• Journal of Korean Society for Quality Management
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• v.30 no.4
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• pp.68-77
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• 2002

EM algorithm has good convergence rate for numerical procedures which converges on very small step. In the case of proportion estimation in a mixed distribution which has very big incomplete data or of update of new data continuously, however, EM algorithm highly depends on a initial value with slow convergence ratio. There have been many studies to improve the convergence rate of EM algorithm in estimating the proportion parameter of a mixed data. Among them, dynamic EM algorithm by Hurray Jorgensen and Titterington algorithm by D. M. Titterington are proven to have better convergence rate than the standard EM algorithm, when a new data is continuously updated. In this paper we suggest dynamic EM algorithm and Titterington algorithm for the estimation of a mixed Poisson distribution and compare them in terms of convergence rate by using a simulation method.

• Communications for Statistical Applications and Methods
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• v.29 no.3
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• pp.373-391
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• 2022

The distribution of observations in most econometric studies with spatial heterogeneity is skewed. Usually, a single transformation of the data is used to approximate normality and to model the transformed data with a normal assumption. This assumption is however not always appropriate due to the fact that panel data often exhibit non-normal characteristics. In this work, the normality assumption is relaxed in spatial mixed models, allowing for spatial heterogeneity. An inference procedure based on Bayesian mixed modeling is carried out with a multivariate skew-elliptical distribution, which includes the skew-t, skew-normal, student-t, and normal distributions as special cases. The methodology is illustrated through a simulation study and according to the empirical literature, we fit our models to non-life insurance consumption observed between 1998 and 2002 across a spatial panel of 103 Italian provinces in order to determine its determinants. Analyzing the posterior distribution of some parameters and comparing various model comparison criteria indicate the proposed model to be superior to conventional ones.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.110-115
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• 2000

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and an internal recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.112-118
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• 2000

Densification behavior of mixed copper and tool steel powder under cold compaction was investigated. By mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms of volume fractions and contact numbers of Cu powder new mixed yield functions were employed for densification of powder composites under cold compaction. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data for densificatiojn of mixed powder under cold isostatic pressing and cold die compaction. finite element calculations by using the yield functions mixed by contact numbers of Cu powder agreed better with experimental data than those by volume fractions of Cu powder.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.393-398
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• 2000

Densification behavior of mixed copper and tool steel powder under cold compaction was investigated. By mixing the yield functions originally proposed by Fleck-Gurson for pure powder, a new mixed yield functions In terms of volume fractions and contact numbers of Cu powder were employed in the constitutive models. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data. and with calculated results from the model of Kim et at. for densification of mixed powder under cold isostatic pressing and cold die compaction. Finite element calculations by using the yield functions mixed by contact numbers of Cu powder agreed better with experimental data than those by volume fractions of Cu powder.

• The Korean Journal of Applied Statistics
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• v.28 no.2
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• pp.353-360
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• 2015

Various statistical models have been proposed over the last decade for spatially correlated Gaussian outcomes. The spatial linear mixed model (SLMM), which incorporates a spatial effect as a random component to the linear model, is the one of the most widely used approaches in various application contexts. Employing link functions, SLMM can be naturally extended to spatial generalized linear mixed model for non-Gaussian outcomes (SGLMM). We review popular SGLMMs on non-Gaussian spatial outcomes and demonstrate their applications with available public data.

• International Journal of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.1-10
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• 2016

This paper considers WiMedia UWB network based wireless ship area network (WSAN) so as to support high-quality multimedia video data services and important shipboard control data. In this paper, prioritized contention access (PCA) and distributed reservation protocol (DRP) based on WiMedia UWB (ECMA-368) MAC protocols are combined and proposed to support mixed high-quality video traffic and shipboard control data traffic applying varying DRP and PCA data periods according to channel condition and link parameter ptimization. It is shown that the proposed dynmaic channel allocation of WiMedia UWB MAC protocol can provide reliable mixed video and shipboard control data traffic as well.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.5
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• pp.455-465
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• 2020

As cities continue to expand and additional underground structures are constructed, a policy is being planned to expand addresses, which are national framework data. In this study, the application scope of a proposed 3D (three-dimensional) mixed-use complex space for assigning 3D addresses was defined, based on past research on 3D address systems and by analyzing related laws. Underpass shopping malls, underground walkways (excluding underground shopping malls), and 3D mixed-use transfer centers with a gross floor area of 2,000㎡ or more are connected with each space by underground walkways or public paths. In addition, the detailed space corresponding to the public space of the 3D mixed-use complex space was presented and distinguished from the space to which the detailed address is assigned. The criteria for setting the road section were presented based on the intermediate space, which is a characteristic of 3D mixed-use complex spaces. The proposed criteria were applied to the Express Bus Terminal station (3D mixed-use transfer center) and COEX mall (underpass shopping malls). Thus, the road section was set for an unfamiliar 3D mixed-use complex space. However, by applying the proposed criteria to various 3D mixed-use complex spaces, additional and detailed criteria for different cases should be prepared.

• Communications for Statistical Applications and Methods
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• v.27 no.6
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• pp.701-714
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• 2020

Quantitative high throughput screening (qHTS) assays are used to assess toxicity for many chemicals in a short period by collectively analyzing them at several concentrations. Data are routinely analyzed using nonlinear regression models; however, we propose a new method to analyze qHTS data using a nonlinear mixed effects model. qHTS data are generated by repeating the same experiment several times for each chemical; therefor, they can be viewed as if they are repeated measures data and hence analyzed using a nonlinear mixed effects model which accounts for both intra- and inter-individual variabilities. Furthermore, we apply a one-step approach incorporating robust estimation methods to estimate fixed effect parameters and the variance-covariance structure since outliers or influential observations are not uncommon in qHTS data. The toxicity of chemicals from a qHTS assay is classified based on the significance of a parameter related to the efficacy of the chemicals using the proposed method. We evaluate the performance of the proposed method in terms of power and false discovery rate using simulation studies comparing with one existing method. The proposed method is illustrated using a dataset obtained from the National Toxicology Program.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.137-138
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• 2023

This study proposed the optimal mixing time for pre-mixed cement and post mixed cement using the statistical analysis method of box plots. Pre-mixed cement can prevent material seegregation, strength loss, and quality variation if mixed for at least 60 seconds, and the data median is shown to be within the box range. Post-mixed cement should be mixed for at least 180 seconds to prevent material segregation, strength loss, and quality variation, and compressive strength tends to increase with longer vibrating times. Therefore, it is suggested that using pre-mixed cement can shorten the vibrating time and increase the productivity of the concrete.