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Function Interpolation (function + interpolation)

Distribution by Scientific Domains

Engineering	75%

Selected Abstracts

Building channel networks for flat regions in digital elevation models

HYDROLOGICAL PROCESSES, Issue 20 2009
Hua Zhang
Abstract Digital elevation models (DEMs) are data sources for distributed rainfall,runoff modelling in terms of providing the channel network for a watershed of interest. Assigning flow directions over flat regions is an important issue in the field of DEM processing and extraction of drainage features. Existing methods cannot fully incorporate the information of known drainage features and terrain surrounding the flat region. This study presented a hydrological correction method that integrates topographic information from different sources to interpolate a convergent surface. It employs radial basis function interpolation to determine elevation increment at every position, utilizes data of digital channel network, incorporates elevation in the surrounding terrain, and ensures a convergent channel network while minimizing the impact of correction on the original DEM. The method can be easily implemented in geographic information system (GIS) environment. It was applied to the DEM of the Heshui Watershed, China. The extracted channel network was visually inspected and quantitatively assessed through analysing the flow direction raster. Results showed that the channel network generated by the hydrological correction was consistent with the known drainage features and contained less parallel channels comparing with the results from two existing methods. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Modeling of microwave devices with space mapping and radial basis functions

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2008
Slawomir Koziel
Abstract We review recent developments in space mapping techniques for modeling of microwave devices. We present a surrogate modeling methodology that utilizes space mapping combined with radial basis function interpolation. The method has advantages both over the standard space mapping modeling methodology and the recently published space mapping modeling with variable weight coefficients. In particular, it provides accuracy comparable or better than the latter method and computational efficiency as good as the standard space mapping modeling procedure. A comparison between the space mapping modeling methodologies as well as application examples of optimization and statistical analysis of microwave structures is presented. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Green's function interpolations for prestack imaging

GEOPHYSICAL PROSPECTING, Issue 1 2000
Manuela Mendes
A new interpolation method is presented to estimate the Green's function values, taking into account the migration/inversion accuracy requirements and the trade-off between resolution and computing costs. The fundamental tool used for this technique is the Dix hyperbolic equation (DHE). The procedure, when applied to evaluate the Green's function for a real source position, uses the DHE to derive the root-mean-square velocity, vRMS, from the precomputed traveltimes for the nearest virtual sources, and by linear interpolation generates vRMS for the real source. Then, by applying the DHE again, the required traveltimes and geometrical spreading can be estimated. The inversion of synthetic data demonstrates that the new interpolation yields excellent results which give a better qualitative and quantitative resolution of the imaging sections, compared with those carried out by conventional linear interpolation. Furthermore, the application to synthetic and real data demonstrates the ability of the technique to interpolate Green's functions from widely spaced virtual sources. Thus the proposed interpolation, besides improving the imaging results, also reduces the overall CPU time and the hard disk space required, hence decreasing the computational effort of the imaging algorithms. [source]

STEERING A MOBILE ROBOT: SELECTION OF A VELOCITY PROFILE SATISFYING DYNAMICAL CONSTRAINTS

ASIAN JOURNAL OF CONTROL, Issue 4 2000
M.A. Benayad
ABSTRACT We present an open loop control design allowing to steer a wheeled mobile robot along a prespecified smooth geometric path, minimizing a given cost index and satisfying a set of dynamical constraints. Using the concept of "differential flatness," the problem is equivalent to the selection of the optimal time parametrization of the geometric path. This parametrization is characterized by a differential equation involving a function of the curvilinear coordinate along the path. For the minimum time problem, as well as for another index (such as the maximum value of the centripetal acceleration) to be minimized over a given time interval, the problem then reduces to the optimal choice of this function of the curvilinear coordinate. Using spline functions interpolation, the problem can be recast as a finite parameter optimization problem. Numerical simulation results illustrate the procedure. [source]