An urban scene has very complex variety of length scales ranging from much larger to much smaller than the wavelength of the radiation emitted by a Synthetic Aperture Radar (SAR). The exact solution to this scattering problem requires the solution of Maxwell's equations for the combination of source and scattering objects present in the scene, which for any reasonable size target area is computationally too intensive to be realistic. Hence while a 'numerically exact' solution at present is not possible, some form of approprite modeffing scheme is used as is usual in electromagnetic problems.The geometrical theory of diffraction (GTD) gives an accurate result with a practical amount of computation. This theory is based on the fact that the most important contributions towards the scattered field come from an area in the neighbourhood of some critical points on the scattering surface. For a planar surface, three critical points may be regarded: specular, edge-diffraction and corner-diffraction points. A physical optics version of GTD was taken with the approximate diffraction coefficients derived using physical optics approximations to canonical problems.In this paper, the new model is described in addition to an overview of a ray-tracing procedure adopted and its resultant images.
An urban scene has a very complex variety oflength scales ranging from much bigger to much smaller than the wavelength of the radiation emitted by a Synthetic Aperture Radar (SAR). The exact solution to this scattering problem requires the solution of Maxwell's equations for the combination of source and scattering objects present in the scene, which for any reasonable size target area is computationally too large to be realistic. Hence a 'numerically exact' solution is ruled out, but, as is usual in electromagnetic problems some form of appropriate modeffing scheme is used.In this case we assume that the major contributors to the scattering are the planar surfaces which are generally many times larger than the wavelength of the radiation used. A geometrical optics ray-tracing approach is employed to calculate the incident field on each surface illuminated by the radar system whether by direct or indirect illumination (multiple bounces within the target environment goemetry). In this way the large amount of multiple scatter that arises from the combination of dihedral and trihedral corners associated with buildings is taken into account. The intensity or amplitude and polarisation characteristics of the radiation returning to the radar can be calculated by applying the Rayleigh-Rice scattering theory at each surface.
A hot-issued research topic in the workflow intelligence arena is the emerging topic of "workflow-supported organizational social networks." These specialized social networks have been proposed to primarily represent the process-driven work-sharing and work-collaborating relationships among the workflow-performers fulfilling a series of workflow-related operations in a workflow-supported organization. We can discover those organizational social networks, and visualize its analysis results as organizational knowledge. In this paper, we are particularly interested in how to visualize the degrees of closeness centralities among workflow-performers by proposing a graphical representation schema based on the Graph Markup Language, which is named to ccWSSN-GraphML. Additionally, we expatiate on the functional expansion of the closeness centralization formulas so as for the visualization framework to handle a group of workflow procedures (or a workflow package) with organizational workflow-performers.
In previous papers {1] [2], a ray-tracing modelfor urban SAR imaging and simulation was described in which a physical optics extension of the geometrical theory of diffraction (GTD) was used to include diffraction returns in calculating the specular backscatter from the scene.This theory is based on that the most important contributions towards the scattered field come from an area in the neighbourhood of some critical points on the scattering surface. For a planar surface, three critical points may be regarded: specular, edge-diffraction and corner-diffraction points. A physical optics version of PoGTD was taken with the approximate diffraction coefficients derived using physical optics approximations to canonical problems.The results from the simulator are examined and validated by comparing them with theoretical and experimental results calculated and found in an annerchaic chamber using simple targets. The objects were chosen to cover different combination of the critical points, i.e. specular, edge-and vertex-diffraction which contribute towards the backscattered field. For both set of data the co-polarised data (HH and VV) are presented and compared.
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