The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Weidong Hu - One of the best experts on this subject based on the ideXlab platform.

  • pseudo maximum likelihood estimation of ballistic missile Precession Frequency
    Signal Processing, 2012
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    In order to estimate a ballistic missile Precession Frequency, which is an important feature parameter in ballistic target recognition, we firstly establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation which is an important factor that cannot be ignored in radar measurement is taken into account in the model establishment, and modeled either as a log-normal or chi-square multiplicative noise. The distribution of obtained RCS signal is non-Gaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. In the paper, we propose three pseudo-MLE approaches to estimate the parameter of missile Precession Frequency. The first approach ignores the multiplicative noise in the measured RCS. The second approach ignores the additive noise (i.e., assuming the infinite signal-to-noise ratio (SNR)). The third approach enforces a Gaussian distribution on both additive and multiplicative noise components. The Cramer-Rao lower bound (CRLB) corresponding to the maximum SNR scenario is derived. Simulations indicate that accounting for the multiplicative noise in the estimation significantly improves estimation performance, and also show the validation and robustness of the proposed methods.

  • Precession missile feature extraction using sparse component analysis of radar measurements
    EURASIP Journal on Advances in Signal Processing, 2012
    Co-Authors: Xiaoyong Du, Weidong Hu, Mounir Ghogho, Des Mclernon
    Abstract:

    According to the working mode of the ballistic missile warning radar (BMWR), the radar return from the BMWR is usually sparse. To recognize and identify the warhead, it is necessary to extract the Precession Frequency and the locations of the scattering centers of the missile. This article first analyzes the radar signal model of the precessing conical missile during flight and develops the sparse dictionary which is parameterized by the unknown Precession Frequency. Based on the sparse dictionary, the sparse signal model is then established. A nonlinear least square estimation is first applied to roughly extract the Precession Frequency in the sparse dictionary. Based on the time segmented radar signal, a sparse component analysis method using the orthogonal matching pursuit algorithm is then proposed to jointly estimate the Precession Frequency and the scattering centers of the missile. Simulation results illustrate the validity of the proposed method.

  • pseudo maximum likelihood estimations of ballistic missile Precession Frequency
    International Conference on Acoustics Speech and Signal Processing, 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ICASSP - Pseudo Maximum Likelihood Estimations of ballistic missile Precession Frequency
    2011 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ballistic missile Precession Frequency extraction by homomorphic filtering
    International Conference on Signal Processing, 2010
    Co-Authors: Des Mclernon, Mounir Ghogho, Weidong Hu
    Abstract:

    In order to extract the Precession Frequency, which is an important feature parameter in ballistic missile target recognition, we first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. A homomorphic filter is designed to remove the scintillation effect in the RCS signal. Simulations show the practical usefulness of the proposed method in extracting an estimate of the Precession Frequency.

Mounir Ghogho - One of the best experts on this subject based on the ideXlab platform.

  • pseudo maximum likelihood estimation of ballistic missile Precession Frequency
    Signal Processing, 2012
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    In order to estimate a ballistic missile Precession Frequency, which is an important feature parameter in ballistic target recognition, we firstly establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation which is an important factor that cannot be ignored in radar measurement is taken into account in the model establishment, and modeled either as a log-normal or chi-square multiplicative noise. The distribution of obtained RCS signal is non-Gaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. In the paper, we propose three pseudo-MLE approaches to estimate the parameter of missile Precession Frequency. The first approach ignores the multiplicative noise in the measured RCS. The second approach ignores the additive noise (i.e., assuming the infinite signal-to-noise ratio (SNR)). The third approach enforces a Gaussian distribution on both additive and multiplicative noise components. The Cramer-Rao lower bound (CRLB) corresponding to the maximum SNR scenario is derived. Simulations indicate that accounting for the multiplicative noise in the estimation significantly improves estimation performance, and also show the validation and robustness of the proposed methods.

  • Precession missile feature extraction using sparse component analysis of radar measurements
    EURASIP Journal on Advances in Signal Processing, 2012
    Co-Authors: Xiaoyong Du, Weidong Hu, Mounir Ghogho, Des Mclernon
    Abstract:

    According to the working mode of the ballistic missile warning radar (BMWR), the radar return from the BMWR is usually sparse. To recognize and identify the warhead, it is necessary to extract the Precession Frequency and the locations of the scattering centers of the missile. This article first analyzes the radar signal model of the precessing conical missile during flight and develops the sparse dictionary which is parameterized by the unknown Precession Frequency. Based on the sparse dictionary, the sparse signal model is then established. A nonlinear least square estimation is first applied to roughly extract the Precession Frequency in the sparse dictionary. Based on the time segmented radar signal, a sparse component analysis method using the orthogonal matching pursuit algorithm is then proposed to jointly estimate the Precession Frequency and the scattering centers of the missile. Simulation results illustrate the validity of the proposed method.

  • pseudo maximum likelihood estimations of ballistic missile Precession Frequency
    International Conference on Acoustics Speech and Signal Processing, 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ICASSP - Pseudo Maximum Likelihood Estimations of ballistic missile Precession Frequency
    2011 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ballistic missile Precession Frequency extraction by homomorphic filtering
    International Conference on Signal Processing, 2010
    Co-Authors: Des Mclernon, Mounir Ghogho, Weidong Hu
    Abstract:

    In order to extract the Precession Frequency, which is an important feature parameter in ballistic missile target recognition, we first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. A homomorphic filter is designed to remove the scintillation effect in the RCS signal. Simulations show the practical usefulness of the proposed method in extracting an estimate of the Precession Frequency.

Des Mclernon - One of the best experts on this subject based on the ideXlab platform.

  • pseudo maximum likelihood estimation of ballistic missile Precession Frequency
    Signal Processing, 2012
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    In order to estimate a ballistic missile Precession Frequency, which is an important feature parameter in ballistic target recognition, we firstly establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation which is an important factor that cannot be ignored in radar measurement is taken into account in the model establishment, and modeled either as a log-normal or chi-square multiplicative noise. The distribution of obtained RCS signal is non-Gaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. In the paper, we propose three pseudo-MLE approaches to estimate the parameter of missile Precession Frequency. The first approach ignores the multiplicative noise in the measured RCS. The second approach ignores the additive noise (i.e., assuming the infinite signal-to-noise ratio (SNR)). The third approach enforces a Gaussian distribution on both additive and multiplicative noise components. The Cramer-Rao lower bound (CRLB) corresponding to the maximum SNR scenario is derived. Simulations indicate that accounting for the multiplicative noise in the estimation significantly improves estimation performance, and also show the validation and robustness of the proposed methods.

  • Precession missile feature extraction using sparse component analysis of radar measurements
    EURASIP Journal on Advances in Signal Processing, 2012
    Co-Authors: Xiaoyong Du, Weidong Hu, Mounir Ghogho, Des Mclernon
    Abstract:

    According to the working mode of the ballistic missile warning radar (BMWR), the radar return from the BMWR is usually sparse. To recognize and identify the warhead, it is necessary to extract the Precession Frequency and the locations of the scattering centers of the missile. This article first analyzes the radar signal model of the precessing conical missile during flight and develops the sparse dictionary which is parameterized by the unknown Precession Frequency. Based on the sparse dictionary, the sparse signal model is then established. A nonlinear least square estimation is first applied to roughly extract the Precession Frequency in the sparse dictionary. Based on the time segmented radar signal, a sparse component analysis method using the orthogonal matching pursuit algorithm is then proposed to jointly estimate the Precession Frequency and the scattering centers of the missile. Simulation results illustrate the validity of the proposed method.

  • pseudo maximum likelihood estimations of ballistic missile Precession Frequency
    International Conference on Acoustics Speech and Signal Processing, 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ICASSP - Pseudo Maximum Likelihood Estimations of ballistic missile Precession Frequency
    2011 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2011
    Co-Authors: Mounir Ghogho, Des Mclernon, Weidong Hu
    Abstract:

    We first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. Scintillation is modeled as a log-normal multiplicative noise. The distribution of the obtained RCS signal is nonGaussian and cannot be obtained in closed-form. Hence, the exact Maximum Likelihood Estimation (MLE) of the pertinent parameter, the missile Precession Frequency, is untractable. We propose three pseudo MLE approaches. The first approach, called GML, enforces a Gaussian distribution on both the additive and multiplicative noise components. The second approach, called ML8, ignores the additive noise in the measured RCS. The third approach, called AOML, ignores the multiplicative noise. Simulations show that accounting for the multiplicative noise in the estimation significantly improves estimation performance.

  • ballistic missile Precession Frequency extraction by homomorphic filtering
    International Conference on Signal Processing, 2010
    Co-Authors: Des Mclernon, Mounir Ghogho, Weidong Hu
    Abstract:

    In order to extract the Precession Frequency, which is an important feature parameter in ballistic missile target recognition, we first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with Precession motion. A homomorphic filter is designed to remove the scintillation effect in the RCS signal. Simulations show the practical usefulness of the proposed method in extracting an estimate of the Precession Frequency.

Akiko Shirakawa - One of the best experts on this subject based on the ideXlab platform.

  • Precession of magnetically driven warped disks and low Frequency quasi periodic oscillations in low mass x ray binaries
    The Astrophysical Journal, 2002
    Co-Authors: Akiko Shirakawa
    Abstract:

    An accretion disk around a rotating magnetized star is subjected to magnetic torques that induce disk warping and Precession. These torques arise generically from interactions between the stellar field and induced surface currents on the disk. Applying these new effects to weakly magnetized (B ~ 107-109 G) neutron stars in low-mass X-ray binaries, we study the global hydrodynamical warping/Precession modes of the disk under the combined influences of relativistic frame dragging, classical Precession due to the oblateness of the neutron star, and the magnetic torques. Under quite general conditions, the magnetic warping torque can overcome the "Bardeen-Petterson" viscous damping and make the modes grow. The modes are confined to the inner region of the disk and have frequencies equal to 0.3-0.95 (depending on the mass accretion rate ) times the sum of the Lense-Thirring Frequency, the classical Precession Frequency, and the magnetically driven Precession Frequency evaluated at the inner disk radius rin. As increases, the mode Frequency is reduced relative to the total Precession Frequency at rin, since the mode becomes less concentrated around rin due to the increasing viscous stress associated with the large . Because of this, and because the magnetically driven Precession is retrograde (opposite to the Lense-Thirring Precession) and depends strongly on , the mode Frequency can have a nonmonotonic dependence on the mass accretion rate. This may account for several observed features of low-Frequency (10-60 Hz) quasi-periodic oscillations (LFQPOs) in low-mass X-ray binaries that are otherwise difficult to explain, such as the flattening/turnover in the LFQPO Frequency- correlation or in the LFQPO Frequency-kHz QPO Frequency correlation (e.g., as seen clearly in GX 17+2).

  • Precession of magnetically driven warped disks and low Frequency qpos in low mass x ray binaries
    arXiv: Astrophysics, 2000
    Co-Authors: Akiko Shirakawa
    Abstract:

    An accretion disk around a rotating magnetized star is subjected to magnetic torques which induce disk warping and Precession. These torques arise from interactions between the stellar field and the induced surface currents on the disk. Applying these new effects to weakly magnetized ($B\sim 10^7-10^9$G) neutron stars in low-mass X-ray binaries, we study the global hydrodynamical warping/Precession modes of the disk under the combined influences of relativistic frame dragging, classical Precession due to the oblateness of the neutron star, and the magnetic torques. Under quite general conditions, the magnetic warping torque can overcome the ``Bardeen-Petterson'' viscous damping and makes the modes grow. The modes are confined to the inner region of the disk, and have frequencies close to the sum of the Lense-Thirring Frequency, the classical Precession Frequency, and the magnetically driven Precession Frequency evaluated at the inner disk radius $r_{in}$. As $\dot M$ increases, the mode Frequency is reduced relative to the total Precession Frequency at $r_{in}$ since the mode is less concentrated around $r_{in}$ due to the increasing viscous stress associated with the large $\dot M$. Because of this, and because the magnetically driven Precession is retrograde and depends strongly on $\dot M$, the mode Frequency can have a non-monotonic dependence on $\dot M$. This may account for several observed features of low-Frequency (10--60 Hz) quasi-periodic oscillations (LFQPOs) in low-mass X-ray binaries which are otherwise difficult to explain, such as the flattening/turnover in the LFQPO Frequency--$\dot M$ correlation or in the LFQPO Frequency--kHz QPO Frequency correlation (e.g., as seen clearly in GX 17+2).

Felix Guillermo Gonzalez Hernandez - One of the best experts on this subject based on the ideXlab platform.

  • acceleration of the Precession Frequency for optically oriented electron spins in ferromagnetic semiconductor hybrids
    Scientific Reports, 2019
    Co-Authors: Flavio Moraes, Saeed Ullah, M A G Balanta, F Iikawa, Yu A Danilov, M V Dorokhin, O V Vikhrova, B N Zvonkov, Felix Guillermo Gonzalez Hernandez
    Abstract:

    Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin Precession Frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin Precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial Precession Frequency, which depends on pump power, while the second process promotes a linear Frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.

  • Acceleration of the Precession Frequency for optically-oriented electron spins in ferromagnetic/semiconductor hybrids.
    Scientific reports, 2019
    Co-Authors: F C D Moraes, Saeed Ullah, M A G Balanta, F Iikawa, Yu A Danilov, M V Dorokhin, O V Vikhrova, B N Zvonkov, Felix Guillermo Gonzalez Hernandez
    Abstract:

    Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin Precession Frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin Precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial Precession Frequency, which depends on pump power, while the second process promotes a linear Frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.