• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.79-86
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• 1999

Electronic Speckle Pattern Interferometry(ESPI) is a powerful tool to measure the vibration mode shape and resonance frequency for modal analysis. As for ESPI this method is very suited for full-field measurement of objects in industrial areas because the interferograms are recorded with a video camera and evaluated in real-time with a computer. In this study We performed experiments at the same constraint conditions as disk brake of the practical vehicle as far as possible and obtained the resonance frequencies and vibration mode shapes by using time-averaged ESPI at once. Finally to assure the expetimental results by time-averaged ESPI we also compare those with results obtained by Laser Doppler Vibrometer and obtained good agreement.

• Journal of Industrial Technology
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• v.24 no.B
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• pp.83-87
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• 2004

A reduced structure model of a wind turbine generator is designed and manufactured. Mode data are obtained by modal testing and analytical method. Vibration response is measured and investigated under various speed condition by using a waterfall plot. Possibility of severe resonance is observed and the mechanism is explained by using the mode data. Simplified theoretical model gives the 1st resonance frequency of wind turbine structure model. The theoretical model can be applied in the design stage of the wind turbine structure to avoid the severe resonance problem.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.102-110
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• 2008

It is well known that the acoustic cavity inside the tire-wheel assembly contributes to vehicle interior noise and ride comfort. In this paper, we performed acoustic and structural modal testings by varying the temperature ranging from $20^{\circ}\;to\;45^{\circ}C$ to investigate the effects of temperature on acoustic cavity resonance and structural vibration characteristics for unloaded and loaded tires. The testing has given us some findings, which are reported in this paper.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• Journal of Korean Foot and Ankle Society
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• v.25 no.1
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• pp.1-5
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• 2021

Physical examination and surgical findings and symptoms are often inconsistent with magnetic resonance imaging (MRI) findings when diagnosing chronic ankle lateral ligament instability, and confirmed surgical findings are used as the gold standard in most clinical studies. Anterior drawer testing is considered unreliable because normal findings are highly variable, and its accuracy ranges from 50% to 100%. Furthermore, radiographic stress imaging, such as in anterior drawer stress view, is performed under manual stress or using a stress device, and its findings also vary widely and confuse when interpreting stress views. The average accuracy of MRI findings is around 85% (range, 66%~91.7%), and thus, cannot be used as a primary indicator for surgery. For patients with suspected lateral ankle ligament instability, based on symptoms and physical examination findings, MRI may be useful for identifying lesions in ankle joints and for differentiating them from other conditions.

• Journal of Korean Neurosurgical Society
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• v.29 no.12
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• pp.1570-1576
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• 2000

Objective : To evaluate objectively the sites of injury in patients with posttraumatic olfactory deficits and to suggest the diagnostic procedure for evaluation of posttraumatic anosmia. Methods : Ten patients with posttraumatic olfactory dysfunction were examined by means of olfactory testing, sinoscopy, contrast filled paranasal sinus computed tomography(contrast filled PNS CT) and magnetic resonance imaging(MRI). Five normal persons without olfactory dysfunction were also evauluated. The aerodynamic patency of olfactory cleft was examined by contrast filled PNS CT. The olfactory system(oflactory bulbs, olfactory tracts, inferior frontal region, hippocampi, or temporal lobes) was investigated in detail with MRI. The difference in the size of the olfactory bulb between normal volunteers and anosmic patients was evaluated by Student's t test. Results : Contrast filled dynamic CT scan was useful method for the evaluation of dynamic patency of the olfactory cleft. Paranasal CT scan of the all anosmic patients showed dynamic reflux of contrast media in olfactory cleft on valsalva maneuver. For the largest cross-sectional area and great height, the difference in olfactory bulb size between normal volunteers and patients was statistically significant(p<0.001) in MRI study. Conclusion : Posttraumatic anosmia was completely evaluated by olfactory testing, sinoscopy, and contrast filled CT scan for differentiation between conductive type and neurogenic type. Neurogenic anosmia was confirmed by perfect localization with MRI study.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.132-138
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• 2010

Vibro-contact of cantilever tip is studied with respect to contact mechanics and an elastic characteristic of nanoscale surface is imaged. The contact resonance frequency is calculated theoretically using the spring-mass and Herzian models, and the variation of resonance frequency of cantilever was analyzed when the cantilever was free and contact. The elasticity imaging was also achieved successfully using phase and amplitude signals obtained from the spheroidized steel specimens by prototype ultrasonic AFM.

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

• Journal of electromagnetic engineering and science
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• v.11 no.4
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• pp.298-303
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• 2011

A capsular endoscope (CE) for inspection of the large intestine requires a motor for backward navigation against the autonomous travel in the intestine. This study proposes an HF power system for generating a magnetic field and for delivering wireless power to the internal or implanted medical devices. The magnetic field is generated by a wound coil (L) around a wooden frame, and the current is driven to the coil through a resonating capacitor (C). The characteristics of the resonance frequency shifting of the L-C series circuit are analyzed. A stable magnetic field intensity in the field coil is maintained by a specially designed frequency tracking system that automatically follows the L-C resonance frequency. Testing confirmed that the oscillation system tracks well the parameter changes of the electric components caused by the operating conditions or environmental variations.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.273-278
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• 2008

In this paper, effects of thermoelastic stress by using lock-in thermography was measured in the cantilever beam. In experiment, a circular holed plate was applied to analyze variation of transient stress under the condition of repeated cyclic loading. And the finite element modal analysis as computational work was performed. According to the surface temperature obtained from infrared thermography, the stress of the nearby hole was predicted based on thermoelastic equation. As results, each stress distributions between 2nd and 3rd vibration mode were qualitatively and quantitatively investigated, respectively. Also, dynamic stress concentration factors according to the change of vibration amplitude were estimated for the resonance frequency.