3,357 research outputs found
NASA advanced turboprop research and concept validation program
NASA has determined by experimental and analytical effort that use of advanced turboprop propulsion instead of the conventional turbofans in the older narrow-body airline fleet could reduce fuel consumption for this type of aircraft by up to 50 percent. In cooperation with industry, NASA has defined and implemented an Advanced Turboprop (ATP) program to develop and validate the technology required for these new high-speed, multibladed, thin, swept propeller concepts. This paper presents an overview of the analysis, model-scale test, and large-scale flight test elements of the program together with preliminary test results, as available
Insect (Arthropoda: Insecta) Composition in the Diet of Ornate Box Turtles (Terrapene ornata ornata) in Two Western Illinois Sand Prairies, with a New State Record for Cyclocephala (Coleoptera: Scarabaeidae)
A study of fecal samples collected over a two-year period from juvenile ornate box turtles (Terrapene ornata ornata Agassiz) revealed diets consisting of six orders of insects representing 19 families. Turtles were reared in captivity from eggs harvested from local, wild populations, and released at two remnant prairies. Identifiable insect fragments were found in 94% of samples in 2013 (n=33) and 96% in 2014 (n=25). Frequency of occurrence of insects in turtle feces is similar to results reported in previous studies of midwestern Terrapene species. A comparison of insect composition presented no significant difference between release sites. There is no significant difference in consumed insect species between turtles released into or outside of a fenced enclosure at the same site. Specimens of Cyclocephala longula LeConte collected during this study represent a new state record for Illinois
Discrete breathers in systems with homogeneous potentials - analytic solutions
We construct lattice Hamiltonians with homogeneous interaction potentials
which allow for explicit breather solutions. Especially we obtain exponentially
localized solutions for -dimensional lattices with .Comment: 10 page
The Sunyaev Zel'dovich effect: simulation and observation
The Sunyaev Zel'dovich effect (SZ effect) is a complete probe of ionized
baryons, the majority of which are likely hiding in the intergalactic medium.
We ran a CDM simulation using a moving mesh hydro code to
compute the statistics of the thermal and kinetic SZ effect such as the power
spectra and measures of non-Gaussianity. The thermal SZ power spectrum has a
very broad peak at multipole with temperature fluctuations
K. The power spectrum is consistent with available
observations and suggests a high and a possible role of
non-gravitational heating. The non-Gaussianity is significant and increases the
cosmic variance of the power spectrum by a factor of for .
We explore optimal driftscan survey strategies for the AMIBA CMB
interferometer and their dependence on cosmology. For SZ power spectrum
estimation, we find that the optimal sky coverage for a 1000 hours of
integration time is several hundred square degrees. One achieves an accuracy
better than 40% in the SZ measurement of power spectrum and an accuracy better
than 20% in the cross correlation with Sloan galaxies for . For
cluster searches, the optimal scan rate is around 280 hours per square degree
with a cluster detection rate 1 every 7 hours, allowing for a false positive
rate of 20% and better than 30% accuracy in the cluster SZ distribution
function measurement.Comment: 34 pages, 20 figures. Submitted to ApJ. Simulation maps have been
replaced by high resolution images. For higher resolution color images,
please download from http://www.cita.utoronto.ca/~zhangpj/research/SZ/ We
corrected a bug in our analysis. the SZ power spectrum decreases 50% and y
parameter decrease 25
Optical manipulation of intrinsic localized vibrational energy in cantilever arrays
Optically-induced real-time impurity modes are used to shepherd intrinsic
localized vibrational modes (discrete breathers) along micromechanical arrays
via either attractive or replulsive interactions. Adding an electrode to the
cantilever array provides control of the sign of lattice anharmonicity, hence
allowing both hard and soft nonlinearities to be studied. A number of dynamical
effects are demonstrated and explained, including the optical tweezing of
localized vibrational energy in a nonlinear lattice.Comment: 11 pages, 4 figures to be published in Europhysics Letter
Fuel savings potential of the NASA Advanced Turboprop Program
The NASA Advanced Turboprop (ATP) Program is directed at developing new technology for highly loaded, multibladed propellers for use at Mach 0.65 to 0.85 and at altitudes compatible with the air transport system requirements. Advanced turboprop engines offer the potential of 15 to 30 percent savings in aircraft block fuel relative to advanced turbofan engines (50 to 60 percent savings over today's turbofan fleet). The concept, propulsive efficiency gains, block fuel savings and other benefits, and the program objectives through a systems approach are described. Current program status and major accomplishments in both single rotation and counter rotation propeller technology are addressed. The overall program from scale model wind tunnel tests to large scale flight tests on testbed aircraft is discussed
On the Complexity of Heuristic Synthesis for Satisficing Classical Planning: Potential Heuristics and Beyond
Potential functions are a general class of heuristics for classical planning. For satisficing planning, previous work suggested the use of descending and dead-end avoiding (DDA) potential heuristics, which solve planning tasks by backtrack-free search. In this work we study the complexity of devising DDA potential heuristics for classical planning tasks. We show that verifying or synthesizing DDA potential heuristics is PSPACE-complete, but suitable modifications of the DDA properties reduce the complexity of these problems to the first and second level of the polynomial hierarchy. We also discuss the implications of our results for other forms of heuristic synthesis in classical planning
Product assurance technology for custom LSI/VLSI electronics
The technology for obtaining custom integrated circuits from CMOS-bulk silicon foundries using a universal set of layout rules is presented. The technical efforts were guided by the requirement to develop a 3 micron CMOS test chip for the Combined Release and Radiation Effects Satellite (CRRES). This chip contains both analog and digital circuits. The development employed all the elements required to obtain custom circuits from silicon foundries, including circuit design, foundry interfacing, circuit test, and circuit qualification
The Cosmic Microwave Background & Inflation, Then & Now
Boomerang, Maxima, DASI, CBI and VSA significantly increase the case for
accelerated expansion in the early universe (the inflationary paradigm) and at
the current epoch (dark energy dominance), especially when combined with data
on high redshift supernovae (SN1) and large scale structure (LSS). There are
``7 pillars of Inflation'' that can be shown with the CMB probe, and at least
5, and possibly 6, of these have already been demonstrated in the CMB data: (1)
a large scale gravitational potential; (2) acoustic peaks/dips; (3) damping due
to shear viscosity; (4) a Gaussian (maximally random) distribution; (5)
secondary anisotropies; (6) polarization. A 7th pillar, anisotropies induced by
gravity wave quantum noise, could be too small. A minimal inflation parameter
set, \omega_b,\omega_{cdm}, \Omega_{tot}, \Omega_Q,w_Q,n_s,\tau_C, \sigma_8},
is used to illustrate the power of the current data. We find the CMB+LSS+SN1
data give \Omega_{tot} =1.00^{+.07}_{-.03}, consistent with (non-baroque)
inflation theory. Restricting to \Omega_{tot}=1, we find a nearly scale
invariant spectrum, n_s =0.97^{+.08}_{-.05}. The CDM density, \Omega_{cdm}{\rm
h}^2 =.12^{+.01}_{-.01}, and baryon density, \Omega_b {\rm h}^2 =
>.022^{+.003}_{-.002}, are in the expected range. (The Big Bang nucleosynthesis
estimate is 0.019\pm 0.002.) Substantial dark (unclustered) energy is inferred,
\Omega_Q \approx 0.68 \pm 0.05, and CMB+LSS \Omega_Q values are compatible with
the independent SN1 estimates. The dark energy equation of state, crudely
parameterized by a quintessence-field pressure-to-density ratio w_Q, is not
well determined by CMB+LSS (w_Q < -0.4 at 95% CL), but when combined with SN1
the resulting w_Q < -0.7 limit is quite consistent with the w_Q=-1 cosmological
constant case.Comment: 20 pages, 8 figures, in Theoretical Physics, MRST 2002: A Tribute to
George Libbrandt (AIP), eds. V. Elias, R. Epp, R. Myer
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