• Journal of Communications and Networks
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• 제14권5호
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• pp.524-532
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• 2012

In this paper, we present the performance evaluation of the reliable cooperative media access control (RCO-MAC) protocol, which has been proposed in [1] by us in order to enhance system throughput in bad wireless channel environments. The performance of this protocol is evaluated with computer simulation as well as mathematical analysis in this paper. The system throughput, two types of average delays, average channel access delay, and average system delay, which includes the queuing delay in the buffer, are used as performance metrics. In addition, two different traffic models are used for performance evaluation: The saturated traffic model for computing system throughput and average channel access delay, and the exponential data generation model for calculating average system delay. The numerical results show that the RCO-MAC protocol proposed by us provides over 20% more system throughput than the relay distributed coordination function (rDCF) scheme. The numerical results show that the RCO-MAC protocol provides a slightly higher average channel access delay over a greater number of source nodes than the rDCF. This is because a greater number of source nodes provide more opportunities for cooperative request to send (CRTS) frame collisions and because the value of the related retransmission timer is greater in the RCO-MAC protocol than in the rDCF protocol. The numerical results also confirm that the RCO-MAC protocol provides better average system delay over the whole gamut of the number of source nodes than the rDCF protocol.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.166-171
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• 2004

Since early 1950's fracture mechanics has brought significant impact on structural integrity assessment in a wide range of industries such as power, transportation, civil and petrochemical industries, especially in nuclear power plant industries. For the last two decades, significant efforts have been devoted in developing defect assessment procedures, from which various fitness-for-purpose or fitness-for-service codes have been developed. From another aspect, recent advances in IT (Information Technologies) bring rapid changes in various engineering fields. IT enables people to share information through network and thus provides concurrent working environment without limitations of working places. For this reason, a network system based on internet or intranet bas been appeared in various fields of business. Evaluating the integrity of structures is one of the most critical issues in nuclear industry. In order to evaluate the integrity of structures, a complicated and collaborative procedure is required including regular in-service inspection, fracture mechanics analysis, etc. And thus, experts in different fields have to cooperate to resolve the integrity problem. In this paper, an internet-based cooperative system for integrity evaluation system which adapts IT into a structural integrity evaluation procedure for reactor pressure vessel is introduced. The proposed system uses Virtual Reality (VR) technique, Virtual Network Computing (VNC) and agent programs. This system is able to support 3-dimensional virtual reality environment and to provide experts to cooperate by accessing related data through internet.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2006년도 춘계공동학술대회 논문집
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• pp.153-158
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• 2006

The emergence of ubiquitous autonomic computing and network environment will change the service architecture information system which will be a new application area in SCM/logistics systems. In this study we surveyed the technical trend map of ubiquitous and its application in SCM/logistics support system design. We described the evolutional model of ubiquitous computing community for SCM/logistics system. It is consisted of three view points; self-growing, autonomic, and context-aware, which will allow the decision makers to be benefited from web and mobile technology and are useful for proactive SCM/logistics support system. Finally, we suggested a cooperative research planning for the development ubiquitous system between the government research center, university, and industry research activities.

• ETRI Journal
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• 제44권4호
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• pp.588-598
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• 2022

Since multi-access edge computing (MEC) was established as a key enabler of 5G, MEC based on 5G networks (5G MEC) has been perceived as a new business opportunity for many industry players, including telecom operators. Numerous 5G MEC cooperation announcements among companies playing their respective roles in the MEC ecosystem have been recently released. However, because of cooperative and competitive relationships among key players in the MEC ecosystem and the uncertainty of 5G MEC, the announcement of 5G MEC cooperation can negatively affect the telecom operators' firm value. This study investigates the market reaction to announcements of 5G MEC cooperation for telecom operators using an event study methodology. The empirical results show that announcements of 5G MEC cooperation have a negative impact on the telecom operators' firm value. The results also show that the early deployment of 5G networks may reduce the negative impact of 5G MEC cooperation announcements by reducing uncertainty.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제12권5호
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• pp.286-299
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• 2006

모델링 시뮬레이션 그리고 센서 장비 기술의 지속적인 발전으로 최근에 매우 높은 해상도를 갖는 방대한 크기의 볼륨 데이타들이 일반화되고 있다. 과학적 가시화 분야에서, 이러한 데이타를 고성능 병렬 컴퓨터를 사용하여 효과적으로 가시화하기 위한 다양한 대화식 실시간 기법들이 제안되어 왔다. 본 논문에서는 모바일 클라이언트, 게이트웨이, 병렬 렌더링 서버로 구성되는 모바일 볼륨 가시화 시스템의 개발에 관해 설명한다. 모바일 클라이언트는 병렬 렌더링 서버에게 전달할 렌더링 / 뷰잉 파라미터를 설정할 수 있는 기능뿐만 아니라, 관심이 있는 특정 영역을 점진적으로 높은 해상도의 영상을 이용해 탐색할 수 있는 기능을 제공한다. 게이트웨이는 안정적인 서비스를 위해 모바일 클라이언트와 병렬 렌더링 서버 사이에서 주고받는 요청과 응답을 관리하는 역할을 한다. 병렬 렌더링 서버는 클라이언트로부터 전달받은 렌더링 컨텍스트를 이용하여 정의된 특정 부분 볼륨을 가시화하고, 고해상도의 최종 영상을 클라이언트에게 되돌려 주는 작업을 수행한다. 제안된 시스템은 PDA를 갖고 있는 여러 사용자가 협력작업(CSCW) 모드를 통해 동시에 볼륨 데이타 가운데 공통으로 관심을 갖는 특정 부분, 렌더링 컨텍스트, 그리고 최종 영상을 공유할 수 있도록 설계되었다.

• 한국정보통신학회논문지
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• 제11권1호
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• pp.198-205
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• 2007

유비쿼터스 환경에 있는 사용자는 현재 자신의 위치, 시간 그리고 주변의 상태에 기반한 상황 인식 서비스를 받을 수 있다. 이러한 상황 인식 컴퓨팅에서 위치 기반서비스는 매우 중요한 역할을 한다. 위치를 측정하기 위하여 전용 장비를 설치하고 운영하는 데 많은 비용이 소요되기 때문에 기존의 WLAN(Wirless Local Area Netowork) 인프라스트럭처가 구축된 환경에서 무선 장비만을 이용하여 위치를 측정하는 방법들이 연구되고 있다. 이미 위치가 알려지고 고정된 AP(Access Point)와 노드간의 RSSI(Received Signal Strength Indicator)만을 이용하는 비콘 기반의 위치 측정 시스템 보다 무선 장비들 간의 RSSI 까지도 이용하는 상호 협력 위치 측정 시스템(Cooperative Positioning System)은 정확성이 높기 때문에 많은 관심을 끌고 있다. 본 논문에서는 상호 협력 위치 측정 시스템 중의 하나인 기존의 WiPS(wireless LAM based indoor Positioning System)의 문제점을 분석하고, 이웃하는 노드간의 영향 관계를 밝히고, 노드의 밀도에 따라 위치 수렴 조정 계수를 결정하여 성능을 개선한 WiCOPS-d(Wireless Cooperative Positioning System using node density)를 제안한다.

• Smart Structures and Systems
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• 제26권1호
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• pp.11-21
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• 2020

The hinge joint is the key to the overall cooperative working performance of the assembled beam bridge, and it is also the weakest part during the service period. This paper proposes a method for monitoring and evaluating the lateral cooperative working performance of fabricated beam bridges based on dynamic strain correlation coefficient indicator. This method is suitable for monitoring and evaluation of hinge joints status between prefabricated girders and overall cooperative working performance of bridge, without interruption of traffic and easy implementation. The remote cloud monitoring and diagnosis system was designed and implemented on a real assembled beam bridge. The algorithms of data preprocessing, online indicator extraction and status diagnosis were given, and the corresponding software platform and scientific computing environment for cloud operation were developed. Through the analysis of real bridge monitoring data, the effectiveness and accuracy of the method are proved and it can be used in the health monitoring system of such bridges.

• International Journal of Contents
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• 제7권4호
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• pp.30-34
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• 2011

A Leader is a Coordinator that supports a set of processes to cooperate a given task. This concept is used in several domains such as distributed systems, parallelism and cooperative support for cooperative work. In completely asynchronous systems, there is no solution for the election problem satisfying both of safety and liveness properties in asynchronous distributed systems. Therefore, to solve the election problem in those systems, one property should be weaker than the other property. If an election algorithm strengthens the safety property in sacrifice of liveness property, it would not nearly progress. But on the contrary, an election algorithm strengthening the liveness property in sacrifice of the safety property would have the high probability of violating the safety property. In this paper, we presents a safety strengthened Leader Election protocol with an unreliable failure detector and analyses it in terms of safety and liveness properties in asynchronous distributed systems.

• 한국컴퓨터정보학회논문지
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• 제21권2호
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• pp.9-16
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• 2016

Recently, many research groups have focused on GPGPUs in order to improve the performance of computing systems. GPGPUs can execute general-purpose applications as well as graphics applications by using parallel GPU hardware resources. GPGPUs can process thousands of threads based on warp scheduling and CTA scheduling. In this paper, we utilize the traditional CTA scheduler to assign a various number of CTAs to SMs. According to our simulation results, increasing the number of CTAs assigned to the SM statically does not improve the performance. To solve the problem in traditional CTA scheduling schemes, we propose a new IPC-based dynamic CTA scheduling scheme. Compared to traditional CTA scheduling schemes, the proposed dynamic CTA scheduling scheme can increase the GPU performance by up to 13.1%.

• 인터넷정보학회논문지
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• 제11권5호
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• pp.105-117
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• 2010

최근 다양한 분야에서 클라우드 컴퓨팅의 사용이 증가하고클라우드 컴퓨팅의 이상적 가치 실현을 위한 클라우드 공급자간의 동적협력은 필수적인 요소가 되고 있다. 이전의 연구를 통해서 다른 클라우드 공급자 간의 동적 협력 플랫폼으로 경매결합 방식 기반의 클라우드 마켓 모델 "CACM"을 제안한 바 있다. CACM모델은 경매에 참여하기 전에 미리 최적화된 클라우드 공급자들간 그룹을 형성하여 동적 협력을 제공할 수 있도록 하고 있으며, 이에 따라 공급자 간 협상시 발생할 수 있는 문제들을 최소화 하고자 하였다. 그러나 어떻게 최적의 입찰 가격 결정 그룹을 결정할 것인지, 어떻게 안정적인 그룹의 조건을 구할 것인지, 또한 입찰 가능 가격 및 이익을 그룹 구성원 간에 분배할 것인지에 대한 연구는 CACM 모델에서 구체적으로 연구되지 못했다. 본 논문에서는, CACM 모델을 N-person 협력 게임 이론에 대입하여 CACM모델에 추가적으로 위에서 제시한 문제들을 공식화하여 제안하고자 한다. 그룹의 안정성은 그룹의 각 구성원에게 코어와 할당량에 대한 개념을 대입해 게임이론에서의 샤플리 값을 사용하여 분석한다. 여러 계산 결과값을 통해 제안하는 기법의 특성평가를 도출한다.