• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.411-419
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• 2002

In this study, the series of ultrasonic irradiation for removal of refractory aromatic compounds has been selected as a model reaction in the batch reactor system in order to obtain the reaction kinetics. The products obtained from the ultrasonic irradiation were analysed by GC and GC/MSD. The decomposition of benzene produced toluene, phenol, and C1-C4 compounds, while the intermediates during the ultrasonic irradiation of 2,4-Dichlorophenol(DCP) were phenol, HCl, catechol, hydroquinone, and benzoquinone. It was found that more than 80% of benzene, and 2,4-DCP solutions were removed within 2 hours in all reaction conditions. The reaction order in the degradation of these three compounds was verified as pseudo-zero or first order. From the fore-mentioned results, it can be concluded that the refractory organic compounds could be removed by the ultrasonic irradiation with radicals, such as $H{\cdot}$ and $OH{\cdot}$ radical causing the high increase of pressure and temperature. Finally, it appeared that the technology using ultrasonic irradiation can be applied to the treatment of refractory compounds which are difficult to be decomposed by the conventional methods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.1
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• pp.1-9
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• 1986

In order to isolate and clarify the antioxygenic substances from the browning reaction products, the antioxidant activity of various amino acids and their browning reaction products were measured when they were reacted with xylose. Among nonpolar amino acids Met and Trp appeared to have stronger antioxidant effect than others. Most of polar and basic amino acids, however, did not have antioxidant activity. Ser and Cys showed a rather slight prooxidant effect. The browning reaction products of Trp and His had a higher level of antioxidant activity than that they were reacted as free amino acids. But the browning product of Met did not show the antioxidant activity. When all amino acids were divided on their polar characteristics, the higher optical density of the browning reaction products showed, the stronger antioxidant activity revealed.

• Human Ecology Research
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• v.53 no.4
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• pp.351-362
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• 2015

This study examined differences in counseling work and work performance in a firm by the individual characteristics of counselors. This study also investigated the effects of consumer counselor's reaction and stress from counseling work on counselor satisfaction in regards to counseling work and work performance. The results of this study are as follows. First, consumer counselor's work satisfaction was high for female counselors, university-educated, with middle or high status occupations, had short work years, had a higher tendency towards consumerism, worked in a counseling department with an active reaction policy towards consumer complaints, and had a lower level. Second, the work performance of a counselor was high for those who were older, university-educated, had short work years, worked in large-size counseling departments in a firm, had a higher tendency of consumerism, and worked in counseling departments with active reaction policies toward consumer and consumer's complaints. Third, consumer counselor's work stress effected work satisfaction but did not influence work performance. The counselor's reaction towards consumer's complaints influenced the work performance but did not influence the work satisfaction of a counselor.

• Bulletin of the Korean Chemical Society
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• v.20 no.1
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• pp.35-41
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• 1999

Stability characteristics of hyperbolic reaction-diffusion equations with a reversible Brusselator model are investigated as an extension of the previous work. Intensive stability analysis is performed for three important parameters, Nrd, β and Dx, where Nrd is the reaction-diffusion number which is a measure of hyperbolicity, β is a measure of reversibility of autocatalytic reaction and Dx is a diffusion coefficient of intermediate X. Especially, the dependence on Nrd of stability exhibits some interesting features, such as hyperbolicity in the small Nrd region and parabolicity in the large Nrd region. The hyperbolic reaction-diffusion equations are solved numerically by a spectral method which is modified and adjusted to hyperbolic partial differential equations. The numerical method gives good accuracy and efficiency even in a stiff region in the case of small Nrd, and it can be extended to a two-dimensional system. Four types of solution, spatially homogeneous, spatially oscillatory, spatio-temporally oscillatory and chaotic can be obtained. Entropy productions for reaction are also calculated to get some crucial information related to the bifurcation of the system. At the bifurcation point, entropy production changes discontinuously and it shows that different structures of the system have different modes in the dissipative process required to maintain the structure of the system. But it appears that magnitude of entropy production in each structure give no important information related for states of system itself.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.25-32
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• 2022

The seismic behaviors of the arch structure vary according to the rise-span ratio of the arch structure. In this study, the rise-span ratio (H/L) of the example arch structure was set to 1/4, 1/6, and 1/8. And the installation angle of the seismic isolator was set to 15°, 30°, 45°, 60° and 90°. The installation angles of the seismic isolator were set by analyzing the horizontal and vertical reaction forces according to the rise-span ratio of the arch structure. Due to the geometrical and dynamic characteristics of the arch structure, the lower the rise-span ratio, the greater the horizontal reaction force of the static load, but the smaller the horizontal reaction force of the dynamic load. And if the seismic isolator is installed in the direction of the resultant force of the reaction forces caused by the seismic load, the horizontal seismic response becomes small. Also, as the installation angle of the seismic isolator increases, the hysteresis behavior of the seismic isolator shows a plastic behavior, and residual deformation appears even after the seismic load is removed. In the design of seismic isolators for seismic response control of large space structures such as arch structures, horizontal and vertical reaction forces should be considered.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.211-224
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• 2008

Characteristics of the esterification reaction between free fatty acid in rice bran oil and methanol was investigated in the presence of catalysts, such as PTS(p-toluene sulfonic acid), Amberlyst 15 dry and SCX(silica gel based strong cation exchange resin). While reaction temperature was kept constant at $65^{\circ}C$, initial feed content of free fatty acid was varied from 100% to 1% by addition of pure free fatty acid which was previously made from rice bran oil. Also, the effect of mole ratio of methanol to fatty acid on the final conversion was examined. When esterification of pure free fatty acid was catalyzed by several acids, final conversions were increased in order of Amberlyst 15 dry, SCX and PTS. Using PTS catalyst, initially the reaction proceeded in homogeneous 2nd oder reaction mechanism. However, phase of reaction mixture changed from homogeneous to heterogeneous along the reaction time and then reaction rate was retarded by mass transfer resistance of methanol. Final conversion of free fatty acid in reaction mixture was depended on initial feed content of free fatty acid, and had maximum value at 30% of initial feed free fatty acid content for all kinds of catalysts used. And the final conversion was increased with mole ratio of methanol by the improvement of reaction rate. When initial feed free fatty acid content below 10% and the reaction was catalyzed by PTS, concentration of free fatty acid in reaction mixture was increased in the middle of reaction time by hydrolysis of triglyceride in reaction mixture. Also, if silica gel was added into the reaction mixture which had initial feed free fatty acid content below 50%, final conversion was increased by the adsorption of moisture produced. The SCX catalyst made the esterification reaction of free fatty acid to progress like in case of PTS catalyst. However, when initial feed free fatty acid content below 10%, concentration of free fatty acid in. reaction mixture was decreased monotonically and not increased in the middle of reaction time on the contrary to the case of PTS. Thus, SCX catalyst accomplished more high value of final conversion than PTS catalyst for the initial feed fatty acid content range from 50% to 5% In case of initial feed free fatty acid content of 1% and mole ratio of methanol was 2, concentration of free fatty acid in reaction mixture increased over the initial feed free fatty acid content for all kind of catalysts used. Although SCX catalyst was added into reaction mixture which had 1% of initial feed fatty acid content, final conversion was hardly raised by mole ratio of methanol.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.256-259
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• 2008

The gasification of biomass, sawdust, was carried out in order to investigate gasification characteristics. The experiment was performed using a down-draft fixed bed gasifier to surpass tar components generation in the gasification process. In the experiments, we investigated synthetic gas composition by varying reaction temperature, steam/carbon ratio, and excess ratio (ER), respectively. Higher reaction temperature, $700^{\circ}C$ to $900^{\circ}C$, could obtain higher $H_2$ yield. However, we could not obtain any meaning data by varying S/C ratio. Using $O_2$-LNG burner in the top of the gasifier may surpass water-gas shift reaction by increasing $CO_2$ concentration from the LNG-$O_2$ combustion reaction.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.919-925
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• 2010

The features of precipitating reaction of fluoride have been examined by employing waste gypsum as a precipitant. The major component of waste gypsum was examined to be CaO with minor components of $SO_3$, $SiO_2$. In the experimental condition, the precipitating reaction of fluoride progressed rapidly within a few minutes after the reaction started and reached its equilibrium in 10 minutes. Kinetic analysis showed that the precipitating reaction of fluoride generally followed a first Oder and second Oder with decreasing rate constant with the initial dosage of precipitant. XRD analysis showed that the crystalline structure of precipitate was mainly $CaF_2$ with partly $Ca_5(PO_4)_3(OH)$.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.17-24
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• 2005

A sub-millimeter scale catalytic combustor with a simple plate-shaped combustion chamber was fabricated. A porous ceramics support coated with platinum catalyst was placed in the chamber. The combustor has a gallium arsenide window on the top that is transparent to infrared ray. The temperature distribution in the combustion chamber was measured using infrared thermal imager while hydrogen-air premixture is steadily supplied to the combustor. The area where the catalytic reaction took place broaden for higher flow rate and lower equivalence ratio made activated area in the combustion chamber broaden. The amount of coated platinum catalyst did not affect the reaction. Stop of reaction, which is similar to flame quenching of conventional combustion, was investigated. Large content of heat generation and broad activated area are essential criteria to prevent stop of reaction that has a bad effect on the combustor performance.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.1-7
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• 2006

A reaction mechanism of methane partial oxidation, which consists of thermal and plasma chemistry reaction pathways, has been investigated using with an arc-jet reactor. The reaction zone of the arc-jet reactor is spatially separated into thermal and non-thermal plasma zone. Methane conversion rates, selectivity of $H_2$ and $C_2$ chemicals in each zone are obtained, which reveals clearly different characteristics of reaction pathways depending on the temperature conditions. The conversion rates obtained in thermal plasma zone is higher than those in non-thermal plasma zone. The selectivity, however, obtained in non-thermal plasma zone is significantly higher than those in thermal plasma zone. Further parametric study on $O_2/C$ ratio, arc length and SED shows that the present process is mainly governed by thermal chemistry pathways.