• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.581-587
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• 2008

This paper presents a railway network design problem (RNDP), which can be formulated as a bi-level program. In bi-level program upper level program is to minimize total travel cost including the construction cost of the railway facilities, whilst lower one describes the railway route choice behavior of passengers. We also propose a heuristic method for solving the program because it is a kind of NP-hard problem. From two numerical railway examples, we confirm that the RNDP and its algorithm produce a reasonable solution and that it is applicable to real world.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.427-436
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• 2009

This paper introduced Railway Network Design Problem (RNDP) to provide priority decisions on high-speed railway investment scenarios defined by various network segments and train systems. The RNDP optimizes the objective functions of minimize total travel time. Results show that the priority of high-speed railway investment is found to be East-west, West-coast, and South-coast line respectively. An entirely new line built with 400km/h is found to be the best alternative to East-west line. Regarding West-coast and South-coast line, the combined alternative of upgrading Geolla and Kyeonjon line with 200km/h and building a new line with 400km/h and 350km/h for remains of each line is the best.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1086-1092
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• 2002

Computer simulation is essential to design the suspension elements of railway vehicle. By computer simulation, engineers can assess the feasibility of a given design factors and change them to get a better design. But if one wishes to perform complex analysis on the simulation, such as railway vehicle dynamic, the computational time can become overwhelming. Therefore, many researchers have used a mega model that has a regression model made by sampling data through simulation. In this paper, the neural network is used a mega model that have twenty-nine design variables and forty-six responses. After this mega model is constructed, multi-objective optimal solutions are achieved by using the differential evolution. This paper shows that this optimization method using the neural network and the differential evolution is a very efficient tool to solve the complex optimization problem.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.535-542
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• 2002

This paper show communication network scheme problem for the railway is solved which were electrical noise and line break in wayside using rerouting communication line, Considering the availability and the maintainability based on the reliability in design of communication networks. At first, Self-Healing Ring algorithm is suggested in that solution which is satisfied with above requirements. And also, in the advanced type, Dual Master scheme is suggested that the problem which is occurred in line break of both main and sub line at the same time can be solved using DMSHR(Dual Master Self Healing Ring). Therefore total reliability in railway system is going to be advanced using DMSHR scheme.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.542-549
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• 2002

Computer simulation is essential to design the suspension elements of railway vehicle. By computer simulation, engineers can assess the feasibility of given design variables and chance them to get a bettor design. Even though commercial simulation codes are used, the computational time and cost remains non-trivial. Therefore, malty researchers have used a mesa model made by sampling data through simulation. In this paper, four mesa-models for each index group such as ride comfort, derailment Quotient, unloading radio and stability index, are constructed by use of neural network. After these meta models are constructed, multi-objective optimization are achieved by using the differential evolution. This paper shows that the optimization of design variables using the neural network model is very efficient to solve the complex optimization Problem.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.320-328
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• 2011

The down town passage segment which follows in the straight line which follows recently in high speed of the railway and rail construction is increasing. Also according to quality of life improvement of the citizens whom follows in national income increase the resident demand only becomes larger day by day about a environmental creation which is comfortable and house environmental etc. Demand of the citizens is not the problem of today yesterday about like this railway mean of transportation and with the fact that continuously will increase in future. This study is to predict and reduce railway noise from the conventional PSC-beam bridges which passes through urban areas under the government strateges of speed and weight increases of railway. The purpose of this study is to recommend a proper noise prediction method for designing pleasant roadside environments. The railway design including existing line reconstructions should minimize curved alignment to increase train speed to 180~200km/hr under the government's long-term planing such as the 4th Comprehensive National Development Plan (2000~2020), National Intermodal Transportation Plan (2000~2019) and National Railroad Network Establishment Plan (2006~2015), Since the PSC-beam bridges are mainly used for bridge structures urban areas, noise measurements were performed and analyzed to recommend the noise prediction methods for each type and speed of train respectively.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.662-669
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• 2012

In 2004, KTX operated in Korea on the 5th in the world. But there are various factor on planed schedule delay of Big National Construction Project like Seoul-Busan High Speed Rail Project(Seoul-Busan HSR). For example, Often change of government policy, project management control problem of design and construction, conflict of interested party like environmental organization/resident are the main delay factors. The suggestions for improvement of the construction schedule through the Seoul-Busan HSR will help to make a new leap forward in rail construction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.853-858
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• 2019

One of the methods which can enhance the efficiency of railroad network is construction of interconnection branch line for several route to share one railway. In Korea, this method already has been implemented or excuted as project level. This study suggests a network design model and a solution algorithm to choice most proper site to construction it and determine the priority of branch lines which can be considered in planning level, not project level. The model is a non-linear optimization program which minimize total cost-construction cost, operating cost and passengers' travel cost. The decision variables are a binary variable to explain whether construction or not and its direction and a integer variable of the frequencies of travel routes. The solution algorithm-problem solution and route choice and also the result of implementation for example network are suggested. This result can be more advanced after application in real network and calibration of parameters.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.483-503
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• 2015

This paper analyzes the optimal user density and power allocation for Device-to-Device (D2D) communication underlaying cellular networks on multiple bands with the target of maximizing the D2D transmission capacity. The entire network is modeled by Poisson point process (PPP) which based on stochastic geometry. Then in order to ensure the outage probabilities of both cellular and D2D communication, a sum capacity optimization problem for D2D system on multiple bands is proposed. Using convex optimization, the optimal D2D density is obtained in closed-form when the D2D transmission power is determined. Next the optimal D2D transmission power is obtained in closed-form when the D2D density is fixed. Based on the former two conclusions, an iterative algorithm for the optimal D2D density and power allocation on multiple bands is proposed. Finally, the simulation results not only demonstrate the D2D performance, density and power on each band are constrained by cellular communication as well as the interference of the entire system, but also verifies the superiority of the proposed algorithm over sorting-based and removal algorithms.