• Fire Science and Engineering
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• v.16 no.3
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• pp.26-31
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• 2002

Bromotrifluoromethane(halon-1301) and bromochlorodifluoromethane(halon-1211) have been widely used as a clean fire extinguishing agents due to their outstanding properties. However, production and use of halon are currently being phased out under an international agreements Montreal Protocol because of global environmental concerns and HFCs have been considered as promising alter-natives for the replacement of halon since their ozone depletion potentials are low. The vapor-liquid equilibrium data are required as important basic information in evaluating the solubility of clean fire extinguishing agents and determining their optimal compositions. In this work, we chose HFCs such as HFC-22 HFC-125, and HFC-l34a for gaseous fire extinguishing agents and nitrogen as a pressurization gas for a proper jet velocity of these agents. Phase equilibria for binary mixtures of nitrogen/HFC-22, nitrogen/HFC-125, and nitrogen/HFC-l34a were measured in the temperature range from 283.15K to 303.15K. For equilibrium measurement, we used a circulation type apparatus in which both vapor and liquid phases were continuously recirculated. The experimental data were relatively well correlated with the Peng-Robinson equation of state with Wong-Sandier mixing rules.

• Journal of agricultural medicine and community health
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• v.16 no.2
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• pp.141-153
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• 1991

Free amino acid(FAA), free fatty acid(FFA), and amino acid obtained by hydrolysis of protein components of cystic fluid(CF) of Cysticercus cellulosae in pig and man were analyzed. FFA was analyzed by gas chromatography using Varian model 2700, and flame ionization detector with 6 feet${\times}$1/4inch glass column. Flow rate of $N_2$ was 30 ml/min, $H_2$ was 30 ml/min, air was 350 ml/min respectively and chart speed was 1 cm/min. Amino acid was analyzed by high performance liquid chromatography using Waters model 441, and fluorescence detector at 338nm/425nm with column of amino acid analyzer. Buffer A of mobile phase was pH 3.05 and pH of buffer B was 9.6 respectively. The results obtained were as follows : Seven FFAs containing 12~18 carbons were detected : Saturated fatty acids were lauric acid ($C_{12}$), myristic acid($C_{14}$), palmitic acid($C_{16}$), Stearic acid($C_{18}$). Unsaturated fatty acids were oleic acid($C_{12}^{=1}$), linoleic acid($C_{12}^{=2}$), and one unidentified fatty acid was detected. Generally much more quantity of FFA was determined in CF obtained from pig than that from man. FFA of the largest quantity was palmitic acid; 0.078 mg/ml. Eighteen FAAs were detected and the largest quantity was alanine. Ouantity of alanine was 386 ug/ml in CF from pig 108 ug/ml in CF from man respectively. while histidine in CF from pig was 273 ug/ml, that from man was only 4.3 ug/ml. Eighteen amino acids were identified by hydrolysis of protein in CF from man. But, histidine was not identified in CF from pig. Amino from pig and ug/ml from man.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.235-242
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• 2004

Si, NH$_4$Cl, NaN$_3$, NaCl, $N_2$ were used as raw materials for preparation of $\alpha$-Si$_3$N$_4$ powder. NH$_4$Cl and NaN$_3$ were used as additives, and NaCl was used as a diluent. Initial $N_2$ gas pressure in the SHS reactor was 60 atm. In preparation of $\alpha$-Si$_3$N$_4$, the reactivity and the properties of the products were examined with the various kinds of additives and the content of diluent. At first, the optimum reaction system for the preparation of $\alpha$-Si$_3$N$_4$ is examined and then the optimum composition was examined in the optimum reaction system. The optimum reaction system was Si-$N_2$-additive(NH$_4$Cl+NaN$_3$)-diluent(NaCl) and the optimum composition was 38 wt%Si+50 wt%(NH$_4$Cl+NaN$_3$)+12 wt%NaCl. The maximum fraction of $\alpha$-phase of Si$_3$N$_4$ produced in this condition was 96.5 wt% and the shape of the $\alpha$-Si$_3$N$_4$ produced in this condition was an irregular fiber with a length of 10 ${\mu}{\textrm}{m}$ and a diameter of 1 ${\mu}{\textrm}{m}$.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.775-780
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• 1995

Thin films of titanium nitride are formed using the tetrakis-dimethyl-amino-titanium (TDMAT(Ti[N($CH_3$)$_2$]$_4$)) under various conditions. The formation of TiN films has been obtained from the thermal decomposition of the Ti-precursor and the gas phase reaction between TDMAT and ammonia(NH$_3$). The resistivity of the MOCVD film can be attributed to their impurity. Especially the curve fitting graph of XPS data is revealed that main impurities in the films as carbon and oxygen make various interstitial compounds which has influenced physical and electrical properties of the film. In the contact hole with the aspect ratio of 3:1 and the diameter of 0.5${\mu}{\textrm}{m}$, the SEM morphology shows that the step coverage is more decreased in the films formed y flowing ammonia additionally than the films formed by pyrolysis of TDMAT and the phenomenon is probably related with the activation energy.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.9
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• pp.1471-1476
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• 2005

The optimization of ethanol treatment was carried out by response surface methodology (RSM) which was expressed through change of ${\Delta}$E value for improvement of color of dried large anchovy. The optimum condition was shown as treatment with 7 volumes (v/m) of ethanol at $50^{\circ}C$ for 9 hrs. At this condition, the removal rates of trimethylamine (TMA) and fat considered as fishy odor-causing materials were 81.1 and $77.4\%$, respectively, when analyzed by solid phase microextraction (SPME)/gas chromatography and soxhlet method, respectively The effect of citric acid on the removal rate of TMA was the highest one among organic acid treatments. The removal rate of TMA was affected greatly by the concentration of organic acid rather than the temperature and time of treatment. $73\%$ of TMA was removed by treatment of $1\%$ of citric acid at $20^{\circ}C$ for 20 min. Specially, above $90\%$ of TMA could be removed by the combination of alcohol and citric acid treatment. In vitro absorption rate of calcium was also increased to $12.3\%$ by the combination of alcohol and citric acid treatment compared with $2.9\%$ of control.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.689-698
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• 2007

A new technique was proposed for the determination of alkylphenols, chlorophenols and bisphenol A in korean aquatic biological samples. The alkylphenols, chlorophenols and bisphenol A in korean aquatic biological samples were extracted with acetonitrile and then acetonitrile layer was refrigerated at $-60^{\circ}C$ for 2 hours(freezing filtration method). Also, solid-phase extraction(SPE) was used to XAD-4 and subsequent conversion to isobutoxycarbonyl(isoBOC) or tert-butyldimethylsilyl(TBDMS) derivatives for sensitive analysis with gas chromatography/mass spectrometry-selected ion monitoring(GC/MS-SIM) mode. For isoBOC derivatization and TBDMS derivatization the recoveries were $70.1\sim150.6%$ and $93.8\sim108.3%$, the method detection limit(MDLs) of bisphenol A for SIM were $0.062{\mu}g/kg$ and $0.010{\mu}g/kg$, and the SIM respectively. When these methods were applied to korean aquatic biological samples, the concentrations of the 11 phenolic EDCs were $0.675\sim1.970{\mu}g/kg$.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.75-83
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• 2014

The present study estimated nitrogen budget of South Korea including nitrogen oxides (NOx) in 2011. Emission sources of NOx were calculated with the higher contributors, such as vehicles, businesses, power plants, based on the IPCC and EPA reports. Moreover, nitrogen budget was separated for city, agriculture livestock and forest. Input and output were chemical fertilizer, crop uptake, fixation, irrigation, compost, leaching, volatilization, imported food, denitrification, runoff, and so on. Annual nitrogen input were 1,692,650 ton/yr and output were 837,739 ton/yr which were increased from 2010 budget. In 2011, NOx emissions by vehicles, power plants, and businesses were 308,207 ton/yr, 601,437 ton/yr, and 469,946 ton/yr, respectively. Including nitrogen oxide, total nitrogen input and output in 2011 was calculated as 5,652,366 ton/yr and 1,425,371 ton/yr, respectively.

• Analytical Science and Technology
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• v.13 no.2
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• pp.136-150
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• 2000

For the identification of unknown drugs in biological samples, we attempted rapid high performance thin layer chromatographic method which is sensitive and selective chromatographic analysis of high performance thin layer chromatography (HPTLC) with automated TLC sampler and ultra-violet (UV) scanner. We constructed HPTLC database (DB) on two hundred five drugs by using the data of Rf values and UV spectra (scan 200-360 nm) as well as gas chromatography/mass spectrometry (GC/MS) DB on ninety six drugs by using the data of relative retention time (RRT) on lidocain and mass spectra. After extracting drugs in biological sample by solid phase extraction (Clean Screen ZSDAU020), we applied them to HPTLC and GC/MS DB. Drugs, especially extracted from biological samples, showed good matching ratio to HPTLC DB and these drugs were confirmed by GC/MS. In conclusion, this DB system is thought to be very useful method for the screening of unknown drugs in biological samples.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.1-11
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• 2004

Foam reduces the mobility of gas phase in porous media to overcome gravity override and to divert acid into desired layers in the petroleum industry and to enhance the efficiency of environmental remediation. Recent experimental studies on foam show that foam exhibits a remarkably different flow rheology depending on the flow regime. This study, for the first time, focuses on the issues of foam diversion process under the conditions relevant to groundwater remediation, combining results from laboratory linear-flow experiments and a simple numerical model with permeability contrasts. Linear flow tests performed at two different permeabilities (k = 9.1 and 30.4 darcy) confirmed that two flow regimes of steady-state strong foams were also observed within the permeability range of shallow geological formations. Foam exhibited a shear-thinning behavior in a low-quality regime and near Newtonian rheology in a high-quality regime. Data taken from linear flow tests were incorporated into a simple numerical model to evaluate the efficiency of foam diversion process in the presence of permeability contrasts. The simple model illustrated that foam in the high-quality regime exhibited a successful diversion but foam in the low-quality regime resulted in anti-diversion, implying that only foam in the high-quality regime would be applicable to the diversion process. Sensitivity study proved that the success of diversion process using foam in the high-quality regime was primarily controlled by the limiting capillary pressures (${P_c}{^*}$) of the two layers of interest. Limitations and implications are also discussed and included.

• Korean Journal of Food Science and Technology
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• v.45 no.3
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• pp.267-273
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• 2013

We aimed to improve the flavor quality of plain yogurt, which is known to be sour and less desirable in flavor, varying concentrations of a buckwheat saccharification solution (BSS) were added to milk, followed by fermentation with commercially available mixed strains of lactic acid bacteria. Volatile compounds were analyzed using the gas chromatography-headspace-solid phase microextraction (GC-HS-SPME) method. Fermentation properties, including pH, titratable acidity, viable cells, viscosity, and color value were also measured. Eleven volatile compounds were identified with GC-MS. Of which, diacetyl, butanoic acid, and 2-heptanone proportionally increased as the levels of BSS increased. Undesirable compounds such as acetic acid and 2-butanone, decreased as BSS concentration increased. Fermentation properties were significantly altered with the addition of BSS. Our findings indicate that the flavor quality of plain yogurt can be improved by adding BSS for fermentation, with an additional health benefit from buckwheat.