• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1065-1070
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• 1996

Antimutagenic effect of chitosan hydrolysates was investigated using Salmonella typhimurium reversion assay and SOS chromotest against 3-amino-1-methyl-5H-pyrido[4,3-b]lindole(Trp-P-2), aflatoxin $B_1$, 2-nitrofluorene and 4-nitroquinoline oxide. After partial acid hydrolysis of chitosan, six fraction of different molecular size were obtained by ultrafiltration. Chitosan hydrolysates showed antimutagenic effect of $0{\sim}78%$ on Trp-P-2, $0{\sim}92%$ on aflatoxin $B_1$ and $0{\sim}51%$ on 2-nitrofluorene in Salmonella typhimurium reversion assay. Inhibitory effect in Salmonella typhimurium reversion assay showed the highest at 5% concentration of fraction 6 in Trp-P-2, 10% concentration of fraction 5 in aflatoxin $B_1$ and 5% concentration of fraction 6 on 2-nitrofluorene. In SOS chromotest, chitosan hydrolysates showed anitimutagenic effect of $0{\sim}54%$ on Trp-P-2 and $0{\sim}77%$ on 4-nitroquinoline oxide, These results suggest that high molecular weight fraction of chitosan hydrolysates (MW>30,000) in most effective to inhibit mutagenicity of tested mutagens.

• Membrane Journal
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• v.26 no.3
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• pp.205-211
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• 2016

Performance of pyrophyllite-based ceramic membranes newly developed were investigated. Membrane fouling caused by microbial suspensions taken from a full-scaled MBR system at domestic wastewater treatment plant was observed at different airflow rate and distance between each membrane. For the pyrophyllite support, pore size was about $1.0{\mu}m$, but surface coating with $Al_2O_3$ solution decreased the pore size with the reduction of the pure water permeability. With the MLSS taken from the full-scaled MBR system (6 g/L), the fouling rate was decreased by increasing airflow rate under $20L/m^2{\cdot}hr$ of setpoint flux. However, the effectiveness of the airflow rate on the fouling control depends strongly upon the gap between each membrane. At fixed airflow rate, the fouling rate was decreased by increasing the gap between each pyrophyllite membrane. Nevertheless, further increasing the membrane distance from 3.5 to 5.4 cm resulted in higher fouling rate. Similar result was observed with the $Al_2O_3$ coated-pyrophyllite membrane. Nevertheless, the fouling rate was lower with the coated membrane than that observed with the uncoated pyrophyllite support. Regardless of surface coating, the suspended solids were removed almost completely and the surface coating on the pyrophyllite support improved organic rejection with PEG solution (MW : 8000 kDa) tested.

• Applied Biological Chemistry
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• v.42 no.1
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• pp.12-19
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• 1999

To improve biopolymer productivity and properties of Bacillus strains, protoplast fusion was performed between biopolymer producing Bacillus subtilis K-1 and lactose utilizing Bacillus coagulans. The results were as follows; Protoplasts mixed in fusion fluid containing 33% PEG 6000, 1% PVP and 10 mM $CaCl_2$ were reacted for 5 min at $37^{\circ}C$ and then centrifused protoplasts were directly overlaid on the selective media containing $100\;{\mu}g/ml$ antibiotics and incubated for 3 days. At this conditions, the frequency of protoplast fusion was generally in the range of $4.6{\times}10^{-5}\;to\;1.8{\times}10^{-7}$ in ratio. Segregation ratio was observed between 1 to 6% indicating genetic stability of all the fusants. Fusants growth were also observed on the media contained amino acid and antibiotics as required marked materials. DNA contents of the selected fusants were 1.6 to 2.7 times more than that of parent strains. With observation by TEM microscopy, spherical protoplasts were first released from the swollen parental cells and then contracted to fuse in the process of fusion. And fused cells were observed representative vesicle. Originally, the parental cells were observed as in the morphology of thick-walled and double membrane-surrounded rod shape with TEM microscopy.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.213-223
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• 2008

The objective of this study was to compare dentin shear bond strength (DSBS) of dentin bonding agents (DBAs) cured with a plasma arc (PAC) light curing unit (LCU) and those cured with a light emitting diode (LED) LCU. Optical properties were also analyzed for Elipar freelight 2 (3M ESPE); LED LCU, Apollo 95E (DMT Systems); PAC LCU and VIP Junior (Bisco); Halogen LCU. The DBAs used for DSBS test were Scotchbond Multipurpose (3M ESPE), Singlebond 2 (3M ESPE) and Clearfil SE Bond (Kuraray). After DSBS testing, fractured specimens were analyzed for failure modes with SEM. The total irradiance and irradiance between 450 nm and 490 nm of the LCUs were different. LED LCU showed narrow spectral distribution around its peak at 462 nm whereas PAC and Halogen LCU showed a broad spectrum. There were no significant differences in mean shear bond strength among different LCUs (P > 0.05) but were significant differences among different DBAs (P < 0.001)

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.10
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• pp.1309-1314
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• 2006

This study analyzed the contents of vitamin C, polyphenol compounds, and evaluated the inhibitory activities against xanthine oxidase and tyrosinase of Lepista nuda extract prepared by the reflux and microwave-assisted methods. The vitamin C content of the fresh L. nude was $9.92{\pm}0.02$ mg/100 g. The content of phenolic compounds in the fresh L. nuda was $1.87{\pm}0.02\;mg/g$. The ethanol extracts prepared by reflux method and microwave-assisted method showed the highest phenol contents of $12.06{\pm}0.12\;mg/g\;and\;11.84{\pm}0.17\;mg/g$, respectively. The inhibitory rates on xanthine oxidase and tyrosinase of ethanol extracts prepared by the microwave assisted method showed the highest value of 99.78% and 30.30% at the concentration of $3,000{\mu}g/mL$. The inhibitory activities on xanthine oxidase and tyrosinase were increased depending on the extract concentration.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.187-196
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• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of pile should be known accurately. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanism of drilled shaft socketed into weathered rock was investigated. For the investigation, five cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the Held test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The f-w (side shear resistance-displacement) curve of the pile in moderately weathered rock reached to yielding point at a for millimeter displacements, and after yielding point, the rate of resistance increment dramatically decreased. However, the f-w curve in the highly/completely weathered rock did not show the obvious yielding point, and the resistance gradually increased showing the hyperbolic pattern until relatively high displacement (>15 mm). The q-w (end bearing resistance-displacement) curves showed linear response at least until the base displacement of approximately 10 mm, regardless of rock mass conditions.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.655-662
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• 2018

To respond effectively to climate change following the launch of the new climate system, the government is seeking to expand the use of distributed power resources. Among them, the district heating system centered on Combined Heat and Power (CHP) is accepted as the most realistic alternative. On the other hand, the government recently announced the change of energy paradigm focusing on eco-friendly power generation from the base power generation through $8^{th}$ Basic Plan for Long-term Electricity Supply and Demand(BPE). In this study, we analyzed the quantitative effects of profit and loss on the CHP operating business by changing patterns of the heat production, caused by the change of energy paradigm. To do this, the power market long-term simulation was carried out according to the $7^{th}$ and $8^{th}$ BPE respectively, using the commercialized power market integrated analysis program. In addition, the CHP operating model is organized to calculate the power and heat production level for each CHP operation mode by utilizing the operating performance of 830MW class CHP in Seoul metropolitan area. Based on this, the operation optimization is performed for realizing the maximum operating profit and loss during the life-cycle of CHP through the commercialized integrated energy optimization program. As a result, it can be seen that the change of the energy paradigm of the government increased the level of the ordered power supply by Korean Power Exchange(KPX), decreased the cost of the heat production, and increased the operating contribution margin by 90.9 billion won for the 30 years.

• KSBB Journal
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• v.15 no.6
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• pp.649-657
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• 2000

The factors affecting the back-extraction efficiency of Bovine Serum Albumin (BSA, Mw. 65kDa, pl 4.9) solubilized in an AOT reverse micellar solution, prepared by the injection method, to an excess aqueous phase were investigated. In particular, the effects of pH, the types of salts, alcohols added as cosurfactants, and their concentrations in the aqueous phase were examined. Furthermore, by comparing the CD spectra of the back-extracted BSA and the feed BSA, the structural changes of BSA during the extraction process were determined. The addition of 1:1 salt such as KCl or NaCl to the aqueous phase resulted in almost a 100% extraction to the aqueous phase at a pH higher than its isoelectric point pl. This high efficiency of back-extraction might be due to the change in the interactions between the protein and micellar aggregates driven by the added salt. For 1:2 salts like $CaCl_2$ and $MgCl_2$, BSA was back-extracted with lower than 20% extraction efficiency. Maximum extraction efficiencies were attained at about pH=7 and pH=8 for monovalent and divalent salts, respectively. The addition of alcohols as cosurfactants led to an improvement in monovalent and divalent salts, respectively. From the CD spectra of BSA extracted to the aqueous phase, it was observed that denaturation of BSA was not significant. In certain back-extraction conditions, the extracted BSA showed even higher activity than the feed BSA.

• Korean Journal of Environment and Ecology
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• v.31 no.2
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• pp.166-173
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• 2017

Morphological and population characteristics of the Cottus koreanus were investigated at Hoam stream from October 2015 and April 2016. This is the first record on C. koreanus not only from Hoam stream (the upstream region of Daejong stream, Gyeongsangbuk-do Gyeongju-si Yangbuk-myeon Hoam-ri) but also from the stream flowing into the Samcheogosip stream, in the southern part of East Sea, Korea. The distribution of C. koreanus ranged from Girim temple to Yongyeon waterfall, about 1.2 km, and the water surface were about $3,600m^2$. The population size was assumed to 1,656 individual number, 46 object per $100m^2$. The morphometric characteristics of C. koreanus in the Hoam stream and the Han river are very similar except that the population at Hoam stream shorter head length, ventral fin ray length, pectoral fin ray length and mouth width when compared with the population at Han river. Other than that, the two populations showed the same meristic characters. Frequency analysis of total length indicated that the group with 40~59 mm in total length was one year old, the 60~79 mm was two years old, and the group over 80 mm was three years old. The average number of eggs in the ovaries was estimated as 361 (239~468) per matured female. The number of matured eggs size in ovaries was $2.6{\pm}0.21$ (23.~3.1) mm and this species was large eggs type. Calculation of the length-weight relation of C. koreanus showed the value of constant a as 0.00001 and b as 3.01, and the Condition factor (K) was 1.26 an on average.

• Wind and Structures
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• v.30 no.4
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• pp.433-450
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• 2020

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon "Megi". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.