• Journal of Korean Society of Transportation
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• v.28 no.4
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• pp.129-139
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• 2010

This study proposes a model for measuring the connectivity of nodes in road networks. The connectivity index between two nodes is characterized by the number of routes, degree of circuitousness, design speed, and route capacity between the nodes. The connectivity index of a node is then defined as the weighted average of the connectivity indexes between the node and other nodes under consideration. The weighting factor between two nodes is determined by the travel demand and distance between them. The application of the model to a toy network shows that it reasonably well quantifies the level of connectivity of nodes in the network. If flow of rail networks can be measured in the same scale as that of road networks and the capacity of rail links can be estimated, the model proposed in this paper could be applied to intermodal transportation networks as well.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.461-470
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• 2018

Beyond river restoration focused on the inside region of main streams up to now, the river restoration including the outside region of streams has been started recently. As a part of this attempt, the restoration of abandoned rivers has been tried, but the development of a suitable model to quantitatively assess the improvement of hydraulic and ecological connectivity is not still satisfying. In this study, a grid - based hydraulic analysis model to evaluate the recovery of ecological connectivity through the restoration of abandoned rivers has been developed. In order to examine the applicability of this model, the ecohydaulic connectivity of the Cheongmi River Project area in Notap region was evaluated. This model can promptly and simply analyze the temporal and spatial distribution of the hydraulic and ecological characteristics, and it can be used as a appropriate tool to assess the hydraulic and ecological connectivity in the future.

• Journal of Korean Society of Transportation
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• v.28 no.3
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• pp.85-98
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• 2010

As transit networks are becoming more multimodal, the concept of connectivity of transit networks becomes important. This study aims to develop a quantitative model for measuring the connectivity of multimodal transit networks. To that end, we select, as evaluation measures of a transit line, its length, capacity, and speed. We then define the connecting power of a transit line as the product of those measures. The degree centrality of a node, which is a widely used centrality measure in social network analysis, is employed with appropriate modifications suited for transit networks. Using the degree centrality of a transit stop and the connecting powers of transit lines serving the transit stop, we develop an index quantifying the level of connectivity of the transit stop. From the connectivity indexes of transit stops, we derive the connectivity index of a transit line as well as an area of a multimodal transit network. In addition, we present a method to evaluate the connectivity of a transfer center using the connectivity indexes of transit stops and passenger acceptance rate functions. A case study shows that the connectivity evaluation model developed in this study takes well into consideration characteristics of multimodal transit networks, adequately measures the connectivity of transit stops, lines, and areas, and furthermore can be used in determining the level of service of transfer centers.

• The Korean Journal of Applied Statistics
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• v.29 no.6
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• pp.1129-1145
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• 2016

Functional neuro-connectivity is one of the main issues in brain science in the sense that it is closely related to neurodynamics in the brain. In the paper, we choose fMRI as a main form of response data to brain activity due to its high resolution. We review methods for analyzing functional neuro-connectivity assuming that measurements are made on physiological responses to neuron activation. This means that we deal with a state-space and measurement model, where the state-space model is assumed to represent neurodynamics. Analysis methods and their interpretation should vary subject to what was measured. We included analysis results of real fMRI data by applying a high-dimensional autoregressive model, which indicated that different neurodynamics were required for solving different types of geometric problems.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.383-389
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• 2011

Until now, in planning and constructing KTX and the Express Way, the connectivity and transfer between these facilities have not been considered. In this study the effect of mode choice behavior by connecting KTX and the Express Way is analyzed through estimating Multinomial Logit Model and Binary Logit Model. The SP and RP surveys to develop these models were carried out and the data were selected from the passengers using the KTX station, Express Bus Terminals and Rest Areas in the Express Way. To test the effect of connectivity and transfer in the field, the case study for Dongtan KTX station was carried out. According to the results, connecting the KTX station and the Express Way has the effect of increasing the demand by 30%. And this is caused by saving about 120 minutes of traveling time from Seoul to Pusan. This study shows that the connectivity and transfer can increase the efficiency of transportation system and the improvement in the mobility and accessibility will maximize the usages of these two facilities.

• Journal of Korean Society of Transportation
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• v.28 no.6
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• pp.167-177
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• 2010

This study proposes a methodology for assessing the improvement of network connectivity of transport hubs. Extending a previously developed model that measures the connectivity of a node in transportation networks, we define two quantities called the supplied connectivity and the experienced connectivity. Using these quantities, we provide a systematic procedure for analyzing the network connectivity of a transport hub and also suggest criteria for determining whether a given project is effective in improving the network connectivity of the transport hub. The application of the methodology to a test site produces reasonable results, and as such it is expected that the methodology can be used for various transport hubs in the national road network. Once enough data from the application of the methodology are accumulated, a further study on the level of service in terms of network connectivity needs to be followed.

• Journal of The Korean Association For Science Education
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• v.32 no.3
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• pp.524-531
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• 2012

Categorization is an important human function used to process different stimuli. It is also one of the most important factors affecting measurement of a person's classification ability. Explicit categorization, the representative system by which categorization ability is measured, can verbally describe the categorization rule. The purpose of this study was to develop a prediction model for categorization ability as it relates to the classification process of living organisms using fMRI. Fifty-five participants were divided into two groups: a model generation group, comprised of twenty-seven subjects, and a model verification group, made up of twenty-eight subjects. During prediction model generation, functional connectivity was used to analyze temporal correlations between brain activation regions. A classification ability quotient (CQ) was calculated to identify the verbal categorization ability distribution of each subject. Additionally, the connectivity coefficient (CC) was calculated to quantify the functional connectivity for each subject. Hence, it was possible to generate a prediction model through regression analysis based on participants' CQ and CC values. The resultant categorization ability regression model predictor was statistically significant; however, researchers proceeded to verify its predictive ability power. In order to verify the predictive power of the developed regression model, researchers used the regression model and subjects' CC values to predict CQ values for twenty-eight subjects. Correlation between the predicted CQ values and the observed CQ values was confirmed. Results of this study suggested that explicit categorization ability differs at the brain network level of individuals. Also, the finding suggested that differences in functional connectivity between individuals reflect differences in categorization ability. Last, researchers have provided a new method for predicting an individual's categorization ability by measuring brain activation.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.17-26
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• 2015

River corridors facilitate dispersal and movement and prevent local extinction of species. As a result of stream restoration projects, which include installation of waterfront and flood control structures, the number of animals, which rely on river corridor, is decreasing. For the study, factors affecting fish assembly were extracted by a species distribution model with the fish data collected from the Seom River in Hoengseong County and City of Wonju, Ganwon Province, Korea between March to October 2013. The riparian connectivity was assessed using species richness and rarity. According to result of the field survey, there were 38 species and 7,061 individuals for fish. The analysis suggests the following. Firstly, factors affecting fish richness in species distribution model results are shown to be velocity, riffle, riparian width, and water width. The accuracy of the model proves to be suitable with the correlation coefficient of 0.83 and MAPE of 19.2%. Secondly, the low rarity area is shown to be straight streams in Jeon river near to Hongseong County and the high rarity area to be streams with large width, existing alluvial area at channel junction between Jeon river and Seom river. Thirdly, according to connectivity results, areas where weirs are installed or riparian buffer area is removed showed low connectivity. The areas where farmland near riparian and forest areas showed high connectivity. The results of this study can be utilized to improve current facilities and enhance connectivity as a restoration guide.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.117-127
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• 2008

After the deregulation of the aviation market in the United States in 1978, airlines took advantage of the possibilities of the liberalized market and reorganized their networks. Then, the hub-and-spoke networks became widely used in the aviation market. The framework of hub-and-spoke network made it feasible to amplify flight networks. Thus, a number of airlines were able to fly to more destinations than ever before through the networks. Amplification of networks can be implementing through the transfer of passengers, transshipment of cargo, or both most researches have been concentrated on the passenger aspect at airports worldwide. Air cargo, however, has become one of the most significant areas at hub airports to keep their leading position in terms of the provision of services and handling volumes. This paper investigates the connectivity of airfreight networks as the temporal concentrations in current network at Incheon International Airport. In order to evaluate airline flight schedule effects to stimulate hubbing at an airport, the indirect connectivity can be considered to be the number of direct frequencies, the minimum connecting times and the quality of the connection determine indirect connectivity. Therefore the connectivity of freight transshipment depends on both the quality of the connection at the hub airport and the quality of the indirect flight compared to the direct flight. In addressing these issues, this paper analyzes the connectivity of flight schedules using a temporal wave-system structure and estimates the degree of connectivity and quality of connectivity applying the NETSCAN model.

• Journal of Korea Port Economic Association
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• v.39 no.4
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• pp.269-283
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• 2023

Based on daily data from January 4, 2016 to September 27, 2022, the impact of extreme movements of BDI on shipping companies' network connectivity was analyzed using CoVaR network connectivity. The main results and policy implications are as follows. First, according to the copula model results, the Student-t copula was selected as the most suitable model for COSCO, HMM, HRAG, MAERSK, and WAN. EVER was selected as a time-varying Gumbel copula, and YANG was selected as a time-varying rotated-Gumbel copula. Second, as a result of analysis using the TVP-VAR model, the linkage between shipping companies tended to increase when the BDI turned into an extreme risk state. In the comparison of net connectivity, the roles of COSCO and EVER changed. In addition, in the analysis of net pairwise connectivity, it was found that the change in the extreme risk state of BDI also affected the connectivity of shipping companies. In particular, EVER, WAN, and COSCO showed large changes. Taken together, the extreme fluctuations in BDI changed the role of Asian shipping companies, intensifying competition among shipping companies and strengthening risk delivery. It was confirmed that BDI has a great influence on the network connectivity of shipping companies and has an important influence on the stability of the stock market network. Therefore, the results of this study should consider not only the connectivity of shipping companies according to market conditions, but also the connectivity in extreme situations.