• Architectural research
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• v.19 no.3
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• pp.79-87
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• 2017

In earthquake engineering, dynamic analyses are usually conducted by using a nonlinear analytical model of the entire building in order to identify the performance against earthquakes. At the same time, a large number of dynamic analyses are required to consider uncertainties on analytical models and ground motions. Therefore, it is necessary for the analytical model to be adequate, that is to say, the runtime should not be too long as the entire building is modeled to be in much detail, or the nonlinear model should not yield outputs very far from the actual ones by excluding important behaviors too much. The analytical model is usually developed based on experimental results, which have been already conducted for reinforced concrete columns with relaxed details. Therefore, this study aimed at making analytical models to be able to simulate the hysteretic behavior of the columns simply and easily. The analytical model utilizes a lumped hinge model to represent nonlinear moment-rotation hysteretic behavior of RC columns, which is feasible for nonlinear dynamic analyses usually conducted in earthquake engineering and for matching the analytical model to test results. For the analytical model, elements and material models provided by OpenSees are utilized. The analytical model can define the envelope curve, pinching, and unloading stiffness deterioration, but shortcoming of this model is not to be able to consider axial force-moment interaction directly and to simulate strength deterioration after post-capping completely. However, the analytical model can still represent test results well by considering that the goal of this study is to propose a general way to represent the hysteretic behavior of RC columns with relaxed details, not to provide parameters for a refined hysteretic model that can be just applied case by case.

• Journal of the Korean Vacuum Society
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• v.11 no.4
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• pp.230-234
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• 2002

Metal-ferroelectric-semiconductor(MFS) capacitors by using rapid thermal annealed $LiNbO_3$/Si structures were successfully fabricated and demonstrated nonvolatile memory operations of the MFS capacitors. The C-V characteristics of MFS capacitors showed a hysteresis loop due to the ferroelectric nature of the $LiNbO_3$thin film. The dielectric constant of the $LiNbO_3$film calculated from the capacitance in the accumulation region in the capacitance-voltage(C-V) curve was about 25. The gate leakage current density of MFS capacitor using a platinum electrode showed the least value of $1{\times}10^{-8}\textrm{A/cm}^2$ order at the electric field of 500 kV/cm. The minimum interface trap density around midgap was estimated to be about $10^{11}/cm^2$.eV. The typical measured remnant polarization(2Pr) value was about 1.2 $\mu\textrm{C/cm}^2$, in an applied electric field of $\pm$ 300 kv/cm. The ferroelectric capacitors showed no polarization degradation up to about $10^{10}$ switching cycles when subjected to symmetric bipolar voltage pulse in the 500 kHz.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.757-762
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• 2010

Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.

• Journal of Magnetics
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• v.9 no.2
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• pp.52-59
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• 2004

As deposited and annealed MTJs with the structure of $Ta(5 nm)/Cu(10 nm)/Ta(5 nm)/Ni_{80}Fe_{20}(2 nm)/Cu(5 nm)/ Ir_{25}Mn_{75}(10 nm)/Co_{70}Fe_{30}(2.5 nm)/Al-O/Co_{70}Fe_{30}(2.5nm)/Ni_{80}Fe_{20}(t)/Ta(5nm)/Ni_{80}Fe_{20}(t)/Ta(5 nm)$, where t=10, 30, 60 and 100 nm were characterized by XRD and magnetic hysteresis loops measurements. The XRD measurements were done in grazing incidence $(GID scan-2{\theta})$ and ${\theta}-2{\theta}$ geometry, by rocking curve $(scan-{\omega})$ and pole figures in order to establish correlation between texture and crystallites size and magnetic parameters of exchange biased and interlayer coupling. The variations of shifting and coercivity field of free and pinned layers after annealing in $300^{\circ}C$ correlate with the improvement of ［111］ texture and grains size of $Ni_{80}Fe_{20}$ and $Ir_{25}Mn_{75}$ respectively. The exchange biased and the coercivity fields of the pinned layer linearly increased with increasing grain size of $Ir_{25}Mn_{75}$, The reciprocal proportionality between interlayer coupling and coercivity fields of the free layer and grain size of $Ni_{80}Fe_{20}$ was found. The enhancement of interlayer coupling between pinned and free layers, after annealing treatment, indicates on the correlated in-phase roughness of dipolar interacting interfaces due to increase of crystallites size of $Ni_{80}Fe_{20}$.

• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.41-46
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• 2018

Six sigma methodology is the management tools not only can cause productivity enhancement through the quality control and cost reduction of products and services but also can be applied to various activities of corporates such as research and development. Development of high-density information storage media and devices is indispensible to accomplish the information convergence era. In this paper, we report the case of applying six sigma methodology and tools to the development project of high-density information storage media. The standard DMAIC process was applied to the project and pursuing goals and tools and results in each stage were explained in detail. By adopting the methodology, we could establish fabrication methods of information storage media of recording density higher than $250Gb/in^2$ with high uniformity and reproducibility. The magnetic property and performance of fabricated media were confirmed through measurement of the magnetic hysteresis curve.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.128-135
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• 2007

In response to anthropogenic global warming due to a buildup greenhouse gas, the effect of the air temperature on water temperature has been noticed. Therefore, effects have been made to build an air/water temperature relationship at three study regions using the data collected by the Ministry of the Maritime Affairs and Fisheries (MOMAF). The air/water relationship varies with time-scale and weekly time-scale was chosen for the study. The data were fitted to the S-shaped non-linear relationship, and the parameters for the S-curve were derived using a single-criteria multi-parameter optimization scheme. Separate regression curves were fitted to consider seasonal hysteresis at the Masan site. The study results support the S-shaped non-linear relationship is the best fit for the air/water relationship at the Korean coastal zone. This study will contribute to determine the future policy regarding water quality and ecosystem for the decision-driving organization.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.118-126
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• 2003

In the present study, the residual stresses can have a significant on the life of structural engineering components. Residual stresses are created by the surface treatment such as shot peening or deep rolling. The objective of this experimental investigation is to study the influence of friction and wear characteristics due to residual stress under dry sliding condition. Friction and wear data were obtained with a specially designed tribometer. Test specimens were made of SUP9(leaf spring material) after they were created residual stress by shot peening treatment. Residual stress profiles were measured at surface by means of the X-ray diffraction. Sliding tests were carried out different contact pressure and same sliding velocity 0.035m/s(50rpm). Leaf spring assembly test used to strain gauge sticked on leaf spring specimen in order to measure interleaf friction of leaf spring. Therefore, we were obtained hysteresis curve. As the residual stresses of surfaces increased, coefficient of friction and wear volume are decreased, but the residual stresses of surfaces are high, and consequently wear volume do not decreased. Coefficient of friction obtained from leaf spring assembly test is lower than that obtained from sliding test. From the results, structural engineering components reduce coefficient of friction and resistant wear in order to have residual stresses themselves.

• Journal of Pharmaceutical Investigation
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• v.26 no.3
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• pp.221-232
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• 1996

An abrasive, calcium hydrogen phosphate dihydrate (DCPD), was synthesized in a Box-wilson experimental design by reactions between phosphoric acid and milk of lime, and calcium chloride and sodium phosphate solutions, and stabilized with TSPP and TMP. The optimum conditions for preparation of DCPD from phosphoric acid with milk of lime were such as; reaction temp.; $51.9^{\circ}C$, conc. of lime; 25.9%, conc. of phosphoric acd; 77.9%, drying temp.; $60.2^{\circ}C$ and final pH; 6.46. The physico-chemical and pharmaceutical properties of DCPD were showed as follows: glycerin absorption value(68 ml/100g), whiteness(99.5%), particle size(10.9 nm), pH(7.8), and set test(pass). XRD and SEM of DCPD indicated a monoclinic system crystallographically. $N_2$ adsorption isotherm curve by BET showed non porous type II form. The micromeritic parameters of DCPD showed that surface area was $3.27{\sim}4.6\;cm^{2}/g$ and pore volume, pore area and pore radius were negligible. The rheogram of the toothpaste containing DCPD showed pseudoplastic flow with yield value of 321, and thixotropic behavior forming hysteresis loop. These results meet the requirements as abrasive standard, and sythesized DCPD is expected as a good dental abrasive such as a high quality grade in practice.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.106-108
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• 2005

The rutile polycrystal $Ti_{0.99}\;^{57}Fe_{0.01}O_2$ prepared with $^{57}Fe$ enriched iron have been studied by $M\ddot{o}ssbauer$ spectroscopy, X-ray diffraction and VSM. The $M\ddot{o}ssbauer$ spectrum of $Ti_{0.99}\;^{57}Fe_{0.01}O_2$ consists of a ferromagnetic and a paramagnetic phase over all temperature ranging from 4 to 300 K. Isomer shifts indicate $Fe^{2+}$ for the ferromagnetic phase, but $Fe^{3+}$ for the paramagneic phase of $Ti_{0.99}\;^{57}Fe_{0.01}O_2$ sample. It is noted that the magnetic hyperfine field of ferromagnetic phase had the value about 1.48 times as large as that of $\alpha$-Fe. The XRD data for $Ti_{0.99}\;^{57}Fe_{0.01}O_2$ showed a pure rutile phase with tetragonal structures without any segregation of Fe into particulates within the instrumental resolution limit The magnetic hysteresis (M-H) curve at room temperature showed an obvious ferromagnetic behavior and the magnetic moment per Fe atom under the applied field of 1 T was estimated to be about $0.71{\mu}_B$, suggesting a low spin configuration of Fe ions.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.14-17
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• 2006

[ $AIFeO_3$ ]has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, Mossbauer spectroscopy. The crystal structure is found to orthorhombic with the lattice parameters being $a_0=4.983\;{\AA},\;b_0=8.554\;{\AA},\;c_0=9.239\;{\AA}$, Magnetic hysteresis curve for $AIFeO_3$ showed weakly ferromagnetic phase at room temperature and a asymmetric shape dependent on the direction of applied field at low temperature. The Curie temperature determined by the temperature dependence of magnetization is 250 K. Mossbauer spectra of $AIFeO_3$ have been taken from 4.2 K to 295 K. Isomer shift at room temperature are found to be $0.11\~0.32\;mm/s$, which is consistent with ferric state. The absorption lines widths become broader with increasing temperature, which is attributed to the Fe ions distribution of each cation site and anisotropy energy difference of each sublattice.