• 한국재료학회지
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• 제17권10호
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• pp.548-554
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• 2007

[ $BaTiO_3$ ] thick film by an interfacial polymerization method was prepared at the liquid/liquid interface between benzyl alcohol saturated solution with the basic catalyst [diethyl amine ($NHEt_2$) or triethylamine ($NEt_3$)], and the water dissolved with $TiO_2$ and $Ba(CH_3COO)_2$. The film thickness increased gradually with an increase in diethyl amine($NHEt_2$) or triethylamine($NEt_3$) volume and the reaction time. The homogeneity of $BaTiO_3$ thick film after sintered at $600^{\circ}C$ was confirmed by EPMA analysis, which showed that both of Ba and Ti element were homogeneously distributed on the surface as well as in the perpendicular direction of the film. The thickness of $BaTiO_3$ film obtained by this process was $8.75\;{\mu}m$.

• 한국의류학회지
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• 제15권3호
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• pp.271-280
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• 1991

Emulsion graft copolymerization of MMA onto cotton fiber using Ce(IV) salt as an initiator was carried out. Graft yield and graft efficiency were observed according to the kinds and concentrations of emulsifier and polymerization conditions. The physical properties of MMA grafted cotton fabric were investigated. The results of this study were as follows: 1. The heighest graft yield of emulsion graft polymerization occurred at the concentration below cmc of emulsifier, which was different from emulsion polymerization. Nonionic sur- factant as an emulsifier was more effective than anionic one. 2. The highest graft yield was obtained at the initiator concentration $1{\times}10^{-2}mol/l$. The viscometric molecular weight of PMMA was in the order of 106. 3. As reaction time increased, the graft yield increased but the graft efficiency decreased. 4. Elevation of reaction temperature resulted in increase of graft yield. The apparent activation energy of MMA graft polymerization was 4.72 Kcal/mol. 5. Physical properties of MMA grafted cotton fabric varied with increase of grafting. Thickness and stiffness showed a noticeable increase, whereas tensile strength and elongation was slightly increased. Crease recovery increased as the graft yield increase up to $50\%$ and decreased thereafter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1158-1162
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• 2005

Drug delivery systems have been developed to reduce the side toxicity of drugs by localizing them in the site of action. But it depends on the circulation of the blood and it doesn't have the function of locomotive mechanism of itself for searching for the region of disease. However, this problem could be solved by nanobot which have the locomotive function. So, we mimic the movement of cell that can move in a human body. In this paper, to polymerize the encapsulated actin within the liposome, electroporation technique is employed. In order to optimize polymerization and depolymerization of the liposome, we compare the time of polymerization and depolymerization by concentration of crown ether. we synthesis the liposome which contain azobenzene Linked crown Ether conjugated Actin protein. Azobenze linked crown ether holds the K+ ion by exposure of UV light and this disturbs the actin polymerization. In result, UV light could control the liposome growth. Finally, we could develop the liposome robot and control the growth and degeneration of the liposome by external stimuli such s UV light. The merit of the controlling by UV light doesn't need to inject proteins which induce polymerization and depolymerization of actin protein.

• 대한화학회지
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• 제19권6호
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• pp.463-467
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• 1975

Tetrahydrofuran(THF)중에서 질산코발트(II)를 개시제로 사용하여 methyl methacrylate(MMA)의 중합반응을 연구하였다. 반응속도론적 연구 결과로 다음과 같은 중합속도식을 얻었다. $R_p=k\;[질산코발트(II)]^{0.5}\;[MMA]^{1.5}$ Chelate를 잘 형성하는 옥살산이 중합속도에 미치는 영향을 고려해 보면, 단위체인 MMA가 질산코발트(II)와 배위착물을 형성한다는 것을 추론할 수 있었다. 또 중합계의 겉보기 총 활성화에너지는 14.0kcal/mole이라는 것을 알았다.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.203-208
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• 2008

Recently, the modern society in development and industrial growth is investing a lot of time and much effort to improvement and environment of life quality. Thus, the casting tape which uses environmentally friendly and human body friendly water hardening process Polymer is rapidly substituted for the gypsum cast product which has been plentifully used in medical treatment. Until currently, prior researches have a tendency to focusing the analysis about chemical creation expense and reaction quality rather than the issue about optimization of the process for this polymerization. In the polymerization process which has been accomplished with actual same chemical creation expense, there has been a problem which is the possibility of getting a different result. This is because the optimization of respectively control factors is not accomplished which affect at polymerization process. Therefore, this research sees the chemical qualities of casting tape Polymer, consequently selects the polymerization process which is suitable. And, by using a experimental design, this research will evaluate the affects which the respective factors have on remaining NCO and viscosity. futhermore, this research will carry out the process optimization which can get the above results.

• 대한치과기공학회지
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• 제44권3호
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• pp.76-80
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• 2022

Purpose: The purpose of this study is to analyze the depth according to curing using photocurable resin for dental three-dimensional printing. Methods: A stainless mold with a height of 4 mm was prepared. Ultraviolet (UV) polymerization resin was injected into the mold. Photocuring was then performed for 5 minutes using a photopolymerizer, and the height was measured using a digital measuring instrument (first group). Second, light polymerization was also performed outside the mold for 5 minutes, and the height was measured using a digital measuring instrument. Third, light polymerization was further performed for 5 minutes, and the height was measured using a digital measuring instrument. Statistical analysis was performed with the Kruskal-Wallis test, which is a nonparametric test (α=0.05). Results: The third group had the largest measurement length, whereas the first group had the smallest. However, the difference between groups was not statistically significant (p>0.05). The color of the first group was different from that of the second and third groups. Conclusion: All of the 4-mm-thick photocured specimens had a curing reaction, but the part that was not directly irradiated with UV did not show its original color.

• International Journal of Oral Biology
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• 제46권4호
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• pp.184-189
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• 2021

When luting indirect restorations with dual-cure resin cement (DCRC), excess cement can be easily removed by performing tack cure of DCRC for a few seconds. The purpose of this study was to evaluate whether different tack cure times affect polymerization shrinkage (PS) of the selected DCRC. One dual-cure resin cement (G-CEM LinkAce, GC) was used for measuring PS in light-cure (LC group), self-cure (SC group), and two tack-cure modes. In the first tack-cure subgroup, tack cure was performed for 1, 2, 3, and 5 seconds, followed by light cure after 2 minutes of remnant removal time in each case (TC-LC groups). In the other tack-cure subgroup, tack cure was performed for the same lengths of time, but followed by self-cure in each case (TC-SC groups). PS was measured by a modified bonded disc method for 1,800 seconds. One-way analysis of variance followed by Duncan's post hoc test was used to determine any statistically significant differences among the test groups (α = 0.05). When the DCRC was self-cured after tack cure, PS was significantly lower than when it was only self-cured (p < 0.05); however, tack cure time did not affect PS (p > 0.05). When the DCRC was light-cured, PS was not affected by tack cure or tack cure time (p > 0.05). Therefore, tack cure within 5 seconds did not negatively affect the final PS when the DCRC was light-cured after cement remnant removal.

• 대한치과보철학회지
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• 제39권5호
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• pp.514-525
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• 2001

The purpose of this study was to compare the marginal fit of provisional restorations by differentiating the removal time and setting temperature during resin polymerization. After mixing autopolymerizing methyl methacrylate resin, the material was placed in a preformed resin shell crown. The crown was seated on a die with 1mm shoulder margin. Crowns were removed after 3, 4, 5, 6 minutes and polymerization was continued under the following conditions : $25^{\circ}C$ air, $30^{\circ}C,\;40^{\circ}C,\;50^{\circ}C,\;60^{\circ}C,\;70^{\circ}C$ water. After polymerization. the crown was sectioned. The marginal & occlusal discrepancies were measured. The mean marginal discrelpancies at 3 minutes, 4 minutes, 5 minutes and 6 minutes of removing time were $96.6{\mu}m.\;84.6{\mu}m,\;86.7{\mu}m$ and $105.6{\mu}m$. The mean occlusal discrepancies at 3 minutes, 4 minutes, 5 minutes and 6 minutes of removing time were $106.7{\mu}m,\;89.3{\mu}m,\;98.6{\mu}m$ and $127.7{\mu}m$. There was significant difference between 4 minutes group and 6 minutes group in occlusal discrepancies. The mean marginal & occlusal discrepancies for crowns polymerized in $25^{\circ}C$ air were $98.2{\mu}m$ and $124.1{\mu}m$. The crowns polymerized in $50^{\circ}C$ water demonstrated the smallest marginal & occlusal. discrepancies. The mean value of marginal & occlusal discrepancies in $50^{\circ}C$ water were $73.1{\mu}m$ and $77.5{\mu}m$. These values were smaller than that of $25^{\circ}C$ air. There were significant differences in the occlusal discrepancies between $25^{\circ}C$ air and water conditions of $50^{\circ}C$ water (${\alpha}=0.05$) but. no significant difference in marginal discrepancies. There was no significant difference in the interaction between time and temperature. 4 minutes waiting time & $50^{\circ}C$ water polymerizing condition produces the best fit at the margin of the provisional crown.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.294-301
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• 2017

PURPOSE. Temperature increase of $5.5^{\circ}C$ can cause damage or necrosis of the pulp. Increasing temperature can be caused not only by mechanical factors, e.g. grinding, but also by exothermic polymerization reactions of resin materials. The aim of this study was to evaluate influences of the form material on the intrapulpal temperature during the polymerization of different self-curing resin materials for temporary restorations. MATERIALS AND METHODS. 30 provisonal bridges were made of 5 resin materials: Prevision Temp (Pre), Protemp 4 (Pro), Luxatemp Star (Lux), Structure 3 (Str) and an experimental material (Exp). Moulds made of alginate (A) and of silicone (S) and vacuum formed moulds (V) were used to build 10 bridges each on a special experimental setup. The intrapulpal temperatures of three abutment teeth (a canine, a premolar, and a molar,) were measured during the polymerization every second under isothermal conditions. Comparisons of the maximum temperature ($T_{Max}$) and the time until the maximum temperature ($t_{TMax}$) were performed using ANOVA and Tukey Test. RESULTS. Using alginate as the mould material resulted in a cooling effect for every resin material. Using the vacuum formed mould, $T_{Max}$ increased significantly compared to alginate (P<.001) and silicone (P<.001). In groups Lux, Pro, and Pre, $t_{TMax}$ increased when the vacuum formed moulds were used. In groups Exp and Str, there was no influence of the mould material on $t_{TMax}$. CONCLUSION. All of the mould materials are suitable for clinical use if the intraoral application time does not exceed the manufacturer's instructions for the resin materials.

• Restorative Dentistry and Endodontics
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• 제17권2호
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• pp.331-341
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• 1992

The purpose of this study was to measure the polymerization contraction stress of two types of composite resins; chemical cured type(Cliarfil F II, Kuraray, Japan) and photo-cured type(Photo-Clearfil Bright, Kuraray, Japan). The stresses of composite resin by contraction measured with specially designed measuring device(Fig. 1). The stresses caused by shrinkage during hardening of specimens were measured according to the type of composite resins, thickness of specimen(0.65, 1.30 and 1.95mm), and ratio of catalyst to base in case of only chemical cured composite resin(0.5, 1.0 and 1.5). As the composite resin specimen shrank on hardening, the load cell recorded force vs time automatically on pen-recorder(Toa, Japan) with a cross-head speed 60mm/hr at 0~10 voltages up to 2 hours. The experiments were conducted in a room maintained at $23{\pm}2^{\circ}C$ and relative humidity $50{\pm}10%$. The results were as follows. 1. The contraction stress during hardening was higher in photo cured composite resin than in chemical cured composite resin. 2. The contraction stress during hardening was increased with thickness of composite resin specimen. 3. In chemical cured composite resin, the polymerization contraction stress was decreased with ratio of catalyst and base. 4. The contraction stress during polymerization was higher in early time after insertion of photo cured composite resin and chemical cured composite resin.