The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform

Michael D. Zoltowski - One of the best experts on this subject based on the ideXlab platform.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    IEEE Journal of Oceanic Engineering, 1997
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based closed form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector hydrophones, whose locations need not be known. Each vector hydrophone consists of two or three identical but orthogonally oriented velocity hydrophones plus one pressure hydrophone, all spatially co-located in a point-like geometry. A velocity hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the nonspatial inter-relations among each vector hydrophone's constituent hydrophones, such that ESPRIT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    IEEE Journal of Oceanic Engineering, 1997
    Co-Authors: K T Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based closed form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector hydrophones, whose locations need not be known. Each vector hydrophone consists of two or three identical but orthogonally oriented velocity hydrophones plus one pressure hydrophone, all spatially co-located in a point-like geometry. A velocity hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the nonspatial inter-relations among each vector hydrophone's constituent hydrophones, such that ESPRIT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    International Symposium on Circuits and Systems, 1997
    Co-Authors: K T Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based, closed-form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector-hydrophones, whose location need not be known. Each vector-hydrophone consists of two or three identical but orthogonally oriented velocity-hydrophones plus one pressure-hydrophone, all spatially co-located in a point-like geometry. A velocity-hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure-hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the non-spatial inter-relation among each vector-hydrophone's constituent Components, such that ESPRTT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme. Aspects of this sonar algorithm is analogous to Jian Li's earlier work (1993) with diversely polarized antennas.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    International Symposium on Circuits and Systems, 1997
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based, closed-form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector-hydrophones, whose location need not be known. Each vector-hydrophone consists of two or three identical but orthogonally oriented velocity-hydrophones plus one pressure-hydrophone, all spatially co-located in a point-like geometry. A velocity-hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure-hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the non-spatial inter-relation among each vector-hydrophone's constituent Components, such that ESPRTT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme. Aspects of this sonar algorithm is analogous to Jian Li's earlier work (1993) with diversely polarized antennas.

  • ESPRIT-based extended-aperture source localization using velocity-hydrophones
    OCEANS 96 MTS IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century, 1996
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    A novel ESPRIT-based 2D angle estimation scheme is proposed using a rectangular array of triads of spatially co-located but orthogonally oriented velocity-hydrophones spaced much farther apart than a half-wavelength. Each velocity-hydrophone measures one Cartesian Component of the sonar velocity-field. The use of such velocity-hydrophone triads enable the measurement of the velocity-field vector of the sonar wavefield. Each source's normalized velocity-field vector is equal to the source's Cartesian direction-cosines. The source's arrival angle can thus be extracted from the velocity-field measurements. On the other hand, when uniformly spaced array elements are spaced beyond a half wavelength, ESPRIT's eigenvalues offer a cyclic ambiguity. The direction-cosine estimates obtained from the velocity-field may serve as reference to clarify the low-variance but cyclically ambiguous direction-cosine estimation obtained from ESPRIT's eigenvalues. Simulations are presented showing the sample variance of direction-cosine estimates decreasing linearly as inter-triad spacing is increased from a half-wavelength to 12 half-wavelengths, with a 33-fold reduction in estimation standard deviation relative to the half-wavelength case. This proposed scheme also outperforms a uniform half-wavelength-spaced array of pressure-hydrophones with comparable hardware and software costs by an order of magnitude in estimation standard deviation.

Kainam Thomas Wong - One of the best experts on this subject based on the ideXlab platform.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    IEEE Journal of Oceanic Engineering, 1997
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based closed form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector hydrophones, whose locations need not be known. Each vector hydrophone consists of two or three identical but orthogonally oriented velocity hydrophones plus one pressure hydrophone, all spatially co-located in a point-like geometry. A velocity hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the nonspatial inter-relations among each vector hydrophone's constituent hydrophones, such that ESPRIT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    International Symposium on Circuits and Systems, 1997
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based, closed-form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector-hydrophones, whose location need not be known. Each vector-hydrophone consists of two or three identical but orthogonally oriented velocity-hydrophones plus one pressure-hydrophone, all spatially co-located in a point-like geometry. A velocity-hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure-hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the non-spatial inter-relation among each vector-hydrophone's constituent Components, such that ESPRTT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme. Aspects of this sonar algorithm is analogous to Jian Li's earlier work (1993) with diversely polarized antennas.

  • ESPRIT-based extended-aperture source localization using velocity-hydrophones
    OCEANS 96 MTS IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century, 1996
    Co-Authors: Kainam Thomas Wong, Michael D. Zoltowski
    Abstract:

    A novel ESPRIT-based 2D angle estimation scheme is proposed using a rectangular array of triads of spatially co-located but orthogonally oriented velocity-hydrophones spaced much farther apart than a half-wavelength. Each velocity-hydrophone measures one Cartesian Component of the sonar velocity-field. The use of such velocity-hydrophone triads enable the measurement of the velocity-field vector of the sonar wavefield. Each source's normalized velocity-field vector is equal to the source's Cartesian direction-cosines. The source's arrival angle can thus be extracted from the velocity-field measurements. On the other hand, when uniformly spaced array elements are spaced beyond a half wavelength, ESPRIT's eigenvalues offer a cyclic ambiguity. The direction-cosine estimates obtained from the velocity-field may serve as reference to clarify the low-variance but cyclically ambiguous direction-cosine estimation obtained from ESPRIT's eigenvalues. Simulations are presented showing the sample variance of direction-cosine estimates decreasing linearly as inter-triad spacing is increased from a half-wavelength to 12 half-wavelengths, with a 33-fold reduction in estimation standard deviation relative to the half-wavelength case. This proposed scheme also outperforms a uniform half-wavelength-spaced array of pressure-hydrophones with comparable hardware and software costs by an order of magnitude in estimation standard deviation.

K T Wong - One of the best experts on this subject based on the ideXlab platform.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    IEEE Journal of Oceanic Engineering, 1997
    Co-Authors: K T Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based closed form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector hydrophones, whose locations need not be known. Each vector hydrophone consists of two or three identical but orthogonally oriented velocity hydrophones plus one pressure hydrophone, all spatially co-located in a point-like geometry. A velocity hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the nonspatial inter-relations among each vector hydrophone's constituent hydrophones, such that ESPRIT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme.

  • closed form underwater acoustic direction finding with arbitrarily spaced vector hydrophones at unknown locations
    International Symposium on Circuits and Systems, 1997
    Co-Authors: K T Wong, Michael D. Zoltowski
    Abstract:

    This paper introduces a novel ESPRIT-based, closed-form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector-hydrophones, whose location need not be known. Each vector-hydrophone consists of two or three identical but orthogonally oriented velocity-hydrophones plus one pressure-hydrophone, all spatially co-located in a point-like geometry. A velocity-hydrophone measures one Cartesian Component of the incident sonar wavefield's velocity-vector, whereas a pressure-hydrophone measures the acoustic wavefield's pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the non-spatial inter-relation among each vector-hydrophone's constituent Components, such that ESPRTT's eigenvalues become independent of array geometry. Simulation results verify the efficacy and versatility of this innovative scheme. Aspects of this sonar algorithm is analogous to Jian Li's earlier work (1993) with diversely polarized antennas.

F J Lowes - One of the best experts on this subject based on the ideXlab platform.

  • vector errors in spherical harmonic analysis of scalar data
    Geophysical Journal International, 2007
    Co-Authors: F J Lowes
    Abstract:

    Summary It has recently been noticed that spherical harmonic analysis (SHA) of the geomagnetic scalar intensity F gives a synthesized field having large errors in the vertical Component near the equator, where the field is predominantly horizontal. It is now shown that this is just one example of a more general ' perpendicular error ' effect; SHA of a scalar property of a vector field is equivalent to analysing one particular Cartesian Component of the vector, and there is a tendency for the resultant synthesized field to have vector errors which are preferentially perpendicular to that Component, and which have magnitudes considerably larger than the errors in that Component. This paper shows how the (relative) average magnitude of the errors in the SH coefficients obtained from a given type of analysis can be estimated, and how these determine the magnitude and nature of the ' perpendicular error ' effect. It also shows that the effect is not directly related to any lack of uniqueness in the theoretical solution. While the effect can be large for the Earth's magnetic field, it is very small for the gravitational field.

N Kikuchi - One of the best experts on this subject based on the ideXlab platform.

  • general topology optimization method with continuous and discrete orientation design using isoparametric projection
    International Journal for Numerical Methods in Engineering, 2015
    Co-Authors: Tsuyoshi Nomura, Ercan M Dede, Shintaro Yamasaki, Tadayoshi Matsumori, Atsushi Kawamoto, N Kikuchi
    Abstract:

    A general topology optimization method, which is capable of simultaneous design of density and orientation of anisotropic material, is proposed by introducing orientation design variables in addition to the density design variable. In this work, the Cartesian Components of the orientation vector are utilized as the orientation design variables. The proposed method supports continuous orientation design, which is out of the scope of discrete material optimization approaches, as well as design using discrete angle sets. The advantage of this approach is that vector element representation is less likely to fail into local optima because it depends less on designs of former steps, especially compared with using the angle as a design variable (Continuous Fiber Angle Optimization) by providing a flexible path from one angle to another with relaxation of orientation design space. An additional advantage is that it is compatible with various projection or filtering methods such as sensitivity filters and density filters because it is free from unphysical bound or discontinuity such as the one at theta = 2 pi and theta = 0 seen with direct angle representation. One complication of Cartesian Component representation is the point-wise quadratic bound of the design variables; that is, each pair of element values has to reside in a given circular bound. To overcome this issue, we propose an isoparametric projection method, which transforms box bounds into circular bounds by a coordinate transformation with isoparametric shape functions without having the singular point that is seen at the origin with polar coordinate representation. A new topology optimization method is built by taking advantage of the aforementioned features and modern topology optimization techniques. Several numerical examples are provided to demonstrate its capability. Copyright (C) 2014 John Wiley & Sons, Ltd.