• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.92-100
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• 1996

For the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(P(3HB-co-3HV)) from butyric acid and valeric acid, 10 strains of bacteria capable of producing P(3HB-co-3HV) were isolated from soil. Among them, the strain HJ-067 showed the best ability of producing P(3HB-co-3HV), and was indentified as a Azotobacter sp. For the production of P(3HB-co-3HV), the optimum concentrations of butyric and valeric acid were 3.0g/l, respectively. The most effective nitrogen source was $(NH_4)_{2}SO_4$ at an optimum concentration of 0.75g/l, which was equivalent to 21.36 in C/N ratio. Deficiency of the cationic metal ions ($Zn^{2+},\;Co^{2+},\;Mn^{2+}$) in the proguction medium had stimulating effect on P(3HB-co-3HV) accumulation, especially in the manganese. deficient medium. The optimum temperature for P(3HB-co-3HV) production was 27$^{\circ}C$ and the optimum initial pH was 7.0. Under the optimum conditions, 1.82g/l of P(3HB-co-3HV) and 3.00g/l of dry biomass were produced after 36 hour cultivation, and the P(3HB-co-3HV) yield and HV% were 60.60% (w/w), 15.92%, respectively.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.50-58
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• 1996

Interspecific hybrids between Aspergillus oryzae var oryzae and A. nidulans 514 were obtained by nuclear transfer technique. Several autotrophic mutants isolated from conidiospores of the two strains were mutagenized with ultraviolet and N-methyl-N-nitrosoguanidine. Optimal conditions for formation of intergeneric hybrids were investigated. Frequencies of hybrid formation by nuclear transfer were $3{\times}10^{-5}{\sim}1{\times}10^{-5}$. From observation of genetic stability, conidial size, DNA content, and nuclear stain, it was suggested that their karyptypes are aneuploid. The hybrids showed 1.1~1.4 fold higher xylanase activities than parental strains did. The xylanase of Aspergiilus sp. TAVD514-3 was purified and some of it's enzymatc characteristics were investigated. The enzyme was purified about 85 fold with an overall yield of 17% from the culture medium by ammonium sulfate fractionation, Sephadex G-75 gel permeation chromatography, and CM-sephadex A-50 ion exchange chromatography. The purified enzyme functions optimally at pH 9.0 and 80$^{\circ}C$. The enzymatic activity was increased by the presence of $Mg^{2+}$ and $Mn^2$ ions.

• Journal of Drive and Control
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• v.14 no.2
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• pp.23-29
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• 2017

In this study, a flexible multi-body dynamic simulation model of a knuckle boom crane is developed to evaluate the stress of spindle and rack gears under dynamic working conditions. It is difficult to predict potential critical damage to a knuckle boom crane if only the static condition is considered during the development process. To solve this issue, a severe working scenario (high speed with heavy load) was simulated as a boundary condition for testing the integrity of the dynamic simulation model. The crane gear model is defined as a flexible body so contact analysis was performed. The functional motion of a knuckle boom crane is generated by applying forces at each end of the rack gear, which was converted from hydraulic pressure measured for the experiment. The bending and contact stress of gears are theoretically calculated to validate the simulation model. In the simulation, the maximum stress of spindle and rack gears are observed when the crane abruptly stops. Peak impact force is produced at the contact interface between pinion and rack gears due to the inertia force of the boom. However, the maximum stress (bending/contact) of spindle and rack are under the yield stress, which is safe from damage. By using the developed simulation model, the experiment process is expected to be minimized.

• Journal of Bio-Environment Control
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• v.10 no.4
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• pp.225-231
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• 2001

This study was conducted to examine effect of different environment conditions in glass, PC, PET and PE greenhouses controlled by different environment control systems on the growth of green pepper. Light transmittance of 64.7% in the glass greenhouse was the highest among different green-houses. Air temperature was the highest in the glass greenhouse when ventilators were closed, and was the highest in the PE greenhouse when ventilators were open. Air relative humidity was the highest in the PE greenhouse during 24 hours. The amount of solar energy accumulated in soil was the greatest in the glass greenhouse and this energy released during the night escaped through covering materials. Latent heat and solar energy affected air temperature increased in greenhouses. The air temperature of glass greenhouse was 27.5$^{\circ}C$ at 11 O clock, which was the highest air temperature among the all greenhouse types. Clear differences were observed in leaf area and plant height at 30 days after transplanting. Days to first flowering was the shortest in the glass greenhouse with 72.7 days. Flower shedding was the greatest in the PE greenhouse with 12.6%. Days to fruit harvesting was the shortest in the glass greenhouse with 14.3 days. Fruit quality, such as fruit length, fruit diameter, fruit flesh thickness, and vitamin C content, was the best in the glass greenhouse. Percent marketable fruits was the highest with 95.3% when the pepper was grown hydroponically in the glass greenhouse.

• Korean Journal of Cognitive Science
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• v.20 no.2
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• pp.155-181
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• 2009

Psychophysiologists are often interested in the EEG signals that accompany certain psychological events. When one is interested in a time series of event-related changes in EEG, one focuses on examining how the waveforms recorded at individual electrode sites vary over time across one or more experimental conditions. This is an analysis of event-related potentials (ERPs). In addition to such a classical EEG analysis in the time domain, the EEG measures can be investigated in the frequency domain. Moreover, it has been demonstrated that spectral analyses can often yield significant insight into the functional cognitive correlations of the signals. Therefore, this review paper tries to summarize essential concepts (e.g. phase-locking) and conventional methods (e.g. wavelet transformation) for understanding spectral analyses of brain oscillatory activity. Phase-coherence is also introduced in relation to functional connectivity of the brain.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.4
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• pp.732-736
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• 2000

The purpose of this study was to investigate the extraction method of phenolic compounds and antioxidant activities of the aerial part of Epimedium koreanum NAKAI (EKN). The antioxidant activities of EKN were tested with by hydrogen donating ability, inhibition of lipid peroxidation, and inhibition of LDL oxidation. The most suitable conditions for the extraction of phenolic compounds from EKN were to use 60% ethanol by 3 times, and the yield of extract (dry basis) was 22%. In the extraction efficiency of phenolic compounds, 60% ethanol as extracting solvent was superior to water. Sixty% ethanol extract of EKN was found to have an ability of hydrogen donating to DPPH. MDA determination showed the 95% inhibitory effect against linoleic acid oxidation by the addition of 700 ppm EKN extract. Also, about 70% of LDL oxidation was inhibited by the addition of 500 ppm.

• Journal of Powder Materials
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• v.17 no.4
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• pp.326-335
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• 2010

In this paper, the effect of electrical characteristics and electrode shape on the alignment and attachment of multi-walled carbon nanotubes (MWNTs) has been studied. The attraction and alignment of MWNTs between the gaps has been investigated by applying electric field which is called electrophoresis and dielectrophoresis. According to the frequency of electric field, positive or negative dielectrophoretic force can be determined. The concentration of MWNTs solution was $5\;{\mu}g/ml$, and a droplet of $1.0{\sim}1.5\;{\mu}l$ was dropped between two electrodes. Through the repeated experiments, the optimal electrical conditions for aligning and attaching MWNTs in the desired places were obtained. Since the frequency range of 100 kHz~10 MHz generated positive dielectrophoretic force, MWNTs were attracted and aligned between the gaps with this frequency range. For generating enough force to attract MWNTs, the appropriate voltage range was $0.3{\sim}1.3\;V_{rms}/{\mu}m$. Furthermore, the effect of electrode shape on the alignment of MWNTs was investigated. A single MWNT attachment was accomplished on the round shaped with 70% yield.

• Journal of the Korean Applied Science and Technology
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• v.25 no.3
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• pp.299-312
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• 2008

The fat of Tra and Basa catfish (Mekong Delta, Viet Nam) was evaluated for the first time as the potential feedstock for biodiesel production, due to its abundance, availability and cheap cost. The unsaturated fatty acid contents of Tra and Basa fat were 57.97% and 64.17%, respectively. Biodiesel was prepared from Tra and Basa fat by methanolysis reaction using alkali catalysts like sodium hydroxide and potassium hydroxide. Effects of various process parameters on biodiesel production, such as molar ratio of methanol to fat, catalyst concentration, temperature and time were investigated. As those results, the transesterification can be performed under moderate conditions, and the biodiesel yields were shown more than 90%. KOH catalyst was the best catalyst for biodiesel production from both Basa and Tra fat. As the feedstock aspect, Basa fat was indicated more efficiency than that of Tra fat. The maximum yield could be achieved by the transesterification from Basa fat with 5:1 molar ratio of methanol to fat, 0.8% KOH catalyst, $50^{\circ}C$, and 50 min. For Tra fat, the optimal condition were at 6:1 molar ratio of methanol to fat, 0.8% KOH catalyst, $50^{\circ}C$, and 45 min. Nowadays, due to cheaper cost and abundance, Tra fat is a promised resource for cheap biodiesel production in Viet Nam.

• Journal of Microbiology and Biotechnology
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• v.25 no.1
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• pp.57-65
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• 2015

β-Glucosidase production by the white rot fungus Flammulina velutipes CFK 3111 was evaluated using different carbon and nitrogen sources under submerged fermentation. Maximal extracellular enzyme production was 1.6 U/ml, corresponding to a culture grown in sucrose 40 g/land asparagine 10 g/l. High production yield was also obtained with glucose 10 g/land asparagine 4 g/l medium (0.5 U/ml). Parameters affecting the enzyme activity were studied using p-nitrophenyl-β-_D-glucopyranoside as the substrate. Optimal activity was found at 50℃ and pHs 5.0 to 6.0. Under these conditions, β-glucosidase retained 25% of its initial activity after 12 h of incubation and exhibited a half-life of 5 h. The addition of MgCl₂, urea, and ethanol enhanced the β-glucosidase activity up to 47%, whereas FeCl₂, CuSO₄, Cd(NO₃)₂, and cetyltrimethylammonium bromide inflicted a strong inhibitory effect. Glucose and cellobiose also showed an inhibitory effect on the β-glucosidase activity in a concentration-dependent manner. The enzyme had an estimated molecular mass of 75 kDa. To the best of our knowledge, F. velutipes CFK 3111 β-glucosidase production is amongst the highest reported to date, in a basidiomycetous fungus.

• Journal of Microbiology and Biotechnology
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• v.19 no.1
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• pp.65-71
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• 2009

Microbial oxidoreductive systems have been widely used in asymmetric syntheses of optically active alcohols. However, when reused in multi-batch reaction, the catalytic efficiency and sustainability of non-growing cells usually decreased because of continuous consumption of required cofactors during the reaction process. A novel method for NADPH regeneration in cells was proposed by using pentose metabolism in microorganisms. Addition of D-xylose, L-arabinose, or D-ribose to the reaction significantly improved the conversion efficiency of deracemization of racemic 1-phenyl-1,2-ethanediol to (S)-isomer by Candida parapsilosis cells already used once, which afforded the product with high optical purity over 97%e.e. in high yield over 85% under an increased substrate concentration of 15 g/l. Compared with reactions without xylose, xylose added to multi-batch reactions had no influence on the activity of the enzyme catalyzing the key step in deracemization, but performed a promoting effect on the recovery of the metabolic activity of the non-growing cells with its consumption in each batch. The detection of activities of xylose reductase and xylitol dehydrogenase from cell-free extract of C. parapsilosis made xylose metabolism feasible in cells, and the depression of the pentose phosphate pathway inhibitor to this reaction further indicated that xylose facilitated the NADPH-required deracemization through the pentose phosphate pathway in C. parapsilosis. moreover, by investigating the cofactor pool, the xylose addition in reaction batches giving more NADPH, compared with those without xylose, suggested that the higher catalytic efficiency and sustainability of C. parapsilosis non-growing cells had resulted from xylose metabolism recycling NADPH for the deracemization.