103,813 research outputs found
Automated Markerless Extraction of Walking People Using Deformable Contour Models
We develop a new automated markerless motion capture system for the analysis of walking people. We employ global evidence gathering techniques guided by biomechanical analysis to robustly extract articulated motion. This forms a basis for new deformable contour models, using local image cues to capture shape and motion at a more detailed level. We extend the greedy snake formulation to include temporal constraints and occlusion modelling, increasing the capability of this technique when dealing with cluttered and self-occluding extraction targets. This approach is evaluated on a large database of indoor and outdoor video data, demonstrating fast and autonomous motion capture for walking people
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The Human Brain: A Multimedia Tutorial For The Independent Learner
The Human Brain is a multimedia, interactive, computer-based tutorial on the structure and function of the human nervous system. In creating it, we aim to solve a number of problems, both subject specific and general. As a subject, the structure and function of the nervous system is difficult to teach using traditional methods and there is a lack of integration in the teaching of structure and function. More generally, we are concerned with the difficulties of both assessing student understanding of a particular subject and remedying any deficiencies when the student is learning independently. Finally, we hope to resolve the conflict between linear and explorative modes of presentation of material in a teaching system
A Portfolio View of Consumer Credit
To compute risk-adjusted returns and gauge the volatility of their portfolios, lenders need to know the covariances of their loans' returns with aggregate returns. Cross-sectional differences in these covariances also provide insight into the nature of the shocks hitting different types of consumers. We use a unique panel dataset of credit bureau records to measure the 'covariance risk' of individual consumers, i.e., the covariance of their default risk with aggregate consumer default rates, and more generally to analyze the cross-sectional distribution of credit, including the effects of credit scores. We obtain two key sets of results. First, there is significant systematic heterogeneity in covariance risk across consumers with different characteristics. Consumers with high covariance risk tend to also have low credit scores (high default probabilities). Second, the amount of credit obtained by consumers significantly increases with their credit scores, and significantly decreases with their covariance risk (especially revolving credit), though the effect of covariance risk is smaller in magnitude.
Topological Defects on the Lattice I: The Ising model
In this paper and its sequel, we construct topologically invariant defects in
two-dimensional classical lattice models and quantum spin chains. We show how
defect lines commute with the transfer matrix/Hamiltonian when they obey the
defect commutation relations, cousins of the Yang-Baxter equation. These
relations and their solutions can be extended to allow defect lines to branch
and fuse, again with properties depending only on topology. In this part I, we
focus on the simplest example, the Ising model. We define lattice spin-flip and
duality defects and their branching, and prove they are topological. One useful
consequence is a simple implementation of Kramers-Wannier duality on the torus
and higher genus surfaces by using the fusion of duality defects. We use these
topological defects to do simple calculations that yield exact properties of
the conformal field theory describing the continuum limit. For example, the
shift in momentum quantization with duality-twisted boundary conditions yields
the conformal spin 1/16 of the chiral spin field. Even more strikingly, we
derive the modular transformation matrices explicitly and exactly.Comment: 45 pages, 9 figure
Highly Deformable Graphene Kirigami
Graphene's exceptional mechanical properties, including its highest-known
stiffness (1 TPa) and strength (100 GPa) have been exploited for various
structural applications. However, graphene is also known to be quite brittle,
with experimentally-measured tensile fracture strains that do not exceed a few
percent. In this work, we introduce the notion of graphene kirigami, where
concepts that have been used almost exclusively for macroscale structures are
applied to dramatically enhance the stretchability of both zigzag and armchair
graphene. Specifically, we show using classical molecular dynamics simulations
that the yield and fracture strains of graphene can be enhanced by about a
factor of three using kirigami as compared to standard monolayer graphene. This
enhanced ductility in graphene should open up interesting opportunities not
only mechanically, but also in coupling to graphene's electronic behavior.Comment: 5 pages, 7 figure
Optically nonlinear energy transfer in light-harvesting dendrimers
Dendrimeric polymers are the subject of intense research activity geared towards their implementation in nanodevice applications such as energy harvesting systems,organic light-emitting diodes, photosensitizers, low-threshold lasers, and quantum logic elements, etc. A recent development in this area has been the construction of dendrimers specifically designed to exhibit novel forms of optical nonlinearity, exploiting the unique properties of these materials at high levels of photon flux. Starting from a thorough treatment of the underlying theory based on the principles of molecular quantum electrodynamics, it is possible to identify and characterize several optically nonlinear mechanisms for directed energy transfer and energy pooling in multichromophore dendrimers. Such mechanisms fall into two classes: first, those where two-photon absorption by individual donors is followed by transfer of the net energy to an acceptor; second, those where the excitation of two electronically distinct but neighboring donor groups is followed by a collective migration of their energy to a suitable acceptor. Each transfer process is subject to minor dissipative losses. In this paper we describe in detail the balance of factors and the constraints that determines the favored mechanism, which include the excitation statistics, structure of the energy levels, laser coherence factors, chromophore selection rules and architecture, possibilities for the formation of delocalized excitons, spectral overlap, and the overall distribution of donors and acceptors. Furthermore, it transpires that quantum interference between different mechanisms can play an important role. Thus, as the relative importance of each mechanism determines the relevant nanophotonic characteristics, the results reported here afford the means for optimizing highly efficient light-harvesting dendrimer devices
Hospital and Physician Capacity Update
Offers an alternative view of healthcare costs by examining trends in hospital capacity and healthcare labor across regions. Outlines how effective management of healthcare capacity would enable affordable quality care that meets patient needs and wants
Effect of Particle Shape and Charge on Bulk Rheology of Nanoparticle Suspensions
The rheology of nanoparticle suspensions for nanoparticles of various shapes
with equal mass is studied using molecular dynamics simulations. The
equilibrium structure and the response to imposed shear are analyzed for
suspensions of spheres, rods, plates, and jacks in an explicit solvent for both
charged and uncharged nanoparticles. For the volume fraction studied,
?, the uncharged systems are all in their isotropic phase and
the viscosity is only weakly dependent on shape for spheres, rods, and plate
whereas for the jacks the viscosity is an order of magnitude larger than for
the other three shapes. The introduction of charge increases the viscosity for
all four nanoparticle shapes with the increase being the largest for rods and
plates. The presence of a repulsive charge between the particles decreases the
amount of stress reduction that can be achieved by particle reorientation.Comment: 15 pages, 9 figures, in pres
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