7,905 research outputs found

    A study of flow past an airfoil with a jet issuing from its lower surface

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    The aerodynamics of a NACA 0018 airfoil with a rectangular jet of finite aspect ratio exiting from its lower surface at 90 deg to the chord were investigated. The jet was located at 50% of the wing chord. Measurements include static pressures on the airfoil surface, total pressures in the near wake, and local velocity vectors in different planes of the wake. The effects of jet cross flow interaction on the aerodynamics of the airfoil are studied. It is indicated that at all values of momentum coefficients, the jet cross flow interaction produces a strong contra-rotating vortex structure in the near wake. The flow behind the jet forms a closed recirculation region which extends up to a chord length down stream of the trailing edge which results in the flow field to become highly three dimensional. The various aerodynamic force coefficients vary significantly along the span of the wing. The results are compared with a jet flap configuration

    Tube coupling device

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    A first annular ring of a tube coupling device has a keyed opening sized to fit around the nut region of a male coupling, and a second annular ring has a keyed opening sized to fit around the nut of a female coupling. Each ring has mating ratchet teeth and these rings are biased together, thereby engaging these teeth and preventing rotation of these rings. This in turn prevents the rotation of the male nut region with respect to the female nut. For tube-to-bulkhead locking, one facet of one ring is notched, and a pin is pressed into an opening in the bulkhead. This pin is sized to fit within one of the notches in the ring, thereby preventing rotation of this ring with respect to the bulkhead

    Effects of a ground vortex on the aerodynamics of an airfoil

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    An experimental investigation was carried out to study the aerodynamics of an airfoil with a rectangular jet exiting from its lower surface at fifty percent of the chord. The airfoil was tested with and without the influence of a ground plane. Surface static pressures were measured on the airfoil at jet to free stream velocity ratios ranging from 0 to 9. From these pressures, the variation of C sub L with velocity ratio was easily determined. The measurements indicated significant positive and negative pressure regions on the lower surface of the airfoil ahead of and after the nozzle exit respectively. The presence of a ground plane enhanced these pressure regions at low velocity ratios, but at a particular ratio for each plane location, a recirculation zone or vortex formed ahead of the jet resulting in decreased pressures and a drop in C sub L

    Neural activity in the visual thalamus reflects perceptual suppression

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    To examine the role of the visual thalamus in perception, we recorded neural activity in the lateral geniculate nucleus (LGN) and pulvinar of 2 macaque monkeys during a visual illusion that induced the intermittent perceptual suppression of a bright luminance patch. Neural responses were sorted on the basis of the trial-to-trial visibility of the stimulus, as reported by the animals. We found that neurons in the dorsal and ventral pulvinar, but not the LGN, showed changes in spiking rate according to stimulus visibility. Passive viewing control sessions showed such modulation to be independent of the monkeys' active report. Perceptual suppression was also accompanied by a marked drop in low-frequency power (9–30 Hz) of the local field potential (LFP) throughout the visual thalamus, but this modulation was not observed during passive viewing. Our findings demonstrate that visual responses of pulvinar neurons reflect the perceptual awareness of a stimulus, while those of LGN neurons do not

    Visual adaptation to convexity in macaque area V4

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    Aftereffects are perceptual illusions caused by visual adaptation to one or more stimulus attribute, such as orientation, motion, or shape. Neurophysiological studies seeking to understand the basis of visual adaptation have observed firing rate reduction and changes in tuning of stimulus-selective neurons following periods of prolonged visual stimulation. In the domain of shape, recent psychophysical work has shown that adaptation to a convex pattern induces a subsequently seen rectangle to appear slightly concave. In the present study, we investigate the possible contribution of V4 neurons of rhesus monkeys, which are thought to be involved in the coding of convexity, to shape-specific adaptation. Visually responsive neurons were monitored during the brief presentation of simple shapes varying in their convexity level. Each test presentation was preceded by either a blank period or several seconds of adaptation to a convex or concave stimulus, presented in two different sizes. Adaptation consistently shifted the tuning of neurons away from the convex or concave adapter, including shifting response to the neutral rectangle in the direction of the opposite convexity. This repulsive shift resembled the known perceptual distortion associated with adaptation to such stimuli. In addition, adaptation caused a nonspecific response decrease, as well as a specific decrease for repeated stimuli. The latter effects were observed whether or not the adapting and test stimuli matched closely in their size. Taken together, these results provide evidence for shape-specific adaptation of neurons in area V4, which may contribute to the perception of the convexity aftereffect

    MicroRNAs Regulate Vascular Medial Calcification

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    Vascular calcification is highly prevalent in patients with coronary artery disease and, when present, is associated with major adverse cardiovascular events, including an increased risk of cardiovascular mortality. The pathogenesis of vascular calcification is complex and is now recognized to recapitulate skeletal bone formation. Vascular smooth muscle cells (SMC) play an integral role in this process by undergoing transdifferentiation to osteoblast-like cells, elaborating calcifying matrix vesicles and secreting factors that diminish the activity of osteoclast-like cells with mineral resorbing capacity. Recent advances have identified microRNAs (miRs) as key regulators of this process by directing the complex genetic reprogramming of SMCs and the functional responses of other relevant cell types relevant for vascular calcification. This review will detail SMC and bone biology as it relates to vascular calcification and relate what is known to date regarding the regulatory role of miRs in SMC-mediated vascular calcification

    Alien Registration- Aube, Leopold A. (Lewiston, Androscoggin County)

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    https://digitalmaine.com/alien_docs/30346/thumbnail.jp

    Keyboardless Visual Programming Using Voice, Handwriting, and Gesture

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    Visual programming languages have facilitated the application development process, improving our ability to express programs, as well as our ability to view, edit and interact with them. Yet even in programming environments, productivity is restricted by the primary input sources: the mouse and the keyboard. As an alternative, we investigate a program development interface which responds to the most natural human communication technologies: voice, handwriting and gesture. Speech- and pen-based systems have yet to find broad acceptance in everyday life because they are insufficiently advantageous to overcome problems with reliability. However, we believe that a visual programming environment with a multimodal user interface properly constrained so as not to exceed the limits of the current technology has the potential to increase programming productivity for not only those people who are manually or visually impaired, but for the general population as well. In this paper we report on such a system

    A User Interface for the Visualization and Manipulation of Arrays

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    The success of spreadsheets has shown that a visual representation of a 2D array greatly facilitates solving certain problems. However, spreadsheets are not general-purpose programming environments and are not suited to many problems that might naturally be solved using multi-dimensional arrays. Furthermore, spreadsheets employ a textual notation for cell references in formulas. This notation, which adds to the programmer\u27\u27s burden by distinguishing between relative and absolute addressing, can be difficult to understand and is error-prone even for the most experienced users. In this paper, we present a user interface for multi-dimensional arrays within Formulate, a form-based visual programming language. This implementation avoids textual array notation and supports the application of formulas to logical regions of an array, rather than just to individual elements
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