• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1168-1175
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• 2000

To observe propagation characteristics of microstrip lines on YIG film, the FDTD is employed. For various GGG substrate and YIG film, the dispersion curves and the bandwidth of the cutoff region are calculated. And the distribution of the electric fields of the transverse plane underneath the conductor strip is obtained near upper and lower cutoff frequency. The results of two and three dimensional FDTD for the upper cutoff frequency are compared with spectral domain approach(SDA). A good agreement is verified, although there is relative error 6% between the results calculated by the two methods.

• 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.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.245-254
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• 2006

Using a natural gradient tracer test, the characteristics of hydrodynamic dispersion according to each depth of a fractured rock were studied, and the effective porosity and longitudinal dispersivity of the fractured rock were estimated. The difference of vertical hydrodynamic dispersion was identified by concentration breakthrough curves linear regression analyses of bromide concentrations according to depths versus time, and hydraulic fracture characteristics at two intervals of the monitoring well. Higher concentration and faster arrival time at GL- 18 m depth (RQD 13%, average joint spacing 2 cm, TCR 100%) than at GL- 25 m depth (RQD 41%, average joint spacing 7 cm, TCR 100%) resulted from shorter distance and more fractures. Tracer was transported through the 1 st fractures until the arrival of its peak concentration and through the 2nd fractures or matrix diffusion after the arrival of its peak concentration. The increase/decrease slopes of bromide concentration versus time were 3.46/-1.57 at GL-18 m depth and 3.l9/-0.47 at GL- 25 m depth of the monitoring well. So the faster bromide transport was confirmed at GL- 18 m depth with more fractures. The concentration increment of bromide was fitted by a Gaussian function and the concentration decrement of bromide was fitted by an exponential function. Effective porosity and longitudinal dispersivity estimated by CATTI code were 10.50% and 0.85 m, respectively.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.13-22
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• 1990

The magnetite ferrofluids of which solvents are water or kerosene have been prepared by making surfactant absorbed on the surface of the magnetite which have been synthesized by air oxidation of Fe(OH)2 at pH 11 and 75$^{\circ}C$, and their basic properties have been measured by XRD, SEM, DTA, TG, viscometer, magnetometer and B-H tracer. The results are as follows ; 1) The shape of magnetite prepared by air oxidation is found to be sphere-like shape and its particle size is smaller than 200A. 2) The maximum amount of sodium oleate adsorbed on the surface of magnetite is about 20% in the weight of the magnetite including the adsorbed sodium oleate. And when magnetite is well dispersed into solvent, R(the weight ratio of the added sodium oleate to Fe3O4) is 0.40-0.48. 3) The dispersion ratio, the viscosity and the magnetization of magnetite ferrofluid are constant regardless of the added amount of sodium oleate above R=0.40-0.48. 4) The magnetic hysteresis curves of magnetite ferrofluid show superparamagnetism-like behavior.

• Advances in materials Research
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• v.12 no.4
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• pp.309-330
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• 2023

The humid thermal vibration characteristics of a nonhomogeneous thermopiezoelectric nonlocal plate of polygonal shape are addressed in the purview of generalized nonlocal thermoelasticity. The plate is initially stressed, and the three-dimensional linear elasticity equations are taken to form motion equations. The problem is solved using the Fourier expansion collocation method along the irregular boundary conditions. The numerical results of physical variables have been discussed for the triangle, square, pentagon, and hexagon shapes of the plates and are given as dispersion curves. The amplitude of non-dimensional frequencies is tabulated for the longitudinal and flexural symmetric modes of the thermopiezoelectric plate via moisture and thermal constants. Also, a comparison of numerical results is made with existing literature, and good agreement is reached.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.771-776
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• 2012

A technique is presented that uses a circular waveguide for the measurement of the bulk shear(S-wave) velocities of unconsolidated, saturated media, with particular application to near surface soils. The technique requires the measurement of the attenuation characteristics of the fumdamental T(0,1) mode that propagates along an embedded pipe, from which the acoustic properties of the surrounding medium are inferred. From the dispersion curve analysis, the feasibility of using T(0,1) mode which is non-dispersive and have constant attenuation over all frequency range is discussed. The principles behind the technique are discussed and the results of an experimental laboratory validation are presented. The experimental data are best fitted for the different depths of wetted sand and the shear velocities as a function of depths are formulated using power law curves.

• 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 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

• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.13-26
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• 2012

In this paper, the wave propagation in a generalized thermo elastic plate embedded in an elastic medium (Winkler model) is studied based on the Lord-Schulman (LS) and Green-Lindsay (GL) generalized two dimensional theory of thermo elasticity. Two displacement potential functions are introduced to uncouple the equations of motion. The frequency equations that include the interaction between the plate and foundation are obtained by the traction free boundary conditions using the Bessel function solutions. The numerical calculations are carried out for the material Zinc and the computed non-dimensional frequency and attenuation coefficient are plotted as the dispersion curves for the plate with thermally insulated and isothermal boundaries. The wave characteristics are found to be more stable and realistic in the presence of thermal relaxation times and the foundation parameter. A comparison of the results for the case with no thermal effects shows well agreement with those by the membrane theory.

• Structural Engineering and Mechanics
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• v.46 no.6
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• pp.827-842
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• 2013

In this paper, the wave propagation in generalized thermo elastic plate immersed in fluid is studied based on the Lord-Shulman (LS) and Green-Lindsay (GL) generalized two dimensional theory of thermo elasticity. Two displacement potential functions are introduced to uncouple the equations of motion. The frequency equations that include the interaction between the plate and fluid are obtained by the perfect-slip boundary conditions using the Bessel function solutions. The numerical calculations are carried out for the material Zinc and the computed non-dimensional frequency, phase velocity and attenuation coefficient are plotted as the dispersion curves for the plate with thermally insulated and isothermal boundaries. The wave characteristics are found to be more stable and realistic in the presence of thermal relaxation times and the fluid interaction.