• 한국응용과학기술학회지
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• 제30권4호
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• pp.592-601
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• 2013

이 연구는 3-(1,8나프탈이미도)프로필메타아크릴레이트(NIPM)와 GMA공중합체의 합성과 물성에 관한 과제로서 나프탈이미드 발색단을 가진 공중합체의 조성, 모노머 반응성비, 공명효과(Q)와 극성효과 (e), 형광특성 등을 조사하였다. Azobisisobutyronitronitryl(AIBN) 개시제와 dimethylformamide(DMF) 용매를 $60^{\circ}C$에서 공중합하였다. Fineman-Ross(F-R)와 Kelen-$T\ddot{\bar{u}}d\ddot{\tilde{o}}s$(K-T)법으로 부터 단량체 반응성비를 구하였으며, $r_1$값이 $r_2$보다 크게 나타났다. NIPM이 공중합체내에서 GMA보다 더 많음을 알 수 있다. 380 nm에서 약한 분자형광띠와 460 nm에서 강한 중합체 엑시머 형광띠가 나타났다.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4130-4136
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• 2021

By polymerization of gadolinium methacrylate (Gd (MAA)₃), lead methacrylate (Pb(MAA)₂) and methyl methacrylate (MMA), Gd and Pb were chemically bonded into polymers. The X-ray shielding performance was evaluated by Monte Carlo simulation method, and the results showed that the more metal functional organic monomer, the better the shielding performance of terpolymers. When the X-ray energy is 65 keV, Gd (MAA)₃-containing polymers have better shielding performance than Pb(MAA)₂-containing polymers. Gd could compensate for the weak absorption region of Pb. Therefore, polymers containing both Gd and Pb enhanced shielding efficiency against X-ray in various low-energy ranges. For obtaining terpolymers with uniform monomer compositions, the relationship between the monomer composition of the terpolymers and the conversion level was optimized by calculating the reactivity ratios. The value of reactivity ratios of r (Gd (MAA)₃/Pb(MAA)₂), r (Pb(MAA)₂/Gd (MAA)₃), r (Gd (MAA)₃/MMA), r (MMA/Gd (MAA)₃), r (Pb(MAA)₂/MMA) and r (MMA/Pb(MAA)₂) was 0.483, 0.004, 0.338, 2.508, 0.255, 0.029. The terpolymers with uniform monomer composition could be obtained by controlling the monomer compositions or conversion levels. The results can provide new radiation protection materials and contribute to the improvement in nuclear safety.

• Advances in concrete construction
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• 제13권1호
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• pp.71-81
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• 2022

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.

• Advances in materials Research
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• 제13권3호
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• 대한화학회지
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• 제58권3호
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• pp.289-296
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• 2014

Electrochemical copolymerization of o-chlorophenol (oCP) with o-hydroxyphenol (oHP) was carried out in aqueous $H_2SO_4$ by using cyclic voltammetry (CV) technique. In addition, CV was used to evaluate the differences in electrochemical characteristics of the copolymer in comparison with the corresponding homopolymers, poly(o-chlorophenol) (PoCP) and poly(o-hydroxyphenol) (PoHP). The variation of peak currents with respect to sweep rates was compared between copolymer and homopolymers, PoCP and PoHP, films. Further support for copolymer characterization was obtained by recording UV-visible, IR spectra and elemental analysis. The mechanism of the electrochemical polymerization has been discussed. The monomer reactivity ratios ($r_1$ and $r_2$) were calculated using Fineman-R$\ddot{o}$ss method and was found to be 0.4 and 1.3 repetitivelly and the copolymer structure is a block structure and more rich in oHP units.

• 공업화학
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• 제7권4호
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• pp.623-632
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• 1996

코모노머와 코모노머의 조성을 변화시켜 프로필렌/부텐-1 및 트로필렌/헥센-1의 공중합을 실시하여 반응성비, 용융점 및 폴리머 형상등을 관찰하였다. 공중합에 사용한 촉매는 담체로서 실리카(촉매 I)와 마그네슘(촉매 II)을 사용한 고활성촉매이다. 코모노머의 조성이 증가함에 따라 폴리머의 용융점이 낮아지며, 또한 코모노머의 조성이 프로필렌/부텐-1 공중합의 경우에는 40% 이상, 프로필렌/헥센-1 공중합의 경우에는 80% 이상이면 폴리머의 형상이 무정형화 되어진다. 반응성비는 Fineman-Ross법과 Kelen-$T{\ddot{u}}d{\tilde{o}}s$법으로 구하였다.

• 한국염색가공학회지
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• 제10권6호
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• pp.49-54
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• 1998

The antimicrobial activities of the copolymer of N,N'-dimethyl-N,N'-diallyl ammonium chloride (DMDAAC) and acrylamide(AA) were investigated. A series of copolymers with various ratios of DMDAAC and AA were prepared by free radical initiation via an intra-intermolecular propagation mechanism, ie, cyclopolymerization, and the antimicrobial activities of the prepared copolymers were measured by minimum inhibitory concentration(MIC) test. The copolymers were, then, methylolated under basic condition for reactivity with hydroxyl group of cellulose. Both antimicrobial activity and fastness to laundering of the cotton fabrics finished using the methylolated copolymers were evaluated. From the results it was shown that the copolymers with different ratios of DMDAAC and AA have MIC values in the range of 1∼100ppm. As the ratio of AA in the copolymers increases, the anitmicrobial activity decreases. The fastness of the cotton fabric finished by the methyolated copolymers to 10 repeated launderings in anionic commercial detergent is good enough to show colony reduction above 90％ regardless of DMDAAC and AA ratios.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.93-100
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• 2002

For natural gas and LPG fuel, measurements on the concentrations of individual exhaust hydrocarbon species have been made as a function of air-fuel ratio in a 2-liter four-cylinder engine using a gas chromatography. NMHC in addition to the species of HC, other emissions such as CO$_2$, CO and NOx were examined for natural gas and LPG at 1800rpm far two compression ratios (8.6 and 10.6). Fuel conversion efficiencies were also investigated together with emissions to study the effect of engine parameters on the combustion performances in gas engines especially under the lean bum conditions. It was found that CO$_2$ emission decreased with smaller C value of fuel, leaner mixture strength and the higher compression ratio. HC emissions from LPG engine consisted primarily of propane (larger 60%), ethylene and propylene, while main emissions from natural gas were mothane (larger than 60%), ethane, ethylene and propane on the average. The natural gas was proved to give the less ozone formation than LPG fuel. This was accomplished by reducing the emissions of propylene, which has relatively high MIR factor, and propane that originally has large portion of LPG. In addition, natural gas shows a benefit in other emissions (i.e. NMHC,NOx, CO$_2$and CO), SR and BSR values except fuel conversion efficiency.

• 대한화학회지
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• 제13권4호
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• pp.373-377
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• 1969

In order to determine the monomer reactivity ratio in copolymerization of acrolein, the copolymerization of acrolein with styrene, methyl methacrylate and vinyl acetate respectively was studied. The Q and e value of acrolein in each copolymerization were also calculated from those of monomer reactivity ratios, but the calculated values were slightly different from each other. The Q and e of acrolein for the system of acrolein-styrene copolymerization were Q = O.64 and e = O.62 respectively. Relations among the Q and e value, the composition and structure of copolymers and the mean sequence length in copolymerization were also discussed for acrolein copolymers.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.63-70
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• 2006

This study tested the alkali-silica reactivity of various types of crushed stones, following the specifications of ASTM C 227 and C 1260, and the results obtained from the tests were compared. This study also analyzed the effects of particle size and grading of reactive aggregate based on the expansion of mortar-bar due to an alkali-silica. The effect of mineral admixtures to reduce the detrimental expansion caused by the alkali-silica reaction was investigated based on the method specified by ASTM C 1260. The mineral admixtures used in this study were fly ash, silica fume, metakaolin and ground granulated blast furnace slag. The replacement ratios of 0, 5, 10, 15, 25 and 35% were uniformly applied to all the mineral admixtures, and the replacement ratios of 45 and 55% were additionally applied for the admixtures that could sustain the workability at these ratios. The results indicate that replacement ratios of 25% for fly ash, 10% for silica fume, 25% for metakaolin and 35% for ground granulated blast furnace slag were the most effective in reducing the expansion due to the alkali-silica reaction under the experimental conditions of this study.