477 research outputs found
Generator for a space power system Patent
Design and development of electric generator for space power syste
Summary of the results of feasibility studies of direct voice broadcasting undertaken for the National Aeronautics and Space Administration
Feasibility study of direct broadcast of voice programs from unmanned satellite to home receiver
Determination of Flame Temperatures from 2000 to 3000 K by Microwave Absorption
Equations are derived for the measurement of flame temperatures from the attenuation of a microwave beam by temperature-induced free electrons from chemical elements introduced in the flame. Corrections are developed to account for the electron distribution in the flame. Procedure for obtaining the temperature from absorption is outlined. The free electron collision frequency and an effective ionization potential for four alkali elements were determined experimentally. The data were taken on a gas burner with a temperature range from 1900deg to 2400deg K. The effective ionization potential of sodium agrees with the spectral-line limit value. From these experimental ionization potentials and the experimental collision frequency, an accuracy of +/-600 K in the temperature was obtained. Fluctuating and average temperature data of a liquid propellant burner are presented primarily from 1.25-centimeter-wavelength microwave measurements in comparison with simultaneous two-color pyrometer and sound intensity measurements in the region from 2200deg to 2900deg K
Helicoidal surfaces with constant anisotropic mean curvature
We study surfaces with constant anisotropic mean curvature which are
invariant under a helicoidal motion. For functionals with axially symmetric
Wulff shapes, we generalize the recently developed twizzler representation of
Perdomo to the anisotropic case and show how all helicoidal constant
anisotropic mean curvature surfaces can be obtained by quadratures
Evidence of unconventional low-frequency dynamics in the normal phase of Ba(Fe1-xRhx)2As2 iron-based supercondutors
This work presents 75As NMR spin echo decay rate (1/T2) measurements in
Ba(Fe1-xRhx)2As2 superconductors, for 0.041 < x < 0.094. It is shown that 1/T2
increases upon cooling, in the normal phase, suggesting the onset of an
unconventional very low-frequency activated dynamic. The correlation times of
the fluctuations and their energy barriers are derived. The motion is favored
at large Rh content, while it is hindered by the application of a magnetic
field perpendicular to the FeAs layers. The same dynamic is observed in the
spin-lattice relaxation rate, in a quantitatively consistent manner. These
results are discussed in the light of nematic fluctuations involving domain
wall motion. The analogies with the behaviour observed in the cuprates are also
outlined
Density Profiles of Subsonic Boundary Layers on a Flat Plate Determined by X-ray and Pressure Measurements
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