• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.9
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• pp.1174-1178
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• 2009

The purpose of this study was to investigate the effect of dietary zinc levels on carbohydrate metabolism and serum zinc, magnesium and chromium contents in obese rats. Animals were divided into three groups by zinc levels, such as low (15 ppm), adequate (30 ppm) and high (60 ppm) levels of dietary zinc. The food intake, weight gain and feed efficiency ratio were not changed by zinc levels. There were no significant differences in liver, kidney and spleen weights. However, serum glucose concentration significantly decreased as the levels of dietary zinc increased, in particular, that of obese rats fed the high level of zinc was remarkably decreased. Insulin concentration of rats fed high level of zinc diet was significantly higher than that in the other groups. However, there were no significant differences in serum zinc and chromium contents, although serum magnesium fed zinc deficient diet was significantly higher than that of the other two groups. Glucose concentrations had negative correlation with insulin concentrations, and positive correlations with serum magnesium content. In conclusion, serum glucose concentrations were decreased and insulin concentrations were increased as the levels of dietary zinc increased in obese rats. These results suggested that zinc supplement at higher level than adequate one would increase insulin concentration and may improve hyperglycemia problem in obese groups.

• Korean Journal of Environmental Agriculture
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• v.19 no.1
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• pp.20-25
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• 2000

Leather processing sludge were amended in sandy loam soil successively to investigate effects on soil properties and radish crop. Total nitrogen concentration of the sludge was $60\;g\;kg^{-1}$, and chromium was $9,048\;mg\;kg^{-1}$. Sludges were treated twice each year for 4 year, and the soils were mixed with sludge to give mixtures equivalent to sludge application rates of 12.5, 25 and $50\;Mg\;ha^{-1}\;yr^{-1}$ in dry matter. Chemical fertilizers $(N-P-K\;:\;280-59-154\;kg\;ha^{-1})$ used as a control. All treated soils were croped to altari and kimjang radish in spring and fall respectively. Organic matter and Cr content in soils were increased with input rate and years of successive application of leather processing sludge, while phosphorous and potassium contents were decreased. Yields of the first harvested altari grown in sludge treated pots were less than control. In the other hand, yields of the first kimjang radish were more than control in proportion with sludge input rates until third year fall. But in fourth year, all sludge treated pot was much less than control in radish yield. Chromium contents of radish in treated soil increased and Cr contents in leaves of radish were higher than roots. Leather processing sludge was considered a potential hazardous resource to soil and crops when it use continuously, because it has high Cr concentration.

• Composites Research
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• v.34 no.5
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• pp.311-316
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• 2021

In this study, TiC/steel metal matrix composites were fabricated by powder metallurgy process using Fealloy powders with 3 wt.% Cr and 10 wt.% Cr, respectively, as matrix material. Subsequently, the composite samples were heat treated by the annealing and quenching-tempering(Q-T), respectively, to understand the effect of heat treatment on the mechanical properties of the composites. The correlation between microstructure and structural strength depending on the chromium content and the heat treatment conditions was studied through tensile, compressive, and transverse rupture test and microstructural analysis. In the case of TiC/steel composite containing 10 wt.% Cr, the tensile strength and transverse rupture strength at room temperature were significantly lowered by the influence of coarse chromium carbide formed at the TiC/steel interface. On the other hand, both TiC/steel composites containing 3 wt.% Cr and 10 wt.% Cr showed much higher compressive strength of about 4 GP after quenching-tempering compared to the annealed specimens regardless of the presence of the chromium carbide.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.1
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• pp.77-84
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• 2024

Four children's cosmetic sets were purchased online, labeled for use from 4 years of age, and 81 components of each were analyzed for lead, cadmium, arsenic, antimony, nickel, cobalt, copper, chromium, and mercury by inductive coupled plasma - mass spectrometry (ICP - MS). The average metal concentrations were as follows: 0.82 ㎍/g for lead, 0.03 ㎍/g for cadmium, 0.97 ㎍/g for arsenic, 0.52 ㎍/g for antimony, 2.32 ㎍/g for nickel and 0.01 ㎍/g for mercury which was lower than the acceptable standards for all products. Higher mean values of lead, antimony, cobalt, and copper were detected in imported than domestic products (p < 0.05). There was a statistically significant difference in the average values of heavy metals according to the type of cosmetics (p < 0.05), with eyeshadow showing the highest mean values of arsenic 2.47 ㎍/g, nickel 6.36 ㎍/g, and chromium 11.06 ㎍/g. and the highest mean concentrations were 1.20 ㎍/g for lead, 1.17 ㎍/g for antimony, and 23.60 ㎍/g for copper in blusher. The levels of cobalt in the 81 children's cosmetics were ND ~ 5.23 ㎍/g, copper were ND ~ 379.61 ㎍/g, and chromium were detected ND ~ 36.95 ㎍/g, respectively. Brown colored cosmetics had the highest mean concentrations of nickel and cobalt. Purple-colored cosmetics had the highest mean concentration of lead and chromium.

• Food Science of Animal Resources
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• v.28 no.2
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• pp.138-145
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• 2008

This study was carried out to compare the meat quality of beef from Hanwoo supplemented with dietary Rhus verniciflua Stokes (RVS) meal, silicate (Si), and chromium-methionine (Cr-Met) during refrigerated storage. The 26 mon-aged Hanwoo steers were fed basal diets containing 4% RVS, 4% RVS+400 ppm Cr-Met, 1.4% $SiO_2$, or 0.14% $SiO_2+400 ppm$ Cr-Met for 4 mon prior to slaughter. The M. longissimus from carcasses were then stored at $4{\pm}0.2^{\circ}C$ for 7 d. The crude fat content was higher in the Si and Si+Cr-Met groups (p<0.05). The water-holding capacity (WHC) and tenderness were highest in the Si+Cr-Met group (p<0.05). With regard to fatty acids, the polyunsaturated fatty acid (PUFA) content was lower in the Si and Si+Cr-Met groups (p<0.05), and the monounsaturated fatty acid (MUFA) content was lowest in the Si+Cr-Met group (p<0.05). The TBARS and MetMb contents were decreased in the Si, Si+Cr-Met, and RVS+Cr-Met groups. Regarding meat color during storage, the Si+Cr-Met group showed the highest L, a, b, C values and total color, and those of the Si and RVS+Cr-Met groups were higher than the RVS group (p<0.05). Consequently, beef from Si-fed Hanwoo had higher fat content, color and oxidation stability, and lower PUFA content than RVS-fed beef. And beef from Si+Cr-Met-fed Hanwoo had higher WHC, tenderness and color stability, and lower MUFA content than Si-fed beef.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.576-584
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• 2020

The extruder screw material is mainly SKD11, but the recent development of synthetic resins have increased the occurrence of chemical corrosion and wear. To solve this issue, high chromium cast iron is needed because of its good abrasion resistance and corrosion resistance, but its use is avoided because of its poor machinability. In this study, to improve the machinability of high chrome cast iron, 0, 0.5, 1.0, 1.5% of nickel, which has excellent workability, was added to high chromium cast iron with a composition of Fe-23Cr-2.5C-1.2Si-1.08Mn-0.48Mo-0.3V, and annealed after casting. Subsequently, the effect of nickel on the machinability and corrosion resistance was analyzed using a turning test and coin polarization test, and compared with SKD11. After casting using a high-frequency vacuum induction furnace, the annealing treatment was performed at 750 ℃ for five hours and then reheated at 1100 ℃ for five hours. A turning test after annealing at 750 ℃ showed that the machinability was improved remarkably when the nickel content was over 1.0%. In the potentiodynamic polarization test in a 5% NaCl solution, the corrosion resistance decreased with increasing nickel content in the as-cast and annealing treatment. On the other hand, after reheating, the corrosion resistance was best with a 1.5% nickel content.

• Journal of Animal Science and Technology
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• v.63 no.6
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• pp.1355-1361
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• 2021

Digestibility of pet food can affect the health of dog, especially of aged animals. To maintain the health of dogs in an overall good status it is necessary to provide nutritionally balanced food. For example, the digestibility of dogs was known to be decreased along aging. In addition, losing teethes is an often event in aged dogs that could induce a problem to eat a large size dry pet food. Nonetheless, few detailed information is available on the most suited feeding for aged dogs. As part of the nutritional study of food for aged dogs, in this study, we tested whether food type impacts on digestibility on adult versus senior dogs. The methodology to measure the digestibility of nutrients was chosen the index method using chromium oxide. Dogs were fed the same commercial dry or wet diets, which were supplemented with 0.5% chromium oxide. The wet food was prepared by adding twice volume of water in the dry food prior to incubated overnight (14-16 hours) at room temperature. After five days, their feces were collected up to a total weight of > 200 g which was the amount to analyze undigested nutrients in feces as 3 repeats. In the apparent total tract digestibility analysis of the experimental breed, no difference in the digestibility of crude protein, crude fat, crude fiber, ash, and energy was observed regarding the moisture content of the food. Noteworthy, the digestibility of nitrogen free extract was significantly increased in senior dogs fed dry dog food compared with adult dogs fed the same diet, whereas no difference was observed between senior and adult dogs fed wet food. The small breed dogs showed similar results to the experimental breed dogs. However, the digestibility of crude fat was additionally affected by age and food type unlike the experimental breed dogs. This finding suggests that the food moisture content affects the digestibility of nutrients in dogs with aging. Hence, it may be helpful to determine the nutrient contents in foods for senior dogs depending on the food type.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.101-109
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• 2004

The influences of solidification rates and carbon contents on the formation of the $\delta$-ferrite were studied by directional solidification in modified 12%Cr-l %Mo steels. Directional solidification experimental results showed that solidification microstructure depended on solidification rate and carbon content and chromium equivalent. The length of the mushy zone increased and the dendrite arm spacings decreased as the solidification rate increased. The volume fraction of the 8-ferrite decreased with increasing the solidification rate and carbon content. The volume fraction of the ferrite showed much higher at low solidification rates with planar and cellular interfaces than that at high solidification rates with dendritic interface. It is expected that macro-segregation of C causes lower C content at the lower solidification fraction in the directionally solidified sample, where lower C results in higher volume fraction of the ferrite. In order to estimate solidification microstructure in modified 12Cr-l%Mo steels, various solidification conditions, such as solidification rate, cooling rate, segregation, alloy composition, should be considered.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.56-56
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• 2001

Ni-W alloy deposit is one of the best alternatives to hard chromium plating because of its good mechanical properties (high hardness, high strength, and good wear resistance). Ni-W alloy is deposited from weakly acidic or alkaline electrolytic bath with nickel sulfate, sodium tungstate or APT, and some kinds of organic hydroxy-acid complex and ammonia salts. W content of the deposit can be changed from 0 to 5Owt% and the coating with high W content is more attracted. But, meanwhile, the deposited layers are always found high internal stress, which cause them to become brittle and to bond insufficiently with the substrate. On the second hand, as the W content is incresed, the current efficiency reduced, which results in large quantities of hydrogen evolution and then produces bubbles on surface and pitting appearance In this paper, the influence of some additives on Ni-W alloy electroplating was investigated by means of compositional analysis and SEM. The initial results showed that 2-butyne-1,4-diol was the best brightener for Ni-W plating process. It could brighten and level deposit, but decreased the cathodic current efficiency. Its optimum concentration range is from O.lgjL to 0.5gjL. Besides, three kinds of additives including 2-butyne-1,4-diol were examined with Dagguchi method.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.161-175
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• 2008

The soil developed from volcanic ash in Jeju Island, Korea, were classified as typical Andisols. The soils had acidic pH, high water contents, high organic matters and clay-silty textures. The crystalline minerals of the samples were mainly composed of ferromagnesian minerals such as olivine and pyroxene, and iron oxides such as magnetite and hematite derived from basaltic materials. A large amount of gibbsite was found at the subsurface horizon as a secondary product from the migration of excessive aluminum. In addition, our study has shown that considerable amounts of poorly ordered minerals like allophane and ferrihydrite were present in Jeju soils. The contents of $SiO_2$ were lower than those of other soil orders, but $A1_2O_3$ and $Fe_2O_3$ contents were higher. These results are some of the important chemical properties of Andisols. The contents of heavy metals were in the range of $84{\sim}198$ for Zn, $56{\sim}414$ for Ni, $38{\sim}150$ for Co, $132{\sim}1164\;mg\;kg^{-1}$ for Cr, which are higher than the worldwide values in most of the soils. Some soil samples contained relatively high levels of Cr exceeding 1000 mg/kg. Mean reduction capacity of the Jeju soils was $6.53\;mg\;L^{-1}$ reduced Cr(VI), 5.1 times higher than that of the non-volcanic ash soils from inland of Korea. The soil reduction capacity of the inland soils had a good correlation with total carbon content (R = 0.90). However, in spite of 20 times higher total carbon contents in the Jeju soils, there was a week negative correlation between the reduction capacity and the carbon content (R = -0.469), suggesting that the reduction capacity of Jeju soils is not mainly controlled by the carbon content and affected by other soil properties. Correlations of the reduction capacity with major elements showed that Al and Fe were closely connected with the reduction capacity in Jeju soil (R = 0.793; R = 0.626 respectively). Moreover, the amounts of Ni, Co and Cr had considerable correlations with the reduction capacity (R = 0.538; R = 0.647; R = 0.468 respectively). In particular, in relation to the behavior of redox-sensitive Cr, the oxidation of the trivalent chromium to mobile and toxic hexavalent chromium can be restricted by the high reduction capacity in Jeju soil. The factors controlling the reduction capacity in Jeju soils may have a close relation with the andic soil properties explained by the presence of considerable allophane and ferrihydrite in the soils.