• 한국세라믹학회지
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• 제29권10호
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• pp.806-814
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• 1992

The aim of this study was to investigate the change in compressive strength, freacture behavior and degradation of piezoelectric properties with compressive cyclic loading in Pb(Zr, Ti)O3 of tetragonal, morphotropic phase boundary and rhombohedral composition. The highest compressive strength was found in rhombohedral composition. After poling treatment the strength increased by 8.4% and 6.5% in tetragonal and morphotropic phase boundary compositions respectively while changed little in rhombohedral. The increase of compressive strength after poling treatment is believed to be due to the internal stress around grain boundary by domain alginment toward electric field direction in the microstructures having tetragonality and the occurrence of domain switching to the direction perpendicular to electrical field during fracture. Fracture mode relatively change from transgranular to intergranular was observed in the large grain sized tetragonal and morphotropic phase boundary compositions before and after poling but the transgranular fracture mode always remained in the rhombohedral composition. From the X-ray diffractometer analysis the domains parallel to the electric field direction is known to undergo rearrangement during the cyclic loading into random direction that is responsible for the degradation of piezoelectric property.

• Elastomers and Composites
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• 제50권4호
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• pp.304-313
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• 2015

In this study, the anionic emulsified asphalt was prepared by dispersing asphalt particles evenly into water with combination of anionic and nonionic surfactants. Effects of NaOH and $CaCl_2$ on the phase stability of the emulsified asphalt were also investigated through zeta potential value and rheology behavior; the emulsified asphalt added with NaOH and $CaCl_2$ showed higher zeta potential value than that the asphalt with addition of only anionic and nonionic surfactants. In addition, with regard to shear thinning behaviors, it was found that pH of the emulsified anionic asphalt and $Ca^{2+}$, counter ion, affected the phase stability. SBR (styrene-butadiene-rubber) latex, EPD (water dispersed Epoxy), PU (polyurethane) and RI-10S, SBS (styrene-butadiene-styrene)-based property improvement additive, were used and studied to enhance the adhesion properties with the aggregates. RI-10S, however, was found to be only compatible with the anionic emulsified asphalt; the coating rate, adhesion and compression strength were increased with the RI-10S content.

• Journal of Magnetics
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• 제10권1호
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• pp.28-32
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• 2005

The magnetic properties and ordering behavior of Nb-doped FePt alloy films prepared by dc-magnetron sputtering were investigated. It was found that Nb addition retarded the ordering reaction from the disordered face-centered-cubic (fcc) Al phase to the ordered face-centered-tetragonal (fct) L1₀ phase. The tetragonality (c/a ratio) of the ordered fct L1₀ phase increased with the Nb concentration. Nb addition hampered c-axis contraction during ordering, probably because the larger Nb atoms occupy Pt sites. Consequently, the coercivity and magnetocrystalline anisotropic energy of Nb-doped FePt alloy films are lower than those of un-doped FePt film under equivalent annealing conditions.

• 한국자기학회지
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• 제8권4호
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• pp.179-184
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• 1998

일반적으로 페로브로스카이트 구조의 망간 산화물에서 많이 관찰되어온 초거대 자기 저항 현상은 임계점 (큐리온도) 부근에서 온도 변화에 의한 상자성-강자성 상전이와 동반한 전기 전도 기수 변화에 따른 급격한 저항 변화와 매우 밀접한 광계가 있다. 본 논문에서는 이러한 전기 저항-온도 거동을 모사하기 위해, 온도에 따른 상분율 변화 함수를 유효매질 이론(effective media theory)을 이용하여 모형식을 마련하엿다. 미 모형식은 실제 La0.7Ca0.3MnO3의 저항-온도 거동을 매우 정확하게 모사하였다.

• 한국전자통신학회논문지
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• 제9권11호
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• pp.1297-1304
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• 2014

사람의 감정 중의 하나인 사랑은 사회학과 심리학에서 주된 관심사로 연구되어 왔다. 본 논문에서는 로미오와 줄리엣의 사랑 방정식[ ]에서 이들의 거동을 시계열과 위상 공간으로 나타내고, 이들 사이에 외부적인 자극인 3자가 개입했을 때의 관계를 시계열과 위상 공간으로 나타내어 이들 사이의 거동 관계를 분석한다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.355-356
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• 2006

WC-TiC-TaC binderless cemented carbide was oxidized under low partial pressure of oxygen (50ppm) at 873K for 1 to 20 h. Surface roughness was measured using atomic force microscope, and effect of TiC amount on oxidation behavior of the carbide was investigated. WC phase was oxidized more easily than WC-TiC-TaC solid solution phase. With an increase in TiC amount, WC-TiC-TaC phase increased and the oxidation resistance of the carbide increased.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.826-831
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• 2019

Experimental data of phase equilibrium is reported for caprolactone acrylate in supercritical carbon dioxide. Bubble-point data was measured by synthetic method at temperatures ranging from (313.2 to 393.2) K and pressures up to 55.93 MPa. In this research, the solubility of carbon dioxide for the (carbon dioxide + caprolactone acrylate) system decreases as temperature increases at a constant pressure. The (carbon dioxide + caprolactone acrylate) system exhibits type-I phase behavior. The experimental result for the (carbon dioxide + caprolactone acrylate) system was correlated with Peng-Robinson equation of state using mixing rule. The critical property of caprolactone acrylate was predicted with the Joback and Lyderson method.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.240-245
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• 1992

The effect of the addition of sodium dodecyl sulfate (SDS) to a buffered mobile phase (pH 3.4) on the retention of nucleotides, nucleosides and bases was investigated with a polyvinyl alcohol (PVA) column. Depending on the concentration of SDS, two different trends in the retention of nucleosides and bases containing an $NH_2$ group were observed. If the concentration of SDS was less than 5.5 mM, the retention of compounds containing an $NH_2$ group increased as the concentration of SDS in the mobile phase increased. In contrast, if the concentration was greater than 5.5 mM, the retention of compounds containing an $NH_2$ group decreased. Thus, the SDS acted as an ion-pairing reagent at lower concentration but formed micelles at higher concentrations. The retention behavior of the nucleosides and bases in the presence of a micellar concentration of SDS in the mobile phase on the PVA column was compared to the retention behavior on other types of columns.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.478-485
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• 2018

The effect of reduced graphene oxide (RGO) addition on the dielectric and piezoelectric behavior of the polyvinylidene fluoride (PVDF) films was studied. Dielectric constant increased by four times and piezoelectric coefficient also increased twice by the addition of RGO in the PVDF films. Based on capacitance-voltage and ellipsometry measurements and the Kramers-Kronig transformation, it is concluded that the enhanced dielectric and piezoelectric properties of the PVDF/RGO films resulted from the increased orientational polarization due to a phase transition from nonpolar crystalline ${\alpha}$ phase to polar crystalline ${\beta}$ phase in the PVDF structure.

• Structural Engineering and Mechanics
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• 제91권6호
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• pp.607-626
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• 2024

This study explores the use of advanced concrete types to improve the performance of composite steel shear walls (CSPSWs), particularly in delaying cracking and failure. A two-phase approach is implemented. Phase I utilizes non-linear finite element analysis and Gene Expression Programming to develop a novel method for determining the minimum concrete thickness required in CSPSWs. Phase II investigates the effect of concrete type, opening area, and location on the behavior of CSPSWs with openings. The results demonstrate that ultra-high performance concrete (UHPFRC) significantly reduces out-of-plane displacement and tensile cracking compared to normal concrete. Additionally, the study reveals a strong correlation between opening position and load-bearing capacity, with position L3 exhibiting the greatest reduction as opening size increases. Finally, UHPFRC's superior energy dissipation translatesto a higher equivalent viscous damping coefficient.