20,517 research outputs found

    Effects of spiral longitudinal vortices on turbulent boundary layer skin friction

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    Effect of spiral longitudinal vortices on turbulent boundary layer skin frictio

    Resource management implications of ERTS-1 data to Ohio

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    Initial experimental analysis of ERTS-1 imagery has demonstrated that remote sensing from space is a means of delineating and inventorying Ohio's strip-mined areas, detecting power plant smoke plumes, and proving the data necessary for periodically compiling land use maps for the entire state. The nature and extent of these problems throughout Ohio, how ERTS data can contribute to their solution, and estimates of the long term significance of these initial findings to overall resource management interests in Ohio are summarized

    The Adiabatic Invariance of the Action Variable in Classical Dynamics

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    We consider one-dimensional classical time-dependent Hamiltonian systems with quasi-periodic orbits. It is well-known that such systems possess an adiabatic invariant which coincides with the action variable of the Hamiltonian formalism. We present a new proof of the adiabatic invariance of this quantity and illustrate our arguments by means of explicit calculations for the harmonic oscillator. The new proof makes essential use of the Hamiltonian formalism. The key step is the introduction of a slowly-varying quantity closely related to the action variable. This new quantity arises naturally within the Hamiltonian framework as follows: a canonical transformation is first performed to convert the system to action-angle coordinates; then the new quantity is constructed as an action integral (effectively a new action variable) using the new coordinates. The integration required for this construction provides, in a natural way, the averaging procedure introduced in other proofs, though here it is an average in phase space rather than over time.Comment: 8 page

    Optical image of a cometary nucleus: 1980 flyby of Comet Encke

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    The feasibility was investigated of obtaining optical images of a cometary nucleus via a flyby of Comet Encke. A physical model of the dust cloud surrounding the nucleus was developed by using available physical data and theoretical knowledge of cometary physics. Using this model and a Mie scattering code, calculations were made of the absolute surface brightness of the dust in the line of sight of the on-board camera and the relative surface brightness of the dust compared to the nucleus. The brightness was calculated as a function of heliocentric distance and for different phase angles (sun-comet-spacecraft angle)

    Flux-Confinement in Dilatonic Cosmic Strings

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    We study dilaton-electrodynamics in flat spacetime and exhibit a set of global cosmic string like solutions in which the magnetic flux is confined. These solutions continue to exist for a small enough dilaton mass but cease to do so above a critcal value depending on the magnetic flux. There also exist domain wall and Dirac monopole solutions. We discuss a mechanism whereby magnetic monopolesmight have been confined by dilaton cosmic strings during an epoch in the early universe during which the dilaton was massless.Comment: 8 pages, DAMTP R93/3

    Consulting parents and carers of children with complex needs who use rehabilitation therapy services about research - what issues are important?

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    With the aim of establishing a foundation for collaboration and partnership in research, parents and carers of children with complex needs were invited through a local parent carer forum to take part in a consultation about their priorities for research, with a focus on rehabilitation therapy. Three meetings were organised where researchers and parents and carers could discuss issues and topics of importance. Potential research ideas were generated at these meetings and shared via email with other parents and carers who were unable to attend face-to-face meetings and professionals who work with children with complex need. A number of researchable questions were developed, based on these topics during the time allocated to the consultation. The aim is to build on this work to develop a proposal for funded research that will make a difference to parents and carers and their families
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