The study of nonlinear elastic wave propagation has been of considerable interest for the last four decades. This, in part, is due to the fact that nonlinear parameters are, in general, more sensitive to structural defects than linear parameters. Although guided waves combine the sensitivity of nonlinear parameters with large inspection ranges there are very few studies of guided nonlinear elas...

The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower bou...

objectives: autism spectrum disorder (asd) is a group of neurodevelopment syndromes with impairments in social communications and restrictive or repetitive behaviors. neurofeedback is a new method that may regulate neuro and metabolic function in brain. this study is semi-experimental, with pre and post test.  methods: in 26 children with asd, 40 sessions of neurofeedback were done. brain waves...

Consider a piezoelectric transducer that is attached to the back of a plate-like structure, such as is the case for guided wave structural health monitoring. This transducer may be excited to produce guided waves that propagate outward from the source through the structure. These waves interact with impedance discontinuities in the structure at defects, bond lines, plate boundaries, and other g...

In this study, response surface methodology (RSM) based on central composite design (CCD) was applied for investigation of the effects of ultrasonic waves, temperature and solvent concentration on viscosity reduction of residue fuel oil (RFO). Ultrasonic irradiation was employed at low frequency of 24 kHz and power of 280 W. The results showed that the combination of ultrasonic waves and solven...