• Title/Summary/Keyword: Hydrogen ambient

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Preparation of Anhydrous Magnesium Chloride for a Fused Salt Electrolysis of Magnesium (마그네슘 용융염전해(溶融鹽電解)를 위한 무수(無水)염화마그네슘 제조(製造))

  • Eom, Hyoung-Choon;Park, Hyung-Kyu;Yoon, Ho-Sung
    • Resources Recycling
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    • v.16 no.1 s.75
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    • pp.37-43
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    • 2007
  • It was studied to prepare anhydrous magnesium chloride which could used as the raw material of a fused salt electrolysis of magnesium by dehydration of magnesium chloride hydrate. The dehydration was carried out in a tube furnace at $350{\sim}580^{\circ}C$. It was confirmed that magnesium chloride hydrate was oxdized to magnesia through the dehydration in ambient atmosphere, but anhydrous magnesium chloride could be obtained in hydrogen chloride gas atmosphere. And the crystallity of the product increased with increasing temperature and time of dehydration. All of the un-reacted hydrogen chloride gases which were generated during the dehydration in hydrogen chloride gas atmosphere could be recovered as hydrochloric solution, and it could be reused for chlorination of magnesia to prepare magnesium chloride hydrate.

Al Doping Effect of Pd/TiO2 for Improved Hydrogen Detection (수소 감지 성능 향상을 위한 Pd/TiO2 분말에서의 Al 도핑 효과)

  • Lee, Yeongan;Seo, Hyungtak
    • Journal of Sensor Science and Technology
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    • v.23 no.3
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    • pp.207-210
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    • 2014
  • $TiO_2$ oxide semiconductor is being widely studied in various applications such as photocatalyst and photosensor. Pd/$TiO_2$ gas sensor is mainly used to detect $H_2$, CO and ethanol. This study focus on increasing hydrogen detection ability of Pd/$TiO_2$ in room temperature through Al-doping. Pd/$TiO_2$ was fabricated by the hydrothermal method. Contacting to Aluminum (Al) foil led to Al doping effect in Pd/$TiO_2$ by thermal diffusion and enhanced hydrogen sensing response. $TiO_2$ nanoparticles were sized at ~30 nm of diameter from scanning electron microscope (SEM) and maintained anatase crystal structure after Al doping from X-ray diffraction analysis. Presence of Al in $TiO_2$ was confirmed by X-ray photoelectron spectroscopy at 73 eV. SEM-energy dispersive spectroscopy measurement also confirmed 2 wt% Al in Pd/$TiO_2$ bulk. The gas sensing test was performed with $O_2$, $N_2$ and $H_2$ gas ambient. Pd/Al-doped $TiO_2$ did not response $O_2$ and $N_2$ gas in vacuum except $H_2$. Finally, the normalized resistance ratio ($R_{H2on}/R_{H2off}$) of Pd/Al-doped $TiO_2$ increases about 80% compared to Pd/$TiO_2$.

Reactive Oxygen Species and Cellular Immune Function of Workers Chronically Exposed to High-Level Dusts (고 농도 분진 만성노출 근로자의 세포성 면역기능과 활성산소종)

  • Kim, Kab Bae;Kim, Ki-Woong
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.26 no.3
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    • pp.286-292
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    • 2016
  • Objectives: This study aimed to evaluate the effects of chronical exposure to high-level dusts on cellular immune function. Methods: The subjects were 110 male workers, among whom 60 were chronically exposed to high-level dusts in mica, limestone and iron mines. The remaining 50 were office workers. Ambient total, respirable dust and crystalline silica in the workplace were sampled using personal air samplers and analyzed according to NIOSH method 0500. Serum levels of hydrogen peroxide, lipid peroxide and superoxide misutase activity were measured using absorption chromatography. The subpopulations of CD4+, CD8+, natural killer cells (CD16+) and CD3+ T-lymphocytes were examined by two-color staining using monoclonal antibodies. Results: The concentration of hydrogen peroxide was significantly higher in exposed workers and superoxide dismutase activity was significantly higher in control workers. No significant difference in numbers of T-lymphocyte subpopulations were observed between exposed and control workers. A significant correlation in exposed workers was observed among total dusts, respirable dusts and crystalline silica. Hydrogen peroxide was significantly correlated with total dust (r=0.720, p<0.01), respirable dust (r=0.770, p<0.01) and crystalline silica (r=0.678, p<0.01). Concentration of hydrogen peroxide showed a significantly negative correlation with numbers of CD8+ cells (r=-0.274, p<0.01), CD3+ cells (r=-0.222, p<0.01) and natural killer cells (r=-0.556, p<0.01). Conclusions: These results suggest that chronical exposure to high-level dust affects cellular immune function and effects might mediate through reactive oxygen species and inflammatory response.

Decomposition of Sulfuric Acid at Pressurized Condition in a Pt-Lined Tubular Reactor (관형 Pt-라이닝 반응기를 이용한 가압 황산분해반응)

  • Gong, Gyeong-Taek;Kim, Hong-Gon
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.1
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    • pp.51-59
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    • 2011
  • Sulfur-Iodine (SI) cycle, which thermochemically splits water to hydrogen and oxygen through three stages of Bunsen reaction, HI decomposition, and $H_2SO_4$ decomposition, seems a promising process to produce hydrogen massively. Among them, the decomposition of $H_2SO_4$ ($H_2SO_4=H_2O+SO_2+1/2O_2$) requires high temperature heat over $800^{\circ}C$ such as the heat from concentrated solar energy or a very high temperature gas-cooled nuclear reactor. Because of harsh reaction conditions of high temperature and pressure with extremely corrosive reactants and products, there have been scarce and limited number of data reported on the pressurized $H_2SO_4$ decomposition. This work focuses whether the $H_2SO_4$ decomposition can occur at high pressure in a noble-metal reactor, which possibly resists corrosive acidic chemicals and possesses catalytic activity for the reaction. Decomposition reactions were conducted in a Pt-lined tubular reactor without any other catalytic species at conditions of $800^{\circ}C$ to $900^{\circ}C$ and 0 bar (ambient pressure) to 10 bar with 95 wt% $H_2SO_4$. The Pt-lined reactor was found to endure the corrosive pressurized condition, and its inner surface successfully carried out a catalytic role in decomposing $H_2SO_4$ to $SO_2$ and $O_2$. This preliminary result has proposed the availability of noble metal-lined reactors for the high temperature, high pressure sulfuric acid decomposition.

Simultaneous treatment of Cr(VI) and EDCs using flat type photocatalytic reactor under solar irradiation (평판형 태양광반응기를 이용한 복합오염물질의 동시처리 연구)

  • Kim, Saewon;Cho, Hyekyung;Joo, Hyunku;Her, Namguk;Yi, Kwangbok;Kim, Jong Oh;Yoon, Jaekyung
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.5
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    • pp.501-509
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    • 2016
  • In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultaneous treatment of target pollutants: reduction of Cr(VI) to Cr(III) and oxidation of EDCs (BPA, EE2, E2). An immobilized type of photocatalyst was fabricated to have self-grown nanotubes on its surface in order to overcome limitations of powdery photocatalyst. Moreover, Ti mesh form was chosen as substrate and modified to have both larger surface area and photocatalyst content. Ti mesh was anodized at 50V and $25^{\circ}C$ for 30min in the mixed electrolytes ($NH_4F-H_2O-C_2H_6O_2$) and annealed at $450^{\circ}C$ for 2 hours in ambient oxygen to have anatase structure. Surface characterization was done with SEM and XRD methodologies. Fabricated NTT was applied to water treatment, and coexisting Cr(VI) and organics (EDCs) enhanced each other's reactions by scavenging holes and electrons and thus impeding recombination. Also, several experiments were conducted outdoor under direct sunlight and it was observed that both solar-tracking and applying modified photocatalyst were proven to enhance reaction efficiency.

Continuous Measurements of Reduced Sulfur Gases in Urban Air (연속측정방법을 이용한 도심권 대기질 내 저농도 황화합물의 관측에 대한 연구)

  • Choi Ye-Jin;Kim Ki-Hyun;Oh Sang-In;Shon Zang-Ho
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.2
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    • pp.195-204
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    • 2004
  • In this study, the concentrations of major reduced sulfur compounds (H$_2$S, $CH_3$SH, DMS, and DMDS) were determined from ambient air in a monitoring station located in the mid-eastern area of Seoul. Measurements of sulfur species were conducted by the combination of on -line air sampling, thermal desorption, and capillary GC/PFPD analysis. A total number of 143 hourly samples were collected in the two time periods set between June and July 2003. The mean concentrations of four sulfur species measured in the whole study period were found on the order: DMS (535$\pm$183) > H$_2$S (47$\pm$10) > DMDS (35$\pm$22) > $CH_3$SH (6.19$\pm$29.4 pptv). The results of this study show that the concentrations of DMS at the study area are generally higher than those reported previously in the oceanic environments, while those of other sulfur species are not easy to compare with due to the lack of data. The H$_2$S concentrations were generally higher during the daytime than the nighttime, whereas those of others generally exhibited a reversed diurnal pattern. The overall results of our study suggest that the distribution of major reduced S compounds should be controlled by diverse processes in the urban area.

The Study for Characteristic of Direct Methanol Fuel Cell in Ambient Temperature (상온 상태에서 직접 메탄올 연료전지의 특성 연구)

  • Yun, Hyo-Jin;Kim, Jeong-Ju;Kim, Dong-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.5
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    • pp.955-961
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    • 2009
  • Present, a portable battery have problem that the volume increases according to capacity Increase. Direct Methanol Fuel Cell is alternative by solution plan of this problem. In this paper, the characteristics of DMFC are analyzed by change in concentration and discharge of fuel in natural convection and room temperature condition. According to the analysis result, polarization by delay of diffusion velocity of hydrogen ion appeared in methanol of low concentration. And if have a lot of supplies of methanol, generation power declines by electric cell cooling effect.

The Annealing Effect of Diamond-like Carbon Films for RF MEMS Switch

  • Hwang, Hyun-Suk;Choi, Won-Seok;Cha, Jae-Sang
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.11A
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    • pp.1091-1096
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    • 2010
  • Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

Experimental Study on Flame-Vortex Interactions in Turbulent Hydrogen Non-premixed Flames with Coaxial Air (동축공기 수소확산 화염에서의 화염과 와류의 상호작용 실험연구)

  • Kim, Mun-Ki;Oh, Jeong-Suk;Choi, Young-Il;Yoon, Young-Bin
    • 한국연소학회:학술대회논문집
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    • 2006.10a
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    • pp.86-94
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    • 2006
  • This paper investigates the effects of acoustic forcing on NOx emissions and mixing process in the near field region of turbulent hydrogen nonpremixed flames. The resonance frequency was selected to force the coaxial air jet acoustically, because the resonance frequency is effective to amplify the forcing amplitude and reduce NOx emissions. When the resonance frequency is acoustically excited, a streamwise vortex is formed in the mixing layer between the coaxial air jet and coflowing air. As the vortex develops downstream, it entrains both ambient air and combustion products into the coaxial air jet to mix well. In addition, the strong vortex pulls the flame surface toward the coaxial air jet, causing intense chemical reaction. Acoustic excitation also causes velocity fluctuations of coaxial air jet as well as fuel jet but, the maximum value of centerline fuel velocity fluctuation occurs at the different phases of $\Phi$=$180^{\circ}$ for nonreacting case and $\Phi$=$0^{\circ}$ for reacting case. Since acoustic excitation enhances the mixing rate of fuel and air, the line of the stoichiometric mixture fraction becomes narrow. Finally, acoustic forcing at the resonance frequency reduces the normalized flame length by 15 % and EINOx by 25 %, compared to the flame without acoustic excitation.

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Study on the global distribution of far-ultraviolet emission in our Galaxy

  • Jo, Young-Soo;Seon, Kwang-Il;Min, Kyoung-Wook;Edelstein, Jerry
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.52.1-52.1
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    • 2015
  • FIMS/SPEAR is a dual-channel far-ultraviolet imaging spectrograph on board the Korean microsatellite STSAT-1, which was launched on 2003 September 27. The primary mission goal of FIMS was to conduct a survey of diffuse far UV emissions in our Galaxy. For this purpose, FIMS completed a survey of about 84% of the sky during its operation of a year and a half. The present study aims to analyze this survey data made in the far UV wavelengths to understand the global evolution of our Galaxy. The far UV wavelength band is known to contain important cooling lines of hot gas: hence, the study will show how the hot gas in our Galaxy, produced by stellar winds and supernova explosion, evolves globally to cool down and become mixed with ambient cooler medium. One of the main findings from previous analyses of the FIMS data is that molecular hydrogen exists ubiquitously in our Galaxy. This discovery leads to another important scientific question: how is molecular hydrogen distributed in our Galaxy and how does it affect globally the evolution of our Galaxy as a cold component? Hence, the present study will cover both the hot and cold components of the ISM, which will also provide the opportunity to investigate the interactions between the two.

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