• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.795-800
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• 2011

In this paper, to promote the production of agricultural products, it is goal to design and implement the growth environmental management monitoring system. Based on the IT convergence technology, it consists of four components such as sensor nodes to sense environmental factors, sink nodes to communicate with sensors, gateway to link sinknodes to monitoring system, and monitoring software. With monitoring process for temperature and humidity, we can obtain the bast growth environment to be maintained deviation value 10% for temperature and humidity.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.35-38
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• 2005

인버터는 전기적으로 DC(직류)를 AC(교류)로 변환하는 역 변환 장치이며, 상용전원(AC 22V/440V)으로부터 공급된 전력을 입력받아 전압과 주파수를 가변시켜 전동기에 공급함으로써 전동기의 속도를 고효율로 이용하게 제어하는 장치이다. 본 논문에서는 550kW급 IGBT, DIODE의 발열에 의한 인버터 내부의 열 및 온도분포를 ICEPAK 상용코드를 통하여 수치적 해석을 수행하였다. 인버터의 발열은 캐패시터의 수명과 소자들의 오작동 등 많은 열적 문제를 가지고 있으며 Heat-sink, Fan, Duck등을 통하여 전도와 대류가 이루어지는 시스템이다. 인버터은 많은 파라미터들에 의해 온도가 결정되기 때문에 실험을 통한 해석은 제한적 일수 밖에 없다. 따라서 수치해석을 통하여 빠른 시간에 효율적인 열 설계를 할 수 있으며, 인버터의 크기는 최종적으로 Heat-sink의 형상에 따라 달라지므로 이를 최적화 하고 소형화 하는 작업이 필요하다. 인버터의 복잡한 내부구조상 하단부(발열원, Heat-sink, Fan등)만 수치해석을 수행하였을 때와 Full Model과는 $15^{\circ}C$ 온도 차이를 보였다. 최종적으로 인버터의 최적 열 설계를 위하여 Frame위치 변경, Heat-Sink 형상변화등 많은 수치해석을 통하여 만족할 만한 결과를 얻었다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.208-215
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• 2013

In recent years, many applications in WSN have increasingly interested in data transfer reliability. In this paper, we propose a dynamic grouping transfer mechanism which maintains both reliability and energy efficiency in transmission from a source to a sink. The proposed scheme considers channel error of each node. Then it uses an end-to-end ACK transmission in a group and a hop-by-hop ACK transmission between groups. Consequently this mechanism minimize the cost of packet transfer along with enhancing the network lifetime and reliability.

• The Journal of Korea Robotics Society
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• v.15 no.4
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• pp.341-349
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• 2020

Recently, interest in ground subsidence in urban areas has increased after a large sinkhole occurred near the high-story building area in Jamsil, Seoul, Korea, in 2014. If a massive sinkhole occurs in an urban area, it is crucial to assess its risk rapidly. Access to humans for on-site safety diagnosis may be difficult because of the additional risk of collapse in the disaster area. Generally, inspection using drones equipped with high-speed lidar sensors can be utilized. However, if the sinkhole is created vertically to a depth of 100 m, similar to the sinkhole in Guatemala, the drone cannot be applied because of the wireless communication limit and turbulence inside the sinkhole. In this study, a three-dimensional (3D) scanning system was fabricated and operated using a towed cable in a massive vertical sinkhole to a depth of 200 m. A high-speed lidar sensor was used to obtain a continuous cross-sectional shape at a certain depth. An inertial-measuring unit was applied to compensate for the error owing to the rotation and pendulum movement of the measuring unit. A reconstruction algorithm, including the compensation scheme, was developed. In a vertical hole with a depth of 180 m in the mining area, the fabricated system was applied to scan 0-165 m depth. The reconstructed shape was depicted in a 3D graph.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.449-461
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• 2017

The uncertain existence and insufficient information of underground structures, such as pipe lines and cable tunnels, is causing many problems related to route plan, design, construction of new underground structures. The theoretical equations that is able to predict the location, size, and direction of underground structures through electric field analysis are suggested at the previous study (Ryu., 2015). Three field tests were performed for predicting the location, size, and direction of underground structures and the existence and size of sink-hole. Prediction results were reflected at the design and follow-up measures were performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.445-450
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• 2011

In this paper, we describe the implementation of an wireless sensor network testbed. We developed a web-based sensor network gateway and enhanced the Surge program which is used for sending and routing of packets in the sensor field. The developed program can transmit the source data of sensor nodes to the sink node via multi-hop routing, and deliver user commands to actuate sensor related equipments. Moreover, in this testbed, the data transport path from a node to the sink can be monitored. Thus we can approximate the network topology and the relative positions of sensor nodes. We also describe an application of the testbed that is used for controlling a remote robot.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.401-405
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• 2007

In sensor network, cluster based routing protocol about efficient energy usage method has researched variously. But existing cluster based routing protocol have problems. one of the problem is sensor nodes's imbalance energy consumption problem at cluster reconstruction. anther is non- connection problem between header node and spc node when they are far from each other, not properly connected. We propose cluster re-division and header node of multihop transmission method in this paper. The cluster re-division method is the method that re-divides existing routing protocol with the small-scale cluster and multihop transmission method is the method regarding the relay transmission between the header nodes. Through the simulation, the proposed routing mechanism shows more excellent than exiting routing protocol in balance energy consumption and energy efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.630-635
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• 2008

Recently, in order to improve the energy efficiency of WSN(Wireless Sensor Network), widely research have teen carried on. But, up to the present, Majority of methods are based on direct communication between CH(cluster head) and sink node, and based on the assumption that node can regulate signal energy actively according to the distance between nodes. So it's hard to implement those methods. Based on the theory that node has fixed radio wave radius, this paper present a multi leveling routing protocol. According to the simulation of the presented protocol, we have proved the energy saving efficiency and the implementation in real WSN.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.3
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• pp.206-210
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• 2009

In this paper, we propose a new routing scheme based on multi-path routing which provides uniform energy consumption for all nodes. This scheme adds a new type of root node for constructing multi-path. The sink node delegates some partial roles to these root nodes. Such root nodes carry out path establishment independently. As a result, each nodes consume energy more uniformly and the network life-time will be extended. Through simulation, we confirmed that energy consumption of the whole network is scattered and the network life-time is extended. Moreover, we show that the proposed routing scheme improves the performance of network compared to previous routing strategies as the number of source nodes increases.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.775-779
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• 2004

For improvement of heat dissipation performance, heat analysis is conducted on the newly designed heat sinks under two convection conditions by using computational fluid dynamics(CFD). Three types of heat sink, plate, wave and top vented wave, are used, and convection conditions are the variations of gravity direction at natural convection and of fan location at forced convection. The results of analysis showed that the heat resistances of top vented wave heat sink were $0.17^{\circ}C$/W(forced convection) and $0.48^{\circ}C$/W(natural convection). In the case of natural convection, gravity direction affected heat flow change, and protection against heat performance was superior in case of z-axis gravity direction. Under the forced convection, all the heat sinks revealed superior thermal characteristics in the fan position of z-axis rather than y-axis. In this study, it was observed that the top vented wave type heat sink showed the best ability of heat radiation comparing with the others.