• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.694-702
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• 2017

In the case of an elevated railway station, structure borne noise and vibration due to structural limitations allow the load and vibration from railway vehicles to be directly transmitted to the station structure, resulting in an increase in the number of civil complaints from customers and staff of the station. The floating slab track system, which is well known as one of the solutions for reducing the noise and vibration from elevated railway stations, usually contains rubber mounts or rubber pads under the railway slab which act as a damper. These types of device have the disadvantage that is difficult to predetermine the exact stiffness and damping ratio under the nonlinear loads resulting from train services. In this study, an isolator with a friction type of wedge is introduced, which can be applied to floating slab track systems and to be designed with precisely the required stiffness. Furthermore, a comparative analysis of the stiffness between the designed and experimental values is carried out, while the damping ratio, which is closely related to the friction wedge blocks, is deduced according to the train load condition. The performance tests of the isolator were conducted in accordance with the DIN 45673-7 standard which includes both static and dynamic load tests. The load conditions for the performance tests are designed to conform to the DIN standard related to the weight of the train and rail track, in order to perform vertical and horizontal load tests, so as to ensure the secure structural safety of the railway. Also, by checking the change aspect of the friction coefficients of the friction elements according to the loading rate, the vibration reduction performance of the friction type isolator with variable loading rate conditions is examined.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.4
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• pp.189-196
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• 2017

BIS(Bus Information System) provides the different information related to buses including predictions of arriving times at stations. BIS have been deployed almost all cities in our country and played active roles to improve the convenience of public transportation systems. Moving average filters, Kalman filter and regression models have been representative in forecasting the arriving times of buses in current BIS. The accuracy in prediction of arriving times depends largely on the forecasting algorithms and traffic conditions considered when forecasting in BIS. In present BIS, the simple prediction algorithms are used only considering the passage times and distances between stations. The forecasting of arrivals, however, have been influenced by the traffic conditions such as traffic signals, traffic accidents and pedestrians ets., and missing data. To improve the accuracy of bus arriving estimates, there are big troubles in building models including the above problems. Hidden Markov Models have been effective algorithms considering various restrictions above. So, we have built the HMM forecasting models for bus arriving times in the current BIS. When building models, the data collected from Sunchean City at 2015 have been utilized. There are about 2298 stations and 217 routes in Suncheon city. The models are developed differently week days and weekend. And then the models are conformed with the data from different districts and times. We find that our HMM models can provide more accurate forecasting than other existing methods like moving average filters, Kalmam filters, or regression models. In this paper, we propose Hidden Markov Model to obtain more precise and accurate model better than Moving Average Filter, Kalman Filter and regression model. With the help of Hidden Markov Model, two different sections were used to find the pattern and verified using Bootstrap process.

• Korean Journal of Remote Sensing
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• v.27 no.5
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• pp.521-534
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• 2011

The high-resolution X-band SAR systems such as COSMO-SkyMED and TerraSAR-X have been launched recently. In addition KOMPSAT-5 will be launched in the early of 2012. In this study we developed the new method for persistent scatterer candidate (PSC) selection and network construction, which is more suitable for PSInSAR analysis using multi-temporal X-band SAR data. PSC selection consists in two main steps: first, selection of initial PSCs based on amplitude dispersion index, mean amplitude, mean coherence. second, selection of final PSCs based on temporal coherence directly estimated from network analysis of initial PSCs. To increase the stability of network the Multi- TIN and complex network for non-urban area were addressed as well. The proposed algorithm was applied to twenty-one TerraSAR-X SAR of New Orleans. As a result many PSs were successfully extracted even in non-urban area. This research can be used as the practical application of KOMPSAT-5 for surface displacement monitoring using X-band PSInSAR.

• Journal of Korean Society of Transportation
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• v.25 no.3
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• pp.145-154
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• 2007

Determining stop spacing is a very important process in transit system planning. This study is involved in an analytical approach to decide the transit stop spacing. Transit stop spacing should be longer as 1) user access speed, 2) user travel time, and 3) dwell time increase, and shorter as 1) passengers (boardings and alightings) and 2) headway increase. In this study, a methodology is proposed to determine transit stop spacing to minimize total cost (user cost plus operator cost) with irregular passenger distribution (boardings and alightings) Without considering in-vehicle passengers, the transit stop spacing should be shorter in the concentrated sections of the passenger distribution than in others to minimize total cost. Through the conceptual analysis, it is verified that the transit stop spacing could be longer as the in-vehicle passengers increase in certain sections. This study proposes a simple practical method to determine transit stop spacing and locations instead of a dynamic programming method which generally includes a complex and difficult calculation. If the space axis is changed to a time axis. the methodology of this study could be expanded to analyze a solution for the transit service (or headway) schedule problem.

• Journal of Korean Society of Transportation
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• v.36 no.1
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• pp.13-22
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• 2018

Buses, one of the representative public transportation modes, are divided into a vareity of service types according to the purpose of operation, operating distance, and management agencies. Although bus-involved crashes may cause large amount of damage due to the higher number of passengers boarded on a bus, prior research has little focused on crash severity according to bus service types. This study aims to investigate factors influencing crash severity in bus-involved crashes and to present policy implications to reduce crash severity by bus service type. To do this, bus-involved crash data from the Traffic Accident Analysis System (TAAS) during five-year period are used. Ordered probit models for three types of bus service, i.e., city bus, suburban and express buses, and charter buses, are estimated to analyze the factors of accident severity. The results show that there are significant differences of factors affecting crash severity among the types of bus services while speed and road surface influence all the types of buses. In case of local buses, time of day, roadway alignment, and installation of a traffic signal are found to be statistically significant factors. Seat belt and road class have significant effects on injury severity of the intercity and express buses. Chartered buses have time of day, driving experience, seatbelt, traffic signal, and day of week as the significant factors. The results of this study are expected to contribute to the reduction of the crash severity by each bus service type.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.6
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• pp.31-42
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• 2019

Among the driving information recorded in the event data recorder (EDR), the speed information of the vehicle before the traffic accident is a very important factor that determines the punishment of the driver of the accident vehicle, the identification of the offender and the victim, and the possibility of avoiding the accident. Also, by analyzing the EDR data, the deceleration of the accident vehicle can be analyzed. In this study, the results of the braking test of the previous study and the analysis of the EDR data of the traffic accident vehicle were compared to suggest an appropriate deceleration value applicable to the calculation of the stopping distance. As a result of the braking test of the vehicle equipped with ABS of the previous study, the average deceleration of the vehicle was 0.79g ~ 0.94g. In addition, the deceleration value was calculated from 0.92g to 0.94g in the recent automobile safety evaluation braking test conducted by the Korea Automobile Testing & Research Institute. In addition, the deceleration value of 0.55g ~ 0.71g was calculated through the analysis of EDR data performed in this study, and the value was smaller than the deceleration value measured in the braking experiment of the previous study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.639-645
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• 2018

This paper is intended to develop a decision model that can be applied to autonomous vehicles and autonomous mobile vehicles. The developed module has an independent configuration for application in various driving environments and is based on a platform for organically operating them. Each module is studied for decision making on lane changes and for securing safety through reinforcement learning using a deep learning technique. The autonomous mobile moving body operating to change the driving state has a characteristic where the next operation of the mobile body can be determined only if the definition of the speed determination model (according to its functions) and the lane change decision are correctly preceded. Also, if all the moving bodies traveling on a general road are equipped with an autonomous driving function, it is difficult to consider the factors that may occur between each mobile unit from unexpected environmental changes. Considering these factors, we applied the decision model to the platform and studied the lane change decision system for implementation of the platform. We studied the decision model using a modular learning method to reduce system complexity, to reduce the learning time, and to consider model replacement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6949-6958
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• 2015

Radio based train control system performs train safe interval control by receiving in realtime the position information of trains driving in the control area of the wayside system and providing onboard system in each train with updated movement authority. The performance of the train control system is evaluated to calculate the minimum operation headway, which reflects the operation characteristics and the characteristics of the train as well as the interval control performance of the train control system. In this paper, we propose the operation headway calculation for radio based train control system and a new train interval control algorithm to improve the operation headway. The proposed headway calculation defines line headway and station headway by the estimation the safety margin distance reflecting the performance of the train control system. Furthermore the proposed Enhanced Train Interval Control(ETIC) algorithm defines a new movement authority including both distance and speed, and improves the train operation headway by using braking distance occurring inevitably in the preceding train. The proposed operation headway calculation is simulated with Korean Radio-based Train Control System(KRTCS) and the simulated result is compared to improved train interval control algorithm. According to the simulated results, the proposed operation headway calculation can be used as performance indicator for radio based train control system, and the improved train control algorithm can improve the line and station headway of the conventional radio based train control system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.778-784
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• 2017

In this paper, we propose wired and wireless distributed control systems designed to improve the freight logistics efficiency and verify wired distributed control systems. The verification condition required that 50 cargo vehicles be connected and operated to travel 21 km from Busan Sinhang station to Jinlye Station at an average speed of about 100km/h. The verification results show that the traction output and braking output of the control and controlled cars are dispersed by the wired distributed control system. The application is expected to more than double the efficiency of the logistics compared to the existing freight transportation system. However, in the case of the wired distributed control system, cable installation and maintenance are difficult, and it is impossible to change the combination of freight vehicles. Through the verification of the wired distributed control system, the applicability of distributed control systems to freight vehicles in Korea was confirmed and the system was further developed to produce a wireless distributed control system. In order to apply the wireless distributed control system, a propagation environment analysis for the ISM band was performed in the testbed and, as a result, it was confirmed that Wifi technology using the ISM band could be utilized. In order to use the WDP (Wireless Distributed Power) devices newly installed in the target vehicles, the transmission / reception control signals associated with the propulsion / braking / total control devices are defined. In the case of wireless distributed control systems, the convenience of their application and operation is guaranteed, but reliability and emergency safety measures should because of the dependence of the control of the vehicle on radio signals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.32-38
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• 2020

Cargo train braking uses the pressure changes in the air braking pipe to operate the braking tightening and releasing service repeatedly. Air-braking release failure means partial braking caused by a failure of the variable load valve after the driver handling the brake release. This phenomenon causes wheel flaws while driving a wagon, resulting in wheel breakage or train derailment. This study developed the air-braking release failure proof valve considering the technical requirements of the railway operation corporations. In addition, a durability test of the valve was carried out using a braking performance simulator, and its operating performance was evaluated from the pneumatic history under cyclic braking conditions. The warranty life of this valve was assessed by performing 160,000 cycles of testing of 12 prototypes in accordance with the zero-failure test method, considering the number of braking cycles while driving the wagon. During the durability test, the pneumatic input time, output time, and release velocity were almost constant. The warranty life of this valve was 59,860 times the 95% confidence level, which means that it can be operated without trouble for four years when the valve is installed in the bogie of the wagon.