• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.304-309
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• 2001

With the development of electromagnetic communication technology and increased use of electromagnetic wave, the countermeasure of EMI(Electromagnetic Interference) becomes more important socially, and interest for the electromagnetic wave absorber has also increased. In this paper, we have studied characteristics of frequency dependency on complex permittivity and complex permeability according to the changes of composition rate and sintering temperature of NiCuZn ferrite also known as electromagnetic wave absorber and further looked into effect of electromagnetic wave absorption properties. From the measurement where the composition of Fe$_2$O$_3$ and ZnO of NiCuZn ferrite was fixed at 49 and 34 mol% respectively while composition of NiO and CuO has been varied at each test, we found out that initial permeability and permittivity were high and the absorbing ability of electromagnetic wave recorded best with loss tangent(${\mu}$r"/${\mu}$r′) displays more than 1 within the frequency band of 2MHz～9.5MHz when the composition ratio of NiO was ranged around 8.5～9.5 mol% and the sintering temperature was 1,080$^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.53-56
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• 2007

미량의 Ru을 증진제로 첨가하여 니켈 촉매의 반응 활성을 증진시킴으로써, 저온 환원성과 장시간 반응에 대한 안정성을 확보하고자 하였다. Ni의 담지량은 12 wt%로 고정하였으며 이에 Ru을 각각 0.1, 0.3, 0.5 wt%로 변화시켜 2차 담지하였다. 메탄의 수증기/이산화탄소 복합 개질 반응에 있어 니켈 촉매에 Ru을 2차 담지 한 촉매는 800 $^{\circ}C$, GHSV(gas hourly space velocity) 265,000 $h^{-1}$ 하에서 100 %에 가까운 $CH_{4}$ 전환율을 보였으며, GHSV 1,060,000 $h^{-1}$ 일 때에도 10시간 동안 90 %의 $CH_{4}$ 전환율을 기록하였다. 또한 이 중 0.3 wt%의 Ru를 담지한 경우가 1,060,000 $h^{-1}$의 조건하에서도 95 %이상으로 가장 높은 $CH_{4}$ 전환율로 유지되었다. $H_{2}-TPR$ 분석 결과, Ni(12)/$MgAl_{2}O_{4}$ 와 비교해 볼 때 Ru(0.5)/Ni(12)/$MgAl_{2}O_{4}$와 Ru(0.3)/Ni(12)/$MgAl_{2}O_{4}$ 촉매의 경우 150 $^{\circ}C$에서 저온 환원이 가능한 $RuO_{2}$의 존재를 확인할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1165-1172
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• 1997

ZrB2 powders were prepared from a mixture of ZrO2, B2O3 and Mg by self-propagating high temperature synthesis method. The combustion product was successfully obtained from a mixture of ZrO2:B2O3:Mg=1:2:8.5 molar ratio. By-product, MgO was effectively removed by leaching with 1M HCl solution at 9$0^{\circ}C$ for over 5hours. After leaching, the Mg content was 0.86~1.42 wt%, and the mean particle size was 4.72${\mu}{\textrm}{m}$. The addition of 7.5 wt%(14Ni:1.0C) as a sintering aid greatly densified ZrB2 bodies compared with that of only Ni. The ZrB2 sintered bodies containing 7.5 wt%(14Ni:1.0C) was 94.3% of the theoretical density. In this case, ZrB2 existed as a major phase and had a bend strength of 300 MPa and a vickers hardness of 2000 kg/$\textrm{mm}^2$.

• Journal of Surface Science and Engineering
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• v.54 no.2
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• pp.43-52
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• 2021

The Ni-based superalloy, Inconel 740, was corroded between 800 and 1100℃ for up to 100 hr in air and Ar-0.2%SO₂ gas in order to study its corrosion behavior in air and sulfur/oxygen environment. It displayed relatively good corrosion resistance in both environment, because its corrosion was primarily dominated by not sulfidation but oxidation especially in Ar-0.2%SO₂ gas. Such was attributed to the thermodynamic stability of oxides of alloying elements when compared to corresponding sulfides. The scales consisted primarily of Cr₂O₃, together with some NiAl₂O₄, MnCr₂O₄, NiCrMnO₄, and rutile-TiO₂. Sulfur from SO₂ gas made scales prone to spallation, and thicker. It also widened the internal corrosion zone when compared to air. The corrosion resistance of IN740 was mainly indebted to the formation of protective Cr₂O₃-rich oxides, and suppression of the sulfide formation.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.768-773
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• 1995

We describe a manufacturing method and characteristics on components of molten carbonate fuel cell. Cr, Al, AI$_{2}$O$_{3}$, Co, MgO powder were mixed with Ni powder for anode components and NiO was used for cathode electrode. The electrolyte plate consisted of LiAIO$_{2}$ and carbonate (Li$_{2}$CO$_{3}$/K$_{2}$CO$_{3}$=62/38) and these three were manufactured by doctor-blade method. As a result, open circuit voltage was 1.05[VI at Ni-10Cr anode and porosity was above 60[%].

• Journal of Magnetics
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• v.7 no.2
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• pp.29-39
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• 2002

The initial NiCuZn synthetic ferrite were acquired from thermally decomposing the metal nitrates $Fe(NO_3)_39H_2O, Zn(NO_3)_26H_2O, Ni(NO_3)_26H_2O, and Cu(NO_3)_23H_2O$ at $150^circ{C}$ for 24 hours, and then we calcined the synthetic powder at $500^circ{C}$, pulverized each of those for 3, 6, 9, 12, and 15 hours in a steel ball mill, sintered each at $700^circ{C}$ to $1,000^circ{C}$ for 1 hour, and thus studied their microstructures and electromagnetic properties. We could make the initial specimens chemically bonded in liquidity at a low-temperature $150^circ{C}$, by using the low melting points less than $200^circ{C}$ of the metal nitrates instead of the mechanical ball-mill pulverization, then narrow a distance between the particles into a molecular one, and thus lower the reaction point of sintering by at least $200^circ{C}$ to $300^circ{C}$. Their initial permeability was 50 to 400 and their maximum magnetic induction density and coercive force, 2,400 G and 0.3 Oe to 0.5 Oe respectively, which was similar to those of NiZnCu ferrite synthesized in the conventional process. In the graph of initial permeability by frequencies, a $180^circ{C}$ rotation of the magnetic domains which appears in a broad band of micro-wave before and after the resonance frequency, could be perceived.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.97.2-97.2
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• 2011

Pt-Ru and Pt-Ni bimetallic catalysts were prepared and tested for heavy hydrocarbon reforming. Metals were supported on CGO($Ce_{0.8}Gd_{0.2}O_{2.0-x}$) by incipient wetness method. The prepared catalysts were characterized by Temperature programmed reduction(TPR). Oxidative steam reforming of n-dodecane was conducted to compare the activity of the catalysts. The reforming temperature was varied from $500^{\circ}C$ to $800^{\circ}C$ at fixed $O_2$/C of 0.3, $H_2O$/C of 3.0 and GHSV of 5,000/h.Reduction peaks of metal oxide, surface CGO and bulk CGO were detected. Reduction temperature of metal oxide decreased over the bi-metallic catalysts. It is considered that interaction between metals leads to decrease interaction between metal and oxygen. On the other hands, reduction temperatures of surface CGO were dectected in the order of Pt-Ru > Pt-Ni > Pt. low reduction temperatures of surface CGO indicates the low activation energy for oxygen ion conduction to metal. Oxygen ion conduction is known as de-coking mechanism of ionic conducting supports such as CGO. In activity test, fuel conversion was in the same order of Pt-Ru > Pt-Ni > Pt. Especially, 100% of fuel conversion was obtained over Pt-Ru catalysts at $500^{\circ}C$.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.4
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• pp.330-336
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• 2018

El $Ni{\tilde{n}}o$ would cause extreme weather conditions, which would result in a negative impact on crop production. The objective of this study was to assess the impact of El $Ni{\tilde{n}}o$ on spring kimchi cabbabe production for the period from 1981- 2016 in South Korea. In this study, years with less than 1.0 Oceanic $Ni{\tilde{n}}o$ index were classified into non El $Ni{\tilde{n}}o$ years. The other years were classified as El $Ni{\tilde{n}}o$ years. The national average production of spring kimchi cabbage in El $Ni{\tilde{n}}o$ years ($3,800kg\;10a^{-1}$) tended to be less than that in non El $Ni{\tilde{n}}o$ years ($4,016kg\;10a^{-1}$). However, there was no significant differences (p = 0.078) in the production between these groups of years. The averaged production of spring kimchi cabbage of El $Ni{\tilde{n}}o$ end years ($3,707{\pm}331kg\;10a^{-1}$) was less than those of El $Ni{\tilde{n}}o$ start years and non El $Ni{\tilde{n}}o$ years by 186 and $309kg\;10a^{-1}$, respectively. Still, such difference was not significant statistically (p=0.127), either. In contrast, there were provinces where the production of spring kimchi cabbage had significant differences by El $Ni{\tilde{n}}o$ occurrence. For example, El $Ni{\tilde{n}}o$ end years had significantly less spring kimchi cabbage production than El $Ni{\tilde{n}}o$ start years and non El $Ni{\tilde{n}}o$ years in Gangwon (p=0.038) and Gyeongbuk (p=0.053) provinces. It appeared that differences in cabbage production resulted from short sunshine duration, which merits further analysis on the impact of extreme weather condtions during El $Ni{\tilde{n}}o$ years on crop production.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2597-2603
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• 2013

The reactions of hydrated $CdCl_2$, $MnCl_2$, and $NiCl_2$ with 2,2'-bipyidine-3,3',6,6'-tetracarboxylic acid ($H_4bptc$) afforded the mononuclear [$Cd^{II}(H_2bptc)(H_2O)_3]{\cdot}H_2O$ (1), linear $\{[Cd(H_2bptc)(H_2O)]{\cdot}3H_2O\}_n$ (2), 3-D heterobimetallic $[NaCd(Hbptc)(H_2O)]$ (3), layer $[Mn(H_2bptc)(H_2O)]_n$ (4) and a dinuclear compound $[Ni_2(H_2bptc)-(H_2O)_2]{\cdot}6H_2O$ (5). These compounds have been characterized by elemental analysis, IR, and their structures have been determined by X-ray crystallography. The thermal stabilities of 1-3 were measured by thermogravimetric analysis (TGA) and their solid state luminescence properties together with the free ligand $H_4bptc$ were investigated at room temperature.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.634-641
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• 2004

The photocatalytic performance of $TiO_2$ thin films coated on porous alumina balls using various aqueous $TiOCl_2$ solutions as starting precursors, to which 1.0 $mol\%$ transition metal ($Ni^{2+},\;Cr^{3+},\;Fe^{3+},\;Nb^{3+},\;and\;V^{5+}$) chlorides had been already added, has been investigated, together with characterizations for $TiO_2$ sols synthesized simultaneously in the same autoclave through hydrothermal method. The synthesized $TiO_2$ sols were all formed with an anatase phase, and their particle size was between several nm and 30 nm showing ${\zeta}-potential$ of $-25{\sim}-35$ mV, being maintained stable for over 6 months. However, the $TiO_2$ sol added with Cr had a much lower value of -potential and larger particle sizes. The coated $TiO_2$ thin films had almost the same shape and size as those of the sol. The pure $TiO_2$ sol showed the highest optical absorption in the ultraviolet light region, and other $TiO_2$ sols containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ showed higher optical absorption than pure sol in the visible light region. According to the experiments for removal of a gas-phase benzene, the pure $TiO_2$ film showed the highest photo dissociation rate in the ultraviolet light region, but in artificial sunlight the photo dissociation rate of $TiO_2$ coated films containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ was measured higher together with the increase of optical absorption by doping.