4,480 research outputs found

    The role of the research simulator in the systems development of rotorcraft

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    The potential application of the research simulator to future rotorcraft systems design, development, product improvement evaluations, and safety analysis is examined. Current simulation capabilities for fixed-wing aircraft are reviewed and the requirements of a rotorcraft simulator are defined. The visual system components, vertical motion simulator, cab, and computation system for a research simulator under development are described

    Electrodynamics of Amorphous Media at Low Temperatures

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    Amorphous solids exhibit intrinsic, local structural transitions, that give rise to the well known quantum-mechanical two-level systems at low temperatures. We explain the microscopic origin of the electric dipole moment of these two-level systems: The dipole emerges as a result of polarization fluctuations between near degenerate local configurations, which have nearly frozen in at the glass transition. An estimate of the dipole's magnitude, based on the random first order transition theory, is obtained and is found to be consistent with experiment. The interaction between the dipoles is estimated and is shown to contribute significantly to the Gr\"{u}neisen parameter anomaly in low TT glasses. In completely amorphous media, the dipole moments are expected to be modest in size despite their collective origin. In partially crystalline materials, however, very large dipoles may arise, possibly explaining the findings of Bauer and Kador, J. Chem. Phys. {\bf 118}, 9069 (2003).Comment: Submitted for publication; April 27, 2005 versio

    Characterizing Deformation of Buildings from Videos

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    We have started to explore the feasibility of extracting useful data on the deformation of buildings and structures based on optical videos, (Taghavi Larigani & Heaton). In the beginning, we look at the characterizations and limitations of the hardware, which is composed of a high-quality digital camera, combined with its optical imaging system capturing a video-footage of the structure under test, and then introduce a straightforward targets-tracking algorithm that produces the time-series displacements of targets that we select on the video. We performed preliminary measurements consisting of testing our targets-tracking algorithm using high definition format videos displaying the structures that we wanted to test. The measurements pertain to a 1) finite-element software-generated video of JPL/NASA principal building, 2) YouTube-video of a seismic dynamic test of a building, 3) YouTube-video of the Millennium London Bridge “Wobbly Bridge”, 4) YouTube-video of a United Boeing 777, 4) YouTube-video of NASA space shuttle rockets during launch. So far, our tests are encouraging. If our approach proves viable, it can be transformative for the field of earthquake engineering and structural health monitoring. Hence, we consider the prospect of using our technique for surveying buildings and other civil structures in high seismic risk urban agglomerations. In parallel, the same technique could be applied for 1) real-time structural health monitoring of civil structures, 2) nuclear plants, 3) oil and gas infrastructures, 4) rail & road networks, 5) aircraft, 6) spacecraft, 7) etc., by simply analyzing the structure-facing camera recorded data

    Error characteristics of SFM with unknown focal length

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    Ph.DDOCTOR OF PHILOSOPH

    c ○ 2003 Kluwer Academic Publishers. Manufactured in The Netherlands. Understanding the Behavior of SFM Algorithms: A Geometric Approach

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    Abstract. We put forth in this paper a geometrically motivated motion error analysis which is capable of supporting investigation of global effect such as inherent ambiguities. This is in contrast with the usual statistical kinds of motion error analyses which can only deal with local effect such as noise perturbations, and where much of the results regarding global ambiguities are empirical in nature. The error expression that we derive allows us to predict the exact conditions likely to cause ambiguities and how these ambiguities vary with motion types such as lateral or forward motion. Given the erroneous 3-D motion estimates caused by the inherent ambiguities, it is also important to study the behavior of the resultant distortion in depth recovered under different motion-scene configurations. Such an investigation may alert us to the occurrence of ambiguities under different conditions and be more careful in picking the solution. Our formulation, though geometrically motivated, was also put to use in modeling the effect of noise and in revealing the strong influence of feature distribution. Experiments on both synthetic and real image sequences were conducted to verify the various theoretical predictions. Keywords: structure from motion, error analysis, epipolar constraint, inherent ambiguity, depth distortio

    Large deployable antenna program. Phase 1: Technology assessment and mission architecture

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    The program was initiated to investigate the availability of critical large deployable antenna technologies which would enable microwave remote sensing missions from geostationary orbits as required for Mission to Planet Earth. Program goals for the large antenna were: 40-meter diameter, offset-fed paraboloid, and surface precision of 0.1 mm rms. Phase 1 goals were: to review the state-of-the-art for large, precise, wide-scanning radiometers up to 60 GHz; to assess critical technologies necessary for selected concepts; to develop mission architecture for these concepts; and to evaluate generic technologies to support the large deployable reflectors necessary for these missions. Selected results of the study show that deployable reflectors using furlable segments are limited by surface precision goals to 12 meters in diameter, current launch vehicles can place in geostationary only a 20-meter class antenna, and conceptual designs using stiff reflectors are possible with areal densities of 2.4 deg/sq m
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