• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.353-360
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• 1998

A bacterial strain PN33 producing large amounts of extracellular pectin lyase (PNL, EC 4.2.2.10) was isolated from soil. The isolated bacterium was identified as a strain of Bacillus sp. Production of PNL by the strain was induced only by pectins, with a higher degree of esterification, which had been added to the culture medium as a sole carbon source. The optimal medium for PNL production was determined to consist of 10 g pectin, 2 g yeast extract, 4 g $K_2HPO_4{\cdot}3H_2O$, 0.6 g $MgSO_4$, and 0.11 g $CaCl_2$ per liter (pH 7.0). The PNL activity in the culture supernatant reached the highest level of 132 mU/ml after 32 h cultivation at $37^{\circ}C$ in the optimal medium. The PNL produced was purified to homogeneity by ammonium sulfate fractionation (50~80%), and cation exchange and size exclusion chromatographies. The molecular mass of the enzyme was estimated to be approximately 52 kDa by SDS-PAGE. Almost the same mass was determined by nondenaturing PAGE, indicating that the functional enzyme had a monomeric structure. As expected, the PNL exhibited higher activities on the highly esterified pectins whereas it gave no detectable activity on polygalacturonic acid. The enzyme showed the highest activity at the acidic pH of 6.0, exceptional for a bacterial PNL. Maximum activity was measured at $40^{\circ}C$, although the stability f the purified enzyme was poor at this temperature. alcium (1 mM) was found to activate the PNL activity by $50\%$, and also remarkably increased the thermal stability f the enzyme. Phenylmethylsulfonylfluoride (PMSF) and iethylpyrocarbonate (DEPC) inhibited the PNL activity lmost completely at the concentration of 5 mM. This result ndicates that some serine and histidine residues of the nzyme may play an essential role for catalytic function of he enzyme.

• Polymer(Korea)
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• v.37 no.2
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• pp.156-161
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• 2013

Phenolic antioxidants are effective stabilizers that provide excellent long-term heat stability by preventing thermo-oxidative degradation during processing and service life. However, under a selected set of circumstances, certain types of phenolics have been susceptible to discoloration due to prolonged storage in an environment containing oxides of nitrogen. It is investigated that the effect of addition of secondary antioxidant and chemical structure of primary antioxidant on discoloration of amorphous poly-${\alpha}$-olefin (APAO), which is especially prone to be decomposed in high processing temperature. From the result, it is concluded that a higher level of steric hindrance of phenolic antioxidant provided by long alkyl chain allows a more enhanced synergic effect with secondary antioxidant.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.1
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• pp.35-43
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• 1997

Handling the emergency problems such as Chemobyl accident require real time prediction of pollutants dispersion. One-point real time sounding at pollutant source and simple model including turbulent-radiation process are very important to predict dispersion at real time. The stability categories obtained by one-dimensional numerical model (including PBL dynamics and radiative process) are good agreement with observational data (Golder, 1972). Therefore, the meteorological parameters (thermal, moisture and momentum fluxes; sensible and latent heat; Monin-Obukhov length and bulk Richardson number; vertical diffusion coefficient and TKE; mixing height) calculated by this model will be useful to understand the structure of stable boundary layer and to handling the emergency problems such as dangerous gasses accident. Especially, this simple model has strong merit for practical dispersion models which require turbulence process but does not takes long time to real predictions. According to the results of this model, the urban area has stronger vertical dispersion and weaker horizontal dispersion than rural area during daytime in summer season. The maximum stability class of urban area and rural area are 'A' and 'B' at 14 LST, respectively. After 20 LST, both urban and rural area have weak vertical dispersion, but they have strong horizontal dispersion. Generally, the urban area have larger radius of horizontal dispersion than rural area. Considering the resolution and time consuming problems of three dimensional grid model, one-dimensional model with one-point real sounding have strong merit for practical dispersion model.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.70-79
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• 2013

The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine (MGT) were numerically investigated. Location of pilot burner, swirl angle and direction were varied as main parameters with the identical thermal load. As a result, the variations in location of pilot nozzle, swirl angle and direction resulted in the significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus the flame stability and emission performance might be significantly changed. With the comparison of experimental results, the case of swirl angle $45^{\circ}$ and co-swirl flow including optimum location of pilot burner were chosen in terms of the flame stability and emissions for the development of hybrid/dual swirl jet combustor.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.29-35
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• 2013

A dense mixed ionic and electronic conducting ceramic membrane is one of the most promising materials because it can be used for separation of oxygen from the mixture gas. The $ABO_3$ perovskite structure shows high chemical stability at high temperatures under reduction and oxidation atmospheres. $BaCo_{1-x-y}Fe_xZr_yO_{3-{\delta}}$ (BCFZ) was well-known material as high mechanical strength, low thermal conductivity and stability in the high valence state. Glycine Nitrate Process (GNP) is rapid and effective method for powder synthesis using glycine as a fuel and show higher product crystallinity compared to solid state reaction and citrate-EDTA method. BCFZ was fabricated by modified glycine nitrate process. In order to control the burn-up reaction, $NH_4NO_3$ was used as extra nitrate. According to X-Ray Diffraction (XRD) results, BCFZ was single phase regardless of Zr dopants from y=0.1 to 0.3 on B sites. The green compacts were sintered at $1200^{\circ}C$ for 2 hours. Oxygen permeability, methane partial oxidation rate and hydrogen production ability of the membranes were characterized by using Micro Gas Chromatography (Micro GC) under various condition. The high oxygen permeation flux of BCFZ 1-451 was about $1ml{\cdot}cm^{-2}s^{-1}$. Using the humidified Argon gas, BCFZ 1-433 produced hydrogen about $1ml{\cdot}cm^{-2}s^{-1}$.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.467-471
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• 2021

A ladder-like polysilsesquioxane (LPMA64) functionalized with a crosslinkable group was synthesized and used for the preparation of organic-inorganic hybrid gel polymer electrolytes through a thermal crosslinking process of the liquid electrolytes. A small weight percent of LPMA64 polymer crosslinker (5 wt%) was able to form a well-developed network structure, resulting in good dimensional stability with high ionic conductivity. The lithium-sulfur batteries fabricated with organic-inorganic hybrid gel polymer electrolytes exhibited stable C-rate and cycling performance with excellent Coulombic efficiency due to the alleviated lithium polysulfide shuttling effect during prolonged cycling. The result demonstrates that the organic-inorganic hybrid gel polymer electrolytes could be a promising candidate electrolyte for application in lithium-sulfur batteries.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.400-404
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• 2011

The activity and stability of the metal filter material Pt coated on NOx and soot oxidation were examined. The catalytic reaction test for NOx and soot were also performed independently and simultaneously. As a result, it showed the NO to $NO_2$ shift reaction with 20% conversion, NOx decomposition (about 10%) and perfect soot oxidation on the material Pt coated proceeded. Onset temperature of soot oxidation shift to lower temperature (about $30^{\circ}C$) by generated $NO_2$. The material also was less affected by thermal shock than $Pt/Al_2O_3$ or $Pt/TiO_3$ catalysts due to its stability of surface structure.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.29-40
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• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.144-149
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• 2006

Non-halogen flame retardants have been the focus of extensive research because of environmental problems. Hexakisp-henoxycyclotriphosphazene was synthesized in order to use as the flame retardant of ABS resin. And using bisphenol A, the polymers containing a cyclotriphosphazene structure were synthesized in order to also use as the flame retardant of ABS resin. All of the synthesized polymers themselves had the excellent flame retardancy. And as their molecular weight and crosslinking density were increased, the thermal stability was increased. But when the synthesized compounds were used as the flame retardant for ABS resin, the lower molecular weight compound in these compounds showed the better flame retardancy and the better physical properties of ABS resin.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.1
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• pp.59-69
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• 2000

The characteristics of liquid crystal polymer composite(LCPC) films are possessed of large-area and flexible display, polarizer free, high contrast, wide angle of visual filed and high responsiveness. It is well known that the LCPC films consisting of a continuous LC phase embeded in a three-dimentional network of polymer matrix are formed by photopolymerization-induced phase separation. In this study, we have investigated the point that both liquid crystals and polymer having different properties have to coexiste as composed films. The purpose of this study has been the development of new application with liquid crystals and UV-curable monomers. In the results abtained on the miscibility of nematic liquid crystal and UV-curable resins, difunctional monomer HX-620 turned out to shows the best. From the results abtained on structures, electro-optical properties and dynamic visocoelasticity for LCPC films, the best mixing ratio of monomer to LC mixture were 3/7(photoinitiator; 4wt%) by weight, and this ratio has been provided the most thermal stability for LCPC films. In the results abtained on structure and discoloration properties of LCPC films, it has been demonstrated that consiste of a 8:2 mixture of chiral nematic liquid crystal and HX-620 has the greatest domain and it was the best discoloration.