• Journal of Welding and Joining
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• 제3권1호
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• pp.40-45
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• 1985

Wire meling characteristics were examined with variation of gas formers such as $MgCO_3, CaCO_3 and Li_ 2CO_ 3$ by self-shielded flux cored arc welding. The flux cored wire of overlap type was welded by DCRP. The results obtainedareas follows. 1) Drop type was observed with no gas former, repelled type with MgCO_3$ added and short circuit type with $Li_2CO_3$ added. The variation of transfer mode was related to the blowing force of $CO_2$ gas and the surface tension of the slag. 2) Droplet size increased with adding gas formers due to the effect of $CO_2$ gas cushion. 3) Core spikes were observed more frequently with increasing the amount of gas formers.

• 한국해양공학회지
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• 제33권6호
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• pp.615-619
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• 2019

Various fluorides, i.e., CaF₂, Na₃AlF₆, K₂SiF₆, MnF₃, MgF₂, were added to the flux cored wire, and their effects on the oxygen content of the weld metal were investigated. The investigation showed that the oxygen content of weld metal was not influenced by the type of metallic elements in the fluoride; rather, it was influenced by the stability of the arc during welding. While the wire containing MgF₂ showed the most stable arc and the least amount of oxygen in the weld metal, the wire containing MnF₃ showed the least stable arc and the greatest amount of oxygen. Since the deoxidation of the weld metal was not affected by the deoxidation elements, such as Ca and Mg, it was possible to predict the oxygen content of the weld metal by the equilibrium Si-Mn deoxidation thermodynamic model.

• 상하수도학회지
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• 제25권4호
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• pp.479-488
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• 2011

Nanofiltration was performed with polyaluminium chloride solutions at different pH conditions to understand effects of inorganic compounds on aluminum hydrolysis products, i.e., three distinctive groups of aluminum species: polymeric Al at low pH; $Al(OH)_3$ at neutral pH; and ${Al(OH)_4}^-$ at high pH. The PACl solution was prepared to be approximately 4.0mM and adjusted to the designated pH. The influence of inorganic compounds on Al species fouling was investigated with 4.9mM $CaCl_2$ and 3.5mM $MgSO_4$ because $Ca^{2+}$, $Mg^{2+}$, $Cl^-$, ${SO_4}^{2-}$ are the most common inorganics in the drinking water. NF membrane fouling was measured by flux decline rate. The impact of $CaCl_2$ was not significant on the individual Al hydrolysis products fouling. However, the flux decline rate was drastically changed in the presence of $MgSO_4$. The concentration of particulate matters was considerably increased possibly due to interaction between Al species and ${SO_4}^{2-}$ where $MgSO_4$ was introduced. The particulates were accumulated on the membrane and enhanced the hydraulic resistance of the cake layer. In addition, conductivity removal of the membrane was decreased when Al-hydroxide was dominant due to reduction of membrane surface charge. The rejection of $Ca^{2+}$and $Mg^{2+}$ were considerably different, which implys that composition of inorganics paly a role on conductivity removal.

• 한국결정학회지
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• 제7권1호
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• pp.20-29
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• 1996

(Sr1-xCax)CuO2 단결정을 융제법으로 제조하고 단결정 X-선 회절법을 이용하여 그 결정구조를 밝혔다. 이 화합물의 결정축계는 사방정계(orthorhombic system)이며, 공간군은 Cmcm(63), 그리고 격자상수 a, b, c는 각각 3.4645Å, 16.1417Å, 3.8727Å이었다. (Sr1-xCax)CuO2 화합물에서 Sr대신 치환되는 Ca이온의 한계를 구조적인 관점에서 연구하였다. 이를 위해 X-선 회절(CAD4), energy dispersive X-ray fluorescence (EDAX) and electron probe micro-analysis (EPMA) 등을 사용하였다. Ca가 치환됨에 따른 Cu-O 결합길이의 변화로부터 Ca의 치환한계를 결정하였는데 그 한계치는 Xca≒0.73이었다.

• 한국세라믹학회지
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• 제16권4호
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• pp.237-242
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• 1979

In order to improve hydration reactivity of blast furnace slag, it's composition was changed by adding of CaO. The slags were quenched in water at 1,400℃. Hydration reactivityof modified slags was studied by x-ray diffractometer, conduction calorimeter and so on. Experimental results were summarized as follows. 1. Glass content and hydration reactivity of slag depend significantly on quenching temperature of the slag melt. To enhance the reactivity, slag melts which belongs to Frenkel-type liquid, must be quenched above 1,300℃. 2. Vitrification of slag melts was confirmed as CaO/SiO2 ratio increased up to 1.57 with flux, 1.51 without flux, also their hydration reactivity was improved.

• Membrane and Water Treatment
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• 제2권1호
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• pp.63-74
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• 2011

A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

• 한국전기전자재료학회논문지
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• 제15권12호
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• pp.1027-1032
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• 2002

(Pb$\_$0.4/Ca$\_$0.6/)(Fe$\_$1/2/Nb$\_$1/2/)O$_3$ system was modified by 10 mol% Pb(Zn$\_$1/2/W$\_$1/2/)O$_3$ addition and their sinterability and microwave properties were investigated as a function of the amount of flux (0.975PbO-0.025SnO$_2$). With increasing flux content, single perovskite phase was maintained up to 3 wt% flux addition and further addition led to the presence of Pb-rich second phase which was confirmed by EDS analysis. The apparent densities of PCFN-PZW specimen increased and showed maximum values at 2.5 wt% flux addition for the Ts=1000$^{\circ}C$ and 2.0wt% flux addition for the Ts=1050$^{\circ}C$, respectively. The dielectric constant and Q$.$f values strongly depended on the variation of density and microstructure, where the optimum values of $\varepsilon$$\_$r/ = 91.95, Q$.$f = 5938GHz, TCF = +8.15ppm/$^{\circ}C$ were obtained for the 2.5wt% flux added PCFN-PZW specimen sintered at 1000$^{\circ}C$ for 4h.

• 한국결정성장학회지
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• 제9권2호
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• pp.137-140
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• 1999

Flux법에 의해 성장된 $Bi_2Sr_2CaCu_2O_{8+{\delta}}(Bi2212)$ 단결정의 초전도 특성에 미치는 열처리 및 불순물의 영향을 자화측정에 의해 조사하였다. 초전도 특성은 불순물인 Mg와 Al의 영향을 받음을 알 수 있었으며, 초전도 전이온도(T,) 는 Mg 불순물의 영향에 의해 보다 낮아졌다. 그러나 성장된 결정은 열처리에 의해 초전도 특성이 개선됨을 알 수 있었 으며, 특히 MgO 도가니 사용에 의해 성장된 결정이 $Al_2O_3$ 도가니에 비해서 반자계특성이 현저하게 증가되었다. 반자계 특성의 개선효과에 의해 Mg 불순물은 초전도 특성 열화의 주요 요소라고 생각될 수 없음을 알 수 있었다.

• 한국막학회:학술대회논문집
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• 한국막학회 2004년도 Proceedings of the second conference of aseanian membrane society
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• pp.155-160
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• 2004

Permeation experiments of a commercial nanofiltration membrane (nominated as ESNA 1) were carried out with aqueous solutions of various single salts, that is, five chlorides (NH$_4$Cl, NaCl, KCl, MgCl$_2$ and $CaCl_2$), three nitrates $(NaNo_3,\;Mg(No_3)_2\;and\;Ca(NO_3)_2)\;and\;three\;sulfates\;((NH_4)_2SO_4,\;Na_2SO_4\;and\;MgSO_4)$. The experimental results showed that (1) the permeate volume flux of the ESNA 1 membrane increased and decreased with the growth of the applied pressure and the feed concentration of salts, respectively. The real rejection of ESNA 1 membrane to most single salts increased with the growth of the permeate volume flux. (2) The reflection coefficients of ESNA 1 membrane to chlorides, nitrates and sulfates are 0.97, 0.96 and 0.99, respectively. The solute permeability of most salts except for magnesium and calcium salts increased with the growth of feed concentration. (3) The sequence of the rejections of ESNA 1 membrane to anions is $R({SO_4}^{2-})>R(CI)>R(NO_3)$ at the same feed concentration. While the sequence of the rejections to cations is cataloged into two cases: $R(Na^+)>R(K^+)>R(Mg^{2+})>R(Ca^{2+})$ at the concentration of 10 mol/$m^3$ and $R(Mg^{2+})>R(Ca^{2+})>R(Na^+)>R(K^+)$ at the concentration of 100 mol/$m^3$. The separation capability of a NF membrane is usually affected by the electrostatic effect and the steric-hindrance effect. In this case, the electrostatic effect is the major factor at low concentration and the steric-hindrance effect is the major factor at high concentration. Both the specific sorption and the hydration also reasonably influenced the separation performance of NF membrane to salts.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.116.2-116.2
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• 2000