100,906 research outputs found
Aerospace vehicle
A dual structure aerospace vehicle is described which has an aeroshell structure and an internally disposed separable and reusable integral tank/thrust structure. The tank/thrust structure is inuslated for cryogenic fuels and the cavity within aeroshell is insulated from the tank/thrust structure. An internal support ring within the cavity serves as an attachment for lugs on the tank/thrust structure via double hinges. The aft end of tank/thrust structure is provided with rocket engines and exit nozzles with a trunnion supporting the tank/thrust structure within the aeroshell
The Arecibo Galaxy Environment Survey VIII : Discovery of an Isolated Dwarf Galaxy in the Local Volume
The Arecibo Galaxy Environment Survey (AGES) has detected a nearby HI source
at a heliocentric velocity of +363 km/s . The object was detected through its
neutral hydrogen emission and has an obvious possible optical counterpart in
Sloan Digital Sky Survey (SDSS) data (though it does not have an optical
redshift measurement). We discuss three possible scenarios for the object : 1)
It is within the Local Group, in which case its HI properties are comparable
with recently discovered ultra-compact high velocity clouds; 2) It is just
behind the Local Group, in which case its optical characteristics are similar
to the newly discovered Leo P galaxy; 3) It is a blue compact dwarf galaxy
within the local volume but not associated with the Local Group. We find the
third possibility to be the most likely, based on distance estimates from the
Tully-Fisher relation and its velocity relative to the Local Group.Comment: 5 pages, 6 figures, accepted for publication in MNRAS. Minor
correction to institution and addres
An atlas of GEOS-3 radar altimeter data for data buoy comparison studies
An atlas is compiled to identify times and dates when GEOS-3 altimeter data was taken in the vicinity of data buoys. The time period covered is from GEOS launch to April 9, 1978. Two buffer areas are considered for each of the various buoy locations to determine the simultaneity of GEOS and buoy data. The two buffer areas are ? or - 0.25 degrees and ? or - 1 degree
Duality of N=2 Heterotic -- Type I Compactifications in Four Dimensions
We discuss type I -- heterotic duality in four-dimensional models obtained as
a Coulomb phase of the six-dimensional U(16) orientifold model compactified on
T^2 with arbitrary SU(16) Wilson lines. We show that Kahler potentials, gauge
threshold corrections and the infinite tower of higher derivative F-terms agree
in the limit that corresponds to weak coupling, large T^2 heterotic
compactifications. On the type I side, all these quantities are completely
determined by the spectrum of N=2 BPS states that originate from D=6 massless
superstring modes.Comment: 22 pages, LaTeX; typos corrected and references adde
Daze fasteners
A daze fastener system for connecting two or more structural elements wherein the structural elements and fastener parts have substantially different coefficient of thermal expansion physical property characteristics is employed in this invention. By providing frusto-conical abutting surfaces between the structural elements and fastener parts any differences in thermal expansion/contraction between the parts is translated to sliding motion and avoids deleterious thermal stresses in the connection. An essential feature for isotropic homogeneous material connections is that at least two sets of mating surfaces are required wherein each set of mating surfaces have line element extensions that pass through a common point
Digital computing cardiotachometer
A tachometer is described which instantaneously measures heart rate. During the two intervals between three succeeding heart beats, the electronic system: (1) measures the interval by counting cycles from a fixed frequency source occurring between the two beats; and (2) computes heat rate during the interval between the next two beats by counting the number of times that the interval count must be counted to zero in order to equal a total count of sixty times (to convert to beats per minute) the frequency of the fixed frequency source
Cardiotachometer displays heart rate on a beat-to-beat basis
Electronics for this system may be chosen so that complete calculation and display may be accomplished in a few milliseconds, far less than even the fastest heartbeat interval. Accuracy may be increased, if desired, by using higher-frequency timing oscillator, although this will require large capacity registers at increased cost
Polarizability of molecular hydrogen
Static dipole electric polarizabilities of molecular hydroge
Flame Instability and Transition to Detonation in Supersonic Reactive Flows
Multidimensional numerical simulations of a homogeneous, chemically reactive
gas were used to study ignition, flame stability, and
deflagration-to-detonation transition (DDT) in a supersonic combustor. The
configuration studied was a rectangular channel with a supersonic inflow of
stoichiometric ethylene-oxygen and a transimissive outflow boundary. The
calculation is initialized with a velocity in the computational domain equal to
that of the inflow, which is held constant for the duration of the calculation.
The compressible reactive Navier-Stokes equations were solved by a high-order
numerical algorithm on an adapting mesh. This paper describes two calculations,
one with a Mach 3 inflow and one with Mach 5.25. In the Mach 3 case, the
fuel-oxidizer mixture does not ignite and the flow reaches a steady-state
oblique shock train structure. In the Mach 5.25 case, ignition occurs in the
boundary layers and the flame front becomes unstable due to a Rayleigh-Taylor
instability at the interface between the burned and unburned gas. Growth of the
reaction front and expansion of the burned gas compress and preheat the
unburned gas. DDT occurs in several locations, initiating both at the flame
front and in the unburned gas, due to an energy-focusing mechanism. The growth
of the flame instability that leads to DDT is analyzed using the Atwood number
parameter
Vegetation boundaries on ERTS-1 imagery
There are no author-identified significant results in this report
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