Sparse spiral phased arrays are advantageous for many emerging air-coupled ultrasonic
applications, since grating lobes are prevented without being constrained to the half …

This article compares different air-coupled ultrasonic testing methods to characterize impact-
type defects in a pultruded quasi-isotropic glass fiber-reinforced plastic (GFRP) composite …

Recent quantum leap in far-field laser techniques has advanced noncontact implementation
of nondestructive ultrasonic imaging, in pursuit of enhanced accessibility, detectability and …

Laser Doppler vibrometry has found application both in nondestructive testing (NDT) of
polymer composite materials (PCMs) and in studies of the amplitude-frequency …

Subwavelength ultrasonic imaging (SUI) can detect subwavelength flaws beyond the
diffraction limit, however, SUI sometimes fails to clearly reveal flaws in C-scans when the …

Air-coupled ultrasound was used for assessing natural defects in wood boards by through-
transmission scanning measurements. Gas matrix piezoelectric (GMP) and ferroelectret (FE) …

This paper reports on investigations of the air-coupled ultrasonic (ACU) method to detect
common defects in solid timber panels made of Chinese fir (Cunninghamia lanceolata …

One of the weaknesses of nonlinear methods is the excitation power required to generate
nonlinear effects such as higher order harmonics (single frequency) and sidebands (dual …

An air parametric array can generate a highly directional beam of audible sound in air,
which has a wide range of applications in targeted audio delivery. Capacitive …

The spatial distribution of a transduction efficiency over the air-coupled probe surface was
proposed as a convenient tool for the probe integrity inspection. In this research, a parabolic …