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Showing 1 to 20 of 106 for “"scatterer"”.
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Non-Rayleigh scattering by a randomly oriented elongated scatterer
… non-Rayleigh and a strong function of shape of scatterer. The tails are shown to increase above that associated with a Rayleigh distribution with increasing degree of elongation (aspect ratio) of the scatterer and when roughness effects are introduced. And, as also shown in previous studies, the …
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Non-Rayleigh scattering by a randomly oriented elongated scatterer
… non-Rayleigh and a strong function of shape of scatterer. The tails are shown to increase above that associated with a Rayleigh distribution with increasing degree of elongation (aspect ratio) of the scatterer and when roughness effects are introduced. And, as also shown in previous studies, the …
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Development of embedded modulated scatterer technique: single- and dual-loaded scatterers
… technology is developed based on the Modulated Scatterer Technique (MST). MST is based on illuminating a probe, commonly a dipole antenna loaded with a PIN diode (also referred to as a single-loaded scatterer, or SLS), with an electromagnetic wave. This impinging wave induces a current along the …
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Exploring scatterer anisotrophy in synthetic aperture radar via sub-aperture analysis
… be exploited as attributes to better distinguish scatterers and their respective targets. With this in mind, this thesis develops an efficient modeling framework based on a sub-aperture pyramid to utilize scatterer anisotropy for the purpose of target classification. Two approaches are presented …
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Theory and applications of scattering and inverse scattering problems
… field from an arbitrarily shaped, inhomogeneous scatterer. By discretizing the object into N subobjects, the scattering solution of an arbitrarily shaped inhomogeneous scatterer can be formulated as a scattering solution of an N-scatterer problem, each of whose scattered fields is approximated by …
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Resonance-Based Techniques for Microwave Breast Cancer Applications
It is well known that a finite-size scatterer has a set of natural resonances, which are uniquely determined by the physical properties of the scatterer. This is also the case for a breast tumor which can be regarded as a dielectric scatterer. Since the scatterer is naturally "tuned" at the …
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Computationally Modeling the Effects of Surface Roughness on Soft X-Ray Multilayer Reflectors
… from a rough two dimensional homogeneous scatterer has been computationally modeled. The scatterer is intended to simulate reflection from a two interface multilayer. The rough scatterer was created from Gaussian random points centered about an ideal interface. The points were connected …
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Translation and rotational motion compensation techniques for Inverse Synthetic Aperture Radar (ISAR) Imaging of sea vessels
… The combination of the weighted multiple scatterer autofocus algorithm and the sub-integer range alignment technique proved to have the most favourable results. Lastly, the Optimal Coherent Processing Interval (CPI) Selection based on Image Contrast Optimisation and the Doppler Spread …
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An Investigation of the Multiple Scattering of Waves in Two-Dimensional Random Media
… of springs was also added to the mesh points. Scatterer density and scatterer strength were varied by changing the number of added springs and their stiffness, respectively. The average center deflection for several hundred mesh configurations of a given scatterer density and strength were …
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Measurement of volumetric blood flow using ultrasound time-domain correlation
… Doppler techniques) of ultrasound reflected from scatterers. If a vessel with moving fluid is insonated by two ultrasonic pulses separated by time T, the scatterers within the ultrasonic beam will move some distance D between the first and second pulse. There will be a difference $\tau$ in the …
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A boundary integral equation approach to three dimensional electromagnetic wave scattering problems
… the size, the shape and the constitution of the scatterer;The development of theoretical models largely relies on the use of numerical techniques such as boundary element method (BEM), finite element method (FEM), or finite difference method (FDM). However, no single numerical method has emerged …
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Ultrasonic Characterization of Three Animal Mammary Tumors From Three-Dimensional Acoustic Tissue Models
… sections for each tumor. Spectral estimates (scatterer size and acoustic concentration) were obtained from the 3DZMs and compared to the same estimates obtained with ultrasound. Scatterer size estimates for three tumors were found to be similar (within 10%). The 3DZMs were also used to extract …
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Development and Application of Three-dimensional Impedance Maps Related to Tissue Pathology
… to estimate properties, such as the effective scatterer size, of the ultrasonic scattering sites in the underlying tissue. These estimates can, in turn, be related to histological features of the tissue. For the fibroadenoma datasets, the average effective scatterer diameter was estimated to be …
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Sonic Crystal Noise Barriers
… the intrinsic acoustic properties of the scatterer are considered. The use of the tube cavity (Helmholtz type) resonances in Split Ring Resonator (SRR) or the breathing mode resonances observed in thin elastic shells is shown to increase Insertion loss (IL) in the low-frequency range below …
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Novel modulated antennas and probes for millimeter wave imaging applications
… of modulating millimeter wave antenna and scatterer structures, directly to increase the overall system sensitivity and reduce the image acquisition time, is central to the development presented herein. To improve upon the conventional modulated scatterer technique (MST) based on dipole …
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Estimating the Medical Ultrasound in Vivo Power Spectrum
… was estimated by assuming model for the scatterers (i.e., spherically symmetric Gaussian impedance distributions of unknown size) and then solving for the size and total attenuation simultaneously from the frequency dependence of the backscattered spectrum. The attenuation and scatterer …
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Advanced Array Imaging for Breast and Prostate Sonography
… With the scattered wave field, determining the scatterer is called the inverse problem. As for the geometry of the scattering theory, the scatterer is assumed to be present in a homogeneous reference medium with known properties. Following the notations used in Lehman8, the acoustic pressure, p, …
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ΕΠΙΛΥΣΗ ΤΟΥ ΠΡΟΒΛΗΜΑΤΟΣ ΣΚΕΔΑΣΗΣ ΑΠΟ ΣΚΕΔΑΣΤΗ ΤΥΧΑΙΑΣ ΓΕΩΜΕΤΡΙΑΣ ΜΕΣΑ ΣΕ ΣΤΡΩΜΑΤΟΠΟΙΗΜΕΝΟ ΜΕΣΟ ΜΕ ΤΗΝ ΒΟΗΘΕΙΑ ΤΩΝ ΔΥΑΔΙΚΩΝ ΣΥΝΑΡΤΗΣΕΩΝ GREEN
… THESIS THE PROBLEM OF SCATTERING BY A DIELECTRIC SCATTERER LOCATED INSIDE A STRATIFIED MEDIUM IS TREATED, BOTH ANALYTICALLY AND NUMERICALLY. THE ANALYSIS MAKES USE OF DYADIC GREEN'S FUNCTIONS (DGF), THE THEORY AND PROPERTIES OF WHICH ARE THOROUGHLY INVESTIGATED. IN THE FIRST PART OF THIS WORK THE …
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Acoustic classification of zooplankton
… identification of three categories of acoustic scatterers: elastic-shelled (e.g. pteropods), fluid-like (e.g. euphausiids), and gas-bearing (e.g. siphonophores). The relationship between backscattered energy and animal biomass has been shown to vary by a factor of —19,000 across these …
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Three-dimensional acoustic impedance map analysis of soft tissue
… power spectrum can be predicted and model based scatterer properties, such as effective scatterer diameter (ESD), can be estimated. Additionally, the 3DZM can be exploited to visualize and identify possible scattering sites, which may aid in the development of more effective scattering models to …
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