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Ultrastrong Graphene-Copper Core-Shell Wires for High-Performance Electrical Cables
Kim, Sang Jin,Shin, Dong Heon,Choi, Yong Seok,Rho, Hokyun,Park, Min,Moon, Byung Joon,Kim, Youngsoo,Lee, Seuoung-Ki,Lee, Dong Su,Kim, Tae-Wook,Lee, Sang Hyun,Kim, Keun Soo,Hong, Byung Hee,Bae, Sukang American Chemical Society 2018 ACS NANO Vol.12 No.3
<P>Recent development in mobile electronic devices and electric vehicles requires electrical wires with reduced weight as well as enhanced stability. In addition, since electric energy is mostly generated from power plants located far from its consuming places, mechanically stronger and higher electric power transmission cables are strongly demanded. However, there has been no alternative materials that can practically replace copper materials. Here, we report a method to prepare ultrastrong graphene fibers (GFs)-Cu core-shell wires with significantly enhanced electrical and mechanical properties. The core GFs are synthesized by chemical vapor deposition, followed by electroplating of Cu shells, where the large surface area of GFs in contact with Cu maximizes the mechanical toughness of the core-shell wires. At the same time, the unique electrical and thermal characteristics of graphene allow a ∼10 times higher current density limit, providing more efficient and reliable delivery of electrical energies through the GFs-Cu wires. We believe that our results would be useful to overcome the current limit in electrical wires and cables for lightweight, energy-saving, and high-power applications.</P> [FIG OMISSION]</BR>
YoungJong Kim,JinKyung Park,WonSub Kang,SuKang Kim,Changsu Han,HaeRi Na,HaeJeong Park,JongWoo Kim,YoungYoul Kim,MoonHo Park,JongWoo Paik 대한신경정신의학회 2017 PSYCHIATRY INVESTIGATION Vol.14 No.1
Objective-Mitochondrial dysfunction is a prominent and early feature of Alzheimer’s disease (AD). The morphologic changes observed in the AD brain could be caused by a failure of mitochondrial fusion mechanisms. The aim of this study was to investigate whether genetic polymorphisms of two genes involved in mitochondrial fusion mechanisms, optic atrophy 1 (OPA1) and mitofusin 2 (MFN2), were associated with AD in the Korean population by analyzing genotypes and allele frequencies. Methods-One coding single nucleotide polymorphism (SNP) in the MFN2, rs1042837, and two coding SNPs in the OPA1, rs7624750 and rs9851685, were compared between 165 patients with AD (83 men and 82 women, mean age 72.3±4.41) and 186 healthy control subjects (82 men and 104 women, mean age 76.5±5.98). Results-Among these three SNPs, rs1042837 showed statistically significant differences in allele frequency, and genotype frequency in the co-dominant 1 model and in the dominant model. Conclusion-These results suggest that the rs1042837 polymorphism in MFN2 may be involved in the pathogenesis of AD.
Roll-to-roll production of 30-inch graphene films for transparent electrodes
Bae, Sukang,Kim, Hyeongkeun,Lee, Youngbin,Xu, Xiangfan,Park, Jae-Sung,Zheng, Yi,Balakrishnan, Jayakumar,Lei, Tian,Ri Kim, Hye,Song, Young Il,Kim, Young-Jin,Kim, Kwang S.,Ö,zyilmaz, Barbaros,Ahn, J Springer Science and Business Media LLC 2010 Nature nanotechnology Vol.5 No.8
Infrared Conductivity and Carrier Mobility of Large Scale Graphene on Various Substrates
Kim, Joo Youn,Rho, Jae Hoon,Lee, Chul,Bae, Sukang,Kim, Sang Jin,Kim, Keun Soo,Hong, Byung Hee,Choi, E.J. American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>It is known that low-field mobility of graphene depends largely on the substrate material on which it is transferred. We measured Drude optical conductivity of graphene on various substrates and determined the carrier density and carrier scattering rate. The carrier density varies widely depending on the substrate material. However the scattering rate is almost constant, approximately 100 cm(-1), for 5 different substrates. We calculate carrier mobility of graphene using the two quantities, i.e., carrier density and scattering rate, to find that it agrees with the mobility measured from dc transport experiment. We conclude that substrate-depent mobility of graphene originates from different carrier density but not from the scattering rate.</P>
Kim, Jung Kyu,Park, Myung Jin,Kim, Sang Jin,Wang, Dong Hwan,Cho, Sung Pyo,Bae, Sukang,Park, Jong Hyeok,Hong, Byung Hee American Chemical Society 2013 ACS NANO Vol.7 No.8
<P>Graphene quantum dots (GQDs) have been considered as a novel material because their electronic and optoelectronic properties can be tuned by controlling the size and the functional groups of GQDs. Here we report the synthesis of reduction-controlled GQDs and their application to bulk heterojunction (BHJ) solar cells with enhanced power conversion efficiency (PCE). Three different types of GQDsgraphene oxide quantum dots (GOQDs), 5 h reduced GQDs, and 10 h reduced GQDswere tested in BHJ solar cells, and the results indicate that GQDs play an important role in increasing optical absorptivity and charge carrier extraction of the BHJ solar cells. The enhanced optical absorptivity by rich functional groups in GOQDs increases short-circuit current, while the improved conductivity of reduced GQDs leads to the increase of fill factors. Thus, the reduction level of GQDs needs to be intermediate to balance the absorptivity and conductivity. Indeed, the partially reduced GQDs yielded the outstandingly improved PCE of 7.60% in BHJ devices compared to a reference device without GQDs (6.70%).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-8/nn402606v/production/images/medium/nn-2013-02606v_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn402606v'>ACS Electronic Supporting Info</A></P>
High-performance graphene-based transparent flexible heaters.
Kang, Junmo,Kim, Hyeongkeun,Kim, Keun Soo,Lee, Seoung-Ki,Bae, Sukang,Ahn, Jong-Hyun,Kim, Young-Jin,Choi, Jae-Boong,Hong, Byung Hee American Chemical Society 2011 NANO LETTERS Vol.11 No.12
<P>We demonstrate high-performance, flexible, transparent heaters based on large-scale graphene films synthesized by chemical vapor deposition on Cu foils. After multiple transfers and chemical doping processes, the graphene films show sheet resistance as low as 43 Ohm/sq with 89% optical transmittance, which are ideal as low-voltage transparent heaters. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional transparent heaters based on indium tin oxide. In addition, we confirmed that mechanical strain as high as 4% did not substantially affect heater performance. Therefore, graphene-based, flexible, transparent heaters are expected to find uses in a broad range of applications, including automobile defogging/deicing systems and heatable smart windows.</P>
유압부하와 흡기스로틀을 이용한 트랙터용 기계식 디젤엔진의 DPF 강제재생에 대한 연구
김영민(Youngmin Kim),표수강(Sukang Pyo),정학섭(Haksup Jung),김홍석(Hongsuk Kim) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.2
A method for active DPF regeneration was studied for a mechanical fuel pump that is equipped with an agricultural diesel engine. In this study, intake air throttling and hydraulic load were applied to increase exhaust gas temperature during the regeneration of DPF, and its characteristics were investigated by using both an experimental method and an empirical equation of the PM oxidation rate, as proposed by previous researchers. A high amount of hydraulic load is needed to achieve reliable DPF regeneration, which causes high fuel penalty due to energy loss as hydraulic pressure increases. Intake air throttling is a practical method of increasing exhaust gas temperature without sizeable energy loss. However, the amount of intake air throttling must be determined to prevent the deterioration of the engine performance and reduce emissions.