48,345 research outputs found
Single-channel digital command-detection system
System, fabricated of highly-reliable digital logic elements, operates on binary pulse-code-modulated signals and derives internal synchronization from data signal. All-digital implementation of detector develops synchronization from data signal by computer cross-correlation of command modulation signal with its expected forms in sequence and adjusts detector phases in accordance with correlation peaks
Method and apparatus for a single channel digital communications system
A method and apparatus are described for synchronizing a received PCM communications signal without requiring a separate synchronizing channel. The technique provides digital correlation of the received signal with a reference signal, first with its unmodulated subcarrier and then with a bit sync code modulated subcarrier, where the code sequence length is equal in duration to each data bit
Advanced techniques for determining long term compatibility of materials with propellants
A method for the prediction of propellant-material compatibility for periods of time up to ten years is presented. Advanced sensitive measurement techniques used in the prediction method are described. These include: neutron activation analysis, radioactive tracer technique, and atomic absorption spectroscopy with a graphite tube furnace sampler. The results of laboratory tests performed to verify the prediction method are presented
Distinct high-T transitions in underdoped BaKFeAs
In contrast to the simultaneous structural and magnetic first order phase
transition previously reported, our detailed investigation on an
underdoped BaKFeAs single crystal unambiguously
revealed that the transitions are not concomitant. The tetragonal (:
I4/mmm) - orthorhombic (: Fmmm) structural transition occurs at
110 K, followed by an adjacent antiferromagnetic (AFM) transition
at 102 K. Hysteresis and coexistence of the and
phases over a finite temperature range observed in our NMR
experiments confirm the first order character of the structural transition and
provide evidence that both and are strongly correlated. Our
data also show that superconductivity (SC) develops in the phase
below = 20 K and coexists with long range AFM. This new observation,
, firmly establishes another similarity between the hole-doped
BaFeAs via K substitution and the electron-doped iron-arsenide
superconductors.Comment: 4 pages, 3 figure
Remarks on the Classical Size of D-Branes
We discuss different criteria for `classical size' of extremal Dirichlet
p-branes in type-II supergravity. Using strong-weak coupling duality, we find
that the size of the strong-coupling region at the core of the (p<3)-branes, is
always given by the asymptotic string scale, if measured in the weakly coupled
dual string metric. We also point out how the eleven-dimensional Planck scale
arises in the classical 0-brane solution, as well as the ten-dimensional Planck
scale in the D-instanton solution.Comment: 8 pp, harvma
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