• Journal of the Korean institute of surface engineering
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• v.19 no.4
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• pp.133-139
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• 1986

The effects of alternating voltage, $Cl^-$ ion and pH on the corrosion of Zn and Zn-Fe alloys have been investigated by using electrochemical techniques in $Ca(OH)_2$ solutions. The passive film $Zn(OH)_2$ was initially formed on the Zn surface and gradually transformed to $Ca(Zn(OH)_3)_2{\cdot}2H_2O$, which was identified with the X-ray diffraction method, SEM micrograph and EPMA. The passivity current increased with increasing alternating voltage and decrease AC frequency. ${\xi}$ phase in Zn-Fe alloys reduced the effects of AC. The effect of $Cl^-$ ion on the passivity current of Zn was similar to the AC effect, resulting in pits on Zn. It was also found that the passive region of Zn decreased rapidly below pH 10.3 of the solution.

• Journal of Biomedical Engineering Research
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• v.26 no.3
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• pp.163-169
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• 2005

Respiratory tubes with a length of 35mm and diameters of 10, 15, and 20mm were made for experimental purpose, and both the static$(P_s)\;and\;dynamic(P_D)$ pressures were simultaneously measured for steady flow rates ranging 1-12//sec. Least squares analysis resulted successful fitting of $P_s\;and\;P_D$ data with quadratic equations with correlation coefficients higher than 0.99(P<0.0001). The spirometric measurement standards of the American Thoracic Society(ATS) were applied to $P_s$ data, which demonstrated the smallest tube diameter of 15mm to satisfy the ATS standards. The maximum $P_D$ value of the velocity type transducer(the functional single use respiratory air flow tube) with the diameter of 15mm was estimated to be approximately $75cmH_2O$, implying more than 7 times larger sensitivity than the widely used pneumotachometers. These results showed that the velocity type respiratory air flow transducer is a unique device accomplishing miniaturization with the sensitivity increased, thus would be of great advantage to develop portable medical devices.

• Applied Biological Chemistry
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• v.40 no.5
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• pp.388-394
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• 1997

Extracellular protease (bassiasin I), from the culture filtrate of entomopathogenic fungus Beauveria bassiana ATCC7159, was successively purified by precipitation with ammonium sulfate followed by DEAE-Sephadex A-50, CM-cellulose and Hydroxyapatite column chromatography. A typical procedure provided 41-fold purification with 13.6% yield. The molecular weight of the purified pretense (bassiasin I) was found to be approximately 32,000 by SDS-PAGE. Isoelectric-focusing analysis of the enzyme showed a pI of 9.5. $NH_2-terminal$ sequence of the pretense showed homology with those of the fungal proteases. The enzyme has an optimal pH for activity at 10.5 and is stable over pH 5.0-11.0. The maximum activity of the enzyme was at $60-65^{\circ}C$, and approximately 20% activity remained at $60^{\circ}C$ after 120 min. The pretense was inhibited by phenylmethylsulfonyl fluoride (PMSF) and diisopropyl fluorophosphate (DIPF).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.111-118
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• 2003

Structural characteristics of concrete filled glass fiber reinforced composite pile was studied. Confinement model of composite pile was derived from experimental data, and numerical method to find P-M diagram of composite pile was developed. The flexure-compression test results were compared with analytical P-M diagram and it is demonstrated that they agree well each other. Utilizing these results, pilot composite pile was designed fabricated, and flexural test were conducted,

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.127-134
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• 2001

In this paper flexure-compression characteristics of concrete filled glass fiber reinforced composite pile was studied. Confinement model of composite pile was derived from experimental data. Also numerical method to find P-M diagram of composite pile was developed. The flexure-compression test results were compared with analytical P-M diagram and it is demonstrated that they agree well each other. Utilizing these results, pilot composite pile was designed and fabricated.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.414-419
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• 2005

This study was performed to compare the treatment efficiencies of two media, newly developed Bio-rock and conventional gravel, in soil clothing contact oxidation process. The composition of synthetic wastewater were $COD_{Cr}$ $150{\sim}370\;mg/L$, $BOD_5$ $150{\sim}270\;mg/L$, T-N $20{\sim}60\;mg/L$, T-P $5{\sim}25\;mg/L$, pH 7 and 2 mL/L of trace element solution. The experiment using two reactors was comparatively conducted for the flow rate of 40 L/d for 13 months, respectively. Initially Bio-rock reactor was increased to pH 12 due to $Ca(OH)_2$ with hydration of cement, but gravel reactor was dropped to pH 4 due to the degradation of organic material and nitrification. This significant pH variation deteriorated the growth and activity of microorganism. But the high pH of Bio-rock seems favorite to ammonia stripping and precipitation of phosphate. Such pH variation of Bio-rock and gravel reactors were finally stabilized to pH 8 and pH 6, respectively. The removal efficiencies of organic compounds from Bio-rock reactor were 96% of $COD_{Cr}$, 98% of $BOD_5$, 80% of T-N and 85% of T-P which stably coping against variation of influent concentration. But those of gravel reactor were 96% of $COD_{Cr}$, 96% of $BOD_5$, 42% of T-N and 40% of T-P, respectively. The Bio-rock was 2 times higher than T-N and T-P in treatment efficiency. And electron-microscopic examination showed that Bio-rock was more favorable to microbial adherence than gravel. The microbial populations were $5.2{\times}10^6\;CFU/mL$ of Bio-rock reactor compared to $2.6{\times}10^6\;CFU/mL$ in gravel reactor. In result Bio-rock was favor to microbial adherence and high treatment efficiency in spite of variation of influent concentration which had the advantages in saving running time and reducing site requirement.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.732-736
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• 2010

Five strains of tannic acid degrading bacteria were isolated and identified by phenotypic characterization. All the five isolates showed cell-associated activity, whereas only three showed extracellular activity. Serratia ficaria DTC, showing the highest cell-associated activity (0.29 U/l), was selected for further shake-flask studies. Tannase synthesis was growth associated and reached the peak in the late stationary phase of growth. Organic nitrogen sources enhanced the tannase production. Peak tannase production of 0.56 U/l was recorded in the medium having the initial pH of 6. The pH and temperature optima of the enzyme were found to be 8.9 and $35^{\circ}C$, respectively. This is the first report of cell-associated activity in the case of bacterial tannase. Cell-associated tannase of Serratia ficaria DTC could be industrially important from the perspective of its activity at broad temperature and pH ranges, and its unusually high activity at pH 8.9.

• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1931-1937
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• 2019

The heterologous expression of the Streptomyces natural product (NP) biosynthetic gene cluster (BGC) has become an attractive strategy for the activation, titer improvement, and refactoring of valuable and cryptic NP BGCs. Previously, a Streptomyces artificial chromosomal vector system, pSBAC, was applied successfully to the precise cloning of large-sized polyketide BGCs, including immunosuppressant tautomycetin and antibiotic pikromycin, which led to stable and comparable production in several heterologous hosts. To further validate the pSBAC system as a generally applicable heterologous expression system, the daptomycin BGC of S. roseosporus was cloned and expressed heterologously in a model Streptomyces cell factory. A 65-kb daptomycin BGC, which belongs to a non-ribosomal polypeptide synthetase (NRPS) family, was cloned precisely into the pSBAC which resulted in 28.9 mg/l of daptomycin and its derivatives in S. coelicolor M511(a daptomycin non-producing heterologous host). These results suggest that a pSBAC-driven heterologous expression strategy is an ideal approach for producing low and inconsistent Streptomyces NRPS-family NPs, such as daptomycin, which are produced low and inconsistent in native host.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.930-937
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• 2005

The Plackett-Burman design and the response surface method (RSM) with a central composite design (CCD) were employed to develop a culture medium for ansamitocin P-3 production using Actinosynnema pretiosum ATCC 31565. Among the 11 nutrients tested using the Plackett-Burman design, two carbon sources, sucrose and dextrin, and two nitrogen sources, polypeptone and yeast extract, were selected. Optimization of the concentrations of the selected nutrients was then performed using RSM with CCD. After two rounds of RSM, the optimum concentrations ($\%w/v$) of sucrose, dextrin, polypeptone, and yeast extract were identified as 4.5, 4.5, 0.16, and 0.89, respectively. The maximum ansamitocin P-3 titer was 45.2 mg/l with the optimized medium, which was about 6 times higher than that (7.315 mg/l) obtained with an $R_{2}YE$ medium before optimization.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1107-1112
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• 2008

Crystallization of calcium carbonate was performed by using aqueous calcium chloride and sodium carbonate for operational simplicity. Reaction time, solute concentrations, pH, and organic additive were varied to get calcium carbonate crystals. Silk fibroin was used as the additive to understand the change of morphology of calcium carbonate crystal. The crystals were analyzed by FE-SEM, XRD, and FT-IR. Reaction time, and pH mainly affected the morphology of crystals. Besides, it was found that silk fibroin inhibited the formation of vaterite and promoted the calcite forms.