• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.494-499
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• 1976

The extraction-polarographic method applied to the determination of micro amount of chromium (Ⅵ). Chromium(Ⅵ) was extracted into methylisobuthylketone(MIBK) layer containing diethyldithiocarbamate(DDTC) as Cr(Ⅲ)-DDTC complex from acetate buffered aqueous, solution of pH 5.4 and the direct current polarogram for the extract was recorded after addition of sodium perchlorate as supporting electrolyte. The reduction current was diffusion controlled. And the half wave potential of this reduction wave was -0.81 volt vs. SCE. The diffusion current was proportional to the chromium concentraticn in aqueous solution in the range of 8∼160 ppm. And the chromium(Ⅵ) could be selectively determined in the presence of chromium(Ⅲ), since the chromium(Ⅲ) did not interfere up to twice the amount of chromium(Ⅵ). Many of other metals such as Mn(Ⅱ), Cu(Ⅲ), Zn(Ⅱ), Mg(Ⅱ), Ni(Ⅱ) and Ag(Ⅰ) were found to have no effect even when present in 1000 times the amount of chromium (Ⅵ).

• Textile Coloration and Finishing
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• v.20 no.6
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• pp.42-50
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• 2008

The objective of this study is to investigate the efficacy of pomegranate hull colorant as a natural hair coloring dye. The extract of pomegranate hull was concentrated and freeze-dried to get colorant powder. Effect of dyeing condition and mordanting on the dye uptake of hair by using Al, Fe, Cu, Cr, Sn compounds, color change and colorfastness were explored. In addition, tensile strength was measured and the surface of the hair was observed. Dye uptake of hair measured by K/S value (400 nm) indicated that ionic bonding seems to be involved in the sorption of pomegranate colorant to hair. Maximum sorption was obtained at pH 3.5 and the concentration of 50% (on the weight of hair, o.w.h.). Acidic dyeing condition (pH $3.5{\sim}5.0$) showed yellow color however alkaline dyeing condition (pH $7{\sim}11$) gave reddish yellow color. Pomegranate hull colorant produced greyish brown color on hair and the hair mordanted with Fe showed dark brown color. Mordants except Fe did not increase dye uptake significantly. Mordants except Cu increased light fastness and mordants except Cr increased washing fastness level slightly. According to SEM observation and the tensile strength retention measurement, the mordant dyed hair gave more damage to hair by ultraviolet light and washing than the hair dyed without mordanting. Experimental results of K/S value and colorfastness(light and washing) supported that pomegranate hull colorant without mordanting can be used as a semi-permanent natural hair coloring dye.

• Journal of the Korean Society of Food Science and Nutrition
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• v.18 no.3
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• pp.348-355
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• 1989

This experiment was conducted to investigate the characteristics of alkaline protease from Aspergillus fumigatus which was isolated from soil as a superior strain for the production of the alkaline protease. The optimum temperature for enzyme activity was $50^{\circ}C$ and optimum pH was 9.0. The enzyme was stable at pH 8.0 to 10.0 and thermal inactivation was shown $30^{\circ}C$. The activity of the enzyme was increased by the addition of $Mn^{++},\;Cu^{++},\;Ba^{++},\;Mg^{++},\;$wheras it was inhibitied by $K^+,\;Fe^{+++},\;Ag^+,\;Pb^{++},\;Na^+,\;Ca^{++},\;Hg^+,\;Zn^{++}$. EDTA. 2, 4-DNP, ${\varepsilon}-amino$ caproic acid did not show inhibitory effect on the proteolytic activity of alkaline protease but P-chloromercuribenzoic acid inhibited the enzyme activity, indicating that reactive sulfhydryl group is required for the enzymatic activity. The reaction of this enzyme followed typical Michael-Menten Kinetics with the Km value of $8.33{\times}10^{-4}mole/{\ell}$ with the Vmax of $47.62{\mu}g/min$. This enzyme had stronger proteolytic activity than trypsin on substrate such as casin and hemoglibin.

• Analytical Science and Technology
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• v.12 no.2
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• pp.130-135
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• 1999

A graphite furnace atomic absorption spectrometry (GFAAS) with matrix modification has been used to determine trace amounts of arsenic, lead and selenium in rice flour samples. A mixed solution of palladium and magnesium nitrate was used as a matrix modifier to convert the analyte elements into a phase of higher thermostability and to increase the volatility of concomitants in graphite furnace. Matrix modification effects by the mixed solution were investigated for several elements (As, Cd, Cu, Pb, Se, Zn). It has been found that the matrix modifier substantially increase the pyrolysis and atomization temperature, and absorbance for As, Pb and Se. The concentration of As, Pb and Se in rice flour samples were determined by standard addition method with Zeeman background correction after microwave acid digestion. In this method the characteristic concentrations of As, Pb and Se are 26 ng/g, 18 ng/g, 24 ng/g on the basis of dry sample respectively.

• Microbiology and Biotechnology Letters
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• v.30 no.4
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• pp.352-358
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• 2002

An amylase that hydrolyzes starch into maltopentaose as a main product was found in the culture supernatant of a strain of Bacillus megaterium KSM B-404 isolated from local soil. The enzyme was purified 129-fold by ammonium sulfate precipitation, DEAE-Toyopearl and Superdex 75 HR 10/30 column using a FPLC system. The molecular weight of the amylase was determined as about 68 kDa by using SDS-PAGE. Optimum pH and temperature of amylase were found to be $50^{\circ}C$ and pH 6.0~7.0, respectively. The enzyme was stable up to $60^{\circ}C$ by addition of $Ca^{2+}$ and its pH stability was in the range of 6.0~10.0. The activity of enzyme was inhibited by $Cu^{2+}$ $Hg^{2+}$ , and $Fe^{3+}$ and maintained by $Ca^{2+}$ and $Mg^{2+}$ . EDTA and pCMB also showed inhibitory effect to the enzyme. TLC and HPLC analysis of the products of the enzyme reaction showed the presence of maltopentaose(52%), maltotriose (25%), maltose (11%), glucose, and maltotetraose in the starch hydrolysates.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.145-153
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• 2013

In this study, shear punch-creep (SP-Creep) at Sn-4Ag/Cu pad the joint was tested by using environment-friendly Pb-free solder alloy Sn-4Ag of electronic components. Pb eutectic alloy (Sn-37Pb) joints limited to environmental issues with reflow time (10sec, 30sec, 100sec, 300sec) according to two types of solder alloy joints are compared and evaluated by creep strain rate, rupture time and IMC (Intermetallic Compound) behavior. As the results, reflow time increases with increasing thickness of IMC can be seen at overall 100sec later in case of two solder joints on the IMC thickness of Sn-4Ag solder joints thicker than Sn-37Pb solder joints. In addition, when considering creep evaluation factors, lead-free solder alloy Sn-4Ag has excellent creep resistance more than Pb eutectic alloy. For this reason, the two solder joints, such as in the IMC (Cu6Sn5) was formed. However, the creep resistance of Sn-4Ag solder joints was largely increased in the precipitation strengthening effect of dispersed Ag3Sn with interface more than Sn-37Pb solder joints.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.617-621
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• 2010

($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ ceramics doped with iron oxide ($Fe_2O_3$) were prepared by a conventional mixed oxide method. And then, their piezoelectric and dielectric properties were investigated as a function of $Fe_2O_3$ addition. X-ray diffraction studies reveal that $Fe^{3+}$ diffuses into the NKN lattices to form a solid solution with a pure perovskite structure at room temperature. At the sintering temperature of $1,060^{\circ}C$, when 0.2 mol% $Fe_2O_3$ was doped, the piezoelectric constant ($d_{33}$), electromechanical coupling factor (Kp), and mechanical quality factor ($Q_m$) showed the excellent values of 131.67 pC/N, 0.436, and 696.36, respectively. Results show that $Fe_2O_3$ deped ($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ lead-free piezoelectric ceramics are a promising lead free material for piezoelectric transformer applications.

• Applied Biological Chemistry
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• v.45 no.3
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• pp.179-184
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• 2002

To examine utilization of Korean black soybean as a natural pigment, the effects of temperature, carbohydrate, organic acid, vitamin C and metal ion were investigated. Korean black soybean pigment was more stable than other anthocyanin pigments when temperature was abused. There was no darkness effect in carbohydrate. In organic acid, the color intensity was increased. The vitamin C addition negatively affected on color of anthocyanin. Among the metal ions tested, $Cu^{2+}$ and $Zn^{2+}$ was not affected but $Mn^{2+}$ makes it unstable. Results indicate that Korean black soybean pigment was more stable than other anthocyanin pigment in various environment at pH 3.

• Applied Biological Chemistry
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• v.36 no.4
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• pp.249-254
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• 1993

The dried cinnamon was extracted with water and 70% ethanol and studied for the several extraction conditions of temperature, time, solvent addition ratio and number of extraction on mineral components and physical properties of the extracts. Mineral components significantly increased as the extraction temperature increased. More than 8 hours of extraction showed a little improving while solvent ratio (V/W) up to 60 times (V/W) significantly increased the mineral components, particularly Cu, Zn, Fe, Na in water extracts and Fe, Mn, K in 70% ethanol extracts. Absorbance at 285 mm decreased as the temperature raised up to the range of $60{\sim}80^{\circ}C$. The Hunter a-value was much affected with extraction conditions and L-value and transmittance were changed similarily while pH was little changed.

• Korean Journal of Metals and Materials
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• v.46 no.9
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• pp.593-603
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• 2008

In this study, effects of alloying elements on the sticking occurring during hot rolling of five kinds of ferritic STS430J1L stainless steels were investigated by analyzing high-temperature hardness and oxidation behavior of the rolled steels. Hot-rolling simulation tests were conducted by a high-temperature wear tester which could simulate actual hot rolling. The simulation test results revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation. Since the hardness continuously decreased as the test temperature increased, whereas the formation of Fe-Cr oxides in the rolled steel surface region increased, the sticking of five stainless steels was evaluated by considering both the high-temperature hardness and oxidation effects. The addition of Zr, Cu, or Si had a beneficial effect on the sticking resistance, while the Ni addition did not show any difference in the sticking. Particularly in the case of the Si addition, Si oxides formed first in the initial stage of high-temperature oxidation, worked as initiation sites for Fe-Cr oxides, accelerated the formation of Fe-Cr oxides, and thus raised the sticking resistance by about 10 times in comparison with the steel without Si content.