• Korean Journal of Materials Research
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• v.20 no.12
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• pp.691-698
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• 2010

Magnesium hydroxide-melamine core-shell particles were prepared through the coating of melamine monomer on the surface of magnesium hydroxide in the presence of phosphoric acid. The melamine monomer was dissolved in hot water but recrystallized on the surface of magnesium hydroxide by quenching to room temperature in the presence of phosphoric acid. The core-shell particle was applied to low-density polyethylene/ ethylene vinyl acetate (LDPE/EVA) resin by melt-compounding at $180^{\circ}C$ as flame retardant. The effect of magnesium hydroxide and melamine content has been studied on the flame retardancy of the core-shell particles in LDPE/EVA resin according to the preparation process and purity of magnesium hydroxide. Magnesium hydroxide prepared with sodium hydroxide rather than with ammonia solution revealed higher flame retardancy in core-shell particles with LDPE/EVA resin. At 50 wt% loading of flame retardant, core-shell particles revealed higher flame retardancy compared to that of the exclusive magnesium hydroxide in LDPE/EVA composite, and it was possible to satisfy the V0 grade in the UL-94 vertical test. The synergistic flame retardant effect of magnesium hydroxide and melamine core-shell particles was explained as being due to the endothermic decomposition of magnesium hydroxide and melamine, which was followed by the evolution of water from the magnesium hydroxide and porous char formation due to reactive nitrogen compounds, and carbon dioxide generated from melamine.

• Elastomers and Composites
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• v.40 no.1
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• pp.12-21
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• 2005

In this work, magnesium carbonate and calcium hydroxide as metallic crosslinking agent were added to chlorosulfonated polyethylene rubber (CSM) emulsion to enhance the mechanical properties of emulsion film such as tensile strength, elongation at break, and tear strength and crosslinking density, thermal features, and surface energy were also investigated. Crosslinking density of the CSM emulsion film with increasing the amount of magnesium carbonate and calcium hydroxide increased, leading to the enhancement of water resistance. It was shown that compared with calcium hydroxide, magnesium carbonate had a little higher crosslinking density and $T_g$ value. The surface energy and mechanical characteristics of the CSM emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.75% for magnesium carbonate and 1.0% for calcium hydroxide were added respectively. Therefore, it can be concluded that as metallic crosslinking agent to improve water resistance and mechanical properties of the CSM emulsion, magnesium carbonate is more preferable to calcium hydroxide.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.17-22
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• 2021

Eco-friendly magnesium-air battery is a kind of metal-air battery known as a primary battery with a very high theoretical discharge capacity. This battery is also called a metal-fuel cell from the viewpoint of using oxygen in the atmosphere as a cathode active material and magnesium alloy as a fuel. Since battery performance is determined by the properties of the magnesium alloy used as a anode, more research and development of the magnesium alloy electrode as a anode material are required in order to commercialize it as a high-performance battery. In this study, the commercialized magnesium alloys(AZ31, AZ61) were selected and then electrochemical measurements and discharge test were conducted. Electrochemical properties of magnesium alloys were investigated by OCP changes, Tafel parameters and CV measurement, and the feasibilities of AZ61 alloy with excellent discharge capacity(1410mAhg^-1) as electrode materials were evaluated through CC discharge experiments.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.3
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• pp.212-218
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• 1983

The effect of dietary calcium and magnesium on the 3-Hydroxy-3-methyl-glutaryl coenzyme A reductase (E.C. 1.1.1.34) in rabbit's liver microsomal protein was studied for a period of 4 weeks using isocalories and isonitro-genous as a basal diet. The experimental rabbits fed the following basal diets, such as crude protein 68.45%, carbohydrates 13.38%, fats 16.17% and added some sorts of calcium and magnesium, according to experimental plan making. The subject rabbits were divided into 9 feeding groups. The results are summarized as follows. Body weight gains per week of the groups fed magnesium and basal diet showed a little bit increase, but the groups fed calcium and basal diet showed a little bit decrease compare with control group. In case of serum magnesium, control group was 9.5mg% groups fed basal diet and magnesium were 8.27mg% in average, groups fed basal diet and calcium were 4.45mg% in average. In case of serum calcium, control group was 15.3mg%, groups fed basal diet and magnesium were 14.6mg% in average, groups fed basal diet and calcium were 14.1mg% in average. There was no great difference between magnesium fed groups in serum calcium. In serum triglyceride, control group was 82.8mg%, groups fed magnesium and basal diet were 60.3mg% in average, groups fed calcium and basal diet were 69.5mg% in average. The calcium fed groups were higher than the magnesium fed groups in serum triglyceride. In serum cholesterol, control group was 80mg%, groups fed magnesium and basal diet were 64.3mg% in average, groups fed calcium and basal diet were 56.3mg% in average. The calcium fed groups were lower than the magnesium fed groups in serum cholesterol. In case of the 3-Hydroxy-3-methylglutaryl coenzyme A reductase activity, control group was 0.998nmol/min/mg protein, groups fed magnesium and basal diet of HMG-CoA were 0.849nmol/min/mg in average.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.4963-4967
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• 2012

In this study, 18-inch wheels, magnesium alloy AZ91D was developed and we compared overseas go on sale magnesium wheels and same specifications of the aluminum wheels mechanical properties. Prototype 18-inch magnesium wheels by a low-pressure casting method to achieve the same specifications of aluminum wheels and reduced 26% of the weight, the new edition of magnesium wheels compared to the same level of elongation, tensile strength, hardness. Casting and heat treatment process to improve future need to improve the yield strength is expected.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.99-104
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• 2010

Magnesium and magnesium alloys, the lightest structural materials, have been received plenty of global attention recently. These alloys could be applied in various fields, especially the electronics industry, because of their excellent electromagnetic interference shielding. However, the welding technique of magnesium alloys has not been established. This study is related to the welding of AZ31B magnesium alloy by a short-pulsed a Nd:YAG laser. Two types of pulse waves, square pulse and variable pulse, were used to control weld defects. Results show that the crack and porosity, generated in the weld, had not been controlled by general square pulse. But through the application of variable pulse, the defects could be prevented and the good weld zone was obtained.

• Journal of the Korean Applied Science and Technology
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• v.26 no.4
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• pp.385-393
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• 2009

Different types magnesium hydroxide groups have been obtained using the hydrothermal precipitation technique from magnesium sulfate and calcium carbonate solution. The Mg atom coordinated around O atom of ${SO_4}^{2-}$ in another layer to form a multi-layer structure crystal. The influence of synthesis parameters on the morphological characteristics and size of magnesium hydroxide groups precipitated in aqueous were investigated such as different of additive and pH. Magnesium hydroxide groups were decomposed gradually and converted finally to MgO particles after heated in air temperature up to $1050^{\circ}C$. The particle size and it's distribution morphology, crystal phase and thermal behavior of the samples were characterized through XRD, SEM, EDS, and TG/DTA.

• Journal of Nutrition and Health
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• v.26 no.8
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• pp.974-981
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• 1993

The longitudinal changes on contents of calcium, phosphorous and magnesium of breast milk of 23 Korean lacto-ovo-vegetarians(primiparae=11, multiparae=12) at 0.5, 1, 2 and 3 months postpartum have been studied. The mean ash content of breast milk per 100ml was 0.21g in total lactating women(n=23), and it decreased significantly during lactation(p<0.05). The mean calcium, phosphorous and magnesium contents of breast milk per 100ml were 26.83mg, 14.01mg and 2.72mg, respectively. Body calcium and phosphorous contents decreased significantly during lactation(p<0.05), but magnesium content tended to increase during lactation. There were no significant differences in ash, calcium, phosphorous and magnesium contents between primiparae and multiparae. The ratio of calcium to phosphorus was about 1.95:1 in breast milk and 0.62 : 1 in maternal dietary intake. In calcium and phosphorous, no correlation was found between maternal dietary intake and the concentration in breast milk. This study suggests that the contents of calcium, phosphorous and magnesium in lacto-ovo-vegetarian breast milk are not different from the concentrations of those in non-vegetarian.

• Journal of Nutrition and Health
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• v.31 no.1
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• pp.102-107
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• 1998

This study was conducted to investigate the relationship of serum calcium and magnesium levels to depression and anxiety symptoms in 80 homemarker. Fasting blood samples were collected and serum calcium and magnesium concentrations were measured. At the same time, psychological conditions of subjects were estimated by questionnaire. As the result of psychological test, eighty homemarkers were divided into two groups according to psychologicaltest scores. The subjects in one group got high pssycholgoical test scores as high score group (HSG) and the others got low physchological test scores as low score group(LSG). Serum calcium and magnesium concentrations were significantly(p<0.05) lower in HSG than in HSG than in LSG. Many a subject who belonged to HSG appeared to have depression and anxiety symptoms. Drepression and anxiety scores of the subjects with calcium supplementation were significantly (p<0.05) lower than those without calcium supplementation . After calcium supplementation, depressiion and anxiety scores were significantly (p<0.05) decreased in HSG and serum calcium and magnesium concentrations in HSG were significantly increased to normal ranges . This results suggested that psychological conditions of homemarkers might be affected by serum calcium and magnesium levels.

• Journal of the Korean Chemical Society
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• v.9 no.1
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• pp.49-54
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• 1965

One of the difficult and time consuming problems in the production of magnesia from sea water is a settling rate of magnesium hydroxide. In this experiments, authors attempted to accelerate its settling rate by addition of various sedimenting agents as C.M.C., Separan and Starch, and sought for optimum calcination temperature for domestic dolomite, as alkali source, mole ratio of dolomite milk to bittern. It is observed through experiments that the small amounts of sedimenting agents, C.M.C., Separan, starch, 20 mg/l, 40 mg/l, 400mg/l, respectively increase the settling rate of magnesium hydroxide by 8 times or more. The following conditions resulted in good yield of magnesium hydroxide from sea water with relatively tolerable calcium oxide contaminated for the magnesium clinker. Calcinating temperature, $1,100{\sim}1,200^{\circ}C$, mole ratio of 10% dolomite milk to magnesium salts in sea water or bittern, 1. 2 : 1.