• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2615-2620
• /
• 2014

Ni/$La_2O_3$ with a high dispersion was prepared by reduction of $La_2O_3$ perovskite oxide to examine the catalytic activity for the $CO_2-CH_4$ reaction. The Ni/$La_2O_3$ catalyst was found to be highly active for the reaction. The ratios of $H_2$/CO were measured in a flow of the reaction mixture containing $CO_2/CH_4$/Ar using an on-line gas chromatography system operated at 1 atm and found to be varied with temperature between 0.66 and 1 in the temperature range of $500-800^{\circ}C$. A kinetic study of the catalytic reaction was performed in a static reactor at 40 Torr total pressure of $CO_2/CH_4/N_2$ by using a photoacoustic spectroscopy technique. The $CO_2$ photoacoustic signal varying with the concentration of $CO_2$ during the catalytic reaction was recorded as a function of time. Rates of $CO_2$ disappearance in the temperature range of $550-700^{\circ}C$ were obtained from the changes in the $CO_2$ photoacoustic signal at early reaction stage. The plot of ln rate vs. 1/T showed linear lines below and above $610^{\circ}C$. Apparent activation energies were determined to be 10.4 kcal/mol in the temperature range of $550-610^{\circ}C$ and 14.6 kcal/mol in the temperature range of $610-700^{\circ}C$. From the initial rates measured at $640^{\circ}C$ under various partial pressures of $CO_2$ and $CH_4$, the reaction orders were determined to be 0.43 with respect to $CO_2$ and 0.33 with respect to $CH_4$. The kinetic results were compared with those reported previously and used to infer a reaction mechanism for the Ni/$La_2O_3$-catalyzed $CO_2-CH_4$ reaction.

• Korean Journal of Food Science and Technology
• /
• v.51 no.6
• /
• pp.531-536
• /
• 2019

In this study, the optimization of the manufacturing process for the oil-in-water emulsification of rice bran oil was performed by response surface methodology (RSM) using varying amounts of the emulsifier (0.05-0.25%), varying rotation speeds of the homomixer (4,000-8,000 rpm), and varying water to oil ratios (0.8-1.6%) as independent variables, and the emulsion stability index (ESI) as the dependent variable. The optimization conditions predicted by the RSM model were 0.2%g of the total amount of the rice bran oil emulsion, emulsified at the homomixer rotation speed of 6,700 rpm using a water to oil ratio of 1:3. The ESI of the rice bran oil emulsion prepared under the optimized conditions was 95.7%, which was similar to the predicted value of 94.4% obtained by the RSM model. The transmission stability and the backscattering values were found to agree with each other over time and the turbiscan stability index was less than 0.7, indicating that the aggregation and upper floatation were less while the dispersion stability was maintained.

• Fire Science and Engineering
• /
• v.31 no.3
• /
• pp.1-10
• /
• 2017

This study examined the risk of accidents when handling hazardous materials in hazardous materials storage facilities without safety facilities. In the case of illegal dangerous cargo containers, the burning rate is very fast in the case of fire, which leads to explosions, that are damaging and difficult to control. In addition, accidents that occur in flammable liquid hazardous materials are caused mostly by accidents that occur in the space due to leakage. Therefore, the variables that affect these accidents were derived and the influence of these variables was investigated. Numerical and computational fluid dynamics programs were used to obtain the following final results. First, when a flammable liquid leaks into a specific space, it is influenced by temperature and relative humidity until a certain concentration (lower limit of combustion) is reached. In the case of temperature, it was found that the reaching time was shorter than the flash point In addition, the effect of variables on pool fire accidents of leakage tanks is somewhat different, but the variables that have the largest influence are the wind speed. Therefore, it is expected that the results of this study will be used as basic data for similar numerical analysis and it will provide useful numerical information about the accidental leakage of hazardous materials under various research conditions.

• Journal of the Korean Applied Science and Technology
• /
• v.33 no.2
• /
• pp.247-254
• /
• 2016

Since microzirconia has excellent thermal and mechanical properties with high chemical and electrical resistance, it can be used in various fields. When the surface of zirconia becomes hydrophilic, its dispersibility in water will be improved as well as the resistance to most hydrophobic contaminants will be increased. In this study, we investigated the introduction of a hydrophilic groups on the microzircornia surface through hydrolysis and condensation reactions with two different silanes containing hydrophilic functional groups, such as ${\gamma}$-aminopropyltrimethoxysilane (APS) and ${\gamma}$-ureidopropyltrimethoxysilane (UPS) at different pH and concentration conditions. A covalent bond formation between the surface hydroxyl groups of zirconia and that of hydrolyzed silanes was confirmed by ninhydrin test and FT-IR spectroscopy. However, the presence of Si on the surfaces of both silane modified microzirconias was unable to detect by SEM/EDS technique. In addition, particle size analysis results provide that the size of microzirconia was changed to smaller or bigger than that of original zirconia due to crushing and aggregation during the modification process. The water dispersibility was improved for only APS modifed zirconia (AS-2 and AS-3) under neutral pH condition, but the water dispersibility and stability for all cases of 0.5~2% UPS modifed zirconia (US series) were much improved.

• Journal of the Korean Society of School Health
• /
• v.23 no.1
• /
• pp.63-70
• /
• 2010

Purpose: To identify the need to reform in the crisis response of Health Teacher, School Nurse, in elementary school during epidemic outbreak of influenza H1N1. Methods: 139 elementary health teachers, school nurse, in seoul elementary school responded in the questionnaire, and we analysed by using frequency and percent, t-test, and paired t-test. Results: The Job status became 121% more 'during influenza H1N1 (flu) outbreak' than Job status of 'before outbreak'. The proportion of the flu-related duty among their daily workload was up to 77.5%. The administration-related workload of the flu-related duty was 30.8%. and students' health assessment including temperature measurement 18.7%. Furthermore, an impediment of usual daily work due to an increaed flu-related workload was 95.7%, and no alternative plan such as disposition of assistant labor force was 86.1%. Especially, an impediment of health education was 61.0%, so the major concern was the loss of health education. We compared average scores (a five-point Likert scale) of health teachers' work motivation, exhaustion, work relationship and Job management of 'during' with 'before' flu-outbreak. The difference range of 'during' minus 'before' work motivation score was from -0.4 points to -0.9; work exhaustion range from 1.8 to 1.9; the difficulty of relationship between students, school personnel, parents of students, and health teachers from 1.4 points to 1.3 points; and the consideration of changing Job, taking time off from the Job and retirement from 1.4 to 1.6 points. Conclusion: The health teachers had a heavy workload due to flu-outbreak. They also experienced the impediment of usual work implementation. However, there was a shortage of alternative plan such as disposition of an assistant labor force. Under their Job status like this, the health teachers' motivation score was decreased and work exhaustion was increased. Furthermore, they had a lot of relation difficulty with students and school personnel. Therefore, we suggested that in contrast to the usual Job status, there is a need to have a prepared response during school crisis like flu-outbreak such as improved response system in seoul metropolitan education office, simplification or dispersion of administrative work, and temporary call-center for simple inquiries or advices.

• Journal of Bio-Environment Control
• /
• v.29 no.1
• /
• pp.73-79
• /
• 2020

The objective of this study is to analyze the heat transfer loss of covering materials in a single-span plastic greenhouse under the steady-state wind environment. To achieve this objective, the following were conducted: (1) design of a small-scaled wind tunnel (SCWT) to analyze heat losses of the greenhouse and its performance; (2) determination of the overall heat transfer coefficient (OHTC) for the covering materials using a small-scaled greenhouse model. The SCWT consists of the blowing, dispersion, steady flow, reduction and testing areas. Each part of the SCWT was customized and designed to maintain air flow at steady state and to minimize the variances in the SCWT test. In this study, the OHTCs of the covering materials were calculated by separating each with the roof, side wall, front and back of the small-scaled greenhouse model. The results of this study show that the OHTC of the roof increases as wind speed increases but the zones in which the increase rate of the OHTC decreased, were distinguished by wind tunnel wing speed of 2 ms^-1. For the side wall, the increase rate of the OHTC was particularly higher in the 0-1 ms^-1 zone.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.4
• /
• pp.705-713
• /
• 2016

For the soft ground construction, the factors not considered in the design stage occurs in the construction stage so that they cause the increase of the construction cost due to the structural stability and the design change. The subject of the study is the construction section of the industrial complex access road made in the Ochang region of Chungcheongbuk-do. The study is concerned with selecting the soft ground handling method such as the replacement method using rock debris and the surcharge reflecting the service load as the soft ground handling measure and analyzing the effect of reducing the construction cost with the stability of structures and the reduction of the construction period. The soft ground in the study section consists of sandy and cohesive soil and is 2.4m to 5.5m deep. It is distributed unevenly between the 1.5m to 5.9m stratums under the ground surface. Settlement is not serious, but the future uneven settlement and difference are expected so that the future settlement behavior is estimated by analyzing the site measurement results after the soft ground treatment. Moreover, in consideration of the regional characteristics and economic efficiency, soil with good quality is replaced with rock debris as the replacement material so that 29% of the construction cost is reduced due to the increase of stability and the reduction of duration. If the estimation of the dispersion of the pore water pressure within the dam body and the change of the underground water level and the relation of the actually measured soft ground with consolidation is studied further on the basis of the study, it is expected that the behavior of the soft ground will be correctly estimated in various site conditions.

• Textile Coloration and Finishing
• /
• v.1 no.1
• /
• pp.19-25
• /
• 1989

In past, dye diffusion and dyeing rate in fibers have been emphasized in dyeing phenomena. However, in the light of the properties of colloids in the surface of disperse phase and dispersion, there exist specific characters such as adsorption or electric double layer, which seems to play important roles in determining the physiochemical properties in the dyeing system. Electrostatic bonding, hydrogen bonding and Van der Waals adsorption are common in dyeing as well as covalent bonding. Particularly, electrostatic bonding is premised on the existance of ionic radicals in fibers. The present study was aimed to clarify the electrokinetic phenomena of dyeing through the role of electric double layer by ion in amphoteric fibers with different ionic effects under different pH. Spectrophotometric analysis method was used to compare dyeing condition of surface, which can be detected by electrokinetic phenomena and the inner of fibers after deceleration of dyed fibers. Nylon and wool, the typical amphoteric fibers were dyed with monoazo acid dyes such as C.I. Acid Orange 20, and C.I. Acid Orange 10. Various combinations were prepared by combining pH, temperature and dye concentration, in order to generate streaming electric potential which were measured by microvolt meter and specific conductivity meter. The results were transformed to zeta potential by Helmholtz-Smoluchowski formular and to surface electric charge density by Suzawa formular, surface dye amount, and effective surface area of fibers. The amount of dyes of inner fibers were also measured by the Lambert-Beer’s law. The main results obtained are as follows. 1. By measuring zeta pontential, it was possible to detect the dyeing mechanism, surface charge density, surface dye amount and effective surface area concerning dye adsorption of the amphoteric fibers. 2. Zeta pontential increases in negative at low pH and high dye concentration in the process of dyeing. This implied that there existed ionic bond formation in the dyeing mechanism between acid dyes and amphoteric fibers. 3. Dibasic acid dye had little changing rate in zeta potential due to the difference in solubility of dye and in number of dissociated ions per dye molecule to bond with amino radicals of amphoteric fibers. The dye adsorption of mono basic acid dye was higher than that of dibasic acid dye. 4. The effective surface areas concerning dyeing were $6.3E+05\;cm^2/g$ in nylon, $1.6E+07\;cm^2/g$ in wool fiber being higher order of wool then nylon.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.11 no.1
• /
• pp.42-45
• /
• 2008

It has been reported that FRP (fiber reinforced plastic) can be recycled by separating into layers instead of crushing into powder. F-fiber obtained from roving layer separated from FRP, has bigger tensile strength than the bundle of glass fibers of which FRP was made (more than 90%). SEM image of F-fiber shows the presence of some resin. Under the proposition of usage of F-fiber in the concrete material, tensile strength is examined after soaking in a basic solution (NaOH+KOH). The reaction mechanism of strength loss may be considered as an attack of hydroxide ion ($OH^-$) on a chemical bond of Si-O-Si of glass fiber. The simulation graph of the strength loss data implies certain reaction mechanism. While in the early stage kinetically controlled reaction results in a fast drop of tensile strength, after 30 days dispersion rate of hydroxide ion plays a major role in strength loss. This result is similar to the one for the AR glass. An extrapolation of the graph would make an assumption about the lift time of F-fiber possible.

• Elastomers and Composites
• /
• v.46 no.2
• /
• pp.164-170
• /
• 2011

In this study, silicone rubber filled with environmentally-friendly perlite was prepared by mechanical mixing in order to improve thermal properties, such as heat and fire resistances. We found that the properties of silicone rubber composites depended on perlite concentration by various characterization methods. Thermogravimetric analysis(TGA) indicated that the initial degradation temperature of silicone/perlite composite was higher than that of pristine silicone rubber. The gas torch test showed that the opposite side temperature of composite materials was remarkably low as compared to that of pristine silicone rubber. In addition, the composites containing 5 wt% and 10 wt% of perlite showed remarkable thermal stability at elevated temperatures according to the results of both fireproof furnace tests under the RABT condition and carbonization furnace tests. The images from a scanning electron microscope(SEM) showed the degree of dispersion of perlite in silicone rubber. Finally, it was confirmed that limited oxygen index(LOI) was increased with perlite concentration.