441 research outputs found

    Low speed wind tunnel tests of 1/10-scale model of a blended-arrow supersonic cruise aircraft

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    Low speed static force tests have been conducted in a full scale tunnel to determine the low speed aerodynamic characteristics of a 1/10-scale model of a blended-arrow supersonic cruise aircraft. A clean configuration and a high lift configuration with several combinations of leading- and trailing-edge flaps to provide improved lift and longitudinal stability in the landing and takeoff modes were used. The tests were made at angles of attack from about -6 deg to 30 deg, sideslip angles from -5 deg to 10 deg, and Reynolds numbers from 6.78 x 1 million to 13.85 x 1 million corresponding to test velocities of 41 to 85 knots

    Low-speed wind tunnel tests of 1/9-scale model of a variable-sweep supersonic cruise aircraft

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    Tests were conducted in the Langley full-scale tunnel to determine the aerodynamic characteristics at low subsonic speeds of a 1/9-scale model of a variable-sweep supersonic cruise aircraft. The model configurations investigated were the basic unflapped arrangement, a take-off flap arrangement, and a landing flap arrangement with several strake leading-edge flow control devices. The tests were conducted at angles of attack from about -5 to 36 deg, sideslip angles from -5 to 10 deg

    A Processor Core Model for Quantum Computing

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    We describe an architecture based on a processing 'core' where multiple qubits interact perpetually, and a separate 'store' where qubits exist in isolation. Computation consists of single qubit operations, swaps between the store and the core, and free evolution of the core. This enables computation using physical systems where the entangling interactions are 'always on'. Alternatively, for switchable systems our model constitutes a prescription for optimizing many-qubit gates. We discuss implementations of the quantum Fourier transform, Hamiltonian simulation, and quantum error correction.Comment: 5 pages, 2 figures; improved some arguments as suggested by a refere

    A short note on the presence of spurious states in finite basis approximations

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    The genesis of spurious solutions in finite basis approximations to operators which possess a continuum and a point spectrum is discussed and a simple solution for identifying these solutions is suggested

    Full QCD with the L\"uscher local bosonic action

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    We investigate L\"uscher's method of including dynamical Wilson fermions in a lattice simulation of QCD with two quark flavours. We measure the accuracy of the approximation by comparing it with Hybrid Monte Carlo results for gauge plaquette and Wilson loops. We also introduce an additional global Metropolis step in the update. We show that the complexity of L\"uscher's algorithm compares favourably with that of the Hybrid Monte Carlo.Comment: 21 pages Late

    Beyond the simple Proximity Force Approximation: geometrical effects on the non-retarded Casimir interaction

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    We study the geometrical corrections to the simple Proximity Force Approximation for the non-retarded Casimir force. We present analytical results for the force between objects of various shapes and substrates, and between pairs of objects. We compare the results to those from more exact numerical calculations. We treat spheres, spheroids, cylinders, cubes, cones, and wings; the analytical PFA results together with the geometrical correction factors are summarized in a table.Comment: 18 pages, 19 figures, 1 tabl

    Low speed wind tunnel tests of a 1/9-scale model of a variable-sweep advanced supersonic transport

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    Tests have been conducted in the Langley full-scale tunnel to determine the aerodynamic characteristics of a 1/9-scale variable-sweep advanced supersonic transport configuration. The model configurations investigated were the basic unflapped arrangement, and a takeoff and landing flap arrangement with several strake leading edge flow control devices. The tests were conducted for an angle-of-attack range from about minus 5 deg to 36 deg and a sideslip range from minus 5 deg to 10 deg. The tests were conducted for a range of Reynolds number from 3.92 million to 5.95 million corresponding to test velocities of about 54.5 knots and 81.7 knots, respectively

    An atlas for tridiagonal isospectral manifolds

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    Let TΛ{\cal T}_\Lambda be the compact manifold of real symmetric tridiagonal matrices conjugate to a given diagonal matrix Λ\Lambda with simple spectrum. We introduce {\it bidiagonal coordinates}, charts defined on open dense domains forming an explicit atlas for TΛ{\cal T}_\Lambda. In contrast to the standard inverse variables, consisting of eigenvalues and norming constants, every matrix in TΛ{\cal T}_\Lambda now lies in the interior of some chart domain. We provide examples of the convenience of these new coordinates for the study of asymptotics of isospectral dynamics, both for continuous and discrete time.Comment: Fixed typos; 16 pages, 3 figure

    The Asymptotics of Wilkinson's Iteration: Loss of Cubic Convergence

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    One of the most widely used methods for eigenvalue computation is the QRQR iteration with Wilkinson's shift: here the shift ss is the eigenvalue of the bottom 2×22\times 2 principal minor closest to the corner entry. It has been a long-standing conjecture that the rate of convergence of the algorithm is cubic. In contrast, we show that there exist matrices for which the rate of convergence is strictly quadratic. More precisely, let TXT_X be the 3×33 \times 3 matrix having only two nonzero entries (TX)12=(TX)21=1(T_X)_{12} = (T_X)_{21} = 1 and let TLT_L be the set of real, symmetric tridiagonal matrices with the same spectrum as TXT_X. There exists a neighborhood UTLU \subset T_L of TXT_X which is invariant under Wilkinson's shift strategy with the following properties. For T0UT_0 \in U, the sequence of iterates (Tk)(T_k) exhibits either strictly quadratic or strictly cubic convergence to zero of the entry (Tk)23(T_k)_{23}. In fact, quadratic convergence occurs exactly when limTk=TX\lim T_k = T_X. Let XX be the union of such quadratically convergent sequences (Tk)(T_k): the set XX has Hausdorff dimension 1 and is a union of disjoint arcs XσX^\sigma meeting at TXT_X, where σ\sigma ranges over a Cantor set.Comment: 20 pages, 8 figures. Some passages rewritten for clarit

    XPS surface analysis of ceria-based materials: Experimental methods and considerations

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    X-ray photoelectron spectroscopy (XPS) analysis of cerium is ubiquitous amongst the catalytic and materials literature however errors in experimental procedure and data analysis are often easily proliferated. In this work we focus on the best practice for experimental construction when approaching the task of understanding chemical environments in cerium-based materials by XPS
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