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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 9 (1993), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Direct observations of feeding sea otters (Enhydra lutris) at 11 sites in southeast Alaska showed infaunal clams to be the primary prey utilized by otters throughout the region. Foraging dive times associated with clam and sea urchin prey were significantly longer than those for more easily captured prey (crabs and mussels). Dive times and surface intervals were also generally correlated with water depth or apparent difficulty in obtaining buried prey. Male otters, which fed more extensively on clams than females, made significantly longer foraging dives than females. Foraging success remained high, even at sites where prey numbers were found to be very low during a related study. The very deeply burrowing geoduck clam (Panope abrupta), while common at several otter feeding sites, was rarely captured by otters. These results, combined with those of a companion study on prey numbers, indicate that butter clams (Saxidomus giganteus) account for the majority of the sea otter diet in southeast Alaska, and that sea urchins may represent relatively short-term prey in comparison to infaunal bivalves in regions where both prey types co-exist. Furthermore, the importance of butter clams in the sea otter diet and the tendency for this bivalve to retain chronically high levels of paralytic shellfish poisoning toxins in southeast Alaska increases the probability that toxic phytoplankton blooms influence sea otter distribution in this region.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1991-07-01
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
    Publication Date: 1990-08-01
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
    Publication Date: 1993-09-01
    Print ISSN: 1063-651X
    Electronic ISSN: 1095-3787
    Topics: Physics
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  • 5
    Publication Date: 2004-12-04
    Description: Control system design for general nonlinear flight dynamic models is considered through numerical simulation. The design is accomplished through a numerical optimizer coupled with analysis of flight dynamic equations. In the analysis, the general nonlinear flight dynamic equations with nonlinear aerodynamics are numerically integrated; and the dynamic characteristics needed in the optimization process are then identified from the dynamic response. To assure a reasonable solution, the initial input values of the design variables are estimated through a sensitivity analysis. To demonstrate the method, the pitch departure prevention for an F-16 configuration is demonstrated.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA. Langley Research Center, The Third Air Force(NASA Symposium on Recent Advances in Multidisciplinary Analysis and Optimization; p 562-568
    Format: text
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  • 6
    Publication Date: 2013-08-31
    Description: Automated Rendezvous and Capture (AR&C) is an important technology to multiple National Aeronautics and Space Administration (NASA) programs and centers. The recent Johnson Spacecraft Center (JSC) AR&C Quality Function Deployment (QFD) has listed on-orbit demonstration of related technologies as a near term priority. Martin Marietta has been evaluating use of the Manned Maneuvering Unit (MMU) for a low cost near term on-orbit demonstration of AR&C technologies such as control algorithms, sensors, and processors as well as system level performance. The MMU Program began in 1979 as the method of repairing the Space Shuttle (STS) Thermal Protection System (the tiles). The units were not needed for this task, but were successfully employed during three Shuttle flights in 1984: a test flight was flown in in February as proof of concept, in April the MMU participated in the Solar Max Repair Mission, and in November the MMU's returned to space to successfully rescue the two errant satellites, Westar and Palapa. In the intervening years, the MMU simulator and MMU Qualification Test Unit (QTU) have been used for Astronaut training and experimental evaluations. The Extra-Vehicular Activities (EVA) Retriever has used the QTU, in an unmanned form, as a free-flyer on the Johnson Space Center (JSC) Precision Air Bearing Floor (PABF). Currently, the MMU is undergoing recertification for flight. The two flight units were removed from storage in September, 1991 and evaluation tests were performed. The tests demonstrated that the units are in good shape with no discrepancies that would preclude further use. The Return to Flight effort is currently clearing up recertification issues and evaluating the design against the present Shuttle environments.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Washington, NASA Automated Rendezvous and Capture Review. A Compilation of the Abstracts; 2 p
    Format: application/pdf
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  • 7
    Publication Date: 2013-08-31
    Description: The results of L-band communications availability work performed to date are presented. Results include a L-band communications availability estimate model and field propagation trials using an INMARSAT-M terminal. American Mobile Satellite Corporation's (AMSC's) primary concern centers on availability of voice communications intelligibility, with secondary concerns for circuit-switched data and fax. The model estimates for representative terrain/vegetation areas are applied to the contiguous U.S. for overall L-band communications availability estimates.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Proceedings of the Eighteenth NASA Propagation Experimenters Meeting (NAPEX 18) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop p 181-210 (SEE N95-146; JPL, Proceedings of
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  • 8
    Publication Date: 2019-06-28
    Description: Induced aerodynamics from thrust vectoring are investigated by a computational fluid dynamic method. A thin-layer Reynolds-averaged Navier-Stokes code with multiblock capability is used. Jet properties are specified on the nozzle exit plane to simulate the jet momentum. Results for a rectangular jet in a cross flow are compared with data to verify the code. Further verification of the calculation is made by comparing the numerical results with transonic data for a wing-body combination. Additional calculations were performed to elucidate the following thrust vectoring effects: the thrust vectoring effect on shock and expansion waves, induced effects on nearby surfaces, and the thrust vectoring effect on the leading edge vortex.
    Keywords: AERODYNAMICS
    Type: NASA-CR-188186 , NAS 1.26:188186
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  • 9
    Publication Date: 2019-06-28
    Description: The method based on Fourier functional analysis and indicial formulation for aerodynamic modeling as proposed by Chin and Lan is extensively examined and improved for the purpose of general applications to realistic airplane configurations. Improvement is made to automate the calculation of model coefficients, and to evaluate more accurately the indicial integral. Test data of large angle-of-attack ranges for two different models, a 70 deg. delta wing and an F-18 model, are used to further verify the applicability of Fourier functional analysis and validate the indicial formulation. The results show that the general expression for harmonic motions throughout a range of k is capable of accurately modeling the nonlinear responses with large phase lag except in the region where an inconsistent hysteresis behavior from one frequency to the other occurs. The results by the indicial formulation indicate that more accurate results can be obtained when the motion starts from a low angle of attack where hysteresis effect is not important.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-190444 , NAS 1.26:190444 , KU-FRL-872-5
    Format: application/pdf
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  • 10
    Publication Date: 2019-06-28
    Description: Due to the requirement of increased performance and maneuverability, the flight envelope of a modern fighter is frequently extended to the high angle-of-attack regime. Vehicles maneuvering in this regime are subjected to nonlinear aerodynamic loads. The nonlinearities are due mainly to three-dimensional separated flow and concentrated vortex flow that occur at large angles of attack. Accurate prediction of these nonlinear airloads is of great importance in the analysis of a vehicle's flight motion and in the design of its flight control system. A satisfactory evaluation of the performance envelope of the aircraft may require a large number of coupled computations, one for each change in initial conditions. To avoid the disadvantage of solving the coupled flow-field equations and aircraft's motion equations, an alternate approach is to use a mathematical modeling to describe the steady and unsteady aerodynamics for the aircraft equations of motion. Aerodynamic forces and moments acting on a rapidly maneuvering aircraft are, in general, nonlinear functions of motion variables, their time rate of change, and the history of maneuvering. A numerical method was developed to analyze the nonlinear and time-dependent aerodynamic response to establish the generalized indicial function in terms of motion variables and their time rates of change.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186630 , NAS 1.26:186630 , KU-FRL-872-1
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