• Title/Summary/Keyword: Green Hydrogen

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Research Trend in Electrocatalysts for Anion Exchange Membrane Water Electrolysis (음이온교환막 수전해 촉매기술 동향)

  • Kim, Jiyoung;Lee, Kiyoung
    • Journal of the Korean Electrochemical Society
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    • v.25 no.2
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    • pp.69-80
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    • 2022
  • The anion exchange membrane (AEM) water electrolysis for high purity hydrogen production is attracting attention as a next-generation green hydrogen production technology by using inexpensive non-noble metal-based catalysts instead of conventional precious metal catalysts used in proton exchange membrane (PEM) water electrolysis systems. However, since AEM water electrolysis technology is in the early stages of development, it is necessary to develop research on AEM, ionomers, electrode supports and catalysts, which are key elements of AEM water electrolysis. Among them, current research in the field of catalysts is being studied to apply a previously developed half-cell catalyst for alkali to the AEM system, and the applied catalyst has disadvantages of low activity and durability. Therefore, this review presented a catalyst synthesis technique that promoted oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) using a non-noble metal-based catalyst in an alkaline medium.

Sintering Charateristics of $UO_2$ with Addition of $SiB_4$ as Burnable Poison (가연성독극물로서 $SiB_4$를 첨가한 이산화우라늄의 소결특성)

  • 윤영수;윤용구;박지연;강영환
    • Journal of the Korean Ceramic Society
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    • v.28 no.10
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    • pp.767-776
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    • 1991
  • Effects of the additions of SiB4 as burnable poison to UO2 on the green density, densification, interdependence between density-grain growth and microstructure of sintered UO2 were studied. UO2 pellets were sintered in flowing hydrogen, at temperature 1200, 1350, 1500, and 168$0^{\circ}C$ for 3 hours and at 168$0^{\circ}C$ for 0, 1, 3, and 10 hours, respectively. Green densities were in the range of about 4.5~5.4 g/㎤, and decreased as the amount of SiB4 increased when green pellets were made by with use of a double action press at 1000 kg/$\textrm{cm}^2$. The density of sintered UO2 pellets was around 92~94% of the theoretical density and did not change significantly as the amount of SiB2 addition increased. However, the density of sintered pellets decreased with the increase in SiB4. The grain growth could be characterized in terms of two stages: Grain growth occurred with the increasing density in the first stage, whereas the second stage was characterized by the grain growth without increasing of density. A liquid phase was observed at grain boundaries and grain edges in the microstructure of sintered UO2 pellets with 5000 ppm and 10,000 ppm SiB4. This liquid, possible formed at about 168$0^{\circ}C$, did not enhance the shrinkage, but appeared to accelarate the grain growth. It seems that the second stage grain growth was due to the presence of pressurized insoluble trapped gas in isolated pores.

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Preparation of Nanoporous Ceramic Membranes by Sol-gel Method and Characterization of Gas Permeation (졸-겔법에 의한 나노기공성 세라믹 막의 제조 및 기체투과 특성)

  • Lee, Yong-Taek;Choi, Ga-Young;Han, Hyuk-Hee
    • Membrane Journal
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    • v.18 no.2
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    • pp.176-184
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    • 2008
  • Nano-porous ceramic membranes was synthesized by the sol-gel method. Gas permeation of hydrogen and nitrogen was determined by single composition gas. Pore size $0.1{\mu}m$ and porosity 32% of flat type ${\alpha}-Al_2O_3$ substrate was manufactured. An intermediate ${\gamma}-Al_2O_3$ layer with pore size of 4 nm was formed by dip-coating. Polymeric silica sol was synthesized by acid catalyzed hydrolysis and condensation of tetra-ethyl-ortho-silicate. Supported membranes on alumina were prepared by dipping and calcining. He, $N_2$ permeation experiments with nanoporous sol-gel modified supported ceramic membranes were peformed to determine the gas transport characteristics. $He/N_2$ permselectivity around $100{\sim}160$ and helium permeation in the order of $10^{-7}mol/m^2{\cdot}s{\cdot}Pa$ were measured in the temperature range of $303{\sim}363K$.

The Properties of Passivation Films on Al2O3/SiNX Stack Layer in Crystalline Silicon Solar Cells (결정질 실리콘 태양전지의 Al2O3/SiNX 패시베이션 특성 분석)

  • Hyun, Ji Yeon;Song, In Seol;Kim, Jae Eun;Bae, Soohyun;Kang, Yoonmook;Lee, Hae-Seok;Kim, Donghwan
    • Current Photovoltaic Research
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    • v.5 no.2
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    • pp.63-67
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    • 2017
  • Aluminum oxide ($Al_2O_3$) film deposited by atomic layer deposition (ALD) is known to supply excellent surface passivation properties on crystalline Si surface. The quality of passivation layer is important for high-efficiency silicon solar cell. double-layer structures have many advantages over single-layer materials. $Al_2O_3/SiN_X$ passivation stacks have been widely adopted for high- efficiency silicon solar cells. The first layer, $Al_2O_3$, passivates the surface, while $SiN_X$ acts as a hydrogen source that saturates silicon dangling bonds during annealing treatment. We explored the properties on passivation film of $Al_2O_3/SiN_X$ stack layer with changing the conditions. For the post annealing temperature, it was found that $500^{\circ}C$ is the most suitable temperature to improvement surface passivation.

Effects of Green Tea (Camellia sinensis) Extract Supplementation at Different Dilution Steps on Boar Sperm Cryopreservation and in vitro Fertilization

  • Park, Sang-Hyoun;Jeon, Yubyeol;Yu, Il-Jeoung
    • Journal of Veterinary Clinics
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    • v.35 no.2
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    • pp.39-45
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    • 2018
  • We evaluated the effects of green tea extract (GTE) supplementation at different dilution steps on boar sperm freezing and in vitro fertilization. Sperm intracellular hydrogen peroxide ($H_2O_2$), motility, viability, acrosome integrity and morphology were determined. In addition, sperm IVF parameters (penetration and monospermy) and glutathione (GSH) levels of presumptive zygotes (PZs) were evaluated. Semen was diluted in lactose egg yolk (LEY) and cooled at $5^{\circ}C$ for 3 h (first dilution step) and then diluted in LEY with 9% glycerol and maintained at $5^{\circ}C$ for 30 min (second dilution step). Four experimental groups were compared: first and second dilution steps without GTE (control), first dilution step with GTE (Step 1), second dilution step with GTE (Step 2) and first and second dilution step with GTE (Step 1+2). The spermatozoa were frozen in nitrogen vapor. Higher sperm motility, viability and acrosome integrity after thawing were observed in Step 1, Step 2 and Step 1+2 groups compared with the control (P < 0.05). Lower $H_2O_2$ level was observed in Step 1+2 compared with control and Step 1 (P < 0.05). For IVF, matured oocytes were co-cultured with spermatozoa frozen according to the experimental groups. GSH levels of PZs were significantly higher in Step 2 and Step 1+2 than in control and Step 1 (P < 0.05) without a significant difference in IVF parameters. In conclusion, supplementation with GTE in both first and second dilution steps during the freezing process resulted in better boar sperm cryopreservation and might be beneficial for further embryo development.

GAP JUNCTION, A BIOMARKER FOR CANCER AND CHEMOPREVENTION: PREVENTIVE EFFECT OF EPICATECHIN AND GINSENOSIDE $Rb_$ ON THE INHIBITION OF GAP JUNCTIONAL INTERCULLULAR COMMUNICATION BY TPA AND $H_2O_2$

  • Kang, Kyung-Sun;Lee, Yong-Soom
    • Proceedings of the Korean Society of Toxicology Conference
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    • 2002.05b
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    • pp.59-72
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    • 2002
  • The anticarcinogenic effects of epicatechin(EC) and ginsenoside Rb2(Rb2), which are major components of green tea and Korea ginsen, respectively, were investigated using a model system of gap junctional intercellular communication (GJIC) in WB-F344 rat liver epithelial cells. 12-O-Tetradecanoylphorbol-13-accetate (TPA) and hydrogen preoxide, known as cancer promoters, inhibited GJIC in the epithelial cells as determined by the scrape loading/dye transfer assay, fluorescence redistribution assay after photobleaching, and immunofluorescent staining of connexin 43 using a laser confocal microscope. The inhibition of GJIC by TPA and H2O2 was prevented with treatment of Rb2 or Ec. The effect of EC on GJIC was stronger in TPA-treated cells than in H2O2-treated cells, while the effect of Rb2 was opoosite to that of EC. EC, at the concentration of 27.8$\mu$g/ml, prevented the TPA-induced GJIC inhibition by about 60%. Rb2, at the concentration of 277$\mu$g/ml, recovered the H2O2-induced GJIC inhibition by about 60%. These results suggest that Rb2 and EC may prevent human cancers by preventing the down-regulation of GJIC during the cancer promotion phase and that the anticancer effect of green tea and Korea ginseng may come from the major respective conponents, EC and Rb2.

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Antioxidant and Anticancer Activities of Yak-Sun Tea Prepared by Oriental Medicinal Herbs (한방생약재를 이용한 약선차의 항산화 및 항암효과)

  • Choi, Il-Sook;Cha, Eun-Jung;Lee, Youn-Ri;Kim, Jae-Keun
    • The Korean Journal of Food And Nutrition
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    • v.25 no.3
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    • pp.447-453
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    • 2012
  • Various types of tea are consumed as a popular beverage worldwide particularly in Asian countries such as Korea, China, and Japan. The purpose of this study was to investigate the mineral contents, antioxidant properties and anticancer activity of Yak-Sun tea that is prepared by six oriental medicinal herbs. The results of the mineral contents were as follows; Ca, Mg, and Na contents were higher than those of green tea, whereas Fe, P, and K contents were lower than those of green tea. The total phenolics and flavonoid content of the Yak-Sun tea were higher than those of green and black teas. The $IC_{50}$ values of DPPH radical, hydroxyl radical, hydrogen peroxide radical scavenging of Yak-Sun tea were 0.78, 1.58, and 2.04 $mg/m{\ell}$, respectively, whereas the radical scavenging values of ${\alpha}$-tocopherol was 0.06, 0.05, and 0.09 $mg/m{\ell}$, respectively. When cancer cells were treated with Yak-Sun tea, the anticancer activity increased in a dose dependent manner. HCT116 colon cancer cell lines were dramatically increased, as compared to other cancer cell lines, such as MCF-7, H460, and MKN45 cell lines. The results of this study demonstrated that Yak-Sun tea could function as a tea to enhance health conditions for antioxidant and anticancer activity.

Influence of Manufacturing Conditions for the Life Time of the Boron-Doped Diamond Electrode in Wastewater Treatment (폐수처리용 붕소 도핑 다이아몬드 전극의 수명에 미치는 제조공정 변수의 영향)

  • Choi, Yong-Sun;Lee, Young-Ki;Kim, Jung-Yuel;Kim, Kyeong-Min;Lee, You-Kee
    • Korean Journal of Materials Research
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    • v.27 no.3
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    • pp.137-143
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    • 2017
  • Boron-doped diamond (BDD) electrode has an extremely wide potential window in aqueous and non-aqueous electrolytes, very low and stable background current and high resistance to surface fouling due to weak adsorption. These features endow the BDD electrode with potentially wide electrochemical applications, in such areas as wastewater treatment, electrosynthesis and electrochemical sensors. In this study, the characteristics of the BDD electrode were examined by scanning electron microscopy (SEM) and evaluated by accelerated life test. The effects of manufacturing conditions on the BDD electrode were determined and remedies for negative effects were noted in order to improve the electrode lifetime in wastewater treatment. The lifetime of the BDD electrode was influenced by manufacturing conditions, such as surface roughness, seeding method and rate of introduction of gases into the reaction chamber. The results of this study showed that BDD electrodes manufactured using sanding media of different sizes resulted in the most effective electrode lifetime when the particle size of alumina used was from $75{\sim}106{\mu}m$ (#150). Ultrasonic treatment was found to be more effective than polishing treatment in the test of seeding processes. In addition to this, BDD electrodes manufactured by introducing gases at different rates resulted in the most effective electrode lifetime when the introduced gas had a composition of hydrogen gas 94.5 vol.% carbon source gas 1.6 vol.% and boron source gas 3.9 vol.%.

Evaluation of Ignition Performance of Green Hypergolic Propellant (친환경 접촉점화 추진제 점화 성능 평가)

  • Sunjin Kim;Minkyu Shin;Jeongyeol Cha;youngsung Ko
    • Journal of Aerospace System Engineering
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    • v.17 no.1
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    • pp.51-58
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    • 2023
  • Hypergolic propellants, which can ignite themselves without an ignition source, are difficult to handle due to their corrosiveness and toxicity. Therefore, it is necessary to develop green hypergolic propellants with little or no toxicity. In this study, basic research on green hypergolic ignition propellants was conducted. With 95% hydrogen peroxide as an oxidizer and CNU_HGFv1 as a fuel, ignition and combustion characteristics of propellants were evaluated through a drop test, an ignition test, and a combustion test. As a result of the drop test, the ignition delay time was 9.7 ms. It was 27 ms in the ignition test, which was fast enough to be used as a propellant. As a result of the combustion test, a combustion efficiency of 95.4~98.1% was achieved at about 11.7 bar. It was confirmed that fast and stable combustion was possible without hard start or combustion instability.

Biological Activities of Methanol Extracts from Green Tea Seed (녹차종자 메탄올추출물의 생리활성)

  • Yang, Hee-Sun;Kim, Jae-Yong;Kim, Hong-Chul;Nou, Ill-Sup;Seo, Kwon-Il
    • Food Science and Preservation
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    • v.13 no.6
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    • pp.769-773
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    • 2006
  • This study was to investigate the biological activities of green tea seed methanol extract (GTSME) and compared those of green tea methanol extract (GTME) for using green tea seed as the functional food material. The hydrogen-donating activity of GTSME was over 50% at the $100 {\mu}g/mL$ concentration the activity of GTME was 21.86% at the $1000{\mu}g/mL$ concentration compared with that of control. The MDA (malondialdehyde) production was 60 Mol/g and 50 Mol/g in the mouse liver homogenate teated with GTME and GTSME of $1000{\mu}g/mL$ concentrations, respectively, and the values were lower than 86 Mol/g of control. GTME and GTSME of $1000{\mu}g/mL$ concentration inhibited the proliferation of over 50% and over 20% in A549 and SW480 human cancer cells, respectively. The morphology transformation was shown in the cancer cells treated with GTSME of $500{\mu}g/mL$ with the decrease of cell numbers lower than that of control cells numbers. The NO production was increased in a dose dependent manner in the RAW264.7 macrophage cells treated with GTME and GTSME of 1, 10, 100 and $1000{\mu}g/mL$ concentrations, and the NO production by GTSME was $2.04{\mu}M$ at $100{\mu}g/mL$ concentration, and the value was higher than $0.77{\mu}M$ by GTME.