• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.836-841
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• 2002

The nonlinear vibration of moving viscoelastic belts excited by the eccentricity of pulleys is investigated through experimental and analytical methods. Laboratory measurements demonstrate the nonlinearities in the responses of the belt, particularly in the resonance region and with the variation of tension. The measurements of the belt motion were made using a noncontact laser sensor Jump and hysteresis phenomenon are observed experimentally and are studied with a model which considers the nonlinear relation of belt stretch. An ordinary differential equation is derived as a working form of the belt equation of motion. Numerical results show good agreements with the experimental observations, which demonstrates the nonlinearity of viscoelastic moving belts

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1922-1927
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• 2003

Nonlinear normal mode (NNM) vibration, in a nonlinear dual mass Hamiltonian system, which has 6$\^$th/ order homogeneous polynomial as a nonlinear term, is studied in this paper. The existence, bifurcation, and the orbital stability of periodic motions are to be studied in the phase space. In order to find the analytic expression of the invariant curves in the Poincare Map, which is a mapping of a phase trajectory onto 2 dimensional surface in 4 dimensional phase space, Whittaker's Adelphic Integral, instead of the direct integration of the equations of motion or the Birkhoff-Gustavson (B-G) canonical transformation, is derived for small value of energy. It is revealed that the integral of motion by Adelphic Integral is essentially consistent with the one obtained from the B-G transformation method. The resulting expression of the invariant curves can be used for analyzing the behavior of NNM vibration in the Poincare Map.

• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.170-175
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• 1988

A study on the dynamic vibration absorber with coil spring and oil damper was carried out both theoretically and experimentally. A main mass is attached to a foundation using coil spring and oil damper. A harmonic motion was applied to the foundation. The effects of the dynamic vibration sbsorber are theoretically summarized in graphs, and tested on a vibratory model for the isolation of actual mechanical vibration. As a result, the first resonance amplitude ratio increased and the second resonance amplitude ratio decreased as the absorber spring constant increased. When the absorber mass increase, the first resonance amplitude ratio is decreased and the second resonace amplitude ratio is increased.

• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.347-362
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• 2022

Current vibration serviceability assessment criteria for wind-induced vibrations in tall buildings are based largely on human 'perception' thresholds which are shown not to be directly translatable to human 'acceptability' of vibrations. There is also a considerable debate about both the metrics and criteria for vibration acceptability, such as frequency of occurrence or peak vs mean vibration, and how these might vary with the nature of the vibration. Furthermore, the design criteria are necessarily simplified for ease of application so cannot account for a range of environmental, situational and human factors that may enhance or diminish the impact of vibrations on serviceability. The dual-site VSimulators facility was created specifically to provide an experimental platform to address gaps in understanding of human response to building vibration. This paper considers how VSimulators can be used to inform general design guidance and support design of specific buildings for habitability, in terms of vibration, which allow engineers and clients to make informed decisions with regard to sustainable design, in terms of energy and financial cost. This paper first provides a brief overview of current vibration serviceability assessment guidelines, and the current understanding and limitations of occupants' acceptability of wind-induced motion in tall buildings. It then describes how the dual-site VSimulators facility at the Universities of Bath and Exeter can be used to assess the effects of motion and environment on human comfort, wellbeing and productivity with examples of how the facility capabilities have been used to provide new, human experience based experimental research approaches.

• Journal of KSNVE
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• v.4 no.1
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• pp.83-88
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• 1994

In many circumstances, it is desired to move a mass from one position to another without inducing and vibration in the mass being moved. Two such problems are considered here : the motion of a mass initiated by another mass, nd the motion of a pendulum initiated by the specified motion of its support. In each case, it is dosired that the system start at rest and come to rest in the second position. A simple strategy for the specified motion is given here. The method is motivated by engine cam-follower design. The force required to move the system in question is determined as well as the maximum value of the force required(and the times at which these forces take place).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.778-783
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• 2003

The problem considered in this paper is about the collocation of sensor and actuator for the active control of sound and vibration. It is well-known that a point collocated sensor-actuator pair offers an unconditional stability with very high performance when it is used with a direct velocity feedback (DVFB) control, because the pair has strictly positive real (SPR) property. In order to utilize this SPR characteristics, a matched piezoelectric sensor and actuator pair is considered, but this pair suffers from the in-plane motion coupling problem with the out-of$.$plane motion due to the piezo sensor and actuator interaction. This coupling phnomenon limits the stability and performance of the matched pair with DVFB control. As a new alternative, a point sensor and piezoelectric actuator pair is also considered, which provides SPR property in all frequency range except at the first resonance in very low frequency. This non-SPR resonance could be minimized by applying a phase lag compensator.

• Journal of International Academy of Physical Therapy Research
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• v.12 no.1
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• pp.2272-2278
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• 2021

Background: Vibration stimulation has emerged as a treatment tool to help reduce spasticity during physical therapy. Spasticity includes problems of reduced range of motion (ROM) and stiffness. However, the benefits of vibration rolling (VR) on interventions for stroke patients are unclear. Objectives: This study aimed to investigate the effect of VR intervention on the ankle ROM and ankle stiffness in stroke patients. Design: A randomized crossover study. Methods: Seven stroke patients completed two test sessions (one VR and one non-VR [NVR]) in a randomized order, with 48 hours of rest between each session. Participants completed intervention and its measurements on the same day. The measurements included ankle dorsiflexion and plantarflexion ROM and stiffness of ankle muscles, including the tibialis anterior, medial, and lateral gastrocnemius muscle. Results: After VR, ankle dorsiflexion ROM, lateral gastrocnemius stiffness, and medial gastrocnemius stiffness improved significantly (all P<.05). After NVR, only the lateral gastrocnemius stiffness improved significantly (P<.05). Furthermore, in the cases of changed values for ankle dorsiflexion ROM and lateral gastrocnemius stiffness were compared within groups, VR showed a more significant difference than NVR (P<.05) Conclusion: VR improved ankle ROM and muscle stiffness. Therefore, we suggest that practitioners need to consider VR as an intervention to improve dorsiflexion ROM and gastrocnemius stiffness in stroke patients.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.476-483
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• 2009

A linear compressor used in a refrigerator has higher energy efficiency than a reciprocating compressor, but its vibration level is still severe than others. The vibration level of linear compressor at the frequency of 60Hz is dominant since it is the exciting frequency of a motor. In this paper, a simulation tool to predict the shell vibration of the linear compressor was developed. The shell and body parts in a compressor were assumed to be 3-dimensional rigid body having both translational and rotational motion, while the reciprocating piston part has only 1-dimensional translational motion. The flexible loop-pipe was modeled by in-house code of finite element method. To verify the developed tool, five cases of different loop-pipe shapes were examined experimentally. The results by the developed tool showed good agreements with those by experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.10-16
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• 2004

There are a lot of roots of errors in a motion of the optical pick-up actuator being one of the most significantcomponents in a CD-ROM drive. Most of the studios recently performed have a tendency to seek for the causes from an actuator itself. This paper presents dynamic characteristics of an actuator affected by the motion of a feeding deck. The feeding system is modeled as a rigid body with eight degree-of-freedom. Using Largrange's equation, we derive linear equations of motion with respect to the rectangular coordinate. We found that the ranges of the natural frequencies of a feeding deck and the actuator are close to each other. The time responses are also computed by the Newmark method and Runge-Kutta method. The result show that it is important effect to consider feeding deck in modeling and designing an optical pick-up.