• Annals of Fuzzy Mathematics and Informatics
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• 제16권3호
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• pp.301-316
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• 2018

In this paper, the concept of connected geodesic number, $gn_c(G)$, of a fuzzy graph G is introduced and its limiting bounds are identified. It is proved that all extreme nodes of G and all cut-nodes of the underlying crisp graph $G^*$ belong to every connected geodesic cover of G. The connected geodesic number of complete fuzzy graphs, fuzzy cycles, fuzzy trees and of complete bipartite fuzzy graphs are obtained. It is proved that for any pair k, n of integers with $3{\leq}k{\leq}n$, there exists a connected fuzzy graph G : (V, ${\sigma}$, ${\mu}$) on n nodes such that $gn_c(G)=k$. Also, for any positive integers $2{\leq}a<b{\leq}c$, it is proved that there exists a connected fuzzy graph G : (V, ${\sigma}$, ${\mu}$) such that the geodesic number gn(G) = a and the connected geodesic number $gn_c(G)=b$.

• 디지털콘텐츠학회 논문지
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• 제9권1호
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• pp.87-99
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• 2008

HAP(High Altitude Platform)은 정지위성, 중궤도위성, 저궤도위성, 무인비행기 및 무인비행선 등을 이용하여 고고도에 네트워크의 인프라스트럭처를 전개하여 이를 매개체로 한 네트워크 시스템을 운용하는 것을 가능하게 해준다. 성층권 비행선 통신 시스템은 위성 통신망과 지상 이동 통신망의 장점을 동시에 보유한 시스템으로 긴급 전개 가능, 저비용 서비스 실현, 고속 광대역 서비스 제공, 휴대 단말 통신 가능, 넓은 커버리지에 의한 서비스 지원, 짧은 전송 지연, 초대용량 회선 공급, 사용자 요구에 대한 유연한 응답, 멀티캐스트와 브로드캐스트에 유리, 지상 관리 시설비용의 절감, 네트워크 망 전체의 유연한 증가 가능 등의 특징을 보유하고 있다. 본 논문에서는 넓은 지역에 전개된 다수의 성층권 플랫폼을 가정하고, 지상 노드를 효율적으로 클러스터링 함으로써 어느 위치에 얼마만큼의 커버리지로 성층권 플랫폼이 전개되어야 할지를 연구하였다. 특정 지역에 전개된 지상 노드들은 그 분포한 영역의 넓이와 그 지상 노드들이 요구하는 대역폭의 함수로 나타내지는 수만큼의 성층권 무인 플랫폼이 필요하다. 이러한 성층권 무인 플랫폼을 적절히 배치하여 광대역 네트워크 서비스가 가능하게 하는 동적 클러스터링 결과를 시뮬레이션으로 나타내었다.

• Journal of Communications and Networks
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• 제12권3호
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• pp.231-239
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• 2010

In cluster-based wireless sensor networks, the energy could be saved when the nodes that have data to transmit participate in cooperative multiple-input multiple-output (MIMO). In this paper, by making the idle nodes that have no data to transmit participate in the cooperative MIMO, it is found that much more energy could be saved. The number of the idle nodes that participate in the cooperative MIMO is optimized to minimize the total energy consumption. It is also found that the optimal number of all the nodes participating in cooperative communication does not vary with the number of nodes that have data to transmit. The proposition is proved mathematically. The influence of long-haul distance and modulation constellation size on the total energy consumption is investigated. A cooperative MIMO scheme with help-node participation is proposed and the simulation results show that the proposed scheme achieves significant energy saving.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.676-682
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• 2018

WSN을 포함하는 IoT 세상이 발전할수록, IoT를 적용하는 주위환경에 따라 정보를 센싱하는 센서 시스템의 수가 매우 가변적이다. 이러한 복잡한 환경에서 각각의 센서 시스템들에 대한 보안을 수행하기 위하여 보안모듈들도 가변적으로 증감을 수행해야 한다. 이러한 문제점은 시스템 효율성과 해킹/크래킹을 고려하였을 경우, 하드웨어/소프트웨어적인 구현을 어렵게 한다. 그러므로 본 논문은 이러한 문제점을 해결하기 위하여 센싱 노드들의 수와 상관없이 일정한 주기를 가지는 의사난수를 발생시키며 이상현상을 탐지할 수 있는 기능을 가진 고정 길이 탭을 가진 의사 난수 발생기(FLT: Pseudo-random Number Generator with Fixed Length Tap unrelated to the variable sensing nodes) 구조를 제안하였다. 제안된 FLT-LFSR 구조는 IoT 환경에서 하드웨어/소프트웨어 구현에 대하여 보안레벨 및 전체 데이터 포맷팅을 일정하게 유지시킬 수 있도록 하였다. 그러므로 제안된 FLT-LFSR 구조는 센서 시스템 구현의 용이성 및 센싱 노드들의 수와 상관없이 네트워크의 확장성을 강조할 수 있도록 하였다.

• 한국CDE학회논문집
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• 제5권3호
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• pp.207-214
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• 2000

For last 20 years, a number of researches and developments on finite element mesh generation has been carried out and most of them are comported of node generation part and node generation part. However these algorithms are inefficient in mesh veneration process and difficult to control the shape of elements when comparing with the generation of nodes and elements concurrently. In this study, therefore, an algorithm it proposed to generate nodes and elements concurrently for various two-dimensional objects having multiple holes. Inner node generation is performed by choosing three consecutive boundary nodes and comparing them with other close boundary nodes. As soon as inner nodes are determined, element generation is conducted based on the comparison of the distances among the generated inner nodes, three consecutive boundary nodes and other close boundary nodes. the generated element nodes become new boundary nodes for further repeated process. The processes are repeated through out each region until three consecutive boundary nodes finally form a tirangular element.

• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.123-128
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• 2019

IETF(Internet Engineering Task Force)는 LLN(Low power and Lossy Networks)의 라우팅 프로토콜로 RPL(IPv6 Routing Protocol for Low-power Lossy Network)을 제안하였다. RPL을 사용하는 네트워크에서는 하나의 parent 노드가 많은 child 노드와 연결되어, 일부 노드로 연결이 몰리는 Thundering Herd Phenomenon이 발생할 수 있다. 이를 해결하기 위해 CNC(Child Number Count)를 사용하여 노드 당 연결되는 최대 child 노드 수를 제한하는 방법이 고려되었으나 여전히 일부 parent 노드에 최대 child 노드 수 만큼 붙을 수 있다는 문제와 최대 child 노드 수를 몇으로 결정하는가 하는 문제가 남아있다. 따라서 본 논문에서는 노드 당 연결되는 child 노드 수를 고르게 분배하는 알고리즘을 제안하여, Thundering Herd Phenomenon 문제를 해결하고자 한다. 기존 CNC를 사용하는 알고리즘과 성능 비교를 진행하였고, 그 결과 제안하는 알고리즘이 load balancing 측면에서 더 좋은 성능을 보이는 것을 검증하였다.

• 대한전기학회논문지
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• 제39권5호
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• pp.494-499
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• 1990

A new compact hierarchical representation method image is proposed. This method represents a binary image with the set of decimal numbers. Each decimal number represents the pattern of nonterminal node(gray node) in the quadtree. This pattern implies the combination of its four child nodes. The total number of gray nodes is one third of that terminal nodes. We show that gray tree method is efficient comparing with others which have been studied.

• 대한임베디드공학회논문지
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• 제2권3호
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• pp.138-144
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• 2007

Wireless Sensor Network(WSN) consists of a lot of light-weight sensor nodes with the capability of wireless communication. Studies have been done to improve stability and fault-tolerancy of WSN because the sensor nodes are basically vulnerable to the harsh environment. Specially, the time synchronization among sensor nodes becomes a challenging issue in WSN. All the local times should always keep the same with each other in the sensor field to perform data aggregation and energy-aware communication in WSN. In this paper, a new time synchronization technique is proposed to operate efficiently irrespective of the number of sensor nodes and the number of hops needed to cover all sensor nodes for synchronization. Simulation results show that the proposed technique has the lowest amount of packet traffic among the several time synchronization techniques.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.99-100
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• 2006

One of the fundamental problems in sensor networks is the deployment of sensor nodes. The Fuzzy C-Means(FCM) clustering algorithm is proposed to determine the optimum location and minimum number of sensor nodes for the specific application space. We performed a simulation using two dimensional L shape model. The actual length of the L shape model is about 100m each. We found the minimum number of 15 nodes are sufficient for the complete coverage of modeled area. We also found the optimum location of each nodes. The real deploy experiment using 15 sensor nodes shows the 95.7%. error free communication rate.

• 대한수의학회지
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• 제37권3호
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• pp.463-469
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• 1997

This study was performed to investigate the gross anatomical features and microscopical structures of the hemal nodes and the hemolymph nodes in the water deer (Hydropotes inermis) found in Kangwon-do, Korea. The hemal nodes and hemolymph nodes were observed mainly in the periphery of the thoracic and abdominal aortae of the animals. The size of hemal nodes was generally smaller than that of the hemolymph nodes, and the shape of the both organs was spherical or ovoid. The color of the hemal nodes was red or black while that of the hemolymph nodes was gray with red bands. The hemal nodes were surrounded by a thin connective tissue capsule and there were extensive subcapsular and deep sinuses distended by a great number of erythrocytes. Although a few number of lymphatic nodules and small areas of diffuse lymphatic tissues were observed in the parenchyma, no typical cortex and medulla were defined in the hemal node. Small numbers of blood vessels were found at the connective tissue capsule but lymph vessel was not observed microscopically in this organ. The hemolymph nodes were covered by a relatively thick connective tissue capsule and there was a hilus in each node. The parenchyma was divided into cortex and medulla. The cortex was composed of a few numbers of lymphatic nodules and some diffuse lymphatic tissues. The medulla comprised medullary sinus and cords. Afferent and efferent lymph vessels were observed at the periphery of the capsule and the hilus, respectively. The subcapsular and medullary sinuses were not extensive but filled with small numbers of erythrocytes. The stroma of hemal node and hemolymph node was composed of reticular cells and fibers, and the capsule and trabecula consisted of collagenous fibers with smooth muscle fibers.