The low frequency reflection characteristics of the fundamental antisymmetric Lamb wave a0 from a rectangular notch in a plate

2002 ◽  
Vol 112 (6) ◽  
pp. 2612-2622 ◽  
Author(s):  
M. J. S. Lowe ◽  
P. Cawley ◽  
J-Y. Kao ◽  
O. Diligent
Keyword(s):  
Lamb Wave ◽  
Low Frequency ◽  
Reflection Characteristics ◽  
Rectangular Notch

scholarly journals Detection of the Lunar Surface Soil Permittivity with Megahertz Electromagnetic Wave

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2466
Author(s):  
Qingwen Rao ◽  
Guanjun Xu ◽  
Wangchen Mao
Keyword(s):  
Lunar Surface ◽  
Scattering Theory ◽  
Surface Soil ◽  
Low Frequency ◽  
Stable Phase ◽  
Em Scattering ◽  
Lunar Dust ◽  
Lunar Ionosphere ◽  
Spaceborne Radar ◽  
Reflection Characteristics

In this paper, the detection of the lunar surface soil permittivity with megahertz electromagnetic (EM) waves by spaceborne radar is studied based on the EM scattering theory, the Boltzmann–Shukla equations, and the improved scattering matrix method (ISMM). The reflection characteristics of the lunar surface soil subject to megahertz waves are analyzed through the EM scattering theory and expressed by the lunar surface soil permittivity. Then, the lunar ionosphere is assumed to be composed of dusty plasma, and its EM characteristics are described with the Boltzmann–Shukla equations. Finally, the transmission and reflection characteristics of the propagation of EM waves in the lunar ionosphere are numerically calculated with ISMM. Thus, the complex permittivity of lunar surface soil is obtained. In addition, the effects of detection environment situations, such as the lunar illumination intensity, characteristics of the lunar dust and dust charging process in the lunar ionosphere, on the amplitude and phase of EM waves are also investigated in this study. The simulation results show that an EM wave at a high frequency induces a strong effective wave with a stable phase shift and a significantly small interferential wave. Moreover, the lunar illumination is more effective under EM waves in low frequency bands; the characteristics of the lunar dust have a notable influence on the transmission and absorption coefficients of the effective waves. These conclusions help in real applications involving the detection of the lunar surface soil permittivity by spaceborne radar in various lunar environments.

Equation Chapter 1 Section 1Precise and target-oriented control of the low-frequency Lamb wave bandgaps

2021 ◽  
pp. 116367
Author(s):  
Yanzheng Wang ◽  
Chuanzeng Zhang ◽  
Weiqiu Chen ◽  
Zhengyang Li ◽  
Mikhail V. Golub ◽  
...  
Keyword(s):  
Lamb Wave ◽  
Low Frequency

scholarly journals Low Frequency Generation and Detection of the Lamb Wave A0 Mode Using EMAT

2007 ◽  
Vol 127 (3) ◽  
pp. 367-372 ◽  
Author(s):  
Songsong Li ◽  
Toshimi Okada ◽  
Xiaoming Chen ◽  
Hongwei Dai
Keyword(s):  
Lamb Wave ◽  
Low Frequency ◽  
Frequency Generation

scholarly journals Control of low-frequency Lamb wave propagation in plates by boundary condition manipulation

2021 ◽  
Vol 129 (9) ◽  
pp. 094903
Author(s):  
Cliff J. Lissenden ◽  
Christopher N. Hakoda ◽  
Parisa Shokouhi
Keyword(s):  
Boundary Condition ◽  
Wave Propagation ◽  
Lamb Wave ◽  
Low Frequency ◽  
Lamb Wave Propagation

Acoustical Design and Measurement of a Circular Hall for Improved Spatial Factors at Each Seat

2000 ◽  
Vol 7 (2) ◽  
pp. 113-125 ◽  
Author(s):  
Akio Takatsu ◽  
Hiroyuki Sakai ◽  
Yoichi Ando
Keyword(s):  
New York ◽  
Low Frequency ◽  
Frequency Range ◽  
Sound Sources ◽  
Spatial Factors ◽  
Architectural Acoustics ◽  
Sound Fields ◽  
Preference Theory ◽  
Subjective Preference ◽  
Reflection Characteristics

A round-shaped multi-purpose event hall (ORBIS Hall, Kobe, Japan) was designed based on the subjective-preference theory of sound fields [Y. Ando, Architectural Acoustics -Blending Sound Sources, Sound Fields, and Listeners-, AIP Press/Springer-Verlag, New York, 1998]. To avoid acoustical problems produced by round-shaped walls, and to maximize the total scale value of the subjective preference at each seat, acoustical features including several kinds of reflectors were carefully designed. The IACC calculated for the design phase, however, did not include all the installed features because these have complicated scattered reflection characteristics. After construction of the hall, therefore, the IACC measurements were conducted using two different music motifs. Results indicate that the values of the IACC are much improved due to these features. Also, the SPL-dip in the low frequency range in the area close to the stage is effectively improved by the inclusion of a perforated floor.

scholarly journals Model-Based Design of Low Frequency Lamb Wave EMATs for Mode Selectivity

2015 ◽  
Vol 34 (3) ◽  
Author(s):  
Matthias Seher ◽  
Peter Huthwaite ◽  
Michael J. S. Lowe ◽  
Peter B. Nagy
Keyword(s):  
Lamb Wave ◽  
Low Frequency ◽  
Model Based ◽  
Mode Selectivity

Assessment of debonding in sandwich CF/EP composite beams using A0 Lamb wave at low frequency

2011 ◽  
Vol 93 (2) ◽  
pp. 483-491 ◽  
Author(s):  
Samir Mustapha ◽  
Lin Ye ◽  
Dong Wang ◽  
Ye Lu
Keyword(s):  
Lamb Wave ◽  
Low Frequency ◽  
Composite Beams

Seismic response and prediction of Ordovician fractured vuggy carbonate reservoirs in the Tazhong Shunnan well A block

2017 ◽  
Vol 5 (1) ◽  
pp. SB45-SB55 ◽  
Author(s):  
Li Zhou ◽  
Hanming Gu ◽  
Lingwei Ma ◽  
Jiao Xue ◽  
Zongjie Li
Keyword(s):  
High Frequency ◽  
Seismic Reflection ◽  
Random Medium ◽  
Low Frequency ◽  
Fault Zones ◽  
Carbonate Reservoirs ◽  
Medium Theory ◽  
Significant Difference ◽  
Seismic Reflections ◽  
Reflection Characteristics

Ordovician fractured vuggy carbonate reservoirs, which are deeply buried in the Tazhong Shunnan area in China, are characterized by high heterogeneity. Meanwhile, there is no significant difference between the geophysical characteristics of the reservoirs and that of the surrounding rocks. We have introduced the multiscale stack random medium theory and built some theoretical seismic-geologic models for the fractured vuggy carbonate reservoirs. Furthermore, we obtained the seismic reflection characteristics corresponding to these models using finite-difference forward modeling. The small random vugs are characterized by weak and chaotic reflections with high frequency, and the large vugs are characterized by strong and chaotic reflections with low frequency. The amplitude of the seismic reflections increases with the increasing vug density, and it decreases with the increasing roughness factor. Combining the synthetic reflection characteristics corresponding to the fractured vuggy carbonate reservoirs and the actual seismic reflections from the drilled reservoirs, we summarized the recognition patterns of the carbonate reservoirs. The predicted results found that the potential fractured vuggy reservoirs at the top of Yijianfang Formation are located in the southwest and northeast, in the vicinity of fault zones. The reservoirs in Peng-Laiba Formation are distributed in the northwest of the block.

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