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Chi-wang Shu - One of the best experts on this subject based on the ideXlab platform.

  • A shock-Fitting Algorithm for the Lighthill–Whitham–Richards model on inhomogeneous highways
    Transportmetrica, 2011
    Co-Authors: Wenjun Sun, Sze Chun Wong, Peng Zhang, Chi-wang Shu
    Abstract:

    The analytical shock-Fitting Algorithm outperforms traditional numerical methods in solving the Lighthill–Whitham–Richards (LWR) traffic flow model for homogeneous highways. In this study, we extend the Algorithm to an inhomogeneous highway in which two homogeneous sections with different fundamental diagrams are connected by a junction (interface). According to the entropy condition of the Riemann problem, the flow conditions at the interface can be categorized into four groups, and the density on both sides of the interface can be uniquely determined. Based on the physical conditions, we construct a fictitious element as an appropriate boundary condition for each homogeneous section. Consequently, the Riemann problem of an inhomogeneous highway can be transformed into a problem of equivalent homogeneous sections to which the shock-Fitting Algorithm can be applied. We apply this Algorithm to some representative traffic flow cases and compare the results with numerical solutions obtained using the Weighte...

  • Efficient implementation of the shock‐Fitting Algorithm for the Lighthill–Whitham–Richards traffic flow model
    International Journal for Numerical Methods in Engineering, 2008
    Co-Authors: Wenqin Chen, Sze Chun Wong, Chi-wang Shu
    Abstract:

    This paper firstly presents the existence and uniqueness properties of the intersection time between two neighboring shocks or between a shock and a characteristic for the analytical shock-Fitting Algorithm that was proposed to solve the Lighthill-Whitham-Richards (LWR) traffic flow model with a linear speed-density relationship in accordance with the monotonicity properties of density variations along a shock, which have greatly improved the robustness of the analytical shock-Fitting Algorithm. Then we discuss the efficient evaluation of the measure of effectiveness (MOE) of the analytical shock-Fitting Algorithm. We develop explicit expressions to calculate the MOE-which is the total travel time that is incurred by travelers, within the space-time region that is encompassed by the shocks and/or characteristic lines. A numerical example is used to illustrate the effectiveness and efficiency of the proposed method compared with the numerical solutions that are obtained by a fifth-order weighted essentially non-oscillatory scheme.

Pedro M. Ramos - One of the best experts on this subject based on the ideXlab platform.

  • Implementation of a least-squares multi-harmonic Fitting Algorithm in the multicore cell processor
    2012 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2012
    Co-Authors: José Maria Santos, Pedro M. Ramos
    Abstract:

    Least squares (LS) methods minimize the LS error between a specific data model and an acquired data set. This is the case of sine-Fitting Algorithms, which are used to determine the sine wave parameters that best fit an acquired signal. In the case of signals with multiple harmonics, one can use a multi-harmonic Fitting Algorithm resembling the sine-Fitting Algorithm to estimate the amplitudes and phases of the harmonics. This paper describes the implementation of a LS multi-harmonic Fitting Algorithm using the multicore Cell processor to determine the fundamental frequency of a multi-harmonic signal and then the harmonic amplitudes and phases.

  • Impedance measurement using multiharmonic least-squares waveform Fitting Algorithm
    Computer Standards & Interfaces, 2008
    Co-Authors: Pedro M. Ramos, A. Cruz Serra
    Abstract:

    In this paper, a multiharmonic least-squares waveform Fitting Algorithm is used to measure impedances. By using analog to digital converters, a function generator, a reference impedance and the Fitting Algorithm, we show that it is possible to obtain the frequency response of a unknown linear impedance at the frequencies that correspond to the harmonics of the stimulus input signal. Results show that, with a 400 Hz triangular signal, harmonics up to the 49th can be used to measure the impedance frequency response of a parallel RLC circuit with experimental standard deviations below 1.5% for the impedance magnitude and 1^o for the impedance phase.

  • Convergence of Least-Squares Multi-Harmonic Fitting Algorithm
    2006 IEEE Instrumentation and Measurement Technology Conference Proceedings, 2006
    Co-Authors: Pedro M. Ramos, A. Cruz Serra
    Abstract:

    Digital signal processing Algorithms are becoming increasingly attractive for instrumentation systems. Their robustness combined with increased processing capabilities of DSPs will enable the development of a new brand of low cost flexible instrumentation. These instruments will implement different Algorithms for each measurement need. Sine-Fitting Algorithms estimate the sinewave parameters of a digitized signal. They can be used to characterize analog to digital converters, measure impedances and test the frequency response of linear systems. In this paper, the convergence of the least-squares multi-harmonic Fitting Algorithm is analyzed. Simple improvements are presented to increase convergence and minimize the number of iterations.

  • Impedance Measurement using a Least-Squares Waveform Fitting Algorithm
    2004 Conference on Precision Electromagnetic Measurements, 2004
    Co-Authors: Pedro M. Ramos, Fonseca M. Da Silva, Cruz A. Serra
    Abstract:

    A waveform Fitting Algorithm is used to measure the frequency response of a linear impedance. This method is capable of determining the harmonic amplitudes of a triangular signal up to the 50th harmonic. Amplitudes 80dB below the fundamental can be measured by using a 16-bit analogue to digital converter (ADC)

Sze Chun Wong - One of the best experts on this subject based on the ideXlab platform.

  • A shock-Fitting Algorithm for the Lighthill–Whitham–Richards model on inhomogeneous highways
    Transportmetrica, 2011
    Co-Authors: Wenjun Sun, Sze Chun Wong, Peng Zhang, Chi-wang Shu
    Abstract:

    The analytical shock-Fitting Algorithm outperforms traditional numerical methods in solving the Lighthill–Whitham–Richards (LWR) traffic flow model for homogeneous highways. In this study, we extend the Algorithm to an inhomogeneous highway in which two homogeneous sections with different fundamental diagrams are connected by a junction (interface). According to the entropy condition of the Riemann problem, the flow conditions at the interface can be categorized into four groups, and the density on both sides of the interface can be uniquely determined. Based on the physical conditions, we construct a fictitious element as an appropriate boundary condition for each homogeneous section. Consequently, the Riemann problem of an inhomogeneous highway can be transformed into a problem of equivalent homogeneous sections to which the shock-Fitting Algorithm can be applied. We apply this Algorithm to some representative traffic flow cases and compare the results with numerical solutions obtained using the Weighte...

  • Efficient implementation of the shock‐Fitting Algorithm for the Lighthill–Whitham–Richards traffic flow model
    International Journal for Numerical Methods in Engineering, 2008
    Co-Authors: Wenqin Chen, Sze Chun Wong, Chi-wang Shu
    Abstract:

    This paper firstly presents the existence and uniqueness properties of the intersection time between two neighboring shocks or between a shock and a characteristic for the analytical shock-Fitting Algorithm that was proposed to solve the Lighthill-Whitham-Richards (LWR) traffic flow model with a linear speed-density relationship in accordance with the monotonicity properties of density variations along a shock, which have greatly improved the robustness of the analytical shock-Fitting Algorithm. Then we discuss the efficient evaluation of the measure of effectiveness (MOE) of the analytical shock-Fitting Algorithm. We develop explicit expressions to calculate the MOE-which is the total travel time that is incurred by travelers, within the space-time region that is encompassed by the shocks and/or characteristic lines. A numerical example is used to illustrate the effectiveness and efficiency of the proposed method compared with the numerical solutions that are obtained by a fifth-order weighted essentially non-oscillatory scheme.

A. Cruz Serra - One of the best experts on this subject based on the ideXlab platform.

  • Impedance measurement using multiharmonic least-squares waveform Fitting Algorithm
    Computer Standards & Interfaces, 2008
    Co-Authors: Pedro M. Ramos, A. Cruz Serra
    Abstract:

    In this paper, a multiharmonic least-squares waveform Fitting Algorithm is used to measure impedances. By using analog to digital converters, a function generator, a reference impedance and the Fitting Algorithm, we show that it is possible to obtain the frequency response of a unknown linear impedance at the frequencies that correspond to the harmonics of the stimulus input signal. Results show that, with a 400 Hz triangular signal, harmonics up to the 49th can be used to measure the impedance frequency response of a parallel RLC circuit with experimental standard deviations below 1.5% for the impedance magnitude and 1^o for the impedance phase.

  • Convergence of Least-Squares Multi-Harmonic Fitting Algorithm
    2006 IEEE Instrumentation and Measurement Technology Conference Proceedings, 2006
    Co-Authors: Pedro M. Ramos, A. Cruz Serra
    Abstract:

    Digital signal processing Algorithms are becoming increasingly attractive for instrumentation systems. Their robustness combined with increased processing capabilities of DSPs will enable the development of a new brand of low cost flexible instrumentation. These instruments will implement different Algorithms for each measurement need. Sine-Fitting Algorithms estimate the sinewave parameters of a digitized signal. They can be used to characterize analog to digital converters, measure impedances and test the frequency response of linear systems. In this paper, the convergence of the least-squares multi-harmonic Fitting Algorithm is analyzed. Simple improvements are presented to increase convergence and minimize the number of iterations.

Wenqin Chen - One of the best experts on this subject based on the ideXlab platform.

  • Efficient implementation of the shock‐Fitting Algorithm for the Lighthill–Whitham–Richards traffic flow model
    International Journal for Numerical Methods in Engineering, 2008
    Co-Authors: Wenqin Chen, Sze Chun Wong, Chi-wang Shu
    Abstract:

    This paper firstly presents the existence and uniqueness properties of the intersection time between two neighboring shocks or between a shock and a characteristic for the analytical shock-Fitting Algorithm that was proposed to solve the Lighthill-Whitham-Richards (LWR) traffic flow model with a linear speed-density relationship in accordance with the monotonicity properties of density variations along a shock, which have greatly improved the robustness of the analytical shock-Fitting Algorithm. Then we discuss the efficient evaluation of the measure of effectiveness (MOE) of the analytical shock-Fitting Algorithm. We develop explicit expressions to calculate the MOE-which is the total travel time that is incurred by travelers, within the space-time region that is encompassed by the shocks and/or characteristic lines. A numerical example is used to illustrate the effectiveness and efficiency of the proposed method compared with the numerical solutions that are obtained by a fifth-order weighted essentially non-oscillatory scheme.