9,448 research outputs found
Rocket injector head
A high number of liquid oxygen and gaseous hydrogen orifices per unit area are provided in an injector head designed to give intimate mixing and more thorough combustion. The injector head comprises a main body portion, a cooperating plate member as a flow chamber for one propellant, a cooperating manifold portion for the second propellant, and an annular end plate for enclosing an annular propellant groove formed around the outer edge of the body. All the openings for one propellant are located at the same angle with respect to a radial plane to permit a short combustion chamber
Parrotts Creek Dredge Channel Data Report
Parrotts Creek is located along the Rappahannock River in Middlesex County, VA. The mouth of the creek is about 850 ft wide, but just inside the mouth of the creek, a spit extends from the upland narrowing the creek to about 300 ft before it widens again. Overall, this is a relatively short, undeveloped creek. Most of the development (wharfs, ramps, piers) occur near the mouth. Most of the more inland areas of the creek are surrounded by woodland. The federally-authorized channel was established in 1955 due to the presence of a public ramp and landing area, as well as oyster and seafood packing houses located on the creek. It is a 4,800 ft long, 60 ft wide channel with a 120 ft by 120 ft turning basin, and a controlling depth of -6 ft MLLW. (...
Town of Colonial Beach Survey of Central and Castlewood Beaches
The Town of Colonial Beach occupies a peninsula between the Potomac River and Monroe Bay. Approximately 2.5 miles of the shoreline is publicly-owned. Two areas on the Potomac River have been enhanced as recreational beaches for swimming and sunbathing. Central Beach is located just south of the Town Pier and is the main recreational beach. Castlewood Beach is south of Central Beach near the entrance to Monroe Bay
Investigation of the Multiple Method Adaptive Control (MMAC) method for flight control systems
The stochastic adaptive control of the NASA F-8C digital-fly-by-wire aircraft using the multiple model adaptive control (MMAC) method is presented. The selection of the performance criteria for the lateral and the longitudinal dynamics, the design of the Kalman filters for different operating conditions, the identification algorithm associated with the MMAC method, the control system design, and simulation results obtained using the real time simulator of the F-8 aircraft at the NASA Langley Research Center are discussed
Green-Schwarz Formulation of Self-Dual Superstring
The self-dual superstring has been described previously in a
Neveu-Schwarz-Ramond formulation with local N=2 or 4 world-sheet supersymmetry.
We present a Green-Schwarz-type formulation, with manifest spacetime
supersymmetry.Comment: 11 pg., (uuencoded dvi file) ITP-SB-92-5
Gauge Field Back-reaction on a Black Hole
The order fluctuations of gauge fields in the vicinity of a blackhole
can create a repulsive antigravity region extending out beyond the renormalized
Schwarzschild horizon. If the strength of this repulsive force increases as
higher orders in the back-reaction are included, the formation of a
wormhole-like object could occur.Comment: 17 pages, three figures available on request, in RevTe
Biology and ecology of the invasive lionfishes, Pterois miles and Pterois volitans
The Indo-Pacific lionfishes, Pterois miles and P. volitans, are now established along the U.S. southeast coast, Bermuda, Bahamas, and are becoming established in the Caribbean. While these lionfish are popular in the aquarium trade, their biology and ecology are poorly understood in their native range. Given the rapid establishment and potential adverse impacts of these invaders, comprehensive studies of their biology and ecology are warranted. Here we provide a synopsis of lionfish biology and ecology including invasion chronology, taxonomy, local abundance, reproduction, early life history and dispersal, venomology, feeding ecology, parasitology, potential impacts, and control and management. This information was collected through review of the primary literature and published reports and by summarizing current observations. Suggestions for future research on invasive lionfish in their invaded regions are provided
Super D-branes from BRST Symmetry
Recently a new formalism has been developed for the covariant quantization of
superstrings. We study properties of Dp-branes and p-branes in this new
framework, focusing on two different topics: effective actions and boundary
states for Dp-branes. We present a derivation of the Wess-Zumino terms for
super (D)p-branes using BRST symmetry. To achieve this we derive the BRST
symmetry for superbranes, starting from the approach with/without pure spinors,
and completely characterize the WZ terms as elements of the BRST cohomology. We
also develope the boundary state description of Dp-branes by analyzing the
boundary conditions for open strings in the completely covariant (i.e., without
pure spinors) BRST formulation.Comment: 31 pp; journal version, expended discussion of D-brane pure spinor
constraints in Section 2.
Space-Time Supersymmetry of Extended Fermionic Strings in Dimensions
The fermionic string theory is revisited in light of its recently
proposed equivalence to the non-compact fermionic string model. The
issues of space-time Lorentz covariance and supersymmetry for the BRST
quantized strings living in uncompactified dimensions are
discussed. The equivalent local quantum supersymmetric field theory appears to
be the most transparent way to represent the space-time symmetries of the
extended fermionic strings and their interactions. Our considerations support
the Siegel's ideas about the presence of Lorentz symmetry as well as
at least one self-dual space-time supersymmetry in the theory of the
fermionic strings, though we do not have a compelling reason to argue about the
necessity of the {\it maximal} space-time supersymmetry. The world-sheet
arguments about the absence of all string massive modes in the physical
spectrum, and the vanishing of all string-loop amplitudes in the Polyakov
approach, are given on the basis of general consistency of the theory.Comment: 29 pages, LaTeX, ITP-UH-1/9
A Finite Quantum Gravity Field Theory Model
We discuss the quantization of Delta gravity, a two symmetric tensors model
of gravity. This model, in Cosmology, shows accelerated expansion without a
cosmological constant. We present the transformation which
defines the geometry of the model. Then we show that all delta type models live
at one loop only. We apply this to General Relativity and we calculate the one
loop divergent part of the Effective Action showing its null contribution in
vacuum, implying a finite model. Then we proceed to study the existence of
ghosts in the model. Finally, we study the form of the finite quantum
corrections to the classical action of the model.Comment: Latex, 33 page
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