1,758 research outputs found

    Mobile radio interferometric geodetic systems

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    Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed

    Feasibility study of the solar scientific instruments for Spacelab/Orbiter

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    The feasibility and economics of mounting and operating a set of solar scientific instruments in the backup Skylab Apollo Telescope Mount (ATM) hardware was evaluated. The instruments used as the study test payload and integrated into the ATM were: the Solar EUV Telescope/Spectrometer; the Solar Active Region Observing Telescope; and the Lyman Alpha White Light Coronagraph. The backup ATM hardware consists of a central cruciform structure, called the "SPAR', a "Sun End Canister' and a "Multiple Docking Adapter End Canister'. Basically, the ATM hardware and software provides a structural interface for the instruments; a closely controlled thermal environment; and a very accurate attitude and pointing control capability. The hardware is an identical set to the hardware that flow on Skylab

    Fivebranes and 4-manifolds

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    We describe rules for building 2d theories labeled by 4-manifolds. Using the proposed dictionary between building blocks of 4-manifolds and 2d N=(0,2) theories, we obtain a number of results, which include new 3d N=2 theories T[M_3] associated with rational homology spheres and new results for Vafa-Witten partition functions on 4-manifolds. In particular, we point out that the gluing measure for the latter is precisely the superconformal index of 2d (0,2) vector multiplet and relate the basic building blocks with coset branching functions. We also offer a new look at the fusion of defect lines / walls, and a physical interpretation of the 4d and 3d Kirby calculus as dualities of 2d N=(0,2) theories and 3d N=2 theories, respectivelyComment: 81 pages, 18 figures. v2: misprints corrected, clarifications and references added. v3: additions and corrections about lens space theory, 4-manifold gluing, smooth structure

    Non-Invasive Fall Risk Assessment in Community Dwelling Elderly with Wireless Inertial Measurement Units

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    Falls are among the most serious accidents among the elderly leading to increased injuries, reduced functioning and mortality. In 2009, about 2.2 million nonfatal fall injuries were reported among the elderly population (CDC, 2010). In this study, eleven community dwelling elderly (aged 65-84 years) participated in fall risk assessment camp at sterling senior center organized by Northern Virginia Fall Prevention Coalition (NVFPC). Three custom made wireless inertial measurement units (IMUs) were attached on trunk and both shanks. All participants performed postural and locomotor tasks such as sit-to-stand (STS) and timed up and go (TUG). Temporal and kinematic parameters were obtained. Raw signals obtained were denoised using ensemble empirical mode decomposition and savistzky-golay filtering. The mean and standard deviation of TUG time and STS completion time for participants were found to be 11.3±6.6 sec and 3.58±2.07 sec respectively. The high variation in the result may be due to the use of assistive devices (i.e., cane and walker) by two participants. The objective of this study is to classify fall prone community dwelling individuals using non-invasive system. Four participants were classified as fall prone, three without fall risk and four were at potential risk based on their objective assessment and task performance. This system provides a platform for identifying fall prone individuals and may be used for early fall interventions among the elderly

    Concept and optical design of the cross-disperser module for CRIRES

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    This is the peer reviewed version of the following article: Oliva, Ernesto, A. Tozzi, D. Ferruzzi, L. Origlia, A. Hatzes, R. Follert, T. Loewinger et al. "Concept and optical design of the cross-disperser module for CRIRES+." In SPIE Astronomical Telescopes+ Instrumentation, pp. 91477R-91477R. International Society for Optics and Photonics, 2014, which has been published in final form at 10.1117/12.2054381

    Geodetic measurements with a mobile VLBI system

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    The Project ARIES 9 meter transportable antenna was used as one element of very long baseline interferometer (VLBI) to begin monitoring locations of six sites in California relative to large diameter fixed antennas at the NASA Deep Space Network, Goldstone, California, and at the Caltech Owens Valley Radio Observatory, Big Pine, California. An accuracy of about 6 cm in the horizontal components was demonstrated by comparison with measurements of the National Geodetic Survey. The root of mean square scatter of the lengths of the baselines between any pair of antennas was about 3 cm except for the Goldstone-JPL (Pasadena) baseline. In the period August 1974 to August 1977 the length of this baseline increased by 15 + or - 5 cm as JPL moved westward relative to Goldstone at the rate of 6 + or - 2 cm/year. The baseline lengths were unaffected by the uncertainties of UT1, polar motion, and tropospheric water vapor, which are the limitations to present three dimensional vector accuracies
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