Experiments were conducted to obtain the modal damping ratios of two hollow cylinders of different thicknesses of Aluminum. An electro dynamic exciter with slip table is used to excite the hollow cylinders. The hollow cylinder (unit under test) is fastened to the exciter. The exciter is placed in the horizontal direction and connected to the slip table. A control accelerometer is placed at the ...

This paper compares the performances of a vibrationpowered electrical generators using PZT piezoelectric ceramic associated to two different power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented and implemented with a particular power conditioning circuit topology. Theoretical predictions and experimental results s...

The extraction of the response from field fluctuations excited by random sources has received considerable attention in a variety of different fields. I show application of this principle to the motion recorded in the Millikan library at the California Institute of Technology in Pasadena, California, after an earthquake. Deconvolution of the recorded motion at different floors unravels the buil...

The reliability of dynamic systems modeled by white noise excited, stochastic, ordinary di erential equations can be computed from deterministic backward Kolmogorov equations. This paper discusses and compares some numerical solution methods for boundary value problems involving backward Kolmogorov equations. The numerical examples concern single degree of freedom oscillators subjected to white...

Thepresent paper discusses active vibration control of a cantilever beam subjected to random base excitation. The smart materials used are piezoelectric patches for both as sensor and actuator, and actuation based on the surface strains. Finite element model of the smart beam is obtained using Euler-Bernoulli formulation. Positive Position Feedback (PPF) controller is proposed for active dampin...

We have developed, manufactured and tested a unimorph deformable mirror for space applications based on piezoelectric actuation. The mirror was designed for the correction of low-order Zernike modes with a stroke of several tens of micrometers over a clear aperture of 50 mm. It was successfully tested in thermal vacuum, underwent lifetime tests, and was exposed to random vibrations, sinusoidal ...

Alpine skiing, both recreational and competitive, is associated with high rates of injury. Numerous studies have shown that occupational exposure to whole-body vibrations is strongly related to lower back pain and some suggest that, in particular, vibrations of lower frequencies could lead to overuse injuries of the back in connection with alpine ski racing. However, it is not yet known which f...