• Food Science and Preservation
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• v.11 no.3
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• pp.319-324
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• 2004

The antimicrobial activity of the extract of citrus peel prepared by the method of hot water, ethanol and sugar was examined. The results showed that the extract of citrus peel prepared by hot water or ethanol did not have antimicrobial activity, but the extract by 10$\%$(w/v) sugar revealed the high antimicrobial activity. Extracted in 10%(w/v) sugar solution for 9 days, showed the highest antimicrobial activity against 8 strains of bacteria. The minimum inhibition concentration was found to be 0.5$\%$(v/v) against S. aureus, 1.5$\%$(v/v) against B. subtilis, M. luteus and E. coli, and 2.0$\%$(v/v) against S. mutans. The antimicrobial activity of the citrus peel extract was stable regardless of the treatment at 40 $\~$ 100 $^{\circ}C$C for 20 min and unstable response to the change of pH. The results suggested the development of citrus peel as heat-stable antimicrobial agents.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.143-149
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• 2020

Calcium phosphates recognized as important bio-materials have been successfully synthesized by simple precipitation using waste abalone shells, which are rich mineral sources of calcium. Calcium hydroxide (Ca(OH)₂) originated from abalone shells was used as calcium source (precursor) for the preparation. Synthesis of calcium phosphates was performed by reacting calcium hydroxide with phosphoric acid (H₃PO₄) in aqueous solution. The initial precursor Ca/P ratios were adjusted to 1.50, 1.59 and 1.67, and the effect of the composition and the heat treatment on the synthesized powders and sintered bodies was investigated. The phases of the sintered ceramics prepared at 1150℃ were hydroxyapatite (HAp), β-tricalcium phosphate (β-TCP), and biphasic phosphate (HAp with β-TCP)), which were determined by the initial precursor Ca/P ratios. The results demonstrate the possibility for the synthesis of high value-added calcium phosphates from economical starting materials with low cost and high availability.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.95-108
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• 1984

Even though the tarnishing and corrosion problems characteristic with dental silver-palladium alloy are not yet fully solved, it is recently widely used because of its low cost. However the effects of major alloying elements on the various properties of this system are not fully understood. The object of this research is to clarify the effects of In and Zn additives on the corrosion and tarnishing resistances and precipitation hardening behavior of this sytem, using electrodynamic polarization, immersion, and Vicker's microhardness test and X-ray diffraction and electron probe micro analysis methods. The obtained results were as follows: I. As indium content is increased, both the corrosion resistance in Cl-solution and microhardness are also increased while the tarnishing resistance is decreased. 2. As Zinc content is increased, the corrosion resistance is decreased, but tarnishing resistance is increased 3. At 70Ag-25Pd-2.5Zn-2.5In composition, the precipitation harding behavior was mot significant. The optimum aging temperature was $450^{\circ}C$ and the time was 2 hrs. The resulting specimen of this work carried 180VHN. 4. Under the heat treatment, the changes in the mechanical property are due to the changes in the shape and composition of dendrite matrix, namely, it is because of the precipitation hardening behavior which has been proved by electron probe micro analysis and optical microscopic finding.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.11
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• pp.1767-1778
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• 2010

This study investigates applying $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via electrospinning for the development of UV-protective materials. To fabricate uniform nanocomposite fibers, three types of $TiO_2$ nanoparticles were applied: powder, colloid, and $TiO_2$ coated polymer pellets. $TiO_2$/polyurethane (PU) and $TiO_2$/poly(vinyl alcohol) (PVA) nanocomposite fibers were electrospun and the morphology was examined using a field-emission scanning electron microscope and a transmission electron microscope. Layered fabric systems with electrospun $TiO_2$ nanocomposite fiber webs were developed at various concentrations of $TiO_2$ in a range of the web area density. The effects of $TiO_2$ concentration and web area density on UV-protective properties were examined. When $TiO_2$ colloid was added into a PVA polymer solution, uniform nanocomposite fiber webs in which $TiO_2$ particles were evenly dispersed were produced. Water-soluble PVA nanofiber webs were given a heat treatment to stabilize the electrospun PVA fibrous structure against dissolution in water. $TiO_2$/PVA nanoeomposite fiber webs with 2wt% $TiO_2$ and 3.0g/$m^2$ web area density exhibited an ultraviolet protection factor of greater than 50, indicating excellent UV protection.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.2
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• pp.188-193
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• 2014

Seed viability testing provides valuable information for assessing seed lot germinability. However, most testing methods require destruction of seed prior to test. Because the dissected seeds for viability test cannot be used further evaluation, the nondestructively X-ray photography technique that can be applied for the evaluation of seed quality has been developed. In order to know the validity and accuracy of X-ray photography technique in seed evaluation test that conducted to remove the abnormal seed from a seed lot, we have compared the results from tetrazolium viability test, germination test and X-ray contrast method in cotton. Metallic salts treatment increased the efficiency of X-ray photographic method by enhancing the penetration of X-ray in abnormal or damaged seeds rather than normal seeds that have strong and well-organized tissues in seed. Cotton seeds presoaked for 16 hr in distilled water followed by soaking into metallic salt solution (5% NaI in water) for 60 min were easily classified seeds into dead seed and viable seed based on the radiography images obtained by X-ray radiation. We concluded that soft X-ray photography was reliable to find out the various defective characters due to heat and mechanical damage of seeds.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.345-351
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• 2005

Physicochemical properties and functionalities of sodium caseinate, whey protein, skim milk, and whole milk with or without transglutaminase (TGase, 200 : 1) at $38^{\circ}C$ were determined. After crosslinking by TGase, whey protein was effective in improving heat stability compared to native protein at over $70^{\circ}C$. Whole milk was stable with lower turbidity compared to native solution. Whey protein showed low hydrolysis degree, fewer than sodium caseinate, during early activation time and increased slightly thereafter Emulsifying activities of sodium caseinate at pH 2 and 8, and whey protein at pH 7 and 8 improved. Emulsion stability of sodium caseinate improved at entire pH range studied. Foam expansion and foam stability of samples improved with TGase-treatment. Viscosities of TGase-treated samples were higher than those of untreated ones.

• Proceedings of the Korean Journal of Food and Nutrition Conference
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• 2001.12a
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• pp.126-126
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• 2001

The Rhus verniciflua contains alkly(en)-catechol type allergens with a saiurated or unsaturated alkly chain of 15 or 17 carbon atoms. It has been recognized as an extremely active allergen causing skin reactions similar In poison ivy. The allergic contact dermatitis induced by the urushiol is known to be mediated be T lymphocytes whicht specifically recognize the hepten urushiol. Therefore. direct use of this plant as a medicinal purpose might imply a considerable hazard in Korea. In this study, using the established method for the detoxification from the stem bark of Rhus verniciflua, an strong antioxidant substance was isolated and characterized DPPH (diphenypricryl hydrazyl) assay measures hydrogen atom-donating activity and hence provides a measure of free radical scavenging antioxidant activity. DPPH, a purple-colored stable free radical, is reduced to yellow-colored diphenylpicryl hydrazine by antioxidants to deducing agents. Antioxidative effects of the water extract from RV were measured by DPPH assay. Twenty microliters of the extract was added to 1ml of 100mM DPPH solution in ethanol The mixture was shaken and left to stand for 10min at room temperature. The crude water extracts was purified by using HPLC method with a DEAE (anionic type), CN, ODS column. The purified compound remained stable at pH 3.0-6,0, but unstable above pH 6.5. It was stable heat at 10$0^{\circ}C$ for 4 hours, but still had about 80% of residual activity after treatment at 10$0^{\circ}C$ for 5 hours. The elemental composition of the HR-EI mass spectrum at m/z 170.02 was estimated the empirical formula as $C_{7}$ $H_{6}$ $O_{5}$. $C_{10}$ $H_4$ $O_2$N$_1$, $C_{5}$ $H_4$ $O_4$N$_3$, $C_{8}$$H_2O$$_1$N$_4$. In antimicrobial test, no inhibition was observed against Gram-positive and negative bacteria. This compound was stronger than that of commercial antioxidant by DPPH test, such as BHT, BHC at the same concentration (20$\mu$g/ml).ml).

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.52-59
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• 2001

Factors to cause accidents were investigated through a systematic analysis of leakage accidents in welded LP-gas cylinder between 199 and 1999. As a result It was showed that most of leakage accident occurred at the pin-hole due to the localized corrosion on welded zone in cylinder. Accordingly, in this paper, we suggested that the problems of heat treatment condition in two-piece welded cylinder and substitute proposal for preventing the tearing of T zone in three-piece welded cylinder. Furthermore, corrosion rate on the weldment and base metal of welded LP-gas cylinder was evaluated using the electrochemical tests in acid rain and $3.5\%NaCl$ solution, Also, the poor adhesion and defects of film which was produced by electrostatic powder spray painting, while the LP-gas cylinder was manufactured, were analyzed using SEM(Scanning Electron Microscopy). And we proposed a optimum coating thickness of the cylinder.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.217-222
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• 1998

Coating films of $SiO_2-TiO_2-AgO$ have been prepared on soda-lime-silica slide glasses and single crystal silicon wafer by the sol-gel method using a spin-coating technique. Commercially available tetraethyl orthosilicate, titanium trichloride, and silver-nitrates were used as starting materials. The heat treatment temperature of this coating films was $500^{\circ}C$ properly, obtained from TG-DTA result. The films with thickness of 310 nm were prepared by 5 times coating. In the case of l0 mol% AgO, the film showed a crack-free and smooth surface, but the higher Ago content exhibited the more pin hole and the segregated cluster of AgO. The IR absorbance of the films decreased in the range of 400 nm to 700 nm with the increase of annealing temperature. And the reflectance of the coating films decreased and the color was changed light yellow to white yellow with the increase of Ago content.

• Journal of computational fluids engineering
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• v.16 no.4
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• pp.39-46
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• 2011

A numerical study of a turbulent natural convection in an enclosure with the lattice Boltzmann method (LBM) is presented. The primary emphasis of the present study is placed on investigation of accuracy and numerical stability of the LBM for the turbulent natural convection flow. A HYBRID method in which the thermal equation is solved by the conventional Reynolds averaged Navier-Stokes equation method while the conservation of mass and momentum equations are resolved by the LBM is employed in the present study. The elliptic-relaxation model is employed for the turbulence model and the turbulent heat fluxes are treated by the algebraic flux model. All the governing equations are discretized on a cell-centered, non-uniform grid using the finite-volume method. The convection terms are treated by a second-order central-difference scheme with the deferred correction way to ensure accuracy and stability of solutions. The present LBM is applied to the prediction of a turbulent natural convection in a rectangular cavity and the computed results are compared with the experimental data commonly used for the validation of turbulence models and those by the conventional finite-volume method. It is shown that the LBM with the present HYBRID thermal model predicts the mean velocity components and turbulent quantities which are as good as those by the conventional finite-volume method. It is also found that the accuracy and stability of the solution is significantly affected by the treatment of the convection term, especially near the wall.