This paper explores theoretically the possibility of using caustics, formed in the ultrasonic field diffracted by defects, as an approach to the inverse scattering problem, The case of crack-like defects is considered in detail, using the geometrical theory of diffraction. The involute of the far field caustic reproduces the projection of the crack edge in the incident beam direction, for a pla...

The distorted Born iterative method (DBIM) is applied to solve electromagnetics and ultrasonics inverse scattering problems. First, we use the DBIM to process the data, which are the scattered fields from two-dimensional cylinders with arbitrary cross section. From this simulation, we confirmed that the first-order Born approximation can be applied to larger objects as long as the phase change ...

The diffraction of ultrasound by a circular disk and an aperture of the same size have been investigated as a demonstration of Babinet‟s principle in the Fresnel regime. The amplitude and the phase of diffracted ultrasonic waves have been measured and a graphical treatment of the results is performed. The results verify Babinet‟s principle. It is also found that the wave without the diffracting...

A very short introduction of the principles of light diffraction by ultrasonic waves is followed by a discussion of acousto-optic imaging (schlieren) techniques. This method is often useful to obtain qualitative results of various acoustic phenomena in ultrasonics, underwater sound, material characterization, transducer performance and other areas of acoustics. Examples from different fields of...

Three-dimensional laser-induced photoacoustic tomography, also referred to as optoacoustic tomography, is developed to image animal brain structures noninvasively with the skin and skull intact. This imaging modality combines the advantages of optical contrast and ultrasonic resolution. The distribution of optical absorption in a mouse brain is imaged successfully. The intrinsic optical contras...

A novel terbium-containing fluorescent material, [Tb(CH3COO)2(H2O)3]Cl (1), has been prepared by a facile approach, i.e. an ultrasonic synthesis. Compound 1 has been structurally characterized via single-crystal X-ray diffraction and it crystallizes in the space group P21/n of the monoclinic system with four formula units in a cell. Compound 1 features a novel one-dimensional (1-D) chain-like s...

The paper gives an outline of the non-destructive evaluation (NDE) methods currently being pursued at the Admiralty Marine Technology Establishment, Dunfermline, Scotland. The methods are being used to locate and characterise fatigue cracks in high yield strength welded steel structures. The techniques have been applied principally to large fatigue models (5' and 9' diameter) as part of a compr...

Orthogonal frequency division multiplexing (OFDM) modulation has been extensively used in both wired and wireless communication systems. The use of OFDM technology allows very high spectral efficiency data transmission without using complex equalizers to correct the effect of a frequency-selective channel. This work investigated OFDM methods in an airborne ultrasonic communication system, using...

We present experimental demonstrations of negative refraction and focusing of ultrasonic waves in twodimensional phononic crystals made of stainless steel rods assembled in a triangular lattice and immersed in a liquid. Negative refraction is achieved for the range of frequencies in the second band, where the directions of the wave vector and group velocity are antiparallel to each other due to...

Abstract Inconel 690 has been extensively used in steam generator tubing materials for pressurized water reactors. In order to improve the weld quality of 690, ultrasonic-assisted pulsed tungsten inert gas (TIG) welding is studied. this study, macrostructure, microstructure, and mechanical properties weldments welded by TIG with without ultrasonic assistance were investigated. The microstructur...