• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1169-1176
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• 2002

Analytical model of beat response is derived on a slightly asymmetric ring and is veryfied by experiment. The asymmetric ring is a simplified model used to explain the beat property of a Korean bell. The asymmetric ring has mode pair having slight frequency difference in each radial mode. Each mode pair produces beat phenomenon by the interaction of the two close frequency components. Based on the analytical model, beat maps are first proposed and characteristics of beat on the circumference are detaily explained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1218-1223
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• 2007

In this study, we experimentally investigate the equivalent ring theory for a slightly asymmetric ring. The slightly asymmetric ring has mode pair and frequency pair due to the small asymmetry and this mode pair generates beat in vibration and sound. In this paper, a slightly asymmetric ring is modeled as the equivalent ring, i.e., the assemblage of a symmetric ring and imperfect point masses. The equivalent ring has the same mode pair condition as that of the original asymmetric ring. Effect of the additional mass attachment is investigated by the equivalent ring theory and the result is compared with those of the measurement and the finite element analysis. It is confirmed that the original ring and the equivalent ring show the same change in frequency and mode under the various additional imperfection mass conditions. The equivalent ring theory explains how the asymmetric elements influence the mode characteristics and provides useful information to tune the beat property.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.685-693
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• 2002

Analytical model of beat response is derived on a slightly asymmetric ring and the model is veryfied by experiment. The asymmetric ring is a simplified model used to explain the beat property of a Korean bell. The asymmetric ring has mode pairs having slight frequency difference in each radial mode. Each mode pair produces beat phenomenon by the interaction of the two close frequency components. Based on the analytical model, beat maps are first proposed and characteristics of beat on the circumference are detaily explained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1925-1932
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• 2000

Damage detection methods using vibration modes are investigated on ring structures and. modal behavior of the slightly asymmetric rings is examined. Mode shapes changes, MSER(modal strain energy ratio) and MCR(modal curvature ratio) are applied to identify the locations of faults or damages. Parameters are calculated and compared by finite element analysis on rings with designed local damages. Damages are modeled as reduced stiffness in the analysis. The results show MSER and MCR can be proper factors to detect local damages in ring structures.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.365-371
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• 2008

In this study, beat control method using an equivalent ring model is proposed to control beat period of a slightly asymmetric ring. Slight asymmetry in a ring generates mode pair and the interaction of the mode pair makes beat in vibration and sound. In a ring, as a simplified bell type structure, mode data are measured and an equivalent ring is determined so that the measured mode condition is satisfied. By the finite element analysis on the equivalent ring, changes of mode pair condition are predicted when local mass is attached or the local thickness is decreased. The predicted results are compared with the experimental result and the validity of the proposed method is verified.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.29-36
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• 2002

A damage detection algorithm using vibration modes is applied to the ring structures and the modal behaviors of the slightly asymmetric rings are examined. Mode shape change, MSER(modal strain energy ratio) and MCR(modal curvature ratio) are investigated to identify the locations of faults or damages The above fault detection parameters are calculated and compared by the finite element analysis on rings with designed local damages. Damages are modeled as a reduced stiffness in the analysis The results show that MSER and MCR can be proper parameters to detect local damages in the ring structures.

• Membrane and Water Treatment
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• v.2 no.1
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• pp.25-37
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• 2011

PES UF membranes containing silver were prepared to impart antibacterial properties for waste water treatment. Asymmetric membranes for antibacterial application were prepared from polyethersulfone (PES) and silver nitrate ($AgNO_3$) (PES/$AgNO_3$=15/2 by weight) solution in N-Methyl-2-pyrrolidone (NMP) via simple wet phase inversion technique. These membranes were characterized by polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) of different molecular weights (1000 ppm in water) at room temperature and on operating pressure of 5 bars. It was observed that the water flux of PES-$AgNO_3$ membrane is slightly lower than virgin PES but still increased linearly with the increment of pressure applied. The morphology of the resulting membranes was examined using Field-Emission Scanning Electron Microscope (FESEM) coupled with Energy Dispersive Spectroscopy (EDS). Elemental analysis using EDS proved that silver is successfully loaded on the membrane surfaces. Due to the success of loading silver on membrane surfaces, antibacterial activities were evaluated via agar diffusion method against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) culture. By incorporating 2 wt% of silver nitrate, PES-$AgNO_3$ showed significant inhibition ring on both E.coli and S.aureus. Filtration of E.coli solution (OD 0.31) showed satisfactory rejection data with ~100% inhibition growth after 24 hours incubation at $37^{\circ}C$. Resultant membranes also exhibit better tensile strength (compared to virgin PES) up to 71% may be due to the suggested interactions. The residual silver during fabrication was measured using ICP-MS and result showed that the residual silver content of PES-$AgNO_3$ membrane was only ~1% of the original silver added in the polymer solution. These studies have shown that PES-$AgNO_3$ UF membranes are potential in improving the filtration in water treatment.