Both diagnostic and therapeutic ultrasound applications require an understanding of the directivity patterns on the transducers to design ultrasound equipment and faithfully characterize the acoustic output from medical ultrasound devices. Since each ultrasound transducer has its own specific directivity pattern, the measurement of the directivity pattern is necessary. The objectives of this wo...

Multimode sound radiation from an unflanged, semi-infinite, rigid-walled circular duct with uniform subsonic mean flow everywhere is investigated theoretically. The multimode directivity depends on the amplitude and directivity function of each individual cut-on mode. The amplitude of each mode is expressed as a function of cut-on ratio for a uniform distribution of incoherent monopoles, a unif...

This papaer studies, from the point of view of the traveling-wave approach, the transient radiation by V-antennas including the dependence of the maximum directivity on the interior angle, on the length of the arms and on the characteristics of the exciting pulse. As particular examples, the cases when the antenna is excited by a harmonic signal and a gaussian pulse are analyzed and the results...

The triple impulse input is used as a simplified version of the forward-directivity near-fault ground motion and a closed-form solution of the elastic–plastic response of a structure by this triple input is obtained. It is noteworthy that only the free-vibration appears under such triple impulse input. An almost critical excitation is defined and its response is derived. The energy approach pla...

Near-fault ground motions are different from ordinary ground motions in that they often contain strong coherent dynamic long period pulses and permanent ground displacements. The dynamic motions are dominated by a large long period pulse of motion that occurs on the horizontal component perpendicular to the strike of the fault, caused by rupture directivity effects. Near fault recordings from r...

Continuous rigid-frame bridges (CRFBs) have been widely constructed in high seismicity areas western China. To investigate the seismic response characteristics and whiplash effect mechanism of CRFBs under near-fault ground motions, a long-span CRFB with piers is selected as prototype bridge, nonlinear finite element model developed based on OpenSees. Three groups namely having forward-directivi...

Terahertz (THz) radiation generation based on a nonlinear induced electron current density in the interaction of two-color femtosecond laser beams with collisional and magnetized plasma is investigated. The that responsible for THz includes share from ponderomotive force part relativistic term. In this work, effects along variation interacting density, external magnetic field, collision frequen...

The current study aims to investigate damage assessment of the RC frames with brick masonry infill (BMI). effects near-source ground motions (GMs) are considerably predominant in seismic response structure as related far-source motion due their forward directivity plus long period. is characterized by enormous everlasting translation, strong peak acceleration (PGA), and a very low-frequency pul...

The present study reveals the existence of an intrinsic spatial code within neuronal spikes that predicts behavior. As rats learnt a T-maze procedural task, simultaneous changes in temporal occurrence of spikes and spike directivity are evidenced in “expert” neurons. While the number of spikes between the tone delivery and the beginning of turn phase reduced with learning, the generated spikes ...