نتایج جستجو برای: backscatter media
تعداد نتایج: 285634 فیلتر نتایج به سال:
Ice sphere backscatter has been calculated using both Mie theory and the discrete dipole approximation (DDA) at a wavelength of 3.2 mm (94 GHz). The electric dipole, magnetic dipole and electric quadrupole contributions to spherical particle backscatter have been analyzed. The results show that there is a resonance area around particle size parameter of 1.5, where the calculated backscatter err...
Simple scattering media fit scattering model theories much better than more complex scattering media. Tissue is much more complex as an acoustic scattering media and to date there has not been an adequate scattering model that fits it well. Previous studies evaluated the scattering characteristics of simple media (grouping of cells at various number densities) and fit them to the concentric sph...
Methods for processing multibeam echo-sounder (MBES) bathymetry data are well established, however, there is no universal and established approach to processing and interpretation of MBES backscatter data. The aim of this paper is to (1) detail the different backscatter logging methods implemented in modern high-frequency MBES systems used primarily in shallow water; (2) describe and suggest ap...
Multibeam sonar (MBS) systems are recognised as one of the most effective tools available to map and characterise the seafloor as they can provide co-located high-resolution bathymetry and acoustic backscatter characteristics from a wide swath across a vessel’s track. While the production of bathymetry maps from MBS is well developed, processing and analysis of MBS backscatter data has not yet ...
Many biological and physical factors potentially affect target strength. While these sources have been identified, few studies have compared the relative effects of individual factors. Modelled and measured target strengths in non-dimensional metrics were used to compare and rank the effects of fish length, tilt, depth, and acoustic frequency on backscatter intensity. Ex situ measurements of ta...
To investigate the independent effect of myocardial wall thickness and myocardial perfusion pressure on integrated backscatter, experiments were designed in which integrated backscatter of normally perfused myocardial tissue was measured while changes in wall thickness during the cardiac cycle were reduced to a minimum. In nine blood-perfused isolated pig hearts, perfusion pressure was uncouple...
Interferometric techniques allow the SuperDARN coherent HF radars to determine the elevation angles of returned backscatter, giving information on the altitude of the scatter volume, in the case of ionospheric backscatter, or the reflection altitude, in the case of ground backscatter. Assumptions have to be made in the determination of elevation angles, including the direction of arrival, or az...
Full-waveform airborne laser scanning has shown potential to better describe land cover features through the additional physical information it can provide alongside the standard geometric information. To fully utilize full-waveform for enhanced object recognition and feature extraction, it is essential to calibrate the backscattered energy of the received signal. The backscatter signal is affe...
Two-dimensional echocardiography is an excellent technique for detecting left ventricular thrombi, however, acute clot is sometimes difficult to differentiate from adjacent myocardium and intracavitary signals. We hypothesized that quantitative assessment of the acoustic properties of acute left ventricular thrombi using a quantitative backscatter imaging system would permit the differentiation...
We have recently shown that the cardiac cycle-dependent variation in myocardial ultrasonic integrated backscatter is blunted with regional ischemia in dogs. To determine if global and intramural regional myocardial contractile performance can be quantified by integrated backscatter, we analyzed ultrasonic responses after induction of increased and decreased contractility in five dogs. A recentl...
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