• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.3
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• pp.352-358
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• 2009

The physicochemical properties of dextran culture fermented by Leuconostoc citreum S5 were evaluated by the addition of various polysaccharides and heat-treatment. The consistency of dextran culture increased with the addition of carrot juice residue (CJR) in submerged culture, resulting in the highest consistency of 150 $Pa{\cdot}s^n$ and viable cell counts of $2.36{\times}10^9$ CFU/mL at 20% level of CJR. The dextran culture showed the pseudoplastic behavior and its consistency was greatly increased with the addition of various polysaccharides at 2% level. Addition of glucomannan indicated the highest consistency of 1275 $Pa{\cdot}s^n$ and their heat-treatment resulted in the increase of consistency except for glucomannan. After heat-treatment, the fermented dextran culture containing CJR fortified with gellan gum and carrageenan showed great change in rheology, indicating the highest consistency and hardness value resulted in the great increase of elastic and viscous moduli. The dynamic viscoelastic properties of dextran culture were greatly increased by the heat-treatment after fortification of various polysaccharides. Thus, the consistency and viable cell counts of dextran culture were increased with the addition of CJR. The rheological properties of dextran culture were manipulated by the fortification of various polysaccharides and heat-treatment.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• Resources Recycling
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• v.8 no.4
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• pp.45-56
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• 1999

The purpose of tlus sludy was to preparc raw material powder for Mn-Zn iclrile, h m mined mill scale and fero-Mn, usins a co-spray roasting process The mill scale and ferra-Mn uscd in this raalins process was rcf~nedb y mesn-ns of a slxc~apl rxcss ~nvolvinm~a te~ialsc ontalning imp~u-ltleso r less than 100 pprn In this study an effeclive spray roaster system. wllich produces fme complex oxide powder, collects produccd ~owder.,m d prcvel~tse ~~llssiooifi HCI gas. was also manufactured. By means of spray~ngp urifcd raw malerial solu~lionl nln a manufacued high tcmpervture rumace. &-ferrite powder and a comnpleu o ~ d e powder of Fe,O; and M,x203 were manufactured. The chmcterlstics of the composllion. surface urca, and p'miicle size dismbulion or the produced powder were exmined. ptoduced powdcr was then ~ m e dwi tli ZnO powder. aid olher addilives of defined cornposnion, and Mn-Zn femite cares werc praiuccil by meuns of Sorlning and closely controlled sintering processes. The magpelic p~oprlieso f c olo~ss, initlal permeability. mauin~u~mnn agnehc flux. coz~civcr orcc and residual magnccic flux for the above cores we,= measured, and fmm Il~ase I-csulls the eflicacy of lhe co-spray roasling pncess to pl.ellare raw material powder lor Mn-Zn ferntc was established

• KSBB Journal
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• v.17 no.1
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• pp.100-105
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• 2002

N-acetyl-D-glucosamine oligosaccharides [(GlcNAc)n] whose degree of polymer-ization is from one to ten (n=1-10) were fractionated by column chromatography on CM-Sephadex. Electro dialysis from a partially deacetylated chitosan hydrolysate prepared crudely with the N-acetyl-D-glucosaminidase(chitinase) and exo-N, N'-diacetylchito-biohydrolase(chitobiase) of Serratia marcescens QM B1466. Reducing sugar compositions and sequences of the N-acetyl-glucosamine oligosaccharides were identified by N-acetylation, randomly cleavage with chitinase and ego-splitting with chitobiase. N-acetyl-glucosamine heterochitooligosaccharides with glucosamine oligosaccharides, (GlcN)n at the reducing end residues together with $(GlcN)_1\sim(GlcN)_4$ were detected. Separation was accomplished by prefractionation with election by 0 to 1.0 M NaCl gradient solution. $(GlcNAc)_1 =4.25%,\; (GlcNAc)_2=4.49%,; (GlcNAc)_3=11.1%,\; (GlcNAc)_4=2.5%,$$ $(GlcNAc)_{5}$=0.64%, $(GlcNAc)_{6}$=2.12% and $(GlcNAc)_{7}$=1.21%, respectively, were crystallized after electrodialysis and lyophilization Each N-acetyl-D-glucosamine oligosaccharides content were detected by HPLC.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.922-930
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• 2008

The selective non-catalytic reduction(SNCR) performance is sensitive to the process parameters such as flow velocity, reaction temperature and mixing of reagent(ammonia or urea) with the flue gases. Therefore, the knowledge of the velocity field, temperature field and species concentration distribution is crucial for the design and operation of an effective SNCR injection system. In this work, a full-scale two-dimensional computational fluid dynamics(CFD)-based reacting model involving a droplet model is built and validated with the data obtained from a pilot-scale urea-based SNCR reactor installed with a 150 kW LPG burner. The kinetic mechanism with seven reactions for nitrogen oxides($NO_x$) reduction by urea-water solution is used to predict $NO_x$ reduction and ammonia slip. Using the turbulent reacting flow CFD model involving the discrete droplet phase, the CFD simulation results show maximum 20% difference from the experimental data for NO reduction. For $NH_3$ slip, the simulation results have a similar tendency with the experimental data with regard to the temperature and the normalized stoichiometric ratio(NSR).

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.914-918
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• 1992

The preferential transport phenomena of neutral cation-anion moieties in neutral macrocycle-facilitated emulsion liquid membrane were described in this study. Emulsion membrane systems consisting of (1) aqueous source phase containing 0.001M $M(NO_3)_2$ (M = $Mn^{2+}$, $Co^{2+}$, $Ni^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Sr^{2+}$, $Cd^{2+}$, $Pb^{2+}$) (2) a toluene membrane containing 0.02M ligand (DB$N_3O_2$, DB18C6) and the surfactant span 80 (sorbitan mono oleate) (3% v/v) and (3) aqueous receiving phase containing $Na_2S_2O_3$ or $NaNO_3$ were studied with respect to the disappearence of metal ions from the source phase as a function of time. Cation transport rates for various two component equimolar mixture of metal ions were determinded. $Cd^{2+}$ was transported higher rates than the other $M^{2+}$ in the mixture solution.

• Composites Research
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• v.33 no.4
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• pp.228-233
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• 2020

In this paper, a single lap shear test was performed using a glass fiber reinforced composite material (GFRC). Pencil lead drawn paper sensor (PLDPS) was applied for single lap shear test being performed. Bisphenol-A epoxy and amine hardener were used as adhesives combining with composite materials. To make a difference in adhesive properties, the adhesive was cured under different conditions. PLDPS was made of a 4B pencil on A4 paper. Because graphite in a pencil was an electrically conductive substance, electric resistance (ER) could be measured. A change in ER was observed by a position where a PLDPS was attached to single lap shear specimens. It was confirmed that the change in ER was different depending on two attached positions and was observed by lap shear strain as well. In case the lap shear strain was large, the change in ER of PLDPS was high. This was because the larger the extension of the adhesive part, the larger the degree of bending of the specimen and thus the larger the distance change between two electrodes.

• Elastomers and Composites
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• v.37 no.1
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• pp.7-13
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• 2002

In this study, mechanical properties of PVC complexes containing the gypsum (Namhae Chemical Co.) which contains phosphte, CaO, etc., Pb-species stabilizer, and $CaCO_3$ were investigated as a function or the content. As a result, mechanical properties increased when the gypsum was mixed with PVC at the extent of 8.46wt%. From this result, it is suggested that the gypsum containing phosphate and CaO is compatible with PVC. Thermogravimetric analysis(TGA) showed that pyrolysis started about at $275^{\circ}C$, and residual weight(%) increased with the amount of the gypsum, and differential scanning calorimetry (DSC) showed that $T_m,\;T_g$ had the maximum and minimum value respectively when the gypsum was mixed with PVC at the extent of 8.46wt%. Comparing all the results, both mechanical and thermal properties of PVC complex were improved. The X-ray diffraction measurement also showed their blonds and structures.

• Elastomers and Composites
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• v.44 no.3
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• pp.336-342
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• 2009

We measured shear viscosity of polystyrene (PS) and poly(butyl methacrylate) (PBMA) particles, with a capillary rheometer, prepared by suspension polymerization with 1.0 wt% hydrophobic silica as a stabilizer by varying the initiator concentration at $75^{\circ}C$. PS particles with weight average molecular weight of 66,500 g/mol displayed a Newtonian behaior at low shear rates at $190^{\circ}C$. With increasing molecular weight, PS particles showed shear thinning over the entire range of shear rates. For PBMA particles, steady shear measurement was carried out at $170^{\circ}C$. PBMA particles with weight average molecular weight of 156,700 g/mol showed a Newtonian behaior only at low shear rates. PBMA particles also showed shear thinning with an increase in molecular weight and its pattern similar to that of PS. When carbon black was incorporated into PS and PBMA polymers, steady shear measurement was conducted at $170^{\circ}C$. An increase in carbon black concentration in PS and PBMA composite particles exhibited a progressive increase in shear viscosity. The increase in shear viscosity, however, was less pronounced compared to an increase as a function of molecular weight. Preparing PS composites containing carbon black by internal mixing resulted in an increase in shear viscosity. Its increase, however, was found to be less than that shown in PS composite particles. We speculate that this is caused by an enhanced dispersion of carbon black particles with an internal mixer. Yield behavior was not observed in any of the samples we selected in this experiment.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.3
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• pp.201-206
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• 2020

Purpose: The purpose of this study is to evaluate the antimicrobial activity on the dental bur with fluoride for S. mutans. Materials and methods: 0 ppm, 300 ppm, 500 ppm, 1,000 ppm, 1,450 ppm fluoride ion is added to a specimen. S. mutans was incubated for 24 hours, the number of S. mutans were counted. Kruskal-Wallis and MannWhitney analysis were used SPSS 25.0 (IBM SPSS 25.0, Chicago, IL, USA). Results: The mean S. mutans counts of 0 ppm, 300 ppm, 500 ppm, 1,000 ppm, and 1,450 ppm were 374.0 ± 12.6, 251.0 ± 66.7, 111.4 ± 35.6, 41.6 ± 11.7 and 13.2 ± 4.6, respectively. All groups except the control and 300 ppm showed statistically significant. Conclusion: Thus, more than 500 ppm fluoride ion showed the statistically significant antimicrobial activity. 1,450 ppm group showed the highest antimicrobial activity. This study showed the clinical possibility for dental caries protection and antimicrobial activity of dental bur.