• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.1-6
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• 2013

In this paper, we implemented a polarimetric strain sensor using a Sagnac birefringence interferometer composed of a polarization-maintaining photonic crystal fiber (PM-PCF). By changing the length of the PM-PCF employed as the sensor head of the proposed sensor, the length dependence of the strain sensitivity was investigated. With respect to 5.0-, 7.5-, and 10.0-cm-long PM-PCFs, strain measurements were done in a measurement range of $0{\sim}6m{\varepsilon}$, and strain sensitivities of ~2.04, ~1.92, and ${\sim}1.73pm/{\mu}{\varepsilon}$ were obtained, respectively. If an ideal PM-PCF with no length dependence of a modal birefringence is used for the proposed sensor, the strain sensitivity is independent of the length of the sensor head (PM-PCF). In the practical PM-PCF used in experiments, however, a shorter PM-PCF has a higher length dependence of the modal birefringence due to its imperfectness and nonuniformity of the internal structure, resulting in a higher length dependence of the strain sensitivity.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.121-125
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• 2005

Magnetoelectric (ME) effects for lanthanum modified $BiFeO_3-PbTiO_3\;(BE-_xPT)$ solid solutions have been investigated. The value of magnetoelectric polarization coefficient, up is 10 times greater than that of $Cr_2O_3$. The results also show that up is due to a linear coupling between polarization and magnetization, and that up is independent of do magnetic bias and ac magnetic field. The ME effect is believed to be significantly enhanced due to breaking of the cycloidal spin state of a long-period spiral spin structure, via randomly distributed charged imperfections.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.308-312
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• 2007

Ferroelectric, magnetic, and magnetoelectric effects for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics have been investigated. The data show that magnetoelectric polarization coefficient, ${\alpha}_p$ is due to a linear coupling between polarization and magnetization, and that ${\alpha}_p$ is independent of dc magnetic bias and ac magnetic field. The values of ${\alpha}_p$ and magnetic induced susceptibility for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics are much larger than those of single $BiFeO_3$ crystal. We believe that the magnetoelectric effect is significantly enhanced by breaking of the cycloidal spin state of a long-period spiral spin structure due to randomly distributed charged imperfections.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.116-121
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• 2003

We have observed a nonclassical effect in a fourth-order interference experiment with the photon pairs produced by parametric down-conversion and the Hong-Ou-Handel interferometer. For interfering classical fields with orthogonal polarizations, the visibility can be no larger than 50%, and it depends on the ratio of the two beam intensities. It is found that not only is our observed visibility of 85％ well above 50％, but it is also independent of the two beam intensities in coincidence measurements made in a two-photon polarization correlation experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.7-13
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• 2009

By incorporating a polarization beam splitter and fiber coupler, we propose a fiber-optic multiwavelength-switchable interleaving filter that can function as a polarizaiton-independent transmission or reflection-type one. The proposed filter consists of a polarizaiton beam splitter and a Sagnac birefringence loop that is composed of a 50:50 coupler, polarizaiton-maintaining fibers, and two quarter-wave plates. In the proposed filter, a transmission-type filter with a channel isolation > 18[dB] or a reflection-type one with a channel isolation ~3[dB], whose channel spacing and switching displacement were 0.8 and 0.4[nm] in common, respectively, could be obtained. Channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.120-128
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• 2022

There are 17,000 reservoir dams in Korea, of which more than 85% were built over 50 years ago. Old embankment dams are weakened by internal erosion and suffusion phenomena due to preferential leakage paths and this ongoing weakening can cause their failure. Therefore, early warning associated with leakage in an embankment dam is crucial to prevent its failure. An electrical resistivity survey is a non-destructive, real-time and in-situ technique for detecting the development of leakage zones and general conditions of embankment dams. Because of its advantages, the electrical resistivity survey is widely used for reservoir safety inspections. However, the electrical resistivity survey is still not officially included in the precise safety inspection of reservoir dams because it cannot present a quantitative index of dam safety. In this study, we propose a method for calculating the leak index according to the water content evaluated from the electrical resistivity survey and/or induced polarization survey. Particularly, by proposing a quantitative leak index calculation method from monitoring surveys and independent surveys, we provide a theoretical basis for including electrical resistivity and induced polarization surveys as components of the precise safety inspection of reservoirs dams.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.150-154
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• 2000

Mobilities of electrons ($\mu_p$) and holes ($\mu_p$) in 2, 5, and 10 mol% $TiO_2$-doped yttria stabilized zirconia (TD-YSZ) have been estimated by a non-steady state gas permeation method using models proposed by Weppner and Maruyama. Values of $\mu_n$ and $\mu_p$ were found to be closed to those in non-doped YSZ reported earlier. The concentration of electrons and holes were calculated from $\mu_n$ and $\mu_p$ values and the partial conductivities of electrons and holes measured by a dc-polarization method. The concentration of electrons at unit oxygen partial pressure increased with increasing $TiO_2$concentration, while the hole concentration was almost independent of $TiO_2$concentration.

• ETRI Journal
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• v.25 no.1
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• pp.41-48
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• 2003

This paper presents a theoretical investigation of power reflection and transmission coefficients for a meander-line polarizer placed periodically on a chiral slab. It is assumed that a linearly polarized transverse magnetic wave is incident on a chiral slab from the air region. In the analysis, we derive the electric and magnetic fields in the modal form in the air and chiral regions. We obtain power reflection and transmission coefficients in a straightforward manner after matching the tangential components of the electric and magnetic fields at the boundaries. We present numerical results for the power reflection and transmission coefficients versus frequency and incident angle for different values of the chirality admittance. A meander-line polarizer placed on a dielectric slab can convert a linearly polarized wave to a circularly polarized wave. The design parameters for a meander-line polarizer are the dimensions of the meander-line and the values of the dielectric slab. Replacing a dielectric slab with a chiral slab introduces a new independent parameter which controls the wave polarization.

• Proceedings of the KWS Conference
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• 1997.05a
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• pp.35-38
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• 1997

In order to investigate quantitative behavior of galvanic corrosion in the weld joint between stainless steel and carbon steel, electrochemical polarization experiments are performed for various pH, water temperature with boric acid concentration 4000ppm. The corrosion rate of stainless steel was almost independent of the variation of pH. The significant corrosion rates of carbon steel and the weld joint of carbon-carbon steel were observed at pH 4. The corrosion rates in the weld joint of the carbon-stainless steel were observed depending on the variation of pH level.

• ETRI Journal
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• v.34 no.1
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• pp.126-129
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• 2012

An ultra-thin hexagonal microwave metamaterial absorber is described. It can absorb any polarized transverse electromagnetic wave because of its hexagonal shape. In spite of its very thin structure, almost $0.028{\lambda}g$, the absorber achieved 99% absorptivity at 11.35 GHz in experimental results because of the increased coupling losses, showing good agreement with simulation results. In addition, this high absorbance is unchanged for any polarized waves with the same frequency.