OBJECTIVES Acoustic stimulation synchronized to slow waves (SWs) can enhance these sleep features and facilitate memory consolidation during nocturnal sleep. Here, we investigated whether a similar benefit could be accrued following stimulation during an afternoon nap. We also evaluated the event-related dynamics of associated EEG spectral changes and their correlation with memory performance. ...

We optically generated and observed GHz ultrasonic waves on liquid surfaces and a liquid/liquid interface for the first time using the transient reflecting grating ~TRG! method. Four kinds of samples were used for measurement of the surfaces; two types of black ink, an aqueous solution of crystal violet ~CV aq solution! and ethanol aqueous solutions of CV. A cyclohexane/CV aq solution interface...

The propagation of Lamb waves in elastic plates is analyzed both numerically and experimentally. A Scanning Laser Doppler Vibrometer (SLDV) is here used to detect and visualize transient waveforms propagating in an elastic plate at low ultrasonic frequencies. The waves are excited by a piezoelectric crystal glued to the plate surface and actuated by sinusoidal pulses of varying frequency. The p...

Ultrasonic motors, as one kind of actuators, have attracted a lot of attention since it was proposed more than 20 years ago. In such kind of motors, the sliders (for linear motors) or the rotors (for rotary motors) are driven by the frictional forces between the sliders (rotors) and the stators when ultrasonic waves are propagating on the stators. Since then, the ultrasonic motors have been dev...

Lamb waves are often used in ultrasonic applications for non-destructive testing of large constructions. The difficulty in the analysis of Lamb waves is their dispersive characteristics, especially their frequency dependent phase and group velocities. This article focuses on the separation of the first symmetric mode S0 and the first asymmetric mode A0 and the reliable estimation of their group...

time-of-flight diffraction method (tofd) is an amplitude-independent sizing method which is based on the measurement of time-of-flight of defect tip diffracted waves. although tofd can measure through-wall length of defect accurately, this method is not capable of measuring horizontal defect size. in this paper, a new tofd method for evaluating horizontal planar defects is presented. the finite...

A series of materials used for oil absorption based on cellulose fiber grafted with butyl acrylate (BuAc) have been prepared by radical polymerization under ultrasonic waves processing. Effects of ultrasonic dose for the maximum graft yield were considered. The dependency of optimum conditions for oil absorption rate on parameters such as ultrasonic processing time and ultrasonic power were als...

onventional ultrasonic techniques have long been recognized for their usefulness in the nondestructive testing of materials and structures. These techniques, based on launching ultrasonic or high-frequency acoustic waves into a material using a coupled transducer, enable the probing of certain material properties. By inducing surface or bulk waves into a material, several material properties, s...

In the non-destructive determination of material properties, the utilization of ultrasound has proven to be a viable tool. In the presented paper, a laser is used to create broadband acoustic waves in plate-shaped specimens by applying the photoacoustic effect. The waves are detected using a purpose-built ultrasonic transducer that is based on piezoceramics instead of the commonly used piezoele...