• The Korean Journal of Ceramics
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• 제3권3호
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• pp.187-190
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• 1997

The aluminum-magnesium (Al-Mg) aklloys have been proved to be an effective solvent for synthesis of cubic-phase boron nitride (cBN) from hexagonal-phase boron nitride (hBN) at the conditions of high pressures and high temperatures (HP/HT). Various kinds of hBN powders having different crystallinity have been tested for cBN synthesis with Al-Mg solvents. The conversion ratio from hBN to cBN and the shape of synthesized cBN crystals appeared to be affected strongly by chemical composition and added amount of Al-Mg solvents as well as crystallinity of BN powders. As the magnesium content increased in the Al-Mg solvents, the conversion ratio increased and the size of cBN crystals became larger. The crystal facets developed well in the specimens with solvents having high Mg content. It was observed that a hBNlongrightarrowcBN transformation occurred more easily in the specimens having well crystallized hBN powders. Amorphous BN having much $B_2O_3$ impurity exhibited a low threshold temperature for transformation to cBN, which was attributed to crystallization of amorphous BN to well crystallized hBN prior to transformation into cBN with help of $B_2O_3$.

• 한국표면공학회지
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• 제49권2호
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• pp.135-140
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• 2016

In this study, we prepared magnesium ion containing oxide films formed on the Ti-6Al-4V using plasma electrolytic oxidation (PEO) treatment. Ti-6Al-4V surface was treated using PEO in Mg containing electrolytes at 270V for 5 min. The phase, composition and morphology of the Mg ion containing oxide films were evaluated with X-ray diffraction (XRD), Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and filed-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometer (EDS). The biocompatibility of Mg ion containing oxide films was evaluated by immersing in simulated body fluid (SBF). According to surface properties of PEO films, the optimum condition was formed when the applied was 270 V. The PEO films formed in the condition contained the properties of porosity, anatase phase, and near 1.7 Ca(Mg)/P ratio in the oxide film. Our experimental results demonstrate that Mg ion containing oxide promotes bone like apatite nucleation and growth from SBF. The phase and morphologies of bone like apatite were influenced by the Mg ion concentration.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.169-177
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• 2023

Phase stability diagrams were constructed for magnesium alanate (Mg(AlH₄)₂) nanoparticles to investigate the reversible hydrogen storage reaction by using density functional theory. Our findings indicate that bulk Mg(AlH₄)₂ shows favorable hydrogen release, but unfavorable hydrogen uptake (adsorption) reactions. However, for Mg(AlH₄)₂ nanoparticles, it was observed that hydrogen release and recharge can be achieved by controlling the particle size and temperature. Furthermore, by predicting the decomposition phase diagram of Mg(AlH₄)₂ nanoparticles with varying hydrogen partial pressure, it was discovered that reversible dehydrogenation reactions can occur even in relatively large nanoparticles by controlling the hydrogen partial pressure.

• The Korean Journal of Pain
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• 제30권3호
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• pp.176-182
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• 2017

Background: Current evidence suggests that intravenous magnesium sulfate might be effective for reducing migraine pain. In a recent pilot study, we showed that intravenous caffeine citrate could reduce the severity of migraine headache. The objective of this study is to investigate the efficacy of intravenous caffeine citrate vs. magnesium sulfate for management of acute migraine headache. Methods: We conducted a prospective quasi-experimental study from January until May 2016 in two educational medical centers of Shahid Beheshti University of Medical Sciences (Shoahadaye Tajrish Hospital and Imam Hossein Hospital), Tehran, Iran. The study included patients who were referred to the emergency department and met the migraine diagnosis criteria of the International Headache Society. Patients were allocated into 2 groups receiving either 60 mg intravenous caffeine or 2 g intravenous magnesium sulfate. The pain scores, based on the visual analog scale, were recorded on admission, as well as one and two hours after receiving the drug. A Chi-Square test and student t-test were used for analysis of baseline characteristics. A Mann-Whitney U test and Wilcoxon singed rank test were used to analyze differences in the visual analogue scale (VAS) score between and within the groups respectively. Results: In total, 70 patients (35 patients in each group) with the mean age of $33.1{\pm}11.3years$ were included (64.3% female). For the Caffeine citrate group, the median pain score decreased from 9.0 (2.0) to 5.0 (4.0) after one hour and to 3.0 (4.0) after two hours. For the magnesium sulfate group, the pain score decreased from 8.0 (2.0) to 2.0 (2.0) after one hour and to 0.0 (1.0) after two hours. Both intravenous caffeine citrate and intravenous magnesium sulfate reduced pain scores significantly but the magnesium sulfate group showed more improvement than the Caffeine citrate group after one hour (P < 0.001) and after two hours (P < 0.001). Conclusions: It is likely that both intravenous caffeine and intravenous magnesium sulfate can reduce the severity of migraine headache. Moreover, intravenous magnesium sulfate at a dose of 2 g might be superior to intravenous caffeine citrate 60 mg for the short term management of migraine headache in emergency departments.

• 대한소아신경학회지
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• 제26권4호
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• pp.205-209
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• 2018

목적: 마그네슘은 N- 메틸 -D- 아스 파르 테이트(NMDA) 이온 채널 수용체를 차단하여 NMDA 관련 발작을 조절하는 데 중요한 역할을 한다는 것이 밝혀져 있다. 경련 시 총 혈청 마그네슘 수치를 주로 측정하고 있는데, 생물학적으로 활성화된 형태인 이온화 마그네슘 수치를 측정하는 것이 체내 마그네슘 양을 평가하기 위한 보다 적절한 방법이다. 이에 연구자는 뇌전증 환아들 중 발열과 동반된 경련 발작(FTS) 이 있었던 환아들과 없었던 환아들에서 혈청 이온화 마그네슘($iMg^{2+}$) 수치를 비교해 보았다. 방법: 2015년 1월부터 2017년 7월까지 고려 대학교 구로 병원 외래 또는 소아 응급실을 방문한 뇌전증 환아들 중 2년 이내에 새로 진단받은 1-8 세의 환아들을 대상으로 하였으며 열과 동반된 경련을 할 수 있는 뇌전증 증후군(드라베 증후군, PCDH19 뇌전증 증후군 등)은 제외하였다. 결과: 12명의 발열을 동반한 경련 발생군(FTS)과 16명의 발열을 동반한 경련이 없었던 군(without FTS)으로 분류를 하였으며, 혈중 $iMg^{2+}$ 농도는 0.93 (0.85-1.14, quartile) mEq/L이었다. 혈청 $iMg^{2+}$ 수치는 without FTS 군(1.10 mEq/L)에 비해 FTS군에서 0.86 mEq/L으로 유의하게 낮았다(P=0.005). 두 군간의 임상 적 변수에는 차이가 없었다. 혈청 $iMg^{2+}$ 수준이 낮을수록 다 변수 로지스틱 회귀 분석(OR=0.028)에 근거하여 뇌전증 환아에서 FTS를 가질 위험이 유의하게 증가했다. 결론: 혈청 $iMg^{2+}$ 수치는 FTS 가 있었던 뇌전증 환아들에서 FTS가 없었던 환아들보다 유의하게 낮았다. 반복적인 FTS를 가진 뇌전증 환아들에서 생물학적으로 활성화 형태인 혈청 $iMg^{2+}$ 수치를 측정을 고려할 수 있겠으며, 앞으로 대규모 전향적 연구가 필요할 것으로 생각된다.

• 한국결정성장학회지
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• 제20권5호
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• pp.237-242
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• 2010

Mg-BCP(Mg Substituted BCP)를 제조하기 위하여 $Ca(NO_3)_2{\cdot}4H_2O$(Katayama chemical, Japan)과 $(NH_4)_2{\cdot}HPO_4$ (Junsei chemical, Japan), $Mg(NO_3)_2{\cdot}6H_2O$(Junsei chemical, Japan)를 출발물질로 공침법(co-precipitation process)을 이용하여 합성하였다. 제조된 분말의 마그네슘의 첨가에 따른 분말의 분광학적 특성은 FT-IR(MAGNA-IR 560, Nicolet)을 통하여 분석하였으며, SEM(S-4200, Hitachi)을 통하여 미세구조를 분석하였다. XRD 회절피크의 면적적분강도를 Integral Analysis (Rigaku, Japan)를 이용하여 HAp와 ${\beta}$-TCP의 비율을 확인하였다. 1.0 wt% 마그네슘이 첨가된 BCP 샘플의 경우 Hank's solution에서의 2주 침적 후 표면에 침상의 HAp로 추정되는 결정이 성장하였다. 이러한 미세구조의 변화는 생활성을 가지는 마그네슘의 첨가가 BCP 조직 내에서 표면의 활성을 증가시켜 결정의 성장을 촉진시킨 것으로 판단된다.

• 한국세라믹학회지
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• 제54권4호
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• pp.303-307
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• 2017

Pure $In_2O_3$, 0.5 and 1.0 wt% Mg doped $In_2O_3$ hollow spheres were synthesized by ultrasonic spray pyrolysis of a solution containing In-, Mg-nitrate and sucrose and their gas sensing characteristics to 5 ppm $C_2H_5OH$, p-xylene, toluene, and HCHO were measured at 250, 300 and $350^{\circ}C$. Although the addition of Mg decreases the specific surface area and the volume of meso-pores, the gas response (resistance ratio) of the 0.5 wt% Mg doped $In_2O_3$ hollow spheres to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ (69.4) was significantly higher than that of the pure $In_2O_3$ hollow spheres (24.4). In addition, the Mg doped $In_2O_3$ hollow spheres showed the highest selectivity to $C_2H_5OH$. This was attributed to the dehydrogenation of $C_2H_5OH$ assisted by basic MgO into reactive $CH_3CHO$ and $H_2$.

• 소성∙가공
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• 제17권1호
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• pp.13-18
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• 2008

Mg and Mg alloys are promising materials for light weight high strength applications. In this paper, grain refinement of pure Mg using severe plastic deformation was tried to enhance the mechanical properties of the hard-to-deform metallic material. The microstructure and the mechanical properties of Mg processed by equal channel angular pressing(ECAP) at various processing temperatures were investigated experimentally. ECAP with channel angle of $90^{\circ}$ and corner angle of $0^{\circ}$ was successful at $300^{\circ}C$ without fracture of the samples during the processing. The hardness of the ECAP processed Mg decreased with increasing ECAP processing temperature. The effect of temperature on the hardness and microstructure of the ECAP processed Mg were explained by the dislocation glide in the basal plane and non-basal slip systems and by the dynamic recrystallization and recovery.

• Corrosion Science and Technology
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• 제16권4호
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• pp.183-186
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• 2017

Galvanic corrosion tests of Zn/steel couples were conducted in 1 M NaCl and $1M\;MgCl_2$ solutions to investigate the impact of magnesium ion on corrosion behavior of the couples. Two types of Zn/steel couples were used for measurements of open circuit potential (OCP) and galvanic current. From the results of OCP transient of Zn/steel couples, the corrosion potential in $1M\;MgCl_2$ was a more positive value than that in 1 M NaCl during the sacrificial dissolution of Zn. However, earlier increase of OCP of the couples in $1M\;MgCl_2$ solution indicates that the sacrificial dissolution rate of Zn in $1M\;MgCl_2$ was enhanced more than that in 1 M NaCl, agreeing with the results on transients of galvanic current. This result is due to that cathodic reaction on the steel surface of the Zn/steel couple was enhanced in $1M\;MgCl_2$ by the occurrence of hydrogen evolution reaction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.62-65
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• 2008

Extrusion characteristics of Mg alloys were studied experimentally. The Al-Zn-Mg alloys, AZ31, AZ6l, AZ80, and AZ91 were extruded with hot hydrostatic extrusion process. The hydrostatic process was efficient to reduce surface friction and extend steady state region in extrusion which made it more convenient to examine deformation behavior of the alloys avoiding the disturbance caused by temporary contact state between billet and die, and billet and container. High pressure was cooperative to expand forming limit of the alloys which were applied on the billet during the extrusion process. Extrusion limits were traced in temperature and extrusion speed domain with changing composition of the alloying elements. Effects of process parameters on extrusion load and microstructure evolution were investigated also.