• 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 the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.63-73
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• 2015

In the end to end data transfer protocols, it is very important to correctly estimate available bandwidth. In UDT (UDP based Data Transfer), receiver estimates the MTR (Maximum Transfer Rate) of the current link using pair packets transmitted periodically from sender and, then sender finally decides the MTR through EWMA (Exponential Weighted Moving Average) algorithm. Here, MTR has to be exactly estimated because available bandwidth is calculated with difference of MTR and current transfer rate. However, when network is congested due to traffic load and where competing flows are coexisted, it bring about a severe fairness problem. This paper proposes a congestion degree based MTR estimation algorithm. Here, the congestion degree stands a relative index for current congestion status on bottleneck link, which is calculated with arriving intervals of a pair packets. The algorithm try to more classify depending on the congestion degree to estimate more actual available bandwidth. With the network simulation results, our proposed method showed that the fairness problem among the competing flows is significantly resolved in comparison with that of UDT.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.3-11
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• 2015

An advanced receiver which can manage inter-cell interference is required to cope with the explosively increasing mobile data traffic. 3rd Generation Partnership Project (3GPP) has discussed network assisted interference cancellation and suppression (NAICS) to improve signal-to-noise-plus-interference ratio (SINR) and receiver performance by suppression or cancellation of interference signal from inter-cells. In this paper, we propose the advanced receiver based on soft decision to reduce the interference from neighbor cell in LTE-Advanced downlink system. The proposed receiver can suppress and cancel the interference by calculating the unbiased estimation value of interference signal using minimum mean square error (MMSE) or interference rejection combing (IRC) receiver. The interference signal is updated using soft information expressed by log-likelihood ratio (LLR). We perform the system level simulation based on 20MHz bandwidth of 3GPP LTE-Advanced downlink system. Simulation results show that the proposed receiver can improve SINR, throughput, and spectral efficiency of conventional system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.2
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• pp.43-57
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• 2021

The Forward Collision Warning, a representative technology of the Advanced Driver Assistance Systems, was selected as the target technology. The cognitive response time, deceleration, and impact were selected as the measures of effectiveness. And the amount of change with and without the Forward Collision Warning was measured. The experimental scenarios included a sudden stop event (1) of the vehicle in front of the driver and an event (2) in which the vehicle intervened in the next lane. All experiments were divided into day and night. As a result of the analysis, response time and the deceleration rate decreased when the forward collision warning system was installed. It was analyzed that the driver's risk situation could be detected quickly and the number of front-end collisions could be reduced as a result. Reflecting the driver's operating habits and diversifying the experimental scenarios will increase the installation effectiveness of ADAS and be used to estimate the effectiveness of other technologies.

• Korean System Dynamics Review
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• v.8 no.2
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• pp.51-82
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• 2007

The purpose of this paper is exploring changes in land use pattern when considering environmental carrying capacity. A sustainable development requires a society to define sustainability constraints, environmental carrying capacity. Environmental carrying capacity can be defined as a level of human activity a region can sustain at a desired level of quality of environment. This concept of environmental carrying capacity can be applied to land use to explore sustainable land use pattern. Since land use pattern can affect environment in an important way, exploring sustainable land use pattern within the limit of environmental carrying capacity can suggest useful implications for a sustainable regional management and planning. For this purpose, this paper built the environmental carrying capacity land use model and applied it to the Metropolitan Area, Korea. System dynamics modeling methods was used to build the model. The model developed in this paper consisted of 6sectors; population, housing, industry, land, environment, and traffic sector. The model limits its main focus on the NO2 level as an indicator of quality of environment in Metropolitan Area. Box model was translated into system dynamics model and combined to urban dynamics model to estimate NO2 level, the maximum number of population, industry structure, housing and maximum amount of land use for industrial, housing, and green space that can sustain desirable NO2 level. Metropolitan area was divided into 16 areas and the model was applied to each area. Since NO2 is flowing in and out from each area, model was built to allow this transboundering nature of air pollutants. Based on the model estimation, several policy implications for a sustainable land use pattern was discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.73-80
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• 2004

Recently, many maritime accidents have been increased and the collisions due to human error are given a great deal of proportions out if them We develop the Real-time Collision Risk Monitoring System (CRMS) for the navigational officers to cope with the emergency situation promptly and thus to reduce the probability if casualty. In this study, the risk of collision is evaluated by two kinds if method. The first method is based on Fuzzy algorithm, which evaluates the risk of collision between traffic ships. The second method is based on Environmental Stress (ES) Model, where the total risk if collision is evaluated by the environmental stress felt by human. The developed real-time CRMS has been installed to the ship handling simulator system and its capabilities have been tested through simulator experiments.

• Journal of Korean Society of Transportation
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• v.29 no.4
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• pp.65-71
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• 2011

It is practically hard to measure vehicle fuel consumption required to evaluate the energy-related governmental policies and traffic management strategies; the existing methods are too simplified due to the limited field data available. Existing methods are even unable to reflect the amount of fuel consumed when vehicles accelerate and decelerate, and such technical limitations have reduced the quality of the policy evaluation. This study proposes a new fuel consumption model that simultaneously considers the effects of both cruising speed and acceleration/deceleration of vehicles. A new fuel consumption model was developed based on the simulation data generated by AVL Cruise, a vehicle simulation program. The estimated by the proposed model was compared against the one from the existing method. Comparison results showed that the proposed model provided much reliable estimate (fuel consumption) than the other did.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1549-1556
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• 2016

By increased moving speed of aircraft, estimating location of itself becomes more important than ever. This requirement is satisfied by appearance of GPS, however it is useless when signal reception from satellite is not good enough by interruption, for example, traffic jamming. Applying link for communication to additional positioning system is capable of providing relative position of aircraft. Estimating location with link for communication is done without additional equipment but with signal processing based on correlation of received signal. ESPRIT is one of the representative algorithm among them. Estimating correlation matrix is possible to have error since it includes average operation needs enough number of samples not impractical. Therefore we propose algorithm that defines, estimates and removes error matrix of correlation. Proposing algorithm shows better performance than previous one when transmitters are close.

• Journal of Urban Science
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• v.6 no.2
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• pp.59-72
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• 2017

Studies on the calculation of accident costs include the approach on calculating damage costs covering all accidents regardless of first or secondary party and the one calculating damage costs generated by a single victim. These two approaches have a limitation of considering a subject for costs analysis as a single entity. In addition, research on estimating the interaction effects caused in the relationship between diverse traffic accident features and factors remains inadequate since most studies focused on calculating costs incurred in a single entity such as a victim, damaged building, or social organization in charge of managing car accident. This study intends to identify the expected range of old age where a specific interaction effect would remain, compare accidents between old age section and the entire age section, and discover an exogenous variable to be applied in accident drop effects in senior people and reduced benefits by calculating and testing additional accident costs in case the first party and the second party all pertain to the senior age section. By classifying the entire accidents caused by old drivers according to the types of cars, significant coefficients representing the influence that affects car accidents according to the characteristics are calculated and set them as the representative variables by selecting top variable in accordance with from low to high order. Furthermore, characteristics on five age groups such as a group of over 65 and less than 70, a group of over 70 and less than 75, a group of over 75 and less than 80, a group of over 80 and less than 85, and a group of over 85 are elicited and compared them with these preselected accident characteristics variables, thereby identifying what changing effects come out.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.173-174
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• 2010

As the quantity of goods transported, port industry and inland transport industry have developing to transport 630million ton goods annually. And the inland transport industry consists of ground transport for almost 80% of total transported goods. But, ground transport causes some serious problems especially the emission of greenhouse gases from trucks. According to issue "global warming", many regulations and agreements with countries in the world are becoming necessary and it is being fulfilled now. It is sure that Korea will have duty to reduce CO2 emission from 2013. Thus inland transport must cut off CO2 emission level. Therefore this paper will address that the calculation of CO2 emission under route of transportation container from six major container ports in Korea. And then, it will predict CO2 emission of inland transport industry according to increasing container traffic rate at ports.