• Title/Summary/Keyword: Localized vibration

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Kinematic Analysis in Reaching Depending on the Localized Vibration Duration in Persons With Hemiparetic Stroke (국소 진동자극이 편마비 뇌졸중 환자의 팔 뻗기 수행에 미치는 영향에 대한 운동학적 분석)

  • Yoo, Eun-Young;Park, Ji-Hyuk;Kwon, Jae-Sung;Cho, Sang-Yoon;Lee, Bo-Mi;Kim, Yeong-Jo;Kim, Jae-Nam;Kim, Sun-Ho
    • Therapeutic Science for Rehabilitation
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    • v.7 no.3
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    • pp.79-88
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    • 2018
  • Objective : Localized vibration has been shown to have a positive effect on recovery of upper-limb motor function in patients with hemiparetic stroke, but there has been little research on kinematic analysis for qualitative changes in movement. This study investigated kinematic changes in elbow motion during reaching after localized vibration in persons with hemiparetic stroke. Methods : This study used a one-group, cross-over trial design. Ten chronic stroke patients randomly received localized vibrations on the affected biceps brachii for 5, 10, or 20 min, at 70 Hz. Kinematic analysis of reaching was measured using a 3-D motion analysis system. Variables included peak angular velocity, time to peak angular velocity, and movement units during elbow motion. Result : Affected side elbow motion during reaching was faster, smoother, and more efficient after 20 min localized vibration. Peak angular velocity increased (p<0.05), and time to peak angular velocity (p<0.05) and the movement unit were significantly decreased (p<0.05) during elbow motion for reaching. Conclusion : Localized vibration can improve kinematic components during reaching motion in persons with hemiparetic stroke.

Stochastic micro-vibration response characteristics of a sandwich plate with MR visco-elastomer core and mass

  • Ying, Z.G.;Ni, Y.Q.;Duan, Y.F.
    • Smart Structures and Systems
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    • v.16 no.1
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    • pp.141-162
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    • 2015
  • The magneto-rheological visco-elastomer (MRVE) is used as a smart core to control the stochastic micro-vibration of a sandwich plate with supported mass. The micro-vibration response of the sandwich plate with MRVE core and supported mass under stochastic support motion excitations is studied and compared to evaluate the vibration suppression capability. The effects of the supported mass and localized magnetic field on the stochastic micro-vibration response of the MRVE sandwich plate are taken into account. The dynamic characteristics of the MRVE core in micro-vibration are described by a non-homogeneous complex modulus dependent on vibration frequency and controllable by applied magnetic fields. The partial differential equations for the coupled transverse and longitudinal motions of the MRVE sandwich plate with supported mass are derived from the dynamic equilibrium, constitutive and geometric relations. The simplified ordinary differential equations are obtained for the transverse vibration of the MRVE sandwich plate under localized magnetic fields. A frequency-domain solution method for the stochastic micro-vibration response of sandwich plates with supported mass is developed based on the Galerkin method and random vibration theory. The expressions of frequency-response functions, response power spectral densities and root-mean-square velocity responses of the plate in terms of the one-third octave frequency band are obtained for micro-vibration evaluation. Finally, numerical results are given to illustrate the large response reduction capacity of the MRVE sandwich plate with supported mass under stochastic support motion excitations, and the influences of MRVE parameters, supported mass and localized magnetic field placement on the micro-vibration response.

Vibration Electrochemical Polishing for Localized Surface Leveling (미세표면 평활화를 위한 진동 전기화학 폴리싱)

  • Kim, Uksu;Kim, Youngbin;Park, Jeongwoo
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.2
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    • pp.148-153
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    • 2013
  • This study demonstrates a novel hybrid surface polishing process combining non-traditional electrochemical polishing(ECP) with external artificial ultrasonic vibration. ECP, typical noncontact surface polishing process, has been used to improve surface quality without leaving any mechanical scratch marks formed by previous mechanical processes, which can polish work material by electrochemical dissolution between two electrodes surfaces. This research suggests vibration electrochemical polishing(VECP) assisted by ultrasonic vibration for enhancing electrochemical reaction and surface quality compared to the conventional ECP. The localized roughness of work material is measured by atomic force microscopy(AFM) for detailed information on surface. Besides roughness, overall surface quality, material removal rate(MRR), and productivity etc. are compared with conventional ECP.

Prevalence of the Vibration Syndrome among Rock-drillers in the Anthracite Mining Area (일부지역 탄광 착암 근로자의 진동증후군 유병율)

  • Roh, Jae-Hoon
    • Journal of Preventive Medicine and Public Health
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    • v.14 no.1
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    • pp.75-80
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    • 1981
  • Due to rapid industrialization and economic development, the occupational diseases have appeared as one of the social problems in Korea. Up until now little has been known about the prevalence rate, predisposing factors and symptomatology of the occupational disease due to localized vibration in Korea. The researcher intends to investigate the prevalence rate and affecting factors of the occupational disease due to localized vibration among rock-drillers in the anthracite mines. A total of 135 rock-drillers were interviewed and examined from May 15th to 31th, 1980. The results were revealed as follows; 1. The prevalence rate of the vibration syndrome among rock-drillers was 12.6%. 2. The latent period of the vibration syndrome was 6.8 years. 3. The prevalence rate of the vibration syndrome was not significantly different between smokers and non-smokers. 4. With the increase of total vibration exposure time, the prevalence rate of the vibration syndrome increased also. 5. The average vibration sensation threshold was high (6.4dB) in stage 1 of the vibration syndrome and low (-0.6dB) in stage 0. 6. The average pain sensation threshold was high (4.4g) in stage 1 of the vibration syndrome and low (2.5g) in stage 0.

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A trigonometric four variable plate theory for free vibration of rectangular composite plates with patch mass

  • Draiche, Kada;Tounsi, Abdelouahed;Khalfi, Y.
    • Steel and Composite Structures
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    • v.17 no.1
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    • pp.69-81
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    • 2014
  • The novelty of this paper is the use of trigonometric four variable plate theory for free vibration analysis of laminated rectangular plate supporting a localized patch mass. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. The Hamilton's Principle, using trigonometric shear deformation theory, is applied to simply support rectangular plates. Numerical examples are presented to show the effects of geometrical parameters such as aspect ratio of the plate, size and location of the patch mass on natural frequencies of laminated composite plates. It can be concluded that the proposed theory is accurate and simple in solving the free vibration behavior of laminated rectangular plate supporting a localized patch mass.

The Detection of Gear Failures Using Wavelet Transform (웨이브렛변환을 이용한 기어결함의 진단)

  • Park, Sung-Tae;Gim, Jae-Woong;Yang, Jianguo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.617-622
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    • 2002
  • This paper presents that the Wavelet Transform can be used to detect the various local defects in a gearbos. Two types of defects which are broken tooth and localized wear, are experimented and the signals are collected by accerometer and analyzed. Because of the complecity of the signals acquired from sensor, it is needed to identify the interesting signal. The natural frequencies of shafts and the gear mesh frequency(GMF) is calculated theretically. DWT, CWT and the aplication are used to extract a gear-localized defect feature from the vibration signal of the gearbox with the defective gear. The results shows the transform is more effective to detect the failures than the Fourier Transform.

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Modeling of Soldering Process using Longitudinal Ultrasonic (종방향 초음파를 이용한 솔더링 공정의 모델링)

  • 김정호;이지혜;유중돈;최두선
    • Journal of Welding and Joining
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    • v.21 no.5
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    • pp.534-539
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    • 2003
  • An efficient soldering process using the longitudinal ultrasonic vibration is introduced in this work for electronic packaging. The effects of the process parameters such as the ultrasonic frequency, amplitude, dimension of the metal bump and solder are analyzed through a viscoelastic lumped model. The viscoelastic properties of the eutectic solder were measured for calculation and evaluation of heat generation capability of the solder. Experiments were conducted to verify the possibility of the proposed ultrasonic soldering method by inserting the Cu and Au bumps into the solder block. Localized heating due to ultrasonic vibration melts the solder near the metal bump, which demonstrates the applicability of the ultrasonic soldering method to the high-density electronic packaging.

Running Monitoring by the Noise and Vibration Measurement near the Wheelset of the High-Speed Trains : A Preliminary Research (고속철도차량 윤축부근의 소음과 진동 측정을 통한 주행중 감시의 기초연구)

  • Lee, Jun-Seok;Choi, Sung-Hoon;Park, Choon-Soo
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.1454-1462
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    • 2008
  • This paper is focused on the analysis of the noise and vibration measured near the wheelset of the high-speed trains using a time-varying frequency transform as a preliminary research of running monitoring. Due to the non-stationary characteristics, it is necessary to examine noise and vibration of the train with time-varying frequency transforms. In this paper, the short-time Fourier transform method is utilized - the stored data is localized by modulating with a window function, and Fourier transform is taken to each localized data. For the examination, the non-stationary noise and vibration of the high-speed train's wheelset are measured by using some microphones and accelerometers, and those signals are stored in a on-board data acquisition system. The non-stationary random signal analyses with the short-time Fourier transform are performed, and the result are classified as follows; auto-spectral density, cross-spectral density, frequency response, and coherence functions. From those functions, it is possible to observe the frequency characteristics of sleepers, switchers, tunnels, and steel bridges. Also, some distinct peaks, which are not dependent upon the train's speed, are identified from the results.

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A Review on the Vibration Exposure Limits in Korea

  • Park, Hee Sok
    • Journal of the Ergonomics Society of Korea
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    • v.34 no.3
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    • pp.217-222
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    • 2015
  • Objective:The objective of this study is to review the exposure limits in the legislation, guidelines, and standards for human vibration in Korea. Background: There have been relatively less interests in vibration than other risk factors in Korea. However, the importance of vibration is increasing as industry and everyday life are more mechanized. Method: Various enforcements were examined including legislation, guidelines, and standards for whole-body vibration and localized vibration. Results: No exposure limits were found in legislation, guidelines, and standards for the human vibration in Korea. Conclusion: It is important to introduce new duties regarding vibration risks to the general duties. Further studies are expected on the vibration exposure limits appropriate for Korean people and job conditions. Application: The results from this study would be of help to induce more interests in human vibration to the occupational health and safety professionals of Korea.

Development of Ultrasonic Bonding Process for Micro Components (미세 부품의 초음파 접합공정 개발)

  • 김정호;이지혜;유중돈;최두선
    • Transactions of Materials Processing
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    • v.11 no.7
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    • pp.596-600
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    • 2002
  • The ultrasonic bonding method and its feasibility are investigated in this work for joining the micro components and MEMS packaging. The ultrasonic bonding process is analyzed using a lumped mode, and preliminary experiments using the eutectic solder and copper pin were carried out to verify possibility to MEMS packaging. The ultrasonic bonding process appears to be adequate for MEMS packaging by providing localized heating at the selected area. Microscopic behavior of the bond joint through ultrasonic vibration needs further investigation.