• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.4 s.181
• /
• pp.60-66
• /
• 2006

For the purpose of finding out the sound field characteristics in a rectangular cavity, analytical and experimental studies are performed with white noise input. Two-microphone impedance tube method is used to measure the impedances of foamed aluminum. Foamed aluminum is well known metallic porous material which has excellent properties of light weight and high absorbing performance. And predicted impedances of foamed aluminum are compared with measured impedances. The predicted acoustical parameters are applied to the theoretical analysis to predict sound pressure field in the cavity. The measured sound absorption effects are compared with the predicted values for both cases with and without foamed aluminum lining in the cavity of the rectangular enclosure.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.3
• /
• pp.406-410
• /
• 2012

This paper looks into the field inside the wide rectangular box structure that is excited by the High Power Electromagnetic(HPEM) source as a potential threat to electric grid and communication networks causing malfunction or destruction. The rectangular box is assumed power/ground planes and its internal field is calculated by the cavity model with the lightning strike excitation as an HPEM pulse. The accuracy of the calculation method employed here is validated through a $156mm{\times}106mm{\times}508{\mu}m$ parallel metallic plate case which is manufactured and tested, and is applied to the size of a building. With the help of the cavity model that takes into account loading, the level of the electric field is shown to decrease when a metal pillar is loaded between the power and ground planes.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.8
• /
• pp.2546-2554
• /
• 1996

In order to investigate the characteristics of sound-structure interaction problems, we modeled a rectangular cavity and the flexible wall of the cavity. Because the governing equations of motion are coupled through velocity terms, we could redefine them using the velocity potential. We calculated the natural frequencies of plate using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz Method. As the result, comparisons of theory and experiment show good agreement. and using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz method show useful method for sound-structure interaction problems too.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.105-116
• /
• 1996

In this paper, we report the experimental results for the flow pattern and the material transport around a cavity subject to a sinusoidal external flow at the far region to ward the open side of the cavity. A tilting mechanism is used to generate a oscillatory flow inside a shallow rectangular container having a cavity at one side. The surface flow visualization is performed to obtain the unsteady behavior of vortices generated at two edges situated at the entrance of the cavity. It was found that at the period 4.5 sec., the behavior of the vortices is asymmetric, and there exists a steady residual flow in the cavity. The bottom flow patterns are also visualized. There are two regions outside of the cavity where the bottom fluid particles concentrate. The material transport in this flow model is very peculiar; fluid particles in the cavity flows outward through the passage along the walls starting from the edges, and particles in the outer region approach the cavity from the central region.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.629-634
• /
• 2004

Cavities are inevitable structures in automobile configuration. The flow-induced noise is generated from the wheel housing section by the interaction between a rotating wheel and the unsteady flows in the cavity. In this research the wheel housing was assumed by a rectangular cavity for simplification. We measured the radiated sound from the 2-D cavity without cylinder and from the rotating cylinder in the cavity by using the sound source localization method with an acoustic mirror system. In the 2-D cavity case of low Mach number(Ma=0.029), the sound sources were found to be located near the leading edge of cavity due to the shear layer instabilities. Comparing the cases of the rotating and the non-rotating cylinder, it is observed that the sound Pressure levels around the rotating cylinder in the cavity increased and the main acoustic sources were located at the rear section of the rotating wheel.

• 한국전산유체공학회:학술대회논문집
• /
• 2006.05a
• /
• pp.157-160
• /
• 2006

• Journal of Electrical Engineering and Technology
• /
• v.10 no.5
• /
• pp.2120-2125
• /
• 2015

In this paper, a rectangular waveguide probe with a ridge-loaded straight slot (RLSS) is presented for a near-field scanning microwave microscope (NSMM). The RLSS is located laterally at the end wall of the cavity and is loaded on double ridges in a narrow straight slot to improve the spatial resolution compared with a straight slot. The probe consists of a rectangular cavity with an RLSS and a feed section of a WR-90 rectangular waveguide. When the proposed NSMM is located at distance of 0.1mm in front of a substrate without patches or strips, the simulated full width at half maximum (FWHM) of the probe improve by approximately 31.5 % compared with that of a straight slot without ridges. One dimensional scanning of the E-plane on a sample under test was conducted, and the reflection coefficient of the near-field scanning probe is presented.

• Journal of electromagnetic engineering and science
• /
• v.11 no.3
• /
• pp.220-226
• /
• 2011

We have proposed a new method to accurately predict the resonance of Fabry-Perot Cavity (FPC) antennas enclosed with conducting side walls. When lateral directions of an FPC antenna are not blocked with metallic walls, the conventional technique is accurate enough to predict the resonance of the FPC antenna. However, when the FPC antenna has side walls, especially for case with only a short distance between the walls, the conventional prediction method yields an inaccurate result, inevitably requiring a tedious, time-consuming tuning process to determine the correct resonant height to provide the maximum antenna gain in a target frequency band using three-dimensional full-wave computer simulations. To solve that problem, we have proposed a new resonance prediction method to provide a more accurate resonant height calculation of FPC antennas by using the well-known resonance behavior of a rectangular resonant cavity. For a more physically insightful explanation of the new prediction formula, we have reinvestigated our proposal using a wave propagation characteristic in a hollow rectangular waveguide, which clearly confirms our approach. By applying the proposed technique to an FPC antenna covered with a partially reflecting superstrate consisting of continuously tapered meander loops, we have proved that our method is very accurate and readily applicable to various types of FPC antennas with lateral walls. Experimental result confirms the validness of our approach.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.131-133
• /
• 2003

The streamfunction-vorticity equations for two-dimentional cavity flow are solved by a new finite element method which uses finite spectral basis functions as interpolation functions for rectangular elements. Results for several cases with different Renold's number are compared with benchmark solutions and found to be in well agreement.

• Proceedings of the Optical Society of Korea Conference
• /
• 1997.08a
• /
• pp.29-29
• /
• 1997