• 산업공학
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• 제25권4호
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• pp.441-449
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• 2012

Solar PV(photovoltaic) is paid great attention to as a possible renewable energy source to overcome recent global energy crisis. However to be a viable alternative energy source compared with fossil fuel, its market competitiveness should be attained. Grid parity is one of effective measure of market competitiveness of renewable energy. In this paper, we forecast the grid parity timing of solar PV energy in Korea using two factor learning curve model. Two factors considered in the present model are production capacity and technological improvement. As a result, it is forecasted that the grid parity will be achieved in 2019 in Korea.

• Journal of Information Technology Applications and Management
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• 제19권4호
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• pp.227-242
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• 2012

It is a daunting task to theorize the process effectiveness of IT convergence based service model. Despite the criticalness of investigating process enhancement impact of IT-convergence based service model, the theoretical research in this field is relatively scarce, possibly due to the too wide and comprehensiveness of research scope. In this vein, we conducted exploratory study to understand the contributional impact of IT convergence based service model on resolving service process limitations. We first identified five IT convergence based service models in the area of typical service industry, which include entertainment, learning, location based services, tourism, and healthcare. Our research model classified value creation factors of the IT convergence model in twofold. The one is defined as basic value creation factor of the IT convergence, which is treated as the second-order factor that consists of two first-order factors of mobile functionality and Internet with digital contents merging functionality. The other is defined as service process limitations resolving factor which are comprised with the two first-order factors of simultaneousity and perishability. Both the second-order factors are modeled, each respectively, with the two first-order factors in formative manner. Using PLS, empirical validation is executed to analyze each value creating factor's contribution impact on the relative advantage, as well as the mediating effect of basic value creation factor on resolving service process limitations. On the basis of the insights revealed from this paper, further theory building research could be elaborated in the area of IT convergence applications for service industry.

• 대한교통학회지
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• 제14권1호
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• pp.29-42
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• 1996

Among trip distribution models, The BPR type Gravity Model is the one which is the most widely used. The key issue associated with this model is a functional form of friction factor which should be calibrated in the process, and interpretation for socioeconomic factor known as K-factor(Kij) which is used to adjust the difference between observed zone-to-zone trips and the estimated trips. In this study, the BPR type Gravity Model has been fitted to 1990 O/D data for Seoul. Two type of function form for friction factor has been employed : one is a form of Generalized function and the orther is UTP function. With above two function, the parameters for travel distance(Skin-tree) are prepared. The relationship between socioeconomic factor and trips is identified by calculating and analyzing the characteristics of Kij. Consequently, both of the friction factor functions are statistically signified. However, it show an overestimation tendency when estimated with UTP function. It is found that the Generalized function is suitable for the city of Seoul, and also, in case there are a lot of trips correlatively, the socioeconomic factor is close to 1, on the other hand if it's small, it shows a bias which is dispersed around 1.

• Journal of the Korean Data and Information Science Society
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• 제15권2호
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• pp.339-345
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• 2004

This paper deals with a mixed logit model for ordered polytomous data. There are two types of factors affecting the response varable in this paper. One is a fixed factor with finite quantitative levels and the other is a random factor coming from an experimental structure such as a randomized complete block design. It is discussed how to set up the model for analyzing ordered polytomous data and illustrated how to estimate the paramers in the given model.

• Asia pacific journal of information systems
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• 제21권2호
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• pp.19-42
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• 2011

This paper proposes a new framework to predict decision performance by investigating the cognitive fit of decision makers. We assume that every decision maker has two kinds of schema: emotional and rational. Cognitive fit is believed to have a close relationship with the two schemata and decision performance. In the literature on decision performance there is few studies investigating the relationship between the two schemata and cognitive fit. Therefore, our research purposes are twofold: (1) to provide a theoretical basis for the proposed framework describing the causal relationships among the two schemata, cognitive fit. and decision performance, and (2) to empirically prove its validity in the application to an Internet shopping environment. Based on the questionnaires from 104 respondents, we used a second order, confirmatory factor analysis (CFA) model to extract valid constructs, and a structural equation model (SEM) to calculate path coefficients and prove the statistical validity of our proposed research model. The experimental results supported our research model.

• International Journal of Human Ecology
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• 제4권2호
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• pp.77-87
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• 2003

This paper tried to construct statistical and econometric models on the basis of economic theory in order to discuss the issue of statistical efficiency and unbiasedness including the sample selection bias correcting problem. Comparative analytical tool were one stage Tobit of Maximum Likelihood estimation and Heckman's two-step Tobit of Ordinary Least Squares. The results showed that the adequacy of model for the analysis on demand and choice, we believe that there is no big difference in explanatory variables between the first selection model and the second linear probability model. Since the Lambda, the self- selectivity correction factor, in the Type II Tobit is not statistically significant, there is no self-selectivity in the Type II Tobit model, indicating that Type I Tobit model would give us better explanation in the demand for and choice which is less complicated statistical method rather than type II model.

• Journal of the Korean Data and Information Science Society
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• 제16권4호
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• pp.1095-1106
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• 2005

When X and Y have independent two parameter exponential distributions, we develop a Bayesian testing procedures for the equality of two location parameters. The reference prior in non-regular exponential model is derived. Under this reference prior, we propose a Bayesian test procedures for the equality of two location parameters using fractional Bayes factor and intrinsic Bayes factor. Simulation study and some real data examples are provided.

• Journal of the Korean Data and Information Science Society
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• 제17권4호
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• pp.1329-1341
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• 2006

When X and Y have independent gamma distributions, we consider the testing problem for two gamma means. We propose a solution based on a Bayesian model selection procedure to this problem in which no subjective input is considered. The reference prior is derived. Using the derived reference prior, we compute the fractional Bayes factor and the intrinsic Bayes factors. The posterior probability of each model is used as a model selection tool. Simulation study and a real data example are provided.

• 설비공학논문집
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• 제21권3호
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• pp.140-148
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• 2009

Capillary tubes are widely used as expansion device in small refrigeration systems. The refrigerant flowing in the capillary tube experiences frictional and accelerational head losses and flashing simultaneously. In this paper flow characteristics of adiabatic capillary tubes were simulated with various friction factor models, two-phase viscosity models, and two-phase frictional multiplier models. The predicted pressure distribution and mass flow rate are compared with experimental data reported in literature. It is confirmed that the predicting accuracy with homogeneous model can be improved by employing suitable correlations of friction factor, two-phase viscosity and two-phase frictional multiplier.

• 한국과학교육학회지
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• 제17권4호
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• pp.481-492
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• 1997

The purpose of this study is to construct validity of Tripartite model of "Attitudes towards Science" using Exploratory and Confirmatory Factor Analyses. Exploratory and confirmatory factor analyses are two major approaches to factor analysis. The primary goal of factor analysis is to explain the covariances or correlations between many observed variables by means of relatively few underlying latent variables. In exploratory factor analysis, the number of latent variables is not determined before the analysis, all latent variables typically influence all observed variables, the measurement errors(${\delta}$) are not allowed to correlate, and unidentification of parameters is common. Confirmatory factor analysis requires a detailed and identified initial model. Confirmatory factor analysis techniques allow relations between latent and observed variables that are not possible with traditional, exploratory factor analysis techniques. As a result of exploratory factor analysis, tripartite model of "Attitudes towards Science" being composed of affection, behavioral intention and cognition is empirically identified. But attitude of science career being composed of affection and behavioral intention is identified. In validity test using confirmatory factor analysis, measurement structure of Tripartite model of "Attitudes towards Science" is not correspondent to data set. Because it is concluded that the object of attitudes are not specific.