NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
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linear interference suppression, <strong>and</strong> signature optimization for combined interference avoidance <strong>and</strong> pre-equalization of<br />
multi-path. Transmitter optimization with limited feedback has also been considered, <strong>and</strong> bounds on the achievable<br />
performance as a function of feedback bits per dimension have been obtained. This project has resulted in a patent application<br />
for an adaptive reduced-rank filter, a paper award (for work on reduced-rank filtering), <strong>and</strong> numerous journal <strong>and</strong> conference<br />
publications on the preceding topics.<br />
DTIC<br />
Multipath Transmission; Multiple Access; Signal Processing; Spread Spectrum Transmission<br />
20040073720 City Univ. of New York, NY<br />
Electromagnetic Propagation, Localization <strong>and</strong> Lasing in R<strong>and</strong>om <strong>and</strong> Periodic Media<br />
Genack, A. Z.; Dec. 30, 2003; 13 pp.; In English; Original contains color illustrations<br />
Contract(s)/Grant(s): DAAD19-00-1-0362<br />
Report No.(s): AD-A422634; ARO-40044.12-PH; No Copyright; Avail: CASI; A03, Hardcopy<br />
Our measurements of the frequency <strong>and</strong> spatial variation of the microwave field in ensembles of r<strong>and</strong>om samples have<br />
revealed the underlying structure of wave correlation <strong>and</strong> photon localization. The intensity correlation was found in terms of<br />
displacement <strong>and</strong> polarization shift of the source <strong>and</strong> detector can be expressed in terms of the square of the corresponding<br />
field correlation function. Nonexponential decay of pulsed transmission through disordered media was found in nominally<br />
diffusive media, in which the level width exceeds the spacing between levels. This departure from diffusion theory is<br />
interpreted in terms of the decay rate statistics of electromagnetic quasi-normal modes. The influence of these modes of the<br />
electromagnetic field is an indication of the breakdown of the particle diffusion theory. Measurements of spatial <strong>and</strong><br />
polarization correlation as a function of time delay from an exciting pulse show that the structure of the intensity correlation<br />
function is the same as found in steady state propagation, being a function only of the corresponding field correlation<br />
functions. The degree of correlation in the speckle pattern is seen to be the key parameter in dynamics <strong>and</strong> hence in steady<br />
state propagation. We have discovered a localization laser in r<strong>and</strong>om one dimensional systems.<br />
DTIC<br />
Electromagnetic Fields; Electromagnetic Wave Transmission; Lasing; Position (Location)<br />
20040074161 Army Engineer Research <strong>and</strong> Development Center, Vicksburg, MS<br />
Ashtubula River, Ohio, Sedimentation Study. Report 3 Erosion Experiments on Bed Sediments<br />
Teeter, Allen M.; Brister, Doug; Parman, Joe W.; Coleman, Clara J.; Sep. 1999; 49 pp.; In English<br />
Report No.(s): AD-A422689; CHL-99-9; No Copyright; Avail: CASI; A03, Hardcopy<br />
Bed-sediment samples from the Ashtabula River in Ohio were subjected to stepwise increasing shear stresses to assess<br />
erodibility. Ten erosion experiments were performed in an oscillating-screen erosion chamber, <strong>and</strong> five experiments were<br />
performed in a water tunnel. Imposed shear stress ranged from 0.2 to 2.33 Pa. Sediments were characterized by grain size,<br />
density, pH, moisture content, loss on ignition, <strong>and</strong> rheological behavior. Sediments were mostly silt (42-72 percent) with clay<br />
content ranging from 15 to 30 percent. Scatter in the experimental erosion results did not appear to be related to sample<br />
location or other factors. Taken by device, the indicated threshold for erosion was 0.34 Pa for the oscillating-screen erosion<br />
chamber <strong>and</strong> 0.8 Pa for the water tunnel. Taking all tests together, a reasonable threshold for erosion was 0.28 Pa. Mean<br />
erosion rate constant, or erosion rate at twice the threshold shear stress, was 7.2 g/sq m/min.<br />
DTIC<br />
Erosion; Hydraulic Test Tunnels; Rivers; Sediments; Water Pollution<br />
71<br />
ACOUSTICS<br />
Includes sound generation, transmission, <strong>and</strong> attenuation. For noise pollution see 45 Environment Pollution. For aircraft noise see also<br />
02 Aerodynamics <strong>and</strong> 07 Aircraft Propulsion <strong>and</strong> Power.<br />
20040070813 Texas A&M Univ., TX, USA<br />
Mitigation of the Impact of Sensing Noise on the Precise Formation Flying Control Problem<br />
Alfriend, K. T.; [2004]; 6 pp.; In English<br />
Contract(s)/Grant(s): NCC5-724; No Copyright; Avail: CASI; A02, Hardcopy<br />
The specific objectives of this proposed research were: 1. Further investigation into the impact of CDGPS sensing errors<br />
for high Earth orbit missions. 2. Identify augmentation approaches of the CDGPS that will improve the relative state for low<br />
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