• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.145-153
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• 2008

This study proposes a facility location model in consideration of spatial coverage and travel cost as an effort to make objective and effective decisions of natural gas filling stations. The proposed model is developed for fixed stations and consists of two stages. The first stage employs a heuristic algorithm to find a set of locations which satisfy the spatial coverage constraints determined by the maximum travel distance between the filling stations and bus depots. In the second stage, the optimal location of filling stations is determined based on the minimum travel cost estimated by using a modified transportation problem as well as the construction and maintenance costs of the filling stations. The applicability of the model is analyzed through finding the optimal location of filling stations for the city of Anyang, a typical medium-sized city in metropolitan Seoul, based on the demand of natural gas buses. This study is expected to help promote the spread of natural gas buses by providing a starting point of a objective and reasonable methodological perspective to address the filling station location problem.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1835-1847
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• 2011

After conducting demonstration of transportation card for bus from Godeok-dong to Sangil-dong in 1996, due to continuously support for public transportation, the transportation card utilization of metropolitan public transportation passengers is currently going beyond 90%. In the current situation, transportation information system is mainly focused on road operation and control, offer of real time information and research of transportation information system using transportation card data which is differentiated by previous transportation information system is needed to study. This paper compare and analyze transportation information system, which is being used to each country, based on foreign examples of activating use of transportation card then introduce figure of advanced transportation information system which provide decision making feature for improving policy and institution of public transportation based on transportation card data, scientific analysis of passenger information, information of demand forecasting, variation and so on for constructing new route.

• Journal of Power Electronics
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• v.17 no.2
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• pp.490-500
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• 2017

Fuel cell (FC) is a promising power supply in electric vehicles (EV); however, it has poor dynamic performance and short service life. To address these shortcomings, a super capacitor (SC) is adopted as an auxiliary power supply. In this study, the frequency decoupling control method is used in electric vehicle energy system. High-frequency and low-frequency demand power is provided by SC and FC, respectively, which makes full use of two power supplies. Simultaneously, the energy system still has rapidity and reliability. The distributed power system (DPS) of EV requires DC-DC converters to achieve the desired voltage. The stability of cascaded converters must be assessed. Impedance-based methods are effective in the stability analysis of DPS. In this study, closed-loop impedances of interleaved half-bridge DC-DC converter and phase-shifted full-bridge DC-DC converter based on the frequency decoupling control method are derived. The closed-loop impedance of an inverter for permanent magnet synchronous motor based on space vector modulation control method is also derived. An improved Middlebrook criterion is used to assess and adjust the stability of the energy system. A theoretical analysis and simulation test are provided to demonstrate the feasibility of the energy management system and the control method.

• Journal of Urban Science
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• v.6 no.2
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• pp.29-34
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• 2017

Although the supply of public parking lots in major cities is steadily increasing, there is still a shortage of parking spaces that take into account the characteristics of actual available parking spaces. These parking problems are caused by conflicts between users, illegal occupation and privatization of roads, interference with traffic roads, and business stagnation in commercial areas and illegal parking problems. In addition, despite various parking demand management policies and continuous supply of public parking facilities, the solution to the parking problem is uneasy due to increased construction costs and changes in social conditions. In order to solve this problem, it was judged that it would be necessary to utilize the existing public parking lots efficiently. Therefore, we collect the variables expected to affect the turnover, and use multiple regression models. The results are summarized as follows. Firstly, public parking lots can be classified into four types using utilization rate and turnover rate. Secondly, influencing factors are found including index of public transportation usage convenience, index of illegal parking, and land use characteristics in central commercial district. Thirdly, it was shown that there was little impact by the size of public parking lots, separation distance to subway distance, separation distance to bus stops, transfer zone, residential zone, and second-rated lots by parking costs. Finally, it is found that public parking lots can be improved by proving accessibility of public transit, enforcement of illegal parking, active approaches supporting public parking lots. It is also recommended that public parking cost rating system based mainly on land use characteristics should be remedied and rearranged.

• Journal of Korean Society of Transportation
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• v.32 no.4
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• pp.389-400
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• 2014

This study finds a way to increase the usability of a subway commuter pass. Usability of the commuter pass on a probabilistic statistical model is calculated when the pass is allowed to used in a different mode(bus). A sunk cost of commuter pass is used to reduce the vehicle travels from public transit. 324 people aged 25 to 35 were surveyed and utilized to build a Nested Logit Model on STRADA 3.5 platform. Main results are as follows. First, commuter passes were issued in various forms. Second, the model turns out to be statistically significant in four explanatory variables (discount rate, inter-usablity between modes, forms of payment and periods). Lastly, the more valid on different modes, the more increased of the rail commuter pass.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.3
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• pp.181-189
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• 2001

The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.

• 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 Electrical Engineering and Technology
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• v.4 no.1
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• pp.55-65
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• 2009

Due to the rapid increase of electricity demand, consideration of environmental constraints in optimal power flow (OPF) problems is increasingly important. In Algeria, up to 90% of electricity is produced by thermal generators (vapor, gas). In order to keep the emission of gaseous pollutants like sulfur dioxide (SO2) and Nitrogen (NO2) under the admissible ecological limits, many conventional and global optimization methods have been proposed to study the trade-off relation between fuel cost and emissions. This paper presents an efficient decomposed Parallel GA to solve the multi-objective environmental/economic dispatch problem. At the decomposed stage the length of the original chromosome is reduced successively and adapted to the topology of the new partition. Two subproblems are proposed: the first subproblem is related to the active power planning to minimize the total fuel cost, and the second subproblem is a reactive power planning design based in practical rules to make fine corrections to the voltage deviation and reactive power violation using a specified number of shunt dynamic compensators named Static Var Compensators (SVC). To validate the robustness of the proposed approach, the algorithm proposed was tested on the Algerian 59-bus network test and compared with conventional methods and with global optimization methods (GA, FGA, and ACO). The results show that the approach proposed can converge to the near solution and obtain a competitive solution at a critical situation and within a reasonable time.

• Journal of Korean Society of Transportation
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• v.31 no.5
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• pp.79-88
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• 2013

Recently, due to THE MOBILITY ENHANCEMENT FOR THE MOBILITY IMPAIRED ACT, local governments have tired to make various efforts on special transport services(STS), low-flow bus, and installing elevator in subway stations for handicapped people. But in case of STS, insufficient numbers of taxi are raised against the increasing demand of hadicapped people due to the limited budget. This study investigated actual use condition of STS and characteristics of selection of handicapped people on Duribal. In addition, an ordered-logistic model was employed for developing taxi use prediction model considering taxi fare discounts for diverting Duribal demands to taxies. The results can be a significant basic data for transportation policies to improve travel efficiency of the handicapped.

• Journal of Korean Society of Transportation
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• v.34 no.4
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• pp.330-340
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• 2016

The main objective of study was to analyze the effectiveness of transit mall. To this end, this study compared operational status of transit malls in operation (Daegu, Seoul and Busan). For the city of Busan where the latest transit mall became operational in 2015, a discriminant model was proposed to determine user satisfaction/dissatisfaction. The outcomes of comparative study showed that each city has different operational focus - Seoul has focus on traffic demand management, Busan has focus on walking environment, and Daegu has focus on accessibility to public transportation. Also, the discriminant model indicated that market sentiment, convenience of bus service, traffic accident risk, number of pedestrian, market user number have effects on user satisfaction. These results implied that, to improve user satisfaction, measures for market revitalization such as opening events and forming consultative groups need to be prepared and traffic conditions should also be improved through expansion of curfew time, linkage with subway station.