• Title/Summary/Keyword: Chemical Processes

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Effect of Pre-Cycling Rate on the Passivating Ability of Surface Films on Li4Ti5O12 Electrodes

  • Jung, Jiwon;Hah, Hoe Jin;Lee, Tae jin;Lee, Jae Gil;Lee, Jeong Beom;Kim, Jongjung;Soon, Jiyong;Ryu, Ji Heon;Kim, Jae Jeong;Oh, Seung M.
    • Journal of Electrochemical Science and Technology
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    • v.8 no.1
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    • pp.15-24
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    • 2017
  • A comparative study was performed on the passivating abilities of surface films generated on lithium titanate (LTO; $Li_4Ti_5O_{12}$) electrodes during pre-cycling at two different rates. The surface film deposited at a faster pre-cycling rate (i.e., 0.5 C) is irregularly shaped and unevenly covers the LTO electrode. Owing to the incomplete coverage of the protective film, this LTO electrode exhibits poor passivating ability. Additional electrolyte decomposition and concomitant film deposition occur during subsequent charge/discharge cycles. As a result of the thick surface film, severe cell polarization occurs and eventually causes cell failure. However, pre-cycling the Li/LTO cell at a slower rate (0.1 C) improves cell polarization and capacity retention; this occurs because the surface film uniformly covers the LTO electrode and provides strong passivation. Accordingly, there is no significant film deposition during subsequent charge/discharge cycling. Additionally, self-discharge is reduced during high-temperature storage.

Effect of Additives on the Contents of Fatty Acid Methyl Esters of Biodiesel Fuel in the Transesterification of Palm oil with Supercritical Methanol (팜유로부터 바이오디젤 연료를 합성하는 초임계유체반응에서 지방산메틸에스테르의 함량에 미치는 첨가물의 영향)

  • Lee, Hong-shik;Choi, Joon-hyuk;Shin, Young Ho;Lim, Youngsub;Han, Chonghun;Kim, Hwayong;Lee, Youn-Woo
    • Korean Chemical Engineering Research
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    • v.46 no.4
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    • pp.747-751
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    • 2008
  • The effect of additives in the synthesis of biodiesel fuel using supercritical methanol was studied in order to examine the possibility of application of spent vegetable oil as a raw material, which has high contents of water or free fatty acid. The experiments were performed by varying the contents of water, free fatty acid or antioxidants respectively in a batch reactor. The contents of fatty acid methyl ester was analyzed by a gas chromatography. As the water contents increased, the contents of fatty acid methyl ester decreased, however, the decrease was very little compared with the alkaline and acid catalyst. The effect of the contents of free fatty acid, vitamin E, and ${\beta}$-carotene was negligible.

Optimization of compression ratio in closed-loop CO2 liquefaction process

  • Park, Taekyoon;Kwak, Hyungyeol;Kim, Yeonsoo;Lee, Jong Min
    • Korean Journal of Chemical Engineering
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    • v.35 no.11
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    • pp.2150-2156
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    • 2018
  • We suggest a systematic method for obtaining the optimal compression ratio in the multi-stage closed-loop compression process of carbon dioxide. Instead of adopting the compression ratio of 3 to 4 by convention, we propose a novel approach based on mathematical analysis and simulation. The mathematical analysis prescribes that the geometric mean is a better initial value than the existing empirical value in identifying the optimal compression ratio. In addition, the optimization problem considers the initial installation cost as well as the energy required for the operation. We find that it is best to use the fifth stage in the general closed-loop type carbon dioxide multi-stage compression process.

Amyloid Polymorphism of α-Synuclein Induced by Active Firefly Luciferase

  • Yang, Jee Eun;Hong, Je Won;Kim, Jehoon;Paik, Seung R.
    • Bulletin of the Korean Chemical Society
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    • v.35 no.2
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    • pp.425-430
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    • 2014
  • Amyloidogenic proteins often exhibit fibrillar polymorphism through alternative assembly processes, which has been considered to have possible pathological implications. Here, firefly luciferase (LUC) is shown to induce amyloid polymorphism of ${\alpha}$-synuclein, the major constituent of Lewy bodies found in Parkinson's disease, by acting as a novel template. The drastically accelerated fibrillation kinetics of ${\alpha}$-synuclein with LUC required the nucleation center produced by the active enzyme of LUC. Fluorescent dye binding, transmission electron microscopy, and Fourier transformed infrared spectroscopy revealed the morphologically distinctive amyloid fibrils of ${\alpha}$-synuclein prepared in the absence or presence of LUC. As the altered morphological characteristics became inherent to the mature fibrils, those properties were inherited to next-generations via nucleation-dependent fibrillation process. The seed control, therefore, would be an effective means to modify amyloid fibrils with different biochemical characteristics. In addition, the LUC-directed amyloid fibrillar polymorphism also suggests that other cellular biomolecules including enzymes in general are able to diversify amyloid fibrils, which could be self-propagated with diversified biological activities, if any, inside cells.