• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.356-361
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• 2013

Lead (II) ion selective poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore as a sulfur containing sensing material is successfully developed. The electrode exhibits good linear response of 25.6 mV / decade (at $20{\pm}0.2^{\circ}C$, r2=0.995) within the concentration range of $1.0{\times}10^{-1}{\sim}4.0{\times}10^{-7}$ M Pb (II). The composition of this electrode was Ionophore : PVC : dioctylphthalate : potassiumtetrakis(4-chlorophenyl)borate : Oleic acid = 5.0 : 20.0 : 25.0 : 4.0 : 5.0. When we consider the results of using different composition electrodes based on only one potassiumtetrakis(4-chlorophenyl)borate or Oleic acid liphophlic additive, poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore with potassiumtetrakis(4-chlorophenyl)borate and Oleic acid liphophlic additive had the best result in response characteristics. The electrode shows good selectivity for lead (II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. This electrode is suitable for use with aqueous solutions of pH 3.0 ~ 7.0 and their standard deviation in the measured emf differences was ${\pm}2.94$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-2}$ M and ${\pm}2.82$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-3}$ M. Their stabilization time was less than 710 s. and response time was less than 16 s.

• Resources Recycling
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• v.23 no.4
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• pp.21-29
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• 2014

Nickel, cobalt and manganese-based(NCM, $Li(Ni_xCo_yMn_z)O_2$) cathode active materials of spent lithium-ion batteries contained valuable metals such as cobalt(15 ~ 20%), nickel(25 ~ 30%), manganese(10 ~ 15%) and lithium(5 ~ 10%). It was investigated the eco-friendly leaching process for the recovery of valuable metal from spent lithium-ion battery NCM cathode active materials by DL-malic acid($C_4H_5O_6$) as an organic leachant in this research. The experiments were carried out to optimize the process parameters for the recovery of cobalt, nickel and lithium by varying the concentration of lixivant, reductant concentration, solid/liquid ratio and temperature. The leaching solution was analyzed using ICP-OES(Inductively Coupled Plasma Optic Emission Spectrometer). Cathode active materials of 5 wt. % were introduced into the leaching solution which was 2 M DL-malic acid in addition of 5 vol. % $H_2O_2$ at $80^{\circ}C$ and it resulted in the recovery of 99.10% cobalt, 99.80% nickel and 99.75% lithium in 120 min. $H_2O_2$ in DL-malic acid solution acts as an effective reducing agents, which enhance the leaching of metals.

• Archives of Pharmacal Research
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• v.26 no.7
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• pp.526-531
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• 2003

KR-31378 is a new drug candidate intended for the use in the prevention of ischemia-reperfusion damage. The objective of this preformulation study was to determine the physicochemical properties of KR-31378. The n-octanol to water partition coefficients of KR-31378 were 0.0504 at pH 3 and 0.8874 at pH 10. Accelerated stability of KR-31378 in solution and solid state was studied at 5, 40, $60^{\circ}C$. The stability testing indicated that the t90 for the drug in solid was estimated to be 2 years and 128.6 days at $25^{\circ}C$, while the that in aquesou solution was 68.6 days at $25^{\circ}C$. The KR-31378 was also found to be unstable under the relative humidity of 76%, probably because of the hygroscopic nature of the drug. In order to study compatibility of KR-31378 with typical excipients, potential change in differential scanning calorimetry spectrum was studied in 1:1 binary mixtures of KR-31378 and Aerosil, Avicel, Eudragit, lactose, PEG, talc, CMC, PVP, starch. As a result, CMC, PVP, and starch were found to be incompatible with KR-31378, indicating the addition of these excipients may complicate the manufacturing of the formulation for the drug. Particle size distribution of KR-31378 powder was in the size range of 9-93 $\mu$ m with the mean particle size of 37.9 $\mu$ m. The flowability of KR-31378 was apparently inadequate, indicating the granulation may be necessary for the processing of the drug to solid dosage forms. Crystallization of the drug with a number of organic solvents did not lead a crystalline polymorphism. In addition, dissolution of the drug from the powder was adequately rapid at $37^{\circ}C$ in water.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.474-479
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• 2020

The effect of precipitation and dissolution of Si on the thermal diffusivity in the Al-Si alloy system is reported in this study and solution heat treatment followed by aging treatment is carried out to determine the effects of heat treatment on the thermal characteristics. The solution treatment is performed at 535 ℃ for 4 and 10 h and then the specimens are cooled by rapid quenching. The samples are aged at 300 ℃ for 4 h to precipitate Si solute. The addition of 9 wt% silicon contents makes the thermal diffusivity decrease from 78 to 74 mm/s² in the cases of solid solution treated and quenched samples. After quenching and aging, the Si solute precipitates on the Al matrix and increases the thermal diffusivity compared with that after the quenched state. In particular, the increase of the thermal diffusivity is equal to 10 mm/s² without relation to the Si contents in the Al-Si alloy, which seems to corresponded to solute amount of Si 1 wt% in the Al matrix.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.115-119
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• 2010

Neutral red5 (BR 5) adsorption from aqueous solution was investigated. New solid adsorbent was prepared from paper sludge incinerated at $250^{\circ}C$ during 2 hours. Experiments were carried out, in batch system, to remove RB5 dye from the synthetic waste water. Maximum adsorption of 374.98 mg/g at pH 5, at room temperature and contact time of 80 min was obtained. The Langmuir and Freundlich adsorption models were applied to interpret the equilibrium isotherm. The Freundlich isotherm fits quite well with the experimental data (with highly regression coefficient $R^2$). The incinerated sludge solid samples untreated and treated with BR5 dye were characterized by FT-IR spectrophotometer.

• Resources Recycling
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• v.8 no.1
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• pp.18-22
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• 1999

In order to utilize incineration fly ash of industrial wastes as resources, we present the recovery and separation of metals included in the fly ash by leaching with aqueous solution A great quantity of Cu, Pb, and Zn as well as a small amount oftoxic heavy metals are contained in the leach liquor of the fly ash, and the concentration of the ingredients of the fly ash depends on the industrial wastes which are fed into incinerators. In this paper, sequential Ieachiog operations are conducted using $H_2O$, $H_2SO_4$, $(NH_4)_2CO_3$ and NaOH as Icachants. Water soluble copper salt was leached by $H_2O$, Zn and Pb were separated by the NaOH leach liquor, and water insoluble copper was selectively leached as chelate ion with the $(NH_4)_2CO_3$ leach liquor of the third Ieaehant. Results show that the reduction percent of the fly ash in the leaching steps using $H_2O$, $H_2SO_4$, and $(NH_4)_2CO_3$ is 77%, and the other leaching procedures lose the weight of fly ash by above 60%.

• Journal of the Korean Ceramic Society
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• v.17 no.4
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• pp.208-212
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• 1980

In order to clarify the mechanism of the hydration of supersulphated slag cement, the experiments of suspension hydration were performed in the mixtures of slag+CaSO4+water or NaOH solutions with a liquid/solid ratio of 10. The liquid and solid phase of the suspension was chemically analysed and discussed. In the slag-$CaSO_4$--NaOH system, $Al_2O_3$ was dissolved under high pH condition, and the ettringite was formed by a reaction of $CaSO_4$ and $Al_2O_3$ released in the solution. As hydration progressed, ettringite coated the surface of unhydrated slag grains and inhibited the hydration reaction of slag. $CaSO_4$ was not only an activator for slag hydration, but a reactant in the hydration.

• Korean Journal of Poultry Science
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• v.17 no.2
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• pp.109-114
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• 1990

Enzymatic activity of isolated Lysozyme from egg white by cation ion-exchange chromatography was detected with various methods and stability of lysozyme in solution was studied by heat and pH treatments. Lysozyme activity refered to mg pure lysozyme/mg sample was more accurate although it needed standard lysozyme. But lysozyme activity refered to units/mg sample could be detected easily and reducted total detection time. Enzymatic activity of isolated lysozyme which dissolved in 0.066M phosphate buffer(pH 6.3) and then incubated at $37^{\circ}C$ for 2hr was increased remarkably on the lysis of Micrococcus lysodeikticus. The activity of isolated lysozyme by CM Sephadex C-25 was higher in eluting solution of above O. D. 1.0 at 640nm and attained 36, 000 units/mg solid. The stability of isolated lysozyme was decreased by various heat treatment. Activity began to decrease above 6$0^{\circ}C$ and dropped rapidly at $100^{\circ}C$. Especially, 35% loss of activity occured in 0.066M phosphate buffer at $100^{\circ}C$. for 15min. The stability of lysozyme was also affected by pH. lysozyme was very stable in acidic solution but in alkaline solution. Enzymatic activity showed maximum value at pH 3.0 solution while decreased rapidly above pH 6.0 solution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.175-182
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• 1992

Freezing of the binary solution ($H_2O-NaCl$) saturating a packed bed of spheres is investigated experimentally. The system is cooled through its top surface, and the bottom is maintained at a temperature above the liquidus. Experiments are performed on the hypolutectic side, and the cold wall temperature is lower than the eutectic point. The effects of initial mixture concentration, superheat and glass bead diameter on temperature and concentration distributions are investigated. Supercooling was observed only at early times of the freezing process for experiments with 5% initial salt concentration. Flow visualization experiments and mushy-liquid interface position observations revealed natural convection in the liquid region. Remelting phenomena was not observed at both the solid-mushy and mushy-liquid interfaces.

• Structural Engineering and Mechanics
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• v.61 no.5
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• pp.563-576
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• 2017

This paper is a continuation of the investigations started in the paper by Akbarov, S.D., Guliyev, H.H and Yahnioglu, N. (2016) "Natural vibration of the three-layered solid sphere with middle layer made of FGM: three-dimensional approach", Structural Engineering and Mechanics, 57(2), 239-263, to the case where the three-layered sphere is a hollow one. Three-dimensional exact field equations of elastodynamics are employed for investigation and the discrete-analytical method is employed for solution of the corresponding eigenvalue problem. The FGM is modelled as inhomogeneous for which the modulus of elasticity, Poison's ratio and density vary continuously through the inward radial direction according to power law distribution. Numerical results on the natural frequencies are presented and discussed. These results are also compared with the corresponding ones obtained in the previous paper by the authors. In particular, it is established that for certain harmonics and for roots of certain order, the values of the natural frequency obtained for the hollow sphere can be greater (or less) than those obtained for the solid sphere.