• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.51-59
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• 2006

The surface wave data obtained in a tidal flat located in the sw coast of the Korean Peninsula were used to analyse the shear wave velocity structure of the area. First, the phase velocity dispersion curves were obtained by the tau-p stacking method and the group velocity dispersion curves by a wavelet transform method and the Multiple Filtering Technique by Dziewonski. The phase velocity dispersion curves exhibited bigger errors than the group velocity curves. The results showed that the wavelet transform method was more effective in separating the fundamental and the 1st higher mode group velocity curves than the Multiple Filtering Technique. Combined use of the fundamental and the 1st higher mode group velocity dispersion curves in the inversion for the shear wave velocity structure gave better spatial resolution compared when the fundamental mode group velocity was used alone. This study indicates that the group velocity dispersion curves can be used in the inversion of Rayleigh waves for the shear wave velocity structure, especially effectively with the higher mode group velocity curves together.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.314-321
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• 2007

Recently, multi-dimensional joint inversion of geophysical data based on fundamentally different physical properties is being actively studied. Joint inversion can provide a way to obtaining much more accurate image of the subsurface structure. Through the joint inversion, furthermore, it is possible to directly estimate non-geophysical material properties from geophysical measurements. In this study, we developed a new algorithm for jointly inverting dc resistivity and seismic traveltime data based on the multiple constraints: (1) structural similarity based on cross-gradient, (2) correlation between two different material properties, and (3) a priori information on the material property distribution. Through the numerical experiments of surface dc resistivity and seismic refraction surveys, the performance of the proposed algorithm was demonstrated and the effects of different regularizations were analyzed. In particular, we showed that the hidden layer problem in the seismic refraction method due to an inter-bedded low velocity layer can be solved by the joint inversion when appropriate constraints are applied.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.73-81
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• 2019

This paper proposes an acoustical inversion method using cepstrum analysis of underwater ship noise. Through the cepstrum analysis, multipath structure can be extracted from the recorded ship noise. The multipath structure comes from interferences between a direct arrival and multiple reflections from the sea surface and the bottom. The acoustic inversion is the optimization process to find the best parameters which show good correlation between cepstrums of the measured signal and the replica. The inversion method was applied to the underwater ship radiated noise data measured at Straits of Korea in order to estimate the acoustic center of the ship and the hydrophone position. The inversion results showed good agreement with the measured information.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.379-382
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• 2003

In gravity data correction process, mass effect of the upper part of base level is removed with Bouguer density. Usually, Bouguer density is estimated as a mean density in the field area. But, this may causes a serious problem when ore body is in the area. To overcome this problem, we tried to apply a new method mixing up mass corrections and inversion (3DGTI). 3-D Gravity Terrain Inversion (3DGTI) includes information of topography and distribution of Bouguer density. For this method does not remove the mass effect above base level, it is no longer useless to use Bouguer density. Numerical model tests have shown that the 3DGIT successfully retrieves the anomalous subsurface density distribution of both surface and deeper layers. Model tests shows that this method shows better results than those of conventional one, especially when main target is ore body. The inversion result well delineates the three-dimensional shape of the intruded granite body and basement.

• Computers and Concrete
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• v.4 no.4
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• pp.285-298
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• 2007

Corrosion of Reinforcement (rebar) is nondestructively estimated by the half-cell potential measurement. As is the case with other nondestructive testings (NDT), understanding of the underlying principles should be clarified in order to obtain meaningful results. Therefore, the measurement of potentials in concrete is analytically investigated. The effect of internal defects on the potentials measured is clarified numerically by the boundary element method (BEM). Thus, a simplified inversion by BEM is applied to convert the potentials on concrete surface to those on rebars, taking into account the concrete resistivity. Because the potentials measured on concrete surface are so sensitive to moisture content, concrete resistivity and surface condition, an inverse procedure to convert the potentials on concrete surface into those on rebars is developed on the basis of BEM. It is found that ASTM criterion is practically applicable to estimate corrosion from the potential values converted. In experiments, an applicability of the procedure is examined by accelerated corrosion tests of reinforced concrete (RC) slabs. For practical use, the procedure is developed where results of IBEM are visualized by VRML (Virtual Reality modeling Language) in three-dimensional space.

• Membrane and Water Treatment
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• v.6 no.5
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• pp.351-363
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• 2015

To increase the surface hydrophilicity of PVDF membranes, in this paper, an electric enhancing method was adopted to treat PVDF nascent membranes during the phase inversion process. It was found that when PEG 600 was taken as the additive, the surface water contact angle of the PVDF membrane treated under 2 kV electric field was decreased from $84.0^{\circ}$ to $65.7^{\circ}$. The reason for the surface elements change of the PVDF membranes prepared under the electric field was analyzed in detail with the dielectric parameters of the polymer dope solutions. Results from BSA adsorption experiment showed that the antifouling ability of the external electric field-treated membranes was distinctly enhanced when compared with that of the untreated membranes. The amount of BSA adsorbed by the treated membranes was lower by 38-43%. Compared with the common chemical reaction methods to synthesize hydrophilic additives or membrane materials, the electric field-assisted processing method did not involve any additional chemical synthesis process and it was capable of realizing better hydrophilicity.

• Electrical & Electronic Materials
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• v.9 no.2
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• pp.174-179
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• 1996

We present a new physically based analytical equation for electron effective mobility in MOS inversion layers. The new semi-empirical model is accounting expicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering. This model shows excellent agreement with experimentally measured effective mobility data from three different published sources for a wide range of effective transverse field, channel doping and temperature. By accounting for screened Coulomb scattering due to doping impurities in the channel, our model describes very well the roll-off of effective mobility in the low field (threshold) region for a wide range of channel doping level (Na=3.0*10$^{14}$ - 2.8*10$^{18}$ cm$^{-3}$ ).

• Journal of Environmental Science International
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• v.5 no.6
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• pp.713-718
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• 1996

We identified two characteristic turbulent flow cases, weakening and strengthening, which appear at the downwind side. Observations were made two times, Dec. 2-3. 1995 and Feb. 13-14. 1996 at Pusan National University site located downwind side of Kumjeong mountain. Meteorological observation system, tethersonde, was adopted to present observation. In the case of the west wind which blows perpendicular to Sanghak mountain located westward from the site, the wind speed highly increased in exponential with height. Therefore, the low level wind speed was so weak just like Taylor(1988)'s review. While the wind speed was intensified at 200-400m layer when the northwest wind blows from the continental Siberian high. We suppose 기 is because of the strong vertical convergence of flow between the surface inversion layer and the upper one, and also the horizontal convergence along the saddle and valley between the two mountains, Kumjeong and Sanghak-because of Bernoulli's effect. The inversion layer existed at surface-l00m and 500-600m level and the strong wind existed at about 200-400m layer.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.4
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• pp.329-334
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• 2010

This paper presents the design of a neural network based adaptive control for missile. Acceleration of missile by tail fin control cannot be controllable by DMI (Dynamic Model Inversion) directly because it is non-minimum phase system. To avoid the non-minimum phase system, dynamic model inversion is applied with output-redefinition method. In order to evaluate performance of the suggested controllers we selected the three cases such as control surface fail, control surface loss and wing loss for model uncertainty. The corresponding aerodynamic databases to the failure cases were calculated by using the Missile DATACOM. Using a high fidelity 6DOF simulation program of the missile the performance was evaluates.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.203-210
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• 2004

The average temperatures by the land cover class, by the elevation extent, by the slope and by the aspect have been calculated using multitemporal Landsat TM band 6 and DEM. For this, the TM band 6 data from October 21, 1985, June 2, 1992, September 1, 1996, May 7, 2000 and the 28.5m x 28.5m grid elevation data of Seoul have been used. From the varying curve of the average land surface temperature by the elevation extent, the presence of the atmospheric inversion phenomenon and the scope of the inversion layer can be inferred. Especially, the average land surface temperature by the aspect can be effective for deciding a road line. For these reasons, it is expected that temperature estimation using remote sensing data shall be effective for the survey of heat damage, environmental temperature monitoring, and urban and environmental Planning usage.