• 전기학회논문지
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• 제59권12호
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• pp.2125-2130
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• 2010

The neutral section on electric railway system is significant sector in order to prevent short circuit of two electric powers. However, while electric trains pass the neutral section, those speed is decreased and the accident of AC electric traction system and the electric train would be occurred. So the countermeasures are urgently needed. The automatic power switching technology system that is current being research and development is system to improve these problems. Because main object of this system is power change using static switch in the neutral section, it's expected to cause a variety of transients. Especially, onboard transformer inrush current for electric railway train can be occurred more than rated current according to switching time. Therefore, the analysis and improvement are needed to ensure the stability of this system. In this paper, we analyze the operating characteristics of the automatic power switching technology system. Especially, it reviews inrush current according to the closing phase angle. And we propose control plan of inrush current considering the case that voltage is maintained due to counter electromotive force and regenerative braking operation of electric railway train. Finally, the proposed control scheme was reviewed using the transient analysis program.

• 대한기계학회논문집A
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• 제20권2호
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• pp.585-593
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• 1996

According to the considerable increase of the length of belt conveyors, the dynamic analysis of systme becomes necessary to consider the variation of tensions and transient motion of components during starting and stopping of conveyor. The mathematical model of system is derived using the lumped parameter method. The input driving force is represented with two functions of time and pulley speed to count the characteristics of motor and fluid coupling. An example system was studied with 14 km in the distance of carrying. At head, it has two drivers and one gravity take-up and at tail ond driver and one power winch take-up. In the example, the transient tensions and responses, calculated using two cases of driving force, are mutually compared in starting mode. Also, the position of maximum tension and the braking force of take-up are obtained in stopping mode.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2009년도 춘계학술대회
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• pp.35-43
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• 2009

The specific feature of trains as a means of transportation is that, on one side, at once they can carry big loads but, at the same time, if an accident occurs, it potentially leads to many human casualties or big material losses. Especially, train accidents caused by bad weather conditions result in many fatal losses of human lives and property. In Korea many railways run either in mountainous areas or along rivers thus making them especially susceptible to natural hazards. The types of damages inflicted by heavy rains resulting from rapidly changing meteorological conditions are diverse; and not only their scope is big but also they repeat regularly. Consequently, this study analyses the reasons why such effects of heavy rains on the railway conditions, damage to the railways caused by heavy rains or cases of stone fall as well as other types of accidents are not avoided. Study also, on the basis of laws related to movement in poor weather conditions and specifics of train braking, identifies systematic and technical problems and suggests and emphasizes new complex measures on their prevention.

• 대한임베디드공학회논문지
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• 제15권3호
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• pp.119-127
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• 2020

The detection and recognition of abnormal driving becomes crucial for achieving safety in Intelligent Transportation Systems (ITS). This paper presents a feature extraction method based on spectral data to train a neural network model for driving behavior recognition. The proposed method uses a two stage signal processing approach to derive time-saving and efficient feature vectors. For the first stage, the feature vector set is obtained by calculating variances from each frequency bin containing the power spectrum data. The feature set is further reduced in the second stage where an intersection method is used to select more significant features that are finally applied for training a neural network model. A stream of live signals are fed to the trained model which recognizes the abnormal driving behaviors. The driving behaviors considered in this study are weaving, sudden braking and normal driving. The effectiveness of the proposed method is demonstrated by comparing with existing methods, which are Particle Swarm Optimization (PSO) and Convolution Neural Network (CNN). The experiments show that the proposed approach achieves satisfactory results with less computational complexity.

• 한국세라믹학회지
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• 제35권7호
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• pp.740-748
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• 1998

The inertia friction properties of C/C composites manufactured by the processes of pressure and at-mospheric carbonizaton with a commerciallized and two kinds of modified coal-tar pitch as a matrix pre-cursor were investigated. The modifications of a pitch such as the introduction of mesophase and the ad-dition of sulphur into a raw pitch were not effective for a impregnation efficiency conducted in a vacuum and at the same time in a pressure of 5kg/cm2 due to the increase of the pitch viscosity. There was not a difference in the densification increment between the pitch modifications however it was revealed that a pressure carbonization was more advantageous than an atmospheric in the densification and the formation of anisotropic carbon matrix. The friction and wear propertis of C/C having higher degree of matrix cry-stallization higher density and hardness of friction surface showed superiority. As the braking energy was increased the friction coefficients were decreased and reached almost same level at the high kinetic energy of 99.6kJ. The wear trends at 99.6kJ were different from the behaviors of friction ceofficient under the same energy in which an oxidation wear is being considered along with a mechnical wear although the wear rates were almost similar to the friction coefficient at the low energy.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.151-161
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• 2014

In this paper, fuel tank of the locomotive ER 24 has been studied. Firstly the behavior of fuel and air during the braking time has been investigated by using a two-phase model. Then, the distribution of pressure on the surface of baffles caused by sloshing has been extracted. Also, the fuel tank has been modeled and analyzed using Finite Element Method (FEM) considering loading conditions suggested by the DIN EN 12663 standard and real boundary conditions. In each loading condition, high stressed areas have been identified. By comparing the distribution of pressure caused by sloshing phenomena and suggested loading conditions, optimization of the tank has been taken into consideration. Moreover, internal baffles have been investigated and by modifying their geometric properties, search of the design space has been done to reach the optimal tank. Then, in order to reduce the mass and manufacturing cost of the fuel tank, Non-dominated Sorting Genetic Algorithm (NSGA-II) and Artificial Neural Networks (ANNs) have been employed. It is shown that compared to the primary design, the optimized fuel tank not only provides the safety conditions, but also reduces mass and manufacturing cost by %39 and %73, respectively.

• 대한교통학회지
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• 제21권6호
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• pp.67-73
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• 2003

본 연구는 기존의 신호등의 시각적 인지도를 향상시켜 운전자의 인지실수를 예방하고 안전운전을 도모하기 위해 보조녹색신호가 추가된 신호등에 대한 연구를 수행하였다. 기존의 3색, 4색 신호등과 보조녹색신호를 추가로 제시한 3색, 4색 신호등을 자동차 모의실험장치를 통하여 비교한 결과 두 가지의 신호등간의 유의한 차이가 있는 것으로 나타났다. 이러한 결과는 개선된 신호등이 현장 적용시 운전자가 스스로 의식하지 못하는 상태에서 제동시점을 다소 앞당겨준다는 점에서 안전운전에 기여할 수 있는 가능성을 보여주었다. 본 연구 결과는 실제 운전자의 반응을 비교함과 동시에 주관적인 행동반응을 조사함으로써, 연구결과의 실제 적용가능성을 제시하였다는데 그 의의가 있다고 할 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.896-899
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• 2003

The electric railway has been widely used as a transportation all over the world. It also was opened in 1973 in korea and it has been steadily proceeded in making electric railway network for a big city and building Keongbu high speed , electric railway. That's why the system of electric railway is able to solve the environmental pollution and operate the useful energy in environmental ways, it helps to increase the ability of transportation and to decrease the cost. Because of the advantage of making the economic situation better, the system of electric railway is trying to do their best in developing technique of electric railway. Because of the increasing of transportation and the high speed operation, cars with regenerative braking system was adapted. Therefore, unbalanced voltage and current of three phase system and the drop and rise of voltage of feeding circuit is expected. Now that building the substation, newly spends lots of costs and time, it is a very difficult situation to solve the problem. We can guess that electric railway line can't receive power from the power system of bigger size in building newly electric railway. In this paper, it was proved that series voltage compensator was suitable as a solution according to voltage drop and voltage fluctuating through computer simulation.

• 한국정밀공학회지
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• 제34권2호
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• pp.145-150
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• 2017

Air brake valves are widely used in automotive braking systems and the Korean automobile industry depends on importing them. Therefore, we should develop the technical expertise for their domestic production. In this study, air brake valves were analyzed that can be used in a variety of automobiles. Computational fluid dynamics analysis, static structural analysis, and hyper-elastic analysis were carried out. Before production of an air brake valve system, the performance of different parts has to be evaluated, for instance by using finite element analysis. The structural stability of the product can be determined using static dynamics. The compression behavior of the O-ring is predictable by nonlinear hyper elastic analysis, although errors are possible due to one-way loading. This simulation study can both save time and reduce costs compared to the development of experimental prototypes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.486-491
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• 2013

Creak noise is kind of scratching noise which is usually generated in drum brake system on the vehicle. When driver brakes vehicle or applies parking lever, drum brake shoe moves to the drum side to stop the vehicle. And at that time, moving shoe scratches backing plate ledge surface, and that makes scratching noise in special condition. This study presents how we can generate creak noise in the laboratory and how we can reduce it by experimental approach. Through several and various type of tests, we could generate creak noise with damage on ledge area of the backing plate in the lab and we verified tab type shoe design can reduce this scratching noise. As a result of this study, we notified how creak noise happens in the vehicle, and that tab type design shoe has good performance of ledge area damage based on lab test(rig & dynamometer equipment), and that this can reduce potential risk of creak noise in the field.