• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.04a
• /
• pp.57.1-60
• /
• 1999

This paper presents the effects of partial dampers on the lateral vibration of beams. Both shear and normal stresses in the viscoelastic layer were studied. Analytical results were compared with those obtained by a finite element method. Effects of the size of partial dampers on the system loss factors and resonant frequencies were discussed.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.4
• /
• pp.62-70
• /
• 2001

Based on the recently developed resonance scattering theory for elastic waves, a relationship between the stress components, which may be measured using ultrasonic transducers, of partial waves scattered from cylindrical fluid scatterer, cavity, and resonance scatterer has been derived. The computed resonance scattered stresses exhibit frequency behaviors similar to the corresponding scattering coefficients: particularly, abrupt changes in phase by 180°near the resonant frequencies. By studying the behavior of pressure in the fluid scatterer, the physics of the theory has been further understood. Using the method studied and developed in this paper, nondestructive characterization of fluid inclusions in elastic media is expected to become more reliable.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.2
• /
• pp.225-233
• /
• 2002

The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer have been quantitatively studied using a finite element analysis in combination with a sine-sweep test. Antisymmetric mode shapes of the flexural vibration were visualized by the holographic interferometry and agreed with those calculated by the finite element simulation. Effects of the beam thickness as well as the length and thickness of partial viscoelastic layers on the system loss factor(η$\_$s/) and resonant frequency($\omega$$\_$r/) were significantly large fur the symmetric and antisymmetric modes of the beam system.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.167-170
• /
• 2000

The flexural vibration of a sandwich beam with partially inserted viscoelastic layer has been studied using the finite element analysis in combination with an experiment. Effects of length and thickness of partial viscoelastic layers on system loss factor(${\eta}_s$) and resonant frequency(${\omega}_r$) were considerably large. The thicker the viscoelastic layer in a sandwich beam, the larger the system loss factor in Mode 1 as compared with that in Mode 2. The loss factor increased almost linearly with increasing the length of partial viscoelastic layer. Effects of thickness of beams were also considered.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.12 no.5
• /
• pp.394-399
• /
• 2007

In this paper, we study on a novel Buck-Boost converter of high efficiency by soft switching method. The proposed Buck-Boost converter is applied to new soft switching method in restraint of increment of switching power loss in the conventional Buck-Boost converter. The soft switching circuit is designed to modification of a energy storage inductor and a snubber circuit used by the conventional converter, and then the proposed converter is simplified. The controlling switches of the proposed converter is operated with soft switching by a partial resonance behavior. The output voltage of the converter is regulated by PWM control technique. The discontinuous mode action of current flowing into inductor makes to simplify control method and control components. The proposed Buck-Boost converter is compared with the conventional converter. Some computer simulative results and experimental results are confirmed to the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.12 no.6
• /
• pp.465-471
• /
• 2007

The system efficiency of the proposed Buck-Boost AC-DC converter is increased by soft switching method. The converter includes to merit of power factor correction (PFC) from sinusoidal control of input current. The switching behavior of control switches operates with soft switching by partial resonance, and then the proposed converter has high system efficiency with decrement of switching power loss. The input current waveform in proposed converter is got to be a sinusoidal form of discontinuous quasi-pulse row in proportion to magnitude of AC input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity. The output voltage of the converter is regulated by PWM control technique. The discontinuous mode action of current flowing into inductor makes to simplify control method and control components. The proposed PFC Buck-Boost converter is analyzed to compare with the conventional PFC Buck-Boost converter. Some computer simulative results and experimental results confirm to the validity of the analytical results.