• Communications for Statistical Applications and Methods
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• v.29 no.1
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• pp.103-125
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• 2022

In this paper, we analyze the time series data of the case and death counts of COVID-19 that broke out in China in December, 2019. The study period is during the lockdown of Wuhan. We exploit functional data analysis methods to analyze the collected time series data. The analysis is divided into three parts. First, the functional principal component analysis is conducted to investigate the modes of variation. Second, we carry out the functional canonical correlation analysis to explore the relationship between confirmed and death cases. Finally, we utilize a clustering method based on the Expectation-Maximization (EM) algorithm to run the cluster analysis on the counts of confirmed cases, where the number of clusters is determined via a cross-validation approach. Besides, we compare the clustering results with some migration data available to the public.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3E
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• pp.97-103
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• 2007

We propose a combined STBC (Space Time Block Coding) and AMC (Adaptive Modulation and Coding) in the underwater multipath communication channel. Performance of UAC (underwater acoustic communication) in shallow water is degraded by complicated multipath and reverberation. For this reason, and considering the variability of the ocean channel, we combined STBC and AMC techniques, which are the spatial diversity in a multi-sensor communication system. BER (Bit error rate) of combined STBC and AMC is improved by 5dB when we compare with the BER of a single sensor based system. The proposed system shows a 3dB improvement when we compare it with the BER of the single sensor based system applying the AMC technique only.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.38-44
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• 1999

This paper primarily directed toward analyzing the frequency response in hydraulic pipe lines with a small diameter. The exact solution to the frequency response is obtained by using the complicated transfer function. The discrepancy with the exact and the approximate is small so the approximation solution is adopted to compare the experimental results with the theoretical analysis. In this experiment the input frequency was generated by the frequency generator with the ball valve and speed controller. In order to compare the theoretical were forms with the experimental ones the trace obtained from the oscilloscope is photographed, The diameter the length of lines and input pressure amplitude are varied to investigate their effects,. the experiment results show that th values of dimensionless parameter are very affected to the phase delay and guide response time in the design of pressure manifold to measure the pressure of hydraulic pipelines.

• Communications for Statistical Applications and Methods
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• v.21 no.4
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• pp.309-316
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• 2014

Testing normality is very important because the most common assumption is normality in statistical analysis. We propose a new plot and test statistic to goodness-of-fit test for normality based on the generalized Lorenz curve. We compare the new plot with the Q-Q plot. We also compare the new test statistic with the Kolmogorov-Smirnov (KS), Cramer-von Mises (CVM), Anderson-Darling (AD), Shapiro-Francia (SF), and Shapiro-Wilks (W) test statistic in terms of the power of the test through by Monte Carlo method. As a result, new plot is clearly classified normality and non-normality than Q-Q plot; in addition, the new test statistic is more powerful than the other test statistics for asymmetrical distribution. We check the proposed test statistic and plot using Hodgkin's disease data.

• Journal of Distribution Research
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• v.2 no.1
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• pp.59-85
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• 1997

The automobile industry in Korea has grown to the fifth in the world in terms of production capacity. In spite of the production growth, the marketing aspects such as distribution and customer service in the auto industry are still behind the world-class. Thus, the major purposes of this paper are as follows. The first is to analyze competitive structure of the industry and to compare distribution strategies of the major auto firms(Hyundai, Daewoo, and Kia). The second is to theoretically explain the transition from the vertical marketing system to the dealer system using transaction cost analysis. The third is to compare auto distribution channels in Korea with those in the U.S. and Japan. Finally, an optimal channel stucture in the auto industry is suggested after reviewing five alternative channel structures such as corporate-owned VMS, sales-specializing firm, multiplex system(VMS+limited dealer system), dual sales channel, and advanced dealer system. In the short-run, sales-specilizing firm was suggested as an optimal channel system to enhance customer satisfaction by integrating sales and customer service. In the long-run, advanced dealer system through regional differentiation was desirable for an optimal channel structure by organically integrating new car sales, used car sales, and after service to provide total marketing service to customers.

• Phonetics and Speech Sciences
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• v.7 no.4
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• pp.35-40
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• 2015

We propose a speech waveform forgery detection algorithm based on the flatness of frequency distribution. We devise a new measure of flatness which emphasizes the local change of the frequency distribution. Our measure calculates the sum of the differences between the energies of neighboring frequency bands. We compare the proposed measure with conventional flatness measures using a set of a large amount of test sounds. We also compare- the proposed method with conventional detection algorithms based on spectral distances. The results show that the proposed method gives lower equal error rate for the test set compared to the conventional methods.

• Journal of applied mathematics & informatics
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• v.38 no.3_4
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• pp.351-373
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• 2020

There is an extensive literature on retrial queueing models. While a majority of the literature on retrial queueing models focuses on the retrial times to be exponentially distributed (so as to keep the state space to be of a reasonable size), a few papers deal with nonexponential retrial times but with some additional restrictions such as constant retrial rate, only the customer at the head of the retrial queue will attempt to capture a free server, 2-state phase type distribution, and finite retrial orbit. Generally, the retrial queueing models are analyzed as level-dependent queues and hence one has to use some type of a truncation method in performing the analysis of the model. In this paper we study a retrial queueing model with threshold-type policy for orbiting customers in the context of nonexponential retrial times. Using matrix-analytic methods we analyze the model and compare with the classical retrial queueing model through a few illustrative numerical examples. We also compare numerically our threshold retrial queueing model with a previously published retrial queueing model that uses a truncation method.

• The Korea Journal of Herbology
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• v.21 no.3
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• pp.83-89
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• 2006

Objectives : To compare limonene, menthone and pulegone content from different part of Schizonepeta tenuifolia Briquet. Methods : The quantitative content of essential oil was determined according to the method of Chinese Pharmacopoeia. GC analysis of essential oil was carried out using a flame ionization detector. The results obtained were confirmed by GC/MS. Results : The content of essential was high on the leaf part. The content of menthone was higher than other ingredients. When compare the content observed by harvesting time, the highest pick was shown on middle of August. Conclusion : This research can be used to modify or feedbackthe article in the Korean Pharmacopoeia.

• Journal of Korea Multimedia Society
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• v.21 no.3
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• pp.391-399
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• 2018

In this paper, we construct and compare various guitar chord classification systems using perceptron neural network and convolutional neural network without pre-processing other than Fourier transform to identify the optimal chord classification system. Conventional guitar chord classification schemes use, for better feature extraction, computationally demanding pre-processing techniques such as stochastic analysis employing a hidden markov model or an acoustic data filtering and hence are burdensome for real-time chord classifications. For this reason, we construct various perceptron neural networks and convolutional neural networks that use only Fourier tranform for data pre-processing and compare them with dataset obtained by playing an electric guitar. According to our comparison, convolutional neural networks provide optimal performance considering both chord classification acurracy and fast processing time. In particular, convolutional neural networks exhibit robust performance even when only small fraction of low frequency components of the data are used.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1625-1631
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• 2004

Investigation on Flue Gas Recirculation(FGR) flame and Fuel Injection Recirculation(FIR) flame was performed with numerical method. Quantitative Reaction Path Diagram(QRPD) is utilized to compare the different chemistry effects between FGR flame and FIR flame. In order to compare flamelets in various oxygen-enrichment conditions reasonably, the adiabatic flame temperature and Damkohler number were held fixed by modulating the amount of diluents to fuel and oxidizer stream and by varying global strain rate of flame respectively. Basic flame structures were compared and characteristics of CH$_4$ decomposition and NO formation were analyzed based on QRPD analysis between FGR flame and FIR flame.