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Moth-eye Structured Polydimethylsiloxane Films for High-Efficiency Perovskite Solar Cells

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Nano-Micro Letters 2019年第3期11卷 271-280页

作者： Mincheol Kim Segeun Jang Jiwoo choi Seong Min Kang Mansoo choi Global Frontier Center for Multiscale Energy Systems Seoul National UniversitySeoul151.744Republic of Korea Department of Mechanical and Aerospace Engineering Seoul National UniversitySeoul151.744Republic of Korea Department of Mechanical Engineering Hanbat National UniversityDaejeon34158Republic of Korea Department of Mechanical Engineering Chungnam National UniversityDaejeon34134Republic of Korea

Large-area polydimethylsiloxane(PDMS)films with variably sized moth-eye structures were fabricated to improve the efficiency of perovskite solar *** approach that incorporated photolithography,bilayer PDMS deposition and replication was used in the fabrication *** simply attaching the moth-eye PDMS films to the transparent substrates of perovskite solar cells,the optical properties of the devices could be tuned by changing the size of the moth-eye *** device with 300-nm moth-eye PDMS films greatly enhanced power conversion efficiency of ~21 % due to the antireflective effect of the moth-eye ***,beautiful coloration was observed on the 1000-nm moth-eye PDMS films through optical interference caused by the diffraction grating *** results imply that moth-eye PDMS films can greatly enhance the efficiency of perovskite solar cells and building-integrated photovoltaics.

关键词： Polydimethylsiloxane films Moth-eye Photolithography Perovskite solar cells Photovoltaic

Advanced Community Identification Model for Social Networks

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Computers, Materials & Continua 2021年第11期69卷 1687-1707页

作者： Farhan Amin Jin-Ghoo choi Gyu Sang choi Department of Computer Engineering Gachon UniversityGyeonggi-do13120Korea Department of Information and Communication Engineering Yeungnam UniversityGyeongsan38541Korea

Community detection in social networks is a hard problem because of the size,and the need of a deep understanding of network structure and *** several methods with significant effort in this direction have been devised,an outstanding open problem is the unknown number of communities,it is generally believed that the role of influential nodes that are surrounded by neighbors is very *** addition,the similarity among nodes inside the same cluster is greater than among nodes from other ***,the global and local methods of community detection have been getting more ***,in this study,we propose an advanced communitydetection model for social networks in order to identify network communities based on global and local *** proposed model initially detects the most influential nodes by using an Eigen score then performs local expansion powered by label *** process is conducted with the same color till nodes reach maximum ***,the communities are formed,and a clear community graph is displayed to the *** proposed model is completely parameter-free,and therefore,no prior information is required,such as the number of communities,*** perform simulations and experiments using well-known synthetic and real network benchmarks,and compare them with well-known state-of-the-art *** results prove that our model is efficient in all aspects,because it quickly identifies communities in the ***,it can easily be used for friendship recommendations or in business recommendation systems.

关键词： Community detection social network analysis complex networks

Influence of the wastewater composition on denitrification and biological P-removal in the S-DN-P process: (c) Dissolved and undissolved substrates

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Journal of Environmental Sciences 2009年第8期21卷 1074-1079页

作者： Hee-Jeong choi Chul-Ho choi Seung-Mok Lee Diwakar Tiwari Department of Environmental Engineering Kwandong University Department of Chemistry School of Physical Sciences Mizoram University

The denitdfication and P-removal in the sorption-denitrification-P-removal （S-DN-P） process were carded out under various wastewater compositions. It is noted that P-removal largely depends on the wastewater composition as well to the quantity of the substrates present in wastewater fraction. Three different wastewater fractions are obtained as： raw wastewater, dissolved wastewater （obtained with filtration using 0.45 μm filter）, and undissolved wastewater （i.e., infiltrate obtained by above filtration）. The ratio of P-release/CODtotal-consumption clearly inferred that undissolved wastewater possess very low value i.e., 0.0008 followed by raw wastewater 0.008 and dissolved wastewater 0.03. When this ratio was nearby 0.01, enhanced P-removal was observed. Moreover, the ratio of P-uptake to NO3^--N decomposition for raw wastewater was two times for dissolved wastewater. Interestingly, it was observed that the P-removal and denitrification depend not only on the dissolved substrates but also the undissolved substrates present in the wastewater. The result of the P-removal obtained with this S-DN-P process did not show a big difference of 36%, 34% and 30%, respectively, for raw, dissolved and undissolved wastewater.

关键词： denitrification polyhydroxybutyrate sequencing batch biofilm reactor sorption denitrification P-removals

An approach to dark energy problem through linear invariants

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Chinese Physics C 2011年第3期35卷 233-242页

作者： Jeong Ryeol choi Department of Radiologic Technology Daegu Health College Division of Semiconductor and Display Engineering College of IT EngineeringKyungpook National University

The time evolution of vacuum energy density is investigated in the coherent states of inflationary universe using a linear invariant approach. The linear invariants we derived are represented in terms of annihilation operators. On account of the fact that the coherent state is an eigenstate of an annihilation operator, the wave function in the coherent state is easily evaluated by solving the eigenvalue equation of the linear invariants. The expectation value of the vacuum energy density is derived using this wave function. Fluctuations of the scalar field and its conjugate momentum are also investigated. Our theory based on the linear invariant shows that the vacuum energy density of the universe in a coherent state is decreased continuously with time due to nonconservative force acting on the coherent oscillations of the scalar field, which is provided by the expansion of the universe. In effect, our analysis reveals that the vacuum energy density decreases in proportion to t-β where β is 3/2 for radiation-dominated era and 2 for matter-dominated era. In the case where the duration term of radiation-dominated era is short enough to be negligible, the estimation of the relic vacuum energy density agrees well with the current observational data.

关键词： cosmological constant problem vacuum energy density coherent state linear invariant

Characteristics of thermally-enhanced bentonite grouts for geothermal heat exchanger in South Korea

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Science China(Technological Sciences) 2010年第1期53卷 123-128页

作者： Chulho LEE Kangja LEE Hangseok choi Hyo-Pum choi School of Civil Environmental and Architectural EngineeringKorea UniversityAnam-dongSeongbuk-guSeoul 136-701Republic of Korea Research & Development Institute KUNHWA Co.LTD.Yeoksam-dongGangnam-guSeoul 135-513Republic of Korea

The thermal conductivity and viscosity of bentonite grouts have been evaluated and compared each other to determine the suitability of these materials for backfilling vertical boreholes of ground heat *** bentonite grouts from different product sources were considered in this *** additives,silica sand and graphite were added in bentonite grouts to enhance thermal *** bentonite grouts indicate that both the thermal conductivity and the viscosity increase with the content of silica sand and ***,it is recommended to select cautiously the amount of silica sand and graphite considering not only thermal conductivity but also viscosity for the optimum condition of ***,the effect of salinity in the pore water on the change of swelling potential of the bentonite-based grouts has been quantitatively evaluated to show the feasibility of bentonite grouts in the coastal area.

关键词： ground heat exchanger bentonite grout thermal conductivity viscosity silica sand and graphite

Sandwich-structure transferable free-form OLEDs for wearable and disposable skin wound photomedicine

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Light(Science & Applications) 2019年第1期8卷 96-110页

作者： Yongmin Jeon Hye-Ryung choi Jeong Hyun Kwon Seungyeop choi Kyung Mi Nam Kyoung-Chan Park Kyung Cheol choi School of Electrical Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Department of Dermatology Seoul National University Bundang Hospital(SNUBH)Seongnam 13620Republic of Korea

Free-form optoelectronic devices can provide hyper-connectivity over space and ***,most conformable optoelectronic devices can only be fabricated on flat polymeric materials using low-temperature processes,limiting their application and *** paper presents free-form optoelectronic devices that are not dependent on the shape or *** medical applications,the transferable OLED(10μm)is formed in a sandwich structure with an ultra-thin transferable barrier(4.8μm).The results showed that the fabricated sandwich-structure transferable OLED(STOLED)exhibit the same high-efficiency performance on cylindricalshaped materials and on materials such as textile and *** the neutral axis is freely adjustable using the sandwich structure,the textile-based OLED achieved both folding reliability and washing reliability,as well as a long operating life(>150 h).When keratinocytes were irradiated with red STOLED light,cell proliferation and cell migration increased by 26 and 32%,*** the skin equivalent model,the epidermis thickness was increased by 39%;additionally,in organ culture,not only was the skin area increased by 14%,but also,reepithelialization was highly *** on the results,the STOLED is expected to be applicable in various wearable and disposable photomedical devices.

关键词： optoelectronic structure transfer

Assessment of the clear-sky bias issue using continuous PM10 data from two AERONET sites in Korea

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Journal of Environmental Sciences 2017年第3期29卷 151-160页

作者： Yongjoo choi Young Sung Ghim Department of Environmental Science Hankuk University of Foreign StudiesYongin 449-791Korea

A bias in clear-sky conditions that will be involved in estimating particulate matter （PM） concentration from aerosol optical depth （AOD） was examined using PM10 from two Aerosol Robotic Network sites in Korea. The study periods were between 2004 and 2007 at Anmyon and between 2003 and 2011 at Gosan, when both PM10 and AOD were available. Mean PM10 when AOD was available （PMAOD） was higher than that from all PM10 data （PMall） by 5.1 and 9.9 μg/m3 at Anmyon and Gosan, which accounted for 11% and 26% of PMall, respectively. Because of a difference between mean PM10 under daytime clear-sky conditions （PMclear） and PMAoD, the variations in APM10, the difference of PMan from PMdear rather than from PMAoD, were investigated. Although monthly variations in APMlo at the two sites were different, they were positively correlated to those in AT, similarly defined as APM10 except for temperature, at both sites. APM10 at Anmyon decreased to a negative value in January due to an influence of the Siberian continental high-pressure system while APM10 at Gosan was high in winter due to an effect of photochemical production at higher temperatures than at Anmyon.

关键词： AERONETData recovery rateCloud amountWind speedPhotochemical productionSiberian high

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Journal of Materials Science & Technology 2022年第16期111卷 99-110页

作者： Vioni Dwi Sartika Won Seok choi Gwanghyo choi Jaewook Han Sung-Jin Chang Won-Seok Ko Blazej Grabowski Pyuck-Pa choi Department of Materials Science and Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea Gangwon Regional Division Korea Institute of Industrial TechnologyGangwon 25440Republic of Korea Division of Measurement and Analysis National Nanofab CenterDaejeon 34141Republic of Korea School of Materials Science and Engineering University of UlsanUlsan 44610Republic of Korea Institute for Materials Science University of StuttgartPfaffenwaldring 5570569 StuttgartGermany

We report laser cladding of pure titanium on a CoCrMo alloy using directed energy *** electron microscopy,the microstructural evolution upon varying the process parameters,especially laser power and powder feed rate,was investigated in relation to crack *** layers showing dilution rates of more than 5%contained cracks due to the formation of the brittle Co_(2)Ti intermetallic *** observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co_(2)Ti phase,as determined by density functional theory and ***,an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles,while a deficient laser energy resulted in a lack of *** cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225–300 W,for which the dilution rate was minimized to less than 5%.For such samples,the cladding layers comprised pureα-Ti and a uniform CoT i interface with Co_(2)Ti islands.

关键词： Additive manufacturing Dissimilar metal joining Titanium Cobalt-based alloy

Steady-state probability density function in wave turbulence under large volume limit

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Chinese Physics B 2011年第5期20卷 139-145页

作者： Yeontaek choi Sang Gyu Jo Division of Fusion and Convergence of Mathematical Sciences National Institute for Mathematical SciencesDaejeon 305-340Republic of Korea Department of Physics Kyungpook National UniversityDaegu 702-701Republic of Korea

We investigate the possibility for two-mode probability density function （PDF） to have a non-zero flux steady state solution. We take the large volume limit so that the space of modes becomes continuous. It is shown that in this limit all the steady-state twoor higher-mode PDFs are the product of one-mode PDFs. The flux of this steady-state solution turns out to be zero for any finite mode PDF.

关键词： wave turbulence probability flux multi-mode probability density function Larguerreequation