• Environmental Engineering Research
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• v.20 no.3
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• pp.230-236
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• 2015

26 multi-regional water treatment plants (WTPs) were investigated, to determine the characteristics of manganese (Mn) concentration and removal in Korea. Mn concentrations of raw water in most WTPs were higher than the drinking water standard (i.e., 0.05 mg/L); thus, proper removal of Mn at the WTPs is needed. Mn concentration was generally higher in lakes than rivers due to seasonal lake turnovers. The Mn concentrations of treated water at 26 WTPs in 2012 were less than 0.05 mg/L, due to strict law enforcement and water treatment processes optimization. However, before 2010, those concentrations were more than 0.05 mg/L, which could have led to an accumulation of Mn oxides in the distribution system. This could be one of the main reasons for black water occurrence. Therefore, regular monitoring of Mn concentration in the distribution system, flushing, and proper Mn removal at WTPs are needed, to supply clean and palatable tap water.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.294-301
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• 2021

In the present study, we investigate the effects of long-term heat treatment at elevated temperatures on the mechanical softening of the Mn-Mo-Ni low-alloy steel. The influence of long-term heat treatment on microstructure and mechanical strength was evaluated. To simulate the long-term material degradation, heat treatment test was interrupted at several stages up to 10,000 hours in an electric furnace. The Mn-Mo-Ni low-alloy steel shows a typical bainitic phase, which consists of a well-developed lath substructure with fine precipitates along the lath boundaries. However, these fine precipitates were redissolved into the matrix with long-term heat treatment, and then the lath substructures were recovered. Consequently, ultimate tensile strength and yield strength decreased during long-term heat treatment showing a mechanical softening phenomenon.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.66-71
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• 2000

The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.

• The Korean Journal of Ecology
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• v.25 no.5
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• pp.349-352
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• 2002

The effects of Mn on growth and nutrient status of Pinus densiflora seedlings grown in a nutrient culture solution were investigated. Mn concentrations was added as manganese chloride at 0, 30 and 60ppm to the nutrient culture solution. The 2-year-old seedlings were transplanted into the solution maintained at pH 4.0, and grown for 90 days in a greenhouse. The Mn treatment induced a significant reduction in the dry weight growth of the seedlings. The relative growth rate(RGR) and net assimilation rate(NAR) of the seedlings decreased with increasing Mn concentrations in the nutrient culture solutions. For the nutrient status of the seedlings, Ca and Mg content in trunk and root was least in 60ppm Mn treatment, and Mn content in needle was about 3 times more than in root. Also the net photosynthetic rate of the seedlings was significantly lower both in 30ppm and 60ppm Mn treatment compared to them in 0ppm. This result suggests that the reductions in the RGR and NAR of the seedlings may be resulted from the inhibition of net photosynthesis by the mixed effect of lower nutrient uptake of roots and excess accumulation of Mn in needle.

• Development and Reproduction
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• v.13 no.4
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• pp.321-327
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• 2009

This study aimed to examine the testis toxicities of metal compound, manganese (Mn), which may be generated as mist or fume in the industrial sites. As well as serum prolactin (PRL) concentration was analyzed because Mn accumulation in basal ganglia up-regulates serum PRL and hyperprolactinemia consecutively induces the testis toxicity. Male F344 rats were divided into the 4 groups (2 controls and 2 Mn treated groups, n=10) on the basis of the test condition (inhalation, Mn $1.5mg/m^3$ or not) and treatment period (for 4-weeks and 13-weeks). The treatment time was 6 hr. a day, 5 days a week for the whole body. Basic tests including changes in body weight, feed rate were observed. Blood and testis Mn concentration, and testis toxicity test such as the number and deformity test of sperm were also observed. Serum PRL level was analyzed by ELISA to certify the relationship between the Mn induced increase of the serum PRL level and sperm production. Blood and testis Mn concentrations were significantly and dose-dependently increased. Sperm count was decreased in Mn-treatment groups than control in a treatment time dependent manner. Morphological analysis of cauda epidydimal sperm showed that the frequencies of morphologically abnormal sperms such as bent tail and small head were increased in the both Mn-treatment groups than control. A significant increase in serum PRL levels was found in response to Mn treatment but it was not hyperprolactinemia range. These results suggest that treatment of Mn up-regulates the serum PRL concentration and induces the testis toxicity. The No Aversed Effect Level (NOAEL) of inhaled Mn on the male rat testis may be under the $1.5mg/m^3$.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.1
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• pp.35-45
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• 1998

The effects of alloying elements and the conditions of reverse transformation studied treatment on the formation of retained austenite in 0.15C-6%Mn-(Ti, Nb) steels has been studied. The addition of Ti and Nb to 0.15C-6%Mn steel shows no effect on the formation of retained austenite. In case of reverse transformation treatment at various temperatures, the shape of retained austenite was lath type, growing toward the longitudinal and thickness direction with increasing the heat treatment temperatures. The retained austenite formed by the reverse transformation treatment at higher temperature has a lot of stacking faults induced by the internal stress. The retained austenite was stabilized chemically by enrichment of C and Mn in the vicinity of a untransformed austenite and the chemical stability of retained austenite was decreased with increasing the heat treatment temperature and the holding time. It was effective to heat treat at $650^{\circ}C$ in order to obtain over 30vol.% of retained austenite, but more desirable to heat treat at $625^{\circ}C$ for a long time, considering the amount and quality of retained austenite.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.74-82
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• 2001

The effects of Al and Mn concentration on dry weight growth, nutrient status and gas exchange rates of 2-Year-old Japanese red pine(Pinus densiflora) seedlings grown in a nutrient culture solution were investigated. Al was added as aluminum chloride at 0, 10, 30 or 60ppm, and Mn was added as manganese chloride at 0, 30 or 60ppm to the nutrient culture solution. The pH of the solution was maintained at 4.0 by adding HCl or NaOH solution. The seedlings were transplanted into the nutrient culture solution, then they were grown in a greenhouse for 90 days. The interactive effects of Al and Mn on the dry weight growth of the seedlings were not significant. There were a main effect of Al or Mn on the dry weight growth and element concentrations of the seedlings. The treatment with Al of ${\geq}10ppm$ or that with Mn of 60ppm induced a significant reduction in the dry weight growth, which indicates that the effect of Al is stronger than that of Mn. The chlorophyll content of needles was not affected by Al treatment, but was significantly reduced by treatment with Mn of 60ppm. Furthermore, the treatment with Al of 60ppm or that with Mn of ${\geq}30ppm$ caused a significant reduction in the dark respiration rate of the roots. The net photosynthetic rate of the seedlings reduced with increasing the concentration of Al or Mn in the nutrient culture solution, which suggests that Al or Mn induced reductions in the relative growth rate(RGR) and net assimilation rate(NAR) of the seedlings were mainly due to the decrease of net photosynthesis.

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.24-29
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• 2002

It was observed that exchange bias field was increased with smooth surface and better ${\gamma}$-FeMn formation. Sputtering conditions were varied for the control of the surface roughness and ${\gamma}$-FeMn formation. From the results of Cu deposition as underlayer, it was found that ${\gamma}$-FeMn formation was closely related with the thickness of underlayer. After heat treatment, exchange bias field was increased over three times. This improvement was likely that the crystallites of ${\gamma}$-FeMn were well formed. In Co/Cu/Co/FeMn spin valve structure, magnetoresistance was increased over 1.4 times through the heat treatment. This was due to the disappearance of Co/Cu intermixed dead layer and removal of defect, and this was examined by AES analysis.

• Journal of Animal Environmental Science
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• v.18 no.sup
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• pp.13-20
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• 2012

This research investigated the effect of $SCOD_{Mn}$ concentrations and pH adjustment at the stage before land application, namely 2nd-aeration treatment stage of liquid fertilizer in the liquid fertilizer treatment process of swine manure on the physicochemical compositions of 2nd-aeration treated liquid fertilizer. The liquid fertilizer used in this research is the alkaline fermented liquid fertilizer of swine manure more than pH 9.0 through aeration treatment (Alkaline fermentation treatment group). About the alkaline liquid fertilizer, phosphate neutralization treatment was conducted with phosphoric acid and it was a phosphate neutralization treatment group. In 2nd-aeration treatment of liquid fertilizer for 30 days, each group was divided into alkaline treatment groups (T-1, T-2, and T-3) and phosphate neutralization treatment groups (T-4, T-5, and T-6) according to early $SCOD_{Mn}$ concentrations. The research results are as follows. 1. As for $SCOD_{Mn}$ reduction rate, the average 29.9% in alkaline treatment groups and the average 36.9% in phosphate neutralization treatment groups were shown and so the relatively high reduction rate was shown in phosphate neutralization treatment groups. 2. After finishing the experiment, the group of the lowest $SCOD_{Mn}$ concentrations was the phosphate neutralization treatment group, T-6 with the lowest inflow concentrations. In case the final goal level of 2nd-aeration treated liquid fertilizer is assumed as concentrations less than $SCOD_{Mn}$ 3,000 ppm, it would be desired that inflow concentrations of 2nd-aeration treatment groups are adjusted less than $SCOD_{Mn}$ 5,500 ppm. 3. As for the persistence rate of nitrogen, the average 29.3% in alkaline treatment groups and the average 38.9% in phosphate neutralization treatment groups were shown and so phosphate neutralization treatment groups showed the relatively low loss rate of nitrogen, meanwhile, in the case of T-P, phosphate neutralization treatment groups maintained high concentrations (average 1,473 ppm). 4. In the event of 2nd-aeration treatment of liquid fertilizer, "alkaline fermentation treatment" condition in 'low phosphate-low nitrogen' type and "phosphate neutralization treatment" condition in 'high phosphate-high nitrogen' type are expected to be favorable.

• Microbiology and Biotechnology Letters
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• v.23 no.6
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• pp.755-762
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• 1995

A phenolic resin industrial wastewater containing about 41,000 mg/l of phenol and 2,800 mg/l of formaldehyde was biologically treated by a mixed culture GE2 immobilized on ceramic beads. This study was carried out with three experimental groups : Control-only added the sludge of papermill wastewater ; GE2 treatment-added GE2 to Control ; Ceramic treatment-applied ceramic carrier to GE2 treatment. When the original wastewater was diluted 80 times with aerated tap-water, influent COD$_{Mn}$ WaS 1,140 mg/l and that of the effluent was in the range of 22-35 mg/l, which was not much different among the experimental groups. However, at 20-times dilution, influent COD$_{Mn}$ was 4,800 mg/l and the effluent COD$_{Mn}$ of Control, GE2 treatment and Ceramic treatment was 179, 128 and 94 mg/l, respectively. COD$_{Mn}$, removal efficiency by Ceramic treatment was the highest, at 98.0%. At this time, the effluent phenol concentration of Control, GE2 treatment and Ceramic treatment was 10.71, 7.93 and 5.60, respectively. As the dilution times decreased, the removal efficiency of COD$_{Mn}$ and phenol did not change much, but COD$_{Mn}$ and phenol concentration of the effluent increased. Consequently, it is likely that the phenolic industrial wastewater containing phenol and formaldehyde can be biologically treated using a GE2 and ceramic carrier and that at 40-times dilution, the effluent completely meets the effluent standards for industrial wastewater treatment plant.