3,653 research outputs found
Delay-induced multistability near a global bifurcation
We study the effect of a time-delayed feedback within a generic model for a
saddle-node bifurcation on a limit cycle. Without delay the only attractor
below this global bifurcation is a stable node. Delay renders the phase space
infinite-dimensional and creates multistability of periodic orbits and the
fixed point. Homoclinic bifurcations, period-doubling and saddle-node
bifurcations of limit cycles are found in accordance with Shilnikov's theorems.Comment: Int. J. Bif. Chaos (2007), in prin
Fabrication and test of lightweight honeycomb sandwich structures Final report
Fabrication and testing of lightweight honeycomb sandwich structure
Potential utilization of the NASA/George C. Marshall Space Flight Center in earthquake engineering research
Earthquake engineering research capabilities of the National Aeronautics and Space Administration (NASA) facilities at George C. Marshall Space Flight Center (MSFC), Alabama, were evaluated. The results indicate that the NASA/MSFC facilities and supporting capabilities offer unique opportunities for conducting earthquake engineering research. Specific features that are particularly attractive for large scale static and dynamic testing of natural and man-made structures include the following: large physical dimensions of buildings and test bays; high loading capacity; wide range and large number of test equipment and instrumentation devices; multichannel data acquisition and processing systems; technical expertise for conducting large-scale static and dynamic testing; sophisticated techniques for systems dynamics analysis, simulation, and control; and capability for managing large-size and technologically complex programs. Potential uses of the facilities for near and long term test programs to supplement current earthquake research activities are suggested
Depletion of carriers and negative differential conductivity in an intrinsic graphene under a dc electric field
The heating of carriers in an intrinsic graphene under an abrupt switching
off a dc electric field is examined taking into account both the energy
relaxation via acoustic and optic phonons and the interband
generation-recombination processes. The later are caused by the interband
transitions due to optical phonon modes and thermal radiation. Description of
the temporal and steady-state responses, including the nonequilibrium
concentration and energy as well as the current-voltage characteristics, is
performed. At room temperature, a nearly-linear current-voltage characteristic
and a slowly-varied concentration take place for fields up to -- 20 kV/cm.
Since a predominant recombination of high-energy carriers due to optical phonon
emission at low temperatures, a depletion of concentration takes place below --
250 K. For lower temperatures the current tends to be saturated and a negative
differential conductivity appears below -- 170 K in the region of fields -- 10
V/cm.Comment: 8 pages, 10 figures, extended versio
Application of advanced technologies to small, short-haul transport aircraft (STAT)
The benefits of selected advanced technologies for 19 and 30 passenger, short-haul aircraft were identified. Advanced technologies were investigated in four areas: aerodynamics, propulsion, structures, and ride quality. Configuration sensitivity studies were conducted to show design tradeoffs associated with passenger capacity, cabin comfort level, and design field length
Best Legume for Permanent Pasture
No other pasture legume now available compares with birdsfoot trefoil in abiliity to withstand continuous grazing once it is established. Trefoil does, however, need more attention than other legumes in getting established. Here are some tips from Iowa State College agronomists
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