• Korean Journal of Materials Research
• /
• v.26 no.4
• /
• pp.173-181
• /
• 2016

In order to use coal tar pitch (CTP) as a raw material for carbon fibers, it should have suitable properties such as a narrow range of softening point, suitable viscosity and uniform optical properties. In this study, raw CTP was modified by heat treatment with three types of polymer additives (PS, PET, and PVC) to make a spinnable pitch for carbon fibers. The yield, softening point, C/H ratio, insoluble yield, and meso-phase content of various modified CTPs with polymer additives were analyzed by changing the type of polymer additive and the heat treatment temperature. The purpose of this study was to compare the properties of CTPs modified by polymer addition with those of a commercial CTP. After the pitch spinning, the obtained green fibers were stabilized and carbonized. The properties of the respective fibers were analyzed to compare their uniformity, diameter change, and mechanical properties. Among three polymer additives, PS220 and PET261 pitches were found to be spinnable, but the carbon fibers from PET261 showed mechanical properties comparable with those of a commercial CTP produced by an air-blowing method (OCI284). The CTPs modified with polymer additive had higher ${\beta}$-resin fractions than the CTP with only thermal treatment indicating a beneficial effect of carbon fiber application.

• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.E2
• /
• pp.69-77
• /
• 2000

Measurements of non-methane hydrocarbons (NMHC) were carried out in the Sangdo tunnel and on a nearby roadway in Seoul during the during the periods of heavy(low speed with ∼20km h(sup)-1) and light(high speed with ∼60kmh(sup)-1) traffic in February 2000. In the tunnel, the total NMHC levels during the heavy traffic period were higher than those during the light traffic period by a factor of 2. This was due to the increase of emissions at the low vehicle speed period and the higher dilution effect derived from faster flow of tunnel air at the high vehicle speed period. The average total NMHC concentration in the tunnel was 1.7 times as high as that on the roadway. The species with the highest concentration in the tunnel was ethylene(50.1 ppb), followed by n-butane(34.1 ppb) and propane (21.9 ppb). The concentration ranking in the tunnel was generally in good agreement with that on the roadway, suggesting that the NMHC compositions in the tunnel and on the nearby roadway were primarily determined by vehicle exhausts. However, the NMHC compositions in the Sangdo tunnel do not agree well with other foreign study results, reflecting that the characteristics of vehicle exhausts of Seoul is different from those of other cities. The most prominent difference between this study and other studies is the high mass fractions of butanes and propane. It was be attributed to the wide use of butane-fueled vehicles.

• Proceedings of the KSAR Conference
• /
• 2001.03a
• /
• pp.73-73
• /
• 2001

This study was to examine whether the vitrified, one-step diluted and direct transferred Hanwoo IVM/IVF/IVC blastocysts can be successfully survived in vivo and they were succeeded into the live birth. For vitrification, blastocysts were serially exposed in glycerol (G) or/and ethylene glycol (EG) mixtures [10% (v/v) G for 5 min, 10% G plus 20% EG (v/v) for 5 min, and 25% G plus 25% EG (v/v) for 30 sect] which is diluted in 10% FBS added D-PBS. Thawing of straw was carried out in air for 10 sec and then in water bath of $25^{\circ}C$ for 20 sec. One-step dilution within the straw was done in water bath of $25^{\circ}C$ for 1 min. Vitrified and one-step diluted embryos were directly transferred into 36 (natural or hormone induced synchronized) recipient cows in 6 areas of Kyungsang Buk-Do. Pregnancies were confirmed at first when recipient cows did not return to the subsequent estrus cycle, and later by manual palpation per rectum on day 45, 90 and then living calves were derived into parturition. Overall pregnancy was 33.3%(12/36), However, higher pregnancy was obtained when the recipients exhibited estrus one day earlier than the age of transferred embryos (53.3 vs 25.0-27.3%), irrespective of synchronization methods. Also, parous recipients became pregnant higher than nulliparous heifers, And, there were not different in pregnancy rates by the aspect of corpus luteum (CL) quality of recipients (good, 29.4; fair, 37.5; poor, 33.3%). One hundred eight of frozen-thawed Hanwoo blastocysts were directly transferred into 36 recipient cows. In 12 of pregnant cows, 3 cows were aborted and 9 cows were calved [single, 66.7% (6/9): twin, 33.3% (3/9)]. Total embryo implantation rate was 11.1% (12/108). However, 9 Hanwoo calves were lived. Therefore, these results demonstrate that direct transfer technique of vitrified and one-step diluted bovine blastocysts can be applied easily and effectively with the higher pregnancy rate on field trial without the equipment and embryological skills.

• Proceedings of the KSAR Conference
• /
• 2001.03a
• /
• pp.7-7
• /
• 2001

Cryopreservation by vitrification of Hanwoo blastocysts derived from nuclear transfer with Hanwoo adult ear cell was compared with that of in vitro fertilized blastocysts. For vitrification, day 7 or day 8 blastocysts were serially exposed in glycerol (G) or/and ethylene glycol (EG) mixtures (10% G for 5 min, 10% G plus 20% EG for 5 min, and 25% G plus 25% EG for 30 sec) which was diluted in 10% FBS added D-PBS. Thawing of straw was carried out in air for 10 sec and then in water bath of $25^{\circ}C$ for 20 sec. The contents of the straw (0.2 ml) was expelled into a culture dish contained with 0.5M sucrose and 10% FBS(S-DPBS) by cutting the cotton plug and then the recovered embryos were put into fresh 0.25M and 0.125M S-DPBS for 30 sec, respectively, The embryos were transferred into D-PBS with 10% FBS for 5 min. and were cultured in a 10u1 droplet of co-culture environment (cumulus cell monolayer + 10% added CRl medium) for 24 h. In the result, survival rates were 88.9% and 85.4% for nuclear transfer embryos and in vitro fertilized embryos, respectively. After transfer of vitrified-thawed blastocysts produced from nuclear transfer, 4 of 5 total recipients did not return to the subsequent estrus cycle at 30 days. It is concluded that the Hanwoo blastocysts derived from nuclear transfer can be successfully cryopreserved using simple and efficient vitrification method.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.3
• /
• pp.403-412
• /
• 2006

The effect of a wall temperature on the soot deposition process from a diffusion flame to a solid wall was investigated in a microgravity environment to attain in-situ observations of the process. The fuel for the flames was an ethylene ($C_2H_4$). The surrounding oxygen concentration was 35% with surrounding air temperatures of $T_a=600K$. In the study, three different wall temperatures. $T_w$=300, 600, 800K, were selected as major test conditions. Laser extinction was adopted to determine the soot volume fraction distribution between the flame and burner wall. The experimental results showed that the maximum soot volume fractions at $T_w$=300, 800 K were $8.8{\times}10^{-6},\;9.2{\times}10^{-6}$, respectively. However, amount of soot deposition on wall surface was decreased because of lower temperature gradient near the wall with increasing wall temperature. A numerical simulation was also performed to understand the motion of soot particles in the flame and the characteristics of the soot deposition to the wall. The results from the numerical simulation successfully predicted the differences in the motion of soot particles by different wall temperature near the burner surface and are in good agreement with observed soot behavior that is, the 'soot line', in microgravity.

• Fire Science and Engineering
• /
• v.24 no.6
• /
• pp.170-175
• /
• 2010

The effect of carbon dioxide addition on soot formation was investigated in jet diffusion flames in coflow. Flame temperature were measured with R-type thermocouple and the boundary temperature between blue and yellow flame was confirmed. Light-extinction method was introduced for the relative soot density (1-I/$I_0$) in the in-flame region. He-Ne laser with wave length at 632.8 nm was used for the light source, and the signal attenuated by absorption and scattering was detected directly. Oxidizer velocity effect on soot formation was studied to know that the thermal influence for soot formation. The results showed that the temperature of both blue and yellow flame were decreased according to the dilution of carbon dioxide but boundary temperature was nearly constant. The relative soot density was lower when carbon dioxide was added in oxidizer stream and oxidizer velocity increased. These were caused by the reduction of flame temperature and shorter residence time for soot growth. Also carbon dioxide addition enhanced the instability of jet flames like flickering, so the flame length was a little longer than pure ethylene/air flame.

• Journal of the Korean Chemical Society
• /
• v.50 no.3
• /
• pp.243-246
• /
• 2006

The LiCoO2 thin films were prepared on the Pt/Ti/SiO2/Si substrate by spin coating using citrate sol. The citrate sol was spin-coated on substrate and dried at 380oC for 15 min. to evaporate the solvents and remove the organic materials. The as-deposited films were annealed at 750oC for 10 min. in air for crystallization. The X-ray diffraction patterns for the film have been indexed hexagonal system with space group R3m. The active area of LiCoO2 films for electrochemical test was about 11cm2. A Li foil and 1M LiClO4 in propylene carbonate(PC) and ethylene carbonate(EC) (1:1)were used as an anode and an electrolyte, respectively. The galvanostatic charge-discharge test was carried out at constant current density ranging from 5 A/cm2 in the voltage window between 4.2 and 3.0 V. The first discharge capacity of the film is 0.35Ah/cm2-m. The cycling behavior of the LiCoO2 film is also reported.

• Journal of the Korean Ceramic Society
• /
• v.40 no.7
• /
• pp.709-714
• /
• 2003

Eu doped $Y_2$ $O_3$ nanoparticles were prepared with the solvothermal synthesis using the ethyleneglycol solvent at 20$0^{\circ}C$ for 3-5 h and then annealed in air at 1000-140$0^{\circ}C$ for 2-4 h. The X-ray diffraction pattern of annealed crystals at 100$0^{\circ}C$ for 2 h could be indexed as pure cubic cell of $Y_2$ $O_3$ phase with lattice parameters a=10.5856 $\AA$ which is very close to the reported data (JCPDS Card File, 41-1105 a=10.6041 $\AA$). Average size of prepared phosphor particles have about 100 nm, which were spherical morphology. The phosphor particle sizes decreased and the emission intensity increased at the annealing temperature. Though PL spectrum analysis, the 3% Eu doped $Y_{2-x}$ $O_3$:E $u_{x}$ $^{3+}$(x=0.06) phosphor showed the excitation spectrum at 250 nm wavelength and the maximum emission spectrum at 611 nm wavelength.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.4
• /
• pp.488-494
• /
• 2011

Gasket plays an important role on sealing of the polymer electrolyte membrane fuel cell (PEMFC) stack. Stack requires gaskets in each cell to keep the hydrogen and air/oxygen within their respective regions. The failure of the gasket creates the problems of fuel leakage, mixing, damage on parts and can be a direct reason for the degrading the efficiency of fuel cell. The purpose of this paper researches on how mechanical properties of EPDM gasket in PEMFC are changed after long-term operations. The EPDM (ethylenepropylene-diene monomer) gaskets are obtained from the stack after long-term operations. DMA (dynamic mechanical analysis) is conducted to access the change of mechanical properties of the EPDM gasket. SEM/EDS (scanning electron microscope/energy dispersive spectroscopy) was used to show the surface topography and chemical characterization on the sample surface.

• KSBB Journal
• /
• v.17 no.2
• /
• pp.176-181
• /
• 2002

Astaxanthin (3,3＇-dihydroxy-${\beta}$, ${\beta}$-carotene-4-4＇-dione), a natural pigment of pink to red color, is widely distributed in nature particularly in the skin layer of salmonoids and the crust of shrimp, lobster, etc. Recently, it was produced from the yeast culture of Phaffia rhodozyma. Because of its high thermal stability and antioxidant functionality, its applications can be extended into food, cosmetics, and pharmaceutical ingredient beyond the traditional feed additive. Because of its very high lipophilicity, astaxanthin has been extracted traditionally by strong organic solvents such as chloroform, petroleum ether, acetone, etc. In this study, we developed a surfactant-based solubillization system for astaxanthin, and used it to extract astaxanthin from disrupted yeast cells. Among Tween 20, Triton X-100 and SDS, Tween 20 was identified as the most suitable surfactant in terms of extraction capacity and safety. The ethylene oxide group of Tween 20 was identified as the most significant factor to increase the HLB value that determined the extraction capacity. The effects of micelle formation condition, such as the molar ratio of astaxanthin and Tween 20, pH, and ionic strength were also investigated. pH and ionic strength showed no significant effects. The optimal molar ratio between astaxanthin and Tween 20 was 1 : 12. Antioxidant activity of astaxanthin was higher than ${\beta}$-carotene and ${\alpha}$-tocopherol. Astaxanthin in the crude extract from the yeast cell was more resistant to air and/or light degradation than pure astaxanthin, probably because of the presence of other carotenoids and lipids.