• Journal of Korea Port Economic Association
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• v.37 no.4
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• pp.127-144
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• 2021

The purpose of this study is to derive service factors based on the "Rail Statistical Yearbook" data of railroad service providers from 1990 to 2019, and to analyze the effect of the service factors on the operating profit ratio(OPR), a representative management performance variable of railroad transport service providers. In particular, it has academic significance in terms of empirical research to evaluate whether the management innovation of the KoRail has changed in line with the purpose of establishing the corporation by dividing the research period into the first period (1990-2003) and the latter (2004-2019). The contents of this study investigated previous studies on the quality of railway passenger transportation service and analyzed the contents of government presentation data related to the management performance evaluation of the KoRail. As an empirical analysis model, a research model was constructed using OPR as a dependent variable and service factor variables of infrastructure, economy, safety, connectivity, and business diversity as explanatory variables based on the operation and management activity information during the analysis period 30 years. On the results of research analysis, OPR is that the infrastructure factor is improved by structural reform or efficiency improvement. And economic factors are the fact that operating profit ratio improves by reducing costs. The safety factor did not reveal the significant explanatory power of the regression coefficient, but the sign of influence was the same as the prediction. Connectivity factor reveals a influence on differences between first period and latter, but OPR impact direction is changed from negative in before to positive in late. This is an evironment in which connectivity is actually realized in later period. On diversity factor, there is no effect of investment share in subsidiaries and government subsidies on OPR.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1080-1084
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• 2011

Urban maglev should have such characteristics as not only environmentally friendliness and excellent driving capability but also curve negotiation performance because its routes have many sharp curves. Due to normal mechanism of urban maglev its relative displacements of secondary spring are bigger than conventional railway vehicle and the centering force of levitation magnet is smaller than wheel-on-rail system. These features of maglev affect the curving negotiation and so the additional steering device is to be required on Urban maglev to improve the running performance at sharp curve of less than about R50m. Some developed urban maglev had the passive steering device which consists of mechanical linkage or hydraulic cylinder and closed-route piping. But it has drawback as complexity of layout of understructure of vehicle and functional limitation of passive mechanism regarding transient curve. These demerits could be solved by using active steering system. But it has a weak point that an active device should have actuators and additional inverter or hydraulic power source. In this paper, the semi-active steering system for urban maglev is to be introduced.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.439-445
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• 2003

Since 1960s. container shipping volume has increased dramatically and continuous on a trend of rapid growth, and so the number of containers handled at the port increases. In order to improve yard crane operating efficiency, the precise position measurement of the yard crane is important. This paper describes the method to measure the absolute position of yard crane using the output pulse of an encoder and infrared sensors. The crane position is calculated by counting the output pulse of an incremental encoder, which is mounted on the wheel in the crane. By the way, the wheel slippage on rail may cause some errors in crane position information obtained from encoder pulses, and the errors in the crane position information are compensated with infrared sensors. The performance of proposed method is verified on experimental results with the simulator of yard crane, the size of which is about 1/10 with the real crane.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.32-37
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• 2011

Biodiesel fuel is already remarkable alternative fuel in many countries. So, many studies are performed on the environmental or economic effects as well as the characteristics of diesel engine fueled biodiesel in combustion and emission. In this study, an CRDI diesel engine used to commercial vehicle was fueled with diesel fuel and 20% biodiesel blended fuel (BDF 20%) with city mode in excess of 300 hours. Engine dynamometer testing was completed at regularly scheduled intervals to monitor the engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. To check the engine parts (valve and injector), the engine was inspected after test. It was concluded that there were no unusual deteriorations of the engine, or any unusual changes in engine power and exhaust emissions in spite of operation of 300 hours with BDF 20%.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.83-88
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• 2013

Recently, PCCI (premixed charge compression ignition) combustion is studied to reduce both NOx and PM because of homogeneous mixture formation and lower combustion temperature. It has also merit of increasing thermal efficiency owing to better air-fuel mixure. However, it is well known that PCCI combustion has a weakness in fuel economy because PCCI combustion tends to start before TDC. Therefore, it is necessary to find an optimal conditions for PCCI combustion which maintains reduction of NOx, PM and increase of thermal efficiency. In this study, pPCCI combustion was realized by adding early injection strategy to a conventional diesel engine. In addition, the characteristics of pPCCI combustion was analized by comparing conventional diesel injection strategy. The results show that NOx and PM per power in pPCCI combution were reduced compared to a conventional diesel combustion.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2411-2418
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• 2017

This study focuses on the effects of using open stator slots in an interior permanent magnet traction motor with a magnetic slot wedge design in order to increase the power density at its base speed. In addition, such a configuration reduces the torque ripple under field-weakening conditions. Five different wedge models were selected, each of which was evaluated using a finite element analysis (FEA). Based on the initial model, we designed magnetic slot wedges for maximum back-EMF and minimum cogging torque. In addition, the d-q axis inductance was slightly altered due to the magnetic slot wedges. Finally, we analyzed the performance of a traction machine under field weakening control. Moreover, we have outlined the requirements for an ideal magnetic slot wedge design.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.288-295
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• 2006

In this study, dynamic behavior of the vehicles is analyzed, while the track is subjected to lateral vibrations due to earthquake and blasting load. A computer program(WERIA, Wheel Rail Interaction Analysis) is used, which can simulate dynamic responses of vehicles subjected to lateral vibrations. The analysis considers two types of vehicles: I.e. power cars of KTX and Busan subway train. It can also consider the interaction with sub-structures such as tracks and soil. The creep force module is considered, and the running safety of railway vehicles subjected to earthquake and blasting loading is studied. Based on the results of this study, the running safety of the vehicles can be confirmed against lateral vibration.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.20-31
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• 1988

This study was undertaken to investigate the load characteristics of the head-feed thresher, which may be affected by various factors such as physical properties of grain, thresher design parameters and its operational condition. The study was conducted at an initial step toward developing an automatic feed-rate control system of the head-feed thresher. A microcomputer-based data acquisition system for the load-speed characteristic of the thresher-shaft and the rail-deflection of the feeding device in accordance with a varied feeding thickness was developed. The sensors being developed and used for sensing the torque and speed of the cylinder and the power-input-shaft and the feeding thickness showed a high accuracy. A microcomputer-based data acquisition system developed in this study was assessed as adequate for a rapid acquisition and analysis of data. The effect of the feed-rate on the torque and speed of the thresher shaft, when fed intermittently by bundles, affected not by the rice varieties but by the dryness of threshing material tested. When fed by the continuous constant thickness, the torque and speed of the cylinder due to the increase of the feed-rate or feeding thickness were given by the relation by the second order parabola.

• The Journal of Engineering Geology
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• v.4 no.3
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• pp.343-356
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• 1994

When most of the industry and social indirect facilities such as the large structure, power plant or road, rail-road are constructed, the new slope may lead to the slope failure. The failure models for slopes have been developed by using the results of in-situ and laboratory tests to investigate the mechanisms and types of the slope failure. The safety factor of a slope may be obtained based on the proposed model and the slope can be reinforced to meet the design criteria. The slope should be reinforced by using the optimum model that properly reflects the site condition, the method of reinforcement includes the increased safety factor either by decreasing a slope angle or by reinforcing the slope.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1694-1700
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• 2007

In the electrified section, both of return current and signal current are flowing in the same rail in common. But signal current shall be allowed to flow in the specific track circuit and not in the other circuit while the traction return current shall come back to power sub-station. This paper presents measuring system that use both sensor and antenna. The aim of the system is to achieve the difference in current between the two rails and the presence of trimming capacitors. In order to improve the transmission level, trimming capacitors are connected between the two rails at constant spacing. To maintain the balance of traction return current, rails of both sides may be jointed by the so-called SVPMM. The traction return current is sometimes unbalanced owing to the ill-contact of SVPMM. In this paper, we propose a diagnosis method based on a short-circuited current(Icc), trimming capacitors and traction return current measured by Korail inspection vehicles. Whether Icc is good or bad depends not only on the presence of trimming capacitors but also on the unbalance of the traction return current.