• 소음진동
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• 제8권1호
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• pp.75-80
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• 1998

It is a well known fact that the shaker used in the vibration test interacts with the test structure and thus influences the test results. A two degree of freedom model of shaker is suggested and the vibration parameters of this model is experimentally extracted. According to this experimental results, the vibration parameters of the shaker can vary with respect to the test structure as well as the stinger used in the connecting mechanism. It is also found that the vibration parameters of the shaker provided by the manufacturer can not be accurate and these parameter values should be revaluated based on the test environments.

• 한국정밀공학회지
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• 제18권1호
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• pp.147-153
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• 2001

This paper proposes a shaker system design for acceleration test of gimbal. Main reason of shaker system design is to give acceleration to the gimbal, which is moving and tracking the target on the tracking test equipment. The shaker system is mounted on the tracking test equipment. It uses the scotch yoke mechanism to have the constant movement in return. The Scotch yoke mechanism changes the rotational movement of constant velocity to simple harmonic motion.

• Advances in aircraft and spacecraft science
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• 제7권1호
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• pp.79-90
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• 2020

The dynamic coupling between shaker and test-article has been investigated by recent research through the so called Virtual Shaker Testing (VST) approach. Basically a VST model includes the mathematical models of the test-item, of the shaker body, of the seismic mass and the facility vibration control algorithm. The subsequent coupled dynamic simulation even if more complex than the classical hard-mounted sine test-prediction, is a closer representation of the reality and is expected to be more accurate. One of the most remarkable benefits of VST is the accurate quantification of the frequency down-shift (with respect to the hard-mounted value), typically affecting the first lateral resonance of heavy test-items, like medium or large size Spacecraft (S/Cs), once mounted on the shaker. In this work, starting from previous successful VST experiences, the parameters having impact on the frequency shift are identified and discussed one by one. A simplified analytical system is thus defined to propose an efficient and effective way of calculating the lower bound frequency shift through a simple equation. Such equation can be useful to correct the S/C lateral natural frequency measured during the test, in order to remove the contribution attributable to the shaker in use. The so-corrected frequency value becomes relevant when verifying the compliance of the S/C w.r.t. the frequency requirement from the Launcher Authority. Moreover, it allows to perform a consistent post-test correlation of the first lateral natural frequency of S/C FE model.

• 대한물리의학회지
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• 제14권1호
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• pp.111-119
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• 2019

PURPOSE: The aim of this study was to determine how biofeedback training with Shaker exercise effects the activation of the cervical myocardial muscle in stroke with swallowing disorder. METHODS: From June 2018 to September 2018, 30 patients who were hospitalized at C hospital and K hospital in Daegu, and K hospital in Gumi were surveyed to meet the criteria for selection. The participants were classified into three groups, and Shaker exercise was applied three times a day, five times a week, for four weeks; visuoauditory biofeedback group (VABG), visual biofeedback group (VBG), and self-exercises group (SG). In addition, the suprahyoid muscle activity was performed three times (before intervention, after intervention, and after two weeks). RESULTS: The pre and post-test comparisons, revealed a significant difference between the three groups (p<.01); VABG had the highest suprahyoid muscle activity. The post-test and follow-up test produced similar results in, the three groups (p>.05). The mean comparison showed the smallest difference in VABG, indicating that muscle persistence was the best. CONCLUSION: Shaker exercise has an effect on suprahyoid muscle activation. Biofeedback training, which provides an input of multi-sensory information in swallowing disorder treatment is recommended because it has the greatest effect when combined with visuoauditory biofeedback.

• 재활복지
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• 제20권3호
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• pp.179-193
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• 2016

저항성 고개 숙이기 운동과 shaker 운동은 목뿔위근의 강화를 사용되는 중재법이다. 이전의 연구들에서는 삼킴 장애가 있는 환자들 대상으로 두 운동을 비교하지 않았다. 본 연구는 삼킴장애를 가진 뇌졸중 노인 환자에게 저항성 고개 숙이기 운동과 shaker 운동이 목뿔위근, 목빗근에 미치는 효과를 알아보고자 하였다. 10명의 삼킴 장애가 있는 뇌졸중 노인 환자가 자발적으로 연구에 참가하였다. 모든 대상자들은 저항성 고개 숙이기 운동(등척성, 등속성), shaker 운동(등척성, 등속성)을 순서대로 수행하였으며, 10회 반복하였다. 저항성 고개 숙이기를 수행한 후, 대상자들은 근피로를 최소화하기 위하여 5분간 휴식을 하였다. 두 운동 동안 목뿔위근과 목빗근의 활성을 표면 근전도를 이용하여 분석하였다. 윌콕슨 부호 순위 검정은 그룹 내 저항성 고개 숙이기와 shaker 운동에서 근활성에 대한 차이를 평가하기 위하여 사용하였다. 저항성 고개 숙이기 운동과 shaker 운동은 목뿔위근에서 유의한 차이를 보이지 않았다(p>.05). 저항성 고개 숙이기 운동은 shaker 운동보다 목빗근에서 유의하게 낮은 활성을 보였다(p<.05). 삼킴 장애가 있는 뇌졸중 노인환자에게 저항성 고개 숙이기 운동이 shaker 운동보다 삼킴 기능 향상을 위한 더 효과적인 치료방법으로 사용될 수 있을 것이다.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.165-175
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• 2018

Jet Propulsion Laboratory has traditionally performed system level vibration testing of flight spacecraft. There have been many discussions in the aerospace community for more than a decade about spacecraft vibration testing benefits or lack thereof. The benefits and potential issues of fully assembled flight spacecraft vibration testing are discussed herein. The following specific topics are discussed: spacecraft screening test to uncover workmanship problems for launch dynamics environments, force- and moment-limited vibration testing, potential issues with structural frequency identification using base shake test data, and failures related to vibration shaker testing and ways to prevent them.

• 반도체디스플레이기술학회지
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• 제14권1호
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• pp.31-37
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• 2015

This paper is on the design and manufacturing of vibration tester (shaker) for experiments about effects on the performance of semiconductor chips and Li-ion batteries by vibration. Shaker in the market are quite expensive, it is difficult for basic researchers to contact. In this study, in order to improve this, we designed and manufactured with an entry-level into mass production possible approaches in terms of performance required to a minimum. The shaker system is operated by Matlab and LabView. The target performances are 200Hz frequency and 5% error, and these were satisfied.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1732-1738
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• 2003

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the under-test, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.

• 한국지진공학회논문집
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• 제11권2호
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• pp.27-38
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• 2007

노스리지 지진에 의해 손상을 받은4층 철근콘크리트조 골조건물을 대상으로 선형가진기 및 대용량의 편심가진기를 이용한 강제진동실험과 상시미진동 측정을 실시하였다. 미진동 가속도데이터 및 선형가진기에 의한 백색잡음 실험시의 가속도데이터로부터 구조물식별을 수행하여 7차모드까지의 고유진동수 및 모드감쇠비를 얻었다. 두대의 대용량 편심가진기를 사용하여 얻은 큰 진폭의 조화 진동하에서는 가속도데이터를 사용하여 각 방향 1차모드를 식별하였으며 변위계와 변형게이지를 이용하여 층간변위각, 기둥과 슬래브와 같은 구조부재의 곡률분포를 측정하였다. 각 경우 고유진동수는 진동의 크기가 클수록 낮아졌다. 즉, 편심가진기가력시 고유진동수는 상시미진동시에 비해 $70{\sim}75%$, 선형가진시가력시에 비해 $92{\sim}93%$ 정도로 낮게 나타났다. 이러한 진동수의 감소폭은 지진에 의해 큰 손상을 받았던 건물의 남북방향에서 크게 나타났다.

• 한국추진공학회지
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• 제2권2호
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• pp.88-98
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• 1998

충격반응 스펙트럼 시험을 수행하기 위한 가진기의 파형이 웨이브레트들을 이온하여 시험규격에서 규정한 충격반응 스펙트럼을 만족하도록 합성된다. 웨이브레트의 매개변수는 중간주파수, 진폭, 반파의 개수, 지연시간 그리고 극성이다. 시험규격에서 규정한 충격반응 스펙트럼과 정합이 되도록 각 웨이브레트의 진폭은 반복하여 조절된다. 이렇게 합성된 파형은 가진기를 이용한 충격반응 스펙트럼 시험의 참조 가속도 파형으로 간주된다. 본 연구에서는 충격 지속시간을 길게 하여 첨두치가 작은 파형을 제안한다. 몇 가지 사례를 통하여 이 방법의 유용성이 확인되었다.