1,860 research outputs found

    User acceptance of intelligent avionics: A study of automatic-aided target recognition

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    User acceptance of new support systems typically was evaluated after the systems were specified, designed, and built. The current study attempts to assess user acceptance of an Automatic-Aided Target Recognition (ATR) system using an emulation of such a proposed system. The detection accuracy and false alarm level of the ATR system were varied systematically, and subjects rated the tactical value of systems exhibiting different performance levels. Both detection accuracy and false alarm level affected the subjects' ratings. The data from two experiments suggest a cut-off point in ATR performance below which the subjects saw little tactical value in the system. An ATR system seems to have obvious tactical value only if it functions at a correct detection rate of 0.7 or better with a false alarm level of 0.167 false alarms per square degree or fewer

    Over-the-Rotor Liner Investigation via the NASA Langley Normal Incidence Tube

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    NASA Langley and Glenn Research Centers have collaborated on the usage of acoustic liners mounted very near or directly over the rotor of turbofan aircraft engines. This collaboration began over a decade ago with the investigation of a metallic foam liner. Similar to conventional acoustic liner applications, this liner was designed to absorb sound generated by the rotor-alone and rotor-stator interaction sources within the fan duct. Given its proximity to the rotor tips, the expectation was that the liner would also serve as a pressure release and thereby inhibit the amount of noise generated. Initial acoustic results were promising, but there was concern regarding potential aerodynamic penalties. Nevertheless, there were sufficient positive results to warrant further investigation. To that end, the current report presents results obtained in the NASA Langley Normal Incidence Tube for 20 acoustic liner candidates for the OTR application. The majority contain grooves at their surface, designed to minimize aerodynamic penalties caused by placing the liner in close proximity to the fan rotor tips. The intent is to assess the acoustic properties of each liner configuration, and in particular to assess the effects of including the grooves on the overall acoustic performance. An additional intent of this paper is to provide documentation regarding recent enhancements to the NASA Langley Normal Incidence Tube

    The Lithium Depletion Boundary and the Age of the Young Open Cluster IC~2391

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    We have obtained new photometry and intermediate resolution (Ī”Ī»=2.7\Delta \lambda = 2.7 \AA\ ) spectra of 19 of these objects (14.9 ā‰¤\le IcI_c ā‰¤\le 17.5) in order to confirm cluster membership. We identify 15 of our targets as likely cluster members based on their VRIVRI photometry, spectral types, radial velocity, and HĪ±\alpha emission strengths. Higher S/N spectra were obtained for 8 of these probable cluster members in order to measure the strength of the lithium 6708 \AA\ doublet and thus obtain an estimate of the cluster's age. One of these 8 stars has a definite lithium detection and two other (fainter) stars have possible lithium detections. A color-magnitude diagram for our program objects shows that the lithium depletion boundary in IC~2391 is at IcI_c=16.2. Using recent theoretical model predictions, we derive an age for IC~2391 of 53Ā±\pm5 Myr. While this is considerably older than the age most commonly attributed for this cluster (āˆ¼\sim35 Myr) this result for IC~2391 is comparable those recently derived for the Pleiades and Alpha Persei clusters and can be explained by new models for high mass stars that incorporate a modest amount of convective core overshooting.Comment: ApJ Letters, acccepte

    The Properties of Radio Galaxies and the Effect of Environment in Large Scale Structures at zāˆ¼1z\sim1

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    In this study we investigate 89 radio galaxies that are spectroscopically-confirmed to be members of five large scale structures in the redshift range of 0.65ā‰¤zā‰¤0.960.65 \le z \le 0.96. Based on a two-stage classification scheme, the radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), hybrid, and star-forming galaxy (SFG). We study the properties of the three radio sub-classes and their global and local environmental preferences. We find AGN hosts are the most massive population and exhibit quiescence in their star-formation activity. The SFG population has a comparable stellar mass to those hosting a radio AGN but are unequivocally powered by star formation. Hybrids, though selected as an intermediate population in our classification scheme, were found in almost all analyses to be a unique type of radio galaxies rather than a mixture of AGN and SFGs. They are dominated by a high-excitation radio galaxy (HERG) population. We discuss environmental effects and scenarios for each sub-class. AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, with these preferences persisting when comparing to galaxies of similar colour and stellar mass, suggesting that their activity may be ignited in the cluster/group virialized core regions. Conversely, SFGs exhibit a strong preference for intermediate-density global environments, suggesting that dusty starbursting activity in LSSs is largely driven by galaxy-galaxy interactions and merging.Comment: 28 pages, 10 figures, accepted to MNRA

    Subtle Deficits in Instrumental Activities of Daily Living in Subtypes of Mild Cognitive Impairment

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    Mild cognitive impairment ļæ½ Functional impairment ļæ½ Activities of daily living ļæ½ Memory performance ļæ½ Executive function domains. These cross-sectional findings support previous longitudinal reports suggesting that cognitive and functional impairments in MCI may be independently associated with dementia risk. Copyright Ā© 2010 S. Karger AG, Basel Background/Aims: Greater cognitive and functional deficits in mild cognitive impairment (MCI) are associated with higher rates of dementia. We explored the relationship between these factors by comparing instrumental activities of daily living (IADLs) among cognitive subtypes of MCI and examining associations between IADL and neuropsychological indices. Methods: We analyzed data from 1,108 MCI and 3,036 normal control subjects included in the National Alzheimerā€™s Coordinating Center Uniform Data Set who were assessed with the Functional Activities Questionnaire (FAQ). Results: IADL deficits were greater in amnestic than nonamnestic MCI, but within these subgroups, did not differ between those with single or multiple domains of cognitive impairment. FAQ indices correlated significantly with memory and processing speed/executive function. Conclusions: IADL deficits are present in both amnestic MCI and nonamnestic MCI but are not related to the number of impaired cognitiv

    Nonā€Insulin Dependent Diabetes Mellitus and Alveolar Bone Loss Progression Over 2 Years

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141702/1/jper0076.pd

    An Effect of Ī±ā€²\alpha' Corrections on Racetrack Inflation

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    We study the effects of Ī±ā€² \alpha ' corrections to the K\"ahler potential on volume stabilisation and racetrack inflation. In a region where classical supergravity analysis is justified, stringy corrections can nevertheless be relevant for correctly analyzing moduli stabilisation and the onset of inflation.Comment: 13 pages, 4 figures. Typos corrected, references added, this version to appear in JHE
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