• Journal of Electrical Engineering and Technology
• /
• v.8 no.5
• /
• pp.1002-1011
• /
• 2013

This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OCRs) to ensure their proper operating time and protective coordination. The application of the proposed algorithm requires digital protection relays with microcontroller and memory. The operating parameters of digital OCRs are adjusted based on the available data whenever system conditions (system with distributed generation (DG)) vary. Moreover, it can reduce the calculation time required to determine the operating parameters for achieving its purpose. To verify its effectiveness, several case studies are performed in time-domain simulation. The results show that the proposed adaptive protection algorithm can keep the proper operating time and provide the protective coordination time interval with fast response.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• autumn
• /
• pp.85-90
• /
• 2002

In the construction industry, projects are becoming increasingly large and complex, involving multiple subcontractors. Traditional centralized coordination techniques used by the general contractors become less effective as subcontractors perform most work and provide their own resources. When subcontractors cannot provide enough resources, they hinder their own performance as well as that of other subcontractors and ultimately the entire project. Thus, construction projects need a new distributed coordination approach wherein all of the concerned subcontractors can reschedule a project dynamically. To enable the new distributed coordination of project schedule changes, I developed a novel agent-based compensatory negotiation methodology, which allows software agents to simulate negotiations on behalf of their human subcontractors. This research formalizes the necessary steps that would help construction project participants to increase the efficiency of their resource use, which in turn will enhance successful completions of whole projects.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.9A
• /
• pp.1075-1082
• /
• 2004

Wireless LAN is a rather mature communication technology connecting mobile terminals. IEEE 802.11 is a representative protocol among Wireless LAN technologies. The basic medium access control (MAC) mechanism of IEEE 802.11 is called distnbuted coordination function (DCF). DCF shows poor throughput and high drop rate as the number of stations and offered traffic load increase. In this paper we propose an effective mechanism using dynamic mimmum contention window(CWmin) in wireless LAN~ and show that performance improves via simulations. Proposed dynamic CWmin scheme exhibits superior performance as the number of stations and offered load grow. As, our proposed scheme is expected to be more effective in highly densed wireless LAN environment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.12
• /
• pp.1811-1813
• /
• 2016

DCF (Distributed Coordination Function) resolves the channel contention problem in a distributed manner by forcing nodes to randomly choose a waiting time in a contention window. However, since the size of a contention is limited, the collision probability increases with the number of sending nodes. To resolve the problem, in this paper, we propose a transmission control method based on the minority game (MG). Each node can determine autonomously whether to send or not without message exchanges with other nodes to maximize its profit. Through simulation studies, we verify that the proposed method can improves the performance of DCF in terms of collision probability in a congestion situation.

• The Journal of Society for e-Business Studies
• /
• v.2 no.2
• /
• pp.55-74
• /
• 1997

In this paper, the concept of coordination under the setting of cooperative multiagent systems is examined. Based on the concept, a computational model in which the key constructs of coordination can be precisely defined is developed. This model can serve as a basis for developing software systems designed to support coordination in Eletronic Commerce. Coordination is viewed as management of conflicting demands on finite resources by actors or acitivities. The model views coordination as a cycle of four phases: the definition phase, the conflict resolution phase, the action phase, and the adaptation phase. Then, a formal model of coordination, both as a phenomenon and as a process is devloped. Within the context of this model, important concepts such as decomposability, informational privacy, informational decentralization, and informational efficiency are examined.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.04a
• /
• pp.487-489
• /
• 2002

최근 무선랜의 편리성으로 인하여 사용자의 수는 크게 증가하고 있는데 반하여 현재 상용되고 있는 무선랜 기술은 사용자의 요구에 대응하지 못하고 있는 실정이다. 본 논문에서는 무선랜의 표준인 IEEE 802.11에서 제안된 DCF(Distributed coordination function)와 PCF(point coordination function)의 두 가지 전송 방식의 성능향상을 위한 방안으로서 신뢰성, 공평성 등의 장점을 가지도록 실시간 데이터 전송방법을 제안한다.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.49-52
• /
• 2003

IEEE 802.11 MAC uses a distributed coordination function (DCF) known as carrier sense multiple access with collision avoidance (CSMA/CA) for medium access. Random back-off algorithm helps to avoid the collision. This paper proposes virtual back-off and modified back-off algorithm for reduce a waiting time by back-off and reduce the collision. The modified DCF is consisted of these two algorithms. We expect to reduce the average waiting time of each transmission by using the modified DCF algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.5
• /
• pp.2279-2284
• /
• 2011

In most of radial distribution systems, the overcurrent protection coordination is adopted for the protection of apparatus and the improvement of electrical power system reliability. The protection coordination structure in distribution substation is composed of several circuit breakers(CB) with distribution lines originating from one substation bus under one transformer, which trip for their fault current. But sufficient analysis is necessary for the capacity of CB's in distribution systems with several distribution generations(DG). In this paper, a protection coordination method not to exceed the traditional capacity of CB's was proposed and certified through simulation by the PSCAD-EMTDC S/W.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2030-2035
• /
• 2005

In this paper, we study the distributed coordination of a set of synchronous, anonymous, memoryless mobile robots that can freely move on a two-dimensional plane but are unable to communicate directly. Based on this model, we analyze the application problem that consists in having a group of robots form a barricade line to protect from car traffic a crowd of demonstrators parading on the street. For the sake of robustness, we privilege fully decentralized solutions to the problem. In particular, we give a self-stabilizing distributed algorithm to address the problem, in this presentation

• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.520-522
• /
• 2006

According to the second scheme of the Korean Government about technology development, utilization and popularization of new renewable energy, the continuous growth of distributed resources are expected. But there is a few paper about recloser and sectionalizer coordination and protection scheme in distribution system interconnected a number of distributed resources. In this paper, it is dealt with that recloser and sectionalizer coordination at the cases concerned with position among protection devices. Adding distributed resource, the problems of each case are investigated through simulation.