Correction of near-field effects in phased array element pattern measurements

NEAR-FIELD EFFECTS OF RESONANT WIRE ANTENNAS

Telecommunications and Radio Engineering ◽

10.1615/telecomradeng.v69.i18.20 ◽

2010 ◽

Vol 69 (18) ◽

pp. 1615-1622

Author(s):

R. I. Tsekhmistro ◽

N. N. Gorobets

Keyword(s):

Near Field ◽

Field Effects ◽

Wire Antennas

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Ultrasonic Imaging of Thick Carbon Fiber Reinforced Polymers through Pulse-Compression-Based Phased Array

Applied Sciences ◽

10.3390/app11041508 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1508

Author(s):

Muhammad Khalid Rizwan ◽

Stefano Laureti ◽

Hubert Mooshofer ◽

Matthias Goldammer ◽

Marco Ricci

Keyword(s):

Carbon Fiber ◽

Pulse Compression ◽

Phased Array ◽

Signal To Noise Ratio ◽

Near Field ◽

Ultrasonic Imaging ◽

Fiber Reinforced Polymers ◽

Fiber Reinforced ◽

Custom Made ◽

Carbon Fiber Reinforced

The use of pulse-compression in ultrasonic non-destructive testing has assured, in various applications, a significant improvement in the signal-to-noise ratio. In this work, the technique is combined with linear phased array to improve the sensitivity and resolution in the ultrasonic imaging of highly attenuating and scattering materials. A series of tests were conducted on a 60 mm thick carbon fiber reinforced polymer benchmark sample with known defects using a custom-made pulse-compression-based phased array system. Sector scan and total focusing method images of the sample were obtained with the developed system and were compared with those reconstructed by using a commercial pulse-echo phased array system. While an almost identical sensitivity was found in the near field, the pulse-compression-based system surpassed the standard one in the far-field producing a more accurate imaging of the deepest defects and of the backwall of the sample.

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Numerical modelling of historical landslide-generated tsunamis in the French Lesser Antilles

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1281-2010 ◽

2010 ◽

Vol 10 (6) ◽

pp. 1281-1292 ◽

Cited By ~ 4

Author(s):

B. Poisson ◽

R. Pedreros

Keyword(s):

Near Field ◽

Pyroclastic Flows ◽

Lesser Antilles ◽

Published Data ◽

Tsunami Height ◽

Tsunami Modelling ◽

Field Effects ◽

Wave Heights ◽

Unique Source ◽

Height Data

Abstract. Two historical landslide-induced tsunamis that reached the coasts of the French Lesser Antilles are studied. First, the Martinique coast was hit by a tsunami down the western flank of Montagne Pelée at the beginning of the big eruption of May 1902. More recently, the northeastern coast of Guadeloupe was affected by a tsunami that had been generated around Montserrat by pyroclastic flows entering the sea, during the July 2003 eruption of the Soufrière Hills volcano. We use a modified version of the GEOWAVE model to compute numerical simulations of both events. Two source hypotheses are considered for each tsunami. The comparison of the simulation results with reported tsunami height data helps to discriminate between the tested source decriptions. In the Martinique case, we obtain a better fit to data when considering three successive lahars entering the sea, as a simplified single source leads to an overstimation of the tsunami wave heights at the coast. In the Montserrat case, the best model uses a unique source which volume corresponds to published data concerning the peak volume flow. These findings emphasize the importance of an accurate description of the relevant volume as well as the timing sequence of the source event in landslide-generated tsunami modelling. They also show that considering far-field effects in addition to near-field effects may significantly improve tsunami modelling.

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Near-field and far-field effects in thermal radiation from metallic carbon nanotubes

10.1117/12.752152 ◽

2007 ◽

Cited By ~ 1

Author(s):

Andrei M. Nemilentsau ◽

Gregory Ya. Slepyan ◽

Sergey A. Maksimenko

Keyword(s):

Carbon Nanotubes ◽

Thermal Radiation ◽

Near Field ◽

Far Field ◽

Field Effects

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Design of Two-Dimensional Ultrasonic Phased Array Transducers

Journal of Pressure Vessel Technology ◽

10.1115/1.1991873 ◽

2005 ◽

Vol 127 (3) ◽

pp. 336-344 ◽

Cited By ~ 5

Author(s):

Shyamal C. Mondal ◽

Paul D. Wilcox ◽

Bruce W. Drinkwater

Keyword(s):

Phased Array ◽

Three Dimensional ◽

Array Element ◽

Two Dimensional ◽

Circular Array ◽

Single Location ◽

Ultrasonic Phased Array ◽

3D Point Spread Function ◽

3D Volume ◽

Simulation And Evaluation

Two-dimensional (2D) phased arrays have the potential to significantly change the way in which engineering components in safety critical industries are inspected. In addition to enabling a three-dimensional (3D) volume of a component to be inspected from a single location, they could also be used in a C-scan configuration. The latter would enable any point in a component to be interrogated over a range of solid angles, allowing more accurate defect characterization and sizing. This paper describes the simulation and evaluation of grid, cross and circular 2D phased array element configurations. The aim of the cross and circle configurations is to increase the effective aperture for a given number of elements. Due to the multitude of possible array element configurations a model, based on Huygens’ principle, has been developed to allow analysis and comparison of candidate array designs. In addition to the element configuration, key issues such as element size, spacing, and frequency are discussed and quantitatively compared using the volume of the 3D point spread function (PSF) as a measurand. The results of this modeling indicate that, for a given number of elements, a circular array performs best and that the element spacing should be less than half a wavelength to avoid grating lobes. A prototype circular array has been built and initial results are presented. These show that a flat bottomed hole, half a wavelength in diameter, can be imaged. Furthermore, it is shown that the volume of the 3D reflection obtained experimentally from the end of the hole compares well with the volume of the 3D PSF predicted for the array at that point.

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