• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.26-33
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• 2011

To evaluate steam oxidation behaviours of Alloy 617 and Haynes 230, oxidation test were performed at $900^{\circ}C$ in steam and $steam+20\;vol.-%\;H_2$ environments. Oxidation rate in steam condition was similar to that in air for Alloy 617, while it was slightly lower for Haynes 230. When hydrogen was added to steam, oxidation rate was enhanced. Isolated $MnTiO_3$ particle were formed on $Cr_2O_3$ oxide layer and sub layer $Cr_2O_3$ were formed in steam and $steam+20\;vol.-%\;H_2$ for Alloy 617. On the other hands, $MnCr_2O_3$ layer were formed on top of $Cr_2O_3$ oxide layer for Haynes 230. The extensive sub layer $Cr_2O_3$ formation was resulted from the oxygen inward diffusion in such environments. When hydrogen was added, the oxide morphology was changed from polygonal to platelet because of the accelerated diffusion of cations under the oxide layer. In addition, decarburized zone was extended as hydrogen participated into the reactions causing carbide dissolution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.499-503
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• 2002

In this study, to develop the high power piezoelectric transformer for adaptor, PSN-PNN-PZT system ceramics were formulated as a function of $MnO_2$ addition and its dielectric and piezoelectric characteristics were investigated. Multi-layer piezoelectric transformer using an excellent composition was also fabricated and its electrical properties evaluated. The composition ceramics added to 0.5wt%$MnO_2$ showed the maximum value of $k_p=0.61$ and $Q_m=1.321$. As the output power of piezoelectric transformer is increased, its temperature rise increased. At the fixed 18W output power, the transformer was stably operated.

• Resources Recycling
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• v.9 no.5
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• pp.16-21
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• 2000

Generation of abnormally large grains in the microstructure of small grains has been investigated on some ferrites. Some fractions of large grains were observed in the microstructue of sintered ZnFe$_2$O$_4$, Mn-ZnFe$_2$O$_4$, Fe$_3$O$_4$(in $N_2$) and MnFe$_2$O$_4$(in air). On the other hand, the large grains were not observed in $NiFe_2$$O_4$ and $CoFe_2$$O_4$, independent of calcining and sintering conditions. The large grains seem to be generated in such ferrites that are easy to very their compositions or valencies at high temperatures. as the sintering proceeded, the number of large grains was increasing to from a continuous structure consisting of large grains, while the size of large grains did not increase remarkably. In addition, the growth of small grains was also very slow during the generation of the large grains. The large grains appeared be suddenly generated after some induction periods. Avrami equation could be applied to the relation between net volume of large grains and sintering time. Thus, the grain boundaries may be strongly stabilized when the large grains are generated. The large grain is generated y the local activation of the stabilized rain boundaries, which is caused by the variation of composition or valencies during sintering. It is concluded that the essence of the abnormal gain growth is not the generation of abnormally large grains, but the abnormal stabilization and the local activation of he grain boundaries.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3281-3289
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• 2011

The materials composed of the 3d series transition metals are introduced into the hydrocarbon steam-reforming reaction in order to enhance the $H_2$ production and abruptly depress the catalytic deactivation resulting from the strong sintering between the Ni component and the ${\gamma}-Al_2O_3$ support. The conventional impregnation method is used to synthesize the Ni/3d series metal/${\gamma}-Al_2O_3$ materials through the sequentially loading Ni source and the 3d series metal (Ti, V, Cr, Mn, Fe, Co, Cu, and Zn) sources onto the ${\gamma}-Al_2O_3$ support. The Mnloaded material exhibits a significantly higher reforming reactivity than the conventional Ni/${\gamma}-Al_2O_3$ and the other Ni/3d series metal/${\gamma}-Al_2O_3$ materials. Particularly the addition of Mn selectively improves the $H_2$ product selectivity by eliminating the formation of $CH_4$ and CO. The $H_2$ production is maximized at a value of 95% over Ni(0.3)/Mn(0.3)/${\gamma}-Al_2O_4$(1.0) with a butane conversion of 100% above $750^{\circ}C$ for up to 55 h.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.687-693
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• 1992

To improve dielectric, piezoelectric and temperature stability in 0.50Pb(SnS11/2TSbS11/2T)OS13T - 0.35PbTiOS13T - 0.60PbZrOS13T + 0.4[wt%]MnOS12T piezoelectric ceramics which is used for surface acoustic wave devices, CrS12TOS13T was added and the specimens were fabricated by Hot Press method, and their characteristics were measured with CrS12TOS13T addition. From the results, in the specimen added by 0.2[wt%]CrS12TOS13T, dielectric constant and mechanical quality factor were 380 and 2307, respectively, and it was suited for surface acoustic wave device and the temperature coefficient of the resonant frequency in the specimen added by 0.4[wt%]CrS12TOS13T was the least value of 74.96[ppm/$^{\circ}C$].

• Applied Biological Chemistry
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• v.24 no.2
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• pp.105-111
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• 1981

Growth responses of Brevibadterium ammoniagenes BA 17-2, which had been obtained by the treatment of several mutagens in our previous report, were investigated to select the preliminary optimal concentrations of phosphate, $Mg^{++}$, $Mn^{++}$ and thiamine for the production of 5'-XMP aminase. In this experiment it was shown that the concentration of phosphate in the medium has an important effect on the growth of microorganism. Using the medium containing 0.2% of $MgSO_4{\cdot}7H_2O$, 3mg/l of $MnSO_4{\cdot}H_2O$and $1\;mg/l$ of thiamine-HCl, the maximum cell mass was obtained at the concentration of 0.4% of $KH_2PO_4$ and $K_2HPO_4$, respectively. Above the concentration of these phosphates, cell growth was inhibited as the phosphate concentration increased to 1%, but the inhibition was overcome by the addition of 1% of $MgSO_4{\cdot}7H_2O$ and 3mg/l of thiamine-HCl. The 5'-XMP aminase activity was also influenced by the concentration of phosphate, $Mg^{++}$, $Mn^{++}$, and thiamine. In addition, the optimal culture pH and temperature for the enzyme activity were found to be 6.8 and $32^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.10
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• pp.5229-5232
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• 2012

The incidence of malignant melanoma increases with age. One significiant effect of aging processes is an accumulation of oxidative damage in the genetical material. In this study, the relationship between malignant melanoma and damage in chromosomes and proliferative effectiveness of human peripheral lymphocytes were investigated by the micronucleus (MN) technique. A total of 15 malignant melanoma patients and appropriately matching 15 healthy controls were involved in the study. MN frequencies and proliferative indexes (PI) after non toxic levels of hydrogen peroxide treatment were also measured to determine damaging effect of oxidative stress in genome in addition to measuring the spontenous levels of micronuclei and PI. The patient group had a significantly higher rate of spontaneous MN than the control group (p<0.01). After treatment with $H_2O_2$, MN frequencies in the patient group was significantly decreased (p<0.01) although there was no difference between the treated and untreated results of control group (p=0.29). There was also difference (p<0.01) between the MN frequencies of the patient and the control group either in the spontaneous levels or in the $H_2O_2$ treated groups. The same significant difference persisted when the PI values were compared between patient and control groups. Increase in the MN frequency in patients could mean the alterations in the chromosomal structure which may lead to the chromosome instability and therefore genetic susceptibility to cancer. This increased number of micronuclei can also be used for cytological marker in identifying high risk cases for malignant melanoma.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.511-516
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• 2002

Hexagonal $YMnO_3$ thin films were prepared from $Y(NO_3)_3{\cdot}5H_2O$ and $Mn(CH_3CO_2)_2{\cdot}4H_2O$ as starting materials on the Si(100) substrates by the sol-gel method. The crystal structure and the electrical properties of the $YMnO_3$ thin films were investigated as a function of heat treatment temperature, the amount of water(Rw) of hydrolysis and the addition of catalysis. The crystallization of the $YMnO_3$ thin film began at 700${\circ}C$ and completed at 800${\circ}C$ for 1 h. The c-axis (0001) preferred orientation of hexagonal $YMnO_3$ was detected for the $YMnO_3$ thin films with Rw=6 and that was decreased for the $YMnO_3$ thin films with Rw=1 and Rw=12. The crystallinity and preferred orientation of the $YMnO_3$ thin films were depended on the addition of acid and/or alkali catalysis, which, in turn, the preferred orientation of c-axis was decreased and the orthorhombic phase of $YMnO_3$ was detected to the specimens with the addition of catalysis. The $YMnO_3$ thin film with Rw=6 showed good leakage current density of $1.2{\times}10-8 A/cm^2$ at the applied voltage of 0.2V and the leakage current density was not changed drastically with applied voltage.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.29-35
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• 1993

This study was performed to obtain optimal conditions for reduction of color in dye wastewaters using coagulation-sedimentation processes with redox reactions. The reduction of color as well as organic matters variation was observed after coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O and NaOCl. Coagulation-redox reaction was done with the dose of Coagulant and oxidant at various pH values. Redox reaction was done through jar-mixing and aeration. The results of study were as follows: 1. In the coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was heigher at pH 3. With variance of dosage of FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was higher at 250 mg/l. When coagulation-sedimentation using FeSO$_4$ $\cdot$ 7H$_2$O 250 mg/l was added at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 47.6%, 21.3% and 22.1%, respectively. 2. When NaOCI was added at level of 100 ppm in raw wastewater at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 30.2%, 5.5% and 6.2%, respectively. 3. After coagulation-sedimentation processes by addition of FeSO$_4$ $\cdot$ 7H$_2$O, when NaOCl was added at level of 250 mg/l in supernant, color reduction was 47.8% in aeration and 37.5% in jar-mixing. 4. Color reduction by aeration was higher than that by jar-mixing.