• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.233-239
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• 2008

It is very important to set a reliability target and verify the requirement when procuring the rolling stock in the aspect of safety, availability and LCC. While there are a few different methods to verify the reliability target, it is required that the most appropriate method should be used considering the characteristics of rolling stock itself and the operation environment. Even though recently the quantitative reliability requirements are widely adopted in domestic market, there is no substantial contents in the various standards and guidelines. In this study we investigate the various reliability demonstration test plans and evaluate them for rolling stock application. And three test plans among them were applied to the real operation data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.321-324
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• 2005

The main purpose of the present study has been placed on investigating the effects of controlled rolling and cooling on the microstructures and mechanical properties of C-Si-Mn-V steels for cold forming. The steels were manufactured in vacuum induction melting(VIM) furnace and casted to 1.1ton Ingots and the ingots were forged to $\Box150$ billet. The forged billets were reheated in walking beam furnace and rolled to coil, the stocks were rolled by Controlled Rolling and Cooling Technology (CRCT), so rolled at low temperature by water spraying applied in rolling stage and acceleratly cooled before coiling. Rolled coils were cold drawed to the degree of $27\%$ of area reduction without heat treatment. Microstructual observation, tensile test, compression test and charpy impact tests were conducted. The mechanical properties of the steels were changed by area reduction of cold drawing and it is founded that there are optimum level of cold drawing to minimize compression stress for these steels. From the result of this study, it is conformed that mechanical properties and microstructure of C-Si-Mn-V steels for cold forming were enhanced by accelerated cooling and founded optimum level of cold drawing.

• Journal of Intelligence and Information Systems
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• v.26 no.1
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• pp.47-73
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• 2020

KTX rolling stocks are a system consisting of several machines, electrical devices, and components. The maintenance of the rolling stocks requires considerable expertise and experience of maintenance workers. In the event of a rolling stock failure, the knowledge and experience of the maintainer will result in a difference in the quality of the time and work to solve the problem. So, the resulting availability of the vehicle will vary. Although problem solving is generally based on fault manuals, experienced and skilled professionals can quickly diagnose and take actions by applying personal know-how. Since this knowledge exists in a tacit form, it is difficult to pass it on completely to a successor, and there have been studies that have developed a case-based rolling stock expert system to turn it into a data-driven one. Nonetheless, research on the most commonly used KTX rolling stock on the main-line or the development of a system that extracts text meanings and searches for similar cases is still lacking. Therefore, this study proposes an intelligence supporting system that provides an action guide for emerging failures by using the know-how of these rolling stocks maintenance experts as an example of problem solving. For this purpose, the case base was constructed by collecting the rolling stocks failure data generated from 2015 to 2017, and the integrated dictionary was constructed separately through the case base to include the essential terminology and failure codes in consideration of the specialty of the railway rolling stock sector. Based on a deployed case base, a new failure was retrieved from past cases and the top three most similar failure cases were extracted to propose the actual actions of these cases as a diagnostic guide. In this study, various dimensionality reduction measures were applied to calculate similarity by taking into account the meaningful relationship of failure details in order to compensate for the limitations of the method of searching cases by keyword matching in rolling stock failure expert system studies using case-based reasoning in the precedent case-based expert system studies, and their usefulness was verified through experiments. Among the various dimensionality reduction techniques, similar cases were retrieved by applying three algorithms: Non-negative Matrix Factorization(NMF), Latent Semantic Analysis(LSA), and Doc2Vec to extract the characteristics of the failure and measure the cosine distance between the vectors. The precision, recall, and F-measure methods were used to assess the performance of the proposed actions. To compare the performance of dimensionality reduction techniques, the analysis of variance confirmed that the performance differences of the five algorithms were statistically significant, with a comparison between the algorithm that randomly extracts failure cases with identical failure codes and the algorithm that applies cosine similarity directly based on words. In addition, optimal techniques were derived for practical application by verifying differences in performance depending on the number of dimensions for dimensionality reduction. The analysis showed that the performance of the cosine similarity was higher than that of the dimension using Non-negative Matrix Factorization(NMF) and Latent Semantic Analysis(LSA) and the performance of algorithm using Doc2Vec was the highest. Furthermore, in terms of dimensionality reduction techniques, the larger the number of dimensions at the appropriate level, the better the performance was found. Through this study, we confirmed the usefulness of effective methods of extracting characteristics of data and converting unstructured data when applying case-based reasoning based on which most of the attributes are texted in the special field of KTX rolling stock. Text mining is a trend where studies are being conducted for use in many areas, but studies using such text data are still lacking in an environment where there are a number of specialized terms and limited access to data, such as the one we want to use in this study. In this regard, it is significant that the study first presented an intelligent diagnostic system that suggested action by searching for a case by applying text mining techniques to extract the characteristics of the failure to complement keyword-based case searches. It is expected that this will provide implications as basic study for developing diagnostic systems that can be used immediately on the site.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1636-1641
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• 2011

Typically Korea Railroad is executing the limited inspection and general inspection about passenger car by mileage and the time elapsed.(ex. one year, two years) These types of inspection system continue from the beginning of the railroad operation of the steam locomotive age to present. According to the rolling stocks modernized and improved, mileage and the time elapsed for periodical inspection has been expanded but the basic maintainability system of rolling stocks is not that different from the past. This fact needs verification that modern inspection method is right from various fields. In this paper, we analyze the data that we get the maintenance record from Korea railroad company about periodical inspection and failure. Next to considering the correlation of periodical inspection with failure based on analyzed data for watching periodical inspection effects. And we desire to need efficient rolling stock maintenance system better than fixed periodical inspection.

• Journal of the Korean Society for Railway
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• v.8 no.4
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• pp.348-353
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• 2005

In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of rolling-stock car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the rolling stocks require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. Use of new material technology as body structures also introduces uncertainties in the material strength. A probabilistic approach is more adaptable in designing reliable structures when the pressure waves from the tunnels pounds and new material technology is adopted. In this paper, it is proposed that a fatigue design and assessment method based on a reliability which deals with the loading variations on a railway vehicle due to the pressure reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1229-1234
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• 2009

The rolling stocks of KORAIL are KTX, Saemaulho Multiple Unit(PP), New Electrical Locomotive(DL), Electrical Locomotive(EL), Diesel Locomotive, Metropolitan Commuter Train(CDC), VVVF and Resistance Controlled Multiple Unit, etc. EMU with the maximum speed of 150km/h is under the test run at the moment. Electrical Multiple Units for mainlines with 180km/h speed are supposed to be introduced as a substitute for Saemaulho Multiple Unit which is scheduled to be out of service. But the specification standard for the control board design of train driver's cab does not exist and there is no a study for layout and type of controlling device with driver's ergonomical approach. That's why the types of controller and operating are different from rolling stocks, which has high possibility of driver's human error and needs education whenever a new car comes in. Based on the opinion poll of drivers, design specification of safety engineering and ergonomics for controlling devices and safety facilities can improve exact control for devices and deal quickly with an emergency so as to improve rolling stock safety and operational efficiency.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.158-166
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• 2007

After constructing the high-speed railroad, KORAIL acquired advanced maintenance techniques about Rolling-stocks. Also RCM theory is applied to maintenance field like as inspection period and method. In the meantime, the development of the maintenance methode for Rolling-stock is slow when it compares to the components and system technology. For this reason KORAIL tries to build the optimal maintenance system which can lead the Rolling-stock maintenance technique. The existing vehicle except High Speed train KTX are separated to electric motor car, electric locomotive, diesel locomotive, diesel car, passenger car and freight car. The inspection period and methode for existing vehicles which mentioned above will be examined and the optimal Rolling-stock maintenance technique will be applied.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.41-47
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• 2016

The rolling stock is composed of several cars. In order to operate in combination, it is necessary to connect the device, called coupler, between the rolling stocks. When the collision occurs between cars, couplers should be able to absorb the shock. Urban railway has used only rubber absorbers. But recently, the hydraulic buffer has been considered in general railway. In order to know the performance of the buffer it should be conducted to experiments. But whenever this combination change, we should experiments to know a lot of the dynamic behavior of each coupler. These experiments are generally replaced by the simulation, since a lot of time and cost consuming. The quasi-static map of hydraulic buffer obtained by the experiments is required for the simulation. However, the experiments for obtaining such a quasi-static map is costly and time consuming. In this paper, it proposes a method for deriving the quasi-static map of hydraulic buffer from the theoretical model.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.390-397
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• 2008

Quantitative RAM (Reliability, Availability, Maintainability) is the one of the important indicator that shows the quality of rolling stock. It is usually required in the domestic and abroad purchase specification of rolling stock. And achieving and demonstrating the quantitative RAM goals is also required. In this study, the method to set up these goals will be proposed in the aspects of service and logistic reliability, operational, achievement or inherent availability and maintainability. And we apply this proposed method to the real operation data.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.802-814
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• 2016

This study examines the relationship between the operational turnaround time and the rolling stock requirements. In this study, the operational turnaround time of rolling stock is divided into physical turnback time and waiting time. This paper presents a variety of models and estimation results of the existing studies on operational turnaround time. The proposed estimation model of the operational turnaround time in this study is designed to minimize the operational turnaround time in terminus stations, while the rolling stock requirement is reduced. The developed estimation model was applied in a real-world example, and it was found that the operational turnaround time and the required rolling stocks were lessened compared with the current condition. The method presented in this paper is expected to be utilized in train operational planning and rolling stock routing plans, thereby minimizing the rolling stock requirements of existing railway operating authorities.