• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.232-239
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• 2006

Guided wave techniques have been used for pipeline inspection because of the long range inspection capability of guided waves. One of main concerns of these technique is how ones decide the axial interval of sensors when they are utilized for pipeline inspection. This question is related to the characteristic of cylindrical guided wave propagation, especially wave attenuation. Thus, attenuation of fundamental longitudinal guided wave propagating liquid-filled steel pipes is numerically investigated in the paper. Several liquids such as water, diesel oil, castor oil etc. are considered for the filing materials in the pipes. Sink is considered for numerical models for abandoning standing wave modes; hence, the attenuation dispersion curves become much simpler. Those attenuation calculations can be utilized for guided-wave-based nondestructive testing of pipelines when one inspects pipelines, using monitoring sensors, which are installed outside pipes.

• Journal of Power System Engineering
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• v.14 no.3
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• pp.46-51
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• 2010

A torsional guided wave was applied to detect a defect in petrochemical pipes. Phase and group velocity dispersion curves for the longitudinal and torsional modes of the inspected pipe were presented for the theoretical analysis. It was found through mode shape analysis that there was mode conversion when torsional wave is incident at an asymmetric defect. An artificial notch was fabricated in the pipe and the detectability was examined from the distance 2m of the end of the pipe by using magnetostrictive sensors. The relativities between the amplitude of the reflected signal and the size of the defect was examined. It was shown that the T(0,1) mode could be used for the long range inspection for the petrochemical pipes.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.151-154
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• 2005

Laboratory column experiments for simultaneous removal of Cd and Cr(VI) are conducted using newly developed material, referred to as Fe-loaded zeolite, which has both reduction ability of iron and ion exchange ability of zeolite. Breakthrough curves were obtained from each column experiment, and described with advection-dispersion equation. Apparent parameters including $K_{app}\;and\;D_{app}$ were newly introduced for effectively describing the Cr(VI) breakthrough curve. $K_{app}$ decreased with increasing initial contaminant concentration and with decreasing flow rates. Whereas, $D_{app}$ were not significantly affected by initial contaminant concentration or flow rate.

• Elastomers and Composites
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• v.29 no.2
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• pp.113-120
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• 1994

The vulcanization characteristics, physical and electrical properties have been measured for magnetite-loaded CM compounds containing various concentration of magnetite. Samples of the various concentration of magnetite are characterized by oscillating disk rheometer, mooney viscometer, tensometer and resistance meter. The morphology and dispersion of magnetite are analyzed by scanning electron microscope(SEM). The results obtained are as follows : 1. The CM compound without magnetite shows plain curve, while the CM compounds containing magnetite show short curves. 2. The maximum volume of magnetite is 600 phr in the CM compounds. The magnetite of 30 to 150 phr of magnetite act as reinforcement agents and the 50 phr magnetite shows maximum tensile strength. 3. The electric conductivity is mostly influenced by the conditions of temperature, compacting pressure, and magnetite orientation. Further efforts should be made to develop a new design in various electric conductivity fillers for the most efficient and applicable rubber products.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1484-1486
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• 1994

In this paper, we performed theoretical computer calculation for ion-exchange embedded channel waveguide using Field Shadow Method. Using the parameters of ${\Delta}n=0.09$, 0.009, $w=8{\mu}m$. d=8.854, $8.189{\mu}m$ we decided the waveguide characteristics. The dispersion curves showed the optimal fabrication conditions of the waveguides. We observed each of the 3-D field distributions in the various waveguides.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1097-1098
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• 2006

The Powder characteristics and sintering behavior of $SiO_2$ coated $BaTiO_3$ were studied. Silica coated $BaTiO_3$ powders were prepared by sol-gel method. The particle size of the $BaTiO_3$ powders were $\sim35$ nm and the thickness of the $SiO_2$ coating layer was $\sim5$ nm. As the $SiO_2$ content increased, the $SiO_2$ layers improved the powder dispersion. The Zeta potential of $SiO_2$ coated $BaTiO_3$ was getting close to that of pure silica with a more negative charge, compared with that of the uncoated $BaTiO_3$. The onset temperature of shrinkage curves shifted to higher temperatures with increasing $SiO_2$ contents

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1512-1517
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• 2008

Laboratory column tests were conducted in this study using $Cl^-$ tracers on Jumunjin sand to analyze contaminant transport in mixed contaminated soils. Results obtained from clean soils and soils containing residual diesel verified heterogeneous distribution of residual diesel, and clear acceleration of solute movement. In addition, asymmetric breakthrough curves indicated development of immobile region where solute movement becomes stagnant and creates tailing phenomenon.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.415-429
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• 2002

Various modeling techniques for ultrasonic wave propagation and scattering problems in finite solid media are presented. Elastodynamic boundary value problems in inhomogeneous multi-layered plate-like structures are set up for modal analysis of guided wave propagation and numerically solved to obtain dispersion curves which show propagation characteristics of guided waves. As a powerful modeling tool to overcome such numerical difficulties in wave scattering problems as the geometrical complexity and mode conversion, the Boundary Element Method(BEM) is introduced and is combined with the normal mode expansion technique to develop the hybrid BEM, an efficient technique for modeling multi-mode conversion of guided wave scattering problems.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.43-46
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• 2000

We generated 9-fs pulses from a Kerr-lens mode-locked Ti:sapphire laser only using commercial optical components. Two sets of prisms pair made of fused silica were used to compensate group delay dispersion inside and outside the laser oscillator respectively, and broadband mirrors were used to obtain a broad spectrum. By comparison between reflectance curves of the broadband mirrors and those of previous ones, broadband mirrors which have high reflectance bandwidth of over 180 nm were found to be essential to produce sub-IO-fs pulses. ulses.

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.26-33
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• 2005

Attenuation of fundamental longitudinal guided wave propagating liquid-filled steel pipes is numerically investigated. Several liquids such as water, diesel oil, castor oil etc. are considered for the filing materials in the pipes. Sink is considered for numerical models for abandoning standing wave modes; hence the attenuation dispersion curves become much simpler. Those attenuation calculations can be utilized for guided-wave-based nondestructive testing of pipelines when one inspects pipelines, using monitoring sensors, which are installed outside pipes.