• Electrical & Electronic Materials
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• v.8 no.1
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• pp.21-26
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• 1995

Highly sensitive and mechanically stable gas sensors have been fabricated using the microfabrication and micromaching techniques. The sensing material used to detect the offensive trimethylarnine ((CH$_{3}$)$_{3}$N) gas is 6 wt% $Al_{2}$O$_{3}$-doped, 1000.angs.-thick ZnO deposited by r. f. magnetron sputtering. The optimum operating temperature of the sensor is 350.deg.C and the corresponding heater power is about 85mW. Excellent thermal insulation is achieved by the use of a double-layer structure of 0.2.mu.m -thick silicon nitride and 1.4.mu.m-thick phosphosilicate glass(PSG) prepared by low pressure chemical vapor deposition(LPCVD) and atmospheric pressure chemical vapor deposition(APCVD), respectively. The sensors are mechanically stable enough to endure at least 43, 200 heat cycles between room temperature and 350.deg. C.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.263-263
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• 2000

Electromagnetic Suspension(EMS) System produces no noise, friction and heat through non-contacting operation Therefore, the applicable device using EMS system has a lot of attraction in case of the high-speed and non-contacting transmission EMS with nonlinear properties requires a precise airgap position control and stable kinematics characteristics under the disturbances, In this study, the nonlinear system was linearized by a Nonlinear Feedback Lineariztion(NFL) method. The NFL method requires that the modelling should be exact, and the state variables should be measured and a rapidly operating controller be necessary on account of a heavy data calculating In the experiments. the ideal control characteristics of the NFL was acquired through simulation at first. then the characteristics of the actual system were compared with those of simulation. In addition, the results by NFL were examined and analysed considering the characteristics of the PID control. The Control by NFL shows much stable control characteristics than the PID control. Whereas, the steady state errors occur for various disturbances. hence a robust control design is remained for a further study.

• Natural Product Sciences
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• v.20 no.2
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• pp.119-125
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• 2014

According to the results of my study on the chromatographic analysis of fresh ginseng (Panax ginseng C. A. Meyer) roots, most of the contents of protopanxadiol ginsenosides $Rb_1$, Rc, $Rb_2$, and Rd are derived from the corresponding malonyl ginsenosides in fresh ginseng by a heat process. Also, I confirmed that acetyl ginsenosides are naturally occurring constituents in fresh ginseng, not decarboxylates from malonyl ginsenosides. Seven neutral ginsenosides $Rg_1$, Re, Rf, Rc, $Rb_1$, $Rb_2$, and Rd were transformed to specific conversions in red ginseng preparation conditions. The conversion paths progress by three rules concluded from my study. These conversion rules are I: the ether bond is stable at positions 3 and 6 in the dammarane skeleton, II: the ether bond between sugars is stable in glycosides, and III: the ether bond to glycosides is unstable at position 20 in the dammarane skeleton.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.593-598
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• 1996

Previously, in trying to prepare perovskite type oxide powders by microwave heating, we found out a non-equilibrium argon plasma is generated around the powders and discharge continues stable at atmospheric pressure. In this study, we tried the plasma decomposition of heat-stable higher organic compound such as palmitic acid which is the principal constituent of the fimger fats. It was proved that suitable amount of coexistence of oxygen radicals into the argon flow accelerates the decomposition of palmitic acid. The argon-oxygen mixed gas plasma was able to perform a complete elimination of higher organic compound.

• Journal of the Korean Society of Combustion
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• v.1 no.2
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• pp.31-39
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• 1996

This study was carried out to delvelop the burner for condensing gas boiler which can save energy by utilizing latent heat of combustion gas. A perforated can-type burner adopting premixed flame was chosen to reduce NOx emission and to simplify the manufacturing process. Basic experiments using unit cell combustor have been conducted to obtain data about the design parameters of perforated burner surface which can make stable flame for a wide operating conditions. Can-type burners designed on the basis of above data shows that flames are stable and also CO and NOx emission are low for a wide operating range.

• Transactions of Materials Processing
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• v.28 no.3
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• pp.123-129
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• 2019

Hypereutectic Al-Si alloys have been widely utilized for wear-resistant components in the automotive industry. In order to expand the application of Hypereutectic Al-Si alloys, the addition of alloying elements forming a stable precipitate at high temperature is required. Thermally stable inter metallic compounds can be formed through the addition of transition elements such as Fe, Ni to Al alloys. However, the amount of transition element to be added to Al alloys is limited due to their low solid solubility. Also, hypereutectic Al-Si-Fe alloys form coarse primary Si phases and needle-shaped intermetallic compounds during solidification in the general casting processes. In this study, the effects of the destruction of Intermetallic compound and Si phase are investigated via hot extrusion. Both the microstructure and mechanical properties are discussed under different extrusion conditions.

• Journal of Food Hygiene and Safety
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• v.6 no.3
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• pp.147-155
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• 1991

Enterotoxigenic E. coli is one of the major causative agents of the infantile diarrhea and traveler's diarrhea. The heat-stable enterotoxin(ST) is thought to be a virulence factor in the pathogenesis of the diarrhea and to be a maker for identification of the enterotoxingeic E. coli from non pathogenic E. coli. The isolate of enterotoxigenlc E. coli was isolated from swine during 1989 year(from 5 to 10 month) in the Kyong-gi and Chung-Cheong provinces, and three strains(KM-4, KM-7 and KM-12) was selected from 189 isolates of ST producing E. coli. The detection of a ST produced of the isolated E. coli was performed by the infant mouse assay(IMA). This study was designed to know optimal conditions for the production of the ST and the molecular properties of plasmids of the enterotoxigenic E. coli. Amount of ST produced were the most at initial pH 8.5~9.0 of succinate salts medium culture. The cultural time of the same medium was accumulated the highest level of ST was at the 14 to 16 hours, and then stationary phase was at the 20 hours. From this experiment the KM-7 strain was selected among ST producing strains by IMA. Partial plasmid-curing experiment was done to select plasmid encoding for ST among other plasmids and then comparing the plasmid pattern of ST producing strain(KM-7) with those of other ST non-producing strains, it is found that ST gene exists on the about 80 Kbp plasmid. Each fragment of this plasmid digested with EcoRl was ligated to vector pBR 322 and transformed into E. coli K-12. A clone producing ST(eKT 53) was selected by IMA. The EcoRl digestion pattern of the isolated plasmid(pKD 37) from the ST producing clone it is indicated that the size of the inserted fragment in eKT 53 strain is 16 Kbp. The cultured supernatant of eKT 53 strain was positive result of ST production in IMA.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.1
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• pp.76-83
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• 1992

Enterotoxigenic E. coli is one of the major causative agents of the infantile diarrhea and traveler's diarrhea. The heat-stable enterotoxin (ST) is thought to be a virulence factor in the pathogenesis of the diarrhea and to be a maker for identification of the enterotoxigenic E. coli from non pathogenic E. coli. ST producing E. coli KM-7 strain was isolated from the swine and molecular cloning of ST gene of KM-7 strain. Transformant eKT-53 $(ST^+,\;LT^-)$ was selected by infant mouse assay (IMA). The culture supernatant of eKT-53 strain was performed purification by multipled steps. The culture supernatant (crude ST) was purified by sequentially applying batch adsorption chromatography on Amberlite XAD-2 resin, ion exchange chromatography on DEAE-Sephacel anion exchanger, gel filtration chromatography on Bio-Gel P-6 and preparative polyacrylamide slab gel electrophoresis. About 113-fold purification was achieved with a yield of about 11% of crude ST and the minimum effective dose(MED) of this purified ST was about 2.8ng in IMA. Homogeneity of purified ST was demonstrated by showing a single band in analytical SDS polyacrylamide disc gel electrophoresis.

• Clean Technology
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• v.21 no.1
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• pp.22-32
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• 2015

In this study, we studied the characteristics of ion exchange for treatment of HSS (heat stable salts) which cause performance reduction in CO₂ gas capture amine solution using anion exchange resins. The optimum HSS removal efficiency, 96.1% was obtained when using strong base anion exchange resin SAR10 at dosage 0.05 g/mL, 316 K, pH 12 and the best resin regeneration efficiency, 78.8% was obtained using NaOH solution of 3 M at 316 K. The adsorption data were described well by the Freundlich model and the sorption intensity(n) was 2.0951 lying within the range of favorable adsorption. The adsorption selectivity coefficients were increased by increasing valences and size of ion and desorption selectivity coefficients showed a contradictory tendency to adsorption selectivity coefficients. By continuous HSS removal experiments, 13.3 BV of HSS contaminated solution was effectively treated and the optimum NaOH solution consumption was 5.2 BV to regenerate resins.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1137-1143
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• 2009

Experiments were conducted to evaluate pool boiling heat transfer performance between plain and micro finned surfaces with FC-72, which is chemically and electrically stable. Three kinds of micro fins with the dimension of $100{\mu}m\;{\times}\;10{\mu}m$, $150{\mu}m\;{\times}\;10{\mu}m$ and $200{\mu}m\;{\times}\;10{\mu}m$ (width $\times$ height) were fabricated on the surface of a silicon chip. The experiments were carried out on the liquid subcooling of 5, 10 and 15 K under the atmospheric condition. The micro finned surface with a larger fin width of $200{\mu}m$ provided a better pool boiling heat transfer performance. Also, the micro finned surfaces showed a sharp increase in heat flux with increasing wall superheat and a larger heat transfer enhancement compared to a plain surface.