568 research outputs found

    Quiet engine program flight engine design study

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    The results are presented of a preliminary flight engine design study based on the Quiet Engine Program high-bypass, low-noise turbofan engines. Engine configurations, weight, noise characteristics, and performance over a range of flight conditions typical of a subsonic transport aircraft were considered. High and low tip speed engines in various acoustically treated nacelle configurations were included

    QCSEE task 2: Engine and installation preliminary design

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    High-bypass turbofan engines with features required for commercial short haul powered lift transports were designed. Two engines were configured for each of the externally blown flap installations, under-the-wing and over-the-wing. Estimates of installed and uninstalled performance, noise, and weight were defined for each propulsion system

    Aerodynamic Optimization of a Golf Driver Using Computational Fluid Dynamics

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143102/1/6.2017-0724.pd

    Transient, Non-Axisymmetric Modes in Instability of Unsteady Circular Couette Flow

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    Laboratory and numerical experiments were conducted to quantitatively determine the modal structure of transient, nonaxisymmetric modes observed during the instability of an impulsively initiated circular‐Couette flow. The instability develops initially as an axisymmetric, Görtler‐vortex state and persists ultimately as a steady, axisymmetric Taylor‐vortex state of different wavelength. The transition between these two states results from the instability of the Görtler mode combined with the underlying developing swirl flow and is dominated by nonaxisymmetric modes. The laboratory experiments employed flow visualization coupled with digital video and image‐processing techniques; numerical experiments were performed using the spectral‐element code

    Hanford Site National Environmental Policy Act (NEPA) characterization. Revision 9

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    This ninth revision of the Hanford Site National Environmental Policy Act (NEPA) Characterization presents current environmental data regarding the hanford Site and its immediate environs. This information is intended for use in preparing Chapters 4 and 6 in Hanford Site-related NEPA documents. Chapter 4.0 (Affected Environment) includes information on climate and meteorology, geology, hydrology, ecology, cultural, archaeological and historical resources, socioeconomics, and noise. Chapter 6.0 (Statutory and Regulatory Requirements) provides the preparer with the federal and state regulations, DOE directives and permits, and environmental standards directly applicable to the NEPA documents on the Hanford Site. Not all of the sections have been updated for this revision. The following lists the updated sections: climate and meteorology; ecology (threatened and endangered species section only); culture, archaeological, and historical resources; socioeconomics; all of Chapter 6

    Distinctive correspondence between separable visual attention functions and intrinsic brain networks

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    Separable visual attention functions are assumed to rely on distinct but interacting neural mechanisms. Bundesen's “theory of visual attention” (TVA) allows the mathematical estimation of independent parameters that characterize individuals' visual attentional capacity (i.e., visual processing speed and visual short-term memory storage capacity) and selectivity functions (i.e., top-down control and spatial laterality). However, it is unclear whether these parameters distinctively map onto different brain networks obtained from intrinsic functional connectivity, which organizes slowly fluctuating ongoing brain activity. In our study, 31 demographically homogeneous healthy young participants performed whole- and partial-report tasks and underwent resting-state functional magnetic resonance imaging (rs-fMRI). Report accuracy was modeled using TVA to estimate, individually, the four TVA parameters. Networks encompassing cortical areas relevant for visual attention were derived from independent component analysis of rs-fMRI data: visual, executive control, right and left frontoparietal, and ventral and dorsal attention networks. Two TVA parameters were mapped on particular functional networks. First, participants with higher (vs. lower) visual processing speed showed lower functional connectivity within the ventral attention network. Second, participants with more (vs. less) efficient top-down control showed higher functional connectivity within the dorsal attention network and lower functional connectivity within the visual network. Additionally, higher performance was associated with higher functional connectivity between networks: specifically, between the ventral attention and right frontoparietal networks for visual processing speed, and between the visual and executive control networks for top-down control. The higher inter-network functional connectivity was related to lower intra-network connectivity. These results demonstrate that separable visual attention parameters that are assumed to constitute relatively stable traits correspond distinctly to the functional connectivity both within and between particular functional networks. This implies that individual differences in basic attention functions are represented by differences in the coherence of slowly fluctuating brain activity

    Effective Programs in Elementary Mathematics: A Meta-Analysis

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    This article reviews research on the achievement outcomes of elementary mathematics programs. 87 rigorous experimental studies evaluated 66 programs in grades K-5. Programs were organized in 6 categories. Particularly positive outcomes were found for tutoring programs (ES=+0.20, k=22). Positive outcomes were also seen in studies focused on professional development for classroom organization and management (e.g., cooperative learning) (ES=+0.19, k=7). Professional development approaches focused on helping teachers gain in understanding of mathematics content and pedagogy had little impact on student achievement. Professional development intended to help in the adoption of new curricula had a small but significant impact for traditional (non-digital) curricula (ES=+0.12, k=7), but not for digital curricula. Traditional and digital curricula with limited professional development, as well as benchmark assessment programs, found few positive effects

    SURVEY OF COLUMBIA RIVER BASIN STREAMS FOR COLUMBIA PEBBLESNAIL Fluminicola columbiana AND SHORTFACE LANX Fisherola nuttalli

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    At present, there are only two remaining sizable populations of Columbia pebblesnail Fluminicola columbiana; those in the Methow and Okanogan rivers, Washington. Smaller populations survive in the Hanford Reach of the Columbia River, Washington; the lower Salmon River and middle Snake River, Idaho; and possibly in Hells Canyon of the Snake River, Idaho, Washington, and Oregon; and the Grande Ronde River, Oregon and Washington. Neither large population is at present protected, and there has been a substantial documented reduction in the species' historical range. Large populations of the shortface lanx Fisherola nuttalli persist in four streams: the Deschutes River, Oregon; the Hanford Reach of the Columbia River, Washington; Hells Canyon of the Snake River, Idaho and Oregon; and the Okanogan River, Washington. Smaller populations, or ones of uncertain size, are known from the lower Salmon and middle Snake rivers, Idaho; the Grande Ronde, Washington and Oregon; Imnaha and John Day rivers, Oregon; Bonneville Dam area of the Columbia River, Washington and Oregon; and the Methow River, Washington. While substantial range reduction has occurred in this species, and the large populations are not well protected, the problem is not as severe as in the case of the Columbia pebblesnail. Both species appear to have been widespread historically in the mainstem Columbia River and the Columbia River Basin prior to the installation of the current dam system. Both are now apparently reduced within the Columbia River: Columbia pebblesnail to a population in the Hanford Reach plus six other sites that are separated by large areas of unsuitable habitat from those in the river's major mbutaries shortface lanx to two populations (in the Hanford Reach and near Bonneville Dam) plus nine other sites that are separated by large areas of unsuitable habitat from those in the river's major tributaries
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