scholarly journals Self-characterization of commercial ultrasound probes in transmission acoustic inverse scattering: transducer model and volume integral formulation

2014 ◽  
Vol 61 (3) ◽  
pp. 467-480 ◽  
Author(s):  
Mark Haynes ◽  
Sacha A.M. Verweij ◽  
Mahta Moghaddam ◽  
Paul L. Carson
Keyword(s):  
Inverse Scattering ◽  
Integral Formulation ◽  
Volume Integral ◽  
Ultrasound Probes ◽  
Acoustic Inverse Scattering

Acoustic Inverse Scattering Images from Simulated Higher Contrast Objects and from Laboratory Test Objects

1988 ◽  
pp. 353-371 ◽  
Author(s):  
M. J. Berggren ◽  
S. A. Johnson ◽  
W. W. Kim ◽  
D. T. Borup ◽  
R. S. Eidens ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Inverse Scattering ◽  
Test Objects ◽  
Acoustic Inverse Scattering

scholarly journals Διάδοση κυμάτων σε ανομοιογενή μέσα

2007 ◽  
Author(s):  
Κωνσταντίνος Αναγνωστόπουλος
Keyword(s):  
Field Equation ◽  
Plane Wave ◽  
Inverse Scattering ◽  
Scattering Problem ◽  
Field Operator ◽  
Sampling Point ◽  
Far Field ◽  
Two Dimensional ◽  
Time Harmonic

The scope of this doctoral thesis is, first, to develop an analytical, in principle, method for the solution of the two-dimensional scattering problem of time-harmonic elastic plane waves by a homogeneous orthotropic scatterer, second, to establish the complete theoretical framework, which is necessary for the application of the Linear Sampling Method (LSM) to the problem of reconstructing the support of twodimensional elastic anisotropic inclusions embedded in isotropic media and, third, to derive an extension of the Factorization Method (FM) to the inverse elastic scattering problem by penetrable isotropic bodies for time-harmonic plane wave incidence. Aconcise description of the contents of the thesis is outlined below. Chapter one contains a detailed bibliographical search, which is related to the analytical and numerical methods (with emphasis on the former) usually employed for the solution of the direct scattering problem by anisotropic elastic bodies as well as to those inverse scattering techniques, which are usually referred to as sampling and probe methods and, in particular, the LSM and the FM. Chapter two commences with a brief discussion of some fundamental results from the linearized theory of dynamic elasticity. The problem of a rigorous analysis of the elasticity equation governing the elastic behaviour of an orthotropic material in two dimensions is then addressed. This analysis, which is based on a suitable diagonalization applied to the underlying differential system and a plane wave expansion of the sought field, results in a Fourier series expansion for the displacement field describing the elastic deformations of the orthotropic medium and is complemented by the results of appendix A. A mathematical model for the solution of the associated transmission scattering problem, taking advantage of the aforementioned expansion, is also settled and analyzed. The details of its numerical treatment can be found in appendix B. Finally, numerical results for several inclusion geometries and a system thereof with material properties characterized by the cubic symmetryclass -a special case of the orthotropic class of symmetry- are presented. In chapter three, the LSM is extended to the case of a two-dimensional homogeneous anisotropic inclusion embedded in an isotropic background medium. The concepts of the elastic Herglotz function, the elastic far-field operator and the corresponding far-field equation, on which the formulation of the LSM heavily relies, are first introduced. Then, the proposed inverse scattering scheme is introduced and discussed in detail. By means of an appropriate operator decomposition of the far-field operator,the main theorem of the method, concerning the characterization of the behaviour of an approximate solution to the far-field equation at the boundary of the scatterer, is proved. In the end of the third chapter, the performance of the LSM is examined by applying it to a set of different geometric configurations of the elastic inclusion, filled with a cubic anisotropic material. An investigation of the effect of the various parameters entering the problem, such as the scatterer’s degree of anisotropy, the polarization of the elastic point source located at the sampling point and the noise level in the synthetic far-field data, on the reconstructed geometric profiles’ quality,is carried out. In the fourth chapter, the FM is elaborated for the shape reconstruction of a penetrable isotropic elastic body from the knowledge of the far-field pattern of the scattered fields for plane incident waves. The theoretical analysis is conducted in three dimensions and focuses on deriving a factorization of the far-field operator, which is the cornerstone for the applicability of the particular inversion scheme, and investigating thorougly the properties of the involved operators. This investigation gave birth to a number of interesting by-products and one of them, namely, a regularity estimate for the solution of a particular form of the corresponding interior transmission problem, is the subject matter of appendix C. By means of the proposed factorization, a series of theorems, which finally lead to an explicit characterization of the scattering obstacle, is then proved. In the end of the chapter, the performance of the investigated inverse scattering technique is demonstrated by applying it to specific two-dimensional elastic scatterer reconstruction problems involving different scatterer configurations and various choices for their constitutive parameters. The effect of using different levels of additive random noise in the forward synthetic data and combining results obtained for different polarizations of the elastic point source located at the sampling point, on the quality of the reconstructed profiles, is also examined. Finally, chapter five draws the conclusions that flow from the foregoing chapters and discusses the contribution of this doctoral thesis. A brief discussion about possible future studies is also included.

A volume integral approach for the modelling and design of HTS coils

2019 ◽  
Vol 38 (4) ◽  
pp. 1133-1140 ◽  
Author(s):  
Yazid Statra ◽  
Hocine Menana ◽  
Lamia Belguerras ◽  
Bruno Douine
Keyword(s):  
Power Law ◽  
Strong Dependence ◽  
Superconducting Devices ◽  
Electromagnetic Properties ◽  
Integral Approach ◽  
Volume Integral ◽  
Content Type ◽  
High Level ◽  
Modelling Approach

Purpose The purpose of this paper is to develop a rapid and realistic modelling approach for the design and characterization of high temperature superconducting (HTS) coils and windings carrying DC currents. Indeed, the strong dependence of the electromagnetic properties of such materials on the magnetic field makes the design and characterization of HTS systems a delicate operation where local quantities have to be evaluated. Design/methodology/approach A volume integral modelling approach has been developed taking into account the electric nonlinearity of the HTS material which is represented by power law. The variations of the characteristic quantities of the HTS (critical current density and power law exponent) with the magnetic flux density are also taken into account by using Kim’s law. The volume integral modelling allows to model only the active parts of the system and thus to overcome the difficulties linked to the multiscale dimensions. Findings The model has been tested in a case study in which simulation results were compared to measurements and to finite element analysis. A good agreement was found which validates the model as a rapid and efficient tool for HTS coils and windings design and modelling. Practical implications HTS coils are important elements of emerging superconducting devices which require a high level of reliability, such as generators or motors. The proposed approach is interesting to speed up the design and optimization procedures of such systems. Originality/value Advanced structures of the basic elements have been used in the volume integral modelling, which results in a considerable gain in computation time and in memory-space saving while keeping a high level of precision and realism of the modelling, which has been verified experimentally.

scholarly journals A Volume Integral Formulation Based on Facet Elements for Nonlinear Magnetostatic Problems

2015 ◽  
Vol 51 (7) ◽  
pp. 1-6 ◽  
Author(s):  
Vinh Le-Van ◽  
Gerard Meunier ◽  
Olivier Chadebec ◽  
Jean-Michel Guichon
Keyword(s):  
Integral Formulation ◽  
Volume Integral

scholarly journals Volume Integral Formulation for the Calculation of Material Independent Modes of Dielectric Scatterers

2018 ◽  
Vol 66 (5) ◽  
pp. 2505-2514 ◽  
Author(s):  
Carlo Forestiere ◽  
Giovanni Miano ◽  
Guglielmo Rubinacci ◽  
Antonello Tamburrino ◽  
Roberto Tricarico ◽  
...  
Keyword(s):  
Integral Formulation ◽  
Volume Integral
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