• 제목/요약/키워드: Flexural Wave

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Resonances of Unconstrained Compressive, Shear and Flexural Waves in Free-Free Cylinder Specimens (자유단 공시체에 있어서 압축파, 전단파, 휨파의 공진특성)

  • Park, Byoung-Sun;Joh, Sung-Ho;Lee, Sang-Heon;Kang, Tae-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.582-589
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    • 2006
  • Shear wane velocity is important property for grasping the dynamic characteristics of material. It is has been used in various fields such as non-destructive testings of structures, seismic analysis of geotechnical structures and maintenance of concrete structure, and etc. Usually, shear wave velocities of rock cores and concrete cylinders are determined by free-free resonance tests, Shear wave measurement in free-free resonance tests is not straightforward, as compared with rod wave and flexural wane measurements. In This study, a new technique using resonance features of flexural and shear waves were proposed in which the nodal points for the fundamental mode of flexural waves were employed to generate and measure the shear waves with the flexural waves minimized. The real measurements for aluminum cylinders proved validity and reliability of the proposed algorithm. In addition to the proposed algorithm, the effects of material properties on elastic-wave velocities in resonance measurements were also studied. In summary, a new framework of the resonance measurements for shear-wave velocity determination was established, based on the results of this thesis.

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Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave (Flexural wave를 이용한 고분자 전해질 연료전지 공기극 내에서의 플러딩 제거)

  • Kim, Kyoung-Rock;Han, Seong-Ho;Ahn, Deuk-Kuen;Choi, Young-Don
    • Journal of Hydrogen and New Energy
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    • v.21 no.1
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    • pp.35-41
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    • 2010
  • Water management is an important issue of PEM fuel cell operation. Water is the product of the electrochemical reactions inside fuel cell. If liquid water accumulation becomes excessive in a fuel cell, water columns will clog the gas flow channel. This condition is referred to as flooding. A number of researchers have examined the water removal methods in order to improve the performance. In this paper, a new water removal method that investigates the use of vibro-acoutic methods is presented. Piezo-actuators which are devices to generate the flexural wave are attached at the end of a cathode bipolar plate. Flexural wave is used to impart energy to resting droplets and thus cause movement of the droplets in the direction of the traveling wave.

A Study on Motion Characteristics of the Ultrasonic Transporting System according to the change of Flexural Beam Shape (Flexural Beam의 형태 변화에 따른 초음파 이송시스템의 동작특성에 관한 연구)

  • 정상화;신병수;차경래
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.696-699
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. There systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

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Transport Characteristics according to Flexural Beam Shape for the Ultrasonic Transport Systems (초음파 물체 이송시스템에서 Flexural Beam 의 형태 변화에 따른 이송특성에 관한 연구)

  • Shin, Byung-Su;Jeong, Sang-Hwa;Cha, Kyung-Rae
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1608-1613
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    • 2003
  • In the semiconductor and the optical industry, a new transport system which can replace the conventional sliding system is required. These systems are driven by the magnetic field and the conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problems. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phasedifference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified. In addition, the system performance for practical use is evaluated.

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Flexural properties of dear specimens made from small diameter thinned trees (국산 주요 간벌 소경재의 무결점재에 대한 휨특성)

  • 차재경
    • Journal of Korea Foresty Energy
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    • v.22 no.1
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    • pp.44-48
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    • 2003
  • Flexural properties were investigated on clear specimens made from small diameter thinned trees of pitch pine (Pinus rigida Mill.), Japanese red pine (Pinus densiflora Sieb. et Zucc), Japanese larch (Larix kaempferi Carr.), and sawtooth oak (Quercus acutissima Carr.). MOR and MOE values of small clear specimen were depended on the species. The highest density of sawtooth oak shows the highest values of MOR and MOE. However, the lowest density of Japanese larch shows the lowest values of MOR. It was also shown that flexural properties could be predicted by stress wave MOE, since the correlations between stress wave MOE and flexural properties were relatively good.

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The analysis of tire's flexural characteristic using wave propagation (Wave Propagation 을 이용한 타이어 굽힘파 분석)

  • Hwang, S.W.;Han, J.H.;Rho, G.H.;Cho, C.T.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1237-1240
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    • 2007
  • Tire noise is a major noise source at high speeds. One of the noise source is controlled by pattern and structure. Pattern noise is effected by the shape of tread. And the bending stiffness of tire is influenced to the resonance of tire‘s belt. But in high frequency region, FEA is not appropriated with application. So this paper discusses about wave propagation of tire. There has been much effort to verify the flexural wave velocity with structure design specification.

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A Study on the Relationship between Flexural Beam Shape and Transport Characteristics for the Ultrasonic Transport Systems (초음파 이송 시스템에서 Flexural Beam의 형태 변화와 물체 이송과의 관계에 대한 연구)

  • 정상화;신병수
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.25-29
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

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Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave

  • Byun, Sun-Joon;Kwak, Dong-Kurl
    • Journal of Electrochemical Science and Technology
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    • v.10 no.2
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    • pp.104-114
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    • 2019
  • Energy is an essential driving force for modern society. In particular, electricity has become the standard source of power for almost every aspect of life. Electric power runs lights, televisions, cell phones, laptops, etc. However, it has become apparent that the current methods of producing this most valuable commodity combustion of fossil fuels are of limited supply and has become detrimental for the Earth's environment. It is also self-evident, given the fact that these resources are non-renewable, that these sources of energy will eventually run out. One of the most promising alternatives to the burning of fossil fuel in the production of electric power is the proton exchange membrane (PEM) fuel cell. The PEM fuel cell is environmentally friendly and achieves much higher efficiencies than a combustion engine. Water management is an important issue of PEM fuel cell operation. Water is the product of the electrochemical reactions inside fuel cell. If liquid water accumulation becomes excessive in a fuel cell, water columns will clog the gas flow channel. This condition is referred to as flooding. A number of researchers have examined the water removal methods in order to improve the performance. In this paper, a new water removal method that investigates the use of vibro-acoustic methods is presented. Piezo-actuators are devices to generate the flexural wave and are attached at end of a cathode bipolar plate. The "flexural wave" is used to impart energy to resting droplets and thus cause movement of the droplets in the direction of the traveling wave.

A study on the dynamic characteristics of exciting Flexural beam by ultrasonic wave (초음파에 의해서 가진되어지는 Flexural Beam의 동특성에 관한 연구)

  • Jeong, Sang-Hwa;Shin, Sang-Moon;Kim, Gwang-Ho;Lee, Sang-Hee;Kim, Ju-Hwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.792-796
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    • 2006
  • In recent years, the semiconductor industry and the optical industry is developed rapidly. The recent demand has expanded for optical components such as a optical lens, a optical semiconductor and a measuring instrument. Object transport systems are driven typically by the magnetic field and the conveyer belt. Recent industry requires more faster and efficient transport system. However, conventional transport systems are not adequate for transportation of optical elements and semiconductors. Because conveyor belts can damage precision optical elements by the contact force and magnetic systems can destroy the inner structure of semiconductor by the magnetic field. In this paper, the levitation transport system using ultrasonic wave is developed for transporting precision elements without damages. This transport system is using 2-mode ultrasonic wave excitation and flexural beam modes shapes are evaluated. It compared simulation results with experimental results

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