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Matched filter concepts are extensively used in radar applications to maximise target detection. Usually, the receiver filter is matched to the transmitted signal, which is optimum for a point target return. For extended targets it is possible to do better by matching with the returned target signal. However, in most cases, the returned target signal is not known a priori. The authors propose a method...
The geometry of inverse synthetic aperture radar (ISAR) imaging suggests in principle a tomographic approach to the reconstruction of a 2D projection of an object illuminated by a radar signal. In theory this is straight forward, but the computational load of such reconstructions have in stead led to the use of fast Fourier transforms (FFTs) on a Cartesian grid. Using FFTs directly in ISAR imaging...
Shadow cast by features on ground can be an important aid in object classification in synthetic aperture radar (SAR) images. Synthetic aperture imaging causes a fundamental limitation to shadow clarity due to the fact that the illuminator is moved during the data collection. This leads to a blend of echo and shadow, or geometrical fill-in in the shadow region. The fill-in is most dominant for wide...
SummaryBackground The evacuation of emergency cases by air, usually by helicopter, is controversial because of the cost of the programme, the possibility of an accident (especially in an urban area), and unproven benefit. But such evacuations cannot be studied by a random intervention (eg, air versus ground ambulance). We used an expert-panel approach to estimate the health outcome for patients transferred...
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