Showing papers in "Ultrasonics in 2002"

TL;DR: In this paper, it was shown that the cross-correlation between diffuse signals in two transducers is very nearly equal to the direct response of one transducer to an impulse applied to the other.

TL;DR: A new class of nonlinear acoustic phenomena has been observed for acoustic wave interaction with simulated and realistic nonbonded contact interfaces (cracked defects) in solids.

TL;DR: It is shown that Coulomb's friction law provides a very good description of the observed phenomena if the kinematics of the system is taken into account and therefore the validity of Coulomb’s friction law even for ultrasonic conditions is shown.

TL;DR: Wave propagation in laminated plates with delaminations was calculated using the semi-analytical finite element method and deeper numerical analyses revealed the following phenomena on the fundamental Lamb modes at delamination regions of laminate plates.

TL;DR: Results showed that subsequent anaerobic digestion of the ultrasonically disrupted sludge could improve biogas production with reduced sludge quantity that is vital to the economic consideration of the wastewater treatment plants.

TL;DR: Numerical simulations of acoustic wave propagation through sonic crystals consisting of local resonators using the local interaction simulation approach (LISA) are performed and three strong attenuation bands are found at frequencies between 0.3 and 6.0 kHz, which do not depend on the periodicity of the crystal.

TL;DR: In the experiments, the first anti-symmetric mode A0 of Lamb waves in plates is excited selectively by means of a piezoelectric transducer, and the wave propagation is studied using Mindlin's theory of plates.

TL;DR: An equivalent-circuit transducer model, coupled with acoustic impedance transfer relationships is used to model cells with regards to both their electrical characteristics and the strength of the resonance produced under different conditions and it is shown that the model can predict the effects of such a layer.

TL;DR: Intravascular elastography appears to be a unique tool to determine local mechanical properties in atherosclerotic lesions to identify fibrous and fatty tissue and the feasibility of this technique to be applied in vivo is demonstrated.

TL;DR: It is shown that contrast is superior to tissue when using low frequencies and imaging the third or fourth harmonic of the transmitted frequency.

TL;DR: This research deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound (0.5-1 MHz), which corresponds to a thin near-to-surface layer with increased porosity and density of microcracks.

TL;DR: The main conclusion from a comparison of the results for the two imaging modes might be that when using THI improvement of TCR is obtained at the expense of a loss in axial resolution, and lesion detection is not significantly improved.

TL;DR: The results show that, depending on the fluid characteristics, either the viscosity or the shear wave velocity can be used for process control.

TL;DR: Aluminum, aluminum alloy and stainless steel plate specimens of 6.0 mm thickness were welded end to end using a 15 kHz ultrasonic butt welding equipment with a vibration source using eight bolt-clamped Langevin type PZT transducers and a 50 kW static induction thyristor power amplifier.

TL;DR: A numerical procedure to estimate the uncertainties due to these approximations in the case of fully developed turbulence is described and influence of mean profiles of temperature and velocity is studied on simple examples.

TL;DR: It is clarified that, when the SL is quenched suddenly at excessive ultrasonic power, the behavior of bubbles clearly changes; the bubbles which form dendritic branches of filaments change into clusters due to the secondary Bjerknes force.

TL;DR: In this paper, a diode-type nonlinearity results in local static elastic fields inside the contact, which are shown to be a source of transient longitudinal and shear DC-acoustic pulses polarized oppositely to a biasing contact stress.

TL;DR: This paper describes a preliminary study of the influence of ultrasonics on the boundary conditions associated with the equipment walls in a soft solid forming operation using Plasticine as a material model.

TL;DR: Different thresholding procedures and threshold selection rules are analysed in this paper using the discrete wavelet transform and decomposition level dependent thresholds to evaluate the denoising performance of a wavelet signal processor.

TL;DR: A Fourier domain numerical reconstruction technique has been created in order to eliminate the time spread of Lamb wave signals caused by their dispersive nature and goes from simple signal analysis to imaging purposes such as the improvement of B-scan images or SAFT processing.

TL;DR: This paper addresses the applications of low intensity ultrasonic in the cheese manufacturing processes and highlights the areas where ultrasonics could be successfully implemented in the future.

TL;DR: An F-SAFT based data processing method especially adapted to laser-ULTrasonic data is presented, which allows for further significant improvements towards laser-ultrasonic imaging of small defects.

TL;DR: The most important aspect of the experimental results was that a more than 100% increase of the maximum biological degradation rate has been achieved by US-transduction with an optimum US-intensity of 1.5 W/l wastewater at 25 kHz.

TL;DR: The influence of quartz particles (2-25 microm) on the chemical effects of ultrasound in aqueous system using a high power ultrasound generator (68-1028 kHz, 100 W, reactor volume 500 ml) is reported.

TL;DR: The energy yield for the formation of radicals from ultrasonic waves appears to be in the order of 5 x 10(-6) J/J and the energy conversion is the highest at low temperatures and at low amplitudes.

TL;DR: In this paper, a magnetostrictive device for low-frequency (<500 kHz) ultrasonic testing of elongated ferromagnetic structures is presented, which consists of two transducers, one transmitter and one detector, and operates in pulse-echo mode.

TL;DR: The role of additional fine slots and castellations are studied with reference to two distinct ultrasonic applications and modes are classified using experimental data from 3D laser Doppler vibrometer measurements and finite element analysis.

TL;DR: An experimental observation of a new nonlinear-modulation effect for longitudinal elastic waves is reported, a direct elastic wave analogy with the so-called Luxemburg-Gorky (L-G) effect known over 60 years for radio waves propagating in the ionosphere.

TL;DR: This contribution presents various experimental results showing the potential of this new technique for rapidly imaging non-linear acoustic effects and thereby selectively detecting defects in most kinds of materials.

TL;DR: The scanning laser source (SLS) technique is simulated numerically using the mass spring lattice model and the amplitude and spectral signatures are shown to be captured very well by the model.