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  • DSC'2001:An integrated system for the whole design process of driving simulation experiments.

    Coma, Inmaculada; Fernández, Marcos; Pollock, Donna; Pareja, Ignacio; Rueda, Silvia

    (2001). Article

    Estructuras de datos para el diseño de ejercicios en simulación de conducción. The use of driving simulators in research provides researchers with a tool that combines the advantages of control in the presentation of driving scenarios, experimental situations, and critical events as well as precision in the measurement of driving performance. In addition, many risk factors that would be dangerous to reproduce in a real driving context, can be safely studied in a simulator.

  • A Discrete Model for the Dynamics of Sandpile Surfaces

    garcía Fernández, I.; Pla Castells, M.; Martínez Durá, R. J.

    (2001). Article

    Proceedings of the Industrial Simulation Conference 2007, 64-68 A new Cellular Automata model for the dynamics of sandpile surfaces is presented in this work. Following the BCRE model (Bouchaud et al., 1994) main ideas, we propose the use of two variables, instead of only the one that has been used in Cellular Automata models so far. The model predicts sandpile properties observed in other models, and in real systems, such as slope roughness decay or uphill propagation of avalanches. In addition, the introduction of the second variable allows the prediction of characteristics, such as the appearance of a second critical angle, that have been predicted by continuous models. The main...

    Proceedings of the Industrial Simulation Conference 2007, 64-68 A new Cellular Automata model for the dynamics of sandpile surfaces is presented in this work. Following the BCRE model (Bouchaud et al., 1994) main ideas, we propose the use of two variables, instead of only the one that has been used in Cellular Automata models so far. The model predicts sandpile properties observed in other models, and in real systems, such as slope roughness decay or uphill propagation of avalanches. In addition, the introduction of the second variable allows the prediction of characteristics, such as the appearance of a second critical angle, that have been predicted by continuous models. The main advantage of the proposed model is that its formulation is simpler and easier to interpret than that of the continuous models. Also, the resulting numerical scheme is simpler and more efficient, allowing for a wider range of applications, including interactive simulation.

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  • Efficient Quantization for Overcomplete Expansions in

    Beferull-Lozano, B.; ortega, A.

    (2001). Article

    The use of quantized redundant expansions is useful in applications where the cost of having oversampling in the representation is much lower than the use of a high-resolution quantization (e.g., oversampled A/D). Most work to date has assumed that simple uniform quantization was used on the redundant expansion and then has dealt with methods to improve the reconstruction. Instead, we consider the design of quantizers for overcomplete expansions. Our goal is to design quantizers such that simple reconstruction algorithms (e.g., linear) provide as good reconstructions as with more complex algorithms. We achieve this goal by designing quantizers with different step sizes for each coefficient...

    The use of quantized redundant expansions is useful in applications where the cost of having oversampling in the representation is much lower than the use of a high-resolution quantization (e.g., oversampled A/D). Most work to date has assumed that simple uniform quantization was used on the redundant expansion and then has dealt with methods to improve the reconstruction. Instead, we consider the design of quantizers for overcomplete expansions. Our goal is to design quantizers such that simple reconstruction algorithms (e.g., linear) provide as good reconstructions as with more complex algorithms. We achieve this goal by designing quantizers with different step sizes for each coefficient of the expansion in such a way as to produce a quantizer with periodic structure.

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  • Construction of Low Complexity Regular Quantizers for Overcomplete Expansions in R^n

    Beferull-Lozano, B.; Ortega, A.

    (2001). Article

    We study the construction of structured regular quantizers for overcomplete expansions in RN. Our goal is to design structured quantizers allowing simple reconstruction algorithms with low (memory and computational) complexity and having good performance in terms of accuracy. Most related work to date in quantized redundant expansions has assumed that uniform scalar quantization with the same stepsize was used on the redundant expansion and then has dealt with more complex methods to improve the reconstruction. Instead, we consider the design of scalar quantizers with different stepsizes for each coefficient of an overcomplete expansion in such a way as to produce an equivalent vector...

    We study the construction of structured regular quantizers for overcomplete expansions in RN. Our goal is to design structured quantizers allowing simple reconstruction algorithms with low (memory and computational) complexity and having good performance in terms of accuracy. Most related work to date in quantized redundant expansions has assumed that uniform scalar quantization with the same stepsize was used on the redundant expansion and then has dealt with more complex methods to improve the reconstruction. Instead, we consider the design of scalar quantizers with different stepsizes for each coefficient of an overcomplete expansion in such a way as to produce an equivalent vector quantizer with periodic structure. The periodicity makes it possible to achieve good accuracy using simple reconstruction algorithms from the quantized coefficients of the overcomplete expansion.

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  • LNCIS:An Architecture for Optimal Management of The Traffic Simulation Complexity in a Driving Simulator

    Fernández, Marcos; Martín, Gregorio; Coma, Inmaculada; Bayarri, Salvador

    (1999). Article

    Arquitectura para gestión de tráfico en simuladores de conducción.

  • Coding Techniques for Oversampled Steerable Transforms

    Beferull-Lozano, B.; Ortega, A.

    (1999). Article

    In this paper we study signal representation using oversampled steerable transforms. While in general it may not be efficient to use an oversampled representation for applications like compression, our work investigates efficient techniques for representing the oversampled data, given that after oversampling there exists substantial redundancy. We discuss different strategies which take advantage of this oversampling by establishing some consistency constraints on the representation that reduce uncertainty in the quantization. This results in a coding gain as we increase the oversampling in the steerable transform (number of orientations). Thus, while in general it will not be possible to...

    In this paper we study signal representation using oversampled steerable transforms. While in general it may not be efficient to use an oversampled representation for applications like compression, our work investigates efficient techniques for representing the oversampled data, given that after oversampling there exists substantial redundancy. We discuss different strategies which take advantage of this oversampling by establishing some consistency constraints on the representation that reduce uncertainty in the quantization. This results in a coding gain as we increase the oversampling in the steerable transform (number of orientations). Thus, while in general it will not be possible to achieve as good compression performance as with a critically sampled transform, having a compressed steerable representation will be useful for applications where a feature is needed (many significant image features can be extracted from an orientation analysis), and where for performance reasons it is preferable not to have to decompress and analyze each image (as may be necessary if standard non-steerable transforms are used for compression).

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