27,786 research outputs found
Kolmogorov-Burgers Model for Star Forming Turbulence
The process of star formation in interstellar molecular clouds is believed to
be controlled by driven supersonic magnetohydrodynamic turbulence. We suggest
that in the inertial range such turbulence obeys the Kolmogorov law, while in
the dissipative range it behaves as Burgers turbulence developing shock
singularities. On the base of the She-Leveque analytical model we then predict
the velocity power spectrum in the inertial range to be E_k ~ k^{-1.74}. This
result reproduces the observational Larson law, ~ l^{0.74...0.76},
[Larson, MNRAS 194 (1981) 809] and agrees well with recent numerical findings
by Padoan and Nordlund [astro-ph/0011465]. The application of the model to more
general dissipative structures, with higher fractal dimensionality, leads to
better agreement with recent observational results.Comment: revised, new material added, 8 page
Treatment of blueberries prior to freeze dehydration
Softening blueberry skin by treatment with weak solution of sodium hydroxide prior to freeze dehydration prevents tough, chewy skins upon rehydration
A study of the relationship of the incidence of physical complaints and the dissatisfactions of students of nursing during their psychiatric nursing experience
Thesis (M.S.)--Boston Universit
Development of non-sweet, flavored food cubes
Food cubes exhibit flavor and quality stability for periods of four weeks in 100 deg F environment. They are suitable for field rations, emergency rations or snacks and should interest the food processing industry
Scaling relations of supersonic turbulence in star-forming molecular clouds
We present a direct numerical and analytical study of driven supersonic MHD
turbulence that is believed to govern the dynamics of star-forming molecular
clouds. We describe statistical properties of the turbulence by measuring the
velocity difference structure functions up to the fifth order. In particular,
the velocity power spectrum in the inertial range is found to be close to E(k)
\~ k^{-1.74}, and the velocity difference scales as ~ L^{0.42}. The
results agree well with the Kolmogorov--Burgers analytical model suggested for
supersonic turbulence in [astro-ph/0108300]. We then generalize the model to
more realistic, fractal structure of molecular clouds, and show that depending
on the fractal dimension of a given molecular cloud, the theoretical value for
the velocity spectrum spans the interval [-1.74 ... -1.89], while the
corresponding window for the velocity difference scaling exponent is [0.42 ...
0.78].Comment: 17 pages, 6 figures include
Flight control system development and flight test experience with the F-111 mission adaptive wing aircraft
The wing on the NASA F-111 transonic aircraft technology airplane was modified to provide flexible leading and trailing edge flaps. This wing is known as the mission adaptive wing (MAW) because aerodynamic efficiency can be maintained at all speeds. Unlike a conventional wing, the MAW has no spoilers, external flap hinges, or fairings to break the smooth contour. The leading edge flaps and three-segment trailing edge flaps are controlled by a redundant fly-by-wire control system that features a dual digital primary system architecture providing roll and symmetric commands to the MAW control surfaces. A segregated analog backup system is provided in the event of a primary system failure. This paper discusses the design, development, testing, qualification, and flight test experience of the MAW primary and backup flight control systems
Statistical analysis of landing contact conditions for three lifting body research vehicles
The landing contact conditions for the HL-10, M2-F2/F3, and the X-24A lifting body vehicles are analyzed statistically for 81 landings. The landing contact parameters analyzed are true airspeed, peak normal acceleration at the center of gravity, roll angle, and roll velocity. Ground measurement parameters analyzed are lateral and longitudinal distance from intended touchdown, lateral distance from touchdown to full stop, and rollout distance. The results are presented in the form of histograms for frequency distributions and cumulative frequency distribution probability curves with a Pearson Type 3 curve fit for extrapolation purposes
Hopf Algebras of Heap Ordered Trees and Permutations
It is known that there is a Hopf algebra structure on the vector space with
basis all heap-ordered trees. We give a new bialgebra structure on the space
with basis all permutations and show that there is a direct bialgebra
isomorphism between the Hopf algebra of heap-ordered trees and the bialgebra of
permutations.Comment: 10 pages LaTeX, minor revisio
Development of compressed nonsweet, flavored snack foods to be used in the Apollo food system Final report, 5 Jan. 1970 - 30 Apr. 1971
Compressed, coated, freeze dried, nonsweet, cheese and meat flavored snack cubes for Apollo food syste
- …