Air-coupled ultrasonic techniques are being increasingly used for material characterization, non-destructive evaluation of composite materials using guided waves as well as for distance measurements. Application of those techniques is mainly limited by the big losses of ultrasonic signals due to attenuation and mismatch of the acoustic impedances of ultrasonic transducers and air. One of the wa...

The need for tissue-engineered constructs as replacement tissue continues to grow as the average age of the world's population increases. However, additional research is required before the efficient production of laboratory-created tissue can be realized. The multitude of parameters that affect cell growth and proliferation is particularly daunting considering that optimized conditions are lik...

The characterization of the signals in terms of linear/ nonlinear and deterministic/stochastic nature may be appropriated for knowledge extraction and machine learning algorithms. Some real-world signals exhibit signal modality characteristics that are strongly related with the physical mechanisms involved in the production of them. As an example, we can mention how the resonant sounds are more...

Ultrasonic polar scans are based on the recording of the reflected or transmitted amplitude of sound, impinging a fiber reinforced composite from every possible angle of incidence. The mechanical anisotropy of such materials makes the reflection coefficient direction dependent, whence an ultrasonic polar scan forms a fingerprint of the investigated material. Such scans have already proved to be...

We analyze and optimize the design of wedge transducers used for the excitation of resonances in the channel of a microfluidic chip in order to efficiently manipulate particles or cells in more than one dimension. The design procedure is based on (1) theoretical modeling of acoustic resonances in the transducer–chip system and calculation of the force fields in the fluid channel, (2) full-syste...

PURPOSE Palpation is used most commonly to assess tissue stiffness despite its well-known deficiencies. As an improvement, a mechanical technique known as ultrasonic indentation has been proposed. The purpose of this study was to compare the accuracy of 3 ultrasonic indentation techniques in quantifying bone displacement in a specially constructed tissue simulator. METHODS Three ultrasonic in...

We have shown recently that tissue characterization of myocardium with ultrasound reflects changes associated with contractile function throughout the cardiac cycle. To determine whether ultrasonic tissue characterization can sensitively detect the impact of ischemic injury and reperfusion on contractile properties of the heart, we studied the time course of change of backscatter after 5, 20, a...

The National Bureau of Standards program in acoustic-ultrasonic calibrations and standards, aimed at solving some of the immediate problems, is reviewed. l~ork on acoustic emission tr~nsducers is.directed at the determination of sensitivity and spectral response by the use of a reproduc1ble stress 1mpulse. Also in the area of acoustic emission is a program to develop a theoretical basis for aco...