8,925 research outputs found
MetaSpace II: Object and full-body tracking for interaction and navigation in social VR
MetaSpace II (MS2) is a social Virtual Reality (VR) system where multiple
users can not only see and hear but also interact with each other, grasp and
manipulate objects, walk around in space, and get tactile feedback. MS2 allows
walking in physical space by tracking each user's skeleton in real-time and
allows users to feel by employing passive haptics i.e., when users touch or
manipulate an object in the virtual world, they simultaneously also touch or
manipulate a corresponding object in the physical world. To enable these
elements in VR, MS2 creates a correspondence in spatial layout and object
placement by building the virtual world on top of a 3D scan of the real world.
Through the association between the real and virtual world, users are able to
walk freely while wearing a head-mounted device, avoid obstacles like walls and
furniture, and interact with people and objects. Most current virtual reality
(VR) environments are designed for a single user experience where interactions
with virtual objects are mediated by hand-held input devices or hand gestures.
Additionally, users are only shown a representation of their hands in VR
floating in front of the camera as seen from a first person perspective. We
believe, representing each user as a full-body avatar that is controlled by
natural movements of the person in the real world (see Figure 1d), can greatly
enhance believability and a user's sense immersion in VR.Comment: 10 pages, 9 figures. Video:
http://living.media.mit.edu/projects/metaspace-ii
Variations in -Mode Parameters with Changing Onset-Time of a Large Flare
It is expected that energetic solar flares releasing large amount of energy
at the photosphere may be able to excite the acoustic (-) modes of
oscillations. We have determined the characteristic properties of mode
parameters by applying the ring diagram technique to 3-D power spectra obtained
for solar active region NOAA 10486 during the long duration energetic X17.2/4B
flare of October 28, 2003. Strong evidence of substantial increase in mode
amplitude and systematic variations in sub-surface flows, i.e., meridional and
zonal components of velocity, kinetic helicity, vorticity, is found from
comparison of the pre- to the post-flare phases.Comment: 14 pages, 4 figure
Tangible user interfaces : past, present and future directions
In the last two decades, Tangible User Interfaces (TUIs) have emerged as a new interface type that interlinks the digital and physical worlds. Drawing upon users' knowledge and skills of interaction with the real non-digital world, TUIs show a potential to enhance the way in which people interact with and leverage digital information. However, TUI research is still in its infancy and extensive research is required in or- der to fully understand the implications of tangible user interfaces, to develop technologies that further bridge the digital and the physical, and to guide TUI design with empirical knowledge. This paper examines the existing body of work on Tangible User In- terfaces. We start by sketching the history of tangible user interfaces, examining the intellectual origins of this field. We then present TUIs in a broader context, survey application domains, and review frame- works and taxonomies. We also discuss conceptual foundations of TUIs including perspectives from cognitive sciences, phycology, and philoso- phy. Methods and technologies for designing, building, and evaluating TUIs are also addressed. Finally, we discuss the strengths and limita- tions of TUIs and chart directions for future research
Attitudes politiques de Tunis dans le conflit entre Aragonais et Français en Sicile autour de 1282
International audienceSimulating the deformation of the human anatomy is a central element of Medical Image Computing and Computer Assisted Interventions. Such simulations play a key role in non-rigid registration, augmented reality, and several other applications. Although the Finite Element Method is widely used as a numerical approach in this area, it is often hindered by the need for an optimal meshing of the domain of interest. The derivation of meshes from imaging modalities such as CT or MRI can be cumbersome and time-consuming. In this paper we use the Immersed Boundary Method (IBM) to bridge the gap between these imaging modalities and the fast simulation of soft tissue deformation on complex shapes represented by a surface mesh directly retrieved from binary images. A high resolution surface, that can be obtained from binary images using a marching cubes approach, is embedded into a hexahedral simulation grid. The details of the surface mesh are properly taken into account in the hexahedral mesh by adapting the Mirtich integration method. In addition to not requiring a dedicated meshing approach, our method results in higher accuracy for less degrees of freedom when compared to other element types. Examples on brain deformation demonstrate the potential of our method
Polymer collapse and crystallization in bond fluctuation models
While the -collapse of single long polymers in bad solvents is
usually a continuous (tri-critical) phase transition, there are exceptions
where it is preempted by a discontinuous crystallization (liquid
solid) transition. For a version of the bond-fluctuation
model (a model where monomers are represented as cubes, and
bonds can have lengths between 2 and ) it was recently shown by F.
Rampf {\it et al.} that there exist distinct collapse and crystallization
transitions for long but {\it finite} chains. But as the chain length goes to
infinity, both transition temperatures converge to the same , i.e.
infinitely long polymers collapse immediately into a solid state. We explain
this by the observation that polymers crystallize in the Rampf {\it et al.}
model into a non-trivial cubic crystal structure (the `A15' or `CrSi'
Frank-Kasper structure) which has many degenerate ground states and, as a
consequence, Bloch walls. If one controlls the polymer growth such that only
one ground state is populated and Bloch walls are completely avoided, the
liquid-solid transition is a smooth cross-over without any sharp transition at
all.Comment: 4 page
A finite element framework for modeling internal frictional contact in three-dimensional fractured media using unstructured tetrahedral meshes
AbstractThis paper introduces a three-dimensional finite element (FE) formulation to accurately model the linear elastic deformation of fractured media under compressive loading. The presented method applies the classic Augmented Lagrangian(AL)-Uzawa method, to evaluate the growth of multiple interacting and intersecting discrete fractures. The volume and surfaces are discretized by unstructured quadratic triangle-tetrahedral meshes; quarter-point triangles and tetrahedra are placed around fracture tips. Frictional contact between crack faces for high contact precisions is modeled using isoparametric integration point-to-integration point contact discretization, and a gap-based augmentation procedure. Contact forces are updated by interpolating tractions over elements that are adjacent to fracture tips, and have boundaries that are excluded from the contact region. Stress intensity factors are computed numerically using the methods of displacement correlation and disk-shaped domain integral. A novel square-root singular variation of the penalty parameter near the crack front is proposed to accurately model the contact tractions near the crack front. Tractions and compressive stress intensity factors are validated against analytical solutions. Numerical examples of cubes containing one, two, twenty four and seventy interacting and intersecting fractures are presented
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