• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2011년도 추계학술대회
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• pp.557-561
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• 2011

The study proposes three types of production lead time according to the production or demand pattern. First of all, it discusses the difference of three lead times. While pitch time and cycle time are used in push system with process stock and mass conveyor production, the tact time is used in pull system like as JIT based lean production system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.306-312
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• 2007

The running safety of rolling stock is assessed by derailment coefficient. It requires lots of preparatory time, expenditure and high measurement technique to measure derailment coefficient. If derailment coefficient could be measured when track or vehicle is maintained, safety will be improved. The measurement and assessment of running safety is necessary for safety especially for the vehicles newly developed and started service. Therefore measurement of derailment coefficient is most important thing to secure running safety. In this paper, we examined new assessment method which could estimate derailment coefficient by measuring vibration acceleration and displacement of vehicle operating at actual track irrespective of time and place. The new method could be used effectively as a mean confirming running safety.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1964-1969
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• 2008

A railway is a complex system integrated with a lot of technical elements such as rolling stock, power, signal control, communications, tracks, stations, operation control systems, and so on. As a mass transportation system, a railway could contain potential risks that may result in a high death rate and property losses. Accordingly, Railroad Safety Technology R&D Corps. is adopting the plan of the construction of Railway Safety Test Facilities as a part of the Railway Total Safety Project to enhance the railway safety, and carrying out researches on effective project management methods with Systems Engineering techniques. To support that, we propose the more effectual management method of constructing the Railway Safety Test Facilities applying the model-based systems engineering tool to the research.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1085-1090
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• 2011

철도차량의 안전성을 확보하기위해서는 견인성능 및 속도의 변동성을 고려하여 감속기의 피로해석에 관한 연구를 수행하는 것이 중요하다. 본 논문은 고속철도차량 감속기 기어의 변동하중하에서 피로파괴에 대하여 준정적 유한요소해석과 선형 Miner's Rule에 의한 내구성해석을 수행하였다. 해석을 위한 변동하중이력은 열차견인성능곡선과 상업운전조건에서 운전선도를 기초로 MSC.ADAMS의 동역학 해석에 의하여 구축하였다. 또한 감속기 피로수명은 기어표면의 침탄부 효과를 고려한 유한요소모델을 사용하여 변형률-수명접근법에 의하여 예측하였다. 해석결과로부터 급출발에 의한 빈번한 높은 기동토크와 정차역수의 증가는 철도차량 감속기 기어수명을 감소시킴을 알 수 있었다.

• 한국산학기술학회논문지
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• 제17권11호
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• pp.629-634
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• 2016

본 연구에서는 철도차량 내장재 화재성능평가기준 중 연기밀도 측정에서 주요 인자들의 영향을 합성고무바닥재를 이용하여 분석 및 검토하였다. 밀폐된 공간에서 운영되는 철도차량의 특성 상, 객실 내부에서 화재 발생 시에 연기로 인해 막대한 인명피해가 발생할 수 있다. 따라서 국내 외의 철도운영국가에서는 내장재의 연기 발생량을 엄격하게 규제하고 있으며, 이를 위해 내장재의 화재성능평가에 있어 연기밀도의 정확한 측정이 요구된다. 연기밀도의 측정에 있어 주요 영향인자로 시료 고유의 균질도, 장비를 이용한 조건 및 측정의 편차 그리고 장비를 운용 관리하는 환경의 영향을 꼽을 수 있다. 각 인자별 연기밀도에 영향도를 확인하기 위하여 불확도 추정에 따른 기여율 분석을 수행하였다. 그 결과, 광센서(PM tube)를 이용한 투과율 측정편차의 기여율이 약 86 %로 연기밀도 측정의 대표 영향인자임을 확인할 수 있었다. 그리고 높은 균질도를 가지는 시료를 대상으로 한 연기밀도 측정에서는 그 외 영향인자(시료연소용 복사열 조건(${\pm}0.5 kW/m^2$) 및 장비의 운용 관리환경)의 기여율이 약 11 %로 낮음을 확인할 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 춘계학술대회 논문집
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• pp.999-1005
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• 2006

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1105-1108
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• 2004

This paper describes the structural analysis result and load test result of accident EMU(Electric Multiple Units). Structural analysis and load test of EMU were performed for the criteria of safety assessment. Structural analysis using commercial I-DEAS software provided important information on the stress distribution and load transfer mechanisms as well as the amount of damages during rolling stock crash. The purpose of the load test is to evaluate a safety which carbody structure shall be considered fully sufficient rigidity so as to satisfy proper system function under maximum load and operating condition. The results have been used to provide the critical information for the criteria of safety assessment.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.144-152
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• 2013

PRT(Personal Rapid Transit) system is a new transportation system which will meet increasing demands of traffic in Korea. It is also an environment-friendly transportation and automatically operated. For these reasons, researches on the PRT system are actively undergoing, but the PRT vehicles have different forms of subway, bus, etc. There are no design standards to evaluate structural integrity, yet. In this paper, Structural design specifications are derived, which are based on the performance test standard for EMU and the ASCE-APM standards. We also perform the static and fatigue analyses by FE simulation and suggest strategies to improve an initial structure design. In addition, we derived the design specifications for energy-absorbing structures to meet the conditions of the collision scenarios predefined from a view point of operation safety.

• 한국안전학회지
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• 제30권5호
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• pp.92-99
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• 2015

The diameter of a new wheel in EMUs is 860mm and it can be used up to 773mm. To obtain an predefined acceleration despite wheel diameter changes, the tractive efforts of the vehicles must be properly controlled. In the commencement of this study, acceleration tests were performed for empty EMUs when the wheel diameter was changed to 860mm, 820mm and 780mm, respectively. In order to deal with more complicated running conditions, we developed dynamic simulation models of the EMUs using VI-Rail, and simulated the models in empty and full passenger loads, respectively. Using the simulation results, we analyzed the gradient of time-velocity graphs by considering the changes of the total weight vehicles and moment of inertia of the wheelsets as well as tractive effort according to the wheel diameter changes. As the results, it was found that there are significant differences in acceleration performances according to the wheel diameters and the payloads of EMUs. In case of 860mm which is the maximum wheel diameter, the test & simulation results show that the vehicle couldn't reach the predefined acceleration, 3.0km/h/s, due to lack of tractive effort.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2004년도 추계학술대회
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• pp.415-438
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• 2004

This dissertation is assumed to continuously occur adjustment cost on present investment. So, I derived from time-nonseparable production-based CAPM and tested the performance of model through data. I also compared time-nonseparable production-based CAPM with time-separable production-based CAPM and CCAPM, CAPM through testifying the performance of model. At the part of applied application, I estimated time-nonseparable PCAPM-betas. The data of Korea consists of 320 listed companies on Korea Stock Exchange (KOSPI) from first quarter 1987 to first quarter 2002. This data also is categorized by scale and industries. Additionally, I estimated time-nonseparable PCAPM-betas through 500 listed companies of New York Stock Exchange (NYSE) from first quarter 1973 to first quarter 2002. I observed the statistical significance of 230 firms by 320 companies in Korea. After that, I compared time-nonseparable PCAPM-betas by firms with time-separable production-based CAPM-betas and CCAPM-betas, CAPM-betas through individual firms. At empirical test, I found that estimated parameter of adjustment cost on time-nonseparable production-based CAPM by scale and industries in Korea had positive value and statistical significance, Moreover, this approach proved to resolve the underestimation of adjustment cost on time-separable production-based CAPM by scale and industries. I also found that the time-nonseparable PCAPM performed better than time-separable production-based CAPM and CCAPM, CAPM. The result from U.S data proved to have similarity to that of Korea. Specifically, I found that time-nonseparable PCAPM-betas by firms performed better than CAPM-betas on individual firms in Korea.