• Journal of the Korean Applied Science and Technology
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• v.24 no.4
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• pp.339-346
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• 2007

The influence of adding urea to phenol-formaldehyde (PF) resins as a co-polymer component were investigated aiming at synthesizing useful phenol-urea-formaldehyde resins. Urea was added at 10% by total resin weight. Several methods for the addition of urea to the PF resins during synthesizing resins to see the co-polymerization occurs between urea and PF resins. The urea was added at the beginning, at three different middle stages, and at the end of PF resin synthesis. The copolymerized methylene bridges between phenol and urea molecules were not observed by $^{13}C-NMR;$ no signal around 50ppm. The curing of urea-modified PF resins, evaluated by dynamic mechanical analysis(DMA), showed some differences among the resins. DMA gel times ranged from 2.75 min to 3.25 min and the resins made with earlier urea additions showed slightly shorter gel times. The longest cure time and gelation time was observed for the resin PFU. Catalyst effects on the DMA cure time values of resins were not significant with different amounts of catalyst or different types of catalyst for all resins tested. Gel times of urea-modified PF resins shortened the most by triacetin catalyst.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.763-768
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• 2002

In this study, methyl methacrylate (MMA) - modified polymer mortar(MMPM) was developed and its setting shrinkage and working life properties were surveyed. In order to study the setting shrinkage, setting shrinkage test for the 24 batches were also conducted with taking the MMA monomer content to the UP resin and the mixed content of shrinkage reducing agent(SRA) as variables. Furthermore, in order to study the working life measured gel time, working time, setting time of MMPM and binder. Experimental resurts show that the workability remarkably improved as the mixed MMA content increased. The working life was proportional to MEKPO content and was shorted. also, showed high interrelationship of binder gel time and MMPM working life. Setting shrinkage markedly reduced as the content of MMA and the SRA increased.

• Journal of Pharmaceutical Investigation
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• v.28 no.2
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• pp.87-92
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• 1998

Kojic acid (KA) is an antimelanogenic agent which has been widely used in cosmetics to whiten the skin color. However, it has the drawbacks of the skin irritancy and the instability against the pH, temperature, and light. In order to overcome these problems, various topical gels and multiple emulsion creams which can control the release of active ingredient, KA, were formulated employing cream bases of mineral oil with caprylic capric triglyceride and hydrophilic polymers such as chitosan, carbopol. and pluronics. Using Franz diffusion cells mounted with a synthetic cellulose membrane (MWCO 12,000), drug release characteristics of the formulations were evaluated by the HPLC assay of KA concentration in the receptor compartment of pH 7.4 phosphate buffered saline solution. Drug release from chitosan-based gels (ChitoGel) obeyed to the first order kinetics with a rapid release especially in the initial period. However, pluronic-based gels (PluGel) and carbopol-based gels (CarboGel) revealed controlled release of drug to some extent, followed by the square root-time kinetics. Moreover, the release of KA was further controlled with the W/O/W multiple emulsion creams (MultiCream), showing the apparent zero order release kinetics by virtue of dynamic ratecontrolling membrane of the oil layer. The flux $(J,\;{\mu}g/cm^2/hr)$ of ChitoGel. CarboGel. PluGel. and MultiCream in the initial period of 6hr were 73.30, 28.67. 24.04 and 7.72, respectively. On the other hand, the skin irritancy score of ChitoGel and MultiCream were observed as 2.5 and 2.3 respectively, in the rabbit skin irritation test. Although there were insignificant differences at p<0.05 between those formulations, it was possible to conclude that the W/O/W multiple emulsion creams containing KA might be a good candidate for an antimelanogenic drug delivery system due to the controlled release of acidic drug molecules.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.369-375
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• 2016

Purpose of this study was to compare the easiness of insertion of three Supraglottic airway devices(SADs) in a neutral and cervical neck collar position in a manikin setting. Three different SADs-Laryngeal Mask Classic (LMA), I-gel and Streamlined Liner of the Pharynx Airway(SLIPA) were applied. Thirty nine emergency medical technicians (EMTs) who are working in Korea 119 rescue services were taught briefly about the use of the LMA, I-gel and SLIPA in a manikin setting. The time to effective ventilation was shorter in I-gel ($10.5{\pm}2.2$, $11.4{\pm}5.7$) and SLIPA ($12.3 {\pm}5.1$, $12.0{\pm}6.8$) than LMA ($17.2{\pm}3.2$, $18.5{\pm}5.5$) in a neutral and cervical neck collar position, respectively(p<0.05). There was no difference between head positions in each of the airways. In conclusion, in the speed of insertion, I-gel and SLIPA were superior to LMA in the neutral and cervical collar setting of a manikin.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.483-486
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• 1995

With a view to increase utility of ethanol fractionated fish skin gelatin as a food source, the effect of gelation condition on physical properties of the gelatin was investigated. The physical properties of gelatins treated with or without ethanol were improved with a concentration of gelatin increased. The properties such as gel strength, melting point and gelling point of 10% gelatin sol or gel were reached to maximum at pH 6.0 in ethanol treated gelatin and pH 5.0 in non treated one, respectively. Gel strength and melting point of both gelatin gels chilled for long time at low temperature were superior to those of both gelatin gels chilled for short time at high temperature. Gel strength, melting point and gelling point of ethanol treated gelatin gel or sol prepared under optimized gelation conditioning were superior to those of non treated one.

• Journal of the Korean Applied Science and Technology
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• v.36 no.1
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• pp.248-257
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• 2019

On this study, we have observed the change of the gel nail morphology as the time elapse and measured the surface roughness/volume, moisture content/purcutaneous moisture vaporizing amount of the nail surface before gel nail treatment and after gel nail removing of the 100%acetone remover, 5%acetone remover and 0%acetone remover and the avocado non acetone remover for the comparison of the effect on the nail surface and the degree of the removing of the gel nail of the removers as the acetone contents. The removing ability were the order of 100%acetone remover, avocado non acetone remover, 5%acetone remover and the 0%acetone remover. There were no statistical significance difference in the nail surface roughness comparision before and after gel nail removing in 5%acetone, 0%acetone and avocado non acetone, and there was no statistical significance difference in the nail surface volume comparision before and after gel nail removing in 0%acetone. We measured the moisture content of the nail surface and the purcutaneous moisture vaporizing amount before gel nail treatment and after gel nail removing, resulted that, the decrease of the moisture content of the nail surface after removing the gel nail is the minimun and the increase of the purcutaneous moisture vaporizing amount of the nail surface after removing the gel nail is the minimun at the case of 0%acetone. In conclusion, 5%acetone remover and 0%acetone remover is possible to use as the gel nail remover and they had revealed that there was the least harmful effect on the nail. We hope that this study is utilized to the development of the non acetone remover and the basic research of the nail beauty industry.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.329-335
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• 1995

Rheological properties of whole soybean gel(soygel) were investigated as affected by the water addition ratio, stirring time and Ca salts. The soygel was prepared by suspension of whole soy flour(WSF, 300 mesh) in boiling water, addition of sodium alginate and Ca salts followed by thorough mixing and gel formation at $4^{\circ}C$. The texture properties of hardness, adhesiveness and cohesiveness of the gel were increased as the stirring time prolonged from 5 to 30 minutes. From the results of the rheological and sensory properties, 20 minutes of stirring time was selected for whole soybean gel preparation. Eventhough increase in water addition ratio from 8 to 12 times(water/WSF, v/w) resulted a decrease in hardness and adhesiveness, 10 times ratio was chosen as proper the water addition based on textural uniformity. Among the Ca salts, $CaSO_4$ produced the highest hardness followed by Ca $gluconate-CaSO_4$ mixture(413g) and Ca gluconate at the water addition level of 10 times. In order to determine the amounts of Ca salts, and 0.125g of Ca gluconate or $CaSO_4$ per g WSF were found to be optimum in terms of textural and sensory properties. The proper mixing ratio of Ca gluconate and $CaSO_4$ was found to be 50 : 50, 25 : 75 and 0 : 100.

• The Korean Journal of Urological Oncology
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• 제15권3호
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• pp.178-186
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• 2017

Purpose: Poloxamer 407 (P407) thermo-sensitive hydrogel formulations were developed to enhance the retention time in the urinary bladder after intravesical instillation. Materials and Methods: P407 hydrogels (P407Gels) containing 0.2 w/w% fluorescein isothiocyanate dextran (FD, MW 4 kDa) as a fluorescent probe were prepared by the cold method with different concentrations of the polymer (20, 25, and 30 w/w%). The gel-forming capacities were characterized in terms of gelation temperature (G-Temp), gelation time (G-Time), and gel duration (G-Dur). Homogenous dispersion of the probe throughout the hydrogel was observed by using fluorescence microscopy. The in vitro bladder simulation model was established to evaluate the retention and drug release properties. P407Gels in the solution state were administered to nude mice via urinary instillation, and the in vivo retention behavior of P407Gels was visualized by using an in vivo imaging system (IVIS). Results: P407Gels showed a thermo-reversible phase transition at $4^{\circ}C$ (refrigerated; sol) and $37^{\circ}C$ (body temperature; gel). The G-Temp, G-Time, and G-Dur of FD-free P407Gels were approximately $10^{\circ}C-20^{\circ}C$, 12-30 seconds, and 12-35 hours, respectively, and were not altered by the addition of FD. Fluorescence imaging showed that FD was spread homogenously in the gelled P407 solution. In a bladder simulation model, even after repeated periodic filling-emptying cycles, the hydrogel formulation displayed excellent retention with continuous release of the probe over 8 hours. The FD release from P407Gels and the erosion of the gel, both of which followed zero-order kinetics, had a linear relationship ($r^2=0.988$). IVIS demonstrated that the intravesical retention time of P407Gels was over 4 hours, which was longer than that of the FD solution (<1 hour), even though periodic urination occurred in the mice. Conclusions: FD release from P407Gels was erosion-controlled. P407Gels represent a promising system to enhance intravesical retention with extended drug delivery.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1903-1907
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• 2013

Heart condition should be observed for long periods of time because it does not appear abnormal all the time. However, there are many difficulties checking our health for a long time due to its size, operation of equipment, and cost. To solve these problems, an electrocardiograms(ECG), specially interfacing three gel-less metal electrodes for low cost portable applications, is designed and implemented. Gel-less metal electrodes are used for ECG monitoring system instead of gel-type electrodes that can cause skin rashes and itching problem. The whole ECG system consists of two parts-analog and digital circuits. The analog measurement circuit that has a 18*25mm size is made up of op-amps maintaining a sufficiently high common-mode noise rejection and passive elements of SMD type. Analog heart signal is converted to digital stream suitable for display on a TFT-LCD by an 8-bit microcontroller. The size of the completed ECG system is 25*80*50mm and its weighing is about 150g, which is small enough to be easily used. Therefore, the implemented ECG system can be used as a portable one.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.228-236
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• 1998

Egg is an important foods containing many good proteins. But it is well known that egg protein has a lot of allergenicity. The purpose of this study is to develop the methods to reduce the allergenicity of egg. I tried various experimental methods ; For example, heat treatment, irradiation with ultraviolet and microwaves, treatment with polyphosphate, enzyme hydrolysis and PCA inhibition test using guinea pigs and degrees of hydrolysis. The results obtained were as follows ; 1. Heat treatment reduced allergenicity of egg protein. The longer the heat time, the better the effect. 2. Irradiating with ultraviolet and microwave increased both the degree of protein hydrolysis and PCA inhibition reduced the allergenicity. Ultraviolet was more effective than microwaves on egg protein. Fertilized eggs did not reduce allergenicity. 3. Enzyme treatment increased the degree of hydrolysis and PCA inhibition, and reduced allergenicity considerably. Alcalase was more effective than neutrase. 4. Adding polyphosphate did not induced protein hydrolysis, but increased PCA inhibition and reduced allergenicity. 5. The picture of various treatments of egg gel by SEM showed a light surface which indicated that protein was desolved. Neutrase was lighter than alcalase, and the longer the heating time, the lighter the surface became. 6. Measurements of the hardness of egg gel by Instron showed that the longer the reaction time with enzyme, the softer it became.