• Journal of Power Electronics
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• v.18 no.3
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• pp.931-943
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• 2018

Wireless power transfer (WPT) technology has been the focus of a lot of research due to its safety and convenience. The Z-source inverter (ZSI) was introduced into WPT systems to realize improved system performance. The ZSI regulates the dc-rail voltage in WPT systems without front-end converters and makes the inverter bridge immune to shoot-through states. However, when the WPT system is combined with a ZSI, the system parameters must be configured to prevent the ZSI from entering an "accidental shoot-through" (AST) state. This state can increase the THD and decrease system power and efficiency. This paper presents a mathematical analysis for the characteristics of a WPT system and a ZSI while addressing the causes of the AST state. To deal with this issue, the impact of the system parameters on the output are analyzed under two control algorithms and the primary compensation capacitance range is derived in detail. To validate the analysis, both simulations and experiments are carried out and the obtained results are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1110-1116
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• 2017

Depending on the operating characteristics, track circuit is installed for the purpose of direct or indirect control of the signal device, point switch machine and other security device. These are mainly used for train detection, transmission of information, broken rail detection and transmission of return current. Especially, the return current is related to signal system, power system and catenary line, and track circuit systems. It is one of the most important component shall be dealt for the safety of track side staff and for the protection of railway-related electrical system according to electrification. Therefore, an accurate analysis of the return current is needed to prevent the return current unbalance and the system induced disorder and failure due to an over current condition. Also, if the malfunction occurred by the return current harmonics, it can cause problems including train operation interruption. In this paper, we presented measurement and analysis method at return current and it's harmonics by high speed train operation on the honam high speed line.

• Journal of Biosystems Engineering
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• v.37 no.5
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• pp.287-295
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• 2012

Purpose: Some of the most representative approaches are to apply next generation technologies to save energy consumption, fully automated control system to appropriately maintain environmental conditions, and autonomous assistance system to reduce labor load and ensure operator's safety. Nevertheless, improvement of upcoming method for soil cultured greenhouse has not been sufficiently achieved. Geometrical complexity of ground in protected crop cultivation might be one of the most dominant factors in design of autonomous vehicle. While there is a practical solution fairly enough to promise an accurate travelling, such as autonomous sprayer guided by rail or induction coil, for various reasons including the limitation of producer's budget, the previously developed sprayer has not been widely distributed to market. Methods: In this study, we developed an autonomous sprayer considering travelling performance on geometrical complexity of ground in soil cultured greenhouse. To maintain a stable travelling and to acquire a real time feedback, common wire with 80 mm thick and body frame and sprayer boom. To evaluate performance of the prototype, tracking performance, climbing performance and spraying boom's uniform leveling performance were individually evaluated by corresponding experimental tests. Results: The autonomous guidance system was proved to be sufficiently suitable for accurate linear traveling with RMS as lower than approximately 10 cm from designated path. Also the prototype could climb $10^{\circ}$ of ground's slope angle with 40 kg of water weight. Uniform leveling of spraying boom was successfully performed within $0.5^{\circ}$ of sprayer boom's slope. Conclusions: Considering more complex pathways and coarse ground conditions, evaluations and improvements of the prototype should be performed for promising reliability to commercialization.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.36-47
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• 2010

The Korean Railroad Research Institute (KRRI) has developed the rubber tired AGT system (Model: K-AGT) between 1999 and 2005. The K-AGT is a light rail transit system does not require a driver and generally operates on an elevated railroad for transporting passengers. Accidents caused by driverless vehicles can severely affect social confidence, safety and economy therefore, it is very important to minimize the occurrences of such faults, and to accurately perform detailed maintenance tasks and thoroughly investigate the cause of any repeated failures. This research develops the web-based Preventive Maintenance (PM) system for the KAGT train system. The framework of the PM system is based on performing a reliability analysis and a failure mode effects analyses (FMEA) procedure on all the sub-systems in the K-AGT system. Out of the devices that have a low reliability, the high failure ranked devices are included high in the list for performing the overall maintenance plans. Through registration of historical failure data, the reliability indexes can be updated. Such a process is repeated continuously and can achieve very accurate predictions for device operational life times and failure rates. Therefore, this research describes the development of the overall PM system consists of a reliability analysis module, a failure mode effect analysis module, and maintenance request module.

• Fire Science and Engineering
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• v.31 no.2
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• pp.74-81
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• 2017

This study analyzed the regulatory actions of disposal gas lighters as well as the situations, causes, and preventive measures of fires, and accidents caused by disposal gas lighters. Since child-resistant lighters became mandatory, the percentage of fires caused by playing with fire has decreased in Korea as it did in America and Japan. Fires caused by disposal gas lighters can occur by afterburning, unintentional lighting, large flames, or explosion or bursting as well as by arson and playing with fire. This study suggests the preventive measures of fires caused by disposal gas lighters as follows: Taking a step not to be used as child's tool for playing with fire, the warning of fire cases caused by afterburning, warning of the dangers of leaving disposal gas lighters on the car dashboard or high temperature places, improving the protective synthetic resin cover of the stop part of a vehicle seat rail, and providing information on precautions for keeping in drawers or disposition methods.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.298-303
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• 2010

The transition zone of the railway is the section which roadbed stiffness is suddenly varied like as tunnel-earthwork, bridge-earthwork and concrete track-ballasted track. There are about 450 tunnel-bridge transition sections on Kyungbu high-speed railway line. It is very important to pay careful attention to construction of these transition zones, in order to secure the train running safety. So, we developed a finite element model of the moving wheel loading to simulate the behavior of bridge-earthwork transitions in this paper. The most distinctive characteristics of the model proposed is to simulate the real wheel behavior on rail. And the main analysis object is to evaluate and compare the deformation characteristics of the transition zone according to the reinforcement methods and length of transition zone which is adopted to high-speed railway. Based on the analysis results, we assessed the effect of the reinforcements on the transition zone of high-speed railway.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1003-1009
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• 2009

The Spatial Image contents of Geomorphology 3-D environment is focused by the requirement and importance in the fields such as, national land development plan, telecommunication facility management, railway construction, general construction engineering, Ubiquitous city development, safety and disaster prevention engineering. The currently used DEM system using contour lines, which embodies geographic information based on the 2-D digital maps and facility information has limitation in implementation in reproducing the 3-D spatial city. Moreover, this method often neglects the altitude of the rail way infrastructure which has narrow width and long length. This As the results, We confirmed the solutions of varieties application for railway facilities management using 3-D spatial image contents and database design. Also, I suggested that U-city using railway modeling about matching methods of high density elevation value using 3-D aerial photo with laser data are best approach for detail stereo modeling and simulation.

• Nuclear Engineering and Technology
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• v.14 no.4
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• pp.196-203
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• 1982

To transport the spent fuel assemblies of Korea Nuclear Unit 1, which is a Westinghouse type two loop pressurized water reactor, it has been found that steel is the most appropriate material for the design of a shipping cask in comparison with lead and depleted uranium. The proposed shipping cask will transport nine fuel assemblies at the same time and is well within the weight limit of transportation by unrestricted rail car. The cask requires 33cm thick steel shield and 27cm thick water region to satisfy the 3 feet apart dose rate limit set forth in 10 CFR 71, and 1.27cm thick steel boron fuel basket to hold the fuel elements inside the cask and control the effective multiplication factor. As a safety analysis, the fuel cladding and centerline temperatures were calculated under the accident condition of complete loss of water coolant, and it was found that the temperature was much lower than the limit of the melting point. k$_{eff}$ was calculated with fresh fuel assemblies, which was found to be well lower than 0.95. For shielding computation, the multipurpose Monte Carlo code MORSE-CG and one dimensional discrete ordinates transport code ANISN were used, and the Monte Carlo codes KENO and MORSE-CG were used for criticality calculation. The radiation source terms were calculated using ORIGEN-79.9.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.703-709
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• 2013

Recently, the study on the commercialization technology of Rope Platform Screen Door (RPSD) is on the process. The study is specifically on RPSD, which the rope screen ascends to allow passage with securing safety of passenger and the condition of aboveground station. For this human-centered design of RPSD, it is important to present system technology. However, it is also necessary to scientifically measure and research the emotions, senses or minds of users in the future. Therefore, this study analyzed the human factors to be considered with designing the system on RPSD, which is installed in Nokdong Station on Gwangju Subway as a trial. Moreover, the emotional evaluation was done by analyzing the factors as how they are effected in general; it processed by checking whether it is safe, height of rope is stable, it has openness (pressure) or strong by examining the moments that a set of ropes blocks rail from platform, and when train is arrived.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.298-304
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• 2013

This paper systematically analyzes the dynamic effects of structure approaches which are expected to have direct effects on train loads - according to the train's acceleration as the area under consideration is located in a section where acceleration of high speed railway vehicles and the train's operating speed happens. In addition, through an examination of the dynamic train loads, dynamic behavioral characteristics of embedded structures and structure approaches were analyzed and a numerical analysis has been carried out in order to evaluate the performance of track subgrade and the safety of the structure. As a result, we reach the conclusion that the dynamic effects by train loads is low, but somewhat high vertical acceleration occurs.