• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.257-260
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• 2006

Coupled shear walls consist of two or more in-plane walls inter-connected with coupling beams. In order to effectively resist seismic loads, coupling beams must be sufficiently stiff, strong and posses a stable load-deflection hysteretic response. Much of requirements to the civil and building structures have recently been changed in accordance with the social and economic progress. Ductility of high performance fiber reinforced cementitious composites(HPFRCCs), which exhibit strain hardening and multiple crackling characteristics under the uniaxial tensile stress is drastically improved. This paper provides background for design guidelines that include a design model to calculate the shear strength of pseudo strain hardening cementitious composite steel coupling beam.

• Journal of the Optical Society of Korea
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• v.9 no.3
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• pp.99-102
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• 2005

Directional couplers of gradient-index plastic optical fibers were fabricated and characterized. In particular, we have employed a core-facet technique to make the directional couplers, which require mechanical side polishing and linkage. We have measured insertion loss, excess loss, and coupling ratio of the fabricated couplers as a function of polishing depth and coupling length. We found that polishing depth of $\~300{\mu}m$ and coupling length of $\~35mm$ are optimum conditions for minimizing the insertion and excess losses and for achieving 1: 1 coupling ratio.

• Textile Coloration and Finishing
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• v.19 no.5
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• pp.37-40
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• 2007

The electrostatic layer-by-layer technique provides a convenient way to control the construction of ultrathin films at nano-scale ranges and can be easily obtained. It can be also applicable to fiber substrate with dye compounds. We have fabricated multilayer dye films using diazonium resin and three couplers, which are prepared by self-assembly approach. This method is based on layer-by-layer deposition using electrostatic attraction between oppositely charged ions. Beside, the diazo coupling reaction proceeded to form azo dye layer on the PET fibers the same time. The corresponding results of the multilayer films have been discussed on the level of color strength (K/S).

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.484-487
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• 2004

Symmetric directional couplers are widely used in interferometers, switches, and various signal processing devices. Recently, several optical couplers using multimode fibers were reported, but these suffer from inefficient coupling of light into a branching fiber and/or low directivity. This paper presents the measurement and analysis of loss in the connection of optical fibers via the optical directional couplers. The functionality of the device is based on the principle that is symmetrical, the power in excited mode can be unambiguously directed into one of the output channel by varying and of its parameters. In this experiment, we measure the power of loss in the optical directional coupler at various radius of curvature. Before the measurement of loss in x-coupler, we polish the contact of the fiber surface in order that light can penetrate through another port. The results show that, when the radius of curvature is increased, the loss power is decreased and also approaches of the straight line case.

• Computers and Concrete
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• v.21 no.3
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• pp.239-248
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• 2018

This study developed and investigated a precast slab track system partially reinforced with glass fiber reinforced polymer (GFRP) rebars in the transverse direction, which mitigated the loss of track circuit current by reducing magnetic coupling between the rails and steel reinforcements. An electric analysis was conducted and the results of the analysis verified that the GFRP rebars mitigate the reduced current strength produced by electro-magnetic induction. In the study, a three-dimensional finite element method and flexural experiments were used to study the mechanical behavior of the proposed slab track.

• Computational Structural Engineering
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• v.8 no.2
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• pp.133-140
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• 1995

The buckling analysis of Glass Fiber Reinforced Plastic pipes was studied through a three dimentsional finite element method. In the finite element analysis, an improved degenerated shell element with incompatible modes and assumed shear strain fields are employed with 3 displacements and 2 rotations for each joints. Buckling analysis is carried out for various thicknesses and different fiber orientations. Finite element results show that the buckling load increases as the thickness does with the variation of coupling stiffness.

• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.514-525
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• 2001

Optimum characteristics of digital X-ray sensor components were analyzed to develop intra- oral dental digital X-ray image sensor using indirect method. Parametric analysis was carried out to optimize the phosphor thickness and the fiber optic plate (FOP) coupling to charge coupled device (CCD). X-ray absorption and light diffusion in the phosphor layer were analyzed by the Monte Carlo method. Real time X-ray image was obtained with prototype X- ray image sensor using general CCD camera with 1∼10 Ip/mm resolution. It has been previously shown that large resolution degradation in X-ray images was caused by miss alignment of FOP to CCD and optical adhesive selection. In this study, we reported that X-ray image quality was greatly improved by using optimized characteristics of alignment device and phosphor thickness.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.4
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• pp.18-23
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• 2007

This paper presents a transmissive dispersion compensator based on tilted chirped fiber Bragg grating pairs which happen mode coupling between core mode and cladding mode. And, as a result of simulation, the phase matching condition and optimum tilted angle to maximize the mode-coupling in the dispersion compensator are shown and the dispersion slope and bandwidth in the proposed dispersion compensator is respectively 3,068ps/nm and 0.45nm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.9
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• pp.7-14
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• 2000

This paper examines the constraints imposed in the usage of the conventional two-mode coupling model in the context of a cascaded long-period fiber grating and presents a set of approximate conditions that must be satisfied for the model to be applicable in the analysis of such a structure. Numerical examples based on the guidelines are provided for a set of realistic grating parameters and their practical implications on the allowed grating period variations for a given bandwidth are discussed.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.485-488
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• 2001

The transmission spectra, the wavelength tunability. and the polarization characteristics of mechanically induced long-period fiber gratings (LPFG's) are investigated experimentally and analyzed theoretically. The transmission and mode coupling characteristics of the fabricated LPFG's agree well with the theoretical results. The resonant wavelengths at which the mode coupling occurs can be tuned over 180 nm and the peak wavelengths for of oethogonally polarized lights are split by -9 nm.