The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Steen Hansen - One of the best experts on this subject based on the ideXlab platform.
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estimation of chord length distributions from small angle scattering using indirect fourier transformation
Journal of Applied Crystallography, 2003Co-Authors: Steen HansenAbstract:It is shown that it is possible to estimate the chord length distribution from small-angle scattering data by indirect Fourier transformation. This is done for several examples of Scatterers varying in structure from globular to elongated as well as Scatterers consisting of separated parts. The presented examples suggest that the chord length distribution may give additional information about the scatterer. Therefore it may be relevant to consider estimation of the chord length distribution as an additional tool for analysis of small-angle scattering data.
Steen Honoré Hansen - One of the best experts on this subject based on the ideXlab platform.
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Estimation of chord length distributions from small‐angle scattering using indirect Fourier transformation
Journal of Applied Crystallography, 2003Co-Authors: Steen Honoré HansenAbstract:It is shown that it is possible to estimate the chord length distribution from small-angle scattering data by indirect Fourier transformation. This is done for several examples of Scatterers varying in structure from globular to elongated as well as Scatterers consisting of separated parts. The presented examples suggest that the chord length distribution may give additional information about the scatterer. Therefore it may be relevant to consider estimation of the chord length distribution as an additional tool for analysis of small-angle scattering data.
William D Obrien - One of the best experts on this subject based on the ideXlab platform.
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structure function for high concentration biophantoms of polydisperse scatterer sizes
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2015Co-Authors: Aiguo Han, William D ObrienAbstract:Ultrasonic backscattering coefficient (BSC) has been used extensively to characterize tissue. In most cases, sparse scatterer concentrations are assumed. However, many types of tissues have dense scattering media. This study addresses the problem of dense media scattering by taking into account the correlation among Scatterers using the structure functions. The effect of scatterer polydispersity on the structure functions is investigated. Structure function models based on polydisperse Scatterers are theoretically developed and experimentally evaluated against the structure functions obtained from cell pellet biophantoms. The biophantoms were constructed by placing live cells of known concentration in coagulation media to form a clot. The BSCs of the biophantoms were estimated using single-element transducers over the frequency range from 11 to 105 MHz. Experimental structure functions were obtained by comparing the BSCs of two cell concentrations. The structure functions predicted by the models agreed with the experimental structure functions. Fitting the models yielded cell radius estimates that were consistent with direct light microscope measures. The results demonstrate the role of scatterer position correlation on dense media scattering, and the significance of scatterer polydispersity on structure functions. This work may lead to more accurate modeling of ultrasonic scattering in dense medium for improved tissue characterization.
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characterization of tissue microstructure using ultrasonic backscatter theory and technique for optimization using a gaussian form factor
Journal of the Acoustical Society of America, 2002Co-Authors: Michael L. Oelze, James F. Zachary, William D ObrienAbstract:Characterization of tissue microstructure through ultrasonic backscatter is hypothesized to aid in detection and classification of diseased tissues. Radio frequency signals backscattered from tissues can be modeled according to the assumed shape, size, and distribution of Scatterers in tissues. Power spectra of rf backscattered signals describe the frequency dependence of Scatterers. Experimental measurements of ultrasonic backscatter from spontaneous mammary tumors in rats are obtained over the frequency range of 4 to 12 MHz. The power spectra measured from rat tumors are compared to theoretical power spectra derived from a 3D spatial autocorrelation function assuming a Gaussian distribution. Independent values of average scatterer diameter and acoustic concentration are obtained by approximating the measured power spectrum with a best-fit line. Enhanced B-mode images are made of the rat tumors and surrounding tissues with superimposed regions of interest quantified by estimated average scatterer sizes a...
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characterization of tissue microstructure using ultrasonic backscatter theory and technique for optimization using a gaussian form factor
Journal of the Acoustical Society of America, 2002Co-Authors: Michael L. Oelze, James F. Zachary, William D ObrienAbstract:Characterization of tissue microstructure through ultrasonic backscatter is hypothesized to aid in detection and classification of diseased tissues. Radio frequency signals backscattered from tissues can be modeled according to the assumed shape, size, and distribution of Scatterers in tissues. Power spectra of rf backscattered signals describe the frequency dependence of Scatterers. Experimental measurements of ultrasonic backscatter from spontaneous mammary tumors in rats are obtained over the frequency range of 4 to 12 MHz. The power spectra measured from rat tumors are compared to theoretical power spectra derived from a 3D spatial autocorrelation function assuming a Gaussian distribution. Independent values of average scatterer diameter and acoustic concentration are obtained by approximating the measured power spectrum with a best-fit line. Enhanced B-mode images are made of the rat tumors and surrounding tissues with superimposed regions of interest quantified by estimated average scatterer sizes and acoustic concentrations. Scattering properties estimated inside the tumors and in surrounding tissues are shown to be distinct. Overall, estimates showed a 44.8% increase of average scatterer diameter inside the tumor as compared to tissues outside the tumor. With the exception of one rat, all estimates of the Scatterers' average acoustic concentration inside the tumor were less than outside the tumors.
Hean-teik Chuah - One of the best experts on this subject based on the ideXlab platform.
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A Study of Fresenel Scattered Field for Non-Spherical Discrete Scatterers - Abstract
Journal of Electromagnetic Waves and Applications, 2012Co-Authors: Hean-teik ChuahAbstract:Scattering from a non-spherical scatterer at microwave frequency has always been an interesting electromagnetic problem. In this paper, the Fresnel zone scattered field of three types of non-spherical discrete Scatterers, namely disks, needles and cylinders, are studied. Scatterers of these shapes are commonly used to model the leaves, branches and trunks of vegetation canopy. Conventionally, a far field approximation of the scattered fields from these Scatterers is applied in the microwave scattering models to account for the interactions among the Scatterers. However, when the Scatterers are in the Fresnel zone of one another, it is necessary to consider the additional interaction effect among the Scatterers. This effect is considered by including two types of corrections into the far field scattered fields of these Scatterers : amplitude correction and Fresnel phase correction. The amplitude correction is considered by including the near field amplitude term of the scattererd fields whereas the Fresnel...
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A Study of Fresnel Scattered Fields for Ellipsoidal and Elliptic-Disk-Shaped Scatterers
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Jun Yi Koay, Hean-teik ChuahAbstract:The study of scattered fields from nonspherical Scatterers is becoming an important subject particularly in the area of theoretical modeling of microwave backscatter from vegetation. The generalized Rayleigh-Gans approximation has been widely used in the calculation of scattered fields from Scatterers where at least one of its dimensions is comparably smaller than the wavelength. In such calculations, far-field approximations are used, which are not accurate when the observation points are in the Fresnel and near-field regions of the scatterer. Hence, the effects of Fresnel phase and amplitude corrections for the scattered field of circular disks, needles, and cylinders have been examined and shown to be significant in the calculation of closely spaced Scatterers. However, the effects of Fresnel corrections in the scattered fields from general ellipsoids and elliptic disks have not yet been studied. In this paper, the scattered fields from general ellipsoids and elliptic disks are formulated based on the generalized Rayleigh-Gans approximation for cases with and without Fresnel corrections. Theoretical analysis shows that the Fresnel effects are important particularly at larger frequencies and at the null locations in the plots of the backscattering cross section. These effects become more important as the ellipticity of the scatterer increases. Comparisons with measurement data demonstrate that the calculated results with Fresnel corrections provide a better match compared with those without.
Smail Tedjini - One of the best experts on this subject based on the ideXlab platform.
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Design rules for chipless RFID tags based on multiple Scatterers
annals of telecommunications - annales des télécommunications, 2013Co-Authors: Arnaud Vena, Etienne Perret, Smail TedjiniAbstract:In this paper, we present some design rules to create a chipless RFID tag that encodes the information in the frequency domain. Some criterions are introduced to make the best choice concerning the elementary Scatterers that act like signal processing antennas. The performance of several Scatterers will be compared before a study on the radiating properties of a versatile C-like scatterer. An electrical model as well as a transfer function model is presented to best understand the frequency response of both a single-layer and a grounded scatterer. An example of the design and the optimization of a chipless RFID tag based on the use of multiple Scatterers are provided, and the frequency optimization step for each resonant peak will be discussed.
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Design rules for chipless RFID tags based on multiple Scatterers
Annals of Telecommunications - annales des télécommunications, 2013Co-Authors: Arnaud Vena, Etienne Perret, Smail TedjiniAbstract:In this paper, we present some design rules to create a chipless RFID tag that encodes the information in the frequency domain. Some criterions are introduced to make the best choice concerning the elementary Scatterers that act like signal processing antennas. The performance of several Scatterers will be compared before a study on the radiating properties of a versatile C-like scatterer. An electrical model as well as a transfer function model is presented to best understand the frequency response of both a single-layer and a grounded scatterer. An example of the design and the optimization of a chipless RFID tag based on the use of multiple Scatterers are provided, and the frequency optimization step for each resonant peak will be discussed. [References: 27]
