• Journal of Korea Foundry Society
• /
• v.27 no.6
• /
• pp.243-249
• /
• 2007

The effect of Re addition and solidification rate on the directional solidification behavior of Ni-Al model alloy has been investigated. Directional solidification (DS) were carried out using the modified Bridgman furnace with various solidification rates. The solid/liquid interface during directional solidification was preserved by quenching the specimen after the desired volume fraction of original liquid was solidified. The equilibrium partition coefficients of Al and Re Were estimated by measuring the compositions at the quenched solid/liquid interface. Then, the effect of Re addition on the elemental segregation behavior was carefully analyzed. The differential scanning calorimetry results showed that the Re addition results in increased ${\gamma}'$ solvus and freezing range of the alloy. It was also shown that the primary dendrite arm spacing gradually decreases with increasing the Re content, while the secondary dendrite arm spacing appears to be independent on the Re content. The compositional analyses clearly revealed that the segregation of Al increased with increasing the Re content and solidification rate, while that of Re was found to be independent on the solidification rate in the range of $10{\sim}100{\mu}m/s$ due to its sluggish diffusion rate in the Ni solid solution.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.7
• /
• pp.682-689
• /
• 2010

The purpose of this study was to determine any detrimental effects on surrounding environments by using bottom ash, waste tire, and mixture as a fill material to raise the ground level. Three different initial pHs (4, 6, 8) were applied to bottom ash and initial pH of 4 was used to waste tire and mixture. Among 7 heavy metals, Pb and Zn were exceeded drinking water standards but their concentrations decreased below drinking water standards within 1 PVE. Among 5 anions, sulfate exceeded 10 times of drinking water standards and further higher partition coefficients resulted in increased PVE of 8.21. For the mixture of bottom ash and waste tire, its concentrations of heavy metals and anions were decreased due to the dilution effect and lowered PVE from 8.21 (BA) to 5.89.

• Environmental Engineering Research
• /
• v.14 no.4
• /
• pp.226-236
• /
• 2009

The performance of phytoremediation has proven effective in the removal of nutrients and metals from aqueous systems. However, little information is available regarding the behavior of pesticides and their removal pathways in aquatic environments involving plant-uptake. A detailed understanding of the kinetics of pesticide removal by plants and information on compound/plant partition coefficients can lead to an effective design of the phytoremediation process for anthropogenic pesticide reduction. It was determined that the reduction rates of four organophosphorus (OP) and two organochlorine (OC) pesticides (diazinon, fenitrothion, malathion, parathion, dieldrin, hexachlorobenzene [HCB]) could be simulated by first-order reaction kinetics. The magnitude of k was dependent on the pesticide species and found within the range of 0.409 - 0.580 $d^{-1}$. Analytical results obtained by mass balances suggested that differential chemical stability, including diversity of molecular structure, half-lives, and water solubility, would greatly influence the removal mechanisms and pathways of OPs and OCs in a phytoreactor (PR). In the case of OP pesticides, plant accumulation was an important pathway for the removal of fenitrothion and parathion from water, while pesticide sorption in suspended matter (SM) was an important pathway for removal of dieldrin and HCB. The magnitude of the pesticide migration factor (${\Large M}_p^{pesticide}$) is a good indication of determining the tendency of pesticide movement from below- to above-ground biomass. The uncertainties related to the different phenomena involved in the laboratory phyto-experiment are also discussed.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.41 no.4
• /
• pp.113-123
• /
• 2004

This paper presents a new collusion-secure fingerprinting scheme to embed fingerprints into three-dimensional(3-D) mesh models efficiently. In the proposed scheme, we make the same number of fingerprints as the number of customers based on the finite projective geometry, partition a 3-D mesh model related to the number of bits assigned to each fingerprint and then embed a watermark representing copyright information into each submesh to be marked. Considering imperceptibility and robustness of the watermarking algorithm we embed the watermark signal into mid-frequency DCT coefficients obtained by transforming vertex coordinates in the triangle strips which are generated from the submeshes to be marked. Experimental results show that our scheme is robust to additive random noises, MPEG-4 SNHC 3-D mesh coding, geometrical transformations, and fingerprint attacks by two traitors' collusion. In addition, we can reduce the number of bits assigned to each fingerprint significantly.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.10 no.1
• /
• pp.99-102
• /
• 2005

Organic solvents are widely used in biotransformation systems. There are many efforts to reduce the consumption of organic solvents because of their toxicity to the environment and human health. In recent years, several groups have started to explore novel organic solvents called room temperature ionic liquids in order to substitute conventional organic solvents. In this work, lipase-catalyzed transesterification in several uni- and bi-phasic systems was studied. Two representative hydrophobic ionic liquids based on 1-butyl-3-methylimidazolum coupled with hexafluorophosphate ([BMIM][$PF_6$]) and bis[{trifluoromethylsulfonyl} imide] ([BMIM] [$Tf_{2}N$]) were employed as reaction media for the transesterification of n-butanol. The commercial lipase, Novozym 435, was used for the transesterification reaction with vinyl acetate as an acyl donor. The conversion yield was increased around $10\%$ in a water/[BMIM][$Tf_{2}N$] bi-phasic system compared with that in a water/hexane system. A higher distribution of substrates into the water phase is believed to enhance the conversion yield in a water/[BMIM][$Tf_{2}N$] system. Partition coefficients of the substrates in the water/[BMIM][$Tf_{2}N$] bi-phasic system were higher than three times that found in the water/hexane system, while n-butyl acetate showed a similar distribution in both systems. Thus, RTILs appear to be a promising substitute of organic solvents in some biotransformation systems.

• Journal of Korean Society for Atmospheric Environment
• /
• v.6 no.1
• /
• pp.85-96
• /
• 1990

Simultaneous removal efficiencies of hydrophilic and hydrophobic gaseous pollutants are experimentally determined, and the macroscopic removal mechanism of pollutants in a dry scrubber is analyzed using the extended model of three phase equilibrium distribution of pollutant at high temperatures that can describe the different morphological conditions of adsorbent and water at varying relative humidities. For the simplicity, the inside of spray dryer is divided into three regions of ; (1) absorption, (2) three-phase equilibrium, and (3) adsorption, and the removal efficiencies of each pollutants at three regions are observed at different experimental conditions to estimate the effects of important parameters of dry scrubber. The laboratory experiments simulate the three regions of spray dryer with the temperature control and thus evaporation rate of water from the slurry particle. $SO_2$ as a hydrophilic gaseous pollutant and vinyl chloride as a hydrophobic toxic gas are selected for the future field application to soid waste incineration, and the two types of slurry are made of the two sorbents ; 10 wt.% $Ca(OH)_2$, and 10 wt.% NaOH. Result of temperature effect shows the height of absorption plus three-phase region is decreased as the operation temperature is increased, which results in the lower removal efficiency of $SO_2$ but higher removal for vinyl chloride in the adsorption region of dry scrubber. The removal efficiency of $SO_2$ is higher by NaOH slurry than by $Ca(OH)_2$ slurry due to the hygroscopic nature of NaOH, while the removal of vinyl chloride is higher in $Ca(OH)_2$ case. From the analysis of redults using three-phase equilibrium distribution model, the effective two-phase partition coefficients can be obtained, and the possible extention in the application of the three-phase equilibrium model in a dry scrubber design has been demonstrated.

• Journal of Pharmaceutical Investigation
• /
• v.31 no.4
• /
• pp.217-224
• /
• 2001

To develop a novel transdermal delivery system of loxoprofen (LP), a potent antiinflammatory and analgesic agent, the effects of various vehicles and penetration enhancers on the skin permeation of LP from solution formulations were investigated. The permeation rate of LP through excised guinea pig skin was measured using a side-by-side permeation system at $32^{\circ}C$. The solubilities of LP in various vehicles were determined by the equilibrium solubility method, and partition coefficients $(P_c)$ were determined. The solubility of LP increased in the rank order of water & isopropyl myristate (IPM) & glyceryl dicaprylate/dicaprate & propylene glycol dicaprylate/caprate & propylene glycol laurate (PGL) & polyethylene glycol 400 & diethylene glycol monoethyl ether (DGME) & ethanol. n-Octanol-water $P_c$ value was 15.5. Among pure vehicles tested, IPM and PGL showed highest fluxes of $89.9{\pm}5.0$ and $45.4{\pm}0.3\;{\mu}g/cm^2/hr$ from saturated solutions, respectively. However, it was not possible to demonstrate any correlation between the solubility of LP and its permeation rate, indicating the change in the barrier property of the skin and/or carrier mechanisms by vehicles tested. The addition of DGME to IPM or PGL markedly increased the solubility of LP, but the permeation rate did not decrease when the concentration of DGME in the cosolvent was increased upto 40%. The addition of linoleic acid (3%) in the cosolvent slightly increased the permeation rate, but others such as lauroyl sarcosine, fatty alcohols and fatty acids tested did not show enhancing effect. In conclusion, the DGME-IPM or DGME-PGL cosolvent system proved to be a good vehicle to enhance the skin permeation of LP.

• Textile Coloration and Finishing
• /
• v.10 no.1
• /
• pp.25-32
• /
• 1998

In the prior study, we found that the dye uptakes of C. I. Disperse Violet 1 on PET in hexane and cyclohexane were higher than those in the other solvents. Therefore, in this study, the dye uptakes and the partition coefficients in alkanes having different number of carbon atoms were obtained and their relationship to the solubilities of the dye in alkanes was also investigated. As the number of carbon atoms of alkanes increases, solubility of the dye increases but the dye uptake decreases. This is due to the fact that the hydrophobicity of alkanes become relatively strong as increasing the number of carbon atoms. It was also found that the dye uptakes in iso-alkanes were larger than those in normal alkanes. This is because that the branched alkanes(iso-alkanes), judging from the tendency of lowering solubility and increasing dye uptake as decreasing the number of carbon atoms of alkanes, behave like the alkanes with less number of carbon atoms rather than the alkanes with the same number of carbon atoms. The logarithmic plot of the dye uptakes vs. the solubilities of the dye showed that the dye uptakes are linearly and inversely proportional to the solubilities. This is in good accordance with the results of the prior study. The heat of dyeing was also calculated from the equilibrium adsorptions at various temperatures. It seemed that the dyeings of PET by C. I. Disperse Violet 1 in nonane, decane, iso-pentane and iso-octane were rather endothermic processes. Dyeing rates in alkanes were somewhat delayed unlike general appearances in solvent dyeing.

• Archives of Pharmacal Research
• /
• v.26 no.12
• /
• pp.1002-1008
• /
• 2003

Ferulic acid (3-methoxy, 4-hydroxy cinnamic acid) is a flavoid component possessing antioxidant property. The compound is currently under development as a new drug candidate for the treatment of the dementia. The objective of this preformulation study was to determine the physicochemical properties of ferulic acid. The n-octanol to water partition coefficients of ferulic acid were 0.375 and 0.489 at the pHs of 3 and 10, respectively. Accelerated stability study for ferulic acid indicated that the t 90 value for the drug was estimated to be 459 days at $25^{\circ}C$. Ferulic acid was also found to be unstable under the relative humidity of more than 76%, probably because of the hygroscopic nature of the drug. In order to study compatibility of ferulic acid with typical excipients, potential change in differential scanning calorimetry spectrum was studied in 1: 1 binary mixtures of ferulic acid and typical pharmaceutical excipients (e.g., Aerosil, Avicel, CMC, Eudragit, lactose, PEG, PVP, starch and talc). Avicel, CMC, PVP and starch were found to be incompatible with ferulic acid, indicating the addition of these excipients may complicate the manufacturing of the formulation for the drug. Particle size distribution of ferulic acid powder was in the size range of 10-190 $\mu$m with the mean particle size of 61 $\mu$m. The flowability of ferulic acid was apparently inadequate, indicating the granulation may be necessary for the processing of the drug to solid dosage forms. Two polymorphic forms were obtained by recrystallization from various solvents used in formulation. New polymorphic form of ferulic acid, Form II, was obtained by recrystallization from 1,4-dioxane. The equilibrium solubility for Form I was approximately twice of that for Form II. The dissolution rate of Form II was higher than that of Form I in the early phase (<6 min). Therefore, these physicochemical information has to be taken in the consideration for the formulation of ferulic acid.

• Journal of the Korean Chemical Society
• /
• v.54 no.4
• /
• pp.363-373
• /
• 2010

Computational studies were carried out on the opiates morphine, heroin, codeine, pentazocine, and buprenorphine, under the density functional theory. The geometric parameters of the pharmacophore and substituents were evaluated at the B3LYP/6-31+G(d) level of theory. The electronic structure calculations were performed using the same hybrid functional at the B3LYP/6-311++G (d,p) level of theory. The atomic charges were obtained by Mulliken population analysis. Given the reported biological activity, calculated partition coefficients, and electronic and geometric analysis, pentazocine and buprenorphine were chosen as models for proposed analogues. These analogues were then studied and compared with the model molecules. The study reveals that the geometry and electronic structure of the pharmacophore remains consistent in the presence of different substituents. Because the proposed analogues preserve the studied properties of the model molecules, it is likely that these analogues display biological activity.