9,618 research outputs found
A flight investigation of a terminal area navigation and guidance concept for STOL aircraft
A digital avionics system referred to as STOLAND has been test-flown in the NASA CV-340 to obtain performance data for time-controlled guidance in the manual flight director mode. The advanced system components installed in the cockpit included an electronic attitude director indicator and an electronic multifunction display. Navigation guidance and control computations were all performed in the digital computer. Approach paths were flown which included a narrow 180-deg turn and a 1-min, 5-deg straight-in approach to the 30-m altitude go-around point. Results are presented for 20 approaches: (1) blended radio/inertial navigation using TACAN and a microwave scanning beam landing guidance system (MODILS) permitted a smooth transition from area navigation (TACAN) to precision terminal navigation (MODILS), (2) guidance system (flight director) performance measured at an altitude of 30.5 m was within that prescribed for category II CTOL operations on a standard runway, and (3) time of arrival at a point about 2 mi from touchdown was about 4 sec plus or minus sec later than the computed nominal arrival time
A flight investigation of a terminal area navigation and guidance concept for STOL aircraft
A digital avionics system was installed in the CV-340 transport aircraft. Flight tests were made to obtain preliminary performance data in the manual flight director mode using time controlled guidance. These tests provide a basis for selection of terminal area guidance, navigation, and control system concepts for short haul aircraft and for investigating operational procedures
Spreading with evaporation and condensation in one-component fluids
We investigate the dynamics of spreading of a small liquid droplet in gas in
a one-component simple fluid, where the temperature is inhomogeneous around
0.9Tc and latent heat is released or generated at the interface upon
evaporation or condensation (with Tc being the critical temperature). In the
scheme of the dynamic van der Waals theory, the hydrodynamic equations
containing the gradient stress are solved in the axisymmetric geometry. We
assume that the substrate has a finite thickness and its temperature obeys the
thermal diffusion equation. A precursor film then spreads ahead of the bulk
droplet itself in the complete wetting condition. Cooling the substrate
enhances condensation of gas onto the advancing film, which mostly takes place
near the film edge and can be the dominant mechanism of the film growth in a
late stage. The generated latent heat produces a temperature peak or a hot spot
in the gas region near the film edge. On the other hand, heating the substrate
induces evaporation all over the interface. For weak heating, a steady-state
circular thin film can be formed on the substrate. For stronger heating,
evaporation dominates over condensation, leading to eventual disappearance of
the liquid region.Comment: 12 pages, 14 figure
Diffusion of Nonequilibrium Quasiparticles in a Cuprate Superconductor
We report a transport study of nonequilibrium quasiparticles in a high-Tc
cuprate superconductor using the transient grating technique. Low-intensity
laser excitation (at photon energy 1.5 eV) was used to introduce a spatially
periodic density of quasiparticles into a high-quality untwinned single crystal
of YBa2Cu3O6.5. Probing the evolution of the initial density through space and
time yielded the quasiparticle diffusion coefficient, and both inelastic and
elastic scattering rates. The technique reported here is potentially applicable
to precision measurement of quasiparticle dynamics, not only in cuprate
superconductors, but in other electronic systems as well.Comment: 5 pages, 4 figure
NMR evidence for Friedel-like oscillations in the CuO chains of ortho-II YBaCuO
Nuclear magnetic resonance (NMR) measurements of CuO chains of detwinned
Ortho-II YBaCuO (YBCO6.5) single crystals reveal unusual and
remarkable properties. The chain Cu resonance broadens significantly, but
gradually, on cooling from room temperature. The lineshape and its temperature
dependence are substantially different from that of a conventional spin/charge
density wave (S/CDW) phase transition. Instead, the line broadening is
attributed to small amplitude static spin and charge density oscillations with
spatially varying amplitudes connected with the ends of the finite length
chains. The influence of this CuO chain phenomenon is also clearly manifested
in the plane Cu NMR.Comment: 4 pages, 3 figures, refereed articl
Design, development, and flight test of a demonstration advanced avionics system
Ames Research Center initiated a program in 1975 to provide the critical information required for the design of integrated avionics suitable for general aviation. The program emphasized the use of data busing, distributed microprocessors, shared electronic displays and data entry devices, and improved functional capability. Design considerations included cost, reliability, maintainability, and modularity. As a final step, a demonstration advanced avionics system (DAAS) was designed, built, and flight tested in a Cessna 402, twin engine, general aviation aircraft. A functional description of the DAAS, including a description of the system architecture, is presented and the program and flight test results are briefly reviewed
Coronagraph particulate measurements. Skylab flight experiment T025
Major results of the Skylab T025 Coronagraph experiment designed to monitor the particulate contamination about the spacecraft and to study the earth's atmospheric aerosol distribution are presented. A model for comet outbursts based on the properties of amorphous ice and ground based narrow-band and white light photography of comet Kohoutek ten days to perihelion are included. The effect of atmospheric refraction on the analysis of the T025 atmospheric data was also investigated
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