109,771 research outputs found
Features and technologies of ERS-1 (ESA) and X-SAR antennas
Features and technologies of planar waveguide array antennas developed for spaceborne microwave sensors are described. Such antennas are made from carbon fiber reinforced plastic (CFRP) employing special manufacturing and metallization techniques to achieve satisfactory electrical properties. Mechanical design enables deployable antenna structures necessary for satellite applications (e.g., ESA ERS-1). The slotted waveguide concept provides high aperture efficiency, good beamshaping capabilities, and low losses. These CFRP waveguide antennas feature low mass, high accuracy and stiffness, and can be operated within wide temperature ranges
Helicopter noise regulations: An industry perspective
A review of helicopter noise measurement programs and noise reduction/economic studies of FAA is given along with a critique of a study which addresses the economic impact of noise reduction on helicopter noise. Modification of several helicopters to reduce noise and demonstrate the economic impact of the application of the current state-of-the-art technology is discussed. Specific helicopters described include Boeing Vertol 347 Helicopter, Hughes OH-6 Helicopter, and Hughes 269C Helicopter. Other topics covered include: (1) noise trends and possible noise limits; (2) accuracy of helicopter noise prediction techniques; (3) limited change possibilities of derivatives; and (4) rotor impulsive noise. The unique operational capabilities of helicopters and the implications relative to noise regulations and certification are discussed
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Pararhabdodon Isonensis and Tsintaosaurus Spinorhinus: A New Clade of Lambeosaurine Hadrosaurids from Eurasia
We present new anatomical information showing that Koutalisaurus kohlerorum, from the Maastrichtian of Lleida Province, northeastern Spain, is most probably the junior synonym of Pararhabdodon isonensis from the same region. Dentary and maxillary characters previously considered as autapomorphies of K. kohlerorum and P isonensis, respectively, are shown to be synapomorphies uniting the latter with Tsintaosaurus spinorhinus from the Campanian of the Wangshi Group, Shandong Province, China. This study provided conclusive evidence of the presence of the Lambeosaurinae in Europe. Tsintaosaurus spinorhinus and Pararhabdodon isonensis were inferred to form a clade of basal lambeosaurines characterized by a maxilla with an elevated articular facet for the jugal (continuous with the ectopterygoid ridge) and an extremely medially projected symphyseal region of the dentary. This clade originated in Asia during the middle or late Campanian. Pararhabdodon isonensis or its ancestors migrated from Asia to the Iberian island of the European archipelago. Reconstruction of ancestral areas by Fitch parsimony attributes the European occurrence of P isonensis to a single dispersal event from Asia no later than middle to late Campanian. (C) 2009 Elsevier Ltd. All rights reserved.Charlotte and Walter Kohler Charitable TrustFlorida State UniversityNational Science Foundation EAR 0207744, DBI 0446224Field Museum of Natural HistoryDepartments of Geosciences and Civil EngineeringGraduate School at Texas Tech UniversityScience Department at South Plains CollegeSigma Xi National Scientific HonoraryUniversity of Texas at AustinNSF IGERTMinistry of Education and Science of Spain CGL2005-07878-C02-01Geological Science
Collapsible loop antenna for space vehicle Patent
Collapsible, space erectable loop antenna system for space vehicl
Upgraded automotive gas turbine engine design and development program, volume 2
Results are presented for the design and development of an upgraded engine. The design incorporated technology advancements which resulted from development testing on the Baseline Engine. The final engine performance with all retro-fitted components from the development program showed a value of 91 HP at design speed in contrast to the design value of 104 HP. The design speed SFC was 0.53 versus the goal value of 0.44. The miss in power was primarily due to missing the efficiency targets of small size turbomachinery. Most of the SFC deficit was attributed to missed goals in the heat recovery system relative to regenerator effectiveness and expected values of heat loss. Vehicular fuel consumption, as measured on a chassis dynamometer, for a vehicle inertia weight of 3500 lbs., was 15 MPG for combined urban and highway driving cycles. The baseline engine achieved 8 MPG with a 4500 lb. vehicle. Even though the goal of 18.3 MPG was not achieved with the upgraded engine, there was an improvement in fuel economy of 46% over the baseline engine, for comparable vehicle inertia weight
A study of local and non-local spatial densities in quantum field theory
We use a one-dimensional model system to compare the predictions of two
different 'yardsticks' to compute the position of a particle from its quantum
field theoretical state. Based on the first yardstick (defined by the
Newton-Wigner position operator), the spatial density can be arbitrarily narrow
and its time-evolution is superluminal for short time intervals. Furthermore,
two spatially distant particles might be able to interact with each other
outside the light cone, which is manifested by an asymmetric spreading of the
spatial density. The second yardstick (defined by the quantum field operator)
does not permit localized states and the time evolution is subluminal.Comment: 29 pages, 3 figure
Discovery and mapping of the Triton seep site, Redondo Knoll: fluid flow and microbial colonization within an oxygen minimum zone
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wagner, J. K. S., Smart, C., & German, C. R. Discovery and mapping of the Triton seep site, Redondo Knoll: fluid flow and microbial colonization within an oxygen minimum zone. Frontiers in Marine Science, 7, (2020): 108, doi:10.3389/fmars.2020.00108.This paper examines a deep-water (∼900 m) cold-seep discovered in a low oxygen environment ∼30 km off the California coast in 2015 during an E/V Nautilus telepresence-enabled cruise. This Triton site was initially detected from bubble flares identified via shipboard multibeam sonar and was then confirmed visually using the remotely operated vehicle (ROV) Hercules. High resolution mapping (to 1 cm resolution) and co-registered imaging has provided us with a comprehensive site overview – both of the geologic setting and the extent of the associated microbial colonization. The Triton site represents an active cold-seep where microorganisms can act as primary producers at the base of a chemosynthesis-driven food chain. But it is also located near the core of a local oxygen minimum zone (OMZ), averaging 100 m across the seafloor, dominate the site, while typical seep-endemic macro-fauna were noticeably absent from our co-registered photographic and high-resolution mapping surveys – especially when compared to all adjacent seep sites within the same California Borderlands region. While such absences of abundant macro-fauna could be attributable to variations in the availability of dissolved oxygen in the overlying water column this need not necessarily be the case. An alternate possibility is that the zonation in microbial activity that is readily observable at the seafloor at Triton reflects, instead, a concentric pattern of radially diminishing fluxes of reductants from the underlying seafloor. This unusual but readily accessible discovery, in close proximity to Los Angeles harbor, provides an intriguing new natural laboratory at which to examine biogeochemical and microbiological interactions associated with the functioning of cold seep ecosystems within an OMZ.Ship time was funded by NOAA – Office of Exploration and Research and the Ocean Exploration Trust. This material is based upon work supported by a National Science Foundation Graduate Research Fellowship (to JW), the Office of Naval Research (to CS), and NASA’s Astrobiology program (to CG)
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