1,721,015 research outputs found
Biologically inspired guidance for motion camouflage
No full textIn the insect world, dragonflies are considered to be amongst the best aerial predators, and are known to use motion camouflage techniques to mask their approach. How they accomplish this remains undiscovered, but using traditional guidance approaches we can attempt to simulate this behaviour. In this paper, we consider the motion camouflage guidance problem within a linear quadratic Gaussian framework and demonstrate that the resulting guidance strategy is effective in achieving the camouflage requirements
Automatic calibration of magnetic field and acceleration sensors using homogeneous coordinates
No full textA miniature autopilot is presented as an example application of automatic of calibration. The deployment concepts and cost sensitivity of potential users is considered. Examples of calibration are presented including data from the calibrated and uncalibrated instrument suite in flight.
A comptational fluid dynamic study of a bioinspired corrugated aerofoil for micro air vehicles
No full textThe role of aerofoil corrugation at Re = 34, 000 with flight manoeuvres at low Angles-of- Attack (AoA) is presented. The impact of surface corrugations in sustaining high aerodynamic efficiency relative to a flat plate configuration is examined for a Micro Aerial Vehicle (MAV) application. A Computational Fluid Dynamics (CFD) methodology scheme is first validated to ensure the aerodynamic data used in support of the noted findings are accurate. A grid dependency analysis confirmed the establishment of an accurate CFD structure with solver output that is within an acceptable wind tunnel error tolerance limit. Following CFD validation, the examination of the critical flow features that represent corrugated geometries is modeled. It is shown that corrugation facilitates extended regions of flow attachment over the aerofoil due to the generation of flow recirculation bubbles that are notable in the valleys. These have the effect of transforming the aerofoil contour into a streamlined shape such that the flow patterns that are present outside of the valleys flow smoothly along the body surface. The behaviour of the boundary layer further showed that energised flow patterns benefit corrugated geometries. At near-wall regions, high turbulent kinetic energy (TKE) facilitates flow suction by pumping in high-speed fluid from the outer freestream region into the near-wall area. This negates the onset of premature flow separation at the leading edge and results in high lift performances. The corrugated geometry has high friction drag relative to a flat plate, hence the aerodynamic efficiency is restricted. Accordingly the analysis confirms that the aerodynamic performances of a corrugated aerofoil are limited at low AoA flight points relative to a flat plate at the modeled Re test point.
A complete panoramic vision system, incorporating imaging, ranging, and three-dimensional navigation.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A method for landmark extraction for autonomous vision based navigation of UAVs
No full textAutonomous navigation of Unmanned Aerial System (UAS) has been achieved with active sensor systems and the Global Positioning System (GPS). These systems are vulnerable to jamming. Passive methods such as vision are considered to be a promising alternative. Vision based systems have operational limitations at night and other invisible periods such as foggy/ cloudy conditions. Even in the presence of sunlight it has to deal with various atmospheric/ environmental conditions. We present an algorithm to address vision based navigation during varying atmospheric/environmental conditions. Our algorithm is tested in synthetic as well as real world environments demonstrating good performance.
Axially displaced optical flow sensors for measuring and controlling the landing height of a UAV
No full textWe argue that this technique is comparable to vision techniques such as stereo in this application and more versatile. The features of our technique will be compared to stereo in detail to explain why we see this technique is rather specifically suitable to UAVs.
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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