• 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.

• KSBB Journal
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• v.25 no.3
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• pp.251-256
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• 2010

A novel method to prepare polyester from wastepaper through liquefaction and crosslinking stages was studied. At the first stage, the liquefaction of wastepaper was carried out in the presence of ethylene glycol under acidic conditions. The factors that affect on liquefaction yield were found to be reaction time, temperature, and acid concentration, and their ranges were 60~120 minutes, $150{\sim}170^{\circ}C$, and 2~4%, respectively. The optimum condition was found to be 100 minutes, $160^{\circ}C$, and 3% sulfuric acid concentration, and the liquefaction yield at this condition was 67%. At the second stage, polyester was prepared from the liquefied wastepaper obtained at the optimum liquefaction condition by crosslinking with succinic anhydride. The effect of reaction time and carboxylic group/hydroxyl group ratio on crosslinkage were investigated at conditions covering 30~50 minutes of reaction time and 1.5~2.5 of carboxylic group/hydroxyl group ratio. The crosslinkages of polyester prepared were 80~90%, which were almost same regardless of reaction conditions.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.281-286
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• 2009

Bitumen extraction and sulfur removal from Athabasca oil sand were conducted using water in sub- and supercritical condition. Bitumen yield in micro reactor was investigated in the pressure range of 15~30 MPa, the temperature of 360 and $380^{\circ}C$ and water density $0.074{\sim}0.61g/cm^3$ for 0~120 min. Bitumen yield increased with reaction pressure irrespective of temperature and dramatically increased in especially supercritical region due to hydrogen formed from water gas shift reaction. Total amount of gas product decreased with reaction pressure but the portion of sulfur and hydrogen increased a little with increasing pressure to 25 and 30 MPa. It is seen that supercritical condition was favourable to the hydrogen formation and sulfur removal. Bitumen yield and sulfur removal from original oil sand reached a maximum 22% and 40% respectively in supercritical condition(the reaction time of 60 min at $380^{\circ}C$ and 25 or 30 MPa).

• KSBB Journal
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• v.22 no.4
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• pp.222-227
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• 2007

Biodiesel (fatty acid methyl esters) have used to as substitutes for petro-diesel by mixed-form with petro-diesel. In several processes of biodiesel production, alkali-catalyst transesterification produced to biodiesel of high contents with short reaction time. In this study, we investigate the optimal condition of alkali-catalyst transesterification of rapeseed oil produced at Jeju island in Korea using response surface methodology. The optimal condition of biodiesel production is reaction temperature 59.7$^{\circ}C$, catalyst amount 1.18%, oil to methanol molar ratio 1:8.75, and reaction time 5.18 min. At that reaction condition, the fatty acid methyl ester contents of product are above 97%. Our results may provide useful information with regard to the development of more economic and efficient biodiesel production system.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.125-132
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• 2017

Objective: The aim of this study was to investigate the effect of targeted knee flexion angle on biomechanical factors of knee joint between upward and downward phases during the forward lunge. Method: Eight elderly subjects (age: $22.23{\pm}1.51years$, weight: $69{\pm}6.63kg$, height: $174.88{\pm}6.85cm$) participated in this study. All reflective marker data and ground reaction force during a forward lunge were collected. The knee joint movement and reaction force and joint moment at maximum knee flexion angle were compared by repeated measures one-way analysis of variance (ANOVA) (p<.05). The peak knee joint reaction force and joint moment between upward and downward phases were compared by repeated measures two-way ANOVA (p<.05). Results: The anterior and vertical knee joint movements, reaction force, and extensor moment of $80^{\circ}$ targeted knee flexion condition at maximum knee flexion angle was greater than both $90^{\circ}$ and $100^{\circ}$ conditions (p<.05). The $80^{\circ}$ knee flexed angle condition had greater peak joint reaction force and extensor moment compared with both $90^{\circ}$ and $100^{\circ}$ conditions between upward and downward phases during the forward lunge. Conclusion: As the targeted knee joint flexion angle increases, knee joint movement and kinetic variables become greater during the forward lunge exercise.

• Journal of Environmental Science International
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• v.20 no.11
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• pp.1499-1507
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• 2011

Practical disposal of transformer insulation oil laden with PCBs (polychlorinated biphenyls) by a chemical treatment has been studied in field work. The transformer insulation oil containing PCBs was treated by the required amounts of PEG (polyethylene glycol) and KOH, along with different reaction conditions such as temperatures and times. The reaction of PEG with PCBs under basic condition produces arylpolyglycols, the products of nucleophilic aromatic substitution. Removal efficiencies of PCBs in insulation oil before and after chemical treatment were examined. The removal efficiency of PCBs was very low at lower temperatures of 25 and $50^{\circ}C$. Under the reaction condition of PEG 600/KOH/$100^{\circ}C$/2hr, removal efficiency of PCBs was approximately 70%, showing completely removal of PCBs containing 7~9 chlorines on biphenyl frame which appear later than PCB IUPAC Number 183 (2,2',3,4,4',5',6-heptaCB) in retention time of GC/ECD. However, when increasing the reaction temperature and time to $150^{\circ}C$ and 4 hours, removal efficiency of PCBs reached 99.99% without any formation of PCDDS/PCDFs during the process. Such reaction conditions were verified by several official analytical institutions. In studying the reaction of PEG with PCBs, it confirmed that the process of chemical treatment led to less chlorinated PCBs through a stepwise process with the successive elimination of chlorines.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.161-167
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• 2007

Gasification characteristics in the fluidized bed reactor are essential for the design of a gasification furnace to optimize the operation condition. Moisture content of the solid fuel is one of the important factors to influence directly the gasification characteristics. So it is necessary to investigate the effect of moisture content of solid fuel in gasification process. Gasification characteristics are investigated with results from thermogravimetric analyser and lab-scale fluidized bed reactor for wood and RDF samples along with changing moisture contents. Additionally lab-scale fluidized bed reactor was run continuously and gas concentrations at the exit were measured. It is observed that the rate of reaction in partial oxidation condition is in between the results from the combustion environment and from the inert condition. Moisture content in a particle slows down the heating rate of a particle. So, reaction time is delayed by the moisture content. However, RDF samples that are easy to break-up doesn't show the effect of moisture content. The results of continuous operation condition shows that proper moisture content promotes gasification because steam from the particles helps gasifcation of the sold fuel.

• Elastomers and Composites
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• v.38 no.2
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• pp.147-156
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• 2003

Synthesis of fullerene oxides by fullerenes [$C_{60},\;C_{70}$] and several oxidants such as benzoylperoxide, trichloroisocyanuric acid, methyltrioxorhenium(VII), iodosobenzene, phosphorous pentoxide take place under ultrasonic condition at room temperature. The MALDI-TOF MS,UV-visible spectra and HPLC analysis confirmed that the products of fullerenes oxidation are [$C_{60}(O)_n$], ($n=1{\sim}3$ or n=1) and [$C_{70}(O)_n$], ($n=1{\sim}2$ or n=1). As compared with the reactivity of epoxidation of fullerenes [$C_{60},\;C_{70}$], the reaction rate of $C_{70}$ was lower than that of $C_{60}$ under same reaction condition.

• KSBB Journal
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• v.26 no.4
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• pp.341-346
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• 2011

This work is focused on the possibility of marine biomass Codium fragile as renewable resources for production of levulinic acid. In an effort to optimize the reaction conditions of levulinic acid production from Codium fragile, response surface methodology was applied. A total of 18 individual experiments were designed to investigate the effect of reaction temperature, catalyst amount, and reaction time. As a result, 4.26 g/L levulinic acid from Codium fragile was produced in the condition of $160.7^{\circ}C$ of reaction temperature, 3.9% of sulfuric acid, and 39.1 min of reaction time. This result will provide the useful information for chemical production from marine resource.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.1-8
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• 2010

Mild combustion is considered as a promising combustion technology for energy saving and low emission of combustion product gases. In this paper, the controllability of reaction region in mild combustion is examined by using co-axial air nozzle. For this purpose, numerical approach is carried out. Propane is considered for fuel and air is considered for oxidizer and the temperature of air is assumed 900K slightly higher than auto ignition temperature of propane. But unlike main air, the atmospheric condition of co-axial air is considered. Various cases are conducted to verify the characteristics of Co-Axial air burner configuration. The use of coaxial air can affect reaction region. These modification help the mixing between fuel and oxidizer. Then, reaction region is reduced compare to normal burner configuration. The enhancement of main air momentum also affects on temperature uniformity and reaction region. The eddy dissipation concept turbulence/chemistry interaction model is used with two step of global chemical reaction model.