• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.85-88
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• 2001

The NdBaCuO superconductor samples were Zone-melted in low oxygen partial pressure (1% $O_{2}+ 99% Ar$ ). The Zone-melting temperature was decreased about $120^{\circ}C$ from $1060^{\circ}C$ the zone-melting temperature in air. Thus the loss of liquid phase ($BaCuO_{2}$ and CuO) was reduced during the zone-melting process. The content of non-superconducting phase Nd422 in zone-melted NdBaCuO samples was clearly decreased, so was the substitution of Nd for Ba. The superconductivity of zone-melted $Nd_{1+x}Ba_{2-x}Cu_{3}O_{y}$ prepared under low oxygen partial pressure was distinctively improved.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.85-88
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• 2001

The NdBaCuO superconductor samples were Zone-melted in low oxygen partial pressure (1% O$_2$+99% Ar). The Zone-melting temperature was decreased about 120$^{\circ}C$ from 1060$^{\circ}C$ the zone-melting temperature in air. Thus the loss of liquid phase (BaCuO$_2$ and CuO) was reduced during the zone-melting process. The content of non-superconducting phase Nd422 in zone-melted NdBaCuO samples was clearly decreased, so was the substitution of Nd for Ba. The superconductivity of zone-melted Nd$\sub$1+x/Ba$\sub$2-x/Cu$_3$O$\sub$y/ prepared under low oxygen partial pressure was distinctively improved.

• Journal of the Korean Wood Science and Technology
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• 제23권2호
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• pp.37-46
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• 1995

The substitution of carboxymethylated hydroxyl group in pulp revealed more hydrophilic than hydroxyl group. And then fibers were more flexible, swell more which leads to better conformation between fibers in turn this raise paper strength. In this paper, we tried to chemical modifyings of recycled fiber, OCCs(old corrugated containers). Many researchers have examined chemical modification of papermaking fiber by partial carboxymethylation(PCM) using a organic solvent processes. We made modified PCM processes adapted waters m replace of the organic solvent. Our testings for the optimum conditions on the new method, conditions as reaction time, temperature, liquor ratios were designed likely plant system. Freenesses(SR$^{\circ}$) were increased following on carboxyl content of the samples. Handsheets of untreated samples and partial carboxymethylated OCCs were made by optimum conditions on different concentrations of the reagent. As results, maximum 25% strength increasing effects were obtained by the new method.

• 한국환경과학회지
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• 제13권7호
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• pp.619-626
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• 2004

We have studied the catalytic combustion of soot particulates over perovskite-type oxides prepared by malic acid method, The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions such as temperature and $O_2$ concentration were investigated. The partial substitution of alkali metals into A site in the $LaMnO_3$ catalyst, enhanced the catalytic activity in the combustion of carbon particulate and the activity was shown in the order: Cs > K > Na. For the $La_{1-x}Cs_{x}MnO_{3}$ catalysts, the catalytic activity showed the maximum value with x=0.3 but no more increase on the catalytic activity was shown with x > 0.3. For the $La_{0.8}Cs_{0.2}MnO_{3}$ catalyst, the substitution of Fe or Ni increased the ignition temperature. The ignition temperature decreased with an increase of $O_2$ concentration, however, no more increase in the catalytic activity was shown with $O_2$ concentration > 0.2. The introduction of NO into reactants showed no effect on the catalytic activity.

• Journal of Advanced Marine Engineering and Technology
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• 제27권6호
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• pp.704-713
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• 2003

The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr-5Ni-3Mo duplex stainless steel(DSS) aging heat treated in a temperature range of 600~$1000^{\circ}C$ has been investigated. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSS had decreased, After aging for 2min at 700~$900^{\circ}C$, the pitting potential of the 3Mo steel decreased remarkably, while that of the W-substituted steel hardly changed. During aging. the intermetallic $\sigma$ and secondary austenite ($\gamma_2$) phases were precipitated. and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700~$750^{\circ}C$ for 10 h, which could be caused by the $\gamma_2$ formation. The ${\gamma}$$_2$ phase could affect the depletion of molybdenum and chromium in the $\gamma_2/\alpha and \gamma_2/\sigma$ boundaries.

• 한국세라믹학회지
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• 제28권9호
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• pp.689-695
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• 1991

Dielectric properties of Ba1-$\chi$Sr$\chi$Ti1-yCayO3-y ceramics, where Sr and Ca were doped to Ba-site and Ti-site within the range of 0 x 0.24 and 0 y 0.05, respectively, were investigated. The substitution of Ca for Ti, which maintained the high resistivity of these formulations after sintering in a reducing atmosphere, was confirmed. Ca addition decreased the tetragonality c/a, increased the unit cell volume, and lowered Curie temperature, which were attributed to the occupancy of Ca2+ ions on Ti-sites. The lowering of Curie temperature by Ca addition was affected by the substitution of Sr for Ba-site; within 2 mol% of Ca, Curie temperature was lowered at a rate of 2$0^{\circ}C$ and 16$^{\circ}C$ per mol% of Ca at x=0 and x=0.08, respectively. Whereas the resistivity of the formulations without Ca was reduced to 107 {{{{ OMEGA }}cm, when sintered at low oxygen partial pressure of 10-9 MPa, the resistivity value higher than 1011 {{{{ OMEGA }}cm was maintained for the formulations containing Ca more than 0.5 mol%. Dielectric loss factor, tan$\delta$, was about 1% for most formulations.

• Bulletin of the Korean Chemical Society
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• 제18권4호
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• pp.390-394
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• 1997

Nucleophilic substitution reactions of 2-thiopheneethyl benzenesulfonates (2-TEB) and 3-thiopheneethyl benzenesulfonates (3-TEB) with anilines and N,N-dimethylanilines (DMA) are investigated in acetonitrile at 60.0 ℃. The cross-interaction constants ρxz determined for the reactions with anilines are large negative (- 0.50) which are comparable to those for the similar predominantly frontside-attack SN2 reactions of 1-phenylethyl (1-PEB), 2-phenylethyl (2-PEB) and cumyl benzenesulfonates. A large negative ρxz value (- 0.4∼- 0.8) is considered to provide a mechanistic criterion for the frontside-attack SN2 mechanism with a four-center transition state. In agreement with this proposal the kinetic isotope effects, kH/kD, involving deuterated aniline nucleophiles are all greater than one reflecting partial N-H(D) bond cleavage in the transition state. The MO theoretical reactant structures of 1-PEB, 2-PEB and 2-TEB based on the PM3 calculation show that the benzene ring blocks the backside nucleophile approach to the reaction center carbon (Cα) enforcing the frontside-attack SN2 mechanism.

• 한국수소및신에너지학회논문집
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• 제9권1호
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• pp.16-24
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• 1998

최근 Ni-MH 전지의 고성능화를 위해 방전용량이 높은 Zr기 $AB_2$ 형의 수소 흡장 합금이 주목받고 있다. 본 연구에서는 이 중에서 $ZrV_{0.1}Mn_{0.7}Ni_{1.2}$ 합금을 선택하여 합금의 열처리 그리고, Mn 대신 Mo의 부분치환이 전극의 특성에 미치는 영향을 조사하였다. 합금은 먼저 아크 용해로를 사용하여 제작하였으며, 이 합금 중 일부를 $1,100^{\circ}C$에서 가열 후 각각 서냉과 급냉 처리를 행하였다. 이 세 가지 종류의 합금들을 이용하여 활성화 거동, 고율 방전 특성, 자기 방전 특성 등의 전극특성을 평가하였다. 그 결과 합금은 열처리에 의해서 방전용량이 감소하고 고율 방전율 또한 감소하였다. 그러나, 전기 화학적으로 구한 압력-조성 등온곡선의 평탄구역의 기울기를 감소시켰다. 또한 $ZrV_{0.1}Mn_{0.7}Ni_{1.2}$ 합금의 Mn을 Mo으로 부분 치환함에 의해서 방전용량의 감소 없이 자기방전특성을 크게 개선할 수 있었다.

• Advances in concrete construction
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• 제9권2호
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• pp.217-225
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• 2020

The recovery of waste proves a solution with two impacts: the environmental impact by the reduction of pollution and the gain of the occupied space by this waste, and the economic impact by the use of these lasts in the building and in the area of public works. The present research consists in recovering a waste marble (thrown powder exposed to the different meteorological phenomena) generated by the quarry marble of Fil-fila, located at the east side of Skikda in the north-east of Algeria, and add it, as sand in the composition of sand concrete. To carry out this research, we analyzed the evolution brought by the substitution of ordinary sand by marble waste sand, with 25%, 50%, 75% and 100% on the properties in the fresh state (density, workability and air content) and in the cured state (compressive strength, tensile strength, surface hardness and sound velocity). For durability we tested water absorption by immersion and chloride penetration. The results obtained are compared with control samples of 0% of substitution rate. In order to have a good filling of the voids in the granular skeleton; we added a quantity of limestone recycled fines from the quarries and for a good workability a super-plasticizing additive. The results showed that the partial substitution modified both the fresh and the hardened characteristics of the tested concretes, the durability parameters also improved.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.267-270
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• 1999

In this paper, the application of limestone powder, which produced by being gathered electrically in the process of manufacturing of cement, to high fluidity concrete are investigated. According to the experimental results, especially, high viscosity and the loss of air content are accomplished by applying limestone powder as the partial substitution of fine aggregates. In case of hardened concrete, high compressive strength can be achieved by using limestone powder.