Browsing by Subject "Shape"

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    ItemOpen Access
    Development of an iterative learning controller for polymer based micro-stereolithography prototyping systems
    (IEEE, 2016) Türeyen, Erkan Buğra; Karpat, Yiğit; Çakmakcı, Melih
    Additive manufacturing has become increasingly popular for a wide range of applications in recent years. Micro-stereolithography (μSLA) is a popular method for obtaining polymer-based parts. Systems using the μSLA approach usually consist of a vertical positioning system, a light source and a container where the component is built gradually as the polymer is cured at the locations where the ultraviolet light is projected. It has been noted that the motion of the positioning system and the intensity of the light source is an important factor to achieve high level dimensional precision. In this paper a three dimensional error based learning scheme is presented to improve the time varying process parameters of the system so that the dimensional accuracy of the product is improved. A mathematical model of the curing process is used for developing the error based learning algorithm. The current process parameters as a function of time and the dimensional error obtained at each layer of the production are used for increasing the quality and precision of the same part in the next iteration. Our initial simulation results show significant improvements can be obtained in a few iterations if the correct learning parameters are used based on the target parts dimensional properties.
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    ItemOpen Access
    European collaboration in conformal antenna research
    (IEEE, 2007-09) Sipus, Z.; Persson P.; Lanne, M.; Heckler, M.; Maci, S.; Campos, J. L. M.; Knott, P.; Ertürk, Vakur; Vandenbosch, G.
    The work carried out within Work Package 2.4-3 of the EU network "Antenna Centre of Excellence" (ACE) is presented in this paper. This work package is concerned with structuring research on conformal antennas. In more details, the work is focused on the problems associated with full benchmarking of conformal antennas, on development of hybrid programs for analyzing different classes of conformal antennas, and on investigation of properties of algorithms for optimizing beam synthesis and beam-steering for conformal arrays.
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    ItemOpen Access
    Preconditioned MLFMA solution of multiple dielectric-metallic composite objects with the electric and magnetic current combined-field integral equation (JMCFIE)
    (IEEE, 2009-06) Ergül, Özgür; Gürel, Levent
    We consider fast and accurate solutions of scattering problems involving multiple dielectric and composite dielectric-metallic structures with three-dimensional arbitrary shapes. Problems are formulated rigorously with the electric and magnetic current combined-field integral equation (JMCFIE), which produces well-conditioned matrix equations. Equivalent electric and magnetic surface currents are discretized by using the Rao-Wilton-Glisson (RWG) functions defined on planar triangles. Matrix equations obtained with JMCFIE are solved iteratively by employing a Krylov subspace algorithm, where the required matrix- vector multiplications are performed efficiently with the multilevel fast multipole algorithm (MLFMA). We also present a four-partition block-diagonal preconditioner (4PBDP), which provides efficient solutions of JMCFIE by reducing the number of iterations significantly. The resulting implementation based on JMCFIE, MLFMA, and 4PBDP is tested on large electromagnetics problems.