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Layer-by-Layer Doping of Few-Layer Graphene Film
Gü,neş,, Fethullah,Shin, Hyeon-Jin,Biswas, Chandan,Han, Gang Hee,Kim, Eun Sung,Chae, Seung Jin,Choi, Jae-Young,Lee, Young Hee American Chemical Society 2010 ACS NANO Vol.4 No.8
<P>We propose a new method of layer-by-layer (LbL) doping of thin graphene films. Large area monolayer graphene was synthesized on Cu foil by using the chemical vapor deposition method. Each layer was transferred on a polyethylene terephthalate substrate followed by a salt-solution casting, where the whole process was repeated several times to get LbL-doped thin layers. With this method, sheet resistance was significantly decreased up to ∼80% with little sacrifice in transmittance. Unlike samples fabricated by topmost layer doping, our sample shows better environmental stability due to the presence of dominant neutral Au atoms on the surface which was confirmed by angle-resolved X-ray photoelectron spectroscopy. The sheet resistance of the LbL-doped four-layer graphene (11 × 11 cm<SUP>2</SUP>) was 54 Ω/sq at 85% transmittance, which meets the technical target for industrial applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-8/nn1008808/production/images/medium/nn-2010-008808_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn1008808'>ACS Electronic Supporting Info</A></P>
Gang Hee Gu,Yongju Kim,Rae Eon Kim,Min Hong Seo,Hyoung Seop Kim 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1
Accurate evaluation of the nonlinear hardening behavior (i.e., wide strain range true stress–strain curve) of developed materialsas structural materials is essential because it is directly related to user safety and is input data of simulation for plasticity,structural analysis, and sheet forming. However, the conventional methods to measure intrinsic mechanical properties canonly characterize homogeneous materials, and the technique to evaluate heterostructured materials such as clad materialsis lacking so far. In this study, the nonlinear hardening behavior of the clad material was evaluated using the tensile test anddigital image correlation (DIC) to introduce the clad materials into the practical industry. The new method considers themechanical properties of all layers constituting the clad material by observing the side surface of the specimen, unlike theconventional DIC methods of obtaining the true stress–strain curves from the images of the front surface of the specimen. The reliability of the obtained wide strain range true stress–strain curve calculated using the proposed method was validatedusing the finite element method simulation. The proposed method can provide trustworthy intrinsic mechanical propertiesof newly developed clad materials, which are promising next-generation materials.
Gang, Myeong Gu,Chae, Ki Woon,Kim, Wook-Bae,Jung, Young Hun,Jun, Martin B.G.,Min, Byung-Kwon Elsevier 2019 Journal of manufacturing processes Vol.37 No.-
<P><B>Abstract</B></P> <P>Microchannels must have appropriate physical (e.g., shape, size and surface roughness) and chemical (e.g., functional groups and wettability) properties to be used in microfluidic devices. In general, microchannels, which are made of polymeric materials, are produced through a molding process and chemically treated to have proper wettability. However, mold fabrication and chemical treatment require a significant amount of time and cost. In this study, we used a micromilling process to fabricate a microchannel on polymer material. The contact angle on the machined surface was changed according to the wettability model by varying the surface roughness controlled by cutting parameters. By mechanical cutting of the naturally hydrophobic polymer, the contact angle could be physically changed from 76° to 109° by changing cutting parameters without any chemical change.</P>
Grouting to Prevent Sulfate Corrosion on Coal Mine Shaft
Gang-Gang Xu,Shuan-Cheng Gu,Xiao-Dong Wang,Hai Wang,Shi-Bin Zhu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11
In the area of high sulfate concentration in China, the problem of sulfate corrosion in coal mine shaft is increasingly prominent. Currently, shaft repair methods are limited to diversion, interception, and backwall grouting. However, after conventional cement stabilization, shafts still must contend with poor durability and weak resistance to sulfate corrosion. To solve these problems, this study combined theoretical research, laboratory tests, and field tests to reveal the corrosion mechanism of shafts, explored novel anti-sulfate corrosion grout, and built a model for the migration of sulfate ions (SO42−) in strata and shafts. According to the results of this study, shaft corrosion was a process of continuous penetration towards the concrete interior following a cycle of concrete compaction, expansion, and cracking. Laboratory tests show that the specimens of ordinary Portland cement mortar with 20 – 30% fly ash not only have good long-term strength, but also have a significantly improved resistance capacity to sulfate solution. Based on the laboratory test results, the HSR42.5 mixed with 20% fly ash was used for wall grouting, and the water-cement ratio of the slurry was 1:1. After wall grouting, the water inflow was effectively controlled in the grouting area in the main shaft, auxiliary shaft, and air shaft, reducing from 18.5 m3/h, 20.9 m3/h, and 10.0 m3/h to 3.5 m3/h, 4.6 m3/h, and 3.2 m3/h, respectively. Moreover, after nearly three years of continuous monitoring, the water inflow did not show any significant increase in the shafts. Based on the migration law of SO42− in concrete, a shaft geological model and a salt solution migration model after grouting reinforcement under sulfate corrosion conditions were constructed. In addition, the analysis of the migration law of sulfate ion in the shaft and grouting reinforcement formation revealed that the service period of the grouting shaft can be extended for approximately 6 – 8 years.
강성철(Gang Sung Chul),박영강(Park Young Gang),문유석(Mun You Suk),김상구(Kim Sang Gu),허철행(Heu Chul Hang) 경성대학교 사회과학연구소 2009 社會科學硏究 Vol.25 No.1
최근 거버넌스가 전통적 관료제를 대체하는 대안적 행정방식으로 제기되었으나 한국의 지방정부 내지 지방행정에 적용하는 것은 한계가 있다고 판단된다. 왜냐하면 거버넌스를 위한 제도적 장치도 미흡했지만 거버넌스 체제의 중요한 일부분이라고 할 수 있는 시민사회와 시민사회단체의 발전이 충분하지 않기 때문이다. 본 연구는 건전한 거버넌스 체제 구축을 위해서는 시민사회단체의 발전이 요청된다고 보고, 기존의 연구결과들과 공무원 및 시민단체관계자들을 대상으로 한 설문조사 자료를 분석하여 다음과 같은 시민단체의 지원방안들을 제시하였다. 첫째, 시민사회단체들의 참여를 위한 제도적 장치가 마련되어야 한다. 둘째, 시민사회단체에 대하여 재정지원사업을 적극 확대해야한다. 셋째, 시민사회단체 지원사업의 평가와 운영을 전담할 독립적 기관의 설립을 고려하야야 한다. 넷째, 조세지원, 행정편의, 사무실지원 등 간접적 지원을 강화하여야 한다. 본 연구는 결론에서 건전한 시민사회의 육성을 위해서는 시민사회단체의 발전이 요구되며, 중앙 및 지방정부의 시민사회단체에 대한 적극적이고 전략적인 지원이 건전한 지역거버넌스 체제 구축을 통한 지역사회발전의 단초를 제공할 수 있다고 주장하고 있다. Governance has been recently proposed as an alternative ways of public service provision in the field of public administration, but it's applicability to the context of local public administration in Korea seems to be limited. That is because most localities are not only poorly-equiped with institutional arrangements for governance but also their civic society and civic organizations have not been fully developed yet, which constitutes a key element of governance. Recognizing the development of civic organizations is essential to construct an effective governance system, this study suggested the following policy directions based upon the results of analyses using data collected through a survey conducted on public servants and staffs of civic organizations serving in Busan Metropolitan areas: First, institutional arrangements to secure participation of civic organization need to be prepared. Second, financial support for civic organizations needs to be expanded. Third, an independent organization to operate and evaluate support programs for civic organizations needs to be established. Fourth, indirect support including tax deduction, administrative assistance, and office provision also needs to be considered. In conclusion, this study further stressed proactive and strategic governmental support for civic organizations is currently desired to construct basis for local development through governance system.