• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.99-100
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• 2017

무선 급전 경전철 차량은 차량이 역에 도착하였을 때 단시간에 배터리에 에너지 충전을 요구함에 따라 1MW이상의 순간 전력을 공급하는 시스템을 요구하게 된다. 때문에 대용량 파워에 따라 손실의 따른 발열량이 커지게 된다. 때문에 높은 효율을 갖는 제어 방식을 선택하는 것이 불가피하게 된다. 이러한 이유로 본 논문에서는 집전 정류기를 PLL을 통하여 스위칭 지점을 ZVS가 가능하도록 제어하고 또한 스위칭 OFF 손실을 줄이기 위하여 주파수를 4분주로 스위칭 하는 방식을 제한고 이를 실제 하드웨어를 통하여 제어 알고리즘의 타당성을 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.248-253
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• 2006

The purpose of this study is to develop a portable gait-event detection system which is necessary for the cycle-to-cycle FES(functional electrical stimulation) control of locomotion. To make the system portable, we made following modifications in the gait signal measurement system. That is, 1) to make the system wireless using Bluetooth communication, 2) to make the system small-sized and battery-powered by using low power consumption ${\mu}$ P(ATmega8535L). The gait-events were analyzed in off-line at the main computer using ANN(Artificial Neural Network). The Proposed system showed no mis-detection of the gait-events of normal subject and hemiplegia subjects. The performance of the system was better than the previous wired-system.

• ETRI Journal
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• v.24 no.2
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• pp.153-160
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• 2002

High Altitude Platforms-craft maintaining stations in the stratosphere at altitudes of around 20 km-have been proposed as a means of supporting wireless telecommunications. They could exploit the best aspects of both terrestrial and satellite systems and support efficient frequency re-use plans. For solar powered platforms the power available for the downlink amplifiers may be minimal, particularly at night and/or higher latitudes. This paper discusses a novel type of link based on a modulated retro-directive transponder carried by the HAP. Relying chiefly on the ground station infrastructure, this would substantially reduce power consumption on the platform. We investigate the efficiency of the transponder aperture as a function of its area by developing general models for losses in the transmission lines which interconnect antenna pairs in the retro-directive array.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.130-139
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• 2012

Energy harvesting has emerged as a powerful technology for complementing current battery-powered communication systems in order to extend their lifetime. In this paper a general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment. Assuming that the energy arrival process is known non-causally at the transmitter, the structure of the optimal transmission scheme, which maximizes the amount of transmitted data by a given deadline, is identified. Our framework includes models with continuous energy arrival as well as battery constraints. A battery that suffers from energy leakage is studied further, and the optimal transmission scheme is characterized for a constant leakage rate.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.197-200
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• 2008

In most sensor networks, nodes can be easily compromised by adversaries due to hostile environments. Adversaries may use compromised nodes to inject false reports into the sensor networks. Such false report attacks will cause false alarms that can waste real-world response effort, and draining the finite amount of energy resource in the battery-powered network. A dynamic enroute scheme proposed by Yu and Guan can detect and drop such false reports during the forwarding phase. In this scheme, choosing a threshold value is very important, as it trades off between security power and energy consumption. In this paper, we propose a threshold determining method which uses the fuzzy rule-based system. The base station periodically determines a threshold value though the fuzzy rule-based system. The number of cluster nodes, the value of the key dissemination limit, and the remaining energy of nodes are used to determine the threshold value.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.87-88
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• 2016

경전철 차량은 1MW이상의 전력을 요구하기 때문에 단일 인버터 시스템으로 구현할 경우 시스템 부피 및 비용 증가, 효율 감소 등 문제점을 가지게 된다. 이러한 이유로, 수 kW급 인버터 스택을 병렬로 구성하여 대용량 시스템을 구현한다. 본 논문에서는 이러한 대용량 인버터 시스템을 구성하는 스택 개발 사례를 보여주고 있다. 실험을 통하여 개발한 무선급전용 인버터 스택의 성능을 검증한다.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.89-90
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• 2016

경전철 차량에 위치한 집전장치는 무선급전 인버터로부터 전력을 공급받아 동력계통 또는 에너지 저장장치에 전력을 전달하는 역할을 한다. 따라서, 집전장치의 손실을 최소화 하고 전력을 안정적으로 전달할 수 있는 제어방법이 필요하다. 본 논문은 이러한 필요를 만족하는 적절한 제어방법을 제안한다. 시뮬레이션을 통하여 제안한 집전장치 제어방법의 유효성을 검증한다.

• Korean journal of aerospace and environmental medicine
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• v.30 no.3
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• pp.100-107
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• 2020

Internet of Things (IoT) is a technology that communicates data between devices, which are things, using an embedded sensor connected through network backbone such as the internet. Here, data communication technology, sensor technology, and actuator (interface) technology are fused into IoT and it turns devices into smart things. As a result, vast sized data are being generated and that data is being processed into useful actions that can control the things that are devices to make our lives much fruitful. Nowadays, the IoT, early defined as Machine-to-Machine (M2M) connection, becomes a key technology powered by growing innovation of wireless communication trends in the internet connectivity through mobile networking. This paper gives an overview of Internet of Things and brief information about major technologies and its applications in various fields focusing aviation.

• The KIPS Transactions:PartC
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• v.17C no.6
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• pp.499-504
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• 2010

The flooding is the simplest and effective way to disseminate a packet to all nodes in a wireless sensor network (WSN). However, basic flooding makes all nodes transmit the packet at least once, resulting in the broadcast storm problem in a serious case, in turn network resources become severely wasted. Particularly, power is one of the most valuable resources of WSNs as nodes are powered by battery, then the waste of energy by the basic flooding lessens the lifetime of WSNs. In order to solve the broadcast storm problem, this paper proposes a dynamic probabilistic flooding that utilizes the neighbor information like the number of child and sibling nodes. Simulation results show that the proposed method achieves a higher packet delivery ratio with the similar number of duplicate packets as compared to existing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.23-29
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• 2006

In wireless sensor networks(WSNs), it is crucial to maintain network connectivity as long as possible since nodes are battery-powered and unchange-able. We propose a new routing protocol called Energy Aware Source Routing(EASR) which can be efficient in respect of network lifetime and long-term connectivity. Our protocol is multipath source routing, only one path will be selected at the same time and each path has probability to be selected like as Energy Aware Routing(EAR) protocol. The route discovery procedure of EASR protocol is reformed from the route discovery procedure of Split Multipath Routing(SMR) protocol. However, there is the difference between SMR and EASR. In EASR, we define an overhearing ratio in order to reduce energy waste due to overhearing effect among each selected path. Thus, we can establish energy efficient multiple paths by making use of overhearing ratio. The simulation results are also demonstrated that our scheme increases in network lifetimes, and achieves reasonable packet latency time.