• 한국통신학회논문지
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• 제34권2A호
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• pp.124-131
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• 2009

Cognitive radio has been proposed to mitigate the spectrum scarcity problem by allowing the secondary users to access the under-utilized frequency bands and opportunistically transmit. Spectrum sensing, as a key technology in cognitive radio, is required to reliably detect the presence of primary users to avoid the harmful interference. However, it would be very hard to reliably detect the presence of primary users due to the channel fading, shadowing. In this paper, we proposed a distributed cooperative spectrum sensing scheme based on conventional DF (decode-and-forward) cooperative diversity protocol. We fist consider the cooperation between two secondary users to illustrate that cooperation among secondary users can obviously increase the detection performance. We then compare the performance of DF based scheme with another conventional AF (amplify-and-forward) protocol based scheme. And it is found that the proposed scheme based on DF has a better detection performance than the one based on AF. After that, we extend the number of cooperative secondary users, and demonstrate that increasing the cooperation number can significantly improve the detection performance.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4642-4647
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• 2011

평면 변형률 상태에 있는 탄성지반의 해를 변분법을 적용하여 유도하여 보았다. 변분법 적용시 종방향 변위분포 함수는 선형함수를 고려하였다. 탄성지반상에 작용하는 하중조건은 집중하중과 분포하중을 고려하였는데 집중하중 작용시 탄성지반의 종방향 변위분포양상은 하중 작용점에서 멀어질수록 변위가 급격하게 감소하는 양상을 나타내었다. 등분포하중 작용시 지표면 변위는 압축층 두께에 대한 재하폭의 반의 비(B/H)값이 클수록 하중재하부분 아래에서 보다 균등하게 발생하였다. 또한 하중재하부분을 벗어난 영역에서는 B/H 값이 커질수록 하중재하 모서리 부분으로부터 짧은 거리에서 변위가 0에 수렴하였다.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3130-3136
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• 2009

본 논문은 분산전원이 연계된 배전계통에 있어서 온 라인 리얼타임으로 조정이 가능한 최적 전압조정방안을 제시한다. 가능한 많은 수용가에게 적정한 전압을 공급하기 위하여 최적 송출전압이 결정되어져야 하는데, 여기서는 급변하는 배전계통의 급격한 부하변동과 분산전원의 불규칙적인 출력특성을 고려하기 위하여, 인공 신경회로망(ANN: Artificial Neural Network)을 이용한 최적 전압조정방안을 제시한다. 본 논문에서 제시한 알고리즘을 이용하여 배전 모델계통에 적용한 결과, 제안한 방법이 다수의 분산전원이 연계된 배전계통의 전압조정에 실용적인 방책임을 확인하였다.

• 한국산학기술학회논문지
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• 제7권1호
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• pp.89-95
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• 2006

공급사슬망에서 분산되어있는 제조시스템에 대한 생산 계획수립은 공급사슬관리의 주요 연구분야 중의 하나이다. 본 논문은 공급사슬망에서 자원제약을 갖는 다단계 다품목 로트사이즈 결정 문제(Multi-Level, multi-item Capacitated Lot Sizing Problem: MLCLSP)를 위한 알고리즘을 제시한다. MLCLSP는 MIP(mixed integer program) 문제에 해당한다. 제안된 알고리즘은 휴리스틱과 최적화 패키지인 LINGO를 이용해 서로 반복적인 방식으로 해를 풀어나가는 혼성적인 성격을 갖는다. 휴리스틱을 이용하여 정수형 변수를 결정한 후, 얻게 되는 LP(linear program) 문제를 LINGO를 이용하여 해를 개선해 나가는 방식을 기본으로 한다. 본 논문에서는 탐색 휴리스틱 기법으로 임의 재시작 타부탐색 알고리즘을 제시한다. 다양한 시나리오의 실험을 통해 제안된 알고리즘들의 성능을 평가한다.

• 한국산학기술학회논문지
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• 제11권11호
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• pp.4543-4552
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• 2010

리더는 그룹 내의 여러 프로세스 중에서 조정자 역할을 하는 특별한 프로세스이다. 분산 시스템에서 하나의 조정자를 선출하는 과정을 리더선출이라 하며 이는 결함허용 분산시스템을 구축하기 위한 매우 중요한 문제이다. 현재 정상 작동하고 있는 두 개의 모바일 ad hoc 네트워크 그룹들이 병합되면 두 개의 리더가 존재하게 된다. 이것은 안전성 속성에 위배되므로 이를 감지하고 처리할 수 있는 메커니즘이 필요하다. 본 논문에서는 모바일 ad hoc 분산 컴퓨팅 시스템에서 그룹 멤버십 탐지 기반의 리더 경쟁 프로토콜을 제안하고 이를 시제논리로 검증하고자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.575-578
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• 2002

With the paradigm shifting from the principal of manufacturing efficiency to business globalization and rapid adaptation to its environments, more and more enterprises are being virtually organized as manufacturing network of different units in web. The formation of these enterprise called as Virtual Enterprise(VE) is becoming a growing trend as enterprises concentrating on core competence and economic benefit. This paper proposes the cooperation methodology for VEs which can be organized by the selection of manufacturing partners, and managed by the information flow infrastructure.

• 품질경영학회지
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• 제39권3호
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• pp.412-421
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• 2011

In this paper, we introduce Quality of Service(QoS) analytic model of a distributed system that decentralizes the process nodes performing each task and communicates through a network for cooperation. The model advances a service reliability model of Dai et a1.(2003) by means of considering the processing time. The service is assumed to be provided by a centralized heterogeneous distributed system which is composed of some subsystems managed by a control center. The QoS is defined as the probability that a service is provided successfully in an allowed time, we consider the hardware/software reliability and the processing time which include program execution time, data transfer time. We derive the processing time distribution for a required service through convolution of corresponding probability density function. An application example is used to explain the procedure of computing quality of service.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 추계학술발표논문집
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• pp.461-465
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• 2009

Normally, a distributed computing environment is flexible in controlling complex embedded systems but their software components are becoming complex as these systems are equipped with several platforms and attached to various electronic devices, sensors, and actuators. These systems requires inter-object communication mechanisms to provide fault tolerant and QoS-enabled middleware service support in a distributed system. Generally, a middleware performs analysis of the parameters to ensure the availability and reliability of data dissemination. This paper focuses in particular to designing an application middleware for the specific scenario to improve the high availability and fault tolerance of data thus improving the QoS (Quality of Service) of a distributed system. The performance of an adaptive and highly reliable middleware can be significant based on the selection of vital parameters of the system.

• International Journal of Automotive Technology
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• 제3권3호
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• pp.89-94
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• 2002

This paper presents an architecture for distributed control systems and its underlying methodological framework. Ideas and concepts of distributed systems, artificial intelligence, and soft computing are merged into a unique architecture to provide cooperation, flexibility, and adaptability required by knowledge processing in intelligent control systems. The distinguished features of the architecture include a local problem solving capability to handle the specific requirements of each part of the system, an evolutionary case-based mechanism to improve performance and optimize controls, the use of linguistic variables as means for information aggregation, and fuzzy set theory to provide local control. A distributed traffic control system application is discussed to provide the details of the architecture, and to emphasize its usefulness. The performance of the distributed control system is compared with conventional control approaches under a variety of traffic situations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.97-100
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• 2000

In previous research of social dilemma, there is no extended game that the players can select one game out of some social dilemma games. We propose this kind of game as ＂Distributed Social Dilemma＂ In this game, each player tries to acquire the adaptive strategy throughout local interactions. We make use of GA as evolutionary operations. In this paper, our purpose is to examine how the game selection of players influences the evolution of cooperation in distributed social dilemma. In order to examine, we formulate distributed social dilemma by Game Theory and use agent-based simulation that each agent is regard as player