2,709 research outputs found

    Active rc networks of low sensitivity for integrated circuit transfer function

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    Active RC network is capable of extremely high Q performance with exceptional stability and has independently adjustable zeros and poles. The circuit consists of two integrators and two summers that are interconnected to produce a complete second-order numerator and a second-order denominator

    MHD Turbulence Revisited

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    Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfv\'en wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfv\'en waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturbations in displacement are not; (iv) 3--wave interactions dominate individual collisions between wave packets, but interactions of all orders n3n\geq 3 make comparable contributions to the intermediate turbulent energy cascade; (v) successive collisions are correlated since wave packets are distorted as they follow diverging field lines; (vi) in common with the weak MHD cascade, there is no parallel cascade of energy, and the cascade to small perpendicular scales strengthens as it reaches higher wave numbers; (vii) For an appropriate weak excitation, there is a natural progression from a weak, through an intermediate, to a strong cascade.Comment: 25 pages, to appear in The Astrophysical Journa

    Design, development and delivery of one /1/ breadboard and three /3/ production units of a 75 VA integrated static inverter Monthly report no. 15

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    Flip-flop arrays, power transistors, epitaxial stress, and other technological developments in integrated static inverter progra

    Renewable Energy Project Financing: Impacts of the Financial Crisis and Federal Legislation

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    Extraordinary financial market conditions have disrupted the flows of equity and debt investment into U.S. renewable energy (RE) projects since the fourth quarter of 2008. The pace and structure of renewable energy project finance has been reshaped by a combination of forces, including the financial crisis, global economic recession, and major changes in federal legislation affecting renewable energy finance. This report explores the impacts of these key market events on renewable energy project financing and development

    Fermat Principle in Finsler Spacetimes

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    It is shown that, on a manifold with a Finsler metric of Lorentzian signature, the lightlike geodesics satisfy the following variational principle. Among all lightlike curves from a point (emission event) to a timelike curve (worldline of receiver), the lightlike geodesics make the arrival time stationary. Here ``arrival time'' refers to a parametrization of the timelike curve. This variational principle can be applied (i) to the vacuum light rays in an alternative spacetime theory, based on Finsler geometry, and (ii) to light rays in an anisotropic non-dispersive medium with a general-relativistic spacetime as background.Comment: 18 pages, submitted to Gen. Rel. Gra

    A Joint Sunyaev-Zel'dovich Effect and X-ray Analysis of Abell 3667

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    We present a 40GHz (7.5 mm) raster scan image of a 3.6x2 degree region centered on the low redshift (z=0.055) cluster of galaxies Abell 3667. The cluster was observed during the Antarctic winter of 1999 using the Corona instrument (15.7' FWHM beam) on the Viper Telescope at the South Pole. The Corona image of A3667 is one of the first direct (i.e. rather than interferometer) thermal Sunyaev-Zel'dovich effect images of a low redshift cluster. The brightness temperature decrement at the X-ray centroid (20h 12m 28.9s, -56 49 51 J2000) was measured to be ΔTCMB=154μK\Delta T_{\rm CMB}=-154\mu K. We have used the 40GHz map of A3667 in conjunction with a deep ROSAT PSPC (X-ray) image of the cluster, to make a measurement of the Hubble Constant. We find H0=6430+96H_0 = 64^{+96}_{-30} km s1^{-1} Mpc1^{-1} (68% confidence interval). Our H0H_0 calculation assumes that the cluster can be described using an isothermal, tri-axial ellipsoidal, β\beta-model and includes several new analysis techniques including an automated method to remove point sources from X-ray images with variable point spread functions, and an efficient method for determining the errors in multi-parameter maximum likelihood analyzes. The large errors on the H0H_0 measurement are primarily due to the statistical noise in the Corona image. We plan to increase the precision of our measurement by including additional clusters in our analysis and by increasing the sensitivity of the Viper SZE maps.Comment: 15 pages, 4 figures, submitted to ApJ (count rate units corrected in Table 1 and Figure 4

    An MPEG-7 scheme for semantic content modelling and filtering of digital video

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    Abstract Part 5 of the MPEG-7 standard specifies Multimedia Description Schemes (MDS); that is, the format multimedia content models should conform to in order to ensure interoperability across multiple platforms and applications. However, the standard does not specify how the content or the associated model may be filtered. This paper proposes an MPEG-7 scheme which can be deployed for digital video content modelling and filtering. The proposed scheme, COSMOS-7, produces rich and multi-faceted semantic content models and supports a content-based filtering approach that only analyses content relating directly to the preferred content requirements of the user. We present details of the scheme, front-end systems used for content modelling and filtering and experiences with a number of users
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