• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2086-2097
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• 2012

A terminal-based dynamic clustering algorithm is proposed in a multi-cell scenario, where the user could select the cooperative BSs from the predetermined static base stations (BSs) set based on dynamic channel condition. First, the user transmission rate is derived based on linear precoding and per-cell feedback scheme. Then, the dynamic clustering algorithm can be implemented based on two criteria: (a) the transmission rate should meet the user requirement for quality of service (QoS); (b) the rate increment exceeds the predetermined constant threshold. By adopting random vector quantization (RVQ), the optimized number of cooperative BSs and the corresponding channel conditions are presented respectively. Numerical results are given and show that the performance of the proposed method can improve the system resources utilization effectively.

• Journal of Korea Spatial Information System Society
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• v.3 no.1 s.5
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• pp.63-73
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• 2001

The purpose of this study is to develop a method of integrating diverse communication networks for effectively providing ITS(Intelligent Transport System) services. In this paper, in oder to integrate communication networks, we have defined ITS services, its requirements and functions of communications. Also, we have analyzed the six important ITS services in the National ITS Architecture along with the characteristics of wireless communications. Based on the ITS service scenarios, we have derived the communication methods for ITS services.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.241-242
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• 2016

Recently, the interests in safety and prevention from disaster are increasing. In particular, lifeline networks such as water line and sewerage, electricity, gas, and road would be damaged from a disaster. If the lifeline networks do not work in normal, national public service will not properly function. Researches in social network analysis have been conducted for analyzing the interdependency between individuals since 1970s. These network analysis are utilized to investigate a spread of information and disease. However, it is hard to discover the analyzed cases including characteristics of nodes of networks in the area of transportation and disaster. Therefore, this study conducts network analysis of flooded road with flooding scenarios, investigates safe evacuation routes in flooded road network, and suggests efficient approaches for preventing damages from a flooding.

• International Journal of Railway
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• v.5 no.2
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• pp.84-88
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• 2012

Derailment due to wheel failure would cause a tremendous social and economical cost in service operation. It is necessary to evaluate quantitatively the safety with respect to high-speed train. Although the safety of railway wheel has been ensured by an regular inspection, all critical defects cannot be detected in inspection cycles and the wheel has been replaced because a defect quickly become critical for safety. Therefore, it is important to calculate quantitatively the fracture limit and remnant life of damaged railway wheel in wheel-rail system. In present paper, the critical crack size of wheel for high-speed train is simulated based on fracture scenario and the safety of wheel is evaluated.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.795-800
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• 2009

Railway safety is one aspect of the transport service quality delivered to passengers, employees and third parties. To improve safety by a cultural shift from a deterministic to a risk based approach, European Railway Agency (ERA) introduces common and transparent methods to monitor safety performance and set targets and establishes safety management systems. The objective of this study is to review the common safety performance management method of the ERA(European Railway Agency) for it's application to the Korea railway. For this end, the risk assessment models were developed based on the accident scenarios and domestic railway accidents had been investigated and quantitative and qualitative analyses was performed using the developed information system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.669-674
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• 2007

To develop a promising hybrid structural health monitoring (SHM) system, a combined use of structural vibration and electro-mechanical (EM) impedance is proposed. The hybrid SHM system is designed to use vibration characteristics as global index and EM impedance as local index. The proposed health monitoring scheme is implemented into prestressed concrete (PSC) girder bridges for which a series of damage scenarios are designed to simulate various prestress-loss situations at which the target bridges car experience during their service life. The measured experimental results, modal parameters and electro-magnetic impedance signatures, are carefully analyzed to recognize the occurrence of damage and furthermore to indicate its location.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.207-216
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• 2013

Vehicular ad-hoc networks (VANETs) are self-organizing, self-healing networks which provide wireless communication among vehicular and roadside devices. Applications in such networks can take advantage of the use of simultaneous connections, thereby maximizing the throughput and lowering latency. In order to take advantage of all radio interfaces of the vehicle and to provide good quality of service for vehicular applications, we developed a seamless flow mobility management architecture based on vehicular network application classes with network-based mobility management. Our goal is to minimize the time of flow connection exchange in order to comply with the minimum requirements of vehicular application classes, as well as to maximize their throughput. Network simulator (NS-3) simulations were performed to analyse the behaviour of our architecture by comparing it with other three scenarios. As a result of this work, we observed that the proposed architecture presented a low handover time, with lower packet loss and lower delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.1058-1060
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• 2005

현재 통신 서비스 및 인터넷 서비스들은 각기 독립적인 형태의 서비스를 재공하고 있으며, 고유의 서비스 체계를 유지하면서 발전해 왔다. 그러나 이러한 서비스들은 향후 통합 및 융합과정을 거처 차세대 네트워크 망 즉, NGN(next generation network)에 통합되어 나가게 될 것이며 기존의서비스에 다양한 서비스를 부가하여 새로운 서비스가 창출 될 것이다. 된 논문은 이러한 추세를 고려하여, NGN에서 요구되는 언제 어디서나 사용자에 다양한 서비스를 제공할 수 있는 서비스인 텔레매틱스에 대한 NGN 서비스 시나리오를 보일 깃이다. 텔레매틱스는 정보기술과 자동차기술의 융합으로 이루어진 서비스로 위치측정시스템과 무선통신량을 이용하여 교통정보, 응급구조 구난, 인터넷 이공 및 전화 등 다양한 서비스를 제공을 수 있는 시스템으로 차세대 네트워크 서비스로 각광 받고 있다. 그리나 아직까지 NGN에서의 활용에 대한 연구는 이루어지고 있지 않은 실정으로 본 논문에서는 텔레매틱스에 대한 NGN 망 및 기존의망과의 접속 시나리오와 서비스 시나리오에 대할 방법을 제안 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1643-1651
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• 1997

Next generation mobile networks will be demanded to support high speed data and multimedia services in addition to extisting serviced including voice communications. In this paper, we discuss the requirements of the wireless service with broad range of appkications, and present several types of architecture for future bobile network. After a brief comparative analysis, we propose a most practical and feasible one. And also, we discuss possible interworking scenarios between radio access system and intelligent network. In consideration of the selected infrastructure and scenario, we present protocol architectures and basic functions of radio access system. Based on the architecture, we believe that the itegrated system can be realized with such advantages of easy interworking, high feasibility on common services, easy introduction to new services, and unified operation.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.5
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• pp.511-520
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• 2015

Inventory, cost, and the level of service are three interrelated key metrics that most supply chain organizations are striving to optimize. One way to achieve this goal is to create a simulation model to conduct sensitivity analysis and optimization on several different supply chain policies that can be implemented in actual operation. In this paper, a case of Xerox global supply chain modeling and analysis to assess several "what if" scenarios for the consumable policy safety stock is presented. The simulation model, combined with analytical cost model and optimization module, is used to optimize the policy safety stock level to achieve the lowest total value chain cost. It was shown quantitatively that the policy safety stock can be reduced, but it is offset by the inbound premium transportation cost to expedite supplies in shortage, and the outbound premium transportation cost to send supplies to customers via express shipment, requiring fine balance.