• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.273-276
• /
• 2005

Performance analysis of a solid oxide fuel cell/micro gas turbine hybrid system is conducted at design-point and part-load conditions and its results are discussed in this study. With detailed considerations of the heat and mass transfer phenomena along various flow streams of the SOFC, the analysis based on a quasi-2D model reasonably predicts its performance at the design-point operating conditions. In case of part-load operations, performance of the hybrid system to three different operation modes(fuel only control, speed control, and VIGV control) is compared. It is found that the simultaneous control of both supplied fuel and air to the system with a variable MGT rotational speed mode is the optimum choice for the high performance operation. And then, the dynamic characteristics of a solid oxide fuel cell are briefly introduced.

• Journal of Korean Society of Transportation
• /
• v.4 no.1
• /
• pp.12-27
• /
• 1986

This study examined user preferences toward transportation modes in Seoul. Two multidimensional scaling models, the ideal point and vector models, were applied to data on mode preferences of 114 adults in the metropolitan area. While both models produced fairly similar results, the vector model performed slightly better than the other in terms of interpretability of the results. The transport attributes elicited are comfort, flexibility, travel cost, travel time, privacy, and safety; among which comfort is salient most. The comfort variable is a multi-faceted attribute in nature. The variations of attribute preferences are most significant between the gender groups as well as worker/nonworker groups. In particular, male workers, female workers and female nonworkers form three distinctive market segments. An unidimensional scaling of the preference data reveals that subway, auto-driver, and subscription bus modes are preferred most, whereas motorcycle and bicycle least. The other modes of express bus, taxt, auto-passenger, bus and walk rank intermediately. An examination of how preference orders vary among modal groups hints that users align their stated attitudes to their choice in order to reduce cognitive dissonance.

• Journal of the Korean Data and Information Science Society
• /
• v.28 no.6
• /
• pp.1271-1278
• /
• 2017

Although the $L_0$-penalty is the most natural choice to identify the sparsity structure of the model, it has not been widely used due to the computational bottleneck. Recently, the adaptive ridge procedure is developed to efficiently approximate a $L_q$-penalized problem to an iterative $L_2$-penalized one. In this article, we proposed to apply the adaptive ridge procedure to solve the $L_0$-penalized weighted support vector machine (WSVM) to facilitate the corresponding optimization. Our numerical investigation shows the advantageous performance of the $L_0$-penalized WSVM compared to the conventional WSVM with $L_2$ penalty for both simulated and real data sets.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.146-148
• /
• 1998

For the shape design of electromagnetic devices using the FEM, the choice of design parameters influence to the success of the optimization process. If the design parameter distribution has a one to one corespondence with finite element model, we can encounter not only serious accuracy problem but also obtain a zigzag shape along the interface. The nodes between those design parameters can be parameterized by interpolating using one among many interpolation methods. The conventional parameterization of design parameters has a limit of application for shape, because design parameters and movable nodes are linearly intepolated. In this paper, using the B-spline curve that use to present any interfaces in computer graphics, the curvilinear parameterization between design parameters and node points is compared with the linear parameterization.

• Journal of Korean Society of Transportation
• /
• v.27 no.1
• /
• pp.143-155
• /
• 2009

A dynamic traffic assignment (DTA) has recently been implemented in many practical projects. The core of dynamic model is the inclusion of time scale. If excluding the time dimension from a DTA model, the framework of a DTA model is similar to that of static model. Similar to static model, with given exogenous travel demand, a DTA model loads vehicles on the network and finds an optimal solution satisfying a pre-defined route choice rule. In most DTA models, the departure pattern of given travel demand is predefined and assumed as a fixed pattern, although the departure pattern of driver is changeable depending on a network traffic condition. Especially, for morning peak commute where most drivers have their preferred arrival time, the departure time, therefore, should be modeled as an endogenous variable. In this paper, the authors point out some shortcomings of current DTA model and propose an alternative approach which could overcome the shortcomings of current DTA model. The authors substitute a traditional definition for time-dependent OD table by a new definition in which the time-dependent OD table is defined as arrival time-based one. In addition, the authors develop a new DTA model which is capable of finding an equilibrium departure pattern without the use of schedule delay functions. Three types of objective function for a new DTA framework are proposed, and the solution algorithms for the three objective functions are also explained.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.12 no.4
• /
• pp.49-57
• /
• 2012

With regard to the culture in cities this study aims to essential understanding and systematic approach to the culture. The "2011 Seoul Survey"report has been used to find out causality among the related variables. In the first place 'satisfaction of cultural condition' was operationally selected as a dependent variable for regression. For the purpose of controlling confounding factors for ceteris paribus effect correlation analysis was done between the dependent variable and all other variables respectively, which resulted in two groups of variables: group (1) - 6 variables of very significant correlations(p-value<0.01) and (2) - the other 6 variables of significant correlations(p-value<0.05). Then hierarchical regression was adopted to these 2 groups to analyse $R^2$ increment, statistical significance of independent variables, and multicollinearity(VIF; variance inflation factor). At last a regression model specified by group (1) as independent variables(they are 'social trust', 'satisfaction of walking condition', 'happiness index', 'preparation against old age', 'satisfaction of traffic condition' and 'hours for internet') shows that only 'social trust' variable has statistically significant and substantially strong effect on 'satisfaction of cultural condition.' This finding should be accepted on the following understanding; (1) urban culture has a collective attribute formed between people and society, (2) culture is somewhat telling and hearing stories and the confidence between tellers and hearers is essential in the mutual response and (3) stimulus is received by relationship in company with sense, emotion, thinking and action. In spite of restrictive external validity this finding can be used as a direction for promoting culture and a basis for related policy choice in cities.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.13 no.4
• /
• pp.51-60
• /
• 2013

With regard to urban culture this study aims to essential understanding and systematic approach to the culture. The "2012 Seoul Survey" report has been used to find out causality among the related variables. In the first place 'satisfaction of cultural condition' was operationally selected as a dependent variable for regression. For the purpose of controlling the third factors for ceteris paribus effect correlation analysis was previously done between the dependent variable and all other variables respectively, which resulted in two groups of variables: group (1) - 2 variables of very significant correlations(p-value<0.01) and (2) - the other 6 variables of significant correlations(p-value<0.05). Then hierarchical regression was adopted to these 2 groups to analyse statistical significance of independent variables, and multicollinearity(VIF; variance inflation factor). Additionally to OLS robust and bootstrapping regressions were done to confirm the validity of this model specification. At last a regression model specified by group (1) as independent variables(they are 'community spirit caring for women, the disabled, the poor and the old,' 'satisfaction of bicycle riding condition' shows that the variables have statistically significant and substantially strong effect on 'satisfaction of cultural condition.' This finding implies the following understanding; (1) urban festivals are regarded as the main of the urban culture as of now and this results from the low level of today's culture, (2) culture is telling and hearing stories but the influential relationship between urban culture and community spirit on the weak is negative, which says that the cultural perception among citizen is somewhat selfish and far from the essential understanding of the urban culture. In spite of restrictive external validity this finding can be used as a direction for promoting culture and a basis for related policy choice in cities.

• The Korean Journal of Applied Statistics
• /
• v.36 no.2
• /
• pp.115-127
• /
• 2023

Multinomial probit model is a popular model for multiclass classification and choice model. Markov chain Monte Carlo (MCMC) method is widely used for estimating multinomial probit model, but its computational cost is high. However, it is well known that variational Bayesian approximation is more computationally efficient than MCMC, because it uses subsets of samples. In this study, we describe multinomial probit model with Gaussian process classification and how to employ variational Bayesian approximation on the model. This study also compares the results of variational Bayesian multinomial probit model to the results of naive Bayes, K-nearest neighbors and support vector machine for the UCI mice protein expression level data.

• The Korean Journal of Food & Health Convergence
• /
• v.9 no.3
• /
• pp.1-9
• /
• 2023

Nowadays, with the development of the internet and e-commerce, opening tea shops online has become an increasing choice for selling tea. However, the product page information of many online tea shops cannot effectively attract consumers, resulting in their profits being compromised. To investigate this, we conducted this paper and hope to provide effective suggestions. This paper is based on 229 questionnaires and selects the product page information of online tea shops as the research object. Using the four dimensions of perceived value theory as independent variables with consumer purchase intention as the dependent variable. A structural equation model was constructed to analyze the role of the perceived value of product page information in online tea shops how influencing consumers' purchase intentions. It was found that information on the perceived functional value of online tea shops did not have a significant positive effect on consumer purchase intentions. However, information on the perceived monetary value, perceived social value, and perceived emotional value of online tea shops had a significant positive impact on consumers' purchase intentions. Based on the above conclusions, online tea shops should focus on the expression of product page information to enhance the level of consumers' perceived value of tea products, thereby enhancing their intention to purchase tea products.

• Korea journal of population studies
• /
• v.33 no.2
• /
• pp.33-59
• /
• 2010

This paper intends to find the determinants of the occupational aspirations of college students in Korea. According to Wisconsin model, the occupational aspiration of youth has a statistically significant influence on his or her actual education level and occupation choice implying that the more motivated with high-level occupational aspiration will obtain the higher level of occupation. The analysis for this study is based on the survey of undergraduate students' perception, attitude and lifestyle in Korea 2004, which was conducted against 1,947 respondents, and multiple regression model was utilized. The dependent variable for occupational aspirations was measured by the Standard International Occupational Prestige Scale (SIOPS) of Donald J. Treiman. Independent variables include social capital and cultural capital as well as demographic variables, socio-economic status, and human capital variables. Social capital variable was measured by the position generator scale of Nan Lin and Mary Dumin, and cultural capital variable was done to our original index. This study shows that social and cultural capitals are factors having significant influence on occupational aspiration, in addition to the well-known factors such as gender, human capital and the occupation of father.