15,432 research outputs found

    Conceptual nonorthogonal gyro configuration for guidance and navigation

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    Nonorthogonal sensor configuration using six single-degree-of-freedom inertial reference gyroscopes and a complete data processing and self-contained failure detection-and-isolation mechanism provides redundant capabilities to guidance and navigation systems. This system has been formulated in a strap-down configuration to attain maximum redundancy

    SIRU development. Volume 1: System development

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    A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results

    Peeling Bifurcations of Toroidal Chaotic Attractors

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    Chaotic attractors with toroidal topology (van der Pol attractor) have counterparts with symmetry that exhibit unfamiliar phenomena. We investigate double covers of toroidal attractors, discuss changes in their morphology under correlated peeling bifurcations, describe their topological structures and the changes undergone as a symmetry axis crosses the original attractor, and indicate how the symbol name of a trajectory in the original lifts to one in the cover. Covering orbits are described using a powerful synthesis of kneading theory with refinements of the circle map. These methods are applied to a simple version of the van der Pol oscillator.Comment: 7 pages, 14 figures, accepted to Physical Review

    Queer expressions: an Interpretative phenomenological analysis of how Irish gay men discuss sexuality with healthcare practitioners

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    Queer Expressions offers an insight into the experience for Irish Gay Men of discussing sexuality with healthcare professionals. It clearly establishes a specific understanding of what sexuality and health mean for Irish Gay Men and how this understanding, along with broader social constructs and experiences, impact on how sexuality is discussed in a healthcare context. Ireland has seen unprecedented progress in the area of LGBT rights in the past three decades; from the decriminalisation of homosexual acts following legal challenges in 1993, to the provision of same-sex marriage following the world’s first popular public vote on the issue in 2015 and the election of an openly gay prime minister in 2017. Despite significant social progress, health disparities remain amongst the Irish gay community, and an EU fundamental rights agency 2020 LGBTI survey (EU, Fundamental Rights Agency, 2020) identified that a quarter of Irish Gay Men have not told any healthcare provider that they are gay. Through the use of Interpretive Phenomenological Analysis (Smith et al., 2009) the experiences of 12 Irish Gay Men are explored and illuminate the specificities of Irish Gay Men’s encounters and discussions of sexuality with healthcare professionals. The layered and multidimensional sexual identities of Irish Gay Men are revealed, along with the ways in which their encounters ‘Queer’ the provision of healthcare within health professional consultations. The men in the study also provide a unique and specific account of how the concept of health is perceived, experienced and embodied for this group. The thesis clearly establishes the implications for practice, policy and research around specific considerations for Irish Gay Men in healthcare professional education and training; and within the systems in which healthcare is provide

    Strapdown system Performance Optimization Test evaluations (SPOT), volume 2

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    A three axis inertial system is packaged in an Apollo gimbal fixture for fine grain evaluation of strapdown system performance in dynamic environments. These evaluations have provided information to assess the effectiveness of real-time compensation techniques and to study system performance tradeoffs to factors such as quantization iteration rate. The strapdown performance and tradeoff studies conducted in this program are discussed

    Sagittarius: The Nearest Dwarf Galaxy

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    We have discovered a new Galactic satellite galaxy in the constellation of Sagittarius. The Sagittarius dwarf galaxy is the nearest galaxy known, subtends an angle of >10> 10 degrees on the sky, lies at a distance of 24 \kpc from the Sun, \sim 16 \kpc from the centre of the Milky Way. Itis comparable in size and luminosity to the largest dwarf spheroidal, has a well populated red horizontal branch with a blue HB extension; a substantial carbon star population; and a strong intermediate age stellar component with evidence of a metallicity spread. Isodensity maps show it to be markedly elongated along a direction pointing towards the Galactic centre and suggest that it has been tidally distorted. The close proximity to the Galactic centre, the morphological appearance and the radial velocity of 140 km/s indicate that this system must have undergone at most very few close orbital encounters with the Milky Way. It is currently undergoing strong tidal disruption prior to being integrated into the Galaxy. Probably all of the four globular clusters, M54, Arp 2, Ter 7 and Ter 8, are associated with the Sagittarius dwarf galaxy, and will probably share the fate of their progenitor.Comment: MNRAS in press, 22pp uuencoded PS file, 26 printed figures available on request from [email protected]

    Dynamical properties of a nonequilibrium quantum dot close to localized-delocalized quantum phase transitions

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    We calculate the dynamical decoherence rate and susceptibility of a nonequilibrium quantum dot close to the delocalized-to-localized quantum phase transitions. The setup concerns a resonance-level coupled to two spinless fermionic baths with a finite bias voltage and an Ohmic bosonic bath representing the dissipative environment. The system is equivalent to an anisotropic Kondo model. As the dissipation strength increases, the system at zero temperature and zero bias show quantum phase transition between a conducting delocalized phase to an insulating localized phase. Within the nonequilibrium functional Renormalization Group (FRG) approach, we address the finite bias crossover in dynamical decoherence rate and charge susceptibility close to the phase transition. We find the dynamical decoherence rate increases with increasing frequency. In the delocalized phase, it shows a singularity at frequencies equal to positive or negative bias voltage. As the system crossovers to the localized phase, the decoherence rate at low frequencies get progressively smaller and this sharp feature is gradually smeared out, leading to a single linear frequency dependence. The dynamical charge susceptibility shows a dip-to-peak crossover across the delocalized-to-localized transition. Relevance of our results to the experiments is discussed.Comment: 7 pages, 7 figure

    A search for evidence of large body Earth impacts associated with biological crisis zones in the fossil record

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    The natural history of the Earth, how the present plant and animal species developed, how others completely died out, etc., was studied. The rock strata sampled and studied were at the time of deposition at sea bottom. It was found that, exactly at the stratigraphic level corresponding to the extinction, a thin clay layer was greatly enriched in the the rare element iridium. It was hypothesized that the excess irridium at the boundary came from a large steroid like object that hit the earth, and that the impact of this object threw up a dust cloud dense enough and long lasting enough to bring about the extinction of a wide variety of plants and animals, producing the unique break in in the fossil record, the cretaceous-tertiary boundary. The same iridium and platinum metals enrichement are found in a thin clay layer that corresponds with the boundary as difined by sudden radical changes in plant populations. The irridium enrichement is confirmed at other fresh water origin rites in the Raton Basin
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