• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.97-103
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• 2015

To achieve the safety and reliability, RAMS activity for a railway signal system of Near Surface Transit is studied. In this paper, preliminary hazard analysis in RAMS activities is studied for the railway signal system of Near Surface Transit. Preliminary hazard analysis is done through automatic train protection, automatic train operation and automatic train supervision. The hazards are defined, then causes and consequence for each hazard are defined. The total 75 preliminary hazards are classified. For high severity hazards are changed to acceptable level by upgrading of system requirement specification.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.1042-1048
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• 2016

This paper presents a lateral displacement restoring force control for the independently rotating wheelsets (IRWs) of shallow-depth subway systems. In the case of the near surface transit, which has recently been introduced, sharp curved driving performance is required for the city center service. It is possible to decrease the curve radius and to improve the performance of the straight running with the individual torque control. Therefore, the individual torque control performance of the motor is the most important point of the near surface transit. This paper deals with a lateral displacement restoring force control for sharp curved driving. The validity and usefulness of the proposed control algorithm is verified by experimental results using a small-scale bogie system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.766-771
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• 2016

This study examined the long-term durability of PC boxes, which was manufactured by low-carbon eco-friendly concrete using an alternative binder to cement and alternative fine aggregate to sand and microwave heat curing system to reduce the construction cost of a near-surface transit system. Based on the test results, the initial compressive strength of microwave heat cured concrete was higher than that of the steam cured concrete, but those were similar in the long-term age. In addition, there was no significant difference between the two curing conditions in the chemical resistance and the freeze-thawing resistance, and the chloride ion penetration level of the concrete cured by two methods was very low. Therefore, low-carbon eco-friendly concrete and microwave heat curing technology are expected to contribute to the economic construction of a near-surface transit system, and reduce carbon dioxide emissions and environmental impact.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.51-58
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• 2014

This paper presents a fire exposure test result to evaluate fire resistance capacity of retrofit method using FRP (Fiber Reinforced Polymer) in reinforcement concrete structure. Especially, this paper focused on near-surface-mounted retrofit method; FRP is mounted into the groove after making a groove in concrete. In the test, main parameters are retrofit method and materials for fire proofing. Spray type of perlite and board type of calcium silicate were considered as external fire proof on surface while particle of calcium silicate and polymer mortar as internal one in groove. By increasing the temperature of inside heating furnace, the transfer of temperature from surface of fire proofing material to groove in specimen was measured. As a result, fire proofing using the board of calcium silicate was more effective to delay the heat transfer from outside than spraying with perlite. It was found that the fire proofing could resist outside temperature of $820^{\circ}C$ at maximum to keep the temperature of epoxy below glass transit temperature (GTT).

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.261-269
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• 2015

To overcome the weaknesses of viaduct bridges and the non-economic efficiency of underground LRT, the study of near-surface railway systems is in progress. To apply a box structure to the low depth transit, a connection joint to precast modules are very important when applying precast modular structures to replace temporary structures. In this study, wall to wall connections were applied in diverse cases such as rebar connections, guiding structures that were used to fit the verticality of precast walls during construction, and non-reinforcement structures used only for waterstop. Experimental performance verification was carried out for the bending, shear and splitting of the wall to wall connection. Precision of construction joints between wall to wall was identified as a factor that influenced the structural performance of the precast wall. A structure that can serve as a guide during the vertical insertion of a wall is confirmed for the most suitable case, but it will be necessary to modify this structure for detailed cases.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.163-168
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• 2013

The maintenance of an urban transit vehicle accounts for 60-70% of total costs over its entire life cycle, so it is critical to reduce maintenance costs and extend the life times of urban transit EMUs (electric multiple units) through research. For these researches, the reliability and availability data management system was constructed through the case study of several industries in the domestic and international in the field of reliability centered maintenance system. And we created a system to manage reliability and availability data for use in urban-EMU maintenance. In this work, we identified the major functions needed to successfully develop the system. Here we report the successful development of a reliability and availability data management system for maintenance of urban transit vehicles.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.459-467
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• 2016

Recently, new open-cut modular construction method, which is built within a 5~7m depth below the road, was proposed for the near-surface transit system to ensure the economic feasibility of underground structures. In this paper, the precast modular construction method was developed for the low-cost and rapid construction of underground structures. For the experiment on the flexural performance of the modular slab connections, a total of eleven specimens were fabricated according to the test variables; section shape, joint type, lap length, and transverse reinforcement. The test results were compared with those of the specimens without loop joints. To verify the performance of the slab connections, the 4-point loading tests of precast RC members with loop joints were conducted. As a result of the test, the flexural performance of the half-depth specimens with a 200mm lap length of loop joints were confirmed to be similar to those of the specimens without joints.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3587-3595
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• 2015

Low-carbon eco-friendly precast concrete (PC) box structure has been recently was developed as an low-cost infrastructure of near-surface transit system. The concrete of PC box was manufactured by industrial byproducts such as ground granulated blast furnace (GGBF) slag, flyash and rapid-cooling electric arc furnace (EAF) oxidizing slag, its mechanical property and durability were estimated in this study. Based on the mechanical and durability tests, it is found that low-carbon eco-friendly concrete shows high initial compressive strength, more than 90% of design strength (35MPa), and high resistance to salt-attack, chemical- attack and freeze-thaw. Therefore, low-carbon eco-friendly PC box concrete technology is expected to contribute to the railway with low environmental impact.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.640-645
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• 2015

Near surface transit system has should be constructed as installation cost of light rail transit with elevated track. So, distance between two substations is longer than conventional system. The long feeding distance results in severe voltage drop. This paper proposes a PWM rectifier instead of diode rectifier. The PWM rectifier has some advantages. This is able to control output voltage constantly to reduce voltage drop and to use regeneration power without additional inverter. This paper analyse on improved voltage profile and cost of substation with PWM rectifier. The analysis of voltage profile use PSIM, and the installation cost of substation with PWM rectifier is compared to substation with diode rectifier.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2255-2262
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• 2015

Recent study about near-surface is proposed to overcome non-economic of underground railway and to reduce people's complaints of ground elevated railway. In this report, precast modular structure system replacing temporary facilities is applied to ensure the construction ability and economic feasibility. To verify the performance of connection joint between permanent structural wall and upper slab, loading test is carried out. As a result of the test, wall replacing temporary structure to slab connection is possible to transfer bending moment. By 30% increase of bending resistant performance for connection joint using coupler, coupler connection joint is more advantageous to resist bending moment compared to channel connection.