2005

In this paper, we consider the noncoherent code acquisition problem using sequential schemes. We show that the outputs of the noncoherent receiver approximately have a central chi-square distribution under the null hypothesis through simulations. Based on this observation, simplified acquisition schemes are obtained using the approximations of the Bessel function. The performance of the simplified and original schemes are compared in additive white Gaussian noise and slowly varying fading channels. Numerical results show that the simplified schemes have essentially the same performance as the original schemes.

• The Korean Journal of Applied Statistics
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• v.30 no.1
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• pp.147-157
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• 2017

The test of transition probabilities in panel Markov chains are introduced. We deal with the hypotheses whether panel Markov chains have the same transition probabilities or not for all times. We suggest a LR test statistic for the test and its limit distribution is derived. We perform a simulation study to examine the limit distribution of test statistics when the number of the individuals are large.