• Earthquakes and Structures
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• v.10 no.5
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• pp.1111-1123
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• 2016

To study seismic performance of steel frame-bent structure, one specimen with one-tenth scale, three-bay, and five-story was tested under reversed cyclic lateral load. The entire loading process and failure mode were observed, and the seismic performance indexes including hysteretic loops, skeleton curve, ductility, load bearing capacity, drift ratio, energy dissipation capacity and stiffness degradation were analyzed. The results show that the steel frame-bent structure has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were in spindle shape, which shape were full and had larger area. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. It can be helpful to design this kind of structure in high-risk seismic zone.

• Computers and Concrete
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• v.17 no.5
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• pp.597-612
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• 2016

The present work focuses on the use of coconut fiber in self compacting concrete. Self-Compacting Concrete (SCC) is a highly flowable, stable concrete which flows readily into place, filling formwork without any consolidation and without undergoing any significant segregation. Use of fibers in SCC bridge the cracks and enhance the performance of concrete by not allowing cracks to propagate. They contribute to an increased energy absorption compared to plain concrete. Coconut fiber has the highest toughness among all natural fibers. It is known that structures in the seismic prone areas are always under the influence of cyclic loading. To justify the importance of strengthening SCC beams with coir fiber, the present work has been undertaken. A comparison is made between cyclic and static loading of coconut fiber reinforced self compacting concrete (FRSCC) members. Using the test data obtained from the experiment, hysteresis loops were drawn and comparison of envelope curve, energy dissipation, stiffness degradation were made and important conclusions were draw to justify the use of coconut fiber in SCC.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.731-736
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• 2017

Friction Pendulum isolators are tools developed in the past few decades. The simplest form of these isolators, are FPS whose main disadvantages are having a constant frequency independent of the frequency of the structure. For this reason, researchers have invented VFPI isolator whose frequency is variable and depends on displacement. Another friction pendulum isolator is DCFP isolator which is a combination of two FPS isolators. In this article, first by changing the geometry of DCFP isolator plates from spherical to elliptical, the motion and frequency equations of DVFPI isolators are defined, and then the seismic behavior of DVFPI isolators are analyzed in various geometric and plate friction settings using motion equations, and confirmed using ABAQUS software. The most important results of this study are that the hysteresis behavior of DVFPI isolators are severely nonlinear, its curve follows two distinct curvatures, and that the restoring force is faced with softening mechanism that limits the seismic force transmitted to the structure, whereas the restoring force in DCFP isolators increases linearly with increasing displacement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.15-20
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• 2000

In this paper, hydraulic damper was studied to solve vibration problems of bridge, structures and several mechanic parts rising magnetic fluid. The damper was modeled using Magneto Rheological fluid and MR damper was manufactured on the basis of design drawing. To investigate the efficacy of magneto rheological phenomenon. experiments were performed on the several design parameters using Universal Testing Machine(UTM). Damping efficacy were examined by frequencies. displacement and electric currents through experiments.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.43-47
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• 2003

Lead zirconate titanate (PZT) thin films were fabricated by the pulsed laser ablation deposition (PLAD) method onto Pt/Ti/SiO$_2$/Si substrates. Crystalline phases as well as preferred orientations in PZT films were investigated by X-ray diffraction analysis (XRD). The well-crystallized perovskite phase and the (101) preferred orientation were obtained by two-step annealing at the conditions of $650^{\circ}C$, 1 hour. It was found that the temperature for the pulsed laser ablated PZT films annealed via a two-step annealing process can be reduced 20$0^{\circ}C$ compared to that of the conventional three-step annealing temperature profile for enhancing the transformation of the perovskite phase. The remanent polarization and the coercive field of this film were about 20 $\mu$C/$\textrm{cm}^2$ and 46 kV/cm, while the dielectric constant and loss values measured at 1 KHz were approximately 860 and 0.04, respectively. The interesting phenomena of this film, such as vertical shift in hysteresis curve, are also discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.65-69
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• 2004

We synthesized photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the photopolymer surface can be obtained. However, the low pretilt angles were obtained below 1$^{\circ}$. The Voltage-transmittance (V-T) curve without backflow bounce in the photoaligned TN cell with UV exposure was observed. The response time of photoaligned TN cell was measured about 24 ms. Finally, The photoaligned TN cell has few hysteresis, and shows the residual DC voltage that is less.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.676-679
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• 1997

The present paper is concerned with the optimal deslgn that the static spring rate of the fiber-reinforcement composite spring is fitted to that of the steel leaf spring. The thickness and w~dth of springs were selected as deslgn variables. And object functions of the regression model were obtained through the analysis with a common analytic program. After regression coefficients were calculated to get functions of the regression model, optimal solutions were calculated with DOT. E-GlassIEpoxy and CarbonIEpoxy were used as fiber reinforcement materials in the design, which were compared and analyzed with the steel leaf spring. It was found that the static spring rate of the optimal model was almost similar to that of the existing spring.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.345-354
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• 1990

The densification behaviro and resulting properties of cordierite-aluminium titanate composites containing 5 to 40wt.% aluminium titanate were investigated. Compared with cordierite monolithics a substantial increase of sintering temperature range for composites was observed, which was due to the formation of cordierite and glass phase at relatively low temperatures. The bending strength of composites showed its maximum at 30wt.% aluminium titanate content, which was about 50% increase relative to the cordierite monolithics, then decreased by a small amount at 40wt.% aluminium titanate content. The decrease was explained by the increase of microcracks whose presence was confirmed by the hysteresis of thermal expansion curve of composites. However, the microcracks formed was not severe enough to produce a significant decrease in strength, which was also evidenced by the continuous increase of thermal expansion coefficient up to 40wt.% aluminium titanate content.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.527-536
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• 1987

PLZT ceramics of composition La/Zr/Ti=X/65/35(X=5-10 at.%) were fabricated by two state sintering technique.Transparent PLZT ceramics were obtained in the composition above 8 at. % La. Variations of electrooptic properties in the compositions between 8 at. % and 9 at. % La were able to be expected from the significant differences of P-E hysteresis curve and the changes of dielectric phase transition. The range of birefringence of 8/65/35 specimen was 4.08${\times}$10-3. Domain switching of 9/65/35 specimen was agreed with the applied electric pulse because input pulse signal corresponds to optical pulse response.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.4
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• pp.158-163
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• 2001

Magnetization losses of a Bi-2223 tape in magnetic fields parallel to the tape surface were measured by a room temperature cancellation and a cryogenic temperature cancellation. The results indicate that the same loss data are observed for both methods. The magnetization losses are hysteretic because the measured losses agree well with calculated ones based on a critical state model. In the full field penetration cases the magnetization losses increase with the frequency but in the partial field penetration cases the influence of the frequency is opposite.