• Food Science and Preservation
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• v.31 no.1
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• pp.126-137
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• 2024

In this study, zinc oxide nanoparticles (ZnONPs) were synthesized using three distinct zinc salts: zinc acetate, zinc chloride, and zinc nitrate. These ZnONPs were subsequently utilized in the fabrication of carrageenan-ZnONPs (Car-ZnONPs) composite films. The study assessed influence of the various ZnONPs on the morphological, water vapor barrier, color, optical, and antimicrobial properties of the Car-ZnONPs composite films. The surface morphology and UV-blocking attributes of the composite films were affected by the type of ZnONPs used, but their surface color, transparency, and chemical structure remained unaltered. The composite film's thickness and elongation at break (EB) significantly increased, while the tensile strength significantly decreased. In contrast, film's elastic modulus (EM) and water vapor permeability coefficient (WVP) showed no significant difference. All the composite films with added ZnONPs demonstrated potent antibacterial activity against Escherichia coli O157:H7 and Listeria monocytogenes . Among the carrageenan-based composite films, Car-ZnONPs^ZC showed the highest antibacterial and UV-blocking properties, and its elongation at break was significantly higher than that of the pure carrageenan films. This suggests that ZnONPs composite films have the potential to be used as an active packaging film, preserve the safety of the packaged food and extend shelf life.

• Clean Technology
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• v.30 no.3
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• pp.159-174
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• 2024

The rapid increase in energy consumption based on fossil fuels is accelerating global warming. In particular, the road transportation sector has high carbon dioxide emissions, so transitioning towards electric vehicles is recommended. Thus, the importance of secondary batteries is increasing. Secondary batteries are reversible batteries that use energy and can be reused through a charging and discharging process. Currently, lithium-ion batteries are widely used. Secondary batteries place importance on six major factors: energy, output, lifespan, environmental friendliness, cost, and stability. Research is actively being conducted to satisfy all six factors by understanding the material characteristics of each component of the battery. As it is difficult to move away from lithium as a cathode material, researchers are investigating higher performance materials that mix materials such as cobalt, nickel, manganese, and aluminum with lithium and use graphite, silicon, and lithium metal to increase capacity. In the case of electrolytes, liquid electrolytes are still mainly used. However, solid electrolytes are being studied due to their stability, but additional research must be conducted to satisfy the energy and output factors. This review paper aims to provide an understanding of secondary batteries through an overview of secondary batteries, the materials and characteristics of their components, their technological trends, and their associated companies.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.11-17
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• 2012

This study focused on application of various $CO_2$ philic adsorbents with amine to improve $CO_2$ uptake in mortar. TGA, phenolphthalein method, FT-IR XRD, and FE-SEM analysis methods were used to evaluate $CO_2$ capture in mortar. When $CO_2$ philic adsorbents was used, $CO_2$absorption efficiency was improved maximum of 58.5%. Carbonation depth was increased 3 times compared with original mortar. Chemical reactions between bicarbonate ion, $CO_2$, $CO_2$ philic adsorbents aqueous solution, and $Ca^{2+}$ ions dissolved from cement formed $CaCO_3$ in the mortar. Therefore, impregnation of the $CO_2$ philic adsorbent on the surface of the mortar can increase the adsorbed $CO_2$.

• Clean Technology
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• v.19 no.1
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• pp.44-50
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• 2013

Tin-based materials for lithium ion battery have been proposed as new anode candidates owing to their higher specific capacity and relatively high lithium insertion potential. Tin-based materials have been extensively studied as possible replacements for carbon anodes in lithium ion batteries. However, the large volume expansion results in severe particle cracking with loss of electrical contact, giving irreversible capacity losses which prevent the widespread use of tin-based materials in lithium batteries. So remaining studies of tin-based materials are alleviating volume expansion and improving cycle performance. In this work, $SnO_2-SiO_2$ composites were manufactured with sol-gel method to overcome their volume expansion. Carbon was coated with 10 vol% propylene gas. The characteristics of active material and the effect of heat treatment were investigated with TG/DTA, XRD, SEM and FT-IR. Electrochemical characteristics of these composites were measured with CR2032 type coin cells. Carbon coated $SnO_2-SiO_2$at $300^{\circ}C$ heat treatment showed the best electrochemical performance.

• Microbiology and Biotechnology Letters
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• v.15 no.5
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• pp.334-339
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• 1987

Enzymatic conversion of pyruvic acid produced by microorganism to tryptophan was investigated. A luminescent bacteria. Beneckea sp., was used for the production of pyruvic acid. As a source of tryptophanase which synthesizes tryptophan from pyruvic acid, indole and ammonia, whole cells of Enterobacter aerogenes ATCC 10031 were used directly in the reaction mixture. To increase the production of tryptophan, nonionic detergents and nonaqeous organic solvents were used ms reserviors of indole in the reaction mixture. In the case of nonionic detergents, TritonX-100 was very effective. When 1.5% of Triton X-100 was used, 7.7g/$\ell$ of tryptophan was produced at 37$^{\circ}C$ for 48hr. In the case of nonaqueous solvents, 8.7g/$\ell$ of tryptophan was produced at 37$^{\circ}C$ for 48 hr, when 10% of benzene was used. This amount of tryptophan corresponds to conversion of 48% of Indole and 36% of pyruvic acid, respectively.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.292-299
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• 2010

Graphene is a two-dimensional nanosheet consisting of honeycomb lattices of $sp^2$ carbon atoms. It is one of promising active materials for the anode of lithium-ion battery and the electrode of supercapacitor, due to its large specific surface area(theoretically $2600m^2\;g^{-1}$), high electric conductivity(typically $8{\times}10^5S\;cm^{-1}$), and mechanical strength. In this review, the synthetic methods of graphene nanosheet and graphene-based nanocomposite are introduced. Also, the electrochemical properties obtainable when the graphene-based materials are adopted to the electrodes of lithium-ion battery and supercapacitor are discussed along with their nanostructures.

• Polymer(Korea)
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• v.24 no.2
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• pp.228-236
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• 2000

The preparation of organophilic clay from Na$^{+}$-MMT was achieved by intercalation of alkylammonium bromide. The dispersed organophilic clay in NMP was then added to the solution of polyamic acids (BPDA-PPD, BTDA-ODA/ MPD) in NMP. After curing at 30$0^{\circ}C$, thin films of the polyimide/clay nanocomposite were prepared. The results of X-ray diffraction (XRD) shelved that the d-spacings of dried polyamic acid (PAA)-clay complexes increased in proportion to the chain length of the onium ion and patterns of two kinds of PAA-clay complexes were similar. The d-spacings of approximately 13.2 $\AA$ for the polyimide/clay nanocomposites were independent of the initial onium ion chain length and the species of PAA. From the study of XRD and transmission electron microscopy (TEM), we found layered silicates were dispersed in polyimide matrix and the resultants were intercalated nanocomposites. TGA result showed thermal stability of polyimide nanocomposite improved a little more than the pure polyimide. From the result of dynamic mechanical property, we found that the storage modulus of the nanocomposites had increased by 1.2-1.8 times of the pure polyimides.s.

• Composites Research
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• v.29 no.6
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• pp.395-400
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• 2016

Recently, many research groups have studied on the epoxy-based multifunctional electrolyte to develop the structural composite bearing high mechanical properties without sacrificing the ionic conductivity at the same time. The studies on the optimal content and material selection for structural electrolyte have been published, while its curing behavior has not much analyzed yet. In this study, epoxy-based structural electrolyte containing solid electrolyte was prepared by varying the curing temperature and time. In addition, the ionic conductivities and mechanical properties of specimens were measured. We also find out the optimal hardening condition where the epoxy domain enables to be hardened within the range of temperature at which the thermal decomposition of electrolyte does not occur. Finally, we propose the multifunctional structural electrolyte showing achievable electrical and mechanical properties (282 MPa and $9{\times}10^{-6}S/cm@25^{\circ}C$).

• Journal of Life Science
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• v.13 no.5
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• pp.618-625
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• 2003

Investigations were carried out to optimize the culture conditions for the production of xylanase by Paenibacillus sp. DG-22, a moderately thermophilic bacterium isolated from timber yard soil. Xylanase production showed a cell growth associated profile. Xylanase activity was found only in the culture supernatant, while $\beta-xylosidase$ activity was mainly associated with the cells. The formation of xylanase activity was induced by xylan and repressed by glucose and xylose. The production profile of xylanase was examined with various commercial xylan and maximum yield was achieved with 0.1∼ 0.5% birchwood xylan. Among various nitrogen sources tested, yeast extract was optimal for the production of xylanase. The xylanase activity was inhibited by $Co^{2+},\; Cu^{2+},\; Fe^{3+},\; Hg^{2+}\;$ and$\;Mn^{2+}$ ions while $Ca^{2+},\; Mg^{2+},\; Ni^{2+},\; Zn^{2+}$ions and DTT stimulated xylanase activity Mercury (II) ion at 5 mM concentration abolished all the xylanase activity. The predominant products of xylan-hydrolysate were xylobiose, xylotriose, and higher xylooligo-saccharides, indicating that the enzyme was an endoxylanase.

• Journal of Forest and Environmental Science
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• v.15 no.1
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• pp.71-76
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• 1999

This study compared soil characteristics and carbon storage between urban and natural lands in Chunchon. Soil pH was lower in natural lands (5.0) than in urban lands (6.6), and therefore exchangeable cation was a little lower in natural lands. Organic matter and cation exchange capacity were respectively, 1.4 and 1.7 times higher in natural lands than in urban lands, while available $P_2O_5$ was about 3.2 times higher in urban lands. Organic carbon storage in soils averaged $24.8{\pm}1.6$ (standard error) t/ha in urban lands and $31.6{\pm}1.6t/ha$ in natural lands, 1.3 times greater than in urban lands. Annual carbon accumulation in soils of natural lands was 1.3 t/ha/yr (litterfall minus decomposition). The carbon storage in Chunchon' s soils equaled about 31% of annual carbon emission (245,590 t/yr).