A flat transducer was constructed, using a 9-microm-thick PVDF (polyvinylidene fluoride) film for generation and detection of high-frequency ultrasonic waves, and used for measurements of the phase velocity of longitudinal waves traveling along the thickness direction in a very thin material. The transducer has a useful wideband frequency characteristic extending from 10 MHz to over 150 MHz. Me...

Time dependence of multiply scattered diffuse ultrasound in polycrystalline media" (1995). Time domain results are presented for the multiply scattered longitudinal intensity backscattered from a polycrystalline medium. The results are solutions to the ultrasonic radiative transfer equation (URTE), the derivation of which is based upon radiative transfer theory. Unlike steady-state solutions ob...

Non-contact ultrasonic, enables rapid testing of structures using ultrasonic tests that are not possible via conventional contact transducers. This paper reports on laser ultrasonic and air/gas coupled ultrasonic measurements that are performed remotely, do not require direct access to test area, do not need traditional ultrasonic coupling and do not have traditional C-scan fixture requirements...

in biological wastewater treatment large quantities of sludge are produced. this sludge is highly putrescible.for disposal and safe usage should be stabilized. the anaerobic digestion is a standard technique for stabilization. due to the rate imiting step of sludge hydrolysis, anaerobic degradation is a slow process with high digestion time. due to high retention time and sludge dewatering prob...

This paper is focused on the problem of mode identification of Lamb waves in ultrasonic testing, and the principle and process of two time-frequency transform method, smooth pseudo Wigner–Ville distribution and two-dimensional Fourier transform, were discussed. The experimental work were carried out in aluminium plates, and the single and multimode Lamb waves were excited by 5MHz oblique incide...

ultrasonic testing (ut), a nondestructive testing (ndt) method, is under development for quality determination of agricultural products, although it has long been used in the food industry. determination and measurement of product quality are important in modern agricultural research. noninvasive/nondestructive quality determination is a novel aspect of the postharvest process in which paramete...

Absorption of ultrasonic longitudinal waves in the nematic liquid crystal 1-(trans4-hexylcyclohexyl)-4-isothiocyanatobenzene (6CHBT) was measured in the temperature (24-56oC) and frequency (3.2-100 MHz) ranges. In the region of the phase transition the anomalous absorption has been observed. This absorption rapidly increases when the frequency of the ultrasonic wave decreases. The experimental ...

Ultrasonic wave propagation in prestressed materials has been studied extensively in the last 40 years. Most of this work was concentrated on the effect of stress on the velocities of different types of ultrasonic waves in homogeneaus materials. Actually stresses affect not only wave velocities but also the boundary conditions at the interface. Many practical applications of ultrasonic stress c...

This paper presents a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic nondestructive evaluation techniques. These SHG techniques exploit the material nonlinearity of metals in order to measure the acoustic nonlinearity parameter,β. In these measurements, a second harmonic wave is generated from a propagati...