• Bulletin of the Korean Chemical Society
• /
• v.29 no.7
• /
• pp.1359-1363
• /
• 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
• /
• v.30 no.1
• /
• pp.214-218
• /
• 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.

• The Journal of Korean Obstetrics and Gynecology
• /
• v.31 no.1
• /
• pp.57-83
• /
• 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
• /
• v.14 no.3
• /
• pp.122-137
• /
• 1982

Analyzed is the sensitivity of reactor transient behavior to various reactor parameters during the reactivity induced accidents (RIA) of the Kori Unit 1. Included in the analysis is a partial spectrum of RIAs with relatively fast transients such as uncontrolled rod cluster control assembly bank withdrawl from a subcritical or low power startup condition and rod ejection accidents. The analysis can be performed generally in three steps: calculation of an average core power change, hot spot heat transfer calculation and DNBR (departure from nucleate boiling ratio) calculation. The computer codes used for the analysis are either developed based on the codes relevent to it. These codes are evaluated to be highly reliable. An extensive sensitivity analysis is performed to study the effects of various reactor design and operating parameters on the reactor transient behavior during the accidents. The assumptions and initial conditions used for the RIA analysis in the Kori Unit 1 FSAR (Final Safety Analysis Report) are reexamined, and the corresponding analysis results are reassessed, based on the sensitivity analysis results, to be conservative and reliable.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.1
• /
• pp.29-36
• /
• 2004

Batch and column tests were performed to develop the design factors for permeable reactive barriers(PRBs) against the contaminated groundwater with ammonium from unsanitary landfill. Clinoptilolite, one of natural zeolites having excellent cation exchange capacity(CEC), was chosen as the reactive material. In batch test, the reactivity of clinoptilolite to ammonium was examined by varying the initial concentration of ammonium and the particle size of clinoptilolites. One gram of clinoptilolite showed removal efficiency about 80% against the ammonium except in very high initial concentration of 80 ppm, but the effect of particle size of clinoptilolite was not noticeable. Permeability test was performed for the specimens made of clinoptilolite and Jumunjin sand with 20 : 80 weight ratio. Flexible wall permeameter was employed far permeability test. The specimen containing the washed 0.42-0.85mm clinoptilolite showed the highest permeability of about $10^{-3}$/s. In column test, the reactivity of mixed materials against ammonium in flowing condition was examined with the landfill leachate. With the test results, clinoptilolite was found to be a suitable material for PRBs against the contaminated groundwater with ammonium.

• Elastomers and Composites
• /
• v.40 no.1
• /
• pp.53-58
• /
• 2005

Carbon tetrachloride is very reactive chain transfer agent due to the resonance stability of the trichlorocarbon radicals after breaking of C-Cl bond. Effect of benzylic radical comparing to trichlorocarbon radicals in the chain tranrfer reactions was investigated. From the structural point of view, cumyl chloride is a good candidate because it has the C-Cl bond with benzylic radicals after displacement of C-Ci bond. The reactivity of free radical polymerization of styrene in the presence of cumyl chloride was compared with that of carbon tetrachloride by calculating chain transfer constants. Results show that the cumyl chloride acts as a stronger chain transfer agent than carbon tetrachloride. The calculated chain transfer constant of cumyl chloride shows higher value (0.0463) than that of carbon tetrachloride (0.0011) in the styrene polymerization. High reactivity of cumyl chloride comparing to that of carbon tetrachloride is probably due to the higher resonance stability or benzylic radical than that or trichlorocarbon radicals after breaking of C-Cl bond. Monte Carlo simulation method is applied for characterizing the validity of kinetic constants according to the ratio of chain transfer agent to monomer.

• Advances in materials Research
• /
• v.13 no.3
• /
• pp.161-171
• /
• 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.

• Textile Coloration and Finishing
• /
• v.27 no.1
• /
• pp.1-10
• /
• 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.

• Journal of the Korean Ceramic Society
• /
• v.40 no.2
• /
• pp.191-197
• /
• 2003

Sr ferrites with various compositions were applied to the decomposition of $CO_2$ to mitigate the greenhouse effect. In the reduction reaction of Sr ferrites up to 80$0^{\circ}C$, starting temperature was lower with increasing of Sr content in Sr ferrite. However, the reactivity was higher with decreasing Sr content. In the $CO_2$ decomposition reaction with reduced Sr ferrites, the amount of CO and C were depended on the ratio of Sr and Fe in Sr ferrite. With increasing Sr content. larger amount of C were deposited on the surface of ferrite. Therefore, in order to apply Sr ferrites for the decomposition of $CO_2$, it is necessary to control the ratio of Sr and Fe according to the conditions used.

• Journal of environmental and Sanitary engineering
• /
• v.20 no.4 s.58
• /
• pp.45-50
• /
• 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.