• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.515-518
• /
• 2006

A vibration test for a cylindrical rod inserted on the grid support structure was tested using the sine sweep excitation method with closed loop force control. The effect of the mounting location of a test rod on the vibration characteristics of a rod continuously supported by the full size($16{\times}16$) grid support was identified. An electromagnetic vibration shaker, non-contact displacement sensor and HP/VXI data acquisition device were used and TDAS software was also used as a data sampling and processing tools. The natural frequencies and mode shape of the test rod were consistent with the previous works of a rod vibration test with partial grids($3{\times}3,\;5{\times}5\;and\;7{\times}7$). The frequency characteristics of the rod according to the mounting location were shown clear discrepancies, but mode shapes were nearly same. As the test rod closes to the bottom clamping region of the spacer grid, peak vibration amplitudes of the rod become smaller.

• Ecology and Resilient Infrastructure
• /
• v.2 no.4
• /
• pp.337-344
• /
• 2015

The purpose of this study is to determine the effects of vibration on primary (e.g. plasma cortisol), secondary (e.g. plasma glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), $Na^+$, $K^+$ and $Cl^-$) and tertiary (e.g. mortality) stress responses in cultured catfish, Silurus asotus. For this purpose, three groups (one control group and two stress groups) were set up. The control group was exposed to vibration corresponding to 48 decibel (dB) volt (V) (produced using electric vibrators) for 15 minutes per hour every day, and the two stress groups were exposed to vibrations corresponding to 58 and 68 dB (V) (produced using the same electric vibrators), equally, for 15 minutes per hour every day. Blood was sampled at day 0 (before starting vibration stress tests), and at days 1, 3, 5, 7, 9 and 11 (after starting vibration stress tests). According to the results, the catfish physiologically showed ''typical'' stress responses when they were exposed to chronic vibration. This indicates that such chronic vibration caused substantial stress to catfish; especially, persistently elevated plasma AST and ALT levels observed caused adverse effects to them. In conclusion, chronic vibration could significantly affect hematological characteristics in catfish.

• Journal of Institute of Control, Robotics and Systems
• /
• v.6 no.8
• /
• pp.682-688
• /
• 2000

To improve the performance of a flexible robot arm one of the important things is the vibration displacement measurement of a flexible arm. Many types of sensors have been used to measure it, The most popular has been strain gauges which measures the deflection of the beam,. Photo sensors have also been for detecting beam displacement and accelerometers are often used to measure the beam vibration. But the vibration displacement can be obtained indirectly from these sensors. In this article a vision sensor is used as a displacement sensor to measure the vibration displacement of a flexible robot arm. Several schemes are proposed to reduce the image processing time and increase its accuracy. From the experimental results it is seen that the vision sensor can be an alternative sensor for measuring the vibration displacement and has a potential for on-line tip position control of flexible robot systems.

• Journal of the Korean Society of Physical Medicine
• /
• v.12 no.4
• /
• pp.61-71
• /
• 2017

PURPOSE: The purpose of the present study was to investigate the effects of whole body vibration exercise on balance, muscle strength and falls efficacy in the elderly. METHODS: In this blinded randomized allocation study, 27 elderly were assigned to a whole-body vibration exercise group (n=14), consisting of 25 min structured exercises for 2 days per week for 6 weeks and a control group (n=13) performing the same program without vibration. At baseline and after the 6-week intervention, balance was measured using the Korean version of the Berg balance scale (K-BBS), timed up and go (TUG) test and functional reach test (FRT). Muscle strength was determined using the 30-s chair stand test (CST). Fear of falling was assessed using the Korean version of falls efficacy scale (K-FES). Paired t-test and independent t-test were used for within and between group comparisons, respectively. RESULTS: After the intervention, the experimental group showed significantly higher changes in all the parameters (K-BBS score, TUG test, CST, K-FES score) (p<.05) compared with the control group. However, there was no significant change in all parameters in the control group (p>.05). CONCLUSION: The whole-body vibration exercise program may be helpful to improve balance, mobility, muscle performance and fear of falling in the elderly.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.3
• /
• pp.237-242
• /
• 2012

Spaceborne pulse tube-type cryogenic compressors are widely used for space applications. To guarantee cooling performance of the compressor, mission life time and micor-vibration stability, suitable thermal control of compressor is required. Micro-vibration of the compressor is the one of the sources to degrade the pointing performance of observation satellite. In the present work, on-orbit thermal design of compressor in order not to degrade the performance of micro-vibration isolation system keeping the thermal control performance has been proposed and investigated through thermo-mechanical analysis.

• Structural Engineering and Mechanics
• /
• v.82 no.5
• /
• pp.571-585
• /
• 2022

As a vital component of power grids, long-span transmission tower-line systems are vulnerable to wind load excitation due to their high flexibility and low structural damping. Therefore, it is essential to reduce wind-induced responses of tower-line coupling systems to ensure their safe and reliable operation. To this end, a shape memory alloy-bidirectional tuned mass damper (SMA-BTMD) is proposed in this study to reduce wind-induced vibrations of long-span transmission tower-line systems. A 1220 m Songhua River long-span transmission system is selected as the primary structure and modeled using ANSYS software. The vibration suppression performance of an optimized SMA-BTMD attached to the transmission tower is evaluated and compared with the effects of a conventional bidirectional tuned mass damper. Furthermore, the impacts of frequency ratios and SMA composition on the vibration reduction performance of the SMA-BTMD are evaluated. The results show that the SMA-BTMD provides superior vibration control of the long-span transmission tower-line system. In addition, changes in frequency ratios and SMA composition have a substantial impact on the vibration suppression effects of the SMA-BTMD. This research can provide a reference for the practical engineering application of the SMA-BTMD developed in this study.

• Nuclear Engineering and Technology
• /
• v.56 no.9
• /
• pp.3812-3825
• /
• 2024

The axial-flow-induced vibration of fuel rods in the nuclear power plant is closely related to nuclear safety. In this article, a numerical study is performed on vibration of two elastic cylinders arranged side-by-side in axial flow. Large eddy simulation is employed to predict the turbulent flow. The numerical method has been verified using the experimental root-mean-square vibration amplitude of a single cylinder. A wide range of inflow velocities u^*, incident turbulence intensity T_u and space ratio P/D have been examined, where D and P are the diameter and centre-to-centre distance of the cylinders, respectively. The results show that the vibration amplitudes increase with an increasing u^*, comparable to the case of a single cylinder in axial flow. However, the two cylinders could bend outwards during a relatively high u^* and low T_u. Although T_u significantly affects the amplitudes of the cylinders, it does not change the vibration frequency and the critical velocity at which buckling instability occurs. As the gap between the two cylinders is sufficiently small, the vibration amplitude enhances significantly due to the pronounced hydrodynamic interaction between the two elastic cylinders and surrounding fluid. The direction of buckling is no longer random but fixed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.10a
• /
• pp.864-865
• /
• 2009

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.449-450
• /
• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.356-357
• /
• 2010