Amplitude

This study is both a qualitative and a quantitative approach of the nonlinear vibrations of the mechanical elastic systems with polynomial damping. It gives the physical and mathematical modelling and numerical simulation of the dynamics of one degree of freedom mechanical systems and shows the diagrams of the curves of different characteristics (amplitude, displacement, power) function of the polynomial coefficients of damping. It also shows the variation of the same characteristics function of the frequency of the harmonic force of excitation. The numerical simulation has done with the data of real technological equipment: an industrial conveyor driven by inertial vibrator which has tested in site by the specialists of The Research Centre of Machines, Mechanic and Technological Equipments - MECMET.

Elastic full waveform inversion of seismic reflection data represents a data-driven form of analysis leading to quantification of sub-surface parameters in depth. In previous studies attention has been given to P-wave data recorded in the marine environment, using either acoustic or elastic inversion schemes. In this paper we exploit both P-waves and mode-converted S-waves in the marine environment in the inversion for both P- and S-wave velocities by using wide-angle, multi-component, ocean-bottom cable seismic data. An elastic waveform inversion scheme operating in the time domain was used, allowing accurate modelling of the full wavefield, including the elastic amplitude variation with offset response of reflected arrivals and mode-converted events. A series of one- and two-dimensional synthetic examples are presented, demonstrating the ability to invert for and thereby to quantify both P- and S-wave velocities for different velocity models. In particular, for more realistic low velocity models, including a typically soft seabed, an effective strategy for inversion is proposed to exploit both P- and mode-converted PS-waves. Whilst P-wave events are exploited for inversion for P-wave velocity, examples show the contribution of both P- and PS-waves to the successful recovery of S-wave velocity.

Transmission/reflection coefficients measurement technique for determining materials complex permittivity at microwave (MW) frequencies with a modified inexpensive arrangement setup is examined in this paper. The general consideration is to use only the amplitudes of the transmission and reflection coefficients in presence of material sample to do permittivity determination. According to the analysis, the permittivity can be uniquely determined by measuring these two amplitudes when sample is prepared with large enough attenuation that multiple reflections between the two surfaces of the sample can be neglected. The validity of the method was proven by experiments, and numerical solutions of the measured data where achieved with the assistance of MathCAD™.

A new wavelet analysis methodology is proposed to estimate the statistics of steep waves. The method is applied to open ocean wave height data from the Southern Ocean Waves Experiment (1992) and from a field experiment conducted at Duck, North Carolina (1997). Results show that high wave slope crests appear over a wide range of wavenumbers, with a large amount being much shorter than the dominant wave. At low wave slope thresholds, all wave fields have roughly the same amount of wave crests regardless of wind forcing. The steep wave statistic decays exponentially with the square of the wave slope threshold, with a decay rate that is larger for the low wind cases than the high wind cases. Comparison of the steep wave statistic with independent measurements of the breaking wave statistic suggests a breaking wave slope threshold of about 0.12. The steep wave statistic does not scale with the cube of the wind speed, suggesting that other factors besides the wind speed also affect its level. Comparison of the steep wave statistic to the saturation spectrum reveals a reasonable correlation at moderate wave slope thresholds.