• Journal of the Korean Chemical Society
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• v.10 no.4
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• pp.166-174
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• 1966

The multistep mechanism of photosensitized curing reaction cinnamoylated photosensitive polymer is proposed from the energy level diagram of cinnamic acid and sensitizer, and from the fact that excess of sensitizer brings the sensitivity to a limiting value etc. Various factors which have effects on the ability of sensitizer are also discussed. The mechanism involves following steps: activation to the first excited singlet states of cinnamoyl group(C) and sensitizer(S) by their absorption of photon, their intersystem crossing to the lowest triplet state, bimolecular internal quenching by formation of excimer of sensitizer, triplet excitation energy transfer and intermolecular addition between cinnamoyl group in ground state and that in triplet state. The rate equation derived from this mechanism is $-\frac{d[C]}{dt} = \frac{K_1[C]}{K_2 + [C]}[\frac{I^c_{abs}}{K_3 + [S]} + \frac{K_4[C]}{(K_5 + [C])(K_6 + [S])}(I^s_{abs} + \frac{K_7I^c_{abs}[S]}{K_8 + [S]})]$ where $I^c_{abs}\;and\;I^s_{abs}$: the rates of absorption of photon by cinnamoyl group and sensitizer $K_n$: Constants. It is proved with the cinnamate of poly(glyceryl phthalate)(PGC) in the absence of sensitizer using the infrared analytical method and successfully applied for the experimental data reported on the effects of the degree of cinnamoyl esterification and the concentration of sensitizer upon the sensitivity.

• Polymer(Korea)
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• v.28 no.5
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• pp.426-432
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• 2004

To reduce volumetric shrinkage of the commercially available polymeric dental composite during curing reaction, (2,2-bis [4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (bis -GMA) derivatives, i.e., (2,2-bis[3-methyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propan) (DMBis-GMA) and (2,2-his [3,5-dimethyl ,4- (2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (TMBis-GMA) were synthesized and then new dental composite resin composed of Bis-GMA derivatives, diluent, spiro orthocarbonate (SOC), and inorganic filler was produced. Among the Bis-GMA derivative/Bis-GMA derivative/diluent mixtures, Bis-GMA/ TMBis-GMA/TEGDMA mixture exhibited the lowest volumetric shrinkage. Volumetric shrinkage of this mixture was further reduced by adding SOC. Volumtric shrinkage of dental composite prepared from commercially available resin monomer mixture was $2.5\%$, while that prepared from resin monomer mixture having minimum volumetric shrinkage was reduced to $0.7\%$. Mechanical strength of this dental composite was nearly the same with that of commercial products but the time required for the curing reaction was retarded.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.240-246
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• 2023

This study was performed to convert NO_x in atmosphere by photochemical reaction utilizing the eco-friendly solar energy. The mortar specimen coated with photocatalyst was fabricated and the photochemical conversion efficiency of NO_x was analyzed. The photocatalyst coated concrete was fabricated by first adding TiO₂ photocatalyst on the bottom of mold first and next adding cement mortar and, then, curing the concrete mortar. The grease was sprayed on the bottom of mold in advance so that the concrete can be demolded easily after curing. The conversion efficiencies of NO_x by photochemical reactions were investigated systematically by changing the process variable conditions of amount of TiO₂ coating, UV-A light intensity, total gas flow rate, relative humidity and initial NO_x concentration. It was confirmed that the photocatalyst coated concrete fabricated in this study could convert NO_x successfully for various process conditions in atmosphere. In future, we believe this research result can be utilized as basic data to design the infrastructure of building, tunnel and road for controlling efficiently the air pollutants such as NO_x, SO_x, and VOCs.

• The Journal of Internal Korean Medicine
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• v.19 no.2
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• pp.438-450
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• 1998

Pleural effusion means the inflammation of pleura which has a majority of respiratory disease. The main clinical manifestation is pleural effusional pain, dyspnea, cough, fever, etc. and at present the Tuberculous pleural effusion has the most frequency in which exists exudate in our country. And during studying oriental medical treatment about Tuberculous exudative pleural effusional patient, we found the clinical case about The Combination therapy of Chinese traditional and Western medicine at journal of traditional Chinese Medicine and considered it would be help in oriental medical treatment, so we adjust and report now. This study was performed by analyzing the six papers reported centering around the clinical case of The Combination therapy of Chinese traditional and Western medicine in journal of traditional Chinese Medicine published between 1990-1996. As these papers have no mistakes on diagnosis because it obtained pleurocentesis, tuberculin test positive reaction on choicing clinical case, definite results on X-ray, ultrasound as well as clinical basis, so it considers an apt conclusion. The results were as follows: 1. Western medical treatment uses chemical remedy same with pulmonary tuberculosis, and in case of tubercular pleuritis, it needs thoracic duct pyorrhea, and according to simple exudation also operates therapheutic pleural paracentesis. 2. In case of hydrothorax absorption about tuberculous pleural effusion, prescription of purge the heat accumulated in the lung and eliminate the retention of fluid with powerful purgatives shows considerable effects. 3. The latter period treatment of tuberculous pleural effusion needs Supplement qi and active the collaterals, Nourishing yin and clearing heat in addition to Supporting healthy energy to eliminate evils. 4. In case of curing tuberculous pleural effusion, The Combination therapy of Chinese traditional and Western medicine shows more considerable effect than single western medical treatment in absorption of hydrothorax. 5. In case of curing tuberculous pleural effusion, The Combination therapy of Chinese traditional and Western medicine shows more considerable effect than single western medical treatment in prevention of disease reappearance. 6. In case of curing tuberculous pleural effusion, The Combination therapy of Chinese traditional and Western medicine shows more considerable effect than single western medical treatment in vitality recovery at the latter period of disease.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.418-424
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• 2016

This study is an experimental study on the recycling of bottom ash in coal ash discharged from a thermal power plant. Bottom ash has limited research on recycling because it has more porous and higher water absorption ratio than fly ash. In this paper, the bottom ash was pulverized to a specific surface area of $4,000cm^2/g$ in order to use as a binder, and the flow, compressive strength test and microstructure analysis of the bottom ash based geopolymer mortar were performed. The flow measurement results of the geopolymer mortar showed that the flow rate was improved by increasing mixing water as the molar concentration of activator was increased. Compressive strength increased with increasing curing temperature and molar concentration. Through the microstructure analysis, we could confirm the geopolymer gel produced by the reaction of the condensation polymerization. It is considered that it is possible to make the bottom ash based geopolymer concrete through proper molar concentration of activator and high temperature curing.

• Journal of Ocean Engineering and Technology
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• v.27 no.5
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• pp.99-104
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• 2013

Recently, various nanoparticles have been used for filler in polymer matrices. The particles of nano size are whether high or not cross-link density in polymer affects the thermal and mechanical properties of one. The properties change as a result of chemical reactions between the nanoparticles and the surface of the polymer. There are two models for nanocomposites: "repulsive interaction" and "attractive interaction" between the nanoparticles and matrix. In this study, the variation in the curing mechanism was examined when nano-size $TiO_2$ was dispersed into an epoxy (Bisphenol A, YD-128) with different curing agents. The results of this study showed that the exothermic temperature and Tg in the case of the nanoparticles used (Jeffamine) (D-180) at room temperature were reduced by an increase in the $TiO_2$ contents because of the "repulsive interaction" between the nanoparticles and the matrix. The tensile strengths were increased by increasing amounts of $TiO_2$ until 3 wt% because of a dispersion strengthening effect caused by the nanoparticles, because of the repulsive interaction. However, such tensile properties decreased at 5 wt% of $TiO_2$, because the $TiO_2$ was agglomerated in the epoxy. In contrast, in the case of the nanoparticles that used NMA and BDMA, the exothermic temperature and Tg tended to rise with increasing amounts of $TiO_2$ as a result of the "attractive interaction." This was because the same amounts of $TiO_2$ were well dispersed in the epoxy. The tensile strength decreased with an increase in the $TiO_2$ contents. In the general attractive interaction model, however, the cross-link density was higher, and tensile strength tended to increase. Therefore, for the nanoparticles that used NMA, it was difficult to conclude that the result was caused by the "attractive model."

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.166-173
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• 2019

In this paper, the reaction properties of silica source in the accelerated curing conditions using autoclave and the fundamental properties of inorganic Micro Defect Free(MiDF) concrete using silica source are studied. Studies show that Si ions elution rate from silica source in autoclave curing is higher in amorphous source. In tap water conditions, solids which is source after autoclaved curing show a higher mass reduction in amorphous materials, which is attributed to the higher elution rate of ion. In $Ca(OH)_2$ solution conditions, amorphous materials show higher mass increase, due to increase in C-S-H minerals. From experiment for influence on the properties of MiDF concrete by using nano silica materials, the specimen with silica fume shows an increase in compressive strength and a decrease in absorption depending on replacement rate up to 5.5%, while nano silica with amorphous phase and high-fineness shows a decrease in compressive strength and decrease in the water absorption. The specimen with nano silica increases the pore below 10,000nm, but reduces pore between 10,000 and 100,000nm. The above results show that the porosity and absorption rate of MiDF concrete can be reduced by using amorphous nano-size silica. However, to reduce the pore of 50 to 10,000nm, better dispersion of nano material in the cement matrix will be necessary. We will focus on the this item in the next research.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.265-285
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• 1999

The purposes of this investigation were to observe the reaction kinetics of five commercial dual cured resin cements (Bistite, Dual, Scotchbond, Duolink and Duo) when cured under varying thicknesses of porcelain inlays by chemical or light activation and to evaluate the effect of the porcelain disc on the rate of polymerization of dual cured resin cement during light exposure by using thermal analysis. Thermogravimetric analysis(TGA) was used to evaluate the weight change as a function of temperature during a thermal program from $25{\sim}800^{\circ}C$ at rate of $10^{\circ}C$/min and to measure inorganic filler weight %. Differential scanning calorimetry(DSC) was used to evaluate the heat of cure(${\Delta}H$), maximum rate of heat output and peak heat flow time in dual cured resin cement systems when the polymerization reaction occured by chemical cure only or by light exposure through 0mm, 1mm, 2mm and 4mm thickness of porcelain discs. In 4mm thickness of porcelain disc, the exposure time was varied from 40s to 60s to investigate the effect of the exposure time on polymerization reaction. To investigate the effect on the setting of dual cured resin cements of absorption of polymerizing light by porcelain materials used as inlays and onlays, the change of the intensity of the light attenuated by 1mm, 2mm and 4mm thickness of porcelain discs was measured using curing radiometer. The results were as follows 1. The heat of cure of resin cements was 34~60J/gm and significant differences were observed between brands (P<0.001). Inverse relationship was present between the heat of reaction and filler weight % the heat of cure decreased with increasing filler content (R=-0.967). The heat of reaction by light cure was greater than by chemical cure in Bistite, Scotchbond and Duolink(P<0.05), but there was no statistically significant difference in Dual and Duo(P>0.05). 2. The polymerization rate of chemical cure and light cure of five commercially available dual cured resin cements was found to vary greatly with brand. Setting time based on peak heat flow time was shortest in Duo during chemical cure, and shortest in Dual during light cure. Cure speed by light exposure was 5~20 times faster than by chemical cure in dual cured resin cements. The dual cured resin cements differed markedly in the ratio of light and chemical activated catalysts. 3. The peak heat flow time increased by 1.51, 1.87, and 3.24 times as light cure was done through 1mm, 2mm and 4mm thick porcelain discs. Exposure times recommended by the manufacturers were insufficient to compensate for the attenuation of light by the 4mm thick porcelain disc. 4. A strong inverse relationship was observed between peak heat flow and peak time in chemical cure(R=0.951), and a strong positive correlations hip was observed between peak heat flow and the heat of cure in light cure(R=0.928). There was no correlationship present between filler weight % or heat of cure and peak time. 5. The thermal decomposition of resin cements occured primarily between $300^{\circ}C$ and $480^{\circ}C$ with maximum decomposition rates at $335^{\circ}C$ and $440^{\circ}C$.

• Resources Recycling
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• v.28 no.6
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• pp.54-63
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• 2019

This study investigated on the compressive strength and the length change test with using the waste glass and graphene oxide for recycling the waste glass as the aggregate. Curing on 3-day and 7-day, the compressive strength was enhanced as the usage of waste glass was increased. Especially, the huge difference in the compressive strength was observed when the amount of substituting on the waste glass was used on 10~50%. With 50% of waste glass condition, the compressive strength was portionally enhanced as the usage of graphene oxide was increased and its value was 42.6 N/㎟ with 0.2% of graphene oxide. In terms of the length change test, the use of high content of waste glass led length change value to increase, but it was dropped down as the portion of waste glass was above 50%. Furthermore, in the case of using 50% of waste glass, the use of high amount of graphene oxide tended to decrease the length change value. That is, graphene oxide may contribute on boosting the cement hydration reaction and blocking the ion's movement.

• Journal of Oriental Neuropsychiatry
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• v.10 no.1
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• pp.95-108
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• 1999

We investigated whether an aqueous extract of Polygala tenuifolia root (PTAE) inhibits secretion of inflammatory cytokines from primary cultures of mouse astrocytes. PTAE dose-dependently inhibited the Tumor necrosis $factor-{\alpha}$ $(TNF-{\alpha})$ secretion by astrocytes stimulated with substance P (SP) and lipopolysaccharide (LPS). Interleukin-1 (IL-1) has been shown to elevate $TNF-{\alpha}$ secretion from LPS-stimulated astrocytes while having no effect on astrocytes in the absence of LPS. We therefore also investigated whether IL-1 mediated inhibition of $TNF-{\alpha}$ secretion from primary astrocytes by PTAE. Treatment of PTAE to astrocytes stimulated with both LPS and SP decreased IL-1 secretion to the level observed with LPS alone. Moreover, incubation of astrocytes with IL-1 antibody abolished the synergistic cooperative effect of LPS and SP. Reverse transcriptase-polymerase chain reaction analysis demonstrated the significantly reduced level of the $TNF-{\alpha}$ mRNA was expressed in astrocytes treated with PTAE. These results suggest that PTAE has an antiinflammatory activity on the central nervous system curing some pathological disease states.