• YAKHAK HOEJI
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• v.17 no.4
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• pp.217-222
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• 1973

Although a considerable amount of work has ben carried out, on the reduction of p-nitrosalicylic acid with Pb, Ni, Cu and Hg cathodes, published results do not proceeded the synthesis of p-aminosalicylic acid. In order to get the reduction potential and the mechanism of reduction, therefore, the electrode reactions occurring during "polarographic reduction" have been studied more fully. As a result, the author found that p-aminosalicylic acid (PAS) can be only produced in a HCl-ethanol solution using Sn cathode with the current density of 4.0A/$dm^{2}$, at 40-$50^{\circ}$.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.25-31
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• 2015

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from electronic devices and system. Specifically, reliability issue of lead-free solder joint have an increasing demand for the car electronics caused by ELV banning. The authors prepared engine control unit and cabin electronics soldered with Sn-3.0Ag-0.5Cu (SAC305). To compare with the degradation characteristics of solder joint strength, thermal cycling test (TC), power-thermal cycling test (PTC) and series tests were conducted. Series tests were conducted for TC and PTC combined stress test using the same sample in sequence and continuously. TC test was performed at $-40{\sim}125^{\circ}C$ and soak time 10 min for 1000 cycles. PTC test was applied by pulse power and full function conditions during 100 cycles. Combined stress test was tested in accordance with automotive company standard. Solder joint degradation was observed by optical microscopy and environment scanning electron microscopy (ESEM). In addition, to compare with deterioration of bond strength of quad flat package (QFP) and chip components, we have measured lead pull and shear strength. Based on the series test results, consequently, we have validated of series test method for lifetime and reliability of Pb-free solder joint in automotive electronics.

• The Korean Journal of Mycology
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• v.24 no.1 s.76
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• pp.8-16
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• 1996

The ${\alpha}-amylase$ of Alternaria alternata was purified through ammonium sulfate precipitation, dialysis and Sephadex G-100 column chromatography. One single band was obtained in SDS-polyacrylamide gel electrophoresis. The optimum pH for enzyme activity was 5.0 and the enzyme activity was maintained at $3.6{\sim}7.0$pH range. The optimum temperature for ${\alpha}-amylase$ activity was $40^{\circ}C$ and 71% of the activity was still maintained until 30 min after heating at $80^{\circ}C$. The ${\alpha}-amylase$ was slightly activated by $Mn^{2+},\;Zn^{2+}\;and\;Sn^{2+}$, but inhibited by $Ba^{2+},\;Pb^{2+},\;Co^{2+}\;and\;Ag^{1+}$. The $Hg^{2+}\;and\;Ag^{2+}$ slightly inhibited the activity of the enzyme at concentrations of $10^{-3}\;and\;10^{-4}M$. The Michaelis constant $(K_m)$ to soluble starch was $6.50{\times}10^{-2}M$ and inhibition constant $(K_i)$ by the 1mM EDTA was $8.0{\times}10^{-2}M$. The inhibition of this enzyme by EDTA was competitive one.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.31-40
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• 2014

In present study, we geochemically investigated the fresh coal ashes and the saline ash pond of an electric power plant in Korea, which burns imported bituminous coals. The goals are to see the chemical changes of the ash pond by reaction with coal ashes and to investigate the relative leachability of elements from the ashes by reaction with saline waters. For this study, one fresh fly ash, one fresh bottom ash, and 7 water samples were collected. All the ash samples and 2 water samples were analyzed for 55 elements. The results indicated that the fly ashes are enriched with chalcophilic elements such as Cu, Zn, Ga, Ge, Se, Cd, Sb, Au, Pb, and B relative to other elements. On the other hand, concentrations of As, Ba, Co, Ga, Li, Mn, Mo, Sb, U, V, W, and Zr are much higher in the ash pond than those dissolved in the seawater. Ag, Bi, Li, Mo, Rb, Sb, Sc, Se, Sn, Sr, and W show high ratios of elemental concentrations in pond water to those in the fly ash. Our results imply that the leaching of trace elements is regulated by geochemical controls such as solubility and adsorption even though the trace elements are relatively enriched on the ash surfaces after the coal combustion due to their volatilities.

• 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 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.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.108-108
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• 2000

급증하는 무선통신 정보수요는 특히, 고주파대역 (300NHz-300GHz)에서 사용되는 공진기, 필터, 발진기 등과 같은 소자의 품질향상을 요구하고 있다. 고주파용 유전체 중 ZrTiO4 는 $\alpha$-PbO2 계열의 사방정구조를 갖고 있는 유전체로서 높은 유전율 ($\varepsilon$=40)과 높은 품질계수 (Q=1/tan$\delta$=4700 at 7GHz)를 갖고 있고, Sn 첨가시 0ppm/$^{\circ}C$의 공진주파수 온도계수를 얻을 수 있다고 보고되어 있다. 본 연구에서는 약 110$0^{\circ}C$ 이상에서 안정한 상으로 존재하는 ZrTiO4를 저온에서 증착하여 준안정한 상태로 결정화되게 한후, 유전손실 (tan$\delta$)과 유전율($\varepsilon$)을 측정하였다. 또한 증착온도와 열처리과정에 따른 박막의 us형 (Strain) 정도의 변화를 X-선 회절결과로부터 분석하였으며 이를 측정된 유전특성 값과 비교하였다. ZrTiO4 박막은 DC magnetron reactive sputter로 Zr과 Ti 타겟으로부터 high phosphorous doped Si (100) 기판위에 증착하였다. 압력은 4mTorr로 유지하고 박막의 화학양론적 조성비를 맞추기 위해 각 타겟에 가해지는 power는 Zr/Ti=500W/650W로 고정하고, 반응가스의 비율을 Ar/O2=17sccm/3.5sccm으로 유지하여 박막내에 인입되는 산소량을 제어하였다. 증착 직후와 열처리 후의 박막특성을 비교하기 위해 증착온도를 상온에서부터 $600^{\circ}C$까지 변호시키고 증착후 각각의 시편을 80$0^{\circ}C$ 산소분위기에서 2시간동안 열처리하여 시편을 준비하였다. 박막의 상형성 여부와 결정성변화는 $ heta$-2$\theta$X-선 회절법을 사용하여 조사하였고, EPMA를 이용하여 박막의 조성을 확인하였다. 유전특성의 측정을 위해 백금 상부전극을 증착한 후, impedance analyzer를 이용하여 100kHz 영역에서의 유전손실을 측정하고, 측정된 정전용량과 박막의 두께로부터 유전율을 계산하였다. ZrTiO4 박막은 증착온도 20$0^{\circ}C$ 이상에서 결정성을 보이기 시작했으며, 열처리 이후에는 상온에서 비정질이었던 시편이 $650^{\circ}C$ 이상의 온도에서 결정화되기 시작하였다. 증착온도에 따라 유전손실은 0.038에서 0.017 정도로 감소하는 경향을 나타냈으며, 각각 열처리에 의해서 0.034, 0.005 정도로 다시 감소하였다. 박막의 유전율은 약 35 정도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.

• Microbiology and Biotechnology Letters
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• v.20 no.5
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• pp.519-526
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• 1992

The gene coding for urease of alkalophilic Bacillus pasteurii had been cloned in Escherichia coli previously. The urease protein was purified 63.1-fold by TEAE-cellulose, DEAE-Sephadex A-50, Sephadex G-150 and Sephadex G-200 chromatographies with a 7.3% yield from the sonicated fluid of the E. coli HB1Ol(pBUll) encoding B. pasteurii urease gene. The ureases of E. coli (pBUll) and B. pasteurii possessed as a $K_m$ for urea, 42.1 mM and 40.4 mM, respectively. They hydrolyzed urea with $V_{max}$ of 86.9$\mu$mol/min and 160$\mu$mol/min, respectively. Both ureases were composed with four subunits (Mrs 67,000) and a subunit (Mr 20,000). The molecular weight of both native enzymes was Mr 280,OOO$pm$10,000 determined by gel filtration chromatography and Coomassie blue staining of the subunits. The optimal reaction pH of both ureases were pH 7.5. The ureases were stabled in pH 5.5-10.5. The optimal reaction temperature of both ureases were $60^{\circ}C$, and the ureases were stable for an hour at $50^{\circ}C$, 40min at $60^{\circ}C$ and 10 min at $70^{\circ}C$ The activity of both enzymes were inhibited completely by $Ag^{2+}$, $Hg^{2+}$, $Zn^{2+}$, $Cu^{2+}$, and were inhibited 60% by CoH, 30% by $Fe^{2+}$ and 10% by $Pb^{2+}$. However it was increased by the addition of $Sn^{2+}$, $Mn^{2+}$, $Mg^{2+}$ at concentration of $1{\times}10^{-3}$M. Both ureases were inhibited completely by p-CMB and acetohydroxamic acid. The urease expressed in E. coli (pBU11) was inhibited 70% by SDS. The urease of B. pasteurii was inhibited 40% by hydroxyurea, whereas the recombinant urease of E. coli strain was inhibited 17%. Both enzymes were not inhibited by cyclohexanediaminetetraacetic acid (CDTA) and ethylendiaminetetraacetic acid (EDTA).