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차량용 가변사판식 압축기의 흡입체크밸브 최적화에 관한 연구
이봉섭(Bongsub Lee),이용주(Yongju Lee),이태진(Taejin Lee),한준석(Junseok Han),배인표(Inpyo Bae),이건호(Geonho Lee) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.6
Development of a compressor for vehicle air conditioning system has been focused on high performance and noise reduction. Suction check valve is used to prevent the noise that is caused by the suction pulsation when a clutch-less compressor is operating in an OFF state. However, the suction pressure drop due to the increased flow resistance reduces the cooling capacity of a compressor. The aim at this study is to predict the cooling capacity drop rate and improving the performance with optimized suction check valve shapes. It proposed the theoretical cooling capacity drop rate, and the experimental studies were carried out in order to verify this. But those were not matched each other so that CFD analysis program was used to look for the cause. Results show that the pressure distribution of a valve surfaces affects the suction pressure drop. The cooling capacity was improved by the suction check valve that is modified to increase average pressure on a valve surface.
Lee, Wooram,Yoon, Sangwon,Choe, Jong Kwon,Lee, Miran,Choi, Yongju Elsevier 2018 Science of the Total Environment Vol.639 No.-
<P><B>Abstract</B></P> <P>This study investigates the effect of anionic surfactant modification on activated carbon (AC) to enhance the adsorption of ammonium ion in aqueous solution. Sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) or sodium octanoate (SO) was used for the modification. At the initial aqueous concentration of 55 mg NH<SUB>4</SUB>-N/L and the adsorbent dose of 50 g/L, the SDS-modified AC showed the highest ammonium removal efficiency of 82% among the modified ACs studied. The hydrophobic group of SDS was strongly attached to AC showing almost negligible desorption after the modification. At the same time, the sulfate functional group of SDS provided ion exchange sites favorable for the ammonium ion adsorption. By maximizing SDS loading to the AC, ammonium removal efficiency can further be improved (5% increase). When Na<SUP>+</SUP>, K<SUP>+</SUP> or Ca<SUP>2+</SUP> coexisted in the ammonium solution at the concentration of 55 mg/L, the inhibition effect of these cations on ammonium removal efficiency was negligible (<5%). This study shows the potential of anionic surfactant-modified ACs as the excellent adsorbents for ammonium removal from water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Surfactant modification improves NH<SUB>4</SUB> <SUP>+</SUP> adsorption capacity of activated carbon (AC). </LI> <LI> Surfactants used for modification are stably bound to AC. </LI> <LI> SDS and SDBS provide AC with ion exchange sites favorable for NH<SUB>4</SUB> <SUP>+</SUP> adsorption. </LI> <LI> Inhibition effect of competing ions at the same concentration as NH<SUB>4</SUB> <SUP>+</SUP> is negligible. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Semantic-based Mashup Platform for Contents Convergence
Yongju Lee,Hongzhou Duan,Yuxiang Sun The Institute of Internet 2023 International journal of advanced smart convergenc Vol.12 No.2
A growing number of large scale knowledge graphs raises several issues how knowledge graph data can be organized, discovered, and integrated efficiently. We present a novel semantic-based mashup platform for contents convergence which consists of acquisition, RDF storage, ontology learning, and mashup subsystems. This platform servers a basis for developing other more sophisticated applications required in the area of knowledge big data. Moreover, this paper proposes an entity matching method using graph convolutional network techniques as a preliminary work for automatic classification and discovery on knowledge big data. Using real DBP15K and SRPRS datasets, the performance of our method is compared with some existing entity matching methods. The experimental results show that the proposed method outperforms existing methods due to its ability to increase accuracy and reduce training time.
Yongju Lee,Swarup Biswas,Hyeok Kim 한국진공학회(ASCT) 2021 Applied Science and Convergence Technology Vol.30 No.6
The use of tiny, micro-powered electronic devices in indoor environments is increasing daily. The demand for high-performing organic photovoltaics (OPVs) to power these devices has been rapidly growing because OPVs have favorable absorption properties for indoor environments, excellent mechanical flexibility, and other advantageous attributes. Recently, inexpensive, less acidic, and water-processable polyaniline:poly (4-styrenesulfonic acid) (PANI:PSS) was shown to deliver remarkably high performance as the hole transport layer (HTL) in an indoor OPV device with poly(3-hexylthiophene): indene-C60 bisadduct as the active layer. However, PANI:PSS has not been tested in combination with other active materials, although its universal applicability is of key importance for its commercialization. Thus, we tested the potentiality of using PANI:PSS as the HTL of a highly suitable active material, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl-l)carbonyl]thieno[3,4-b]thiophendiyl]:phenyl-C70-butyric acid methyl ester (PTB7:PC70BM) in an OPV device under an LED lamp. The results reveal that the OPV device based on the PANI:PSS HTL and PTB7:PC70BM as the active material has high efficiency (11.80%) and a maximum power density of 42.5 W/cm² under a 1,000 lx LED.
Graphene–nanowire hybrid structures for high-performance photoconductive devices
Lee, Hyungwoo,Heo, Kwang,Park, Jaesung,Park, Yongju,Noh, Seunguk,Kim, Kwang S.,Lee, Changhee,Hong, Byung Hee,Jian, Jikang,Hong, Seunghun The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.17
<P>Graphene–CdS nanowire (NW) hybrid structures with high-speed photoconductivity were developed. The hybrid structure was comprised of CdS NWs which were selectively grown in specific regions on a single-layer graphene sheet. The photoconductive channels based on graphene–CdS NW hybrid structures exhibited much larger photocurrents than graphene-based channels and much faster recovery speed than CdS NW network-based ones. Our graphene–CdS NW structures can be useful because they were much faster than commercial CdS film-based photodetectors and had photocurrents large enough for practical applications.</P> <P>Graphic Abstract</P><P>We have developed a photoconductive channel based on graphene–CdS nanowire hybrid structures which exhibited large photocurrent and fast recovery speed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm16565a'> </P>
최용주 ( Yongju Choi ),이종욱 ( Jonguk Lee ),박대희 ( Daihee Park ),이종현 ( Jonghyun Lee ),정용화 ( Yongwha Chung ),김희영 ( Heeyoung Kim ),윤석한 ( Sukhan Yoon ) 한국정보처리학회 2016 한국정보처리학회 학술대회논문집 Vol.23 No.1
열차의 진로를 제어하는 선로전환기는 열차의 안정적인 주행에 있어서 매우 중요한 시설이다. 본 논문에서는 선로전환기의 작동 시 발생하는 소리 정보를 이용하여 선로전환기의 스트레스를 탐지하는 시스템을 제안한다. 먼저 제안하는 시스템은 선로전환기에 스트레스가 쌓인 상태의 소리 정보와 스트레스가 제거된 소리 정보를 수집한 후, 다양한 소리특징들을 추출한다. 추출된 특징들로 부터 t-test를 이용하여 유의성이 확보된 소리 특징 파마미터만을 최종 특징벡터로 선택한다. 마지막으로, 소리 특징 벡터를 입력으로 하는 이진 분류기인 SVM(Support Vector Machine)을 이용하여, 선로전환기의 스트레스 상태 여부를 실시간으로 탐지한다. 실제 테스트용 선로전환기에서 취득한 소리 정보 데이터 셋을 이용하여 본 논문에서 제안하는 시스템의 성능을 실험적으로 검증한다.
열가소성 폴리우레탄과 미세결정 셀룰로오스 복합체의 제조 및 기계적 물성 분석
김용주(Yongju Kim),윤혁준(Hyeok Jun Yoon),이상연(Sang Yeon Lee),이종혁(Jong Hyeok Lee),문성박(Seong Bak Moon),남정민(Jeong Min Nam),정경호(Kyongho Jung),위정재(Jeong Jae Wie) 한국고분자학회 2020 폴리머 Vol.44 No.6
셀룰로오스는 식물 세포벽의 기본 구조 성분으로 자연에서 추출할 수 있는 가장 풍부한 천연고분자이다. 셀룰로오스는 열분해성 및 생분해성이 뛰어나며 가벼운 무게 대비 높은 기계적 물성을 나타내는 특성으로 인해, 고분자-셀룰로오스 복합체를 통해 자동차 경량화 소재, 신발, 코팅 및 건축용 소재 등의 다양한 산업 분야에 적용하기 위한 연구가 널리 진행되고 있다. 본 연구에서는 가볍고 신축성이 좋은 열가소성 폴리우레탄(TPU)의 낮은 기계적 강도를 증가시키고 미세 플라스틱에 의한 환경오염을 방지하기 위해 미세결정 셀룰로오스(MCC)를 보강재로 사용하여 친환경 복합체를 제조하고자 한다. 사용된 MCC의 사이즈는 입도 분석기(PSA)로 측정 시 88.4 μm로 측정되었으며 TPU의 우레탄기와 MCC의 수산기 사이의 수소결합을 통한 상호작용은 적외선 분광분석(FTIR)을 통해 확인했다. 열중량분석(TGA)을 통해 열안정성을 측정한 결과 MCC의 열안정성이 낮기 때문에 TPU-MCC 복합체의 MCC 함량이 증가할수록 열안정성은 감소함을 나타냈다. 주사전자현미경(SEM) 측정결과 0.5 wt% 함량에서는 MCC가 매트릭스 내부에 골고루 분산된 모습이 관찰되었으나 1wt% 이상의 함량에서는 응집이 발생하는 현상을 관찰했다. 만능재료시험기(UTM) 측정 결과 0.5 wt%와 같은 소량의 MCC 함량 첨가는 인장강도 12.7%, 연신율 36.7%, 그리고 인성 25.9%가 증가함을 확인했지만 1 wt% 이상의 MCC 함량에서는 기계적 물성이 감소하는 경향을 나타냈다. 결론적으로 보강재를 소량 첨가함으로써 매트릭스 물질의 기계적 물성을 증가시킬 수 있음을 확인했다. Cellulose is the most abundant polymer found in nature. Owing to the lightweight mechanical properties and biodegradability of cellulose, polymer-cellulose composites have widely been investigated for various applications. In this study, microcrystalline cellulose (MCC) is employed as a reinforcement agent for eco-friendly TPU-MCC composites to enhance the mechanical strength of thermoplastic polyurethane (TPU). The size of the MCC was measured to be 88.4 μm by particle size analyzer, and the hydrogen bonding between the urethane group of TPU and the hydroxyl group of MCC was characterized by Fourier transform infrared spectroscopy. As evident from SEM analysis, MCC was evenly dispersed in TPU matrix at 0.5 wt% MCC loading, but we observed the aggregation at 1 wt% or higher MCC loading. From the universal testing machine analysis, we observed an increase in tensile strength by 12.7%, elongation by 36.7%, and toughness by 25.9% at a small amount of 0.5 wt% MCC content.