• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.85-93
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• 2015

Previous studies have estimated crash prediction models with the fixed effect model which assumes the fixed value of coefficients without considering characteristics of each intersections. However the fixed effect model would estimate under estimation of the standard error resulted in over estimation of t-value. In order to overcome these shortcomings, the random effect model can be used with considering heterogeneity of AADT, geometric information and unobserved factors. In this study, data collections from 89 intersections in Daejeon and estimates of crash prediction models were conducted using the random and fixed effect negative binomial regression model for comparison and analysis of two models. As a result of model estimates, AADT, speed limits, number of lanes, exclusive right turn pockets and front traffic signal were found to be significant. For comparing statistical significance of two models, the random effect model could be better statistical significance with -1537.802 of log-likelihood at convergence comparing with -1691.327 for the fixed effect model. Also likelihood ration value was computed as 0.279 for the random effect model and 0.207 for the fixed effect model. This mean that the random effect model can be improved for statistical significance of models comparing with the fixed effect model.

• Journal of Technology Innovation
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• v.26 no.4
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• pp.29-56
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• 2018

The purpose of this research is to examine whether investment portfolio composition affects the technological performance of corporate venture capital (CVC). The stages of investment are categorized from "start-up/seed", "early", and "expansion", to "later" stage. We posit and test that the investment stage composition in a portfolio is highly correlated with the growth potential and downside risk of the portfolio, which in turn influences an investor's innovation performance. To test this hypothesis, we used negative binomial panel regression with 21 years of deal data from 70 cases of CVC. The results show that there is an inverted U shaped relationship between investment portfolio composition and technological performance. This means that the more seed or early stage investment within the investment portfolio, the higher the innovation performance; however, if the amount of seed or early stage investment is over a certain level, the performance decreases. Further, this study finds that the external partners of a venture negatively moderate the inverted U shaped relationship between portfolio composition and innovation performance. We believe that corporate planners, venture capitalists, and policy makers will be helped by these results showing that companies can maximize their investment performance by considering the investment stage and progress of investments.

• Journal of the Korean Regional Science Association
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• v.38 no.1
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• pp.3-20
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• 2022

The purpose of this study is to exploratory analyze the transition pattern of establishments and workers in new growth industries in the metropolitan area from 2010 to 2019 and to identify regional factors affecting the inflow and outflow of new growth industry start-ups. As for the analysis, the original data of the Census on Establishments were used, and spatial data at the sigungu level were constructed based on the inflow and outflow data of the number of new growth industry businesses and workers. For the analysis, the degree centrality of connection to outflow inflow by region was calculated, and an empirical analysis was conducted on regional-level factors affecting the inflow and outflow of new growth industries by applying a negative binomial regression model. According to the results, the new growth industry manufacturing sector was actively relocated in southern Gyeonggi Province, and the new growth industry service sector in Gangnam and Guro-Geumcheon-gu, and the impact of regional-level factors on the inflow and outflow of new growth industry start-ups varies depending on the industry. This study presented implications for regional industrial policies to improve the competitiveness of the local economy by attracting new industries by identifying spatial transition patterns for new growth industries and conducting empirical analysis to identify influencing factors.

• Journal of the Korean Regional Science Association
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• v.40 no.3
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• pp.95-108
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• 2024

This study analyzes the location determinants of newly established and relocated manufacturing firms in South Korea using the National Business Survey data from 2016 to 2019. Both new establishments and relocations are concentrated in the Seoul metropolitan area, Chungcheong, Yeongnam, and Daegyeong regions, with relocated firms showing a higher degree of spatial concentration. Employing a negative binomial regression model, we find that manufacturing concentration, population density, industrial diversity, and lower wage levels positively influence both new establishments and relocations. The proportion of highly educated workers, accessibility to producer services, and average land prices only positively affect the frequency of new establishments, suggesting that firms in the early stages of their life cycle, which are more dependent on human capital and producer services, demonstrate a higher willingness to pay for land use. Conversely, increased travel time to Seoul and improved transportation accessibility enhance the probability of attracting relocated firms. This implies that cost reduction incentives associated with distance from Seoul may outweigh the benefits of proximity to the capital in relocation decisions. Our findings suggest that strengthening agglomeration economies and improving transportation infrastructure efficiency could increase the likelihood of attracting relocated manufacturing firms to non-capital regions.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.101-108
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• 2012

This study deals with the traffic accidents of circular intersections in Korea. The goal of this study is to develop the traffic accident models using ZAM. The main results are as follows. First, in the case of 'violating the operational method of intersection', ZINB(zero-inflatednegative binomial) models were analyzed to be the best fit to the data. Second, in the case of' no maintaining the safe distance', ZINB models were also analyzed to be the best fit to the data. Finally, such the common variables as traffic volume and width of circular roadway were selected as the independent variables. The more traffic volume and the less width of circulatory roadway were evaluated to make the more accidents. Such the specific variables as the number of approach lanes and speed reduction facilities were selected as the explanatory variables. The more approach lanes and the less speed reduction facilities were evaluated to give the more accidents. This study might be expected to give some implications to the accident research on the circular intersections.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2829-2840
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• 2018

The random variable with an arbitrary value or more is called semi-continuous variable or zero-inflated one in case that its boundary value is more frequently observed than expected. This means the boundary value is likely to be practically observed more than it should be theoretically under certain probability distribution. When the distribution considered is continuous, the variable is defined as semi-continuous and when one of discrete distribution is assumed for the variable, we regard it as zero-inflated. In this study, we introduce the two-part model, which consists of one part for modelling the binary response and the other part for modelling the variable greater than the boundary value. Especially, the zero-inflated regression models are explained by using Poisson distribution and negative binomial distribution. In real data analysis, we employ the zero-inflated regression models to estimate the number of days under extreme heat-wave circumstances during the last 10 years in South Korea. Based on the estimation results, we create prediction maps for the estimated number of days under heat-wave advisory and heat-wave warning by using the universal kriging, which is one of the spatial prediction methods.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.111-116
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• 2012

This study deals with the traffic accidents of circular intersections in Korea. The purposes are to comparatively analyze the characteristics by operational type, and to develop the models using the data of 82 intersections. In pursuing the above, this study gives particular emphasis to modeling such the accidents as the roundabout and rotary in urban area. The main results analyzed are as follows. First, the null hypotheses that the number of accidents are the same in both the urban and rural intersections, and roundabout and rotary in urban area, were analyzed to be rejected. Second, 3 accident models were developed, which were all statistically significant. The independent variables used in the above models are the ADT, number of approach lane, bus stop, parking facilities, and others. This study could be expected to give some implications to the traffic safety policy decision-making.

• The Korean Journal of Applied Statistics
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• v.31 no.4
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• pp.475-484
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• 2018

Gamma generalized linear models are useful for non-negative and skewed responses. However, these models have received less attention than Poisson and binomial generalized linear models. In particular, hypothesis testing for the significance of regression coefficients has not been thoroughly studied. In this paper we assess the performance of various test statistics for gamma generalized linear models based on numerical studies. Our results show that the likelihood ratio test and F-type test are generally recommended and that the partial deviance test should be avoided in practice.

• Journal of Information Technology Services
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• v.10 no.4
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• pp.191-204
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• 2011

Recently, many software companies are trying to improve the software quality and project outcome with more costs and efforts in development time. In the software convergence and integration environments, it is required efforts to gain high quality of software. In other words, it is required to utilize software engineering knowledge and technology for higher software quality and better software project productivity. The Software development productivity can be varied by software process capability according to building a framework for software development, selection and use of appropriate technology, human resource management. Software process capability will influence software project outcome which is the general opinion. This study provides empirical evidence about software engineering efforts and investment approach to lead software project performance. We measured the software engineering efforts by SW engineering level and analyzed the corelation between software engineering level and schedule deviation. And, we verified that this performance is affected by the size of software company. As a result, software process capability is important to build a infrastructure and develop systematically software project. The higher software engineering level can lead to improved software project performance.

• Research in Community and Public Health Nursing
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• v.29 no.3
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• pp.279-289
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• 2018

Purpose: This study has been conducted to identify factors that influence the initiation of treatment after the diagnosis of Korean patients with HIV. Methods: A cross-sectional study design was used, and 290 patients with HIV from outpatient departments of 7 hospitals participated. Self-report questionnaires included items on the days from the primary diagnosis to the initiation of treatment, and the patients' demographic and disease related characteristics. Negative binomial regression model (NBR) was utilized to determine risk factors influencing the initiation of treatment after the diagnosis of the patients with HIV. Results: The skewness of days was 6.62, and the degree of asymmetry of distribution was severe. In NBR, patients who were in their 40s and 50s, female, unmarried and living with their family, jobless, in a middle or high level of economic status, and diagnosed before 2014 showed a higher risk of delayed treatment than patients who were younger, male, married and living with family, in a low level of economic status, and diagnosed in 2014 or afterwards. Conclusion: The findings suggest the necessity of intervention to promote HIV patients' early entry into treatment based on the participants' characteristics.