Spectral processing algorithms employed in millimeter-wave profiling radars typically obtain good signal-to-noise ratios from weakly scattering clouds by incoherently averaging many spectra. Radar operating characteri...
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Spectral processing algorithms employed in millimeter-wave profiling radars typically obtain good signal-to-noise ratios from weakly scattering clouds by incoherently averaging many spectra. Radar operating characteristics dictate sampling times on the order of a few seconds. Presented here are analyses showing that changes in the vertical wind during the sampling period can be a major contributor to the measured spectrum width. Such broadened spectra violate the assumptions made in spectral inversion techniques, and may lead to incorrect interpretations of the turbulent and microphysical characteristics of the radar volume. Moreover, it is shown that there are several factors involved in determining the measured spectral shape: the averaging time window and horizontal advection velocity of the cloud, as well as horizontal inhomogeneities in cloud vertical velocity and microphysical fields. Current processing algorithms do not allow for distinction between these effects, leading to potential for large errors in retrievals. In this paper a simple technique is presented to remove this effect for monomodal spectra. A side product of this algorithm is high temporal resolution estimates of the volume-mean vertical wind.
Laser speckle techniques are well known in the non-destructive evaluation community(1-4). One particular application is to infer strain by monitoring the motion of the speckle pattern that results from coherently illu...
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ISBN:
(纸本)0819435309
Laser speckle techniques are well known in the non-destructive evaluation community(1-4). One particular application is to infer strain by monitoring the motion of the speckle pattern that results from coherently illuminating the object. Typically a reference image of the speckle pattern is acquired before deformation of the object. Motion (with respect to this reference image) of subsequent speckle patterns, which occurs when the object is stressed, are used to infer the resulting strain. A problem experienced in using this technique for measurements of hydrated tissues is the rapid decorrelation of the speckle patterns'. Thus, application of speckle techniques to assessment of strain in biological tissues relies on rapid sampling of the speckle patterns and the use of processing algorithms that are aimed at inferring strain rates rather than absolute strains. We discuss a number of approaches to estimating strain rates based on sequential speckle patterns. Maximum likelihood methods are shown to be especially useful.
The parameter values for a Navy's IRST (Infrared Search and Track) sensor are determined by 1) the operational requirements, 2) the available best technology, and 3) past experience with IRST system design. The se...
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ISBN:
(纸本)0819424765
The parameter values for a Navy's IRST (Infrared Search and Track) sensor are determined by 1) the operational requirements, 2) the available best technology, and 3) past experience with IRST system design. The selection process for the parameter values is illustrated by use of a set of operational requirements representative of the North Sea. Initial values of the optics parameters are determined by use of a design diagram. The approximate sensor parameter values are input to the TEDIS design computer algorithm for optimization. The effectiveness of the false-alarm reduction algorithms will depend on some of the sensor parameter values, The final assessment of these values can therefore be made only after performance resting of the algorithms. The design of a combined radiometer - IRST testbed, the SIRDAS, is outlined, This system is used for measuring high quality target and clutter data in the potential battlefields, This data is essential for testing and fine-tuning of the all-important false alarm reduction algorithms.
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