• 대한임베디드공학회논문지
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• 제6권6호
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• pp.369-376
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• 2011

Since wireless sensor networks generally have the capability of network recovery, malfunction of a few sensor nodes in a sensor network does not cause a crucial problem paralyzing the sensor network. The malfunction of the sink node, however, is critical. If the sink node of a sensor network stops working, the data collected by sensor nodes cannot be delivered to the gateway because no other sensor nodes can take the place of the sink node. This paper proposes a TDMA-based wireless sensor network equipped with dual sink nodes, with a view to preventing data loss in the case of malfunction of a sink node. A secondary sink node, which synchronizes with a primary sink node and receives data from other sensor nodes in normal situations, takes the role of the primary sink node in the case of malfunction of the primary sink, thereby eliminating the possibility of data loss. The effectiveness of the proposed scheme is demonstrated through experiments.

• 한국작물학회지
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• 제47권3호
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• pp.151-156
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• 2002

초다수성 품종 개발의 기초자료로 활용하고자 새로이 도입된 신초형 소얼 수중형 유전자원을 이용하여 F$_2$-F$_{5}$상관에 의한 sink-source관련 형질의 유전력을 추정한 결과를 요약하면 아래와 같다. 1. 일품벼에 YR15965 Acp 33이 교배된 F2와 F5세대간 상관정도에 의해 추정된 sink 및 source관련 형질들의 유전력은 specific leaf area, sink-source ratio와 harvest index의 0.009, 0.121, 0.013을 제외한 모든 형질에서 0.224이상의 높은 유전력을 보였다. 2. IR 66738-118-1-2에 가야벼가 교배된 후대에서는 모든 sink 및 source관련 형질이 0.001-0.286의 낮은 유전력을 보였다. 3. Sink 및 source관련 형질들과 수량과는 두 조합 모두 높은 싱관정도를 보였으나 등숙률과는 IR 66738-118-1-2에 가야벼가 교배된 후대에서는 대부분의 형질이 상관이 없었다. 그러나 일품벼에 YR 15965Acp33의 교배 후대에서는 등숙율과 source형질과는 높은 정상관이, sink capacity와 sink-source ratio등 sink형질과는 유의한 부의 상관이 있었다.

• 한국컴퓨터정보학회논문지
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• 제23권2호
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• pp.35-43
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• 2018

In this paper, we propose a grid-based efficient routing protocol for a mobile sink in wireless sensor networks. In the proposed protocol, the network is partitioned into grids and each grid has a grid head. For the efficient routing to a mobile sink, the proposed protocol uses a mobile sink representative node to send the data to a mobile sink and grid heads are used as a mobile sink representative node. Furthermore, the proposed protocol uses nodes in the boundary of the center grid as position storage nodes. The position storage nodes store the position of a mobile sink representative node and provide source nodes with it for data delivery. With these features, the proposed protocol can reduce a lot of overhead to update the position information and improve the delay of data delivery to a mobile sink. The proposed protocol performs better than other protocols in terms of the delay and the energy consumption per node in the performance evaluation.

• 한국컴퓨터정보학회논문지
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• 제22권9호
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• pp.33-40
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• 2017

In this paper, we propose a sink-location management and data-routing scheme to effectively support the mobile sink in solar-powered WSN. Battery-based wireless sensor networks (WSNs) have a limited lifetime due to their limited energy, but solar energy-based WSNs can be supplied with energy periodically and can operate forever. On the other hand, introduction of mobile sink in WSNs can solve some energy unbalance problem between sink-neighboring nodes and outer nodes which is one of the major challenges in WSNs. However, there is a problem that additional energy should be consumed to notify each sensor node of the location of the randomly moving mobile sink. In the proposed scheme, one of the nodes that harvests enough energy in each cluster are selected as the cluster head, and the location information of the mobile sink is shared only among the cluster heads, thereby reducing the location management overhead. In addition, the overhead for setting the routing path can be removed by transferring data in the opposite direction to the path where the sink-position information is transferred among the heads. Lastly, the access node is introduced to transmit data to the sink more reliably when the sink moves frequently.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.83-88
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• 2004

In this study, the flow and thermal performance of the heat sink and fan-sink were experimentally studied to predict the operating condition of the fan-sink. The experiments of the flow and thermal resistance of the heat sink with various inlet blockage, which were occurred by the shapes of the axial fans, were conducted for the proof of the effects of the inlet blockages. The greater the inlet blockage of the heat sink, the higher the pressure drop and lower the thermal resistance of the heat sink will be. The operating point of the fan-sink was predicted by the pressure drop curve with the inlet blockage, which was corresponded to the selected fan and the fan performance curve, and verified by the performance test of the fan-sink. The predicted operating point of the fan-sink had good agreement with the result of the performance test of the fan-sink within $0.7\%$ of the volume flow rates. Measured thermal resistance of the fan-sink was equivalent to that of the heat sink with the same inlet blockage of the fan-sink. It was shown that the heat transfer characteristics of the heat sink were influenced by the flow interaction between the selected fan and the heat sink. To improve the thermal resistance of the heat sink, it is necessary to consider appropriate flow patterns of the fan outlet entering into the heat sink.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2473-2492
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• 2012

Energy conservation is a vital issue in wireless sensor networks. Recently, employing mobile sinks for data gathering become a pervasive trend to deal with this problem. The sink can follow stochastic or pre-defined paths; however the controlled mobility pattern nowadays is taken more into consideration. In this method, the sink moves across the network autonomously and changes its position based on the energy factors. Although the sink mobility would reduce nodes' energy consumption and enhance the network lifetime, the overhead caused by topological changes could waste unnecessary power through the sensor field. In this paper, we proposed EEDARS, an energy-efficient dual-sink algorithm with role switching mechanism which utilizes both static and mobile sinks. The static sink is engaged to avoid any periodic flooding for sink localization, while the mobile sink adaptively moves towards the event region for data collection. Furthermore, a role switching mechanism is applied to the protocol in order to send the nearest sink to the recent event area, hence shorten the path. This algorithm could be employed in event-driven and multi-hop scenarios. Analytical model and extensive simulation results for EEDARS demonstrate a significant improvement on the network metrics especially the lifetime, the load and the end-to-end delay.

• 한국재료학회지
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• 제14권12호
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• pp.870-875
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• 2004

Heat flow characteristics in the newly developed Wave Heat Sink were analyzed under natural and forced convections by Icepak program using the finite volume method. Temperature distribution and thermal resistance of Wave Heat Sink with/without air vent hole on the top of fin were compared with those of a commercial Al extruded heat sink(Intel Heat Sink). Under the natural convection, the maximum temperature was $45.1^{\circ}C$ in the air vent hole typed Wave Heat Sink, which was superior to that of Intel Heat Sink. The thermal resistance was $2.51^{\circ}C/W$ in the air vent hole typed Wave Heat Sink, and it changed to $2.65^{\circ}C/W\;and\;2.16^{\circ}C/W$ with changes of gravity direction and fin height, respectively. Under the forced convection, the maximum temperature became lower than that under the natural convection. In addition, the thermal resistance lowered in the air vent hole typed Wave Heat Sink with higher fin height and it decreased with increasing the air flux.

• 한국컴퓨터정보학회논문지
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• 제10권4호
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• pp.239-248
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• 2005

대규모 무선 센서 네트워크는 네트워크의 신뢰성과 에너지 효율을 동시에 고려해야 한다. 네트워크의 신뢰성을 높이기 위해서는 유니 캐스트 기반 데이터 전송 방법보다 브로드캐스트 기반 데이터 전송 방법을 사용해야 한다. 최근 발표된 GRAdient Broadcast (GRAB)는 브로드캐스트 기반 데이터 전송으로 네트워크의 신뢰성을 높일 수 있다. 하지만 한 개의 sink를 사용하기 때문에 네트워크 전체 에너지를 고르게 사용하지 못한다. 결국 네트워크의 동작 시간이 단축되는 단점이 있다. 이에 본 논문에서는 대규모 무선센서 네트워크에 적합한 Selective Multi Sink Gradient Broadcast (SMSGB)를 제안한다. SMSGB 는 여러 개의 sink를 사용하여 네트워크를 구성하고 한 개의 sink만 데이터를 수집한다. 특정한 이벤트가 발생이 되면 다른 sink가 데이터를 수집하게 된다. 이러한 방법을 통해 전체 네트워크의 에너지를 고르게 소모 할 수 있다. 또한 GRAB와 동일한 브로드캐스트 기반 데이터 전송으로 대규모 무선 센서 네트워크에서 신뢰성을 보장할 수 있다. 기존의 GRAB와 SMSGB를 비교한 모의실험을 통해 GRAB와 비슷한 신뢰성을 유지하면서 GRAB보다 SMSGB의 네트워크 동작 시간이 약 18% 이상 연장됨을 보인다.

• 한국통신학회논문지
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• 제36권12A호
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• pp.994-1005
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• 2011

본 논문에서는 센서 네트워크 환경에서 에너지 효율적인 mobile sink node의 최적의 경로를 설정 할 수 있는 방법인 AMSP(Adaptive Mobile Sink Path)를 제안한다. 기존의 논문들은 mobile sink node 이동시 random way point 방식을 사용하여 불필요한 데이터 전송으로 인한 에너지 소모를 야기했다. 또한, sink node의 이동이 random으로 이동하기 때문에 같은 지역을 중복으로 이동할 수 있는 단점이 있다. 이를 해결하기 위하여 본 논문에서 제안하는 방법은 센서 노드가 설치되어진 필드의 크기에 따라 정적인 그리드를 생성하고 그리드 안에서 mobile sink node가 이동하는 최적의 경로를 설정하여 준다. 이 경로는 네트워크의 크기, 밀도에 따라 효율적인 경로 탐색을 위해 이동 경로를 변경하여 준다. 또한 각각의 노드가 mobile sink node의 주행 경로 및 속도를 인지하고 있음으로 데이터 전송에 대한 에너지 소모량을 감소시킬 수 있다. 이렇게 sink node의 위치를 예상할 수 있기 때문에 에너지의 추가적인 절약을 위해 일정 시간 동안 sleep상태로 두고 active와 교대하는 duty cycle을 사용한다. 이 기법을 사용하여 본 논문에서는 기존의 방법들인 TTDD나 CBPER에 비해 최대 80% 이상의 에너지 소모량을 감소시킬 수 있는 것으로 나타났다.

• 한국멀티미디어학회논문지
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• 제22권6호
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• pp.676-683
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• 2019

Wireless Sensor Networks (WSNs) consist of multiple tiny and power constrained sensors which use radio frequencies to carry out sensing in a designated sensor area. To effectively design and implement reliable WSN, it is critical to consider models, protocols, and algorithms that can optimize energy consumption of all the sensor nodes with optimal amount of packet delivery. It has been observed that deploying a single sink node comes with numerous challenges especially in a situation with high node density and congestion. Sensor nodes close to a single sink node receive more transmission traffic load compared to other sensors, thus causing quick depletion of energy which finally leads to an energy hole and sink hole problems. In this paper, we proposed the use of multiple energy efficient sink nodes with brute force technique under optimized parameters to improve on the number of packets delivered within a given time. Simulation results not only depict that, deploying N sink nodes in a sensor area has a maximum limit to offer a justifiable improvement in terms of packet delivery ratio but also offers a reduction in End to End delay and reliability in case of failure of a single sink node, and an improvement in the network lifetime rather than deploying a single static sink node.