• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.967-972
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• 2004

Hardness and surface property of coated gel materials are considerably different according to kinds(particle size/stabilized ion) of colloidal silica(CS), kinds of silanes, content ratio of silane versus CS, and reaction degree in sol solution. We report the properties of sol-gel coating materials in which the factors of reaction are kinds of CS, contents ratio of CS and MTMS, and reaction time of sol. The contact angles of the coated films obtained from the mixed CS system showed a little good relationship with MTMS content increase to those from HSA CS reaction system and the change of contact angle didn't have much effect on reaction time of sol. In the coating films obtained from HSA CS reaction system, the surface was much rough in case of that the content MTMS decreased and the reaction of sol kept long. The surface roughness of films obtained from the mixed CS reaction system showed similar tendency, though its degree was a little different. In synthesis of sol-gel coating materials, we could identify that choice of CS kinds and content ratio of CS and silane were important and it was desirable the reaction time of sol is not long.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.2
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• pp.144-144
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• 1999

Phantom phenomena on the signal light was observed and change of perception-reaction time of the observer was measured. If phantom phenomena occurs, signal light perception- reaction time by the drivers is prolonged, the extent of which may disturb driving. Length of the perception-reaction time is affected by the luminance contrast between the turned-on and tuned-off signals. Based on the measured results, several methods to prevent phantom phenomena were suggested.

• Honam Mathematical Journal
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• v.43 no.4
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• pp.667-678
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• 2021

Blow-up phenomena for a nonlocal reaction-diffusion system with time-dependent coefficients are investigated under null Dirichlet boundary conditions. Using Kaplan's method with the comparison principle, we establish new blow-up criteria and obtain the upper bounds for the blow-up time of the solution under suitable measure sense in the whole-dimensional space.

• The Journal of Korean Physical Therapy
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• v.22 no.5
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• pp.103-108
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• 2010

Purpose: The aim of this study is to investigate whether motor cortex excitability by transcranial direct current stimulation (tDCS) over primary motor cortex (M1) affects motor performance of serial reaction task. Methods: Cathodal, anodal and sham tDCS (1 mA) are applied over right M1 of 24 subjects for 30 minutes including 11minutes for task period time. We applied two electrodes at the same position to both an experimental group and a sham-controlled group, and we made 2 groups recognize to be applicated of stimulation. Flexion, extension of wrist and thumb flexion are carried out following colors of arrows on the monitor. Serial reaction time task was applied to confirm the difference of the reaction time between 2 groups. Results: Reaction time is decreased in both tDCS-group and Sham-controlled tDCS group, and the degree of reduction is much greater in the post-test than pre-test. Reduction of reaction time between groupsis statistically significant. Conclusion: We consider that anodal tDCS increased the cortical excitability of the underlying motor cortex and it can be helpful to modulate motor performance. It seems that tDCS is an effective modality to modulate brain function, and it will be great help to mediate strategy for the brain injury patients.

• The Journal of Korean Physical Therapy
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• v.21 no.1
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• pp.81-87
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• 2009

Purpose: Human brain was lateralized to dominant or non-dominant hemisphere, and could be reorganized by the processing of the motor learning. We reported four cases which showed the changes of the cortical activation patterns resulting from two weeks of training with the serial reaction time task. Methods: Four right-handed healthy subjects were recruited, who was equally divided to two training conditions (right hand training or left hand training). They were assigned to train the serial reaction time task for two weeks, which should press the corresponding four colored buttons as fast as accurately as possible when visual stimulus was presented. Before and after two weeks of training, reaction time and function magnetic resonance image (fMRI) was acquired during the performance of the same serial reaction time task as the training. Results: The reaction time was significantly decreased in all of subjects after training. Our fMRI result showed that widespread bilateral activation at the pre scanning was shifted toward the focused activation on the contralateral hemisphere with progressive motor learning. However, the bilateral activation was still remained during the performance of the non-dominant hand. Conclusion: These findings showed that the repetitive practice of the serial reaction time task led to increase the movement speed and accuracy, as described by motor learning. Such motor learning induced to change the cortical activation pattern. And, the changed pattern of the cortical activation resulting from motor learning was different each other in accordance with the hand dominance.

• Journal of the Korean Chemical Society
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• v.4 no.1
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• pp.70-77
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• 1957

4,5-Diphenyl Imidazolone is synthesized from Benzoin, Urea, and Acetic acid catalyser. Nowadays, it is being used as an optical bleaching agent for wool and nylon textiles. Up to now, only one process of synthesis has been known. In order to find out the best conditions governing the yield were examined under various catalysers and conditions. In this experiment, the summary of results were as follows. a. On Acetic acid catalyser. The maximum yield conditions were mol ratio (Benzoin: Urea: Acetic acid) 1 : 2 : 14, Acetic acid concentration 99.9%. Reaction temperature 115$^{\circ}$. Under reaction time of 2 hours, above yield was 96.4%. b. On Mineral acid Catalyser. In using of Sulfonic acid, the color of solution was changed dark purlish black. With other mineral acid catalysers, in spite of increasing of temperature, it was proved that Benzoin floats on the solution, so that this reaction could not be continue. c. On Phosphoric acid catalyser. It was made clear that it can not be used for this reaction. d. On Sodium hydroxide catalyser. As one of Alkali catalyser, Sodium hydroxide was examined but this was unsuitable substance for this reaction. e. On Formic acid catalysers. The maximum yield conditions were mol ratio (Benzoin: Urea: Formic acid) 1: 2: 30. Formic acid concentration 85.%. Reaction temperature 150∼110$^{\circ}$. Under reaction time of 90 minutes, the best yield was 87%. Hereby, it was proved that organic acids such as Acetic acid and Formic acid can be used. When using Acetic acid, the yield was better than Formic acid, but it takes longer reaction time than Formic acid. About the fluorescent effect, the temperature of dye-bath must not be over 904,5-Diphenyl Imidazolone is synthesized from Benzoin, Urea, and Acetic acid catalyser. Nowadays, it is being used as an optical bleaching agent for wool and nylon textiles. Up to now, only one process of synthesis has been known. In order to find out the best conditions governing the yield were examined under various catalysers and conditions. In this experiment, the summary of results were as follows. a. On Acetic acid catalyser. The maximum yield conditions were mol ratio (Benzoin: Urea: Acetic acid) 1 : 2 : 14, Acetic acid concentration 99.9%. Reaction temperature 115$^{\circ}$. Under reaction time of 2 hours, above yield was 96.4%. b. On Mineral acid Catalyser. In using of Sulfonic acid, the color of solution was changed dark purlish black. With other mineral acid catalysers, in spite of increasing of temperature, it was proved that Benzoin floats on the solution, so that this reaction could not be continue. c. On Phosphoric acid catalyser. It was made clear that it can not be used for this reaction. d. On Sodium hydroxide catalyser. As one of Alkali catalyser, Sodium hydroxide was examined but this was unsuitable substance for this reaction. e. On Formic acid catalysers. The maximum yield conditions were mol ratio (Benzoin: Urea: Formic acid) 1: 2: 30. Formic acid concentration 85.%. Reaction temperature 150∼110$^{\circ}$. Under reaction time of 90 minutes, the best yield was 87%. Hereby, it was proved that organic acids such as Acetic acid and Formic acid can be used. When using Acetic acid, the yield was better than Formic acid, but it takes longer reaction time than Formic acid. About the fluorescent effect, the temperature of dye-bath must not be over 90$^{\circ}$. and the ratio of 4,5-Diphenyl Imidazolone and water should be from 1:50000. to 1:10000. It proved that the best effect on textiles, and the best condition were dye-temperature near 704,5-Diphenyl Imidazolone is synthesized from Benzoin, Urea, and Acetic acid catalyser. Nowadays, it is being used as an optical bleaching agent for wool and nylon textiles. Up to now, only one process of synthesis has been known. In order to find out the best conditions governing the yield were examined under various catalysers and conditions. In this experiment, the summary of results were as follows. a. On Acetic acid catalyser. The maximum yield conditions were mol ratio (Benzoin: Urea: Acetic acid) 1 : 2 : 14, Acetic acid concentration 99.9%. Reaction temperature 115$^{\circ}C$. . Under reaction time of 2 hours, above yield was 96.4%. b. On Mineral acid Catalyser. In using of Sulfonic acid, the color of solution was changed dark purlish black. With other mineral acid catalysers, in spite of increasing of temperature, it was proved that Benzoin floats on the solution, so that this reaction could not be continue. c. On Phosphoric acid catalyser. It was made clear that it can not be used for this reaction. d. On Sodium hydroxide catalyser. As one of Alkali catalyser, Sodium hydroxide was examined but this was unsuitable substance for this reaction. e. On Formic acid catalysers. The maximum yield conditions were mol ratio (Benzoin: Urea: Formic acid) 1: 2: 30. Formic acid concentration 85%. Reaction temperature 150∼110$^{\circ}C$. Under reaction time of 90 minutes, the best yield was 87%. Hereby, it was proved that organic acids such as Acetic acid and Formic acid can be used. When using Acetic acid, the yield was better than Formic acid, but it takes longer reaction time than Formic acid. About the fluorescent effect, the temperature of dye-bath must not be over 90$^{\circ}C$. and the ratio of 4,5-Diphenyl Imidazolone and water should be from 1:50000. to 1:10000. It proved that the best effect on textiles, and the best condition were dye-temperature near 70$^{\circ}C$. and dye-time 15 minutes. . and dye-time 15 minutes. . and the ratio of 4,5-Diphenyl Imidazolone and water should be from 1:50000. to 1:10000. It proved that the best effect on textiles, and the best condition were dye-temperature near 70$^{\circ}C$. and dye-time 15 minutes.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.838-850
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• 2015

In this study, dilute acid pretreatment was operated using small-diameter Quercus mongolica for evaluating the yield change of furfural and levulinic acid depending on pretreatment factors. The dilute acid pretreatment was conducted depending on reaction temperature ($140-180^{\circ}C$), reaction time (10-30 min), and sulfuric acid concentration (0-2%, w/w). Then, glucose, XMG (xylose + mannose + galactose), furfural, and levulinic acid contents in the liquid hydrolyzate were measured and analyzed after pretreatment. Glucose content increased to 16.02% as reaction temperature, reaction time, and sulfuric acid concentration increased, but it decreased at the sulfuric acid concentration of 2% (reaction temperature: > $170^{\circ}C$, reaction time: > 20 min). On the other hand, reaction temperature had a strong influenced on XMG content, and XMG content decreased to 1.63% through increasing of reaction temperature and sulfuric acid concentration, but XMG content was less affected by changes of reaction time. Furfural content increased with the increase of reaction temperature, reaction time, and sulfuric acid concentration, and maximum furfural content was 7.61% (reaction temperature: $180^{\circ}C$, reaction time: 20 min, sulfuric acid concentration: 1%) based on a weight of raw material, while furfural content was dropped in more severe condition than in maximum furfural content condition. Levulinic acid content also increased with higher reaction temperature, reaction time, and sulfuric acid concentration. Especially, the sharp increase of levulinic acid content was observed above $170^{\circ}C$, and maximum levulinic acid content was 10.98% (reaction temperature: $180^{\circ}C$, reaction time: 30 min, sulfuric acid concentration: 2%). However, less than 1% of furfural and levulinic acid content was obtained in non-acidic catalyst condition that in whole conditions of reaction temperature and reaction time.

• Preventive Nutrition and Food Science
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• v.22 no.1
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• pp.37-44
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• 2017

Sulfur-containing amino acids play important roles in good flavor generation in Maillard reaction of non-enzymatic browning, so aqueous model systems of glucosamine and cysteine were studied to investigate the effects of reaction temperature, initial pH, reaction time, and concentration ratio of glucosamine and cysteine. Response surface methodology was applied to optimize the independent reaction parameters of cysteine and glucosamine in Maillard reaction. Box-Behnken factorial design was used with 30 runs of 16 factorial levels, 8 axial levels and 6 central levels. The degree of Maillard reaction was determined by reading absorption at 425 nm in a spectrophotometer and Hunter's L, a, and b values. ${\Delta}E$ was consequently set as the fifth response factor. In the statistical analyses, determination coefficients ($R^2$) for their absorbance, Hunter's L, a, b values, and ${\Delta}E$ were 0.94, 0.79, 0.73, 0.96, and 0.79, respectively, showing that the absorbance and Hunter's b value were good dependent variables for this model system. The optimum processing parameters were determined to yield glucosamine-cysteine Maillard reaction product with higher absorbance and higher colour change. The optimum estimated absorbance was achieved at the condition of initial pH 8.0, $111^{\circ}C$ reaction temperature, 2.47 h reaction time, and 1.30 concentration ratio. The optimum condition for colour change measured by Hunter's b value was 2.41 h reaction time, $114^{\circ}C$ reaction temperature, initial pH 8.3, and 1.26 concentration ratio. These results can provide the basic information for Maillard reaction of aqueous model system between glucosamine and cysteine.

• Journal of environmental and Sanitary engineering
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• v.16 no.4
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• pp.62-68
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• 2001

The advantages of hydrogen peroxide dissolution method were no discharge of noxious matter when dissolution of iron wire which used as the center supporter, reactions occur in room temperature and easy to recover dissolved iron. This study was aimed at gathering the basic data of iron wire dissolution- recovery process and proposes the reaction condition of iron wire dissolution- recovery process rind the factors influencing those reactions. The results were as follows : 1 . Hydrogen peroxide dissolution method used hydrochloric acid as the catalyst. 1. In the dissolution of iron wire(1.668 g), the condition of reaction was E1702(30 ml), HCI(20 ml) and $H_2O$(200 ml) ; time of the reaction was 18 min. P.W.(Piece weight) was 7.75 mg, and C.R. was $2.34{\;}{\Omega}$ 2. In the dissolution of iron wire(1.529 g), the condition of reaction was H7O2(30 ml), HCI(20 ml) and $H_2O$(200 ml), time of the reaction was 21 min., P.W.(Piece weight) was 7.73 mg, and C.R. was $2.35{\;}{\Omega}$. Hydrogen peroxide dissolution method used sulfuric acid as the catalyst. 1. In the dissolution of iron wire(0.834 g), the condition of reaction was $H_2O$(65 ml), $H_2SO_4$(5 ml) and 1702(5 ml) ; time of the reaction was 5 min.30 sec, P.W.(Piece weight) was 7.74 mg, and C.R. was $2.33{\;}{\Omega}$ 2. In the dissolution of iron wire(1.112 g), the condition of reaction was $H_2O$(65 ml), $H_2SO_4$(5 ml) and $H_2O_2$(5 ml) ; time of the reaction was 4 min.30 sec, P.W.(Piece weight) was 7.75 mg, and C.R. was $2.33{\;}{\Omega}$. Hydrogen peroxide dissolution method used hydrochloric acid and sulfuric acid as the catalyst confirmed a clean technology, because there were not occurred a pollutant discharged in the existing method.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.