• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.297-303
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• 2016

This paper introduces auxiliary power supply systems (APS) for railroad applications and proposes a new power conversion structure for highly-efficient and lightweight APS systems. The proposed structure focuses on an improvement of the power density in APS. It eliminates unnecessary power conversion stages in the conventional APS structure by modulating the dc/dc converter circuit and the structure of the system. The dc/dc converter circuit used in the proposed structure is based on a multi-level half-bridge converter, a widely used topology in railroad APS applications; a flying capacitor is newly added to the conventional circuit. The added capacitor is used not only to enhance the soft switching condition of the switches, but also so that the new pantograph will have a side voltage source of a battery charger in the APS structure. Since the battery charger uses the pantograph side voltage source in the proposed structure, rather than using the output of the main dc/dc converter in the conventional structure, the size and efficiency of the main dc/dc converter are reduced and increased, respectively. To verify the effectiveness of the proposed structure, simulation results will be presented with metropolitan transit APS specifications.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.1
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• pp.65-72
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• 2012

With the development of MEMS, small and low-priced sensors integrating IMU and GPS have produced and exploited for diverse field. In this research, we have judged that MEMS-based IMU/GPS sensor is suitable for light-weighted mobile mapping system and carried out experiments to analyze the characteristics of MTi-G, which was developed from XSens company. From a sensor which fixed to dashboard, coordinates results with no post-processing were achieved for test area. On the whole, the results show satisfactory performances but some errors also were discovered from parts of the road due to sensor properties, XKF characteristics and GPS reception environment. We could confirm the potential of light-weighted mobile mapping system. Experiments considering various GPS reception environments and road condition and more detailed level of accuracy analysis will be performed for further research.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.370-375
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• 2011

In this paper, as a follow-up PRT studies of "J. Lee & K. Kim[2]", in terms of public transportation systems, economic feasibility of PRT systems was investigated. Based on previous studies, PRT demand was estimated and the required number of PRT vehicles has been calculated and the benefit was estimated. To ensure the economic feasibility, construction cost of a PRT system should be the level of 8 billion won per km, and the annual operating costs of the PRT system construction should be approximately 4.63% level. As a result, how much to reduce PRT construction costs, depending on whether decisions are considered to be economically feasible. Thus, PRT technology development will be conducted by targeting the most lightweight and by minimizing the infrastructure and vehicles of PRT.

• Composites Research
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• v.33 no.6
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• pp.360-364
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• 2020

Although research and development of existing steel-made Cowl Cross Member(CCM) was carried out with magnesium and plastic to make vehicles lighter, it is difficult to apply them to performance problems in the vehicle's mounting condition. Recently, the company is conducting research on the injection CCM of the composite insert as a lightweight component that is most suitable for mass-production of automotive parts. This is a manufacturing process that inserts composite injection bracket parts into aluminum bar, and the adhesion of the two parts is one of the important factors considering the vehicle's mounting conditions. In this study, the joint strength of Aluminum bar is one of the important factors as a study for the injection of aluminum bar into PA6-GF60 composite material. For the analysis of these research, the method of spraying adhesive to the aluminum bar and the case of knurling treatment have been analyzed and the bonding strength of the direction of rotation and lateral direction has been analyzed for each part between the aluminum bar of the cowl cross member and the shape of the injection component of composite materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.457-463
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• 2016

The newly developed super ductile duplex stainless steel (SDSS) has good strength and ductility, and it can be used to reduce weight and improve the fabrication efficiency of a carbody of a rolling stock. In this study, spot weldability tests were conducted to take advantage of SDDSS in a carbody for an intermodal tram. Specimens of various thickness (0.4 to 5.0 mm) were prepared to find the proper welding conditions, and tensile load tests were conducted to evaluate the tensile-shear strength of spot welded joints. Then, nugget diameters were measured to verify the quality. The tensile-shear strength was found to be proportional to the heat parameter. It was verified that the tensile-shear strengths and nugget sizes of the joints satisfy the standard requirements. The overall weldability tests confirmed that SDDSS can be used effectively for the carbody of an intermodal tram.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.158-164
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• 2015

The main mission of OTM(On-The-Move) satellite communication system is to provide satellite communication service while moving on a vehicle. So it should have a capability to maintain a reliable communication channel when it travels at high speeds or in a severe fluctuation region. This paper presents a small-sized multi-mode monopulse structure applicable to OTM satellite communication system which has only single mode-coupler with a pair of slot using a feature of circular polarized received signal. And tracking error signal is defined using fundamental and high-order modes.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.46-54
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• 2014

The hollow design of a railway axle is one of the most effective methods to reduce the weight of an axle. However, the conventional hollow axle has the limitation of a lightweight design because it has the same bore diameter along the axial position. The new type of railway axle, the tapered inner surface railway axle, has a different inner diameter between the journal bearing seat and wheel seat. This design method is one way to increase the weight reduction possibility. The purpose of the present study is to establish and evaluate the design of the tapered inner surface railway axle. The case study and Finite Element Method(FEM) are applied to evaluate the strength of the lightweight railway axle according to the European Norm(EN 13103). Finally, the best design case for reducing the weight of the axle is drawn from the results of the case study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1559-1565
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• 2013

This study aims to investigate the dynamic interaction characteristics between Maglev vehicles and an elevated guideway. A more detailed model for the dynamic interaction of the vehicle/guideway is proposed. The proposed model incorporates a 3D full vehicle model based on prototyping, flexible guideway by a modal superposition method, and levitation electromagnets including the feedback controller into an integrated model. The proposed model was applied to an urban transit Maglev developed for a commercial application to analyze the dynamic response of the vehicle and guideway, and the effect of the surface roughness of the rail, mid-span guideway deflections, and air gap variations are then investigated from the numerical simulation.

• Composites Research
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• v.36 no.3
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• pp.186-192
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• 2023

Recently, in the field of railway vehicles, interest in the use of composite materials for weight reduction and transportation efficiency is increasing. Accordingly, research and commercialization development to apply composite materials to various vehicle parts are being actively conducted, and evaluation is conducted centering on post-measurement such as mechanical performance evaluation of finished products to verify quality when composite materials are applied. However, the analysis of heat and stress generated during the molding process of composite materials, which are factors that greatly affect manufacturing quality, is insufficient. Therefore, in this study, in order to verify the molding quality of composite parts for railway vehicles, the molding quality analysis was conducted for the two types of composite interior panels (laminate panel and sandwich panel) that are most actively used. To this end, temperature and strain changes were monitored during the molding process by using an FBG fiber optic sensor, which is easy to apply to the inside of the composite, and the residual strain value generated after molding was completed was measured. As a result, it was confirmed that overheating and excessive residual stress did not occur, thereby verifying the excellent molding quality of the composite interior panel for railway vehicles.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.41-47
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• 1994

본 공에서는 3회에 걸쳐 7000계열을 중심으로 하여 알루미늄 합금의 용접특성을 용접방법, 각종 결함과 대책, 시효경화와 응력부식균열 등으로 나누어 기술하였다. 7000계열의 고강도 알루미늄 합금은 수송기기 분야의 최대 기술적 과제인 연비개선과 고속화 실현을 해결할 수 있는 차량 차체의 경량소재로 수요가 증가하고 있다. 또한 거의 완벽한 재활용이 가능하여 환경문제로 인한 물자 재활용의 계속적인 요구를 해결할 수 있어 그 잠재성은 매우 크다. 그러나 현재 국내에서는 7000계열 등 고강도 알루미늄 용접의 기술수준이 선진국에 비해 떨어지기 때문에, 이에 대한 기술개발에 보다 많은 관심을 기울어야 할 것으로 사료된다.