• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.1
• /
• pp.131-137
• /
• 1998

A composite copper coated powder was generated by pressure hydrogen stripping copper from Kelex 100 solvent extractant in the presence of silica powder. Within the limitation of solvent extraction under constant conditions, both loading level and stripping rate were reproducible. The stripping copper kinetics are reduced from a divalent state to a metallic state and then deposited on the surface of the silica powder. Copper nucleates heterogeneously on the seed particles. They are giving an agglomerated and non - uniform powder.

• Journal of Korean Society on Water Environment
• /
• v.26 no.6
• /
• pp.919-925
• /
• 2010

The features of precipitating reaction of fluoride have been examined by employing waste gypsum as a precipitant. The major component of waste gypsum was examined to be CaO with minor components of $SO_3$, $SiO_2$. In the experimental condition, the precipitating reaction of fluoride progressed rapidly within a few minutes after the reaction started and reached its equilibrium in 10 minutes. Kinetic analysis showed that the precipitating reaction of fluoride generally followed a first Oder and second Oder with decreasing rate constant with the initial dosage of precipitant. XRD analysis showed that the crystalline structure of precipitate was mainly $CaF_2$ with partly $Ca_5(PO_4)_3(OH)$.

• Journal of Applied Biological Chemistry
• /
• v.58 no.4
• /
• pp.295-301
• /
• 2015

Five phenylpropanoids (1-5), a benzofuran neolignan (6), two 8-O-4'-neolignans (7-8), and five tetrahydrofuran lignans (9-13) were isolated from a methanol extract of Myristica fragrans seeds. The structures of 1-13 were determined by $^1H$- and $^{13}C$-NMR spectroscopic data analyses and a comparison with the literature data. Compound 3 was isolated for the first time from this plant. All the isolated compounds were evaluated for their inhibitory activity against tyrosinase. Among them, safrole (1) showed significant inhibitions against both the monophenolase ($IC_{50}=32.11{\mu}M$) and diphenolase ($IC_{50}=27.32{\mu}M$) activities of tyrosinase. The kinetic analysis shows that safrole (1) is competitive inhibitors for both monophenolase and diphenolase. The apparent inhibition constant ($K_i$) for safrole (1) binding with free enzyme was determined to be 16.05 and $13.66{\mu}M$ for monophenolase and diphenolase, respectively.

• Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.197-202
• /
• 2008

This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

• Microbiology and Biotechnology Letters
• /
• v.24 no.6
• /
• pp.738-742
• /
• 1996

An efficient packed-bed type biofilm reactor charged with immobilized phototrophs was developed to treat organic wastewater at an extremely high volumetric loading rate. The packed bed reactor (PBR) charged with porous ceramic beads was superior to a fluidized-bed reactor suspended with activated carbon powders in terms of many aspects such as BOD removal efficiency, operational stability, and overall economics. For wastewater with BOD concentration as high as 20, 000mg/l, the BOD removal efficiency was maintained above 90% when the hydraulic retention time (HRT) was longer than 1 day. The allowable volumetric BOD loading rate of this reactor (20gBOD/l day) is more than ten-folds higher than that of an ordinary activated sludge method. The behaviour of the reactor was represented well by a Monod type kinetic equation with a maximum specific BOD loading rate(P) of 22.2gBOD/l day and a half saturation constant(K$_{s}$) of 1, 750 mgBOD/l.

• Journal of the Korean Chemical Society
• /
• v.25 no.4
• /
• pp.214-218
• /
• 1981

Kinetic studies were carried out on urethane polymerization reaction of hydroxyl-terminated polybutadiene with isophorone diisocyanate under presence of Hexogen as solid additive. The rate was found to increase with the amount of Hexogen added. However the rate acceleration was not a catalytic effect but solely due to an increase of activation entropy. The reaction was a good 2nd order process with nearly constant activation energy of 8.4 kcal/mole.

• Structural Engineering and Mechanics
• /
• v.2 no.3
• /
• pp.257-267
• /
• 1994

Motions of an unsymmetric rigid body on a rigid floor subjected to earthquake excitations with special attention to coefficient of friction are investigated. Motions of a body in a plane are classified (Ishiyama 1980) into six types, i.e. (1) rest, (2) slide, (3) rotation, (4) slide rotation, (5) translation jump, (6) rotation jump. Based upon the theoretical and experimental research work special attention is paid to the sliding of a body. The equations of motions and the behavior of coefficient of friction in the time of floor excitation are studied. One of the features of this investigation is the introduction and estimation of the "time dependent" coefficient of friction. It has been established that the constant kinetic coefficient of friction $${\mu}(kin){\sim_\sim}0.8{\mu}(stat)$$ does not give the appropriate results. The method for the estimation of the friction coefficient variation during the time is given.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1754-1758
• /
• 2014

The nucleophilic substitution reactions of bis(Y-aryl) chlorothiophosphates (1) with X-pyridines are investigated kinetically in acetonitrile at $35.0^{\circ}C$. The free energy relationships with both X and Y are biphasic concave upwards with a break point at X = 3-Ph and Y = H, respectively. The sign of cross-interaction constants (CICs; ${\rho}_{XY}$) is positive with all X and Y. Proposed mechanism is a stepwise process with a rate-limiting leaving group departure from the intermediate with all X and Y. The kinetic results of 1 are compared with those of Y-aryl phenyl chlorothiophosphates (2). In the case of Y = electron-withdrawing groups, the cross-interaction between Y and Y, due to additional substituent Y, is significant enough to change the sign of ${\rho}_{XY}$ from negative with 2 to positive with 1, indicative of the change of mechanism from a rate-limiting bond formation to bond breaking.

• Journal of Hydrogen and New Energy
• /
• v.15 no.1
• /
• pp.12-22
• /
• 2004

In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP (normal temperature and pressure) condition in a constant-pressure combustion chamber. With propane being the substituent, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using a recent kinetic mechanism. Results show substantial reduction of laminar burning velocities with propane substitution, and support the potential of propane as a suppressant of both diffusional-thermal and hydrodynamic cellular instabilities in hydrogen-air flames.

• Journal of the Korean Ceramic Society
• /
• v.36 no.9
• /
• pp.991-996
• /
• 1999

Effect of solution property on the weight varation and microstructural change of film was studied by electrophoretic deposition in order to obtain a homogeneous and dense zirconia film. As a result of weight kinetics of film which obtained in alcohol or aqueous solution having different polarity experimental data showed large deviation from theoretical ones calculated by Zhang's kinetic model. It had been shown that the weight affecting factors was largely dependent on properties other than dielectric constant and viscosity of solvent zeta potential appiled field and time. In initial stage a main factor of the drastic weight increase was the capillary drag of porous substrate. The cause of weight decrease with time in aqueous solution after 300 s was attributed to the defect of film by sagging and electrolytic reaction. The electrolyte film which prepared in alcohol solution with good wetting for substrate had better homogeneous and dense microstructure than one in aqueous solution with high surface tension.