• Journal of Food Hygiene and Safety
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• v.3 no.1
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• pp.7-18
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• 1988

In 1987, the level of heavy metals were determined ina total of 200 samples of 9 species of shellfish of Korea. The samples were collected at the fish. markets by 10 Public Institute of Health. The samples were whelk (Buccinum striatiBBimum), oyster (Crassostrea gigas), ark shell(Tegillarca granesa), shartnecked clam (Venerupis semidecussta), hard clam (Meretrix lusoria), top shell (Turbo cornutus), abalone (Haliotis gigantea), ark shell (Scapharea broughtonii), sea-mussel (Mytilus conuscus gould), respectively. The levels of total mercury, lead, cadmium, arsenic, copper, zinc and manganese were determined. The total mercury levels were determined by mercury analyzer using the combustion gold amalgamation method. The arsenic level were determined by spectrophotometry using colorimetric sil ver diethyldithiocarbamate method after dry ash dige8tion of the samples with magnesium oxide and magnesium nitrate. The levels of other metals were determined by inductively coupled pluma spectrophotometry after wet digestion of the samples with nitric acid and su1furic acid. The results were summerized as follows; 1. The overallranges and mean(ppm) were; Hg, ND-O.221 (0.036); Pb, 0.05-1.51 (0.37); Cd, 0.02-1.86 (0.61); As, 0.5-3.97 (1.22); Cu, 0.14-54.16 (4.93); Zn, 7.40-207.17 (30.09); Mn, 0.13-s.72 (3.40). 2. The levels of all 6 metals were found to be below the maximum permissible Iimits set by the Japan lor mercury, the Netherland for lead the Hong Kong for cadmium. The Finland for Arsenic no statutory Iimits for Zn and Mn in shellfish in any countries. 3. The results show that all the 9 species of shellfish studied, none have accumulated levels dangerous enough to pose a health problem.roblem.

• Journal of Electrochemical Science and Technology
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• v.9 no.1
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• pp.37-43
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• 2018

In order to improve current efficiency and decrease energy consumption in the electrosynthesis of ammonium persulfate, electrolytic properties of four cation exchange membranes, namely, the $JCM-II^{(R)}$ membrane, $Nafion^{(R)}$ 324 membrane CMI-$7000^{(R)}$ membrane and a self-made perfluorosulfonic ion exchange membrane (PGN membrane) were investigated using a sintered platinized titanium anode and a Pb-Sb-Sn alloy cathode in a self-made electrolytic cell. The effect of cell voltage and electrolyte flow rate on the current efficiency and the energy consumption were investigated. The results indicated that the PGN membrane could improve current efficiency to 94.85% and decrease energy consumption to $1119kWh\;t^{-1}$ (energy consumption per ton of the ammonium persulfate generated) under the optimal operating conditions and the highest current efficiency of the $JCM-II^{(R)}$ membrane, $Nafion^{(R)}$ 324 membrane and CMI-$7000^{(R)}$ membrane were 80.73%, 77.76% and 73.22% with their lowest energy consumption of $1323kWh\;t^{-1}$, $1539kWh\;t^{-1}$ and $2256kWh\;t^{-1}$, respectively. The PGN membrane has the advantages of high current efficiency and energy power consumption and has sufficient mechanical strength with the reinforced mesh. Therefore the PGN membrane will has good value in popularization in the industrial electrosynthesis of ammonium persulfate in the future.

• Journal of ILASS-Korea
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• v.11 no.2
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• pp.59-68
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• 2006

Experimental results of the metal powder production with internal mixing, internal impinging and the atomizer coupled with substrate design are presented in this paper. In a test with internal mixing atomizer, mean powder size was decreased from $37{\mu}m\;to\;23{\mu}m$ for Pb65Sn35 alloy as the gas-to-melt mass ratio was increased from 0.04 to 0.17. The particle size further reduces to $16.01{\mu}m$ as the orifice area is increased to $24mm^2$. The micrograph of the metal powder indicates that very fine and spherical metal powder has been produced by this process. In a test program using the internal impinging atomizers, the mean particle size of the metal powder was decreased from $22{\mu}m\;to\;12{\mu}m$ as the gas-to-melt-mass ratio increased from 0.05 to 0.22. The test results of an atomizer coupled with a substrate indicates that the deposition rate of the molten spray on the substrate is controlled by the diameter of the substrate, the height of the substrate ring and the distance of the substrate from the outlet of the atomizer. This in rum determines the powder production rate of the spraying processes. Experimental results indicate that the deposition rate of the spray forming material decreases as the distance between the substrate and the atomizer increases. For example, the deposition rate decreases from 48% to 19% as the substrate is placed at a distance from 20cm to 40cm. On the other hand, the metal powder production rate and its particle size increases as the subsrate is placed far away from the atomizer. The production of metal powder with mean particle size as low as $3.13{\mu}m$ has been achieved, a level which is not achievable by the conventional gas atomization processes.

• Progress in Medical Physics
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• v.27 no.3
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• pp.125-130
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• 2016

Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.6
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• pp.547-557
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• 1986

The characteristics of the three alkaline proteinases, Enz. A, B and C, from the pyloric caeca of mackerel have been investigated. The optimum condition for the activity of the Enz. A, B and C was pH 9.4, 9.8 and 9.8 at $45^{\circ}C$ for $2\%$ casein solution, and was pH 9.2 10.2 and 9.8 at $45^{\circ}C$ for $5\%$ hemoglobin denatured by urea, respectively. Enz. A, B and C by heat treatment at $50^{\circ}C$ for 5 min were inactivated 90, 33 and $37\%$, respectively, over the original activity. The reaction rate of the three alkaline proteinases was constant to the reaction time to 40 min in the reaction condition of $2{\mu}g/ml$ of enzyme concentration and $2\%$ casein solution. The reaction rate equation and Km value against casein substrate determined by the method of Lineweaver and Burk were: Enz. A, Y=3.6X and $Km=5.0{\times}10^{-3}\%$; Enz. B, Y=6.0X and $Km=1.0{\times}10^{-3}\%$; Enz. C, Y=4.2X and $Km=3.6{\times}10^{-3}\%$. The three alkaline proteinases were inactivated by $Ag^+$ and $Hg^{2+}$, but activated by $Mn^{2+},\;Sn^{2+}\;and\;Pb^{2+}$, Enz. B and C were remarkably inhibited by the soybean trypsin inhibitor. Molecular weight of Enz. A, B and C determined by SDS-polyacrylamide gel electrophoresis and Sephadex G-100 gel filtration was in the range of $27,500{\pm}2,500,\;20,500{\pm}1,500\;and\;15,250{\pm}250$, respectively.

• Applied Biological Chemistry
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• v.39 no.5
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• pp.349-354
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• 1996

The Polyvinyl alcohol(PVA) oxidase involved in PVA degradation by microorganism has been purified to homogeneity from culture broth of Xanthomonas campestris J2Y grown in a minimal medium containing PVA as a sole carbon source. The enzyme was purified by DEAE-cellulose chromatograpy and Sephadex G-150 gel filtration. The purified PVA oxidase was electrophoretically homogeneous both in the absence and presence of SDS. The molecular weight of the enzyme was estimated to be about 55,000 daltons by SDS-polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The native enzyme existed as a monomer. The optimal pH and temperature was shown to be pH 7 and $37^{\circ}C$ respectively. The activity of enzyme was stable below $55^{\circ}C$ and between pH range of $5{\sim}11$. The enzyme activity was significantly inhibited by metal compounds such as $Ag^{2+},\;Hg^{2+}$. While, metal ions such as $Mn^{2+},\;and\;Cu^{2+}$ stimulated the reaction. Km value of the enzyme for PVA was $7.04{\times}10^{-2}mmol/{\ell}$.