Spherical projectile impact using compressed air for frequency response function measurements in vibration tests

Vibration Control Design for Nonlinear Systems using Frequency Response Function

A nonlinear frequency response based adaptive vibration controller is proposed for a class of nonlinear mechanical systems. In order to obtain the nonlinear Frequency Response Function (FRF), the convergence properties of the system are studied by using the convergence (contraction) theory. If the system under consideration is: 1) convergent, it directly enables to derive a nonlinear FRF for a ...

Impact of nonlinear friction on frequency response function measurements

This paper discusses the impact of nonlinear friction on frequency response function (FRF) measurements of mechanical systems with nonlinear friction. Having an idea of the level of nonlinear distortion is valuable information for robust linear control design: it allows to estimate the level of accuracy of a linear approximation of the system under consideration. The impact of nonlinear distort...

Analysis of windowing/leakage effects in frequency response function measurements

Performance of Air Foam Flooding under Low Frequency Vibration

Foam injection is widely applied in amounts of fields to drilling, production, and formation protection. Sometimes, the application result is disappointing, which is caused by the failure of bubble generation in foam flooding. Therefore, it is necessary to seek ways for improving the performance of foam injection. An increased disturbance to the stratum, like the vibration caused by a seismic o...

Pulmonary function tests in air conditioner users

Air-conditioners (AC) are devices/systems that are used indoors to cool air by reducing the humidity of the air following condensation of the water vapour. It is observed that hyperventilation of cold dry air causes bronchoconstriction in asthmatic patients. [1,2] Modern styles of living in urban areas are considered potentially responsible for the development of airway allergic diseases due to...