• 비파괴검사학회지
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• 제33권6호
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• pp.505-510
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• 2013

An encircling send-receive type pulsed eddy current (PEC) probe is designed for use in aluminum tube inspection. When bare receive coils located away from the exciter were used, the peak time of the signal did not change although the distance from the exciter increased. This is because the magnetic flux from the exciter coil directly affects the receive coil signal. Therefore, in this work, both the exciter and the sensor coils were shielded in order to reduce the influence of direct flux from the exciter coil. Numerical simulation with the designed shielded encircling PEC probe showed the corresponding increase of the peak time as the sensor distance increased. Ferrite and carbon steel shields were compared and results of the ferrite shielding showed a slightly stronger peak value and a quicker peak time than those of the carbon steel shielding. Simulation results showed that the peak value increased as the defect size (such as depth and length) increased regardless of the sensor location. To decide a proper sensor location, the sensitivity of the peak value to defect size variation was investigated and found that the normalized peak value was more sensitive to defect size variation when the sensor was located closer to the exciter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.504-505
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• 2011

Decreasing actual greenhouse gas will be difficult if it is not solved addressed in architectural fields. Zero emission building or zero energy building, maximize the efficiency of energy, which means the building can operate by their own renewable energy facility without any other supplying. To be a zero emission building, a building needs realization of high efficiency low energy consumption, construction of building its own energy production facilities and lastly a power grid connection. According to increasing of DC load about TV, LED lighting, computer, IT in building for living and business, it is expected the save of energy when the system of AC power distribution change into the system of DC power distribution. Renewable energy exists a big different rate produced by outside environment. When electrical power overproduce, it can supply for system. Otherwise, if electrical power produce less, it can receive supply from system. Send and receive power can lead to zero to annual standard. This paper shows the simulation about efficient control of power conversion which is related to DC power distribution of architecture and DC output of renewable energy by using L-type converter.

• 한국군사과학기술학회지
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• 제7권4호
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• pp.20-25
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• 2004

The existing antenna that equipped with Micro Aerial Vehicle, microstrip antenna only can send and receive image signal because of limited bandwidth. But, proposed antenna that equipped with Micro Aerial Vehicle flight introduces tapered type patch antenna, also improves bandwidth then can transfer present location, altitude, movement speed. Furthermore, as a result of introduce stacked type, it transfers more quality of image signal, and represents most suitable performance in Korean peninsula that has many mountain peaks. In this paper, to transmit and receive the wideband signals with a antenna system, the wideband microstrip antenna is proposed and designed. This antenna operates at 2.4GHz. In this thesis, the resonance frequency of 2.4GHz and the reflective loss of the antenna of -22dB were calculated by measuring the fabricated Tapered Microstrip Patch Antenna which was designed with the resonance of 2.4GHz. The calculated gain and efficiency of antenna were 6.7dB and $60\%$ respectively. The characteristic of the bandwidth shows with $50\~60MHz$ which is $6.02\%$ at the basis of -l5dB reflective loss. The experimental results can be used in the characteristic of the resonators and this antenna produces a greatly enhanced bandwidth.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.778-798
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• 2014

This paper proposes a novel exposed-terminal-eliminated medium access control (ETE-MAC) protocol by combining channel reservation, collision avoidance and concurrent transmissions to improve multi-access performance of the multihop wireless networks. Based on the proposed slot scheduling scheme, each node senses the control channel (CCH) or the data channel (DCH) to accurately determine whether it can send or receive the corresponding packets without collisions. Slot reservation on the CCH can be simultaneously executed with data packet transmissions on the DCH. Therefore, it resolves the hidden-terminal type and the exposed-terminal type problems efficiently, and obtains more spatial reuse of channel resources. Concurrent packet transmissions without extra network overheads are maximized. An analytical model combining Markov model and M/G/1 queuing theory is proposed to analyze its performance. The performance comparison between analysis and simulation shows that the analytical model is highly accurate. Finally, simulation results show that, the proposed protocol obviously outperforms the link-directionality-based dual-channel MAC protocol (DCP) and WiFlex in terms of the network throughput and the average packet delay.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.159-162
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• 2003

In this paper, we present a middleware that using routing scheme that support easily for various type of network in a home network based heterogeneous network. The protocol presented in this paper, consist two layers that Network Adaptation Layer(NAL) to allow access varience networks and Network Interface Layer(NIL) to deal network dependent parts. The middleware presentedl in this paper, can easily send data to any digital appliance or receive data from any digital appliance by using our routing scheme.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.280-285
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• 2008

ZigBee는 저전력 저속 근거리 무선 통신 프로토콜로서 센서 네트워크에 많은 적용이 되는 프로토콜이다. ZigBee가 PAN을 구성하는 방법은 Beacon Enabled PAN과 Non Beacon Enabled PAN의 두 가지가 존재 한다. Non Beacon Enabled PAN에서 데이터 전송방식은 End-Device가 원하는 시점에 Active 상태에 진입하여 데이터를 보내는 방법으로 저전력을 지원한다. 그러므로 Router는 End-Device가 데이터를 보내는 시간을 정확히 알 수 없게된다. 이런 문제를 해결하기 위해서 Router는 항상 Active 상태로 존재해야 한다. 이로 인해 Non Beacon Enabled PAN을 사용하는 센서 네트워크에서 Router는 별도의 상시 전원을 공급 받아야한다. 그러나 Non Beacon Enabled PAN의 ZigBee Router가 건전지와 같은 한정적인 전력 공급원을 가지게 되는 상황에서는 안정적인 네트워크 구축이 불가능하게 된다. 본 논문에서는 이를 해결하기 위해서 PAN Time을 통한 네트워크 동기화를 사용한 저전력 알고리즘을 제안한다. End-Device는 PAN Time을 사용하여 PAN의 동기화를 수행하며, PAN Time을 통해 Router의 저전력 진입을 지원한다.

• 정보처리학회논문지D
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• 제9D권2호
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• pp.313-322
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• 2002

멀티미디어 회의는 크게 밀결합 회의와 소결합 회의로 구분되며, 전자의 경우는 ITU-T의 H.323 표준에 근거한 일대일 또는 다자간 멀티미디어 회의가 있고, 후자의 경우로는 H.323 표준을 확장한 ITU-T의 H.332 표준이 있다. H.332 표준을 근거로 한 소결합 멀티미디어 회의는 송수신 능력을 갖는 소수의 패널과 수신능력 만을 갖는 다수의 청중들로 이루어진다. H.332에서는 참가자가 다수일 때 능력교환의 어려움을 극복하기 위해 회의의 주제나 미디어 형식등을 회의가 열리기 전에 미리 알리며 이를 위해 IETF의 SDP를 이용한다. 이와 같은 방법으로 H.323 멀티미디어 회의의 단점인 확장성을 극복할 수 있다. 본 논문에서는 소결합 멀티미디어 회의를 위하여 표준화되고 있는 H.332를 분석하고, 분석된 결과를 토대로 구현된 시스템을 소개한다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.57-60
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• 2001

본 논문은 멀티캐스트 주소 할당 기술 및 표준화 동향에 대하여 살펴보고자 한다. 멀티캐스트라 함은 단일 메시지를 전송하여, 다수의 수신자에게 정보를 전달할 수 있는 프로토콜로, 일반적으로 MAAs 서버나 MADCAP과 길은 서버를 이용하여 주소를 할당받는다. 그러나 오늘날 급속하게 증가하고 있는 홈 네트워킹 기술과 같은 자동네트워킹 메커니즘의 수요 증가로 인하여, 호스트 IP주소의 자동설정요구 뿐만 아니라 멀티캐스트 주소 또한 자동 생성하는 메커니즘을 요구하고 있다. 이에 본 문서에서는 호스트 내에서 주소를 자동 할당하는 방법 및 관리 기술에 대하여 서술할 것이며, 현재 IETF등에서 논의되고 있는 멀티캐스트 주소 파동생성 및 할당 현황을 보일 것이다.

• 한국태양에너지학회 논문집
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• 제29권1호
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• pp.50-57
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• 2009

Heliostat in the tower type solar thermal power plant is a mirror system tracking the sun's movement to collect the solar energy and it is the most important subsystem determining the efficiency of solar thermal power plant. Thus a good performance of it, which is mostly the accurate sun tracking performance under the various hazardous operating condition, is required. Heliostat control system is a system to manage the heliostat sun tracking movement and other operations. It also communicates with the master controller through the heliostat filed control system to receive and send the informations required to operate the heliostat as a part of the solar thermal power plant. This study presents a heliostat control system designed and developed for the 1MW solar thermal power plant. We first define the functionality of heliostat control system. Then sun tracking controller as well as the sun tracking algorithm satisfying the required functionality have been developed. We tested the developed heliostat control system and it showed a good performance in regulation of heliostat motion and communication.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.143-150
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• 2023

Underwater wireless communication is a challenging issue for realizing the smart aqua-farm and various marine activities for exploring the ocean and environmental monitoring. In comparison to acoustic and radio frequency technologies, the visible light communication is the most promising method to transmit data with a higher speed in complex underwater environments. To send data at a speedier rate, high-performance photodetectors are essentially required to receive blue and/or cyan-blue light that are transmitted from the light sources in a light-fidelity (Li-Fi) system. Here, we fabricated high-performance organic phototransistors (OPTs) based on P-type donor polymer (PTO2) and N-type acceptor small molecule (IT-4F) blend semiconductors. Bulk-heterojunction (BHJ) PTO2:IT-4F photo-active layer has a broad absorption spectrum in the range of 450~550 nm wavelength. Solution-processed OPTs showed a high photo-responsivity >1,000 mA/W, a large photo-sensitivity >10³, a fast response time, and reproducible light-On/Off switching characteristics even under a weak incident light. BHJ organic semiconductors absorbed photons and generated excitons, and efficiently dissociated to electron and hole carriers at the donor-acceptor interface. Printed and flexible OPTs can be widely used as Li-Fi receivers and image sensors for underwater communication and underwater internet of things (UIoTs).