• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.1055-1067
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• 2017

Most previous works to study for the depression of the disabilities in Korea have analyzed the repeated measured data of each individual under the mutually independent assumption. In this study, Korea Welfare Panel data of the disabilities surveyed additionally every three years are analyzed to detect the significant exploratory variables by the linear mixed models. A suitable correlation matrix is considered for the dependency of repeated measurement of each individual. The random effect to reflect the characteristics of the individuals as well as the fixed effect is included in the fitted linear mixed model. By the residual plot of the fixed effect model, the problem that the averages of residuals of each individual do not seem to be around zero is described. Further, the residual plot and the Q-Q plot coming from the selected final model are shown that the problem is modified well.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.2
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• pp.169-174
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• 2010

A meta-analysis was conducted to summarize the results of studies which have described the profiles of hormones during the oestrous cycle in buffalo using a fixed effect model and a random effect model. Plasma progesterone concentrations were lowest (0.30${\pm}$0.06 ng/ml) during the peri-oestrous phase and increased (p = 0.067) through the early luteal phase to a maximum concentration (1.94${\pm}$0.03 ng/ml) during the mid-luteal phase. Circulating plasma inhibin and estradiol concentrations were lowest (0.31${\pm}$0.01 and 11.04${\pm}$0.13 ng/ml) during the mid-luteal phase, increased through the late luteal phase to maximum concentrations (0.44${\pm}$0.02 and 22.48${\pm}$0.32 ng/ml) during the peri-oestrous phase. Plasma FSH concentrations were lowest during the early luteal phase and increased through the mid-luteal phase to a maximum concentration during the peri-oestrous phase. Peripheral prolactin concentrations were lowest during the late luteal phase and increased to a maximum concentration during the peri-oestrous phase which then declined (p = 0.716) during the early luteal phase. Peripheral plasma cortisol concentrations decreased from 2.68${\pm}$0.14 ng/ml during the early luteal phase to 1.43${\pm}$0.27 ng/ml during the mid-luteal phase (p<0.001) which then increased to 2.06${\pm}$0.17 ng/ml during the late luteal phase. Plasma $T_{5}$ concentrations decreased from the late luteal phase to the peri-oestrous phase (p<0.001) which then increased during the early luteal phase. $T_{4}$ concentrations increased from the late luteal phase to the peri-oestrous phase which then decreased during the early luteal phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.221-230
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• 2021

In this study, a firm's internationalization level was measured as the ratio of foreign sales to total sales (FSTS) of individual firms. A demonstration was conducted with several control variables that affect the persistence of the firm's profits using the Sloan (1996) model as a proxy for its primary relationship between net profit and the next profit. An empirical analysis of the end-December settlement firms listed on the securities market from 2011 to 2016 was conducted using a fixed-effect model to confirm that the persistence of the firm's internationalization and accounting profits was positive at the 1% significant level, indicating that the persistence of the firm's profits also increased as the level of individual firm's internationalization increased. In addition, the firm size, financial soundness, cash accompanying, growth, and investment ability, consistent with forecasts, represented a statistically significant (+) relationship with globalization. These results suggest that firms can maintain and expand their value stably by securing new overseas markets and promoting growth by implementing internationalization strategies.

• Communications for Statistical Applications and Methods
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• v.29 no.3
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• pp.353-371
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• 2022

This paper analyzes death counts after World War II of several countries to identify and to compare their stochastic structures. The stochastic structures that this paper entertains are three structural time series models, a local level with a random walk model, a fixed local linear trend model and a local linear trend model. The structural time series models assume that a time series can be formulated directly with the unobserved components such as trend, slope, seasonal, cycle and daily effect. Random effect of each unobserved component is characterized by its own stochastic structure and a distribution of its irregular component. The structural time series models use the Kalman filter to estimate unknown parameters of a stochastic model, to predict future data, and to do filtering data. This paper identifies the best-fitted stochastic model for three types of death counts (Female, Male and Total) of each country. Two diagnostic procedures are used to check the validity of fitted models. Three criteria, AIC, BIC and SSPE are used to select the best-fitted valid stochastic model for each type of death counts of each country.

• International Commerce and Information Review
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• v.9 no.4
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• pp.439-460
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• 2007

The purpose of this paper is to study on export factor of Korean into China by 31 Province and City. Using the panel data on Korean export factor in China for the years 1998-2005, we examined the factors determinants of import in China(by region)from Korean firms. This study based on Gravity Model to extend and fixed & random effect Model. The result of analysis is as follows : The effect of significant on Import from Korean is FDI from Korea, export into world, import from world, population in region. But per GRDP, consumption, FDI into world variable is statistically insignificant. Also coastal region variable is not a clear.

• Journal of Korea Technology Innovation Society
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• v.21 no.1
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• pp.385-419
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• 2018

This study suggests an integrated model composed of factors of industrial environments and technology capacity for corporate diversification decision based on industrial organization theory and resource based perspectives. We examine the proposed model using patents and financial data of 272 applicants for 6 years (2010~2015) in the smart factory ICT convergence technology (application and platform field) sectors. The result of analyzing the fixed effect panel model shows that technological competitiveness has a positive effect on corporate diversification. Also, the additional result of analyzing the two-stage least square fixed effect model indicates that the convergence patent ratio increases technological competitiveness. Based on the results, we provide implications for corporate diversification strategies and government R & D policies for commercialization of corporate convergence technology resources and competencies.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.425-439
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• 2011

A review of the development history of interatomic potential models for ionic materials was carried out paying attention to the way of future development of an interatomic potential model that can cover ionic, covalent and metallic bonding materials simultaneously. Earlier pair potential models based on fixed point charges with and without considering the electronic polarization effect were found to satisfactorily describe the fundamental physical properties of crystalline oxides (Ti oxides, $SiO_2$, for example) and their polymorphs, However, pair potential models are limited in dealing with pure elements such as Ti or Si. Another limitation of the fixed point charge model is that it cannot describe the charge variation on individual atoms depending on the local atomic environment. Those limitations lead to the development of many-body potential models(EAM or Tersoff), a charge equilibration (Qeq) model, and a combination of a many-body potential model and the Qeq model. EAM+Qeq can be applied to metal oxides, while Tersoff+Qeq can be applied to Si oxides. As a means to describe reactions between Si oxides and metallic elements, the combination of 2NN MEAM that can describe both covalent and metallic elements and the Qeq model is proposed.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.131-139
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• 1993

The newly proposed model of the future reliability results in earlier fault-fixes having a greater effect than the fault which make the greatest contribution to the overall failure rate tend to show themselves earlier, and so are fixed earlier. The suggested model allows a variety of reliability measures to be calculated. Predictions of total execution time(debugging time) is to achieve a target reliability. This model could also apply to computer-hardware reliability growth resulting from the elimination of design error and fault.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.299-306
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• 2018

Changes in demographic and economic conditions affect corporate strategy, labor market and social welfare. The purpose of this study is to examine the effects of changes in population and economic situation on library use and to examine the income effect of library use. In order to achieve the purpose of this study, we analyzed the 10 year fixed library of public library statistics and statistical census data from 2008 to 2017 using the panel fixed effect model using the data of regional gross production and unemployment rate. And the changes in the economic and demographic characteristics of the region are used to confirm the regularity of the relationship between the changes in the usage situation of the libraries belonging to a certain region and the changes in the economic and demographic conditions in the respective regions. As a result of the analysis, the changes in the economic environment did not significantly affect the number of visitors to the library and the number of library users, but it was an important factor in the number of borrowers. This study is significant in that it shows how the economic environment changes affect the library. The result of this study is expected to be a theoretical basis for establishing the service policy of public libraries.

• Journal of the Korea Society of Computer and Information
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• v.20 no.3
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• pp.47-56
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• 2015

Automated detection of interesting web pages could be used in many different application domains. Determining a user's interesting web pages can be performed implicitly by observing the user's behavior. The task of distinguishing interesting web pages belongs to a classification problem, and we choose white box learning methods (fixed effect logit regression and support vector machine) to test empirically. The result indicated that (1) fixed effect logit regression, fixed effect SVMs with both polynomial and radial basis kernels showed higher performance than the linear kernel model, (2) a personalization is a critical issue for improving the performance of a model, (3) when asking a user explicit grading of web pages, the scale could be as simple as yes/no answer, (4) every second the duration in a web page increases, the ratio of the probability to be interesting increased 1.004 times, but the number of scrollbar clicks (p=0.56) and the number of mouse clicks (p=0.36) did not have statistically significant relations with the interest.