• Title, Summary, Keyword: Reversibility

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A Study on The Effects of Three Different Carbon Catalysts on Performance of Vanadium Redox Flow Battery (세가지 다른 형태의 탄소촉매 적용에 따른 바나듐레독스흐름전지 성능 변화에 관한 연구)

  • Chu, Cheounho;Jeong, Sanghyun;Jeong, Jooyoung;Chun, Seung-Kyu;Lee, Jinwoo;Kwon, Yongchai
    • Transactions of the Korean hydrogen and new energy society
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    • v.26 no.2
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    • pp.170-178
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    • 2015
  • In this study, we carry out a study on how to improve performance of vanadium redox flow battery (VRFB) through promoting reaction rate of rate determining vanadium reaction ($[VO]^{2+}/[VO_2]^+$). In order to do that, three different carbons like Vulcan (XC-72), CMK3 and MSU-F-C are adopted as the catalysts, while their catalytic activity and reaction reversibility are evaluated using half-cell tests. Their topological images are also measured by TEM. For estimation of the VRFB performance, multiple charge-discharge curves of VRFBs including the catalysts are measured by single cell tests. As a result of that, MSU-F-C shows relatively excellent catalytic activity and reaction reversibility as well as large surface area compared to those of Vulcan (XC-72) and CMK3. Also, in terms of the performance of VRFBs including the catalysts, VRFB including MSU-F-C indicates (i) low charging/discharging overpotentials and low internal resistance, (ii) high charge/discharge capacities and (iii) high energy efficiency. These VRFB performance data are well agreed with results on catalytic activity and reaction reversibility. The reason that MSU-F-C induces superior VRFB performances is attributed to (i) its large surface area and (ii) its hydrophilic surface functional groups that mainly consist of hydroxyl bonds that are supposed to play active surface site role for facilitaing $[VO]^{2+}/[VO_2]^+$ redox reaction. Based on the above results, it is found that adoption of MSU-F-C as catalyst for VRFB results in improvement in VRFB performance by promoting the languid $[VO]^{2+}/[VO_2]^+$ redox reaction.

A Study on the Reinforcement of the Damaged Stone Surface by Dismantling of Stone Cultural Heritages - Focusing on the Experiment of a Sublimation(Reversibility) type Consolidant - (석조문화재 해체에 따른 표면 손상부분 보강방안 연구 - 승화성(가역성) 강화처리제 적용실험을 중심으로 -)

  • Lee, Tae Jong;Oh, Hyeon Jung;Cho, Ha Jin;Kim, Sa Dug
    • Journal of Conservation Science
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    • v.31 no.4
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    • pp.351-360
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    • 2015
  • This is the result of the study on the temporary fortifier using sublimation type Consolidate is Cyclododecane to prepare plan for reinforcement of the surface part that can be damaged during the dismantling of stone cultural heritages. To supplement the disadvantages of the existing reinforcement methods using intumescent urethane foam, Cyclododecane was diluted in solvent to reinforce the surface and inside desquamation, and after dismantling the framework, it sublimated by imposing heat of about $60^{\circ}C$. Such method can guarantee the strength needed for reinforcement of the damaged surface with outstanding reversibility of Cyclododecane being entirely sublimated. But, it shows big difference of effect according to the solvent, so it shall be diluted in petroleum ether or heated in a double boiler. Therefore, considering the working conditions at the site, it seems the most appropriate to use petroleum ether double boiler heating method for injection and filling of the desquamation part and temporary reinforcement processing with Cyclododecane diluted in petroleum ether for surface spraying.

피치계 카본 부극재료의 리튬이차전지 반응특성 연구

  • 박영태;김정식
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • pp.119-122
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    • 1999
  • 페트롤리엄 피치와 콜타르 피치를 열분해하여 제조한 카본을 리튬이차전지용 부극재료로 사용한 반쪽전지를 제작하여 전극의 충방전 용량 및 cycle 특성, 카본의 열처리 온도와 용량과의 관계에 대하여 고찰하였다. 열처리 온도가 증가함에 따라 초기 충방전 용량은 콜타르 피치 카본의 경우 현저한 증가를 보였으며 페트롤리엄 피치 카본에서는 지속적인 증가를 보이다가 100$0^{\circ}C$ 이상의 온도부터는 다소 감소하는 경향을 나타내었다. 또한, 충방전 횟수가 증가할수록 충전용량은 감소하지만, 가역특성(reversibility)은 90% 이상으로 향상되었다.

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A Laplacian Autoregressive Moving-Average Time Series Model

  • Son, Young-Sook
    • Journal of the Korean Statistical Society
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    • v.22 no.2
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    • pp.259-269
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    • 1993
  • A moving average model, LMA(q) and an autoregressive-moving average model, NLARMA(p, q), with Laplacian marginal distribution are constructed and their properties are discussed; Their autocorrelation structures are completely analogus to those of Gaussian process and they are partially time reversible in the third order moments. Finally, we study the mixing property of NLARMA process.

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Origami inspired Temperature Sensor based on Stimuli-Responsive Hydrogel (종이접기 기반 자극 반응성 하이드젤 온도 센서 연구)

  • Na, Jun-Hee
    • Journal of Sensor Science and Technology
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    • v.26 no.1
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    • pp.35-38
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    • 2017
  • A thermally responsive hydrogel has reversibility with temperature during swelling. Here, we proposed origami inspired temperature sensor by using multi-layered hydrogel film. The formation of patterned stripes on microscale film drives bending to an angle that can be controlled linearly. Although temperature range was not wide, measured sensitivity of sensors has high resolution and accuracy. It providing a powerful platform for the design of sensitive sensors and that easily adapt other type of sensors in microscale.

SOME RESULTS ON IFP NEAR-RINGS

  • Cho, Yong-Uk
    • Honam Mathematical Journal
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    • v.31 no.4
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    • pp.639-644
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    • 2009
  • In this paper, we begin with to introduce the concepts of IFP and strong IFP in near-rings and then give some characterizations of IFP in near-rings. Next we derive reversible IFP, and then equivalences of the concepts of strong IFP and strong reversibility. Finally, we obtain some conditions to become strong IFP in right permutable near-rings and strongly reversible near-rings.

Quasi-reversibility of the Ring of 2 × 2 Matrices over an Arbitrary Field

  • Heidari, Dariush;Davvaz, Bijan
    • Kyungpook Mathematical Journal
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    • v.60 no.1
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    • pp.71-72
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    • 2020
  • A ring R is quasi-reversible if 0 ≠ ab ∈ I(R) for a, b ∈ R implies ba ∈ I(R), where I(R) is the set of all idempotents in R. In this short paper, we prove that the ring of 2×2 matrices over an arbitrary field is quasi-reversible, which is an answer to the question given by Da Woon Jung et al. in [Bull. Korean Math. Soc., 56(4) (2019) 993-1006].