• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.9
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• pp.767-773
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• 2016

A Weibull statistical analysis of the mechanical properties of SiC ceramics was carried out by immersion in acidic and alkaline solutions. The heat treatment was carried out at 1373 K. The corrosion of SiC was carried out in acidic and alkaline solutions under KSL1607. The bending strength of corroded crack-healed specimens decreased 47% and 70% compared to those of uncorroded specimens in acidic and alkaline solutions, respectively. The corrosion of SiC ceramics is faster in alkaline solution than in acid solution. The scale and shape parameters were evaluated for the as-received and corroded materials, respectively. The shape parameter of the as-received material corroded in acidic and alkaline solutions was significantly more apparent in the acidic solution. Further, the heat-treated material was large in acidic solution but small in alkaline solution. The shape parameters of the as-received and heat-treated materials were smaller in both acidic and alkaline solutions.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.323-323
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• 2010

Saw damage of crystalline silicon wafer is unavoidable factor. Usually, alkali treatment for removing the damage has been carried out as the saw damage removal (SDR) process for priming the alkali texture. It usually takes lots of time and energy to remove the sawed damages for solar grade crystalline silicon wafers We implemented two different mixed acidic solution treatments to obtain the improved surface structure of silicon wafer without much sacrifice of the silicon wafer thickness. At the first step, the silicon wafer was dipped into the mixed acidic solution of $HF:HNO_3$=1:2 ration for polished surface and at the second step, it was dipped into the diluted mixed acidic solution of $HF:HNO_3:H_2O$=7:3:10 ratio for porous structure. This double treatment to the silicon wafer brought lower reflectance (25% to 6%) and longer carrier lifetime ($0.15\;{\mu}s$ to $0.39\;{\mu}s$) comparing to the bare poly-crystalline silicon wafer. With optimizing the concentration ratio and the dilution ratio, we can not only effectively substitute the time consuming process of SDR to some extent but also skip plasma enhanced chemical vapor deposition (PECVD) process. Moreover, to conduct alkali texture for pyramidal structure on silicon wafer surface, we can use only nitric acid rich solution of the mixed acidic solution treatment instead of implementing SDR.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.2
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• pp.215-223
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• 2017

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent $K^+$ and $Ca^{2+}$ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent $K^+$currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent $K^+$ currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker $Cs^+$ (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent $Ca^{2+}$ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

• Journal of Environmental Science International
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• v.11 no.3
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• pp.263-269
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• 2002

This study was conducted to know the removal characteristics of ammonia nitrogen by commercially available cation exchange resins. Eight acidic cation exchange resins were investigated in batch reactors. Among them, the most effective resin for ammonia removal in solution was PK228, which was a strong acidic resin of $Na^{+}$ type. PK228 was compared with activated carbon and natural zeolite. The effects of cation exchange capacity, ammonia concentration, resin amount, temperature and pH on ammonia removal by PK228 were investigated in batch reactor, and the effect of effluent velocity in continuous column reactor. Strong acidic resins of porous type were more effective than week acidic resins or gel type resins for ammonia removal in solution. PK228 was more effective than activated carbon and natural zeolite for ammonia removal in batch reactor. With increasing initial ammonia concentration, the amount of ammonia removed by PK228 increased, but the proportion of removed ammonia to initial ammonia concentration decreased. The effect or temperature on ammonia removal by PK228 was very slight. The ammonia removal to acidic solution was more effective than that at basic solution. With decreasing effluent velocity of solution through column, breakthrough point extended, and ammonia removal capacity increased.d.

• Journal of Pharmaceutical Investigation
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• v.27 no.4
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• pp.313-321
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• 1997

Ion exchange resin complexes of famotidine have been prepared by the reaction of famotidine solution with activated ion exchange resins. Complex formation efficiency between famotidine and ion exchange resin was about $80{\sim}90%$ in average, calculated by HPLC determination. Drug release characteristics from the resin complexes were evaluated by the modified percolation method. Famotidine release was dependent on the type of ion exchange resins. In the case of weakly acidic resin complexes, the cumulative released amount of famotidine was more than 90% for 1hr in pH 1.2 buffer solution. However, in the case of strongly acidic resin complexes, it was less than 5% for 3hr in the same medium. Strongly acidic resins revealed some advantages over weakly, acidic resins for overcoming instability of famotidine in gastric juice. In addition, strongly acidic resin complexes showed controlled release of famotidine in pH 6.8 buffer solution, showing the result of about 60 to 70% of drug release for 5hr. After oral administrations of famotidine-resin complexes to rats as dose of 40 mg equivalent/kg, the pharmacokinetic parameters of famotidine were obtained by model independent analysis and compared with those of famotidine solution or suspension. $C_{max}$ of famotidine-resin complex was lower than that of famotidine solution or suspension. MRT, MAT, and MDT of the complexes were greater than those of famotidine solution or suspension. From these results, it was expected that famotidine was released slowly from the complexes and absorbed continuously into systemic circulation. It was recognized that drug release from the complexes was the rate-limiting step in drug absorption, since there were close correlations between in vitro drug release and in vivo pharmacokinetic parameters.

• Journal of the Korean institute of surface engineering
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• v.39 no.4
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• pp.190-197
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• 2006

The effects of blasting and acidic treatment on the corrosion characteristics of dental implant fabricated with Cp-Ti and Ti-6Al-4V alloy have been researched by using electrochemical methods. The fabricated implants were cleaned and sandblasted by $Al_2O_3$ powder and then acidic treatment was carried out in nitric acid solution. The surface morphology were observed using scanning electron microscope. The corrosion behaviors were investigated using potentiosat and EIS in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The potentio-dynamic test in 0.9% NaCl indicated that the corrosion potential of blasting and acidic treated implant was lower than that of non treated implant, but current density was higher than that of non treated implant. From the cyclic potentiodynamic test results of Ti implant, the passivation current density of blasting and acidic treated implant slightly higher than that of non treated implant. From A.C. impedance test results in 0.9% NaCl solution, polarization resistance($R_p$) value of blasting and acidic treated implant was lower than that of non treated implant. In case of blasting and acidic treated implant surface, the pits were observed in valley and crest of implant surface.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.113-118
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• 2017

Natural and expandable graphites were chemically treated in acidic aqueous solutions such as acetic acid or mixtures of acetic acid and nitric acid. Structures and thermal conductivities of the as-treated graphites were characterized in detail. Both graphites were significantly oxidized in the mixed acidic solution of $H_2SO_4$ and $HNO_3$, which condition was generally used for the oxidation of carbon nanotubes. This considerable oxidation of graphites caused a depression of their thermal conductivity. The structural characteristics, obtained by XRD and XPS, show that the graphites treated in the relatively weak acidic conditions (acetic acid or mixture of acetic acid and nitric acid) were quite similar to the untreated graphites. However, the thermal conductivities of both acidic-treated graphites were remarkably increased.

• Journal of Ginseng Research
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• v.17 no.2
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• pp.139-144
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• 1993

The method for colorimetric determination of acidic polysaccharide from Panax ginseng was investigated. It is possible to apply the method of carbazole-sulfuric acid to determination of pectin, and also to measure the amount of pectin in the mixture of various high molemlu compounds such as starch. cellulose and gum, etc. When the method of carbazole-sulfuric acid was applied to determine the amount of acidic polysaccharide, optical density at 525 nm increased linearly with an increase in the concentration of pure acidic polysaccharide. Effective extraction temperature with water for the determination of the amount of ginseng acidic polysaccharide (GAP) was $80{\circ}C$. In order to separate or concentrate GAP it was appropriate to precipitate the extract only once with 80% ethyl alcohol. GAP was very stable at $100{\circ}C$ for 4 hrs in aqueous solution and between pH values of 5.0~ 12.0.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.732-738
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• 2009

An acidic polygalacturonase (PG) from Aspergillus kawachii was produced by solid state fermentation employing a polyurethane foam support. The conditions used for the production of acidic PG were particle size of support (0.6 or 500 $mm^3$) and fermentation time. From the factors studied, the particle size had important influence on enzyme production. The best conditions for acidic PG production were $0.6\;mm^3$ particle size, 18 hr at $30^{\circ}C$ and initial pH of 5.0. In addition, pectin was extracted from citrus pomaces (grapefruit, lime, and tangerine) by acidic PG at $50^{\circ}C$ for 24 hr with citric acid solution. Infrared spectroscopy showed that lime pomace had more high-methoxylated (65%) endogenous pectin than was obtained than from grapefruit or tangerine pomaces. The enzymatically extracted pectin yield in dry basis (d.b.) for grapefruit and lime pectins were 6.95 and 4.25%, respectively. The citric acid solution alone also contributed to pectin extraction from citrus pomaces (7-9%, d.b.). Limited pectin extraction by acidic PG from tangerine pomace was most likely due to the presence of low-methoxylated endogenous pectin. The enzymatic method for pectin extraction using acidic PG from A. kawachii is a promising technique for releasing highly polymerized pectic substances from high-methoxylated lime or grapefruit pomaces.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.70-76
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• 2006

Micro-droplet cell with free droplet as a micro-electrochemical technique has been limited to apply to electrochemical systems with high wetting properties such as an acidic solution and low grade stainless steels(Type 316L). By loading negative pressure to a droplet, control of droplet size, and use of hydrophobic gasket, the cell is modified to be allowed to use for electrochemical systems with high wetting properties. For giving the reliability of new cell, studies on local corrosion were conducted for three different systems-an acidic chloride solution and high chromium ferritic stainless steel, the other acidic chloride solution and type 316, and a neutral chloride solution and type 316. stainless steel. Firstly, the modified micro-droplet cell allows the anodic polarization curves in an acidic chloride solution to show the fact that the local corrosion of high chromium stainless steel near the $\alpha/\sigma$ interface is due to the Cr depleted zone. Secondly, the local anodic polarization test of type 316 L in the other acidic chloride solution can be successfully conducted in the cell. Furthermore, the local polarization curves help elucidating the corrosion of type 316 with $\delta-ferrite$ phase. Finally, the polarization curves of type 316 L in a neutral chloride solution indicates that the factor affecting the pitting corrosion resistance was inclusions rather than $\delta-ferrite$.