• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.1
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• pp.7-12
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• 1997

This study was intended to investigate the proper shape and size of calcium carbonate for the improvement of paper properties and its end use performance. We loaded calcium carbonate of various shapes and size in the handsheet and measured their physical and optical properties. Results obtained from the study are summarized as follows : 1. Due to different particle shapes and sizes, precipitated calcium carbonate (PCC) contributed greater to bulk improvement than ground calcium carbonate (GCC). Scalenohedral form of PCC produced the bulkiest sheet, GCC made the sheet bulkier as average particle size increases. 2. Tensile strength increased as average particle size was increasing. GCC kept tensile strength more effectively than PCC. The effect of particle size on tensile strength was much more pronounced as filler addition level was increasing. 3. Over the average particle size of 6.99$\mu$m, GCC gave much higher burst strength and internal bond than PCC did. In the filler levels of 20% and 30%, GCC by using bigger size fillers showed 50~100% improvement in some cases than PCC at the same filler content. 4. Tear strength increased as average particle size was increasing. At the filler level of 30%, PCC decreased tear greatly. 5. Over the average particle size of 13.56$\mu$m, GCC kept bending stiffness greater than PCC. Due to its shape, Scalenohedral form of PCC showed higher stiffness than others at the same particle size. 6. Cubic and acicular form of PCC improved light scattering coefficient very effectively. Light scattering coefficient of GCC decreased as average particle size increased. 7. Both of particle shape and size of filler were important factor in developing optical properties and bending stiffness. Particle size was the only important factor in developing other strength properties

• The Korean Journal of Community Living Science
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• v.13 no.2
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• pp.53-61
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• 2002

This study is to find out how the 4 types of calcium salt such as calcium carbonate, calcium phosphate, calcium lactate and calcium citrate in soy protein diet, the vegetable protein source, affect the calcium utilization in the body. To do so, calcium, phosphate and creatinine concentration and ALP activity in blood as well as the content of calcium and ash, the length, weight strength, and the calcium utilization in the bone were measured. Four groups of Sprague-Dawley male rats with the weight of around 180g were fed for 3 weeks with the experimental diet. Each group was fed with the isolated soy protein containing 14% of the diet and the above mentioned 4 types of calcium salt as the calcium source. The results are as follows; 1. There were no differences of the feed intake, weight gain, and feed efficiency among groups. 2. ALP activity in blood was sinificantly high in calcium lactate group(P<0.05), but there were no differences of concentration of calcium, phosphates, and creatinine in blood among groups. 3. The weight, calcium content, calcium ratio in ash and the strength of bone were low when calcium lactate was provided(P<0.05). 4. The content of calcium in the liver was high in calcium lactate group and calcium citrate group(P<.0.05). 5. The exceretion of feces was low in calcium lactate group(P<0.05) and the excretion of urine was also relatively low. In addition, the ratio of absorption and the retention of calcium were high(P<0.05). In summary, out of four types of calcium salt such as calcium carbontate, calcium phosphate, calcium lactate and calcium citrate when calcium lactate was provided the ALP activity in blood was high and the weight, calcium content, calcium ratio in ash and the strength of bone were low. In calcium utilization, the ratio of absorption and retention of calcium were high, however it has lower effect than 3 other calcium types in improving weight, the content of calcium and the strength of bone.

• Korean Journal of Veterinary Research
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• v.21 no.1
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• pp.51-58
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• 1981

Two experiments were conducted to establish a program for the prevention of swine parakeratosis occurred recently in Korea. In the first experiment, 11 rations which were considered to be related clinico-pathologically to the incidence of parakeratosis and 5 rations not to be related were collected at farms during the period from June, 1979 to December, 1980. In addition, 23 commercial rations and 10 ingredients were also collected at feed dealers or farms. The feed samples were analyzed for calcium, zinc and unsaturated fatty acid. In the second experiment, the efficiencies of adding zinc carbonate (150mg/kg diet) with or without soybean oil (5ml/kg diet) to two control rations were tested using 20 weanling pigs. One of the control rations had low zinc (41mg/kg) and normal calcium (0.64%) and the other low zinc (57mg/kg) and high calcium (1.42%). The results obtained are as follow: 1. Content of zinc in the rations induced parakeratosis ranged from 35 to 80mg/kg with a mean of 49mg/kg; whereas those of rations not induced ranged from 97 to 182mg/kg with a mean of 182mg/kg. The difference between two means was highly significant (p<0.01). 2. The calcium content in rations related to parakeratosis was ranged from 0.56 to 1.80% with a mean of 1.30% whereas that of not related was ranged from 0.63 to 1.37% with a mean of 1.07%. The highly significant difference of calcium content between two rations were recognized (p<0.01). The calcium contents of both rations were markedly higher than that of generally recommended value of 0.40~0.80%. 3. The contents of unsaturated fatty acid in induced rations was a mean of 4.42% and it was significantly lower (p<0.01) compared with those in not induced rations with a mean of 6.70%. The content of unsaturated fatty acid of commercial rations was ranged from 5.25 to 7.81% with a mean of 6.29%. 4. Zinc content of 15 commercial ration samples among 23 were less than 97mg/kg and 21 rations contained more than 1.03% of calcium. 5. Addition of zinc carbonate to the two control rations which are low in zinc content or high in calcium content were resulted in preventive effect on the incidence of swine parakeratosis. 6. It may be concluded that the incidence of swine parakeratosis was closely related to the low zinc, excess calcium and low unsaturated fatty acid in rations, most of the commercial rations contained low in zinc and high in calcium as compared with the recommended contents. Content of Unsaturated fatty acids in the commercial rations, however, were sufficient for the prevention of parakeratosis in swine.

• Elastomers and Composites
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• v.57 no.3
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• pp.107-113
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• 2022

The effects of fillers [talc, calcium carbonate, glass fiber, and EBR (ethylene-butene rubber)] on the shrinkage and mechanical properties of injection-molded polypropylene composites were investigated. The shrinkage correlated with the shape of the filler particles: at the same amount added, glass fibers with a large aspect ratio had the greatest effect on the shrinkage of polypropylene composites, followed by flake-shaped talc and granular calcium carbonate. It was confirmed that the addition of EBR rubber as an impact strength modifier reduced shrinkage proportionally to the added content. In addition, the addition of glass fiber resulted in the greatest increases in tensile and flexural strengths.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.315-320
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• 1996

In this paper, we investigated the retention amounts(ash contents) according to the addition amounts of retention aid and calcium carbonate and compared the mechanical and optical properties of sheets under the same ash content. As the addition amounts of retention aid increase, the retention of calcium carbonate, that is, ash contents of sheets increase in all retention system. In this case, the sheets included ash content as already expected is produced by adjusting the addition amounts of retention aid and calcium carbonate. Tensile index, burst index, tear index, internal bonding strength of sheets straightly decrease as the ash content of sheets increases. Especially, in the same ash content, all sorts of strength are high in compozil system, low in dual polymer system. Opacity increases along with according to the increase of ash content, and is high in hydrocol system, the worst in dual polymer system. In equal opacity, the strength of paper decreases compozil, hydrocol, and dual polymer system in order. But to judge she superiority or inferiority of retention aids, it should consider the various factors such as the optimum production and process conditions besides the retention amounts of filler and the sheet strength.

• Preventive Nutrition and Food Science
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• v.12 no.4
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• pp.217-221
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• 2007

Within the elderly population, the use of calcium supplements and the intake of calcium from food are on the rise in order to maintain health. Calcium is absorbed as an ion in vivo, leading to speculation that absorption efficiency is affected by the solubility of the calcium consumed. In our study, the bioavailability of two types of calcium supplements with different solubilities was evaluated. Experimental animals were fed water-soluble or insoluble calcium supplements for 6 weeks. We found that blood alkali phosphatase activity, osteocalcin content, and urine crosslinks values were not different between the groups. Similarly, the degree of apparent calcium absorption between the two calcium supplements was not significantly different. The bone mineral density and bone mineral content of the femur and the tibia increased in the group that consumed insoluble calcium compared with those of the water-soluble calcium supplemented group. However, when considering body weight, the bone mineral density value for all areas, including the spine, was significantly higher in the group that consumed the water-soluble calcium supplement.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.347-359
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• 2023

With the development of infrastructure, there is a critical shortage of filling materials all over the word. However, a large amount of silt accumulated in the lower reaches of the Yellow River is treated as waste every year, which will cause environmental pollution and waste of resources. Microbial induced calcium carbonate precipitation (MICP) technology, with the advantage of efficient, economical and environmentally friendly protection, is selected to solidify the abandoned Yellow River silt with poor mechanical properties into high-quality filling material in this paper. Based on unconfined compressive strength (UCS) test, determination of calcium carbonate (CaCO₃) content and scanning electron microscope (SEM) test, the effects of cementation solution concentration, treatment times and relative density on the solidification effect were studied. The results show that the loose silt particles can be effectively solidified together into filling material with excellent mechanical properties through MICP technology. The concentration of cementation solution have a significant impact on the solidification effect, and the reasonable concentration of cementation solution is 1.5 mol/L. With the increase of treatment times, the pores in the soil are filled with CaCO₃, and the UCS of the specimens after 10 times of treatment can reach 2.5 MPa with a relatively high CaCO₃ content of 26%. With the improvement of treatment degree, the influence of relative density on the UCS increases gradually. Microscopic analysis revealed that after MICP reinforcement, CaCO₃ adhered to the surface of soil particles and cemented with each other to form a dense structure.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.15-22
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• 2008

The effects of fillers on the mechanical and thermal properties of glass/novolac composites have been studied. The matrix polymer and reinforcement were novolac type phenolic resin and milled glass fiber, respectively. Three different fillers, such as calcium carbonate, aluminum oxide, and wood powder were used for glass fiber reinforced plastic(GFRP) manufacture. Gravity, moisture content, tensile and flexural strength were measured to analyze the mechanical properties of GFRP and the final composites was burned in the electronic furnace at $1000^{\circ}C$ to confirm thermal properties GFRP containing aluminium oxide shows the highest thermal stability with 32% of weight loss at $1000^{\circ}C$ for one hour. GFRP containing calcium carbonate shows the maximum flexural strength (146 MPa), but that containing wood powder dose the highest tensile strength (65 MPa). Conclusively, we found that the characteristics of final composites strongly depend on several factors, such as types of materials, contents and chemical affinity of fillers. Therefore, it is very important to set up the combination of fillers for GFRP manufacturing to improve both mechanical and thermal properties at the same time.

• The Journal of Natural Sciences
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• v.4
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• pp.95-102
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• 1991

The influences of various concentrations of thallium carbonate on the hydration of tricalcium silicate which is widely used to the inorganic materials have been studied using an isothermal microcalorime-ter. The experimental results indicate that the hydration of tricalcium silicate is accelerated in the presence of thallium carbonate, namely the concentration of thallium carbonate is increased, the rate of hydration is also increased. The x-ray diffraction analysis shows that the concentration of tricalcium silicate decreases rapidly in the presence of thallium carbonate. Differential thermal analysis of tricalcium silicate hydrated in the persence of thallium carbonate indicates the presence of calcium carbonate. The nonevaporable water content and the degree of hydration of tricalcium silicate show that the accelerating action of thallium carbonate is more pronounced only during the early period of hydration. Analytical results of the liquid phase in contact with the tricalcium silicate paste indicate that the concentrations of calcium and hydroxyl ions are changed considerably in the presence of thallium carbonate.

• Food Science and Preservation
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• v.12 no.5
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• pp.501-506
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• 2005

This study was conducted to investigate the effect of organic acids on solubility of calcium. As a results, acetic and lactic acid showed the most excellent solubility of calcium. Calcium solubility was increased at initial total acid (4%) in citric acid but calcium was insoluble in tartaric acid. After solving, pH and residuals were decreased where as total acidity and calcium content were increased as increment of initial acidity of acetic and lactic acid. Calcium content in seaweed calcium and calcium carbonate were higher than that of nano calcium. Solubility of calcium was more conspicuous at lactic acid than acetic acid.