21,670 research outputs found
Almost rolling motion: An investigation of rolling grooved cylinders
We examine the dynamics of cylinders that are grooved to form N teeth for
rolling motion down an inclined plane. The grooved cylinders are experimentally
found to reach a terminal velocity. This result can be explained by the
inclusion of inelastic processes which occur whenever a tooth hits the surface.
The fraction of the angular velocity that is lost during an inelastic collision
is phenomenologically found to be proportional to
(2*sin^2*pi/N)-(alpha*sin^3*pi/N), and the method of least squares is used to
find the constant alpha=0.98. The adjusted theoretical results for the time of
rolling as well as for terminal velocity are found to be in good agreement with
the experimental results.Comment: 8 pages, 6 figures http://link.aip.org/link/?AJPIAS/66/202/
Chemistry: Space resources for teachers including suggestions for classroom activities and laboratory experiments
Curriculum supplement to assist general chemistry teachers in updating instruction materials with aerospace development
Orbiting multi-beam microwave radiometer for soil moisture remote sensing
The effects of soil moisture and other factors on soil surface emissivity are reviewed and design concepts for a multibeam microwave radiometer with a 15 m antenna are described. Characteristic antenna gain and radiation patterns are shown and losses due to reflector roughness are estimated
A structural model for composite rotor blades and lifting surfaces
Composite material systems are currently candidates for aerospace structures, primarily for the design flexibiity they offer i.e., it is possible to tailor the material and manufacturing approach to the application. Two notable examples are the wing of the Grumman/USAF/DARPA X-29 and rotor blades under development by the U.S.A. Aerostructures Directorate (AVSCOM), Langley Research Center. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to improve the single-cell beam model for composite rotor blades or lifting surfaces and to demonstrate its usefullness in applications
PILOT: design and capabilities
The proposed design for PILOT is a general-purpose, wide-field 1 degree 2.4m,
f/10 Ritchey-Chretien telescope, with fast tip-tilt guiding, for use 0.5-25
microns. The design allows both wide-field and diffraction-limited use at these
wavelengths. The expected overall image quality, including median seeing, is
0.28-0.3" FWHM from 0.8-2.4 microns. Point source sensitivities are estimated.Comment: 4 pages, Proceedings of 2nd ARENA conference 'The Astrophysical
Science Cases at Dome C', Potsdam, 17-21 September 200
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