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이종망 환경에서 오버헤드 감소와 수율 향상을 위한 자율적인 펨토셀 전송 전력 조절 기법
조영훈(Younghoon Jo),임재찬(Jaechan Lim),홍대형(Daehyoung Hong) 한국통신학회 2013 韓國通信學會論文誌 Vol.38 No.1B
저전력, 저가의 초소형 기지국인 펨토셀은 heterogeneous network 의 중요 구성 요소 중 하나이다. 그러나 펨토셀 설치에 따른 셀 구조의 변화는 셀 간 간섭과 signaling overhead 증가와 같은 기술적인 문제를 야기할 수 있다. 이와 같은 기술적인 문제의 해결 방법 중 하나는 펨토셀이 SON(Self-Organized Network)과 같은 기법을 이용하여 자율적으로 전송전력을 조절하는 것이다. 펨토셀은 전송전력 조절을 통해 시스템 throughput을 향상시키거나 overhead를 감소시킬 수 있다. 일반적으로 시스템 throughput을 최대화하기 위한 펨토셀 전송 전력과 시스템 overhead 감소를 위한 펨토셀 전송 전력은 일치하지 않는다. 따라서 본 연구에서는 펨토셀이 시스템 overhead를 감소시키는 동시에 시스템 throughput을 향상시키도록 전송 전력을 조절하는 방법을 제안한다. 모의실험을 통해 제안 기법이 throughput만을 최대화하는 기법에 비하여 시스템 overhead를 41% 감소시키는 것을 확인하였다. 또한 커버리지만을 최적화 하는 기법에 비하여 throughput이 63% 향상되는 것을 확인하였다. Femto-cells are low power/cost, micro-base stations and are main components in heterogeneous networks. However, some of technical issues arise when femto-cells are initially installed. One approach to resolve the problems is to control the transmission (TX) power autonomously via SON(Self-Organized Network) scheme. By controlling the femto-cell TX power, the system throughput performance can be improved or the system overhead is highly reduced. Generally, the TX power for maximizing the system throughput and that for reduced system overhead may not be identical. Therefore, we propose a TX power control scheme by which we can improve the system throughput and reduce the system overhead, simultaneously. When we apply the proposed method, the simulation results show that the system overhead can be reduced by up to 41% compared to the performance of the method which maximizes throughput performance only, and the throughput performance can be improved by up to 63% compared to that of the method which only optimizes the coverage area.
광학식 표면스캐닝 및 X-선 CT를 활용한 유물의 3차원 융합모델 제작 : 국립진주박물관 소장 삼총통
조영훈,김다솔,김해솔,허일권,송민규 국립중앙박물관 2019 박물관보존과학 Vol.22 No.-
이 연구에서는 표면형상 취득에 최적화되어 있는 광학식 정밀스캐닝과 내부 형상 획득에 사용되는 X-선 CT스캐닝 결과를 이용하여 삼총통의 내·외부 형상을 다각적으로 분석할 수 있는 3차원(이하 3D) 융합 모델을 제작하였다. 먼저 두 스캐닝 결과를 호환 가능한 확장자로 변환한 다음 상호간의 정합성을 검증하고자 3D 편차분석을 수행하였다. 이 결과, 두 스캐닝 모델은 대부분(56.98%) ±0.1mm 이내의 편차를 보였으며, 이 수치는 ICP 알고리즘 기반의 정합 및 병합에 큰 영향을 주지 않았다. 병합된 데이터는 총통의 외부 표면색 및 미세형상, 내부 두께 및 구조를 잘 표현하였다. 광학식 표면스캐닝과 X-선 CT스캐닝의 3D 융합 모델은 문화유산의 디지털기록화뿐만 아니라 제작기법 해석에 유용하게 사용되었다. 향후 박물관 전시 영역에서 전시품의 과학적 조사 정보를 보다 쉽게 관람객에게 전달하는 효과를 발휘 할 것으로 기대된다. This study was focused on the three-dimensional convergence modeling that can multilaterally analyze internal and external shapes of the Sam-Chongtong Hand Canon by optical precision scanning optimized for acquiring the surface shape and X-ray CT scanning used for obtaining the internal shape. First, the scanning results were converted by compatible extension, after which three dimensional deviation analysis was conducted to verify mutual conformities. Accordingly, most(56.98%) deviations between the two scanning models was found be ±0.1mm. This result did not influence registration and merging based on the ICP algorithm. The merged data exhibited the external surface color, detailed shapes, internal width, and structure of the hand canon. The three-dimensional model based on optical surface scanning and X-ray CT scanning can be used for traditional technique interpretation as well as digital documentation of cultural heritage. In the future, it will contribute to deliver accessible scientific information of exhibits for visitors.
Jo, Changshin,An, Sunhyung,Kim, Younghoon,Shim, Jongmin,Yoon, Songhun,Lee, Jinwoo The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.16
<P>Mesocellular carbon foam (MSU-F-C) is functionalized with hollow nanographite by a simple solution-phase method to enhance the intrapenetrating electrical percolation network. The electrical conductivity of the resulting material, denoted as MSU-F-C-G, is increased by a factor of 20.5 compared with the pristine MSU-F-C. Hollow graphite nanoparticles are well-dispersed in mesocellular carbon foam, as confirmed by transmission electron microscopy (TEM), and the <I>d</I> spacing of the (002) planes is 0.343 nm, which is only slightly larger than that of pure graphite (0.335 nm), suggesting a random combination of graphitic and turbostratic stacking. After nanographitic functionalization, the BET surface area and total pore volume decreased from 928 m<SUP>2</SUP> g<SUP>−1</SUP> and 1.5 cm<SUP>3</SUP> g<SUP>−1</SUP> to 394 m<SUP>2</SUP> g<SUP>−1</SUP> and 0.7 cm<SUP>3</SUP> g<SUP>−1</SUP>, respectively. Thermogravimetric analysis in air shows that the thermal stability of MSU-F-C-G is improved relative to that of MSU-F-C, and the one-step weight loss indicates that the nanographite is homogeneously functionalized on the MSU-F-C particles. When the resulting mesocellular carbon materials are used as electrode materials for an electric double layer capacitor (EDLC), the specific capacitances (<I>C</I><SUB>sp</SUB>) of the MSU-F-C and MSU-F-C-G electrodes at 4 mV s<SUP>−1</SUP> are 109 F g<SUP>−1</SUP> and 93 F g<SUP>−1</SUP>, respectively. The MSU-F-C-G electrode exhibited a very high area capacitance (<I>C</I><SUB>area</SUB>, 23.5 μF cm<SUP>−2</SUP>) compared with that of the MSU-F-C electrode (11.7 μF cm<SUP>−2</SUP>), which is attributed to the enhanced intraparticle conductivity by the nanographitic functionalization. MSU-F-C-G exhibited high capacity retention (52%) at a very high scan rate of 512 mV s<SUP>−1</SUP>, while only a 23% capacity retention at 512 mV s<SUP>−1</SUP> was observed in the case of the MSU-F-C electrode. When applied as an anode in a lithium ion battery, a significant increase in the initial efficiency (44%), high reversible discharge capacity (580 mA h g<SUP>−1</SUP>) in the lower voltage region, and a higher rate capability were observed. The high rate capability of the MSU-F-C-G electrode as charge storage was due to the low resistance derived from the nanographitic functionalization.</P> <P>Graphic Abstract</P><P>Nano-graphite functionalized mesocellular carbon foam exhibits advanced electrochemical performances as electrode materials in EDLC and LIB due to the role of graphite as an intrapenetrating electrical network. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp40657h'> </P>
Acid-Assisted Ligand Exchange Enhances Coupling in Colloidal Quantum Dot Solids
Jo, Jea Woong,Choi, Jongmin,Garcí,a de Arquer, F. Pelayo,Seifitokaldani, Ali,Sun, Bin,Kim, Younghoon,Ahn, Hyungju,Fan, James,Quintero-Bermudez, Rafael,Kim, Junghwan,Choi, Min-Jae,Baek, Se-Woong American Chemical Society 2018 NANO LETTERS Vol.18 No.7
<P>Colloidal quantum dots (CQDs) are promising solution-processed infrared-absorbing materials for optoelectronics. In these applications, it is crucial to replace the electrically insulating ligands used in synthesis to form strongly coupled quantum dot solids. Recently, solution-phase ligand-exchange strategies have been reported that minimize the density of defects and the polydispersity of CQDs; however, we find herein that the new ligands exhibit insufficient chemical reactivity to remove original oleic acid ligands completely. This leads to low CQD packing and correspondingly low electronic performance. Here we report an acid-assisted solution-phase ligand-exchange strategy that, by enabling efficient removal of the original ligands, enables the synthesis of densified CQD arrays. Our use of hydroiodic acid simultaneously facilitates high CQD packing via proton donation and CQD passivation through iodine. We demonstrate highly packed CQD films with a 2.5 times increased carrier mobility compared with prior exchanges. The resulting devices achieve the highest infrared photon-to-electron conversion efficiencies (>50%) reported in the spectral range of 0.8 to 1.1 eV.</P> [FIG OMISSION]</BR>
Kim, Younghoon,Jo, Changshin,Lee, Jinwoo,Lee, Chul Wee,Yoon, Songhun The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.4
<P>An ordered nanocomposite of polyethylene glycol–organic radical polymer–mesocellular carbon foam (PEG–ORP–MCF) was prepared by incorporation of ORP into acidified MCF and following PEG coating. The prepared nanocomposite was employed as the cathode material in lithium ion batteries. The nanocomposite electrode exhibited an improvement of high-temperature cycling performance (70% capacity retention after 50 cycles at 50 °C) with a high capacity (111 mA h g<SUP>−1</SUP>), a good rate performance (67% under 20 C current rate) and a smaller polarization under ambient conditions. This improved cathode performance was ascribed to the protective effect of PEG polymer that prevented the ORP from being dissolved in the electrolyte and the high electrical percolation network by the MCF carbon framework.</P> <P>Graphic Abstract</P><P>An ordered nanocomposite electrode of polyethylene glycol–organic radical polymer–mesocellular carbon foam exhibited a high discharge capacity (111 mA h g<SUP>−1</SUP>), a good rate capability (67% retention at 20 C) under ambient temperature and a greatly improved cycle performance at 50 °C (70 retention at 50 cycles) due to the protective effect of PEG layer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm15053g'> </P>
윤영훈(Younghoon Yoon),조재득(Jaedeuk Jo),유영환(Younghwan You),강정호(Jeongho Kang),조민경(Minkyoung Cho),정건우(Gunwoo Jeong) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The Experimental Study on the mechanism occurred of white smoke of Diesel Particulate Filter were investigated in DI injection TCI diesel engine. The diesel particulate filter mounted the diesel engine in this study were performed to leave the 10 hours in sub-zero temperatures to same of field conditions. As the result, it is shown that the white smoke was occurred around 50℃before the filter temperature and raised some liquid from the system about 120~130℃. Most of the ingredients in liquids have been formed by water.