Transmission and reflection of ultrasonic waves in layered media

1977 ◽  
Vol 62 (5) ◽  
pp. 1102-1109 ◽  
Author(s):  
D. L. Folds ◽  
C. D. Loggins
2015 ◽  
Vol 1101 ◽  
pp. 471-479
Author(s):  
Georges Freiha ◽  
Hiba Othman ◽  
Michel Owayjan

The study of signals propagation inside porous media is an important field especially in the biomedical research related to compact bones. The purpose of this paper is to determine a mathematical formulation of the global coefficients of transmission and reflection of nondestructive ultrasonic waves in any bi-phase porous medium. Local coefficients of transmission and reflection on the interface of the porous medium will be determined based on a study of boundary conditions. The behavior of different waves inside the porous medium will be developed so that we can derive a new formulation of global coefficients that takes interior phenomena into consideration. Results are found independently of the geometrical and physical characteristics of the medium. Note that this study is based on normal incident ultrasonic wave propagation.


1988 ◽  
pp. 23-34
Author(s):  
Adnan H. Nayfeh ◽  
Timothy W. Taylor

Author(s):  
Y Raach ◽  
Y Derouiche ◽  
F Messelmi

This paper presents the influence of the composite age on the variation of the transmission and reflection coefficients. The composite is the concrete in our case. The studied structure is a multilayer structure composed of two elastic and isotropic layers where each one is characterized by its own physical properties. The problem is simplified in two-dimensional plane waves, and the influence of the attack angle on the acoustic impedances is also examined. Moreover, an experimental study is realized in the formulation of concrete and the measurement of waves propagation velocity. In this work, during the concrete formulation, three different types of concrete were developed: sand concrete, ordinary concrete, and high-performance concrete. The results of simulation and experiments demonstrate that the age of concrete and the internal concrete structure have a direct influence on the evolution of the acoustic parameters as well as the angle of incidence, which has considerably changed the behavior of the transmission and reflection coefficients. This internal structure is directly related to the age of the concrete where its maturity is not reached until after a certain age, which influences the behavior of the waves through the layers of the multilayer structure.


Author(s):  
Christoph Schaal ◽  
Vibhav Durgesh

High-intensity focused ultrasound (HIFU) can be used for the ablation of tissue, such as in the case of prostate cancer. However, targeting tissue deeper inside the body remains challenging due to the increased attenuation and scattering of the ultrasonic waves. In this work, the partial and complete obstruction of the ultrasonic beam from a HIFU transducer at bones is investigated. Ultrasonic transmission and reflection under such conditions have scarcely been the focus of previous research. Thus, this work provides a reference based on numerical and experimental results. To this end, numerical simulations are conducted for various bone obstruction configurations. In addition, a diffraction-based shadowgraph technique is used for the ultrasound visualization in laboratory experiments. Imaging of focused ultrasonic waves is performed in water with no obstruction, varying partial obstruction, as well as with complete obstruction by bones phantoms. It is shown that there is reasonable agreement between the findings from experiments and simulations. While the field of view in experiments is limited, the entire pressure field in the area of interest can be investigated in numerical simulations. Overall, the results of this work provide a basis for future research in the field of therapeutic ultrasound.


Author(s):  
William Krakow

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.


Biofouling ◽  
2003 ◽  
Vol 19 (3) ◽  
pp. 159-168 ◽  
Author(s):  
Nadia Oulahal- Lagsir ◽  
Adele Martial- Gros ◽  
Marc Bonneauc ◽  
Loic Bluma

Biofouling ◽  
2003 ◽  
Vol 19 (3) ◽  
pp. 159-168 ◽  
Author(s):  
NADIA OULAHAL-LAGSIR ◽  
ADELE MARTIAL-GROS ◽  
MARC BONNEAU ◽  
LOIC BLUM

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