• The KIPS Transactions:PartD
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• v.16D no.6
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• pp.945-960
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• 2009

The purpose of this study is to define determinants of VoIP user acceptance and to verify significant causality among latent variables - performance expectancy, effort expectancy, cost expectancy, social influence, facilitating conditions, behavioral intend, use behavior - based on UTAUT model. We presented the expanded hypotheses including the new factor, cost expectancy and analyzed the moderating effect of user age, gender and usage experience variables. For a accuracy of predicted results, we focused on survey analysis with 641 real user samples. Compared to previous studies, it is meaningful that this research verified the conceptual difference between behavioral intention and usage behavior. As a result, all proposed hypotheses accepted and moderating effects are supported significantly in age and use experience moderating variables.

• Proceedings of the KOR-KST Conference
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• 1999.03a
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• pp.95-109
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• 1999

기존의 추정된 화물 수요모형은 화물의 출하특성과 관련된 설명변수를 중심으로 추정되었으며, 이에 따라 수송수단 선택 과정에서 화주가 느끼는 실제의 인식 상황을 모형내에 적절히 반영하지 못하였다. 본 연구는 기존 연구가 갖는 한계점을 극복하고자 화주가 수송수단을 선택할 때 느끼는 인식상황을 모형 내에 적용시켜 수단 선택 특성을 분석하였다. 연구대상은 우리나라의 188개 제조업체에서 화물자동차로 출하한 내수용 화물이며, 연구의 범위도 현실 운송체계 내에서 화주의 수단선택 행태를 설명하는 단기간의 예측으로 제한하였다. 모형추정결과 우리나라의 공로화물수송을 해석하기 위해서는, 출하중량까지를 고려한 다항로짓모형 형태이면서 인식 요소를 행태변수로 추가한 모형을 이용하는 것이 가장 적절하다는 결론을 내렸다. 그리고 이에 따라 주요한 설명 변수들의 탄력성과 화주의 인식 요소에 대한 특성값을 분석하여 제시하였다. 연구결과는 활용성 측면에서 직접 활용이 가능한 것과 잠재적인 변화를 예측하는데 이용되는 것으로 구분된다. 먼저 직접활용이 가능한 것은 수송수단과 관계된 변수들을 해석하여 얻는데, 수송비용과 수송시간에 대한 계수값의 크기와 부호, 그리고 탄력성은 정부의 정책부서나 운송인의 계획수립에 직접 적용된다. 다음으로 화주의 인식 요소는 잠재적인 변화를 예측하는데 이용되며 각 요소가 갖는 탄력성 및 특징은 운송인의 고객관리 기준이된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.2
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• pp.47-56
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• 2020

Decline of pine forests happens in Korea due to various disturbances such as insect pests, forest fires and extreme climate, which may further continue with ongoing climate change. For conserving and reestablishing pine forests, understanding climate-induced future shifts of pine tree distribution is a critical concern. This study predicts future geographical distribution of Pinus densiflora, using Maximum Entropy Model (MaxEnt). Input data of the model are locations of pine tree stands and their environmental variables such as climate were prepared for the model inputs. Alternative future projections for P. densiflora distribution were conducted with RCP 4.5 and RCP 8.5 climate change scenarios. As results, the future distribution of P. densiflora steadily decreased under both scenarios. In the case of RCP 8.5, the areal reductions amounted to 11.1% and 18.7% in 2050s and 2070s, respectively. In 2070s, P. densiflora mainly remained in Kangwon and Gyeongsang Provinces. Changes in temperature seasonality and warming winter temperature contributed primarily for the decline of P. densiflora., in which altitude also exerted a critical role in determining its future distribution geographic vulnerability. The results of this study highlighted the temporal and spatial contexts of P. densiflora decline in Korea that provides useful ecological information for developing sound management practices of pine forests.

• Journal of the Korean Geographical Society
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• v.38 no.6
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• pp.949-960
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• 2003

The marginal implicit price of air quality can be measured by taking a partial derivative of hedonic price function (HPF) with respect to the level of air quality. It has been pointed out that the size of the marginal implicit price varies with the use of different function forms, different estimation methods, and the different ways of measuring air quality level in estimating HPF. In addition to these factors, this study shows theoretically and empirically the way housing properties are represented on a digital map could differentiate the size of marginal implicit price of air quality when GIS is used to measure location attributes of the housing properties in the Korean apartment market. Furthermore, this study shows that the degree of difference in the marginal implicit price due to the manner in which housing properties are represented on a digital map can be larger than the degree of difference in the marginal implicit price due to using different function forms and estimation methods. The major implication from the results of this study is that one should carefully try diverse ways of representing housing properties in the Korean apartment market on a digital map in the process of estimating HPF, as he or she usually tries diverse function forms and estimation methods, to see if the value of the marginal implicit price of air quality varies substantially.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.939-945
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• 2014

In most of mobility enhancing plans for the transportation disabled, decisions for the investment priorities are firstly made by the facilities that have lower installation rate or lower satisfaction rate; the decisions are made without analyzing the importance factor (path loading factor) between the facility installation rate and the satisfaction rate together. In this study, a novel method of finding causality between the exogenous latent variables and the endogenous latent variables is provided by using the Structural Equation Model (SEM). The results show that the most influential facilities for the transportation disabled are bus stops, crosswalks and sidewalks in order. Also, a curb height around bus stops, a smoothness of sidewalks and installation of crosswalks traffic light are identified as an important facilities for the Transportation disabled.

• Journal of The Korean Association For Science Education
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• v.37 no.1
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• pp.113-123
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• 2017

The purpose of this study is to investigate engineering students' attitude toward convergence and relevance with engineering education accreditation, gender, and academic year and attitude toward convergence. To be specific, fist, we examined whether the instrument for measuring attitudes toward convergence were reliable and valid for engineering students. Second, we compared levels of attitudes toward convergence in terms of engineering education accreditation, gender and academic year. Third, latent classes, which were distinguished in terms of attitudes toward convergence, were identified. Participants were 2076 engineering students. By using factor analysis and Rasch analysis, validity and reliability of instrument measuring attitudes toward convergence were confirmed. The differences in attitude toward convergence in terms of engineering education accreditation experience, gender, and academic year were examined by independent t-test and ANOVA. There were significant differences in attitude towards convergence in terms of engineering education accreditation, gender, and academic year. Students who experience engineering education accreditation program and male and high academic year have higher levels of attitude toward convergence than others. Lastly latent class analysis (LCA) was conducted to identify subgroups underlying engineering students in terms of attitude toward convergence and five latent classes were identified. In addition, the chi-square results showed that there were significant relationships between identified latent classes and engineering education accreditation, gender, and academic year. Based on these results, engineering education considering students' characteristics and diversity in attitude toward convergence were discussed.

• Survey Research
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• v.10 no.3
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• pp.37-58
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• 2009

The purpose of this study were to identify the subgroups (i.e., latent classes) depending on early adolescents' change patterns in aggression and to test the effects of individual-background variables on determining the latent classes. For these goals, we applied Nagin's(1999) semi-parametric group-based approach to the Korean Youth Panel Study. Results showed that four latent classes were identified, which could be defined based on the patterns as low-level group, increasing group, intermediate-level group, and high-level group. By adding gender, self-control, parent attachment, teacher attachment, and the number of delinquent friends to the unconditional latent class model, we tested the effects of the variables on the latent classes. Multinomial logit analysis showed that gender, self-control, teacher attachment, and the number of delinquent friends were significant determinants of the latent classes. Findings from this study suggest the need to consider heterogeneity in the study of early adolescents' aggression to facilitate more refined targeting of intervention program.

• Journal of Korea Game Society
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• v.9 no.3
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• pp.107-119
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• 2009

Online games belong to a technology-oriented service industry that has emerged from the assimilation of game contents and communication networks in the respective realms of culture technology (CT) and information technology (IT). This study examines the individual acceptance of online games as entertainment-oriented technology based on the belief-attitude-intention paradigm and the underlying hedonic and utilitarian motivations. To measure the latent variables influencing the acceptance process, a structured questionnaire was developed based on the existing Technology Acceptance Model. Research model analysis and hypothesis testing were carried out using a structural equation model. Results indicated that latent variables reflecting hedonic and utilitarian characteristics had a significant influence on user behavior in the acceptance of online games. By uncovering the core factors in! fluencing the acceptance of online games and thereby theoretically verifying the latent variables influencing the acceptance of entertainment-oriented technology, this study provides strategic implications for business models by game companies aimed at attracting a large user base and dominating the market.

• Journal of Labour Economics
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• v.38 no.1
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• pp.1-30
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• 2015

The aggregate matching function is estimated to explain dynamics among job seekers, vacancies and new hires in Korea. Due to measurement errors inherent in vacancies data, I introduce a latent variable for job openings and use the instrumental variables to correct its endogeneity. Matching efficiency is also estimated using some explanatory variables like job seekers' characteristics and public employment services. The result shows that Korea's matching function also exhibits a constant returns to scale.

• The Korean Journal of Applied Statistics
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• v.33 no.1
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• pp.25-46
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• 2020

This paper presents ordinal probit semiparametric regression models using Bayesian Spectral Analysis Regression (BSAR) method. Ordinal probit regression is a way of modeling ordinal responses - usually more than two categories - by connecting the probability of falling into each category explained by a combination of available covariates using a probit (an inverse function of normal cumulative distribution function) link. The Bayesian probit model facilitates posterior sampling by bringing a latent variable following normal distribution, therefore, the responses are categorized by the cut-off points according to values of latent variables. In this paper, we extend the latent variable approach to a semiparametric model for the Bayesian ordinal probit regression with nonparametric functions using a spectral representation of Gaussian processes based BSAR method. The latent variable is decomposed into a parametric component and a nonparametric component with or without a shape constraint for modeling ordinal responses and predicting outcomes more flexibly. We illustrate the proposed methods with simulation studies in comparison with existing methods and real data analysis applied to a Korean National Health and Nutrition Examination Survey (KNHANES) 2016 for investigating nonparametric relationship between smoking behavior and coffee intake.