The Experts below are selected from a list of 16419 Experts worldwide ranked by ideXlab platform
Mikhail V Medvedev - One of the best experts on this subject based on the ideXlab platform.
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generation of magnetic fields in the relativistic shock of gamma ray burst sources
The Astrophysical Journal, 1999Co-Authors: Mikhail V Medvedev, Abraham LoebAbstract:We show that the relativistic two-stream instability can naturally generate strong magnetic fields with 10-5-10-1 of the equipartition energy density, in the collisionless shocks of gamma-ray burst (GRB) sources. The generated fields are parallel to the shock front and fluctuate on the very short scale of the plasma skin depth. The synchrotron radiation emitted from the limb-brightened source image is linearly polarized in the radial direction relative to the source center. Although the net polarization vanishes under Circular Symmetry, GRB sources should exhibit polarization scintillations as their radio afterglow radiation gets scattered by the Galactic interstellar medium. Detection of polarization scintillations could therefore test the above mechanism for magnetic field generation.
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generation of magnetic fields in the relativistic shock of gamma ray burst sources
arXiv: Astrophysics, 1999Co-Authors: Mikhail V Medvedev, Abraham LoebAbstract:We show that the relativistic two-stream instability can naturally generate strong magnetic fields with 1e-5 - 1e-1 of the equipartition energy density, in the collisionless shocks of Gamma-Ray-Burst (GRB) sources. The generated fields are parallel to the shock front and fluctuate on the very short scale of the plasma skin depth. The synchrotron radiation emitted from the limb-brightened source image is linearly polarized in the radial direction relative to the source center. Although the net polarization vanishes under Circular Symmetry, GRB sources should exhibit polarization scintillations as their radio afterglow radiation gets scattered by the Galactic interstellar medium. Detection of polarization scintillations could therefore test the above mechanism for magnetic field generation.
Abraham Loeb - One of the best experts on this subject based on the ideXlab platform.
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generation of magnetic fields in the relativistic shock of gamma ray burst sources
The Astrophysical Journal, 1999Co-Authors: Mikhail V Medvedev, Abraham LoebAbstract:We show that the relativistic two-stream instability can naturally generate strong magnetic fields with 10-5-10-1 of the equipartition energy density, in the collisionless shocks of gamma-ray burst (GRB) sources. The generated fields are parallel to the shock front and fluctuate on the very short scale of the plasma skin depth. The synchrotron radiation emitted from the limb-brightened source image is linearly polarized in the radial direction relative to the source center. Although the net polarization vanishes under Circular Symmetry, GRB sources should exhibit polarization scintillations as their radio afterglow radiation gets scattered by the Galactic interstellar medium. Detection of polarization scintillations could therefore test the above mechanism for magnetic field generation.
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generation of magnetic fields in the relativistic shock of gamma ray burst sources
arXiv: Astrophysics, 1999Co-Authors: Mikhail V Medvedev, Abraham LoebAbstract:We show that the relativistic two-stream instability can naturally generate strong magnetic fields with 1e-5 - 1e-1 of the equipartition energy density, in the collisionless shocks of Gamma-Ray-Burst (GRB) sources. The generated fields are parallel to the shock front and fluctuate on the very short scale of the plasma skin depth. The synchrotron radiation emitted from the limb-brightened source image is linearly polarized in the radial direction relative to the source center. Although the net polarization vanishes under Circular Symmetry, GRB sources should exhibit polarization scintillations as their radio afterglow radiation gets scattered by the Galactic interstellar medium. Detection of polarization scintillations could therefore test the above mechanism for magnetic field generation.
Ko Okumura - One of the best experts on this subject based on the ideXlab platform.
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bursting dynamics of viscous film without Circular Symmetry the effect of confinement
Physical Review Fluids, 2018Co-Authors: Mayuko Murano, Ko OkumuraAbstract:Experimental observations of bubbles bursting between two confining plates find a constant speed of the rim and a tip that does not grow. The dynamics is governed by surface energy transformed into viscous dissipation. Left and right tip shapes look different due to a difference in focal point.
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bursting dynamics of viscous film without Circular Symmetry the effect of confinement
arXiv: Fluid Dynamics, 2017Co-Authors: Mayuko Murano, Ko OkumuraAbstract:We experimentally investigate the bursting dynamics of confined liquid film suspended in air and find a viscous dynamics distinctly different from the non-confined counterpart, due to lack of Circular Symmetry in the shape of expanding hole: the novel confined-viscous bursting proceeds at a constant speed and a rim formed at the bursting tip does not grow. We find a confined-viscous to confined-inertial crossover, as well as a nonconfined-inertial to confined-inertial crossover, at which bursting speed does not change although the Circular Symmetry in the hole shape breaks dynamically.
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bursting of a thin film in a confined geometry rimless and constant velocity dewetting
Physical Review E, 2010Co-Authors: Ayako Eri, Ko OkumuraAbstract:We study the bursting dynamics of a thin oil film sandwiched by glycerol aqueous solution in a confined geometry where the Circular Symmetry of the bursting hole is broken. We find that the bursting proceeds with a constant velocity except for initial times and the velocity is governed by the viscosity of the surrounding glycerol. Different from previous studies where the bursting speed is constant, in our confined geometry no rims are formed at the bursting tip as a result of the Symmetry breaking. Our findings can be explained by original and simple scaling arguments.
Guy A E Vandenbosch - One of the best experts on this subject based on the ideXlab platform.
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radial crlh tl based dual band antenna with frequency agility
IEEE Transactions on Antennas and Propagation, 2020Co-Authors: Jiahao Zhang, Sen Yan, Guy A E VandenboschAbstract:A novel reconfigurable radial composite right/left-handed transmission line (CRLH-TL) is proposed and used in a dual-band antenna with frequency agility. Varactors are used to tune the TL dispersion properties. Using the 10 dB return loss criterion, the proposed antenna has a stable relative band of 4.1% fully covering the 2.4–2.5 GHz ISM band, and a tunable operating band from 3.05 to 3.89 GHz fully covering the 3.1–3.8 GHz WiMAX band. A frequency tuning range of 24.2% is obtained in this higher band. The lower and higher resonances work at the 0 mode and 1 mode, respectively, resulting in an omni-directional pattern for both the operating bands, due to the Circular Symmetry. A prototype antenna is fabricated, and the simulations and experiments match well, proving the validity of the new concept.
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low profile dual band pattern diversity patch antenna based on composite right left handed transmission line
IEEE Transactions on Antennas and Propagation, 2017Co-Authors: Sen Yan, Guy A E VandenboschAbstract:A low-profile patch antenna with pattern diversity is proposed. The topology combines an annular ring together with a center-fed Circular patch. The composite right/left-handed transmission line is loaded on both the annular ring and the Circular patch, to realize the 2.4/3.5-GHz dual-band operation. The outer annular ring works at its first pair of symmetric modes, which results in broadside radiation patterns, while the inner Circular patch provides omnidirectional patterns in the horizontal plane, as a consequence of its physical Circular Symmetry. The field distribution is analyzed to verify the operational principle. By optimizing the feeding network, the antenna reaches a good impedance matching in both bands. A prototype is fabricated, and the measured results agree well with the simulated ones. The measured correlation coefficient is lower than 0.04 and 0.05 in the lower and upper band, respectively.
Arjun K. Gupta - One of the best experts on this subject based on the ideXlab platform.
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Distribution and percentage points of the likelihood ratio statistic for testing Circular Symmetry
Computational Statistics & Data Analysis, 2004Co-Authors: Daya K. Nagar, Jie Chen, Arjun K. GuptaAbstract:Abstract In this paper, the distribution of the likelihood ratio statistic for testing the hypothesis that the covariance matrix of a p -variate normal distribution is Circular symmetric has been derived. The distribution is obtained in series form using the inverse Mellin transform and the residue theorem. Percentage points for p =4,5,6 and 7 have been computed using distributional results derived in this article.