• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.2
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• pp.1-12
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• 1971

This paper describes, firstly, on analytical method of computing the eigenvalues of vertical vibration of ships, taking into account for the distribution of hull weight including added mass and the effect of shear deflection and rotary inertia. The frequency equation is solved by Galerkins method into form of numerical integration. Applying the above described equation, model experiment of vertical vibration was carried out in order to varify the validity of the analytical method of vertical vibration. The model, which was made of acrylite plate, was ship-shaped wall-sided vessel with bulkheads, deck openings, and fore and after peak tank at both ends. The results of experiments carried out both in air and on water showed that the observed natural frequencies and the observed patterns of natural modes of vibration were in good agreement with analytically calculated values for 2,3, and 4-node vibration.

• Journal of the Korean Society of Physical Medicine
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• v.4 no.1
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• pp.49-56
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• 2009

Purpose : The Purpose of this study was to investigate the effects of image training and vibration on performance of vertical jumping. Methods : Subjects was classified into two groups, which were image training group(n=20) and vibration application group(n=20). The standard methods of each intervention were image training with listening recorded indication for 5 minute and vibration with speed of $1200{\pm}200\;rpm$. Muscle strength was measured using vertical jump performance. Results : The vertical jump performance was significantly increased after image training and vibration application(p<.05), however, it was more significantly after image training(p<.05). Conclusion : This study showed that image training and vibration application were effective treatment strategy on increase of muscle strength. Therefore, it could be considered as a treatment method in the patients with musculoskeletal disease including fracture, chronic degenerative disease and disuse atrophy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.779-781
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• 2005

In this paper, Firstly, it is shown that the bending mode vibration source of vertical pump system is comparatively large because resonance. Secondly in order to reduce the bending mode vibration of vertical pump, The improvement of some boundary condition have been developed and its effectiveness is investigated as appling it at the vertical pump system pratically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.510-513
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• 2001

Several kinds of vibration problems have been frequently encountered in industrial vertical pumps in spite of their widespread use for long time. In fact, vibration problems of the vertical pumps are so complicated and difficult with compared to those of the horizontally mounted pumps that more careful attention should be taken for solving the vibration problems. This paper introduces a case study experienced from troubleshooting for excessive vibration occurred in a vertical-type condensate pump for combined cycle power plants. Subsynchronous whirl vibration was caused by the instability of the guide bearing whose lubricant is water. A newly modified guide bearing has solved the vibration problem, which should be the best countermeasure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.897-904
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• 2011

When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/$s^2$ r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.108-113
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• 2007

This study aims to find equivalent comfort contours, reciprocal of frequency weighting curves, for vertical steering wheel vibration. Psychophysical responses were measured from twelve male subjects by using magnitude estimation of relative discomfort due to vertical steering wheel vibrations of magnitude of 0.1 to 1.58 $m/s^2$ in the frequency range of 4 to 250 Hz. Relative discomfort were estimated with a reference vibration of 0.4 $m/s^2$ at 31.5 Hz. Equivalent comfort contours were produced from the median of sensation magnitudes judged by twelve subjects, which showed variation in the shapes with increase of vibration magnitude. A shape of the contour came close to the perception threshold curve with decrease of vibration magnitude. When the vibration magnitude increases, the shape changed close to those in the references of Hong and et al (2003). It is also recommended frequency weighting curves for vertical steering wheel vibration must be expressed as a function of vibration magnitude as well as frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.656-660
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• 2009

Various dynamic models of seated posture human body have been developed because the importance about the ride comfort assessment of vehicles is highly emphasized from day to day. The dynamic models of human body make possible the simulation of ride comfort assessment by applied to the vehicle dynamic model. Recently, the importance of ride comfort is also regarded to working vehicles such as excavators and the research of the ride comfort assessment for working vehicle is required. Only vertical vibration dominantly occurs on the seat of the private car driving with constant velocity. In contrast, vertical/fore-and-aft/pitch vibration seriously occurs on the seat of the working excavator. So, the dynamic models of seated human body applied to working vehicles should describe the dynamic characteristics for vertical/fore-and-aft/pitch direction. In this paper, the dynamic characteristics of seated human body are represented as apparent inertia matrix. The apparent inertia matrix is obtained by the vertical/fore-and-aft/pitch excitation of seated human body. 6 resonance frequencies are observed in apparent inertia matrix. This result can be applied to develop the dynamic model for seated posture human body.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.51-58
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• 2017

The characteristics and effectiveness of double tuned mass dampers (DTMD) have been studied by many researchers. DTMD usually consists of one larger mass block and one smaller mass block. In this study, DTMD was proposed to reduce the vibration of vertical pumps in industrial plants. In order to assess the efficiency of the proposed method, numerical analysis for the simplified vertical pump model with single and double TMDs was carried out. It was also investigated that the effects of optimal TMD parameters such as frequency ratio and damping ratio on dynamic responses of the main structure. According to analysis results, DTMD are more effective to control the vibration of the vertical pump and show good robustness to the change in the stiffness of TMD.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.274-278
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• 2012

Vertical pumps are structurally weak in terms of vibration because of installed heavy motor on top of the pumps in form of cantilever. So high vibration on top of the pumps can occur with low vibration in the bottom. These vibration problems experienced very frequently. Majority of studies have been related to the unbalance of rotating parts or structural resonance. In this paper, we introduce an unusual case, vibration variation caused by VPF(Vane Passing Frequency) according to water level.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.120-127
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• 1994

Noise and vibration induced by subway operation are one of the major factor which annoy residents living near railway tracks. While lateral vibration is a major factor in analyzing seismic effect of the structure, vertical vibration became a major concern in considering the subway induced vibration because relatively smaller energy affects only nearby areas than that of earthquake. A characteristics of structural response induced by subway operation has been studied with different total height of the building and different number of spans. Also the frame with different span length has been studied. As the numbers of degrees freedom increase the higher mode effect on vertical vibration increases. Accordingly, the total affecting vertical modes are distributive as the numbers of degrees of freedom increase. Though the total degree of freedom increases, only some of the dominant modes actively affects to the vertical response of the structure. A frame with the number of equal spans could be analyzed by replacing the whole frame as one when we want to predict the response of the vertical vibration. Also it has been found that the seperate frame analysis will give little different result when adjacent span is relatively longer than others.