• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1993.11a
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• pp.3-3
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• 1993

In mechanical testing of W-Ni-Pe heavy alloys, the cracks nucleate at W/W interface and propagate through W/ Imatrix interface or through matrix phase together with the cleavage of W grains. The mechanical properties can therefore be improved by control of the interfacial strength and area. In this presentation, some experimental result and techniques on this subject will be reviewed and discussed. The hydrogen embrittlement caused by the hydrogen segregation at interfaces during sintering in an hydrogen atmosphere can be removed by an heat-treattnent in vacuum or in an inert atmosphere. The heat-treatment condition can be estimated by using a diffusion equation for a cylindrical shape. The mechanical properties, in particular the impact property, are degraded by the segregation of non-metallic impurities, such as Sand P. The degradation can be prevented by adding a fourth element, such as La or Ca, active with the non-metallic impurities. The cyclic heat-treatment at usual heat-treattnent tempemture causes the penetration of matrix between W/W grain boundaries and results in remarkable increase in impact energy. This is due to an increase in the area of ductile failure during the impact test. The instability of W/matrix interface casued by addition of Mo or Re can be controlled by using W powders of different size. The increase in the interfacial area in found to be related to the presence of non-equilibrium pure W gmins among W(Mo or Re) solid solution gmins.

• Economic and Environmental Geology
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• v.25 no.3
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• pp.225-232
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• 1992

The hydrothermal alteration is evaluated using multicomponent equilibrium calculations with the program CHILLER for the reactions between hydrothermal water and rhyolite at the temperature of $300^{\circ}C$ and pressure of 500 bars. The chemical-reaction model on the depositional processes of the sericitite confirms that the hydrothermal water-rock interaction(hydrothermal alteration) is the main mechanism of the sericitite formation. The principal change in the aqueous phase during the reaction is the pH increase. Overall trends for the major species are the increase in total molalities of K, Ca, $SiO_2$, Al, Mg, Fe, Na, and sulfide in solid phase with hydrothermal water-rhyolite reaction and the decrease of them in aqeous solution by precipitation of hydrothermal products. Quartz and sericite are the first minerals to form. The sequence of minerals to precipitate following them is chlorite, epidote, pyrite and microcline as water/rock ratio decreases. Although calculated results cannot duplicate the complexities of natural hydrothermal alteration, the calculation provides thermodynamic constraints on the natural process. The calculation results resemble those of experimental studies. Sericitite forms where pH decreases and water/rock ratio increases.

• Journal of the Korean Society of Food Science and Nutrition
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• v.9 no.1
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• pp.59-73
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• 1980

A detailed procedure was described for the isolation of cratine kinase (ATP-Creatine phosphotransferase, E. C. 2. 7. 3. 2.) from the muscle of the snake Bungarus fasciatus. The original isolation procedure of Kuby et al. for the rabbit muscle enzyme has been modified and extended to include a chromatographic step. The properties of the enzyme have been investigated and kinetic constants for the reverse reactions determined as the followings: 1) A molecular weight of the enzyme was determined by gel filteration on Sephadex G-100 and by electrophoresis on SDS-polyacrylamide was 86,000. 2) Two reactive sulphydryl groups were detected with dithiobis nitrobenzoic acid (DTNB). 3) The nucleotide substrate specificity in the reverse reaction was determined as ADP*2'-dADP＞GDP＞XDP＞UDP with magnesium as the activating metal ion. 4) The order of the metal specificity in the reverse reaction Mg>Mn>$Ca{\sim}Co$ was determined with ADP as substrate. 5) A detailed kinetic analysis was carried out in the reverse direction with $MaADP^-$ as the nucleotide substrate. Initial velocity and product inhibition studies($MaADP^{2-}$ competitive with respect to MgADP- and noncompetitive with respect to $N-phosphorycreatine^{2-}$ ; Creatine competitive with respect to $N-phosphorycreatine^{2-}$ and noncompetitive with respect to Ma $ADP^-)$ indicated that the reaction obeyed a sequential mechanism of the rapid equilibrium random type.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.498-503
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• 2006

Adsorption features of $Cd^{2+}$ on waste tire particles have been investigated for the purpose of enhanced wastes recycling along with the development of an economic process for wastewater treatment. The isoelectric point of waste tire particles was found to be ca. pH 7 and the adsorbed amount of $Cd^{2+}$ was increased with pH under experimental conditions. The variation of the adsorption behavior of $Cd^{2+}$ with pH was well explained by the change of the electrokinetic potential of waste tire particles according to the pH. Adsorption of $Cd^{2+}$ was observed to reach its equilibrium within 45 minutes after the adsorption started under experimental conditions and followed the Freundlich model well. Kinetic analysis showed that the adsorption reaction of $Cd^{2+}$ was second order and thermodynamic estimation substantiated the endothermic behavior of $Cd^{2+}$ adsorption. As the amount of adsorbent increased, more adsorption of $Cd^{2+}$ was accomplished and the adsorption capacity of adsorbent was found to be enhanced by its pre-treatment with NaOH. Also, the adsorption of adsorbate was promoted as the ionic strength of wastewater was increased.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.849-854
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• 2000

The protonation and divalent cation complexation equilibria of several quinolone antibiotics such as nalidixic acid (NAL),flumequine (FLU), oxolinic acid (OXO), ofloxacin (OFL), norfloxacin (NOR) and enoxacin (ENO) have been examined by potentiome tric titration and spectrophotometric method. The antibacterial activity of these drugs depends upon the pH and the concentration of metal cations such as Mg2+ , Ca2+ in solu-tion. The apparent ionization constants of NAL, FLU, OXO, OFL, NOR and ENO in aqueous solution were found to be 6.33, 6.51, 6.72, 7.18, 7.26, and 7.53, respectively. In aqueous solution, NAL, FLU and OXO were found to be present mainly as two chemical species : molecularand anionic; but OFL, NOR and ENO were present mainly as three chemical species : anionic, neutral zwitterionic and cationic form, in equilibrium. The pKa1 and pKa2are found to be 6.10 and 8.28 for OFL; 6.23 and 8.55 for NOR; 6.32 and8.62 for ENO, respec-tively. The complex formation constants between OFL, NOR or FLU and some divalent cations are measured at pH 7.5. The 1 : 1 complexes are formed mainly by ion-dipole interaction. FLU has somewhat larger Kf values than OFL and NOR because its molecular size is small and the FLU is present asanionic form at pH 7.5.

• Journal of the Mineralogical Society of Korea
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• v.26 no.4
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• pp.229-244
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• 2013

Arsenic contamination may be brought about by a variety of natural and anthropogenic causes. Among diverse naturally-occurring chemical speciations of arsenic, trivalent (As(III), arsenite) and pentavalent (As(V), arsenate) forms have been reported to be the most predominant ones. It has been well known that the behavior of arsenic is chiefly affected by aluminum, iron, and manganese oxides. For this reason, this study was initiated to evaluate the applicability of manganese slag (Mn-slag) containing high level of Mn, Si, and Ca as an efficient sorbent of arsenic. The main properties of Mn-slag as a sorbent were investigated and the sorption of each arsenic species onto Mn-slag was characterized from the aspects of equilibrium as well as kinetics. The specific surface area and point of zero salt effect (PZSE) of Mn-slag were measured to be $4.04m^2/g$ and 7.73, respectively. The results of equilibrium experiments conducted at pH 4, 7 and 10 suggest that the sorbed amount of As(V) was relatively higher than that of As(III), indicating the higher affinity of As(V) onto Mn-slag. As a result of combined effect of pH-dependent chemical speciations of arsenic as well as charge characteristics of Mn-slag surface, the sorption maxima were observed at pH 4 for As(V) and pH 7 for As(III). The sorption of both arsenic species reached equilibrium within 3 h and fitting of the experimental results to various kinetic models shows that the pseudo-second-order and parabolic models are most appropriate to simulate the system of this study.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.130-136
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• 1996

This study was carried out easily to determine the refreshing time of natural Zeolite used for the clearing of Livestock waste water and to investigate the relationship between EC of solution and adsorption amount on Zeolite. During the adsorption reaction, EC of supernatant solution decreased till the equilibrium was reached and kept a constant level after it. EC was greatly decreased with the concentration of solution and the magnitude of adsorbent. Decrease in EC of suspension was found to be lesser in addition of Na-Zeolite than Ca-Zeolite. EC change of Livestock waste water was shown to be similar tendency to that of the simulated waste water. On the cumulative adsorption isotherm, the EC of suspension increased until the EC value of the initial solution as the increase in treatment times. Therefore, it is apparent that the exchange point of natural zeolite should be in the vicinity of the EC value of initial waste water.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.9
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• pp.641-647
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• 2014

In this study, sludge waste which has a difficulty in treating it was used to manufacture a fiber type of biosorbent. To solve the problems such as the release of organic pollutants and the difficulty in separating solid from treated water, entrapment method using Ca-alginate was used to immobilize sludge waste. Considering ease of manufacture as well as improvement of adsorptive ability, the biosorbent was manufactured in the form of fiber type. Optimum immobilization condition for minimizing the amount of alginate used and maximizing the performance of biosorbent was determined to be 10 g/L alginate concentration, 40 g/L sludge concentration, and 0.3-0.4 mm fiber diameter. The maximum Cd(II) uptake of the biosorbent was 60.73 mg/g. Pseudo-second-order kinetic model and Langmuir isotherm model adequately described the dynamic and equilibrium behaviors of Cd(II) biosorption onto the biosorbent, respectively. In conclusion, sludge waste generated from wastewater treatment process is a cheap raw material for the manufacture of biosorbent which can be used to remove toxic heavy metals from industrial wastewaters efficiently.

• Polymer(Korea)
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• v.35 no.4
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• pp.363-369
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• 2011

To study the effect of incorporation of a surface crosslinking layer on a crosslinked poly (sodium acrylate) (cPSA) absorbent with ethylene glycol dimethacrylate CEGDMA), we synthesized several surface crosslinked cPSAs with EGDMA by an inverse emulsion polymerization method to delay the absorption of excess water in concrete, Liquid paraffin was used as a continuous phase. cPSA was synthesized with acrylic acid (AA) neutralized with aqueous 8 M sodium hydroxide solution as a monomer, N,N-methylene bisacrylamide (MBA) as crosslinking agent and ammonium persulfate (APS) and sodium metabisulfite (SMBS) as a redox initiator system by inverse emulsion polymerization. FTIR spectroscopy was used to characterize $Ca^{2+}$ ion interaction with cPSA and cPSA-EGDMAs. The swelling ratios of synthesized absorbents were evaluated from the absorption in deionized water, cement saturated aqueous solution and aqueous solution of calcium hydroxide (pH 12). Equilibrium swelling times for cPSA and surface crosslinked cPSA with EGDMA were 2 and 3 hrs, respectively. We also observed an increase in setting time of the cement and an increase in the compressive strength of mortar by addition of the synthesized cPSA-EGDMA.

• Applied Biological Chemistry
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• v.17 no.3
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• pp.219-234
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• 1974

A series of experiments was conducted to study the behavior of the phosphorus added to the soils having the high phorphorus fixing capacity derived from volcanic ash in Cheju Island. Soil samples were taken from different depths of 0-10, 10-30, and 30-50cm in six citrus orchards where heavy application of phosphate fertilizer has been practised. Various forms of phosphorus were determined and phosphorus adsorption experiments were performed. The results obtained can be summarized as follows: 1. The content of inorganic phosphorus fractions determined by the method of Chang and Jackson was: water soluble P