• Elastomers and Composites
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• v.43 no.4
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• pp.259-263
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• 2008

An effect of low-temperature long-term thermal degradation on a degree of crystallinity of a low density polyethylene (LDPE) was investigated by using $^1H$ solid state nuclear magnetic resonance (SSNMR). Firstly, the long-term thermal treatment makes a color of LDPE from white to pale yellow which is indicative of thermal oxidation. Secondly, it makes the $^{1}H$ NMR spin-spin and spin-lattice relaxation times ($T_1$) to be long. Lastly, the degree of crystallinity of the semicrystalline aged-LDPE also decreases with thermal treatment. Above all, the $T_1$ increase is envisaged to be due to either a decrease of the amorphous regions governing overall spin-lattice relaxation mechanism in LDPEs or a dynamically restricted motion of specific molecular motions by intermolecular hydrogen bonding or crosslinking. However, since the decrease of crystallinity implies an increase of amorphous regions by the thermal treatment, the former case is contrast to our results. Accordingly, we concluded that the latter effect is responsible for the $T_1$ increase.

• Korea-Australia Rheology Journal
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• v.12 no.3_4
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• pp.165-173
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• 2000

Three-dimensional numerical simulation of isothermal/nonisothermal coextrusion process of two immiscible polymers through a rectangular channel has been done using the finite element method. The encapsulation phenomenon with the less viscous layer encapsulating the more viscous layer was investigated with the generalized Newtonian fluids. The interface position around the symmetric plane obtained by numerical simulation nearly coincided with the one observed in experiments, but the degree of encapsulation was less than the one observed experimentally. Open boundary condition method was found to be applied to the simulation of nonisothermal coextrusion process, however, the results are not far from those using the fully developed boundary condition, because the temperature development along the downstream direction is very slow in the case of convection dominated flow. When the inlet velocity is increased, the interface profile does not change in isothermal flow, while it moves upward in nonisothermal situation. The degree of encapsulation decreases along the downstream direction in nonisothermal flow. When the inlet temperature increases compared to the wall temperature, the outlet interface moves downward and the degree of encapsulation increases. The difference of degree of encapsulation between the simulation and the experiments seems to arise from the viscoelastic effect of the materials. It was concluded that the nonisothermal effect alone does not explain the complex coextrusion process and the viscoelastic effect needs to be considered.

• Journal of Korean society of Dental Hygiene
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• v.23 no.4
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• pp.227-234
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• 2023

Objectives: Cetylpyridinium chloride CPC-based mouthwashes are well known to have no harmful ingredients in the mouth and can be used for a long time. The purpose of this study was to evaluate the effect of using CPC-based mouthwashes to suppress the biofilm formation and antibiotics for handling orthodontic appliances. Methods: To measure the antibacterial effect, Streptococcus mutans (S. mutans) cultured orthodontic appliances were precipitated in Gargreen and Polident for 5 minutes, incubated at 37℃ for 24 hours(h). In order to measure the biofilm removal effect, the degree of biofilm formation on the orthodontic appliances was stained with a methylene blue and the difference before and after was compared using image J software program (NIH Image J; NIH, Bethesda, MD). Results: The viability of S. mutans according to the concentration showed that Gargreen and Polident inhibited colony formation compared to the control, respectively (p<0.01). The degree of biofilm formation was significantly higher in the control, however both Gargreen and Polident significantly reduced it compared to the before and after condition on removable orthodontic appliances (p<0.01). Conclusions: This study suggests that the use of Gargreen, a cetylpyridinium chloride based oral cleaning cleanser, could be replaced by Polident for antibacterial effect and biofilm formation on removable orthodontic appliances.

• The Journal of Korean Medicine
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• v.31 no.2
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• pp.36-47
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• 2010

Objective: The purpose of this study was to investigate the effects of skin application with Gelidium amansii extract on skin with deep second degree burns in mice. Methods: BALB/c mice were divided into four groups: normal (NOR) group; burn-elicited mice (CON) group, Silmazine-treated mice after burn elicitation (ST) group, and Gelidium amansii-extract treated mice after burn elicitation (GT) group. To examine the skin recovery effect after burn, changes of burn area, angiogenesis and histologic structure were analyzed. To measure effect of edema regulation, matrix metalloproteinase-9 (MMP-9) was analyzed. To estimate the skin regenerative & stable effect, 5-bromo-2'-deoxyuridine (BrdU) and substance P were analyzed. Results: 2 weeks later, 1. The size of burn area decreased in the GT and ST groups more than the CON group. 2. Alleviation of angiogenesis appeared in the GT and ST groups more than in the CON group. 3. Blood clot, epithelial cell hyperplasia, and inflammatory cell infiltration declined in the GT and ST groups more than in the CON group. 4. MMP-9, BrdU, and substance P positive reaction decreased in the GT and ST groups more than in the CON group 5. In the comparative study, the GT group was superior to the ST group. Conclusion: The skin application of Gelidium amansii extract could lessen skin damage by the medium of regulation MMP-9 activation. This skin stabilization was induced in mice with deep second degree burns.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.169-172
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• 2022

본 연구에서는 고령화패널(KLoSA) 7차년도 데이터 중 60세이상 치매판정 노인(경도인지장애 포함)을 대상으로 치매노인의 삶의 만족에 영향을 미치는 일상생활 주변도움 필요정도와 우울의 영향력을 분석하고, 치매노인의 일상생활 주변도움 필요정도와 삶의 만족 사이에서 우울이 매개효과를 갖는지를 검증하고자 한다.

• Korean Journal of Child Studies
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• v.23 no.6
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• pp.33-47
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• 2002

This study examined the effects of conditions of generation(0, 1, or 2 cognitive operations) and task difficulty in children's recall. Subjects were 40 children in each age group, 8-year-olds and 10-year-olds. Each subject was shown 12 simple or difficult multiplication problems in one of the conditions of generation. After a buffer task, subjects were required to recall correct answers to the problems in random order. The data were analyzed by ANOVA and simple main effect analyses. Results showed that generation effect(GE) occurred among children younger than 12, and GE improved with age. Learning from cognitive operations was more effective than learning through simple repetition. Easier tasks led to greater GE, a phenomenon explained by procedures used in this study.

• Culinary science and hospitality research
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• v.10 no.4
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• pp.201-214
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• 2004

The brand image had an effect on customer loyalty degree "Traditional characteristic", "Reliability", "Future events sliced raw fish directivity". With it appears, causing the effect which is powerful in customer loyalty degree "Traditional characteristic or reputation of restaurant", "Reliability of advertisement". The brand image had an effect on customer satisfaction "Reliability", "Customer directivity", "Traditional characteristic". With appears and with it is referred from above together "Traditional characteristic of restaurant" or "Reliability of advertisement public information", "Policy of the restaurant management customer first of all poem".

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.5
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• pp.905-914
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• 1996

To study the effect of the bleaching agents in detergents on the degradation of cotton fabrics, the carboxyl contents, copper numbers, degree of polymerization, the change of tensile strengths and fiber surfaces of cotton fabric before and after washing were examined. The results obtained were as follows: As the cycles and temperature of washing increased, the carboxyl content of washed cotton fabric changed little but the copper unmber of cotton fabric was increased. At 6$0^{\circ}C$ , 8$0^{\circ}C$ the copper number of cotton fabric washed with soidum perborate (PB) was higher than that of with sodium percarbonate (PC). The degree of polymeriazation and tensile strength of cotton fabric were decreased and at higher temperature those were more decreased but were less decreased when tetraacetyehylenediamine (TAED) was added. The degree of polymerization had negative relation with copper unmber but with tensile strength of cotton fabric had positive relation. Cotton fiber surface was more degraded by bleaching agents and hydrogen peroxide exhaustion was increased as the temperature of washing increased. And hydrogen peroxide exhaustion had negative relation with the degree of polymerization.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.3
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• pp.13-21
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• 2012

This study was carried out to evaluate the stability of archival documents produced using papers. The properties of archival documents depend on the type of fillers of papers that are used such as fiber, non cellulose fiber, and mineral. The physio-chemical characteristics of archival documents were analyzed by employing acid hydrolysis against cellulose fiber substances. Fibers of Korean hand-made (Hanji), flex, and cotten papers showed higher pH and the degree of polymerization (DP) than wood fiber and mechanical fiber. Mechanical pulp containing 12.8% of lignin showed the greatest decrease of DP due to acid hydrolysis, and this resulted in increase of degree of aging. The filler found to clay and talc did not contain metal such as $Fe^{+2}$, $Fe^{+3}$, and $Cu^{+2}$. The alkaline metals such as Mg, Ca, and Ti showed greater resistance to acid hydrolysis.

• Carbon letters
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• v.10 no.4
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• pp.300-304
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• 2009

Thermal emissivity of nuclear graphite was measured with its oxidation degree. Commercial nuclear graphites (IG-110, PECA, IG-430, and NBG-18) have been used as samples. Concave on graphites surface increased as its oxidation degree increased, and R value (Id/Ig) of the graphites decreased as the oxidation degree increased. The thermal emissivity increased depending on the decrease of the R (Id/Ig) value through Raman spectroscopy analysis. It was determined that the thermal emissivity was influenced by the crystallinity of the nuclear graphite.