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Electron–Lattice Coupling in Correlated Materials of Low Electron Occupancy
Eom, Kitae,Choi, Euiyoung,Yoon, Jonghyun,Choi, Minsu,Song, Kyung,Choi, Si-Young,Lee, Daesu,Lee, Jung-Woo,Eom, Chang-Beom,Lee, Jaichan American Chemical Society 2017 NANO LETTERS Vol.17 No.9
<P>In correlated materials including transition metal oxides, electronic properties and functionalities are modulated and enriched by couplings between the electron and lattice degrees of freedom. These couplings are controlled by external parameters such as chemical doping, pressure, magnetic and electric fields, and light irradiation. However, the electron-lattice coupling relies on orbital characters, i.e., symmetry and occupancy, of t(2g) and e(g) orbitals, so that a large electron-lattice coupling is limited to eg electron system, whereas t(2g) electron system exhibits an inherently weak coupling. Here, we design and demonstrate a strongly enhanced electron-lattice coupling in electron-doped SrTiO3, that is, the t(2g) electron system. In ultrathin films of electron-doped SrTiO3 [i.e., (La0.25Sr0.75)TiO3], we reveal the strong electron-lattice-orbital coupling, which is manifested by extremely increased tetragonality and the corresponding metal-to-insulator transition. Our findings open the way of an active tuning of the charge-lattice-orbital coupling to obtain new functionalities relevant to emerging nanoelectronic devices.</P>
스마트폰 촬영 영상을 이용한 딥러닝 기반 위조 지폐 판별
최범휘(Beom-Hwi Choi),엄소정(So-Jeong Eom),김창민(Chang-Min Kim),이해연(Hae-Yeoun Lee) 한국정보기술학회 2021 한국정보기술학회논문지 Vol.19 No.3
Counterfeit bills identification studies use expensive equipments or high-quality scanners. However, the image quality of the current smartphone camera is excellent enough to acquire images with sufficient resolution. This paper proposes a counterfeit bill identification method based on deep learning using smartphone camera shooting images. A convolutional neural network model composed of 3 convolutional layers and 2 fully-connected layers is designed and optimized. A training data collection and a patch unit processing technique to train high-resolution images in limited memory are applied. In addition, an identification method in image units using majority voting of the patch unit identification results is adapted. Through experiments using counterfeit bills forged by 4 printers, the proposed method shows an accuracy of 95.85% in patch units and 100% in images units. Results support that the proposed method can identify counterfeit bills only with smartphone images without the use of UV or optical equipments.
Kim, Chang Ki,Kim, Hong Mo,Aftabuzzaman, M.,Jeon, In-Yup,Kang, Sung Ho,Eom, Yu Kyung,Baek, Jong Beom,Kim, Hwan Kyu Elsevier 2018 Materials today energy Vol.9 No.-
<P><B>Abstract</B></P> <P>Edge-functionalized graphene nanoplatelets (GnPs) were synthesized by a simple ball-milling process of graphite in the presence of halogen (F, I), metalloids (Se, Te and Sb) and subsequently applied to dye-sensitized solar cells (DSSCs) as counter electrodes (CEs). In our previous works, a series of edge-functionalized GnPs were thoroughly studied and successfully utilized as CEs in DSSCs, with the aim of finding possible alternatives to the noble and expensive Pt metal as CE. However, in each study, the GnP-CEs were not only fabricated with different dyes and electrolytes but were also evaluated on different occasions, and thus, it was difficult to identify which type of edge-functionalized GnPs was the best. Herein, DSSCs with different edge-functionalized GnP-CEs were fabricated under the same environmental conditions, photovoltaic performances were then evaluated employing both I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> and Co(bpy)<SUB>3</SUB> <SUP>2+/3+</SUP> (bpy = 2,2′-bipyridine) redox couples with three different sensitizers to assess the electrocatalytic activity of the different GnP-CEs. Photovoltaic performances of edge-halogenated GnP-CEs with <B>N719</B> dye employing the I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> redox couple were lower than those of the metalloid-doped GnP-CEs and were even inferior to Pt-CE, which was consistent with the <I>R</I> <SUB> <I>ct</I> </SUB> values. Conversely, among the metalloid-doped GnP-CEs, SbGnP-CE exhibited a higher <I>R</I> <SUB> <I>ct</I> </SUB> value and lower power conversion efficiency (PCE) value of 8.70% and 6.60% with <B>N719</B> and <B>SGT-130</B> dyes, respectively. However, when the devices were fabricated with the Co(bpy)<SUB>3</SUB> <SUP>2+/3+</SUP> redox couple, the opposite occurred and SbGnPs displayed the highest PCE of 10.42% with <B>SGT-130</B> dye and 12.08% with <B>SGT-021</B> dye. Furthermore, SeGnP-CE and TeGnP-CE showed superior compared to the Pt-CE with both I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> and Co(bpy)<SUB>3</SUB> <SUP>2+/3+</SUP> electrolyte solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Edge-functionalized (F, I, Se, Te and Sb) graphene nanoplatelets (GnPs) were synthesized by a simple ball-milling process for DSSC CEs. </LI> <LI> PCE of edge-halogenated GnP-CEs employing the I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> redox couple was inferior to Pt-CE. </LI> <LI> Except SbGnP-CE, SeGnP-CE and TeGnP-CE shows superior PCE compared to Pt-CE employing the I<SUP>−</SUP>/I<SUB>3</SUB> <SUP>−</SUP> redox couple. </LI> <LI> All metalloid-doped GnP-CEs show superior PCE compared to Pt-CE employing the Co(bpy)<SUP>32+/3+</SUP> redox couple. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
초기 동맥혈 Carboxyhemoglobin 농도가 높았던 화상 환자들의 예후지표에 관한 연구
최창순 ( Choe Chang Sun ),김철홍 ( Kim Cheol Hong ),김근숙 ( Kim Geun Sug ),이태유 ( Lee Tae Yu ),정연손 ( Jeong Yeon Son ),엄광석 ( Eom Gwang Seog ),박용범 ( Park Yong Beom ),장승훈 ( Jang Seung Hun ),김동규 ( Kim Dong Gyu ),박 대한결핵 및 호흡기학회 2003 Tuberculosis and Respiratory Diseases Vol.55 No.2
마이크로채널 내부의 이상유동조건에서 구간별 압력 변화에 관한 연구
엄혜원(Hye Won Eom),이범용(Beom Yong Lee),박창용(Chang Yong Park) 대한설비공학회 2015 대한설비공학회 학술발표대회논문집 Vol.2015 No.11
Experimental study on pressure drop at multi-ported micro channels was performed. The test section of system consisted of oxygen free copper having 38 micro- scale channels by electric discharge machining. The hydraulic diameter of the channels was about 516 μm. Under an adiabatic single-phase flow condition, micro channels pressure drop was measured. In order to compare experimental results with calculated values, pressure drop prediction was performed by exiting several correlations. The comparison analysis showed that there was very small difference between the two. Also pressure drop was measured under two-phase flow condition. Measured data presented the increase of pressure drop with the increase of vapor quality, which followed the previously well-known trend.