• The Korean Journal of Rheology
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• v.10 no.4
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• pp.195-201
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• 1998

We have studied the rheological and electrical properties of two types of electrorheological (ER) fluids based on semi-conductive polymers (poly(p-phenylene) and polyaniline). These semi-conductive polymer-based suspensions showed a dramatic increase in viscosity on the application of the static electric field due to the large value of conductivity ratio between particle and medium. The dynamic yield stresses of these ER suspensions exhibited a quadratic dependence on electric field strength at low electric fields and a linear one for high fields. They showed a maximum and then decreased with increasing bulk conductivity of particles. These yield stress behaviors under the static electric field were found to be closely related to the dielectric properties, which is in accord with Maxwell-Wagner interfacial polarization induced by the conductivity effects. In order to achieve better understanding of interfacial polarization effect on ER response and to improve the stability of ER suspension, different kinds of surfactants were employed for controlling the ER activity as well as for enhancing the colloidal stability of suspensions.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.83-90
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• 1999

Although the chitosan has many functional properties due to its cationic amino groups, the application of chitosan in foods is limited by its poor water solubility, bitter taste and astringency. This study was conducted to investigate physicochemical and sensory properties of chitosan hydrolysates in various molecular weights obtained by ultrafiltration after enzymatic hydrolysis. As molecular weight decreased, the solubility of chitosan hydrolysates increased, while the viscosity and emulsion stability decreased. High molecular weight chitosan hydrolysates (>30 kDa) exhibited 800% of fat binding capacity, while low molecular weight ones $(3{\sim}30\;kDa)$ showed 500% of fat binding capacity. Water soluble chitosan hydrolysates exhibited no color differences. Freeze-thaw stability of chitosan hydrolysates was good, without variations among fractions. Cholesterol binding capacity of chitosan hydrolysates was changed from 24% to 36% with increasing molecular weights. From sensory evaluation of chitosan hydrolysates, it was found that bitterness, astringency, chemical flavor and fish flavor of chitosan hydrolysates were very weak.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.725-730
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• 2017

The strength ratio of the main structures of buildings gradually increasing, due to the advances made in analysis and cost saving techniques. In this study, to examine the stability of industry buildings using sandwich panels as roof assemblies, we examine the changes in the moment strength ratio of the main structures caused by increasing the roof load. This study adopts the PEB structure and three H-steel structure as the structural analysis models. In the case where the additional load exceeds about 11% of the roof design load, the strength ratio exceeds 1 for the main structure. In the case where the additional load exceeds about 36%(of the roof design load), the working moment exceeds the plastic moments, which leads to major damage to the structure. This study compares 1) the maximum load according to the purlin spaces, 2) the maximum load by KS, and 3) the maximum load calculated from the test results of the manufacturer.The maximum bearing load of the panels determined by all three methods exceeds the structure failure threshold load of the main structure. This study provides evidence that an unexpected increase in the roof load might cause the whole structure to collapse, due to the failure of the main structural members, before the failure of the roof assemblies. Therefore, information on the structural performance of the sandwich panels is required for the structural design, and the sandwich panels should be considered to be an integral part of the overall structural design.

• Journal of Microbiology and Biotechnology
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• v.23 no.11
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• pp.1519-1528
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• 2013

Bacillus pumilus SG2, a halotolerant strain, expresses two major chitinases designated ChiS and ChiL that were induced by chitin and secreted into the supernatant. The present work aimed to obtain a mutant with higher chitinolytic activity through mutagenesis of Bacillus pumilus SG2 using a combination of UV irradiation and nitrous acid treatment. Following mutagenesis and screening on chitin agar and subsequent formation of halos, the mutated strains were examined for degradation of chitin under different conditions. A mutant designated AV2-9 was selected owing to its higher chitinase activity. To search for possible mutations in the whole operon including ChiS and ChiL, the entire chitinase operon, including the intergenic region, promoter, and two areas corresponding to the ChiS and ChiL ORF, was suquenced. Nucleotide sequence analysis of the complete chitinase operon from the SG2 and AV2-9 strains showed the presence of a mutation in the catalytic domain (GH18) of chitinase (ChiL). The results demonstrated that a single base change had occurred in the ChiL sequence in AV2-9. The wild-type chitinase, ChiL, and the mutant (designated ChiLm) were cloned, expressed, and purified in E. coli. Both enzymes showed similar profiles of activity at different ranges of pH, NaCl concentration, and temperature, but the mutant enzyme showed approximately 30% higher catalytic activity under all the conditions tested. The results obtained in this study showed that the thermal stability of chitinase increased in the mutant strain. Bioinformatics analysis was performed to predict changes in the stability of proteins caused by mutation.

• Journal of environmental and Sanitary engineering
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• v.15 no.2
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• pp.18-26
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• 2000

In order to improve the quality of Kamju(sikhae), Korean traditional sweat fermentated rice drink, Kamju made with laboratory fermenting from both covered barley malt and that added to commercial $\alpha-amylase$ and commercial sikhae can were investigated and analyzed ad follows 1. The amylase activities in L-malt(laboraory made malt), C-malt(commercial malt) were 25,065 units, 20,498 units at $60^{\circ}C$ and when heating at $60^{\circ}C$ for one hour their heat stability was getting lower and while at $70^{\circ}C$ after 2 hours both their heat stability was under 21%. 2. The external appearance, of all samples, in beating test, flipper, springer and leaker test were excellent and good valued. On the open test of sample can, head space was 7.9~9.0mm, net weight 247~250g, 432~435g, pH 4.96-5.76, Brix 13.2~14.0 and vacuum degree was 29~35cmHg. 3. The sucrose content of sample 1~5 was 8,57~10.01% highest ammount than sample 6(0.91%) 7(0.43%) and maltose content of sample 1~5 was 0.65~1.41% lower than 6 was 7.91% and 7 was 8,36%. The good traditional flavor texture and saccharides components content of glucose of sample 1~5 was 1.09~1.51, 6(3.86%), 7(3.97%), fructose content of sample 1~5 was 0.45~0.95%, 6(2.76%), 7(2.81%), maltotriose and raffinose of sample 1~5 were 0.04~0.291, 6(0.61%), 7(2.81%), and solid content of sample 1~5(3.1~3.8) was lower than 6(10.25%), 7(10.09%). 4. The result of sensory test as measured as lemone yellow of sample 6 and milky of sample 7, and weetness, flavor, color, traditional texture and sensory value for sample 1~5(3.1~3.8) was lower degree than that for 6(4.5), 7(4.0). 5. Among the heavy metals analyzed from sample cans, tin, iron and lead content for sample 1~5 were 31.95~36.71ppm, 5.84~6.39ppm and 0.075~0.09ppm while their content of sample 6.7, tin, 32.91ppm, 32.87ppm, iron 5.51ppm, 5.41ppm and lead, 0.074ppm, 0.079ppm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.309-312
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• 2017

The ceria powder is excellent in oxygen storage capacity (OSC) through the oxidation and reduction reaction of Ce ions and is used as a typical material for a three-way catalyst of an automobile which purifies the exhaust gas. However, since ceria generally has poor thermal stability at high temperatures, it is doped with metal ions to improve thermal stability. Therefore, in this study, Zr ions were doped into ceria powder, and their characteristics were further improved due to the increase of specific surface area with decreasing particle size due to doping. In this study, the synthesis of zirconium doped ceria nanopowder was synthesized by hydrothermal process. In order to synthesis Zr ion doped ceria nanopowder, the precursor reaction at was $200^{\circ}C$ for 6 hours. The average particle size of synthesized Zr doped $CeO_2$ nanopowder was below 20 nm. The specific surface area of synthesized Zr ion doped ceria nanopowder increased from $52.03m^2/g$ to $132.27m^2/g$ with Zr increased 30 %.

• Korean Journal of Food Science and Technology
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• v.30 no.1
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• pp.42-48
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• 1998

Physicochemical properties of waxy maize starch and oxidized waxy maize starch with sodium hypochlorite $(0{\sim}60\;mg\;CL_2/g\;starch,40^{\circ}C,\;pH\;10,\;3.0\;hr)$ were studied. As sodium hypochlorite concentration was increased, the content of crude lipid and crude protein of the oxidized starch were decreased. And crude protein content and whiteness was considered to show negative regression. However, the crude ash content of the oxidized starch increased significantly with oxidation and bore a positive regression to the chlorine content. There was a progressive increase in the carboxyl content with increasing oxidant level. After pasting in hot water and cooling, viscosity of the oxidized starches were drastically lower than that of native starch . As carboxyl contents of the oxidized starch increased, the solubility and swelling power was increased. When waxy maize starch treated with 0, 1.5, 3.0 and 6.0% sodium hypochlorite, temperature of initial gelatinization of oxidized starch was shown to 65, 65, 60 and $50^{\circ}C$, respectively. The oxidized waxy maize starches also form clearer pastes. Water binding capacity of the oxidized starch decreased as the degree of carboxyl group substitution increased. Waxy maize starch has polygonal and some round granules which range from about 3.7 to $20\;{\mu}m$ in diameter. Surface appearance of the waxy maize starch became rough when oxidized with sodium hypochlorite. When homogenate of the oxidized waxy maize starch solution and corn germ oil was stored under room temperature for 24 hours, the emulsion stability was considered to depend on starch concentration and degree of substitution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.5
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• pp.345-355
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• 1991

In order to effectively utilize the by-products of sea-food, the utilization of enzyme-modified flounder(Limanda aspera) skin gelatin as an emulsifier was investigated. In the experiment, the gelatin was extracted from the flounder skin with the heat-treatment at $60^{\circ}C$ and in pH 5.0 for 3 hrs with four volumes of distilled water and emulsifiers were enzymatically modified L-leucine alkyl esters$(L-leucine-OC_n$ : n= 2, 4, 6, 8 and 10) to the gelatin$(EMFSG-C_2,\;EMFSG-C_4,\;EMFSG-C_6,\;EMFSG-C_8,\;EMFSG-C_{10})$ for improving the functional properties such as emulsifying activity, emulsifying viscosity, whippability, electric conductivity, critical micelle concentration and interface tension, etc. Also, the functional properties of the L-leucine alkyl ester modified gelatins were compared with those of Tween-60 as reference. Molecular weights of the enzymatically modified flounder skin gelatin(EMFSG) were 20.5kDa. in $EMFSG-C_2.\;19.5 kDa.\;in\;EMFSG-C_4\;and\;16.5kDa.\;in\;EMFSG-C_6,\;EMFSG-C_8$ and $EMFSG-C_{10}$. respectively. Emulsifying activity and emulsifying viscosity in the modified gelatins were risen with increase of carbon number of the introduced L-leucine alkyl esters. Among the modified gelatins, $EMFSG-C_6$ exhibited the highest emulsifying stability and foaming stability, whereas $EMFSG-C_8$ showed the highest whippability. The electric conductivities of the all $EMFSG-C_n$ were linearly risen to critical micelle concentration(CMC) , therefore $EMFSG-C_{10}$ exhibited the lowest CMC value and interface tension, and dense particles in the microscopic observation. In conclusion, the best quality in functional properties was assured on $EMFSG-C_{10}$.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.697-703
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• 2005

Iron-coated sand(ICS) was prepared with variation of particle size of Joomoonjin sand, primary and secondary coating temperature, coating time, and dosage of initial Fe(III). An optimum condition of the preparation ICS was selected from the coating efficiency, stability of coated Fe(III), and removal efficiency of As(V). Coated amount of Fe(III) increased as primary coating temperature increased with smaller particle size of sand. Coating efficiency was quite similar over the investigated secondary coating temperature and time, while adsorption efficiency of As(V) onto ICS was severely reduced with ICS prepared at higher secondary coating temperature. By considering these results, an optimum secondary coating temperature and time for the preparation of ICS was selected as $150^{\circ}C$ and 1-hr, respectively. Coating efficiency increased us the dosage of initial Fe(III) up to 0.8 Fe(III) mol/kg sand and then no distinct increase was noted. Maximum As(V) adsorption was observed at 0.8 Fe(III) mol/kg sand. Secondary coating temperature and time were important parameters affecting stability of ICS, showing decreased dissolution of Fe(III) from ICS prepared at higher coating temperature and at longer coating time. From anionic type adsorption of As(V) onto ICS, it is possible to suggest the application of ICS for the removal of As(V) contaminated in acidic water system.

• Food Science of Animal Resources
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• v.22 no.2
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• pp.179-182
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• 2002

Using differential scanning calorimetry (DSC), changes underwent by a mixture of $\alpha$-lactalbumin ($\alpha$-La) and $\beta$-lactoglobulin ($\beta$-Lg) during heat treatment were studied, yielding useful information for the dairy industry. Results of the DSC showed that the heat denaturation temperature of the hobo-$\alpha$-La was higher than that of apo-$\alpha$-La, suggesting hole-$\alpha$-La‘s greater stability. The denaturation temperature of a mixture of holo-$\alpha$-La and $\beta$-Lg was also slightly lower than that of holo-$\alpha$-La alone. The denaturation temperature of an apo-$\alpha$-La and $\beta$-Lg mixture was higher than that of holo-$\alpha$-La and $\beta$-Lg, suggesting that the heat stability of apo-$\alpha$-La was increased by $\beta$-Lg. Based on these results, it is possible to conclude that a mixture of holo-$\alpha$-La and $\beta$-Lg is more intensively affected by an increase in temperature than other samples, and that free sulphydryl groups seem to take part in this heat-induced denaturation.