• The Journal of the Acoustical Society of Korea
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• v.25 no.2E
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• pp.60-68
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• 2006

High-frequency bistatic scattering measurements from a corrugated surface were made in an acoustic water tank. First the azimuthal scattering pattern was measured from an artificially corrugated surface which has varying impedance. The corrugated surface was installed both transverse to the direction of incident wave and longitudinal to the direction of incident wave. The angle between the corrugated surface and the direction of the incident wave was about $45^{\circ}$. Second, the scattering strengths were measured from the flat sediment and the corrugated sediment. A critical angle of about $37^{\circ}$ was calculated in the acoustic water tank. The measurements were made at three fixed grazing angles: $33^{\circ}$ (lower than critical angle), $37^{\circ}$ (critical angle), and $41^{\circ}$ (higher than critical angle). The scattering angle and the grazing angle are equal in each measurement. Frequencies were from 50 kHz to 100 kHz with an increment of 1 kHz. The corrugated sediment was made transverse to the direction of the incident wave. The first measurement indicates that the scattering patterns depend on the relations between the corrugated surface and the direction of the incident wave. In the second measurement, the data measured from the flat sediment were compared to the APL-UW model and to the NRL model. The NRL model's output shows more favorable comparisons than the APL-UW model. In case of the corrugated sediment, the model and the measured data are different because the models used an isotropic wave spectrum of sediment roughness in the scattering calculations. The isotropic wave spectrum consists of $w_2$ and ${\gamma}_2$. These constants derived from sediment names or bulk size. The model which used the constants didn't consider the effect of a corrugated surface. In order to consider a corrugated surface, the constants were varied in the APL-UW model.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.889-896
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• 2023

Changes in the energy spectrum were analyzed using ^99mTc as a point source and a scattering phantom, and the shielding effect of the lead apron according to the changed gamma ray energy was evaluated. In the gamma ray energy spectrum of the scattering phantom, the photo peak area decreased and the compton scattering area increased compared to the point source. The coefficients for each energy range according to the change in the shape of the gamma ray source showed a reduction rate of up to 66.1 % at a distance of 20 cm compared to the coefficient of the point source, and in the compton scattering area, the coefficient of the scattering phantom was 122.2 % at a distance of up to 40 cm compared to the coefficient of the point source. In the difference in shielding rate according to the distance between the source and the scattering phantom using a gamma camera, the photo peak area showed similar results, but in the Compton scattering area, the shielding rate of the scattering phantom at a distance of 20 cm increased by 29.2 % compared to the shielding rate of the point source. As the distance increased, the difference in shielding rate decreased. In measuring the shielding rate of the lead apron using a radiation dosimeter, the difference in the shielding rate of the scattering phantom was up to 15.3 %, and as the distance increased, the difference in the shielding rate between the two sources decreased. The shielding rate of the lead apron of the scattering phantom is higher than that of the point source, and the effectiveness of the lead apron increases as the distance to the source increases. As a result, wearing a lead apron when directly confronting a patient who has injected radioactive pharmaceuticals is expected to be helpful in reducing radiation exposure.

• Journal of the Korean earth science society
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• v.30 no.1
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• pp.40-48
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• 2009

The attenuation mechanism of seismic waves in the crust is controlled both by intrinsic absorption and scattering of energy. The amount of scattering and intrinsic energy losses from the total attenuation is separately estimated in this study for the southern Korean Peninsula. The formula to be deduced from the theoretical relationship between single back-scattered coda Q and multiple scattering theory was used to separate the total attenuation into the intrinsic Q and the scattering Q. It was found that the intrinsic Q was considerably lower than that of the scattering Q in the frequency range of 1.5 to 20 Hz. This fact implies that the energy loss caused by the intrinsic absorption is relatively larger than one by the scattering effect within the crust of the southern Korean Peninsula. Both intrinsic and scattering Q values appeared to be comparatively larger than those measured in other seismically active regions except for intrinsic Q in the frequency range of 1.5 to 3 Hz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.1 s.118
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• pp.41-47
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• 2007

Scattering fields of two dimensional acoustic waves by a circular cylinder are investigated. The present numerical approach for the acoustic scattering problem has difficulties of numerical robustness, long-time stability and suitability of far-field boundary treatments. The time-dependent periodic acoustic source is used to analyze Interference patterns between incident waves and waves reflected by the cylinder. Characteristic boundary algorithms coupled with 4th order Modified-Flux-Approach ENO(essentially non-oscillatory) schemes are employed in generalized coordinates to examine the effect of the wane frequency on the interference patterns. Non-reflecting boundary conditions, which is crustal for accurate computations of aeroacoustic problems, are used not to contaminate scattering fields by reflected waves at the outer boundary. Computed scattering fields show the circumferential acoustic modes generated by interacting between acoustic sources and scattered waves. At a lower frequency, the wave passes almost straight through the cylinder without Interacting with circular cylinder. Simulation results are presented and compared with the analytic solution. Computed RMS-pressure distribution on the cylinder wall is good agreement with exact solution.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.252-261
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• 1988

Employed the new invese scattering scheme based on the moment mehtod, which was presented in the Part I of these companion papers, numerical simulations are performed to investigate the effect of measurement errors and noise contaminating the field scattered from dielectric objects. In order to reduce those effects on the reconstructed permittivity profiles, some techniques such as regularization, iterative matrix inversion, and multiple incidence are applied to this problem.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.181-187
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• 1998

The ionization energy and degree of ionization for p-type $Si_{1-x}Ge_x$ with boron doping are calculated taking into account the screening and broadening effects. The drift and Hall mobilities are then calculated using the relaxation time approximation and compared with the previously reported measurement data for relaxed and strained $Si_{1-x}Ge_x$ alloys to estimate the alloy scattering potential. From a fit, the alloy scattering potential is found to be 0.5 eV. The in-plane drift mobility for p-type strained $Si_{1-x}Ge_x$ grown on (001) Si substrate is approximately 1+$10x^2$ times higher than that for bulk Si in the high doping range.

• Journal of the Optical Society of Korea
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• v.17 no.3
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• pp.275-278
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• 2013

The effect of the wavelength-dependent scattering on the change of the color chromaticity in the lightguide panel of a liquid crystal display is examined. The white light emitted from the white LEDs located at the edge of the lightguide propagates in the lightguide and is scattered by the patterned dots that are placed on the bottom of the lightguide. The scattered lights that are far from the LEDs showed reddish color compared to the bluish color that is scattered from the near area from the LEDs. The color difference was between 0.01 to 0.06 depending on the resin and the thickness of the lightguide.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.468-474
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• 2011

Underwater radiated noises from marine vehicles are mostly due to the propulsion systems. Recently, the propeller noise problems are becoming crucial issues in terms of habitability of passenger ships. Especially in military area, propeller noise is directly related to the survivability of submarines and warships, and thus propeller noise analysis and reductions are very important. Generally, propeller noise can be classified into non-cavitating noise and cavitating noise which is dominant. In this paper the methodology of propeller noise analysis is announced and new approach to consider scattering effect is proposed. Unsteady blade surface pressure and sheet cavity volume analyzed with potential based panel method are used as noise source.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.87-93
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• 1997

Radiometers in UV and visible wavelengths were onboard the Korean Sounding Rocket(KSR)-1 and 2 which were launched on June 4th and September 1st, 1993. These radiometers were designed to capture the solar radiation during the ascending period of the rocket flight. The purpose of the instrument was to measure the vertical profiles of stratospheric ozone densities. Since the instrument measured the solar radiation from the ground to its apogee, it is possible to investigate the altitude variation of the measured intensity and to estimate the effect of atmospheric scattering by comparing the UV and visible intensity. The visible channel was a reference because the 450-nm wavelength is in the atmospheric window region, where the solar radiation is transmitted through the atmosphere without being absorbed by other atmospheric gases. The use of 450-nm channel intensity as a reference should be limited to the altitude ranges above the certain altitudes, say 20 to 25km where the signals are not perturbed by atmospheric scattering effects.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.91-94
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• 2017

AThe effect of localized surface plasmon on silicon substrates was studied using silver nanoparticles. The nanoparticles were formed by self-arrangement through the surface energy using rapid thermal annealing (RTA) technique after the thin nanolayer of silver was deposited by thermal evaporation. By the theoretical calculation based on Mie scattering and dielectric function of air, indium tin oxide (ITO), and silver, the strong peak of scattering cross section of silver nanoparticles was found at 358 nm for air, and 460 nm for ITO, respectively. Accordingly, the strong suppression of reflectance under the condition of induced light of $30^{\circ}$ occurred at the specific wavelength which is almost in accordance with peak of scattering cross section. When the external quantum efficiency was measured using silicon solar cells with silver nanoparticles, there was small enhancement peak near the 460 nm wavelength in which the light was resonated between silver nanoparticles and ITO.