• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.25-34
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• 2008

A new hybrid oedometer cell is designed and manufactured to investigate a behavior of soft soils by using elastic and electromagnetic waves during consolidation test. Bender elements, which generate and detect shear waves, are placed in the top cap and the bottom plate and mounted on the oedometer wall. Double wedge type electrical resistance probe, which measures local void ratio change, is positioned onto the top cap of the oedometer cell. The bender elements and the electrical resistance probe are anchored into a nylon set screw with epoxy resin. The nylon set screw with epoxy resin minimizes directly transmited elastic waves through the oedometer cell due to impedence mismatch and allows for easy replacement of defected bender elements and electrical resistance probe. Primary consolidation time can be estimated from the slope of electrical resistance versus log time curve and the evolution of shear wave velocity. The shear wave velocity can be used to assess inherent anisotropy when disturbance effects are minimized because particle alignment affects the shear wave velocity. The void ratios evaluated by the electrical resistance probe are similar to those by the settlement during consolidation. This study suggests that the shear wave velocity and the electrical resistance can provide complementary imformations to understand consolidation characteristics such as primary consolidation, anisotropy, and void ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.1849-1860
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• 1994

Domain wall dynamics in thin film of amorphous Rare Earth-Transistion Metal alloys were investigated using numerical integration of the Landau-Lifshitz-Gilbert equation. The thin film was divided into a two-dimensional square lattice ($30\times30$) of dipoles. Nearest-neighbor exchange interaction magnetic anisotropy, applied magnetic field, and demagnetiing field of interacting anisotropy, applied magnetic field, and demagnetizing field of interacting dipoles were considered. It was assumed that the film had perfect uniaxial anisotropy in the perpendicular direction and the magnetization reversal existed in the film. The time of domain wall creation and the thickness of the wall were investigated. Also the motion of domain walls under an applied field was considered. Simulation results showed that the time of domain wall creation was decreased significantly and the average velocity of domain wall was increased somewhat when the demagnetizing field was considered.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.303-315
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• 2021

A rigorous and generic similarity solution is developed for assessment of the undrained expansion responses of a cylindrical cavity expansion in K₀-consolidated anisotropic soils. A K₀-consolidated anisotropic modified Cam-clay (K₀-AMCC) model that can represent the initial stress anisotropy and the effects of stress-induced anisotropy is used to model the soil behaviors during cavity expansion. All the seven basic unknowns, the three stress components, the pore water pressure, the particle velocity, the specific volume and the hardening parameter, are reduced to the functions of a dimensionless radial coordinate and are taken as coupled variables to formulate the problem. The governing equations are formulated by making use of the equilibrium equation, the constitutive equation, the consistency condition, the continuity condition and the undrained condition, which are then solved as an initial value problem. The proposed rigorous similarity solution is compared with some well-documented rigorous solutions to validate the solution and to highlight the special expansion responses in anisotropic soils. The results reveal that the present solution can yield more predictions for cavity expansion problems in soils with initial anisotropic stresses.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.272-277
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• 2004

The elastic waves in the plate are dispersive waves with the characteristics of Lamb waves. However, $S_0$ symmetric mode is less dispersive in the frequency region less than first cut-off frequency. And, in anisotropic plates such as CFRP plates, the propagation velocities vary with the direction. So, the wave vector direction to be the phase velocity direction is not accord with the energy flow direction to be the group velocity direction. In this work, the group velocities of the $S_0$ symmetric mode less than the first cut-off frequency was analyzed with the group velocity dispersion curves in unidirectional CFRP plate. And, the group velocity curve obtained by the group velocity dispersion curves are compared with the measured velocities as varied the propagation direction of the Lamb wave. The measured velocities are good agreement with the corrected group velocity curve except near the fiber direction which is called the cusp region. When the propagation direction is not accorded with the principal axis, the direction of the group velocities declines to the fiber direction in the unidirectional CFRP plates. This implies that the energy propagates preferentially toward fiber direction.

• Structural Engineering and Mechanics
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• v.53 no.2
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• pp.277-296
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• 2015

The objective of this paper is to investigate the surface waves in fibre-reinforced anisotropic thermoelastic medium subjected to gravity field. The theory of generalized surface waves has firstly developed and then it has been employed to investigate particular cases of waves, viz., Stoneley waves, Rayleigh waves and Love waves. The analytical expressions for displacement components, force stress and temperature distribution are obtained in the physical domain by using the harmonic vibrations. The wave velocity equations have been obtained in different cases. The numerical results are given and presented graphically in Green-Lindsay and Lord-Shulman theory of thermoelasticity. Comparison was made with the results obtained in the presence and absence of gravity, anisotropy, relaxation times and parameters for fibrereinforced of the material medium. The results indicate that the effect of gravity, anisotropy, relaxation times and parameters for fibre-reinforced of the material medium are very pronounced.

• Smart Structures and Systems
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• v.18 no.5
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• pp.911-930
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• 2016

The main purpose of this paper is to study the effects of initial stress, gravity, anisotropy and porosity on the propagation of shear wave (SH-waves) in a fiber-reinforced layer placed over a porous media. The frequency equations in a closed form have been derived for SH-waves by applying suitable boundary conditions. The frequency equations have been expanded and approximated up to $2^{nd}$ order of Whittaker's function. It has been observed that the SH-wave velocity decreases as width of fiber-reinforced layer increases. However, with the increase of initial stress, gravity parameter and porosity, the phase velocity increases. The results obtained are in perfect agreement with the standard results investigated by other relevant researchers.

• Tunnel and Underground Space
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• v.18 no.3
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• pp.214-218
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• 2008

Dynamic fracturing of anisotropic granite was investigated by SHPB (Split Hopkinson Pressure Bar). Energy absorption during the test and maximum stress were increased as strain rate increased. Maximum stresses in every direction were dependent on the strain rate but not so sensitive to anisotropy. Elastic wave velocity was decreased as strain rate increased and dependent on strain rate in every direction. Especially, elastic wave velocity decreased more rapidly in a strong rock.

• 한국해양학회지
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• v.21 no.2
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• pp.92-100
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• 1986

Laboratory investigations of physical (density and porosity), acoustic (velocity and velocity anisotropy), and electrical (resistivity and resistivity anisotropy) properties in deep-sea carbonate sequences at DSDPsites 288 and 289 in the western equatorial Pacific were made and correlated as a function of diagenesis. Profile of resistivity shows almost a mirror image of velocity indicating that electrical resistivity can be a useful variable to determine the diagenetic stage. Some fluctuations in acoustic and electrical properties near the zones of cherty and siliceous limestones for both sites imply significant changes in pore geometry due to interbedded silica. The significantly reduced pore throat size by the presence of silica which provides excess calcium carbonate to adjacent pore spaces is partly responsible for several jumps in acoustic and electrical properties of the zones. These observed geophysical data are interpreted as the result of silica diagenesis influencing carbonate diagenesis.

• Publications of The Korean Astronomical Society
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• v.7 no.1
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• pp.39-50
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• 1992

A velocity inhomogeneity, which is the regional preponderence of either radial or tangential orbits, is searched with the new technique proposed by Kim (1992) for Coma, Hydra I, and Abell 2256 cluster of galaxies. Conspicuous inhomogeneities are found in the Coma and A2256 which X-ray isophotes are indicative for their underlying potentials being ellipitcal in shape, Even in their central regions, zones that are dominated by radial orbits are clearly distinguishable from that of the tangential orbits, and defining the cluster 'equator' as the direction of maximum elongation of the X-ray isophotes, radial orbits dominate along this direction whereas tangential orbits dominate the 'polar' zones. Merger events that are evidenced in X-ray observations occur in the equatorial zones of Coma and A2256, suggesting preponderence of radial orbits in the zones, which is in good agreement with their velocity structures. On the other hand, the inhomogeneity in Hydra I turns out to be insignificant in the central regions and this is just what is expected from a cluster whose X-ray isophotes is nearly circular. The velocity distribution in regions further out, however, shows significant inhomogeneity and this seems to support the previous results that this cluster is likely to have substructures and velocity anisotropy.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.341-344
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• 2019

Liquid crystal (LC) mesophase materials manifest a variety of phase transitions. The optical properties of LCs are highly dependent upon the phase and orientation of the optical axis with respect to the polarization of incoming light. Studying the LC phase transitions is significantly important for a wide range of scientific and industrial applications. In this study, we demonstrate the propagation velocity of the phase boundary between the nematic and isotropic phase of 4-Cyano-4-pentylbiphenyl (5CB) liquid crystal for different electric fields using a polarized optical microscope. The results demonstrate that the propagation velocity of the phase boundary exhibits a peak value for a specific voltage, attributed to the supercooling of the isotropic phase of the LC. The analysis of the propagation velocity for different electric fields also provides a simple optical platform to measure the thermal anisotropy and voltage dependent thermal properties of the homogeneously aligned LC.