• Title/Summary/Keyword: 온도분포특성

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Characterization of Alternative Anode Catalysts for Direct Formic Acid Fuel Cell (직접 개미산 연료전지용 연료극 촉매의 특성 연구)

  • Yu, Jae Keun;Lee, Hyo Song;Kim, Ki Ho;Kim, Young Chun;Han, Jong Hee;Oh, In Hwan;Rhee, Young Woo
    • Korean Chemical Engineering Research
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    • v.44 no.3
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    • pp.314-318
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    • 2006
  • Direct formic acid fuel cells (DFAFCs) are potential alternative power sources for portable devices such as cellular phone, personal digital assistants (PDA) and laptop computers. In this study, we developed the catalysts for great performance of fuel cell, and investigated their characteristics by using EDS and SEM. Pt-Pd catalysts showed uniform size and homogeneous distribution. As the content of palladium increased, the performance of DFAFC increased. Pd black showed the greatest performance among the five catalysts tested. Also, Pt-Pd (1:1) catalyst had an excellent maximum power density of $120mW/cm^2$. As the operating temperature increased, fuel cell performance was increased due to a reaction activity increases of catalyst. But, temperature had only a slight effect on the performance of fuel cell in the best activity range of membrane.

Physicochemical Characteristics of Powder from Hot Air and Freeze Dried Leaves and Roots of Acorous calamus L. (열풍건조와 동결건조에 따른 수창포(Acorous calamus L.) 분말의 부위별 이화학적 특성)

  • Beom, Hee-Ju;Kang, Dae-Jin;Lee, Byung-Doo;Shon, Jin-Han;Im, Ji-Soon;Eun, Jong-Bang
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.36 no.11
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    • pp.1451-1457
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    • 2007
  • The physical and chemical characteristics of powders from hot air and freeze dried leaves and roots of Acorous calamus L. were investigated. Two parts, upper and lower, of leaves, and two kinds of roots, 4 and 6 years old, were dried at 30 and $40^{\circ}C$, freeze-dried, and ground to make powder. Contents of moisture, ash, crude fat, and crude protein in freeze dried powder of upper leaf were 4.87%, 6.73%, 2.22%, and 3.57%, respectively. Water absorption index (WAI) and water solubility index (WSI) in freeze dried powder of lower and upper leaves were 8.476 and 0.077 g/mL. Contents of chlorophyll a, chlorophyll b and total chlorophyll in freeze dried powder of upper leaves were 12.18, 16.86, and 29.11 mg/100 g, respectively. Contents of total and reducing sugar in freeze dried powder of 4 and 6 years roots were $111.89{\sim}119.21$ ppm and $5.02{\sim}5.22$ ppm, $109.92{\sim}114.65$ ppm and $5.21{\sim}5.32ppm$. Contents of total polyphenols and flavonoids in freeze dried powder of upper leaf were 125.02 and $21.02{\mu}g/mg$, respectively.

Physical and Chemical Characteristics of Oilsands Bitumen Using Vacuum Distillation (감압증류장치를 이용한 Oilsands Bitumen의 물리화학적 특성 연구)

  • Kim, Kyoung-Hoon;Jeon, Sang-Goo;Roh, Nam-Sun;Kim, Kwang-Ho;Shin, Dae-Hyun;Park, Hyo-Nam;Han, Myung-Wan
    • Journal of Energy Engineering
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    • v.17 no.1
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    • pp.15-22
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    • 2008
  • This study was carried out to investigate physical and chemical characteristics of the distillates and residue of Athabasca oilsand bitumen obtained from Canada, using a vacuum distillation unit. The distillates and residue produced from the vacuum distillation were characterized through atomic analysis, SARA analysis, and measurement of boiling point distribution, molecular weight, and API gravity. The vacuum distillation equipment consisted of a 6-litter volume vessel, a glass-packed column, a condenser, a reflux device, a flask fer collecting distillates, and a temperature controller. The cutting of distillates was performed with four steps under the condition of full vacuum and maximum temperature of $320^{\circ}C$. The results showed that the sulfur amount and average molecular weight of the distillates were significantly reduced compared to those of oilsand bitumen. As the cutting temperature increased, the hydrogen amount decreased but the sulfur amount and average molecular weight increased in the distillates.

Characteristics of Carbidization for Iron Ore Fines with a Wide Size Range (입도분포가 넓은 분철광석의 탄화특성)

  • Hwang Ho-Sun;Chung Uoo-Chang;Chung Won-Sub;Chung Won-Bae
    • Resources Recycling
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    • v.12 no.5
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    • pp.42-49
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    • 2003
  • Characteristics of reduction and carbidization for hematite ore with a wide size range have been investigated at high temperature(590∼64$0^{\circ}C$) under $H_2$ and $H_2$-CO gas mixtures. The apparent activation energy for reduction of hematite ore with H2 gas was found to be 20 kJ/mol. The weight loss by reduction was about 28% md the weight gain by carbidization was about 5%. The measured values of weight change were compared with those calculated from equation (3) & (5) and fairly good agreement was obtained. The rate of carbidization was increased with an decrease in temperature, particle diameter and gas ratio($H_2$/ CO). The free carbon was increased with decrease in gas ratio($H_2$/ CO). The rate of carbidization was increased with mixing of $H_2$ gas but this effect was not proportional to fraction of $H_2$ gas. It was also found that the rate of carbidization was the maximum in the $H_2$ gas fraction of 0.5. It is considered that $H_2$ plays a part as a catalyst for formation of iron carbide($Fe_3$C).

Scientific Comparison Study on Characteristics of Firing and Making Materials for Sherds Excavated from Celadon Kiln Site of Punggil-ri, Jangheung (장흥 풍길리 청자요지 출토 도자기들의 소성특성 및 재료학적 상관성 비교 연구)

  • Han, Min Su;Lee, Jang Jon
    • Journal of Conservation Science
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    • v.36 no.2
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    • pp.112-122
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    • 2020
  • The purpose of this study was to find out the correlation through comparative analysis of used materials and manufacturing techniques such as firing characteristics for sherds excavated from celadon kiln site in Punggil-ri, Jangheung. The color difference of the sherds was very wide, and even in the microstructure of the cross section of the glaze layer and the body layer, the celadons, whitewares, blackware, and stonewares could not be characterized because they did not show distinct differences from each other. As a result of estimating the firing temperature through the analysis of constituent minerals and thermal analysis, most of them were estimated to have been fired at 1000℃, but some were fired at high temperatures above 1200℃. It was difficult to clearly distinguish between celadon and whiteware even in the major compositional content of bodies. In the statistical analysis, glaze could be classified three group according to the type of sherds, but the bodies of celadons, whitewares, and blackware classified into one similar group. It is considered that it is not more likely differences in raw materials but some ingredients were removed or added during the purification process. Conclusionally, in this kiln site was found through scientific analysis that there were technical attempts to produce various ceramics, and that the manufacturing techniques and materials of ceramics were in an early stage that was not stabilized.

Thermal and Flow Analysis of a Driving Controller for Active Destruction Protections (능동 파괴 방호 구동제어기의 열 유동 해석)

  • Ryu, Bong-Jo;Oh, Bu-Jin;Kim, Youngshik
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.2
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    • pp.235-242
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    • 2017
  • A driving controller for active destruction protections can be applied to machinery, aerospace and military fields. In particular, this controller can be used to track and attack enemy flying objects through the active control. It is important to ensure reliability of the driving controller since its operation should be kept with precision to the target point. The temperature of the environment where the driving controller is used is about -32 C ~ 50 C (241~323 ). Heat generated in the driving controller should be maintained below a certain threshold (85 C (358 )) to ensure reliability; therefore, the study and analysis of the heat flow characteristics in the driving controller are required. In this research, commercial software Solid-Works Flow Simulation was used for the numerical simulation assuming a low Reynolds number turbulence model and an incompressible viscous flow. The goal of this paper is to design the driving controller safely by analyzing the characteristics of the heat flow inside of the controller composed of chips or boards. Our analysis shows temperature distributions for boards and chips below a certain threshold.

Effect of buoyancy and thermocapillarity on the melt motion and mass transfer for different aspect ratio of flow field in magnetic Czochralski crystal growth of silicon (Cusp 자장이 걸려있는 초크랄스키 실리콘 단결정성장에서 유동장의 종횡비에 따라 부력과 열모세관 현상이 용융물질의 유동과 물질전달에 미치는 영향)

  • 김창녕
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.10 no.3
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    • pp.177-184
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    • 2000
  • The effect of the buyancy and thermocapillarity for differnent aspect ratio of flow field on melt motion and mass transfer has been numerically investigated in magnetic Czochralski crystal growth of silicon. During the process of crystal growth, the melt depth of crucible reduces so the aspect ratio of flow field also reduces. Therefore the shape of magnetic field of the flow field changes and the flow pattern also changes significantly. Together with the melt flow which forms the Marangoni convection (or thermocapillary flow) that comes from the inside the flow field, a flow circulation is observed near the corner close both to the crucible wall and the free surface. Due to this circulation, buoyancy effect has been turned out to be local rather than global. As the aspect ratio decreases, the radial component of the magnetic field prevails compared with the axial component in the flow field. Under the influence of this magnetic field, the melt flow and the temperature distribution in a meridional plane tend to depend on the radial position. As the aspect ratio decreases, the temperature gradient near the edge of the crystal decreases yielding smaller thermocapillarity, and the oxygen concentration near the crystal and the oxygen incorporation rate also decrease.

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Effects of Manufacturing Process Variables on Characteristics of Microcapsules with Self-Healing Agent (제조공정변수에 따른 자가치료용 마이크로캡슐의 특성 고찰)

  • 윤성호
    • Composites Research
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    • v.16 no.2
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    • pp.54-61
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    • 2003
  • In this study, manufacturing process for microcapsules with the self-healing agent was introduced and the characteristics of microcapsules manufactured by varying with various manufacturing process variables were evaluated through a particle size analyzer, an optical microscope, and a TGA. Urea-formaldehyde resin was used for the thin wall of microcapsules and DCPD (dicyclopentadiene) was used for the self-healing agent. The various manufacturing process variables, such as (1) 24hr, 40hr, 48hr, 60hr of the solution time of the EMA copolymer, (2) pH3.5, pH4.0, pH4.5 of the hydrogen ion concentration of the emulsified solution, (3) 400rpm, 500rpm, 600rpm, 1000rpm of the agitation speed of the emulsified solution, (4) $50^{\circ}$, $55^{\circ}$, $60^{\circ}$ of the reaction temperature of the emulsified solution, were considered. According to the results, the particle size distribution of microcapsules was affected on the agitation speed, and the thermal stability of microcapsules was influenced by the solution time of the EMA copolymer, the hydrogen ion concentration, and the reaction temperature of the emulsified solution. Therefore, suitable manufacturing process variables should be applied to obtain thermally stable microcapsules capable of containing the healing agent capable until the thin wall of microcapsules were to be burned.

Synthesis and Characterization of Biodegradable MethoxyPoly(ethylene glycol)-Poly$(\varepsilon-caprolactone-co-L-lactide)$ Block Copolymers (메톡시폴리(에틸렌 글리콜)-폴리(카프로락톤-co-L-락타이드) 공중합체의 합성 및 특성 분석)

  • Hyun Hoon;Cho Young Ho;Jeong Sung Chan;Lee Bong;Kim Moon Suk;Khang Gilson;Lee Hai Bang
    • Polymer(Korea)
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    • v.30 no.1
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    • pp.28-34
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    • 2006
  • A series of methoxypoly(ethylene glycol) $(MPEG)-poly(\varepsilon-co-L-lactide)$ (PCLA) diblock copolymers were synthesized by ring-opening polymerization of a mixture of $\varepsilon-caprolactone$ and L-lactide with different ratios in the presence of $Sn(Oct)_2$. The characterization of MPEG-PCLA diblock copolymers were examined by $^1H-NMR$, GPC, DSC, and XRD. Kinetic study on ring-opening polymerization of monomer mixtures was carried out in various conditions such as a variation with polymerization time, amount of catalyst, and temperature. The highest conversion obtained in 1.2 ratic of initiator venn catalyst at $110\;^{\circ}C$. The biodegradable characterization of MPEG-PCLA diblock copolymers in aqueous solution was carried out by using GPC for $1\~14$ weeks. The biodegradability of MPEG-PCLA diblock copolymers increased as the L-lactide content of diblock copolymers increased. In conclusion, we confirmed the dependence of polymerization rate according to various conditions. In addition, we can control the biodegradability of MPEC-PCLA diblock copolymers by changing the ratio of PCL and PLA block segment.

Properties of Pb(Zr, Ti)$\textrm{O}_3$ Ferroelectric Thin Films on MgO/Si Substrate by RF Sputtering (RF 스퍼터링에 의해 MgO/Si 기판위에 증착된 Pb(Zr, Ti)$\textrm{O}_3$ 강유전체 박막의 특성연구)

  • Jang, Ho-Jeong;Seo, Gwang-Jong;Jang, Ji-Geun
    • Korean Journal of Materials Research
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    • v.8 no.12
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    • pp.1170-1175
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    • 1998
  • PZT films without lower electrode were deposited on the highly doped Si(100) substrate with MgO buffer layer (Mgo/si) by RF magnetron sputtering method followed by the rapid thermal annealing at $650^{\circ}C$ . We investigated the dependences of the crystalline and electrical properties on the MgO thickness and the RTA post annealing. The PZT films on bare Si (without MgO) showed pyrochlore crystal structure while those on MgO(50 )/Si substrates showed the typical perovskite crystal structures. From SEM and AES analysis, the thickness of PZT films was about 7000 showing relatively smooth interface. The depth profiles indicated that atomic species were distributed homogeneously in the PZT/MgO/Si substrate. The dielectric constant($\varepsilon_{r}$ ) and remanent polarization(2Pr) were about 300 and $14\mu$C/$\textrm{cm}^2$;, respectively. The leakage current was about $3.2\mu$/A$\textrm{cm}^2$.

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