26,008 research outputs found
Wind energy system time-domain (WEST) analyzers
A portable analyzer which simulates in real time the complex nonlinear dynamics of horizontal axis wind energy systems was constructed. Math models for an aeroelastic rotor featuring nonlinear aerodynamic and inertial terms were implemented with high speed digital controllers and analog calculation. This model was combined with other math models of elastic supports, control systems, a power train and gimballed rotor kinematics. A stroboscopic display system graphically depicting distributed blade loads, motion, and other aerodynamic functions on a cathode ray tube is included. Limited correlation efforts showed good comparison between the results of this analyzer and other sophisticated digital simulations. The digital simulation results were successfully correlated with test data
Pyrotechnic shock analysis and testing methods
Pyrotechnic shock analysis and testing methods for Ranger and Mariner spacecraft measurement
Implicit marching solution of compressible viscous subsonic flow in planar and axisymmetric ducts
A new streamwise marching procedure was developed and coded for compressible viscous subsonic flow in planar or axisymmetric ducts with or without centerbodies. The continuity, streamwise momentum, cross-flow momentum, and energy equations are written in generalized orthogonal curvilinear coordinates. To allow the use of a marching procedure, second derivatives in the streamwise momentum equation are written as the sum of a known two dimensional imposed pressure field and an unknown one dimensional viscous correction. For turbulent flow, the Reynolds stress and heat flux terms are modeled using two-layer eddy viscosity turbulence models
Controlled Manipulation of Individual Vortices in a Superconductor
We report controlled local manipulation of single vortices by low temperature
magnetic force microscope (MFM) in a thin film of superconducting Nb. We are
able to position the vortices in arbitrary configurations and to measure the
distribution of local depinning forces. This technique opens up new
possibilities for the characterization and use of vortices in superconductors
The compatible conversion system
Compatible conversion system centralizes the solution of general problems arising from the use of direct access mass storage. It also provides a simple stable interface for the conversion of production programs to process on third generation computer system
A terminal guidance scheme for lifting body entry vehicles
Perturbation feedback guidance for terminal phase of lifting body entry vehicl
A Four-Unit-Cell Periodic Pattern of Quasiparticle States Surrounding Vortex Cores in Bi2Sr2CaCu2O8+d
Scanning tunneling microscopy is used to image the additional quasiparticle
states generated by quantized vortices in the high-Tc superconductor
Bi2Sr2CaCu2O8+d. They exhibit a Cu-O bond oriented 'checkerboard' pattern, with
four unit cell (4a0) periodicity and a ~30 angstrom decay length. These
electronic modulations may be related to the magnetic field-induced, 8a0
periodic, spin density modulations of decay length ~70 angstroms recently
discovered in La1.84Sr0.16CuO4. The proposed explanation is a spin density wave
localized surrounding each vortex core. General theoretical principles predict
that, in the cuprates, a localized spin modulation of wavelength L should be
associated with a corresponding electronic modulation of wavelength L/2, in
good agreement with our observations.Comment: 10 pages, 3 figure
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