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신광호(Kwangho Shin),최송(Song Choi),정호종(Hojong Jeong),이진우(Jinwoo Lee),양동근(Dong-keun Yang),정백영(Baikyoung Chung) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.11
This study is describing a method for improving reliability and energy efficiency of GHP system. First of all, capacitance level sensor was evaluated for detecting oil level and in the oil separator. As the result of applying the oil level sensor in GHP system, it was confirmed that oil return operation was unnecessary. It provided a continuous heating operation under the sufficient presence of oil in oil separator. Therefore, GHP system applying the oil level sensor was able to reduce energy consumption as compared with the conventional system. Second of all, a control method for the refrigerant charge amount is performed using receiver. The energy efficiency was improved in the cooling and heating mode through changing refrigerant charge amount. The difference of refrigerant charge amount between optimal cooling and heating mode was about 27%, and it was controlled with relationship between high pressure and degree of subcooling.
무선 센서 네트워크를 위한 하이브리드 Inter-Cell TDMA/Intra-Cell CSMA 아키텍처 (pp.690-694)
이한선(Hansun Lee),원광호(Kwangho Won),이상신(Sangshin Lee),정광수(Kwangsue Chung) 한국정보과학회 2009 정보과학회 컴퓨팅의 실제 논문지 Vol.15 No.9
본 논문에서는 무선 센서 네트워크에서 센서 노드의 에너지 소모를 줄이고 네트워크의 수명을 최대화하기 위한 하이브리드 MAC 아키텍처를 제안한다. 하이브리드 MAC 아키텍처는 싱크노드와 센서노드로 구성되는 계층적 센서 네트워크 구조에서 싱크노드의 최대 전송 영역은 스케줄 기반의 TDMA를 사용하고, 이외의 영역은 경쟁 기반의 CSMA를 사용함으로써 많은 데이터 트래픽이 집중하여 혼잡상황이 잦은 싱크노드 주변의 송수신을 관리하여 불필요한 에너지 소비를 줄이도록 설계되었다. 또한 ns-2 시뮬레이터를 이용한 실험을 통하여 제안한 기법의 성능을 CSMA, TDMA와 비교하였다. 실험 결과를 통해 제안하는 기법이 에너지 효율적으로 동작하는 것을 확인하였다. In this paper, we propose a hybrid MAC architecture for reducing energy consumption and maximizing network lifetime in wireless sensor networks. For this purpose, the hybrid MAC architecture is proposed for energy efficient by combining inter-cell TDMA and intra-cell CSMA scheme. Based on the ns-2 simulation result, we prove that the proposed architecture improves energy efficiency as compared with CSMA and TDMA.
이정욱(Jungwook Lee),원광호(Kwangho Won),정광수(Kwangsue Chung) 한국정보과학회 2010 정보과학회 컴퓨팅의 실제 논문지 Vol.16 No.5
멀티 홉을 이용하는 무선 센서 네트워크에서는 환경적 요인과 노드의 하드웨어적 제약으로 인해 링크의 품질변화가 불규칙하게 일어난다. 이러한 불규칙성에 대응하여 적절한 경로를 선택하지 못한다면 데이터의 손실이 빈번하게 일어날 수 있다. 기존에는 비컨을 주기적으로 브로드캐스팅하여 링크의 품질을 측정하였지만, 이 기법은 불규칙하게 변화하는 링크의 품질을 효율적으로 측정할 수 없다. 본 논문에서는 네트워크의 상태에 따라 링크의 품질 측정 주기를 적응적으로 측정하는 기법을 제안한다. 링크의 품질이 변화할 때 민첩하게 변화에 대응하여 패킷 손실을 줄이고 변화가 없을 때는 긴 주기로 링크 품질을 측정하여 에너지 소모를 줄이고자 한다. 실험을 통하여 제안된 기법이 기존에 제안된 기법보다 에너지 효율 및 패킷 수신율을 향상시킬 수 있음을 확인하였다 In the wireless sensor networks using a multi-hop, quality variation of links occurs irregularly due to the hardware restriction and environmental factor. If an appropriate route, which is affected by the quality variation, is not selected. Traditionally, a beacon is periodically broadcasted and the link quality is estimated. However, the periodically beacon based scheme cannot efficiently estimate the quality of the link changing irregularly. In this paper, a scheme to estimate the link quality adaptively according to network state is proposed. When the link quality changes, the scheme adapts to a change agilely and packet losses are reduced. When there is no change of the link quality, the link quality is estimated in the long period and the energy consumption is reduced. Through performance evaluations, we prove that our adaptive link estimation scheme improves the energy efficiency and packet reception ratio than the periodic estimation scheme.
대규모 무선 센서 네트워크를 위한 신뢰적인 태스크 할당 프로토콜
이동호(Dongho Lee),원광호(Kwangho Won),김재호(Jaeho Kim),정광수(Kwangsue Chung) 한국정보과학회 2008 한국정보과학회 학술발표논문집 Vol.35 No.2
최근의 IT 기술 발전은 도시인들의 삶의 질을 향상시킬 수 있는 u-City의 구축을 가능케 하였다. 이러한 u-City의 다양한 서비스를 현실화시키기 위한 인프라로 무선 센서 네트워크 기술이 주목받고 있다. 하지만 u-City를 위한 무선 센서 네트워크 기술은 에너지 효율이 강조되던 기존 연구와는 달리 대규모의 망을 지원할 수 있는 확장성과 신뢰할 수 있는 서비스 품질이 우선시 되어야 한다. 본 논문에서는 대규모 무선 센서 네트워크를 위한 태스크 할당 프로토콜인 RTAP(Reliable Task Assignment Protocol)을 제안하였다. RTAP는 대규모의 망을 지원할 수 있는 계층 구조로 동작하며 태스크 할당 및 데이터 수집에 신뢰성을 제공한다. 실험을 통해 RTAP는 기존에 제안된 계층 구조의 프로토콜보다 데이터 전달에 있어 더욱 신뢰적이고 안정적인 성능을 보임을 알 수 있었다.
SungWook Cho,RyungAh Lee,SoonSup Chung,KwangHo Kim 대한외과학회 2010 Annals of Surgical Treatment and Research(ASRT) Vol.78 No.1
Purpose: This study is to introduce our preliminary experience of the Doppler-guided hemorrhoidal artery ligation and Rectoanal repair (DG-HAL & RAR) as a new treatment for symptomatic or prolapsed hemorrhoids. Methods: A Doppler probe incorporated proctoscope was inserted under the lithotomy position and the location of the hemorrhoidal artery was identified. The identified artery was ligated as a ‘figure of eight’ method with an absorbable suture into the submucosa. Then the prolapsed hemorrhoidal pile was lifted at the rectal mucosa by continuous suture to 5 ㎜ above the dentate line and tied. The procedure was repeated at the 1, 3, 5, 7, 9, and 11 o’clock positions. We evaluated post-operative hospital stay, degree of pain, time to return to work, and recurrence. Results: The patient’s mean age was 50.2±15 years old and the mean follow-up time was 415±75 days. The constitution of the type of internal hemorrhoids was as follows: Grade Ⅱ: 13, Grade Ⅲ: 16, and Grade Ⅳ: 5. The mean operation time was 35 minutes and post-operative hospital stay was 1.4 days. The mean time it took to return to work was 1.8 days. There were no severe pains requiring injection of analgesics or other severe complications. So far, 2 patients have had recurrence of symptoms. Conclusion: The DG-HAL & RAR is a safe and less painful procedure. The DG-HAL & RAR is an effective alternative for the treatment of symptomatic or prolapsed hemorrhoids.
Effect of Surface Oxidation Layer on Tensile Strength of Cu-Ni Alloy in Friction Stir Welding
Taejin Yoon,Sangwon Park,Sungwook Chung,Joongsuk Noh,Kwangho Kim,Chungyun Kang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3
Friction stir welding (FSW) of thick Cu-Ni plate was successfully completed. The fracture position after tensile testing was located at the weld nugget zone (WNZ), where surface oxidation occurred. The oxidation morphologies on the surface of the base metal were analyzed by SEM, EPMA and XRD, with the oxide layer being obtained by simple and useful way to analyze the oxide products, namely, collecting oxide powders after immersing of the oxidized specimen into HNO3 solution. The results highlighted that an oxide layer of 30 μm thickness consists of a mixture of two phases, Cu2O and NiO, on the surface of the base metal. After FSW, the thickness of the oxide layer on the surface was decreased to approximately 5 μm, and broken oxide particles, which is NiO, penetrated into the WNZ by the rotating tool. NiO was preferentially formed at the surface after FSW because it has a lower Gibbs free energy value at 950 °C, which is the peak temperature measured during FSW. Oxide layer of Cu-Ni plate was clearly only removed by mechanical method grinding with 1200-grit SiC paper. The removal of oxide layer results in improved mechanical strength.