• The Pure and Applied Mathematics
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• v.20 no.1
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• pp.59-70
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• 2013

The purpose of this study was to develop a zero-inflated Rasch (ZI-Rasch) model, a combination of the Rasch model and the ZIP model. The ZI-Rasch model was considered in this study as an appropriate alternative to the Rasch model for zero-inflated data. To investigate the relative appropriateness of the ZI-Rasch model, several analyses were conducted using PROC NLMIXED procedures in SAS under various simulation conditions. Sets of criteria for model evaluations (-2LL, AIC, AICC, and BIC) and parameter estimations (RMSE, and $r$) from the ZI-Rasch model were compared with those from the Rasch model. In the data-model fit indices, regardless of the simulation conditions, the ZI-Rasch model produced better fit statistics than did the Rasch model, even when the response data were generated from the Rasch model. In terms of item parameter ${\lambda}$ estimations, the ZI-Rasch model produced estimates similar to those of the Rasch model.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.35-42
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• 2001

The characteristics of water quality variation were predicted by stochastic model in Chungju dam, north Chungcheong province of south Korea, Monthly time series data of water quality from 1989 to 2001;temperature, BOD, COD and SS, were obtained from environmental yearbook and internet homepage of ministry of environment. Development of model was carried out with Box-Jenkins method, which includes model identification, estimation and diagnostic checking. ACF and PACF were used to model identification. AIC and BIC were used to model estimation. Seosonal multiplicative ARIMA(1, 0, 1)(1, 1, 0)$_{12}$ model was appropriate to explain stochastic characteristics of temperature. BOD model was ARMa(2, 2, 1), COD was seasonal multiplicative ARIMA(2. 0. 1)(1. 0, 1)$_{12}$, and SS was ARIMA(1, 0, 2) respectively. The simulated water quality data showed a good fitness to the observed data, as a result of model verification.ion.

• Communications for Statistical Applications and Methods
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• v.21 no.4
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• pp.335-347
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• 2014

This paper employs dynamic conditional correlation (DCC) model to examine time-varying comovement in the Korean stock market with a focus on the financial industry. Analyzing the daily returns of KOSPI 200 eight sector indices from January 2008 to December 2013, we find that stock market correlations significantly increased during the GFC period. The Financial Sector had the highest correlation between the Constructions-Machinery Sector; however, the Consumer Discretionary and Consumer Staples sectors indicated a relatively lower correlation between the Financial Sector. In terms of model fitting, the DCC with t distribution model concludes as the best among the four alternatives based on BIC, and the estimated shape parameter of t distribution is less than 10, implicating a strong tail dependence between the sectors. We report little asymmetric effect in correlation dynamics between sectors; however, we find strong asymmetric effect in volatility dynamics for each sector return.

• The Korean Journal of Applied Statistics
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• v.21 no.5
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• pp.825-833
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• 2008

Discriminant analysis based on Gaussian mixture models, an useful tool for multi-class classifications, can be extended to semi-supervised learning. We consider a model selection problem for a Gaussian mixture model in semi-supervised learning. More specifically, we adopt Bayesian information criterion to determine the number of subclasses in the mixture model. Through simulations, we illustrate the usefulness of the criterion.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1645-1648
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• 2008

We successfully fabricated lowest-cost superior perform ance MVA LCDs with highest-yield, high transmission, high contrast-ratio, and wide viewing angle. Using the amplified intrinsic fringe field (AIFF) controlled MVA invented by Ong, we eliminated all protrusions and ITO slit geometries. We further achieved: (1) faster gray-gray response times without the over-drive technology, (2) faster tough mura, and (3) lower flicker and cross-talk in the row inversion driving schemes.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.8
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• pp.8-21
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• 1997

In this paper, we consider resistive shorts on gate-source, gate-drain, and drain-source as well as opens in MOS FETs included in typical memory cell of VLSI SRAM and analyze behavior of memory by using PSPICE simulation. Using conventional fault models and this behavioral analysis, we propose linear testing algorithm of complexity O(N) which can be applied to both functional testing and IDDQ (quiescent power supply current) testing simultaneously to improve functionality and reliability of memory. Finally, we implement BIST (built-in self tsst) circuit and BICS(built-in current sensor), which are embedded on memory chip, to carry out functional testing efficiently and to detect various defects at high-speed respectively.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.1-14
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• 2013

ARIMA and ARIMA+IGARCH models are fitted and compared for daily Korean won/US dollar exchange rate data over 17 years. A linear structural change model and an autoregressive structural change model are fitted for multiple change-point estimation since there seems to be structural change with this data.

• Communications for Statistical Applications and Methods
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• v.20 no.6
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• pp.439-454
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• 2013

This study presents a Bayesian multiple change-point detection approach to segment and classify the observations that no longer come from an initial population after a certain time. Inferences are based on the multiple change-points in a sequence of random variables where the probability distribution changes. Bayesian multiple change-point estimation is classifies each observation into a segment. We use a truncated Poisson distribution for the number of change-points and conjugate prior for the exponential family distributions. The Bayesian method can lead the unsupervised classification of discrete, continuous variables and multivariate vectors based on latent class models; therefore, the solution for change-points corresponds to the stochastic partitions of observed data. We demonstrate segmentation with real data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.832-837
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• 2006

Antennas were fabricated by physical(adhesive) and chemical(deposition+plating) method on organic-inorganic composite material. And antennas were measured dielectric constant and gain. Dielectric constant of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness and number of conduction material composition. But antennas were fabricated by chemical method was reached to 90 % of dielectric material. Gain of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness. But they were unrelated with conduction material composition. The other side antennas were fabricated by chemical method excelled more 0.8 dBic than antennas were fabricated by physical method in gain of antenna. Finally, chemical method can expect excellent product process because it can produce smaller size, higher gain and elimination of many handworks.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.23-23
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• 2015

Rice blast disease caused by M. oryzae is the most devastating fungal disease in rice. During the infection process, M. oryzae secretes a large number of glycosyl hydrolase (GH) proteins into the apoplast to digest host cell wall and assist fungal ingress into host tissues. In this study, we identified a novel M. oryze arabinofuranosidase B (MoAbfB) which is secreted during fungal infection. Live-cell imaging exhibited that fluorescent labeled MoAbfB was highly accumulated in fungal invasive structures such as appressorium, tips of penetration peg, biotrophic interfacial complex (BIC), as well as invasive hyphal tip. Deletion of MoAbfB mutants extended biotrophic phase followed by enhanced disease severity, whereas, over-expression of OsMoAbfB mutant induced rapid defense responses and enhanced rice resistance to M. oryzae infection. Furthermore, exogenous treatment of MoAbfB protein showed inhibition of fungal infection via priming of defense gene expression. We later found that the extract of MoAbfB degraded rice cell wall fragments could also induce host defense activation, suggesting that not MoAbfB itself but oligosaccharides (OGs) derived from MoAbfB dissolved rice cell wall elicited rice innate immunity.