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Al-Doped ZnO as a Switching Layer for Transparent Bipolar Resistive Switching Memory
Hyeongwoo Yu,Minho Kim,Yoonsu Kim,Jeongsup Lee,김경국,최상준,조수행 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.2
In this report, we employ an Al-doped ZnO (AZO) layer as a resistive switching layer for transparent resistive switching random access memory devices. An Indium-Tin-Oxide (ITO)/AZO/ITO/glass device exhibits a transmittance of ~80% (including a glass substrate) in the visible wavelength region and demonstrates reliable bipolar resistive switching behavior over d.c. 300 sweeping cycles with a low operation voltage and a very low variation in the switching threshold voltage. These results indicate that the AZO film is a promising transparent resistive switching layer.
Kim, Hyeongwoo,Lee, Jong-Won,Byun, Dongjin,Choi, Wonchang The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.40
<P>MnFe2O4@PDA-coated MWCNT coaxial nanocables are successfully designed <I>via</I> a simple one-pot process by utilizing the adhesion property of polydopamine (PDA) with cations in aqueous solutions and employing a modified co-precipitation synthesis at a low temperature. The incorporation of the PDA coating layer on the MWCNT leads to the well-dispersed state of the MWCNTs in the aqueous solution due to the hydrophilic functional group of the PDA coating layer. In addition, the catechol-based functional group of the PDA coating layer effectively anchors the Mn and Fe ions from the aqueous solution before the co-precipitation process, eventually resulting in the preferential and homogeneous formation of MnFe2O4 nanoparticles on the MWCNT. The final MnFe2O4@PDA-coated MWCNT electrode exhibits excellent power characteristics such as a high rate capacity of around of 367 mA h g<SUP>−1</SUP> at a 5C-rate condition (= 4585 mA g<SUP>−1</SUP>). Cycling tests reveal that the stable performance of the MnFe2O4@PDA-coated MWCNT electrode persists even after 350 cycles.</P>
Kim, Hyeongwoo,Hwang, Ye Ji,Han, Inhyuk,Joo, Jung Min The Royal Society of Chemistry 2018 Chemical communications Vol.54 No.50
<P>A palladium-catalyzed C-H alkenylation of imidazoles has been developed. High C5 selectivity was achieved for C2-unsubstituted and C2-substituted imidazoles using oxygen and copper(ii) acetate, respectively, as oxidants. The obtained products were applied to benzannulation through a sequence involving transposition of <I>N</I>-alkyl groups to give C4-alkenyl imidazoles, alkenylation, thermal 6π-electrocyclization, and oxidation, affording unsymmetrically substituted benzimidazoles.</P>
재난 약자시설의 정량적평가에 따른 대피경로 개선방안 연구
김형우(Kim, Hyeongwoo),최인수(Choi, Insu),이동호(Rie, Dongho) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.1
본 연구는 노인 요양병원을 대상으로 피난 약자 대피 특성을 반영하여 FDS를 이용해 발화 시간으로부터 재실자 ASET을 산출하였다. 대피시간은 Pathfinder를 사용해 피난 약자의 대피조건별 RSET을 산출하였다. 결과로부터 피난약자 동반대피를 반영한 대피로 성능에 따른 대피 효율에 대해 검토하였다. 단독 대피와 분산대피 효율은 FED를 기반 정량적 사망자 예측으로부터 재난 시 인명피해의 최소화를 꽤하였다. 그 결과로 재난 약자 시설의 경사로의 당위성과 가연물 관리의 중요성에 대해 밝혔다. In this study, the available safe egress time of occupants in elderly nursing hospitals was calculated from the ignition time using Fire Dynamics Simulator by considering the evacuation characteristics of the vulnerable. The required safe egress time for each evacuation condition was also calculated using Pathfinder to determine the evacuation time. Finally, the calculated results were used to assess evacuation efficiency according to the performance of the selected evacuation route. FED-based quantitative death prediction indicated that the efficiency of single and distributed evacuation caused minimization of casualties in the event of a disaster. The results collectively justify the need for a ramp in disaster-prone facilities and highlight the importance of managing fire hazards.
Enhancement of the solubility of recombinant proteins by fusion with a short-disordered peptide
Ren Jun,Hwang Suhee,Shen Junhao,Kim Hyeongwoo,Kim Hyunjoo,Kim Jieun,Ahn Soyoung,Kim Min-gyun,Lee Seung Ho,Na Dokyun 한국미생물학회 2022 The journal of microbiology Vol.60 No.9
In protein biotechnology, large soluble fusion partners are widely utilized for increased yield and solubility of recombinant proteins. However, the production of additional large fusion partners poses an additional burden to the host, leading to a decreased protein yield. In this study, we identified two highly disordered short peptides that were able to increase the solubility of an artificially engineered aggregationprone protein, GFP-GFIL4, from 0.6% to 61% (D3-DP00592) and 46% (D4-DP01038) selected from DisProt database. For further confirmation, the peptides were applied to two insoluble E. coli proteins (YagA and YdiU). The peptides also enhanced solubility from 52% to 90% (YagA) and from 27% to 93% (YdiU). Their ability to solubilize recombinant proteins was comparable with strong solubilizing tags, maltosebinding protein (40 kDa) and TrxA (12 kDa), but much smaller (< 7 kDa) in size. For practical application, the two peptides were fused with a restriction enzyme, I-SceI, and they increased I-SceI solubility from 24% up to 75%. The highly disordered peptides did not affect the activity of I-SceI while I-SceI fused with MBP or TrxA displayed no restriction activity. Despite the small size, the highly disordered peptides were able to solubilize recombinant proteins as efficiently as conventional fusion tags and did not interfere with the function of recombinant proteins. Consequently, the identified two highly disordered peptides would have practical utility in protein biotechnology and industry.
Sb-AlC<sub>0.75</sub>-C composite anodes for high-performance sodium-ion batteries
Jung, Gyu Jin,Lee, Yongho,Mun, Yoo Seok,Kim, Hyeongwoo,Hur, Jaehyun,Kim, Tae Young,Suh, Kwang S.,Kim, Ji Hyeon,Lee, Daeho,Choi, Wonchang,Kim, Il Tae Elsevier 2017 Journal of Power Sources Vol.340 No.-
<P><B>Abstract</B></P> <P>Antimony (Sb) nanoparticles dispersed in a hybrid matrix consisting of aluminum (Al) and carbon, AlC<SUB>0.75</SUB>-C were synthesized via one-step high-energy mechanical milling (HEMM) process and assessed as potential anode materials for use in sodium-ion batteries. The introduction of carbon during HEMM led to the formation of individual Sb nanoparticles dispersed in the AlC<SUB>0.75</SUB>-C matrix; in the absence of carbon during HEMM, an AlSb alloy was formed. The Sb-AlC<SUB>0.75</SUB>-C composite anodes demonstrated better cycling performance as well as higher rate capability compared to an AlSb anode; these improved properties could be due to the well-developed Sb phase, which acts as an electrochemically active nanocrystalline material in the AlC<SUB>0.75</SUB>/carbon conductive matrix. Furthermore, when fluoroethylene carbonate (FEC) was added to the electrolyte, the sodium-ion cells exhibited the best electrochemical performances, corresponding to a capacity retention of 83% at 100 cycles at 100 mA g<SUP>−1</SUP> and a high rate capacity retention of 58% at 5000 mA g<SUP>−1</SUP>. In addition, the as-prepared Sb-AlC<SUB>0.75</SUB>-C composite has a high tap density; thus, its volumetric capacity was approximately three times that of carbon.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sb composite with AlC<SUB>0.75</SUB> and C as a matrix was prepared via one-step HEMM. </LI> <LI> The Sb-AlC<SUB>0.75</SUB>-C composite shows better cyclability compared to AlSb. </LI> <LI> FEC additive makes Sb-AlC<SUB>0.75</SUB>-C to exhibit stable cyclic and high-rate performance. </LI> <LI> Sb-AlC<SUB>0.75</SUB>-C anode demonstrates high volumetric capacity compared to carbon. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Digital operating tip-enhanced Raman spectroscopy
Kim Hwanhee,Moon Taeyoung,Lee Hyeongwoo,Koo Yeonjeong,Kang Mingu,Park Kyoung-Duck,An Sangmin 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.6
Tip-enhanced Raman spectroscopy (TERS) can investigate structural and optical characteristics of a range of materials with high optical sensitivity. However, it is not widely deployable due to the complicated hardware confguration of atomic-force microscopy (AFM) part, which is required for TERS. Here, we present a digital operating TERS by replacing the conventional instruments, such as a function generator, a lock-in amplifer, and a PID controller, with the digital algorithms in computer to simplify the confguration. We verify the comparable performance of the digital AFM and the conventional analog AFM by performing control experiments, e.g., frequency response curves, approach curves, and topography measurements. In addition, we demonstrate the simple digital processes to decrease the AFM noise level by optimizing the time constant and the data sampling rate. Furthermore, we demonstrate the gap-dependent and time-dependent TERS spectra for brilliant cresyl blue molecules, which confrms the robust acquisition of nano-spectroscopic responses in ambient conditions. This work provides a facile way to easily build tip-enhanced nano-spectroscopy with a compact apparatus.