Since many rotor systems normally operate above their critical speeds, the problem of accelerating the machine through its critical speeds without excessive vibration draws increasing attention. This paper provides an analytical imbalance response of the Jeffcott rotor under constant acceleration. The response consists of three parts: transient vibration due to the initial condition of the roto...

Purpose. To examine the effects of two doses of low-frequency (12 Hz), low-magnitude (0.3 g), whole body vibration on markers of bone formation and resorption in postmenopausal women. Methods. Women were recruited and randomized into a sham vibration control group, one time per week vibration group (1×/week), or three times per week vibration group (3×/week). Vibration exposure consisted of 20 ...

This study presents a basic idea for the self·excitation mechanism of reed valves in refrigerant compressors used for air conditioners or refrigera· tors. The detailed experimental data on the phase lag of fluid pressure, which were obtained from a forced vibration test on a simple axisymmetrical model, namely a resonator, composed of the valve, the valve plate, the cylinder and the piston, wer...

According to the linear viscoelastic model, the population discrete elements under the vibration working condition of the seed tray of the seeder were assumed as rigid conditions to analyze the collision process. The dynamic characteristics among the population collision process for the vibration process of the seeder were analyzed by tracing the microcosmic motion of each seed. The following c...

PURPOSE The purpose of this study was to investigate the effect of whole body vibration in oxygen uptake during intense squatting exercise with an added weight and whole body vibration compared with the same exercise without vibration. METHODS Nine male sub- jects performed three trials of dynamic squatting with an additional load of 50% of their body weight during 3 min. One trial without vi...

The purpose of this study was to examine the acute effects of different vibration loads (frequency and amplitude) of whole-body vibration (WBV) on flexibility and explosive strength of lower limbs in springboard divers. Eighteen male and female divers, aged 19 ± 2 years, volunteered to perform 3 different WBV protocols in the present study. To assess the vibration effect, flexibility and explos...

Track induced self-excited vibration is commonly encountered in EMS (electromagnetic suspension) maglev systems, and a solution to this problem is important in enabling the commercial widespread implementation of maglev systems. Here, the coupled model of the steel track and the magnetic levitation system is developed, and its stability is investigated using the Nyquist criterion. The harmonic ...

In machining, due to the tool vibration the forces, temperatures and stresses vary during the cutting process, so as the residual stresses over the machined surface. This variation of the residual stress has never been measured and, therefore, imposes new experimental challenges. The objective of this work is to correlate the variation of the residual stresses along the cutting path with the fr...

Vibration is a manual technique used widely to assist with the removal of pulmonary secretions. Little is known about how vibration is applied or its effect on the respiratory system. The purpose of this study was to describe mechanical consequences of vibration on the chest wall of a normal subject and the effects of vibration on expiratory flow rates and volumes. The effects of vibration were...

[Purpose] The present study compared the muscle activity of the upper trapezius with those of the serratus anterior and the lower trapezius when slings, unstable surfaces, were laterally vibrated, to examine the effects of vibration during sling exercises on shoulder stabilization muscles. [Methods] The subjects performed push-up exercises on a sling and maintained isometric contraction in the ...