• Proceedings of the Korean Magnestics Society Conference
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• 2005.06a
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• pp.26-26
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• 2005

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.84-87
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• 2020

The properties of ultra-thin two-dimensional (2D) organic ferroelectric Langmuir-Blodgett (LB) films of the poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] were investigated to find possible applicability in flexible and wearable electronics applications. In the C-V characteristics of the MFM capacitor of 2-monolayer of 5 nm films, a butterfly hysteresis curve due to the ferroelectricity of P(VDF-TrFE) was confirmed. Typical residual polarization value was measured at 2μC/㎠. When the MFM capacitor with ultra-thin ferroelectric film was measured by applying a 10 Hz bipolar pulse, it was shown that 65% of the initial polarization value in 105 cycles deteriorated the polarization. The leakage current density of the 2-monolayer film was maintained at about 5 × 10-8 A/㎠ for the case at a 5MV/cm electric field. The resistivity of the 2-monolayer film in the case at an electric field at 5 MV/cm was more than 2.35 × 1013 Ω·cm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.375-377
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• 1998

The magneto-optical properties of Co/Co$_2$TiSn two-phase magnet films were studied. These films show that relatively large Kerr rotations which are -0.4 deg. at the wavelength of 400 nm, compared to that of pure Co. It is conceivable that the magneto-optical effects may be due to both contributions of ferromagnetic Co matrix and ferromagnetic Co$_2$TiSn Heusler alloy precipitate. The perpendicular magnetization curve domonstrates a typical bubble domain hysteresis loop. the saturation magnetization change of the annealed film is less sensitive to temperature in the low temperature region and the Curie temperature of Co$_2$TiSn Heusler alloy precipitate is a little higher in the annealed film. These can be explained by the increase of the number of Co-Co exchange interaction in Heusler alloy structure resulting from the change of chemical ordering by annealing.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.123-128
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• 2017

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field ($H_{ex}$), coercivity ($H_c$), and MR ratio of Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/Ta(4 nm) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/Ta(4 nm) SV multilayer film showed $H_{ex}=2Oe$, $H_c=316Oe$, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/CoFe(3 nm)/Cu(2.5 nm)/CoFe(6 nm)/Ta(4 nm) SV multilayer film showed $H_c=37.5Oe$ and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of $H_{ex}$ and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.53-60
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• 2010

The comprehensive tests on unsaturated weathered granite soils are carried out to obtain the soil-water characteristic curve that is the one of the essential requisites to study the unsaturated soil. The weathered granite soils were obtained at Palgong mountain in Daegu. The existing test results have been carried out without overburden pressures and volume changes. In this study, the volumetric pressure plate extractor is improved to consider two factors such as overburden pressure and volume change. The applied overburden pressures were 0, 25, 50, 75, 100kPa and volume changes were measured at each phase. he results of this study are summarized as follows: As the overburden pressure increases, the volumetric water content decreases at the same matric suction and the air entry value increases and gradient of curve at the transition zone and the size of the hysteresis loops decreases. As the overburden pressure increases, the degree of saturation increases at the same matric suction and degree of saturation of the wetting curve is higher than that of dry curve. The SWCC with volume changes are slightly larger than those without volume changes. The general equation proposed by Fredlund & Xing(1994) to fit the experimental result of the SWCC indicates good agreement. The empirical parameters a, n, m as overburden pressure show similar inclination as the existing results.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.25-34
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• 2018

The physical properties and unsaturated characteristics of acid sulfate soils were investigated and analyzed. As the results of measuring physical properties of the acid sulfate soils obtained around the Ilkwang mine area, the dry unit weight is $1.246t/m^3$ and this soil is classified into the silty sand (SM) by USCS. Soil Water Characteristics Curves (SWCC) of the drying and wetting paths were measured by the automated SWCC apparatus. Also, Hydraulic Conductivity Functions (HCF) of the drying and wetting paths were estimated by the van Geunchten (1980) model which is the most well-known parameter estimation method. The hydraulic conductivity of acid sulfate soils in the dry path was continuously decreased with increasing the matric suction. However, the hydraulic conductivity in the wetting path was decreased relatively small with increasing matric suction and decreased suddenly just before water entry value of matric suction. Meanwhile, the hysteresis phenomenon was occurred in SWCCs and HCFs during the drying and wetting paths.

• Journal of the Korea Fashion and Costume Design Association
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• v.10 no.3
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• pp.173-180
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• 2008

Cotton, wool, cotton/wool blended (80:20) and tencel fabrics were treated with low temperature oxygen plasma, enzymes (cellulase or protease), or oxygen plasma-enzyme and they were examined for dyeing and handling properties for environment friendly finishing. The appropriate conditions for cellulase treatment were enzyme concentration of 3g/l, pH of 5, and $60^{\circ}C$ for one hour, and for protease treatment were enzyme concentration of 4g/l, pH of 8, and $60^{\circ}C$ for one hour. The equilibrium uptake of a direct dye on cotton changed with plasma treatment and plasma-cellulase treatment, and the rate of dyeing slightly decreased. When wool was dyed with acid dye, the equilibrium dye uptake did not change with plasma, protease treatment nor plasma-protease treatment, however, the rate of dyeing had increased with plasma-protease treatment. From these results, it is assumed that plasma attacks the surface of the fiber, and enzyme mainly affects the inner part of the fiber. Plasma treatment did not affect mechanical properties related to the handling of fabrics. The handling test showed increased extension at maxmum load(EM), tensile energy(WT) with decreased tensile resilience (RT), and the fabrics became softer but resilience decreased slightly with enzyme treatment. The bending recidity(B), hysteresis of bending moment(2HB), and hysteresis of shear force at five degrees(2HG5) decreased, however, shear stiffness(G) increased. I knew the plasma pre-treatment made fabrics softer with lower koshi(stiffness). The handling of plasma pre-treated fabrics was better than that of enzyme-treated fabrics. When we pre-treated fabrics, the handling test showed decreased coefficient of friction(MIU), geometrical roughness(SMD), while the surface of fabrics became smoother and numeri increased. Even though compression resilience(RC) increased, fukurami(bulky property) and compressive elasticity, decreased due to the linearity of compression-thickness curve(LC) and compression energy(WC).

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.948-952
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• 2001

PZT thick films were fabricated on alumina substrates by a screen printing method. They were sintered at $750^{\circ}C{\sim}1050^{\circ}C$ for 1 h under air or Pb atmosphere. Pyrochlore was observed as a second phase in PZT thick films sintered in air at temperatures of $950^{\circ}C$ and higher. PZT thick films sintered under Pb atmosphere showed denser microstructure, higher dielectric constant, and better-developed P-E hysteresis curve than the films sintered in air. PZT thick films sintered at $900^{\circ}C$ under Pb atmosphere showed the typical ferroelectric hysteresis with remanent polarization of $29.8{\mu}C/cm^2$ and coercive field of 48.4 kV/cm.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.701-709
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• 2003

The paper presented the seismic performance of T-stiffener moment connections for use in steel moment-resisting frames. The connections were strengthened by welding the vertical and horizontal clement of the T-stiffener to the beam flange and column f1ange. Finite clement analysis and experiments were conducted to determine the behavior of T-stiffener-reinforced connections. The results of the finite element analysis confirmed the effectiveness of the T-stiffener, whose horizontal element lengthened to mitigate local stress concentrations of the beam flange on the horizontal stiffener. Full-scale specimens were also tested cyclically to study hysteresis behavior. The main parameters used were the ratio of the T-stiffener to beam strength and the shape of the horizontal element. As the length of the horizontal element increased, the deformation capacity of the connections enhanced. Likewise, all specimens behaved according to the Ramberg-Osgood curve and showed stable hysteresis behavior.

• Earthquakes and Structures
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• v.22 no.6
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• pp.539-548
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• 2022

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.