• Journal of the Ergonomics Society of Korea
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• v.32 no.6
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• pp.535-540
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• 2013

Objective: The aim of this study is to evaluate the effectiveness and efficiency of causal links between various error causes in human error analysis. Background: As finding root causes of human error in safety-critical systems is often a cognitively demanding and time-consuming task, it is particularly necessary to develop a method for improving both the quality and efficiency of the task. Although a few methods such as CREAM have suggested causal linking between error causes as a means to enhance the quality and efficiency of human error analysis, no published research to date has evaluated the performance of the causal links. Method: The performance of the CREAM links between error causes were evaluated with 80 railway accident investigation reports from the UK. From each report, errorneous actions of operators were derived, and for each error, candidate causes were found by following the predefined links. Two measures, coverage and selectivity, were used to evaluate the effectiveness and efficiency of the links, respectively. Results: On average, 96% of error causes actually included in the accident reports were found by following the causal links, and among the total of 121 possible error causes, the number of error causes to be examined further was reduced to one-tenth on average. As an additional result of this work, frequent error causes and frequently used links are provided. Conclusion: This result implies that the predefined causal links between error causes can significantly reduce the time and effort required to find the multiple levels of error causes and their causal relations without losing the quality of the results. Application: The CREAM links can be applied to human error analysis in any industry with minor modifications.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.461-466
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• 2020

In this study, the relationship between the track support stiffness and the track impact factor for a sleeper floating track and a turnout system with wood ties currently employed in Korean urban transit was assessed by performing field tests using actual vehicles running along the service lines. Field tests were performed on four track systems (i.e., sleeper floating track, and point, lead and crossing sections of turnout system). The theoretically designed track impact factor and track support stiffness were compared with the corresponding track impact factor and track support stiffness measured through field tests for the target tracks on the service line. The track impact factor for the service line appeared to increase with the deviation of track support stiffness according to vehicle driving direction; therefore, it was inferred that the deviation of track support stiffness between each track section directly affected the track impact factor.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.448-457
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• 2017

In this paper, for high speed railway propulsion systems, a single phase PWM Converter using discontinuous PWM (DPWM) was investigated. The conventional PWM Converter uses a low frequency modulation index of less than 10 to reduce switching losses due to high power characteristics, which results in low control frequency bandwidth and requires an additional compensation method. To solve these problems, the DPWM method, which is commonly used in three phase PWM Inverters, was adopted to a single phase PWM Converter. The proposed method was easily implemented using offset voltage techniques. Method can improve the control performance by doubling the frequency modulation index for the same switching loss, and can also bring the same dynamic characteristics among switches. Proposed DPWM method was verified by simulation of 100 kW PWM converter.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.985-988
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• 2008

Maglev is a system that a train runs levitated above a rail. Therefore it is very important to maintain a constant levitation gap for achieving serviceability and ride comfort. This study is a cooperation research subject of the 3-1 subject, performance improvement of maglev track structures, of the Center for Urban Maglev Program in Korea, started in 2006. The aim of this study is development of rapid constructions of bridge superstructure for maglev. At present, precast deck is widely used because of its superiority to cast-in-place concrete on quality and the term of works. The research group suggested basic systems of maglev guideway with PSC-U type and trapezoidal open steel box type girder, and precast deck, cooperating with Korea Railroad Research Institute, the managing institute of the 3-1 subject. In this study, full-scale structure was fabricated for structural safety evaluation of precast decks and rail, and a static performance test of those structures was performed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.57-60
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• 2008

Maglev is a system that a train runs levitated above a rail. Therefore it is very important to maintain a constant levitation gap for achieving serviceability and ride comfort. This study is a cooperation research subject of the 3-1 subject, performance improvement of maglev track structures, of the Center for Urban Maglev Program in Korea, started in 2006. The aim of this study is development of rapid constructions of bridge superstructure for maglev. At present, precast deck is widely used because of its superiority to cast-in-place concrete on quality and the term of works. The research group suggested basic systems of maglev guideway with PSC-U type and trapezoidal open steel box type girder, and precast deck, cooperating with Korea Railroad Research Institute, the managing institute of the 3-1 subject. In this study, a mock-up consisted of girders, decks and rail was fabricated and test was performed for constructability, serviceability and maintenance evaluation of PSC U-type girder, precast deck, and new guide rail system.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.899-905
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• 2016

Wireless access in vehicle environment (WAVE) communication is currently being researched as core wireless communication technologies for cooperative intelligent transport systems (C-ITS). WAVE consists of both vehicle to vehicle (V2V) communication, which refers to communication between vehicles, and vehicle to infrastructure (V2I) communication, which refers to the communication between vehicles and road-side stations. V2I has a longer communication range than V2V, and its communication range and reception rate are heavily influenced by various factors such as structures on the road, the density of vehicles, and topography. Therefore, domestic environments in which there are many non-lines of sight (NLOS), such as mountains and urban areas, require optimized communication channel modeling based on research of V2I propagation characteristics. In the present study, the received signal strength indicator (RSSI) was measured on both an experience road and a test road, and the large-scale characteristics of the WAVE communication were analyzed using the data collected to assess the propagation environment of the WAVE-based V2I that is actually implemented on highways. Based on the results of this analysis, this paper proposes a WAVE communication channel model for domestic public roads by deriving the parameters of a dual-slope logarithmic distance implementing a two-ray ground-reflection model.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.471-480
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• 2015

Reliance on road transport in domestic logistics can lead to intensified congestion and greenhouse gas emissions due to the rise in oil prices, any increase in logistics costs can have a high social cost. The government policy on Low Carbon Green Growth is seeking to take advantage of the railway system. However, existing railway transport logistics systems, for reasons such as low speed, low track capacity constraints, and the impossibility of implementing a Door to Door system, make it difficult to activate a railway logistics program. As a result of this study, a national R&D project to develop a High-Speed Passenger/Baggage Mixed Train(Hy-SoBex) utilizing the rail capacity constraints to overcome the difficulties of linking an air cargo and freight railway logistics system, we propose a variety of service models and select the optimal service model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2738-2744
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• 2014

For balanced development of the Sejong City, early settlement in transport infrastructure should precede the most. Of various means of transport, this study focus on BRT(Bus Rapid Transit) and the railway. Than the subway construction costs only a tenth. Equipped with a system of underground transport capacity to significantly increase the new concept of public transport in the BRT, utilizing the existing line railway to be constructed broad Chungcheong. The extension revolves 1 line of Daejeon subway to Jeongbuse kind government complex and the communication facilities is cooked for the rapid increase in the transportation demand according to the before central administration organization and Sejong city inflow of population.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.213-218
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• 2020

In this study, we propose a control algorithm to reduce the unbalanced characteristics of a three-phase system power caused by the unbalanced load of the AC electric railway. Then, we verify its performance through the design of a power compensator and experiments applying it. Like electric railway systems, a Scott transformer is applied, and the load and single-phase back-to-back converters are connected to the M-phase and T-phase outputs. The back-to-back converter monitors the difference in active power between the unbalanced loads in real-time and compensates for the power by using bidirectional characteristics. The active power is performed through PI control in the synchronous coordinate system, and DC link overall voltage and voltage balancing control are controlled jointly by M-phase and T-phase converters to improve the responsiveness of the system. To verify the performance of the proposed power compensation device, an experiment was performed under the condition that M-phase 5 kW and T-phase 1 kW unbalanced load. As a result of the experiment, the unbalance rate of the three-phase current after the operation of the power compensator decreases by 58.66% from 65.04% to 6.38%, and the excellent performance of the power compensator proposed in this study is verified.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.45-54
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• 2013

In this paper, a theoretical weight-reduction method was suggested to substitute an underframe material of a box-type bodyshell having cut-outs with an alternative light-weight material. To utilize the material substitution method previously developed for a box-type hybrid bodyshell not having cut-outs, we derived a box-type baseline model without cut-outs which is similar to the stiffness condition of a box-type bodyshell having cut-outs. To do this, the thicknesses of roof and walls of the baseline model were determined such that the deflection of the baseline model under a distributed vertical load condition is equal to the sum of the theoretical section deflections of the original box model with cut-outs. Next, to derive a hybrid bodyshell by under-frame material substitution, the material substitution method for a box-type hybrid bodyshell without cut-outs was applied to the box-type baseline model. Finally, we compared the FE simulation results of the derived hybrid bodyshells having cut-outs for various materials with the theoretical results of the suggested method, and we obtained their good correlations.