• Journal of Pharmaceutical Investigation
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• 제35권2호
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• pp.81-87
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• 2005

We have prepared karaya gum patches containing ketoprofen and investigated the effect of short-time current pretreatment of skin on the permeability. Hairless mouse skin was treated with current before the patch was mounted on the skin. The effect of current density and current duration on the flux of ketoprofen was studied. The possibility of additive effect with penetration enhancer (PGML) was also investigated. Iontophoretic pretreatment of skin increased the passive flux up to 3 folds at 0.4 $mA/cm^2$ current density, when the matrix contained no PGML. As the duration of current-pretreatment and current density increased, flux increased. PGML increased the average passive flux markedly, about 6 to 12 folds, depending on the concentration in the patch. Current pretreatment further increased the flux from this PGML containing patch, exhibiting additive effect. These results indicate that short-duration current pretreatment of skin can be an useful method for the enhancement of ketoprofen permeability through skin.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권3호
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• pp.159-167
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• 1999

This study performed experiments for measuring corrosion potential and current density variations in the polarzation curves of polyvinylchloride. The results were examined to identify particular influences affectingthe corrosion potential such as temperature, pH, enzyme, and salt. The lines representing active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme and salt. The Tafel slope for the anodic dissolution was determined using the polarization effect with varying conditions. The slope of the polarization curves describing the active-to-passive transition region was noticeably shifted in the potential direction. In addition, using the variation in conditions, the best temperature and pH were determined for the corrosion rate, and resistance of corrosion. The second anodic current density peak and maximum passive current density were designated as degraded(IP/I0). The value of IP/I0 was used in measuring the extent of the degradation of the polyvinychloride. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

• 동력기계공학회지
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• 제15권2호
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• pp.42-48
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• 2011

440A martensitic stainless steels which were modified with reduced carbon content(~0.5%) and addition of small amount of nickel, vanadium, tungsten and molybdenum were manufactured. Effects of alloying elements and tempering temperatures on the uniform corrosion in the solution of lN H2S04 were investigated through the electrochemical polarization test. When tempering temperature is constant, corrosion current density in active-passive transition point, Icorr, decreased a little with an increase of austenitizing temperature. In addition to this, when austenitizing temperature is constant, longer holding time showed a little lower Icorr and Ipass, passive current density. And when austenitized at $1050^{\circ}C$ and tempered in a range of $350{\sim}750^{\circ}C$, best anti-corrosion properties were obtained at $350^{\circ}C$ tempering temperature while worst at $450^{\circ}C$ or $550^{\circ}C$. The specimens tempered at below $450^{\circ}C$ and above $550^{\circ}C$, similar and good anti-corrosion characteristics were obtained regardless of alloying elements added, showing anti-corrosion characteristics are influenced more by tempering temperature than by alloying elements.

• Journal of Pharmaceutical Investigation
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• 제34권4호
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• pp.275-281
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• 2004

We have studied the effect of polarity, current density, current duration, crosslinking density, swelling ratio, and permeation enhancers on the transdermal flux of ketoprofen from acrylamide hydrogel. Hydrogel was prepared by free radical crosslinking polymerization of acrylamide. Drug loading was made just before transport experiment by soaking the hydrogel in solution containing drug. In vitro flux study using hairless mouse skin was performed at $36.5^{\circ}C$ using side-by-side diffusion cell, and the drug was analysed using HPLC/UV system. The result showed that, compared to passive flux, the total amount of drug transported increased about 18 folds by the application of $0.4\;mA/cm^2$ cathodal current. Anodal delivery with same current density also increased the total amount of drug transported about 13 folds. It seemed that the increase in flux was due to the electrorepulsion and the increase in passive permeability of the skin by the current application. Flux increased as current density, the duration of current application and loading amount (swelling duration) increased. As the cross linking density of the hydrogel increased, flux clearly decreased. The effect of hydrophilic enhancers (urea, N-methyl pyrrolidone, Tween 20) and some hydrophobic enhancers (propylene glycol monolaurate and isopropyl myristate) was minimal. However, about 3 folds increase in flux was observed when 5% oleic acid was used. Overall, these results provide some useful information on the design of an optimized iontophoretic delivery system of ketoprofen.

• 대한치과보철학회지
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• 제38권1호
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• pp.85-97
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• 2000

The purpose of this study was to compare the corrosion characteristics between implant fixture and two types of abutment screw ; gold screw, titanium screw. The anodic polarization behavior, the galvanic corrosion behavior, and the crevice corrosion behavior of prepared samples were investigated using potentiostat and scanning electron microscope. The results were as follows: 1. Anodic polarization behavior of samples; The primary passivation potential of implant fixture was -420mV, implant abutment was -560mV. titanium screw was -370mV and gold screw was -230mV. All samples were shown to have a high corrosion potential and good formation of passive film. The critical passive current density of gold screw was higher than that of other samples and the sample of gold screw showed a unstable passive film formation at passive region. 2. Galvanic corrosion behavior of samples; Contact current density between implant fixture and titanium screw showed $8.023{\times}10^{-5}C/cm^2$. Contact current density between implant fixture and gold screw showed $5.142{\times}10^{-5}C/cm^2$. 3. Crevice corrosion behavior of samples; The crevice corrosion resistance of sample using titanium screw was higher than that of sample using gold screw, and a severe corrosion morphologies were observed at the fixture-screw interface by the scanning electron microscope.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권3호
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• pp.165-171
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• 2000

Experiments were carried out to measure variations in the oxidation potential and current density using the polarization curves of polycarbonate. The results were then examined to identify the influences affecting the oxidation potential related to various conditions, such as temperature, pH, and oxydase(citrate and lipase). The lines representing the active anodic and cathodic dissolution shifted only slightly in the potential direction relative to temperature, pH, and the effect of the enzyme. The Tafel slope for the anodic and cathodic dissolution was determined such that the reversibility polarization was indicated as being effected by various conditions. The slope of the polarization curves describing the active-to-passive transition region shifted noticeably in their direction. Also, by varying the conditions, the optimum conditions for the most ready transform were identified, including temperature, pH, oxidation rate, and resistance of oxidation potential. The critical oxidation sensitivity(I(sub)r/I(sub)f) of the anodic current density peak and maximum passive current density was also determined, which is used in measuring the critical corrosion sensitivity of a polycarbonate.

• Nuclear Engineering and Technology
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• 제32권6호
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• pp.595-604
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• 2000

Flow-Accelerated Corrosion Behavior of SA106 Gr.C steel in room temperature alkaline solution simulating the CANDU primary water condition was studied using Rotating Cylinder Electrode. Systems of RCE were set up and electrochemical parameters were applied at various rotating speeds. Corrosion current density decreased up to pH 10.4 then it increased rapidly at higher pH. This is due to the increasing tendency of cathodic and anodic exchange half-cell current. Corrosion potential shifted slightly upward with rotating velocity. Passive film was formed from pH 9.8 by the mechanism of step oxidation and the subsequent precipitation of ferrous species into hydroxyl compound. Above pH 10.4, the film formation process was active and the film became stable. Corrosion current density showed increment in pH 6.98 with the rotating velocity, while it soon saturated from 1000 rpm above pH 9.8. This seems that activation process which represents formation of passive film on the bare metal surface controls the entire corrosion process

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 춘계학술발표대회 및 제12회 신소재 심포지엄
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• pp.37.1-37.1
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• 2007

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권1호
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• pp.43-50
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• 2000

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.453-459
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• 2003

In this study, the effect of heat treatment to the electrochemical polarization resistance for the Ti-6Al-4V alloy was measured. The solution heat treatments were carried out at $1066^{circ}E, 966^{\circ}$E$, followed by aging heat treated $550^{circ}E, 600^{circ}E, and 650^{circ}E$. The electrochemical polarization resistance behavior was measured by potentio-dynamic polarization in the 1N $HNO_3$ + 15ppm HF solution. The obtained results were as follows. 1. As solution heat temperature increased. the corrosion potential was increased, whereas passive current density and critical current density were decreased. 2. As aging heat temperature increased, the corrosion potential was almost constant, but passive current density was decreased 3. The results of composition test measured by EDS at grain boundary and near $\gamma'$ precipitates indicated that S, Cl. and Si which originated from base metal were segregated at the grain boundaries Al and Ti which were the main alloying element in $\gamma'$ were depleted at the $\gamma'$ precipitated. The depletion of Al and Ti in $\gamma'$ was caused to early breakdown of passive film.