• The Journal of Advanced Prosthodontics
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• v.7 no.5
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• pp.386-391
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• 2015

PURPOSE. The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing. MATERIALS AND METHODS. Cylindrical specimens (N=60, n=30 per group, ${\phi}5mm{\times}1mm$) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: $840mW/cm^2$) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (${\alpha}$=.05). RESULTS. In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin. CONCLUSION. The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1597-1604
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• 2020

In this study, a synthesized poly(amino acid) self-assembly grafted with valine molecules was investigated on the skin activity of skin growth factors. The amphiphilic grafted poly(amino acid) derivatives were successfully synthesized by varying of degree of substitution(DS) and polymerization (DP) with valine molecules forming a β-sheet structure. Then, the pro-collagen biosynthesis of EGF(epidermal growth factor) was improved by 20%, and the inhibitory ability of tyrosinase activity was increased by 6.5 times by self-assembling of EGF with the poly(amino acid)s having β-sheet structures. This strategy of preparing protein self-assembly with poly(amino acid) derivatives will help improve the stability of protein growth factors and use it in medicals as well as cosmeceuticals through skin improvement.

• Fashion & Textile Research Journal
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• v.6 no.3
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• pp.377-383
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• 2004

Photografting of styrene (St) on polypropylene (PP) nonwoven fabric using benzoin ethyl ether (BEE) as a photosensitizer was investigated. Inhibition of homopolymerization was achieved by adding various concentrations of $FeSO_4{\cdot}7H_2O$, $CuSO_4{\cdot}5H_2O$ and Mohr's salt. As St concentration was increased, the degree of grafting was increased as to a specific value and then decreased, and the effect of BEE concentration showed the same tendency. It was also found that the degree of grafting increased with reaction time and reaction temperature. Addition of the polyfunctional monomers and $H_2SO_4$ to the grafting system accelerated the photografting. The melting temperature, molecular weight, tensile strength and elongation were decreased with the increase in the degree of grafting.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.373-380
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• 2020

This study was carried out to convert the hydrophobic characteristics of PVDF to hydrophilic. Poly(-vinylidene fluorine) (PVDF) was grafted by electron beam irradiation and sulfonated. The grafting degree of modified PVDF increased with the monomer concentration, but not the conversion degree. From the results of FTIR and XPS, it was shown that the amount of converted sulfur increased with the grafting degree. The radiation-induced graft polymerization led to decrease fluorine from 35.7% to 21.3%. Meanwhile, the oxygen and sulfur content increased up to 8.1% and 3.2%. The pore size of modified membranes was shrunken and the roughness sharply decreased after irradiation. The ion exchange capacity and contact angle were investigated to show the characteristics of PVDF. The enhanced ion exchange capacity and lower contact angle of modified PVDF showed that the hydrophilicity played a role in determining membrane fouling. Electron beam irradiation successfully modified the hydrophobic characteristics of PVDF to hydrophilic.

• Polymer(Korea)
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• v.25 no.5
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• pp.617-624
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• 2001

The core-shell composite latexes were synthesized by stage emulsion polymerization of methyl methacrylate (MMA) and styrene (St) with ammonium persulfate after preparing monomer pre-emulsion in the presence of anionic surfactant. However, in preparation of core-shell composite latex, several unexpected results are observed, such as, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve the disadvantages, We study the effect of initiator concentrations, surfactant concentrations, and reaction temperature on the core-shell structure of polymethyl methacrylate/polystyrene and polystyrene/polymethyl methacrylate. Particle size and particle size distribution were measured using particle size analyzer, and the morphology of the core-shell composite latex was determined using transmission electron microscope. Glass temperature was also measured using differential scanning calorimeter. To identify the core-shell structure, pH of the two composite latex solutions were measured.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.365-373
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• 2016

Composites are the most useful restorative material. However, composites have some disadvantages such as polymerization shrinkage, long working time, and susceptibility to water and contamination, which are stood out more especially when treating children. To solve these problems, bulk-fill composites have been developed. The aim of this study is to compare mechanical properties of bulk-fill and conventional composites. Bulk-fill composites (SureFil SDR flow (SDR), Tetric N-Ceram bulk fill (TBF)) and conventional composites (Filtek Z-350 (Z-350), Unifil Flow (UF), Unifil Loflo Plus (UL)) were used. The Vickers hardness tester was used to measure the microhardness of materials, and Fourier transform infrared spectroscopy was used to measure the degree of conversion. Polymerization shrinkage was measured by using a linometer. Flexural and compressive properties were measured by using the universal testing machine. Data were statistically analyzed by ANOVA and Scheffe's post hoc test. The level of significance was set to p < 0.05. Most conventional composites showed higher microhardness than bulk-fill composites. However, bulk-fill composites showed a higher top/bottom microhardness ratio than conventional composites. Bulk-fill composites showed a higher top/bottom degree of conversion ratio than conventional composites. The polymerization shrinkage was highest in UL and lowest in Z-350. The polymerization shrinkage of flowable composites was higher than that of non flowable composites. The compressive properties were highest in Z-350 and lowest in SDR and UL. In terms of flexural properties, Z-350 was the highest. However, none of the bulk-fill composites exhibited mechanical properties as good as those of conventional composites. Nonetheless, the ratio of microhardness and degree of conversion, which are important properties of bulk filling, were higher in bulk-fill composites. Therefore, the bulk-fill composites might be considered suitable restorative materials in pediatric dentistry.

• Journal of Fashion Business
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• v.11 no.6
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• pp.101-114
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• 2007

This research aimed to identify the differences, in terms of the pattern, of using wool and jersey for designing jackets and to provide a theorized solution. The object of this study is development of women's tailored jacket pattern by the traits of fabrics with fabrics those are generally used to develop the power of manufacturing technique about fit of jacket. Basic bodies prototype, graphics of sleeves prototype and graphics of jacket pattern those a clothing company at present(on&on, a brand of Beaucre Merchandising Co.,Ltd) is using were used as basics of tailored jacket pattern. Three kinds of fabric(wool, polyester, jersey) were chosen, we made jackets in the same manufacturing process of the clothing company, modified and made up for the weak points and then we compared and analyzed differences of pattern by the traits of fabrics, the results are as follows: 1) We drafted basic tailored style jacket pattern, made a jacket with wool fabric, made wearing experiment, modified and made up for the weak points by the trend, then developed JacketⅠ for study; 2) With JacketⅠ for study as the basic, we made a jacket with polyester fabric, made wearing experiment, modified and made up for the weak points, then developed Jacket II for study; 3) With JacketⅠ for study as the basic, we made a jacket with jersey fabric, made wearing experiment, modified and made up for the weak points, then developed Jacket III for study; 4) We presented final degree of polymerization of pattern with Jacket I II III for study; 5) We compared and analyzed the differences of pattern with the degree of polymerization of pattern with Jacket I(Wool) for study and Jacket II(Polyester), there was no change of size overall except extra amount which happens because of the trait of the fabric in 20 items of body format pattern, there were differences of size in 3 items(height of a sleeve, width of a sleeve, length of a sleeve) among 5 items of sleeves pattern; 6) We compared and analyzed the differences of pattern with the degree of polymerization of pattern with Jacket I(Wool) for study and Jacket III(Jersey) for study, there were differences of size by the kinds of fabric in 11 items(neck point to shoulder point length, Bishoulder point length, back interscye length, front interscye length, armhole circumference, depth of armhole, chest circumference, bust circumference, waist circumference, hip circumference, waist dart) among 20 items of body format pattern, there were differences of size by the kinds of fabric in 5 items(height of a sleeve, circumference of a sleeve, width of a sleeve, length of a sleeve, width of bottom of a sleeve) among 5 items of sleeves pattern.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.1
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• pp.1-8
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• 2016

The objective of this study was to evaluate quality properties, including amylopectin content, and texture analysis of brown rice and germinated brown rice cultivars in Korea for rice processing products. The amylopectin short chain content of germinated brown rice was significantly higher than that of brown rice. Texture analysis test showed that germinated brown rice Jinbo had the lowest hardness and toughness as well as and highest stickiness and adhesiveness. The correlation between degree of polymerization of amylopectin and texture analysis was also evaluated. In particular, germinated brown rice, short-chain amylopectin showed a negative correlation with hardness and toughness, whereas long-chain amylopectin showed a positive correlation with hardness, toughness, and adhesiveness. These results indicate that there is a relationship between degree of polymerization and texture analysis.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.6
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• pp.1092-1096
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• 2002

Ethyl acetate and butanol fractions among the serial solvent fractions of grape seed ethanol extract contained the catechin at the levels of 35.7 mg/g and 20.2 mg/g, respectively However, the POV increasing patterns of two linoleic acid samples containing each solvent fraction were so similar that the difference in antioxidant activity by the catechin content of each solvent fraction could not be found. Each solvent fraction was fractionated on C18 cartridges into three subfractions which were mono-, dimers fraction (FI), oligomers fraction (FII) and polymers fraction (FIII) to examine the effect by the difference in degree of Polymerization of proanthocyanidin. The catechin contents of ethyl acetate subfractions (E-F) were in the order of E-FI (26.0 mg/g) > E-FII (18.6 mg/g) > E-FIII (13.7 mg/g) but the three subfractions showed nearly similar antioxidant activities, by the POV measurement at 1,000 ppm concentration. Also the catechin contents of butanol subfractions (B-F) were in the order of B-FI (35.3 mg/g) > B-FII (30.8 mg/g) > B-FIII (22.7 mg/g) but similar antioxidant activities were observed in all subfractions. In this study, similar antioxidant activities of each solvent subfraction in spite of different catechin contents inform that the degree of polymerization of proanthocyanidin as well as the total catechin content should be considered in quality control of grape seed extract produced for natural antioxidant.

• Journal of the Korean Wood Science and Technology
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• v.28 no.3
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• pp.34-41
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• 2000

Recently many scientists have tried to synthesize biodegradable polymers due to durable and non-biodegradable products of conventional synthetic plastics when these were wasted in nature. So to reuse the wastepapers for biodegradable polymer resources, ONP (old newsprint), OCC (old corrugated containerbpard) were carried out by the pretreatment of chlorinite, hypochlorite and oxygen-alkali treatment conditions. For manufacturing of biodegradable polymer with wastepaper, this study performed to investigate change of chemical components and optimal pretreatment condition. The summarized results in this study were as follows: Lignin content in ONP and OCC was was higher than in MOW and ash content was the highest in MOW. More amount of ash components were reduced by wet defiberation than by dry defiberation. Wet defiberation fiber are better than dry defiberated fiber in chemical pretreatment condition for wastepapers, and the best result was obtained in the condition of sodium chlorite at $70^{\circ}C$, because it has high delignification ratio, ${\alpha}$-cellulose contents and degree of polymerization in this treatment condition. Oxygen-alkali treatment condition is the worst method because of low yield, low degree of polymerization in this pretreatments.