5,767 research outputs found

    he geometry of statistical efficiency

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    We will place certain parts of the theory of statistical efficiency into the author’s operator trigonometry (1967), thereby providing new geometrical understanding of statistical efficiency. Important earlier results of Bloomfield and Watson, Durbin and Kendall, Rao and Rao, will be so interpreted. For example, worse case relative least squares efficiency corresponds to and is achieved by the maximal turning antieigenvectors of the covariance matrix. Some little-known historical perspectives will also be exposed. The overall view will be emphasized

    Optical diodes

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    Research on metal-barrier-metal structures is reviewed. Topics discussed include: demonstration of antenna coupling and rectification characteristics with high resistance evaporated structures at a wavelength of 10 microns; application of these devices to coherent conversion of laser radiation and infrared and optical circuit elements; and comparison of the point-contact type of diode structure and the newly developed photolithographic structures

    Development and evaluation of braze alloys for vacuum furnace brazing

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    Copper and copper-base alloys tested for use in vacuum furnace brazing of rocket engine tubular thrust chamber

    Collaborative research in tunneling and field emission pumped surface wave local oscillators and amplifiers for infrared and submillimeter wavelengths under director's discretionary fund

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    Progress is reported in work towards the development of surface wave sources for the infrared and sub-millimeter portion of the spectrum to be based upon electron pumping by tunneling electrons in metal-barrier-metal or metal-barrier-semiconductor devices. Tunneling phenomena and the coupling of radiation to tunnel junctions were studied. The propagation characteristics of surface electro-magnetic modes in metal-insulator-p(++) semiconductor structures as a function of frequency were calculated. A model for the gain process based upon Tucker's formalism was developed and used to estimate what low frequency gain might be expected from such structures. The question of gain was addressed from a more fundamental viewpoint using the method of Lasher and Stern

    Global dispersive solutions for the Gross-Pitaevskii equation in two and three dimensions

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    We study asymptotic behaviour at time infinity of solutions close to the non-zero constant equilibrium for the Gross-Pitaevskii equation in two and three spatial dimensions. We construct a class of global solutions with prescribed dispersive asymptotic behavior, which is given in terms of the linearized evolution

    Nondiffusive suprathermal ion transport in simple magnetized toroidal plasmas

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    We investigate suprathermal ion dynamics in simple magnetized toroidal plasmas in the pres- ence of electrostatic turbulence driven by the ideal interchange instability. Turbulent fields from fluid simulations are used in the non-relativistic equation of ion motion to compute suprathermal tracer ion trajectories. Suprathermal ion dispersion starts with a brief ballistic phase, during which particles do not interact with the plasma, followed by a turbulence interaction phase. In this one simple system, we observe the entire spectrum of suprathermal ion dynamics, from subdiffusion to superdiffusion, depending on beam energy and turbulence amplitude. We estimate the duration of the ballistic phase and identify basic mechanisms during the interaction phase that determine the character of suprathermal ion dispersion upon the beam energy and turbulence fluctuation amplitude.Comment: 5 pages, 3 figures, accepted in PR
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