• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.112-120
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• 1998

This study was performed to investigate the synergistic effect of chitosan and sorbic acid as a new food preservative. So it was performed to investigate inhibitory effect on growh of E. coli 0157:H7, gram negative pathogenic food borne disease bacteria and of S. aureus, gram positive food borne disease bacteria in chitosan, sorbic acid and combination of chitosan and sorbic acid. Minimun Inhibitory Concentration (MIC) of chitosan in E. coli 0157:H7 was 500 ppm at pH 5.0, 250 ppm at pH 5.5, 500 ppm at pH 6.0, and 2000 ppm at pH 6.5, while in Staph. aureus 31.25 ppm at pH 5.0 and 62. 5 ppm at more than pH 5.5. also, MIC of sorbic acid in E. coli 0157:H7 was 500 ppm at pH 5.0, 1500 ppm at pH 5.5, and 2000 ppm at more than pH 6.0, while in Staph. aureus 1500 ppm at pH 5.0 and more than 2000 ppm at more than pH 5.5. Due to the effect of pH in E. coli 0157:H7, MIC of combined chitosan and sorbic acid was 500 ppm of chitosan with 500 ppm of sorbic acid at pH 6.5, but 250 ppm of chitosan with 31.3 ppm of sorbic acid at pH 5.0. In Staph. aureus, there was great effect of chitosan, but neither effect of pH nor sorbic acid. When E. coli 0157:H7 were treated with 500 ppm of chitosan with 500 ppm of sorbic acid and 250 ppm of chitosan with 250 ppm of sorbic acid at pH 6.5, they were inhibited. But, they were increased at the initial concentration of bacteria at 1000 ppm of chitosan in 18 hours, at 500 ppm of chitosan in 36 hours. There was no effect of growth inhibition with sorbic acid but great effect with chitosan on Staph. aureus. The correl~tions between MICs of chitosan and sorbic acid in E. coli 0157:H7 accoding to pH were higher than those in Staph. aureus. R values in E. coli 0157:H7 were 0.95 (p<0.01), 0.99 (p<0.01), 0.97 (p<0.01), and 0.99 (p<0.01) at pH 6.5, 6.0, 5.5, and 5.0 respectively. The synergistic effect of chitosan and sorbic acid in E. coli 0157:H7 could be confirmed from the result of this experiment. Therefore, it was expected that the food preservation would increase or maintain by using sorble acid together with chitosan, natural food additive that did no harm to human body.

• Resources Recycling
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• v.20 no.5
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• pp.34-39
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• 2011

Metallurgical grade silicon(MG-Si) was melted with Ca at 1500$^{\circ}C$ under Ar atmosphere. The sample was cooled at 10 $^{\circ}C$/min to room temperature and leached in aqua regia. In the present study, the effect of Ca addition and conditions of acid leaching on removal of Fe and P in MG-Si were investigated. CaSi$_2$ phase was formed at the grain boundary of MG-Si melting with Ca. Also FeSi$_2$ phase was precipitated in CaSi$_2$ phase. By the formation of CaSi$_2$ phase, 97% of Fe and 66 % of P were removed from Ca added MG-Si with the particle size of 600~850${\mu}m$ by aqua regia(more than 30%) leaching.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3597-3601
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• 2013

In this study, a wet cleaning process, P II, using aqua-regia and sulfuric acid mixture with oxidant agent ($K_2S_2O_8$, $P_2O_5$, $KMnO_4$, $H_2O_2$ etc) is proposed to remove the metastable phase of graphite such as graphene and DLC for high quality synthetic diamonds. The process employed the conventional acid cleaning process (P I) as well as P I+P II to remove the graphite related impurities from the 200um-diamond powders synthesized at 7GPa-$1500^{\circ}C$-5minutes. The degree of cleaning after P I and P I+P II has been observed by naked-eye, optical microscopy, micro-Raman spectroscopy, and TGA-DTA. After P I+P II, the color of diamond became more vividly yellow with enhanced saturation with naked eye and optical microscopy analysis. Moreover, the disappearance of diamond-like-carbon (DLC) peak ($1440cm^{-1}$) observed by Raman spectroscopy confirmed the decrease in amount of remaining impurities. TGA-DTA results showed that the graphite impurities first started to dissolve at $770.91^{\circ}C$ after PI process. However, the pyrolysis started at $892.18^{\circ}C$ after P I+P II process because of the dissolution of pure diamonds. This result proved the effective dissolution of the metastable phase of graphite. We expect that the proposed P II process may enhance the quality of diamonds through effective removal of surface impurities.

• Journal of Korean Society of Forest Science
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• v.30 no.1
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• pp.19-29
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• 1976

The fiberboard and paper mills in this country are much affected by the price hikes and shortage of phenolic resins, since phenolic acid as a raw material depends on imported good. It is prerequisite to fiberboard industry to help replace with other sized and stabilize the prices and supply of them, improving the quality of boards. Thus, the present study was carried out to examine the effect of strength increasing sized such as urea formaldehyde resin (anion and cation type) and urea melamine copolymer resin, on the quality of the wet forming hardboard, and comparing them with two types of proprietary modified melamine resins, and ordinary size, phenol resin. The Asplund pulp was prepared from wood wastes mixed with 20 percent of lauan and 80 percent of pines as a fibrous material. After sizing agents were added at a pH of 4.5 for 10 minutes with alum in the beater, the stock was made in the form of wet sheet, prepared, and then performed by hot pressing cycle: $180^{\circ}C$, $50-6-5kg/cm^2$, 1-2-7 minutes. The properties of hardboard were examined after air conditioning. The results obtained are summarized as follows: 1. There is a significant difference in specific gravity among hardboards that were treated with strength increasing resins, but no difference is effected by the increase in the resin content. In the case of modified melamine resin, its specific gravity is highest. The middle group comprises cation type of urea resin, anion type of urea resin, and acid colloid of urea-melamine copolymer resin. The lowest is phenolic resin. 2. The difference of the moisture content of hardboard both by the resins and by the amount of each resin applied is significant. The moisture content of hardboard becomes lower along with the increase of each resin content, but there is no difference between 2 and 3 percent. 3. For water absorption, there is a significant difference both in the adhesives used and in the amount of paraffin wax emulsion. The water resistance becomes higher inn proportion to the content of the paraffin wax emulsion. To satisfy KS F standards of the water resistance, a proprietary modified melamine resin (p-6100) and modified cation type of urea resin (p-1500) do not require any paraffin wax emulsion, but in the case of anion type of urea resin, cation type of urea resin, and urea-melamine copolymer resin, 1 percent of paraffin wax emulsion is needed, and 2 percent of paraffin wax emulsion in the case of phenolic resin. 4. The difference of flexural strength of hardboard both by the resins and by the amount of each resin is significant. Modified melamine resin shows the highest degree of flexural strength. Among the middle group are urea-melamine copolymer resin, p-1500, anion type of urea resin, and cation type of urea resin. Phenolic resin is the lowest. The cause may be attributable to factors combined with the pressing temperature, sizing effect, and thermal efficiency of press platens heated electrically. 5. Considering the economic advantages and properties of hardboard, it is proposed that urea-melamine copolymer resin and cation type of urea resin be used for the development of the fiberboard industry. It is desirable to further develop the modified urea-melamine copolymer resin and cation type of urea resin through continuous study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.132-136
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• 2002

In this paper, aging characteristics of outdoor silicone rubber insulator resulting from the acid rain have been investigated with regards to nitrate ion $({NO_{3}}^{-1})$. For this purpose, silicone rubber was aged by immersing into the nitric solutions with different level pH during 1500 hours and various tests (tracking, $tan{\delta}$, breakdown voltage, SEM, EDS, contact angle) were performed. It was observed that the degradation was increased to pH 2.5 slightly and at pH 1.5 highly. And thus, it could be expected that there is certain critical point between pH 1.5 and 2.5, which leads to throught degradation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.28-33
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• 2001

In this paper, aging characteristics of outdoor silicone rubber insulator resulting from the acid rain have been investigated with regards to nitrate ion ($NO^{-1}_{3}$ ). For this purpose, silicone rubber was aged by immersing into the nitric solutions with different level pH during 1500 hours and various tests (tracking, tan $\delta$, breakdown voltage, SEM, EDS, contact angle) were performed. It was observed that the degradation was increased to pH 2.5 slightly and at pH 1.5 highly. And thus, it could be expected that there is certain critical point between pH 1.5 and 2.5, which leads to throught degradation.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.473-476
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• 1987

Low temperature phosphorus-nitride CVD was newly developed for a high quality gate insulator on InP substrate. This film showed the Poole-Frenkel type conduction in high electric field with resistivity higher than $1{\times}10^{14}$ ohm-cm near the electric field of $1{\times}10^7\;volt/cm$. The C-V hysteresis width was very small as 0.17 volt. The density of interface trap states was $2{\times}10^{11}cm^{-2}ev^{-1}$ below the conduction band edge of InP substrate. Effective electron mobility was about $1200-1500\;cm^2/Vsec$ and showed the instability of PN-InP MISFETs drain current reduced less than 10 percent for the period $0.5-10^3sec$.

• Analytical Science and Technology
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• v.7 no.1
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• pp.115-124
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• 1994

The corroded surface of cold rolled steel sheet in the process of rinsing after alkali-cleaning was examined by means of X-ray Photoelectron Spectroscopy(XPS). In addition, the surface-treated cold rolled steel with 0.05wt% $Na_5P_3O_{10}$ solution for the purpose of preventing the corrosion was examined by means of XPS and the results were compared with those for the non-treated cold rolled steel. It was found that the corroded surface consists of $Fe_2O_3$, FeO and $Fe(OH)_3$ and the thickness of the oxide layer is about $1500{\AA}$. On the other hand, in the case of surface-treated cold rolled steel, the phosphate layer of $60{\AA}$ thickness was found to act as a protective film over the relatively thin Fe oxide layer.

• Journal of IKEEE
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• v.14 no.3
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• pp.190-198
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• 2010

This paper describes a auto focus piezo actuator driver IC for portable digital camera. The 80[V] DC voltage is generated by a DC-DC converter and supplied to power of piezo moving control circuit. The voltage of piezo actuator needs range -20[V] to 80[V] proportional to 1[Vp-p] input control voltages. The dimensions and number of external parts are minimized in order to get a smaller hardware size. IIC(Inter-IC) interface logic is designed for data interface and it makes debugging easy, test for mass productions. The power consumption is around 40[mW] with supply voltage of 3.6[V]. This device has been fabricated in a 0.6[um] double poly, triple metal 100[V] BCD MOS process and whole chip size is 1600*1500 [$um^2$].

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.288-291
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• 2005

Resol type phenol-formaldehyde (PF) resin was synthesized by addition reaction of formaldehyde (F) and phenol (P). And the PF resin was synthesized by condensation reaction in which water was removed. In this work, we studied the influence of experimental parameters in the addition reaction, such as F/P mole ratio, amount of catalyst, reaction temperature, reaction time, and so on. Also, we studied the influence of molecular weight and viscosity of PE resin as a function of condensation time. As a result, in addition reaction, the reaction time decreased remarkably as the catalyst concentration increased, and the time decreased with increasing reaction temperature at a constant catalyst concentration. Also, in condensation reaction, the viscosity of resol type PF resin increased from 1500 to 9000 cps as a function of condensation time; molecular weight showed from 500 to 1100 g/mol.