• Journal of KSNVE
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• v.9 no.1
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• pp.174-183
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• 1999

An analytical model for the lateral vibration of beams with a bonded lap joint and partial layered dampers has been proposed in this paper. Both shear and normal forces acting along the interface between the elastic and viscoelastic layers were considered in the vibration analysis. Analytical results were compared with those obtained by a finite element method. Effects of the size and location of layers in partial dampers on system loss factor($\eta_s$) and resonant frequency($\omega_r$) were studied. which showed that partial dampers adhered to the site exhibiting the maximum amplitude of vibration were most influential in the increase of $\eta_s$ and the decrease of $\omega_r$. Specific system loss factor( $\eta_s$ divided by total mass of system) was also evaluated in the analysis.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.541-543
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• 1997

In this paper, a proposed resonant PWM switching technique makes the boost AC/DC converter to high input power factor and less switching loss. Also, the switching control scheme is used which minimize harmonic components employing novel PWM technique. In addition, an employment of resonant circuit for switching makes zero current switching(ZCS) and zero voltage switching(ZVS) for control switches without switching losses. The result shows that high power factor is still for varying load and switching loss is very low.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.700-703
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• 2003

The test method of ASTM E 756 and KS D 0076 to estimate vibration-damping properties is compared. Comparison method depending on specimen support, exciting method and calculation method for loss factor is used. Half-power bandwidth method and vibration decay method is used in the calculation method for loss factor, and Young's modulus is decided by geometric character and density for specimen and resonance frequency. Vibration measurement sensor is compared by using non-contact displacement detector, velocity detector and accelerometer. This paper is also presented the matter which is able to cause error in the measurement

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.95-101
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• 1997

A general method is presented for the analysis of the damping effectiveness of viscoelastic layer applied to elastic beam. The damping is attributed to the shear deformations of the treatment. Specific results are then given for sandwich beams with dissipative cores. The calculated results by this method are validated by comparison with the experimental results. Optimum design of a viscoelastic damping layer which is constrainedly cohered on a steel beam is discussed from the viewpoint of the modal loss factor. An object function is a loss factor of 3-layered beam and design variable is the thickness of constraining layer and viscoelastic layer. Optimum thickness can be obtained when 3-layered beam has a maximum loss factor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.391-397
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• 2001

The characteristic values of damping materials are variant on frequency and temperature. We measure the characteristic values(loss factor, young\\\\`s modulus) of damping materials in vibration test. We can not measure characteristic values of damping materials by themselves. So, we proposed a method, sticking damping material to thin steel beam and measuring of characteristic values of damping material on frequency and temperature. We didn\\\\`t use constraining layer but we measured characteristic values on conditioning temperature.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.470-474
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• 1996

The dielectric properties, dielectric constant (${\varepsilon}‘$) and loss factor (${\varepsilon}’$), of skin and pulp of fresh ginseng were measured from $25^{\circ}C$ to $67^{\circ}C$ using an open-ended coaxial probe technique for 915 MHz and 2450 MHz. Pulp and skin had dielectric constant of $30{\sim}64$ and loss factor between 10 and 20, each variable having a respective frequency dependence typical of materials with high water content. Although the loss factor was nearly constant, the dielectric constant increased as moisture content increased. The dielectric constant of ginseng pulp increased as temperature increased (temperature ${\leq}56^{\circ}C$), but any significant differences were not found in skin dielectric properties. Penetration depth for fresh ginseng were about 2 cm at 91.5 MHz and 1cm at 2450 MHz.

• The Journal of the Acoustical Society of Korea
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• v.13 no.2
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• pp.13-22
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• 1994

A theoretical model is studied to describe the sound radiation by the surface vibration of in-service tires. The tire is modeled as a circular ring model. The effects of normalized frequency and structrual loss factor are included. Through numerical integration of the sound pressure, the radiated sound power is calculated as a fuction of normalized frequency and structural loss factor. The basic sound radiation mechanism is shown to be the damped progressive wave field on the structure in the vicinity of the applied force. The results indicate that the potential sound reduction might be obtained if values of normalized frequency and structural loss factor are investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.439-442
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• 2003

The test method of ASTM E 756 and JIS G 0602 to estimate vibration-damping properties is presented. Measurement method depending on specimen support, exciting method and calculation method for loss factor is used. Half-power bandwidth method and vibration decay method is used in the calculation method for loss factor, and Young's modulus is decided by geometric character and density for specimen and resonance frequency. Vibration measurement sensor is compared by using non-contact displacement detector, velocity detector and accelerometer. The cause of measurement error is also presented.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.284-286
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• 2004

When Power market is restructured, we have an argument with selecting Transmission loss factors. First, we determine the method of calculating Transmission loss factor using OPF (Optimal Power Flow) or PF (Power Flow Equation). Then, we decide that we applicate the factor which are identical value all the year or which are floating Transmission loss factor every each hour. In this study, we accomplish the method of computing Transmission cost in competitive market.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.942-945
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• 2005

The purpose of this study is to suggest a fundamental data for change of dynamic properties according to the loading time of resilient materials. 18 kinds of resilient materials included 4 representative types were measured at the load time of 24hours and 2hours by the method of Korea standard (KS F 2868) measuring the dynamic stiffness and the loss factor of materials under floating floors. As a result, the dynamic stiffness was increased rapidly in case of expandable polystyrene and rubber materials according to the load time, especially before 2 hours. The loss factor was represented that rubber materials with high elasticity are high, and expandable polystyrene, polyester, poly ethylene materials with low elasticity are low.