• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.545-551
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• 2016

In this study, we evaluate the braking performance of an urban railway vehicle to verify its basic safety condition. The braking performance evaluation methods, deceleration measurement and braked weight percentage, were compared for trains with different numbers of cars, in order to assess the advantages of each method and their compatibility. With a probabilistic braking model, the effect of the adhesion coefficient distribution was analyzed in accordance with the train composition. A train with many cars has a narrower deceleration distribution width than one with few cars. The braked weight percentage method is expected to be useful in the design of train signal systems, because it allows the braking distance to be calculated for various initial brake velocities. The deceleration distribution model and its results are expected to be useful as a basis for precise train signal design.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.41-47
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• 1994

An optimal brake pad must have stable friction, low wear and least amount of squeal. In this study, the friction, wear and squeal behavior of some non-asbestos Kevlar materials have been evaluated experimentally. Four specimens with different formulations and a pin-on-disk machine were used for this study. To determine the role of each component in friction and squeal of a brake pad, statistical correlations have been obtained and discussed. The components tested were : Kevlar, Steel Powder, Barium Sulfate and fillers combined by Resin.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.786-791
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• 2007

Korean high speed train(HSR-350x) has adopted a combined electrical and mechanical(friction) braking system. Brake blending control unit(BBCU) controls each brake system to fulfill the required brake performances such as braking distance, deceleration and jerk. Also the braking system should be designed considering the economical management, such as effective use of generated braking energy and the minimum wear of friction materials(a pad and a brake shoe). In this paper, we establish the disc braking force pattern that reduces the wear of pad in the disc braking system by minimizing the variance of the instantaneous disk baking energy during braking time, and compare the wear mass of pad between the conventional disc braking force pattern and the established results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.541-549
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• 2018

This paper deals with the braking dynamic behavior of diesel electric locomotive pulling domestic cargo and passenger vehicles. Friction coefficient, pneumatic pressure, and running resistance affecting the braking system were tested. For the friction coefficient, the Dynamo test was performed with reference to UIC 541-4. The results are analyzed by multivariate regression and the relationship between braking force and ititial velocity is presented. The pneumatic pressure were classified into service braking and emergency braking. In order to reflect the characteristics of the brake valve and piping, the pressure rising over time was measured in the vehicle. In order to reflect the external force acting on the vehicle, we carried out the test of EN 14067-4 and presented the second order polynomial formula on a running resistance. The running resistance test results were compared with other countries. The dynamic behavior of a diesel electric locomotive running on a straight flat track based on vehicle resources, friction coefficient, braking pressure, and running resistance is simulated using the time integration presented in EN 14531-1. The simulation results were compared and verified with the vehicle braking test results. The results of this study can be used to analyze the dynamic braking behavior of a train. Also, it is expected that various parameters affecting braking in vehicle design can be analyzed and used as basic data for braking performance improvement.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.212-218
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• 2009

In order to investigate the thermal cracking of the rolling stock brake disc, finite element analysis was conducted on the temperature distribution and thermal stress of the disc during braking. In case of initial vehicle speed of 90, 106, 120km/h, the maximum temperature on the disk surface due to braking was $135.9^{\circ}C,\;157.9^{\circ}C,\;178.7^{\circ}C$, respectively. And, the maximum von-Mises stress at the disc surface was 42.4, 50.3, 57.1MPa at a speed of 90, 105, 120km/h, respectively, indicating that the stress increases with an increment in the speed. Damage fraction due to braking during one year running on the Seoul - Busan line was determined as 14.6%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.887-895
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• 2018

This paper presents a braking model that can be used to design the safety distance of a train control system and a train braking system to increase the volume of traffic. For the braking model, a train set (electric multiple unit composed 6 cars) was tested. The factors that can affect the braking characteristics include the friction coefficient, braking pressure, and regenerative braking. The braking pressure was classified into service and emergency braking and reflected the characteristics of the vehicle. The external force acting on the running railway car was tested in accordance with KS R 9217, and the running resistance of the train is presented in the form of a polynomial. The dynamic behavior of the train running on a straight flat line was simulated using UM 8.3. The results were validated with experimental data, and the results were reasonable. With the validated model, a stopping distance was determined according to the initial braking speed and compared with the deceleration braking model. In addition, a safety distance for the train control system could be changed according to the frictional coefficient limits. These results are expected to be useful for analyzing the dynamic behavior of trains, and for analyzing various railway environments and improving the braking performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.496-503
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• 2003

SFC system has come to be used as drive large synchronous machine in many industry applications. Many papers have been presented on the control algorithm of SFC system, not the acceleration and start-up but the rated speed operation with line connection and the braking operation with regeneration which is used in the industry. This paper presents the whole section control algorithm for a large synchronous machine using SFC system. The results of experiment show that the proposed algorithm is proper and effective.

• 전기의세계
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• v.10
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• pp.55-61
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• 1963

본 논문에서 취급한 제동권선이 없는 철극선의 3상단락현상을 해명하는데 있어 우선 임의력율의 전류를 횡축분과 직축분으로 분리해서 취급하는 소위 Blonde의 2반작용법(two reaction method)를 썼고, 각종 Reactance를 표시하는데는 편리한 단위법(perunit notation)을 사용했으며, 전기자의 1상저항은 각종 Reactance ( $X_{x}$, $X_{q}$ )의 어느것 보담도 극소치임으로 실제계산에는 무시했으나 과도전류의 변화를 좌우하는 감쇠정수[decrement factor)에는 큰 영향을 준다는 것이 규명되었다. 해석결과로서 3상단락전류의 초기치는 특수치보다 훨씬 큰 이유로서 단락전류가 계자자속을 약하게 만들어 그 반동으로 계자회로에 일정자속을 유지하기 위하여 부문적으로 개자전류가 증대함을 알게되었고, 단락전류의 직축분과 횡축분의 구성분이 규명검토되었고, 발전기의 돌발단락저류는 일반적으로 직류분, 기본파교류분 및 제2조파등을 포함하나 그 전부가 시정수의 역수인 감쇠정수에 지배되어서 지수함수곡선에 따라 감쇠되어 결국에는 지속단락전류에 귀착한다는 사실과 3상단락은 평형단락사고임으로 영상전류는 영이며 각상과도전류의 위상차가 120.deg.라는 것엔 변함이 없다는 것과 끝으로 철극기를 정격속도로 운전해 놓고 이것을 여자해서 무부하전압을 수기시켜 그의 3상전단자를 돌연 단락해서 그의 과도전류의 파형을 Oscillograph로 촬영하면 본론에서 해석한 결과식의 그것과 일치하게 됨을 알 수 있을 것이다.것이다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.301-303
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• 2015

디지털 운행기록장치는 대한민국의 경우 2011년부터 상용차에 대해 법령으로 장착이 의무화되었다. 이 장치는 자동차의 속도, 주행거리, 브레이크 상태, GPS 위지청보 등을 수집하는 기록 장치로서 이를 통해 수집된 정보로 운전 형태를 파악하고 분석해준다. 그러나 초기 장치 구입비용과 전송 방식에 따른 월별 통신서비스 비용 때문에 일반 운전자의 사용이 제한된다. 따라서 본 연구는 일반 운전자도 위험운전행동을 분석하고 파악하여, 결과를 제공하는 스마트폰 어플리케이션의 설계 및 구현을 목적으로 한다. ECU(Electronic Control Unit)에서 얻을 수 있는 주행 데이터(가속 제동, 속도, 운전 시간 등)를 OBD-II(On-Board Diagnostic version II) Scanner를 통해 수집한다. 이 정보를 바탕으로 위험운전평가 알고리즘을 이용하여 실시간 분석한다. 상기 알고리즘은 대한민국의 교통안전공단에서 제공하는 위험운전(11종)에 대한 정의를 바탕으로 한다. 이를 통해 분석된 결과는 실시간으로 사용자에게 제공되며, SQLite를 이용하여 DB에 저장되고 통신사의 이동통신(3G,4G) 혹은 Wifi의 네트워크를 이용하여 연계 서버에 전송된다. 이 위험 운전 분석 어플리케이션을 통해 운전자들의 안전 운전을 유도하고자하며, 추후 운전습관 연계 보험의 도입에 따라 합리적이고 공정한 데이터를 제공하고자 한다.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.59-66
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• 2018

The utilized coefficient of friction (UCOF) as a ratio of the shear force to the normal force on the ground during walking is used to identify the point at which slip is likely to occur. Shoe walking will change the utilized coefficient of friction by shoe design such as sole thickness and hardness, heel shape, and outsole pattern. In this study, subjects are 21 adults (10 female, 11 male, age: $25.2{\pm}2.3yrs$, height: $165.6{\pm}7.2cm$), analysis variables were walking speed, GRF, when the UCOF is maximal, and Tangent of CoP-CoM angle, and correlation analysis with the utilized friction coefficient (UCOF). As a result, First, for the shod walking the time point which UCOF is maximum about heel strike was faster and the magnitude was larger than for barefoot walking. Second, the correlation between the tangent of CoP-CoM and UCOF of right foot was higher at the left heel striking point (UCOF2_h) which occurred in the post propulsion phase than at the right heel striking point (UCOF1_h). This suggests that the right foot UCOF is related to the braking phase of left foot( which is the propulsion phase of right foot) rather than the braking phase of right foot.