• Journal of the Korea Institute of Building Construction
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• v.18 no.5
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• pp.439-446
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• 2018

The PHC pile has been increasingly used due to its implementation of the top-base method, which is advantageous in high penetration rate and bearing capacity reinforcement. Typically, when a PHC pile is manufactured, high-strength mixed materials are mainly used to enhance the compressive strength. However, recent studies have been conducted to utilize ground granulated blast-furnace slag (GGBS) in terms of economic efficiency. For this reason, this study manufactured PHC pile considering the replacement ratio and curing conditions of GGBS instead of high-strength mixed materials, and further investigated the engineering properties of the PHC pile. According to the experimental results, the compressive strength of GGBS-replaced PHC pile increased by steam curing, and particularly, PHC pile with 20% replacement of GGBS under $80^{\circ}C$ steam curing condition showed a compressive strength of approximately 84MPa. Furthermore, the experimental results confirmed that more hydration products were generated under the $80^{\circ}C$ steam curing condition than that under the $20^{\circ}C$ steam curing condition, which would affect the higher density of the PHC pile as well as the increase in the compressive strength.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.461-464
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• 2002

A Chemoautotroph identified as an Aeromonas sp. strain JS-1 was isolated from fresh water. Aeromonas sp. strain JS-1 used the $H_2$ and $CO_2$ as energy and carbon sources, respectively. Growth characteristics for improving the $CO_2$ fixation rate were examined in batch cultivation. Its results shown that the optimal growth appeared at culture conditions of $35^{\circ}C$, pH 7 and NaCl 0.1%(w/v). Some hydrogen-oxidizing bacteria were reported that the enzyme activity of ribulose 1,5-bisphosphate carboxylase- oxygenase (RubisCO-EC 4.1.1.39), in the key enzyme of the Calvin-Benson cycle. A RubisCO was purified from a chemoautotrophic bacterium, Aeromonas sp. strain JS-1. the enzyme was purified by ammonium sulfate precipitation, DEAE-sepharose CL-6B and gel filtration chromatography. The RubisCO showed that molecular mass was about 560KDa from gel filtration chromatography and nondenaturing PAGE, and the RubisCO was confirmed to consist of $L_8S_8$ enzyme structure by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A large subunit was about 56KDa and small one was about 15kDa. The Km values of the enzyme for ribulose 1,5-bisphosphate(RUBP), $NaH^{14}CO_3$, and $Mg^{++}$ were estimated to be 0.25mM, 5.2mM, and 0.91mM, respectively. The optimum temperature for RubisCO enzymatic activity were $50^{\circ}C$, and the enzymatic activity was stable up to $45^{\circ}C$.

• KSBB Journal
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• v.21 no.4
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• pp.255-259
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• 2006

The biodegradable hyaluronic acid(HA) membranes cross-linked with lactide using the crosslinking agent, 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide(EDC) were prepared as a potential biocompatible material for tissue engineering. HA membranes having different mechanical properties were synthesised by varying degree of the mole ratio of lactide to HA, EDC concentration, and crosslinking temperature. HA membranes were degradable in water solution and the degradation became slower with the increasing mole ratio of lactide to HA. HA membranes were sterilized using ethylene oxide gas and extracted with cell culture medium for 24 h at $37^{\circ}C$ and 200 rpm. Cytotoxicity of the extract was tested using NIH/3T3 mouse embryo fibroblast as a model cell. Growth inhibition was not observed in the extracts of HA membranes with the mole ratios of lactide to HA, 5 or 10, and 10% EDC concentration, however 11% of growth inhibition was observed in the extract with the mole ratio of 13. Growth inhibition was not observed in the extracts of HA membranes prepared with 5% EDC or 10% EDC and the mole ratio of lactide to HA, 10, however 12% of growth inhibition was observed in the extract with 20% EDC. Cytotoxicity was not observed in the extracts of HA membranes prepared at varying crosslinking temperatures, $15^{\circ}C,\;25^{\circ}C,\;and\;28^{\circ}C$ with the mole ratio of lactide to HA, 10 and 10% EDC.

• KSBB Journal
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• v.24 no.5
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• pp.489-494
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• 2009

Two-step pretreatment process was investigated to efficiently hydrolyzed rape stems for obtaining fermentable sugars. The process was consisted of two consecutive steps as $200^{\circ}C$ and 15 MPa and $374^{\circ}C$ and 24 MPa with the flow rate of 5 mL/min. Under this condition, 5.5 (g/L) of glucose and 25.6 (g/L) of xylose were obtained from rape stems, showing 18% of glucose yield based on 25% cellulose in the rape stems. It was also found that this process could generate less amounts of toxic residues, such as HMF (Hydroxy- Methyl-Furfural) and other fulfural components during hydrolysis process. It could reaction maintain relatively high ethanol production yield as 90% of theoretical conversion yield from glucose. Therefore, this pretreatment process could be applied to hydrolyze other cellulosic and marine resources such as woods, stem and algae for bioethanol production.

• KSBB Journal
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• v.23 no.1
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• pp.65-69
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• 2008

The culture broth of a ${\beta}$-glucan-producing bacterium, Paenibacillus polymyxa JB115, was confirmed to show the antibiosis against pathogenic bacteria of livestock disease. The antibacterial substance produced by P. polymyxa JB115 exhibited strong bactericidal or bacteriostatic effect on the growth of livestock pathogenic bacteria including Staphylococcus aureus, Salmonella choleraesuis, Escherichia coli and Pseudomonas aeruginosa. This antibacterial substance also showed high stabilities in broad pH range (pH 3-11) and in broad temperature range $(40-121^{\circ}C)$, which is good enough to apply spray-dry method for the formulation of culture broth. It was also found that the antibacterial substance was very stable in artificial gastric fluid and bile acid, which implies the anticipated antibacterial activity against gastrointestinal bacteria harmful for livestocks. In conclusion, the culture broth of P. polymyxa JB115 can be developed as a multifuctional feed additive containing immune-enhancing ${\beta}$-glucan as well as antibacterial agent against livestock pathogenic bacteria.

• KSBB Journal
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• v.23 no.1
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• pp.83-89
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• 2008

Food wastewater derived from the three-stage methane fermentation system developed in this lab contained high concentration organic substances. The organic wastewater should be treated through advanced wastewater treatment system to satisfy the "Permissible Pollutant Discharge Standard of Korea". In order to treat the organic wastewater efficiently, several optimum operation conditions of a modified $UV/TiO_{2}$ photocatalytic system have been investigated. In the first process, wastewater was pre-treated with $FeCl_{3}$. The optimum pH and coagulant concentration were 4.0 and 2000mg/L, respectively. Through this process, 52.6% of CODcr was removed. The second process was $UV-TiO_{2}$ photocatalytic reaction. The optimum operation conditions for the system were as follows: UV lamp wavelength, 254 nm; wastewater temperature, $40^{\circ}C$; pH 8.0; and air flow rate, 40L/min, respectively. Through the above two combined processes, 69.7% of T-N and 70.9% of CODcr contained in the wastewater were removed.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.404-409
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• 2006

The catalytic combustion of toluene over Pd-Cu/USY zeolite has been examined by using FT-IR spectroscopy in a closed system under dry and humid conditions. The catalytic combustion of toluene (700 ppmv) in the temperature range of $80-220^{\circ}C$ has been investigated by using a fixed bed reactor. The Pd-Cu/USY catalyst showed the highest catalytic performance with respects to the PdO-CuO/USY and Pd/USY. Comparing to $PdO/Al_2O_3$ catalysts, the slight improvement in conversion was observed over PdO/USY catalysts under humid condition since USY zeolite is hydrophobic substrate and water give an additional oxygen source to zeolite surface like oxygen. The reduced catalysts showed more enhanced catalytic activity due to the reduced activation energy of combustion of toluene than oxidized catalysts such as PdO/USY and PdO-CuO/USY.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.437-442
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• 2016

A new route for PBT (Poly butylene terephthalate) production from recycled PET (Poly ethylene terephthalate) has been explored. The route consists of glycolysis of PET (Poly ethylene terephthalate) wastes using 1,4-butandiol into BHBT oligomers and polycondensation of the oligomers into PBT oligomer. This process uses post-consumer or post-industrial recycled PET and converts it into high-end PBT type engineering thermoplastic via a chemical recycling process. Zink acetate was used as a catalyst for both glycolysis and polycondensation. Two types of reactor for the glycolysis, batch and semi-batch reactor, were investigated and their performances were compared. Semi-batch reactor removes ethylene glycol (EG) and THF (tetrahydrofuran) during the reaction. Amounts of EG and THF generated during the glycolysis reaction were measured and used as criteria for the reactor performance. Performance of semi-batch reactor was shown to be better than that of batch reactor. Optimum reaction condition for the semi-batch reactor was BD/PET ratio of 4, and reaction temperature of $220^{\circ}C$, giving high EG yield (max 91%) and low production of THF. In addition, it was confirmed that the molecular weight of PBT oligomer increases in accordance with the progress of the polycondensation reaction.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.47-55
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• 2011

The optimum mold design and the optimum process condition were constructed upon executing process simulation of rubber injection molding with the commercial CAE program of MOLDFLOW (Ver. 5.2) in order to solve the process-problems of K company relating to cracks, which occurs at the inner cavity wall of C. V. joint boots. As a result it was confirmed that the real cracks occurs at the exactly same position of the cavity as exhibits the defects of weld and meld line and unsatisfactory curing according to the result of simulation. In order to prevent the occurrence of weld and meld line at the defect-position, the location of gate was altered to the optimum position of the cavity. Consequently the filling pattern was established to minimize the degree of the melt-fronts confronting or the melt-flows melding to prevent the occurrence of weld and meld line at the defect-position. It was observed that both gate-positions to maximize the degree of the formation of weld and meld line and air traps are located, respectively, in opposite direction each other with reference to the optimum gate position. In addition, the temperature of mold was raised by $10^{\circ}C$ and maintained at $170^{\circ}C$ for satisfactory curing.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.101-104
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• 2011

Cellobiose dehydrogenase(CDH) as a hemoflavoenzyme is secreted out of cell in the cellulose degradation. As CDH strongly bound to amorphous cellulose, it helps cellulose hydrolysis by cellulase. CDH may have an important role of saccharification process for bioethanol production. In this study, Phanerochaete chrysosporium ATCC 32629 was selected for the production of CDH among other strains tested. The optimal temperature and pH of CDH produced by P. chrysosporium ATCC 32629 were ${55^{\circ}C}$ and 4, respectively. To improve the activity of CDH, the mutation of P. chrysosporium was performed using proton beam that has high energy level partially. As a result, P. chrysosporium mutant with the high activity was selected at 1.2 kGy in a range of 99.9% lethal rate. The CDH and $\beta$-glucosidase activities of mutant were 1.4 fold and 20 fold higher than those of wild strain. Therefore, P. chrysosporium mutant with the high activities of CDH and $\beta$-glucosidase was obtained from mutation by proton beam irradiation.