• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1359-1363
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• 2008

Second-order rate constants have been determined spectrophotometrically for reactions of 2,4-dinitrophenyl 2- thiophenecarboxylate (2) with a series of alicyclic secondary amines in 80 mol % $H_2O$/20 mol % DMSO at 25.0 ${\pm}$ 0.1 ${^{\circ}C}$. The Brønsted-type plot exhibits a downward curvature, i.e., the slope decreases from 0.74 to 0.34 as the amine basicity increases. The $pK_a$ at the center of the Brønsted curvature, defined as $pK_a^o$, has been determined to be 9.1. Comparison of the Brønsted-type plot for the reactions of 2 with that for the corresponding reactions of 2,4-dinitrophenyl 2-furoate (1) suggests that reactions of 1 and 2 proceed through a common mechanism, although 2 is less reactive than 1. The curved Brønsted-type plot has been interpreted as a change in RDS of a stepwise mechanism. The replacement of the O atom in the furoyl ring by an S atom (1 $\rightarrow$ 2) does not alter the reaction mechanism but causes a decrease in reactivity. Dissection of the apparent second-order rate constants into the microscopic rate constants has revealed that the $k_2/k_{-1}$ ratio is not influenced upon changing the nonleaving group from furoyl to thiophenecarbonyl. However, $k_1$ has been calculated to be smaller for the reactions of 2 than for the corresponding reactions of 1, indicating that the C=O bond in the thiophenecarboxylate 2 is less electrophilic than that in the furoate 1. The smaller k1 for the reactions of 2 is fully responsible for the fact that 2 is less reactive than 1.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.214-218
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• 2009

Second-order rate constants ($k_N$) have been measured for nucleophilic substitution reactions of S-4-nitrophenyl thiobenzoate with a series of alicyclic secondary amines in $H_2O$ containing 20 mol % DMSO at 25.0 ${\pm}$ 0.1 ${^{\circ}C}$. The Br$\phi$nsted-type plot exhibits a downward curvature, i.e., $\beta_{nuc}$ decreases from 0.94 to 0.34 as the amine basicity increases. The reactions in the aqueous DMSO have also been suggested to proceed through a zwitterionic tetrahedral intermediate (T${\pm}$) with change in the RDS on the basis of the curved Br$\phi$nsted-type plot. The reactions in the aqueous DMSO exhibit larger $k_N$ values than those in the aqueous EtOH. The macroscopic rate constants ($k_N$) for the reactions in the two solvent systems have been dissected into the microscopic rate constants ($k_1\;and\;k_2/k_{-1}$ ratio) to investigate effect of medium on reactivity in the microscopic level. It has been found that the $k_2/k_{-1}$ ratios are similar for the reactions in the two solvent systems, while $k_1$ values are larger for the reactions in 20 mol % DMSO than for those in 44 wt % EtOH, indicating that the larger $k_1$ is mainly responsible for the larger $k_N$. It has been suggested that the transition state is more stabilized in 20 mol % DMSO through mutual polarizability interaction than in 44 wt % EtOH through H-bonding interaction.

• 대한한방부인과학회지
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• 제31권1호
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• pp.57-83
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• 2018

Purpose: This research has been carried out to find out correlation between test results of ABR-2000 and other diagnostic equipments to enhance significance of accurate diagnosis and clinical usage of ABR-2000. Methods: Duration of the 31 months from December 2012 to June 2015, records of 564 outpatients at gynecology department have been selected. The 564 patients were tested, using all 3 different test equipments of ABR-2000, DSOM, and 3D Blood Pressure Pulse Analyzer (3D-MAC) without test errors or mis-recordings. Correlation between 3D Blood pressure Pulse Analyzer, DSOM and ABR-2000 were analyzed by frequency & ratio factor of statistic data records of patients groups devided by 8 different disease symptom and by comparison of the groups in the form of Regulation and Graph presented on ABR-2000 equipment. Results: 1. The indicator L in all 1, 2, and 3 quadrant in the graph means the activity and reactivity of the upper body biodynamics detection rate is low and which result is very common symptom among gynecological patients. 2. The portion of patients with hypermenorrhea, endometritis, and menstrual pain symptom among the indicator L group in the reactivity 1-3 quadrantin is significantly high. 3. When 3D Mac analyzer indicates H, diastole decreases while systole increases and tachycardia increases then the blood circulation is expected to increase. In case of indication L, diastole increases and systole decreases then, the blood circulation is expected to decrease.

• Nuclear Engineering and Technology
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• 제14권3호
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• pp.122-137
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• 1982

고리 1호기 일부 반응도사고에 대한 민감도 분석을 수행하였다. 본 민감도 분석에 고려한 반응도 사고는 비교적 진행속도가 빠른 사고로서 미임계나 저출력 시동조건에서 발생한 제어뱅크 인출사고와 제어봉 일출사고가 이에 속한다. 본 분석작업은 다음과 같이 세단계로 수행하는 바 원자로 평균출력의 변동 계산과 최고점에서의 열전달계산 그리고 DNBR계산 단계로 나눌 수 있다. 계산에 사용된 전산코드들은 본 분석을 위하여 개발하거나 기존 전산코드들을 수정ㆍ보완하여 제작하였으며 신뢰도도 평가하였다. 원자로 설계 및 운전변수들이 사고발생시 원자로의 거동에 미치는 영향을 조사하기 위하여 민감도 분석을 수행하였다. 본 민감도 분석 결과에 근거하여 고리 1호기 반응도사고 분석에 사용된 최종안전분석보고서의 가정과 초기조건이 타당한가를 조사하였고, 또한 계산 결과도 보수적이고 신뢰할 수 있는지 판별하였다. 고리 1호기 반응도사고 분석에 사용된 가정 및 초기조건을 재검토하고 민감도를 분석한 결과 최종안전분석보고서의 해석결과는 보수적이고 신뢰 할 수 있는 것으로 평가되었다.

• 한국지반공학회논문집
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• 제20권1호
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• pp.29-36
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• 2004

암모늄으로 오염된 불량 매립지의 주변지반 지하수를 정화함에 있어 반응벽체를 적용할 경우, 고려해야 할 주요 설계인자를 평가하기 위해 회분식 실험, 투수시험, 주상실험을 수행하였다. 반응물질로는 높은 양이온교환능(CEC)를 가지는, 천연 제올라이트의 일종인 Clinoptilolite를 사용하였다. 회분식 실험의 경우, 암모늄 오염액의 초기농도와 Clinoptilolite 입자크기를 변화시키며 Clinoptilolite의 암모늄에 대한 제거율을 평가하였다. 암모늄의 초기농도가 80ppm으로 고농도인 경우를 제외하고는 단위 량의 Clinoptilolite로 약 80% 암모늄을 제거할 수 있었다. Clinoptilolite의 입자크기에 의한 영향은 뚜렷하지 않았다. 투수시험은 Clinoptilolite와 주문진사를 무게비 20 : 80으로 혼합한 후 시편을 성형하여 수행하였다. 투수시험에는 연성벽체 투수기를 사용하였다. 시험결과, 세척된 0.42∼0.85mm의 크기를 가지는 Clinoptilolite를 포함하는 시편이, 약 $10^{-3}$cm/s의 투수계수로 가장 높은 값을 보였다. 주상실험에서는 실제 매립지 침출수를 이용해, 유동 상태에서 암모늄 이온을 포함한 침출수와 Clinoptilolite 혼합토의 반응성을 검토하였다. 본 연구를 통해 Clinoptilolite는 암모늄을 정화하고자 하는 반응벽체에 적용 가능한 반응물질로 판단되었다.

• Elastomers and Composites
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• 제40권1호
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• pp.53-58
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• 2005

사염화탄소는 C-Cl결합이 끊어진 후에 생성되는 삼염화탄소 라디칼의 공명 안정성에 의해 매우 반응성이 높은 사슬이동제로 알려져 있으며, 본 논문은 벤질 라디칼과 삼염화탄소 라디칼의 안정성을 비교연구하였다. 큐밀클로라이드는 C-Cl결합이 끊어진 후에 벤질 라디칼을 생성하므로 이 연구에 적합한 구조이다. 큐밀클로라이드와 사염화탄소의 반응성은 스티렌을 단량체로 한 자유라디칼 중합을 통해 계산된 사슬 이동 상수로 비교하였다. 실험 결과에 따르면 큐밀클로라이드는 사염화탄소보다 더 반응성이 높았다. 계산된 큐밀클로라이드의 스티렌에 대한 사슬이동상수 값이 약 0.0463으로 0.0011인 사염화탄소 보다 훨씬 높았다. 이 결과는 벤질 라디칼이 삼염화탄소 라디칼보다 훨씬 높은 안정성을 보여주기 때문인 것으로 추정된다. 큐밀클로라이드의 사슬이동상수의 유효성을 조사하기 위하여 Monte Carlo 모의 실험방법을 사용하였다.

• 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.

• 한국염색가공학회지
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• 제27권1호
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• pp.1-10
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• 2015

The aim of the current study is to identify the dimerization and decomposition kinetics of the F-$D_M$ type. The regeneration of F-VS from $F_iF_j-D_M$ or the reversibility of the dimerizations were investigated. The order of real rate constants of the dimerization('$K_D{^{ij}}$) would seem to be similar to that of rate constants of a dimerization($K_D{^{ij}}$) for VS dyes at a given pH because of the constancy of the equilibrium constants($K_a{^j}$-value). The reverse reactions of the $D_M$ types are appeared to occur in two steps, the deprotonation of ${\alpha}$-carbon of the $D_M$ types and disproportionation. The ratio of the decomposition of the $D_M$ type to F-Hy and F-VS appears to be related with the ratio of $K_i/K_j$. Similarities were also found among various other reactions, including homo- and mixed dimerization. VS dyes undergoing fast hydrolysis have difficulty in forming a dimer. The higher the reactivity with cellulose or hydroxide ion, the smaller the dimerization. The easiness of the dimerization was thus found to be inversely proportional to the rate of hydrolysis.

• 한국세라믹학회지
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• 제40권2호
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• pp.191-197
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• 2003

지구온난화의 주요원인인 $CO_2$의 분해를 위해 다양한 조성의 Sr 페라이트를 이용하여 $CO_2$분해능을 비교하였다. Sr 페라이트를 80$0^{\circ}C$까지 환원시킨 결과, Sr 페라이트 내 Sr 함량이 감소할수록 높은 온도에서 환원반응이 시작되었지만, 온도가 증가함에 따라 그 환원반응성은 높아졌다. 환원된 Sr 페라이트를 이용한 $CO_2$분해 반응에서는 Sr:Fe 조성비에 따라CO나 C의 생성량이 달라졌다. 이 반응에서 Sr 페라이트 내 Sr의 비율이 감소할수록 CO의 생성량은 증가하였으며, Sr의 비율이 증가할수록 페라이트 표면에 많은 양의 C가 흡착되었다. 따라서, $CO_2$분해 반응에 Sr 페라이트를 적용할 경우, 사용 조건에 따라 Sr:Fe의 조성비를 제어할 필요가 있다.

• 환경위생공학
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• 제20권4호통권58호
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• pp.45-50
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• 2005

Titania gel formations were prepared by sol-gel method using titanium(IV) chloride $(TiCl_4)$, and its characteristics were analyzed by varying the $epoxide/TiCl_4$ ratio and the amount of water In the end, titania $(TiO_2)$ aerogel were prepared using supercritical drying process. VOCs such as benzene, toluene, and m-xylene (BTX) were oxidized using prepared titania aerogel and commercially available $TiO_2$, and its performance was compared. The surface area, pore volume, and average pore diameter of 1,2-epoxybutane are significantly smaller than the propylene oxide. And the titania aerogels with 6 moi of epoxides have high surface areas, pore volumes, and average pore diameters. As a result of photo-oxidation, conversion of benzene was reached about $70\%$, and other reactants were reached about $60\%$ similarly. The conversion of BTX was increased as inlet concentration decreased. The reactivity of titania calcined at $600^{\circ}C$ was greater than $400^{\circ}C$ and $800^{\circ}C$. Water is required as a reactants for the oxidation of VOCs, and the continuous consumption of hydroxyl radicals required replenishments to maintain catalyst activity. The activity ratio increased with increasing reaction time when enough amount of water was present in the reactor.