• Wind and Structures
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• 제9권1호
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• pp.1-22
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• 2006

The response characteristics and suppression of flow-induced vibrations of rectangular prisms with various width-to-depth ratios were experimentally investigated. The prisms were rigid and elastically mounted at both ends to enable constrained torsional vibrations only. The present study focused on torsional vibrations, one of the three types of flow-induced vibrations generated in a rectangular prism. First, the response characteristics of torsional vibrations generated in rectangular prisms were investigated by free-vibration tests. It was found that the response characteristics of torsional vibrations generated in rectangular prisms could be classified into six patterns depending on the width-to-depth ratio. Next, the response characteristics of torsional vibrations observed in the free-vibration tests were reproduced by forced-vibration tests, and the mechanisms by which the three types of flow-induced vibrations, low-speed torsional flutter, vortex excitation and high-speed torsional flutter, are generated in the rectangular prisms were elucidated on the basis of characteristics of fluid forces and visualized flow patterns. Experiments were also carried out to establish an effective method for suppressing flow-induced vibrations generated in the rectangular prisms, and it was found that low-speed torsional flutter and high-speed torsional flutter could be suppressed by placing a small normal plate upstream of the prism, which results in suppression of the alternating rolling-up of the shear layers separating from the leading edges of the prism. It was also found that vortex excitation could be suppressed by placing a splitter plate downstream of the prism, which results in suppression of the generation of wake vortices.

• International Journal of Computer Science & Network Security
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• 제22권8호
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• pp.362-370
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• 2022

The assessment of specific impacts on the environment is a preventive measure for environmental protection which is based on the definition and proposal of measures that can prevent harmful effects, reduce or eliminate them. In the physical sense, vibration is the oscillating motion of an object with the effect of internal or external forces applied to it. People who touch a vibrating surface or object will feel these vibrations. In general, there are two types of vibration exposure. The first are the vibrations of the hands and arms transmitted by the held parts of tools or machinery. The second are whole-body vibrations transmitted from a seat or surface to a motorized car. The risk of injury to workers exposed to vibration varies depending on the size, frequency, type, duration of exposure, and organ affected. The purpose of this paper is to review the measurements of vibrations in the Kosovo Energy Corporation in the mine Sibovc Southwest, where coal with a rotary excavator is exploited and the evaluation of vibrations for working conditions for workers working in that environment and improving working conditions for the measurement of vibrations we have used the device Minimate DS 078, the purpose of such environmental impact assessment is to collect data and predict the harmful impacts on the environment, namely the impact on water, air, soil, life and health of as well as identify and propose measures that could prevent, reduce or eliminate altogether.

• 구강회복응용과학지
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• 제32권1호
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• pp.38-46
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• 2016

목적: 단순악관절 진동군에서 좌/우 진동 중 유의한 진동의 감별법을 연구하는 것이다. 연구 재료 및 방법: 단순악관절 진동만을 갖고 있고 측두하악관절 질환의 제 증상이 없는 단순악관절 진동그룹 30명의 60개 관절에서 44쌍의 진동을 기록하였고 대상자의 인지와 검사자의 촉진, JVA 검사 결과를 비교하였다. JVA로 기록된 진동의 주파수 스펙트럼, 진동파형 시간차 위상변위 분석, 수치 분석을 통해 좌/우 진동 중 유의한 진동을 감별하였다. 결과: JVA 분석결과 양측성 진동은 한 건도 없었으며 유의한 편측 진동은 42개로 감별되었다. 시간차 위상변위를 보이는 것은 11쌍이었고 이 중 한 쌍을 제외한 모든 진동에서 전달된 측의 진동이 발생측 진동보다 진동 총에너지(total integral) 값은 더 작고 > 300 / < 300 ratio는 같거나 더 큰 특징을 보이는 것을 관찰하였다. 또한 진동 총에너지 값이 10 이하로 작고 시간차 위상변위를 보이지 않아 좌/우 감별의 근거가 모호한 나머지 진동 모두에서 진동 총에너지 값이 더 작은 쪽의 > 300 / < 300 ratio가 더 큼을 관찰하여 이를 좌/우 감별의 근거로 삼을 수 있었다. 결론: JVA로 좌/우 진동 중 유의한 진동을 감별하기 위해서는 주파수 스펙트럼, 시간차 위상변위 및 수치 분석 등이 모두 고려되어야 한다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.83-87
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• 2003

Experimental blast studies were carried out in a limestone quarry to study the effects of blasting on structures. To have an in-depth understanding of the possible relation between parameters like vibrations, frequency and scale distance and ten trial blast were conducted. 29 monitoring stations were located in such a pattern to give a true representation of blast induced vibrations for the entire mining in this area. The vibrations were monitored in the vicinity of structures surrounding the quarry in the direction towards the village, road, railway line, office building, etc. Scale distances were determined to identify the maximum charge permissible to cause damage to structures.

• Journal of Biosystems Engineering
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• 제33권3호
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• pp.151-156
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• 2008

This study was conducted to evaluate ride vibrations experienced by tractor operators during plowing, rotovating, and transporting operations in Korea. Field data of ride vibrations were taken at the operator-seat interface from 49 tractors and analyzed on the basis of ISO 2631-1 and EU Directive 2002/44. Of the measured ride vibrations 15.4% in the plowing and 12.5% in farm road transport exceeded the 8-hour fatigue decreased proficiency boundary in the fore and aft directions at frequencies from 1 to 5 Hz. 93.9% exceeded the 8-hour potential health risk of ISO 2631-1. The ride vibrations exceeding the 8-hour exposure limit were 38.5% in plowing, 31.6% in rotovating, 100% in farm road transport and 88.9% in concrete road transport. Although most tractor operators were not exposed to ride vibrations greater than the 8-hour exposure limit value (ELV) of EU Directive 2002/44, 7.7% of the operators in the plowing experienced greater vibrations than the ELV in the fore-aft direction. Farm road transport produced greater vibrations than any other operations. Concrete road transport, plowing and rotovating operations followed next. Limit criteria for ride vibration exposure differ depending upon the guidelines. Exposure limit of the health guidance caution zone of ISO 2631-1 is lowest among its kinds.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.458-463
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• 1998

The paper describes the methods and means of measurement and study of vibrations, stresses and shocks affecting electronic equipment during its use and in the testing stage as well as original units to determine shapes and frequencies of vibrations of functional boards. Particular attention has been given to the development of methods and means to protect sturctures against vibrations and shocks.

• 에너지공학
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• 제11권3호
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• pp.262-268
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• 한국소음진동공학회논문집
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• 제15권1호
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• pp.46-52
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of free-free beam. In general, the rigid-body motions and elastic vibrations are analyzed separately. However, the rigid-body motions cause vibrations and elastic vibrations also affect rigid-body motions in turn, which indicates that the rigid-body motions and elastic vibrations are coupled in nature. The resulting equations of motion are hybrid and nonlinear. We can discretize the equations of motion by means of admissible functions but still we have to cope with nonlinear equations. In this paper, we propose the use of perturbation method to the coupled equations of motion. The resulting equations consist of zero-order equations of motion which depict the rigid-body motions and first-order equations of motion which depict the perturbed rigid-body motions and elastic vibrations. Numerical results show the efficacy of the proposed method.

• Journal of Biosystems Engineering
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• 제26권3호
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• pp.237-244
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• 2001

This work was intended to investigate the effect of vibration transmission paths on the ride vibration of tractor during the rotavating and transporting operations by applying the vibration path analysis method. Accelerations at the cab mounts were measured during the rotavating and transporting operations. Ride vibrations at the sear were than calculated using the measured accelerations at the cab mounts, and the frequency response functions and inertances between the seat and cab mounts, which were derived experimentally by the impact hammer test in static condition. The human sensitivity to vibration frequency was also taken into consideration for the calculation of ride vibrations at the 1/3 octave center frequencies in the frequency domain. Vibrations transmitted through rear cab mounts affected more significantly the ride vibration of tractor. The peak accelerations at the seat occurred at the frequencies of the engine and crank speed, and the frequency induced by tire lugs on the road transportation. It was found that the rear cab mounts should be improved in order to reduce the ride vibrations more effectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.957-962
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• 2010

Foundation systems in urban sites are often necessary to be constructed with little vibrations and displacements to surroundings. In order to assess applicability of a new foundation system for urban sites based on soil-cement mixing technique, vibrations and displacements induced by soil-cement construction process is evaluated. Soil-cement columns were constructed to reinforce soft ground near an old masonry wall in an urban redevelopment site, and the vibrations and displacements of the old masonry wall during construction were measured. Results indicate that the vibrations and displacements induced by soil-cement construction were little and not critical to the stability of the masonry wall.