• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.665-671
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• 2003

Length of an unconstrained viscoelastic damping layer on beams is determined to maximize loss factor using a numerical search method. The fractional derivative model can describe damping characteristics of the viscoelastic damping material, and is used to represent nonlinearity of complex modulus with frequencies and temperatures. Equivalent flexural rigidity of the unconstrained beam is obtained using Ross, Ungar, Kerwin(RUK) equation. The loss factors of partially covered unconstrained beam are calculated by a modal strain energy method. Optimal lengths of the unconstrained viscoelastic damping layer of beams are obtained with respect to ambient temperatures and thickness ratios of beam and damping layer.

• Steel and Composite Structures
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• v.46 no.3
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• pp.367-383
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• 2023

In this investigation, an improved integral trigonometric shear deformation theory is employed to examine the vibrational behavior of the functionally graded (FG) sandwich plates resting on visco-Pasternak foundations. The studied structure is modelled with only four unknowns' variables displacements functions. The simplicity of the developed model being in the reduced number of variables which was made with the help of the use of the indeterminate integral in the formulation. The current kinematic takes into consideration the shear deformation effect and does not require any shear correction factors as used in the first shear deformation theory. The equations of motion are determined from Hamilton's principle with including the effect of the reaction of the visco-Pasternak's foundation. A Galerkin technique is proposed to solve the differentials governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for various clamped and simply supported FG sandwich plates resting on visco-Pasternak foundations. The validity of proposed model is checked with others solutions found in the literature. Parametric studies are performed to illustrate the impact of various parameters as plate dimension, layer thickness ratio, inhomogeneity index, damping coefficient, vibrational mode and elastic foundation on the vibrational behavior of the FG sandwich plates.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.656-661
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• 2005

An optimization formulation of unconstrained damping treatment on beams is proposed to minimize vibration responses using a numerical search method. The fractional derivative model is combined with RUK's equivalent stiffness approach in order to represent nonlinearity of complex modulus of damping materials with frequency and temperature. The loss factors of partially covered unconstrained beam are calculated by the modal strain energy method. Vibration responses are calculated by using the modal superposition method, and of which design sensitivity formula with respect to damping layout is derived analytically. Plugging the sensitivity formula into optimization software, we can determine optimally damping treatment region that gives minimum forced response under a given boundary condition. A numerical example shows that the proposed method is very effective in minimizing vibration responses with unconstrained damping layer treatment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1463-1466
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• 2007

Visco-elastic damping material for reducing heavy-weight floor impact noise and vibration in reinforced concrete structures was tested according to its thickness in the damping layer. The effect of damping material was compared with 20, 15, 10 and 5mm thickness. The wave propagation characteristics was measured for suggestion of an efficient method to reduce the floor impact noise. The method was proposed using the flexural wave propagation characteristics. The result showed that reduction of the thickness of damping layer made a slight difference; the natural frequency moved to higher frequency and the amplitude increased at low frequencies with 5mm thickness of damping material.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.7 s.100
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• pp.829-835
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• 2005

An optimization formulation of unconstrained damping treatment on beam is proposed to minimize vibration responses using a numerical search method. The fractional derivative model is combined with RUK's equivalent stiffness approach in order to represent nonlinearity of complex modulus of damping materials with frequency and temperature. Vibration responses are calculated by using the modal superposition principle, and of which design sensitivity formula with respect to damping layout is derived analytically. Plugging the sensitivity formula into optimization software, we can determine optimally damping treatment region that gives minimum forced response under a given boundary condition. A numerical example shows that the proposed method is very effective in suppressing nitration responses by means of unconstrained damping layer treatment.

• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.317-333
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• 2022

Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

• The Journal of the Acoustical Society of Korea
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• v.8 no.1
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• pp.31-37
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• 1989

The effectiveness of using a composite beam with constrained visco-elastic layer as a dynamic vibration absorber is investigated. The performance of this absorber is evaluated in terms of displacement transmissibility when to a primary beam with built-in ends and compared to that of the uniform beam absorber. The results of analysis and design show that it is possible to suppress simultaneoulsy the peak transmissibilities at two or more resonance frequencies and the optimal parameters are located within the available viscoelastic material properties.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.300-303
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• 2004

In this paper, floor impact noise reduction in a cruise ship cabin by using floating floor is studied. A mock-up is built by using 61 steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7 It is shown that effect of VL(Visco-elastic Layer) is negligible when it is used between deck and mineral wool, since most vibration absorption occurs in the wool. In addition, direction of the mineral wool fiber affects impact noise significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.751-755
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• 2003

In this paper, floor impact noise reduction in a steel structure is studied. A mock-up is built by using 6t steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7. In addition, floor SBN(Structure-borne Noise) and floor damping are measured to study the effect of floating floor. structure. It is shown that VL(Visco-elastic Layer) is more effective when hard plates are added above the VL.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.3
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• pp.356-360
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• 2005

The maintenance of intestinal health is complex and relies on a delicate balance between the diet, the normal microflora and mucosa, including the digestive epithelium and overlying mucus layer. The colorectal mucosa is protected by a visco-elastic mucus gel formed by high molecular mass glycoproteins referred to as mucins. Abnormality of mucin have been identified with colorectal disease. Constipation increases with age, and is more common among women than men in all age groups, e.g. 10% of men and 20% of women in the USA. The aim of the present study was conducted to investigate that the effects of formulation KTG075 from edible plants on intestinal function on mucus secretion, were examined by loperamide-induced constipation method using Sprague Dawley male rats. Epithelial cells of colonic crypt contained more mucus in the KTG075 group compared with those of the control group and the thickness of the mucus layer stained with alcian blue was significantly thicker in KTG075 treated rats compared with in control rats. Mucus production of epithelial cells of crypt and mucus contents at fecal and mucosa surfaces were reduced by loperamide-induced constipation. These results indicates that a poly herbal formulation KTG075 accelerates evacuation and activated intestines.