90,552 research outputs found
A preliminary shield design for a SNAP-8 power system
A preliminary shield design for a nuclear power system utilizing a SNAP-8 reactor for space base application is presented. A representative space base configuration was selected to set the geometry constraints imposed on the design. The base utilizes two independent power packages each with a reactor operating at 600 kwt and each producing about 50 kwe. The crew compartment is located about 200 feet from each reactor and is large enough in extent to intercept a total shadow angle of 60 deg measured about the center line of each reactor
Zebra battery technologies for all electric smart car
This paper describes the operational behaviour and advantages of the high temperature, sodium nickel chloride (Zebra) battery, for use in all electric urban (city) vehicles. It is shown that an equivalent parallel electrical circuit can be employed to accurately simulate the electrochemical behaviour inherent in the most recent generation of Zebra cells. The experimental procedure is outlined and summary attributes of the investigation validated by both simulation studies, and experimentally, via measurements from a prototype battery module intended for use in an all electric smart ca
Wind tunnel investigation of rotor lift and propulsive force at high speed: Data analysis
The basic test data obtained during the lift-propulsive force limit wind tunnel test conducted on a scale model CH-47b rotor are analyzed. Included are the rotor control positions, blade loads and six components of rotor force and moment, corrected for hub tares. Performance and blade loads are presented as the rotor lift limit is approached at fixed levels of rotor propulsive force coefficients and rotor tip speeds. Performance and blade load trends are documented for fixed levels of rotor lift coefficient as propulsive force is increased to the maximum obtainable by the model rotor. Test data is also included that defines the effect of stall proximity on rotor control power. The basic test data plots are presented in volumes 2 and 3
Testing Algorithms for Finite Temperature Lattice QCD
We discuss recent algorithmic improvements in simulating finite temperature
QCD on a lattice. In particular, the Rational Hybrid Monte Carlo(RHMC)
algorithm is employed to generate lattice configurations for 2+1 flavor QCD.
Unlike the Hybrid R Algorithm, RHMC is reversible, admitting a Metropolis
accept/reject step that eliminates the errors
inherent in the R Algorithm. We also employ several algorithmic speed-ups,
including multiple time scales, the use of a more efficient numerical
integrator, and Hasenbusch pre-conditioning of the fermion force.Comment: 4 pages, 2 figures, poster presented at International Conference on
Strong and Electroweak Matter 2006 (SEWM2006), BNL, May 10-13, 200
Light transport and general aviation aircraft icing research requirements
A short term and a long term icing research and technology program plan was drafted for NASA LeRC based on 33 separate research items. The specific items listed resulted from a comprehensive literature search, organized and assisted by a computer management file and an industry/Government agency survey. Assessment of the current facilities and icing technology was accomplished by presenting summaries of ice sensitive components and protection methods; and assessments of penalty evaluation, the experimental data base, ice accretion prediction methods, research facilities, new protection methods, ice protection requirements, and icing instrumentation. The intent of the research plan was to determine what icing research NASA LeRC must do or sponsor to ultimately provide for increased utilization and safety of light transport and general aviation aircraft
Generation of twin Fock states via transition from a two-component Mott insulator to a superfluid
We propose the dynamical creation of twin Fock states, which exhibit
Heisenberg limited interferometric phase sensitivities, in an optical lattice.
In our scheme a two-component Mott insulator with two bosonic atoms per lattice
site is melted into a superfluid. This process transforms local correlations
between hyperfine states of atom pairs into multi-particle correlations
extending over the whole system. The melting time does not scale with the
system size which makes our scheme experimentally feasible.Comment: 4 pages, 4 figure
The Close Binary Fraction of Dwarf M Stars
We describe a search for close spectroscopic dwarf M star binaries using data from the Sloan Digital Sky Survey to address the question of the rate of occurrence of multiplicity in M dwarfs. We use a template-fitting technique to measure radial velocities from 145,888 individual spectra obtained for a magnitude-limited sample of 39,543 M dwarfs. Typically, the three or four spectra observed for each star are separated in time by less than four hours, but for ~17% of the stars, the individual observations span more than two days. In these cases we are sensitive to large-amplitude radial velocity variations on timescales comparable to the separation between the observations. We use a control sample of objects having observations taken within a four-hour period to make an empirical estimate of the underlying radial velocity error distribution and simulate our detection efficiency for a wide range of binary star systems. We find the frequency of binaries among the dwarf M stars with a < 0.4 AU to be 3%-4%. Comparison with other samples of binary stars demonstrates that the close binary fraction, like the total binary fraction, is an increasing function of primary mass
Thermochemical ablation of rocket nozzle insert materials Final report
Resistance of rocket nozzle throat insert materials to corrosion and meltin
Probabilistic Quantum Control Via Indirect Measurement
The most basic scenario of quantum control involves the organized
manipulation of pure dynamical states of the system by means of unitary
transformations. Recently, Vilela Mendes and Mank'o have shown that the
conditions for controllability on the state space become less restrictive if
unitary control operations may be supplemented by projective measurement. The
present work builds on this idea, introducing the additional element of
indirect measurement to achieve a kind of remote control. The target system
that is to be remotely controlled is first entangled with another identical
system, called the control system. The control system is then subjected to
unitary transformations plus projective measurement. As anticipated by
Schrodinger, such control via entanglement is necessarily probabilistic in
nature. On the other hand, under appropriate conditions the remote-control
scenario offers the special advantages of robustness against decoherence and a
greater repertoire of unitary transformations. Simulations carried out for a
two-level system demonstrate that, with optimization of control parameters, a
substantial gain in the population of reachable states can be realized.Comment: 9 pages, 2 figures; typos added, reference added, reference remove
Interim prediction method for externally blown flap noise
An interim procedure for predicting externally blown flap (EBF) noise spectra anywhere below a powered lift aircraft is presented. Both engine-under-the-wing and engine-over-the-wing EBF systems are included. The method uses data correlations for the overall sound pressure level based on nozzle exit area and exhaust velocity along with OASPL directivity curves and normalized one-third-octave spectra. Aircraft motion effects are included by taking into account the relative motion of the source with respect to the observer and the relative velocity effects on source strength
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