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Investigating the Intelligibility of a Computer Vision System for Blind Users
Computer vision systems to help blind usersare becoming increasingly common yet often these systems are not intelligible. Our work investigates the intelligibility of a wearable computer vision system to help blind users locate and identify people in their vicinity. Providing a continuous stream of information, this system allows us to explore intelligibility through interaction and instructions, going beyond studies of intelligibility that focus on explaining a decision a computer vision system might make. In a study with 13 blind users, we explored whether varying instructions (either basic or enhanced) about how the system worked would change blind users’ experience of the system. We found offering a more detailed set of instructions did not affect how successful users were using the system nor their perceived workload. We did, however, find evidence of significant differences in what they knew about the system, and they employed different, and potentially more effective, use strategies. Our findings have important implications for researchers and designers of computer vision systemsfor blind users, as well more general implications for understanding what it means to make interactive computer vision systems intelligible
Cell-Type Specific Changes in Glial Morphology and Glucocorticoid Expression During Stress and Aging in the Medial Prefrontal Cortex.
Repeated exposure to stressors is known to produce large-scale remodeling of neurons within the prefrontal cortex (PFC). Recent work suggests stress-related forms of structural plasticity can interact with aging to drive distinct patterns of pyramidal cell morphological changes. However, little is known about how other cellular components within PFC might be affected by these challenges. Here, we examined the effects of stress exposure and aging on medial prefrontal cortical glial subpopulations. Interestingly, we found no changes in glial morphology with stress exposure but a profound morphological change with aging. Furthermore, we found an upregulation of non-nuclear glucocorticoid receptors (GR) with aging, while nuclear levels remained largely unaffected. Both changes are selective for microglia, with no stress or aging effect found in astrocytes. Lastly, we show that the changes found within microglia inversely correlated with the density of dendritic spines on layer III pyramidal cells. These findings suggest microglia play a selective role in synaptic health within the aging brain
Observation of Enhanced Beaming from Photonic Crystal Waveguides
We report on the experimental observation of the beaming effect in photonic
crystals enhanced via surface modes. We experimentally map the spatial field
distribution of energy emitted from a subwavelength photonic crystal waveguide
into free-space, rendering with crisp clarity the diffractionless beaming of
energy. Our experimental data agree well with our numerical studies of the
beaming enhancement in photonic crystals with modulated surfaces. Without loss
of generality, we study the beaming effect in a photonic crystal scaled to
microwave frequencies and demonstrate the technological capacity to deliver
long-range, wavelength-scaled beaming of energy.Comment: 4 pages, 6 figure
Design improvement of a pump wear ring labyrinth seal
The investigation was successful in obtaining two improved designs for the impeller wear ring seal of the liquid hydrogen turbopump of interest. A finite difference computer code was extensively used in a parametric computational study in determining a cavity configuration with high flow resistance due to turbulence dissipation. These two designs, along with that currently used, were fabricated and tested. The improved designs were denoted Type O and Type S. The measurements showed that Type O and Type S given 67 and 30 percent reduction in leakage over the current design, respectively. It was found that the number of cavities, the step height and the presence of a small stator groove are quite important design features. Also, the tooth thickness is of some significance. Finally, the tooth height and an additional large cavity cut out from the stator (upstream of the step) are of negligible importance
Evolving database systems : a persistent view
Submitted to POS7 This work was supported in St Andrews by EPSRC Grant GR/J67611 "Delivering the Benefits of Persistence"Orthogonal persistence ensures that information will exist for as long as it is useful, for which it must have the ability to evolve with the growing needs of the application systems that use it. This may involve evolution of the data, meta-data, programs and applications, as well as the users' perception of what the information models. The need for evolution has been well recognised in the traditional (data processing) database community and the cost of failing to evolve can be gauged by the resources being invested in interfacing with legacy systems. Zdonik has identified new classes of application, such as scientific, financial and hypermedia, that require new approaches to evolution. These applications are characterised by their need to store large amounts of data whose structure must evolve as it is discovered by the applications that use it. This requires that the data be mapped dynamically to an evolving schema. Here, we discuss the problems of evolution in these new classes of application within an orthogonally persistent environment and outline some approaches to these problems.Postprin
Complex Line Bundles over Simplicial Complexes and their Applications
Discrete vector bundles are important in Physics and recently found
remarkable applications in Computer Graphics. This article approaches discrete
bundles from the viewpoint of Discrete Differential Geometry, including a
complete classification of discrete vector bundles over finite simplicial
complexes. In particular, we obtain a discrete analogue of a theorem of Andr\'e
Weil on the classification of hermitian line bundles. Moreover, we associate to
each discrete hermitian line bundle with curvature a unique piecewise-smooth
hermitian line bundle of piecewise constant curvature. This is then used to
define a discrete Dirichlet energy which generalizes the well-known cotangent
Laplace operator to discrete hermitian line bundles over Euclidean simplicial
manifolds of arbitrary dimension
Resonance solutions of the nonlinear Schr\"odinger equation in an open double-well potential
The resonance states and the decay dynamics of the nonlinear Schr\"odinger
(or Gross-Pitaevskii) equation are studied for a simple, however flexible model
system, the double delta-shell potential. This model allows analytical
solutions and provides insight into the influence of the nonlinearity on the
decay dynamics. The bifurcation scenario of the resonance states is discussed,
as well as their dynamical stability properties. A discrete approximation using
a biorthogonal basis is suggested which allows an accurate description even for
only two basis states in terms of a nonlinear, nonhermitian matrix problem.Comment: 21 pages, 14 figure
Relaminarisation of Re_Ď„=100 channel flow with globally stabilising linear feedback control
The problems of nonlinearity and high dimension have so far prevented a complete solution of the control of turbulent flow. Addressing the problem of nonlinearity, we propose a flow control strategy which ensures that the energy of any perturbation to the target profile decays monotonically. The controller’s estimate of the flow state is similarly guaranteed to converge to the true value. We present a one-time off-line synthesis procedure, which generalises to accommodate more restrictive actuation and sensing arrangements, with conditions for existence for the controller given in this case. The control is tested in turbulent channel flow (Re_τ = 100) using full-domain sensing and actuation on the wall-normal velocity. Concentrated at the point of maximum inflection in the mean profile, the control directly counters the supply of turbulence energy arising from the interaction of the wall-normal perturbations with the flow shear. It is found that the control is only required for the larger-scale motions, specifically those above the scale of the mean streak spacing. Minimal control effort is required once laminar flow is achieved. The response of the near-wall flow is examined in detail, with particular emphasis on the pressure and wall-normal velocity fields, in the context of Landahl’s theory of sheared turbulence
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