The Experts below are selected from a list of 21 Experts worldwide ranked by ideXlab platform

Leopold B Felsen - One of the best experts on this subject based on the ideXlab platform.

  • Time-domain Green's function for an infinite sequentially excited periodic planar array of dipoles
    eScholarship University of California, 2003
    Co-Authors: Capolino F, Leopold B Felsen
    Abstract:

    The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic understanding of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antenna and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green's functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity η = c/v , where v and c are the excitation phase speed along a preferred phasing direction u in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case η < 1, reserving the more intricate slowly phased η > 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD-FWs. Physical interpretation of the formal TD-FW solutions is obtained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD-FWs emerge along "equal-delay" ellipses from the array plane; this furnishes a novel and physically appealing interpretation of the planar array TD-FW phenomenology. u1 u1 1 (p) (p

  • time domain green s function for an infinite sequentially excited periodic planar array of dipoles
    IEEE Transactions on Antennas and Propagation, 2000
    Co-Authors: Filippo Capolino, Leopold B Felsen
    Abstract:

    The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic understanding of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antennas and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green's functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity /spl eta/=c/v/sup (p)//sub u1/, where v/sup (p)//sub u1/ and c are the excitation phase speed along a preferred phasing direction u/sub 1/ in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case /spl eta/ 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD-FWs. Physical interpretation of the formal TD-FW solutions is obtained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD-FWs emerge along "equal-delay" ellipses from the array plane; this furnishes a novel and physically appealing interpretation of the planar array TD-FW phenomenology.

  • Time domain Green’s function for an infinite sequentially excited periodic line array of dipoles
    2000
    Co-Authors: Leopold B Felsen, Life Fellow
    Abstract:

    Abstract—The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic under-standing of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antenna and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green’s functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity = () 1, where () and are the excitation phase speed along a preferred phasing direction 1 in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case 1, reserving the more intricate slowly phased 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD–FWs. Physical interpretation of the formal TD–FW solutions is ob-tained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD–FWs emerge along “equal-delay” ellipses from the array plane; this furnishes a novel and phys-ically appealing interpretation of the planar array TD–FW phenomenology

Filippo Capolino - One of the best experts on this subject based on the ideXlab platform.

  • time domain green s function for an infinite sequentially excited periodic planar array of dipoles
    IEEE Transactions on Antennas and Propagation, 2000
    Co-Authors: Filippo Capolino, Leopold B Felsen
    Abstract:

    The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic understanding of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antennas and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green's functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity /spl eta/=c/v/sup (p)//sub u1/, where v/sup (p)//sub u1/ and c are the excitation phase speed along a preferred phasing direction u/sub 1/ in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case /spl eta/ 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD-FWs. Physical interpretation of the formal TD-FW solutions is obtained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD-FWs emerge along "equal-delay" ellipses from the array plane; this furnishes a novel and physically appealing interpretation of the planar array TD-FW phenomenology.

Life Fellow - One of the best experts on this subject based on the ideXlab platform.

  • Time domain Green’s function for an infinite sequentially excited periodic line array of dipoles
    2000
    Co-Authors: Leopold B Felsen, Life Fellow
    Abstract:

    Abstract—The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic under-standing of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antenna and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green’s functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity = () 1, where () and are the excitation phase speed along a preferred phasing direction 1 in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case 1, reserving the more intricate slowly phased 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD–FWs. Physical interpretation of the formal TD–FW solutions is ob-tained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD–FWs emerge along “equal-delay” ellipses from the array plane; this furnishes a novel and phys-ically appealing interpretation of the planar array TD–FW phenomenology

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

  • Time-domain Green's function for an infinite sequentially excited periodic planar array of dipoles
    eScholarship University of California, 2003
    Co-Authors: Capolino F, Leopold B Felsen
    Abstract:

    The present paper is a continuation of previous explorations by the authors, aimed at gaining a basic understanding of the time domain (TD) behavior of large periodic phased (i.e., sequentially turned-on) array antenna and related configurations. Our systematic investigation of the relevant canonical TD dipole-excited Green's functions has so far included those for infinite and truncated sequentially pulsed line periodic arrays, parameterized in terms of radiating (propagating) and nonradiating (evanescent) conical TD Floquet waves (FW) and truncation-induced TD FW-modulated tip diffractions. The present contribution extends these investigations to an infinite periodic sequentially pulsed planar array, which generates pulsed plane propagating and evanescent FW. Starting from the familiar frequency domain (FD) transformation of the linearly phased element-by-element summation synthesis into summations of propagating and evanescent FWs, we access the time domain by Fourier inversion. The inversion integrals are manipulated in a unified fashion into exact closed forms, which are parameterized by the single Nondimensional Quantity η = c/v , where v and c are the excitation phase speed along a preferred phasing direction u in the array plane and the ambient wave speed, respectively. The present study deals with the practically relevant rapidly phased propagating case η < 1, reserving the more intricate slowly phased η > 1 regime for a future manuscript. Numerical reference data generated via element-by-element summation over the fields radiated by the individual dipoles with ultrawide band-limited excitation are compared with results obtained much more efficiently by inclusion of a few TD-FWs. Physical interpretation of the formal TD-FW solutions is obtained by recourse to asymptotics, instantaneous frequencies and wavenumbers, and related constructs. Of special interest is the demonstration that the TD-FWs emerge along "equal-delay" ellipses from the array plane; this furnishes a novel and physically appealing interpretation of the planar array TD-FW phenomenology. u1 u1 1 (p) (p

Mj Gollner - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of particulate-matter emissions from liquid-fueled pool fires and fire whirls
    eScholarship University of California, 2021
    Co-Authors: Sb Hariharan, Hf Farahani, As Rangwala, Jl Dowling, Es Oran, Mj Gollner
    Abstract:

    In-situ burning (ISB) is one of the most effective means of removing oil spilled over open water. While current ISB practices can eliminate a large fraction of the spilled oil, they still result in significant airborne emissions of particulate matter. ISBs are classified as large, free-buoyant pool fires, from which black smoke consisting of particulate matter (PM, soot) emanates as a plume. An experimental investigation of soot emissions from pool fires (PF) and fire whirls (FW) was conducted using liquid hydrocarbon fuels, n-heptane and Alaska North Slope (ANS) crude oil, in fuel pools 10−70 cm in diameter. Burning attributes such as burning rate, fuel-consumption efficiency, and emissions of PM, unburned hydrocarbons, carbon dioxide, and oxygen consumption were measured. For both fuels and all pool diameters, compared to PFs, FWs consumed fuel at a higher rate, had lower post-combustion residual mass and PM emission rates. Collectively, these resulted in consistently lower PM emission factors (EF ) for FWs at all scales. For FWs, EF decreased linearly with a Nondimensional Quantity defined as the ratio of inverse Rossby number to Nondimensional heat-release rate. These results show that the addition of ambient circulation to free-burning PFs to form FWs can increase burning efficiency, reducing both burning duration and EF across length scales. The reduction in EF with increasing influence of circulation is attributed to a feedback loop of higher temperatures, heat feedback, burning rate and air-entrainment velocity, which in turn contributes to maintaining the structure of a FW. Boilover was observed for fires formed with ANS crude oil at the 70 cm scale, although the overall EF was not affected significantly. This investigation presents a foundation to evaluate the detailed mechanisms further, such that appropriate configurations can be developed help minimize the environmental impact of ISBs. PM PM PM PM P