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Zhai X. Garate E. Prohaska R. Benford G. Fisher A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(1):142-150
Experimental studies of a plasma-filled X -band backward-wave oscillator (BWO) are presented. Depending on the background gas pressure, microwave frequency upshifts of up to 1 GHz appeared along with an enhancement by a factor of 7 in the total microwave power emission. The bandwidth of the microwave emission increased from ⩽0.5 GHz to 2 GHz when the BWO was working at the RF power enhancement pressure region. The RF power enhancement appeared over a much wider pressure range in a high beam current case (10-100 mT for 3 kA) than in a lower beam case (80-115 mT for 1.6 kA). The plasma-filled BWO has higher power output than the vacuum BWO over a broader region of magnetic guide field strength. Trivelpiece-Gould modes (T-G modes) are observed with frequencies up to the background plasma frequency in a plasma-filled BWO. Mode competition between the T-G modes and the X -band Tm01 mode prevailed when the background plasma density was below 6×1011 cm-3 . At a critical background plasma density of ≃8×1011 cm-3 power enhancement appeared in both X -band and the T-G modes. Power enhancement of the S -band in this mode collaboration region reached up to 8 dB. Electric fields measured by the Stark-effect method were as high as 34 kV/cm while the BWO power level was 80 MW. These electric fields lasted throughout the high-power microwave pulse 相似文献
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C. B?uerle Yu M. Bunkov S. N. Fisher H. Godfrin G. R. Pickett 《Czechoslovak Journal of Physics》1996,46(Z1):5-6
During studies of the impact of single neutrons on superfluid3He at around 100μK we have measured the thermal energy released in the superfluid following the nuclear reaction, n+3He→p+3H+764keV. However, we find that the measured energy deposited in the quasiparticle system shortly after this reaction is substantially
less than what we expect. We believe that this energy deficit represents that energy which has gone into the creation of vortices,
in analogy to the creation of cosmic strings in the early universe via the Kibble mechanism. Furthermore, from the magnitude
of the deficit, we can infer the vortex density which compares favorably with that predicted in Zurek’s scenairo. 相似文献
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A new method for the solution of the damped Burgers' equation is described. The marker method relies on the definition of a convective field associated with the underlying partial differential equation; the information about the approximate solution is associated with the response of an ensemble of markers to this convective field. Some key aspects of the method, such as the selection of the shape function and the initial loading, are discussed in some details. The marker method is applicable to a general class of nonlinear dispersive partial differential equations. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
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O. Maksimov P. Fisher M. Skowronski P.A. Salvador M. Snyder J. Xu X. Weng 《Journal of Crystal Growth》2008,310(11):2760-2766
MgO films were grown on (0 0 1) yttria-stabilized zirconia (YSZ) substrates by molecular beam epitaxy (MBE). The crystalline structures of these films were investigated using X-ray diffraction and transmission electron microscopy. Growth temperature was varied from 350 to 550 °C, with crystalline quality being improved at higher temperatures. The MgO films had a domain structure: (1 1 1)[1 1 2¯]MgO(0 0 1)[1 0 0]YSZ with four twin variants related by a 90° in-plane rotation about the [1 1 1]MgO axis. The observed epitaxial orientation was compared to previous reports of films grown by pulsed laser deposition and sputtering and explained as resulting in the lowest interface energy. 相似文献
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Nicolas Gaillard Alain Guyot Jerome Claverie 《Journal of polymer science. Part A, Polymer chemistry》2003,41(5):684-698
Amphiphilic block copolymers of poly(acrylic acid‐b‐butyl acrylate) were prepared by reversible addition–fragmentation chain transfer polymerization in a one‐pot reaction. These copolymers were characterized by NMR, static and dynamic light scattering, tensiometry, and size exclusion chromatography. The aggregation characteristics of the copolymers corresponded to those theoretically predicted for a star micelle. In a butyl acrylate and methyl methacrylate emulsion polymerization, low amounts of these copolymers could stabilize latices with solid contents up to 50%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 684–698, 2003 相似文献