THE ACOUSTICAL FIELD NEAR A CIRCULAR TRANSDUCER

1952 ◽  
Vol 30 (2) ◽  
pp. 119-122 ◽  
Author(s):  
E. W. Guptill ◽  
A. D. MacDonald
Keyword(s):  
Approximate Solution ◽  
Plane Wave ◽  
Wave Velocity ◽  
Particle Velocity ◽  
Near Field ◽  
Measured Particle

An approximate solution for the near field of a circular transducer is given. The results indicate that, if a similar transducer is used as a receiver, the measured particle velocity is equal to 1 + (2.70/(ka)2) times the plane wave velocity, where ka is the number of wave lengths in the perimeter of the transducer.

scholarly journals Micro Non-Uniform Linear Array (MNULA) for Ultrasound Plane Wave Imaging

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 640
Author(s):  
Yujia Tang ◽  
Zhangjian Li ◽  
Yaoyao Cui ◽  
Chen Yang ◽  
Jiabing Lv ◽  
...  
Keyword(s):  
Plane Wave ◽  
Linear Array ◽  
Near Field ◽  
Uniform Linear Array ◽  
Imaging Technology ◽  
Linear Arrays ◽  
Imaging Quality ◽  
Imaging Results ◽  
Wave Imaging ◽  
Laboratory Technology

Ultrasound plane wave imaging technology has been applied to more clinical situations than ever before because of its rapid imaging speed and stable imaging quality. Most transducers used in plane wave imaging are linear arrays, but their structures limit the application of plane wave imaging technology in some special clinical situations, especially in the endoscopic environment. In the endoscopic environment, the size of the linear array transducer is strictly miniaturized, and the imaging range is also limited to the near field. Meanwhile, the near field of a micro linear array has serious mutual interferences between elements, which is against the imaging quality of near field. Therefore, we propose a new structure of a micro ultrasound linear array for plane wave imaging. In this paper, a theoretical comparison is given through sound field and imaging simulations. On the basis of primary work and laboratory technology, micro uniform and non-uniform linear arrays were made and experimented with the phantom setting. We selected appropriate evaluation parameters to verify the imaging results. Finally, we concluded that the micro non-uniform linear array eliminated the artifacts better than the micro uniform linear array without the additional use of signal processing methods, especially for target points in the near-field. We believe this study provides a possible solution for plane wave imaging in cramped environments like endoscopy.

Quiet Zone Verification of Plane Wave Synthesizer Using Polar Near-Field Scanner

2020 ◽  
Author(s):  
Adam Tankielun ◽  
Anes Belkacem ◽  
Mustafa Akinci ◽  
Mert Celik ◽  
Hendrik Bartko ◽  
...  
Keyword(s):  
Plane Wave ◽  
Near Field

Development of acoustic target strength near-field equation for underwater vehicles

2018 ◽  
Vol 233 (3) ◽  
pp. 714-721
Author(s):  
Jae-Yong Kim ◽  
Suk-Yoon Hong ◽  
Byung-Gu Cho ◽  
Jee-Hun Song ◽  
Hyun-Wung Kwon
Keyword(s):  
Field Equation ◽  
Plane Wave ◽  
Pressure Field ◽  
Near Field ◽  
Target Strength ◽  
Detection Capability ◽  
Weapon Systems ◽  
Active Sonar ◽  
Acoustic Target ◽  
Definition Of

For modern weapon systems, the most important factor in survivability is detection capability. Acoustic target strength is a major parameter of the active sonar equation. The traditional target strength equation used to predict the re-radiated intensity for the far field is derived with a plane-wave assumption. In this study, a near-field target strength equation was derived without a plane-wave assumption for a polygonal plate. The target strength equation for polygonal plates, which is applicable to the near field, is provided by the Helmholtz–Kirchhoff formula that is used as the primary equation for solving the re-radiated pressure field. A generalized definition of the sonar cross section is suggested that is applicable to the near field. In comparison experiments for a cylinder, the target strength equation for polygonal plates in near field was executed to verify the validity and accuracy of the analysis. In addition, an underwater vehicle model was analyzed with the developed near-field equation to confirm various parameter effects such as distance and frequency.

Analysis of near-field Cassegrain reflector: plane wave vs. element by element approach

2003 ◽  
Author(s):  
B. Houshmand ◽  
S.W. Lee ◽  
Y. Rahmat-Samii ◽  
P.T. Lam
Keyword(s):  
Plane Wave ◽  
Near Field ◽  
Element Approach

scholarly journals Low Scattering Plane Wave Generator Design Using a Novel Non-Coplanar Structure for Near-Field Over-the-Air Testing

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 211348-211357
Author(s):  
Zhaolong Qiao ◽  
Zhengpeng Wang ◽  
Wei Fan ◽  
Xue Zhang ◽  
Steven Gao ◽  
...  
Keyword(s):  
Plane Wave ◽  
Near Field ◽  
Wave Generator ◽  
Generator Design

scholarly journals Shock-Wave Studies Of Ice Under Uniaxial Strain Conditions

1984 ◽  
Vol 30 (105) ◽  
pp. 235-240 ◽  
Author(s):  
Donald B. Larson
Keyword(s):  
Shock Wave ◽  
Wave Velocity ◽  
Particle Velocity ◽  
Uniaxial Strain ◽  
Mixed Phase ◽  
Stable Form ◽  
Static Compression ◽  
Compression Cycle ◽  
Stress Levels ◽  
Time Histories

AbstractShock-wave studies of ice under uniaxial strain conditions have been conducted at stress levels up to 3.6 GPa. A light-gas gun accelerated the flat-faced projectile used to impact the ice-containing targets. The ice samples were initially at ambient pressure and at temperatures of –10 ± 2° C. Gages were implaced at different distances in the ice along the path of the shock wave to measure particle velocity time histories inside the ice samples. The recorded time histories of particle velocity show a precursor wave with an average wave velocity of 3.7 km/s and an average particle velocity amplitude of 0.06 km/s. This wave is travelling at a wave velocity approximately 10% greater than longitudinal sound speed and is believed to originate because of the onset of melting of ice I.The particle velocity data from these experiments were converted to stresses and volumes using Lagrangian gage analysis and the assumption of a simple non-steady wave. This conversion provides a complete compression cycle (which includes both loading and unloading paths) for comparison with static measurements. All experiments show the onset of melting at 0.15 to 0.2 GPa. Experiments with maximum stress states between 0.2 and 0.5 GPa yield results which suggest that a mixed phase of ice I and liquid water exists at these conditions. For maximum loading stresses between 0.6 and 1.7 GPa the experimental results suggest that the final state is predominately ice VI. In these experiments the specific volume upon compression is changed from 1.09 m3/Mg to approximately 0.76 m3/Mg, which represents compaction of approximately 30%. The unloading paths determined from these experiments indicate that ice VI remains in a “frozen” or metastable state during most of the unloading process. This hysteresis in the compression cycle gives rise to a large “loss” of shock-wave energy to the transformation process. At stress levels above 2.2 GPa, ice VII should be the stable form for water according to static compression measurements. Experimental data at 2.4 and 3.6 GPa suggest that ice VII may be formed but these results indicate a mixed phase of ice VI and ice VII rather than complete transformation to ice VII.

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