• 한국기계연구소 소보
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• s.9
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• pp.83-93
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• 1982

The influence of different heat treatment conditions on microstructure, mechanical and fatigue properties of Spheroidal Graphite cast Iron with 0.4-0.6% Mn was investigated. 1) Maximum tensile strength was arrived by tempering at about $450^{\circ}C$after quenching. Tempering at higher than $600^{\circ}C$ was changed martensitic structure to ferritic structure and secondary graphites were precipitated. 2) The relationship between matrix hardness and total hardness of the specimens are as following. [HB]$T$=0.7[HB] [HB]$M$+35 Maximum tensile strength was arrived at the total hardness of HB400-450. 3) Endurance ratio decreases with increasing total hardness, and fatigue limits can be presumed from as following. $\sigmaf$=$\sigmat$

• Journal of Sericultural and Entomological Science
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• v.31 no.2
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• pp.121-126
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• 1989

Two kinds of solution for the measurement of solubilities of Sericin are prepared as followings at temperature 90 deg. C. One has the total carbonate concentration as 0, 50, 100mg CO2/l prepared with non-carbonate distilled water, sodium hydrogen carbonate and 0.1N HCI and NaOH, the other has total hardness, that is, calcium hardness or magnesium hardness as 0, 20, 50, 100mg CaCO2/l respectively prepared with non-carbonate distilled water, calcium carbonate and magnesium oxide. Solubilities of Cocoon layer Sericin at above solution gives following results ; 1. pH shows little effect on the solubility of Sericin at the non-carbonate solution but at the carbonate solution pH shows a sensitive effect on the solubility of Sericin. These means that pH controls the concentration of H2CO3, HCO3-and CO32- which prevent and promote the solution of Sericin. 2. After the cocoon layer treatment at the solution, the initial pH of 4.0, 7.0, 9.0 of the solution changed to 6.0-6.5 at the lower total carbonate solution. However in the higher total carbonate solution pH did not changed very much. This may be explained by the buffer action of carbonate. 3. The effect of the hardness on the solubility of Sericin was not found in the non-carbonate solution with the standard hardness after treatment of cocoon layer.

• Journal of Food Hygiene and Safety
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• v.9 no.4
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• pp.229-235
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• 1994

It is very important to investigate the sanitary chemical conditions of farmwaters used for cattle breeding in the dairy farms. For this purpose we examined pH, KMnO4 consumption, total hardness, chloride, sulfate, NH3-N, NO3-N, fluoride, lead, iron, manganese, cadmium, copper, zinc and chrome in the farmwaters sampled 2 times(spring and summer)in Choongcheongnam and Kangwon Province. The pH of farmwaters in Choongcheongnam and Kangwon Province was 6.49$\pm$0.09, 6.70$\pm$0.06, total hardness 90.21$\pm$7.07, 64.53$\pm$6.38 mg/ι, consumption of KMnO4 4.13$\pm$0.62, 4.34$\pm$0.26mg/ι, NO3-N 6.51$\pm$0.55, 3.61$\pm$0.58 mg/ι, chloride ion 20.51$\pm$1.99, 5.41$\pm$1.36 mg/ι and sulfate ion 6.61$\pm$1.02, 7.28$\pm$1.30 mg/ι, respectively. But NH3-N was scarcely detected. Fluoride, iron, lead, cadmium, zinc, manganese and chrome were not detected from the tested farmwaters. There was high significance between each other in total hardness, NO3-N, chloride ion and sulfate ion. There was regional and seasonal significance in only NO3-N but only regional significance in total hardness and chloride ion.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.22-28
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• 1993

In order to investigate the hygienic chemical conditions of farm waters used as the potable and cleaning water for cow, we examined the pH, turbidity, KMnO$_4$ consumption, total hardness, chlorine, sulfate, NH$_3$-N, NO$_3$-N, lead, maganese, copper, zinc, fluoride and chrome for 78 farm waters around Kyunggi Province. Of 78 farm waters tested, average pH was 6.70+_0.06, turbidity 0.724 $\pm$ 0.081, KMnO$_4$ consumption 4.200 $\pm$ 0.256 mg/l, total hardness 107.46 $\pm$ 6.90 mg/l, NH$_3$-N 0.043 $\pm$ 0.037 mg/l, NO$_3$-N 8.096 $\pm$ 0.652 mg/l, chlorine 21.414 $\pm$ 2.187 mg/l, sulfate 12.737 $\pm$ 1.511 mg/l, lead 0.076 $\pm$ 0.001 mg/l, manganese 0.029 $\pm$ 0.004 mg/l, copper 0.018 $\pm$ 0.002 mg/l, zinc 0.055 $\pm$ 0.005 mg/l, chrome 0.048 $\pm$ 0.002 mg/l and fluorine 0.011 $\pm$ 0.001 mg/l. According to the geological characteristics, the concentrations of total hardness, NO$_3$-N, pH and chlorine in farm waters of Hwasung gun were higher than those in Yangpyung and Kwangju gun. In hygienic chemical items tested, there were high significanc among NO$_3$-N, total hardness, sulfate and chlorine. KMnO$_4$ consumption was significant with NH$_3$-N, sulfate and pH. But in heavy metals, there were significance between lead and copper, copper and chrome, and copper and fluorine.

• Journal of Aquaculture
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• v.15 no.1
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• pp.49-60
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• 2002

Research on practices for improving water quality in channel catfish Ictalurus punctatus ponds was conducted at the Auburn University Fisheries Research Station, Auburn, Alabama, in 1998 and 1999. The objective of this two-year study was to determine better management practices to enhance water quality and improve production efficiency. In the first year, oxidation of bottom soil by drying, tilling, and applying sodium nitrate was performed (dry-till and dry-till with sodium nitrate treatments). The second year, based on the results obtained during the first year, precipitation of phosphorus (P) from water by applying gypsum was compared to the dry-till treatment (dry-till and dry-till with gypsum treatments). Control ponds were not subjected to bottom drying, tilling, sodium nitrate, or gypsum treatment. Channel catfish fingerings were stocked at 15,000/ha. In the first year, water in ponds from dry-till and dry-till with sodium nitrate treatments had lower concentrations (P < 0.01) of soluble reactive P, nitrate ($NO_{3} ^{-}) and nitrite ($NO_{2} ^{-}) nitrogen (N), total ammonia ($NH_3$) nitrogen, total suspended solids and turbidity, and higher values of pH, Secchi disk visibility, total alkalinity, total hardness, and calcium ($Ca^{2+}) hardness than water in control ponds. Ponds of the dry-till treatment also had lower concentrations (P < 0.01) of total P and total N than control ponds. Total fish production and survival rate did not differ among the treatments (P > 0.05). The findings suggested that drying and tiling pond bosoms between crops could achieve water quality improvement. Applying sodium nitrate to dry, tilled pond bosoms did not provide water quality improvement. In the second year, the treatment with the best results from the first year, dry-till, was compared with a dry-till with gypsum treatment. Enough gypsum was applied to give a total hardness of about 200 mg/L, and gypsum was reapplied as needed to maintain the hardness. Compared to the control, dry-till and dry-till with gypsum treatments had lower concentrations (P < 0.01) of total and soluble reactive P, total N, and total $NH_3$-N, and higher concentrations (P < 0.01) of dissolved oxygen. Ponds of the duty-till with gypsum treatment also had lower concentrations (P < 0.01) of chlorophyll $\alpha$, chemical oxygen demand, and total alkalinity than the control. Total fish production and survival rate did not differ (P > 0.05) among the treatments. These findings suggest that drying and tilling pond bosoms between crops and treating low hardness waters with gypsum could achieve water Quality improvement.

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.545-550
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• 2001

Effects of high hydrostatic pressure on pH, titratable acidity, color, hardness and microorganisms of Chinese Cabbage Kimchi were investigated. Kimchi was pressurized at $200{\sim}600$ MPa for 5 min. There were no significant differences in color and hardness between control and pressurized Kimchi (p>0.05). Total aerobes and lactic acid bacteria were effectively inactivated by high hydrostatic pressure above 400 MPa. Changes in pH, titratable acidity, color, hardness and microbial counts for 4 weeks storage of Kimchi were investigated Kimchi was pressurized at 400 MPa for 5 min and stored at $4^{\circ}C$. The pH of control decreased to 3.94 but pressurized Kimchi maintained its initial pH value throughout the storage. The color of control showed significantly low values compared with pressureized Kimchi (p<0.05), but hardness was not significantly changed (p>0.05). Total aerobes and lactic acid bacteria in the control were reduced from the initial value of $10^8{\sim}10^9$ CFU/mL to $10^6$CFU/mL after 4 weeks storage. Whereas microbial counts in pressurized Kimchi was maintained about $10^3{\sim}10^4$ CFU/mL during storage.

• Journal of Sericultural and Entomological Science
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• v.15 no.2
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• pp.45-53
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• 1973

1. The sericin solubility increased rapidly as the increase of water M-alkalinity. 2. The acidity of the treated water was nutralized at the over 25ppm of M-alkalinity. 3. The more M-alkalinity of the sample water is, the more M-alkalinity was found after cocoon treat. 4. The total hardness of sample water seemed to be droped as M-alkalinity increased. 5. The sericin solubility also seemed to be droped as the increase of water acidity. 6. In case of treat finish with cocoon, the acidity and total hardness seemed to increase as the acidity of the water increased, but M-alkalinity was nutralized at 20~40 ppm of water acidity or the M-alkalinity could not be found in case over 40ppm of acidity. 7. In case increase of iron component with sample water, sericin solubility seemed to drop down, and mangan component showed the same nature but dull drop. 8. After cocoon was treated with water, acidity, M-alkalinity and total hardness were increased by the extraction from cocoon shell because of pH and treating temperature but not because of iron componnent. Mangan component, however, affected as to increase of acidity and total hardness but to decrease for M-alkalinity. 9. In case change of M-alkalinity and total hardness, sericin solubility has increased also. 10. In case constant pH and total hardness, the more M-alkalinity is, the more sericin solubility was found. 11. In case constant pH, total hardness, and M-alkalinity, the more acidity is, the less sericin solubility was found. 12. In case constant pH(6.8) and M-alkalinity, the more total hardness is, the less sericin solubility was found. 13. Though the combination of water, high solubility water, medium solubility water and low solubility water were prepared. The high solubility water desolved sericin 2.2% more than low solubility water. And the medium solubility water desolved sericin as much as 2.4~2.9%. 14. It was found that the most important factors for filature water are pH, M-alkalinity, acidity and total hardness which may need more words for optimum filature water development. 15. In case of repeat use of water, the buffer action of water has increased so that the sericin solubility to be decreased.

• Restorative Dentistry and Endodontics
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• v.2 no.1
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• pp.38-49
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• 1976

Central and lateral incisors of 20, 40 and 60 age groups were bisected pararelly to long axis and middle portion of mesio-distal of teeth. And author measured the hardness of various areas in enamel and dentin with vickers hardness tester. Measured levels were divided into the labio-middle portion, middle portion of incisal edge and linguo-middle portion in enamel and dentin of all age groups. The results were as follows; 1) Total average hardness of enamel for 20, 40 and 60 age groups were respectively Hv. 366.5${\pm}$5.75, Hv. 372.9${\pm}$8.16 and Hv. 389.8${\pm}$10.27. 2) Total average hardness of dentin for 20, 40 and 60 age groups were respectively Hv. 51.0${\pm}$2.14, Hv. 54.0${\pm}$1.87 and Hv. 55.3${\pm}$2.23. 3) Total microhardness values in enamel and dentin of 60 age group was highered than 20 and 40 age groups. 4) The hardness values of enamel and dentin in all age groups were detected lower value on the middle portion of incisal edge than the labio-middle portion and linguo-middle portion. 5) Microhardness values of enamel was highered gradually from the dentinoenamel junction to the outer surface and it lowered at the outermost surface in all age groups. The microhardness values of dentin were the highest values at 600${\mu}$ from dentino-enamel junction and the lowest values at near the pulp chamber in all age groups.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.101-106
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• 1982

This study was undertaken to determine tensile properties and low-cycle fatigue behavior of 0.6%C high carbon steel used of structural purposes at temperatures up to 500.deg.C. In the low-cycle fatigue test the upper limit was decided by elongation(i.e. the total strain range), while the lower limit was defined by the load (i.e. zero load). The following results were obtained. Both, the ultimate tensile strength and low-cycle fatigue resistance attain the maximum values near 250.deg.C. Above this temperature the values decrease rapidly as the temperature increases. The low-cycle fatigue resistance decreases whenever there is an increase of the total strain range. Because the hardness of cycle fatigued specimen correlates cyclic hardening and cyclic softening, therefore the hardness of cycle fatigued specimen is smaller than that of the nonfatigued specimen at room temperature and 500.deg.C but much larger than the hardness of the nonfatigued specimen near 250.deg.C.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.461-466
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• 1998

One hundred and thirty two ground water samples from the Usan area were divided into urban and non-urban groupings and were assessed between 1993 and 1996. The results of statistical analysis were as follows: There were significant differences between the two groupings in the average value of the following water quality parameters: total hardness, nitrate , pH, iron, ammonia and chloride ion in the order of Z-score . Because total hardness, nitrate, and pH were also significant in ANOVA test, these three parameters can be regarded as the most sensitive parameters of artirial pollutants. By the comprehensive com- parison of Ulsan water Quality to that of Kangwon-do, all of the major parameters(pH, KMnO4 consumption, sulfate, chloride and hardness except nitrated were confirmed as being significantly Increased levels.