• Korean Journal of Food Science and Technology
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• v.45 no.1
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• pp.120-125
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• 2013

Food poisoning by Bacillus cereus is one of the common food-borne diseases and B. cereus is widely distributed in natural and commercial products owing to the strong resistance caused by biofilm or spore. The ethanol, NaCl, and organic acids of acetic acid, citric acid, and lactic acid for biocontrol of biofilm-forming B. cereus on glass wool were investigated. The biofilm on glass wool was observed in many developments after 48 h incubation. As the results of reduction of biofilm-forming B. cereus by sanitizers, reduction levels of each organic acid treatment ranged to 5-6 log CFU/g-glass wool. In case of combination treatments of 20% ethanol, 10% NaCl, and 1% of each organic acid for 1-5 min, the reduction level of biofilm-forming B. cereus was 7-8 log CFU/g-glass wool. Therefore, combination treatments of ethanol, NaCl, and an organic acid might effectively reduce biofilm-forming B. cereus in various food processes and industries.

• Journal of the Korean institute of surface engineering
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• v.38 no.4
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• pp.137-143
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• 2005

CrSiN coatings of stepwise changing Si concentration were deposited on stainless steel by closed field unbalanced magnetron sputtering (CFUBM) system. Microstructure of the films due to the Si concentration is measured by XRD. The corrosion behavior of CrSiN coatings in deaerated $3.5\%$ NaCl solution was investigated by potentiodynamic test, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of CrSiN film depends on the Si concentration. When Si/(Cr+si) was under $11.7\%$, preferred orientation is defined at CrN(220), CrN(311) and $Cr_2N(111).$ The results of potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr+si) ratio. EIS measurements showed that the corrosion resistance of Si-bearing CrN was improved by phase transformation of the film, which leads to increase of pore resistance and charge transfer resistance. At the Si(Cr+si) ratio of 20, the Si-bearing CrN possesses the best corrosion resistance due to the highest pore resistance and charge transfer resistance.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.195-201
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• 1999

The repassivation characteristics of Fe-Cr steels in deaerated 0.1 M $Na_2SO_4$ solution have been investigated with the variation of Cr content, applied potential and Cl- concentration. In the absence of chloride ion, abrading electrode test showed that, slope -n, of log i=k -n log t, a parameter of repassivation rate, approached to -1, regardless of Cr content but as Cr content increased, repassivation current density decreases with increasing Cr content. A.C. Impedance spectroscopy showed that the charge transfer resistance of passive film became higher as Cr content and applied potential increased. However, in the presence of chloride ion, it was observed that chloride ion suppressed the passive film formation, whose effect became greater with increasing applied potential.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.3
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• pp.469-477
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• 2002

One of the major deficiencies of composite restorative resins is their insufficient resistance to wear. Of the multitude of factors that have been associated with wear, subsurface degradation within the restoration is considered to be one. The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Z100(3M), Clearfil AP-X(Kuraray), Tetric Ceram(Vivadent), Aelit flo(Bisco). Resistance to degradation was evaluated on the basis of the following parameters: (a) mass loss(%) - determined from pre-and post-exposure specimen weights: (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth(${\mu}m$) - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were as follows: 1. The sequence of the mass loss was in ascending order by AE, EL, TC, Z100. There was statistically significant difference of mass loss between AE, CL group and TC, Z100 group(p<0.05). 2. The sequence of the degree of degradation layer depth was in ascending order by AE, CL, TC, Z100. But there was no statistically significant difference of degree of degradation layer depth between AE and CL(p<0.05). 3. For the Si concentration, Z100 was the highest of all. 4. The correlation coefficient between mass loss and degradation depth was relatively high(r=0.71 p<0.05).

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.255-263
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• 2021

In this study, we assessed the technological characteristics and safety of 88 Enterococcus faecium strains isolated from meju; the strains possess the glutamate decarboxylase gene gadA/B involved in γ-aminobutyric acid production. The study was conducted to evaluate the possibility of introducing E. faecium meju isolates as food fermentation starters. We observed that a NaCl concentration of 6% (w/v) facilitated the growth and acid production of all strains. At a NaCl concentration of 7%, 21 strains (24%) exhibited a low growth rate, 72 strains (82%) a weak acid production, and 16 strains (18%) showed no acid production. All strains exhibited protease activity at a NaCl concentration of 4%. At a NaCl concentration of 5%, 86 strains exhibited weak activity, and one strain showed no protease activity. We could not detect any lipase activity in the investigated strains. None of the strains exhibited an acquired antibiotic resistance to the seven antibiotics tested in the present study, namely ampicillin, chloramphenicol, ciprofloxacin, gentamicin, penicillin G, tetracycline, and vancomycin. We could identify the Enterococcus endocarditis antigen gene efaA and the tyrosine decarboxylase gene tdc contributing to tyramine production, in 88 meju isolates. We could not detect the Enterococcus surface protein gene esp, which is specifically possessed by human-originated E. faecium strains, in any of the 88 strains tested in the study.

• Membrane Journal
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• v.19 no.4
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• pp.324-332
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• 2009

This study aimed to measure chemical resistance properties of the microfiltration flat-sheet membrane made by Chlorinated Polyvinyl Chloride (CPVC) with respect to the immersed time. The solutions of effective chlorine 0.5 wt% NaClO, HCl 1 wt% and pH 4 buffer under acidic condition, NaOH 4 wt% and pH 10 buffer under alkine condition were used as widely applied chemicals for membrane washing. The CPVC membrane samples were immersed in the above chemical solutions during 1, 3, 5 and 10 days at 5, 25 and $50^{\circ}C$, respectively. After then, the tensile strength and elongation at break as the chemical durability for the samples were measured and evaluated. The tensile strength decreased within 5% at $5^{\circ}C$, but decreased up to 17% at 25 and $50^{\circ}C$ for 0.5 wt% NaClO solution mainly used for membrane cleaning. The chemical resistance of CPVC membrane was good enough for HCl 1 wt% and pH 4 buffer acid solutions, but the most vulnerable for NaOH 4 wt% solution.

• Food Science and Biotechnology
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• v.14 no.1
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• pp.108-111
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• 2005

To improve water-resistance and physical properties of sodium alginate film, effects of sodium alginate and plasticizer concentrations, divalent cation types and concentrations, and immersion time of films into divalent cation solutions on sodium alginate films were evaluated, based on elongation strength (ES), elongation rate (E), water vapor permeability (WVP), and water solubility (WS). Film made from 1.5% sodium alginate solution (w/w) had low WVP and WS, which are optimal characteristics for application of film preparation. Addition of plasticizer increased E and WS. Less than 2% $CaCl_2$ addition and 15min immersion time reduced WVP, WS, and E significantly (p<0.05). Sodium alginate films treated with $CuCl_2$, and $ZnCl_2$ solutions had lower WVP and WS, whereas $MgCl_2$ had no influence on improving water resistance of films.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1259-1264
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• 2010

This paper was researched about effectiveness of the electrochemical cell which is composed of the sea water and the Cu/Zn electrode. The electric potential difference between copper and zinc finally reached 0.51 volts. Short current decreased with time. It might depend on the electromotive force decreasing. Confirmed the load resistance and electrode affect in electromotive force and electric current. The resistance which shows a maximum output power was 20[$\Omega$], and the maximum output power from this resistance was evaluated as 0.736mW. In order to calculate the energy which creates from electrochemical cell, charging voltage of the capacitor with various capacitance was investigated. It was found that energy harvesting possibility of the cell which is made of a sea water electrolyte and the copper/the zinc.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.784-788
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• 1999

In this work, we analyzed the viscoelastic characteristics of electrochemically polymerized polypyrrole(PPy) thin film in various electrolyte solutions, $Na_2SO_4,\;Na_2CO_3$ and SDS + $NaClO_4$, using QCA. The characteristics of redox reaction of electrochemically polymerized PPy thin film for 180 sec in each electrolyte, was investigated in 0.1 M $NaClO_4$ electrolyte solution by cyclic voltammetry method. We used one side of quartz crystal electrode as a working electrode and measured the resonant frequency, resonant resistance and current as analytical parameters. As the results, we suggest that electrochemically polymerized PPy thin film in various electrolyte solutions shows tendency changing from elastic characteristics to viscoelastic one in the order of $ClO_4{^{-}}\;+\;DS^-,\;SO_4{^{-2}}$ and $CO_3{^{-2}}$.

• Corrosion Science and Technology
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• v.20 no.3
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• pp.129-142
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• 2021

Effects of corrosion inhibitors (i.e., sodium nitrite, sodium hexametaphosphate, trimethylamine (TEA), sugar, and urea) on the corrosion resistance of carbon steel in CaCl₂ solution were investigated. The test solution was designed with response surface methodology of design of experiments (DOE) in the range of 0 ~ 50 ppm for NaNO₂, 0 ~ 200 ppm for (NaPO₃)₆, 0 ~ 2000 ppm for TEA, 0 ~ 3000 ppm for sugar, 0 ~ 200 ppm for urea with 3 wt% CaCl₂. The corrosion potential and the corrosion rate were measured with potentiodynamic polarization tests and analyzed statistically to find main effects of inhibitor concentrations and interactions between them. As a result, hexametaphosphate was the most effective compound in reducing the corrosion rate. Sugar also reduced the corrosion rate significantly possibly because it covered the surface effectively with a high molecular weight. The inhibiting action of sugar was found to be enhanced by adding trimethylamine into the solution. Nevertheless, trimethylamine did not appear to be effective in inhibiting corrosion by itself. However, urea and sodium nitrite showed almost no inhibition on corrosion resistance of steel.