• 한국재료학회지
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• 제23권2호
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• pp.112-115
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• 2013

One of the most important characteristics of Mg alloys is the high ratio of strength to weight. This is why there is a high demand for applications with these alloys in the transportation industries to reduce the fuel consumption and to save energy. In addition, magnesium (and its alloys) is of considerable interest as a structural material, especially in the aerospace and automotive industries thanks to its low density. However, its major drawback is its high sensitivity to corrosion. Therefore, its use requires the application of a surface treatment. This study used a die-casted AZ91D Mg alloyand all the samples were annealed (in $120^{\circ}C$). The surface microstructure and phase distribution in thin-walled AZ91D magnesium components cast on a hot-chamber die-casting machine were investigated by optical microscopy and scanning electron microscopy. The reflectance differences in the bulk state comparison with the annealing state are caused by hydrogenation presence of the Mg layer under an oxidation surface layer.

• 한국물환경학회지
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• 제31권4호
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• pp.387-391
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• 2015

This study was performed to evaluate the effect of pH (8-12) and molar ratio of magnesium and phosphate ($[Mg^{2+}]/[PO_4{^{3-}}]$) (0.6-1.4) on struvite crystallization of anaerobic digester supernatant using seawater as magnesium source. pH range of 9-10 is favorable for ammonium and phosphate recoveries. The recovery efficiency of ammonium was highest at $[Mg^{2+}]/[PO_4{^{3-}}]$ of 1.0 and pH 10. On the other hand, high phosphate recovery efficiency (> 99%) was achieved at ($[Mg^{2+}]/[PO_4{^{3-}}]$) of 1.4 and pH 10. The results demonstrated that seawater can be considered as low-cost magnesium source to recover phosphorus from anaerobic digester supernatant.

• 소성∙가공
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• 제13권6호
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• pp.535-539
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• 2004

Although magnesium has high potential for structural material due to the lightweight and high specific strength, the structural application has been limited by the low ductility at room temperature. The reason of the poor ductility is few activated slip systems of magnesium (HCP structure) during deformation. As temperature increases, however, additional non-basal slip systems are incorporated to exhibit higher ductility comparable to aluminum. In the present study, a series of tensile tests of Mg-Al alloy has been carried out to study deformation behavior with temperature variation. Analysis of load relaxation test results based on internal variable approach gave information about relationship between the micromechanical character and corresponding deformation behavior of magnesium. Especially, the material parameter, p representing dislocation permeability through barriers was altered from 0.1 to 0.15 as the non-basal slip systems were activated at high temperature.

• 암석학회지
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• 제23권3호
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• pp.221-227
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• 2014

최근 분석법의 발달에 따라 금속 안정동위원소의 지질학적인 활용이 두드러지고 있다. 이 논평에서는 Mg 동위원소 분석 자료를 화강암류의 성인 해석에 활용하는 원리와 분석 방법, 적용의 예를 소개한다. 먼저 Mg 동위원소가 분별되는 원리를 설명하고 다검출기 유도결합 플라즈마 질량분석기를 활용한 분석 방법을 기술하며 마지막으로 북미 서해안과 호주, 중국의 I형, S형, A형 화강암에 대한 최근의 적용 사례를 살펴볼 것이다.

• The Korean Journal of Pain
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• 제13권1호
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• pp.31-37
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• 2000

Background: Recent studies suggested that a preoperative block of N-methyl-D-aspartate (NMDA) receptors with NMDA antagonists may reduce postoperative pain. In this double-blind study, magnesium sulfate, a natural NMDA receptor antagonist, was administered preoperatively to investigate the effects of magnesium sulfate on postoperative pain and pulmonary function. Methods: Seventy patients who were to undergo gastrectomy under general anesthesia were randomly assigned to one of three groups. Groups 2 and 3 received intravenous magnesium, preoperatively (Group 2: 50 mg/kg bolus, 7.5 mg/kg/hr for 20 hr, Group 3: 50 mg/kg bolus, 15 mg/kg/hr for 20 hr). Group 1 received normal saline as the control group. Visual analog scale (VAS) for postoperative pain and mood, cumulative analgesic consumption, recovery of pulmonary function and side effects were evaluated at 6, 24, 48 and 72 hours after the operation. Results: In Groups 2 and 3, plasma concentration of magnesium were significantly higher than in Group 1 at 6 and 20 hours after infusion (P<0.05). There were no significant differences in the analgesic consumption, and recovery of pulmonary function and the incidence of side effects at 6, 24, 48 and 72 hours after the operation among the three groups. In Group 3, pain scores at rest measured 24 and 48 hours after operation were lower than the control group, and pain scores when deep breathing were significantly lower than the control group at postoperative 6, 24, 48, and 72 hours. Conclusions: We conclude that intravenous infusion of greater amount of magnesium has little effectiveness in reducing postoperative pain. However, further studies are needed to characterize the clinical significance of these effects on postoperative pain.

• 한국가스학회지
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• 제17권4호
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• pp.33-38
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• 2013

본 연구에서는 마그네슘(Mg)분진의 폭발특성에 미치는 평균 입경의 영향을 조사하였다. 이를 위해 20-L분진 폭발시험장치와 10 kJ의 에너지를 갖는 화학 점화기를 사용하여 실험을 수행하였다. 실험에 사용한 Mg분진은 평균입경이 서로 다른 3가지 시료(38, 142, $567{\mu}m$)를 대상으로 분진농도를 $2250g/m^3$까지 조사하였다. Mg분진의 폭발하한농도(LEL)는 평균입경 38, $142{\mu}m$에 있어서 각각 30, $40g/m^3$ 이 얻어졌다. LEL은 입경 증가에 의해 감소 경향을 나타냈는데 Mg분진은 입경이 증가할수록 폭발 확률이 감소함을 의미한다. 최대폭발압력($P_m$)과 폭발지수($K_{st}$)는 입경이 증가하면 감소하였지만, 평균입경 $567{\mu}m$의 Mg분진의 경우에는 5 kJ의 착화에너지에서는 폭발 현상이 관찰되지 않았다.

• Journal of Nutrition and Health
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• 제26권8호
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• pp.933-941
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• 1993

The present study was carried out to investigate the effects of magnesium supplement levels and periods on lipid metabolism in male Sprague-Dawley rats given low protein and magnesium deficient diets. The effect of magnesium supplement levels and periods on lipid metabolism in rats given a low protein and magnesium deficient diet for 2 weeks were investigated. Serum total lipid and triglyceride contents were significantly lower in magnesium supplement group compared with magnesium deficient group. Serum HDL-cholesterol/total cholesterol ratio was significantly increased as magnesium supplement level was increased. Liver total lipid, triglyceride, total cholesterol and phospholipid contents were significantly lower in magnesium supplement group than those in magnesium deficient group. Serum ALP, GOT and GPT activities were significantly decreased in magnesium supplement group compared with magnesium deficient group. In summary, the effect of magnesium supplement on lipid metabolism and enzyme activities were significant and we can see that magnesium supplement level propered to be requirement level(400 mg/kg diet)in the other cases except serum lipid contents.

• 한국주조공학회지
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• 제35권2호
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• pp.36-43
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• 2015

In this study, the influences of aluminum and tin additions (individual and combined) on corrosion behavior of magnesium alloy have been determined. The studied alloys were fabricated by permanent mold casting method to measure the corrosion properties, a potentiodynamic test, hydrogen evolution test and immersion test were carried out in a 3.5% NaCl solution at pH 7.2. From the results of microstructure analysis, the Mg-9Al-1Zn alloy was found to be composed of ${\alpha}$-Mg and rod-like $Mg_{17}Al_{12}$ phase and the Mg-5Sn-5Al-1Zn alloy was found to be composed of ${\alpha}$-Mg, rod-like $Mg_{17}Al_{12}$ and $Mg_2Sn$ phases. In the case of the Mg-9Sn-1Zn alloy, the microstructure was composed of ${\alpha}$-Mg and eutectic $Mg_2Sn$ phase. With Sn addition (individual and combined), the corrosion resistance of the Mg alloys improved.

• Journal of Nutrition and Health
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• 제31권9호
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• pp.1404-1410
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• 1998

The purpose of this study was to investigate the effects of calcium intake levels on magnesium utilization in young and adult rats fed various levels of calcium(50, 100 or 200% of requirement) for 3 weeks. Feed intake, body weight gain, and feed efficiency ratios of the young group were significantly higher than those of the adult group. In calcium levels of tissues, serum calcium levels in young group were higher than in the adult group and kidney calcium levels in HCa(high-calcium group) were higher than in other groups. There was no significant difference in magnesium intake among age and diet groups. However, magnesium excretions through feces and urine in the adult group were higher than in the young group. Therefore, magnesium retention in the young group was higher than in the adult group. Especially in the young group, fecal magnesium excretion was increased with increasing levels of dietary calcium. Serum magnesium levels were lowest in YHCa(young 8t high-calcium) group, and there was no significant difference in liver and kidney levels among the calcium-diet groups. These results indicate that high calcium consumption promotes of fecal magnesium excretion and decreased magnesium retention rates in growing rats. Therefore, it is suggested that mineral interactions should be considered in the supplementation of dietary calcium intake for growth. (Korean J Nutrition 31(9) 1404-1410, 1998)

• 대한금속재료학회지
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• 제50권9호
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• pp.619-627
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• 2012

One of the barriers limiting wide applications of magnesium alloys to various industries is their poor corrosion resistance. The corrosion properties of AZ91 magnesium alloy, which is the most popular magnesium casting alloy, are affected by microstructural and environmental factors. The corrosion properties of AZ91 magnesium alloy are affected by the corrosion properties of ${\alpha}-Mg$ and ${\beta}$ phases, the volume fraction and distribution of ${\beta}$ phase and area ratio of ${\alpha}-Mg/{\beta}$ phases. The corrosion properties of AZ91 magnesium alloy under various environments also change according to the passivity of films and types of corrosion products formed on its surface. The corrosion resistance of the magnesium alloys can be improved by microstructural control through the addition of alloying elements and optimization of the production process.